JP4786979B2 - Image forming apparatus - Google Patents

Description

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

  An electrophotographic image forming apparatus such as a copying machine, a printer, or a facsimile forms an electrostatic latent image by uniformly charging an image carrier made of a photosensitive member with a charging device and exposing it with an exposure device. The electrostatic latent image is developed by a developing device and transferred to a transfer material such as transfer paper by a transfer device. In this image forming apparatus, a toner adhesion pattern for image adjustment is formed in a non-image area on the image carrier, the density of the toner adhesion pattern is detected by a light reflection type photosensor, and the toner is determined according to the detection result. Conventionally, a toner density control method for controlling toner supply from a replenishing device to a developing device has been generally used.

  In this toner density control method, among the output values of the light reflection type photosensor, the output of the light reflection type photosensor with respect to the toner adhesion pattern on the image carrier is Vsp, and the light reflection with respect to the toner non-adhesion portion on the image carrier. When the output value of the photosensor is Vsg, toner supply control is normally performed so that Vsp / Vsg is constant. When the toner adhesion amount of the toner adhesion pattern decreases, Vsp / Vsg increases, and it is determined that the toner concentration of the developer in the developing device is low, and the toner concentration is kept constant by supplying toner from the toner replenishing device to the developing device. Keep on. On the other hand, when Vsp / Vsg is low, it is determined that the toner concentration of the developer in the developing device is high, and toner replenishment is not performed.

  On the other hand, since the image is not stable under certain image forming conditions such as charging, exposure, and development due to sensitivity deterioration with time of the photoconductor and changes in sensitivity due to the environment in which the image forming apparatus is used, the surface potential of the photoconductor is measured by a potential sensor. In general, the image quality is stabilized by controlling the image forming condition based on the detection result. However, the potential sensor is relatively expensive, and is not often installed except for high-end models. There are the following methods as a method for controlling the image forming conditions without the potential sensor.

This is to detect the background stain level on the surface of the photoreceptor using a light reflection type photosensor for controlling the toner density, and the charging voltage applied to the charging device is detected in the background stain level detection area on the surface of the photoreceptor. The background potential, which is the difference between the dark portion potential Vd on the photoreceptor surface and the developing bias voltage Vb, is set to be lower than that of the normal image portion. Under this image forming condition, since background stain is slightly generated on the surface of the photoreceptor, the output value Vsdp detected by the light reflection type photosensor in the background contamination level detection region on the surface of the photoreceptor is slightly lower than Vsg.
Even when the same charging voltage is applied to the charging device, if the dark portion potential Vd on the surface of the photoconductor fluctuates due to photoconductor degradation, charging device degradation, environmental fluctuations, etc., the background stain level fluctuates, and the above-described Vsdp fluctuation increases. . That is, the change in Vsdp is detected by the light reflection type photosensor, and is fed back to the charging device applied voltage so that Vd becomes the target potential.

In addition, in color copying machines and color printers, a color image is formed by superimposing and transferring a plurality of color toner images formed on a plurality of photosensitive members onto an intermediate transfer member, and transferring the color image to a transfer material. Therefore, it is necessary to strictly control the toner adhesion amount in the development process, the transfer process, and the like, and image forming condition control such as halftone correction is indispensable.
However, these image forming condition controls are difficult to be performed simultaneously with normal image forming operations because a plurality of pattern images with different toner adhesion amounts are created by changing the image forming conditions. During this, it is necessary to temporarily stop the image forming operation. Since the time during which the image forming operation is temporarily suspended becomes a downtime during which the operator of the image forming apparatus cannot work, the execution timing of the image forming condition control has an influence on the operation of the image forming apparatus as much as possible. The period when there is no image is suitable, and is generally performed during warm-up immediately after the image forming apparatus main body is turned on. However, with the recent trend toward energy saving and ease of use, it is necessary to shorten the warm-up time of the image forming apparatus main body and the down time between jobs as much as possible.

  As a measure for reducing the downtime, it is also effective to perform various operations such as image forming condition control by selecting a timing at which it is difficult for the operator of the image forming apparatus to feel the waiting time. There are times when usage frequency decreases. It is also effective to change the execution frequency of various image forming condition control operations according to the usage state of the image forming apparatus.

Also for the various control operations described above, it is necessary to execute a plurality of operations in parallel instead of serially to complete the image forming condition control, the reference value setting of the toner density control, and other condition settings in a short time. As a method of shortening the execution time of the control operation by parallel processing, the above-mentioned light reflection type photosensor is mainly used when controlling the charging device application voltage and development bias voltage of a plurality of colors using the above light reflection type photosensor. Conventionally, it has been considered that a plurality of colors are arranged in the scanning direction to simultaneously control image forming conditions for a plurality of colors. Here, with respect to the main scanning direction, the direction in which the laser beam is deflected and scanned is referred to as the main scanning direction, and the direction in which the photosensitive member and the intermediate transfer member that are orthogonal to the main scanning direction are conveyed is referred to as the sub-scanning direction. Although this sensor multiple arrangement method is effective in reducing the execution time of the control operation, the influence of the characteristic variation of the light reflection type photosensor used for each toner color becomes the control variation for each toner color, resulting in poor image quality such as color variation. Can be a factor.
Therefore, a plurality of toners are set for the purpose of completing various condition settings in a short time and performing optimum image forming condition control according to the state of the image forming apparatus without inconvenience to the operator and maintaining stable image quality. An image forming apparatus that switches the arrangement of the adhesion pattern has been proposed.

  Patent Document 1 discloses a pattern forming unit that forms a color misregistration detection pattern composed of a combination of different color toner images on an intermediate transfer member over the entire circumference, and a pattern formed from the pattern formed by the unit. A positional deviation detecting means for detecting a relative positional deviation in the moving direction of the intermediate transfer member of the toner image of the formed color, and correcting the positional deviation based on the positional deviation information detected by the positional deviation detecting means. Thus, there is described an intermediate transfer device provided with a moving speed correcting means for correcting the moving speed of the intermediate transfer member.

