JP2013057896A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device capable of preventing damage to each component including a fixing belt by suppressing heat deformation of a heating member and the fixing belt to a prescribed amount or less, and to provide an image forming apparatus.SOLUTION: A fixing device comprises: a fixing belt 21; a heating pipe 22 which is constituted of a pipe-shaped metal body and heats up the fixing belt 21; a heater 25 which heats up the heating pipe 22 by radiation heat; a pressure roller 31 which makes the fixing belt 21 rotate; a nip forming member 26 which contacts with the pressure roller 31 via the fixing belt 21; a temperature sensor 28 for detecting a surface temperature of the fixing belt 21; a body control part 110 which controls the heater 25 so that the surface temperature of the fixing belt 21 is at a prescribed surface temperature on the basis of the detected surface temperature; and displacement detection means 27 which detects deformation of the heating pipe 22 via the fixing belt 21. When deformation of the heating pipe 22 is detected, heat transfer amount to the heating pipe 22 is reduced by the body control part 110.

Description

  The present invention relates to a fixing device having an endless belt fixing member, and an image forming apparatus such as a FAX, a printer, a copying machine, or a composite machine using an electrophotographic method, an electrostatic recording method, or the like equipped with the fixing device. is there.

  Conventionally, various image forming apparatuses using an electrophotographic system have been devised as image forming apparatuses such as copying machines and printers, and are well known in the art. In the image forming process, an electrostatic latent image is formed on the surface of the photosensitive drum as an image carrier, and the electrostatic latent image on the photosensitive drum is developed with a toner as a developer to be visualized and developed. This is established by a process in which the transferred image is transferred onto a recording sheet (also referred to as a sheet or a recording medium) by a transfer device to carry the image, and a toner image on the recording sheet is fixed by a fixing device using pressure, heat, or the like.

  In this fixing device, a fixing member and a pressure member constituted by opposing rollers or belts or a combination thereof are arranged so as to contact each other to form a nip portion, and a recording sheet is sandwiched in the nip portion, Heat and pressure are applied to fix the above-described toner image on the recording paper.

  As an example of the fixing device, a technique using a fixing belt stretched around a plurality of roller members as a fixing member is known (see, for example, Patent Document 1). An apparatus using such a fixing belt includes a fixing belt (endless belt) as a fixing member, a plurality of roller members including a fixing roller and a heating roller for stretching and supporting the fixing belt, and a plurality of roller members. Of these, a heater provided in one roller member and a pressure roller (pressure member) are included. The heater heats the fixing belt via the roller member. Then, the toner image on the recording medium conveyed toward the nip formed between the fixing belt and the pressure roller is fixed on the recording medium by receiving heat and pressure at the nip. Belt fixing method).

  Further, a fixing device described below is known instead of the fixing device provided with a fixing belt stretched and supported by a plurality of roller members as described above (see, for example, Patent Document 2).

  A fixing device disclosed in Patent Document 2 is fixedly provided so as to face an inner peripheral surface of a fixing belt composed of an endless belt member, and contacts a pressure roller via the fixing belt. A heating member that forms a nip portion, a reinforcing member that reinforces the strength of the heating member in the nip portion, a heat insulating member provided between the reinforcing member and the heating member, a heater as a heat source, and a fixing belt. And a pressure roller for forming a desired nip portion between the two members, and a temperature sensor provided to face the fixing belt. The heating member is made of a pipe-shaped metal heat conductor and is heated by the radiant heat of the heater, and the heat is transmitted to the fixing belt. Further, the heating member needs to be as thin as possible in the pipe-like heating member (metal heat conductor) in order to improve the heating efficiency of the fixing belt.

  With such a configuration, the fixing device disclosed in Patent Document 2 is relatively inexpensive to manufacture, has high heating efficiency of the fixing belt, and has a short warm-up time and first print time, thus speeding up the device. Even in this case, it is possible to prevent problems such as fixing failure.

  However, in the conventional fixing device disclosed in Patent Document 2, since the fixing belt can be rotated relative to the heating member, the fixing belt is rotated by rotational driving from the pressure roller. In this case, sagging of the fixing belt occurs in the cross-sectional direction and in the downstream direction of the nip portion, and a temperature difference occurs between the upstream side of the nip portion and the downstream side of the nip portion of the heating member. For this reason, the metal conductor constituting the heating member is thermally deformed into a convex shape on the upstream side of the nip portion, particularly in the axial center portion, and a gap is generated between the heating member and the fixing belt at both axial end portions. As a result, abnormal heat is generated particularly at both ends in the axial direction of the heating member, and each component including the fixing belt may be damaged.

  In the fixing device disclosed in Patent Document 2, it is conceivable that the inner surface of the fixing belt is blackened and the fixing belt is directly heated using radiant heat from a heat source without providing a heating member. Also in this case, the fixing belt is thermally deformed into a convex shape on the upstream side of the nip portion, particularly in the center in the axial direction, and each component including the fixing belt may be damaged.

  The present invention has been made in view of the problems in the prior art as described above. By suppressing the thermal deformation of the heating member and the fixing belt to a certain amount or less, each component including the fixing belt is prevented from being damaged. An object of the present invention is to provide a fixing device and an image forming apparatus that can be used.

  In order to achieve the above object, a fixing device according to the present invention is composed of a flexible endless belt-shaped fixing member, a pipe-shaped metal body disposed inside the fixing member, and the fixing member. A heating member that heats the fixing member in direct or indirect contact with an inner peripheral surface, a heat source that heats the heating member, and an outer peripheral side of the fixing member that can press the fixing member, and A pressure member that rotates while sliding the member, and a nip forming member that faces the pressure member inside the fixing member and forms a nip portion by contacting the pressure member via the fixing member And a temperature detecting means for detecting the surface temperature of the fixing member, and the heat source is controlled based on the surface temperature detected by the temperature detecting means so that the surface temperature of the fixing member is set to a preset surface temperature. A fixing device including a control means for controlling, and further comprising a displacement detection means for detecting deformation of the heating member via the fixing member, wherein the deformation detection means detects the deformation of the heating member. In addition, the control means is configured to reduce the amount of heat transfer to the heating member.

  According to the present invention, it is possible to provide a fixing device and an image forming apparatus capable of preventing each component including the fixing belt from being damaged by suppressing thermal deformation of the heating member and the fixing belt to a certain amount or less. .

