Optical Scanning Device and Image Forming Apparatus

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 Art

[0002] Patent Document 1 discloses an optical scanning device including a housing provided with an Fθ first lens that condenses reflected light from a polygon mirror, a thermal expansion suppression plate provided so as to face the back surface of the bottom plate of the housing, and a heater provided so as to face the thermal expansion suppression plate. According to Patent Document 1, when the heater is energized, condensation inside the housing can be prevented, and the housing can be suppressed from expanding due to heat from the heater by the thermal expansion suppression plate provided so as to face the back surface of the housing.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] According to the optical scanning device disclosed in Patent Document 1, a thermal expansion suppression plate also extends below the Fθ first lens via the bottom plate of the housing. Therefore, when heat from the heater is also transmitted to the Fθ first lens via the thermal expansion suppression plate, the direction of light condensed and transmitted by the Fθ first lens may be slightly shifted due to the expansion of the Fθ first lens. An object of the present disclosure is to provide an optical scanning device and an image forming apparatus in which expansion of the Fθ lens due to heat is suppressed by suppressing transmission of heat from the heater unit to the Fθ lens.

Means for Solving the Problems

[0005] An optical scanning device according to an aspect of the present disclosure includes a light source that emits a beam, a polygon mirror that reflects the beam emitted from the light source, an Fθ lens that receives the beam reflected by the polygon mirror, 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. The bottom includes a first region where the Fθ lens is provided and a second region adjacent to the first region where the heat diffusion member is provided, and the first region includes a heat diffusion suppression unit that suppresses the transfer of heat from the heat diffusion member to the Fθ lens.

Advantages of the Invention

[0006] According to the optical scanning device and the image forming apparatus according to an aspect of the present disclosure, by suppressing the transfer of heat from the heater unit to the Fθ lens, it is possible to suppress the expansion of the Fθ lens due to heat.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

DETAILED DESCRIPTION OF THE INVENTION

[0008] 〔Embodiment〕 Hereinafter, this embodiment will be described with reference to the drawings. In the drawings, the main scanning direction is the X direction, the sub-scanning direction (width direction), which is the direction orthogonal to the main scanning direction, is the Y direction, and the height direction, which is the direction orthogonal to the XY plane, is the Z direction. The same or equivalent elements are denoted by the same reference numerals, and redundant descriptions are omitted. Note that the embodiment described below does not unduly limit the content described in the claims. Also, not all of the configurations described in this embodiment are essential constituent elements of the present disclosure.

[0009] FIG. 1 is a cross-sectional view showing the configuration of an image forming apparatus 100 including an optical scanning device 1 according to the embodiment. In each of the figures shown hereinafter, the main scanning direction is the X direction, the sub-scanning direction (width direction), which is the direction orthogonal to the main scanning direction, is the Y direction, and the height direction, which is the direction orthogonal to the XY plane, is the Z direction.

[0010] For example, the image forming apparatus 100 is an apparatus having an image forming function of forming a color image or a monochrome image and a printing function of printing the formed image. 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 the present embodiment, as an example, the image forming apparatus 100 will be described as a multifunction peripheral. For example, the image forming apparatus 100 has a printing function of forming a color image or a monochrome image and printing the formed color image or monochrome image on a document. The types of colors used when the image forming apparatus 100 prints a color image are not limited, but for example, each color of black (Bk), cyan (Cy), magenta (Mg), and yellow (Ye) can be mentioned. Further, the image forming apparatus 100 prints a monochrome image on a document using, for example, a single color (for example, black).

[0011] For example, the image forming apparatus 100 includes an apparatus main body 101 and an apparatus cover portion 102 that is attached to the apparatus main body 101 in an openable and closable manner. For example, the apparatus cover portion 102 includes a transport portion 102a for transporting the document. For example, the apparatus main body 101 includes an image reading device 110, a feed tray 120, a plurality of transport rollers, an optical scanning device 10, image forming stations Pa, Pb, Pc, Pd, an intermediate transfer belt 151, a belt cleaning device 152, a secondary transfer device 153, a fixing device 154, a discharge tray 170, and the like. The plurality of transport rollers can be referred to as a document transport mechanism for transporting the document, and for example, include a pickup roller 131, a transport roller 132, a registration roller 133, and a discharge roller 134. As will be described later, since the optical scanning device 10 and the image forming stations Pa, Pb, Pc, Pd are mechanisms for forming a toner image (image for printing) to be transferred (printed) onto the document, they may also be referred to as an image forming mechanism. Further, the intermediate transfer belt 151, the belt cleaning device 152, the secondary transfer device 153, and the fixing device 154 are mechanisms for printing by transferring the toner image (image for printing) formed by the image forming mechanism onto the document, and thus may also be referred to as a printing mechanism.

