JP2008213402A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce degradation in image quality due to difference in the width of effective exposure to light of each LED printing head in an image forming device equipped with a plurality of LED printing heads having different resolution. <P>SOLUTION: In the image forming device, latent images are formed by an LED element corresponding to first and second element Nos. RA and LA of LED printing heads (LPH) 33Y, 33M and 33C and an LED element corresponding to first and second element Nos. RA and LA of an LED printing head (LPH) 33K, respectively. Then the LED element corresponding to the first and second element Nos RA and LA of the LPH 33K is changed to another LED element according to a determination result whether or not the position in the main scanning direction based on the latent image formed by the LED element corresponding to the first and second element Nos. RA and LA of the LPH 33Y, 33M and 33C read by first and second read sensors SE1 and SE2 matches the position in the main scanning direction of the image based on the latent image formed by the LED element corresponding to the first and second element Nos RA and LA of the LPH33K. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus including a plurality of LED printer heads in which a plurality of LED elements are arranged.

  In recent years, an image forming apparatus using an LED printer head (hereinafter referred to as LPH) as an exposure unit has been developed. The LPH collects and irradiates light emitted from a plurality of LED (Light Emitting Diode) elements arranged according to a resolution set in advance along the main scanning direction and LED elements emitted according to image data. An optical means such as a GRIN (Graded-Index) lens for forming a latent image on the body is provided (see Patent Document 1).

Also, a tandem type color image forming apparatus employing LPH as an exposure means has been put into practical use. In this type of image forming apparatus, Y (yellow), M (magenta), C (cyan), and K (black) are used. An LPH is provided for each color.
JP 2004-82583 A

  However, different performance is required for monochrome image formation and color image formation. For example, the resolution of K LPH is another, such as 600 dpi for LPH of three colors Y, M, and C, and 1200 dpi for K LPH. It may be desirable to set the resolution higher than the LPH resolution.

  However, even if the resolution of K LPH is an integral multiple of the resolution of other LPHs as in the above example, the effective exposure width in the main scanning direction differs between K LPH and other LPHs. . This is because the manufacturing accuracy of general semiconductor manufacturing equipment is managed by the metric system, whereas the unit of LPH resolution is dpi using inches of the yard / pound method, and the metric accuracy is converted to dpi. This is because an error occurs when used. In order to reduce the accuracy error to such an extent that the image quality is not affected, it is necessary to manage the manufacturing accuracy in units of 1 μm. However, this increases the manufacturing cost and is not practical.

  As described above, in an image forming apparatus including a plurality of LPHs having different resolutions in the yard / pound method, the effective exposure width is different when the resolutions are different due to manufacturing accuracy. For this reason, the recording width differs between LPHs, and there arises a problem that the maximum recording width varies depending on the apparatus model due to the resolution to be adopted, and the image quality is deteriorated.

  In addition, it is known that the LED mounting substrate included in the LPH expands in the main scanning direction due to thermal expansion in accordance with a temperature change caused by lighting of the LED element and a change in ambient temperature. The expansion of the LED mounting substrate due to this temperature change also causes the recording width to fluctuate, which causes a reduction in image quality.

  An object of the present invention is to reduce a decrease in image quality due to a difference in effective exposure width of each LPH in an image forming apparatus including a plurality of LPHs having different resolutions.

  In the first aspect of the present invention, a plurality of LED elements are arranged in the main scanning direction, and a first exposure unit that forms a latent image of a color image by lighting the LED elements, and the plurality of LED elements are arranged in the main scanning direction. Based on the latent image formed on the transfer belt, a second exposure unit that is arranged and forms a latent image of a black and white image by lighting the LED element, and has a higher resolution than the first exposure unit. Reading means for reading an image, LED element corresponding to a preset position among the plurality of LED elements included in the first exposure means, and the first exposure means among the plurality of LED elements included in the second exposure means A latent image is formed by the LED elements arranged at positions corresponding to the LED elements set in Step 1, and is set in the first exposure means read by the reading means. Discrimination for discriminating between the position in the main scanning direction of the image based on the latent image by the LED element and the position in the main scanning direction of the image based on the latent image by the LED element set in the second exposure means An image forming apparatus comprising: a switching unit configured to change an LED element set in the second exposure unit to another LED element according to a determination result by the determination unit.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the changing unit includes an image based on a latent image formed by the LED element set in the first exposure unit by the determining unit and the first unit. Changing the LED element set in the second exposure means to another LED element according to the difference in position where the image based on the latent image by the LED element set in the two exposure means is formed. It is a feature.

  According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the LED element corresponding to the position preset in the first exposure unit is a plurality of the first exposure unit. Among the LED elements, the LED elements are arranged at a distance set in advance in the direction of one end and the other end from the LED element located in the center in the main scanning direction.

  According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the resolution of the second exposure unit is an integral multiple of the first exposure unit. It is said.

  The invention according to claim 5 is detected by a plurality of exposure means in which a plurality of LED elements are arranged in the main scanning direction, a plurality of temperature detection means for detecting the temperature of the exposure means, and the temperature detection means. Detected temperature storage means for storing temperature, temperature characteristic storage means for storing temperature-dependent characteristic information of the array of the LED elements of the exposure means, temperature detected by the temperature detection means, and detected temperature storage means On the basis of the temperature stored in the temperature characteristic storage information stored in the temperature characteristic storage means, the LED elements corresponding to a preset position among the plurality of LED elements included in the exposure means And an LED element changing unit that changes to an LED element.