1 is an overall configuration diagram showing a configuration of an image forming apparatus according to a first embodiment of the present invention. 1 is a partial cross-sectional view of a fixing device according to a first embodiment of the present invention. (A) shows a cold state, (b) shows a deformed state of the first fixing belt, and (c) shows a deformed state of the second fixing belt. FIG. 2 is a perspective view of peripheral parts of a heating pipe constituting the fixing device according to the first embodiment of the present invention. 1 is a schematic top view of a fixing device for explaining a displacement detection unit according to a first embodiment of the present invention. It is a figure for demonstrating the main body control part which concerns on 1st Embodiment which concerns on this invention. It is a flowchart showing the process of the main body control part which concerns on 1st Embodiment based on this invention. The deformation amount of the fixing belt, the heater lighting rate, the surface temperature of the fixing belt and the heating pipe, with and without the displacement detection unit of the image forming apparatus according to the first embodiment of the present invention It is a graph for demonstrating. FIG. 4 is a partial cross-sectional view of a fixing device according to a second embodiment of the present invention. (A) shows a cold state, (b) shows a deformed state of the first fixing belt, and (c) shows a deformed state of the second fixing belt.

Embodiments of the present invention will be described below with reference to the drawings.
(First embodiment)
First, the configuration will be described.
As shown in FIG. 1, the image forming apparatus 1 is a tandem type color printer. Four toner bottles 102Y, 102M, 102C, and 102K corresponding to the respective colors (yellow, magenta, cyan, and black) are detachably installed in the bottle housing portion 101 above the image forming apparatus main body 1. For this reason, these four toner bottles 102Y, 102M, 102C, and 102K are exchangeable by a user or the like.

  An intermediate transfer unit 85 is disposed below the bottle housing portion 101. Image forming units 4Y, 4M, 4C, and 4K corresponding to the respective colors (yellow, magenta, cyan, and black) are arranged in parallel so as to face the intermediate transfer belt 78 of the intermediate transfer unit 85.

  Photosensitive drums 5Y, 5M, 5C, and 5K are disposed in the image forming units 4Y, 4M, 4C, and 4K, respectively. Further, around each of the photosensitive drums 5Y, 5M, 5C, and 5K, a charging unit 75, a developing unit 76, a cleaning unit 77, a neutralizing unit (not shown), and the like are disposed. Then, an image forming process (charging process, exposure process, development process, transfer process, cleaning process) is performed on each of the photoconductive drums 5Y, 5M, 5C, and 5K. An image of each color is formed on 5K.

  The photosensitive drums 5Y, 5M, 5C, and 5K are rotationally driven in a clockwise direction in FIG. 1 by a drive motor (not shown). Then, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K are uniformly charged at the position of the charging unit 75 (charging process). Thereafter, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach the irradiation position of the laser light L emitted from the exposure unit 3, and electrostatic latent images corresponding to the respective colors are formed by exposure scanning at this position. (It is an exposure process).

  Thereafter, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach a position facing the developing device 76, and the electrostatic latent image is developed at this position to form toner images of each color (developing process). ) Thereafter, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach positions facing the intermediate transfer belt 78 and the first transfer bias rollers 79Y, 79M, 79C, and 79K, and the photosensitive drums 5Y, 5M are located at this position. The toner images on 5C and 5K are transferred onto the intermediate transfer belt 78 (first transfer step). At this time, a small amount of untransferred toner remains on the photosensitive drums 5Y, 5M, 5C, and 5K.

Thereafter, the surfaces of the photoconductive drums 5Y, 5M, 5C, and 5K reach a position facing the cleaning unit 77, and untransferred toner remaining on the photoconductive drums 5Y, 5M, 5C, and 5K is removed at this position. It is mechanically recovered by 77 cleaning blades (this is a cleaning process).
Finally, the surfaces of the photoconductive drums 5Y, 5M, 5C, and 5K reach a position facing a neutralization unit (not shown), and the residual potential on the photoconductive drums 5Y, 5M, 5C, and 5K is removed at this position. The Thus, a series of image forming processes performed on the photosensitive drums 5Y, 5M, 5C, and 5K is completed.

  Thereafter, the toner images of the respective colors formed on the respective photosensitive drums through the developing process are transferred onto the intermediate transfer belt 78 in an overlapping manner. In this way, a color image is formed on the intermediate transfer belt 78. Here, the intermediate transfer unit 85 includes four primary transfer bias rollers 79Y, 79M, 79C, and 79K of the intermediate transfer belt 78, a secondary transfer backup roller 82, a cleaning backup roller 83, a tension roller 84, and an intermediate transfer cleaning unit 80. Etc. The intermediate transfer belt 78 is stretched and supported by the three rollers 82 to 84 and is endlessly moved in the direction of the arrow in FIG.

  The four primary transfer bias rollers 79Y, 79M, 79C, and 79K respectively sandwich the intermediate transfer belt 78 with the photosensitive drums 5Y, 5M, 5C, and 5K to form primary transfer nips. Then, a transfer bias reverse to the polarity of the toner is applied to the primary transfer bias rollers 79Y, 79M, 79C, and 79K. The intermediate transfer belt 78 travels in the direction of the arrow, and sequentially passes through the primary transfer nips of the primary transfer bias rollers 79Y, 79M, 79C, and 79K. In this way, the toner images of the respective colors on the photosensitive drums 5Y, 5M, 5C, and 5K are primarily transferred while being superimposed on the intermediate transfer belt 78.

  Thereafter, the intermediate transfer belt 78 onto which the toner images of the respective colors are transferred in an overlapping manner reaches a position facing the secondary transfer roller 89. At this position, the secondary transfer backup roller 82 sandwiches the intermediate transfer belt 78 between the secondary transfer roller 89 and forms a secondary transfer nip. The four color toner images formed on the intermediate transfer belt 78 are transferred onto the recording medium P conveyed to the position of the secondary transfer nip. At this time, untransferred toner that has not been transferred to the recording medium P remains on the intermediate transfer belt 78. Thereafter, the intermediate transfer belt 78 reaches the position of the intermediate transfer cleaning unit 80. At this position, the untransferred toner on the intermediate transfer belt 78 is collected. Thus, a series of transfer processes performed on the intermediate transfer belt 78 is completed.

