Image forming device

Abstract

To provide a fixation device with which it is possible to suppress a rise in gear temperature due to heat transfer from a fixing nip part.SOLUTION: A side frame includes a support frame that supports the longitudinal end of a heating unit and / or a pressure applying member, and a main frame that supports a gear and is located appropriately in parallel to the support frame. The support frame and the main frame are secured in a fixing part that is provided in a mutually overlapping region, the support frame being located on the surface opposite the side where the gear is provided, with the main frame serving as a boundary.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a fixing device that is installed in an image forming apparatus such as an electrophotographic printer or copier, and that fixes a toner image formed on a recording material onto the recording material. [Background technology]

[0002] One type of fixing device is a film heating type fixing device that is excellent in on-demand performance.

[0003] A film heating type fixing device forms a fixing nip with a film unit in which a heater is disposed inside a cylindrical film, and a pressure roller. Then, while the recording material is nipped and conveyed through the fixing nip, an unfixed toner image on the recording material is heated and fixed to the recording material. Patent Document 1 describes such a fixing device.

[0004] The film unit and pressure roller are supported at both ends by the frame of the fixing device, and a fixing nip is formed by biasing each end of the film unit toward the pressure roller with a spring. The pressure roller has a shaft rotatably supported by the frame, and a gear that receives power from a motor is attached to the shaft located outside the frame. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-114621 Summary of the Invention [Problem to be solved by the invention]

[0006] As printing speeds increase, the heater's target control temperature tends to rise, leading to higher temperatures in the fixing nip. As image forming devices become smaller, heat from the fixing nip tends to be transferred not only to the film unit and pressure roller, but also to the gear attached to the pressure roller shaft, causing the gear temperature to rise. Resin is often used as the material for the pressure roller gear, and measures are needed to prevent accelerated gear wear and strength loss due to temperature increases. This phenomenon occurs in devices other than those using a film heating method, and measures to address this problem are needed.

[0007] SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has an object to provide a fixing device that can suppress a temperature rise of the gear due to heat transfer from the fixing nip portion. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, the present invention provides a fixing device including: a heating unit for heating a recording material; a rotatable pressure member for forming a fixing nip portion together with the heating unit; of the equipment Provided at one end in the longitudinal direction and a mechanism for rotating the pressure member. a gear and an apparatus frame having side frames supporting the heating unit and the longitudinal ends of the pressure member; While the recording material is nipped and conveyed in the fixing nip portion, In a fixing device that fixes a toner image formed on a recording material to the recording material, the side frame includes a support frame that supports an end portion in the longitudinal direction of at least one of the heating unit and the pressure member, and a main frame that is disposed substantially parallel to the support frame and supports the gear, and the support frame and the main frame , when viewed in the direction of the rotation axis of the pressure member overlap each other fit The fixed part in the area The support frame is welded to prevent it from moving relative to the main frame. The support frame is fixed to the main frame. of The gear is provided surface The opposite side of the side of the surface facing the fixing nip portion The present invention is characterized in that the [Effects of the Invention]

[0009] As described above, according to the present invention, it is possible to provide a fixing device that can suppress a temperature rise of the gear due to heat transfer from the fixing nip portion. [Brief explanation of the drawings]

[0010] [Figure 1] Exploded view of the side frame periphery of the first embodiment [Figure 2] FIG. 1 is a diagram showing the overall configuration of an image forming apparatus according to a first embodiment. [Figure 3] 1 is a cross-sectional view of a fixing device according to a first embodiment of the present invention; [Figure 4] FIG. 1 is a perspective view of an overall configuration of a frame of a fixing device according to a first embodiment; [Figure 5] Enlarged view of the frame on the drive transmission means side of the first embodiment [Figure 6] An enlarged view of the frame on the non-drive transmission means side of the first embodiment. [Figure 7] FIG. 1 is a perspective view of a side frame according to a first embodiment; [Figure 8] 10A and 10B are perspective and cross-sectional views of a side frame according to a second embodiment of the present invention; [Figure 9] FIG. 10 is a perspective view of a side frame according to a third embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0011] [Example 1] The best mode for carrying out the present invention will be described in detail below with reference to the drawings. However, the dimensions, materials, shapes, and relative positions of the components described in this embodiment may be changed as appropriate depending on the configuration of the device to which the invention is applied and various conditions, and the scope of the present invention is not intended to be limited to the following mode.

