JP2008298971A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To carry out calibration in any image forming area at low cost. <P>SOLUTION: An image forming apparatus 1 has a conveyance section 90 which conveys a form, an image forming section 20 which forms patching images for correction on the conveyed form, a color sensor unit 32 which detects the patching images formed on the form, a drive section 31c which moves the color sensor unit 32 to patching image forming positions on the form which are formed by the image forming section 20, and an engine controlling section 42 which controls image forming condition in the image forming section 20 based on the detected results detected in the color sensor unit 32 and the patching image forming positions on the form. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus.

  2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a printer, a correction test pattern (hereinafter referred to as “patch image”) is used to maintain image formation on a recording medium such as paper (hereinafter referred to as “paper”) at a certain level. ), And the patch image is detected by a sensor to perform calibration.

  Specifically, in an image forming apparatus that forms a color image on a sheet, changes in image quality such as color and density are easily recognized on the sheet, so that cyan (C), magenta (M), yellow (Y) , Black (K) single-color gradation patch images and CMY mixed-color patch images are formed, and the density and chromaticity of the patches are detected by a color sensor to adjust the formation of each color.

For example, in Patent Documents 1 and 2, in an image forming apparatus that forms a color image, a patch image is formed, the patch image is detected using a color sensor, and calibration is performed based on the detection result. Is disclosed.
JP 2006-11205 A JP 2006-58565 A

  However, in the above-described conventional image forming apparatus, the area where the patch image can be detected by the sensor in both the main and sub scanning directions is limited to the detection range of the sensor. For this reason, stable image formation can be performed for the image forming area calibrated by the patch image and the sensor, but the density and chromaticity unevenness of the other area cannot be effectively dealt with. .

  For example, even if an electrophotographic image forming apparatus forms a patch image with the same image signal in the scanning direction, unevenness occurs in density and chromaticity. This is because the transfer characteristics of the toner and the fixing characteristics of the fixing device that fixes the toner transferred to the paper by heating and pressing are slightly different between the central portion and the end portion in the main and sub scanning directions. Yes. Therefore, in the above-described electrophotographic image forming apparatus, it is important to perform calibration not only in a part of the image forming area but also in an arbitrary image forming area in order to form a high-quality image.

  In addition, in order to increase the area where stable image formation is possible by calibration using patch images and sensors, there is a problem that the cost increases when a large number of sensors are provided.

  An object of the present invention has been made in view of the above problems of the prior art, and is to perform calibration of an arbitrary image forming region at a low cost.

In order to solve the above-described problem, the invention according to claim 1 includes a conveying unit that conveys a sheet,
An image forming unit that forms a patch image for correction on a sheet conveyed by the conveying unit;
Detecting means for detecting a patch image formed on the paper;
Moving means for moving the detection means to a patch image forming position on the paper formed by the image forming means;
Control means for controlling an image forming condition in the image forming means based on a detection result detected by the detecting means and a patch image forming position on the paper;
Have

According to a second aspect of the present invention, in the first aspect of the invention, the image forming unit is substantially parallel to the transport direction at a formation position in a direction substantially perpendicular to the transport direction on the paper. Forming a patch image,
The moving means moves the detecting means to a patch image forming position on the paper formed substantially parallel to the transport direction by the image forming means.

According to a third aspect of the present invention, in the first aspect of the present invention, the image forming unit prints a patch image in a direction substantially perpendicular to the transport direction at any one of the transport positions on the paper. Forming,
The moving means moves the detecting means to a patch image forming position on the sheet formed by the image forming means in a direction substantially orthogonal to the transport direction.

According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the detecting unit reads a sheet conveyed by the conveying unit after the image formation and places the sheet on the sheet. Detect the formed patch image,
The moving means moves the detection means in a direction substantially perpendicular to the paper conveyance direction by the conveyance means.

According to a fifth aspect of the present invention, in the invention according to the fourth aspect of the present invention, a retreating place for the detection means is provided outside a paper conveyance path area by the conveyance means,
The control means causes the moving means to move the detecting means to the retreat location while not detecting the patch image.

  According to a sixth aspect of the present invention, in the fifth aspect of the present invention, a reading member serving as a reference for the reading state of the detecting means is provided at the retreat location.

The invention according to claim 7 is the invention according to any one of claims 1 to 6, wherein the image forming unit forms a patch image related to correction of any color,
The detecting means detects a color condition of a patch image formed on the paper;
The control means controls the image forming condition of any one of the colors in the image forming means based on the color condition detected by the detecting means.

  According to the first aspect of the present invention, the detection means for detecting the patch image for correction can be moved to the patch image forming position on the paper to control the image forming condition, and calibration of an arbitrary image forming area can be performed. Can be performed at low cost.

  According to the second aspect of the present invention, it is possible to detect a patch image formed substantially parallel to the conveyance direction at any formation position in a direction substantially orthogonal to the conveyance direction on the paper.

  According to the third aspect of the present invention, it is possible to detect a patch image formed in a direction substantially perpendicular to the transport direction at any formation position in the transport direction on the paper.

