JP7447653B2 - 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.
A rotating polygon mirror rotates at a high speed of about 40,000 rpm, so in an optical deflector that uses it, the pressure distribution around the rotating polygon mirror increases, causing problems such as increased noise and rotational resistance. be. When the rotational resistance increases, the driving force required for rotation increases, which increases the amount of heat generated, leading to fluctuations in the performance of optical elements such as lenses and a reduction in mechanical life. Furthermore, an increase in rotational resistance leads to fluctuations in rotational speed, leading to a reduction in image quality (density unevenness).

Therefore, as a technology for suppressing the noise of an optical deflector using a rotating polygon mirror, a configuration 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).
Furthermore, a configuration has been disclosed in which the window is projected to be separated from the rotating polygon mirror and the air flow path is smoothly connected (see, for example, Patent Document 2).

Japanese Patent Application Publication No. 8-152573 JP2005-301081A

However, in the configuration using a flat window described in Patent Document 1 (light deflector 3001), as shown in FIGS. 18(A) to 18(C), the distance between the rotating polygon mirror 31 and the window 36 is The pressure gradient becomes large at the point where the pressure becomes narrow (symbol F in the figure), which causes noise. Here, FIG. 18(A) shows a plan view of a conventional optical deflector (however, the top plate 37c of the housing 37 is omitted), and FIG. 18(B) shows the reference numerals in FIG. 18(A). FIG. 18C shows an enlarged view of the area indicated by W, and a cross-sectional view taken along the line T1-T1 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 to a large extent, resulting in a significant increase in cost. Furthermore, 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.

Furthermore, in the configuration described in Patent Document 2 that smoothly connects the air flow path between the protrusion (window) and the housing wall surface, rapid expansion/compression of air in the vicinity of the protrusion can be suppressed. , it becomes possible to reduce the pressure difference between the space near the window and the space far from the window, and the generation of noise can be reduced.

Below, with reference to FIG. 19, fluid analysis results near the window 36 in the configuration (shape) of the optical deflector 3002 described in Patent Document 2 will be described. FIG. 19(A) is a diagram showing an example of air flow in the configuration of the optical deflector 3002 described in Patent Document 2. FIG. 19(B) is a diagram showing an example of the pressure distribution around the rotating polygon mirror 31. FIG. 19C is a diagram showing an example of the flow velocity distribution around the rotating polygon mirror 31.
SolidWorks(R) Flow Simulation was used as software for fluid analysis. 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.

In FIGS. 19(B) and 19(C), the horizontal axis of the graph indicates the position along the circumference around the rotation axis of the rotating polygon mirror 31, with the bottom being 0°, and the position being rotated clockwise. This is what is expressed. In FIG. 19(B), the vertical axis of the graph is the pressure based on the pressure at the 0° point as 0 Pa (because the pressure shifts overall depending on the overall distance between the wall surface and the rotating polygon mirror 31). In the pressure distribution shown in FIG. 19(B), there is a point J1 where the pressure drops sharply on the upstream side in the rotational direction of the rotating polygon mirror 31 (near 270°) than the window 36 (near 0°), and the pressure distribution is suppressed. I haven't been able to do it. Note that the Max-min of the pressure distribution was 44.4 Pa. In FIG. 19(C), the vertical axis of the graph is the flow velocity [m/s].

In the configuration described in Patent Document 2, a flow in which the pressure rapidly decreases will be explained. First, if the flow velocity of the air around the rotating polygon mirror 31 does not change at a point where the channel width increases in the rotational direction of the rotating polygon mirror 31, the volumetric flow rate increases as the channel cross-sectional area increases. To go. Next, at a location where the flow path width begins to expand in the rotational direction of the rotating polygon mirror 31, air is pulled to a location where the volumetric flow rate increases, and the pressure drops rapidly.

An object of the present invention is to provide an optical deflector, an optical writing device, and an image forming device that can reduce noise/rotational resistance near a flat window.

