Optical scanning device and image forming device

Abstract

To suppress expansion of an Fθ lens due to heat.SOLUTION: An optical scanning device includes: a light source emitting a beam; a polygon mirror reflecting the beam emitted from the light source; an Fθ lens where the beam reflected by the polygon mirror enters; a housing having a bottom part on which the Fθ lens is installed; a heater part provided on a lower side of the bottom part; and a thermal diffusion member provided between the bottom part and the heater part, having heat conductivity higher than that of the housing and diffusing heat from the heater part. The bottom part includes: a first area provided with the Fθ lens; and a second area adjacent to the first area and provided with the thermal diffusion member, where the first area includes a thermal diffusion suppressing part suppressing heat transfer from the thermal diffusion member to the Fθ lens.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present disclosure relates to an optical scanning device and an image forming apparatus. [Background technology]

[0002] Patent Document 1 discloses an optical scanning device having a housing provided with a first Fθ lens that collects reflected light from a polygon mirror, a thermal expansion suppressing plate provided opposite the back surface of the bottom plate of the housing, and a heater provided opposite the thermal expansion suppressing plate. According to Patent Document 1, when electricity is applied to the heater, condensation inside the housing is prevented, and the thermal expansion suppressing plate provided opposite the back surface of the housing can suppress expansion of the housing due to heat from the heater. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-223833 Summary of the Invention [Problem to be solved by the invention]

[0004] According to the optical scanning device disclosed in Patent Document 1, a thermal expansion suppression plate is provided below the first Fθ lens via the bottom plate of the housing. Therefore, if heat from the heater is transmitted to the first Fθ lens via the thermal expansion suppression plate, the first Fθ lens may expand, causing a slight shift in the direction of light focused and transmitted by the first Fθ lens. The present disclosure aims to provide an optical scanning device and an image forming apparatus in which the transmission of heat from the heater to the Fθ lens is suppressed, thereby suppressing thermal expansion of the Fθ lens. [Means for solving the problem]

[0005] An optical scanning device according to one aspect of the present disclosure comprises a light source that emits a beam, a polygon mirror that reflects the beam emitted from the light source, an Fθ lens onto which the beam reflected by the polygon mirror is incident, a housing having a bottom on which the Fθ lens is installed, a heater unit provided below the bottom, and a heat diffusion member provided between the bottom and the heater unit, having a higher thermal conductivity than the housing, and diffusing heat from the heater unit, wherein the bottom includes a first region in which the Fθ lens is installed and a second region adjacent to the first region in which the heat diffusion member is installed, and the first region includes a heat diffusion suppression member that suppresses the transfer of heat from the heat diffusion member to the Fθ lens. [Effects of the Invention]

[0006] According to the optical scanning device and image forming apparatus according to an aspect of the present disclosure, the heat transfer from the heater unit to the Fθ lens is suppressed, thereby suppressing thermal expansion of the Fθ lens. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a cross-sectional view showing the configuration of an image forming apparatus including an optical scanning device according to an embodiment. [Figure 2] FIG. 2 is a perspective view of the optical scanning device according to the embodiment, seen obliquely from above. [Figure 3] FIG. 3 is a plan view of the bottom surface of the optical scanning device according to the embodiment. [Figure 4] FIG. 4 is a perspective view of the optical scanning device according to the embodiment with the cover removed, viewed obliquely from above. [Figure 5] FIG. 5 is a plan view of the optical scanning device according to the embodiment when cut parallel to the XY plane so that the polygon mirror is exposed. [Figure 6] FIG. 6 is a perspective view of the optical scanning device shown in FIG. 5 as seen obliquely from above. [Figure 7] 7 is a cross-sectional view of the optical scanning device taken along the A1-A1 line in FIG. [Figure 8]8 is a perspective view of the optical scanning device when cut along the A1-A1 cutting line in FIG. 5 and viewed obliquely from above. [Figure 9] FIG. 9 is a perspective view of the optical scanning device 10 cut along the A1-A1 cutting line in FIG. 5, seen from obliquely below. [Figure 10] FIG. 10 is a perspective view of the optical scanning device according to the embodiment when the heater cover is removed, as viewed obliquely from below. [Figure 11] FIG. 11 is a plan view of the bottom surface of the optical scanning device according to the embodiment with the heater unit removed. [Figure 12] FIG. 12 is a plan view of the bottom surface of an optical scanning device according to a modified example of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] [Embodiment] Hereinafter, the present embodiment will be described with reference to the drawings. In the drawings, identical or equivalent elements are designated by the same reference numerals, and duplicate explanations will be omitted. Note that the present embodiment described below does not unduly limit the content described in the claims. Furthermore, not all of the configurations described in the present embodiment are necessarily essential components of the present disclosure.

[0009] 1 is a cross-sectional view showing the configuration of an image forming apparatus 100 including an optical scanning device 1 according to an embodiment. In the following drawings, the main scanning direction is defined as the X direction, the sub-scanning direction (width direction) perpendicular to the main scanning direction is defined as the Y direction, and the height direction perpendicular to the XY plane is defined as the Z direction.

[0010] For example, the image forming apparatus 100 is an apparatus having an image forming function for forming color or monochrome images and a printing function for printing the formed images. The image forming apparatus 100 may be a printer, a printer with a scanner function, or a multifunction peripheral (MFP) having various functions including an image forming function and a printing function. In this embodiment, the image forming apparatus 100 will be described as an MFP, for example. For example, the image forming apparatus 100 has a printing function for forming color or monochrome images and printing the formed color or monochrome images on a document. The types of colors used by the image forming apparatus 100 when printing color images are not limited, but may include, for example, black (Bk), cyan (Cy), magenta (Mg), and yellow (Ye). The image forming apparatus 100 may also print monochrome images on a document using a single color (e.g., black).

