JP7359003B2 - Optical deflector, optical writing device and image forming device - Google Patents

Description

The present invention relates to an optical deflector used for deflection scanning using a rotating polygon mirror, an optical writing device using the optical deflector, and an image forming apparatus using the optical writing device.

Conventionally, printers and copying machines that form images on paper (recording media) are known. Image forming devices such as printers and copying machines use an optical writing device to form an electrostatic latent image, create a toner image using the formed electrostatic latent image, and transfer the toner image to a fixing unit. An image is formed on the paper by applying heat and pressure to fix it on the paper.

In general, in this type of image forming apparatus, a light beam from a light source such as a semiconductor laser is deflected and scanned by an optical deflector using a rotating polygon mirror, and is applied onto a charged image carrier such as a photoreceptor using a scanning lens system. It is imaged as a light spot and an electrostatic latent image is written.
Since a rotating polygon mirror rotates at a high speed of about 40,000 rpm, noise may become a problem in an optical deflector using the polygon mirror.

Therefore, as a technology for suppressing the noise of an optical deflector using a rotating polygon mirror, a technology has been disclosed in which the area surrounded by the housing of the rotating polygon mirror and a flat window is made approximately circular, thereby smoothing the flow of air. (For example, see Patent Document 1).

Japanese Patent Application Publication No. 8-152573

However, in the configuration using a flat window described in Patent Document 1, as shown in FIGS. 11A to 11C, the distance between the rotating polygon mirror 31 and the window 36 becomes narrow ( Since the pressure gradient becomes large at middle symbol F), it becomes a cause of noise. Here, FIG. 11(A) shows a plan view of a conventional optical deflector (however, the top plate 37c of the housing 37 is omitted), and FIG. 11(B) shows the reference numerals in FIG. 11(A). FIG. 11C shows an enlarged view of the area indicated by W, and a cross-sectional view taken along line A2-A2 in FIG. Therefore, as configurations for suppressing the above-mentioned pressure gradient, there are a configuration in which the window is formed into an arcuate shape, and a configuration in which the window is made to protrude away from the rotating polygon mirror.

However, in the configuration where the window is shaped like an arc, the width of the flow path can be made constant near the window, and pressure gradients can be suppressed. It is necessary to process the material into 3 types, which leads to a significant increase in costs. In addition, by making the window arc-shaped, the window surface has optical power (that is, it converges/diverges light rays), so unless the window is precisely processed, it will affect the optical performance of the optical writing device. There is a risk that the focal position and beam shape will be distorted.

On the other hand, in a configuration in which the window protrudes and is separated from the rotating polygon mirror, the rate of change in the distance between the window and the rotating polygon mirror can be reduced, so noise can be reduced in areas where the distance is narrow. However, since air is rapidly expanded/compressed near the protrusion, the vicinity of the protrusion may become a source of noise. In addition, a configuration in which the entire wall surface of the housing other than the window is separated from the rotating polygon mirror to eliminate the protrusion can be considered, but the optical deflector may compress the space inside the optical writing device and reduce the degree of freedom in design. The distance between the parts and the optical deflector may become close, making assembly difficult.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical deflector, an optical writing device, and an image forming apparatus that can reduce noise in the vicinity of a flat window of an optical deflector with a simple configuration.

The invention according to claim 1 is made to achieve the above object,
In the optical deflector,
a rotating polygon mirror that has a mirror surface on its outer peripheral surface and reflects the light rays emitted from the light source on the mirror surface;
a drive unit that rotationally drives the rotating polygon mirror;
a transparent flat plate-shaped window that allows light rays incident on the rotating polygon mirror and light rays reflected by the rotating polygon mirror to pass through;
a casing having a bottom surface, a wall surface, and a top plate, and storing the rotating polygon mirror together with the window disposed in the opening part of the wall surface;
Equipped with
A groove is formed in at least one of the bottom surface and the top plate in a region between the window and a circumscribed circle of the rotating polygon mirror ,
The groove portion is characterized in that it is formed to include a range from the upstream side to the downstream side of the window with respect to the rotation direction of the rotating polygon mirror.

The invention according to claim 2 is the optical deflector according to claim 1,
The wall surface is characterized in that it is formed into a circular shape in plan view.