[0012] (1) Overall configuration of the image forming device First, the overall configuration of the image forming apparatus will be described with reference to Fig. 2. The image forming apparatus 1 is a laser beam printer.

[0013] The image forming apparatus 1 comprises a recording material feeding section and an image forming section. In the recording material feeding section, recording materials P stacked in a cassette 2 are picked up one by one from the topmost recording material P by a paper feed roller 3 and sent to a registration section. The recording materials P are aligned in the conveyance direction by a registration section consisting of registration rollers 4 and 5, and then fed to the image forming section.

[0014] The image forming unit has a photosensitive drum 6, a charger 7 that charges the photosensitive drum 6, a developer 8 that develops the electrostatic latent image formed on the photosensitive drum 6 with toner, and a cleaner 9 that removes residual toner from the photosensitive drum 6. The photosensitive drum 6 is driven to rotate in the direction of the arrow. The charger 7 uniformly charges the circumferential surface of the photosensitive drum 6. Above the image forming unit, a laser scanner 10 is disposed that scans the charged photosensitive drum 6 with a laser beam corresponding to image information. The electrostatic latent image is developed into a toner image by the developer 8. The developed toner image is then transferred to a recording material P that passes through a transfer unit 12 consisting of a transfer roller 11 and the photosensitive drum 6.

[0015] The recording material P onto which the toner image has been transferred is conveyed to the fixing device 13. The fixing device 13 heats and fixes the toner image on the recording material P to the recording material P.

[0016] The recording material P that has passed through the fixing device 13 is discharged by a pair of discharge rollers 14 onto a recording material stacking section 15 at the top of the image forming apparatus 1.

[0017] (2) Fixing device 3 is a cross-sectional view of the fixing device 13 of this embodiment. The film heating type fixing device 13 rotates the pressure roller 16 in the CCW direction indicated by the arrow, thereby rotating the film 20 of the film unit (heating unit) 28 in the CW direction indicated by the arrow by the conveying force of the pressure roller (pressure member) 16.

[0018] Film unit 28 has a cylindrical film 20, a plate-shaped heater 21 arranged in the internal space of film 22, a heater holder 17 made of heat-resistant resin such as liquid crystal polymer that holds heater 21, and a metal stay 22 that reinforces heater holder 17. It also has two flanges F100 (see FIG. 1) that restrict deviation of film 20 in the longitudinal direction of the fixing device. Pressure roller 16 contacts the outer peripheral surface of film 20, and a fixing nip N is formed between heater 21 and pressure roller 16 via film 20.

[0019] The heater 21 is a ceramic substrate on which a heating resistor is printed. Alternatively, the heater may be configured such that the surface of a metal substrate is insulated with a glass layer or the like and a heating resistor is provided on top of the insulated surface. The pressure roller 16 has a shaft 18 and a rubber layer 19.

[0020] While the recording material P is nipped and conveyed in the direction of arrow A in the fixing nip portion N, the unfixed toner image T on the recording material P is fixed to the recording material P by heat.

[0021] (3) Overall structure of the frame Fig. 4 is a perspective view showing the overall structure of the frame of the fixing device 13. Figs. 5 and 6 are enlarged views of the frame at the longitudinal end of the fixing device.

[0022] As shown in Fig. 4, side frames 23 and 24 are disposed at both longitudinal ends of the fixing device. A base frame 25 and support frames 26 and 27 are disposed to connect the side frames 23 and 24. The side frames 23 and 24, the base frame 25, and the support frames 26 and 27 are fixed to one another with screws (not shown), and have sufficient rigidity to withstand the biasing force of a spring 34 (see Fig. 5) that forms the fixing nip portion N. In this embodiment, the side frames 23 and 24, the base frame 25, and the support frames 26 and 27 that constitute the frame of the fixing device 13 are made of galvanized steel sheets.

