JP4057992B2 - Support method of reflecting mirror in optical scanning device, optical scanning device, and image forming apparatus - Google Patents

Description

  The present invention relates to a method for supporting a reflecting mirror in an optical scanning device, an optical scanning device, and an image forming apparatus including the same.

  2. Description of the Related Art Conventionally, optical scanning devices are used in image forming apparatuses such as laser beam printers, laser facsimiles, and digital copying machines. As this type of optical scanning device, a semiconductor laser as a light source, a polygon mirror (rotating polygon mirror), a first imaging optical system that linearly forms a light beam from the semiconductor laser on the polygon mirror, and a scanned object A second imaging optical system that forms a uniform spot on the surface at a constant speed, a scanning start signal detector that detects a light beam scanned by a polygon mirror, and a light beam from a semiconductor laser as a scanning start signal detector An apparatus including a detection optical system that collects light is known (for example, see Patent Document 1).

  As described above, the second imaging optical system exhibits an advanced function of forming a uniform spot on the surface to be scanned at a uniform speed. If it is going to be comprised by this, it is necessary to form the optical element in a complicated shape. By the way, in many cases, a glass lens which is a light transmission type optical element is used for the second imaging optical system. However, it is difficult to process a glass lens into a complicated shape. Therefore, it is difficult to configure the second imaging optical system with a single glass lens. Accordingly, when the second imaging optical system is configured with a glass lens, it is necessary to combine a plurality of glass lenses. In general, a combination of these lenses is called an fθ lens.

  However, a glass lens is an expensive optical element. For this reason, if the second imaging optical system is configured with a glass lens, a plurality of expensive glass lenses are required, and it is difficult to reduce the size and cost of the optical scanning device.

  Therefore, in order to reduce the size and cost of the optical scanning device, an apparatus using a reflecting mirror having a curved reflecting surface in the second imaging optical system has been proposed. That is, it has been proposed to use a light reflecting optical element instead of a light transmitting optical element as the second imaging optical system.

Further, the applicant of the present application has proposed that the second imaging optical system is configured only by the reflecting mirror by using a reflecting mirror having a reflecting surface formed of a so-called free-form surface (for example, Patent Document 2). reference). As shown in FIG. 8, in this type of reflecting mirror 100, the cross section is substantially C-shaped, but the shape of the cross section is not constant along the axial direction, and the whole is a twisted shape. Yes. With such a shape, the reflecting mirror 100 can scan the spot in a straight line on the surface to be scanned.
JP 2001-166239 A JP 2002-148539 A

  In recent years, downsizing of optical scanning devices has progressed, and the influence of vibration on optical elements is becoming ignorable. However, reflecting mirrors as optical elements are more susceptible to vibration than light-transmitting optical elements (such as lenses). Therefore, a measure for suppressing the influence of vibration on the reflecting mirror is desired.

  In the scanning optical device of Patent Document 1, in order to suppress the influence of vibration, support members 102, 103, and 104 are respectively provided below both ends and the center of the reflecting mirror 101 in the longitudinal direction as shown in FIG. The reflecting mirror 101 was supported at three points at both ends and the center in the longitudinal direction. Further, at both ends, the reflecting mirror 101 is pressed in a direction orthogonal to the reflecting surface 105 by an elastic member (not shown). On the other hand, at the central portion, the reflecting mirror 101 is pressed in a direction parallel to the reflecting surface 105 by the elastic member 106. In this apparatus, the three support members 102, 103, and 104 that support the reflecting mirror 101 are arranged in a substantially straight line along the longitudinal direction of the reflecting mirror 101.

  However, as shown in FIG. 9B, if the position of the center of gravity G of the reflecting mirror 101 and the support point S are shifted with respect to the front-rear direction of the reflecting mirror 101 (the left-right direction in FIG. 9B), When a force was applied, the reflecting mirror 101 was easy to vibrate around the support point S.

  In the scanning optical device, the reflecting surface 105 of the reflecting mirror 101 is not a curved surface but a flat surface. In addition, the reflecting mirror 101 has a rectangular cross section and is formed in a shape that is easy to support. Therefore, it was possible to try to suppress the vibration of the reflecting mirror 101 by the above support method in which the support points S are arranged substantially linearly. In the reflecting mirror 101, the cross-sectional shape is constant along the longitudinal direction. Therefore, the shape of the reflecting mirror 101 is relatively simple and originally has a shape that is easy to support.

  However, a reflecting mirror having a curved reflecting surface is complicated in shape. Therefore, the above support method cannot be used as it is, and a new support method has been desired.

  The reflecting mirror of Patent Document 1 is merely a so-called folding mirror and does not constitute the second imaging optical system by itself. However, in particular, a reflecting mirror whose reflecting surface is a so-called free-form surface is formed in a twisted shape as a whole, so that it has been difficult to sufficiently suppress vibration with the conventional support method.

