Fixing device

Abstract

This invention provides a fixing device that is an advanced version of the conventional design. [Solution] The heating unit comprises an endless belt and a heater provided in the internal space of the belt; a pressure roller that forms a nip portion for transporting recording material together with the heater via the belt; a pressure spring; a pressure arm that pressurizes the heating unit in a direction that moves the heating unit toward the pressure roller by the spring force of the pressure spring; and a resin frame that supports the heating unit, wherein a metal support member is attached to the frame, and the frame rotatably supports the heating unit and the pressure roller via the support member.

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】 Japanese Patent Application Laid-Open No. 2024-31208 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0004】 It is an object to further develop the above-described conventional technology. 【Means for Solving the Problems】 【0005】 To solve the above problems, the present invention includes a heating unit having an endless belt and a heater provided in an internal space of the belt, a pressure roller that forms a nip portion for conveying a recording material together with the heater via the belt, a pressure spring, and a pressure arm that presses the heating unit in a direction in which the heating unit approaches the pressure roller by a spring force of the pressure spring, and a resin frame that supports the heating unit, wherein a metal support member is attached to the frame, and the frame rotatably supports the heating unit and the pressure roller via the support member. 【Effects of the Invention】 【0006】 A fixing device that further develops the conventional configuration is provided. 【Brief Description of the Drawings】 【0007】 [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] Exploded perspective view of the fixing device in Comparative Example 1. [Figure 14] Exploded perspective view of the fixing device in Example 2. [Modes for carrying out the invention] 【0008】 [Example 1] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 【0009】 [Image forming apparatus] Figure 1 is a perspective view of the fixing device in this embodiment. Figure 2 is a cross-sectional view of the electrophotographic image forming apparatus 1 in this embodiment. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment may be appropriately changed depending on the configuration and various conditions of the apparatus to which the present invention is applied. Therefore, unless otherwise specifically stated, the scope of the present invention is not limited thereto. In the following description, the left side of Figure 2 is defined as the front side of the image forming apparatus 1, and the right side is defined as the rear side of the image forming apparatus 1. The front of the page is defined as the right side of the image forming apparatus 1, and the back of the page is defined as the left side of the image forming apparatus 1. Also, the top and bottom sides of Figure 2 are defined as the top and bottom sides of the image forming apparatus 1, respectively. 【0010】 As shown in Figure 2, the image forming apparatus 1 comprises a main unit 2 and a process cartridge 10, the process cartridge 10 being detachably installed in the main unit 2. The main unit 2 is equipped with a paper feed tray 3, a recording material feeding unit 4, a transport path P, an image forming unit 5, a fixing device 6, a recording material discharge unit 7, a paper discharge tray 8, a laser scanner 9, and the like. The cartridge 10, on the other hand, is equipped with a photosensitive drum 11, a developing roller 12 as a developer carrier, and the like. 【0011】 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. 【0012】 The recording material feeding unit 4 includes a paper feed roller 41, a separation roller 42, a separation pad 42a, and a pair of conveyance rollers 43. Based on a print start signal, the recording material S stored in the paper feed tray 3 is sent out to the conveyance path P by the recording material feeding unit 4 and conveyed toward the image forming unit 5 through the registration roller pair 44. When the recording material S is conveyed to a predetermined position, an image forming start signal is issued and the image forming process starts. The photosensitive drum 11 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 based on image information by a laser scanner 9, and the charge in the exposed portion 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 to develop the latent image. Thereby, the latent image is visualized as a toner image on the photosensitive drum 11. 【0013】 The image forming unit 5 includes a process cartridge 10 and a transfer roller 51 disposed opposite to the photosensitive drum 11 of the process cartridge 10. When the recording material S conveyed by the registration roller pair 44 reaches the image forming unit 5 and passes through the transfer nip portion between the photosensitive drum 11 and the transfer roller 51, a voltage is applied from the apparatus main body 2 to the transfer roller 51, and the toner image on the photosensitive drum 11 is transferred to the recording material S. Thereafter, the recording material S onto which the toner image has been transferred is conveyed to a fixing device 6 including a heating unit 61 and a pressure roller 62 that contacts the outer peripheral surface of the cylindrical belt 614. When the recording material S is sandwiched and conveyed by the fixing nip portion NP1 of the heating unit 61 and 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 onto which the toner image has been fixed is discharged to the paper discharge tray 8 through the recording material discharge unit 7. 【0014】 [Fixing Device] Next, the specific configuration of the fixing device will be described with reference to FIGS. 3 to 8. As shown in FIG. 3, the heating unit 61 included in the fixing device 6 includes a heater 611, a holder 612, a stay 613, and a belt 614. The heater 611, the holder 612, and the stay 613 are arranged in the internal space of the belt 614. When defining the X, Y, and Z directions as shown in FIG. 3, the heater 611 is in the shape of a flat plate extending in the Y direction, and the Y direction coincides with the longitudinal direction of the heater 611. Further, it has a first surface 611a and a second surface 611b on the opposite side of the first surface 611a, and the first surface 611a is supported by the holder 612. 【0015】 The holder 612 is formed of a resin having heat resistance 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 peripheral surface 614a of the belt 614 to guide the belt 614, and the support wall 612b has a support surface 612b1 for supporting 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 steel plate having a rigidity greater than that of the holder 612, for example, a steel plate with a thickness of 1.6 mm, into a substantially U shape. 【0016】 The belt 614 is an endless belt having heat resistance and flexibility. For example, there are those in which a fluororesin is coated on a metal sleeve such as stainless steel, and those in which a polyimide resin, a silicone rubber, a fluororesin, etc. are laminated. The heater 611, the holder 612, and the stay 613 are arranged inside the belt 614, and the belt 614 rotates around them. Further, the inner peripheral surface 614a of the belt 614 contacts the second surface 611b of the heater 611. 【0017】 The pressure roller 62 has a metal shaft 62a, which is the shaft portion, and a roller 62b made of an elastic material that covers 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, forming a fixing nip portion 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 portion NP1. 【0018】 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. 【0019】 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. 【0020】 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. 【0021】 As shown in Figure 5, the lower frame 63 directly supports the heating unit 61. The lower frame 63 has a pair of rails 63b at each end in the Y direction. As shown in Figure 5, the support member 637 is fitted and attached to the rails 63b provided on both sides of the lower frame 63. Here, the rails 63b may be U-shaped grooves. The rails 63b are columnar parts that extend in the Z direction from the main body 63c of the lower frame 63. A bearing 62c is mounted on the support member 637, and the pressure roller 62 is positioned and supported on top of it. 