  Here, the recording medium P transported to the position of the secondary transfer nip is transported from the paper feeding unit 12 disposed below the apparatus main body 1 via the paper feeding roller 97 and the registration roller pair 98. It is a thing. Specifically, a plurality of recording media P such as transfer paper are stored in the paper supply unit 12 in an overlapping manner. When the paper feed roller 97 is rotationally driven in the counterclockwise direction in FIG. 1, the uppermost recording medium P is fed between the rollers of the registration roller pair 98.

  The recording medium P conveyed to the registration roller pair 98 is temporarily stopped at the position of the roller nip of the registration roller pair 98 that has stopped rotating. Then, the registration roller pair 98 is rotationally driven in synchronization with the color image on the intermediate transfer belt 78, and the recording medium P is conveyed toward the secondary transfer nip. In this way, a desired color image is transferred onto the recording medium P.

  Thereafter, the recording medium P on which the color image is transferred at the position of the secondary transfer nip is conveyed to the position of the fixing device 20. At this position, the color image transferred to the surface is fixed on the recording medium P by heat and pressure generated by the fixing belt 21 and the pressure roller 31. Thereafter, the recording medium P is discharged out of the apparatus through a pair of paper discharge rollers 99. The recording medium P having the transferred image discharged outside the apparatus by the discharge roller pair 99 is sequentially stacked on the stack unit 100 as an output image. Thus, a series of image forming processes in the image forming apparatus is completed.

  Next, the configuration of the fixing device 20 will be described in detail with reference to FIGS.

  2 and 3, the fixing device 20 includes a fixing belt 21, a heating pipe 22 as a heating member, a nip forming member 26, a support member 23, a heater 25 as a heat source, and a pressure roller 31 as a pressure member. A temperature sensor 28 as a temperature detecting means and a main body control unit are provided.

  The fixing belt 21 is formed of a thin and flexible endless belt and travels in the direction of arrow A shown in FIG. The fixing belt 21 is formed such that a base material layer, an elastic layer, and a release layer are sequentially laminated from the inner peripheral surface 21a side that is a sliding contact surface with the nip forming member 26, and the total thickness is 1 mm or less. ing.

  The base material layer of the fixing belt 21 has a layer thickness of 25 to 35 μm and is formed of a metal material such as nickel or stainless steel or a resin material such as polyimide. The elastic layer of the fixing belt 21 has a layer thickness of 100 to 300 μm and is formed of a rubber material such as silicone rubber, foamable silicone rubber, or fluorine rubber. By providing this elastic layer, minute irregularities on the surface of the fixing belt 21 in the fixing nip portion 38 are not formed, and heat is uniformly transmitted to the toner image T on the recording medium P, thereby preventing the generation of a crushed skin image. The

  The release layer of the fixing belt 21 has a layer thickness of 10 to 50 μm, and includes PFA (tetrafluoroethylene bar fluoroalkyl vinyl ether copolymer resin), PTFE (tetrafluoroethylene resin), polyimide, polyetherimide, It is formed of PES (polyether sulfide) or the like. By providing this release layer, the releasability (peelability) for the toner image T is ensured.

  The diameter of the fixing belt 21 is preferably set to 15 to 120 mm. In the present embodiment, the diameter of the fixing belt 21 is set to about 30 mm.

  Further, the fixing belt 21 constitutes a fixing member according to the present invention. A film using a metal material such as nickel or SUS or a resin material such as polyimide may be used. On the inner peripheral surface side of the fixing belt 21, a heating pipe 22, a nip forming member 26, a support member 23, a heater 25, a first sheet metal 29, and a second sheet metal 41 are provided.

  The heating pipe 22 is disposed inside the fixing belt 21, has a thickness of 0.1 mm, and has a substantially pipe shape in cross section. Moreover, the heating pipe 22 is comprised with the metal which has heat conductivity, such as aluminum, iron, stainless steel, for example. Here, when the thickness of the heating pipe 22 is set to 0.2 mm or less, the heating efficiency of the heating pipe 22 is improved, so that the heating efficiency of the fixing belt 21 is also improved.

  The heating pipe 22 is formed so as to be in direct sliding contact with the inner peripheral surface of the fixing belt 21 at a position excluding the fixing nip portion 38, while the inner peripheral surface of the fixing belt 21 in the range of the fixing nip portion 38. It is formed so as to be in sliding contact with. For this reason, the heating pipe 22 is formed in a concave shape at the position of the fixing nip portion 38 and has an opening 22a (see FIG. 3). The heating pipe 22 is fixed to the first sheet metal 29 and the second sheet metal 41 with screws while being sandwiched between the first sheet metal 29 and the second sheet metal 41. Thereby, the heating pipe 22 is fixed to the flange part 35 mentioned later in the state which maintained the shape. In addition, the nip forming member 26 is fitted into the concave portion formed in the concave shape.

  The heating pipe 22 is heated by the radiant heat of the heater 25 installed on the inner peripheral side, and the fixing belt 21 is heated by the heated heating pipe 22. That is, the heating pipe 22 is directly heated by the heater 25, and the fixing belt 21 is indirectly heated via the heating pipe 22.

  The fixing belt 21 and the heating pipe 22 are configured to contact and slide in the heating region (in the present embodiment, the region upstream of the fixing nip portion 38), or have a gap δ of 0.3 mm or less. It is configured. As a result, the fixing belt 21 can be efficiently heated by the heating pipe 22, but it is more desirable to have a configuration in which both are in contact with and slide in the heating region because of high heating efficiency. However, when the fixing belt 21 and the heating pipe 22 are brought into close contact with each other in the heating region, the torque of the fixing belt 21 increases and wears even if the pressure contact force between the fixing belt 21 and the heating pipe 22 in the heating region becomes excessive. There is a risk of accelerating. Therefore, in such a case, it is preferable that the pressure contact force between the fixing belt 21 and the heating pipe 22 be 0.3 kgf / cm 2 or less.

  Further, fluorine grease as a lubricant is applied to the outer peripheral portion of the heating pipe 22 so as to reduce wear of the fixing belt 21. In order to reduce the sliding resistance between the heating pipe 22 and the fixing belt 21, the sliding contact surface of the heating pipe 22 is formed of a material having a low friction coefficient, or the inner peripheral surface 21a of the fixing belt 21 contains fluorine. A surface layer made of a material may be formed.

  The nip forming member 26 is fixed so as to be in sliding contact with the inner peripheral surface of the fixing belt 21. When the nip forming member 26 is pressed against the pressure roller 31 via the fixing belt 21, a fixing nip portion 38 for conveying the recording medium P is formed. Therefore, the nip forming member 26 is disposed on the inner peripheral side of the fixing belt 21, and comes into contact with the pressure roller 31 via the fixing belt 21 by the pressing of the pressure roller 31 to form the fixing nip portion 38. ing.

