JP4639099B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a plotter, and more particularly to an image forming apparatus that performs process control or toner density control based on a detection result of a toner adhesion amount of a toner adhesion pattern.

An electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile, etc., uniformly charges an image carrier made of a photosensitive member with a charger, forms a latent image with an exposure device, and forms the latent image with a developer. The image is developed and transferred onto a transfer paper by a transfer device.
In this type of image forming apparatus, a toner adhesion pattern 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 replenishing device is selected according to the detection result Conventionally, a toner density control method for controlling toner replenishment to the developing device has been generally used.

  In this toner density control method, of the output values of the light reflection type photosensor, the output of the light reflection type photosensor for the toner adhesion pattern on the image carrier is Vsp, and the light reflection to the non-toner 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 is replenished from the toner replenishing device to the developing device. On the contrary, when Vsp / Vsg is low, it is determined that the toner concentration of the developer in the developing device is high, and the toner is not replenished. Thereby, the toner concentration in the developing device is kept constant.

  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 over time of the photoconductor and changes in sensitivity due to the usage environment of the copying machine, the surface potential of the photoconductor is controlled by a potential sensor. In general, image quality is stabilized by detecting and controlling the image forming conditions based on the detection result. However, the potential sensor is relatively expensive, and is not often installed except for high-end models.

  As a method of controlling the potential without the potential sensor, there is a method of detecting the background dirt level on the surface of the photoreceptor using a light reflection type photosensor for controlling the toner density. In this method, the image forming condition of the background dirt level detection region is set to a lower charging voltage to be applied than in a normal image portion so that the background potential, which is the difference between the dark portion potential Vd and the developing bias voltage Vb, is reduced. To do. Under this image forming condition, since the background stain is usually slightly generated, the output value Vsdp obtained by detecting this image forming region with the light reflection type photosensor is also slightly lower than Vsg. Even if the same charging voltage is applied, if the dark portion potential Vd varies due to photoreceptor deterioration, charging unit degradation, environmental variation, etc., the background stain level varies, and the variation in Vsdp increases. That is, the change in Vsdp is detected by a light reflection type photosensor, and control is performed so that Vd is fed back to the charging applied voltage so that Vd becomes a target potential.

  Further, in a color copying machine or a color printer, it is necessary to more strictly control the toner adhesion amount in a development process, a transfer process, and the like in order to superimpose a plurality of color toners. Therefore, image forming condition control such as halftone correction is indispensable. In these image forming condition controls, a plurality of image adhering patterns for image adjustment with different toner adhering amounts by changing the image forming conditions are created on an intermediate transfer belt (transfer member) or the like. Then, the image density of the plurality of toner adhesion patterns is detected by the light reflection type photosensor, and the image forming condition is set based on the detection result. Since it is necessary to create a plurality of toner adhesion patterns by changing the image forming conditions in this way, it is difficult to execute it at the same time as the normal image forming operation. It is necessary to pause the printer operation temporarily. Since this operation pause time is a downtime that makes it impossible for an operator of an image forming apparatus such as a copier or printer, the execution timing of the image forming condition control has an influence on the operation of the copy or printer as much as possible. The period when there is no is suitable, and generally it is often performed during warm-up immediately after the 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 main body and the down time between jobs as much as possible. As a measure for reducing this downtime, it is also effective to execute 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 it falls. 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.
In addition, for the various control operations described above, parallel processing is performed in which these operations are performed in parallel instead of serial, and other condition settings such as image formation condition control and toner density control reference value setting are completed in a short time. There is a need. As a method of shortening the execution time of the control operation by this parallel processing, a sensor multiple array method that simultaneously sets image forming conditions for a plurality of colors has been conventionally considered. This sensor multiple array system is a system in which a plurality of light-reflective photosensors for each color are arranged in the width direction of the transfer member (intermediate transfer belt or the like). Then, a toner adhesion pattern of each color is formed side by side in the width direction of the transfer member (intermediate transfer belt or the like), and the image density of the toner adhesion pattern of each color is simultaneously detected by the plurality of light reflective photosensors. Image forming conditions such as a color charging application voltage and a developing bias voltage are set.

