阅读说明：本技术 光扫描装置及图像形成装置 (Optical scanning device and image forming apparatus ) 是由 青木礼至 中尾笃夫 山本弥史 元山贵晴 于 2020-04-08 设计创作，主要内容包括：本发明提供一种能使传递到壳体的热散逸、能防止因热膨胀引起的被扫描位置的偏离光扫描装置。光扫描装置(10)具有上部开口的下壳体(50)、覆盖下壳体(50)的上部的上壳体(40)、对光束进行反射的旋转多面镜(85)、供经旋转多面镜(85)反射的光束入射的fθ透镜(86)、及对光束进行反射的反射镜(87)。下壳体(50设有使旋转多面镜(85)与反射镜(87)之间的底面形成开口的底面开口部(56)。(The invention provides an optical scanning device which can dissipate heat transmitted to a housing and can prevent a scanned position from deviating due to thermal expansion. The optical scanning device (10) has a lower housing (50) having an upper opening, an upper housing (40) covering the upper portion of the lower housing (50), a rotary polygonal mirror (85) that reflects a light beam, an f [ theta ] lens (86) that receives the light beam reflected by the rotary polygonal mirror (85), and a reflecting mirror (87) that reflects the light beam. The lower case (50) is provided with a bottom surface opening (56) which opens the bottom surface between the rotary polygonal mirror (85) and the reflecting mirror (87).)

1. An optical scanning device includes:

a light source emitting a light beam;

a rotary polygon mirror that reflects the light beam emitted from the light source;

an f theta lens for incidence of the light beam reflected by the rotary polygon mirror; and

a mirror for guiding the light beam emitted from the f θ lens to a scanned object; and is

The optical scanning device scans a scanned object with a light beam, and is characterized in that:

the shell is composed of a lower shell with an opening at the upper part and an upper shell covering the upper part of the lower shell,

the rotary polygonal mirror is mounted to the lower case,

the lower case is provided with a bottom surface opening portion that opens a bottom surface between the rotary polygonal mirror and the reflecting mirror.

2. The optical scanning device according to claim 1, characterized in that:

the lower case has a raised portion provided opposite to the bottom surface opening and raised to the upper side than the bottom surface,

the f θ lens is attached toward a lower side of the ridge portion.

3. The optical scanning device according to claim 2, characterized in that:

the lower case is provided with a lead-out opening at a position overlapping the bottom opening and on both sides of the protrusion with the protrusion therebetween in a sub-scanning direction along the light beam passing through the f θ lens.

4. The optical scanning device according to claim 3, characterized in that:

one of the lead-out openings is provided between the rotary polygonal mirror and the f θ lens, and a folding opening is provided for guiding the light beam reflected by the mirror to the object to be scanned.

5. The optical scanning device according to claim 3 or claim 4, characterized in that:

the other of the lead-out openings is provided between the f θ lens and the mirror, and is provided with a coupling opening that guides the light flux that has passed through the f θ lens to the mirror.

6. The optical scanning device according to claim 5, characterized in that:

the connection opening portion includes an upper connection opening portion and a lower connection opening portion,

the width of the upper connecting opening is smaller than the width of the lower connecting opening in a main scanning direction in which the light beam is scanned by the rotary polygon mirror.

7. The optical scanning device according to any one of claims 1 to 6, characterized in that:

a metal bottom plate member covering the bottom opening is attached to the housing.

8. The optical scanning device according to claim 7, characterized in that:

the lower case is combined with the bottom plate member and has a heat dissipation flow path for circulating air,

the rotational axis of the rotary polygonal mirror faces the heat radiation flow path.

9. The optical scanning device according to claim 8, characterized in that:

the lower case has a duct opened to the outside,

the heat dissipation flow path is connected to the duct.

10. An image forming apparatus having the optical scanning apparatus according to any one of claims 1 to 9.

Technical Field

The present invention relates to an optical scanning device and an image forming apparatus for scanning a scanning target object with an optical beam.

Background

In an image forming apparatus having a plurality of photoreceptors and an intermediate transfer belt, such as a tandem multi-color image forming apparatus, toner images formed on the photoreceptors are sequentially transferred (1-time transfer) from an upstream side to a downstream side onto the rotating intermediate transfer belt. The photoreceptor is scanned with a light beam by a light scanning device, and an electrostatic latent image is formed on the surface thereof and developed with toner, thereby forming a toner image.

In an optical scanning device, a lens, a mirror, and the like are disposed in a housing, and a light beam is set so as to be folded back without interfering with an optical path of the light beam. In order to emit a light beam from the housing, it is proposed to provide an opening covered with a transparent member (see, for example, patent documents 1 and 2).