[0012] Also, although not shown, the apparatus main body 101 has an operation unit that is an input interface for receiving input operations from the user, a control unit that integrally 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 a RAM or the like. Further, for example, the storage unit can be configured using a non-volatile memory such as a hard disk device or a 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 conveyed by the conveying unit 102a and placed on the image reading device 110, or may be directly placed on the image reading device 110 by the user. The feeding tray 120 stores the document before printing. The feeding tray 120 is provided in the apparatus main body 101 so as to be pullable, for example.

[0014] The image forming stations Pa, Pb, Pc, and Pd form a toner image (image) by transferring it onto the surface of the intermediate transfer belt 151. Each of the image forming stations Pa, Pb, Pc, and Pd is provided for each type of color used when the image forming apparatus 100 prints an image. For example, the image forming stations Pa, Pb, Pc, and Pd are arranged side by side in the sub-scanning direction (Y direction) in this order. 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 when the image forming apparatus 100 prints only monochrome images instead of color images, only one of the image forming stations Pa, Pb, Pc, and Pd may be provided.

[0015] The image forming stations Pa, Pb, Pc, and Pd each include a developing device 141, a photosensitive drum 142, a drum cleaning device 143, a charger 144, and the like. In 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 on the surface of the photosensitive drum 142. Thereafter, the surface of the photosensitive drum 142 is uniformly charged to a predetermined potential by the charger 144. Then, the surface of the charged photosensitive drum 142 is exposed by light from the optical scanning device 10 (details will be described later), and an electrostatic latent image is formed on the surface of the photosensitive drum 142. Thereafter, the electrostatic latent image formed on the surface of the photosensitive drum 142 is developed by the developing device 141. As a result, toner images of respective colors are formed on the respective photosensitive drums 142 provided in each of the image forming stations Pa, Pb, Pc, and Pd.

[0016] The intermediate transfer belt 151 is provided so as to contact the surfaces of the respective photosensitive drums 142 provided in each of the image forming stations Pa, Pb, Pc, and Pd. The intermediate transfer belt 151 moves in a circulating manner in the direction of arrow C. As a result, the toner images of respective colors formed on the surfaces of the respective photosensitive drums 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 the document conveyed so as to contact 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 contacts the surface of the intermediate transfer belt 151 at a position in the downstream direction of the direction of arrow C in which the intermediate transfer belt 151 moves in a circulating manner, rather than at the position where the intermediate transfer belt 151 transfers the toner image to the document. As a result, 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 provided to face the surface of the intermediate transfer belt 151 so that a nip area is formed between the transfer roller 153a and the intermediate transfer belt 151. The original document (the original document before printing) that has been conveyed so as to come into contact with the transfer roller 153a through the substantially S-shaped original document conveyance path R1 (the conveyance path of the original document from when it is discharged from the feed tray 120 until it reaches the discharge tray 170) is sandwiched in the nip area between the transfer roller 153a and the intermediate transfer belt 151 and conveyed, and the toner image formed on the surface of the intermediate transfer belt 151 is transferred. After that, the original document (the original document on 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 conveyed to the fixing device 17.

[0019] The fixing device 154 has a heating roller 154a and a pressure roller 154b. The original document on 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. Thereby, the toner image transferred to the original document is fixed. That is, the printing of the image on the surface of the original document is completed.

[0020] In the original document conveyance path R1, a pickup roller 131, which is a plurality of rollers, a conveyance roller 132, a registration roller 133, the above-described intermediate transfer belt 151 and transfer roller 153a, the above-described heating roller 154a and pressure roller 154b, and a discharge roller 134 are provided in this order. The pickup roller 131 is provided so as to be adjacent to the feed tray 120 and is the roller that is closest to the feed tray 120 (the farthest from the discharge tray 170) among the plurality of rollers. The discharge roller 134 is provided so as to be adjacent to the discharge tray 170 and is the roller that is closest to the discharge tray 170 (the farthest from the discharge tray 170) among the plurality of rollers.

[0021] An unprinted document stored in the feed tray 120 is pulled out from the feed tray 18 by the pickup roller 131, and is transported along the document transport path R1 by the transport roller 132 and the registration roller 133. The document discharged from the registration roller 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 roller 134.

