JP2020118805A - Optical scanner and image forming apparatus - Google Patents

Abstract

To detect a skew amount without forming a toner pattern for skew adjustment in an optical scanner body.SOLUTION: A laser diode 21 emits a light beam, and the light beam is scanned in a housing 2a; photosensors 42a to 42d receive the light beam and output sensor signals corresponding to the received light beam. A skew amount detection unit 61 detects the amount of skew of the light beam based on the sensor signals. A skew adjustment unit 62 executes skew adjustment corresponding to the detected skew amount. A light receiving surface of the photosensor 41a includes inclined edges 41a1, 41a2 inclined with respect to a direction vertical to the light beam scanning direction. The skew amount detection unit 61 (a) specifies a timing at which the light beam passes through the inclined edges 41a1, 41a2 based on the sensor signals, and (b) detects the skew amount based on the specified timing.SELECTED DRAWING: Figure 5

Description

The present invention relates to an optical scanning device and an image forming apparatus.

In an electrophotographic image forming apparatus, (a) an exposure device (optical scanning device) irradiates a photosensitive drum with laser light to form an electrostatic latent image, and (b) a developing device forms the electrostatic latent image. Toner is attached and development is performed to form a toner image, (c) the toner image is directly or indirectly transferred to print paper, and (d) the toner image is fixed to the print paper by a fixing device.

In an image forming apparatus, a resist correction pattern is formed, a color misregistration in the sub-scanning direction is detected based on the resist correction pattern, and the amount of skew from the detected color misregistration (scanning of light rays in the main scanning direction, The amount of positional deviation in the sub-scanning direction) is derived and skew adjustment is performed (see, for example, Patent Document 1). The skew adjustment is performed by rotating a mirror that reflects the scanned light on the photosensitive drum with a motor.

On the other hand, in another image forming apparatus, the light transmissive member of the optical path window at the position where the laser beam is emitted from the optical scanning device is cleaned regularly or for every predetermined number of prints (for example, refer to Patent Document 2).

JP, 2008-132677, A JP, 2005-215295, A

However, in the above-described image forming apparatus, since the resist correction pattern is formed and the skew amount is derived from the color misregistration detected by the resist correction pattern, the toner is consumed for the skew adjustment and the skew is consumed. Adjustment takes a relatively long time.

The present invention has been made in view of the above problems, and an object thereof is to obtain an optical scanning device and an image forming apparatus that detect a skew amount without forming a toner pattern for skew adjustment in the optical scanning device body. And

An optical scanning device according to the present invention includes a housing, a light source that emits a light beam scanned in the housing, a photosensor that receives the light beam, and outputs a sensor signal corresponding to the received light beam, A skew amount detection unit that detects the skew amount of the light beam based on a sensor signal, and a skew adjustment unit that performs skew adjustment corresponding to the detected skew amount. Further, the light receiving surface of the photo sensor includes an inclined edge inclined with respect to a direction perpendicular to the scanning direction of the light beam. The skew amount detection unit (a) specifies a timing at which the light ray passes the inclined edge based on the sensor signal, and (b) detects the skew amount based on the specified timing.

An image forming apparatus according to the present invention includes the above-described optical scanning device, a photosensitive drum irradiated with the light beam emitted from the optical scanning device, and a static drum formed by the irradiation of the light beam on the photosensitive drum. A developing device that forms a toner image by applying toner to the latent image and develops the latent image, and a fixing device that fixes the toner image transferred onto the print sheet onto the print sheet are provided.

According to the present invention, it is possible to obtain an optical scanning device and an image forming apparatus that detect a skew amount without forming a toner pattern for skew adjustment in the optical scanning device main body.

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description in conjunction with the accompanying drawings.

FIG. 1 is a side view showing a part of a mechanical internal configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a diagram showing an example of the configuration of the optical scanning device main body 2 in FIG. FIG. 3 is a perspective view showing the configuration of the optical scanning device according to the embodiment of the present invention. FIG. 4 is a side view of the optical scanning device according to the embodiment of the present invention. FIG. 5 is a diagram showing the light receiving surface of the photo sensor 41a in FIGS. FIG. 6 is a timing chart for explaining the sensor signal of the photo sensor 41a in FIGS. 3 and 4. FIG. 7 is a block diagram showing an electrical configuration of the optical scanning device according to the embodiment of the present invention.

