JP6106920B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device and an image forming apparatus, and more particularly to a belt fixing mechanism using a belt as a fixing member.

  As is well known, in an electrophotographic image forming apparatus, an electrostatic latent image formed on a photoreceptor, which is a latent image carrier, is subjected to visible image processing with toner, and the toner image is a recording medium such as recording paper. After being transferred to the image, it is fixed by applying heat and pressure to obtain a copy output.

As a fixing method used in the image forming apparatus, a fixing roller and a pressure roller which are in contact with each other with a recording paper conveyance path interposed therebetween are used, and the heat from the heat source provided in the fixing roller is sandwiched between the pressure roller and the fixing roller. A heat roller fixing method is known in which a toner image is fixed by heat and pressure by action.
In the heat roller fixing method, it takes time to rise to the fixing temperature due to the large heat capacity of the roller.

Therefore, a belt fixing method using a belt having a smaller heat capacity than a roller is known as a configuration for improving the rising of the fixing temperature (for example, Patent Document 1).
FIG. 5 is a diagram showing the configuration of the fixing device disclosed in Patent Document 1, and the configuration will be described as follows.
In FIG. 5, the fixing device A is configured to include a fixing roller B on one side and a pressure roller C on the other side across the conveyance path of the transfer paper S.
A fixing belt E is wound around the fixing roller B between the fixing roller B and a heating roller D disposed at a position different from the fixing roller B. The fixing belt E is subjected to a tension load by the tension roller F. It moves in conjunction with the rotation of the fixing roller B.

A heater D1 is disposed inside the heating roller D, and the temperature of the fixing belt E heated by the heater D1 is controlled by a thermistor G in contact with the belt surface.
Each of these rollers is disposed in the housing 1A of the fixing device A, and when the fixing roller B and the pressure roller C pass through a fixing nip formed at a position where they are in contact with each other, the transfer S generates heat and heat. The toner image is fixed under pressure.
After the fixing, the transfer sheet S is discharged with its discharge direction regulated by a separation claw H located behind the fixing nip.

Further, as another example of the above-described belt heating method, a configuration in which the belt is heated facing the fixing nip has been proposed (for example, Patent Document 2).
FIG. 6 is a diagram showing this configuration, in which a heat-resistant film (fixing film) K is sandwiched between a ceramic heater J as a heating element and a pressure roller C as a pressure member. Form a nip portion, introduce a recording paper carrying an unfixed toner image to be fixed between the film K and the pressure roller C in the fixing nip portion, and nip and convey the recording paper together with the film K Thus, a configuration is used in which the heat of the ceramic heater J is applied to the recording paper through the film K in the nip portion, and the unfixed toner image is fixed to the recording paper surface with heat by the pressure applied in the fixing nip portion. The ceramic heater J is attached to a stay N corresponding to a fixing member via a holder M.
In the above configuration, unlike the roller, by using the heat capacity, the rise to the fixing temperature can be accelerated, and accordingly, power saving can be achieved.

  On the other hand, in addition to improving the rise in temperature, as a configuration to improve the heat transfer efficiency at the fixing nip, heat fixing that heats the endless belt by the endless belt and a heat source installed in contact with the endless belt There has been proposed a configuration in which a pressure body is provided on the back surface of the endless belt to increase the width of the fixing nip by abutting the endless belt and applying pressure to the heat fixing roller (for example, Patent Document 3). 4).

However, these configurations have the following problems.
Since the heat resistant film moves while in contact with the ceramic heater, the surface of the film becomes rough due to the occurrence of rubbing friction. If the surface becomes rough in this way, slip may occur between the recording paper carrying the toner image and the load on the driving member of the film may increase. When slip occurs, an image shifts and an abnormal image is generated, and an increase in load on the drive member causes damage to the drive member.

On the other hand, in the case where a pressure member that contacts the back surface of the moving endless belt is provided, a configuration in which a low friction sheet or a lubricant is supplied to the surface that contacts the endless belt on the pressure member side is used to reduce the friction resistance. Mitigation is planned.
However, since the heating to the endless belt is a heating and fixing roller facing each other across the endless belt, the heat capacity of the roller itself is low, and furthermore, since the heating is for the fixing nip, the temperature of the roller is increased. It takes a long time for warming up due to slowness.

