Image forming apparatus

• US 20060051122A1
• Filed: 11/02/2005
• Published: 03/09/2006
• Est. Priority Date: 01/21/2003
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Takahashi, Atsuya, Mochizuki, Masataka, Kawazu, Takao
• Granted Patent: US 7,139,500 B2
• Time in Patent Office: Days
• US Class Current: 399/88
• CPC Class Codes: G03G 15/2039 with means for controlling the fixing temperature

Abstract

This invention is intended to control the amount of power to be supplied to a fusing heater below a maximum applicable current value. The engine controller supplies electricity to both of two heating bodies at the same fixed duty D1. At a phase angle α1 corresponding to the fixed duty D1, pulse signals ON1 and ON2 are issued in response to a ZEROX signal as a trigger. A current value I1 is detected based on a HCRRT signal from the current detection circuit. The engine controller calculates an upper limit of applicable power duty Dlimit based on the detected current value I1, the fixed duty D1 and the preset applicable current value Ilimit. Then, a PI temperature control is performed at a duty below the upper limit duty Dlimit.

Claims

1-25. -25. (canceled)

26. An image forming apparatus having a fusing device, comprising:

a current-voltage conversion unit for converting an input current to the fusing device into a voltage;

a half-wave rectification unit for half-wave rectifying the voltage obtained by the current-voltage conversion unit;

an integral unit for integrating a half-wave rectified output produced by the half-wave rectification unit;

a differential amplification unit for amplifying a difference between an integrated result produced by the integral unit and the half-wave rectified output;

a maximum value holding unit for holding a maximum output of the differential amplification unit as a maximum value of the input current;

a first pulse signal output unit for outputting a pulse signal when an input supply voltage to the fusing device falls below a predetermined threshold; and

a discharge unit for discharging a capacitor making up the integral unit and a capacitor making up the maximum value holding unit in response to the pulse signal from the first pulse signal output unit.

27. An image forming apparatus according to claim 26, wherein the maximum value holding unit outputs a maximum value held therein at the rising edge of the pulse signal from the first pulse signal output unit.

28. An image forming apparatus according to claim 26, wherein the first pulse signal output unit is replaced with a second pulse signal output unit that outputs a pulse signal a predetermined time after the input supply voltage to the fusing device falls below a predetermined threshold.

29. An image forming apparatus according to claim 28, wherein the maximum value holding unit outputs a maximum value held therein at the rising edge of the pulse signal from the second pulse signal output unit.

30. An image forming apparatus according to claim 28, wherein the discharge unit discharges a capacitor making up the integral unit and a capacitor making up the maximum value holding unit in response to the pulse signal from the second pulse signal output unit.