JP2010244048A - Image forming apparatus - Google Patents

Abstract

An image forming apparatus capable of determining a failure of each light emitting element without printing on paper.
An optical scanning unit including a plurality of light emitting units including a plurality of light emitting elements, a plurality of photoconductors provided corresponding to the light emitting units, and electrostatic latent images formed on the photoconductors. A developing unit that develops an image with different color toners, a transferred unit to which each image developed by the developing unit is transferred, and a density detection that detects the density of each image transferred to the transferred unit And a light emitting element included in the first light emitting unit among the plurality of light emitting units at the time of alignment control based on the first test image transferred from each of the plurality of photosensitive members. An image forming apparatus comprising: a failure determination unit that detects the density of the two test images formed on the transferred portion by the density detection unit and determines a failure of the light emitting element based on the detection result.
[Selection] Figure 9

Description

  The present invention relates to an image forming apparatus including an optical scanning unit including a plurality of light emitting units including a plurality of light emitting elements.

  Conventionally, in a conventional color image forming apparatus having four colors Y, M, C, and K, assuming that the reference color of the main scanning reference position signal BD is Y, for example, laser control of other colors based on the Y color BD signal Had gone. Such an image forming apparatus is a medium speed machine up to about 45 PPM and has a laser (single beam) configuration for each color. When realizing a higher-speed color image forming apparatus, it is often difficult to achieve with one laser per color due to the upper limit of polygon rotation speed, and this is achieved by using multiple lasers per color. is doing. In addition, when a higher quality image is formed, it is realized by increasing the number of lasers and reducing the laser interval, such as replacing a 600 dpi single laser with a 1200 dpi 2 LD array.

  However, in the above configuration, the failure of the BD signal laser of the reference color Y can be detected by the presence or absence of the BD signal, but the failure detection of other lasers (laser that is not used for the BD signal of the reference color Y and laser for other colors) Therefore, another detection means was necessary. For example, a method of determining based on an image printed on paper has been used. However, the conventional method involves many other factors besides various lasers, such as abnormalities in the high-pressure system and mechanical misalignment, making it difficult to determine whether a failure is caused by the laser not emitting light. was there. Therefore, there is a need for means capable of detecting the failure of each laser without including other factors than the laser.

  In order to solve the above-described problem, this specification includes an optical scanning unit including a plurality of light-emitting units including a plurality of light-emitting elements, and a light-emitting unit provided for each of the light-emitting units. A plurality of photoconductors on which electrostatic latent images are formed, a developing unit that develops each electrostatic latent image formed on each photoconductor with a different color toner, and each image developed by the developing unit To which the image is transferred, a density detection unit for detecting the density of each of the images transferred to the transfer unit, and alignment control based on each first test image transferred from each photoconductor In this case, the density detector detects the density of the two test images formed on the transferred part by causing any one of the light emitting elements included in the first light emitting part to emit light. Based on the detection result, the light emitting element And determining malfunction determining unit failure of an image forming apparatus having a.

  In this specification, an optical scanning unit having a plurality of light emitting units including a plurality of light emitting elements, and an electrostatic latent image are formed by the light emitted from each of the light emitting units. A plurality of photoconductors, a developing unit that develops each electrostatic latent image formed on each photoconductor with a different color toner, and a transferred unit to which each image developed by the developing unit is transferred , An alignment detection unit that acquires information for alignment control from each image transferred to the transfer target portion, and image quality maintenance control based on each first test image transferred from each photoconductor. In this case, the alignment detection unit detects the second test image formed on the transferred portion by causing the light emitting element of the first light emitting unit to emit light among the plurality of light emitting units. Failure to determine failure of the light emitting element based on And tough, an image forming apparatus having a.

  In this specification, a writing position in the main scanning direction is obtained by receiving light emitted from a first light emitting unit among the plurality of light emitting units and a light scanning unit including a plurality of light emitting units including a plurality of light emitting elements. More than the first sensor that receives the light emitted from the first sensor that obtains correction information for correction and the second light emitting unit that is different from the first light emitting unit among the plurality of light emitting units. Based on the presence or absence of light reception in the first sensor when each of the light emitting elements included in the first light emitting unit emits light, a failure of the first light emitting unit is detected. And determining whether or not the second light emitting unit has failed based on the presence or absence of light reception in the second sensor when each of the light emitting elements included in the second light emitting unit emits light. And an image forming apparatus.

  This specification includes an optical scanning unit including a plurality of light emitting units including a plurality of light emitting elements, a sensor for optically acquiring correction information for correcting a writing position in the main scanning direction, and each of the light emitting units. The present invention relates to an image forming apparatus including a failure determination unit that determines a failure of each light emitting unit based on the presence or absence of light reception by the sensor when each light emitting element is caused to emit light.

  As described above in detail, according to the present invention, failure of each light emitting element can be determined without printing on paper.

1 is a cross-sectional view illustrating an example of an internal configuration of a digital multifunction peripheral. It is a block diagram which shows roughly the example of a structure of the control system in a digital multifunctional device. FIG. 5 is a layout diagram illustrating the layout of each unit in the optical scanning unit. It is the figure which showed the structural example of the optical system in an optical scanning part. It is a figure for demonstrating the scanning of the laser beam in an optical scanning part. 3 is a diagram illustrating a configuration example of an LD array 72. FIG. 3 is a diagram illustrating a configuration example of a laser control unit 68. FIG. It is the figure which put together the operation | movement and setting matter in the laser control part shown in FIG. It is a top view of a transfer belt. It is explanatory drawing explaining the detection method by a density sensor. 3 is a plan view illustrating a test pattern for detecting the density of a toner image. FIG. It is the schematic diagram which showed the test pattern for alignment (1st test image) and the test pattern for failure detection (2nd test image). It is the flowchart which showed the procedure of failure detection. It is a schematic diagram which shows the test pattern for image quality maintenance, and the test pattern for failure detection. It is the flowchart which showed the method of failure detection. FIG. 6 is a plan view of a transfer belt in which test patterns are arranged in the main scanning direction. FIG. 10 is a diagram for explaining scanning of laser light in an optical scanning unit according to a third embodiment. 10 is a timing chart of the third embodiment. 10 is another timing chart of the third embodiment. 10 is another timing chart of the third embodiment. 10 is a flowchart illustrating a failure inspection method according to a third embodiment. FIG. 10 is a diagram for explaining scanning of laser light in an optical scanning unit according to a fourth embodiment. 6 is a flowchart illustrating a failure inspection method according to a fourth embodiment. FIG. 10 is a diagram for explaining scanning of laser light in an optical scanning unit according to a fifth embodiment. FIG. 10 is a diagram for explaining scanning of laser light in an optical scanning unit according to a sixth embodiment.

(References to related applications)
This application claims the benefit of US provisional application 61 / 167,076, US provisional application 61 / 167,806, filed April 6, 2009. The disclosure content of this application is hereby incorporated by reference in its entirety and forms part of this application.

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

  FIG. 1 is a sectional view showing an example of the internal configuration of a color digital multifunction peripheral 1 according to the image processing apparatus of the present invention. A digital multifunction machine 1 shown in FIG. 1 includes a reading optical system 2 and an image forming unit 3. The reading optical system 2 reads an image on a document as color image data (multi-valued image data) by optically scanning the document surface. The image forming unit 3 forms an image based on color image data (multi-valued image data). Further, the digital multi-function peripheral 1 has a facsimile interface (not shown) for transmitting and receiving facsimile data or a network interface (not shown) for network communication as means for inputting and outputting image data. With this configuration, the digital multifunction device 1 functions as a copier, scanner, printer, facsimile, or network communication device.

  First, the configuration of the reading optical system 2 will be described. As shown in FIG. 1, the reading optical system 2 includes a document table 10, a light source 11, a reflector 12, a first mirror 13, a first carriage 14, a second mirror 16, a third mirror 17, a second carriage 18, and a light collecting. A lens 20, a three-line CCD sensor 21, a CCD substrate 22, and a CCD control substrate 23 are included.

  A document O is placed on the document table 10. The document table 10 is made of glass, for example. The light source 11 exposes the document O placed on the document table 10. The reflector 12 adjusts the light distribution from the light source 11. The first mirror 13 guides light from the document surface to the second mirror 16. The first carriage 14 mounts the light source 11, the reflector 12, and the first mirror 13. The first carriage 14 moves at a predetermined speed (V) in the sub-scanning direction of the document surface by a driving force transmitted from a driving unit (not shown).

  The second mirror 16 and the third mirror 17 guide the light from the first mirror 13 to the condenser lens 20. The second carriage 18 carries the second mirror 16 and the third mirror 17. The second carriage 18 moves in the sub-scanning direction at a speed (V / 2) that is half the speed (V) of the first carriage 14. The second carriage 18 is driven at a speed half that of the first carriage, so that the distance from the reading position on the document surface to the light receiving surface of the 3-line CCD sensor 21 is maintained at a constant optical path length.

