JP2006126467A - Fixing apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress an operating speed from becoming too high, regarding a pressure releasing mechanism for attaching/detaching a pressure member to/from a fixing roll. <P>SOLUTION: The apparatus is provided with a pressure-setting means for setting the pressure pad 64 for pressurizing the fixing roller 61 with a prescribed pressure from the inside of an endless belt 62 which can move in contact with the fixing roller 61, in a state where the fixing roller 61 is pressurized by the pad with the prescribed pressure and in a state where the fixing roller 61 is released from being pressurized with the prescribed pressure, and a rubber roll 212 for adjusting the operating speed, when the pressure pad 64 is made to actuate by the pressure-setting means is arranged in the pressure-setting means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fixing device used in an image forming apparatus using, for example, an electrophotographic method, and more particularly to a fixing device including a rotatable belt member.

  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.

  Conventionally, in a fixing device used in such an image forming apparatus, a fixing roll formed by laminating a heat-resistant elastic body layer and a release layer on a cylindrical metal core having a heating source disposed therein, A pressure roll formed by laminating a heat-resistant elastic body layer and a release layer made of a heat-resistant resin film or a heat-resistant rubber film on the core is configured to be in pressure contact with each other. Then, the recording paper carrying the unfixed toner image is passed between the fixing roll and the pressure roll, and the unfixed toner image is heated and pressed to thereby form the toner image on the recording paper. It has become established. Such a fixing device is called a roll nip method and is generally widely used.

In recent years, with the progress of high productivity and colorization in image forming apparatuses, and the spread of double-sided printing mechanisms, it has been required that fixing apparatuses also support high speed. At that time, in the roll nip type fixing device, it is necessary to set the nip width widely 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 widening the nip width, 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 are conceivable.
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. There is a problem in image quality such that it is likely to occur. In addition, the method of increasing the roll diameter causes problems that the apparatus is enlarged 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 technology regarding is developed (for example, refer patent document 1).

  In the fixing device described in Patent Document 1 (referred to as “belt nip method”), the endless belt is brought into pressure contact with the fixing roll using a pressure pad instead of the pressure roll in the conventional roll nip type fixing device. 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, since the heat capacity of the endless belt pressed against the fixing roll is small, and 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 if the 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 amount of temperature decrease at the belt nip is also small. There is also an advantage that the fixing property of the toner can be improved.

Japanese Patent No. 3298354 (pages 4-7)

  By the way, the above-described belt nip type fixing device employs a configuration in which the endless belt (belt member) is pressed against the fixing roll by the pressure member. Therefore, when the image forming apparatus is stopped, the pressure member is It will continue to press a certain area of the fixing roll. For this reason, when the image forming apparatus is in a stopped state for a long time, a dent when pressed by a pressure member on a partial region of the surface of the fixing roll tends to remain as a history. If such a dent remains on the surface of the fixing roll, a belt-like fixing unevenness may occur in the fixed image during the image forming operation. Therefore, in such a belt nip type fixing device, when the image forming apparatus is stopped and the fixing device is in a non-operating state, in order to release the pressing state of the pressure member and the fixing roll at a predetermined pressure, A pressure release mechanism is provided that can move the pressure member in a direction to separate the pressure member from the fixing roll.

  However, in the pressure release mechanism, during the operation of separating the pressure member from the fixing roll (separating operation), the pressure member acting on the direction of the fixing roll is operated so as to be separated from the fixing roll. The pressing force acts as a load on the pressure release mechanism. On the other hand, during the operation of pressing the pressure member against the fixing roll (pressing operation), the pressure member having a pressing force acting in the direction of the fixing roll is operated along this pressing force. A force that pushes the pressure release mechanism acts on the release mechanism. For this reason, the operating speed of the pressure release mechanism becomes too fast during the pressing operation than during the separation operation, and a phenomenon occurs in which the components strongly collide with each other at the operation position where the pressure member is brought into contact with and separated from. As a result, there is a problem in that abnormal noise is generated, and the image quality is affected by the deformation of the parts due to long-term use. Furthermore, since the pressure release mechanism overruns during the pressing operation, the position sensor provided in the pressure release mechanism erroneously detects, making it difficult to set the pressure member at a predetermined position. There was also.

  The present invention has been made to solve the technical problems as described above. The object of the present invention is to increase the operating speed of a pressure release mechanism that makes a pressure member contact and separate from a fixing roll. It is to suppress passing.

  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 includes a rotating member, a belt member movable while contacting the rotating member, and a belt. A pressing member that presses the rotating member with a predetermined pressure from the inside of the member, a state in which the rotating member is pressed with a predetermined pressure against the pressing member, and a state in which the pressing with the predetermined pressure on the rotating member is released. It is characterized by comprising pressure setting means for setting, and speed adjusting means for adjusting the operating speed when the pressure setting means operates the pressing member.

Here, the speed adjusting means may include a rotating member disposed in the driving force transmission path of the pressure setting means, and an elastic member pressed against the rotating member. In particular, the rotating member may be formed in a flange shape, and the elastic member may be constituted by an elastic roll that is pressed against the rotating member. Further, the elastic member can be configured to be pressed against the rotating member with a predetermined amount of biting. Furthermore, the elastic member may be characterized by rotating in the same direction at the contact portion with the rotating member and at a peripheral speed substantially the same as the peripheral speed of the rotating member. Further, the elastic member may be configured to be disposed in the driving force transmission path of the pressure setting means.
Further, the speed adjusting means may be characterized in that the operating speed when the pressure setting means sets the pressing member in a pressing state at a predetermined pressure can be characterized.

