Scanning optical device

Abstract

To prevent dust from attaching to a polygon mirror.SOLUTION: A scanning optical device 1 comprises a semiconductor laser 10, a coupling lens 20, a deflector 50, a scanning optical system, a frame F, and a cover C1. The deflector 50 includes a polygon mirror rotatable about a rotation axis X1 extending in a first direction. The frame F includes a base wall Fb1 on which the deflector 50 is provided. The cover C1 covers the deflector 50 from a side opposite to the base wall Fb1. The frame F includes a first wall (first surrounding wall F20). The first wall extends in a direction from the base wall Fb1 toward the cover C1. The first wall includes an opening F21 through which a beam travels from the deflector 50 toward the scanning optical system, and a first notch F22 arranged away from the opening F21 in a second direction parallel to a main scanning direction. The cover C1 includes a second wall C12 covering the entire first notch F22 when viewed from a third direction orthogonal to the first direction and the second direction.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to a scanning optical device including a polygon mirror and a scanning optical system. [Background technology]

[0002] Conventionally, a known scanning optical device includes a coupling lens that converts light from a semiconductor laser into a beam, a deflector having a polygon mirror that deflects the beam from the coupling lens, a scanning optical system that focuses the beam deflected by the deflector on an image plane, and a frame that holds the coupling lens, the deflector, and the scanning optical system (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-206910 A Summary of the Invention [Problem to be solved by the invention]

[0004] When dust adheres to the mirror surface of a polygon mirror, the optical performance is degraded, for example, the reflectance is reduced.

[0005] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to prevent dust from adhering to a polygon mirror. [Means for solving the problem]

[0006] In order to achieve the above object, a scanning optical device according to the present invention includes a semiconductor laser, a coupling lens, a deflector, a scanning optical system, a frame, and a cover. The coupling lens converts the light emitted from the semiconductor laser into a beam. The deflector deflects the beam that passes through the coupling lens in the main scanning direction. The deflector has a polygon mirror that is rotatable around a rotation axis that extends in a first direction. The scanning optical system forms an image of the beam deflected by the deflector on a surface to be scanned. The frame has a base wall on which the deflector is installed. The cover covers the deflector from the side opposite the base wall. The frame has a first wall extending from the base wall toward the cover, the first wall having an opening through which the beam from the deflector to the scanning optical system passes, and a first notch disposed away from the opening in a second direction parallel to the main scanning direction. The cover has a second wall that covers the entire first cutout when viewed from a third direction perpendicular to the first and second directions.

[0007] In a configuration in which the frame has a base wall on which the deflector is mounted, a first wall extending from the base wall, and a first notch arranged in the first wall, the second wall of the cover covers the entire first notch of the frame when viewed from the third direction, making it difficult for dust to enter the deflector housing through the first notch, and preventing dust from adhering to the polygon mirror.

[0008] Furthermore, in the third direction, at least a portion of the second wall may be located between the first wall and the deflector.

[0009] Additionally, in the third direction, the first wall may be located between at least a portion of the second wall and the deflector.

[0010] The second wall may have a first portion located between the first wall and the deflector in the third direction and a second portion located away from the first portion in the third direction, and the first wall may be located between the first portion and the second portion in the third direction.

[0011] Since the first wall is located between the first and second parts of the second wall, the path that dust can take to get in is complicated, making it more difficult for dust to enter the deflector housing through the first notch, and thus preventing dust from adhering to the polygon mirror.

[0012] Additionally, the first portion may have a larger dimension in the first direction than the second portion.

[0013] The second wall may further include a rib connecting the first portion and the second portion, and the rib may be at least partially located within the first notch.

[0014] By positioning at least a part of the rib connecting the first and second parts within the first notch, the rigidity of the first and second parts is increased and the dimensional accuracy of the gap between the first and second parts is improved. This makes it difficult for dust to enter the deflector housing through the first notch, and prevents dust from adhering to the polygon mirror.

[0015] The scanning optical system may include a first scanning lens and a second scanning lens located downstream of the first scanning lens in the traveling direction of the beam. The first wall may overlap with the second scanning lens when viewed from the third direction, and the first cutout may overlap with an end region that is distant from the center of the second scanning lens in the second direction when viewed from the third direction.

[0016] When viewed from the third direction, the first notch overlaps with a part of the second scanning lens, and the first notch exposes a part of the second scanning lens, making it easy to attach the second scanning lens to the frame. For example, when attaching the second scanning lens to the frame, the attachment work can be facilitated by inserting a worker's hand, a jig, a robot arm, or the like into the first notch.