The invention according to claim 3 is the optical deflector according to claim 1 or 2,
The rotating polygon mirror is characterized in that it is sealed by the window and the housing.

The invention according to claim 4 is the optical deflector according to any one of claims 1 to 3,
The groove portion is characterized in that it is formed to include a portion that contacts the window in plan view.

The invention according to claim 5 is the optical deflector according to any one of claims 1 to 4,
The groove portion is characterized in that it is formed to include a portion that overlaps an inscribed circle of the rotating polygon mirror in plan view.

The invention according to claim 6 is the optical deflector according to any one of claims 1 to 5 ,
The depth of the groove portion becomes deeper as the distance between the circumscribed cylinder of the rotating polygon mirror and the window becomes shorter.

The invention according to claim 7 is the optical deflector according to claim 6 ,
The depth of the groove is determined in the direction of the rotation axis of the circumscribed cylinder of the casing, the window, and the rotation polygon mirror in a side cross section at an arbitrary angle passing through the window and the rotation axis of the rotation polygon mirror. The feature is that the extension line of and the area of the part surrounded by are set to be constant.

The invention according to claim 8 is the optical deflector according to any one of claims 1 to 7 ,
The groove is characterized in that the surface on which it is formed is connected to other parts in a curved shape.

The invention according to claim 9 is the optical deflector according to any one of claims 1 to 8 ,
The depth of the groove portion is characterized by changing in a first-order differentiable manner in a direction parallel to the window.

The invention according to claim 10 is the optical deflector according to any one of claims 1 to 9 ,
The depth of the groove portion is characterized in that it changes in a first-order differentiable manner with respect to a direction perpendicular to the window.

The invention according to claim 11 is the optical deflector according to any one of claims 1 to 10 ,
The distance between the rotation center of the rotating polygon mirror and the window is shorter than the distance between the rotation center of the rotating polygon mirror and the wall surface.

The invention according to claims 1 and 2 is
In an optical writing device,
a light source and
The optical deflector according to any one of claims 1 to 11 , which deflects the light beam emitted from the light source;
an imaging optical system that forms an image of the light beam deflected by the optical deflector on a scanned surface of an image carrier;
It is characterized by having the following.

The invention according to claims 1 to 3 is
In the image forming device,
an image carrier;
a charging unit that charges the image carrier;
The optical writing device according to claim 12 , wherein an electrostatic latent image is formed on the image carrier by irradiating the image carrier charged by the charging unit with a light beam;
a developing section that visualizes the electrostatic latent image into a toner image by supplying toner to the image carrier irradiated with the light beam;
a transfer unit that transfers the toner image to paper;
a fixing unit that fixes the toner image transferred by the transfer unit to the paper;
It is characterized by having the following.

According to the present invention, noise near the flat window of the optical deflector can be reduced with a simple configuration.

1 is a diagram showing a schematic configuration of an image forming apparatus according to an embodiment. FIG. 2 is a perspective view showing the configuration of an optical writing device. FIG. 3 is a side cross-sectional view showing the configuration of an optical deflector. FIG. 1 is an external perspective view and a plan view showing a schematic configuration of an optical deflector. FIG. 3 is a plan view illustrating an example of a groove portion provided in a region where an air flow path is narrowed. FIG. 2 is a plan view and a side sectional view of an optical deflector showing an example of a cross-sectional area of an air flow path near a window. FIG. 3 is a diagram showing the relationship between the cross-sectional area of the air flow path near the window and the bottom position in a direction parallel to the window. FIG. 7 is a side view showing an example of how the boundary between the groove and another location on the bottom surface is connected in a curved shape. It is a figure which shows an example of the fluid analysis result regarding pressure distribution in the vicinity of a window. FIG. 7 is a plan view showing a modification of the optical deflector in which a part of the wall surface is made flat. FIG. 3 is a diagram showing an example of how the pressure gradient becomes large at a point where the distance between the rotating polygon mirror and the window becomes narrow in a conventional optical deflector.

Embodiments of the present invention will be described in detail below with reference to the drawings. In the following description, the direction parallel to the window 36 shown in FIG. 4(B) will be referred to as the X direction, the direction perpendicular to the window 36 will be referred to as the Y direction, and the direction perpendicular to the X and Y directions will be referred to as the Z direction.

