Fixing device capable of detecting wrap jam of recording sheet and image forming apparatus

Patent metadata

Field	Value
Publication number	US-9235182-B2
Application number	US-201113098720-A
Country	US
Kind code	B2
Filing date	May 2, 2011
Priority date	May 6, 2010
Publication date	Jan 12, 2016
Grant date	Jan 12, 2016

Abstract

A fixing device capable of easily detecting a wrap jam of a recording sheet without increasing costs. A fixing roller fixes a toner image on a recording medium under heating control. A central thermistor and an end thermistor detect first and second temperatures of the fixing roller in respective sheet-passing and non-sheet-passing areas. A first temperature difference-detecting circuit compares a temperature difference between the first and second detected temperatures and a first threshold and outputs a first comparison result. A second temperature difference-detecting circuit compares the temperature difference and a second threshold larger than the first threshold and outputs a second comparison result. A switching circuit selects one of the first or second comparison results according to a switching signal from a CPU, and the CPU controls heating of the fixing roller based on the selected comparison result.

First claim

What is claimed is:

1. A fixing device comprising:
a fixing unit configured to be subject to heating control to thereby fix a toner image on a recording medium;
a first temperature-detecting unit configured to detect a temperature of the fixing unit in an area where the recording medium passes to obtain a first detected temperature;
a second temperature-detecting unit configured to detect a temperature of the fixing unit in an area where the recording medium does not pass to obtain a second detected temperature;
a temperature difference-comparing unit configured to compare a temperature difference between the first and second detected temperatures with at least one of a first threshold or a second threshold, which is larger than the first threshold; and
a control unit configured to:
control heating of the fixing unit so that the temperature detected by the first temperature-detecting unit reaches a target temperature;
control, until the temperature detected by the second temperature-detecting unit is at or surpasses a first reference temperature, which is lower than the target temperature, the temperature difference-comparing unit to compare the temperature difference with the second threshold, and stop heating of the fixing unit and generate a signal indicating a second abnormality based on the temperature difference being larger than the second threshold; and
control, upon the temperature detected by the second temperature-detecting unit being at or surpassing the first reference temperature, the temperature difference-comparing unit to compare the temperature difference with the first threshold, and stop heating of the fixing unit and generate a signal indicating a first abnormality based on the temperature difference being smaller than the first threshold.

2. The fixing device according to claim 1 , wherein the control unit controls, upon the temperature detected by the second temperature-detecting unit being at or surpassing a second reference temperature, which is higher than the first reference temperature, the temperature difference-comparing unit to compare the temperature difference with the second threshold, and stop heating of the fixing unit and notify the second abnormality when the temperature difference is larger than the second threshold.

3. The fixing device according to claim 2 , wherein the control unit stops comparing the temperature difference with the second threshold upon the temperature detected by the first temperature-detecting unit is at or surpasses the target temperature, after the temperature detected by the second temperature-detecting unit become higher than the second reference temperature.

4. The fixing device according to claim 1 , wherein the temperature difference-comparing unit comprises:
a first comparison circuit configured to compare, with the first threshold, the difference between the temperature detected by the first temperature-detecting unit and the temperature detected by the second temperature-detecting unit; and
a second comparison circuit configured to compare, with the second threshold, the difference between the temperature detected by the first temperature-detecting unit and the temperature detected by the second temperature-detecting unit.

5. The fixing device according to claim 1 , wherein the first abnormality means an abnormality where the recording medium is wrapped around the fixing unit, and the second abnormality means an abnormality of the first temperature-detecting unit or the second temperature-detecting unit.

6. An image forming apparatus comprising:
a transfer unit configured to transfer a toner image onto a recording medium according to image data;
a fixing unit configured to be subject to heating control to thereby fix the toner image transferred by the transfer unit on the recording sheet;
a first temperature-detecting unit configured to detect a temperature of the fixing unit in an area where the recording medium passes to obtain a first detected temperature;
a second temperature-detecting unit configured to detect a temperature of the fixing unit in an area where the recording medium does not pass to obtain a second detected temperature;
a temperature difference-comparing unit configured to compare a temperature difference between the first and second detected temperatures with at least one of a first threshold or a second threshold, which is larger than the first threshold; and
a control unit configured to:
control heating of the fixing unit so that the temperature detected by said first temperature-detecting unit reaches a target temperature;
control, until the temperature detected by the second temperature-detecting unit is at or surpasses a first reference temperature, which is lower than the target temperature, the temperature difference-comparing unit to compare the temperature difference with the second threshold, and stop heating of the fixing unit and notify a second abnormality based on the temperature difference being larger than the second threshold; and
control, upon the temperature detected by the second temperature-detecting unit being at or surpassing the first reference temperature, the temperature difference-comparing unit to compare the temperature difference with the first threshold, and stop heating of the fixing unit and notify a first abnormality based on the temperature difference being smaller than the first threshold.

7. The image forming apparatus according to claim 6 , wherein the control unit controls, upon the temperature detected by the second temperature-detecting unit being at or surpassing a second temperature, which is higher than the first reference temperature, the temperature difference-comparing unit to compare the temperature difference with the second threshold, and stop heating of the fixing unit and notify the second abnormality when the temperature difference is larger than the second threshold.

8. The image forming apparatus according to claim 7 , wherein the control unit stops comparing the temperature difference with the second threshold upon the temperature detected by the first temperature-detecting unit being at or surpassing the target temperature, after the temperature detected by the second temperature-detecting unit become higher than the second temperature.

9. The image forming apparatus according to claim 6 , wherein the temperature difference-comparing unit comprises:
a first comparison circuit configured to compare, with the first threshold, the difference between the temperature detected by the first temperature-detecting unit and the temperature detected by the second temperature-detecting unit; and
a second comparison circuit configured to compare, with the second threshold, the difference between the temperature detected by the first temperature-detecting unit and the temperature detected by the second temperature-detecting unit.

10. The image forming apparatus according to claim 6 , wherein the first abnormality means an abnormality where the recording medium is wrapped around the fixing unit, and the second abnormality means an abnormality of the first temperature-detecting unit or the second temperature-detecting unit.

11. A fixing device comprising:
a fixing unit configured to be subject to heating control to thereby fix a toner image on a recording medium;
a first temperature-detecting unit configured to detect a temperature of the fixing unit in an area where the recording medium passes to obtain a first detected temperature;
a second temperature-detecting unit configured to detect a temperature of the fixing unit in an area where the recording medium does not pass to obtain a second detected temperature; and
a control unit configured to:

Assignees

• Fukushi Kenji
• Canon Kk

Inventors

• Fukushi Kenji

Classifications

• G03G15/55

  Self-diagnostics; Malfunction or lifetime display · CPC title

• G03G15/2039 Primary

  with means for controlling the fixing temperature · CPC title

• G03G15/70 Primary

  Detecting malfunctions relating to paper handling, e.g. jams · CPC title

• G03G15/205

  specially for the mode of operation, e.g. standby, warming-up, error (G03G15/2046 takes precedence) · CPC title

• G03G15/2078

  Physics · mapped topic