JP2006284692A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device for performing suitable heating control of a fixing member, without performing strict initial setting for a gap distance between the fixing member and a contactless temperature sensing means. <P>SOLUTION: The fixing device 1 comprises a fixing roller 11 for incorporating a halogen lamp 15; a pressure roller 21 for pressure-contacting it; a contact thermistor 16 brought into contact with a non-paper passing region of the surface of the fixing roller 11; a non-contact thermistor 17 provided spacing a prescribed gap from a paper-passing region surface of the fixing roller 11; and a dection means moving mechanism 40 for modifying the gap distance. A control means 50 stabilizes the surface temperature of the fixing roller 11, on the basis of information from the contact thermistor 16, modifies the position of the non-contact thermistor 17 by the detection means moving mechanism 40, on the basis of information from the contact thermistor 16 and the non-contact thermistor 17 after the surface temperature has stabilized, and performs heating control, on the basis of the information from the non-contact thermistor 17, after the position change. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention inserts a sheet carrying an unfixed toner image into a fixing nip formed by press-contacting a fixing member having a heating unit and a pressure member, and heats and pressurizes the toner image to fix it on the surface of the sheet. The present invention relates to a fixing device.

  In an electrophotographic image forming apparatus, a heating unit is incorporated in at least one of a fixing member and a pressure member that are pressed against each other to form a fixing nip, and between the members heated by the heating unit A thermal fixing method is widely used in which a paper carrying an unfixed toner image is inserted into a fixing nip, whereby the toner image is heated and pressurized to be fixed on the paper surface. A fixing device using such a heat fixing system usually includes a fixing roller as a fixing member and a pressure roller as a pressure member, and a heating unit is arranged inside the fixing roller, and the pressure roller The structure which does not arrange | position a heating means inside is employ | adopted.

  Conventionally, the surface temperature of the fixing roller has been detected by contact-type temperature detecting means that contacts the non-sheet passing area of the surface. Based on the surface temperature of the non-sheet passing area, the temperature of the fixing roller is controlled by the heating means. However, while the sheet passing area is deprived of heat by the paper and toner and the surface temperature is lowered, the non-sheet passing area is not deprived of heat and the surface temperature is different from each other. In addition to this, in a situation where the speed of the recent image forming apparatus and the diversification of usable papers have progressed, the fixing operation corresponding to each condition has become difficult. Therefore, there has been a high possibility that a fixing failure in which an image is disturbed due to insufficient fixing or uneven fixing occurs.

In view of this, there has been proposed a technique aimed at realizing a suitable fixing operation by detecting the temperature of the sheet passing area on the surface of the fixing roller. The temperature of the paper passing area is detected by a non-contact temperature detecting means provided at a position slightly away from the surface of the fixing roller. An example of a fixing device that detects the temperature of the sheet passing area on the surface of the fixing roller by such a non-contact type temperature detecting means can be seen in Japanese Patent Application Laid-Open No. H10-228707.
Japanese Patent No. 2673455 (page 2-3, FIG. 2-4)

  In the heat roller fixing device described in Patent Document 1, a correction temperature sensor (when the fixing device is idling) (in order to eliminate the problem of performing temperature detection only with a non-contact temperature sensor (non-contact temperature detecting means)). The surface temperature of the heat roller (fixing member) is detected by the contact type temperature detecting means) to control the heating means. During the copying (image forming) operation, the output value of the non-contact temperature sensor and the idling temperature sensor for idling Heating control is performed by calculating the output value. However, the temperature detection by the non-contact temperature detection means is greatly affected by the distance of the gap with the fixing member. As a result, the initial setting of the gap is important, and it is necessary to pay sufficient attention to misalignment due to transport and changes over time. In the heat roller fixing device described in Patent Document 1, such a gap between the fixing member and the non-contact type temperature detecting means is not considered, but in order to perform heating control of the fixing member with higher accuracy. Needs to know as accurately as possible how far this gap is.

  The present invention has been made in view of the above points, and uses contact-type temperature detection means that contacts a non-sheet-passing area on the surface of the fixing member and non-contact-type temperature detection means provided for the sheet-passing area. In the fixing device that controls the heating of the fixing member, it is possible to perform suitable heating control of the fixing member without performing a strict initial setting in advance with respect to the gap distance between the fixing member and the non-contact temperature detecting means. It is an object to provide a simple fixing device.

