Like a heating device

Abstract

To provide a configuration capable of preventing transmission of reaction force from a cam to a motor M2 while suppressing increase in size and cost.SOLUTION: A pressure drive device 391 switches applied pressure at a nip part by changing a position of a pressure roller with respect to a fixation belt 310. The pressure drive device 391 includes the motor M2, a pressure drive gear 395, a worm 393, a gear 394, a worm wheel 392 and a cam shaft 338. The gear 394 is attached to one end of the worm 393 and receives drive force from the pressure drive gear 395. The worm wheel 392 engages with the worm 393 and receives drive force from the worm 393. The cam shaft 338, to which the worm wheel 392 is attached, is rotatable. The cam is attached to the cam shaft 338, a pressure arm comes into contact with the cam and the pressure roller is displaced with respect to the fixation belt 310 due to rotation of the cam.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to an image heating apparatus for heating an image on a recording material. [Background technology]

[0002] A known fixing device, which is an image heating device, includes a cam that changes the pressure applied to the nip formed by the heating roller and the pressure roller. A proposed configuration includes a drive transmission device that transmits drive from a drive source to the cam, and a clutch that blocks the reaction force from the cam from being transmitted to the drive source (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-198949 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the configuration described in Patent Document 1, a clutch is provided to prevent the reaction force from the cam from being transmitted to the drive source, which increases the cost of the drive transmission device and increases the size of the device due to the provision of the clutch.

[0005] An object of the present invention is to provide a configuration that can suppress the reaction force from the cam from being transmitted to the drive source while suppressing increases in size and cost. [Means for solving the problem]

[0006] One aspect of the present invention is a recording medium conveying device comprising: a first rotating member that heats a recording material; a second rotating member that contacts the first rotating member and nip-conveys the recording material together with the first rotating member to form a nip portion where a toner image is fixed to the recording material; a pair of side plates that support the second rotating member; and a switching mechanism that changes the position of the second rotating member relative to the first rotating member to switch the pressure force at the nip portion, wherein the switching mechanism has: a motor; a worm that is driven to rotate by the motor; a worm wheel that meshes with the worm and to which driving force is transmitted from the worm; a cam that rotates as the rotation of the worm wheel is transmitted; a pair of bearings that rotatably support the worm; and a displacement mechanism that contacts the cam and displaces the second rotating member relative to the first rotating member as the cam rotates; On one of the side panels teeth, Each of the pair of bearings support plate is fixed The image heating apparatus is characterized by the above.

[0007] One aspect of the present invention is a recording medium conveying device comprising: a first rotating member that heats a recording material; a second rotating member that contacts the first rotating member and sandwiches and conveys the recording material together with the first rotating member to form a nip portion where a toner image is fixed to the recording material; a pair of side plates that support the second rotating member; and a switching mechanism that changes the position of the second rotating member relative to the first rotating member to switch between applying pressure and releasing the pressure at the nip portion, wherein the switching mechanism has: a motor; a worm that is driven and rotated by the motor; a worm wheel that meshes with the worm and to which driving force is transmitted from the worm; a cam that rotates when the rotation of the worm wheel is transmitted; a pair of bearings that rotatably support the worm; and a displacement mechanism that contacts the cam and displaces the second rotating member relative to the first rotating member as the cam rotates; On one of the side panels teeth, Each of the pair of bearings support plate is fixed The image heating apparatus is characterized by the above. One aspect of the present invention is a recording medium conveying device comprising: a first rotating member that heats a recording material; a second rotating member that contacts the first rotating member and sandwiches and conveys the recording material together with the first rotating member to form a nip portion where a toner image is fixed to the recording material; a pair of side plates that support the second rotating member; and a switching mechanism that changes the position of the second rotating member relative to the first rotating member to switch the pressure force at the nip portion, wherein the switching mechanism has: a motor; a worm that is driven to rotate by the motor; a worm wheel that meshes with the worm and to which driving force is transmitted from the worm; a cam that rotates as the rotation of the worm wheel is transmitted; a bearing that rotatably supports the worm at a position farther from the motor in the rotational axis direction of the worm than the meshing position where the worm meshes with the worm wheel; and a displacement mechanism that contacts the cam and displaces the second rotating member relative to the first rotating member as the cam rotates; On one of the side panels teeth, The bearing support plate is fixed The image heating apparatus is characterized by the above. [Effects of the Invention]

[0008] According to the present invention, it is possible to suppress the reaction force from the cam from being transmitted to the drive source while suppressing increases in size and cost. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view showing a schematic configuration of an image forming apparatus according to an embodiment. [Figure 2] FIG. 2 is a perspective view of a fixing device according to the embodiment. [Figure 3] Cross section AA of Figure 2. [Figure 4] Cross section B-B of Figure 2. [Figure 5] FIG. 2 is a cross-sectional view showing a schematic configuration of a drive transmission mechanism to a heating roller according to the embodiment. [Figure 6] FIG. 2 is a front view of the fixing device according to the embodiment, showing the drive transmission device exposed. [Figure 7](a) Graph showing the relationship between the cam rotation angle and the cam radius, (b) Schematic diagram of the cam showing each point in (a), (c) Graph showing the relationship between the cam rotation angle and the cam's axial torque. [Figure 8] FIG. 3 is a cross-sectional view taken along CC in FIG. 2 in a separated state. [Figure 9] 3 is a cross-sectional view taken along CC in FIG. 2 in a pressurized state for an envelope. [Figure 10] 2 in a pressurized state other than an envelope. [Figure 11] FIG. 7 is a view similar to FIG. 6 of a fixing device according to Comparative Example 1. [Figure 12] FIG. 2 is a perspective view of the fixing device according to the embodiment, seen from the front side in a state where the fixing device is pulled out from the device main body. [Figure 13] FIG. 11 is a perspective view of a fixing device according to Comparative Example 2, seen from the rear side, in a state where the fixing device is pulled out from the device main body. DETAILED DESCRIPTION OF THE INVENTION

[0010] The embodiment will be described with reference to Figures 1 to 13. First, the schematic configuration of an image forming apparatus according to the present embodiment will be described with reference to Figure 1.

[0011] [Image forming device] Image forming apparatus 1 is an electrophotographic full-color printer having four image forming units Pa, Pb, Pc, and Pd corresponding to the four colors of yellow, magenta, cyan, and black. In this embodiment, the image forming units Pa, Pb, Pc, and Pd are arranged in tandem along the rotation direction of an intermediate transfer belt 204 (described later). Image forming apparatus 1 forms a toner image (image) on a recording material in response to an image signal from an image reading unit (document reading device) 2 connected to image forming apparatus main body 3 or from a host device such as a personal computer connected to image forming apparatus main body 3 so as to be able to communicate with the image forming apparatus main body 3. Examples of recording materials include sheet materials such as paper, plastic film, and cloth.