First, the configuration of image forming apparatus 1000 in this embodiment will be described.
The image forming apparatus 1000 according to the present embodiment is used as, for example, a laser printer or a digital copying machine, and as shown in FIG. The apparatus 100, an image carrier 200 such as a photoconductor provided corresponding to the optical writing device 100, a charging section 210 that charges the image carrier 200, and a toner toner to the image carrier 200 irradiated with light. A developing section 220 that develops an electrostatic latent image into a toner image by supplying it, an intermediate transfer belt 300, a transfer section 400 that transfers the toner image onto paper P, and a toner image transferred by the transfer section 400. A fixing unit 500 that fixes onto the paper P is configured.

The image forming apparatus 1000 forms a toner image on the image carrier 200 exposed to laser light emitted from the optical writing device 100, and transfers the toner image onto the intermediate transfer belt 300. Next, the image forming apparatus 1000 presses and transfers the toner image transferred to the intermediate transfer belt 300 onto the paper P by the transfer unit 400, and heats and pressurizes the paper P by the fixing unit 500, thereby producing the toner image. is fixed on the paper P. Then, the image forming apparatus 1000 performs image forming processing by conveying the paper P using a paper discharge roller (not shown) or the like and discharging the paper onto a tray (not shown).

As shown in FIG. 2, the optical writing device 100 is a device that irradiates a laser beam (light beam) L in the main scanning direction onto an image carrier 200 charged by a charging unit 210 to expose the image carrier 200 to light. It is.
The optical writing device 100 includes a light source 1 such as a semiconductor laser that emits a laser beam L, a light source optical system 2 that shapes the laser beam L emitted from the light source 1 and guides it to an optical deflector 3, and a side surface (outer peripheral surface). The optical deflector 3 deflects the laser beam L using a rotating polygonal mirror 31 (see FIG. 3) having a polygonal prism shape made of mirror surfaces, and the laser beam L deflected by the optical deflector 3 is directed to the image carrier 200. It is configured with a scanning optical system 4 that focuses and scans light onto a surface to be scanned, a housing 5 that holds each of the above-mentioned elements, and a cover member 6 that is placed over the housing 5 to prevent dust from the surrounding environment. There is.

As shown in FIG. 3, the optical deflector 3 includes a rotating polygon mirror 31 that has a mirror surface on its outer peripheral surface and reflects the laser beam L emitted from the light source 1 on the mirror surface, and a magnet bonded to the rotating polygon mirror 31. 32, a coil 33a that rotates the rotating polygon mirror 31 at high speed using electromagnetic force, a connector 33b that receives power/control signals from the image forming apparatus 1000, and a drive board that holds a control IC 33c and supplies power to/controls the coil 33a. 33, a rotation shaft 34 of the rotating polygon mirror 31, a bearing 35 for smoothly rotating the rotating polygon mirror 31, a transparent flat plate shape, and a laser beam L incident on the rotating polygon mirror 31 and the rotating polygon mirror 31. The device includes a glass window 36 through which the laser beam L reflected by the laser beam L passes through, and a casing 37 in which the above-described elements are housed. The magnet 32 and the drive board 33 (coil 33a, connector 33b, control IC 33c) function as a drive unit of the present invention that rotates the rotating polygon mirror 31.

The casing 37 has a bottom surface 37a, a wall surface 37b, and a top plate 37c, and seals the rotating polygon mirror 31 together with a window 36 disposed in the opening of the wall surface 37b. In this embodiment, the drive board 33 also serves as the top plate 37c, but the drive board 33 and the top plate 37c may be separate bodies, and the top plate 37c may hold the drive board 33. The bottom surface 37a and the wall surface 37b are manufactured by aluminum die casting (injection molding and cutting using a mold).

The wall surface 37b is formed into a substantially circular shape when viewed from above, and the center of the circle is located at the same position as the rotation center (rotation axis 34) of the rotating polygon mirror 31. The distance between the rotation center of the rotating polygon mirror 31 and the window 36 is shorter than the distance between the rotation center of the rotating polygon mirror 31 and the wall surface 37b.

FIG. 4(A) shows an external perspective view of the casing 37, window 36, and groove 38, and FIG. 4(B) shows a plan view in which the rotating polygon mirror 31 is added. Moreover, FIG. 5 shows a plan view showing an example of how the groove portion 38 is provided in the region where the flow path through which the air E flows is narrowed.