Disclosure of Invention

Technical problem to be solved by the invention

The optical scanning device described in patent document 1 includes: a light deflector for scanning the laser beam emitted from the light source; a housing having a through hole provided on a light path of the laser light; a plate member blocking the through hole; and a plurality of plate mounting portions to which the plate members can be mounted at a plurality of angles.

The optical scanning device in patent document 2 includes: a deflection scanning means for deflecting and scanning the light beam emitted from the light source; a housing having an opening for passing the light beam to the outside; the 1 st light-transmitting part is arranged at the opening; and a 2 nd light transmitting member for dust prevention of the 1 st light transmitting member.

In the optical scanning device described above, a rotatable polygon mirror (rotary polygon mirror) is used as the optical deflector, but a driving unit provided to rotate the polygon mirror generates heat. The housing is thermally expanded due to the influence of the heat, and a problem such as overlapping of toner images may occur due to positional displacement of a lens, a mirror, or the like attached to the housing.

The present invention has been made to solve the above-described problems, and an object thereof is to provide an optical scanning device and an image forming apparatus that can dissipate heat transmitted to a housing and prevent a scanned position from being shifted due to thermal expansion.

Means for solving the problems

An optical scanning device of the present invention includes: a light source emitting a light beam; a rotary polygon mirror that reflects the light beam emitted from the light source; an f theta lens for incidence of the light beam reflected by the rotary polygon mirror; and a reflecting mirror for guiding the light beam emitted from the f theta lens to a scanned object; and the light beam scans the scanned body; the optical scanning device is characterized in that: the housing includes a lower housing having an upper opening, and an upper housing covering the upper portion of the lower housing, the rotary polygon mirror is attached to the lower housing, and the lower housing is provided with a bottom opening that opens a bottom surface between the rotary polygon mirror and the reflecting mirror.

In the optical scanning device according to the present invention, the lower housing may have a protrusion portion provided to face the bottom surface opening portion and protruding upward from the bottom surface, and the f θ lens may be attached to the lower side of the protrusion portion.

In the optical scanning device according to the present invention, the lower housing may be provided with a guide opening at a position overlapping the bottom opening and on both sides of the ridge portion in a sub-scanning direction along the light beam passing through the f θ lens.

In the optical scanning device according to the present invention, one of the lead-out openings may be provided between the rotary polygonal mirror and the f θ lens, and a return opening for guiding the light beam reflected by the reflecting mirror to the object to be scanned may be provided.

In the optical scanning device according to the present invention, the other of the lead-out openings may be provided between the f θ lens and the mirror, and a coupling opening may be provided to guide the light flux having passed through the f θ lens to the mirror.

In the optical scanning device according to the present invention, the coupling opening includes an upper coupling opening and a lower coupling opening, and a width of the upper coupling opening is smaller than a width of the lower coupling opening in a main scanning direction in which the beam is scanned by the rotary polygon mirror.

In the optical scanning device of the present invention, a metal chassis member covering the bottom opening may be attached to the housing.

In the optical scanning device according to the present invention, the lower housing may be combined with the bottom plate member, and may have a heat radiation flow path through which air flows, and the rotation axis of the rotary polygonal mirror may be directed toward the heat radiation flow path.

In the optical scanning device according to the present invention, the lower housing may have a duct (duct) opening to the outside, and the heat radiation flow path may be connected to the duct.

An image forming apparatus according to the present invention is characterized in that: the optical scanning device of the present invention is provided.

Effects of the invention

According to the present invention, heat generated by the operation of the rotary polygon mirror and transferred to the housing can be dissipated, and the displacement of the scanning position due to thermal expansion can be prevented.

Drawings

Fig. 1 is a schematic side view showing an image forming apparatus according to an embodiment of the present invention.

Fig. 2 is an external perspective view of the optical scanning device viewed from above.

Fig. 3 is an external perspective view showing the optical scanning device viewed from the lower side.

Fig. 4 is an external perspective view showing a state of the lower case from the upper side after the upper case is detached.

Fig. 5 is an external perspective view showing a state of the lower case from the upper side after the bottom plate member is removed.

Fig. 6 is an external plan view showing a state of the lower case from above after the upper case and the bottom plate member are removed.

Fig. 7 is an external plan view showing a state of the lower case when the upper case and the bottom plate member are removed, as viewed from the lower side.

Fig. 8 is a schematic cross-sectional view showing an internal structure of the optical scanning device.

Fig. 9 is a schematic cross-sectional view of the vicinity of the ridge portion as viewed from the exit side of the f θ lens.