[0011] For example, the image forming apparatus 100 includes an apparatus main body 101 and an apparatus cover 102 attached to the apparatus main body 101 so as to be openable and closable. For example, the apparatus cover 102 includes a transport unit 102a for transporting documents. For example, the apparatus main body 101 includes an image reading device 110, a feed tray 120, multiple transport rollers, an optical scanning device 10, image forming stations Pa, Pb, Pc, and Pd, an intermediate transfer belt 151, a belt cleaning device 152, a secondary transfer device 153, a fixing device 154, and an output tray 170. The multiple transport rollers can be referred to as an original transport mechanism for transporting documents, and include, for example, a pickup roller 131, a transport roller 132, a registration roller 133, and an output roller 134. As will be described later, the optical scanning device 10 and the image forming stations Pa, Pb, Pc, and Pd may be referred to as an image forming mechanism because they are mechanisms for forming toner images (images for printing) to be transferred (printed) onto an original. Also, the intermediate transfer belt 151, the belt cleaning device 152, the secondary transfer device 153, and the fixing device 154 may be referred to as a printing mechanism because they are mechanisms for printing by transferring the toner images (images for printing) formed by the image forming mechanism onto an original.

[0012] Although not shown, the apparatus main body 101 has an operation unit which is an input interface that accepts input operations from the user, a control unit that comprehensively controls the operation of the image forming apparatus 100, and a storage unit that stores various data. For example, the control unit can be configured using a processor such as a CPU (Central Processing Unit) and RAM. For example, the storage unit can be configured using a hard disk drive or non-volatile memory such as flash memory, and stores various data and programs.

[0013] The image reading device 110 reads an image on a document placed on the image reading device 110 and stores image data representing the read image in a storage unit (not shown). The document placed on the image reading device 110 may be transported by the transport unit 102a and placed on the image reading device 110, or may be placed directly on the image reading device 110 by a user. The feed tray 120 stores documents before printing. The feed tray 120 is provided in the device main body 101 so as to be removable, for example.

[0014] The image forming stations Pa, Pb, Pc, and Pd form toner images (images) by transferring them onto the surface of the intermediate transfer belt 151. Each of the image forming stations Pa, Pb, Pc, and Pd is provided for a different color used when the image forming apparatus 100 prints an image. For example, the image forming stations Pa, Pb, Pc, and Pd are arranged in this order in the sub-scanning direction (Y direction). For example, the image forming station Pa transfers a yellow toner image, the image forming station Pb transfers a magenta toner image, the image forming station Pc transfers a cyan toner image, and the image forming station Pd transfers a black toner image. Note that if the image forming apparatus 100 prints only monochrome images rather than color images, only one of the image forming stations Pa, Pb, Pc, and Pd may be provided.

[0015] Each of the image forming stations Pa, Pb, Pc, and Pd includes a developing device 141, a photosensitive drum 142, a drum cleaning device 143, and a charger 144. At each of the image forming stations Pa, Pb, Pc, and Pd, a toner image is formed as follows: The drum cleaning device 143 removes and collects residual toner from the surface of the photosensitive drum 142. The charger 144 then uniformly charges the surface of the photosensitive drum 142 to a predetermined potential. The charged surface of the photosensitive drum 142 is then exposed to light from the optical scanning device 10 (details of which will be described later), forming an electrostatic latent image on the surface of the photosensitive drum 142. The developing device 141 then develops the electrostatic latent image formed on the surface of the photosensitive drum 142. As a result, a toner image of each color is formed on each of the photosensitive drums 142 included in each of the image forming stations Pa, Pb, Pc, and Pd.

[0016] The intermediate transfer belt 151 is provided so as to come into contact with the surface of each photosensitive drum 142 provided in each of the image forming stations Pa, Pb, Pc, and Pd. The intermediate transfer belt 151 moves in a circular motion in the direction of arrow C. As a result, the toner images of each color formed on the surface of each photosensitive drum 142 provided in each of the image forming stations Pa, Pb, Pc, and Pd are sequentially transferred onto the surface of the intermediate transfer belt 151. In this way, a color toner image is formed on the surface of the intermediate transfer belt 151. Then, the toner image formed on the surface of the intermediate transfer belt 151 is transferred onto the surface of a document that is transported so as to come into contact with the surface of the intermediate transfer belt 151.

[0017] The belt cleaning device 152 cleans the surface of the intermediate transfer belt 151. The belt cleaning device 152 comes into contact with the surface of the intermediate transfer belt 151 at a position downstream of the position where the intermediate transfer belt 151 transfers a toner image onto a document, in the direction of arrow C, where the intermediate transfer belt 151 moves around. In this way, the belt cleaning device 152 removes and collects residual toner on the surface of the intermediate transfer belt 151.

[0018] The secondary transfer device 153 has a transfer roller 153a. The transfer roller 153a is disposed opposite the surface of the intermediate transfer belt 151 so as to form a nip area between the transfer roller 153a and the intermediate transfer belt 151. A document (an unprinted document) transported to contact the transfer roller 153a through a substantially S-shaped document transport path R1 (a transport path for documents after being discharged from the feed tray 120 to the discharge tray 170) is sandwiched in the nip area between the transfer roller 153a and the intermediate transfer belt 151 and transported therethrough, whereby the toner image formed on the surface of the intermediate transfer belt 151 is transferred onto the document. Thereafter, the document (the document to which the toner image has been transferred) that has passed through the nip area between the transfer roller 153a and the intermediate transfer belt 151 is transported to the fixing device 17.

[0019] The fixing device 154 has a heating roller 154a and a pressure roller 154b. The document onto which the toner image has been transferred by the transfer roller 153a and the intermediate transfer belt 151 is sandwiched between the heating roller 154a and the pressure roller 154b and heated and pressurized. This fixes the toner image transferred onto the document. In other words, printing of the image on the surface of the document is completed.

[0020] The document transport path R1 is provided with a plurality of rollers, in this order: pickup roller 131, transport roller 132, registration roller 133, the above-mentioned intermediate transfer belt 151 and transfer roller 153a, the above-mentioned heating roller 154a and pressure roller 154b, and discharge roller 134. Pickup roller 131 is provided adjacent to feed tray 120, and is the roller located closest to feed tray 120 (located farthest from discharge tray 170) among the plurality of rollers. Discharge roller 134 is provided adjacent to discharge tray 170, and is the roller located closest to discharge tray 170 (located farthest from discharge tray 170) among the plurality of rollers.