  According to the fourth aspect of the present invention, it is possible to detect the correction patch image on the sheet conveyed by the conveying unit by moving the detecting unit in a direction substantially orthogonal to the conveying direction of the sheet.

  According to the fifth aspect of the present invention, it is possible to move the detection means to a retreat place provided outside the sheet conveyance path area while not detecting the patch image.

  According to the invention described in claim 6, while the detecting means is in the retreat place, the reading condition of the detecting means can be calibrated.

  According to the seventh aspect of the present invention, it is possible to correct the image forming condition of any color.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments. The embodiment of the present invention shows the most preferable mode of the invention, and the scope of the invention is not limited to this.

  First, the internal configuration of the image forming apparatus will be described with reference to FIG. FIG. 1 shows an outline of the internal configuration of the image forming apparatus 1. As shown in FIG. 1, the image forming apparatus 1 includes an image reading unit 10, an image forming unit 20, a detection unit 30, and a conveyance unit 90.

  The image reading unit 10 includes an automatic document feeder 11 and a document image scanning device 12. The automatic document feeder 11 conveys the document d placed on the document table by the conveyance mechanism and sends it to the document image scanning device 12. The document image scanning device 12 optically scans the conveyed document d, The original image is read by photoelectric conversion by the sensor CCD.

  A document image (analog image signal) read by the image reading unit 10 is output to an image processing unit described later, and various images such as analog processing, A / D conversion processing, shading processing, and image compression processing are processed in the image processing unit. After the processing is performed, color separation is performed on each color of Y (yellow), M (magenta), C (cyan), and K (black), and the exposure units 2Y, 2M, and 2C of the image forming unit 20 are output as image data. 2K.

  The automatic document feeder 11 has a conveyance mechanism for reading both sides of the document, and continuously reads images (including both sides) of a large number of documents d conveyed from the document table all at once. Is possible. The read document image data is stored in an image memory inside the image forming unit 20, and is sequentially read as output data at the time of output, and is output to the exposure units 2Y, 2M, 2C, and 2K. This function can be used when copying a large number of original images by the copying function, or when transmitting data of a large number of originals d by the facsimile function.

  The image forming unit 20 performs tandem image formation. The exposure units 2Y, 2M, and 2C are light emitting elements arranged in a line in the main scanning direction for each of Y, M, C, and K colors. 2K, developing units 3Y, 3M, 3C, and 3K, photosensitive drums 4Y, 4M, 4C, and 4K as photosensitive members, primary transfer rollers 7Y, 7M, 7C, and 7K, and an intermediate transfer belt 8. Around the photosensitive drums 4Y, 4M, 4C, and 4K, charging units 5Y, 5M, 5C, and 5K that perform charging, and cleaning units 6Y and 6M that remove residual toner on the photosensitive drums 4Y, 4M, 4C, and 4K. , 6C, 6K are provided.

  The image forming unit 20 includes a secondary transfer roller 21 that transfers the toner image transferred onto the intermediate transfer belt 8 onto a sheet, and a fixing unit 22 that thermally fixes the toner image after transfer onto the sheet. .

  The intermediate transfer belt 8 is wound around a plurality of rollers and is rotatably supported. A cleaning unit 9 is provided facing the intermediate transfer belt 8 to remove residual toner on the intermediate transfer belt 8.

  The detection unit 30 is arranged on the downstream side of the fixing unit 22 and the like, and detects the density and the like of the image formed by reading on the image-formed paper. The detection unit 30 can be applied with an optical sensor including, for example, a phototransistor and an LED (Light Emitting Diode), and detects the amount of reflected light by irradiating inspection light on a sheet. A density value can be obtained by converting the measured value of the reflected light amount by a known arithmetic expression (for example, log conversion).

  The transport unit 90 has a function of transporting the paper placed on the paper feed trays T1 to T3 to each unit along the transport path by a transport roller mechanism and the like, and discharging the paper to a paper discharge tray outside the machine (not shown). Part.

  Specifically, the transport unit 90 transports the paper placed on the paper feed trays T1 to T3 to the secondary transfer roller 21, and fixes the paper after the toner image is transferred by the secondary transfer roller 21. 22, the sheet after image formation heat-fixed by the fixing unit 22 is conveyed to the detection unit 30, and the sheet read by the detection unit 30 is discharged to the discharge tray.

Hereinafter, an image forming process by the image forming unit 20 will be described.
First, exposure is performed by the exposure unit 2Y based on the input output image data, and an electrostatic latent image of the output image is formed on the photosensitive drum 4Y. Next, the developing unit 3Y blows toner onto the photosensitive drum 4Y for development, and a toner image is formed on the photosensitive drum 4Y. The development is performed by reversal development in which a development bias in which an AC voltage is superimposed on a DC voltage having the same polarity as that of the toner to be used is applied.

  The toner image formed on the photosensitive drum 4Y is transferred onto the rotating intermediate transfer belt 8 by a primary transfer roller 7Y to which a primary transfer bias having a polarity opposite to that of the used toner is applied (this is called primary transfer). ), A Y toner image is formed on the intermediate transfer belt 8. Such processing is sequentially performed for each of the colors M, C, and K, and a color image in which the toner images of the respective colors are synthesized is formed on the intermediate transfer belt 8.

