Optical deflector, scanning optical device, and image forming apparatus

Abstract

To provide an optical deflector that reduces the possibility that the movement of a driving source of a rotary polygon mirror is inhibited, a scanning optical device, and an image forming apparatus.SOLUTION: An optical deflector comprises: a housing; a rotary polygon mirror that is accommodated in the housing, and has mirror surfaces formed on its outer peripheral surfaces; a substrate 502 on which at least part of a driving source driving the rotary polygon mirror is mounted; a heat radiation member 42 that radiates heat of the substrate 502 to the outside; a heat transfer member 41 that is formed of an elastic body, is interposed between the substrate 502 and the heat radiation member 42, and transfers the heat of the substrate 502 to the heat radiation member 42; screws 61 that fix the substrate 502 to a casing 34; and elastic members 55 that elastically press the heat radiation member 42 and the heat transfer member 41 against the substrate 502 with urging force smaller than fixing force of the screws 61 to be supported on the substrate 502.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to an optical deflector, a scanning optical device, and an image forming apparatus. [Background technology]

[0002] Rotating polygon mirrors are used as a means for electrostatically forming images on a photosensitive drum in image forming devices such as printers and copiers. Rotating polygon mirrors are regular polygonal prisms with mirrored sides that are driven to rotate at high speeds by electromagnetic force. Specifically, the rotating polygon mirror reflects light from a light source such as a semiconductor laser, and deflects and scans the light across the photosensitive drum using an optical deflector. This optically writes an electrostatic latent image onto the charged photosensitive drum.

[0003] Rotating polygon mirrors rotate at high speeds, sometimes reaching as high as 58,000 rpm. In image forming devices using such rotating polygon mirrors, the high-speed rotation can increase the power consumption and heat dissipation of the substrate, resulting in temperature rise. The substrate in this case is the one on which the drive source for the rotating polygon mirror and the power and control circuits that drive and control it are mounted. This temperature rise causes thermal expansion of the rotating polygon mirror and scanning lens, resulting in component position and shape shifts from the initial assembly and adjustment state of the optical deflector. This can lead to deterioration of the optical deflector's optical performance, such as shifts in the optical imaging position and beam diameter. Furthermore, the adhesive used to bond the optical deflector's components can creep and deform when subjected to centrifugal force at high temperatures, potentially degrading the optical scanning performance from the initial adjustment. If this deformation becomes too great, the rotating polygon mirror's rotational orientation can become unstable, potentially damaging the drive source (polygon motor).

[0004] Patent Document 1 is an example of a technology for suppressing the above-mentioned temperature rise in an optical deflector using a rotating polygon mirror. The technology in Patent Document 1 uses a heat dissipation member (heat sink), with a heat transfer member (thermal conduction sheet) sandwiched between the substrate and the heat sink. This allows the heat generated in the substrate to escape to the heat sink (heat sink) in an attempt to dissipate the heat efficiently. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-113982 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the technology of Patent Document 1, the substrate is fastened to the heat sink with ordinary screws. Furthermore, no technology is disclosed regarding suppressing deformation of the substrate. This creates the problem that the substrate may deform, preventing the generation of the required driving force and impeding the rotation of the polygon motor, which is the driving source. SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an optical deflector, a scanning optical device, and an image forming apparatus that are less likely to impede the movement of the drive source of the rotary polygon mirror. [Means for solving the problem]

[0007] (1) The present invention provides an optical deflector comprising: a housing; a rotary polygon mirror housed within the housing and having a mirror surface formed on its outer periphery; a substrate on which at least a portion of a drive source for driving the rotary polygon mirror is mounted; a heat dissipation member for dissipating heat from the substrate to the outside; a heat transfer member formed of an elastic body and interposed between the substrate and the heat dissipation member for transferring heat from the substrate to the heat dissipation member; a fixing member for clamping and fixing the substrate to the housing; and an elastic member for elastically pressing the heat dissipation member and the heat transfer member against the substrate with a force weaker than the clamping force of the fixing member, thereby supporting them on the substrate.

[0008] (2) The optical deflector according to (1), wherein the elastic member generates the biasing force when pressed by the fixed member.

[0009] (3) The optical deflector according to (2), wherein the elastic member is wound around the fixed member.

[0010] (4) The optical deflector according to claim 1, wherein the elastic member is a compression coil spring.

[0011] (5) The optical deflector according to (1), wherein the fixing member is a screw.

[0012] (6) The optical deflector according to (1), wherein the fixing member regulates the position of the heat dissipation member in the thickness direction.

[0013] (7) The optical deflector according to (1), wherein a sealing material is sandwiched between the substrate and the housing.

[0014] (8) The optical deflector according to (7), wherein the sealing material surrounds the entire periphery of the driving source.

