JP2019159246A - Fixing device and image forming device - Google Patents

Abstract

To easily rotate a fixing member in a reverse direction than at the time of fixing operation and smoothly carry out removal operation to for removing foreign matter accumulated between the fixing member and a separation member.SOLUTION: Provided is a fixing device 12 comprising: a fixing roller 18; a pressure roller 19 for forming a nip part between the fixing roller 18 and itself; a separation member for coming in contact with the fixing roller 18 and separating paper P from the fixing roller 18; and a contact separation mechanism 90 for moving the pressure roller 19 closer to or away from the fixing roller 18. The pressure roller 19 is provided switchably between a pressurizing state where it is brought closer to the fixing roller 18 and a depressurizing state where it is more part from the fixing roller 18 than in the pressurizing state by contact separation motion of the contact separation mechanism 90. When rotation in which the fixing roller 18 conveys paper P is defined as forward rotation motion and rotation reverse thereto is defined as reverse rotation motion, the pressure roller 19 is placed in a depressurizing state at other than the motion for fixation to paper P and the fixing roller 18 is rotated in forward by a prescribed amount after being rotated in reverse by a prescribed amount.SELECTED DRAWING: Figure 26

Description

  The present invention relates to a fixing device and an image forming apparatus.

  Generally known fixing devices are provided with a separating member for separating the recording medium that has passed through the fixing nip from the fixing member.

  Among such separating members, in particular, in a configuration in which the recording medium is separated from the fixing member by bringing the separating member into contact with the fixing member, foreign matters such as toner accumulate between the fixing member and the separating member. Then, the accumulated foreign matter is carried to the fixing nip by the rotation operation of the fixing member, and has a problem that it adheres to the surface of the recording medium during the separation operation of the recording medium.

  For example, in Patent Document 1 (Japanese Patent Laid-Open No. 2000-159407), such a problem is caused by causing the fixing roller to perform a reverse operation in which the fixing roller rotates in a direction opposite to the conveyance direction of the recording medium. Is conveyed upstream to prevent foreign matter from accumulating at the contact portion between the fixing roller and the separation claw.

  In the conventional configuration, a sufficient rotational force can be transmitted from the drive source to the fixing member in the rotational direction during the normal fixing operation, but a sufficient rotational force can be applied to the fixing member in the reverse direction. In other words, the foreign matter accumulated between the fixing member and the separating member cannot be removed smoothly.

  In view of such circumstances, the present invention has an object to smoothly carry out a removing operation in which the fixing member is easily rotated in the direction opposite to that during the fixing operation, and foreign matter accumulated between the fixing member and the separating member is removed. It is said.

  In order to solve the above problems, the present invention provides a fixing member, a pressure member that forms a nip portion between the fixing member, and a separation that contacts the fixing member and separates the recording medium from the fixing member. A fixing device including a member and a contact / separation mechanism for contacting and separating the pressure member with respect to the fixing member, wherein the pressure member is moved by the fixing member by the contact / separation operation of the contact / separation mechanism. A pressurizing state approaching and a depressurizing state further away from the fixing member than the pressurizing state are provided so as to be switchable, and the rotation of the fixing member in the direction in which the recording medium is conveyed is forwardly rotated. Assuming that the rotation in the opposite direction is a reverse rotation operation, the fixing member is reversely rotated by a predetermined amount and then the predetermined amount after the pressure member is in the depressurized state, except during the fixing operation to the recording medium. It is characterized by forward rotation.

  In the present invention, in addition to the fixing operation to the recording medium, the fixing member is rotated in the reverse pressure and the normal rotation in the depressurized state, thereby rotating the fixing member with a smaller rotational torque, so that the fixing member and the separation claw Foreign matter accumulated in the meantime can be removed.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. 1 is a schematic configuration diagram of a fixing device. FIG. 3 is a perspective view of the front side of the fixing device as viewed obliquely from above. FIG. 3 is a side view of the fixing device viewed from the left side. FIG. 2 is a schematic cross-sectional view of the apparatus main body with the fixing device mounted. It is the schematic of the guide rail provided in the apparatus main body. It is a figure which shows an example of how to hold a handle part. It is a figure which shows a mode that a fixing device is removed. It is a figure which shows a mode that a fixing device is removed. It is a figure which shows a mode that a fixing device is removed. It is a figure which shows the state which closed the opening / closing cover. FIG. 4 is a perspective view of the fixing device with an upper portion removed. FIG. 4 is a side view illustrating a configuration around a contact / separation mechanism provided in the fixing device. It is a schematic block diagram of the drive system of the contact-separation mechanism which concerns on this embodiment. It is a figure for demonstrating the separation operation | movement of the pressure roller by a cam member. It is a figure for demonstrating the approaching operation of the pressure roller by a cam member. 2 is a perspective view of a drive transmission mechanism provided in the image forming apparatus main body. FIG. It is a front view of a 1st transmission gear. It is a front view of a 2nd transmission gear. It is a figure which shows the 1st transmission gear and the 2nd transmission gear at the time of forward rotation operation | movement. It is a figure which shows the 1st transmission gear at the time of reverse rotation operation | movement, and a 2nd transmission gear. It is ZZ sectional drawing of FIG. 21a. It is a figure equivalent to the ZZ sectional view of Drawing 21c. It is a figure explaining taking-out of jam paper. FIG. 4 is a diagram for explaining adhesion of foreign matter accumulated between a fixing roller and a separation member to a sheet. It is a figure for demonstrating the removal operation | movement of the foreign material of this embodiment. It is a figure explaining reverse rotation operation in a decompression state.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

  FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. First, the overall configuration and operation of the image forming apparatus will be described with reference to FIG.

  The image forming apparatus shown in FIG. 1 is a monochrome image forming apparatus. A process unit 1 as an image forming unit is detachably mounted on the apparatus main body (image forming apparatus main body) 100. The process unit 1 visualizes a photoreceptor 2 as an image carrier that carries an image on the surface, a charging roller 3 as a charging unit that charges the surface of the photoreceptor 2, and a latent image on the photoreceptor 2. A developing device 4 as a developing unit and a cleaning blade 5 as a cleaning unit for cleaning the surface of the photoreceptor 2 are provided. Further, an LED head array 6 as an exposure unit that exposes the surface of the photoconductor 2 is disposed at a position facing the photoconductor 2.

  The process unit 1 is detachably mounted with a toner cartridge 7 as a powder container for storing toner, which is powder for image formation. The toner cartridge 7 includes an unused toner storage unit 8 that stores unused toner, and a waste toner storage unit 9 that stores used waste toner.