[0021] An unprinted document stored in the feed tray 120 is picked up from the feed tray 18 by the pickup roller 131 and transported along the document transport path R1 by the transport rollers 132 and the registration rollers 133. The document discharged from the registration rollers 133 is transported between the intermediate transfer belt 151 and the transfer roller 153a and between the heating roller 154a and the pressure roller 154b, and is discharged to the discharge tray 170 via the discharge rollers 134.

[0022] The registration rollers 133 are provided in a position immediately upstream of the intermediate transfer belt 151 and transfer rollers 153a, which transfer the toner image onto the document, in the document transport path R1. The registration rollers 133 then temporarily stop the document before discharging it onto the intermediate transfer belt 151 and transfer rollers 153a, aligning the leading edges of the document. After temporarily stopping the document, the registration rollers 133 transport the document in accordance with the timing of the transfer of the toner image in the nip area between the intermediate transfer belt 151 and transfer rollers 153a. The transport rollers 132 encourage the transport of the document from the pickup roller 131 to the registration rollers 133.

[0023] Next, the outline of the external structure of the optical scanning device 10 provided in the image forming apparatus 100 will be described mainly with reference to Figures 2 and 3. Figure 2 is a perspective view of the optical scanning device 10 according to the embodiment, seen obliquely from above. Figure 3 is a plan view of the bottom surface of the optical scanning device 10 according to the embodiment.

[0024] The optical scanning device 10 includes an optical scanning device main body 15 and a heater unit 30. The optical scanning device main body 15 includes a housing 20, a heat diffusion plate (heat diffusion member) 40, and a duct sheet 57. For example, the housing 20 can be formed using resin. However, the material for forming the housing 20 is not limited to resin and may be other materials. The housing 20 includes a bottom 21, a lid 22, a first side 23, a second side 24, a third side 25, and a fourth side 26. The lid 22 is disposed opposite the bottom 21. The planar shapes of the bottom 21 and the lid 22 can be, for example, rectangular, but are not limited to rectangular. The first side 23, the second side 24, the third side 25, and the fourth side 26 are each provided on an end of the bottom 21. The first side portion 23 and the second side portion 24 are arranged opposite each other, and the third side portion 25 and the fourth side portion 26 are arranged opposite each other. The second side portion 24 and the first side portion 23 are arranged side by side in this order in the main scanning direction (X direction). The third side portion 25 and the fourth side portion 26 are arranged side by side in this order in the sub-scanning direction (Y direction) so as to face each other.

[0025] The cover 22 is supported by its top on each of the first side 23, second side 24, third side 25, and fourth side 26. The cover 22 is formed with a plurality of through-holes 22a, 22b, 22c, and 22d, the longitudinal direction of which is the main scanning direction (X direction). The through-holes 22a, 22b, 22c, and 22d are arranged in this order in the sub-scanning direction (Y direction). Light from each of a plurality of light sources provided within the housing 20 (described later) passes through each of the through-holes 22a, 22b, 22c, and 22d and is emitted to each of the image forming stations Pa, Pb, Pc, and Pd. When the optical scanning device 10 is installed in the image forming apparatus 100 (see Figure 1), for example, the through hole 22a is positioned opposite the image forming station Pa, the through hole 22b is positioned opposite the image forming station Pb, the through hole 22c is positioned opposite the image forming station Pc, and the through hole 22d is positioned opposite the image forming station Pd.

[0026] Each of the through holes 22a, 22b, 22c, and 22d is covered with a protective cover 22g made of transparent glass or the like to prevent dust from entering the housing 20.

[0027] The heater unit 30 is provided outside the housing 20, below the bottom 21 of the housing 20. The heater unit 30 extends along the main scanning direction (X direction). The heater unit 30 applies heat to the inside of the housing 20 through the housing 20 in order to suppress condensation from forming inside the housing 20. The heater unit 30 has a heater section 31 (see FIG. 7, etc.) inside that generates heat.

[0028] The heat diffusion plate 40 is provided between the bottom 21 of the housing 20 and the heater unit 30. The heat diffusion plate 40 diffuses heat from the heater unit 30. The duct sheet 57 is provided below the bottom 21 of the housing 20 and next to the heat diffusion plate 40. The duct sheet 57 is provided below the polygon mirror unit 50 (see FIG. 7, etc.) described below, and protects the polygon mirror unit 50 from below. The bottom 21 of the housing 20 has a shape that prevents excessive diffusion of heat from the heat diffusion plate 40. The bottom 21, the heat diffusion plate 40, etc. will be described in detail later.

[0029] Next, various optical components and the like provided inside the optical scanning device 10 will be described mainly with reference to FIGS. 4 to 7. FIG. 4 is a perspective view of the optical scanning device 10 according to the embodiment, with the cover 22 removed, viewed obliquely from above. FIG. 5 is a plan view of the optical scanning device 10 according to the embodiment, cut parallel to the XY plane so that the polygon mirror 51 is exposed. FIG. 6 is a perspective view of the optical scanning device 10 shown in FIG. 5, viewed obliquely from above. FIG. 7 is a cross-sectional view of the optical scanning device 10 cut along the A1-A1 line in FIG. 5. Note that the heater unit 30 is not shown in FIGS. 5 and 6.

[0030] The heater unit 30 has a heater section 31 that generates heat when powered, and a heater cover 32 that covers the periphery of the heater section 31. The heater section 31 is provided below the bottom section 21 of the housing 20. The heater section 31 extends, for example, along the main scanning direction, and is provided so as to face the heat diffusion plate 40 at a distance from it, with the heater cover 32 interposed therebetween.

[0031] The optical scanning device main body 15 of the optical scanning device 10 has a polygon mirror unit 50, a polygon mirror mounting plate 55, a plurality of light sources 61a, 61b, 61c, and 61d, a plurality of collimator lenses 62a, 62b, 62c, and 62d, a plurality of first mirrors 63a, 63b, 63c, and 63d, a cylindrical lens 64, a second mirror 65, an Fθ first lens (Fθ lens) 71, a plurality of Fθ second lenses 72a, 72b, 72c, and 72d, reflecting mirrors 73a1 and 73a2, reflecting mirrors 73b1, 73b2, and 73b3, reflecting mirrors 73c1 and 73c2, and a reflecting mirror 73d, etc. The polygon mirror unit 50 has a polygon mirror (deflector) 51, a base portion 52, and a shaft portion G. The polygon mirror 51 rotates around a shaft G as the center of rotation. The polygon mirror 51 and the shaft G are attached to a base 52. The base 52 is installed on the surface of a polygon mirror mounting plate 55. For example, the base 52 is fixed to the polygon mirror mounting plate 55 using screws or the like.

