JP2001242741A - A method for controlling the temperature of a fuser using a non-contact temperature sensor - Google Patents

Abstract

(57) [Summary] [Problem] When a heat roller of a fixing device of an electrophotographic printer continuously transports recording paper, the surface temperature of a paper passing area becomes lower than the surface temperature of a non-paper passing area. For this reason, the surface temperature of the paper passing area is detected by a non-contact temperature detector, and the heat roller is turned on / off such that the detected temperature becomes a predetermined temperature to control the temperature of the heat roller. However, a delay in heat transfer due to a gap between the surface of the heat roller and the temperature detector causes the surface temperature of the heat roller to fluctuate greatly during temperature control. SOLUTION: A judgment temperature during a cleaning sequence is set lower than a judgment temperature during a printing operation, and when the surface temperature of a heat roller 102 increases during the cleaning sequence, the halogen lamp 106 is set to a lower judgment temperature. Is turned off, and a delay in off timing due to a delay in heat transfer is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature control for a fixing device of an electrophotographic printer, and more particularly to a temperature control method for controlling a heat generating portion based on surface temperature information of a heat roller detected by a non-contact temperature sensor.

[0002]

2. Description of the Related Art FIG. 8 is a perspective view schematically showing a main part of a general fixing device of an electrophotographic printer.
FIG. 9 is a sectional view of a main part at the position of the instruction lines A, A in FIG. In the figure, a heat roller 102 is rotatably disposed inside a housing 111 of the fixing device 101, and is driven by a driving unit (not shown) to rotate around an axis 103 as a rotation axis. The heat roller 102 has an outer shell formed of a hollow hollow shell 104 (FIG. 9) made of aluminum, iron, or the like. The outer peripheral surface of the heat roller 102 is made of PFA (PFA) to protect the hollow shell itself and prevent toner adhesion. It is covered with a heat-resistant release layer 105 made of a fluoro resin such as perfluoroalkoxy fluororesin) or PTFE (polytetrafluoroethylene resin).

[0003] Inside the hollow shell 104, a halogen lamp 106 is arranged along an axis 103 for the purpose of heating the heat roller 102. The heat is transmitted to the entire surface to heat it.

[0004] The backup roller 107 includes a core metal 108.
Is covered with an elastic layer 109 made of rubber or the like, and is rotatably held inside the housing 111 around the axis 110 as a rotation axis. At this time, the axis 103 of the heat roller 102 and the axis 110 of the backup roller 107 are arranged in parallel with each other, and the peripheral surface of the backup roller 107 is pressed by the urging means (not shown) so as to press against the peripheral surface of the heat roller 102. Be inspired.

Therefore, when the heat roller 102 is rotationally driven by the driving means in the direction of arrow P1 (FIG. 9), the backup roller 107 also rotates by receiving the rotational force due to the frictional force, and the recording paper transferred between the rollers. 112 (FIG. 9) are transferred in the direction of arrow P2 in cooperation. During this time, the recording paper 11
2 is heated and pressed by the heat roller 102 to fix the toner.

[0006] In order to prevent the recording paper 112 from being wound around the peripheral surface of the heat roller 102, a separation claw 113 (which separates the adhered recording paper and prevents the recording paper from entering the subsequent area is provided. FIG. 9) is arranged.

The contact thermistor 114 is a heat roller 1
No. 02, that is, in contact with the peripheral surface near the end of the heat roller 102, and detects the surface temperature of that portion. The contact thermistor 114 disposed in contact with the peripheral surface of the heat roller 102 is disposed in the non-sheet passing area at the end of the heat roller 102 because the toner adhered to the peripheral surface of the heat roller 102 is contacted with the contact thermistor 114. This is to prevent the recording paper 112 from being stained by the toner that has fallen in contact with the toner and has fallen.

The surface temperature of the heat roller 102 is detected by a contact thermistor 114, and the temperature data is sent to a control unit (not shown). The control unit controls the power of the halogen lamp 106 on and off based on the temperature data so that the surface temperature of the heat roller 102 maintains a predetermined value.

By the way, the hollow shell 104 of the fixing device 101
In FIG. 9, it is desired to reduce the wall thickness in order to save energy or shorten the warm-up time. However, in the fixing device 101 as described above, if the temperature of the hollow shell 104 is simply controlled by reducing the thickness, the following inconvenience occurs.