  In order to solve the above-described problems, the present invention provides a fixing member, a pressure member that forms a fixing nip that presses against the fixing member and allows a sheet to pass therethrough, a heating unit that heats the fixing member, and the fixing member Contact temperature detecting means provided in contact with the non-sheet passing area on the surface, non-contact temperature detecting means provided in non-contact with the sheet passing area on the surface of the fixing member, and the contact temperature In a fixing device comprising a detection means and / or a control means for controlling the heating means based on information from the non-contact temperature detection means, by changing the position of the non-contact temperature detection means, A detection unit moving mechanism capable of changing a gap distance between the fixing member and the non-contact type temperature detection unit is provided, and the control unit controls the heating unit based on information from the contact type temperature detection unit and fixes the fixing unit. Member surface The position of the non-contact temperature detection means is changed by the detection means moving mechanism based on information from the contact temperature detection means and the non-contact temperature detection means after the surface temperature of the fixing member is stabilized, After this position change, the heating means is controlled based on information from the non-contact temperature detecting means.

  The control means stores reference detection temperature information of the non-contact temperature detection means for a predetermined surface temperature of the fixing member and a position correction table corresponding to the reference detection temperature information, and After the surface temperature is stabilized, the fixing member and the non-contact type temperature based on the temperature obtained from the non-contact type temperature detection unit and the position correction table when the contact type temperature detection unit detects a predetermined temperature. Estimating the distance of the gap with the detection means, the position of the non-contact type temperature detection means is changed by the detection means moving mechanism based on the estimated distance of the gap, and after this position change, the non-contact type temperature detection means The heating means was controlled based on the information from

  The detecting means moving mechanism includes an urging means for urging the non-contact type temperature detecting means in a direction away from the fixing member, and a cam for causing the non-contact type temperature detecting means to approach the fixing member. It was.

  Further, the control means controls the heating means by turning on / off every predetermined time.

  Further, the control means controls the heating means by adjusting its output.

  According to the configuration of the present invention, the contact-type temperature detecting means provided in contact with the non-sheet passing area on the surface of the fixing member and the non-contact type provided without contacting the sheet passing area on the surface of the fixing member. The fixing device including the temperature detecting means includes a detecting means moving mechanism capable of changing a gap distance between the fixing member and the non-contact temperature detecting means, and the control means is based on information from the contact temperature detecting means. And controlling the heating means to stabilize the surface temperature of the fixing member, and after the surface temperature of the fixing member is stabilized, based on information from the contact temperature detecting means and the non-contact temperature detecting means, Since the position is changed by the detection means moving mechanism and the heating means is controlled based on the information from the non-contact type temperature detection means after this position change, the contact type temperature detection means and the non-contact type temperature detection means Information By the position of the non-contact type temperature detection means is changed Zui, it is possible to accurately position the non-contact type temperature sensing means. Therefore, the accuracy of temperature prediction by the non-contact temperature detecting means is improved. In this way, it is possible to obtain a fixing device capable of performing suitable heating control of the fixing member without performing strict initial setting in advance with respect to the gap between the fixing member and the non-contact temperature detecting means.

  In the fixing device having the above configuration, the control unit stores reference detection temperature information of the non-contact type temperature detection unit with respect to a predetermined surface temperature of the fixing member, and a position correction table corresponding to the reference detection temperature information. After the surface temperature of the fixing member is stabilized, the contact type temperature detecting means detects the predetermined temperature, and the fixing member is not contacted based on the temperature obtained from the non-contact type temperature detecting means and the position correction table. Estimating the distance of the gap with the temperature detector, the position of the non-contact temperature detector is changed by the detecting means moving mechanism based on the estimated gap distance, and after this position change, the non-contact temperature detection Since the heating means is controlled based on the information from the means, the distance between the fixing member and the non-contact temperature detecting means is automatically determined based on the information from the two types of temperature detecting means. To be able to grasp. As a result, even when there is a variation in the initial setting of the gap during production, or when a positional deviation occurs during conveyance or due to changes over time, it is possible to perform heating control corresponding to these problems. Therefore, the heating efficiency of the fixing device can be further increased.

