Ricoh FT6645 Service manual

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SECTION 1

OVERALL MACHINE

INFORMATION

23 April 1993 SPECIFICATIONS

1. SPECIFICATIONS

Configuration: Console Copy Process: Dry electrostatic transfer system Toner Supply Control: Fuzzy Control Photoconducto r: OPC drum Originals: Sheet/Book Original Size: Maximum A3/11" x 17" Original Alignment: Left rear corner Copy Paper Size: Maximum A3/11" x 17"

Minimum A5/51/2" x 81/2" (Tray)

B5/81/2" x 11" (1.5K LCT) A6/51/2" x 81/2" (By-pass)

Duplex Copying: Maximum A3/11" x 17"

Minimum A5/51/2" x 81/2" (sideways)

Copy Paper Weight: Paper tray: 52 ~ 128 g/m2, 14 ~ 34 lb

Bypass feed table: 52 ~ 157 g/m2, 14 ~ 42 lb Duplex copying: 64 ~ 104 g/m2, 17 ~ 24 lb

Overall

Information

Reproduction Ratios: 4 Enlargement and 6 Red uction

A4/A3 Version LT/LDG Version

Enlargement 200%

141% 122% 115%

Full Size 100% 100%

Reduction 93%

82% 75% 71% 65% 50%

200% 155% 129% 121%

93% 85% 77% 74% 65% 50%

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SPECIFICATIONS 23 April 1993

Power Source: 115V, 60Hz, more than 20A (for N.A)

220 ~ 240V, 50Hz/60Hz, more than 10A (f or EU and AA)

Power Consumption: A095 and A096 copiers

Copier only Full system* Warm-up 0.9 kVA 0.9 kVA Stand-by 0.25 kVA 0.25 kVA

Copying 1.2 kVA 1.3 kVA

Maximum 1.45 kVA 1.5 kVA

*Full System:

• Mainframe with dual job feeder, compact

sorter stapler and 3,500-she et la rge capa city tray

• Mainframe with dual job feeder, floor type

sorter stapler and 3,500-she et la rge capa city tray

Noise Emission:

sound pressure level: The measurements are made according to ISO7779

• Mainframe with recirculating document

handler, finisher and 3,500-sh ee t larg e capacity tray

Copier only Full system*

Copying 55 dB (A) 61 dB (A)

Full System:

• Mainframe with dual job feeder, compact

sorter stapler and 3,500-she et la rge capa city tray

• Mainframe with dual job feeder, floor type

sorter stapler and 3,500-she et la rge capa city tray

• Mainframe with recirculating document

handler, finisher and 3,500-sh ee t larg e capacity tray

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23 April 1993 SPECIFICATIONS

Dimensions: 690 x 690 x 980 (W x D x H Mainframe only)

1280 x 690 x 1020 (W x D x H Mainframe with copy tray, platen cove r )

Weight: Copier only:(Without the optional platen cover

= Approximately 2 kg) A095 copier: Approximately 151 kg A096 copier: Approximately 163 kg

Zoom: From 50% to 200% in 1% steps Copying Speed:

A4/LT (sideways) A3/DLT B4/LG A095 copier 45 23 27 A096 copier 55 28 35

Warm-up Time: Less than 5 minutes (20°C) First Copy Time: 3.1 seconds (A4/81/2" x 11" sideways from the

1st feed station) Copy Number Input: Numbe r keys, 1 to 999 (count up or count down) Manual Image Density

7 steps Selection:

Overall

Information

Automatic Reset: 1 minute standard se tt ing; can also be set from 1

second to 999 secon ds or no auto reset. Copy Paper Capacity: • By-pass feed table: ap pro ximat ely 50 shee ts

• Paper tray: approximately 550 sheets

• Tandem tray: approximately 500 sheets

• Large capacity tray: approximately 1500

sheets

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SPECIFICATIONS 23 April 1993

Toner Replenishment: 1,100 g/cartridge Optional Equipment: • Platen cover

• Dual job feeder

• Recirculating document handler

• 20 bin sorter stapler (Floor type)

• 20 bin compact sorter stapler

• Finisher

• 3500-sheet Large capacity tray

• Receiving Tray

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23 April 1993 MACHINE CONFIGURATION

2. MACHINE CONFIGURATION

2.1 COPIER OVERVIEW

There are two types of mainfra me.

A095 copier

Three 550-sheet paper trays Optional 3,500-sheet large capacity tray

Overall

Information

550 550

550

A096 copier

500 x 2 or 500 550

(3,500)

Tandem paper tray (including two 500-sheet paper tray) One 550-sheet paper t ray 1,500-sheet built-in large capa city tra y Optional 3,500-sheet large capacity tray

(3,500)

1,500

1-5

3,500-sheets large capacity tray (A380)

MACHINE CONFIGURATION 23 April 1993

2.2 SYSTEM OVERVI E W

System A

(The mainframe (A095) with du al job fee der and compa ct sorter stapler)

Dual job feeder (A376)

Compact sorter stapler (A374)

System B

(Mainframe type (A095/A096) with dual job feeder and floor type sorter stapler. The mainframe in the illustrat ion belo w is the A096.)

Dual job feeder (A376)

Floor type sorter stapler (A377)

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3,500-sheets large capacity tray (A380)

23 April 1993 MACHINE CONFIGURATION

System C

(The mainframe (A096) with recircu lating document handler and fin isher)

Finisher (A379)

Recirculating document hand ler (A3 78 )

Overall

Information

1-7

COPY PROCESS AROUND THE DRUM 23 April 1993

3. COPY PROCESS AROUND THE DRUM

1. OPC DRUM

The organic photo conductive (OPC) drum (10 0 mm diame te r) has hig h resistance in the dark and low resistance under light.

2. DRUM CHARGE

In the dark, the charge corona unit gives a uniform negative ch arg e to the OPC drum. The charge remains on the surfa ce of the drum. The amo unt of negative charge on the drum is propo rtio na l to the ne gative grid bias voltage applied to the grid plat e on the charg e coro na unit .

3. EXPOSURE

An image of the original is reflected to the OPC drum surfa ce via th e optics section. The charge on the drum su rfa ce is dissipated in direct proportion to the intensity of the reflected light, thus producing an electrical late nt ima ge on the drum surface.

The amount of charge remainin g as a laten t imag e on the drum depe nds on the exposure lamp intensity controlled by the exposure lamp voltage.

4. ERASE

The erase lamp illuminates the areas of th e cha rge d dru m su rfa ce th at will not be used for the copy image. The resistance of drum in the illuminated areas drops and the charge on those areas dissipates.

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23 April 1993 COPY PROCESS AROUND THE DRUM

5. DRUM POTENTIAL SENSOR

The drum potential sensor detects the electric potential on the drum to compensate image processing elements.

6. DEVELOPMENT Positively charged toner is attra cte d to the negat ively charged areas of the drum, thus developing the latent ima ge. (The posit ive trib oe lect ric charg e of the toner is caused by friction between the carrier and toner particle s.)

The development bias volt ag e ap plied to the developmen t rolle r shaft controls two things:

1) The threshold level if tone r is attracted to the drum or toner remain s on the development ro ller.

2) The amount of toner to be attracted to the drum.

The higher the negative develo pme nt bias volt ag e is, th e less toner is attracted to the dru m surface.

7. PRE-TRANSFER LAMP (PTL)

The PTL illuminates the drum to remove almost all the negative charge from the exposed areas of the dru m. This makes image transfer easier.

8. IMAGE TRANSFER

Paper is fed to the drum surface at the prop er timing so as to align the copy paper and the develope d image on the drum surface. Then, a neg at ive charge is applied to the reverse side of the copy paper by th e transfer belt, producing an electrical force which pulls the toner particles from the drum surface onto the copy paper. At the same time, the copy paper is electrically attracted to the tra nsf er be lt.

Overall

Information

9. PAPER SEPARATION

Paper separates from the OP C drum by th e ele ctrica l att raction between the paper and the transfer belt. The pick-o ff pawls help to separate the paper from the drum.

10. CLEANING

The cleaning brush remo ves toner remaining on the dru m after image transfer and the clean ing blade scrapes off all the rema ining toner.

11. QUENCHING

Light from the quenching lamp electrically neutralizes the charge pot ential of the drum surface.

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MECHANICAL COMPONENT LAYOUT 23 April 1993

4. MECHANICAL COMPONENT LAYOUT

14 15 16 17

19 20

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23 April 1993 MECHANICAL COMPONENT LAYOUT

1. 3rd Mirror

2. 2nd Mirror

3. 1st Mirror

4. Exposure Lamp

5. Lens

6. Cleaning Brush

7. Cleaning Blade

8. Quenching Lamp

9. Charge Corona Unit

10. OPC Drum

11. 6th Mirror

12. 4th Mirror

13. 5th Mirror

21. Separation Roller

22. Registration Rollers

23. Transfer Belt

24. Vertical Transport Rollers

25. Tandem Tray (A096 copier) 550-sheet Tray (A095 copier)

26. Universal Tray

27. 1500-sheet LCT (A096 copier) 550-sheet Tray (A095 copier)

28. Toner Collection Bott le

29. Transfer Belt Cleaning Blade

30. Hot Roller

31. Pressure Roller

32. Jogger Fences

Overall

Information

14. Erase Unit

15. Drum Potential Sensor

16. Toner Hopper

17. Development Unit

18. Pre-Transfer Lamp

19. Pick-up Roller

20. Feed Roller

33. Duplex Positioning Roller

34. Duplex Pick-up Roller

35. Duplex Feed Roller

36. Separation Belt

37. Junction Gate

38. Exit Rollers

39. Optics Cooling Fan

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DRIVE LAYOUT 23 April 1993

5. DRIVE LAYOUT

❾

❽

❼

❻

❺

❶

❷

❸

❹

❶ Main Motor ❷ Scanner Drive Motor ❸ Fusing/Duplex Drive Motor ❹ Paper Feed Motor ❺ Toner Collection Motor ❻ Registration Clutch ❼ By-Pass Feed Motor ❽ BY-Pass Feed Clutch ❾ Development Drive Motor

1. OPC Drum

2. Scanner Unit

3. Transfer Belt Unit

4. Paper Exit Unit

5. Fusing Unit

6. Duplex Unit

7. Paper Trays

8. Paper Feed Units

9. Toner Hopper

10. Development Unit

11. Cleaning Unit

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23 April 1993 PAPER PATH

6. PAPER PATH

6.1 STANDARD COPYING

[F]

[D]

[C]

[B]

Overall

Information

[E]

Paper feed begins from the exte rior LCT, by-pa ss fee d ta ble or pap er fe ed stations in the paper tray unit . The copy pa pe r the n follows on e of two path s inside the copier. The path fo llowe d depe nd s on which mode the operator has selected. For copy processing, all sheets follow the same pat hs fro m t he paper feed mechanism [A] through the registration rollers [B ], transfer belt [C], and fusing unit [D] . Af ter that, copies are delivere d to the sorter bins [E] or proof tray [F], however, 2 sided copie s are diverted for further processing.

[A]

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PAPER PATH 23 April 1993

6.2 MULTIPLE 2-SIDED CO PYING

a. Front Side

[B]

[A]

[D]

[C]

b. Rear Side

In this mode the junction gat e [A ] directs sheets exiting th e fu sing unit to the duplex tray entrance. Aft er that, all sheets follo w the pat h th rou gh the dup lex entrance rollers [B].

After all front side cop ying is comp let ed , the sheets on the duple x tray are fed in order from the bottom to the top and follow the path throu gh the duplex feed mechanism and vertical transport rollers [C] to the registration rollers [D]. After that , th ese sheets follow the same pat h as sta nd ard copying from the registration rollers to the sorter.

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23 April 1993 ELECTRICAL COMPONENT DESCRIPTION

7. ELECTRICAL COMPONENT DESCRIPTION

Refer to the electrical compone nt layou t on the reverse side of the att ach ed Point to Point for symbols and ind ex numbers.

