JP2008040441A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the cost and space of a cleaning device, while employing an intermediate transfer system that has high accuracy in image superposition, to reduce down-time of an image forming apparatus resulting from process control for image formation, using a test pattern and to obtain stable image quality. <P>SOLUTION: While a second transfer device 108 is kept in contact with a first transfer device 105, the test patters 201 and 202 are not transferred to the second transfer device. The axial width of the second transfer device is greater than the length width of the second transfer device; the maximum width of a transfer material 115 is equal to or shorter than the length width of the second transfer device; and the test patterns are formed in a region of difference between the axial width of the first transfer device 105 and the length width of the second transfer device. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, a printer, and a multifunction machine.

  A widely known method is to create a test pattern outside the print area on the photoconductor or transfer belt, and to control the image process conditions related to image density, image position, etc. by inferring density and position information from the reflectance data. Yes. In the control of the image process conditions, the created test pattern is not discharged as a printed image after the completion of reading the test pattern, and therefore is discarded by a belt cleaner or the like or reused by a recycling apparatus or the like. Such image process condition control includes creating a test pattern during a preparation period from when the power is turned on until printing is possible, and creating a test pattern in a non-image area during printing.

  Incidentally, in recent years, the toner has been made smaller in size to improve the granularity, and the particle size has become spherical and uniform by a production method such as a polymerization method toner. It is generally known that it is difficult to clean these small particle warp toner and spherical toner. The toner that is not properly cleaned remains on the image carrier and is generated as an abnormal image on the transfer material.

  In order to prevent such a cleaning failure from occurring and improve the cleaning performance per time, it is necessary to increase the contact pressure in the case of a blade cleaning device, but in that case, the load on the belt and the cleaning blade increases. The blade wear due to this is promoted, resulting in misalignment and jitter.

  In the case of bias roller cleaning, it is necessary to provide a plurality of rollers, both of which have an effect on cost reduction and space saving. A method of improving the cleaning property by rotating the transfer belt a plurality of times is also used. However, this method increases the downtime of the apparatus.

  A color image forming apparatus that forms a color image by superimposing a plurality of images transfers a plurality of photosensitive member images to a transfer material on a conveying belt and a plurality of photosensitive member images once on a transfer belt. There is an intermediate transfer method in which the image is superimposed on the transfer material and then transferred to the transfer material, but since the intermediate transfer method once forms a color image on the transfer belt, the image overlay accuracy is high, and the thickness of the transfer material and the tolerance for the material are high. There are advantages such as high.

  In the intermediate transfer system, as means for performing a transfer process, (1) a primary transfer device (a primary transfer belt as an example) for superimposing images and (2) a secondary transfer device for transferring an image to a transfer material such as paper There is an intermediate transfer system using two transfer devices (second transfer roller as an example). In the intermediate transfer method using these two transfer devices, a device that enables the primary transfer belt and the secondary transfer roller to contact and separate from each other is required so that the test pattern is not transferred to the secondary transfer roller. Before reaching the transfer roller, it is necessary to separate the primary transfer belt and the secondary transfer roller.

  Therefore, since a contact / separation mechanism is required, there are problems such as high cost, large equipment, and increased layout restrictions. In particular, when it is necessary to create a test pattern during a printing operation, performing the contact / separation during the printing operation is used to change the load on an image carrier such as a transfer belt or a photoconductor or to form a latent image. Since image shift or jitter occurs due to a shock to the exposure apparatus or the like, there is a restriction that the above contact / separation operation cannot be performed from the start of exposure for printing to the end of primary transfer, and throughput is reduced.

  On the other hand, when the mechanism that does not contact and separate the secondary transfer roller is used, the test pattern is inevitably transferred to the secondary transfer roller, thereby requiring a cleaning device for the secondary transfer roller. Furthermore, since the test pattern needs to be read before being transferred to the secondary transfer roller, the layout of the reading device is limited.

In addition, as a known technique, in an image forming apparatus provided with a detection unit that detects the toner adhesion amount of a toner image for adhesion amount detection from each transferred photoreceptor, and a toner adhesion amount control unit that controls image formation conditions, Transfer where X <Z−Y, where X is the length in the axial direction of the transfer paper, Y is the length in the axial direction of the toner image for detecting the toner adhesion amount, and Z is the length in the axial direction of the printable area. 2. Description of the Related Art There is an image forming apparatus that includes a toner image creating unit that creates a toner image for toner adhesion amount detection outside a printing area when printing is performed in a paper size (see, for example, Patent Document 1).
For example, in the case of A4 longitudinal paper, since a margin is formed in the axial direction on the intermediate transfer belt, a test pattern is formed at that portion. However, a test pattern cannot be formed because there is no margin in a mode that uses the image area in the entire axial direction, such as A4 landscape paper.

JP 2006-17868 A

  The present invention realizes cost reduction and space saving of a cleaning device while adopting an intermediate transfer method with high image overlay accuracy, and downtime of the device by process control for image formation using a test pattern. And to obtain a stable image quality.

In order to achieve the above object, according to a first aspect of the present invention, there is provided a first image carrier comprising a plurality of photosensitive members, a charging device for charging the first image carrier, and the first image carrier. An exposure device for forming a latent image, a developing device for developing the latent image formed on the first image carrier, and an image formed on the first image carrier are superimposed on the image carrier. In an image forming apparatus having a first transfer device that obtains a color image and a second transfer device that transfers an image formed on the first transfer device to a transfer material, a test pattern is transferred to the first transfer device. A test pattern generation device that can be formed in the device, a test pattern detection device that can detect the state of the test pattern, and an image process control means that determines an image process condition based on a detection result of the test pattern, The second transfer device Serial first said test pattern with constant contact to the transfer device has a structure that is not transferred to the second transfer device.
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the image carrier in the first transfer device is in a belt shape, and the second transfer device is in a belt shape or a roller shape. It was supposed to be.
According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, an axial width (hereinafter referred to as an image carrier width) of a belt-like member as the image carrier in the first transfer device is the above. It is larger than the axial width (hereinafter referred to as second transfer device width) of the belt-like or roller-like one as the second transfer device, and the maximum width of the transfer material is smaller than the second transfer device width. And the test pattern is formed in a region of a dimensional difference between the width of the image carrier and the width of the second transfer device.
According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, the test pattern forming regions are formed at both ends of an axial width of a belt-like member as the image carrier in the first transfer device. It was decided to be done.
According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect, the test pattern comprises a pattern for detecting the amount of toner adhesion and a pattern for detecting the image position.
According to a sixth aspect of the present invention, in the image forming apparatus according to the first aspect, there is provided a test pattern detecting device capable of creating the test patterns at a plurality of locations of the first transfer device and detecting these test patterns. It was decided that it was installed in several places.
According to a seventh aspect of the present invention, in the image processing apparatus according to the sixth aspect, the image process condition is determined according to the detection results of the plurality of test patterns.

  According to the present invention, while adopting an intermediate transfer method with high image overlay accuracy, it is possible to reduce the cost and space of the cleaning device, and to reduce the downtime of the device by process control for image formation using a test pattern. And stable image quality can be obtained.

  First, the configuration of the printer of this embodiment will be described. FIG. 1 is a schematic configuration diagram showing an image forming process part (process engine part) that performs exposure, charging, development, transfer, and fixing in the printer of this embodiment.

  In addition to the components shown in FIG. 1, the printer includes a print controller (indicated by reference numeral 410 in FIG. 4 to be described later) that processes image data sent from a PC (personal computer) or the like and converts it into exposure data, and a high pressure. A high pressure generator (denoted by reference numeral 416 in FIG. 4 described later), a main body control unit (denoted by reference numeral 406 in FIG. 4 described later) for controlling the image forming operation, and a transfer material serving as a recording material. A paper supply device (not shown) for supplying the paper 115, a manual feed tray (not shown) for manually feeding the transfer paper 115, and a paper output tray (not shown) for discharging the image-formed transfer paper 115 are provided. Yes.

  In FIG. 1, the main body is provided with an endless belt-like intermediate transfer belt 105 as an intermediate transfer member and a charging device (primary transfer device 106) as a first transfer device. The intermediate transfer belt 105 has a three-layer structure including a base layer, an elastic layer, and a coat layer. The base layer is configured, for example, by combining a fluorine resin having a small elongation or a rubber material having a large elongation with a material that is difficult to stretch, such as a canvas.

  The elastic layer is made of, for example, fluorine rubber or acrylonitrile-butadiene copolymer rubber, and is formed on the base layer. The coat layer is formed by coating the surface of the elastic layer with, for example, a fluorine resin. The intermediate transfer belt 105 is rotationally driven by a support roller 112 having a function as a drive roller while being stretched around four support rollers 112, 113, 114, and 119.

There are four image forming units for each color of yellow (Y), cyan (C), magenta (M), and black (K) in the stretched portion of the intermediate transfer belt. The four image forming units for each color have the same configuration and are composed of the same constituent members. In FIG. 1, the same constituent members represent numerical parts with the same numerals, and end with color identification codes Y (yellow), C (cyan), M ( Magenta) and K (black). In each image forming unit, photoreceptor units 103Y, 103C, 103M, and 103K and developing units 102Y, 102C, 102M, and 102K are arranged side by side.
The developing units 102Y, 102C, 102M, and 102K are supplied with toner from the toner bottles 104K, 104Y, 104C, and 104M.

  Below these image forming units, an exposure apparatus 200 is provided. Based on the image information, a semiconductor laser is driven from a laser exposure unit (not shown) provided in the exposure apparatus 200 to write light. Lb is emitted to form an electrostatic latent image on the photosensitive drums 101Y, 101C, 101M, and 101K as the first image carriers provided in the respective photosensitive units. Here, the emission of the writing light is not limited to the laser, but may be, for example, an LED (light emitting diode).

  The configuration of the image forming unit will be described. Hereinafter, an image forming unit that forms a black toner image will be described as an example with reference to FIG. 2, but image forming units that form toner images of other colors also have the same configuration.

[Image forming unit]
In FIG. 2, constituent members of the image forming unit for black toner are originally provided with a symbol K at the end of the symbol, but are omitted here. In this image forming unit, a charging device 301 for charging the photosensitive drum, a developing device 102, and a photosensitive member cleaning device 308 are provided around the photosensitive drum 101. Further, a primary transfer device 106 as a charging device is provided at a position facing the photosensitive drum 101 via the intermediate transfer belt 105.