FIG. 10 shows the surface temperature distribution of the heat roller 102 in the paper passing area and the non-paper passing area when the recording paper 112 is transferred by the heat roller 102 and the backup roller 107 to fix the toner. . When the fixing of the recording paper is performed continuously, the surface temperature of the non-paper passing area decreases while the surface temperature of the non-paper passing area decreases as shown in FIG. This is because, although the heat on the surface of the paper passing area of the heat roller 102 moves to the recording paper and the temperature is lowered, the thickness of the hollow shell 104 is thin, so that the heat conduction path is narrowed and the longitudinal direction is reduced. It is considered that the apparent heat conduction in the direction became poor, and the heat became difficult to flow in the longitudinal direction.

To solve this problem, a heat roller 1
No. 02 (FIG. 8) near the peripheral surface of the paper passing area, for example, near the outer peripheral surface at the longitudinal center of the heat roller.
15 (FIG. 8), the surface temperature of the paper passing area is directly detected, and the temperature is controlled so that the temperature of this portion becomes a desired value.

[0012]

However, when temperature control is performed using the non-contact thermistor 115 (FIG. 8), the surface of the heat roller 102 and the non-contact thermistor 11 are controlled.
Since the gap D exists between the five, a time delay occurs before the surface temperature of the heat roller 102 is detected by the non-contact thermistor 115. Due to the existence of this time delay,
There is a problem that the surface temperature of the heat roller 102 during the temperature control varies depending on various use conditions described later.

FIG. 11 detects the surface temperature of the paper passing area of the heat roller 102 by (FIG. 8), and turns on / off the halogen lamp 106 so that the detected surface temperature y maintains a predetermined value. 6 is a graph showing a change in the surface temperature of the heat roller 102 when performing continuous printing while controlling the temperature. Note that continuous printing refers to a mode in which the rotation of the heat roller 102 and the backup roller 107 is not stopped after printing of one page of recording paper is completed, and the next page is printed. Therefore, the heat roller 102 may run idle without transferring the recording paper.

The vertical axis indicates the surface temperature, and the horizontal axis indicates the passage of time. Further, in the drawing, xj is a surface temperature curve showing a change in the surface temperature x in the sheet passing area of the heat roller 102 facing the non-contact thermistor 115, and is a bar-shaped indication line P below the graph.
P indicates the presence or absence of the recording paper 112 passing through the heat roller 102, and the black bar indicates the time region in which the recording paper 112 exists.

The blank time regions L1, L2,
L3 corresponds to a time region of a cleaning sequence that is periodically performed during the continuous printing. During this time, the heat roller 102 rotates in a temperature-controlled state, but the printing paper 112 is not printed because printing is not performed. do not do.

As described above, when the blank time areas L1, L2, L3 of the recording paper for a predetermined time or more exist during continuous printing,
The surface temperature x in the paper passing area of the heat roller 102 shows a relatively large fluctuation as shown in FIGS. That is, when recording paper is continuously present outside the blank time area, the temperature control is in a steady state, and the surface temperature of the paper passing area fluctuates to some extent but is relatively stable.
In L2 and L3, since the heat in the paper passing area does not flow to the recording paper, the temperature in this area increases.

This temperature rise is caused by the non-contact thermistor 115
(FIG. 8), and when the detected surface temperature y exceeds a predetermined judgment temperature hy, the halogen lamp 10 is detected.
6 is turned off, but since the gap D exists between the surface of the heat roller 102 and the non-contact thermistor 115, the off timing is delayed by the delay time Δt, and as a result, the surface temperature becomes higher than the set value. Large temperature ripples like A and B in FIG. 11 occur.

FIG. 12 shows a non-contact thermistor 1 when recording paper is continuously present and temperature control is in a steady state.
15 and the heat roller 102
6 is a graph showing a change in a surface temperature x of a portion of the sheet passing area facing the non-contact thermistor 115. As is clear from the figure, the detected surface temperature y becomes lower than the surface temperature x, and a delay time Δt occurs before the surface temperature is detected.

In this case, the surface temperature x decreases and the time t1
After reaching the set temperature hx, the halogen lamp is kept off, and at time t2 after the delay time Δt, the halogen lamp is turned on when the detected surface temperature y reaches the determination temperature hy. As described above, since the on / off switching timing of the halogen lamp is always delayed by the delay time Δt,
Even in the steady state described above, a predetermined level of ripple occurs on the heat roller surface.