[0017] The first scanning lens may be disposed so as to cover the opening.

[0018] Since the first scanning lens covers the opening, dust is less likely to enter the deflector housing through the opening, and dust can be prevented from adhering to the polygon mirror.

[0019] Furthermore, one of the frame and the cover may have a boss extending in the first direction, and the other may have a tubular portion into which the boss fits when the cover is attached to the frame.

[0020] When the cover is attached to the frame, the boss and the cylindrical portion engage with each other to guide the cover to the attachment position on the frame, making it easy to attach the cover to the frame.

[0021] The frame may have an outer wall that extends in the first direction and surrounds the scanning optical system, and the cover may have an engagement portion that engages with the frame when the cover is attached to the frame.

[0022] By engaging the engaging portion with the frame, it is easy to attach the cover to the frame in the correct position.

[0023] The outer wall may have a second cutout, and the cover may have a third wall that entirely covers the second cutout when viewed from a third direction.

[0024] By having the third wall provided on the cover cover the entire second cutout, dust is less likely to enter the frame through the second cutout, and dust can be prevented from adhering to the scanning optical system.

[0025] The scanning optical system may include a first scanning lens and a second scanning lens located downstream of the first scanning lens in the traveling direction of the beam. The outer wall may overlap with the second scanning lens when viewed from the third direction, and the second cutout may overlap with an end region away from the center of the second scanning lens in the second direction when viewed from the third direction.

[0026] The second notch exposes a part of the second scanning lens to the outside of the frame, which makes it easier to attach the second scanning lens to the frame. For example, when attaching the second scanning lens to the frame, the attachment work can be facilitated by inserting a worker's hand, a jig, a robot arm, or the like into the second notch. Effect of the Invention

[0027] According to the present invention, it is possible to prevent dust from adhering to the polygon mirror. [Brief description of the drawings]

[0028] [Figure 1] 2 is a perspective view of the scanning optical device as seen from the other side in the first direction. FIG. [Diagram 2] 2 is a perspective view of the scanning optical device as seen from one side in a first direction. FIG. [Diagram 3] 2 is a cross-sectional view taken along line AA in FIG. 1. [Figure 4] FIG. 2 is a perspective view showing a scanning optical device with its cover removed. [Diagram 5] FIG. 2 is a perspective view showing the scanning optical device without the cover and the four second scanning lenses attached. [Figure 6] 11 is a perspective view of the cover as viewed from the other side in the first direction. FIG. [Figure 7] 7 is a perspective view of the cover as viewed from the other side in the first direction, and from an angle different from that of FIG. 6. FIG. [Figure 8] 6 is a cross-sectional view taken along line CC in FIG. 5 and a cross-sectional view of a cover corresponding to the cross-sectional view taken along line CC. [Figure 9] 6 is a cross-sectional view taken along line CC in FIG. 5 when the cover is attached. [Figure 10] FIG. 6 is a cross-sectional view taken along the line DD in FIG. 5 . [Figure 11] 11 is a cross-sectional view of FIG. 10 taken along line E-E. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] As shown in FIG. 1, the scanning optical device 1 includes a frame F, a cover C1, an incident optical system Li, a deflector 50, and a scanning optical system Lo. The scanning optical device 1 is applied to an electrophotographic image forming device. In the following description, a direction along a rotation axis X1 of a polygon mirror 51 of the deflector 50 is referred to as a "first direction". A direction perpendicular to the first direction and parallel to the main scanning direction in which the deflector 50 deflects is referred to as a "second direction". A direction perpendicular to the first direction and the second direction is referred to as a "third direction". An arrow indicating each direction in the drawings indicates "one side" in each direction.

[0030] The frame F and the cover C1 constitute a housing of the scanning optical device 1 (see also FIG. 2). Although details will be described later, the incident optical system Li, the deflector 50, and the scanning optical system Lo are housed in the housing formed by the frame F and the cover C1.

[0031] The incidence optical system Li includes four semiconductor lasers 10, four coupling lenses 20, an aperture plate 30, and a condenser lens 40.

[0032] The semiconductor laser 10 is a device that emits light. Four semiconductor lasers 10 are provided corresponding to four photosensitive drums 200 (see FIG. 3) that are scanned and exposed by the scanning optical device 1. A toner image of a different color is formed on each photosensitive drum 200.

