JP2017167490A - Image forming apparatus and fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent foreign substances, such as toner and paper powder from being accumulated on a roller temperature detection member of a fixing device.SOLUTION: A contact/separation state of a temperature detection member 41(42) with respect to a fixing roller 21 or a pressure roller 22 is changed between an operation temperature and non-operation temperature of the fixing roller 21.SELECTED DRAWING: Figure 3A

Description

The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine of these, and a fixing device used in the image forming apparatus.

In this type of image forming apparatus, a toner image formed by an electrophotographic recording method or the like is transferred onto a recording medium such as paper or an OHP sheet. Thereafter, the toner image is heated and fixed on the recording medium by a contact heating type fixing device such as a heat roller type, a film heating type, or an electromagnetic induction heating type. As a fixing device, one using a fixing roller and a pressure roller is known as disclosed in, for example, Japanese Patent Application Laid-Open No. 2005-128048.

In order to detect the surface temperature of these rollers, a temperature detection member such as a thermistor is disposed in contact with the rollers. The temperature detection member controls on / off of the heater for the fixing roller so as to maintain the surface temperature of the fixing roller and the pressure roller at a predetermined operating temperature.

For example, as shown in FIG. 2, separation claws 24 and 25 for separating the recording medium, rollers 26 for transmitting the rotational force, and the like are arranged around the fixing roller and the pressure roller in addition to the temperature detection members 41 and 42. Yes. Since these components are always in contact with the fixing roller 21 and the pressure roller 22, foreign matters such as toner and paper dust are likely to accumulate between the rollers.

Therefore, these components are arranged so as not to overlap each other in the rotational direction so as not to pick up the accumulated foreign matters. However, even with such a component arrangement, if foreign matter accumulates between the temperature detection members 41 and 42 and the fixing roller 21 or the pressure roller 22, the original detection function of the temperature detection members 41 and 42 is impaired.

Accordingly, an object of the present invention is to prevent foreign matters such as toner and paper dust from accumulating between a temperature detection member and a rotating member.

In order to solve the above problems, the present invention includes a fixing member heated to a predetermined operating temperature, and a pressure member that presses against the fixing member, and a contact portion between the fixing member and the pressure member. In a fixing device for fixing an unfixed toner image to the recording medium by heat and pressure by passing a recording medium carrying an unfixed toner image through a certain nip portion, at least the fixing member and the pressure member A temperature detection member for detecting one surface temperature is provided, and the contact state of the temperature detection member with respect to the fixing member or the pressure member is changed between an operating temperature and a non-operating temperature of the fixing member. The fixing device is characterized in that.

According to the present invention, the temperature detecting member changes the contact / separation state of the temperature detecting member with respect to the rotating member between the operating temperature and the non-operating temperature of the rotating member. Accumulation of foreign matter such as paper dust can be prevented.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. 1 is a schematic configuration diagram of a fixing device. 1 is a schematic configuration diagram of a fixing device according to a first embodiment of the present invention. It is a schematic block diagram of the fixing device which concerns on 2nd Embodiment of this invention. It is a schematic block diagram of the fixing device which concerns on 3rd Embodiment of this invention. It is a schematic block diagram of the fixing device which concerns on 4th Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In each of the drawings for explaining the embodiments of the present invention, constituent elements such as members and components having the same function or shape are described once by giving the same reference numerals as much as possible. Then, the explanation is omitted.

(Image forming device)
An image forming apparatus 1 shown in FIG. 1 is a color laser printer. In the center of the apparatus main body, four image forming units 4Y, 4M, 4C, and 4K are provided. Each of the image forming units 4Y, 4M, 4C, and 4K stores developers of different colors of yellow (Y), magenta (M), cyan (C), and black (K) corresponding to the color separation components of the color image. The configuration is the same except that.

Specifically, each of the image forming units 4Y, 4M, 4C, and 4K includes a drum-shaped photoconductor 5 as a latent image carrier, a charging device 6 that charges the surface of the photoconductor 5, and a surface of the photoconductor 5. A developing device 7 for supplying toner to the toner, and a cleaning device 8 for cleaning the surface of the photoreceptor 5. In FIG. 1, only the photoconductor 5, the charging device 6, the developing device 7, and the cleaning device 8 included in the black image forming unit 4 </ b> K are denoted by reference numerals, and the other image forming units 4 </ b> Y, 4 </ b> M, and 4 </ b> C are denoted by reference numerals. ing.