  The charging device 301 is of a contact charging type employing a charging roller, and uniformly charges the surface of the photosensitive drum 101 by applying a voltage in contact with the photosensitive drum 101. As the charging device 301, a non-contact charging type using a non-contact scorotron charger or the like can be used.

  The developing device 102 uses a two-component developer composed of a magnetic carrier and a nonmagnetic toner. As the developer, a one-component developer may be used. The developing device 102 can be roughly divided into an agitating unit 303 and a developing unit 304 provided in the developing case. In the agitation unit 303, a two-component developer (hereinafter simply referred to as “developer”) is conveyed while being agitated and supplied onto a developing sleeve 305 as a developer carrier.

  The stirring unit 303 is provided with two parallel screws. A partition plate is provided between the two screws 306 to partition the two screws 306 so as to communicate with each other. Further, a toner density sensor 104 for detecting the toner density of the developer in the developing device 102 is attached to the developing case. On the other hand, in the developing unit 304, the toner in the developer attached to the developing sleeve 305 is transferred to the photosensitive drum 101.

  The developing unit 304 is provided with a developing sleeve 305 that faces the photosensitive drum 101 through the opening of the developing case, and a magnet (not shown) is fixedly disposed in the developing sleeve 305. A doctor blade 307 is provided so that the tip approaches the developing sleeve 305. In the present embodiment, the distance at the closest portion between the doctor blade 307 and the developing sleeve 305 is set to 0.9 mm.

  In the developing device 102, the developer is conveyed and circulated while being stirred by two screws 306, and is supplied to the developing sleeve 305. The developer supplied to the developing sleeve 305 is drawn up and held by a magnet. The developer pumped up by the developing sleeve 305 is conveyed as the developing sleeve 305 rotates, and is regulated to an appropriate amount by the doctor blade 307.

  The regulated developer is returned to the stirring unit 303. The developer transported to the developing area facing the photosensitive drum 101 in this manner is brought into a spiked state by a magnet and forms a magnetic brush. In the developing region, a developing electric field that moves the toner in the developer to the electrostatic latent image portion on the photosensitive drum 101 is formed by the developing bias applied to the developing sleeve 305.

  As a result, the toner in the developer is transferred to the electrostatic latent image portion on the photosensitive drum 101, and the electrostatic latent image on the photosensitive drum 101 is visualized to form a toner image. The developer that has passed through the developing region is transported to a portion where the magnetic force of the magnet is weak, thereby leaving the developing sleeve 305 and being returned to the stirring unit 303.

  When the toner concentration in the agitation unit 303 becomes light by repeating such operations, the toner concentration sensor 104 detects this, and toner is replenished to the agitation unit 303 based on the detection result.

  A primary transfer roller is employed as the primary transfer device 106 and is installed so as to be pressed against the photosensitive drum 101 with the intermediate transfer belt 105 interposed therebetween. Further, both ends of the primary transfer roller are in contact with each other in the axial range 203 corresponding to the maximum width of the transfer material in the axial width of the intermediate transfer belt 105 in FIG.

  The primary transfer device 106 may not be a roller shape, but may be a conductive brush shape, a non-contact corona charger, or the like. Further, in the axial range 203, the transfer paper 115 of the transfer paper 115 having the longest length in the direction perpendicular to the rotation direction of the intermediate transfer belt (transfer paper in a form in which the maximum used paper is laterally fed) is primarily transferred. It is set so as to be sandwiched between the apparatus 106 and the intermediate transfer belt 105.

  The photoconductor cleaning device 308 includes a cleaning blade 309 made of, for example, polyurethane rubber, which is disposed so that the front end is pressed against the photoconductor drum 101. In this embodiment, in order to improve the cleaning performance, a conductive fur brush 310 that contacts the photosensitive drum 101 is also used.

  A bias is applied to the fur brush 310 from a metal electric field roller (not shown), and the tip of a scraper (not shown) is pressed against the electric field roller. The toner removed from the photosensitive drum 101 by the cleaning blade 309 and the fur brush 310 is accommodated in the photosensitive member cleaning device 308 and collected by a waste toner collecting device (not shown).

  A specific setting of the image forming unit will be described. The diameter of the photosensitive drum 101 is 40 mm, and the photosensitive drum 101 is driven at a linear speed of 200 mm / s. The developing sleeve 305 has a diameter of 25 mm, and the developing sleeve 305 is driven at a linear speed of 564 mm / s.

  The charge amount of the toner in the developer supplied to the development area is preferably in the range of about −10 to −30 μC / g. The development gap, which is the gap between the photosensitive drum 101 and the development sleeve 305, can be set in the range of 0.5 to 0.3 mm, and the development efficiency can be improved by reducing the value.

  The thickness of the photosensitive layer of the photosensitive drum 101 is 30 μm, the beam spot diameter of the optical system of the exposure apparatus 200 is 50 × 60 μm, and the amount of light is about 0.47 mW. As an example, the surface of the photosensitive drum 101 is uniformly charged to −700 V by the charging device 301, and the potential of the electrostatic latent image portion irradiated with the laser by the exposure device 200 is −120 V. On the other hand, the developing bias voltage is set to -470V, and a developing potential of 350V is secured. Such process conditions are changed as appropriate according to the result of the potential control.

  In the image forming unit of FIG. 2 having the above configuration, first, the surface of the photosensitive drum 101 is uniformly charged by the charging device 301 as the photosensitive drum 101 rotates. Next, based on the image information from the print controller, laser beam writing light Lb is emitted from the exposure device 200 to form an electrostatic latent image on the photosensitive drum 101. Thereafter, the electrostatic latent image is visualized by the developing device 102 to form a toner image.

  The toner image is primarily transferred onto the intermediate transfer belt 105 by the primary transfer device 106. The transfer residual toner remaining on the surface of the photosensitive drum 101 after the primary transfer is removed by the photosensitive member cleaning device 308 and used for the next image formation.

  1 and 3, a secondary transfer roller 108 is provided as a second transfer device at a position facing the support roller 112 with the intermediate transfer belt 105 interposed therebetween. The secondary transfer roller 108 transfers the toner image formed on the intermediate transfer belt 105 onto the transfer paper with an electrostatic force. When the toner image on the transfer belt 105 is secondarily transferred onto the transfer paper 115, the secondary transfer roller 108 is pressed against the portion of the intermediate transfer belt 105 wound around the support roller 112 to perform secondary transfer.

The secondary transfer device may not be configured using the secondary transfer roller 108 but may be configured using, for example, a transfer belt or a non-contact transfer charger.
The axial width of the intermediate transfer belt 105 is larger than the longitudinal width (axial width) of the secondary transfer roller 108, and the maximum width of the transfer paper 115 (during lateral feed) is the longitudinal width (axial width) of the secondary transfer roller 108. ) Is the following size,
The test pattern formation region is set in a region having a dimensional difference between the axial width of the intermediate transfer belt 105 and the longitudinal width (axial width) of the secondary transfer roller 108, and the test pattern is formed in the test pattern formation region. Is formed.
Here, an example in which a roller-like secondary transfer roller 108 is used as the secondary transfer device has been described. However, when a transfer belt or a non-contact transfer charger is used instead of the secondary transfer roller 108, the same applies to the above. Similarly, a test pattern can be formed.
In the example shown in FIG. 3, the axial range 203 corresponding to the longitudinal width of the secondary transfer roller 108 is located at the center of the axial width of the intermediate transfer belt 105, and the test pattern formation region is the intermediate transfer belt 105. It is formed in a strip shape at both ends of the axial width of the.

  Since the secondary transfer roller 108 is arranged at a position shifted from the test pattern formation region by the above-described configuration, it is not in contact with the test pattern, and a transfer sheet is interposed between the secondary transfer roller 108 and the intermediate transfer belt 105 at the time of transfer. Therefore, the toner image on the intermediate transfer belt 105 is not in contact with the toner image and does not adhere to the toner, so that it is not necessary to attach a cleaning unit that is in sliding contact with the peripheral surface of the secondary transfer roller 108.

  In FIG. 1, a fixing device 111 for fixing the toner image transferred onto the transfer paper 115 is provided on the downstream side of the secondary transfer roller 108 in the conveyance direction of the transfer paper 115. The fixing device 111 has a configuration in which a pressure roller 118 is pressed against a heating roller 117.

  1 and 3, photosensors 109F (front side) and 109R (rear side) for estimating the density and relative position of the test pattern are located at positions facing the support roller 112 with the intermediate transfer belt 105 in between. Thereafter, P / TM sensors 109) are provided at two locations on the front side and the back side of the support roller 112 in the axial direction. A belt cleaning device 110 is provided at a position facing the support roller 113 with the intermediate transfer belt 105 interposed therebetween. The belt cleaning device 110 is for removing residual toner remaining on the intermediate transfer belt 105 after the toner image on the intermediate transfer belt 105 is transferred to the transfer paper 115.

  In the schematic diagram of the P / TM sensor 109 shown in FIG. 4, the P / TM sensor 109 has one light emitting element and two light receiving elements. This light emitting element is an infrared LED 602. The two light receiving elements are a specular reflection light receiving element 603 and a diffuse reflection light receiving element 604 provided at two positions, a position where the light reflected by the mirror on the intermediate transfer belt 105 can be received and a position where the specular reflection light is not received, respectively. It is. As the light emitting element, a laser light emitting element or the like may be used instead of the infrared LED.

  Phototransistors are used as the regular reflection light receiving element 603 and the diffuse reflection light receiving element 604, but photodiodes may be amplified and used. A condensing lens 605 is provided in the middle of the optical path. In this configuration, the regular reflection light receiving element 604 and the diffuse reflection light receiving element 604 are provided as the light receiving elements, but either one may be used depending on the detection target and necessary information.

FIG. 5 is a block diagram showing an electrical connection of each unit provided in the printer of this embodiment.
As shown in FIG. 5, the printer according to the present embodiment includes a main body control unit 406 having a computer configuration, and the main body control unit 406 controls driving of each unit. A main body control unit 406 includes a ROM (Read Only Memory) 405 that stores in advance fixed data such as a computer program via a bus line 409 in a CPU (Central Processing Unit) 402 that executes various calculations and drive control of each unit. A RAM (Random Access Memory) 403 that functions as a work area for storing various data in a rewritable manner is connected.

