JP2005266716A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a high-quality image by restraining damage at both ends of an endless belt and preventing paper wrinkles and an image defect or the like from occurring over a long term. <P>SOLUTION: The fixing device is equipped with a turnable fixing roll 61, an endless belt 62 capable of moving while coming into contact with the roll 61, and a pressure pad 64 arranged inside the belt 62 and bringing the belt 62 into press-contact with the roll 61 so as to form a nip part N through which paper P passes between the roll 61 and the belt 62. The belt 62 and the pad 64 are constituted so that frictional force between the belt 62 and the pad 64 may differ in accordance with directions. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fixing device and the like, and more particularly to a fixing device used in an image forming apparatus using an electrophotographic system.

  In an image forming apparatus such as a copying machine or a printer using an electrophotographic system, for example, a photosensitive member (photosensitive drum) formed in a drum shape is uniformly charged, and the photosensitive drum is controlled based on image information. An electrostatic latent image is formed on the photosensitive drum by exposure with the exposed light. The electrostatic latent image is converted into a visible image (toner image) with toner, and the toner image is transferred onto the recording paper from the photosensitive drum, and then the toner image is fixed on the recording paper with a fixing device.

  As shown in FIG. 11, the fixing device used in such an image forming apparatus includes a heat source 113 inside a cylindrical metal core 111, and a release layer 112 is formed on the outer peripheral surface of the metal core 111. A fixing roll 110 and a press roll disposed on the fixing roll 110, and a heat-resistant elastic body layer 122 and a release layer 123 made of a heat-resistant resin film or a heat-resistant rubber film are formed on the outer peripheral surface of the core metal 121. It is comprised with the pressure roll 120. Then, the recording paper carrying the unfixed toner image is passed between the fixing roll 110 and the pressure roll 120, and the unfixed toner image is heated and pressed to thereby apply the toner to the recording paper. Fix the image. Such a fixing device is called a heating roll method and is generally widely used.

By the way, in order to increase the speed of the heating roll type fixing device, it is necessary to increase the nip width in proportion to the fixing speed so that a sufficient amount of heat can be supplied to the toner and the recording paper. As a method of increasing the nip width, there are a method of increasing the load between the fixing roll and the pressure roll, a method of increasing the thickness of the elastic layer, and a method of increasing the roll diameter.
However, in the method of increasing the load or the method of increasing the thickness of the elastic layer, the shape of the nip width due to the deflection of the roll becomes non-uniform along the roll axis. This causes a problem in image quality such as occurrence. In addition, the method of increasing the roll diameter causes problems that the apparatus is increased in size and the time (warm-up time) until the roll is raised from room temperature to a fixable temperature is increased.

  Therefore, in order to solve these problems and realize a fixing device corresponding to the speeding up of the image forming apparatus, the applicant of the present invention has a rotatable fixing roll whose surface is elastically deformed and remains in contact with the fixing roll. An endless belt capable of traveling and a pressure pad arranged in a non-rotating state inside the endless belt, and the endless belt is pressed against the fixing roll so that a contact surface with the fixing roll is formed by the pressure pad. And a belt nip so that the sheet can be passed between the endless belt and the fixing roll, and a fixing device configured to locally elastically deform the exit side of the sheet on the surface of the fixing roll. The technique regarding this is proposed (for example, refer patent document 1).

  In the fixing device (referred to as “belt nip method”) described in Patent Document 1, an endless belt is used as a fixing roll by using a pressure pad as a pressure member instead of the pressure roll in the conventional heating roll type fixing device. Press contact. By adopting such a configuration, the width of the belt nip formed by the fixing roll and the endless belt can be easily made larger than the width of the conventional roll nip between the fixing roll and the pressure roll. Since a uniform and high nip pressure can be applied to the portion, it is possible to cope with a high speed, and it is easy to reduce the size of the apparatus.

  Furthermore, the heat capacity of the endless belt pressed against the fixing roll is small, and in addition, since the pressure pad is arranged in a non-rotating state, a configuration in which heat transmitted from the fixing roll is not easily dissipated to the outside is realized. Therefore, even when rotation of the fixing roll is started, the amount of heat taken from the fixing roll to the endless belt side is small, the thermal efficiency at the time of melting the toner can be increased, and the temperature drop at the belt nip is also small. There is also an advantage that the fixing property can be improved.

Japanese Patent No. 3298354 (pages 4-7)

  By the way, in a belt nip type fixing device in which an endless belt is pressed against a fixing roll by a pressure member, for example, flange-shaped regulating members are arranged at both ends of the endless belt to move the endless belt in the width direction (belt walk). ) To prevent the endless belt from shifting. Thereby, the fixing roll and the endless belt are always kept in contact with each other in a certain longitudinal region.

However, as the rotational speed of the endless belt increases as the speed of the image forming apparatus increases, the force (thrust force) for moving the endless belt in the width direction also increases proportionally. Therefore, when regulating the belt walk of the endless belt and suppressing the deviation, the frictional force between the end of the endless belt and the regulating member also becomes large, and bending, buckling, cracking, etc. at both ends of the endless belt A new problem arises that breakage tends to occur. In particular, in the belt nip type fixing device, since a lubricant is interposed between the friction surfaces of the low friction member disposed on the pressure member and the endless belt to improve the slipping property of the both, the endless belt Tends to move in the width direction, and the frictional force between the end of the endless belt and the regulating member tends to increase.
And damage such as folding, buckling, cracking, etc. at both ends of the endless belt not only prevents the endless belt from rotating smoothly but also causes paper wrinkles and image defects, but also eventually breaks the endless belt itself. May cause it.

  Accordingly, the present invention has been made to solve the technical problems as described above, and the object of the present invention is to suppress the thrust force acting on the endless belt and to generate damage at both ends of the endless belt. It is to suppress.

For this purpose, the fixing device of the present invention is a fixing device for fixing a toner image carried on a recording material, and is a rotatable rotating member and an endless movable member in contact with the rotating member. A belt, and a pressure member that is disposed inside the endless belt, presses the endless belt against the rotating member, and forms a nip portion through which the recording material passes between the rotating member and the endless belt. The pressure member is characterized in that the frictional force between the endless belt and the pressure member is different depending on the direction.
Here, the endless belt may be characterized in that movement of the endless belt in the thrust direction is restricted by a frictional force with the pressure member. Further, the pressure member may be configured such that a low friction member is disposed on a friction surface with the endless belt.

  The fixing device of the present invention is a fixing device that fixes a toner image carried on a recording material, and is capable of moving while contacting a rotating member that can rotate the recording material and a rotating member that conveys the recording material. An endless belt, a pressure member disposed inside the endless belt, press-contacting the endless belt to the rotating member to form a nip portion through which the recording material passes between the rotating member and the endless belt, and the endless belt and pressure A low friction member that reduces frictional resistance with respect to the sliding direction between the endless belt and the endless belt. The endless belt and the low friction member have a frictional force in a direction perpendicular to the moving direction rather than a frictional force in the moving direction of the endless belt. Is characterized by a large construction.

Here, the endless belt has grooves or projections formed on the inner peripheral surface thereof in the direction of movement of the endless belt, and the low friction member is formed on the sliding surface of the endless belt toward the direction of movement of the endless belt. It can be set as the structure in which the convex part or groove | channel which fits the groove | channel or convex part of an endless belt was formed. In particular, the grooves or protrusions formed on the endless belt may have a different cross-sectional shape from the protrusions or grooves formed on the low friction member. Moreover, the groove | channel or convex part formed in the endless belt, and the convex part or groove | channel formed in the low friction member can be formed in 4-20 micrometers in height or depth. Further, the groove or convex portion formed on the endless belt and the convex portion or groove formed on the low friction member can be formed with a width of 120 μm or less.
Moreover, the heating member which heats a rotation member, or the heating member which heats an endless belt can be further provided.

Further, the present invention is regarded as an image forming apparatus. The image forming apparatus of the present invention includes a toner image forming unit that forms a toner image, and a transfer unit that transfers a toner image formed by the toner image forming unit onto a recording material. A fixing unit that fixes the toner image transferred onto the recording material to the recording material, and the fixing unit is movable while contacting the rotating member and a rotatable rotating member that conveys the recording material. An endless belt, a pressure member disposed inside the endless belt, press-contacting the endless belt to the rotating member to form a nip portion through which the recording material passes between the rotating member and the endless belt, and the endless belt and pressure A low friction member that reduces the frictional resistance with respect to the sliding direction between the member, and the endless belt is formed with a groove or a convex portion on the inner peripheral surface in the moving direction of the endless belt, Friction member, the rubbing surface of an endless belt, toward the moving direction of the endless belt, is characterized in that projections or grooves that grooves or protrusions and the fitting of the endless belt is formed.
Here, the movement of the endless belt in the thrust direction is restricted by the frictional force with the low friction member.

  As an effect of the present invention, it is possible to suppress the occurrence of breakage at both ends of the endless belt and to form a high-quality image while suppressing the occurrence of paper wrinkles and image defects over a long period of time.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
[Embodiment 1]
FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus to which the exemplary embodiment is applied. The image forming apparatus shown in FIG. 1 is an intermediate transfer type image forming apparatus generally called a tandem type, and a plurality of image forming units 1Y, 1M, 1C, and 1K on which toner images of respective color components are formed by electrophotography. The primary transfer unit 10 that sequentially transfers (primary transfer) the color component toner images formed by the image forming units 1Y, 1M, 1C, and 1K to the intermediate transfer belt 15, and the superimposed toner image transferred onto the intermediate transfer belt 15. Are provided with a secondary transfer unit 20 that collectively transfers (secondary transfer) to a paper P that is a recording material (recording paper), and a fixing device 60 that fixes the secondary transferred image onto the paper P. Moreover, it has the control part 40 which controls operation | movement of each apparatus (each part).

