Joining unit, optical scanning device, and image forming apparatus

Abstract

To improve assembly workability, reduce deformation of a first member and a second member, and improve sealability at a relatively inexpensive price.SOLUTION: A junction unit has a cover 600 (first member) and a housing 500 (second member) that are joined to each other. The cover 600 is provided with a substantially annular groove part 600a that can be filled with hot melt HM (sealant) having viscoelasticity, and the housing 500 (second member) is provided with a substantially annular projection 500a that can be fitted to the groove part 600a with the hot melt HM therebetween. The groove part 600a is provided with a wide groove width part 600a1 that has a wide groove width compared with a reference groove width part 600a2 (the other portion). The projection 500a is formed such that the height in a projection direction of at least part of a portion fitted to the wide groove width part 600a1 becomes lower than the height in the projection direction of a portion fitted to the reference groove width part 600a2 (the other portion).SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a joint unit in which a first member such as a cover and a second member such as a housing are joined together, an optical scanning device in which an optical deflector or the like is installed, and an image forming device such as a copier, printer, facsimile, or a combination thereof. [Background technology]

[0002] Conventionally, in image forming devices such as copiers and printers, a technique has been known in which a joining unit (optical scanning device) is installed in which a first member such as a cover (case member) is joined to a second member such as a housing (optical housing) (see, for example, Patent Document 1).

[0003] On the other hand, Patent Document 1 discloses a technology for improving the airtightness (dustproofness) within the writing device (junction unit) by inserting a sealing member (sealing material) made of a sponge material into the gap between a case member (first member) and an optical housing (second member). Furthermore, Patent Document 1 discloses a technique for forming a thin portion in the sealing member to prevent the optical housing or the cover member from being locally deformed due to the reaction force of the compressively deformed sealing member. Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional joining units, the sealing material interposed between the first and second members is expensive and the application process is difficult. One possible solution to this problem is to interpose a viscoelastic sealant, such as hot melt, between the first and second members. However, even in this case, it is necessary to prevent the problem of localized deformation of the first and second members due to the reaction force of the compressively deforming sealant.

[0005] The present invention has been made to solve the above-mentioned problems, and aims to provide a joining unit, an optical scanning device, and an image forming device that are relatively inexpensive, easy to assemble, have little deformation of the first member and the second member, and are highly sealed. [Means for solving the problem]

[0006] The joining unit of this invention is a joining unit for joining a first member and a second member, wherein the first member has a substantially annular groove formed therein that can be filled with a viscoelastic sealing material, and the second member has a substantially annular protrusion formed therein that can be fitted into the groove via the sealing material, the groove having a wide groove width portion that is wider than other portions, and the protrusion is formed so that the height in the protrusion direction of at least a portion of the portion that fits into the wide groove width portion is lower than the height in the protrusion direction of the portion that fits into the other portion. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a joint unit, an optical scanning device, and an image forming apparatus that are relatively inexpensive, have high assembly workability, cause little deformation of the first member and the second member, and have high sealing properties. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is an overall configuration diagram showing an image forming apparatus according to an embodiment of the present invention; [Figure 2] FIG. 2 is a cross-sectional view showing an image forming unit in the image forming apparatus. [Figure 3] FIG. 2 is a perspective view showing the inside of the optical scanning device. [Figure 4] 1A is a side view showing an optical scanning device, and FIG. 1B is an enlarged view of a portion enclosed by a dashed line in the side view. [Figure 5] 10A to 10C are diagrams illustrating a procedure for joining the cover and the housing. [Figure 6] 10A to 10C are diagrams illustrating a procedure for fitting a protrusion into a groove. [Figure 7](A) is a diagram showing a cross section A1-A1 in FIG. 5(B), and (B) is a diagram showing a cross section A2-A2 in FIG. 5(B). [Figure 8] 5(A) is a diagram showing a cross section B1-B1 of the protrusion in FIG. 5(C), and FIG. 5(B) is a diagram showing a cross section B2-B2 of the protrusion in FIG. 5(C). [Figure 9] 10A and 10B are diagrams illustrating an operation in which a protrusion is fitted into a wide groove portion filled with a sealing material. [Figure 10] 10A and 10B are diagrams illustrating, as a comparative example, the operation of fitting a protrusion into a wide groove portion filled with a sealing material. [Figure 11] 10 is a cross-sectional view showing a modified example of a protrusion of a housing fitted into a wide groove width portion. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are designated by the same reference numerals, and redundant explanations will be appropriately simplified or omitted.

