Fixing device and image forming apparatus

Abstract

To provide a fixing device and an image forming apparatus with which the fixing device can be accurately positioned with respect to an image forming apparatus body.SOLUTION: A fixing device 8 is attached to an image forming apparatus body, and comprises: a heater; an endless belt BL that is heated by the heater; a pressure roller 82 that forms a nip part with the belt BL; a frame 40 that is made of resin and supports the belt BL and the pressure roller 82, the frame 40 having a first side wall 40A located at one end of the frame 40 in a longitudinal direction of the pressure roller 82; and a reinforcing plate 50 that is made of metal and fixed to the first side wall 40A. The reinforcing plate 50 has a projection 51 projecting in the longitudinal direction for positioning the fixing device 8 with respect to the image forming apparatus body.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a fixing device and an image forming apparatus. [Background technology]

[0002] Conventionally, a known fixing device includes a heater, an endless belt heated by the heater, a pressure roller that forms a nip between the heater and the endless belt, and a resin frame that supports the pressure roller (Patent Document 1). In this technology, an engagement portion that protrudes from the side wall of the resin frame is provided, and the engagement portion engages with an engagement rib provided on the image forming device main body, thereby positioning the fixing device relative to the image forming device main body. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-206346 Summary of the Invention [Problem to be solved by the invention]

[0004] However, if the resin frame is provided with a positioning portion, such as an engagement portion, for positioning relative to the image forming device body, there is a possibility that the fixing device will not be able to be positioned accurately relative to the image forming device body if the temperature of the frame becomes high due to the thermal fixing of the toner image.

[0005] Therefore, an object of the present invention is to provide a fixing device and an image forming apparatus that can accurately position the fixing device relative to the main body of the image forming apparatus. [Means for solving the problem]

[0006] The fixing device is attached to the image forming device main body and includes a heater, a heating member heated by the heater, a pressure member that forms a nip portion between the heating member and the pressure member, a resin frame that supports the heating member and the pressure member, the frame having a side wall located at one end of the frame in the longitudinal direction of the pressure member, and a metal reinforcing plate fixed to the side wall. The reinforcing plate has a protrusion that protrudes in the longitudinal direction for positioning the fixing device in the image forming apparatus main body.

[0007] With this configuration, the fixing device can be positioned with respect to the image forming apparatus main body with precision even if the temperature of the frame becomes high, by positioning the fixing device to the image forming apparatus main body using the protrusions of the metal reinforcing plate fixed to the side wall of the frame of the fixing device. Also, the resin frame, which becomes hot, can be reinforced by the metal reinforcing plate.

[0008] The fixing device may also include a first gear arranged on the outside of the reinforcing plate in the longitudinal direction, the first gear being attached to one end of the heating member or pressure member in the longitudinal direction, and a second gear arranged on the outside of the reinforcing plate in the longitudinal direction, the second gear transmitting driving force to the first gear, and the protrusion may rotatably support the second gear.

[0009] This allows the protrusion to have the functions of determining the position of the fixing device and rotatably supporting the second gear. This allows the fixing device to be positioned with high precision relative to the image forming apparatus body, and improves the rigidity of the support shaft for the second gear. Furthermore, the fixing device can be made compact.

[0010] The second gear may also be in mesh with the first gear.

[0011] This allows the fixing device to have a compact configuration.

[0012] The reinforcing plate and the first gear may be arranged with a gap therebetween in the longitudinal direction.

[0013] This prevents the reinforcing plate from coming into contact with the first gear, thereby suppressing wear and the generation of contact noise.

[0014] As an example, the heating member is an endless belt that rotates around a heater, and the pressure member is a pressure roller having a first gear attached to one end in the longitudinal direction.

[0015] The protrusion may be disposed at a position inside the outer periphery of the heating member when viewed in the longitudinal direction.

[0016] This allows the fixing device to have a compact configuration.

[0017] The side wall may have a first wall portion extending in a movement direction that is perpendicular to the longitudinal direction, a second wall portion extending in the movement direction and supporting a heating member or a pressure member between the first wall portion and the second wall portion so that the heating member or the pressure member can move in the movement direction, a third wall portion connecting one end of the first wall portion in the movement direction to one end of the second wall portion in the movement direction, and a recess formed by the first wall portion, the second wall portion, and the third wall portion, the recess being open on the side opposite to the side on which the third wall portion is located in the movement direction, and the reinforcing plate may be arranged across the first wall portion and the second wall portion and fixed to the first wall portion and the second wall portion.