[0033] In this embodiment, the first color is "yellow (Y)", the second color is "magenta (M)", the third color is "cyan (C)", and the fourth color is "black (K)". In the following description, the names of the components corresponding to the first color may be distinguished by adding "first" to the beginning of the name and adding "Y" to the end of the reference numerals of the components corresponding to the first color. Similarly, the names of the components corresponding to the second, third, and fourth colors may be distinguished by adding "second", "third", and "fourth" to the beginning of the name and adding "M", "C", and "K" to the end of the reference numerals.

[0034] The first semiconductor laser 10Y is arranged in the first direction with a gap between them and the second semiconductor laser 10M. The first semiconductor laser 10Y is located on one side in the first direction with respect to the second semiconductor laser 10M.

[0035] The third semiconductor laser 10C is arranged at an interval from the second semiconductor laser 10M in the third direction. The third semiconductor laser 10C is located on the other side in the third direction from the second semiconductor laser 10M. The fourth semiconductor laser 10K is arranged at an interval from the third semiconductor laser 10C in the first direction, and is arranged at an interval from the first semiconductor laser 10Y in the third direction.

[0036] The coupling lens 20 is a lens that converts the light from the semiconductor laser 10 into a beam. The coupling lenses 20Y, 20M, 20C, and 20K corresponding to each color are disposed at positions facing the corresponding semiconductor lasers 10Y, 10M, 10C, and 10K.

[0037] The diaphragm plate 30 is a portion having an aperture diaphragm 31 through which the beam from the coupling lens 20 passes, and is formed integrally with the frame F. The diaphragm plate 30 is located between the coupling lens 20 and the condenser lens 40.

[0038] The condenser lens 40 is a lens that condenses the beam from the coupling lens 20 in the sub-scanning direction onto the polygon mirror 51. The condenser lens 40 is a lens through which the beams BY, BM, BC, and BK pass in common, and has a cylindrical entrance surface and a flat exit surface (see also FIG. 9).

[0039] As shown in FIG. 3, the deflector 50 has a polygon mirror 51 and a motor 52. The polygon mirror 51 is a mirror that deflects the beam that has passed through the coupling lens 20 in the main scanning direction. The polygon mirror 51 is rotatable about a rotation axis X1 that extends in the first direction. The polygon mirror 51 has five mirror surfaces that are equidistant from the rotation axis X1. The motor 52 is a motor that rotates the polygon mirror 51. The motor 52 is installed on a base wall Fb1 of the frame F (see also FIG. 9).

[0040] The scanning optical system Lo is an optical system that forms an image of the beam deflected by the polygon mirror 51 on a surface to be scanned. In this embodiment, the scanning optical system Lo forms an image of the beam deflected by the polygon mirror 51 on the surface of the photosensitive drum 200 as an image surface. The scanning optical system Lo is fixed to a frame F. The scanning optical system Lo has a first scanning optical system LoY corresponding to yellow, a second scanning optical system LoM corresponding to magenta, a third scanning optical system LoC corresponding to cyan, and a fourth scanning optical system LoK corresponding to black.

[0041] The first scanning optical system LoY and the second scanning optical system LoM are disposed on one side of the polygon mirror 51 in the third direction. The third scanning optical system LoC and the fourth scanning optical system LoK are disposed on the other side of the polygon mirror 51 in the third direction. A beam deflected in the main scanning direction by the polygon mirror 51 is incident on each of the scanning optical systems LoY, LoM, LoC, and LoK.

[0042] The first scanning optical system LoY has a first scanning lens 60YM, a second scanning lens 70Y, and a reflecting mirror 81Y.

[0043] The first scanning lens 60YM is a lens that refracts the beams BY and BM deflected by the deflector 50 in the main scanning direction to form an image on the image plane. The first scanning lens 60YM has an fθ characteristic that causes the light scanned at a constant angular velocity by the deflector 50 to move at a constant velocity on the image plane. The first scanning lens 60YM is the scanning lens closest to the polygon mirror 51 in the first scanning optical system LoY.

[0044] The reflecting mirror 81Y is a mirror that reflects the beam BY from the first scanning lens 60YM toward the image surface. The second scanning lens 70Y is a lens that refracts the beam BY reflected by the reflecting mirror 81Y in the sub-scanning direction to form an image on the image surface. The second scanning lens 70Y is disposed at a position on one side in the first direction with respect to the polygon mirror 51. The second scanning lens 70Y is located downstream of the first scanning lens 60YM in the traveling direction of the beam BY, and is the scanning lens closest to the image surface in the first scanning optical system LoY.

[0045] The second scanning optical system LoM has a first scanning lens 60YM, a second scanning lens 70M, a reflecting mirror 81M, and a mirror 82M.

