Canon 3260 manual Developing bias generation, Transfer charging roller voltage generation

CHAPTER 2

1. Outline

In response to the instruction from the microprocessor (CPU) on the DC controller PCB, the high-voltage power supply applies a voltage to the primary charging roller, developing cylinder, transfer charging roller, static charge eliminator, and upper fixing roller. It applies a voltage of DC voltage and AC voltage to the primary charging roller and developing cylinder, applies a pos- itive or negative DC voltage to the transfer charging roller, and a negative DC voltage to the sta- tic charge eliminator and the upper fixing roller.

2. Principle of operation

a. Primary charging roller voltage generation

When the /PRNT signal sent from the video controller becomes “L”, initial rotation starts, and the DC controller sets the PRIMARY AC BIAS DRIVE signal (/PRIACD) to "L." The circuit then applies the primary AC bias to the primary charging roller. After the specified period of time has elapsed the PRIMARY DC BIAS DRIVE signal (/PR1DCD) goes “L” and the voltage superimpos- ing primary AC bias onto primary DC bias is applied to the primary charging roller.

The primary DC bias changes with the developing DC bias according to the IMAGE DENSITY ADJUSTMENT signal (DENADJ) sent from the DC controller.

b. Developing bias generation

When the DEVELOPING DC BIAS DRIVE signal (/DEVDCD) from the DC controller becomes “L”, a developing DC bias is applied to the developing cylinder.

When the VERTICAL SYNC signal (/VSYNC) is sent from the video controller, the DC con- troller outputs the DEVELOPING AC BIAS DRIVE signal (/DEVACD) and DEVELOPING AC BIAS FREQUENCY OUTPUT signal (/DEVACCLK). This circuit then applies the voltage superimpos- ing developing DC bias and developing AC bias to the developing cylinder.

The developing DC bias changes according to the IMAGE DENSITY ADJUSTMENT signal (DENADJ), making the image density adjustable.

c. Transfer charging roller voltage generation

The negative, between-page, and print bias are applied to the transfer charging roller according to the print sequence.

The negative bias voltage is applied to the transfer charging roller at an appropriate timing to move the toner attached to the transfer charging roller onto the photosensitive drum to clean the roller.

For the between-page bias, a positive low voltage is applied to the transfer charging roller at an appropriate timing so that the toner remaining on the photosensitive drum is not attracted to the transfer charging roller.

For print bias, a positive voltage is applied to the transfer charging roller in order to transfer the toner on the photosensitive drum surface to the paper.

When the /PRNT signal sent from the video controller becomes “L”, initial rotation starts and a negative bias is applied to the roller for a certain time to clean the transfer charging roller. Between-page bias is then applied, and a print bias is applied to the transfer charging roller after the prescribed time has elapsed since the /VSYNC signal going “L”.

A print bias is applied during the print sequence to transfer the toner onto the paper. A between-page bias is applied between pages.

After the completion of printing, a between-page bias and a negative bias are applied again to clean the transfer charging roller.

d. Generation of print voltage to the discharger

2 voltage loads, high and low output bias are applied to the discharger according to the various print sequences.

The discharger bias drive signal (/DCHGBD) output from the DC Controller is “L”, and when

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