  The fixing device of the present invention is a fixing device for fixing a toner image carried on a recording material, and includes a rotating member, a belt member movable while contacting the rotating member, and an inner side of the belt member. Pressure setting that sets a pressing member that presses the rotating member with a predetermined pressure, a state in which the rotating member is pressed with a predetermined pressure with respect to the pressing member, and a state in which the pressing with the predetermined pressure on the rotating member is released. The pressure setting means includes an operating portion that moves the pressing member in the direction of the rotating member, a drive transmission portion that transmits a driving force to the operating portion, and a speed adjustment that adjusts the operating speed of the operating portion. It is characterized by providing a part.

  Here, the pressure setting means may be characterized in that the speed adjusting portion is disposed at a coupling portion between the drive transmission portion and the operating portion. The operating portion of the pressure setting means includes a shaft, a cam fixed to the shaft, a gear that is externally fitted to the shaft and receives a driving force from the drive transmission unit, and a gear that is externally fitted to the shaft, from the speed adjusting unit. And a flange that receives a braking force. Furthermore, the speed adjusting part of the pressure setting means may be formed of an elastic roll that is pressed against the flange of the operating part.

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 the toner image formed by the toner image forming unit onto a recording material. A fixing means for fixing the toner image transferred onto the recording material to the recording material. The fixing means includes a rotating member, a belt member movable while contacting the rotating member, and an inner side of the belt member. Pressure setting that sets a pressing member that presses the rotating member with a predetermined pressure, a state in which the rotating member is pressed with a predetermined pressure with respect to the pressing member, and a state in which the pressing with the predetermined pressure on the rotating member is released. And a speed adjusting means for adjusting an operating speed when the pressure setting means operates the pressing member.
Here, the speed adjusting means can be characterized by being disposed in the driving force transmission path of the pressure setting means.

  According to the present invention, it is possible to prevent the operating speed of the pressure release mechanism from becoming too fast. As a result, the parts do not collide strongly at the operation position where the pressure member is contacted / separated, and the generation of abnormal noise can be suppressed to a very low level, and normal contact / separation operation can be maintained for a long time. .

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
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 constituted by a film-like endless belt in which an appropriate amount of an antistatic agent such as carbon black is contained in a resin such as polyimide or polyamide. The volume resistivity is 10 ⁶ to 10 ¹⁴ Ωcm, and the thickness is, for example, about 0.1 mm. The intermediate transfer belt 15 is circulated and 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 the intermediate transfer belt 15 from meandering, 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 includes a shaft and a sponge layer as an elastic layer fixed around the shaft. The shaft is a cylindrical bar made of metal such as iron or SUS. The sponge layer is a sponge-like cylindrical roll formed of a blend rubber of NBR, SBR, and EPDM containing a conductive agent such as carbon black and having a volume resistivity of 10 ⁷ to 10 ⁹ Ωcm. 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 composed of a tube of EPDM and NBR blend rubber with carbon dispersed on the surface, and EPDM rubber on the inside. The surface resistivity is 10 ⁷ to 10 ¹⁰ Ω / cm, and the hardness is set to 70 ° (Asker C), for example. The backup roll 25 is disposed on the back side of the intermediate transfer belt 15 to form 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 disposed in contact with the backup roll 25. ing.

On the other hand, the secondary transfer roll 22 includes a shaft and a sponge layer as an elastic layer fixed around the shaft. The shaft is a cylindrical bar made of metal such as iron or SUS. The sponge layer is a sponge-like cylindrical roll formed of a blend rubber of NBR, SBR, and EPDM containing a conductive agent such as carbon black and having a volume resistivity of 10 ⁷ to 10 ⁹ Ωcm. 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 the 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 placement unit provided in a discharge unit 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 mainly includes a fixing roll 61 as an example of a rotating member, an endless belt 62 as an example of a belt member, and a pressure pad 64 as an example of a pressure member that presses the fixing roll 61 via the endless belt 62. The part is composed.

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. Rotates at a predetermined surface speed.
Inside the fixing roll 61, for example, a halogen heater 66 having a rating of 600 W 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 the 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, 175 ° C.). It is adjusted to.

  The endless belt 62 is a seamless endless belt, the pressure pad 64 disposed inside the endless belt 62, the upstream belt guide member 63 a and the downstream belt guide member 63 b, and both ends of the endless belt 62. It is rotatably supported by an edge guide member 80 (see FIG. 3 in the subsequent stage) arranged in the section. The endless belt 62 is disposed so as to be in pressure contact with the fixing roll 61 at the nip portion N, and rotates following the fixing roll 61.

Here, FIG. 3 is a 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, both ends in the width direction of the endless belt 62 are supported by edge guide members 80 fixed to both ends of a support frame 65 as a support disposed inside the endless belt 62. Yes. The edge guide member 80 is provided on the outer side of the belt traveling guide portion 801 having 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 C-shaped cross section, A flange portion 802 formed with an outer diameter larger than the outer diameter of the endless belt 62, and further provided on the outer surface of the edge guide member 80, the edge guide member 80 is coupled to a support lever 400 held by the fixing device 60 main body. The holding part 803 for this is comprised.
The endless belt 62 rotates at the both ends in the width direction of the endless belt 62 following the fixing roll 61 while the inner peripheral surfaces of both ends are supported by the edge guide member 80. Further, the endless belt 62 is restricted from moving in the width direction of the endless belt 62 (belt walk) by the flange portion 802, so that the endless belt 62 is prevented from being displaced.

  On the other hand, in the region excluding both end portions in the width direction of the endless belt 62, the endless belt 62 is supported by the pressure pad 64, the upstream belt guide member 63a, and the downstream belt guide member 63b (see also FIG. 2). The pressure pad 64, the upstream belt guide member 63a, and the downstream belt guide member 63b are attached to the support frame 65 inside the endless belt 62 along the longitudinal direction. And in the area | region except the both ends of the endless belt 62, the low friction sheet | seat 68 arrange | positioned so that the internal peripheral surface of the endless belt 62 may cover the pressure pad 64 and the upstream belt guide member 63a, and a downstream belt guide It rotates while rubbing against the member 63b.