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

FIG. 1 is a side view showing a part of a mechanical internal configuration of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus shown in FIG. 1 is an apparatus having an electrophotographic printing function, such as a printer, a facsimile machine, a copying machine, and a multifunction machine.

The image forming apparatus of this embodiment has a tandem type color developing device. This color developing device has photoconductor drums 1a to 1d, an optical scanning device main body 2 and developing devices 3a to 3d. The photoconductor drums 1a to 1d are photoconductors of four colors of cyan, magenta, yellow and black.

The optical scanning device main body 2 scans a laser beam and irradiates the photoconductor drums 1a to 1d to form an electrostatic latent image. The optical scanning device main body 2 includes a laser diode which is a light source of a laser beam, and an optical element (lens, mirror, polygon mirror, etc.) that guides the laser beam to the photosensitive drums 1a to 1d.

Further, a charging device such as a scorotron, a cleaning device, a static eliminator and the like are arranged around the photoconductor drums 1a to 1d. The cleaning device removes the residual toner on the photoconductor drums 1a to 1d after the primary transfer, and the charge eliminator removes the charge on the photoconductor drums 1a to 1d after the primary transfer.

Toner cartridges filled with four color toners of cyan, magenta, yellow, and black are mounted on the developing devices 3a to 3d, respectively, and the toners are supplied from the toner cartridges to constitute a developer together with the carrier. The developing devices 3a to 3d adhere the toner to the electrostatic latent images on the photosensitive drums 1a to 1d to form toner images. The photosensitive drum 1a, the optical scanning device main body 2, and the developing device 3a perform black development, and the photosensitive drum 1b, the optical scanning device main body 2, and the developing device 3b perform yellow development. Cyan development is performed by the drum 1c, the optical scanning device main body 2, and the developing device 3c, and magenta development is performed by the photoconductor drum 1d, the optical scanning device main body 2, and the developing device 3d.

That is, the photosensitive drums 1a to 1d are irradiated with the light beam emitted from the optical scanning device main body 2, and the developing devices 3a to 3d are electrostatic latent images formed by the irradiation of the light beams on the photosensitive drums 1a to 1d. A toner image is formed by adhering toner to the toner and developing the toner.

The intermediate transfer belt 4 is an annular image carrier that contacts the photosensitive drums 1a to 1d and primarily transfers the toner images on the photosensitive drums 1a to 1d. The intermediate transfer belt 4 is stretched around a driving roller 5, and is rotated by a driving force from the driving roller 5 in a direction from a contact position with the photosensitive drum 1d to a contact position with the photosensitive drum 1a.

The transfer roller 6 brings the conveyed paper into contact with the intermediate transfer belt 4, and secondarily transfers the toner image on the intermediate transfer belt 4 onto the paper. The sheet on which the toner image is transferred is conveyed to the fixing device 9 and the toner image is fixed on the sheet.

The roller 7 has a cleaning brush, and the cleaning brush is brought into contact with the intermediate transfer belt 4 to remove the toner remaining on the intermediate transfer belt 4 after the transfer of the toner image to the paper.

The sensor 8 is an optical sensor that measures the density of the developed toner image, irradiates the intermediate transfer belt 4 with light rays, and detects the reflected light. For example, when adjusting the toner concentration, the sensor 8 irradiates a predetermined area of the intermediate transfer belt 4 with a light beam, detects the reflected light, and outputs an electric signal according to the light amount.

The fixing device 9 fixes the toner image transferred to the print paper on the print paper by, for example, a pressure heating method.

The registration roller 10 temporarily stops the sheet conveyed by the primary sheet feeding from the sheet feed tray or the like, and conveys the sheet to the transfer position by the intermediate transfer belt 4 and the transfer roller 6 at the secondary sheet feeding timing. The secondary paper feed timing is designated so that the toner image on the intermediate transfer belt 4 is transferred to the designated position on the paper. The registration sensor 11 is a sensor that is installed in the vicinity of the registration roller 10 and optically detects that the paper has reached the registration roller 10 (registration position).