[0022] The registration rollers 133 are provided at a position immediately upstream in the document transport path R1 from the intermediate transfer belt 151 and transfer roller 153a where the toner image is transferred to the document. The registration rollers 133 stop the document once before discharging it to the intermediate transfer belt 151 and transfer roller 153a, and align the leading edge of the document. After stopping the document once, the registration rollers 133 transport the document in accordance with the transfer timing of the toner image in the nip area between the intermediate transfer belt 151 and transfer roller 153a. The transport rollers 132 facilitate 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 included in the image forming apparatus 100 will be described mainly with reference to Fig. 2 and Fig. 3. Fig. 2 is a perspective view of the optical scanning device 10 according to the embodiment, seen obliquely from above. Fig. 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 formed using other materials. The housing 20 has a bottom portion 21, a lid portion 22, a first side portion 23, a second side portion 24, a third side portion 25, and a fourth side portion 26. The lid portion 22 is provided so as to face the bottom portion 21. As the planar shape of each of the bottom portion 21 and the lid portion 22, for example, a rectangle can be used, but the planar shape of each of the bottom portion 21 and the lid portion 22 is not limited to a rectangle. The first side portion 23, the second side portion 24, the third side portion 25, and the fourth side portion 26 are each erected at an end of the bottom portion 21. The first side portion 23 and the second side portion 24 are provided so as to face each other, and the third side portion 25 and the fourth side portion 26 are provided so as to face each other. The second side portion 24 and the first side portion 23 are arranged side by side in the main scanning direction (X direction) in this order. The third side portion 25 and the fourth side portion 2 are arranged side by side in the sub-scanning direction (Y direction) so as to face each other in this order.

[0025] The lid portion 22 is supported by a top portion on each of the first side portion 23, the second side portion 24, the third side portion 25, and the fourth side portion 26. A plurality of through holes 22a, 22b, 22c, and 22d whose longitudinal direction is the main scanning direction (X direction) are formed in the lid portion 22. The through holes 22a, 22b, 22c, and 22d are arranged side by side in the sub-scanning direction (Y direction) in this order. Light from each of a plurality of light sources provided in 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 device 100 (see FIG. 1), for example, the through hole 22a is arranged to face the image forming station Pa, the through hole 22b is arranged to face the image forming station Pb, the through hole 22c is arranged to face the image forming station Pc, and the through hole 22d is arranged to face the image forming station Pd.

[0026] Each of the through holes 22a, 22b, 22c, and 22d is covered by a protective cover 22g formed 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 and 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 dew condensation generated inside the housing 20. The heater unit 30 has a heater part 31 (see FIG. 7 etc.) that generates heat inside.

[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 the heat from the heater unit 30. The duct sheet 57 is provided below the bottom 21 of the housing 20 and beside the heat diffusion plate 40. The duct sheet 57 is provided below the polygon mirror unit 50 (see FIG. 7 etc.) described later and protects the polygon mirror unit 50 from below. The bottom 21 of the housing 20 has a shape such that the heat from the heat diffusion plate 40 does not diffuse too much. Details of the bottom 21, the heat diffusion plate 40, etc. will be described later.

[0029] Next, mainly with reference to FIGS. 4 to 7, various optical components and the like provided inside the optical scanning device 10 will be described. FIG. 4 is a perspective view of the optical scanning device 10 with the lid portion 22 removed as seen obliquely from above according to the embodiment. FIG. 5 is a plan view of the optical scanning device 10 cut in parallel to the XY plane so that the polygon mirror 51 is exposed according to the embodiment. FIG. 6 is a perspective view of the optical scanning device 10 shown in FIG. 5 as seen obliquely from above. FIG. 7 is a cross-sectional view of the optical scanning device 10 cut along the cutting line A1 - A1 in FIG. 5. Note that in FIGS. 5 and 6, the illustration of the heater unit 30 is omitted.

[0030] The heater unit 30 has a heater part 31 that generates heat when energized, and a heater cover 32 that covers the periphery of the heater part 31. The heater part 31 is provided below the bottom part 21 in the housing 20. The heater part 31 extends, for example, along the main scanning direction, and is provided so as to face away from the heat diffusion plate 40 via the heater cover 32.

[0031] The optical scanner main body 15 in 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, 61d, a plurality of collimator lenses 62a, 62b, 62c, 62d, a plurality of first mirrors 63a, 63b, 63c, 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, 72d, reflecting mirrors 73a1, 73a2, reflecting mirrors 73b1, 73b2, 73b3, reflecting mirrors 73c1, 73c2, a reflecting mirror 73d, and the like. The polygon mirror unit 50 has a polygon mirror (deflector) 51, a base part 52, and a shaft part G. The polygon mirror 51 rotates about the shaft part G as the rotation center. The polygon mirror 51 and the shaft part G are attached to the base part 52. The base part 52 is installed on the surface of the polygon mirror mounting plate 55. For example, the base part 52 is fixed to the polygon mirror mounting plate 55 using screws or the like.

[0032] Of the optical components provided in the housing 20, the plurality of collimator lenses 62a, 62b, 62c, 62d, the plurality of first mirrors 63a, 63b, 63c, 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 plurality of light sources 61a, 61b, 61c, 61d to the polygon mirror 51. Also, among the optical components provided in the housing 20, the Fθ first lens 71, the plurality of Fθ second lenses 72a, 72b, 72c, 72d, the reflection mirrors 73a1, 73a2, the reflection mirrors 73b1, 73b2, 73b3, the reflection mirrors 73c1, 73c2, and the reflection mirror 73d may be referred to as imaging optical components for guiding the beam reflected by the polygon mirror to the respective photoreceptor drums 142 of the image forming stations Pa, Pb, Pc, Pd (see FIG. 1).

