PURPOSE: To stabilize the startup of the circulation of developer and to perform excellent development where a void image is not generated by making the force of attracting a recording medium to the aperture part of a developer supply groove stronger at the time from starting the driving of a negative pressure generating means till starting development than while the development is being performed.
CONSTITUTION: When a recording action is started after a standby state, both electromagnetic valves 11 and 14 are turned on and the driving of a pump motor 12 is started. Since air does not flow from a valve 15 for adjusting negative pressure by making a supply pipe 9 in a shutoff state and turning on the electromagnetic valve 14, the attracting action of the motor 12 is all allotted for attracting the air from the aperture part of the developer supply grooves 31 and 32 through a gap between the surface of a developing head 3 and the surface of a recording paper. Then, the recording paper is surely attracted to the aperture part and contacts to the surface of the head 3, so that the aperture part is nearly tightly closed and the negative pressure in the grooves 31 and 32 rapidly becomes high. By turning off the electromagnetic valve 11, the developer is pumped to the grooves 31 and 32, the air flows from the valve 15, and the negative pressure in the grooves 31 and 32 is kept at a negative pressure adjusting level after it is lowered to the negative pressure adjusting level.
SUZUKI SHIGERU
MIYAGAWA SEIICHI
OSHIMA KIYOSHI
IIZUKA KAZUAKI
SHIMIZU KENICHI