[0010] First, the overall configuration and operation of an image forming apparatus 100 will be described with reference to FIGS. 1, an intermediate transfer belt device 15 is installed in the center of the image forming apparatus main body 100. In addition, process cartridges 6Y, 6M, 6C, and 6BK corresponding to each color (yellow, magenta, cyan, and black) are arranged side by side so as to face the intermediate transfer belt 8 of the intermediate transfer belt device 15. Furthermore, optical scanning devices 5A and 5B are arranged side by side above the process cartridges 6Y, 6M, 6C, and 6BK as two joining units.

[0011] 2, the process cartridge 6Y corresponding to yellow includes a photosensitive drum 1Y as an image carrier, a charging device 4Y (charging unit), a developing device 3Y (developing unit), a cleaning device 2Y (cleaning unit), a discharging unit (not shown), and the like, which are arranged around the photosensitive drum 1Y, and are configured as a single unit that is detachable (replaceable) from the image forming apparatus main body 100. An image creation process (charging process, exposure process, development process, transfer process, cleaning process, and discharging process) is performed on the photosensitive drum 1Y, and a yellow image is formed on the photosensitive drum 1Y. In other words, the process cartridge 6Y, together with a primary transfer roller 9Y (primary transfer device), and the like, constitutes an image creation unit.

[0012] The other three process cartridges 6M, 6C, and 6BK (imaging units) are configured almost identically to the process cartridge 6Y (imaging unit) corresponding to yellow, except for the toner colors they use, and form images corresponding to their respective toner colors. Below, we will omit the explanation of the other three process cartridges 6M, 6C, and 6BK (imaging units) as appropriate, and will only explain the process cartridge 6Y (imaging unit) corresponding to yellow.

[0013] 2, the photosensitive drum 1Y (image carrier) is rotated clockwise by a motor (not shown), and the surface of the photosensitive drum 1Y is uniformly charged at the position of the charging device 4Y (charging roller) (charging process). Thereafter, the surface of the photosensitive drum 1Y reaches the irradiation position of the exposure light L (laser light) emitted from the optical scanning devices 5A and 5B (junction unit), and an electrostatic latent image corresponding to yellow is formed by exposure scanning at this position (exposure process).

[0014] Thereafter, the surface of the photosensitive drum 1Y reaches a position facing the developing device 3Y, where the electrostatic latent image is developed to form a yellow toner image (developing step). Thereafter, the surface of the photosensitive drum 1Y reaches a position facing the intermediate transfer belt 8 and the primary transfer roller 9Y, where the toner image on the photosensitive drum 1Y is transferred onto the intermediate transfer belt 8 (the primary transfer step). At this time, a small amount of untransferred toner remains on the photosensitive drum 1Y.

[0015] Thereafter, the surface of the photosensitive drum 1Y reaches a position facing the cleaning device 2Y, and at this position, the untransferred toner remaining on the photosensitive drum 1Y is collected into the cleaning device 2Y by the cleaning blade 2a (cleaning process). Finally, the surface of the photosensitive drum 1Y reaches a position facing a charge removal unit (not shown), where the residual potential on the photosensitive drum 1Y is removed. Thus, a series of image forming processes performed on the photosensitive drum 1Y is completed.

[0016] The above-described image formation process is also performed in the other process cartridges 6M, 6C, and 6BK (imaging units) in the same manner as in the yellow process cartridge 6Y (imaging unit). That is, exposure light L based on image information is irradiated onto the photosensitive drums of the process cartridges 6M, 6C, and 6BK from the optical scanning devices 5A and 5B disposed above the imaging units. Thereafter, the toner images of each color formed on each photosensitive drum through the development process are transferred onto the intermediate transfer belt 8 in a superimposed manner, thereby forming a color image on the intermediate transfer belt 8.

[0017] 1, the intermediate transfer belt device 15 is composed of an intermediate transfer belt 8, four primary transfer rollers 9Y (see FIG. 2), a drive roller, a driven roller, etc. The intermediate transfer belt 8 is stretched and supported by the drive roller, the driven roller, and the primary transfer roller, and is moved endlessly in the direction of the arrow in FIG. 1 (counterclockwise) by the rotational drive of the drive roller.