  In addition, the image forming apparatus includes a transfer device 10 that transfers an image to a sheet as a recording medium, a paper feeding device 11 that supplies the sheet, a fixing device 12 that fixes the image transferred to the sheet, and a sheet outside the apparatus. And a pair of registration rollers 17 as timing rollers.

  The transfer device 10 includes a transfer roller 14 as a transfer member. The transfer roller 14 is disposed so as to come into contact with the photoreceptor 2 in a state where the process unit 1 is mounted on the apparatus main body 100. The transfer roller 14 is connected to a power source (not shown) so that a predetermined direct current voltage (DC) and / or alternating current voltage (AC) is applied.

  The paper feeding device 11 includes a paper feeding cassette 15 that stores paper P and a paper feeding roller 16 that feeds the paper P stored in the paper feeding cassette 15.

  The fixing device 12 includes a fixing roller 18 as a fixing member that fixes an image on a sheet, and a pressure roller 19 as a pressure member that is disposed to face the fixing roller 18. The fixing roller 18 is heated by a heating means such as a heater. The pressure roller 19 is pressed toward the fixing roller 18 and contacts the fixing roller 18 to form a fixing nip.

  The paper discharge device 13 includes a pair of paper discharge rollers 20 that discharge the paper to the outside of the device. Further, a paper discharge tray 21 for placing the paper discharged by the paper discharge roller 20 is formed on the upper surface of the exterior of the apparatus main body 100.

  Further, in the apparatus main body 100, a paper discharge roller 20 is supplied from a paper feed cassette 15 through a registration roller 17, an image transfer portion (transfer nip) between the transfer roller 14 and the photoreceptor 2, and a fixing device 12. A transport path R1 for transporting the paper P is provided. Further, the image forming apparatus 100 is provided with a double-sided conveyance path R2 for conveying the paper P that has passed through the fixing device 12 to the image transfer unit again when performing double-sided printing.

Next, an image forming operation of the image forming apparatus according to the present embodiment will be described with reference to FIG.
When the image forming operation is started, the photosensitive member 2 is rotationally driven, and the surface of the photosensitive member 2 is uniformly charged to a predetermined polarity by the charging roller 3. Next, the LED head array 6 exposes the charged surface of the photoreceptor 2 based on image information from a reader or a computer, and an electrostatic latent image is formed. Then, the toner is supplied to the electrostatic latent image on the photoconductor 2 by the developing device 4, whereby the electrostatic latent image is visualized (visualized) as a toner image.

  When the image forming operation is started, the paper feed roller 16 starts to rotate and the paper P is sent out from the paper feed cassette 15. The fed paper P is temporarily stopped by the registration roller 17. Thereafter, rotation of the registration roller 17 is started at a predetermined timing, and the paper P is conveyed to the image transfer unit in accordance with the timing at which the toner image on the photoconductor 2 reaches the image transfer unit.

  Then, when the paper P is conveyed to the image transfer unit, the toner image on the photosensitive member 2 is transferred onto the paper P by a transfer electric field generated by applying a predetermined voltage to the transfer roller 14. At this time, the toner on the photosensitive member 2 that has not been transferred to the paper P is removed by the cleaning blade 5 and collected in the waste toner container 9 of the toner cartridge 7.

  The paper P on which the toner image has been transferred is conveyed to the fixing device 12 and heated and pressurized by passing through a fixing nip formed by the fixing roller 18 and the pressure roller 19, and the toner on the paper P The image is fixed. Then, the paper P is discharged out of the apparatus by the paper discharge roller 20 and placed on the paper discharge tray 21.

  Further, when performing duplex printing, the paper P that has passed through the fixing device 12 is switched back without being discharged out of the device, and is sent to the duplex conveyance path R2. The sheet P passes through the double-sided conveyance path R2 and is sent to the conveyance path R1 on the near side of the registration roller 17, and is conveyed again to the image transfer unit by the registration roller 17. Then, after the image is transferred to the back surface of the paper P and the image on the back surface side is fixed by the fixing device 12, the paper P is discharged out of the device.

FIG. 2 is a schematic cross-sectional view of the fixing device 12.
As shown in FIG. 2, the fixing device 12 includes a resin frame member 23 that constitutes an exterior portion in which the fixing roller 18 and the pressure roller 19 are housed, and a separation member that separates the paper P from the fixing roller 18. Separating claws 24. An inlet 23a for allowing the paper to enter the fixing device 12 is formed on the front surface of the frame member 23, and an outlet 23b for discharging the paper from the fixing device 12 is formed on the back surface of the frame member 23. ing. Here, the “front” of the fixing device 12 refers to the front of the image forming apparatus in a state where the fixing device 12 is mounted on the image forming apparatus, that is, an operation unit (operating panel) provided on the image forming apparatus by an operator. Etc.) means the surface on the side that stands when issuing a print instruction. Further, a halogen heater 22 as a heating element is provided in the fixing roller 18. The pressure roller 19 is pressed against the fixing roller 18 by a pressure lever described later, and a fixing nip N is formed at a position where the fixing roller 18 and the pressure roller 19 are in pressure contact with each other.

  The separation claw 24 is provided at a position facing the fixing roller 18, and a tip 24 a protruding toward the fixing roller 18 is in contact with the surface of the fixing roller 18.

  When a driving force is transmitted from the driving source on the apparatus main body 100 side to the fixing roller 18, the fixing roller 18 is rotationally driven in the direction indicated by an arrow A1 in FIG. Further, the pressure roller 19 is configured to be driven to rotate in the direction indicated by the arrow B1 in FIG. In contrast to this embodiment, the pressure roller 19 may be a driving roller and the fixing roller 18 may be a driven roller. In the following description, rotation of the fixing roller 18 in the direction of arrow A1 is referred to as forward rotation, and rotation in the opposite direction is referred to as reverse rotation.

The operation of the fixing device 12 will be briefly described with reference to FIG.
The fixing roller 18 is heated to a predetermined temperature by the radiant heat generated from the halogen heater 22, and the fixing nip 18 and the pressure roller 19 are rotating, so that the sheet is fixed from the direction indicated by the arrow C1 in FIG. When entering N, the sheet is conveyed while being sandwiched between the fixing roller 18 and the pressure roller 19. At this time, the unfixed image on the paper is heated by the heat of the fixing roller 18 and is pressed by the fixing roller 18 and the pressure roller 19, whereby the image is fixed on the paper. Then, the sheet on which the image is fixed is separated from the surface of the fixing roller 18 by the separation claw 24 and discharged in the direction of arrow C2 in FIG.