  In the fixing device having the above-described configuration, the detection unit moving mechanism includes a biasing unit that biases the non-contact type temperature detection unit in a direction away from the fixing member, and a cam that causes the non-contact type temperature detection unit to approach the fixing member. Therefore, it is possible to easily change the position of the non-contact temperature detecting means by rotating the cam. Therefore, a detection means moving mechanism that can change the gap distance between the fixing member and the non-contact type temperature detection means, which is very important in controlling the heating of the fixing member, can have a simpler configuration. It is possible to prevent the control from becoming complicated and costly.

  In the fixing device having the above-described configuration, since the control unit controls the heating unit by turning it on / off every predetermined time, a predetermined surface temperature of the fixing member can be obtained by a simple operation of ON / OFF. Can be obtained. Thereby, it is possible to easily control the heating means.

  Further, in the fixing device having the above configuration, since the control unit controls the heating unit by adjusting the output thereof, the predetermined surface temperature of the fixing member can be obtained without turning on / off the heating unit. be able to. Thereby, the power consumption of the heating unit can be reduced, and the heating efficiency of the fixing device can be further increased.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  First, the configuration of the fixing device according to the embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic vertical sectional front view of a fixing device and a schematic diagram of a control circuit. FIG. 2 is a schematic horizontal sectional top view of a fixing roller. In FIG. 2, an area indicated by an arrow L indicates a sheet passing area of a maximum size sheet that can be used in the fixing device.

  As shown in FIG. 1, the fixing device 1 includes a fixing unit 10 and a pressure unit 20. A paper entry guide 30 is provided at a location where the paper enters toward the fixing device 1.

  The fixing unit 10 includes a fixing roller 11 as a fixing member. The fixing roller 11 is provided with an elastic member layer 13 made of silicon rubber or sponge on the outside of a cored bar 12 made of metal such as iron or aluminum. A release layer 14 is provided outside the elastic member layer 13 and on the surface of the fixing roller 11 to enhance the toner releasability. The release layer 14 is made of a fluorine-based resin such as PFA (tetrafluoroethylene-per-fluoroalkyl vinyl ether copolymer) and is provided by covering with a coating or a tube by spraying. The fixing roller 11 is rotated by a driving device (not shown) so that the peripheral speed thereof is the same as the paper conveyance speed.

  Inside the fixing roller 11, as shown in FIGS. 1 and 2, a halogen lamp 15 as a heating unit is provided. The halogen lamp 15 extends in the axial direction of the fixing roller 11, that is, in the sheet width direction perpendicular to the sheet conveying direction, and heats the fixing roller 11 from the inside. This halogen lamp 15 has a length in the paper width direction that is longer than the width of the maximum size paper that can be passed through a fixing nip described later.

  Further, outside the fixing roller 11, a contact thermistor 16 that is a contact temperature detecting unit and a non-contact thermistor 17 that is a non-contact type temperature detecting unit are provided. As shown in FIG. 2, the contact thermistor 16 is provided in contact with the outside of the sheet passing area on the surface of the fixing roller 11, that is, the non-sheet passing area. The non-contact thermistor 17 is provided in a non-contact manner with a predetermined gap with respect to the surface of the fixing roller 11 in the central portion in the sheet width direction, which is a sheet passing area on the surface of the fixing roller 11. The surface temperature of the fixing roller 11 is detected by the contact type thermistor 16 and the non-contact type thermistor 17.

  The non-contact thermistor 17 is supported by the detection means moving mechanism 40 as shown in FIG. The detection means moving mechanism 40 includes an arm 41, a compression spring 42, and a cam 43.

  The arm 41 is supported by a housing (not shown) of the fixing device 1 so as to be rotatable about a support shaft 41a provided at one end thereof. A non-contact type thermistor 17 is fixed to a substantially central portion in the longitudinal direction of the arm 41. A compression spring 42 is attached to the other end of the arm 41. As the arm 41 rotates about the support shaft 41a, the non-contact thermistor 17 approaches or separates from the fixing roller 11.

  The compression spring 42 is provided between the end of the arm 41 opposite to the support shaft 41 a and the frame 2 of the housing of the fixing device 1, and attaches the end of the arm 41 away from the fixing roller 11. It is fast. As a result, the arm 41 tends to rotate the non-contact thermistor 17 away from the fixing roller 11 around the support shaft 41a, that is, clockwise in FIG. Accordingly, the compression spring 42 functions as a biasing unit that biases the non-contact thermistor 17 in a direction away from the fixing roller 11.

