JP2011028298A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress wrinkles of paper by satisfying position accuracy of a cam even when a fixing device is constituted to be detachably attached to an image forming apparatus body. <P>SOLUTION: A pressure lever 22 is rotatably supported on a bracket 20 which holds a heating roller 14. A stud 26 to be inserted through an open hole 23B of a moving strip 23A of the pressure lever 22 is provided in a guide strip 21A of the bracket 20, and a compression spring 28 is arranged between a flange part 26A and the moving strip 23A. The moving strip 23A is pressured to the side of the bracket 20 by the compression spring 28, and the pressure roller 16 is brought into press-contact with the heating roller 14. A contact strip 23C which can contact a cam 30 is provided on the pressure lever 22. In an envelope mode, when the cam 30 is rotated to contact the contact strip 23C, the moving strip 23A moves, the compression spring 28 is compressed and the pressure lever 22 rotates. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fixing device that fixes a toner image on a recording medium between a heating member and a pressure member, and an image forming apparatus such as a copying machine or a laser printer provided with the fixing device.

  In an image forming apparatus such as a copying machine or a printer, an image carrier such as a photoconductor is charged, and a laser beam is irradiated to form an electrostatic latent image on the surface of the image carrier. A toner image made of powder toner is formed by visualization. Then, after the toner image is transferred to a recording medium such as paper, the toner image on the recording medium is fixed by a fixing device to form an image.

  The fixing device includes a heating roller in which a heater is built in a rotating body, and a pressure roller that presses a recording medium against the heating roller. Then, the recording medium on which the toner image is formed is passed between the heating roller and the pressure roller, and the toner image is melted and fixed on the recording medium by heating and pressing. The fixing device may be configured as a unit that can be attached to and detached from the image forming apparatus main body in consideration of maintenance and the like.

  In such a fixing device, when a toner image on a recording medium is fixed at a pressure contact portion between a heating roller and a pressure roller, the recording medium such as an envelope generates wrinkles when a high load is applied. For this reason, there has been proposed one that can change the load of the pressure roller by manual operation. However, the user's manual operation cannot prevent the occurrence of wrinkles on the recording medium, and wrinkles are generated due to erroneous operations.

  In Patent Documents 1 and 2, there is a fixing device that automatically adjusts the load of the pressure roller brought into pressure contact with the heating roller by swinging the swing arm that presses the support shaft of the pressure roller. Proposed. However, these fixing devices combine various parts such as a one-way clutch, a motor, and a cam follower, and have a large number of parts and are expensive. Also, Patent Document 3 proposes a configuration in which the number of parts is reduced by providing a reference position changing cam. However, even if the cost can be reduced, the detachability as a unit and the accuracy stability of the unit and the cam position are improved. It is not a consideration. That is, there is no conventional fixing device that can satisfy the accuracy stability of the unit and the cam position while maintaining the detachability of the unit with respect to the image forming apparatus main body.

JP-A-8-69202 Japanese Patent Laid-Open No. 2001-249469 JP 2004-109521 A

  In the present invention, a pressure lever is supported on a bracket provided with a heating member, a spring is in contact, and a shaft provided with a plurality of cams is supported, and the plurality of cams are pressurized. By contacting the upper part of the lever and rotating in a direction that does not engage with the rotation direction of the pressure lever, the pressure lever rotates smoothly, and the fixing device is moved relative to the image forming apparatus main body. It is an object of the present invention to provide a fixing device and an image forming apparatus that can satisfy the positional accuracy of a cam and suppress the occurrence of paper wrinkles even when the configuration is removable.

  In order to solve the above problems, a fixing device according to a first aspect of the present invention is a fixing device that can be attached to and detached from an image forming apparatus main body, and the fixing device includes a heating source and the heating source. A heating member that is heated and rotated by the roller, and a pressure member that heats and presses the paper on which the toner image is transferred between the heating member and the heating member so as to fix the toner image on the paper. A member, a bracket provided with the heating member, and a pressure lever supported rotatably on the bracket, wherein the lower portion of the pressure lever is supported rotatably on the bracket A lever, a spring that applies pressure to the paper transported between the heating member and the pressure member by contacting the bracket and the pressure lever, and a bracket rotatably supported by the bracket Shi Connected to the shaft, provided on one side and the other side of the shaft, contacting the upper part of the pressure lever, and rotated in a direction not engaged with the rotation direction of the pressure lever. A plurality of cams for adjusting the pressurizing force by rotating a portion above the pressure lever, and a drive force transmitted from a drive source provided on the image forming apparatus main body side, provided on the shaft. A gear for rotating a plurality of cams and a reading unit provided on the shaft for reading the rotational position of the cams are provided.

  According to the first aspect of the present invention, the pressure lever is supported, the spring is in contact with the bracket provided with the heating member, and the shaft provided with the plurality of cams is supported, and The plurality of cams come into contact with the upper portion of the pressure lever and are rotated in a direction not engaged with the rotation direction of the pressure lever, so that the pressure lever smoothly rotates, and the fixing device Even if it is configured to be detachable from the image forming apparatus main body, it is possible to satisfy the cam position accuracy and suppress the occurrence of paper wrinkles.

