JP6601626B2 - Optical scanning device and image forming apparatus including the optical scanning device - Google Patents

Description

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

  2. Description of the Related Art Conventionally, an optical scanning device that is mounted on an electrophotographic image forming apparatus and irradiates the surface of a photosensitive drum with a light beam corresponding to image data to scan in the main scanning direction is known.

  The optical scanning device includes a light source, a light deflecting unit that reflects and scans a light beam emitted from the light source, and an imaging lens that forms an image of light reflected by the light deflecting unit on a surface to be scanned. It has. The light deflection unit is configured by, for example, a rotating polygon mirror or a vibrating mirror unit.

  In this type of optical scanning device, a folding mirror may be provided in the optical path from the rotary polygon mirror to the scanned surface in order to increase the degree of freedom of the optical path layout (see, for example, Patent Document 1).

  The folding mirror has a rectangular column shape that is long in the main scanning direction. The folding mirror is supported from the surface side (reflection surface side) by four support pins. The folding mirror part is pressed against these four support pins by a pressing spring. The four support pins are in contact with the four corners of the surface of the folding mirror.

  When the rotating polygon mirror is rotated in accordance with the operation of the optical scanning device, vibration from the rotating polygon mirror is transmitted to the folding mirror. As a result, bending vibration and rotational vibration occur in the folding mirror.

  The bending vibration is a vibration in which the central portion of the folding mirror in the main scanning direction is reciprocally displaced in the mirror thickness direction with respect to both ends. When the flexural vibration is generated, the density unevenness is remarkably generated in the central portion of the printed image in the main scanning direction.

  The rotational vibration is vibration in which the mirror is alternately displaced in the clockwise direction and the counterclockwise direction when the folding mirror is viewed from the main scanning direction. The rotation axis of the folding mirror is determined by the support position of the folding mirror by a plurality of support pins. When rotational vibrations of the folding mirror occur, density unevenness significantly occurs over the entire area of the printed image in the main scanning direction.

  Here, the bending vibration is more likely to occur as the dimension of the folding mirror in the longitudinal direction (main scanning direction) is longer. Accordingly, as the length of the folding mirror in the main scanning direction becomes shorter with the recent miniaturization of the optical scanning device, the above-described bending vibration is less likely to occur. On the other hand, since the rotational vibration is affected by the support position of the folding mirror by the support pin rather than the dimension of the folding mirror in the main scanning direction, it is difficult to suppress even if the size of the folding mirror in the main scanning direction is reduced. Therefore, it is important to suppress the rotational vibration of the folding mirror in order to improve the image quality while realizing downsizing of the optical scanning device.

  Therefore, in the optical scanning device disclosed in Patent Document 1, a rotation preventing member is brought into contact with the folding mirror to prevent rotational vibration of the folding mirror.

JP 09-015523 A

  However, in the optical scanning device shown in Patent Document 1, when the position of the rotation preventing member with respect to the folding mirror (optical element) is not appropriate, the rotational vibration of the folding mirror (optical element) is amplified instead, and jitter appears in the printed image. Image defects such as the above will occur remarkably.

  The present invention has been made in view of such a point, and an object of the present invention is to reliably suppress image defects such as jitter caused by rotational vibration of an optical element.

  An optical scanning device according to one aspect of the present invention includes a light source, a light deflection unit including a rotary polygon mirror or a vibrating mirror that reflects and scans the light beam emitted from the light source in the main scanning direction, and the light deflection. And an optical element that is provided so as to extend in the main scanning direction on the optical path between the light beam reflected by the unit and the surface to be scanned.

The optical element includes a first folding mirror that reflects the light beam and a second folding mirror that reflects the light beam reflected by the first folding mirror, and the first folding mirror. And a pair of holding plates fixed to the reflection surface of the second folding mirror portion, and are integrally formed with the reflection surfaces forming a predetermined angle with each other and the second folding mirror portion. A first support pin that is in contact with one side surface in the thickness direction of the holding plate, and a first support pin that is in contact with one side surface in the thickness direction of the other holding plate and spaced in the sub-scanning direction of the second folding mirror portion. A second support pin and a third support pin arranged side by side, wherein a support position of one holding plate by the first support pin and a support position of the other holding plate by the second support pin and the third support pin A straight line passing through the midpoint is the main scan It extends toward coincides with the line of intersection between the reflecting surface and the reflecting surface of the second folding mirror portion of the first folding mirror unit.

  An optical scanning device according to another aspect of the present invention includes a light source, a light deflecting unit including a rotating polygon mirror or a vibrating mirror that reflects and scans the light beam emitted from the light source in the main scanning direction, and the light. And an optical element that is provided to extend in the main scanning direction on an optical path between the light beam reflected by the deflecting unit and the surface to be scanned, and reflects the light beam.