Below each image forming unit 4Y, 4M, 4C, 4K, an exposure device 9 for exposing the surface of the photoreceptor 5 is disposed. The exposure device 9 includes a light source, a polygon mirror, an f-θ lens, a reflection mirror, and the like, and irradiates the surface of each photoconductor 5 with laser light based on image data.

A transfer device 3 is disposed above the image forming units 4Y, 4M, 4C, and 4K. The transfer device 3 includes an intermediate transfer belt 30 as an intermediate transfer member and four primary transfer rollers 31 as primary transfer means. Further, a secondary transfer roller 36 as a secondary transfer unit and a secondary transfer backup roller 32 are provided. Further, a cleaning backup roller 33, a tension roller 34, and a belt cleaning device 35 are provided.

The intermediate transfer belt 30 is an endless belt and is stretched by a secondary transfer backup roller 32, a cleaning backup roller 33, and a tension roller 34. Here, when the secondary transfer backup roller 32 is driven to rotate, the intermediate transfer belt 30 runs (rotates) in the direction indicated by the arrow in FIG.

Each of the four primary transfer rollers 31 sandwiches the intermediate transfer belt 30 with each photoconductor 5 to form a primary transfer nip. Further, a power source (not shown) is connected to each primary transfer roller 31 so that a predetermined DC voltage (DC) and / or AC voltage (AC) is applied to each primary transfer roller 31.

The secondary transfer roller 36 sandwiches the intermediate transfer belt 30 with the secondary transfer backup roller 32 to form a secondary transfer nip. Similarly to the primary transfer roller 31, a power source (not shown) is also connected to the secondary transfer roller 36, and a predetermined DC voltage (DC) and / or AC voltage (AC) is applied to the secondary transfer roller 36. It has come to be.

The belt cleaning device 35 includes a cleaning brush and a cleaning blade disposed so as to contact the intermediate transfer belt 30. A waste toner transfer hose (not shown) extending from the belt cleaning device 35 is connected to an entrance of a waste toner container (not shown).

A bottle container 2 is provided in the upper part of the printer body, and four toner bottles 2Y, 2M, 2C, and 2K that store replenishing toner are detachably attached to the bottle container 2. . A replenishment path (not shown) is provided between each of the toner bottles 2Y, 2M, 2C, and 2K and each of the developing devices 7, and each development from the toner bottles 2Y, 2M, 2C, and 2K is performed via the replenishment path. The toner is supplied to the device 7.

On the other hand, at the lower part of the printer main body, a paper feed tray 10 that stores paper P as a recording medium, a paper feed roller 11 that carries the paper P out of the paper feed tray 10, and the like are provided. In addition to plain paper, the recording medium includes cardboard, postcard, envelope, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, OHP sheet, and the like. Although not shown, a manual paper feed mechanism may be provided.

In the printer main body, a transport path R is provided for discharging the paper P from the paper feed tray 10 through the secondary transfer nip to the outside of the apparatus. In the transport path R, a pair of timing rollers 12 serving as timing rollers for transporting the paper P to the secondary transfer nip at the transport timing is arranged upstream of the position of the secondary transfer roller 36 in the paper transport direction. Has been.

Further, a fixing device 20 for fixing the unfixed image transferred onto the paper P is disposed downstream of the position of the secondary transfer roller 36 in the paper transport direction. Further, a pair of paper discharge rollers 13 for discharging the paper to the outside of the apparatus is provided downstream of the fixing device 20 in the paper conveyance direction of the conveyance path R. A discharge tray 14 for stocking sheets discharged outside the apparatus is provided on the upper surface of the printer main body.

Next, a basic operation of the printer according to the present embodiment will be described with reference to FIG. When the image forming operation is started, each photoconductor 5 in each of the image forming units 4Y, 4M, 4C, and 4K is rotationally driven clockwise by a driving device (not shown), and the surface of each photoconductor 5 is charged by the charging device 6. Are uniformly charged to a predetermined polarity.

The surface of each charged photoconductor 5 is irradiated with laser light from the exposure device 9 to form an electrostatic latent image on the surface of each photoconductor 5. At this time, the image information to be exposed on each photoconductor 5 is single-color image information obtained by separating a desired full-color image into color information of yellow, magenta, cyan, and black. In this way, toner is supplied to each electrostatic latent image formed on each photoconductor 5 by each developing device 7, whereby the electrostatic latent image is visualized (visualized) as a toner image. .