[0018] The primary transfer roller 9Y sandwiches the intermediate transfer belt 8 between itself and the photosensitive drum 1Y to form a primary transfer nip. A transfer voltage (transfer bias) opposite in polarity to the toner is applied to the primary transfer roller 9Y. The intermediate transfer belt 8 then travels in the direction of the arrow and passes through the primary transfer nips of the primary transfer rollers (9Y) in sequence. In this way, the toner images of each color on the photosensitive drums (1Y) are primarily transferred onto the intermediate transfer belt 8 in an overlapping manner.

[0019] Thereafter, the intermediate transfer belt 8, onto which the toner images of each color have been transferred and superimposed, reaches a position facing the secondary transfer roller 19. At this position, a drive roller (secondary transfer opposing roller) sandwiches the intermediate transfer belt 8 between itself and the secondary transfer roller 19, forming a secondary transfer nip. The four-color toner images formed on the intermediate transfer belt 8 are then transferred onto a sheet P, such as transfer paper, that has been transported to the position of this secondary transfer nip (this is the secondary transfer process). At this time, untransferred toner that has not been transferred to the sheet P remains on the intermediate transfer belt 8.

[0020] Thereafter, the intermediate transfer belt 8 reaches the position of the intermediate transfer cleaning device 16 (intermediate transfer cleaning blade). At this position, untransferred toner on the intermediate transfer belt 8 is mechanically removed by the intermediate transfer cleaning blade (intermediate transfer cleaning device 16) that is in pressure contact with the intermediate transfer belt 8. The intermediate transfer cleaning blade is a substantially plate-shaped member made of an elastic material such as urethane rubber, and is in contact with the intermediate transfer belt 8 at a predetermined contact pressure and angle. Thus, the series of transfer processes performed on the intermediate transfer belt 8 is completed.

[0021] Referring to FIG. 1, the sheet P transported to the secondary transfer nip position is transported from a paper feed section 26 disposed below the device main body 100 via a paper feed roller 27, a pair of registration rollers 28 (a pair of timing rollers), etc. More specifically, a plurality of sheets P such as paper are stacked and stored in the paper feed unit 26. When the paper feed roller 27 is rotated counterclockwise in FIG. 1, the topmost sheet P is fed toward between the pair of registration rollers 28.

[0022] The sheet P conveyed to the registration roller pair 28 stops temporarily at the roller nip position of the registration roller pair 28, which has stopped rotating. Then, the registration roller pair 28 is rotated in synchronization with the color image on the intermediate transfer belt 8, and the sheet P is conveyed toward the secondary transfer nip. In this way, the desired color image is transferred onto the sheet P.

[0023] Thereafter, the sheet P onto which the color image has been transferred at the secondary transfer nip position is transported to the position (fixing nip) of the fixing device 20. Then, at this position, the color image (toner image) transferred onto the surface is fixed onto the sheet P by heat and pressure from the fixing belt 21 (fixing member) and the pressure roller 22 (pressure member) (fixing process). Thereafter, the sheet P is discharged to the outside of the apparatus by a pair of discharge rollers. The sheets P discharged to the outside of the apparatus by the pair of discharge rollers are sequentially stacked on a stack unit (main body cover 110) as output images. In this way, a series of image forming processes in the image forming apparatus is completed.

[0024] The optical scanning devices 5A and 5B will be described below with reference to FIGS. As previously described with reference to FIG. 1, the image forming apparatus 100 of this embodiment is equipped with two optical scanning devices (a first optical scanning device 5A and a second optical scanning device 5B). The first optical scanning device 5A is used to perform an exposure process on the photosensitive drum of the black process cartridge 6BK and the photosensitive drum of the cyan process cartridge 6C. The second optical scanning device 5B is used to perform an exposure process on the photosensitive drum of the magenta process cartridge 6M and the photosensitive drum of the yellow process cartridge 6Y.

[0025] The two optical scanning devices 5A and 5B (writing devices) are configured almost identically except for the target onto which the exposure light is irradiated, as described above. Therefore, in the following, we will appropriately omit the explanation of the second optical scanning device 5B and only explain the first optical scanning device 5A. Referring to Figure 4(A) etc., in this embodiment, the two optical scanning devices 5A and 5B each function as a joined unit in which a cover 600 as a first member and a housing 500 (optical housing) as a second member are joined together, which will be explained in detail later.