  As shown in FIG. 3, the frame member 23 is provided with a handle portion 71 that is held by an operator when the fixing device 12 is attached to and detached from the apparatus main body 100. The handle portion 71 is provided at each of the left and right end portions of the back surface of the frame member 23.

  The pair of handle portions 71 are configured to be symmetrical to each other. Specifically, each handle portion 71 has a grip portion 71a extending in the vertical direction and a pair of arm portions 71b extending forward (front side) from the upper end portion and the lower end portion of the grip portion 71a. It is fixed to the back surface of the frame member 23 via a pair of arm portions 71b. And between each holding part 71a and the back surface of the frame member 23, space part S1 in which an operator can insert a hand or a finger | toe is formed.

  Further, the frame member 23 is provided with a plurality of positioning portions 77 to 79 for positioning the fixing device 12 with respect to the apparatus main body 100. The plurality of positioning portions 77 to 79 include a first positioning projection 77 provided at the front right end portion of the frame member 23 and a pair of second positioning projections provided on the front side of the left side surface and the right side surface of the frame member 23. 78 and a pair of third positioning projections 79 provided on the left side and the back side of the right side of the frame member 23, respectively.

  Further, on the left side surface and the right side surface of the frame member 23, there are guide projections 80 as convex guide portions that are guided along a main body side guide portion described later when the fixing device 12 is attached to and detached from the device main body 100. Is provided. Each guide protrusion 80 is formed in a rectangle (substantially rectangular or substantially square), and functions as sliding surfaces 80a and 80b on which the upper and lower planes slide with respect to the main body side guide portion. In particular, in this embodiment, when the fixing device 12 is attached / detached, a portion other than the guide protrusion 80 in the fixing device 12 does not slide with respect to the apparatus main body 100 (does not exhibit the guide function), thereby reducing the sliding resistance. The operability is improved.

FIG. 4 is a side view of the fixing device 12 as viewed from the left side.
As shown in FIG. 4, the fixing device 12 is provided with a lock portion 83 that fixes the fixing device 12 so as not to be detached when the fixing device 12 is attached to the apparatus main body 100. The lock part 83 is provided in a part of a turning member 81 that is rotatably provided on the handle part 71. The rotation member 81 is formed in a substantially L shape, and a lock portion 83 is provided at the tip of a portion extending forward (front side) from the rotation center (fulcrum 82). On the other hand, a portion extending upward from the rotation center (fulcrum 82) of the rotation member 81 is an operation unit 84 for the operator to rotate the rotation member 81.

  The lock portion 83 is always urged downward by a coil spring 85 as an urging member disposed between the upper surface thereof and the lower surface of the frame member 23. Therefore, in a state where the rotation member 81 is not rotated by the operator, the lower portion of the rotation member 81 abuts on the bottom 71c of the lower arm portion 71b, and the distal end portion (lower end portion) of the lock portion 83 is lowered. The arm portion 71b on the side is held in a state of protruding greatly downward (a state indicated by a solid line in FIG. 4) below the bottom portion 71c. In this state, the lock portion 83 is in a lockable state in which it can be engaged with an engagement portion described later provided on the apparatus main body 100 side.

  On the other hand, when the operator rotates the rotating member 81 counterclockwise in FIG. 4 against the urging force of the coil spring 85, the distal end portion of the lock portion 83 is retracted upward, and the apparatus body It becomes the lock impossible state (state shown with the dashed-two dotted line in FIG. 4) which does not engage with the engaging part of 100 side. Thus, the operator can switch the lock unit 83 between the lockable state and the lock disabled state by operating the operation unit 84 and rotating the rotation member 81. The rotating member 81 is also provided on the right handle 71 in the same manner.

FIG. 5 is a schematic cross-sectional view of the apparatus main body 100 with the fixing device 12 mounted.
As shown in FIG. 5, an opening / closing cover 101 is provided on the back surface (left surface in the drawing) of the apparatus main body 100. The opening / closing cover 101 opens and closes by rotating in the direction of arrow H in FIG. The state shown in FIG. 5 is a state in which the opening / closing cover 101 is opened and an opening 102 is formed on the back surface of the apparatus main body 100. In this state, the fixing device 12 can be removed rearward from the opening 102. The method for attaching and detaching the fixing device 12 will be described in detail later.

  In addition, the open / close cover 101 is integrally provided with a double-sided conveyance unit 104 that constitutes a part of the double-sided conveyance path R2. For this reason, as shown in FIG. 5, when the opening / closing cover 101 is opened, the duplex conveying unit 104 rotates together with the opening / closing cover 101 and is retracted from the vicinity of the back surface of the fixing device 12.

  A pair of guide rails 103 are provided on the inner surfaces of the left and right side walls of the apparatus main body 100 as main body side guide portions for guiding the fixing apparatus 12 when the fixing apparatus 12 is attached to and detached from the apparatus main body 100. . Each guide rail 103 has an upper guide surface 103a and a lower guide surface 103b. When the fixing device 12 is attached or detached, the fixing device 12 is guided by sliding the upper sliding surface 80a and the lower sliding surface 80b of the guide projection 80 with respect to the guide surfaces 103a and 103b. .

  Further, as shown in FIG. 6, the upper guide surface 103a and the lower guide surface 103b of each guide rail 103 are formed on the back side horizontal planes 105a and 105b extending in the substantially horizontal direction on the back side far from the opening 102 and the back side. It has front side inclined surfaces 106a and 106b that extend while being inclined upward from the side horizontal surfaces 105a and 105b toward the opening 102 side (front side). Furthermore, the lower guide surface 103b has a front horizontal surface 107b arranged in a substantially horizontal direction on the front side closer to the opening 102 than the front inclined surface 106b.

  As shown in FIG. 5, the apparatus main body 100 is provided with a plurality of main body side positioning portions 108 to 110 that position the fixing device 12 with respect to the apparatus main body 100. The plurality of main body side positioning units 108 to 110 are engaged with a first positioning projection 77 provided on the fixing device 12 to fix the fixing device 12 in the left-right direction, and the fixing. A second main body side positioning portion 109 that engages with a second positioning protrusion 78 provided in the apparatus 12 to mainly position the fixing apparatus 12 in the forward and vertical directions, and a third positioning provided in the fixing apparatus 12. The third main body side positioning unit 110 is engaged with the projection 79 and performs positioning in the rotational direction mainly around the second positioning projection 78 of the fixing device 12.

  Further, the apparatus main body 100 is provided with an engaging portion 111 that engages with the lock portion 83 of the fixing device 12. The state shown in FIG. 5 is a state in which the lock portion 83 is engaged with the engaging portion 111, and in this state, the rearward positioning of the fixing device 12 is performed and the movement in the separation direction is restricted.