[0012] The image forming apparatus 1 comprises an image reading unit 2 and an image forming apparatus main body 3. The image reading unit 2 reads an original placed on a platen glass 21. Light emitted from a light source 22 is reflected by the original and forms an image on a CCD sensor 24 via optical components 23 such as a lens. This optical unit scans in the direction of the arrow, converting the original into a line-by-line electrical signal data stream. The image signal obtained by the CCD sensor 24 is sent to the image forming apparatus main body 3, where it is subjected to image processing in accordance with each image forming unit (described later) by a control unit 30. The control unit 30 also receives external inputs as image signals from external host devices such as a print server.

[0013] The image forming apparatus main body 3 includes multiple image forming units Pa, Pb, Pc, and Pd, and each image forming unit forms an image based on the image signal. That is, the image signal is converted into a laser beam that is PWM (pulse width modulation) controlled by a control unit 30. A polygon scanner 31 serving as an exposure device scans the laser beam in accordance with the image signal. The laser beam is then irradiated onto photosensitive drums 200a to 200d serving as image carriers of each image forming unit Pa to Pd.

[0014] Note that Pa is a yellow (Y) image forming unit, Pb is a magenta (M) image forming unit, Pc is a cyan (C) image forming unit, and Pd is a black (Bk) image forming unit, each forming an image of the corresponding color. Since the image forming units Pa to Pd are substantially identical, the Y image forming unit Pa will be described in detail below, and descriptions of the other image forming units will be omitted. In the image forming unit Pa, a toner image is formed on the surface of the photosensitive drum 200a based on an image signal, as will be described below.

[0015] A charging roller 201a, which serves as a primary charger, charges the surface of the photosensitive drum 200a to a predetermined potential to prepare for the formation of an electrostatic latent image. A laser beam from a polygon scanner 31 forms an electrostatic latent image on the surface of the photosensitive drum 200a, which has been charged to a predetermined potential. A developing unit 202a develops the electrostatic latent image on the photosensitive drum 200a to form a toner image. A primary transfer roller 203a discharges electricity from the back surface of the intermediate transfer belt 204 and applies a primary transfer bias of opposite polarity to the toner, transferring the toner image on the photosensitive drum 200a onto the intermediate transfer belt 204. After transfer, the surface of the photosensitive drum 200a is cleaned by a cleaner 207a.

[0016] The toner image on intermediate transfer belt 204 is then conveyed to the next image forming station, where the toner images of each color formed at each image forming station are transferred in the order of Y, M, C, and Bk, forming a four-color image on the surface. The toner image that has passed through Bk image forming station Pd, which is located at the most downstream side in the rotation direction of intermediate transfer belt 204, is conveyed to a secondary transfer station made up of a pair of secondary transfer rollers 205 and 206. In the secondary transfer station, a secondary transfer electric field of opposite polarity to the toner image on intermediate transfer belt 204 is applied, thereby secondarily transferring the toner image onto the recording material.

[0017] The recording material is stored in a cassette 9, and the recording material fed from the cassette 9 is transported to a registration unit 208, which is made up of, for example, a pair of registration rollers, and waits at the registration unit 208. Thereafter, the timing of the registration unit 208 is controlled to align the position of the toner image on the intermediate transfer belt 204 with the position of the paper, and the recording material is transported to a secondary transfer unit.

[0018] The recording material onto which the toner image has been transferred in the secondary transfer section is transported to a fixing device 8, where the toner image carried on the recording material is fixed to the recording material by heating and pressing. The recording material that has passed through the fixing device 8 is discharged onto a discharge tray 7. When forming images on both sides of the recording material, after the toner image has been transferred and fixed onto the first side (front side) of the recording material, the recording material is turned over via a reversing conveyance section 10, and the toner image is transferred and fixed onto the second side (rear side) of the recording material, and the recording material is then stacked on the discharge tray 7.

[0019] As described above, the control unit 30 controls the entire image forming apparatus 1. The control unit 30 can also perform various settings based on inputs from the operation unit 4 and display unit 5 of the image forming apparatus 1. The operation unit 4 and display unit 5 are provided in the image forming apparatus 1 and are, for example, a touch panel or buttons that can be operated by touch.

[0020] Such a control unit 30 has a CPU (Central Processing Unit), ROM (Read Only Memory), and RAM (Random Access Memory). The CPU controls each unit by reading a program corresponding to a control procedure stored in the ROM. In addition, working data and input data are stored in the RAM, and the CPU performs control by referring to the data stored in the RAM based on the aforementioned program, etc.

[0021] [Fusing device] Next, a schematic configuration of the fixing device 8 in this embodiment will be described with reference to FIGS. 2 to 5. FIG. 2 is a perspective view of the fixing device 8, with the lower left side of FIG. 2 being the front side and the upper right side being the rear side. Here, the front side refers to the front side of the image forming apparatus 1, the side from which an operator operates the image forming apparatus 1. On the other hand, the rear side refers to the rear side of the image forming apparatus 1. In this embodiment, the fixing device 8 is movable relative to the housing 3a (see FIG. 1) of the image forming apparatus 1. By pulling the fixing device 8 out from the housing 3a to the front side, the fixing device 8 is exposed from the housing 3a, allowing replacement of the fixing belt 310, which will be described below, and the like. On the other hand, the fixing device 8 can be stored in the housing 3a by pushing the fixing device 8 into the housing 3a.

[0022] 3 is a view of the fixing device 8 in FIG. 2 cut at section F1, as viewed from the direction of arrow A. Section F1 is a cross section of the fixing device 8 that is perpendicular to the rotation axis of a pressure roller 330 (described below), and FIG. 3 is a view of the fixing device 8 taken at section F1, as viewed from the front. Meanwhile, FIG. 4 is a view of the fixing device 8 in FIG. 2 cut at section F1, as viewed from the direction of arrow A, and is a view of the fixing device 8 taken at section F1, as viewed from the rear. FIG. 5 is a cross-sectional view showing the drive configuration of a heating roller 340 (described below).

