Unit fixing structure, fixing device, and image forming apparatus

Abstract

To simplify a unit fixing structure to save space.SOLUTION: A unit fixing structure of the present invention detachably fixes a unit 100a to a device body, and the unit fixing structure inserts a projection 70 disposed on the device body into a positioning hole 69 of the unit 100a to position the unit 100a, and fixes the unit 100a in the positioned state to the device body 1a with fastening members (screws B1, B2). In the unit fixing structure, insertion holes 67, 68 for inserting the fastening members are formed in the unit 100a, the positioning hole 69 is formed below the insertion holes 67, 68, and a receiving part 70a for the fastening members is formed in the projection 70 projecting from the positioning hole 69.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a unit fixing structure for detachably fixing a unit to an apparatus main body, a fixing apparatus having the fixing structure, and an image forming apparatus.

Background Art

[0002] In general, a fixing unit of an image forming apparatus is detachably fixed to a machine main body for unit replacement or maintenance in case of failure. The fixing of the fixing unit is performed by positioning and fastening (screwing) the fixing unit with respect to the machine main body.

[0003] If this positioning and fastening are performed by the same member, the structure of the member becomes complicated and large-sized. Therefore, positioning and fastening are often performed by separate members.

[0004] That is, the fixing unit is positioned by inserting a protrusion (positioning pin) provided on the machine main body into a positioning hole of the fixing unit. Further, a screw is inserted into an insertion hole of the fixing unit, and the fixing unit is fastened by tightening the tip of the screw to a screw hole of the machine main body.

Summary of the Invention

Problems to be Solved by the Invention

[0005] When fastening the fixing unit to the machine main body with a screw, the screw may accidentally fall off. Parts are densely arranged around the fixing unit and there are many narrow gaps. If the screw falls into such a narrow gap, it takes time to recover the screw.

[0006] Conventionally, for example, as disclosed in Patent Document 1 (Japanese Patent Application Laid-Open No. 2011-107334), there is a structure in which a screw receiving recess is formed to prevent the screw from falling off. That is, a screw receiving recess is formed above a through hole of the screw, and a positioning recess is formed below. However, if the positioning recess and the screw receiving recess are formed separately, the structure becomes complicated and takes up space.

[0007] Therefore, the present invention aims to simplify the unit fixing structure and save space. [Means for solving the problem]

[0008] To solve the aforementioned problems, the present invention provides a unit fixing structure for detachably fixing a unit to a device body, wherein the unit is positioned by inserting a projection disposed on the device body into a positioning hole of the unit, and the unit is fixed to the device body by a fastening member in the positioned state, characterized in that an insertion hole for inserting the fastening member is formed in the unit, the positioning hole is formed below the insertion hole, and a receiving portion for the fastening member is formed on the projection protruding from the positioning hole. [Effects of the Invention]

[0009] According to the present invention, the unit fixing structure can be simplified and space can be saved. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram of a color printer, which is one embodiment of an image forming apparatus. [Figure 2] (a) A conventional perspective view showing the unit fixing structure, (b) A conventional enlarged view, (c) A perspective view of this embodiment, and (d) A cross-sectional view of this embodiment. [Figure 3] This is a side view showing the unit fixing structure of this embodiment. [Figure 4] (a) Perspective view, (b) Vertical cross-sectional side view, and (c) Horizontal cross-sectional plan view show the fixing structure of a unit with a resin cover. [Figure 5] This is a schematic diagram of the fixing device. [Figure 6] This is an exploded perspective view of the nip-forming member. [Modes for carrying out the invention]

[0011] Embodiments of the present invention will be described below based on the attached drawings. In each drawing, components such as members and parts having the same function or shape will be denoted by the same reference numerals to the extent possible, and their description will be omitted after they have been described once.

[0012] (●Image forming apparatus) Figure 1 is a schematic diagram showing a cross-section of a color printer, which is one embodiment of the image forming apparatus 1. This color printer uses a tandem system in which image-forming units that form multiple color images are arranged side by side along the tension direction of the belt, but this embodiment is not limited to this system. Furthermore, it is possible to apply this to not only printers but also copiers, facsimile machines, and other devices.

