JP7056192B2 - Optical writing device and image forming device equipped with it - Google Patents

Description

The present invention relates to an electrophotographic image forming apparatus, and more particularly to a heat dissipation structure of an optical writing apparatus that exposes a photoconductor.

The optical writing device is also called a "print head (PH)" and is used for exposing the surface of a photoconductor in an electrophotographic image forming device such as a printer or a copier. The optical writing device irradiates a linear region (hereinafter referred to as "1 line") extending in one direction on the surface of the photoconductor with modulated light based on image data. By repeating the exposure in line units, a two-dimensional distribution of the amount of charge according to the image data, that is, an electrostatic latent image is formed on the surface of the photoconductor.

The optical writing device includes an optical scanning method and a light emitting element arrangement method. The "optical scanning method" continuously exposes one line on the surface of the photoconductor by deflecting the laser beam with a polygon mirror. The "light emitting element arrangement method" is an arrangement of light emitting elements such as light emitting diodes (LEDs) and semiconductor lasers (LD), and a gradient index (GRIN) such as rod lenses (registered trademark) and selfoc (registered trademark) lenses. ) Simultaneously expose one line on the surface of the photoconductor with the lens arrangement. Unlike the optical scanning method, the light emitting element arrangement method is compact because there is no noise due to the polygon mirror and its drive motor and the optical path length from the light emitting element to the photoconductor is short, so an electrophotographic image forming apparatus is particularly suitable. It is advantageous for further dissemination to offices and homes.

The light emitting element arrangement method includes a light source substrate and a lens array. The light source substrate has an elongated plate shape as a whole, and includes an array of light emitting elements in a linear region in the elongated direction (hereinafter referred to as "light emitting region"). The emission direction of light from each light emitting element, that is, the optical axis direction of each light emitting element is aligned with the normal direction of the plate surface of the light emitting region. The light source substrate is arranged on a flat table surface of a holding table (also referred to as a "light source holder"), and is supported at a plurality of points in the long direction by support members protruding in the normal direction from the table surface. As a result, the long direction of the light source substrate is kept parallel to the main scanning direction, and the optical axis direction of each light emitting element is aligned with the normal direction of the table surface of the holding table. The photoconductor is located at the point where the normal direction of the table surface extends. The lens array is an integrally molded product of an array of GRIN lenses arranged perpendicular to the optical axis, and the entire lens array has a long plate shape in the array direction. The lens array is surrounded by a holding frame (also referred to as a "lens holder"). By fixing this holding frame to the holding table, the lens array is arranged between the light source substrate and the photoconductor, and the long direction is kept parallel to the main scanning direction, and the optical axis of the GRIN lens is placed on the holding table. It coincides with the normal direction of the pedestal surface, that is, the optical axis direction of the light emitting element. In this way, the lens array forms the light on the surface of the photoconductor.

The image of the light emitting region by the lens array remains as an electrostatic latent image on the surface of the photoconductor. In order to improve the image quality of this electrostatic latent image, the image in the light emitting region must be reproduced at an accurate position on the surface of the photoconductor, in which the optical axis direction is further increased between the light emitting element and the GRIN lens. It is necessary to match with high accuracy. For example, in the lens holder disclosed in Patent Document 1, an array of screws protruding toward the lens array is arranged parallel to the optical axis direction of the light emitting element, and the tips thereof are brought into contact with the lens array at a plurality of points in the optical axis direction. ing. Each screw rotates about its axis to displace its tip perpendicular to a plane parallel to both the optical axis direction of the light emitting element and the elongated direction of the lens array. Depending on the difference in tip position between the screws, the lens array changes the angle of rotation around an axis parallel to its longitudinal direction. In this way, the inclination of the optical axis of the GRIN lens with respect to the optical axis of the light emitting element can be adjusted by the amount of protrusion of each screw from the lens holder.

Japanese Unexamined Patent Publication No. 2002-160401

Further improvement in performance is required for the light emitting element arrangement method. As a device for that purpose, for example, it is considered to use an organic light emitting diode (OLED) as a light source. Compared to LEDs, OLEDs are advantageous in that they have a low black level, high color expression, low power consumption, and are easy to be compact / thin / lightweight. On the other hand, OLEDs emit less light than LEDs. Therefore, it is necessary to increase the F value of the GRIN lens in order to use the OLED. Increasing the F-number narrows the depth of focus, further limiting the position error allowed between the image of the light emitting region by the lens array and the surface of the photoconductor. That is, the positioning of the light emitting element and the GRIN lens with respect to the surface of the photoconductor must be further improved in accuracy.

However, it is difficult to further improve the accuracy of matching in the optical axis direction between the light emitting element and the GRIN lens. For example, if the screw of the lens holder is used as disclosed in Patent Document 1, the lens array is rotated around an axis parallel to the long direction to tilt the optical axis of the GRIN lens with respect to the optical axis of the light emitting element. It is possible to change. However, strictly speaking, it is not only the inclination of the optical axis between the light emitting element and the GRIN lens that changes depending on the difference in the tip position between the screws, but also the rotation axis of the lens array with respect to the surface of the photoconductor. The position is also included. With the displacement of the rotation axis, the lens array is displaced with respect to the surface of the photoconductor, particularly in the optical axis direction of the light emitting element. If this displacement is excessive, the positional error between the image of the light emitting region due to the lens array and the surface of the photoconductor may exceed the allowable range. Eliminating the tilt of the optical axis between the light emitting element and the GRIN lens while preventing excessive displacement of the lens array with respect to the surface of the photoconductor is not easy by simply adjusting the position of the tip for each screw. It is not preferable because it complicates the manufacturing process of the built-in device.

An object of the present invention is to solve the above-mentioned problems, and in particular, an optical book capable of removing the tilt of the optical axis between the light emitting element and the GRIN lens without displacing the lens array with respect to the surface of the photoconductor. The purpose is to provide a built-in device.

The optical writing device in one aspect of the present invention writes information to the photoconductor by light. This optical writing device includes a flat pedestal, a holding pedestal installed so that the pedestal faces the photoconductor, and the whole has a long plate shape and extends in the long direction. A light source substrate that includes a light emitting region and is held by a holding table so that the table surface and the plate surface are parallel to each other, and the whole has a long plate shape and is perpendicular to the long direction. A lens array that includes an array of lenses that are aligned in one of the directions and aligned in that long direction, and a lens array that is parallel to both the long direction of this lens array and the optical axis of each lens. It is provided with a holding member that sandwiches the lens array from both sides of the central surface of the lens array and holds the lens array so that the light source substrate and the lens array are parallel to each other in the long direction. In this holding member, each of the surfaces facing the lens array on both sides of the central surface of the lens array makes point contact with the lens array at at least one position in the elongated direction of the lens array in the normal direction of the pedestal surface of the holding table. Includes contact area. The contact points between the contact portion of the holding member and the lens array are all located equidistant from the table surface of the holding table.
The position where the lens array makes point contact with the contact portion of the holding member in the normal direction of the table surface of the holding table includes the central portion in the long direction of the lens array, and the central portion includes the lens array and the holding portion. The gap between the contact portion of the member and the contact portion is thinly bonded, and the gap between the lens array and the holding member is thickly bonded except for the central portion.

The contact portion of the holding member may include a protrusion that projects toward the lens array and makes point contact with the lens array at the tip in the normal direction of the table surface of the holding table. The holding member may include an adhesive layer that adheres the lens array to itself. Until the adhesive layer is formed, the lens array is the line of intersection between the plane parallel to the pedestal surface of the holding table including all the contact points between the lens array and the contact portion of the holding member and the center surface of the lens array. It may be rotatable around. The lens array may include a curved surface facing the contact portion of the holding member. This curved surface may include at least a part of a cylindrical surface about a straight line extending in a long direction on the central surface of the lens array. The contact portion of the holding member is inclined from a common optical axis direction between the lenses of the lens array, and may include a curved surface of the lens array and a slope that makes point contact in the normal direction of the table surface of the holding table. The lens array may also be displaceable in the normal direction of the pedestal surface of the holding table while being sandwiched between the contact portions of the holding members until the adhesive layer is formed.