  Both ends in the width direction of the nip forming member 26 are fixedly supported by flanges 35 described later of the fixing device 20. The configuration of the nip forming member 26 will be described in more detail later.

  As shown in FIG. 2, the heater 25 as a heat source includes a plurality of halogen heaters in the axial direction. Halogen heaters at both ends protrude from the opening of the flange 35 and the main body ( For example, it is fixed to a side plate or the like.

  Further, the heater 25 may be IH, a resistance heating element, a carbon heater, or the like, but it is more efficient that the region where the temperature of the belt is raised is the region immediately before the nip on the lower side in FIG. Can heat well.

  The temperature sensor 28 is provided so as to face the surface of the fixing belt 21 and is configured by a known thermistor or the like. The temperature sensor 28 is disposed, for example, in the central region and the end region in the longitudinal direction of the fixing belt 21 and detects the temperature of the fixing belt 21. Since the temperature sensor 28 detects the surface temperature of the fixing belt 21, it constitutes a temperature detecting means according to the present invention.

  As described above, the temperature sensor 28 is provided with the temperature sensors at the closest positions of the center and the end, so that the temperature can be detected with higher accuracy and the temperature can be controlled. Therefore, a higher quality image can be obtained. It is more preferable that the temperature sensor 28 is not in contact with the fixing belt 21 because the surface thereof is not damaged by sliding. Examples of the non-contact type include a thermopile and a non-contact type thermistor. Examples of the contact type include a contact type thermistor.

  The heater 25 is supplied with power from the power supply unit of the apparatus main body 1, and the output of the heater 25 is controlled by a main body control unit 110 described later. The main body control unit 110 acquires a signal representing the detection result of the surface temperature of the fixing belt 21 by the temperature sensor 25 and controls the output of the heater 25 according to this signal. The main body control unit can set the temperature of the fixing belt 21 (fixing temperature) to a desired temperature by controlling the heater 25 to be turned off.

  Further, the fixing belt 21 is heated via the heating pipe 22 particularly on the upstream side of the fixing nip portion 38 and passes through the fixing nip portion 38. As a result, heat is applied to the toner image T on the recording medium P from the surface of the heated fixing belt 21.

  As described above, in the fixing device 20 in the present embodiment, the fixing belt 21 is heated by the heater 25 over a wide range in the circumferential direction around the position near the upstream side of the fixing nip portion 38 in the rotational direction. Even when the conveyance speed of P is increased, the fixing belt 21 is sufficiently heated to prevent the occurrence of fixing failure. Therefore, since the fixing belt 21 can be efficiently heated with a relatively simple configuration, the warm-up time and the first print time are shortened, and the size of the apparatus is reduced.

  The support member 23 is configured to support the nip forming member 26 that forms the fixing nip portion 38, and is disposed on the inner peripheral surface side of the fixing belt 21. The support member 23 holds the nip forming member 26 against the pressing direction of the pressure roller 31.

  The support member 23 has substantially the same length as the nip forming member 26, and both end portions in the width direction are fixed to the main body (for example, side plate) of the fixing device 20 via the flange 35. The support member 23 is formed of a metal material having high mechanical strength such as stainless steel or iron. With this configuration, the support member 23 contacts the pressure roller 31 via the nip forming member 26 and the fixing belt 21, so that the nip forming member 26 is greatly deformed by receiving pressure from the pressure roller 31 in the fixing nip portion 38. Can be suppressed. As described above, the support member 23 is configured to hold the nip forming member 26 in the pressing direction of the pressure roller 31.

  The support member 23 is provided with a reflector (not shown) on the surface on the heater 25 side in order to efficiently heat the heating pipe 22. For this reason, by preventing the support member 23 from being heated by providing the reflecting plate, it is possible to suppress wasteful energy consumption of the apparatus and to concentrate the heating pipe 22 on a heating range described later. be able to. In the present embodiment, the reflection plate is attached to the support member 23. However, instead of this, the surface of the support member 23 on the heater 25 side may be subjected to a mirror surface treatment.

  The pressure roller 31 is in pressure contact with the outer peripheral surface of the fixing belt 21 as a pressure rotator, and forms a desired fixing nip portion 38 between both members. In the present embodiment, the pressure roller 31 has a diameter of 30 mm, and an elastic layer 36 is formed on a hollow cored bar 34. The elastic layer 36 of the pressure roller 31 is formed of a material such as foamable silicone rubber, silicone rubber, or fluorine rubber. The pressure roller 31 may be provided with a thin release layer made of PFA, PTFE or the like on the surface layer of the elastic layer 36. The pressure roller 31 is pressed against the fixing belt 21 by a spring or the like (not shown), and has a predetermined nip width when the rubber layer is crushed and deformed. The pressure roller 31 may be a solid roller, but a hollow roller may have a smaller heat capacity.

  The pressure roller 31 is rotationally driven in the direction of arrow B in FIG. 2 by a drive mechanism (not shown). In addition, the pressure roller 31 is rotatably supported at both ends in the width direction by a side plate of the fixing device 20 via a bearing. A heat source such as a halogen heater may be provided inside the pressure roller 31.

  In the case where the elastic layer 36 of the pressure roller 31 is formed of a sponge-like material such as foamable silicone rubber, the pressure applied to the fixing nip portion 38 can be reduced. Deflection can be reduced. Further, since the heat insulation of the pressure roller 31 is increased and the heat of the fixing belt 21 is difficult to move to the pressure roller 31, the heating efficiency of the fixing belt 21 is improved. The elastic layer 36 may be solid rubber.

  The pressure roller 31 is arranged on the outer peripheral side of the fixing belt 21 so as to be able to press the fixing belt 21 and rotates while rotating the fixing belt 21. Therefore, the pressure roller 31 constitutes a pressure member according to the present invention.

  The nip forming member 26 has a flat plate shape and has a length in the axial direction of the fixing belt 21, and at least a portion in pressure contact with the pressure roller 31 via the fixing belt 21 is LCP (liquid crystal polymer) or PAI (polyamideimide resin). And a heat-resistant resin member such as PI (polyimide resin), and is fixed by a support member 23 while being held at a predetermined position on the inner peripheral side of the fixing belt 21.