As described above, the endless belt 62 includes the edge guide members 80 fixed at both ends of the support frame 65, the pressure pads 64 fixed along the longitudinal direction of the support frame 65, and the upstream belt guide member. 63a and the downstream belt guide member 63b.
In addition, the edge guide members 80 fixed to both ends of the support frame 65 are coupled to a support lever 400 having a holding portion 803 held by the fixing device 60 main body. The support lever 400 will be described later. The pressure release mechanism is configured to swing. Therefore, when the pressure release mechanism swings the support lever 400, the edge guide member 80 moves in a direction away from the fixing roll 61 (an arrow in FIG. 3), and the entire endless belt 62 is moved from the fixing roll 61. It is comprised so that it can isolate.

Next, the pressure pad 64 is supported by the metal support frame 65 inside the endless belt 62 as described above. Then, the fixing roll 61 is pressed through the endless belt 62 to form a nip portion N with the fixing roll 61. The pressure pad 64 is an example of a pre-nip member 64a as an example of a pressing member disposed on the inlet side (upstream side) of the nip portion N, and an example of a local pressing member disposed on the outlet side (downstream side) of the nip portion N. The peeling nip member 64b. The pre-nip member 64a has a function of forming a wide nip portion N to which a uniform nip pressure is applied. Further, the peeling nip member 64b locally presses the surface of the fixing roll 61, thereby smoothing the surface of the toner image and imparting image gloss, and also imparting distortion (dent) to the surface of the fixing roll 61. It has a function of forming a down curl on P and separating the paper P from the surface of the fixing roll 61.
In addition, when the edge guide member 80 is moved away from the fixing roll 61 by the pressure releasing mechanism described above, the pressing force to the fixing roll 61 is released.

Further, the pressure pad 64 is provided with a low friction sheet 68 as an example of a low friction member on the surface in contact with the endless belt 62 in order to reduce the sliding resistance between the inner peripheral surface of the endless belt 62 and the pressure pad 64. It has been.
The low friction sheet 68 has an upstream end of the nip portion N fixed to the bottom surface of the support frame 65 by a downstream belt guide member 63b. The upstream belt guide member 63a is covered and disposed in a state of being sandwiched between the pressure pad 64 and the inner peripheral surface of the endless belt 62 in the entire nip portion N. The downstream side of the nip portion N of the low friction sheet 68 is set in a free end (free) state without being fixed so that the low friction sheet 68 is not distorted. The low friction sheet 68 has an inner peripheral surface of the endless belt 62 and the pressure pad 64 in a state where a pressing force (nip pressure) is applied between the pressure pad 64 and the fixing roll 61 at the nip portion N. The sliding resistance (friction resistance) is reduced.

  In such a configuration, the fixing roll 61 is connected to a drive motor (not shown) and rotates in the direction of arrow C, and the endless belt 62 rotates in the same direction as the fixing roll 61 following this rotation. 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 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 a baffle 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 611 is formed of a cylindrical body made of a metal having high thermal conductivity such as iron, aluminum, or SUS, for example, an outer diameter of 30 mm, a wall thickness of 1.8 mm, and a length of 360 mm. . The heat-resistant elastic body layer 612 is composed 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 rubber hardness of about 15 to 45 ° (JIS-A). Specifically, silicone rubber, fluorine rubber, or the like can be used. In the fixing device 60 of the present embodiment, the core 611 is coated with a silicone HTV rubber having a rubber hardness of 35 ° (JIS-A) with a thickness of 600 μm. For the release layer 613, for example, a heat-resistant resin such as a silicone resin or a fluororesin is used, and a fluororesin is suitable from the viewpoint of the release property to the toner and the wear resistance. As the fluororesin, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP) and the like can be used. The thickness of the release layer 613 is preferably 5 to 30 μm. In fixing device 60 of the present embodiment, PFA having a thickness of 30 μm is coated.

The endless belt 62 is a seamless endless belt whose original shape is formed in a cylindrical shape so that a defect caused by the seam does not occur in the output image. The base layer and the surface of the base layer on the fixing roll 61 side ( Outer peripheral surface) or a release layer coated on both sides. For the base layer, a polymer such as a thermosetting polyimide resin, a thermoplastic polyimide resin, a polyamideimide resin, or a polybenzimidazole resin is preferably used from the viewpoint of heat resistance, mechanical properties, and the like. The thickness is set to about 30 to 200 μm, preferably 50 to 125 μm, more preferably about 75 to 100 μm.
As the release layer to be coated on the surface of the base layer, a fluororesin is used. Here, as the fluororesin, polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-perfluoromethyl vinyl ether, particularly from the viewpoint of heat resistance, mechanical properties and the like. A copolymer (MFA), a tetrafluoroethylene-perfluoroethyl vinyl ether copolymer (EFA), and a tetrafluoroethylene-hexafluoropropylene copolymer (FEP) are preferably used. The thickness is set to about 5 to 100 μm, preferably about 10 to 30 μm.
In the fixing device 60 of the present embodiment, the endless belt 62 has a configuration in which a release layer made of PFA having a thickness of 30 μm is laminated on a base layer made of thermosetting polyimide having a peripheral length of 94 mm, a thickness of 75 μm, and a width of 320 mm. Is used.

The low friction sheet 68 is formed of a material having a small coefficient of friction and excellent wear resistance and heat resistance in order to reduce sliding friction (sliding resistance) between the inner peripheral surface of the endless belt 62 and the pressure pad 64. Is suitable. Further, the low friction sheet 68 is configured so as not to be infiltrated into the lubricant (i.e., difficult to pass through) so that the lubricant penetrates and does not leak from the back surface. Specifically, a porous resin fiber cloth made of a fluororesin is used as a base layer, and a surface of the pressure pad 64 is wrapped with a PET resin sheet, a sintered PTFE resin sheet, and Teflon (registered trademark) are impregnated. A glass fiber sheet or the like can be used.
The low friction sheet 68 may be configured separately from the pre-nip member 64a and the peeling nip member 64b, or may be configured integrally with the pre-nip member 64a and the peeling nip member 64b.