  In addition, since the fixing nip is an object of the heating region, the heat-resistant film and the endless belt that have passed through the fixing nip may be lowered in temperature due to heat radiation immediately after passing through, and may cause a fixing failure.

  As a configuration to cope with the above-described problems, an endless belt is spread over a pipe-shaped heating member disposed inside the endless belt so that the outer peripheral portion of the heating member circulates, and at a position facing the fixing nip, heating is performed. There has been proposed a configuration in which a nip forming member support capable of pressing an endless belt toward a pressure member disposed at a position facing the heating member is provided in a lack portion provided in the member (for example, Patent Document 5, Patent Document 5). 6).

  In the above configuration, by heating the heating member with the heat source arranged inside the heating member, the region in contact with the heating member other than the fixing nip of the endless belt can be heated.

In the fixing devices disclosed in Patent Documents 4 and 5, the heat source for heating the endless belt in a range other than the fixing nip is disposed in an exposed state on the side opposite to the fixing nip side with the fixing member interposed therebetween. For this reason, it is difficult to effectively guide the heat from the heat source radiated in all directions to the fixing belt.
In view of this, a configuration has been proposed in which a reflection member is provided between the heat source and the fixing member so that heat directed toward the nip forming member support is reflected and guided to the fixing belt (for example, Patent Document 7).

When the reflecting member disclosed in Patent Document 7 is provided, a structure for supporting the reflecting member is required. Specifically, a nip forming member support as disclosed in Patent Documents 5 and 6 is used. Thus, a configuration for supporting the reflecting member can be considered.
Providing the reflecting member in the vicinity of the nip forming member support is effective in suppressing the nip forming member support from being directly heated by the heat from the heat source, but the nip supporting the reflecting member. The forming member support and the reflecting member supporting member attached to the nip forming member instead of the forming member support are in a state in which heat is easily transferred by direct contact with the reflecting member.
For this reason, there is a possibility that the radiant heat from the heat source is transmitted to the support structure portion via the reflecting member. From this, when the fixing operation is continued and heating is continued for a long time, heat is transmitted to the fixing member and the supporting member, and the position of the nip forming member provided on the fixing member may be distorted due to thermal expansion. In the worst case, there is a problem that part of the member melts. If the position of the nip forming member is changed, the fixing nip width may be changed, or the nip pressure may be changed to cause a fixing failure.

On the other hand, since the size of the reflecting member is set for the entire light emitting region in the extending direction of the heat source, the region corresponding to the outside of the sheet passing region on the fixing belt is often heated. In other words, the light emitting member used for the heat source is provided with a light emitting region for the entire paper passing region, and the light emission amount gradually decreases at both ends in the extending direction corresponding to both ends of the light emitting region.
Accordingly, since the light emitting area outside the paper passing area is also included in the light emitting area at the heat source, if light emission continues outside the paper passing area, such as during continuous paper feeding, the area outside the paper passing area at the fixing belt May accumulate and be overheated to an abnormal temperature.

  An object of the present invention is to provide a support member for a nip forming member that has a reflecting member that directs a part of radiant heat from a heating source that heats a belt having a small heat capacity to the belt side in view of the problems in the conventional fixing device. Another object of the present invention is to provide a fixing device and an image forming apparatus having a configuration in which the heat transfer to the support member is prevented and the support state of the nip forming member is prevented from changing and the fixing nip condition is not changed. .