  In the present embodiment, each of the image forming units 1Y, 1M, 1C, and 1K has a charger 12 that charges the photosensitive drum 11 around the photosensitive drum 11 that rotates in the direction of arrow A, and the photosensitive drum 11. A laser exposure device 13 for writing an electrostatic latent image thereon (exposure beam is indicated by a symbol Bm in the figure), each color component toner is accommodated, and the electrostatic latent image on the photosensitive drum 11 is visualized with toner. A developing unit 14, a primary transfer roll 16 that transfers each color component toner image formed on the photosensitive drum 11 to the intermediate transfer belt 15 in the primary transfer unit 10, and a drum cleaner that removes residual toner on the photosensitive drum 11. 17 and the like are sequentially arranged. These image forming units 1Y, 1M, 1C, and 1K are arranged substantially linearly in the order of yellow (Y), magenta (M), cyan (C), and black (K) from the upstream side of the intermediate transfer belt 15. Has been.

  The intermediate transfer belt 15 as an intermediate transfer member is formed of a film-like endless belt containing a resin such as polyimide or polyamide as a base layer and containing an appropriate amount of an antistatic agent such as carbon black. And it is cyclically driven (rotated) at a predetermined speed in the direction B shown in FIG. 1 by various rolls. As these various rolls, a drive roll 31 that is driven by a motor (not shown) having excellent constant speed and rotates the intermediate transfer belt 15, and an intermediate that extends substantially linearly along the arrangement direction of the photosensitive drums 11. A support roll 32 that supports the transfer belt 15, a tension roll 33 that functions as a correction roll that applies a constant tension to the intermediate transfer belt 15 and prevents meandering of the intermediate transfer belt 15, and a backup provided in the secondary transfer unit 20. A cleaning backup roll 34 provided in a cleaning unit for scraping off residual toner on the roll 25 and the intermediate transfer belt 15 is provided.

The primary transfer unit 10 includes a primary transfer roll 16 that is disposed to face the photosensitive drum 11 with the intermediate transfer belt 15 interposed therebetween. The primary transfer roll 16 is placed in pressure contact with the photosensitive drum 11 with the intermediate transfer belt 15 in between, and the primary transfer roll 16 has a voltage (with negative polarity; the same applies hereinafter) having a polarity opposite to that of the toner. (Primary transfer bias) is applied. As a result, the toner images on the respective photosensitive drums 11 are sequentially electrostatically attracted to the intermediate transfer belt 15 so as to form superimposed toner images on the intermediate transfer belt 15.
The secondary transfer unit 20 includes a secondary transfer roll 22 disposed on the toner image carrying surface side of the intermediate transfer belt 15 and a backup roll 25. The backup roll 25 is arranged on the back side of the intermediate transfer belt 15 to constitute a counter electrode of the secondary transfer roll 22, and a metal power supply roll 26 to which a secondary transfer bias is stably applied is in contact with the backup roll 25. Has been. The secondary transfer roll 22 is disposed in pressure contact with the backup roll 25 with the intermediate transfer belt 15 interposed therebetween. Further, the secondary transfer roll 22 is grounded, and a secondary transfer bias is formed between the secondary transfer roll 22 and the backup roll 25. The toner image is secondarily transferred onto the paper P conveyed to the transfer unit 20.

  Further, on the downstream side of the secondary transfer portion 20 of the intermediate transfer belt 15, an intermediate transfer belt that removes residual toner and paper dust on the intermediate transfer belt 15 after the secondary transfer and cleans the surface of the intermediate transfer belt 15. A cleaner 35 is provided so as to be able to contact and separate. On the other hand, on the upstream side of the yellow image forming unit 1Y, a reference sensor (home position sensor) 42 that generates a reference signal serving as a reference for taking image forming timings in the image forming units 1Y, 1M, 1C, and 1K. It is arranged. Further, an image density sensor 43 for adjusting image quality is disposed on the downstream side of the black image forming unit 1K. The reference sensor 42 recognizes a predetermined mark provided on the back side of the intermediate transfer belt 15 and generates a reference signal. Each image forming unit is instructed by an instruction from the control unit 40 based on the recognition of the reference signal. 1Y, 1M, 1C, and 1K are configured to start image formation.

  Further, in the image forming apparatus according to the present embodiment, as a paper transport system, a paper tray 50 that stores paper P, a pickup roll 51 that picks up and transports the paper P accumulated in the paper tray 50 at a predetermined timing, and a pickup A transport roll 52 that transports the paper P fed by the roll 51, a transport chute 53 that feeds the paper P transported by the transport roll 52 to the secondary transfer unit 20, and transported after being secondarily transferred by the secondary transfer roll 22. A conveyance belt 55 that conveys the paper P to be fixed to the fixing device 60 and a fixing inlet guide 56 that guides the paper P to the fixing device 60 are provided.

  Next, a basic image forming process of the image forming apparatus according to the present embodiment will be described. In an image forming apparatus as shown in FIG. 1, image data output from an image reading device (IIT) not shown or a personal computer (PC) not shown is subjected to predetermined image processing by an image processing device (IPS) not shown. After being applied, the image forming operation is executed by the image forming units 1Y, 1M, 1C, and 1K. In IPS, the input reflectance data is subjected to predetermined image processing such as shading correction, position shift correction, brightness / color space conversion, gamma correction, frame deletion, color editing, moving editing, and other various image editing. Is done. The image data that has undergone image processing is converted into color material gradation data of four colors, Y, M, C, and K, and is output to the laser exposure unit 13.

  The laser exposure unit 13 irradiates the photosensitive drums 11 of the image forming units 1Y, 1M, 1C, and 1K, for example, with an exposure beam Bm emitted from a semiconductor laser in accordance with the input color material gradation data. Yes. In each of the photosensitive drums 11 of the image forming units 1Y, 1M, 1C, and 1K, the surface is charged by the charger 12, and then the surface is scanned and exposed by the laser exposure unit 13 to form an electrostatic latent image. The formed electrostatic latent images are developed as toner images of respective colors Y, M, C, and K by the respective image forming units 1Y, 1M, 1C, and 1K.

  The toner images formed on the photosensitive drums 11 of the image forming units 1Y, 1M, 1C, and 1K are transferred onto the intermediate transfer belt 15 in the primary transfer unit 10 where the photosensitive drums 11 and the intermediate transfer belt 15 come into contact with each other. Transcribed. More specifically, in the primary transfer portion 10, a voltage (primary transfer bias) having a polarity opposite to the toner charging polarity (minus polarity) is applied to the base material of the intermediate transfer belt 15 by the primary transfer roll 16, and the toner image. Are sequentially superimposed on the surface of the intermediate transfer belt 15 to perform primary transfer.

  After the toner images are sequentially primary transferred onto the surface of the intermediate transfer belt 15, the intermediate transfer belt 15 moves and the toner image is conveyed to the secondary transfer unit 20. When the toner image is transported to the secondary transfer unit 20, in the paper transport system, the pick-up roll 51 rotates in accordance with the timing at which the toner image is transported to the secondary transfer unit 20, and the paper of a predetermined size is transferred from the paper tray 50. P is supplied. The paper P supplied by the pickup roll 51 is transported by the transport roll 52 and reaches the secondary transfer unit 20 via the transport chute 53. Before reaching the secondary transfer unit 20, the paper P is temporarily stopped, and a registration roll (not shown) rotates in accordance with the movement timing of the intermediate transfer belt 15 on which the toner image is carried. And the position of the toner image are aligned.

  In the secondary transfer unit 20, the secondary transfer roll 22 is pressed against the backup roll 25 via the intermediate transfer belt 15. At this time, the sheet P conveyed at the same timing is sandwiched between the intermediate transfer belt 15 and the secondary transfer roll 22. At this time, when a voltage (secondary transfer bias) having the same polarity as the toner charging polarity (negative polarity) is applied from the power supply roll 26, a transfer electric field is formed between the secondary transfer roll 22 and the backup roll 25. Is done. The unfixed toner image carried on the intermediate transfer belt 15 is collectively electrostatically transferred onto the paper P in the secondary transfer unit 20 pressed by the secondary transfer roll 22 and the backup roll 25. .

Thereafter, the sheet P on which the toner image has been electrostatically transferred is transported as it is while being peeled off from the intermediate transfer belt 15 by the secondary transfer roll 22, and transported downstream of the secondary transfer roll 22 in the sheet transport direction. It is conveyed to the belt 55. The conveyance belt 55 conveys the paper P to the fixing device 60 in accordance with the optimum conveyance speed in the fixing device 60. The unfixed toner image on the paper P conveyed to the fixing device 60 is fixed on the paper P by being subjected to a fixing process by heat and pressure by the fixing device 60. Then, the paper P on which the fixed image is formed is conveyed to a paper discharge mounting portion (not shown) provided in the discharge portion of the image forming apparatus.
On the other hand, after the transfer onto the paper P is completed, the residual toner remaining on the intermediate transfer belt 15 is conveyed to the cleaning unit as the intermediate transfer belt 15 rotates, and the cleaning backup roll 34 and the intermediate transfer belt cleaner 35 are transferred. Is removed from the intermediate transfer belt 15.

  Next, the fixing device 60 used in the image forming apparatus of the present embodiment will be described. FIG. 2 is a side sectional view showing a configuration of the fixing device 60 of the present embodiment. The fixing device 60 includes a fixing roller 61 as an example of a rotating member, an endless belt 62, and a pressure pad 64 as an example of a pressure member pressed from the fixing roll 61 via the endless belt 62. Yes.