  Next, a lubricant application member 67 is disposed on the bottom surface of the downstream side belt guide member 63 b 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. Further, it has an effect of suppressing wear on the inner peripheral surface of the endless belt 62 and the surface of the low friction sheet 68.

  As the lubricant, a lubricant that has durability against long-term use under a fixing temperature environment and can maintain wettability with the inner peripheral surface of the endless belt 62 is suitable. For example, liquid oil such as silicone oil or fluorine oil, synthetic lubricating oil grease in which a solid substance and a liquid are mixed, or a combination thereof can be used. Silicone oils include dimethyl silicone oil, dimethyl silicone oil with organometallic salt addition, dimethyl silicone oil with hindered amine addition, dimethyl silicone oil with organometallic salt and hindered amine addition, methylphenyl silicone oil, amino-modified silicone oil, amino-modified silicone-added amino-modified silicone. Oil, hindered amine-added amino-modified silicone oil, carboxy-modified silicone oil, silanol-modified silicone oil, sulfonic acid-modified silicone oil, and the like can also be used. Moreover, as fluoro oil, perfluoropolyether oil and modified perfluoropolyether oil can be used. In the fixing device 60 of the present embodiment, amino-modified silicone oil is used.

Next, the pressure pad 64 that is disposed inside the endless belt 62 and presses the fixing roll 61 will be described.
As described above, the pressure pad 64 includes the pre-nip member 64a and the peeling nip member 64b. First, the prenip member 64a is supported on the support frame 65 via a pressure spring so as to press the fixing roll 61 with a predetermined pressure (for example, a load of 35 kgf). Further, as a material constituting the prenip member 64a, an elastic body such as silicone rubber or fluorine rubber, a leaf spring, or the like can be used. In the fixing device 60 of the present embodiment, the width is 10 mm, the thickness is 5 mm, and the length is 320 mm silicone rubber is used. Further, the surface on the fixing roll 61 side is formed with a concave curved surface that substantially follows the outer peripheral surface of the fixing roll 61. Since the wide nip portion N can be formed by the pre-nip member 64a having such a configuration, a sufficient amount of heat is applied from the fixing roll 61 to the toner image on the paper P in response to the increase in the speed of the image forming apparatus. be able to.

The peeling nip member 64b is configured separately from the pre-nip member 64a and is supported by the support frame 65 separately and independently. The support frame 65 is pressed toward the fixing roll 61 by a pressing mechanism (not shown) through a support lever 400 (see FIG. 3) held by the fixing device 60 main body. Then, the peeling nip member 64 b comes into contact with the fixing roll 61 with a predetermined pressing force by setting the support frame 65 at a predetermined position with respect to the fixing roll 61 while being pressed toward the fixing roll 61. It is configured as follows.
The peeling nip member 64b is formed of a high-stiffness material such as heat-resistant resin such as PPS, polyimide, polyester, and polyamide, or metal such as iron, aluminum, or SUS, and has a width (along the rotation direction of the endless belt 62). (Length) is 3 to 4 mm, and the longitudinal direction is formed of a plate-like member extending over substantially the entire region of the nip portion N. Further, the outer surface shape of the peeling nip member 64b on the fixing roll 61 side is a convex curved surface having a predetermined curvature.
With such a configuration, the peeling nip member 64 b presses against the fixing roll 61 with a locally high pressure. As a result, a high-pressure region is formed in the longitudinal direction of the nip portion N in the region of 3 to 4 mm in width on the nip portion N outlet side (the most downstream portion). By passing through the high-pressure portion, the toner image surface is smoothed, and a desired image gloss can be obtained. Further, since the surface of the fixing roll 61 is locally distorted (indented), the paper P passes through the indentation so that a down curl is formed on the paper P, and the paper P is peeled off from the surface of the fixing roll 61. can do.

  By the way, since the pressure pad 64 (the pre-nip member 64a and the peeling nip member 64b) is arranged so as to press the endless belt 62 against the fixing roll 61 in this way, in a state where the image forming apparatus is stopped, The pressure pad 64 continues to press a certain area of the fixing roll 61. For this reason, when the image forming apparatus is in a stopped state for a long time, a dent when pressed by the pressure pad 64 on a partial region of the surface of the fixing roll 61 tends to remain as a history. If a dent remains on the surface of the fixing roll 61, a belt-like fixing unevenness may occur in the fixed image during the image forming operation.

Therefore, in the fixing device 60 of the present embodiment, when the image forming apparatus is stopped and the fixing device 60 is in a non-operating state, the pressing state of the pressure pad 64 and the fixing roll 61 with a predetermined pressure is released. For this purpose, a pressure release mechanism for separating the entire endless belt 62 from the fixing roll 61 is provided. Hereinafter, a pressure release mechanism disposed in the fixing device 60 of the present embodiment will be described.
FIG. 4 is a diagram for explaining a pressure release mechanism disposed in the fixing device 60 of the present embodiment. As shown in FIG. 4, the pressure release mechanism of the present embodiment includes a driving force passive unit 100 that receives a driving force from the fixing roll 61, a cam mechanism unit 200 that separates the entire endless belt 62 from the fixing roll 61, and Is composed of a shaft 300 that transmits driving force from the driving force passive portion 100 to the cam mechanism portion 200.

  First, a fixing roll gear 90 that rotationally drives the fixing roll 61 by receiving a driving force from a driving motor (not shown) provided in the image forming apparatus is externally fitted to one end of the fixing roll 61. Yes. The driving force passive unit 100 is configured to receive a rotational driving force from the fixing roll 61. That is, as shown in FIG. 4, the driving force passive unit 100 includes a transmission gear 101 that is gear-coupled to the fixing roll gear 90, a transmission gear 103 that is coupled to the shaft 300, and between the transmission gear 101 and the transmission gear 103. The transmission gear 102 is provided. In the driving force passive unit 100, the rotational driving force of the fixing roll 61 is transmitted in the order of the fixing roll gear 90 → the transmission gear 101 → the transmission gear 102 → the transmission gear 103 to rotate the shaft 300.

