Okidata OKICOLOR 8 MAINTENANCE MANUAL
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OKICOLOR 8
Color LED Page Printer
Maintenance Manual
1999.7.14 Rev. 1
PREFACE
This maintenance manual provides procedures and techniques for the troubleshooting, maintenance, and
repair of OKICOLOR 8.
This manual is written for maintenance personnel, but it should always be accompanied with the
OKICOLOR 8 User’s Manual for procedures for handling and operating the OKICOLOR 8.
For repairing each component of OKICOLOR 8, see the Troubleshooting manual.
[Notices]
The contents of this manual are subject to change without prior notice.
Although reasonable efforts have been taken in the preparation of this manual to assure its accuracy, this
manual may still contain some errors and omissions. OKI will not be liable for any damage caused or
alleged to be caused, by the customer or any other person using this maintenance manual to repair,
modify, or alter the OKICOLOR 8 in any manner.
[Warning]
Many parts of OKICOLOR 8 are very sensitive and can be easily damaged by improper
servicing. We strongly suggest that OKICOLOR 8 be serviced by OKI’s authorized technical service
engineers.
41057610TH Rev. 1 2 /
CONTENTS
1.SPECIFICATIONS............................................................................................6
1.1 Basic System Configuration.............................................................................................6
1.2 Printer Specifications.......................................................................................................7
1.3 Option Specifications.......................................................................................................8
1.4 Basic Specifications........................................................................................................9
2.OPERATION...................................................................................................12
2.1 Main Control Board (PCE PCB)....................................................................................13
2.2 Engine Control Board (PX4 PCB)..................................................................................16
2.3 Power/Units....................................................................................................................17
2.4 Mechanical Processes...................................................................................................18
2.4.1 Electrophotographic processing mechanism....................................................19
2.4.2 Paper running process.....................................................................................25
2.5 Sensors..........................................................................................................................34
2.5.1 Paper related sensors......................................................................................34
2.5.2 Other sensors...................................................................................................35
2.6 Correction of Color Deviation.........................................................................................36
2.7 Transfer Control according to Environmental Changes
(Room Temperatures and Relative Humidities).............................................................36
2.8 Form Jam Detection.......................................................................................................37
2.9 Cover Opening...............................................................................................................37
2.10Toner Low Detection......................................................................................................38
2.11Page Size Detection......................................................................................................39
2.12Power-on Processing.....................................................................................................40
2.12.1Self-diagnostic test...........................................................................................40
3.PARTS REPLACEMENT................................................................................41
3.1 Precautions for Parts Replacement...............................................................................41
3.2 Parts Layout...................................................................................................................43
3.3 How to Change Parts.....................................................................................................47
3.3.1 Cover Assy Rear..............................................................................................48
3.3.2 Motor-Fan (80-25)............................................................................................49
3.3.3 Paper Eject Assy..............................................................................................50
3.3.4 Cover Assy Stacker, Guide Eject FD Assy.......................................................51
3.3.5 Frame Assy Upper............................................................................................52
3.3.6 Plate Support Assy...........................................................................................53
3.3.7 Limiter 2way (L), (R) / Plate Guide (L) , (R)......................................................54
3.3.8 Cover55
3.3.9 PCB Assy : PCE...............................................................................................56
3.3.10Motor Fan (CU).................................................................................................57
3.3.11PXF PCB/PX4 PCB..........................................................................................58
3.3.12Gear Heat Assy................................................................................................59
3.3.13Main Motor (A), (B) Assy..................................................................................60
3.3.14Gear One-way (Z30).........................................................................................61
3.3.15Motor Assy BT..................................................................................................62
3.3.16Power Supply Unit, Holder Inlet, Sheet Insulation............................................63
3.3.17Sensor Assy Box Toner....................................................................................64
3.3.18Square-shaped Connector...............................................................................65
3.3.19Hopping Motor..................................................................................................66
3.3.20Gear One-way..................................................................................................67
3.3.21Feeder Unit Front.............................................................................................68
3.3.22Manual Feed Hopper Assy...............................................................................69
3.3.23Guide Paper Input Assy....................................................................................70
3.3.24Two Lever Input Sensors, Lever 2nd Feed Sensor..........................................71
3.3.25Roller Registration, Roller Assy Hopping.........................................................72
41057610TH Rev. 1 3 /
3.3.26Roller Hopping..................................................................................................73
3.3.27PXU PCB/PXM PCB, Lever Resist Sensor......................................................74
3.3.28Paper End Lever...............................................................................................75
3.3.29PCO PCB (Operator Panel)..............................................................................76
3.3.30Holder Gear Toner Assy...................................................................................77