The fixing roll 61 is a cylindrical roll configured by laminating a heat-resistant elastic body layer 612 and a release layer 613 around a metal core (cylindrical cored bar) 611, and is rotatably supported. Yes.
Inside the fixing roll 61, a halogen heater 66 is disposed as a heat source. On the other hand, a temperature sensor 69 is disposed in contact with the surface of the fixing roll 61. The control unit 40 of the image forming apparatus controls lighting of the halogen heater 66 based on the temperature measurement value by the temperature sensor 69 so that the surface temperature of the fixing roll 61 maintains a predetermined set temperature (for example, 150 ° C.). It is adjusted to.

The endless belt 62 is rotatable by a pressure pad 64 and a belt guide member 63 disposed inside the endless belt 62 and edge guides 80 (see FIG. 3 in the subsequent stage) disposed at both ends of the endless belt 62. It is supported. The nip portion N is disposed so as to be pressed against the fixing roll 61.
Here, FIG. 3 is a cross-sectional configuration diagram illustrating a configuration in which the endless belt 62 is supported, and shows one end region of the fixing device 60 as viewed from the downstream side in the conveyance direction of the paper P.
As shown in FIG. 3, edge guides 80 are fixed to both end portions of the holder 65 disposed inside the endless belt 62. The edge guide 80 is provided in a cylindrical shape in which a notch is formed in a portion corresponding to the nip portion N and the vicinity thereof, that is, a belt traveling guide portion 801 having a C-shaped cross section, and provided outside the belt traveling guide portion 801. A flange portion 802 formed with an outer diameter larger than the inner diameter of the belt 62 and a holding portion 803 provided on the outer side of the flange portion 802 for positioning and fixing the edge guide 80 to the fixing device 60 main body. Yes.

The endless belt 62 is supported by the outer peripheral surface of the belt traveling guide portion 801 except for the nip portion N and the vicinity thereof, and rotates along the outer peripheral surface of the belt traveling guide portion 801. . Accordingly, the belt traveling guide portion 801 is formed of a material having a small friction coefficient so that the endless belt 62 can smoothly rotate, and further has a low thermal conductivity so that it is difficult to remove heat from the endless belt 62. It is made of material.
Further, the flange portion 802 is disposed such that inner surfaces of both flange portions 802 disposed so as to face each other at both end portions of the holder 65 have an interval substantially matching the width of the endless belt 62. When the endless belt 62 rotates, the end of the endless belt 62 abuts against the inner surface of the flange portion 802, so that the movement of the endless belt 62 in the width direction (belt walk) is limited. . In this way, the endless belt 62 is supported by the edge guide 80 so that the deviation is regulated.

Further, the endless belt 62 is supported by the pressure pad 64 and the belt guide member 63 in the longitudinal region excluding both ends of the endless belt 62 (see also FIG. 2). In the region excluding both ends of the endless belt 62, the inner peripheral surface of the endless belt 62 rotates while sliding on the pressure pad 64 and the belt guide member 63.
The belt guide member 63 is attached to a holder 65 disposed inside the endless belt 62, and is formed of a material having a small friction coefficient so that the endless belt 62 can smoothly rotate. Further, it is preferable that the endless belt 62 is made of a material having low thermal conductivity so that it is difficult to remove heat from the endless belt 62.

  Next, the pressure pad 64 is disposed inside the endless belt 62 while being pressed against the fixing roll 61 via the endless belt 62, and forms a nip portion N with the fixing roll 61. In the pressure pad 64, a pre-nip member 64a for securing a wide nip portion N is disposed on the inlet side of the nip portion N, and a peeling nip member 64b for imparting distortion (dent) to the fixing roll 61 is provided in the nip portion N. It is arranged on the exit side. Further, in order to reduce the sliding resistance between the inner peripheral surface of the endless belt 62 and the pressure pad 64, a low friction sheet as an example of a low friction member on the surface of the pre-nip member 64a and the peeling nip member 64b in contact with the endless belt 62. 68 is provided. The pressure pad 64 and the low friction sheet 68 are supported by a metal holder 65.

  The fixing roll 61 is connected to a drive motor (not shown) and rotates in the direction of arrow C. Following this rotation, the endless belt 62 also rotates in the same direction as the fixing roll 61. The sheet P on which the toner image is electrostatically transferred in the secondary transfer unit 20 of the image forming apparatus shown in FIG. 1 is guided by the fixing inlet guide 56 and conveyed to the nip N. When the paper P passes through the nip portion N, the toner image on the paper P is fixed by the pressure acting on the nip portion N and the heat supplied from the fixing roll 61. In the fixing device 60 of the present embodiment, since the nip portion N can be configured widely by the concave pre-nip member 64a that substantially follows the outer peripheral surface of the fixing roll 61, stable fixing performance can be ensured.

In addition, in the fixing device 60 of the present embodiment, the surface of the fixing roll 61 is provided in the exit region (peeling nip portion) of the nip portion N by disposing the separation nip member 64b so as to protrude from the outer peripheral surface of the fixing roll 61. The heat-resistant elastic body layer 612 and the release layer 613 disposed in FIG. If the separation nip member 64b is arranged in this manner, the sheet P after fixing passes through a locally formed dent when passing through the separation nip portion. Is formed with a down curl, and can effectively peel off the paper P without being wound around the fixing roll 61.
In particular, when the dent of the fixing roll 61 is locally increased, high peeling performance can be obtained with a small dent amount. Therefore, even when a thin heat-resistant resin is used as the release layer 613 of the fixing roll 61, the occurrence of paper wrinkles on the paper P can be suppressed. Further, peeling between the heat-resistant elastic layer 612 and the release layer 613 hardly occurs, and the reliability of the component performance over a long period can be improved together with maintaining the peeling performance.

Furthermore, since the dent amount of the fixing roll 61 can be reduced by locally increasing the dent of the fixing roll 61, the heat-resistant elastic body layer 612 of the fixing roll 61 can be thinned. Therefore, since the heat capacity of the fixing roll 61 can be reduced, the warm-up time can be shortened and the power consumption can be reduced. Further, since the heat-resistant elastic body layer 612 having a low thermal conductivity can be thinned, the thermal resistance between the inner surface and the outer surface of the fixing roll 61 can be reduced and the thermal responsiveness can be improved. It is also suitable for conversion.
Further, in the vicinity of the downstream side of the nip portion N, the paper P peeled off from the fixing roll 61 by the peeling nip member 64b is completely separated from the fixing roll 61 and guided to the paper discharge path toward the discharge portion of the image forming apparatus. A peeling assisting member 70 is provided for this purpose. The peeling auxiliary member 70 is held by the holder 72 in a state in which the peeling baffle 71 is close to the fixing roll 61 in a direction (counter direction) opposite to the rotation direction of the fixing roll 61.

Next, each member constituting the fixing device 60 will be described in detail. First, in the fixing roll 61, the core (base material) 611 is formed of a cylindrical body having an outer diameter of 25 mm and a length of 350 mm formed of a metal having high thermal conductivity such as iron, aluminum, and SUS.
The heat resistant elastic layer 612 is made of an elastic body having high heat resistance, and it is particularly preferable to use an elastic body such as rubber or elastomer having a hardness of about 15 to 45 ° (JIS-A). Specifically, silicone rubber, fluorine rubber, or the like can be used.

  For the release layer 613, for example, a heat-resistant resin such as a silicone resin or a fluororesin is used, but a fluororesin is suitable from the viewpoint of the releasability to the toner and the wear resistance. As the fluororesin, PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), PTFE (polytetrafluoroethylene), FEP (tetrafluoroethylene-hexafluoropropylene copolymer), or the like can be used. The thickness of the release layer 613 is preferably 5 to 30 μm, more preferably 10 to 20 μm.

The endless belt 62 is a seamless endless belt formed in a cylindrical shape with a diameter of 30 mm so that a defect due to the seam does not occur in the output image. The base layer and the fixing roll 61 side of the base layer And a release layer coated on both sides.
The base layer is formed of a heat-resistant resin such as polyimide, polyamide, polyimide amide, or polybenzimidazole, or a metal such as SUS or nickel, and has a thickness of 30 to 200 μm, preferably 50 to 125 μm, more preferably 75 to It is about 100 μm. Moreover, it is also possible to form the endless belt 62 having higher strength by blending the above heat resistant resins. In that case, since the thickness of the base layer can be reduced, the heat capacity of the endless belt 62 can be further reduced.
The release layer coated on the surface of the base layer is formed of a fluororesin such as PFA, PTFE, or FEP, and has a thickness of about 5 to 100 μm, preferably about 10 to 30 μm. The release layer is provided to prevent the toner from adhering to the surface of the endless belt 62. Therefore, the release layer may be arranged only on the surface of the base layer on the fixing roll 61 side.

As described above, the pressure pad 64 includes the pre-nip member 64a and the peeling nip member 64b, and is supported by the holder 65 so as to urge the fixing roll 61 by a spring or an elastic body. An elastic body such as silicone rubber or fluorine rubber, a leaf spring, or the like can be used for the prenip member 64 a, and the surface on the fixing roll 61 side is formed in a concave shape that substantially follows the outer peripheral surface of the fixing roll 61.
The peeling nip member 64b is formed of a heat-resistant resin such as PPS (polyphenylene sulfide), polyimide, polyester, polyamide, or a metal such as iron, aluminum, or SUS. As the shape of the peeling nip member 64b, the outer surface shape in the nip portion N is formed in a convex curved surface shape having a constant radius of curvature.