[0013] As shown in Figure 1, the central part of the image forming apparatus 1 has four photoreceptors, 20Y, 20C, 20M, and 20Bk, arranged side by side. Each photoreceptor, 20Y, 20C, 20M, and 20Bk, is capable of forming images corresponding to yellow (Y), cyan (C), magenta (M), and black (Bk), respectively. Since these image forming means have the same configuration except for the difference in developer (toner) color, the subscripts Y, C, M, and Bk in the reference numerals will be omitted as appropriate in the following description.

[0014] A charging member 30, a developing device 40, and a cleaning means 50 are provided around each photoreceptor 20. The photoreceptor 20 is driven to rotate clockwise, and the charging member 30 is pressed against the surface of the photoreceptor 20. The charging member 30 rotates in conjunction with the rotation of the photoreceptor 20.

[0015] Furthermore, a predetermined bias voltage is applied to the charging member 30 by a high-voltage power supply, allowing the surface of the rotating photoreceptor 20 to be uniformly charged. The photoreceptor 20, charging member 30, developing device 40, and cleaning means 50 are each detachably arranged from the image forming apparatus 1.

[0016] Below and diagonally to the lower side of the four photoreceptors 20, an exposure device 8 is provided in parallel thereto. This exposure device 8 has constituent members such as a light source, a polygon mirror, an f-θ lens, and a reflection mirror.

[0017] The exposure device 8 exposes each of the photoreceptors 20 charged by the charging member 30 based on the image information formed according to the image data of each color toner, creating an electrostatic latent image on each photoreceptor 20. The electrostatic latent image formed on the photoreceptor 20 using this exposure device 8 is developed and visualized when each color toner is applied as it passes through the developing device 40 due to the rotation of the photoreceptor 20.

[0018] Above the inside of the image forming apparatus 1, toner bottles 9Y, 9C, 9M, and 9Bk filled with yellow, cyan, magenta, and black color toners respectively are arranged. Toner of a predetermined replenishment amount is replenished from these toner bottles 9Y, 9C, 9M, and 9Bk to the developing devices 40Y, 40C, 40M, and 40Bk of each color via a conveyance path not shown.

[0019] Furthermore, an endless belt-shaped intermediate transfer belt 11 configured as an intermediate transfer member is arranged facing the photoreceptor 20 of each image forming means, and each photoreceptor 20 is in contact with the surface of this intermediate transfer belt 11. The intermediate transfer belt 11 is configured by being wound around a plurality of support rollers (for example, support rollers 72, 73, etc.).

[0020] In the illustrated example, the support roller 73 is connected to a drive motor as a drive source not shown, and due to the drive of this drive motor, the intermediate transfer belt 11 rotates and moves counterclockwise in the figure, and accordingly, the support roller 73 that can rotate passively also rotates. Also, inside the intermediate transfer belt 11, a primary transfer roller 12 is arranged facing the photoreceptor 20 with the belt interposed therebetween.

[0021] A primary transfer bias is applied from a high-voltage power source to the primary transfer roller 12, and the toner image visualized by the developing device 40 is primarily transferred to the intermediate transfer belt 11. The primary transfer residual toner left on the photoreceptor 20 without being primarily transferred is removed by the cleaning means 50 in preparation for the next image forming operation by the photoreceptor 20, and the toner on the photoreceptor 20 is completely removed.

[0022] Furthermore, a secondary transfer roller 5 as a secondary transfer device is provided on the downstream side in the driving direction of the intermediate transfer belt 11. This secondary transfer roller 5 faces the support roller 72 with the intermediate transfer belt 11 interposed therebetween, and a secondary transfer nip portion is formed by the secondary transfer roller 5 and the support roller 72 via the intermediate transfer belt 11.

[0023] The image forming apparatus 1 further includes a sheet feeding device 61 as a stacking portion for the paper S which is a recording material, a feed roller 3, and a registration roller pair 4 in addition to others. Further, a fixing device 100 and a discharge roller pair 7 are provided on the downstream side in the conveyance direction of the paper S as viewed from the secondary transfer roller 5.

[0024] Subsequently, the image forming operation will be described. First, the photoreceptor 20 is rotationally driven clockwise by a drive source, and at this time, the surface of the photoreceptor 20 is irradiated with light from a charge removing device (not shown) and the surface potential is initialized.