[0023] Next, the configuration around the side frames 23, 24 will be described using Figures 5 and 6. A drive transmission mechanism for rotating the pressure roller 16 is disposed in the side frame 23. Specifically, the tip of the end of the shaft portion 18 of the pressure roller 16 is machined into a D-cut cross section, and a pressure roller gear 29, which also has a D-cut cross section and a through-hole, is fitted onto the shaft portion 18. Furthermore, an idler gear 30 is disposed so as to mesh with the teeth of the pressure roller gear 29. The idler gear 30 is rotatably fitted onto a gear shaft 43 that is crimped to the side frame 23. This transmits drive force from the main body of the image forming apparatus 1 via the idler gear 30 to the pressure roller gear 29, causing the pressure roller 16 to rotate. The pressure roller gear 29 and idler gear 30 are made of a resin material such as polyacetal or nylon.

[0024] An encoder 31 is disposed coaxially with the idler gear 30, and rotates together with the idler gear 30. An encoder sensor 32 is disposed in the fixing device 13, and detects the number of rotations of the pressure roller 16. A spring 34 for forming the fixing nip N biases the film unit 28 toward the pressure roller 16 via the pressure plate 33. The pressure plate 33 and spring 34 are also disposed on the side of the side frame 24. The biasing force of the spring 34 is applied in the following order: pressure plate 33, flange F100, stay 22, heater holder 17, heater 21, film 20, and pressure roller 16.

[0025] A cam 35 is disposed on the side of the pressure plate 33 opposite to the side on which the spring 34 is disposed. The cam 35 is connected to a cam gear 36 and is fixed so as not to rotate together with the cam gear 36 relative to a cam shaft 37. When drive is transmitted from the main body of the image forming apparatus 1 to the cam gear 36 and the cam gear 36 rotates, the cam 35 pushes up the pressure plate 33 against the biasing force of the spring 34. As the pressure plate 33 is pushed up, the pressure applied to the fixing nip portion N is reduced (or eliminated). This makes it easy to clear jammed recording material P near the fixing nip portion N.

[0026] A cam 38 is also disposed on the side frame 24 shown in FIG. 6 and is fixed so as not to rotate relative to the cam shaft 37. A flag 39 is disposed on the rotation shaft of the cam 38 and rotates together with the rotation of the cam 38. When the flag 39 rotates, the signal from the flag sensor 40 switches. This makes it possible to detect whether the state is a pressurized state in which the fixing nip N is formed or a separated state in which the fixing nip N is released. The cams 35, 38 and cam gear 36 are made of a resin material such as polyacetal or nylon. The flag 39 is made of a black resin material such as PPE+PS that does not transmit light in the thickness direction.

[0027] (4) Side frame configuration The configuration of the side frame, which is a feature of this embodiment, will be described below. Figure 1 is an exploded view of the periphery of the side frame. Figure 7 is a perspective view of the side frame.

[0028] As shown in FIG. 1, each of the side frames 23 and 24 is made up of two frames. The side frame 23 is made up of a support frame 100 and a first frame ( Idler gear 30The side frame 24 is composed of a support frame 100 and a second frame (main frame supporting the sensor 40) 300, and the support frame 100 is disposed between the first frame 200 and the fixing nip N in the longitudinal direction of the fixing device. That is, the pressure roller gear 29 and idler gear 30, which are drive transmission means, are located on the surface of the first frame 200 opposite the surface on which the support frame 100 is disposed. Similarly, the side frame 24 is composed of the support frame 100 and a second frame (main frame supporting the sensor 40) 300, and the support frame 100 is disposed between the second frame 300 and the fixing nip N in the longitudinal direction of the fixing device. The side frames 23 and 24 use support frames 100 of the same shape to improve dimensional accuracy. The film unit 28 and the pressure roller 16 are fitted and held in U-shaped fitting portions formed by edges 101A, 101B, and 101C of the two support frames 100, respectively. Specifically, a bearing B100 (see FIG. 1) that rotatably holds the shaft 18 of the pressure roller 16 and a flange F100 fit into a U-shaped fitting portion. The fitting portion positions the film unit 28 and the pressure roller 16 in both the recording material conveyance direction A and the longitudinal direction of the fixing device. The biasing force of the spring 34 causes the bearing B100 to abut against an edge 101C that forms the bottom surface of the U-shaped fitting portion.

