JP2013086329A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress misalignment of scanning positions occurring caused by a temperature difference between respective optical scanners, with no restriction on arrangement positions and sizes of the optical scanners.SOLUTION: An image forming device includes the plurality of optical scanners scanning a photoreceptor with laser light. The optical scanner includes a rotating polygon mirror, a motor rotating the rotating polygon mirror, a scanning lens deflecting the laser light reflected by the rotating polygon mirror to make it scan the photoreceptor and a temperature detection unit detecting a temperature involving the optical scanner. The image forming device includes a temperature range set unit setting the highest temperature in the plurality of detected temperatures as a reference temperature and defining a range from a temperature lower than the reference temperature by the mount of a preset temperature to the reference temperature as a predetermined temperature range, and a temperature adjustment unit, when any one of detected temperatures is out of the predetermined temperature range, driving the motor of the optical scanner with the temperature detection unit detecting that temperature until the temperature falls within the predetermined temperature range.

Description

  The present invention relates to an image forming apparatus, and more particularly to a technique for suppressing a shift in scanning position caused by a temperature difference between optical scanning apparatuses.

  Conventionally, an image forming unit for forming a toner image on the surface of a photosensitive drum is provided for each of a plurality of colors, and each image forming unit is disposed on a transport belt for transporting a recording paper along a transport direction of the recording paper. There is known an image forming apparatus that multiplex-transfers toner images of respective colors onto a recording sheet conveyed in the conveying direction.

  In this type of image forming apparatus, the laser beam output from the light source of each image forming unit is reflected by a rotary polygon mirror that is driven to rotate, and then scanned using an optical resin having good optical characteristics. The surface of the photosensitive drum is scanned at a constant speed by being deflected by a lens. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum.

  Here, the surface of the photoconductive drum is used to multiplex-transfer the toner images of the respective colors formed on the photoconductive drum by attaching the toner to the electrostatic latent image without causing positional deviation on the recording paper. Control for adjusting the writing position (scanning position) of the latent image to be formed is performed. For example, control is performed to adjust the operation of another rotating polygon mirror so that the rotating polygon mirror in a predetermined image forming unit and the rotating polygon mirror in another image forming unit rotate with a predetermined phase difference.

  However, if the temperature of each image forming unit differs depending on the usage frequency and the arrangement position of each image forming unit, the refractive index of the optical resin constituting the scanning lens may change depending on the temperature. As a result, the optical path of the laser beam is deviated between the image forming units, and even when the above control is performed, the scanning position of the laser beam may be deviated between the image forming units.

  Therefore, in order to suppress the deviation of the scanning position of the laser beam caused by such a temperature difference between the image forming units, for example, in Patent Document 1 below, there is a temperature difference in the scanning optical device for each color. The cooling fan for suppressing the temperature rise inside the apparatus, the air path for efficiently discharging the heat inside the apparatus to the outside, and the air path carrying this heat and the scanning optical device are isolated. A technique for preventing only a part of the scanning optical device from being heated or cooled by providing a member to be described is described.

  In Patent Document 2 below, a rectangular sheet metal is externally attached to the side wall of each housing of the four optical scanning devices arranged in the vertical direction in order from the top, and the size of the sheet metal is gradually increased from the bottom. A technique is described in which the heat radiation amount of the optical scanning device located in the upper stage is made larger than the heat radiation amount of the optical scanning device located in the lower stage, thereby reducing the temperature difference between the optical scanning devices. .

  In Patent Document 3 below, the first optical scanning unit and the second optical scanning unit are provided in the same optical housing, and the rotation direction of the polygon mirror in each optical scanning unit and the rotation start and rotation end timings are described. A technique for making the temperature distribution in the apparatus, the air flow, and the thermal deformation amount of the scanning lens the same by aligning them is described.

JP 2003-295739 A JP 2006-171338 A JP 2010-134062 A

  However, in order to apply the technique described in Patent Document 1, a space for providing a cooling fan, an air passage, and a member for isolation is required, and there is a problem that the size of the image forming apparatus is limited. . In addition, in order to apply the technique described in Patent Document 2, it is necessary to arrange a plurality of optical scanning devices in the vertical direction, and there is a problem that the positions where the optical scanning devices are disposed are limited. It was. In the technique described in Patent Document 3, the amount of heat transferred from a heat radiating unit such as a power supply device or a fixing heater differs depending on the position where the optical scanning unit is disposed. There was a possibility that the temperature difference between the means could not be reduced.

