Image fusing device and image forming apparatus

• US 7,139,500 B2
• Filed: 11/02/2005
• Issued: 11/21/2006
• Est. Priority Date: 01/21/2003
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Takahashi, Atsuya, Mochizuki, Masataka, Kawazu, Takao
• Primary Examiner(s): Chen, Sophia S.
• Application Number:
  US11/263,987
• Publication Number:
  US 20060051122A1
• Time in Patent Office: 384 Days
• Field of Search: 399/320, 399/67, 399/69, 399/328, 399/88, 347/156, 318/98, 315/307, 315/291, 363/19, 363/125, 363/21.01
• US Class Current: 399/69
• 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. A current detection apparatus, comprising:

a current-voltage conversion unit for converting a current to an electric load 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 peak value holding unit for holding a peak value of an output from the integral unit; and

a resetting unit for resetting the peak value holding unit at a predetermined timing in each period of an AC power source.

2. An apparatus according to claim 1, wherein the integral unit comprises an integral circuit for integrating a half-wave rectified output produced by the half-wave rectification unit, and a differential amplification unit for amplifying a difference between an integrated result produced by the integral circuit and the half-wave rectified output,

wherein the integral circuit comprises a capacitor discharged at a predetermined timing in each period of the AC power source.

3. An apparatus according to claim 1, wherein the peak value holding unit has a capacitor and the resetting unit comprises a timing signal output unit that outputs a timing signal for discharging the capacitor thereby resetting the peak value holding unit.

4. An apparatus according to claim 1, wherein the resetting unit comprises a zero-cross detection circuit and at least one of a reset signal output circuit and a time constant circuit for outputting a signal for resetting the peak value holding unit at a predetermined time after the zero-cross detection timing.

5. An apparatus according to claim 1, further comprising a phase control unit for performing a phase-control of a supply of the AC power source to the electric load.

6. An image forming apparatus using a current detection apparatus according to claim 1, wherein said image forming apparatus has a fusing device for heat-fixing an image on a recording material as the electric load, and the current detection apparatus detects a current supplied to the fusing device.