  The ROM 405 stores the test pattern formation position and density information necessary for generating the test pattern, the bias conditions for forming the test pattern gradation, and the TM / P sensor 109 for estimating the test pattern adhesion amount. An output adhesion amount conversion LUT (Look up table) is stored (see FIG. 10).

  A print controller 410 is connected to the main body control unit 406, and the print controller 410 transmits image information from a PC (personal computer), a FAX (facsimile), a scanner, or the like as unified image data to the main body control unit 406. . An A / D conversion circuit 401 that converts various sensor information into digital data, a drive circuit that drives a motor and a clutch, and a high-voltage generator that generates a voltage necessary for image formation are also connected.

  Next, the operation of the printer of this embodiment will be described with reference to FIGS. When printing with information from a PC using a printer having the above configuration, first, image information is transmitted using a printer driver on the PC. The print controller 410 receives print information from the printer driver and sends an exposure signal to the exposure apparatus 200.

  Upon receiving the print command, the main body control unit 406 drives a drive motor (not shown) so that the support roller 112 is rotated and the intermediate transfer belt 105 is rotated. At the same time, the photosensitive drums 101Y, 101C, 101M, and 101K of each image forming unit are also rotated.

  Thereafter, based on information from the print controller, the exposure apparatus 200 irradiates the writing light Lb onto the photosensitive drums 101Y, 101C, 101M, and 101K of the respective image forming units. As a result, electrostatic latent images are formed on the respective photosensitive drums 101Y, 101C, 101M, and 101K, and are visualized by the developing devices 102Y, 102C, 102M, and 102K. Then, yellow, cyan, magenta, and black toner images are formed on the photosensitive drums 101Y, 101C, 101M, and 101K, respectively.

  The respective color toner images formed in this way are primarily transferred by the primary transfer devices 106Y, 106C, 106M, and 106K so as to sequentially overlap the intermediate transfer belt 105. As a result, a composite toner image in which the toner images of the respective colors overlap is formed on the intermediate transfer belt 105. The transfer residual toner remaining on the intermediate transfer belt 105 after the secondary transfer is removed by the belt cleaning device 110.

  In response to the image information, a paper feed roller of a paper feed device (not shown) corresponding to the transfer paper 105 selected by the user rotates, and the transfer paper 105 is sent out from one of the paper feed cassettes (not shown). The fed transfer paper 105 is separated into one sheet by a separation roller (not shown), enters a paper feed path (not shown), and is conveyed to a conveyance path in the printer main body by a conveyance roller (not shown). The transfer paper 105 conveyed in this way is stopped when it hits the registration roller 107.

  When the transfer paper 105 not set in the paper feed cassette (not shown) is used, the transfer paper 105 set on the manual feed tray (not shown) is fed by a paper feed roller (not shown) and separated into one sheet by a separation roller (not shown). Thereafter, the sheet is conveyed through a manual sheet feeding path (not shown). Then, it stops when it hits the registration roller 107.

  The registration roller 107 starts to rotate in accordance with the timing at which the composite toner image formed on the intermediate transfer belt 105 as described above is conveyed to the secondary transfer unit facing the secondary transfer roller 108. Here, in general, the registration roller 107 is often used while being grounded, but a bias may be applied to remove the paper dust of the transfer paper 105.

  The transfer paper 105 sent out by the registration roller 107 is sent between the intermediate transfer belt 105 and the secondary transfer roller 108, and the composite toner image on the intermediate transfer belt 105 is transferred onto the transfer paper 105 by the secondary transfer roller 108. Secondary transfer is performed.

  Thereafter, the transfer paper 105 is conveyed to the fixing device 111 while being attracted to the secondary transfer roller 108, and heat and pressure are applied by the fixing device 111 to perform a toner image fixing process. The transfer sheet 105 that has passed through the fixing device 111 is discharged and stacked on a discharge tray (not shown) by a discharge roller (not shown).

  When image formation is also performed on the back surface of the surface on which the toner image is fixed, the transfer direction of the transfer paper 105 that has passed through the fixing device 111 is switched by a switching claw (not shown) and sent to a paper reversing device (not shown). The transfer paper 105 is reversed there and guided to the secondary transfer roller 108 again.

  Next, image process control performed by the CPU 402 according to the present embodiment based on a computer program will be described with reference to FIG. FIG. 6 is a schematic diagram showing a flowchart showing a flow of execution in the image process control.

  The image process control determines whether it is necessary when the power switch of the main body is turned on or when printing is started, and is executed if necessary (steps S501, S502, S503). Immediately after the power is turned on, the heating time of the fixing heater and the preparation time of the print controller are necessary, and the image processing control should be performed because it may be left until then or the usage environment may change. There is.

  Further, during the printing operation, there is a possibility that toner supply and consumption, and changes in the characteristics of the photosensitive member of the photosensitive drum 101 and the intermediate transfer belt 105 may occur, and image process control may be performed. Immediately after the power is turned on, image process control is executed when the photoreceptor stop time is 6 hours or more, the temperature in the machine has changed by 10 ° C or more, or the relative humidity in the machine has changed by 50% or more. To do.

  Among the above, the stop time of the photosensitive member is obtained as follows. When the photosensitive member stops, time information is acquired from the real-time clock held by the print controller 410 shown in FIG. Similarly, at the time of power-on, time information is acquired from the real-time clock, and the photoreceptor stop time is obtained from the difference. The temperature and humidity changes are obtained by acquiring temperature information and relative humidity information from the in-machine temperature / humidity sensor 414 when the photosensitive member is stopped, and acquiring temperature information and relative humidity information from the temperature / humidity sensor 414 in the same manner at power-on. The temperature change amount and the relative humidity change amount are obtained from the difference.

  During printing, a test pattern is created when the number of printed sheets reaches a predetermined interval. The interval in this case is determined by the amount of process variation obtained in advance through experiments or the like. In addition to the number of prints, the travel distance of the developing sleeve 305 and the intermediate transfer belt 105 may be set as a threshold value.

  Next, when it is determined that image process control is necessary, a test pattern is formed (step S504 in FIG. 6). FIG. 7 shows a state where the test pattern is formed on the transfer belt. Reference numeral 201 in FIG. 7 indicates a test pattern (P pattern) for detecting the toner adhesion amount. Reference numeral 202 in FIG. 7 denotes a test pattern (TM pattern) for detecting the image position. The P pattern and the TM pattern are formed on the near side and the far side in the axial direction, and the near side P pattern is denoted by 201F, the far side P pattern is denoted by 201R, the near side TM pattern is denoted by 202F, and the far side TM pattern is denoted by 202R. The P patterns denoted by reference numerals 201R and 201F form one group of four patterns with different shades, and are composed of cyan, magenta, yellow, and black groups.

  Image process control includes potential potential control, toner density target value correction control, and alignment correction control, and the test pattern formation conditions differ depending on which control is performed. First, conditions for forming a test pattern for controlling potential potential will be described.

  The test pattern 201 is used for potential potential control. Of the test patterns 201, only 201F is formed, but if necessary, only 201R may be formed, and both 201F and 201R may be formed. 201F and 201R are formed to have a size of 10 mm in the axial direction (main scanning) and 15 mm in the traveling direction of the intermediate transfer belt 105 (sub scanning).

  The size in the main scanning direction includes the irradiation range (spot diameter) of the P / TM sensor 109 on the intermediate transfer belt 105, the conditions under which the test pattern is stably formed in the process (a region where no edge effect or the like occurs), and the main size. It is determined from the maximum scanning position deviation amount.

  The size in the sub-scanning direction needs to be the same as that in the main scanning. However, when the sampling frequency or gradation pattern of the A / D conversion circuit is formed with the developing bias variable, the rise time of the high-voltage generator 416 is increased. Etc. need to be considered. The exposure value is the same as that for printing, and is 0.47 mW in this embodiment.

  The development bias is switched to about 50 msec immediately before the test pattern exposure unit comes on the photosensitive member 101 and the developing sleeve 305. This switching timing is set in consideration of the response of the high voltage generation circuit. Five types of test patterns are formed, and the value of the developing bias is switched from the first to −100V, −150V, −200V, −250V, and −300V.

  The charging bias is set so as to always maintain a potential of 200 V with respect to the developing bias. In this case, the charging bias is set to -300 V, -350 V, -400 V, -450 V, and -500 V. In this case, the test pattern for controlling the potential potential is formed by changing the developing bias and cannot be executed simultaneously with the printing operation. Therefore, the test pattern is formed at the timing of the non-image forming area 710 during printing shown in FIG. However, when the exposure energy is made variable in order to obtain a gradation (development γ) by the development potential of the test pattern, the test pattern may be formed simultaneously with printing. Toner density target value correction control is also performed using the same test pattern as this potential potential control.

  Next, test pattern formation conditions for alignment correction control will be described. In the alignment correction control, the front side TM pattern 202F and the back side TM pattern 202R are used. The near-side TM pattern 202F and the back-side TM pattern 202R are formed by inclining 45 ° of the same size as 10 mm in the main scanning direction and 1 mm in the sub-scanning direction.

  The size in the sub-scanning direction is determined by the irradiation range (spot diameter) of the P / TM sensor 109 on the intermediate transfer belt 105. Each color is formed in the order of K, M, C, and Y. The exposure value is the same as that for printing (0.47 mW in this embodiment), but a dedicated exposure pattern may be used. The development bias and the charging bias are the same as those for printing. However, if the toner adhesion amount of the test pattern portion is a condition that the surface of the intermediate transfer belt 105 is covered, if it is not simultaneous with printing, it can be set individually. Good. Details of the positional deviation correction control will be described later.

  Next, a test pattern detection method and calculation method for potential potential control will be described. Before the first formed test pattern passes the P / TM sensor 109, the light emission amount adjustment (Vsg adjustment) of the light emitting element 603 is performed for the P / TM sensor 109F (front side) and the P / TM sensor 109R (back side). I do. The Vsg adjustment only needs to be completed before the test pattern passes through the P / TM sensor 109.

  The Vsg adjustment will be described. When Vsg adjustment starts, turn on the LED. As the current PWM value at this time, the previous adjustment value (IF) stored in the RAM 403 is used. Next, the output data of the regular reflection output element 603 is read. The sampling time interval at this time is 2 msec, and 10 points are sampled to obtain the average value so as not to be affected by the uneven reflection of the intermediate transfer belt 105. This average value is referred to as Vsg_REG.