[0015] (9) An optical deflector described in (7), wherein the sealing material is formed of an elastic material and is thicker than the gap between the substrate and the housing when not sandwiched between the substrate and the housing.

[0016] (10) The optical deflector according to (7), wherein at least one of the fixing members is located outside the sealing material.

[0017] (11) The optical deflector according to (7), wherein the portion of the sealing material located outside the fixing member has a narrower width sandwiched between the housing and the substrate than the other portions.

[0018] (12) The optical deflector according to (1), wherein the elastic member is disposed on the opposite side of the substrate from the housing side.

[0019] (13) The optical deflector according to claim 1, wherein the substrate does not directly support the rotating polygon mirror and is spaced apart from the rotating polygon mirror.

[0020] (14) The optical deflector according to (1), wherein the substrate is made of iron or an alloy containing iron.

[0021] (15) The optical deflector according to (1), wherein the heat transfer member has a constant thickness.

[0022] (16) A scanning optical device comprising the optical deflector described in (1), a light source, and an optical system that performs at least one of irradiating the light emitted from the light source onto the rotating polygon mirror and irradiating the light reflected by the rotating polygon mirror onto a predetermined destination.

[0023] (17) An image forming apparatus comprising: a photosensitive member; a scanning optical device according to claim 16 that exposes the photosensitive member to light to form an electrostatic latent image; and a developing device that develops the electrostatic latent image on the photosensitive member with toner. [Effects of the Invention]

[0024] According to the present invention, it is possible to provide an optical deflector, a scanning optical device, and an image forming apparatus in which the movement of the drive source of the rotary polygon mirror is less likely to be obstructed. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a perspective view of an image forming apparatus main body provided in an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic plan view of the inside of a scanning optical device provided in the image forming apparatus according to the present embodiment. [Figure 3] 3 is a schematic diagram illustrating the internal configuration of the scanning optical device taken along line AA in FIG. 2. FIG. [Figure 4] FIG. 2 is a perspective view of a heat dissipation member provided in the image forming apparatus according to the present embodiment. [Figure 5] FIG. 2 is a perspective view of a heat transfer member provided in the image forming apparatus according to the present embodiment. [Figure 6] FIG. 2 is a perspective view of a heat transfer member provided in the image forming apparatus according to the present embodiment. [Figure 7] FIG. 2 is a perspective view of a coil of a driving source provided in the image forming apparatus according to the embodiment. [Figure 8] FIG. 2 is a perspective view of a magnet and other components of a driving source provided in the image forming apparatus according to the present embodiment. [Figure 9]2 is a conceptual cross-sectional view showing a support structure for a heat dissipation member, a substrate, and the like of the image forming apparatus according to the present embodiment. FIG. [Figure 10] FIG. 10 is a perspective view showing another example of an elastic member used in the image forming apparatus according to the present embodiment. [Figure 11] FIG. 2 is a plan view of a heat dissipation member used in the image forming apparatus according to the present embodiment. [Figure 12] 5A and 5B are conceptual vertical cross-sectional views illustrating forces acting on a substrate used in the image forming apparatus according to the present embodiment. [Figure 13] 3 is an enlarged plan view of a part of a sealing material and a casing used in the image forming apparatus according to the embodiment. FIG. [Figure 14] FIG. 2 is an enlarged plan view of a portion of a heat dissipation member used in the image forming apparatus according to the present embodiment. [Figure 15] 10A and 10B are conceptual cross-sectional views showing modified examples of the support structure for the heat dissipation member, the substrate, and the like of the image forming apparatus according to the present embodiment. [Figure 16] 10A and 10B are conceptual vertical cross-sectional views for explaining a simulation of a support structure for a heat dissipation member, a substrate, and the like of the image forming apparatus according to the present embodiment. [Figure 17] 10A and 10B are contour diagrams showing simulation results of the support structure for the heat dissipation member, the substrate, and the like of the image forming apparatus according to the present embodiment. [Figure 18] 10A and 10B are contour diagrams showing simulation results of the support structure for the heat dissipation member, the substrate, etc. of the image forming apparatus according to the present embodiment. [Figure 19] 10A and 10B are contour diagrams showing simulation results of the support structure for the heat dissipation member, the substrate, etc. of the image forming apparatus according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0026] An embodiment of the present invention will be described below. Note that the following embodiment is merely an example and does not limit the present invention, and the present invention can be implemented in various forms within the scope of the present invention. First, we will explain the problems of this embodiment. In Patent Document 1, a heat transfer member is sandwiched between a substrate and a heat dissipation member, and the substrate is fastened to the heat dissipation member with screws. Furthermore, since there is no mention of suppressing deformation of the substrate, there is a risk that pressure from the screws will be transmitted to the substrate via the heat transfer member, causing deformation of the substrate. If this deformation occurs, the distance between the coil and magnet of the polygon motor, which is the driving source of the rotating polygon mirror, will change from a predetermined distance. This could result in an insufficient driving force (electromagnetic force) being generated by the driving source, resulting in a deterioration in the rotation performance of the rotating polygon mirror or even a complete failure to rotate. Regarding this issue, experiments and studies by the present inventors have confirmed that the rotating polygon mirror will not rotate even if the heat transfer member is compressed by 0.1 mm.