The optical element includes a first folding mirror that reflects the light beam and a second folding mirror that is separate from the first folding mirror and reflects the light beam reflected by the first folding mirror. A connecting member for connecting the first folding mirror unit and the second folding mirror unit in a state where the reflecting surfaces form a predetermined angle, and a sub-scanning direction of the first folding mirror unit. And a pair of holding plates fixed to the reflection surface of the second folding mirror portion, and a thickness of one of the holding plates. A first support pin that is in contact with one side surface in the vertical direction, a second support pin that is in contact with one side surface in the thickness direction of the other holding plate and is arranged at intervals in the sub-scanning direction of the second folding mirror portion; A third support pin, and the first support A straight line passing through the supporting position of one holding plate by the sensor and the midpoint of the supporting position of the other holding plate by the second support pin and the third support pin extends in the main scanning direction, and This coincides with the line of intersection between the reflecting surface of the first folding mirror portion and the reflecting surface of the second folding mirror portion .

  An image forming apparatus according to another aspect of the present invention includes the optical scanning device.

  According to the present invention, it is possible to reliably suppress image defects such as jitter caused by rotational vibration of an optical element that reflects a light beam deflected and scanned by an optical deflecting unit.

FIG. 1 is an overall view illustrating an image forming apparatus including an optical scanning device according to the first embodiment. FIG. 2 is a schematic view of the polygon mirror showing the scanning optical system in the optical scanning device as seen from the rotational axis direction. FIG. 3 is a schematic view of the scanning optical system in the optical scanning device viewed from the main scanning direction. FIG. 4A is a side view of the optical element provided in the optical scanning device as seen from the main scanning direction. FIG. 4B is an explanatory diagram for explaining that the reflection direction of the light beam does not change even when rotational vibration occurs in the optical element. FIG. 4C is an explanatory diagram for explaining that the reflection direction of the light beam does not change even when rotational vibration occurs in the optical element. FIG. 4D is a perspective view illustrating an example of a support structure of the optical element. FIG. 4E is a view corresponding to FIG. 4C showing a comparative example of the first embodiment. FIG. 5A is a view corresponding to FIG. 4A showing a first modification of the first embodiment. FIG. 5B is a diagram corresponding to FIG. 4B in the first modification of the first embodiment. FIG. 5C is a diagram corresponding to FIG. 4C in the first modification of the first embodiment. FIG. 5D is a diagram corresponding to FIG. 4E illustrating a comparative example of the first modification of the first embodiment. FIG. 6A is a view corresponding to FIG. 4A showing a second modification of the first embodiment. FIG. 6B is a diagram corresponding to FIG. 4B, illustrating a second modification of the first embodiment. FIG. 6C is a view corresponding to FIG. 4C, showing a second modification of the first embodiment. 6D is a diagram corresponding to FIG. 4E illustrating a comparative example of the second modification of the first embodiment. FIG. 7A is a view corresponding to FIG. 6B showing the second embodiment. FIG. 7B is a perspective view showing a support structure for an optical element in Embodiment 2. FIG. 7C is a view taken in the direction of arrow VII C in FIG. 7B. FIG. 8 is a view corresponding to FIG. 6C, showing a first modification of the second embodiment. FIG. 9 is a view corresponding to FIG. 6C showing a second modification of the second embodiment. FIG. 10 is a view corresponding to FIG. 4A showing the third embodiment. FIG. 11 is a view corresponding to FIG. 4A showing a first modification of the third embodiment. FIG. 12 is a view corresponding to FIG. 4A showing a second modification of the third embodiment. FIG. 13 is a view corresponding to FIG. 4A showing the fourth embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following embodiment.

Embodiment 1
FIG. 1 is a cross-sectional view showing a schematic configuration of a laser printer 1 as an image forming apparatus in the present embodiment.

  As shown in FIG. 1, the laser printer 1 includes a box-shaped printer main body 2, a manual paper feed unit 6, a cassette paper feed unit 7, an image forming unit 8, a fixing unit 9, and a paper discharge unit 10. It has. Thus, the laser printer 1 is configured to form an image on a sheet based on image data transmitted from a terminal (not shown) while conveying the sheet along a conveyance path H in the printer body 2. ing.

  The manual paper feed unit 6 includes a manual feed tray 4 that can be opened and closed on one side of the printer body 2, and a manual feed roller 5 that is rotatably provided inside the printer body 2. ing.

  The cassette paper feeding unit 7 is provided at the bottom of the printer main body 2. The cassette paper feed unit 7 separates the paper feed cassette 11 that stores a plurality of papers stacked on each other, a pick roller 12 that takes out the paper in the paper feed cassette 11 one by one, and the paper that is taken out one by one. The feed roller 13 and the retard roller 14 are fed to the transport path H.

