Ricoh FT8780 Service manual

RICOH FT8780

SERVICE MANUAL

IMPORTANT SAFETY NOTICES

PREVENTION OF PHYSICAL INJURY

1. While the machine warms up, it will suddenly start turning to perform the process control data initialization. Keep hands away from any mechanical and electrical components during this period.

2. Before disassembling or assembling parts of the copier and peripherals, make sure that the copier and the second sorter power cord is unplugged.

3. The wall outlet should be near the copier and easily accessible.

4. Note that some components of the copier, the paper tray unit, and the 2nd sorter are supplied with electrical voltage even if the main switch is turned off.

5. If any adjustment or operation check has to be made with exterior covers off or open while the main switch is turned on, keep hands away from electrified or mechanically driven components.

6. The inside and the metal parts of the fusing unit become extremely hot while the copier is operating. Be careful to avoid touching those components with your bare hands.

HEALTH SAFETY CONDITIONS

1. Never operate the copier without the ozone filters installed.

2. Always replace the ozone filters with the specified ones at the specified intervals.

3. Toner and developer are non-toxic, but if you get either of them in your eyes by accident, it may cause temporary eye discomfort. Try to remove with eye drops or flush with water as first aid. If unsuccessful, get medical attention.

OBSERVANCE OF ELECTRICAL SAFETY STANDARDS

1. The copier and its peripherals must be installed and maintained by a customer service representative who has completed the training course on those models.

2. The RAM board on the main control board has a lithium battery which can explode if replaced incorrectly. Replace the battery only with an identical one. The manufacturer recommends replacing the entire RAM board. Do not recharge or burn this battery. Used batteries must be handled in accordance with local regulations.

SAFETY AND ECOLOGICAL NOTES FOR DISPOSAL

1. Do not incinerate the toner cartridge or the used toner. Toner dust may ignite suddenly when exposed to open flame.

2. Dispose of used toner, developer, and photoconductors according to local regulations.

3. Dispose of replaced parts in accordance with local regulations.

4. When keeping used lithium batteries in order to dispose of them later, do not put more than 100 batteries per sealed box. Storing larger numbers or not sealing them apart may lead to chemical reactions and heat build-up.

SECTION 1

OVERALL MACHINE

INFORMATION

Overall

Information

6 March 1992 SPECIFICATIONS

1. SPECIFICATIONS

Main Copier

Copier

Configuration: Console Copy Process: Dry Electrostatic Transfer System Originals: Sheet/Book Original Size: Maximum: 11" x 17", A3 Copy Paper Size: Maximum: 1st and 2nd tray 8

1/2" x 14", A4

3rd tray 11" x 17", A3

Minimum: 1st and 3rd tray 5

2nd tray 8

1/2" x 81/2", A5 1/2" x 11", A4

Copy Paper Weight: Standard Copying: 14 ~ 42 lb, 52 ~ 157 g/m

Duplex Copying: 17 ~ 28 lb, 64 ~ 105 g/m Warm Up Time: Within 8.0 minutes (room temp. 68°F, 20°C) First Copy Time: 3.9 seconds (8 Copying Speed: 80 copies/minute (8

1/2" x 11", A4, feed from 3rd tray)

1/2" x 11", A4)

Optional Equipment: 20 Bin Sorter 1

20 Bin Sorter 2

Menu Reader

Key Counter

Receiving Tray

Guidance ROM Kit

2 2

1-1

SPECIFICATIONS 6 March 1992

Reproduction Ratios: See the following table:

LT/DLT version A4/A3 version

200% 200%

Enlargement

155% 141% 129% 122% 121% 115%

Full Size 100% 100%

93% 93% 77% 82%

Reduction

74% 71% 65% 65% 50% 50%

Zoom: 50 ~ 200% Copy Exit Tray Capacity: 250 Sheets Toner Replenishment: Cartridge exchange (1500 g) Paper Feed: 1st tray (550 sheets)

2nd tray (3,000 sheets) 3rd tray (1,500 Sheets)

Power Source: 120 V, more than 20 A (LT/DLT version)

220, 230, 240 V, more than 10 A (A4/A3 version)

Power Consumption:

Maximum during LT/DLT version A4/A3 version

Stand-by 1.90 kw 2.00 kw

Copying Cycle 1.71 kw 1.75 kw

Dimensions: Copier Only: 49.3" x 29.9" x 56.9"

(1253 x 760 x 1444.5 mm)

With Sorter: 81.5" x 34.4" x 56.9"

(2070 x 873 x 1444.5 mm)

Weight: Copier Only: 892 lb (405 kg)

With 2 Sorters: 1308 lb (593 kg)

Noise Emission: Copier Only: 63 dB

With Sorter: 64 dB

1-2

Overall

Information

6 March 1992 SPECIFICATIONS

Document Feeder

Original Size:

Stack feed mode Single feed mode Duplex mode

Maximum 11" x 17", A3 11" x 17", A3 11" x 17", A3

Minimum 8

1/2" x 11", A4 51/2" x 81/2", A5 81/2" x 11", A4

Original Weight:

Stack feed mode Single feed mode Duplex mode

Maximum 34 lb, 128 g/m

Minimum 14 lb, 52 g/m

43 lb, 157 g/m

11 lb, 35 g/m

Feed-in Unit Capacity: 50 Sheets (80 g/m2, 20 lb) CFF Original Stack Height:Maximum: 50 mm Original Set: First sheet on top, stack face down

25 lb, 93g/m

14 lb, 52 g/m

1-3

COPY PROCESSES AROUND THE DRUM 6 March 1992

2. COPY PROCESSES AROUND THE DRUM

1-4

Overall

Information

6 March 1992 COPY PROCESSES AROUND THE DRUM

1. DRUM CHARGE In the dark, the charge corona unit gives a uniform positive charge to the selenium drum. The charge remains on the surface of the drum because the photoconductive selenium has electrical resistance in the dark.

2. EXPOSURE An image of the original is reflected to the selenium drum surface via the optics assembly. The charge on the drum surface is dissipated in direct proportion to the intensity of the reflected light, thus producing an electrical latent image on the drum surface.

3. ERASE The erase lamp illuminates the areas of the charged drum surface that will not be used for the copy image. The resistance of the drum in the illuminated areas drops and the charge on those areas dissipates.

4. DRUM POTENTIAL SENSOR The drum potential sensor detects the electric lines of force from the electric potential on the drum to compensate image processing elements.

5. DEVELOPMENT Negatively charged toner is attracted to the positively charged areas of the drum, thus developing the latent image. (The negative triboelectric charge is caused by friction between the carrier and toner particles.)

6. PRE-TRANSFER The pre-transfer corona (PTC) applies a negative dc charge and an ac charge to the drum. The dc charge increases the negative potential of the toner to improve toner transfer to paper. The ac charge decreases positive charge on the drum and makes paper separation easier. The pre-transfer lamp (PTL) also makes paper separation easier by illuminating the drum and decreasing the positive charge on the drum.

7. IMAGE TRANSFER Paper is fed to the drum surface at the proper time so as to align the copy paper and the developed image on the drum surface. Then, a strong positive charge is applied to the back side of the copy paper, providing an electrical force which causes the copy paper to be attracted to the drum’s surface. At the same time, the toner particles are pulled to the copy paper from the drum’s surface.

8. PAPER SEPARATION A strong ac corona discharge is applied to the back side of the copy paper, reducing the positive charge on the copy paper and breaking the electrical attraction between the paper and the drum. Then, the stiffness of the copy paper causes it to separate from the drum surface. The pick-off pawls help to separate paper which has low stiffness.

9. CLEANING The cleaning brush first removes remaining toner on the drum surface. Then, the cleaning blade which is angled against drum rotation (counter blade system) removes the rest of the toner. The flick roller mechanically removes the toner on the cleaning brush.

10. QUENCHING

Light from the quenching lamp electrically neutralizes the drum surface.

1-5

MECHANICAL COMPONENT LAYOUT 6 March 1992

3. MECHANICAL COMPONENT LAYOUT

3.1 COPIER

18 19

22 23 24 25 26 27 28 29 30 31 1 2

3 4

7891011121314151617

1. First Mirror

2. Second Mirror

3. Third Mirror

4. Inverter Guide Plates

5. Duplex Tray

6. Third Tray

7. Pick-up Roller

8. Separation Roller

9. Paper Feed Roller

10. Vertical Transport Unit

11. Relay Rollers

12. Pick-off Pawls

13. Transfer and Separation Corona Unit

14. Horizontal Transport Unit

15. Registration Rollers

16. Pre-transfer Corona Unit

17. Second Tray

18. First Tray

19. Toner Hopper

20. Development Unit

21. Drum Thermistor and Drum Potential Sensor

22. Erase Lamp

23. Fifth Mirror

24. Fourth Mirror

25. Sixth Mirror

26. Charge Corona Unit

27. Quenching Lamp

28. Cleaning Unit

29. Transport Unit

30. Pressure Roller

31. Hot Roller

1-6

Overall

Information

6 March 1992 MECHANICAL COMPONENT LAYOUT

3.2 ARDF

1 2 3 4 5 6 7 8 9

12131415161718

1. Original Tray Extension

2. Upper Exit Rollers

3. Upper Inverter Gate

4. Lower Inverter Rollers

5. Upper Inverter Rollers

6. Switch Back Gate

7. Switch Back Tray

8. Upper Relay Roller

9. Friction Tab

10. 1st Pick-up Rollers

11. 2nd Pick-up Rollers

12. Separation Rollers

13. Lower Relay Roller

14. Pressure Rollers

15. Transport Belt

16. Lower Inverter Gate

17. Lower Exit Rollers

18. CFF Guide

1-7

ELECTRICAL COMPONENT DESCRIPTIONS 6 March 1992

4. ELECTRICAL COMPONENT DESCRIPTIONS

Refer to the electrical component layout on the reverse side of the Point to Point (Water proof paper) index numbers.

4.1 COPIER

Name Function Index. No.