[0018] With this, the portion of the side wall that is weakened by the recess can be effectively reinforced by the metal reinforcing plate.

[0019] The reinforcing plate may also have a configuration including a plate body fixed to the side wall and a metal rod serving as a protrusion, the metal rod being crimped to the plate body.

[0020] The fixing device may also include a pressure arm that presses one of the heating member and the pressure member toward the other, the frame having a boss extending in the longitudinal direction, the boss having a hole for fixing the reinforcing plate to the frame with a screw, and the pressure arm engaging with the boss and being rotatably supported on the frame.

[0021] This allows the boss to have the function of fixing the reinforcing plate and the function of supporting the pressure arm so that it can rotate, thereby making it possible to make the fixing device compact in configuration.

[0022] The image forming apparatus may also be an image forming apparatus comprising an image forming apparatus main body and the above-mentioned fixing device that is attached to the image forming apparatus main body along a predetermined attachment direction, and the image forming apparatus main body may be configured to have a groove that extends in the attachment direction and is open on the upstream side in the attachment direction and closed on the downstream side in the attachment direction, into which the protrusion fits, and a drive gear that meshes with the second gear and rotates so as to urge the protrusion that supports the second gear toward the downstream side in the attachment direction of the groove.

[0023] With this configuration, when the drive gear rotates, the protrusion can be forced toward the closed side of the groove, thereby preventing the protrusion from coming out of the groove and ensuring that the fixing device is reliably positioned relative to the image forming device main body.

[0024] The groove may also have a width that increases toward the upstream side in the mounting direction.

[0025] This allows the protrusions to be easily fitted into the grooves when the fixing device is attached to the image forming apparatus main body. [Effects of the Invention]

[0026] According to the fixing device and image forming apparatus described above, the fixing device can be positioned with high precision relative to the main body of the image forming apparatus. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 is a diagram illustrating a schematic configuration of an image forming apparatus. [Figure 2] FIG. 2 is a perspective view showing a fixing device. [Figure 3] 10 is a cross-sectional view showing the nip pressure changing mechanism in a state where the nip pressure between the heating unit and the pressure roller is set to a first nip pressure. FIG. [Figure 4] 10 is a cross-sectional view showing the nip pressure changing mechanism in a state where the nip pressure is set to a second nip pressure that is lower than the first nip pressure. FIG. [Figure 5] FIG. 2A is a perspective view showing the frame, and FIG. 2B is a side view. [Figure 6] FIG. 2 is a perspective view showing one end of a frame, a reinforcing plate, a first gear, a second gear, and a gear cover. [Figure 7] 1A is a side view showing the fixing device, and FIG. 1B is a side view showing the fixing device with a gear cover removed. [Figure 8] FIG. 7(b) is a cross-sectional view showing the XX cross section of FIG. [Figure 9] FIG. 2 is a perspective view showing a side frame of the image forming apparatus main body. [Figure 10] FIG. 4 is an enlarged side view of the side frame showing the vicinity of a groove. [Figure 11] FIG. 2 is a perspective view showing the vicinity of one end of a fixing device attached to a main body of an image forming apparatus. [Figure 12] FIG. 1(a) is a side view showing the fixing device in a state where the protrusion is fitted into a groove in the image forming apparatus main body and the second gear is engaged with the drive gear, and FIG. 1(b) is a diagram explaining the force applied from the drive gear to the second gear. DETAILED DESCRIPTION OF THE INVENTION

[0028] Next, an embodiment of a fixing device and an image forming apparatus will be described. As shown in Fig. 1, the image forming apparatus 1 is a monochrome printer and includes an image forming apparatus main body 1A and a fixing device 8. The image forming apparatus main body 1A includes a housing 2, a sheet supply unit 3, and an exposure device 4. A drum cartridge 6 and a developing cartridge 7 are detachably attached to the image forming apparatus main body 1A.

[0029] The sheet supply unit 3 includes a sheet tray 31, a pressure plate 32, and a sheet supply mechanism 33. The sheet tray 31 is detachable from the housing 2. The sheet supply unit 3 moves the sheets S stored in the sheet tray 31 toward the sheet supply mechanism 33 using the pressure plate 32, and the sheet supply mechanism 33 supplies the sheets one by one toward between the photosensitive drum 6A and the transfer roller 6C.

[0030] The exposure device 4 includes a light source (not shown), a polygon mirror (denoted by omitted reference numerals), a lens, a reflecting mirror, etc. The exposure device 4 exposes the surface of the photosensitive drum 6A by irradiating the surface of the photosensitive drum 6A with a light beam (denoted by a dashed dotted line).

