JP4725080B2 - Fixing apparatus and image forming apparatus - Google Patents

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 when 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.

  On the other hand, such a belt nip type fixing device employs a configuration in which an endless belt (belt member) is pressed against a fixing roll by a pressure member. Therefore, when the image forming apparatus is stopped, the pressure member 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 away from the fixing roll.

Japanese Patent No. 3298354 (pages 4-7)

By the way, in the pressure release mechanism used in the belt nip type fixing device described above, when releasing the pressing state of the pressure member and the fixing roll at a predetermined pressure, if the movement amount of the pressure member is set large, the pressure member The load received also increases. Therefore, in such a pressure release mechanism, the pressure member that does not completely separate the pressure member from the fixing roll and reduces the pressing force between the pressure member and the fixing roll within a range in which no dent remains on the surface of the fixing roll. The amount of movement is set. As a result, the load received by the pressure release mechanism can be reduced as much as possible.
Further, regarding the driving means for operating such a pressure release mechanism, the configuration of the entire fixing device becomes large and complicated if installed independently. Therefore, in the pressure release mechanism, a driving unit used for driving the fixing roll is used. That is, the pressure release mechanism is operated by rotating it in the direction opposite to the rotation direction of the fixing roll during the normal fixing operation. This makes it possible to reduce the size and cost of the fixing device.

  However, when the pressure release mechanism having the above-described configuration is adopted in the fixing device, a paper jam (jam) occurs in the fixing device, the image forming apparatus stops, and the pressure release mechanism sets the pressure release state. Even when the recording paper is operated, a slight pressing force remaining between the pressure member and the fixing roll acts on the jammed recording paper. For this reason, when an attempt is made to pull out a sheet for jamming, the fixing roll rotates due to the pressing force. At that time, if the sheet is pulled out in the direction in which the fixing roll is rotated in the reverse direction, the rotation of the fixing roll is transmitted to the pressure release mechanism, whereby the pressure release mechanism is activated and the pressure member is released from the pressure release state. It may switch to the setting state. In this case, the jammed recording paper is pressed between the pressure member and the fixing roll at a predetermined pressure during the normal fixing operation, and therefore the recording paper can be removed from the fixing device. There was a problem of difficulty.

  The present invention has been made to solve the technical problems as described above, and an object of the present invention is to provide a fixing device configured to press a belt member against a fixing roll with a predetermined pressure by a pressure member. It is to facilitate the paper removal process when a jam occurs.

  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, and a state in which the rotating member is pressed with a predetermined pressure against the pressing member and a predetermined pressure applied to the rotating member. The pressure setting means for setting the state in which the pressure is released and the switching means for switching the transmission of the driving force in the pressure setting means between connection and disconnection are provided.

Here, the switching means switches at least one gear in the gear train disposed in the pressure setting means between a state in which the gear train is coupled to the gear train and a state in which the gear coupling with the gear train is released. Can be characterized. In particular, the one gear may include a pushing member that pushes the gear into the gear train and an elastic member that biases the gear in a direction of releasing the gear from the gear train.
Further, the pressure setting means is configured to operate by receiving a driving force from the rotating member, and the switching means switches the transmission of the driving force from the rotating member between connection and disconnection. it can. In particular, the pressure setting means may be configured to operate by receiving a driving force from the rotating member when the rotating member rotates in a direction opposite to that during normal fixing operation. it can.

  The fixing device of the present invention is a fixing device that is detachably disposed on an image forming apparatus that forms a toner image on a recording material, and includes a rotating member and a belt member that is 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, and a state in which the rotating member is pressed against the pressing member with a predetermined pressure by receiving a rotational driving force from the rotating member; Pressure setting means for setting a state in which the pressing at the predetermined pressure against the rotating member is released, and the pressure setting means includes an operation mode for transmitting a rotational driving force from the rotating member, and a pressure from the rotating member. The non-operation mode in which the rotational driving force is not transmitted is set.

  Here, the pressure setting means is characterized in that the non-operation mode is set by releasing the gear coupling of at least one gear in the gear train disposed in the pressure setting means. it can. The pressure setting means may be characterized in that an operation mode is set when installed in the image forming apparatus main body and a non-operation mode is set when removed from the image forming apparatus main body.