[0046] The first scanning lens 60YM is shared with the first scanning optical system LoY. The second scanning lens 70M and the reflecting mirror 81M have the same functions as the second scanning lens 70Y and the reflecting mirror 81Y of the first scanning optical system LoY. The mirror 82M is a mirror that reflects the beam BM from the first scanning lens 60YM to the reflecting mirror 81M.

[0047] The third scanning optical system LoC has a structure that is generally symmetrical to the second scanning optical system LoM with respect to the rotation axis X1 of the polygon mirror 51. Specifically, the third scanning optical system LoC has a first scanning lens 60CK, a second scanning lens 70C, a reflecting mirror 81C, and a mirror 82C that have the same functions as the respective members of the second scanning optical system LoM.

[0048] The fourth scanning optical system LoK has a structure that is generally symmetrical to the first scanning optical system LoY with respect to the rotation axis X1 of the polygon mirror 51. Specifically, the fourth scanning optical system LoK has a first scanning lens 60CK, a second scanning lens 70K, and a reflecting mirror 81K that have the same functions as the respective members of the first scanning optical system LoY.

[0049] The polygon mirror 51 deflects the beams BY, BM, BC, and BK toward the corresponding scanning optical systems LoY, LoM, LoC, and LoK. The beam BY toward the first scanning optical system LoY passes through the first scanning lens 60YM, is reflected by the reflecting mirror 81Y, and passes through the second scanning lens 70Y to be emitted toward an image plane on one side in the first direction. The beam BY is emitted from the second scanning lens 70Y at a predetermined angle with the first direction. The beam BY is imaged on the surface of the first photosensitive drum 200Y and is scanned in the main scanning direction.

[0050] The beam BM heading toward the second scanning optical system LoM passes through the first scanning lens 60YM, is reflected by the mirror 82M and the reflecting mirror 81M, and is emitted toward an image surface on one side in the first direction through the second scanning lens 70M. The beam BM is emitted from the second scanning lens 70M at a predetermined angle with the first direction. The beam BM is imaged on the surface of the second photosensitive drum 200M and scanned in the main scanning direction. The beams BC and BK are also similarly emitted toward an image surface on one side in the first direction by the corresponding scanning optical systems LoC and LoK, are imaged on the surfaces of the corresponding photosensitive drums 200C and 200K, and are scanned in the main scanning direction.

[0051] Next, the configurations of the frame F and the cover C1 will be described in detail. As shown in Fig. 4, the frame F has a shape that opens to one side in the first direction. The frame F has a base wall Fb1 and an outer wall F40. The base wall Fb1 forms the bottom surface of the frame F. The base wall Fb1 is a wall that is perpendicular to the first direction. The outer wall F40 extends from the periphery of the base wall Fb1 to one side in the first direction.

[0052] The outer wall F40 is made up of a first side wall F41, a second side wall F42, a third side wall F43, and a fourth side wall F44. The first side wall F41, the second side wall F42, the third side wall F43, and the fourth side wall F44 surround the scanning optical system Lo on all four sides.

[0053] The first side wall F41 and the second side wall F42 are spaced apart from each other in the second direction. The deflector 50 is located between the first side wall F41 and the second side wall F42.

[0054] The second side wall F42 is located between the semiconductor laser 10 and the deflector 50. The first side wall F41 is located on the opposite side to the semiconductor laser 10 with the deflector 50 interposed therebetween.

[0055] The third side wall F43 and the fourth side wall F44 are spaced apart from each other in the third direction. The deflector 50 is located between the third side wall F43 and the fourth side wall F44. The third side wall F43 is located on one side of the deflector 50 in the third direction. The fourth side wall F44 is located on the other side of the deflector 50 in the third direction.

[0056] The third side wall F43 has a first claw F431. The first claw F431 protrudes toward the outside of the frame F. The first claw F431 is provided on each of both ends in the second direction.

[0057] The fourth side wall F44 has a second claw F441 and a second cutout F442. The second claw F441 protrudes toward the outside of the frame F. The second claw F441 is provided at each end in the second direction. The second cutout F442 is cut out in a rectangular shape from one end of the fourth side wall F44 in the first direction toward the other side in the first direction. The second cutout F442 is provided at each end in the second direction. In the second direction, the two second claws F441 are located between the two second cutouts F442.

[0058] The fourth side wall F44 overlaps with the second scanning lens 70K corresponding to black when viewed from the third direction. When viewed from the third direction, the second cutout F442 overlaps with an end region away from the center of the second scanning lens 70K in the second direction. Therefore, the second cutout F442 exposes the end region away from the center of the second scanning lens 70K in the second direction to the outside of the frame F when the cover C1 is not attached to the frame F.