[0023] The fixing device 8 of this embodiment employs a belt heating method using an endless belt. In Fig. 3, the recording material is conveyed from right to left as indicated by the arrow α. The fixing device 8 includes a heating unit 300 having a fixing belt 310 as an endless rotatable belt, and a pressure roller 330 as a pressure rotating body that contacts the fixing belt 310 and forms a nip N together with the fixing belt 310.

[0024] The heating unit 300 includes a fixing belt 310 as a first rotating member, a fixing pad 390 as a nip portion forming member and a pad member, a heating roller 340 as a tension member, and a steering roller 350.

[0025] The endless fixing belt 310 has thermal conductivity, heat resistance, and the like, and is a thin-walled cylindrical shape. In this embodiment, it has a three-layer structure consisting of a base layer, an elastic layer on the outer periphery of the base layer, and a release layer on the outer periphery of the elastic layer. The base layer is 60 μm thick and made of polyimide resin (PI), the elastic layer is 300 μm thick and made of silicone rubber, and the release layer is 30 μm thick and made of PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin) as a fluororesin. The fixing belt 310 is stretched by a fixing pad 390, a heating roller 340, and a steering roller 350.

[0026] The fixing pad 390, which serves as a nip portion forming member, is disposed inside the fixing belt 310 so as to face the pressure roller 330 with the fixing belt 310 sandwiched therebetween, and forms a nip portion N between the fixing belt 310 and the pressure roller 330, which sandwiches and conveys the recording material. In this embodiment, the fixing pad 390 is a generally plate-shaped member that is long in the width direction of the fixing belt 310 (the longitudinal direction intersecting the rotation direction of the fixing belt 310, the direction of the rotation axis of the heating roller 340). The fixing pad 390 is pressed against the pressure roller 330 with the fixing belt 310 sandwiched therebetween, thereby forming the nip portion N having a predetermined width in the conveyance direction of the recording material. The fixing pad 390 is made of LCP (liquid crystal polymer) resin.

[0027] At least a portion of the portion of fixing pad 390 that forms nip portion N is formed in a flat shape. That is, the portion that contacts the inner circumferential surface of fixing belt 310 via a lubricating sheet (not shown) is formed in a substantially flat shape, making the shape of the nip portion substantially flat. This configuration can prevent wrinkles and image misalignment from occurring on the envelope, particularly when a toner image is fixed to an envelope as a recording material.

[0028] The fixing pad 390 is supported by a stay 360 serving as a support member disposed inside the fixing belt 310. That is, the stay 360 is disposed on the opposite side of the fixing pad 390 from the pressure roller 330, and supports the fixing pad 390. Such a stay 360 is a reinforcing member having long rigidity along the longitudinal direction of the fixing belt 310, and contacts the fixing pad 390 to back it up. That is, the stay 360 provides strength to the fixing pad 390 and ensures the pressure force at the nip N when the fixing pad 390 is pressed by the pressure roller 330.

[0029] The stay 360 is made of metal such as stainless steel, and has a substantially rectangular cross section (transverse cross section) perpendicular to the longitudinal direction of the stay 360, which intersects with the rotation direction of the fixing belt 310. Both ends of the stay 360 are supported by a fixing frame (frame, housing) 380 of the fixing device 8. As shown in FIG. 2 , the fixing frame 380 is made up of a front side plate 320, a rear side plate 321, a right stay 322, a left stay 323, and a bottom plate 324.

[0030] A lubricating sheet (not shown) is interposed between the fixing pad 390 and the fixing belt 310. In this embodiment, a PTFE (polytetrafluoroethylene) coated PI (polyimide) sheet with a thickness of 100 μm is used as the lubricating sheet. The PI sheet has 100 μm protrusions formed at 1 mm intervals, which reduces the contact area with the fixing belt 310 and thereby reduces sliding resistance.

[0031] A lubricant is applied in advance to the surface of the lubricating sheet that comes into contact with the fixing belt 310 to improve sliding properties. In this embodiment, oil is used as the lubricant. Silicone oil is preferably used as the lubricant from the standpoint of heat resistance, and oils of various viscosities are used depending on the conditions of use.

[0032] 3 and 4, the heating roller 340 is disposed inside the fixing belt 310 and tensions the fixing belt 310 together with the fixing pad 390 and the steering roller 350. As described above, a lubricant is applied to the inner peripheral surface of the fixing belt 310, and the heating roller 340 tensions the fixing belt 310 via this lubricant. The heating roller 340 is disposed downstream of the fixing pad 390 and upstream of the steering roller 350 in terms of the rotation direction of the fixing belt 310. This allows the driving force of the heating roller 340 to directly pull the fixing belt 310 that has passed through the nip portion N without using a tension roller in between.

[0033] Heating roller 340 is formed into a cylindrical shape from metal such as aluminum or stainless steel, and has a plurality of halogen heaters 341 disposed therein as heaters for heating fixing belt 310 (FIG. 3). Heating roller 340 is heated to a predetermined temperature by halogen heaters 341.

[0034] In this embodiment, the heating roller 340 is formed from a stainless steel pipe with a thickness of 1 mm, and multiple halogen heaters 341 are arranged inside. It is desirable to have multiple halogen heaters in consideration of temperature distribution control in the longitudinal direction (direction of the rotation axis) of the heating roller 340. The multiple halogen heaters 341 have different light distributions in the longitudinal direction, and the lighting ratio is controlled according to the size of the recording material. The heater is not limited to a halogen heater, and may be another heater capable of heating the heating roller 340, such as a carbon heater. The fixing belt 310 is heated by the heating roller 340 heated by the halogen heater 341, and is controlled to a predetermined target temperature according to the type of recording material based on temperature detection by a thermistor (not shown).

[0035] The heating roller 340 is rotatably supported by the fixing frame 380. As shown in Fig. 5, a gear 385a is fixed to one end (rear end) of the heating roller 340 in the direction of its rotation axis, and the heating roller 340 is connected to a motor M1, which serves as a heating roller drive source, via an idler gear 385b and a motor gear 385c, and is driven to rotate. The idler gear 385b is rotatably supported by a heating roller drive support plate 325 fixed to the rear side plate 321, and transmits rotational driving force to the heating roller 340 by meshing with the motor gear 385c and gear 385a. These gears 385a, 385b, and 385c constitute a gear train 385, which serves as a drive transmission mechanism from the motor M1 to the heating roller 340.

[0036] In this way, heating roller 340 is connected to motor M1 via gear train 385 and is driven to rotate. A driving force is applied to fixing belt 310 by the rotation of heating roller 340. Note that the drive transmission mechanism from the motor may be other mechanisms than gears, such as a pulley and belt, or a mechanism that presses a roller driven by the motor from the outside.

