JP6986205B2 - Fixing device, image forming device - Google Patents

Description

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

As a fixing device, one provided with a separating member for separating the recording medium that has passed through the fixing nip from the fixing member is generally known.

Among such separating members, 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 matter such as toner is deposited between the fixing member and the separating member. Then, there is a problem that the accumulated foreign matter is carried to the fixing nip by the rotational operation of the fixing member and adheres to the surface of the recording medium during the separation operation of the recording medium.

To deal with such a problem, for example, in Patent Document 1 (Japanese Unexamined Patent Publication No. 2000-159407), a foreign matter deposited is caused by causing a fixing roller to perform a reversing operation of rotating the recording medium in a direction opposite to the transport direction. Is transported to the upstream side to prevent foreign matter from accumulating on 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 rotation direction during the normal fixing operation, but a sufficient rotational force can be applied to the fixing member in the rotation in the opposite direction. It is not possible to smoothly remove the foreign matter accumulated between the fixing member and the separating member.

Under these circumstances, it is an object of the present invention to easily rotate the fixing member in the direction opposite to that during the fixing operation, and smoothly perform a removing operation for removing foreign matter accumulated between the fixing member and the separating member. It is supposed to be.

In order to solve the above-mentioned problems, in the present invention, the fixing member, the pressure member forming a nip portion between the fixing member, and the separation which comes into contact with the fixing member and separates the recording medium from the fixing member. A fixing device including a member and a contact / detachment mechanism for bringing the pressurizing member into contact with the fixing member. A pressurizing state that is close to each other and a depressurizing state that is farther from the fixing member than the pressurizing state are provided so that the fixing member rotates in the direction of transporting the recording medium in a forward rotation operation. When the rotation in the opposite direction is a reverse rotation operation, the pressure member is put into the depressurized state, the fixing member is rotated in the reverse direction by a predetermined amount, and then a predetermined amount is applied, except during the fixing operation to the recording medium. It is characterized by rotating in the forward direction.

In the present invention, the fixing member is rotated in the reverse rotation and the forward rotation in the depressurized state, except when the fixing operation is performed on the recording medium, so that the fixing member is rotated with a smaller rotational torque, and the fixing member and the separation claw are separated from each other. Foreign matter accumulated in the meantime can be removed.

It is a schematic block diagram of the image forming apparatus which concerns on embodiment of this invention. It is a schematic block diagram of the fixing device. It is a perspective view which looked at the front side of a fixing device from diagonally above. It is a side view which looked at the fixing device from the left side. It is the schematic sectional drawing of the apparatus main body with the fixing apparatus attached. It is a schematic diagram 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 the state of removing a fixing device. It is a figure which shows the state of removing a fixing device. It is a figure which shows the state of removing a fixing device. It is a figure which shows the state which the opening / closing cover is closed. It is a perspective view of the state which the upper part of the exterior part of a fixing device is removed. It is a side view which shows the structure around the contact / separation mechanism provided in the fixing device. It is a schematic block diagram of the drive system of the attachment / detachment mechanism which concerns on this embodiment. It is a figure for demonstrating the separation operation of a pressure roller by a cam member. It is a figure for demonstrating the approaching operation of a pressure roller by a cam member. It is a perspective view of the drive transmission mechanism provided in the image forming apparatus main body. It is a front view of the first transmission gear. It is a front view of the 2nd transmission gear. It is a figure which shows the 1st transmission gear and the 2nd transmission gear at the time of a forward rotation operation. It is a figure which shows the 1st transmission gear and the 2nd transmission gear at the time of a reverse rotation operation. FIG. 21 is a cross-sectional view taken along the line ZZ of FIG. 21a. It is a figure corresponding to the ZZ sectional view of FIG. 21c. It is a figure explaining the taking out of the jam paper. It is a figure explaining the adhesion to the paper of the foreign matter accumulated between a fixing roller and a separating member. It is a figure for demonstrating the operation of removing a foreign substance of this embodiment. It is a figure explaining the reverse rotation operation in a decompressed state.

Hereinafter, embodiments according to the present invention will be described with reference to the drawings. In each figure, the same or corresponding parts are designated by the same reference numerals, and the duplicated description thereof will be appropriately simplified or omitted.

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

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 attached to the apparatus main body (image forming apparatus main body) 100. The process unit 1 visualizes a photoconductor 2 as an image carrier that carries an image on the surface, a charging roller 3 as a charging means for charging the surface of the photoconductor 2, and a latent image on the photoconductor 2. A developing device 4 as a developing means, a cleaning blade 5 as a cleaning means for cleaning the surface of the photoconductor 2, and the like are provided. Further, an LED head array 6 as an exposure means for exposing the surface of the photoconductor 2 is arranged at a position facing the photoconductor 2.