[0026] 3 and 4A, optical scanning device 5A (junction unit) includes optical components such as LD unit 51, optical deflector 53 (polygon scanner unit), scanning lens 54 (fθ lens), reflecting mirrors 55C, 55BK, and 56BK, and scanning lenses 57BK and 57C having power in the sub-scanning direction, which are installed inside housing 500 (second member). As shown in FIG. 4, the ceiling of housing 500 (second member) is covered with a cover (first member), creating a substantially sealed space inside optical scanning device 5A to prevent dust from entering the interior. LD unit 51 and optical deflector 53 are installed on the end side of housing 500 (left side in FIGS. 3 and 4A).

[0027] The LD unit 51 is provided with a black light source 52BK consisting of a semiconductor laser for irradiating the surface of the photosensitive drum of the black process cartridge 6BK with exposure light LBK (scanning light beam), and a cyan light source 52C consisting of a semiconductor laser for irradiating the surface of the photosensitive drum of the cyan process cartridge 6C with exposure light LC (scanning light beam). The LD unit 51 mounts and holds the light sources 52BK and 52C so that the light (light beam) emitted from the black light source 52BK and the light (light beam) emitted from the cyan light source 52C are irradiated at the same position on the polygon mirror 53a.

[0028] The optical deflector 53 is composed of a polygon mirror 53a (rotating polygonal mirror) formed in the shape of a regular polygonal prism, a polygon motor 53b that rotates the polygon mirror 53a, and a substrate 53c that holds the polygon mirror 53a and the polygon motor 53b. Electronic components (circuit board) for controlling the rotation of the polygon motor 53b are also mounted on the substrate 53c. Reflecting mirrors are formed on each of the six side surfaces of the polygon mirror 53a. In this embodiment, the polygon mirror 53a is formed in the shape of a regular hexagonal prism, but the shape of the polygon mirror 53a is not limited to this.

[0029] The optical scanning device 5A configured in this manner operates as follows. First, a light beam emitted from a black light source 52BK fixed to the LD unit 51 is converted from a divergent light beam into a parallel light beam by a collimator lens 59a arranged on the optical path between the LD unit 51 and the polygon mirror 53a, and then passes through a cylindrical lens 59b to be condensed in the sub-scanning direction (a direction corresponding to the movement direction (rotation direction) of the photosensitive drum on the surface of the photosensitive drum) and incident on the polygon mirror 53a. The light incident on the polygon mirror 53a is deflected in the main scanning direction (a direction corresponding to the rotation axis direction of the photosensitive drum on the surface of the photosensitive drum) while being reflected by the reflecting mirror of the polygon mirror 53a, and then passes through the scanning lens 54, and the moving speed of the light beam deflected in the main scanning direction by the polygon mirror 53a at a constant angular velocity is converted to a constant speed. The light that passes through the scanning lens 54 is reflected sequentially by the first reflecting mirror 55BK and the second reflecting mirror 56BK, and then passes through a scanning lens 57BK that has power in the sub-scanning direction, thereby correcting the surface tilt of the polygon mirror 53a. The light that passes through the scanning lens 57BK then passes through a dustproof glass 58BK that is provided so as to cover an opening 504BK formed in the bottom surface of the housing 500, and is irradiated (optically scanned) onto the surface of the photosensitive drum of the black process cartridge 6BK.

[0030] The operation of irradiating the surface of the photosensitive drum of the cyan process cartridge 6C with light emitted from the cyan light source 52C fixed to the LD unit 51 is the same as that for black described above, except that the optical path after passing through the scanning lens 54 (the optical path on which the reflective mirror 55C, scanning lens 57C, and dustproof glass 58C (opening 504C) are installed) is different.

[0031] Hereinafter, the characteristic configuration and operation of the optical scanning device 5A (5B) as the joining unit in this embodiment will be described in detail with reference to FIGS. The protrusion 500a of the housing 500 shown in Figure 5(C) is a simplified version of the protrusion 500a shown in Figure 3. Accordingly, the cover 600 shown in Figure 5 is also simplified.

[0032] As shown in FIG. 4(A), in this embodiment, the optical scanning device 5A functions as a joined unit in which a cover 600 as a first member and a housing 500 (optical housing) as a second member are joined together. As previously explained using Figures 3 and 4(A), the housing 500 as the second member is equipped with an optical deflector 53 that deflects light emitted from the light sources 52BK and 52C, and the cover 600 as the first member covers the housing.