[0037] The steering roller 350 is disposed inside the fixing belt 310, stretches the fixing belt 310 together with the fixing pad 390 and the heating roller 340, and is rotated by the fixing belt 310. The steering roller 350 tilts relative to the rotation axis direction (longitudinal direction) of the heating roller 340, thereby controlling the position (offset position) of the fixing belt 310 relative to this rotation axis direction. That is, the steering roller 350 has a rotation center at the center of the rotation axis direction (longitudinal direction) of the steering roller 350, and tilts relative to the longitudinal direction of the heating roller 340 by swinging around this rotation center. This generates a tension difference between one side and the other side of the fixing belt 310 in the longitudinal direction, causing the fixing belt 310 to move in the longitudinal direction.

[0038] The steering roller 350 may be oscillated by a driving source such as a motor, or may be configured to oscillate by self-alignment. The rotation center may be the center in the longitudinal direction as in this embodiment, or may be an end in the longitudinal direction. In this embodiment, a motor M3 is provided to tilt the steering roller 350.

[0039] In this embodiment, the steering roller 350 is biased by a spring supported by the frame of the heating unit 300, and also serves as a tension roller that applies a predetermined tension to the fixing belt 310. By applying tension to the fixing belt 310 using the steering roller 350 in this manner, the fixing belt 310 is caused to follow the fixing pad 390.

[0040] The pressure roller 330, which serves as the second rotating member, is a roller having an elastic layer formed on the outer periphery of its shaft and a release layer formed on the outer periphery of the elastic layer. The shaft is made of stainless steel, the elastic layer is 5 mm thick and made of conductive silicone rubber, and the release layer is 50 μm thick and made of PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin) which is a fluororesin.

[0041] 3 and 4, the fixing frame 380 has the front plate 320 and the rear plate 321, and as shown in FIG. 3 and FIG. 4, the front plate 320 and the rear plate 321 have heating unit positioning portions 381 and 382, ​​respectively. The heating unit positioning portions 381 and 382 have pressure direction regulating surfaces 381a and 382a that face the pressure roller 330, and transport direction regulating surfaces 381b and 382b that are abutting surfaces in the insertion direction of the heating unit 300.

[0042] The heating unit 300 is positioned on the fixing frame 380 by inserting the stay 360 into the heating unit positioning portions 381 and 382 and fixing the stay 360 to the heating unit positioning portions 381 and 382 by a fixing means (not shown). At this time, the stay 360 is fixed in a state where its movement is restricted by the pressure direction restricting surfaces 381a and 382a and the conveying direction restricting surfaces 381b and 382b.

[0043] A pressure arm support plate 326 (FIG. 3) is fixed to the rear plate 321, and a pressure arm support plate 327 (FIG. 4) is fixed to the front plate 320 by welding. The pressure arm support plate 326 is a component for rotatably supporting the pressure arm 328, and the pressure arm 328 rotatably supports the pressure roller 330. Similarly, the pressure arm support plate 327 is a component for rotatably supporting the pressure arm 334, and the pressure arm 334 is a component for rotatably supporting the pressure roller 330. In other words, both ends of the pressure roller 330 are rotatably supported by the front and rear pressure arms 328, 334.

[0044] The front and rear pressure arms 328, 334 are connected to a motor M2 serving as a pressure drive source around front and rear rotary shafts 333, 335, and are lifted by front and rear pressure cams (pressure cams) 329, 336. The front and rear cams 329, 336 are coupled to a cam shaft 338 serving as a rotary shaft. Specifically, the cams 329, 336 are fixed to both ends of the cam shaft 338, respectively, and are rotatable in phase with each other. When the front and rear pressure arms 328, 334 are lifted by the cams 329, 336, the pressure roller 330 presses the fixing pad 390 via the fixing belt 310, and a predetermined pressure force is applied by the pressure springs 331, 337. That is, the pressure arms 328, 334 serving as a displacement mechanism abut against the cams 329, 336, and displace the pressure roller 330 relative to the fixing belt 310 as the cams 329, 336 rotate.

[0045] As described above, both ends of the pressure roller 330 are supported by the front and rear pressure arms 328, 334, and the pressure arms 328, 334 are lifted by the cams 329, 336, forming a nip N between the fixing belt 310 and the pressure roller 330. In the nip N, the recording material P carrying a toner image is sandwiched and conveyed, and the toner image is heated and fixed to the recording material P.

[0046] On the other hand, while the fixing process to the recording material P is not being performed, the fixing belt 310 and the pressure roller 330 can be separated from each other by moving the pressure arms 328 and 334 in the separation direction using cams 329 and 336 connected to the motor M2, thereby releasing the nip and allowing the device to wait. In other words, the cams 329 and 336 can move the pressure roller 330 toward or away from the fixing belt 310 by rotating.

[0047] [Drive transmission device] Next, referring to FIG. 6, a description will be given of a pressure drive device 391 serving as a switching mechanism having a drive transmission device 400 that transmits drive from motor M2, which serves as a drive source, to front and rear cams 329 and 336 (see FIGS. 3 and 4). The pressure drive device 391 includes a pressure drive support plate 389, motor M2, and drive transmission device 400, and is fixed as a unit to the front plate 320 of the fixing device 8. Therefore, when removing the fixing device 8 from the image forming apparatus, the motor M2 and drive transmission device 400 are removed together with the fixing belt 310 and the pressure roller 330. Meanwhile, motors M1 and M3 are attached to the rear plate 321. As a result, in this embodiment, when removing the fixing device 8 from the image forming apparatus, the motors M1 to M3 and drive transmission device 400 are removed together with the fixing belt 310 and the pressure roller 330.

[0048] The drive transmission device 400 includes a worm gear 401, a pair of bearings 399, a pressure drive gear 395 as a first drive transmission member, and a gear 394 as a second drive transmission member. The worm gear 401 includes a worm wheel 392 and a worm 393. The worm wheel 392 is fixed to one end of a cam shaft 338, which is the rotation shaft of the cams 329 and 336. The worm 393 is provided on a rotation shaft 393a (on the rotation shaft) that rotates by drive from the motor M2, and meshes with the worm wheel 392. In this embodiment, the worm 393 is made of metal, specifically stainless steel. It is preferable that the worm wheel 392 is made of the same metal as the worm 393. It is also preferable that the pressure drive gear 395 and the gear 394 are made of metal. The pair of bearings 399 respectively support the rotary shaft 393a on both ends of the worm 393 in the direction of the rotation axis of the worm 393. That is, the pair of bearings 399 are arranged to sandwich the worm 393 from both sides, and rotatably support the rotary shaft 393a.

