JP2013080182A - Exposure device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a temperature difference caused inside a casing with rotation of a polygon mirror, thereby reducing the strain of the casing.SOLUTION: Polygon mirrors 114Y-114K of laser scanners 110Y-110K are arranged at positions where their rotation centers are away from the centers of respective casings 111Y-111K, and casing faces (high temperature faces) on the nearer side to the rotation centers of the polygon mirrors 114Y-114K and casing faces (low temperature sides) on the farther side from the rotation centers are connected with high heat transfer members 151 having higher heat conductivity than the casings 111Y-111K.

Description

  The present invention relates to an exposure apparatus including a plurality of units each including a rotating mirror, a lens that guides light reflected by the mirror to a photosensitive member, and a housing that houses the mirror and the lens.

  A printer that forms toner images of different colors on a plurality of photoconductors and outputs a full color image is known. In addition, a configuration is known that employs a laser scanner to form an electrostatic image that is developed into a toner image on a photoreceptor.

  The laser scanner includes a mirror (polygon mirror) that rotates and reflects light to scan, a lens that guides the light reflected by the polygon mirror to a photosensitive member, and a housing that houses the polygon mirror and the lens.

  Here, the polygon mirror is arranged in the housing, and the housing is deformed by heat generated by the rotation of the polygon mirror. When the housing is deformed, a minute shift occurs in the positional relationship between the polygon mirror and the lens arranged inside the housing, and as a result, the electrostatic image formed by the laser scanner on the photoconductor is tilted or curved.

  In particular, in a configuration in which a plurality of laser scanners expose to different photoconductors, if the temperature distribution inside each laser scanner is different, the electrostatic image formed on each photoconductor is similarly deformed (tilted or curved). Color misregistration occurs.

  In order to suppress color misregistration, Patent Document 1 uses a heat transfer member having a higher thermal conductivity than the housing material of the laser scanner so that the temperature distribution in each housing is similar. It is disclosed.

  Specifically, in a laser scanner in which a polygon mirror as a heat source is deviated from the center of the housing, the temperature on the side where the polygon mirror inside the housing is located (high temperature portion) is the temperature on the side where the polygon mirror is not located (low temperature portion) Higher than. In such a configuration, the high temperature portions of adjacent laser scanners are connected by a heat transfer member, and the low temperature portions are connected by different heat transfer members, thereby making the temperature distribution inside each laser scanner substantially similar. Is disclosed.

JP 2005-305897 A

  As in Japanese Patent Application Laid-Open No. 2004-133620, color distribution can be reduced by making the temperature distribution inside each laser scanner substantially similar and by making the distortion of the electrostatic images formed on each photoconductor substantially the same. However, even if the temperature distribution inside each laser scanner is substantially similar, the distortion (decrease in geometric accuracy) itself due to heat generation cannot be reduced.

  Specifically, in a laser scanner in which a polygon mirror as a heat source is deviated from the center of the housing, the temperature on the side where the polygon mirror inside the housing is located (high temperature portion) is the temperature on the side where the polygon mirror is not located (low temperature portion) Higher than. Naturally, the housing is distorted due to the difference between the deformation amount of the high temperature portion and the deformation amount of the low temperature portion of the housing, and the geometric accuracy of the electrostatic image formed on the photoconductor by the laser scanner is lowered.

  Therefore, an object is to reduce the distortion of the casing by reducing the temperature difference generated inside the casing as the polygon mirror rotates.

  Therefore, the exposure apparatus of the present invention is provided with “a rotatable mirror and a housing for housing the mirror, and the center of rotation of the mirror is a distance from the first surface to the first surface. An exposure apparatus comprising a plurality of units closer than the distance to two surfaces, wherein the first surface and the second surface of the units adjacent to each other among the plurality of units have heat conductivity higher than that of the housing. It is characterized by being connected by members ".

  The distortion of the casing can be reduced by reducing the temperature difference generated inside the casing as the polygon mirror rotates.

1 is a diagram for explaining a schematic configuration of an image forming apparatus. It is the schematic for demonstrating the structure of a laser scanner. It is a figure for demonstrating the connected optical box. It is an enlarged view for demonstrating the connection part of an optical box. It is the graph which showed the heat transfer simulation result. It is a figure for demonstrating the connected optical box. It is a figure for demonstrating the connected optical box.

