fixing device

Abstract

A fixing device includes a heating unit, a pressure roller, a pressure spring, a pressure arm, and a resin frame, the heating unit includes a belt and a heater provided in an inner space of the belt, the pressure roller is configured to form a nip for conveying a recording material together with the belt and the heater, the pressure arm is configured to press the heating unit toward the pressure roller by a spring force of the pressure spring, the resin frame is configured to support the heating unit, wherein a metal support member is attached to the frame, and the frame rotatably supports the pressure roller via the support member.

Description

Technical Field

[0001] The present invention relates to a fixing device installed in an image forming apparatus employing an electrophotographic method. Background Technology

[0002] In image forming apparatus employing electrophotographic methods, as described in Japanese Patent Application Publication No. 2024-31208, a fixing device employing an on-demand fixing method is known. Summary of the Invention

[0003] According to some embodiments of this disclosure, the fixing apparatus includes a heating unit, a pressure roller, a pressure spring, a pressure arm, and a resin frame. The heating unit includes an annular belt and a heater disposed within the belt's internal space. The pressure roller is configured to form a clamping portion for conveying recording material via the belt and the heater. The pressure arm is configured to press the heating unit against the pressure roller by the spring force of the pressure spring. The resin frame is configured to support the heating unit, wherein a metal support member is attached to the frame, and the frame rotatably supports the pressure roller via the support member.

[0004] A fixing device that improves upon conventional configurations is provided.

[0005] The features of this disclosure will become apparent from the following description of embodiments with reference to the accompanying drawings. The following description of embodiments is by way of example. Attached Figure Description

[0006] Figure 1A and 1B This is a perspective view of the fixing device according to the first embodiment.

[0007] Figure 2 This is a cross-sectional view of the image forming apparatus according to the first embodiment.

[0008] Figure 3 This is a cross-sectional view of the heating unit and pressure roller according to the first embodiment.

[0009] Figure 4 This is a cross-sectional view of the fixing device according to the first embodiment.

[0010] Figure 5A This is a cross-sectional view of the fixing device according to the first embodiment. Figure 5B It is its exploded perspective view.

[0011] Figure 6 This is a top view of the retainer according to the first embodiment.

[0012] Figure 7 This is an exploded perspective view of the heating unit according to the first embodiment.

[0013] Figure 8 This is a top view of the heating unit according to the first embodiment.

[0014] Figure 9A It is a front view. Figure 9B , Figure 9C and Figure 9D This is a cross-sectional view of the fixing device according to the first embodiment.

[0015] Figure 10A It is a top view. Figure 10B and Figure 10C This is an enlarged view of the lower frame and pressure roller according to the first embodiment.

[0016] Figure 11A It is a cross-sectional view of the pressure mechanism and pressure relief mechanism under pressure. Figure 11B This is a cross-sectional view of the pressure mechanism and pressure relief mechanism according to the first embodiment under pressure relief conditions.

[0017] Figure 12 It is an exploded perspective view of the lower frame, upper frame, camshaft, and cam according to the first embodiment.

[0018] Figure 13A This is a cross-sectional view of the fixing device based on Comparative Example 1. Figure 13B It is its exploded perspective view.

[0019] Figure 14A This is a cross-sectional view of the fixing device according to the second embodiment. Figure 14B It is its exploded perspective view. Detailed Implementation

[0020] [First Embodiment]

[0021] In the following, various exemplary embodiments, features and aspects of this disclosure will be described in detail with reference to the accompanying drawings.

[0022] [Image forming apparatus]

[0023] Figure 1A and Figure 1B This is a perspective view of the fixing device according to the first embodiment. Figure 2 This is a cross-sectional view of the image forming apparatus 1 employing an electrophotographic method according to this embodiment. However, the dimensions, materials, shapes, and relative arrangements of the components described in the embodiments may be appropriately varied depending on the configuration of the apparatus to which this disclosure is applied and various conditions. Therefore, unless otherwise specifically stated, the scope of this disclosure is not limited thereto. In the following description, Figure 2 The left side of the image forming device 1 is defined as the front side, the right side is defined as the rear side, the near side is defined as the right side of the image forming device 1, and the far side is defined as the left side of the image forming device 1. Figure 2The upper and lower sides are defined as the upper and lower sides of the image forming device 1, respectively.