Fig. 10 is a schematic sectional view of the vicinity of the ridge portion as viewed from the incident side of the f θ lens.

Fig. 11 is an enlarged side view showing the vicinity of the holding portion in an enlarged manner.

Fig. 12 is an explanatory plan view showing an optical path of a light beam in the optical scanning device.

Fig. 13 is an explanatory side view showing an optical path of a light beam in the optical scanning device.

Detailed Description

Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings.

Fig. 1 is a schematic side view showing an image forming apparatus according to an embodiment of the present invention.

The image forming apparatus 1 is a multifunction peripheral having a scanner function, a copy function, a printer function, a facsimile function, and the like, and transmits an image of a document read by an image reading apparatus provided at an upper portion to the outside (corresponding to the scanner function), and forms the read image of the document or an image received from the outside on a sheet in color or monochrome (corresponding to the copy function, the printer function, and the facsimile function).

An original document feeder (ADF) is provided above the image reading apparatus and supported to be openable and closable with respect to the image reading apparatus. The document feeder automatically feeds a loaded document to the image reading device. The image reading apparatus reads an original conveyed by the original conveying apparatus and generates image data.

The image forming apparatus 1 includes an optical scanning device 10, a developing device 12, a photoconductive drum 13, a drum cleaning device 14, a charger 15, an intermediate transfer belt 21, a fixing device 17, a sheet conveying path 31, a sheet feeding cassette 18, a stack tray 39, and the like.

The image forming apparatus 1 can process image data corresponding to a color image using each color of black (K), cyan (C), magenta (M), yellow (Y), or a monochrome image using a single color (for example, black). The image forming apparatus 1 is provided with 4 developing devices 12, photoreceptor drums 13, drum cleaning devices 14, and chargers 15 for forming 4 kinds of toner images, respectively, and these devices constitute 4 image stations Pa, Pb, Pc, and Pd corresponding to black, cyan, magenta, and yellow, respectively.

The drum cleaning device 14 removes and recovers the residual toner on the surface of the photosensitive drum 13. The charger 15 uniformly charges a predetermined potential to the surface of the photoreceptor drum 13. The optical scanning device 10 exposes the surface of the photosensitive drum 13 to form an electrostatic latent image. The developing device 12 develops the electrostatic latent image on the surface of the photosensitive drum 13, thereby forming a toner image on the surface of the photosensitive drum 13. Through the above-described series of operations, toner images of respective colors are formed on the surfaces of the respective photosensitive drums 13. The detailed structure of the optical scanning device 10 will be described with reference to fig. 2 and 3, which will be described later.

The intermediate transfer belt 21 is moved around, residual toner is removed and recovered by a belt cleaning device 22, toner images of respective colors formed on the surfaces of the respective photosensitive drums 13 are sequentially transferred and superimposed, and a toner image of a color is formed on the surface of the intermediate transfer belt 21.

The 2-pass transfer device 23 has a nip area formed between the transfer roller 23a and the intermediate transfer belt 21, and conveys the sheet conveyed through the sheet conveying path 31 while sandwiching the sheet between the nip area. When the sheet passes through the nip area, the toner image on the surface of the intermediate transfer belt 21 is transferred and then conveyed to the fixing device 17.

The fixing device 17 includes a fixing roller 24 and a pressure roller 25 that rotate with the paper therebetween. The fixing device 17 sandwiches the sheet to which the toner image is transferred between the fixing roller 24 and the pressure roller 25, and heats and presses the sheet, thereby fixing the toner image to the sheet.

The paper feed cassette 18 is provided on the lower side of the optical scanning device 10 to store paper sheets for forming an image. The sheet is fed from the sheet cassette 18 by the sheet pickup roller 33, conveyed through the sheet conveying path 31, passed through the 2-pass transfer device 23 and the fixing device 17, and then discharged to the stack tray 39 by the discharge roller 36. The paper conveyance path 31 is provided with: a paper positioning roller 34 that stops the paper once and starts conveying the paper in accordance with the transfer timing of the color toner image in the nip region between the intermediate transfer belt 21 and the transfer roller 23a after aligning the front end of the paper; a paper conveying roller 35 for facilitating paper conveyance; and a paper exit roller 36.

Further, the image forming apparatus 1 can form an image not only on the front surface of a sheet but also on the back surface thereof, and is provided with a path for conveying the sheet in the reverse direction from the sheet discharge roller 36. The sheet is guided again to the sheet positioning roller 34 with the front and back surfaces thereof reversed, and after an image is formed on the back surface in the same manner as the front surface, the sheet is carried out to the stack tray 39.

