Fixing device

Abstract

This invention provides a fixing device that is an advanced version of the conventional design. [Solution] The transmission member has an opposing portion that faces the edge of the frame forming the recess, which is located downstream of the center of the fixing nip in the recording material transport direction. The opposing portion is provided with a first convex portion that protrudes toward the downstream edge in the recording material transport direction, and a second convex portion that is located at a different position from the first convex portion in the first direction and also protrudes toward the downstream edge in the recording material transport direction. When the pressure roller rotates with the fixing nip formed, both the first and second convex portions come into contact with the downstream edge in the recording material transport direction.

Description

Technical Field

[0001] The present invention relates to a fixing device provided in an image forming apparatus using an electrophotographic method.

Background Art

[0002] In an image forming apparatus using an electrophotographic method, a fixing device adopting an on-demand fixing method as disclosed in Patent Document 1 is known.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] It is an object to further develop the above-described prior art.

Means for Solving the Problems

[0005] To achieve the above objective, the fixing device of the present invention comprises a heating unit having a cylindrical belt, a heater disposed in the internal space of the belt, a holder for holding the heater, a stay disposed to contact the holder and to reinforce the holder, and a transmission member disposed at a position overlapping both ends of the stay in the longitudinal direction when viewed in a direction perpendicular to the longitudinal direction of the belt, and transmitting pressure from the stay toward the heater to the stay; a pressure roller that contacts the outer surface of the belt and, together with the heater, clamps the belt to form a fixing nip between itself and the belt; a frame that rotatably holds the pressure roller and holds the heating unit by holding the transmission member, and has a recess for mounting the transmission member; and a pressure arm rotatably provided on the frame for applying the pressure to the transmission member while it is mounted on the frame, and the device holds the recording material by clamping and conveying the recording material with the fixing nip formed by the pressure, and transmits the toner image formed on the recording material In a fixing device that fixes to a recording material, the frame is made of resin, the frame has a pivot axis for supporting the rotation of the pressure arm, and when viewed in the longitudinal direction, the pivot axis is located upstream of the fixing nip in the recording material transport direction and in a first direction perpendicular to the longitudinal direction and the recording material transport direction, between the rotation center of the pressure roller and the end of the holder furthest from the rotation center of the pressure roller in the first direction, and the transmission member is located at the edge of the frame that forms the recess, the fixing nip A fixing device having an opposing portion facing an edge located downstream of the center of the portion in the recording material transport direction, wherein the opposing portion is provided with a first convex portion projecting toward the edge downstream in the recording material transport direction, and a second convex portion provided at a position different from the position of the first convex portion in the first direction and projecting toward the edge downstream in the recording material transport direction, wherein when the pressure roller rotates while the fixing nip portion is formed, both the first convex portion and the second convex portion contact the edge downstream in the recording material transport direction.

[0006] Furthermore, in order to achieve the above objective, another fixing device of the present invention comprises a heating unit having a cylindrical belt, a heater disposed in the internal space of the belt, a holder for holding the heater, a stay disposed to contact the holder and reinforcing the holder, and a transmission member disposed at a position overlapping both ends of the stay in the longitudinal direction when viewed in a direction perpendicular to the longitudinal direction of the belt, and transmitting pressure from the stay toward the heater to the stay; a pressure roller that contacts the outer surface of the belt and, together with the heater, clamps the belt and forms a fixing nip portion between itself and the belt; a frame that rotatably holds the pressure roller and holds the heating unit by holding the transmission member, the frame having a recess for mounting the transmission member; and a pressure arm rotatably provided on the frame for applying the pressure to the transmission member while it is mounted on the frame, wherein the fixing device fixes a toner image formed on the recording material to the recording material while clamping and conveying the recording material with the fixing nip portion formed by the pressure, the The frame is made of resin, and the frame has a pivot axis for supporting the rotation of the pressure arm, and when viewed in the longitudinal direction, the pivot axis is located upstream of the fixing nip in the recording material transport direction and in a first direction perpendicular to the longitudinal direction and the recording material transport direction, between the rotation center of the pressure roller and the end of the holder furthest from the rotation center of the pressure roller in the first direction, and the holder is located upstream of the fixing nip in the recording material transport direction relative to the fixing nip in the longitudinal direction at the position where the transmission member is provided. The transmission member has a first surface and a second surface located downstream of the fixing nip portion in the recording material transport direction, and the transmission member has a first opposing portion facing the first surface upstream of the first surface in the recording material transport direction and a second opposing portion facing the second surface downstream of the second surface in the recording material transport direction, and the distance between the first opposing portion and the second opposing portion in the recording material transport direction is set to be 0.02 to 0.16 mm greater than the distance between the first surface and the second surface in the recording material transport direction. [Effects of the Invention]