An object of the present invention is to detect the surface temperature of the paper passing area of the heat roller 102 by a non-contact thermistor, and to set the temperature of this portion to a desired value based on the detected surface temperature. Is to control the temperature by turning on / off the temperature, regardless of the use conditions, so that the temperature can be controlled with the fluctuation of the surface temperature kept as small as possible.

[0021]

In order to heat an outer peripheral surface of a heat roller of a fixing device, a heating element that can be turned on / off is disposed inside the heat roller, and an outer peripheral surface of a paper passing area of the heat roller is provided. When a non-contact temperature sensor is arranged in the vicinity, and the heating element is turned on / off based on the temperature detected by the non-contact temperature sensor, and the surface temperature of the heat roller is controlled,
During the rotation of the heat roller, a first determination temperature is set during a first period during which the recording paper is continuously transported, and during the operation of the heat roller, a second determination is made during which the recording paper is not transported for a predetermined period. A second judgment temperature lower than the first judgment temperature is set in a period, and the detected temperature and the first judgment temperature are set in the first period.
The heating element is turned on / off based on a comparison with the determination temperature, and the heating element is turned on / off based on a comparison between the detected temperature and the second determination temperature during the second period. Thus, the surface temperature of the heat roller is controlled.

In another aspect of the invention, a heating element that can be turned on / off is disposed inside the heat roller in order to heat the outer peripheral surface of the heat roller of the fixing device, and the outer peripheral surface of the heat roller in a paper passing portion area is provided. A non-contact temperature sensor is disposed in the vicinity, and the heating element is turned on / off based on the temperature detected by the non-contact temperature sensor to control the surface temperature of the heat roller. In a first situation where the detected temperature is within the predetermined temperature range and the rate of change is positive and larger than a first set value, the heating element is turned off and the detected temperature is set to the predetermined temperature. In a second situation where the rate of change is negative and the absolute value is greater than the second set value, the heating element is turned on, and the detected temperature is other than the first and second situations. The detected temperature is higher than the determination temperature. When have is turned off the heating element, the detected temperature is outside the first and second conditions,
When the detected temperature is lower than the determination temperature, the heating element is turned on to control the surface temperature of the heat roller.

Further, the heating element may be constituted by a halogen lamp.

Further, the non-contact temperature sensor may be constituted by a thermistor.

Further, the non-contact temperature sensor may be arranged near an outer peripheral surface of a central portion in a longitudinal direction of the heat roller.

[0026]

FIG. 1 is a block diagram of a control system for executing a control method according to the present invention. This control system 1
This is for controlling the surface temperature of the heat roller 102 of the fixing device 101 shown in FIG. In the figure, the control circuit 2 receives the surface temperature information TINF of the heat roller 102 detected by the non-contact thermistor 115 and outputs a switching signal CONV for controlling on / off of the halogen lamp 106 according to a predetermined processing procedure. .

FIG. 2 is a flowchart showing a processing procedure of the first embodiment according to the control method of the present invention, which is executed by the control circuit 2. According to this flow, at the time of the continuous printing, it is checked whether the printing operation is being performed or the cleaning sequence is being performed (step 1). In the case of the cleaning sequence, the determination temperature hy to be compared with the detected surface temperature y detected by the non-contact thermistor 115 is set as hy = reference temperature h0−correction temperature h1 (step 2). Sets this determination temperature hy to hy = reference temperature h0 (step 3). Therefore, the determination temperature hy during the cleaning sequence is set lower than the determination temperature during the printing operation by the correction temperature h1. The control circuit 2 determines the determination temperature hy,
It has a register for storing the reference temperature h1, the correction temperature h0, and the like.

Next, the detected surface temperature y detected by the non-contact thermistor 115 is read (step 4), and it is determined whether or not the detected surface temperature y is lower than the judgment temperature hy (step 5). If it is low, the halogen lamp 106 is turned on, and if it is high, the halogen lamp 106 is turned off (steps 6 and 7). Then, after a predetermined time interval A seconds has elapsed (step 8), the flow returns to step 1 again, and the same flow is repeated.