Symbol Name Function Index

No.

Motors

Overall

Information

M 1 Scanner Drive Drives the 1st and 2nd scanne rs

(dc servo).

M 2 Exhaust Fan Removes the heat from around

the fusing unit. M 3 Main Drives the main unit components. 44 M 4 Development Drive Drives the development unit. 45 M 5 By-pass Feed Drives the by-pass feed rollers. 46 M 6 3rd Scanner Drive Drives the 3rd scanner (dc

stepper) M 7 Toner Bottle Drive Rotates the toner bottle to supply

toner to the toner hopper. M 8 Charge Wire Cleaner

Drive

M 9 Jogger Drives the jogger fences to

M10 Lens Horizont al Drive Shifts the lens horizontal position. 51 M11 Lens Vertica l Drive Shifts the lens vertical position . 52

Drives the main charge wire

cleaner to clean the charge wire.

square the paper stack in th e

duplex tray (dc stepper).

M12 Optic Cooling Fan Removes heat from the optics

unit. M13 Fusing/ Duplex Drive Drives the fusing unit, the duplex

unit, and the paper exit rollers. M14 Paper Feed Drives all feed and transport

rollers in the paper tray unit. M15 1st Lift Raises the bottom plate in the 1st

paper tray. M16 2nd Lif t Raises the bottom pla te in the

2nd paper tray. M17 Toner Colle ction Transport s the collect ed toner to

the toner collection bott le.

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ELECTRICAL COMPONENT DESCRIPTION 23 April 1993

Symbol Name Function Index

No.

M18 3rd Lift

(A095 copier only)

M19 Side Fen ce Drive

(A096 copier only)

Raises the bottom plate in the 3rd

paper tray.

Opens and closes the front and

the rear side fences of the

tandem tray. M20 Rear Fence Drive

(A096 copier only)

Moves the papers stacked in the

left tandem tray to the right

tandem tray. M21 LCT Motor

(A096 copier only)

Lifts and lowers the LCT bottom

plate to bring paper to the feed

position and allow loading of the

paper.

Magnetic Clutches

MC1 Toner Supply Turns the toner supply roller to

supply toner to the development

unit.

MC2 Registration Drives the registration rollers. 58

127

MC3 By-pass Feed Starts paper feed from the

by-pass feed table.

MC4 Duplex Transport Drives the duplex tra nsport rollers

to transport the paper to the

vertical transport rollers.

MC5 Duplex Feed S tarts pa per fee d from the duplex

tray to the duplex transport rollers.

MC6 1st Feed Starts paper fee d from the 1st

feed tray.

MC7 2nd Feed Starts paper feed from the 2nd

feed tray.

MC8 3rd Feed Starts paper feed from the 3rd

feed tray.

101

104

1-16

23 April 1993 ELECTRICAL COMPONENT DESCRIPTION

Symbol Name Function Index

No.

Switches

SW1 By-pass Table Detects if the by-pass feed tab le

is open or closed.

SW2 Front Door Safety Cuts the ac power line and

detects if the front door is open or

not.

SW3 1st Tray Set

Detects if the 1st tray is set or no t. 66

(A095 copier only)

SW4 2nd Paper Size Determines what size paper is in

the 2nd (universal) paper tray.

SW5 Toner Overflow Detects when the toner collection

bottle is full.

SW6 Toner Collection

Bottle Set

SW7 Lower Front Door

Safety

SW8 3rd Tray Set

Detects if the toner collection

bottle is set or not.

Detects if the front door is open

or not.

Detects if the 3rd tray is set or no t. 84

(A095 copier only)

Overall

Information

SW9 Main Provides power to the copier 122

SW10 Tray Down

Lowers the LCT bottom plate. 126

(A096 copier only)

Solenoids

SOL 1 Junction Gate Moves the junction gate to dire ct

copies to the duplex t ray or to the

paper exit.

SOL 2 Duplex Positioning Controls the up-down move ment

of the positioning roller.

SOL 3 By-pass Pick-up Controls the up-down movemen t

of the pick-up roller for by-pass

feed.

SOL 4 Guide Plate Opens the guide plate when a

paper misfeed occurs around this

area.

SOL 5 Transfer Belt

Positioning

Controls the up-down movement

of the transfer belt un it.

1-17

ELECTRICAL COMPONENT DESCRIPTION 23 April 1993

Symbol Name Function Index

No.

SOL 6 Pressure Arm Presses the paper on the duplex

tray against the duple x fee d

rollers.

SOL 7 Tandem Lock Locks the left tandem feed tray

and separates the righ t an d lef t

tandem trays.

SOL 8 1st Pick-up Controls the up-down movemen t

of the pick-up roller in the 1st

feed station.

SOL 9 1st Separation Roller Controls the up-down movement

of the separation roller in the 1st

feed station.

SOL10 2nd Pick-up Controls the up-do wn movement

of the pick-up roller in the 2nd

feed station.

SOL11 2nd Separat ion Roller Controls the up-down movement

of the separation roller in the 2nd

feed station.

SOL12 3rd Pick-up Controls th e up -do wn movement

of the pick-up roller in the 3rd

feed station.

100

102

103

105

SOL13 3rd Separa tio n Rolle r Controls the up-down move men t

of the separation roller in the 3rd

feed station.

Sensors

S 1 Scanner HP Informs the CPU when the 1st

and 2nd scanners are at the

home position.

S 2 Platen Cover

Position–1

Informs the CPU that the platen

cover is in the up or down

position (related to APS/ARE

function).

S 3 Platen Cover

Position–2

Informs the CPU that the platen

cover is in the up or down

position to detect if th e original

has been removed or not.

106

1-18

23 April 1993 ELECTRICAL COMPONENT DESCRIPTION

Symbol Name Function Index

No.

S 4 Lens Vertical HP Informs the CPU that the lens is

at the full-size position.

S 5 Lens Horizontal HP Informs the CPU that the lens is

at the horizontal home position.

S 6 3rd Scanner HP Informs the CPU when the 3rd

scanner is at the home position.

S 7 By-Pass Paper End Informs th e CPU that there is no

paper in the by-pass feed tab le.

S 8 Guide Plate Position I nforms th e CPU if the

registration guid e pla te is closed

or not.

S 9 Jogger HP Detects if the duplex jogg er

fences are at the home position

or not.

S10 Vertical Transport Detects the leading edge of the

paper to determine the paper

feed timing of the next sheet.

S11 Duplex Exit Detects the leading edge of the

paper to determine the duplex

transport clutch on timing .

Overall

Information

S12 Duplex Entrance

Sensor

Detects the leading edge of the

paper to determine the duplex

feed clutch off timing.

S13 Duplex Paper End Detects paper in the duplex tray. 13 S14 Duplex Transport Detects the lea din g ed ge of th e

14 paper to control the jogger motor and the positioning solenoid on timing.

S15 Exit Detects misfeeds. 15 S16 Fusing Exit Detects misfeeds. 16 S17 Paper Guide Detects misfeeds. 17 S18 Auto Image Density Senses the ba ckgro un d de nsit y

20 of the original.

S19 Original Length–1 Detects original length. 21 S20 Original Length–2 Detects original length. 22 S21 Original Width Detects original width. 23

1-19

ELECTRICAL COMPONENT DESCRIPTION 23 April 1993

Symbol Name Function Index

No.

S22 By-Pass Paper Size Informs the CPU what size pape r

26 is in the by-pass feed table.

S23 Toner Density Senses the amount of toner in th e

27 black developer.

S24 Registration Detects misfeeds and controls

28 registration clutch off-on timing.

S25 Toner End Detects toner end cond itio n. 30 S26 Auto-Response Returns the display fro m the

34 screen saver.

S27 Drum Potential Detects the drum surface

39 potential.

S28 Image Density Detects the density of the ID

41 sensor pattern on the drum.

S29 1st Paper End Informs the CPU when the 1st

68 cassette runs out of paper.

S30 1st Paper Near End Informs the CPU when the 1st

69 cassette is in near end condition.

S31 1st Paper Feed Controls the 1st paper feed clutch

70 off/on timing and the 1st pick-up solenoid off timing.

S32 2nd Paper Near End Informs the CPU when the 2nd

cassette is in near end condition.

S33 1st Lift Detects the correct fe ed heig ht of

the 1st cassette.

S34 2nd Paper End Informs the CPU when the 2nd

cassette runs out of paper.

S35 Toner Collection

Motor

Detects the toner co llect ion motor operation.

S36 2nd Lift Detects the correct fe ed heig ht of

the 2nd cassette.

S37 3rd Lift Detects th e correct feed height of

the 3rd cassette.

S38 3rd Paper Near End

(A095 copier only)

Informs the CPU when the 3rd cassette is in near end condition.

S39 3rd Paper End Informs the CPU when the 3rd

cassette runs out of paper.

1-20

23 April 1993 ELECTRICAL COMPONENT DESCRIPTION

Symbol Name Function Index

No.

S40 3rd Paper Feed Controls the 3rd paper feed

clutch off/on timing and the 3rd pick-up solenoid off timing.

S41 2nd Paper Feed Controls the 2nd paper feed

clutch off/on timing and the 2nd pick-up solenoid off timing.

S42 Base Plate Down

(A096 copier only)

Detects when the bottom plate is completely lowered to stop the 1st lift motor.

S43 Side Fence

Positioning

Informs the CPU when the tandem tray side fences are open.

(A096 copier only)

S44 Rear Fence Return

(A096 copier only)

Informs the CPU when the tandem tray rear fence is in the return position.

S45 Rear Fence HP

(A096 copier only)

Informs the CPU when the tandem tray rear fence is in the home position.

S46 Left Tandem Paper

End

Informs the CPU when the left tandem tray runs out of paper.

(A096 copier only)

Overall

Information

S47 LCT Near End

(A096 copier only)

S48 Tray Down

(A096 copier only)

Detects the paper nea r e nd condition.

Detects when the tra y is completely lowered to stop the LCT motor.

S49 Tray Paper Set

(A096 copier only)

Informs the CPU when the paper is set on the LCT bottom tray.

PCBs

PCB 1 AC Drive Provides AC power to the

exposure lamp and fusing lamp.

PCB 2 Main Controls all machine fun ctio ns. 109 PCB 3 Optic Control Controls all optics components. 110 PCB 4 High Voltage Con tro l Controls the output of both power

packs and development bias.

123

124

125

108

111

1-21

ELECTRICAL COMPONENT DESCRIPTION 23 April 1993

Symbol Name Function Index

No.

PCB 5 Paper Feed Cont rol Controls all components in the

paper bank.

PCB 6 DC Power Supply

Provides DC power. 113

Unit PCB 7 Guidance Controls the guidance displa y. 120 PCB 8 Operation Panel Controls the LED matrix, and

monitors the key matrix.

Lamps

L1 Exposure Applies high intensity light to the

original for exposure. L2 Fusing Provides heat to the hot roller. 32 L3 Quenching Neutralizes any charge remaining

on the drum surface after

cleaning. L4 Erase Discharg es th e drum outside the

image area. L5 Pre-transfer Reduces the charge on the dru m

surface before transfer.

112

121

Power Packs

PP1 Transfer Provides high voltage for the

transfer belt and controls the

transfer belt positioning solenoid.

PP2 Charge Provides high voltage for the

charge corona wires, and the grid

plate. Controls QL, PTL, and

charge wire cleaner motor

functions.

Others

TS1 Optics Thermoswitch Opens the exposure lamp circuit

if the optics unit overheats.

TF1 Fusing Thermofuse Opens the fu sing lamp circuit if

the fusing unit overhe at s.

TH1 Fusing Thermistor Senses the temperat ure of the

hot roller.

117

119

1-22

23 April 1993 ELECTRICAL COMPONENT DESCRIPTION

Symbol Name Function Index

No.