[0025] Next, the surface of the photoreceptor 20 is uniformly charged to a predetermined polarity by the charging member 30. Then, the surface of the photoreceptor 20 is irradiated with laser light from the exposure device 8, and an electrostatic latent image is formed on the surface of the photoreceptor 20 thereby.

[0026] At this time, the image information exposed to each photoreceptor 20 is monochromatic image information obtained by decomposing a desired full-color image into yellow, cyan, magenta, and black toner color information. Then, the electrostatic latent image formed on the photoreceptor 20 is provided with toner of each color (developer) from the developing device 40 when passing through the developing device 40, and is visualized as a visualized toner image.

[0027] Furthermore, the intermediate transfer belt 11 is driven to move counterclockwise in the figure, while a primary transfer voltage with the opposite polarity to the toner charge polarity of the toner image formed on the photoreceptor 20 is applied to the primary transfer roller 12. As a result, a transfer electric field is formed between the photoreceptor 20 and the intermediate transfer belt 11, and the toner image on the photoreceptor 20 is electrostatically transferred to the intermediate transfer belt 11, which is driven to rotate in sync with the photoreceptor 20. In this way, the primary transferred toner images of each color are superimposed on the intermediate transfer belt 11 sequentially from the upstream side in the transport direction of the intermediate transfer belt 11, with synchronized timing, to form the desired full-color image.

[0028] Meanwhile, the paper sheets S on which the image is formed are separated one by one from the stack of paper loaded in the sheet feeder 61 to the pair of register rollers 4 by transport members such as the feed rollers 3 and fed. At this time, the leading edge of the transported paper sheet S abuts against the nip portion of the pair of register rollers 4, which has not yet started rotating, forming a loop and registering the paper sheet S. Then, in coordination with the full-color toner image carried on the intermediate transfer belt 11, the rotational drive of the pair of register rollers 4 is started, and the paper sheet S is fed towards the secondary transfer nip portion, which is composed of the support roller 72 and the secondary transfer roller 5.

[0029] In this embodiment, a transfer voltage with the opposite polarity to the toner charge polarity of the toner image on the surface of the intermediate transfer belt 11 is applied to the secondary transfer roller 5, thereby transferring the full-color toner image formed on the surface of the intermediate transfer belt 11 onto the paper S all at once. Next, the paper S on which the toner image has been transferred is transported to the fuser 100, where heat and pressure are applied as it passes through the fuser 100, fixing the toner image onto the paper S as a permanent image.

[0030] The paper S is then discharged to the paper output section, such as the paper output tray 17, via the paper output roller pair 7, and the image forming operation is completed. Any residual toner that remains on the intermediate transfer belt 11 without being transferred at the secondary transfer nip section is removed and recovered by the intermediate transfer belt cleaning means 13.

[0031] The above description concerns the image formation operation when forming a full-color image on paper S, but it is also possible to form a monochrome image, or a two-color or three-color image using any one of the photoreceptors 20. Furthermore, when performing monochrome printing using the printer of this embodiment, an electrostatic latent image can be formed only on the photoreceptor 20Bk, developed by the same means, transferred to paper S, and fixed with the fuser 100.

[0032] (●Unit fixing structure) Figure 2 shows a unit fixing structure in which a fixing unit 100a, which is a unitized version of the fixing device 100 shown in Figure 1, is detachably fixed to the main body 1a of the image forming apparatus 1. Figures 2(a) and 2(b) show a conventional unit fixing structure, while (c) and 2(d) show the unit fixing structure of this embodiment.

[0033] Figure 2 shows only a portion of the fixing unit 100a, and the illustrated example shows the bracket portions at both ends in the longitudinal direction of the fixing unit 100a. In this unit fixing structure, the unit 100a of the fixing device 100 is detachably fixed to the main body 1a of the image forming apparatus 1.

[0034] Conventionally, two cylindrical protrusions 60 and 61 are arranged separately on the left and right sides of the main body 1a. These protrusions 60 and 61 are used to position the unit 100a.

[0035] On the side of the main body 1a, two screw holes 62 and 63 are formed near the protrusions 60 and 61. By screwing two screws B1 and B2, which will be described later as fastening members, into these screw holes 62 and 63, the unit 100a is fastened and fixed to the side of the main body 1a.