An optical writing device according to another aspect of the present invention writes information to a photoconductor by light. This optical writing device includes a flat pedestal, a holding pedestal installed so that the pedestal faces the photoconductor, and the whole has a long plate shape and extends in the long direction. A light source substrate that includes a light emitting region and is held by a holding table so that the table surface and the plate surface are parallel to each other, and the whole has a long plate shape and is perpendicular to the long direction. A lens array that includes an array of lenses that are aligned in one of the directions and aligned in that long direction, and a lens array that is parallel to both the long direction of this lens array and the optical axis of each lens. It is provided with a holding member that sandwiches the lens array from both sides of the central surface of the lens array and holds the lens array so that the light source substrate and the lens array are parallel to each other in the long direction. In this holding member, each of the surfaces facing the lens array on both sides of the central surface of the lens array makes point contact with the lens array at at least one position in the elongated direction of the lens array in the normal direction of the pedestal surface of the holding table. Includes contact area. The contact points between the contact portion of the holding member and the lens array are all located equidistant from the table surface of the holding table. The lens array includes at least a part of a cylindrical surface having a straight line extending in the long direction of the lens array as a central axis on the central surface of the lens array, and includes a curved surface facing the contact portion of the holding member, and the holding member. The contact portion of the lens array is tilted from a common optical axis direction between the lenses of the lens array, and includes a curved surface of the lens array and a slope that makes point contact in the normal direction of the pedestal surface of the holding table. The lens array is rotatable around the line of intersection between the plane parallel to the pedestal surface of the retainer, including all contact points between the lens array and the contact points of the holding member, and the center plane of the lens array. The line and the central axis of this cylindrical surface are located on the same straight line.

The image forming apparatus according to one aspect of the present invention is an electrophotographic image forming apparatus, and includes a photoconductor, the above-mentioned optical writing apparatus that exposes the surface of the photoconductor to form an electrostatic latent image, and the above-mentioned optical writing apparatus. It includes a developing unit that develops an electrostatic latent image with toner, and a transfer unit that transfers the toner image developed by the developing unit from the photoconductor to the sheet.

In the optical writing device according to the present invention, as described above, the holding member includes contact portions on both sides of the central surface of the lens array and each of the surfaces facing the lens array. These contact portions make point contact with the lens array at at least one point in the long direction of the lens array in the normal direction of the base surface of the holding table. In any of the contact points, the contact points are located equidistant from the table surface of the holding table. This not only allows the lens array to rotate around an axis parallel to the longitudinal direction while still in contact with the holding member, but the axis remains in place regardless of the angle of rotation. In this way, this optical writing device can remove the inclination of the optical axis between the light emitting element and the lens without displacing the lens array with respect to the surface of the photoconductor.

(A) is a perspective view showing the appearance of a printer which is an image forming apparatus according to an embodiment of the present invention. (B) is a schematic cross-sectional view of the printer along the straight line bb indicated by (a). (C) is one enlarged view of the photoconductor unit shown in (b). (A) is an exploded assembly view of the optical writing unit shown in FIG. 1 (c), and (b) is a top view of the optical writing unit. (A) is a vertical sectional view of an optical writing unit along the straight line IIIa-IIIa shown in FIG. 2 (a). (B) is a block diagram of an electronic circuit system incorporated in the light source substrate shown in (a). (A) and (b) are cross-sectional views of the optical writing section along the straight lines IVa-IVa and IVb-IVb shown in FIG. 2A, respectively. (C) is a schematic diagram showing an optical path in one of the GRIN lenses shown in (a). (D) is a partial cross-sectional view of a lens holder including one of the contact portions shown in (b). (A) and (b) are partial cross-sectional views of the lens holder in a state where the lens array shown in FIG. 4 is fixed with an adhesive, and (c) is a partial top view of the lens holder. be. (A) is a perspective view of one end portion in a long direction of an optical writing unit to which an example of a stopper is added. (B) is a cross-sectional view of the optical writing unit along the straight line bb shown in (a), and (c) is a front view of the cross section shown in (a). (D) is a perspective view of a single rocker member shown in (a). (A) is a perspective view of one end portion in a long direction of an optical writing unit to which an example of a torque transmission unit is added. (B) is a front view of the cross section thereof.

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

[Appearance of image forming apparatus]
FIG. 1A is a perspective view showing the appearance of the image forming apparatus 100 according to the embodiment of the present invention. The image forming apparatus 100 is a printer. A paper ejection tray 41 is provided on the upper surface of the housing, and a sheet ejected from the paper ejection port 42 opened at the back thereof is accommodated. An operation panel 51 is embedded in front of the output tray 41. A paper cassette 11 is attached to the bottom of the printer 100 so that it can be pulled out.

[Internal structure of image forming apparatus]
FIG. 1B is a schematic cross-sectional view of the printer 100 along the straight line bb shown in FIG. 1A. The printer 100 is an electrophotographic color printer, and includes a feeding unit 10, an image forming unit 20, a fixing unit 30, and a paper ejection unit 40.

First, the feeding unit 10 uses a pickup roller 12 to separate the sheets SH1 one by one from the bundle of sheets housed in the paper cassette 11. Next, the feeding unit 10 uses the timing roller 13 to send the separated sheets to the image forming unit 20 in time with the operation. "Sheet" refers to a thin or thin plate material, article, or printed matter made of paper or resin. The type or type of sheet that can be accommodated in the paper cassette 11 is, for example, plain paper, woodfree paper, color paper, or coated paper, and the size is, for example, A3, A4, A5, or B4. Furthermore, the posture of the seat can be set to either vertical or horizontal.

The image forming unit 20 is, for example, an intermediate transfer method, and is a tandem-arranged photoconductor unit 20Y, 20M, 20C, 20K, an intermediate transfer belt 21, a primary transfer roller 22Y, 22M, 22C, 22K, and a secondary transfer roller 23. including. The intermediate transfer belt 21 is rotatably hung between the driven pulley 21L and the driving pulley 21R. In the space between these pulleys 21L and 21R, four photoconductor units 20Y-20K and four primary transfer rollers 22Y-22K are arranged so as to form a pair, and an intermediate transfer belt 21 is interposed. They are facing each other. The secondary transfer roller 23 sandwiches the intermediate transfer belt 21 in between to form a nip with the drive pulley 21R. The sheet SH2 sent out from the timing roller 13 is passed through this nip.

In the photoconductor unit 20Y-20K, the photoconductor drums 24Y, 24M, 24C, and 24K are in contact with the facing primary transfer rollers 22Y-22K with the intermediate transfer belt 21 sandwiched between them to form a nip. .. The photoconductor unit 20Y-20K has the same surface portion as the primary transfer roller 22Y-22K and the photoconductor drum 24Y-24K while the intermediate transfer belt 21 rotates (counterclockwise in (b) of FIG. 1). As it passes through the nip between, it forms a toner image of one different color of yellow (Y), magenta (M), cyan (C), and black (K) on its surface portion. These four color toner images are superimposed on the surface portion of the intermediate transfer belt 21 to form one color toner image. The sheet SH2 is passed from the timing roller 13 to the nip at the timing when the color toner image passes through the nip between the drive pulley 21R and the secondary transfer roller 23. As a result, the color toner image is transferred from the intermediate transfer belt 21 to the sheet SH2 at the nip.