A toner cartridge 7 as a powder container for accommodating toner, which is powder for image formation, is detachably attached to the process unit 1. The toner cartridge 7 has an unused toner accommodating portion 8 for accommodating unused toner and a waste toner accommodating portion 9 for accommodating used waste toner.

Further, the image forming apparatus includes a transfer device 10 for transferring an image to paper as a recording medium, a paper feeding device 11 for supplying the paper, a fixing device 12 for fixing the image transferred to the paper, and the paper outside the apparatus. It is provided with a paper ejection device 13 for discharging to, and a pair of resist rollers 17 as timing rollers.

The transfer device 10 includes a transfer roller 14 as a transfer member. The transfer roller 14 is arranged so as to come into contact with the photoconductor 2 in a state where the process unit 1 is attached to the apparatus main body 100. Further, the transfer roller 14 is connected to a power supply (not shown), and a predetermined direct current voltage (DC) and / or alternating current voltage (AC) is applied.

The paper feed device 11 includes a paper feed cassette 15 in which the paper P is housed, and a paper feed roller 16 for feeding the paper P housed in the paper feed cassette 15.

The fixing device 12 includes a fixing roller 18 as a fixing member for fixing an image on paper, and a pressure roller 19 as a pressure member arranged facing the fixing roller 18. The fixing roller 18 is heated by a heating means such as a heater. The pressure roller 19 is pressurized to the fixing roller 18 side and comes into contact with the fixing roller 18 to form a fixing nip.

The paper ejection device 13 includes a pair of paper ejection rollers 20 for ejecting paper to the outside of the device. Further, a paper ejection tray 21 for placing the paper ejected by the paper ejection roller 20 is formed on the outer upper surface portion of the apparatus main body 100.

Further, in the apparatus main body 100, the paper ejection roller 20 is entered from the paper feed cassette 15 via the resist roller 17, the image transfer portion (transfer nip) between the transfer roller 14 and the photoconductor 2, and the fixing device 12. A transport path R1 for transporting the paper P to is provided. Further, the image forming apparatus 100 is provided with a double-sided transport path R2 for transporting the paper P that has passed through the fixing device 12 to the image transfer unit again when printing on both sides.

Subsequently, with reference to FIG. 1, the image forming operation of the image forming apparatus according to the present embodiment will be described.
When the image forming operation is started, the photoconductor 2 is rotationally driven, and the surface of the photoconductor 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 photoconductor 2 based on the image information from the reader, a computer, or the like, and an electrostatic latent image is formed. Then, the developing device 4 supplies toner to the electrostatic latent image on the photoconductor 2, so that the electrostatic latent image is visualized (visualized) as a toner image.

Further, when the image drawing operation is started, the paper feed roller 16 starts the rotation drive, and the paper P is fed out from the paper feed cassette 15. The paper P that has been sent out is temporarily stopped from being conveyed by the resist roller 17. After that, the rotation drive of the resist roller 17 is started at a predetermined timing, and the paper P is conveyed to the image transfer unit at the timing when 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 photoconductor 2 is transferred onto the paper P by the transfer electric field generated by applying a predetermined voltage to the transfer roller 14. Further, the toner on the photoconductor 2 that has not been transferred to the paper P at this time is removed by the cleaning blade 5 and collected in the waste toner accommodating portion 9 of the toner cartridge 7.

The paper P on which the toner image is transferred is conveyed to the fixing device 12, 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 is transferred. The image is fixed. Then, the paper P is discharged to the outside of the device by the paper ejection roller 20 and placed on the paper ejection tray 21.

When double-sided printing is performed, the paper P that has passed through the fixing device 12 is switched back without being discharged to the outside of the device and sent to the double-sided transfer path R2. The paper P is fed to the transport path R1 on the front side of the resist roller 17 through the double-sided transport path R2, and is again conveyed to the image transfer unit by the resist roller 17. Then, the image is transferred to the back surface of the paper P, the image on the back surface side is fixed by the fixing device 12, and then the paper P is discharged to the outside 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 is used as a separating member for separating the fixing roller 18, the resin frame member 23 constituting the exterior portion in which the pressure roller 19 is housed, and the paper P from the fixing roller 18. Has a separation claw 24 and. An inlet portion 23a for allowing paper to enter the fixing device 12 is formed on the front surface of the frame member 23, and an outlet portion 23b for ejecting paper from the fixing device 12 is formed on the back surface of the frame member 23. ing. The "front" of the fixing device 12 here means the front of the image forming device in a state where the fixing device 12 is attached to the image forming device, that is, an operation unit (operation panel) provided on the image forming device by an operator. Etc.) means the side that stands when giving 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 the tip 24a protruding toward the fixing roller 18 is in contact with the surface of the fixing roller 18.