Hereinafter, a method for attaching and detaching the fixing device 12 will be described.
When removing the fixing device 12 from the apparatus main body 100, first, as shown in FIG. 5, the open / close cover 101 is opened. Then, the handle 71 is grasped with both hands through the opening 102 of the apparatus main body 100. For example, as shown in the example shown in FIG. 7, the operator places his thumb on the upper arm 71 b of the handle 71 and holds the grip 71 a and the operation unit 84 together with other fingers. In this state, by pulling and rotating the operation portion 84 in the direction of arrow J in FIG. 7, the engagement of the lock portion 83 with the engagement portion 111 on the apparatus main body 100 side is released. Then, the fixing device 12 is pulled in the disengagement direction (the direction of the arrow K in FIG. 7) while keeping the lock portion 83 in the unlocked state (unlockable state).

  As a result, as shown in FIG. 8, the fixing device 12 moves in the left direction (withdrawal direction) along the guide rail 103 on the apparatus main body 100 side, and the positioning protrusions 77 to 79 provided on the fixing device 12. Is disengaged from the apparatus main body side positioning portions 108 to 110 on the apparatus main body 100 side. When the fixing device 12 starts to move, the guide projection 80 of the fixing device 12 initially slides with respect to the back horizontal surfaces 105a and 105b of the guide rail 103, and the fixing device 12 moves in a substantially horizontal direction. . Next, as shown in FIG. 9, the guide protrusion 80 slides with respect to the front inclined surfaces 106a and 106b of the guide rail 103, so that the fixing device 12 moves obliquely upward. Thereafter, as shown in FIG. 10, the fixing device 12 is completely pulled out from the apparatus main body 100 and removed.

  Thus, in the present embodiment, the fixing device 12 can be guided and removed obliquely upward so as not to contact the double-sided conveyance unit 104. If the fixing device 12 is configured to be guided only in the horizontal direction, the mounting position of the fixing device 12 and the upper end position of the opening 102 are set in order to avoid contact of the fixing device 12 with the duplex conveyance unit 104. The height of the apparatus main body 100 becomes high. On the other hand, in this embodiment, the fixing device 12 can be prevented from coming into contact with the duplex conveying unit 104 without increasing the mounting position of the fixing device 12 or the upper end position of the opening 102. The height of the apparatus main body 100 can be reduced, and the size can be reduced.

  Next, when the fixing device 12 is attached to the apparatus main body 100, the procedure may be the reverse of the procedure at the time of removal. That is, while holding the handle portion 71 and the operation portion 84, the fixing device 12 is inserted into the apparatus main body 100 along the guide rail 103, and the positioning protrusions 77 to 79 are engaged with the main body side positioning portions 108 to 110. At the time of joining, the force to grip the handle portion 71 and the operation portion 84 is loosened. As a result, the lock portion 83 is engaged with the engagement portion 111 on the apparatus main body 100 side by the urging force of the coil spring 85, and a locked state is established. In the present embodiment, when the driving force is transmitted to the fixing device 12 thereafter, it is mounted between the driving gear provided on the apparatus main body 100 side and the fixing gear provided at the end of the fixing roller 18. Since the directional force acts, the fixing device 12 is positioned more reliably.

  As shown in FIG. 11, in the present embodiment, when the open / close cover 101 is closed, the duplex conveyance unit 104 is disposed between the left and right handle portions 71. Thus, by disposing the double-sided conveyance unit 104 between the handle parts 71, the space between the handle parts 71 can be effectively used as a part of the double-sided conveyance path R2, and further miniaturization can be achieved.

Hereinafter, a contact / separation mechanism provided in the fixing device 12 for separating the pressure roller from the fixing roller and its peripheral configuration will be described.
12 is a perspective view of the fixing device 12 with the upper portion of the exterior portion removed, and FIG. 13 is a side view of the fixing device.

  As shown in FIG. 12, metal support members 25 are attached to one end side and the other end side in the longitudinal direction of the frame member 23. As shown in FIG. 13, the fixing roller 18 and the pressure roller 19 are rotatably supported by bearings 26 and 27 provided on each support member 25.

  The pressure roller 19 is supported by the support member 25 so as to be close to and away from the fixing roller 18 in the direction of arrow D in FIG. Specifically, a bearing 27 that supports the pressure roller 19 is fitted into a bearing guide portion 25b that is a rectangular hole provided in the support member 25, and the bearing 27 is moved along the bearing guide portion 25b. By being guided, the pressure roller 19 approaches and separates from the fixing roller 18. On the other hand, the bearing 26 that supports the fixing roller 18 is fitted into a bearing fitting portion 25a that is a circular hole provided in each support member 25, and the axial position of the fixing roller 18 is perpendicular to the axial direction. It has been fixed so as not to move.

  Further, the fixing device 12 according to the present embodiment includes a pressure lever 31 that presses the pressure roller 19 against the fixing roller 18 and a pressurizing member that biases the pressure lever 31 in the pressing direction. And a spring 32. One pressure lever 31 and one pressure spring 32 are provided on each side of the pressure roller 19. One end 31 a of the pressure lever 31 is attached to a support shaft 33 provided below the support member 25, and is configured to be rotatable about the support shaft 33 in the direction of arrow E in FIG. 13. Each pressure spring 32 is attached by being hooked to hooks 31 c and 25 c provided on the other end 31 b side of the pressure lever 31 and the upper portion of the support member 25. As a result, the other end 31b of the pressure lever 31 is held in a state of being always pulled upward in FIG. The pressure lever 31 presses the bearing 27 that supports the pressure roller 19 via the pad 34 fitted in the bearing guide portion 25 b of the support member 25, and applies the pressure roller 19 toward the fixing roller 18. Pressure.

  Further, the fixing device 12 according to the present exemplary embodiment includes a contact / separation mechanism 90 that moves the pressure roller 19 toward and away from the fixing roller 18. The contact / separation mechanism 90 mainly includes an optical sensor 51, a light shielding member 52, and the like as a rotation position detection unit that detects the rotation position (rotation angle) of the cam member 41 and the cam member 41.

