JP2017198718A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device and an image forming apparatus that, when receiving a request for released printing while in standby in a released state, can reduce the time required until the start of printing and suppress the generation of a switching sound due to a switching operation.SOLUTION: There is provided an image forming apparatus comprising: a developer image forming part that forms a developer image on a recording medium; a fixing part including a heating target member that is heated by a heating member, a pressing member that presses the heating target member, and a temperature detection part that detects the temperature of the heating target member; and a control part that controls to switch the pressure member between a nip position to press the heating target member at a first nip part pressure state and a release position to press the heating target member at a second nip part pressure state having a smaller pressure at a nip part than that of the first nip part pressure state, wherein the control part performs the switching control and executes a warm-up operation on the basis of a result of detection performed by the temperature detection part upon reception of a printing request.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image forming apparatus using an electrophotographic system, such as a printer, a copying machine, a facsimile machine, or a multifunction machine.

  In the conventional image forming apparatus, a pressure roller disposed opposite to the fixing roller is pressed against the fixing roller via an endless fixing belt heated by a heating means such as a heater, and the nip portion is formed. Some include a belt heating type fixing device that clamps and conveys a recording medium after transferring the developer image and applies heat and pressure to fix the developer image.

  For example, Patent Document 1 includes a separation / contact mechanism that switches the contact state between a fixing roller and a pressure roller in order to cope with fixing of a developer image transferred to a special recording medium such as an envelope or a medicine package. The fixing device is described.

JP 2013-073207 A

  However, in a conventional apparatus, when there is a request for printing of a special recording medium (hereinafter referred to as release printing) while waiting in a reduced pressure state (hereinafter referred to as a release state) in which the fixing roller and the pressure roller are separated from each other, In order to avoid idling of the fixing belt, after switching to a pressure state (hereinafter referred to as a nip state) where the fixing roller and the pressure roller are in contact with each other, a warm-up operation is performed, and after switching to a release state again It was necessary to perform a printing operation.

  In such a conventional apparatus, when repeatedly using release printing, there is a problem that it takes time to switch between the released state and the nip state, and a switching sound accompanying the switching operation is generated for each print job. It was.

  The present invention has been made in view of such a situation, and an object of the present invention is to reduce the time required to start printing when there is a request for release printing during standby in the released state, and An object of the present invention is to provide an image forming apparatus capable of suppressing the generation of a switching sound accompanying a switching operation.

  In order to solve the above problems, an image forming apparatus according to the present invention presses a developer image forming unit that forms a developer image on a recording medium, a heated member heated by a heating member, and the heated member. A fixing unit having a pressure member and a temperature detecting unit for detecting a temperature of the heated member; a nip position for pressing the pressing member against the heated member in a first nip portion pressure state; A control unit that performs switching control with a release position that presses the heating member in a second nip portion pressure state in which the pressure of the nip portion is weaker than the first nip portion pressure state with respect to the heating member, The switching control is performed based on the detection result of the temperature detection unit at the time of a print request, and warm-up is executed.

  According to the present invention, when there is a request for release printing during standby in the release state, an image that can reduce the time required to start printing and suppress the generation of switching sound associated with the switching operation. A forming apparatus can be provided.

1 is a configuration diagram illustrating an outline of a printer as an image forming apparatus according to an embodiment. 5 is a side view for explaining main members constituting the fixing nip portion N. FIG. FIG. 3 is a side view illustrating a release state in which a nip state by the fixing nip portion N described in FIG. 2 is released. FIG. 10 is a table summarizing a relationship between a fixing device state and operation when there is a print request in the related art. 10 is a flowchart illustrating an operation until the fixing device reaches a warm-up operation when there is a release print request in which a recording medium to be printed is a special recording medium in the related art. FIG. 10 is a table summarizing a relationship between a fixing device state and operation when a print request is made in the present embodiment. 6 is a graph for explaining a relationship between a temperature detected by a fixing device by a temperature detecting unit provided in the fixing device and a torque necessary for rotation of a fixing roller. 6 is a flowchart illustrating an operation until the fixing device reaches a warm-up operation when there is a release print request in which the recording medium to be printed is a special recording medium in the present embodiment.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, this invention is not limited to the following description, In the range which does not deviate from the summary of this invention, it can change suitably.