  The image forming unit 8 is provided above the cassette paper feeding unit 7 in the printer main body 2. The image forming unit 8 includes a photosensitive drum 16, a charger 17, a developing unit 18, a transfer roller 19, a cleaning unit 20, a toner hopper 21, and an optical scanning device 30. The image forming unit 8 forms a toner image on a sheet supplied from the manual sheet feeding unit 6 or the cassette sheet feeding unit 7.

  The transport path H is provided with a pair of registration rollers 15 that supply the fed sheet to the image forming unit 8 at a predetermined timing after temporarily waiting.

  The fixing unit 9 is disposed on the side of the image forming unit 8. The fixing unit 9 includes a fixing roller 22 and a pressure roller 23 that are pressed against each other and rotate. The fixing unit 9 fixes the toner image transferred to the sheet by the image forming unit 8 on the sheet.

  The paper discharge unit 10 is provided above the fixing unit 9. The paper discharge unit 10 includes a paper discharge tray 3, a paper discharge roller pair 24 for transporting paper to the paper discharge tray 3, and a plurality of transport guide ribs 25 for guiding paper to the paper discharge roller pair 24. . The paper discharge tray 3 is formed in a concave shape at the top of the printer body 2.

  When the laser printer 1 receives the image data, the photosensitive drum 16 is rotationally driven in the image forming unit 8, and the charger 17 charges the surface of the photosensitive drum 16.

  Then, based on the image data, a light beam is emitted from the optical scanning device 30 to the photosensitive drum 16. An electrostatic latent image is formed on the surface of the photosensitive drum 16 by irradiation with a light beam. This electrostatic latent image is visualized as a toner image by being developed with toner charged in the developing unit 18.

  Thereafter, the sheet supplied from the sheet feeding cassette 11 passes between the transfer roller 19 and the photosensitive drum 16. At this time, the toner image carried on the surface of the photosensitive drum 16 receives the electrostatic attraction from the transfer roller 19 and moves to the printing surface of the paper. As a result, the toner image on the photosensitive drum 16 is transferred to the paper. The sheet on which the toner image is transferred is heated and pressed by the fixing roller 22 and the pressure roller 23 in the fixing unit 9. As a result, the toner image is fixed on the paper.

  Next, the details of the optical scanning device 30 will be described with reference to FIGS. The optical scanning device 30 includes a housing (not shown), a polygon mirror 35 that is housed in the housing and deflects and scans the light beam from the light source 32, and reflects the light beam deflected and scanned by the polygon mirror 35. And an imaging lens 36 that forms an image of the light beam reflected by the optical element 50.

  The polygon mirror 35 is attached to the housing via a polygon motor 40. The polygon mirror 35 is a rotary polygon mirror and is driven to rotate by a polygon motor 40.

  The light source 32 is disposed on the side wall of the housing. The light source 32 is a laser light source having a laser diode, for example. The light source 32 emits a laser beam (light beam) toward the polygon mirror 35. A collimator lens 33 (see FIG. 2) and a cylindrical lens 34 are arranged between the light source 32 and the polygon mirror 35.

  As shown in FIG. 2, the imaging lens 36 extends in the main scanning direction on the side of the polygon mirror 35. The optical element 50 is provided on the opposite side of the imaging lens 36 from the polygon mirror 35 side. The optical element 50 is a columnar member extending in the main scanning direction, and reflects the light beam from the polygon mirror 35.

The optical element 50, as shown in FIG. 4, and a first and a second folding mirror 51 and 52. Both folding mirror parts 51 and 52 are combined in an L-shaped cross section by integral molding. The reflection surface (hereinafter referred to as the first reflection surface) 51a of the first folding mirror portion 51 and the reflection surface (hereinafter referred to as the second reflection surface) 52a of the second folding mirror portion 52 are 90 ° as viewed from the main scanning direction. They intersect at an angle.

  The laser light emitted from the light source 32 is collimated by the collimator lens 33 (see FIG. 2) and then condensed on the reflection surface of the polygon mirror 35 by the cylindrical lens 34. The light condensed on the polygon mirror 35 is reflected by the reflection surface of the polygon mirror 35. The light beam reflected by the polygon mirror 35 is reflected by the optical element 50 and returns its optical path. The light beam passes through the imaging lens 36 and forms an image on the surface of the photosensitive drum 16. The scanning light imaged on the surface of the photosensitive drum 16 scans the surface of the photosensitive drum 16 in the main scanning direction by the rotation of the polygon mirror 35, and scans in the sub-scanning direction by the rotation of the photosensitive drum 16. An electrostatic latent image is formed on the surface of the body drum 16.