JP 2002-91114 A JP 2002-287459 A JP 2003-186278 A Japanese Patent Laid-Open No. 7-168212

However, since the above-described sensor multiple arrangement method can simultaneously detect the image density of a plurality of color toner adhesion patterns as described above, it is effective in shortening the time in the case of an apparatus state in which the image forming speed is prioritized. There are problems like this. That is, 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. Due to the control variation for each toner color, there is a problem that it is not possible to cope with the case of an apparatus state in which high-precision image forming condition control is prioritized, and this may cause image quality defects such as color fluctuation.
Accordingly, the present applicant has proposed an image forming apparatus capable of performing image forming condition control by forming an optimal toner adhesion pattern according to the apparatus state of the image forming apparatus when the above-described sensor multiple array system is adopted ( (See Japanese Patent Application No. 2005-033386).

  The present invention relates to a further improvement of the proposed image forming apparatus. The purpose of the image forming apparatus is to form an optimum toner adhesion pattern according to the apparatus state of the image forming apparatus and execute the image forming condition control when the above-described sensor multiple array system is adopted. An object of the present invention is to provide an image forming apparatus capable of shortening the execution time of creation and detection of an adhesion pattern.

In order to achieve the above object, the invention of claim 1 includes a plurality of image carriers, a toner image forming unit that forms toner images of a plurality of colors composed of different color toners on each of the image carriers, Transfer means for transferring a toner image formed on each image carrier to the surface of a transfer member that moves at a transfer position facing the image carrier or a recording material that is carried and moved on the surface of the transfer member, and each image A plurality of image density detecting means for detecting a toner adhesion amount of each of the color adjustment toner adhesion patterns formed on the carrier and transferred onto the transfer member; and a toner adhesion amount of the plurality of color toner adhesion patterns. Control means for performing at least one of process control for changing an image forming condition and toner density control for changing a toner replenishment amount based on a detection result, and the plurality of image carriers have a surface movement direction of the transfer member. The plurality of image density detectors are arranged in a line, and are arranged in a direction intersecting the surface movement direction of the transfer member, and the image forming apparatus includes at least a use state and a use history of the apparatus main body. A device state recognizing unit for recognizing a device state including one of the devices, the device state recognizing the device state prioritizing the image forming speed by the device state recognizing unit, and the device state prioritizing highly accurate image forming condition control. switching between when recognizing by the state recognition means, a sequence of a plurality of colors toner adhesion pattern formed by transferring onto the transfer member, and order of image formation timing of the toner deposition pattern of the plurality of colors, and image formation If the priority device status speed recognized by the device status recognition means is formed by different color toners as a one-to-one correspondence with the plurality of image density detection means Toner deposition pattern of a plurality of rows are formed that, when it is recognized by the device state recognizing means priority device status with high accuracy image forming condition control, corresponding to one of said plurality of image density detection means Thus, one row of toner adhesion patterns formed sequentially with the above-described plurality of colors of toner is formed .
Also, the invention of claim 2, a plurality of image bearing members, a toner image forming means for forming a toner image of a plurality of colors of a toner of a different color from each other in the respective image carriers, each image carrier and the opposite A transfer means for transferring the toner image formed on each image carrier to the surface of the intermediate transfer member that moves the transfer position, a secondary transfer member that can contact and separate from the surface of the intermediate transfer member, A plurality of image density detecting means for detecting a toner adhesion amount of each of the plurality of color image adjustment toner adhesion patterns formed on the image bearing member and transferred onto the intermediate transfer material; and the toner adhesion of the plurality of color toner adhesion patterns Control means for performing at least one of process control for changing the image forming condition and toner density control for changing the toner replenishment amount based on the detection result of the amount, and the plurality of image carriers are moved on the surface of the intermediate transfer member. Line up in the direction And the plurality of image density detecting means are arranged so as to be aligned in a direction intersecting the surface movement direction of the intermediate transfer member, and the toner image on the intermediate transfer