  FIG. 1 is a configuration diagram illustrating an outline of a printer 10 as an image forming apparatus according to the present embodiment. The printer 10 is, for example, an electrophotographic printer capable of printing an electrophotographic image on a recording medium such as plain paper as a first recording medium or a special recording medium such as an envelope as a second recording medium.

  In the printer 10, a plain paper as the recording medium 1 and a recording medium cassette 2 containing a special recording medium such as an envelope are detachably attached to the lower part of the apparatus. The printer 10 is upstream in the transport direction along a recording medium transport path S formed in a substantially S shape starting from the recording medium cassette 2 and ending in a stacker 7 formed using the outer casing of the printer 10. A plurality of recording medium conveying units 3a, 3b, 3c, 3d composed of a pair of conveying rollers from the side are arranged in order.

  Between the recording medium transport units 3b and 3c, a developer image forming unit 4 that forms a developer (for example, toner) image 1t in order from the upstream side in the transport direction and a fixing device 100 positioned on the downstream side are disposed. Has been. The developer image forming unit 4 is provided with an LED (Light Emitting Diode) head 5 as an exposure device adjacent thereto. The developer image forming unit 4 forms a developer image 1t corresponding to the printing light emitted from the LED head 5 on the surface of the photosensitive drum (not shown), and transfers the developer image 1t to the recording medium 1. It is.

  The fixing device 100 is a device that heats and presses the developer image 1t adhering to the recording medium 1 to fix it, and then discharges it to the recording medium conveyance unit 3c.

  By the way, when printing on one side of the recording medium 1 in the printer 10, the recording medium 1 is discharged from the fixing device 100, then transferred to the recording medium transfer section 3d as it is, and discharged to the stacker 7 outside the apparatus. On the other hand, when printing on both sides of the recording medium 1, the recording medium 1 is discharged from the fixing device 100 and then conveyed to the recording medium reversing unit 6. Here, the developer image 1t forming surface of the recording medium 1 is reversed, and the recording medium 1 is conveyed to the recording medium conveying portion 3a. Then, after the developer image 1t is formed again in the developer image forming unit 4, the recording medium 1 is conveyed to the recording medium conveying unit 3d and discharged to the stacker 7 outside the apparatus.

  The printer 10 includes a control unit 8 that comprehensively controls the printing operation of the printer 10. The control unit 8 includes, for example, a calculation device such as a CPU (Central Processing Unit) and a storage device such as a RAM (Random Access Memory) and a ROM (Read Only Memory), and a developer image based on image information received from an external device. In order to form 1t, the drive of the recording medium conveying units 3a, 3b, 3c, 3d, the developer image forming unit 4, the LED head 5, the fixing device 100, and the recording medium reversing unit 6 is controlled.

  Next, a configuration of main members necessary for forming the fixing nip portion in the fixing device 100 will be described with reference to FIG. FIG. 2 is a side view for explaining main members constituting the fixing nip portion N. FIG. FIG. 3 is a side view illustrating a released state in which the nip state by the fixing nip portion N described in FIG. 2 is released.

  As shown in FIG. 2, the fixing device 100 is a belt heating type device, and a fixing roller 102 as a member to be heated, a pressure pad 103, a guide on the inner peripheral surface side of the fixing belt 101 as a belt member. A roller 104, a heat diffusion member 105, a guide member 106, a plate heater 107, and a temperature detection unit 111 are disposed. The fixing device 100 is configured such that the fixing roller 102 and the pressure pad 103 can press the pressure roller 108 as a pressing member via the fixing belt 101, and a fixing nip portion N is formed by the pressing portion. . In the fixing nip N, heat and pressure are applied when the recording medium 1 and the developer image 1t are passed from the direction of arrow B in the figure, and the developer image 1t is fixed.

  The fixing belt 101 includes, for example, a heat-resistant elastic layer formed of silicone rubber, a fluororesin, or a release layer formed of a fluororesin on an endless belt base made of nickel, polyimide, stainless steel, or the like. Are sequentially stacked. The fixing belt 101 is stretched on the inner peripheral surface by a heat diffusion member 105 that receives pressure by a pressing force f1 by a biasing member such as a compression coil spring and a pressure pad 103 that receives pressing force f2. Guided by a roller 102, a guide roller 104, a heat diffusion member 105, and a guide member 106. The fixing belt 101 is driven to rotate by the fixing roller 102 by friction on the contact surface with the fixing roller while being heated by the plate heater 107. For example, the fixing belt 101 according to this embodiment has an inner diameter φ of 45 mm, a 0.1 mm thick polyimide base material, a heat resistant elastic layer made of silicone rubber having a thickness of 0.2 mm, PFA (tetrafluoro). (Ethylene-perfluoroalkyl vinyl ether copolymer) A release layer composed of a tube is sequentially laminated.