  According to the present invention, a pressure lever is supported on a bracket provided with a heating member, a spring is in contact, and a shaft provided with a plurality of cams is supported. By contacting the upper part of the pressure lever and rotating it in a direction that does not engage with the rotation direction of the pressure lever, the pressure lever smoothly rotates, and the fixing device is moved to the main body of the image forming apparatus. However, the fixing device and the image forming apparatus that can suppress the occurrence of paper wrinkles while satisfying the cam position accuracy can be provided.

1 is a schematic configuration diagram illustrating an image forming apparatus including a fixing device according to a first embodiment of the present invention. 1 is a perspective view showing a fixing device according to a first embodiment of the present invention. FIG. 3 is a perspective view seen from the direction of a cam of the fixing device shown in FIG. 2. FIG. 3 is a perspective view showing a mounting structure of a pressure lever holding a pressure roller, a bracket holding a heating roller, and a cam of the fixing device shown in FIG. 2. FIG. 3 is an exploded perspective view showing a mounting structure of a cam and a reading plate of the fixing device shown in FIG. 2. FIG. 3 is an exploded perspective view showing a mounting structure of a gear and a shaft of the fixing device shown in FIG. 2. FIG. 3 is a side view showing a mounting structure of a pressure lever holding a pressure roller, a bracket holding a heating roller, and a cam of the fixing device shown in FIG. 2. FIG. 3A is a plan view showing a mounting structure of a pressure lever holding a pressure roller, a bracket holding a heating roller, and a cam of the fixing device shown in FIG. 2, and FIG. FIG. FIG. 3 is a side view showing a state where a cam of the fixing device shown in FIG. 2 rotates and a pressure lever rotates. FIG. 3 is a configuration diagram showing an example of a cam drive mechanism of the fixing device shown in FIG. 2. FIG. 6 is a partial perspective view illustrating a main part of a fixing device according to a second embodiment of the present invention. FIG. 9 is a partial perspective view illustrating a main part of a fixing device according to a third embodiment of the present invention. FIG. 10 is a partial perspective view and an exploded perspective view showing a main part of a fixing device according to a third embodiment of the present invention. It is a side view which shows the attachment structure of the pressure lever of the fixing device which concerns on 4th Embodiment of this invention, a bracket, and a compression spring.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, exemplary embodiments of a fixing device and an image forming apparatus according to the invention will be described with reference to the drawings.

  FIG. 1 shows an image forming apparatus 11 to which the fixing device 10 of the first embodiment is applied.

  The image forming apparatus 11 is provided with a fixing device 10 composed of a unit that can be attached to and detached from the image forming apparatus main body 200. The image forming apparatus main body 200 is provided with an opening / closing cover 202, and the fixing device 10 is loaded in the image forming apparatus main body 200 by opening the opening / closing cover 202. When the fixing device 10 is loaded into the image forming apparatus main body 200, the connector 252 of the fixing device 10 is coupled to the connector 250 of the image forming apparatus main body 200 at the same time, so that the fixing device 10 can be powered and the fixing device. The completion of loading 10 is detected. After the fixing device 10 is loaded in the image forming apparatus main body 200, the image forming apparatus 11 becomes operable by closing the opening / closing cover 202.

  Further, the image forming apparatus main body 200 is provided with a process cartridge 204 in which an image forming unit is integrated into a unit. A photosensitive drum 216 that rotates in a predetermined direction is provided inside the process cartridge 204. Around the photosensitive drum 216, from the upstream side in the rotation direction, a charging roller 218 for charging the photosensitive drum, a developing roller 220 for developing an electrostatic latent image formed on the photosensitive drum, and the photosensitive drum A transfer roller 222 for transferring the developed toner image on the sheet to the paper is provided. Further, a cleaning member 224 for cleaning the surface of the photosensitive drum after transfer is provided on the downstream side of the transfer roller 222 in the rotation direction of the photosensitive drum 216. Further, the image forming apparatus main body 200 is provided with an exposure device 214 that irradiates the photosensitive drum 216 with image light between the charging roller 218 and the developing roller 220.

  Under the image forming apparatus main body 200, paper feed cassettes 206 and 208 for storing paper are disposed so as to be able to be pulled out to the outside. Paper feed rollers 205 and 207 are provided for picking up and carrying the sheets one by one. Further, transport rollers 210, 211, 212, and 213 are provided for transporting the paper supplied from the paper feed rollers 205 and 207 to a position where the photosensitive drum 216 and the transfer roller 222 face each other. The fixing device 10 is loaded on the downstream side of the transfer roller 222 in the paper transport direction, and a paper discharge tray 230 for discharging the fixed paper is provided on the downstream side of the fixing device 10. The fixing device 10 fixes the toner image on the paper between the heating roller 14 and the pressure roller 16. The fixing device 10 will be described later.

  In such an image forming apparatus 11, the photosensitive drum 216 is charged by the charging roller 218, and image light is irradiated from the exposure device 214, thereby forming an electrostatic latent image on the surface. The electrostatic latent image is developed by the developing roller 220, and a toner image is formed on the photosensitive drum 216.