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

[0034] Among the plurality of first mirrors 63a, 63b, 63c, 63d, the first mirrors 63a, 63b, 63c reflect the parallel light from each of the plurality of light sources 61a, 61b, 61c that have passed through the collimator lenses 62a, 62b, 62c to the first mirror 63d. The first mirror 63d reflects the reflected light from each of the plurality of first mirrors 63a, 63b, 63c to the cylindrical lens 64. Also, 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 reflected light reflected by each of the first mirrors 63a, 63b, 63c, 63d and the beam from the light source 61d that has passed through the collimator lens 62d so as to be parallel in the sub-scanning direction and transmits it to the second mirror 65. The second mirror 65 condenses the beam parallel in the sub-scanning direction that has passed through the cylindrical lens 64 onto the reflecting surface of the polygon mirror 51.

[0036] The polygon mirror 51 reflects the beams emitted from each of the plurality of light sources 61a, 61b, 61c, 61d. That is, the polygon mirror 51 rotates at high speed about the shaft portion G as the center of rotation, and repeatedly deflects the beam reflected by the second mirror 65 in the main scanning direction (X direction) by reflecting it at each reflecting surface. Then, the beams La, Lb, Lc, Ld (see FIG. 7) reflected by the polygon mirror 51 at each reflecting surface pass through the common Fθ first lens 71, and then the beam La is reflected by the reflecting mirrors 73a1, 73a2, passes through the Fθ second lens 72a, and is imaged on the photosensitive drum 142 of the image forming station Pa (see FIG. 1). The beam Lb is reflected by the reflecting mirrors 73b1, 73b2, 73b3, passes through the Fθ second lens 72b, and is imaged on the photosensitive drum 142 of the image forming station Pb (see FIG. 1). The beam Lc is reflected by the reflecting mirrors 73c1, 73c2, passes through the Fθ second lens 72c, and is imaged on the photosensitive drum 142 of the image forming station Pc (see FIG. 1). 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 FIG. 1).

[0037] The Fθ first lens 71 receives each of the beams La, Lb, Lc, and Ld reflected by the polygon mirror 51. That is, the Fθ first lens 71 is installed on the bottom 21 in the housing 20 so as to extend in the main scanning direction (X direction). The Fθ first lens 71 is provided in front of the traveling direction in the optical path of the beams La, Lb, Lc, and Ld reflected by the reflecting surface of the polygon mirror 51. The Fθ first lens 71 can be formed using, for example, resin, but the material used for forming the Fθ first lens 71 is not limited to resin. The Fθ first lens 71 condenses and transmits each of the beams La, Lb, Lc, and Ld reflected by the reflecting surface of the polygon mirror 51 so as to have a predetermined beam diameter on the surface of the photosensitive drum 142 (see FIG. 1). Further, the Fθ first 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 as to move at a constant speed along the surface of each photosensitive drum 142 in the main scanning direction. Thereby, the beams La, Lb, Lc, and Ld repeatedly scan the surface of each photosensitive drum 142 along the main scanning direction.

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

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

[0040] The reflection mirror 73c1 and the reflection mirror 73c2 are installed in this order in front of the advancing direction in the optical path of the beam Lc that has passed through the Fθ first lens 71. The reflection mirror 73c1 is provided to reflect the beam Lc that has passed through the Fθ first lens 71 to the reflection mirror 73c2, and the reflection mirror 73c2 is provided to reflect the beam Lc reflected from the reflection mirror 73c1 to the Fθ second lens 72c. The reflection mirror 73d is installed in front of the advancing direction in the optical path of the beam Ld that has passed through the Fθ first lens 71. The reflection mirror 73d is provided 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 respective photoreceptor drums 142 of the image forming stations Pa, Pb, Pc, and Pd. Each of the Fθ second lenses 72a, 72b, 72c, and 72d extends in the main scanning direction (X direction). For example, one end thereof 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, and is installed inside the housing 20. 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 for forming 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 condenses the beams La, Lb, Lc, and Ld, which are mainly parallel light in the sub-scanning direction (Y direction), so as to have a predetermined beam diameter (spot diameter) on the surface of each photoreceptor drum 142, and transmits through the surface of each photoreceptor 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 reflecting surface of the polygon mirror 51 travels along each optical path in the housing 20 and repeatedly scans the surface of each photoreceptor drum 142 of the image forming stations Pa, Pb, Pc, and Pd. Then, as each photoreceptor drum 142 rotates, an electrostatic latent image is formed on the surface of each photoreceptor drum 142.