  The fixing roller 102 includes a cored bar portion made of a metal pipe or shaft such as iron or aluminum alloy, and a heat-resistant elastic layer formed of silicone sponge, fluororesin or the like, and both ends of the cored bar portion are not shown. It is supported by a sheet metal (not shown) via a bearing. A driving gear (not shown) is provided at one end of the cored bar, and the power is transmitted to the driving gear, whereby the fixing roller 102 rotates in the direction of arrow A1 in FIG. For example, the fixing roller 102 according to the present embodiment has an outer diameter φ of 34 mm, and the heat-resistant elastic layer is made of a silicone sponge having a thickness of 2 mm.

  The pressure pad 103 includes a support base material made of a metal such as iron or an aluminum alloy, a heat resistant elastic material bonded and fixed to the support base material, and a sliding layer formed on the surface of the heat resistant elastic material. . The pressure pad 103 receives a pressure f2 from an urging member such as a compression coil spring and presses the pressure roller 108, for example.

  The guide roller 104 includes a cored bar portion made of a metal pipe such as iron or aluminum alloy or a shaft, and a heat-resistant elastic layer formed of silicone sponge, fluorine resin, or the like. The guide roller 104 is driven to rotate with the rotation of the fixing belt 101 that is driven to rotate by the fixing roller 102.

  The heat diffusing member 105 is pressed by the plate heater 107 pressed by the applied pressure f1, diffuses the heat of the plate heater 107 that contacts, and transfers the heat to the fixing belt 101 that also contacts. Between the plate heater 107 and the heat diffusing member 105 in contact with each other, semi-solid grease or the like that has high heat resistance and heat conductivity and can be arbitrarily deformed may be disposed (applied). For example, the heat diffusing member 105 according to the present embodiment is formed by using A6063, which is an extruded aluminum material, as a part of a cylindrical shape having a thickness of 1 mm and a curvature radius of the curved surface portion of about 50 mm. Yes.

  The guide member 106 guides driving of the fixing belt 101 together with the fixing roller 102, the guide roller 104, and the heat diffusion member 105.

  The plate heater 107 is a heat source for heating the fixing belt 101. The plate heater 107 is pressed against the heat diffusing member 105 by the applied pressure f <b> 1 and generates heat while in contact with the heat diffusing member 105. The plate heater 107 generates heat when a current flows through a resistance wire as a heating element on the plate substrate. A power source and a control circuit are connected to the resistance wire by a connector (not shown), and heat is generated at an arbitrary timing. Is configured to be possible. For example, the plate heater 107 according to this embodiment is configured by laminating resistance wires on a stainless steel (SUS) substrate having a length of 350 mm in the longitudinal direction, a width of 10 mm in the lateral direction, and a thickness of 1 mm. The output of the line is 1000W.

  The temperature detection unit 111 includes, for example, a thermistor, detects the temperature of the fixing belt 101 or the vicinity of the fixing belt 101, and outputs the detection result to the control unit 8. The temperature detection unit 111 may be provided on the inner peripheral surface side of the fixing belt 101 as in this embodiment, or may be provided on the outer peripheral surface side of the fixing belt 101 or in the vicinity of the pressure roller 108. Further, the temperature detecting unit 111 may detect the vicinity of the fixing belt 101 and the apparatus temperature instead of the temperature of the fixing belt 101 instead.

  The pressure roller 108 includes a cored bar portion made of a metal pipe or shaft such as iron or aluminum alloy, and a heat-resistant elastic layer formed of silicone sponge, fluororesin or the like, and both ends of the cored bar portion are not shown. It is supported by a pressure roller support member 109 via a rotary bearing. The pressure roller 108 that presses against the fixing roller 102 via the fixing belt 101 is driven by the fixing belt 103 that is driven by the rotation of the fixing roller 102, and rotates in the direction of arrow A3 in FIG. For example, the pressure roller 108 according to the present embodiment is configured by laminating a release layer made of a PFA tube on a heat-resistant elastic layer made of silicone rubber having a thickness of 2 mm.