FIG. 2 is a diagram showing an example of the configuration of the optical scanning device main body 2 in FIG. It should be noted that the optical scanning device main body 2 shown in FIG. 2 shows a portion for the photoconductor drum 1a, and does not show a portion for the photoconductor drums 1b to 1d.

In FIG. 2, the laser diode 21 is a light source that emits a laser beam. The optical system 22 is a group of various lenses arranged between the laser diode 21 and the polygon mirror 23 and/or between the polygon mirror 23 and the photosensitive drum 1 a and the PD sensor 24. An fθ lens or the like is used for the optical system 22. The optical system 22 also includes a mirror 22a parallel to the scanning direction of the laser beam. For example, the mirror 22a can be rotated by a motor (not shown) or the like.

The polygon mirror 23 is an element that has an axis perpendicular to the axis of the photosensitive drum 1a, has a polygonal cross section perpendicular to the axis, and has a side surface serving as a mirror. The polygon mirror 23 rotates about its axis and scans the laser beam emitted from the laser diode 21 along the axial direction (main scanning direction) of the photosensitive drum 1a. This laser beam is reflected by the mirror 22a, is emitted from the optical path window 25a, and is incident on the photosensitive drum 1a.

The polygon motor unit 23a rotates the polygon mirror 23 according to a control signal from the driver circuit 31.

The PD sensor 24 is a sensor that receives a laser beam scanned by the polygon mirror 23 to generate a main scanning synchronization signal at a predetermined position. When light is incident on the PD sensor 24, the PD sensor 24 induces an output voltage according to the amount of light. The PD sensor 24 is arranged at a predetermined position on the line where the light is scanned, detects a timing (hereinafter, referred to as a synchronization timing) Tpd at which the spot of the light passes through the position, and a pulse formed at the synchronization timing Tpd. Is output as a main scanning synchronization signal.

The driver circuit 31 controls the laser diode 21 to cause the laser diode 21 to emit a laser beam, and also controls the polygon motor unit 23a to rotate the polygon mirror 23 at a predetermined rotation speed. The driver circuit 31 controls the laser diode 21 so as to be exposed by the laser beam in a pattern according to the image to be formed in synchronization with the main scanning synchronization signal (synchronization timing Tpd).

The controller 32 includes an ASIC (Application Specific Integrated Circuit), a microcomputer, and the like, and supplies an analog control signal corresponding to an image to be printed to the driver circuit 31, so that the light emission amount of the laser diode 21 is set to the scanning position of the laser beam. Control accordingly. In the image area in the main scanning direction (range in which an electrostatic latent image corresponding to the image can be formed), the amount of irradiation light to the photoconductor drum 1a varies due to the optical characteristics of the optical system 22, The amount of light emitted from the laser diode 21 is adjusted so that the amount of light emitted to the photosensitive drum 1a in the scanning direction is uniform.

Further, the controller 32 is an ASIC, a microcomputer, or the like, and controls the internal devices of the image forming apparatus and performs image processing.

FIG. 3 is a perspective view showing the configuration of the optical scanning device according to the embodiment of the present invention. As shown in FIG. 3, this optical scanning device includes a housing 2a of the optical scanning device main body 2, optical path windows 25a to 25d, and a cleaning member 26 that cleans the light transmissive members of the optical path windows 25a to 25d. .. The cleaning member 26 is provided with cleaning pads 26a to 26d.

The optical path windows 25a to 25d are provided corresponding to the photoconductor drums 1a to 1d, and when the laser beam emitted by the laser diode 21 in the housing 2a travels from inside the housing 2a to outside the housing 2a as described above. And a light transmitting member (glass plate, resin plate, etc.) through which the laser beam passes.

The laser diode 21, the optical system 22 (including the mirror 22a), the polygon mirror 23, and the like described above are arranged in the housing 2a, and the light beam emitted from the laser diode 21 is scanned by the polygon mirror 23. Then, the light is emitted through the optical path window 25a.

In addition, in this embodiment, the light rays travel from the inside of the housing 2a to the outside of the housing 2a substantially vertically, and the optical path windows 25a to 25d are arranged substantially horizontally.

Further, the optical scanning device includes photosensors 41a to 41d, as shown in FIG. Each of the photosensors 41a to 41d is a photodiode, a phototransistor, or the like, receives a light beam scanned by the polygon mirror 23 and reflected by the mirror 22a, and outputs a sensor signal corresponding to the received light beam.