  On the other hand, the transport unit 90 transports the paper placed on the paper feed trays T <b> 1 to T <b> 3 to the secondary transfer roller 21. In the secondary transfer roller 21, the color image formed on the intermediate transfer belt 8 is collectively transferred onto one surface of the paper (this is called secondary transfer). The sheet on which the color image has been transferred is conveyed to the fixing unit 22 by the conveying unit 90 and subjected to a fixing process. The image-formed paper subjected to the fixing process is discharged by the transport unit 90 through the detection unit 30 onto a discharge tray outside the apparatus.

  When the image forming cycle for one image is completed, the toner remaining on the photosensitive drums 4Y, 4M, 4C, 4K and the intermediate transfer belt 8 after the transfer is removed by the cleaning units 6Y, 6M, 6C, 6K, and 9. Then, the process proceeds to the image forming cycle of the next image.

  That is, the image forming cycle in the image forming unit 20 forms an electrostatic latent image on the photosensitive drum, and transfers the toner image having the toner attached to the electrostatic latent image on the intermediate transfer belt in a superimposed manner. A color image is formed by a photographic method. Note that the image forming method on the paper is not limited to the electrophotographic method exemplified in this embodiment, and other printing methods such as an ink jet method and a heat sublimation method may be applied.

  Next, the detail of the detection part 30 is demonstrated with reference to FIGS. FIG. 2 shows a state where the detection unit 30 is viewed from above. FIG. 3 shows a state where the detection unit 30 is viewed from the side. FIG. 4 shows a state where the detection unit 30 is seen from above with the top plate 351 removed. FIG. 5 shows a state where the detection unit 30 is seen from the side with the side plate 352 removed. FIG. 6 illustrates the configuration of the color sensor unit 32. FIG. 7 illustrates a circuit configuration of the color sensor unit 32. FIG. 8 shows the relationship between the wavelength of light detected by the color sensor unit 32 and its output voltage.

  As shown in FIGS. 2 and 3, the detection unit 30 includes a sensor moving shaft 31a, a support unit 31b, a drive unit 31c, a color sensor unit 32, a home position sensor 33, a storage position sensor 34, and a sensor storage unit 35. Is done.

  The sensor moving shaft 31a is a ball screw that can be rotationally driven by a drive unit 31c such as a stepping motor connected to one end, and extends over a region R1 including a conveyance path along which a sheet is conveyed by the conveyance unit 90 and a region R2 outside thereof. Installed. The installation direction of the sensor moving shaft 31a is the X1-X2 direction substantially orthogonal to the Y1-Y2 direction, which is the direction in which the sheet is conveyed in the region R2.

  A support portion 31b that supports the color sensor unit 32 is fitted to the sensor moving shaft 31a. In the support portion 31b, a male screw of the sensor moving shaft 31a and a female screw in the support portion 31b are screwed together at a fitting portion with the sensor moving shaft 31a. For this reason, the support part 31b is movable in the installation direction of the sensor moving shaft 31a when the sensor moving shaft 31a is rotationally driven.

  The color sensor unit 32 supported by the support portion 31b includes a phototransistor, an LED, and the like, and irradiates inspection light directly below the sensor to detect the amount of reflected light. That is, when the color sensor unit 32 irradiates the inspection light onto the paper and detects the amount of reflected light, the color sensor unit 32 can detect the image state of one area that is the irradiation range of the inspection light.

  The home position sensor 33 and the storage position sensor 34 are optical sensors for detecting the movement position of the support portion 31b. By detecting the moving position of the support portion 31b with the home position sensor 33 and the storage position sensor 34, the position of the color sensor unit 32 supported by the support portion 31b can be detected. Here, the home position sensor 33 is a sensor that detects that the color sensor unit 32 is at the home position P1. The storage position sensor 34 is a sensor that detects that the color sensor unit 32 is in the storage position P <b> 2 stored in the sensor storage unit 35.

  The sensor storage unit 35 has a top plate 351 slidable in the X1-X2 direction on the top surface, side plates 352 and 353 on the side surface, and a bottom plate 356 on the bottom surface, and stores when the color sensor unit 32 moves to the storage position P2. It is a configuration.

  The top plate 351 is connected to a top plate spring 354 having an urging force in the X1 direction. When the color sensor unit 32 is not near the storage position P2, the sensor storage unit surrounded by the side plates 352 and 353 and the bottom plate 356 is provided. 35 is covered. The top plate 351 has a contact portion M3 with which the edge of the color sensor unit 32 comes into contact. When the color sensor unit 32 moves to the storage position P2 in the X2 direction, the color sensor unit 32 comes into contact. The part M3 is pressed against and slides.