  In Patent Document 2, an image forming apparatus that obtains a color image by transferring a toner image formed by electrophotography on a plurality of rotationally driven image carriers to an intermediate transfer member, the image carrier for each image carrier. A plurality of first detectors for optically detecting a density of a toner image formed on the image carrier that is provided opposite to the body and opposed to the intermediate transfer member; A second detector for optically detecting the density of the toner image transferred to the transfer body, and a toner patch forming means for forming a reference toner patch as a toner image on each of the image carriers and transferring it to the intermediate transfer body; Correction means for correcting the detection result of the first detector based on the detection result of the second detector; and image density control based on the corrected detection result of the first detector Forming an image density control means Location have been described.

JP 2004-280016 A JP-A-2005-92118

However, even in the image forming apparatus that switches the arrangement of the plurality of toner adhesion patterns, in the case of a color copying machine or a color printer that creates a large number of toner adhesion patterns in the rotation direction on the intermediate transfer body, the surface of the intermediate transfer body However, the cleaning device for cleaning the toner has a large burden, resulting in poor cleaning and filming of the intermediate transfer member.
Although the present invention is an image forming apparatus that switches the arrangement of a plurality of toner adhesion patterns, the burden on the cleaning apparatus for cleaning the surface of the intermediate transfer member can be reduced, and the cleaning and filming of the surface of the intermediate transfer member can be reduced. It is an object of the present invention to provide an image forming apparatus that can be avoided and can perform a control operation as simple as possible.

In order to achieve the above object, the invention according to claim 1 includes a plurality of sets of image forming means each having a developing device for forming a plurality of color toner images on an image carrier, and a rotationally driven intermediate transfer member. And primary transfer means for primary transfer by superimposing the toner images of the respective colors formed on the image bearing members of the plurality of sets of image forming means on the intermediate transfer member, and superimposing the toner images on the intermediate transfer member. Secondary transfer means for collectively transferring the toner images of the respective colors that have been primarily transferred onto the transfer material, and each color for image adjustment in a non-image area on each image carrier of the plurality of sets of image forming means Toner adhesion pattern forming means for forming a toner adhesion pattern of each of the toner images and primarily transferring the toner adhesion patterns on the intermediate transfer body so as to be arranged in a direction perpendicular to the running direction of the intermediate transfer body; Paired with the intermediate transfer member Then, a plurality of optical elements that are provided in a line at a predetermined interval in a direction perpendicular to the rotation direction of the intermediate transfer body downstream of the plurality of sets of image forming means and detect the toner adhesion pattern of each color on the intermediate transfer body In an image forming apparatus having an image sensor and a control means for performing a predetermined control operation according to a detection value of the sensor, an arrangement of toner adhesion patterns of each color detected by the plurality of optical sensors and the plurality of optical sensors Of the plurality of optical sensors and the plurality of toner colors in a one-to-one correspondence, and an optical type dedicated to black toner among the plurality of optical sensors. An array B that uses only two sensors, that is, a sensor and an optical sensor for color toner, and an arrangement that uses all the toner colors in association with one of the plurality of optical sensors. And the order of image formation of the toner adhesion patterns of the respective colors by the plurality of sets of image forming means is changed according to the arrangements A, B, C, and the optical sensor and the toner adhesion patterns of the respective colors When the frequency of setting the arrangement B or C as the arrangement B or C is equal to or greater than a predetermined value, the optical sensor to be used among the plurality of optical sensors and the creation position of the toner adhesion pattern are set to a predetermined toner adhesion pattern detection execution interval. And an operation counter that integrates the rotational drive time of the intermediate transfer member, and the switching timing of the optical sensor to be used or the creation position of the toner adhesion pattern according to the integrated value of the operation counter. The timing is changed.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the operation counter is a counter that integrates the rotational driving distance of the intermediate transfer member .

  According to the present invention, it is possible to reduce the burden on the cleaning device for cleaning the surface of the intermediate transfer member, despite the fact that the image forming device switches the arrangement of a plurality of toner adhesion patterns. Therefore, a simple control operation can be performed as much as possible.

  FIG. 1 shows an image forming apparatus according to an embodiment of the present invention. The image forming apparatus of this embodiment is a color copying machine as an electrophotographic image forming apparatus, and a normal image forming operation is general as shown below. That is, an image reading apparatus as an exposure apparatus (not shown) exposes a document placed on a contact glass while scanning with an exposure lamp, reads the reflected light into three primary colors and reads the three primary colors. Is converted into digital image information of three primary colors and output. The three primary color digital image information from the image reading apparatus is subjected to a predetermined process by an image processing unit (not shown), and a plurality of colors, for example, yellow, cyan, magenta, black: black (hereinafter referred to as Y, C, M, K). ) Of the recording color image signal.

  The present embodiment includes image forming units 6Y, 6C, 6M, and 6K as a plurality of sets of image forming units that form toner images of a plurality of colors, for example, Y, C, M, and K, respectively. The image forming units 6Y, 6C, 6M, and 6K include drum-shaped photoreceptors 1Y, 1C, 1M, and 1K as image carriers, and a cleaning device 2Y disposed around the photoreceptors 1Y, 1C, 1M, and 1K. 2C, 2M, 2K, a static eliminator (not shown), charging devices 4Y, 4C, 4M, 4K, developing devices 5Y, 5C, 5M, 5K having developing rollers 51Y, 51C, 51M, 51K, and the like.

  In each of the image forming units 6Y, 6C, 6M, and 6K, the photoreceptors 1Y, 1C, 1M, and 1K are rotationally driven in a clockwise direction by a driving unit (not shown), and uniform by the charging devices 4Y, 4C, 4M, and 4K. Is charged. The exposure device 7 drives the semiconductor lasers as the light sources by the Y, C, M, and K color image signals from the image processing unit, respectively, so that the Y, C, M, and K image signals are output from the semiconductor laser. A plurality of modulated laser beams are emitted, and these laser beams are deflected and scanned by polygon mirrors, respectively, and irradiated to charged photoreceptors 1Y, 1C, 1M, and 1K through an fθ lens. By exposing and scanning the bodies 1Y, 1C, 1M, and 1K, electrostatic latent images are formed on the respective photoreceptors 1Y, 1C, 1M, and 1K. The electrostatic latent images on the photoreceptors 1Y, 1C, 1M, and 1K are developed by developing devices 5Y, 5C, 5M, and 5K to become toner images of Y, C, M, and K colors.