3.3.31Plate Latch Lever (FD), Spring Latch Lever (FD).............................................78
3.3.32Belt Cassette Assy...........................................................................................79
3.3.33High Voltage Power Supply Unit, Bracket HV (BT) Assy.................................80
3.3.34Eraser Bracket Assy, Eraser Bracket (KCM) Assy...........................................81
3.3.35Shaft Link..........................................................................................................82
3.3.36Contact (BL-R) Assy, Contact (CL-R) Assy......................................................83
3.3.37Contact (BL-L) Assy, Contact (CL-L) Assy.......................................................84
3.3.38Contact SB Assy...............................................................................................85
3.3.39PXC PCB..........................................................................................................86
3.3.40Heat Unit Assy..................................................................................................87
3.3.41Oil Roller Assy..................................................................................................88
3.3.42Lever Lock Heat (L)/(R), Guide Side Heat, Spring Lock...................................89
3.3.43PXL PCB..........................................................................................................90
3.3.44Heat Unit Guide Assy.......................................................................................91
3.3.45Holder LED Assy, LED Head............................................................................92
4.ADJUSTMENTS.............................................................................................93
4.1 Maintenance Modes and Their Functions......................................................................93
4.1.1 User maintenance mode..................................................................................93
4.1.2 System maintenance mode..............................................................................95
4.1.3 Engine maintenance mode...............................................................................97
4.2 Adjustments after Parts Replacement.........................................................................100
4.2.1 Confirm the LED head driving time.................................................................100
4.2.2 Color deviation correction...............................................................................102
5.PERIODIC MAINTENANCE.........................................................................105
5.1 Periodically Replaced Parts.........................................................................................105
5.2 Cleaning.......................................................................................................................105
5.3 Cleaning the LED Lens Array......................................................................................105
5.4 Cleaning the Pickup Roller...........................................................................................105
6.TROUBLESHOOTING PROCEDURES.......................................................106
6.1 Troubleshooting Tips...................................................................................................106
6.2 Points to Check before Correcting Image Problems....................................................106
6.3 Tips for Correcting Image Problems............................................................................106
6.4 Preparation for Troubleshooting..................................................................................107
6.5 Troubleshooting Flow...................................................................................................107
6.5.1 LCD status message/trouble list.....................................................................107
6.5.2 LCD message troubleshooting.......................................................................116
6.5.3 Image troubleshooting....................................................................................128
7.WIRING DIAGRAM......................................................................................145
7.1 Resistance Check........................................................................................................145
7.2 Program/Font ROM Location.......................................................................................149
8.Parts List......................................................................................................153
41057610TH Rev. 1 4 /
Appendix A CENTRONICS PARALLEL INTERFACE.....................................173
Appendix B HIGH CAPACITY SECOND PAPER FEEDER............................177
1. OUTLINE................................................................................................177
1.1Functions.............................................................................................................177
1.2External View and Component Names................................................................177
2. MECHANISM DESCRIPTION................................................................178
2.1General Mechanicsm...........................................................................................178
2.2Hopper Mechanism.............................................................................................179
3. PARTS REPLACEMENT.......................................................................180
3.1Precautions Concerning Parts Replacement.......................................................180
3.2Parts Layout........................................................................................................182
3.3Parts Replacement Methods...............................................................................183
3.3.1Idle rollers.............................................................................................184
3.3.2AOLT-PCB...........................................................................................185
3.3.3Hopping motor......................................................................................186
3.3.4Feed roller............................................................................................187
3.3.5Hopping roller.......................................................................................188
3.3.6Side frame (L) assy..............................................................................189
3.3.7Side frame (R) assy..............................................................................190
4. TROUBLESHOOTING...........................................................................191
4.1Precautions Prior to the Troubleshooting............................................................191
4.2Preparations for the Troubleshooting..................................................................191
4.3Troubleshooting Method......................................................................................192
4.3.1LCD Status Message List.....................................................................192
4.3.2Troubleshooting Flow...........................................................................193
5. CONNECTION DIAGRAM.....................................................................194
5.1Interconnection Diagram.....................................................................................194
5.2PCB Layout.........................................................................................................195
6. PARTS LIST..........................................................................................196
41057610TH Rev. 1 5 /
1. SPECIFICATIONS
1.1 Basic System Configuration
The basic system configuration of OKICOLOR 8 is illustrated in Figure 1.1.