  The present invention has been made in view of such circumstances, and scanning generated due to a temperature difference between the optical scanning devices without being restricted by the position and size of the optical scanning device. It is an object of the present invention to provide an image forming apparatus capable of suppressing positional deviation.

  An image forming apparatus according to the present invention is an image forming apparatus including a plurality of optical scanning devices that scan a photosensitive member with laser light, and the optical scanning device reflects a rotating polygon mirror that reflects laser light output from a light source. A motor that rotates the rotary polygon mirror, a scanning lens that deflects the laser light reflected by the rotary polygon mirror and scans the photosensitive member, and a temperature detection unit that detects a temperature related to the optical scanning device. And the image forming apparatus uses a highest temperature among the temperatures detected by the plurality of temperature detection units as a reference temperature, and a temperature range from a temperature lower than the reference temperature by a predetermined temperature to the reference temperature. When any one of the temperatures detected by each of the temperature detection units is outside the predetermined temperature range. A temperature adjustment unit that drives the motor of the out-of-range device that is the optical scanning device including the temperature detection unit that detects the temperature until the temperature detected by the temperature detection unit falls within the predetermined temperature range. .

  Depending on the position at which each optical scanning device is disposed, for example, the amount of heat transferred from a heat radiating unit such as a power supply device or a fixing heater is different, and therefore there is a possibility that the temperature related to each optical scanning device is different. However, according to this configuration, the temperature range setting unit determines the predetermined temperature range with the highest temperature among the temperatures detected by the plurality of temperature detection units as the reference temperature, and the temperature detected by the temperature detection unit is In an out-of-range device that is outside the predetermined temperature range, the temperature adjustment unit adjusts the temperature to be within the predetermined temperature range.

  For this reason, the temperature difference between the optical scanning devices can be reduced without being restricted by the position and size of the optical scanning devices. As a result, it is possible to reduce the difference in the refractive index of the scanning lens between the optical scanning devices due to the temperature difference between the optical scanning devices, and the scanning that occurs due to the difference in the refractive index. Position shift can be suppressed.

  The temperature adjustment unit preferably drives the motor of the out-of-range device until the temperature detected by the temperature detection unit of the out-of-range device becomes equal to the reference temperature.

  According to this configuration, in an out-of-range device in which the temperature detected by the temperature detection unit is outside the predetermined temperature range, the temperature adjustment unit adjusts the temperature to be equal to the reference temperature. For this reason, even when there are a plurality of out-of-range devices, the temperature related to the plurality of out-of-range devices can be equalized to the reference temperature, and the temperature difference between the optical scanning devices can be accurately reduced.

  Moreover, it is preferable that the temperature detection unit is provided outside the optical path of the laser beam and within a predetermined short distance from the scanning lens.

  According to this configuration, the temperature detection unit detects the temperature in the vicinity of the scanning lens, and the temperature adjustment unit adjusts the temperature in the vicinity of the scanning lens of each optical scanning device to be within a predetermined temperature range. For this reason, it is possible to accurately reduce the difference in the refractive index of the scanning lens between the respective optical scanning devices, and it is possible to further suppress the deviation of the scanning position caused by the difference in the refractive index.

  According to the present invention, image formation that can suppress the deviation of the scanning position caused by the temperature difference between the optical scanning devices without being restricted by the position and size of the optical scanning device. Can be provided.

1 is a schematic configuration diagram of a tandem type color printer that is an example of an image forming apparatus. FIG. 1 is a schematic configuration diagram showing an example of an internal configuration of an optical scanning device. The block diagram which shows an example of a structure of the temperature control system of an optical scanning device. Explanatory drawing for demonstrating an example of the relationship between the temperature detected by each temperature detection part, a reference temperature, and a predetermined temperature range. 5 is a flowchart showing an example of a temperature control flow of each optical scanning device. 6 is a flowchart showing another example of the temperature control flow of each optical scanning device, different from FIG.

  Embodiments according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a tandem type color printer 1 which is an example of an image forming apparatus according to the present invention.

  As shown in FIG. 1, the color printer 1 includes a paper storage unit 10, an image forming unit 20, a fixing unit 30, a paper discharge unit 40, a paper conveyance path 50, and a control unit 80. The unit 10, the image forming unit 20, the fixing unit 30, the paper conveyance path 50, and the control unit 80 are housed in a substantially box-shaped apparatus main body 1A, and the paper discharge unit 40 is provided on the top of the apparatus main body 1A.