  The pressure roller support member 109 receives a pressing force f3 from an urging member such as a compression coil spring, thereby generating a rotational moment about the central axis of the rotation fulcrum hole 109a. The pressure roller 108 can press the pressure pad 103 and the fixing roller 102 by the generated rotation moment.

  The cam 110 is fixed to a shaft inserted through the cam rotation shaft hole 110a, and a gear (not shown) is fixed to the end of the shaft so that it can be rotated by receiving an external force. ing. By the rotation of the cam 110, the pressure of the cam 110 received by the pressure roller support member 109 is changed, and further, the pressure of the pressure roller 108 against the pressure pad 103 and the fixing roller 102 is changed. The applied pressure also changes.

  The distance between the cam rotation shaft hole 110a and the pressure roller support member 109 is determined by the posture of the cam 110. Specifically, in the nip state, which is the fixing state (first nip portion pressure state) shown in FIG. 2, there is a gap between the cam 110 and the pressure roller support member 109, and the distance is L1. Become. At this time, the pressure roller 108 is pressed against the pressure pad 103 and the fixing roller 102 to form the fixing nip portion N.

  On the other hand, in the release state, which is the fixing state (second nip portion pressure state) shown in FIG. 3, the cam 110 rotates to press the pressure roller support member 109, and as a result, the cam 110 and the pressure roller support. The distance to the member 109 is L1 ′. At this time, the pressure roller 108 moves away from the pressure pad 103 and the fixing roller 102 to form a fixing nip portion N ′ in which the nip range is reduced. Note that the pressures f1, f2, and f3 shown in FIG. 2 and the pressures f1 ′, f2 ′, and f3 ′ shown in FIG. 3 are different depending on the fixing state in the nip state and the release state. It is shown that. 2 and 3, the fixing roller 102, pressure pad 103, guide roller 104, heat diffusion member 105, guide member 106, plate heater 107, and pressure roller 108 are orthogonal to the driving direction of the fixing belt 101. It is a long member extending in the Z-axis direction in the figure.

  Next, the printing operation of the printer 10 according to the present embodiment will be described. First, when receiving a print command b including image information from an external device, the control unit 8 of the printer 10 starts printing based on the received image information. The control unit 8 controls the recording medium conveying units 3 a and 3 b to convey the recording medium 1 fed from the recording medium cassette 2 to the developer image forming unit 4.

  The control unit 8 controls the developer image forming unit 4 and the LED head 5 to form a developer image 1t based on the image information and transfer the developer image 1t to the conveyed recording medium 1.

  The recording medium 1 to which the developer image 1t has been transferred is applied with heat and pressure when passing through the fixing nip portion N of the fixing device 100 maintained at a predetermined temperature, and the developer is melted to melt the developer. The image 1t is fixed.

  The recording medium 1 on which the developer image 1t has been fixed is nipped and conveyed by the recording medium conveying units 3c and 3d, discharged to the stacker 7, and accumulated, and a series of printing operations is completed.

  Next, in the fixing device 100 according to the present embodiment, an operation up to the start of feeding when there is a print request will be described. First, prior to the description of the operation of the fixing device 100 according to the present embodiment, the operation of the fixing device in the prior art will be described.

  FIG. 4 is a table summarizing the relationship between the fixing device state and operation when there is a print request in the prior art.

  For example, if printing on a special recording medium such as a square 2 envelope is requested as a print request and the initial state of the fixing device is the nip state, the fixing device warms up as it is, then switches the cam and releases it. And then start printing. On the other hand, when the initial state of the fixing device is the release state, the fixing device temporarily warms up after switching to the nip state by switching the cam, and starts printing after switching the cam again to the release state.

  On the other hand, when printing on a recording medium such as plain paper is requested as a print request, if the initial state of the fixing device is the nip state, the fixing device warms up as it is and then starts printing. To do. On the other hand, when the initial state of the fixing device is the release state, the fixing device switches to the cam to make the nip state, warms up, and starts printing.