【0022】 As shown in Figure 5, the heating unit 61 is supported by a groove in the transmission member 651 that fits into a groove 637b in the metal support member 637. The position of the bearing 62d is determined by a projection 62d1 on the bearing 62d fitting into a groove 637b on the support member 637. The pair of grooves 637b face each other in the X direction. The opposing surfaces of the grooves 637b engage with grooves 651a1 and 651b1 provided on the transmission members 651a and 651b, respectively. In this embodiment, the rail 63b is a columnar portion extending in the Z direction, but it is not limited to the shape of this embodiment, as long as it is a shape that can support the holder 612 so that it can move in the Z direction. 【0023】 Furthermore, the pressure roller 62 is rotatably held to the lower frame 63 via bearings 62c and 62d at both longitudinal ends of a metal shaft 62a. 【0024】 In this embodiment, it is desirable that the bearing 62c be a resin sliding bearing to prevent metal-to-metal contact with the support member 637. The transmission member 651 transmits spring force in the Z direction to the stay 613 by being pressed by the pressure arm 652. Furthermore, the pressure applied to the stay 613 is applied to the holder 612 and the heater 611, forming a fixing nip N between the heater 611 and the pressure roller 62. The support member 637 is made of a 1.0 mm thick stainless steel plate (SUS304) and has sufficient rigidity to hold the transmission member 651 in place. Alternatively, the rail 63b may be a U-shaped groove, and the support member 637 may be shaped like a U so that it fits into the U-shaped groove. 【0025】 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. 【0026】 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. 【0027】 [Pressurization mechanism] As shown in Figures 9 to 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. 【0028】 The pressurizing mechanism 65 includes a member (transmission member 651) that supports the heating unit 61 at its end in the Y direction and transmits pressure to a stay that is supported so as to be movable in the Z direction by a groove 637b. 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 and the support member 637, 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. 【0029】 At least a portion of the pivot 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 Z-direction end of the holder 612 on the pressure arm side (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 pivot 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 fixing nip NP1 to the photosensitive drum 11 in the X direction. 【0030】 [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. 【0031】 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. 【0032】 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). 【0033】 Here, a diagram of Comparative Example 1 is shown in Figure 13. In the Comparative Example, as shown in Figure 13, no support member 637 is provided, and the bearing 62c directly contacts the lower frame 63. In contrast, in this embodiment, by making the side plate portion itself a metal component, the rigidity for holding the pressure roller can be increased compared to Comparative Example 1, and precise holding of the heating unit 61 and the pressure roller 62 can be achieved. It is desirable that the positional relationship between the pressure roller 62, which is the drive source, and the heating unit 61 be maintained throughout the product life without being affected by external factors such as load, heating, and sliding friction. In this embodiment, by incorporating a support member 637 that partially applies a metal material with superior material properties of higher strength, higher heat resistance, and wear resistance than the lower frame 63, the occurrence of creep can be prevented, and stable fixing, image quality, and high durability can be achieved throughout the product life. 【0034】 [Example 2] In this embodiment, the same reference numerals are used for the same components and controls as in Embodiment 1, and their explanation is omitted. In this embodiment, as shown in Figure 14, the support member 637 is larger than that in Embodiment 1, and the support member 637 covers the entire side of the fixing device 6. The support member 637 is fixed to the lower frame 63. With the configuration of this embodiment, the rigidity of the fixing device can be increased compared to Embodiment 1. 【0035】 [Example 3] In this embodiment, the same reference numerals are used for the same configuration and control as in Examples 1 and 2, and their descriptions are omitted. The metal support member 637 described in Examples 1 and 2 may be replaced with a super engineering plastic. The material of the support member 637 may be, for example, polyacetal (POM), polyamide (PA), polycarbonate (PC), modified polyphenylene ether (m-PPE), or polybutylene terephthalate (PBT). By using a super engineering plastic for the support member 637, it is possible to achieve high heat resistance and high rigidity while preventing discharge from inside the image forming apparatus, compared to the case of metal. 【0036】 [Example 4] In this embodiment, the same reference numerals are used for the same configuration and control as in Embodiments 1 to 3, and their explanation is omitted. In Embodiment 1, the bearing 62c was made of resin, but in this embodiment, the bearing is made of metal, such as a ball bearing. In this case, a resin member may be provided between the bearing and the support member 637 to prevent metal-to-metal contact between the bearing and the support member 637. By using a metal bearing, the load capacity can be increased compared to a resin bearing. 【0037】 [Note] Furthermore, the disclosure of this embodiment includes the following configuration examples and method examples. 【0038】 (Item 1) The heating unit comprises an endless belt and a heater provided in the internal space of the belt; a pressure roller that forms a nip section for transporting recording material together with the heater via the belt; a pressure spring; a pressure arm that pressurizes the heating unit in a direction toward the pressure roller by the spring force of the pressure spring; and a resin frame that supports the heating unit. A fixing device characterized in that a metal support member is attached to the frame, and the frame rotatably supports the pressure roller via the support member. 【0039】 (Item 2) The fixing device described in item 1, The fixing device is characterized in that the frame movably supports the heating unit via the support member. 【0040】 (Item 3) Fixing device as described in items 1-2, The fixing device is characterized in that the frame directly supports the heating unit. 【0041】 (Item 4) Fixing devices as described in items 1 to 3, The fixing device is characterized in that the support member is U-shaped and is attached along the U-shaped groove of the frame. 【0042】 (Item 5) Fixing devices as described in items 1 to 4, The fixing device is characterized in that the support member is a plate-shaped member, and the portion that supports the pressure roller is recessed so as to support the pressure roller. 【0043】 (Item 6) Fixing devices as described in items 1 to 5, The pressure roller has a shaft portion, an elastic portion provided around the shaft portion, and a bearing attached to the shaft portion. The fixing device is characterized in that the support member directly supports the bearing, and the bearing is a sliding bearing. 【0044】 (Item 7) Fixing devices as described in items 1 to 6, The pressure roller has a shaft portion, an elastic portion provided around the shaft portion, and a bearing attached to the shaft portion. The fixing device is characterized in that the bearing is made of metal, a resin member is provided between the bearing and the support member, and the bearing is supported by the support member via the resin member. [Explanation of Symbols] 【0045】 2. Main unit of the device 6. Fuser 61 Heating Unit 611 Heater 612 Holder 613 Stay 617 Flange 614 Belt (fixing film) 62 Pressurized Rotating Body (Pressure Roller) 62c bearing 63 Lower frame 637 Support member 64 Upper Frame 65 Pressurization mechanism 651 Transmission member 652 Pressure Arm 653 Compression spring