[0031] The drum cartridge 6 can be attached to and detached from the housing 2 through an opening in the housing 2 with the front cover 21 of the housing 2 open. The drum cartridge 6 includes a photosensitive drum 6A, a charger 6B, and a transfer roller 6C.

[0032] The developing cartridge 7 is detachable from the drum cartridge 6. The developing cartridge 7 is detachable from the housing 2 while attached to the drum cartridge 6. The developing cartridge 7 includes a developing roller 71, a supply roller 72, a layer thickness regulating blade 73, a storage portion 74 that stores toner, and an agitator 75.

[0033] The developer cartridge 7 supplies the toner contained in the container 74 to the supply roller 72 while stirring it with the agitator 75, and then supplies it from the supply roller 72 to the developing roller 71. The toner supplied to the developing roller 71 enters between the developing roller 71 and the layer thickness regulating blade 73 as the developing roller 71 rotates, and is carried on the developing roller 71 as a thin layer of a uniform thickness.

[0034] The fixing device 8 includes a heating unit 81 and a pressure roller 82 as an example of a pressure member. The heating unit 81 includes a heater 10, a holder 20, and a belt BL as an example of a heating member. The heater 10 is a so-called ceramic heater. The belt BL is an endless belt that rotates around the heater 10 and is heated by the heater 10. The holder 20 supports the heater 10 and the belt BL and also functions to guide the rotation of the belt BL. The pressure roller 82 includes a metal shaft 82A and a roller portion 82B made of rubber or the like that covers part of the shaft 82A, and forms a nip portion NP with the belt BL.

[0035] The image forming apparatus 1 uniformly charges the surface of the photosensitive drum 6A using the charger 6B and exposes the surface of the photosensitive drum 6A using the exposure device 4, thereby forming an electrostatic latent image based on image data on the photosensitive drum 6A. Next, toner is supplied from the developing roller 71 to the electrostatic latent image formed on the photosensitive drum 6A, thereby forming a toner image on the photosensitive drum 6A.

[0036] Next, the sheet S supplied from the sheet supply unit 3 passes between the photosensitive drum 6A and the transfer roller 6C, whereby the toner image formed on the photosensitive drum 6A is transferred onto the sheet S. The fixing device 8 transports the sheet S, onto which the toner image has been transferred, between a heating unit 81 and a pressure roller 82, thereby thermally fixing the toner image onto the sheet S. The sheet S, onto which the toner image has been thermally fixed, is discharged onto the discharge tray 22 by the transport rollers 23 and the discharge rollers 24.

[0037] 2, fixing device 8 includes a resin frame 40, a metal reinforcing plate 50, a first gear G1, a second gear G2, and a gear cover 90. Also, as shown in FIGS. 3 and 4, fixing device 8 includes a nip pressure changing mechanism NM for changing the nip pressure between heating unit 81 and pressure roller 82.

[0038] The frame 40 supports the belt BL and the pressure roller 82. More specifically, the frame 40 supports the belt BL via the holder 20, and rotatably supports the pressure roller 82 via a bearing BR. The frame 40 also supports the heating unit 81 so that it can move in the movement direction. More specifically, the frame 40 supports the heater 10 and the belt BL via the holder 20 so that they can move in a predetermined movement direction.

[0039] The movement direction of the heating unit 81 (heater 10, holder 20, and belt BL) is a direction perpendicular to the longitudinal direction of the pressure roller 82. In the following description, the movement direction of the heating unit 81 will also be simply referred to as the "movement direction," and the longitudinal direction of the pressure roller 82 will also be simply referred to as the "longitudinal direction."

[0040] 5(a), the frame 40 has a first side wall 40A as an example of a side wall located at one end of the frame 40 in the longitudinal direction, and a second side wall 40B located at the other end of the frame 40 in the longitudinal direction. As shown in FIGS. 5(b) and 6, the first side wall 40A has a first wall portion 41, a second wall portion 42, a third wall portion 43, and a recess 44.

[0041] The first wall 41 and the second wall 42 are disposed at an interval in an opposing direction perpendicular to the movement direction and extend in the movement direction. The second wall 42 supports the holder 20 movably in the movement direction with one end of the holder 20 in the longitudinal direction sandwiched between the first wall 41 and the second wall 42, thereby supporting the belt BL supported by the holder 20 movably in the movement direction. The third wall 43 connects one end of the first wall 41 in the movement direction to one end of the second wall 42 in the movement direction.