[0043] Next, mainly with reference to FIGS. 4 to 11, details of the bottom portion 21 in the housing 20 and the heat diffusion plate 40 and the like will be described.

[0044] FIG. 8 is a perspective view of the optical scanning device 10 as viewed obliquely from above when the optical scanning device 10 is cut along the cut line A1-A1 in FIG. 5. FIG. 9 is a perspective view of the optical scanning device 10 as viewed obliquely from below when the optical scanning device 10 is cut along the cut line A1-A1 in FIG. 5. FIG. 10 is a perspective view of the optical scanning device 10 as viewed obliquely from below when the heater cover is removed according to the 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 the embodiment. Note that, in FIGS. 8 to 11, the illustration of the duct sheet 57 is omitted.

[0045] Here, of the two main surfaces of the bottom portion 21, the surface facing the lid portion 22 on the side within the housing 20 is referred to as the first surface 21a, and the back surface opposite to the surface is referred to as the second surface 21b.

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

[0047] The first region AR1 is a region of the bottom portion 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 opposite to 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 in which the largest number of a plurality of reflection mirrors are arranged side by side in the sub-scanning direction (Y direction) so as to face the first surface 21a among the first region AR1, the second region AR2, and the third region AR3. The third region AR3 is a region adjacent to the first region AR1 and located on the side opposite to the second region AR2 with respect to the first region AR1, and is a region 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 arranged side by side in the sub-scanning direction (Y direction) in this order.

[0048] In the third region AR3 at the bottom 21, a base portion 213a that is mainly a flat portion and a polygon mirror housing portion 213b that is a convex portion protruding in the height direction (Z direction) from the first surface 21a of the base portion 213a are provided. The polygon mirror housing portion 213b includes a side portion 231b1 erected on the first surface 21a of the base portion 213a and a plate-like upper portion 231b2 supported at the top of the side portion 231b1. And, a polygon mirror unit 50 provided on the polygon mirror mounting plate 55 is housed in the internal space surrounded by the polygon mirror housing portion 213b. That is, 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 portion 213a around the polygon mirror housing portion 213b using screws or the like. Thereby, the polygon mirror unit 50 is sealed in the internal space of the polygon mirror mounting plate 55 and the polygon mirror housing portion 213b, and it is suppressed that dust and dirt adhere to each reflecting surface of the polygon mirror 51.

[0049] Note that, among the side portions 231b of the polygon mirror housing portion 213b, an opening 21h is formed on the optical path of the reflected light that the second mirror 65 reflects the light transmitted through the cylindrical lens 64 to the reflecting surface of the polygon mirror 51. And, the opening 21h1 is covered by a protective cover 67a formed of transparent glass or the like. Thereby, when the second mirror 65 reflects the light transmitted through the cylindrical lens 64, the reflected light reaches each reflecting surface of the polygon mirror 51 through the protective cover 67a and the opening 21h1.

[0050] Also, among the side portions 231b, an opening 21h2 extending in the main scanning direction is formed on the optical path where the beams La·Lb·Lc·Ld reflected by each reflecting surface of the polygon mirror 51 reach the Fθ first lens 71. And, the opening 21h2 is covered by a protective cover 67b formed of transparent glass or the like. Thereby, the beams La·Lb·Lc·Ld reflected by each reflecting surface of the polygon mirror 51 reach the Fθ first lens 71 through the opening 21h2 and the protective cover 67b.

[0051] Among the bottom 21, in the second region AR2, as described above, a number of reflecting mirrors are arranged side by side in the sub-scanning direction so as to face the first surface 21a. For example, in the example of the present embodiment, among the eight reflecting mirrors provided in the housing 20, six reflecting 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, the second region AR2, and the third region AR3 in the bottom 21 are viewed in plan, the area of the second region AR2 is the largest. Therefore, a heat diffusion plate 40 is provided in the second region AR2 of the bottom 21 so as to face the second surface 21b. Thereby, the area of the heat diffusion plate 40 can be made wider than the case where the heat diffusion plate 40 is provided only in the regions other than the second region AR2. Thereby, the heat from the heater portion 31 provided inside the heater unit 30 can be diffused in a planar shape by the heat diffusion plate 40, and can be efficiently transmitted to the inside of the housing 20 through the second region AR2 in the bottom 21. Thereby, it is possible to more reliably suppress the occurrence of dew condensation on each optical component inside the housing 20 efficiently.

[0052] Here, in the first region AR1 adjacent to the second region AR2 of the bottom 21, an Fθ first lens 71 is provided so as to face the first surface 21a. Since the Fθ first lens 71 is a lens through which the beams La·Lb·Lc·Ld (see FIG. 7) reflected by the polygon mirror 51 at each reflection surface commonly pass, if the expansion due to heat or the like becomes large, positional deviation is likely to occur when each of the beams La·Lb·Lc·Ld reaches the photoreceptor drum 142.