  Further, the portion of the nip forming member 26 that is in contact with the inner peripheral surface of the fixing belt 21 is slidable and abrasion-resistant such as a mesh sheet woven with PTFE (polytetrafluoroethylene) fibers or a Teflon (registered trademark) sheet. A sheet material (not shown) having excellent wear properties is fixed in a wound state. The nip forming member 26 has a plurality of protrusions 22 a provided in the axial direction, and comes into contact with the support member 23.

  The nip forming member 26 is opposed to the pressure roller 25 inside the fixing belt 21 and abuts against the pressure roller 26 via the fixing belt 21 to form a fixing nip portion 38 (nip portion). The nip forming member according to the invention is configured. As described above, the fixing belt 21 rotates while being sandwiched between the nip forming member 26 and the pressure roller 31, but the upstream side of the fixing nip portion 38 becomes the tension side of the belt, and recording is performed on the fixing nip portion 38. The medium P is guided.

  As shown in FIG. 3, the first sheet metal 29 is formed by forming a stainless steel plate having a thickness of 1.5 mm into a U-shape, and a plurality of first sheet metals 29 are provided so that the support member 23 comes into contact with the nip forming member 26. The groove 29b is formed.

  The second sheet metal 41 is formed by forming a U-shaped stainless steel plate thinner than the first sheet metal 29, and the first sheet metal 29 so that the support member 23 contacts the nip forming member 26. A plurality of grooves 41a are formed in the same manner as in FIG. The second sheet metal 41 covers the nip forming member 26 from the inner peripheral surface side of the fixing belt 21.

  The first sheet metal 29 and the second sheet metal 41 are fixed by bolting. The first sheet metal 29 is formed with a plate-like protrusion 29 a extending in the axial direction of the fixing belt 21, and the plate-like protrusion 29 a is inserted through an opening 35 c formed in the flange 35. ing. Therefore, the first sheet metal 29 is fixed to a side plate (not shown) of the fixing device 20 via the flange 35, and at the same time, the second sheet metal 41 is also fixed to the side plate of the fixing device 20.

  Further, the nip forming member 26 is fitted to the U-shaped portion of the second sheet metal 41, and is fitted to the projection 35c of the flange 36 by the end portions 26b provided at both ends. It has become. For this reason, the nip forming member 26 is fixed to the side plate of the fixing device 20 via the second sheet metal 41, the first sheet metal 29, and the flange 35.

  As shown in FIG. 3, the flange 35 has a first flange portion 35 a that is in sliding contact with the inner peripheral surface portion at both ends of the fixing belt 21, and a first flange portion 35 a that is in sliding contact with both end edge portions of the fixing belt 21 and performs axial positioning. 2 flange portions 35f.

  Further, the flange 35 is formed with an opening 35 d that accommodates both ends of the support member 23, and the flange 35 is formed with a groove 35 e that allows the support member 23 to be positioned. As a result, the flange 35 can regulate the rotation of the support member 23 in the circumferential direction, and as a result, the nip forming member 26 can be stably held. Further, although not shown, the flange 35 is formed with a groove for restricting the movement of the support member 23 in the axial direction.

  Further, the flange 35 is formed with an opening 35b into which the end 29a of the first sheet metal 29 and the end 26b of the nip forming member 26 are inserted, and a U formed at the end 26b of the nip forming member 26 is formed. A protrusion 35c that engages with the groove 26c is formed. Therefore, the first sheet metal 29 and the nip forming member 26 are fixed to the main body 1 when the fixing device 20 is assembled.

  The first flange portion 35 a of the flange 35 is configured to maintain the shape of the heating pipe 22 by directly slidingly contacting the inner peripheral surface at both ends of the heating pipe 22. Further, the first flange portion 35 a of the flange 35 is configured to maintain the shape of the fixing belt 21 by being in sliding contact with the inner peripheral surface at both ends of the fixing belt 21.

  As shown in FIGS. 2 and 4, the displacement detection means 27 includes a rotation shaft 27a, a contact roller 27b, a first filler portion 27c, a second filler portion 27d, a first sensor 27e, and a second sensor 27f. It is equipped with.

  The rotating shaft 27a is composed of a rod-like member and is rotatably supported by the apparatus main body 1. The rotating shaft 27a is urged in a direction in which a contact roller 27b described later contacts the fixing belt 21 by a torsion spring (not shown).

  The contact roller 27b is fixed to the rotary shaft 27a via a support member 27g in the vicinity of the center in the axial direction of the fixing belt 21, and rotates along with the contact with the fixing belt 21. Does not affect the. Therefore, the contact roller 27b formed by the roller member constitutes the contact portion according to the present invention.

  The 1st filler part 27c is comprised by the flat member, and is being fixed to the rotating shaft 27a so that it may extend in the direction of the 1st sensor 27e. On the other hand, the second filler portion 27d is formed of a flat plate-like member, and is fixed to the rotating shaft 27a so as to extend in the direction of the second sensor 27f near the center portion.

  The first sensor 27e is a known sensor that detects the first filler portion 27c, and the position at which the first filler portion 27c is detected when the contact roller 27b shown in FIG. 2B moves to the first position. Is arranged. Here, the first position means a position where the amount of deformation that allows deformation of the fixing belt can be detected, and is set to a position that does not significantly reduce the fixing temperature increase time.

On the other hand, the second sensor 27f is a known sensor that detects the second filler portion 27d, and detects the second filler portion 27d when the contact roller 27b shown in FIG. 2C moves to the second position. Placed in position. Here, the second position means a position where an amount of deformation where the deformation of the fixing belt is unacceptable can be detected, and is set to a value such that the temperature rise of the heating pipe does not exceed the heat resistant temperature T _pmax .

  As shown in FIG. 4, the displacement detecting means 27 is fixed to the projection 27i projecting radially outward near the end of the rotating shaft 27a and the side plate of the one device body 1, and the rotation of the rotating shaft 27a. And a restricting member 27h that engages with the protruding portion 27i. The regulating member 27h opposes a torsion spring (not shown) in the urging direction, and the contact roller 27b is fixed to the fixing belt 21 when the fixing belt 21 shown in FIG. The rotation of the rotary shaft 27a is regulated so as to be positioned at a predetermined interval. Such a configuration that restricts the rotation of the rotating shaft 27a at a position where the contact roller 27b does not contact the fixing belt 21 is not limited thereto.