[0042] The recess 44 is formed by a first wall 41, a second wall 42, and a third wall 43. The recess 44 has a shape that is open on the side opposite to the side where the third wall 43 is located in the movement direction. The recess 44 has a roller support part 44A that supports one longitudinal end of the shaft 82A of the pressure roller 82 via a bearing BR, and a rail part 44B that supports one longitudinal end of the holder 20 movably in the movement direction.

[0043] The rail portion 44B is located farther from the third wall portion 43 in the movement direction than the roller support portion 44A. The direction in which the first wall portion 41 and the second wall portion 42 face each other is perpendicular to both the movement direction and the longitudinal direction. In the following description, the direction in which the first wall portion 41 and the second wall portion 42 face each other is also referred to as the "facing direction."

[0044] The frame 40 has a first boss 45, a second boss 46, a third boss 47, and a fourth boss 48, which are examples of bosses. The first boss 45, the second boss 46, the third boss 47, and the fourth boss 48 are provided to extend in the longitudinal direction.

[0045] The first boss 45 is provided near the center in the movement direction of the first wall portion 41. The second boss 46 is provided near the center in the movement direction of the second wall portion 42 so as to face the first boss 45 in the facing direction. The third boss 47 is provided on the third wall portion 43. The third boss 47 is disposed at a position between the first boss 45 and the second boss 46 in the facing direction. The first boss 45, the second boss 46, and the third boss 47 have holes 45H, 46H, and 47H for fixing the reinforcing plate 50 to the frame 40 with screws SC1, SC2, and SC3.

[0046] The fourth boss 48 is provided on the second wall portion 42. The fourth boss 48 is disposed on the opposite side of the second boss 46 from the side on which the first boss 45 is located in the opposing direction. The fourth boss 48 has a hole 48H for fixing the gear cover 90 to the frame 40 with a screw SC4. The fourth boss 48 extends further outward in the longitudinal direction than the first boss 45, the second boss 46, and the third boss 47.

[0047] 5(a), the second side wall 40B has a recess 44 having a configuration similar to that of the recess 44 of the first side wall 40A. The recess 44 of the second side wall 40B supports the other longitudinal end of the shaft 82A of the pressure roller 82 via a bearing (not shown), and also supports the other longitudinal end of the holder 20 movably in the movement direction. The heating unit 81 having the belt BL is supported by the first side wall 40A and the second side wall 40B movably in the movement direction.

[0048] 3, the nip pressure change mechanism NM includes a pressure arm 60, a pressure spring 70, and a cam 80. The pressure arm 60, the pressure spring 70, and the cam 80 are respectively disposed at one end and the other end in the longitudinal direction of the frame 40. Below, the nip pressure change mechanism NM will be described while illustrating the pressure arm 60, the pressure spring 70, and the cam 80 disposed at one end in the longitudinal direction of the frame 40.

[0049] The pressure arm 60 presses one of the belt BL and the pressure roller 82 toward the other. In the embodiment, the pressure arm 60 presses the holder 20 toward the pressure roller 82, thereby pressing the belt BL supported by the holder 20 toward the pressure roller 82. The pressure arm 60 has a main body portion 61, a supported portion 62, a first tip portion 63, and a second tip portion 64.

[0050] The main body 61 has a pressure surface F1 that presses the holder 20 against the pressure roller 82. The supported portion 62 is rotatably supported by the frame 40. The pressure arm 60, which is arranged at one end in the longitudinal direction, is rotatably supported by the frame 40 with the supported portion 62 engaging with the first boss 45. The supported portion 62 has a substantially C-shape when viewed in the longitudinal direction, and engages with the first boss 45 by being arranged inside the supported portion 62.

[0051] First tip portion 63 has a base portion 63A made of metal and a cam follower 63B made of resin. Main body portion 61, supported portion 62, base portion 63A, and second tip portion 64 are made of metal and integrally formed. Cam follower 63B is fitted into base portion 63A and has a pressed surface F2 that is pressed by cam 80. The second tip portion 64 extends from the end of the main body portion 61 in a direction different from that of the first tip portion 63. The second tip portion 64 has a spring catch 64A on which the end of the pressure spring 70 is hooked.

[0052] The pressure spring 70 is a tension coil spring that biases the pressure arm 60 toward the pressure roller 82. The frame 40 has a spring catch 40H on which an end of the pressure spring 70 is hooked, and one end of the pressure spring 70 is hooked to the spring catch 40H of the frame 40, and the other end is hooked to the spring catch 64A of the pressure arm 60.