  According to the first aspect of the present invention, an image based on the latent image formed by the LED element set in the first exposure unit and an image based on the latent image formed by the LED element set in the second exposure unit are provided. The LED element set in the second exposure means having a higher resolution than the first exposure means can be changed to another LED element depending on whether or not the formed position is coincident in the main scanning direction. In an image forming apparatus including a plurality of exposure units having different resolutions, the difference in effective exposure width between exposure units can be adjusted by an exposure unit having a high resolution, so that a reduction in image quality can be reduced.

  According to the second aspect of the present invention, the same effect as in the first aspect can be obtained, and the image based on the latent image by the LED element set in the first exposure unit and the second exposure unit The LED element corresponding to the LED element set in the first exposure means is changed from the LED element set in the second exposure means according to the difference in position where the image based on the latent image by the set LED element is formed. And the difference in effective exposure width between the exposure means can be eliminated.

  According to the third aspect of the present invention, the same effect as in the first or second aspect can be obtained, and the effective exposure width is centered in the main scanning direction among the plurality of LED elements having the first exposure means. The LED element positioned at the center can be set as a reference, and an image can be formed on the recording medium based on the center position in the direction orthogonal to the conveyance direction of the recording medium.

  According to the fourth aspect of the present invention, the same effect as in any one of the first to third aspects can be obtained, and the resolution of the second exposure means for forming a latent image of a monochrome image can be increased. By setting it as an integral multiple of the resolution of the first exposure means, it is possible to sharpen the formed image and improve the image quality.

  According to the fifth aspect of the present invention, the exposure unit is preset based on the detected temperature of the exposure unit detected by the temperature detection unit, the temperature stored in the detected temperature storage unit, and the temperature-dependent characteristic information. Since the LED element corresponding to the position can be changed to another LED element, the variation in the effective exposure width of the exposure means due to the change in temperature due to the lighting of the LED element included in the exposure means and the extension of the LED mounting substrate due to the ambient temperature change Since it can be eliminated, it is possible to reduce the degradation of image quality.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
First, the configuration will be described.
FIG. 1 is a schematic cross-sectional configuration diagram of an image forming apparatus 1 according to the present embodiment.
The image forming apparatus 1 reads an image from a document, forms an image of the read image on a recording medium P such as paper, and receives image data from an external device such as a PC, and displays an image represented by the image data as a recording medium. This is a digital multifunction machine having a printer function and the like that is formed on P and output. As shown in FIG. 1, the image forming apparatus 1 includes an image reading unit 10 and a printing unit 20.

The image reading unit 10 includes an automatic document feeder 11 called an ADF (Auto Document Feeder) and a reading unit 12.
The automatic document feeder 11 sequentially conveys the documents stacked on the document tray from the top, passes the documents while being in close contact with the contact glass, which is a reading portion of the documents, and completes the reading through the contact glass. The finished document is discharged to the discharge tray.

  The reading unit 12 includes a scanner including a light source, a lens, a contact glass, a CCD (Charge Coupled Device) image sensor, and the like, and forms an image of reflected light of the light irradiated on the document and photoelectrically converts the light. A document image (analog image signal) is read, A / D conversion and various image processing are performed on the read document image, and then output to the print unit 20 as print data. Here, the image means not only image data such as graphics and photographs but also text data such as characters and symbols.

  The print unit 20 performs electrophotographic image formation based on input print data, and includes an image forming unit 30, a cleaning unit 40, a transfer belt 50, a paper feeding unit 60, and a conveyance unit. 70, a fixing unit 80, and a first reading sensor SE1 and a second reading sensor SE2.

  The image forming unit 30 according to the present embodiment is filled with toners of different colors when forming images of up to four colors (yellow (Y), magenta (M), cyan (C), and black (K)). The image forming units 30Y, 30M, 30C, and 30K for each possible color are provided.

  For example, the image forming unit 30Y includes a photosensitive drum 31Y, a charging device 32Y, an LED printer head (hereinafter referred to as LPH) 33Y as an exposure unit, a developing device 34Y, a transfer device 35Y, and a cleaning device 36Y. And a yellow (Y) image is formed.

  The LPH 33Y includes a plurality of light emitting diodes (LEDs) arranged in the main scanning direction as an exposure light source, and an optical member in which a plurality of GRIN (Graded-Index) lenses are arranged in the main scanning direction X. The LEDs are selectively driven based on the image data, and the light emitted from the driven LEDs is condensed on the photosensitive drum 31Y to form an image.

  Specifically, a latent image is formed by irradiating light corresponding to yellow (Y) image data from LPH 33Y onto photosensitive drum 31Y charged by charging device 32Y. The developing device 34Y develops the latent image by attaching charged yellow (Y) toner to the surface of the photosensitive drum 31Y on which the latent image is formed. The photosensitive drum 31Y to which the toner is attached by the developing device 34Y is transferred to a transfer belt 50 described later while being rotated at a constant speed to a transfer position where the transfer device 35Y is disposed. After the toner image is transferred to the transfer belt 50, the cleaning device 36Y removes residual charges, residual toner, and the like on the surface of the photosensitive drum 31Y.

  In addition, the LPH 33Y is mounted with LED elements in consideration of the fact that the LED element mounting substrate on which the LED elements are mounted expands and contracts in the main scanning direction due to the effect of temperature changes caused by lighting of the LED elements and changes in the surrounding environment. An optical member corresponding to the substrate and the LED element is fixed only at one end in the main scanning direction. Each LED element included in the LPH 33Y is assigned a number (hereinafter referred to as an element number) for identifying each LED element from the fixed end of the LED element mounting substrate.