When the driving force is transmitted from the drive source on the device main body 100 side to the fixing roller 18, the fixing roller 18 is rotationally driven in the direction indicated by the 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. 2 with respect to the rotation-driven fixing roller 18. Contrary to the present embodiment, the pressurizing roller 19 may be used as a driving roller and the fixing roller 18 may be used as a driven roller. Further, in the following description, the rotation of the fixing roller 18 in the arrow A1 direction is referred to as forward rotation, and the 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 paper is fixed from the direction indicated by the arrow C1 in FIG. 2 in a state where the fixing roller 18 and the pressure roller 19 are rotating. Upon entering N, the paper 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, so that the image is fixed on the paper. Then, the paper on which the image is fixed is separated from the surface of the fixing roller 18 by the separation claw 24, and is 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 gripped by an operator when the fixing device 12 is attached to and detached from the device main body 100. Handles 71 are provided at the left and right ends of the back surface of the frame member 23, respectively.

The pair of handle portions 71 are configured to have a symmetrical shape with 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, and the grip portion 71a has. It is fixed to the back surface of the frame member 23 via a pair of arm portions 71b. A space portion S1 into which an operator can insert a hand or a finger is formed between each grip portion 71a and the back surface of the frame member 23.

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 device main body 100. The plurality of positioning portions 77 to 79 include a first positioning protrusion 77 provided at the front right end portion of the frame member 23, and a pair of second positioning protrusions provided on the front side of the left side surface and the right side surface of the frame member 23, respectively. It is composed of 78 and a pair of third positioning protrusions 79 provided on the left side surface and the back surface side of the right side surface of the frame member 23, respectively.

Further, on the left side surface and the right side surface of the frame member 23, guide protrusions 80 as convex guide portions are guided along the main body side guide portion described later when the fixing device 12 is attached to and detached from the apparatus main body 100, respectively. It is provided. Each guide protrusion 80 is formed in a rectangular shape (a substantially rectangular shape or a substantially square shape), and functions as sliding surfaces 80a and 80b on which the upper plane and the lower plane slide with respect to the guide portion on the main body side. In particular, in the present embodiment, when the fixing device 12 is attached or detached, the portion of the fixing device 12 other than the guide protrusion 80 does not slide with respect to the device main body 100 (does not exhibit the guide function), thereby causing sliding resistance. Is reduced and 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 for fixing the fixing device 12 in a state of being attached to the device main body 100 so as not to be detached. The lock portion 83 is provided on a part of the rotating member 81 rotatably provided on the handle portion 71. The rotating 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, the portion extending upward from the rotation center (fulcrum 82) of the rotating member 81 is an operation unit 84 for the operator to rotate the rotating member 81.

Further, the lock portion 83 is constantly urged downward by a coil spring 85 as a urging member arranged between the upper surface thereof and the lower surface of the frame member 23. Therefore, in a state where the rotating member 81 is not rotated by the operator, the lower portion of the rotating member 81 comes into contact with the bottom portion 71c of the lower arm portion 71b, and the tip 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 significantly downward from the bottom portion 71c (the state shown by the solid line in FIG. 4). In this state, the lock portion 83 is in a lockable state in which it can engage with the engagement portion described later provided on the device main body 100 side.

On the other hand, when the operator rotates the rotating member 81 counterclockwise against the urging force of the coil spring 85, the tip portion of the lock portion 83 retracts upward and the device main body. It is in a non-lockable state (a state shown by a two-dot chain line in FIG. 4) in which the engagement portion on the 100 side is not engaged. In this way, the operator can operate the operation unit 84 to rotate the rotating member 81, so that the lock unit 83 can be switched between the lockable state and the non-lockable state. The rotating member 81 is also provided on the right handle portion 71 in the same manner.

FIG. 5 is a schematic cross-sectional view of the apparatus main body 100 in a state where the fixing apparatus 12 is attached.
As shown in FIG. 5, an opening / closing cover 101 is provided on the back surface (left side surface in the drawing) of the apparatus main body 100. The opening / closing cover 101 opens / 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 the 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 of attaching and detaching the fixing device 12 will be described in detail later.

Further, the open / close cover 101 is integrally provided with a double-sided transport unit 104 that constitutes a part of the double-sided transport path R2. Therefore, as shown in FIG. 5, when the open / close cover 101 is opened, the double-sided transfer unit 104 rotates together with the open / close cover 101 and is retracted from the vicinity of the back surface of the fixing device 12.

