JP6256243B2 - Optical scanning device and image forming apparatus having the same - Google Patents

Description

  The present invention relates to an optical scanning apparatus that scans a photosensitive member by deflecting light emitted from a light source, and an image forming apparatus including the optical scanning apparatus.

  An electrophotographic image forming apparatus includes an optical scanning device that irradiates a photoconductor with a light beam and optically scans the photoconductor. The optical scanning device is provided with a deflector such as a polygon mirror that deflects the light beam and scans the scanning region on the photosensitive member. The optical scanning device exposes the photosensitive member by scanning in the axial direction of the photosensitive member while deflecting a light beam corresponding to the image signal. Such scanning is also called main scanning. A beam detector (light receiving unit) is mounted on the optical scanning device (see, for example, Patent Document 1). During the main scanning, the light beam is detected by the beam detector before moving to the scanning start position on the photosensitive member. Conventionally, the scanning start timing (writing timing) on the photosensitive member is determined based on the detection timing of the detection signal (referred to as BD signal).

JP 2013-120335 A

  The housing of the optical scanning device may be distorted due to various factors, and the scanning direction of the light beam may be shifted up and down due to the distortion. If the light beam is deviated, the light beam may not be applied to the light receiving surface of the beam detector, and the BD signal may not be detected. In this case, the scanning start timing is not determined, and the optical scanning on the photosensitive member cannot be performed normally. When the cause of the deviation is a dimensional tolerance or a mounting error of a lens constituting the optical scanning device, the deviation can be eliminated by adjusting the light beam after assembly. However, after the image forming apparatus is shipped, if the light beam shifts up and down due to changes in the temperature around the optical scanning device or distortion of the frame due to aging, the optical scanning device is disassembled and adjusted. Adjustment work is difficult.

  An object of the present invention is to provide an optical scanning device capable of easily adjusting the position of a light beam with respect to a light receiving unit and an image forming apparatus including the same.

  An optical scanning device according to one aspect of the present invention includes a light source, an optical deflector, a light receiving unit, a moving mechanism, and a movement control unit. The light deflector scans the photosensitive member by deflecting light emitted from the light source. The light receiving unit receives a light beam emitted from the light source before scanning the photosensitive member. The moving mechanism moves the light receiving unit in a direction perpendicular to a direction in which the light beam passes through the light receiving unit. The movement control unit drives the moving mechanism based on the intensity of the light beam detected by the light receiving unit to move the light receiving unit.

An image forming apparatus according to another aspect of the present invention includes the optical scanning device and a transfer device. The transfer device transfers an image based on the electrostatic latent image on the photosensitive member scanned by the optical scanning device to a transfer sheet.

  According to the present invention, the position of the light beam with respect to the light receiving unit can be easily adjusted.

1 is a diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a top perspective view of an optical scanning device according to an embodiment of the present invention. It is a figure which shows the beam detector and moving mechanism with which the optical scanning apparatus shown in FIG. 2 is provided. FIG. 2 is a block diagram illustrating a configuration of a control unit included in the image forming apparatus illustrated in FIG. 1. It is a figure which shows the light reception time of the light beam which the beam detector received. 5 is a flowchart illustrating an example of a procedure of light beam correction processing executed by a control unit illustrated in FIG. 4. It is a figure which shows the structure of the color image forming apparatus which concerns on other embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.

[Image forming apparatus 10]
FIG. 1 is a schematic diagram showing a configuration of an image forming apparatus 10 (an example of the image forming apparatus of the present invention) according to an embodiment of the present invention. The image forming apparatus 10 forms an image on a printing paper (an example of a transfer sheet according to the present invention) based on the read image data of a document or image data input from the outside. As shown in FIG. 1, the image forming apparatus 10 includes a scanner 12 at the top and an electrophotographic image forming unit 14 at the bottom. The specific example of the image forming apparatus 10 according to the embodiment of the present invention has a function of performing image processing on input image data. For example, a printer, a copier, a facsimile, or each of these functions is provided. It is a multifunction machine equipped.