M M
M
Pulse motors
Discharging indicators
LED head
Controller
Operator panel
M M
M M M
C EPM EPY EPK EPBELTHEATERREGISTFF
Junction board
x4
SIMM
x2
PSIMM
Paper width sensor
Form size detector (4 bits)
<Sensors, switches, and thermistors>
interface
interface
Form end sensor
Engine controller
FF form end
FF home switch
Form feed sensor 1
Form feed sensor 2
Write sensor
Ejection sensor
Toner Low (Y.M.C.K)
Second tray
High-voltage
power unit
Low-voltage
EP Up/Down (Y.M.C.K)
Waste toner sensor
Resist Up/Down
Cover open switch (High-voltage
interlock switch)
power unit
Fixing unit
Heater temperature thermistor
Backup temperature thermistor
Environment temperature sensor
Environment humidity sensor
Oil Roller switch
Fixing unit interlock switch
Waste toner box switch
Figure 1.1
Y-EP unit M-EP unit C-EP unit B-EP unit
Belt unit
Centronics
interface
41057610TH Rev. 1 6 /
1.2 Printer Specifications
This printer unit is composed with the following hardware.
• Electro-photographric processor
• Paper feeder
• Controller (CU part / PU Part)
• Operator panel
• Power board (High voltage part / PU part)
Figure 1-2 show the printer unit configuration.
Face-up Stacker Assy
Stacker Cover Assy
Rear Cover
Side Cover (L) Assy
Base Unit
Figure 1.2
I/F Cover Assy
Operator Panel Assy
41057610TH Rev. 1 7 /
1.3 Option Specifications
Options available for OKICOLOR 8 are as follows.
(1) 2nd-Feeder
(2) RAM SIMM module (72 pin SIMM, 4MB/8MB/16MB/32MB)
* Make sure to use a set of 2 of the same volume size modules.
41057610TH Rev. 1 8 /
1.4 Basic Specifications
(1) Dimensions
Width: 18.8" (478mm) Length: 24.5" (622mm) Height: 15.6" (396mm)
(2) Weight
Approx. 48kg (106lbs)
(3) Form
Type: Ordinary paper (Hammermill 24lbs) and OHP (Only 3M CG3710)
Recommended paper (for color printing)
Color laser paper (20lb to 24lbs)
Note: The printout color tones are dependent upon the whiteness of the print
paper
Sizes: Letter, Legal (13"or 14"), Executive, A4, A5, B5, and A6 (1st tray and front feeder)
Reams:1st tray 20lbs to 28lbs
2nd tray 20lbs to 28lbs
Front feeder 20lbs to 53lbs (110lbs index)
(4) Printing speed
8 pages per minute (5 pages per minute: Card Stock, Labels & OHP/ 34lbs ~44lbs)
(5) Resolution
600 dots per inch x 600 dots per inch
(6) Input voltage
120VAC +5.5%, -15%
230VAC ±10%
(7) Power consumption
Peak: Typical operation
Idle: Power-save mode
(8) Frequency
50Hz or 60Hz +2%, -2%
(9) Noise
Operating: 54dB (without 2nd tray), 55dB (with 2nd tray)
Standby: 45dB
Power-saving: 43dB
(10)Consumables and service life
Toner cartridge: Approx. 3000 pages (5% duty) (each of C, M, Y, and K)
(Approx. 2000 sheets for the first)
Image drum: Up to 13,000 pages (5% duty, continuous) (each of C, M, Y, and K)
Waste Toner Box:Up to 25,000 Sheets
(under typical printout conditions: Single images of 5% density,
equivalent to printout using 14 toner cartridges)
Oil Roller Unit: Up to 10,000 sheets (Life defined in the number of actually printed
paper sheets)
(11)Periodically-replaced parts
Heat Unit Assy: 60,000 pages
Belt Cassette Assy:50,000 pages
41057610TH Rev. 1 9 /
(12)Temperatures and relative humidities
Temperature
Temperature conditions
Temperature (in _F) Temperature (in _C) Remarks
Operating
Non-operating
Storage (1 year max.)