  On the other hand, paper is supplied from the paper feed cassette 206 by the paper feed roller 205, and is transported to a position where the photosensitive drum 216 and the transfer roller 222 are opposed by the transport rollers 210, 211, 212, and 213. Then, the toner image on the photosensitive drum 216 is transferred onto the sheet by the transfer roller 222 and further heated and pressed between the heating roller 14 and the pressure roller 16 of the fixing device 10 to melt the toner image. The image is fixed on the paper. Thereafter, the paper on which the image is formed is discharged to the paper discharge tray 230.

  Next, the fixing device 10 will be described.

  As shown in FIGS. 2 and 4, the fixing device 10 includes a heating roller 14 that is heated to a predetermined fixing temperature and a pressure roller 16 that presses the sheet against the heating roller 14 inside the housing 12. ing. The heating roller 14 includes a heater (not shown) inside a hollow cylindrical portion (for example, a steel base tube) provided with a release layer (not shown) having a low friction coefficient on the surface. The pressure roller 16 is provided with a heat-resistant elastic layer (for example, silicone sponge or silicone rubber) on an iron core, and the elastic layer of the pressure roller 16 is in pressure contact with the heating roller 14.

  As shown in FIG. 4, the heating roller 14 is rotatably supported by support portions 20A provided on the brackets 20 at both ends. The pressure roller 16 is rotatably supported by support portions 22A provided on the pressure levers 22 at both ends. The pressure lever 22 is supported so as to be pivotable about a pivot point 24 in the lower part with respect to the bracket 20. As shown in FIG. 7, a guide piece 21A extends substantially parallel to the axis of the heating roller 14 above the left and right brackets 20, and a stud 26 is fastened to the guide piece 21A. Above the pressure levers 22 at both ends, a moving piece 23A extends substantially parallel to the guide piece 21A, and an opening 23B formed in the moving piece 23A is inserted through the stud 26. A compression spring 28 is mounted around the stud 26. One end of the compression spring 28 is in contact with the flange portion 26A of the stud 26, and the other end is in contact with the moving piece 23A. The compression spring 28 presses the moving piece 23 </ b> A toward the guide piece 21 </ b> A of the bracket 20, so that the pressure roller 16 held by the pressure lever 22 is pressed against the heating roller 14 with a predetermined load (pressing force).

  As shown in FIG. 4, the extending portion 23 of the pressure lever 22 is provided with a contact piece 23C substantially parallel to the moving piece 23A. Cams 30 are rotatably supported by the holding portions 20B of the bracket 20 at positions facing the contact pieces 23C, and the cams 30 at both ends are connected by shafts 32. A gear 34 that transmits a driving force to the cam 30 is provided at one end of the cam 30. As shown in FIG. 7 and FIG. 8A, the cam 30 is substantially circular and is offset from the center of the shaft 32.

  In the fixing device 10, a first mode for conveying plain paper or the like and a second mode for conveying an envelope or the like are set. Paper is detected by a sensor (not shown), and a control unit (not shown) has two modes. Any one of these is selected. In the first mode, the cam 30 does not contact the contact piece 23C, but in the second mode, the cam 30 rotates to a predetermined position and contacts the contact piece 23C. When the cam 30 comes into contact with the contact piece 23C, the moving piece 23A compresses the compression spring 28, moves to a predetermined pressure position, and rotates the pressure lever 22 to pressurize the pressure lever 22. Is adjusted (see FIG. 9). Thereby, in the second mode (envelope or the like), the load (pressing force) of the pressure roller 16 on the heating roller 14 is smaller than that in the first mode (plain paper or the like).

  As shown in FIGS. 2 to 4, the image forming apparatus main body 200 is provided with a gear 256 that meshes with the gear 34, and a driving unit 258 including a motor that transmits a driving force to the gear 256 is attached to a frame (not shown). It has been. As a result, the drive unit 258 transmits a driving force to the gear 256 to rotate the gear 34, and one cam 30 connected to the shaft 32 (the back side in FIG. 3) rotates, while the other via the shaft 32. The cam 30 (front side in FIG. 3) rotates.

  Further, a drive unit (not shown) for rotating the heating roller 14 is connected to the support unit 20 </ b> A of the bracket 20 on the opposite side (front side in FIG. 4) of the drive unit 258 with respect to the shaft 32. . A driving force is transmitted from a driving unit (not shown) to rotate the heating roller 14, and the pressure roller 16 is rotated by the rotation of the heating roller 14. Since the drive unit 258 for rotating the cam 30 and the drive unit (not shown) for rotating the heating roller 14 are arranged on the opposite side, the drive unit 258 is efficiently arranged inside the image forming apparatus 11 and space is advantageous. .

  As shown in FIG. 4, a reading plate 40 having a slit (not shown) for reading the rotational position of the cam 30 is provided on the shaft 32 opposite to the drive unit 258. In addition, a sensor 42 that detects a slit is provided at a position opposed to each other across the reading plate 40. The sensor 42 is attached to a frame (not shown) of the image forming apparatus main body 200 and remains in the image forming apparatus main body 200 when the fixing device 10 is detached, so that the cost can be reduced.