The low friction sheet 68 is provided on the inner peripheral surface side of the endless belt 62 of the pressure pad 64 in order to reduce sliding resistance (friction resistance) between the inner peripheral surface of the endless belt 62 and the pressure pad 64, and has a small friction coefficient. Materials with excellent wear resistance and heat resistance are suitable. Specifically, a sintered-molded PTFE resin sheet, a glass fiber sheet impregnated with Teflon (registered trademark), a laminated sheet obtained by heat-sealing a glass fiber sheet made of a fluororesin, and the like can be used. .
Here, if the low friction sheet 68 is disposed on the inner peripheral surface side of the endless belt 62 of the pressure pad 64, the low friction sheet 68 may be separated from the pressure pad 64 even if the low friction sheet 68 is configured separately from the pressure pad 64. It may be configured integrally or any of them.

Further, as described above, the belt guide member 63 disposed in the holder 65 slidably rubs against the inner peripheral surface of the endless belt 62, so that the friction coefficient is low and it is difficult to take heat from the endless belt 62. A material having low thermal conductivity is suitable, and a heat-resistant resin such as PFA or PPS is used.
Further, the holder 65 is provided with a lubricant application member 67 along the longitudinal direction of the fixing device 60. The lubricant application member 67 is disposed so as to contact the inner peripheral surface of the endless belt 62 and supplies an appropriate amount of lubricant. As a result, the lubricant is supplied to the sliding portion between the endless belt 62 and the low friction sheet 68, and the sliding resistance between the endless belt 62 and the pressure pad 64 via the low friction sheet 68 is further reduced. 62 is smoothly rotated. In addition, it has an effect of preventing the inner peripheral surface of the endless belt 62 and the surface of the low friction sheet 68 from being worn.

  Here, as the lubricant, a lubricant having durability against long-term use under a fixing temperature environment and capable of maintaining wettability with the inner peripheral surface of the endless belt 62 is suitable. For example, liquid oil such as silicone oil or fluorine oil, grease in which a solid substance and a liquid are mixed, or a combination thereof can be used. Examples of the silicone oil include dimethyl silicone oil, amino-modified silicone oil, carboxy-modified silicone oil, silanol-modified silicone oil, sulfonic acid-modified silicone oil, and the like. Modified silicone oil is preferred.

  Next, the shape of the inner peripheral surface of the endless belt 62 according to the present embodiment will be described. FIG. 4 is a view for explaining the shape of the inner peripheral surface of the endless belt 62. FIG. 4 (a) is a plan view showing a part of the inner peripheral surface of the endless belt 62, and FIGS. ) Shows an example of the cross-sectional shape of the endless belt 62. In particular, FIG. 4B is an XX cross-sectional view of the endless belt 62 shown in FIG. As shown in FIG. 4, the endless belt 62 according to the present embodiment includes a base layer 621 and a release layer 622 that covers the outer peripheral surface of the base layer 621. In the endless belt 62 of the present embodiment, a large number of grooves 623 are formed on the inner peripheral surface in parallel to each other at equal intervals in the circumferential direction (rotation direction). As the shape of the groove 623, for example, a triangular wave shape as shown in FIG. 4B or a rectangular wave shape as shown in FIG. 4C can be used. Furthermore, a curved surface shape such as a semicircular shape can also be used.

The depth of the groove 623 depends on the thickness of the endless belt 62, but as described above, the thickness of the endless belt 62 is preferably about 100 μm, and thus is formed with a thickness of 20 μm or less. This is because if the depth of the groove 623 exceeds 20 μm, the thickness of the endless belt 62 in the portion (groove portion) where the groove 623 is disposed becomes thin, and the strength of the endless belt 62 in the width direction decreases. . When the strength in the width direction of the endless belt 62 is reduced, the endless belt 62 is buckled in the groove while the endless belt 62 is rotated, causing paper wrinkles, poor fixing, or the like, or, for example, paper jam. In some cases, when an external force is applied to the endless belt 62, the endless belt 62 may break at the groove. Therefore, in order to maintain the strength in the width direction of the endless belt 62, the depth of the groove 623 is preferably set to 20 μm or less. Since the groove 623 is formed in the circumferential direction (rotation direction) of the endless belt 62, the groove 623 has little influence on the strength of the endless belt 62 in the rotation direction.
The width of the groove 623 is preferably set to 120 μm or less. This is because, when the width of the groove 623 is formed to be larger than 120 μm, the meshing effect due to the fitting with the convex portion provided on the surface of the low friction sheet 68 described later is lowered.
Further, the interval between the grooves 623 is set to several 10 to several 100 μm.

By the way, as a manufacturing method of the endless belt 62, when the endless belt 62 is formed of a heat resistant resin such as polyimide, a heat resistant resin solution (resin varnish) is applied to the surface of the cylindrical metal mold. A heat resistant resin coating film is formed, dried, and a release layer is applied to the dried heat resistant resin coating film, and then the heat resistant resin coating film is baked. Then, the fired heat-resistant resin film is peeled off from the cylindrical metal mold. In general, the endless belt 62 is manufactured in this manner. Therefore, the groove 623 can be formed on the inner peripheral surface of the endless belt 62 by forming a convex portion or groove having a desired height and shape on the surface of the cylindrical metal mold.
Further, when the endless belt 62 is formed of a metal such as SUS, the groove 623 can be formed on the inner peripheral surface of the endless belt 62 when the endless belt 62 is formed into a belt shape by ironing from a pipe shape.

  Next, the shape of the outer surface of the low friction sheet 68 of the present embodiment will be described. FIG. 5 is a view for explaining the shape of the outer surface of the low friction sheet 68. FIG. 5 (a) is a plan view showing a part of the outer surface of the low friction sheet 68, and FIGS. ) Shows an example of the cross-sectional shape of the low friction sheet 68. In particular, FIG. 5B is a YY cross-sectional view of the low friction sheet 68 of FIG. As shown in FIG. 5, in the low friction sheet 68 of the present embodiment, the outer surface of the low friction sheet 68 corresponds to the groove 623 formed on the inner peripheral surface of the endless belt 62, and the paper P conveying direction (of the endless belt 62). A large number of convex portions 681 are formed in parallel to each other at equal intervals toward the rotation direction. As the shape of the convex portion 681, for example, a triangular wave shape as shown in FIG. 5B or a trapezoidal shape as shown in FIG. 5C corresponding to the groove 623 of the endless belt 62 is used. Can do. Furthermore, a curved surface shape such as a semicircular shape can also be used.

Here, the convex portion of the low friction sheet 68 can be fitted to the groove 623 of the endless belt 62 with a gap in at least one of the height direction and the width direction. The cross-sectional shape of 681 is different from the cross-sectional shape of the groove 623 of the endless belt 62.
Specifically, as a first case, the height of the convex portion 681 is different from the depth of the groove 623 of the endless belt 62 (whether the height of the convex portion 681 is higher than the depth of the groove 623 of the endless belt 62 or not). The width of the convex portion 681 is the same as or different from the width of the groove 623 of the endless belt 62.
As a second case, the width of the convex portion 681 is formed different from the width of the groove 623 of the endless belt 62, and the height of the convex portion 681 is the same as or different from the depth of the groove 623 of the endless belt 62. This is the case. However, the width of the groove 623 of the endless belt 62 is preferably larger than the width of the convex portion 681 of the low friction sheet 68 in order to increase the effect of engagement between the convex portion 681 and the groove 623 described later.
In that case, the shape of the convex portion 681 of the low friction sheet 68 and the groove 623 of the endless belt 62 are different from each other such that one is a triangular wave shape and the other is a rectangular wave shape, a trapezoidal shape, a semicircular shape, or the like. May be formed.
The interval in the width direction between the protrusions 681 is formed in the same manner as the interval in the width direction between the grooves 623.

Here, as a method of forming the convex portion 681 of the low friction sheet 68, a method of forming a resin sheet by a mold when molding, or when a fiber sheet is used as a base material, the direction of the fiber is set to the endless belt 62. It is possible to adopt a method of forming the layers so as to coincide with the rotation directions of the two.
Moreover, the convex part 681 can also be formed by pressing a type | mold to a resin sheet. At that time, the resin sheet can be heated at the same time.

  Thus, when the low friction sheet 68 having the convex portion 681 formed on the outer surface and the endless belt 62 having the groove 623 formed on the inner peripheral surface slide with each other in the nip portion N, the convex portion 681 is formed. And the groove 623 are positioned so as to be fitted. That is, since the interval between the grooves 623 (convex portions 681) is set to several tens to several hundreds of micrometers, the endless belt 62 is slightly moved in the width direction during the rotation (movement of several tens to several hundreds of micrometers). Thus, the convex portion 681 and the groove 623 can be easily fitted. Then, as shown in FIG. 6, once the convex portion 681 and the groove 623 are fitted, the nip portion N is pressed, so the groove 623 of the endless belt 62 gets over the convex portion 681 of the low friction sheet 68. Thus, since a large force in the width direction is required to move in the width direction, the endless belt 62 is less likely to move in the width direction (also referred to as “meshing effect”). As a result, the frictional force in the thrust direction (width direction) between the endless belt 62 and the low friction sheet 68 is configured to be large.