The fixing unit 30 heat-fixes the toner image on the sheet SH3 sent from the image forming unit 20. Specifically, the fixing portion 30 passes the sheet SH2 through the nip between the fixing roller 31 and the pressure roller 32 while rotating them. At this time, the fixing roller 31 applies the heat of the built-in heater to the surface of the sheet SH3, and the pressure roller 32 applies pressure to the heated portion of the sheet SH3 and presses it against the fixing roller 31. The toner image is fixed to the surface of the sheet SH3 by the heat from the fixing roller 31 and the pressure from the pressure roller 32. The fixing section 30 further sends the sheet SH3 to the paper ejection section 40 by the rotation of the fixing roller 31 and the pressure roller 32.

The paper ejection unit 40 ejects the sheet SH3 on which the toner image is fixed from the paper ejection port 42 to the paper ejection tray 41. Specifically, the paper ejection unit 40 uses the paper ejection roller 43 arranged inside the paper ejection port 42 to remove the sheet SH3 that has moved from the upper part of the fixing portion 30 to the paper ejection port 42. And put it on the output tray 41.

[Structure of photoconductor unit and image formation processing by it]
FIG. 1 (c) is an enlarged view of one of the photoconductor units shown in FIG. 1 (b), 20K. In addition to the photoconductor drum 24K, the photoconductor unit 20K includes a charging unit 201, an optical writing unit 202, a developing unit 203, a cleaning blade 204, and an eraser 205. These are arranged around the photoconductor drum 24K, and perform other than fixing, that is, charging, exposure, development, transfer, cleaning, and static elimination in the electrophotographic image forming process on the outer peripheral surface thereof. Other photoconductor units 20Y, 20M, 20C also include a common structure.

The photoconductor drum 24K is a cylindrical member made of a conductor such as aluminum whose outer peripheral surface 241 is covered with a photoconductor, and its central axis (in FIG. 1C, the center of the circular cross section of the photoconductor drum 24K is used. It is rotatably supported around a shaft) 242 that penetrates perpendicular to the paper surface. The photoconductor is a material whose charge amount changes depending on the exposure amount, and includes an inorganic material such as amorphous selenium, a selenium alloy, and amorphous silicon, or a laminated structure (OPC) of a plurality of organic materials. Although not shown in FIG. 1 (c), the central shaft 242 of the photoconductor drum 24K is connected to the drive motor through a rotational force transmission mechanism such as a gear and a belt. When the photoconductor drum 24K makes one rotation (clockwise in (c) of FIG. 1) due to the rotational force from the drive motor, each surface portion of the photoconductor becomes a peripheral processing unit 201, 202, 203, 204, 205. Face in turn and receive those processes.

The charging unit 201 includes a wire or a thin plate-shaped electrode 211 extending in the axial direction thereof at a distance from the outer peripheral surface 241 of the photoconductor drum 24K. By applying, for example, a negative high voltage to the electrode 211, the charging unit 201 causes a corona discharge between the electrode 211 and the outer peripheral surface 241 of the photoconductor drum 24K. This discharge negatively charges the surface portion of the photoconductor facing the charging portion 201.

The optical writing unit 202 is a main functional unit of the optical writing device according to the embodiment of the present invention, and is a linear region extending in the axial direction (main scanning direction) of the charged portion of the photoconductor drum 24K, that is, one line. To expose. At this time, the optical writing unit 202 modulates the amount of irradiation light to the photoconductor drum 24K based on the gradation value represented by the image data. In one line on the photoconductor drum 24K, the charge amount decreases as the exposure amount increases, so that a charge amount distribution corresponding to the gradation value distribution represented by the image data, that is, an electrostatic latent image is formed. The optical writing unit 202 repeats this exposure operation for one line in synchronization with the rotation of the photoconductor drum 24K. As a result, the exposed lines are connected to the outer peripheral surface of the photoconductor drum 24K in the rotation direction, that is, the sub-scanning direction, and the electrostatic latent image is two-dimensionally expanded.

The developing unit 203 develops the electrostatic latent image on the photoconductor drum 24K with K-color toner. Specifically, the developing unit 203 first agitates the two-component developer DVL with two auger screws 231 and 232, and the toner contained in the developer DVL is negatively charged by the friction at that time. The developing unit 203 then uses the developing roller 233 to convey the developer DVL to the nip between the photoconductor drum 24K. In parallel with this, the developing unit 203 applies a negative high voltage to the developing roller 233. As a result, the potential of the electrostatic latent image in the region where the charge amount is relatively small is higher than that of the developing roller 233, so that the amount of toner corresponding to the decrease in the charge amount is separated from the developer conveyed by the developing roller 233. And adhere. In this way, the electrostatic latent image becomes apparent as a toner image.

This toner image moves to the nip between the photoconductor drum 24K and the primary transfer roller 22K as the photoconductor drum 24K rotates. Since a positive high voltage is applied to the primary transfer roller 22K, the negatively charged toner image is transferred from the outer peripheral surface of the photoconductor drum 24K to the intermediate transfer belt 21.

The cleaning blade 204 is a thin rectangular plate-shaped member formed of a thermosetting resin such as polyurethane rubber, and its length is substantially the same as the portion of the outer peripheral surface 241 of the photoconductor drum 24K covered with the photoconductor. equal. Of the plate surface of the blade 204, the one facing the outer peripheral surface 241 of the photoconductor drum 24K has one of its long sides (edges) parallel to the axial direction of the photoconductor drum 24K on the outer peripheral surface 241. The toner that comes into contact with the toner and remains on the transfer mark of the toner image is scraped off from the outer peripheral surface 241. In this way, the outer peripheral surface is cleaned.

The eraser 205 irradiates the outer peripheral surface 241 of the photoconductor drum 24K with light from, for example, LEDs arranged in the axial direction of the photoconductor drum 24K. The remaining charge disappears from the portion of the outer peripheral surface 241 that has been irradiated with the irradiation light. In this way, the outer peripheral surface 241 is statically eliminated.

[Structure of optical writing unit]
FIG. 2A is an exploded assembly view of the optical writing unit 202, and FIG. 2B is a top view of the optical writing unit 202. FIG. 3A is a vertical cross-sectional view of the optical writing unit 202 along the straight line IIIa-IIIa shown in FIG. 2A. 4 (a) and 4 (b) are cross-sectional views of the optical writing unit 202 along the straight lines IVa-IVa and IVb-IVb shown in FIG. 2 (a), respectively. The vertical cross section is a cross section perpendicular to the width direction of the optical writing unit 202 (Y-axis direction in the figure), and the cross section is the long direction of the optical writing unit 202 (X-axis direction in the figure). It is a vertical cross section. The optical writing unit 202 is a light emitting element arrangement system and includes a light source substrate 310, a lens array 320, and a lens holder 330.

-Light source board-
The light source substrate 310 is a transparent glass substrate or a resin substrate having a long shape as a whole, and is, for example, several tens of centimeters in length × several cm in width × several hundred μm in thickness. The light source substrate 310 includes a light emitting region 311, a sealing member 312, and an integrated circuit (IC) chip 313. The light emitting region 311 is, for example, a rectangular region having a length of several tens of centimeters and a width of several mm, and extends the central portion of the light source substrate 310 in the width direction (Y-axis direction) over almost the entire length direction (X-axis direction). There is. The light emitting region 311 includes a plurality of solid light emitting elements such as LEDs and OLEDs directly formed on the plate surface 314 (lower surface in the figure) on one side. When these elements emit light, the light passes through the light source substrate 310 and is emitted from the opposite plate surface 315 (upper surface in the figure) in the normal direction (positive direction of the Z axis in the figure). The sealing member 312 is, for example, a multilayer structure of glass, a metal oxide or a nitride, and a polymer, and surrounds the light emitting region 311 on the plate surface 314 on the light emitting element side of the light emitting region 311 and is airtight from the outside. Isolate. This protects the light emitting element from moisture and oxygen in the outside air. The IC chip 313 is mounted on the plate surface 314 on the light emitting element side at one end in the long direction of the light source substrate 310 (the left end in FIG. 3A). The IC chip 313 has an elongated rectangular shape in the long direction (X-axis direction) of the light source substrate 310, and a drive circuit for a light emitting element is incorporated therein.