  The image forming unit 14 forms an image on a print sheet based on image data read by the scanner 12 or print data (print job) input from the outside. The image forming unit 14 mainly includes an operation display unit 17, a paper feed tray 16, a conveyance roller 19, an optical scanning device 11 (an example of the optical scanning device of the present invention), and a photosensitive member 13 (the photosensitive member of the present invention). ), A transfer device 15 (an example of the transfer device of the present invention), a fixing device 18 (an example of the fixing device of the present invention), and a control unit 5 that controls these operations. These components are arranged inside a casing 20 that constitutes a housing of the image forming unit 14.

  A plurality of printing sheets are held in the sheet feeding tray 16. The optical scanning device 11 exposes the photosensitive member 13 by irradiating the photosensitive member 13 charged to a constant potential with a light beam such as a laser beam in the axial direction of the photosensitive member 13. As a result, an electrostatic latent image is formed on the surface of the photoreceptor 13. The transfer device 15 includes a developing device 15A. The electrostatic latent image on the photoreceptor 13 is developed with toner by the developing device 15A. The transfer device 15 transfers the developed toner image from the photoreceptor 13 to the printing paper.

  The fixing device 18 fixes the toner image transferred to the printing paper on the printing paper. The fixing device 18 includes a heating roller 18A that is heated by a heating device, and a pressure roller 18B that pressurizes the printing paper. The heating device heats the heating roller 18A to, for example, about 170 ° C. to 200 ° C. The heating roller 18A and the pressure roller 18B are pressed against each other, and when the printing paper is conveyed while being sandwiched between the pressure contact portions (nip portions), heat and pressure are applied to the printing paper to print a toner image. Fixed on paper.

  Between the upper part of the casing 20 and the scanner 12, a paper discharge space 21 that is open at the front is formed. A paper discharge tray 23 is provided in the paper discharge space 21. The printing paper fed from the paper feed tray 16 is transported by the transport roller 19 along a transport path 20A provided in the casing 20. Then, after the transfer by the transfer device 15 and the fixing by the fixing device 18 are performed in the conveyance process, the printing paper is discharged into the paper discharge space 21 and held on the paper discharge tray 23.

[Optical scanning device 11]
As shown in FIG. 2, the optical scanning device 11 includes a housing 25, a light source 26 (an example of the light source of the present invention), a polygon mirror 27 (an example of the optical deflector of the present invention), an fθ lens 28, and the like. , A condenser lens 30, a total reflection mirror 31, and a slit (exit port) 32. Further, as shown in FIG. 3, the optical scanning device 11 includes a beam detector 40 (an example of a light receiving unit of the present invention) and a moving mechanism 50.

  The light source 26 emits a light beam such as a laser beam and has a semiconductor laser element and a drive circuit for driving the semiconductor laser element.

  The polygon mirror 27 deflects the light beam emitted from the light source 26 and scans the photosensitive member 13 with the light beam. The side surface of the polygon mirror 27 is constituted by a reflecting surface having a polygonal shape (hexagonal shape in FIG. 2 as an example). The polygon mirror 27 is rotationally driven by a polygon motor 33 (see FIG. 4) attached to the housing 25. The controller 5 is rotationally driven. The polygon motor 33 is inside the housing 25 and is interposed between the polygon mirror 27 and the bottom surface of the housing 25. A driver board 34 is provided between the polygon motor 33 and the polygon mirror 27. A temperature sensor 35 for detecting the temperature inside the housing 25 is mounted on the driver board 34.

  The polygon mirror 27 is rotated at a high speed by the polygon motor 33 to reflect the light beam from the light source 26 and scan in the main scanning direction. The condenser lens 30 converts the light beam into parallel light together with the fθ lens 28. The total reflection mirror 31 changes the optical path of the light beam that has passed through the condenser lens 30 to a predetermined angle. The slit 32 is formed in the housing 25 and is an exit for guiding the optical path of the light beam from the total reflection mirror 31 to the surface of the photoreceptor 13.