member transferred to the recording material is subjected to secondary transfer. An image forming apparatus in which the secondary transfer member is separated from the intermediate transfer member after passing through a position, and the toner adhesion pattern is formed after the separation of the secondary transfer member. A device state recognizing unit that recognizes a device state including at least one of histories, and a device state that prioritizes highly accurate image forming condition control when a device state that prioritizes image forming speed is recognized by the device state recognizing unit. In the case where the apparatus state recognition means recognizes the arrangement of the plurality of color toner adhesion patterns formed on the intermediate transfer member and the order of the image formation timing of the plurality of color toner adhesion patterns. When switching, and if the priority device state image formation speed recognized by the device state recognition unit, the toner deposition pattern of a plurality of rows corresponding to the plurality of image density detection unit is formed, the intermediate transfer start the image forming toner adhesion patterns in order from the most upstream image bearing member in a surface movement direction of the body to the downstream image bearing member, a high image forming condition control the device state priority device state accuracy When recognized by the recognizing unit, a row of toner adhesion patterns corresponding to one of the plurality of image density detecting units is formed, and the most downstream image carrier in the surface movement direction of the intermediate transfer member is formed. Image formation of the toner adhesion pattern is started in order from the body to the upstream image carrier.
According to a third aspect of the present invention, a plurality of image carriers, a toner image forming unit for forming a plurality of color toner images made of different colors of toner on each image carrier, and each image carrier are opposed to each other. Transfer means for transferring the toner image formed on each image carrier to the surface of the transfer member that moves the transfer position or a recording material that is carried and moved on the surface of the transfer member; Based on a plurality of image density detection means for detecting the amount of toner adhesion of each of the plurality of color image adjustment toner adhesion patterns transferred onto the transfer member, and a detection result of the toner adhesion amount of the plurality of color toner adhesion patterns, Control means for performing at least one of process control for changing image forming conditions and toner density control for changing toner replenishment amount, and the plurality of image carriers are arranged so as to be aligned in the surface movement direction of the transfer member. The plurality of image density detection means are image forming apparatuses arranged to be aligned in a direction intersecting the surface movement direction of the transfer member, and the apparatus state includes at least one of a use state and a use history of the apparatus body. A device state recognition unit is provided for recognizing the device state prioritizing the image forming speed by the device state recognizing unit and the device state recognizing the device state prioritizing highly accurate image forming condition control. In some cases, switching between the arrangement of the plurality of color toner adhesion patterns formed by transferring onto the transfer member and the order of image formation timing of the plurality of color toner adhesion patterns, the plurality of image carriers, It is composed of an image carrier on which a toner image of black toner is formed and a plurality of image carriers on which toner images of color toners of different colors other than black toner are formed. The arrangement of the toner adhesion pattern includes a first arrangement composed of a plurality of rows of toner adhesion patterns formed of different color toners so as to correspond one-to-one with the plurality of image density detection means, and the black toner only. A black toner adhesion pattern formed with black toner so as to correspond to one image density detecting means, and a plurality of color toners sequentially corresponding to one image density detecting means for the color toner. A second array of color toner adhesion patterns formed in one row and a third array of toner adhesion patterns formed in sequence of the plurality of color toners so as to correspond to one image density detecting means. It is characterized by including these.
According to a fourth aspect of the present invention, in the image forming apparatus of the third aspect , when switching to the first arrangement, the image carrier on the downstream side from the image carrier on the most upstream side in the surface movement direction of the transfer member. When the image formation of the toner adhesion pattern is started in order on the body and switched to the second arrangement, the color toner adhesion pattern is transferred from the image carrier on the most downstream side in the surface movement direction of the transfer member. When image formation of the toner adhesion pattern is started in order on the upstream image carrier and switched to the third arrangement, the upstream image from the most downstream image carrier in the surface movement direction of the transfer member. The image forming of the toner adhesion pattern is started in order on the carrier.