FIG. 3B is a block diagram of an electronic circuit system incorporated in the light source substrate 310. This system includes a light emitting device array 351 and a selection circuit 352, and a drive circuit 353. The light emitting element array 351 is an array of solid light emitting elements, for example, an OLED, which is directly formed in the light emitting region 311 of the light source substrate 310. In the example shown in FIG. 3B, the light emitting element 360 has a rectangular shape of several μm − ten and several μm square, and several thousand × 3 rows at a pitch of several tens of μm along the long direction of the light source substrate 310. They are lined up in a staggered arrangement. The light emitting element 360 changes the amount of drive current according to the luminance signal from the outside. The larger the amount of drive current, the higher the brightness of the light emitting element 360. The selection circuit 352 is a thin film transistor (TFT) circuit directly formed on the light source substrate 310, and the light emitting elements 360 are sequentially connected to the drive circuit 353. The drive circuit 353 is composed of an application specific integrated circuit (ASIC) or a programmable integrated circuit (FPGA) and is incorporated in an IC chip 313 mounted directly on the light source substrate 310 (chip on grass:). COG). The drive circuit 353 is connected to the light source control unit 355 in the printer 100 through the flexible printed circuit board (FPC) 354, and receives digital image data from the light source control unit 355. The drive circuit 353 converts this image data into an analog luminance signal and transmits it to the light emitting element connected by the selection circuit 352.

-Lens array-
The lens array 320 is a transparent glass plate or a resin plate having a long shape as a whole, and is, for example, several tens of centimeters in length × several cm in width × several cm in thickness. An array of GRIN lenses 323 arranged in the long direction (X-axis direction in FIGS. 2 to 4) is sealed between the two plate surfaces 321 and 322 of the lens array 320. Each GRIN lens 323 is a transparent glass or resin cylinder, for example, having a diameter of several hundred μm-a few mm x a length of several cm. In each GRIN lens 323, the optical axis is one direction perpendicular to the long direction (X-axis direction) of the lens array 320, particularly the short side direction of the plate surfaces 321 and 322 of the lens array 320 (FIGS. 2-FIG. 4). Aligned in the Z-axis direction). Each GRIN lens 323 has one end surface 324 (lower surface in the figure) facing the light emitting surface 315 of the light source substrate 310, and the other end surface 325 (upper surface in the figure) facing the outer peripheral surface 241 of the photoconductor drum 24K. As a result, each GRIN lens 323 emits light incident on one end surface 324 from the light source substrate 310 from the other end surface 325 to the outer peripheral surface 241 of the photoconductor drum 24K.

FIG. 4 (c) is a schematic diagram showing an optical path in one of the GRIN lenses, 323. Inside the GRIN lens 323, the refractive index is distributed so as to decrease in a parabolic shape from the central axis toward the outer peripheral surface. Due to this refractive index distribution, the light incident from one end surface 324 of the GRIN lens 323 propagates while drawing a sinusoidal trajectory along the axial direction, and travels a certain distance, for example, several mm to a dozen mm each time. Repeat imaging. Therefore, the light emitted from the other end surface 325 of the GRIN lens 323 forms an upright image or an inverted image according to the axial length AXL of the GRIN lens 323. In (c) of FIG. 4, it is an upright image as shown by the white arrow. This blurring of the image is suppressed to an allowable level before and after the imaging point PBF and within the range of the depth of focus DOC of the GRIN lens 323 = several hundred μm.

-Lens holder-
The lens holder 330 is a long plate-shaped member as a whole, and is made of, for example, resin. The lens holder 330 includes a recess 331 on one side of the plate surface (lower surface in FIGS. 2 to 4). The recess 331 extends almost entirely in the long direction (X-axis direction) of the lens holder 330. The edge of the recess 331 has a long rectangular shape as a whole, and both the length and the width are larger than the plate surface of the light source substrate 310. The recess 331 is also deeper than the thickness of the light source substrate 310. Therefore, when the lens holder 330 covers the light source substrate 310 from above as shown in FIG. 2A, the recess 331 is shown in FIGS. 3A, 4A, and 4B. The entire light source substrate 310 is housed inside.

The lens holder 330 further includes a slit 332 on the plate surface (upper surface in FIGS. 2-FIG. 4) opposite to the recess 331. The slit 332 extends almost entirely in the long direction (X-axis direction) of the lens holder 330. The edge of the slit 332 has a long rectangular shape as a whole, and is larger in length and width than the end faces 324 and 325 of the lens array 320. The space inside the slit 332 extends in the height direction of the lens holder 330 (in the Z-axis direction in FIGS. 2 to 4) and communicates with the space inside the recess 331. Therefore, the lens array 320 can be inserted into the slit 332 in a posture in which one of the end faces 324 is directed toward the light emitting surface 315 of the light source substrate 310. Inside the slit 332, the inner surfaces 333 and 334 of the lens holder 330 extend in the long direction (X-axis direction). All of these inner surfaces 333 and 334 are planes parallel to the long direction (X-axis direction), and have high parallelism with each other. When the lens array 320 is inserted into the slit 332, it faces the plate surfaces 321 and 322 one by one. As shown by (b) in FIG. 2, (a) in FIG. 3, and (b) in FIG. 4, each inner surface 333, 334 has both ends and a central portion in the long direction (X-axis direction) of the lens holder 330. Also includes contact portions 335, 336, 337. Each contact portion 335-337 is a protrusion toward the plate surface 321 and 322 of the lens array 320 from the inner surface 333, 334, and has a hemispherical shape having a diameter of several hundred μm to several mm, for example. When the lens array 320 is inserted into the slit 332, these protrusions 335-337 come into contact with the plate surfaces 321 and 322 thereof, that is, the apex of the hemisphere (see (b) in FIG. 4). As a result, the lens holder 330 is a lens array from both sides of the central surface CPL of the lens array 320 parallel to both the long direction (X-axis direction) of the lens array 320 and the optical axis (Z-axis direction) of the GRIN lens 323. The lens array 320 is held so as to sandwich the 320 and to be parallel to the light source substrate 310 in the long direction. In this state, the lens array 320 and the lens holder 330 are fixed to each other with an adhesive (not shown). Details of the contact portion 335-337 will be described later.

[Support structure of optical writing unit]
FIG. 2-FIG. 4 shows a support structure thereof in addition to the optical writing unit 202. This support structure includes a holding base 400 and a plurality of support members 410. The optical writing device according to the embodiment of the present invention is configured by the optical writing unit 202 and the support structure as a whole.

The holding table 400 is a long rod-shaped member fixed to the chassis of the printer 100 (not shown), and is made of a highly rigid material such as electrozinc plated steel (SECC) or stainless steel (SUS). It is made of a channel steel plate made of metal such as aluminum (a steel plate having a "U" shape in cross section). The pedestal surface 401 of the holding table 400 has a substantially plane extending in the long direction (X-axis direction in FIGS. 2-FIG. 4) of the holding table 400 (that is, deviation from the ideal plane is within the allowable range. Curved surface). The pedestal surface 401 is, for example, the back surface of channel steel (the vertical line portion of the “U” shape), and is exposed to light in the normal direction (Z-axis direction) as shown in FIGS. 4 (a) and 4 (b). The body drum 24K is installed so as to be located. The pedestal 401 further supports both edges of the lens holder 330 at both edges in the width direction (Y-axis direction) as shown in FIGS. 4A and 4B, and as shown in FIG. 3A. Both ends of the lens holder 330 are supported at both ends in the long direction (X-axis direction). In this state, the countertop 401 and the lens holder 330 are fixed to each other with an adhesive (not shown).

