JP5392365B2 - Optical scanning device - Google Patents

Description

  The present invention relates to an optical scanning device for performing optical writing in an electrophotographic image forming apparatus and an image forming apparatus equipped with the optical scanning device.

  There are various types of optical scanning devices used in image forming apparatuses such as copying machines, printers, facsimiles, etc., but those using a semiconductor laser (laser light emitting element) as a light source are disclosed in, for example, Patent Documents 1 and 2 It is well known. In such an optical scanning device, an LD unit for holding a semiconductor laser (hereinafter referred to as LD) is mounted and supported on an optical housing.

  In the configuration in which the LD unit is fixed to the optical housing with a fastening member such as a screw, the position of the LD unit does not generally move relative to the optical housing after the LD unit is fastened. However, in the configuration in which the LD unit is mounted on the optical housing by an elastic member such as a leaf spring, the LD unit can move relative to the optical housing by the clearance of the positioning portion with respect to the optical housing, although it is minute. There is sex. Due to this minute movement, the position of the beam emitted from the LD unit changes, resulting in a beam position shift on the surface of the photoreceptor. In a monochrome machine such as a one-beam machine, image degradation due to the above-mentioned influence is small, but in a full-color machine having a plurality of photosensitive drums, there is a problem of color misregistration on the image. In addition, the multi-beam LD unit has a problem that the pitch of each beam on the image plane is shifted and the image quality is remarkably deteriorated.

  The present invention provides an optical scanning apparatus and an image forming apparatus that solve the above-described problems in the conventional optical scanning apparatus and that can maintain the image quality continuously by stabilizing the LD unit position. Is an issue.

According to the present invention, the light mounting unit is mounted on and supported by the optical housing according to the present invention, and the light beam emitted from the light source is deflected by the deflecting means and imaged on the surface to be scanned via the optical element. In the scanning device, the optical housing has a convex portion that protrudes in the optical axis direction and is formed around the optical axis, and the unit on which the light source is mounted is provided with a concave portion that is fitted outside the convex portion. , the concave portion and the convex portion has a clearance in the peripheral direction of the optical axis, urges for pressing the urging to the optical housing the unit for mounting the light source in a predetermined direction perpendicular to the optical axis The urging means is solved by urging the unit on which the light source is mounted from the outside of the recess .

According to the optical scanning apparatus of the present invention prevents the relative movement with respect to the optical housing of the light source unit, a unit in a stable state with time continuously can be kept in optical Haujin grayed. For this reason, it is possible to prevent deterioration in image quality and continuously maintain high image quality.

1 is a cross-sectional configuration diagram showing an outline of a digital copying machine as an example of an image forming apparatus that can be equipped with an optical scanning device according to the present invention. 2 is a cross-sectional view showing a document reading unit of the digital copying machine. FIG. FIG. 2 is a perspective view showing a writing optical unit of the digital copying machine. It is an enlarged view showing the vicinity of the LD unit mounting portion of the optical scanning device. It is the side view. It is the figure which removed the LD board of LD unit. It is the figure which looked at LD unit from the other side. It is a figure which shows the optical housing of LD unit mounting part vicinity. It is a schematic diagram which shows another example of LD unit urging means. It is a schematic diagram for demonstrating the effect | action of a LD unit rotation adjustment mechanism. It is a figure which shows another example of the holder mounting hole provided in an optical housing. It is a schematic diagram which shows the structural example which gave elasticity to a part of LD unit. It is the figure which looked at the structural example of FIG. 9 from the cross-sectional direction of the optical housing. It is a figure which shows the structure for suppressing the influence of a rotational moment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional configuration diagram showing an outline of a digital copying machine as an example of an image forming apparatus that can be equipped with an optical scanning device according to the present invention. 2 and 3 are a cross-sectional view and a perspective view, respectively, showing the configuration of the document reading unit and the writing optical unit of the digital copying machine. As the overall configuration and operation of the digital copying machine will be described later, an optical scanning device as a writing optical unit will be described first.