  If Vsg_REG is within 4.0V ± 0.5V, IF is not updated and the previous value is maintained. If Vsg_REG is not within 4.0V ± 0.5V, adjustment operation is performed. An IF that makes Vsg_REG closest to 4.0 V is detected using a two-part search method as the adjustment operation.

  If the IF is found, the IF data on the RAM 403 is updated. If the IF is not found, an adjustment abnormality is detected, the abnormality is notified to the print controller 410, and the abnormality is displayed on the printer driver or the operation unit of the main body. Further, when Vsg_REG is detected using the final IF, the output voltage of the diffuse reflection light receiving element 604 is also detected at the same time. This value is called Vsg_DIF.

  Next, Vsg_REG and Vsg_DIF are stored in the RAM 403. When the infrared LED 602 for the P / TM sensor is continuously turned on, the test pattern reaches the light irradiation portion position of the intermediate transfer belt 105 of the P / TM sensor 109. The output is sampled every 2 msec at the timing when the test pattern reaches the P / TM sensor 109 and converted into digital data by the A / D conversion circuit 401.

  The digitally converted data is returned to analog output data by a conversion formula preset in the ROM 405. In the CPU 402, since the size of the sub-scan of the test pattern is 15 mm and the linear velocity is 200 mm / sec, the sampling is (15/200 × 1000) / 2≈38 data.

  In order to remove noise, 10 pieces of sampled data are removed from a large value and 10 pieces from a small value, an average value of the remaining data is obtained, and the first test pattern regular reflection output data (Vsp [1 ] _REG). Similarly, the output data of the diffusion light receiving element is also obtained as Vsp [1] _DIF. The same applies to the second and subsequent test patterns (Vsp [2-5] _REG, Vsp [2-5] _DIF).

  Next, a method for converting (Vsp [n]) data into toner adhesion amount data will be described. FIG. 9A shows the relationship between the color toner adhesion amount and the output voltage of the regular reflection light receiving element 603. FIG. 9B shows the relationship between the color toner adhesion amount and the output voltage of the diffuse reflection light receiving element 604. FIG. 9C shows the relationship between the black toner adhesion amount and the output voltage of the regular reflection light receiving element 603. Since the black toner does not have a diffuse reflection component, the diffuse reflection light receiving element 604 is not used for detecting the black toner.

In the present embodiment, a case where only the regular reflection light receiving element 603 is used for conversion of the color toner adhesion amount will be described. The following sensitivity correction coefficient (K2) of the regular reflection light receiving element 603 is obtained from the relationship of the data Vsp [1-5] _REG and Vsp [1-5] _DIF obtained first. K2 is obtained from the following equation (1).
K2 = MIN (Vsp [n] _REG / Vsp [n] _DIF) Expression (1)

Next, an expression (2) for obtaining a value (K [n]) obtained by removing the toner diffuse reflection component from the output voltage of the regular reflection light receiving element 603. This value represents a regular reflection light component from the intermediate transfer belt 105 in the test pattern portion.
K [n] = (Vsp [n] _REG−Vsp [n] _DIF × K2) / (Vsg [n] _REG−Vsg [n] _DIF × K2) (2)

Next, the diffuse reflection component from the intermediate transfer belt 105 is removed from the output voltage of the diffuse reflection light receiving element 604, and only the diffuse reflection component from the color toner is separated. This separation method is obtained by the following equation (3).
Vsp [n] _DIF_dush = Vsp [n] _DIF−Vsg [n] _DIF × K [n] — Expression (3)

Next, gain adjustment is performed to correct variations in the toner output of the diffuse reflection light receiving element 604. This gain adjustment is performed by obtaining a gain adjustment coefficient K5. Equation (4) shows how to obtain K5.
K5 = 1.63 / (α × 0.15 ^ 2 + β × 0.15 × γ) (4)
In equation (4), α, β, and γ are square terms obtained by quadratic approximation when the test axis is K [n] on the X axis and Vsp [n] _DIF_dush of each test pattern is on the Y axis. Coefficient, coefficient of the first power term, and y-intercept. The approximate straight line is obtained by the method of least squares. In addition, the constant in the equation (4) is a value obtained in advance by experiments or the like.

Next, normalization calculation is performed. An equation for obtaining the normalized value (R [n]) is shown in Equation (5).
R [n] [YCMK] = K5 × Vsp [n] _DIF_dush (5)
At this point, the sensor attachment and individual variation of the detection system and the reflection characteristic change of the intermediate transfer belt 105 are substantially canceled and determined uniquely. Next, the toner adhesion amount is calculated from the LUT, R [n], and [YCMK] shown in FIG. Find MA [n].

Next, how to determine the black toner adhesion amount will be described. In the case of black toner, it is determined only by the regular reflection light reflectance from the intermediate transfer belt 105 and the light absorption characteristics of the toner, so the relationship of the following equation (6) may be obtained.
R [n] [Bk] = Vsp_REG / Vsg_REG Formula (6)
When R [n] [Bk] is obtained, the LUT and R [n] shown in FIG. 10 are shown in a table showing the relationship between R [n] [Bk] obtained in advance through experiments or the like and the toner adhesion amount in the same manner as for color toners. , [Bk], the toner adhesion amount MA [n] [Bk] is obtained for black Bk.

  When the adhesion amount MA [n] is obtained, the relationship between the developing bias Vb [n] of the test pattern and the adhesion amount MA [n] is linearly approximated. The linear approximation is obtained by the least square method. Next, the optimum developing bias Vb is obtained from the target value (MA_REF) of the adhesion amount obtained in advance and the approximate linear equation, and stored in the RAM. The charging bias Vc is determined by the relationship of Vc = Vb + 200 (V) and is similarly stored in the RAM.

  The determined Vc and Vb are used in the next printing operation. The toner density target value correction control is performed using the slope data of an approximate linear equation. Since the inclination of the approximate linear equation is an alternative characteristic of development γ (the inclination when the Y-axis is the toner adhesion amount on the photoconductor and the X-axis is the development potential), toner supply control is performed with respect to the approximate linear inclination target value. Control the target value.

Hereinafter, with respect to the positional deviation correction control, an embodiment will be described with reference to Japanese Patent Laid-Open No. 2002-207338.
FIG. 11 shows the contents of “color matching” (CPA). When proceeding to this “color matching” (CPA), the CPU 402 first performs “test pattern formation and measurement” (PFM) on the intermediate transfer belt 105 on the rear r side (axial direction) as shown in FIG. A test pattern of start marks Msr, Msf and 8 sets (front 1st set to front 8th set) is formed on each of the rear side) and the front f side (front side in the axial direction), and the P / TM sensor 109F, A mark is detected at 109R (steps S505 and S506 in FIG. 6), and the mark detection signals Sdr and Sdf are converted into digital data, that is, mark detection data Ddr and Ddf by the A / D conversion circuit 401 and read.
In the flowchart of FIG. 6, the process condition is determined (step S508) through the calculation process in step S507. Details of the calculation process in step S507 are as described below.

  The position (distribution) of the center point of each mark on the intermediate transfer belt 105 is calculated. Further, an average pattern of the rear side 8 sets (an average value group of mark positions) and a similar average pattern of the front side 8 sets are calculated. The contents of this “test pattern formation and measurement” (PFM) will be described later.

  When the average pattern is calculated, the image forming deviation amount by each of the Bk, Y, C, and M image forming units is calculated based on the average pattern (DAC), and adjustment for eliminating the deviation based on the calculated deviation amount is performed. (DAD).

  FIG. 13 shows a flowchart of “test pattern formation and measurement” (PFM). When proceeding to this, as shown in FIG. 12, the CPU 402 simultaneously, for example, the width of the mark in the Y direction on each of the rear r side and front f side surfaces of the intermediate transfer belt 105 driven at a constant speed of 200 mm / sec. Formation of start marks Msr and Msf and 8 sets of test patterns having w of 1 mm, length A in the X direction of, for example, 10 mm, pitch d of, for example, 6 mm, and interval c between the sets of, for example, 9 mm is started. The timer Tw1 whose time limit value is Tw1 for starting the timing immediately before Msf arrives immediately below the P / TM sensors 109F and 109R is started (step 1) and waits for the timing.

  That is, it waits for the timer Tw1 to time out (step 2). When the timer Tw1 is over, this time, the timer Tw2 whose time limit is Tw2 is used to determine when the last of the eight test patterns in the rear and front ends through the P / TM sensors 109F and 109R. Is started (step 3).

  When the Bk, Y, C, or M mark is not present in the field of view of the P / TM sensors 109F and 109R, the detection signals Sdr and Sdf of the P / TM sensors 109F and 109R are at a high level H (about 4V) and the mark is present. The detection signal Sdr is at a low level L (about 1 V), and the detection signal Sdr varies as shown in FIG. 14 due to the constant speed movement of the intermediate transfer belt 105. A part of the fluctuation is enlarged and shown in FIG.

  In FIG. 15A, the descending area where the level of the mark detection signal is reduced corresponds to the leading edge area of the mark, and the rising area where the mark is rising corresponds to the trailing edge area of the mark. A region having a mark width w is between the rising region and the rising region.

  In step 4 of FIG. 13, in the process where the start marks Msr and Msf arrive in the field of view of the P / TM sensors 109F and 109R and the detection signals Sdr and Sdf change from H to L, the window comparator 39r or 39f of FIG. The detection signal Sdr or Sdf waits until the detection signal Swr = L or Swf = L indicating that the detection signal Sdr or Sdf is 2 to 3V. That is, it is monitored whether at least one edge region of the start marks Msr and Msf has arrived in the visual field of the P / TM sensors 109F and 109R.

  When it arrives, the timer Tsp whose time limit value is Tsp (for example, 50 μsec) is started, and when it times out, the “timer Tsp interrupt” (TIP) shown in FIG. 17 is executed and the timer interrupt is permitted (step of FIG. 13). 5). Then, the sampling number value Nos of the sampling number register Nos is initialized to 0, and writing to the r memory (rear side mark read data storage area) and the f memory (front side mark read data storage area) allocated to the FIFO memory in the CPU 402 is performed. Addresses Noar and Noaf are initialized to start addresses (step 6 in FIG. 13). Then, it waits for the timer Tw2 to time out. That is, it waits for all the eight sets of test patterns to finish passing through the field of view of the P / TM sensors 109F and 109R (step 7 in FIG. 13).