  When the recording medium to be printed is plain paper or the like, and the initial state of the fixing device is the nip state, the cam switching operation is not necessary. In addition, even if the initial state is the release state, only one cam switching operation for switching to the nip state is required, so the time required for the cam switching is about 0.5 [s].

  However, if the recording medium to be printed is a special recording medium such as an envelope and the initial state of the fixing device is the nip state, the time required for switching the cam to the released state is about 1.3 [s]. Further, when the initial state is the release state, the nip state is once set and then the release state is set again, so that two cam switching operations are required, and the time required for the cam switching is about 1.8 [s].

  As described above, in the prior art, particularly when the recording medium to be printed is a special recording medium such as an envelope and the initial state of the fixing device is in the released state, it takes time to start printing, and further, the cam The switching sound accompanying the switching operation is generated.

  FIG. 5 is a flowchart for explaining the operation until the fixing device reaches the warm-up operation when there is a release print request in the related art where the recording medium to be printed is a special recording medium.

  First, when a release print request is received, the fixing device checks whether or not the fixing state (initial state) is the released state. Here, when the fixing state is the release state (YES in step S10), the fixing device shifts to the nip state by performing a cam switching operation (step S11), and starts warm-up (step S12). On the other hand, if the fixing state is not the release state (NO in step S10), the fixing device starts warm-up without performing the cam switching operation (step S12).

  When the warm-up is completed, the fixing device performs a cam switching operation, and after entering the release state (step S13), paper feeding is started.

  As described above, in the conventional technology, when the release print request is received, if the fixing state is the release state, the transition to the nip state accompanying the cam switching operation is inevitably performed. On the other hand, in the present embodiment, when a release print request is received, even if the fixing state is the release state, if the temperature of the fixing device is equal to or higher than the predetermined temperature, the nip state associated with the cam switching operation It is allowed not to make the transition to. The details will be described below.

  FIG. 6 is a table summarizing the relationship between the state of the fixing device and the operation when there is a print request in this embodiment.

  For example, when a print request is made to print on a special recording medium such as a square 2 envelope, and the initial state of the fixing device 100 is a nip state, the fixing device 100 warms up as it is, and then switches the cam 110. Start printing after setting the release state. On the other hand, when the initial state of the fixing device 100 is the release state, the fixing device 100 determines whether its own temperature (initial temperature) is equal to or higher than a predetermined temperature (Hot) or lower than a predetermined temperature (Cold). Branch an action. Specifically, when the temperature is equal to or higher than a predetermined temperature (Hot), the fixing device 100 warms up in the released state and starts printing. On the other hand, when the temperature of the fixing device 100 is less than a predetermined temperature (Cold), the fixing device 100 warms up after switching the cam 110 and then warms up, and then switches and releases the cam 110 again. Start printing after setting the status.

  On the other hand, when printing on a recording medium such as plain paper is requested as a print request, when the initial state of the fixing device 100 is the nip state, the fixing device 100 performs warm-up as it is before printing. To start. On the other hand, when the initial state of the fixing device 100 is the release state, the fixing device 100 switches to the nip state by switching the cam 110, warms up, and starts printing.

  When the recording medium to be printed is plain paper or the like and the initial state of the fixing device 100 is the nip state, the switching operation of the cam 110 is not necessary. Further, even if the initial state is the release state, only one cam 110 switching operation for switching to the nip state is required, so the time required for the cam switching is about 0.5 [s].

  On the other hand, when the recording medium to be printed is a special recording medium such as an envelope and the initial state of the fixing device 100 is the nip state, the time required for switching the cam 110 to the released state is about 1.3 [s]. . When the initial state is the release state and the temperature of the fixing device 100 is lower than the predetermined temperature, since the nip state is once changed to the release state again, two cam switching operations are required, and the time required for the cam switching However, if the temperature of the fixing device 100 is equal to or higher than a predetermined temperature, the fixing device 100 is warmed up while the release device is in a released state, and printing is started. The time required is 0 [s], and a time reduction of about 1.8 [s] is expected. Further, the switching sound associated with the switching operation of the cam 110 is not generated.

  FIG. 7 is a graph for explaining the relationship between the temperature detected by the fixing device 100 by the temperature detection means 111 provided in the fixing device 100 and the torque necessary for the rotation of the fixing roller 102. In this embodiment, 110 ° C., which is an inflection point, is set as the predetermined temperature related to the operation branch of the fixing device 100 while the torque necessary for the rotation of the fixing roller 102 tends to decrease as the detected temperature increases.