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
The wall surface is
In the rotation direction of the rotating polygon mirror, at least one of the upstream side and the downstream side of the window is provided with a resistance generating part that generates resistance to the air flow due to the rotation of the rotating polygon mirror,
The resistance generating section is configured to narrow a cross-sectional area of the air flow path between the circumscribed circle of the rotating polygon mirror in at least one of the width direction and the height direction of the flow path. established in
On the downstream side of the resistance generating section in the rotational direction , there is a region where the cross-sectional area of the flow path increases between the resistance generating section and the circumscribed circle, and a region between the circumscribed circle toward the downstream in the rotational direction . A region where the cross-sectional area of the flow path is narrowed and a flow velocity relaxation section provided in this order are adjacent to each other ,
The wall surface is characterized in that a surface facing the window is formed in a curved shape so that a distance from the circumscribed circle is constant .

The invention according to claim 2 is the optical deflector according to claim 1,
The resistance generating section is provided on the upstream side and the downstream side of the window.

The invention according to claim 3 is the optical deflector according to claim 1 or 2,
In the rotation direction,
The cross-sectional area of the flow path at the starting point of the resistance generating part is A1,
When the cross-sectional area of the flow path at the end point of the resistance generating part is A2,
It is characterized by satisfying A1≧A2.

The invention according to claim 4 is the optical deflector according to any one of claims 1 to 3,
The resistance generating section is characterized in that it is formed by bending the wall surface inward.

The invention according to claim 5 is the optical deflector according to any one of claims 1 to 4,
The resistance generating portion is characterized in that a convex portion is provided inside the wall surface.

The invention according to claim 6 is the optical deflector according to any one of claims 1 to 5,
The resistance generating section is characterized in that at least one of the top plate and the bottom surface protrudes inward.

The invention according to claim 7 is the optical deflector according to any one of claims 1 to 6,
The resistance generating section is characterized in that a plurality of protrusions are provided on at least one of the wall surface, the top plate, and the bottom surface.

The invention according to claim 8 is the optical deflector according to any one of claims 1 to 7,
The flow velocity moderating section is characterized in that a channel width, which is a width in the channel between the circumscribed circle, is adjusted so that the channel cross -sectional area changes.

The invention according to claim 9 is the optical deflector according to claim 8,
The flow velocity relaxation section is characterized in that it is formed in a planar shape.

The invention according to claim 10 is the optical deflector according to any one of claims 1 to 9,
The flow velocity relaxation part is characterized in that a flow path height, which is a height in the flow path between the circumscribed circle and the flow path, is adjusted so that the cross-sectional area of the flow path changes .

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

The invention according to claim 12 is the optical deflector according to any one of claims 1 to 11 ,
The present invention is characterized in that a plurality of windows are provided.

The invention according to claims 1 to 3 is
In an optical writing device,
a light source and
The optical deflector according to any one of claims 1 to 12 , 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 claim 14 is:
In the image forming device,
an image carrier;
a charging unit that charges the image carrier;
The optical writing device according to claim 13 , 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/rotational resistance near the flat window 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. It is a figure explaining the fluid analysis result of the window vicinity in the structure of an optical deflector. FIG. 3 is a plan view showing a configuration in which a resistance generating section is provided only on the downstream side of the window. It is a figure explaining the fluid analysis result concerning pressure distribution. FIG. 3 is a diagram illustrating a flow velocity vector diagram under conditions where the pressure distribution is the smallest. FIG. 3 is a diagram illustrating a pressure distribution contour diagram under conditions where the pressure distribution is the smallest. FIG. 3 is a diagram illustrating a pressure distribution contour diagram under conditions where the pressure distribution becomes large. FIG. 7 is a diagram illustrating a fluid analysis result near a window in the configuration of an optical deflector according to Modification 1. FIG. 7 is a diagram illustrating a fluid analysis result near a window in the configuration of an optical deflector according to Modification 2. FIG. It is a figure which shows the modification 3 which made the resistance generation part the structure which provided the convex part inside the wall surface. It is a figure which shows the modification 4 which made the resistance generation part the structure which made the bottom protrude inward. It is a figure which shows the modification 5 which made the resistance generation part the structure which provided the several convex part in the wall surface. It is a figure which shows the modification 6 which had the structure which made the bottom surface protrude inward and adjusted the flow path height in a flow velocity relaxation part. It is a figure which shows the modification 7 which has a structure in which two windows are provided, one on each opposing wall surface. FIG. 12 is a diagram showing a modified example 8 in which two windows are arranged adjacent to each other with different arrangement angles. FIG. 7 is a diagram showing an example of how the pressure gradient increases at a location where the distance between the rotating polygon mirror and the window becomes narrow in the optical deflector described in Patent Document 1. FIG. 6 is a diagram illustrating a fluid analysis result near a window in the configuration of the optical deflector described in Patent Document 2.