  The paper storage unit 10 stores the paper P, and feeds out the paper P under the control of the control unit 80. A paper cassette 11 is provided in the paper storage unit 10 so as to be detachable with respect to the apparatus main body 1A. At the upstream end of the paper cassette 11 (upper left of the paper cassette 11 in the example shown in FIG. 1), a pickup roller 12 that feeds the paper P from the paper bundle one by one is provided. The sheet P fed out of the sheet cassette 11 by driving the pickup roller 12 is fed to the sheet conveyance path 50.

  Under the control of the control unit 80, the image forming unit 20 applies each sheet of paper P fed out from the sheet bundle stored in the paper storage unit 10 based on an image signal received from an interface circuit (not shown) from a computer or the like. On the other hand, an image transfer process is performed. The interface circuit is connected to an external device such as a computer via a LAN (Local Area Network) or the like, and transmits / receives various signals to / from the external device. For example, a network interface (10 / 100Base-TX) Etc. are used.

  The image forming unit 20 includes image forming units 21Y, 21C, 21M, and 21K that form toner images, and a transfer device that transfers the toner images formed by the image forming units 21Y, 21C, 21M, and 21K to a sheet P. 27.

  The image forming units 21Y, 21C, 21M, and 21K are sequentially arranged in a substantially horizontal direction from the upstream side (right side in FIG. 1) to the downstream side, and the yellow image forming unit 21Y, the cyan image forming unit 21C, The magenta image forming unit 21M and the black image forming unit 21K are arranged in this order. The image forming units 21Y, 21C, 21M, and 21K have the same configuration, and are positioned and attached to each device in the apparatus main body 1A with a predetermined relative positional relationship.

  Each of the image forming units 21Y, 21C, 21M, and 21K includes a photosensitive drum (photosensitive member) 22, a charger 23, an optical scanning device 24, a developing device 25, and a cleaning device 26, respectively. . The photosensitive drum 22 is provided to be rotatable around a drum axis extending in the front-rear direction (a direction orthogonal to the paper surface of FIG. 1). The charger 23, the optical scanning device 24, the developing device 25, and the cleaning device 26 are in the rotational direction of the photosensitive drum 22 from a position immediately below the photosensitive drum 22 along the peripheral surface of the photosensitive drum 22. In the counterclockwise direction, the charger 23, the optical scanning device 24, the developing device 25, and the cleaning device 26 are arranged in this order.

  The photosensitive drum 22 forms an electrostatic latent image and a toner image according to the electrostatic latent image on the peripheral surface.

  The charger 23 forms a uniform charge on the circumferential surface of the photosensitive drum 22 rotating counterclockwise around the drum axis. The charger 23 includes, for example, a charging roller that applies a charge to the photosensitive drum 22 while being rotated while the peripheral surface is in contact with the peripheral surface of the photosensitive drum 22.

  The developing device 25 supplies toner to the peripheral surface of the photosensitive drum 22 to attach the toner to the portion where the electrostatic latent image is formed on the peripheral surface, and thereby the toner image is formed on the peripheral surface of the photosensitive drum 22. To form. The developing device 25 of the yellow image forming unit 21Y contains yellow (Y) toner, and the developing device 25 of the cyan image forming unit 21C contains cyan (C) toner. The developing device 25 of the image forming unit 21M contains magenta (M) toner, and the developing device 25 of the black image forming unit 21K contains black (K) toner.

  The cleaning device 26 is for removing the toner remaining on the peripheral surface of the photosensitive drum 22 after the primary transfer, which will be described later, for cleaning. The peripheral surface of the photosensitive drum 22 cleaned by the cleaning device 26 is again directed to the charger 23 for the next image forming process.

  The optical scanning device 24 irradiates the rotating surface of the photosensitive drum 22 between the charger 23 and the developing device 25 with a laser beam to which intensity is applied based on the image data. An electrostatic latent image is formed on the peripheral surface. Each optical scanning device 24 in each image forming unit 21Y, 21C, 21M, 21K applies laser light corresponding to each color of cyan, magenta, and black to each photosensitive drum 22 in each image forming unit 21Y, 21C, 21M, 21K. Irradiate. When the peripheral surface of the charged photoconductive drum 22 is irradiated with laser light, the charge of the irradiated portion is erased in accordance with the intensity of the laser light, whereby an electrostatic latent image is formed on the peripheral surface of the photoconductive drum 22. It is formed. The image data includes, for example, development colors yellow, cyan, and magenta generated by performing a process such as a known color correction process on an image signal from an external device such as a computer received by an unillustrated interface circuit. And black image data.