On the other hand, the cam mechanism 200 includes a transmission gear 201 having a one-way clutch coupled to an end of the shaft 300, a transmission gear 202 gear-coupled to the transmission gear 201, a transmission gear 203 gear-coupled to the transmission gear 202, A transmission gear 204 that is gear-coupled to the transmission gear 203, a transmission gear 205 that is coaxially coupled to the transmission gear 204, a transmission gear 206 that is gear-coupled to the transmission gear 205, a shaft 207 on which the transmission gear 206 is externally fitted, and a shaft 207 The cam 208 and the cam 209 are externally fitted. Here, the transmission gears 201 to 205 constitute a drive transmission part of the cam mechanism part 200, and the transmission gear 206, the shaft 207, the cam 208 and the cam 209 constitute an operation part of the cam mechanism part 200.
The transmission gear 201 provided with the one-way clutch rotates idly even if it receives the rotation of the shaft 300 when the fixing roll 61 rotates in the normal direction, that is, in the normal rotation during the image forming operation. The driving force is not transmitted to the cam mechanism unit 200. On the other hand, the drive motor disposed in the image forming apparatus is configured to be able to rotate in the direction opposite to the normal rotation during the image forming operation, and the fixing roll 61 rotates in the reverse direction due to the reverse rotation of the drive motor. In this case, the transmission gear 201 including the one-way clutch receives the rotation of the shaft 300 and transmits the rotational driving force from the shaft 300 to the cam mechanism unit 200.

  FIG. 5 is a diagram illustrating a configuration of the cam mechanism unit 200 of the pressure release mechanism. Referring to FIG. 5, when the fixing roll 61 is reversely rotated by the reverse rotation of the drive motor, in the cam mechanism unit 200, the rotational driving force from the shaft 300 is provided with the one-way clutch from the shaft 300. Via the transmission gear 201, transmission is performed in the order of transmission gear 202 → transmission gear 203 → transmission gear 204 → transmission gear 205 → transmission gear 206, and the shaft 207 rotates. Then, the rotation of the shaft 207 causes the cam 208 (and the cam 209) to rotate by a predetermined angle (more precisely, an angle smaller than a half circumference). At that time, the cam 208 (and the cam 209) pushes down the bearing 401 attached to the support lever 400 held by the fixing device 60 main body, and thereby the joint portion where the support lever 400 and the fixing device 60 main body are coupled. The support lever 400 is pushed down with reference to 402 as the swing center. Then, the edge guide member 80 (see FIG. 3) coupled to the support lever 400 is pushed down. As a result, the entire endless belt 62 is pushed down, and the endless belt 62 is separated from the fixing roll 61, so that the pressing state of the pressure pad 64 and the fixing roll 61 at a predetermined pressure is released.

On the other hand, when the endless belt 62 is brought into pressure contact with the fixing roll 61 again, the fixing roll 61 is reversely rotated by further reverse rotation of the drive motor, and the rotational driving force from the shaft 300 is similarly applied by the gear train of the cam mechanism section 200. Then, the cam 208 and the cam 209 are rotated to the start position (initial nip position). Then, the edge guide members 80 at both ends of the endless belt 62 are pressed against the fixing roll 61 by a pressing mechanism (not shown) via the support lever 400, so that the entire endless belt 62 is pushed up. Then, it is pressed against the fixing roll 61 with a predetermined pressure. As described above, the pressure release mechanism functions as a pressure setting unit that sets the pressing state of the pressure pad 64 and the fixing roll 61 at a predetermined pressure and the release of the pressing state at the predetermined pressure.
An actuator 210 is disposed at the end of the shaft 207, and a photosensor 211 (see FIG. 6 at a later stage) is disposed in the movement region of the actuator 210. As the actuator 210 rotates along with the rotation of the shaft 207, the actuator 210 crosses the photosensor 211, and the rotation angles of the cam 208 and the cam 209 fixed to the shaft 207 are detected. Based on the rotation angles of the cam 208 and the cam 209, the reverse rotation amount of the drive motor is controlled.

  As described above, in the pressure release mechanism provided in the fixing device 60 of the present embodiment, the fixing roll 61 is reversely rotated by the reverse rotation of the drive motor, whereby the rotational driving force of the fixing roll 61 is driven by the driving force passive unit. 100 → shaft 300 → cam mechanism unit 200 is transmitted to rotate cam 208 and cam 209 to a predetermined angle. As a result, the edge guide member 80 can be swung via the support lever 400, and the entire endless belt 62 is brought into contact with and separated from the fixing roll 61, whereby a predetermined pressure between the pressure pad 64 and the fixing roll 61 is obtained. The pressing state and the pressure releasing state can be selectively set.

In the pressure release mechanism provided in the fixing device 60 of this embodiment, the cam mechanism unit 200 is provided with speed adjusting means for applying a braking force to the driving force transmitted to the cam mechanism unit 200. It is characterized by having.
FIG. 6 is a perspective view showing the cam mechanism 200 of the pressure release mechanism from the side opposite to FIG. In FIG. 6, a transmission gear 206 coupled to a shaft 207 to which a cam 208 (and a cam 209) is externally fitted includes a gear portion 206a in which gear teeth are formed, and a flange-like flange roll in which gear teeth are not formed. Part 206b. The transmission gear 205 that transmits the driving force from the shaft 300 is gear-coupled to the gear portion 206 a of the transmission gear 206.
On the other hand, at a position facing the flange roll portion 206b of the transmission gear 206, a rubber roll 212 that is coaxial with the transmission gear 205 and is integrally formed with the transmission gear 205 is disposed. The rubber roll 212 is a fluoro rubber excellent in heat resistance and wear resistance, and rotates in accordance with the rotation of the transmission gear 205 while contacting the flange roll portion 206b of the transmission gear 206 with a biting amount. Here, as shown in FIG. 7, the “biting amount” refers to the original outer peripheral surface of the rubber roll 212 and the outer peripheral surface of the flange roll portion 206 b when the flange roll portion 206 b of the transmission gear 206 is not disposed. This is the radial depth of the overlapping area. For the rubber roll 212, silicone rubber having excellent heat resistance can be used in addition to fluorine rubber.