FIG. 4 is a side view of the optical scanning device according to the embodiment of the present invention. As shown in FIG. 4, when the photosensitive drum 1a is irradiated with a light beam to generate an electrostatic latent image, the cleaning member 26 and the photosensor 41a do not exist in the image region in the light beam scanning range, Retreat to the home position. The home position is also within the scanning range, and even if the photo sensor 41a is at the home position, the light beam is scanned on the photo sensor 41a.

In this embodiment, the photosensors 41a to 41d are provided on the cleaning member 26 and receive light rays through the optical path windows 25a to 25d. Here, the photo sensors 41a to 41d are provided adjacent to the cleaning pads 26a to 26d.

FIG. 5 is a diagram showing a light receiving surface of the photo sensor 41a in FIGS. 3 and 4. As shown in FIG. 5, the light-receiving surface of each photosensor 41a is parallel to the optical path window 25a and has inclined edges 41a1 and 41a2 that are inclined with respect to the vertical direction of the scanning direction of the light beam. Here, the light receiving surface has a parallelogram shape (that is, two inclined edges), but it may have a trapezoidal shape (that is, one inclined edge). Although FIG. 5 shows the light receiving surface of the photo sensor 41a, the other photo sensors 41b to 41d also have the same light receiving surface.

FIG. 6 is a timing chart for explaining the sensor signal of the photo sensor 41a in FIGS. 3 and 4.

As shown in FIG. 5, when the scanning position in the sub-scanning direction is the reference value (that is, when there is no skew), the irradiation position of the light beam passes the inclined edge 41a1 at the predetermined time Ts_ref from the synchronization timing Tpd, and the synchronization is achieved. The irradiation position of the light ray passes the inclined edge 41a2 at a predetermined time Te_ref from the timing Tpd. Thus, as shown in FIG. 6, when there is no skew, the sensor signal has a rising edge at Ts_ref and a falling edge at Te_ref.

Then, as shown in FIG. 5, when the scanning position in the sub-scanning direction is deviated from the reference value (that is, when there is a skew), the irradiation position of the light beam is an inclined edge at predetermined times Ts1 and Ts2 from the synchronization timing Tpd. 41a1 and the irradiation position of the light beam passes the inclined edge 41a2 at the predetermined times Te1 and Te2 from the synchronization timing Tpd. Thus, as shown in FIG. 6, when there is skew, the sensor signal has rising edges at Ts1 and Ts2 and falling edges at Te1 and Te2.

Then, the difference between the passage timing Ts_ref of the irradiation position of the light beam of the inclined edge 41a1 when there is no skew and the passage timing Ts1 and Ts2 of the irradiation position of the light beam of the inclined edge 41a1 when there is a skew (Ts1-Ts_ref, Ts2-Ts_ref) corresponds to the skew amount.

Similarly, the difference (Te1-Te_ref) between the passage timing Te_ref of the irradiation position of the light beam of the inclined edge 41a2 when there is no skew and the passage timing Te1 and Te2 of the irradiation position of the light beam of the inclined edge 41a2 when there is a skew. , Te2-Te_ref) correspond to the skew amount.

FIG. 7 is a block diagram showing an electrical configuration of the optical scanning device according to the embodiment of the present invention. As shown in FIG. 7, this optical scanning device includes a cleaning member driving device 51 and a storage device 52 in addition to the above-described optical scanning device main body 2.

The cleaning member driving device 51 linearly moves the cleaning member 26 along the longitudinal direction of the optical path windows 25a to 25d so that the cleaning pads 26a to 26d of the cleaning member 26 become the light transmitting members of the optical path windows 25a to 25d. The light-transmissive members of the optical path windows 25a to 25d are cleaned by bringing them into contact with each other. The cleaning member 26 cleans the light-transmissive members of the optical path windows 25a to 25d and removes dust attached to the surfaces of the optical path windows 25a to 25d.

The storage device 52 is a non-volatile storage device such as a flash memory for storing various data.

Further, the controller 32 is an ASIC, a microcomputer, or the like, and operates as the skew amount detection unit 61, the skew adjustment unit 62, and the cleaning processing unit 63.