In order to achieve the above-described object, the present invention achieves this object by providing a rotatable endless fixing belt, a nip forming member disposed inside the fixing belt, and the fixing belt through the fixing belt. An opposing rotating body that forms a nip portion with the fixing belt by contacting the nip forming member, a heating source that directly heats the fixing belt at a location other than the nip portion, and the nip forming member are supported. A support member; and a reflective member that extends in the direction of the rotation axis of the fixing belt and reflects heat radiated from the heating source toward the support member toward the fixing belt, and is not fixed to the nip portion. In a fixing device that conveys a recording medium carrying an image and fixes the unfixed image on the recording medium, the reflection member is disposed in proximity to the support member, and between the support member The heat insulating layer is provided, the support member has a recess in which a pair of bent portions in which the heating source is folded toward a side provided to form the pair of bent portions includes a first facing each other And a second surface opposite to the first surface and facing the fixing belt, the reflecting member is supported by the second surface, and the heat insulating layer includes The fixing device is provided at a tip of the concave portion and the bent portion between the reflecting member and the support member .

According to the present invention, since the reflection member that irradiates the fixing belt with the radiant heat from the heating source is provided via the heat insulating layer with respect to the support member that supports the nip forming member, heat transfer between both members is achieved. Is suppressed.
This prevents the occurrence of thermal stress due to the temperature rise of the support member of the nip forming member or the deformation of the nip forming member so as to prevent the position of the nip forming member from being displaced. It is possible to prevent the fixing nip condition from changing.

1 is a diagram for explaining a configuration of an image forming apparatus using a fixing device according to an embodiment of the present invention. FIG. FIG. 2 is a schematic diagram for explaining a configuration of a fixing device used in the image forming apparatus shown in FIG. 1. FIG. 3 is a schematic diagram illustrating a modification example of a main part of the fixing device illustrated in FIG. 2. It is a perspective view for demonstrating the structure of the heating part concerning another embodiment of this invention. It is a schematic diagram for explaining one of conventional examples of a fixing device using a belt. It is a schematic diagram for explaining another conventional example of a fixing device using a belt.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the 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.

First, an overall configuration and operation of an image forming apparatus according to an embodiment of the present invention will be described with reference to FIG.
An image forming apparatus 1 shown in FIG. 1 is a color laser printer, and four image forming units 4Y, 4M, 4C, and 4K are provided in the center of the apparatus main body. Each of the image forming units 4Y, 4M, 4C, and 4K contains 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 has 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 and a cleaning device 8 for cleaning the surface of the photoreceptor 5 are provided. 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. In the other image forming units 4 </ b> Y, 4 </ b> M, and 4 </ b> C, The reference numerals are omitted.

  Under the image forming units 4Y, 4M, 4C, and 4K, an exposure device 9 that exposes 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 a transfer member, four primary transfer rollers 31 as primary transfer means, a secondary transfer roller 36 as secondary transfer means, a secondary transfer backup roller 32, and a cleaning device. A 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 the figure.

  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 become so.

  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 main body, and four toner bottles 2Y, 2M, 2C, and 2K containing replenishing toner are detachably attached to the bottle container 2. A replenishment path (not shown) is provided between each toner bottle 2Y, 2M, 2C, 2K and each developing device 7, and each development from each toner bottle 2Y, 2M, 2C, 2K is performed via this 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. Here, the recording medium includes thick paper, postcard, envelope, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, OHP sheet and the like in addition to plain paper. 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 registration rollers 12 serving as transport means for transporting the paper P to the secondary transfer nip is disposed upstream of the position of the secondary transfer roller 36 in the paper transport direction.

  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, the configuration of the fixing device 20 will be described with reference to FIG.
As shown in FIG. 2, the fixing device 20 includes a fixing belt 21 as a rotatable fixing rotating body, a pressure roller 22 as an opposing rotating body provided so as to be rotatable facing the fixing belt 21, and fixing. Radiation from the halogen heater 23 as a heating source for heating the belt 21, a nip forming member 24 disposed inside the fixing belt 21, a stay 25 as a support member for supporting the nip forming member 24, and the halogen heater 23. The reflection member 26 that reflects the light to the fixing belt 21, the temperature sensor 27 as temperature detecting means for detecting the temperature of the fixing belt 21, the separation member 28 that separates the paper from the fixing belt 21, and the pressure roller 22 And a pressing means (not shown) that pressurizes the fixing belt 21 to the fixing belt 21.