  The “column” of the toner adhesion patterns in the above array includes not only one in which two or more toner adhesion patterns are arranged, but also one consisting of one toner adhesion pattern.

According to the present invention, the device state recognition unit recognizes a device state including at least one of the use state and the use history of the device body. Based on the recognition result of the device state, when the device state that prioritizes the image forming speed is recognized by the device state recognizing unit, and when the device state that prioritizes high-precision image forming condition control is recognized by the device state recognizing unit. Thus, the arrangement of the toner adhesion patterns of a plurality of colors formed by transferring onto the transfer member is switched. Here, when the apparatus state giving priority to the image forming speed is recognized, the toner adhesion pattern is switched to the following arrangement. In other words, each of the image density detecting means arranged so as to be arranged in a direction intersecting with the surface movement direction of the transfer member can detect the image density of the toner adhesion patterns having different colors in parallel. Switch to an array. In addition, when an apparatus state that prioritizes high-precision image forming condition control is recognized, the toner adhesion pattern of all colors is detected by one image density detection unit in consideration of variations in detection characteristics of the image density detection unit. Is switched to an arrangement of toner adhesion patterns that can detect the image density of the toner. As described above, a plurality of color toners formed by transferring onto a transfer member when a device state that prioritizes image forming speed is recognized and when a device state that prioritizes highly accurate image forming condition control is recognized. By switching the arrangement of the adhesion patterns, it is possible to create an appropriate toner adhesion pattern and detect the image density according to the state of the apparatus. Therefore, in each of the apparatus state that prioritizes the image forming speed and the apparatus state that prioritizes highly accurate image forming condition control, an optimal toner adhesion pattern corresponding to the apparatus state is formed to control the image forming condition. Can be executed.
Here, the plurality of image carriers are arranged so as to be aligned in the surface movement direction of the transfer member, and the toner adhesion pattern formed on each image carrier has a position of the transfer member passing through a position facing each image carrier. Sequentially transferred to the surface. Accordingly, when the image formation timing of the toner adhesion pattern on the image carrier of each color changes, the position of the toner adhesion pattern of each color transferred to the transfer member changes. For this reason, depending on how the image formation timing of each color toner adhesion pattern is set, the time required to create and detect all of the toner adhesion patterns for each of the switching target arrays becomes longer than necessary. May occur. Therefore, in the present invention, the arrangement of the toner adhesion pattern is switched between a case where the apparatus state prioritizing the image forming speed is recognized and a case where the apparatus state prioritizing the high-accuracy image forming condition control is switched. The order of image forming timings of the color toner adhesion patterns is switched. By switching the order of the image formation timings of the toner adhesion patterns, the toner adhesion patterns of each array can be created and detected in the minimum necessary time according to the arrangement of the toner adhesion patterns. Accordingly, there is an effect that it is possible to shorten the execution time of the creation and detection of the toner adhesion pattern used for the image forming condition control.

Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 3.
First, an outline of an electrophotographic laser copying machine (hereinafter referred to as “copying machine”) as an image forming apparatus in the present embodiment will be described with reference to FIG. The normal image forming operation of this copying machine is general as shown below. That is, the document on the contact glass is exposed by an exposure lamp (not shown), and the reflected light is read by the scanner. An analog signal read by the scanner is converted into a digital signal by an AD converter (not shown) and becomes image data of a document. The photosensitive member 1 uniformly charged by the charging device 4 is irradiated with a laser from a light source (for example, a semiconductor laser: LD) modulated based on image data by the exposure device 7 to correspond to the image of the document. An electrostatic latent image is formed on the photoreceptor 1. The electrostatic latent image on the photoreceptor 1 is visualized by the developing device 5 and becomes a toner image. The toner image on the photoreceptor 1 is transferred onto a primary transfer belt 6 which is an intermediate transfer member as a transfer member, and further transferred onto a transfer paper P as a recording material in a secondary transfer step. The transfer paper P onto which the toner image has been transferred is finally discharged through the fixing device 20.

  A plurality of photoreceptors on which toner images of different colors (yellow, cyan, magenta, black) are formed are formed in the order of yellow (yellow), cyan (cyan), magenta (magenta), and black (black). As described above, they are arranged in parallel immediately below the primary transfer belt 8. Image forming stations (image forming units) as toner image forming means of a plurality of sets (four sets in the present embodiment) are arranged around the corresponding photoconductor as one station for each toner color, and yellow (yellow) ), Cyan (cyan), Magenta (magenta), and Black (black) in this order, they are arranged in parallel immediately below the primary transfer belt 8.

  More specifically, the copying machine according to the present embodiment includes four image forming stations (image forming units) for generating toner images of yellow, cyan, magenta, and black (hereinafter referred to as Y, C, M, and K). Image units) 6Y, 6M, 6C, 6K. These use Y, C, M, and K toners of different colors as image forming substances, but the other configurations are the same and are replaced when the lifetime is reached.

The structure of the image forming station 6Y for generating a Y toner image will be described as a representative. The image forming station 6Y includes a drum-shaped photosensitive member 1Y as an image carrier, a drum cleaning device 2Y, a charge eliminating device (not shown). ), A charging device 4Y, a developing device 5Y, and the like.
The charging device 4Y uniformly charges the surface of the photoreceptor 1Y that is driven to rotate clockwise in the drawing by a driving unit (not shown). The surface of the uniformly charged photoreceptor 1Y is exposed and scanned by laser light (LD light) to carry a Y electrostatic latent image. The Y electrostatic latent image is developed into a Y toner image by a developing device 5Y using Y toner, and is transferred onto an intermediate transfer belt (primary transfer belt) 8 which is an endless belt-like intermediate transfer member as a transfer member. Is done.
The drum cleaning device 2Y removes the toner remaining on the surface of the photoreceptor 1Y after the intermediate transfer process. The static eliminator neutralizes residual charges on the photoreceptor 1Y after cleaning. By this charge removal, the surface of the photoreceptor 1Y is initialized and prepared for the next image formation.
The other image forming stations 6C, 6M, and 6K have the same configuration. Similarly, C, M, and K toner images are formed on the photoreceptors 1C, 1M, and 1K, and the intermediate transfer belt 8 is formed. Is transferred to. The other image forming stations 6C, 6M, and 6K are denoted by corresponding reference numerals and description thereof is omitted.