TH2 Optics Thermistor Monitors the temperature of the

optics cavity.

TH3 Drum Thermistor

(Located on the ID

Monitors the tempe rature of the

OPC drum.

Sensor Ass’y)

H1 Transfer

Anti-Condensation

Turns on when the main switch is

off to prevent moisture from

forming on the transfer belt.

H2 Optics

Anti-Condensation

Turns on when the main switch is

off to prevent moisture from

forming on the optics.

RA1 Main Power Relay Controls main power. 107

CO1 Total Counter Keeps track of the total number of

114

copies made.

NF1 Noise Filter Removes electrical noise. 115 CB1 Circuit Breaker Provides back-up high current

116 protection for the electrica l components.

Overall

Information

LA1 Lightening Arrestor Removes current surg es fro m the

AC input lines.

118

1-23

SECTION 2

DETAILED SECTION

DESCRIPTIONS

VL Pattern

Original

Toner Supply On time Development. Bias

TD Sensor

Image Density Control

23 April 1993 PROCESS CONTROL

1. PROCESS CONTROL

1.1 OVERVIEW

Original Scale

Image Density Control (Fuzzy Control)

Latent Image Control

ADS Pattern

VD Pattern

Latent image Control

Exposure Control

Charge Control

Temperature Sensor

Main PCB

Lamp Voltage

Grid Voltage

Paper

VD Pattern

ID Sensor

VL Pattern

Erase Lamp

Drum Potential Sensor

(Fuzzy Control)

Toner Supply Control

Exposure Glass

Detailed

Descriptions

This model uses two process control methods. One compensates for variation in the drum potential (latent image control) and the othe r con tro ls the toner concentratio n an d tone r supply a mou nt (image density control).

2-1

Erase

PROCESS CONTROL 23 April 1993

1.1.1 Latent Image Control

Charge

Exposure

Black White

Potential Sensor

Drum

The figure shows the changes of the drum pote nt ial du ring the copy process. Vo: The drum potential just afte r charg ing the drum. VD (Dark Potential): The drum potential just after exposing the black

pattern (VD pattern)

VL (Light Potential): The drum potential ju st af ter exposing the white

pattern (VL pattern)

VR (Residual Voltage ): The drum potential just after t he expo sure of the

erase lamp.

After long usage following installation or a PM, drum potentia l will gra dually increase due to the following factors:

Dirty optics or exposure lamp deterioration Dirty charge corona wire and grid plate Change of the drum sensitivity

In this copier, th e change in drum potential is detected by the drum potentia l sensor and the following it ems are cont rolle d to maint ain goo d cop y quality.

The grid bias voltage The exposure lamp voltage The development bias voltage.

A drum thermistor detects the drum tempera ture an d this data is also use d to control the above voltages. It is impossible to explain simply because it is controlled by methods developed in our laboratories using an artificia l n eural network.

2-2

23 April 1993 PROCESS CONTROL

1.1.2 Image Density Control

Image density is controlled by the following sensors:

Toner density sensor (TD sensor) Image density sensor (ID sensor)

Data from the TD sensor is used to keep the toner con centration in the developer at a constant level. However, the image on the OPC drum varies due to the variation of toner charge ab ility (inf luenced by the environment) even if the toner concentration is constant. By the ID sensor compensation, toner concentratio n is change d to keep the ima ge den sity on the OPC dru m constant.

The following items are contro lled to main ta in a con sta nt copy imag e density:

Toner supply clutch on time

Detailed

Descriptions

Toner supply level data (VREF) of the TD sensor

2-3

PROCESS CONTROL 23 April 1993

1.2 PROCESS CONTROL DATA INITI AL SE TTI NG

The following flow chart shows all the steps that will be perf orme d whene ver the machine is turned on while the hot ro ller te mpe rature is below 100°C. This initializes all the process control sett ings.

Main SW On (Fusing Temp. < 100°C)

Charge wire cleaning (if more than 5 K copie s are mad e since last cleaning

Drum Potential Sensor Calibration

①

Drum Conditioning Start (Fusing Temp . = 180° C)

VSG Adjustment

VR Measurement

VD/VL Correction

TD Sensor Detection

②

ID Sensor Detection/Correctio n

③

ADS Adjustment

① : See Latent Image Control section (Page 2-5) for details. ② : See Image Density Control section (Pa ge 2-12 ) for deta ils. ③: See Optics section (Page 2-3 9) for details.

2-4

23 April 1993 PROCESS CONTROL

1.3 LATENT IMAGE CONTROL

1.3.1 Drum Potential Sensor Calibra tion

[A]

RA601

-100 V

RA602

-800 V

Drum

[B]

Case

Sensor

Output

Amp.

Detailed

Descriptions

Main PCB

The drum potential se nso r [ A] is located just above the development unit. The sensor has a detector which dete cts th e stre ngth of the ele ctric field from the electric potential on the drum. The output of the sensor depends on the strength of the electric field.

Since the output of the sensor is affected by environmental conditions, such as temperature and humidity, the sensor outp ut is calibrat ed durin g pro cess control data initial setting.

The High Voltage Contro l PCB [B] has two relay contacts. Usually RA 602 grounds the drum. However, during the initial setting, th e main PCB tu rns RA601 on and RA602 off an d ap plie s t he volta ge to th e drum shaft.

By measuring the output of the drum po te ntial sensor when –100 V and –800 V are applied to the drum, the sensor output is calibrated auto mat ically. (The machine recognize s t he re lat ionship between actua l drum po te ntial and the potent ial sensor output.)

2-5

Light

New Drum

Used Drum

PROCESS CONTROL 23 April 1993

1.3.2 Drum Conditioning

When the fusing tempe r at ure reaches 180°C, the machin e sta rts the drum conditioning proc ess. In th is mo de , th e main motor, main charge corona , erase lamp and developme nt bias are activated for about 30 second s and drum sensitivity and residual volt age (VR) are stabilized , as in con tin uo us copy runs.

1.3.3 VSG Adjustment

During drum conditioning , th e ID sen sor checks the bare drum’s reflectivity and calibrates the output of the ID sensor to 4 ±0.2 V.

1.3.4 VR Measurement

Drum Potential

[V]

[–V]

Original DensityDark

The above figure shows t he relationship between th e dru m pot en tia l a nd the original density. To get consta nt copy quality, this relation ship must be maintained.

Since this relationsh ip te nd s to cha ng e to the one represente d by th e do tted line by various factors, compen sat ions are required.

The residual voltage (VR) cannot be compensated even if the exposure lamp voltage is increased. Therefore, the VR change has to be compensated by other means.

The main control board checks th e drum potential just afte r t he erase lamp exposure by the drum pote nt ial sensor after drum conditioning. This measured drum potential is in fact VR. This VR is used as the standard for the VD and VL corrections.

NOTE: In the figu re ab ove, the residual voltage (VR) for the new drum is

0V. Actually, there is some re sidu al voltage even on the new drum.

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Original Density

23 April 1993 PROCESS CONTROL

1.3.5 VD Correction

[-V] VD

Exposure Glass

VD Pattern

Drum Potential

VD Compensated

–770

After many copies

New Drum

Dark

Light

The drum potential ju st af ter the black pattern (VD Pattern) is exposed (VD: Dark Potential) tends to lo wer during drum life due to a decrease in the drum’s capacity to carry a charge.

To check the actual VD , th e first scanner moves to the home position and the VD pattern (Black) stuck on the bottom side of the exposure glass bracket is exposed on the drum.

The main control board measures VD through the drum potential sensor and adjusts it to a target value by adjusting the grid bias voltage (V G RID).

Detailed

Descriptions

On the other hand, ther e is a chan ge of th e dru m residual voltage (VR), so that the target VD voltage is compensa te d as follows:

Target VD Value : VD = VR + (–770)

The adjusted grid bias voltage (VGRID) is kept in memory until the next process control data initial setting.

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PROCESS CONTROL 23 April 1993

1.3.6 VL Correction

[-V]

Exposure Glass

VL Pattern

Drum Potential

–770

Dark

Dirty optics and/or exposure lamp deteriora tio n decrea ses th e int ensity of the light that reaches the drum. In addit ion to this, the drum sensitivity also changes during the drum’s life. These factors change the drum potential ju st after white pattern exposure (VL : Light Potential).

–140

Original Density

Only VD Compensated

VD and VL Compensated

New Drum

Light

To check the actual VL , the first scanner moves under th e VL pattern (White) stuck underneath th e orig inal scale. The pattern is exposed on the drum.

The main control board measures VL through the drum potential sensor and adjusts it to a target value by adjusting the exposure lamp voltage (VLAMP).

The residual voltage (VR) change also affe cts V L, so that VL’s target voltage is compensated as follows:

Target VL Value : V L = VR + (–140) The adjusted exposure lamp voltage (VLAMP) is stored in memory unt il the

next process control data initial setting.

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23 April 1993 PROCESS CONTROL

1.3.7 VR Correction

[-V]

Drum

VD and VL Compensated

Potential

Development Bias (VBB)

New Drum

–770

–140

Dark

Original Density

Light

Potentials (VR, VD, VL) are mon itored by the potential sensor. (This is don e only when the fusing temp erature is less than 100°C after t he machine is turned on.) During the check cycle, the VD and VL patterns are exposed and the drum potential on th e are a where exposed by each pa tt ern is checked by the potential sensor.

Compare the curve of the VD and V L compensated drum potential with the curve of the new drum, they are para llel but the compensated potentia l is still higher (VR) than the new drum p oten tia l. To prevent dirty backgrounds due to increased residual po te ntial, development bias (VBB) is applied as follows:

Detailed

Descriptions

VBB= VR + (–220)

2-9

New VL

PROCESS CONTROL 23 April 1993

1.3.8 Initial Setting Sequence

The following graph shows the seque nce of eve nt s durin g pro cess con trol data initial setting.

Scanner Motor

Exposure Lamp

Potentia l Sensor Output

forward reverse

V800

V100

1. Potential sensor calibration

VD New VD

New VR

2. VR’, VD’, VL’ potential detection

Latent Image Control

3. VD, VL correction

for the purpose of ADS sensor correction

4. ID sensor pattern potential detection

1. Potential sensor calibration By measuring the output of the drum po te ntial sensor when –100 V and –800 V are applied to the dru m , th e sensor output (V 100 and V800) is calibrated automatically (See page 2-5 for details).

2. VR, VD, VL potential detection After about 30 seconds of drum conditioning, VD and VL Patterns are developed by using the previous grid bias voltage (VGRID) data and exposure lamp voltage (V LAMP) da ta to detect the VR, VD, VL data .

The machine calculate s the new VGRID and VLAMP data using the detected VR, VD, VL data.

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23 April 1993 PROCESS CONTROL

3. VD and VL corrections Using the calculated VGRID and VLAMP data, VR, VD, and VL patterns are developed again and the new VR, VD, and VL data are detected.

If both VD and VL data are within specificat ions, the new V GRID, VLAMP and development bias (VBB) are determined based on the new VD, V L, and VR values.

Specifications:

VD = –770 + VR ± 20 V VL = –140 + VR ± 20 V

If VD is outside specifications, VGRID is shifte d on e step. Then the VD pattern is measured again and VD is detected again. The same is done for VL and VLAMP. The above process continues until both V D and VL fall within spe cifica tions. The graph on the previou s pag e sho ws t he examp le whe n on ly VL was outside specifications at the first VL detection and it became within specifications after on e V L corre ction (VLAMP is changed 0.5V/step , VGRID is changed 20 V/step).

If V100 or V800 at drum potential sensor calibration is outsid e spe cifica tions or if VD or VL do not fall within specificat ions after VGRID or VLAMP are shifted to the maximum or minimum level, the machine stops VD or VL correction and uses the previous V GRID and VLAMP values during copying. In this case, nothing is in dica ted on the machine but the SC counter is incremented.