[0053] Therefore, in the optical scanning device 10, the bottom portion 21 includes a heat diffusion suppression portion 211 having a shape that suppresses the heat transfer from the heat diffusion plate (heat diffusion member) 40 to the Fθ first lens (Fθ lens) 71 in the first region AR1 of the bottom portion 21. The heat diffusion suppression portion 211 is a region included in the first region AR1 of the bottom portion 21. By including the heat diffusion suppression portion 211 that suppresses the heat transfer from the heat diffusion plate 40 to the Fθ first lens 71 in the first region AR1 of the bottom portion 21 in this way, compared with the case where the heat diffusion suppression portion 211 is not provided, the heat from the heater portion 31 can be suppressed from being transmitted to the Fθ first lens 71 through the heat diffusion plate 40. For this reason, it is possible to suppress the Fθ first lens 71 from expanding due to heat. As a result, it is possible to suppress the positions of the beams La, Lb, Lc, and Ld, which are reflected by each reflecting surface of the polygon mirror 51 and transmitted through the Fθ first lens 71, from being displaced when they reach the photosensitive drum 142.

[0054] And the image forming apparatus 100 preferably includes the optical scanning device 10 and the photosensitive drum 142 that is exposed by the light from the optical scanning device 10. Thereby, since the photosensitive drum 142 is exposed by the optical scanning device 10 in which the expansion of the Fθ first lens 71 due to heat is suppressed, it is possible to obtain an image forming apparatus 100 capable of forming a high-quality image.

[0055] For example, the diffusion suppression portion 211 has a shape capable of suppressing heat transfer. Next, specific examples will be described regarding the shape of the heat diffusion suppression portion 211 that suppresses heat transfer. The shape of the heat diffusion suppression portion 211 that suppresses heat transfer means, for example, a shape in which the heat transfer path passing through the heat diffusion suppression portion 211 becomes longer compared to the case where the heat diffusion suppression portion 211 is not provided, that is, a flat plate-like shape, or a shape in which an opening H1 (see FIG. 12) is formed for heat dissipation into the air. Specific examples will be described below.

[0056] For example, the heat diffusion suppression unit 211 includes a base portion 211a, which is mainly a flat portion where the Fθ first 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 in the base portion 211a. For example, each of the base portion 211a and the protruding portions 211b and 211c extends such that the main scanning direction is the longitudinal direction. The protruding portion 211b is in contact with the second region AR2, and the protruding portion 211c is in contact with the third region AR3. The protruding portion 211b is in contact with an end portion 21e2 adjacent to the first region AR1, which is opposite to an end portion 21e1 (the end portion far from the first region AR1) that overlaps with the first side portion 23 among both end portions extending in the main scanning direction in the first region AR1 of the bottom portion 21. The protruding portion 211c is in contact with an end portion adjacent to the first region AR1, which is opposite to an end portion (the end portion far from the first region AR1) that overlaps with the second side portion 24 among both end portions extending in the main scanning direction in the third region AR3 of the bottom portion 21.

[0057] In this way, the heat diffusion suppression unit 211 includes at least one protruding portion 211b or 211c, which is a rib protruding downward (in the direction opposite to the height direction (Z direction)) from the second surface 21b on the side opposite to the first surface 21a where the Fθ first lens 71 is provided. As a result, compared with the case where at least one protruding portion 211b or 211c is not provided in the first region AR1 of the bottom portion 21, that is, compared with the case of a flat plate-like shape, the heat transfer path of the heat transmitted from the heat diffusion plate 40 to the first region AR1 through the second region AR2 in the bottom portion 21 can be lengthened, and the surface area for heat dissipation in the first region AR1 of the bottom portion 21 can be increased. Therefore, at least one protruding portion 211b or 211c can promote the heat dissipation of the heat transmitted from the second region AR2 in the first region AR1 of the bottom portion 21. As a result, it is possible to suppress the heat from the heater unit 31 from being transmitted to the Fθ first lens 71 through the heat diffusion plate 40.

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

[0059] Further, 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 portion 21. Thereby, compared with the case where the protrusion 211b does not protrude downward from the second surface 21b in the second region AR2, the heat transfer path of the heat transmitted from the heat diffusion plate 40 and the second region AR2 in the protrusion 211b can be lengthened, and the surface area for heat dissipation can be increased. As a result, the heat dissipation of the heat transmitted from the second region AR2 can be further promoted, and the heat from the heater unit 31 being transmitted to the Fθ first lens 71 via the heat diffusion plate 40 can be further suppressed.