  The transfer device 27 is a device for transferring the toner image formed on the peripheral surface of the photosensitive drum 22 onto the paper P, and includes an intermediate transfer belt 271, a primary transfer roller 272, a driving roller 273, a driven roller 274, and a second roller. A next transfer roller 275 is provided.

  The intermediate transfer belt 271 is endless, and is stretched to a position immediately above the image forming units 21Y, 21C, 21M, and 21K by a primary transfer roller 272, a driving roller 273, and a driven roller 274, and the driving roller 273 rotates. It can be rotated clockwise by the driving force.

  The primary transfer roller 272 is provided so as to face the respective photosensitive drums 22 of the respective image forming units 21Y, 21C, 21M, and 21K, presses the intermediate transfer belt 271 and the intermediate transfer belt 271 is lifted from the photosensitive drum 22. It arrange | positions so that it may prevent. The primary transfer roller 272 is configured to be applied with a transfer bias. When a transfer bias is applied to the primary transfer roller 272, the toner image formed on the peripheral surface of the photosensitive drum 22 is primarily transferred to the intermediate transfer belt 271.

  The secondary transfer roller 275 is disposed at a position facing the drive roller 273 on the outer peripheral surface of the intermediate transfer belt 271. The secondary transfer roller 275 is configured to be applied with a transfer bias. When a transfer bias is applied to the secondary transfer roller 275, the toner image primarily transferred to the intermediate transfer belt 271 is secondarily transferred to the paper P.

  Further, an intermediate transfer belt cleaning device 276 is provided on the right side of the driven roller 274 on the paper surface, and toner remaining on the surface of the intermediate transfer belt 271 after the toner image is secondarily transferred to the paper P is intermediate. The intermediate transfer belt 271 removed by the transfer belt cleaning device 276 and cleaned thereby is supplied to the photosensitive drum 22.

  The fixing unit 30 performs a fixing process by heating the toner image secondarily transferred to the paper P under the control of the control unit 80, and includes a heat roller 31 in which an energized heating element is mounted, and the heat roller 31. A pressure roller 32 is provided so as to face the roller 31 and whose peripheral surfaces are arranged to face each other. The sheet P after the secondary transfer is between the heat roller 31 that is driven to rotate clockwise around the roller axis and the pressure roller 32 that is driven to rotate counterclockwise around the roller axis. By passing through the nip portion, the heat from the heat roller 31 is obtained and the fixing process is performed. The paper P subjected to the fixing process is discharged to the paper discharge unit 40 through the paper conveyance path 50.

  The paper discharge unit 40 discharges the paper P on which the fixing process has been performed by the fixing unit 30, and stores the discharged paper P. The paper discharge unit 40 is formed by recessing the top of the apparatus main body 1A, and a paper discharge tray 41 for receiving the discharged paper P is formed at the bottom of the concave recess.

  The paper conveyance path 50 conveys the paper P fed from the paper storage unit 10 to the paper discharge unit 40 via the image forming unit 20 and the fixing unit 30 under the control of the control unit 80.

  The control unit 80 is connected to the sheet storage unit 10, the image forming unit 20, the fixing unit 30, the sheet conveyance path 50, and the like, and controls the operation of these units. The control unit 80 includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory) that stores various programs executed by the CPU, data necessary for the execution in advance, and a RAM (so-called working memory of the CPU). Random Access Memory) and its peripheral circuit.

  An image forming operation in the color printer 1 having such a configuration will be described. First, after the photosensitive drum 22 is charged by the charger 23, exposure is performed by the optical scanning device 24, and an electrostatic latent image is formed on the surface of the photosensitive drum 22. The electrostatic latent image is converted into a toner image by the developing device 25, and the toner image formed on the surface of the photosensitive drum 22 is transferred onto the intermediate transfer belt 271 by a transfer bias applied to the primary transfer roller 272. The Then, the residual toner remaining on the photosensitive drum 22 without being transferred to the intermediate transfer belt 271 is cleaned by the cleaning device 26 and stored in a collection bottle (not shown). Such exposure, development, and primary transfer operations are sequentially performed on the development colors of yellow, cyan, magenta, and black, and the toner images of the respective colors are superimposed on the surface of the intermediate transfer belt 271 so that the intermediate transfer belt. A full-color toner image is formed on 271.