Delivery (1 month max.)
Delivery (1 month max.)
60.8 to 89.6
50 to 109.4
33 to 109.4
-20 to 122
-20 to 122
Humidity
Humidity condition
Relative humidity (%)Wet-bulb temperature Remarks
Operating
Non-operating
Storage
Delivery
20 to 80
10 to 90
10 to 90
10 to 90
for the packed unit only
16 to 32
10 to 43
0.6 to 43
-29 to 50
-29 to 50
25
26.8
35
40
17_C to 27_C (for assurance
of full-color printout quality)
Power off
with drum and toner
without drum and toner and
Belt Cassette Assy
with drum and toner
50% to 70% (for assurance of
full-color printout quality)
Power off
(13)Printer life
3,000,000 (A4) pages or 5 years
41057610TH Rev. 1 10 /
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41057610TH Rev. 1 11 /
2. OPERATION
OKICOLOR 8 is a tandem color electrophotographic page printer, using 4992-LED technologies,
OPC, dry single-component non-magnetic developing, roller transfer, heatcompression fixing and so on. The printing method used is a Black Writing method which applies
light beams to printout areas.
Figure 2.1 shows the functional block diagram of OKICOLOR 8.
Ejection sensor
Crimp-style terminal
AC-IN AC switch
PXL
PXL board
thermistor
Heat roller
6P
thermistor
6P'
Interlock switch
Backup roller
JST3P
PD6 board
Heater unit
Oil PAD MSW
K600 14P
KPOW 12P
Y600 14P
YPOW 12P
FAN 1
3P
Low-voltage power supply
Heat
motor
Belt
motor
motor
K-IDU
12P
HEADPOW
RSENS 7P
13P
HEAD1
14P
HEAD2
15P
HEAD3
panel
Operator
PCO
THE.RM 6P
POWER 30P
CUIF 40P
PX4 board
board
CM
PCE
PU 40P
6P
36P
Parallel
64P
OKI HSP
72PX4
D-RAM SIMM
72PX2
PS SIMM
MSW
Cover open
Form size detector
PXC board
M600 14P
MPOW 12P
C600 14P
CPOW 12P
LED head:C M Y K
SUMi card x 4
Discharging lamp:C M Y K
HEAD1 13P HEAD2 14P HEADPOW 12P HEAD3 15P
Toner sensor x 4
ID sensor x 4
FF form
FF Pos MSW
sensor
motor
Y-IDU
motor
M-IDU
motor
C-IDU
motor
Resist
FF
motor
FAN 2
sensor
REG.POS
Paper supply sensor board
12P
UPDOWN
PXM board
40095001YU
8P
HETBELT
12P
MCKID
8P
YIDREG
14P
TONER
JODEN 8P
FF 12P
PXF board
FSENS 8P
HVOLT 16P COVOPN 2P PSIZE 6P
PXFIF 30P
PENDTNR 6P
PXFIF 30P
OPTION 7P
High-voltage power supply
sensor
Waste toner
sensor
Form end
(option)
2nd tray
Figure 2.1
41057610TH Rev. 1 12 /
2.1 Main Control Board (PCE PCB)
The control board consists of a CPU (200MHz) block, a memory control LSI block, an
interface control LSI block, a DRAM block, an EEPROM block, a mask ROM block, and an interface
block. Figure 2.2 shows the functional block diagram of the main control board (PCE PCB).
