JP2012242758A - Adjustment mechanism of optical element and scanning optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mechanism capable of smoothly and surely performing skew adjustment of an optical element, a scanning optical device and an image forming apparatus.SOLUTION: A holding member 7 is held between a spring 81 and a body 60. A pin 91 of moving means 9 is made to abut on a lower surface of the holding member 7 and the holding member 7 is energized downward by a tension coil spring 82. A pressed member 72 of the holding member 7 includes an inclined surface 722 which becomes higher toward a lower side in a direction away from the body 60, and a plate spring 81 is made to abut on the inclined surface 722. When the holding member 7 moves downward from an upper end position, downward pressing force by the tension coil spring 82 becomes small, and at the same time, the plate spring 81 is also deformed by the inclined surface 722 of the pressed member 72 and the pressing force becomes small. Accordingly, the pressing force by the tension coil spring 82 is not smaller than frictional resistance force between the holding member 7 and the body 60.

Description

  The present invention relates to an optical element adjustment mechanism and a scanning optical apparatus, and more particularly to an optical element adjustment mechanism and a scanning optical apparatus that are suitably used as an exposure apparatus for a tandem full-color image forming apparatus.

  In a tandem full-color image forming apparatus, yellow (Y), magenta (M), cyan (C), and black (K) images are formed on the surfaces of four juxtaposed photoconductors, respectively. The images are primarily transferred from each photoconductor onto the intermediate transfer belt and superimposed, and then transferred onto the recording material. Here, in order to prevent color misregistration, it is important to align the four images on the intermediate transfer belt.

  Among image alignment adjustments, regarding the inclination (skew) of the scanning line, for example, in Patent Documents 1 and 2, at least one end side in the main scanning direction of the deflection mirror of the optical writing system is driven by a motor or the like. There has been proposed a mechanism for adjusting the skew of the deflecting mirror by sandwiching it between the moving means and the biasing member and driving the moving means to move the deflecting mirror.

  FIG. 10 is a schematic diagram of a conventional adjustment mechanism that adjusts the skew of the optical member by moving the optical member in the sub-scanning direction (Z direction). The optical member 70 is pressed against the pin 91 of the moving means 9 by a pressing force Fz by a spring member (not shown) in the Z direction, and a pressing force Fx by a spring member (not shown) in the optical axis direction (X direction). Is pressed against the housing 60. The skew adjustment of the optical member 70 is performed by moving the pin 91 of the moving means 9 in and out of the Z direction.

JP-A-9-269455 Japanese Patent Laid-Open No. 10-39194

  By the way, the pressing force Fz by the spring member changes in proportion to the deformation amount of the spring member accompanying the movement of the optical member 70. That is, the smaller the amount of change of the spring member, the smaller the pressing force Fz by the spring member. On the other hand, since the spring member does not deform even when the optical member 70 moves, the pressing force Fx by the spring member does not change. Accordingly, the frictional resistance μ · Fx (where μ is a friction coefficient) between the optical member 70 and the housing 60 does not change.

  FIG. 11 shows a relationship between the deformation amount of the spring member, the pressing force Fz, and the frictional resistance force μ · Fx (where μ is a friction coefficient). When the frictional resistance force μ · Fx between the optical member 70 and the housing 60 is always smaller than the pressing force Fz, the optical member 70 is moved to Z by the movement of the pin 91 of the moving means 9 and the pressing force Fz of the spring member. Move smoothly in the direction. However, when a region (inside the ellipse in the figure) where the frictional resistance μ · Fx between the optical member 70 and the housing 60 is larger than the pressing force Fz occurs, the pressing force Fz by the spring member in that region. Then, the optical member 70 does not move in the direction of the moving means 9. Since the friction coefficient μ changes depending on the surface state of the optical member 70 and the housing 60, the above-described problem that the optical member 70 does not move smoothly may occur depending on the surface state of the optical member 70 and the housing 60.

  An object of the present invention is made in view of such a conventional problem, and an object of the present invention is to provide a mechanism, a scanning optical apparatus, and an image forming apparatus that can smoothly and surely perform skew adjustment of an optical element. is there.