A pair of guide rails 103 as main body side guides for guiding the fixing device 12 when the fixing device 12 is attached to and detached from the device main body 100 are provided on each inner surface of the left side wall and the right side wall of the device main body 100, respectively. .. 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 protrusion 80 with respect to these 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 the inner horizontal planes 105a and 105b extending in a substantially horizontal direction on the inner side far from the opening 102. It has front-side inclined surfaces 106a and 106b extending upward from the side horizontal planes 105a and 105b toward the opening 102 side (front side). Further, the lower guide surface 103b has a front side horizontal plane 107b arranged in a substantially horizontal direction on the front side closer to the opening 102 than the front side inclined surface 106b.

Further, as shown in FIG. 5, the apparatus main body 100 is provided with a plurality of main body side positioning portions 108 to 110 for positioning the fixing device 12 with respect to the apparatus main body 100. The plurality of main body side positioning portions 108 to 110 are fixed to the first main body side positioning portion 108 which engages with the first positioning protrusion 77 provided on the fixing device 12 to mainly position the fixing device 12 in the left-right direction. A second main body side positioning unit 109 that engages with a second positioning protrusion 78 provided on the device 12 to mainly perform positioning in the front direction and the vertical direction of the fixing device 12, and a third positioning provided on the fixing device 12. It is mainly composed of a third main body side positioning portion 110 that engages with the protrusion 79 to perform positioning in the rotation direction centered on the second positioning protrusion 78 of the fixing device 12.

Further, the apparatus main body 100 is provided with an engaging portion 111 with which the lock portion 83 of the fixing device 12 is engaged. 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 fixing device 12 is positioned in the rear direction and the movement in the disengagement direction is restricted.

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

As a result, as shown in FIG. 8, the fixing device 12 moves in the left direction (disengagement direction) of the figure along the guide rail 103 on the device main body 100 side, and the positioning protrusions 77 to 79 provided on the fixing device 12 are provided. Is separated from the positioning portions 108 to 110 on the device main body side on the device main body 100 side. Further, when the fixing device 12 starts to be pulled, the guide protrusion 80 of the fixing device 12 initially slides with respect to the inner horizontal planes 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, since the guide protrusion 80 slides on the front side inclined surfaces 106a and 106b of the guide rail 103, the fixing device 12 moves diagonally upward. After that, as shown in FIG. 10, the fixing device 12 is completely pulled out from the device main body 100 and is in a state of being removed.

As described above, in the present embodiment, the fixing device 12 can be guided and removed diagonally upward so as not to come into contact with the double-sided transport unit 104. Here, 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 double-sided transfer unit 104. The height must be increased, and the height of the apparatus main body 100 becomes high. On the other hand, in the case of the present embodiment, it is possible to avoid the contact of the fixing device 12 with the double-sided transfer unit 104 without raising the mounting position of the fixing device 12 or the upper end position of the opening 102. The height of the device main body 100 can be lowered, and the size can be reduced.

Next, when the fixing device 12 is attached to the device main body 100, the procedure at the time of removal may be reversed. That is, while gripping the handle portion 71 and the operation portion 84, the fixing device 12 is inserted into the device main body 100 along the guide rail 103, and the positioning protrusions 77 to 79 engage with the main body side positioning portions 108 to 110. At the time of fitting, the force for gripping the handle portion 71 and the operation portion 84 is relaxed. As a result, the lock portion 83 is engaged with the engaging portion 111 on the device main body 100 side by the urging force of the coil spring 85, and is in the locked state. In this embodiment, when the driving force is subsequently transmitted to the fixing device 12, it is mounted between the driving gear provided on the device main body 100 side and the fixing gear provided at the end of the fixing roller 18. Since the force in the direction acts, the positioning of the fixing device 12 is more reliable.

Further, as shown in FIG. 11, in the present embodiment, when the opening / closing cover 101 is closed, the double-sided transport unit 104 is arranged between the left and right handle portions 71. By arranging the double-sided transport unit 104 between the handle portions 71 in this way, the space between the handle portions 71 can be effectively utilized as a part of the double-sided transport path R2, and further miniaturization can be achieved.

Hereinafter, a contact / separation mechanism for separating the pressure roller from the fixing roller and a peripheral configuration thereof provided in the fixing device 12 will be described.
FIG. 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 of the frame member 23 in the longitudinal direction, respectively. 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 separated from the fixing roller 18 in the direction of arrow D in FIG. Specifically, the bearing 27 that supports the pressure roller 19 is fitted into the bearing guide portion 25b, which is a rectangular hole provided in the support member 25, and the bearing 27 is formed 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 fixing roller 18 has a direction in which its axial position is orthogonal to the axial direction. It is fixed so that it does not move to.