Related SC codes (see troublesh oo tin g section for details):

Code Condition

361 Incomplete drum potential sensor

calibration

364 Abnormal VD detection

Detailed

Descriptions

365 Abnormal VL detection

Development bias is also de cide d by using VR as follows. VBB = VR + (–220)

4. ID sensor pattern potential detection This is performed to determine ID Sensor Bias Volt age. The details are explained in the develo pment control section (se e page 2-16).

2-11

VD (12 V) GND

PROCESS CONTROL 23 April 1993

1.4 IMAGE DENSITY CONTROL

1.4.1 Toner Density Sensor

A: VOUT (Gain data) is high.

OUT is within the specification.

B: V

OUT (Gain data) is low.

C: V

VOUT = VIN x

New Developer

1234

Toner Weight %

= 12 x

Main PCB

VOUT

AGC

Gain

256

Gain

256

TD Sensor

Sensor Output

Sensor Output (V)

REF

Developer consists of carrier particles (iron ) and toner particle s (re sin and carbon). Inside th e de velo pment unit, developer passes through a magnetic field created by coils inside the ton er de nsit y senso r. When the toner concentration chan ge s, th e voltage output by the sensor changes accordingly.

When new developer with th e sta nd ard toner concentratio n (2.0% by weight, 20 g of toner in 1000 g of developer) is installed, developer initial settin g must be performed by using SP mod e ( SP Adjustment – PAG E 1).

During this setting, the outpu t volt ag e (VOUT) from the auto gain control circuit (AGC) on the main control board PCB varies to cha nge the output voltage from the toner density (TD) senso r. This is don e by cha ng ing the gain data, see below.

VOUT = VIN x

Gain Data

256

= 12 x

Gain Data

256

If the data is high, VOUT becomes high, and the sen sor ou tp ut voltage becomes high. As a result, the sensor characteristic becomes as illustrated by curve A. If the data is low, VOUT becomes low, and the sensor ou tput voltage becomes low. As a result, the sensor characte ristic shifts as illustrated by curve C.

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23 April 1993 PROCESS CONTROL

By selecting the proper ga in da ta , the sensor output is set wit hin the targeted control level (VREF, VREF = 2.5 ± 0.1 V). Now, the sensor characteristic is illustrated by curve B and the TD sensor initial settin g is comple ted.

The selected gain data is sto red in me mory, and VOUT from the auto gain control circuit stays consta nt during the toner senso r d et ect ion cycle.

At every copy cycle, toner density in the deve lop er is det ect ed once . The sensor output voltag e (VTD) during the detectio n cycle is compared with the toner supply level voltage (VREF).

Sensor

Output (V)

Detailed

Descriptions

REF

12345

Toner Weight %

2-13

PROCESS CONTROL 23 April 1993

To stabilize toner concentrat ion , to ne r supp ly amou nt (t oner supply clutch on time) is controlled by referring to V REF and VTD. The toner supply amount is calculated at every copy. The toner supply amount is determined by using the following factors.

① VREF – VTD ② VREF – VTD’(VTD’ = VTD of the previou s copy cycle)

VTD’

Previous Copy Last Copy Next Copy

VTD

VREF

By referring to these fact ors, the machine recognizes th e difference between the current toner concentration and the target toner concentration. The machine also understan ds ho w much toner concentration has changed and predicts how much the toner supply amount will probably cha nge. By changing the toner supply amount precisely, toner concentration (image density) is kept at a constant level. Since the toner supply clutch on time up dating is under fuzzy control, the relation among VTD, VTD’, VREF cannot be expressed by a simple algebraic formula.

The image on the OPC drum changes due to varia tio n of ton er cha rgeability (influenced by the environment) even if the toner concentration is constant. The image density sensor (ID sensor) direct ly checks th e image on the OPC drum and shifts VREF data (under fuzzy control) to keep the image on the OPC drum constant, as expla ined in the next section.

NOTE: 1. Toner end cond ition is detected by the toner en d sen sor (see the

development sect ion for de tails).

2. The toner supply clutch turns on at the inte rvals be twe en each copy process while image develop men t is not perf ormed.

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3rd Series of Copies (17 copies)

23 April 1993 PROCESS CONTROL

1.4.2 Image Density Sensor Dete ction

[B]

[C]

[A]

Drum

bias

LED

4 V

LED

VSG and VSP are checked by the ID senso r [A] . The ID se nso r is located underneath the drum clea ning section. There is no ID sensor pattern in th e optics, however, a pattern image is made on the OPC drum by the charge corona unit [B] and the erase lamp [C].

VSG is the ID sensor output when checkin g th e era sed drum surf ace . VSP is the ID sensor output when checking the ID sensor pattern image.

To compensate for any variat ion in light inte nsity from the sensor LED, the reflectivity of both the erased drum surface and the pa tt ern on the drum are checked.

Detailed

Descriptions

VSP Detection

12345678 9101112

VSG Detection

1st Series of Copies (8 copies)

2nd Series of Copies

(5 copies)

Detection

SP Detection

14 15

V Detection

SP Detection

VSG is detected eve ry time the machine starts copyin g. During VSG detection, the development sleeve rollers do not rotate and no development bias is applie d. VSP is detected after copying is completed if 10 or mo re cop ies ha ve be en made since VSP was last detected . Since the transfer belt must be rele ased when checking VSP, a VSP check cannot be done during continuous copying.

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Detection

PROCESS CONTROL 23 April 1993

① Potential

Sensor Detection

–700 V

①

②

③

② ID Sensor

Bias Level

4.0 V

③ ID Sensor Output

While developing the ID sen sor pa tt ern , ID sensor bias is applied. ID sensor bias is determined during process control dat a init ial set tin g as follows:

Apply charge while grid voltage is –700 V to creat e th e ID sensor pa tt ern.

–300

VSP

VIDB = VP +300 (V)

Check the drum potentia l (V P) of the latent image created by the charge with –700 V grid.

Adjust the ID sensor bia s (VIDB) so that it satisfies the following formula.

VIDB = VP – (–300) (V)

= VP + 300 (V)

Change the bias to the calculated VIDB and detect VSP. VSG detecte d du ring VSG adjustment sequen ce in th e pro cess cont rol data initial setting and V SP are used to determine VREF data at pro cess con trol data initial setting. VIDB is not changed until the next process contro l d ata init ial setting is done.

After the series of cop ies is completed in the case that 10 or mo re cop ies have been made, VREF is updated by referring to the previous VREF (VREF’), VSG, VSP and the current TD sensor ou tp ut (VTD).

Since this VREF data updating is under fuzzy control, the relationship among VREF, VREF’, VSG, VSP and V TD cannot be expressed by a simple algebraic formula.

VREF is updated not only at the ab ove case. But also during developer initial setting and during pro cess control data initial setting.

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23 April 1993 PROCESS CONTROL

1.4.3 Sensor Abnormal Conditions

a. ID sensor (VSG,VSP) abnormal Whenever VSG falls under 2.5 V or VSP rises over 2.5 V, the CPU fixes th e

VREF data and toner concent ration is controlled only by using TD se nso r output.

VSG and VSP are still detected as usual during abnorma l co nditions and if output returns to normal levels (V SG ≥ 2.5 V, VSP ≤ 2.5 V), the CPU returns the toner concentratio n con trol to normal mode.

b. TD sensor (VTD) abnormal Whenever VTD rises over 4.0 V or VTD falls under 0.5 V, the CPU shifts the

toner supply to the fixed supp ly mo de. In this condition, the CPU ne ver stops the toner supply. The fixe d toner supply amount can be chan ge d in fo ur steps (4%, 7%, 11%, 14%) by usin g SP mode. The default fixed to ne r su pp ly amount is 4%.

VTD is still detected as usual durin g th e abnormal condition and if its output returns to a normal level, the CPU returns the toner conce nt rat ion cont rol to normal mode.

Detailed

Descriptions

c. Drum Potential Sensor abnormal Whenever V100 rises over 1. 6 V or V 100 falls under 0.1 V or whenever V800

rises over 5.0 V or V800 falls under 2.7 V, the CPU also shifts the toner supply to the fixed supply mode, as for a TD sensor (VTD) abnormal condition.

Related SC codes. (See troub lesh oo tin g section of details.):

Code Condition

351 Abnormal VSG Detection (VSG > 4.2 V) 352 Incomplete TD Sensor Initial Setting 353 Abnormal VSP Detection (VSP > 2.5 V) 354

Abnormal VSG Detection (VSG ≤ 2.5 V) 355 Abnormal VTD Detection (VTD > 4 V) 356 Abnormal VTD Detection (VTD < 0.5 V) 357 Abnormal VSP/VSG Detection (VSP/VSG ≥ 0.25 V) 358 Abnormal VSP/VSG Detection (VSP/VSG < 0.25 V) 361 Incomplete Drum Potential Sensor Calibration

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DRUM UNIT 23 April 1993

2. DRUM UNIT

2.1 OVERVIEW

7. 8

The drum unit consists of the components as shown in the ab ove illustration. An organic photoconductor drum (dia met er: 100 mm) is used for th is model.

1. OPC Drum

2. OPC Drum Protective Shutter

3. Erase Lamp

4. Drum Potential Sensor

5. Pre-transfer Lamp

6. Pick-off Pawl

7. Image Density Sensor

8. Drum Thermistor

9. Cleaning Brush

10. Toner Collection Coil

11. Cleaning Blade

12. Ozone Filter

13. Cleaning Filter

14. Charge Power Pack

15. Quenching Lamp

16. Main Charge Corona Unit

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23 April 1993 DRUM UNIT

2.2 OPC DRUM CHARACTERISTICS

An OPC has the characteristics of:

1. Being able to accept a high negative elect rical charge in the dark. (The electrical resistance of a photocon ductor is high in the absence of light.)

2. Dissipating the electrical charge when exposed to light. (Exposure to light greatly increases the conduct ivity of a photo con du cto r.)

3. Dissipating an amount of charge in direct proportion to the inte nsity of the light. That is, where stronger light is directed to the photoconduct or surface, a smaller voltage remains on the OPC.

4. Being less sensitive to changes in temperature (wh en compared to selenium F type drums).

5. Being less sensitive to changes in rest time (light fatigue). This makes it unnecessary to compensate development bia s voltage for variations in rest time.

Detailed

Descriptions

2-19

DRUM UNIT 23 April 1993

2.3 DRUM CHARGE

2.3.1 Overview

[A]

This copier uses a double corona wire scorotron system for drum charge. Two corona wires are required to give suff icien t ne ga tive charg e on the drum surface because of a rather hig h dru m spee d (33 0 mm/se c.). The sta inle ss steel grid plate makes th e corona charge uniform and controls the amount of negative charge on the drum surfa ce by ap plyin g th e negative grid bias voltage.

The charge power pack [A ] gives a constant corona curren t to the corona wires (1100 µA) and bias voltage to the grid pla te is automat ically con tro lled to maintain proper image den sity acco rding to the change of the OP C drum potential due to dirty grid plate and charge corona casing.

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23 April 1993 DRUM UNIT

2.3.2 Air Flow Around the Drum

[A]

Detailed

Descriptions

[B]

The exhaust fan [A] located above the fusin g un it pro vides an air flow to the charge corona unit to pre vent uneven built-up of negat ive ions that can cause an uneven charge of th e drum surface as shown.

An ozone filter [B] abso rbs the ozone (O3 ) around the drum. The exhaust fan rotates slowly during stan d-b y and rota te s quickly during

copying to keep the temperature inside the machine constant.

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DRUM UNIT 23 April 1993

2.3.3 Charge Wire Cleaning Mechanism

[A]

[C]

[A]

[C]

[B]

The flow of air around the charge corona wire may deposit tone r part icles on the corona wires. These particles may int erfere with charging and cause low density bands on copies.

The wire cleaner pads [A] automa tica lly clean the wires to pre ven t such a problem.