  In the optical scanning device 27 shown in FIG. 3, a laser beam emitted from a semiconductor laser in an LD (semiconductor laser) unit 40 is converted into a parallel light beam by a collimating lens in the LD unit 40 and is provided in the LD unit 40. By passing through the aperture, the light beam is shaped into a fixed shape. This light beam is compressed in the sub-scanning direction by the cylindrical lens 41 and enters the polygon mirror 42. The polygon mirror 42 has an accurate polygon shape, and is driven to rotate at a constant speed in a constant direction by a polygon motor 43 (FIG. 1). The rotation speed of the polygon mirror 42 is determined by the rotation speed of the photosensitive drum 25, the writing density of the optical scanning device 27, and the number of surfaces of the polygon mirror 42. The laser beam incident on the polygon mirror 42 from the cylindrical lens 41 is deflected by the reflection surface of the polygon mirror and enters the fθ lens 44. The fθ lens 44 converts the scanning light having a constant angular velocity from the polygon mirror 42 so as to be scanned at a constant velocity by the photosensitive drum 25, and the laser beam from the fθ lens 44 is exposed through the reflecting mirror 45 and the dust-proof glass 46. An image is formed on the body drum 25. The fθ lens 44 also has a surface tilt correction function. Further, the laser beam that has passed through the fθ lens 44 is reflected by the synchronization detection mirror 47 outside the image area and guided to the synchronization detection sensor 48. A synchronization signal serving as a reference for cueing in the main scanning direction is obtained from the detection output of the synchronization detection sensor 48.

FIG. 4 is an enlarged view showing the vicinity of the LD unit mounting portion of the optical scanning device 27. FIG. 5 is a side view of the vicinity of the LD unit mounting portion.
The optical housing 60 of the optical scanning device 27 holds the above-described deflector, lens system, mirror, LD unit 40 and the like with high accuracy. An LD board 52 is attached to the holder 51 of the LD unit 40 by screws 53 and 53. Further, as shown in FIG. 6 which is a diagram in which the LD board 52 is removed, two semiconductor lasers 54 and 55 are press-fitted into the holder 51. Although this example shows a two-beam method using two semiconductor lasers, the same applies to the case of one beam. In addition to this, a collimating lens 56 (FIG. 7) is attached to the holder 51, and the focus (depth direction) and the optical axis direction (beam emission direction) are adjusted.

  As shown in FIG. 7 in which the LD unit 40 is viewed from the inside of the housing, a cylindrical portion 57 projects from the inner surface of the holder 51. On the other hand, a holder mounting hole 61 is provided in the optical housing 60 as shown in FIG. 8 showing the optical housing in the vicinity of the mounting portion with the LD unit 40 removed. The LD unit 40 is attached to the optical housing 60 by fitting the cylindrical portion 57 of the holder 51 into the holder mounting hole 61 that is a cylindrical hole. Boss portions 62, 63, 64 are provided around the holder mounting hole 61.

  The LD unit 40 attached to the optical housing 60 is pressed by the LD unit 40 against the optical housing 60 by attaching a plate spring 65 from below and sandwiching the optical housing 60 and the LD unit 40 from the front and back with the plate spring. Is done. That is, the leaf spring 65 has rising portions on both the front and rear sides in the same manner as the leaf spring 165 of another example shown in FIG. In FIG. 13, 165c and 165b are front and rear rising parts. The leaf spring 65 of this example also has front and rear raised portions 65c and 65b as in the leaf spring 165 of FIG. 13, but only the two raised portions 65c and 65c on the front side are shown in FIGS. The rear raising portion 65b is not visible. Furthermore, as shown in FIGS. 4 to 6, the leaf spring 65 of this example has a holder pressing portion 65 a at one end on the front side (right end portion in FIG. 5). The operation of the holder pressing portion 65a will be described later.

