JP6740697B2 - Scanning optical device and image forming apparatus - Google Patents

Description

The present invention relates to a scanning optical device and an image forming apparatus.

An image forming apparatus represented by a copying machine includes a scanning optical device. The scanning optical device exposes while scanning the surface of the photosensitive drum to form a predetermined electrostatic latent image on the surface of the photosensitive drum. The scanning optical device is fixed to a main body (skeletal structure of the main body) of the image forming apparatus. Therefore, when vibration occurs in the image forming apparatus main body, the vibration is transmitted to the scanning optical device. When this vibration is transmitted to the optical element mounted on the housing of the scanning optical device, fluctuations of the scanning line or the like occur and image deterioration occurs.

For example, Patent Document 1 discloses a countermeasure against vibration in an optical scanning device. The optical scanning device includes a deflecting unit, a housing to which the deflecting unit is attached, and a load changing unit. The load changing means is arranged at one or a plurality of predetermined positions of the housing, and by changing the load of that portion, the frequency of the vibration generated by the driving of the deflection means and the predetermined fixed frequency of the housing are separated from each other. According to the configuration of Patent Document 1, even when the deflecting unit changes to a plurality of frequencies, resonance can be correspondingly prevented.

Japanese Patent Laid-Open No. 9-54265

In order to reduce the cost of the scanning optical device, it is required to change the material forming the housing from metal (for example, aluminum or aluminum alloy) to resin. However, such a material change may lead to a reduction in the weight and rigidity of the housing, which may reduce the vibration resistance of the scanning optical device. Although it is possible to improve the vibration resistance by applying the technique of Patent Document 1, in the technique of Patent Document 1, it is necessary to add components such as an electromagnet to configure the load changing means, and it is difficult to reduce the cost. ..

The present invention has been made in view of the above points, and an object of the present invention is to provide a technique that realizes cost reduction due to resinization of a housing while suppressing deterioration of vibration resistance.

In order to achieve the above object, a scanning optical device according to the present invention comprises a deflector for scanning light from a light source, a plurality of optical elements for forming an image of the light from the deflector on an object to be scanned, and a bottomed box type. And a plurality of optical elements mounted on the housing and made of a resin, and a substantially flat weight member attached to the bottom wall of the housing, when viewed from a direction orthogonal to the bottom wall. In addition, the weight member has a portion overlapping at least one of the plurality of optical elements.

According to this configuration, the weight member can compensate for the weight reduction due to the case being made of resin. Since the weight member is provided in a substantially flat plate shape, it can be arranged over a wide range without disturbing the light beam from the deflector. Therefore, according to this configuration, it is possible to reduce the cost while suppressing the deterioration of the vibration resistance.

In the scanning optical device having the above configuration, the casing is provided so as to be fixed to an external object to be attached, and the weight member is outside the at least one of the plurality of optical elements in the side view. It is preferably fixed to the body, and the location where the housing is fixed to the attachment target is preferably located outside the location where the weight member is fixed. With this configuration, it is possible to more effectively prevent transmission of vibration to the optical element.

In the scanning optical device configured as described above, it is preferable that the weight member extends over at least two of the plurality of optical elements. With this configuration, the weight of the weight member can be increased, and the vibration resistance can be improved.

In the scanning optical device having the above configuration, it is preferable that the weight member is located inside the housing. With this configuration, it is possible to prevent the size of the scanning optical device from increasing. However, the weight member may be located outside the housing.

In the scanning optical device having the above configuration, the weight member may be made of the same resin as the case. With this configuration, it is possible to make the characteristics of the housing and the weight member related to thermal expansion uniform, and it is possible to prevent distortion of the housing even when a temperature change occurs around the apparatus.

In the scanning optical device having the above configuration, the weight member and the housing have substantially the same linear expansion coefficient in a region where the weight member and the housing overlap with each other when viewed from a direction orthogonal to the bottom wall. It is preferable to have anisotropy of. According to this structure, even if a temperature change occurs around the device, distortion is unlikely to occur in the housing.

In the scanning optical device having the above configuration, the weight member and the housing are fixed at a plurality of points, and the weight member and the housing are provided in a region surrounded by the plurality of fixing points sequentially connected by a line segment. It is preferable that they have substantially the same anisotropy of linear expansion coefficient. According to this structure, even if a temperature change occurs around the device, distortion is unlikely to occur in the housing.