  The light beam reflected by the polygon mirror 27 by the rotation is irradiated not only on the irradiation region irradiated on the total reflection mirror 31 but also on the outside of the irradiation region of the total reflection mirror 31. At this time, the light beam is also applied to the side wall 25 </ b> A of the housing 25 before the light beam is scanned with respect to the photoconductor 13. A through window 36 (see FIG. 2) for guiding the light beam to the outside is formed on the side wall 25A. That is, the through window 36 is formed outside the irradiation region. The through window 36 guides the light beam to the beam detector 40 outside the side wall 25A. The light beam traverses the through window 36 (see FIG. 2) when scanning the photosensitive member 13.

  The beam detector 40 detects the light beam before scanning the photosensitive member 13. As shown in FIG. 3A, the beam detector 40 is disposed outside the side wall 25A. The beam detector 40 includes a photo IC 41 such as a phototransistor and a substrate 42 on which the photo IC 41 is mounted. The photo IC 41 of the beam detector 40 receives a light beam passing through the through window 36 (see FIG. 2) formed on the side wall 25A to the outside of the side wall 25A, and generates a detection signal corresponding to the intensity of the received light beam. Output to the control unit 5. The detection signal output from the photo IC 41 has a signal level HIGH when receiving a light beam, and has a signal level LOW when no light beam is received. Based on this detection signal, specifically, the control unit 5 uses the beam for taking the scanning start timing for each line based on the timing T0 (see FIG. 5) when the signal level changes from LOW to HIGH. A detect signal (also referred to as a BD signal or a main scanning synchronization signal) is generated. The BD signal is a signal for determining a scanning start timing at which scanning of the light beam is actually started on the photosensitive member 13 by the optical scanning device 11. This signal is output from the control unit 5 to a drive circuit for generating a light beam according to the density of the pixel data.

  In the present embodiment, the beam detector 40 is supported by the moving mechanism 50 so as to be movable in the vertical direction D1 outside the side wall 25A. Specifically, the beam detector 40 is supported so as to be movable in the vertical direction D1 perpendicular to the direction in which the light beam passes across the light receiving surface of the photo IC 41.

  The moving mechanism 50 supports the beam detector 40 so as to be movable in the vertical direction D1. As shown in FIG. 3B, the moving mechanism 50 includes an actuator 51 and a motor 58. The actuator 51 includes a spiral shaft 52, a bearing portion 53, and an arm 54. The spiral shaft 52 is a cylindrical shaft member extending in the vertical direction D1, and a spiral guide groove 55 is formed on the outer peripheral surface thereof. A rotating shaft 52A is provided at both ends of the spiral shaft 52, and the rotating shaft 52A is rotatably supported by the support frame 56. The output shaft of the motor 58 is connected to one rotating shaft 52A. The support frame 56 is provided on the casing 20 or the casing 25.

  The bearing portion 53 is formed in a cylindrical shape that fits the spiral shaft 52 from the outside. A protrusion that engages with the guide groove 55 is provided on the inner surface of the bearing portion 53. Therefore, when the spiral shaft 52 rotates, the protrusion is guided by the guide groove 55 and the bearing portion 53 moves in the vertical direction D1. In the present embodiment, when the spiral shaft 52 is rotated in the rotation direction D2 (hereinafter also referred to as the forward direction D2), the bearing portion 53 moves in the upward direction D11, and the spiral shaft 52 is rotated in the rotation direction D3 (hereinafter, reverse). When it is rotated in the direction D3), the bearing portion 53 moves in the downward direction D12. The spiral shaft 52 is rotated in the rotation direction (forward direction) D2 or the rotation direction (reverse direction) D3 when the motor 58 is driven and controlled in both directions by a motor driver 66 of the control unit 5 described later.

  An arm 54 is fixed to the bearing portion 53. The arm 54 extends from the bearing portion 53 in the horizontal direction, in other words, in a direction orthogonal to the longitudinal direction of the spiral shaft 52. The substrate 42 of the beam detector 40 is fixed to the arm 54. For this reason, when the bearing portion 53 moves in the vertical direction D1 according to the rotation of the spiral shaft 52, the beam detector 40 also moves in the vertical direction D1. Since the moving mechanism 50 is configured in this way, the moving mechanism 50 can move the beam detector 40 in the vertical direction D1 perpendicular to the direction in which the light beam passes so as to cross the beam detector 40.