  Similarly, the image forming units 30M, 30C, and 30K include charging devices 32M, 32C, and 32K, LPHs 33M, 33C, and 33K, and developing devices 34M, 34C, and 34K, which are arranged around the photosensitive drums 31M, 31C, and 31K. Apparatuses 35M, 35C, and 35K and cleaning apparatuses 36M, 36C, and 36K are provided to form magenta (M), cyan (C), and black (K) toner images, respectively.

The transfer belt 50 is a semiconductive endless belt that is suspended and supported rotatably by a plurality of rollers, and is driven to rotate as the rollers rotate.
The transfer belt 50 is pressure-bonded to the photosensitive drums 31Y, 31M, 31C, and 31K by transfer devices 35Y, 35M, 35C, and 35K, respectively. As a result, the toners developed on the surfaces of the photoconductive drums 31Y, 31M, 31C, and 31K are yellow and magenta on the recording medium P conveyed on the transfer belt 50 at the transfer positions by the transfer devices 35Y, 35M, 35C, and 35K. , Cyan and black toners are sequentially transferred in a superimposed manner.

  When forming a color image on the recording medium P, in order to reduce the consumption of yellow, magenta, and cyan toners and reduce the total amount of toner deposited on the recording medium P, sharpen the image and improve the image quality. In addition to the toner images of three colors of yellow, magenta, and cyan, it is known to superimpose a black toner image having a higher resolution than yellow, magenta, and cyan.

  Therefore, the LPHs 33Y, 33M, and 33C are arranged such that a plurality of LED elements are arranged in the main scanning direction, and a color image (other than a black and white image) latent image, that is, a yellow, magenta, and cyan latent image is generated by lighting the LED elements. A function as the first exposure means to be formed is realized. The LPH33K has a plurality of LED elements arranged in the main scanning direction to form a black-and-white latent image, that is, a black latent image by lighting the LED elements, and has a higher resolution than the LPH33Y, 33M, and 33C. A function as a certain second exposure means is realized.

  In this embodiment, it is assumed that the resolution of LPH 33Y, 33M, and 33C is 600 [dpi], and the resolution of LPH 33K is 1200 [dpi]. The resolution of LPH33K is not limited to this, and is preferably an integer multiple of LPH33Y, 33M, and 33C in order to realize high image quality.

The paper feed unit 60 includes a plurality of paper feed trays 61 and a manual feed tray 62.
The paper feed tray 61 stores recording media P that are identified in advance for each size and type for each paper feed tray 61, and transports the recording media P stored by the paper feed rollers 61a one by one from the top. Transport toward 60.
The manual feed tray 62 can be loaded with various types of recording media P according to the needs of the user each time, and the recording media P stacked by the paper feed rollers 62a are fed one by one from the top to the transport unit 70. Transport toward.

  The transport unit 70 transports the recording medium P transported from the paper feed tray 61 or the manual feed tray 62 to the transfer device 35Y and the like via a plurality of intermediate rollers 71a and 71b and a registration roller 72.

  The fixing unit 80 thermally fixes the toner image transferred to the recording medium P conveyed by the conveyance unit 70. The recording medium P that has been subjected to the fixing process is sandwiched between the paper discharge rollers 73 and output onto the paper discharge tray 74.

  After the toner image is transferred to the recording medium P by the transfer devices 35Y, 35M, 35C, and 35K, the transfer belt 50 from which the recording medium P is curved and electrostatically separated has residual toner and the like removed by the cleaning unit 40. The

  The first reading sensor SE1 and the second reading sensor SE2 realize a function as reading means for reading an image (toner image) based on the latent image formed on the transfer belt 50. FIG. 2 is a schematic top view of the transfer belt 50, and the arrangement positional relationship between the LPHs 33Y, 33M, 33C, and 33K and the first reading sensor SE1 and the second reading sensor SE2 with respect to the transfer belt 50 will be described.

  As shown in FIG. 2, the LPHs 33Y, 33M, 33C, and 33K are provided to extend across the transfer belt 50 in a direction (main scanning direction X) perpendicular to the recording medium conveyance direction Y. Ly1 and Ly2 shown in FIG. 2 are arbitrary LED elements arranged in the vicinity of one end and the other end in the main scanning direction X among the plurality of LED elements included in the LPH 33Y (first and second element numbers described later). Lk1 and Lk2 are arbitrary LED elements arranged in the vicinity of one end and the other end in the main scanning direction X of the plurality of LED elements included in the LPH 33K. It is a toner image by a latent image formed by LED elements (LED elements corresponding to first and second element numbers described later).

  The first reading sensor SE1 and the second reading sensor SE2 are respectively provided at positions downstream of the recording medium P in the transport direction Y in the image forming unit 30, and the first reading sensor SE1 is LPH33Y, 33M, 33C, 33K. The toner image (for example, Ly1, Lk1) formed by the latent image by the LED element provided in the vicinity of one end in the main scanning direction X is provided at a position where the toner image (for example, Ly1, Lk1) can be read. The toner images (for example, Ly2 and Lk2) formed by the latent image formed by the LED elements provided in the vicinity of the other end portion in the main scanning direction X of the LPHs 33Y, 33M, 33C, and 33K are provided at positions where they can be read. .