  When the full-color toner image is formed on the intermediate transfer belt 271, the secondary transfer roller 275 is brought into contact with the intermediate transfer belt 271 and conveyed from the sheet storage unit 10 to the transfer position by the sheet conveyance path 50 in time. The full color toner image formed on the intermediate transfer belt 271 is secondarily transferred onto the paper P by the secondary transfer bias applied to the secondary transfer roller 275. The full color toner image transferred to the paper P is fixed to the paper P by heating and pressurization by the fixing unit 30, and the paper P is discharged to the paper discharge unit 40. The toner remaining on the intermediate transfer belt 271 is cleaned by bringing the intermediate transfer belt cleaning device 276 of the intermediate transfer belt 271 into contact with the intermediate transfer belt 271 after the secondary transfer, and is stored in a collection bottle (not shown). Is done.

  FIG. 2 is a schematic configuration diagram illustrating an example of an internal configuration of the optical scanning device 24. Since the configuration of the optical scanning device 24 in each of the image forming units 21Y, 21C, 21M, and 21K is the same, the image forming unit 21K will be described below as an example.

  As shown in FIG. 2, the optical scanning device 24 includes a laser irradiation unit (light source) 61, a collimator lens 62, a prism 63, a polygon mirror (rotating polygonal mirror) 64, an fθ lens (scanning lens) 65, a polygon motor (motor). 66, a beam detection sensor (hereinafter referred to as BD (Beam Detect) sensor) 67, and a temperature sensor (temperature detection unit) 68. Note that a controller 80 is electrically connected to each optical scanning device 24.

  The laser irradiation unit 61 includes a laser light source such as a laser diode (LD). Laser light output from the laser light source is converted into parallel light by the collimator lens 62, the prism 63, and the like. The parallel light is reflected toward the polygon mirror 64 by a reflection mirror (not shown) and is incident on the rotating polygon mirror 64 by driving the polygon motor 66.

  The polygon mirror 64 has a plurality of reflection surfaces that reflect the laser light output from the laser irradiation unit 61 toward the photosensitive drum 22 (for example, eight surfaces in FIG. 2). The polygon mirror 64 is driven to rotate at a constant speed by the polygon motor 66 in the direction of the arrow in FIG. 2, for example, so that the laser light emitted from the laser irradiation unit 61 is reflected by each reflecting surface of the polygon mirror 64.

  For example, the fθ lens 65 is configured by molding an optical resin having good optical characteristics. The fθ lens 65 deflects the laser beam reflected by the polygon mirror 64 and scans the photosensitive drum 22 at a constant speed in the rotation axis direction of the photosensitive drum 22 (main scanning direction, arrow A direction in FIG. 2). Remove the charge on the surface. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 22.

  The BD sensor 67 is configured using, for example, a photodiode, and is used to adjust the timing of performing light beam scanning (hereinafter referred to as image writing operation) for forming a toner image on the photosensitive drum 22. When the laser light reflected by the polygon mirror 64 rotating in the arrow direction shown in FIG. 2 passes through the fθ lens 65 and enters the BD sensor 67, a detection signal is output from the BD sensor 67. The detection signal of the BD sensor 67 is input to an image writing timing adjustment unit 83 to be described later, and is used to adjust the image writing timing of laser light scanned on the surface of the photosensitive drum 22.

  The temperature sensor 68 detects the temperature related to each optical scanning device 24. Specifically, the temperature sensor 68 is provided outside the optical path of the laser beam and within a predetermined short distance from the fθ lens 65, detects the temperature near the fθ lens 65, and indicates the detected temperature. A detection signal is output to the control unit 80.

  The refractive index of the fθ lens 65 changes depending on the temperature in the vicinity. For this reason, when a temperature difference occurs in the temperature in the vicinity of the fθ lens 65 between the optical scanning devices 24, the refractive index of the fθ lens 65 is different between the optical scanning devices 24. There is a possibility that the moving speed (main scanning magnification) of the laser light in the main scanning direction changes. For this reason, as will be described later, the temperature of each optical scanning device 24 is controlled by the control unit 80 in order to reduce the temperature difference in the vicinity of the fθ lens 65 between the optical scanning devices 24. The detection signal of the temperature sensor 68 is used for temperature control of each optical scanning device 24.