[0053] The cam 80 is rotatably supported by the frame 40 and is capable of pressing the pressure arm 60 against the biasing force of the pressure spring 70. The cam 80 is rotatable between a first position shown in Fig. 3 and a second position shown in Fig. 4. The cam 80 arranged at one end in the longitudinal direction and the cam 80 (not shown) arranged at the other end in the longitudinal direction are fixed to a metal shaft SF and rotate integrally.

[0054] As shown in Fig. 3, when the cam 80 is located at the first position, the nip pressure becomes a first nip pressure. At this time, the pressure surface F1 of the main body 61 comes into contact with the holder 20 and presses the holder 20 toward the pressure roller 82. As shown in Fig. 4, when the cam 80 is located at the second position, the nip pressure becomes a second nip pressure that is smaller than the first nip pressure. At this time, the pressure surface F1 of the main body 61 is separated from the holder 20.

[0055] 6, the reinforcing plate 50 is fixed to the first side wall 40A. The reinforcing plate 50 has a protrusion 51 for positioning the fixing device 8 in the image forming apparatus main body 1A. The protrusion 51 has a cylindrical shape and protrudes outward from the frame 40 in the longitudinal direction. The reinforcing plate 50 has a plate main body 50A and a metal rod 50B.

[0056] The plate body 50A is made of a metal plate and is fixed to the first side wall 40A. The metal rod 50B is a member that forms the protrusion 51, and its end portion in the longitudinal direction that is closer to the first side wall 40A is fixed to the plate body 50A with being crimped to the plate body 50A. As shown in Fig. 7(a) , the protrusion 51 is disposed at a position inside the outer periphery of the belt BL when viewed in the longitudinal direction.

[0057] 7(b), the reinforcing plate 50 is disposed on the outer side of the first side wall 40A in the longitudinal direction, spanning the first wall portion 41 and the second wall portion 42. Furthermore, the reinforcing plate 50 is disposed so as to cover the recess 44 and overlap with a portion of the first wall portion 41, a portion of the second wall portion 42, and a portion of the third wall portion 43, when viewed in the longitudinal direction.

[0058] The reinforcing plate 50 is fixed to the first wall portion 41, the second wall portion 42, and the third wall portion 43. More specifically, as shown in FIG. 6 , a plate body 50A of the reinforcing plate 50 has a hole 55 provided corresponding to the first boss 45, a notch 56 provided corresponding to the second boss 46, and a hole 57 provided corresponding to the third boss 47. The reinforcing plate 50 is fixed to the first wall portion 41 by fastening a screw SC1 through the hole 55 to the first boss 45, and is fixed to the second wall portion 42 by fastening a screw SC2 through the notch 56 to the second boss 46. As a result, the reinforcing plate 50 is fixed to the first wall portion 41 and the second wall portion 42 on both sides in the opposing direction of the recess 44 (see FIG. 7( b)). The reinforcing plate 50 is also fixed to the third wall portion 43 by fastening a screw SC3 through the hole 57 to the third boss 47.

[0059] The first gear G1 is attached to one end of the pressure roller 82 in the longitudinal direction and rotates integrally with the pressure roller 82. More specifically, the first gear G1 engages with one end of the shaft 82A of the pressure roller 82 in the longitudinal direction and is secured to the shaft 82A by an E-ring ER to prevent it from slipping off. The first gear G1 is arranged so as to be surrounded by the first boss 45, the second boss 46, and the third boss 47 when viewed in the longitudinal direction. As shown in FIG. 8 , the first gear G1 is arranged on the outer side of the reinforcing plate 50 in the longitudinal direction. The plate body 50A of the reinforcing plate 50 and the first gear G1 are arranged with a gap GP1 between them in the longitudinal direction.

[0060] The plate body 50A also has a hole 59 through which one longitudinal end of the shaft 82A of the pressure roller 82 and part of the first gear G1 pass, and the inner circumferential surface of the hole 59 and the first gear G1 are arranged with a gap GP2 also in the radial direction of the shaft 82A. In other words, the plate body 50A of the reinforcing plate 50 and the first gear G1 are arranged so as not to come into contact with each other.