[0049] The pressure application drive gear 395 is provided on a drive shaft 395a of the motor M2 (on the drive shaft). That is, the pressure application drive gear 395 is fixed to the drive shaft 395a and rotates together with the drive shaft 395a. The gear 394 is provided on the rotation shaft 393a at one end of the worm 393 in the direction of the rotation axis of the worm 393, and receives drive from the pressure application drive gear 395. Specifically, the gear 394 is fixed to an end of the rotation shaft 393a on one side of the bearing 399 on one side of a pair of bearings 399, and meshes with the pressure application drive gear 395, thereby rotating together with the rotation shaft 393a and the worm 393 when driven by the motor M2. The pressure application drive gear 395 and the gear 394 are spur gears that mesh with each other.

[0050] In this embodiment, with this configuration, the cams 329 and 336 are rotated by the drive of the motor M2. That is, when the drive shaft 395a and the pressure drive gear 395 rotate by the drive of the motor M2, the gear 394 meshing with the pressure drive gear 395 rotates, and the worm 393 rotates together with the gear 394. Furthermore, the worm wheel 392 meshing with the worm 393 rotates, and the cams 329 and 336 rotate via the cam shaft 338 to which the worm wheel 392 is fixed. This changes the positions of the pressure arms 328 and 334 (FIGS. 3 and 4), and as described above, the fixing belt 310 and the pressure roller 330 are brought into contact with or separated from each other. The following describes their arrangement. The motor M2 is disposed above the worm 393 in the vertical direction. When viewed from above, the motor M2 overlaps with the worm 393. The motor M2 is also disposed above the worm wheel 392 in the vertical direction.

[0051] [How to change pressure] In this embodiment, the fixing belt 310 and the pressure roller 330 are brought into contact with and separated from each other by rotating the cams 329 and 336 as described above. In addition to bringing them into contact with and separating them, the pressure applied by the pressure roller 330 can be changed to change the nip pressure between the fixing belt 310 and the pressure roller 330. That is, by changing the position of the pressure roller 330 relative to the fixing belt 310, it is possible to switch between applying and removing pressure at the nip. With the increasing diversity of media supported by image forming devices in recent years, fixing devices are required to perform optimal fixing processing for a variety of recording materials, from plain paper to special paper such as envelopes. For this reason, in this embodiment, the pressure applied to the nip (nip pressure) can be changed to accommodate a variety of media.

[0052] This method of changing the pressure force will be described with reference to FIGS. 7(a) through 10. FIG. 7(a) shows a cam diagram of the front and rear cams 329 and 336, FIG. 7(b) shows a schematic diagram of the corresponding cams 329 and 336, and FIG. 7(c) shows the axial torque of the cams 329 and 336. FIGS. 8 through 10 are views of the fixing device 8 in FIG. 2 cut at section F2, as viewed from the direction of arrow C. Section F1 is a cross section perpendicular to the rotation axis of the pressure roller 330 of the fixing device 8, and FIGS. 8 through 10 are views of the fixing device 8 taken at section F2 as viewed from the front. Also, FIGS. 8 through 10 show the pressure states resulting from the transition of the front and rear cams 329 and 336.

[0053] The cams 329 and 336 are formed so that the fixing belt 310 and the pressure roller 330 can be brought into contact with and separated from each other, and so that the pressure force acting on the nip portion N can be changed in multiple stages when the fixing belt 310 and the pressure roller 330 are in contact with each other. First, Fig. 7(a) shows the relationship (cam diagram) between the rotation angle (phase) of the cams 329 and 336 and the cam radius when the front and rear cams 329 and 336 start from point D in Fig. 7(b) and rotate counterclockwise to point E. Note that Fig. 7(a) shows the cam radius with point D as the reference (0 mm).

[0054] Cam surface 370 of cams 329 and 336 is made up of cam flat surface 371a, which is a separation phase range including point A where pressure roller 330 and fixing belt 310 are separated, and cam slope surface 371b, which is a pressure contact phase range of pressure roller 330 that forms nip portion N. Cam surface 370 is a surface that comes into contact with cam follower 372 (FIGS. 8 to 10), which will be described later. Cam flat surface 371a is a flat surface that is approximately perpendicular to the direction of the reaction force acting from cam follower 372 when in contact with cam follower 372.

[0055] Cam slope surface 371b is the surface where pressure roller 330 comes into contact with fixing belt 310 within this phase range, and is the surface that changes the pressure applied by pressure roller 330. With respect to the counterclockwise direction in FIG. 7B, cam transition surface 371c is formed between cam flat surface 371a and cam slope surface 371b, which moves pressure roller 330 from a position separated from fixing belt 310 to a position where pressure roller 330 comes into contact with fixing belt 310.

[0056] The cam gradient surface 371b and the cam transition surface 371c are formed so that the distance (cam radius) from the rotation center O of the cams 329 and 336 gradually increases in the counterclockwise direction in Figure 7(b). Furthermore, the rate of increase in the cam radius is smaller for the cam gradient surface 371b than for the cam transition surface 371c.

[0057] Furthermore, point B on cam inclined surface 371b is the point at which pressure is applied when fixing an envelope. Point C on cam inclined surface 371b is the point at which pressure is applied when fixing a recording material other than an envelope. For this reason, in this embodiment, cams 329 and 336 can change the pressure acting on the nip portion in two stages. However, the cams may also be configured to change the pressure in three or more stages. For example, for recording materials with a high basis weight, such as cardboard, a pressure greater than the pressure at point C may be set.

[0058] Figure 7(c) shows the axial torque of the cams 329 and 336 when a pressure force is applied to the nip portion N by the cam slope surface 371b including points B and C shown in Figures 7(a) and 7(b). Figure 7(c) also shows the amount (cam lift amount) by which the pressure arms 328 and 334 are moved by the cams 329 and 336. Figure 7(c) shows that the axial torque increases as the rotation angle of the cams 329 and 336 increases, i.e., as the cam radius increases, on the cam slope surface 371b.

[0059] Fig. 8 shows a state in which pressure roller 330 is separated from fixing belt 310. Note that Fig. 8 is a view of cross section F in Fig. 2 as seen from the direction of arrow C, and therefore front pressure arm 334 and cam 336 are visible. However, the same is true for rear pressure arm 328 and cam 329, and therefore in the following description, they will be described as front and rear pressure arms 328, 334 and cams 329, 336, as described above. The same is true for Figs. 9 and 10.