In the scanning optical device having the above configuration, when viewed from a direction orthogonal to the bottom wall, in the region where the weight member and the casing overlap, the weight member and the casing are made of resin during molding. It is preferable to have the gate traces indicating that they were the portions flowing into the mold at substantially the same position. According to this configuration, in the region where the weight member and the housing overlap, the anisotropic states of the linear expansion coefficients of the both can be made uniform.

In the scanning optical device having the above structure, the weight member may be made of a metal having a specific gravity larger than that of the resin forming the housing. According to this configuration, it is possible to make the weight member smaller than when the weight member is made of resin.

In the scanning optical device having the above-mentioned configuration, the weight member has a plurality of fixing portions serving as fixing points with the housing, and one of the plurality of fixing portions is provided with respect to the housing of the weight member. A first fixing part that can prohibit movement in all directions, and the rest of the plurality of fixing parts is the casing of the weight member in a specific direction parallel to the main surfaces of the weight member. It may be a second fixing part that allows movement with respect to the body. According to this structure, even if a temperature change occurs around the device, distortion is unlikely to occur in the housing.

In the scanning optical device having the above structure, it is preferable that an auxiliary member that assists the movement of the weight member with respect to the housing is provided at least in the vicinity of the second fixing portion. With this configuration, it is possible to smoothly perform the relative movement between the weight member and the housing, which is caused by the difference in the linear expansion coefficient.

In the scanning optical device having the above configuration, the weight member may be composed of a plurality of members that overlap each other in a direction orthogonal to the bottom wall of the housing.

In the scanning optical device having the above configuration, the weight member may be provided so that at least one of the plurality of optical elements can be installed.

Further, in order to achieve the above object, an image forming apparatus of the present invention is characterized by including the scanning optical device having the above configuration.

With this configuration, it is possible to manufacture an image forming apparatus including a scanning optical device having low cost and excellent vibration resistance.

The image forming apparatus having the above-described configuration may be configured to include, in addition to the scanning optical device, at least one other scanning optical device that is used next to the scanning optical device and that does not have the weight member.

According to the present invention, it is possible to provide a scanning optical device that realizes cost reduction by using a resin case while suppressing deterioration of vibration resistance. Further, according to the present invention, it is possible to provide an image forming apparatus including such a scanning optical device.

1 is a partial vertical sectional view of an image forming apparatus according to an embodiment of the present invention. 1 is a schematic plan view of a scanning optical device included in an image forming apparatus according to an embodiment of the present invention. 1 is a perspective view showing a detailed configuration of a weight member included in a scanning optical device according to an embodiment of the present invention. Schematic diagram of the scanning optical device according to the embodiment of the present invention when viewed from the side. A schematic diagram for explaining a problem assumed when the casing and the weight member of the scanning optical device are made of the same resin. Schematic diagram showing the behavior of the housing and the weight member during thermal expansion in the scanning optical device according to the embodiment of the present invention. FIG. 3 is a perspective view showing an example of a fixed position of a weight member included in the scanning optical device according to the embodiment of the present invention A schematic perspective view showing a modification of the weight member included in the scanning optical device according to the embodiment of the present invention. Schematic diagram showing a configuration of a modified example of the image forming apparatus of the embodiment of the present invention

An embodiment of the present invention will be described below with reference to the drawings. The present invention is not limited to the contents below.
<Outline of image forming apparatus>

First, regarding the image forming apparatus of the embodiment of the present invention, the image output operation will be described while the outline of the structure is described with reference to FIG. FIG. 1 is an example of a partial vertical sectional view of an image forming apparatus. The two-dot chain line with an arrow in the figure indicates the sheet conveyance path and the conveyance direction.

The image forming apparatus 1 is a so-called tandem type color copying machine as shown in FIG. 1, and includes an image reading unit 2 that reads an image of a document, a printing unit 3 that prints the read image on a transfer material such as paper, and the like. An operation unit 4 for inputting printing conditions and displaying the operating status, and a main control unit 5 are provided.