  By the way, the endless belt 62 receives a frictional force from the fixing roll 61 at the nip portion N to receive a driving force, and rotates following the fixing roll 61. Even when the paper P is conveyed to the nip portion N, the driving force is transmitted by receiving the frictional force from the fixing roll 61 via the paper P. At this time, the frictional force from the fixing roll 61 to the endless belt 62 is generated by the pressing force (nip pressure) between the fixing roll 61 and the pressure pad 64 in the nip portion N, and therefore the driving force received by the endless belt 62. Varies depending on the nip pressure between the fixing roll 61 and the pressure pad 64 in the nip portion N. That is, the distribution of the nip pressure in the width direction of the endless belt 62 is caused by factors such as a slight variation in the nip pressure in the width direction at the nip portion N and the size, thickness, and quality of the paper P passing through the nip portion N. Therefore, the driving force received by the endless belt 62 from the fixing roll 61 has a driving force distribution in the width direction of the endless belt 62. Therefore, the endless belt 62 rotates at a constant speed in a certain direction while maintaining a balance as a whole while having non-uniformity of the driving force in the width direction. However, the endless belt 62 is moved in the width direction because the driving force on the rear side sometimes becomes relatively large or the driving force on the front side sometimes becomes relatively large due to the fluctuation factors of the nip pressure. A belt-walking force (called “thrust force”) is generated. Therefore, the endless belt 62 may be displaced toward the rear side or the front side.

  On the other hand, in the fixing device 60 of the present embodiment, the low friction sheet 68 and the endless belt 62 are fitted with the convex portion 681 and the groove 623, so that the endless belt 62 and the low friction sheet 68 are The frictional force in the thrust direction (width direction) is increased. For this reason, the endless belt 62 is prevented from being displaced toward the rear side or the front side. That is, the endless belt 62 receives the thrust force and tries to move in the thrust direction, whereas the frictional force between the low friction sheet 68 and the endless belt 62 functions as a “brake” in the thrust direction. 62 belt walks can be suppressed. Therefore, even if the end portion of the endless belt 62 contacts the inner surface of the flange portion 802, it is suppressed that the end portion of the endless belt 62 is pressed against the inner surface of the flange portion 802 with a large thrust force. The frictional force between the two is reduced, and it is possible to suppress the occurrence of breakage such as folding, buckling or cracking at both ends of the endless belt 62.

If the width of the groove 623 (the convex portion 681) is formed large, the groove 623 of the endless belt 62 can easily get over the convex portion 681 of the low friction sheet 68, and the endless belt 62 can easily move in the width direction. Therefore, it becomes difficult to configure a large frictional force between the endless belt 62 and the low friction sheet 68 in the thrust direction. Therefore, as described above, in order to effectively act the meshing effect between the groove 623 of the endless belt 62 and the convex portion 681 of the low friction sheet 68, the width of the groove 623 (convex portion 681) is a predetermined value (120 μm). ) It is preferable to set the following.
When the height of the convex portion 681 is as low as 3 μm or less, the frictional force due to the meshing effect with the groove 623 formed in the endless belt 62 does not work sufficiently, and the thrust direction between the endless belt 62 and the low friction sheet 68 It becomes difficult to make the frictional force in the (width direction) large. Therefore, it is preferable that the height of the convex portion 681 is 4 μm or more. Correspondingly, the groove 623 of the endless belt 62 is also preferably formed to 4 μm or more. Therefore, in combination with the above-described conditions, the depth of the groove 623 of the endless belt 62 is preferably 4 to 20 μm. Similarly, the height of the convex portion 681 of the low friction sheet 68 is preferably 4 to 20 μm.

  Furthermore, in the fixing device 60 of the present embodiment, the case where the groove 623 of the endless belt 62 and the convex portion 681 of the low friction sheet 68 are fitted is described as an example, but as shown in FIG. The inner peripheral surface of the endless belt 62 and the outer surface of the low friction sheet 68 have, for example, a cross-sectional shape in which triangular wave-shaped grooves and projections having the same width and different depth / height are continuously formed. In addition, a configuration in which the respective grooves and the protrusions are fitted may be employed.

In the fixing device 60 of the present embodiment, the frictional force in the thrust direction (width direction) between the endless belt 62 and the low friction sheet 68 is configured to be large, whereas in the rotational direction of the endless belt 62, the friction is low. Since the convex portion 681 of the seat 68 and the groove 623 of the endless belt 62 are formed in the rotational direction, the frictional force in the direction that prevents the endless belt 62 from rotating is configured to be extremely small.
Moreover, the convex portion 681 of the low friction sheet 68 is configured to fit into the groove 623 of the endless belt 62 with a gap in at least one of the height direction and the width direction. Therefore, for example, as shown in FIG. 6, the convex portion 681 of the low friction sheet 68 and the groove 623 of the endless belt 62 are not in close contact with each other, and the contact area can be set to be small. Furthermore, the lubricant can be sufficiently held in the gap between the two. Thereby, the effect of further improving the slidability of the endless belt 62 is obtained, and the sliding resistance in the rotational direction can be kept low. In particular, even in the nip portion N where the nip pressure is applied, the lubricant can be reliably held.

  As a result, since the sliding resistance in the rotation direction of the endless belt 62 can be maintained at a very low state, the endless belt 62 can rotate smoothly. Therefore, the sliding resistance that the sheet P conveyed by the fixing roll 61 receives from the endless belt 62 is extremely small. Therefore, the conveyance of the sheet P at a constant speed with the fixing roll 61 corresponding to the rotation of the fixing roll 61 is maintained. As a result, the occurrence of slip between the paper P and the fixing roll 61 can be suppressed.

  In this way, by configuring the frictional force in the thrust direction (width direction) between the endless belt 62 and the low friction sheet 68 to increase, the endless belt 62 receives the thrust force and tries to move in the thrust direction. On the other hand, the frictional force between the low friction sheet 68 and the endless belt 62 functions as a “brake” against the thrust force, and the belt walk of the endless belt 62 can be suppressed. Therefore, when the end portion of the endless belt 62 abuts on the inner surface of the flange portion 802 of the edge guide 80 and the belt walk in the width direction of the endless belt 62 is restricted, the end portion of the endless belt 62 becomes the flange portion. Contact with the inner surface of 802 with a large thrust force is suppressed, and the frictional force between them is reduced. As a result, the occurrence of breakage, buckling, cracks, etc. at both ends of the endless belt 62 can be suppressed, so that the endless belt 62 can be smoothly rotated, and paper wrinkles and image defects can be suppressed. In addition, the endless belt 62 itself can be prevented from breaking.

  Further, since the low friction sheet 68 and the endless belt 62 are configured so that the frictional force in the rotation direction of the endless belt 62 is extremely small, the endless belt 62 can rotate smoothly. Therefore, the sliding resistance that the sheet P conveyed by the fixing roll 61 receives from the endless belt 62 is extremely small. Therefore, the conveyance of the sheet P at a constant speed with the fixing roll 61 corresponding to the rotation of the fixing roll 61 is maintained. Is done. As a result, it is possible to suppress the occurrence of slip between the paper P and the fixing roll 61 and to form a high-quality image without paper wrinkles or image displacement of the paper P over a long period of time.

In the fixing device 60 of the present embodiment, the low friction sheet 68 having the convex portion 681 formed on the outer surface and the endless belt 62 having the groove 623 formed on the inner peripheral surface are used. It is also possible to use a configuration in which grooves are formed on the outer surface 68 and convex portions are formed on the inner peripheral surface of the endless belt 62.
Further, when the low friction sheet 68 is not used, a configuration in which convex portions or grooves are directly formed on the surface of the pressure pad 64 can be adopted.

Hereinafter, based on an Example and the comparative example with respect to this, the endless belt 62 of this Embodiment is demonstrated concretely. The endless belt 62 of the present embodiment is not limited to the examples.
(Example 1)
As the cylindrical metal mold, an aluminum cylinder having a length of 500 mm in which a triangular wave groove is formed in the circumferential direction by cutting, a silicone mold release agent (manufactured by Shin-Etsu Chemical Co., Ltd.) is used on the surface of the cylindrical metal mold. : KS700) was applied, baked, and cooled to room temperature, and the release treatment of the surface of the cylindrical metal mold was performed. Next, a polyimide precursor solution (manufactured by Ube Industries, Ltd .: U varnish S) is applied to the surface of the cylindrical metal mold by a flow coat coating apparatus and baked to form a polyimide resin substrate having a thickness of 100 μm. did. As a result, a triangular wave-shaped convex portion was formed with a height of 18 μm and a width of 116 μm on the inner peripheral surface of the polyimide resin substrate. A 30 μm-thick PFA tube was adhered and laminated on the surface of this polyimide resin substrate via a primer to form an endless belt.
As the low-friction sheet, a glass fiber base material bonded with a PTFE sheet was used, and a groove having a depth of 25 μm and a width of 130 μm was formed on the surface thereof in parallel with the paper conveyance direction.

The endless belt and the low friction sheet are aligned with the rotation axis direction of the endless belt and the width direction of the low friction sheet, and the rotation axis direction of the endless belt (the width direction of the low friction sheet), and the direction orthogonal thereto ( When the frictional force in the direction of rotation of the endless belt was measured, the frictional force in the rotational axis direction of the endless belt could be configured to be greater than the frictional force in the rotational direction of the endless belt.
In this case, an amino-modified silicone oil having a viscosity of 300 cs was applied to the inner peripheral surface of the endless belt as a lubricant.
This polyimide endless belt and low-friction sheet were mounted on a fixing device and tested through Fuji Xerox Co., Ltd. JD paper (trade name) carrying an unfixed toner image. Even when the paper was passed through, the endless belt did not break, buckle or crack. In addition, no paper wrinkles or image misalignment of the paper P was observed.

(Example 2)
In the same manner as in Example 1, a polyimide resin base material having a film thickness of 70 μm was formed, and a triangular wave-shaped convex part having a height of 6 μm and a width of 90 μm was formed on the inner peripheral surface of the polyimide resin base material.
As the low friction sheet, a glass fiber base material bonded with a PTFE sheet was used, and a groove having a depth of 15 μm and a width of 100 μm was formed on the surface thereof in parallel with the paper conveyance direction.
By forming in this way, the frictional force in the rotational axis direction of the endless belt can be configured to be larger than the frictional force in the rotational direction of the endless belt.
In this case as well, in the same paper passing test as in Example 1, no breakage, buckling, cracking, or the like occurred in the endless belt even when 200,000 sheets were passed. In addition, no paper wrinkles or image misalignment of the paper P was observed.