  The present invention has been made in view of such points, and an object of the present invention is to support a reflecting mirror including a curved reflecting surface in an optical scanning device so as to suppress the influence of vibration. It is in. It is another object of the present invention to provide an optical scanning device that realizes such a support method and an image forming apparatus including the same.

A method of supporting a reflecting mirror according to the present invention is a method of supporting the reflecting mirror in an optical scanning device including a reflecting mirror that reflects a scanned light beam, and the reflecting mirror is long in the scanning direction of the light beam. First, second, and third support points that include a reflecting surface that is a curved surface having a positive power in the scanning direction at least and that surrounds the center of gravity of the reflecting mirror in plan view. The reflecting mirror has a front side portion on which the reflecting surface is formed and a rear side portion on the back side of the reflecting surface, and the longitudinal direction of the reflecting mirror is in the middle of the front and rear direction of the reflecting mirror. This is a method of forming a symmetrical shape with respect to a plane formed by the support direction of each support point .

According to the above support method, since the center of gravity of the reflecting mirror is located inside the virtual triangle formed by connecting the first to third supporting points, even if a force is applied from the outside, the reflecting mirror is either At one support point, a force in the direction opposite to the vibrating direction is received. Therefore, the vibration of the reflecting mirror is suppressed. Further, since the reflecting mirror is formed in a shape that is stable and easily supported, the reflecting mirror is supported more stably.

Another method of supporting the reflecting mirror according to the present invention is a method of supporting the reflecting mirror in an optical scanning device provided with a reflecting mirror that reflects a scanned light beam, the reflecting mirror being in the scanning direction of the light beam. The reflecting surface is formed of a long and curved surface having a positive power in at least the scanning direction, and the reflecting mirror is disposed so as to surround the shear center of the cross section in the longitudinal direction of the reflecting mirror in plan view. The reflecting mirror is supported at first, second, and third supporting points, and the reflecting mirror includes a front portion on which the reflecting surface is formed and a rear portion on the back side of the reflecting surface in the front-rear direction of the reflecting mirror. In the middle, the method is formed in a symmetrical shape with respect to a plane formed by the longitudinal direction of the reflecting mirror and the supporting direction of each of the supporting points .

According to the above support method, the shear center of the cross section of the central portion of the reflecting mirror is located inside the virtual triangle formed by connecting the first to third support points. Therefore, even when a force is applied from the outside, at least the vicinity of the central portion of the reflecting mirror is difficult to twist. Therefore, the tilting of the reflecting surface is less likely to occur, and the influence of vibration is suppressed. Further, since the reflecting mirror is formed in a shape that is stable and easily supported, the reflecting mirror is supported more stably.

  The first and second support points are preferably located near one end in the longitudinal direction of the reflecting mirror, and the third support point is located near the other end in the longitudinal direction of the reflecting mirror. .

  According to the above support method, since the first to third support points are all located at the end of the reflecting mirror, the occurrence of distortion due to being supported other than the end of the reflecting mirror is prevented. . Therefore, surface tilting is effectively suppressed except at the end of the reflecting surface.

  The first support point is located near one end in the longitudinal direction of the reflecting mirror, and the second support point is located near the other end in the longitudinal direction of the reflecting mirror, and the third support point The point may be located near the center of the reflecting mirror in the longitudinal direction.

  According to the above support method, the distance between the support points becomes relatively uniform, and the reflecting mirror is supported more stably.

  The third support point is preferably located on the concave side of the reflecting surface of the reflecting mirror with respect to an imaginary straight line connecting the first support point and the second support point.

  Accordingly, the first to third support points are arranged along the bending direction so as to correspond to the reflection surface being curved in the longitudinal direction. Therefore, support according to the shape of the reflecting surface is realized, and the reflecting mirror is supported more stably.

  It is preferable that the center of gravity of the reflecting mirror coincides with the shear center of the central cross section in the longitudinal direction of the reflecting mirror.

  Thereby, the vibration and twist of the reflecting mirror are suppressed, and the surface tilt of the reflecting surface is further suppressed.

An optical scanning device according to the present invention is disposed between a light source that outputs a light beam, an optical deflector that scans the light beam from the light source, and the light source and the optical deflector, and the light beam from the light source is A first imaging optical system that guides to the deflection surface of the optical deflector and forms a line image on the deflection surface, and is disposed between the optical deflector and the surface to be scanned, and transmits the light beam from the optical deflector. An optical scanning device including a second imaging optical system that guides to the scanned surface and forms a uniform spot on the scanned surface at a constant speed, wherein the second imaging optical system includes a light beam A reflecting mirror having a reflecting surface that is long in the scanning direction and has a curved surface having at least a positive power in the scanning direction, and supports the reflecting mirror at first, second, and third support points, respectively. , Further comprising a second and a third support member, and the reflecting mirror in plan view Heart, the first, located inside the imaginary triangle formed by connecting the second and third supporting point, said reflector, rear corresponding to the back side of the front portion of said reflecting surface is formed as the reflecting surface The portion is formed in a symmetrical shape with respect to a plane formed by the longitudinal direction of the reflecting mirror and the supporting direction of each of the supporting points in the middle of the longitudinal direction of the reflecting mirror .

