| 摘要 |
PURPOSE: To provide an image forming device provided with a voltage variable type developing bias voltage impressing means whose cost is low and whose constitution is simple in comparison with a voltage variable type inverter system power source, etc., exclusive for impressing developing bias voltage. CONSTITUTION: In this image forming device, the output terminal 51 of a charge high-voltage power source 5 for impressing negative high voltage on a charger 2 is grounded through a voltage drop resistor element 6 on the output terminal 51 side and a PNP type transistor 7 in series in this order, and the collector of the transistor 7 on the resistor element 6 side is connected to a developing roller 3. The device is provided with a control part 9 changing a resistance value between the emitter-collector of the transistor 7 by giving a negative control signal to the bases of the transistor 7. It is good to use a transfer high- voltage power source 8 impressing negative high voltage to a transfer charger 4 instead of the high-voltage power source 5. It is good to connect Vcc(+5V) to the emitter of the transistor 7 instead of grounding the emitter and give a positive control signal to the base of the transistor 7. |