  Here, with reference to FIG. 17, the contents of the “interrupt of timer Tsp” (step TIP in FIG. 17) will be described. It should be noted that this process is executed every time the timer Tsp whose time limit value is Tsp expires. At the beginning of this process, the CPU 402 restarts the timer Tsp (step 11 in FIG. 17) and instructs the A / D conversion circuit 401 to perform A / D conversion (step 12 in FIG. 17). That is, the instruction signals Scr and Scf are temporarily set to the A / D conversion instruction level L. Then, the sampling number value Nos in the sampling number register Nos, which is the number of instructions, is incremented by 1 (step 13 in FIG. 17).

  As a result, the elapsed time since Nos × Tsp detected the leading edge of the start mark Msr or Msf (= the belt movement direction y along the surface of the intermediate transfer belt 105 based on the start mark Msr or Msf). This represents the current detected position on the intermediate transfer belt 105 by the P / TM sensors 109F and 109R.

  Then, it is checked whether the detection signal Swr of the window comparator 39R (see FIG. 16) is L (P / TM sensor 20R is detecting the edge portion of the mark and 2V ≦ Sdr ≦ 3V) (step of FIG. 17). 14) If so, the sampling number value Nos of the sampling number register Nos and the A / D conversion data Ddr (value of the mark detection signal Sdr of the P / TM sensor 109R) are written as write data to the address Noar of the r memory. Write (step 15 in FIG. 17).

  Then, the write address Noar of f memory is incremented by 1 (step 16 in FIG. 17). When the detection signal Swr of the window comparators 39R and 39f is H (Sdr <2V or 3V <Sdr), data is not written to the r memory. This is for reducing the amount of data written to the memory and simplifying subsequent data processing.

  Next, similarly, it is checked whether the detection signal Swf of the window comparator 39f is L (P / TM sensor 109f is detecting the edge portion of the mark and 2V ≦ Sdf ≦ 3V) (step 17 in FIG. 17). If so, the sampling number value Nos of the sampling number register Nos and the A / D conversion data Ddf (the value of the mark detection signal Sdf of the P / TM sensor 109f) are written as write data to the address Noaf of the f memory. (Step 18 in FIG. 17). Then, the write address Noaf of the f memory is incremented by 1 (step 19 in FIG. 17).

  Since such interrupt processing is repeatedly executed in the Tsp cycle, when the mark detection signals Sdr and Sdf of the P / TM sensors 109F and 109R change to high and low as shown in FIG. In the r memory and the f memory allocated to the FIFO memory, only the digital data Ddr and Ddf of the detection signals Sdr and Sdf within the range of 2V to 3V shown in FIG. Stored.

  Since the sampling number value Nos of the sampling number register Nos is incremented by 1 in the Tsp cycle, and the intermediate transfer belt 105 moves at a constant speed, the number value Nos is based on the detected start mark as the intermediate transfer belt 105. It shows the y position along the top surface.

  In addition, as shown in FIG. 15B, the center position “a” of the descending area where the level of the mark detection signal is lowered and the center position “b” of the ascending area that is rising next are within the range of 2V to 3V. Is the center position of one mark Akr in the y direction, and similarly, the center position c of the descending area where the level of the mark detection signal that appears next to the mark Akr decreases, and the next rising position. The middle point Ayrp of the center position d of the rising area is the center position of the other mark Ayr in the y direction. These mark center positions Akrp, Ayrp,... Are calculated by calculation CPA (FIG. 13, FIG. 18) of the mark center point position described later.

  Reference is again made to FIG. After the last mark of the last 8th set in the test pattern passes the P / TM sensors 109F and 109R, the timer Tw2 times out. Then, the CPU 402 prohibits interruption of the timer Tsp (steps 7 and 8 in FIG. 13).

  As a result, the A / D conversion of the detection signals Sdr and Sdf in the Tsp cycle shown in FIG. 17 stops. The CPU 402 calculates the center position of the mark based on the detection data Ddr and Ddf in the R memory and f memory of the FIFO memory therein (step CPA in FIG. 13), and sets 8 sets for each of the rear R and the front f. In this pattern, the appropriateness of the distribution of the detected mark center point positions is verified, the inappropriate detection pattern (set) is deleted (step SPC in FIG. 13), and the average pattern of the proper detection patterns is obtained ( Step MPA in FIG. 13).

  FIG. 13 and FIG. 18 show the contents of “calculation of mark center point position” (CPA). Here, “calculation of mark center point position of rear r” (CPAr) and “calculation of mark center point position of front f” (CPAf) are executed.

  In “calculation of mark center point position of rear r” (CPAr), the CPU 402 first initializes the read address RNoar of the r memory allocated to the FIFO memory in the first, and the data of the center point number register Noc is set to the first edge. Is initialized to 1 (step 21 in FIG. 18).

  Then, the data Ct in the one-edge region sample number register Ct is initialized to 1, and the data Cd and Cu in the descending number register Cd and the ascending number register Cu are initialized to 0 (step 22 in FIG. 18). Then, the read address RNoar is written into the edge area data group start address register Sad (step 23 in FIG. 18). The above is preparation processing for data processing of the first edge region.

  Next, the CPU 402 sends data (y position Nos: N · RNoar, detection level Ddr: D · RNoar) from the r memory address RNoar, and data (y position Nos: N · (RNoar + 1) from the next address RNoar + 1. ), Detection level Ddr: D · (RNoar + 1)), and first, whether the y position difference between the two data is E (for example, E = w / 2 = for example, a value corresponding to 1/2 mm) or less (on the same edge region). A check is made (step 24 in FIG. 18), and if so, it is checked whether the mark detection data Ddr has a downward trend or an upward trend (step 25 in FIG. 18). Cd is incremented by 1 (step 27 in FIG. 18), and if there is an upward trend, the data Cu in the rise count register Cu is incremented by 1 That (step 26 in FIG. 18).

  Then, the data Ct in the one-edge sample number register Ct is incremented by one (28). Then, it is checked whether the r memory read address RNoar is the end address of the r memory (step 29 in FIG. 18). If it is not the end address, the memory read address RNoar is incremented by 1 (step 30 in FIG. 18). The above-described processing (steps 24 to 30 in FIG. 18) is repeated.

  When the y position (Nos) of the read data is changed to that of the next edge area, the position difference between the position data of the front and rear memory addresses checked in step 24 of FIG. 18 is larger than E, and the CPU 402 From step 24, the process proceeds to step 31 in FIG. Here, all the sampling data of one mark edge (leading edge or trailing edge) area have been checked for downward and upward tendency.

  Therefore, it is checked whether the sample number data Ct in the one-edge sample number register Ct at this time is an equivalent value in one edge region (in the range of 2V to 3V). That is, it is checked whether F ≦ Ct ≦ G (step 31 in FIG. 19). F is a lower limit (setting of the number of times of writing the sample value Ddr to the r memory while the detection signal Sdr is 2 V or more and 3 V or less when the leading edge or the trailing edge of the mark formed normally is detected. Value) and G are upper limit values (set values).

  If Ct is F ≦ Ct ≦ G, the correctness / incorrectness of the data of one mark edge that has been normally read and stored is completed, and the result is “appropriate”. It is checked whether the obtained detection data group has a downward tendency or an upward tendency as a whole of the edge region (2 V or more and 3 V or less) (steps 32 and 34 in FIG. 19).

  In this embodiment, when the data Cd in the descending number register Cd is 70% or more of the sum Cd + Cu of the data Cu in the descending number register Cu and the data Cu in the ascending number register Cu, the edge No. When the information Down indicating the descending is written to the address addressed to Noc (step 33 in FIG. 19) and the data Cu in the ascending number register Cu is 70% or more of Cd + Cu, the memory edge No. Information Up indicating an increase is written in the address addressed to Noc (step 35 in FIG. 19). Further, the average value of the y position data of the edge region, that is, the center point position of the edge region (a, b, c, d,... Write to the address addressed to Noc (step 36 in FIG. 19).

  Next, the edge No. It is checked whether Nos has become 130 or more, that is, calculation of the center positions of the leading edge region and trailing edge region of all of the start mark Msr and the eight sets of mark patterns has been completed (step 37 in FIG. 19). . If this has been completed, or if all of the stored data has been read from the r memory, the mark center point position is calculated based on the edge center point position data (y position calculated in step 36). (Step 39 in FIG. 19).

  That is, the memory edge No. The address data (falling / rising data & edge center point position data) is read, and the position difference between the center point position of the preceding falling edge area and the center point position of the immediately following rising edge area is the width of the mark in the y direction. It is checked whether it is within the range corresponding to w, and if it is out, these data are deleted.

  If it is within the range, the average value of these data is set as the center point position of one mark. Write to memory. If mark formation, mark detection, and detection data processing are all appropriate, with respect to rear r, start mark Msr and 8 sets of marks (1 set 8 marks × 8 sets = 64 marks), a total of 65 mark center points Position data is obtained and stored in memory.

  Next, the CPU 402 executes “calculation of the mark center point position of the front f” (step CPAf in FIG. 19), and performs the data processing of the “calculation of mark center point position of the rear r” CPAr (see FIG. 18). Are similarly performed on the measurement data in the f memory. With respect to the front f, if mark formation, measurement, and measurement data processing are all appropriate, start mark Msf and 8 sets of marks (64 marks), a total of 65 mark center point position data are obtained and stored in memory. Is done.

  Refer to FIG. 13 again. When the mark center point position is calculated as described above (step CPA in FIG. 13), the CPU 402 performs the following “verification of the pattern of each set” (step SPC in FIG. 13) and the mark center point position written in the memory. It is verified whether the data group is the center point distribution corresponding to the mark distribution shown in FIG. Here, data deviating from the mark distribution equivalent to that shown in FIG. 17 is deleted in units of sets, and only the data set (one set is eight position data groups) corresponding to the mark distribution shown in FIG. leave. If all are appropriate, 8 sets of data remain on the rear r side and 8 sets on the front f side.

  Next, the CPU 402 changes the center point position data of the first mark in each set after the second set to the first center point position of the first set in the rear r-side data set. The center point position data of the second to eighth marks are also changed by the changed difference value. That is, the center point position data group of each set after the second set is changed to a value shifted in the y direction so that the top of each set is aligned with the top of the first set. Similarly, the center point position data in each set after the second set on the front f side is also changed.