[0007] This invention provides a fixing device that is an advanced version of the conventional design. [Brief explanation of the drawing]

[0008] [Figure 1] Perspective view of the fixing device in Example 1. [Figure 2] Cross-sectional view of the image forming apparatus in Example 1. [Figure 3] Cross-sectional view of the heating unit and pressure roller in Example 1. [Figure 4] Cross-sectional view of the fixing device in Example 1. [Figure 5] Exploded perspective view of the fixing device in Example 1. [Figure 6] Top view of the holder in Example 1. [Figure 7] Exploded perspective view of the heating unit in Example 1. [Figure 8] Top view of the heating unit in Example 1. [Figure 9] Front view and cross-sectional view of the fixing device in Example 1. [Figure 10] Top view and enlarged view of the lower frame and pressure roller in Example 1. [Figure 11] Cross-sectional views of the pressurizing mechanism and the pressure release mechanism in the pressurized and pressure release states in Example 1. [Figure 12] Exploded perspective view of the lower frame, upper frame, camshaft, and cam in Example 1. [Figure 13] Front view and cross-sectional view of the lower frame and pressure roller in Example 1. [Figure 14] Schematic diagrams of the pressurizing mechanism in Example 1 when the pressurizing roller is not driven and when the pressurizing roller is driven. [Figure 15] Front view and cross-sectional view of the holder in Example 2. [Figure 16] Side views of the drive-side and non-drive-side transmission members in Example 2. [Figure 17]Front view and cross-sectional view of the holder and the transmission member in Example 2. [Figure 18] Schematic diagram showing the distance between the holder and the transmission member in Example 2 and the comparative example. [Figure 19] Side view of the transmission members on the driving side and the non-driving side in Example 3.

Mode for Carrying Out the Invention

[0009] [Example 1] Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

[0010] [Image Forming Apparatus] FIG. 2 is a cross-sectional view of the electrophotographic image forming apparatus 1 in the present embodiment. However, the dimensions, materials, shapes, relative arrangements, etc. of the component parts described in the present embodiment may be appropriately changed according to the configuration and various conditions of the apparatus to which the present invention is applied. Therefore, unless otherwise specifically described, the scope of the present invention is not limited thereto. In the following description, the left side in FIG. 2 is defined as the front side of the image forming apparatus 1, the right side as the rear side of the image forming apparatus 1, the front side of the paper as the right side of the image forming apparatus 1, and the back side of the paper as the left side of the image forming apparatus 1. Also, the upper side and the lower side in FIG. 2 are defined as the upper side and the lower side of the image forming apparatus 1, respectively.

[0011] As shown in FIG. 2, the image forming apparatus 1 has an apparatus main body 2 and a process cartridge 10, and the process cartridge 10 is detachably installed on the apparatus main body 2. The apparatus main body 2 is provided with a paper feed tray 3, a recording material feeding unit 4, a conveyance path P, an image forming unit 5, a fixing device 6, a recording material discharging unit 7, a paper discharge tray 8, a laser scanner 9, etc. On the other hand, the cartridge 10 is provided with a photosensitive drum 11, a developing roller 12 as a developer carrier, etc.

[0012] The main body of the device 2 is equipped with an opening / closing door 21 to close the opening 2A provided for attaching and detaching the process cartridge 10. The opening / closing door 21 is supported so as to be rotatable around a pivot axis 21a and is movable between a closed position that closes the opening 2A and an open position that opens the opening 2A.

[0013] The recording material feeding unit 4 includes a paper feed roller 41, a separation roller 42, a separation pad 42a, and a transport roller pair 43. Based on the print start signal, the recording material S stored in the paper feed tray 3 is sent to the transport path P by the recording material feeding unit 4 and transported towards the image forming unit 5 via the registration roller pair 44. When the recording material S has been transported to a predetermined position, an image forming start signal is issued and the image forming process begins. The photosensitive drum 11, which is rotationally driven by a drive source (motor) not shown, is uniformly charged to a predetermined potential by a charging means not shown. After charging, the surface of the photosensitive drum 11 is exposed by a laser scanner 9 based on image information, and the charge in the exposed area is removed to form an electrostatic image. The toner in the process cartridge 10 is carried on the developing roller 12 and supplied to the photosensitive drum 11 according to the electrostatic latent image, developing the latent image. As a result, the latent image is made visible on the photosensitive drum 11 as a toner image.