Fig. 2 is an external perspective view showing the optical scanning device 10 viewed from the upper side, and fig. 3 is an external perspective view showing the optical scanning device 10 viewed from the lower side.

In the optical scanning device 10 according to the embodiment of the present invention, the housing includes a lower housing 50 having an upper opening, and an upper housing 40 covering an upper portion of the lower housing 50. The housing of the optical scanning device 10 is formed in a substantially rectangular parallelepiped shape with a small thickness.

The upper case 40 is formed substantially entirely of an opaque material, a part of the upper surface thereof is opened, and an exit window 40a formed of a transparent material is provided to cover the opening. The exit window 40a is rectangular in length when viewed from the upper surface, and the length in the longitudinal direction is such that the end reaches the outer edge of the upper case 40. The exit windows 40a are provided at 4 positions corresponding to the 4 photosensitive drums 13, and are arranged apart from each other in the short-side direction of the exit windows. For convenience of explanation, hereinafter, the short side direction of the exit window 40a may be referred to as a sub-scanning direction X, and the long side direction of the exit window 40a may be referred to as a main scanning direction Y.

The lower case 50 is a container for accommodating optical components therein, and has a side wall along the outer periphery of the lower case bottom surface 55. As for the side walls of the lower case 50, the lower case 1 st side wall 51 faces the lower case 2 nd side wall 52 in the sub scanning direction X, and the lower case 3 rd side wall 53 faces the lower case 4 th side wall 54 in the main scanning direction Y. For convenience of explanation, the side of the sub-scanning direction X on which the 1 st side wall 51 of the lower casing is provided may be referred to as the 1 st sub-scanning direction X1, and the side of the sub-scanning direction X on which the 2 nd side wall 52 of the lower casing is provided may be referred to as the 2 nd sub-scanning direction X2.

A bottom opening 56 (for example, fig. 7) is provided in a part of the lower case bottom 55, and a metal bottom plate member 60 is attached by screws or the like so as to cover the bottom opening 56. In the bottom plate member 60, a portion in contact with the lower case 50 may be bonded with a foam (Moltopren) made of sponge or the like to improve the sealing property. The positional relationship between the bottom surface opening 56 and the bottom plate member 60 will be described with reference to fig. 8 described later.

Next, the internal structure of the lower case 50 will be described with reference to fig. 4 to 8.

Fig. 4 is an external perspective view showing a state in which the upper case 40 is removed and the lower case 50 is seen from the upper side, fig. 5 is an external perspective view showing a state in which the bottom plate member 60 is removed and the lower case 50 is seen from the lower side, fig. 6 is an external plan view showing a state in which the upper case 40 and the bottom plate member 60 are removed and the lower case 50 is seen from the upper side, fig. 7 is an external plan view showing a state in which the upper case 40 and the bottom plate member 60 are removed and the lower case 50 is seen from the lower side, and fig. 8 is a schematic sectional view showing an internal structure of the optical scanning device 10. In addition, fig. 6 and 7 show a state where a part of the reflecting mirror 87 and the exit lens 88 provided in the vicinity of the ridge portion 70 are removed in consideration of the ease of drawing.

The lower case 50 is mounted with a light source 81, a pre-deflection 1-time mirror 82, a pre-deflection 2-time mirror 83, a cylindrical lens 84, a rotary polygon mirror 85, an f θ lens 86, a mirror 87, and an exit lens 88.

The light source 81 is mounted on the 1 st side wall 51 of the lower case and is disposed in a portion close to the 3 rd side wall 53 of the lower case. The pre-deflection 1-time mirror 82 is provided at a position facing the light source 81 in the sub-scanning direction X, and guides the light beam emitted from the light source 81 to the pre-deflection 2-time mirror 83.

In the present embodiment, 4 light sources 81 are provided corresponding to 4 photosensitive drums 13, and light beams emitted from the light sources 81 are irradiated to the corresponding photosensitive drums 13, respectively. The 4 light sources 81 are arranged at different positions in the height direction Z, and the 4 pre-deflection 1-time mirrors 82 are provided at heights corresponding to the 4 light sources 81, and the heights are adjusted so that a part of the light beams pass above the pre-deflection 1-time mirrors 82. The positions of the light sources 81 and the pre-deflection 1-time mirrors 82 with respect to the pre-deflection 2-time mirrors 83 may be appropriately adjusted, and the number of the pre-deflection 1-time mirrors 82 may be changed as long as the light sources are arranged so that the light beams emitted from the plurality of light sources 81 are incident on the 1 pre-deflection 2-time mirrors 83.