[0032] Of the optical components provided within the housing 20, the multiple collimator lenses 62a, 62b, 62c, and 62d, the multiple first mirrors 63a, 63b, 63c, and 63d, the cylindrical lens 64, and the second mirror 65 are each installed on the bottom 21 of the housing 20, and may be referred to as incident optical components for guiding the beams emitted from the multiple light sources 61a, 61b, 61c, and 61d to the polygon mirror 51. Furthermore, among the optical components provided within the housing 20, the Fθ first lens 71, the multiple Fθ second lenses 72a, 72b, 72c, and 72d, the reflecting mirrors 73a1 and 73a2, the reflecting mirrors 73b1, 73b2, and 73b3, the reflecting mirrors 73c1 and 73c2, and the reflecting mirror 73d may also be referred to as imaging optical components that guide the beam reflected by the polygon mirror to the respective photosensitive drums 142 of the image forming stations Pa, Pb, Pc, and Pd (see Figure 1).

[0033] Each of the plurality of light sources 61a, 61b, 61c, and 61d may be, for example, a semiconductor laser element capable of emitting a semiconductor laser beam. The plurality of collimator lenses 62a, 62b, 62c, and 62d convert the beam emitted from each of the plurality of light sources 61a, 61b, 61c, and 61d into parallel light. Collimator lens 62a is arranged to face light source 61a, collimator lens 62b is arranged to face light source 61b, collimator lens 62c is arranged to face light source 61c, and collimator lens 62d is arranged to face light source 61d.

[0034] Of the multiple first mirrors 63a, 63b, 63c, and 63d, the first mirrors 63a, 63b, and 63c reflect the parallel light from the multiple light sources 61a, 61b, and 61c that has passed through the collimator lenses 62a, 62b, and 62c, respectively, to the first mirror 63d. The first mirror 63d reflects the reflected light from the multiple first mirrors 63a, 63b, and 63c, respectively, to the cylindrical lens 64. Furthermore, the light from the light source 61d that has passed through the collimator lens 62d passes above the first mirror 63c and enters the cylindrical lens 64.

[0035] The cylindrical lens 64 converges the light reflected by each of the first mirrors 63a, 63b, 63c, and 63d and the beam from the light source 61d that has passed through the collimator lens 62d to be parallel to the sub-scanning direction, and transmits the converged light to the second mirror 65. The second mirror 65 focuses the beam that has passed through the cylindrical lens 64 and is parallel to the sub-scanning direction onto the reflecting surface of the polygon mirror 51.

[0036] The polygon mirror 51 reflects the beams emitted from the multiple light sources 61a, 61b, 61c, and 61d. That is, the polygon mirror 51 rotates at high speed around an axis G as the center of rotation, and repeatedly deflects the beams reflected by the second mirror 65 in the main scanning direction (X direction) by reflecting them off each of its reflecting surfaces. The beams La, Lb, Lc, and Ld (see FIG. 7) reflected by each of the reflecting surfaces of the polygon mirror 51 pass through a common Fθ first lens 71. After that, the beam La is reflected by reflecting mirrors 73a1 and 73a2, passes through the Fθ second lens 72a, and is focused on the photosensitive drum 142 of the image forming station Pa (see FIG. 1), and the beam Lb is reflected by reflecting mirrors 73b1, 73b2, and 73b3, and is focused on the photosensitive drum 142 of the image forming station Pa (see FIG. 1). The beam Lc is reflected by the reflecting mirrors 73c1 and 73c2, passes through the Fθ second lens 72c, and is imaged on the photosensitive drum 142 of the image forming station Pc (see Figure 1), and the beam Ld is reflected by the reflecting mirror 73d, passes through the Fθ second lens 72d, and is imaged on the photosensitive drum 142 of the image forming station Pd (see Figure 1).

[0037] The beams La, Lb, Lc, and Ld reflected by the polygon mirror 51 are incident on the Fθ first lens 71. That is, the Fθ first lens 71 is installed on the bottom 21 of the housing 20 and extends in the main scanning direction (X direction). The Fθ first lens 71 is provided ahead of the beams La, Lb, Lc, and Ld reflected by the reflecting surface of the polygon mirror 51 in the traveling direction of the beams. The Fθ first lens 71 can be formed using, for example, resin, but the material used to form the Fθ first lens 71 is not limited to resin. The Fθ first lens 71 focuses and transmits each of the beams La, Lb, Lc, and Ld reflected by the reflecting surface of the polygon mirror 51 to a predetermined beam diameter on the surface of the photosensitive drum 142 (see FIG. 1). Furthermore, the first Fθ lens 71 converts each of the beams La, Lb, Lc, and Ld deflected at a constant angular velocity in the main scanning direction by the polygon mirror 51 so that they move at a constant velocity along the main scanning direction on the surface of each photosensitive drum 142. As a result, the beams La, Lb, Lc, and Ld repeatedly scan the surface of each photosensitive drum 142 along the main scanning direction.

[0038] Reflecting mirrors 73a1 and 73a2, reflecting mirrors 73b1, 73b2, and 73b3, reflecting mirrors 73c1 and 73c2, and reflecting mirror 73d extend in the main scanning direction (X direction) and are installed, for example, on bottom 21 of housing 20, or are installed within housing 20 away from bottom 21, with one end of each supported by the inner wall of third side portion 25 and the other end supported by the inner wall of fourth side portion 26, for example.