Each support member 410 is a pin made of a highly rigid material such as metal or hard resin, and has a cylindrical shape having a diameter of several mm and a length of several mm to a dozen or so mm, for example. The tip surface (upper end surface in FIGS. 2-FIG. 4) of each support member 410 is a plane perpendicular to the long direction (Z-axis direction in the figure). Each support member 410 protrudes from the through hole of the pedestal surface 401 in the normal direction of the pedestal surface 401 (positive direction of the Z axis in the figure), and the tip surface contacts the vicinity of the light emitting region 311 in the light source substrate 310, particularly the sealing member 312. Let me. The distance (height in the figure) from the pedestal surface 401 to the tip surface of the support member 410 is, for example, several tens of μm to several hundred μm, and in the assembly process of the optical writing unit 202, for each support member 410, for example, several hundred nm-. It can be adjusted in units of several μm.

In the example shown in FIG. 2-FIG. 4, two through holes of the pedestal surface 401 are arranged in the width direction (Y-axis direction) of the pedestal surface 401, and are equally spaced in the long direction (X-axis direction) of the pedestal surface 401, for example, several cm. Several to a dozen are lined up at intervals. Therefore, the support members 410 are arranged in two rows similar to these through holes, and the tip surface is brought into contact with the central portion in the width direction of the light source substrate 310 at a plurality of points in the elongated direction thereof. As a result, the light source substrate 310 is kept parallel in the length direction (X-axis direction) and the width direction (Y-axis direction) of the pedestal surface 401 in the length direction and the width direction, respectively.

[Contact part of lens holder with respect to lens array]
As shown in FIG. 2B, the contact portions 335-337 of the lens holder 330 are paired with the lens array 320 between both end portions and the center portion in the long direction (X-axis direction) of the lens holder 330. They are facing each other across the board. As shown in FIG. 3A, these contact portions 335-337 are located equidistant from the pedestal surface 401 of the holding pedestal 400, that is, at the same height HFX. As a result, the points where the contact portion 335-337 comes into contact with the lens array 320 are all parallel to each other of the inner surfaces 333 and 334 of the lens holder 330 and with respect to the normal direction (Z-axis direction) of the base surface 401 of the holding base 400. Regardless of the parallelism, the height HFX from the pedestal 401 is equal. This is due to the following reasons.

FIG. 4D is a partial cross-sectional view of the lens holder 330 including one of the contact portions 336. When the lens holder 330 is fixed to the pedestal surface 401 of the holding table 400 in the process of assembling the optical writing unit 202, the hemispherical center CNT of each contact portion 335-337 is positioned equidistant from the pedestal surface 401 to the HFX. .. In this case, even if the inner surface 334 of the lens holder 330 located inside the slit 332 is tilted from the normal direction (Z-axis direction) of the pedestal surface 401, the hemispherical surface of the contact portion 336 is located on the pedestal surface 401 from the center CNT thereof. The farthest point PDM in the width direction (Y-axis direction) is maintained at the same value HFX as the center CNT at a distance from the pedestal 401. Since this farthest point PDM comes into contact with the plate surface of the lens array 320 inserted into the slit 332, the contact point PDM with the lens array 320 of any contact portion 335-337 is at the same height as the table surface 401 of the holding table 400. It is located in HFX.

In the assembly process of the optical writing unit 202, the light source substrate 310 and the lens holder 330 are first positioned on the table surface 401 of the holding table 400 and fixed by a jig. Next, the lens array 320 is inserted into the slit 332, and its longitudinal direction is adjusted to be parallel to the pedestal surface 401. At this stage, the lens array 320 is still only sandwiched between the contact portions 335-337 facing each other. In each of the contact portions 335-337, the contact point PDM with the lens array 320 is located at the same height HFX from the pedestal surface 401. Therefore, the lens array 320 is rotatable around the line of intersection LNT between the virtual plane VPL parallel to the pedestal 401 including all of these contact points PDM and the center plane CPL of the lens array 320 (FIG. 4 (FIG. 4). b) See). In particular, the line of intersection LNT, that is, the axis of rotation of the lens array 320, is maintained at the same height from the table surface 401 regardless of the angle of rotation of the lens array 320. In the assembling step of the optical writing unit 202, the light emitting region 311 of the light source substrate 310 is subsequently made to emit light, and the position of the imaging point by the lens array 320 is measured. From the result of this measurement, the inclination of the optical axis of the GRIN lens 323 with respect to the normal direction (Z-axis direction) of the table surface 401 is specified. The adjustment of the rotation angle of the lens array 320 around the line of intersection LNT and the position measurement of the imaging point by the lens array 320 are repeated so that this inclination is removed. During this period, the rotation axis of the lens array 320 is maintained at the same height from the table surface 401, so that the distance from the outer peripheral surface 241 of the photoconductor drum 24K to the lens array 320 does not change. Therefore, the position of the lens array 320 does not need to be readjusted except for the angle of rotation. In this way, the inclination of the optical axis of the GRIN lens 323 with respect to the normal direction (Z-axis direction) of the pedestal surface 401 is easily removed regardless of the flatness and parallelism of the inner surface 333 and 334 of the lens holder 330.

[Adhesive layer between lens array and lens holder]
After the inclination of the optical axis of the GRIN lens 323 with respect to the normal direction (Z-axis direction) of the table surface 401 of the holding table 400 is removed, the lens array 320 is fixed to the lens holder 330 with an adhesive. At this time, the adhesive layer formed of the cured adhesive is preferably given appropriate elasticity under the following conditions, and the arrangement in the slit 332 is determined.

When the temperature rises due to the heat generated by the light emitting element in the light source substrate 310 and its drive circuit, the light source substrate 310, the lens array 320, the lens holder 330, and the base surface 401 of the holding base 400 are all particularly long due to thermal expansion. It greatly extends in the direction (X-axis direction). The amount of extension at this time differs between these members 310-330 and 401. When the temperature rise is excessive, the deviation of the optical axis between the light emitting element and the GRIN lens due to the difference between these elongation amounts becomes excessive, and the position error of the imaging point on the outer peripheral surface 241 of the photoconductor drum 24K becomes excessive. Can approach the permissible upper limit. In order to suppress this positional error as much as possible, the starting point (fixed point) of thermal expansion with respect to the pedestal surface 401 is set to the center in the common long direction (X-axis direction) for all of the light source substrate 310, the lens array 320, and the lens holder 330. You just have to have it.

5A and 5B are partial cross-sectional views of the lens holder 330 in a state where the lens array 320 is fixed with an adhesive, and FIG. 5C is a partial upper surface of the lens holder 330. It is a figure. As shown by the straight lines aa and bb in FIG. 5 (c), the cross section shown in FIG. 5 (a) includes the central contact portion 335 in the long direction (X-axis direction) of the lens array 320. , The cross section shown in FIG. 5B includes a contact portion 336 at one end.