  Further, the present invention is regarded as an image forming apparatus, and the image forming apparatus of the present invention is an image forming apparatus that forms a toner image on a recording material, and includes a toner image forming unit that forms a toner image and a toner image forming unit. A transfer unit that transfers the formed toner image onto the recording material; and a fixing unit that fixes the toner image transferred onto the recording material to the recording material and is detachably disposed on the image forming apparatus main body. The fixing means is operated by a rotation member, a belt member movable while being in contact with the rotation member, a pressing member that presses the rotation member with a predetermined pressure from the inside of the belt member, and a predetermined driving force. A pressure setting unit that sets 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 of the rotating member with the predetermined pressure is released; and a fixing unit that is attached to the image forming apparatus main body. In conjunction with, and characterized in that a switching means for switching to the blocking and connecting the transmission of driving force in the pressure setting means.

  Here, the switching unit of the fixing unit transmits the driving force to the pressure setting unit in a state where the fixing unit is installed in the image forming apparatus main body, and the fixing unit is detached from the image forming apparatus main body. The transmission of the driving force to the pressure setting means can be cut off. The fixing unit is mounted on a mounting member configured to be detachable with respect to the image forming apparatus main body, and the switching unit of the fixing unit is connected to transmission of driving force in conjunction with the mounting / detaching of the mounting member. It can also be characterized by switching to blocking. Further, the fixing means switching means sets at least one gear in the gear train disposed in the pressure setting means to be in a gear-coupled state with the gear train when the fixing means is installed in the image forming apparatus main body. Further, when the fixing unit is detached from the main body of the image forming apparatus, a state where the gear coupling with the gear train is released can be set.

  According to the present invention, in the fixing device configured to press the belt member against the fixing roll with a predetermined pressure by the pressure member, it is possible to facilitate the paper removal process when a paper jam occurs.

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 in a substantially straight line from the upstream side of the intermediate transfer belt 15 in the order of yellow (Y), magenta (M), cyan (C), and black (K). 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) excellent in 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 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. And it is formed so that the surface resistivity may be 10 ⁷ to 10 ¹⁰ Ω / □, 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 63a and the downstream belt guide member 63b, 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 move to the direction which leaves | separates.

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, but a fluororesin is suitable from the viewpoint of the releasability 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 fluororubber, 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. 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. In order to achieve this, a pressure release mechanism is provided that moves the entire endless belt 62 in a direction in which it is separated from the fixing roll 61. 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 that the transmission gear 206 is externally fitted to, and a shaft 207 The cam 208 and the cam 209 are externally fitted.
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. The cam 208 (and the cam 209) is rotated from the initial position to a predetermined angle by the rotation of the shaft 207. 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 moves away 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 from the predetermined angle to the initial 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 photo sensor (not shown) is disposed in the movement region of the actuator 210. As the actuator 210 rotates with the rotation of the shaft 207, the actuator 210 crosses the photosensor, 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 200 is transmitted to rotate cam 208 and cam 209 by half a cycle. Accordingly, the edge guide member 80 can be swung via the support lever 400, and the pressure pad 64, the fixing roll 61, and the endless belt 62 are moved in a direction in which the endless belt 62 contacts and separates from the fixing roll 61. It is possible to selectively set the pressing state and the pressure releasing state at a predetermined pressure.

  In the pressure release mechanism disposed in the fixing device 60 of this embodiment, in the gear train that transmits the driving force from the fixing roll gear 90 of the driving force passive unit 100 to the shaft 300, the transmission gear 101, the transmission gear 103, The transmission gear 102 disposed between the transmission gear 102 and the transmission gear 103 is configured to be slidable in the direction of the rotation axis, and the gear coupling between the transmission gear 101 and the transmission gear 103 can be released. In the driving force passive unit 100, transmission of the driving force from the fixing roll gear 90 to the shaft 300 can be blocked by releasing the gear coupling between the transmission gear 102 and the transmission gear 101 and the transmission gear 103. It is configured to be able to.