  According to the present invention, one end side in the longitudinal direction of the holding member holding the long optical element is attached to the housing so as to be rotatable about an axis parallel to the optical axis, and the first biasing member The holding member is urged in the housing direction of the optical axis to hold the holding member between the first urging member and the housing, and the second urging member holds the holding member in one direction of the rotation direction. An adjustment mechanism that urges the member and allows the moving member to move the holding member to the other side in the rotation direction. When an inclined surface that increases in a direction away from the housing as it goes in a direction in which the biasing force of the biasing member decreases, the holding member moves in a direction in which the biasing force of the second biasing member decreases. The urging force of the first urging member is also reduced. Settling mechanism is provided.

  Here, the first biasing member may be a leaf spring.

  The optical element may be an imaging lens.

  According to the invention, there is provided a scanning optical device comprising any one of the adjustment mechanisms described above.

  Furthermore, according to the present invention, there is provided an image forming apparatus characterized in that the scanning optical device described above is used as an exposure device.

  In the optical element adjustment mechanism and the scanning optical device according to the present invention, the holding member is moved from the housing toward the contact region of the first urging member with the urging force of the second urging member becoming smaller. An inclined surface that increases in the direction of separation is provided, and when the holding member moves in a direction in which the urging force of the second urging member decreases, the urging force of the first urging member also decreases. As a result, the pressing force applied to the holding member by the second urging member does not become smaller than the frictional resistance force between the holding member and the housing, and the skew adjustment of the optical element can be performed smoothly and reliably.

  Further, since the scanning optical device is used as the exposure device in the image forming apparatus according to the present invention, in the tandem full-color image forming device, four images can be accurately superimposed on the intermediate transfer belt, and high image quality can be obtained. It is done.

1 is a schematic configuration diagram illustrating an example of a color printer including a scanning optical apparatus according to the present invention as an exposure apparatus. It is a schematic sectional drawing of exposure apparatus. FIG. 6 is an explanatory diagram illustrating a toner pattern for color misregistration adjustment. It is a perspective view which shows the adjustment mechanism of a 3rd imaging lens. It is a partial perspective view of the pressed member of the holding member and its periphery. It is a side view of a pressed member and its periphery. It is a vertical sectional view showing an example of moving means. It is explanatory drawing which shows the force which acts on a holding member. It is a graph which shows the relationship between the deformation amount of a spring member, pressing force Fz, and frictional resistance force (micro | micron | mu) Fx. It is explanatory drawing which shows the force which acts on the optical member in the conventional adjustment mechanism. It is a graph which shows the relationship between the deformation amount of a spring member, pressing force Fz, and frictional-resistance force (micro | micron | mu) Fx in the conventional adjustment mechanism.

  Hereinafter, the present invention will be described in more detail with reference to the drawings. However, the present invention is not limited to these embodiments.

  FIG. 1 is a schematic view showing an embodiment of an image forming apparatus using the scanning optical apparatus according to the present invention as an exposure apparatus. The image forming apparatus D in FIG. 1 is a so-called tandem color printer. The image forming apparatus D includes an endless intermediate transfer belt 33 having conductivity. The intermediate transfer belt 33 is hung on a pair of rollers 31 and 32 disposed on both the left and right sides in the drawing. The roller 32 is connected to a motor (not shown), and the roller 32 rotates counterclockwise by driving the motor, whereby the intermediate transfer belt 33 and the roller 31 in contact therewith are driven to rotate. A secondary transfer roller 34 is in pressure contact with the outside of the belt portion supported by the roller 32. The toner image formed on the intermediate transfer belt 33 at the nip portion (secondary transfer region) between the secondary transfer roller 34 and the intermediate transfer belt 33 is transferred onto the conveyed paper P.

  A cleaning member 35 for cleaning the surface of the intermediate transfer belt 33 is provided outside the belt portion supported by the roller 31. The cleaning member 35 is in pressure contact with the roller 31 via the intermediate transfer belt 33, and untransferred toner is collected at the contact portion.