  Light from the document surface enters the condenser lens 20 via the first, second, and third mirrors 13, 16, and 17. The condenser lens 20 guides incident light to a three-line CCD sensor 21 that converts the light into an electrical signal. In other words, the reflected light from the document surface passes through the glass of the document table 10, is sequentially reflected by the first mirror 13, the second mirror 16, and the third mirror 17, and passes through the condensing lens 20 to the three-line CCD sensor 21. An image is formed on the light receiving surface.

  The 3-line CCD sensor 21 is configured by a line sensor in which photoelectric conversion elements that convert light into electric signals are arranged in the main scanning direction. The 3-line CCD sensor 21 converts light from the document into an electrical signal composed of three-color image signals constituting a color image. For example, when a color image is read with three primary colors of light composed of R (red), G (green), and B (blue), the 3-line CCD sensor 21 includes an R line sensor 21R that reads an R (red) image; A G line sensor 21G that reads a green image and a B line sensor 21B that reads a blue image are used.

  The CCD substrate 22 includes a sensor drive circuit (not shown) for driving the 3-line CCD sensor 21. The CCD control board 23 controls the CCD board 22 and the 3-line CCD sensor 21. The CCD control board 23 includes a control circuit (not shown) for controlling the CCD board 22 and the 3-line CCD sensor 21, and an image processing circuit (not shown) for processing the image signal output from the 3-line CCD sensor 21. Have.

  Next, the configuration of the image forming unit 3 will be described. As shown in FIG. 1, the image forming unit 3 includes a paper supply unit 30, an optical scanning unit 40, first to fourth photosensitive drums 41a to 41d, first to fourth developing devices 43a to 43d, and a transfer belt. 45, cleaners 47a to 47d, a transfer device 49, a fixing device 51, a belt cleaner 53, and a stock portion 55.

  The optical scanning unit 40 emits laser light (exposure light) for forming latent images on the first to fourth photosensitive drums 41a to 41d. Here, it is assumed that the first to fourth photosensitive drums 41a to 41d correspond to three colors (Y, M, C) and black (K) that form a color image, respectively. The optical scanning unit 40 irradiates each photosensitive drum 41a to 41d as an image carrier for each color with exposure light corresponding to each color component in the image data. Electrostatic latent images corresponding to the intensity of the laser light (exposure light) emitted from the optical scanning unit 40 are formed on the photosensitive drums 41a to 41d. The first to fourth photoconductive drums 41a to 41d hold electrostatic latent images as images of the formed colors.

  The first to fourth developing devices 43a to 43d develop the latent images held by the photosensitive drums 41a to 41d with specific colors, respectively. That is, the developing devices 43a to 43d develop the image by supplying toner of each color to the latent images held by the corresponding photosensitive drums 41a to 41d. For example, the image forming unit is configured to obtain a color image by subtractive color mixing using three colors of yellow (yellow), magenta (magenta), and cyan (cyan, deep purple). In this case, the first to fourth developing devices 43a to 43d visualize the latent images held by the photosensitive drums 41a to 41d in any one of yellow, magenta, cyan, and black. (develop. That is, each of the first to fourth developing devices 43a to 43d stores toner of any one color of yellow, magenta, cyan, and black (Black). The colors stored in the first to fourth developing devices 43a to 43d (the order in which the images of the respective colors are developed) are determined according to the image forming process or the characteristics of the toner. In the present embodiment, the photosensitive drums 41 a to 41 d and the developing devices 43 a to 43 d correspond to yellow (Y), magenta (M), cyan (C), and black (K), respectively.

  The transfer belt 45 functions as an intermediate transfer member. The toner images of the respective colors formed on the photosensitive drums 41a to 41d are sequentially transferred to a transfer belt 45 as an intermediate transfer member. For example, the toner images on the photosensitive drums 41a to 41d conveyed to the intermediate transfer position are transferred onto the transfer belt 45 by the intermediate transfer voltage. As a result, a color toner image in which images of four colors (yellow, magenta, cyan, and black) are overlaid is formed on the transfer belt 45. The transfer device 49 transfers the toner image generated on the transfer belt 45 onto a sheet as an image forming medium. A displacement sensor 26 and a density sensor 27 are provided on the downstream side of the photosensitive drum 41d in the transport direction of the transfer belt 45. Details of the position shift sensor 26 and the density sensor 27 will be described later.

  The paper supply unit 30 supplies paper to which a toner image is transferred from a transfer belt 45 as an intermediate transfer member to a transfer device 49. The paper supply unit 30 supplies paper at an appropriate timing with respect to the transfer position of the toner image by the transfer device 49. The paper supply unit 30 includes a plurality of cassettes 31, pickup rollers 33, a separation mechanism 35, a plurality of transport rollers 37, and aligning rollers 39.

  Each of the plurality of cassettes 31 stores a sheet as an image forming medium. The cassette 31 can store a predetermined number of sheets of any size. The pickup roller 33 takes out the sheets one by one from the designated cassette 31. For example, as the cassette 31, a cassette directly designated by the user is designated, or a cassette in which an optimal paper size calculated by the document size and magnification is designated.

  The separation mechanism 35 prevents the pickup roller 33 from taking out two or more sheets from the cassette (separates into one sheet). The plurality of transport rollers 37 transport the paper separated by the separating mechanism 35 toward the aligning roller 39. The aligning roller 39 moves the sheet to a transfer position where the transfer device 49 and the transfer belt 45 are in contact with the timing when the transfer device 49 transfers the toner image from the transfer belt 45 (the toner image moves (at the transfer position)). Transport.

  The fixing device 51 fixes the toner image on the sheet. For example, the fixing device 51 fixes the toner image on the paper by heating the paper in a pressurized state. The fixing device 51 conveys the fixed sheet to the stock unit 55. The stock unit 55 is a paper discharge unit that discharges paper on which image forming processing (images have been printed). In the configuration example shown in FIG. 1, the stock unit 55 is provided in a space between the reading optical system 2 and the image forming unit 3.

  Further, the belt cleaner 53 cleans the transfer belt 45. The belt cleaner 53 contacts the transfer belt 45 at a predetermined position. The belt cleaner 53 removes waste toner remaining on the transfer surface onto which the toner image on the transfer belt 45 is transferred from the transfer belt 45.

  Next, the configuration of the control system of the digital multi-function peripheral 1 will be described.

  FIG. 2 is a block diagram schematically illustrating a configuration example of a control system in the digital multi-function peripheral 1. As shown in FIG. 2, in addition to the reading optical system 2 and the image forming unit 3, the digital multi-function peripheral 1 includes an operation unit 60, a CPU 61, a main memory 62, an HDD 63, an input image processing unit 64, A page memory 65 and an output image processing unit 66 are included.

  The operation unit (control panel) 60 is used by a user to input an operation instruction or display guidance for the user. The operation unit 60 includes a display device and operation keys. For example, the operation unit 60 includes a liquid crystal display device with a built-in touch panel and hard keys such as a numeric keypad.

  The CPU 61 comprehensively controls the entire digital multi-function peripheral 1. The CPU 61 implements various functions by executing a program stored in a program memory (not shown), for example. The main memory 62 is a memory that stores work data and the like. The CPU 61 implements various processes by executing various programs using the main memory 62. For example, the CPU 61 realizes copy control by controlling the scanner 2 and the printer 3 in accordance with a copy control program. That is, the digital multi-function peripheral 1 functions as a copier when the CPU 61 executes a copy control program.

  The HDD (hard disk drive) 63 is a nonvolatile large-capacity memory. For example, the HDD 63 stores image data. Further, the HDD 63 stores setting values (default setting values) for various processes. Further, the HDD 63 may store a program executed by the CPU 61.

  The input image processing unit 64 processes the input image. The input image processing unit 64 functions as, for example, a scanner-type image processing unit that processes an image read by the scanner 2 as an input image. In this case, the input image processing unit 64 performs shading correction processing, gradation conversion processing, interline correction processing, scaling processing, compression processing, and the like on the image data read by the scanner 2. Note that the input image processing unit 64 may process an image input by a facsimile interface or network interface (not shown).

  For example, the shading correction process is a process for correcting the image data in accordance with the sensitivity variation of each photoelectric conversion element in the CCD or the light distribution characteristic of a lamp (not shown) for illuminating the document. The gradation conversion process is a process of converting the value of each pixel constituting the image data (for example, R, G, and B signal values) according to a lookup table (LUT) (not shown). The inter-line correction process is a process for correcting physical positional deviations of the RGB sensors in the CCD line sensor of the scanner 2. The scaling process is to reduce or enlarge the image data to a desired size by image processing. The compression process is a process of quantizing the image data in order to compress the data amount. Code data as compressed image data (quantized image data) is stored in the page memory 65.

  The page memory 65 is a memory that stores image data to be processed. For example, the page memory 65 stores color image data for one page. The page memory 65 is controlled by a page memory control unit (not shown). In the configuration example illustrated in FIG. 2, the page memory 65 stores image data as a processing result processed by the input image processing unit 64. The output image processing unit 66 processes the output image. In the configuration example illustrated in FIG. 2, the output image processing unit 66 functions as a printer-type image processing unit that generates image data to be printed on paper by the printer 3. The output image processing unit 66 converts the image data stored in the page memory 65 into image data for a printer.

