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The operations of the image forming section are corrected in order to maintain stable and high-quality print even though any changes occur in the
temperature, humidity, consumable parts characteristics, engine conditions, or other environmental conditions.

In concrete, the correction is performed by controlling various control parameters related to the image forming section (process) operations. 

With the above correction operations, stable print quality is always provided, reducing service calls and service works. 

There are following items of the image forming section correction operations (process correction operations).

Image forming section correction operations (process correction operations) list

Item No.

Correction operations

Purpose, effect

Execution conditions, operating timing

1

Image density sensor sensitivity
correction (Calibration) (Gain
adjustment)

Allows the image density sensor to always
detect the correct image patch density. 

Before process correction operation

2

OPC drum marking sensor sensitivity
correction

Allows the OPC drum marking sensor to
always detect the OPC drum marking
normally.

 1

3

Developing bias voltage correction

Prevents against density change and
background copy.

 1

4

Laser beam power correction 1

Prevent against a decrease in print density
due to OPC drum membrane decrease.

Specified rotating time of the OPC drum
(Every 20,000 sec)

Laser beam power correction 2

Outputs the laser beam power
corresponding to the main charger grid
voltage (to maintain the constant voltage). 

Immediately after correction of the main
charger grid voltage (

1)

5

Main charger grid voltage correction 1

Corrects a decrease in the charging voltage
due to the OPC drum membrane decrease,
maintains the correct density of print and
prevent against background copy.

Specified rotating time of the OPC drum
(Every 20,000 sec)

Main charger grid voltage correction 2

Maintains the relations between the
developing bias voltage and the main
charger grid voltage at constant (to prevent
against background copy).

Immediately after correction of the
developing bias voltage (

1)

6

Toner concentration correction

Maintains the normal toner concentration to
maintain the proper density of print and
prevent against background copy.

When the developing bias voltage correction
is performed for the voltage higher than the
specified level is made immediately after the
developing bias voltage correction. (

1)

 1 During warm-up after turning on the power.

During warm-up after cancelling SIM 7-1, 24-7, 25-2, 44-2.
After completion of printing when the accumulated print time reaches 30 min from the previous correction.
When the next print is made when non-print status continues one hour.

The image forming section correction operation (process correction operation) is performed under the following conditions and timing. 

1) During warm-up after turning on the power.

2) During warm-up after cancelling SIM 7-1, 24-7, 25-2, 44-2.

3) After completion of printing when the accumulated print time reaches 30 min from the previous correction.

4) When the next print is made when non-print status continues one hour.

12 – 1

The sensor sensitivity is adjusted to allow correct detection of the OPC drum marking. 

The sensor LED drive voltage (current)  is changed, and when the sensor output voltage reaches the specified level, the sensor LED drive current
control value is stored. In actual operations, the sensor LED is driven by the voltage corresponding to the control value and detection is performed. 

In the developing bias voltage correction, the image sensor sensitivity is adjusted to allow correct detection of the toner image patch density and
normal operation of the developing bias voltage correction. 

The sensor LED drive voltage (current)  is changed, and when the sensor output voltage reaches the specified level, the sensor LED drive current
control value is stored. In actual operations, the sensor LED is driven by the voltage corresponding to the control value and detection is performed. 

Deterioration of photo sensitivity due to deterioration of OPC drum is corrected by adjusting the laser beam power according to the OPC drum
rotating time (operation time) to maintain the correct density print. 

The main charger grid voltage is increased according to deterioration of the OPC drum to maintain the proper density print and prevent against
background copy.

[mW]

Laser beam power

5

10

15

20

25

30

35

Photoconductor drum correction counter

1 count: 20,000sec(Photoconductor drum rotation time)

0.2mW(max)
Laser beam power correction value(

∆  

LPc1)

[v]

Main charger grid voltage correction value

5

10

15

20

25

30

35

Photoconductor drum correction counter

1 count: 20,000sec(Photoconductor drum rotation time)

95v
Main charger grid voltage correction value

12 – 2

Deterioration of developer leads to changes in the environmental conditions.

To solve the above problem, the developing bias voltage is changed according to the situation to maintain the proper density print and prevent
against background copy. 