MPU Memory controller ROM, Flash Max 32M
SysAD
SysCmd
Control
NMI
INTO
µ
PD30500
S2-200
ExtReg
INT1
Reset
ColdReset
VCCOK
ModeIn
ModeClock
MasterClock
2nd cache
controller
SysAD
SysCmd
Control
Control
64
9
5
1
1
1
1
64
9
5
1
1
1
1
1
1
SysAD
SysCmd
Control
uPD94704
NMI
S1-001-F6
INT
CLK
RST
Interface controller
SysAD
SysCmd
Control
ExtReq
INT
ColdReset
VCCOK
ModeIn
ModeClk
uPU66044
GN-014-LMU
A
D
Control
A
D
Control
WDATA
FSYNC
Control
PU I/F
OP I/F
EEPD
EEPCLK
EEPCS0
PD
PCO
22
64
11
11
64
25
8
4
4
9
4
1
1
1
74LVC161284 Bi-Centro
8
5
D-RAM Max 144M
Engine
WDATA
ESYNC
Control
Operator
panel
EE-PROM
DI
CLK DO
CS
4
16
D
18
A
12
C
10
(TE6135 (6137), 16550, 53C80)
OKI HSP
Host I/F(Not installed)
Control
Reset circuit
SysAD
OSC
DIP SW
PCI
1
Reset
1
CLK
1
RSTIN
2
M
Figure 2.2
41057610TH Rev. 1 13 /
(1) CPU
The CPU is a 64-bit RISC architecture processor (provided by NEC). It inputs a frequency
of 50MHz and runs at 200MHz. It transfers data to and from memory at 50MHz.
(2) MASK ROM
The Mask ROM block consists of four 16Mbit (1M x 16bits) chips and its total size is 8M bytes.
The chips are mounted on the PCE-PCB by means of IC sockets and store programs and
character fonts.
(3) DRAM
The DRAM block consists of eight 16Mbit (1M x 16bits) chips and its total size is 16M bytes.
The chips are mounted on the PCE-PCB and can be expanded up to 144M bytes by adding
the 32M byte SIMMs to the SIMM slots on the PCE-PCB.
(4) EEPROM
The EEPROM block consists of 16K-bit chips mounted on a board by means of IC sockets
and stores the following:
- Menu data
- Counter values
- Adjustment values
(5) Flash ROM
The Flash ROM block consists of four 4M bit (256K x 16bits) chips and its total size is 2M
bytes. The chips are mounted on the PCE-PCB and are used for storing fonts, macro and
demo pages.
(6) Memory control LSI
This block mainly consists of memory control, CPU control, compression and decompression, and video interface functions.
(7) Interface control LSI
This block mainly consists of PU interface control, operator panel interface control, EEPROM
control, parallel interface control, and HSP control functions.
(8) Host interface
This printer has the following interfaces to the host.
• Centronics bidirectional parallel interface
• Network interface (Option)
The single effective interface or the automatic interface select mode can be selected using
the menu. If the busy state of the printer continues for a long time period, the buffer near-full
control releases the busy status at constant intervals even if the host side is busy so as not
to cause interface time-out at the host side.
(a)Centronics bidirectional parallel interface
This is an interface conforming to IEEE-1284 and provides either unidirectional and
bidirectional communications according to each of the following communication modes.
• Compatibility mode
Unidirectional communications from the host to the printer.
• Nibble mode
This mode transfers 4-bit wide data from the printer to the host. In this mode, each
bit of 1-byte data is transmits in the form of two nibbles using ERROR, BUSY, FAULT,
and SELECT signal leads. This mode can provide bidirectional operation in
combination with the compatibility mode.
41057610TH Rev. 1 14 /
• ECP mode
This mode provides the asynchronous bidirectional interface and transmits and
receives 1-byte data using eight data signal leads under semi-duplex control by the
host.
When the power is turned on, the compatibility mode is automatically selected. The
change to another mode from the compatibility mode is made through negotiation.
(When the BI DIRECTION is set to ENABLE in the menu, this change can be performed.)
(For the electrical/physical characteristics of this interface, see APPENDIX B)
(b) Network interface (Option)
Network interface card uses the power line only.
Printer
Network, etc.
Control board
Power Line only
LAN
expansion board
interface
Figure 2.3
(9) 2nd Cache and 2nd Cache Controller
This printer has the 2nd Cache unit which type is Write Through Cache and size is 512 KByte.
There are any difference between the instruction and data. All of the CPU read/write access
are cached to same 2nd cache memory.