  Hereinafter, the image forming apparatus according to the present invention will be described in more detail with reference to the drawings. Note that the dimensions, materials, shapes, relative positions, and the like of the components of the image forming apparatus are not intended to limit the scope of the present invention only to those unless otherwise specified.

  Hereinafter, after describing the schematic configuration of the printer, the laser scanner of this embodiment will be described in detail.

§1. {About the schematic configuration of the printer}
FIG. 1 is a diagram for explaining a schematic configuration of a tandem color printer (image forming apparatus) 100.

  The printer 100 includes photosensitive drums 101Y to 101K as image carriers that carry toner images corresponding to yellow, magenta, cyan, and black colors. Further, the printer 100 includes laser scanners 110Y to 110K as exposure apparatuses corresponding to yellow, magenta, cyan, and black colors.

  The photosensitive drums 101Y to 101K rotate in the directions of arrows, respectively, and primary chargers 102Y to 102Y and developing devices 103Y to 103K are arranged in the rotation direction. The surface of each of the photosensitive drums 101Y to 101K is charged by primary chargers 102Y to 102K as corresponding charging means. Then, the laser scanners 110Y to 110K as exposure devices irradiate (scan) the laser beams (113Y to 113K) to the charged photosensitive drums. The electrostatic image formed on the photosensitive member by exposure is developed into a toner image by developing units 103Y to 103K as developing means.

  The developed toner images of the respective colors are transferred to an intermediate transfer belt 121 as an intermediate transfer member, and the toners remaining on the photosensitive drums 101Y to 101K without being transferred are cleaned by the cleaning devices 104Y to 104K.

  The full-color toner image superimposed on the intermediate transfer belt is transferred onto a sheet 132 as a recording material conveyed from the cassette 131. Specifically, the paper 132 fed from the cassette 131 is conveyed to the registration roller pair by the paper feed roller pair and the paper feed guide. In accordance with the image formation timing, the registration roller pair conveys the sheet to the secondary transfer unit.

  The toner image carried on the intermediate transfer belt 121 is transferred onto a sheet as a recording material by a transfer roller 124. The toner image transferred onto the paper is fixed onto the recording material by the fixing unit 141, and the paper on which the image has been fixed is discharged out of the apparatus by a paper discharge roller.

  The above is the description regarding the schematic configuration of the printer 100. Next, the laser scanner as the exposure apparatus of this embodiment will be described in detail.

§2. {About laser scanners}
Subsequently, a single laser scanner as a unit accommodating a polygon mirror as a rotating polygonal mirror of this embodiment will be described in detail.

■ (About the layout of each element inside the optical box)
FIG. 2 is a schematic diagram for explaining the inside of the laser scanner 110 of the present embodiment. The laser scanner 110 includes a semiconductor laser 112 as a light source, optical elements such as a rotatable polygon mirror 114, a lens 115, and a mirror 116 as an optical deflector, and an optical box 111 as a housing for housing them.

  The semiconductor laser 112 is driven in accordance with image information input to the printer 100, and the laser beam 113 is irradiated onto the polygon mirror 114 that rotates at high speed. The laser beam 113 deflected and reflected by the polygon mirror 114 is guided to the photosensitive member by the lens 115 and the mirror 116.

  Here, the polygon mirror 114 that rotates at high speed is arranged to be deviated from the center of the optical box 111 to the left side of FIG. This is because if the polygon mirror 114 is arranged at the center of the optical box 111, the space inside the optical box cannot be effectively used to secure the optical path length from the semiconductor laser 112 to the photosensitive member 101.

  As described above, in the configuration in which the polygon mirror 114 is arranged to be deviated to the left in FIG. 2, the temperature rises in the vicinity of the polygon mirror 114 as the polygon mirror 114 rotates. Here, when the heat generated by the rotation of the polygon mirror is about 4 W, and the structural material of the casing 111 is aluminum (specifically, an aluminum alloy), there is a gap between the high temperature part near the polygon mirror and the low temperature part near the mirror 116. A temperature difference of about 2 ° C. will occur. The above is the detailed configuration of the laser scanner alone and the temperature distribution inside the optical box. Although the material used as the housing can reduce the temperature difference by using a material having high thermal conductivity, it is more important to make a housing with high geometric accuracy easily. Therefore, an aluminum alloy having excellent machinability and the like and capable of easily creating a highly geometrical precision casing is used for the casing of this example.