[0060] Also, among the heat diffusion suppression parts 211, by forming the protrusion 211b adjacent to the second region AR2 in the bottom portion 21 into a shape protruding downward from the second surface 21b in the second region AR2 of the bottom portion 21, when attaching the heat diffusion plate 40 so as to face the second surface 21b of the second region AR2 in the bottom portion 21, the end portion of the heat diffusion plate 40 can be slid along the protrusion 211b protruding downward to position the attachment position of the heat diffusion plate 40. In this way, by forming the protrusion 211b into a shape protruding downward from the second surface 21b in the second region AR2 of the bottom portion 21, it can also function as a guide member when attaching the heat diffusion plate 40, so that the working efficiency when attaching the heat diffusion plate 40 can be improved.

[0061] Note that in the heat diffusion suppression part 211, at least one of the protrusion 211b and the protrusion 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] Further, the heat diffusion suppression portion 211 preferably has a protruding shape such that the height of the first surface 21a where the Fθ first lens 71 is provided is higher than that of the second region AR2 of the bottom portion 21. That is, the first surface 21a of the base portion 211a in the heat 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 heat 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 portion 211a, and the protruding portion 211c protrude in the height direction. Thereby, compared with the case where the first surface 21a in the second region AR2 and the first surface 21a of the base portion 211a in the heat diffusion suppression portion 211 have the same height, the heat transfer path of the heat transmitted from the heat diffusion plate 40 and the second region AR2 in the heat diffusion suppression portion 211 can be lengthened, and the surface area for heat dissipation can be increased. Thereby, further, the heat dissipation of the heat transmitted from the second region AR2 can be promoted, and the heat from the heater portion 31 being transmitted to the Fθ first lens 71 via the heat diffusion plate 40 can be further suppressed.

[0063] Also, when the heat diffusion plate 40 is viewed from the normal direction (when viewed in a plan view 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 and to overlap with the second region AR2 at the bottom portion 21. Thereby, the heat from the heat diffusion plate 40 being directly transmitted to the heat diffusion suppression portion 211 can be suppressed, and as a result, the heat from the heater portion 31 being transmitted to the Fθ first lens 71 via the heat diffusion plate 40 can be more reliably suppressed.

[0064] Further, the housing 20 has a first side portion 23 erected at an end portion 21e1 far from the first region AR1 in the second region AR2 of the bottom portion 21. And, it is preferable that the heat diffusion plate 40 extends so as to overlap with the first side portion 23 via the second region AR2. Thereby, compared with the case where the heat diffusion plate 40 has an area such that it does not overlap with the first side portion 23, the heat diffusion plate 40 becomes wider, and the heat from the heater portion 31 by the heat diffusion plate 40 can be diffused over a wider range. Thereby, heat can be efficiently transmitted into the housing 20.

[0065] Also, it is preferable that the heat diffusion suppression portion 211 has a shape extending along the direction (X direction) in which the Fθ first lens 71 extends. In other words, it is preferable that the base portion 211a, the protruding portion 211b, and the protruding portion 211c each have a shape extending along the direction in which the Fθ first lens 71 extends. Thereby, the heat transmitted from the heat diffusion plate 40 to the heat diffusion suppression portion 211 via the second region AR2 of the bottom portion 21 can be released in the extending direction of the heat diffusion suppression portion 211. As a result, it is possible to more surely suppress the heat from the heater portion 31 from being transmitted to the Fθ first lens 71 via the heat diffusion plate 40.

[0066] Here, in the optical scanning device 10, the heater portion 31 is a heat source that generates heat by energization. And, the heat diffusion plate 40 disposed so as to overlap with the heater portion 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. Thereby, the heat diffusion plate 40 can efficiently diffuse the heat from the heater portion 31 in a planar shape and transmit it into the housing 20 via the second region AR2 of the bottom portion 21. As a result, it is possible to efficiently suppress the occurrence of dew condensation on each optical component in the housing 20.

[0067] Also, as described above, for the polygon mirror 51, the light emitted from the plurality of light sources 61a, 61b, 61c, 61d is commonly condensed on each reflecting surface. Therefore, since the temperature rises due to the heat of the light from each light source, the polygon mirror 51 can also be referred to as a heat source in the optical scanning device 10.

[0068] Therefore, the polygon mirror mounting plate 55 on which the polygon mirror 51 is mounted preferably contains a material with a higher thermal conductivity than the resin material, for example, a metal material, when the housing 20 contains a resin material. Thereby, the heat of the polygon mirror 51 can be efficiently dissipated by the polygon mirror mounting plate 55. As a result, it is possible to suppress the occurrence of distortion or the like caused by the polygon mirror 51 becoming too hot.