  As shown in FIG. 5, an L-shaped protrusion 41 </ b> A protrudes outward from the peripheral surface of the shaft 41 on the shaft 41 of the reading plate 40. The protrusion 41A is fitted into a concave fitting portion 31A formed in the direction orthogonal to the rotation direction inside the shaft portion 31 of the cam 30. Further, an elastically deformable snap fit 41B protrudes inside the shaft portion 41 of the reading plate 40, and this snap fit 41B is locked to a groove portion 32A formed on the peripheral surface of the shaft 32. A reading plate 40 is fixed to the shaft 32. Thereby, compared with the case where the cam 30 and the reading plate 40 are each directly attached to the shaft 32, the accuracy of the rotation direction of the cam 30 and the reading plate 40 can be increased. Further, as shown in FIG. 4, among the cams 30 at both ends, the cam 30 on the side opposite to the drive unit 258 of the gear 34 (the front side in FIG. 4) has a resistance to rotation, so that the shaft 32 may be twisted. However, reading accuracy can be improved by reading the rotational position of the twisted cam 30 with the reading plate 40.

  As shown in FIG. 6, a D-cut surface 33 </ b> A is formed at a shaft end portion 33 through which the shaft 32 passes, and a shaft portion 35 having a D-cut surface of a gear 34 is inserted into the shaft end portion 33. Is done. Further, an elastically deformable snap fit 35A is provided inside the shaft portion 35, and the gear 34 is fixed by locking the snap fit 35A to the groove portion 33B of the shaft end portion 33. By fixing the gear 34 to the shaft end portion 33 with the snap fit 35A, it is not necessary to screw the gear 34 to the shaft end portion 33, and the assembly is simplified.

  A circular end 33C is formed at the end of the D-cut surface 33A of the shaft end 33, and the circular end 33C protrudes when the gear 34 is fixed. The circular end portion 33 </ b> C can be inserted into a horizontal U-shaped bearing 260 </ b> A formed on the bearing member 260. The bearing member 260 is attached to a frame (not shown) of the image forming apparatus main body 200, and the fixing device 10 is fixed and positioned with respect to the image forming apparatus main body 200 by inserting the circular end portion 33 </ b> C into the bearing 260 </ b> A. Doubles as By providing the bearing 260A of the gear 34 in the image forming apparatus main body 200 and holding the circular end portion 33C outside the gear 34, the gear 34 can be firmly fixed. Thereby, even if the torque of the cam 30 is large, the shaft 32 and the fixing device 10 itself do not move due to the rotation of the gear 34. Further, the gear 34 is directly attached to the shaft end portion 33 of the shaft 32, and the circular end portion 33C is guided by the bearing 260A, whereby the position and the drive transmission accuracy can be improved. For this reason, when the fixing device 10 is mounted on the image forming apparatus main body 200, the fixing device 10 is difficult to move, so that the positional accuracy of the reading plate 40 is increased. Even if the sensor 42 is provided on the image forming apparatus main body 200, the accuracy is high. Detection is possible. For this reason, the cost can be reduced as compared with the case where the sensor 42 is arranged in the fixing device 10.

  Further, as shown in FIG. 8B, the teeth 34A of the gear 34 are high teeth. For this reason, when the fixing device 10 is attached to the image forming apparatus main body 200, the teeth of the gear 34 and the gear 256 of the image forming apparatus main body 200 do not easily collide with each other, and the fixing device 10 can be smoothly attached to the image forming apparatus main body 200. On the other hand, when the gear is a general tooth, the gear and the tooth tip of the gear 256 of the image forming apparatus main body 200 collide with each other, and the fixing device cannot be mounted smoothly. This problem can be solved by sharpening the tip of the gear 34, and there are two types of methods: high teeth and a shift gear. In the case of a shift gear, the drive tangent is slanted and the fixing device moves easily and skips teeth. If the teeth 34A of the gear 34 are high teeth, the drive tangent is vertical and the teeth do not skip.

  Next, the operation of the fixing device 10 will be described.

  As shown in FIG. 7, in the first mode (plain paper or the like), the cam 30 rotates to a position (a fixed position) where it does not contact the contact piece 23 </ b> C of the pressure lever 22. Thereby, the moving piece 23 </ b> A of the pressure lever 22 is moved to the guide piece 21 </ b> A side of the bracket 20 by the pressing force of the compression spring 28. For this reason, the pressure roller 16 held by the pressure lever 22 is pressed against the heating roller 14 held by the bracket 20 with a predetermined load. In the first mode, the pressure roller 16 has a constant load, and the elastic body layer of the pressure roller 16 is elastically deformed by being pressed against the heating roller 14 with a high load. Thereby, plain paper or the like can be conveyed between the heating roller 14 and the pressure roller 16 and the toner image can be fixed.