  Next, the CPU 402 calculates average values Mar to Mhr (FIG. 20) of the center point position data of each mark in all sets on the rear r side in “calculation of average pattern” (step MPA in FIG. 13). Then, average values Maf to Mhf (FIG. 20) of the center point position data of each mark of all sets on the front f side are calculated. These average values are distributed as shown in FIG. 20, virtual average position marks MAkr (representative of Bk rear orthogonal mark), MAyr (representative of Y rear orthogonal mark), MAcr (rear orthogonal mark of C). Representative), MAmr (representative of M rear orthogonal mark), MBkr (representative of Bk rear oblique mark), MByr (representative of Y rear oblique mark), MBcr (representative of C rear oblique mark), And MBmr (representative of M rear oblique mark), MAkf (representative of front orthogonal mark of Bk), MAyf (representative of front orthogonal mark of Y), MAcf (representative of front orthogonal mark of C), MAmf (Representative of M front orthogonal mark), MBkf (representative of Bk front oblique mark), MByf (representative of Y front oblique mark), MBcf (representative of C front flow mark) Representative DOO diagonal mark), and indicates the center point position of MBmr (representative of front diagonal mark of M). The above is the content of “test pattern formation and measurement” (PFM) shown in FIG.

  Reference is again made to FIG. Please also refer to FIG. 21 showing the distribution of the test pattern formed in one circumference of the intermediate transfer belt 105 together with the mark formation position shift corresponding to the rotation angle of the photosensitive drum. In the displacement amount calculation (DAC) shown in FIG. 11, the CPU 402 calculates the image formation displacement amount as follows. The calculation (Acy) of the image forming deviation amount of Y is specifically shown below.

Sub-scanning deviation amount dyy: deviation amount dyy = (Mbr−Mar) − of the difference (Mbr−Mar) in the center point position between the Bk orthogonal mark MAkr and the Y orthogonal mark MAyr on the rear r side with respect to the reference value d (FIG. 17) d.

Main scanning deviation amount dxy: deviation amount dxyr = (Mfr−Mbr) −4d with respect to the reference value 4d (FIG. 17) of the difference (Mfr−Mbr) of the center point position between the orthogonal mark MAyr on the rear r side and the oblique mark MByr
And the deviation dxyf = (Mff−Mbf) −4d of the difference (Mff−Mbf) between the center point positions of the orthogonal mark MAyf and the oblique mark MByf on the front f side with respect to the reference value 4d (FIG. 17).
And the average value dxy = (dxyr + dxyf) / 2
= (Mfr-Mbr + Mff-Mbf-8d) / 2.

Skew dSqy: difference dSqy = (Mbf−Mbr) between the center points of the orthogonal mark MAyr on the rear R side and the orthogonal mark MAyf on the front f side.

Main scanning line length deviation amount dLxy: Skew dSqy = (Mff−Mfr) is subtracted from the difference (Mff−Mfr) of the center point position between the oblique mark MByr on the rear r side and the oblique mark MByf on the front f side. Value dLxy = (Mff−Mfr) −dSqy
= (Mff-Mfr)-(Mbf-Mbr).

  The other C and M image forming deviation amounts are calculated in the same manner as the calculation related to Y (Acc, Acm). Although Bk is substantially the same, in this embodiment, since color matching in the sub-scanning direction y is based on Bk, the positional deviation amount dyk in the sub-scanning direction is not calculated for Bk (Ack). .

  In the shift adjustment (DAD) shown in FIG. 11, the CPU 402 adjusts the image forming shift amount of each color as follows. The Y shift amount adjustment (Ady) is specifically shown below.

  Adjustment of sub-scanning deviation amount dy: The start timing of image exposure (latent image formation) for forming a Y toner image is set by shifting the calculated deviation amount dyy from the reference timing (y direction).

  Adjustment of main scanning deviation amount dxy: The image data at the head of the line to the exposure laser modulator of the exposure device 109 for the line synchronization signal representing the head of the line in image exposure (latent image formation) for Y toner image formation. The sending timing (x direction) is set to be shifted from the reference timing by the calculated shift amount dxy.

  Adjustment of the skew dSqy: The rear r side of the axially extending mirror that reflects the laser beam modulated by the Y image data facing the photosensitive drum 101 and projects it onto the photosensitive drum 101 of the exposure device 109 is supported by a fulcrum. The front f side is supported by a block slidable in the y direction. The skew dSqy can be adjusted by moving this block back and forth in the y direction with a y drive mechanism mainly composed of a pulse motor and a screw. In “adjustment of skew dSqy”, the pulse motor of this y driving mechanism is driven to drive the block from the reference y position by an amount corresponding to the calculated skew dSqy.

  Adjustment of main scanning line length shift amount dLxy: The frequency of the pixel synchronization clock for allocating image data in units of pixels on the line is set to reference frequency × Ls / (Ls + dLxy). Ls is the reference line length.

  The other adjustments of C and M image formation shift amounts are adjusted in the same manner as the adjustment for Y (Adc, Adm). Although Bk is generally the same, in this embodiment, since color matching in the sub-scanning direction y is based on Bk, the positional deviation amount dyk in the sub-scanning direction is not adjusted for Bk (Adk). . Until the next “color matching”, a color image is formed under the adjusted conditions.

[Example of controlling toner density using test pattern detectors installed at multiple locations]
As described with reference to FIGS. 2 and 3, both ends of the primary transfer device 6 (primary transfer roller) have an axial range 203 corresponding to the maximum width of the transfer material in the axial width of the intermediate transfer belt 105. The part is touching. That is, the axial range 203 corresponds to the maximum width (maximum transfer paper width) of the transfer paper used in the image forming apparatus on the intermediate transfer belt 105, and is shifted to two positions outside the axial width 203. Since a test pattern can be created in a band-like region that occupies each of the back side and the near side, a test pattern can be formed in parallel with image formation and density control can be executed. In the following example, one or both of the back side P pattern 201R on the back side and the front side P pattern 201F on the front side can be created as necessary. These test patterns are created and controlled by functions of the main body control unit 406 and the ROM 405.

  In FIGS. 1 and 3, the test pattern density and relative position are located at positions facing the support roller 112 with the intermediate transfer belt 105 in between, corresponding to the passage paths of the back side P pattern 201R and the near side P pattern 201F. Photo sensors 109F (front side) and 109R (back side) (hereinafter referred to as P / TM sensor 109) for estimating the position are provided. Thus, test patterns can be created at a plurality of locations on the intermediate transfer belt, and test pattern detection devices for detecting these test patterns are installed at a plurality of locations.

  In the developing device 102 shown in FIG. 2, the screws 306 and 306 are rotated so as to convey the developer so as to be refluxed while stirring in the opposite direction in the longitudinal direction of the respective axes. Is supplied to the photosensitive drum 101 via the developing sleeve 305.

  FIG. 22 shows a developer circulation path from toner replenishment to reaching the developing sleeve 305. The developer circulates around the partition plate 6 as indicated by arrows 2, 3, 4, and 5. The toner is replenished into the developing device 102 in a width region along the axial direction as indicated by an arrow 1 on the way from the front side F to the back side R in the axial direction. Then, the developer is pumped up and supplied to the developing sleeve 305 in the width region along the axial direction indicated by the arrow 6 that is agitated with the magnetic carrier and extends from the rear side R to the front side F in the axial direction, and is further supplied to the photosensitive drum. 101 and supplied for development. The toner image visualized with toner is transferred from the photosensitive drum 101 to the intermediate transfer belt 105.

  A back side P pattern 201R and a front side P pattern 201F are created on the photosensitive drum 101 at the developing end (back side R and front side F) outside the transfer paper region (axial range 203), and the intermediate transfer is performed. Since the toner density is controlled by being transferred onto the belt 105, these patterns are created on the rear side R or the front side F of the developing device 102.

  Here, the toner density on the back side R and the near side F is a developer immediately after receiving toner replenishment in the transport process indicated by the arrow 2 on the back side R, so that a sufficient toner density is maintained. On the other hand, since the front side F is a developer after passing through the developing region and being subjected to development in the conveyance process indicated by the arrow 4, the toner density is low. FIG. 23 schematically shows the change in toner density between the back side R and the front side F. FIG.

  Thus, the toner density difference between the back side R and the near side F is reflected in the image, and the image density is different between one side and the other side of the image. For this reason, the image density tends to become unstable by a method of controlling the toner density by forming a test pattern only on the back side R or only on the near side F as conventionally performed.

  In order to eliminate such instability of the image density, a test pattern is created on the back side R and the near side F, the density is detected and compared, and the toner density is controlled so that the toner density becomes uniform. It is desirable. By doing so, a stable toner density can always be secured.

  In addition, it is preferable that the test patterns on the back side R and the front side F are created frequently and controlled, but on the other hand, a lot of toner is consumed. Further, it is easy to cause toner scattering in the developing device because the pattern is created at both ends in the axial direction.

  Therefore, with respect to the creation of the test pattern, as shown in FIG. 24, a back side P pattern 201R and a near side P pattern 201F are created on each of the back side R and the near side F, and the toner density is controlled by detecting them. As shown in FIG. 25, it is desirable to create a front side P pattern 201F only on the front side F, and to detect and control the toner density to form two patterns for controlling the toner density.

  Hereinafter, the toner density control procedure will be described with reference to the flowchart of FIG. The first and second counters count and accumulate each time printing is performed. Execution of the designated number of prints is one of the job end conditions, and the integrated value of the counter is reset when the job ends. The counter is reset with a predetermined number of count values.

  When the driving of the developing device 102 is suspended, a pre-rotation operation for a predetermined time is required in order to start the developer to a developable state, for example, when the suspension time is long. Therefore, it is determined in step S-1 whether or not pre-rotation is necessary. If it is determined that pre-rotation is not necessary, a job is started and image formation processing (printing) is executed (step S-19). The toner density control in that case is based on the last data in the previous job (step S-20). Until the first counter counts the number of prints specified in step S-10 (in this case, 10 from the start of the job), an image is formed under the toner density control condition of step S-20.

  When it is determined in step S-1 that the pre-rotation is necessary (for example, when the fixing temperature when the image forming apparatus is turned on is low), the pre-rotation is started (step S-2). At the time of forward rotation, in step S-3, a test pattern is created at positions corresponding to both sides of the rear side R and the front side F (see FIG. 24), and the test pattern is created by the photosensors 109F (front side) and 109R (back side). Is detected. Here, if the back side detection value is A and the near side detection value is B, the toner density on the near side F is usually lower than that on the back side R, and A> B, so toner replenishment (step S-4) and the developer is circulated while stirring. As a result, the toner density of the near side detection value B increases, and the difference between the back side detection value A and the near side detection value B is reduced.