[0036] On the other hand, unit 100a has positioning holes 64 and 65 into which the two protrusions 60 and 61 can be inserted. By inserting (fitting) the protrusions 60 and 61 into the positioning holes 64 and 65, respectively, unit 100a can be positioned relative to the main body 1a. One (right) positioning hole 64 is circular, corresponding to the outer diameter of the protrusion 60, while the other (left) positioning hole 65 is formed in a horizontally elongated ellipse shape. This is because the horizontally elongated ellipse shape allows for positional errors in the left-right direction of the protrusion 61 inserted into the positioning hole 65.

[0037] Near the positioning holes 64 and 65, through holes 67 and 68 are formed for inserting two screws B1 and B2. These through holes 67 and 68 are round holes corresponding to the outer diameters of screws B1 and B2, and it is preferable to form them about 1 to 2 mm larger than the screw diameter to avoid interference with the screw diameter.

[0038] In the conventional unit fixing structure shown in Figures 2(a) and 2(b), if screws B1 and B2 fall out when being inserted into the insertion holes 67 and 68, the screws can enter the machine, making retrieval time-consuming. If the screws are left unretrieved, they can damage other parts, leading to problems such as abnormal images, sheet transport failures, and component damage.

[0039] Therefore, in this embodiment, as shown in Figures 2(c) and 2(d), a screw receiving portion 70a is formed on the positioning projection 70. That is, the projection 70 is made to protrude outward (towards the front in Figure 2(c)) below the insertion holes 67 and 68 through which the screws B1 and B2 are inserted, and the projection 70 is formed in a U-shape with an upward opening. Here, "U-shape" means a shape in which the central part is lower than the peripheral part. Therefore, a so-called dish shape with a shallow depth is also included in the U-shape.

[0040] The positioning hole 69 for inserting (penetrating) the projection 70 is also formed in a U-shape that opens upward, as shown in Figure 2(d). Forming the projection 70 in a U-shape and the positioning hole 69 in a U-shape is relatively easy from a manufacturing perspective. Therefore, it is easy to achieve positioning accuracy for the unit 100a.

[0041] The U-shaped width, height, and axial length of the protrusion 70 are preferably optimized as appropriate according to the sizes of the screws B1 and B2, visibility, and the positional relationship with surrounding components. Also, it is possible to employ sheet metal that is easy to process as the frame material of the unit 100a. Thus, the degree of freedom in the design layout can be increased.

[0042] When adding anti-drop members for the screws B1 and B2 as dedicated components, it will cause an increase in cost due to the increase in the number of components and a deterioration in assembly property. In contrast, in this embodiment, since the receiving portions 70a of the screws B1 and B2 are constituted by utilizing the protrusions 70 that are indispensable for positioning the unit 100a, problems such as an increase in the number of components and an increase in cost do not occur. Also, by separating the insertion holes 67 and 68 and the positioning hole 69, miniaturization of the unit 100a is possible.

[0043] As shown in FIG. 2(d), the horizontal width W1 on the right side of the right positioning hole 69 is formed to be slightly wider than the horizontal width W2 on the right side of the protrusion 70 (W2 < W1) so that the unit 100a does not rattle in the left-right direction. Also, the height H1 of the horizontal portion of the positioning hole 69 is formed to be slightly wider than the height H2 of the horizontal portion of the protrusion 70 (H2 < H1) so that the unit 100a does not rattle in the up-down direction. Thus, by reducing the fitting tolerance at the right corner of the positioning hole 69, rattling of the unit 100a in the up-down and left-right directions can be prevented.

[0044] In contrast, other portions such as the horizontal width on the left side of the right positioning hole 69 are formed wider with a margin than the horizontal width on the left side of the protrusion 70 in order to avoid interference due to dimensional variations when inserting the protrusion 70 into the positioning hole 69. Thereby, it becomes easier to insert the protrusion 70 into the positioning hole 69.

[0045] On one hand, the left and right widths W1' of the positioning hole 69 on the left side of FIG. 2(d) are formed wider with a margin than the left and right widths W2' of the protrusion 70 in order to avoid interference due to dimensional variations when inserting the protrusion 70 into the positioning hole 69. Also, the height H1' of the horizontal portion of the positioning hole 69 is formed slightly wider than the height H2' of the horizontal portion of the protrusion 70 (H2' < H1') so that the unit 100a does not rattle in the vertical direction.