  The contact roller 27b that constitutes the displacement detection means 27 is disposed in the vicinity of the center with respect to the axial direction of the fixing belt 21, and is disposed in the heating range with respect to the cross-sectional direction of the heating pipe 27b. Here, the heating range means a range of 225 ° to 270 ° counterclockwise with reference to FIG. Further, since the heating pipe 22 and the fixing belt 21 have substantially the same length in the axial direction, the vicinity of the center with respect to the axial direction of the fixing belt 21 is also near the center with respect to the axial direction of the heating pipe 22.

  The displacement detecting means 27 is disposed at a position where the contact roller 27b does not contact the fixing belt 21 when the heater 25 is not heated, and detects the first position where the fixing belt 21 is deformed to the heating range side by the heater 25. In addition, the second position where the fixing belt 21 is further deformed to the heating range side is detected by the heater 25.

  As shown in FIG. 5, the main body control unit 110 constitutes a control unit according to the present invention, and includes a CPU (central processing unit) 110a that performs various operations for controlling the apparatus main body 1, and a read-only memory. A ROM (Read Only Memory) 110b, a temporary storage RAM (Random Access Memory) 110c, and an input / output interface (not shown) are included. The main body control unit 110 executes a control program including a control program stored in the ROM while using a temporary storage function of the RAM.

  Specifically, the main body control unit 110 includes, for example, a first sensor 111 that detects the first position, a second sensor 112 that detects the second position, the temperature sensor 28 described above, and the fixing nip portion 38. Based on detection information from the paper discharge sensor 113 provided in the paper discharge path on the discharge side, the heater driving circuit 114 and the driving device 115 are controlled.

  The heater drive circuit 114 is connected to an external power source and the heater 25, and the amount of power supplied from the power source to the heater 25 is controlled by a control signal from the main body control unit 110. Therefore, the heater 25 is controlled by the heater drive circuit 114 so as to obtain a desired lighting rate.

  Further, the ROM has a control map in which the power supply amount to the heater 25 is associated with the detected temperature output from the temperature sensor 28 and the deformation amount detected by the displacement detection means. Thus, the desired lighting rate is controlled.

  As described above, the main body control unit 110 controls the heater 25 based on the surface temperature of the fixing belt 21 detected by the temperature sensor 28 to control the surface temperature of the fixing belt to a preset surface temperature. ing. Further, the main body control unit 110 reduces the amount of heat transferred to the heating pipe 22, that is, the lighting rate of the heater 25 when the deformation detecting unit detects the deformation of the heating pipe 22.

  Specifically, the main body control unit 110, when the displacement detection unit 27 detects the deformation to the first position, the heater 25 reduces the lighting rate of the heater 25 from the maximum lighting rate 100% to 75%. The drive circuit 114 is controlled, and when the deformation to the second position is detected, the heater drive circuit 114 is controlled to turn off the heater 25. Here, the lighting rate of the heater 25 is merely an example, and is not limited to this. The main body control unit 110 may control the lighting rate of the heater 25 to be further reduced in two or more stages.

  Next, the operation will be described.

Next, the operation of the fixing device 20 will be described with reference to FIG.
First, when the image forming apparatus receives an output signal (for example, when there is a print request to the image forming apparatus due to a user's operation on the operation panel or the like), in the fixing device 20, the pressure roller 31 is fixed to the fixing belt by the pressure releasing means. The nip forming member 26 is pressed through 21 to form a fixing nip portion 38.

  Next, when the pressure roller 31 is rotationally driven in the clockwise direction (arrow B direction) in FIG. 2 by a driving device (not shown), the fixing belt 21 is also rotated in the counterclockwise direction (arrow A direction). Rotate.

  In synchronism with this, electric power is supplied from an external power source to the heater 25, and heat is efficiently transferred from the heater 25 in the circumferential direction and the entire axial width of the heater 25, so that the heating pipe 22 is rapidly heated. Further, heat from the heating pipe 22 is transmitted to the fixing belt 21 and is rapidly heated. The operation of the driving device and the heating by the heater 25 do not have to be started at the same time, but may be started with a time difference as appropriate.

  At this time, the heating control by the heater 25 is performed so that the fixing belt 21 at the fixing nip portion 38 has a predetermined temperature based on the temperature detected by the temperature sensor 28, and the temperature is increased to a temperature necessary for fixing. After that, the recording medium P is held and the sheet feeding of the recording medium P is started.

  Thus, in the fixing device 20, since the heat capacities of the fixing belt 21 and the heater 25 are small, it is possible to shorten the warm-up time and the first print time while saving energy.

  When there is no output signal to the image forming apparatus 1, the pressure roller 31 and the fixing belt 21 are normally non-rotated and the heater 25 is deenergized in order to reduce power consumption. When it is desired to start (return), it is possible to energize the heater 25 even when the pressure roller 31 and the fixing belt 21 are not rotating. In this case, the heater 25 is energized to keep the entire fixing belt 21 warm.

  Next, a processing flow of the image forming apparatus 1 according to the present embodiment will be described with reference to FIG. The following processing is started on the condition that the apparatus main body 1 is turned on and the user presses the copy start button from the operation panel. Further, the following processing is executed at a processing interval T as will be described later.

  The main body control unit 110 controls the heater drive circuit 114 to start supplying power at a maximum lighting rate of 100% (step S10).

  Next, the main body control unit 110 determines whether or not the displacement detection unit 27 has detected the first position (step S11). When the displacement detection unit 27 does not detect the first position, the main body control unit 110 controls the heater drive circuit to supply power at a maximum lighting rate of 100% (step S16). On the other hand, the main body control part 110 transfers to step S12, when the displacement detection means 27 detects a 1st position.

  Next, the main body control unit 110 determines whether or not the displacement detection unit 27 has detected the second position (step S12). When the displacement detector 27 does not detect the second position, the main body controller 110 controls the heater drive circuit to supply power with a lighting rate of 75% (step S15). On the other hand, when the displacement detection unit 27 detects the second position, the main body control unit 110 controls the heater drive circuit 114 to make the lighting rate 0%, and cuts off the power supply (step S13).

  Next, the main body control unit 110 determines whether the sheet passing is completed (Step S14). Specifically, the determination is made based on whether or not the last recording medium P is no longer detected by the paper discharge sensor 113 (step S14). When the signal from the paper discharge sensor 113 is detected, the main body control unit 110 proceeds to step S11, and when the signal from the paper discharge sensor 113 is not detected, the main body control unit 110 ends.