  For example, the output image processing unit 66 performs various processes such as an expansion process, a pixel conversion process, a filter process, an inking process, a gamma correction, and a gradation process on the image data read from the page memory 65. In the decompression process, the quantized (encoded) data (compressed image data) stored in the page memory 65 is decompressed. The pixel conversion process converts a color image composed of R, G, and B signals read from the page memory 65 into print color image data composed of Y, M, C, and K (Black) signals. The filter process is a process for correcting image data in accordance with the type of image. The inking process is a process of detecting an area such as a black character printed in black (K) single color in the image data. The gamma correction process is a process for correcting image data in accordance with the gamma characteristic of the printer 3. In the gradation processing, the image data subjected to gamma correction is subjected to screen processing.

  The output image processing unit 66 is connected to a laser control unit 68 provided in the light scanning unit 40 in the printer 3. In the optical scanning unit 40, a laser control unit 68 is connected to a laser light unit 70 that emits laser light. The laser control unit 68 is formed on a control board provided for each color. The laser control unit 68 controls the laser light applied to the photosensitive drums 41a, 41b, 41c, and 41d for each color based on the image signals of the respective colors supplied from the output image processing unit 66. The laser light unit 70 emits laser light according to the control by the laser control unit 68. Configuration examples of the laser control unit 68 and the laser beam unit 70 in the optical scanning unit 40 will be described later in detail.

  Next, the configuration of the optical scanning unit 40 will be described. FIG. 3 and FIG. 4 are diagrams showing a configuration example in the optical scanning unit 40. FIG. 3 shows the arrangement of each part in the optical scanning unit 40. FIG. 4 shows a configuration example of the optical system in the optical scanning unit 40. As shown in FIG. 3, the optical scanning unit 40 includes a laser light unit 70 (70Y, 70M, 70C, 70K), three pre-deflection mirrors 81, 82, 83, a polygon mirror 84, a polygon motor 85, and two fθ lenses. F1, F2, BD sensor 86, three mirror motors 87 (87M, 87C, 87K), and a plurality of mirror groups Y, M1-M3, C1-C3, K1-K3.

  Each laser beam unit 70 (70Y, 70M, 70C, 70K) includes a laser drive substrate 71 (71Y, 71M, 71C, 71K), a laser diode (LD) array 72 (72Y, 72M, 72C, 72K), and a finite focus. It has a lens 73 (73Y, 73M, 73C, 73K), an aperture 74 (74Y, 74M, 74C, 74K), and a cylinder lens 75 (75Y, 75M, 75C, 75K). The laser light unit 70 corresponds to a light emitting unit.

  In each laser light unit 70, the laser drive substrate 71 is connected to the laser control unit 68. The laser drive substrate 71 outputs a drive signal for emitting laser light based on the image signal from the laser control unit 68. The laser drive substrate 71 emits laser light from the light emitting portion in the laser diode (LD) array 72 by a drive signal. In each laser light unit 70, the laser diode (LD) array 72 emits laser light based on the drive signal output from the laser drive substrate 71 in accordance with the image data supplied from the laser controller 68. In the optical scanning unit 40, the LD array 72 is a multi-beam array type laser diode capable of emitting a plurality of laser beams. In the present embodiment, it is assumed that the LD array 72 is a four-beam array type laser diode capable of emitting four laser beams. A configuration example of the LD array 72 will be described later in detail.

  Each laser beam unit 70 emits each laser beam emitted from the LD array 72 via a finite focal lens 73, an aperture 74 and a cylinder lens 75. Each laser beam unit 70 is installed so that any of the pre-deflection mirrors 81 and 82 or directly the polygon mirror 84 is irradiated so that each laser beam to be emitted enters the polygon mirror 84.

  For example, the laser light unit 70K transmits laser light (black laser light) reflected by the pre-deflection mirror 81 and the pre-deflection mirror 82 to the polygon mirror 84 via the pre-deflection lens 83. Installed to irradiate. Further, the laser light unit 70M irradiates the polygon mirror 84 with laser light (magenta laser light) for forming a magenta image reflected by the pre-deflection mirror 82 via the pre-deflection lens 83. It is installed. Further, the laser light unit 70 </ b> C is configured so that laser light (cyan laser light) for forming a cyan image reflected by the pre-deflection mirror 82 is irradiated to the polygon mirror 84 through the pre-deflection lens 83. It is installed. Further, the laser beam unit 70Y is installed so that a laser beam (yellow laser beam) for forming a yellow image is directly irradiated to the polygon mirror 84 through the pre-deflection lens 83.

  The polygon mirror 84 is composed of a multi-face (8 faces) mirror and is rotated by a polygon motor 85. The laser light for each color irradiated on the polygon mirror 84 is scanned in the main scanning direction by each mirror surface of the polygon mirror 84. In the optical scanning unit 40, an optical system is formed so that laser light for each color scanned in the main scanning direction by the polygon mirror 84 is guided to the surface of the photosensitive drum for each color.

  For example, the black laser light that has passed through the two fθ lenses F1 and F2 is sequentially reflected by the three black mirrors B1, B2, and B3 and applied to the photosensitive drum 41d. That is, as shown in FIG. 4, the black mirrors B1, B2, and B3 are installed so as to guide the black laser beam scanned in the main scanning direction by the polygon mirror 84 to the photosensitive drum 41d. . The black mirrors B1, B2, and B3 are configured to be adjusted by a mirror motor 87K.

  The magenta laser light that has passed through the two fθ lenses F1 and F2 is sequentially reflected by the three magenta mirrors M1, M2, and M3 and applied to the photosensitive drum 41b. That is, as shown in FIG. 4, the magenta mirrors M1, M2, and M3 are installed so as to guide the magenta laser beam scanned in the main scanning direction by the polygon mirror 84 to the photosensitive drum 41b. Further, the magenta mirrors M1, M2, and M3 are configured to be adjusted by a mirror motor 87M.

  The cyan laser light that has passed through the two fθ lenses F1 and F2 is sequentially reflected by the three cyan mirrors C1, C2, and C3 and applied to the photosensitive drum 41c. That is, as shown in FIG. 4, the cyan mirrors C1, C2, and C3 are installed so as to guide the cyan laser beam scanned in the main scanning direction by the polygon mirror 84 to the photosensitive drum 41c. The positions of the cyan mirrors C1, C2, and C3 are adjusted by driving the mirror motor 87C.

  The yellow laser light that has passed through the two fθ lenses F1 and F2 is reflected by one yellow mirror Y and applied to the photosensitive drum 41a. That is, as shown in FIG. 4, the yellow mirror Y is installed so that the yellow laser beam scanned in the main scanning direction by the polygon mirror 84 is guided to the photosensitive drum 41a. Here, it is assumed that the installation position of the yellow mirror Y is fixed.

  As described above, the laser light emitted from each laser light unit is reflected by the plurality of mirrors before reaching the photosensitive drum 41. The configuration of the optical system for guiding each laser beam to each photosensitive drum 41 is determined by the configuration of each unit in the image forming apparatus. For example, in the image forming apparatus, the installation conditions (for example, the installable area) of the optical scanning unit 40 are considered to be different for each model of the image forming apparatus. Also, the number of mirrors installed or the position of the mirrors in the optical scanning unit 40 can be changed depending on the configuration of the LD array itself.

  Next, laser beam scanning in the optical scanning unit 40 will be described.

  FIG. 5 is a diagram for explaining the scanning of the laser beam in the optical scanning unit 40. FIG. 5 schematically shows a scanning path of yellow laser light. In FIG. 5, the magenta laser light unit 70M, the cyan laser light unit 70C, the black laser light unit 70K, the pre-deflection mirrors 81 and 82, the pre-deflection lens 83, and the mirror Y for each color. , M1 to M3, C1 to C3, K1 to K3, and the like are omitted.

  As shown in FIG. 5, in the optical scanning unit 40, the laser light emitted from each laser light unit 70 is reflected by the polygon mirror 84 and irradiated to each photosensitive drum 41 through the fθ lenses F <b> 1 and F <b> 2. The As described above, the polygon mirror 84 rotated by the polygon motor 85 is a mirror on one surface, and scans the laser beam once in the main scanning direction. Thereby, an electrostatic latent image is formed on the photosensitive drum 41 by the laser beam scanned in the main scanning direction. The laser light that scans the photosensitive drum 41 in the main scanning direction has a desired interval in the sub-scanning direction. For example, the interval between the plurality of light emitting elements in the LD array 72 of each laser beam unit 70 described later is designed to correspond to the interval in the sub-scanning direction.

  Further, the BD sensor 86 is installed so as to detect a laser beam as a BD signal (or also referred to as an HSYNC signal) every time the laser beam is scanned once in the main scanning direction. A plurality of BD sensors 86 may be provided for each color, or may be installed so as to detect only laser light corresponding to a predetermined color (for example, yellow or black). FIG. 5 shows a configuration example in which a BD sensor 86 for detecting a specific color beam is provided. In the configuration example shown in FIG. 5, a BD mirror for guiding a desired laser beam to the BD sensor 86 is provided. Further, the BD mirror is installed so as to guide a desired laser beam passing through the upstream side of the second fθ lens F2 in the main scanning direction to the BD sensor 86. With such a configuration, the optical scanning unit 40 can measure the timing at which the laser beam starts scanning in the main scanning direction based on the BD signal detected by the BD sensor 86.