As shown in FIGS. 3 to 5, a groove 38 is formed in the bottom surface 37a in a region between the window 36 and the circumscribed circle C1 of the rotating polygon mirror 31, which is recessed from other parts of the bottom surface 37a. There is. Note that the groove portion 38 does not necessarily need to be formed on the bottom surface 37a, and may be formed on at least one of the bottom surface 37a and the top plate 37c. In a direction perpendicular to the window 36 (Y direction in the figure), the groove 38 extends from the part that contacts the window 36 to the inside of the inscribed circle C2 of the rotating polygon mirror 31 (that is, the part that overlaps with the inscribed circle C2) in a plan view. It is formed including the area up to. Note that if the groove part 38 goes too far inside the inscribed circle C2, it may affect the pressure gradient around the part where it goes in. It is more preferable to include the following. Further, the groove portion 38 is formed to include a range from the upstream side to the downstream side of the window 36 in the direction parallel to the window 36 (X direction in the figure) with respect to the rotation direction of the rotating polygon mirror 31 (arrow B in the figure). has been done.

As described above, by providing the groove portion 38, the flow path of the air E around the window 36 can be widened, so that the pressure gradient around the window 36 can be suppressed, and noise can be suppressed. Furthermore, by making the groove portion 38 include more areas where the flow path of the air E is narrow, it becomes possible to suppress the pressure gradient more effectively, and it becomes possible to suppress the noise more effectively. can.

6(A) is a plan view of the optical deflector 3 (however, the drive board 33 (top plate 37c) is omitted), and FIG. 6(B) is a plan view of the optical deflector 3 taken along the line A1-A1 in FIG. 6(A). A cross-sectional view of (however, the drive board 33 (top plate 37c) is shown) is shown. In addition, FIG. 7A shows a graph showing the relationship between the distance L1 between the circumscribed cylinder C11 of the rotating polygon mirror 31 and the window 36, and the bottom position in the direction parallel to the window 36 (X direction in the figure). FIG. 7(B) is a graph showing the relationship between the depth L2 of the groove and the bottom position in the direction parallel to the window 36 (X direction in the figure), and FIG. 7(C) is a graph showing the relationship between L1×L2, Graphs showing the relationship between the bottom surface position in a direction parallel to the window 36 (X direction in the figure) are shown.

As shown in FIGS. 7A and 7B, the depth L2 of the groove portion 38 becomes deeper as the distance L1 between the circumscribed cylinder C11 of the rotating polygon mirror 31 and the window 36 becomes shorter. In particular, the depth L2 of the groove 38 is determined by the depth L2 of the housing 37 (the groove 38, the top plate 37c), the window 36, and the extension line of the circumscribed cylinder C11 of the rotating polygon mirror 31 in the direction of the rotation axis 34, so that the area S (see FIG. 6(B)) is approximately constant. It is preferable that it is set to .

As described above, by making the cross-sectional area of the air flow path in the vicinity of the window 36 constant, it becomes possible to suppress pressure gradients more effectively, and noise can be suppressed even more effectively.

The groove portion 38 is preferably connected to other portions in a curved shape on the surface on which it is formed (the bottom surface 37a in this embodiment). That is, as shown in FIG. 8, the boundary D between the groove 38 and other parts of the surface (bottom surface 37a) on which the groove 38 is formed is smoothly connected with no corners, for example, in an R shape or a spline curve shape. It is preferable.
Further, the depth of the groove portion 38 is set to vary in a first-order differentiable manner in a direction parallel to the window 36 (X direction in the figure) and in a direction perpendicular to the window 36 (Y direction in the figure). is preferred.

As mentioned above, the shape of the boundary D between the groove 38 and other parts, the direction parallel to the window 36 (X direction in the figure), and the direction perpendicular to the window 36 (Y direction in the figure) is made smooth. This makes it possible to suppress the generation of pressure loss (that is, suppress the generation of vortices and smooth the air flow), making it possible to suppress the generation of pressure gradients due to sudden changes in the shape of the flow path. Noise can be suppressed.