■ (Connecting optical boxes to reduce temperature distribution)
FIG. 3 is a diagram for explaining the arrangement of the laser scanner according to the present embodiment. FIG. 3A is a plan view for explaining the arrangement of a plurality of laser scanners. 3B is a cross-sectional view of the laser scanner cut along the AA ′ cross section in FIG.

  In the laser scanners 110Y to 110K of the present embodiment, the rotation axis center of the polygon mirror is disposed at a position off the center of the casing. Specifically, the rotation center of the laser scanner 110 is arranged on the left side in the width direction from the center of the housing in FIG. Here, the housing surface on the side near the rotation center of the polygon mirror in each optical box is defined as a first surface (high temperature surface), and the surface facing the first surface is defined as a second surface (low temperature surface). In other words, the distance from the rotation center of the polygon mirror to the first surface (high temperature surface) of the housing is shorter than the distance from the second surface (low temperature surface) facing the first surface.

  As shown in FIGS. 3A and 3B, in the exposure apparatus of this embodiment, the first surface (high temperature surface) of the laser scanner 110M is adjacent to the second surface (low temperature surface) of the laser scanner 110Y. Are arranged as follows. Further, the second surface (low temperature surface) of the laser scanner 110M and the first surface (high temperature surface) of the adjacent laser scanner 110C are arranged adjacent to each other.

  In other words, the laser scanners 110 </ b> Y to 110 </ b> K are arranged in a row, and two surfaces of each housing 111 perpendicular to the row direction are defined as housing side surfaces. At that time, the polygon mirror 114 is arranged so that the positional relationship between the polygon mirror 114 and the housing side surface in each housing 111 is close to one housing side surface and far from the other housing side surface.

  Subsequently, the connection of the optical box by the heat transfer member 151 having a higher thermal conductivity than the material of the housing will be described. The laser scanners 110 </ b> Y to 110 </ b> K of this embodiment are connected by a heat transfer member 151. Specifically, the low temperature surface of the laser scanner 110Y and the high temperature surface of the laser scanner 110M are connected by a heat transfer member 151. Similarly, the low temperature surface of the laser scanner 110M and the high temperature surface of the laser scanner 110C, and the low temperature surface of the laser scanner 110C and the high temperature surface of the laser scanner 110K are connected by a heat transfer member 151.

  The optical boxes 111Y to 111K as the housings of the laser scanners 110Y to 110K are provided with attachment portions 152 for attaching to the frame of the printer body, and the heat transfer member 151 is fixed on the attachment portions 152 with screws. Yes.

  Thereby, the heat transfer member 151 is contact-fixed to the side surfaces of the respective casings 111Y to 111K, and conducts heat so as to reduce the heat distribution between the casings. Adjacent locations of the respective housings 111Y to 111K are configured such that the housing side surface near the optical deflector 114 of one housing 111 and the housing side surface far from the optical deflector 114 of the other housing 111 are connected by the heat transfer member 151. . Thereby, the plurality of laser scanners 110Y to 110K are integrally connected via the heat transfer member. In the optical box 111 as each housing, the housing side surface close to the light deflector 114 becomes a high temperature surface and the housing side surface far from the light deflector becomes a low temperature surface due to heat generated by the polygon mirror 114 as the light deflector. By connecting each laser scanner with the heat transfer member 151 as described above, the low temperature side surface of the laser scanner exerts a cooling effect on the high temperature side surface of another adjacent laser scanner. Similarly, the high temperature side of the laser scanner exerts a heating effect on the low temperature side of the adjacent laser scanner.

■ (About the structure of the heat transfer connection)
FIG. 4 shows a mounting view of the heat transfer member 151. FIG. 4A shows an example in which one heat transfer member 151 is used to connect laser scanners. The heat transfer member 151 is fixed to a mounting portion 152 provided on the side surface of the housing 110 with screws. In addition, the heat transfer grease 151 is uniformly applied to the contact surfaces of the heat transfer member 151, the mounting portion 152, and the side surface of the housing, thereby improving the heat conductivity between the two objects.