  The time required for the near side detection value B to approximate the back side detection value A is input as control data. When the predetermined pre-rotation time has elapsed, in step S-5, the toner density target value is set to the back side detection value A, the pre-rotation is terminated (step S-6), and the job is started (step S). -7).

  After the job starts, in step S-8, a test pattern is created only at a position corresponding to one side of the near side F (see FIG. 25), and toner density control is performed so that the near side detection value B approaches the target value A. . Printing is executed when the job starts, and the number of prints is counted by a counter. When the number of printed sheets (10 sheets) specified in step S-10 is counted, the cumulative count value of the first counter is reset, and in step S-13, a test pattern is created and detected only on the near side, and the detected value B is detected. Compared with the target value A, the toner is replenished so that the detected value B approaches the target value A if necessary. On the other hand, after resetting, the first counter starts counting every time printing is performed again.

  In this way, a test pattern is created only at a position corresponding to one side of the front side F every 10 sheets, and toner density control is executed so that the detection value B of the front side F approaches the target value A (step S-). 10, S-11, S-12, S-13). Further, every 100 sheets, test patterns are created and detected at positions corresponding to both sides of the back side R and the near side F, and the back side detection value A ′ at that time is changed to a new target value and changed every 10 sheets. The toner is compared with the detected value on the near side (steps S-14, S-15, S-16, S-17).

  Specifically, in step S-10, it waits for 10 sheets from the previous single-sided detection, and when 10 sheets are counted by the first counter, the accumulated count value of the first counter is reset in step S-11 (count value 10). Set to 0) and proceed to Step S-12. In step S-12, a test pattern is created only at one side position corresponding to the near side F, the detection value B of the near side F is detected, and the process proceeds to step S-13. In step S-13, toner replenishment control is performed so that the detected value on the near side F approaches the target value A (or the target value A 'changed in step S-17 described later). Such pattern creation, detection, and toner supply control are performed every ten sheets from the previous one-side detection.

  In step S-14, it waits for 100 sheets from the previous double-sided detection (step S-16). When 100 sheets are counted by the second counter, the accumulated count value of the second counter is reset in step S-15 ( Proceed to step S-16 (count value 100 is set to 0). In step S-16, a test pattern is created and detected at positions corresponding to both the back side R and the near side F. Here, if the back side detection value is A ′ and the near side detection value is B ′, the control target value is changed from the previous target value to A ′ in step S-17, and the near side detection value is set. The toner density control is performed so as to approach the new target value A ′. Such pattern creation, detection, and toner replenishment control are performed every 100 sheets from the previous double-sided detection.

  As described above, since the test pattern and its pattern detection device are provided at a plurality of locations for detection and control, stable and high image quality can be obtained more reliably.

  If you always create and detect multiple test patterns (back side, near side), you can obtain a more stable image, but if you do not need it, you will waste toner. In addition, it is expected that toner scattering will increase. As in this example, depending on the case, if a test pattern at one location and a corresponding 9t pattern detection device are used, and a test pattern at multiple locations and the pattern detection device are used, the operation can be performed separately. In addition, it is possible to reliably use a single or multiple pattern depending on the case and to obtain a stable image and to eliminate wasteful consumption of toner.

  In the case of using a plurality of test patterns and the pattern detection apparatus, if the creation timing and detection timing of the plurality of test patterns are made simultaneous, stable and high image quality can be obtained more reliably.

  At the end of the job, test patterns are created and detected at positions corresponding to both sides of the back side R and the front side F (see FIG. 24), and the detection values of the back side R at that time are stored in memory, and the next pre-rotation It is also possible to set the control target value up to both-side pattern creation and detection (step S-3).

[Example of determining image process conditions according to detection results of multiple test patterns]
As shown in FIG. 7, based on the detection results of the near side P pattern 201F and the far side P pattern 201R formed outside the image area of the intermediate transfer belt 105, the determined image process conditions (charging application voltage, development bias) are determined. The voltage or exposure power) is not fed back as it is, but the result of the following arithmetic processing is fed back.

[Method of obtaining average value]
Each of the image process conditions determined by the detection of the near side P pattern 201F,
Charging applied voltage: Vc (F)
Development bias voltage: Vb (F)
Each of the image process conditions determined by the detection of the back side P pattern 201R,
Charging applied voltage: Vc (R)
Development bias voltage: Vb (R)
Then, when a density deviation of the test pattern occurs in the axial direction of the driving roller 112 of the intermediate transfer belt 105, each of the above Vc (F) and Vc (R), Vb (F) and Vb (R) has a value. Come different.

For example, as shown in FIG. 27, when the toner adhesion amount of the near side P pattern 201F is larger than the toner adhesion amount of the back side P pattern 201R created under the same test pattern imaging conditions, the image area to be originally controlled is Since it is located between the two (the intermediate position of the image area in the axial direction of the drive roller 112), the average value of the image process conditions determined from the test pattern detection results of both is fed back.
In other words, as an image process condition,
Vc = {Vc (F) + Vc (R)} / 2
Vb = {Vb (F) + Vb (R)} / 2
And
In the example of the developing bias voltage shown in FIG. 28, the developing bias voltage Vb to be fed back is the developing bias voltage Vb (F) in the near side P pattern 201F and the developing bias voltage Vb (R) corresponding to the far side P pattern 201R. Average value. Although not shown, the same applies to the charging application voltage Vb.

As a result, even if a test pattern formed outside the image area has a larger or smaller amount of toner adhesion than in the image area without hindering the normal image forming operation, it is possible to assume an appropriate The image process conditions are determined.
The above-described density deviation often occurs due to deviations in the direction of each unit rotation axis such as development ability deviation and intermediate transfer ability deviation.

[Method of obtaining correction values and using them as appropriate]
Each of the image process conditions determined by the detection of the near side P pattern 201F,
Charging applied voltage: Vc (F)
Development bias voltage: Vb (F)
Each of the image process conditions determined by the detection of the back side P pattern 201R,
Charging applied voltage: Vc (R)
Development bias voltage: Vb (R)
Then, when the density deviation of the test pattern occurs in the axial direction of the driving roller 112 of the intermediate transfer belt, the values of the above Vc (F) and Vc (R), Vb (F) and Vb (R) are different. Come.

For example, when the toner adhesion amount of the near side P pattern 201F is larger than the toner adhesion amount of the back side P pattern 201R created under the same test pattern imaging conditions, the image area to be originally controlled is the intermediate (drive roller) between the two. 112 in the axial direction of the image area in the axial direction)
The average value of the image process conditions determined from the test pattern detection results of both images is Vc as the image process condition in the image area.
Vc = {Vc (F) + Vc (R)} / 2
Vb = {Vb (F) + Vb (R)} / 2
And
In this case, the difference between the image process condition in the image area and the near side P pattern 201F and the far side P pattern 201R is set as a correction value of the image process condition obtained from each test pattern detection result.

That is,
Vc correction value (F) = Vc−Vc (F)
Vb correction value (F) = Vb−Vb (F)
age,
Vc correction value (R) = Vc−Vc (R)
Vb correction value (R) = Vb−Vb (R)
And
Then, the correction values Vc correction value (F), Vb correction value (F), Vc correction value (R), and Vb correction value (R) are stored in the storage RAM 403 (see FIG. 5) of the main body. .

  Each correction value stored here is fed back, for example, by correcting the Vc correction value (F) and the Vb correction value (F) with respect to the image process condition obtained from the detection result of the near side P pattern 201F. Determined as image process conditions. Similarly, in the case of the back side P pattern 201R, the Vc correction value (R) and the Vb correction value (R) are corrected.

  By using these correction values, there is no need to always create and detect a test pattern in both the front P pattern 201F and the back P pattern 201R, and only one of the test pattern detection results can be used in the image area. The image process conditions are determined to appropriate values.

  When obtaining the image process condition correction value, pattern image formation and detection are required at two locations, the front side P pattern 201F and the back side P pattern 201R, outside the image area as described above. Compared to the case where only one test pattern is formed, the toner consumption associated with the test pattern image formation is doubled, and wasteful toner consumption, increased waste toner amount, intermediate transfer belt cleaning and There are concerns about the occurrence of problems such as an increase in the load on photoconductor cleaning.

  In this example, therefore, one of the near side P pattern 201F and the far side P pattern 201R is imaged and detected except when the image process condition correction value is determined from the above viewpoint.

  Further, the image formation and detection operations of the near side P pattern 201F or the back side P pattern 201R are switched at a timing at which the cumulative number of times of either one of the test pattern image formation and detection operations is an integral multiple of 10.

The timing for determining the image process condition correction value is set when the developing unit is replaced or when the intermediate transfer belt or the intermediate transfer device is replaced, assuming that there is a high possibility that the image density deviation in the rotation direction of the intermediate transfer belt is changed. This is also performed when the P / TM sensor 109 is replaced.
When the development unit is replaced, it is automatically detected by the development unit replacement detection means installed in the development unit (such as a non-contact type ID chip or a method of detecting a mechanical protrusion using a sensor installed in the main unit). By determining that the developing unit has been replaced and setting a unit replacement flag in the RAM 403, image formation and detection are performed at a plurality of locations on the near side P pattern 201F and the back side P pattern 201R during the next test pattern image formation. .
Further, when the intermediate transfer belt 105 or the intermediate transfer device is replaced and the P / TM sensor 109 is replaced, a unit replacement flag is set in the RAM 403 by manually setting from the main body operation unit. As a result, at the next test pattern image formation, image formation and detection are performed at a plurality of locations on the near side P pattern 201F and the back side P pattern 201R.

  The density deviation between the near side P pattern 201F and the far side P pattern 201R may change depending on the use state of the image forming apparatus main body such as the image area ratio to be used, the print volume, and the installation environment. In order to do this, the determination of the image process condition correction value is executed at a timing at which the integration number of test pattern imaging and detection operations is an integral multiple of 20 other than when the unit is replaced.