  FIG. 6 is a perspective view showing the configuration of the driving force passive unit 100. As shown in FIG. 6, the shaft 104 is pivotally supported by the transmission gear 102 and a pressing member 105 that presses the transmission gear 102 toward the gear train (inward direction) including the transmission gear 101 and the transmission gear 103. . Further, inside the transmission gear 102 (on the shaft 104 side), a spring member 107 that urges the transmission gear 102 in a direction (outward direction) to release the transmission gear 102 from the gear train including the transmission gear 101 and the transmission gear 103 along the shaft 104. Is arranged. One of the spring members 107 is in contact with a shaft holder 106 that supports the shaft 104, and the transmission gear 102 is urged outwardly with the shaft holder 106 as a base.

Next, the operation of the transmission gear 102 in the driving force passive unit 100 will be described. 7 shows a setting state (gear coupling state) when transmission gear 102 is gear-coupled to transmission gear 101 and transmission gear 103, and FIG. 8 shows gear coupling between transmission gear 101 and transmission gear 103. The setting state (gear release state) when is released is shown.
In the gear coupling state shown in FIG. 7, the outer end portion of the pushing member 105 is pressed from the side wall 120 of the image forming apparatus, and the transmission gear 102 is opposed to the pressing force of the spring member 107 from the transmission gear 101 and the transmission gear 103. It is pressed against the gear train side. Thereby, the transmission gear 102 is gear-coupled to the transmission gear 101 and the transmission gear 103, and the driving force is transmitted from the fixing roll gear 90 to the shaft 300 (see also FIG. 4).
This gear coupling state is a setting when the fixing device 60 is installed in the image forming apparatus in a normal state. That is, when the fixing device 60 is installed in the image forming apparatus in a normal state, the outer end portion of the pushing member 105 contacts the side wall 120 of the image forming apparatus, and the pushing member 105 is pressed from the side wall 120. Thus, as described above, the transmission gear 102 is set to be pressed against the gear train side.

On the other hand, in the gear released state shown in FIG. 8, the outer end portion of the pushing member 105 is separated from the side wall 120 of the image forming apparatus, and the transmission gear 102 is released from the pushing from the pushing member 105, thereby It moves to a position where it abuts against the stopper 110 by the pressing force of the member 107. Then, the gear train composed of the transmission gear 101 and the transmission gear 103 is released. As a result, the transmission gear 102 is disengaged from the transmission gear 101 and the transmission gear 103, so that the transmission of the driving force from the fixing roll gear 90 to the shaft 300 is blocked (see also FIG. 4).
This gear release state is a setting when the fixing device 60 is removed from the image forming apparatus. That is, the fixing device 60 is disposed in a drawer unit configured to be slidable with respect to the image forming apparatus main body. For example, when a paper jam occurs in the fixing device 60, the drawer unit 60 is arranged. By pulling out the whole from the image forming apparatus, the fixing device 60 is removed from the image forming apparatus, and the removal process of the jammed paper P is facilitated. When the entire drawer unit is pulled out from the image forming apparatus during jam processing or the like, since the fixing device 60 is separated from the image forming apparatus, the outer end portion of the pushing member 105 is separated from the side wall 120 of the image forming apparatus. As described above, the transmission gear 102 is released from the gear coupling between the transmission gear 101 and the transmission gear 103.

  By the way, 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 pressure release mechanism is activated, and the pressure pad 64 and the fixing roll 61 are predetermined. Release the pressure state. At this time, the pressure release mechanism operates the pressure pad 64 pressed against the fixing roll 61 in a direction in which the pressure pad 64 is brought into contact with and separated from the fixing roll 61, so that the pressure release mechanism fixes the pressure pad 64. When separating from the roll 61, the pressing force acting on the fixing roll 61 from the pressure pad 64 acts as a load on the pressure release mechanism. Therefore, if the amount of movement when separating the pressure pad 64 is increased, the load received by the pressure release mechanism is increased accordingly, which is not preferable. On the other hand, in the pressure release mechanism, the pressing force of the pressure pad 64 against the fixing roll 61 is reduced to such an extent that a dent when pressed by the pressure pad 64 does not remain as a history in a partial region of the surface of the fixing roll 61. This is sufficient, and it is not necessary to move the pressure pad 64 to a position where all the pressing force against the fixing roll 61 is released. From this point of view, in the pressure release mechanism of the present embodiment, the contact operation of the pressure pad 64 is performed so as to reduce the pressing force between the pressure pad 64 and the fixing roll 61 within a range where the surface of the fixing roll 61 is not recessed. Is doing.