(Comparative Example 1)
As the cylindrical metal mold, an aluminum cylinder having a length of 500 mm with no irregularities by surface polishing is used, and a silicone mold release agent (manufactured by Shin-Etsu Chemical Co., Ltd .: KS700) is applied to the surface of the cylindrical metal mold, Baking treatment was performed, and cooling to room temperature was performed to release the surface of the cylindrical metal mold. Next, a polyimide precursor solution (manufactured by Ube Industries, Ltd .: U varnish S) is applied to the surface of the cylindrical metal mold by a flow coat coating apparatus and baked to form a polyimide resin substrate having a thickness of 100 μm. did. A 30 μm-thick PFA tube was adhered and laminated on the surface of this polyimide resin substrate via a primer to form an endless belt.
As the low friction sheet, a glass fiber base material having a smoothed PTFE sheet adhered thereto was used.

The endless belt and the low friction sheet are aligned with the rotation axis direction of the endless belt and the width direction of the low friction sheet, and the rotation axis direction of the endless belt (the width direction of the low friction sheet), and the direction orthogonal thereto ( When the frictional force in the rotation direction of the endless belt was measured, the frictional force was substantially the same regardless of the direction.
In this case, an amino-modified silicone oil having a viscosity of 300 cs was applied to the inner peripheral surface of the endless belt as a lubricant.
This polyimide endless belt and low-friction sheet were mounted on a fixing device and tested for passing through JD paper (trade name) manufactured by Fuji Xerox Co., Ltd. carrying an unfixed toner image. When the sheet was fed, the slidability of the endless belt deteriorated, the driving torque of the motor driving the fixing roll increased, and image misalignment and paper wrinkles occurred in the fixed image. Further, when the paper passing test was continued, when 50,000 sheets were passed, the end of the endless belt was cracked at the contact portion with the edge guide.

  This is because both the inner peripheral surface of the endless belt and the outer surface of the low friction sheet are smoothed, and as a result, the contact area between the endless belt and the low friction sheet increases. This is thought to be the cause. Furthermore, both the smooth interface and the amino-modified silicone oil, which is a lubricant, were pushed out of the nip by the nip pressure, and the effect of reducing the sliding resistance of the lubricant was not fully obtained. It is thought that.

(Comparative Example 2)
As the cylindrical metal mold, an aluminum cylinder having a length of 500 mm on which irregularities of random shape were formed by sandblasting, a silicone mold release agent (manufactured by Shin-Etsu Chemical Co., Ltd .: KS700) was used on the surface of the cylindrical metal mold. ) Was applied, baked, and allowed to cool to room temperature to release the cylindrical metal mold surface. Next, a polyimide precursor solution (manufactured by Ube Industries, Ltd .: U varnish S) is applied to the surface of the cylindrical metal mold by a flow coat coating apparatus and baked to form a polyimide resin base material having a thickness of 70 μm. did. As a result, irregularities having a random shape were transferred to the inner peripheral surface of the polyimide resin base material, and a rough surface was formed on the inner peripheral surface. A 30 μm-thick PFA tube was adhered and laminated on the surface of this polyimide resin substrate via a primer to form an endless belt.
As the low friction sheet, a glass fiber base material bonded with a PTFE sheet that had been roughened by sandblasting in advance was used.

The endless belt and the low friction sheet are aligned with the rotation axis direction of the endless belt and the width direction of the low friction sheet, and the rotation axis direction of the endless belt (the width direction of the low friction sheet), and the direction orthogonal thereto ( When the frictional force in the rotation direction of the endless belt was measured, the frictional force was substantially the same regardless of the direction.
In this case, an amino-modified silicone oil having a viscosity of 300 cs was applied to the inner peripheral surface of the endless belt as a lubricant.
When this endless belt made of polyimide and a low friction sheet were mounted on a fixing device and tested through JD paper (trade name) manufactured by Fuji Xerox Co., Ltd. carrying an unfixed toner image, 60,000 sheets were tested. At the time when the paper was passed, buckling began to occur near the center of the endless belt, and when the paper passing test was continued, the contact portion with the edge guide was reached when 70,000 sheets were passed. , Cracks occurred at the end of the endless belt.

  This is because both the inner peripheral surface of the endless belt and the outer surface of the low friction sheet are roughened, and as a result, the holding capacity of the lubricant is increased, resulting in the sliding resistance between the endless belt and the low friction sheet. Although there was no image misalignment due to ascending, the endless belt moved closer to the thrust direction because the slipperiness in the direction of the axis of rotation of the endless belt and the direction perpendicular to it (the direction of rotation of the endless belt) were the same. It can be presumed that the number of collisions with the edge guide that regulates the deviation of the endless belt increases, and the damage caused by the impact at that time finally caused the end of the endless belt to crack.

(Comparative Example 3)
As the cylindrical metal mold, an aluminum cylinder having a length of 500 mm in which a triangular wave groove is formed in the circumferential direction by cutting, a silicone mold release agent (manufactured by Shin-Etsu Chemical Co., Ltd.) is used on the surface of the cylindrical metal mold. : KS700) was applied, baked, and cooled to room temperature, and the release treatment of the surface of the cylindrical metal mold was performed. Next, a polyimide precursor solution (manufactured by Ube Industries, Ltd .: U varnish S) is applied to the surface of the cylindrical metal mold by a flow coat coating apparatus and baked to form a polyimide resin base material having a thickness of 70 μm. did. As a result, triangular wave-shaped convex portions were formed with a height of 3 μm and a width of 150 μm on the inner peripheral surface of the polyimide resin substrate. A 30 μm-thick PFA tube was adhered and laminated on the surface of this polyimide resin substrate via a primer to form an endless belt.
As the low friction sheet, a glass fiber base material bonded with a PTFE sheet was used, and a groove having a depth of 15 μm and a width of 100 μm was formed on the surface thereof in parallel with the paper conveyance direction.

The endless belt and the low friction sheet are aligned with the rotation axis direction of the endless belt and the width direction of the low friction sheet, and the rotation axis direction of the endless belt (the width direction of the low friction sheet), and the direction orthogonal thereto ( When measuring the frictional force in the direction of rotation of the endless belt, the height of the convex part formed on the endless belt is low, and the frictional force due to the engagement with the groove formed on the low friction sheet does not work sufficiently, depending on the direction. The frictional force was almost the same.
In this case, an amino-modified silicone oil having a viscosity of 300 cs was applied to the inner peripheral surface of the endless belt as a lubricant.
When this endless belt made of polyimide and a low friction sheet were mounted on a fixing device and tested through JD paper (trade name) manufactured by Fuji Xerox Co., Ltd. carrying an unfixed toner image, 60,000 sheets were tested. At the time when the paper was passed, buckling began to occur near the center of the endless belt, and when the paper passing test was continued, the contact portion with the edge guide was reached when 70,000 sheets were passed. , Cracks occurred at the end of the endless belt.

  This is because the inner peripheral surface of the endless belt and the outer surface of the low-friction sheet have irregularities, and as a result, the retention capacity of the lubricant is increased, resulting in an increase in sliding resistance between the endless belt and the low-friction sheet. Although there was no deviation, the endless belt was shifted in the thrust direction because the slipperiness in the direction of the axis of rotation of the endless belt and the direction perpendicular to it (the direction of rotation of the endless belt) were equivalent. It can be presumed that the number of collisions with the edge guide that regulates the deviation of the endless belt increases, and the damage caused by the impact at that time finally caused the end of the endless belt to crack.

FIG. 8 summarizes the results of the above examples and comparative examples. As shown in FIG. 8, in the fixing device 60 using the endless belt 62 and the low friction sheet 68 of the present embodiment, the frictional force in the thrust direction (width direction) between the endless belt 62 and the low friction sheet 68 is increased. By making it large, the occurrence of breakage, buckling, cracking and the like in the endless belt 62 can be suppressed even when 200,000 sheets are passed. Further, since the frictional force in the rotation direction of the endless belt 62 is extremely small, the endless belt 62 can rotate smoothly, and the occurrence of image defects such as paper wrinkles and image misalignment can be suppressed. it can.
The effect of the endless belt 62 of this embodiment is clear by comparison with the comparative example.

As described above, according to the fixing device 60 of the present embodiment, the endless belt 62 is configured such that the frictional force in the thrust direction (width direction) between the endless belt 62 and the low friction sheet 68 is increased. Occurrence of breakage, buckling, cracks, and the like at both end portions can be suppressed. Therefore, it is possible not only to maintain the smooth rotation of the endless belt 62 but also to prevent the endless belt 62 itself from being broken, so that the reliability of the fixing device 60 can be further improved. .
Further, since the low friction sheet 68 and the endless belt 62 are configured so that the frictional force in the rotation direction of the endless belt 62 is extremely small, the endless belt 62 can rotate smoothly. For this reason, it is possible to suppress the occurrence of slip between the paper P and the fixing roll 61 and form a high-quality image over a long period of time.

[Embodiment 2]
In the first embodiment, the image forming apparatus is described in which the fixing roll 61 having a heat source is used as the heating unit and the fixing device 60 using the endless belt 62 with the pressure pad 64 pressed as the pressing unit is mounted. In the second embodiment, a fixing device mounted on the image forming apparatus shown in FIG. 1 is a fixing device using a fixing belt with a heat generation source pressed as a heating unit and a pressure roll as a pressing unit. explain. In addition, about the structure similar to Embodiment 1, the same code | symbol is used and the detailed description is abbreviate | omitted here.