[0024] like Figure 2 As shown, the image forming apparatus 1 includes a main body 2, and a processing cartridge 10 is detachably mounted on the main body 2. The main body 2 includes a paper feed tray 3, a recording material supply unit 4, a transport path P, an image forming unit 5, a fixing device 6, a recording material discharge unit 7, a discharge tray 8, a laser scanner 9, and other units. The cartridge 10 includes a photosensitive drum 11, a developing roller 12 serving as a developer carrier, and other components.

[0025] The main body 2 is provided with an opening 2A for attaching and removing the processing box 10 and an opening / closing door 21 for closing the opening 2A. The opening / closing door 21 is rotatably supported about a rotation axis 21a and can move between a closed position for closing the opening 2A and an open position for opening the opening 2A.

[0026] The recording material supply unit 4 includes a paper supply roller 41, a separation roller 42, a separation pad 42a, and a transport roller pair 43. Recording material S stored in the paper supply tray 3 is supplied by the recording material supply unit 4 to the transport path P based on a print start signal, and is transported toward the image forming unit 5 via the alignment roller pair 44. When the recording material S is conveyed to a predetermined position, an image forming start signal is emitted, and image forming processing begins. The photosensitive drum 11, driven by a drive source (motor) not shown, is uniformly charged to a predetermined potential by a charging unit not shown. The surface of the charged photosensitive drum 11 is exposed by a laser scanner 9 based on image information, and the charge in the exposed portion is removed to form an electrostatic image. Toner in the processing cartridge 10 is carried on a developing roller 12 and supplied to the photosensitive drum 11 according to the electrostatic latent image to develop the latent image. Therefore, the latent image is visualized as a toner image on the photosensitive drum 11.

[0027] The image forming unit 5 includes a processing cartridge 10 and a transfer roller 51 positioned facing the photosensitive drum 11 of the processing cartridge 10. When the recording material S, conveyed by the alignment roller pair 44, arrives at the image forming unit 5 and passes through the transfer clamping section between the photosensitive drum 11 and the transfer roller 51, voltage is applied from the main body 2 to the transfer roller 51, and the toner image on the photosensitive drum 11 is transferred to the recording material S. The recording material S with the transferred toner image is then conveyed to a fixing device 6, which includes a heating unit 61 and a pressure roller 62 that contacts the outer peripheral surface of a cylindrical belt 614. As the recording material S is clamped and conveyed through the fixing clamping section NP1 between the heating unit 61 and the pressure roller 62, the toner image transferred to the recording material S is heated and pressurized to fix it onto the surface of the recording material S. The recording material S with the fixed toner image is discharged to a discharge tray 8 via the recording material discharge unit 7.

[0028] [Fixing device]

[0029] Next, we will refer to Figures 3 to 8 Describe the specific configuration of the fixing device. For example... Figure 3 As shown, the heating unit 61 included in the fixing device 6 includes a heater 611, a retainer 612, a support bar 613, and a belt 614. The heater 611, retainer 612, and support bar 613 are disposed within the internal space of the belt 614. When the X, Y, and Z directions are as shown... Figure 3 As defined, heater 611 is a flat plate extending along the Y direction, which is aligned with the longitudinal direction of heater 611. Heater 611 has a first surface 611a and a second surface 611b opposite to the first surface 611a, the first surface 611a being supported by a retainer 612.

[0030] The retainer 612 is made of a heat-resistant resin, such as polyphenylene sulfide (PPS) or a 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 guide strip 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 contacts the first surface 611a of the heater 611. The support bar 613 is a component that supports the retainer 612 and is formed by bending a sheet material (e.g., a steel plate with a thickness of 1.6 mm) having higher rigidity than the retainer 612 into a generally U-shape.