  The intermediate transfer device includes an intermediate transfer belt 8 as an endless intermediate transfer member, a driving roller 12 that also serves as a secondary transfer backup roller on which the intermediate transfer belt 8 is stretched, a driven roller 13 that is a cleaning backup roller, There are tension rollers 14 and 15, transfer bias rollers 9Y, 9C, 9M, and 9K as primary transfer means (primary transfer members), a cleaning device 10, and the like, and the drive roller 12 is driven to rotate by a drive source (not shown). The intermediate transfer belt 8 rotates.

  The image forming units 6Y, 6C, 6M, and 6K are arranged in a line immediately below the intermediate transfer belt 8 as an intermediate transfer member so that toner images of Y, C, M, and K colors are sequentially formed. . When the intermediate transfer belt 8 passes through the nip portions of the transfer bias rollers 9Y, 9C, 9M, and 9K and the photosensitive members 1Y, 1C, 1M, and 1K, the transfer bias rollers 9Y, 9C, 9M, and The toner images of the respective colors formed on the photoreceptors 1Y, 1C, 1M, and 1K are sequentially superimposed and transferred by a transfer electric field due to a transfer bias applied to 9K to form a full color image.

  A paper feeding device having a paper feeding cassette 26 and a paper feeding roller 27 is disposed below the exposure device 7. A plurality of transfer papers P as recording materials are stored in the paper feed cassette 26, and the uppermost transfer paper P is fed by a paper feed roller 27 and conveyed to a registration roller 28. The registration roller 28 rotates at a timing to convey the transfer paper P to the secondary transfer nip portion.

  The secondary transfer backup roller 12 forms a secondary transfer nip portion by sandwiching the intermediate transfer belt 8 between the secondary transfer roller 19 as a secondary transfer means (secondary transfer member), and a secondary transfer nip is formed from a power source (not shown). A transfer bias is applied to the transfer roller 19 to form a transfer electric field. The full color image formed on the intermediate transfer belt 8 is transferred onto the transfer paper P by the transfer electric field at the secondary transfer nip portion. The secondary transfer roller 19 is brought into contact with the intermediate transfer belt 8 during transfer of a full-color image and separated at other times by a contact / separation mechanism as contact / separation means (not shown). The transfer paper P on which the full-color image is transferred at the secondary transfer nip portion is fixed with the full-color image by heat and pressure when passing through the nip portion between the fixing roller 20a and the pressure roller 20b of the fixing device 20. The paper is discharged outside by a paper discharge roller. In each of the image forming units 6Y, 6C, 6M, and 6K, the residual toner is removed by the cleaning devices 2Y, 2C, 2M, and 2K after the toner image is transferred, and a static eliminator (not shown) is used. The charge is removed to prepare for the next image formation.

  A plurality of optical sensors 40 (40Y and 40C shown in FIG. 2) are disposed near the secondary transfer backup roller 12, that is, immediately above the secondary transfer nip portion in the rotation direction of the intermediate transfer belt 8. , 40M, 40K) are arranged in a direction perpendicular to the rotation direction of the intermediate transfer belt 8 and are provided facing downward on the surface of the intermediate transfer belt 8. The plurality of optical sensors 40 are light-reflective photosensors, and detect the toner adhesion amount of each color toner adhesion pattern formed outside the image forming area on the intermediate transfer belt 8.

  Each of the developing devices 5Y, 5C, 5M, and 5K contains a two-component developer containing magnetic toners and carriers of Y, C, M, and K colors, and the two-component developer is stirred by a stirring member. The developing rollers 51Y, 51C, 51M, and 51K as the developer carrying member carry and carry the developer by an internal magnet. The developer on the developing rollers 51Y, 51C, 51M, and 51K is regulated to a fixed amount by a doctor member (not shown), and the electrostatic latent images on the photoreceptors 1Y, 1C, 1M, and 1K are the photoreceptors 1Y, 1C, 1M, and 1K. Development on the developing rollers 51Y, 51C, 51M, and 51K of the developing devices 5Y, 5C, 5M, and 5K in the developing area between the top and the developing rollers 51Y, 51C, 51M, and 51K of the developing devices 5Y, 5C, 5M, and 5K Developed with an agent. The toner concentration of the two-component developer in each of the developing devices 5Y, 5C, 5M, and 5K is detected by a toner concentration sensor as a toner concentration detecting unit (not shown). A predetermined developing bias is applied to the developing rollers 51Y, 51C, 51M, and 51K from a developing bias power source (not shown). The developing devices 5Y, 5C, 5M, and 5K are replenished with toner of each color Y, C, M, and K via paths 52Y, 52C, 52M, and 52K, respectively, from a toner replenishing device (not shown).

  The present embodiment has a mode for forming a full-color image as described above, but further, only one of the image forming units 6Y, 6C, 6M, and 6K is operated to form a monochrome image on the transfer paper P. Mode and a mode in which only two of the image forming units 6Y, 6C, 6M, and 6K are operated to form a two-color image on the transfer paper P.

  FIG. 2 shows a part of the control system in this embodiment. The main control unit 30 as a control means is constituted by a microcomputer having a CPU 32, a RAM 33, a ROM 34, and an I / O interface 35. The main control unit 30 receives setting information and the like from an operation panel as an operation unit (not shown), and also includes a black photosensor 40K, a yellow photosensor 40Y, and a cyan photosensor 40C as black optical sensors. Detection information from the magenta photosensor 40M and detection information from the toner density sensor are input.