The first 2-pass deflecting mirror 83 causes the reflected light beam to pass through a cylindrical lens 84 and then to be incident on a rotating polygon mirror 85. The mounting structure of the first 2-pass mirror 83 and the cylindrical lens 84 will be described with reference to fig. 9 and 10 described later.

The rotary polygon mirror 85 is, for example, a polygon mirror having 6 surfaces (specifically, see fig. 12), has a rotary shaft rotated by a driving unit such as a motor, and reflects an incident light beam while rotating the light beam, thereby scanning the surface of the photosensitive drum 13 with the light beam. The rotary polygonal mirror 85 is provided along the lower casing 1 st side wall 51, and is located in the lower casing 50 at substantially the center in the main scanning direction Y. The lower surface of the rotary polygonal mirror 85 is covered with a support plate 85a, and a bearing 85b including a rotation shaft protrudes downward from the support plate 85 a. The lower case bottom surface 55 is provided with projections and recesses for accommodating the rotary polygonal mirror 85, and a transparent dust-proof glass 91 is provided in a portion through which the light beam passes.

The f θ lens 86 is attached so as to face the lower side of the bulging portion 70 bulging toward the upper side than the lower case bottom surface 55. The bump 70 is provided at a position of the lower case 50 near the 1 st side wall 51 of the lower case in the sub-scanning direction X, and the end of the bump 70 in the main scanning direction Y is continuous with the 3 rd side wall 53 of the lower case and the 4 th side wall 54 of the lower case. The f θ lens 86 is located at a position substantially in the center of the lower case 50 in the main scanning direction Y and opposed to the rotary polygon mirror 85 in the sub scanning direction X, and the light flux emitted from the rotary polygon mirror 85 enters the f θ lens 86. The structure near the ridge portion 70 will be described with reference to fig. 9 and 10 described later.

The mirrors 87 are appropriately arranged at each portion of the lower case 50, and in the present embodiment, 8 mirrors 87 are provided. Any one of the light beams emitted from the 4 light sources 81 is incident on the reflecting mirror 87, and is incident on the corresponding exit lens 88. The exit lens 88 is provided at a position facing the exit window 40a, and in the present embodiment, 4 exit lenses 88 are provided. The number of the reflecting mirrors 87 corresponding to 1 light beam can be changed as appropriate, and the light beams can be emitted more than 2 times.

The lower case 50 is provided with a duct 54a that opens to the outside, and the duct 54a has a square tubular shape and extends outward from a portion of the lower case 4-th side wall 54 that is close to the lower case 1-th side wall 51. A pipe having a fan or the like provided outside the optical scanning device 10 is connected to the duct 54a, and air can be circulated through the duct 54 a.

A duct extension 54b extending along the side wall of the duct 54a is provided on the lower surface of the lower case bottom surface 55. The floor member 60 described above is formed in a substantially planar shape along the lower surface of the lower case 50, and a flow path forming portion 61 is provided by bending a part of the end portion upward. As shown in fig. 3, when the bottom plate member 60 is attached to the lower case 50, the structure is: the flow path constituting portion 61 is located along the conduit extension portion 54b, and the flow path constituting portion 61 extends the conduit extension portion 54 b. The rotational axis of the rotary polygonal mirror 85 is located along the flow path forming portion 61, and the lower side of the rotational axis is covered with the bottom plate member 60. That is, by combining the lower case 50 and the bottom plate member 60, the heat radiation flow path connected to the duct 54a is extended, and the rotation axis faces the heat radiation flow path. Specifically, the rotation shaft of the rotary polygonal mirror 85 is supported by a bearing 85b, and the bearing 85b including the rotation shaft is positioned inside the heat radiation flow path. Thereby, an air flow for cooling the rotation shaft of the rotary polygon mirror 85 is formed. In this case, the rotary shaft, which is likely to generate heat by operation, is provided in the heat dissipation flow path to be cooled by air, thereby further dissipating heat.

The lower case 50 has a bottom opening 56 that opens a portion facing the ridge 70. That is, the lower case bottom surface 55 is provided along approximately the lower end of the side wall, and is interrupted at the bottom surface opening 56. The portion interrupted by the bottom surface opening 56 is covered with the bottom plate member 60. The light beam emitted from the rotary polygon mirror 85 passes through an f θ lens 86 provided at a position overlapping with the raised portion 70, travels in the 2 nd sub-scanning direction X2, and is incident on the reflecting mirror 87. Therefore, the bottom surface opening 56 is positioned between the rotary polygonal mirror 85 and the reflecting mirror 87.

Fig. 9 is a schematic cross-sectional view of the vicinity of the ridge portion 70 as viewed from the exit side of the f θ lens 86, and fig. 10 is a schematic cross-sectional view of the vicinity of the ridge portion 70 as viewed from the entrance side of the f θ lens 86.