[0039] The reflecting mirror 73a1 and the reflecting mirror 73a2 are arranged, in this order, ahead in the traveling direction of the optical path of the beam La that has passed through the Fθ first lens 71. The reflecting mirror 73a1 is arranged to reflect the beam La that has passed through the Fθ first lens 71 to the reflecting mirror 73a2, and the reflecting mirror 73a2 is arranged to reflect the beam La reflected from the reflecting mirror 73a1 to the Fθ second lens 72a. The reflecting mirrors 73b1, 73b2, and 73b3 are arranged, in this order, ahead in the traveling direction of the optical path of the beam Lb that has passed through the Fθ first lens 71. The reflecting mirror 73b1 is arranged to reflect the beam Lb that has passed through the Fθ first lens 71 to the reflecting mirror 73b2, the reflecting mirror 73b2 is arranged to reflect the beam Lb reflected from the reflecting mirror 73b1 to the reflecting mirror 73b3, and the reflecting mirror 73b3 is arranged to reflect the beam Lb reflected from the reflecting mirror 73b2 to the Fθ second lens 72b.

[0040] The reflecting mirror 73c1 and the reflecting mirror 73c2 are arranged, in this order, ahead in the traveling direction of the beam Lc that has passed through the Fθ first lens 71. The reflecting mirror 73c1 is arranged to reflect the beam Lc that has passed through the Fθ first lens 71 to the reflecting mirror 73c2, and the reflecting mirror 73c2 is arranged to reflect the beam Lc reflected from the reflecting mirror 73c1 to the Fθ second lens 72c. The reflecting mirror 73d is arranged ahead in the traveling direction of the beam Ld that has passed through the Fθ first lens 71. The reflecting mirror 73d is arranged to reflect the beam Ld that has passed through the Fθ first lens 71 to the Fθ second lens 72d.

[0041] The Fθ second lenses 72a, 72b, 72c, and 72d are lenses for guiding the beams La, Lb, Lc, and Ld to the photosensitive drums 142 of the image forming stations Pa, Pb, Pc, and Pd, respectively. Each of the Fθ second lenses 72a, 72b, 72c, and 72d extends in the main scanning direction (X direction) and is installed inside the housing 20 so that, for example, one end is supported by the inner wall of the third side portion 25 and the other end is supported by the inner wall of the fourth side portion 26. The Fθ second lens 72a faces the through hole 22a in the lid portion 22, the Fθ second lens 72b faces the through hole 22b in the lid portion 22, the Fθ second lens 72c faces the through hole 22c in the lid portion 22, and the Fθ second lens 72d faces the through hole 22d in the lid portion 22. Each of the Fθ second lenses 72a, 72b, 72c, and 72d can be formed using, for example, resin, but the material used to form each of the Fθ second lenses 72a, 72b, 72c, and 72d is not limited to resin. Each of the Fθ second lenses 72a, 72b, 72c, and 72d narrows the beams La, Lb, Lc, and Ld, which are parallel light mainly in the sub-scanning direction (Y direction), to a predetermined beam diameter (spot diameter) on the surface of each photosensitive drum 142, and transmits the beams through the surface of each photosensitive drum 142.

[0042] As described above, in the optical scanning device 10, each of the beams La, Lb, Lc, and Ld reflected and deflected by each reflective surface of the polygon mirror 51 travels along each optical path within the housing 20 and repeatedly scans the surface of each photosensitive drum 142 of each image forming station Pa, Pb, Pc, and Pd. Then, as each photosensitive drum 142 rotates, an electrostatic latent image is formed on the surface of each photosensitive drum 142.

[0043] Next, details of the bottom portion 21 of the housing 20, the heat diffusion plate 40, etc. will be described mainly with reference to FIGS.

[0044] FIG. 8 is a perspective view of the optical scanning device 10 when cut along the A1-A1 cutting line in FIG. 5, as viewed obliquely from above. FIG. 9 is a perspective view of the optical scanning device 10 when cut along the A1-A1 cutting line in FIG. 5, as viewed obliquely from below. FIG. 10 is a perspective view of the optical scanning device 10 when cut along the A1-A1 cutting line in FIG. 5, as viewed obliquely from below, according to an embodiment. FIG. 11 is a plan view of the bottom surface of the optical scanning device 10 when the heater unit 30 is removed, according to an embodiment. Note that the duct sheet 57 is not shown in FIGS. 8 to 11.

[0045] Here, of the two main surfaces of bottom portion 21, the surface inside housing 20 that faces lid portion 22 is referred to as first surface 21a, and the back surface opposite to the front surface is referred to as second surface 21b.

[0046] The bottom 21 is formed into various shapes according to the optical components provided in the housing 20. For example, the bottom 21 can be defined into three areas: a first area AR1, a second area AR2, and a third area AR3.

[0047] The first region AR1 is a region of the bottom 21 where the Fθ first lens 71 is provided so as to face the first surface 21a. For example, the Fθ first lens 71 is mounted on the first surface 21a in the first region AR1 via a connecting member. The Fθ first lens 71 may be in direct contact with the first surface 21a in the first region AR1, or may be disposed facing the first surface 21a in the first region AR1 at a distance. The second region AR2 is a region adjacent to the first region AR1, and is the region among the first region AR1, second region AR2, and third region AR3 that has the largest number of reflecting mirrors arranged side by side in the sub-scanning direction (Y direction) so as to face the first surface 21a. The third region AR3 is a region adjacent to the first region AR1 and located on the opposite side of the second region AR2 with respect to the first region AR1, where the polygon mirror 51 is provided. The third region AR3, the first region AR1, and the second region AR2 each extend in the main scanning direction (X direction) and are aligned in order in the sub-scanning direction (Y direction).

[0048] The third area AR3 of the bottom 21 includes a base 213a, which is a primarily flat portion, and a polygon mirror housing portion 213b, which is a convex portion protruding in the height direction (Z direction) from the first surface 21a of the base 213a. The polygon mirror housing portion 213b includes a side portion 231b1 erected on the first surface 21a of the base 213a and a plate-shaped upper portion 231b2 supported on the top of the side portion 231b1. The polygon mirror unit 50 mounted on the polygon mirror mounting plate 55 is housed in the internal space surrounded by the polygon mirror housing portion 213b. In other words, the polygon mirror housing portion 213b covers the polygon mirror unit 50. The edge portion of the polygon mirror mounting plate 55 is fixed to the second surface 21b of the base 213a around the polygon mirror housing portion 213b using screws or the like. As a result, the polygon mirror unit 50 is sealed in the space inside the polygon mirror mounting plate 55 and the polygon mirror accommodating portion 213b, and adhesion of dust and dirt to the reflective surfaces of the polygon mirror 51 is suppressed.