However, when a jam of the paper P occurs in the fixing device 60, if the image forming apparatus stops and the pressure releasing mechanism is activated, the surface of the fixing roll 61 in the pressure releasing mechanism of the present embodiment is Since the pressing force between the pressure pad 64 and the fixing roll 61 is only reduced to such an extent that the pressure pad 64 and the fixing roll 61 are not depressed, the pressing force between the pressure pad 64 and the fixing roll 61 is not completely released. A slight residual pressing force acts between the fixing roller 61 and the fixing roll 61. Therefore, if the paper P is to be pulled out during the jam processing, the fixing roll 61 is rotated.
In that case, when the jammed paper P is pulled out from the paper discharge side of the fixing device 60, the rotation of the fixing roll 61 is the same as the rotation direction (normal rotation) of the normal operation. Even if the force is transmitted from the driving force passive unit 100 to the shaft 300, the cam mechanism unit 200 rotates idly even if the transmission gear 201 provided with the one-way clutch receives the rotation of the shaft 300, and the rotational driving force from the shaft 300. Is not transmitted to the cam mechanism unit 200. Therefore, the pressure release mechanism maintains the pressure release state, and the pressing force between the pressure pad 64 and the fixing roll 61 is in a low state, so that the jammed paper P can be easily removed.

On the other hand, when the jammed paper P is pulled out from the paper feeding side of the fixing device 60, the rotation of the fixing roll 61 is opposite to the normal operation rotation direction (forward rotation). When the rotational driving force 61 is transmitted from the driving force passive unit 100 to the shaft 300, in the cam mechanism unit 200, the transmission gear 201 including the one-way clutch rotates in response to the rotation of the shaft 300, The rotational driving force is transmitted to the cam mechanism unit 200.
Therefore, when the fixing roll 61 is rotated in the reverse direction, the cam mechanism unit 200 rotates the cam 208 and the cam 209 and operates to switch from the pressure release state to the pressure setting state. For this reason, the jammed paper P is subjected to a pressing force of a predetermined pressure that is normally applied between the pressure pad 64 and the fixing roll 61, so that it is difficult to remove the paper P.

Therefore, in the fixing device 60 of the present embodiment, when the drawer unit is pulled out from the image forming apparatus and the fixing device 60 is detached from the image forming apparatus in order to perform the jam processing, the driving force passive portion of the pressure release mechanism. In FIG. 100, the outer end portion of the pushing member 105 is separated from the side wall 120 of the image forming apparatus, and the transmission gear 102 is configured to be released from the gear coupling between the transmission gear 101 and the transmission gear 103 as described above. ing. Therefore, when the jammed paper P is pulled out from the paper feeding side of the fixing device 60, the rotation of the fixing roll 61 is reversed, but the rotation of the fixing roll 61 is not transmitted from the transmission gear 101 to the transmission gear 103. The cam mechanism 200 is not transmitted. Accordingly, since the pressure release mechanism does not operate so as to switch from the pressure release state to the pressure setting state, the pressure release mechanism maintains the pressure release state, and thus the jammed paper P can be easily removed.
As described above, in the pressure release mechanism provided in the fixing device 60 of the present embodiment, the transmission gear 102 is configured to be able to be released from the gear coupling between the transmission gear 101 and the transmission gear 103. The pressure release mechanism maintains the pressure release state even when the discharged paper P is pulled out from either the paper feed side or the paper discharge side of the fixing device 60, and the jammed paper P can be easily removed. It becomes.