Motors

1st Tray Drive Drives the bottom plate in the 1st tray. 132 2nd Tray Drive Drives the bottom plate in the 2nd tray. 139 3rd Tray Drive Drives the bottom plate in the 3rd tray. 65 Charge Wire Cleaner Drives the charge corona wire cleaner. 74 Development Drives the development unit. 51 Fusing Cooling Fan Cools fins of the de-curling roller. 58 Fusing Exhaust Fan Removes the heat in the de-curling unit. 56 Lens Horizontal Drive Shifts the lens horizontal position. 54 Lens Vertical Drive Shifts the lens vertical position. 57 Main Drives the main unit components. 73 Mirror Unit Drive Positions the mirror unit. 78 Optics Cooling Removes the heat from the optics unit. 77 Scanner Drive Drive the 1st and 2nd scanners. 55 T & S Wire Cleaner Drives the transfer and separation wire cleaner. 72 Toner Supply Rotates the toner supply roller. 75 Vaccum Fan Removes the heat and dust in the machine. 52

Clutches

LCT Drive Transmits the main copier drive to the 1st and 2nd

feed sections. Paper Feed - 1st Tray Drives the paper feed roller of the 1st tray. 134 Paper Feed - 2nd Tray Drives the paper feed roller of the 2nd tray. 159 Paper Feed - 3rd Tray Drives the paper feed roller of the 3rd tray. 66 Paper Feed - Duplex Drives the paper feed roller of the duplex unit. 67 Vertical Transport Unit

Drive Registration Drives the registration roller. 79

PCBs

DC Drive Drives dc components. 116 Drum Current Detection Measures the corona current. 106 Main Controls overall machine operation. 122 Motor Control Controls the dc motors. 123 DC Motor Drive Drives the dc motors. 101 Operation Unit Controls the monitor display. 124 PTL Controls the pre-transfer lamp operation. 121 Quenching Lamp Controls the quenching lamp operation. 120

Transmits the main copier drive to the vertical

transport unit and the 3rd tray.

1-8

Overall

Information

6 March 1992 ELECTRICAL COMPONENT DESCRIPTIONS

Name Function Index. No.

Interface Interface between the main PCB and other PCBs. 115 Vaccum Motor Controls the vacuum fan motor operation. 108

Power Packs

Charge Provides power for the charge corona wire. 103 Development Bias Provides power for the development bias. 104 PTC Provides power for the pre-transfer corona wire. 107 Separation Provides power for the separation corona wire. 105 Transfer Provides power for the transfer corona wire. 102 Power Supply Unit Provides dc power to dc components. 119

Relays

Anticondensation Heater Provides power to the anticondensation heater. 113 Drum Heater 1 Provides power to the drum heater. 114 Drum Heater 2 Provides power to the drum heater. 110 Fusing SSR (16 A) Provides power to the 720 W fusing lamp. 111 Fusing SSR (20 A) Provides power to the 900/950 W fusing lamp. 112 Relay Unit Provides ac power to ac components. 118

Sensor

Auto Responce Turns on the display from the screen saver condition. 93 Drum Potential Detects the drum surface voltage. 95 Duplex Entrance Detects misfeeds. 12 Exit Detects misfeeds. 10 Fusing Unit Detects misfeeds. 9 Image Density Measures the density of the image on the drum. 87 Jogger Home Position Detects when the duplex side plate is at the home

position. Lens Horizontal Encoder Detects the lens horizontal drive motor operation. 5 Lens Horizontal Home

Position Lens Vertical Encoder Detects the lens vertical drive motor operation. 7 Lens Vertical Home

Position Lower Limit - 1st Tray Turns off the 1st tray motor when the tray reaches

Lower Limit - 2nd Tray Turns off the 2nd tray motor when the tray reaches

Lower Limit - 3rd Tray Turns off the 3rd tray motor when the tray reaches

Mirror Unit Encoder Detects the mirror drive motor operation. 29 Mirror Unit Home

Position Paper End - 1st Tray Detects the presence of paper in the 1st tray. 159 Paper End - 2nd Tray Detects the presence of paper in the 2nd tray. 146

Detects when the lens is at the horizontal home

position.

Detects when the lens is at the vertical home

position.

the down position.

Detects when the mirror unit is at the home position.

138

140

1-9

ELECTRICAL COMPONENT DESCRIPTIONS 6 March 1992

Name Function Index. No.

Paper End - 3rd Tray Detects the presence of paper in the 3rd tray. 42 Paper End - Duplex Detects the presence of paper in the duplex tray. 13 Paper Feed - 1st Tray Turn off the 1st tray paper feed clutch. 154 Paper Feed - 2nd Tray Turn off the 2nd tray paper feed clutch. 147 Paper Feed - 3rd Tray Turns off the 3rd tray paper feed clutch. 16 Paper Feed - Duplex Turns off the duplex paper feed clutch. 18 Paper Size 1 - 1st Tray Determines what paper size is in the 1st tray. 133 Paper Size 1 - 2nd Tray Determines what paper size is in the 2nd tray. 142 Paper Size 1 - 3rd Tray Determines what paper size is in the 3rd tray. 35 Paper Size 2 - 1st Tray Determines what paper size is in the 1st tray. 157 Paper Size 2 - 2nd Tray Determines what paper size is in the 2nd tray. 143 Paper Size 2 - 3rd Tray Determines what paper size is in the 3rd tray. 34 Paper Size 3 - 1st Tray Determines what paper size is in the 1st tray. 137 Paper Size 3 - 2nd Tray Determines what paper size is in the 2nd tray. 144 Paper Size 3 - 3rd Tray Determines what paper size is in the 3rd tray. 33 Paper Size 4 - 1st Tray Determines what paper size is in the 1st tray. 135 Paper Size 4 - 3rd Tray Determines what paper size is in the 3rd tray. 32 Paper Size 5 - 3rd Tray Determines what paper size is in the 3rd tray. 39 Paper Size 6 - 3rd Tray Determines what paper size is in the 3rd tray. 38 Paper Size 7 - 3rd Tray Determines what paper size is in the 3rd tray. 37 Paper Size 8 - 3rd Tray Determines what paper size is in the 3rd tray. 36 Paper Volume - 1st Tray Detects the amount of paper in the 1st tray. 131 Paper Volume - 2nd

Tray

Detects the amount of paper in the 2nd tray.

149

Paper Volume - 3rd Tray Detects the amount of paper in the 3rd tray. 31 Pick-up Position -

Duplex Registration Sensor Detects the lead edge of paper to determine the stop

Return Home Position Detects when the 1st scanner is at the return

Scanner Home Position Detects when the 1st scanner is at the home

Detects the duplex pick-up roller position.

timing of a feed clutch and detects misfeeds.

position.

Toner Cartridge Detects when a toner cartridge is in the machine. 2 Toner Coil Overload Detects the toner collection coil drive gear operation. 1 Toner Near End Detects toner near end condition. 28 Transport Detects misfeeds. 20 Tray Paper Position Detects the top sheet position in the 2nd tray. 141 Upper Limit - 1st Tray Sends signal to stop lifting up the 1st tray bottom

plate. Upper Limit - 2nd Tray Sends signal to stop lifting up the 2nd tray bottom

plate. Upper Limit - 3rd Tray Sends signal to stop lifting up the 3rd tray bottom

plate.

161

158

1-10

Overall

Information

6 March 1992 ELECTRICAL COMPONENT DESCRIPTIONS

Name Function Index. No.

Solenoids

2nd Tray Lock Locks the 2nd tray. 136 Cleaning Brings the cleaning blade into contact with the drum. 53 Fork Gate 1 Varies the paper path in the duplex unit depending

on paper size. Fork Gate 2 Varies the paper path in the duplex unit depending

on paper size. Inverter Gate Drives the inverter gate up and down. 61 Junction Gate Drives the junction gate up and down. 60 Pick-up - 1st Tray Lifts the pick-up roller of the 1st tray. 155 Pick-up - 2nd Tray Lifts the pick-up roller of the 2nd tray. 148 Pick-up - 3rd Tray Lifts the pick-up roller of the 3rd tray. 70 Pinch Roller Brings the return pinch rollers into contact with a

paper. Pressure Plate Brings the pressure plate on papers in the duplex

unit. Positioning Lowers the positioning roller in the duplex unit. 64 Duplex Paper Stopper Lowers the paper stopper in the duplex unit. 71

Switches

1st Tray Down Lowers the 1st tray bottom plate. 151 1st Tray Set De-energizes power when the 1st tray is slided to

the left. 2nd Tray Down Lowers the 2nd tray bottom plate. 150 3rd Tray Down Lowers the 3rd tray bottom plate. 40 Anticondensation Turns on the tray heaters. 23 Error Reset Resets error condition. 11 Left Door 1 Turns off the main motor when the left door is open. 25 Left Door 2 Turns off dc 24 volts lines when the left door is open. 24 Main Supplies power to the copier. 26 Right Door 1 Turns off dc 24 volts lines when the right door is

open. Right Door 2 Turns off the main motor when the right door is open. 19 Tray Cover Turns off components when the tray left top cover is

open.

Heaters

1st Tray Removes humidity from the paper in the 1st tray. 156 2nd Tray Removes humidity from the paper in the 2nd tray. 145 3rd Tray Removes humidity from the paper in the 3rd tray. 92 Anticondensation Prevents moisture from forming on the lens and

mirrors. Drum Warms the drum when it gets too cool. 96 Exposure Lamp Warms the exposure lamp when it gets too cool. 86

160

153

1-11

ELECTRICAL COMPONENT DESCRIPTIONS 6 March 1992

Name Function Index. No.

Lamps

Exposure Exposes the original with high intensity light. 85 Fusing 1 Provides heat to the hot roller and keeps the roller at

the operating temperature.

Fusing 2 Provides heat to the hot roller during warm-up. 90 Pre-Transfer Removes excessive positive charge from the drum

surface to the transfer and separation process. Quenching Electrically neutralizes the drum surface prior to

charging.

Thermistors

Drum Monitors the drum temperature. 94 Fusing Monitors the hot roller temperature. 88

Other Components

Total Counter Keeps a count of the number of copies made. 117 FL Stabilizer Stabilizes power to the exposure lamp. 109 Thermofuse Provides back-up overheat protection in the fusing

unit. Anticondensation

Turns off the anticondensation and drum heaters. Thermoswitch

1-12

Overall

Information

6 March 1992 ELECTRICAL COMPONENT DESCRIPTIONS

4.2 ARDF

Symbol Name Function Index. No.

Motors

M1 M2 Belt Drives the transport belt. 16

M3 Inverter Drives the inverter rollers and the exit rollers. 17 M4 Job Separation Drives the job separator. 5

Circuit Boards

PCB1 DF Main Controls overall ARDF functions. 3 PCB2

Solenoids

SOL1

SOL2 Inverter Gate Opens the inverter gate. 23

Feed-in Drives the pick-up rollers, separation rollers

and relay rollers.

Indicator Indicates the Insert Original indicator and the

Auto Feed indicator.

Switch Back Switches the switch back gate position to

directs the original to the switch back tray or onto the exposure glass.