[0049] In addition, an opening 21h1 is formed in the side portion 231b of the polygon mirror housing portion 213b on the optical path of reflected light when the second mirror 65 reflects light that has passed through the cylindrical lens 64 onto the reflective surface of the polygon mirror 51. The opening 21h1 is covered with a protective cover 67a made of transparent glass or the like. As a result, when the second mirror 65 reflects light that has passed through the cylindrical lens 64, the reflected light passes through the protective cover 67a and the opening 21h1 and reaches each reflective surface of the polygon mirror 51.

[0050] Furthermore, an opening 21h2 extending in the main scanning direction is formed in the side portion 231b on the optical path along which the beams La, Lb, Lc, and Ld reflected by the reflective surfaces of the polygon mirror 51 reach the first Fθ lens 71. The opening 21h2 is covered with a protective cover 67b made of transparent glass or the like. As a result, the beams La, Lb, Lc, and Ld reflected by the reflective surfaces of the polygon mirror 51 reach the first Fθ lens 71 via the opening 21h2 and the protective cover 67b.

[0051] As described above, in the second region AR2 of the bottom 21, numerous reflective mirrors are arranged in a line in the sub-scanning direction so as to face the first surface 21a. For example, in this embodiment, of the eight reflective mirrors provided in the housing 20, six reflective mirrors are provided so as to face the first surface 21a in the second region AR2 of the bottom 21. Therefore, when the second surfaces 21b of the first region AR1, second region AR2, and third region AR3 of the bottom 21 are viewed in plan, the second region AR2 has the largest area. Therefore, a thermal diffusion plate 40 is provided in the second region AR2 of the bottom 21 so as to face the second surface 21b. This allows the area of ​​the thermal diffusion plate 40 to be larger than when the thermal diffusion plate 40 is provided only in regions other than the second region AR2. As a result, heat from the heater section 31 provided inside the heater unit 30 can be diffused in a planar manner by the heat diffusion plate 40 and efficiently conducted to the inside of the housing 20 via the second area AR2 in the bottom 21. This makes it possible to efficiently and more reliably prevent condensation from occurring on the optical components inside the housing 20.

[0052] Here, an Fθ first lens 71 is provided in a first region AR1 of the bottom 21 adjacent to the second region AR2 so as to face the first surface 21a. As described above, the Fθ first lens 71 is a lens through which the beams La, Lb, Lc, and Ld (see FIG. 7) reflected by the respective reflective surfaces of the polygon mirror 51 pass in common. Therefore, if the expansion of the Fθ first lens 71 increases due to heat or the like, positional deviations are likely to occur when the beams La, Lb, Lc, and Ld reach the photosensitive drum 142.

[0053] Therefore, in the optical scanning device 10, the first region AR1 of the bottom 21 includes a thermal diffusion suppression portion 211 having a shape that suppresses heat transfer from the thermal diffusion plate (thermal diffusion member) 40 to the Fθ first lens (Fθ lens) 71. The thermal diffusion suppression portion 211 is a region included in the first region AR1 of the bottom 21. By including the thermal diffusion suppression portion 211 that suppresses heat transfer from the thermal diffusion plate 40 to the Fθ first lens 71 in the first region AR1 of the bottom 21, heat transfer from the heater unit 31 to the Fθ first lens 71 via the thermal diffusion plate 40 can be suppressed compared to when the thermal diffusion suppression portion 211 is not provided. This suppresses expansion of the Fθ first lens 71 due to heat. As a result, it is possible to suppress deviation in the position of each of the beams La, Lb, Lc, and Ld that are reflected by the reflective surfaces of the polygon mirror 51 and transmitted through the Fθ first lens 71 when they reach the photosensitive drum 142.

[0054] The image forming apparatus 100 preferably includes an optical scanning device 10 and a photosensitive drum 142 that is exposed to light from the optical scanning device 10. This allows the photosensitive drum 142 to be exposed by the optical scanning device 10, in which thermal expansion of the Fθ first lens 71 is suppressed, thereby making it possible to obtain an image forming apparatus 100 that can form high-quality images.

[0055] For example, the diffusion suppression portion 211 has a shape that can suppress heat transfer. Next, specific examples of the shape of the thermal diffusion suppression portion 211 that suppresses heat transfer will be described. Examples of the shape of the thermal diffusion suppression portion 211 that suppresses heat transfer include a shape that makes the heat transfer path through the thermal diffusion suppression portion 211 longer than when the thermal diffusion suppression portion 211 is not provided, i.e., compared to a flat plate-like shape, or a shape that has an opening H1 (see FIG. 12) formed to release heat into the air. Specific examples will be described below.

[0056] For example, the thermal diffusion suppression portion 211 has a base 211a, which is a primarily flat portion on which the first Fθ lens 71 is provided on the first surface 21a, and protruding portions 211b and 211c that protrude downward (in the direction opposite to the height direction (Z direction)) from the second surface 21b of the base 211a. For example, the base 211a and the protruding portions 211b and 211c each extend such that the main scanning direction is their longitudinal direction. The protruding portion 211b contacts the second region AR2, and the protruding portion 211c contacts the third region AR3. The protruding portion 211b contacts an end 21e2 adjacent to the first region AR1, opposite an end 21e1 (the end farther from the first region AR1) that overlaps with the first side portion 23, of both end portions that extend in the main scanning direction in the first region AR1 of the bottom 21. The protrusion 211c contacts the end adjacent to the first region AR1 opposite the end overlapping with the second side 24 (the end farther from the first region AR1) of both end portions extending in the main scanning direction in the third region AR3 of the bottom 21.