  Next, the configuration of the LD array 72 in the laser light unit 70 will be described. FIG. 6 is a diagram illustrating a configuration example of the LD array 72 in the laser light unit 70. Each laser beam unit 70 has an LD array 72 having a function of simultaneously emitting a plurality of laser beams. In the configuration example shown in FIG. 6, the LD array 72 includes four light emitting units (four laser diodes) LD <b> 1 to LD <b> 4 for emitting four laser beams. The LD array 72 is designed on the assumption that the light emitting elements LD1 to LD4 are arranged obliquely.

  That is, the LD array 72 is designed so that the four light emitting elements LD1 to LD4 for emitting four laser beams are obliquely aligned with respect to the main scanning direction (for example, inclined by 45 degrees). Has been. In addition, the LD array 72 is designed so that the interval in the sub-scanning direction becomes a desired interval (for example, 1200 dpi) while being obliquely aligned with respect to the main scanning direction.

  Next, the configuration of the laser control unit 68 for each color connected to the laser light unit 70 for each color will be described in detail. FIG. 7 is a diagram illustrating a configuration example of the laser control unit 68 for each color. The laser control unit 68 as shown in FIG. 7 is provided for each color (for example, four colors Y, M, C, and K) for forming an image. The laser control unit 68 is formed by, for example, an integrated circuit (ASIC) installed on a substrate. The laser control unit 68 is physically and electrically connected to the laser light unit 70 for each color.

  In the configuration example shown in FIG. 7, the laser control unit 68 includes various setting control units 91, four data clock (CLK) conversion units 92 (92a, 92b, 92c, 92d), a signal selection unit 93, a sequence control unit 94, There are four signal synthesis units 95 (95a, 95b, 95c, 95d), four PWM (pulse wide modulation) units 96 (96a, 96b, 96c, 96d), and the like. Note that the laser control unit 68 in the configuration example shown in FIG. 7 corresponds to the laser light unit 70 having the four-beam LD array 72. For this reason, the laser control unit 68 is provided with four data CLK conversion units 92, four signal synthesis units 95, and four PWM units 96 each configured to control each laser beam individually.

  The various setting control units 91 govern control in the laser control unit 68. The various setting control unit 91 performs various settings for the signal selection unit 93 and the sequence control unit 94, for example. The various setting control unit 91 receives information indicating various settings from the CPU 61 as a host control device, and outputs the setting information to the signal selection unit 93 and the sequence control unit 94. That is, the various setting control units 91 function not only as a control element such as a CPU but also as an interface.

  The data CLK conversion unit 92 adjusts the timing for outputting data. Each of the data CLK converters 92 receives one piece of laser beam image data. In the example shown in FIG. 7, the data CLK conversion units 92a, 92b, 92c, and 92d receive image data A, B, C, and D in synchronization with the M clock (CLK) signal, respectively. Image data input to each data conversion unit 92 is supplied from the output image processing unit 66. The laser control unit 68 and the output image processing unit 66 are physically connected by a predetermined connector (harness) or the like, and predetermined image data is input to each data CLK conversion unit 92. That is, the image data input to each data CLK conversion unit 92 is predetermined image data regardless of the connection status with the laser light unit.

  The data CLK converter 92 has an internal memory 97 (97a, 97b, 97c, 97d) that stores image data for at least one main scanning line. The data CLK conversion unit 92 outputs the image data stored in the internal memory 97 based on a P clock (CLK) signal and a horizontal synchronization signal (HSYNC signal) selected by the signal selection unit 93. That is, the data CLK conversion unit 92 outputs the image data input by the MCLK signal using the PCLK signal synchronized with the HSYNC signal selected by the signal selection unit 93.

  The data CLK converter 92 has a function of converting the clock signal of the image data into a clock signal selected by the signal selector 93 and outputting the HSYNC signal selected by the signal selector 93 as a reference. It means that As a result, the laser control unit 68 realizes clock conversion and timing control corresponding to each unit in the subsequent stage without adding a configuration such as a buffer memory separately.

  The signal selection unit 93 supplies the four image data A, B, C, and D acquired from each data CLK conversion unit 92 to each signal synthesis unit 95 based on the setting information given from the various setting control units 91. Select the image data to be used. Image data to be supplied to each signal combining unit 95 is selected based on setting information (for example, order in the sub-scanning direction) given from the various setting control units 91. For example, when the laser light to be controlled by the PWM unit 96a is the first in the sub-scanning direction, the signal selection unit 93 uses the image data A as image data to be supplied to the signal synthesis unit 95a corresponding to the PWM unit 96a. select.

  The signal selection unit 93 receives four P clock (CLK) signals and four horizontal synchronization (HSYNC) signals, reads image data from each data CLK conversion unit 92, and supplies the image data to each signal synthesis unit 95. PCLK signal and HSYNC signal are selected. The PCLK signal and the HSYNC signal for reading image data are selected based on setting information (for example, order in the main scanning direction) given from the various setting control units 91. For example, if the clock signal of the laser beam to be controlled by the PWM unit 96a is the PCLK signal 1 and the order of the laser beam in the main scanning direction is the first, the signal selection unit 93 is the PWM unit 96a. The PCLK signal 1 and the HSYNC signal 1 are selected as signals for reading the image data A supplied to the signal synthesizer 95a corresponding to.

  The PCLK signals 1 to 4 are clock signals that are set independently according to each laser beam to be controlled by each PWM unit 96. This is because when all the laser beams are controlled by the same clock signal, in actuality, there are many cases where deviations occur due to the optical system configuration (each mirror or lens) of each laser beam. For this reason, as the PCLK signals 1 to 4, clock signals suitable for the laser beams L1 to L4 to be controlled by the PWM units 96 are set. The HSYNC signals 1 to 4 are signals serving as a reference for outputting image data. The signal selection unit 93 reads the selected image data from the internal memory 97 of each data acquisition unit 92 and combines each signal. Used as a reference signal for supply to the unit 95.

  In the configuration example shown in FIG. 7, the signal selection unit 93 selects either image data A or image data D as data to be supplied to the signal synthesis unit 95a. For example, the signal selection unit 93 reads the selected image data from the data acquisition unit 92a (or 92d) at the timing when the PCLK signal 1 is synchronized with the HSYNC signal 1 (or the PCLK signal 4 is the HSYNC signal 4), and receives the signal. The data is output to the synthesis unit 95a. The signal selector 93 selects either the image data B or the image data C as data to be supplied to the signal synthesizer 95b, and the PCLK signal 2 is set to the HSYNC signal 2 (or the PCLK signal 3 is set to the HSYNC signal 3). The selected image data is read from the data acquisition unit 92b (or 92c) and output to the signal synthesis unit 95b at a timing synchronized with the signal synthesis unit 95b.

  The signal selector 93 selects either image data C or image data B as data to be supplied to the signal synthesizer 95c, and the PCLK signal 3 is set to the HSYNC signal 3 (or the PCLK signal 2 is set to the HSYNC signal 2). The selected image data is read from the data acquisition unit 92c (or 92d) and supplied to the signal synthesis unit 95c at a timing synchronized with the signal synthesis unit 95c. The signal selector 93 selects either the image data D or the image data A as data to be supplied to the signal synthesizer 95d, and the PCLK signal 4 is set to the HSYNC signal 4 (or the PCLK signal 1 is set to the HSYNC signal 1). The selected image data is read from the data acquisition unit 92d (or 92a) and output to the signal synthesis unit 95d at a timing synchronized with the signal synthesizing unit.

  The sequence control unit 94 supplies various setting information based on the setting information given from the various setting control unit 91 to each signal synthesis unit 95 (95a, 95b, 95c, 95d). For example, in the configuration example shown in FIG. 7, the sequence control unit 94 is supplied with setting information indicating the head laser beam together with setting information for each signal combining unit 95 from the various setting control units 91. As a result, the sequence controller 94 supplies setting signals to the signal synthesizers 95a, 95b, 95c, and 95d, respectively.

  The sequence control unit 94 receives four P clock (CLK) signals and a horizontal synchronization (HSYNC) signal. For example, the PCLK signals 1 to 4 and the HSYNC signals 1 to 4 are supplied from each PWM unit 96 to the sequence control unit 94. Further, the sequence control unit 94 outputs an HSYNC signal for acquiring image data based on the HSYNC signals 1 to 4 acquired from the PWM units 96 as an MHSYNC signal to the output image processing unit 66 or an upper control device.