The image reading unit 2 is a known unit that reads an image of an original placed on the upper surface of a platen glass (not shown) by moving a scanner (not shown). The image of the original is separated into three colors of red (R), green (G), and blue (B), and converted into an electric signal by a CCD (Charge Coupled Device) image sensor (not shown). As a result, the image reading unit 2 obtains image data for each color of red (R), green (G), and blue (B).

The image data for each color obtained by the image reading unit 2 is subjected to various kinds of processing in the main control unit 5, and image data for each reproduced color of yellow (Y), magenta (M), cyan (C), and black (K). Is stored in a memory (not shown) inside the main control unit 5. The image data for each reproduced color stored in the memory is processed for positional deviation correction, and thereafter, in order to perform optical scanning with respect to the photoconductor drum 21 which is an image bearing member, each scanning line is synchronized with the conveyance of the paper. Read out.

The printing unit 3 forms an image by an electrophotographic method and transfers the image onto a sheet or the like. The printing unit 3 includes an intermediate transfer belt 11 in which the intermediate transfer body is formed as an endless belt. The intermediate transfer belt 11 is wound around a driving roller 12, a tension roller 13 and a driven roller 14. Tension is applied to the intermediate transfer belt 11 by urging the tension roller 13 upward in FIG. 1 by a spring (not shown). The intermediate transfer belt 11 is rotationally moved counterclockwise in FIG. 1 by the drive roller 12.

The drive roller 12 is pressed against the secondary transfer roller 15 that faces the intermediate transfer belt 11 with the intermediate transfer belt 11 interposed therebetween. At the position of the driven roller 14, the intermediate transfer cleaning unit 16 provided so as to face the driven roller 14 with the intermediate transfer belt 11 interposed therebetween contacts the outer peripheral surface of the intermediate transfer belt 11. The intermediate transfer cleaning unit 16 scrapes off and cleans the toner remaining on the outer peripheral surface of the intermediate transfer belt 11 after the secondary transfer.

Below the intermediate transfer belt 11, image forming units 20Y, 20M, 20C, and 20K corresponding to reproduced colors of yellow (Y), magenta (M), cyan (C), and black (K) are provided. In this description, the identification symbols “Y”, “M”, “C”, and “K” are omitted, unless otherwise specified, and are collectively referred to as, for example, “image forming unit 20”. Sometimes. The four image forming units 20 are arranged in a line along the rotation direction of the intermediate transfer belt 11 from the upstream side to the downstream side in the rotation direction. The four image forming units 20 have the same configuration, and are provided with a charging unit, a developing unit, a cleaning unit, and a primary transfer roller around the photosensitive drum 21 that rotates clockwise in FIG.

Below the image forming unit 20, a scanning optical device 60, which is an exposing unit, is arranged. One scanning optical device 60 corresponds to four image forming units 20. The scanning optical device 60 modulates four semiconductor lasers (not shown) according to the image gradation data of each reproduction color, and emits laser light corresponding to each reproduction color.

Above the intermediate transfer belt 11, there are provided toner bottles 31 and toner hoppers 32 corresponding to the four image forming units 20 of respective reproduced colors. For the developing unit and the toner hopper 32, a toner remaining amount detecting unit (not shown) for detecting the amount of toner inside is provided. Further, a toner replenishing device (not shown) is provided between the developing unit and the toner hopper 32 and between the toner hopper 32 and the toner bottle 31, respectively. When the remaining amount detecting unit detects a decrease in the amount of toner inside the developing unit, the replenishing device drives the toner hopper 32 to replenish the developing unit with toner. Further, when the remaining amount detecting unit detects a decrease in the amount of toner inside the toner hopper 32, the replenishing device drives the toner bottle 31 to replenish the toner hopper 32 with toner. The toner bottle 31 is detachably attached to the main body of the apparatus, and can be replaced with a new one as needed.

A paper feeding device 40 is provided below the scanning optical device 60, and the paper P is stored therein. The sheets P stored in the sheet feeding device 40 are sequentially sent out to the sheet conveying path Q from the uppermost sheet by the feeding section 50. The sheet P sent out from the sheet feeding device 40 to the sheet conveying path Q reaches the position of the registration roller pair 71. Then, the registration roller pair 71 corrects the skew feed of the paper P (skew correction) and synchronizes with the rotation of the intermediate transfer belt 11, and the contact portion between the intermediate transfer belt 11 and the secondary transfer roller 15 (secondary transfer). The paper P is sent toward the nip portion).