Another optical scanning device according to the present invention is disposed between a light source that outputs a light beam, an optical deflector that scans the light beam from the light source, and the light source and the light deflector. Is arranged between the optical deflector and the surface to be scanned, and the first imaging optical system that guides the light to the deflection surface of the optical deflector and forms a line image on the deflection surface. A second imaging optical system that guides a light beam to the surface to be scanned and forms a uniform spot on the surface to be scanned at a uniform speed, the second imaging optical system comprising: A reflecting mirror having a reflecting surface that is long in the scanning direction of the light beam and has a curved surface having at least positive power in the scanning direction, and supports the reflecting mirror at first, second, and third support points, respectively. A first support member, a second support member, and a third support member; Front shear center of the central portion transverse of the longitudinal direction is positioned inside of the first, imaginary triangle formed by connecting the second and third supporting point, said reflector, it said reflecting surface is formed of The portion and the rear portion corresponding to the back side of the reflecting surface are symmetrical with respect to the plane formed by the longitudinal direction of the reflecting mirror and the supporting direction of each supporting point in the middle of the longitudinal direction of the reflecting mirror. Is formed .

  The first and second support points are preferably located near one end in the longitudinal direction of the reflecting mirror, and the third support point is located near the other end in the longitudinal direction of the reflecting mirror. .

  The first support point is located near one end in the longitudinal direction of the reflecting mirror, and the second support point is located near the other end in the longitudinal direction of the reflecting mirror, and the third support point The point may be located near the center of the reflecting mirror in the longitudinal direction.

  The third support point is preferably located on the concave side of the reflecting surface of the reflecting mirror with respect to an imaginary straight line connecting the first support point and the second support point.

  It is preferable that the center of gravity of the reflecting mirror coincides with the shear center of the central cross section in the longitudinal direction of the reflecting mirror.

  In the reflecting mirror, the front side portion on which the reflecting surface is formed and the rear side portion on the back side of the reflecting surface are in the middle of the longitudinal direction of the reflecting mirror and the longitudinal direction of the reflecting mirror and the support of each support point It is preferable that it is formed in a symmetrical shape with respect to the plane formed by the direction.

  The reflecting mirror is preferably composed of a synthetic resin member having a curved surface and a mirror film formed on the curved surface of the synthetic resin member.

  Accordingly, since the synthetic resin member can be easily processed, even a complicated curved surface shape can be formed relatively easily. Moreover, it can comprise at low cost compared with a glass member.

  The second imaging optical system is preferably composed only of the reflecting mirror.

  Since the reflecting surface of the reflecting mirror is a so-called free-form surface, the second imaging optical system can be configured only by the reflecting mirror.

  The image forming apparatus according to the present invention is configured to rotate the optical scanning device, a substantially cylindrical photosensitive member whose outer peripheral surface forms the surface to be scanned and extending in a scanning direction of a light beam of the optical scanning device, and the photosensitive member. A driving unit; a developing unit that supplies toner to the photoconductor; and a transfer unit that transfers a toner image formed on the photoconductor to a recording medium.

  As a result, an image forming apparatus that is less susceptible to vibration is realized.

  According to the present invention, the reflection mirror is supported at three points so that the center of gravity of the reflection mirror is located inside the virtual triangle formed by connecting the first to third support points in plan view. Can be suppressed.

  Further, by supporting the reflecting mirror at three points so that the shear center of the cross section of the central portion of the reflecting mirror is located inside the virtual triangle formed by connecting the first to third supporting points in plan view, the twist due to vibration can be prevented. Generation | occurrence | production can be suppressed and the influence of a vibration can be suppressed.

  If the first and second support points are located in the vicinity of one end of the reflecting mirror and the third support point is located in the vicinity of the other end, surface tilt other than at the end of the reflecting mirror is effectively suppressed. be able to.

  If the first support point is located near one end of the reflector, the second support point is located near the other end, and the third support point is located near the center, the distance between the support points Can be made relatively uniform, and the reflecting mirror can be stably supported.

  If the third support point is located on the concave side of the reflecting surface of the reflecting mirror with respect to the imaginary straight line connecting the first supporting point and the second supporting point, the mode according to the curved shape of the reflecting surface Can support the reflector.

  By making the center of gravity of the reflecting mirror coincide with the shear center of the cross section at the center, the surface tilt of the reflecting mirror can be further suppressed.