The wire cleaner is driven by a dc motor [B]. No rmally th e wire clea ne r [C] is located at the front end position (home position). After 5000 or more copie s are made and fusing temperature is less than 100°C after the main switch is turned on, the wire cleaner motor turns on to bring the wire cleaner to the rear end and then back to the home position.

When the wire cleaner moves from the rear to the home position (black arrow in the illustration), the wire clean er pads clean the wires.

There are no home position and retu rn po sitio n sen sors. The CPU monitors the input voltage (5 V). When the wire clean er rea che s the end, it is stop pe d and the motor is locked. At this time, in put voltage slightly decreases (to about 4 V) and the CPU judges to rotate the motor in reverse.

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23 April 1993 DRUM UNIT

2.4 ERASE

2.4.1 Overview

Detailed

Descriptions

LOES

LE: Lead edge erase marg in 3.5 ± 2.5 mm SE: Side era se margin total of both sides 3 mm or less Lo: Original width Lc: Charged width of drum EL: Lead edge erase Es: Side erase

The erase lamp unit consist s of a line of 12 3 LE Ds extending across the full width of the drum, the width of each bein g abou t 2. 5 mm. In edit ing mo de, th e appropriate LED’s turn on acco rdin g to the custo mer’s de sign ation.

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DRUM UNIT 23 April 1993

2.4.2 Lead Edge and Trail Edge Erase

The entire line of LEDs turns on when the main mot or tu rns on . The y stay on until the erase margin slight ly overla ps the lead edge of the original ima ge on the drum (lead edge erase margin). It preve nts the shadow of the original lead edge from appearing on the copy paper. This lead erase margin is also necessary for the lead edge of the copy pape r to sep ara te from th e hot roller. The width of the lead edg e era se marg in can be adjusted by SP mode

( SP Adjustment mode: PAGE 3). When the scanner reache s the return position, the charg e coro na , the grid

bias, and the exposure la mp tu rn off. However, the charged area on the drum surface is a little longer than the actu al orig ina l le ngth in order to have the entire latent image of the original. The entire line of LEDs turn on when the trail edge of the latent image has passed under the erase la mp un it. This p reve nts developing unnece ssary parts of the drum surfa ce, reducing toner consump tio n an d drum cleaning load. The LEDs stay on to erase th e lead edge of the laten t image in the next copy cycle. After the fina l copy, the erase lamps turn off at the same time as the main motor.

2.4.3 Side Erase

Based on the combinat ion of copy paper size and the reproduction ratio data, the LEDs turn on in blocks. This prevent s the shad ow of the origin al side edge and unexposed fro nt and rear sides of the drum surface in reduction mode from being develop ed . This red uces toner consumption an d dru m cleaning load.

In the DJF mode, the horizontal original standard position on the exposu re glass is 5 mm away from the rear scale. In the RDH mode, the horizontal center of the original is aligned with the center of the exposure glass. On the other hand, the horizontal origin al sta nd ard posit ion on the exposure glass in the platen cove r mode is the rear scale edge. To erase the shadow made by th e ed ge of th e rea r sca le in pla ten cover mode, one more LED at the fron t side turns on. This is in addition to th e LED’s on in DJF and RDH modes.

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23 April 1993 DRUM UNIT

2.5 CLEANING

2.5.1 Overview

[A]

[C]

[B]

[D]

Detailed

Descriptions

4 mm

This copier uses the counter blade system for drum cleaning. The blade [A] is angled against drum rotation. This counter blade system has the following advantages:

• Less wearing of the cleaning blade edge.

• High cleaning efficiency.

Due to the high efficiency of this cleaning system, the pre-cleaning corona and cleaning bias are not used for this copier.

The cleaning brush [B ] is used to support the cleanin g bla de . The brush collects toner from the dru m surface and scraped by the cleaning blade. Toner on the cleaning brush is scraped off by th e mylar [C] and falls to the toner collection coil [D]. Ton er is transported to the toner collectio n bottle by the toner collection coil.

To remove the accumulated toner at the edge of the cleaning blade, the drum turns in reverse for about 4 mm a t th e en d of every copy job. The accumulated toner is removed by the cleaning brush by this action.

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DRUM UNIT 23 April 1993

2.5.2 Drive Mechanism

[C]

[E]

[A]

[B]

[D]

The drive force from the main motor is transmitted to the cleaning unit drive gear via the timing belt [A] and the cleaning unit coupling [B]. The cleaning unit drive gear [C] then transmits the force to th e fro nt side through the cleaning brush [D]. The force at the front side is used for the toner collection coil gear [E].

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23 April 1993 DRUM UNIT

2.5.3 Cleaning Blade Pressur e Mechanism and Side-to-Side Moveme nt

[C]

[A]

[D]

[B]

The spring [A] always push es the cleaning blade against the OPC drum. The cleaning blade pressure can be manually released by pushing up the release lever [B]. To prevent clean ing blade deformation durin g the transportation , the release lever is locked in the pre ssure release (upper) position .

The pin [C] at the rear end of the cleaning blade holder touches the cam gear [D] which gives a side-to-side moveme nt to the blade. This movement helps to disperse accumulated toner to prevent early blade edge deterioration.

Detailed

Descriptions

2-27

[D]

DRUM UNIT 23 April 1993

2.5.4 Toner Collection Mechanism

[B]

[E]

[G]

[F]

[C]

[A]

Toner collected by the cleaning unit is transported to the toner collection bottle [A] through the tone r collect ion tubes. Three helical coils are use d for toner transport.

One coil [B] is driven by the main motor via drive belts and the other coil [C] is driven by an independent toner collection drive motor [D].

The actuator disk [E] on the toner collection drive mot or mon ito rs the proper rotation of the toner collectio n coil [C] to pre ven t th e coil fro m being damaged by toner clogged in the colle ction tube. The main PCB monitors the sensor output and increases t he mo to r sp ee d if th e sensor monitors that the to ne r collection motor rotates at a speed lower th an norma l. Also , th e CPU will display an SC 342 if no signal changes (ON → OFF) are detecte d for more than 2.55 seconds while the toner collection motor is turning.

When the toner collection bottle [A] become full, the toner pressure in the bottle increases and presses the gear [F] against the toner overflo w swit ch [G]. After the toner ove rflo w switch is a ctiva te d, the finishing of the copy job, or up to 100 continuou s copie s, is a llowed, then copying is prohib ite d an d the service call "full toner collection bottle" indication is displayed on the LCD.

This condition can be cleared by de-a ctuating the toner overflo w switch while de-actuating then actua tin g the to ner co llect ion bot tle swit ch ([C] in next page).

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23 April 1993 DRUM UNIT

[B]

[C]

[A]

Detailed

Descriptions

2.5.5 Pick-off mechanism

The pick-off pawls are always in contact with the drum surface with weak spring pressure. They move side to side during the copy cycle. This movement is made via a shaft [A] and an ecce nt ric ca m [B] .

2.5.6 Toner Collection Bottle Set Detection

The toner collection bottle set switch [C] prohibits machine operation by indicating SC343 wh ile th e toner collection bottle is not set .

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DRUM UNIT 23 April 1993

2.6 QUENCHING

[A]

In preparation for the ne xt cop y cycle , ligh t fro m t he que nch ing la mp (QL ) [A] neutralizes any charge remaining on the drum.

The quenching lamp consist s o f a line of 16 LEDs extending across the full width of the drum.

Yellow colored LEDs are used fo r Q L to reduce ultra violet light which would cause light fatigue on the OPC drum.

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[D]

23 April 1993 OPTICS

3. OPTICS

3.1 OVERVIEW

[A]

[C]

[B]

[E]

Detailed

Descriptions

The optics unit reflects an image of the origin al on the expo sure glass onto the OPC drum. This forms a latent electrical image of the origin al.

On this model a halogen lamp (85 V 23 0 W) is use d fo r t he expo sure la mp [A]. Lamp surface is frosted to ensure even exposu re.

Six mirrors are used to make the optics unit smaller and obtain the wide reproduction ratio ran ge (50 ~ 200 %).

The lens [B] is driven by two stepping motors for (1) vertica l direction (parallel to the paper feed direction) an d (2) horizontal direction movement s.

To correct focal length change in reduction and enlargement modes, the third scanner unit [C] (4th and 5th mirrors) posit ion is changed by a stepping motor.

The toner shielding filte r [ D] is gree n (a gree n filter partly absorbs red light) to improve red original duplication.

The optic anti-condensation heate r [ E] (located on the optic base plate) turns on while main switch is turned off to preve nt the moistu re from forming on the optics.

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OPTICS 23 April 1993

3.2 SCANNER DRIVE

[A]

[C]

[B]

[D]

[E]

A dc servo motor is used as the scanner drive moto r [ A] . Sca nn er drive speed is 330 mm/sec. during scanning, and 1950 mm/sec. whe n the scanner goes back.

The scanner drive motor drives the first [B ] and second scanners [C] using two scanner drive wires via the timing belt [D] and the scanner drive shaft [E]. The second scanner speed is half of the first scan ne r spee d.

The scanner drive wire is not directly wound around the pulley on the scanner drive motor.

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23 April 1993 OPTICS

3.3 VERTICAL LENS DRIVE

[B]

[A]

Detailed

Descriptions

HP (100%)

ReduceEnlarge

(Enlarge → HP) (Reduce → HP)

(Enlarge → Enlarge) (Reduce → Reduce)

(Enlarge → Reduce)

(Reduce → Enlarge)

steps30 30 30 30

The lens vertical drive motor [A] changes the lens vertical position in accordance with the selected re pro du ctio n rat io.

A stepping motor (approx. 0. 09 5 mm/st ep) is use d to drive th e len s thro ug h the lens drive belt. The maximum lens vertica l shift dista nce is 290 mm (from the position at 50% to the position at 200%).

The lens vertical home position sensor [B] detects the lens vertical position for full size mode. The optic control PCB keep s track of the lens po sitio n based on the number of pulse s sent to the lens vertical drive motor.

2-33

OPTICS 23 April 1993

3.4 HORIZONTAL LENS DRIVE

[A]

steps

Enlarge

Reduce

The original horizont al position on the exposure glass varies dependin g on the mode (such as platen, DJF and RDH modes) for easy original handling . However, the cente r is th e sta nd ard position for paper feed.

Therefore, the lens ho rizontal position has to be cha ng ed accord ing to paper size, reproduction ratio, original feed modes an d th e ed it mod es (centering, margin adjust, etc.).

A stepping motor (ap pro x. 0.07 mm/step) is used to drive the lens through the lens drive belt.

The lens horizontal ho me position sensor [A] is used to dete ct the lens horizontal position fo r A4/ LT side ways, in full size an d pla ten mode.

The other positions are determined by counting the number of moto r drive pulses.

Since this model has a horizontal lens drive mechanism, side-to-side registration adju stme nt for each feed station can be don e easily b y using SP mode ( SP Adjustment mode: PAGE 4).

2-34

23 April 1993 OPTICS

3.5 HORIZONTAL LENS POSITIONI N G

3.5.1 For Original Position

Platen DJF

100%

[A]

[C]

143.5

RDH (Center)

Horizontal

2.5

Lens Position

Copy Paper

[B]

There are three standard orig ina l positions for the platen, DJF and RDH modes.

In platen mode, the original is align ed with both the rear [A ] an d the lef t [B] original scales (rear left corner [C] is the standard position).

In RDH mode, the original position is the cen te r of th e left scale [B]. In DJF mode, the original position is 5 mm to front of the pla te n mod e original

position to maintain th e orig ina l t ran spo rt pa th (5 mm from the rear scale). The above figure shows the le ns horizontal positions for each original mode

when identical size paper is used.

Detailed

Descriptions

3.5.2 For Paper Size

Original Rear Edge

Horizontal

100%

Lens Position

Copy Paper

To keep high paper feed performance, the center is assigned as the paper feed standard position . The ref ore, the lens horizontal position is chan ged according to the paper size.