Further, the fixing device 12 according to the present embodiment has a pressurizing lever 31 that pressurizes the pressurizing roller 19 against the fixing roller 18, and a pressurizing member that urges the pressurizing lever 31 in the pressurizing direction. It is equipped with a spring 32. A pressure lever 31 and a pressure spring 32 are provided on both ends of the pressure roller 19. The pressure lever 31 has one end 31a attached to a support shaft 33 provided at the lower part of the support member 25, and is configured to be rotatable around the support shaft 33 in the direction of arrow E in FIG. Each pressure spring 32 is attached by being hooked on the hooking portions 31c and 25c provided on the other end 31b 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 always held in a state of being pulled upward in FIG. 13 by the pressure spring 32. Then, the pressure lever 31 presses the bearing 27 that supports the pressure roller 19 via the pad 34 fitted in the bearing guide portion 25b of the support member 25, and applies the pressure roller 19 toward the fixing roller 18. I'm pressing.

Further, the fixing device 12 according to the present embodiment includes a contact / detachment mechanism 90 that brings the pressure roller 19 close to and separated from the fixing roller 18. The contact / detachment mechanism 90 mainly includes a cam member 41, an optical sensor 51, a light-shielding member 52, and the like as rotation position detecting means for detecting the rotation position (rotation angle) of the cam member 41.

The cam member 41 is provided on both end sides of the rotary shaft 42 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. Further, the cam member 41 has a cam surface 41a whose distance from the center of rotation changes in the direction of rotation. By pulling the pressure lever 31 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 pressurizing lever 31 is pushed downward in FIG. 13 by the cam surface 41a, so that the pressurizing roller 19 is separated from the fixing roller 18 and the cam member is separated. When the 41 rotates in the reverse direction, the pressurizing lever 31 is returned upward in FIG. 13, so that the pressurizing roller 19 approaches the fixing roller 18. The detailed contact / detachment operation by the cam member 41 will be described later.

The optical sensor 51 is a transmission type optical sensor, and has a light projecting unit that irradiates 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 between the presence and absence of light reception. be. The optical sensor 51 and the light-shielding member 52 are provided only on the cam member 41 side of one of the two cam members 41.

The cam surface 41a provided on the cam member 41 is formed so 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 the half circumference (180 °) in the rotation direction. Specifically, in the present embodiment, the range is about 270 ° from the lowest point e1 where the distance from the rotation center of the cam surface 41a is the smallest to the highest point e2 where the distance from the rotation center of the cam surface 41a is the largest. It is provided across. Further, the cam surface 41a has a stepped portion 41b whose distance from the center of rotation changes abruptly with the uppermost point e2 as a boundary.

FIG. 14 is a schematic configuration diagram of a drive system of the contact / detachment 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 the driving force from the motor 43 to the cam member 41 and the light-shielding member 52. In this embodiment, a small and inexpensive DC brush motor is used as the motor 43. The gear train 44 serves as a drive transmission member integrally provided with 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 second worm gear 46. The first spur gear 47 is composed of a second spur gear 48 as a drive transmission member that meshes with (engages with) the first spur gear 47 and is provided integrally 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, 46 and the spur gears 47, 48 rotate, and the second spur gear 48 and the light-shielding member 52 rotate integrally. Each cam member 41 rotates in one direction (direction indicated by arrow F in FIG. 14) and in the opposite direction (direction indicated by arrow G in FIG. 14) via the rotation shaft 42.

By the way, when two layers of paper such as envelopes are passed through the fixing nip, wrinkles occur on the paper when the fixing roller and the pressure roller are pressed with the same pressing force as when passing plain paper. there is a possibility. Therefore, when passing paper such as envelopes, it is preferable to form the fixing nip with a smaller pressing force than the 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 brought close to and separated from the fixing roller so that the pressing force at the fixing nip can be changed according to the paper type. .. Hereinafter, the depressurization operation when depressurizing from the normal pressing force and the pressurizing operation when returning to the normal pressing force will be described.

First, the contact / detachment operation of the pressure roller 19 by the cam member 41 will be described.
In FIG. 15, (a) shows a state in which the cam receiving portion 31d of the pressurizing lever is in contact with the cam surface 41a on the lowest point e1 side. In this state, the pressurizing roller approaches the fixing roller and is pressurized by a normal pressing force.

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

Then, as shown in FIG. 15 (c), when the contact position of the cam receiving portion 31d with respect to the cam surface 41a reaches the uppermost point e2 side, the separating operation of the pressure roller with respect to the fixing roller is completed, and the pressure is applied to the fixing nip. It becomes a depressurized state where the pressure becomes smaller than the normal pressurization. At this point, the rotation of the cam member 41 is stopped.