  By forming the reflecting mirror in a symmetrical shape in the front-rear direction, the reflecting mirror can be supported more stably.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  As shown in FIGS. 1 and 2, the optical scanning device 1 according to the embodiment includes a light source unit 2, a polygon mirror 9, a reflecting mirror 10, and a synchronization sensor 13, which are included in a housing 15. It is provided inside. For convenience, in the following description, the right side of FIG. 1 is referred to as the rear side, and the left side of FIG. 1 is referred to as the front side.

  The light source unit 2 is configured by assembling a laser drive substrate (hereinafter referred to as a semiconductor laser) 3 provided with a semiconductor laser circuit, a collimator lens 4, a main concave cylinder lens 5, and a sub convex cylinder lens 6. Yes. A folding mirror 7 is disposed in the irradiation direction of the laser light of the light source unit 2, that is, in front of the light source unit 2. A main convex cylinder lens 8 is provided between the folding mirror 7 and the polygon mirror 9.

  The collimator lens 4, the main concave cylinder lens 5, the sub-convex cylinder lens 6, and the main convex cylinder lens 8 guide the beam (light beam) from the semiconductor laser 3 to the deflection surface of the polygon mirror 9 and line it on the deflection surface. A first imaging optical system for forming an image is configured. In the present specification, it is assumed that an element that simply reflects light by a flat reflecting surface such as the folding mirror 7 is not included in the imaging optical system.

  The polygon mirror 9 is a rotating polygon mirror having a plurality of reflecting surfaces (deflection surfaces), and is rotated by a motor (not shown). The light reflected by the polygon mirror 9 due to the rotation of the polygon mirror 9 is scanned in the order of the beams 60a to 60c. For convenience of explanation, the three beams 60 a to 60 c are shown in the drawing at the same time, but actually one beam is scanned in the longitudinal direction of the reflecting mirror 10. A reflecting mirror 10 that reflects the beam from the polygon mirror 9 is provided in front of the folding mirror 7. Details of the reflecting mirror 10 will be described later.

  As shown in FIG. 2, folding mirrors 11 and 12 are provided behind the reflecting mirror 10. The folding mirrors 11 and 12 are also formed long like the reflecting mirror 10. The folding mirror 12 is disposed below the folding mirror 11. Then, the beam reflected by the reflecting mirror 10 is reflected in the order of the folding mirror 11 and the folding mirror 12 and irradiated forward.

  A folding mirror 14 that reflects light only when the beam is at the position is disposed behind the start position in the scanning direction of the reflecting mirror 10 (the position at the left end in FIG. 2). The light reflected by the folding mirror 14 enters the synchronization sensor 13. That is, at the start of scanning, light enters the synchronous sensor 13 and the start of scanning is detected.

  As shown in FIG. 3, the beam emitted from the optical scanning device 1 is guided onto a cylindrical photosensitive drum 16. The outer peripheral surface of the photosensitive drum 16 is a surface to be scanned on which the beam from the optical scanning device 1 is scanned, and is covered with a photosensitive member whose charge changes when irradiated with light. Since the beam from the optical scanning device 1 is scanned, the beam spot is scanned on the photosensitive drum 16 in a direction (main scanning direction) parallel to the axial direction of the photosensitive drum 16. The photosensitive drum 16 is rotationally driven by a motor (rotating unit) (not shown). By combining the beam scanning and the rotation of the photosensitive drum 16 in this manner, a two-dimensional latent image is formed on the surface of the photosensitive drum 16.

  Next, the reflecting mirror 10 and its supporting method will be described.

  The reflecting mirror 10 constitutes a second imaging optical system that guides the beam from the polygon mirror 9 to the surface to be scanned of the photosensitive drum 16 and forms a uniform spot on the surface to be scanned at a constant speed. As described above, the reflecting mirror 10 is formed long along the light scanning direction. The reflecting mirror 10 includes a thin plate-like reflecting mirror body 23 (see FIG. 1) having a reflecting surface 20, and a rear side direction (leftward direction in FIG. 1 from the upper and lower ends of the reflecting mirror body 23. In other words, in front of the optical scanning device 1. ) And upper and lower ribs 21a and 21b (see FIG. 4B) and end ribs 22 extending from the left and right ends of the reflector main body 23 in the back side direction, and are integrally made of synthetic resin (plastic). Molded. The ribs 21a and 21b are formed long in the scanning direction in the same manner as the reflecting mirror body 23.

  A metal layer is formed on one surface (front surface) of the reflecting mirror body 23, and the metal layer forms a reflecting surface 20 as a mirror surface. The reflecting surface 20 is a curved surface that is long in the scanning direction of the light beam and has a positive power at least in the scanning direction. In addition, the reflecting surface 20 is a three-dimensional curved surface having a substantially C-shaped transverse section and a substantially C-shaped longitudinal section. Moreover, the reflecting surface 20 is formed by a so-called free-form surface whose cross-sectional shape is not constant in the longitudinal direction. This is because the second imaging optical system is constituted by only the reflecting mirror 10. The specific shape of the reflecting surface 20 can be appropriately set based on the distance between the optical scanning device 1 and the photosensitive drum 16, the specifications of each optical system, and the like.