Sensors

S1 Entrance Cover Detects if the entrance cover is open. 4 S2 Lift Detects if the transport unit is open. 14 S3 Inverter Cover Detects if the inverter cover is open. 22

S8 S9 Inverter Jam Detects paper jams in switch back operation. 18

S10

S11

S12 Exit Detects paper jams. 21

S13

S14 Original Width Detects the original width. 13 S15 Timing Supplies timing pulses to the DF main board. 10

Pick-up Roller H.P. Detects if the pick-up roller is in the home

position.

Job Separation H.P.

Job Completion Detects that last original of the first job is fed

Original Detects if the original is set on the original

Registration Sets the feed-in motor, belt motor and inverter

Inverter Registration

Inverter Entrance Sets the inverter motor and the belt motor off,

CFF Detects if the computer form is set in the CFF

Detects if the job separator is in the home position.

from the original table.

table.

motor off timing. Detects original misfeed.

Sets the inverter motor and the belt motor off, reversing timing. Detects original jams.

reversing timing, inverter solenoid and switch back solenoid off timing.

guide. Counts the holes lined up on the computer form.

1-13

DRIVE LAYOUT 6 March 1992

5. DRIVE LAYOUT

1. Main Motor

2. Development Drive Motor

A : Development Unit B : Cleaning Unit C : Relay Transport Unit (to 1st & 2nd Tray) D : Fusing Unit E : Vertical Transport Unit F : Duplex Unit

1-14

Overall

Information

6 March 1992 PAPER PATH

6. PAPER PATH

6.1 SINGLE SIDED COPY -- COPY FACE DOWN

6.2 DUPLEX MODE (1ST SIDE)

1-15

PAPER PATH 6 March 1992

6.3 DUPLEX MODE (2ND SIDE)

6.4 IMAGE OVERLAY MODE (1ST SIDE)

1-16

Overall

Information

6 March 1992 PAPER PATH

6.5 IMAGE OVERLAY MODE (2ND SIDE)

1-17

SECTION 2

DETAILED SECTION

DESCRIPTIONS

6 March 1992 PROCESS CONTROL

1. PROCESS CONTROL

1.1 OVERVIEW

The characteristics of each unit which is related to the copy image reproduction are changed by various factors. To get stable images over long periods and in continuous copy runs, these characteristic changes have to be compensated. The following figure and table show how these factors are compensated on this copier.

Detailed

Descriptions

Potential Sensor

Toner Supply

Development Bias

Exposure Lamp

PTC

Main PCB

Transfer Corona

Charge Corona

ID Sensor

Drum Current Detection PCB

Separation Corona

: Sensing Item : Controlled Item

2-1

PROCESS CONTROL 6 March 1992

Section Characteristics Causes of Change Compensation Method

Drum Charge

Potential

Sensitivity Repeat Stress

Residual Voltage

Charge Corona

Exposure Lamp Intensity Repeat Stress Measure the drum potential of a part

Development Amount of

Charge Potential

Mirror Reflectivity Lens Clearness

Toner Charge

Repeat Stress Temperature Humidity

Temperature Humidity Repeat Stress Temperature Humidity

Dirtiness Temperature Humidity

Dirtiness

Repeat Stress Temperature Humidity

Measure the drum potential of a part that was not exposed (Dark Potential) with the potential sensor and adjust the charge corona output.

Measure the drum potential of a part that was exposed (Light Potential) and adjust the exposure lamp voltage.

Measure the drum potential of a part that was erased by the erase lamp (residual voltage) and adjust the development bias, light potential, and dark potential

Measure the drum potential of a part that was not exposed (dark potential) and adjust the charge corona output.

that was exposed (light potential) and adjust the exposure lamp voltage.

Measure the reflected light intensity of the ID sensor pattern and adjust the toner density in the development unit.

2-2

6 March 1992 PROCESS CONTROL

1.2 IMAGE CONTROL

1.2.1 Latent Image Control

Charge

Exposure

Black White

Erase

Potential Sensor

Drum

The figure shows the changes of the drum potential during the copy process. V0: The drum potential just after charging the drum. Vd (Dark Potential): The drum potential just after exposing the black

pattern (Vd pattern)

Detailed

Descriptions

VL (Light Potential): The drum potential just after exposing the white

pattern (VL pattern)

Vr (Residual Voltage): The drum potential just after the exposure of the

erase lamp.

2-3

PROCESS CONTROL 6 March 1992

[V]

Drum Potential

LightOriginal DensityDark

The above figure shows the relationship between the drum potential and the original density (exposing light intensity). To get constant copy quality, this relationship must be maintained.

Since this relationship tends to change to the one represented by the dotted line by various factors, compensations are required as follows:

A decrease in dark voltage (Vd) is compensated for by increasing the charge corona output. A increase in light voltage (VL) is compensated for by increasing the exposure lamp voltage. Since the residual voltage (Vr) increase cannot be compensated for by increasing the lamp voltage, it is compensated by increasing the development bias voltage and changing the Vd and VL standard value.

1.2.2 Image Density Control

To maintain constant copy image density, the ID sensor detects the toner amount of the ID sensor pattern. From this, it is understood that drum potential is stabilized with the above compensations. According to the detection results, the toner density in the development unit is controlled so that the toner amount on the sensor pattern is constant.

The following sections explain the details of these compensations.

2-4

6 March 1992 PROCESS CONTROL

1.3 PROCESS CONTROL DATA INITIALIZATION

The following flow chart shows all the steps that will be performed whenever the main switch is turned on while the hot roller temperature is below 100°C. This initializes all the process control settings.

Main SW On (Fusing Temp. < 100°C)

Drum Potential Sensor Calibration

Drum Conditioning Start (Fusing Temp. = 160°C)

• Exposure lamp ON

Vsg Adjustment

Lamp Intensity Sensor Calibration

Detailed

Descriptions

Charge Corona Current Adjustment

Vr Measurement

• Lens position shift

• Exposure lamp OFF

• Scanner moves to return position (Vd Pattern)

• Exposure lamp ON

Vd Correction

• Exposure lamp OFF

• Scanner returns to home position (VL Pattern)

• Exposure lamp ON

VL Correction

• Exposure lamp OFF

V01 Detection

• Scanner moves to return position (ADS Pattern)

• Exposure lamp ON

ADS Adjustment

2-5

PROCESS CONTROL 6 March 1992

1.3.1 Drum Potential Sensor Calibration

[A]

Potential Sensor

Bias P.P.

Case

Sensor

Output

Amp.

Drum

RA2

RA1

Drum Current Detection PCB

Relay

TRIG 1 (800V) TRIG 2 (100V) PWM Sensor

Main PCB

The drum potential sensor [A] is located just above the development unit. The sensor has a detector which detects the electric lines of force from the electric potential on the drum. The output of the sensor depends of the number of electric lines of force.

Since the output of the sensor is affected by environmental conditions, such as temperature and humidity, the sensor output is calibrated during process control data initialization.

The drum current detection board has two relay contacts. Usually RA2 grounds the drum. However, during the initialization, the main PCB turns RA1 on and RA2 off and applies the development bias to the drum shaft.

By measuring the outputs of the drum potential sensor when +100 V and +800V are applied to the drum, the sensor output is calibrated automatically.

2-6

6 March 1992 PROCESS CONTROL

1.3.2 Drum Conditioning

When the drum temperature reaches 160°C, the machine starts the drum conditioning process. In this mode, all the coronas and lamps around the drum are activated and drum sensitivity is stabilized, as in continuous copy runs.

1.3.3 Vsg Adjustment

During drum conditioning, the ID sensor checks the bare drum’s reflectivity and calibrates the output of the ID sensor to +4 V.

1.3.4 Lamp Intensity Sensor Calibration

Detailed

Descriptions

Main PCB

PWM

FL Stabilizer

The exposure lamp intensity is monitored by the main PCB through the fiber optics cable. A photodiode on the main PCB converts the light intensity to a dc voltage. The main PCB sends a PWM signal with a 100% duty cycle to the FL stabilizer and checks the monitored voltage, adjusting it to +3 V. This +3 V is used as the light intensity standard.

2-7

PROCESS CONTROL 6 March 1992

1.3.5 Charge Corona Current Adjustment

+12V

GND

-12V

CN342-3

CN342-2 CN342-1

CN341-4

RA1

CN341

-1

CN341-2

Potential S.

CN103-B24

Id Set

CN103-A14

CN104-A28

CN104-B1

CN104-A1

RA2

RA1

HIC1

CN342

-4

T343

CN342

-5

-6

-7

-8

Drum Current Detect PCB MainPCB

PCL

The charge corona current is measured and adjusted automatically by the drum current detect PCB.

The charge corona current flows to the drum current detect PCB through the drum and the drum shaft. The drum shaft is grounded by the drum current detect PCB usually. However, during the process control data initialization, the main PCB activates the corona current circuit in the drum current detection PCB which converts the drum current to a voltage and separates it into ac and dc component outputs. Then, the main PCB reads them through A/D converters as digital data. The main PCB adjusts the corona current by controlling the PWM signal to the charge corona power pack.

When the auto drum current adjustment mode is selected by the SP mode, the drum current detect PCB is used to measure and adjust other corona outputs in the same way.

2-8

6 March 1992 PROCESS CONTROL

1.3.6 Vr Measurement

[V]

Drum Potential

Dark Light

Original Density

The drum residual voltage (Vr) tends to increase during the drums life due to electrical fatigue. The residual voltage cannot be reduced even if the exposure lamp voltage is increased. Therefore, the Vr change has to be compensated by other means.

Detailed

Descriptions

The main PCB checks the drum potential just after the erase lamp exposure, by the drum potential sensor during drum conditioning. The drum potential is in fact Vr. This measured Vr is used as the standard for the following other compensations.

1. Vd Correction

2. VL Correction

2-9

PROCESS CONTROL 6 March 1992

1.3.7 Vd Correction

[V]

Drum Potential

Exposure Glass

Vd Pattern

Dark

Original Density

Light

The drum potential just after the black pattern (Vd Pattern) is exposed (Vd: Dark Potential) tends to lower during drum life due to a decrease in the drum’s capacity to carry a charge.

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

The main PCB measures Vd through the drum potential sensor and adjust it to a target value by adjusting the charge power pack output.

On the other hand, there is a change of the drum residual voltage (Vr), so that the target Vd voltage is compensated as follows:

Target Vd Value: Vd = Vr + 770 V

The adjusted charge power pack output control value (PWM value) is kept in memory until the next initialization.