  The developing device 5Y is filled with a two-component developer containing at least a magnetic carrier and Y toner, and is attracted and conveyed to a developing roller 51Y having a magnet disposed therein. The developer is regulated to a fixed amount by a doctor blade, brought into contact with the photoreceptor 1Y, and developed by electrostatically attaching toner to the latent image formed on the photoreceptor 1Y. Since the toner concentration in the developer is lowered by developing the toner, it is necessary to replenish the toner, and the toner is replenished from the toner cartridge (not shown) into the developing device through the toner replenishment path 52Y. The amount of toner (toner density) in the developer is detected by a toner density sensor (not shown). The electric signal from the toner density sensor is sent to the main control unit 30 as the control means shown in FIG. 2, the toner supply amount is determined according to a predetermined standard, and a drive motor for a toner supply roller (not shown) is driven. .

  As shown in FIG. 1, an exposure device 7 is disposed below the image forming stations 6Y, 6M, 6C, and 6K. The exposure device 7 serving as the latent image forming means irradiates the respective photoconductors in the image forming stations 6Y, 6C, 6M, and 6K with laser light emitted based on the image data that is the above-described document image information. To do. By this exposure, electrostatic latent images for Y, C, M, and K are formed on the photoreceptors 1Y, 1C, 1M, and 1K. The exposure apparatus 7 of the present embodiment has a known configuration in which a laser beam emitted from a light source is irradiated onto a photoconductor via a plurality of optical lenses and mirrors while being scanned with a polygon mirror that is rotationally driven by a motor. is doing.

  On the lower side of the exposure apparatus 7 in the figure, a paper feed unit having a paper feed cassette 26, a paper feed roller 27 incorporated in the paper feed cassette 26, a registration roller pair 28, and the like is disposed. A plurality of transfer papers P as recording materials are stored in the paper supply cassette 26, and a paper supply roller 27 is in contact with the uppermost transfer paper P. When the paper feeding roller 27 is rotated counterclockwise in the drawing by a driving means (not shown), the uppermost transfer paper P is fed toward the roller (nip) of the registration roller pair 28. The registration roller pair 28 rotationally drives both rollers to sandwich the transfer paper P, but temporarily stops rotating immediately after sandwiching. Then, the transfer paper P is sent out toward a secondary transfer nip described later at an appropriate timing.

  Above the image forming stations 6Y, 6M, 6C, and 6K in the figure, an intermediate transfer unit that moves endlessly while stretching an intermediate transfer belt 8 as an intermediate transfer member is disposed. In addition to the intermediate transfer belt 8, the intermediate transfer unit includes primary transfer bias rollers 9Y, 9C, 9M, and 9K as a primary transfer unit (primary transfer member), a cleaning device 10, and the like. The intermediate transfer unit also includes a secondary transfer backup roller 12, a cleaning backup roller 13, tension rollers 14 and 15, and the like. The intermediate transfer belt 8 is endlessly moved in the counterclockwise direction in the figure by the rotational drive of at least one of the rollers while being stretched around these four rollers. The primary transfer bias rollers 9Y, 9M, 9C, and 9K sandwich the intermediate transfer belt 8 that is moved endlessly in this manner from the photoreceptors 1Y, 1C, 1M, and 1K to form primary transfer nips. In these methods, a transfer bias having a polarity opposite to that of toner (for example, plus) is applied to the back surface (loop inner peripheral surface) of the intermediate transfer belt 8.

  All the rollers except the primary transfer bias rollers 9Y, 9C, 9M, and 9K are electrically grounded. The intermediate transfer belt 8 sequentially passes through the primary transfer nips for Y, C, M, and K along with the endless movement thereof, and Y, C, M, and Y on the photoreceptors 1Y, 1C, 1M, and 1K. K toner images are superimposed and primarily transferred. As a result, a four-color superimposed toner image (hereinafter referred to as “four-color toner image”) is formed on the intermediate transfer belt 8.