When the image forming operation is started, the secondary transfer backup roller 32 is driven to rotate counterclockwise in the figure, and the intermediate transfer belt 30 is caused to run in the direction indicated by the arrow in the figure. Further, by applying a constant voltage having a polarity opposite to the toner charging polarity or a voltage controlled by a constant current to each primary transfer roller 31, the primary transfer nip between each primary transfer roller 31 and each photoreceptor 5 is applied. A transfer electric field is formed.

Thereafter, when each color toner image on the photoconductor 5 reaches the primary transfer nip as each photoconductor 5 rotates, the toner image on each photoconductor 5 is generated by the transfer electric field formed in the primary transfer nip. Are sequentially superimposed and transferred onto the intermediate transfer belt 30. Thus, a full color toner image is carried on the surface of the intermediate transfer belt 30.

Further, the toner on each photoconductor 5 that could not be transferred to the intermediate transfer belt 30 is removed by the cleaning device 8. Then, the surface of each photoconductor 5 is neutralized by a neutralizing device (not shown), and the surface potential is initialized.

In the lower part of the printer, the paper feed roller 11 starts to rotate, and the paper P is sent out from the paper feed tray 10 to the transport path R. The paper P sent to the transport path R is temporarily stopped by the timing roller pair 12.

Thereafter, rotation of the timing roller pair 12 is started at a predetermined timing, and the paper P is conveyed to the secondary transfer nip in accordance with the timing at which the toner image on the intermediate transfer belt 30 reaches the secondary transfer nip. At this time, a transfer voltage having a polarity opposite to the toner charging polarity of the toner image on the intermediate transfer belt 30 is applied to the secondary transfer roller 36, thereby forming a transfer electric field in the secondary transfer nip. .

Then, the toner images on the intermediate transfer belt 30 are collectively transferred onto the paper P by this transfer electric field. At this time, the residual toner on the intermediate transfer belt 30 that could not be transferred onto the paper P is removed by the belt cleaning device 35, and the removed toner is conveyed to a waste toner container (not shown) and collected.

Thereafter, the paper P is conveyed to the fixing device 20, and the toner image on the paper P is fixed to the paper P by the fixing device 20. Then, the paper P is discharged out of the apparatus by the paper discharge roller 13 and stocked on the paper discharge tray 14.

The above description is an image forming operation when a full-color image is formed on a sheet. A single-color image is formed using any one of the four image forming units 4Y, 4M, 4C, and 4K. Two or three image forming units can be used to form a two-color or three-color image.

(Fixing device)
FIG. 2 is a schematic configuration diagram of the fixing device 20 described above. As shown in FIG. 2, the fixing device 20 includes a fixing roller 21 and a pressure roller 22 as an opposing member that comes into contact with the outer peripheral surface of the fixing roller 21.

Inside the fixing roller 21, a heater 23 such as a halogen heater is disposed as a heating source for heating the fixing roller 21. A nip portion N is formed between the fixing roller 21 and the pressure roller 22.

  Around the fixing roller 21 and the pressure roller 22, temperature detection members 41 and 42 constituted by a thermistor and separation claws 24 and 25 for separating a recording medium are disposed in contact with the rollers. . A roller 26 for transmitting rotational force is disposed around the pressure roller 22. The roller 26 is connected to a recording medium conveying roller 28 via an intermediate roller 27 and a belt 29. In addition, you may drive not with a roller but with the gear provided in one edge part of the axial direction of the pressure roller 22, and a motor.

The temperature detection members 41 and 42 detect the surface temperatures of the fixing roller 21 and the pressure roller 22. Based on these detected temperatures, the heater 23 in the fixing roller 21 is controlled to be turned on and off by the temperature control means so that predetermined surface operating temperatures of the fixing roller 21 and the pressure roller 22 are maintained.

(First embodiment)
In the first embodiment of the present invention, the temperature detection member 41 (42) is fixedly supported on the tip of the heat-resistant support member 50 in a cantilever state as shown in FIG. 3A. The support member 50 can be made of a heat resistant metal or heat resistant resin.