  On the other hand, as shown in FIG. 9, in the second mode (such as an envelope), the drive unit 258 rotates the gear 256 in the direction of the arrow to rotate the gear 34 that meshes with the gear 256. Thereby, the cam 30 connected with the gear 34 and the shaft 32 rotates in the arrow A direction. Then, the cam 30 contacts the contact piece 23C by rotation, and the opening 23B of the moving piece 23A is inserted into the stud 26. Therefore, the moving piece 23A compresses the compression spring 28 and moves to a predetermined pressure position. To do. As a result, the pressure lever 22 rotates about the rotation point 24 in the direction of the arrow B to a predetermined pressure position, and the pressure roller 16 held by the pressure lever 22 is separated from the heating roller 14 between the axes. Move in the direction of increasing. At this time, the pressure roller 16 has a constant displacement (fixed between the axes). Thereby, in the second mode (envelope or the like), the load on the heating roller 14 of the pressure roller 16 is smaller than that in the first mode.

  In such a fixing device 10, the load of the pressure roller 16 to the heating roller 14 can be appropriately adjusted according to the type of paper such as plain paper or envelope, and the generation of paper wrinkles can be suppressed. Further, since the force relationship among the bracket 20, the pressure lever 22, the compression spring 28, and the cam 30 is closed only in four parts, it is advantageous in terms of deformation and accuracy of components. Also, the assembly of the component parts is easy. Moreover, since the stroke amount of the pressure lever 22 is small, it is advantageous in designing the cam 30.

  As shown in FIG. 9, the rotation direction (arrow A direction) of the cam 30 is set to the forward direction that does not bite with the rotation direction (arrow B direction) of the pressure lever 22. If the rotation direction of the cam is the direction in which the pressure lever is engaged, the movement of the pressure lever is jerky and does not move smoothly, but the rotation direction of the cam 30 is the forward direction that does not engage with the pressure lever 22. Thus, the movement of the pressure lever 22 can be made smooth.

  FIG. 10 shows an example of a driving unit 270 that transmits a driving force to the gear 256. The drive unit 270 is provided with a motor 271, and a worm 272 is connected to the motor 271. A worm gear 274 is engaged with the worm 272, and a transmission gear 276 is provided coaxially with the worm gear 274. The transmission gear 276 meshes with the transmission gear 276, and the gear 256 meshes with the transmission gear 278. The motor 271 is a DC motor, and the worm gear 274 is rotated in the arrow direction by the worm 272, and the transmission gears 276 and 278 and the gear 256 are respectively rotated in the arrow direction. Through the worm 272 and the worm gear 274, the high-rotation motor 271 can be geared down to transmit the driving force. Since the required rotation of the cam 30 is an extremely low rotation and a high load, the combination of the DC motor, the worm 272 and the worm gear 274 is advantageous in terms of space, cost, and output.

  Further, since the motor 271 has only a very limited rotation time when the cam 30 is rotated, a low-cost brush motor can be used.

  In the fixing device, a bearing (not shown) may be provided on the contact surface of the cam 30. By providing the bearing, it is possible to reduce the sliding resistance between the cam 30 and the contact piece 23C.

  Next, a fixing device according to a second embodiment of the present invention will be described.

  In addition, the same code | symbol is attached | subjected to the member same as 1st Embodiment, and the overlapping description is abbreviate | omitted.

  As shown in FIG. 11, in this fixing device, a pressure lever 62 that holds the pressure roller 16 is rotatably supported by a bracket 60 that holds the heating roller 14. One end portion 66 </ b> A of the tension spring 66 is engaged with the guide portion 62 </ b> A of the pressure lever 62. A groove portion 64A is formed on the circumferential surface of the cam 64 provided in the holding portion 60B of the bracket 60, and a hook 66B formed on the other end portion of the tension spring 66 is hooked on the groove portion 64A. The pressure lever 62 is pulled toward the bracket 60 by the tension spring 66, and the pressure roller 16 is pressed against the heating roller 14.

  The rotation axis of the cam 64 is eccentric, and the rotation of the pressure lever 62 is rotated by the rotation of the cam 64, and the distance between the heating roller 14 and the pressure roller 16 is varied. Adjusted. Thereby, a structure can be simplified in the type which varies the distance between axes. Further, the hook 66B can be securely held on the cam 64 by engaging the hook 66B of the tension spring 66 with the groove 64A.

  Next, a fixing device according to a third embodiment of the present invention will be described.

  In addition, the same code | symbol is attached | subjected to the member same as 1st Embodiment and 2nd Embodiment, and the overlapping description is abbreviate | omitted.

  As shown in FIGS. 12, 13A, and 13B, in this fixing device, a groove 74A is formed on the outer periphery of the cam 74 supported by the holding portion 60B, and a bearing 76 is provided in the groove 74A. It has been. A hook 66 </ b> B of a tension spring 66 is hooked on the bearing 76.

  In this fixing device, the hook 66B of the tension spring 66 is hooked on the bearing 76, so that the sliding resistance between the cam 74 and the hook 66B decreases when the cam 74 rotates.

  Next, a fixing device according to a fourth embodiment of the present invention will be described.