  As shown in FIG. 4, the reflecting mirror 10 is supported at three points by the first to third protrusions 31 to 33 provided on the housing 15 at both ends and the center. That is, the reflecting mirror 10 includes a first support point S1 located near one end in the longitudinal direction, a second support point S2 located near the other end, and a third support point located near the center. Supported in S3. As shown in FIG. 4A, the third support point S3 is closer to the concave side (back side) of the reflective surface 20 than the virtual straight line V1 connecting the first support point S1 and the second support point S2. positioned. Therefore, the first support point S1, the third support point S3, and the second support point S2 are not aligned on the same straight line, but are arranged along the curved shape of the reflector body 23.

  Furthermore, the first to third support points S1 to S3 are arranged so that the center of gravity G of the reflecting mirror 10 is located inside a virtual triangle V3 connecting these support points S1 to S3 in plan view. Although not shown, the shear center in the longitudinal section of the reflecting mirror 10 is also located inside the virtual triangle V3.

  In order to stably support the reflecting mirror 10, the distance L1 between the third support point S3 and the virtual straight line V1 is preferably as long as possible. Here, the distance L1 between the third support point S3 and the virtual straight line V1 is larger than the sag amount L2 in the scanning direction of the reflecting mirror body 23.

  First to third pressing springs 41 to 43 are provided at positions corresponding to the first to third support points S1 to S3 on the upper side of the reflecting mirror 10, respectively. The corresponding position may be a position directly above each support point or may be a position in the vicinity of the directly above position. Each of the pressing springs 41 to 43 presses the reflecting mirror 10 downward. Therefore, the reflecting mirror 10 is sandwiched between the first to third pressing springs 41 to 43 and the first to third protrusions 31 to 33.

  In the first to third support points S1 to S3, the protrusions 31 to 33 are in contact with the lower rib 21b. The first to third pressing springs 41 to 43 press the upper rib 21a. However, the protrusions 31 and 32 may be in contact with the reflecting mirror body 23 at the first and second support points S1 and S2. Further, the first and second pressing springs 41 and 42 may press the reflecting mirror body 23. If both end portions of the reflecting mirror body 23 are pressed or supported, there is a risk of distortion in the vicinity of the pressing portion or supporting portion of the reflecting mirror body 23, but in this embodiment, both end portions of the reflecting mirror 10 are not used as reflecting surfaces. This is because practical problems hardly occur because light is not reflected at both ends. By pressing or supporting the reflector body 23 at both ends, the area of the virtual triangle V3 formed by connecting the first to third support points S1 to S3 can be increased, and the reflector 10 is more stable. Can be supported.

  As described above, according to the present optical scanning device 1, the reflecting mirror 10 is supported so that the center of gravity G is positioned inside the virtual triangle V3 formed by connecting the supporting points S1 to S3. Therefore, even when a force (for example, vibration of the motor of the polygon mirror 9 or impact from the outside) is applied from the outside, the reflecting mirror 10 is in a direction opposite to the vibrating direction at any one support point. Will receive the power of. For example, even when the reflecting mirror 10 is likely to rotate backward about the virtual straight line V1 connecting the first supporting point S1 and the second supporting point S2 by receiving a force from the outside, the reflecting mirror 10 is At the third support point S3, a force in the direction opposite to the direction of rotation is received from the protrusion 33. Therefore, the rotation of the reflecting mirror 10 is prevented. Therefore, according to the present optical scanning device 1, even when a force is applied to the reflecting mirror 10 from the outside, the reflecting mirror 10 hardly vibrates and effectively suppresses the tilting of the reflecting surface 20. Can do.

  Further, the shear center in the cross section of the central portion in the longitudinal direction of the reflecting mirror 10 is also located inside the virtual triangle V3 formed by connecting the support points S1 to S3. Therefore, even when a force is applied to the reflecting mirror 10, the occurrence of twist can be suppressed.

  In particular, in the present embodiment, since the three points near the both ends and the center of the reflecting mirror 10 are supported, the distance between the supporting points can be made uniform. Therefore, the reflecting mirror 10 can be supported more stably.

  Moreover, in this embodiment, since the reflective mirror 10 was pressed in the position corresponding to 1st-3rd support points S1-S3, the reflective mirror 10 can be hold | maintained firmly.