The figure shows the lens horizont al po sitio n fo r each paper size in fu ll size mode.

2-35

Copy Paper

OPTICS 23 April 1993

3.5.3 For Reproduction Ratio

Original Rear Edge

100% 50%

Original

200%

100%

3rd Scanner Position

50%

200%

When the reproduction ratio is changed, the vertical position of the lens is changed. At th e same time, the total focal len gt h ha s t o be chan ge d to adjust the image focusing. For this focal length change , th e ho rizon tal position of the 3rd scanner is also adjusted. The maximu m 3rd mirror shif t distance is 50 mm (from the position at 100% to the position at 50, 200%).

The figure shows the lens horizont al po sitio n fo r 50, 100 and 200%.

2-36

23 April 1993 OPTICS

3.6 3RD SCANNER DRIVE

[B]

[A]

(Initialize)

Detailed

Descriptions

(Reduce/Enlarge → HP)

(Reduce/Enlarge → Reduce/Enlarge)

(Reduce/Enlarge →Enlarge/Reduce)

40 steps 40 steps

To compensate the focus for reproduction and lens po sition changes, the 3rd scanner (4th and 5th mirrors) position is changed.

A stepping motor [A ] (ap prox. 0.095 mm/step) is used fo r the 3rd scan ne r drive.

The 3rd scanner home positio n sen sor [B] is used to detect the un it po sitio n for full size mode. The optic control PCB keep s track of the unit posit ion based on the number of motor drive pulses.

2-37

Optic Thermistor

Scanner Drive

Horizontal Lens Drive

Vertical Lens Drive

3rd Scanner Drive

Optic Cooling Fan

OPTICS 23 April 1993

3.7 OPTICS CONTROL CIRCUIT

Main Control Board

Main CPU

Sensors

Data Bus

Optics Control Board

Optics Control CPU

M M M M

Encoder

Exposure Lamp

AC Drive Board

The optic control board communicates with the main board through a data bus. The optics control board mon ito rs all t he sensor signals, encoder output, thermistor output and controls all motors in the opt ics.

At the programmed time, the main CPU sen ds a scan ne r start signal to the optics control CPU.

The CPU generates a pulse-width modulation (PWM) signal. The PWM signal goes to a driver circuit, which sen ds drive pulse s to th e scan ne r drive motor.

An encoder in the scanner drive mot or ge nerates pulse signals. A speed/direction contro l circu it mon ito rs t he sca nner speed and the direction of the signals, and uses th is dat a to re gu lat e the motor speed.

The home position sensor mon itors the position of the scan ne r. Whe n the main switch is turned on, the main CP U conf irms t he posit ion of the scanner by moving the scanner out of the home posit ion and back ag ain . This da ta is sent to the optics control CPU.

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23 April 1993 OPTICS

3.8 AUTOMATIC IMAGE DENSITY CONTROL SYSTEM (ADS)

[B]

[A]

Detailed

Descriptions

In ADS mode the original backgroun d densit y is sensed by the ADS sensor [A] and the main CPU determines an appro pria te deve lopment bias voltage for the original to preven t dirty backgrounds from appearing on copie s.

The ADS sensor board is moun te d on the rear side of the optics side plate. The sensor board is covered by the sensor housing cover which has a small hole to direct the reflected lig ht from th e orig ina l t o the ADS senso r.

The ADS sensor standard voltage is adjusted to 2.7 V when proce ss co nt rol data initial setting is performed. The exposu re lamp turns on with ID level 4 at the home position and the light refle cte d by th e ADS patte rn [B ] (white painted) reache s the ADS sen sor. The main CPU adjusts the ADS gain dat a automatically to make the out pu t 2. 7 V. This gain data is stored in the RAM board.

2-39

20 mm

OPTICS 23 April 1993

90 mm

9.7

A =

(mm)

M = 1.0 (m = 50 ~ 100)

M =

B =

(m = 101 ~ 200)

100

8.25

x 100 (mm)

m m: reproduction ratio

[V]

(50 ~ 200)

ADS Sensor Output

ADS Original Voltage

Peak hold

For the first scanning of an original in ADS mode, the CPU starts samplin g of the ADS sensor output while exposing the ADS patte rn at the scann er ho me position. Then the CPU stores th e maximu m ADS sen sor ou tp ut as a reference voltage. This me ans tha t eve ry ADS check cycle, the first scanning for the original, th e ADS re fe rence voltage is renewed by the la te st exposure light reflected by the ADS pattern.

In the full size mode, th e CPU samp les the ADS sensor output whe n th e scanner scans the original from 9.7 mm to 18 mm from th e left scale edge. The CPU takes the maximum ADS sen sor ou tput during the sampling period and compares it with the ADS refere nce voltage to determine the proper development bias vo lta ge . (See development bias con tro l se ctio n for details.)

The sampling length of ADS senso r o ut pu t fo r t he original differs dependin g on the reproduction ratio because the scanner speed is different.

2-40

Darker

23 April 1993 OPTICS

3.9 MANUAL IMAGE DENSITY CONTROL

When the image density is set manually, th e volt ag e ap plie d to the expo sure lamp changes as shown in the table below.

Dev. Bias Voltage (negative)

Exposure Lamp Voltage

V VBB –60

LAMP +4.5

LAMP +3.0

VLAMP +0.5

LAMP –1.5

LAMP –3.5

BB –90

VBB

LAMP

Lighter

Detailed

Descriptions

LAMP –5.5

VLAMP: Exposure lamp voltage at ID level 4.

This value is determined at process control data initial setting.

VBB: Development bias (negative) voltage at ID level 4.

This value is determined at process control data initial setting.

Manual ID Position

2-41

[D]

OPTICS 23 April 1993

3.10 UNEVEN LIGHT INTENSITY CORRECTION

[D]

original

[D]

exposure intensity

illumination

Shading plate

[A] [B] [C]

distribution

[A] [B] [C]

The entire exposure lamp surface is frosted to ensu re eve n exposure. To compensate for red uced light at the edge of the lens, a shading plate is

placed in front of the lens. The shading plate is fixed to th e lens unit. The shading plate compensates the light intensity when the lens horizontal position is shifted ([A] to [C]).

Also three shading mylars [D] int ercept any diffused refle cte d light from outside the light path.

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23 April 1993 OPTICS

3.11 ORIGINAL SIZE DETECTION IN PLATEN MODE

[E]

[B]

[D]

[C]

Detailed

Descriptions

[A]

There are three reflective sensors (APS sensors) in the optics cavity for the original size detection. Origin al widt h Se nso r [ A] is used fo r se nsin g th e original width and Original Lengt h Sensor-1 [B] and Original Length Sensor-2 [C] sense the origina l leng th.

Inside each APS sensor, there is a n LED [D] an d th ree pho to ele ctric de vices [E]. The light generated by the LED is broken up in three beams and each beam scans a different point of the exp osu re gla ss. If the original or platen cover is present over the scan ning point, the beam is refle cte d an d ea ch reflected beam expose s a photo ele ctric de vice and act ivates it.

While the main switch is on, these sensors are active and the origin al size data is always sent to the main CPU. Howeve r, the main CPU checks the data only when the platen cover is opened.

2-43

OPTICS 23 April 1993

[A]

Original Size Length Sensor 1 Length Sensor 2 Width Sensor

A4/A3 version LT/DLT version 1 2 3456789

A3 11 x 7 OOOOOOOOO B4 10 x 14 XOOOOOOOO

—8

F4 8 x 13 XXOOOOOOX A4–L 8 B5–L — X X X OOOOXX A5–L 5 B6–L — X X X X O O X X X A6–L — X XXXXOXXX A4–S 11 x 8 B5–S — X X X X OOOOO A5–S 8

A6–S — X XXXXXXXX

1/2 x 14 X O O – O – O O X

1/2 x 11 XXXOOOOOX

1/2 x 81/2 XXXOOOXXX

1/2 XXXOOOOOO

1/2 x 51/2 XXXXXOOXX

NOTE: –L: Lengthwise

–S: Sideways Sensors #4 and #6 are not used fo r L T/DL T version machines.

The check is done when the platen position sensor [A] turns on. This is when the platen is positioned about 15 cm above the expo sure glass. At th is time, only the sensor(s) locate d unde rneath the original receive the reflected light and are on. Other sensor(s) are off. Throu gh the on/ of f data of the nin e (seven for LT/DLT version machine) sensors, the main CPU can reco gn ize the original size. In case the copy is made with the platen open, the main CPU decides the original size only through the da ta when the Print key is pre ssed . This original size detection method eliminat es the necessit y for a pre -scan and increases the machine ’s prod uctivity.

2-44

23 April 1993 DEVELOPMENT

4. DEVELOPMENT

4.1 OVERVIEW

[C]

[D]

[A]

This copier uses a double roller (diameter 20 mm each ) deve lop men t (DRD) system. This system differs from single rolle r development systems in that (1) it develops the image in a narrower area, (2) it develops the image twice, and (3) the relative speed of each development roller against the drum is reduced. Also, finer to ne r (App rox. 9 µ m) a nd deve loper (Approx. 70 µm) are used. Both the DRD system and new sup plie s improve the image quality, especially of thin horizontal line s, th e tra iling edg es of the half -to ne area s, and black cross points.

[B]

Detailed

Descriptions

The paddle roller [A] picks up develope r in it s paddles and transports it to the upper development roller [B ]. Int ern al pe rman en t mag ne ts in th e development rollers att ract the deve lop er to the deve lop men t roller sleeve. The upper development roller carries the developer past the doct or bla de [C]. The doctor blade trims th e de velo pe r to the desired thickness and creates backspill to the cross mixing mechanism.

The development rollers con tin ue s to tu rn, carrying the deve lop er to the OPC drum [D]. When the develo pe r b rush contacts the drum surface, the negatively charged areas of the drum surface attract and hold the positively charged toner. In th is wa y, th e latent image is develop ed .

The development roller is g iven a neg at ive bia s to prevent the toner form being attracted to the non-imag e are as on the drum surf ace that may have a slight residual negative charge.

After turning another 100 degrees, th e de velo pe r is ret urn ed to th e pa dd le roller [A].

2-45

DEVELOPMENT 23 April 1993

4.2 DRIVE MECHANISM

[C]

[D]

[E]

[A]

[B]

The gears of the develop ment unit are driven by the deve lop ment drive gear [A] when the developmen t mot or [B ] (dc servomotor) turns.

The gears of the toner hopper are driven by the toner supply roller drive ge ar [C] when the toner supply clu tch [D] act ivates.

The above gears are helical gears. Helical gears are more quiet than normal gears. The teeth of the de velo pment drive gear are chamfered so that they smoothly engage with th e de velo pment roller gear [E] when the unit is installed.

2-46

[C]

23 April 1993 DEVELOPMENT

4.3 CROSSMIXING

[A]

[B]

[C]

[E]

[F]

[D]

Detailed

Descriptions

[E]

[F]

[D]

This copier uses a standard cross-mixing mechanism to keep the toner and developer evenly mixed . It also he lps ag ita te the developer to preve nt developer clumps from forming and help s create the trib oelectric charge.

The developer on the tu rning development rollers [A ] is sp lit int o two parts by the doctor blade [B]. The part tha t sta ys on th e de velo pme nt rollers forms the magnetic brush an d develops the latent imag e on the drum. The part that is trimmed off by the doctor blade goes to the backspill plate [C].

As the developer slides down the backspill plate to the agit ator [D], the mixing vanes [E] move it slightly to ward the rear of the unit. Part of the deve loper falls into the auger inlet and is transp ort ed to the fro nt of the unit by th e auge r [F].

The agitator moves th e de velo pe r slig ht ly t o th e fro nt as it turns, so the developer stays level in th e de velo pment unit.