[0060] As shown in Figure 8, the front and rear pressure arms 328, 334 (see Figures 3 and 4) are made up of upper arm portions 328U, 334U, lower arm portions 328L, 334L, cam followers 372, pressure screws 373, and pressure springs 331, 337. The base ends of the upper arm portions 328U, 334U and the lower arm portions 328L, 334L are supported relatively rotatably about front and rear rotation shafts 333, 335, respectively.

[0061] Pressure springs 331 and 337 are disposed in an elastically compressed state between the tips of the upper arm portions 328U and 334U and the lower arm portions 328L and 334L, respectively. Pressure springs 331 and 337 bias the tips of the upper arm portions 328U and 334U and the lower arm portions 328L and 334L in a direction that widens the gap between them. Furthermore, pressure screws 373 restrict the relative movement of the tips of the upper arm portions 328U and 334U and the lower arm portions 328L and 334L so that the gap does not widen beyond a predetermined distance. However, relative movement of the tips of the upper arm portions 328U and 334U and the lower arm portions 328L and 334L in a direction that narrows the gap is permitted. The cam follower 372 is rotatably supported by the lower arm portions 328L and 334L so as to come into contact with the front and rear cams 329 and 336, respectively.

[0062] First, while the fixing process on the recording material is not being performed, the fixing belt 310 and the pressure roller 330 are separated, the nip is released, and the device is on standby. At this time, as shown in Figure 8, the cam follower 372 and the front and rear cams 329 and 336 are in contact with each other at point A shown in Figures 7(a) and 7(b). Also, at this time, the gap between the tip ends of the upper arm portions 328U and 334U and the lower arm portions 328L and 334L is regulated by the pressure screw 373.

[0063] Next, when fixing an envelope, motor M2 is driven to rotate cams 329 and 336 in the direction of the arrow, as shown in Fig. 9. When cams 329 and 336 rotate, lower arm portions 328L and 334L are pushed up via cam follower 372, and upper arm portions 328U and 334U are further pushed up via pressure springs 331 and 337. Then, pressure roller 330 supported by upper arm portions 328U and 334U comes into contact with fixing belt 310. When cams 329 and 336 rotate until they come into contact with cam follower 372 at point B, a nip is formed between fixing belt 310 and pressure roller 330, which applies pressure for an envelope.

[0064] At this time, the pressure roller 330 comes into contact with the fixing belt 310, restricting the movement of the upper arm portions 328U and 334U, while the lower arm portions 328L and 334L move upward relative to the pressure roller 330, compressing the pressure springs 331 and 337 by W1. As a result, the upper arm portions 328U and 334U are biased by the pressure springs 331 and 337, and a pressure of, for example, 1000 N, which is a pressure for an envelope, can be applied to the nip portion N.

[0065] Finally, when fixing a recording material other than an envelope, as shown in FIG. 10, motor M2 is driven to further rotate cams 329 and 336 in the direction of the arrow from the state shown in FIG. 9. This further pushes up lower arm portions 328L and 334L, further compressing pressure springs 331 and 337. When cams 329 and 336 rotate until they abut cam follower 372 at point C, the compression amount of pressure springs 331 and 337 becomes W2, which is larger than W1, the compression amount for envelopes. This causes upper arm portions 328U and 334U to be biased against pressure springs 331 and 337, applying a pressure of, for example, 1500 N to nip portion N, which is a pressure for recording materials other than envelopes. Of course, the pressure for recording materials other than envelopes is larger than that for envelopes.

[0066] In this way, when fixing processing is performed on the recording material, the cams 329 and 336 come into contact with the cam follower 372 at point B or point C. As shown in Figures 7(a) to 7(c), at points B and C, the camshaft 338 receives a reaction force as an axial torque from the cams 329 and 336. Because the camshaft 338 is driven by the motor M2, there is a risk that the reaction force may also act on the motor M2 depending on the drive transmission device from the motor M2 to the camshaft 338.

[0067] In this embodiment, a worm gear 401 is used in the drive transmission path from the motor M2 to the camshaft 338. The worm gear 401 can obtain a large reduction ratio without using many gears. The worm gear 401 also has a so-called self-locking function that makes it difficult for drive to be transmitted from the worm wheel 392 to the worm 393. As described above, the worm wheel 392 is fixed to one end of the camshaft 338, and the worm wheel 392 is drivingly connected to the worm 393. Therefore, in this embodiment, the self-locking function of the worm gear 401 itself locks the reaction force from the cams 329 and 336, preventing the reaction force from being transmitted to the motor M2.

[0068] As a result, even when the cams 329 and 336 are stopped at any location on cam gradient surface 371b, including points B and C, in order to change the pressure force, it is possible to maintain the cam phase while preventing the transmission of a reaction force to motor M2 via drive transmission device 400. This eliminates the need to supply a drive force to motor M2 for maintaining the cam phase, making it possible to change the pressure force at nip portion N with energy conservation. In other words, it becomes possible to adjust the pressure force steplessly in accordance with various recording materials, including envelopes, with energy conservation.

[0069] Furthermore, although it is conceivable to provide a clutch in the drive transmission path to prevent the reaction force from the camshaft 338 from being transmitted to the motor M2, in this embodiment, such a clutch need not be provided. Therefore, it is possible to prevent the reaction force from the cams 329, 336 from being transmitted to the motor M2 while suppressing increases in size and cost.

[0070] On the other hand, a load (thrust force) acts on the worm 393 in the direction of the rotation axis due to reaction forces from the cams 329 and 336. This point will be explained using Comparative Example 1 in Fig. 11. In Comparative Example 1, in contrast to the configuration of this embodiment shown in Fig. 6, the worm 393 is provided on the drive shaft 393b of the motor M2, and both sides of the worm 393 are not supported by bearings.

[0071] 11, if the worm 393 is disposed on the drive shaft 393b of the motor M2, the drive shaft 393b will receive a thrust force in the direction A due to the reaction force from the cam. This will increase the load on the internal parts of the motor M2, which may reduce the durability of the motor M2.

[0072] However, in this embodiment, as shown in FIG. 6, the rotation shaft 393a of the worm 393 and the drive shaft 395a of the motor M2 are separate bodies and are drive-coupled by gears. In this embodiment, the rotation shaft 393a is disposed substantially parallel to the drive shaft 395a at a position offset from the drive shaft 395a. A gear 394 is fixed to the end of the rotation shaft 393a, and a pressure drive gear 395 fixed to the drive shaft 395a is meshed with the gear 394. The gear 394 and the pressure drive gear 395 are spur gears. Therefore, even if a thrust force acts on the worm 393 and the rotation shaft 393a due to a reaction force from the cam, the thrust force can be reduced from acting on internal components of the motor M2, thereby preventing a decrease in the durability of the motor M2.