Next, the image forming condition control operation of this embodiment will be described.
In the present embodiment, there are the following operations for automatically adjusting the image forming conditions around the photoreceptors 1Y, 1C, 1M, and 1K.
(1) Initial setting of light-reflective photosensors 40Y, 40C, 40M, and 40K The main control unit 30 outputs the photosensors 40Y, 40C, 40M, and 40K to the background portion of the surface of the primary transfer belt 8 as an intermediate transfer belt. Based on Vsg, the light emitting portions of the photosensors 40Y, 40C, 40M, and 40K are controlled to set the output Vsg of the photosensors 40Y, 40C, 40M, and 40K to the background portion of the surface of the primary transfer belt 8 to 4.0 v. . This is because the output Vsg of the photosensors 40Y, 40C, 40M, and 40K with respect to the background portion of the surface of the intermediate transfer belt 8 depends on the sensitivity of the photosensors 40Y, 40C, 40M, and 40K, and the reflectance of the photoconductors 1Y, 1C, 1M, and 1K. Since it changes, this operation is essential when the intermediate transfer belt 8 and the photosensors 40Y, 40C, 40M, and 40K are replaced.
(2) Surface potential control of the photoreceptors 1Y, 1C, 1M, and 1K The main control unit 30 controls the power supply for the charging device (not shown) to transfer the surface potential of the photoreceptor from the power supply for the charging device to the charging devices 4Y, 4C, 4M, and 4K. A lower level of charging voltage than that during normal image formation is applied at the time of control, and the level of background stain on the intermediate transfer belt 8 to which toner is transferred from the area where the background stain on the surface of the photoreceptors 1Y, 1C, 1M, and 1K occurs. (Toner adhesion amount) is detected by the photosensors 40Y, 40C, 40M, and 40K. The main control unit 30 feeds back the charging device power supply based on the detection results of the photosensors 40Y, 40C, 40M, and 40K and applies the voltage applied from the charging device power supply to the charging devices 4Y, 4C, 4M, and 4K. By controlling, the surface potentials of the photoreceptors 1Y, 1C, 1M, and 1K are controlled. Since the surface potential fluctuations of the photoconductors 1Y, 1C, 1M, and 1K occur due to the film scraping of the photoconductors 1Y, 1C, 1M, and 1K over time and the deterioration of sensitivity, the surface of the photoconductors 1Y, 1C, 1M, and 1K The potential control needs to be executed sequentially.
(3) Development potential potential control The main control unit 30 fixes the semiconductor laser light emission power of the exposure device 7 and the voltage applied from the charging device power supply to the charging devices 4Y, 4C, 4M, and 4K, and controls the developing bias power source. By changing the developing bias voltage from the developing bias power source to the developing rollers of the developing devices 5Y, 5C, 5M, and 5K in multiple steps, a plurality of toner adhesion patterns can be statically formed on the surfaces of the photoreceptors 1Y, 1C, 1M, and 1K. An electrostatic latent image is formed. The electrostatic latent images of the plurality of toner adhesion patterns are developed by the developing devices 5Y, 5C, 5M, and 5K to become a plurality of toner adhesion pattern images having different toner adhesion amounts. These toner adhesion pattern images are transferred outside the image forming area of the intermediate transfer belt 8, and the toner adhesion amounts of the toner adhesion pattern images are detected by the photosensors 40Y, 40C, 40M, and 40K. The main control unit 30 adjusts and determines the developing bias voltage by controlling the developing bias power supply so that the toner adhesion amount detected by the photosensors 40Y, 40C, 40M, and 40K becomes a target value.
(4) Setting of toner density control reference value When the machine of this embodiment is left for a long time, the toner density control level may change due to a decrease in toner charge amount. Therefore, the main control unit 30 fixes the semiconductor laser emission power of the exposure device 7 and the voltage applied to the charging devices 4Y, 4C, 4M, and 4K from the charging device power source, and controls the developing bias power source to control the developing bias power source. By changing the developing bias voltage to the developing rollers of the developing devices 5Y, 5C, 5M, and 5K in multiple stages, electrostatic latent images of a plurality of toner adhesion patterns are formed on the surfaces of the photoreceptors 1Y, 1C, 1M, and 1K. To do. The electrostatic latent images of the plurality of toner adhesion patterns are developed by the developing devices 5Y, 5C, 5M, and 5K to become toner adhesion pattern images, and are transferred outside the image forming area of the intermediate transfer belt 8. The photosensors 40Y, 40C, 40M, and 40K detect the toner adhesion amount of the toner adhesion pattern, and the main control unit 30 develops the developing devices 5Y, 5C, and 5M according to the detection results of the photosensors 40Y, 40C, 40M, and 40K. Control (optimize) the control reference value (toner density control reference value) of the toner density sensor for detecting the toner density of the developer within 5K.
(5) Developer Stirring In order to recover the toner charge amount that has decreased after leaving the machine in the present embodiment as in (3) above, the main control unit 30 uses the stirring members in the developing devices 5Y, 5C, 5M, and 5K. The agitating member is driven to rotate by controlling the drive unit that rotationally drives the developer in the developing devices 5Y, 5C, 5M, and 5K.
(6) Toner replenishment control The main control unit 30 calculates a toner replenishment time from the output signal of the toner density sensor, the toner density control reference value, and pixel detection data (pixel data detected from the image signal). The toner replenishing motor that causes the toner replenishing device to replenish the toner is driven for the toner replenishing time.
(7) Halftone correction The main control unit 30 controls the development bias power source and the charging device power source to output a predetermined development bias voltage and charging voltage, and changes the emission power of the semiconductor laser in the exposure device 7. An electrostatic latent image is formed on the surface of each of the photoreceptors 1Y, 1C, 1M, and 1K, and this electrostatic latent image is developed by developing devices 5Y, 5C, 5M, and 5K, thereby forming a plurality of toner adhesion patterns. These toner adhesion pattern images are transferred outside the image forming area of the intermediate transfer belt 8, and the toner adhesion amounts of the toner adhesion pattern images are detected by the photosensors 40Y, 40C, 40M, and 40K. The main control unit 30 obtains input / output characteristics of the developing devices 5Y, 5C, 5M, and 5K from the output signals of the photosensors 40Y, 40C, 40M, and 40K, and the semiconductor in the exposure apparatus 7 so that these characteristics become target values. Change the laser emission power.
(3) The development potential potential control and (7) halftone correction are required for a relatively long time because 10 patterns with different toner adhesion amounts are formed.
The toner adhesion patterns formed outside the normal image forming areas on the photoreceptors 1Y, 1C, 1M, and 1K are transferred onto the intermediate transfer belt 8 and are arranged downstream of the secondary transfer process. , 40M, and 40K detect the amount of reflected light, that is, the toner adhesion amount. At this time, the secondary transfer roller 19 is separated from the intermediate transfer belt 8 by contact / separation means (not shown) so as not to disturb the toner adhesion pattern on the intermediate transfer belt 8.