  By the way, in the conventional optical scanning device 30, the rotational vibration of the polygon mirror 35 is transmitted to the optical element 50, whereby the optical element 50 vibrates alternately in the clockwise direction and the counterclockwise direction when viewed from the main scanning direction. (Hereinafter referred to as rotational vibration). When this rotational vibration occurs, the light beam incident on the imaging surface (the surface of the photosensitive drum 16) may vibrate in the sub-scanning direction, and image defects such as jitter may occur in the printed image.

  On the other hand, in the present embodiment, the optical element 50 includes the first folding mirror portion 51 and the second folding mirror portion 52, and the first folding mirror portion 51 and the second folding mirror portion 52 are integrally formed. I made it. Thereby, even if rotational vibration occurs in the optical element 50, it is possible to prevent the light beam from greatly vibrating in the sub-scanning direction on the imaging surface. The reason will be described with reference to FIGS. 4B and 4C.

  4B and 4C show a case where the angle formed by the first reflecting surface 51a and the second reflecting surface 52a is 90 °. In each figure, in order to simplify description, the 1st reflective surface 51a and the 2nd reflective surface 52a, and the rotating shaft A of the optical element 50 are shown typically. In the present embodiment, the rotation axis A is located on a plane L1 that bisects the angle formed by the first reflecting surface 51a and the second reflecting surface 52a when viewed from the main scanning direction (the direction perpendicular to the paper surface). The rotation axis A and the intersection line L2 between the reflecting surfaces 51a and 52a are separated by a predetermined distance.

  FIG. 4B shows a basic state in which no rotational vibration is generated in the optical element 50. The incident angle θ1 of the light beam reflected by the polygon mirror 35 and incident on the first reflecting surface 51a is 45 °, and the light beam is folded at a right angle on the first reflecting surface 51a. The folded light beam is incident on the second reflecting surface 52a. The incident angle θ2 of the light beam with respect to the second reflecting surface 52a is 45 °, and the light beam is folded again at a right angle by the second reflecting surface 52a. That is, since the light beams reflected by the first reflecting surface 51a and the second reflecting surface 52a are folded back 180 ° (= 2θ1 + 2θ2 = 90 ° + 90 °), the light beam incident on the optical element 50 is reflected by the optical element 50. Is parallel to the light beam.

  FIG. 4C shows a state in which the optical element 50 is rotated by β ° in the clockwise direction from the state shown in FIG. 4A due to rotational vibration. In this state, assuming that the incident angle θ1 ′ of the light beam to the first reflecting surface 51a is θ1 ′ = θ1-β, the light beam is folded at an angle of 90 ° −2β on the first reflecting surface 51a. The folded light beam is incident on the second reflecting surface 52a. If the incident angle θ2 ′ of the light beam with respect to the second reflecting surface 52a is θ2 ′ = θ2 + β, the light beam is folded back at an angle of 90 ° + 2β on the second reflecting surface 52a. Therefore, the light beam is folded 180 ° (= 2θ1 ′ + 2θ2 ′ = 90 ° -2β + 90 ° + 2β) by two reflections, so that the direction of the reflected light beam by the optical element 50 is maintained in the same direction before and after the occurrence of rotational vibration. can do.

  Therefore, even if rotational vibration occurs in the optical element 50, it is possible to avoid the light beam from greatly shaking in the sub-scanning direction with the incident position as a fulcrum. As a result, it is possible to suppress the occurrence of image defects such as jitter in the printed image.

Here, the position of the rotation axis A of the optical element 50 is determined by the support position of the optical element 50 by a plurality of support pins. FIG. 4D shows an example of the support structure of the optical element 50 in the present embodiment. Both ends of the optical element 50 in the main scanning direction are held by a holding member 70, and the holding member 70 has a support position 71 located on a plane L1 that bisects the first reflecting surface 51a and the second reflecting surface 52a. These are supported by support pins (not shown) at support positions 72 and 73 arranged symmetrically across the plane L1. Thus, in the present embodiment, the rotation axis A is located on the plane L1 that bisects the first reflecting surface 51a and the second reflecting surface 52a when viewed from the main scanning direction. Therefore, as shown in FIG. 4E, the positional deviation amount δ in the sub-scanning direction of the light beam reflected by the optical element 50 can be made smaller than when the rotation axis A is separated from the plane L1. Therefore, it is possible to more reliably suppress image defects caused by the rotational vibration of the optical element 50.
<Modification 1>
FIG. 5A shows an optical element 50 according to the first modification of the first embodiment. The first modification differs from the first embodiment in that the angle formed between the first reflecting surface 51a and the second reflecting surface 52a is an obtuse angle. Also in this modified example 1, as in the first embodiment, it is possible to prevent the light beam from greatly vibrating in the sub-scanning direction on the imaging plane. The reason will be described with reference to FIGS. 5B and 5C.