The fixing belt 21 is composed of a thin and flexible endless belt member (including a film).
The fixing belt 21 includes a base material on the inner peripheral side formed of a metal material such as nickel or SUS or a resin material such as polyimide (PI), a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), or polytetra It is comprised by the mold release layer of the outer peripheral side formed with fluoroethylene (PTFE) etc. Further, an elastic layer formed of a rubber material such as silicone rubber, foamable silicone rubber, or fluorine rubber may be interposed between the base material and the release layer.

The pressure roller 22 includes a cored bar 22a, an elastic layer 22b made of foamable silicone rubber, silicone rubber, or fluorine rubber provided on the surface of the cored bar 22a, and a PFA provided on the surface of the elastic layer 22b. Alternatively, it is constituted by a release layer 22c made of PTFE or the like. The pressure roller 22 is pressed toward the fixing belt 21 by a pressure unit (not shown) and is in contact with the nip forming member 24 via the fixing belt 21.
At the place where the pressure roller 22 and the fixing belt 21 are in pressure contact, the elastic layer 22b of the pressure roller 22 is crushed to form a nip portion N having a predetermined width.

  The pressure roller 22 is configured to be rotationally driven by a drive source such as a motor (not shown) provided in the printer main body. When the pressure roller 22 is rotationally driven, the driving force is transmitted to the fixing belt 21 at the nip portion N, and the fixing belt 21 is driven to rotate.

  In the present embodiment, the pressure roller 22 is a solid roller, but may be a hollow roller. In that case, a heating source such as a halogen heater may be disposed inside the pressure roller 22. Further, when the elastic layer 22b is not provided, the heat capacity is reduced and the fixability is improved. It can happen. In order to prevent this, it is desirable to provide an elastic layer having a thickness of 100 μm or more.

  By providing the elastic layer 22b having a thickness of 100 μm or more, minute irregularities can be absorbed by elastic deformation of the elastic layer 22b, so that occurrence of uneven gloss can be avoided. The elastic layer 22b may be solid rubber, but if there is no heat source inside the pressure roller 22, sponge rubber may be used. Sponge rubber is more preferable because heat insulation is enhanced and heat of the fixing belt 21 is less likely to be taken away. Further, the fixing rotator and the counter rotator are not limited to being brought into pressure contact with each other, and may be configured to simply contact each other without applying pressure.

  Both ends of the halogen heater 23 are fixed to a side plate (not shown) of the fixing device 20. Each halogen heater 23 is configured to generate heat by being output controlled by a power supply unit provided in the printer body, and the output control is based on the detection result of the surface temperature of the fixing belt 21 by the temperature sensor 27. Done. By such output control of the heater 23, the temperature of the fixing belt 21 (fixing temperature) can be set to a desired temperature. In addition to the halogen heater, an IH, a resistance heating element, a carbon heater, or the like may be used as a heating source for heating the fixing belt 21.

  The nip forming member 24 includes a base pad (for convenience, reference numeral 24 is used) and a sliding sheet (low friction sheet) 50 around which the base pad 24 is wound. Then, the fixing belt 21 is disposed in the longitudinal direction in the axial direction of the fixing belt 21 or in the axial direction of the pressure roller 22, and is fixedly supported by a stay 25 used as a supporting member of the nip forming member 24. Thus, the nip forming member 24 is prevented from being bent by the pressure of the pressure roller 22, and a uniform nip width is obtained along the axial direction of the pressure roller 22. The stay 25 is preferably made of a metal material having high mechanical strength such as stainless steel (SUS) or iron in order to satisfy the function of preventing the nip forming member 24 from bending, but the stay 25 is made of resin. It is also possible.

  The base pad 24 is made of a heat resistant member having a heat resistant temperature of 200 ° C. or higher. As a result, the deformation of the base pad 24 due to heat is prevented in the toner fixing temperature region, and a stable state of the nip portion N is secured to stabilize the output image quality. For the nip forming member 24, polyether sulfone (PES), polyphenylene sulfide (PPS), liquid crystal polymer (LCP), polyether nitrile (PEN), polyamide imide (PAI), polyether ether ketone (PEEK), etc. It is possible to use a typical heat resistant resin.