  In this example, the test pattern for control for determining the image process condition outside the image region is created in a plurality of locations, and the image process condition is determined according to the test pattern detection result of each of the plurality of locations. Even when density deviation due to position occurs, it is possible to make it less susceptible to density deviation in determining the image process conditions, while adopting an intermediate transfer method with high image overlay accuracy and low cost of the cleaning device And space saving, the downtime of the apparatus by process control for image formation using a test pattern can be reduced, and stable image quality can be maintained.

The above technical matters can be organized as follows.
(1) In the image forming apparatus, a plurality of test pattern arrangements are arranged outside the image areas on both sides of the image area in a direction normal to the rotation direction of the first transfer apparatus (intermediate transfer belt 105). In the image forming apparatus, an image determined based on the image process condition K1 [for example, Vc (F), Vb (F)] determined based on the detection result of the test pattern on one side and the detection result of the test pattern on the other side. The average value of the process condition K2 [eg, Vc (R), Vb (R)] is controlled as the image process condition (eg, Vc, Vb).
In the image forming apparatus in which a plurality of test pattern arrangements are arranged outside the image areas on both sides of the image area in a direction normal to the rotation direction of the first transfer device, the test pattern detection result on one side When the average value of the image process condition K1 determined based on the detection result of the other one side test pattern and the image process condition K2 determined based on the other one side test pattern is controlled as the image process condition, the one side test pattern and the other one side test Even if there is a density deviation with the pattern, the test pattern is created outside the image area without creating a test pattern in the image area, so test pattern creation and image formation can be performed in parallel. Image process conditions suitable for the image area can be determined without causing downtime. Thereby, stable maintenance of image quality can be achieved.

(2) The image process condition is corrected according to the plurality of test pattern detection results.
In this way, the image process conditions are corrected according to the results of multiple test pattern detections, so even if a density deviation occurs in each test pattern, test patterns are created and detected outside the image area where no downtime occurs. As a result, an appropriate image process condition in the image region can be determined, and as a result, stable maintenance of the image quality can be achieved.

(3) The average value of the image process condition K1 determined based on the detection result of the test pattern on one side and the image process condition K2 determined based on the detection result of the test pattern on the other side is defined as the image process condition K3. The image process condition correction values when the test pattern or other one side iron and each pattern are used are as follows.
a. Image process condition correction value A [eg, Vc correction value (F) or Vb correction value (F)] = [Image process condition C (eg, Vc or Vb) − [Image process condition A (eg, Vc (F ) Or Vb (F))]
b. Image process condition correction value B [eg, Vc correction value (R) or Vb correction value (R)] = [Image process condition C (eg, Vc or Vb) − [Image process condition B (eg, Vc (F ) Or Vb (R))]
In this way, the average value of the image process condition A determined based on the detection result of the test pattern on one side and the image process condition B determined based on the detection result of the test pattern on the other side is used as the image process condition C, and Since the image process condition correction value is determined when each of the test pattern of the other side or the test pattern of the other side is used, the detection result of only one of the test pattern of the other side or the test pattern of the other side is used. Image process conditions can be determined and stable image quality can be maintained.

(4) The image process condition correction value is determined at a predetermined timing, and the image process condition correction value is stored.
Since the determination of the image process condition correction value is executed at a predetermined timing determined as an appropriate value and the image process condition correction value is stored, a certain amount of test patterns can be created every time without creating a large number of test patterns at a plurality of locations. By using stored image process correction values for the test pattern detection results created at locations, appropriate image processes can be achieved without wasting toner and reducing the burden on cleaning as much as possible. Conditions can be determined.

(5) Every time image process condition control is executed a predetermined number of times, determination of an image process condition correction value is executed.
Since the image process condition correction value is determined every time the image process condition control is executed a predetermined number of times, even if a density deviation occurs in each test pattern or when the density deviation changes over time, Since the image process condition correction value is reviewed, an appropriate image process condition can always be determined by an appropriate image process condition correction value, and stable maintenance of image quality can be achieved.

(6) The image process condition correction value is determined when any one of the development unit replacement, the first transfer device replacement, or the test pattern detection device replacement is executed.
Since the image process condition correction value is determined when either the development unit replacement, the first transfer device replacement, or the test pattern detection device replacement is executed, the test created at a plurality of locations When the density deviation of the pattern changes, an image process condition correction value suitable for the new density deviation can be stored, an appropriate image process condition can be determined, and stable image quality can be achieved. .

(7) Except when obtaining the image process condition correction value, only one of the plurality of test patterns is set as a detection target.
Since only one of the test patterns is to be detected except when obtaining the image process condition correction value, appropriate image process conditions can be set without wasting toner and reducing the burden on cleaning as much as possible. Can be determined.

(8) The switching between the case where the test pattern A is a detection target and the case where the test pattern B is a detection target is executed every time the number of times each test pattern is detected reaches a predetermined value.
Since switching between the case where the test pattern on one side is the detection target and the case where the test pattern on the other side is the detection target is performed each time the number of times the test pattern detection reaches a predetermined value determined as an appropriate value, cleaning This reduces the burden on the printer and improves the margin for problems such as cleaning failure caused by the concentration of toner used for the test pattern in one place.

It is the schematic of the image forming apparatus which shows an image formation process part. It is a front view of an image forming unit. FIG. 2 is a perspective view during a test pattern creation operation in the image forming apparatus of FIG. 1. It is a block diagram of a P / TM sensor. 1 is an overall schematic diagram of an image forming process control system. 3 is a flowchart of image forming process control. FIG. 2 is a top view of an intermediate transfer belt during a test pattern creation operation in the image forming apparatus of FIG. FIG. 2 is a top view of an intermediate transfer belt during a test pattern creation operation in the image forming apparatus of FIG. 1. FIG. 5A is a characteristic diagram when the amount of color toner adhesion of a test pattern on an intermediate transfer belt is detected by a regular reflection light receiving element, and FIG. FIG. 6C is a characteristic diagram when the black toner adhesion amount of the test pattern on the intermediate transfer belt is detected by the regular reflection light receiving element. FIG. 6 is a diagram illustrating a table used when converting normalized values into toner adhesion amounts. It is a flowchart which shows the outline | summary of "color matching" CPA. FIG. 3 is a plan view schematically showing an intermediate transfer belt and each color mark formed on the surface thereof. It is a flowchart which concerns on formation and measurement of a test pattern. FIG. 6 is a view showing side by side time charts showing the distribution of color marks formed on an intermediate transfer belt and the change in mark detection signal level of an optical sensor. (A) is a time chart showing an enlarged part of the time chart of the detection signal shown in FIG. 14, and (b) is the A / D conversion data of the detection signal shown in (a) whose CPU is CPU. It is the time chart which extracted and showed only the range written in the FIFO memory inside. It is the block diagram which showed the structure of a part of main body control part. It is a flowchart which shows the content of the interruption process permitted at step 5 in FIG. 14 is a flowchart showing a part of the content of “calculation of mark center point position” CPA shown in FIG. 13; It is a flowchart which shows the remainder of the content of "calculation of mark center point position" CPA shown in FIG. It is a top view which shows the average value data calculated by "calculation of an average pattern" MPA shown in FIG. 13, and the virtual mark which becomes a center point position. 6 is a graph showing the distribution of test patterns formed on the circumference of the intermediate transfer belt, along with mark formation position deviation corresponding to the rotation angle of the photosensitive drum. FIG. 5 is a diagram illustrating a developer circulation path and replenishment and supply portions in the developing device. FIG. 10 is a diagram illustrating a difference in toner density between a back side (upstream side) and a near side (downstream side) in the developing device. It is explanatory drawing of the both-sides test pattern formation example of a back side and a near side. It is explanatory drawing of the example of test pattern formation of only one side (front side). 6 is a flowchart of an example of toner density control. FIG. 6 is a diagram illustrating toner adhesion amounts in a test pattern on the back side and the near side. It is the figure which showed the image process condition deviation.

Explanation of symbols

101Y, 101C, 101M, 101K Photosensitive drum (first image carrier)
102Y, 102C, 102M, 102K Developing device 105 (constituting the first transfer device) Intermediate transfer belts 106Y, 106C, 106M, 106K (constituting the first transfer device) Primary transfer device 108 Secondary transfer roller (constituting the first transfer device) Second transfer device)
200 Exposure apparatus 201 Test pattern (P pattern)
201F Front P Pattern 201R Back P Pattern 202F Front TM Pattern 202R Back TM Pattern 202 Test Pattern (TM Pattern 301 Charging Device

Claims (7)

A first image carrier comprising a plurality of photosensitive members; a charging device for charging the first image carrier; an exposure device for forming a latent image on the first image carrier; and the first image. A developing device that develops the latent image formed on the carrier, a first transfer device that obtains a color image by superimposing the image formed on the first image carrier on the image carrier, and the first An image forming apparatus having a second transfer device that transfers an image formed on the transfer device to a transfer material;
A test pattern generation device capable of forming a test pattern on the first transfer device, a test pattern detection device capable of detecting the state of the test pattern, and an image process for determining an image process condition based on the detection result of the test pattern An image forming apparatus comprising: a control unit; wherein the second transfer device is configured to prevent the test pattern from being transferred to the second transfer device while constantly contacting the first transfer device. The image forming apparatus according to claim 1.
The image forming apparatus according to claim 1, wherein the image carrier in the first transfer device has a belt shape, and the second transfer device has a belt shape or a roller shape. The image forming apparatus according to claim 2.
The axial width (hereinafter referred to as image carrier width) of the belt-like member as the image carrier in the first transfer device is the axial width (hereinafter referred to as image carrier width) of the belt-like or roller-like member as the second transfer device. Hereinafter, the maximum width of the transfer material is larger than the second transfer device width), and is equal to or smaller than the second transfer device width.
The image forming apparatus, wherein the test pattern is formed in an area of a dimensional difference between the width of the image carrier and the width of the second transfer device. The image forming apparatus according to claim 3.
2. The image forming apparatus according to claim 1, wherein the test pattern forming areas are formed at both ends of an axial width of a belt-like member as the image carrier in the first transfer device. The image forming apparatus according to claim 4.
An image forming apparatus comprising: a pattern for detecting a toner adhesion amount and a pattern for detecting an image position as the test pattern. The image forming apparatus according to claim 1.
An image forming apparatus, wherein the test pattern can be created at a plurality of locations of the first transfer device, and test pattern detection devices for detecting these test patterns are installed at a plurality of locations. The image processing apparatus according to claim 6.
An image forming apparatus, wherein an image process condition is determined according to detection results of the plurality of test patterns.

Images