  Below the intermediate transfer belt 33 suspended between the rollers 31 and 32, yellow (Y), magenta (M), cyan (C), black ( K) four image forming units 2Y, 2M, 2C, and 2K (hereinafter may be collectively referred to as “image forming unit 2”). In these image forming units 2, a toner image of a corresponding color is created using each color developer.

  The image forming unit 2 includes a cylindrical photosensitive member (electrostatic latent image carrier) 20 as an electrostatic latent image carrier. Then, around the photosensitive member 20, a charger (charging unit) 21, a developing device (developing unit) 23, a primary transfer roller 24, and a photosensitive member cleaning member 25 are sequentially arranged along the rotation direction (clockwise direction). Is arranged. The primary transfer roller 24 is in pressure contact with the photoconductor 20 with the intermediate transfer belt 33 interposed therebetween to form a nip portion (primary transfer region). An exposure device 6 is disposed below the image forming unit 2. The exposure apparatus 6 corresponds to one of the four image forming units 2, modulates four semiconductor lasers (not shown) according to the image gradation data of each color, and lasers corresponding to the respective colors from the respective semiconductor lasers. Light is emitted according to the gradation data. The structure of the exposure apparatus 6 will be described in detail later.

  Above the intermediate transfer belt 33, hoppers 4Y, 4M, 4C, and 4K that store toner to be supplied to the developing devices 23 of the respective colors are arranged. A paper feed cassette 50 is detachably disposed as a paper feed device below the exposure device 6. The sheets (transferred members) P stacked and accommodated in the sheet feeding cassette 50 are sent out one by one to the conveyance path in order from the uppermost sheet by the rotation of the sheet feeding roller 51 disposed in the vicinity of the sheet feeding cassette 50. The paper P sent out from the paper feed cassette 50 is conveyed to the registration roller pair 52 and is sent out to the secondary transfer area at a predetermined timing.

  In the image forming apparatus D having such a configuration, image formation is performed as follows. First, in each image forming unit 2, the outer peripheral surface of the photoconductor 20 that is rotationally driven at a predetermined peripheral speed is charged by the charger 21. Next, light corresponding to image information is projected from the exposure device 6 on the surface of the charged photoconductor 20 to form an electrostatic latent image. Subsequently, the electrostatic latent image is made visible by toner as a developer supplied from the developing device 23. When the toner images of the respective colors formed on the surface of the photoconductor 20 reach the primary transfer area by the rotation of the photoconductor 20, the toner image is transferred from the photoconductor 20 to the intermediate transfer belt in the order of yellow, magenta, cyan, and black. 33 is transferred (primary transfer) and superimposed.

  Untransferred toner remaining on the photoconductor 20 without being transferred to the intermediate transfer belt 33 is scraped off by the photoconductor cleaning member 25 and removed from the outer peripheral surface of the photoconductor 20.

  The superimposed four color toner images are conveyed to the secondary transfer region by the intermediate transfer belt 33. On the other hand, the paper P is conveyed from the registration roller pair 52 to the secondary transfer area in accordance with the timing. Then, the four color toner images are transferred (secondary transfer) from the intermediate transfer belt 33 to the paper P in the secondary transfer region. The sheet P on which the four color toner images are transferred is conveyed to the fixing device 1. In the fixing device 1, the paper P passes through a nip portion between the pressure roller 12 and a fixing roller 11 having a bar-shaped halogen heater 13 built therein. During this time, the paper P is heated and pressurized, and the toner image on the paper P is melted and fixed on the paper P. The paper P on which the toner image is fixed is discharged to the paper discharge tray 54 by the discharge roller pair 53.

  On the other hand, the intermediate transfer belt 33 that has passed through the secondary transfer region is cleaned by the cleaning blade 35. Thereafter, the rotational drive of each photoconductor 20 and the intermediate transfer belt 33 is stopped.

  FIG. 2 shows a schematic block diagram of the exposure apparatus 6. The exposure apparatus 6 includes a housing 60, a polygon mirror 61 provided in the housing 60, a first imaging lens 62, a second imaging lens 63, and mirrors 65Y, 65M provided for each optical path. 65C, 65K (hereinafter collectively referred to as “mirror 65”), mirror 66Y, 66M, 66C (hereinafter collectively referred to as “mirror 35”), mirror 67C, and third imaging lenses 64Y, 64M, 64C, 64K (hereinafter collectively referred to as “third imaging lens 64”). The polygon mirror 61 is attached to a motor m fixed to the plate. A heat radiating plate 68 is further attached to the plate.