  The control unit 5 is a computer having control devices such as a CPU 61, a ROM 62, and a RAM 63. The control unit 5 is an example of the movement control unit of the present invention, and includes a calculation unit 64 having a CPU 61, a ROM 62, and a RAM 63, a comparison unit 65, and a motor driver 66. The temperature sensor 35 is connected to the calculation unit 64, and a signal from the temperature sensor 35 is input to the calculation unit 64 of the control unit 5. A photo IC 41 is connected to the comparison unit 65, and a signal from the photo IC 41 is input to the comparison unit 65 of the control unit 5. A motor 58 is connected to the motor driver 66, and the motor 58 is rotationally driven in both directions in response to a drive signal from the motor driver 66. The control unit 5 may be configured by an electronic circuit such as an integrated circuit (ASIC, DSP) or may be provided separately from the main control unit that controls the image forming apparatus 10. .

  When receiving a signal from the temperature sensor 35, the calculation unit 64 calculates a temperature corresponding to the level (signal level) of the signal. The control unit 5 determines that the temperature calculated by the calculation unit 64 is the temperature inside the housing 25.

  The detection signal output from the photo IC 41 becomes HIGH level when receiving a light beam, and becomes LOW level when the light beam is not received. The comparison unit 65 calculates ON times (T1, T2) described later, and compares whether the calculated value is longer or shorter than a predetermined reference value T70 (threshold value). The ON times (T1, T2) are times from the rise timing T0 when the detection signal from the photo IC 41 changes from the LOW level to the HIGH level to the return to the LOW level.

  The CPU 61 is a processor that executes various arithmetic processes. The ROM 62 stores in advance information such as a control program for causing the CPU 61 to execute various processes including a light beam correction process described later. The ROM 62 stores the reference value T70, a threshold value used for light beam correction processing described later, a set value, and the like. The RAM 63 stores information such as the calculated temperature in the casing 25, the ON time, the number of printings performed in the image forming apparatus 10, and the number of printed sheets.

  By the way, the photo IC 41 has the highest sensitivity at the center of the light receiving surface, and the sensitivity decreases from the center toward the end. For this reason, for example, as shown in FIG. 3A, if the ON time when the light beam B1 passes across the center of the light receiving surface of the photo IC 41 (the center in the vertical direction D1) is T1, The ON time T2 when the beam B2 passes the upper end of the light receiving surface is shorter than the ON time T1. That is, when the light beam irradiated to the center of the light receiving surface shifts in the vertical direction D1 due to various factors, the ON time is shortened according to the shift amount. In the present embodiment, paying attention to such a phenomenon, when the ON time becomes shorter than the reference value T70, it is determined that the deviation of the light beam has exceeded the allowable range, and a light beam correction process described later is performed. Is executed. Here, the reference value T70 is set to a numerical value of 70% of the ON time T1.

  Hereinafter, an example of the procedure of the light beam correction process executed by the control unit 5 will be described with reference to the flowchart of FIG. This light beam correction process is a process of driving the moving mechanism 50 to correct the irradiation position of the light beam on the light receiving surface of the photo IC 41 to an appropriate position.

  In step S11, the control part 5 determines whether it is a predetermined start timing. In the present embodiment, it is determined whether the number of printed sheets in the image forming apparatus 10 is equal to or larger than a predetermined set number. This determination is made based on whether the count value of the number of printed sheets has reached a set number of sheets as a threshold value stored in the ROM 62. The start timing may be a timing at which a predetermined set time has elapsed. The start timing may be when a predetermined set number of scans are performed, or when the temperature in the optical scanning device 11 reaches a predetermined set temperature.

  If it is determined in step S11 that the number of printed sheets is equal to or larger than a predetermined set number (for example, 1000 sheets), the control unit 5 sets the current operation mode of the image forming apparatus 10 to the optical mode in the next step S13. Transition to an operation mode in which beam correction processing can be performed.

  On the other hand, if it is determined in step S11 that the number of printed sheets is less than the set number, the temperature difference ΔTh between the temperature in the casing 25 at the previous processing and the current temperature in the casing 25 is determined in step S12. It is determined whether or not a predetermined set value is exceeded. If it is determined that the temperature difference ΔTh is greater than or equal to the set value, the process proceeds to step S12. If it is determined that the temperature difference ΔTh is less than the set value, the process returns to step S11.