  The secondary transfer backup roller 12 forms a secondary transfer nip with the intermediate transfer belt 8 sandwiched between the secondary transfer roller 19 as a secondary transfer means (secondary transfer member). The four-color toner image formed on the intermediate transfer belt 8 is transferred onto the transfer paper P at the secondary transfer nip. The secondary transfer roller 19 can be brought into and out of contact with the intermediate transfer belt 8 by a contact and separation mechanism (not shown). Transfer residual toner that has not been transferred to the transfer paper P adheres to the intermediate transfer belt 8 after passing through the secondary transfer nip. The transfer residual toner on the intermediate transfer belt 8 is cleaned by the cleaning device 10.

  In the secondary transfer nip, the transfer paper P is sandwiched between the intermediate transfer belt 8 and the secondary transfer roller 19 whose surfaces move in the forward direction, and is conveyed in the opposite direction to the registration roller pair 28 side. When the transfer paper P sent out from the secondary transfer nip passes between the fixing roller 20a and the pressure roller 20b of the fixing device 20, the four-color toner image transferred to the surface is fixed by heat and pressure. The Thereafter, the transfer paper P is discharged out of the apparatus through a pair of paper discharge rollers (not shown).

In FIG. 1, in the upper vicinity of the secondary transfer backup roller (primary transfer belt drive roller) 12, a direction (in this embodiment, the intermediate transfer belt running) intersecting the running direction (surface movement direction) of the intermediate transfer belt 8. A reflection type photosensor (hereinafter referred to as “photosensor”) 40 is provided as image density detection means so as to face the surface of the intermediate transfer belt 8 in a direction perpendicular to the direction). The photo sensor 40 is disposed downward in the vicinity of the secondary transfer backup roller 12, that is, at a position immediately after the secondary transfer process in order to avoid contamination such as toner scattering.
In addition, since the detection of the four color toner adhesion patterns of K, M, C, and Y is performed in a short time as much as possible, the toner adhesion pattern detection can be performed exclusively for each color in the main scanning direction on the intermediate transfer belt 8. A total of four photosensors 40K, 40Y, 40C, and 40M are arranged so that the toner adhesion patterns can be detected simultaneously.

  FIG. 2 is a block diagram showing an example of the configuration of the main part of the control system in the copying machine according to the present embodiment. As shown in FIG. 2, the main control unit 30 as a control means is constituted by a microcomputer having an I / O interface 35, a CPU 32, a RAM 33, and a ROM 34. The main control unit 30 receives setting information from the operation panel 31 and detection information from the black photosensor 40K, the yellow photosensor 40Y, the cyan photosensor 40C, and the magenta photosensor 40M. .

Next, the image forming condition control operation in the copying machine of this embodiment will be described.
There are the following items as the operation of the image forming condition control for automatically adjusting the image forming condition around the photosensitive member.
(1) Initial setting of the photosensor 40:
The output (Vsg) of the photosensor 40 detected for the background portion of the surface of the intermediate transfer belt 8 is set to 4.0 v. Since the output Vsg to the background portion varies depending on the sensitivity of the photosensor 40 and the reflectance of the surface of the intermediate transfer belt 40, this initial setting operation is an essential operation when the intermediate transfer belt 8 and the photosensor 40 are replaced. .
(2) Photoconductor surface potential control:
A lower charging voltage than that at the time of normal image formation is applied, and an area where background stain occurs is detected by the photo sensor 40 on the intermediate transfer belt 8 after transfer. The detection result is fed back to the charging voltage output. Since the surface potential of the photoconductor 1 fluctuates due to erosion of the photoconductor film, sensitivity deterioration, etc. over time or in the environment, it is necessary to execute it sequentially.
(3) Development potential potential control:
By fixing the power of the light source (LD) and the charging application voltage and changing the development bias voltage output in multiple stages, a plurality of toner pattern images with different toner adhesion amounts are formed and detected by the photosensor 40. The development bias voltage is adjusted and determined so that the toner adhesion amount becomes a target value.
(4) Setting a reference value for toner density control:
The toner density control level may change due to a decrease in the toner charge amount when the image forming apparatus is left for a long time. Accordingly, the toner adhesion pattern is detected by the photosensor 40, and the control reference value of the toner concentration sensor that detects the toner concentration in the developing device 5 is optimized according to the result.
(5) Developer stirring:
As in the case of (4) above, the developer is stirred by rotating the stirring member in the developing device 5 in order to recover the toner charge amount lowered after the image forming apparatus is left unattended.
(6) Toner replenishment control:
The toner replenishment time is calculated from the output of the toner density sensor, the toner density control reference value and the pixel detection data, and the toner replenishment motor is driven.
(7) Halftone correction control:
A predetermined developing bias voltage and charging voltage are output, and a plurality of toner adhesion patterns are formed while changing the power of the light source (LD), and are detected by the photosensor 40. The development input / output characteristic is obtained from the output of the photosensor 40, and the power of the light source (LD) is changed so that this characteristic becomes the target characteristic.