  The control unit 80 takes an operation timing based on the reference clock signal output from the reference oscillator 91, adjusts the image writing timing at the operation timing, and drives and controls the laser irradiation unit 61 based on the image data of the image to be written. .

  The control unit 80 particularly functions as an LD drive control unit 81, a drawing unit 82, and an image writing timing adjustment unit 83 in order to control the scanning of the laser beam by the optical scanning device 24.

  The LD drive control unit 81 drives and controls the laser irradiation unit 61 based on an instruction from the drawing unit 82. The drawing unit 82 starts driving the LD drive control unit 81 based on the image data of the writing target image. The image writing timing adjustment unit 83 adjusts the image writing timing for scanning the surface of the photosensitive drum 22 based on the BD signal output from the BD sensor 67 and outputs the adjusted image writing timing to the drawing unit 82.

  FIG. 3 is a block diagram illustrating an example of the configuration of the temperature control system of the optical scanning device 24. In the following description, the polygon mirrors 64 of the optical scanning device 24 for each color of yellow Y, cyan C, magenta M, and black K are denoted as “64Y”, “64C”, “64M”, and “64K”, respectively. write. Further, the polygon motor 66 of the optical scanning device 24 of each color of yellow Y, cyan C, magenta M, and black K is expressed as “66Y”, “66C”, “66M”, and “66K”, respectively. Further, the temperature sensors 68 of the optical scanning device 24 for each color of yellow Y, cyan C, magenta M, and black K are denoted as “68Y”, “68C”, “68M”, and “68K”, respectively.

  The control unit 80 particularly functions as a temperature range setting unit 84 and a temperature adjustment unit 85 in connection with the temperature control of the optical scanning device 24 for each color of yellow Y, cyan C, magenta M, and black K.

  The temperature range setting unit 84 includes the optical scanning device 24 for each color of yellow Y, cyan C, magenta M, and black K indicated by detection signals input to the control unit 80 from the temperature sensors 68Y, 68C, 68M, and 68K. Of the temperatures near the fθ lens 65, the highest temperature is determined as the reference temperature and stored in the RAM. Then, the temperature range setting unit 84 determines a temperature range from a temperature lower than the reference temperature by a predetermined temperature to the reference temperature as a predetermined temperature range, and stores it in the RAM.

  The temperature adjustment unit 85 includes fθ of the optical scanning device 24 for each color of yellow Y, cyan C, magenta M, and black K indicated by detection signals input to the control unit 80 from the temperature sensors 68Y, 68C, 68M, and 68K. The optical scanning device 24 includes a temperature sensor 68 that detects a temperature outside the predetermined temperature range when any of the temperatures near the lens 65 is outside the predetermined temperature range determined by the temperature range setting unit 84. The polygon motor of the out-of-range device is driven until the temperature detected by the temperature sensor 68 falls within a predetermined temperature range.

  FIG. 4 shows the temperature in the vicinity of the fθ lens 65 of the optical scanning device 24 for each color of yellow Y, cyan C, magenta M, and black K detected by the temperature sensors 68Y, 68C, 68M, and 68K, and the temperature range setting unit 84. It is explanatory drawing for demonstrating an example of the relationship with the reference temperature defined by (1) and a predetermined temperature range. FIG. 5 is a flowchart showing an example of the temperature control flow of the optical scanning device 24 for each color of yellow Y, cyan C, magenta M, and black K.

  Specifically, as shown in FIG. 5, for example, when the control unit 80 starts temperature control at a predetermined time when the image forming operation is not performed in the color printer 1, first, the temperature sensors 68 </ b> Y, 68 </ b> C, The temperatures near the fθ lens 65 of the optical scanning device 24 for each color of yellow Y, cyan C, magenta M, and black K are detected by 68M and 68K (S1). The predetermined time may be every predetermined time (periodically), or may be a timing input from a user via an operation input unit (not shown) such as a touch panel. Good.

  For example, as shown in FIG. 4, the fθ lens of the optical scanning device 24 for each color of yellow Y, cyan C, magenta M, and black K detected by the temperature sensors 68Y, 68C, 68M, and 68K in step S1. The description will be made assuming that the temperatures around 65 are 34 ° C., 37 ° C., 38 ° C., and 40 ° C., respectively.