  The heat transfer member for conducting heat between adjacent laser scanners is not limited to the configuration shown in FIG. For example, as shown in FIG. 4B, two heat transfer members may be used to connect adjacent housings. Specifically, the heat transfer member 151 may be fixed to the fixing portion with the same screw using two upper and lower electric heat members with respect to the attachment portion 152. In the configuration shown in FIG. 4B, the heat conductivity can be increased by using more heat transfer members 151 than in the configuration shown in FIG. In this embodiment, the heat transfer member connects adjacent housings at approximately the center in the height direction and depth direction of each housing.

■ (About heat transfer simulation results)
As described above, the exposure apparatus of the present embodiment employs a configuration in which the high temperature portion and the low temperature portion of adjacent laser scanners are connected by the heat transfer member. A description will be given of how much the temperature difference inside the laser scanner can be reduced by using a member having a thermal conductivity in the above-described configuration, using a simulation result. The following results were analyzed using a finite element method by separating the laser scanner housing at 0.5 mm intervals.

  As a result of the heat transfer simulation, about ¼ of the amount of heat generated with the rotation of the polygon mirror 114 is transmitted from the high temperature side surface of the case 111 to the low temperature side surface of the other case 111 through the heat transfer member 151, and the temperature difference between the adjacent points of the case 111 Becomes uniform. Thereby, the temperature difference between the left and right side surfaces of each housing 111 can be reduced from about 2 ° C. to within about 0.5 ° C.

  However, although the temperature of the adjacent part of each housing | casing 111 becomes uniform, since the heat_generation | fever in the housing | casing 111 is repeatedly transmitted to another housing next to the housing 111, it was integrated by the heat-transfer member 151. Between the enclosures, the temperatures of the enclosure surfaces located at the extreme ends are not uniform. That is, among the chassis surfaces located at the extreme ends, the chassis side surface close to the polygon mirror 114 becomes high temperature, and the chassis side surface far from the polygon mirror 114 becomes lower temperature than the adjacent portion between the chassis.

  Therefore, among the side surfaces of the chassis located at the extreme ends between the integrated chassis, the cooling fan 161 as a cooling means for the chassis side surface close to the polygon mirror 114 as the optical deflector (the left side surface of the chassis 111Y in the figure). Is provided. On the other hand, a heater 171 as a heating means is provided on the side of the casing far from the polygon mirror 114 (the right side of the casing 111K in the figure).

  Thus, by cooling the high-temperature side surface and heating the low-temperature side surface among the side surfaces of the housing located at the extreme ends between the integrated housings, adjacent locations between these two surfaces and the other housings The temperature difference can be reduced. As one design example, forced air cooling is performed by adjusting the wind speed of the provided cooling fan 161 to about 1.3 m / s, while heating is performed by adjusting the heat generation amount of the heater 171 to about 1 W. To do.

  From the heat transfer simulation result, the temperature difference between the left and right side surfaces of all the casings 111 can be reduced to within about 0.3 ° C. (see FIG. 5). Thereby, the temperature difference which arises between several housings and the internal temperature difference which arises in each housing can be reduced, and the color shift by the thermal strain of a housing can be reduced. In view of cost reduction, a heat insulating material can be used instead of the heater 171.

  In this case, when a general glass wool heat insulating material (thermal conductivity: about 0.04 W / mK) is disposed over the entire side surface of the housing and the thickness of the heat insulating material is about 10 cm, the same effect as the heater can be obtained. Further, even if the thickness is about 2 to 3 cm, the temperature difference between the left and right side surfaces of all the casings 111 can be reduced to within about 0.4 ° C., and the cost can be suppressed.

■ (Temperature difference between heat transfer member and housing)
As the heat transfer member 151, it is desirable to use a heat transport means such as a metal plate having a high thermal conductivity (for example, pure aluminum) or a heat pipe using boiling heat transfer. In this case, the contact area between the heat transfer member 151 and each side surface of the casing may be small as long as the two objects are interposed by the high thermal conductive grease 153. For example, a contact area with a width of about 30 mm and a thickness of about 10 mm is sufficient. A soaking effect is obtained. In addition, the temperature difference between each housing | casing can further be reduced to about 0.1 degrees C or less by using a heat pipe.

  With the configuration of this embodiment, not only the temperature difference between the optical scanning devices but also the temperature distribution inside the optical scanning device can be reduced.