(10) RAM module
• Pin layout
1363772
• Basic specificaton
- Type: 72 pins SIMM (32 bits buss width)
- Access time: 60ns, 70ns, 80ns
- Capacity: 4, 8, 16 or 32MB
- Parity: None
41057610TH Rev. 1 15 /
2.2 Engine Control Board (PX4 PCB)
NM93C66N-NW
CPU BUS
VIDEO I/F
RESET
(Heater temperatures and environment humidity and temperature)
EEPROM
VIDEO MEM
HM658512
OSC 28MHz
ANALOG INPUT
CPU
MSM65524
(containing AD converter)
INT
LSI
MB87D
113PFV
ROM
27512
C HEAD I/F (3.3V)
M HEAD I/F (3.3V)
Y HEAD I/F (3.3V)
B HEAD I/F (3.3V)
MT DRIVER
MTD2005F
MT DRIVER
MTD2005F
MT DRIVER
MTD2005F
PULSE MOTOR x 8
HIGH-VOLTAGE POWER SUPPLY
SERIAL INTERFACE (2 channels)
GENERAL INPUT PORT
GENERAL OUTPUT PORT
Figure 2.4
The engine control block (PU) is controlled by the engine control board (PX4 PCB) which consists
of a CPU (MSM65524), general purpose LSI chips, EPROM, EEPROM, pulse motor drivers, and
video memory. (See Figure 2.4.)
(1) CPU
This is an 8-bit CPU (OKI MSM65524) containing the AD converter and controls the whole
system.
(2) General-purpose LSI
This LSI (MB87D113PFV) is provided in the printer engine control block and has controllerengine video interface, LED interface, motor control, sensor input, video memory control,
main scanning color correction, skew correction, high-voltage power control, and OST-EX2
functions.
41057610TH Rev. 1 16 /
(3) EPROM
This EPROM (27C512-150) has a storage capacity of 512K bits and stores programs for the
PU block.
(4) EEPROM
This EEPROM (NM93C66N-NW) having a storage capacity of 4K bits is mounted on the
board by means of IC socket and stores adjustment values etc.
(5) Pulse motor drivers
These drivers (MTD2005F) drive eight pulse motors for moving up and down the EP and
transferring medium.
(6) Video memory
This SRAM receives print data through video interface and stores it.
2.3 Power/Units
The power supply unit comprises of the low voltage power supply unit which consists of an AC filter
circuit, low voltage power supply circuit and heater driver circuit, and the high voltage power supply
unit.
(1) Low voltage power supply unit
This circuit generates the following voltages.
Output voltage Use
+3.3 V CU Unit CPU, LED HEAD
+5 V Logic circuit supply voltage
+32 V Motor and fan drive voltage and source voltage for high-voltage supply, discharge lamp
+12 V HSP, OP Amp, high voltage power supply
–12 V HSP
(2) High voltage power supply unit
This circuit generates the following voltages necessary for electro-photographic processing
from +32 V in accordance with the control sequence from the control board. When cover open
state is detected, +32 V supply is automatically interrupted to stop the supply of all the highvoltage outputs.
Output Voltage Use Remarks
CH -1.35 KV ± 50V Voltage applied to charging roller
DB Normal paper Voltage applied to developing roller
Y. M. C : -250V/+300V, -232V/+300V(First paper. Y only)
K : -275V/+300V
Transparency
Y. M. C. : -200V/+300V, K. : -250V/+300V
SB Y. M. C.K : -650V/0V Voltage applied to toner supply roller
TR 0 to 4 KV Voltage applied to transfer roller Variable
FIX 0 to 2.5 KV Voltage applied to transfer roller Variable
41057610TH Rev. 1 17 /
2.4 Mechanical Processes
Paper
ejection
roller
Paper
ejection
(Face down)
Power
supply
Charging
roller
Cleaning
blade
Paper
path
selection
Heat roller
Ejection
roller
Fixing
Backup roller
Control signal
LED head
Developing
roller
Power
supply
Toner
cartridge
Transfer
roller
Paper
resist
Resist
roller 1
Paper
feed
Hopping
roller
Power
supply
Resist
roller 2
Paper ejection Fixing Cleaning Transferring
Paper pickup
Paper conveying Paper hopping
Movement of
paper
Rotation of
OPC drum
Transferring
Charging
Exposure
Developing
Cleaning
Paper ejection
sensor
Form feed sensor 1
Paper
ejection
(Face up)
Form feed sensor 2
Front
feeder
Paper
cassette
Paper
resist
Paper
pickup
(FF, 1ST, 2ND)
Write sensor
x 4
Y M C K
Figure 2.5 shows the mechanical processes of OKICOLOR 8.
Figure 2.5
41057610TH Rev. 1 18 /
2.4.1 Electrophotographic processing mechanism
(1) Electrophotographic processes
Each process of the electrophotographic processing mechanism is outlined below.