  The transmission gear 205 rotates the transmission gear 206 to transmit the driving force from the shaft 300 to the shaft 207. At this time, the rubber roll 212 integrally coupled with the transmission gear 205 is connected to the flange roll of the transmission gear 206. It rotates while contacting the portion 206b with a biting amount. Therefore, the flange roll portion 206 b of the transmission gear 206 receives a braking force from the rubber roll 212. That is, since the rubber roll 212 is in contact with the flange roll portion 206b with a biting amount, the rubber roll 212 is compressed from the flange roll portion 206b to the rubber roll 212 at the contact portion between the rubber roll 212 and the flange roll portion 206b. Power works to let you. On the other hand, in the rubber roll 212, an elastic force for expanding the rubber roll 212 acts as a reaction force against the compressive force from the flange roll portion 206b. Since the elastic force of the rubber roll 212 also acts on the rotation direction of the flange roll portion 206b, a part of the elastic force becomes a force in a direction that hinders the rotation of the flange roll portion 206b, and against the rotation of the transmission gear 206. Brake. As described above, the rubber roll 212 that rotates while contacting the flange roll portion 206b with a biting amount functions as a speed adjusting means (speed adjusting portion of the cam mechanism portion 200) that applies a braking force in the cam mechanism portion 200.

Here, the force acting on the cam 208 and the cam 209 of the cam mechanism 200 when setting the pressed state and the pressure released state between the pressure pad 64 and the fixing roll 61 will be described.
FIG. 8 is a diagram for explaining a state in which the cam 208 swings the support lever 400. FIG. 8A illustrates a state in which the support lever 400 is pressed down to separate the pressure pad 64 from the fixing roll 61 (separation operation). (B) shows a state during an operation (pressing operation) of returning the support lever 400 to the original position and pressing the pressure pad 64 against the fixing roll 61.
A force that constantly urges the support lever 400 in the direction of the fixing roll 61 (in the direction of the arrow) by the pressing mechanism 403 acts. Accordingly, a force in the direction of the fixing roll 61 (in the direction of the arrow) is also applied to the bearing 401 serving as an operating position when the pressure pad 64 is moved away from the fixing roll 61. For this reason, during the separation operation shown in FIG. 8A, the rotation of the cam 208 causes the surface 208a of the cam 208 that contacts the bearing 401 to push down the bearing 401, whereas the cam 208 A force to push up from the bearing 401 acts on the surface 208a. Therefore, the cam 208 pushes down the bearing 401 (support lever 400) while resisting the push-up force from the bearing 401 by the rotational force from the drive motor transmitted through the cam mechanism unit 200.

  On the other hand, in the pressing operation shown in FIG. 8B, the surface 208 b that contacts the bearing 401 of the cam 208 moves away from the bearing 401, so that the bearing 401 pushes up the cam 208. And the direction of movement of the surface 208b of the cam 208 coincide with each other. Therefore, in addition to the rotational force from the drive motor, a force for rotating the cam 208 from the bearing 401 acts on the cam 208, and the cam 208 is accelerated. For this reason, a phenomenon occurs in which the rotational speed during the pressing operation of the cam 208 (and the cam 209) exceeds the assumed speed (speed during the separation operation).

  When the rotational speed of the cam 208 (and the cam 209) becomes higher than expected, a collision occurs between the bearing 401 and the cam 208 (and the cam 209), and the return speed of the support lever 400 increases, so that the pressure is increased. A member that supports the pad 64 (for example, the support frame 65) or the like may collide with other members, and the collision sound may be abnormal and cause discomfort to the operator. It becomes a factor which deform | transforms a member (for example, support frame 65) etc., and has a bad influence on an image. Further, when such a collision between members continues for a long period of time, for example, the cam 208 and the cam 209 are worn, and an accurate swinging operation with respect to the support lever 400 cannot be performed. No normal contact / separation operation with 61 can be performed. Furthermore, since the cam 208 (and the cam 209) overruns, the stop position of the actuator 210 deviates from the normal position, so that the photo sensor 211 erroneously detects and sets the pressure pad 64 to a predetermined position. May be difficult.

Therefore, in the fixing device 60 of the present embodiment, the rubber roll 212 and the flange roll of the transmission gear 206 are applied so that the braking force is applied to the driving force transmitted to the gear train in the cam mechanism portion 200 of the pressure release mechanism. A speed adjusting means including a portion 206b is provided. By arranging such speed adjusting means, a force to rotate the cam 208 from the bearing 401 is applied to the cam 208 in addition to the rotational force from the drive motor during the pressing operation. Even in this case, the braking force from the rubber roll 212 is applied to the shaft 207 to which the cam 208 is fixed via the transmission gear 206 connected to the shaft 207. Thereby, acceleration of the cam 208 is suppressed. Therefore, the rotational speed during the pressing operation of the cam 208 (and the cam 209) can be suppressed to substantially the same level as the speed during the separation operation.
Even during the separation operation, the braking force from the rubber roll 212 is applied to the shaft 207 on which the cam 208 is fixed, but it rotates at a predetermined speed without being substantially decelerated by the rotational force from the drive motor. .