As described above, according to the processing procedure of the first embodiment of the present invention, the judgment temperature hy = h0−h1 during the cleaning sequence is changed to the judgment temperature hy = h0 during the printing operation.
Is set lower than the correction temperature h1. For this reason, when the surface temperature of the heat roller 102 increases during the cleaning sequence, the timing for turning off the halogen lamp 106 becomes faster by the lower the determination temperature is set, and the above-described delay in turning off the halogen lamp 106 is eliminated. In addition, unnecessary temperature rise can be prevented. Note that the correction temperature h1 is determined by the heat roller 1 during the heat transmission time delay Δt due to the existence of the gap D (FIG. 8).
No. 02 is set in consideration of the temperature range in which the surface temperature increases.

FIG. 3 shows a change curve x of the surface temperature x of the heat roller 102 when the temperature is controlled by turning on / off the halogen lamp 106 according to the processing procedure of the first embodiment.
12 is a graph showing j, and other settings are the same as the graph of FIG. As is apparent from FIG. 6, even if blank time regions L1, L2, and L3 of the recording paper indicating the time region of the cleaning sequence during continuous printing are present, the surface temperature x of the heat roller 102 is affected by this. Large fluctuations do not appear.

FIG. 4 is a characteristic diagram for explaining basic features of the second embodiment according to the control method of the present invention. In the control method according to the second embodiment, (h
A predetermined temperature range hf is set with (y + α) as the upper limit and (hy−β) as the lower limit. Then, the detected surface temperature y is detected, and the rate of change of the detected surface temperature y (hereinafter, referred to as a gradient) is detected.
k is calculated, and the surface temperature of the heat roller 102 is controlled.

The control method will be described with reference to the characteristic diagram of FIG. 4 in accordance with the flowchart of FIG. 5 showing the processing procedure of the second embodiment. Note that this flow is the same as that in FIG.
Is executed by the control circuit 2 in the control system 1 of FIG.

When the program starts, the detected surface temperature y is fetched, and the slope k at that time is calculated (step 1). The slope k is calculated by calculating a temperature difference of the detected surface temperature y detected every unit time, for example, every 40 msec.

The detected surface temperature y is lower than the lower limit (hy-
If the detected surface temperature y is higher than the upper limit (hy + α), the halogen lamp 106 is turned off (steps 2, 3, 4, and 5).
5).

When the detected surface temperature y is (hy-β) ≦ y ≦
If (hy + α) is satisfied and the slope k is positive and larger than a predetermined positive slope K1, the halogen lamp 106 is turned off (steps 6, 7, 8). When the detected surface temperature y is (h
If (y−β) ≦ y ≦ (hy + α) is satisfied, and the slope k is negative and the absolute value is larger than a predetermined negative slope K2, the halogen lamp 106 is turned on (steps 6, 9, 1).
0).

In other cases, that is, when the detected surface temperature y is
If (hy-β) ≦ y ≦ (hy + α) is satisfied and the positive / negative slope is gentler than the above-described value, the process proceeds to step 11 and if the detected surface temperature y is higher than the determination temperature hy, the halogen lamp 106 is turned off. On the other hand, if it is low, normal control for turning on the halogen lamp 106 is performed (steps 11, 12, and 13). Thereafter, the process returns to step 1 and the above control flow is repeated. The control circuit 2
Has a register for storing a lower limit value (hy-β), an upper limit value (hy + α), and positive and negative slopes K1, K2, and the like.

FIG. 6 shows that the halogen lamp 106 is turned on / off in accordance with the above-described processing procedure, and the surface temperature of the heat roller 102 whose temperature is controlled is measured by a non-contact thermistor 115.
9 is a graph showing a change in the detected surface temperature y detected by (FIG. 8).

Before time t0, the detected surface temperature y is lower than the lower limit (hy-β) of the predetermined temperature range hf, so that the halogen lamp 106 is turned on. From time t0 to t
During 1, the halogen lamp is turned off because the detected surface temperature y is within the temperature range hf and its slope k is greater than the positive slope K1. During the period from time t1 to t2, the detected surface temperature y exceeds the upper limit (hy + α) of the temperature region hf, and the halogen lamp 106 continues to be kept off during this time.

During the period from time t2 to time t3, the detected surface temperature y is within the temperature range hf, the slope k is negative, and the absolute value is larger than the negative slope K2.
Turns on. Further, from time t3 to t4, the detected surface temperature y is lower than the lower limit (hy-β) of the predetermined temperature range hf, so that the halogen lamp is continuously turned on.