The base pad 24 has a low friction sheet 50 on the surface thereof.
The low friction sheet 50 is configured such that when the fixing belt 21 rotates, the fixing belt 21 slides on the surface thereof, and the driving torque generated in the fixing belt 21 when the fixing belt 21 slides is reduced. It is a member that can reduce the load caused by the frictional force. Examples of the material of the low friction sheet 50 include PTFE and the like.

  The base pad 24 has a function of determining the shape of the nip portion N formed by the pressure roller 22 facing the low friction sheet 50 therebetween. Therefore, the surface facing the nip portion N is substantially flat, in other words, has a straight shape, and a material that is hard to some extent is used as a material for maintaining this shape. Specifically, a crystalline thermoplastic used for liquid crystal polymer (LCP) or the like, for example, a molded product such as an aramid fiber is used. Further, in place of the resin, a material capable of maintaining the shape such as metal or ceramics may be used.

  The reflecting member 26 is disposed between the stay 25 and the halogen heater 23 using aluminum, stainless steel (SUS), or the like whose surface can be used as a reflecting surface. In the present embodiment, the reflecting member 26 is fixed to the stay 25. Further, since the reflecting member 26 is directly heated by the halogen heater 23, it is desirable that the reflecting member 26 be formed of a metal material having a high melting point. By arranging the reflection member 26 in this way, the light emitted from the halogen heater 23 toward the stay 25 is reflected to the fixing belt 21. As a result, the amount of light applied to the fixing belt 21 can be increased, and the fixing belt 21 can be efficiently heated. Further, since it is possible to suppress the radiant heat from the halogen heater 23 from being transmitted to the stay 25 and the like, energy saving can be achieved.

  Further, the reflective surface may be formed by subjecting the surface of the stay 25 on the side of the halogen heater 23 to mirror processing such as polishing or painting without providing the reflective member 26 as in the present embodiment. The reflectance of the reflecting surface of the reflecting member 26 or the stay 25 is desirably 90% or more.

  However, since the shape and material of the stay 25 cannot be freely selected in order to ensure the strength thereof, the separate provision of the reflecting member 26 as in this embodiment increases the degree of freedom in selecting the shape and material, and the reflection. The member 26 and the stay 25 can be specialized for each function. Further, since the reflecting member 26 is provided between the halogen heater 23 and the stay 25, the position of the reflecting member 26 with respect to the halogen heater 23 is reduced, so that the fixing belt 21 can be efficiently heated.

The characteristics of the fixing device 20 used in the image forming apparatus 1 having the above configuration will be described as follows.
Point, wherein the fixing device 20 according to the present embodiment is that in which a different area of the reflective region a structure that prevents heat transfer to the point a reflective member 26 provided on the reflective member 26.

The features of the former will be described as follows.
In FIG. 2, the reflecting member 26 is a bent aluminum sheet metal member, and has a shape capable of covering the surface of the halogen heater 23 opposite to the side facing the fixing belt 21 at a position spaced apart by a predetermined distance. Yes.
The surface of the reflecting member 26 that faces the halogen heater 23 is subjected to a coating process capable of vapor-depositing aluminum or mirror finishing to constitute a reflecting surface.

The reflection member 26 is attached to and supported by the stay 25. As the support structure, the bottom surface facing the recess of the stay 25 forms a space SP with a gap between the reflection member 26 and the recess. doing. This space SP constitutes a heat insulating layer by the presence of air.
Further, a thermal insulation member 100 such as a washer made of a heat shielding member is interposed between the tip of the bent piece of the stay 25 and the opposing surface of the reflection member 26, and the thickness of the thermal insulation member 100 is also in this portion. A space commensurate with the size is formed. This space corresponds to a heat insulating portion between the reflecting member 26 and the stay 25 by the heat insulating member 100, and the space formed by the interposition of the heat insulating layer 100 is a heat insulating layer due to the presence of air.

  The position where the heat insulating member 100 is provided is considerably smaller in the area between the tip of the bent piece of the stay 25 and the opposing surface of the reflecting member 26 than the area of the opposing portion between the concave portion of the stay 25 and the bottom surface of the reflecting member 26. Although heat transfer is relatively small, the heat insulation effect can be enhanced by adopting the above-described configuration.