  In addition, the same code | symbol is attached | subjected to the member same as 1st Embodiment, and the overlapping description is abbreviate | omitted.

  As shown in FIG. 14, the fixing device includes a front end 81 of a bracket 80 that holds the heating roller 14 and a front end of the pressure lever 82 on the rotating end side of the pressure lever 82 that holds the pressure roller 16. The part 83 is crossed. The distal end portion 81 is formed with a spring receiving portion 81A substantially parallel to the axial direction of the heating roller 14, and the distal end portion 83 is provided with a spring receiving portion 83A spaced from the spring receiving portion 81A. A boss 86 is attached to the spring receiving portion 81A, and a boss 87 is attached to the spring receiving portion 83A, and both ends of the compression spring 88 are held by these bosses 86 and 87. Further, a contact piece 23 </ b> C with which the cam 30 can contact is formed at the distal end portion 83.

  In this fixing device, when the cam 30 rotates in the arrow A direction and contacts the contact piece 23C, the compression spring 88 is compressed and the spring receiving portion 83A moves in the arrow C direction. As a result, the pressure lever 82 rotates in the direction of arrow B, and the load of the pressure roller 16 held by the pressure lever 82 is adjusted.

  In this fixing device, by providing the compression spring 88 between the spring receiving portion 81A of the bracket 80 and the spring receiving portion 83A of the pressure lever 82, the stud 26 shown in FIG. 7 can be omitted, and the number of parts can be reduced. can do.

  The first to fourth embodiments can be conceptually understood as follows. The fixing device according to the first aspect includes a heating member including a heating source, and the heating member. A fixing device that is detachably attached to the main body of the image forming apparatus, wherein the fixing device is detachably attached to the image forming apparatus main body, and the bracket that holds the heating member and the pressure member that holds the pressure member and is movably supported A pressure lever, an urging means for pressing the pressure lever in a direction in which the pressure member presses the heating member, and rotatably supported by the bracket. And a cam for adjusting the pressing force of the pressing member.

  According to the invention described in the first aspect, the pressure lever holds the pressure member, and is movably supported by the bracket holding the heating member. The pressure lever is pressurized by the urging means, and the pressure member pressurizes the heating member. Then, by rotating the cam rotatably supported by the bracket, the cam comes into contact with the pressure lever, and the pressing force of the pressure member is adjusted. Thereby, it becomes possible to adjust appropriately the load of the pressurization member to a heating member, and generation | occurrence | production of the wrinkle of a recording medium is suppressed. In addition, the drive source for rotating the cam is provided on the image forming apparatus side where the fixing device is mounted, and can be configured by closing the bracket, the pressure lever, the urging means, and the cam. This is advantageous in terms of stability. Also, assembly is easy.

  The fixing device according to the second aspect of the present invention is the fixing device according to the first aspect, wherein the cam does not contact the pressure lever and the first mode in which the cam does not contact the pressure lever. And a second mode in which the pressure lever moves to a predetermined pressure position.

  According to the invention described in the second aspect, it is possible to switch between the first mode and the second mode depending on the type of the recording medium. For example, in the first mode such as plain paper, the cam does not contact the pressure lever, and the pressure member is a constant load. In the second mode such as an envelope, the pressure lever is at a predetermined pressure position. It can be a constant displacement that moves (fixed between axes). Thereby, the stroke amount of the pressure lever can be reduced, which is advantageous in designing the cam.

  A fixing device according to a third aspect of the present invention is the fixing device according to the first aspect or the second aspect, wherein the pressure lever and the cam are disposed at both ends of the pressure member, A shaft that transmits the rotation of one cam to the other cam; and a reading plate provided at an end of the shaft for reading the rotation position of the cam; It is provided on the cam side.

  According to the invention described in the third aspect, the cam on the driving side (one cam) and the cam on the opposite side (the other cam) among the cams on both ends have a rotational resistance, so the shaft is twisted. The reading accuracy can be increased by reading the rotational position of the twisted cam (the other cam) with the reading plate.

  The invention according to a fourth aspect is characterized in that, in the fixing device according to the third aspect, the reading plate is attached to the other cam.

  According to the invention described in the fourth aspect, the reading plate is attached to the cam on the side opposite to the cam on the driving side, so that the reading accuracy in the rotational direction of the cam is improved as compared with the configuration in which the reading plate is fitted to the shaft or the like. It is possible.

  According to a fifth aspect of the present invention, in the fixing device according to the third aspect or the fourth aspect, a gear for transmitting a driving force is provided to the shaft, and the bearing of the gear is used as the image forming apparatus main body. It is characterized in that it was provided.

  According to the fifth aspect of the invention, the gear can be firmly held by the bearing by providing the bearing of the gear for transmitting the driving force to the shaft in the image forming apparatus main body. For this reason, even if the torque of the cam is large, the shaft and the fixing device itself do not move by driving the gear.

  The invention according to a sixth aspect is the fixing device according to the fifth aspect, wherein the gear is fixed to a D-cut surface of the shaft, and an end portion of the shaft penetrating the gear is supported by the bearing. It is characterized by that.