Embodiments of the present invention will be described in detail below with reference to the drawings. In the following description, the horizontal direction shown in FIG. 4(A) is referred to as the X direction, the vertical direction as the Y direction, and the direction orthogonal to the X direction and the Y direction as the Z direction.

First, the configuration of image forming apparatus 1000 according to 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 photoreceptor 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. The fixing unit 500 fixes onto the paper P.

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 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 bottom surface 37a and the wall surface 37b are manufactured by aluminum die casting (injection molding and cutting using a mold).

FIG. 4 explains the fluid analysis results near the window 36 in the configuration (shape) of the optical deflector 3. FIG. 4(A) is a plan view showing the configuration of the optical deflector 3. FIG. FIG. 4(B) is a diagram showing an example of the pressure distribution around the rotating polygon mirror 31. FIG. 4C is a diagram showing an example of the flow velocity distribution around the rotating polygon mirror 31.

As shown in FIG. 4A, the wall surface 37b generates resistance to the air flow due to the rotation of the rotating polygon mirror 31 on the upstream side of the window 36 (near 0°) in the rotation direction of the rotating polygon mirror 31. A resistance generating section 371 is provided. The resistance generating section 371 is provided so as to narrow the cross-sectional area of the air flow path between the rotary polygon mirror 31 and the circumscribed circle C1 (see symbol E1 in FIG. 4(A)). . Here, the resistance generating portion 371 is formed by bending the wall surface 37b inward. Adjacent to the downstream side of the resistance generation section 371 is a flow velocity relaxation section 372 in which a region E2 and a region E3, in which the cross-sectional area of the flow path between the circumscribed circle C1 and the circumscribed circle C1, are provided in order in the downstream direction. With the above configuration, the flow path width narrows (E1) → widens (E2) → narrows (E3) from the resistance generation part 371 to the flow velocity relaxation part 372, and the cross-sectional area of the flow path changes. There is. That is, in the example shown in FIG. 4(A), the flow path width, which is the width of the flow path between the flow velocity relaxation part 372 and the circumscribed circle C1, is adjusted. In the example shown in FIG. 4(A), the wall surface 37b of the flow velocity relaxation section 372 is formed in a planar (linear) shape, so that design, analysis, and dimensional management can be simplified.
Note that in the example shown in FIG. 4A, a configuration in which the resistance generation section 371 (and the flow velocity relaxation section 372) is provided on the upstream side of the window 36 is illustrated and explained; It may also be configured so that it is provided on the side.

Further, as shown in FIG. 4A, the wall surface 37b is formed in a curved shape so that the surface facing the window 36 (around 180 degrees) is at a constant distance from the circumscribed circle C1. Thereby, the cross-sectional area of the flow path on the side facing the window 36 can be made constant, so it is possible to suppress the occurrence of pressure distribution.

Further, as shown in FIG. 4A, the distance D1 between the window 36 and the rotation center (rotation axis 34) of the rotating polygon mirror 31 is the distance D1 between the window 36 and the rotation center (rotation axis 34) of the rotating polygon mirror 31. 34) is longer than the distance D2. Thereby, it is possible to suppress the pressure drop in the portion where the cross-sectional area of the flow path is reduced near the window 36.

In the configuration of the optical deflector 3 according to this embodiment, the Max-min of the pressure distribution is 41.4 Pa, which is different from the configuration (44.4 Pa) of the optical deflector 3002 according to the conventional technology (see FIG. 19(A)). It is smaller in comparison. In particular, the minimum pressure distribution is -35 Pa for the conventional technology (see FIG. 19(B)) → -25 Pa for the present embodiment (see FIG. 4(B)), and the minimum pressure distribution is 360°).

In addition, in the configuration of the optical deflector 3 according to the present embodiment, the flow velocity in the channel cross-sectional area enlarged portion (region of 270° to 360°) is 8 m/s or more as compared with the conventional technology (see FIG. 19(C)). This embodiment (see arrow R1 in FIG. 4(C)): The speed has fallen to 2 m/s. This suppresses air being pulled in the portion where the flow path width begins to widen, thereby suppressing a drop in pressure near 270°.