When the temperature rises, the outer diameter of the fixing roller 21 and the pressure roller 22 increases due to thermal expansion (D1). Conversely, when the temperature decreases, the outer diameter shrinks (D2). Thus, the diameter of the roller 21 (22) increases or decreases depending on the temperature. The first embodiment of the present invention pays attention to the change of the roller diameter due to this temperature, and the temperature detecting member 41 (42) is brought into contact with or separated from the roller outer peripheral surface between the operating temperature and the non-operating temperature of the fixing roller 21. I will let you. As shown in FIG. 3A, the contact form of the temperature detection member 41 (42) with the outer peripheral surface of the roller is a trading contact that becomes a fulcrum of the support member on the upstream side in the rotation direction and a contact point of the temperature detection means on the downstream side. On the contrary, the counter contact may be arranged so as to be the fulcrum of the support member on the downstream side in the rotation direction and the contact point of the temperature detecting means on the upstream side.

Thus, the temperature detection member 41 (42) is brought into contact with the roller 21 (22) when the roller 21 (22) reaches the operating temperature (high temperature), and the temperature detection member 41 (42) at the non-operation temperature (low temperature). ) Is separated from the outer peripheral surface of the roller. By doing so, it is possible to reduce the chance that foreign matters such as toner and paper dust accumulate in the gap between the roller 21 (22).

Further, while the temperature detection member 41 (42) is separated, even if foreign matter flows from the upstream side of the roller, it is not picked up by the temperature detection member 41 (42) side. Moreover, since the chance that the temperature detection member 41 (42) contacts the roller 21 (22) is reduced, it is possible to suppress the occurrence of scratches on the roller surface that may cause the accumulation of foreign matter.

3A shows a state in which the temperature detection member 41 (42) is in contact with the outer peripheral surface of the roller at the operating temperature (high temperature), and FIG. 3B shows the temperature detection member 41 (42) at the non-operation temperature (low temperature). Shows a state separated from the outer peripheral surface of the roller. The temperature at which the contact / separation change of the temperature detection member 41 (42) occurs can be, for example, 40 ° C. between the operating temperature and the non-operating temperature.

The gap C1 between the temperature detection member 41 (42) and the roller outer peripheral surface at the non-operating temperature (low temperature) is a temperature difference between the operating temperature (high temperature) and the non-operating temperature (low temperature), and the material of the roller 21 (22). It can be decided by etc. The gap C1 can be set in a range of 0.01 mm to 1.0 mm, for example, and is desirably provided with a thickness of 0.1 mm or more. This is because the larger the gap C1, the higher the effect of suppressing the accumulation of foreign matter. That is, in the ON state of the heater 23 (roller surface operating temperature), the radius C1 is equal to or smaller than the radius length R1 {= (D1-D2) / 2} in which the roller is heated and expanded. A gap (interval) C1 between the temperature detection member and the roller facing the temperature detection member.

In the first embodiment, in a configuration in which the rubber thickness of the roller is thick, the roller diameter changes particularly greatly due to thermal expansion. Specifically, when the roller has a rubber thickness of 10 mm or more, the surface of the roller and the temperature detection member change by about 0.5 mm due to thermal expansion of the rubber. Therefore, the temperature detection member 41 (42) is in a contact state at a high temperature, and the gap C1 is 0.1 mm or more at a low temperature, so that the temperature detection member 41 (42) is in a non-contact state.

With the recent energy saving, the rubber layer of the roller 21 (22) tends to be thin. In that case, as will be described later, the bimetal 60 is used to change the contact / separation state between the roller 21 (22) and the temperature detection member 41 (42).

(Second Embodiment)
FIG. 3B shows a second embodiment of the present invention, in which the temperature detection member 41 (42) is contacted / separated by the bimetal 60, not by increase / decrease due to temperature change of the roller diameter itself. is there. That is, the support member that supports the temperature detection member 41 (42) is configured by the bimetal 60, and the temperature detection member 41 (42) is contacted and separated by the temperature deformation of the bimetal 60 that is heated by radiation from the roller 21 (22). Let FIG. 3B (a) shows a state in which the temperature detection member 41 (42) is in contact with the outer peripheral surface of the roller at the operating temperature (high temperature), and FIG. 3B shows the temperature detection member 41 (42) at the non-operation temperature (low temperature). The state which separated from the roller outer peripheral surface is shown.