  A cam 43 is disposed at a position facing the compression spring 42 and the arm 41 across the arm 41. As the cam 43 rotates and engages and rotates with the arm 41, the arm 41 moves in the direction in which the cam 43 moves closer to the fixing roller 11 against the elastic force of the compression spring 42, that is, the support. It rotates counterclockwise in FIG. 1 about the shaft 41a. Therefore, the non-contact thermistor 17 is moved in the direction approaching the fixing roller 11 by the cam 43.

  The pressure unit 20 includes a pressure roller 21 that is a pressure member. The pressure roller 21 is provided with an elastic member layer 23 made of silicon rubber or sponge on the outside of a cored bar 22 made of metal such as stainless steel. The pressure roller 21 is pressed against the fixing roller 11 to form a fixing nip through which the sheet is inserted. The pressure roller 21 does not have a driving device and is rotated according to the rotation of the fixing roller 11 by being pressed against the fixing roller 11. The sheet is passed through the fixing nip, that is, the center of the fixing roller 11 and the pressure roller 21 in the sheet width direction.

  In addition, the fixing device 1 includes a control unit 50. Information on the contact-type thermistor 16 and the non-contact-type thermistor 17 is sent to the control means 50. Based on the temperature information from each of the thermistors, the control unit 50 controls the output of the halogen lamp 15 and the detection unit moving mechanism 40 to control the heating of the fixing roller 11 according to a preprogrammed procedure.

  Next, the heating operation of the fixing device 1 will be described with reference to FIGS. 3 and 4 in addition to FIGS. 1 and 2. 3 is a temperature transition diagram of the surface of the fixing roller and each thermistor after the toner replenishment operation, and FIG. 4 is a position correction table of the non-contact type thermistor. Note that “separation direction” and “approach direction” shown in FIG. 4 represent the direction in which the non-contact thermistor 17 is separated from the fixing roller 11 and the direction in which it approaches.

  In the image forming apparatus provided with the fixing device 1, while the fixing operation such as after replenishing toner is not performed, the control unit 50 controls the fixing roller 11 at a temperature lower than the fixing temperature in order to reduce power consumption. Keep warm. As shown in FIG. 3, the surface temperature of the fixing roller 11 is 180 ° C., and the control means 50 repeats ON / OFF control of the halogen lamp 15 at ON 1 second and OFF 0.5 second. To maintain. The temperature control during the heat retention is performed such that the contact thermistor 16 maintains 150 ° C. The control means 50 repeats the control of the halogen lamp 15 at ON 1 second and OFF 0.5 second, but the time interval may be changed, and the output of the halogen lamp 15 is, for example, 80% for 3 seconds, 40 seconds. You may repeat by control of 1 second in%.

  Here, the non-contact thermistor 17 shown in FIGS. 1 and 2 is provided in a non-contact manner by providing a clearance of 0.8 mm with respect to the surface of the fixing roller 11. Then, the control means 50 stores, as reference detection temperature information, a detection temperature of 160 ° C. as a reference by the non-contact thermistor 17 with respect to a surface temperature of 180 ° C. of the fixing roller 11. The control means 50 also stores a position correction table shown in FIG. 4 corresponding to the reference detected temperature. As described above, the position of the non-contact thermistor 17 is changed by rotating the cam 43 of the detection means moving mechanism 40. Therefore, the rotation angle of the cam 43 is stored in the position correction table as a condition for changing the position of the non-contact thermistor 17.

  When the surface temperature is stabilized after the elapse of a predetermined time after the heat retention of the fixing roller 11 is started, the control unit 50 calculates the average value of the temperature information obtained from the non-contact type thermistor 17 for 30 seconds shown in FIG. . Then, the control unit 50 refers to the position correction table shown in FIG. 4, and if the average value of the detected temperatures is in the range of 158 ° C. to 162 ° C., the control unit 50 determines the clearance between the non-contact thermistor 17 and the fixing roller 11. It is estimated that the distance is 0.8 mm. Further, since the position correction corresponding to the distance of the gap, that is, the correction of the rotation angle of the cam 43 is ± 0 degrees from the position correction table shown in FIG. 4, the control means 50 does not rotate the cam 43 and does not rotate. The detection means moving mechanism 40 provided with the thermistor 17 is held as it is. Thereafter, the control unit 50 performs ON / OFF control of the halogen lamp 15 so that the temperature detected by the non-contact thermistor 17 is 160 ° C. in order to maintain the surface temperature of the fixing roller 11 at 180 ° C.