  The cam member 41 is provided on each end of the rotating shaft 42 that is rotatably supported by the pair of support members 25. When the rotating shaft 42 rotates, the pair of cam members 41 rotate integrally with the rotating shaft 42. The cam member 41 has a cam surface 41a whose distance from the rotation center changes in the rotation direction. When the pressure lever 31 is pulled by the pressure spring 32, the cam receiving portion (contact member) 31d provided on the pressure lever 31 is held in contact with the cam surface 41a. In this state, when the cam member 41 rotates in one direction, the pressure lever 31 is pushed downward in FIG. 13 by the cam surface 41a, whereby the pressure roller 19 is separated from the fixing roller 18, and the cam member When 41 reversely rotates, the pressure lever 31 is returned upward in FIG. 13 so that the pressure roller 19 approaches the fixing roller 18. The detailed contact / separation operation by the cam member 41 will be described later.

  The optical sensor 51 is a transmissive optical sensor and includes a light projecting unit that emits light and a light receiving unit that receives light emitted from the light projecting unit. The light shielding member 52 is a member to be detected whose rotational position is detected by the optical sensor 51 by rotating integrally with the cam member 41 to shield or transmit the irradiation light of the optical sensor 51 and switching the presence or absence of light reception. is there. The optical sensor 51 and the light shielding member 52 are provided only on one cam member 41 side of the two cam members 41.

  The cam surface 41a provided on the cam member 41 is formed such that the distance from the center of rotation gradually increases clockwise in the figure. The cam surface 41a is provided over a region larger than a half circumference (180 °) in the rotation direction. Specifically, in the present embodiment, the range from the lowest point e1 having the smallest distance from the rotation center of the cam surface 41a to the highest point e2 having the largest distance from the rotation center of the cam surface 41a is in a range of about 270 °. It is provided across. Further, the cam surface 41a has a step portion 41b whose distance from the rotation center changes abruptly with the uppermost point e2 as a boundary.

FIG. 14 is a schematic configuration diagram of a drive system of the contact / separation mechanism according to the present embodiment.
As shown in FIG. 14, the drive system includes a motor 43 as a drive mechanism, and a gear train 44 that transmits a drive force from the motor 43 to the cam member 41 and the light shielding member 52. In the present embodiment, a small and inexpensive DC brush motor is used as the motor 43. The gear train 44 is a first worm gear 45 attached to the output shaft of the motor 43, a second worm gear 46 that meshes with the first worm gear 45, and a drive transmission member provided integrally with the second worm gear 46. The first spur gear 47 and the second spur gear 48 that meshes with (engages with) the first spur gear 47 and that is integrally provided with the light shielding member 52. When the output shaft of the motor 43 rotates in one direction or in the opposite direction, the worm gears 45 and 46 and the spur gears 47 and 48 rotate, and the second spur gear 48 and the light shielding member 52 rotate integrally. Each cam member 41 rotates in one direction (the direction indicated by arrow F in FIG. 14) and the opposite direction (the direction indicated by arrow G in FIG. 14) via the rotation shaft 42.

  By the way, when two sheets of paper such as envelopes are passed through the fixing nip, if the fixing roller and the pressure roller are pressed with the same pressure as when plain paper is passed, the paper is wrinkled. there is a possibility. For this reason, when a sheet such as an envelope is passed, it is preferable to form the fixing nip with a pressing force smaller than a normal pressing force when passing plain paper.

  Therefore, in the fixing device according to the present embodiment, as described above, the pressure roller can be moved toward and away from the fixing roller, so that the pressing force in the fixing nip can be changed according to the paper type. . Hereinafter, the depressurization operation when depressurizing from the normal pressurization force and the pressurization operation when returning to the normal pressurization force will be described.

First, the contact / separation operation of the pressure roller 19 by the cam member 41 will be described.
15A shows a state where the cam receiving portion 31d of the pressure lever is in contact with the cam surface 41a on the lowest point e1 side. In this state, the pressure roller approaches the fixing roller and is pressurized with a normal pressure.

  When the cam member 41 is rotated counterclockwise in the drawing as shown in FIG. 15B from the state shown in FIG. 15A, the cam surface 41a slides against the cam receiving portion 31d. The contact position of the cam receiving portion 31d with respect to the cam surface 41a relatively moves from the lowest point e1 side to the highest point e2 side. Along with this, the cam receiving portion 31d is pushed downward by the cam surface 41a and the pressure lever is retracted from the bearing of the pressure roller, so that the pressure roller is separated from the fixing roller. Moving.

  As shown in FIG. 15C, when the contact position of the cam receiving portion 31d with the cam surface 41a reaches the uppermost point e2, the separation operation of the pressure roller with respect to the fixing roller is completed, and the addition at the fixing nip is completed. A depressurized state in which the pressure is smaller than the normal pressure is obtained. At this time, the rotation of the cam member 41 is stopped.

  On the contrary, from the depressurized state shown in FIG. 16A, the cam member 41 is rotated clockwise in the figure as shown in FIG. 16B (the direction opposite to the rotational direction at the time of depressurizing transition). When rotating, the cam surface 41a slides relative to the cam receiving portion 31d, and the contact position of the cam receiving portion 31d with respect to the cam surface 41a relatively moves from the uppermost point e2 side to the lowermost point e1 side. Along with this, the cam receiving portion 31d is pulled upward in the drawing by the urging force of the pressure spring, and the pressure lever presses the bearing of the pressure roller so that the pressure roller approaches the fixing roller. Move in the direction.

  Then, as shown in FIG. 16C, when the contact position of the cam receiving portion 31d with the cam surface 41a reaches the lowest point e1, the approaching operation of the pressure roller to the fixing roller is completed, and the fixing nip is completed. The pressure is returned to the normal pressurization state where the applied pressure is increased. At this time, the rotation of the cam member 41 is stopped.

  Thus, in the fixing device according to the present embodiment, the cam member 41 is rotated in one direction when the pressure roller is separated, and the cam member 41 is rotated in the reverse direction when the pressure roller is approached. Then, the pressing lever is pushed and moved using the same cam surface 41a. For this reason, in the cam member 41 which concerns on this embodiment, the cam surface 41a can be provided over an area | region larger than the half periphery of a rotation direction. Accordingly, even if the gradient of the cam surface 41a is made gentle, it is possible to avoid a decrease in the maximum height difference of the gradient, so that the cam surface can be secured while ensuring a sufficient distance between the pressure roller and the fixing roller. It is possible to moderate the slope of 41a and suppress the increase in rotational torque and the generation of operating noise (abnormal noise).

Next, the configuration of a drive transmission mechanism provided in the image forming apparatus main body for transmitting a driving force to the fixing roller will be described.
As shown in FIGS. 17A and 17B, the drive transmission mechanism 60 includes a shaft 61, a first transmission gear 62 and a second transmission gear 63 as drive transmission members, and a spring as an urging member. 64 mainly.