[0029] Next, the side frames 23 and 24 will be described in detail using FIG. 7 . The surfaces of the support frame 100 and the first frame 200 of the side frame 23 are arranged approximately parallel, and the support frame 100 and the first frame 200 are fixed by welding. Specifically, there are four welds W on each side frame 23 and 24. The positions of the welds W correspond to the positions of the film unit 28 and the pressure roller 16 in the biasing direction F of the spring 34. Furthermore, the welds W are provided upstream and downstream of the U-shaped fitting portion in the recording material conveying direction A. In this embodiment, welding is performed with a fiber laser to reduce the weld area of ​​the welds W for the purpose of compactness. Furthermore, the laser scanning direction of the welds W (the longitudinal direction of the welds) is approximately parallel to the biasing direction F, improving the strength of the welds W to withstand the biasing force of the spring 34. Similarly, in the side frame 24, the surfaces of the support frame 100 and the second frame 300 are arranged substantially parallel to each other, and the support frame 100 and the second frame 300 are fixed by welding.

[0030] When assembling the side frame 23, the fixing holes 102, 103, and 104 of the support frame 100 and the fixing holes 201, 202, and 203 of the first frame 200 are passed through the shafts of an assembly jig to position the frame in the thickness direction. Furthermore, a laser is irradiated while the frame is pressed in the thickness direction, and welded at a welded portion W. Similarly, when assembling the side frame 24, the fixing holes 102, 103, and 104 of the support frame 100 and the fixing holes 301, 302, and 303 of the second frame 300 are passed through the shafts of an assembly jig to position the frame in the thickness direction. Furthermore, a laser is irradiated while the frame is pressed in the thickness direction, and welded at a welded portion W. Although positioning is performed using the shafts of the assembly jig in this embodiment, any method that can accurately position the frame, such as positioning the support frame 100, the first frame 200, and the second frame 300 using embossments and fitting holes, may be used. (5) Effects of the Invention of Example 1 The configuration of this embodiment can prevent heat generated from the fixing nip N from being transferred to the pressure roller gear 29 and idler gear 30, which are drive transmission means located on the outside of the side frames 23 and 24. Specifically, the support frame 100, first frame 200, and second frame 300 are made of galvanized steel sheets with an organic coating on the surface. For example, the thermal conductivity of the steel sheets is 60 W / m K and the thickness is 1.0 mm, while the thermal conductivity of the organic coating is 0.3 W / m K and the thickness on one side is 0.1 mm. Compared to when a single galvanized steel sheet is used, the amount of thermal energy transferred from the fixing nip N to the outside of the side frames 23 and 24 is reduced by half. Furthermore, the gaps caused by the surface roughness of the support frame 100 and the first frame 200, and the support frame 100 and the second frame 300, reduce the effective contact area between the support frame 100 and the first frame 200, and between the support frame 100 and the second frame 300. This causes contact thermal resistance, further reducing the amount of heat energy transferred, and suppressing heat transfer to the pressure roller gear 29 and the idler gear 30.

[0031] Furthermore, in this embodiment, the frames are welded together in limited locations using a fiber laser, which leaves a larger area of ​​the organic coating on the galvanized steel sheet than if the frames were welded continuously, further enhancing the heat transfer suppression effect. The heat insulating structure between the support frame 100 and the first frame 200, and the support frame 100 and the second frame 300, which are located near the fixing nip N, makes it possible to efficiently suppress heat diffusion. Conversely, if the support frame 100 were located between the drive transmission means and the first frame 200, heat from the fixing nip N would be transferred to the support frame 100 and then directly to the drive transmission means.

[0032] In this embodiment, the support frame 100, first frame 200, and second frame 300 are made of galvanized steel plates, but resin may also be used. Although the support frame 100, first frame 200, and second frame 300 are welded together using a fiber laser, any other method of fastening, such as screwing, caulking, gluing, or engagement, may be used. However, to effectively utilize thermal contact resistance, it is desirable to limit the contact area. In this embodiment, the encoder sensor 32, cam 35, cam 38, and flag sensor 40 are arranged on the side frames 23 and 24. However, providing a support frame 100 on each of the side frames 23 and 24 prevents sensor malfunction and reduces cam wear. Furthermore, if components such as the flag sensor 40 are not arranged on the outside of the side frame 24, the support frame 100 and second frame 300 may be configured as a single frame without being separated. In this embodiment, the pressure roller 16 is driven by the drive transmission means, but if the film unit 28 is a highly rigid heat roller, the heat roller may be driven instead.