  The signal synthesis units 95a, 95b, 95c, and 95d and the PWM units 96a, 96b, 96c, and 96d each correspond to one of the four laser beams. In the configuration example described above, the signal synthesis unit 95a and the PWM unit 96a correspond to the laser beam L1 or L4, and the signal synthesis unit 95b and the PWM unit 96b correspond to the laser beam L2 or L3, and the signal synthesis unit 95c and the PWM unit 96b. The unit 96c corresponds to the laser beam L3 or L2, and the signal synthesis unit 95d and the PWM unit 96d correspond to the laser beam L4 or L1.

  Each of the signal synthesis units 95 (95a, 95b, 95c, 95d) supplies the image data supplied from the signal selection unit 93 to each PWM unit 96 based on setting information given from the sequence control unit 94. To do. Each signal combining unit 95 also outputs a control signal for controlling the emission of each laser beam in the laser beam unit 70.

  Each signal synthesizer 95 corresponds to four laser beams. However, the laser beam corresponding to each signal combining unit varies depending on the connection state of the laser beam unit 70. That is, each signal synthesis unit 95 is supplied with image data to be formed by the corresponding laser beam from the signal selection unit 93. Each signal synthesis unit 95 outputs the image data from the signal selection unit 93 to each PWM unit 96 at a timing given from the sequence control unit 94.

  Each PWM unit 96 (96a, 96b, 96c, 96d) is provided corresponding to each signal synthesis unit 95 (95a, 95b, 95c, 95d). Each PWM unit 96 outputs a signal for controlling the laser beam in accordance with the image data given from the corresponding signal synthesis unit 95. Each PWM unit 96 acquires a BD signal detected by the BD sensor 86 and generates an HSYNC signal used for laser light control. For example, the PWM unit 96 a supplies the BD signal 1 detected by the BD sensor 86 as the HSYNC signal 1 to the sequence control unit 94. Similarly, the PWM units 96b, 96c, and 96d supply the BD signals 2, 3, and 4 detected by the BD sensor 86 to the sequence control unit 94 as HSYNC signals 2, 3, and 4, respectively.

  FIG. 8 is a table summarizing operations and setting items in the laser control unit 68 shown in FIG. As shown in FIG. 8, the laser control unit 68 shown in FIG. 7 can select the HSYNC order or replace the image data. For example, in the PWM unit 96a, the image data output as CH1 is either image data A or D, and the HSYNC order is set to either the first or the fourth. The PWM unit 96b sets the image data to be output as CH2 as either image data B or C, and the HSYNC order is set to either the second or the third. Further, the PWM unit 96c sets the image data to be output as CH3 as either image data C or B, and the HSYNC order is set to either the third or the second. The PWM unit 96d sets the image data output as CH4 as either image data D or A, and the HSYNC order is set to either the fourth or the first. Next, the positional deviation sensor 26 will be described in detail with reference to FIG.

  FIG. 9 is a plan view of the transfer belt 45. The positional deviation sensor 26 includes a rear side positional deviation sensor 26a and a front side positional deviation sensor 26b that respectively detect test patterns (first test images) formed on both ends of the transfer belt 45 in the main scanning direction. . The rear side displacement sensor 26a detects a test pattern formed on one end side of the transfer belt 45 in the main scanning direction, and the front side displacement sensor 26b is formed on the other end side of the transfer belt 45 in the main scanning direction. Detect the test pattern. The test pattern has a configuration in which a plurality of wedge-shaped figures formed using yellow (Y), magenta (M), cyan (C), and black (K) are arranged in the sub-scanning direction. This wedge-shaped figure is composed of a line segment extending in the main scanning direction and a line segment extending obliquely with respect to the main scanning direction.

  The CPU 61 performs alignment control based on the detection results of the rear side displacement sensor 26a and the front side displacement sensor 26b. Here, the alignment control means that the sub-scanning direction parallel shift, the main scanning direction writing position shift, the main scanning magnification adjustment, and the inclination correction. The alignment in the sub-scanning direction is performed by changing the start line data output start timing of each color. The alignment of the main scanning direction writing position is performed by changing the laser writing position.

  Next, the density sensor 27 will be described in detail with reference to FIG. The density sensor 27 includes a light emitting element 100 and a light receiving element 101, and is used for maintaining image quality. A light source control voltage corresponding to the light amount designated by the CPU 61 is output from the D / A converter, and light corresponding to the light amount control voltage is projected onto the transfer belt 45 by the light emitting element 100. The light receiving element 101 receives reflected light reflected on the transfer belt 45 and the toner image formed on the transfer belt 45. The output voltage corresponding to the amount of reflected light is converted into a digital value by the A / D converter and transmitted to the CPU 61.

  FIG. 11 shows a test pattern for detecting the density of the toner image formed on the transfer belt 45. This test pattern is configured by forming a plurality of toner images by changing the density for each color of yellow (Y), magenta (M), cyan (C), and black (K). The toner image for density detection is formed at the center of the transfer belt 45 in the main scanning direction. The CPU 61 compares the detected density of the test pattern with a reference value, and determines whether it is an allowable range value that does not hinder image formation. If it is outside the allowable range, the image forming conditions are changed. Thereby, image quality can be maintained.

  In the present embodiment, the density sensor 27 used for maintaining the image quality is also used for detecting the failure of the laser light unit 70. This failure detection is performed in parallel with the alignment control using the displacement sensor 26. The failure detection method will be described in detail with reference to FIGS. FIG. 12 is a schematic diagram showing an alignment test pattern (first test image) and a failure detection test pattern (second test image). FIG. 13 is a flowchart illustrating a failure detection method. Since the test pattern for alignment has been described above, description thereof will not be repeated.

  In Act 101, the controller (failure determination unit) 61 drives the LD1, LD2, LD3, and LD4 of the LD array 72Y in this order, so that the electrostatic latent images corresponding to the toner images Y1 to Y4 in FIG. Is formed on the photosensitive drum 41a. Here, the toner image Y1 corresponds to the LD1 of the LD array 72Y, and is formed by scanning the LD1 a plurality of times. The toner image Y2 corresponds to the LD2 of the LD array 72Y and is formed by scanning the LD2 a plurality of times. The toner image Y3 corresponds to the LD3 of the LD array 72Y and is formed by scanning the LD3 a plurality of times. The toner image Y4 corresponds to the LD4 of the LD array 72Y and is formed by scanning the LD4 a plurality of times.

  In Act 102, the controller 61 drives the LD1, LD2, LD3, and LD4 of the LD array 72M in this order, thereby generating an electrostatic latent image corresponding to the toner images M1 to M4 in FIG. 12 with the second photosensitive drum 41b. Form on top. Here, the toner image M1 corresponds to the LD1 of the LD array 72M, and is formed by scanning the LD1 a plurality of times. The toner image M2 corresponds to the LD2 of the LD array 72M, and is formed by scanning the LD2 a plurality of times. The toner image M3 corresponds to the LD3 of the LD array 72M and is formed by scanning the LD3 a plurality of times. The toner image M4 corresponds to the LD4 of the LD array 72M and is formed by scanning the LD4 a plurality of times.

  In Act 103, the controller 61 drives the LD1, LD2, LD3, and LD4 of the LD array 72K in this order to form electrostatic latent images corresponding to the toner images K1 to K4 on the third photosensitive drum 41c. To do. Here, the toner image K1 corresponds to the LD1 of the LD array 72K, and is formed by scanning the LD1 a plurality of times. The toner image K2 corresponds to the LD2 of the LD array 72K and is formed by scanning the LD2 a plurality of times. The toner image K3 corresponds to the LD3 of the LD array 72K and is formed by scanning the LD3 a plurality of times. The toner image K4 corresponds to the LD4 of the LD array 72K and is formed by scanning the LD4 a plurality of times.

  In Act 104, the controller 61 drives the LD1, LD2, LD3, and LD4 of the LD array 72C in this order, thereby generating the electrostatic latent images corresponding to the toner images C1 to C4 in FIG. 12 with the third photosensitive drum 41c. Form on top. Here, the toner image C1 corresponds to the LD1 of the LD array 72C, and is formed by scanning the LD1 a plurality of times. The toner image C2 corresponds to the LD2 of the LD array 72C and is formed by scanning the LD2 a plurality of times. The toner image C3 corresponds to the LD3 of the LD array 72C and is formed by scanning the LD3 a plurality of times. The toner image C4 corresponds to the LD4 of the LD array 72C and is formed by scanning the LD4 a plurality of times.

  In Act 105, each color toner image (that is, each test pattern) formed on each photoconductive drum 41a to 41d is sequentially transferred to a transfer belt 45 as an intermediate transfer body. It should be noted that when these test patterns are transferred to the transfer belt 45, the test patterns detected by the displacement sensor 26 are also transferred at the same time.

  In Act 106, detection operations by the positional deviation sensor 26 and the density sensor 27 are started. In Act 107, the CPU 61 determines whether there is a toner image having a density lower than the predetermined density among the toner images Y1 to Y4 formed on the transfer belt 45. If there is a toner image below the predetermined density, the process proceeds to ACT108. Here, the “predetermined density” is a value set according to the color type of the toner, and is appropriately set from the viewpoint of determining a failure of the LD as the light emitting element. Accordingly, the value of the predetermined density varies depending on the toners Y, M, C, and K.