  The first transmission gear 62 has an insertion hole 62a into which the shaft 61 is inserted, and the second transmission gear 63 has an insertion hole 63a into which the shaft 61 is inserted.

  One end side of the shaft 61 is rotatably attached to a housing 65 provided in the image forming apparatus main body. A drive motor as a drive source is provided on one end side of the shaft 61, and the shaft 61 can be rotated by the driving force of the drive motor.

  One end of the spring 64 is fixed to a predetermined position of the shaft 61, and the other end 64 a is fixed to the housing 65.

  One end of the shaft 61 is provided by being inserted into the insertion hole 62a and the insertion hole 63a. In this state, the shaft 61 presses the first transmission gear 62 in the direction of arrow F by the urging force of the spring 64 wound around the shaft 61.

  When the driving motor on the image forming apparatus main body side is driven, the driving force is transmitted from the shaft 61 to the first transmission gear 62 and the first transmission gear 62 rotates. In a state where the first transmission gear 62 and the second transmission gear 63 are engaged with each other, the driving force is transmitted from the first transmission gear 62 to the second transmission gear 63.

  On the second transmission gear 63 side, a fixing roller and a gear for transmitting a driving force to the fixing roller are provided, and the driving force is transmitted from the second transmission gear 63. That is, the driving force of the drive motor is transmitted to the fixing roller via the shaft 61, the first transmission gear 62, the second transmission gear 63, the gear meshing with the fixing roller, and the fixing roller rotates.

  As shown in FIG. 18, the first transmission gear 62 has three ribs 62b, 62c, and 62d extending in the radial direction of the first transmission gear 62 from the insertion hole 62a side. Each rib is arranged with a phase shift of 120 degrees in the circumferential direction. Each rib has an inclined portion extending in the circumferential direction. The rib 62b has inclined portions 62b1 and 62b2, the rib 62c has inclined portions 62c1 and 62c2, and the rib 62d has inclined portions 62d1 and 62d2. The inclined surface provided in each inclined portion is an inclined surface that descends from one side (each rib side) in the circumferential direction toward the other side (see FIG. 17a).

  The contact surface X1 is provided on the surface opposite to the side on which the inclined surfaces of the ribs 62b, 62c, 62d are provided. The contact surface X1 is a flat surface provided in a direction perpendicular to the paper surface of FIG.

  As shown in FIG. 19, the second transmission gear 63 has three ribs 63b, 63c, 63d extending in the radial direction of the second transmission gear 63 from the outer wall 63a1 of the insertion hole 63a. Each rib is arranged with a phase shift of 120 degrees in the circumferential direction. Each rib has an inclined portion extending in the circumferential direction. The rib 63b has inclined portions 63b1 and 63b2, the rib 63c has inclined portions 63c1 and 63c2, and the rib 63d has inclined portions 63d1 and 63d2. The inclined surface provided in each inclined portion is an inclined surface that descends from one side (each rib side) in the circumferential direction toward the other side (see FIG. 17b).

  The abutted surface X2 is provided on the surface opposite to the side on which the inclined surface of each rib 63b, 63c, 63d is provided. The abutted surface X2 is a flat surface provided in a direction perpendicular to the paper surface of FIG.

  In addition, in the state where the first transmission gear 62 and the second transmission gear 63 are assembled to the shaft 61, the inclined portions 62b1, 62c1, 62d1 provided in the first transmission gear 62 and the inclination provided in the second transmission gear 63. The parts 63b1, 63c1, 63d1 are arranged concentrically (see FIG. 20). Further, the inclined portions 62b2, 62c2, 62d2 provided in the first transmission gear 62 and the inclined portions 63b2, 63c2, 63d2 provided in the second transmission gear 63 are arranged concentrically.

  The drive transmission mechanism described above applies only the rotational force in the positive rotation direction of the drive motor provided in the main body of the image forming apparatus in the pressure state of the pressure roller to the fixing roller (the cam member is in the state shown in FIG. 14A). It functions as a one-way clutch that transmits from the transmission gear 62 to the second transmission gear 63 and does not correctly transmit the rotational force in the reverse rotation direction. Hereinafter, the operation as the one-way clutch mechanism will be described.

  As shown in FIG. 20, when the driving force in the normal rotation direction of the fixing roller is transmitted from the driving motor of the image forming apparatus main body, the first transmission gear 62 rotates in the direction of arrow G1. By this rotation, the contact surface X1 of the first transmission gear 62 contacts the contacted surface X2 of the second transmission gear 63, and a force in the direction of the arrow G1 is applied to the second transmission gear 63. As a result, the first transmission gear 62 and the second transmission gear 63 are engaged with each other, and both the first transmission gear 62 and the second transmission gear 63 rotate in the direction of the arrow G1. With the rotation of the second transmission gear 63, the fixing roller rotates in the forward direction. In this way, the rotational force in the positive direction of the drive motor is transmitted to the fixing roller via the first transmission gear 62 and the second transmission gear 63. Although only the contact of the contact surface X1 provided on the rib 62b to the second transmission gear 63 side is illustrated, the contact surface X1 of the ribs 62c and 62d is similarly illustrated. It abuts against the abutted surface X2 provided on any of the ribs.

  On the other hand, as shown in FIG. 21A, when the driving force in the reverse rotation direction of the fixing roller is transmitted from the driving motor, the first transmission gear 62 rotates in the direction of arrow G2.

  FIGS. 21A to 21C are views showing a state in which the first transmission gear 62 rotates in the arrow G2 direction. FIG. 22 shows a ZZ cross-sectional view of FIG. In the following description, the operation of the inclined portion 62b1 of the rib 62b among the inclined portions provided in the first transmission gear 62 will be described.

  As shown in FIG. 21A, when the rib 62b is rotated toward the rib 63c by the rotation of the first transmission gear 62 in the direction of the arrow G2, the inclined portion 63c1 is changed to the inclined portion 62b1 as shown in FIG. Get on. At this time, as shown in FIG. 22, the first transmission gear 62 is pressed against the second transmission gear 63 by the biasing force F of the spring 64 (see FIG. 17a), and the first transmission gear 62 is moved to the arrow G2. By rotating in the direction, the inclined portion 63c1 receives a force in the direction of the arrow G2 from the inclined portion 62b1. Although only the inclined portion 62 b 1 is described here, each slope provided on the first transmission gear 62 is in contact with each slope of the second transmission gear 63. Each inclined surface is inclined in the rotational direction of the first transmission gear 62 with respect to the transmission direction of the driving force from the first transmission gear 62 to the second transmission gear 63.