  In the next step S14, the control unit 5 determines whether the intensity of the light beam detected by the photo IC 41 is less than a predetermined threshold value. Specifically, the control unit 5 determines whether or not the ON time that is the light receiving time of the light beam is less than the reference value T70. Here, if it is determined that the ON time is equal to or greater than the reference value T70, the controller 5 once ends the light beam correction process and waits for the timing of the next light beam correction process. On the other hand, when it is determined that the ON time is less than the reference value T70, the control unit 5 proceeds to step S15.

  In step S15, the control unit 5 drives the moving mechanism 50 based on the intensity of the light beam detected by the photo IC 41, and moves the photo IC 41 together with the substrate 42 of the beam detector 40 in any one of the vertical directions D1. . In the present embodiment, the control unit 5 moves the photo IC 41 in the upward direction D11 by a predetermined distance. Specifically, the control unit 5 rotates the motor 58 by a predetermined rotation amount via the motor driver 66 to rotate the spiral shaft 52 in the forward direction D2. As a result, the photo IC 41 moves in the upward direction D11 by a distance corresponding to the predetermined rotation amount.

  In the next step S16, the control unit 5 determines whether or not the ON time has decreased. For example, when the photo IC 41 is moved further upward when the light beam is irradiated on the lower end of the photo IC 41, the irradiation point of the light beam moves relatively downward. In this case, the ON time is further reduced. Therefore, the control unit 5 can recognize (determine) that the irradiation point of the light beam is moving in a direction opposite to the direction to be corrected based on the decrease in the ON time. For this reason, if it is determined in step S16 that the ON time has decreased, the control unit 5 moves the photo IC 41 in the downward direction D12 opposite to the upward direction D11 (S17). In this case, the control unit 5 rotates the motor 58 in the reverse direction and rotates the spiral shaft 52 in the reverse direction D3 to move the photo IC 41 in the downward direction D12. Thereafter, in step S18, the control unit 5 determines whether or not the ON time is equal to or greater than the reference value T70. The process of step S17 is performed until it is determined in step S18 that the ON time is equal to or greater than the reference value T70. If it is determined in step S18 that the ON time is equal to or greater than the reference value T70, the control unit 5 stops the movement of the photo IC 41 (S21) and ends a series of processes.

  On the other hand, when it is determined in step S16 that the ON time has increased, the control unit 5 determines whether the ON time is equal to or greater than the reference value T70 (S19). If it is determined in step S19 that the ON time is equal to or greater than the reference value T70, the control unit 5 stops the movement of the photo IC 41 (S21) and ends a series of processes. If it is determined in step S19 that the ON time is less than the reference value T70, the control unit 5 continues to move the photo IC 41 in the same direction (upward) D11. The process of step S20 is performed until it is determined in step S19 that the ON time is equal to or greater than the reference value T70. If it is determined in step S19 that the ON time is equal to or greater than the reference value T70, the control unit 5 stops the movement of the photo IC 41 (S21) and ends a series of processes.

  As described above, the optical scanning device 11 of the image forming apparatus 10 includes the moving mechanism 50 and the control unit 5 that controls the moving mechanism 50 and moves the photo IC 41 in the vertical direction D1. Therefore, the light beam is affected by factors such as changes in the environment in which the image forming apparatus 10 is used, the ambient temperature of the optical scanning device 11, deterioration over time due to use, and the like (for example, distortion and distortion of the casing 20 and the casing 25). Even when is shifted in the vertical direction D1, the irradiation point of the light beam on the light receiving surface of the photo IC 41 is easily corrected to an appropriate position. Further, the irradiation point of the light beam is automatically corrected without requiring correction adjustment work by the maintenance worker.

  In the above-described embodiment, the mechanism for moving the photo IC 41 in the up-down direction D1 by the motor 58 is exemplified, but the present invention is not limited to this. For example, a moving mechanism that combines a reciprocating mechanism such as a solenoid and a rotating mechanism that rotates the spiral shaft 52 by a predetermined angle each time the plunger of the solenoid reciprocates can be employed.