The bimetal 60 is composed of two layers of upper and lower plates, and a metal having a low coefficient of thermal expansion is disposed in the upper layer and a metal having a high coefficient of thermal expansion is disposed in the lower layer. At the operating temperature (high temperature) in FIG. 3B (a), the bimetal 60 extends linearly, but when the temperature falls below this state and reaches the non-operating temperature (low temperature) in FIG. 3B (b), the lower layer is lower than the upper layer. Since the shrinkage amount of the metal is large, the bimetal 60 bends downward. As a result, the temperature detection member 41 (42) is separated from the roller 21 (22).

The temperature at which the contact / separation change of the temperature detection member 41 (42) occurs can be set to 40 ° C., for example. By using the deformation of the bimetal 60, the temperature detection member 41 (42) can be moved more easily than the change in the outer diameter due to the thermal expansion of the roller 21 (22), as compared with the configuration of the first embodiment. . For this reason, the gap C2 between the roller 21 (22) and the temperature detection member 41 (42) is further enlarged (C1 <C2), and the above-described accumulation of foreign matters can be more effectively suppressed.

(Third embodiment)
FIG. 3C is configured such that one end of the bimetal 60 abuts on and away from the temperature detection member 41 (42) with respect to the support shaft of the temperature detection member provided at one end of the support member. Specifically, the temperature detection member 41 (42) is fixed and supported in a cantilever manner by the support member 50, as in FIG. 3A, and between the support member 50 or the temperature detection member 41 (42) and the roller 21 (22). In addition, a bimetal 60 is disposed. Here, the support member 50 uses an elastically deformable material.

The bimetal 60 has a proximal end portion fixed and a distal end portion extending to one side of the support member 50. By arranging the bimetal 60 in this way, the bimetal 60 extends straight at the operating temperature (high temperature) as shown in FIG. 3A due to temperature deformation of the bimetal 60 heated by radiation from the roller 21 (22). To abut one side of the support member 50.

In this state, the temperature detection member 41 (42) contacts the outer peripheral surface of the roller. Further, as shown in (b), the bimetal 60 bends downward at a non-operating temperature (low temperature) and presses one side of the support member 50, whereby the temperature detection member 41 (42) is separated from the roller outer peripheral surface.

The gap C3 when separated is larger than the gap C1 in FIG. 3A (b) and the gap C2 in FIG. 3B (b) (C3> C2). The first reason is that the bimetal 60 is arranged closer to the roller 21 (22) side than the second embodiment of FIG. 3B, thereby increasing the radiant heat received by the second bimetal 60 and its deformation amount itself. It is because it can increase.

The second reason is that the gap C3 can be mechanically enlarged by the lever effect by causing the distal end portion of the bimetal 60 to act on the proximal end side of the support member 50. The temperature at which the contact / separation change of the roller 21 (22) occurs can be a temperature between the operating temperature and the non-operating temperature, for example, 40 ° C.

Further, as shown in FIG. 3C (c), when the temperature becomes higher, the bimetal 60 slightly warps upward and is separated from the support member 50. For this reason, the contact state between the temperature detection member 41 (42) and the roller 21 (22) does not change at all. The temperature at the time of the separation can be, for example, 50 ° C. between the operating temperature and the non-operating temperature.

When the temperature detection member 41 (42) is supported by the bimetal 60 as shown in FIG. 3B, when the temperature further rises from the state of FIG. 3B (a), the bimetal 60 bends upward to detect the temperature of the roller 21 (22). The contact pressure of the member 41 (42) tends to be excessive. By arranging the bimetal 60 as shown in FIG. 3C, it is possible to prevent the contact pressure from becoming excessive, and to avoid the occurrence of scratches on the roller surface and the life reduction of the temperature detection member 41 (42).

In FIG. 3C, the second bimetal 60 is disposed between the support member 50 or the temperature detection member 41 (42) and the roller 21 (22), but on the opposite side of the roller 21 (22), that is, below the support member 50. It is also possible to arrange the bimetal 60 on the side (outside). In this case, the support member 50 is extended straight by its elastic force in a natural state at a low temperature in FIG. 3C (b) so that the temperature detection member 41 (42) is separated from the roller 21 (22).

Then, the bimetal 60 disposed on the lower side (outside) of the support member 50 is heated by radiation from the roller 21 (22) and deforms in temperature at a high temperature, and presses the support member 50 against its elastic force at its tip. And push it up. As a result, the temperature detection member 41 (42) at the tip of the support member 50 comes into contact with the roller 21 (22).