If the target value cannot be achieved within the charge power pack output control range, the copier indicates the system error on the CRT screen. The copier tries the Vd check again after the error reset. Even if the second Vd adjustment fails, no SC condition is displayed. The previous power pack output control data will be used in this case.

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6 March 1992 PROCESS CONTROL

1.3.8 VL Correction

[V]

VL Pattern

Drum Potential

Dark

Original Density

Light

Detailed

Descriptions

Dirty optics and/or exposure lamp deterioration decreases the intensity of the light that reaches the drum. In addition to this, the drum sensitivity also changes during the drum’s life. These factors change the drum potential just after white pattern exposure (VL: Light Potential).

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

The main PCB measures the VL through the drum potential sensor and adjusts it to a target value by adjusting the exposure lamp output.

The residual voltage change also affects VL, so that VL’s target voltage is compensated as follows:

Target Value of VL: VL1 = Vr + 50 -- 5N (volt) NOTE: N is the setting for the exposure lamp adjustment in the SP mode.

Maximum of 5N = 50

The adjusted exposure lamp output control value (PWM value) is kept in memory until the next initialization.

If the target value cannot be achieved within the exposure lamp output control range, the copier indicates the system error on the CRT screen. The copier tries the VL check again after the SC reset. Even if the second VL adjustment fails, no SC condition is displayed. The previous exposure lamp output control data will be used in this case.

2-11

PROCESS CONTROL 6 March 1992

1.3.9 V01 Measuring

[V]

Drum Potential

Dark

Original Density

Light

Since the ID sensor pattern on the drum is made by the erase lamp and charge corona (except for B4/81/2" x 14" copy mode due to the lens horizontal movement. See toner density detection and supply section for details), the sensor pattern density varies with drum potential just after the charge corona (V0) is applied.

To measure the toner density properly, the development bias for the ID sensor pattern is corrected by measuring the actual drum potential after the charge corona.

During the process control data initialization, the drum potential after the charge corona is applied when the drum sensitivity is stabilized (V01) will be measured and used to determine the bias voltage for the ID sensor pattern development in continuous copy run. The details will be explained in the toner density detection section.

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6 March 1992 PROCESS CONTROL

1.3.10 ADS Adjustment

Exposure Glass

ADS Pattern

Detailed

Descriptions

The ADS pattern is located underneath the exposure glass bracket. During the process control data initialization, the ADS reference voltage is adjusted.

When the first scanner is moved to the return position for the Vd adjustment, the main PCB checks the ADS voltage through the ADS fiber optics cable. The measured voltage is calibrated to the standard voltage (3 V) as the reference for the auto image density control.

2-13

PROCESS CONTROL 6 March 1992

1.4 COMPENSATIONS DURING COPY CYCLE

During continuous copying, the drum sensitivity changes due to the electrical fatigue. The drum sensitivity also changes during rest time.

The following compensations are used for the drum sensitivity changes in the copy cycle:

VL Pattern

[V]

Drum Potential

VBB

Dark Light

Original Density

1.4.1 VL Compensation

The drum light potential (VL) is changed during the copy cycle. To get constant image quality in continuous copy runs, the development base bias is compensated during the copy cycle.

At the beginning of each original scanning, the VL sensor pattern is developed on the drum. The main PCB monitors the drum potential (VL2) of the latent image of the VL sensor pattern through the drum potential sensor, and adjusts the development base bias. See development bias section for details.

Development Base Bias: VBB = VL2 + 170 + 5N

NOTE: N is the setting for the exposure lamp adjustment in the SP mode.

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6 March 1992 PROCESS CONTROL

1.4.2 V02 Measuring

Start key

Charge Corona

Exposure Lamp

Scanner

Drum Potential Sensor

F R

V02 VL2 VL2 VL2 VL2 VL2 VL2 VL2 VL2

9 10 112 3 4 51

Detailed

Descriptions

During the process control data initialization, V01 is measured to determine the development bias for the ID sensor pattern in continuous copy runs. This bias cannot be used for the initial part of the copy run (less that 10 copies) due to the different drum potential after the charge corona is applied.

Whenever the Start key is pressed, the drum potential after the charge corona is measured at the beginning of the copy run (V02).

V02 is used to determine the development bias voltage for the ID sensor pattern which is made at the first copy.

The details will be explained in the Image Density Control section.

2-15

DRUM 6 March 1992

2. DRUM

2.1 OVERVIEW

[E]

[A]

This model uses an FO-type drum made by applying an urethane resin coating [A] on an F-type drum [B]. This coating provides a long life and minimize the white line problems on the half-tone areas.

[C]

[B]

[F]

[D]

For the F-type drum, the charge carrying layer [C] is made by the drum conditioning. Since the FO-type drums are coated after the charge carrying layer has been made, it is not necessary to perform the drum conditioning at the new drum installation.

When drum temperature drops below the permissible level, extreme sensitivity changes occur. Additionally, the temperature changes can cause condensation. To maintain a constant drum temperature, a drum heater [D] (100 V 140 W) which is controlled by a thermistor [E] and two thermoswitches [F] is used.

2-16

6 March 1992 DRUM

2.2 DRUM HEATER CONTROL

160°C 65°C

CN-3 CN-2 CN-1

RA354

RA353

AC100V

Drum Heater

Drum Thermistor

RA353RA354

Drum Heater 1

Drum Heater 2

24V

CN251-B25

24V

CN251-B30

CN251-B26

CN251-A30

Relay PCB

Drum Thermistor

CN255-B9

CN255-A28

CN104-A4

Drum Heater 1

Drum Heater 2

A/D Converter

CN102-A2

CN103-B26

Main PCB

24V

The drum thermistor monitors the drum surface temperature. When the measured temperature reaches 41°C, the main PCB determines that the copier is ready to make copies.

When the main switch is off, the drum heater relays (RA353 and RA354) are off, so that the drum heater is controlled by the 65°C thermoswitch. The thermoswitch is on at 50°C and off at 65°C.

Detailed

Descriptions

When the main switch is on, RA354 is on and bypasses the 65°C thermoswitch from the drum heater control circuit. RA353 turns on or off according to the temperature detected by the drum thermistor.

The drum surface temperature is controlled between 41°C and 50°C. To minimize the power consumption, RA353 is turned on to bypass the drum

heater during the copy cycle.

2-17

DRUM CHARGE 6 March 1992

3. DRUM CHARGE

3.1 CHARGE CORONA UNIT

[A]

This copier uses a dual carbon coated tungsten wire corotron for the drum charge. The corona wire generates a corona of positive ions when the charge power pack [A] applies a high voltage.

The output of the charge power pack is determined by the CPU based on the process control data.

The charge power pack has a leakage sensor. If a leak (short circuit) is sensed, the output is interrupted.

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6 March 1992 DRUM CHARGE

3.2 CORONA UNIT VENTILATION

Detailed

Descriptions

If ozone produced by the corona charge stays in the charge corona area, it may cause uneven corona charging to the drum. To prevent this, ozone is vacuumed out by the vacuum fan through the duct and toner filter in the transport unit, then changed to oxygen by the ozone filter before blown out of the copier.

2-19

DRUM CHARGE 6 March 1992

3.3 CORONA WIRE CLEANER

Paper dust, or toner particles on the charge corona wires may interfere with charging and cause an uneven charge on the drum. The wire cleaner prevents this problem by automatically wiping the charge corona wires clean. Once every 5000 copies, the wire cleaner is activated when the main switch is turned on. The hot roller temperature must be less than 100°C for the wire cleaner to be activated.

When the dc motor in the front end block turns on, it drives the cleaner bracket from the home position to the rear end of the corona unit and then back again.

2-20

6 March 1992 DRUM CHARGE

3.4 CHARGE CORONA POWER PACK

CN311-8 CN311-1 CN311-10

24VP 24V GND24VP

DC Power Supply

CN302-3 CN302-4 CN304-1

CN303-2

303

CN341-6

CN341-8

Door SW

24 V

GND

Drum Current

CN103-A22

DC Drive PCB

Detect PCB

PWM TRIG

Main PCB

Charge Corona P.P.

The main PCB sends a PWM (Pulse Width Modulation) signal to the charge corona power pack. According to the PWM ratio, the dc power pack outputs a high dc voltage to the charge corona wires. The main PCB determines the PWM ratio based on the process control data.

Detailed

Descriptions

There is a safety relay (RA303) on the dc drive board which is activated by a signal from the main PCB. In case of the SC conditions related to the high voltage devices and the abnormal exposure lamp on, the main PCB turns the RA303 to cut the power of dc 24 V to the power pack through its contact.

2-21

ERASE 6 March 1992

4. ERASE

4.1 OVERVIEW

[A]

The electrical charge of the area that does not require any image will be removed by the erase lamp unit [A].

This reduces toner consumption, and the load of the cleaning unit. The erase lamp unit consists of 90 yellow-green LEDs. This reduces drum

light fatigue and allows precise control of the light width. The erase lamp unit is controlled by the main PCB based on factors such as

the reproduction ratio, paper size, SP mode settings, and the image editing settings.

The maximum erase margin error in the image editing mode is 6 mm.

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6 March 1992 ERASE

4.2 ERASE LAMP CIRCUIT

OFF ON

CLOCK

LATCH

CN113-6 CN113-2 CN113-7 CN113-3 CN113-1 CN113-4 CN113-5

S-IN

GND IS

GND CK

LATCH

5V 5V

CN651-5 CN651-E CN651-6 CN651-F CN651-4 CN651-2 CN651-8

S-IN

CLK

DCKQ

LATCH

CN651-C CN561-1 CN561-A CN561-3

GND

5V LED

GND-LED

CN311-8

CN311-15 CN311-16

Main PCB Erase Lamp Unit DC Power

Supply

The main PCB sends the serial bit data to the erase lamp unit with the clock signal. The latch signal holds the ON/OFF condition of the LEDs.

The following charts show the erase lamp control timing.

1. When the ID sensor pattern is not made. (A4/LT, Full Size, and 3rd Feed Mode)

Start Main Motor ON Regist Trail Edge Main Motor OFF

Detailed

Descriptions

1102*1 420* 1633

300 204

VL Pattern

All ON

816 *1

All ON

47*3

53*3

2. When the ID sensor pattern is made. (A4/LT, Full Size, and 3rd Feed Mode)

Start Main Motor ON Regist Trail Edge Main Motor OFF

300 204

All ON

816*1

1466 *1

1602 *1

108

5954

420*2 1633

All ON

47*3

53*3

VL Pattern

ID PatternV02

NOTE: 1. Depends on the paper feed station.