[0014] The image forming unit 5 includes a process cartridge 10 and a transfer roller 51 positioned opposite the photosensitive drum 11 of the process cartridge 10. When the recording material S, transported by the registration roller pair 44, reaches the image forming unit 5 and passes through the transfer nip between the photosensitive drum 11 and the transfer roller 51, a voltage is applied to the transfer roller 51 from the main body of the device 2, and the toner image on the photosensitive drum 11 is transferred to the recording material S. Subsequently, the recording material S with the transferred toner image is transported to a fixing device 6 equipped with a heating unit 61 and a pressure roller 62 that contacts the outer surface of a cylindrical belt 614. When the recording material S is held and transported between the heating unit 61 and the fixing nip NP1 of the pressure roller 62, the toner image transferred onto the recording material S is heated and pressurized and fixed to the surface of the recording material S. The recording material S with the fixed toner image is discharged to the paper output tray 8 via the recording material discharge unit 7.

[0015] [Fusing device] Next, the specific configuration of the fixing device will be described using Figures 3 to 8. As shown in Figure 3, the heating unit 61 of the fixing device 6 comprises a heater 611, a holder 612, a stay 613, and a belt 614. The heater 611, holder 612, and stay 613 are arranged in the internal space of the belt 614. Defining the X, Y, and Z directions as shown in Figure 3, the heater 611 is a flat plate extending in the Y direction, and the Y direction coincides with the longitudinal direction of the heater 611. It also has a first surface 611a and a second surface 611b opposite to the first surface 611a, with the first surface 611a being supported by the holder 612.

[0016] The holder 612 is made of a heat-resistant resin such as PPS or liquid crystal polymer, and has a guide surface 612a and a support wall 612b. The guide surface 612a contacts the inner circumferential surface 614a of the belt 614 to guide the belt 614, and the support wall 612b has a support surface 612b1 that supports the heater 611. The support surface 612b1 of the support wall 612b is in contact with the first surface 611a of the heater 611. The stay 613 is a member that supports the holder 612, and is formed by bending a plate material with greater rigidity than the holder 612, for example, a steel plate with a thickness of 1.6 mm, into a roughly U-shape.

[0017] The belt 614 is an endless belt that is heat-resistant and flexible. For example, it may be made of a metal sleeve such as stainless steel coated with fluororesin, or made of laminated polyimide resin, silicone rubber, fluororesin, etc. Inside the belt 614 are a heater 611, a holder 612, and a stay 613, and the belt 614 rotates around these components. The inner circumferential surface 614a of the belt 614 is in contact with the second surface 611b of the heater 611.

[0018] The pressure roller 62 has a metal shaft 62a and a roller 62b made of an elastic material covering the shaft 62a, and is pressed against the heater 611 via a belt 614. The pressure roller 62 sandwiches the belt 614 between itself and the heater 611 to form a fixing nip section NP1 for nipping, heating, and pressurizing the recording material S. In other words, the pressure roller 62 heats and pressurizes the recording material S together with the heater 611 at the fixing nip section NP1.

[0019] The pressure roller 62 is configured to rotate when a driving force is transmitted from a drive source provided by the image forming apparatus 1. As the pressure roller 62 rotates, the belt 614 rotates passively due to the frictional force between the belt 614 and the recording material S held between the fixing nip NP1. As a result, the recording material S on which the toner image has been transferred is transported between the pressure roller 62 and the heated belt 614, and the toner image is heat-fixed.

[0020] As shown in Figures 4 to 8, the fixing device 6 has a lower frame 63 that supports the heating unit 61 and the pressure roller 62, and an upper frame 64 located above the lower frame 63 and covering the heating unit 61. The upper frame 64 has an upper recording material guide 64a that guides the upper surface of the recording material S being transported along the transport path P on the downstream side in the recording material transport direction of the heating unit 61 and the pressure roller 62. The lower frame 63 has a lower recording material guide 63a that guides the lower surface of the recording material S being transported along the transport path P on the downstream side in the recording material transport direction of the heating unit 61 and the pressure roller 62.

[0021] The transport path P in the fixing device 6 extends in the X direction. In this embodiment, the lower frame 63 and the upper frame 64 are formed from, for example, a non-conductive molded material. For example, the material of the molded material may be polyethylene terephthalate (PET), polybutylene terephthalate (PBT), or polyphenylene sulfide (PPS). Furthermore, PET or PBT may be reinforced with glass fibers.

[0022] As shown in Figure 5, the lower frame 63 supports the heating unit 61 and the pressure roller 62. The lower frame 63 has a pair of rails 63b at each end in the Y direction. The rails 63b support the holder 612 so that it can move in the Z direction (first direction) via transmission members 651a and 651b, which are members that transmit pressure to the stay 613 (details will be described later). The rails 63b are columnar portions that extend in the Z direction from the main body 63c of the lower frame 63. The pair of rails 63b face each other in the X direction. The opposing surfaces of the rails 63b engage with grooves 651a1 and 651b1 provided on the transmission members 651a and 651b, respectively. In this embodiment, the rails 63b are columnar portions that extend in the Z direction, but any shape that can support the holder 612 so that it can move in the Z direction is acceptable, and the shape is not limited to that of this embodiment.