The skew amount detector 61 detects the amount of skew of the light beam based on the sensor signals from the photo sensors 41a to 41d.

Specifically, the skew amount detection unit 61 (a), based on the sensor signal, the timing Ts when the scanned light beam (irradiation position thereof) passes through the inclined edges 41a1 and 41a2 of the photosensors 41a to 41d. Te is specified, and (b) the skew amount is detected based on the specified timings Ts and Te.

That is, as described above, since the difference (Ts-Ts_ref, Te-Te_ref) between the specified timing Ts, Te and the known reference timing Ts_ref, Te_ref corresponds to the skew amount, the skew amount detection unit 61 determines the predetermined amount. The skew amount is derived from the specified timings Ts and Te according to the calculation formula. The calculation formula is specified in advance by experiments or the like.

The skew adjustment unit 62 performs skew adjustment according to the detected skew amount. For example, the skew adjustment unit 62 performs skew adjustment by adjusting the angle of the mirror 22a arranged in parallel to the above-described light ray scanning direction or adjusting the above-described light ray scanning timing. The angle adjustment of the mirror 22a is performed by controlling a stepping motor or the like (not shown).

The cleaning processing unit 63 uses the cleaning member driving device 51 at a predetermined cleaning timing to perform cleaning of the optical path windows 25a to 25d by the cleaning member 26. At that time, the cleaning pads 26a to 26d of the cleaning member 26 reciprocate on the optical path windows 25a to 25d. The cleaning timing of the optical path windows 25a to 25d is determined by the elapsed time from the previous cleaning of the optical path windows 25a to 25d or the number of prints from the previous cleaning.

When the cleaning processing unit 63 irradiates the photosensitive drum 1a with a light beam to generate an electrostatic latent image, the cleaning processing unit 63, together with the photosensor 41a, retracts the cleaning member 26 from the image area in the scanning range of the light beam to the home position.

Further, the cleaning processing unit 63 controls the optical scanning device main body 2 to cause the light scanning device main body 2 to emit and scan the light beam at the time of the above-described cleaning, and the photosensors 41a to 41d cause each of the main scanning directions. Measure the light intensity at the location. Then, based on the measurement result of the light intensity distribution in the main scanning direction, the controller 32 determines the light emission amount of the laser diode 21 at each position in the main scanning direction based on the measurement result of the light intensity distribution in the main scanning direction. Adjust so that it is even.

Next, the operation of the image forming apparatus will be described.

First, the print operation will be described.

The controller 32 specifies the light emission amount pattern of the laser diode 21 at each scanning position in the sub-scanning direction based on the image data after predetermined image processing for printing such as halftoning and color conversion, and the optical scanning device main body 2 In this state, the driver circuit 31 is caused to emit laser light in the emitted light amount pattern in a state where the irradiation position is repeatedly scanned in the main scanning direction.

As a result, the laser light is applied to the photoconductor drums 1a to 1d, and electrostatic latent images are formed on the photoconductor drums 1a to 1d. Then, the developing devices 3a to 3d attach toner to the electrostatic latent image and develop the electrostatic latent image to form a toner image. The toner image of each toner color is primarily transferred to the intermediate transfer belt 4 and then secondarily transferred from the intermediate transfer belt 4 to the print paper. Then, the transferred toner image is fixed on the print paper by the fixing device 9.

Next, the cleaning operation of the optical scanning device will be described.

As described above, when executing the printing operation, the cleaning member 26 is retracted to the home position. When the predetermined cleaning timing arrives, the cleaning processing unit 63 controls the cleaning member driving device 51 to move the cleaning member 26 and clean the optical path windows 25a to 25d at timings other than the printing operation. As described above, at that time, the light intensity distribution in the main scanning direction is measured, and the light emission amount of the laser diode 21 at each position in the main scanning direction is adjusted based on the light intensity distribution.

Next, skew adjustment will be described.