[0057] As described above, the thermal diffusion suppression portion 211 includes at least one protrusion 211b / 211c, which is a rib protruding downward (in the direction opposite to the height direction (Z direction)) from the second surface 21b opposite the first surface 21a on which the first Fθ lens 71 is provided. This makes it possible to lengthen the transmission path within the first region AR1 of heat transferred from the thermal diffusion plate 40 to the first region AR1 via the second region AR2 of the bottom 21, and also to increase the surface area for heat dissipation within the first region AR1 of the bottom 21, compared to a case in which the first region AR1 of the bottom 21 does not include at least one protrusion 211b / 211c, i.e., compared to a case in which the first region AR1 of the bottom 21 has a flat, plate-like shape. Therefore, the at least one protrusion 211b / 211c can promote the dissipation of heat transferred from the second region AR2 within the first region AR1 of the bottom 21. As a result, the heat from the heater section 31 can be prevented from being transmitted to the first Fθ lens 71 via the heat diffusion plate 40.

[0058] The thermal diffusion suppression portion 211 may have only one protrusion (either one of the protrusions 211b and 211c) as the at least one protrusion 211b and 211c. However, from the viewpoint of improving the heat dissipation effect, it is preferable that the thermal diffusion suppression portion 211 has a plurality of protrusions 211b and 211c as the at least one protrusion.

[0059] Furthermore, it is preferable that the protrusion 211b protrudes downward (in the direction opposite to the height direction (Z direction)) from the second surface 21b in the second region AR2 of the bottom 21. This makes it possible to lengthen the transmission path within the protrusion 211b of the heat transferred from the heat diffusion plate 40 and the second region AR2 and increase the surface area for heat dissipation, compared to when the protrusion 211b does not protrude downward from the second surface 21b in the second region AR2. This further promotes the dissipation of heat transferred from the second region AR2 and further suppresses the transfer of heat from the heater unit 31 to the Fθ first lens 71 via the heat diffusion plate 40.

[0060] Furthermore, by configuring the protrusion 211b of the thermal diffusion suppression portion 211 adjacent to the second region AR2 of the bottom 21 to protrude downward beyond the second surface 21b in the second region AR2 of the bottom 21, when attaching the heat diffusion plate 40 so that it faces the second surface 21b in the second region AR2 of the bottom 21, the end of the heat diffusion plate 40 can be slid along the downwardly protruding protrusion 211b to determine the attachment position of the heat diffusion plate 40. By configuring the protrusion 211b to protrude downward beyond the second surface 21b in the second region AR2 of the bottom 21 in this manner, it can also function as a guide member when attaching the heat diffusion plate 40, thereby improving the efficiency of the work involved in attaching the heat diffusion plate 40.

[0061] In the thermal diffusion suppression portion 211, at least one of the protrusions 211b and 221c may protrude downward (in the direction opposite to the height direction (Z direction)) from the second surface 21b in the second region AR2 of the bottom portion 21.

[0062] Furthermore, the thermal diffusion suppression portion 211 preferably has a protruding shape such that the height of the first surface 21a, on which the first Fθ lens 71 is provided, is higher than the second region AR2 of the bottom portion 21. That is, the first surface 21a of the base 211a of the thermal diffusion suppression portion 211 is higher in the height direction (Z direction) than the first surface 21a in the second region AR2. In other words, the thermal diffusion suppression portion 211 has a shape in which the protruding portion 211b forms a side surface of a step, and the protruding portion 211b, the base 211a, and the protruding portion 211c protrude in the height direction. This makes it possible to lengthen the transmission path within the thermal diffusion suppression portion 211 of the heat transferred from the thermal diffusion plate 40 and the second region AR2, and also to increase the surface area for heat dissipation, compared to when the first surface 21a in the second region AR2 and the first surface 21a of the base 211a of the thermal diffusion suppression portion 211 are at the same height. This further promotes the dissipation of heat transmitted from the second region AR2, and further prevents heat from the heater section 31 from being transmitted to the Fθ first lens 71 via the heat diffusion plate 40.

[0063] Furthermore, when the heat diffusion plate 40 is viewed from the normal direction (when viewed in a plane in the Z direction), it is preferable that the heat diffusion plate 40 does not overlap with the heat diffusion suppression portion 211. In other words, it is preferable that the heat diffusion plate 40 is provided so as not to overlap with the first region AR1 but to overlap with the second region AR2 of the bottom portion 21. This makes it possible to suppress the heat from the heat diffusion plate 40 from being transferred directly to the heat diffusion suppression portion 211, and as a result, it is possible to more reliably suppress the heat from the heater unit 31 from being transferred to the first Fθ lens 71 via the heat diffusion plate 40.

[0064] The housing 20 also has a first side portion 23 erected at an end 21e1 of the second region AR2 of the bottom 21 that is far from the first region AR1. The heat diffusion plate 40 preferably extends across the second region AR2 to overlap the first side portion 23. This makes the heat diffusion plate 40 wider than when the heat diffusion plate 40 has an area that does not overlap the first side portion 23, allowing the heat diffusion plate 40 to diffuse heat from the heater unit 31 over a wider area. This allows heat to be transferred efficiently into the housing 20.

[0065] Furthermore, it is preferable that the thermal diffusion suppression portion 211 has a shape that extends along the direction in which the Fθ first lens 71 extends (X direction). In other words, it is preferable that the base portion 211a, the protruding portion 211b, and the protruding portion 211c each have a shape that extends along the direction in which the Fθ first lens 71 extends. This allows heat that has been transferred from the thermal diffusion plate 40 to the thermal diffusion suppression portion 211 via the second region AR2 of the bottom portion 21 to escape in the direction in which the thermal diffusion suppression portion 211 extends. As a result, it is possible to more reliably suppress the heat from the heater unit 31 from being transferred to the Fθ first lens 71 via the thermal diffusion plate 40.

[0066] Here, the heater unit 31 of the optical scanning device 10 is a heat source that generates heat when energized. The heat diffusion plate 40, which is disposed so as to overlap the heater unit 31, preferably contains, for example, a metal material having a higher thermal conductivity than the resin material when the housing 20 contains a resin material. This allows the heat diffusion plate 40 to efficiently diffuse the heat from the heater unit 31 across the surface and transfer it into the housing 20 via the second region AR2 of the bottom 21. As a result, condensation on the optical components inside the housing 20 can be efficiently suppressed.