2-47

DEVELOPMENT 23 April 1993

4.4 DEVELOPMENT BIAS

4.4.1 Overview

[A]

[B]

[C]

The high voltage control Board [A] applie s the neg at ive de velo pment bias to the lower sleeve roller through the receptacle [B] and the lower sleeve roller shaft [C]. Then th e bia s is applied to the upper sleeve roller through the rear sleeve roller holder made of condu ctive resin.

The development bias pre vents toner from being attracted to the background area of the non-image area on the OPC drum where there is resid ual volta ge . Also, the developmen t bias is used to adjust image de nsit y according to the conditions the customer selected.

2-48

Light

23 April 1993 DEVELOPMENT

4.4.2 Bias Control In Copy Cycle

The bias output is determined by five fa cto rs. The total bias is described as;

ADS Mode: VB = VBB + VBU + VBMG + VBA Manual ID Mode: VB = VBB + VBU + VBMG+ VBM

VB: Total bias VBB: Base bias VBA: ADS Compensation VBU: User Tool mode ID Selection Compensat ion VBMG: Magnification Compensation VBM: Manual ID Selection Compensation

Detailed

Descriptions

1) Base Bias (VBB)

[V]

Drum Potential

Dark

Original Density

As explained in the pro cess con trol section, the base bias fo r d eve lopment is determined by the residual voltage (VR) measured in pro cess con tro l d ata initial setting.

VBB = VR + (–220)

2) ADS Compensation (VBA)

VBA (negative)

–300

1.02 V

122.7

1 2 2.3

Dark V

ADS (V) Light

According to the original background density, the bias is compensate d. Th e compensation valu e is determined with the voltage measured by the ADS sensor (ADS sensor outp ut : VADS) as follows:

VBA = 234 x (VADS –2.3)

NOTE: VBA has a limited range from 0 V to –300 V.

2-49

Manual ID Position

DEVELOPMENT 23 April 1993

3) Manual ID Selection Position Compensation (VBM)

According to the manua l I D selection position, the bias is compensated as follows:

Exposure Lamp Voltage

V V V

V V

Lighter Darker

LAMP+4.5 LAMP+3.0 LAMP+0.5

LAMP →

LAMP –1.5 LAMP –3.5

LAMP –5.5

V (negative)

–90 –60 0

56341

VLAMP: Exposure lamp voltage at ID level 4. This valu e is d et ermin ed at

process control data initial set tin g.

4) User Tool Mode ID Selection Compensation (VBU)

In the User Tool mode, the imag e de nsit y level can be selected from five steps. The VBU is determined by the User Tool ID po sitio n setting as follows:

VBU (negative)

Lighter Darker

–60 –30

54321

+30

+60

User Tool ID Position

2-50

142%

23 April 1993 DEVELOPMENT

5) Magnification Compensation (VBMG)

VBMG is determined by th e sele cted reproduction ratio as follows:

–100

Dev. Bias Voltage (negative)

–60 –40

–30 –20

50%

62%

81%

116%

115%80%61%

122%

123%

161%

141% 160%

4.4.3 Bias Control Out of Copy Cycle

To hold the toner on the sleeve rollers while the development sleeve rollers are rotating with out image development, a constant –300 V bias is applied.

Detailed

Descriptions

2-51

DEVELOPMENT 23 April 1993

4.4.4 ID Sensor Pattern Bias

–700 V

①

① Potential

Sensor Detection

③

② ID Sensor

Bias Le vel

4.0 V

VSG

③ ID Sensor Output

While developing the ID sen sor pa tt ern , ID sensor bias is applied. ID sensor bias is determined during process control in itia l sett ing as follo ws:

A charge is applied while grid volta ge is –700 V to crea te the ID senso r pattern.

–300

VSP

VIDB = VP +300 (V)

②

The drum potential (VP) of the ID sensor pattern is checked. The ID sensor bias (VIDB) is adjusted so that it satisf ies th e followin g formula : VIDB = VP – (–300)

= VP + 300 (V)

2-52

[E]

[F]

23 April 1993 DEVELOPMENT

4.5 TONER SUPPLY

4.5.1 Toner Supply Mechanism

[A]

[B]

[F]

[C]

[D]

When the toner supply clut ch [A ] turns on, the agitator [B] moves the tone r from front to rear and sends the toner to the toner supply roller.

The toner supply clutch [A] lo cat ed inside the deve lop men t motor [C] applies the rotation from the deve lop men t mot or to the toner supply roller gear [D], which drives the agitator ge ar [E]. Toner is caught in the grooves on the toner supply roller [F]. Then, as the groo ves tu rn pa st the opening, the to ne r f alls into the development unit.

Detailed

Descriptions

2-53

DEVELOPMENT 23 April 1993

4.5.2 Toner End Detection

[A]

The toner end sensor [A] detects if sufficient toner remains in the toner hopper or not. The ton er en d sen sor monitors toner end condition once when the toner supply clutch turns on . Whe n th ere is little toner inside the toner hopper and toner pressure on the toner end senso r b eco mes low, the toner end sensor outputs a pulse signal for each (one detection per one copy).

The toner near end indication is displayed on the LCD after receiving the pulse signal 150 times (If no pulse signal is out pu t twice cont inu ally, the pulse count is canceled).

Fifty copies are allowed afte r ent ering toner near end condition. After fifty copies are made in tone r nea r end cond ition, the machine enters the toner end condition and copying is prohibited.

When the main switch is turned off and on, or th e fro nt doo r is opened and closed, the machine drives to ne r supp ly mechanism and monitors the toner end sensor output. If th e toner end sensor does not out pu t th e pu lse signal twice continually, the toner end condition is canceled.

2-54

23 April 1993 DEVELOPMENT

4.5.3 Toner Supply Control

By using an SP mode ( Adjustment mode: PA GE 7), the following 3 kind s

of toner supply controls can be sele cted.

• Auto Process Control Mode

• Detect Mode

• Fixed Mode

1) Auto Process Control Mode Originals have various image proportio ns and imag e densit ies. For the best toner supply control, it is necessary to link the amou nt of toner supplied on each copy cycle to th e amo un t of ton e r con sumed for each copy. Fuzzy control is used in this model to pro vide this kind of toner supply control.

Fuzzy Control 1

According to data of the ID se nso r and TD sen sor, the CPU ch ecks th e following at every copy cycle:

1. The results of toner sup ply con trol (TD sensor output) in the previous copy cycle.

Detailed

Descriptions

2. How quickly the toner density is changing. Then the CPU decides the most suitable toner sup ply amo un t (toner supply clutch on time) for the next copy cycle by using fuzzy logic.

2-55

DEVELOPMENT 23 April 1993

Fuzzy Control 2

The image on the OPC drum changes due to variat ions in toner chargeability (influence d by the en viron men t) even if toner concentration is constant. The ID sensor directly checks the image on the OPC dru m and shift s the VREF data under fuzzy control to keep the image on the OPC drum constant.

NOTE: The toner supply amount is changed at every copy cycle.

The target toner density sensor output is updat ed und er th e following conditions:

1. During toner density sensor initial setting

2. During process control data initial setting

3. After the copy job is completed in case that 10 or more copies have been made since the last update.

(Refer to section 2.1.4 "Ima ge Densit y Co nt rol" for de ta ils.)

2) Detect Mode In this mode, only the TD sensor is used to con tro l t he ton er concentration (VREF data is fixed). The machine pe rfo rms only fuzzy control 1. In ID sensor abnormal condition or Drum Pot en tia l se nso r abn orma l condition, the machine au to matically enter this mode.

3) Fixed Mode In this mode, a fixed amount of ton er is supp lied every cop y cycle as

determined (4%, 7%, 11%, 14%) by SP mode

( Adjustment mode:

PAGE 7). There is no overtoning detect ion mechanism. In TD sensor abnormal condition, the machine automatically enters this

mode.

2-56

23 April 1993 DEVELOPMENT

4.5.4 Bottle Drive Mechanism

[C]

[D]

[E]

[B]

For easy access, the toner bot tle is just inside the fron t cove r. The bot tle is positioned horizontally.

Detailed

Descriptions

[A]

The bottle drive mechanism tra nsp orts toner from the bottle to the to ner hopper [A]. A worm gear [B] on the bot tle drive mot or drive s t his mech an ism.

The toner bottle has a spiral groove [C] that helps move the toner to the tone r hopper.

To prevent toner from sca tt ering when the toner bottle is removed from the holder, toner shutter [D] which covers the hole [E] is installe d on the ton er bottle.

When the toner is set on the hold er an d the lever is lowered, the toner shutter [D] opens to supply toner t o th e to ne r h oppe r .

The bottle drive moto r turns on 0.7 seconds when the ton er en d sensor turns on twice continually.

2-57

IMAGE TRANSFER 23 April 1993

5. IMAGE TRANSFER

5.1 PRE-TRANSFER LAMP

[A]

The pre-transfer lamp [A] locat ed in the drum unit is used to pre vent incomplete toner t ran sfer.

After the latent image is developed but bef ore the image is transferre d to the copy paper, the drum surface is illuminated by the pre -tra nsf er lamp. This illumination reduces the negat ive pote nt ial on the drum surf ace charged by the main charge corona and partia lly d ischa rge d by th e exp osu re. Th is makes image transfer easier.

The pre-transfer lamp is turne d on and off by the charg e power pa ck at the same time as when the main motor turns on and off .

2-58

23 April 1993 IMAGE TRANSFER

5.2 IMAGE TRANSFER AND PAPER SEPARATION

OVERVIEW

[E]

[F]

[A]

[D]

[B]

[C]

This model uses a unique transf er belt un it inst ea d of the tran sfer and separation corona unit. The tra nsf er be lt un it con sists of the following parts:

[A] Transfer belt

A belt (length: 321 mm) with high electrical resistance which holds a high negative electrical po tential and attracts the toner on the OPC drum onto the paper. Also the electrical potential att racts the paper itself and helps paper separation fro m the OPC dru m.

Detailed

Descriptions

[B] Transfer bias roller

Applies transfer voltage to the tran sfe r belt.

[C] Transfer belt lift leve r (driven by a solen oid)

Lifts the transfer belt to contact the tra nsfer belt with the OPC drum.

[D] Transfer power pack

Generates the constant transfer current.

[E] Transfer belt cleanin g bla de

Removes toner atta che d on the transfer belt to prevent the rear side of the paper from being stained.

[F] Discharge plate

Helps paper separation from th e transfer belt by discharging the remaining negative cha rge on the transfer belt.

2-59

IMAGE TRANSFER 23 April 1993

5.3 IMAGE TRANSFER AND PAPER SEPARATION

MECHANISM

The registration rollers [A] start s feeding th e pa per [B] to the gap between the OPC drum [C] and the transfer belt [D] in proper timing.

Immediately when th e lea ding edge of the paper reaches the gap between the tra nsfer belt and the OPC drum, the transf er belt lift lever [E] raises the tra nsf er belt to contact the transfer belt and the OPC drum. The lift lever is driven by a solenoid

[D]

[C]

[E]

[A]

[B]

Then a negative transfer bias –1.5 K ~ –2.0 KV is applied to the transfer bias ro ller [F] and attracts the positively charged toner [G] on the OPC drum. It also attracts the paper and separate s the pap er from the OPC drum.

–800 V

[F]

[G]

–1.3 K~ –1.8KV

–1.5 K ~ 2.0 KV

2-60

23 April 1993 IMAGE TRANSFER

After the image tra nsf er is completed, the charge on the transfer belt holds the paper to the transfer belt. Before separating the paper from the transfer belt, the transfer belt is discharged by the discharge plate [A].

The transfer power pack [B] inside the transfer belt unit monitors the current fed back from the discharge plate to adjust the transfer current. This way, the current stays const ant even if the paper, environmental conditions, and the transfer belt surface resistance are change d.