  In the present embodiment, the photosensors 40Y, 40C, 40M, and 40K are disposed downward in the vicinity of the driving roller 12, that is, immediately after the secondary transfer process, in order to avoid contamination such as toner scattering. In addition, in order to detect the toner adhesion patterns of four colors K, M, C, and Y in as short a time as possible, a total of four toner adhesion patterns can be detected exclusively for each color in the sub-scanning direction on the intermediate transfer belt 8. The light-reflective photosensors 40Y, 40C, 40M, and 40K are arranged to enable simultaneous detection of the toner adhesion patterns of the four photosensors 40Y, 40C, 40M, and 40K. That is, the photosensors 40Y, 40C, 40M, and 40K are arranged in a line at a predetermined interval in a direction perpendicular to the rotation direction (sub-scanning direction) of the intermediate transfer belt 8.

Next, the arrangement of the photosensors 40Y, 40C, 40M, and 40K and the image forming condition control toner adhesion patterns for each color will be described with reference to FIG.
In the present embodiment, in order to shorten the execution time of the control operation as described above, the four photosensors 40Y, 40C, 40M, and 40K are arranged in the main scanning direction as described above. The operation can be executed with the following three control specifications.
Array A
The array A includes photosensors 40Y, 40C, 40M, and 40K as shown in FIG. 3A and toner adhesion patterns for controlling the image forming conditions of each color on the intermediate transfer belt 8 (black toner adhesion pattern KP, yellow toner). An adhesion pattern YP, cyan toner adhesion pattern CP, magenta toner adhesion pattern MP), and all four sensors 40Y, 40C, 40M, and 40K have toner adhesion patterns KP, YP, CP, and MP for each color. Is detected.

  The photosensors 40Y, 40C, 40M, and 40K are arranged at predetermined intervals in a direction perpendicular to the rotation direction of the intermediate transfer belt 8. The photosensors 40Y, 40C, 40M, and 40K are arranged on the intermediate transfer belt 8. The toner adhesion patterns KP, YP, CP, and MP for each color are created in the sub-scanning direction (the rotation direction of the intermediate transfer belt 8) in accordance with the positions of the image sensors 40Y, 40C, and 40M. , 40K detect toner adhesion pattern images KP, YP, CP, and MP having different toner adhesion amounts, and the main controller 30 calculates the toner adhesion amounts.

Since the toner adhesion patterns KP, YP, CP, and MP for four colors are simultaneously formed and detected for each position P1 to P10 on the intermediate transfer belt 8, detection of the toner adhesion patterns KP, YP, CP, and MP is performed. The time required for this is substantially equivalent to only one color. The arrangement A is the most effective toner adhesion pattern arrangement for shortening the operation time. However, since the photosensors to be detected are different for each color, the arrangement A is easily affected by variations in the characteristic values of the photosensors. Slightly disadvantageous for image quality degradation. The main control unit 30 sets the pattern array A to the initial setting state.
Array B
In the arrangement B, only two photosensors 40K and 40M at both ends are used, the photosensor 40K on the front side is a black photosensor, and the black toner adhesion pattern KP is set in the middle corresponding to the position on the intermediate transfer belt 8. An image is formed on the transfer belt 8. On the other hand, the photosensor 40M on the back side is a photosensor for Y, C, and M, and forms ten Y, C, and M toner adhesion patterns YP, CP, and MP in correspondence with the positions.

In this array B, the photosensor 40M1 on the back side detects three colors (30 toner adhesion patterns), so the time required for detecting the toner adhesion pattern is three times as long as that in the above array A. Although there are disadvantages, since the three color toner adhesion patterns Y, C, and M are detected for one photosensor 40M, the detection results of the three color toner adhesion patterns YP, CP, and MP vary in the characteristics of the photosensors. It is possible to uniformly control the toner adhesion amount of the three color toner adhesion patterns. The main control unit 30 is configured such that, for example, when one or two photosensors have failed or become undetectable due to toner scattering, etc., or in a state where there is a time margin, and the characteristics between the photosensors as described above. Switch to the array B for the purpose of active use such as when it is desired to avoid variations.
Array C
The array C is an array in which the black toner adhesion pattern is further detected by the single photosensor 40M in the array B described above. Since the toner adhesion pattern for four colors is detected by one photosensor 40M, the time required for detection of the toner adhesion pattern is four times that of the arrangement A. There is an advantage that the image forming condition can be controlled by the remaining sensors even when the unit fails or cannot be detected.
For reducing the variation in characteristics of the photosensor, the arrangement B is usually sufficient.

The use state / use history information indicating the use state or use history of the image forming apparatus main body according to the present embodiment includes the following, and the use state / use history information recognition unit that recognizes the use state / use history information. There are the following.
Full-color image forming frequency information: The main control unit 30 counts the number of transfer sheets P on which a full-color image has been formed, and the total image forming counter that counts all the numbers of transfer sheets P on which images have been formed. And a counter. The full-color image forming counter and the entire image forming counter are included in the main control unit 30. Accordingly, the main control unit 30 also serves as a use state / use history information recognition unit for recognizing use state / use history information such as the number of full-color images formed and the total number of formed images.
Information about whether or not it is immediately after a print (image formation) operation: The main control unit 30 stores a print (image formation) job reception signal, and prints (image formation) based on the print job reception signal It is determined whether or not it is immediately after the operation, and information indicating whether or not it is immediately after the printing (image forming) operation is obtained. Therefore, the main control unit 30 also serves as a use state / use history information recognition unit for recognizing information indicating whether or not the print (image formation) operation is immediately after.
Current time information: The main control unit 30 acquires the current time from the built-in clock of the image forming apparatus main body of the present embodiment. Therefore, the main control unit 30 also serves as a use state / use history information recognition unit for recognizing current time information.
Elapsed time information after the end of the previous image forming operation: The main control unit 30 obtains an elapsed time after the end of the previous image forming operation from the built-in clock of the image forming apparatus main body of the present embodiment, or a timer. Causes the elapsed time from the end of the previous imaging operation to be counted. Therefore, the main control unit 30 also serves as a use state / use history information recognition unit that recognizes an elapsed time since the end of the previous image forming operation.
Normal / abnormal information of optical sensors 40Y, 40C, 40M, and 40K outputs ... The main control unit 30 determines the optical sensors 40Y, 40Y, 40C, 40M, and 40K from the output signals (initial adjustment values, etc.) of the photosensors 40Y, 40C, 40M, and 40K. It is determined whether the 40C, 40M, and 40K outputs are normal or abnormal. Therefore, the main control unit 30 also serves as a use state / use history information recognition unit for recognizing whether the outputs of the optical sensors 40Y, 40C, 40M, and 40K are normal or abnormal.