(Example)
Below, fluid analysis results related to the effect of providing the resistance generating section 371 in the optical deflector 3 of this embodiment will be explained. SolidWorks(R) Flow Simulation was used as software for fluid analysis. The model shape for the fluid analysis (computer simulation) was such that the resistance generating section 371 was provided only on the downstream side of the window 36 (see FIG. 5). In the above configuration, by reducing the number of parameters, the relationship between the parameters and changes in pressure distribution is made easier to see. The parameters are "distance between the center of rotation (of the rotating polygon mirror 31) and the diagonal wall (resistance generating part 371) (reference symbol G1 in the figure)" and "distance between the upstream (window 36) (of the resistance generating part 371) and the diagonal wall (resistance generating part 371)". 371) (represented by reference numeral G2 in the figure). The output was the pressure and flow velocity near the diagonal wall (resistance generating section 371) around the rotating polygon mirror 31.

Figure 6 shows the fluid analysis results regarding pressure distribution.
As shown in Figure 6, the pressure distribution (Max-min: unit [Pa]) is the smallest when the "distance G1 between the center of rotation and the diagonal wall" is 27.5 mm and the "angle G2 between the upstream and the diagonal wall" is 129°. became.

Next, a flow velocity vector diagram and a pressure distribution contour diagram under conditions where the pressure distribution is the smallest are shown in FIG. 7 and FIG. 8, respectively. Further, FIG. 9 shows a pressure distribution contour diagram under conditions where the pressure distribution becomes large.
In the example shown in FIG. 7, locations where the flow velocity is relatively fast are indicated by arrows H1, and locations where the flow velocity is relatively slow are indicated by arrows H2. From the velocity distribution shown in FIG. 7, it can be seen that the flow velocity is faster at a location where the channel width is narrower (symbol H3 in the figure). In addition, the air flow exiting the narrow channel width point (H3 in the figure) is caused mainly by the flow along the wall surface 37b, in addition to the slow flow that rotates around the rotating polygon mirror 31 (see the arrow H2). It can be seen that there is a flow (see arrow H1) with a high flow velocity that blows against the diagonal wall (resistance generating portion 371).
Furthermore, from the pressure distribution shown in FIG. 8, it can be seen that the pressure decreases at locations where the flow velocity is high and the channel cross-sectional area is small (locations where the channel width is narrow: reference numeral H3 in the figure). Furthermore, it can be seen that the air blown onto the diagonal wall (resistance generating portion 371) accumulates at the bending corner of the wall surface 37b (near the starting point of the resistance generating portion 371: reference numeral H4 in the figure).

Next, the conditions under which the pressure distribution becomes the smallest (see FIG. 8) and the conditions under which the pressure distribution becomes large (see FIG. 9) were compared. In addition, under the condition where the pressure distribution is the smallest (see Fig. 8), the wall surface dimension from the point where the cross-sectional area of the flow path is narrow to the corner (symbol H5 in the figure) is 11.76 mm, and under the condition where the pressure distribution is large (see Fig. 8) (see FIG. 9), the wall surface dimension from the point where the cross-sectional area of the flow path is narrow to the corner (symbol H6 in the figure) is 14.77 mm. The flow velocity (10.3 m/s) under the condition where the pressure distribution is the smallest (see Figure 8) is lower than the flow velocity (11.3 m/s) under the condition where the pressure distribution is large (see Figure 9). . This means that in the case of the condition where the pressure distribution is the smallest (see Figure 8), the wall dimension from the point where the cross-sectional area of the flow path is narrow (reference numeral H5 ) is short, and the point where the air pool occurs (symbol H4 in the figure) is close to the point where the cross-sectional area of the flow path is narrow (symbol H3 in the figure), so the velocity at the point where the cross-sectional area of the flow path is narrow decreases more. This is because it is thought that the pressure drop was further reduced.

From the above, by providing the resistance generating portion 371 formed by bending the wall surface 37b inward downstream of a location where the flow channel cross-sectional area is narrow, a pool of air is formed and the flow velocity at the location where the flow channel cross-sectional area is narrow is reduced. This makes it possible to suppress the pressure drop. In particular, the effect of suppressing pressure drop can be enhanced by placing the location where the snowdrift occurs close to a location where the cross-sectional area of the flow path is narrow.