The skew amount detection unit 61 controls the optical scanning device body 2 at a predetermined skew adjustment timing to generate and scan a light beam in the optical scanning device body 2 to detect sensor signals from the photosensors 41a to 41d. The skew amount is detected as described above. At that time, the skew amount detection unit 61 turns off the laser diode 21 during a period in which the irradiation position (scanning position) of the light beam (a) is within the image region, and the irradiation position (scanning position) of the light beam (b) is changed. The laser diode 21 may be turned off during the period of passing through the photo sensors 41a to 41d. Then, when the skew amount is detected, the skew adjustment unit 62 rotates the mirror 22a, for example, by an adjustment amount according to the skew amount (that is, an adjustment amount for bringing the skew amount close to zero), Reduce the amount of skew.

As described above, according to the above-described embodiment, the laser diode 21 emits a light beam, the light beam is scanned in the housing 2a, and the photosensors 41a to 41d receive and receive the light beam. It outputs the sensor signal corresponding to the light beam. The skew amount detector 61 detects the skew amount of the light beam based on the sensor signal. The skew adjustment unit 62 performs skew adjustment according to the detected skew amount. The light receiving surface of the photo sensor 41a includes inclined edges 41a1 and 41a2 that are inclined with respect to the direction perpendicular to the scanning direction of the light beam. The skew amount detection unit 61 (a) identifies the timing at which the light ray passes the inclined edges 41a1 and 41a2 based on the sensor signal, and (b) detects the skew amount based on the identified timing.

As a result, the skew amount is detected without forming a toner pattern for adjusting the skew in the optical scanning device body 2.

Various changes and modifications to the above-described embodiment will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the subject matter and without diminishing its intended advantages. That is, such changes and modifications are intended to be covered by the appended claims.

For example, in the above-described embodiment, the controller 32 executes the calibration at a predetermined timing. In the calibration, the adjusted toner pattern of each toner color is formed on the intermediate transfer belt 4, and the sensor 8 forms the adjusted toner pattern. By detecting the color misregistration, the color misregistration is detected and the color misregistration is corrected. The skew adjustment unit 62 may perform skew adjustment before the controller 32 performs color misregistration correction by calibration. In that case, the controller 32 performs calibration after the skew adjustment in each optical scanning device is completed, so that the amount of color misregistration correction at that time can be small, and the color misregistration can be effectively suppressed.

The present invention is applicable to, for example, an electrophotographic image forming apparatus.

2 Optical Scanning Device Main Body 2a Housing 22a Mirror 25a to 25d Optical Path Window 26 Cleaning Member 26a to 26d Cleaning Pad 32 Controller 41a to 41d Photo Sensor 41a1, 41a2 Inclined Edge 61 Skew Amount Detection Section 62 Skew Adjustment Section

Claims (5)

A housing,
A light source that emits a light beam that is scanned within the housing,
A photosensor that receives the light beam and outputs a sensor signal corresponding to the received light beam,
A skew amount detection unit that detects the skew amount of the light beam based on the sensor signal,
A skew adjustment unit that performs skew adjustment corresponding to the detected skew amount,
The light-receiving surface of the photosensor includes an inclined edge inclined with respect to a vertical direction of the scanning direction of the light beam,
The skew amount detection unit (a) specifies a timing at which the light ray passes the inclined edge based on the sensor signal, and (b) detects the skew amount based on the specified timing.
An optical scanning device. An optical path window including a light transmissive member through which the light beam passes when traveling from the inside of the housing to the outside of the housing, and a cleaning member for cleaning the light transmissive member of the optical path window,
The photo sensor is provided in the cleaning member, and receives the light beam through the optical path window,
The optical scanning device according to claim 1, wherein The skew adjustment unit performs the skew adjustment by adjusting an angle of a mirror arranged in parallel with a scanning direction of the light beam or adjusting a scanning timing of the light beam. 2. The optical scanning device according to 2. An optical scanning device according to any one of claims 1 to 3,
A photosensitive drum irradiated with the light beam emitted from the optical scanning device;
A developing device for forming a toner image by applying toner to the electrostatic latent image formed by irradiation of the light beam on the photosensitive drum to develop the electrostatic latent image;
A fixing device for fixing the toner image transferred onto the print sheet onto the print sheet;
An image forming apparatus comprising: Further equipped with a controller that performs calibration to correct color misregistration,
The skew adjustment unit performs the skew adjustment before the controller performs the color misregistration correction,
The image forming apparatus according to claim 4, wherein.

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