  In this embodiment, since the optical sensors 40Y, 40C, 40M, and 40K are arranged downstream of the secondary transfer portion in the rotation direction of the intermediate transfer belt 8, the toner adhesion pattern on the intermediate transfer belt 8 is detected by the optical sensor 40Y. , 40C, 40M, and 40K, the secondary transfer roller 19 needs to be separated from the intermediate transfer belt 8 by contact / separation means (not shown).

  The main control unit 30 uses the optical sensors 40Y, 40C, 40M, and 40K according to the use state / use history information of the use state / use history information recognition means (according to the use state / use history of the present embodiment). Of these, the optical sensor used and the array switching means for switching the arrays A, B, and C by switching the creation position of the toner adhesion pattern are also used.

For example, the main control unit 30 switches to the array A immediately after the image forming operation based on the use state / use history information of the use state / use history information recognizing means, and generates a toner adhesion pattern for halftone density correction control. create. The case where a toner adhesion pattern for halftone density correction control is created in array A immediately after this image forming operation will be described in detail below.
After the trailing edge of the image of the final print (final formation) on the intermediate transfer belt 8 has passed the secondary transfer step, the contact / separation means separates the secondary transfer roller 19 from the intermediate transfer belt 8 under the control of the main controller 30. The separating operation is started. Thereafter, the main control unit 30 controls the image forming units 6Y, 6C, 6M, and 6K to create toner adhesion patterns for the respective colors. That is, the main control unit 30 controls the developing bias power source and the charging device power source to output a predetermined developing bias voltage and a charging voltage, and changes the light emission power of the semiconductor laser in the exposure device 7 to change the photoconductor 1Y, An electrostatic latent image is formed on the surface of 1C, 1M, and 1K, and this electrostatic latent image is developed by developing devices 5Y, 5C, 5M, and 5K, thereby creating a plurality of toner adhesion patterns KP, YP, CP, and MP. Let me image. These toner adhesion patterns KP, YP, CP, MP are transferred outside the image forming area of the intermediate transfer belt 8, and the toner adhesion amounts of the toner adhesion patterns KP, YP, CP, MP are photosensors 40Y, 40C, 40M, Detected at 40K. The main control unit 30 obtains input / output characteristics of the developing devices 5Y, 5C, 5M, and 5K from the output signals of the photosensors 40Y, 40C, 40M, and 40K, and the semiconductor in the exposure apparatus 7 so that these characteristics become target values. Change the laser emission power.

  When the toner adhesion patterns KP, YP, CP, and MP of each color are created on the intermediate transfer belt 8, the most upstream side image formation (the main image formation) is compared with the most downstream side image formation (the black image formation in this embodiment). In the embodiment, yellow image formation) is on the upstream side by the distance between the image formation units 6Y and 6K, so that the toner adhesion patterns KP, YP, CP, and MP of all colors are represented by the optical sensors 40Y, 40C, 40M, and 40K. Until the detection is completed, a moving time that is three times the distance between the image forming units 6Y, 6C, 6M, and 6K of the intermediate transfer belt 8 (the distance between the image forming units 6Y to 6K) becomes a loss time.

  Accordingly, the main control unit 30 causes the image formation units 6Y, 6C, 6M, and 6K for each color to form a toner adhesion pattern immediately after the image formation at the rear end of the final print image is completed. That is, the main control unit 30 sequentially attaches toner immediately after image formation at the rear end of the print image from the most upstream side (yellow image forming unit 6Y side) toward the most downstream side (black image forming unit 6K side). By creating the pattern, the toner adhesion patterns KP, YP, CP, and MP of the respective colors are formed in parallel on the intermediate transfer belt 8 in the same state as the print image (formed image). Avoid such loss time.

  In the separation operation of the secondary transfer roller 19 with respect to the intermediate transfer belt 8, the secondary transfer roller 19 is separated from the intermediate transfer belt 8 immediately after the rear end of the print image has passed the secondary transfer step, so The toner adhesion patterns KP, YP, CP, and MP are not transferred to the secondary transfer roller 19, and even if an impact is generated during the separation operation, the impact of the impact on the toner adhesion pattern is not improved after the secondary transfer. Since it is only a moment during the separation operation of the secondary transfer roller 19, only the toner adhesion pattern formed by the main control unit 30 at that timing is excluded from the detection target, and the impact has a great influence on the halftone correction control. And halftone correction control can be executed in a short time.

  As described above, when the parallel processing by the plurality of optical sensors 40Y, 40C, 40M, and 40K as in the array A is executed, the toner adhesion patterns are sequentially arranged from the upstream side to the downstream side in the rotation direction of the primary transfer belt 8. By forming the images, it is possible to reduce the loss time of detecting a plurality of toner adhesion patterns and to shorten the execution time.

  Next, a case where the toner adhesion patterns KP, YP, CP, and MP are created and detected in the array C will be described. As shown in FIG. 3C, since only one optical sensor 40M is used, a plurality of toner adhesion patterns KP, YP, and the like simultaneously in the main scanning direction perpendicular to the rotation direction of the intermediate transfer belt 8 are used. CP and MP cannot be created. Accordingly, the main control unit 30 controls the image forming units 6Y, 6C, 6M, and 6K to create the toner adhesion patterns KP, YP, CP, and MP for each color so as to be aligned in the sub-scanning direction. Regardless of whether the image formation order of the toner adhesion patterns KP, YP, CP, and MP of each color is the same as that of the array A or the reverse image formation order, the toner adhesion pattern of one color is the primary transfer belt 8. Immediately after the formation on the top, the image forming timing is determined so that the toner adhesion pattern of the next color is formed on the primary transfer belt 8, so that no loss time is generated.

  However, in order to avoid the influence of the impact at the time of separation of the secondary transfer roller 19, the secondary transfer roller 19 is brought into contact with the primary transfer belt 8 by the contacting / separating means immediately after the rear end of the image of the final print has passed the secondary transfer process. The operation sequence of creating and detecting the toner adhesion pattern immediately after the separation is essential. In this case, when the creation of the toner adhesion pattern is started from the most upstream side (yellow image forming unit 6Y side), the intermediate transfer belt 8 is formed on the most downstream side (black image forming unit 6K side) from the image forming start position. A plurality of toner adhesion pattern detection loss times occur as much as the distance to the image position is moved. On the other hand, when the creation of the toner adhesion pattern is started from the most downstream side (the black image forming unit 6K side), the formation and detection of the toner adhesion pattern is started from the position closest to the secondary transfer process, so the loss time Disappears.