  Here, for example, when the average value of the detected temperature of the non-contact thermistor 17 for 30 seconds after the surface temperature of the fixing roller 11 is stabilized is 153 ° C. to 157 ° C., as shown in FIG. 50, it is estimated that the gap distance between the non-contact thermistor 17 and the fixing roller 11 is 1.0 mm to 1.4 mm, that is, the gap is wider than the standard 0.8 mm. In order to perform position correction corresponding to the distance of the gap, the control unit 50 refers to the position correction table shown in FIG. 4 and moves the cam 43 in the direction in which the non-contact type thermistor 17 approaches the fixing roller 11. Rotate degrees. Thereafter, the control unit 50 performs ON / OFF control of the halogen lamp 15 so that the temperature detected by the non-contact thermistor 17 is 160 ° C. in order to maintain the surface temperature of the fixing roller 11 at 180 ° C.

  Similarly, for example, when the average value of the detected temperature of the non-contact thermistor 17 for 30 seconds after the surface temperature of the fixing roller 11 is stabilized is 163 ° C. to 167 ° C., as shown in FIG. The means 50 estimates that the distance between the non-contact thermistor 17 and the fixing roller 11 is 0.2 mm to 0.6 mm. In order to perform position correction corresponding to the distance of the gap, the control unit 50 rotates the cam 43 by 5 degrees in the direction in which the non-contact thermistor 17 is separated from the fixing roller 11.

  In this way, the contact thermistor 16 which is a contact-type temperature detecting means provided in contact with the non-sheet passing area on the surface of the fixing roller 11 which is a fixing member, and the non-sheet passing area on the surface of the fixing roller 11. In the fixing device 1 provided with a non-contact type thermistor 17 which is a non-contact type temperature detecting means provided in contact, the control means 50 is based on information from the contact type thermistor 16 and the halogen lamp 15 which is a heating means. Is controlled to stabilize the surface temperature of the fixing roller 11, and after the surface temperature of the fixing roller 11 is stabilized, the position of the non-contact type thermistor 17 is detected based on information from the contact type thermistor 16 and the non-contact type thermistor 17. Since the halogen lamp 15 is controlled on the basis of information from the non-contact thermistor 17 after the position change is performed by the moving mechanism 40, the contact is made. By the position of the non-contact type thermistor 17 is changed based on the information from the thermistor 16 and the non-contact type thermistor 17, it is possible to accurately position the non-contact type thermistor 17. Therefore, the accuracy of temperature prediction by the non-contact thermistor 17 is improved. In this way, it is possible to obtain the fixing device 1 capable of performing suitable heating control of the fixing roller 11 without performing strict initial setting in advance for the gap between the fixing roller 11 and the non-contact thermistor 17. it can.

  In the fixing device 1 configured as described above, the control unit 50 stores reference detection temperature information by the non-contact type thermistor 17 for a predetermined surface temperature of the fixing roller 11 and a position correction table corresponding to the reference detection temperature information. In addition, after the surface temperature of the fixing roller 11 is stabilized, the fixing roller 11 and the fixing roller 11 based on the temperature obtained from the non-contact thermistor 17 when the contact thermistor 16 detects a predetermined temperature and the position correction table. The distance between the non-contact thermistor 17 is estimated, the position of the non-contact thermistor 17 is changed by the detection means moving mechanism 40 based on the estimated gap distance, and the non-contact thermistor is changed after this position change. Since the halogen lamp 15 is controlled based on the information from 17, the fixing is performed based on the information from the two types of temperature detecting means. Distance of the gap between the over La 11 and the non-contact type thermistor 17 can be automatically grasped. As a result, even when there is a variation in the initial setting of the gap during production, or when a positional deviation occurs during conveyance or due to changes over time, it is possible to perform heating control corresponding to these problems. Therefore, the heating efficiency of the fixing device 1 can be further increased.