  However, when the pressure roller is in a pressurized state and strongly pressed against the fixing roller (the state in which the pressure roller 19 is closer to the fixing roller 18 in FIG. 13), a large rotational torque is required to rotate the fixing roller. The force transmitted from the slope cannot obtain a force sufficient to rotate the fixing roller. That is, the second transmission gear 63 cannot be rotated in the direction of the arrow G2, and the inclined portion 63c1 relatively moves so as to slide on the inclined portion 62b1 (see the dotted line portion in FIG. 22), and FIG. ) → (b), only the first transmission gear 62 rotates in the direction of the arrow G2. In other words, the first transmission gear 62 idles with respect to the second transmission gear 63.

  At this time, as shown in FIG. 22, as the first transmission gear 62 rotates in the direction of the arrow C2, the inclined portion 63c1 climbs on the inclined surface of the inclined portion 62c1, so that the dotted line portion of FIG. As described above, the second transmission gear 63 moves relative to the first transmission gear 62 upward in the drawing. In other words, the first transmission gear 62 moves downward in the figure against the biasing force F of the spring, and moves in a direction away from the second transmission gear 63.

  Further, as shown in FIG. 21 (b) → (c), when the first transmission gear 62 rotates in the direction of the arrow G2 and the rear end of the rib 62b passes through the rib 63c as shown in FIG. 23, the rib of the rib 63c. The ride to 62b is cancelled. Then, the first transmission gear 62 moves in the direction of arrow F by the urging force of the spring 64 (see FIG. 17a), and the first transmission gear 62 approaches the second transmission gear 63 again.

  Thereafter, when the first transmission gear 62 rotates in the direction of the arrow G2 from the position of FIG. 21 (c), the rib 62b moves from the rib 63d → the rib 63b → the rib 63c again, and the rib 63b is moved to the respective ribs 63b, 63c, 63d. 62c rides (see FIG. 22) → passes (see FIG. 23). In the above description, of the ribs provided in the first transmission gear 62, only the movement of the rib 62b has been described, but at the timing when any one of the ribs of the second transmission gear 63 rides on the rib 62b, the ribs 62b, 62d. In addition, a corresponding rib of the second transmission gear 63 rides on.

  As described above, when the first transmission gear 62 rotates in the reverse direction, each inclined portion provided in the first transmission gear 62 slides with respect to each inclined portion provided in the second transmission gear 63. As a result, the first transmission gear 62 idles and the driving force of the drive motor is not transmitted from the first transmission gear 62 to the second transmission gear 63. As described above, the first transmission gear 62 repeats the operation of moving toward and away from the second transmission gear 63 while idling in the direction of the arrow G2.

  By the way, in this embodiment, when the fixing device is mounted on the image forming apparatus main body (when the fixing device is inserted into the image forming apparatus main body in the direction opposite to the arrow K direction in FIG. 7), the second transmission is performed. A force in the idling direction (for example, a force that rotates the second transmission gear 63 counterclockwise in FIG. 21A) is applied to the gear. In this case, if the fixing roller is not rotated in the reverse direction, resistance is generated at the meshing portion of the first transmission gear 62 and the second transmission gear 63, and the fixing device cannot be correctly attached to the image forming apparatus main body. A large load is applied to the mounting operation. However, in the present embodiment, the above-described one-way clutch mechanism allows the second transmission gear to idle with respect to the first transmission gear when the fixing device is mounted, so that the mounting operation of the fixing device to the image forming apparatus body can be performed smoothly. It can be carried out.

  Further, in the fixing device of the present embodiment, as shown in FIG. 24, when the jammed paper P1 jammed in the nip portion N is taken out, the jammed paper P1 is pulled out from the downstream side of the nip portion N. That is, the jammed paper is pulled out in the direction of the arrow H, and a rotational force in the direction of the arrow A1 is applied to the fixing roller 18 by this removal operation.

  When the fixing roller 18 rotates in the direction of the arrow A1, as shown in FIG. 21A, the second transmission gear 63 receives a force that rotates counterclockwise, and the second transmission gear 63 becomes the first transmission gear. Idle with respect to 62. That is, since the second transmission gear 63 idles at the time of taking out jammed paper, the first transmission gear 62 does not rotate, and it is possible to prevent extra resistance from being taken out from the jammed paper.

  As described above, the one-way clutch is provided in the drive transmission mechanism that transmits the driving force from the image forming apparatus main body side to the fixing roller, so that the second drive gear is idled when the fixing device is mounted or when jammed paper is taken out. Prevents resistance.

  Next, a foreign matter removing operation for preventing foreign matter from accumulating between the fixing roller and the separation claw will be described.

  As shown in FIG. 25A, during the conveyance and fixing operation of the paper P, the fixing roller 18 rotates in the arrow A1 direction, and the pressure roller 19 is driven and rotated in the arrow B1 direction. In the fixing nip N, the unfixed image on the paper is heated by the heat of the fixing roller 18 and is pressed by the fixing roller 18 and the pressure roller 19, thereby fixing the image on the paper. .

  During the fixing operation, foreign matters such as unfixed toner and paper dust that have not been fixed on the paper P adhere to the surface of the fixing roller 18. Then, the foreign matter W is conveyed to the downstream side by the normal rotation of the fixing roller 18 and is accumulated near the contact position between the separation claw 24 and the fixing roller 18.

  As shown in FIG. 25B, when the fixing roller 18 and the pressure roller 19 further rotate in the forward direction, the accumulated foreign matter W adheres to the surface of the fixing roller 18 and is conveyed to the downstream side, and part of the pressure is pressed. It also adheres to the surface of the roller 19.

  Then, as shown in FIG. 25C, when the paper P is conveyed to the fixing nip N, the foreign matter W is transferred from the surface of the pressure roller 19 to the surface of the paper P and is fixed to the surface of the paper P. End up.

  In order to remove the foreign matter W as described above, in the present embodiment, forward and reverse rotation operations of the fixing roller are performed.

  That is, as shown in FIG. 25A, when the foreign matter W accumulates at the contact position between the separation claw 24 and the fixing roller 18, the sheet is not passed through the fixing device (when the fixing device is not in a fixing operation). Then, as shown in FIG. 26A, the fixing roller 18 is rotated reversely by a predetermined amount (rotated in the direction of arrow A2). As a result, the pressure roller 19 is rotated in the direction of the arrow B2.

  Due to the reverse rotation operation of the fixing roller 18, the foreign matter W accumulated near the contact position between the separation claw 24 and the fixing roller 18 is conveyed on the surface of the fixing roller 18 and conveyed upstream of the separation claw 24.