In the image forming unit 20, an electrostatic latent image is formed on the surface of the photosensitive drum 21 by the laser light emitted by the scanning optical device 60, and the electrostatic latent image is visualized as a toner image by the developing unit. .. The toner image formed on the surface of the photoconductor drum 21 is primarily transferred onto the outer peripheral surface of the intermediate transfer belt 11 at a position where the photoconductor drum 21 faces the primary transfer roller with the intermediate transfer belt 11 interposed therebetween. Then, as the intermediate transfer belt 11 rotates, the toner images of the image forming units 20 are sequentially transferred to the intermediate transfer belt 11 at a predetermined timing, so that yellow, magenta, cyan, and black are formed on the outer peripheral surface of the intermediate transfer belt 11. A color toner image is formed by superimposing the four color toner images.

The color toner image primarily transferred to the outer peripheral surface of the intermediate transfer belt 11 is formed by contacting the intermediate transfer belt 11 and the secondary transfer roller 15 with the paper P sent in synchronization by the registration roller pair 71. And is transferred at the secondary transfer nip portion.

A fixing portion 72 is provided above the secondary transfer nip portion. The paper P on which the unfixed toner image is transferred at the secondary transfer nip is sent to the fixing unit 72 and is sandwiched by the heating roller and the pressure roller, and the toner image is heated and pressed to melt and fix the paper P. To be done. The paper P that has passed through the fixing unit 72 is discharged to a paper discharge unit 73 provided above the intermediate transfer belt 11.

The operation unit 4 is provided on the front side of the image reading unit 2. The operation unit 4 inputs settings such as printing conditions such as the type and size of paper P used for printing by a user, enlargement/reduction, presence/absence of double-sided printing, and settings such as fax number and sender name in facsimile transmission. Accept. The operation unit 4 also serves as an informing unit for informing the user of the device status, cautions, error messages, and the like by displaying them on the display unit 4w.

Further, the image forming apparatus 1 is provided with a CPU, an image processing unit (not shown), and a main control unit 5 including other electronic components (not shown) for controlling the entire operation of the image forming apparatus 1. The main control unit 5 uses a CPU which is a central processing unit and an image processing unit, and controls components such as the image reading unit 2 and the printing unit 3 based on a program and data stored in a memory and input to control a series of The image forming operation and the printing operation are realized.
<Details of scanning optical device>

Next, the configuration of the scanning optical device 60 will be described in more detail. FIG. 2 is a schematic plan view of the scanning optical device 60. The light source scanning optical device 60 includes a housing 61 provided in the shape of a box with a bottom. In this specification, the direction orthogonal to the bottom wall 61a of the housing 61 (the direction orthogonal to the paper surface of FIG. 2) is the vertical direction. The surface that is not the top and bottom of the housing 61 is the side surface. The vertical direction is the Z direction. The left-right direction in FIG. 2 is defined as the X direction. The direction orthogonal to the X and Z directions is the Y direction.

The housing 61 is made of resin. The type of resin is not particularly limited, but fiber reinforced plastic (FRP) is used, for example. A light source unit 62, a deflector 63, and a scanning optical element unit 64 are mounted on the housing 61. A lid (not shown) is attached to the upper surface of the housing 61. The lid is appropriately provided with an opening through which light passes.

The light source unit 62 includes four light sources (not shown) corresponding to the four image forming units 20. In this embodiment, the light source is a semiconductor laser. Further, the light source unit 62 includes a plurality of optical components (not shown) that guide the respective laser beams emitted from the four light sources to the deflector 63.

The polarizer 63 scans the light from the light source. The deflector 63 includes a polygon mirror 63a that is a rotary polygon mirror. The deflector 63 also includes a motor (not shown). The polygon mirror 63a is rotated by driving a motor. The laser light for each reproduction color emitted from the four light sources is guided to the same surface of the polygon mirror 63a with a slight angle shift in the sub-scanning direction (Z direction), and is mainly moved based on the rotation of the polygon mirror 63a. Scanning is performed at a constant angular velocity in the scanning direction (X direction).