(Operation)

1) Three toner image patches are made on the OPC drum with the three voltages Vdbc and Vdbc 

±

 (n)a. (a = 50V)

2) Connect the three points of three toner patch density points with strait lines, and check that it reaches the reference density "38" (set with SIM

44-4).

If the above condition is satisfied, obtain the correction developing bias voltage (Vdbc(n)) for the reference density "38" by linear approximation. 

3) Calculate the developing bias correction voltage (

 Vdbc(n)).

The developing bias correction voltage (  Vdbc(n)) is applied to the developing bias voltage correction in all the operation modes. 

If the condition of 2) is not satisfied, change the condition of 1) as follows and make three toner image patches similarly to 1). 

(Contents of change)

Change the three developing bias voltages of correction for making toner image patches to Vdbc + (n 

±

 1) 

α

, Vdbc + (n 

±

 2) 

α

, and Vdbc + (n 

±

 3) 

α

, and execute 1) and 2). (

α

 = 50V)

Repeat the above operation until the condition of 2) is satisfied. (n = Number of toner patch forming. 3 toner image patches are made for once.)

The correction operation of the developing bias voltage should be in the range of 0 

∼

 –750V. 

Develping bias voltage

Reference level
(Set by T.C 44-4)

Limit(-750v)

800

Vdbc

Vdbc + (n)

α

Vdbc - (n)

α

Vdbc + (n+1)

α

Vdbc + (n+2)

α

Vdbc + (n+3)

α

60

Lower

50

40
38

Image patch density

30

20

10

Higher

0

100

200

300

400

500

600

700

∆  

Vdbc(n)

α

 = 50

PT2/BS2(1D1)2

PT3/BS3(1D2)3

PT2/BS2(1D1)2

PT3/BS3(1D1)3

 

∆  

Vdbc(n)

CASE 1

CASE 2

Vdbc(n)

Vdbc(n)

PT2/BS2(1D2)2

PT1/BS1(1D2)1

PT3/BS3(1D1)3

PT1/BS1(1D1)1

PT1/BS1(1D1)1

Develping bias voltage

60

Lower

50

40
38

Image patch density

30

20

10

Higher

0

100

200

300

400

500

600

700

∆  

Vdbc(n)

PT1/BS1(1D1)1

PT3/BS3(1D1)3

PT1/BS1(1D1)1

PT2/BS2(1D1)2

PT3/BS3(1D1)3

∆  

Vdbc(n+1)

FIRST

SECOND

Vdbc(n)

Vdbc(n+1)

α

 = 50

Vdbc

Vdbc + (n)

α

Vdbc - (n)

α

Vdbc(n) - (n)

α

Vdbc(n)

Vdbc(n) + (n)

α

800

Reference level
(Set by T.C 44-4)

PT2/BS2(1D1)2

Limit(-750v)

12 – 3

When the developing bias voltage is changed, the main charger grid voltage correction 2 is performed to maintain the relation between the
developing bias voltage and the main charger grid voltage at constant. 

After the developing bias voltage correction, the voltage of correction of the developing bias voltage is automatically added to the main charger grid
voltage.

Actual main charger grid voltage variable range: –200 to –900V

To maintain the OPC drum bright potential at constant for changes in the main charger grid voltage due to main charger grid voltage correction 1
and 2, the laser beam power must be changed accordingly. 

Laser beam power correction 2 is performed to output the laser beam power according to the above situation. 

This correction provides stable print density. 

This correction is used to correct changes in the developer characteristics due to aging and change in the environmental conditions. 

When any change occurs in the developer characteristics, it causes under-toner or over-toner, resulting in improper print density. 

To prevent against this, the reference toner control level is changed according to the conditions to maintain the specified toner concentration. 

This correction provides stable print density.

When the developing bias correction voltage (  Vdbc(n)) is minus-corrected (shifted to the positive polarity direction), it is recognized as an
increase in developing capability, and the reference toner concentration control level set with SIM 25-2 is increased. 

With the above operation, toner concentration is decreased to maintain the proper print density. 

The correction data is cleared to "0" when SIM 25-2 is executed.

1

99

MAX 20

5

Operated process(DV bias correction) correction

Original reference toner
concentration control 
level(Set by SIM25-2)

12 – 4