[0061] As shown in FIG. 7(b), the second gear G2 is a gear that transmits driving force to the first gear G1. When the fixing device 8 is attached to the image forming apparatus main body 1A, the first gear G1 meshes with a driving gear GD provided on the image forming apparatus main body 1A. Driving force is input to the first gear G1 from the driving gear GD. The second gear G2 is disposed on the outer side of the reinforcing plate 50 in the longitudinal direction. The second gear G2 meshes with the first gear G1. The second gear G2 engages with a protrusion 51 of the reinforcing plate 50 and is rotatably supported by the protrusion 51. In other words, the protrusion 51 rotatably supports the second gear G2.

[0062] As shown in FIG. 6, the fixing device 8 further includes a third gear G3. The image forming apparatus 1 includes an intermediate discharge roller (not shown) that conveys the sheet S, which is discharged from between the heating unit 81 and the pressure roller 82, toward the conveyance roller 23 (see FIG. 1), and the third gear G3 is a gear that transmits driving force to the intermediate discharge roller. The third gear G3 meshes with the second gear G2. The third gear G3 engages with the fourth boss 48 and is rotatably supported by the fourth boss 48.

[0063] The gear cover 90 is a member that covers part of the gears G1 to G3 from the outside in the longitudinal direction, and is attached to the first side wall 40A. The gear cover 90 has holes 91 through which the protrusions 51 of the reinforcing plate 50 pass, and holes 98 that engage with the tips of the fourth bosses 48 provided on the first side wall 40A. The gear cover 90 is fixed to the first side wall 40A by fastening screws SC4 into the fourth bosses 48.

[0064] As shown in FIG. 9, the image forming apparatus main body 1A has a side frame 25 and a drive gear GD. The side frame 25 is one of the members forming the housing 2 of the image forming apparatus main body 1A, and is arranged at one end in the longitudinal direction of the fixing device 8 when the fixing device 8 is attached to the image forming apparatus main body 1A. One end in the longitudinal direction of the fixing device 8 is fixed to the side frame 25.

[0065] The side frames 25 have grooves 26 into which the protrusions 51 of the fixing device 8 fit. As shown in Fig. 10, the fixing device 8 is attached to the image forming apparatus main body 1A in a predetermined attachment direction, and the grooves 26 extend along the attachment direction. The grooves 26 open toward the fixing device 8 that is disposed inside the side frames 25 in the longitudinal direction. When viewed from the longitudinal direction, the grooves 26 are open on the upstream side in the attachment direction and closed on the downstream side in the attachment direction.

[0066] The groove 26 becomes wider toward the upstream side in the installation direction. More specifically, the groove 26 has a fitting portion 26A into which the protrusion 51 of the fixing device 8 fits, and a guide portion 26B that guides the protrusion 51 to the fitting portion 26A. The width of the guide portion 26B becomes wider from the downstream side to the upstream side in the installation direction, in other words, as it moves away from the fitting portion 26A. The fitting portion 26A is closed on the downstream side in the installation direction. The width of the fitting portion 26A is approximately the same as the diameter of the protrusion 51.

[0067] 11, one longitudinal end of the fixing device 8 is fixed to the side frame 25 (image forming apparatus main body 1A) by a screw SC5 with the protrusion 51 fitted in the groove 26. More specifically, the frame 40 has a plate-shaped fixing portion 40F extending outward in the longitudinal direction from the first side wall 40A, and the fixing device 8 is fixed to the image forming apparatus main body 1A by fastening the screw SC5 to the side frame 25 through a hole 40G (see FIG. 5(a)) formed in the fixing portion 40F.

[0068] 12(a), when the fixing device 8 is attached to the image forming apparatus main body 1A, the drive gear GD meshes with the second gear G2 of the fixing device 8. A driving force is input to the drive gear GD from a motor (not shown) provided in the image forming apparatus main body 1A.

[0069] The drive gear GD rotates so as to urge the protrusion 51 supporting the second gear G2 toward the downstream side in the mounting direction of the groove 26. More specifically, as shown in Figures 12(a) and 12(b), the drive gear GD rotates so that a force P with which the gear teeth GD1 of the drive gear GD press against the gear teeth G21 of the second gear G2 has a horizontal component P1 that urges the protrusion 51 toward the downstream side in the mounting direction of the groove 26 (the back side of the fitting portion 26A). In this embodiment, the drive gear GD rotates counterclockwise in Figure 12.

[0070] According to the fixing device 8 described above, the fixing device 8 is positioned to the image forming apparatus main body 1A by the protrusions 51 of the metal reinforcing plate 50 fixed to the first side wall 40A of the frame 40 of the fixing device 8, so that the fixing device 8 can be accurately positioned to the image forming apparatus main body 1A even if the temperature of the resin frame 40 becomes high. In addition, the resin frame 40, which becomes hot, can be reinforced by the metal reinforcing plate 50.