The scanning optical element unit 64 forms an image of the light from the deflector 63 on the object to be scanned. In the present embodiment, the scanning optical element unit 64 forms an image of the laser light for each reproduced color from the deflector 63 on the photoconductor drum 21. The photoconductor drum 21 is an example of a scan target. The scanning optical element section 64 includes a plurality of optical elements. The plurality of optical elements include a lens 64a and a long folding mirror 64b. In this embodiment, the long folding mirror 64b is fixed to the housing 61.

The scanning optical device 60 includes a weight member 65 having a substantially flat plate shape. The thickness of the weight member 65 is not particularly limited, but may be, for example, about 3 to 4 mm. The weight member 65 whose schematic shape is indicated by a one-dot chain line in FIG. 2 is attached to the bottom wall 61 a of the housing 61. In the present embodiment, the weight member 65 is arranged between the bottom wall 61a of the housing 61 and at least one of the plurality of optical elements 64a and 64b.

The weight member 65 has a portion overlapping at least one of the plurality of optical elements 64a and 64b when viewed from a direction orthogonal to the bottom wall 61a. The weight member 65 extends over at least two of the plurality of optical elements 64a and 64b. In the present embodiment, the weight member 65 is arranged between the bottom wall 61a and the lens 64a and the three long folding mirrors 64b. When viewed from a direction orthogonal to the bottom wall 61a, the weight member 65 has a portion overlapping the lens 64a and the three long folding mirrors 64b. The weight member 65 extends across the lens 64a and the three long folding mirrors 64b.

FIG. 3 is a perspective view showing a detailed configuration of the weight member 65 included in the scanning optical device 60. The weight member 65 is required not to block the light beam from the deflector 63. In consideration of this point, in the present embodiment, the weight member 65 is provided in a substantially flat plate shape and arranged in contact with the bottom wall 61a. As shown in FIG. 3, the weight member 65 has a step portion, a notch, and a through hole according to the shape of the bottom wall 61a. The weight member 65 may be provided so that at least one of the plurality of optical elements 64a and 64b can be installed. In this embodiment, an installation portion 65a for installing the lens 64a is formed. In other words, the weight member 65 may contact at least a part of the plurality of optical elements 64a and 64b.

The scanning optical device 60 is fixed to the main body of the image forming apparatus. In detail, the housing 61 is fixed to the frame member forming the main body. When the main body of the image forming apparatus vibrates, the vibration is transmitted to the optical element mounted in the housing 61. The ease with which vibration is transmitted is related to the weight of the housing 61. When the weight of the housing 61 is light, vibration is easily transmitted. In the present embodiment, the weight of the housing 61 itself is reduced by changing the housing 61 from a conventional metal material to a resin material. However, the weight reduction is compensated by the weight member 65 mounted on the housing 61. Therefore, in the scanning optical device 60, the deterioration of the vibration resistance is suppressed.

In addition, it is preferable that the weight member 65 has a large size in order to gain weight in a range that does not obstruct the optical path. The weight member 65 preferably has a larger outer shape than at least one long folding mirror 64b. The weight member 65 preferably has a size that straddles the plurality of long folding mirrors 64b. Further, it is preferable that the weight member 65 be provided with, for example, a convex portion or the like to increase the size (weight) within a range that does not obstruct the optical path.

FIG. 4 is a schematic diagram when the scanning optical device 60 is viewed from the side. FIG. 4 assumes a side view from the Y direction. As shown in FIG. 4, the housing 61 is fixed to the external mounting object 10. Concavities and convexities that facilitate the fixation to the attachment target 10 may be formed on the housing 61. The method of fixing the housing 61 is not particularly limited. For example, the housing 61 is fixed to the attachment target 10 using screws, an adhesive, a double-sided tape, or the like. In addition, the housing 61 may be fixed to the attachment target 10 by welding. In the present embodiment, the attachment target 10 is the main body of the image forming apparatus 1.