  In the above-described embodiment, in step S11, it is determined whether or not the number of printed sheets in the image forming apparatus 10 is equal to or larger than a predetermined set number. However, the set number is variable even if it is fixed. It doesn't matter. For example, the first set number of sheets after the image forming apparatus 10 is used for the first time may be set to 200, and the set number of sheets may be changed to 1000 as the start timing thereafter. Further, since the internal temperature becomes high and the casing 20 and the housing 25 are easily distorted at a time when the temperature is high, the set number of times when the temperature is high may be less than the set number when the temperature is low. .

  In the above-described embodiment, the image forming apparatus 10 on which the single transfer device 15 is mounted is illustrated, but the present invention is not limited to this. For example, as shown in FIG. 7, the present invention can also be applied to a color image forming apparatus 100 in which a plurality of transfer devices 15 are arranged along the intermediate transfer belt 101. In FIG. 7, the same reference numerals are given to configurations having the same functions as those in the above-described embodiment. In this case, in the color image forming apparatus 100, a plurality of transfer devices 15 and one fixing device 18 are mounted. Two optical scanning devices 11 corresponding to the plurality of transfer devices 15 are provided in parallel to the intermediate transfer belt 101. In this configuration, of the two optical scanning devices 11, the right optical scanning device 11 </ b> A in FIG. 7 is arranged at a position close to the fixing device 18, and the left optical scanning device 11 </ b> B is arranged at a position far from the fixing device 18. Has been. In this case, the optical scanning device 11A is strongly affected by the temperature from the fixing device 18 that is heated to a high temperature. Therefore, in the color image forming apparatus 100 shown in FIG. 7, the start timings of the optical scanning device 11A and the optical scanning device 11A are made different. In this case, the control unit 5 starts the movement control for the moving mechanism 50 individually for each of the optical scanning devices 11A and 11B at the start timing different for each of the plurality of optical scanning devices 11A and 11B. As the different start timing, it can be considered that the start timing of the optical scanning device 11A is made earlier than the start timing of the optical scanning device 11B. Thereby, the light beam correction process according to each environment can be executed for each of the optical scanning devices 11A and 11B having different environments.

5: Control unit 10: Image forming apparatus 11: Optical scanning device 26: Light source 27: Polygon motor 40: Beam detector 41: Photo IC
50: Movement mechanism

Claims (4)

A plurality of optical scanning devices;
A transfer device for transferring an image based on electrostatic latent images on a plurality of photosensitive members scanned by the plurality of optical scanning devices to a transfer sheet;
A fixing device for fixing an image on the transfer sheet;
A movement control unit,
Each of the optical scanning devices
A light source;
An optical deflector that scans the photosensitive member by deflecting light emitted from the light source;
A light receiving unit that receives a light beam emitted from the light source before scanning the photosensitive member;
A moving mechanism for moving the light receiving unit in a direction perpendicular to a direction in which the light beam passes through the light receiving unit ,
The movement control unit
Based on the intensity of the light beam detected by the light receiving unit, the moving mechanism is driven to move the light receiving unit , and the plurality of light beams are moved at different start timings for each of the plurality of light scanning devices. The movement control for the movement mechanism is started for each scanning device,
The start timing for the optical scanning device arranged at a position close to the fixing device among the plurality of optical scanning devices is earlier than the start timing for the optical scanning device arranged at a position far from the fixing device. An image forming apparatus. The image forming apparatus according to claim 1, wherein the movement control unit drives the movement mechanism on condition that a light receiving time of the light beam is less than a predetermined threshold. The movement control unit drives the moving mechanism on the condition that the light receiving time is less than the threshold value, and moves the light receiving unit in a predetermined forward direction, and the light receiving time after the light receiving unit is moved. 3. The image forming apparatus according to claim 2, wherein when the temperature further decreases, the moving mechanism is driven to move the light receiving unit in the reverse direction. The start timing includes the temperature in the optical scanning device when a predetermined set number of prints are performed, when a predetermined set time has elapsed, when a predetermined set number of scans are performed, The image forming apparatus according to any one of claims 1 to 3, wherein when the temperature reaches a predetermined set temperature.

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