  By attaching such a leaf spring 65, the optical housing 60 and the LD unit 40 are sandwiched by the leaf spring having the above-described rising portion, and as shown in FIG. 6, the two rising portions 65c and 65c are on the front side. The holder 51 is pressed against the optical housing 60 from the (outside). Thereby, the holder 51 of the LD unit is pressed against the end faces of the boss portions 62, 63, 64 of the optical housing, and the position of the LD unit 40 in the optical axis direction is accurately determined by the boss portions 62, 63, 64. The plate spring rising portions 65c and 65c are inserted between the LD unit holder 51 and the LD board 52 and directly urge the holder 51.

  Furthermore, in this example, positioning in the rotational direction (the circumferential direction of the holder mounting hole 61) is also provided so as to be adjustable. In other words, the adjustment mechanism holding portion 58 is provided so as to protrude from the upper right holder corner in FIGS. 4 and 5 of the holder 51 of the LD unit. The adjustment mechanism holding portion 58 is provided with a screw hole (not shown), and an adjustment screw 71 is fitted into the screw hole and the optical housing 60. Therefore, by rotating the adjustment screw 71, the LD unit 40 can be accurately adjusted in the rotation direction. A compression spring 72 as a second urging member is fitted around the adjustment screw 71. Although not shown in the drawing, it is possible to adopt a configuration in which the rotation direction is adjusted by a motor or the like.

  Further, a configuration without an adjustment mechanism in the rotation direction is also possible. In this case, a boss (not shown) provided in the holder 51 of the LD unit enters a hole 67 (FIG. 8) provided in the optical housing. Positioning in the rotational direction is performed.

  As described above, in this example, the LD unit 40 has a configuration capable of accurately positioning the LD unit 40 in the optical axis direction and the rotation direction. However, there is a slight clearance between the holder mounting hole 61 of the optical housing and the cylindrical portion 57 of the LD unit holder so that the cylindrical portion 57 can be inserted into the holder mounting hole 61. Due to the presence of this slight clearance, for example, when an impact or vibration is applied to the optical scanning device (image forming apparatus), or the connector mounting portion 59 (see FIGS. 4 and 5) provided on the LD board 52 of the LD unit. ), When an external force is applied to the LD unit 40 by attaching / detaching the connector, the LD unit 40 mounted on the optical housing 60 may move in a direction perpendicular to the optical axis direction. The optical axis direction is a direction perpendicular to the drawing in FIG.

  Therefore, in the present example, as described above, the holder pressing portion 65a is provided in the plate spring 65 that presses the LD unit 40 against the optical housing 60, and the plate spring 65 is provided in the arrow A direction shown in FIG. Always energized. The direction of the urging force by the leaf spring 65 (the direction of the arrow A) is a direction that almost passes through the rotation center F of the LD unit 40, so that the LD unit 40 is always moved toward one direction with respect to the holder mounting hole 61. It will be attached (pressed in one direction). Therefore, after the LD unit 40 is mounted on the optical housing 60 and after the rotation direction of the LD unit 40 is adjusted, the LD unit 40 can be held in the optical housing 60 in a stable state over time. It becomes possible.

  If the LD unit is moved in a direction perpendicular to the optical axis after the LD unit is mounted on the optical housing, the optical path of the laser beam is changed to deteriorate the optical characteristics, or the beam position on the image plane is shifted. Degradation of image quality occurs due to the above. Alternatively, when the LD unit is a two-beam system, the pitch between the two beams changes to deteriorate the image quality. However, as described above, in this example, the LD unit 40 is always urged by the leaf spring 65, so that the relative movement of the LD unit 40 with respect to the optical housing 60 is prevented, and the image quality is prevented from deteriorating continuously. High image quality can be maintained.