From time t4 to time t5, the detected surface temperature y
Is within the temperature range hf, and its slope k is larger than the positive slope K1, so that the halogen lamp 106 is turned off. From the subsequent time t5 to t6, the detected surface temperature y is within the temperature range hf, and the positive and negative slopes are gentler than the predetermined slope and higher than the threshold hy, so that the halogen lamp 106 is continuously turned off. Between the time t6 and the time t7, the detected surface temperature y is within the temperature region hf, the slope k is negative, and the absolute value is larger than the negative slope K2, so that the halogen lamp 106 is turned on.

From time t7 to time t9, the detected surface temperature y
Represents that the halogen lamp 10 is in the temperature range hf, and the positive and negative slopes are smaller than a predetermined slope and lower than the threshold hy.
6 is subsequently turned on. After time t9, since the detected surface temperature y is within the temperature range hf and the positive / negative slope is gentler than the predetermined slope, the halogen lamp 106 is turned on / off depending on whether or not it is higher than the threshold value hy. On the other hand, if it is low, it is turned on.

As described above, according to the processing procedure of the second embodiment of the present invention, when the detected surface temperature y detected by the non-contact thermistor does not reach the lower limit (hy-β) of the temperature region hf. When the halogen lamp 106 is turned on, the temperature range hf
If the temperature exceeds the upper limit (hy + α), the halogen lamp is turned off. If the temperature is within the predetermined temperature range hf, the halogen lamp 106 is turned on / off according to the magnitude of the gradient of the temperature rise or the temperature drop to heat. The surface temperature of the roller 102 is controlled.

For this reason, when it is expected that the amplitude of the temperature change becomes large by monitoring the slope of the temperature change, the halogen lamp 106 is turned on / off in a direction to suppress the increase, so that the temperature ripple is reduced. It becomes possible.

The graph of FIG. 7 shows the blank time regions L4 and L5 of the recording paper according to the cleaning sequence during continuous printing.
The processing procedure of the first embodiment for suppressing the fluctuation of the surface temperature of the heat roller in the case where the temperature is present, and the processing procedure of the second embodiment for suppressing the fluctuation of the surface temperature of the heat roller 102 when the temperature control is in a steady state. 9 shows a change curve xj of the surface temperature x when the processing procedure is executed together with the processing procedure.

The processing procedure by this combination is the same as the processing from step 1 to step 13 in the dotted frame in the flowchart of FIG. 5 showing the processing procedure of the second embodiment, and FIG. 2 showing the processing procedure of the first embodiment. This is made possible by replacing the flow from step 4 to step 7 in the dotted frame of the flowchart. In this case, as is apparent from the figure, the blank time areas L4 and L4 of the recording paper 112 during continuous printing.
5, ripples in the surface temperature x of the heat roller 102 can be suppressed over the entire time range.

In the above-described embodiment, the blank time area of the recording paper during continuous printing has been described assuming a cleaning sequence. However, the recording paper is not transported with the heat roller rotated for a predetermined time. This corresponds to a situation in which the motor runs idle and is not limited to this cleaning sequence.

[0047]

According to the method of controlling the temperature of the fixing device according to the present invention, the determination temperature in the blank time area where the recording paper does not pass for a predetermined time during the rotation of the heat roller is changed to the determination temperature in the time area where the recording paper sequentially passes. If the surface temperature of the heat roller rises during the blank time of the recording paper, the timing for turning off the halogen lamp is accelerated by the lower judgment temperature, and the halogen lamp is turned off. Unnecessary temperature rise due to timing delay can be prevented. According to the method of controlling the temperature of the fixing device according to the present invention, the inclination of the temperature change is monitored, and when the amplitude of the temperature change is expected to increase, the halogen lamp is turned on / off in a direction to suppress the increase. Therefore, the temperature ripple can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram of a control system that executes a control method according to the present invention.

FIG. 2 is a flowchart showing a processing procedure according to the first embodiment by the control method of the present invention.

FIG. 3 is a graph showing a change in the surface temperature of the heat roller 102 when controlled by the processing procedure of the first embodiment.

FIG. 4 is a characteristic diagram for explaining basic features of a second embodiment according to the control method of the present invention.