  FIG. 5B shows a basic state in which no rotational vibration is generated in the optical element 50. In the figure, the angle formed by the first reflecting surface 51a and the second reflecting surface 52a is indicated by 90 ° + η. The angle formed by the plane L1 that bisects the angle formed by both reflecting surfaces 51a and 52a when viewed from the main scanning direction (the direction perpendicular to the paper surface) and the light beam incident on the first reflecting surface 51a is 2η1, and the second reflecting surface. If the angle between the light beam reflected by 52a and the plane L1 is 2η2, the incident angle θ1 of the light beam incident on the first reflecting surface 51a is 45 ° + η1, and the light beam is reflected on the first reflecting surface 51a. At an angle of 90 ° + 2η1. The incident angle θ2 of the light beam that is folded back on the first reflecting surface 51a and incident on the second reflecting surface 52a becomes 45 ° + η2, and the light beam is folded at an angle of 90 ° + 2η2 on the second reflecting surface 52a. That is, the light beam incident on the optical element 50 is folded back at 180 ° + 2η (= 2θ1 + 2θ2 = 90 ° + 2η1 + 90 ° + 2η2), so that the angle between the light beam incident on the optical element 50 and the reflected light beam is 2η. = 2η1 + 2η2. That is, when the light beam is incident on the optical element 50 in which the angle α formed by the two reflecting surfaces 51a and 52a is 90 ° + η, the angle formed by the incident light beam and the reflected light microbeam is always 2η.

  FIG. 5C shows a state in which the optical element 50 is rotated by β ° in the clockwise direction from the state of FIG. 5A due to rotational vibration. In this state, if the incident angle of the light beam on the first reflecting surface 51a is θ1 ′, θ1 ′ = θ1−β, and the light beam is folded at an angle of 90 ° + 2η1-2β on the first reflecting surface 51a. It is. If the incident angle θ2 ′ of the light beam that is folded back at the first reflecting surface 51a and incident on the second reflecting surface 52a is θ2 ′ = θ2 + β, the light beam is folded at an angle of 90 ° + 2η2 + 2β at the second reflecting surface 52a. It is. Therefore, the light beam is folded 180 ° + 2η (= 2θ1 ′ + 2θ2 ′ = 90 ° + 2η1-2β + 90 ° + 2η2 + 2β) by two reflections. Therefore, the light beam emission direction from the optical element 50 can be maintained in the same direction before and after the occurrence of rotational vibration.

  Further, since the rotation axis A of the optical element 50 is located on a plane L1 that is equal to the first reflecting surface 51a and the second reflecting surface 52a when viewed from the main scanning direction, it rotates as shown in FIG. 5D. Compared to the case where the axis A is separated from the plane L1, the positional deviation amount δ in the sub-scanning direction of the reflected light beam by the optical element 50 can be reduced.

  Therefore, the same effect as the first embodiment can be obtained.

<Modification 2>
FIG. 6A shows an optical element 50 of Modification 2 of Embodiment 1. Modification 2 is different from Embodiment 1 and Modification 1 in that the angle formed between the first reflection surface 51a and the second reflection surface 52a is an acute angle. Also in the second modification, similarly to the first embodiment and the first modification, it is possible to prevent the light beam from greatly vibrating in the sub-scanning direction on the imaging surface. The reason will be described with reference to FIGS. 6B and 6C.

  FIG. 6B shows a basic state in which no rotational vibration is generated in the optical element 50. In the drawing, the angle formed by the first reflecting surface 51a and the second reflecting surface 52a is indicated by 90 ° −η. When viewed from the main scanning direction (perpendicular to the paper surface), the angle formed by the plane L1 that bisects the angle formed by the reflecting surfaces 51a and 52a and the light beam incident on the first reflecting surface 51a is 2η1, and the second reflecting surface. If the angle between the light beam reflected by 52a and the plane L1 is 2η2, the incident angle θ1 of the light beam incident on the first reflecting surface 51a is 45 ° −η1, and the light beam is reflected on the first reflecting surface. It is folded at an angle of 90 ° -2η1 at 51a. The incident angle θ2 of the light beam that is folded back on the first reflecting surface 51a and incident on the second reflecting surface 52a is 45 ° −η2, and the light beam is folded back on the second reflecting surface 52a at an angle of 90 ° −2η2. It is. That is, the light beam incident on the optical element 50 is folded at 180 ° −2η (= 2θ1 + 2θ2 = 90 ° −2η1 + 90 ° −2η2), and the angle between the incident light beam and the reflected light beam is 2η = 2η1 + 2η2. That is, when the light beam is incident on the optical element 50 having the relative angle α = 90 ° −η between the two reflecting surfaces 51a and 52a, the relative angle between the incident light beam and the reflected light beam is always 2η.