Fig. 9 and 10 show a state in which a part of the components are removed, as in fig. 7 and 8. The lower end of the coupling portion 78 extending from the end of the bump 70 on the 2 nd sub-scanning direction X2 side is coupled to the lower case bottom surface 55, and the bump 70 has an incident side wall surface 72 extending downward from the end on the 1 st sub-scanning direction X1 side. The lower end of the incident side wall surface 72 does not reach the lower case bottom surface 55 and is not connected to the lower case bottom surface 55. The bulging portion 70 includes a holding portion 74 extending downward, and the holding portion 74 holds the lower portion of the f θ lens 86. As described above, by providing the coupling portion 78 that couples the lower case bottom surface 55 and the bulge portion 70, the strength of the case can be further improved. The detailed structure of the holding portion 74 will be described with reference to fig. 11 described later.

A 2-time before deflection mirror 83 and a cylindrical lens 84 (an example of an optical component) are attached to the lower side of the ridge portion 70 at a position close to the 3 rd side wall 53 of the lower case. Specifically, the bulging portion 70 is provided with a component fixing portion 70d extending downward. The front end of the component fixing portion 70d is formed in a claw shape, and the lower end of the first-2-time deflection mirror 83 is hooked thereon. The first 2-time mirror 83 may be bonded to the ridge portion 70 and the component fixing portion 70d, instead of being held by the component fixing portion 70 d. In the present embodiment, the cylindrical lens 84 is located near the first 2 nd mirror 83 before deflection, and a concave portion is provided in the ridge portion 70, so that it is configured to be inserted from above. Further, the present invention is not limited to this, and may be configured such that: another part fixing portion 70d holding the cylindrical lens 84 is further provided, and the cylindrical lens 84 is fixed to the lower side of the swelling portion 70. By mounting other optical components such as the f θ lens 86 on the ridge portion 70 in this way, the degree of freedom in the arrangement of the components in the housing can be increased, and space can be saved.

The raised portion 70 has upper surface reinforcing ribs 70a on the upper surface thereof and lower surface reinforcing ribs 70b on the lower surface thereof. In this way, by forming the reinforcing ribs on the surface of the raised part 70, the strength in the vicinity of the raised part 70 is ensured. The upper surface reinforcing rib 70a and the lower surface reinforcing rib 70b may be set to have an appropriate shape according to the size of the bulging portion 70, and for example, may be formed linearly from the lower case 3 rd side wall 53 to the lower case 4 th side wall 54. Further, a plurality of upper surface reinforcing ribs 70a and lower surface reinforcing ribs 70b may be provided, or a portion for connecting them may be provided. The lower surface reinforcing rib 70b is provided so as not to avoid a component attached to the lower side of the ridge portion 70, and is formed so as not to obstruct the passage of the light beam. The lower surface reinforcing rib 70b extends downward by approximately the same length as the f θ lens 86, and provides a wide space below the f θ lens 86, thereby increasing the strength of the lower case 50 in the vicinity of the ridge portion 70.

The coupling portion 78 has a coupling opening 71 formed by partially opening in the main scanning direction Y. The connection opening 71 is composed of an upper connection opening 71a provided in a portion facing the f θ lens 86 and a lower connection opening 71b located below the upper connection opening 71 a. The width of the upper connecting opening 71a in the main scanning direction Y is formed slightly larger than the width of the f θ lens 86, and the width of the lower connecting opening 71b in the main scanning direction Y is formed larger than the upper connecting opening 71 a. The widths of the upper connecting opening 71a and the lower connecting opening 71b are set according to the degree of expansion of the light beam to be transmitted, and the relationship between the irradiation direction of the light beam and the degree of expansion will be described with reference to fig. 12 described later.

The incident side wall surface 72 is partially opened to form a wall surface opening 72a, a mirror incident port 72b, and a lens exit port 72 c. The wall surface opening 72a is provided in a portion facing the f θ lens 86, substantially the same as the upper connection opening 71 a. The mirror entrance port 72b is provided in a portion facing the 2 nd mirror 83 before deflection, and allows a light beam traveling from the 1 st mirror 82 before deflection to the 2 nd mirror 83 before deflection to pass therethrough. The lens exit 72c is provided on a straight line connecting the cylindrical lens 84 and the rotary polygonal mirror 85, and passes a light flux emitted from the 2-time mirror 83 before deflection to the rotary polygonal mirror 85.