[0023] Furthermore, the pressure roller 62 is rotatably held by the lower frame 63 via bearings 62c and 62d at both longitudinal ends of a metal shaft 62a. At this time, the position of bearing 62c is determined when a projection 62c1 provided on bearing 62c fits into a groove 63d1 provided on the lower frame 63. Similarly, the position of bearing 62d is determined when a projection 62d1 provided on bearing 62d fits into a groove 63d2 provided on the lower frame 63. Bearing 62c is made of a conductive material. In this embodiment, projections 62c1 and 62d are provided on bearings 62c and 62d, and grooves 63d1 and 63d2 are provided on the lower frame 63, but grooves may be provided on bearings 62c and 62d, and projections may be provided on the lower frame 63.

[0024] As shown in Figure 6, the support wall 612b of the holder 612 has a plurality of holes 612b2, 612b3. As shown in Figure 6, temperature sensors 613a and 613b are provided on the back surface 612b4 of the holder 612, opposite to the support surface 612b1. As shown in Figure 7, the temperature sensors 613a and 613b contact the first surface 611a of the heater 611 through the holes 612b2, 612b3. The temperature sensors 613a and 613b are pressed against the first surface 611a of the heater 611 (see Figure 3) by biasing members 613c and 613d provided between the stay 613 and the temperature sensors 613a and 613b. Temperature sensor 613a is located at one end of the holder 612 in the Y direction. Temperature sensor 613b is located closer to one end than to the center of the holder 612 in the Y direction. The temperature sensors 613a and 613b are thermistors in this case, but other temperature sensors such as thermostats may also be used. The biasing members 613c and 613d are coil springs in this case, but other biasing members may also be used.

[0025] As shown in Figures 5 and 8, the holder 612 extends in the Y direction through the interior of the belt 614, with both ends in the Y direction extending outward from the belt 614. The holder 612 supports the heater 611, and one end of the heater 611 in the Y direction is provided with a first wire spring 615a that holds the heater 611 in the holder 612, and a connector 616 that supplies power to the heater 611 and clamps the heater 611 and the holder 612. The other end of the heater 611 in the Y direction is provided with a second wire spring 615b that holds the heater 611 in the holder 612. The temperature sensors 613a and 613b are located closer to the first wire spring 615a than to the second wire spring 615b in the Y direction. The first wire spring 615a is provided between the belt 614 and the connector 616. The second spring 615b is provided in the region extending outward from the belt 614 on the other end where the first spring 615a is located. In this embodiment, the pressure roller 62 comprises a shaft 62a and a roller 62b, but it is not limited to this and may also include a pressure belt that is pressed against the heating roller by an elastic member.

[0026] [Pressurization mechanism] As shown in Figures 9-10, the fixing device 6 has a pressurizing mechanism 65 that applies pressure to form a fixing nip portion NP1 between the heating unit 61 and the pressure roller 62. The pressurizing mechanism 65 is located at both ends of the lower frame 63 in the Y direction. Since the structure of one side of the pressurizing mechanism 65 in the Y direction and the structure of the other side are substantially the same, the following description will mainly focus on the one side in the Y direction.

[0027] The pressurizing mechanism 65 supports the heating unit 61 at its end in the Y direction and includes a member (transmission member 651) that transmits pressure to a stay supported by rail 63b so as to be movable in the Z direction. The pressurizing mechanism 65 also includes a pressurizing arm 652 for applying pressure to the transmission member 651, which is mounted on the lower frame 63, in order to form the fixing nip portion NP1. In addition, the pressurizing mechanism 65 includes a pressurizing spring 653 stretched between the lower frame 63 and the pressurizing arm 652, which generates pressure to press the pressurizing arm 652 against the transmission member 651. The lower frame 63 has a support portion 64d that supports the pressurizing arm 652 so as to be rotatable around a pivot axis X1. The support portion 64d is a substantially cylindrical projection. The pressurizing spring 653 is a tension coil spring that biases the pressurizing arm 652 toward the pressurizing roller 62. The lower frame 63 has a spring attachment portion 63m on which one end of the pressure spring 653 is hooked. For example, the support portion 64d of the resin lower frame 63 may be made of metal, or a metal member may be attached only to the portion of the support portion 64d that contacts the pressure arm 652. Also, the spring attachment portion 63m of the resin lower frame 63 may be made of metal.