  Therefore, the main control unit 30 controls the image forming units 6Y, 6C, 6M, and 6K for the respective colors when performing the series of toner adhesion pattern creation and detection by one optical detection sensor such as the array C. Then, from the downstream side to the upstream side in the rotation direction of the primary transfer belt 8, an image is formed in order of [black toner adhesion pattern KP → magenta toner adhesion pattern MP → cyan toner adhesion pattern CP → yellow toner adhesion pattern YP. In this way, the loss time of detecting a plurality of toner adhesion patterns is reduced, and the execution time is shortened.

  When the image formation of the toner adhesion pattern of the next color is started after the image formation of the tenth toner adhesion pattern of one color is completed, the moving time of the distance between the image forming units 6Y, 6C, 6M, 6K Therefore, the main controller 30 controls each of the image forming units 6Y, 6C, 6M, and 6K to suppress the occurrence of the loss time, and the tenth toner adhesion pattern for one color is controlled. After the image formation is completed, an operation of moving the intermediate transfer belt 8 between the image formation units 6Y, 6C, 6M, and 6K by a distance and starting the toner adhesion pattern image formation operation for the next color is started. repeat.

In the case of array B, as shown in FIG. 3B, the main control unit 30 controls the image forming units 6Y, 6C, 6M, and 6K for each color to display [magenta toner adhesion pattern] and [cyan [Toner Adhesion Pattern] and [Yellow Toner Adhesion Pattern], in the same manner as in array C, images are formed in the order from the most downstream side (magenta toner adhesion pattern) to the most upstream side (yellow toner adhesion pattern). The toner adhesion amount of the toner adhesion pattern is detected by the optical sensors 40Y, 40C, and 40M on the intermediate transfer belt 8, and only one color of [Black toner adhesion pattern] is created, and only one color is created by the dedicated optical sensor 40K. Let it be detected. Therefore, the timing to start creating toner deposition pattern of black, the timing for starting image formation immediately after image formation of the image rear end of the final print, the main and Toner deposition pattern of yellow] on the primary transfer belt 8 Any position may be used as long as it is between a position aligned in the scanning direction and a timing for starting image formation. In this case, the timing at which the secondary transfer roller 19 is separated from the primary transfer belt 8 is [magenta toner adhesion pattern] passes through the secondary transfer process immediately after the image trailing edge of the final print passes through the secondary transfer process. Until the previous timing.

Next, a problem avoidance measure when the toner adhesion pattern creation and detection operation of array B or array C is repeated will be described.
In the array B or the array C, the two optical sensors 40M and 40K or the one optical sensor 40M detects the toner adhesion patterns KP, YP, CP, and MP of the plurality of colors, and thus the sub-scanning direction on the primary transfer belt 8 is detected. Thus, a plurality of toner adhesion patterns are formed.

  In the present embodiment, ten toner adhesion patterns of each color are formed, and in the case of the array B, 30 toner adhesion patterns are formed intensively in a very narrow sub-scanning region on the primary transfer belt 8. In the case of the arrangement C, 40 toner adhesion patterns are intensively formed in an extremely narrow region in the sub-scanning direction on the primary transfer belt 8, and there is a concern that the surface of the primary transfer belt 8 may be poorly cleaned.

  This tends to become conspicuous when the cleaning performance is deteriorated in a low temperature environment or when the cleaning device 10 is worn over time. Therefore, in order to avoid the occurrence of such a problem, in the present embodiment, the main control unit 30 calculates the frequency of creating the toner adhesion patterns of the arrays B and C, and the frequency increases to a predetermined value or more. In this case, the two optical sensors 40M, 40K or one optical sensor 40M to be used are switched at a predetermined toner adhesion pattern detection execution interval, and according to the optical sensor that uses the creation position of the toner adhesion pattern accordingly. Switch.

Regarding the switching timing of the optical detection sensor and the switching timing of the creation position of the toner adhesion pattern, the main control unit 30 executes the execution ratio of the arrays B and C with respect to the total number of executions (use count) of the arrays A, B, and C. (Use ratio) is 20% or more (initial).
Further, the main control unit 30 switches the optical detection sensor to be used at a predetermined toner adhesion pattern detection execution interval even when the number of executions of the arrays B and C is 10 or more times (initial) continuously. The toner adhesion pattern creation position is changed at a predetermined toner adhesion pattern detection execution interval.

Further, the main control unit 30 determines the timing of switching the optical sensor to be used or the timing of switching the creation position of the toner adhesion pattern as described above, that is, the execution ratio or the number of continuous executions of the arrays B and C described above. It changes according to the input information arbitrarily input from the main body operation part by the user according to the installation environment and the use state by the user.
Generally, in the cleaning device 10, the wear of the cleaning blade progresses with time, and the cleaning performance also decreases with time. In this embodiment, the operation amount (intermediate amount of the intermediate transfer belt 8 is detected by the intermediate transfer belt operation counter. The rotation driving time of the transfer belt 8 or the rotation driving distance of the intermediate transfer belt 8) is integrated and accumulated in the main body memory. The main control unit 30 switches the switching interval of the optical sensor used and the creation position of the toner adhesion pattern. The interval (the switching timing of the optical sensor to be used and the timing for switching the creation position of the toner adhesion pattern) is shortened according to the rotational drive time integrated value or the rotational drive distance integrated value of the intermediate transfer belt 8 stored in the main body memory. Change as follows.