[0031] The belt 614 is a heat-resistant and flexible annular belt, examples of which include a metal sleeve coated with a fluoropolymer, such as stainless steel, or a laminated structure of polyimide resin, silicone rubber, fluoropolymer, etc. A heater 611, a retainer 612, and a support 613 are disposed inside the belt 614, and the belt 614 rotates about these components. The inner circumferential surface 614a of the belt 614 contacts the second surface 611b of the heater 611.

[0032] The pressure roller 62 includes a metal shaft 62a serving as a shaft portion and a roller 62b made of an elastic member covering the shaft 62a, and is pressed against the heater 611 via a belt 614. The pressure roller 62 forms a fixing clamping portion NP1 for clamping, heating, and pressurizing the recording material S by clamping the belt 614 between the pressure roller 62 and the heater 611. That is, the pressure roller 62 heats and pressurizes the recording material S together with the heater 611 at the fixing clamping portion NP1.

[0033] The pressure roller 62 is configured to be rotated by a driving force transmitted from a drive source provided in the image forming apparatus 1. When the pressure roller 62 is rotated, the belt 614 is rotated passively by friction with the pressure roller 62 or the recording material S clamped in the fixing clamp NP1. As a result, the recording material S with the toner image transferred is conveyed between the pressure roller 62 and the heated belt 614, thereby heat-fixing the toner image.

[0034] like Figures 4 to 8 As shown, the fixing device 6 includes a lower frame 63 supporting 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, which guides the upper surface of the recording material S conveyed along the conveying path P downstream of the heating unit 61 and the pressure roller 62 in the recording material conveying direction. The lower frame 63 has a lower recording material guide 63a, which guides the lower surface of the recording material S conveyed along the conveying path P downstream of the heating unit 61 and the pressure roller 62 in the recording material conveying direction.

[0035] 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 of, for example, non-conductive molded components. For example, the material of the molded components may be polyethylene terephthalate (PET), polybutylene terephthalate (PBT), or PPS. PET or PBT may be reinforced with glass fiber.

[0036] like Figure 5A As shown, the lower frame 63 directly supports the heating unit 61. The lower frame 63 has a pair of tracks 63b at the corresponding ends in the Y direction. Figure 5B As shown, the support member 637 is assembled and attached to tracks 63b disposed on both sides of the lower frame 63. Here, each track 63b can be a U-shaped groove. Each track 63b is a columnar portion extending from the main body 63c of the lower frame 63 along the Z direction. The bearing 62c is attached to the support member 637, and the pressure roller 62 is disposed and supported on the bearing 62c.

[0037] like Figure 5BAs shown, the heating unit 61 is supported by fitting a groove in the transfer member 651 into a groove 637b in the metal support member 637. Furthermore, a protrusion 62c1 on the bearing 62c is fitted into the groove 637b in the support member 637, thereby positioning the bearing 62c. A pair of inner surfaces of the groove 637b face each other in the X direction. The opposing inner surfaces of the groove 637b engage with grooves 651a1 and 651b1 respectively in the transfer members 651a and 651b. Note that although the tracks 63b are all columnar portions extending in the Z direction according to this embodiment, the shape is not limited to this, as long as the retainer 612 can be supported by the tracks 63b to facilitate movement in the Z direction.

[0038] The pressure roller 62 is rotatably held on the lower frame 63 via bearings 62c and 62c at the two longitudinal ends of the metal shaft 62a.

[0039] In this embodiment, bearing 62c is preferably a resin sliding bearing to prevent metal-to-metal contact with support member 637. Transmission member 651 is pressed by pressure arm 652 to transmit spring force in the Z direction to support bar 613. Furthermore, the pressure applied to support bar 613 is applied to retainer 612 and heater 611, thereby forming fixing clamping portion NP1 between heater 611 and pressure roller 62. Support member 637 is formed of a 1.0 mm thick stainless steel plate (stainless steel (SUS) 304) to have sufficient rigidity to maintain engagement of transmission member 651. Track 63b may be a U-shaped groove, and support member 637 may have a U-shaped configuration to fit into the U-shaped groove.