2. Depends on the paper size.

3. Will be changed in Margin Adjustment and Image Editing Mode.

2-23

OPTICS 6 March 1992

5. OPTICS

5.1 OVERVIEW

[A]

[C]

[B]

The optics unit reflects an image of the original on the exposure glass onto the selenium drum. This forms a latent electrical image of the original.

On this model, to minimize power consumption, a fluorescent lamp is used for the exposure lamp [A].

Six high reflection mirrors are used to make the optics unit smaller and obtain a the wide reproduction ratio range (50 -- 200%).

The lens [B] is driven by two stepper motors for (1) vertical direction (parallel to the paper feed direction) and (2) horizontal direction movements.

To correct focal length change in reduction and enlargement modes, the mirror unit [C] (4th and 5th mirrors) position is adjusted by a stepper motor.

The exposure glass has a special coating on one side to minimize the static electricity which may be produced by the original using the document feeder. The coated side is marked and should face up.

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6 March 1992 OPTICS

5.2 SCANNER DRIVE

[C]

[D]

[A]

Detailed

Descriptions

[B]

A dc servo motor is used as the scanner drive motor [A]. The scanner drive motor drives first [B] and second scanner [C] using four

scanner drive wires. The second scanner speed is half of the first scanner speed.

The first and second scanners are supported by the front and rear guide rails [D]. To minimize the friction between the scanners and guide rails, the play of the scanner movement is minimized by high wire tension.

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OPTICS 6 March 1992

5.3 SCANNER POSITION SENSORS

[A]

[B]

There are two scanner position sensors located at the front side of the optics unit.

The scanner home position sensor [A] is used to detect the home position at the machine initialization and during the scan cycle.

The scanner return position sensor [B] is used to detect the scanner position for the process control data initialization (Vd and ADS data). The return position sensor is not used during normal copying.

2-26

6 March 1992 OPTICS

5.4 VERTICAL LENS DRIVE

[B]

[A]

The lens vertical drive motor [A] changes the lens vertical position in accordance with the selected reproduction ratio.

A stepper motor (Approx. 1.8° (0.05 mm)/step) is used to drive the lens through the lens drive belt.

The lens vertical home position sensor [B] detects the lens vertical position for full size mode. The motor control PCB keeps track of the lens position based on the number of pulses sent to the lens vertical drive motor.

[C]

Detailed

Descriptions

The lens vertical drive encoder [C] installed on the drive pulley is used to detect if the vertical lens base locks.

2-27

OPTICS 6 March 1992

5.5 HORIZONTAL LENS DRIVE

[B]

[A]

The original horizontal position on the exposure glass varies in modes (such as platen, ADF, and CFF modes) for easy original handling. On the other hand, the center is the standard position of the paper feed.

Therefore, the lens horizontal position has to be changed according to paper size, reproduction ratio, and the original modes.

A stepper motor (approx. 7.5° (0.35 mm)/step) is used to drive the lens through the lens drive wire.

The lens horizontal home position sensor [A] is used to detect the lens horizontal position for A4/LT sideways, full size, and ADF mode.

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

The lens horizontal drive encoder [B] installed on the drive pulley is used to detect if the horizontal lens base locks.

2-28

6 March 1992 OPTICS

5.6 HORIZONTAL LENS POSITIONING

5.6.1 For Original Position

Copy Paper

6.35

2.5

100%

Lens Position

Horizontal

CFF

12.7 ADF

Platen

Original Front Edge

There are three standard original positions for the platen, ADF, and CFF modes.

ADF mode original position is 5 mm to rear of the platen mode original position to maintain the original transport path (5 mm from the front scale).

CFF mode original position is 17.7 mm (5 + 12.7 mm) to rear of the platen mode original position. This is to maintain the traction hole part transport path (12.7 mm) in ADF.

The above figure shows the lens horizontal positions for each original mode when the identical size paper is used.

Detailed

Descriptions

5.6.2 For Paper Size

Copy Paper

100%

Lens Position

Horizontal

Original Front Edge

To keep the high paper feed performance, the center is assigned as the paper feed standard position. Therefore, the lens horizontal position is changed according to the paper size.

The figure shows the lens horizontal position for each paper size in full size mode.

2-29

OPTICS 6 March 1992

5.6.3 For Reproduction Ratio

50%

Copy Paper

Vertical

100% 200%

Horizontal

Lens Position

Original Front Edge

When the reproduction ratio is changed, the vertical position of the lens is changed. At the same time, the total focal length has to be changed to adjust the image focusing. For this focal length change, the horizontal position of the lens is also adjusted.

The figure shows the lens horizontal position for 50, 100 and 200%.

2-30

6 March 1992 OPTICS

5.7 MIRROR UNIT DRIVE

[A]

Detailed

Descriptions

To compensate the focus change at the reproduction change, the mirror unit (4th and 5th mirrors) position is changed.

A stepper motor (Approx. 7.5° (0.1 mm)/step) is used for the mirror unit drive. A mirror unit home position sensor [A] is used to detect the unit position for

full size mode. The motor control PCB keeps track of the unit position based on the number of motor drive pulses.

2-31

OPTICS 6 March 1992

5.8 MOTOR DRIVE CIRCUIT

Sensors Encoders

Main PCB

Serial Interface

Motor Control PCB

Encoder

DC Motor Drive PCB

Scanner

Drive

Horizontal

Drive

Vertical Drive

Mirror Unit

Drive

The motor control PCB communicates with the main PCB through the serial interface lines. The motor control PCB monitors all the sensor signals and controls the motors through the dc motor drive PCB.

The development motor and the main motor are also be controlled by the dc motor control PCB.

2-32

6 March 1992 OPTICS

5.9 EXPOSURE LAMP UNIT

[C]

[A]

Detailed

Descriptions

[B]

[D]

This copier uses a fluorescent lamp [A] (100 V 84 W). This has the following advantages:

• Low power consumption

• There is no bright point and it is easy to get even luminescence

• A narrow light wave band allows more accurate focusing for various

kinds of originals

• High-speed scanner operation vibration resistance

• Omni-directional luminescence reduces original shadow

Since low fluorescent tube temperature will result in delayed lighting and intensity variation, a tube-type heater (38 V 60 W) [B] is used to maintain the fluorescent tube temperature at approximately 40°C.

The lamp unit has a thermofuse [C] to monitor the lamp temperature and a thermofuse [D] (139°C) for safety.

2-33

OPTICS 6 March 1992

5.10 EXPOSURE LAMP CONTROL

[C]

PWM

[B]

[A]

Exposure lamp intensity must be stabilized during the copy cycle to get a constant latent image on the drum. The main PCB [A] monitors and maintains the light intensity through a fiber optics cable [B]. According to the measured value, a lamp power signal (PWM signal) is sent to the fluorescent lamp stabilizer [C].

The PWM signal output is determined based on the standard value (+3 V at PWM 100% duty cycle) which is set at the process control data initialization (see the Process Control Section for details).

2-34

6 March 1992 OPTICS

5.11 AUTO IMAGE DENSITY CONTROL

50 mm 26 mm

26 mm

50 mm

166 mm

Detailed

Descriptions

The original background density is read through a fiber optics cable on the exposure lamp unit. The sampled strip is at the leading edge of the original and the size depends on the scanner speed (reproduction ratio).

The fiber optics cable conducts the light to a photodiode on the main PCB. The photodiode then converts the density to the ADS voltage. The CPU compares it with the standard ADS value (+3 V), which is set at the process control data initialization by checking density of the white pattern underneath the left exposure glass holder and adjust the development bias accordingly. Detailed bias control is described in the development bias section.

2-35

OPTICS 6 March 1992

5.12 UNEVEN LIGHT INTENSITY CORRECTION

[B]

[A]

[C]

The slit plate [A] corrects the uneven light intensity at the ends and center of the fluorescent lamp [B] and evenly distributes light reflected from the original.

To compensate for reduced light at the lens edges, the shading plate [C] is located in front of the lens. Additionally, the shading plate compensates the light intensity when the lens horizontal position is shifted.

2-36

6 March 1992 OPTICS

5.13 ANTI-CONDENSATION HEATER

[B]

[A]

To prevent condensation in the optics unit, a 40 W anti-condensation heater [A] is installed at the bottom of the lens unit. The anti-condensation heater is controlled by a thermoswitch [B] (On at 17°C, Off at 25°C) under the following conditions:

Detailed

Descriptions

1. The main switch is off.

2. The main switch is on, fusing lamp off in stand-by mode.

3. Machine off condition in weekly timer mode. The anti-condensation heater has a thermofuse (169°C).

5.14 OPTICS COOLING FAN

[B]

[A]

[C]

The light intensity will be decreased if the fluorescent lamp temperature becomes too high. The optics cooling fan [A] blows in cool air from outside through an air filter [B]. Air from the fan also passes through the 6th mirror slit [C] to the drum area. This prevents the optics area from being contaminated by scattered toner in the drum unit.

2-37

DEVELOPMENT 6 March 1992

6. DEVELOPMENT

6.1 OVERVIEW

[E]

[G]

[D]

[C]

[F]

[A]

[B]

This copier uses a double roller (diameter 20 mm each) development system. This system differs from single roller development system in that (1) it develops the image in a narrow area and (2) it develops the image twice. Also, fine toner and developer (smaller particle size) are used. As a result, the image quality, especially of thin lines, the trailing edge of half-tone areas, and black solid areas are improved.

A dc motor is used to drive the development unit. The developer is supplied to the developer guide [A] upper side by the

paddle roller [B]. The magnet of the upper development roller [C] attracts the developer to the roller surface.

The doctor blade [D] trims the developer to the desired thickness and creates back spill to the cross mixing mechanism [E]. The developer is transferred to the lower development roller [F] and then returned to the agitator roller [G] area via a paddle roller.

The development motor has two speeds. When the motor turns at high speed, the developer is supplied to the development rollers. After image development, the motor turns at slower speed to return the developer to the development unit from the development roller sleeves. This prevents developer spillage during the unit replacement.

The development rollers are given a positive bias to prevent the toner from being attracted to the non-image areas, on the drum surface, that may have a slight residual positive charge. The bias voltage is determined based on the factors checked by the process control system.

2-38

6 March 1992 DEVELOPMENT

6.2 DRIVE MECHANISM

[G]

[E]

[F]

[A]

[D]

[C]

[B]

All the development unit parts, except the toner supply brush, are driven by the development drive motor (dc motor).