  Then, as shown in FIG. 26 (b), the foreign matter W adhering to the surface of the fixing roller 18 can be scraped off by the separation claw 24 by rotating the fixing roller 18 forward by a predetermined amount.

  By the forward and reverse rotation operations of the fixing roller 18 when the sheet is not passed, the foreign matter W accumulated near the contact position between the separation claw 24 and the fixing roller 18 is removed, and the foreign matter W is prevented from sticking to the paper P. can do.

  However, as described above, since the one-way clutch mechanism is provided in the drive transmission mechanism between the fixing roller and the drive motor, the fixing roller 18 does not rotate correctly in the reverse direction in the pressurized state. That is, as shown in FIG. 22, the force by which each inclined portion (inclined portion 62 b 1 in FIG. 22) of the first transmission gear 62 presses each inclined portion (inclined portion 63 c 1 in FIG. 22) of the second transmission gear 63. The fixing roller cannot be rotated, and the first transmission gear 62 is idled. For this reason, the above-described removal operation cannot be performed.

  Therefore, in the present embodiment, the rotation required to rotate the fixing roller by reducing the pressure applied to the fixing roller by reducing the pressure roller to the depressurized state (the cam member is in the state shown in FIG. 14c). Torque is reduced.

  Thus, as shown in FIG. 27, each inclined portion (inclined portion 62b1 in FIG. 27) of the first transmission gear 62 is inclined by the rotation of the first transmission gear 62 in the direction of the arrow G2. The part (inclined part 63c1 in FIG. 27) can be pressed in the direction of arrow G2 ′ in FIG. 27 to rotate the second transmission gear 63 (see the dotted line part in FIG. 27). That is, the driving force can be transmitted from the first transmission gear 62 to the second transmission gear 63, and the fixing roller can be rotated in the reverse direction. Therefore, the removal operation can be performed to remove foreign matter accumulated between the fixing roller and the foreign matter.

  As described above, in the configuration of the present embodiment, when a driving force in the reverse rotation direction is applied, the driving transmission mechanism makes contact between the inclined surface and the inclined surface, so that the rotation torque of the fixing roller is large, that is, the applied force is increased. In the pressure state, the inclined surfaces slip and the first transmission gear rotates idly, and the fixing roller does not rotate in the reverse direction. On the other hand, when the rotation torque of the fixing roller is small, that is, in the depressurized state, the second transmission gear is rotated by the force with which the inclined surface of the first transmission gear presses the inclined surface of the second transmission gear, and the fixing roller is moved in the reverse direction. Can be rotated. As described above, when the removal operation is performed, the fixing roller can be rotated in the reverse direction. In other cases, the second transmission gear is idled so that no extra resistance is generated. .

  The forward rotation and reverse rotation operations of the fixing roller 18 may be performed once or repeatedly. Further, the rotation amount of each fixing roller 18 can be set to a rotation amount smaller than the distance from the fixing nip N to the contact position between the separation claw 24 and the fixing roller 18.

  The forward rotation and reverse rotation operations when the fixing roller is not passing are performed each time a predetermined number of sheets are passed through the fixing device. Alternatively, it may be performed every time the rotation amount of the fixing roller reaches a predetermined value. As a result, foreign matter accumulated near the contact position between the separation claw and the fixing roller can be removed each time.

  Further, it is desirable that the above-described removal operation is performed at a temperature at which the fixing roller can perform the fixing operation. As a result, the foreign matter deposited near the contact position between the separation claw and the fixing roller can be brought to a high temperature state and can be easily moved from the deposition position during the removal operation.

  The embodiment of the present invention has been described above, but the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the gist of the present invention.

  The image forming apparatus according to the present invention is not limited to the monochrome image forming apparatus shown in FIG. 1, but may be a color image forming apparatus, a copying machine, a printer, a facsimile, or a complex machine thereof.

  Recording media include paper P (plain paper), thick paper, postcards, envelopes, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, OHP sheet, plastic film, prepreg, copper foil, etc. included.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 12 Fixing apparatus 18 Fixing roller (fixing member)
19 Pressure roller (Pressure member)
24 separation claw 60 drive transmission mechanism 61 shaft 62 first transmission gear (drive transmission member)
62a Insertion hole 62b, 62c, 62d Rib 63 Second transmission gear (drive transmission member)
62a Insertion hole 63b, 63c, 63d Rib 64 Spring (biasing member)
90 Contact / separation mechanism N Fixing nip P Paper (recording medium)
X1 Contact surface X2 Contacted surface W Foreign matter

JP 2000-159407 A

Claims (6)

A fixing member;
A pressure member that forms a nip portion with the fixing member;
A separation member that contacts the fixing member and separates the recording medium from the fixing member;
A fixing device comprising a contact / separation mechanism for contacting and separating the pressure member with respect to the fixing member;
The pressing member is provided so as to be switchable between a pressing state that is closer to the fixing member and a depressurizing state that is farther from the fixing member than the pressing state by the contact / separation operation of the contact / separation mechanism,
When the rotation in the direction in which the fixing member conveys the recording medium is a forward rotation operation, the rotation in the opposite direction is a reverse rotation operation.
In addition to the fixing operation on the recording medium, the fixing device is configured to rotate the fixing member by a predetermined amount and then rotate the fixing member by a predetermined amount after rotating the pressure member in the depressurized state.   The fixing device according to claim 1, wherein the predetermined amount of reverse rotation and forward rotation are performed when the number of recording media passed through the fixing device exceeds a predetermined number.   The fixing device according to claim 1, wherein the predetermined amount of reverse rotation and forward rotation are performed when the fixing member is at a temperature at which the fixing operation is possible.   An image forming apparatus comprising the fixing device according to claim 1. The image forming apparatus main body has a drive transmission mechanism that transmits a driving force of a driving source to the fixing member.
The drive transmission mechanism transmits a driving force in the forward rotation direction to the fixing member and does not transmit a driving force in the reverse rotation direction to the fixing member when the pressure member is in the pressurized state. Have
The drive transmission mechanism transmits the driving force in the reverse rotation direction to the fixing member when a torque for rotating the fixing member decreases from the pressure state in the pressure-removed state of the pressure member. The image forming apparatus according to claim 4, wherein the image forming apparatus is configured to be possible. The drive transmission mechanism has at least two drive transmission members,
The two drive transmission members have inclined portions,
6. The drive transmission mechanism according to claim 5, wherein when the driving force in the reverse rotation direction is transmitted, inclined surfaces provided on the inclined portion of one drive transmission member and the other drive transmission member are in contact with each other. Image forming apparatus.