  Light beams emitted from light sources (not shown) of the respective colors are guided to the same surface of the polygon mirror 61 at a predetermined angle in the sub-scanning direction (vertical direction in FIG. 2), and based on the rotation of the polygon mirror 61. After being deflected at a constant angular velocity in the main scanning direction (perpendicular to the paper surface in FIG. 2) and transmitted through the first imaging lens 62 and the second imaging lens 63, the light beam Bk passes through the third imaging lens 64K. Then, the light is reflected by the mirror 65K, and the photosensitive drum 20K is scanned and exposed. The light beam Bc is reflected by the mirror 65C and the mirror 66C, passes through the third imaging lens 64C, is further reflected by the mirror 67C, and scans and exposes the photosensitive drum 20C. The light beam Bm is reflected by the mirror 65M, passes through the third imaging lens 64M, is further reflected by the mirror 66M, and scans and exposes the photosensitive drum 20M. The light beam By is reflected by the mirror 65Y, passes through the third imaging lens 64Y, is further reflected by the mirror 66Y, and scans and exposes the photosensitive drum 20Y.

  For example, color misregistration detection including skew adjustment is performed by forming toner patterns Py, Pm, Pc, and Pk in which the ends of two straight lines are connected at an acute angle as shown in FIG. The transfer is performed by primary transfer onto the belt 33 and detecting the toner patterns Py to Pk with a pair of optical sensors 36. Specifically, the skew is detected by comparing the lengths of the two straight lines of the toner pattern in the moving direction of the intermediate transfer belt 33 with the left and right toner patterns, and the lengths of the left and right toner patterns are compared. Skew adjustment is performed based on the difference. Hereinafter, the skew adjustment will be described.

  In the present embodiment, the skew adjustment is performed by rotating the third imaging lens 64 around an axis parallel to the optical axis. In the present embodiment, the skew adjustment is performed on the light beams Bc, Bm, and By using the light beam Bk as a reference. Therefore, the skew adjustment mechanism is provided in the third imaging lens 64K disposed with respect to the light beam Bk. The third imaging lenses 64C, 33M, and 33Y disposed for the light beams Bc, Bm, and By are provided. Of course, the skew adjustment may be performed on the light beam Bk.

  FIG. 4 is a perspective view showing a skew adjustment mechanism of the third imaging lens 64. The holding member 7 includes a long holder 71 and a pressed member 72 attached to one end side of the holder 71. The long third imaging lens 64 is held by a holder 71, and one end side in the longitudinal direction of the holder 71 is rotatably attached to a housing 60 by a pin 73. Further, the other side of the holder 71 in the longitudinal direction where the pressed member 72 is screwed is attached to the other side of a tension coil spring (second biasing member) 82 whose one end is fixed to the housing 60. ing. Thereby, the holder 71 is always urged downward by the tension coil spring 82. The pressed member 72 is formed with an inclined portion 721 having an inclined surface 722 that protrudes outward as it goes downward. In this embodiment, the holding member 7 includes the holder 71 and the pressed member 72, but the holder 71 and the pressed member 72 may be integrally formed.

  FIG. 5 is a partial perspective view of the pressed member 72 and its periphery, and FIG. 6 is a side view thereof. A hemispherical convex portion 811 of a leaf spring (first urging member) 81 bent in a substantially U shape comes into pressure contact with an inclined surface 722 formed in the inclined portion 721 of the pressed member 72, and the housing 60 A holder 71 is sandwiched between the two. Further, the pin 91 of the moving means 9 is in contact with the lower surface of the pressed member 72.