  FIG. 6C shows a state in which the optical element 50 is rotated by β ° in the clockwise direction from the state of FIG. 6B due to rotational vibration. In this state, assuming that the incident angle θ1 ′ of the light beam to the first reflecting surface 51a is θ1 ′ = θ1−β, the light beam is folded at an angle of 90 ° −2η1-2β on the first reflecting surface 51a. . If the incident angle θ2 ′ of the light beam that is folded back at the first reflecting surface 51a and enters the second reflecting surface 52a is θ2 ′ = θ2 + β, the light beam has an angle of 90 ° −2η2 + 2β at the second reflecting surface 52a. Wrapped at Therefore, the light beam is folded by 180 ° −2η (= 2θ1 ′ + 2θ2 ′ = 90 ° −2η1-2β + 90 ° −2η2 + 2β) by reflection twice. Therefore, the direction of the reflected light beam reflected by the optical element 50 can be maintained in the same direction before and after the occurrence of rotational vibration.

  Further, since the rotation axis A of the optical element 50 is located on a plane L1 that bisects the first reflecting surface 51a and the second reflecting surface 52a when viewed from the main scanning direction, it rotates as shown in FIG. 6D. As compared with the case where the axis A is separated from the plane L1, the positional deviation amount δ in the sub-scanning direction of the reflected light beam by the optical element 50 can be reduced.

  Therefore, the same effect as the first embodiment can be obtained.

<< Embodiment 2 >>
FIG. 7A is a schematic diagram illustrating a folded optical path of a light beam by the optical element 50 according to the second embodiment. The second embodiment is different from the first embodiment in the position of the rotation axis A.

  That is, in the present embodiment, the position of the rotation axis A coincides with the intersection line L2 between the first reflecting surface 51a and the second reflecting surface 52a when viewed from the main scanning direction.

  Here, as described above, the position of the rotation axis A is determined by the support position of the optical element 50 by the plurality of support pins 61 to 63. With reference to FIG. 7B and FIG. 7C, the support structure of the optical element 50 by the some support pins 61-63 is demonstrated.

  The optical element 50 is fixed using a fixing bolt 65 to a pair of holding plates 60 fixed to both ends of the second reflecting surface 52a in the main scanning direction. The holding plate 60 is supported by first to third support pins 61 to 63. That is, the optical element 50 is indirectly supported via the holding plate 60 by the first to third support pins 61 to 63.

  As shown in FIG. 7C, the first support pin 61 supports the base end of one holding plate 60, and the second and third support pins 62 and 63 support the base end of the other holding plate 60. Yes. The figure formed by connecting the support positions of the holding plate 60 by the support pins 61 to 63 has an isosceles triangle shape. A straight line passing through the support position of the holding plate 60 by the first support pin 61 and the midpoint of the support position of the holding plate 60 by the second and third support pins 62 and 63 is the rotation axis A of the optical element 50. The rotation axis A extends in parallel with the main scanning direction. In this embodiment, the holding plate is arranged so that the rotation axis A coincides with the intersection line L2 between the first reflection surface 51a and the second reflection surface 52a. The length of 60, the fixed position of the optical element 50 with respect to the holding plate 60, the support position of the optical element 50 by the support pins 61 to 63, and the like are determined.

  As described above, according to the optical scanning device 30 of the present embodiment, the rotation axis A at the time of the rotational vibration of the optical element 50 is the intersection line L2 between the first reflecting surface 51a and the second reflecting surface 52a when viewed from the main scanning direction. It matches. Therefore, as compared with the optical element 50 of Embodiment 1, the positional deviation amount δ (see FIG. 7A) of the reflected light beam due to the rotational vibration of the optical element 50 in the sub-scanning direction is reduced. Therefore, the same effect as Embodiment 1 can be obtained more reliably.

<Modification 1>
FIG. 8 shows a first modification of the second embodiment. The first modification is different from the second embodiment in that the angle formed between the first reflecting surface 51a and the second reflecting surface 52a is an obtuse angle. As shown in FIG. 8, it can be seen that even when the angle formed by the reflecting surfaces 51a and 52a is an obtuse angle, the positional deviation amount δ in the sub-scanning direction of the reflected light beam by the optical element 50 is reduced.

<Modification 2>
FIG. 9 shows a second modification of the second embodiment. The second modification is different from the second embodiment in that the angle formed by the first reflecting surface 51a and the second reflecting surface 52a is an acute angle. FIG. 9 shows that the positional deviation amount δ in the sub-scanning direction of the reflected light beam by the optical element 50 is reduced even when the angle formed by both the reflecting surfaces 51a and 52a is an acute angle.

<< Embodiment 3 >>
FIG. 10 is a diagram of the optical element 50 according to the third embodiment viewed from the main scanning direction. In this embodiment, the point from which the 1st folding mirror part 51 and the 2nd folding mirror part 52 which comprise the optical element 50 are comprised separately is different from said each embodiment and each modification.