  On the other hand, when the jam processing is completed and the drawer unit is installed in the image forming apparatus, the fixing device 60 is installed at a normal position of the image forming apparatus, and thus the outside of the pushing member 105 of the driving force passive unit 100. The end portion is installed so as to be pressed from the side wall 120 of the image forming apparatus. Thereby, transmission gear 102 is set to be pressed against the gear train side, and gear coupling is performed between transmission gear 101 and transmission gear 103. Therefore, it is possible to transmit the driving force from the fixing roll gear 90 to the shaft 300, the normal fixing operation is performed, and the pressure release mechanism is in a state of pressing the pressure pad 64 and the fixing roll 61 with a predetermined pressure. It is possible to selectively set the release of the pressed state at a predetermined pressure.

  As described above, in the fixing device 60 according to the present embodiment, the entire endless belt 62 is separated 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 pressure release mechanism is provided for movement. 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, in the pressure release mechanism provided in the fixing device 60 of the present embodiment, when the drawer unit is pulled out from the image forming apparatus and the fixing device 60 is removed from the image forming apparatus in order to perform jam processing, In the driving force passive portion 100 of the pressure release mechanism, the transmission gear 102 is configured to be released from the gear coupling between the transmission gear 101 and the transmission gear 103. Therefore, even when the jammed paper P is pulled out from either the paper feeding side or the paper ejection side of the fixing device 60, the jammed paper P can be easily removed. That is, when the jammed paper P is pulled out from the paper feeding side of the fixing device 60, the rotation of the fixing roll 61 is reversed, but the rotation of the fixing roll 61 is transmitted from the transmission gear 101 to the transmission gear 103. In other words, it is not transmitted to the cam mechanism unit 200. Accordingly, since the pressure release mechanism does not operate so as to switch from the pressure release state to the pressure setting state, the pressure release mechanism maintains the pressure release state, and thus the jammed paper P can be easily removed.

  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 method, for example, application to a fixing apparatus that fixes an unfixed toner image carried on a 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, 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. 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 structure of the driving force passive part. It is a figure showing the gear coupling state of the transmission gear. It is a figure showing the gear release state of the transmission gear.

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, 90 ... Fixing device, 61 ... Fixing roll, 62 ... Endless belt, 63a ... Upstream belt guide member, 63b ... Downstream belt guide member, 64 ... Pressure pad, 64a ... Prenip member 64b ... peeling nip member, 65 ... support frame, 66 ... halogen heater, 67 ... lubricant application member, 68 ... low friction sheet, 69 ... temperature sensor, 70 ... peeling aid member, 80 ... edge guide member, 801 ... belt Traveling guide part, 802... Flange part, 803 .. holding part, 90... Fixing roll gear, 100... Driving force passive part, 101, 102, 103, 201, 2 2, 203, 204, 205, 206 ... transmission gear, 104 ... shaft, 105 ... pushing member, 106 ... shaft holder, 107 ... spring member, 110 ... stopper, 120 ... side wall, 200 ... cam mechanism, 207, 300 ... Shaft, 208, 209 ... cam, 210 ... actuator, 400 ... support lever, 401 ... bearing

Claims (12)