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 (driving board 33 ) that rotationally drives the rotating polygon mirror 31 , and a window 36 that is in the shape of a transparent flat plate and allows the light rays incident on the rotating polygon mirror 31 and the light rays reflected by the rotating polygon mirror 31 to pass through. , a housing 37 that has a bottom surface 37a, a wall surface 37b, and a top plate 37c, and stores the rotating polygon mirror 31 together with a window 36 disposed in the opening of the wall surface 37b. Furthermore, the wall surface 37b includes a resistance generating section 371 that generates resistance to the air flow due to the rotation of the rotating polygon mirror 31, on at least one of the upstream side and the downstream side of the window 36 in the rotation direction of the rotating polygon mirror 31. Further, the resistance generating section 371 is provided so as to narrow the cross-sectional area of the air flow path between the rotary polygon mirror 31 and the circumscribed circle C1, and on the downstream side of the resistance generating section 371, Adjacent is a flow velocity relaxation section 372 in which a region where the cross-sectional area of the flow path between the circumscribed circle C1 widens and narrows in order toward the downstream.
Therefore, according to the optical deflector 3 according to the present embodiment, it is possible to suppress the flow velocity and the flow velocity change in the portion where the cross-sectional area of the flow path changes, so it is possible to suppress the pressure distribution around the rotating polygon mirror 31. , noise/rotational resistance near the flat window 36 can be reduced.

Further, according to the optical deflector 3 according to the present embodiment, the resistance generating section 371 is formed by bending the wall surface 37b inward.
Therefore, according to the optical deflector 3 according to the present embodiment, it is possible to suppress the flow velocity and the flow velocity change in the portion where the cross-sectional area of the flow path changes with a simple configuration, so that noise/rotational resistance near the flat window 36 can be suppressed. can be reduced with a simple configuration.

Moreover, according to the optical deflector 3 according to the present embodiment, the flow path width, which is the width of the flow path between the flow velocity relaxation part 372 and the circumscribed circle C1, is adjusted.
Therefore, according to the optical deflector 3 according to the present embodiment, it is possible to easily suppress the flow velocity and the flow velocity change in the portion where the cross-sectional area of the flow path changes, so that the noise/rotational resistance in the vicinity of the flat window 36 can be easily suppressed. can be reduced to

Further, according to the optical deflector 3 according to the present embodiment, the flow velocity relaxation section 372 is formed in a planar shape.
Therefore, according to the optical deflector 3 according to the present embodiment, design, analysis, and dimensional control can be simplified compared to the case where the wall surface 37b is a curved surface, so that molding can be facilitated.

Further, according to the optical deflector 3 according to the present embodiment, the wall surface 37b is formed in a curved shape such that the surface facing the window 36 is at a constant distance from the circumscribed circle C1.
Therefore, according to the optical deflector 3 according to the present embodiment, the cross-sectional area of the flow path can be made constant on the opposite side of the window 36, so that the factors that cause pressure distribution can be reduced.

Further, according to the optical deflector 3 according to the present embodiment, the distance between the window 36 and the rotation center of the rotating polygon mirror 31 is longer than the distance between the surface facing the window 36 and the rotation center of the rotating polygon mirror 31. .
Therefore, according to the optical deflector 3 according to the present embodiment, since the window 36 can be separated from the rotating polygon mirror 31, it is possible to suppress a pressure drop in the reduced cross-sectional area of the flow path near the window 36.

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.

(Modification 1)
For example, in the above embodiment, as shown in FIG. 4A, the resistance generating section 371 (and the flow velocity reducing section 372) is provided on the upstream side of the window 36. , but is not limited to this. That is, the resistance generating section 371 only needs to be provided on at least one of the upstream side and the downstream side of the window 36. In particular, as shown in FIG. The configuration provided is desirable.

FIG. 10 is a diagram illustrating a fluid analysis result near the window 36 in the configuration (shape) of the optical deflector 3A according to the first modification. FIG. 10(A) is a plan view showing the configuration of the optical deflector 3A. FIG. 10(B) is a diagram showing an example of the pressure distribution around the rotating polygon mirror 31. FIG. 10C is a diagram showing an example of the flow velocity distribution around the rotating polygon mirror 31.

As shown in FIG. 10A, the wall surface 37b includes resistance generating portions 371 on the upstream and downstream sides of the window 36 in the rotation direction of the rotating polygon mirror 31. Furthermore, flow velocity reducing sections 372 are adjacent to the downstream sides of the resistance generating sections 371 provided on the upstream and downstream sides of the window 36, respectively.