  Both the first folding mirror part 51 and the second folding mirror part 52 have a rectangular plate column shape extending in the main scanning direction. The angle formed by the first reflecting surface 51a and the second reflecting surface 52a is 90 °. One end surface of the first folding mirror 51 in the sub-scanning direction is in contact with one end of the reflecting surface of the second folding mirror 52 in the sub-scanning direction.

  A pair of through holes 51b penetrating in the sub-scanning direction are formed at both ends of the first folding mirror 51 in the main scanning direction. A counterbore hole 51c having a larger diameter than the through hole is formed at the end of the through hole 51b opposite to the second folding mirror portion 52 side. A through hole 52 b that is coaxial with the through hole and penetrates in the thickness direction of the second folding mirror portion 52 is formed at a position corresponding to the through hole 51 b in the second folding mirror portion 52.

  The first folding mirror part 51 and the second folding mirror part 52 are connected by a bolt 53 that penetrates the through holes 51b and 52b. The head of the bolt 53 is located in the counterbore 51 c of the first folding mirror 51. The front end portion of the bolt 53 protrudes from the second folding mirror portion 52, and a fastening nut 54 is screwed into this protruding portion.

  According to this embodiment, since the 1st folding mirror part 51 and the 2nd folding mirror part 52 are connected and rotate integrally, the same effect as said each embodiment can be acquired.

  In the present embodiment, since the first folding mirror 51 and the second folding mirror 52 which are separate from each other are connected, the optical element 50 having a complicated shape as in the first and second embodiments is used. Eliminates the need for integral molding. Therefore, the processing cost of the optical element 50 can be reduced.

  In the present embodiment, the case where the first reflecting surface 51a and the second reflecting surface 52a are 90 ° has been described. However, the present invention is not limited to this, and the angle formed by both the reflecting surfaces 51a and 52a is an obtuse angle or It may be an acute angle. FIG. 11 shows an example in which the angle formed by both reflecting surfaces 51a and 52a is an obtuse angle. In this example, the connecting surface between the first folding mirror 51 and the second folding mirror 52 is a plane L1 that bisects the angle formed by the first reflecting surface 51a and the second reflecting surface 52a when viewed from the main scanning direction. Located on the top. The through holes 51b and 52b are formed perpendicular to the connection surface, and counterbore holes 51c and 52c are formed on the opposite side of the through holes 51b and 52b from the connection surface. The head of the bolt 53 is accommodated in the counterbore hole 51c, and the nut 54 is accommodated in the counterbore hole 52c.

<< Embodiment 4 >>
FIG. 12 is a diagram of the optical element 50 according to the fourth embodiment viewed from the main scanning direction. In this embodiment, the point from which the 1st folding mirror part 51 and the 2nd folding mirror part 52 are connected via the connection member 55 differs from said each embodiment and each modification.

  The first folding mirror unit 51 and the second folding mirror unit 52 have a rectangular plate shape extending in the main scanning direction. The connecting member 55 is a columnar body having a square cross section extending in the main scanning direction. One end surface of the first folding mirror unit 51 in the sub-scanning direction and one end surface of the second folding mirror unit 52 in the sub-scanning direction are fixed to the connecting member 55. A plane L1 that bisects the angle formed by the first reflecting surface 51a and the second reflecting surface 52a coincides with the diagonal line of the connecting member 55 when viewed from the main scanning direction.

  Each folding mirror part 51 and 52 and the connection member 55 may be connected with a volt | bolt like Embodiment 3, and may be made to connect using an adhesive agent etc.

  According to the present embodiment, the first folding mirror part 51 and the second folding mirror part 52 are connected via the connecting member 55 and rotate integrally, so that the same effects as those of the above embodiments can be obtained. it can.

  In the present embodiment, the end surface in the sub-scanning direction of the first folding mirror unit 51 and the end surface in the sub-scanning direction of the second folding mirror unit 52 are connected by the connecting member 55, so the first folding mirror unit 51. And compared with the case where the back surfaces of the 2nd folding | return mirror part 52 are connected with the connection member 55, the shape of the connection member 55 can be simplified and high connection rigidity can be obtained. Therefore, the first folding mirror part 51 and the second folding mirror part 52 can be reliably rotated integrally without phase shift when the optical element 50 is rotated and vibrated. Therefore, the same effect as each said embodiment can be acquired reliably.

  In the present embodiment, since the first folding mirror 51 and the second folding mirror 52 which are separate from each other are connected, the optical element 50 having a complicated shape as in the first and second embodiments is used. Eliminates the need for integral molding. Therefore, the processing cost of the optical element 50 can be reduced.

