Fixing device and image forming apparatus

• US 20050163524A1
• Filed: 01/24/2005
• Published: 07/28/2005
• Est. Priority Date: 01/28/2004
• Status: Active Grant

• Current Assignee: Oki Data Corporation (OKI Electric Industry Company Limited)
• Original Assignee: Oki Data Corporation (OKI Electric Industry Company Limited)
• Inventors: Shiobara, Toshimasa, Aida, Koji
• Granted Patent: US 7,555,233 B2
• Time in Patent Office: Days
• US Class Current: 399/69
• CPC Class Codes: G03G 15/2039 with means for controlling the fixing temperature

Abstract

A fixing device includes a non-contacting thermistor (54) disposed in the vicinity of the surface of a heat roller (21) and an upper cover temperature thermistor (60) for detecting the temperature of a pressure roller (22). The calculated surface temperature (T) of the heat roller 21 is calculated based on the detected temperature (T1) detected by the non-contacting thermistor (54), the detected temperature (T2) detected by the upper cover temperature thermistor (60), the distance (L1) from the non-contacting thermistor (54) to the surface of the heat roller (21) and the distance (L2) from the non-contacting thermistor (54) to the upper cover (51).

Claims

1. A fixing device for fixing a developer image to a recording medium, said fixing device comprising:

a heat source;

a heating member heated by said heat source so as to heat said recording medium;

a first temperature detecting unit that detects a temperature of said heating member and is remote from said heating member;

a second temperature detecting unit provided in the proximity of said first temperature detecting unit; and

a control unit that controls said heat source according to detected temperatures detected by said first and second temperature detecting units.

2. The fixing device according to claim 1, wherein said second temperature detecting unit detects a surrounding temperature of said heating member.

3. The fixing device according to claim 1, further comprising a cover that supports said heating member or covers said heating member to reduce the radiation of heat from said heating member,

wherein said second temperature detecting unit detects a temperature of said cover.

4. The fixing device according to claim 3, wherein said control unit controls said heating member based on a calculated surface temperature T of said heating member determined by the following equation:

T=T1+(T1−

T2)×

(L1/L2)×

C

where T1 indicates a detected temperature detected by said first temperature detecting unit, T2 indicates a detected temperature detected by said second temperature detecting unit, L1 indicates a distance between said heating member and said first temperature detecting unit, L2 indicates a distance between said first and second temperature detecting units in a radial direction of said heating member, and C is a constant.

5. The fixing device according to claim 3, wherein said first and second temperature detecting units are substantially aligned on a line perpendicular to a tangential plane of a part of a circumferential surface of said heating member.

6. The fixing device according to claim 5, further comprising a partition wall that defines a space in which said part of said circumferential surface of said heating member, said first temperature detecting unit and said second temperature detecting unit are disposed.

7. The fixing device according to claim 1, wherein said first and second temperature detecting units respectively comprise thermistors.

8. The fixing device according to claim 1, further comprising an adjusting mechanism for adjusting the distance between a surface of said heating member and said first temperature detecting unit.

9. The fixing device according to claim 3, wherein said first and second temperature detecting units are constituted by a common temperature detecting unit,

wherein said fixing device further comprises a moving mechanism that moves said common temperature detecting unit between a first position in the vicinity of a surface of said heating member and a second position in which said common temperature detecting unit contacts said cover, and

wherein said common temperature detecting unit acts as said first temperature detecting unit when said common temperature detecting unit is in said first position, and acts as said second temperature detecting unit when said common temperature detecting unit is in said second position.

16. An image forming apparatus having said fixing device according to claim 1, said image forming apparatus further comprising:

a medium feeding unit that feeds said recording medium; and

an image forming unit that forms a developer image on said recording medium,

wherein said fixing device fixes said developer image on said recording medium.

10. A fixing device for fixing a developer image to a recording medium, said fixing device comprising:

a heat source;

a heating member heated by said heat source so as to heat said recording medium;

a first temperature detecting unit that detects a temperature of said heating member, and is remote from said heating member;

a third temperature detecting unit that detects a temperature transmitted from said heating member; and

a control unit that compensates a detected temperature detected by said first temperature detecting unit based on a detected temperature detected by said third temperature detecting unit, and controls said heat source based on a compensated detected temperature.

11. The fixing device according to claim 10, further comprising a pressure member urged against said heating member so as to nip said recording medium therebetween,

wherein said third temperature detecting unit detects a temperature of said pressure member.

12. The fixing device according to claim 10, wherein said control unit controls said heating member based on a calculated surface temperature T of said heating member based on the following equation:

T=T1+a×

T3+b

where T1 indicates a detected temperature detected by said first temperature detecting unit, T3 indicates a detected temperature detected by said third temperature detecting unit, and a and b are constants.

13. The fixing device according to claim 12, wherein said control unit determines an accumulated value Q of a detected temperature T1 detected by said first temperature detecting unit and a detected temperature T3 detected by said third temperature detecting unit, and

wherein, when said accumulated value Q is greater than or equals to a predetermined threshold, said control unit controls said heating member based on a calculated surface temperature T determined by the following equation:

T=T1+d

where d is a constant.

14. The fixing device according to claim 13, wherein said heating member and said pressure member respectively comprise rollers, and said control unit compensates said accumulated value Q based on a rate of decrease in said detected temperature T3 when said rollers stop rotating after said rollers rotate for a predetermined time.

15. The fixing device according to claim 14, wherein said rate Δ

T of decrease in said detected temperature T3 is determined based on the following equation;

Δ

T=Δ

T3/(T1−

T3)×

100,

where Δ

T3 indicates the amount of decrease in said detected temperature T3, and

wherein, when Δ

T is greater than or equals to a predetermined value, said control unit determines an initial value of said accumulated value Q as follows;

Q(initial value)=−

e×

Δ

T+f

where e and f are constants.

17. An image forming apparatus having said fixing device according to claim 10, said image forming apparatus further comprising:

a medium feeding unit that feeds said recording medium; and

an image forming unit that forms a developer image on said recording medium,

wherein said fixing device fixes said developer image on said recording medium.