  In addition, as a structure which urges | biases LD unit 40 to the predetermined direction orthogonal to an optical axis, the structure typically shown in FIG. 9 is also possible. In the illustrated example, apart from the plate spring 165 that presses the holder 151 of the LD unit in the optical axis direction, the holder 151 is biased toward the rotation center of the LD unit by a plate spring 166 of another member from above the holder. The LD unit shown here is a one-beam type. In this configuration, the leaf spring 165 below the holder has only a function of holding the LD unit in an optical housing (not shown).

  Although the configuration shown in FIG. 9 is possible, in the configuration of the above-described embodiment described with reference to FIGS. 4 to 8, the leaf spring 65 has a function of holding the LD unit in the optical housing and the LD unit is orthogonal to the optical axis. Since it has a function to urge in a predetermined direction, it is not necessary to prepare a separate member (another urging member) or its mounting member, reducing the number of parts and reducing the cost, and it is necessary around the LD unit. The optical scanning apparatus which requires only a small amount of space and usually does not have enough space around the LD unit and does not have enough layout, has a great advantage in terms of design freedom.

FIG. 10 is a schematic diagram for explaining the operation of the rotation adjusting mechanism of the LD unit 40 provided in the embodiment.
As described above, the holder 51 of the LD unit 40 is provided with the adjustment mechanism holding portion 58, and the adjustment screw 71 and the compression spring 72 are attached thereto. When such an adjusting mechanism is provided, the direction in which the LD unit 40 moves in the clearance portion between the holder mounting hole 61 of the optical housing and the cylindrical portion 57 of the LD unit is substantially determined. That is, if the connecting point of the adjusting screw 71 and the holder 51 is C, the LD unit 40 has a degree of freedom in the rotation direction with C as a fulcrum. In other words, the cylindrical portion 57 of the LD unit can rotate in the direction of the double-headed arrow D within the holder mounting hole 61 by the clearance (with a degree of freedom in the rotational direction). Therefore, in order to efficiently suppress the play in this direction (arrow D direction), the direction connecting the fulcrum C and the rotation center F of the LD unit (center of the holder mounting hole 61) F: a direction substantially perpendicular to B, for example, What is necessary is just to pressurize the LD unit (the holder 51) in the direction of E or G. In the rotation adjusting mechanism in this embodiment, the direction of the adjusting screw 71 is the direction of the pressing force of the compression spring 72, and the pressing direction is a direction substantially perpendicular to the line B. Therefore, it is possible to efficiently suppress the backlash of the degree of freedom of rotation in the rotation adjustment mechanism (the backlash in the direction of arrow D).

  By the way, with respect to the directions E and G of the urging force, the direction of the arrow G is the direction passing through the rotation center F of the LD unit 40, and the influence on the moment for rotating the LD unit 40 is small. On the other hand, when an urging force is applied as indicated by an arrow E, the LD unit 40 as a whole receives a moment in the clockwise direction in the drawing, in addition to the effect of suppressing the play in the D direction. Therefore, a force in this direction (a direction that does not pass through the rotation center F and is perpendicular to the line B) can also be used for removing the rotation of the rotation adjusting mechanism. That is, the pressing direction can be effectively utilized by determining the pressing position in a direction perpendicular to the line B and the pressing position so that an optimal moment can be obtained in each unit (optical scanning device). It becomes possible. Note that the direction of each pressing force (biasing force) described here is in a predetermined direction (in a plane orthogonal to or substantially orthogonal to the optical axis) that is orthogonal to or approximately orthogonal to the optical axis. The pressing force of the holder pressing portion 65a of the spring 65 and the compression spring 72 is also an urging force in a predetermined direction orthogonal or substantially orthogonal to the optical axis.

  FIG. 11 is a view showing another example of a holder mounting hole provided in the optical housing 60. The holder mounting hole 61B shown in this figure has a substantially pentagonal shape, and the lower two planes (two sides in the figure) 68 and 69 intersect each other. The holder (cylindrical portion 57) of the LD unit 40 is pressed against and held by the two flat surfaces 68 and 69 of the holder mounting hole 61B by a biasing member (for example, a leaf spring) 166 disposed above, and is orthogonal to the optical axis direction. It is positioned in the direction to do. The two planes 68 and 69 are planes that intersect the urging direction by the urging member 166.