  Further, since the reflecting mirror 10 is formed of synthetic resin, the reflecting surface 20 can be realized at a low cost even though the reflecting surface 20 has a complicated shape. In addition, since the ribs 21a, 21b, and 22 extending from the reflecting mirror body 23 to the back side are provided, the overall strength of the reflecting mirror 10 can be kept high even if the reflecting mirror body 23 is formed thin. By forming the reflecting mirror main body 23 to be thin, it is possible to suppress the occurrence of sink marks in the material during processing, and it is possible to improve the processing accuracy of the reflecting surface 20.

  Since the ribs 21a and 21b are supported and pressed at the third support point S3 and the corresponding pressing point, the supporting force and the pressing force do not directly act on the reflecting mirror body 23. Accordingly, it is possible to suppress the distortion of the reflecting surface 20 due to supporting and pressing the central portion of the reflecting mirror 10.

  As described above, according to the present optical scanning device 1, it is possible to stably support the reflecting mirror 10 including the reflecting surface 20 formed of a free-form surface. In the present optical scanning device 1, the second imaging optical system is composed of only a reflective optical element, so that it is inherently susceptible to vibration compared to an apparatus using a transmissive optical element. . However, in this optical scanning device 1, since the reflecting mirror 10 can be supported stably, the vibration of the reflecting mirror 10 can be highly suppressed. Therefore, the performance of the optical scanning device 1 can be improved. Further, it becomes possible to promote downsizing of the apparatus.

  The shape and supporting method of the reflecting mirror 10 are not limited to the above-described shape and supporting method. Next, a modification of the shape of the reflecting mirror 10 and the support method will be described.

  In the modification shown in FIG. 5, the position of the support point and the position and number of the pressing springs are changed. That is, in this example, the first support point S1 and the second support point S2 are both located near one end of the reflecting mirror 10, while the third support point S3 is located near the other end of the reflecting mirror 10. is doing. The first support point S1 and the second support point S2 are aligned in the front-rear direction (vertical direction in FIG. 5A). Also in this example, the center of gravity G of the reflecting mirror 10 and the shear center (not shown) in the central section in the longitudinal direction are located inside the virtual triangle V3 formed by connecting the support points S1 to S3.

  Therefore, also in this example, even when a force is applied to the reflecting mirror 10 from the outside, the reflecting mirror 10 is less likely to vibrate, and at least the central portion is less likely to be twisted. Therefore, the surface collapse of the reflecting surface 20 can be effectively suppressed.

  In addition, in this example, the first to third support points S <b> 1 to S <b> 3 are all located in the vicinity of the end of the reflecting mirror 10. For this reason, in a portion other than the vicinity of both end portions of the reflecting mirror 10, it is possible to prevent the occurrence of local minute distortion caused by the supporting force. In this example, the portion of the reflecting surface 20 that is actually used for reflecting light is a portion excluding both ends. Therefore, even if a minute distortion due to the supporting force occurs at both ends, no problem is actually caused.

The modification shown in FIG. 6 , that is, the embodiment of the present invention, is a modification of the shape of the reflecting mirror 10. The reflecting mirror 10 of this example is formed in a symmetrical shape in the front-rear direction. That is, the front portion where the reflection surface 20 is formed and the rear portion corresponding to the back side of the reflection surface 20 are in the longitudinal direction (the left-right direction in FIG. 6B) in the middle of the front-rear direction of the reflection mirror 10 and each support. It is formed in a symmetrical shape with respect to a virtual plane L3 formed in the support direction of the points S1 to S3 (the vertical direction in FIG. 6B). In this example, the reflecting mirror 10 is formed of a solid rod-like body.

  Also in this example, the center of gravity G of the reflecting mirror 10 is located inside a virtual triangle V3 formed by connecting the first to third support points S1 to S3. In the reflecting mirror 10, the center of gravity G coincides with the shear center of the central section of the reflecting mirror 10 in the longitudinal direction. Therefore, the shear center is also located inside the virtual triangle V3.

  According to this example, in addition to the above-described effects, the reflecting mirror 10 itself is formed in a shape that is stable and easily supported, so that the reflecting mirror 10 can be supported more stably and the influence of vibration can be reduced. Further suppression can be achieved. In addition, since the center of gravity G and the shear center of the central section coincide with each other, vibration and twist of the reflecting mirror 10 can be effectively suppressed.

  Next, an embodiment of an image forming apparatus equipped with the optical scanning device 1 will be described. An image forming apparatus equipped with the optical scanning apparatus 1 can be used as various image forming apparatuses such as a laser beam printer, a laser facsimile, and a digital copying machine. The optical scanning apparatus 1 includes the above-described embodiments and modifications. Any of the reflecting mirrors 10 can be used.

