The DVACC signal is a clock signal to generate the AC bias and the developing AC bias is generated according to this signal. The developing DC bias is generated

according to the developing AC bias generated in the developing AC bias generation circuit. The superimposed voltage of the developing DC bias and the devel-

oping AC bias is applied to the developing cylinder.

The developing DC bias changes with the primary charging DC bias, in response to the image density information sent from the video controller.

2.4.2.4 Transfer charging bias generation

LBP3370 / LBP3310

The transfer bias (TR) is generated by three signals output from the CPU: the TRANSFER POSITIVE BIAS DRIVE signal (TRPFOT), the TRANSFER NEGA-

TIVE BIAS DRIVE signal (TRNFOT), and the TRANSFER OUTPUT SWITCHING signal (TRPWM).

The TRPFOT signal is a clock signal to generate the positive bias and the transfer positive bias is generated according to this signal. The TRNFOT signal is a clock

signal to generate the negative bias and the transfer negative bias is generated according to this signal. The voltage of either the transfer positive bias or the transfer

negative bias is applied to the transfer charging roller.

The CPU controls a constant current control by switching the values of the TRPWM signal in response to the TRANSFER CURRET FEEDBACK signal (TFRAD)

sent from the transfer charging bias circuit.

The transfer charging roller is applied with the cleaning bias, the between-sheets bias, and the print bias according to each print equence.

Cleaning bias:

The cleaning bias is to transfer the toner adhered to the transfer charging roller onto the photosensitive drum during the warm-up or the last rotation sequence.

The transfer negative bias is applied to the transfer charging roller to operate.

Between-sheets bias:

The between-sheets bias is to prevent the residual toner on the photosensitive drum from adhering to the transfer charging roller during the between-sheets in

continuous printing.

Infinitesimal transfer positive bias is applied to the transfer charging roller.

Print bias:

The print bias is to transfer the toner on the photosensitive drum surface onto print paper during the print sequence. The transfer positive bias is applied to the

transfer charging roller.

2.4.2.5 Fixing bias generation

LBP3370 / LBP3310

The fixing bias is generated by dividing up the voltage of the primary charging DC bias, in order to avoid the toner particles adhering to the fixing film and to avoid

making smeared images at the trailing edge. The fixing bias applies the bias to the fixing film through a core bar and a rubber ring of the pressure roller at the timing

of that the primary charging DC bias is applied to the primary charging roller.

2.4.2.6 Cartridge presence detection

LBP3370 / LBP3310

The CPU detects the presence of cartridge by checking the voltage of the CARTRIDGE DETECTION signal (CRGSNS), which is a feed back signal of the primary

charging AC bias.

The primary charging bias circuit detects the voltage value of the primary charging AC bias applied to the primary charging roller, and feeds back the CRGSNS

signal to the CPU, when the PRIMARY CHARGING AC BIAS DRIVE signal (PRACC) is output from the CPU and primary charging AC bias is output from the

AC generation circuit.

The CPU detects the presence of cartridge by checking the voltage of the CRGSNS signal at the timing of the primary charging AC bias is output during the wait

period.

2.5 PICKUP AND FEEDING SYSTEM

2.5.1 Overview/Configuration

2.5.1.1 Outline

LBP3370 / LBP3310

The pick-up/feed system picks up and feeds a print paper, and it consists of various feed rollers.

This printer has two pick-up slots; the cassette and the manual feed slot, and two delivery slots; face-down tray and face-up delivery slot.

The engine controller controls 1 motor and 3 solenoids in order to drive each feed roller.

There are two paper detection sensors (delivery sensor and reversing sensor are the same but 2 sensor flags) in the feeding path of a print paper. The sensors detect

the print paper arrival or pass. If the sensors cannot detect the paper arrival/pass within the prescribed time, the CPU on the engine controller determines a jam and

notifies it to the video controller.

The paper detect sensor detects the presence of print paper in the cassette and manual feed slot. Also the top of page sensor detects the paper length, and the paper

width detection sensor detects the paper width.

Chapter 2

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0018-3118

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Table of Contents