[0071] Furthermore, since the protrusion 51 rotatably supports the second gear G2, the protrusion 51 can have the function of determining the position of the fixing device 8 and the function of rotatably supporting the second gear G2. This allows the fixing device 8 to be positioned with high precision relative to the image forming apparatus main body 1A, and also improves the rigidity of the support shaft of the second gear G2. More specifically, compared to when the support shaft of the second gear G2 is provided on the resin frame 40, the rigidity of the support shaft of the second gear G2 can be improved. Furthermore, compared to when the support shaft of the second gear G2 is provided separately from the protrusion 51, the fixing device 8 can be made more compact.

[0072] Furthermore, since the second gear G2 directly meshes with the first gear G1, the fixing device 8 can be made more compact than when there is another gear between the first gear G1 and the second gear G2.

[0073] Furthermore, since the reinforcing plate 50 and the first gear G1 do not come into contact with each other, wear and contact noise can be suppressed.

[0074] Furthermore, since the protrusion 51 is positioned inside the outer periphery of the belt BL when viewed from the longitudinal direction, the fixing device 8 can be made more compact than when the protrusion is positioned outside the outer periphery of the belt BL when viewed from the longitudinal direction.

[0075] Furthermore, since the reinforcing plate 50 is positioned across the first wall portion 41 and the second wall portion 42 of the first side wall 40A and is fixed to the first wall portion 41 and the second wall portion 42, the portion of the first side wall 40A where the strength is weakened due to the presence of the recess 44 can be effectively reinforced by the metal reinforcing plate 50.

[0076] Furthermore, since the pressure arm 60 engages with the first boss 45 of the frame 40 and is rotatably supported by the frame 40, the first boss 45 can function as a fixing portion for the reinforcing plate 50 and also as a portion for rotatably supporting the pressure arm 60. This allows the fixing device 8 to have a more compact configuration than when a portion for rotatably supporting the pressure arm 60 is provided separately from the first boss 45.

[0077] Furthermore, according to the image forming apparatus 1 described above, when the drive gear GD rotates, the protrusion 51 can be biased toward the closed side of the groove 26, thereby preventing the protrusion 51 from coming out of the groove 26 and enabling the fixing device 8 to be reliably positioned relative to the image forming apparatus main body 1A.

[0078] Furthermore, since the groove 26 becomes wider toward the upstream side in the mounting direction, the protrusion 51 can be easily fitted into the groove 26 when the fixing device 8 is mounted to the image forming apparatus main body 1A.

[0079] Although the embodiments have been described above, the fixing device and the image forming apparatus can be modified as appropriate as exemplified below.

[0080] In the above embodiment, the heater 10 is a ceramic heater, but the heater may be, for example, a halogen heater, a carbon heater, an IH heater, etc. Also, in the above embodiment, the heating member is an endless belt BL, but the heating member may be, for example, a so-called heating roller, etc. Also, in the above embodiment, the pressure member is a pressure roller 82, but the pressure member may be, for example, a pressure unit including an endless belt and a pad that sandwiches the belt between the belt and the heating member.

[0081] In the above embodiment, the frame 40 is configured to support the belt BL, which is the heating member, so that it can move in the movement direction. However, for example, the frame may be configured to support a pressure member so that it can move in the movement direction. In this case, the pressure arm may be configured to press the pressure member toward the heating member. Also, for example, the pressure arm may not be configured to include the cam follower 63B of the above embodiment.

[0082] In the above embodiment, the first gear G1 is attached to one end in the longitudinal direction of the pressure roller 82, which is a pressure member. However, for example, the first gear may be attached to one end in the longitudinal direction of a heating roller, which is another example of a heating member.

[0083] In the above embodiment, the second gear G2 is configured to directly mesh with the first gear G1 to transmit driving force to the first gear G1, but for example, the second gear may be configured to transmit driving force to the first gear via one or more gears.

[0084] In the above embodiment, the reinforcing plate 50 and the first gear G1 are arranged with gaps GP1 and GP2 between them, but for example, if wear and contact noise can be suppressed by a method other than leaving a gap, the reinforcing plate and the first gear may be arranged in contact with each other.