[0040] like Figure 6 As shown, the support wall 612b of the retainer 612 is provided with multiple holes 612b2 and 612b3. For example... Figure 7 As shown, temperature sensors 613a and 613b are configured to face the rear surface 612b4 of the retainer 612, which is opposite to the support surface 612b1. Figure 7 As shown, temperature sensors 613a and 613b contact the first surface 611a of heater 611 through holes 612b2 and 612b3. Temperature sensors 613a and 613b are pressed against the first surface 611a of heater 611 by pushing members 613c and 613d disposed between support bar 613 and temperature sensors 613a and 613b (see Figure 1). Figure 3Temperature sensor 613a is located at one end of retainer 612 in the Y direction. Temperature sensor 613b is closer to one end of retainer 612 in the Y direction than the center of retainer 612. In this embodiment, temperature sensors 613a and 613b are thermistors, but other temperature sensors, such as thermostats, may also be used. In this embodiment, pushing members 613c and 613d are helical springs, but other pushing members may also be used.

[0041] like Figure 5B and Figure 8 As shown, the retainer 612 extends through the interior of the belt 614 in the Y direction, with both ends in the Y direction protruding outward from the belt 614. The retainer 612 supports the heater 611, and one end of the heater 611 in the Y direction is provided with a first wire spring 615a for holding the heater 611 on the retainer 612 and a connector 616 for supplying power to the heater 611 and clamping the heater 611 and the retainer 612. The other end of the heater 611 in the Y direction is provided with a second wire spring 615b for holding the heater 611 on the retainer 612.

[0042] Temperature sensors 613a and 613b are closer to the first wire spring 615a in the Y direction than the second wire spring 615b. The first wire spring 615a is disposed between the belt 614 and the connector 616. The second wire spring 615b is disposed in a region protruding outward from the belt 614, located at the opposite end where the first wire spring 615a is disposed. In this embodiment, the pressure roller 62 includes a shaft 62a and a roller 62b, but the construction is not limited to this, and a pressure band pressed against the heating roller by an elastic member may be provided.

[0043] [Pressure mechanism]

[0044] like Figures 9A to 9D and Figures 10A to 10C As shown, the fixing device 6 includes a pressure mechanism 65 that applies pressure to form a fixing clamping portion NP1 between the heating unit 61 and the pressure roller 62. The pressure mechanism 65 is located at each end of the lower frame 63 in the Y direction. Since the structure of one side of the pressure mechanism 65 in the Y direction is substantially the same as that of the other side, the following description focuses mainly on the side of the pressure mechanism 65 in the Y direction.

[0045] The pressurizing mechanism 65 includes a pressure transmission member (transmission member 651) that transmits pressure to a support bar. One end of the support bar supports the heating unit 61 in the Y direction and is supported by a recessed portion 637b for movement in the Z direction. The pressurizing mechanism 65 also includes a pressure arm 652 that applies pressure to the transmission member 651 when the transmission member 651 is mounted on the lower frame 63 and the support member 637 to form the fixing clamping portion NP1. Furthermore, the pressurizing mechanism 65 includes a pressure spring 653 that generates pressure to press the pressure arm 652 against the transmission member 651, and the pressure spring 653 is stretched between the lower frame 63 and the pressure arm 652. The lower frame 63 has a support portion 64d that rotatably supports the pressure arm 652 about a rotational central axis X1. The support portion 64d is a generally cylindrical protrusion. The pressure spring 653 is a tension helical spring that biases the pressure arm 652 toward the pressure roller 62. The lower frame 63 has a spring hook portion 63m, on which one end of the pressure spring 653 is hooked. For example, the portion of the resin lower frame 63 corresponding to the support portion 64d can be made of metal, or the portion of the support portion 64d that only contacts the pressure arm 652 can be provided with a metal component. The portion of the resin lower frame 63 corresponding to the spring hook portion 63m can also be made of metal.