1 Paper pickup
This process causes the roller to give a DC voltage to the paper to have a negative charge.
With this negative charge, the paper is electrostatically attracted to the roller.
2 Charging
This process gives a DC voltage to the CH roller so that the OPC drum may have a uniform
negative charge on its surface.
3 Exposure
This process causes the LED head to apply light beams according to image signals to the
negatively-charged surface of the OPC drum. The negative charge on the illuminated
surface of the OPC drum is reduced according to magnitudes of the light beams.
Thus, a latent image is formed on the surface of the OPC drum according to the resulting
surface potentials.
4 Developing and recovery of excessive toner
This process applies negatively-charged toner to the surface of the OPC drum. The toner
is electrostatically attracted to the latent image to form a visible image on the surface of
the OPC drum. Simultaneously, this process electrostatically transfers excessive toner
from the OPC drum to the developing roller.
5 Transferring
This process fits paper to the surface of the OPC drum, applies positive charge (opposite
to the charge of the toner) to the back side of the paper from the transfer roller. The toner
image is transferred to the paper.
6 Cleaning
Cleaning blade scrapes off the remaining toner from the OPC drum which has been used
to transfer.
7 Fixing
This process fixes the toner image on the paper by pressing and fusing the image.
41057610TH Rev. 1 19 /
(2) Paper pickup
Pickup roller
Paper (medium)
Conveying belt
A
Conveying belt
Driven roller
B
Power
supply
A DC voltage (0V to 2KV) is applied to the driven roller A to positive charge the lower surface
of the paper. The negatively-charged paper is electrostatically attracted to the pickup roller.
With this, the paper is in close-contact with the conveying Belt and conveyed steadily.
41057610TH Rev. 1 20 /
(3) Charging
This process applies a DC voltage to the charging roller in contact with the surface of the OPC
drum.
Power
supply
unit
OPC drum
Charging roller
(4) Exposure
The light beams from the LED head are applied to the surface of the OPC drum which is
charged negatively. The negative charge on the illuminated surface of the OPC drum is
reduced according to magnitudes of the light beams and a latent image is formed on the
surface of the OPC drum according to the resulting surface potentials.
Power
supply
unit
Charging roller
OPC drum
LED head
Paper
LED head
OPC drum
41057610TH Rev. 1 21 /
(5) Developing
This process applies toner to the latent image on the surface of the drum to convey it into a
toner image. Developing is carried out on the surface of the OPC drum at which the OPC drum
is in contact with the developing roller.
1 The sponge roller transfers toner to the developing roller. The toner is charged negatively.
Developing toner blade
Charging roller
Sponge roller
Developing roller
OPC drum
2 The toner blade scrapes away excessive toner on the developing roller to form a thin
film of toner on the surface of the developing roller.
3 The toner is attracted to the latent image on the surface of the OPC drum at which
the OPC drum is in contact with the developing roller. The latent image on the
surface of the OPC drum is made visible with the toner.
41057610TH Rev. 1 22 /
(6) Transferring
The transfer roller made of conductive sponge presses the paper
against the surface of the OPC drum so that the paper may be close contact with the surface
of the OPC drum.
This process fits the paper to the surface of the OPC drum by the transfer roller and applies
positive charge (opposite to the charge of the toner) from under the paper.
When a positive high voltage is applied to the transfer roller from the power supply, the
positive charge induced on the transfer roller jumps to the upper surface of the paper at which
the transfer roller touches the paper and attracts the negatively-charged toner from the
surface of the OPC drum onto the surface of the paper.
OPC drum
Conveying belt
Paper
Transfer roller
Power
supply unit
41057610TH Rev. 1 23 /
(7) Fixing The toner image just transferred to the paper is fused and fixed to the paper while
the paper is passing through the gap between the heat roller and the backup roller.
The teflon-coated surface of the heat roller is heated up by the 800-watt heater (or a
halogen lamp) provided in the heat roller. The temperature of the heat roller surface is
controlled by a thermistor in contact with the surface of the heat roller. A thermostat is
provided for safety. When the heat roller temperature goes higher than the preset
temperature, the thermostat opens and shut off power to the heater in the heat roller.
The backup roller is evenly pushed against the heat roller by two end springs.