[0085] In the above embodiment, the protrusion 51 has the function of determining the position of the fixing device 8 and the function of rotatably supporting the second gear G2, but for example, the protrusion may not be used as a support shaft that rotatably supports the second gear. Also, in the above embodiment, the reinforcing plate 50 has the plate main body 50A and the metal rod 50B that constitutes the protrusion 51 and that is crimped to the plate main body 50A, but for example, the reinforcing plate may have a configuration in which the plate main body 50A and the protrusion 51 of the above embodiment are integrally molded from a single metal plate.

[0086] In the above embodiment, a monochrome printer is exemplified as the image forming apparatus 1, but the image forming apparatus may be, for example, a color printer. Also, the image forming apparatus may be, for example, a copier, a multifunction peripheral, or the like.

[0087] The elements described in the above-described embodiment and modified examples may be implemented in any combination. [Explanation of symbols]

[0088] 1. Image forming device 1A Image forming device main body 8 Fixing device 10 Heater 40 frames 40A First side wall 50 Reinforcement plate 51 protrusion 82 Pressure roller BL Belt

Claims

1. A fixing device attached to a main body of an image forming apparatus, A heater and a heating member heated by the heater; a pressure member that forms a nip portion between itself and the heating member; a resin frame supporting the heating member and the pressure member, the frame having a side wall located at one end of the frame in the longitudinal direction of the pressure member; a metal reinforcing plate fixed to the side wall, the reinforcing plate has a protrusion that protrudes in the longitudinal direction for positioning the fixing device in the image forming apparatus main body, The side wall is a first wall portion extending in a movement direction that is a direction perpendicular to the longitudinal direction; a second wall portion extending in the movement direction, the second wall portion supporting the heating member or the pressure member between the second wall portion and the first wall portion so as to be movable in the movement direction; a third wall portion connecting one end of the first wall portion in the movement direction and one end of the second wall portion in the movement direction; a recess formed by the first wall portion, the second wall portion, and the third wall portion, the recess being open on a side opposite to a side on which the third wall portion is located in the movement direction; The fixing device, wherein the reinforcing plate is disposed across the first wall portion and the second wall portion and is fixed to the first wall portion and the second wall portion.

2. A fixing device attached to a main body of an image forming apparatus, A heater and a heating member heated by the heater; a pressure member that forms a nip portion between itself and the heating member; a resin frame supporting the heating member and the pressure member, the frame having a side wall located at one end of the frame in the longitudinal direction of the pressure member; a metal reinforcing plate fixed to the side wall; a pressure arm that presses one of the heating member and the pressure member toward the other member, the reinforcing plate has a protrusion that protrudes in the longitudinal direction for positioning the fixing device in the image forming apparatus main body, The frame has a boss extending in the longitudinal direction, the boss has a hole for fixing the reinforcing plate to the frame with a screw; The fixing device is characterized in that the pressure arm is engaged with the boss and is rotatably supported by the frame.

3. a first gear disposed on an outer side of the reinforcing plate in the longitudinal direction, the first gear being attached to one end of the heating member or the pressing member in the longitudinal direction; a second gear disposed on an outer side of the reinforcing plate in the longitudinal direction, the second gear transmitting a driving force to the first gear, 3. The fixing device according to claim 1, wherein the protrusion rotatably supports the second gear.

4. 4. The fixing device according to claim 3, wherein the second gear meshes with the first gear.

5. 5. The fixing device according to claim 3, wherein the reinforcing plate and the first gear are arranged with a gap therebetween in the longitudinal direction.

6. the heating member is an endless belt that rotates around the heater, 6. The fixing device according to claim 3, wherein the pressure member is a pressure roller having the first gear attached to one end in the longitudinal direction.

7. 7. The fixing device according to claim 1, wherein the protrusion is disposed at a position inside the outer periphery of the heating member when viewed in the longitudinal direction.

8. 8. The fixing device according to claim 1, wherein the reinforcing plate has a plate body fixed to the side wall and a metal rod serving as the protrusion, the metal rod being crimped to the plate body.

9. the image forming apparatus main body; 7. An image forming apparatus comprising: the fixing device according to claim 3, which is attached to the image forming apparatus main body along a predetermined attachment direction; The image forming apparatus main body includes: a groove extending in the mounting direction, open on an upstream side in the mounting direction and closed on a downstream side in the mounting direction, into which the protrusion fits; a drive gear that meshes with the second gear and rotates so as to urge the protrusion that supports the second gear toward the downstream side of the groove in the mounting direction.

10. 10. The image forming apparatus according to claim 9, wherein the groove has a width that increases toward the upstream side in the mounting direction.

Images