[0027] The thickness of the heat transfer material is, for example, about 1 mm ±0.2 mm, and because of the large tolerance, it is difficult to insert a spacer of a fixed thickness. It is also possible to use the heat transfer material itself as a spacer. However, because the heat transfer material is soft, with a Young's modulus of only a few MPa, even a force sufficient to hold the board or heat dissipation member will significantly compress the heat transfer material. As a result, the board will deform due to the pressure from the screw, and the same problem will occur.

[0028] The configuration and effects of this embodiment, which solves these problems, will be described below. 1 is a perspective view of an image forming apparatus main body provided in an image forming apparatus according to this embodiment. The image forming apparatus main body is housed in a housing 32 (FIG. 3). The image forming apparatus 1 (image forming apparatus main body) includes, for example, four image forming units 2 to 5 arranged in a vertical row, a first transfer belt 6, and a fixing unit 8. Each of the image forming units 2 to 5 is a device that forms a toner image of a different color on a corresponding photoconductor (photoconductor drum). The different colors are, for example, yellow (Y), cyan (C), magenta (M), and black (K). The photoconductors are photoconductors 11Y, 11C, 11M, and 11K.

[0029] In this example, image forming unit 2 is a device that forms a yellow (Y) toner image on photoreceptor 11Y. Image forming unit 3 is a device that forms a cyan (C) toner image on photoreceptor 11C. Image forming unit 4 is a device that forms a magenta (M) toner image on photoreceptor 11M. Image forming unit 5 is a device that forms a black (K) toner image on photoreceptor 11K. Note that in this example, there are four image forming units, and image formation is possible using four colors of toner. However, the image forming device 1 may use five or more colors of toner, or may use only one color.

[0030] The image forming unit 2 includes a charging device 12Y that charges the photoreceptor 11Y, and a scanning optical device 13Y that optically writes an electrostatic latent image on the photoreceptor 11Y. The image forming unit 2 also includes a developing device 14Y that develops the electrostatic latent image on the photoreceptor 11Y with yellow (Y) toner. The image forming unit 2 also includes a static eliminator 15Y that eliminates static electricity from the photoreceptor 11Y. Each of these devices is provided around the photoreceptor 11Y. The photoconductor 11C, charging device 12C, scanning optical device 13C, developing device 14C, and static eliminator 15C of the image forming unit 3 also have the same configuration as those of the image forming unit 2.

[0031] The photosensitive member 11M, charging device 12M, scanning optical device 13M, developing device 14M, and static eliminator 15M of the image forming unit 4 are configured in the same manner as those of the image forming unit 2. The photosensitive member 11K, charging device 12K, scanning optical device 13K, developing device 14K, and static eliminator 15K of the image forming unit 5 also have the same configuration as those of the image forming unit 2. When describing each of the above components collectively without distinguishing between the toner colors used, the component names will simply be indicated by the numerical references. For example, photoreceptors 11Y, 11C, 11M, and 11K will be collectively referred to as photoreceptor 11.

[0032] The first transfer belt 6 is a belt conveyor-like device. In this example, the first transfer belt 6 is disposed along the photoconductors 11Y-11K of the image forming units 2-5, with the vertical direction as the longitudinal direction. The toner images formed on the photoconductors 11 are transferred onto the first transfer belt 6 so that the toner images are superimposed on one another. This toner image, in which the toners of each color are superimposed, is transferred onto a sheet of paper (not shown, which may be sheet paper or continuous paper) supplied from a paper supply unit (not shown). This transfer is performed by a second transfer device (transfer unit), not shown. The paper onto which the toner image has been transferred is then transported to a fixing unit 8. The fixing unit 8 fixes the toner image onto the paper, forming a color image on the paper.

[0033] The scanning optical device 13 will be described in detail below. Fig. 2 is a schematic plan view of the inside of the scanning optical device 13. The scanning optical device 13 according to this embodiment includes a light source 311 and predetermined optical systems. One of the optical systems is a collimator lens (not shown) that shapes the light emitted from the light source 311 into approximately parallel light. The scanning optical device 13 includes, as its optical system, a light source folding mirror 312 and scanning lenses 313 to 315. The scanning optical device 13 further includes, as its optical system, long folding mirrors 317 to 319, scanning lenses 316 and 320, and other optical elements required for the scanning optical device 13.