In a side view, the weight member 65 is fixed to the housing 61 outside of at least one of the plurality of optical elements 64a and 64b. In other words, the weight member 65 is fixed to the housing 61 at a position closer to the side wall 61b of the housing 61 than at least one of the plurality of optical elements 64a and 64b. In the present embodiment, the weight member 65 is fixed to the housing 61 outside the at least one long folding mirror 64b fixed to the housing 61 in a side view. The method of fixing the weight member 65 is not particularly limited. In this embodiment, the screw 80 is used as the fixing means. In addition, an adhesive, a double-sided tape, or the like may be used as the fixing means. In addition, the weight member 65 may be welded to the housing 61 in some cases. In the present embodiment, as an example, the long folding mirror 64b is also fixed to the housing 61 with screws 80.

Further, in a side view, the fixed portion FP1 of the housing 61 to the attachment target 10 is located outside the fixed portion FP2 of the weight member 65 to the housing 61. In other words, the fixed portion FP1 of the housing 61 to the attachment target 10 is located closer to the side wall 61b of the housing 61 than the fixed portion FP2 of the weight member 65 to the housing 61. As a result, the weight member 65 and the fixing point FP2 of the case 61 are located between the fixing point FP1 of the case 61 and the attachment target 10 and the long folding mirror 64b and the fixing point FP3 of the case 61. In this case, the vibration transmitted from the fixed portion FP1 to the housing 61 is easily attenuated by the weight member 65 existing between them until reaching the long folding mirror 64b, and the vibration damping effect can be improved.

In the present embodiment, the weight member 65 is made of the same resin as the housing 61. When the housing 61 is made of resin, the housing 61 has anisotropy in the coefficient of linear expansion. The anisotropy of the coefficient of linear expansion easily occurs when an inorganic filler or an organic filler is added to the resin. A fibrous reinforcing material such as glass fiber is added to the resin forming the housing 61 to ensure rigidity, and the housing 61 has anisotropy of linear expansion coefficient. The reinforcement has a large aspect ratio. At the time of molding, the plurality of reinforcing materials are oriented and cured in the same direction along the flow of the resin. Therefore, the above-described anisotropy of the linear expansion coefficient occurs.

FIG. 5 is a schematic diagram for explaining a problem that may occur when the housing of the scanning optical device and the weight member are made of the same resin. For example, when an image is output in the image forming apparatus 1, a temperature rise occurs around the scanning optical device 60. Due to this temperature rise, the housing 61 and the weight member 65 cause thermal expansion. If the anisotropy of the linear expansion coefficient is different between the housing 61 and the weight member 65 and the housing 61 and the weight member 65 are fixed at a plurality of locations, as shown in FIG. The difference in elongation inside may appear as strain in the Z direction. When such distortion occurs, the optical elements 64a and 64b mounted on the housing 61 may be displaced.

FIG. 6 is a schematic diagram showing the behavior of the housing 61 and the weight member 65 in the scanning optical device 60 during thermal expansion. In FIG. 6, the solid line shows the state before thermal expansion occurs, and the broken line shows the state after thermal expansion occurs. In the present embodiment, the weight member 65 and the housing 61 have substantially the same anisotropy of linear expansion coefficient in the region where the main surfaces of the weight member 65, which are the front and back surfaces, and the housing 61 overlap. The main surface of the weight member 65 is a surface parallel to the XY directions. In the configuration of the present embodiment, even in a situation where thermal expansion occurs, the weight member 65 and the housing 61 extend in substantially the same amount in the overlapping region. Therefore, as shown in FIG. 6, it is possible to suppress the occurrence of strain due to the difference in the amount of elongation.

FIG. 7 is a perspective view showing an example of a fixing portion FP2 of the weight member 65 included in the scanning optical device 60. There are a plurality of fixing points FP2 between the weight member 65 and the housing 61. In this example, there are three or more fixed points FP2, and more specifically, four. In such a configuration, the weight member 65 and the housing 61 have substantially the same linear expansion coefficient in a region (a region surrounded by a square in this example) surrounded by a plurality of fixed portions FP2 sequentially connected by line segments. It should have anisotropy. Outside the region surrounded by the fixed portion FP2, even if the anisotropy of the linear expansion coefficient is different, the influence is small and the occurrence of strain can be suppressed. A convex portion or the like may be positively formed outside the region surrounded by the fixed portion FP2 in order to secure weight.