  The first reading sensor SE1 and the second reading sensor SE2 are sensors having color response characteristics of a toner image formed on the transfer belt 50. For example, light having a wavelength λ of about 630 [nm] is transferred to the transfer belt 50. A one-dimensional line sensor including a light emitting unit that irradiates upward and a light receiving unit that receives reflected light reflected from the transfer belt 50 is preferable.

FIG. 3 shows a control block diagram of the image forming apparatus 1.
As shown in FIG. 3, the image forming apparatus 1 includes a main body control unit 100, a mechanism control unit 200, an operation display unit 300, an external I / F 400, an image reading unit, a printing unit (not shown), and the like. They are connected by a bus 500 as communication means.

The main body control unit 100 includes a CPU (Central Processing Unit) 110 and a ROM (Read Only).
Memory) 120, nonvolatile memory 130, RAM (Random Access Memory) 140, image processing unit 151, LPH control unit 152 connected to image processing unit 151, I / O (Input / Output) 161, 162, and the like. .

  The CPU 110 reads the system program, each processing program, and data stored in the ROM 120 or the non-volatile memory 130 and develops them in the non-volatile memory 130 or the RAM 140, and concentrates the operation of each part of the image forming apparatus 1 according to the developed program. Control. Timing control of the entire system, storage and storage control of image data using the nonvolatile memory 130 or RAM 140, input / output control of image data to the print unit 20, interface with other applications (FAX, printer, scanner, etc.) F) and operation control.

Further, the CPU 110 receives a PC (Personal Computer) received via the external I / F 400.
The image data transmitted from the external device such as) or the image data transmitted from the image reading unit 10 is temporarily stored in the nonvolatile memory 130 or the RAM 140, and the print data based on the image data is stored in the image processing unit 151. Expand to. The CPU 110 outputs a start instruction signal to the mechanism control unit 200 and causes each unit of the image forming apparatus 1 to operate.

  Further, when assembling the image forming apparatus 1 or adjusting the mechanism, the CPU 110 includes an LED element corresponding to a preset position among a plurality of LED elements included in the LPHs 33Y, 33M, and 33C and a plurality of LED elements included in the LPH 33K. LPH33Y, LPH33Y, which has formed latent image images by LED elements arranged at positions corresponding to the LED elements set in LPH33Y, 33M, 33C, respectively, and has been read by first reading sensor SE1 and second reading sensor SE2. The position at which the image (toner image) based on the latent image formed by the LED elements set in 33M and 33C and the image (toner image) based on the latent image formed by the LED elements set in LPH33K is formed as the main scan. It is determined whether or not they match in the direction X, and according to the determination result Executing the effective exposure width adjustment process LPH changing the LED element set in LPH33K other LED elements.

  The CPU 110 also detects the temperature detected by a temperature sensor provided in each LPH described later during the startup or operation of the image forming apparatus 1, the temperature of each past LPH stored in the nonvolatile memory 130, and the nonvolatile Based on temperature-dependent characteristic information described later stored in the memory 130, effective exposure of LPH for changing an LED element corresponding to a preset position among other LED elements of each LPH to another LED element Execute width adjustment processing.

  Among the plurality of LED elements included in the LPHs 33Y, 33M, and 33C, the LED element corresponding to a preset position is the LED element that is positioned in the center in the main scanning direction X among the plurality of LED elements included in the LPHs 33Y, 33M, and 33C. LED elements (LED elements corresponding to the first and second element numbers RA and LA) arranged at a predetermined distance from the (LED element corresponding to the center element number CE) in the direction of one end and the other end. .

  The center element number CE is the element number of the LED element located in the center in the main scanning direction X among the plurality of LED elements arranged in the main scanning direction X of each LPH.

  The first element number RA is the element number of the LED element number corresponding to the distance preset in the direction from the LED element of the center element number CE to the one end in the main scanning direction X of each LPH. The second element number LA is the element number of the LED element whose element number corresponds to a preset distance from the LED element of the center element number CE to the other end in the main scanning direction X of each LPH. .

  The ROM 120 stores programs and data corresponding to the image forming apparatus 1 in advance, and stores a system program, various processing programs corresponding to the system, and data necessary for processing by the various processing programs.

  In the present embodiment, the ROM 120, in this embodiment, the LPH effective exposure width adjustment process executed when the image forming apparatus 1 is assembled or when the mechanism is adjusted, and the LPH executed when the image forming apparatus 1 is started or operated. A program for executing the effective exposure width adjustment process and various data necessary for executing the program are stored in advance.

  The nonvolatile memory 130 is configured by a flash memory or the like, and stores various programs and data in a rewritable manner. In addition, the nonvolatile memory 130 according to the present embodiment has a detection temperature storage means for storing a temperature (detection temperature) detected by a temperature sensor provided in each LPH, which will be described later, and a temperature based on an array of LED elements of each LPH. A function as temperature characteristic storage means for storing dependence characteristic information is realized.

FIG. 4 shows an example of a temperature dependence graph as temperature dependence characteristic information of LPH33K of 1200 [dpi].
In the temperature dependence characteristic graph shown in FIG. 4, the horizontal axis indicates the temperature [° C.] of the central portion in the main scanning direction of the LPH 33K, and the vertical axis indicates the dot position variation [mm] in the LPH 33K. In the main scanning direction, the dot position variation amount according to the temperature change formed by the LED element B near the center and the LED element C near the free end is shown.