[0059] The frame F further includes a first surrounding wall F20, a second surrounding wall F30, a third surrounding wall F45, a fourth surrounding wall F46, and a boss F50. The first surrounding wall F20 is an example of a first wall.

[0060] The first surrounding wall F20, the second surrounding wall F30, the third surrounding wall F45, and the fourth surrounding wall F46 surround the four sides of the deflector 50. The first surrounding wall F20, the second surrounding wall F30, the third surrounding wall F45, and the fourth surrounding wall F46 are walls that separate the accommodation chamber LS of the deflector 50 from other spaces in the internal space of the frame F.

[0061] The third surrounding wall F45 and the fourth surrounding wall F46 extend in a direction from the base wall Fb1 toward the cover C1. The third surrounding wall F45 and the fourth surrounding wall F46 are located apart from each other in the second direction. The third surrounding wall F45 is located on one side of the deflector 50 in the second direction. The fourth surrounding wall F46 is located on the other side of the deflector 50 in the second direction. The fourth surrounding wall F46 is a part of the second side wall F42.

[0062] The first surrounding wall F20 is located on one side of the deflector 50 in the third direction, and connects the third surrounding wall F45 and the fourth surrounding wall F46. The first surrounding wall F20 extends in a direction from the base wall Fb1 toward the cover C1. Specifically, the first surrounding wall F20 extends from the base wall Fb1 to one side in the first direction. As shown in FIG. 3 and FIG. 4, the first surrounding wall F20 overlaps with the second scanning lens 70M when viewed from the third direction. As shown in FIG. 5, the first surrounding wall F20 has an opening F21 and a first notch F22.

[0063] The opening F21 has a rectangular shape and is located at the center of the first surrounding wall F20 in the second direction. A first scanning lens 60YM is disposed in the opening F21 so as to cover the opening F21. As a result, the beam traveling from the polygon mirror 51 toward the scanning optical system Lo passes through the opening F21.

[0064] The first notches F22 have a rectangular shape and are provided at two locations on either side of the opening F21. The two first notches F22 are disposed away from the opening F21 in the second direction. As shown in FIG. 4, when viewed from the third direction, the first notches F22 overlap with an end region that is away from the center of the second scanning lens 70M in the second direction (see also FIG. 11). The first notches F22 expose the end region that is away from the center of the second scanning lens 70M in the second direction when the cover C1 is not attached to the frame F.

[0065] The second surrounding wall F30 is located on the other side of the deflector 50 in the third direction, and connects the third surrounding wall F45 and the fourth surrounding wall F46. The second surrounding wall F30 extends from the base wall Fb1 to one side in the first direction. As shown in Figs. 3 and 4, the second surrounding wall F30 overlaps with the second scanning lens 70C when viewed from the third direction. As shown in Fig. 5, the second surrounding wall F30 has an opening F31.

[0066] The boss F50 is located between the first side wall F41 and the third surrounding wall F45. The boss F50 has a cylindrical shape and extends in the first direction. The tip of the boss F50 protrudes furthest to one side in the first direction among the parts that configure the frame F.

[0067] 6, the cover C1 has a base portion C10, a tube portion C11, a second wall C12, a third wall C13, a fourth wall C14, an engagement portion C15, and a slit C16. The base portion C10 is a wall having a flat plate shape and perpendicular to the first direction.

[0068] The cylindrical portion C11 has a cylindrical shape. The boss F50 fits into the cylindrical portion C11 when the cover C1 is attached to the frame F. The cylindrical portion C11 guides the boss F50 to a predetermined position when the cover C1 is attached to the frame F.

[0069] The second wall C12 is a wall perpendicular to the third direction. The second wall C12 extends from the base portion C10 to the other side in the first direction. As shown in FIG. 11, when the cover C1 is attached to the frame F, the second wall C12 overlaps with the first surrounding wall F20 and divides the accommodation chamber LS of the deflector 50 in the first recess CP1 from the space in which the second scanning lens 70M corresponding to magenta is disposed, together with the first surrounding wall F20. The second wall C12 has a first portion C121, a second portion C122, a rib C123, and an extension portion C124.

[0070] As shown in Fig. 11, the first portion C121 is located between the first surrounding wall F20 and the polygon mirror 51 in the third direction. At least a portion of the second wall C12 is located between the first surrounding wall F20 and the polygon mirror 51 in the third direction. As shown in Fig. 6, two first portions C121 are provided corresponding to the first cutouts F22. Each of the first portions C121 has a rectangular shape.