[0046] FIG. 2(d) shows the case of positioning the unit 100a based on the positioning hole 69 on the right side and the protrusion 70, but it is also possible to position the unit 100a based on the positioning hole 69 on the left side. In that case, either the left or right width W1' is formed slightly wider than the width W2' of the protrusion 70 (W2' < W1'). Also, FIG. 2(d) is based on the width W1 on the right side of the protrusion 70, but it is also possible to be based on the width on the left side of the protrusion 70.

[0047] FIG. 3 shows the protrusion 70 in FIG. 2(d) with its actual shape. With one set of the protrusion 70 and the positioning hole 69 on the right side, the horizontal and vertical directions of the unit 100a can be positioned as in FIG. 2(d). Also, with the other set of the protrusion 70 and the positioning hole 69 on the left side, the vertical positioning of the unit 100a can be done.

[0048] Below the insertion holes 67 and 68, there is a protrusion 70 that protrudes outward from the positioning hole (positioning hole 69 in FIG. 2(d)) of the unit 100a. The protrusion 70 is formed in a U-shaped cross-section that opens upward.

[0049] A concave receiving portion 70a is formed inside the U-shape of the protrusion 70. The receiving portion 70a can receive and accommodate the screws B1 and B2 that have fallen off from the insertion holes 67 and 68.

[0050] (● Resin Cover) Figure 4 shows a heat-resistant resin cover 100b attached as a cover member to the outer surface of unit 100a opposite to the main body 1a of the device. Unit 100a, as a fixing device, has a heat source 82 (halogen heater) as described later. Therefore, if the unit frame is made of sheet metal, the frame may become hot due to its high thermal conductivity. To address this, it is common practice to integrally provide a heat-resistant resin cover on the outer surface of the frame of unit 100a to prevent burns.

[0051] On the other hand, as mentioned above, if the positioning hole 69 is U-shaped, the rigidity of the frame decreases as the size of the positioning hole 69 increases. Therefore, in this embodiment, as shown in Figure 4, the projection 70 and the positioning hole 69 are made L-shaped in order to ensure the rigidity of the frame. An L-shape can increase the frame rigidity more than a U-shape, thus increasing the design freedom for the size of the positioning hole 69 and other factors.

[0052] If the projection 70 is simply made L-shaped, the screw may fall out because the projection 70 is open laterally. Therefore, it was decided to form an I-shaped projection 71 extending vertically on the inner surface of the resin cover 100b.

[0053] The I-shaped protrusion 71 and the L-shaped projection 70 form a U-shaped receiving portion 70a that opens upward as a whole. The receiving portion 70a formed inside the protrusion 71 and projection 70 can accommodate the screw B1 that has fallen through the insertion hole 67. Figure 4 shows the receiving portion 70a for one screw B1, but the receiving portion 70a for the screw B2 on the opposite side can be configured similarly. This embodiment prevents the screw from falling out while increasing the freedom of design layout, such as enabling miniaturization and selection of sheet metal.

[0054] It is also possible to change the protrusion 71 of the resin cover 100b from an I-shape to a U-shape and form the screw receiving part using only the U-shaped protrusion. However, this would lead to increased costs due to the increased amount of resin material used for the resin cover 100b. In addition, it would be necessary to place the projection 70 without a receiving part in a different location, making it difficult to miniaturize the unit 100a.

[0055] (● Fixing device) The configuration of the fixing device 100 shown in Figure 1 will be described below with reference to Figures 5 and 6. Figure 5 is a schematic configuration diagram showing a fixing device according to one embodiment of this embodiment, and Figure 6 is an exploded perspective view of the nip forming member. The fixing device 100 comprises a rotatable endless fixing belt 81, a heat source 82 (halogen heater) for heating the fixing belt 81, and a pressure roller 83 which is a pressure member that contacts the outer circumferential surface of the fixing belt 81.

[0056] A nip-forming member 86 is provided within the fixing belt 81, which slides indirectly with the inner surface of the fixing belt 81 via a sliding sheet. This nip-forming member 86, together with the opposing pressure roller 83 via the fixing belt 81, forms a nip portion N.

[0057] In Figure 5, the nip portion N is flat, but it may be concave or have other shapes. When the nip portion N is concave, the discharge direction of the recording material tip is closer to the pressure roller 83, improving separation and suppressing jamming.