In the configuration of the optical deflector 3A according to Modification Example 1, the Max-min of the pressure distribution is 36.7 Pa, which is different from the configuration (44.4 Pa) of the optical deflector 3002 according to the prior art (see FIG. 19(A)). It is smaller in comparison. In particular, the minimum pressure distribution is -35 Pa for the conventional technology (see Fig. 19 (B)) → -22 Pa for modification 1 (see Fig. 10 (B)), and the minimum pressure distribution is 360°).

In addition, in the configuration of the optical deflector 3A according to Modification Example 1, the flow velocity in the enlarged channel cross-sectional area section (area from 270° to 360°) is as follows: 8 m/s → deformation Example 1 (see arrow R1 in FIG. 10(C)): The speed has fallen to 2 m/s. In addition, the flow velocity in the other passage cross-sectional area enlarged portion (0° to 90° region) is 7 m/s in the conventional technology (see FIG. 19(C))→Modification 1 (arrow R2 in FIG. 10(C)). Reference): It has fallen to 3m/s. In addition, the flow velocity at the part where the flow path begins to expand decreases from 9 m/s in the conventional technology (see Fig. 19 (C)) to 7 m/s in Modification 1 (see arrow R3 in Fig. 10 (C)). . In addition, the flow velocity at the part where the other flow path starts to expand is 12.8 m/s in the conventional technology (see FIG. 19(C)) → 8 m/s in modification example 1 (see arrow R4 in FIG. 10(C)). It has fallen to With the above configuration, the change in flow velocity becomes gradual and the air is prevented from being pulled at the part where the flow path width starts to widen, so it is possible to suppress the drop in pressure near 0° and 270°. is made of.

As described above, by providing the resistance generating portions 371 on the upstream and downstream sides of the window 36, it is possible to more effectively suppress the flow velocity and flow velocity change in the portion where the cross-sectional area of the flow path changes. Noise/rotational resistance near the window 36 can be reduced more effectively.

(Modification 2)
Further, as shown in FIG. 11, in the rotation direction of the rotating polygon mirror 31, when the flow path cross-sectional area at the starting point of the resistance generating section 371 is set to A1, and the flow path cross-sectional area at the end point of the resistance generating section 371 is set to A2, A configuration that satisfies A1≧A2 is desirable.

FIG. 11 is a diagram illustrating a fluid analysis result near the window 36 in the configuration (shape) of the optical deflector 3B according to the second modification. FIG. 11(A) is a plan view showing the configuration of the optical deflector 3B. FIG. 11B is a diagram showing an example of the pressure distribution around the rotating polygon mirror 31. FIG. 11C is a diagram showing an example of the flow velocity distribution around the rotating polygon mirror 31.

In the configuration of the optical deflector 3B according to Modification 2, the Max-min of the pressure distribution is 11.2 Pa, which is different from the configuration (44.4 Pa) of the optical deflector 3002 according to the prior art (see FIG. 19(A)). It is smaller in comparison. In particular, the minimum pressure distribution is -35 Pa for the conventional technology (see FIG. 19(B)) → -4.4 Pa for modification 2 (see FIG. 11(B)), and The pressure drop can be suppressed.

In addition, in the configuration of the optical deflector 3B according to Modification Example 2, the flow velocity in the enlarged channel cross-sectional area section (area from 270° to 360°) is 8 m/s in the conventional technology (see FIG. 19(C)) → deformation Example 2 (see arrow R1 in FIG. 11(C)): The speed has fallen to 1.2 m/s. In addition, the flow velocity in the other passage cross-sectional area enlarged portion (0° to 90° region) is 7 m/s in the conventional technology (see FIG. 19(C))→Modification 2 (arrow R2 in FIG. 11(C)). Reference): It has fallen to 2.3 m/s. In addition, the flow velocity at the part where the flow path begins to expand decreases from 9 m/s in the conventional technology (see Figure 19 (C)) to 3 m/s in Modification 2 (see arrow R3 in Figure 11 (C)). . In addition, the flow velocity at the part where the other flow path starts to expand is 12.8 m/s in the conventional technology (see FIG. 19(C)) → 5 m/s in modification example 2 (see arrow R4 in FIG. 11(C)). It has fallen to As mentioned above, by appropriately adjusting the cross-sectional area of the flow path of the flow velocity relaxation section 372, the change in flow velocity becomes more gradual, and the flow velocity suddenly drops (that is, air stagnates and pressure increases). is suppressed, so that the decrease in pressure near 0° and 270° can be further suppressed.