Detailed

Descriptions

The toner supply brush is driven by the toner supply motor. The development motor drives the development drive gear through two

timing belts. The rotation is transferred as follows:

Upper/Lower

Development Drive Gear [A]

Auger Drive Gear [B]

Idle Gear [C]

Timing Belt [E]

Dev. Roller [D]

Toner Mixing Vane Drive Gear [F]

Idle Gear

Paddle Roller [G]

Since reversed toner mixing vane rotation could damage something, a one-way clutch is installed to the mixing vane drive gear.

2-39

DEVELOPMENT 6 March 1992

6.3 CROSS MIXING

[E]

[A]

[D]

[C]

[B]

This copier uses a standard cross-mixing mechanism to keep the toner and developer evenly mixed. It also helps agitate the developer to prevent developer clumps from forming, and helps create the triboelectric charge.

The developer on the turning upper development roller is split into two parts by the doctor blade. The part trimmed by the doctor blade goes to the backspill plate [A].

As the developer slides down the backspill plate to the agitator [B], the mixing vanes [C] move it slightly toward the rear of the unit.

Part of the developer falls into the auger inlet [D] and is transported to the front of the unit by the auger [E].

The agitator moves the developer slightly to the front as it turns, so the developer stays level in the development unit.

2-40

6 March 1992 DEVELOPMENT

6.4 DEVELOPMENT BIAS

6.4.1 Bias Power Pack

Potential Sensor

Bias P.P.

PWM Duty Cycle = t2/t1 x 100 (%) Output = 10 x PWM Duty Cycle (V)

TRIG 1 (800V) TRIG 2 (100V) PWM Sensor

RA2

RA1

Drum Current Detection PCB

Relay

Main PCB

Detailed

Descriptions

TRIG1 TRIG2 OUTPUT (V)

L H +800

H L +100

L L depends on the PWM signal

H H 0

The bias power pack has three input terminals. Two of them are used as the output selector as shown in the table. When both terminals are low, the output can be controlled by the other input terminal which receives the PWM signal from the main PCB.

+800 and +100 V are used to calibrate the drum potential sensor in the process control data initialization.

2-41

DEVELOPMENT 6 March 1992

6.4.2 Bias Control In Copy Cycle

The bias output is determined by four factors. The total bias is described as;

VB = VBB + VBA + VBS (ADS Mode) VB = VBB + VBM (Manual ID Mode)

1) Base Bias (VBB)

[V]

Drum Potential

Dark

Original Density

VBB

Light

As explained in the process control section, the base bias for development is determined by the drum light potential (VL) measured in each original scan. The base bias is also affected by the exposure lamp adjustment setting in the SP mode.

VBB = VL2 + 170 + 5N NOTE: N = Number of the lamp adjustment setting in SP mode.

2) ADS Compensation (VBA)

(V)

260 200

100

Dark ADS voltage (V) Light

1 2 3

0.97 V

2.75 V

According to the original background density, the bias is compensated. The compensation value is determined with the voltage measured by the ADS sensor (ADS Voltage) as follows:

VBA = --146 x (VADS -- 2.75) NOTE: VBA has a limited range from 0 V to +260 V.

2-42

6 March 1992 DEVELOPMENT

3) Manual ID Selection Position Compensation (VBM)

(V)

120

7 4

--60

--120

--180

ID Selection

According to the manual ID selection position, the bias is compensated as follows:

VBM = 60 x M -- 240 (When M = 1 to 6)

60 x M -- 360 (When M = 7)

NOTE: M = Manual ID selection position. M ranges from 1 (darkest) to 7

(lightest). When manual ID is set to 7 (lightest), the charge corona output is lowered by 10% PWM duty cycle.

Detailed

Descriptions

4) SP Mode ID Selection Compensation (VBS)

In the SP mode, the image density level in the ADS mode can be selected from four steps. The VBS is determined by the SP setting as follows:

Selected level VBS (V)

L +60 N 0 (Default) H --60

VH --120

2-43

DEVELOPMENT 6 March 1992

6.4.3 Bias for the ID Sensor Pattern

A3/11" x 17"

Lens Position

VL Pattern

B4/81/2" x 14"

A4/81/2" x 11"

Exposure Glass

ID Sensor Pattern

Outside

The lens horizontal position is different in the used paper size on this mode. On the other hand, the ID sensor position is fixed at one position. Therefore, the ID sensor pattern on the back side of the exposure glass bracket will be positioned on the drum only when B4/81/2" x 14" size paper is used.

The sensor pattern on the drum is made for each paper size as follows (100%):

Paper Size Pattern (Black) A4/A5/81/2" x 11"/51/2" x 81/2" Outside image of exposure glass (no light) B4/81/2" x 14" ID sensor pattern on the exposure glass

bracket

A3/11" x 17" Exposure lamp off (no light)

The potential of the drum in these cases, the no light and the ID sensor pattern exposure, is not the same. So the ID sensor bias (VBP) is determined using two base voltages, V0 for the no-light condition and VD for the pattern.

VBP (no light) = --360 + V0 VBP (ID Pattern) = --360 + Vd

The Vd value which is determined during the process control data initialization will be used.

V01 and V02, which are explained in the process control section, are used for the VBP calculation as the V0 (drum potential after the charge corona) value.

The VBP can be changed by the SP mode (Toner Density Correction). The following compensation will be applied to the above VBP.

Setting L N H VH

(V) --60 0 +60 +120

Default: H (+60 V)

2-44

6 March 1992 TONER DENSITY DETECTION AND SUPPLY

7. TONER DENSITY DETECTION AND SUPPLY

7.1 TONER SUPPLY MECHANISM

[B]

[A]

[B]

[D]

[C]

The main PCB monitors the ID sensor pattern density on the drum through the ID sensor once every ten copies and turns on the toner supply motor

when the pattern density is low (if Vsp/Vsg ≥ 1/13). The toner supply motor [A] turns the toner supply roller [B] for a certain period

based on the paper size and the supply amount set by SP mode.

Detailed

Descriptions

A brush roller with low rotation torque and that can supply large amounts of toner even with low operation speed, is used for the toner supply roller.

Toner mixing vanes [C] turn slowly while contacting the inner wall surface of the toner tank whenever the development motor is turning. This prevents toner blockages, and supplies toner to the toner agitator [D].

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TONER DENSITY DETECTION AND SUPPLY 6 March 1992

7.2 TONER DENSITY DETECTION

7.2.1 ID Sensor Pattern Production

Main SW ON

Counter A Counter B

ID Sensor Pattern

Start Key

Start Key Start Key

1 2 3 1 2 10

1 2 3 1 2 10 11 1 2 1 2 3 4 5 13 1 2 3

1 2

Drum sensitivity varies from copy to copy. Especially, drum rest time affects drum sensitivity.

To compensate the sensitivity changes in the copy run, the ID sensor development timing and development bias is controlled using two copy counters.

Counter A: Counts the copy number. Resets when the Start key is pressed.

Counter B: Counts the copy number. Resets if the accumulated number is 10 or above when the Start key is pressed, or when the ID sensor pattern is made.

NOTE: Both counters are reset when the main switch is turned on or the

doors are opened.

The ID sensor pattern is made in the following conditions:

1) At the leading edge of the first copy cycle after the main switch is turned on or when the doors are opened.

2) If A ≥ 10 At the trailing edge of the copy cycle when; A = 10n (n: any numeric number)

3) If A < 10 When the last copy is finished and B ≥ 10, then the pattern is

developed at the leading edge of the next copy cycle.

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6 March 1992 TONER DENSITY DETECTION AND SUPPLY

7.2.2 Toner Density Detection

(V)

Vsg = 4.0

1/13 Vsg = 0.31

LED ON

LED

Detailed

Descriptions

Vsg

Bare drum

Sensor pattern

(T)

Vsp

Vsg

Vsp

Low image density

1/13 Vsg

High image density

The ID sensor measures the density of the ID sensor pattern developed on the drum. The main PCB receives two values of the sensor output, the value for the sensor pattern (Vsp) and the value for the bare drum (Vsg).

Toner will be supplied under the following condition:

Vsp/Vsg ≥ 1/13

2-47

TONER DENSITY DETECTION AND SUPPLY 6 March 1992

7.2.3 ID Sensor Abnormal Conditions

a. Vsp Abnormal

If the measured Vsp is 1.4 V (when Vsg = 4 V) or more and this condition is detected five times in a row, a system error condition will be indicated on the CRT and the 7% fixed toner supply control will be used for the rest of the copy run.

b. Vsg Abnormal

If the measured Vsg during ID sensor pattern detection is 2.5 V or less and this condition is detected five times in a row, a system error condition will be indicated on the CRT and the 7% fixed toner supply control will be used for the rest of the copy run.

If both abnormal values return to normal during the copy run, the toner supply control will also be returned to normal.

7.3 TONER SUPPLY AMOUNT

Vsp (V)

(at Vsg = 4.0 V)

0.3 ≤ Vsp < 0.4

0.4 ≤ Vsp < 0.5

0.5 ≤ Vsp

The toner supply ratio is determined based on the supply amount data in SP mode and Vsp values as shown in the above table.

The table shows the amount for the A3/DLT mode. When smaller paper is used, the supply amount becomes half.

The toner supply roller turns for a period based on the selected supply ratio.

Toner Supply Amount Data in SP Mode

15% 30% 45% 60%

7 15 15 30 15 30 45 45 30 45 60 60

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6 March 1992 TONER DENSITY DETECTION AND SUPPLY

7.4 TONER CARTRIDGE

[A]

Detailed

Descriptions

[B]

When the toner cartridge is set, the toner cartridge sensor [A] is de-actuated. The main PCB monitors the toner cartridge sensor signal and detects if the cartridge is replaced at the toner end condition. The main PCB inhibits copying if there is no toner cartridge.

The toner cartridge is also used as the used toner collection tank. The copy image becomes poor if the collected toner is re- used. To prevent accidental re-used of the collected toner, a spring plate lock mechanism [B] is installed. The lock allows the toner cartridge shutter to be pulled and returned only once.

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TONER DENSITY DETECTION AND SUPPLY 6 March 1992

7.5 TONER END DETECTION

7.5.1 Toner Near End Detection

[C]

[B]

[A]

[D]

[E]

Toner near end is detected by measuring physical amount of toner remaining in the toner tank by the following mechanism.

The toner near end feeler [A] has a magnet [B] and is installed on the toner mixing vane drive shaft [C]. The toner near end sensor [D] is located underneath the toner tank (outside) and has the sensor actuator [E] with a magnet. When the toner tank has enough toner, the toner near end feeler does not lower due to the resistance of toner.