  As shown in FIG. 7, an optical scanning device 1 having a light source unit 2, a polygon mirror 9, and a reflecting mirror 10 (a casing 15 and other elements are not shown) inside a casing 51 of the image forming apparatus 50. ) Is stored. Further, the casing 51 is provided with the photosensitive drum 16, a primary charger 52 for charging by charging electrostatic ions on the outer peripheral surface of the photosensitive drum 16, a developing unit 53 for attaching charged toner to the printing unit, and the attached toner. A transfer charger 54 for transferring to the paper, a cleaner 55 for removing the remaining toner, a fixing device 56 for fixing the transferred toner to the paper, and a paper feed cassette 57 are provided.

  According to the image forming apparatus 50, since the optical scanning apparatus 1 described above is used, it is possible to reduce the size of the apparatus, reduce costs, improve performance, and the like.

  In the optical scanning device 1, the reflecting mirror 10 is supported by the protrusions 31 to 33 formed on the housing 15. However, the protrusions 31 to 33 may not be integrated with the housing 15 and may be formed by a member separate from the housing 15. Further, the projections 31 to 33 can be provided on the reflecting mirror 10.

  In the embodiment shown in FIG. 4, the third support point S <b> 3 does not have to be at the intermediate position in the longitudinal direction of the reflecting mirror 10, and may be at a position shifted from the intermediate position. That is, the third support point S3 only needs to be substantially located near the center.

  The pressure springs 41 to 43 are provided at positions corresponding to the support points S1 to S3, but may be provided at positions different from those. Further, the number of pressing springs does not necessarily need to match the number of supporting points. Further, the pressure springs 41 to 43 are useful for firmly supporting the reflecting mirror 10, but are not necessarily required elements.

  The material of the reflecting mirror 10 is not limited to synthetic resin, and other materials can be used. When the second imaging optical system is not composed of only the reflecting mirror 10, the reflecting surface 20 of the reflecting mirror 10 may not be a free-form surface.

  As described above, the present invention is useful for image forming apparatuses such as laser beam printers, laser facsimiles, and digital copying machines, and optical scanning apparatuses used therefor.

It is a top view of the optical scanning device concerning an embodiment. It is a perspective view of the principal part of the optical scanning device concerning an embodiment. It is a perspective view of an optical scanning device and a photosensitive drum. It is explanatory drawing of the reflective mirror which concerns on embodiment, (a) is a top view, (b) is a front view, (c) is a side view. It is explanatory drawing of the reflective mirror which concerns on a modification, (a) is a top view, (b) is a front view, (c) is a side view. It is explanatory drawing of the reflective mirror which concerns on a modification, (a) is a top view, (b) is a front view, (c) is a side view. 1 is a schematic cross-sectional view of an image forming apparatus according to an embodiment. It is explanatory drawing of the reflective mirror which has a reflective surface which consists of free-form surfaces. It is explanatory drawing of the reflective mirror in the conventional optical scanning apparatus, (a) is a top view, (b) is XX sectional drawing of (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical scanning device 2 Light source unit 3 Laser drive board | substrate (light source)
9 Polygon mirror (optical deflector)
DESCRIPTION OF SYMBOLS 10 Reflecting mirror 13 Synchronization sensor 16 Photosensitive drum 20 Reflecting surface 21a, 21b Rib 23 Reflecting mirror main body 31,32,33 Protrusion 41,42,43 Pressing spring G Center of gravity S1 1st support point S2 2nd support point S3 3rd Support point V1 Virtual straight line connecting the first support point and the second support point V3 Virtual triangle formed by connecting the first to third support points

Claims (15)