  As described above, according to the present embodiment, the toner adhesion patterns KP, YP, CP, and MP for image adjustment are formed in the non-image areas on the photoreceptors 1Y, 1C, 1M, and 1K as image carriers. A plurality of optical sensors 40Y, 40C, and 40M that are primarily transferred onto an intermediate transfer belt 8 serving as an intermediate transfer member, and are provided perpendicular to the traveling direction of the intermediate transfer member 8 and opposed to the surface of the intermediate transfer member 8. , 40K to detect the toner adhesion amount of the toner adhesion patterns KP, YP, CP, and MP and change the image forming condition according to the detection value of the detection sensor to perform process control, or change the toner replenishment amount to change the toner density. The image forming apparatus having the main control unit 30 as control means for controlling includes means for recognizing the use state or use history of the image forming apparatus, and information recognized by the means. Accordingly, the plurality of optical sensors 40Y, 40C, 40C, 40C, 40C, 40C, 40K, 40C, 40M, 40K, and the plurality of optical sensors 40Y, 40C, An array A that uses a plurality of toner colors 40M and 40K in a one-to-one correspondence, and an array B that uses only two sensors, an optical sensor 40K dedicated to black toner and an optical sensor 40M for color toner And an optical sensor used in an image forming apparatus that switches the arrangement C in which all the toner colors correspond to one sensor 40M and changes the image forming order of each color depending on the plurality of toner adhesion pattern arrays A, B, and C. When the frequency of setting the arrangement of the toner adhesion patterns of multiple colors to B or C exceeds a predetermined value, an optical sensor and toner attached are used for detecting the toner adhesion amount. Since the pattern creation position is switched at a predetermined toner adhesion pattern detection execution interval, it is possible to suppress problems such as defective cleaning and filming of the primary transfer belt 8 due to a large number of toner adhesion patterns being concentrated in one place. .

  According to the present embodiment, since the optical sensor to be used and the creation position of the toner adhesion pattern are switched, a ratio in which the optical sensor to be used and the multi-color toner adhesion pattern array is B or C is used. Only when a burden is imposed on the cleaning of the transfer belt, the optical sensor to be used and the creation position of the toner adhesion pattern can be switched, and a simple control operation can be performed as much as possible.

  According to this embodiment, since the optical sensor to be used and the creation position of the toner adhesion pattern are switched, the continuous number of times that the optical sensor to be used and the multi-color toner adhesion pattern array is B or C is used. Only when a burden is imposed on the cleaning of the primary transfer belt, the optical sensor to be used and the creation position of the toner adhesion pattern can be switched, and a simple control operation can be performed as much as possible.

  According to the present embodiment, since the switching timing of the optical sensor to be used and the creation position of the toner adhesion pattern can be changed, the switching frequency can be changed more appropriately according to the installation environment and usage status of the image forming apparatus. Image adjustment operations such as toner density control can be performed without imposing a load on the cleaning of the primary transfer belt.

  According to this embodiment, the image forming apparatus includes the operation counter that integrates the operation amount of the intermediate transfer belt, and the optical sensor to be used or the toner adhesion pattern creation position switching timing according to the integrated value of the operation counter. Therefore, it is possible to prevent the occurrence of poor cleaning with respect to the intermediate transfer belt or the intermediate transfer belt cleaning device 10 whose cleaning ability has deteriorated over time.

  According to this embodiment, since the operation counter that accumulates the rotational driving time of the intermediate transfer belt is used as the operation counter, the position of the toner adhesion pattern creation can be determined without detecting the degree of decrease in the intermediate transfer belt cleaning capability. By increasing the frequency of switching, it is possible to prevent the occurrence of defective cleaning.

  According to the present embodiment, since the operation counter that accumulates the rotational driving distance of the intermediate transfer belt is used as the operation counter, the creation position of the toner adhesion pattern can be determined without detecting the degree of decrease in the intermediate transfer belt cleaning capability. By increasing the frequency of switching, it is possible to prevent the occurrence of defective cleaning.

It is sectional drawing which shows one Embodiment of this invention. It is a block diagram which shows a part of control system in the embodiment. FIG. 3 is a diagram illustrating an arrangement of a photosensor to be used and a toner adhesion pattern for controlling image forming conditions for each color in the embodiment.

Explanation of symbols

1Y, 1C, 1M, 1K Photoconductor 6Y, 6C, 6M, 6K Image forming unit 8 Intermediate transfer belt 19 Secondary transfer roller 40, 40Y, 40C, 40M, 40K Optical sensor 10 Cleaning device 30 Main control unit

Claims (2)

A plurality of sets of image forming means each having a developing device and respectively forming a plurality of color toner images on the image carrier, an intermediate transfer body driven to rotate, and the image carriers of the plurality of sets of image forming means A primary transfer means for primary transfer by superimposing the toner images of the respective colors formed thereon on the intermediate transfer member, and a transfer material for collectively transferring the toner images of the respective colors superimposed and primary on the intermediate transfer member. Secondary transfer means for secondary transfer to each other, and a toner adhesion pattern of each color for image adjustment is formed in a non-image area on each image carrier of each of the plurality of sets of image forming means, and these toner adhesion patterns are formed. Toner adhesion pattern forming means for primary transfer on the intermediate transfer body so as to be arranged in a direction perpendicular to the running direction of the intermediate transfer body, and the plurality of sets of image forming means facing the intermediate transfer body Front downstream A plurality of optical sensors that are arranged in a line at a predetermined interval in a direction perpendicular to the rotation direction of the intermediate transfer body and detect a toner adhesion pattern of each color on the intermediate transfer body, and a predetermined control operation based on a detection value of the sensor In the image forming apparatus having the control means for performing the above, the arrangement of the toner adhesion pattern of each color detected by the plurality of optical sensors and the optical sensor to be used among the plurality of optical sensors are the plurality of optical sensors. Two sensors, that is, an array A that uses a color sensor and a plurality of toner colors in a one-to-one correspondence, and an optical sensor dedicated to black toner and an optical sensor for color toner among the plurality of optical sensors Can be switched to an array B that uses all the toner colors and one of the plurality of optical sensors in correspondence with each other, , B, and C, the image forming order of the toner adhesion patterns of the respective colors by the plurality of sets of image forming means is varied, and the frequency with which the arrangement of the optical sensor and the toner adhesion pattern of each color is the array B or C is a predetermined value. When it is above, the optical sensor to be used among the plurality of optical sensors and the creation position of the toner adhesion pattern are switched at a predetermined toner adhesion pattern detection execution interval,
Includes a clock counter for integrating the rotation drive time of the intermediate transfer member, the timing of the switching of the creation positions of the timing or the toner deposition pattern of the switching of the optical sensor in which the use in accordance with the accumulated value of the clock counter An image forming apparatus that is changed.   2. The image forming apparatus according to claim 1, wherein the operation counter is a counter that integrates a rotational driving distance of the intermediate transfer member.

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