[0034] Fig. 3 is a cross-sectional view of the inside of the scanning optical device taken along line AA in Fig. 2. The scanning optical device 13 includes an optical deflector 31 according to this embodiment. The optical deflector 31 includes a housing 32. The housing 32 includes a housing 33 and a casing 34. Fig. 3 is shown upside down.

[0035] A rotary polygon mirror 306 (polygon mirror) having a mirror surface on its outer periphery is supported on the flat plate portion 303 of the casing 34. A magnet 505 is joined to the rotary polygon mirror 306. The magnet 505 constitutes a driving source 501 (polygon motor) that drives and rotates the rotary polygon mirror 306. A substrate 502 is disposed facing the magnet 505. Mounted on the substrate 502 are a coil 506 that constitutes the driving source 501, and power supply and control circuits (not shown) that drive and control the driving source 501. The rotary polygon mirror 306 rotates around a rotary shaft 305 supported on the flat plate portion 303. A bearing 504 is provided between the rotary shaft 305 and the rotary polygon mirror 306 to smoothly rotate the rotary polygon mirror 306. Transparent, flat-plate-shaped window glasses 511 and 513 are provided between the housing 33 and the casing 34, which transmit the reflected light L from the rotating polygon mirror 306. The reflected light L is ultimately irradiated onto the photosensitive element 11. A sealant 512 is provided between the casing 34 and the substrate 502 to fill the gap between these components. A heat dissipation member 42 (heat dissipation fins) is provided on the surface of the substrate 502 opposite the side on which the coil 506 is mounted, with a heat transfer member 41 (heat transfer sheet) sandwiched between them. Heat from the substrate 502 is conducted to the heat dissipation member 42 via the heat transfer member 41 and dissipated to the outside of the heat dissipation member 42.

[0036] Casing 34 has wall 509 standing upright from one side of flat plate portion 303. Casing 34 holds rotating shaft 305 and substrate 502. Casing 34 also seals rotating polygon mirror 306 together with substrate 502, window glasses 511 and 513, and sealant 512. Sealing stabilizes the air flow around rotating polygon mirror 306, making it possible to stabilize the rotational speed of rotating polygon mirror 306.

[0037] The casing 34 is molded integrally with the housing 33. By molding them integrally, costs can be reduced by reducing the number of parts compared to when the two are separate components. Furthermore, by molding them integrally, it is possible to reduce assembly position errors of each part. Furthermore, by reducing the thickness of the flat plate portion 303 and the wall portion 509, it is possible to improve the efficiency of heat dissipation to the outside air. Here, "assembly position error" means the following. In other words, when the casing 34 of the optical deflector 31 and the housing 33 are separate components, it is necessary to attach the optical deflector 31 to the housing 33. Then, the position error of the optical deflector 31 caused by machining errors in the positioning used in this process or slight gaps between the fitting holes is called "assembly position error."

[0038] The rotating shaft 305 of the rotating polygon mirror 306 is fixed to the casing 34 with screws. The substrate 502 is held in the housing 32. The material of the substrate 502 is a metal or a metal alloy, preferably iron or an iron alloy. The surface of the substrate 502 is coated with an epoxy resin to prevent electrical conduction. If the material of the substrate 502 is iron or an iron alloy, it has higher rigidity than a glass epoxy substrate or the like, and is less susceptible to deformation or vibration. Furthermore, if the material of the substrate 502 is iron or an iron alloy, it has the advantage of high thermal conductivity and easy heat dissipation.

[0039] Bearing 504 and rotating polygon mirror 306 are mounted on a flanged rotating shaft 305. This allows them to be attached to casing 34 without disassembly after adjusting or measuring their rotation performance. The sealant 512 is applied to the substrate 502. It may also be applied to the casing 34. However, after application, the sealant 512 needs time to harden. Therefore, if the casing 34 is integrally formed with the housing 33 and is relatively large, it is better to apply the sealant to the substrate 502. In other words, the space occupied while the sealant 512 is waiting to harden can be reduced, which is advantageous in terms of the production process.

[0040] The heat transfer member 41 is, for example, an elastic member made of resin, and has a constant thickness. Because the thickness is constant, the heat transfer member 41 can be processed during production by cutting a base sheet in a straight line or by punching with a simple die, thereby reducing production costs. The heat dissipation member 42 has a shape in which multiple thin ribs stand up on a flat plate. It can be manufactured by aluminum die casting or by extrusion molding using an extrusion die and cutting. The image forming apparatus 1 is configured so that outside air is blown onto the heat dissipation member 42 within its housing by a fan or air duct (not shown). This allows the board 502 and other components to be cooled efficiently.