[0071] The second portion C122 is located away from the first portion C121 in the third direction. Specifically, the second portion C122 is provided on the other side of the first portion C121 in the third direction. Two second portions C122 are provided corresponding to the first portions C121. Each second portion C122 has a rectangular shape. The second portion C122 extends parallel to the first portion C121, and the first portion C121 and the second portion C122 face each other.

[0072] The first portion C121 has a larger dimension in the first direction than the second portion C122. As shown in Fig. 9, when the cover C1 is attached to the frame F, each first portion C121 covers the entire first cutout F22 when viewed from the third direction.

[0073] 11, when the cover C1 is attached to the frame F, the first surrounding wall F20 is located between the first portion C121 and the second portion C122 in the third direction. That is, the first surrounding wall F20 is located between at least a part of the second wall C12 and the polygon mirror 51 in the third direction.

[0074] As shown in Fig. 7, the rib C123 extends in the third direction and connects the first portion C121 and the second portion C122. As shown in Fig. 10, when the cover C1 is attached to the frame F, at least a portion of the rib C123 is located in the first cutout F22.

[0075] Two third walls C13 are provided at the other end of the base C10 in the third direction. The third walls C13 extend from the base C10 to the other end in the first direction. The third walls C13 are walls perpendicular to the third direction. The third walls C13 have a rectangular shape. As shown in FIG. 2, when the cover C1 is attached to the frame F, the third walls C13 cover the entire second cutout F442 when viewed from the third direction.

[0076] Returning to FIG. 6, the extension portion C124 is a portion that extends from the first portion C121 to the other side in the third direction. The extension portion C124 is a portion that narrows the gap between the first scanning lens 60YM arranged in the opening F21 and the base portion C10. Specifically, as shown in FIG. 9, the first scanning lens 60YM is pressed and fixed by the extension portion C124 via the sponge SP in a state where the first scanning lens 60YM is inserted into the opening F21 of the first surrounding wall F20. The sponge SP fills the gap between the extension portion C124 and the first scanning lens 60YM.

[0077] Returning to FIG. 6, the fourth wall C14 is a wall perpendicular to the third direction. The fourth wall C14 extends from the base portion C10 to the other side in the first direction. As shown in FIG. 11, when the cover C1 is attached to the frame F, the fourth wall C14 overlaps with the second surrounding wall F30. When the cover C1 is attached to the frame F, the fourth wall C14, together with the second surrounding wall F30, separates the accommodation chamber LS of the deflector 50 in the first recess CP1 from a space in which the second scanning lenses 70C and 70K corresponding to cyan and black are arranged.

[0078] Returning to FIG. 6, the fourth wall C14 has an extension C144. The extension C144 is a portion that extends to the other side in the third direction. The extension C144 has the same function as the extension C124. That is, the extension C144 presses the first scanning lens 60CK arranged in the opening F31 of the second surrounding wall F30 via a sponge SP (not shown).

[0079] The engagement portion C15 is a portion that engages with the frame F when the cover C1 is attached to the frame F. The engagement portions C15 are provided at two locations on one end of the base portion C10 in the third direction and at two locations on the other end. Each engagement portion C15 extends from the base portion C10 toward the other end in the first direction. Each engagement portion C15 has a rectangular engagement hole, and when the cover C1 is attached to the frame F, the first claw F431 and the second claw F441 engage with each engagement hole. The engagement portion C15 also serves as a guide that guides the frame F to the attachment position when the cover C1 is attached to the frame F.

[0080] The base portion C10 is provided with four slits C16. The slits C16 are elongated and extend in the second direction. The beam emitted from the second scanning lens 70 passes through the slits C16. A transparent plate may be fitted in the slits C16.

[0081] 9, the cover C1 covers the opening of the frame F from one side in the first direction. That is, the cover C1 covers the polygon mirror 51 from the side opposite to the base wall Fb1.

[0082] Next, a description will be given of some steps in assembling the scanning optical device 1. Here, a process of attaching the cover C1 to the frame F after the second scanning lens 70 is attached to the frame F will be described.

[0083] When assembling the scanning optical device 1, the four second scanning lenses 70 are attached to the frame F as shown in FIG. 4 from a state in which the second scanning lenses 70 are not attached as shown in FIG. 5. In this case, the distance between the second scanning lens 70M and the first surrounding wall F20 is very narrow, but by inserting a finger, a jig, a robot arm, or the like into the first notch F22, the end region of the second scanning lens 70M can be easily grasped and the second scanning lens F70M can be attached to the frame F. In addition, the position can be adjusted by inserting a shim between the second scanning lens F70M and the frame F. Similarly, the distance between the second scanning lens 70K and the fourth side wall F44 is also very narrow, but by inserting a finger, a jig, a robot arm, or the like into the second notch F442, the second scanning lens 70K can be easily grasped and the second scanning lens F70K can be attached to the frame F. In addition, the position can be adjusted by inserting a shim between the second scanning lens 70K and the frame F.