[0046] When viewed from the Y direction, at least a portion of the rotational center axis X1 around which the pressure arm 652 rotates is located upstream of the recording material transport direction relative to the fixing clamp NP1, and Figure 9B Within the range T in the Z direction shown. Here, Figure 9B The Z-direction range T shown is the range between the rotation center of the pressure roller 62 in the Z-direction and the end of the retainer 612 on the pressure arm side in the Z-direction (the end of the retainer 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 portion of the pressure arm 652 that presses against the transmission member 651 and the rotation center axis X1, the pressure arm 652 is bent into an L-shape. The upstream side in the recording material transport direction refers to the side in the X-direction closer to the photosensitive drum 11 than the fixing clamp NP1.

[0047] [Pressure relief mechanism]

[0048] like Figure 11A and Figure 11B As shown, the fixing device 6 also includes a pressure release mechanism 67 for releasing pressure applied to the image. Figure 9BThe clamping pressure of the fixing clamping part NP1 between the heating unit 61 and the pressure roller 62. The pressure release mechanism 67 includes 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 each end of the lower frame 63 in the Y direction. Since the structure of the pressure release mechanism 67 on one side of the Y direction is basically the same as the structure on the other side, the following description mainly refers to the structure on the Y direction side.

[0049] like Figure 12 As shown, camshaft 671 extends along the Y direction. Camshaft 671 is made of, for example, metal. Cam 672 is fixed to each end of camshaft 671 along the Y direction. In other words, cam 672 has camshaft 671. Cam 672 rotates together with camshaft 671. Lower frame 63 has shaft support portion 63l that rotatably supports camshaft 671. Figure 12 As shown, shaft support portions 63l are respectively provided at one end and the other end of the lower frame 63 along the Y direction. Each shaft support portion 63l has a hole H for rotatably supporting the camshaft 671.

[0050] like Figure 12 As shown, the upper frame 64 has a groove 64C that rotatably supports the camshaft 671. The groove 64C is respectively provided at one end and the other end of the upper frame 64 along the Y direction. The camshaft 671 is held between the upper frame 64 and the lower frame 63. Figure 11A and Figure 11B As shown, the camshaft 671 is rotatably supported about axis X2. The cam 672 can press the pressure arm 652 against the biasing force of the pressure spring 653. Specifically, the cam 672 can... Figure 11A The first position shown and Figure 11B Rotate between the second positions shown.

[0051] Comparative Example 1 Figure 13A and Figure 13B As shown. In the comparative example, as Figure 13AAs shown, without the support member 637, the bearing 62c directly contacts the lower frame 63. In contrast, according to the first embodiment, by forming the side plate portion itself as a metal member, the rigidity for holding the pressure roller can be improved compared to Comparative Example 1, and precise holding of the heating unit 61 and the pressure roller 62 can be achieved. The positional relationship between the pressure roller 62, which serves as the drive source, and the heating unit 61 ideally remains unchanged throughout the product life, unaffected by external factors such as load, heat, and sliding friction. In this embodiment, the support member 637 is partially made of a metal material with higher strength, higher heat resistance, and better wear resistance than the lower frame 63. By combining the support member 637 with the above-mentioned material properties, creep can be prevented, and stable fixing performance, image quality, and high durability can be achieved throughout the product life.

[0052] [Second Embodiment]

[0053] In this embodiment, the same configurations and controls as in the first embodiment are represented by the same reference numerals, and their descriptions are omitted. In this embodiment, as... Figure 14A As shown, the support member 637 is larger than the support member in the first embodiment and covers the entire side of the fixing device 6. The support member 637 is fixed to the lower frame 63. With this configuration, the rigidity of the fixing device can be improved compared to the first embodiment.

[0054] [Third Embodiment]

[0055] In the third embodiment, the same configuration and controls as in the first and second embodiments are indicated by the same reference numerals, and their description is omitted. The metal support member 637 described in the first and second embodiments can be replaced with a super engineering plastic. Examples of materials for the support member 637 include polyacetal (POM), polyamide (PA), polycarbonate (PC), modified polyphenylene ether (m-PPE), and polybutylene terephthalate (PBT).

[0056] By using super engineering plastic as the support component 637, high heat resistance and high rigidity can be achieved while preventing discharge from inside the image forming device, compared to the use of metal.