  The side plate 352 and the side plate 353 form an opening E by the contact portions M1 and M2 on the X1 direction side of the sensor storage portion 35, and have a biasing force in the direction of closing the opening E in the vicinity of the opening E. A side plate opening / closing spring 355 is connected. Further, as shown in FIGS. 4 and 5, the side plate 352 and the side plate 353 are connected by a side plate rotation shaft 357 on the direction X2 side of the sensor storage unit 35.

  As shown in FIG. 2, when the color sensor unit 32 moves in the vicinity of the opening E in the X1-X2 direction, the contact portions M1 and M2 contact the edges of the color sensor unit 32 so that the opening E It is formed in a curved surface shape so that the side plates 352 and 353 are moved in the opening direction.

  As shown in FIGS. 4 and 5, the bottom plate 356 includes a reference plate 358 on the upper surface thereof. The reference plate 358 is installed at a position where the color sensor unit 32 is properly read when the color sensor unit 32 is at the storage position P2 (for example, a position where the focal length of the color sensor unit 32 is appropriate). This is a reading member of a color (for example, “white”) that serves as a reference for density and chromaticity.

  As described above, the sensor storage unit 35 closes the opening E in a normal state where the color sensor unit 32 is not in the vicinity of the opening E, and opens when the color sensor unit 32 passes through the opening E. The unit 32 is made freely accessible. Therefore, the sensor storage unit 35 can store the color sensor unit 32 moving in the X1-X2 direction at the storage position P2, and can prevent paper dust and dust from adhering to the color sensor unit 32.

  The sensor storage unit 35 has a configuration in which the opening E is closed except when the color sensor unit 32 is moved in and out. Therefore, the sensor storage unit 35 can prevent paper dust and dust from entering the sensor storage unit 35.

  In addition, the sensor storage unit 35 includes a reference plate 358 that serves as a reference for reading the color sensor unit 32. When the color sensor unit 32 is in the storage position P2, the reading state calibration using the reference plate 358 is performed. Can be done.

  Here, details of the color sensor unit 32 will be described. As shown in FIG. 6, the color sensor unit 32 includes an LED 321 for irradiating the patch image G formed on the paper Y with inspection light to correct the image forming condition in the image forming unit 20 and the amount of reflected light. And a light receiving element portion 322 which is a phototransistor or the like for detection.

  The light receiving element unit 322 includes a red light receiving element 322a that detects red (R) light, a green light receiving element 322b that detects green (G) light, and a blue light receiving element 322c that detects blue (B) light. The RGB light receiving elements are arranged such that a plurality of elements are filled in a staggered pattern or a honeycomb, and the effective light receiving area is widened and the amount of reflected light is detected without deviation.

  As shown in FIG. 7, the red light receiving element 322a, the green light receiving element 322b, and the blue light receiving element 322c are grounded via a resistor 323, and output the potential changed by receiving the reflected light to the amplifying unit 324. . The amplifying unit 324 amplifies the potential that changes according to the amount of reflected light received and inputs the amplified potential to the A / D input terminal of the control unit 40.

  The output characteristics for each wavelength in the red light receiving element 322a, the green light receiving element 322b, and the blue light receiving element 322c are as shown in FIG. Data relating to the output characteristics is stored in advance in a memory or the like. The control unit 40 can detect the wavelength included in the reflected light amount based on the data relating to the output characteristics and the voltage values of the red light receiving element 322a, the green light receiving element 322b, and the blue light receiving element 322c.

  Next, the configuration of the control system of the image forming apparatus 1 will be described with reference to FIG. FIG. 9 schematically shows a functional configuration of the image forming apparatus 1. As shown in FIG. 9, the image forming apparatus 1 includes an image reading unit 10, an image forming unit 20, a detection unit 30, a control unit 40, an image processing unit 43, an image memory 44, a correction operation execution unit 45, an operation unit 50, The display unit 60, the communication unit 70, and the storage unit 80 are configured. Since the image reading unit 10, the image forming unit 20, and the detection unit 30 are as described above, description thereof is omitted here.

  The control unit 40 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and the like (not shown). The CPU uses a predetermined area of the RAM as a work area and stores it in the ROM or the storage unit 80. By reading and sequentially executing the control program and application program, the operation of the image forming apparatus 1 is comprehensively controlled.

  Specifically, the control unit 40 has functions as an overall control unit 41 and an engine control unit 42. The overall control unit 41 performs various calculations according to a control program stored in the storage unit 80 and the like, and controls each unit such as the operation unit 50, the display unit 60, and the communication unit 70. The overall control unit 41 generates various control information such as instruction information related to output and setting information related to the correction operation based on the operation signal input from the operation unit 50 and outputs the control information to the engine control unit 42.

  The engine control unit 42 functions to control each unit related to the image forming operation such as the image reading unit 10, the image forming unit 20, the detecting unit 30, the image processing unit 43, the image memory 44, the correction operation executing unit 45, and the conveying unit 90. And generally controls output processing in accordance with control information input from the overall control unit 41.