[0084] 8, after the four second scanning lenses 70 are attached to the frame F, the cover C1 is attached to the frame F. Since the tip of the boss F50 protrudes furthest from the frame F to one side in the first direction, when the cover C1 is brought closer to the frame F, the tube portion C11 of the cover C1 first comes into contact with the tip of the boss F50. At this time, the second wall C12 is not in contact with the first surrounding wall F20.

[0085] After the cylindrical portion C11 engages with the boss F50, when the cover C1 is further moved closer to the frame F, the tips of the four engagement portions C15 of the cover C1 come into contact with the third side wall F43 and the fourth side wall F44. The four engaging portions C15 contact the third side wall F43 and the fourth side wall F44 to determine the orientation of the cover C1 around an axis parallel to the rotation axis X1. The four engaging portions C15 guide the cover C1 to the attachment position while maintaining the orientation of the cover C1 in a predetermined direction.

[0086] When the cover C1 is moved to the mounting position, the first claws F431 and the second claws F441 enter the respective engagement holes of the engagement portion C15, so that the cover C1 does not easily come off the frame F.

[0087] As described above, the following effects can be obtained in this embodiment. In this embodiment, a first surrounding wall F20, a second surrounding wall F30, a third surrounding wall F45, and a fourth surrounding wall F46 are provided in the frame F to surround the accommodation chamber LS of the deflector 50. The first surrounding wall F20 has a first notch F22 to facilitate assembly of the second scanning lens 70 to the frame F. In this embodiment, when the cover C1 is attached to the frame F, the second wall C12 of the cover C1 covers the entire first notch F22 of the frame F when viewed from the third direction, so that dust is less likely to enter the accommodation chamber LS of the deflector 50 through the first notch F22, and therefore, adhesion of dust to the polygon mirror 51 can be suppressed.

[0088] 11, the second wall C12 has a first portion C121 and a second portion C122, and the first portion C121 and the second portion C122 are located on both sides of the first surrounding wall F20. This makes the path along which dust enters the housing chamber LS of the deflector 50 complicated. As a result, dust is less likely to enter the housing chamber LS of the deflector 50 through the first notch F22, and adhesion of dust to the polygon mirror 51 can be suppressed.

[0089] The second wall C12 further includes a rib C123 connecting the first portion C121 and the second portion C122, and at least a portion of the rib C123 is located in the first notch F22. This increases the rigidity of the first portion C121 and the second portion C122, and improves the dimensional accuracy of the gap between the first portion C121 and the second portion C122. As a result, dust is less likely to enter the housing chamber LS of the deflector 50 through the first notch F22, and dust can be prevented from adhering to the polygon mirror 51.

[0090] Furthermore, the first cutout F22 exposes a portion of the second scanning lens 70, which facilitates attachment of the second scanning lens 70 to the frame F. For example, when attaching the second scanning lens 70 to the frame F, the attachment work can be facilitated by inserting fingers, a jig, a robot arm, or the like that holds the second scanning lens 70 into the first cutout F22.

[0091] Furthermore, since the first scanning lens 60YM closes the opening F21 of the first surrounding wall F20, dust is less likely to enter the accommodation chamber LS of the deflector 50 through the opening F21, and adhesion of dust to the polygon mirror 51 can be suppressed.

[0092] Furthermore, when the cover C1 is attached to the frame F, the boss F50 of the frame F and the cylindrical portion C11 of the cover C1 engage with each other to guide the cover C1 to the attachment position on the frame F. This makes it easy to attach the cover C1 to the frame F.

[0093] In addition, by engaging the engaging portion C15 of the cover C1 with the frame F, the cover C1 can be easily attached to the frame F in the correct position.

[0094] In addition, the third wall C13 provided on the cover C1 covers the entire second notch F442 of the frame F, making it difficult for dust to enter the frame F through the second notch F442, and preventing dust from adhering to the scanning optical system Lo.

[0095] Furthermore, the second cutout F442 exposes a portion of the second scanning lens 70 to the outside of the frame F, which facilitates attachment of the second scanning lens 70 to the frame F. For example, when attaching the second scanning lens 70 to the frame F, the attachment work can be facilitated by inserting fingers, a jig, a robot arm, or the like that holds the second scanning lens 70 into the second cutout F442.

