Transfer Block - Canon LBP3300 Series Service Manual

Table of Contents

Chapter 2

The exposed area on the photosensitive drum is indicated positive in figure despite of the fact that the actual potential on the drum is negative. This means that the

potential of the photosensitive drum is higher than that of the cylinder relative to the potential of the cylinder.

The developing unit is structured by the developing cylinder, which consists the fixed magnet, the developing cylinder rotating around the magnet and the rubber

blade.

The single-component developing material is called toner. The toner is mainly composed of magnetic particles and resin and it is caught onto the cylinder by the

magnetic force. The toner is insulating property and it is charged negative potential by the friction force with the rotating cylinder.

The area of the photosensitive drum, where the laser beam exposed, has higher potential than the toner that is charged negatively on the cylinder. That is, when this

area contacts the toner layer (negatively charged), the toner jumps onto the drum surface by the potential difference between the drum surface and the cylinder

(higher potential on drum side).

This phenomenon is called the projection development and it visualizes the electrostatic latent image on the drum.

The developing cylinder is applied the AC bias in order to make the toner jump easier onto the drum surface and improve the contrast of the output image.

The central voltage of the AC bias (1600Vp-p) changes according to the developing DC bias.

This printer enables to adjust the image density by changing the potential difference between the cylinder and the photosensitive drum according to changing the

developing DC bias based

on the IMAGE DENSITY INFORMATION signal from the video controller.

2.4.1.5 Transfer block

The transfer block transfers the toner image on the photosensitive drum onto a print paper.

Step 4: Transfer

The toner on the photosensitive drum surface is transferred onto a paper according to the positive charge from the back side of the paper. The transfer charging

roller of this printer interlocks the photosensitive drum in order to improve the image quality.

Step 5: Separation

2-10

Blade

Photosensitive

drum

Developing cylinder

surface potential

Voltage (V)

-V

Time (t)

Cylinder