[A]

[B]

Detailed

Descriptions

[B]

2-61

IMAGE TRANSFER 23 April 1993

5.4 TRANSFER BELT UNIT LIFT MECHANISM

[E]

[C]

[E]

[A]

[B]

[F]

[D]

The transfer belt lift solenoid [A] located inside the transfer belt unit turns on to raise the transfer belt to con ta ct th e OPC d rum at the appropriate timing. The front lever [B] and the rear lever [C] are connected to the solenoid by links [D] and push up the stays [E ] whe n the solenoid turns on. The support spring [F] helps the solenoid to raise the tr an sfer belt. The solenoid turns off after the copy job is finished. The transfer belt must be released from t he OPC dru m for th e followin g reasons:

1. To prevent the ID sensor pattern on the OPC drum from being rubbed by the transfer belt because the transfer belt is located between the development unit an d th e ID sensor.

2. To decrease the load to the transfer be lt clea ning blade, it is better to keep toner on the non-image area (fo r example VD, VL, ID sensor pattern developed during process control data initial setting) from being transferred onto th e transfer belt.

3. To prevent change of OPC drum characteristics by the influence of additives inside the rubber belt.

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[E]

23 April 1993 IMAGE TRANSFER

5.5 PAPER TRANSPORTATION AND BELT DRIVE

MECHANISM

[C]

[A]

[E]

[F]

[B]

[F]

[D]

The transfer belt is driven by the ma in drive moto r [ A] thro ug h belt an d gears. Since the transfer belt elect rically attracts the paper [B], the transport fan is not required.

Detailed

Descriptions

The charge on the transfer belt is discharged by the discharge plate to reduce paper attraction and paper is separated by the paper stiffness above the transfer belt drive roller [ C] whe re th e tra nsf er be lt is turn ing.

The tapered parts [D] at both sides of the roller [ E] help ke ep the transfer belt [F] at the center position.

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IMAGE TRANSFER 23 April 1993

5.6 TRANSFER BELT CLEANING MECHANISM

[D]

[A]

[B]

[C]

Some toner may adhere to transfer belt when paper jams occur, or whe n the by-pass feed table side fences are set in the wrong position causing the erase lamp to miss some toner. The adhe red ton er must be remo ved to prevent the rear side of th e copy paper from being sta ined. The cleaning blade [A] scrapes off any toner re main ing on the transfer belt. A counter blade system is used for the transfer belt cleaning. The surface of the transfer belt is coa te d to make it smooth and so preve nt the clean ing blade from being flip pe d by th e transfer belt.

The lever [B] on the fro nt end of the cleaning blade releases the cleaning blade when the tra nsf er be lt un it is lowered and the lever is pushe d by th e transfer belt unit support prop. (The transfer belt unit is lowered when the lever [C] is turned anti-clockwise)

When the cleaning blad e is released, the edge of the cleaning blade rubs the seal so that the seal [D] remove s t he tone r or pape r d ust on th e cleaning blade edge .

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23 April 1993 IMAGE TRANSFER

5.7 TONER COLLECTION MECHANISM

[B]

[A]

Detailed

Descriptions

Through idle gears [A], transfer belt drive is transmitted to the toner collection coil [B]. The toner collectio n coil tra nsp ort s t he collected toner to the toner collection bottle. Se e section 2.2.5 for details.

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PAPER FEED 23 April 1993

6. PAPER FEED

6.1 OVERVIEW

[A]

[B]

[A]

[B]

[C]

This model has three drawer tray pa per f eed sta tions. The following table shows the configuration of each feed stations of the A095 and A096 copiers.

Feed station A095 copier A096 copier

1st 550 sheets tray 500 + 500 sheets tandem feed tray

2nd 550 sheets universal tray 550 sheets universal tray

3rd 550 sheets tray 1500 sheets built-in LCT

Paper can also be fed using the by-pass fee d ta ble which ha s an independent feed mechanism. The by-pass feed table can hold 50 sheets of paper.

All feed stations use an FRR feed system. Rotation of the pick-u p roller [ A] drives the top sheets of paper from each tray to the feed [B] and the separation [C] rollers. The feed an d separation rollers then take over paper drive. If more than one sheet is fed by the pick-up roller, the separa tio n rollers rotates in the opposit e direction and prevents all but the top sheet from passing through to th e registration rollers.

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23 April 1993 PAPER FEED

6.2 FRR FEED SYSTEM

[B]

[A]

Detailed

Descriptions

[C]

This copier uses an FRR paper feed system using thre e rollers.

6.2.1 Pick-up Roller

The pick-up roller [A] is not in contact with the paper sta ck bef ore it starts feeding paper. Short ly a ft er the Start key is pressed, the pick-up roller drops down and feeds the top sheet betwee n the feed [B] and the separation rollers [C]. At almost the same time th at the paper’s leading edge arrives at the feed roller, the pick-up roller lifts off the paper stack so that it does no t int erf ere with the operation of the feed and sep ara tio n rolle rs. The feed and separation rollers then take over the paper feed pro cess.

6.2.2 Feed and Separation Rollers

There is a one-way bearing inside the fee d rolle r so it can tu rn on ly in one direction. The separat ion roller is driven in the opposite direction to the feed roller. The separatio n rolle r, ho weve r, is driven through a slip clutch (torqu e limiter clutch) which allows it to turn in either directio n depe nding on the friction between the rollers. The sep ara tion roller solenoid keeps the separation roller in conta ct with the feed rolle r.

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F2F3F3

PAPER FEED 23 April 1993

[B]

[A]

The direction in which the separat ion roller [A] turns depends on the frictional forces acting on it. The slip clutch applies a constant clockwise fo rce (F1). When there is a single sheet of paper being driven between the rollers, the force of friction betwee n the feed roller [B] and the paper (F2) is greater than F1. So, the separation rolle r turns counterclockwise.

If two or more sheets are fed betwe en the rollers, the forwa rd fo rce on the second sheet (F3), be come s le ss tha n F1 because the friction between the two sheets is small. So, the separation roller sta rts tu rnin g clockwise and drives the second sheet back t o th e tra y.

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[C]

23 April 1993 PAPER FEED

6.3 SLIP CLUTCH MECHANISM

[A]

Detailed

Descriptions

[G]

[D]

[F]

[B]

[E]

The slip clutch [A] consists of the inpu t hub [B ] an d the outp ut hub [C] which is the case of the clutch as well. The mag ne tic ring [D] and the steel spa cers [E] are fitted onto the input hub. The ferrite ring [F] is fitted int o the output hub. Ferrite powder [G] packe d between the magnetic ring and th e fe rrite ring [F] generates a consta nt torque due to magnetic force. The input hub and the output hub slip when the rotational force exceeds the constant torque.

This type of slip clutch does not require lubrication.

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[J]

[F]

[I]

PAPER FEED 23 April 1993

6.4 FRR FEED DRIVE MECHANISM

[D]

[B]

[K]

[B]

[L]

[D]

[G]

[C]

[A]

[E]

[H]

The rotation of the paper feed mot or [A ] is t ran smitt ed to the gear [B] via the timing belt [C], and then transmitted to the separation roller via the feed clutch gear [D], gear [E], gear [F] and gear [G].

If the paper feed station is not select ed , th e sep ara tio n rolle r so len oid [H] de-activates and the separation roller [I] rotates freely in the reverse direction of paper f ee ding.

Gear [B] also transmits the drive to the vertical tran spo rt rolle r [ J] via gear [D] , idle gear [K] and gear [L ].

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[E]

23 April 1993 PAPER FEED

[A]

[F]

[D]

[C]

[B]

[I]

[G]

[H]

When the paper feed station is selected and the start key is pressed, the feed clutch [A], separa tio n roller solenoid [B], an d th e pick-up solenoid [C] turn on at once.

When the feed clutch [A] activates to rotate the feed roller [D], the feed roller and the pick-up roller [E] turn togeth er be cau se th ey are linked by the idle gear [F].

Detailed

Descriptions

When the separation roller sole no id [B ] tu rns on , th e separation roller [G] contacts the feed roller [D] then rotates tog ethe r with the feed roller in spit e of the separation roller’s drive in the opposite dire ctio n due to the torq ue limit er function in the separatio n rolle r [G] .

When the pick-up solenoid [C] act ivat es, the pick-up roller [E] lowers to make contact with th e to p sheet of the paper stack and send it to the feed an d separation rollers. When the paper feed senso r [ H] de te cts the leading edge of the paper [I], the pick-up solenoid de-energizes to lift the pick-up roller and the paper f eed clutch de-energizes at a certain time to wait until it is re ady to feed to the registration roller.

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PAPER FEED 23 April 1993

6.5 SEPARATION ROLLER RELEASE MECHANISM

[B]

[A]

[C]

In this model, the separation roller [A] is normally awa y from th e feed roller [B]. When the paper feed statio n is select ed , th e sep ara tio n rolle r so len oid [C] contacts the separation roller to the feed roller as explained in the previou s two pages.

This contact/relea se mechanism has the followin g three advantages:

1. When the paper feed motor turns on, all separation rollers in each fe ed stations rotate. If the separat ion roller is away from the feed roller, it reduces the mechanical loa d to the paper feed moto r and drive mechanism, and also reduces we ar of the rubb er surf ace of th e separation roller due to the frictio n between the separation roller and th e feed roller.

2. After paper feeding is completed, paper sometimes remains in the gap between the feed roller and the separation roller. If the feed tray is drawn out in this con dition, it is possible for the remaining paper to be torn. When the separation roller is away from the feed rolle r, rema inin g paper is released from the gap between th e feed and the sepa rat ion rollers.

3. When paper misfeeds occur around this area , the customer can easily pull out the jammed paper between the fe ed and the sepa rat ion ro llers because the separation roller is a way fro m the feed rolle r.

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[D]

[C]

23 April 1993 PAPER FEED

6.6 PAPER RETURN MECHANISM

[A]

[E]

[C]

[B]

[F]

[C]

3 mm

When the paper feed clutch [A] activates and the feed roller drive shaft [B] rotates, the leve r [ C] rot at es together with the shaft. However, the lever is immediately stopped by the stopp er [D] .

Detailed

Descriptions

After all paper is fed and th e pa pe r fee d clut ch turns off, the paper feed motor still rotates to turn the separa tio n rolle r [E] in the reverse direction. The separation roller, still contact ing the fee d roller, tu rns the feed roller in th e reverse direction un til the lever hits the rubber cushion [F].

By this feed roller reverse mechanism, the paper remaining in the gap between the feed and the separation rollers return s 3mm to the paper f eed tray.

After that, th e sep aration roller solenoid turns off to move the separat ion ro ller away from the feed roller. This releases the leading edge of the paper and drops the paper to the paper feed tray.

This prevents remaining paper from being to rn when the feed tray is drawn out.

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PAPER FEED 23 April 1993

6.7 PAPER SKEW PREVENTION MECHANIS M

[A]

[B]

In this model, paper corner hold ers [A ] are not used to facilita te pap er loa din g. Instead of the corner hold ers, both pa per press arms [B] press down both

paper side edges, especially in the case of paper with a face curl. This helps to keep paper from being guid ed by the tray side fen ces to prevent paper skew or jam.

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[A]

[D]

23 April 1993 PAPER FEED

6.8 PAPER LIFT MECHANISM

[B]

[C]

[F]

[E]

When the tray is set in the machine, the machine detects this condition by using several detection methods as shown in the table:

Detailed

Descriptions

Feed station A095 copier A096 copier

1st Tray set switch Tray set signal through the connector

2nd Paper size switch Paper size switch

3rd Tray set switch LCT set signal through the connector

When the machine dete cts th at the paper tray is set in the machine, the lift motor [A] rotates and the coupling gear [ B] on th e tray lift motor engages the pin [C] of the lift arm shaft [D], then turns the tray lift arm [E] to lift the tray bottom plate [F].

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Ricoh FT6645 Service manual

Specifications and Main Features

Frequently Asked Questions

User Manual