[0028] At least a portion of the rotation axis X1 on which the pressure arm 652 rotates is located upstream of the fixing nip NP1 in the recording material transport direction when viewed in the Y direction, and within the range T in the Z direction shown in Figure 9(b). Here, the range T in the Z direction shown in Figure 9(b) is the distance in the Z direction from the rotation center of the pressure roller 62 to the pressure arm side end of the holder 612 in the Z direction (the end of the holder 612 furthest from the rotation center of the pressure roller in the Z direction). Because there is a distance in the Z direction between the point where the pressure arm 652 pressurizes the transmission member 651 and the rotation axis X1, the pressure arm 652 is bent in an L shape. Furthermore, the upstream side in the recording material transport direction is the side of the photosensitive drum 11 from the fixing nip NP1 in the X direction.

[0029] [Pressure release mechanism] As shown in Figure 11, the fixing device 6 further includes a pressure release mechanism 67 for releasing the nip pressure applied to the fixing nip portion NP1 between the heating unit 61 and the pressure roller 62 in Figure 9. The pressure release mechanism 67 comprises a camshaft 671 and a cam 672. The lower frame 63 supports the pressure spring 653 and rotatably supports the pressure arm 652 and the cam 672. The cam 672 is located at the ends of the lower frame 63 in the Y direction. Since the structure of one side of the pressure release mechanism 67 in the Y direction and the structure of the other side are substantially the same, the structure of one side in the Y direction will be mainly described as representative below.

[0030] As shown in Figure 12, the camshaft 671 extends in the Y direction. The camshaft 671 is made of metal, for example. Cams 672 are fixed to each end of the camshaft 671 in the Y direction. In other words, the cam 672 has the camshaft 671. The cam 672 rotates in conjunction with the rotation of the camshaft 671. The lower frame 63 has shaft support portions 63l that rotatably support the camshaft 671. As shown in Figure 12, the shaft support portions 63l are located at one end and the other end of the lower frame 63 in the Y direction. The shaft support portions 63l have holes H that rotatably support the camshaft 671.

[0031] Furthermore, as shown in Figure 12, the upper frame 64 has grooves 64C that rotatably support the camshaft 671. The grooves 64C are located at one end and the other end of the upper frame 64 in the Y direction. The camshaft 671 is held between the upper frame 64 and the lower frame 63. As shown in Figure 11, the camshaft 671 is rotatably supported about axis X2. The cam 672 is capable of pressing the pressurizing arm 652 against the biasing force of the pressurizing spring 653. Specifically, the cam 672 is rotatable between a first position shown in Figure 11(a) and a second position shown in Figure 11(b).

[0032] [Transmission member and lower frame] As shown in Figures 10 to 14, the transmission member 651 is mounted in a recess in the lower frame 63 that includes a rail 63b. The rail 63b has an opposing portion 651a that faces the edge 634 located downstream of the fixing nip portion NP1 in the recording material transport direction. The opposing portion 651a has a protruding first convex portion 6511 and a second convex portion 6512 that is located at a different position from the first convex portion 6511 in the mounting direction (Z direction) of the transmission member 651 to the lower frame 63, and protrudes toward the edge 634 of the lower frame 63. Since the first distance 635 between the rails 63b in the X direction is longer than the first width 651b of the transmission member 651 in the X direction, the transmission member 651 is tilted in the pressing direction shown in Figure 14(a) due to the pressure from the pressure arm 652 before the pressure roller 62 is driven to rotate.

[0033] When the pressure roller 62 is rotated with the fixing nip portion NP1 formed, as shown in Figure 14(b), the heating unit 61 receives a force downstream in the recording material transport direction due to the frictional force between the belt 614 and the recording material S sandwiched between the fixing nip portion NP1. At this time, both the first protrusion 6511 and the second protrusion 6512 of the transmission member 651 contact the edge 634 of the lower frame 63, thereby defining the orientation of the heating unit 61 relative to the frame 63 and stabilizing the fixing and transport performance of the fixing device. Here, the first protrusion 6511 and the second protrusion 6512 may be provided at both ends of the opposing portion 651a in the Z direction. By providing them at both ends of the opposing portion 651a in the Z direction, the inclination of the transmission member 651 can be reduced even if there is a difference due to dimensional tolerances in the amount of protrusion of the first protrusion 6511 and the second protrusion 6512 downstream in the recording material transport direction.

[0034] [Example 2] In this example, the same reference numerals are used for the same configurations and controls as in Example 1, and their descriptions are omitted.