As described above, in the rotation direction, when the flow path cross-sectional area at the starting point of the resistance generating section 371 is A1, and the flow path cross-sectional area at the end point of the resistance generating section 371 is A2, the resistance can be increased by satisfying A1≧A2. Since it is possible to suppress pressure increase due to the passage cross-sectional area becoming too wide downstream of the generating portion 371 and the air flow velocity becoming too slow, it is possible to more effectively reduce noise/rotational resistance.

(Modification 3)
Further, in the above embodiment, the resistance generating section 371 is formed by bending the wall surface 37b inward, but the present invention is not limited to this. For example, as in the optical deflector 3C according to modification 3 (see FIG. 12), the resistance generating section 371C may have a configuration in which a convex section is provided inside the wall surface 37b.
As described above, by forming the resistance generating portion 371C with a convex portion provided inside the wall surface 37b, it is possible to suppress the flow velocity and flow velocity change in the portion where the cross-sectional area of the flow path changes with a simple configuration. Therefore, noise/rotational resistance near the flat window 36 can be reduced with a simple configuration.

(Modification 4)
Furthermore, as in the optical deflector 3D according to modification 4 (see FIG. 13), the resistance generating section 371D may have a configuration in which the bottom surface 37a protrudes inward. In addition, although the modification 4 illustrates and explains the structure in which the bottom surface 37a protrudes inward, it is not limited to this. For example, a top plate 37c may be configured to protrude inward instead of or in addition to the bottom surface 37a.
As described above, by forming the resistance generating portion 371D with at least one of the top plate 37c and the bottom surface 37a protruding inward, the flow velocity and flow velocity change in the portion where the cross-sectional area of the flow path changes can be suppressed with a simple configuration. Therefore, noise/rotational resistance near the flat window 36 can be reduced with a simple configuration.

(Modification 5)
Furthermore, as in the optical deflector 3E according to Modification 5 (see FIG. 14), the resistance generating section 371E may have a configuration in which a plurality of convex portions (for example, Braille, ribs, etc.) are provided on the wall surface 37b. FIG. 14(A) is a plan view showing the configuration of an optical deflector 3E according to modification example 5. FIG. 14(B) is a cross-sectional view taken along the line QQ in FIG. 14(A). In addition, although the modification 5 is described by exemplifying a configuration in which a plurality of convex portions are provided on the wall surface 37b, the present invention is not limited to this. For example, a plurality of convex portions may be provided on at least one of the top plate 37c and the bottom surface 37a instead of or in addition to the wall surface 37b.
As described above, by forming the resistance generating portion 371E with a plurality of convex portions on at least one of the wall surface 37b, the top plate 37c, and the bottom surface 37a, the cross-sectional area of the flow path can be changed with a simple configuration. Since the flow velocity and flow velocity change in the portion can be suppressed, noise/rotational resistance in the vicinity of the flat window 36 can be reduced with a simple configuration.

(Modification 6)
Further, as shown in FIG. 15, the flow velocity relaxation section 372F of the optical deflector 3F according to Modification Example 6 has a flow passage height that is the height in the flow passage adjusted. Specifically, in the example shown in FIG. 15, the flow path height narrows (E4) in the resistance generation portion 371F, and the flow path height widens (E5) → narrows (E6) in the flow velocity relaxation portion 372F. The cross-sectional area of the flow path changes. In the regions E4 and E6 where the channel height is narrow, the bottom surface 37a is configured to protrude inward compared to the region E5 where the channel height is wide.
As described above, by adjusting the flow passage height, which is the height in the flow passage between the flow velocity relaxation part 372F and the circumscribed circle C1, the flow velocity and flow velocity change in the part where the flow passage cross-sectional area changes. Since the noise/rotational resistance in the vicinity of the flat window 36 can be easily reduced.