Heater
Paper
Backup roller
Heat roller
Thermistor
(8) Cleaning
The toner which remains on the OPC Drum without being fused is scraped by a cleaning blade
and discarded in the waste toner tank.
OPC drum
Cleaning blade
Transfer roller
41057610TH Rev. 1 24 /
2.4.2 Paper running process
face down stacker
oil roller
fuser
low-voltage power supply
AC switch
transfer roller
x4 light rejector
x4
transfer belt unit
ID unit up / down actuater
belt cleaning
high voltage power supply
pick up roller
pinch roller up / down
transfer belt
1st tray
2nd tray
front feeder
KCMY
I/D unit
LED Head
pinch roller 2
pinch roller 1
regist
roller 2
regist
roller 1
hopping roller
backup roller
Eject roller
oil cleaning roller
heat roller
Figure 2.6 shows how paper moves in the OKICOLOR 8.
Figure 2.6 Paper Route
41057610TH Rev. 1 25 /
(1) Paper hopping and transfer and up/down movement of pinch roller 2
Paper is hopped and delivered by the mechanism shown below. This mechanism is driven
by a single pulse motor.
Resist roller 2
One-way gear C
Resist roller 1
Idle gear C
One-way gear B
Idle gear A
a
b
Idle gear B
First hopping roller
Pulse motor
One-way gear A
The pulse motor turns in the arrow direction (a) and drives the hopping roller in the direction of
“b.” The hopping roller drives the resist roller.
Each of the one-way clutch gears A, B, and C has a one-way clutch to prevent the rollers from
rotating reversely.
41057610TH Rev. 1 26 /
(a) Hopping
1 The pulse motor turns in the arrow direction of “a” (counterclockwise) and drives the
hopping roller to move the paper until the Entrance sensor turns on. Although the oneway gears B and C are also driven, the resist roller 2 does not turn because the
reverse rotations of the one-way clutch gears are not transmitted to the resist roller.
2 After the Entrance sensor turns on, the hopping roller keeps on feeding the paper until
it hit the resist roller 1. (This operation corrects any paper skew.)
One-way gear C
Resist roller 1
Resist roller 2
One-way gear B
Entrance sensor
Paper
a
First hopping roller
(b) Conveying
1 After paper hopping is completed, the pulse motor turns right (in the direction of “b”)
to drive the resist rollers 1 and 2. The resist rollers feed the paper until the Form
sensor turns on.
Although the one-way gear A is also driven, the hopping roller does not turn because
of the one-way clutch.
2 The paper is further fed in synchronism with the print data.
Form sensor
Resist roller 1
Resist roller 2
b
Paper
First hopping roller
One-way gear A
41057610TH Rev. 1 27 /
(2) The hopping operation of the front feeder and the up/down operation of the pinch roller 2 are
performed by a single pulse motor, as shown below.
Cam
b
a
Idle gear A
One-way clutch gear B
Sensor position
From front
Hopping roller
One-way clutch gear A Idle gear B
Entrance sensor
Up/down
Pinch roller
Form sensor
Resist roller 2
When the pulse motor of the front feeder turns right (in the direction of “A”), the front hopping
roller turns left (in the direction of “b”) to drive the cam. This cam moves up and down
the pinch roller 2. The one-way clutch gears are made to turn only in a preset direction by
means of the one-way clutches.
41057610TH Rev. 1 28 /
(a) First and second hopping rollers
1 When the front edge of the paper passes by the pickup roller, the pulse motor of the
front feeder turns left (in the direction of “b” to drive the cam. The cam moves up the
pinch roller 2. Although the one-way clutch gear A is also rotating, the hopping roller
of the front feeder does not rotate by means of the one-way clutch.
2 When the rear edge of the paper passes by the Entrance sensor 2, the pulse motor
of the front feeder turns left (in the direction of “b”) to drive the cam. The cam moves
down the pinch roller 2 until it is sensed by the sensor. Although the one-way clutch
gear A is also rotating, the hopping roller of the front feeder does not rotate by means
of the one-way clutch.
Cam
b
One-way clutch gear B
Idle gear A
Hopping roller
One-way clutch gear A
Idle gear B
b
b
Paper from the tray
b
Entrance sensor 2
b
Up
Cam
Sensor
Pickup roller
Form sensor
Pinch roller 2
Resist roller 2
41057610TH Rev. 1 29 /
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