When the remaining toner amount in the toner tank becomes below approximately 250 grams, the near end feeler lowers and repulses the sensor actuator by the magnet’s repulsion force. This actuates the toner near end sensor. When the main PCB senses the toner near end sensor actuation three times in a row, the toner near end condition is displayed on the CRT screen to let the operator know to replace the toner cartridge. In the toner near end condition, copies can be made until the toner end is detected by the ID sensor.

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6 March 1992 TONER DENSITY DETECTION AND SUPPLY

7.5.2 Toner End Detection

When little toner remains in the toner tank, the amount of toner supplied to the development unit decreases, and the image of the ID sensor pattern gets lighter.

When the Main PCB detects the low ID sensor pattern density condition (Vsp/Vsg > 1/8) more than three times in a row during the toner near end condition (physical check), the toner end condition is displayed on the CRT screen and copying is inhibited until the toner cartridge is replaced.

Detailed

Descriptions

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IMAGE TRANSFER AND PAPER SEPARATION 6 March 1992

8. IMAGE TRANSFER AND PAPER SEPARATION

8.1 PRE-TRANSFER DISCHARGE

[A]

[B]

The pre-transfer corona (PTC) [A] and pre-transfer lamp (PTL) [B] are used to prevent incomplete toner transfer and pick-off pawl marks on the copy.

To prevent incomplete toner transfer, the PTC reduces drum potential by applying an ac corona. The PTC also applies a dc negative charge at the same time to keep the toner potential negative.

The PTL further reduces the drum potential. Since the PTC gave a negative charge not only to the toner but also to the non image (no toner) area on the drum, PTL reduces the negative charge on the drum which may attract copy paper and cause pick-off pawl marks.

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6 March 1992 IMAGE TRANSFER AND PAPER SEPARATION

8.2 IMAGE TRANSFER

[A]

Detailed

Descriptions

[B]

The copy paper is fed from the registration section to the transfer and separation section through the guide mylar [A] which holds the copy paper so that the paper sticks to the drum surface.

The transfer corona [B] applies a positive charge from the back side of the copy paper to attract the negatively charged toner image from the drum to the copy paper.

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IMAGE TRANSFER AND PAPER SEPARATION 6 March 1992

8.3 PAPER SEPARATION

[A]

To break the attraction between the paper and the drum, the separation corona applies an ac corona to the back side of the paper. The stiffness of the paper then causes it to separate from the drum. The pick-off pawls [A] which are installed on the cleaning unit assist paper separation.

Two corona wires are used to improve separation by widening the discharge area. Also, a larger corona current is applied at the leading edge of the paper for the same purpose.

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6 March 1992 IMAGE TRANSFER AND PAPER SEPARATION

8.4 TC/SC WIRE CLEANER

Detailed

Descriptions

The transfer and separation corona unit has the wire cleaners to remove paper dust and/or toner particles which may get on the corona wires.

Once every 5000 copies, the wire cleaners are activated when the main switch is on. The hot roller temperature must be less than 100°C for the wire cleaner to be activated.

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IMAGE TRANSFER AND PAPER SEPARATION 6 March 1992

8.5 PICK-OFF PAWLS

[A]

The pick-off pawls assist the paper separation process. The pick-off pawls are kept normally in contact with the drum.

When the transport unit is lowered, the pick off pawls are released from the drum.

The pick-off pawl shaft is contacted to the cam gear [A] which is located at the front side and driven by the drum flange gear. The cam gear gives side-to-side movement to the pick-off pawl shaft to prevent toner from accumulating on the pick-off pawls.

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6 March 1992 IMAGE TRANSFER AND PAPER SEPARATION

8.6 TRANSPORT UNIT

Detailed

Descriptions

Four transport belts are used to transport the copied paper to the fusing section. The vacuum fan sucks the air through the holes on the transport unit to hold the paper on the transport belts.

The transport unit is pushed up and locked into position by the front and rear guide rollers. Turning the transport unit release lever to the left releases the lock and lowers the unit to clear paper jams.

If ozone produced by the corona charges stays in the drum area, it may cause uneven corona charging or affect drum sensitivity causing poor image problems.

The vacuum fan sucks the ozone through the air duct and transports it to the ozone filter. Ozone is changed to oxygen by the filter and blown outside the copier.

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CLEANING 6 March 1992

9. CLEANING

9.1 OVERVIEW

[B]

[C]

[A] This copier uses the counter blade system for drum cleaning. The blade 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 PCC and cleaning bias are not used for this copier.

The cleaning brush is used to support the cleaning blade. A looped-type brush is used for better efficiency. The brush collects toner from the drum surface and scraped by the cleaning blade. The flick bar [A] and the flick roller [B] mechanically remove toner on the cleaning brush. Toner is transported to the toner cartridge by the toner collection coil [C].

To remove the accumulated toner at the edge of the cleaning blade, the drum turns in reverse for about 20 mm at the end of every copy job. The accumulated toner is removed by the cleaning brush by this action. All the driven gears except the drum drive gear have one-way clutches to prevent reverse rotation during this operation.

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6 March 1992 CLEANING

9.2 DRIVE MECHANISM

[B]

[A]

[C]

[E]

[G]

[D]

Detailed

Descriptions

[F]

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 then transmits the force to the front side through the cleaning brush [C] and flick roller [D]. The force at the front side is used for the blade cam gear [E] and toner collection coil gear [F].

There is a one-way clutch in the transport unit drive gear [G] to prevent the drive parts in the cleaning unit from receiving the reverse rotation force.

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CLEANING 6 March 1992

9.3 CLEANING BLADE PRESSURE MECHANISM

[A]

[B]

[C]

[D]

When the cleaning solenoid [A] is energized, the solenoid arm lowers the pressure arm [B]. This frees the pressure release lever [C] and the blade spring [D] applies pressure to the cleaning blade.

To ensure cleaning blade operation, +38 V is applied to the solenoid for 0.3 seconds as initial activation, then +24 V is applied.

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6 March 1992 CLEANING

9.4 CLEANING BLADE SIDE-TO-SIDE MOVEMENT

[A]

[B]

The cleaning blade is held on the cleaning blade holder with a shoulder screw [A] at its center so that the cleaning pressure is evenly applied to the drum surface.

The cleaning blade holder touches the cam gear [B] which gives a side-to-side movement to the blade. This movement prevents the cleaning blade from being damaged.

Detailed

Descriptions

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CLEANING 6 March 1992

9.5 TONER COLLECTION MECHANISM

[B]

[A]

Toner collected by the cleaning unit is transported to the toner cartridge through the toner collection tubes. Three helical coils are used for the toner transport.

A magnetic disk torque limiter [A] is used on the toner collection coil drive mechanism to prevent the coil from being damaged by toner clogged in the collection tube. The toner collection coil drive gear [B] has two actuators for the coil overload sensor. The main PCB monitors the sensor output and display an SC code if no signal changes are detected for more than 3 seconds while the development motor is turning.

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6 March 1992 CLEANING

9.6 TONER SCATTERING PREVENTION

[A]

Detailed

Descriptions

[B]

The cleaning unit has two air outlets covered by the cleaning filter on its back side. The vacuum fan draws the air from the cleaning unit through the cleaning filters [A] and the toner filter [B] located above the transport section. This prevents the toner in the cleaning unit from being scattered to the drum area.

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CLEANING 6 March 1992

9.7 CLEANING SOLENOID CIRCUIT

Main PCB

24V

38V

Scan 2

CN103-A3

-A2

-B11

-B6

CN104-B24

Cleaning Sol

Scan 2

DATA10

DC Drive PCB

CN304

-5 RA301

CN303-5

CN303-2

301

303

Interface PCB

CN256

-B1

-A10

RA303

CN302-5

CN304-1

CN258

38VFL OUT 38VFL IN

24V

-6

-3

-4

-5

-7

-8

12V 24V GND GND 5V

Overload Sensor

GND

12V

The main PCB energizes RA301 and 303 for 0.3 seconds to supply +38 V for the cleaning blade solenoid at the initial solenoid activation. The RA301 and 303 are then turned off and +24 V is supplied to the cleaning solenoid.

The main PCB sends a pulse signal to the coil overload sensor through the interface PCB. When the overload sensor is actuated, the pulse signal is returned to the main PCB. The main PCB is monitoring this signal change for toner collection coil blocking.

2-64

6 March 1992 CLEANING

9.8 CLEANING BLADE SOLENOID CONTROL

Detailed

Descriptions

1500

[A]

38V

200

24V

Cleaning Sol.

Main MotorFR

Start Key

38V

300

24V

300

[B]

500

1500

[B]

The main motor turns in reverse for 40 pulses at the end of every copy job. At this time, the cleaning solenoid is kept on to clean off the toner on the cleaning blade edge. When the drum temperature is more than 49°C [A], the toner on the cleaning blade edge may soften and clog due to heat. To prevent this, the cleaning blade is released from the drum at the start of the drum reverse rotation. The blade touches the drum again while drum is still turning in reverse (due to inertia) to clean the edge of the blade.

The cleaning solenoid off timing [B] is determined based on the accumulated number of copies as follows:

Accumulated copy number Off Timing

≥ 100 copies

15 seconds after the main motor off

< 100 copies

5 minutes after the main motor off

This is to minimize toner scattering in the machine. The cleaning solenoid is turned off when the main switch is off or the front

doors are opened.

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QUENCHING 6 March 1992

10.QUENCHING

[B]

[A]

To neutralize any charges remaining on the drum, a cold cathode fluorescent lamp [A] (CFL) is used as the quenching device.

When the main PCB sends a trigger signal to the the CFL stabilizer [B], an ac power (ac 480 V/5 mA) is supplied to the CFL.

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6 March 1992 PAPER FEED

11. PAPER FEED

11.1 OVERVIEW

[A]

[B]

This machine feeds paper from three trays. (Capacity: 1st tray [A]: 550, 2nd tray [B]: 3000, 3rd tray [C]: 1500).

Paper is positioned at the center of the trays.

Detailed

Descriptions

[C]

This copier uses an FRR (Feed + Reverse Roller) paper feed system which uses three rollers: pick-up roller, feed roller, and separation roller. A permanent magnet is used as a torque limiting device for the separation roller.

One anticondensation switch for all tray heaters is installed on this copier. A tray heater is installed on each tray and turns on when the anticondensation switch is on while the main switch is off.