[0096] The present invention is not limited to the above-described embodiment, but can be used in various forms as exemplified below.

[0097] In the above embodiment, the frame F has a boss F50 extending in the first direction, and the cover C1 has a tubular portion C11 into which the boss F50 fits, but the cover C1 may have a boss extending in the first direction, and the frame F may have a tubular portion into which the boss fits.

[0098] In the above embodiment, a scanning optical device applied to a color image forming apparatus has been exemplified, but the scanning optical device may be applied to a monochrome image forming apparatus that scans with only one beam.

[0099] The elements described in the above-mentioned embodiment and modified examples may be implemented in any combination. [Explanation of symbols]

[0100] 1. Scanning optical device 10 Semiconductor laser 20 Coupling Lens 40 Condenser Lens 50 Deflector 51 Polygon Mirror 60CK 1st scanning lens 60YM 1st scanning lens 70 Second scanning lens C1 Cover C10 Base C11 Cylinder part C12 2nd wall C121 Part 1 C122 2nd part C13 3rd wall C14 4th wall C15 Engagement part F Frame Fb1 Base Wall F20 First Enclosure Wall F21 aperture F22 First notch F30 Second Enclosure Wall F40 Exterior F41 1st side wall F42 2nd side wall F43 3rd side wall F44 4th side wall F442 Second notch F50 Boss

Claims

1. A semiconductor laser; a coupling lens that converts the light emitted from the semiconductor laser into a beam; a deflector that deflects the beam that has passed through the coupling lens in a main scanning direction, the deflector having a polygon mirror that is rotatable about a rotation axis that extends in a first direction; a scanning optical system that forms an image of the beam deflected by the deflector on a surface to be scanned; a frame having a base wall on which the deflector is mounted; a cover that covers the deflector from an opposite side to the base wall, the frame includes a first wall extending in a direction from the base wall toward the cover, the first wall having an opening through which a beam traveling from the deflector toward the scanning optical system passes, and a first notch disposed away from the opening in a second direction parallel to the main scanning direction; The scanning optical device according to claim 1, wherein the cover has a second wall that covers the entirety of the first cutout when viewed from a third direction perpendicular to the first direction and the second direction.

2. 2. The scanning optical device according to claim 1, wherein at least a portion of the second wall is located between the first wall and the deflector in the third direction.

3. 2. The scanning optical device according to claim 1, wherein the first wall is located between at least a portion of the second wall and the deflector in the third direction.

4. The second wall is a first portion located between the first wall and the deflector in the third direction; a second portion located away from the first portion in the third direction, 2. The scanning optical device according to claim 1, wherein the first wall is located between the first portion and the second portion in the third direction.

5. 5. The scanning optical device according to claim 4, wherein the first portion has a dimension in the first direction larger than that of the second portion.

6. The second wall further includes a rib connecting the first portion and the second portion, 5. The scanning optical device according to claim 4, wherein at least a portion of the rib is located within the first notch.

7. the scanning optical system includes a first scanning lens and a second scanning lens located downstream of the first scanning lens in a traveling direction of the beam, When viewed from the third direction, the first wall overlaps with the second scanning lens, 2 . The scanning optical device according to claim 1 , wherein, when viewed from the third direction, the first cutout overlaps with an end region of the second scanning lens that is distant from a center of the second scanning lens in the second direction.

8. 8. The scanning optical device according to claim 7, wherein the first scanning lens is disposed so as to cover the opening.

9. The frame and the cover are one of the bosses extending in the first direction; 2. The scanning optical device according to claim 1, wherein the other of the two frames has a cylindrical portion into which the boss is inserted when the cover is attached to the frame.

10. the frame has an outer wall extending in the first direction and surrounding the scanning optical system; 2. The scanning optical device according to claim 1, wherein the cover has an engagement portion that engages with the frame when the cover is attached to the frame.

11. The outer wall has a second notch, 11. The scanning optical device according to claim 10, wherein the cover has a third wall that covers the entire second cutout when viewed from the third direction.

12. the scanning optical system includes a first scanning lens and a second scanning lens located downstream of the first scanning lens in a traveling direction of the beam, When viewed from the third direction, the outer wall overlaps with the second scanning lens, 12. The scanning optical device according to claim 11, wherein, when viewed from the third direction, the second cutout overlaps with an end region of the second scanning lens that is distant from a center of the second scanning lens in the second direction.

Images