  Specifically, the engine control unit 42 outputs a control signal to the transport unit 90 to transport the sheets stored in the paper feed trays T1 to T3 to the image forming unit 20, and sends a control signal to the image forming unit 20. Image formation based on the image data output and stored in the image memory 44 or the like is controlled. Further, the engine control unit 42 performs image data conversion processing (for example, gradation conversion) related to image formation and adjustment of the developing bias in the image forming unit 20 by a correction operation executed by a correction operation execution unit 45 described later. The image formation on the paper is controlled by forming an image based on the adjusted value. Then, the engine control unit 42 outputs a control signal to the transport unit 90 and discharges the paper after the image formation to the paper discharge tray through the detection unit 30.

  In addition, the engine control unit 42 outputs a control signal to the drive unit 31 c and performs control related to the movement of the color sensor unit 32. Specifically, the engine control unit 42 drives the drive unit 31c during the correction operation by the correction operation execution unit 45 to control the movement of the relative position between the reading position of the color sensor unit 32 and the paper. In addition, the engine control unit 42 drives the drive unit 31c until the color sensor unit 32 is detected by the storage position sensor 34 while the correction operation by the correction operation execution unit 45 is not performed, so that the color sensor unit 32 is driven. It is stored in the sensor storage unit 35.

  The image processing unit 43 performs various processes on the analog image signal input from the image reading unit 10 to generate digital image data, and performs compression or expansion processing on the data stored in the image memory 44. Further, various image processing such as rotation / reversal processing, gradation processing, and sharpness adjustment processing is performed on the output target data for image formation by the image forming section 20 in accordance with instructions from the engine control section 42.

  The image memory 44 is configured by a DRAM (Dynamic RAM) or the like, and stores output target data such as image data read by the image reading unit 10 and data received via the communication unit 70.

  The correction operation execution unit 45 is a part of the functional unit of the engine control unit 42 realized by the control unit 40 executing the control program, and the image forming unit 20 can perform stable image formation that satisfies the user. The image forming condition of the image forming unit 20 controlled by the engine control unit 42 is corrected. The correction operation execution unit 45 may be configured to use, for example, a dedicated IC (Integrated Circuit) as a configuration other than that realized by the control unit 40 executing the control program.

  The correction operation performed by the correction operation execution unit 45 is a correction operation called stabilization control for maintaining the stability of the image quality of the image formed on the paper in the image forming unit 20. In the stabilization control, surface potential correction for matching the surface potential of the photosensitive drum, or Dmax correction for correcting the maximum density by creating a patch image for correction on the paper and detecting the patch image by the detection unit 30. Or, gradation correction is performed. These correction operations are performed by the user when the number of output sheets reaches a predetermined number (for example, 1000 sheets) or when the sheet feeding time (idling time or power-off time) has elapsed (for example, 360 minutes). This is executed when an instruction to execute a correction operation is issued via 50.

  In the surface potential correction, the correction operation executing unit 45 performs control-related correction on the surface potentials of the photosensitive drums 4Y, 4M, 4C, and 4K. Specifically, the surface potentials of the photosensitive drums 4Y, 4M, 4C, and 4K are measured using a surface potential meter (not shown) so that the surface potential of a portion that is not charged and is not exposed is within the reference. Make corrections.

  In the Dmax correction, the correction operation execution unit 45 performs correction related to the control of the developing bias in the developing units 3Y, 3M, 3C, and 3K, and adjusts so that the maximum density at the time of output becomes a specified value. Specifically, the correction operation execution unit 45 forms a patch image of each color at a predetermined density on a sheet in the image forming unit 20 in order to perform Dmax correction, and a driving unit on the sheet conveyed after the image formation. The color sensor unit 32 is moved by driving 31c. Then, the density of each color patch image is detected by the color sensor unit 32, and the correction related to the control of the developing bias is performed based on the position of the color sensor unit 32 in the main scanning direction and the detection result.

  Similarly, in the gradation correction, the correction operation execution unit 45 performs correction related to the control of the developing bias in the image forming unit 20 and adjusts the change in the gradation at the time of output. Specifically, the correction operation execution unit 45 forms patch images of each color divided in stages from light gradations to dark gradations on the paper in the image forming unit 20 in order to perform gradation correction. The color sensor unit 32 is moved by driving the drive unit 31c onto the sheet conveyed after the formation. Then, the density of each color patch image is detected by the color sensor unit 32, and the correction related to the control of the developing bias is performed based on the position of the color sensor unit 32 in the main scanning direction and the detection result.

  In the gradation correction, the correction operation execution unit 45 may be configured to change the conditions at the time of gradation processing in the image processing unit 43 based on the detection result of the position of the color sensor unit 32 in the main scanning direction. Good. Also in this case, since the gradation of image data to be formed by the image forming unit 20 can be adjusted in advance, gradation correction at the time of image formation in the image forming unit 20 can be performed.

  In addition, the correction operation execution unit 45 detects that the position of the color sensor unit 32 is stored in the sensor storage unit 35 based on the output signal from the storage position sensor 34, and the color sensor unit 32. Then, the reference plate 358 is detected, and the reading of the color sensor unit 32 is calibrated. Specifically, the correction operation execution unit 45 compares the detection value of the reference plate 358 detected by the color sensor unit 32 with the value related to the reference plate 358 stored in the storage unit 80 in advance, so that the color sensor unit 32. Calibration of the detection signal output from.