[0041] 4 to 8 are perspective views of the periphery of the optical deflector on the back surface of the scanning optical device. As shown in FIG. 4, the heat dissipation member 42 is at the bottommost part under the casing 34. As shown in FIG. 5, the heat transfer member 41 is located directly above the heat dissipation member 42. As shown in FIG. 6, the substrate 502 is located directly above the heat dissipation member 42. The heat dissipation member 42 and the substrate 502 are fixed to the casing 34 at multiple locations with screws 61, which are fixing members, in this example at four locations. The heat transfer member 41 is sandwiched and fixed between the heat dissipation member 42 and the substrate 502.

[0042] As shown in Fig. 7, coil 506 of drive source 501 is disposed directly above substrate 502. Sealing material 512 is formed on the edge of casing 34 that surrounds coil 506. As shown in Fig. 8, in addition to magnet 505 of drive source 501, a rotor and a yoke are also provided above coil 506.

[0043] Figure 9 is a conceptual vertical cross-sectional view of the structure shown in Figures 4 to 8. The screw 61 is a shoulder thread and has a threaded portion 61a with threads cut on the outer periphery. The screw 61 has a head portion 61b with a larger diameter than the threaded portion 61a, which extends from a tip end 61b1 of the threaded portion 61a. A flange 61c with a larger diameter than the head portion 61b is formed at the base end of the head portion 61b. The screw portion 61a is screwed into and fixed in a screw hole 34a of the casing 34. As a result, the screw portion 61a is inserted into a hole 502a that penetrates the substrate 502. The tip portion 61b1 of the head 61b and the casing 34 sandwich and fix the substrate 502. A sealing material 512 is interposed between the casing 34 and the substrate 502 in a compressed state due to pressure from both components.

[0044] An elastic member 55 is interposed between the lower surface 61c1 of the flange 61c and the end of the heat dissipation member 42. This elastic member 55 is, for example, a compression coil spring inserted into the head 61b. This elastic member 55 is compressed by the lower surface 61c1 of the flange 61c and urges the heat dissipation member 42 toward the board 502, thereby supporting and fixing the heat dissipation member 42. Furthermore, since the heat transfer member 41 is sandwiched between the heat dissipation member 42 and the board 502, the heat transfer member 41 is also supported and fixed to the board 502.

[0045] The substrate 502 is firmly fixed to the casing 34 by the threaded portions 61a of the screws 61, for example, with a force of about 500 N per screw 61. This force F can be calculated by "tightening torque T0.2 [N m] = constant k0.2 × nominal diameter 0.002 [m] × axial force F [N]" (Reference: https: / / d-engineer.com / kikaiyouso / toruq.html).

[0046] 9, the rotating polygon mirror 306 and the coil 506 are not shown, but as described above with reference to FIG. 3, they are on the same side of the substrate 502 as the casing 34. On the substrate 502, on the opposite side from the casing 34, the heat dissipation member 42 is provided with the heat transfer member 41 sandwiched between them. The heat dissipation member 42 is pressed and held toward the substrate 502 by the flanges 61c of the screws 61 and the elastic members 55 with a biasing force that is weaker than the fixing force of the substrate 502 (the force with which the heads 61b press the substrate 502). This biasing force is, for example, about 10 N per elastic member 55.

[0047] In this way, elastic member 55 presses heat dissipation member 42 with a force weaker than the fixing force of screws 61 that are screwed and fixed to substrate 502. This fixing force is the force that presses substrate 502 with tip portions 61b1 of heads 61b. This reduces the reaction force of heat transfer member 41 and suppresses deformation of substrate 502. This reduces the risk that a predetermined driving force will not be generated and that the rotation of polygon motor, which is driving source 501, will be hindered. This reduces the possibility that the movement of driving source 501 of rotating polygon mirror 306 will be hindered.

[0048] Furthermore, the elastic member 55 generates the above-mentioned biasing force when pressed by the screw 61, which serves as the fixing member. Therefore, it is possible to fix the substrate 502 and hold the heat dissipation member 42 at the same time. This makes it possible to shorten the work time and reduce the number of parts during manufacturing, compared to when fixing the substrate 502 and holding the heat dissipation member 42 are done using separate parts. Elastic member 55, which is a compression coil spring or the like, is wound around screw 61, which serves as a fixing member. This makes it easy to attach elastic member 55 and screw 61 together, improving workability during manufacturing and also enabling space savings in the placement location of elastic member 55.