(Example)
Below, fluid analysis results regarding the pressure distribution near the window 36 in the optical deflector 3 of this embodiment will be explained. SolidWorks(R) Flow Simulation was used as software for fluid analysis. Two model shapes for fluid analysis (computer simulation) were created: one with groove 38 (example) and one without groove 38 (comparative example). In the example, similar to the optical deflector 3 of the present embodiment, a groove portion 38 whose depth changes in an arc shape in a direction parallel to the window 36 is provided on the bottom surface 37a of the housing 37 near the window 36. ing. The groove portion 38 has a depth of 2.5 mm and a width of 18.6 mm, and the window 36 has a length of 18.1 mm. In addition, in the comparative example, the groove portion 38 of the example is not provided, and the bottom surface 37a is made flat. The conditions for the fluid analysis are a rotational speed of 40,150 rpm, and the analysis specifications require that the rotating body be rotationally symmetrical, so the circumscribed cylinder C11 of the rotating polygon mirror 31 is rotated.

FIG. 9 shows an example of fluid analysis results regarding the pressure distribution near the window 36. G1 in the figure is a graph showing the pressure distribution of the example, and G2 is a graph showing the pressure distribution of the comparative example.
Regarding the Max-min of the pressure distribution near the window 36 (M1 in the figure is the Max-min of the example, M2 is the Max-min of the comparative example), as shown in FIG. 9, it is 76 Pa in the comparative example, whereas , was 43 Pa in the example. Thus, in the example, the effect of reducing the pressure distribution by about 40% was recognized by providing the groove 38 compared to the comparative example in which the groove 38 was not provided.

As described above, the optical deflector 3 of the image forming apparatus 1000 according to the present embodiment has a mirror surface on the outer peripheral surface, and the rotating polygon mirror 31 reflects the light beam (laser light L) emitted from the light source 1 on the mirror surface. , a drive unit (magnet 32, drive board 33) that rotationally drives the rotating polygon mirror 31; The housing 37 includes a window 36, a bottom surface 37a, a wall surface 37b, and a top plate 37c, and houses the rotating polygon mirror 31 together with the window 36 disposed in the opening of the wall surface 37b. Further, a groove portion 38 is formed in at least one of the bottom surface 37a and the top plate 37c in a region between the window 36 and the circumscribed circle C1 of the rotating polygon mirror 31.
Therefore, according to the optical deflector 3 according to the present embodiment, the air flow path around the flat window 36 can be widened, so that the pressure gradient accompanying the change in the cross-sectional area of the flow path around the window 36 can be suppressed. This makes it possible to reduce noise near the window 36 with a simple configuration.

Moreover, according to the optical deflector 3 according to the present embodiment, the wall surface 37b is formed in a circular shape in plan view.
Therefore, according to the optical deflector 3 according to the present embodiment, the air flow in the area surrounded by the housing 37 can be made smooth, so that the noise of the optical deflector 3 can be suppressed.

Further, according to the optical deflector 3 according to the present embodiment, the rotating polygon mirror 31 is sealed by the window 36 and the housing 37.
Therefore, according to the optical deflector 3 according to the present embodiment, the rotating polygon mirror 31, which is the source of the noise, can be isolated from the outside world, so that the noise generated from the rotating polygon mirror 31 can be suppressed.

Moreover, according to the optical deflector 3 according to the present embodiment, the groove portion 38 is formed to include a portion that contacts the window 36 in a plan view.
Therefore, according to the optical deflector 3 according to the present embodiment, the groove portion 38 can include more areas where the air flow path is narrow, so that the pressure gradient can be suppressed more effectively. This makes it possible to suppress noise more effectively.

Moreover, according to the optical deflector 3 according to the present embodiment, the groove portion 38 is formed to include a portion that overlaps with the inscribed circle C2 of the rotating polygon mirror 31 in plan view.
Therefore, according to the optical deflector 3 according to the present embodiment, the groove portion 38 can include more areas where the air flow path is narrow, so that the pressure gradient can be suppressed more effectively. This makes it possible to suppress noise more effectively.

Further, according to the optical deflector 3 according to the present embodiment, the groove portion 38 is formed to include the range from the upstream side to the downstream side of the window 36 in the rotation direction of the rotating polygon mirror 31.
Therefore, according to the optical deflector 3 according to the present embodiment, the groove portion 38 can include more areas where the air flow path is narrow, so that the pressure gradient can be suppressed more effectively. This makes it possible to suppress noise more effectively.