  The operation unit 50 includes various function keys such as numeric keys and a start key, a touch panel configured integrally with the display unit 60, an operation signal corresponding to the operated key, and an input operation on the touch panel. An operation signal corresponding to the above is generated and output to the overall control unit 41.

  The display unit 60 includes a display such as an LCD (Liquid Crystal Display), and displays various display information such as various operation screens, processing results of the overall control unit 41, and output results of the image forming unit 20.

  The communication unit 70 includes a communication interface such as a network interface card or a FAX modem, and transmits / receives information to / from an external device such as another image forming apparatus or a user terminal. For example, data to be output can be received from the user terminal, or the image data read by the image reading unit 10 can be transmitted to another image forming apparatus or user terminal.

  The storage unit 80 is an HDD (Hard Disk Drive), a nonvolatile memory, or the like. In addition to various control programs executed by the control unit 40, various setting information, parameters and various data necessary for execution of program processing, and processing results The data etc. are memorized. The various data necessary for executing the program processing stored in the storage unit 80 includes data relating to the formation of the correction patch image of the image forming unit 20.

  Next, the formation of the correction patch image on the sheet and the detection of the patch image formed on the sheet in the image forming apparatus 1 will be described with reference to FIGS. FIG. 10 illustrates a patch image G formed on the paper Y by the image forming unit 20. 11 and 12 show the positional relationship between the patch image G formed on the paper Y by the image forming unit 20 and the color sensor unit 32. FIG.

  As shown in FIG. 10, the image forming apparatus 1 forms a patch image G on the paper Y when performing Dmax correction and gradation correction of the image forming unit 20. Specifically, as described above, the image forming apparatus 1 stores the correction patch image from the storage unit 80 when performing the Dmax correction and the gradation correction by the correction operation executing unit 45 under the control of the engine control unit 42. Data relating to the formation is read, and image formation based on the read data is performed by the image forming unit 20 to form the patch image G on the paper Y.

  For example, in the case of gradation correction, the patch image G is composed of patch images that are divided in stages from a dark gradation patch image G11 to a light gradation patch image G21 as shown in FIG. Further, in the case of Dmax correction, the patch image G includes a patch image (for example, the patch image G11) having the darkest gradation.

  This patch image G is applied to a sheet conveyed by the conveyance unit 90 based on data relating to formation such as a formation position and a formation direction on the sheet stored in the storage unit 80 under the control of the engine control unit 42. The image forming unit 20 forms the image.

  Specifically, as shown in FIG. 11, the patch image G is in a direction substantially parallel to the conveyance direction (sub-scanning direction) of the paper Y, in other words, in a direction substantially orthogonal to the main scanning direction in the image forming unit 20. It is formed. Specifically, the patch image G10 for correcting the Y color, the patch image G20 for correcting the M color, the patch image G30 for correcting the C color, and the K color are corrected at a predetermined position in the main scanning direction. A patch image G40 is formed along the transport direction.

  Next, when the patch image G is formed on the paper Y, the image forming apparatus 1 drives the drive unit 31 c so that the color sensor unit 32 moves on the patch image G. Specifically, as described above, when the correction operation is started by the correction operation execution unit 45 and the patch image G is formed on the paper Y under the control of the engine control unit 42, the image forming apparatus 1 A control signal based on data (formation position, formation direction) relating to the formation of the patch image G is output to the drive unit 31c to move the color sensor unit 32. Accordingly, the color sensor unit 32 can detect the patch image G formed along the transport direction at a predetermined position in the main scanning direction on the paper Y transported by the transport unit 90.

  Therefore, the image forming apparatus 1 detects the patch image G formed at a predetermined position in the main scanning direction on the paper Y by moving the color sensor unit 32 to the forming position, thereby detecting the predetermined position in the main scanning direction. It is possible to correct (calibrate) the image forming condition of the image forming unit 20 in FIG. For example, the image forming apparatus 1 can correct the image forming condition of each color of YMCK at the formation position of the patch image G in the main scanning direction by forming the patch image G as shown in FIG.

  Further, even when the image forming apparatus 1 forms and corrects the patch image G at an arbitrary position (center position, end position, etc.) in the main scanning direction, the color sensor unit 32 is moved to the patch image G. Since it can be detected by moving to the formation position, it is not necessary to provide a large number of sensors and can be realized at low cost.

  In addition, as shown in FIG. 12, the patch image G is formed in a direction substantially perpendicular to the conveyance direction (sub-scanning direction) of the paper Y, in other words, in a direction substantially parallel to the main scanning direction in the image forming unit 20. Also good. Specifically, for example, patch images G41 to G4n for correcting the image forming condition of K color are formed at a predetermined position in the transport direction of the paper Y along the main scanning direction.