  By the way, as the urging member for urging the LD unit in a predetermined direction perpendicular to the optical axis direction, the plate spring has been described in each of the above examples. However, any urging member can be used. For example, in addition to a leaf spring, a chemical product such as a coil spring, rubber or plastic can be used. It is also possible to give elasticity to a part of the LD unit. Further, in addition to direct urging by the urging member, a configuration in which urging is performed via another member such as a link is possible. The same applies to the second urging member that urges the LD unit in a predetermined direction orthogonal to the optical axis direction.

  FIG. 12 is a schematic diagram showing a configuration example in which a part of the LD unit is given elasticity. In the illustrated example, the LD unit 151 </ b> B is pressed in the optical axis direction by the leaf spring 165. An elastic part 152 of the unit itself is provided at the upper part of the unit. When the LD unit 151B is attached to the optical housing, the elastic portion 152 is provided so as to contact the boss portion 167 of the optical housing, and the LD unit is moved in the H direction perpendicular to the optical axis by the elastic portion 152 of the unit itself. It will always be energized. In this example, by configuring the LD unit or a part of its holder as an urging member, the present invention can be implemented while reducing costs and saving space.

  FIG. 13 is a view of the configuration example shown in FIG. 9 as viewed from the cross-sectional direction of the optical housing. In the configuration example shown in FIG. 9, the holder 151 is urged by a leaf spring 166 from above. When the pressure is applied at a position close to the front surface of the holder 151 as indicated by an arrow J in FIG. 13, the LD unit receives a moment as indicated by an arrow K. There is no particular problem when the pressing force of the leaf spring 165 that presses the holder against the housing sufficiently exceeds the pressing force of the leaf spring 166, but when the LD unit has a rotation adjustment mechanism, the pressing force of the leaf spring 165 It is not desirable to make it too strong. This is because when the pressure force of the leaf spring 165 is increased, the frictional force at the contact point in the optical axis direction between the LD unit and the optical housing increases, and the smooth movement of the LD unit in the rotation direction is hindered. Therefore, when the pressure force of the leaf spring 165 is not large, the emitted beam L of the LD unit receiving the moment is shifted in the M direction. As a result, the optical characteristics such as the bending and inclination of the scanning line on the image plane and the deterioration of the beam diameter may be deteriorated, and the image may be seriously affected.

  Therefore, in the configuration example as shown in FIG. 9, as shown in FIG. 14, the optical housing 60 is provided with a convex portion 60a, and the holder 151 is provided with a concave portion 151a into which the convex portion 60a is fitted, and a leaf spring is provided. It is preferable to set the pressing position of 166 to a position close to the housing (position of arrow N). By configuring as shown in FIG. 14, the urging force of the leaf spring 166 can be received from the concave portion 151a of the holder by the convex portion 60a of the housing, and the LD unit receives a moment that deviates the direction of the emitted beam. Instead, the plate spring 166 is biased to bias the holder in a predetermined direction orthogonal to the optical axis, so that stable optical performance can be maintained.

Finally, the overall configuration and operation of the digital copying machine of FIG. 1 will be described.
The digital copying machine shown in FIG. 1 includes an image reading device 11, a printer unit 12 having a laser beam scanning device, and an automatic document feeder 13. The automatic document feeder 13 conveys the set documents one by one, sets them on the contact glass 14, and discharges the documents on the contact glass 14 after copying.