The adhesive layer between the lens array 320 and the lens holder 330 includes a thin layer adhesive portion 501 and a thick adhesive portion 502. As shown in FIG. 5A, the thin-layer adhesive portion 501 is a thin film of adhesive that is filled and cured in the gap between the tip PDM of the central contact portion 335 and the plate surface of the lens array 320, and is a lens. The thickness of the holder 330 in the width direction (Y-axis direction) is about the same as the surface roughness of the contact portion 335, for example, several μm. As shown in FIG. 5B, the thick-walled adhesive portion 502 has the edge of the slit 332 and the plate of the lens array 320 whose position in the long direction (X-axis direction) of the lens holder 330 is equal to the contact portion 336 at one end. It is a layer of adhesive that is filled and hardened in the gap between the surface and the surface. The thick-walled adhesive portion 502 is also formed in the gap between the edge of the slit 332 and the plate surface of the lens array 320 whose position in the long direction (X-axis direction) of the lens holder 330 is equal to the contact portion 337 at the opposite end. ing. As shown in FIG. 5C, the thickness of the thick-walled adhesive portion 502 in the width direction (Y-axis direction) of the lens holder 330 is about the same as the gap between the edge of the slit 332 and the lens array 320, for example, a number. It is tens of μm to several hundreds of μm, and the center of the contact portion 336 and 337 at one end in the long direction (X-axis direction) is at the same position. The adhesive is, for example, an elastic adhesive such as a silicone resin, and both the adhesive portions 501 and 502 have sufficiently high rigidity, that is, adhesive strength with respect to the weight of the lens array 320. On the other hand, the thin layer adhesive portion 501 is considerably thinner than the thick adhesive portion 502, and is only 0.01-0.1 times thicker, so that it is parallel to the long direction (X-axis direction) of the lens holder 330. High rigidity (shear elastic modulus) against a large shear force. As a result, in the lens array 320, the contact point with the central contact portion 335 always becomes the starting point (immobility point) of thermal expansion in the long direction (X-axis direction), and the portions of the lens array 320 located on both sides thereof are long. It extends in the direction (X-axis direction) to increase the distance from the starting point. This is due to the following reasons. The thermal stress generated in the adhesive layers 501 and 502 due to the difference in the amount of thermal expansion between the lens array 320 and the lens holder 330 is a shear force SHF parallel to the long direction (X-axis direction). Therefore, if the thermal stress SHF is of the same strength, the thick-walled adhesive portion 502 bends in the long direction (X-axis direction) before the thin-layer adhesive portion 501 (see (c) in FIG. 5). The upper limit of the area of the thick-walled adhesive portion 502 is designed so that this deflection occurs according to the thermal stress. Similar measures are taken for the adhesive layer between the light source substrate 310 and the pedestal surface 401, and the adhesive layer between the lens holder 330 and the pedestal surface 401. As a result, the light source substrate 310, the lens array 320, and the lens holder 330 all have a starting point (fixed point) of thermal expansion with respect to the pedestal surface 401 in the center of the long direction (X-axis direction). Therefore, even if the temperature rise is excessive, the excessive deviation of the optical axis between the light emitting element and the GRIN lens due to the difference in the amount of thermal expansion is caused by both ends of the lens array 320 in the long direction (X-axis direction). The positional error of the imaging point on the outer peripheral surface 241 of the photoconductor drum 24K is suppressed in the central portion in the main scanning direction.

[Advantages of Embodiment]
In the printer 100 according to the embodiment of the present invention, as described above, the lens holder 330 of the optical writing unit 202 touches each of the inner surfaces 333 and 334 facing the lens array 320 on both sides of the central surface CPL of the lens array 320. Includes -337. These contact portions 335-337 are provided at the center and both ends of the lens array 320 in the long direction (X-axis direction) in the normal direction (Z-axis direction) of the lens array 320 and the pedestal surface 401 of the holding table 400. Make point contact. In any of the contact portions 335-337, the contact point PDM is located equidistant from the table surface 401 of the holding table 400 to the HFX. Therefore, the lens array 320 is rotatable around the line of intersection LNT between the virtual plane VPL containing all of these contact points PDM and the center plane CPL of the lens array 320. This rotation axis LNT is maintained at the same height HFX from the table surface 401 regardless of the rotation angle of the lens array 320. That is, during the work of removing the inclination of the optical axis of the GRIN lens 323 with respect to the normal direction (Z-axis direction) of the pedestal surface 401, the rotation axis LNT of the lens array 320 is maintained at the same height HFX from the pedestal surface 401. The distance from the outer peripheral surface 241 of the photoconductor drum 24K to the lens array 320 does not change either. Therefore, the position of the lens array 320 does not need to be readjusted except for the angle of rotation. In this way, the optical writing unit 202 removes the inclination of the optical axis of the GRIN lens 323 with respect to the normal direction (Z-axis direction) of the pedestal surface 401 regardless of the flatness and parallelism of the inner surface 333 and 334 of the lens holder 330. Can be simplified.

[Modification example]
(A) The image forming apparatus 100 shown in FIG. 1 is an intermediate transfer type color printer including a tandem-arranged photoconductor unit 20Y-20K and an intermediate transfer belt 21. The image forming apparatus according to the embodiment of the present invention may also be a direct transfer type color printer, monochrome printer, facsimile machine, copier, or multifunction device (MFP).

(B) In (c) of FIG. 1, the outer peripheral surface 241 of the drum 24K is covered with a photoconductor. Alternatively, instead of the drum 24K, the outer peripheral surface of the belt may be covered with a photoconductor. Like the drum 24K, this belt is arranged so as to be surrounded by a charging unit, a developing unit, a cleaning blade, and an eraser. When the belt makes one rotation, each surface portion of the photoconductor faces these processing portions in order, and undergoes charging, exposure, development, transfer, cleaning, and static elimination processing.

(C) In the light source substrate 310 shown in FIG. 3 (c), the arrangement of the OLEDs is a three-row staggered arrangement along the long direction of the light source substrate 310. In addition, the arrangement of the light emitting elements may have 1, 2, or 4 or more rows, and may have a grid arrangement instead of the staggered arrangement.

(D) The contact portion 335-337 shown in FIGS. 2 to 4 is a hemispherical protrusion protruding from the inner surface 333 of the lens holder 330 toward the plate surface 321 and 322 of the lens array 320. However, the present invention is not limited to this example, and the contact portion may have another shape. In the cross section of the contact portion (the cross section perpendicular to the long direction (X-axis direction) of the lens holder 330), the contact point with the lens array 320 and its vicinity form an arc, and the center of the arc eventually becomes. The contact portion may also be located at an equal distance from the platform surface 401 of the holding platform 400. Further, the contact portion may be integrally molded with the lens holder 330, or may be another member such as a pin fitted in the hole of the lens holder 330.

The contact portions 335-337 shown in FIGS. 2 to 4 are provided at three locations, a central portion and both end portions, in the long direction (X-axis direction) of the lens holder 330. However, the present invention is not limited to this example, and the contact portion may be only one location, two locations, or four or more locations in the long direction. Further, the point contact may be made only in the normal direction (Z-axis direction) of the table surface 401, or may be a line contact in the long direction (X-axis direction) of the lens holder 330. That is, the contact portion may be a rod-shaped protrusion extending in the elongated direction on the inner surface 333, 334 of the lens holder 330.

(E) The adhesive layers 501 and 502 between the lens array 320 and the lens holder 330 shown in FIG. 5 are centered at the contact portion 335-337 of the lens holder 330 and the lens holder 330 in the long direction (X-axis direction). Is common. Not limited to this example, the adhesive layer may have another arrangement. For example, each adhesive layer has a larger number than the contact portion 335-337 of the lens holder 330 even if the center position of the lens holder 330 in the long direction (X-axis direction) is deviated from the contact portion 335-337. May be good. Further, the deviation of the optical axis between the light emitting element and the GRIN lens due to the difference in the amount of thermal expansion between the light source substrate 310, the lens array 320, the lens holder 330, and the table surface 401 of the holding table 400 does not become a problem. The thin layer adhesive portion 501 may be omitted, and the adhesive layer may be provided over the entire circumference of the slit 332.

(F) Since the lens array 320 is simply sandwiched between the protrusions 335-337 of the lens holder 330 until it is adhered to the lens holder 330, the table surface 401 of the holding table 400 may be affected by vibration or impact received from the outside. Can be displaced in the normal direction (Z-axis direction) of. Even after the lens array 320 is adhered to the lens holder 330, there remains a risk that the displacement of the pedestal surface 401 in the normal direction (Z-axis direction) due to the creep distortion of the adhesive layer due to the weight of the lens array 320 remains excessive. .. A structure for preventing these displacements (hereinafter referred to as a stopper) may be further added to both the lens array 320 and the lens holder 330.