  As shown in FIG. 4, there is a tendency that the dot position fluctuation amount increases as the temperature rises, and the dot position fluctuation amount accompanying the temperature rise varies depending on the position of the LED element. LPH33Y, 33M, and 33C have a resolution similar to that of LPH33K, and the total number of LED elements and lighting control are different. Therefore, the inclination (change amount) of the dot position variation amount accompanying the temperature rise is different from LPH33K, but the same tendency ( Characteristic).

  The RAM 140 is a temporary storage area for programs, input or output data and parameters read from the ROM 120 in various processes executed by the CPU 110.

  The image processing unit 151 performs image processing (magnification, filter, γ conversion, etc.) on image data sent from the image reading unit 10 or the external I / F 400, and generates data to be printed.

  The LPH control unit 152 stores the print data generated by the image processing unit 151 and outputs various signals based on the generated print data to the LPHs 33Y, 33M, 33C, and 33K.

  The I / O 161 is provided in each LPH (LPH 33Y, 33M, 33C, 33K), and temperature sensors (first temperature sensor SE11, second temperature sensor SE12, third temperature sensor) as temperature detecting means for detecting the temperature of each LPH. The temperature sensor SE13 and the fourth temperature sensor SE14) are connected, and the detected temperature detected from each temperature sensor is output to the CPU 110 and stored in the nonvolatile memory 130.

  As the temperature sensors (first temperature sensor SE11, second temperature sensor SE12, third temperature sensor SE13, fourth temperature sensor SE14), a thermistor, a thermocouple, an infrared sensor, or the like can be used. Any device capable of detecting the temperature in the vicinity of each LPH may be used.

  The I / O 162 is connected to the first reading sensor SE1 and the second reading sensor SE2, and outputs signals detected from the first reading sensor SE1 and the second reading sensor SE2 to the CPU 110.

  The mechanism control unit 200 comprehensively controls various drive mechanisms and various sensors in the image forming apparatus 1 based on signals from the main body control unit 100. For example, the mechanism control unit 200 rotates the photosensitive drum 31Y at a constant speed. The motor to be driven is controlled.

  The operation display unit 300 includes a display screen using an LCD (Liquid Crystal Display) or an organic EL (Electronic Luminescent) element, an operation key group including a power switch, an operation display control unit, and the like. A touch panel is provided on the display screen so as to cover the display screen, and the operation display control unit is configured to input various setting screens and images for inputting various setting conditions in accordance with a display signal input from the main body control unit 100. The operating state of the forming apparatus and the processing result are displayed on the display screen. In addition, the operation display control unit transmits an operation signal input from the operation key group or the touch panel to the main body control unit 100.

  The external I / F 400 is configured with various interfaces such as a network interface card (NIC), a modem (MODEM: Modulator-DEModulator), and a USB (Universal Serial Bus), and is connected to be communicable. Send and receive information to and from each other.

Next, the operation of the present embodiment will be described.
5 to 10 are operations realized by the cooperation of the CPU 110, the ROM 120, the nonvolatile memory 130, the RAM 140, and the like in the main body control unit 100.

  First, an LPH effective exposure width adjustment process executed when the image forming apparatus 1 is assembled or when a mechanism is adjusted will be described with reference to FIGS.

  The CPU 110 temporarily holds the temperature of each LPH detected from the first to fourth temperature sensors SE11, SE12, SE13, SE14 (step S1), and sets the center element number CE of each LPH (step S2). .

  The setting of the center element number CE in step S2 is, for example, when the total number of LED elements included in each LPH is n (n; even number), the element number of the (n / 2) + 1st LED element is the center element number CE. Is temporarily set.

  After step S2, the CPU 110 sets the first element number RA and the second element number LA in the main scanning direction of each LPH (step S3).

  In step S3, the first and second element numbers RA and LA are set in the number of LED elements corresponding to a predetermined distance from the LED element having the center element number CE in the direction of one end and the other end. A number is set. The preset distance from the LED element of the center element number CE when setting the first element number RA and the second element number LA in step S3 is a common distance between the LPHs. The corresponding number of LED elements is calculated according to the resolution of each LPH.

  The CPU 110 first adjusts the effective exposure width between the yellow (Y) LPH 33Y and the black (K) LPH 33K. The CPU 110 sets the LED elements corresponding to the first and second element numbers RA and LA of the yellow (Y) LPH33Y and the black (K) LPH33K to ON (step S4), and lights the LPH33Y and LPH33K. A toner image based on the latent image is formed on the intermediate transfer bell 50 (step S5).

  The CPU 110 causes the first reading sensor SE1 to read the toner image formed with the first element number RA of LPH33Y and the toner image formed with the first element number RA of LPH33K, and causes the second reading sensor SE2 to read the second image of LPH33Y. The toner image formed by the element number LA and the toner image formed by the second element number LA of the LPH 33K are read (step S6).

  The CPU 110 has a single formation position in the main scanning direction X between the toner image formed by the first element number RA of LPH33Y read by the first reading sensor SE1 and the toner image formed by the first element number RA of LPH33K. And the main scanning direction X between the toner image formed by the second element number LA of LPH33Y read by the second reading sensor SE2 and the toner image formed by the second element number LA of LPH33K. An analysis is performed as to whether or not the formation positions of the two coincide with each other (step S7).

  The CPU 110 determines whether or not the toner images read by the first reading sensor SE1 and the second reading sensor SE2 match the formation positions in the main scanning direction X according to the analysis result in step S7 (step S8). ).