On the contrary, from the depressurized state shown in FIG. 16 (a), as shown in FIG. 16 (b), the cam member 41 is moved clockwise in the figure (in the direction opposite to the rotation direction at the time of depressurization transition). When rotated, the cam surface 41a slides with respect to the cam receiving portion 31d, and the contact position of the cam receiving portion 31d with respect to the cam surface 41a moves relatively from the highest point e2 side to the lowest point e1 side. Along with this, the cam receiving portion 31d is pulled upward in the figure 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. 16 (c), when the contact position of the cam receiving portion 31d with respect to the cam surface 41a reaches the lowest point e1, the approaching operation of the pressure roller with respect to the fixing roller is completed, and the pressure roller is in the fixing nip. It is returned to the normal pressurization state where the pressurization pressure is increased. At this point, the rotation of the cam member 41 is stopped.

As described above, 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 opposite direction when the pressure roller is brought close to the pressure roller. Then, the pressure lever is pushed and moved back and forth using the same cam surface 41a. Therefore, in the cam member 41 according to the present embodiment, the cam surface 41a can be provided over a region larger than the half circumference in the rotation direction. As a result, even if the gradient of the cam surface 41a is made gentle, it is possible to prevent the maximum height difference of the gradient from becoming small. Therefore, the cam surface can be sufficiently secured from the pressure roller with respect to the fixing roller. The gradient of 41a can be made gentle to suppress an increase in rotational torque and generation of operating noise (abnormal noise).

Next, the configuration of the drive transmission mechanism for transmitting the drive force to the fixing roller provided in the image forming apparatus main body 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. Mainly equipped with 64.

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 drive force of the drive motor.

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

The shaft 61 is provided with one end side 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 the arrow F by the urging force of the spring 64 wound around the shaft 61.

When the drive 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. Then, in a state where the first transmission gear 62 and the second transmission gear 63 are meshed with each other, the driving force thereof is transmitted from the first transmission gear 62 to the second transmission gear 63.

A gear for transmitting a driving force to the fixing roller and the fixing roller is provided on the side of the second transmission gear 63, 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 that meshes with the fixing roller, and the like, and the fixing roller rotates.

As shown in FIG. 18, the first transmission gear 62 has three ribs 62b, 62c, 62d extending radially from the side of the insertion hole 62a to the first transmission gear 62. The ribs are arranged so as to be out of phase by 120 degrees in the circumferential direction. Further, 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, respectively. The inclined surface provided in each inclined portion is an inclined surface that descends from one side (the side of each rib) in the circumferential direction toward the other side (see FIG. 17a).

The contact surface X1 is provided on the surface of the ribs 62b, 62c, 62d opposite to the side on which the inclined surface is 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 radially from the outer wall 63a1 of the insertion hole 63a. The ribs are arranged so as to be out of phase by 120 degrees in the circumferential direction. Further, 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, respectively. The inclined surface provided on each inclined portion is an inclined surface that descends from one side (the side of each rib) in the circumferential direction toward the other side (see FIG. 17b).

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

In a 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 on the first transmission gear 62 and the inclination provided on the second transmission gear 63 are inclined. The portions 63b1, 63c1, and 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.

In the drive transmission mechanism described above, in the pressurizing state of the pressurizing roller to the fixing roller (the cam member is in the state of FIG. 14a), only the rotational force in the forward rotation direction of the drive motor provided in the image forming apparatus main body is first. It is transmitted from the transmission gear 62 to the second transmission gear 63, and functions as a one-way clutch that 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 forward rotation direction of the fixing roller is transmitted from the drive 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 abuts on 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 mesh with each other, and both the first transmission gear 62 and the second transmission gear 63 rotate in the direction of the arrow G1. The rotation of the second transmission gear 63 causes the fixing roller to rotate in the positive direction. In this way, the positive rotational force 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 with the side of the second transmission gear 63 is shown, the contact surface X1 of the ribs 62c and 62d is also similarly the second transmission gear 63. It is in contact with the contacted 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 drive motor, the first transmission gear 62 rotates in the direction of arrow G2.

21 (a) to 21 (c) are views showing how the first transmission gear 62 rotates in the direction of arrow G2. Further, FIG. 22 shows a cross-sectional view taken along the line ZZ of FIG. 21 (a). In the following description, among the inclined portions provided on the first transmission gear 62, the operation of the inclined portion 62b1 of the rib 62b will be described.

As shown in FIG. 21A, when the rib 62b rotates toward the rib 63c due to the rotation of the first transmission gear 62 in the arrow G2 direction, the inclined portion 63c1 becomes the inclined portion 62b1 as shown in FIG. Ride on. At this time, as shown in FIG. 22, the first transmission gear 62 is pressed against the second transmission gear 63 by the urging force F of the spring 64 (see FIG. 17a), and the first transmission gear 62 is referred to by 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 62b1 is described here, each slope provided on the first transmission gear 62 is in contact with each slope of the second transmission gear 63. Further, each inclined surface is inclined in the rotation 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, in a state where the pressure roller is in a pressure state and is strongly pressed against the fixing roller (a state in which the pressure roller 19 is closer to the fixing roller 18 in FIG. 13), a large rotational torque is required for the rotation of the fixing roller. , The force transmitted from the above slope cannot be enough 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 slides on the inclined portion 62b1 and moves relatively (see the dotted line portion in FIG. 22), and FIG. 21 (a). ) → (b), only the first transmission gear 62 rotates in the direction of the arrow G2. In other words, the first transmission gear 62 slips 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 slope of the inclined portion 62c1. As such, the second transmission gear 63 moves relative to the upper part of the figure with respect to the first transmission gear 62. In other words, the first transmission gear 62 moves downward in the figure against the urging force F of the spring, and moves in a direction away from the second transmission gear 63.