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PAPER FEED 6 March 1992

11.2 PAPER FEED AND SEPARATION

[A]

[D]

[B]

[C]

While the main motor is rotating, the paper feed clutch gear [A] is being driven from the main motor drive and is always rotating. The separation roller shaft [B] is turning in the direction indicated by the arrow in the illustration. The separation roller driven by the separation roller shaft is prevented from turning in the paper feed direction by the built-in torque limiter [C]. The separation roller uses a friction mechanism to overcome the torque and stop the roller. The separation roller shaft speed is reduced by the low rotational drive ratio of the drive gear [D] against the feed clutch gear. This reduces the main motor load.

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6 March 1992 PAPER FEED

[B]

[A]

[C]

[E]

[D]

[F]

[G]

Using the paper feed trigger signal from the main control board the paper feed clutch [A] turns on and paper feed roller shaft [B] begins to turn. A one-way clutch drives the paper feed roller [C]. The pick-up roller [D] rotates via an idler gear. Then, paper feed begins. A one-way clutch allows the separation roller shaft to drive at high speed in the direction indicated by the white arrows in the illustration. This is because the high rotational drive ratio of the drive gear [E] against the feed clutch gear. However, as the separation roller [F] rotates in contact with the paper feed roller, the separation roller rotates in the direction of the black arrow.

Detailed

Descriptions

Paper is fed by the operation described above. The paper feed sensor [G] senses the paper and the pick-up solenoid activates. The pick-up roller is then lifted up to its upper position which is out of the paper path. Simultaneously, the paper feed clutch temporarily turns off.

This process of turning off the paper feed clutch as paper reaches the paper feed sensor is called pre-registration and is necessary due to the high copy speed. The paper waits at that point until the proper time, and then the clutch turns on again to feed the paper to the following transport relay rollers.

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PAPER FEED 6 March 1992

11.3 FRR OPERATION

[A]

[D]

[E]

[B]

[C]

The direction in which the separation roller turns depends on the frictional forces acting on it. The magnetic torque limiter applies a constant clockwise force [F1]. When there is a single sheet of paper being driven between the rollers, the force of the friction between the feed roller and paper [F2] is greater than F1. So, the separation roller turns counter clockwise.

If 2 or more sheets are fed between the rollers, the forward force on the second sheet [F3] becomes less than F1 because the friction between the two sheets is small. So, the separation roller starts turning clockwise and drives the second sheet back to the tray.

11.4 MAGNETIC TORQUE LIMITER

Depending on the inner and outer magnetic force, the torque is transmitted to the separation roller shaft as shown below.

Separation roller drive [A] → Rotor [B] → Inner magnet [C] ←→ Outer magnet [D] → Casing [E] → Separation roller rotation

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6 March 1992 PAPER FEED

11.5 PAPER RETURN MECHANISM

[C]

[B]

[A]

Detailed

Descriptions

[C]

3 mm

[E]

[F]

[D]

The paper feed clutch [A] turns on and the paper feed roller shaft turns in the direction indicated by the arrow in the illustration. The swing lever [B] is raised by spring tension until it contacts the stopper [C]. In this condition, paper feed begins.

When the clutch turns off, the swing arm remains in the raised position. The separation roller [D] and feed roller [E] can rotate in the direction of paper return until the swing lever meets the inside stay [F]. Then, the separation roller and feed roller stop rotating. This operation returns paper between the reverse and feed rollers to the tray to prevent paper damage when the tray unit is pulled out.

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PAPER FEED 6 March 1992

11.6 PAPER END DETECTION

[B]

3rd Tray

[A]

[B]

1st and 2nd Tray

The paper end sensor [A] is installed at the rear of the tray bottom plate. The paper end condition is detected by the photo-interrupter and feeler [B]. When there is no paper remaining in the tray, the feeler rises from the tray bottom hole to deactuate the photo-interrupters for the 1st and 2nd tray, and to actuate the photo-interrupter for the 3rd tray.

[A]

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6 March 1992 PAPER FEED

11.7 PAPER VOLUME DETECTION

[A]

Detailed

Descriptions

Each tray uses a pulse generator [A] to determine the quantity of paper in the tray. The amount of paper present is based on the number of pulses generated between the time the tray starts moving up and the time the upper limit sensor turns off.

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[A]

PAPER FEED 6 March 1992

11.8 PAPER TRAY DRIVE MECHANISM

11.8.1 1st & 3rd Tray

[D]

[B]

1st Tray

[E]

[C]

[B]

[D]

[A]

3rd Tray

[H]

[F]

[G]

Drive from a reversible motor [A] is transmitted trough a worm gear [B] to the drive pulley [C] shaft. The tray wires have metal beads on them. These beads are inserted in the slots at the ends of the tray support bracket [D] of the bottom plate, so, when the wire pulley turns (counterclockwise, rear view), the beads on the wires drive the tray support bracket and the tray moves upward. The tray goes up until the upper limit sensor [E] is actuated by the top sheet pushing up the pick-up roller [F].

To lower the tray, the pulley turns clockwise until the lower limit sensor [G] is actuated by the actuator of the bottom plate [H].

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6 March 1992 PAPER FEED

[H]

[A]

[B]

11.8.2 2nd Tray

[D]

[C]

[E]

[F]

Detailed

Descriptions

[G]

Drive from a reversible motor [A] is transmitted trough a timing belt and a worm gear [B] to the drive gear [C] shaft. The tray chains connect the ends of the tray support bracket [D] of the bottom plate, so, when the drive gear turns (clockwise, rear view), the chains drive the tray support bracket and the tray moves upward. The tray bottom plate goes up until the upper limit sensor [E] is actuated by the top sheet pushing up the pick-up roller [F].

If the tray down switch is pressed or paper runs out, the drive gear rotates counterclockwise to lower the bottom plate. However, it is not lowered all the way down at this time. When the tray paper position sensor [G] turns off, the drive gear stops once. At this point, the bottom plate (or the top sheet of paper) is positioned about 70 mm below the feed position. This gives enough space for the customer to replenish about 500 sheets of paper. If the tray down switch is then pressed again, the bottom plate moves down and again stops once the top sheet of the paper just passes the paper position sensor. In this way, the bottom plate is lowered 70 mm at each press of the tray down switch. This allows the customers to replenish paper in convenient amounts and at the same position.

The bottom plate stops going down when the lower limit sensor [H] is actuated by the actuator of the bottom plate even if the paper tray position sensor is on.

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PAPER FEED 6 March 1992

11.9 TRAY LOCK MECHANISM

11.9.1 1st & 3rd Tray

[D]

[A]

[B]

[A]

[B]

[C]

[D]

[C]

[E]

1st Tray

3rd Tray

When the tray is set, it is positioned by the lock arm [A]. The roller of the lock arm presses against the lock plate [B]. And the lock lever [C] engages the 1st tray top cover stopper [D] (in case of the 3rd tray: tray stopper [E]) to prevent the top cover or 3rd tray from being opened or pulled out while the tray is in the up position.

When the tray moves to the down position, the tray bottom pushes the release lever and 1st tray top cover stopper or 3rd tray stopper is de-engaged, allowing the top cover or 3rd tray to be opened or pulled out.

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6 March 1992 PAPER FEED

11.9.2 2nd Tray

[C]

[E]

[B]

[C]

[E]

[D]

[A]

When the tray is set, it is positioned by the lock arm [A]. The roller of the lock arm presses against the lock plate [B]. And the lock lever [C] engages the right side plate stopper [D] to prevent the tray from being pulled out while the tray is in the up position.

Detailed

Descriptions

When the tray moves to the down position, the lock solenoid [E] turns on. The lock lever then releases the right side stopper, allowing the tray to be pulled out. The solenoid will remain on for one minute. After one minute, the lock solenoid and tray down switch turns off. The tray cannot be pulled out. The lock solenoid will turn off while the tray is pulled out. This lock solenoid on off operation is performed to keep the solenoid reliable.

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PAPER FEED 6 March 1992

11.10 SIDE-TO-SIDE REGISTRATION

11.10.1 1st Tray

[A]

The plate [A] under the tray bottom plate can be moved from rear to front by loosening 5 screws. This plate position determines the side-to-side registration.

11.10.2 2nd & 3rd Tray

[C]

[B]

[C]

[B]

2nd Tray

3rd Tray

The tray stopper [B] is fixed to the tray side. The tray stopper bumper [C] is fixed to the main body or tray body. The tray stopper and bumper determine the side-to-side registration.

2-78

Ricoh FT8780 Service manual

Specifications and Main Features

Frequently Asked Questions

User Manual

6 March 1992 SPECIFICATIONS

COPY PROCESSES AROUND THE DRUM 6 March 1992

MECHANICAL COMPONENT LAYOUT 6 March 1992

3.1 COPIER

3.2 ARDF

ELECTRICAL COMPONENT DESCRIPTIONS 6 March 1992

4.1 COPIER

4.2 ARDF

DRIVE LAYOUT 6 March 1992

6 March 1992 PAPER PATH

6 March 1992 PROCESS CONTROL

1.1 OVERVIEW

1.2 IMAGE CONTROL

1.3 PROCESS CONTROL DATA INITIALIZATION

1.4 COMPENSATIONS DURING COPY CYCLE

DRUM 6 March 1992

2.1 OVERVIEW

2.2 DRUM HEATER CONTROL

DRUM CHARGE 6 March 1992

3.1 CHARGE CORONA UNIT

3.2 CORONA UNIT VENTILATION

3.3 CORONA WIRE CLEANER

3.4 CHARGE CORONA POWER PACK

ERASE 6 March 1992

4.1 OVERVIEW

4.2 ERASE LAMP CIRCUIT

OPTICS 6 March 1992

5.1 OVERVIEW

5.2 SCANNER DRIVE

5.3 SCANNER POSITION SENSORS

5.4 VERTICAL LENS DRIVE

5.5 HORIZONTAL LENS DRIVE

5.6 HORIZONTAL LENS POSITIONING

5.7 MIRROR UNIT DRIVE

5.8 MOTOR DRIVE CIRCUIT

5.9 EXPOSURE LAMP UNIT

DEVELOPMENT 6 March 1992

6 March 1992 TONER DENSITY DETECTION AND SUPPLY

IMAGE TRANSFER AND PAPER SEPARATION 6 March 1992

CLEANING 6 March 1992

QUENCHING 6 March 1992

6 March 1992 PAPER FEED

11.1 OVERVIEW

11.2 PAPER FEED AND SEPARATION

11.3 FRR OPERATION

11.4 MAGNETIC TORQUE LIMITER

11.5 PAPER RETURN MECHANISM

11.6 PAPER END DETECTION

11.7 PAPER VOLUME DETECTION

11.8 PAPER TRAY DRIVE MECHANISM

11.9 TRAY LOCK MECHANISM