[0035] [Transmission members and holders] As shown in Figures 15 to 18, the holder 612 has a first surface 612c on the upstream side in the recording material transport direction of the fixing nip portion NP1 and a second surface 612d on the downstream side in the recording material transport direction. The transmission member 651 is assembled to the holder 612 via a first opposing portion 651c and a second opposing portion 651d, which are located on the upstream and downstream sides in the recording material transport direction, respectively, and face the first surface 612c and the second surface 612d. The second width 612e of the first surface 612c and the second surface 612d in the recording material transport direction is 0.02 to 0.16 mm smaller than the distance (second distance) 651e between the upstream and downstream sides of the first opposing portion 651c and the second opposing portion 651d in the recording material transport direction. Figure 18(a) shows the case where the second distance 651e is 0.02 to 0.16 mm larger than the second width 612e, and Figure 18(b) shows the case where the second distance 651e is 0.16 mm or more larger than the second width 612e, but this embodiment corresponds to Figure 18(a). When the transmission member 651 is pressurized by the pressurizing arm 652, the transmission member 651 tilts in the pressing direction shown in Figure 18 and abuts against the lower frame 63, causing the first opposing portion 651c to receive a force P from the lower frame 63 in the direction of approaching the fixing nip portion NP1. At this time, by narrowing the gap between the holder 612 and the transmission member 651, the tilting of the transmission member 651 with respect to the lower frame 63 is suppressed as shown in Figure 18(a), and deformation of the first opposing portion 651c by being pressed in the direction of approaching the fixing nip portion NP1 by the force P is suppressed.

[0036] In this embodiment, the first surface 612c and the second surface 612d are provided by the holder 612, but the present invention is not limited to this configuration. The invention is sufficient if the difference between the second distance 651e between the first opposing portion 651c and the second opposing portion 651d of the transmission member 651 and the width of the member adjacent to the first opposing portion 651c and the second opposing portion 651d is 0.02 to 0.16 mm. For example, as in this embodiment, the stay 613 may have portions corresponding to the first surface 612c and the second surface 612d, and the stay 613 may be assembled to the transmission member 651.

[0037] [Example 3] In this embodiment, the same reference numerals are used for the same configuration and control as in Embodiments 1 and 2, and their explanation is omitted. In this embodiment, as shown in Figure 19, a first projection 651f and a second projection 651g are provided at the lowest ends in the Z direction of the first opposing portion 651c and the second opposing portion 651d. By providing these projections, even if there is a bulge on the surface of the first opposing portion 651c or the second opposing portion 651d due to dimensional tolerances, the portions corresponding to the first surface 612c and the second surface 612d can be made into projections 651f and 651g. This makes it possible to suppress errors in the positional relationship between the transmission member 651 and the holder 612.

[0038] [Note] Furthermore, the disclosure of this embodiment includes the following configuration examples and method examples.

[0039] (Item 1) A heating unit comprising: a cylindrical belt; a heater disposed in the internal space of the belt; a holder for holding the heater; a stay positioned to contact the holder and to reinforce the holder; and a transmission member positioned to overlap both ends of the stay in the longitudinal direction when viewed in a direction perpendicular to the longitudinal direction of the belt, and transmitting pressure in the direction from the stay toward the heater to the stay. A pressure roller that contacts the outer surface of the belt, and together with the heater, sandwiches the belt and forms a fixing nip portion between itself and the belt, A frame that rotatably holds the pressure roller and holds the heating unit by holding the transmission member, the frame having a recess for mounting the transmission member, A pressurizing arm is rotatably mounted on the frame and applies the pressure to the transmission member while it is mounted on the frame, A fixing device having the fixing nip portion formed by the pressure, which holds and conveys the recording material while fixing a toner image formed on the recording material to the recording material, The material of the aforementioned frame is resin. The frame has a pivot axis for supporting the rotation of the pressurizing arm, When viewed in the longitudinal direction, the pivot axis is located upstream of the fixing nip portion in the recording material transport direction and between the rotation center of the pressure roller and the end of the holder furthest from the rotation center of the pressure roller in the first direction, in a first direction perpendicular to the longitudinal direction and the recording material transport direction. The transmission member has an opposing portion that faces the edge of the frame forming the recess, which is located downstream in the recording material transport direction from the center of the fixing nip portion. The opposing portion is provided with a first protrusion that projects toward the downstream edge in the recording material transport direction, and a second protrusion that is located at a position different from the position of the first protrusion in the first direction and also projects toward the downstream edge in the recording material transport direction. A fixing device characterized in that when the pressure roller rotates while the fixing nip portion is formed, both the first and second protrusions contact the edge on the downstream side in the recording material transport direction.

[0040] (Item 2) The fixing device described in item 1, The fixing device is characterized in that the first protrusion and the second protrusion are provided at both ends of the opposing portion in the first direction.