  According to the invention described in the sixth aspect, the gear is directly fixed to the D-cut surface of the shaft, and the position accuracy can be improved by guiding the end of the shaft with the bearing.

  The invention described in a seventh aspect is characterized in that, in the fixing device according to the fifth aspect or the sixth aspect, the teeth of the gear are high teeth.

  According to the seventh aspect of the invention, since the gear teeth are high teeth, when the fixing device unit is attached to the image forming apparatus main body, the gear teeth collide with each other on the gear on the image forming apparatus main body side. The fixing device can be smoothly mounted on the image forming apparatus main body. When the gear is a general tooth, the gear and the gear teeth on the image forming apparatus main body collide with each other, and the fixing device cannot be mounted smoothly. This problem can be solved by sharpening the tooth tip of the gear, and there are two types of methods: high teeth and shift gears. In the case of a shift gear, the drive tangent is slanted and the fixing device moves easily and skips teeth. If the teeth are high, the drive tangent is vertical and the teeth do not skip.

  According to an eighth aspect of the present invention, in the fixing device according to any one of the fifth to seventh aspects, a snap fit provided in the gear is formed in a groove formed in the shaft. It is characterized by being locked.

  According to the invention described in the eighth aspect, since the gear is locked and fixed to the groove of the shaft by snap fit, it is not necessary to screw the gear to the shaft, and the assembly is simplified.

  According to a ninth aspect of the present invention, in the fixing device according to any one of the third to eighth aspects, a sensor that detects a slit of the reading plate is provided in the image forming apparatus main body. It is characterized by that.

  According to the ninth aspect of the invention, when the fixing device is mounted on the image forming apparatus main body, the fixing device is difficult to move. Therefore, even if a sensor is provided on the image forming apparatus main body, accurate detection is possible. Further, the cost can be reduced by providing the sensor in the image forming apparatus main body.

  According to a tenth aspect of the present invention, in the fixing device according to the fifth aspect or the sixth aspect, the bearing also serves to fix or position the fixing device with respect to the image forming apparatus main body. Yes.

  According to the invention described in the tenth aspect, since the bearing also serves to fix or position the unit and the position accuracy of the reading plate can be high, the sensor of the reading plate is provided in the image forming apparatus main body. It becomes possible to arrange. For this reason, cost reduction is possible.

  The eleventh aspect of the present invention is the fixing device according to any one of the first to tenth aspects, wherein the pressure lever and the cam are not engaged with each other in the rotation direction of the cam. It is characterized by the forward feed direction.

  In the invention described in the eleventh aspect, if the rotation direction of the cam is the direction of engagement with the movement of the pressure lever, the movement of the pressure lever becomes jerky and not smooth, but the cam is engaged with the pressure lever. It is possible to make the movement of the pressure lever smooth by setting the forward feeding direction not to be.

  The invention described in a twelfth aspect is the fixing device according to any one of the fifth aspect to the eleventh aspect, on the opposite side of the drive mechanism that drives the heating member or the pressure member. The gear for transmitting a driving force to the shaft is provided.

  In the invention described in the twelfth aspect, the drive mechanism for driving the heating member or the pressure member and the drive mechanism for the cam each require a space. However, by providing each drive mechanism on the opposite side, It will be advantageous.

  According to a thirteenth aspect of the present invention, in the fixing device according to any one of the first to twelfth aspects, the motor that drives the cam is a DC motor, and the gear is lowered by a worm gear. It is characterized by transmitting driving force.

  In the invention described in the thirteenth aspect, since the required cam rotation is ultra-low rotation and high load, by combining the worm gear with the DC motor and transmitting the driving force by transmitting the driving force, space, cost, This is advantageous in terms of output.

  According to a fourteenth aspect, in the fixing device according to the thirteenth aspect, the motor is a brush motor.

  In the invention described in the fourteenth aspect, since the time for rotating the cam is extremely limited, it is possible to use a low-cost brush motor and reduce the cost.

  According to a fifteenth aspect of the present invention, in the fixing device according to the first aspect or the second aspect, the urging means is formed on a guide portion extending from the bracket and the pressure lever. An opening that is inserted into the guide portion, and a compression spring that is inserted into the guide portion, one end of which is in contact with the edge of the opening, and the other end is in contact with a flange portion formed at the end of the guide portion. It is characterized by being composed.

  In the invention according to the fifteenth aspect, the pressure is applied by providing a compression spring whose one end hits the edge of the hole formed in the pressure lever and the other end hits the flange formed at the end of the guide portion. The lever is pressurized in the direction of the guide part of the bracket. Then, by compressing the compression spring by rotation of the cam, the pressure lever can be easily moved to a predetermined movement position.

  According to a sixteenth aspect of the present invention, in the fixing device according to the first or second aspect, the urging means is formed on the first spring receiver formed on the bracket and the pressure lever. And a second spring receiver on the cam side with respect to the first spring receiver, and a spring spring for spring reception mounted between the first spring receiver and the second spring receiver. It is characterized by.