  The temperature range setting unit 84 includes, among the temperatures near the fθ lens 65 of the optical scanning device 24 for each color of yellow Y, cyan C, magenta M, and black K, detected by the temperature sensors 68Y, 68C, 68M, and 68K. The temperature 40 ° C. detected by the temperature sensor 68K, which is the highest temperature, is determined as the reference temperature Td and stored in the RAM (S2).

  Then, the temperature range setting unit 84 sets a temperature range from 36 ° C. which is a temperature ΔT (for example, 4 ° C. in FIG. 4) lower than the reference temperature Td to 40 ° C. which is the reference temperature Td. A predetermined temperature range is determined and stored in the RAM (S3). Note that the predetermined temperature ΔT is predetermined based on experimental values such as test operation and stored in the ROM.

  Next, the temperature adjustment unit 85 detects the temperatures near the fθ lens 65 of the optical scanning device 24 for each color of yellow Y, cyan C, magenta M, and black K detected by the temperature sensors 68Y, 68C, 68M, and 68K. Among these, it is determined whether or not there is a temperature outside the predetermined temperature range (36 ° C. to 40 ° C.) determined by the temperature range setting unit 84 (S4).

  In step S4, the temperature adjustment unit 85 determines that the temperature (34 ° C.) near the fθ lens 65 of the yellow Y optical scanning device 24 is a predetermined temperature range (from 36 ° C. to 40 ° C.) determined by the temperature range setting unit 84. Since it is outside (S4; YES), the yellow Y optical scanning device 24 having the temperature sensor 68Y is set as an out-of-range device, and the polygon motor 66Y of the out-of-range device is driven (S5). As a result, the polygon motor 66Y generates heat, and the temperature of the yellow Y optical scanning device 24 rises.

  Then, the temperature adjustment unit 85 determines that the temperature detected by the temperature sensor 68Y of the out-of-range device is not within the predetermined temperature range (36 ° C. to 40 ° C.) (S6; NO), and the polygon motor 66Y of the out-of-range device. When the temperature detected by the temperature sensor 68Y of the out-of-range device falls within a predetermined temperature range (from 36 ° C. to 40 ° C.) (S6; YES), the polygon motor 66Y of the out-of-range device is driven. Is stopped (S7), and the process returns to step S4 again.

  Depending on the position where each optical scanning device 24 is disposed, for example, the amount of heat transfer from a heat-dissipating unit such as a power supply device (not shown) or the heat roller 31 provided in the fixing unit 30 differs. 24 may have different temperatures. However, according to the configuration of the above embodiment, the temperature range setting unit 84 defines a predetermined temperature range with the highest temperature among the temperatures detected by the temperature sensors 68Y, 68C, 68M, 68K as the reference temperature Td, In an out-of-range device in which the temperatures detected by the temperature sensors 68Y, 68C, 68M, and 68K are outside the predetermined temperature range, the temperature detected by the temperature sensor of the out-of-range device by the temperature adjustment unit 85 is within the predetermined temperature range. The polygon motor of the out-of-range device is driven until it is inside.

  For this reason, the temperature difference between the optical scanning devices 24 can be reduced without being restricted by the position and size of the optical scanning devices 24. As a result, it is possible to reduce the difference in the refractive index of the fθ lens 65 between the respective optical scanning devices 24 due to the temperature difference between the respective optical scanning devices 24. The generated scan position shift can be suppressed.

  In the above embodiment, the temperature sensor 68 is provided outside the optical path of the laser beam and within a predetermined short distance from the fθ lens 65. However, the position where the temperature sensor 68 is provided is described above. It is not intended to be limited to.

  For example, the temperature sensor 68 may be provided so as to be in contact with the end of the fθ lens 65, whereby the temperature sensor 68 may be configured to detect the temperature of the fθ lens 65 itself. Alternatively, when there is no space where the temperature sensor 68 is provided in the vicinity of the fθ lens 65, the temperature sensor 68 may be disposed as close to the fθ lens 65 as possible in the optical scanning device 24.

  However, as the temperature sensor 68 is arranged closer to the fθ lens 65, the temperature of the fθ lens 65 can be detected with higher accuracy. As a result, the temperature in the vicinity of the fθ lens 65 between the optical scanning devices 24 is controlled by the temperature control. The difference can be reduced with high accuracy, and the difference in refractive index of the fθ lens 65 between the optical scanning devices 24 can be reduced with high accuracy.