[0067] As described above, the light emitted from the multiple light sources 61a, 61b, 61c, and 61d is collected on each of the common reflecting surfaces of the polygon mirror 51. Therefore, the temperature of the polygon mirror 51 rises due to the heat of the light from each light source, and therefore the polygon mirror 51 can also be called a heat source in the optical scanning device 10.

[0068] For this reason, when the housing 20 contains a resin material, for example, it is preferable that the polygon mirror mounting plate 55 on which the polygon mirror 51 is mounted contains a material with a higher thermal conductivity than the resin material, such as a metal material. This allows the heat of the polygon mirror 51 to be efficiently dissipated by the polygon mirror mounting plate 55. As a result, it is possible to prevent distortion and other problems caused by the polygon mirror 51 becoming too hot.

[0069] The thermal diffusion suppression portion 211 is preferably provided between the thermal diffusion plate 40 provided in the second region AR2 of the bottom portion 21 and the polygon mirror mounting plate 55 provided in the third region AR3 of the bottom portion 21. In other words, the thermal diffusion suppression portion 211 is provided to separate the thermal diffusion plate 40 from the polygon mirror mounting plate 55. This allows the thermal diffusion suppression portion 211 to lengthen the transmission path within the thermal diffusion suppression portion 211 for heat transmitted from the thermal diffusion plate 40 via the second region AR2 of the bottom portion 21 and heat transmitted from the polygon mirror mounting plate 55 via the third region AR3 of the bottom portion 21, and also increases the surface area for heat dissipation. This further promotes the dissipation of heat transmitted from the second region AR2. As a result, it is possible to suppress the transmission of heat from the polygon mirror 51, in addition to heat from the heater unit 31, to the Fθ first lens 71 via the polygon mirror mounting plate 55.

[0070] 12 is a plan view of the bottom surface of the optical scanning device 10 according to a modified example of the embodiment. As shown in FIG. 12, for example, an opening H1 may be formed in the thermal diffusion suppression portion 211. This allows heat transferred to the thermal diffusion suppression portion 211 via the second region AR2 of the bottom portion 21 to be dissipated into the air via the opening H1. This also makes it possible to prevent heat from the heater unit 31 from being transferred to the first Fθ lens 71 via the thermal diffusion plate 40.

[0071] The elements appearing in the above-described embodiments and modifications may be combined as appropriate within the scope of not causing any contradiction. [Explanation of symbols]

[0072] 1: optical scanning device, 10: optical scanning device, 15: optical scanning device main body, 20: housing, 21: bottom, 21a: first surface, 21b: second surface, 22: lid, 23: first side, 24: second side, 25: third side, 26: fourth side, 30: heater unit, 31: heater unit, 32: heater cover, 40: heat diffusion plate (heat diffusion member), 50: polygon mirror unit, 51: polygon mirror, 55: polygon mirror mounting plate, 61a to 61d: light source, 62a to 62d: collimator lenses, 63a to 63d: first mirror, 64: cylindrical lens, 65: second mirror, 71: Fθ first Lens (Fθ lens), 72a to 72d: Fθ second lens, 73a1 and 73a2: reflecting mirror, 73b1 to 73b3: reflecting mirror, 73c1 and 73c2: reflecting mirror, 73d: reflecting mirror, 100: image forming apparatus, 142: photosensitive drum, 211: heat diffusion suppression section, 211a: base, 211b: protruding section, 211c: protruding section, 213a: base, 213b: polygon mirror housing section, 221c: protruding section, 231b: side section, 231b1: side section, 231b2: upper section, AR1: first region, AR2: second region, AR3: third region, H1: opening, Pa to Pd: image forming station

Claims

1. a light source that emits a beam; a polygon mirror unit that reflects the beam emitted from the light source; an Fθ lens onto which the beam reflected by the polygon mirror unit is incident; a housing having a bottom on which the Fθ lens is installed, the bottom portion includes a first region in which the Fθ lens is provided and another region adjacent to the first region in which the polygon mirror unit is provided, and a heat diffusion suppression portion that is provided between the polygon mirror unit and the Fθ lens in the first region and that suppresses heat transfer from the polygon mirror unit to the Fθ lens, Further, a heater unit is provided below the bottom unit, the bottom portion includes a second region adjacent to the first region at a position separate from the other region and in which the heater portion is provided, the thermal diffusion suppression portion is provided between the Fθ lens provided in the first region and the heater portion provided in the second region, and between the Fθ lens provided in the first region and the polygon mirror unit provided in the other region, The optical scanning device, wherein the thermal diffusion suppression portion includes at least one protrusion protruding from a second surface opposite to a first surface on which the Fθ lens is provided.

2. The optical scanning device according to claim 1 , wherein the at least one protrusion protrudes downward from the second surface in the other region of the bottom portion.

3. The optical scanning device according to claim 1 , wherein the thermal diffusion suppression portion has a protruding shape such that the height of the first surface on which the Fθ lens is provided is higher than a part of the first region.

4. a polygon mirror mounting plate on which the polygon mirror unit is mounted and which is formed using a material having a higher thermal conductivity than the housing; 4. The optical scanning device according to claim 1, wherein the polygon mirror mounting plate does not overlap the heat diffusion suppressing portion when viewed from a normal direction of the polygon mirror mounting plate.

5. The optical scanning device according to claim 1 , wherein the thermal diffusion suppressing portion has a shape extending along a direction in which the Fθ lens extends.

6. In the second region, a heat diffusion member is provided between the bottom and the heater portion, the heat diffusion member has a higher thermal conductivity than the housing, and diffuses heat from the heater portion; The optical scanning device according to claim 1 , wherein the heat diffusion suppressing portion is provided between the heat diffusion member and the polygon mirror unit.

7. The optical scanning device according to claim 1 , wherein the heat diffusion suppressing portion has an opening formed therein.

8. a polygon mirror mounting plate on which the polygon mirror unit is mounted, The optical scanning device according to claim 1 , wherein the housing includes a resin material, and the polygon mirror mounting plate includes a metal material.

9. 9. An image forming apparatus comprising: the optical scanning device according to claim 1; and a photosensitive drum exposed to light from the optical scanning device.

Images