  FIG. 5 shows a heat transfer simulation related to the temperature rise of the left side surface and the right side surface of each case 111 in this embodiment, when the heat transfer member 151 is attached, and when the heat transfer member is attached and further cooled and heated. Each result is shown. As described above, the temperature difference between the left and right sides of the housing was about 2 ° C. before the implementation, but in the present embodiment, it can be reduced to about 0.3 ° C.

  Table 1 is a table showing the results of heat transfer simulation when materials having different thermal conductivities are used as the heat transfer member 151. The temperature difference in Table 1 represents the difference in temperature rise when comparing the side faces of all the laser scanners 110. The temperature difference can be reduced by adjusting the wind speed of the cooling fan 161 and the amount of heat generated by the heater 171 in accordance with the material of the heat transfer member 151.

  This embodiment will be described below. In addition, about the structure same as Example 1, the overlapping description is abbreviate | omitted suitably by attaching | subjecting the same code | symbol. In Example 1, a dedicated heater was provided at the end of the optical box connected by the heat transfer member that was not connected by the heat transfer member. However, in the configuration in which a dedicated heater is provided to heat the end of the optical box, the cost increases. Therefore, in this embodiment, in order to reduce the cost, waste heat of the fixing device is used instead of heating by the heater.

  The configuration will be specifically described below. FIG. 6 is a diagram for explaining the arrangement of the laser scanner according to the present embodiment. In the present embodiment, a fixing device is disposed on the surface side (low temperature surface) far from the rotation axis of the polygon mirror 114 among the side surfaces of the housings positioned at both ends of the plurality of laser scanners 110 integrated from the heat transfer member 151. .

  Specifically, as shown in FIG. 6A, in order to prevent overheating of the optical box on the bottom surface of the optical box, a heat insulating member 172 is provided only in the laser scanner at the right end of the plurality of laser scanners. Thereby, the heat from the fixing unit can be appropriately received and the heating by the heater can be minimized.

  Further, a configuration for adjusting the amount of heat from the fixing device will be described as an example in which the above configuration is modified. FIG. 6B shows a configuration for transferring the exhaust heat of the fixing device 141 as a heating means only to the low temperature side surface. Specifically, a duct 181 is provided for guiding the heat from the fixing device to the low-temperature surface side of the end of the optical box arranged in parallel. The shape and angle of the duct 181 are in consideration of the amount of heat necessary for heating the low temperature side surface.

  This embodiment will be described below. In addition, about the structure same as Example 1, the overlapping description is abbreviate | omitted suitably by attaching | subjecting the same code | symbol. In Example 1, the cooling fan for exclusive use was provided in the edge part which is not connected by the heat-transfer member among the optical boxes connected by the heat-transfer member. However, in the configuration in which a dedicated fan is provided to heat the end of the optical box, the cost increases. For this reason, in this embodiment, the cost is reduced by applying air to the end using an intake fan for guiding air to each part inside the printer and an exhaust fan for exhausting air from the inside.

  Specifically, as shown in FIG. 7, in order to remove heat from the high-temperature surface side of the optical box ends of the plurality of laser scanners 110 connected by the heat transfer members, the air circulation in the printer 100 is performed. An intake fan 181 as a cooling means used in the above is disposed. More specifically, an intake fan 181 is disposed near the side of the housing near the polygon mirror 114 of the laser scanner 110Y.

100 printer (image forming apparatus)
110 Laser scanner (exposure equipment)
111 Optical box (enclosure)
114 Polygon mirror (Optical deflector / Rotating polygon mirror)
151 Heat conduction plate (Heat transfer member)
152 Connecting protrusion (Mounting part)
161 Cooling fan (Cooling means)
171 Heater (heating means)

Claims (3)

A rotatable mirror and a housing for housing the mirror are provided, and the center of rotation of the mirror is closer to the first surface of the housing than the distance to the second surface facing the first surface An exposure apparatus comprising a plurality of units,
An exposure apparatus, wherein a first surface and a second surface of units adjacent to each other among the plurality of units are connected by a heat transfer member having a higher thermal conductivity than the housing. Among the plurality of units, the first surface that does not face the adjacent unit is heated by the heating means,
The exposure apparatus according to claim 1, wherein a second surface of the plurality of units that does not face an adjacent unit is cooled by a cooling unit.   The exposure apparatus according to claim 1, wherein the unit includes a lens that collects light reflected by the mirror, and the lens is disposed closer to the second surface than the mirror. .

Images