  As shown in FIG. 2, the document reading device 11 includes a first carriage A equipped with a light source composed of an illumination lamp 15 and a reflecting mirror 16 and a first mirror 17, and a second carriage 18 and a third mirror 19 equipped with a third mirror 19. 2 carriages B. When reading a document, the first carriage A moves forward at a constant speed, and the second carriage B follows the first carriage A at a speed half that of the first carriage A. The document on the contact glass 14 is optically scanned, and the document on the contact glass 14 is illuminated by the illumination lamp 15 and the reflecting mirror 16, and the reflected light image is a first mirror 17, a second mirror 18, a third mirror 19, and a color filter 20. The image is formed on the CCD sensor 22 by the lens 21 via The CCD sensor 22 photoelectrically converts the reflected light image of the imaged document, outputs an analog image signal, and reads the document. Then, after the image reading is completed, the first carriage A and the second carriage B return to the home position. It is to be noted that a color original can be read by using a three-line CCD provided with R (red), G (green), and B (blue) filters as CCD sensors.

  The analog image signal from the CCD sensor 22 is converted into a digital image signal by an analog / digital converter, and various image processing (binarization, multi-value conversion, gradation processing, scaling processing, Editing process).

  In the printer unit 12, the image carrier 25 made of a photosensitive member is rotationally driven by a driving unit and is uniformly charged by a charging device 26 during a copying operation, and then image processing is performed on the image processing plate 23. A digital image signal is sent to a semiconductor drive plate (not shown), and image exposure using the digital signal is performed by the laser beam scanning device 27 to form an electrostatic latent image. Then, the electrostatic latent image on the photosensitive drum is developed by the developing device 28.

  The transfer paper is fed from the selected one of the paper feeding devices 33 to 35 to the registration roller 36 and sent out in time with the image on the photosensitive drum 25 by the registration roller 36, and is transferred onto the photosensitive drum by the transfer device 30. The formed visible image is transferred onto the transfer paper. Then, the transfer paper is separated from the photosensitive drum 25 by the separation device 31, conveyed by the conveyance device 37, fixed by the fixing device 38, and then discharged as a copy onto the tray 39. Further, the photosensitive drum 25 is cleaned by the cleaning device 32 after the transfer paper is separated, and the residual toner is removed.

As mentioned above, although this invention was demonstrated by the example of illustration, this invention is not limited to this.
For example, the configuration of the urging means for urging the LD unit in a predetermined direction orthogonal to the optical axis is arbitrary, and an appropriate one can be used. Further, the urging direction and the urging position of the urging means can be appropriately set within the scope of the present invention. The configuration of the LD unit and the configuration of the optical scanning device are the same.

  The image forming apparatus is not limited to a monochrome apparatus, and may be a multicolor machine or a full color apparatus. In addition, an image forming apparatus having various configurations such as a system using an intermediate transfer member and a tandem type can be provided. Of course, the image forming apparatus is not limited to a copying apparatus, and may be a printer or a facsimile, or a multi-function machine having a plurality of functions.

27 Optical scanning device 40 LD unit (semiconductor laser unit)
51 Unit Holder 52 LD Board 54 Semiconductor Laser 56 Collimating Lens 57 Holder Cylindrical Part 60 Optical Housing 61 Holder Mounting Holes 62, 63, 63 Boss Part 65 Plate Spring (Biasing Means)
65c Rising part 65a Holder pressing part 71 Adjustment screw 72 Compression spring (biasing means)
FL unit rotation center

JP 2000-182138 A JP 2003-266787 A

Claims (1)

In an optical scanning device in which a unit on which a light source is mounted is mounted and supported on an optical housing, a light beam emitted from the light source is deflected by a deflecting unit, and an image is formed on a scanned surface through an optical element.
The optical housing has a convex portion that protrudes in the optical axis direction and is formed around the optical axis,
The light source in the unit for mounting the provided recesses fitted on the outside of the convex portion, the concave portion and the convex portion has a clearance in the peripheral direction of the optical axis,
Urging means for urging the unit mounting the light source in a predetermined direction orthogonal to the optical axis direction and pressing the unit against the optical housing;
The optical scanning device according to claim 1, wherein the urging unit urges a unit on which the light source is mounted from outside the concave portion .

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