[0073] Furthermore, because both sides of the worm 393 are supported by a pair of bearings 399, the thrust force acting on the worm 393 and the rotating shaft 393a can be received by the pair of bearings 399. This also reduces the thrust force acting on the internal components of the motor M2. Furthermore, when the motor M2 is running, the reaction force acting on the worm 393 from the worm wheel 392 meshing with the worm 393 makes it difficult for the worm 393 to separate from the worm wheel 392, thereby improving drive transmission efficiency.

[0074] Furthermore, in this embodiment, the rotational speed of the drive shaft 395a of the motor M2 is reduced by the worm gear 401, so the reduction ratio can be increased without using multiple gears. For example, it is possible to arrange multiple idler gears between the gear 394 and the pressure drive gear 395 to obtain the reduction ratio, but this would result in an increased device size. In contrast, in this embodiment, the reduction ratio can be increased without providing multiple idler gears, so the device can be made more compact. As described above, this embodiment makes it possible to provide a drive transmission device 400 and a pressure drive device 391 that can change the pressure force in the nip portion while achieving energy savings and compactness.

[0075] [Durability during maintenance of the fixing unit] Next, the durability of the fixing device 8 during maintenance will be described with reference to Figures 12 and 13. As shown in Figure 12, in this embodiment, the fixing device 8 is detachably unitized from the housing 3a of the image forming apparatus 1 (see Figure 1), taking into consideration the ease of maintenance of the pressure drive device 391, the heating unit 300, the pressure roller 330, etc.

[0076] For this purpose, the fixing device 8 is placed on a fixing device drawer 501, which is configured to be able to be pulled out from inside the housing 3a to a predetermined position outside. A support rail 502 is provided between the fixing device drawer 501 and the housing 3a, and a guide member 503 is attached to the rear or side of the fixing device drawer 501. A driven wheel engaged with the support rail 502 is provided on the guide member 503. When pulling out the fixing device 8 from the housing 3a, the user opens a front door (not shown) of the image forming apparatus 1, operates a lock lever 504, and then grasps the lock lever 504 to pull out the fixing device drawer 501 toward the user (in the direction of the arrow in FIG. 12 ). At this time, the fixing device drawer 501 is guided by the guide member 503, and the driven wheel rotates on the support rail 502, thereby pulling out the fixing device 8 forward. In this state, the fixing device 8 can be attached to or detached from the fixing device drawer 501 for maintenance, for example, by holding a handle (not shown).

[0077] Here, the durability of the fixing device 8 during maintenance will be examined using Comparative Example 2 in FIG. 13. In Comparative Example 2, of the pressure drive device 391A for transmitting drive from the motor M2 to the cam, the members downstream of the worm wheel 392 in the drive transmission direction, including the worm wheel 392, are fixed to the fixing device 8A, and the rest are provided in the housing 3a. In Comparative Example 2, the worm wheel 392 provided on the fixing device 8A side and the worm 393 provided on the housing 3a side are engaged and disengaged by pulling out and inserting the fixing device 8A. For this reason, the pressure drive device 391A is disposed on the rear side plate 321 side of the fixing frame 380.

[0078] In the case of Comparative Example 2, when the pulled-out fixing device 8A is inserted into the housing 3a during maintenance, the worm wheel 392 provided on the fixing device 8A side meshes with the worm 393 provided on the housing 3a side. At this time, the phases of the worm wheel 392 and the worm 393 are shifted, and there is a risk that the tooth surfaces will collide with each other and be damaged.

[0079] In contrast, in this embodiment, the pressure drive device 391 is fixed to the fixing frame 380. That is, the drive transmission device 400 including the worm wheel 392 and the worm 393 and the motor M2 are fixed to the fixing frame 380. Specifically, they are fixed to the front side plate 320 of the fixing frame 380. Therefore, even when the fixing device 8 is attached to or detached from the housing 3a, the worm wheel 392 and the worm 393 move together with the fixing device 8. Therefore, when the fixing device 8 is inserted into the housing 3a, the tooth surfaces of the worm wheel 392 and the worm 393 do not collide with each other. This ensures durability during maintenance of the fixing device 8.

[0080] <Other embodiments> In the above embodiment, the drive force is transmitted between the drive shaft 395a of the motor M2 and the rotary shaft 393a of the worm 393 by means of gears, but it may also be configured using, for example, a pulley and a belt.

[0081] Furthermore, the pressure roller 330, which forms a nip portion with the fixing belt 310, may be a drive roller that rotates in contact with the outer circumferential surface of the fixing belt 310 and applies a driving force to the fixing belt 310. For example, the pressure roller 330 may have a gear fixed to one end thereof, and be connected to a motor serving as a pressure roller drive source via the gear so as to be driven to rotate. In this case, it is preferable that the peripheral speed of the heating roller 340 is set higher than that of the pressure roller 330. The heating roller 340 may also be connected to a motor that drives the pressure roller 330 so as to be driven to rotate.

[0082] In the above embodiment, the heating roller 340 is disposed downstream of the fixing pad 390 and upstream of the steering roller 350 with respect to the rotation direction of the fixing belt 310. However, the positions of the heating roller 340 and the steering roller 350 may be interchanged. That is, the heating roller 340 may be disposed downstream of the steering roller 350 and upstream of the fixing pad 390 with respect to the rotation direction of the fixing belt 310.

[0083] In the above-described embodiments, the fixing pad 390 is used as a member (nip portion forming member) that forms a nip portion in the fixing belt 310 between itself and the pressure roller 330, but the nip portion forming member may be a rotating body such as a roller. In the above-described embodiments, the pressure roller 330 is used as the driving rotating member, but the driving rotating member may be a belt that is driven to rotate. That is, in the above-described embodiments, the first rotating member is the fixing belt 310 and the second rotating member is the pressure roller 330, but both the first rotating member and the second rotating member may be belts. Furthermore, both the first rotating member and the second rotating member may be rollers.