[0033] [Example 2] Next, the configuration of the side frame of Example 2 will be described. In this example, as shown in Fig. 8, the side frame 41 is composed of a support frame 100 and a third frame 400. To provide an air gap between the support frame 100 and the third frame 400, the third frame 400 is in contact with the support frame 100 only around the welded portion W of the fiber laser. In addition, the third frame 400 is provided with an offset portion 401 that is offset in the direction in which the drive transmission means is disposed, other than around the welded portion W of the third frame 400.

[0034] With this configuration, the air layer created by the offset portion 401 can suppress heat transfer from the support frame 100 to the third frame 400. This air layer can be used as a heat insulating layer because it has a convection-free structure. The air layer created by the offset portion 401 is 0.3 mm thick, and the thermal conductivity of air is 0.02 W / m K. Compared to the first embodiment, the amount of heat energy generated from the fixing nip portion N that is transferred to the outside of the side frame 41 is approximately 1 / 12. In this embodiment, the third frame 400 also has an offset portion 401, but the support frame 100 may also have an offset shape to create an air layer.

[0035] [Example 3] Next, the configuration of the side frame of the third embodiment will be described. In this embodiment, as shown in Fig. 9, the side frame 42 is composed of a support frame 500, a support frame 600, and a fourth frame 700. First, the film unit 28 is positioned with respect to the recording material conveyance direction A and the longitudinal direction of the fixing device by the film unit positioning portions 501, 601 of the support frames 500 and 600. Furthermore, the pressure roller 16 is positioned with respect to the recording material conveyance direction A, the longitudinal direction of the fixing device, and the biasing direction F by the U-shaped fitting portion 701 of the fourth frame 700. The fourth frame 700 has offset portions 702, 703 formed therein, similar to those of the second embodiment.

[0036] Even with this configuration, if it is not possible to form a heat insulating structure around the pressure roller 16, the support frames 500 and 600 that position the film unit 28 can still provide heat insulation. In this embodiment, the thickness of the air layer formed by the offset portions 702 and 703 is set to 0.6 mm, twice that of embodiment 2, so that even if the area to be insulated is reduced, the thickness is increased and heat transfer to the drive transmission means can be suppressed.

[0037] In this embodiment, support frames 500 and 600, which are separate components from the fourth frame 700, are provided to support only the film unit 28. However, a support frame that supports only the pressure roller 16 may be provided, and this support frame may be fixed to the surface of the fourth frame 700 on the fixing nip N side. Alternatively, depending on the amount of heat generated from the fixing nip N and the direction of air convection within the fixing device, the film unit 28 may be positioned using only one of the support frames 500 and 600 of this embodiment and the fourth frame 700. [Explanation of symbols]

[0038] N Fixing nip W welded section 13 Fixing device 23 Side frame 24 Side frame 25 base frame 26 Support Frame 27 Support Frame 29 Pressure roller gear 30 Idler gear

Claims

1. a heating unit for heating the recording material; a rotatable pressure member that forms a fixing nip portion together with the heating unit; a gear provided at one end of the device in the longitudinal direction for rotating the pressure member; an apparatus frame having side frames supporting the heating unit and the longitudinal ends of the pressure member; a fixing device for fixing a toner image formed on a recording material to the recording material while nipping and conveying the recording material through the fixing nip portion, the side frames include a support frame that supports an end portion in the longitudinal direction of at least one of the heating unit and the pressing member, and a main frame that is disposed substantially parallel to the support frame and supports the gear, the support frame and the main frame are fixed by welding at fixing portions provided in areas where they overlap each other when viewed in the direction of the rotation axis of the pressing member so that the support frame does not move relative to the main frame; The fixing device is characterized in that the support frame is disposed on the surface of the main frame opposite to the surface on which the gear is provided and facing the fixing nip portion.

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

3. 3. The fixing device according to claim 1, wherein the support frame and the main frame are fixed by welding so that a gap is formed between the support frame and the main frame.

4. A fixing device as described in any one of claims 1 to 3, characterized in that the heating unit has a cylindrical film and a heater arranged in the internal space of the film, and the fixing nip portion is formed by the heater and the pressure member via the film.

Images