FIG. 5 is a flowchart showing a processing procedure according to a second embodiment according to the control method of the present invention.

FIG. 6 is a graph showing a change in a detected surface temperature y when controlled according to a processing procedure according to a second embodiment of the present invention.

FIG. 7 is a graph showing a change in the surface temperature of the heat roller 102 when the processing procedures of the first embodiment and the second embodiment are performed simultaneously.

FIG. 8 is a perspective view schematically showing a main part configuration of a general fixing device of the electrophotographic printer.

FIG. 9 is a sectional view of a main part of the fixing device shown in FIG. 8;

FIG. 10 is a surface temperature distribution diagram of the heat roller 102 in a sheet passing area and a non-sheet passing area when recording paper is continuously passed.

FIG. 11 is a graph showing a change in the surface temperature of the heat roller 102 during continuous printing when the temperature is controlled by a conventional control method.

FIG. 12 shows the surface temperature a of the heat roller 102 and the detected surface temperature y detected by the non-contact thermistor 115 when the temperature is controlled by a conventional control method and recording paper is continuously present and the control is in a steady state. It is a graph which showed the change.

[Explanation of symbols]

Reference Signs List 1 control system, 2 control circuit, 101 fixing device, 1
02 heat roller, 103 axis, 104 hollow shell, 105 heat-resistant release layer, 106 halogen lamp, 107 backup roller, 108 cored bar,
109 elastic layer, 110 axis, 111 housing,
112 recording paper, 113 separation claw, 114 contact thermistor, 115 non-contact thermistor.

Continued on the front page F term (reference) 2H033 BA31 BA32 BB18 CA04 CA05 CA30 CA32 CA45 3K058 AA12 AA72 BA18 CA12 CA23 CA61 CA91 CB02 CE02 CE12 CE17 DA17 GA02 5H323 AA35 BB04 CA06 CB04 GG04 HH02 KK05 MM02

Claims (5)

[Claims] 1. A heating element which can be turned on / off inside a heat roller for heating an outer peripheral surface of a heat roller of a fixing device, and which is in non-contact with a vicinity of an outer peripheral surface of a paper passing portion area of the heat roller. A temperature control method comprising: disposing a temperature sensor; turning on / off the heating element based on a temperature detected by the non-contact temperature sensor; and controlling a surface temperature of the heat roller. Setting a first determination temperature during a first period in which the recording paper is continuously transported, and performing the first determination in a second period during which the recording paper is not transported for a predetermined period during rotation of the heat roller. Setting a second determination temperature lower than the temperature; turning on / off the heating element based on a comparison between the detected temperature and the first determination temperature during the first period; The detected temperature and the second determination temperature A method of controlling the temperature of the fixing device by a non-contact temperature sensor for controlling the surface temperature of the heat roller by turning on / off the heating element based on the comparison of the above. 2. A heating element which can be turned on / off inside the heat roller for heating the outer peripheral surface of the heat roller of the fixing device, and which is in non-contact with the vicinity of the outer peripheral surface of the paper passage area of the heat roller. A temperature control method for disposing a temperature sensor, turning on / off the heating element based on a temperature detected by the non-contact temperature sensor, and controlling a surface temperature of the heat roller, wherein a predetermined temperature including a determination temperature is included. Setting a range, in a first situation where the detected temperature is within the predetermined temperature range and the rate of change is positive and greater than a first set value, the heating element is turned off, and the detected temperature is the In a second situation where the rate of change is negative and the absolute value is greater than a second set value within a predetermined temperature range, the heating element is turned on, and the detected temperature is in the first and second situations. The detection temperature is the judgment temperature When the temperature is higher, the heating element is turned off. When the detected temperature is other than the first and second situations, and when the detected temperature is lower than the determination temperature, the heating element is turned on and the heat roller is turned off. A method for controlling the temperature of a fixing device using a non-contact temperature sensor for controlling a surface temperature. 3. The method for controlling the temperature of a fixing unit by a non-contact temperature sensor according to claim 1, wherein the heating element is formed of a halogen lamp. 4. The method according to claim 1, wherein the non-contact temperature sensor comprises a thermistor. 5. The method for controlling the temperature of a fixing device using a non-contact temperature sensor according to claim 1, wherein the non-contact temperature sensor is disposed near an outer peripheral surface of a central portion in a longitudinal direction of the heat roller.