  Next, referring to FIG. 7, the deformation amount of the fixing belt 21 and the lighting rate of the heater 25 in each of the cases where the displacement detection unit 27 of the image forming apparatus 1 according to the present embodiment is present and absent. The surface temperature of the fixing belt 21 and the heating pipe 22 will be described.

First, as shown in FIG. 7A, when there is no displacement detection means 27, the surface temperatures of the fixing belt 21 and the heating pipe 22 rise at time t _A immediately after the lighting rate shifts to 100%. At this time, the deformation amount of the fixing belt 21 reaches _Xmax . Thereafter, the temperature of the fixing belt 21 and the heating pipe 22 is lowered by the recording medium P, but rises again after the recording medium P passes through the fixing device 20. At this time, the deformation amount of the fixing belt 21 also increases so as to follow the temperature increase of the fixing belt 21 and the heating pipe 22.

Thereafter, at time t _B , the temperature of the heating pipe 22 exceeds the heat resistance temperature T _{pmax of the} components including the fixing belt 21. As described above, the heating pipe 22 generates abnormal gaps between the fixing belt 21 at both axial end portions, and abnormal heat generation occurs particularly at both axial end portions of the heating pipe 22.

  Next, as shown in FIG. 6B, when the displacement detecting means 27 is provided, the surface temperatures of the fixing belt 21 and the heating pipe 22 rise immediately after the lighting rate shifts to 100%.

  Next, when reaching t1, the surface temperatures of the fixing belt 21 and the heating pipe 22 further increase, and the deformation amount of the fixing belt 21 reaches the first position. Therefore, the main body control unit 110 controls the heater to the heater driving circuit 114 at a lighting rate of 75%. Thus, it can be seen that the rate of increase in the surface temperature of the heating pipe 22 is suppressed as compared with the case where the displacement detecting means 27 of FIG.

  Next, when reaching t2, the surface temperatures of the fixing belt 21 and the heating pipe 22 further increase, and the deformation amount of the fixing belt 21 reaches the second position. For this reason, the main body control unit 110 controls the heater 25 to the heater drive circuit 114 at a lighting rate of 0%. As a result, at least the surface temperature of the heating pipe 22 can be controlled so as not to exceed the heat resistance temperature.

  Next, when t3 is reached, the surface temperature of the fixing belt 21 and the heating pipe 22 is lowered along with the passage of the recording medium P in addition to the lighting rate of the heater 25, and the deformation amount of the fixing belt 21 is less than the first position. ing. For this reason, the main body control unit 110 causes the heater drive circuit 114 to control the heater 25 again at a lighting rate of 100%.

  Next, when t4 is reached, the surface temperatures of the fixing belt 21 and the heating pipe 22 rise again, and the deformation amount of the fixing belt 21 reaches the first position again. Therefore, the main body control unit 110 causes the heater driving circuit 114 to control the heater 25 with a lighting rate of 75%.

  Next, when reaching t5, the surface temperatures of the fixing belt 21 and the heating pipe 22 are lowered, and the deformation amount of the fixing belt 21 is again below the first position. Therefore, the main body control unit 110 causes the heater driving circuit 114 to control the heater 25 with a lighting rate of 100%.

  Next, when t6 is reached, the surface temperatures of the fixing belt 21 and the heating pipe 22 rise again, and the deformation amount of the fixing belt 21 reaches the first position again. Therefore, the main body control unit 110 causes the heater driving circuit 114 to control the heater 25 with a lighting rate of 75%.

  Next, when t7 is reached, the surface temperatures of the fixing belt 21 and the heating pipe 22 are lowered, and the deformation amount of the fixing belt 21 is again below the first position. Therefore, the main body control unit 110 causes the heater driving circuit 114 to control the heater 25 with a lighting rate of 100%.

Thus, when the displacement detection means 27 is provided, the temperature of the heating pipe 22 does not exceed the heat resistance temperature T _{pmax of the} components including the fixing belt 21 by variably controlling the lighting rate. Note that the interval from t1 to t7 in FIG. 7B corresponds to the processing interval T in the main body control unit 110 described above.

  As described above, in the fixing device according to the present embodiment, when the deformation of the heating pipe 22 is detected via the fixing belt 21, at least the heating pipe is reduced by reducing the amount of heat transfer to the heating pipe 22. Since the deformation of 22 can be suppressed to a certain amount or less, the gap between the heating pipe 22 and the fixing belt 21 can be suppressed and an excessive temperature rise of the heating pipe 22 can be prevented. As a result, it is possible to prevent each component including the fixing belt 21 from being damaged.

  Further, in the fixing device according to the present embodiment, the fixing belt 21 is deformed by disposing the detection position of the fixing belt 21 in the vicinity of the center with respect to the axial direction and in the heating range with respect to the cross-sectional direction. Detection is possible at the maximum position, and deformation of the fixing belt 21 can be detected with high accuracy.

  Further, the fixing device according to the present embodiment detects the deformation of the heating pipe 22 by detecting the deformation of the fixing belt 21 even if the fixing belt 21 is deformed due to the deformation of the heating pipe 22. Can do. In addition, since the deformation of the fixing belt 21 can be detected in stages, the lighting rate of the heater 25 can be reduced in stages, and the amount of heat transfer to the heating pipe 22 can be optimally controlled. Specifically, until the deformation amount of the heating pipe 22 is allowable, the main body control unit 110 reduces the lighting rate of the heater 25 to keep the deformation constant without significantly decreasing the heating time to the fixing temperature. On the other hand, when the heating pipe 22 is deformed until the deformation is not acceptable, the heater 25 is turned off by the main body control unit 110 so that the heating pipe 22 is overheated and the components including the fixing belt 21 are heated. Breakage can be prevented.

  Further, the fixing device according to the present embodiment can prevent local wear on the surface of the belt constituting the fixing belt 21 due to the contact roller 27b coming into contact with the fixing belt 21, thereby suppressing deterioration in image quality. can do.

  In addition, when the deformation of the heating pipe 22 is detected, the image forming apparatus according to the present embodiment reduces the amount of heat transfer to the heating pipe 22 to suppress the deformation of the heating pipe 22 to a certain amount or less. Therefore, it is possible to prevent each component including the fixing belt 21 from being damaged.