[0057] [Fourth Embodiment]

[0058] In the fourth embodiment, the same configuration and control as in the first to third embodiments are indicated by the same reference numerals, and their description is omitted. In the first embodiment, the bearing 62c is made of resin, but in the fourth embodiment, the bearing is made of metal, such as a ball bearing. In this case, to prevent metal-to-metal contact between the bearing and the support member 637, a resin member can be provided between the bearing and the support member 637. Compared with resin bearings, the load-bearing capacity can be improved by using metal bearings.

[0059] [Additional Notes]

[0060] The disclosure of the embodiments also includes the following configuration examples.

[0061] (Project 1)

[0062] A fixing apparatus includes: a heating unit comprising an annular belt and a heater disposed within an internal space of the belt; a pressure roller configured to form a clamping portion for conveying recording material together with the heater via the belt; a pressure spring; a pressure arm configured to press the heating unit against the pressure roller by the spring force of the pressure spring; and a resin frame configured to support the heating unit, wherein a metal support member is attached to the frame, and the frame rotatably supports the pressure roller via the support member.

[0063] (Project 2)

[0064] According to the fixing device of Project 1, the frame movably supports the heating unit by means of the support member.

[0065] (Project 3)

[0066] The fixing apparatus according to any one of items 1 to 2, wherein the frame directly supports the heating unit.

[0067] (Project 4)

[0068] The fixing device according to any one of items 1 to 3, wherein the support member is U-shaped and is attached along the U-shaped groove of the frame.

[0069] (Project 5)

[0070] According to any one of items 1 to 4, the fixing apparatus wherein the supporting member is a plate-shaped member and the portion supporting the pressure roller is recessed to support the pressure roller.

[0071] (Project 6)

[0072] According to any one of items 1 to 5, the fixing apparatus includes a pressure roller comprising a shaft portion, an elastic portion disposed around the shaft portion, and a bearing attached to the shaft portion, the support member directly supporting the bearing, and the bearing being a sliding bearing.

[0073] (Project 7)

[0074] According to any one of items 1 to 6, the fixing apparatus includes a pressure roller comprising a shaft portion, an elastic portion disposed around the shaft portion, and a bearing attached to the shaft portion, wherein the bearing is made of metal, and wherein a resin member is disposed between the bearing and the support member such that the bearing is supported by the support member via the resin member.

[0075] While this disclosure has been described with reference to embodiments, it should be understood that this disclosure is not limited to the disclosed embodiments. The scope of the following claims should be given the broadest interpretation to cover all such modifications and equivalent structures and functions.

Claims

1. A fixing device, the fixing device comprising: A heating unit comprising an annular belt and a heater disposed within the internal space of the belt; A pressure roller is configured to form a clamping portion for conveying recording material together with the heater via the belt; Compression spring; A pressure arm is configured to press the heating unit against the pressure roller by the spring force of the pressure spring; as well as A resin frame is configured to support the heating unit. The metal support member is attached to the frame, and the frame rotatably supports the pressure roller via the support member.

2. The fixing device according to claim 1, wherein, The frame movably supports the heating unit via the support member.

3. The fixing device according to claim 1, wherein, The frame directly supports the heating unit.

4. The fixing device according to claim 1, wherein, The support member is U-shaped and is attached along the U-shaped groove of the frame.

5. The fixing device according to claim 1, wherein, The support member is a plate-shaped member, and the portion supporting the pressure roller is recessed to support the pressure roller.

6. The fixing device according to claim 1, in, The pressure roller includes a shaft portion, an elastic portion disposed around the shaft portion, and a bearing attached to the shaft portion. The supporting member directly supports the bearing, and The bearing in question is a sliding bearing.

7. The fixing device according to claim 1, in, The pressure roller includes a shaft portion, an elastic portion disposed around the shaft portion, and a bearing attached to the shaft portion. The bearing is made of metal, and The resin component is disposed between the bearing and the support component, such that the bearing is supported by the support component via the resin component.

Images