  FIG. 9 is a side sectional view showing the configuration of the fixing device 90 in the present embodiment. As shown in FIG. 9, the fixing device 90 according to the present embodiment includes a fixing belt 92 and a pressure roll 91 as an example of a rotating member. The fixing belt 92 is disposed on the toner image carrying surface side of the paper P, and a ceramic heater 82 which is a resistance heating element as an example of a heat generation source is disposed inside the fixing belt 92. The nip portion N is configured to supply heat.

The ceramic heater 82 has a substantially flat surface on the pressure roll 91 side. Then, it is arranged in a state of being pressed against the pressure roll 91 via the fixing belt 92 and forms a nip portion N. Therefore, the ceramic heater 82 also functions as a pressure member. The sheet P that has passed through the nip portion N is peeled off from the fixing belt 92 by the change in the curvature of the fixing belt 92 in the exit region (peeling nip portion) of the nip portion N.
Further, a low friction sheet 68 is disposed between the inner peripheral surface of the fixing belt 92 and the ceramic heater 82 in order to reduce sliding resistance between the inner peripheral surface of the fixing belt 92 and the ceramic heater 82. The low friction sheet 68 may be configured separately from the ceramic heater 82 or may be configured integrally with the ceramic heater 82.

On the other hand, the pressure roll 91 is disposed so as to face the fixing belt 92, and is configured to rotate in the direction of arrow D by a drive motor (not shown), and the fixing belt 92 is rotated following the rotation. The pressure roll 91 includes a core (cylindrical cored bar) 911, a heat-resistant elastic body layer 912 coated on the outer peripheral surface of the core 911, and a release layer 913 made of a heat-resistant resin coating or a heat-resistant rubber coating. Has been configured.
Further, in the fixing device 90 of the present embodiment, the fixing belt 92 is an endless belt whose original shape is formed in a cylindrical shape, and is formed of a heat-resistant resin such as polyimide, polyamide, and polyimideamide, or a metal such as SUS or nickel. The base layer 921 and a release layer 922 made of a fluororesin or the like coated on the surface or both surfaces of the base layer 921 on the pressure roll 91 side.
Further, as a peeling auxiliary means, a peeling auxiliary member 70 can be disposed on the downstream side of the nip portion N of the fixing belt 92. The peeling assisting member 70 is held by the holder 72 in a state where the peeling baffle 71 is close to the fixing belt 92 in a direction (counter direction) opposite to the rotation direction of the fixing belt 92.

  In addition, edge guides (not shown) are disposed at both ends of the holder 65. The edge guides are arranged such that inner surfaces of both edge guides arranged so as to face each other at both end portions of the holder 65 have a distance substantially matching the width of the fixing belt 92. When the fixing belt 92 rotates, movement of the fixing belt 92 in the width direction (belt walk) is restricted by the end portions of the fixing belt 92 coming into contact with the inner surfaces of the both edge guides. . Thus, the fixing belt 92 is set so that the deviation is regulated by the edge guide.

  The paper P on which the toner image has been electrostatically transferred in the secondary transfer unit 20 of the image forming apparatus shown in FIG. 1 is guided to the nip N of the fixing device 90 by the fixing inlet guide 56. When the paper P passes through the nip portion N, the toner image on the paper P is fixed by the pressure acting on the nip portion N and the heat supplied from the ceramic heater 82 on the fixing belt 92 side. Also in the fixing device 90 of the present embodiment, since the nip portion N can be configured widely between the pressure roll 91 and the ceramic heater 82, stable fixing performance can be ensured.

  In the fixing device 90 of the present embodiment, the fixing belt 92 has a plurality of grooves formed in parallel at equal intervals in the circumferential direction (rotation direction) on the inner peripheral surface. Further, the low friction sheet 68 is parallel to each other at equal intervals toward the paper P conveyance direction (the rotation direction of the fixing belt 92) on the outer surface corresponding to the grooves formed on the inner peripheral surface of the fixing belt 92. In addition, a large number of convex portions are formed. With this configuration, the frictional force in the thrust direction (width direction) between the fixing belt 92 and the low friction sheet 68 can be increased. Therefore, while the fixing belt 92 receives the thrust force and tries to move in the thrust direction, the friction force between the low friction sheet 68 and the fixing belt 92 functions as a “brake” against the thrust force, and the fixing belt The belt walk of 92 can be suppressed. Accordingly, when the end portion of the fixing belt 92 abuts on the inner surface of the edge guide and the belt walk in the width direction of the fixing belt 92 is restricted, the end portion of the fixing belt 92 is brought into contact with the inner surface of the edge guide. On the other hand, contact with a large thrust force is suppressed, and the frictional force between the two is reduced, and the occurrence of breakage such as folding, buckling or cracking at both ends of the fixing belt 92 can be suppressed. As a result, the smooth rotation of the fixing belt 92 can be maintained, and not only paper wrinkles and image defects can be suppressed, but also the fixing belt 92 itself can be prevented from breaking.

  Furthermore, since the low friction sheet 68 and the fixing belt 92 are configured so that the frictional force in the rotating direction of the fixing belt 92 is extremely small, the fixing belt 92 can rotate smoothly. Therefore, the sliding resistance that the paper P conveyed by the pressure roll 91 receives from the fixing belt 92 is extremely small. Therefore, the paper P is at a constant speed with the pressure roll 91 corresponding to the rotation of the pressure roll 91. Conveyance is maintained. As a result, it is possible to suppress the occurrence of slip between the paper P and the pressure roll 91 and form a high-quality image over a long period of time.

[Embodiment 3]
In the first embodiment, the image forming apparatus is described in which the fixing roll 61 having a heat source is used as the heating unit and the fixing device 60 using the endless belt 62 with the pressure pad 64 pressed as the pressing unit is mounted. In the third embodiment, the fixing device is mounted on the image forming apparatus shown in FIG. 1, and a fixing roll having a heat generation source is used as a heating unit, and pressure is stretched by three rolls as a pressing unit. A fixing device using a belt will be described. In addition, about the structure similar to Embodiment 1, the same code | symbol is used and the detailed description is abbreviate | omitted here.

FIG. 10 is a side sectional view showing the configuration of the fixing device 100 according to the present embodiment. The fixing device 100 includes a fixing roll 61 as an example of a rotating member, a pressure belt 620, and a pressure pad 64 as an example of a pressure member pressed from the fixing roll 61 via the pressure belt 620. Has been.
The pressure belt 620 is stretched by three rolls of an inlet roll 631, a pressure roll 632, and a tension roll 633. Then, as the fixing roll 61 rotates in the direction of arrow E, the pressure belt 620 rotates in the direction of arrow F following the fixing roll 61. The traveling speed is the same as the surface speed of the fixing roll 61.

The pressure belt 620 abuts on the outer peripheral surface of the fixing roll 61 to form a nip portion N. In the nip portion N, a pressure pad 64 is placed inside the pressure belt 620 via the pressure belt 620. Thus, it is arranged in a state of being biased toward the fixing roll 61. Therefore, a high nip pressure is uniformly applied to the nip portion N.
Further, the pressure belt 620 includes a base layer and a release layer coated on the surface (the surface on the fixing roll 61 side or both surfaces). And as a base layer, it is formed with resin with high heat resistance strength, for example, polyimide, polyamide, polyamideimide, etc. are suitable. The base layer is formed to have a thickness of about 50 to 125 μm, for example. As the release layer formed on the surface of the base layer, a layer in which a fluororesin such as PFA is coated with a thickness of 5 to 20 μm is preferable. Furthermore, if necessary, it is possible to adopt a configuration in which an elastic layer having a thickness of 100 to 200 μm is laminated between the base layer and the release layer. Silicone rubber or the like can be used as the material for the elastic layer.

Further, the three rolls for stretching the pressure belt 620 are a stainless steel inlet roll 631, a pressure roll 632 in which a steel core is coated with silicone rubber as an elastic body layer, and a stainless steel tension roll 633. The pressure belt 620 is stretched with a tension of 10 kg. A halogen heater 635 is disposed inside the inlet roll 631 as a heating source. The surface temperature is controlled to 120 ° C. by a temperature sensor and control unit 40 (see FIG. 1) (not shown), and the pressure belt 620 is preheated.
Further, the pressure roll 632 is provided with flanges 632 a at both ends, and the inner surfaces of both flanges 632 a arranged to face each other at both ends of the pressure roll 632 substantially coincide with the width of the pressure belt 620. It is set to have an interval. When the pressure belt 620 rotates, the end of the pressure belt 620 contacts the inner surface of the flange 632a, so that the movement of the pressure belt 620 in the width direction (belt walk) is restricted. ing. As described above, the pressure belt 620 is set so that the deviation is regulated by the both flanges 632 a arranged at both ends of the pressure roll 632.
In addition to the pressure roll 632, both or any one of the inlet roll 631 and the stretching roll 633 may be provided with flanges at both ends in order to restrict the belt walk.

Next, the pressure pad 64 as a pressing member includes an elastic member for securing a wide nip portion N, and a low friction provided on the surface where the elastic member contacts the inner peripheral surface of the pressure belt 620. And is held by a holder 65 made of metal or the like. The elastic member having the low friction layer on the surface is formed in a concave shape in which the fixing roll 61 side substantially follows the outer peripheral surface of the fixing roll 61, and is pressed against the fixing roll 61. Is forming. As the elastic member, an elastic body having high heat resistance such as silicone rubber or fluorine rubber, a leaf spring, or the like can be used. The low friction layer formed on the elastic member is provided to reduce the sliding resistance between the inner peripheral surface of the pressure belt 620 and the pressure pad 64, and is a material having a low friction coefficient and wear resistance. It is desirable. Specifically, a glass fiber sheet impregnated with Teflon (registered trademark), a fluororesin sheet, a fluororesin coating film, or the like can be used.
The pressure pad 64 may be, for example, a roll-shaped one in addition to the pad-shaped one as in the present embodiment, and may be a fixing roll 61 via a pressure belt 620. The surface may be urged and driven to rotate. However, the pressure pad 64 molded into a pad shape as in the present embodiment can apply a nip pressure more widely and uniformly over the entire nip portion N in contact.