As a means for making the anisotropy of the linear expansion coefficient the same between the housing 61 and the weight member 65, the same gate position at the time of resin molding can be mentioned. This is because the anisotropy occurs when the reinforcing materials are aligned in the same direction as the resin flows. The gate position is a position where the resin flows into the mold. The gate position remains as a gate mark on the molded product. Reference numeral 65b shown in FIG. 3 indicates a gate mark. In the present embodiment, the weight member 65 has two gate marks and two gate positions.

In the present embodiment, the weight member 65 and the housing 61 are portions where the resin flows into the mold during molding, in the region where the front and back main surfaces of the weight member 65 and the housing 61 overlap. Gate marks indicating that are provided at substantially the same position. In other words, the gate traces 65b of the weight member 65 substantially overlap with the gate traces (not shown) of the casing 61 in the region where the main surfaces forming the front and back of the weight member 65 and the casing 61 overlap. In the present embodiment, the two gate marks on the weight member 65 and the two gate marks on the housing 61 substantially overlap.

In the present embodiment, the weight member 65 is arranged to suppress the deterioration of the vibration resistance, and at the same time, the above-mentioned problems (problems shown in FIG. 5) related to the anisotropy of the coefficient of linear expansion are also reduced. This is solved by making the anisotropy of 65 almost the same. For this reason, for example, fluctuations in scanning lines and displacement of optical elements are less likely to occur, and the image quality of the image forming apparatus can be stabilized.
<Modifications, etc.>

In the embodiment described above, the weight member 65 is made of the same resin as the case 61. However, this is merely an example. For example, the weight member 65 may be made of a metal having a higher specific gravity than the resin that forms the housing 61. The metal forming the weight member 65 is not particularly limited, but may be, for example, aluminum, aluminum alloy, iron, stainless steel, or the like.

FIG. 8 is a schematic perspective view showing a modified example of the weight member 65 included in the scanning optical device 60 according to the embodiment of the present invention. The weight member 65 is made of the above-mentioned metal. The weight member 65 has a plurality of fixing portions 651 which are fixed to the housing 61. In this example, the number of fixing parts 651 is four. One of the plurality of fixing portions 651 is a first fixing portion 651a that can prevent the weight member 65 from moving in all directions with respect to the housing 61. Specifically, the first fixing portion 651a prohibits movement in all directions of the X direction, the Y direction, and the Z direction. The first fixing portion 651a is a complete fixing portion. The first fixing portion 651a is, for example, a round hole and is used in combination with a screw.

The rest of the plurality of fixing portions 651 is the second fixing portion 651b that allows the movement of the weight member 65 with respect to the housing 61 in a specific direction parallel to the main surfaces of the weight member 65. The specific direction is determined in consideration of the anisotropy of the linear expansion coefficient of the resin forming the casing 61. The second fixed portion 651b is configured to allow movement in the X direction and prohibit movement in the Y direction and the Z direction, for example. Alternatively, the second fixing portion 651b is configured to allow movement in the Y direction and prohibit movement in the X direction and the Z direction, for example. The second fixing portion 651b is, for example, a long hole and is used in combination with a screw.

In this example, the second fixing portion 651b can allow relative movement between the housing 61 and the weight member 65 due to thermal expansion. Therefore, it is possible to suppress the occurrence of strain due to the difference in linear expansion coefficient between the housing 61 and the weight member 65. In this example, it is preferable that an auxiliary member that assists the relative movement of the weight member 65 with respect to the housing 61 is provided at least in the vicinity of the second fixing portion 651b. As a result, it is possible to more effectively suppress the occurrence of strain due to temperature change. The auxiliary member may be, for example, grease or polyacetal resin (POM). The grease and the polyacetal resin may be arranged between the housing 61 and the weight member 65. The auxiliary member may be a combination of a plurality of types of members.

In the above, the weight member 65 is arranged inside the housing 61, but this is merely an example. The weight member 65 may be arranged outside the housing. The weight member 65 may be composed of a plurality of members that overlap in the Z direction. In addition to the weight member 65 attached to the bottom wall 61a of the housing 61, a weight member may be attached to the side wall 61b of the housing 61. Thereby, the weight of the housing 61 can be increased and the vibration resistance can be improved. When the weight member attached to the side wall is made of resin, it is preferable that the anisotropy state of the linear expansion coefficient be aligned with that of the housing 61.