[0033] 5(A), 5(B), etc., in this embodiment, a cover 600 as a first member is formed with a substantially annular groove 600a (a portion surrounded by a bottom surface and both wall surfaces, which is a continuous groove that goes around without a break) that can be filled with a hot melt HM as a viscoelastic sealing material. Note that, as shown in FIG. 5(A), groove 600a in this embodiment is formed in a substantially convex annular shape, but groove 600a is not limited to this as long as it is a substantially annular shape. The groove portion 600a1 is provided with a wide groove width portion 600a1 having a groove width wider than the other portion (standard groove width portion 600a2).

[0034] Specifically, the other portion of the groove 600a (reference groove width portion 600a2) is formed so that its groove width D0 (the distance between the inner wall and the outer wall) is substantially constant, except for corners K (portions where the groove bends at a predetermined angle). In contrast, the wide groove width portion 600a1 is formed so that its groove width D1 is wider than the groove width D0 of the reference groove width portion 600a2 (D1>D0). The wide groove width portion 600a1 is a portion where a portion connected to one end of the reference groove width portion 600a2 (other portion) and a portion connected to the other end are offset in a direction (vertical direction in FIG. 5) that is approximately perpendicular to the extension direction of the groove portion 600a. That is, the wide groove width portion 600a1 is not aligned in the extension direction of the groove portion 600a, but the portion connected to one end of the reference groove width portion 600a2 (other portion) and the portion connected to the other end are offset (without a distance) so as to overlap in the groove width direction (vertical direction in FIG. 5(A)). Therefore, the groove width D1 of the wide groove width portion 600a1 is approximately twice the groove width D0 of the reference groove width portion 600a2 (D1 ≈ 2 × D0).

[0035] Furthermore, referring to Figure 5(A), in this embodiment, groove portion 600a is formed so as to be able to guide the relative movement of filling nozzle 700 (see Figure 6(B)) as a filling means for filling hot melt HM as a sealing material with respect to cover 600 (first member). Specifically, hot melt HM stored in a filling device (not shown) is dispensed from a filling nozzle 700 of the filling device. As shown in FIG. 5(A), the filling nozzle 700 is guided along a groove 600a of a cover 600 fixed to a fixed base (not shown), and moves once in a substantially circular fashion in the direction of the arrow (clockwise) from a movement start position 700a to a movement end position 700b, filling the entire area of the groove 600a with hot melt HM (as shown in FIG. 5(B)). To ensure smooth operation of the filling nozzle 700, the filling nozzle 700 is formed so that its outer diameter is equal to or slightly larger than the groove width D0 of the reference groove width portion 600a2.

[0036] Further, wide groove width portion 600a1 is the portion where the position where the movement of filling nozzle 700 (filling means) starts (movement start position 700a) and the position where the movement ends (movement end position 700b) are adjacent to each other. In detail, in this embodiment, the wide groove width portion 600a1 is an adjacent portion where the trajectory of the filling nozzle 700 moving from the movement start position 700a and the trajectory of the filling nozzle 700 moving to the movement end position 700b are shifted in the groove width direction and slightly overlap each other.

[0037] The hot melt HM has viscoelasticity when filled, and it is difficult to align the filling start position (movement start position 700a) and the filling end position (movement end position 700b), which is why the wide groove width portion 600a1 having the shape described above is necessary. Furthermore, in order to fill the groove portion 600a with hot melt HM without leaving any gaps, it is necessary to connect the hot melt HM between the movement start position 700a and the movement end position 700b. Therefore, it is preferable that the portion of the wide groove width portion 600a1 corresponding to the movement start position 700a and the portion corresponding to the movement end position 700b are not too far apart.

[0038] On the other hand, as shown in Figures 4(B), 5(C), 6(C), etc., the housing 500 as the second member has an approximately annular protrusion 500a formed thereon that can be fitted into the groove 600a via a hot melt HM (sealing material). 3 and 4(A), the protrusion 500a is a wall (rib) formed in a substantially annular shape so as to stand up from the bottom surface of the optical scanning device 5A in the direction in which the cover 600 is installed. Moreover, as shown in FIG. 5(C), the protrusion 500a is formed along the groove 600a of the cover 600 so as to be positioned at substantially the center of the groove width of the groove 600a.