  In step S5 to step S7, the temperature adjustment unit 85 determines that the temperature detected by the temperature sensor 68 of the out-of-range device is within the predetermined temperature range determined in step S3. Was configured to drive. However, instead of this, the temperature adjustment unit 85 drives the polygon motor of the out-of-range device until the temperature detected by the temperature sensor 68 of the out-of-range device becomes equal to the reference temperature Td determined in step S2. You may comprise.

  Hereinafter, the flow of temperature control in the configuration will be described with reference to FIGS. 4 and 6. FIG. 6 is a flowchart showing another example of the temperature control flow of the optical scanning device 24 for each color of yellow Y, cyan C, magenta M, and black K, as shown in FIG. Note that steps S1 to S5 in FIG. 6 have the same processing contents as steps S1 to S5 in FIG.

  As shown in FIGS. 4 and 6, the temperature adjustment unit 85 operates while the temperature detected by the temperature sensor 68Y of the out-of-range device is not equal to the reference temperature Td (40 ° C.) determined in step S2 (S9; NO), when the driving of the polygon motor 66Y of the out-of-range device is continued and the temperature detected by the temperature sensor 68Y of the out-of-range device becomes equal to the reference temperature Td (40 ° C.) (S9; YES), out of the range The driving of the polygon motor 66Y of the apparatus is stopped (S7), and the process returns to step S4 again.

  According to this configuration, in the out-of-range device in which the temperature detected by the temperature sensor 68 is outside the predetermined temperature range, the temperature adjustment unit 85 adjusts the temperature to be equal to the reference temperature Td. For this reason, even when there are a plurality of out-of-range devices, the temperature of the plurality of out-of-range devices is made uniform to the reference temperature Td by repeating the processing from step S5 to step S7, and each optical scanning device The temperature difference between 24 can be accurately reduced.

  In the above embodiment, the color printer 1 has been described as an example of the image forming apparatus according to the present invention. However, the present invention is applied to a copying machine capable of color printing, a facsimile, and a multifunction machine having various functions. It is also possible. Furthermore, although the tandem type color printer has been described as an example in the above-described embodiment, other printing methods may be used as long as the image forming apparatus includes a plurality of optical scanning devices that scan the photosensitive member with laser light.

  Further, the present invention is not limited to the configuration of the above embodiment, and various modifications can be made. The configuration and processing shown in FIGS. 1 to 6 are merely examples of the embodiment according to the present invention, and are not intended to limit the present invention to the above-described embodiment.

1 Color printer (image forming device)
21Y Image forming unit for yellow 21C Image forming unit for cyan 21M Image forming unit for magenta 21K Image forming unit for black 22 Photosensitive drum (photosensitive member)
24 Optical scanning device 61 Laser irradiation part (light source)
62 Collimator lens 63 Prism 64 Polygon mirror (Rotating polygon mirror)
65 fθ lens (scanning lens)
66, 66Y, 66C, 66M, 66K Polygon motor (motor)
67 BD sensor 68, 68Y, 68C, 68M, 68K Temperature sensor (temperature detector)
80 Control unit 84 Temperature range setting unit 85 Temperature adjustment unit Td Reference temperature

Claims (3)

An image forming apparatus including a plurality of optical scanning devices that scan a photosensitive member with laser light,
The optical scanning device includes:
A rotating polygon mirror that reflects the laser light output from the light source;
A motor for rotating the rotary polygon mirror;
A scanning lens that deflects the laser beam reflected by the rotary polygon mirror and scans the photosensitive member;
A temperature detection unit for detecting a temperature related to the optical scanning device;
With
The image forming apparatus includes:
A temperature range in which the highest temperature among the temperatures detected by the plurality of temperature detection units is set as a reference temperature, and a temperature range from a temperature lower than the reference temperature by a predetermined temperature to the reference temperature is set as a predetermined temperature range A setting section;
Out of the range of the optical scanning device provided with a temperature detection unit that detects a temperature outside the predetermined temperature range when any of the temperatures detected by the temperature detection units is out of the predetermined temperature range A temperature adjustment unit that drives the motor of the apparatus until the temperature detected by the temperature detection unit falls within the predetermined temperature range; and
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the temperature adjustment unit drives the motor of the out-of-range device until the temperature detected by the temperature detection unit of the out-of-range device becomes equal to the reference temperature.   The image forming apparatus according to claim 1, wherein the temperature detection unit is provided outside the optical path of the laser light and within a predetermined short distance from the scanning lens.

Images