[0049] Instead of the compression coil spring, the elastic member 55 may be, for example, a hollow cylindrical elastic part, such as a cylindrical part with a thickness of about 0.5 mm made of resin or iron as shown in Fig. 10. However, by using a compression coil spring as the elastic member 55, the spring constant (force / displacement) can be reduced. Therefore, the elastic member 55, which is a compression coil spring or the like, can be made less susceptible to the effects of component tolerances. As mentioned above, the fixing member is a screw 61 (shoulder screw), which makes it easier to attach and remove the fixing member than adhesive fixing, caulking fixing, etc., and also provides a strong fixing force with a small tightening force.

[0050] The elastic member 55 is disposed on the opposite side of the casing 34 (housing 32) from the substrate 502. Therefore, when the elastic member 55 is attached to the substrate 502, the heat transfer member 41, and the heat dissipation member 42, there is little lift of the casing 34 from the seating surface of the substrate 502. Therefore, the elastic member 55 can be easily attached.

[0051] As shown in Fig. 3, substrate 502 does not directly support rotating polygon mirror 306 and is spaced apart from rotating polygon mirror 306. Therefore, if substrate 502 were to deform, the change in the distance between coil 506 on substrate 502 and magnet 505 would likely be large. However, as described above, in this embodiment, deformation of substrate 502 is suppressed, and the effect of suppressing deformation is more pronounced. As a result, the change in the distance between coil 506 and magnet 505 is less likely to be large.

[0052] The difference between the outer diameter of the screw 61 and the diameter of the hole 42a (FIG. 11) in the heat dissipation member 42 through which the screw 61 passes is, for example, 1 mm. That is, there is a slight gap between the two. This allows the screw 61 in the optical deflector 31 to restrict the widthwise position of the heat dissipation member 42. This restriction is relatively light. This allows the heat dissipation member 42 to be held in position without significant deviation when attached. This also improves the ease of attachment of the heat dissipation member 42. Furthermore, even when the elastic member 55 holds the heat dissipation member 42 with the weak force described above, deformation of the heat transfer member 41 due to creep deformation can be suppressed. This also prevents the heat dissipation member 42 from momentarily lifting up due to an impact, which could cause the heat dissipation member 42 to be misaligned in the horizontal direction.

[0053] FIG. 12 illustrates the force and deformation acting on the substrate. Referring to FIGS. 9 and 12, it will be explained that the sealant 512 between the casing 34 and the substrate 502 can further suppress deformation of the substrate 502. As described above, even when the substrate 502 is pressed by a weak force (downward arrow 67 in FIG. 9 ) of the elastic member 55, a force capable of deforming the substrate 502 is generated. That is, a force capable of deforming the substrate 502 is generated by the reaction force of the heat transfer member 41, as indicated by the downward arrow 65 in FIG. 12 . The sealant 512 is thicker than the size of the gap between the substrate 502 and the casing 34 before the substrate 502 is attached. Therefore, when the sealant 512 is crushed during attachment of the substrate 502, a reaction force is generated (upward arrow 68 in FIG. 9 , upward arrow 66 in FIG. 12 ). Therefore, a force is generated on the substrate 502 in the direction opposite to the reaction force of the heat transfer member 41 that deforms the substrate 502, thereby suppressing deformation of the substrate 502.

[0054] The sealing material 512 is made of an elastic material. When the sealing material 512 is not sandwiched between the substrate 502 and the casing 34 (housing 32), the sealing material 512 is thicker than the gap between the substrate 502 and the casing 34. Therefore, the sealing material 512 can reliably fill the gap between the substrate 502 and the casing 34. This makes it possible to stably prevent dust from entering the optical deflector 31, stabilize its rotation, and prevent deformation of the substrate 502.

[0055] 7, the sealing material 512 surrounds the driving source 501 on the substrate 502. Therefore, compared to a case where the sealing material 512 is interrupted midway, it is possible to more effectively protect the optical deflector 31 from dust, stabilize its rotation, and suppress deformation of the substrate 502. 9, at least one of the screws 61, which are fixing members for fixing the substrate 502, is located outside the sealing material 512 (FIG. 3). This causes the reaction force of the sealing material 512 to be as shown in FIG. 12, as described above. This causes a force to be applied to the substrate 502 in the opposite direction to the force that deforms the substrate 502 due to the reaction force of the heat transfer member 41. This makes it possible to make the substrate 502 less likely to warp.