(Fourth embodiment)
FIG. 3D shows a fourth embodiment of the present invention, in which a heat insulating member 70 is attached to the tip of the bimetal 60 in the third embodiment described above. Thereby, it can prevent that the heat of the supporting member 50 is transmitted to the bimetal 60, and the bimetal 60 malfunctions.

The heat insulating member 70 can be attached to the support member 50 side instead of being attached to the bimetal 60 side. As the heat insulating member 70, a thin sheet-like heat insulating member such as a nonwoven fabric having high heat insulating properties can be used, and the sheet-like heat insulating member can be easily attached to the bimetal 60 or the support member 50.

The embodiment of the present invention has been described above. However, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention. For example, the fixing device using the fixing roller 21 is shown in the above embodiment, but in the second to fourth embodiments of the present invention using the bimetal 60, a fixing film (fixing belt) with high energy saving can be used instead of the fixing roller 21. The present invention can also be applied to a rotating member method such as a film heating method (belt heating method) using a magnetic field and a fixing device such as an electromagnetic induction heating method. In addition to the thermistor, any temperature detecting member such as a thermocouple or a thermopile can be used as the temperature detecting members 41 and 42.

1: Image forming device 2: Bottle storage unit 2Y, 2M, 2C, 2K: Toner bottle 3: Transfer device 4Y, 4M, 4C, 4K: Image forming unit 5: Photoconductor 6: Charging device 7: Developing device 8: Cleaning Device 9: Exposure device 10: Paper feed tray 11: Paper feed roller 12: Timing roller pair 13: Paper discharge roller 14: Paper discharge tray 20: Fixing device 21: Fixing roller 22: Pressure roller 23: Heating heater 24, 25: Separation claw 26: Roller 27: Intermediate roller 28: Guide roller 29: Belt 30: Intermediate transfer belt 31: Primary transfer roller 32: Secondary transfer backup roller 33: Cleaning backup roller 34: Tension roller 35: Belt cleaning device 36 : Secondary transfer roller 41, 42: Temperature detection member 50: Support member 60: Bimetal C1 to C3: Clearance N: Nip part P: Paper R: Transport path

JP 2005-128048 A

Claims (8)

A fixing member that is heated to a predetermined operating temperature and a pressure member that presses against the fixing member are provided, and an unfixed toner image is carried in a nip portion that is a contact portion between the fixing member and the pressure member. In the fixing device for fixing the unfixed toner image to the recording medium by heat and pressure by passing the recorded recording medium,
A temperature detection member for detecting a surface temperature of at least one of the fixing member and the pressure member; and a contact / separation state of the temperature detection member with respect to the fixing member or the pressure member is determined as non-operating temperature of the fixing member. A fixing device characterized in that it changes between operating temperatures. The fixing member or the pressure member facing the temperature detection member is a roller-shaped fixing roller or pressure roller,
2. The fixing device according to claim 1, wherein the contacting / separating state of the temperature detecting member is changed by thermal expansion and contraction in a radial direction of the fixing roller or the pressure roller.   The temperature detection member is supported by a bimetal, and the contact state of the temperature detection member is changed by the bimetal being deformed by heat of the fixing member or the pressure member. 1 fixing device;   The temperature detection member is supported by an elastic support member, and a bimetal is disposed on the side of the support member, and the bimetal is deformed by the temperature of the fixing member or the pressure member, so that the non-operation is performed. The temperature detecting member is separated from the fixing member or the pressure member at a temperature, and the temperature detecting member is brought into contact with the fixing member or the pressure member at the operating temperature. 1 fixing device;   The bimetal is disposed between the support member and the fixing member or the pressure member, and the support member is moved away from the fixing member or the pressure member at the non-operating temperature. The pressure is pressed by the bimetal, and the pressure of the bimetal against the support member is reduced at the operating temperature so that the temperature detection member is brought into contact with the fixing member or the pressure member. 4 fixing device;   The bimetal is disposed outside the support member on the side opposite to the fixing member or the pressure member, and at the non-operating temperature, the support member uses the elastic force to move the temperature detection member to the fixing member or the additional member. It is separated from the pressure member, and at the operating temperature, the bimetal presses the support member against its elastic force to bring the temperature detection member into contact with the fixing member or the pressure member. The fixing device according to claim 4.   The fixing device according to claim 4, wherein a heat insulating member is disposed between the temperature detection member and the bimetal.   An image forming apparatus comprising the fixing device according to claim 1.