  As described above, since the speed adjusting means prevents the cam 208 (and the cam 209) from rotating too fast during the pressing operation, a collision occurs between the bearing 401 and the cam 208 (and the cam 209). Or a member that supports the pressure pad 64 (for example, the support frame 65) or the like is prevented from colliding with other members, and the collision sound becomes abnormal and causes discomfort to the operator. In addition to being able to prevent, deformation of members and the like due to collision can be prevented. Further, it is possible to suppress the wear of the cam 208 and the cam 209 due to the collision between the members over a long period of time, and to maintain a normal contact / separation operation between the pressure pad 64 and the fixing roll 61. It becomes possible. Furthermore, since the cam 208 (and the cam 209) can be prevented from overrunning, the actuator 210 can be accurately stopped at the normal position, so that the malfunction of the photosensor 211 can be suppressed and the pressure can be reduced. It is possible to stably set the pad 64 at a predetermined position.

Next, the relationship between the peripheral speed ratio between the rubber roll 212 and the flange roll portion 206b of the transmission gear 206 and the braking effect by the rubber roll 212 will be described.
Regarding the peripheral speed ratio between the rubber roll 212 and the flange roll portion 206b of the transmission gear 206, the greater the peripheral speed ratio, the greater the speed difference in the contact area between the two, and the greater the braking effect on the transmission gear 206. Here, Type 1 and Type 2 having different settings of the rubber roll 212 and the flange roll portion 206b of the transmission gear 206 were prepared. FIG. 9 is a diagram showing the setting of the outer diameter and the peripheral speed, and the peripheral speed ratio of the rubber roll 212 and the flange roll portion 206b in Type 1 and Type 2. In Type 1, the peripheral speed of the rubber roll 212 is set lower than that of the flange roll portion 206b, and the peripheral speed ratio is set to 1.33. In Type 2, the peripheral speed ratio between the rubber roll 212 and the flange roll portion 206b is set to substantially the same 1.00. And when both brake effects are compared, it can be confirmed that Type 1 having a large peripheral speed ratio is superior to Type 2 having substantially the same peripheral speed ratio.

However, when Type 1 and Type 2 are incorporated in the fixing device 60 and a running test is performed in a predetermined mode by the image forming apparatus, the larger the peripheral speed ratio between the rubber roll 212 and the flange roll portion 206b of the transmission gear 206 is, It has been found that the amount of wear of the rubber roll 212 increases as the running test elapses, and the braking effect by the rubber roll 212 gradually decreases. The result is shown in FIG.
As shown in FIG. 10, in Type 1 where the peripheral speed ratio is 1.33, the wear rate (wear amount / bite amount) increases in proportion to the number of running sheets, and when 60,000 pieces have passed Thus, the wear rate (amount of wear / bite-in amount) exceeded 0.5 and reached a state where the brake effect was not recognized. On the other hand, in Type 2 where the peripheral speed ratio is 1.00, the increase in the wear rate is moderate, and even when the number of running sheets is 200,000, the level at which the braking effect is exhibited is sufficiently satisfied. Thus, from the viewpoint of sustaining the braking effect due to the wear rate of the rubber roll 212, the peripheral speed ratio between the rubber roll 212 and the flange roll portion 206b of the transmission gear 206 is the same level (the peripheral speed ratio is close to 1). Setting is effective.

On the other hand, regarding the amount of biting, when the biting amount is set to 0.5 mm and the biting amount set to 1.426 mm, the braking effect of the one set to 1.426 mm is excellent. As described above, as the amount of biting increases, the elastic force to expand the rubber roll 212 against the compressive force from the flange roll portion 206b also increases, so that the braking force against the rotation of the transmission gear 206 also increases. It can be guessed that it is.
From these results, regarding the braking effect by the rubber roll 212, the biting amount is increased to about 1.426 mm from the viewpoint of realizing the braking effect sufficiently and realizing the durability of the braking effect by suppressing the wear of the rubber roll 212. It is preferable to set the peripheral speed ratio between the rubber roll 212 and the flange roll portion 206b of the transmission gear 206 at the same level.

  The larger the contact area between the rubber roll 212 and the flange roll portion 206b, the greater the braking effect. Therefore, in the rubber roll 212 of the present embodiment, the width is formed to 4.5 mm. Further, the higher the hardness of the rubber roll 212, the greater the elastic force, and thus the greater the braking effect. Therefore, in the rubber roll 212 of the present embodiment, the rubber hardness is set to 80 ° (JIS K6253). Further, the smoother the surface roughness of the circumferential surface of the flange roll portion 206b in contact with the rubber roll 212, the more the friction force acts on the rubber roll 212, so that local wear is prevented and a long life effect is obtained. Therefore, in the flange roll 206b of the present embodiment, the surface roughness Ra (arithmetic average roughness) is set to 1.6.

  As described above, in the fixing device 60 of the present embodiment, the pressure release for separating the entire endless belt 62 from the fixing roll 61 in order to release the pressing state of the pressure pad 64 and the fixing roll 61 at a predetermined pressure. A mechanism is provided. Thereby, when the stopped state of the image forming apparatus continues for a long time, it is possible to suppress a dent when being pressed by the pressure pad 64 in a partial area of the surface of the fixing roll 61 as a history, and a fixed image during an image forming operation. It is possible to suppress the occurrence of band-like fixing unevenness. Further, the paper removal process when a paper jam (jam) occurs in the fixing device 60 is facilitated.

  Further, in the pressure release mechanism disposed in the fixing device 60 of the present embodiment, the rubber roll is applied so that the braking force is applied to the driving force transmitted to the gear train of the cam mechanism unit 200 in the cam mechanism unit 200. 212 and a speed adjusting means including a flange roll portion 206b disposed to face the rubber roll 212 are provided. As a result, a collision between the bearing 401 and the cam 208 and the cam 209 is prevented, and a member (for example, the support frame 65) that supports the pressure pad 64 is prevented from colliding with another member. It is possible to prevent an unpleasant feeling for the operator due to the abnormal sound, and to prevent the parts from being deformed due to a collision, thereby preventing an adverse effect on the image. Further, the deformation of the cam 208, the cam 209, and the like due to the collision between the members for a long time is suppressed, and the normal contact / separation operation between the pressure pad 64 and the fixing roll 61 is maintained for a long time. It becomes possible to do. Furthermore, since the overrun of the cam 208 and the cam 209 can be suppressed, the actuator 210 can be accurately stopped at the normal position, so that the malfunction of the photosensor 211 is suppressed and the pressure pad 64 is suppressed. Can be stably set at a predetermined position.