  Note that the patch image G is formed in the sheet conveyance direction by moving the color sensor unit 32 and moving the color sensor unit 32 on the positional relationship where the detection unit 30 is disposed downstream of the fixing unit 22 as shown in FIG. It is preferable that the rear end in the sheet conveyance direction is on the rear end side so that the fixing unit 22 does not heat the sheet during detection.

  In this case, as described above, the image forming apparatus 1 starts the correction operation by the correction operation execution unit 45 under the control of the engine control unit 42 and moves along the main scanning direction at a predetermined position in the transport direction of the paper Y. When the patch image G is formed, a color sensor is output on the formation position of the patch image G by outputting a control signal to the transport unit 90 based on data (formation position, formation direction) relating to the formation of the patch image G. The paper Y is transported to a position where the unit 32 can move. Next, the image forming apparatus 1 detects the patch image G by moving the color sensor unit 32 by outputting a control signal to the drive unit 31 c under the control of the engine control unit 42. Thereby, the color sensor unit 32 can detect the patch image G formed along the main scanning direction at a predetermined position in the transport direction of the paper Y.

  Therefore, the image forming apparatus 1 corrects the image forming state of the image forming unit 20 in the main scanning direction by detecting the patch image G formed along the main scanning direction at a predetermined position in the transport direction on the paper Y. (Calibration) can be performed. For example, the image forming apparatus 1 can correct the K image forming condition in the main scanning direction by forming the patch image G as shown in FIG. Similarly, the image formation can be corrected for other colors.

  When the patch image G is formed along the main scanning direction, the patch image G is formed from one end to the other end in the main scanning direction so that the entire patch in the main scanning direction can be detected by detecting the patch image G once. It is possible to correct the image forming condition.

  As described above, the image forming apparatus 1 detects the transport unit 90 that transports the paper, the image forming unit 20 that forms a patch image for correction on the transported paper, and the patch image formed on the paper. The color sensor unit 32, the drive unit 31c that moves the color sensor unit 32 to the patch image forming position on the paper formed by the image forming unit 20, the detection result detected by the color sensor unit 32, and the patch on the paper And an engine control unit 42 that controls the image forming condition in the image forming unit 20 based on the image forming position.

  For this reason, the image forming apparatus 1 can move the color sensor unit 32 for detecting the patch image formed on the sheet to the patch image forming position on the sheet. The patch image can be detected, and the calibration of the image forming condition can be performed at low cost without providing the plurality of color sensor units 32. For example, even when the reading range of the color sensor unit 32 is narrower than the image forming area on the paper, the patch image in an arbitrary image forming area can be obtained by moving the color sensor unit 32 to the patch image forming position. Can be detected.

  Further, the image forming apparatus 1 can move the color sensor unit 32 to a patch image formed in one area on the paper, and there is no need to form a patch image over the entire paper.

  Further, the image forming apparatus 1 forms a patch image substantially parallel to the conveyance direction at any formation position in the main scanning direction of the image forming unit 20 and in a direction substantially orthogonal to the conveyance direction on the paper ( For example, FIG. 11), the color sensor unit 32 is moved to the formation position.

  For this reason, the image forming apparatus 1 can perform correction at any position in the main scanning direction of the image forming unit 20 with a patch image formed substantially parallel to the transport direction. For example, the image forming apparatus 1 can perform correction at any position in the main scanning direction by forming a plurality of patch images for each density for correcting gradation and the like in the transport direction.

  In addition, the image forming apparatus 1 forms a patch image in a direction orthogonal to the conveyance direction, that is, in the main scanning direction of the image forming unit 20 at any one of the formation positions in the sheet conveyance direction (for example, FIG. 12). The color sensor unit 32 is moved to the formation position.

  Therefore, the image forming apparatus 1 can correct the image forming condition in the section in the main scanning direction in which the patch image is formed only by detecting the patch image formed in the main scanning direction of the image forming unit 20. it can.

  Further, the image forming apparatus 1 reads a sheet conveyed by the conveyance unit 90 by the color sensor unit 32 to detect a patch image formed on the sheet, and is substantially orthogonal to the conveyance direction of the sheet by the conveyance unit 90. In this configuration, the color sensor unit 32 is moved in the direction.

  For this reason, the image forming apparatus 1 can detect the patch image by the color sensor unit 32 regardless of the area on the sheet where the patch image is formed.

  Further, the image forming apparatus 1 includes a sensor storage unit 35 as a retreat location of the color sensor unit 32 outside the paper conveyance path area by the conveyance unit 90, and a patch image by the color sensor unit 32 under the control of the engine control unit 42. In this configuration, the color sensor unit 32 is stored in the sensor storage unit 35 by the drive unit 31c.

  For this reason, the image forming apparatus 1 can retreat the color sensor unit 32 from the paper conveyance path to which paper dust or dust easily adheres, and can improve the accuracy of correction using the patch image.

  Further, the image forming apparatus 1 is configured to include a reference plate 358 for calibrating the color sensor unit 32 in the sensor storage unit 35. Therefore, the image forming apparatus 1 can calibrate the color sensor unit 32 using the reference plate 358 while the color sensor unit 32 is stored in the sensor storage unit 35. Further, since the image forming apparatus 1 has a configuration in which the reference plate 358 is provided inside the sensor storage unit 35 outside the paper conveyance path, where paper dust and dust are difficult to adhere to the color sensor unit 32, the color sensor unit 32. The accuracy for calibrating can be maintained for a long time.