[0058] The fixing belt 81 can be a metal belt such as nickel or SUS, an endless belt made of a resin material such as polyimide, or a film. The surface layer of the fixing belt 81 has a release layer such as a PFA or PTFE layer to prevent toner from adhering to it.

[0059] It is desirable that there be an elastic layer, such as a silicone rubber layer, between the substrate and the PFA or PTFE layer of the fixing belt 81. If the silicone rubber layer is absent, the heat capacity will be reduced, and the fixing performance will be improved.

[0060] However, when the unfixed image is compressed and fixed, minute irregularities on the belt surface may be transferred to the image, potentially leaving orange peel-like gloss unevenness (orange peel image) in the solid areas of the image. This can be improved by providing a silicone rubber layer of 100 μm or more. The deformation of the silicone rubber layer absorbs the minute irregularities, thus improving the orange peel image.

[0061] Furthermore, a support member 87 (stay) is provided inside the fixing belt 81 to support the nip portion N. This prevents the nip forming member 86 from bending due to the pressure of the pressure roller 83, and ensures a uniform nip width in the axial direction.

[0062] This support member 87 is held and fixed at both ends by retaining members 88 (flanges) and positioned accordingly. Furthermore, a reflecting member 89 is provided between the heat source 82 and the support member 87 to suppress wasted energy consumption caused by the support member 87 being heated by radiant heat from the heat source 82.

[0063] Instead of providing the reflective member 89, the same effect can be obtained by applying an insulating treatment or mirror finish to the surface of the support member 87. The heat source 82 may be the halogen heater shown in the figure, but it may also be an induction heater, a resistance heating element, or a carbon heater.

[0064] The pressure roller 83 has a core metal 84 and an elastic rubber layer 85, and a release layer (PFA or PTFE layer) is provided on its surface to obtain release properties. The pressure roller 83 rotates when driving force is transmitted to it via gears from a drive source such as a motor provided in the image forming apparatus 1.

[0065] Furthermore, the pressure roller 83 is pressed against the fixing belt 81 by a spring or the like, and the elastic rubber layer 85 is compressed and deformed, thereby having a predetermined nip width. The pressure roller 83 may be a hollow roller, and may have a heating source such as a halogen heater inside the pressure roller 83.

[0066] The elastic rubber layer 85 may be made of solid rubber, but if there is no heat source inside the pressure roller 83, sponge rubber may be used. Sponge rubber is preferable because it has better heat insulation properties and prevents heat from being lost from the fixing belt 81.

[0067] When the pressure roller 83 rotates due to the drive source, the driving force is transmitted to the fixing belt 81 at the nip section N, causing the fixing belt 81 to rotate along with it. The fixing belt 81 rotates while being gripped by the nip section N, and is guided by the holding members 88 (flanges) at both ends outside the nip section N as it travels. With the above configuration, an inexpensive fixing device with a fast warm-up time can be realized.

[0068] (●Nip-forming member) Figure 6 is an exploded perspective view of a nip-forming member according to one embodiment of this model. This configuration aims to reduce overheating in the non-paper-feeding area by reducing the heat source (reducing the halogen heaters to two) and by providing a substitute function for the light-shielding member 90. As a result, the light-shielding member 90 and the drive unit that drives it are unnecessary, leading to significant cost reductions.

[0069] As shown in Figure 6, the nip-forming member 86 comprises a heat-sensing member 66 as a first heat transfer means and a sliding sheet 67 provided on the heat-sensing member 66. When the fixing belt 81 rotates, the fixing belt 81 slides against the sliding sheet 67, thereby reducing the driving torque generated on the fixing belt 81 and reducing the load on the fixing belt 81 due to frictional force.

[0070] The heat-distributing member 66 is made of a material with high thermal conductivity, such as copper, and is formed along the longitudinal direction of the fixing belt 81. It can absorb excess heat accumulated in the non-paper-passing portion of the fixing belt 81 and transfer the heat along its longitudinal direction.

[0071] As shown in Figure 6, the nip-forming member 86 includes a first heat insulating member 77a, a second heat insulating member 77b, a first heat-absorbing member 76, and a second heat-absorbing member 75. The first heat insulating member 77a is made of a material with a lower thermal conductivity than the heat-sensing member 66, such as resin, and partially extends in the longitudinal direction of the fixing belt 81, positioned between the heat-sensing member 66 and the second heat-absorbing member 75, where the first heat-absorbing member 76 is not present.