FIG. 6A is a perspective view of one end of the optical writing unit 202 to which an example of the stopper is added in the long direction (X-axis direction). Since the outer part (positive direction of the X-axis) is cut off from this end in the long direction, the cross section of the stopper can be seen. FIG. 6B is a cross-sectional view of the optical writing unit 202 along the straight line bb shown in FIG. 6A, and FIG. 6C is a front view of the cross section shown in FIG. 6A. The stopper includes a rocker member 601 and a receiving portion 602. Although not shown, a similar stopper is preferably attached to the other end of the optical writing unit 202. The stopper may be provided inside the end of the optical writing unit 202 as long as the light from the light source substrate 310 is not blocked.

FIG. 6D is a perspective view of a single rocker member 601. The rocker member 601 is, for example, a semi-cylindrical metal member or a resin member whose diameter is longer than the width (size in the Y-axis direction) of the lens array 320. The rocker member 601 may be an integrally molded product or an aggregate in which two or more parts are combined. There is a recess 612 in the plane region 611 (upper surface in the figure) including the semi-cylindrical shaft AXS on the outer surface of the rocker member 601. The recess 612 is a rectangular parallelepiped hole symmetrical with respect to the axis AXS of the rocker member 601. The width WDT (size in the Y-axis direction in the figure) is equal to the width of the lens array 320, and the depth DPT (Z-axis in the figure). The size in the direction) is equal to half the height of the lens array 320. As shown in FIG. 6A, the end portion of the lens array 320 is inserted into the recess 612. As a result, the axis AXS of the rocker member 601 extends on the central surface CPL of the lens array 320 in the long direction (X-axis direction) of the lens array 320, and the outer peripheral surface 613 of the rocker member 601 has the axis AXS as the central axis. It becomes half of the cylindrical surface.

The receiving portion 602 is a pair of protrusions protruding in the height direction (Z-axis direction) from the end portion in the long direction (X-axis direction) of the plate surface of the lens holder 330 including the slit 332. These protrusion pairs have a shape symmetrical with respect to the central plane perpendicular to the width direction (Y-axis direction) of the lens holder 330, and the slope 621 inclined from the height direction (Z-axis direction) of the lens holder 330. , 622, respectively. These slopes 621 and 622 face each other with the space inside the slit 332 interposed therebetween, and the closer they are to the inside of the slit 332, the closer to the light source substrate 310 (lower in the figure). The distance between the slopes 621 and 622 is wider than the diameter of the rocker member 601 at the portion farthest from the light source substrate 310 (upper end in the figure) and narrower than the diameter at the nearest portion (lower end in the figure). Therefore, when the lens array 320 is inserted into the slit 332, the outer peripheral surface 613 of the rocker member 601 makes point contact with the slopes 621 and 622 of the receiving portion 602 in the height direction (Z-axis direction). That is, these slopes 621 and 622 are included in the contact portion of the lens holder 330 together with the protrusions 335-337. In particular, since these slopes 621 and 622 are inclined from the normal direction (Z-axis direction) of the pedestal surface 401 of the holding table 400, the distance of the lens array 320 from the pedestal surface 401 due to contact with the outer peripheral surface 612 of the rocker member 601 ( Height) is decided. This height is designed to meet the following conditions. As shown in FIGS. 6B and 6C, the axis AXS of the rocker member 601 is from the pedestal surface 401 together with the central CNT of the contact portion 336 of the lens holder 330, that is, the contact point PDM between the lens array 320 and the lens holder 330. Positioned equidistant HFX. As a result, the axis AXS of the rocker member 601 is located on the same straight line as the rotation axis LNT of the lens array 320.

In the process of assembling the optical writing unit 202, when the lens array 320 rotates around the rotation axis LNT, the rocker member 601 also rotates around the same axis AXS. At this time, the distance from the axis AXS of the rocker member 601 to the contact point STP between the outer peripheral surface 613 and the slopes 621 and 622 of the receiving portion 602 is maintained equal to the radius RRC of the rocker member 601. Therefore, the axis AXS of the rocker member 601 and the rotation axis LNT of the lens array 320 are maintained at the same height HFX from the table surface 401 regardless of the rotation angle of the lens array 320, so that the outer peripheral surface 241 of the photoconductor drum 24K is maintained. The distance from the lens array 320 to the lens array 320 does not change either. Therefore, the position of the lens array 320 does not need to be readjusted except for the angle of rotation. In particular, since the rocker member 601 is supported by the receiving portion 602, the height of the lens array 320 from the pedestal surface 401 is more stably maintained at a constant value HFX while the rotation angle of the lens array 320 is being adjusted. In this way, the optical writing unit 202 can further simplify the work of removing the inclination of the optical axis of the GRIN lens 323 with respect to the normal direction (Z-axis direction) of the table surface 401.

Note that the recess 612 of the rocker member 601 may be a notch without a bottom 614, unlike (d) in FIG. When the end portion of the lens array 320 is inserted into the recess 612, if there is no bottom 614 shown by the broken line in FIG. The height of the array 320 is not completely determined. However, unlike the contact portion 335-337 of the lens holder 330, the rocker member 601 comes into surface contact with the plate surface of the lens array 320, so that the frictional force applied to the plate surface is strong. Therefore, the lens array 320 is less likely to be displaced in the normal direction (Z-axis direction) of the pedestal surface 401 than when it is sandwiched only by the contact portion 335-337. Thereby, even after removing the inclination of the optical axis of the GRIN lens 323 with respect to the normal direction (Z-axis direction), the height of the lens array 320 from the table surface 401 can be further finely adjusted as needed.

(G) In the assembly process of the optical writing unit 202, the lens array 320 is directly supported by a jig and rotated around the rotation shaft LNT. In addition, a structure for transmitting an external rotational force to the lens array 320 (hereinafter referred to as a torque transmission unit) may be provided at the end of the lens array 320.

FIG. 7A is a perspective view of one end of the optical writing unit 202 to which an example of the torque transmission unit is added in the long direction (X-axis direction). Since the outer side (positive direction of the X-axis) is cut off from this end in the long direction, the cross section of the torque transmission part can be seen. FIG. 7B is a front view of the cross section thereof. The torque transmitting portion includes a pin 701 and a receiving portion 702. Although not shown in the figure, a similar torque transmission unit may be added to the other end of the optical writing unit 202.

The pin 701 is, for example, a cylindrical metal member or a resin member whose diameter is shorter than the width (size in the Y-axis direction) of the lens array 320. One end surface of the pin 701 is adhered to or embedded in one end surface of the lens array 320 in the long direction (X-axis direction), and in particular, the axis SHF of the pin 701 is in the long direction (X-axis direction) of the lens array 320. ) Is located on the extension of its central axis.

The receiving portion 702 is a notch provided at the edge of the slit 332 in the long direction (X-axis direction) of the lens holder 330. The notch 702 has a shape symmetrical with respect to the central plane perpendicular to the width direction (Y-axis direction) of the lens holder 330, and the slope 721 inclined from the height direction (Z-axis direction) of the lens holder 330. , 722. These slopes 721 and 722 face each other with the space inside the notch 702 interposed therebetween, and the closer they are to the inside of the notch 702, the closer to the light source substrate 310 (lower in the figure). The distance between the slopes 721 and 722 is wider than the diameter of the pin 701 at the portion farthest from the light source substrate 310 (upper end in the figure) and narrower than the diameter at the nearest portion (lower end in the figure). Therefore, when the lens array 320 is inserted into the slit 332, the outer peripheral surface 711 of the pin 701 comes into contact with the slopes 721 and 722 of the receiving portion 702, so that the distance (height) of the lens array 320 from the table surface 401 of the holding table 400 is reached. ) Is decided. This height is designed to meet the following conditions. The axis SHF of the pin 701 is positioned at the same height HFX as the center of the contact portion 335-337 of the lens holder 330 with respect to the pedestal surface 401. As a result, the central axis SHF of the lens array 320 coincides with the rotation axis LNT of the lens array 320 determined by the contact point between the plate surface of the lens array 320 and the contact portion 335-337 of the lens holder 330.