Further, according to the optical deflector 3 according to the present embodiment, the depth of the groove portion 38 becomes deeper as the distance L1 between the circumscribed cylinder C11 of the rotating polygon mirror 31 and the window 36 becomes shorter.
Therefore, according to the optical deflector 3 according to the present embodiment, the cross-sectional area of the air flow path near the window 36 can be made substantially constant, so that it is possible to suppress the pressure gradient more effectively. Noise can be suppressed more effectively.

Further, according to the optical deflector 3 according to the present embodiment, the depth of the groove portion 38 is such that the depth of the groove portion 38 is the same as that of the housing 37 in a side cross section at an arbitrary angle passing through the window 36 and the rotation axis 34 of the rotating polygon mirror 31. The area S of the portion surrounded by the window 36 and the extension line of the circumscribed cylinder C11 of the rotating polygon mirror 31 in the direction of the rotation axis 34 is set to be constant.
Therefore, according to the optical deflector 3 according to the present embodiment, the cross-sectional area of the air flow path near the window 36 can be made constant, so that it is possible to suppress the pressure gradient more effectively, and Noise can be effectively suppressed.

Further, according to the optical deflector 3 according to the present embodiment, the groove portion 38 is connected to other portions in a curved shape on the surface in which the groove portion 38 is formed.
Therefore, according to the optical deflector 3 according to the present embodiment, by smoothing the shape of the boundary between the groove 38 and other parts, the generation of pressure loss is suppressed (that is, the generation of vortices is suppressed and the air is Since the flow can be smoothed), it is possible to suppress the generation of a pressure gradient due to a sudden change in the shape of the flow path, and it is possible to suppress noise.

Further, according to the optical deflector 3 according to the present embodiment, the depth of the groove portion 38 changes in a first-order differentiable manner in a direction parallel to the window 36.
Therefore, according to the optical deflector 3 according to the present embodiment, by smoothing the shape of the groove portion 38 in the direction parallel to the window 36 (X direction in the figure), the generation of pressure loss is suppressed (that is, the vortex Since it is possible to suppress the generation of pressure gradients and smooth the air flow, it is possible to suppress the generation of pressure gradients due to sudden changes in the shape of the flow path, and it is possible to suppress noise.

Further, according to the optical deflector 3 according to the present embodiment, the depth of the groove portion 38 changes in a first-order differentiable manner in a direction perpendicular to the window 36.
Therefore, according to the optical deflector 3 according to the present embodiment, by smoothing the shape of the groove portion 38 in the direction perpendicular to the window 36 (Y direction in the figure), the generation of pressure loss is suppressed (i.e., the vortex is reduced). Since it is possible to suppress the generation of pressure gradients and smooth the air flow, it is possible to suppress the generation of pressure gradients due to sudden changes in the shape of the flow path, and it is possible to suppress noise.

Further, according to the optical deflector 3 according to the present embodiment, the distance between the rotation center of the rotating polygon mirror 31 and the window 36 is shorter than the distance between the rotation center of the rotating polygon mirror 31 and the wall surface 37b.
Therefore, according to the optical deflector 3 according to the present embodiment, the pressure gradient in the entire interior of the optical deflector 3 can be suppressed by widening the air flow path around the window 36. Noise can be reduced.

Although the present invention has been specifically described above based on the embodiments, the present invention is not limited to the above embodiments, and can be modified without departing from the gist thereof.

For example, in the above embodiment, the rotating polygon mirror 31 is sealed by the housing 37 and the window 36, but the present invention is not limited to this. For example, instead of a closed configuration, it may be a partially open configuration. As described above, by partially opening the rotating polygon mirror 31, the noise from the rotating polygon mirror 31 is more likely to go outside and the noise increases, but it promotes heat dissipation from the rotating polygon mirror 31 and reduces the temperature of the rotating polygon mirror 31. be able to. Of course, noise can also be reduced by providing the groove 38 compared to a configuration in which the groove 38 is not provided as in the prior art.

Further, in the above embodiment, the groove portion 38 is provided on at least one of the bottom surface 37a and the top plate 37c near the window 36, but the present invention is not limited to this. For example, if the groove portion 38 is formed at another location (for example, as shown in FIG. 10, when a part of the wall surface 37b (the part facing the window 36 in FIG. 10) is made into a flat surface 37d due to space constraints, the bottom surface near the flat surface 37d 37a and at least one of the top plate 37c).