As described above, the length of the incident side wall surface 72 extending downward is approximately the same as the f θ lens 86, and the lower side thereof is formed into an opening shape. That is, an opening larger than the lower connecting opening 71b is formed in the main scanning direction Y at a portion facing the lower connecting opening 71 b. As shown in fig. 8, the incident side wall surface 72 is not continuous with the lower housing bottom surface 55 on the rotary polygon mirror 85 side in the sub scanning direction X, and a folding opening 73 that opens in the height direction Z is provided between the incident side wall surface and the rotary polygon mirror 85.

As shown in fig. 8, any one of the plurality of mirrors 87 (opening mirror 87a) is located above the bottom surface opening 56 and below the folding opening 73. Further, the exit lens 88 (opening exit lens 88a) corresponding to the opening reflector 87a faces the opening reflector 87a through the folding opening 73.

In the present embodiment, the connection opening 71 and the folding opening 73 are located at positions overlapping the bottom surface opening 56 in the sub-scanning direction X, and serve as lead-out openings with the ridge portion 70 interposed therebetween.

The coupling opening 71 is located between the f θ lens 86 and the first incident mirror 87 in the sub-scanning direction X, and is provided so as to penetrate from the bottom opening 56 to the upper surface side of the lower case 50. As described above, the f θ lens 86 is mounted on the lower surface of the ridge portion 70 and is located on the lower surface side of the lower case 50. That is, the light flux emitted from the f θ lens 86 passes through the coupling opening 71 from the lower surface side to the upper surface side of the lower case 50, and is directed to the reflecting mirror 87.

The folding opening 73 is located between the rotary polygonal mirror 85 and the f θ lens 86 in the sub scanning direction X, and is provided so as to penetrate from the bottom opening 56 to the upper surface side of the lower case 50. That is, the light flux reflected by the opening portion mirror 87a passes through the folding opening portion 73 from the lower surface side to the upper surface side of the lower housing 50, and is emitted to the photosensitive drum 13.

Fig. 11 is an enlarged side view showing the vicinity of the holding portion 74 in an enlarged manner.

The holding portions 74 are provided at portions overlapping both ends of the f θ lens 86 in the main scanning direction Y. In fig. 11, one of the holding portions 74 provided at 2 is shown in an enlarged manner. The holding portion 74 is formed so as to surround an end portion of the f θ lens 86, and the f θ lens 86 is inserted from below the holding portion 74. A boss 86a protruding from the front surface is formed at the other end of the f θ lens 86. The holding portion 74 has a groove 74a extending in the height direction Z, and the boss 86a is inserted along the groove 74 a. The width of the groove 74a is approximately the same as the size of the boss 86a, and the f θ lens 86 is positioned in the main scanning direction Y by hooking the boss 86a to the groove 74 a. Since the holding portion 74 is formed so as to surround the surface on the incident side and the surface on the emission side of the f θ lens 86, the f θ lens 86 is positioned in the sub-scanning direction X by inserting the f θ lens 86 into the holding portion 74.

Near the holding portion 74, a screw fixing portion 75 is provided. The screw fixing portion 75 extends to the lower side of the swelling portion 70, and the front end is provided with a hole into which the screw 76 is inserted. The screw 76 is attached to the screw fixing portion 75 via a plate spring 77. The front end of the plate spring 77 is in contact with the lower end of the f θ lens 86, and urges the f θ lens 86 to be pushed. That is, the f θ lens 86 is pushed by the plate spring 77 to contact a reinforcing rib (protrusion: not shown) provided on the lower surface of the ridge portion 70, and is positioned in the height direction Z. Further, the holding portion 74 may be provided with a recess portion in a portion facing the plate spring 77 so as to fit the plate spring 77, thereby suppressing the backlash. In the present embodiment, the use of the plate spring 77 and the screw 76 makes it possible to realize the holding structure without requiring complicated processing such as fastening of the f θ lens 86. Further, although a flat plate spring 77 is shown in fig. 11, the present invention is not limited to this, and an uneven surface may be provided at the tip of the plate spring 77 to reduce the area in contact with the f θ lens 86.

Fig. 12 is an explanatory plan view showing an optical path of a light beam in the optical scanning device 10, and fig. 13 is an explanatory side view showing an optical path of a light beam in the optical scanning device 10. In fig. 12 and 13, a part of the optical components in the optical scanning device 10 is shown in consideration of the ease of drawing. In fig. 13, the optical path of the light beam LB emitted from 1 light source 81 among the light beams LB emitted from 4 light sources 81 will be described in detail.