(Second Embodiment)
Next, an image forming apparatus according to a second embodiment of the present invention will be described with reference to FIG.
The image forming apparatus according to the present embodiment differs from the image forming apparatus according to the first embodiment in that the configuration is different in that it does not have a heating pipe, but the other configurations are substantially the same. . Therefore, description will be made using the same reference numerals as those of the first embodiment shown in FIGS. 1 to 7, and only differences will be described in detail.

  As shown in FIG. 8, radiant heat from a heat source disposed inside the fixing belt 21 is efficiently and quickly transmitted to the belt surface on the inner peripheral surface portion 21a of the fixing belt 21 to a portion not in sliding contact with the flange portion 35a. Therefore, it is painted black to make it black with high heat absorption rate. Accordingly, heat from the heat source can be efficiently transmitted to the surface of the fixing belt 21 in the vicinity of the center in the longitudinal direction of the fixing belt 21, that is, at a position where the unfixed toner is permanently fixed in the fixing nip portion 38.

  As described above, the image forming apparatus according to the second embodiment includes the fixing device from which the heating pipe is removed. In the image forming apparatus according to the second embodiment, the fixing belt 21 is deformed similarly to the image forming apparatus according to the first embodiment. Therefore, the image forming apparatus according to the second embodiment is displaced as in the image forming apparatus according to the first embodiment. Detection means 27 is provided. Accordingly, in the image forming apparatus according to the second embodiment, similarly to the image forming apparatus according to the first embodiment, the main body controller 110 follows the control flow shown in FIG. The displacement detection means 27 is controlled.

  When the deformation of the fixing belt 21 is detected by the displacement detection means, the main body control unit 110 reduces the amount of heat transferred to the fixing belt 21, that is, the lighting rate of the heater 25.

  Specifically, the main body control unit 110, when the displacement detection unit 27 detects the deformation to the first position, the heater 25 reduces the lighting rate of the heater 25 from the maximum lighting rate 100% to 75%. The drive circuit 114 is controlled, and when the deformation to the second position is detected, the heater drive circuit 114 is controlled to turn off the heater 25.

  As described above, the fixing device and the image forming apparatus according to the present embodiment detect at least deformation of the fixing belt 21 by reducing the amount of heat transfer to the fixing belt 21 when the deformation of the fixing belt 21 is detected. Since the deformation can be suppressed to a certain amount or less, each component including the fixing belt 21 can be prevented from being damaged.

  Further, since the fixing device according to the present embodiment can detect the deformation of the fixing belt 21 in a stepwise manner, the lighting rate of the heater 25 can be decreased in a stepwise manner, and the amount of heat transfer to the fixing belt 21. Can be optimally controlled. Specifically, until the deformation amount of the fixing belt 21 is allowable, the main body control unit 110 reduces the lighting rate of the heater 25 to keep the deformation constant without significantly decreasing the temperature rising time to the fixing temperature. On the other hand, when the heating pipe 22 is deformed to an unacceptable degree, the heater 25 is turned off by the main body control unit 110 to prevent the components including the fixing belt 21 from being damaged. .

  Further, when the deformation of the fixing belt 21 is detected, the image forming apparatus according to this embodiment suppresses the deformation of the fixing belt 21 to a certain amount or less by reducing the heat transfer amount to the fixing belt 21. Therefore, it is possible to prevent each component including the fixing belt 21 from being damaged.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 20 Fixing apparatus 21 Fixing belt (fixing member)
22 Heating pipe (heating member)
23 support member 25 heater (heat source)
26 Nip forming member 27 Displacement detecting means 27b Contact roller (contact portion)
28 Temperature sensor (temperature detection means)
29 1st sheet metal 31 Pressure roller (Pressure member)
35 Flange 38 Fixing nip 41 Second sheet metal 110 Main body controller (control means)

JP 2007-206265 A JP 2009-3410 A

Claims (6)

An endless belt-like fixing member having flexibility;
A heating member disposed inside the fixing member and configured by a pipe-shaped metal body, which heats the fixing member by directly or indirectly slidingly contacting an inner peripheral surface of the fixing member;
A heat source for heating the heating member;
A pressure member that is arranged so as to be able to press the fixing member on an outer peripheral side of the fixing member, and that rotates while sliding the fixing member;
A nip forming member that faces the pressure member inside the fixing member and forms a nip portion by contacting the pressure member via the fixing member;
Temperature detecting means for detecting the surface temperature of the fixing member;
Control means for controlling the heat source based on the surface temperature detected by the temperature detection means to control the surface temperature of the fixing member to a preset surface temperature, and a fixing device comprising:
Displacement detection means for detecting deformation of the heating member via the fixing member is further provided, and when the deformation of the heating member is detected by the displacement detection means, the amount of heat transfer to the heating member is reduced by the control means. A fixing device. A flexible endless belt-shaped fixing member whose inner surface is blackened;
A heat source disposed inside the fixing member and for heating the fixing member;
A pressure member that is arranged so as to be able to press the fixing member on an outer peripheral side of the fixing member, and that rotates while sliding the fixing member;
A nip forming member that faces the pressure member inside the fixing member and forms a nip portion by contacting the pressure member via the fixing member;
Temperature detecting means for detecting the surface temperature of the fixing member;
Control means for controlling the heat source based on the surface temperature detected by the temperature detection means to control the surface temperature of the fixing member to a preset surface temperature, and a fixing device comprising:
Displacement detecting means for detecting deformation of the fixing member is further provided, and when the deformation of the fixing member is detected by the displacement detecting means, the amount of heat transfer to the fixing member is reduced by the control means. Fixing device.   3. The displacement detection unit according to claim 1, wherein the displacement detection unit is disposed in the vicinity of a center with respect to an axial direction of the fixing member, and is disposed in a heating range with respect to a cross-sectional direction of the fixing member. Fixing device. The displacement detecting means is disposed at a position where the heat source is not in contact with the fixing member in a non-heated state, detects a first position where the fixing member is deformed to the heating range side by the heat source, and the heat source A second position where the fixing member is further deformed toward the heating range;
When deformation to the first position is detected by the displacement detection means, the lighting rate of the heat source is decreased by the control means, and when deformation to the second position is further detected. The fixing device according to claim 1, wherein the heat source is turned off by the control unit.   5. The fixing device according to claim 1, wherein the displacement detection unit includes a contact portion formed of a roller member that can be rotated when the displacement detection unit comes into contact with the fixing member.   An image forming apparatus using the fixing device according to claim 1 to fix the toner image transferred to the recording medium by heat and pressure.

Images