[0069] Also, the heat diffusion suppression portion 211 is preferably provided between the heat 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 heat diffusion suppression portion 211 is provided so as to divide the heat diffusion plate 40 and the polygon mirror mounting plate 55. Thereby, the heat diffusion suppression portion 211 can lengthen the transmission path of the heat transmitted from the heat diffusion plate 40 through the second region AR2 of the bottom portion 21 and the heat transmitted from the polygon mirror mounting plate 55 through the third region AR3 of the bottom portion 21 within the heat diffusion suppression portion 211, and can also increase the surface area for heat dissipation. As a result, it is further possible to promote the heat dissipation of the heat transmitted from the second region AR2. As a result, it is also possible to suppress the heat from the polygon mirror 51 from being transmitted to the Fθ first lens 71 via the polygon mirror mounting plate 55 in addition to the heat from the heater unit 31.

[0070] FIG. 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 heat diffusion suppression portion 211. Thereby, the heat transmitted to the heat diffusion suppression portion 211 through the second region AR2 of the bottom portion 21 can be dissipated into the air through the opening H1. Also by this, it is possible to suppress the heat from the heater unit 31 from being transmitted to the Fθ first lens 71 through the heat diffusion plate 40.

[0071] In addition, each element appearing in the above-described embodiment and modified example may be appropriately combined within a range where no contradiction occurs.

Description of Symbols

[0072] 1: Optical scanning device, 10: Optical scanning device, 15: Optical scanning device body, 20: Housing, 21: Bottom, 21a: First surface, 21b: Second surface, 22: Lid part, 23: First side part, 24: Second side part, 25: Third side part, 26: Fourth side part, 30: Heater unit, 31: Heater part, 32: Heater cover, 40: Heat diffusion plate (heat diffusion member), 50: Polygon mirror unit, 51: Polygon mirror, 55: Polygon mirror mounting plate, 61a - 61d: Light sources, 62a - 62d: Collimator lenses, 63a - 63d: First mirrors, 64: Cylindrical lens, 65: Second mirror, 71: Fθ first lens (Fθ lens), 72a - 72d: Fθ second lenses, 73a1·73a2: Reflecting mirrors, 73b1 - 73b3: Reflecting mirrors, 73c1·73c2: Reflecting mirrors, 73d: Reflecting mirror, 100: Image forming apparatus, 142: Photoconductor drum, 211: Heat diffusion suppression part, 211a: Base part, 211b: Protrusion part, 211c: Protrusion part, 213a: Base part, 213b: Polygon mirror housing part, 221c: Protrusion part, 231b: Side part, 231b1: Side part, 231b2: Upper part, AR1: First region, AR2: Second region, AR3: Third region, H1: Opening, Pa - Pd: Image forming stations

Claims

1. A light source that emits a beam, A polygon mirror that reflects the beam emitted from the light source, An Fθ lens into 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, A heat diffusion member provided between the bottom and the heater unit, having a higher thermal conductivity than the housing and diffusing the heat from the heater unit, The bottom includes a first region where the Fθ lens is provided and a second region adjacent to the first region where the heat diffusion member is provided, and the first region includes a heat diffusion suppression portion that suppresses the transfer of heat from the heat diffusion member to the Fθ lens. An optical scanning device.

2. The optical scanning device according to claim 1, wherein the heat diffusion suppression portion includes at least one protruding portion that protrudes from a second surface opposite to a first surface on which the Fθ lens is provided.

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

4. The optical scanning device according to any one of claims 1 to 3, wherein the heat 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 that of the first region.

5. The optical scanning device according to any one of claims 1 to 4, wherein the heat diffusion member does not overlap with the heat diffusion suppression portion when viewed from the normal direction.

6. The optical scanning device according to any one of claims 1 to 5, wherein the heat diffusion suppression portion has a shape extending along the direction in which the Fθ lens extends.

7. Having a polygon mirror mounting plate on which the polygon mirror is mounted and formed of a material having a higher thermal conductivity than the housing, The bottom includes a third region adjacent to the first region and where the polygon mirror mounting plate is provided, The optical scanning device according to any one of claims 1 to 6, wherein the heat diffusion suppression portion is provided between the heat diffusion member and the polygon mirror mounting plate.

8. The housing has a first side portion erected at an end far from the first region in the second region of the bottom, The optical scanning device according to any one of claims 1 to 7, wherein the heat diffusion member extends so as to overlap the first side portion through the second region.

9. The optical scanning device according to any one of claims 1 to 8, wherein an opening is formed in the heat diffusion suppression portion.

10. The optical scanning device according to any one of claims 1 to 9, wherein the housing contains a resin material and the heat diffusion member contains a metal material.

11. The optical scanning device according to claim 7, wherein the polygon mirror mounting plate contains a metal material.

12. An image forming apparatus comprising the optical scanning device according to any one of claims 1 to 11 and a photosensitive drum exposed by light from the optical scanning device.

Images