  In the present embodiment, the case where the first reflecting surface 51a and the second reflecting surface 52a are 90 ° has been described. However, the present invention is not limited to this, and the angle formed by both the reflecting surfaces 51a and 52a is an obtuse angle or It may be an acute angle. FIG. 13 shows an example in which the angle formed by both reflecting surfaces 51a and 52a is an obtuse angle. In this example, the connecting member 55 has an isosceles triangular prism shape extending in the main scanning direction. The first folding mirror unit 51 and the second folding mirror unit 52 are respectively fixed to side surfaces adjacent to each other with one vertex of the connecting member 55 viewed from the main scanning direction.

<< Other embodiments >>
In each of the above embodiments and modifications, the polygon mirror 35 has been described as an example of the light deflecting unit that deflects and scans the light beam. However, the light deflecting unit is, for example, a resonance-type vibrating mirror that is driven by a piezoelectric element or the like. There may be.

  In the second embodiment, the optical element 50 is indirectly supported by the plurality of support pins 61 to 63 via the holding plate 60. However, the present invention is not limited to this, and the plurality of support pins 61 to 63 is supported. You may make it support directly by. Needless to say, the number of support pins that support the optical element 50 is not limited to three, but may be two or less, or may be four or more. For example, when there are four support pins, both ends of the optical element 50 in the main scanning direction may be supported by two support pins. In this case, the midpoint of the support position by two support pins provided at one end of the optical element 50 in the main scanning direction and the midpoint of the support position by two support pins provided at the other end in the main scanning direction. Is a rotation axis A.

  In each of the above-described embodiments and modifications, a laser printer has been described as an example of an image forming apparatus on which the optical scanning device 30 is mounted. However, the present invention is not limited to this, and the image forming apparatus may be, for example, a multifunction peripheral (MFP). ), A copying machine, a facsimile, or the like.

  As described above, the present invention is useful for an optical scanning device and an image forming apparatus including the optical scanning device.

1 Laser printer (image forming device)
30 Optical scanning device 32 Light source 35 Polygon mirror (light deflection unit)
50 Optical Element 51 First Folding Mirror Part 51a First Reflecting Surface 52 Second Folding Mirror Part 52a Second Reflecting Surface 55 Connecting Member 60 Holding Plate 61 First Support Pin 62 Second Support Pin 62 Third Support Pin 63 Third Support Pin A Rotation axis L1 Plane L2 Intersection line

Claims (3)

A light source, a light deflector comprising a rotating polygon mirror or a vibrating mirror that reflects and scans the light beam emitted from the light source in the main scanning direction, and the light beam reflected by the light deflector and the surface to be scanned An optical scanning device provided with an optical element provided to extend in the main scanning direction in the optical path between and an optical element that reflects a light beam,
The optical element includes a first folding mirror unit that reflects a light beam, and a second folding mirror unit that reflects a light beam reflected by the first folding mirror unit.
The first folding mirror part and the second folding mirror part are integrally formed or directly connected with each other's reflecting surfaces forming a predetermined angle ,
A pair of holding plates fixed to the reflecting surface of the second folding mirror part;
A first support pin that contacts one side surface of the holding plate in the thickness direction;
A second support pin and a third support pin that are in contact with one side surface in the thickness direction of the other holding plate and are arranged at intervals in the sub-scanning direction of the second folding mirror portion;
A straight line passing through the support position of the one holding plate by the first support pin and the midpoint of the support position of the other holding plate by the second support pin and the third support pin extends in the main scanning direction. An optical scanning device that coincides with a line of intersection between the reflection surface of the first folding mirror portion and the reflection surface of the second folding mirror portion . A light source, a light deflector comprising a rotating polygon mirror or a vibrating mirror that reflects and scans the light beam emitted from the light source in the main scanning direction, and the light beam reflected by the light deflector and the surface to be scanned An optical scanning device provided with an optical element provided to extend in the main scanning direction in the optical path between and an optical element that reflects a light beam,
The optical element includes a first folding mirror unit that reflects a light beam and a second folding mirror that is separate from the first folding mirror unit and reflects the light beam reflected by the first folding mirror unit. And
A connecting member that connects the first folding mirror part and the second folding mirror part in a state in which the reflecting surfaces form a predetermined angle;
An end face in the sub-scanning direction of the first folding mirror part and an end face in the sub-scanning direction of the second folding mirror part are fixed to the connecting member ,
A pair of holding plates fixed to the reflecting surface of the second folding mirror part;
A first support pin that contacts one side surface of the holding plate in the thickness direction;
A second support pin and a third support pin that are in contact with one side surface in the thickness direction of the other holding plate and are arranged at intervals in the sub-scanning direction of the second folding mirror portion;
A straight line passing through the support position of the one holding plate by the first support pin and the midpoint of the support position of the other holding plate by the second support pin and the third support pin extends in the main scanning direction. An optical scanning device that coincides with a line of intersection between the reflection surface of the first folding mirror portion and the reflection surface of the second folding mirror portion . An image forming apparatus including an optical scanning device according to claim 1 or 2.

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