  Note that the description in the above-described embodiment shows an example, and the present invention is not limited to this. The configuration and operation in the embodiment described above can be changed as appropriate.

  For example, the moving mechanism of the color sensor unit 32 in the image forming apparatus 1 is exemplified by a mechanism in which the supporting member of the color sensor unit 32 fitted to the ball screw is moved by a stepping motor and a ball screw. There is no particular limitation, and a configuration in which the slider is moved by a linear motor or the like may be used.

1 is a conceptual diagram illustrating an internal configuration of an image forming apparatus. It is a figure which shows a mode that the detection part was looked down on from the top. It is a figure which shows a mode that the detection part was looked down at from the side. It is a figure which shows a mode that the detection part was looked down on from the state which removed the top plate. It is a figure which shows a mode that the detection part was looked down on from the side in the state which removed the side plate. It is a conceptual diagram which shows the structure of a color sensor unit. It is a block diagram which shows the circuit structure of a color sensor unit. It is a graph which shows the relationship between the wavelength of the light detected with a color sensor unit, and its output voltage. 1 is a block diagram schematically showing a functional configuration of an image forming apparatus. It is a conceptual diagram which illustrates the patch image formed on a paper. It is a conceptual diagram which shows the positional relationship of the patch image formed on a paper, and a detection part. It is a conceptual diagram which shows the positional relationship of the patch image formed on a paper, and a detection part.

Explanation of symbols

1 Image forming apparatus 2Y, 2M, 2C, 2K Exposure unit 3Y, 3M, 3C, 3K Development unit 4Y, 4M, 4C, 4K Photosensitive drum 5Y, 5M, 5C, 5K Charging unit 6Y, 6M, 6C, 6K Cleaning unit 7Y, 7M, 7C, 7K Primary transfer roller 8 Intermediate transfer belt 9 Cleaning unit 10 Image reading unit 11 Automatic document feeder 12 Document image scanning unit 20 Image forming unit 21 Secondary transfer roller 22 Fixing unit 30 Detection unit 31a Sensor movement Shaft 31b Support section 31c Drive section 32 Color sensor unit 33 Home position sensor 34 Storage position sensor 35 Sensor storage section 40 Control section 41 Overall control section 42 Engine control section 43 Image processing section 44 Image memory 45 Correction operation execution section 50 Operation section 60 Display unit 70 Communication unit 80 Storage unit 90 Transport unit 321 LED
322 Light receiving element unit 322a Red light receiving element 322b Green light receiving element 322c Blue light receiving element 323 Resistance 324 Amplifying unit 351 Top plate 352, 353 Side plate 354 Top plate spring 355 Side plate opening / closing spring 356 Bottom plate 357 Side plate rotation shaft 358 Reference plate d Original CCD sensor E Openings G, G10 to G4n Patch images M1, M2, and M3 Contact portions T1 to T3 Paper feed tray P1 Home position P2 Storage position Y Paper

Claims (7)

Conveying means for conveying paper;
An image forming unit that forms a patch image for correction on a sheet conveyed by the conveying unit;
Detecting means for detecting a patch image formed on the paper;
Moving means for moving the detection means to a patch image forming position on the paper formed by the image forming means;
Control means for controlling an image forming condition in the image forming means based on a detection result detected by the detecting means and a patch image forming position on the paper;
An image forming apparatus. The image forming unit forms a patch image substantially parallel to the transport direction at any formation position in a direction substantially orthogonal to the transport direction on the paper,
The image forming apparatus according to claim 1, wherein the moving unit moves the detecting unit to a patch image forming position on the sheet formed substantially parallel to the transport direction by the image forming unit. The image forming unit forms a patch image in a direction substantially perpendicular to the transport direction at any one of the transport positions on the paper;
The image forming apparatus according to claim 1, wherein the moving unit moves the detecting unit to a patch image forming position on the paper formed in a direction substantially orthogonal to the transport direction by the image forming unit. The detection unit reads a sheet conveyed by the conveyance unit after the image formation, detects a patch image formed on the sheet,
The image forming apparatus according to claim 1, wherein the moving unit moves the detection unit in a direction substantially orthogonal to a sheet conveyance direction by the conveyance unit. Provided with a retreat place of the detection means outside the transport path area of the paper by the transport means,
The image forming apparatus according to claim 4, wherein the control unit moves the detection unit to the retreat location by the moving unit while the patch image is not detected.   The image forming apparatus according to claim 5, wherein a reading member serving as a reference of a reading condition of the detection unit is provided at the retreat location. The image forming unit forms a patch image related to correction of any color,
The detecting means detects a color condition of a patch image formed on the paper;
The image forming apparatus according to claim 1, wherein the control unit controls the image forming state of any one of the colors in the image forming unit based on a color state detected by the detecting unit. apparatus.

Images