Further, as shown in FIGS. 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 is ribbed. The ride to 62b is canceled. 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.

After that, when the first transmission gear 62 rotates in the direction of arrow G2 from the position shown in FIG. 21C, the rib 62b moves from the rib 63d to the rib 63b to the rib 63c again, and ribs to the ribs 63b, 63c, and 63d, respectively. 62c will repeat riding (see FIG. 22) → passing (see FIG. 23). In the above description, only the movement of the rib 62b among the ribs provided on the first transmission gear 62 has been described, but the ribs 62b and 62d are at the timing when any of the ribs of the second transmission gear 63 rides on the rib 62b. Also, the corresponding rib of the second transmission gear 63 is on board.

In this way, when the first transmission gear 62 rotates in the opposite direction, each inclined portion provided on the first transmission gear 62 slides with respect to each inclined portion provided on the second transmission gear 63. The first transmission gear 62 slips, 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 in and out of the second transmission gear 63 while idling in the direction of the arrow G2.

By the way, in the present embodiment, when the fixing device is attached to the image forming device main body (when the fixing device is inserted into the image forming device 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 for rotating 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 between the first transmission gear 62 and the second transmission gear 63, and the fixing device cannot be correctly mounted on the image forming apparatus main body. , A large load is applied to the mounting operation. However, in the present embodiment, the 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 fixing device can be smoothly mounted on the image forming apparatus main body. It can be carried out.

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

When the fixing roller 18 rotates in the direction of arrow A1, as shown in FIG. 21A, the second transmission gear 63 receives a force that rotates counterclockwise, and the second transmission gear 63 receives the first transmission gear. It spins against 62. That is, since the second transmission gear 63 spins when the jam paper is taken out, the first transmission gear 62 does not rotate around, and it is possible to prevent an extra resistance force from being generated when the jam paper is taken out.

As described above, by providing a one-way clutch in the drive transmission mechanism that transmits the driving force from the image forming device main body side to the fixing roller, the second drive gear is idled when the fixing device is attached or when the jam paper is taken out, and extra It prevents the generation of resistance.

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

As shown in FIG. 25 (a), during the transporting and fixing operations of the paper P, the fixing roller 18 rotates in the direction of arrow A1, and the pressurizing roller 19 is driven to rotate in the direction of arrow B1. Then, 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, so that the image is fixed on the paper. ..

During the fixing operation, foreign substances 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 forward rotation of the fixing roller 18, and is deposited 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 a part of the foreign matter W is pressurized. It also adheres to the surface of the roller 19.

Then, as shown in FIG. 25 (c), 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 adheres to the surface of the paper P. Will end up.

In order to remove the foreign matter W as described above, in the present embodiment, the fixing roller is rotated in the forward direction and in the reverse direction.

That is, as shown in FIG. 25A, when the foreign matter W is deposited at the contact position between the separation claw 24 and the fixing roller 18, the paper is not passed through the fixing device (when the fixing operation of the fixing device is not performed). In addition, as shown in FIG. 26A, the fixing roller 18 is rotated in the reverse direction by a predetermined amount (rotated in the direction of arrow A2). As a result, the pressure roller 19 is driven to rotate in the direction of arrow B2.

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

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

By the forward rotation and reverse rotation operations of the fixing roller 18 when the paper 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 drive transmission mechanism between the fixing roller and the drive motor is provided with a one-way clutch mechanism, the fixing roller 18 does not rotate correctly in the opposite direction in the pressurized state. That is, as shown in FIG. 22, with the force that each inclined portion of the first transmission gear 62 (inclined portion 62b1 in FIG. 22) presses each inclined portion of the second transmission gear 63 (inclined portion 63c1 in FIG. 22). The fixing roller cannot be rotated, and the first transmission gear 62 slips. Therefore, the above removal operation cannot be performed.

Therefore, in the present embodiment, by depressurizing the pressurizing roller (the cam member is in the state shown in FIG. 14c), the pressing force of the pressurizing roller on the fixing roller is reduced, and the rotation required to rotate the fixing roller is reduced. The torque is reduced.