  When the CPU 110 determines that the toner images read by the first reading sensor SE1 or the second reading sensor SE2 do not coincide with each other in the main scanning direction X (step S8; No), the first element of the LPH 33Y. A positional deviation amount in the main scanning direction X (hereinafter referred to as a first positional deviation amount) between the toner image formed by the number RA and the toner image formed by the first element number RA of the LPH 33K, and the second element number LA of the LPH 33Y. A positional shift amount (hereinafter referred to as a second positional shift amount) in the main scanning direction X between the formed toner image and the toner image formed by the second element number LA of LPH33K is calculated, and the first and second positions are calculated. The center element number CE, the first element number RA, and the second element number LA of LPH33K are changed according to the amount of deviation (step S9). Back-up to S4.

  As the change of the center element number CE, the first element number RA, and the second element number LA in step S9, for example, the change of the first element number RA is an LED corresponding to the resolution of LPH33K corresponding to the first positional deviation amount. The number of elements is calculated and changed by adding the calculated number of LED elements to the first element number RA. The second element number LA is changed by calculating the number of LED elements corresponding to the resolution of the LPH 33K corresponding to the second positional shift amount and adding the calculated number of LED elements to the second element number LA. The center element number CE is changed by calculating the total number n1 from the changed first element number RA to the changed second element number LA and calculating the center element number CE based on the total number n1. .

  If the CPU 110 determines that the toner images read by the first reading sensor SE1 and the second reading sensor SE2 have the same formation position in the main scanning direction X (step S8; Yes), the CPU 110 sets the toner images to LPH33Y and LPH33K. Each of the center element number CE, the first element number RA, and the second element number LA that have been set is temporarily held in the nonvolatile memory 130 or the RAM 140 together with the detected temperature detected in step S1 (step S10).

  Next, the CPU 110 adjusts the effective exposure width between the magenta (M) LPH 33M and the black (K) LPH 33K. The CPU 110 sets the LED elements corresponding to the first and second element numbers RA and LA of the magenta (M) LPH33M and the black (K) LPH33K to ON (step S11), and turns on the LPH33M and LPH33K. A toner image based on the latent image is formed on the intermediate transfer bell 50 (step S12).

  The CPU 110 causes the first reading sensor SE1 to read the toner image formed by the first element number RA of LPH33M and the toner image formed by the first element number RA of LPH33K, and causes the second reading sensor SE2 to read the second image of the LPH33M. The toner image formed by the element number LA and the toner image formed by the second element number LA of the LPH 33K are read (step S13).

  The CPU 110 has a single formation position in the main scanning direction X between the toner image formed by the first element number RA of LPH33M read by the first reading sensor SE1 and the toner image formed by the first element number RA of LPH33K. And the main scanning direction X between the toner image formed by the second element number LA of LPH33M read by the second reading sensor SE2 and the toner image formed by the second element number LA of LPH33K. An analysis is performed as to whether or not the formation positions in FIG.

  The CPU 110 determines whether or not the toner images read by the first reading sensor SE1 and the second reading sensor SE2 match the formation positions in the main scanning direction X according to the analysis result in step S7 (step S15). ).

  When the CPU 110 determines that the toner images read by the first reading sensor SE1 or the second reading sensor SE2 do not coincide with each other in the main scanning direction X (Step S15; No), the first element of the LPH33M The positional deviation in the main scanning direction X between the toner image formed with the number RA and the toner image formed with the first element number RA of LPH33K, the toner image formed with the second element number LA of LPH33M and the first of the LPH33K The positional deviation amount in the main scanning direction X with respect to the toner image formed by the two element number LA is calculated, and the center element number CE and the first element number of LPH33K are calculated in accordance with the positional deviation amount. RA and the second element number LA are changed (step S16), and the process returns to step S11.

  Since the center element number CE, the first element number RA, and the second element number LA in step S16 can be changed in the same manner as in step S9, description thereof is omitted.

  If the CPU 110 determines that the toner images read by the first reading sensor SE1 and the second reading sensor SE2 are coincident with each other in the main scanning direction X (step S16; Yes), the nonvolatile memory 130 or the RAM 140 The first element number RA of the LPH 33K temporarily held in the first and the first element number RA of the currently set LPH 33K, the second element number LA of the held LPH 33K and the second element number of the currently set LPH 33K Each LA is compared (step S17).

  The CPU 110 is currently set with the first element number RA of the LPH 33K temporarily held in the nonvolatile memory 130 or the RAM 140, the first element number RA of the currently set LPH 33K, and the second element number LA of the held LPH 33K. It is determined whether or not the second element numbers LA of the LPHs 33K coincide with each other (step S18).

  The CPU 110 is currently set with the first element number RA of the LPH 33K temporarily held in the nonvolatile memory 130 or the RAM 140, the first element number RA of the currently set LPH 33K, and the second element number LA of the held LPH 33K. When it is determined that at least one of the second element number LA of the LPH 33K that has not been matched (step S18; No), the first element number RA of the held LPH 33K and the first LPH 33K currently set The center element number of LPH33K according to the difference (element misalignment) between the number of LED elements of the element number RA, the second element number LA of LPH33K being held and the second element number LA of LPH33K currently set The CE, the first element number RA, and the second element number LA are changed (step S19). Back to S4.

  Since the change of the center element number CE, the first element number RA, and the second element number LA in step S19 can be performed in the same manner as in step S9, description thereof is omitted.