  The pressure release mechanism according to the present embodiment includes a fixing belt configured such that a heat source is pressed from the inside as a heating unit, and a belt nip in which a pressure roll is pressed as a pressing unit against the fixing belt. With respect to the fixing device of the type, the configuration in which the fixing belt is separated from the pressure roll can also be applied to a case where a heat source in a pressed state is brought into contact with or separated from the pressure roller.

  As an application example of the present invention, application to an image forming apparatus such as a copying machine or a printer using an electrophotographic system, for example, application to a fixing apparatus that fixes an unfixed toner image carried on recording paper (paper). is there. 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 illustrating an image forming apparatus of the present invention. FIG. 3 is a side sectional view showing a configuration of a fixing device. It is a figure explaining the structure by which an endless belt is supported. It is a figure explaining a pressure release mechanism. It is the figure which showed the structure of the cam mechanism part of a pressure release mechanism. It is the perspective view which showed the cam mechanism part of the pressure release mechanism from the opposite side to FIG. It is a figure explaining the amount of biting of a rubber roll. It is a figure explaining the state which a cam rocks a support lever. It is the figure which showed the setting of the outer diameter of a rubber roll and a flange roll part, a peripheral speed, and a peripheral speed ratio. It is the figure which compared the abrasion rate of the rubber roll by the difference in peripheral speed ratio.

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 section, 60 ... fixing device, 61 ... fixing roll, 62 ... endless belt, 63a ... upstream belt guide member, 63b ... downstream belt guide member, 64 ... pressure pad, 64a ... pre-nip member, 64b ... Peeling nip member, 65 ... Support frame, 66 ... Halogen heater, 67 ... Lubricant application member, 68 ... Low friction sheet, 69 ... Temperature sensor, 70 ... Peeling auxiliary member, 80 ... Edge guide member, 801 ... Belt travel guide , 802 ... Flange, 803 ... Holding part, 90 ... Fixing roll gear, 100 ... Driving force passive part, 101, 102, 103, 201, 202, 03, 204, 205, 206 ... transmission gear, 200 ... cam mechanism, 206a ... gear, 206b ... flange roll, 207, 300 ... shaft, 208, 209 ... cam, 210 ... actuator, 211 ... photosensor, 212 ... Roll roll, 400 ... Support lever, 401 ... Bearing, 403 ... Pressing mechanism

Claims (13)

A fixing device for fixing a toner image carried on a recording material,
A rotating member;
A belt member movable while contacting the rotating member;
A pressing member that presses the rotating member with a predetermined pressure from the inside of the belt member;
Pressure setting means for setting a state of pressing the rotating member with the predetermined pressure with respect to the pressing member and a state in which the pressing with the predetermined pressure on the rotating member is released;
A fixing device comprising: a speed adjusting unit that adjusts an operating speed when the pressure setting unit operates the pressing member.   The fixing according to claim 1, wherein the speed adjusting unit includes a rotating member disposed in a driving force transmission path of the pressure setting unit, and an elastic member pressed against the rotating member. apparatus.   The fixing device according to claim 2, wherein the rotating member is formed in a flange shape, and the elastic member is constituted by an elastic roll pressed against the rotating member.   The fixing device according to claim 2, wherein the elastic member is pressed against the rotating member with a predetermined amount of biting.   The fixing device according to claim 2, wherein the elastic member rotates in the same direction at a contact portion with the rotating member and at a peripheral speed substantially the same as a peripheral speed of the rotating member.   The fixing device according to claim 2, wherein the elastic member is disposed in a driving force transmission path of the pressure setting unit.   The fixing device according to claim 1, wherein the speed adjusting unit reduces an operation speed when the pressure setting unit sets the pressing member in a pressing state at the predetermined pressure. A fixing device for fixing a toner image carried on a recording material,
A rotating member;
A belt member movable while contacting the rotating member;
A pressing member that presses the rotating member with a predetermined pressure from the inside of the belt member;
Pressure setting means for setting a state of pressing the rotating member with the predetermined pressure with respect to the pressing member and a state of releasing the pressing with the predetermined pressure on the rotating member;
The pressure setting means includes an operating unit that moves the pressing member in the direction of the rotating member, a drive transmitting unit that transmits a driving force to the operating unit, and a speed adjusting unit that adjusts the operating speed of the operating unit. And a fixing device.   9. The fixing device according to claim 8, wherein the pressure setting unit includes the speed adjusting unit disposed at a coupling portion between the drive transmission unit and the operating unit.   The operating portion of the pressure setting means includes a shaft, a cam fixed to the shaft, a gear externally fitted to the shaft, receiving a driving force from the drive transmission portion, and externally fitted to the shaft. The fixing device according to claim 8, further comprising a flange that receives a braking force from the adjustment unit.   The fixing device according to claim 10, wherein the speed adjusting unit of the pressure setting unit includes an elastic roll pressed against the flange of the operating unit. 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 rotating member;
A belt member movable while contacting the rotating member;
A pressing member that presses the rotating member with a predetermined pressure from the inside of the belt member;
Pressure setting means for setting a state of pressing the rotating member with the predetermined pressure with respect to the pressing member and a state in which the pressing with the predetermined pressure on the rotating member is released;
An image forming apparatus comprising: a speed adjusting unit that adjusts an operating speed when the pressure setting unit operates the pressing member.   13. The image forming apparatus according to claim 12, wherein the speed adjusting unit is disposed in a driving force transmission path of the pressure setting unit.

Images