  With such a configuration, in the fixing device 100 of the present embodiment, the sheet P on which the toner image is electrostatically transferred in the secondary transfer unit 20 of the image forming apparatus shown in FIG. Thus, the paper P conveyed to the nip portion N and carrying the toner image is heated and pressurized when passing through the nip portion N, and the toner image is fixed on the paper P. Also in the fixing device 100 of the present embodiment, since the nip portion N can be widely configured by the concave pressure pad 64 that substantially follows the outer peripheral surface of the fixing roll 61, stable fixing performance can be ensured.

A pressure roll 632 disposed downstream of the pressure pad 64 in the sheet P conveyance direction is a central axis of the fixing roll 61 via a pressure belt 620 by a compression coil spring (not shown) as pressure means. And a local high pressure is generated at the contact portion of the fixing roll 61. As a result, the elastic layer 612 on the surface of the fixing roll 61 is elastically deformed and distorted, and the sheet P is peeled from the fixing roll 61 side at the exit of the nip portion N due to the distortion of the fixing roll 61. Here, in order to efficiently apply a local high pressure to the fixing roll 61 with a low load, it is desirable that the pressure roll 632 has a smaller diameter than the fixing roll 61 and has a hard surface.
Note that, as an auxiliary means for peeling, a peeling auxiliary member 70 can be disposed on the downstream side of the nip portion N of the fixing roll 61. The peeling auxiliary member 70 is held by the holder 72 in a state in which the peeling baffle 71 is close to the fixing roll 61 in a direction (counter direction) opposite to the rotation direction of the fixing roll 61.

  In the fixing device 100 of the present embodiment, the pressure belt 620 has a plurality of grooves formed on the inner peripheral surface thereof in parallel to each other at equal intervals in the circumferential direction (rotating direction). Further, the low friction layer of the pressure pad 64 is directed to the paper P conveyance direction (the rotation direction of the pressure belt 620) on the outer surface corresponding to the groove formed on the inner peripheral surface of the pressure belt 620. A large number of convex portions are formed in parallel with each other at equal intervals. With this configuration, the frictional force in the thrust direction (width direction) between the pressure belt 620 and the pressure pad 64 can be increased. For this reason, the pressure belt 620 receives the thrust force and tries to move in the thrust direction, whereas the frictional force between the pressure pad 64 and the pressure belt 620 functions as a “brake” against the thrust force. The belt walk of the pressure belt 620 can be suppressed. As a result, the end of the pressure belt 620 comes into contact with the inner surface of the flange 632a of the pressure roll 632 and the belt walk in the width direction of the pressure belt 620 is restricted. Is restrained from contacting the inner surface of the flange 632a with a large thrust force, the frictional force between the two is reduced, and the occurrence of breakage, buckling, cracking, etc. at both ends of the pressure belt 620 is prevented. Can be suppressed. As a result, smooth rotation of the pressure belt 620 can be maintained, and not only paper wrinkles and image defects can be suppressed, but also the pressure belt 620 itself can be prevented from breaking.

  Furthermore, since the pressure pad 64 and the pressure belt 620 are configured so that the frictional force in the rotation direction of the pressure belt 620 is extremely small, the pressure belt 620 can rotate smoothly. Therefore, the sliding resistance that the sheet P conveyed by the fixing roll 61 receives from the pressure belt 620 is extremely small. Therefore, the sheet P can be conveyed at a constant speed with the fixing roll 61 corresponding to the rotation of the fixing roll 61. Maintained. As a result, it is possible to suppress the occurrence of slip between the paper P and the fixing roll 61 and form a high quality image over a long period of time.

  As an application example of the present invention, it is applied to an image forming apparatus such as a copying machine or a printer using an electrophotographic method, for example, an application to a fixing device that fixes an unfixed toner image carried on a recording paper (paper), Furthermore, there are applications to transfer belts, photoreceptor belts, and charging belts. Further, there is application to an image forming apparatus such as a copying machine or a printer using an ink jet method, for example, to a fixing device that dries an undried ink image carried on a recording paper (paper).

1 is a schematic configuration diagram showing an image forming apparatus of the present invention. 2 is a side cross-sectional view illustrating a configuration of a fixing device according to Embodiment 1. FIG. FIG. 3 is a partial cross-sectional view including an end portion of the fixing device for explaining a state where an endless belt is supported. It is a figure explaining the shape of the internal peripheral surface of an endless belt. It is a figure explaining the shape of the outer surface of a low friction sheet. It is a figure explaining the contact state of an endless belt and a low friction sheet. It is a figure explaining the contact state of an endless belt and a low friction sheet. It is the figure which showed the result of having changed the outer surface shape of the low friction sheet | seat, and the inner peripheral surface shape of an endless belt, and evaluating each performance. FIG. 4 is a side sectional view illustrating a configuration of a fixing device according to a second embodiment. FIG. 6 is a side cross-sectional view illustrating a configuration of a fixing device according to a third embodiment. FIG. 10 is a side sectional view showing a configuration of a conventional fixing device.

Explanation of symbols

1Y, 1M, 1C, 1K ... image forming unit, 11 ... photosensitive drum, 12 ... charger, 13 ... laser exposure device, 14 ... developing device, 15 ... intermediate transfer belt, 16 ... primary transfer roll, 17 ... drum cleaner , 20 ... secondary transfer part, 60, 90, 100 ... fixing device, 61 ... fixing roll, 62 ... endless belt, 623 ... groove, 63 ... belt guide member, 64 ... pressure pad, 64a ... pre-nip member, 64b ... peeling Nip member, 65 ... Holder, 66 ... Halogen heater, 67 ... Lubricant application member, 68 ... Low friction sheet, 681 ... Projection, 69 ... Temperature sensor, 70 ... Peeling assisting member, 82 ... Ceramic heater, 91 ... Pressurization Roll, 92 ... Fusing belt, 620 ... Pressure belt, 631 ... Inlet roll, 632 ... Pressure roll, 632a ... Flange, 633 ... Stretching roll

Claims (11)

A fixing device for fixing a toner image carried on a recording material,
A pivotable pivot member;
An endless belt movable while contacting the rotating member;
A pressure member that is disposed inside the endless belt, presses the endless belt against the rotating member, and forms a nip portion through which the recording material passes between the rotating member and the endless belt;
The fixing device, wherein the endless belt and the pressure member are configured such that a frictional force between the endless belt and the pressure member varies depending on a direction.   The fixing device according to claim 1, wherein the endless belt is restricted from moving in a thrust direction by a frictional force with the pressure member.   The fixing device according to claim 1, wherein the pressure member is provided with a low friction member on a friction surface with the endless belt. A fixing device for fixing a toner image carried on a recording material,
A rotatable turning member for conveying the recording material;
An endless belt movable while contacting the rotating member;
A pressure member that is disposed inside the endless belt, presses the endless belt against the rotating member, and forms a nip portion through which the recording material passes between the rotating member and the endless belt;
A low friction member that reduces the frictional resistance with respect to the sliding direction between the endless belt and the pressure member;
The fixing device, wherein the endless belt and the low friction member are configured such that a frictional force in a direction perpendicular to the moving direction is larger than a frictional force in the moving direction of the endless belt.   The endless belt has a groove or a convex portion formed on an inner peripheral surface thereof in the moving direction of the endless belt, and the low friction member is directed to a sliding surface with the endless belt in the moving direction of the endless belt. The fixing device according to claim 4, wherein a protrusion or groove that fits into the groove or protrusion of the endless belt is formed.   The fixing device according to claim 5, wherein the groove or the protrusion formed in the endless belt has a different cross-sectional shape from the protrusion or the groove formed in the low friction member.   6. The groove or protrusion formed in the endless belt and the protrusion or groove formed in the low friction member are formed with a height or depth of 4 to 20 [mu] m. Fixing device.   The fixing device according to claim 5, wherein the groove or the convex portion formed on the endless belt and the convex portion or the groove formed on the low friction member are formed with a width of 120 μm or less.   The fixing device according to claim 4, further comprising a heating member that heats the rotating member or a heating member that heats the endless belt. Toner image forming means for forming a toner image;
Transfer means for transferring the toner image formed by the toner image forming means onto a recording material;
Fixing means for fixing the toner image transferred onto the recording material to the recording material,
The fixing means is
A rotatable turning member for conveying the recording material;
An endless belt movable while contacting the rotating member;
A pressure member that is disposed inside the endless belt, presses the endless belt against the rotating member, and forms a nip portion through which the recording material passes between the rotating member and the endless belt;
A low friction member that reduces the frictional resistance with respect to the sliding direction between the endless belt and the pressure member;
The endless belt has a groove or a convex portion formed on an inner peripheral surface thereof in a moving direction of the endless belt, and the low friction member is directed on a sliding surface with the endless belt in a moving direction of the endless belt. An image forming apparatus characterized in that a convex portion or a groove that fits into the groove or convex portion of the endless belt is formed.   The image forming apparatus according to claim 10, wherein the fixing unit restricts movement of the endless belt in a thrust direction by a frictional force with the low friction member.

Images