[0056] As shown in Figures 13 and 14, in the area indicated by arrow A in Figure 8, a portion of the sealant 512 is located outside the screw 61, which is a fixing member. The shape of the substrate 502 is shaped to protrude slightly to the right in Figure 14. As shown in Figure 14, the receiving surface of the sealant 512 on the casing 34 does not protrude to the right, but is partially biased to the left relative to the sealant 512. This also serves as a location for inserting a tool when removing the substrate 502. As such, the casing 34 is slightly offset to the left in Figure 14 from the outer shape of the sealant 512. Therefore, the width of the sealant 512 that is crushed by being sandwiched between the casing 34 and the substrate 502 is narrower than in other areas. Therefore, the reaction force of the sealant 512 is smaller in the area not contacting the casing 34 than in other areas. If the reaction force of the sealant 512 occurs outside the screw 61, a force may be generated in a direction that promotes deformation of the substrate 502 due to the reaction force of the heat transfer member 41. However, in this embodiment, the reaction force of the sealing material 512 at that location can be reduced, thereby reducing the force that promotes deformation of the substrate 502. As a result, deformation of the substrate 502 can be suppressed.

[0057] The heat transfer member 41 and the heat dissipation member 42 may be attached to the substrate 502 either before or after placing the substrate 502 in the casing 34. If air bubbles are trapped between the heat transfer member 41 and the substrate 502 or between the heat transfer member 41 and the substrate 502 or the heat dissipation member 42, the efficiency of heat conduction from the substrate 502 to the heat dissipation member 42 will deteriorate. For this reason, it is desirable to press these members with a roller or the like to expel or crush the air bubbles. It is desirable to give the surfaces of the heat transfer member 41 and the heat dissipation member 42 adhesive properties using an adhesive or the like. This makes the members less likely to slip off during work, improving workability.

[0058] 15 is a diagram corresponding to FIG. 9 and shows a modification of the above embodiment. In the above embodiment, elastic member 55 is located on the opposite side of substrate 502 from casing 34. Rotating polygon mirror 306 and rotation shaft 305 (FIG. 3) are spaced apart from substrate 502, which is held in casing 34. However, as shown in FIG. 15, elastic member 55 may be located on the casing 34 side of substrate 502. Rotating polygon mirror 306 and rotation shaft 305 may be fixed to substrate 502.

[0059] In the configuration of the above-described modified example, a screw hole 34a for fixing a substrate 502 is formed in a cylindrical fixed portion 34b formed in the casing 34. The substrate 502 is firmly fixed to the casing 34 by a screw 71 having only a non-stepped screw head 71a and a threaded portion 71b. A coil 506 of a drive source 501 for rotating the rotating polygon mirror 306 and a rotation shaft 305 of the rotating polygon mirror 306 are provided on the upper portion of the substrate 502 (the opposite side of the casing 34) (not shown in FIG. 15). A heat transfer member 41 and a heat dissipation member 42 are attached to the lower portion of the substrate 502 (the same side as the casing 34). An elastic member 55, such as a compression coil spring, is attached in a compressed state around the cylindrical fixed portion 34b formed in the casing 34. This presses the heat dissipation member 42 with a force weaker than the fixing force of the screw 61, thereby holding the heat transfer member 41 and the heat dissipation member 42 to the substrate 502. In this modified example, a standard screw 71 that is not stepped and has only a screw head 71a and a threaded portion 71b can be used. Therefore, in this modified example, the manufacturing cost of the optical deflector 31 can be reduced. [Example]

[0060] The inventors performed the following simulation to confirm the effects of the present invention. Specifically, structural analysis was performed using "ANSYS 2023 R1 Mechanical" ("ANSYS" is a trademark). A simulation model is shown in FIG. 16, and contour diagrams of the simulation results are shown in FIGS. 17 to 19. In this simulation, the screw 61 (shoulder screw) was omitted. In this example, the displacement due to the pressure of the screw 61 and the compressive force of the elastic member 55 were expressed by applying them to the heat dissipation member 42. The casing 34 was omitted, and the fixation of the substrate 502 was expressed by fixing the portions of the substrate 502 pressed by the flanges 61c of the screws 61 in the simulation. The omitted components are shown by imaginary lines in FIG. 16. The substrate 502 was made of iron, and the heat dissipation member 42 was made of aluminum. The heat transfer member 41 had a Young's modulus of 3 MPa and a thickness of 1 mm. The sealing material 512 had a Young's modulus of 1 MPa and a thickness of 0.5 mm.

[0061] As a result of such simulation, the maximum deformation amount of the substrate 502 was as follows: (1) Conventional configuration (comparison example) When the heat dissipation member 42 was pressed firmly with the screws 61 and no sealing material 512 was used, the maximum deformation amount of the substrate 502 was 0.17 mm (FIG. 17). (2) In the case of the configuration of Example 1 of the present application The heat dissipation member 42 was pressed weakly by the elastic member 55, and no sealing material 512 was used. The maximum deformation amount of the substrate 502 was 0.04 mm (FIG. 18). (3) In the case of the configuration of Example 2 of the present application The heat dissipation member 42 was weakly pressed by the elastic member 55, and the sealing material 512 was present. The maximum deformation amount of the substrate 502 was 0.02 mm (FIG. 19). (4) Simulation results Compared to the comparative example (1), the examples (2) and (3) of the present invention were able to significantly reduce the maximum deformation amount of the substrate 502. Therefore, the effects of the present invention were confirmed by Examples 1 and 2.