In the assembly process of the optical writing unit 202, in order to rotate the lens array 320 around the rotation axis LNT, the pin 701 may be rotated. At this time, the distance from the axis SHF of the pin 701 to the contact point STP between the outer peripheral surface 711 and the slopes 721 and 722 of the receiving portion 702 is maintained equal to the radius RPN of the pin 701. Therefore, the axis SHF of the pin 701 and the rotation axis LNT of the lens array 320 are maintained at the same height HFX from the table surface 401 regardless of the rotation angle of the lens array 320, so that from the outer peripheral surface 241 of the photoconductor drum 24K. The distance to the lens array 320 does not change either. Therefore, the position of the lens array 320 does not need to be readjusted except for the angle of rotation. In particular, since the pin 701 is supported by the receiving portion 702, the height of the lens array 320 from the table surface 401 is more stably maintained at a constant value HFX while the rotation angle of the lens array 320 is being adjusted. Further, since the jig does not have to be brought into direct contact with the lens array 320, the risk of accidentally displacing the lens array 320 is low. Further, the torque required for rotation of the lens array 320 can be easily designed by the diameter of the pin 701 and the contact area between the pin 701 and the receiving portion 702. In this way, the optical writing unit 202 can further simplify the work of removing the inclination of the optical axis of the GRIN lens 323 with respect to the normal direction (Z-axis direction) of the table surface 401.

The stoppers 601 and 602 shown in FIG. 6 may be further added to the inside of the torque transmission units 701 and 702 as long as the light from the light source substrate 310 is not blocked.

The present invention relates to an optical writing device included in an electrophotographic image forming apparatus, as described above, the lens array is held by point contact with a lens holder, and all contact points are maintained at the same height. As such, the invention is clearly industrially applicable.

100 Printer 20Y, 20M, 20C, 20K Photoreceptor Unit 21 Intermediate Transfer Belt 21L Driven Pulley 21R Drive Pulley 22Y, 22M, 22C, 22K Primary Transfer Roller 23 Secondary Transfer Roller 24Y, 24M, 24C, 24K Photoreceptor Drum 202 Light Writing unit 310 Light source board 311 Light emitting area 312 Sealing member 313 IC chip 314, 315 Light source board plate surface 320 Lens array 321, 322 Lens array plate surface 323 GRIN lens 324, 325 Lens array end surface 330 Lens holder 331 lens Holder recess 332 Slit 333 334 Lens holder inner surface 335-337 Lens holder contact part 400 Holding base 401 Holding base base surface 410 Support member

Claims (8)

An optical writing device that writes information to a photoconductor with light.
A holding table that includes a flat table surface and is installed so that the table surface faces the photoconductor.
A light source substrate that has a long plate shape as a whole, includes a light emitting region extending in the long direction, and is held by the holding table so that the table surface and the plate surface of the holding table are parallel to each other. ,
A lens array that has a long plate shape as a whole and includes an array of lenses that are lined up in the long direction with the optical axis aligned in one of the directions perpendicular to the long direction.
The lens array is sandwiched from both sides of the central surface of the lens array parallel to both the long direction of the lens array and the optical axis of each lens, and the lens is parallel to the light source substrate in the long direction. With the holding member holding the array
Equipped with
Each of the surfaces of the holding member facing the lens array on both sides of the central surface of the lens array is normal to the lens array and the pedestal surface of the holding table at at least one position in the longitudinal direction of the lens array. Includes contact points that make point contact in the direction
The contact points between the contact portion of the holding member and the lens array are all located equidistant from the table surface of the holding table.
The position where the lens array makes point contact with the contact portion of the holding member in the normal direction of the table surface of the holding table includes the central portion in the elongated direction of the lens array.
In the central portion, the gap between the lens array and the contact portion of the holding member is thinly bonded.
An optical writing device characterized in that a gap between the lens array and the holding member is thickly adhered to other than the central portion. The contact portion of the holding member is
The optical writing device according to claim 1, further comprising a protrusion that projects toward the lens array and makes point contact with the lens array at the tip in the normal direction of the pedestal surface of the holding table. The holding member includes an adhesive layer that adheres the lens array to itself.
Until the adhesive layer is formed, the lens array has a plane parallel to the pedestal surface of the holding table including all contact points between the lens array and the contact portion of the holding member, and a central surface of the lens array. The optical writing device according to claim 1 or 2, wherein the optical writing device is rotatable around an intersection line between the two. The lens array is
It includes at least a part of a cylindrical surface having a straight line extending in the long direction of the lens array as a central axis on the central surface of the lens array, and includes a curved surface facing the contact portion of the holding member.
The contact portion of the holding member is
Any of claims 1 to 3 including a curved surface of the lens array that is tilted from a common optical axis direction between the lenses of the lens array and includes a slope that makes point contact in the normal direction of the pedestal surface of the holding table. The optical writing device described in Kana. The holding member includes an adhesive layer that adheres the lens array to itself.
From claim 1, the lens array can be displaced in the normal direction of the pedestal surface of the holding table while being sandwiched between the contact portions of the holding member until the adhesive layer is formed. The optical writing device according to any one of claims 4. The optical writing device according to any one of claims 1 to 5 , wherein the holding member is composed of a member in which the contact portion and the portion other than the contact portion are different from each other. An optical writing device that writes information to a photoconductor with light.
A holding table that includes a flat table surface and is installed so that the table surface faces the photoconductor.
A light source substrate that has a long plate shape as a whole, includes a light emitting region extending in the long direction, and is held by the holding table so that the table surface and the plate surface of the holding table are parallel to each other. ,
A lens array that has a long plate shape as a whole and includes an array of lenses that are lined up in the long direction with the optical axis aligned in one of the directions perpendicular to the long direction.
The lens array is sandwiched from both sides of the central surface of the lens array parallel to both the long direction of the lens array and the optical axis of each lens, and the lens is parallel to the light source substrate in the long direction. With the holding member holding the array
Equipped with
Each of the surfaces of the holding member facing the lens array on both sides of the central surface of the lens array is normal to the lens array and the pedestal surface of the holding table at at least one position in the longitudinal direction of the lens array. Includes contact points that make point contact in the direction
The contact points between the contact portion of the holding member and the lens array are all located equidistant from the table surface of the holding table.
The lens array is
A curved surface that includes at least a part of a cylindrical surface having a straight line extending in the long direction of the lens array as a central axis on the central surface of the lens array and faces the contact portion of the holding member.
Including
The contact portion of the holding member is
A slope that is tilted from a common optical axis direction between the lenses of the lens array and makes point contact with the curved surface of the lens array in the normal direction of the pedestal surface of the holding table.
Including
The lens array is rotatable around the line of intersection between a plane parallel to the pedestal surface of the holding table including all contact points between the lens array and the contact portion of the holding member and the center surface of the lens array. Yes, the line of intersection and the central axis of the cylindrical surface are located on the same straight line.
An optical writing device characterized by this. It is an electrophotographic image forming device.
Photoreceptor and
The optical writing device according to any one of claims 1 to 7, wherein the surface of the photoconductor is exposed to form an electrostatic latent image.
A developing unit that develops the electrostatic latent image with toner,
A transfer unit that transfers the toner image developed by the developing unit from the photoconductor to the sheet, and a transfer unit.
An image forming apparatus equipped with.

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