  In ACT 108, the CPU 61 outputs a signal to notification means (not shown). The notification means notifies that the LD array 72 has failed. The notification means displays identification information indicating the color type of the failed LD array 72 and the LD No. on the touch panel display (not shown) of the color digital multifunction peripheral 1, or communicates this identification information to the management center via the Internet. Means can be used.

  If it is determined in Act 107 that there is no toner image lower than the predetermined density, the process proceeds to Act 109. In Act 109, the CPU 61 determines whether or not there is a toner image lower than a predetermined density among the toner images M1 to M4 formed on the transfer belt 45. If there is a toner image lower than the predetermined density, the process proceeds to Act 110. In Act 110, the CPU 61 outputs a signal to the notification unit. Since the details of the notification means have been described above, the description will not be repeated.

  If it is determined in Act 109 that there is no toner image having a density lower than the predetermined density, the process proceeds to Act 111. In Act 111, the CPU 61 determines whether or not there is a toner image lower than a predetermined density among the toner images K1 to K4 formed on the transfer belt 45. If there is a toner image lower than the predetermined density, the process proceeds to Act 112. In Act 112, the CPU 61 outputs a signal to the notification means. Since the details of the notification means have been described above, the description will not be repeated.

  If it is determined in Act 111 that there is no toner image lower than the predetermined density, the process proceeds to Act 113. In Act 113, the CPU 61 determines whether there is a toner image having a density lower than a predetermined density among the toner images C1 to C4 formed on the transfer belt 45. If there is a toner image lower than the predetermined density, the process proceeds to Act 114. In Act 114, the CPU 61 outputs a signal to the notification means. Since the details of the notification means have been described above, the description will not be repeated.

  As described above, according to the configuration of the present embodiment, the density information of the toner image formed on the transfer belt 45 is acquired, so that it is possible to determine whether or not there is a failure in all the arrays 72. Therefore, it is not necessary to determine the failure by printing on paper as in the prior art.

  Here, as described above, in this embodiment, the position shift detection using the position shift sensor 26 and the failure detection of the laser light unit 70 using the density sensor 27 are performed in parallel. Therefore, the downtime of the digital multi-function peripheral 1 can be shortened as compared with a method of performing these detections separately. In addition, since it is configured to detect a failure using the density sensor 27 used for maintaining the image quality, it is not necessary to provide a failure detection sensor independently. Thereby, cost can be reduced.

(Embodiment 2)
In the first embodiment, the failure is detected using the density sensor 27 used for maintaining the image quality. However, in the present embodiment, the failure is detected using the displacement sensor 26. This failure detection is performed in parallel with the image quality maintenance control using the density sensor 27. A failure detection method will be described in detail with reference to FIGS. FIG. 14 is a schematic diagram illustrating a test pattern for maintaining image quality and a test pattern for failure detection. FIG. 15 is a flowchart showing a failure detection method. Since the test pattern for maintaining image quality has been described above, description thereof will not be repeated.

  In Act 201, the controller 61 drives the LD array 72K in the order of LD1, LD2, LD3, and LD4 to generate fourth electrostatic latent images corresponding to the wedge-shaped toner images K1 to K4 shown in FIG. Formed on the photosensitive drum 41d. Here, the toner image K1 (second test image) corresponds to the LD1 of the LD array 72K and is formed by scanning the LD1 a plurality of times. The toner image K2 (second test image) corresponds to the LD2 of the LD array 72K, and is formed by scanning the LD2 a plurality of times. The toner image K3 (second test image) corresponds to the LD3 of the LD array 72K, and is formed by scanning the LD3 a plurality of times. The toner image K4 (second test image) corresponds to the LD4 of the LD array 72K and is formed by scanning the LD4 a plurality of times.

  In Act 202, the controller 61 drives the LD array 72C in the order of LD1, LD2, LD3, and LD4 to generate third electrostatic latent images corresponding to the wedge-shaped toner images C1 to C4 shown in FIG. On the photosensitive drum 41c. Here, the toner image C1 (second test image) corresponds to the LD1 of the LD array 72C, and is formed by scanning the LD1 a plurality of times. The toner image C2 (second test image) corresponds to the LD2 of the LD array 72C and is formed by scanning the LD2 a plurality of times. The toner image C3 (second test image) corresponds to the LD3 of the LD array 72C and is formed by scanning the LD3 a plurality of times. The toner image C4 (second test image) corresponds to the LD4 of the LD array 72C and is formed by scanning the LD4 a plurality of times.

  In Act 203, the controller 61 drives the LD array 72M with the LD1, LD2, LD3, and LD4 in this order to generate second electrostatic latent images corresponding to the wedge-shaped toner images M1 to M4 shown in FIG. Is formed on the photosensitive drum 41b. Here, the toner image M1 (second test image) corresponds to the LD1 of the LD array 72M, and is formed by scanning the LD1 a plurality of times. The toner image M2 (second test image) corresponds to the LD2 of the LD array 72M, and is formed by scanning the LD2 a plurality of times. The toner image M3 (second test image) corresponds to the LD3 of the LD array 72M, and is formed by scanning the LD3 a plurality of times. The toner image M4 (second test image) corresponds to the LD4 of the LD array 72M and is formed by scanning the LD4 a plurality of times.

  In Act 204, the controller 61 drives the LD array 72Y with the LD1, LD2, LD3, and LD4 in this order, thereby generating first electrostatic latent images corresponding to the wedge-shaped toner images Y1 to Y4 shown in FIG. Is formed on the photosensitive drum 41a. Here, the toner image Y1 (second test image) corresponds to the LD1 of the LD array 72Y, and is formed by scanning the LD1 a plurality of times. The toner image Y2 (second test image) corresponds to the LD2 of the LD array 72Y and is formed by scanning the LD2 a plurality of times. The toner image Y3 (second test image) corresponds to the LD3 of the LD array 72Y and is formed by scanning the LD3 a plurality of times. The toner image Y4 (second test image) corresponds to the LD4 of the LD array 72Y and is formed by scanning the LD4 a plurality of times.

  In Act 205, the toner images of the respective colors formed on the photosensitive drums 41a to 41d are sequentially transferred onto a transfer belt 45 as an intermediate transfer member. It is assumed that a test pattern (first test image) detected by the density sensor 27 when the image is transferred to the transfer belt 45 is also formed.

  In Act 206, detection operations by the positional deviation sensor 26 and the density sensor 27 are started. In Act 207, the CPU 61 determines whether any of the toner images K1 to K4 formed on the transfer belt 45 has a line width X in the sub scanning direction lower than a predetermined value. If it is lower than the predetermined value, the process proceeds to ACT 208.

  In ACT 208, the CPU 61 outputs a signal to notification means (not shown). The notification means notifies that the LD array 72 has failed. As the notification means, the identification information indicating the color type of the failed LD array 72 and the LD No. is displayed on the touch panel display (not shown) of the color digital multifunction peripheral 1, or the identification information is displayed on the management center via the Internet. Means for communicating can be used.

  If it is determined in Act 207 that there is no toner image having a line width X lower than the predetermined value, the process proceeds to Act 209. In Act 209, the CPU 61 determines whether any of the toner images C1 to C4 formed on the transfer belt 45 has a line width X in the sub-scanning direction lower than a predetermined value. If there is a toner image lower than the predetermined value, the process proceeds to Act 210. In Act 210, the CPU 61 outputs a signal to the notification means. Since the details of the notification means have been described above, the description will not be repeated.

  In Act 209, if there is no toner image lower than the predetermined value, the process proceeds to Act 211. In Act 211, the CPU 61 determines whether any of the toner images M1 to M4 formed on the transfer belt 45 has a line width X in the sub-scanning direction lower than a predetermined value. If there is a toner image lower than the predetermined value, the process proceeds to Act 212. In Act 212, the CPU 61 outputs a signal to the notification means. Since the details of the notification means have been described above, the description will not be repeated.

  In Act 211, when there is no toner image lower than the predetermined value, the process proceeds to Act 213. In Act 213, the CPU 61 determines whether any of the toner images Y1 to Y4 formed on the transfer belt 45 has a line width X in the sub-scanning direction lower than a predetermined value. If there is a toner image lower than the predetermined value, the process proceeds to Act 214. In Act 214, the CPU 61 outputs a signal to the notification means. Since the details of the notification means have been described above, the description will not be repeated.

  As described above, according to the configuration of the present embodiment, by acquiring the density information of the toner image formed on the transfer belt 45, it is possible to determine the failure of the LDs included in all the LD arrays 72. Therefore, it is not necessary to determine the failure by printing on paper as in the prior art.

  Here, as described above, in this embodiment, the image quality maintenance based on the detection result of the density sensor 27 and the failure detection of the laser light unit 70 using the positional deviation sensor 26 are performed in parallel. Therefore, the downtime of the digital multi-function peripheral 1 can be shortened compared to a method in which these detections are performed separately.

  In addition, since the failure detection is performed using the position shift sensor 26 for alignment control, it is not necessary to provide a failure detection sensor independently. Thereby, cost can be reduced.