[0062] The analysis conditions for the above example are as follows (1) to (3) (corresponding to the numbers above): (1) The heat dissipation member 42 was pressed firmly with the screws 61, without the use of the sealing material 512. The displacement of the pressing points of the screws 61 on the heat dissipation member 42 was 0.2 mm for each of the four screws 61. It was assumed that the heat transfer member 41 with a thickness of 1 mm was compressed until it abutted against a 0.8 mm spacer. (2) The heat dissipation member 42 was weakly pressed by the elastic member 55, and no sealing material 512 was used. A force of 10 N was applied to each of the four screws 61 at the pressing points of the elastic member 55 on the heat dissipation member 42. (3) The elastic member 55 weakly presses the heat dissipation member 42, and the sealing material 512 is present. As in (2), the sealing material 512 is added to the simulation. [Explanation of symbols]

[0063] 1. Image forming device 11Y,11C,11M,11K photoreceptor 13Y, 13C, 13M, 13K, 13 Scanning optical device 14Y, 14C, 11M, 11K developing device 31 Optical deflector 32 Case 33 Housing 34 Casing 41 Heat transfer material 42 Heat dissipation material 55 Elastic member (compression coil spring) 61 Screws (step screws, fixing parts) 311 Light source 306 Rotating Polygonal Mirror 312 Light source folding mirror (optical system) 313~315 Scanning lens (optical system) 316,320 Scanning lens (optical system) 317~319 Long folding mirror (optical system) 501 Power Source 502 board 512 Sealing material

Claims

1. The housing and a rotary polygonal mirror housed in the housing and having a mirror surface formed on its outer circumferential surface; a substrate on which at least a part of a drive source for driving the rotary polygon mirror is mounted; a heat dissipation member that dissipates heat from the substrate to the outside; a heat transfer member formed of an elastic body and interposed between the substrate and the heat dissipation member to transfer heat from the substrate to the heat dissipation member; a fixing member that fixes the substrate to the housing; an elastic member that elastically presses the heat dissipation member and the heat transfer member against the substrate with a biasing force that is weaker than the fixing force of the fixing member, thereby supporting the heat dissipation member and the heat transfer member on the substrate.

2. 2. The optical deflector according to claim 1, wherein the elastic member generates the biasing force when pressed by the fixed member.

3. 3. The optical deflector according to claim 2, wherein the elastic member is wound around the fixed member.

4. 2. The optical deflector according to claim 1, wherein the elastic member is a compression coil spring.

5. 2. The optical deflector according to claim 1, wherein the fixing member is a screw.

6. 2. The optical deflector according to claim 1, wherein the fixing member regulates the position of the heat dissipation member in a width direction.

7. 2. The optical deflector according to claim 1, wherein a sealing material is sandwiched between the substrate and the housing.

8. 8. The optical deflector according to claim 7, wherein the sealing material surrounds the entire periphery of the driving source.

9. 8. The optical deflector according to claim 7, wherein the sealing material is formed of an elastic material and is thicker than the gap between the substrate and the housing when not sandwiched between the substrate and the housing.

10. 8. The optical deflector according to claim 7, wherein at least one of the fixing members is located outside the sealing material.

11. 8. The optical deflector according to claim 7, wherein a portion of said sealing material located outside said fixing member has a width sandwiched between said housing and said substrate that is narrower than other portions.

12. 2. The optical deflector according to claim 1, wherein the elastic member is disposed on the opposite side of the substrate from the housing side.

13. 2. The optical deflector according to claim 1, wherein the substrate does not directly support the rotating polygon mirror and is spaced apart from the rotating polygon mirror.

14. 2. The optical deflector according to claim 1, wherein the substrate is made of iron or an alloy containing iron.

15. 2. The optical deflector according to claim 1, wherein the heat transfer member has a constant thickness.

16. The optical deflector according to claim 1 ; A light source and an optical system that performs at least one of irradiating the rotating polygon mirror with light emitted from the light source and irradiating the light reflected by the rotating polygon mirror onto a predetermined destination.

17. A photoreceptor; 17. The scanning optical device according to claim 16, wherein the photosensitive member is exposed to light to form an electrostatic latent image; a developing device that develops the electrostatic latent image on the photosensitive member with toner.

Images