[0072] The presence of the first heat insulating member 77a prevents excessive heat absorption by the fixing belt 81. As a result, temperature drops in the paper feeding section can be prevented. Furthermore, warm-up time can be shortened and power consumption can be reduced.

[0073] The second heat insulating member 77b is made of a material with lower thermal conductivity than the heat uniforming member 66, such as resin, and is provided between the heat uniforming member 66 and the first heat absorbing member 76. By providing the second heat insulating member 77b, the amount of heat transferred from the heat uniforming member 66 to the second heat absorbing member 75 via the first heat absorbing member 76 can be reduced.

[0074] Furthermore, if the second heat insulating member 77b is made too thick, the heat accumulated in the fixing belt 81 will not be able to move to the second heat absorbing member 75, making it easier for the temperature of the non-paper-feeding section to rise. Therefore, the thickness and length of the second heat insulating member 77b need to be optimized according to the magnitude of the temperature rise in the non-paper-feeding section that occurs, but its thickness is smaller than that of the first heat insulating member 77a.

[0075] The second heat-absorbing member 75 is made of a material with a higher thermal conductivity than the first heat-insulating member 77a and the second heat-insulating member 77b. The second heat-absorbing member 75 extends in the longitudinal direction of the fixing belt 81 and is positioned in contact with the first heat-insulating member 77a and the first heat-absorbing member 76.

[0076] The first heat-absorbing member 76 is also made of a material with a higher thermal conductivity than the first heat-insulating member 77a and the second heat-insulating member 77b, and partially extends in the longitudinal direction of the fixing belt 81, and is positioned between the second heat-insulating member 77b and the second heat-absorbing member 75. In particular, the first heat-absorbing member 76 is provided at a position corresponding to a location other than the central region of the fixing belt 81, that is, a location corresponding to the position where the temperature rise occurs in the non-paper-passing portion of the fixing belt 81.

[0077] In this embodiment, the first heat-absorbing member 76 is provided in a location corresponding to the non-paper-feeding area, but the invention is not limited to this configuration. For example, the first heat-absorbing member 76 may be extended in its longitudinal direction to a position corresponding to the paper-feeding area.

[0078] The heat-distributing member 66 promotes heat transfer in its longitudinal direction, thereby equalizing the heat distribution of the fixing belt 81 and suppressing the temperature rise of the non-paper-passing section. In contrast, the first heat-absorbing member 76 and the second heat-absorbing member 75 promote heat transfer in the thickness direction and absorb heat.

[0079] In other words, the first heat-absorbing member 76 and the second heat-absorbing member 75 compensate for the insufficient heat capacity of the heat-dissipating member 66. Therefore, it is desirable that the second heat-absorbing member 75 has a large heat capacity or a large surface area to increase the amount of heat dissipated.

[0080] These heat-absorbing members, heat-insulating members, and bent portions 66b and 66c clamp the end region of the sliding sheet 67 in the sliding direction, allowing the sliding sheet 67 to be fixed more firmly. Furthermore, temperature drops in the paper-feeding section can be prevented. Additionally, warm-up time can be shortened and power consumption reduced.

[0081] Next, the characteristic configuration of this embodiment will be described. Generally, the sliding sheet 67 is made of a material with low friction characteristics and is often coated with a lubricant in order to improve the durability of the anchoring belt 81. Although a low viscosity material is used as the lubricant, its high fluidity makes it easy to flow out of the anchoring belt 81, which leads to the problem of increased sliding load (torque).

[0082] Furthermore, the lubricant applied to the sliding sheet 67 tends to flow in one direction due to factors such as the nip deviation in the longitudinal direction and the weave direction of the sliding sheet 67. Here, nip deviation refers to the pressure imbalance caused by the static load deviation during pressurization and the dynamic load deviation during driving by a one-sided drive system.

[0083] If the lubricant is partially depleted along the longitudinal direction of the sliding sheet 67, fluctuations in the linear velocity of the fixing belt 81 (friction fluctuations between the fixing belt 81 and the sliding sheet 67) occur in the longitudinal direction, resulting in transport defects such as wrinkles in the recording material. Furthermore, the shifting speed of the fixing belt 81 also increases, which increases the load on the end face of the fixing belt 81 and reduces its lifespan.