  FIG. 8 is a flowchart for explaining the operation until the fixing device 100 reaches the warm-up operation when there is a release print request in which the recording medium to be printed is a special recording medium in the present embodiment.

  First, when a release print request is received, the control unit 8 of the fixing device 100 checks whether or not the fixing state (initial state) is the released state. Here, when the fixing state is the release state (step S20 YES), the control unit 8 confirms whether or not the temperature (control temperature) of the fixing device 100 detected by the temperature detecting unit 111 is 110 ° C. or higher. Here, when the temperature of the fixing device 100 is 110 ° C. or higher (YES in step S21), the control unit 8 performs warm-up while keeping the fixing device 100 in the released state (step S22), and starts feeding.

  On the other hand, when the temperature of the fixing device 100 is lower than 110 ° C. (NO in step S21), the control unit 8 performs the cam switching operation to shift the fixing device 100 to the nip state (step S23) and start warm-up (step S23). Step S24). When the warm-up is completed, the control unit 8 performs a cam switching operation, shifts the fixing device 100 to the release state (step S25), and starts paper feeding.

  When the fixing state is not the release state (NO in step S20), the control unit 8 starts warm-up without performing the cam switching operation. (Step S24) When the warm-up is completed, the control unit 8 performs a cam switching operation, shifts the fixing device 100 to the release state (Step S25), and starts paper feeding.

  As described above, according to the present embodiment, when there is a request for release printing while waiting in the released state, the time required for starting printing is shortened and the switching sound accompanying the switching operation is generated. A fixing device and an image forming apparatus that can be suppressed can be provided.

  In the description of the present invention, an electrophotographic printer has been described as an example of a preferred image forming apparatus. However, the present invention is not limited to this, and may be applied to a facsimile, a copying machine, a multifunction machine, and the like. Is possible.

DESCRIPTION OF SYMBOLS 1 Recording medium 1t Developer image 2 Recording medium cassette 3a, 3b, 3c, 3d Recording medium conveyance part 4 Developer image formation part 5 LED head 6 Recording medium inversion unit 7 Stacker 8 Control part 10 Printer 100 Fixing apparatus 101 Fixing belt 102 Fixing roller 103 Pressure pad 104 Guide roller 105 Heat diffusion member 106 Guide member 107 Plate heater 108 Pressure roller 109 Pressure roller support member 109a Rotation fulcrum hole 110 Cam 110a Cam rotation fulcrum hole 111 Temperature detection means

Claims (8)

A developer image forming unit for forming a developer image on a recording medium;
A fixing member having a heated member heated by the heating member, a pressing member that presses the heated member, and a temperature detection unit that detects the temperature of the heated member;
A nip position that presses the pressing member against the member to be heated in a first nip portion pressure state, and a pressure at the nip portion that is lower than the first nip portion pressure state relative to the member to be heated. And a control unit that performs switching control with a release position that is pressed in the nip pressure state of 2,
The image forming apparatus, wherein the control unit performs switching control based on a detection result of the temperature detection unit at the time of a print request and performs warm-up. The image forming apparatus according to claim 1, wherein the control unit changes the switching control based on a position of the pressing member at the time of a print request. The image forming apparatus according to claim 1, further comprising a medium information acquisition unit that acquires medium information of a recording medium, wherein the control unit performs switching control according to the medium information. The image forming apparatus according to claim 3, wherein the medium information is information relating to a thickness of the recording medium. The image forming apparatus according to claim 3, wherein the medium information is information regarding whether or not two or more sheets are combined. When the recording medium is thick and the initial state of the pressing member is a release state at a predetermined temperature or more when a print request is made, the control unit performs a warm-up in the release state and then performs a fixing operation in the release state. The image forming apparatus according to claim 4, wherein the image forming apparatus is performed. When the recording medium is thick and the initial state of the pressing member is in the released state when the printing request is made and the temperature is lower than a predetermined temperature, the control unit controls the position of the pressing member and performs warm-up in the nip state. The image forming apparatus according to claim 6, wherein the fixing operation is performed in a released state after the release. The image forming apparatus according to claim 6, wherein the predetermined temperature is set based on a relationship between an apparatus temperature and a torque for driving the member to be heated.