As described above, in the optical scanning device 10, the light beam LB is emitted from the light source 81. The light beam LB is reflected by the rotating polygon mirror 85 and then scanned, thereby traveling along the optical path, and the irradiation range in the main scanning direction Y is expanded. That is, when the light beam LB passes through the f θ lens 86 through the wall surface opening 72a, the distance from the rotary polygon mirror 85 is short, and therefore, the irradiation range in the main scanning direction Y is not so wide. When the light beam LB passes through the upper coupling opening 71a and reaches the mirror 87 which is first incident, the irradiation range in the main scanning direction Y is expanded. The light beam LB is reflected by the mirror 87, passes through the folding opening 73 by passing through the lower connection opening 71b and the opening mirror 87a, and reaches the opening exit lens 88 a. In this case, since the distance traveled by the light beam LB on the optical path is long, the irradiation range in the main scanning direction Y is expanded, and therefore, it is preferable that the widths of the lower connecting opening 71b and the folding opening 73 are formed to be wide. That is, the width of the coupling opening 71 (particularly, the upper coupling opening 71a) is preferably smaller than the width of the folding opening 73 in the main scanning direction Y. In this way, the opening range is narrowed in accordance with the light flux to be passed, whereby the intensity of the ridge portion 70 can be increased.

Further, since the connection opening 71 is provided, the optical path of the light beam LB is not obstructed. Further, the light path of the light beam LB is secured by providing the folding opening 73, and the space left vacant by providing the bottom opening 56 is used, whereby the components can be collected and the housing can be downsized.

In the optical scanning device 10, the position of the light beam LB is determined according to the photosensitive drum 13, and the reduction of the interval between the exit windows 40a is restricted. Therefore, if the housing is made longer in the sub-scanning direction X, the arrangement of the optical components is eased, but the apparatus becomes larger. In the present embodiment, the exit window 40a (exit lens 88) is disposed at a position closer to the rotary polygon mirror 85 than the f θ lens 86 in the sub-scanning direction X, and thereby the interval from the other exit windows 40a is secured, and the housing is shortened.

Further, if the attachment portion is provided below the f θ lens 86, the optical path of the light beam LB can be lowered downward avoiding the attachment portion, and therefore the thickness of the housing is increased. In contrast, in the present embodiment, the f θ lens 86 is suspended below the bump 70, so that the housing can be made thin while ensuring the strength of the portion where the f θ lens 86 is mounted, the portion being disposed upward.

In the optical scanning device 10, the temperature in the vicinity of the rotating polygonal mirror 85 as a driving source tends to increase. When the housing is thermally expanded, the positions of the lens and the mirror held by the housing may be displaced, and the emitted light beam may be displaced. In contrast, in the present embodiment, since the bottom surface opening 56 is provided in the lower casing bottom surface 55 so as to be partially interrupted, heat generated by the operation of the rotary polygon mirror 85 and transmitted to the casing can be dissipated, and the displacement of the scanning position due to thermal expansion can be prevented. Further, by attaching the bottom plate member 60 so as to cover the bottom surface opening 56, it is possible to prevent dust and the like from entering and further improve the heat radiation effect. That is, heat is transferred from the rotary polygonal mirror 85 side to the bottom plate member 60 facing the bottom surface opening 56, but heat can be efficiently dissipated from the bottom plate member 60 having high thermal conductivity.

Further, since the ridge portion 70 is disposed in the portion interrupted by the provision of the bottom surface opening portion 56 and the f θ lens 86 is attached to the ridge portion 70, the space in the housing can be effectively utilized.

The embodiments disclosed herein are illustrative in all respects and should not be construed as restrictive. Therefore, the technical scope of the present invention is not to be interpreted only by the embodiments described above, but is defined based on the description of the claims. Further, the present invention includes all modifications within the meaning and range equivalent to the claims.

Description of the reference numerals

1 image forming apparatus

10 optical scanning device

13 photosensitive drum (one example of scanned body)

40 upper shell

50 lower casing

51 lower case No. 1 side wall

52 lower case 2 nd side wall

53 lower case 3 rd side wall

54 lower case 4 th side wall

54a pipe

54b pipe extension

55 bottom surface of lower casing

56 bottom opening

60 floor element

61 flow path constituting part

70 raised portion

70d parts fixing part

71 connection opening (an example of a lead-out opening)

71a upper side connecting opening

71b lower connecting opening

72 incident side wall surface

72a wall opening

72b mirror entrance port

72c lens outlet

73 folding opening (an example of a lead-out opening)

74 holding part

76 screw

77 plate spring

78 connecting part

81 light source

82 deflection first 1 time reflector

83 first 2 times deflection mirror (an example of optical component)

84 cylindrical lens (an example of optical component)

85 rotating polygon mirror

85a support plate

85b bearing

86 f theta lens

87 reflector

88 exit lens