  In the fixing device 1 configured as described above, the detection unit moving mechanism 40 includes the compression spring 42 that is a biasing unit that biases the non-contact thermistor 17 in a direction away from the fixing roller 11, and the non-contact thermistor 17. Since the cam 43 close to the fixing roller 11 is provided, the position of the non-contact thermistor 17 can be easily changed by the rotation of the cam 43. Therefore, the detection means moving mechanism 40 that can change the gap distance between the fixing roller 11 and the non-contact thermistor 17, which is very important in controlling the heating of the fixing roller 11, can have a simpler configuration. It is possible to prevent the control from becoming complicated and costly.

  Further, in the fixing device 1 configured as described above, the control unit 50 controls the halogen lamp 15 as the heating unit by turning it on / off every predetermined time, so that the fixing roller 11 can be operated by a simple operation of ON / OFF. The predetermined surface temperature can be obtained. Thereby, the halogen lamp 15 can be easily controlled.

  Further, in the fixing device 1 having the above-described configuration, the control unit 50 controls the halogen lamp 15 as the heating unit by adjusting its output, so that the fixing roller 11 can be turned on / off without turning the halogen lamp 15 on / off. A predetermined surface temperature can be obtained. Thereby, the power consumption of the halogen lamp 15 can be reduced, and the heating efficiency of the fixing device 1 can be further increased.

  Although the embodiments of the present invention have been described above, the scope of the present invention is not limited to these embodiments, and various modifications can be made without departing from the spirit of the invention.

  The present invention can be used in all fixing devices.

1 is a schematic vertical sectional front view of a fixing device according to an embodiment of the present invention. FIG. 2 is a schematic horizontal sectional top view of the fixing roller shown in FIG. 1. FIG. 2 is a temperature transition diagram of the surface of the fixing roller and each thermistor shown in FIG. 1 after a toner supply operation. It is a position correction table of the non-contact type thermistor shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fixing device 10 Fixing part 11 Fixing roller (fixing member)
15 Halogen lamp (heating means)
16 Contact thermistor (contact temperature detection means)
17 Non-contact thermistor (Non-contact temperature detection means)
20 Pressure part 21 Pressure roller (Pressure member)
40 detection means moving mechanism 41 arm 42 compression spring (biasing means)
43 Cam 50 Control means

Claims (5)

A fixing member, a pressure member that forms a fixing nip that presses against the fixing member and inserts the paper, a heating unit that heats the fixing member, and a non-sheet passing area on the surface of the fixing member. Contact-type temperature detection means, non-contact-type temperature detection means provided in non-contact with the sheet passing area on the surface of the fixing member, the contact-type temperature detection means and / or the non-contact-type temperature detection means A fixing device comprising a control means for controlling the heating means based on information from
A detecting means moving mechanism capable of changing a gap distance between the fixing member and the non-contact temperature detecting means by changing a position of the non-contact temperature detecting means, and the control means includes the contact temperature Based on information from the contact-type temperature detection means and the non-contact-type temperature detection means after the heating means is controlled based on information from the detection means to stabilize the surface temperature of the fixing member, and after the surface temperature of the fixing member is stabilized. The fixing device is characterized in that the position of the non-contact temperature detecting means is changed by the detecting means moving mechanism, and the heating means is controlled based on information from the non-contact type temperature detecting means after the position change. The control means stores reference detection temperature information of the non-contact type temperature detection means for a predetermined surface temperature of the fixing member, and a position correction table corresponding to the reference detection temperature information,
After the surface temperature of the fixing member is stabilized, the fixing member and the non-fixing member are determined based on the temperature obtained from the non-contact temperature detecting means when the contact temperature detecting means detects a predetermined temperature and the position correction table. Estimating the distance of the gap with the contact-type temperature detection means, and changing the position of the non-contact-type temperature detection means by the detection means moving mechanism based on the estimated gap distance, and after this position change, the non-contact type The fixing device according to claim 1, wherein the heating unit is controlled based on information from a temperature detection unit.   The detecting means moving mechanism includes an urging means for urging the non-contact temperature detecting means in a direction away from the fixing member, and a cam for causing the non-contact temperature detecting means to approach the fixing member. The fixing device according to claim 1 or 2.   4. The fixing device according to claim 1, wherein the control unit controls the heating unit by turning on and off at predetermined time intervals. 5.   The fixing device according to claim 1, wherein the control unit controls the heating unit by adjusting an output of the heating unit.

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