Claims

[Claim 1] The heating unit comprises an endless belt and a heater provided in the internal space of the belt; a pressure roller that forms a nip section for transporting recording material together with the heater via the belt; a pressure spring; a pressure arm that pressurizes the heating unit in a direction toward the pressure roller by the spring force of the pressure spring; and a resin frame that supports the heating unit. A fixing device characterized in that a metal support member is attached to the frame, and the frame rotatably supports the pressure roller via the support member. [Claim 2] The fixing device according to claim 1, characterized in that the frame movably supports the heating unit via the support member. [Claim 3] The fixing device according to claim 1, characterized in that the frame directly supports the heating unit. [Claim 4] The fixing device according to claim 1, characterized in that the support member is U-shaped and the support member is attached along the U-shaped groove of the frame. [Claim 5] The fixing device according to claim 1, characterized in that the support member is a plate-shaped member, and the portion that supports the pressure roller is recessed so as to support the pressure roller. [Claim 6] The pressure roller has a shaft portion, an elastic portion provided around the shaft portion, and a bearing attached to the shaft portion. The fixing device according to any one of claims 1 to 5, characterized in that the support member directly supports the bearing, and the bearing is a sliding bearing. [Claim 7] The pressure roller has a shaft portion, an elastic portion provided around the shaft portion, and a bearing attached to the shaft portion. The fixing device according to any one of claims 1 to 5, characterized in that the bearing is made of metal, a resin member is provided between the bearing and the support member, and the bearing is supported by the support member via the resin member.

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