A method of supporting the reflecting mirror in an optical scanning device including a reflecting mirror that reflects a scanned light beam,
The reflecting mirror includes a reflecting surface made of a curved surface that is long in the scanning direction of the light beam and has at least positive power in the scanning direction;
The reflector is supported by first, second, and third support points that are disposed so as to surround the center of gravity of the reflector in plan view .
In the reflecting mirror, the front side portion on which the reflecting surface is formed and the rear side portion on the back side of the reflecting surface are in the middle of the longitudinal direction of the reflecting mirror and the longitudinal direction of the reflecting mirror and the support of each support point A method of supporting a reflecting mirror that is formed in a symmetrical shape with respect to a plane formed by a direction . A method of supporting the reflecting mirror in an optical scanning device including a reflecting mirror that reflects a scanned light beam,
The reflecting mirror includes a reflecting surface made of a curved surface that is long in the scanning direction of the light beam and has at least positive power in the scanning direction;
The reflecting mirror is supported by first, second, and third supporting points arranged so as to surround the shear center of the central cross section in the longitudinal direction of the reflecting mirror in plan view ,
In the reflecting mirror, the front side portion on which the reflecting surface is formed and the rear side portion on the back side of the reflecting surface are in the middle of the longitudinal direction of the reflecting mirror and the longitudinal direction of the reflecting mirror and the support of each support point A method of supporting a reflecting mirror that is formed in a symmetrical shape with respect to a plane formed by a direction . The first and second support points are located near one end in the longitudinal direction of the reflecting mirror,
The method of supporting a reflecting mirror according to claim 1 or 2, wherein the third supporting point is located in the vicinity of the other end of the reflecting mirror in the longitudinal direction. The first support point is located near one end in the longitudinal direction of the reflecting mirror,
The second support point is located near the other end in the longitudinal direction of the reflecting mirror,
The method of supporting a reflecting mirror according to claim 1 or 2, wherein the third supporting point is located in the vicinity of the center in the longitudinal direction of the reflecting mirror.   The said 3rd support point is a support of the reflective mirror of Claim 4 located in the concave side of the reflective surface of the said reflective mirror rather than the virtual straight line which connects the said 1st support point and the said 2nd support point. Method.   The method of supporting a reflecting mirror according to any one of claims 1 to 5, wherein a center of gravity of the reflecting mirror coincides with a shear center of a cross section at a central portion in the longitudinal direction of the reflecting mirror. A light source that outputs a luminous flux;
An optical deflector that scans a light beam from the light source;
A first imaging optical system that is disposed between the light source and the optical deflector, guides a light beam from the light source to a deflection surface of the optical deflector, and forms a line image on the deflection surface;
A second image formed between the optical deflector and the surface to be scanned, guides a light beam from the optical deflector to the surface to be scanned, and forms a uniform spot on the surface to be scanned at a uniform speed. An optical scanning device comprising an optical system,
The second imaging optical system includes a reflecting mirror having a reflecting surface that is long in the scanning direction of the light beam and has a curved surface that has at least positive power in the scanning direction;
Further comprising first, second and third support members for supporting the reflecting mirror at first, second and third support points, respectively.
The center of gravity of the reflecting mirror in a plan view is located inside a virtual triangle formed by connecting the first, second and third support points ,
In the reflecting mirror, the front side portion on which the reflecting surface is formed and the rear side portion on the back side of the reflecting surface are in the middle of the longitudinal direction of the reflecting mirror and the longitudinal direction of the reflecting mirror and the support of each support point The optical scanning device is formed in a symmetrical shape with respect to the plane formed by the direction . A light source that outputs a luminous flux;
An optical deflector that scans a light beam from the light source;
A first imaging optical system that is disposed between the light source and the optical deflector, guides a light beam from the light source to a deflection surface of the optical deflector, and forms a line image on the deflection surface;
A second image formed between the optical deflector and the surface to be scanned, guides a light beam from the optical deflector to the surface to be scanned, and forms a uniform spot on the surface to be scanned at a uniform speed. An optical scanning device comprising an optical system,
The second imaging optical system includes a reflecting mirror having a reflecting surface that is long in the scanning direction of the light beam and has a curved surface that has at least positive power in the scanning direction;
Further comprising first, second and third support members for supporting the reflecting mirror at first, second and third support points, respectively.
In plan view, the center of shear across the center of the reflector in the longitudinal direction is located inside a virtual triangle formed by connecting the first, second and third support points,
In the reflecting mirror, the front side portion on which the reflecting surface is formed and the rear side portion on the back side of the reflecting surface are in the middle of the longitudinal direction of the reflecting mirror and the longitudinal direction of the reflecting mirror and the support of each support point The optical scanning device is formed in a symmetrical shape with respect to the plane formed by the direction . The first and second support points are located near one end in the longitudinal direction of the reflecting mirror,
The optical scanning device according to claim 7 or 8 , wherein the third support point is located in the vicinity of the other end of the reflecting mirror in the longitudinal direction. The first support point is located near one end in the longitudinal direction of the reflecting mirror,
The second support point is located near the other end in the longitudinal direction of the reflecting mirror,
9. The optical scanning device according to claim 7, wherein the third support point is located in the vicinity of the center of the reflecting mirror in the longitudinal direction. The optical scanning device according to claim 10 , wherein the third support point is located on the concave side of the reflection surface of the reflecting mirror with respect to an imaginary straight line connecting the first support point and the second support point. 12. The optical scanning device according to claim 7 , wherein a center of gravity of the reflecting mirror coincides with a shear center of a cross section at a central portion in a longitudinal direction of the reflecting mirror. The optical scanning according to any one of claims 7 to 12 , wherein the reflecting mirror includes a synthetic resin member having a curved surface and a mirror film formed on the curved surface of the synthetic resin member. apparatus. The optical scanning device according to claim 7 , wherein the second imaging optical system includes only the reflecting mirror. An optical scanning device according to any one of claims 7 to 14 ,
A substantially cylindrical photosensitive member having an outer peripheral surface forming the surface to be scanned and extending in a scanning direction of a light beam of the optical scanning device;
Drive means for rotating the photoreceptor;
A developing device for supplying toner to the photoreceptor;
Transfer means for transferring a toner image formed on the photoreceptor to a recording medium;
An image forming apparatus.

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