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;
The actuator is operated by a predetermined driving force, and a pressing state in which the rotating member is pressed with the predetermined pressure and a released state in which the pressing with the predetermined pressure with respect to the rotating member is released are set with respect to the pressing member. Pressure setting means;
And a switching means for switching those piezoelectric setting means and the cutoff state of not performing the transmission of the connection state and the driving force that allows the transmission of the driving force in the pressure setting means,
When performing a fixing operation for fixing the toner image carried on the recording material, the switching unit sets the pressure setting unit to the connected state, and the pressure setting unit sets the pressing member to the pressed state.
When the fixing operation is not performed, the switching unit sets the pressure setting unit to the connected state, the pressure setting unit sets the pressing member to the released state,
When the recording material is clogged, the pressure setting unit sets the pressing member to the released state, and the switching unit sets the pressure setting unit to the blocking state . The pressure setting means includes a gear train composed of a plurality of gears,
Said switching means, when said connection state of said pressure setting means from the cutoff state, at least one gear in said gear train, and the gear train and state gear bound, the a person piezoelectric setting means when the connection state with the cut-off state, the fixing device according to claim 1, characterized in that a state of releasing the gear coupling with the gear train.   The fixing device according to claim 2, wherein the first gear includes a pushing member that pushes the gear into the gear train, and an elastic member that biases the gear in a direction of releasing the gear from the gear train.   The pressure setting means is configured to operate by receiving the driving force from the rotating member when the rotating member rotates in a direction opposite to that during normal fixing operation, and is in the connected state. The driving force from the rotating member can be transmitted when the rotating member is transmitted, and the driving force from the rotating member cannot be transmitted when the shut-off state is established. 4. The fixing device according to claim 1. Said pressure setting means, when the pressing member was the release state, wherein by using the pressing member, and wherein the contacting said rotating member and the belt member in weaker pressure than the pressing state Item 5. The fixing device according to any one of Items 1 to 4. A fixing device that is detachably disposed in an image forming apparatus that forms a toner image 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;
By receiving a rotational driving force from the rotating member, a pressing state in which the rotating member is pressed against the pressing member with the predetermined pressure, and a release in which the pressing with respect to the rotating member at the predetermined pressure is released. Pressure setting means for setting the state,
The pressure setting means, when installed in the image forming apparatus main body, sets the pressing member in the pressing state and transmits a rotational driving force from the rotating member to the pressing member; A second mode in which the pressing member is set in the released state and the rotational driving force from the rotating member is transmitted to the pressing member when the pressing member is installed in the image forming apparatus main body; And a third mode in which the pressing member is set in the released state and the rotational driving force from the rotating member is not transmitted to the pressing member.   The pressure setting means includes a gear train composed of a plurality of gears, and in the third mode, the gear coupling of at least one gear in the gear train is performed in accordance with the removal from the image forming apparatus main body. The fixing device according to claim 6, wherein the fixing device is released.   The pressure setting means, when the release state is set with respect to the pressing member, uses the pressing member to bring the rotating member and the belt member into contact with a pressure weaker than the pressing state. The fixing device according to claim 6 or 7. An image forming apparatus for forming a toner image on a recording material,
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 the toner image transferred onto the recording material to the recording material, and fixing means detachably disposed on the image forming apparatus main body,
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;
The actuator is operated by a predetermined driving force, and a pressing state in which the rotating member is pressed with the predetermined pressure and a released state in which the pressing with the predetermined pressure with respect to the rotating member is released are set with respect to the pressing member. Pressure setting means;
And a switching means for switching those piezoelectric setting means and the cutoff state of not performing the transmission of the connection state and the driving force that allows the transmission of the driving force in the pressure setting means,
When performing a fixing operation for fixing the toner image transferred to the recording material by the toner image forming unit and the transfer unit, the switching unit sets the pressure setting unit to the connected state, and the pressure setting unit The pressing member is in the pressing state,
When the fixing operation is not performed, the switching unit sets the pressure setting unit to the connected state, the pressure setting unit sets the pressing member to the released state,
An image forming apparatus, wherein when the recording material is clogged, the pressure setting unit sets the pressing member to the released state, and the switching unit sets the pressure setting unit to the blocking state . The fixing unit is mounted on a mounting member configured to be detachable from the image forming apparatus main body,
The fixing unit switching unit sets the pressure setting unit to the connected state when the fixing unit mounted on the mounting member is installed in the main body of the image forming apparatus, and sets the fixing unit on the mounting member. The image forming apparatus according to claim 9, wherein when the fixed fixing unit is removed from the main body of the image forming apparatus, the pressure setting unit is set in the blocking state. The pressure setting unit of the fixing unit includes a gear train composed of a plurality of gears,
Said switching means of said fixing means, at least one gear in said gear train, at the time of installation into the image forming apparatus main body of the fixing means to said connected state to those piezoelectric setting means from the blocking state A state in which the gear train is released from the gear train in order to change the pressure setting device from the connected state to the disconnected state when the fixing device is removed from the image forming apparatus main body. the image forming apparatus according to claim 9 or 10 further characterized in that a. Said pressure setting means of said fixing means, when the pressing member was the released state, by using the pressing member, the said rotating member and the belt member contacting with weaker pressure than the pressing state The image forming apparatus according to claim 9, wherein the image forming apparatus is an image forming apparatus.

Images