Further, in the above embodiment, the case 37 is made of aluminum die-casting, but it may be made of other materials, for example, made of resin molding. Further, although the window 36 is described as being made of glass, it may be made of other materials, or may be made of a transparent resin material.

In addition, the detailed configuration of each device constituting the image forming apparatus and the detailed operation of each device can be changed as appropriate without departing from the spirit of the present invention.

1000 Image forming apparatus 100 Optical writing device 1 Light source 2 Light source optical system 3 Optical deflector 31 Rotating polygon mirror 32 Magnet (drive unit)
33 Drive board (drive part)
33a Coil 33b Connector 33c Control IC
34 Rotating shaft 35 Bearing 36 Window 37 Housing 37a Bottom surface 37b Wall surface 37c Top plate 38 Groove section 4 Scanning optical system 5 Housing 6 Cover member 200 Image carrier 210 Charging section 220 Developing section 300 Intermediate transfer belt 400 Transfer section 500 Fixing section L Laser light (ray)

Claims (13)

a rotating polygon mirror that has a mirror surface on its outer peripheral surface and reflects the light rays emitted from the light source on the mirror surface;
a drive unit that rotationally drives the rotating polygon mirror;
a transparent flat plate-shaped window that allows light rays incident on the rotating polygon mirror and light rays reflected by the rotating polygon mirror to pass through;
a casing having a bottom surface, a wall surface, and a top plate, and storing the rotating polygon mirror together with the window disposed in the opening part of the wall surface;
Equipped with
A groove is formed in at least one of the bottom surface and the top plate in a region between the window and a circumscribed circle of the rotating polygon mirror ,
The optical deflector is characterized in that the groove portion is formed to include a range from the upstream side to the downstream side of the window with respect to the rotation direction of the rotating polygon mirror. The optical deflector according to claim 1, wherein the wall surface is formed into a circular shape when viewed from above. 3. The optical deflector according to claim 1, wherein the rotating polygon mirror is hermetically sealed by the window and the housing. The optical deflector according to any one of claims 1 to 3, wherein the groove portion is formed to include a portion that contacts the window in plan view. The optical deflector according to any one of claims 1 to 4, wherein the groove portion is formed to include a portion that overlaps an inscribed circle of the rotating polygon mirror in plan view. The optical deflector according to any one of claims 1 to 5 , wherein the depth of the groove becomes deeper as the distance between the circumscribed cylinder of the rotating polygon mirror and the window becomes shorter. The depth of the groove is determined in the direction of the rotation axis of the circumscribed cylinder of the casing, the window, and the rotation polygon mirror in a side cross section at an arbitrary angle passing through the window and the rotation axis of the rotation polygon mirror. 7. The optical deflector according to claim 6 , wherein the area of the portion surrounded by the extension line and is set to be constant. The optical deflector according to any one of claims 1 to 7 , wherein the groove portion is curvedly connected to another portion on the surface on which the groove portion is formed. 9. The optical deflector according to claim 1, wherein the depth of the groove varies in a first-order differentiable manner in a direction parallel to the window. 10. The optical deflector according to claim 1, wherein the depth of the groove varies in a first-order differentiable manner in a direction perpendicular to the window. The distance between the rotation center of the rotating polygon mirror and the window is shorter than the distance between the rotation center of the rotating polygon mirror and the wall surface, according to any one of claims 1 to 10 . light deflector. a light source and
The optical deflector according to any one of claims 1 to 11 , which deflects the light beam emitted from the light source;
an imaging optical system that forms an image of the light beam deflected by the optical deflector on a scanned surface of an image carrier;
An optical writing device comprising: an image carrier;
a charging unit that charges the image carrier;
The optical writing device according to claim 12 , wherein an electrostatic latent image is formed on the image carrier by irradiating the image carrier charged by the charging unit with a light beam;
a developing section that visualizes the electrostatic latent image into a toner image by supplying toner to the image carrier irradiated with the light beam;
a transfer unit that transfers the toner image to paper;
a fixing unit that fixes the toner image transferred by the transfer unit to the paper;
An image forming apparatus comprising:

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