[0039] As shown in FIG. 4 and other figures, the gap between the cover 600 (first member) and the housing 500 (second member) is sealed with a hot melt HM (sealing material). This improves the airtightness (dustproofness) inside the optical scanning device 5A (junction unit), thereby reducing problems such as abnormal images caused by dust contamination. Like known materials, hot melt HM is a sealing material that has viscoelasticity when filled (at high temperatures) and hardens (cools and solidifies) as the temperature decreases over time. Using such hot melt HM as a sealing material reduces the cost of the sealing material compared to when a sponge material is used, and also simplifies the process of applying the sealing material to the cover 600, reducing the operating cost.

[0040] The procedure for joining the cover 600 to the housing 500 will be described below with reference to FIGS. First, as shown in Figures 5(A) and 6(A), cover 600 is set on a filling device (not shown) so that groove 600a opens upward. Then, as shown in Figures 5(A) and 6(B), filling nozzle 700 of the filling device is inserted into movement start position 700a of groove 600a. Thereafter, the filling nozzle 700 is moved from the movement start position 700a along the groove 600a in the direction of the arrow (clockwise) in Fig. 5(A), while filling the groove 600a with hot melt HM from the filling nozzle 700. Then, when the filling nozzle 700 reaches the movement end position 700b and the entire area (entire circumference) of the groove 600a is filled with hot melt HM as shown in Fig. 5(B), the filling nozzle 700 is released from the groove 600a. 5(C) and 6(C), the housing 500 is joined (attached) to the cover 600 from above so that the protrusion 500a fits into the groove 600a via the hot melt HM. Then, when the hot melt HM hardens, the assembly of the optical scanning device 5A as a joined unit is completed.

[0041] Here, referring to FIGS. 5(C) and 8, in the present embodiment, at least a part (V-shaped portion 500a10) of the portion (concave protrusion portion 500a1) of the protrusion portion 500a of the housing 500 that fits into the wide groove width portion 600a1 is formed such that the height in the protrusion direction (the direction perpendicular to the paper surface of FIG. 5 and the vertical direction of FIG. 8) is lower than the height in the protrusion direction of the portion (flat protrusion portion 500a2) that fits into the other portion (reference groove width portion 600a2).

[0042] Specifically, as shown in FIG. 8(B), the flat protrusion portion 500a2 (the portion of the protrusion portion 500a that fits into the reference groove width portion 600a2 (the other portion)) is formed such that the height in its protrusion direction is substantially constant. Also, the thickness E0 of the flat protrusion portion 500a2 is configured to be smaller than the groove width D0 of the reference groove width portion 600a2 (E0 < D0). Specifically, the tip portion (the portion facing the bottom surface of the reference groove width portion 600a2) of the flat protrusion portion 500a2 is formed in a flat shape. On the other hand, as shown in FIG. 8(A), the concave protrusion portion 500a1 (the portion of the protrusion portion 500a that fits into the wide groove width portion 600a1) is formed such that at least a part of it has a gradually decreasing height in the protrusion direction from both ends toward the central portion. Specifically, the thickness E1 of the concave protrusion portion 500a1 is configured to be larger than the thickness E0 of the flat protrusion portion 500a2 and smaller than the groove width D1 of the wide groove width portion 600a1 (E0 < E1 < D1). And a V-shaped portion 500a10 (a substantially V-shaped groove) is formed in the tip portion (the portion facing the bottom surface of the wide groove width portion 600a1) of the concave protrusion portion 500a1. Note that the concave protrusion portion 500a1 is not limited to that of the present embodiment, and it may be formed such that at least the height in the protrusion direction of a part of it is lower than the height in the protrusion direction of the flat protrusion portion 500a2. For example, it may be formed such that the entire height in the protrusion direction gradually decreases from both ends toward the central portion.

[0043] In this way, by making the height of the concave protrusion portion 500a1 in the protrusion direction lower than the height of the flat protrusion portion 500a2 in the protrusion direction, when the housing 500 and the cover 600 are fitted together as shown in Figures 5(C) and 6(C), it is possible to reduce the problem of the housing 500 and the cover 600 being locally deformed by the reaction force in the direction of the black arrow of the compressively deformed hot melt HM.

[0044] Specifically, as shown in Fig. 7(B) (and Fig. 5(B)), the hot melt HM filled in the standard groove width portion 600a2 may form a slight mountain-like shape, but the height is generally uniform in the groove width direction and in the direction perpendicular thereto (the groove extension direction), and no large localized protrusions are formed in either direction. Therefore, even if the flat protrusion portion 500a2 is fitted into the standard groove width portion 600a2 filled with the hot melt HM, the force that the flat protrusion portion 500a2 receives from the hot melt HM (this is a reaction force in the direction of the black arrow that occurs when the hot melt MH is pushed by the protrusion in the direction of the white arrow in Fig. 6(C)) is generally uniform, and problems such as localized deformation of the housing 500 or the cover 600 are unlikely to occur.