  In the development potential potential control in (3) and the halftone correction control in (7), ten patterns with different toner adhesion amounts are imaged, and therefore the time for performing the control is relatively long. .

  The toner adhesion pattern formed on the surface of the photoreceptor outside the normal image forming area is transferred onto the intermediate transfer belt 8 and reflected by the photosensor 40 arranged downstream of the secondary transfer process, that is, the toner adhesion amount. Is detected. At this time, the secondary transfer roller 19 needs to be separated from the intermediate transfer belt 8 belt so that the toner adhesion pattern on the intermediate transfer belt 8 is not disturbed.

Next, the relationship between the photosensor 40 and the arrangement of toner adhesion patterns for controlling the image forming conditions for each color will be described with reference to FIG.
In the present embodiment, in order to shorten the execution time of the image forming condition control operation as described above, four photosensors 40K, 40Y, 40C, and 40M are arranged in parallel. The operation can be executed with the same control specifications.

[Array A: First Toner Adhesion Pattern Array]
All of the four photosensors 40K, 40Y, 40C, and 40M detect the toner adhesion patterns of the corresponding colors. The arrangement of the photosensors 40 is for B, Y, C, and M from the front of FIG. 1, and 10 different image forming patterns of the toner adhesion patterns of the respective colors in the sub-scanning direction are associated with the positions of the respective photosensors 40. Created with conditions. Then, each toner adhesion pattern having a different toner adhesion amount is detected to calculate the toner adhesion amount.
In the case of this arrangement A, since the toner adhesion patterns for four colors are simultaneously detected, the time required for pattern detection is substantially the same as that for only one color. As described above, the array A is the most effective toner adhesion pattern array for shortening the operation time. However, since the photosensor 40 to be detected is different for each color, it is easily affected by variations in the characteristic values of the photosensor 40. However, it has a disadvantage against image quality degradation such as gray balance. This array A is set to the initial setting state.

[Array B: Second toner adhesion pattern array]
In this arrangement B, only two photosensors 40K and 40M at both ends in the intermediate transfer belt width direction are used. The photosensor 10K located on the near side in FIG. 1 is used for K. A black toner adhesion pattern is formed in correspondence with the position of the photosensor 10K. On the other hand, the photosensor 40M located on the back side in FIG. 1 is used for Y, C, and M colors. Corresponding to the position of the photo sensor 40M, one row of toner adhesion patterns is formed by directly arranging ten toner adhesion patterns of yellow, cyan, and magenta. In this arrangement B, a total of two rows of toner adhesion patterns are obtained.
In this toner adhesion pattern array B, one back side photosensor 40M detects three colors (30 patterns). Therefore, there is a demerit that the time required for detecting the toner adhesion pattern is three times that in the case of the arrangement A. However, since one of the photosensors 40M detects the three colors M, C, and Y, the detection result of the three-color toner adhesion pattern has no variation in the characteristics of the photosensors, and the three-color toner adhesion amounts are evenly distributed. It is possible to control.
Further, this toner adhesion pattern array B is used when, for example, (i) one or two of the plurality of photosensors 40 becomes undetectable due to failure or toner scattering, or (ii) temporally. This is used for the purpose of active utilization such as when there is a margin and it is desired to avoid the characteristic variation between the photosensors as described above.
In the example of the array B in FIG. 3, the photosensors used for image forming condition control are the photosensors 40K and 40M at both ends, but other photosensors may be selected and used.

[Array C: Third toner adhesion pattern array]
In this case, K is also detected by the single photosensor 40M with respect to the array B. Corresponding to the position of the photosensor 40M, one row of toner adhesion pattern groups in which 10 toner adhesion patterns of yellow, cyan, magenta, and black are directly arranged are formed.
When this arrangement C is adopted, detection of four colors is performed by one photosensor 40M, so that the time required for detecting the toner adhesion pattern has a demerit that is four times that of the arrangement A. However, even if, for example, three photosensors 40 fail or become undetectable, there is an advantage that the image forming condition can be controlled by the remaining photosensors.
In the example of the array C in FIG. 3, the photosensor used for image forming condition control is the photosensor 40M on the back side. However, any one of the other photosensors 40K, 40Y, and 40C is used. It may be used.