As a result, as shown in FIG. 27, due to the rotation of the first transmission gear 62 in the direction of the arrow G2, each inclined portion of the first transmission gear 62 (inclined portion 62b1 in FIG. 27) is inclined of each of the second transmission gears 63. The second transmission gear 63 can be rotated by pressing the portion (inclined portion 63c1 in FIG. 27) in the direction of the arrow G2'in FIG. 27 (see the dotted line portion 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 opposite direction. Therefore, the above removing operation can be performed to remove the foreign matter accumulated between the fixing roller and the foreign matter.

As described above, in the configuration of the present embodiment, when the driving force in the reverse rotation direction is applied, the inclined surface and the inclined surface are brought into contact with each other in the drive transmission mechanism, so that the rotational torque of the fixing roller is large, that is, the addition is applied. In the pressure state, the inclined surfaces slip and the first transmission gear slips, and the fixing roller does not rotate in the opposite direction. On the other hand, when the rotational torque of the fixing roller is small, that is, in the depressurized state, the second transmission gear is rotated by the force that the inclined surface of the first transmission gear presses against the inclined surface of the second transmission gear, and the fixing roller is rotated in the opposite direction. Can be rotated. As described above, when the removal operation is performed, the fixing roller can be rotated in the reverse direction, and in other cases, the second transmission gear is idled so that an extra resistance force is not generated. ..

The forward rotation and reverse rotation operations of the fixing roller 18 may be performed once or repeatedly. Further, each rotation amount of the 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 of the fixing roller when the paper is not passed are performed every time the number of sheets of paper passed through the fixing device reaches a predetermined number. Alternatively, it may be carried out 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 removing operation is performed at a temperature at which the fixing roller can perform the fixing operation. As a result, it is possible to make the foreign matter accumulated near the contact position between the separation claw and the fixing roller into a high temperature state so that it can be easily moved from the accumulation position during the removal operation.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it goes without saying 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, and may be a color image forming apparatus, a copying machine, a printer, a facsimile, or a combination machine thereof.

Recording media include paper P (plain paper), thick paper, postcards, envelopes, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, transparencies, plastic films, prepregs, copper foil, etc. included.

1 Image forming device 12 Fixing device 18 Fixing roller (fixing member)
19 Pressurized roller (pressurized 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 holes 63b, 63c, 63d Ribs 64 Springs (urgency members)
90 Contact / detachment mechanism N Fixing nip P Paper (recording medium)
X1 Contact surface X2 Contact surface W Foreign matter

Japanese Unexamined Patent Publication No. 2000-159407

Claims (6)

With the fixing member
A pressure member that forms a nip between the fixing member and
A separating member that comes into contact with the fixing member and separates the recording medium from the fixing member.
A fixing device provided with a contact / detachment mechanism for bringing the pressurizing member into contact with the fixing member.
The pressurizing member is provided so as to be able to switch between a pressurizing state closer to the fixing member and a depressurization state farther from the fixing member than the pressurizing state by the contact / detachment operation of the contact / detachment mechanism.
Assuming that the rotation of the fixing member in the direction of transporting the recording medium is a forward rotation operation and the rotation in the opposite direction is a reverse rotation operation.
A fixing device characterized in that, other than during the fixing operation to the recording medium, the pressure member is put into the depressurized state, the fixing member is rotated in the reverse direction by a predetermined amount, and then the fixing member is rotated in the forward direction by a predetermined amount. The fixing device according to claim 1, wherein the predetermined amount of reverse rotation and forward rotation operations is performed when the number of recording media passed through the fixing device exceeds a predetermined number. The fixing device according to claim 1 or 2, wherein the predetermined amount of reverse rotation and forward rotation operation is performed when the fixing member is at a temperature at which the fixing operation is possible. An image forming apparatus comprising the fixing apparatus according to any one of claims 1 to 3. The image forming apparatus main body has a drive transmission mechanism for transmitting the drive force of the drive source to the fixing member.
The drive transmission mechanism is a one-way clutch mechanism that transmits the driving force in the forward rotation direction to the fixing member and does not transmit the driving force in the reverse rotation direction to the fixing member in the pressurized state of the pressurizing member. Have,
In the depressurized state of the pressurizing member, the drive transmission mechanism transmits the driving force in the reverse rotation direction to the fixing member by reducing the torque for rotating the fixing member from the pressurizing state. The image forming apparatus according to claim 4, which is configured to be possible. The drive transmission mechanism has at least two drive transmission members.
The two drive transmission members have an inclined portion and have an inclined portion.
The fifth aspect of claim 5, wherein in the drive transmission mechanism, when a drive force in the reverse rotation direction is transmitted, an inclined surface provided on the inclined portion of one drive transmission member and the other drive transmission member comes into contact with each other. Image forming device.

Images