  In the invention described in the sixteenth aspect, the pressure lever can be pressurized toward the bracket side by mounting the spring spring for compression between the first spring receiver and the second spring receiver, and the configuration is simplified. It is possible to

  According to a seventeenth aspect, in the fixing device according to any one of the first to sixteenth aspects, a bearing is provided on a contact surface on which the cam contacts the pressure lever. It is characterized by that.

  In the invention described in the seventeenth aspect, the sliding resistance of the cam is lowered by providing the bearing on the contact surface.

  A fixing device according to an eighteenth aspect of the present invention is a fixing device that includes a heating member incorporating a heating source and a pressure member that presses against the heating member, and is detachable from the main body of the image forming apparatus. A bracket that holds the heating member, a pressure lever that holds the pressure member and is movably supported by the bracket, and one end connected to the pressure lever, and the pressure member is connected to the heating member. A tension spring that pulls the member in a pressure-contact direction; and a tension force adjusting means that is rotatably supported by the bracket, supports the other end of the tension spring, and changes a support position of the tension spring. It is a feature.

  According to the invention described in the eighteenth aspect, one end of the tension spring is connected to the pressure lever, and the pressure member pulls the pressure lever in a direction in which the heating member is pressed against the heating member. The tension force adjusting means is rotatably supported by the bracket, and the other end of the tension spring is supported to change the support position of the tension spring. Therefore, it is possible to adjust the pressing force of the pressure member. For this reason, the configuration can be further simplified.

  According to a nineteenth aspect, in the fixing device according to the eighteenth aspect, the tensile force adjusting means is a tension spring cam on which a tip of the tension spring is hooked.

  In the invention according to the nineteenth aspect, the tension of the tension spring can be adjusted by rotating the tension spring cam.

  According to a twentieth aspect, in the fixing device according to the nineteenth aspect, the tension spring cam is provided with a groove that matches a hook formed at the other end of the tension spring. It is a feature.

  In the invention according to the twentieth aspect, the hook of the tension spring can be firmly held on the cam by hooking the hook in the groove provided in the cam for the tension spring.

  According to a twenty-first aspect, in the fixing device according to the nineteenth aspect or the twentieth aspect, a bearing is provided on an outer periphery of the tension spring cam.

  In the invention described in the twenty-first aspect, the sliding resistance between the cam, the spring and the hook is reduced by providing the bearing on the outer periphery of the tension spring cam.

  An image forming apparatus according to a twenty-second aspect is characterized by including the fixing device according to any one of the first to twenty-first aspects.

  In the invention described in the twenty-second aspect, since the fixing device described in any one of the first aspect to the twenty-first aspect is provided, the pressure of the pressure member to the heating member is appropriately adjusted. And the occurrence of wrinkles on the recording medium is suppressed. Further, it is possible to suppress the movement of the fixing device attached to the image forming apparatus main body, and to improve the accuracy and stability.

DESCRIPTION OF SYMBOLS 10 Fixing apparatus 11 Image forming apparatus 12 Housing 14 Heating roller (heating member)
16 Pressure roller (Pressure member)
20 Bracket 20B Holding portion 21A Guide piece (biasing means)
22 Pressure lever 23A Moving piece (biasing means)
23B Opening (biasing means)
23C Contact piece 24 Rotation point 26 Stud (guide part)
26A Flange 28 Compression spring (biasing means)
30 cam 31A fitting portion 32 shaft 32A groove portion 33 shaft end portion 33A D cut surface 33B groove portion 33C circular end portion 34 gear 34A tooth 35A snap fit 40 reading plate 41B snap fit 41A projection portion 42 sensor 60 bracket 60B holding portion 62 pressure lever 64 Cam 64A Groove portion 66 Spring 66B Hook 66A End portion 74 Cam 74A Groove portion 76 Bearing 80 Bracket 81A Spring receiving portion 82 Pressure lever 83A Spring receiving portion 88 Compression spring 200 Image forming apparatus main body 256 Gear 258 Drive portion 270 Drive portion 271 Motor 272 Worm 274 Worm gear

Claims (2)

A fixing device detachable from the image forming apparatus main body,
The fixing device includes:
A heating source;
A heating member that is heated and rotated by the heating source; and
A pressure member that is rotatably provided and heats and presses the paper on which the toner image is transferred between the pressure member and the toner image.
A bracket provided with the heating member;
A pressure lever supported rotatably on the bracket, the pressure lever supported rotatably on the bracket at a lower portion of the pressure lever;
A spring that applies pressure to the paper transported between the heating member and the pressure member by contacting the bracket and the pressure lever;
It is connected to the bracket by a shaft rotatably supported, is provided on one side and the other side of the shaft, contacts the upper part of the pressure lever, and bites in the rotation direction of the pressure lever A plurality of cams for adjusting the pressure by rotating the upper part of the pressure lever by being rotated in a direction not to be inserted,
A gear which is provided on the shaft and transmits a driving force from a driving source provided on the image forming apparatus main body side to rotate the plurality of cams;
A reading unit provided on the shaft for reading the rotational position of the cam;
A fixing device comprising:   An image forming apparatus comprising the fixing device according to claim 1.

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