  Further, the CPU 110 temporarily stores the first element number RA of the LPH 33K temporarily held in the nonvolatile memory 130 or the RAM 140, the first element number RA of the LPH 33K currently set, the second element number LA of the held LPH 33K, and the current When it is determined that the second element numbers LA of the set LPH 33K match each other (step S18; Yes), the effective exposure width adjustment between the cyan (C) LPH 33C and the black (K) LPH 33K is performed. Do. Steps S20 to S28 are the same as steps S11 to S19 except that the magenta (M) LPH 33M is replaced with the cyan (C) LPH 33C, and thus the description thereof is omitted.

  The CPU 110 is currently set with the first element number RA of the LPH 33K temporarily held in the nonvolatile memory 130 or the RAM 140, the first element number RA of the currently set LPH 33K, and the second element number LA of the held LPH 33K. If it is determined that the second element numbers LA of the LPHs 33K match each other (step S27; Yes), the center element numbers CE, the first element numbers RA, the first element numbers of all the LPHs set in this process are determined. The two-element number LA is stored in the nonvolatile memory 130 together with the detected temperature of each LPH (step S29), and this process is terminated.

  Next, an LPH effective exposure width adjustment process executed when the image forming apparatus 1 is started or operated will be described with reference to FIGS.

  The CPU 110 temporarily holds the temperature of each LPH detected from the first to fourth temperature sensors SE11, SE12, SE13, and SE14 (step S31), and detects from the first to fourth temperature sensors SE11, SE12, SE13, and SE14. Based on the temperature of each LPH thus set, the center element number CE of each LPH is set (step S32).

  The setting of the center element number CE in step S32 is, for example, in each LPH, the detected temperature detected in step S31 from the temperature sensor provided in each LPH, and each LPH stored in the nonvolatile memory 130 together with the center element number CE. Based on the detected temperature of each and the temperature-dependent characteristic information of each LPH, the fluctuation amount of the dot position is calculated, the calculated fluctuation amount is converted into the number of LED elements according to the resolution of each LPH, and the calculated number of LED elements is calculated. This is set by adding to the center element number CE of each LPH stored in the nonvolatile memory 130.

  After step S32, the CPU 110 determines the first element number RA and the second element number LA in the main scanning direction of each LPH based on the temperature of each LPH detected from the first to fourth temperature sensors SE11, SE12, SE13, and SE14. Is set (step S33).

  The setting of the first element number RA in step S33 is stored, for example, in each LPH, the detected temperature detected in step S31 from the temperature sensor provided in each LPH, and the first element number RA in the nonvolatile memory 130. Based on the detected temperature and the temperature-dependent characteristic information of each LPH, the amount of fluctuation of the dot position is calculated, the calculated amount of fluctuation is converted into the number of LED elements corresponding to the resolution of each LPH, and the calculated number of LED elements is nonvolatile. This is set by adding to the first element number RA of each LPH stored in the memory 130. The second element number LA is set in the same manner as the first element number RA.

  The CPU 110 first adjusts the effective exposure width between the yellow (Y) LPH 33Y and the black (K) LPH 33K. Since steps S34 to S40 are the same as steps S4 to S10, description thereof is omitted.

  Next, the CPU 110 adjusts the effective exposure width between the magenta (M) LPH 33M and the black (K) LPH 33K. Since steps S41 to S49 are the same as steps S11 to S19, the description thereof is omitted.

  Further, the CPU 110 adjusts the effective exposure width between the cyan (C) LPH 33C and the black (K) LPH 33K. Steps S50 to S58 are the same as steps S20 to S28, and a description thereof will be omitted.

  The CPU 110 is currently set with the first element number RA of the LPH 33K temporarily held in the nonvolatile memory 130 or the RAM 140, the first element number RA of the currently set LPH 33K, and the second element number LA of the held LPH 33K. If it is determined that the second element numbers LA of the LPHs 33K match each other (step S57; Yes), the center element numbers CE, the first element numbers RA, the first element numbers of all the LPHs set in this process are determined. The two-element number LA is stored in the nonvolatile memory 130 together with the detected temperature of each LPH (step S59), and this process is terminated.

  As described above, according to the image forming apparatus 1 of the present embodiment, the toner image based on the latent image formed by the LED elements set in the LPHs 33Y, 33M, and 33C and the latent image formed by the LED elements set in the LPH 33K. The LED elements set in the LPH 33K having a resolution higher than that of the LPHs 33Y, 33M, and 33C are used as other LED elements depending on whether or not the position where the toner image based on the toner image is aligned in the main scanning direction X. Since it can be changed, in the image forming apparatus 1 having a plurality of LPHs with different resolutions, the difference in effective exposure width between the LPHs can be adjusted by the LPH 33K having a high resolution, so that a reduction in image quality is reduced. be able to.

  Further, a difference (position shift amount) between positions where a toner image based on a latent image formed by LED elements set in LPH 33Y, 33M, and 33C and a toner image based on a latent image formed by LED elements set in LPH 33K are formed. Accordingly, the LED elements set in the LPH 33K can be changed to LED elements corresponding to the LED elements set in the LPHs 33Y, 33M, and 33C, and the difference in effective exposure width between the LPHs can be eliminated.

  Further, based on the detected temperature of each LPH detected by each temperature sensor, the detected temperature that has been held, and the temperature-dependent characteristic information of each LPH, the LED element corresponding to the position preset in each LPH is replaced with another LED element. Since the variation of the effective exposure width of each LPH due to the LED mounted substrate expansion due to the temperature change due to the lighting of the LED element or the surrounding temperature change can be eliminated, the image quality is degraded. Can be reduced.