Since the present embodiment is configured as described above, a heat insulating layer is provided between the reflecting member 26 and the stay 25 on which the reflecting member 26 is supported to block heat transfer.
Thereby, since the temperature rise of the stay 25 is suppressed, the position shift of the base pad 24 which is a nip forming member is prevented by the thermal expansion of the stay.
When the position shift of the base pad 24 is prevented, the nip width and nip pressure at the fixing nip are prevented from changing, and the fixing failure that occurs when the fixing conditions change can be prevented.

On the other hand, FIG. 3 shows a modification of the reflecting member 26, and the reflecting member (indicated by reference numeral 26 'in the figure) has a bottom face shape shown in FIG.
In the present embodiment, the heart position O2 in forming the arcuate bottom surface, are biases the stay 25 side with respect to the cross-sectional center O1 of the halogen heater 23.
Note that the heat insulating layer is provided on the opposing surface between the bottom surface of the reflecting member 26 and the concave portion of the stay 25 and the opposing surface between the bent piece tip of the stay 25 and the bent piece of the reflecting member 26 as shown in FIG. Same as the case.
This is considered to be because the amount of heat received by the halogen heater 23 is reduced by separating the reflecting surface from the halogen heater 23.

  In the present embodiment, as shown in FIG. 4, the both ends of the reflecting member 26 in the extending direction are configured by curved surfaces that can cover the entire circumference of the halogen heater 23 at positions facing the outside of the sheet passing area of the fixing belt 21. The heat shield 26a is provided.

Since the present embodiment is configured as described above, heat radiation is blocked by the heat shield portion 26a of the reflecting member 26 outside the paper passing area of the fixing belt 21. As a result, a temperature rise outside the sheet passing area in the fixing belt 21 is suppressed.
As a result, inadvertent heat storage of the fixing belt 21 is prevented, and deterioration of durability can be prevented.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 20 Fixing apparatus 21 Fixing belt 23 Halogen heater 26 Reflective member 26a Heat shield part SP Space which makes a part of heat insulation layer

JP 2009-104001 A JP 04-44075 A JP 08-262903 A JP-A-10-213948 JP 2009-3410 A JP 2010-96782 A JP 2005-92080 A

Claims (6)

A rotatable endless fixing belt;
A nip forming member disposed inside the fixing belt;
An opposing rotating body that forms a nip portion with the fixing belt by contacting the nip forming member via the fixing belt;
A heating source for directly heating the fixing belt at a place other than the nip portion;
A support member for supporting the nip forming member;
A reflective member that extends in the direction of the rotation axis of the fixing belt and reflects heat radiated from the heating source toward the support member toward the fixing belt,
In a fixing device that conveys a recording medium carrying an unfixed image to the nip portion and fixes the unfixed image on the recording medium.
The reflective member is disposed close to the support member, and a heat insulating layer is provided between the reflective member,
The support member has a recess formed by a pair of bent portions bent toward the side on which the heat source is provided,
The pair of bent portions includes a first surface facing each other, and a second surface positioned on the opposite side of the first surface and facing the fixing belt,
The reflective member is supported by the second surface ,
The fixing device according to claim 1, wherein the heat insulating layer is provided at a tip of the concave portion and the bent portion between the reflecting member and the support member .   The fixing device according to claim 1, wherein the heat insulating layer includes an air layer in a space formed by separating the reflecting member and the support member or a heat insulating material disposed in the space. .   The fixing device according to claim 1, wherein the reflecting member has an arc shape in a direction perpendicular to the extending direction of the heating source.   The fixing device according to claim 3, wherein an arc center of the reflecting member is biased toward the support member with respect to the heating source with respect to the center of the cross section of the heating source.   5. The reflective member according to claim 1, wherein the reflective member has a piece that can cover the entire circumference of the heating source outside a sheet passing area of the fixing belt. 6. Fixing device.   An image forming apparatus comprising the fixing device according to claim 1.

Images