In this machine, one transparency sensor is used for material difference detection. The transparency sensor is allocated at the almost same position of the pre-reg-

istration sensor (a point where 21.5 mm upstream from the registration roller) on the feeding path. (In addition, the pre-registration sensor is allocated at the point

where 19.9 mm upstream from the registration roller.) The transparency sensor is comprised of 2 PCBs of LED; the light emission area (UN18) and the light re-

ception area (UN19).

In this machine, the material difference is detected according to the transmittance of material being fed. The transmittance of material is calculated according to the

sensor output (reference value A) under the condition that no shielding material presents at the transparency sensor, and the sensor output (measured value B) under

the condition that a fed material presents.

1. Reading the Reference Value

The reading of the reference value is executed at the following timing:

- After warm-up rotation when turning the power on.

- After warm-up rotation after opening/closing the right door.

The prism facing to the transparency sensor is allocated at the right door side. Because the detected voltage changes by opening/closing the right door, the reference

value must be measured after opening/closing it. Measurement method of the reference value is as follow:

1) Turn ON the LED of transparency sensor, and read the sensor output 3 times with constant interval (every 16 ms).

2) Among the read values, save the smallest value as the reference value A (the 3 read values fall somewhere into the predetermined range).

3) Turn OFF the LED and finish the measurement.

2. Reading the Measured Value

Start to read the transparency sensor when a paper is fed from a source of paper to the registration roller and the pre-registration sensor turns ON.

1) Turn ON the LED of transparency sensor, and read the sensor output 3 times with constant interval (every 16 ms).

2) Among the read values, save the largest value as the measured value B.

3) Turn OFF the LED and finish the measurement.

4) Based on the reference value A and the measured value B, calculate the transmittance of material. If the transmittance is the predetermined value (=45%) or

above, the detected material is judged as a transparency. If the result is less than the predetermined value, the material is judged as non-transparency (e.g., plain

paper, heavy paper, color paper, tracing paper).

If the result of the step 4 indicates that the material is non-transparency while transparency is set and vice versa, the machine considers as a jam due to the material

difference, and stops the machine. (Jam code: 0D93)

Reference:

The detection is not designed to protect a transparency for CLC (a transparency with a white mark on the leading edge) from being fixed in order to avoid the

occurrence of symptoms that cause damage on the fixing assembly or error codes when it is used.

In this machine, a transparency for CLC might be wrapped around the fixing assembly when using it, and it causes the fixing inside delivery delay jam (0107 jam).

When the fixing motor is stopped because of a jam detection processing, a transparency is not completely wrapped around the fixing roller. By executing the jam

processing from the upstream of feeding as a jam processing flow, it prevents the sheet to be wrapped around the fixing assembly. Therefore, the control detecting

a transparency for CLC and stopping print is not executed.

8.8 Pre-Fixing Feeding

8.8.1 Fixing Arch Control

/ / / / iR C3380i / iR C3380 / iR C2880i / iR C2880

1. Fixing Arch Control

This is the control performed between the secondary transfer unit and the fixing unit. The perimeter of the roller increases due to heat expansion on the pressure

roller of the fixing unit. Therefore, the paper feeding speed on the fixing side becomes faster than the one for secondary transfer at constant rotation speed. This

causes papers to be pulled towards the fixing side. When making the speed on the fixing side lower than the one for secondary transfer to make larger arch of paper,

papers are pushed into the fixing side from the secondary transfer side. Too large and small arch of papers affects the image. To feed papers to the fixing unit at

optimum status, this control system monitors the arch of papers and changes the feeding speed due to according its status.

2. Control Mechanism

The sensors and motors regarding the fixing arch control are shown as below.

8-22

PS16

PS2

FUSE_M_XA

FUSE_M_A

FUSE_M_B

FUSE_M_XB

LOOP_SNS

DC Driver