[0045] In contrast, as shown in Figure 7(A) (and Figure 5(B)), the hot melt HM filled in the wide groove width portion 600a1 overlaps with a portion of the hot melt HM filled at the movement start position 700a and a portion of the hot melt HT filled at the movement end position 700b, resulting in the formation of a localized raised portion HM1 that is significantly higher than the height of the hot melt HM filled in the standard groove width portion 600a2. 10, when the protrusion 1500a1 having a flat tip is fitted into the wide groove 600a1 filled with the hot melt HM having the raised portion HM1, the force F2 that the protrusion 1500a1 receives from the hot melt HM becomes locally large, which tends to locally deform the housing 500 and the cover 600. When such local deformation occurs, the positional accuracy of the various optical elements installed in the optical scanning device 5A decreases, resulting in abnormal images due to writing errors and the like. 9, the concave projection 500a1 having the V-shaped portion 500a10 formed at the tip is fitted into the wide groove 600a1 filled with the hot melt HM and having the raised portion HM1. This causes a portion of the raised portion HM1 to flow into the V-shaped portion 500a10, and the force F1 that the concave projection 500a1 receives from the hot melt HM is small and substantially uniform. This reduces the likelihood of problems such as localized deformation of the housing 500 or the cover 600. Due to this mechanism, it is preferable that the V-shaped portion 500a10 of the concave protrusion 500a1 be formed to match the position of the protruding portion HM1.

[0046] <Modification> FIG. 11 is a cross-sectional view showing the concave projection 500a1 of the housing 500 fitted into the wide groove width portion 600a1 of the cover 600, and corresponds to FIG. 8(A) described above. 11, the central portion (the central portion in the groove width direction) of the concave protrusion 500a1 of the housing 500 in this modification is curved. Specifically, the concave protrusion 500a1 has a V-shaped portion 500a10 with an R-tip portion 500a10a. In other words, the top of the V-shaped portion 500a10 is not angular, but is rounded. With this configuration, even if the concave projection 500a1 is fitted into the wide groove width portion 600a1 and the raised portion HM1 (see FIG. 9(A)) of the hot melt HM flows into the V-shaped portion 500a10, the force F1 received from the hot melt HM at the apex is more easily dispersed than when the apex of the V-shaped portion 500a10 is formed into a square shape. This further reduces the likelihood of the housing 500 or the cover 600 being locally deformed.

[0047] As described above, the optical scanning devices 5A and 5B in this embodiment are joined units in which a cover 600 (first member) and a housing 500 (second member) are joined together. The cover 600 has a substantially annular groove 600a that can be filled with a viscoelastic hot melt HM (sealing material). The housing 500 (second member) has a substantially annular protrusion 500a that can be fitted into the groove 600a via the hot melt HM. The groove 600a includes a wide groove width portion 600a1 that is wider than a reference groove width portion 600a2 (other portion). The protrusion 500a is formed such that the height in the protrusion direction of at least a portion of the portion that fits into the wide groove width portion 600a1 is smaller than the height in the protrusion direction of the portion that fits into the reference groove width portion 600a2 (other portion). This makes it possible to achieve a relatively low cost, high assembly workability, little deformation of the cover 600 (first member) and the housing 500 (second member), and high sealing performance.

[0048] In this embodiment, the present invention is applied to optical scanning devices 5A and 5B installed in a color image forming apparatus 100, but the present invention can naturally also be applied to optical scanning devices installed in a monochrome image forming apparatus. Furthermore, in this embodiment, the present invention is applied to optical scanning devices 5A and 5B in which two optical paths of exposure light L corresponding to two colors are formed inside, but the present invention can also naturally be applied to optical scanning devices in which one or three or more optical paths of exposure light are formed inside. Even in these cases, the same effects as those of this embodiment can be obtained.