[0084] In the above embodiment, the drive transmission device 400 is applied to a fixing device, but the drive transmission device 400 can be applied to other configurations as long as it is provided in a drive transmission path from a motor to a cam. For example, the drive transmission device 400 can be applied to a mechanism that raises and lowers recording materials loaded on a stacking tray of an image forming apparatus. [Explanation of symbols]

[0085] 8···Fusing device / 310···Fusing belt (first rotating member) / 328, 334···Pressure arm (displacement mechanism) / 329, 336···Cam / 330···Pressure roller (second rotating member) / 338···Cam shaft / 380···Fusing frame / 391···Pressure drive device (switching mechanism) / 392···Worm wheel / 393···Worm / 393a···Rotary shaft / 394···Gear (second drive transmission member) / 395···Pressure drive gear (first drive transmission member) / 395a···Drive shaft / 399···Bearing / 400···Drive transmission device / M2···Motor (drive source)

Claims

1. a first rotating member that heats the recording material; a second rotating member that contacts the first rotating member and nip-conveys a recording material together with the first rotating member to form a nip portion where a toner image is fixed onto the recording material; A pair of side plates supporting the second rotary member; a switching mechanism that changes the position of the second rotating member relative to the first rotating member to switch the pressure force at the nip portion, The switching mechanism includes: A motor; a worm that is driven to rotate by the motor; a worm wheel that meshes with the worm and to which a driving force is transmitted from the worm; a cam that rotates when rotation of the worm wheel is transmitted to it; a pair of bearings that rotatably support the worm; a displacement mechanism that abuts against the cam and displaces the second rotary member relative to the first rotary member as the cam rotates, an image heating apparatus, wherein support plates constituting the pair of bearings are fixed to one of the pair of side plates;

2. a first drive transmission member attached to a shaft of the motor; a second drive transmission member attached to one end of the worm in the rotational axis direction of the worm, to which driving force is transmitted from the first drive transmission member, the first drive transmission member and the second drive transmission member are each spur gears; 2. An image heating apparatus according to claim 1, wherein the first drive transmission member meshes with the second drive transmission member.

3. 3. The image heating apparatus according to claim 1, wherein when the image heating apparatus is removed from an image forming apparatus that supports the image heating apparatus, the motor and the worm are removed integrally with the image heating apparatus.

4. 4. An image heating apparatus according to claim 1, wherein the motor and the worm are supported by one of the pair of side plates.

5. When the motor is a first motor, the motor has a second motor that rotates at least the first rotating member or the second rotating member, 5. An image heating apparatus according to claim 4, wherein the second motor is supported by the other side plate.

6. a first drive transmission member attached to a shaft of the motor; a second drive transmission member attached to one end of the worm in the rotational axis direction of the worm, to which driving force is transmitted from the first drive transmission member, 2. An image heating apparatus according to claim 1, wherein the first drive transmission member, the second drive transmission member, the worm, and the worm wheel are each made of metal.

7. the first rotating member is a belt; 7. The image heating apparatus according to claim 1, further comprising: a steering roller that can be tilted and that stretches the belt; a pad that presses the second rotating member via the belt; and a heating roller that stretches the belt and heats the belt.

8. the motor and the worm are supported by one of the pair of side plates; 8. An image heating apparatus according to claim 7, wherein a steering motor for tilting said steering roller is supported on the other side plate.

9. 9. An image heating apparatus according to claim 1, wherein the motor is disposed above the worm wheel in the vertical direction.

10. a first rotating member that heats the recording material; a second rotating member that contacts the first rotating member and nip-conveys a recording material together with the first rotating member to form a nip portion where a toner image is fixed onto the recording material; A pair of side plates supporting the second rotary member; a switching mechanism that switches between applying pressure and releasing the pressure at the nip portion by changing the position of the second rotating member relative to the first rotating member, The switching mechanism includes: A motor; a worm that is driven to rotate by the motor; a worm wheel that meshes with the worm and to which a driving force is transmitted from the worm; a cam that rotates when rotation of the worm wheel is transmitted to it; a pair of bearings that rotatably support the worm; a displacement mechanism that abuts against the cam and displaces the second rotary member relative to the first rotary member as the cam rotates, an image heating apparatus, wherein support plates constituting the pair of bearings are fixed to one of the pair of side plates;

11. a first drive transmission member attached to a shaft of the motor; a second drive transmission member attached to one end of the worm in the rotational axis direction of the worm, to which driving force is transmitted from the first drive transmission member, the first drive transmission member and the second drive transmission member are each spur gears; 11. An image heating apparatus according to claim 10, wherein the first drive transmission member meshes with the second drive transmission member.

12. 12. The image heating apparatus according to claim 10, wherein when the image heating apparatus is removed from an image forming apparatus that supports the image heating apparatus, the motor and the worm are removed integrally with the image heating apparatus.

13. 13. An image heating apparatus according to claim 10, wherein the motor and the worm are supported by one of the pair of side plates.

14. When the motor is a first motor, the motor has a second motor that rotates at least the first rotating member or the second rotating member, 14. An image heating apparatus according to claim 13, wherein the second motor is supported by the other side plate.

15. a first drive transmission member attached to a shaft of the motor; a second drive transmission member attached to one end of the worm in the rotational axis direction of the worm, to which driving force is transmitted from the first drive transmission member, 11. An image heating apparatus according to claim 10, wherein the first drive transmission member, the second drive transmission member, the worm, and the worm wheel are each made of metal.

16. 16. An image heating apparatus according to claim 1, wherein the worm wheel meshes with the worm between the pair of bearings.

17. a first drive transmission member attached to a shaft of the motor; 11. The image heating apparatus according to claim 1, further comprising: a second drive transmission member attached to one end of the worm in the direction of the rotation axis of the worm, and receiving a drive force transmitted from the first drive transmission member.

18. a first rotating member that heats the recording material; a second rotating member that contacts the first rotating member and nip-conveys a recording material together with the first rotating member to form a nip portion where a toner image is fixed onto the recording material; A pair of side plates supporting the second rotary member; a switching mechanism that changes the position of the second rotating member relative to the first rotating member to switch the pressure force at the nip portion, The switching mechanism includes: A motor; a worm that is driven to rotate by the motor; a worm wheel that meshes with the worm and to which a driving force is transmitted from the worm; a cam that rotates when rotation of the worm wheel is transmitted to it; a bearing that rotatably supports the worm at a position farther from the motor than an engagement position where the worm engages with the worm wheel in a rotational axis direction of the worm; a displacement mechanism that abuts against the cam and displaces the second rotary member relative to the first rotary member as the cam rotates, an image heating apparatus, wherein a support plate constituting the bearing is fixed to one of the pair of side plates;

Images