(Modification of Embodiment 2)
As shown in FIG. 16, toner images (second test images) may be formed side by side in the main scanning direction by being modulated by each laser control unit 68. Thereby, a test pattern can be formed in a shorter time. These toner images need to be formed in the detection range of the positional deviation sensor 26. In the illustrated example, a failure of each LD in the LD array 72Y is detected.

(Embodiment 3)
In the first and second embodiments described above, the failure of each LD included in the LD arrays 72Y to 72K is determined by inspecting the image transferred to the transfer belt 45. In this embodiment, each LD is emitted. The failure of each LD is determined based on the light reception result.

  FIG. 17 is a diagram for explaining scanning of laser light in the optical scanning unit 110 of the present embodiment. FIG. 17 schematically shows scanning optical paths of the yellow laser light and the magenta laser light. Note that the respective photoconductors corresponding to magenta, cyan, and black laser beams are not shown.

  Referring to the figure, in the optical scanning unit 110, the laser light emitted from each of the laser light units 112 to 115 is reflected by the polygon mirror 111 and irradiated to each photosensitive drum via the fθ lenses F3 and F4. The As described above, the polygon mirror 111 is a mirror of one surface, and scans the laser beam once in the main scanning direction. Thereby, an electrostatic latent image is formed on the photosensitive drum 120 by the laser light scanned in the main scanning direction. Each of the laser light units 112 to 115 includes a 2LD array type light emitting unit including two LDs (light emitting elements).

  The BD sensor (first sensor) 116 detects a laser beam as a BD signal every time it scans in the main scanning direction. When the polygon mirror 111 is rotated to the position indicated by the dotted line, the yellow laser light emitted from the laser light unit 112 is reflected by the polygon mirror 111 and then by the Y reflecting mirror 117 and is reflected by the BD sensor 116. Received light.

  The beam detection sensor (second sensor) 119 detects ON / OFF of light emitted from the laser light units 113 to 115. By rotating the polygon mirror 111 and adjusting the angle, the light emitted from the laser light units 113 to 115 can be received by the beam detection sensor 119 via the fθ lens F3 and the reflection mirror 118, respectively.

  Here, the beam detection sensor 119 only needs to have a detection accuracy enough to detect ON / OFF of the laser light units 113 to 115. Therefore, an inexpensive sensor with lower detection accuracy than the BD sensor 116 can be used. Thereby, cost can be reduced.

  FIG. 18 is a timing chart showing the behavior of various signals when the laser beam unit 112 is scanned twice in the main scanning direction. In the illustrated example, a BD error signal is output due to a failure of the laser beam unit 112.

  In the present embodiment, the failure of the laser light units 113 to 115 is determined by comparing the number of times of light reception detection of the BD sensor 116 and the beam detection sensor 119. FIG. 19 is a timing chart showing an example thereof, corresponding to the failure detection of the laser light unit 113. In the illustrated example, both the BD sensor 116 and the beam detection sensor 119 receive light twice. Therefore, it is determined that the laser beam unit 113 has not failed.

  FIG. 20 is also a timing chart showing an example of failure detection, and corresponds to failure detection of the laser light unit 113. In the illustrated example, the number of light reception detections of the BD sensor 116 is 1, and the number of light reception detections of the beam detection sensor 119 is 0. Therefore, it is determined that the laser beam unit 113 has failed.

  Next, with reference to FIG. 21, the failure detection method of the present embodiment will be described more specifically. FIG. 21 is a flowchart showing a failure detection procedure. In Act 301, the LD 1 included in the laser light unit 112 is instructed to emit light. In Act 302, the failure of the LD 1 is determined based on the light reception result of the BD sensor 116. If LD1 has not failed, the process proceeds to Act 303. In Act 303, it is determined whether failure detection has been performed for all the LDs included in the laser light unit 112. In this example, since the failure inspection of the LD 2 of the laser light unit 112 is not performed, the process proceeds to Act 304.

  In Act 304, the failure detection by the BD sensor 116 is stopped, the failure detection target is changed from LD1 to LD2 of the laser light unit 112, the failure inspection of the LD2 is started, and the processing returns to Act302.

  In Act 302, when it is determined that one of the LDs 1 and 2 of the laser light unit 112 has failed, the process proceeds to Act 305. In Act 305, the LD number of the LD (for example, LD2) determined to be faulty is stored in a memory (not shown).

  In Act 306, it is determined whether the failure inspection has been completed for all the LDs included in the laser beam unit 112. If failure inspection has been completed for all LDs, the process proceeds to Act 307. If failure inspection has not been completed for all LDs, the process proceeds to Act 304.

  In Act 307, information on the failed LD number is read from the memory, and it is determined whether all of the LDs included in the laser beam unit 112 have failed. If at least one has not failed, the process proceeds to Act 308, and if all have failed, the process proceeds to Act 318.

  In Act 308, information on the failed LD number is read from the memory, and it is determined whether at least one (except all) LDs included in the laser beam unit 112 have failed. If at least one LD has failed, the process proceeds to Act 312, and if there is no failed LD, the process proceeds to Act 309.

  In Act 312, the LD that has not failed is selected from the laser light unit 112 to emit light, and the detection operation by the BD sensor 116 is performed. That is, the detection operation shown in Act 312 corresponds to “BD sensor output” in the timing chart of FIG.

  In Act 310, the laser light unit to be inspected and the LD to emit light are selected from the laser light units 113 to 115. In Act 311, the LD selected in Act 310 is emitted, a failure is determined, and the result is stored in the memory. In Act 313, it is determined whether all LDs of the laser beam unit selected in Act 310 have been inspected. If all the LDs have not been inspected, the process proceeds to Act 314 to switch to another LD. When all the LDs have been inspected, the process proceeds to Act 315 to determine whether the inspection has been completed for all the laser light units 113 to 115.

  When all the laser light units 113 to 115 are not inspected in Act 315, the process returns to Act 310, and when all the laser light units 113 to 115 are inspected, the process proceeds to Act 316. In Act 316, it is determined whether or not there is an abnormality in the LD in the above-described failure inspection. If there is no abnormality, the process proceeds to Act 317 and the failure inspection ends. If there is an abnormality, the process proceeds to Act 318, and information on the color type of the failed laser beam unit and the LD No is read from the memory and notified. Here, as a means for notifying the information, printing on a sheet and display on a display can be used.

  According to the present embodiment, it is possible to determine the failure of the LD included in each of the laser units 112 to 115 without printing on paper.

(Embodiment 4)
In the present embodiment, the failure inspection of all the laser light units is performed using the BD sensor 216. FIG. 22 is a diagram for explaining scanning of laser light in the optical scanning unit 210. FIG. 22 schematically shows a scanning optical path of yellow laser light. The same components as those of the third embodiment are denoted by the same reference numerals and description thereof is omitted.

  Light emitted from the laser light unit 112 is reflected by the polygon mirror 111 and received by the BD sensor 216 via the Fθ1 lens F3 and the Y reflection mirror 117. Based on the light reception result, the writing position in the main scanning direction is corrected, and the failure inspection of each LD included in the laser beam unit 112 is performed.

  Light emitted from the laser beam unit 113 is reflected by the polygon mirror 111 and received by the BD sensor 216 via the Fθ1 lens F3 and the M reflection mirror (not shown). Based on this light reception result, a failure inspection of each LD included in the laser light unit 113 is performed.

  Light emitted from the laser light unit 114 is reflected by the polygon mirror 111 and received by the BD sensor 216 via the Fθ1 lens F3 and the C reflection mirror (not shown). Based on this light reception result, failure inspection of each LD included in the laser light unit 114 is performed.

  The light emitted from the laser beam unit 115 is reflected by the polygon mirror 111 and received by the BD sensor 216 via the Fθ1 lens F3 and the K reflection mirror (not shown). Based on this light reception result, a failure inspection of each LD included in the laser light unit 115 is performed.

  Next, the failure inspection method will be described more specifically with reference to FIG. FIG. 23 is a flowchart showing a procedure for failure inspection. In Act 401, the LD 1 included in the laser light unit 112 is instructed to emit light. In Act 402, the failure of the LD1 is determined based on the light reception result of the BD sensor 216. If the LD 1 has not failed, the process proceeds to Act 403. In Act 403, it is determined whether failure inspection has been performed for all the LDs included in the laser light unit 112. In this example, since the failure inspection of the LD 2 of the laser light unit 112 is not performed, the process proceeds to Act 404.

  In Act 404, the failure detection by the BD sensor 216 is stopped, the failure detection target is changed from LD1 to LD2 of the laser light unit 112, the failure inspection of the LD2 is started, and the processing returns to Act402.

  If it is determined in Act 402 that one of the LDs 1 and 2 of the laser beam unit 112 has failed, the process proceeds to Act 405. In Act 405, the LD number of the LD (eg, LD2) determined to be faulty is stored in a memory (not shown).

  In Act 406, it is determined whether failure inspection has been performed for all the LDs included in the laser light unit 112. If failure inspection has been performed for all LDs, the process proceeds to Act 407. If failure inspection has not been completed for all LDs, the process returns to Act 404.