[0049] In addition, in this embodiment, the housing 500 (second member) is configured to be covered from above with the cover 600 (first member), but it is also possible to configure the housing (second member) to be covered from above with a first cover (first first member) and the housing (second member) to be covered from below with a second cover (second first member). In the present embodiment, the cover 600 is the first member and is provided with the groove 600a, and the housing 500 is the second member and is provided with the protrusion 500a. Alternatively, the cover may be the second member and is provided with the protrusion, and the housing may be the first member and is provided with the groove. In addition, in this embodiment, hot melt HM is used as a viscoelastic sealing material, but the sealing material is not limited to this, and for example, a sealing material that has viscoelasticity when filled and hardens over time when exposed to air can also be used. Furthermore, in this embodiment, the present invention is applied to the optical scanning devices 5A and 5B as joining units in the image forming apparatus 100, but the present invention can also be applied to all other joining units in the image forming apparatus that join a first member and a second member, and the present invention can also be applied to all joining units installed in equipment other than the image forming apparatus that join a first member and a second member, and the present invention can also be applied to all stand-alone (single) joining units that join a first member and a second member. Even in these cases, the same effects as those of this embodiment can be obtained.

[0050] It is to be noted that the present invention is not limited to the present embodiment, and it is clear that the present embodiment can be appropriately modified within the scope of the technical concept of the present invention in addition to the modifications suggested in the present embodiment. Furthermore, the number, position, shape, etc. of the components are not limited to the present embodiment, and the number, position, shape, etc. of the components can be any number, position, shape, etc. that is suitable for implementing the present invention.

[0051] In this specification, a "substantially annular" groove (or protrusion) is defined to include not only a ring-shaped groove having no corners and consisting only of a curved surface, but also an approximately ring-shaped groove having one or more corners (for example, as shown in Figure 5), and all other grooves with an endless shape. [Explanation of symbols]

[0052] 5A, 5B Optical scanning device (joint unit), 53 Optical deflector, 100 Image forming apparatus (image forming apparatus main body), 500 housing (second member), 500a protrusion, 500a1 concave protrusion (protrusion that fits into the wide groove width portion), 500a2 flat projection (projection that fits into another part), 500a10 V-shaped part, 500a10a R tip, 600 Cover (second member), 600a groove, 600a1 wide groove width section, 600a2 standard groove width section, 700 filling nozzle (filling means), 700a: Movement start position; 700b: Movement end position; HM hot melt (sealing material), HM1 raised part, K corner part. [Prior art documents] [Patent documents]

[0053] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-66431

Claims

1. A joining unit for joining a first member and a second member, The first member has a substantially annular groove formed therein that can be filled with a viscoelastic sealing material, the second member has a substantially annular protrusion formed thereon that can be fitted into the groove with the sealing material interposed therebetween; The groove portion has a wide groove width portion having a groove width wider than other portions, The protrusion portion is formed so that the height in the protrusion direction of at least a part of the portion that fits into the wide groove width portion is lower than the height in the protrusion direction of the part that fits into the other portion.

2. the groove portion is formed to be able to guide a relative movement of a filling means that fills the sealing material with respect to the first member, 2. The joining unit according to claim 1, wherein the wide groove width portion is a portion where a position where the movement of the filling means starts and a position where the movement of the filling means ends are adjacent to each other.

3. the other portion of the groove is formed so that the groove width is substantially constant except for corners, The joining unit according to claim 1 or claim 2, characterized in that the wide groove width portion is a portion connected to one end side of the other portion and a portion connected to the other end side of the other portion, the portions being shifted in a direction approximately perpendicular to the direction in which the groove portion extends.

4. A joining unit as described in any one of claims 1 to 3, characterized in that at least a part of the portion of the protrusion that fits into the wide groove width portion is formed so that its height in the protrusion direction gradually decreases from both ends toward the center.

5. The joint unit according to claim 4, wherein the central portion is formed into a curved surface.

6. The joint unit according to any one of claims 1 to 4, wherein the portion of the protrusion that is fitted into the other portion is formed so that its height in the protrusion direction is approximately constant.

7. 7. The joint unit according to claim 1, wherein a gap between the first member and the second member is sealed by the sealing material.

8. 8. The joint unit according to claim 1, wherein the sealing material is a hot melt.

9. An optical scanning device as a joining unit according to any one of claims 1 to 8, The second member may be a housing in which an optical deflector that deflects light emitted from a light source is installed, or a cover that covers the housing, The optical scanning device, wherein the first member is the cover or the housing.

10. 10. An image forming apparatus comprising: the joining unit according to claim 1; or the optical scanning device according to claim 9.

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