(Modifications 7 and 8)
Further, in the above embodiment, a configuration in which one window 36 is provided is illustrated and explained, but the present invention is not limited to this. That is, a configuration may be adopted in which a plurality of windows 36 are provided. For example, as in the optical deflector 3G according to Modification Example 7 (see FIG. 16), two windows 36G are provided, one each on the opposing wall surface 37b, and each of them allows light to enter and exit. , a configuration may be adopted in which one rotating polygon mirror 31 scans two or more surfaces at the same time (both-side deflection method). Further, as in the optical deflector 3H according to Modification 8 (see FIG. 17), two windows 36H are arranged adjacent to each other by changing the arrangement angle, and a window 361H for incident light and a window 362H for output light are arranged. By dividing the angle, a configuration may be adopted in which the deflection angle is widened while suppressing the width of the flat window 36H (one-sided deflection method). In this case, the window 361H for incident light also serves as the resistance generating section 371H. Note that the symbol L in FIGS. 16 and 17 indicates laser light.
As mentioned above, by providing a plurality of windows 36G and 36H, multiple flat windows 36G and 36H are provided, and multiple pressure distribution locations occur, resulting in more noise/rotation than in the case of a single window. Even if the resistance increases, it is possible to suppress the flow velocity and the flow velocity change in the portion where the cross-sectional area of the flow path changes, so it is possible to suppress the pressure distribution around the rotating polygon mirror 31, and the flat window 36G, Noise/rotational resistance near 36H can be reduced. Therefore, noise/rotational resistance near the flat window 36H can be reduced even in the case of a double-sided deflection method or in the case of a single-side deflection method where the incident light window 361H and the output light window 362H are separated to widen the deflection angle. be able to.

(Other variations)
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 device 100 Optical writing device 1 Light source 2 Light source optical system 3, 3A to 3H 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 Bearings 36, 36G, 36H Window 37 Housing 37a Bottom surface 37b Wall surface 37c Top plate 371, 371C to 371F, 371H Resistance generation section 372, 372F Flow velocity relaxation 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 (light beam)

Claims (14)

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
The wall surface is
In the rotation direction of the rotating polygon mirror, at least one of the upstream side and the downstream side of the window is provided with a resistance generating part that generates resistance to the air flow due to the rotation of the rotating polygon mirror,
The resistance generating section is configured to narrow a cross-sectional area of the air flow path between the circumscribed circle of the rotating polygon mirror in at least one of the width direction and the height direction of the flow path. established in
On the downstream side of the resistance generating section in the rotational direction , there is a region where the cross-sectional area of the flow path increases between the resistance generating section and the circumscribed circle, and a region between the circumscribed circle toward the downstream in the rotational direction . A region where the cross-sectional area of the flow path is narrowed and a flow velocity relaxation section provided in this order are adjacent to each other ,
An optical deflector , wherein the wall surface is formed in a curved shape such that a surface facing the window is at a constant distance from the circumscribed circle . The optical deflector according to claim 1, wherein the resistance generating section is provided on the upstream side and the downstream side of the window. In the rotation direction,
The cross-sectional area of the flow path at the starting point of the resistance generating part is A1,
When the cross-sectional area of the flow path at the end point of the resistance generating part is A2,
The optical deflector according to claim 1 or 2, characterized in that A1≧A2 is satisfied. The optical deflector according to claim 1, wherein the resistance generating section is formed by bending the wall surface inward. The optical deflector according to any one of claims 1 to 4, wherein the resistance generating portion has a convex portion provided inside the wall surface. 6. The optical deflector according to claim 1, wherein the resistance generating section has at least one of the top plate and the bottom surface protruding inward. The optical deflector according to any one of claims 1 to 6, wherein the resistance generating section is provided with a plurality of convex portions on at least one of the wall surface, the top plate, and the bottom surface. . Claims 1 to 7, wherein the flow velocity relaxation part has a flow passage width, which is a width in the flow passage between the circumscribed circle, adjusted so that the cross-sectional area of the flow passage changes. The optical deflector according to any one of the items. 9. The optical deflector according to claim 8, wherein the flow velocity relaxation part is formed in a planar shape. 2. The flow rate reducing section is characterized in that a flow path height, which is a height in the flow path between the circumscribed circle and the flow path, is adjusted so that the cross-sectional area of the flow path changes. 9. The optical deflector according to any one of 9. 11. A distance between the window and the center of rotation of the rotating polygon mirror is longer than a distance between a surface facing the window and the center of rotation of the rotating polygon mirror. The optical deflector described in . The optical deflector according to claim 1 , wherein a plurality of windows are provided. a light source and
The optical deflector according to any one of claims 1 to 12 , 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 13 , 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:

Images