  In Act 407, the laser light unit to be inspected and the LD to emit light are selected from the laser light units 113 to 115. In Act 408, the LD selected in Act 407 is caused to emit light, a failure is determined, and the result is stored in the memory. In Act 409, it is determined whether or not the failure inspection has been completed for all the LDs of the laser beam unit selected in Act 407. If all the LDs have not been inspected, the process proceeds to Act 410 to switch to another LD. If all the LDs have been inspected, the process proceeds to Act 411 to determine whether the inspection has been completed for all the laser light units 113 to 115.

  If all the laser light units 113 to 115 are not inspected in Act 411, the process returns to Act 407, and if all the laser light units 113 to 115 are inspected, the process proceeds to Act 412. In Act 412, it is determined whether or not there is an abnormality in the LD in all the above-described failure inspections. If there is no abnormality, the process proceeds to Act 413 and the failure inspection ends. If there is an abnormality, the process proceeds to Act 414, and information on the color type of the failed laser beam unit and the LD No is read from the memory and notified. Here, as a means for notifying the information, printing on a sheet and display on a display can be used.

  According to the present embodiment, it is possible to detect failure of all the laser light units 112 to 115 using the BD sensor 216 used for outputting the reference position signal in the main scanning direction. Therefore, since the beam detection sensor 119 of Embodiment 3 can be omitted, the cost can be reduced. Further, it is possible to determine the failure of each LD included in the laser light units 112 to 115 without printing on paper.

(Embodiment 5)
FIG. 24 is a diagram for explaining the laser beam scanning in the optical scanning unit according to the fifth embodiment. Referring to the figure, the light emitted from the Y laser light unit 302 is received by the Y BD sensor 311 via the polygon mirror 301, the front-side Fθ1 lens 306 and the mirror 310. Based on this light reception result, the failure of each LD included in the laser light unit 302 is determined.

  Light emitted from the M laser beam unit 303 is received by the M beam detection BD detection sensor 314 via the polygon mirror 301, the front-side Fθ1 lens 306, and the mirror 313. Based on this light reception result, the failure of each LD included in the laser beam unit 303 is determined.

  Light emitted from the C laser light unit 304 is received by the C beam detection sensor 316 via the polygon mirror 301, the rear-side Fθ1 lens 308, and the mirror 315. Based on this light reception result, the failure of each LD included in the laser beam unit 304 is determined.

  Light emitted from the K laser light unit 305 is received by the K BD sensor 313 via the polygon mirror 301, the rear-side Fθ1 lens 308, and the mirror 312. Based on the light reception result, the failure of each LD included in the laser light unit 305 is determined. That is, in this embodiment, it is the structure which performs a failure inspection of each laser beam unit 302-305 using a separate sensor.

(Embodiment 6)
FIG. 25 is a diagram for explaining the laser beam scanning in the optical scanning unit according to the sixth embodiment. Referring to the drawing, the light emitted from the Y laser light unit 402 is received by the Y and M BD sensors 411 via the polygon mirror 401, the front-side Fθ1 lens 406 and the mirror 410. Based on the light reception result, the failure of each LD included in the laser beam unit 402 is determined.

  The light emitted from the M laser beam unit 403 is received by the Y and M BD sensors 411 via the polygon mirror 401, the front-side Fθ1 lens 406, and a mirror (not shown). Based on the light reception result, the failure of each LD included in the laser light unit 403 is determined.

  Light emitted from the C laser light unit 404 is received by the K and C BD sensors 413 through the polygon mirror 401, the rear-side Fθ1 lens 408 and the mirror 412. Based on this light reception result, the failure of each LD included in the laser beam unit 404 is determined.

  Light emitted from the K laser beam unit 405 is received by the K and C BD sensors 413 via the polygon mirror 401, the rear-side Fθ1 lens 408, and a mirror (not shown). Based on this light reception result, the failure of each LD included in the laser beam unit 405 is determined. That is, the failure inspection of the laser light units 302 and 303 is performed using one BD sensor 411, and the failure inspection of the laser light units 304 and 305 is performed using one BD sensor 413.

  The present invention can be implemented in various other forms without departing from the spirit or main features thereof. Therefore, the above-described embodiment is merely an example in all respects and should not be interpreted in a limited manner. The scope of the present invention is indicated by the scope of claims, and is not restricted by the text of the specification. Further, all modifications, various improvements, alternatives and modifications belonging to the equivalent scope of the claims are all within the scope of the present invention. As described in detail above, according to the present invention, it is possible to provide an image forming apparatus capable of detecting a failure of a light emitting element of each light emitting unit without printing on paper.

27 Density Sensor 40 Optical Scanning Sections 41a to 41d First to Fourth Photosensitive Drums 43a to 43d First to Fourth Developing Devices 45 Transfer Belt 49 Transfer Device 51 Fixing Device 61 Controller 70 Laser Light Unit

Claims (14)

An optical scanning unit including a plurality of light emitting units including a plurality of light emitting elements;
A plurality of photoconductors provided corresponding to each of the light emitting units, each having an electrostatic latent image formed by the light emitted from each of the light emitting units;
A developing unit that develops each electrostatic latent image formed on each photoconductor with a different color toner;
A transferred portion to which each image developed by the developing portion is transferred;
A density detector for detecting the density of each of the images transferred to the transferred part;
In the alignment control based on each first test image transferred from each photoconductor,
The density detector detects the density of two test images formed on the transferred part by causing any one of the light emitting elements included in the first light emitting part to emit light, and this detection is performed. A failure determination unit for determining failure of the light emitting element based on the result. The device according to claim 1,
The failure determination unit is configured such that the density of each of the second test images detected by the density detection unit is lower than a density threshold set in accordance with the color type of toner corresponding to the first light emitting unit. Is determined to have failed the first light emitting unit. The device according to claim 1,
The second test images are arranged in the sub-scanning direction. The device according to claim 1,
The transferred portion is a primary transfer belt that rotates endlessly,
The first test image is formed at both ends of the rotation axis direction of the primary transfer belt,
The second test image is formed at the center of the primary transfer belt in the rotation axis direction. The device according to claim 1,
The alignment control is control including correction processing for correcting at least the writing position in the main scanning direction. An optical scanning unit including a plurality of light emitting units including a plurality of light emitting elements;
A plurality of photoconductors provided corresponding to each of the light emitting units, each having an electrostatic latent image formed by the light emitted from each of the light emitting units;
A developing unit that develops each electrostatic latent image formed on each photoconductor with a different color toner;
A transferred portion to which each image developed by the developing portion is transferred;
An alignment detection unit that acquires information for alignment control from each image transferred to the transferred portion;
At the time of image quality maintenance control based on each first test image transferred from each photoconductor,
The alignment detection unit detects a second test image formed on the transferred portion by causing the light emitting element of the first light emitting unit to emit light among the plurality of light emitting units, and based on the detection result, A failure determination unit that determines failure of the light emitting element. In an apparatus according to claim 6,
The failure determination unit determines that the light emitting element is in failure when the detection information acquired by the alignment detection unit is lower than a threshold value. In an apparatus according to claim 6,
The second test images are arranged in the sub-scanning direction. In an apparatus according to claim 6,
The second test images are arranged in the main scanning direction within a region that can be detected by the alignment detection unit. In an apparatus according to claim 6,
The transferred portion is a primary transfer belt that rotates endlessly,
The first test image is formed at the center of the rotation axis direction of the primary transfer belt,
The second test image is formed at both ends of the primary transfer belt in the rotation axis direction. An optical scanning unit including a plurality of light emitting units including a plurality of light emitting elements;
A first sensor that acquires correction information for correcting a writing position in a main scanning direction by receiving light emitted from a first light emitting unit among the plurality of light emitting units;
A second sensor having a detection accuracy lower than that of the first sensor, receiving light emitted from a second light emitting unit different from the first light emitting unit among the plurality of light emitting units;
Based on the presence or absence of light reception in the first sensor when each of the light emitting elements included in the first light emitting unit is caused to emit light, a failure of the first light emitting unit is determined, and the second light emitting unit An image forming apparatus comprising: a failure determination unit that determines failure of the second light emitting unit based on presence or absence of light reception in the second sensor when each of the light emitting elements included in the light emitting element is caused to emit light. A device according to claim 11, comprising:
The plurality of light emitting units include a third light emitting unit different from the first and second light emitting units,
The second sensor receives light emitted from the third light emitting unit,
The failure determination unit determines a failure of the third light emitting unit based on presence or absence of light reception in the second sensor when each of the light emitting elements included in the third light emitting unit emits light. A device according to claim 11, comprising:
The optical scanning unit includes a polygon mirror and an fθ lens that corrects optical characteristics of light reflected by the polygon mirror,
The fθ lens has a first region located in an optical path of light reflected by a polygon mirror and imaged on a photosensitive member,
The second sensor receives light passing through a second region of the fθ lens that is different from the first region. A device according to claim 13, comprising:
A reflection mirror configured to reflect the light having passed through the second region toward the second sensor;

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