[0041] (Item 3) Fixing device as described in items 1-2, The fixing device is characterized in that, when viewed in the longitudinal direction, the pressure arm is bent in an L-shape.

[0042] (Item 4) Fixing devices as described in items 1 to 3, A fixing device characterized in that a spring for generating the pressure is placed between the pressure arm and the frame downstream of the fixing nip in the direction of conveying the recording material.

[0043] (Item 5) Fixing devices as described in items 1 to 4, A fixing device characterized in that the portion of the support that supports the pressurizing arm on the pivot axis is made of metal and is in contact with the pressurizing arm.

[0044] (Item 6) Fixing devices as described in items 1 to 5, A fixing device characterized in that a metal member is attached to the portion of the frame on which the spring is hung.

[0045] (Item 7) A heating unit comprising: a cylindrical belt; a heater disposed in the internal space of the belt; a holder for holding the heater; a stay positioned to contact the holder and to reinforce the holder; and a transmission member positioned to overlap both ends of the stay in the longitudinal direction when viewed in a direction perpendicular to the longitudinal direction of the belt, and transmitting pressure in the direction from the stay toward the heater to the stay. A pressure roller that contacts the outer surface of the belt, and together with the heater, sandwiches the belt and forms a fixing nip portion between itself and the belt, A frame that rotatably holds the pressure roller and holds the heating unit by holding the transmission member, the frame having a recess for mounting the transmission member, A pressurizing arm is rotatably mounted on the frame and applies the pressure to the transmission member while it is mounted on the frame, A fixing device having the fixing nip portion formed by the pressure, which holds and conveys the recording material while fixing a toner image formed on the recording material to the recording material, The material of the aforementioned frame is resin. The frame has a pivot axis for supporting the rotation of the pressurizing arm, When viewed in the longitudinal direction, the pivot axis is located upstream of the fixing nip portion in the recording material transport direction and between the rotation center of the pressure roller and the end of the holder furthest from the rotation center of the pressure roller in the first direction, in a first direction perpendicular to the longitudinal direction and the recording material transport direction. The holder has, in the longitudinal direction at the position where the transmission member is provided, a first surface located upstream of the fixing nip portion in the recording material transport direction, and a second surface located downstream of the fixing nip portion in the recording material transport direction. The transmission member has a first opposing portion that faces the first surface upstream of the first surface in the recording material transport direction, and a second opposing portion that faces the second surface downstream of the second surface in the recording material transport direction. A fixing device characterized in that the distance between the first opposing portion and the second opposing portion in the recording material transport direction is set to be 0.02 to 0.16 mm greater than the distance between the first surface and the second surface in the recording material transport direction.

[0046] (Item 8) The fixing device described in item 7, The first opposing portion has a first projection that protrudes toward the first surface at the position closest to the pressure roller in the first direction, The fixing device is characterized in that the second opposing portion has a second projection that protrudes toward the second surface at the position closest to the pressure roller in the first direction.

[0047] (Item 9) Fixing device as described in items 7-8, The fixing device is characterized in that, when viewed in the longitudinal direction, the pressure arm is bent in an L-shape.

[0048] (Item 10) Fixing devices as described in items 7 to 9, A fixing device characterized in that a spring for generating the pressure is placed between the pressure arm and the frame downstream of the fixing nip in the direction of conveying the recording material.

[0049] (Item 11) Fixing devices as described in items 7 to 10, A fixing device characterized in that the portion of the support that supports the pressurizing arm on the pivot axis is made of metal and is in contact with the pressurizing arm.

[0050] (Item 12) Fixing devices as described in items 7 to 11, A fixing device characterized in that a metal member is attached to the portion of the frame on which the spring is hung. [Explanation of Symbols]

[0051] 2. Main unit of the device 6. Fixing device 61 Heating Unit 611 Heater 612 Holder 613 Stay 614 Belt 614b surface 62 Pressure rollers 62a shaft 62c bearing 63 Lower frame 64 Upper Frame 65 Pressurization mechanism 652 Pressure Arm 653 Compression spring 671 Camshaft 672 Cam