  Of the plurality of LED elements having the first element number RA and the second element number LA in the LPHs 33Y, 33M, and 33C, the LED element located at the center in the main scanning direction X (the LED element corresponding to the center element number CE) is Since the first element number RA to the second element number LA are effective exposure widths, the recording medium P can be set with reference to the center position in the direction perpendicular to the transport direction Y of the recording medium P. An image can be formed on top.

  The present invention is not limited to the contents of the above-described embodiment, and can be appropriately changed without departing from the gist of the present invention.

1 is a schematic cross-sectional configuration diagram of an image forming apparatus 1 in the present embodiment. 2 is a schematic top view of a transfer belt 50. FIG. 2 is a control block diagram of the image forming apparatus 1. FIG. It is an example of the temperature dependence graph as temperature dependence characteristic information of LPH33K of 1200 [dpi]. 5 is a flowchart of an LPH effective exposure width adjustment process executed when the image forming apparatus 1 is assembled or a mechanism is adjusted. 6 is a flowchart of an LPH effective exposure width adjustment process executed when the image forming apparatus 1 is assembled or a mechanism is adjusted (continuation of FIG. 5). FIG. 7 is a flowchart of an LPH effective exposure width adjustment process executed when the image forming apparatus 1 is assembled or when a mechanism is adjusted (continuation of FIG. 6). 4 is a flowchart of an LPH effective exposure width adjustment process executed when the image forming apparatus 1 is started or operated. FIG. 9 is a flowchart of LPH effective exposure width adjustment processing that is executed when the image forming apparatus 1 is activated or in operation (continuation of FIG. 8). FIG. 10 is a flowchart of LPH effective exposure width adjustment processing executed when the image forming apparatus 1 is activated or operated (continuation of FIG. 9).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Image reading part 11 Automatic document feeding part 12 Reading part 20 Printing part 30, 30Y, 30M, 30C, 30K Image forming part 31Y, 31M, 31C, 31K Photosensitive drum 32Y, 32M, 32C, 32K Charging device 33Y, 33M, 33C, 33K LPH
34Y, 34M, 34C, 34K Developing devices 35Y, 35M, 35C, 35K Transfer devices 36Y, 36M, 36C, 36K Cleaning device 40 Cleaning unit 50 Transfer belt 60 Paper feed unit 61 Paper feed tray 61a, 62a Paper feed roller 62 Manual feed tray 62 70 Conveyance units 71a and 71b Intermediate rollers 72 Registration rollers 73 Paper discharge rollers 74 Paper discharge tray 80 Fixing unit 100 Main body control unit 110 CPU
120 ROM
130 Nonvolatile memory 140 RAM
151 Image processing unit 152 LPH control unit 161, 162 I / O
200 Mechanism Control Unit 300 Operation Display Unit 400 External I / F
500 Bus P Recording medium CE Center element number LA Second element number RA First element number SE1 First reading sensor SE2 Second reading sensor SE11 First temperature sensor SE12 Second temperature sensor SE13 Third temperature sensor SE14 Fourth temperature sensor X Main scanning direction Y Transport direction

Claims (5)

A first exposure means in which a plurality of LED elements are arranged in the main scanning direction and a latent image of a color image is formed by lighting the LED elements;
A plurality of LED elements arranged in the main scanning direction to form a black and white latent image by lighting the LED elements, and a second exposure means having a higher resolution than the first exposure means;
Reading means for reading an image based on the latent image formed on the transfer belt;
The LED element corresponding to a preset position among the plurality of LED elements included in the first exposure unit, and the LED element set in the first exposure unit among the plurality of LED elements included in the second exposure unit. The main scanning direction of the image based on the latent image formed by the LED elements set in the first exposure unit, which is formed by the LED elements arranged in the corresponding positions, respectively, and read by the reading unit Discriminating means for discriminating the position in the main scanning direction of the image based on the latent image by the LED element set in the second exposure means;
A changing unit that changes the LED element set in the second exposure unit to another LED element in accordance with a determination result by the determining unit;
Providing
An image forming apparatus. The changing means is
The difference between the positions where the image based on the latent image by the LED element set in the first exposure means and the image based on the latent image by the LED element set in the second exposure means are formed by the determining means. In response, changing the LED element set in the second exposure means to another LED element,
The image forming apparatus according to claim 1. The LED element corresponding to the position preset in the first exposure means is
Among the plurality of LED elements included in the first exposure means, the LED elements are arranged at a predetermined distance from the LED element located in the center in the main scanning direction in the direction of one end and the other end,
The image forming apparatus according to claim 1, wherein: The resolution of the second exposure means is an integral multiple of the first exposure means;
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. A plurality of exposure means in which a plurality of LED elements are arranged in the main scanning direction;
A plurality of temperature detection means for detecting the temperature of the exposure means;
Detection temperature storage means for storing the temperature detected by the temperature detection means;
Temperature characteristic storage means for storing temperature dependent characteristic information of the arrangement of the LED elements of the exposure means;
A plurality of LED elements included in the exposure unit based on the temperature detected by the temperature detection unit, the temperature stored in the detection temperature storage unit, and the temperature dependent characteristic information stored in the temperature characteristic storage unit LED element changing means for changing the LED element corresponding to a preset position to another LED element,
Providing
An image forming apparatus.

Images