[0084] The embodiment has been described in detail above using the embodiments described. This embodiment is an example and can be used with various modifications without departing from the spirit of the invention. For example, the unit to which the fixing structure of the present invention is applied is not limited to the fixing unit 100a. The fixing structure of the present invention is applicable to all kinds of units fixed to the main body of the device. Furthermore, the fastening members are not limited to screws. For example, bolts may be used instead of screws.

[0085] Furthermore, any configuration can be adopted for the fixing device 100 and the image forming apparatus 1, as long as this embodiment is applicable. The image forming apparatus 1 is not limited to a copier or printer, but may also be a facsimile or a multifunction device with multiple functions. [Explanation of Symbols]

[0086] 1: Image forming apparatus 1a: Main unit of the apparatus 3: Feeding roller 4: Resist roller 5: Secondary transfer roller 7: Paper output roller pair 8: Exposure unit 9Y, 9M, 9C, 9Bk: Toner bottles 11: Intermediate transfer belt 12Y, 12M, 12C, 12Bk: Primary transfer roller 13: Intermediate transfer belt cleaning means 17: Output tray 20Y, 20M, 20C, 20Bk: Photoreceptor; 30Y, 30M, 30C, 30Bk: Electrostatic charger 40Y, 40M, 40C, 40Bk: Developing device; 50Y, 50M, 50C, 50Bk: Cleaning device 61: Sheet feeding device 62, 63: Screw holes 64, 65: Positioning holes 66: Heat distribution member 66a: Contact area 66b, 66c: Bending area 66d: Holding part 67: Sliding sheet 67a: Opening 68: Protrusion 70: Protrusion 70a: Receptacle 71: Convex part 72, 73: Support roller 74: Sliding sheet 75: Second heat-absorbing member 76: First heat-absorbing member 77a: First heat-insulating member 77b: Second insulation member 81: Fixing belt 82: Heat source 83: Pressure roller 84: Core metal 85: Elastic rubber layer 86: Nip forming member 87: Support member 88: Holding member 89: Reflective member 90: Light-shielding material 100: Fixing device 100a: Fixing unit 100b: Resin cover B1, B2: Screw N: Nib part S: Paper (recording material) t: Weave [Prior art documents] [Patent Documents]

[0087] [Patent Document 1] Japanese Patent Publication No. 2011-107334

Claims

1. A unit fixing structure for detachably fixing a unit to a device body, wherein the unit is positioned by inserting a projection provided on the device body into a positioning hole of the unit, and the unit is fixed to the device body by a fastening member in the positioned state, An insertion hole for inserting the fastening member is formed in the unit, a positioning hole is formed below the insertion hole, and the receiving portion of the fastening member is formed on the projection protruding from the positioning hole in an L-shaped cross-section with an upward opening. A unit fixing structure characterized in that the side of the unit opposite to the device body is covered by a cover member, and a U-shaped cross-section with an upward opening is formed by a protrusion formed on the inner surface of the cover member and the receiving portion.

2. A unit fixing structure for detachably fixing a unit to a device body, wherein the unit is positioned by inserting a projection disposed on the device body into a positioning hole of the unit, and the unit is fixed to the device body by a fastening member in the positioned state, An insertion hole for inserting the fastening member is formed in the unit, a positioning hole is formed below the insertion hole, and a receiving portion for the fastening member is formed on the projection that protrudes from the positioning hole. A unit fixing structure characterized in that the projection, positioning hole, and insertion hole are formed in at least two locations, the horizontal and vertical directions of the unit are positioned by one pair of the projection and the positioning hole, and the vertical direction of the unit is positioned by the other pair of the projection and the positioning hole.

3. The fixing structure of claim 2, characterized in that the receiving portion has a U-shaped cross-section that opens upward.

4. The fixing structure of claim 2, characterized in that the receiving portion has an L-shaped cross-section that opens upward.

5. The fixing structure of claim 4, characterized in that the side of the unit opposite to the device body is covered with a cover member, and a U-shaped cross-section with an upward opening is formed by a protrusion formed on the inner surface of the cover member and the receiving portion.

6. The fixing device as a unit, characterized in that it is configured to be fixable to the main body of the device by the fixing structure of claim 1 or 2.

7. An image forming apparatus characterized by having a fixing device according to claim 6.

Images