  FIG. 7 shows a schematic cross-sectional view of the moving means 9. The moving means 9 has a motor 90 and a pin 91, and a male screw portion 93 fixed to the tip of the rotating shaft 92 of the motor 90 is formed on the pin 91. Screwed into the hole 94. When the rotation shaft 92 of the motor 90 is rotated, the male screw portion 93 is rotated, whereby the pin 91 is moved in the axial direction. The motor 90 is controlled to rotate according to the skew state detected from the toner patterns Py to Pk (shown in FIG. 3). When the pin 91 protrudes outward in the axial direction by the rotation of the motor 90, the pin 91 presses the pressed member 72 and pushes up the third imaging lens 64 together with the holding member 7. On the other hand, when the pin 91 is sunk inward in the axial direction due to the reverse rotation of the motor 90, the holding member 7 is pushed downward while being in contact with the pin 91 by the urging force of the tension coil spring 82.

  FIG. 8 shows the force acting on the holding member 7. FIG. 4A is a state diagram in which the holding member 7 is at the upper end position, and FIG. 4B is a state diagram in which the holding member 7 is at the lower end position. When the holding member 7 is in the upper end position, a pressing force Fx1 is applied to the holding member 7 in the optical axis direction by the leaf spring 81, and a pressing force Fz1 is applied downward by the tension coil spring 82. At this time, the frictional resistance between the holding member 7 and the housing 60 is (μ · Fx1). On the other hand, when the holding member 7 moves downward, the downward pressing force by the tension coil spring 82 is reduced to Fz2, but at the same time, the leaf spring 81 is also deformed by the inclined surface 722 of the pressed member 72 and the pressing force is reduced. The pressure is reduced to Fx2. Accordingly, the frictional resistance force (μ · Fx2) between the holding member 7 and the housing 60 is also reduced.

  FIG. 9 is a graph showing the relationship between the deformation amount of the spring members 81 and 82, the pressing force Fz, and the frictional resistance force μ · Fx (where μ is a friction coefficient). As can be understood from this graph, even if the holding member 7 moves and the amount of deformation of the spring changes, the pressing force Fz becomes smaller than the frictional resistance force μ · Fx between the holding member 7 and the housing 60. However, the holding member 7 moves smoothly, and the skew adjustment of the third imaging lens 64 is performed smoothly and reliably.

  In the embodiment described above, the optical element is the third imaging lens, but the adjustment mechanism of the present invention can be applied to other optical elements such as a mirror. Further, as the first urging member, a conventionally known urging member such as a coil spring can be used in addition to the plate spring. Similarly for the second biasing member, a conventionally known biasing member such as a compression coil spring or a leaf spring can be used in addition to the tension coil spring.

  According to the optical element adjustment mechanism and the scanning optical apparatus according to the present invention, the optical element can be smoothly moved, and the skew adjustment of the optical element can be reliably performed. In the image forming apparatus according to the present invention, since the scanning optical device is used as an exposure device, in the tandem full-color image forming apparatus, four images are accurately superimposed on the intermediate transfer belt, and high image quality can be obtained.

D color printer (image forming device)
6 Exposure device (scanning optical device)
7 Holding member 9 Moving means 60 Housing 64 Third imaging lens (optical element)
71 Holder 72 Pressed member 81 Leaf spring (first biasing member)
82 Tension coil spring (second biasing member)
90 motor 91 pin 721 inclined portion 722 inclined surface

Claims (5)

One end side in the longitudinal direction of the holding member holding the long optical element is attached to the housing so as to be rotatable about an axis parallel to the optical axis,
Urging the holding member by the first urging member in the housing direction of the optical axis to hold the holding member between the first urging member and the housing;
An adjustment mechanism that urges the holding member toward one direction of the rotation direction by a second urging member and allows the holding member to move to the other side of the rotation direction by a moving unit,
In the contact region of the holding member with the first urging member, an inclined surface is provided that increases in a direction away from the casing as the urging force of the second urging member decreases.
An adjustment mechanism for an optical element, wherein the urging force of the first urging member is also reduced when the holding member is moved in a direction in which the urging force of the second urging member is reduced.   The optical element adjustment mechanism according to claim 1, wherein the first biasing member is a leaf spring.   The optical element adjustment mechanism according to claim 1, wherein the optical element is an imaging lens.   A scanning optical device comprising the adjusting mechanism according to claim 1.   An image forming apparatus using the scanning optical apparatus according to claim 4 as an exposure apparatus.