In the image forming apparatus 1 described above, the scanning optical device 60 corresponds to one of the four image forming units 20. However, this is an example. For example, as shown in FIG. 9, a plurality of scanning optical devices may be arranged side by side. In FIG. 9, as an example, scanning optical devices 60A and 60B for two colors are arranged side by side. The scanning optical device 60A corresponds to yellow and magenta. The scanning optical device 60B corresponds to cyan and black. In such a case, the weight member may be arranged in both of the two scanning optical devices 60A and 60B, but the weight member may be arranged in only one of them. Occurrences of vibration may differ depending on the installation location, and it is possible not to provide a weight member on the scanning optical device on the side where the influence of vibration is small.

Further, in the above, the configuration is shown in which the image forming apparatus 1 is an image forming apparatus for color printing in which the toner image is transferred onto the paper P using the intermediate transfer belt 11. However, the application target of the present invention is not limited to such a model. The present invention is applicable to, for example, an image forming apparatus that does not use an intermediate transfer belt, an image forming apparatus for monochrome printing, and the like. In that case, the configuration of the scanning optical device to which the present invention is applied is appropriately changed.

The configurations of the embodiments and the modifications described above are merely examples of the present invention. The configurations of the embodiments and the modifications may be appropriately modified without departing from the technical idea of the present invention. Further, a plurality of embodiments and modified examples may be combined and implemented within a possible range.

The present invention can be used in an image forming apparatus such as a copying machine.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Attachment target 21 Photosensitive drum (scanned object)
60 scanning optical device 61 housing 61a bottom wall 62 light source part 64 optical element part 64a lens 64b long folding mirror 65 weight member 65b gate mark 651 fixing part 651a first fixing part 651b second fixing part

Claims (10)

A deflector for scanning light from a light source,
A plurality of optical elements for forming an image of light from the deflector on the object to be scanned,
A resin housing provided in the shape of a box with a bottom and on which the plurality of optical elements are mounted,
A substantially flat weight member attached to the bottom wall of the housing,
Equipped with
When viewed from the direction perpendicular to the bottom wall, wherein the weight member is to have at least one overlaps portions of the plurality of optical elements,
The scanning optical device, wherein the weight member is made of the same resin as that of the housing and is located inside the housing . The housing is provided so as to be fixed to an external object to be attached,
In a side view, the weight member is fixed to the housing outside at least one of the plurality of optical elements,
The scanning optical device according to claim 1, wherein a fixing portion of the housing to the attachment target is located outside of a fixing portion of the weight member. The scanning optical device according to claim 1, wherein the weight member extends over at least two of the plurality of optical elements. When viewed from a direction orthogonal to the bottom wall, in the region where the weight member and the casing overlap, the weight member and the casing have substantially the same anisotropy of linear expansion coefficient. The scanning optical device according to claim 1 , wherein the scanning optical device is a scanning optical device. There are a plurality of fixing points for the weight member and the housing,
4. The weight member and the housing have substantially the same anisotropy of linear expansion coefficient in a region surrounded by the plurality of fixing points sequentially connected by line segments . the scanning optical apparatus according to any one. When viewed from a direction orthogonal to the bottom wall, in the region where the weight member and the casing overlap, the weight member and the casing are locations where resin flows into the mold during molding. the scanning optical apparatus according to any one of claims 1 to 3, characterized in that it has a gate mark at substantially the same position indicating that the. The weight member, the scanning optical apparatus according to any one of claims 1 to 6, characterized in that it is composed of a plurality of members that overlap in a direction perpendicular to the bottom wall of the housing. The scanning optical device according to any one of claims 1 to 7 , wherein the weight member is provided so that at least one of the plurality of optical elements can be installed. An image forming apparatus comprising: a scanning optical apparatus according to any one of claims 1 to 8. The image forming apparatus according to claim 9 , further comprising, in addition to the scanning optical device, at least one other scanning optical device that is used side by side with the scanning optical device and does not have the weight member.