Claims

1. A heating unit comprising: a cylindrical belt; a heater disposed in the internal space of the belt; a holder for holding the heater; a stay positioned to contact the holder and to reinforce the holder; and a transmission member positioned to overlap both ends of the stay in the longitudinal direction when viewed in a direction perpendicular to the longitudinal direction of the belt, and transmitting pressure in the direction from the stay toward the heater to the stay. A pressure roller that contacts the outer surface of the belt, and together with the heater, sandwiches the belt and forms a fixing nip portion between itself and the belt, A frame that rotatably holds the pressure roller and holds the heating unit by holding the transmission member, the frame having a recess for mounting the transmission member, A pressurizing arm is rotatably mounted on the frame and applies the pressure to the transmission member while it is mounted on the frame, A fixing device having the fixing nip portion formed by the pressure, which holds and conveys the recording material while fixing a toner image formed on the recording material to the recording material, The material of the aforementioned frame is resin. The frame has a pivot axis for supporting the rotation of the pressurizing arm, When viewed in the longitudinal direction, the pivot axis is located upstream of the fixing nip portion in the recording material transport direction and between the rotation center of the pressure roller and the end of the holder furthest from the rotation center of the pressure roller in the first direction, in a first direction perpendicular to the longitudinal direction and the recording material transport direction. The transmission member has an opposing portion that faces the edge of the frame forming the recess, which is located downstream in the recording material transport direction from the center of the fixing nip portion. The opposing portion is provided with a first protrusion that projects toward the downstream edge in the recording material transport direction, and a second protrusion that is located at a position different from the position of the first protrusion in the first direction and also projects toward the downstream edge in the recording material transport direction. A fixing device characterized in that when the pressure roller rotates while the fixing nip portion is formed, both the first and second protrusions contact the edge on the downstream side in the recording material transport direction.

2. The fixing device according to claim 1, characterized in that the first protrusion and the second protrusion are provided at both ends of the opposing portion in the first direction.

3. The fixing device according to claim 1, characterized in that the pressure arm is bent in an L-shape when viewed in the longitudinal direction.

4. The fixing device according to claim 3, characterized in that a spring for generating the pressure is placed between the pressure arm and the frame downstream of the fixing nip portion in the direction of conveying the recording material.

5. The fixing device according to claim 4, characterized in that the portion of the support that supports the pressurizing arm on the pivot axis is made of metal and is in contact with the pressurizing arm.

6. The fixing device according to claim 5, characterized in that a metal member is attached to the portion of the frame on which the spring is hung.

7. A heating unit comprising: a cylindrical belt; a heater disposed in the internal space of the belt; a holder for holding the heater; a stay positioned to contact the holder and to reinforce the holder; and a transmission member positioned to overlap both ends of the stay in the longitudinal direction when viewed in a direction perpendicular to the longitudinal direction of the belt, and transmitting pressure in the direction from the stay toward the heater to the stay. A pressure roller that contacts the outer surface of the belt, and together with the heater, sandwiches the belt and forms a fixing nip portion between itself and the belt, A frame that rotatably holds the pressure roller and holds the heating unit by holding the transmission member, the frame having a recess for mounting the transmission member, A pressurizing arm is rotatably mounted on the frame and applies the pressure to the transmission member while it is mounted on the frame, A fixing device having the fixing nip portion formed by the pressure, which holds and conveys the recording material while fixing a toner image formed on the recording material to the recording material, The material of the aforementioned frame is resin. The frame has a pivot axis for supporting the rotation of the pressurizing arm, When viewed in the longitudinal direction, the pivot axis is located upstream of the fixing nip portion in the recording material transport direction and between the rotation center of the pressure roller and the end of the holder furthest from the rotation center of the pressure roller in the first direction, in a first direction perpendicular to the longitudinal direction and the recording material transport direction. The holder has, in the longitudinal direction at the position where the transmission member is provided, a first surface located upstream of the fixing nip portion in the recording material transport direction, and a second surface located downstream of the fixing nip portion in the recording material transport direction. The transmission member has a first opposing portion that faces the first surface upstream of the first surface in the recording material transport direction, and a second opposing portion that faces the second surface downstream of the second surface in the recording material transport direction. A fixing device characterized in that the distance between the first opposing portion and the second opposing portion in the recording material transport direction is set to be 0.02 to 0.16 mm greater than the distance between the first surface and the second surface in the recording material transport direction.

8. The first opposing portion has a first projection that protrudes toward the first surface at the position closest to the pressure roller in the first direction, The fixing device according to claim 7, characterized in that the second opposing portion has a second projection that protrudes toward the second surface at the position closest to the pressure roller in the first direction.

9. The fixing device according to claim 7, characterized in that, when viewed in the longitudinal direction, the pressure arm is bent in an L-shape.

10. The fixing device according to claim 9, characterized in that a spring for generating the pressure is placed between the pressure arm and the frame downstream of the fixing nip portion in the direction of conveying the recording material.

11. The fixing device according to claim 10, characterized in that the portion of the support that supports the pressurizing arm on the pivot axis is made of metal and is in contact with the pressurizing arm.

12. The fixing device according to claim 11, characterized in that a metal member is attached to the portion of the frame on which the spring is hung.

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