  Note that the array B is usually sufficient for reducing the variation in characteristics of the photosensor 40.

FIG. 4 is a flowchart showing an example of image forming condition control according to the present embodiment. In this image forming condition control, first, processing for recognizing the device state of the image forming apparatus is performed by the following various device state recognition means (step 1). Here, the apparatus status information of the image forming apparatus includes the following, and the following apparatus status recognition means can be used.
(1) Full-color image forming frequency: full-color image forming counter, all-image forming counter In this embodiment, the main control unit 30 also functions as a full-color image forming counter and an all-image forming counter.
(2) Information on whether or not it is immediately after the printing operation: Print job reception signal The print job reception signal is stored by the main control unit 30. Therefore, here, the main control unit 30 is the apparatus state recognition means.
(3) Current time: built-in clock of the apparatus main body The built-in clock of the apparatus main body can be controlled by the control means 30. Therefore, here, the main control unit 30 is the apparatus state recognition means.
(4) Elapsed time since the end of the previous image forming operation: built-in clock or timer of the apparatus body The built-in clock or timer of the apparatus body can be used by the main control unit 30 as well. Therefore, here, the main control unit 30 is the apparatus state recognition means.
(5) Photo sensor output normal / abnormal: Photo sensor output signal (initial adjustment value, etc.)
Based on the photosensor output signal, the main control unit 30 as the device state recognition means determines whether the state is normal or abnormal.

Next, the arrangement of the toner adhesion pattern is switched based on the recognition result of the apparatus state recognition means (step 2).
For example, when the apparatus state that gives priority to the image forming speed is recognized, each of the photosensors 40K, 40Y, 40C, and 40M can detect the image density of the toner adhesion patterns having different colors in parallel. Switch to.
In addition, for example, when recognizing an apparatus state that prioritizes high-precision image forming condition control in order to perform high-precision process control and toner replenishment accuracy, considering that there is variation in detection characteristics of the photosensor, The arrangement is switched to the arrangement C in which the image density of the toner adhesion pattern of all colors can be detected by one photosensor.
In addition, for example, when any of a plurality of photosensors recognizes a device state in which a malfunction or is unusable, the above-described image sensor can detect the image density of the toner adhesion pattern of all colors with another usable photosensor. Switch to array B or array C.
That is, in accordance with the recognition result, the three types of sequences A, is switched to the sequence of optimal toner deposition pattern from sequence B and sequence C (Step 2).

  Next, according to the above switched arrangement, the image forming stations 6Y, 6M, 6C, and 6K are switched between a pattern image forming mode and a pattern detection mode, which are different in image forming timing, as shown below. Image conditions are set (steps 3 to 5). If the image forming timings of the image forming stations 6Y, 6M, 6C, and 6K are inappropriate, it may take more time than necessary to create and detect the toner adhesion pattern when the arrangement is switched. In this embodiment, since the photo sensor is disposed on the downstream side of the secondary transfer position, the secondary transfer roller 19 needs to be separated from the intermediate transfer belt 8 when detecting the toner adhesion pattern. . Since the secondary transfer roller 19 may be affected by an impact during the contact / separation operation, it is also necessary to set the image forming timing so as to avoid the impact.

In the case of the arrangement [A], the toner adhesion pattern for halftone density correction control is created and detected immediately after the image forming operation (steps 3A and 4A).
After the image trailing edge of the final print has passed the secondary transfer process, the separation operation of the secondary transfer roller 19 is started, and then a toner adhesion pattern for each color is created. Here, compared with the image formation on the most downstream side (black in this example), the image formation on the most upstream side (yellow in this example) is upstream by the distance between the image formation stations. Until the detection of the adhesion pattern by the photo sensors 40Y, 40M, 40C, and 40K, the moving time that is three times the distance between the image forming stations (the distance between the yellow image forming station 6Y and the black image forming station 6K) is a loss time. It becomes.
On the other hand, in each color image forming station 6Y, 6M, 6C, 6K, a toner adhesion pattern is formed immediately after the image trailing edge of the final print is completed, that is, from the most upstream side (yellow) to the most downstream side. If the creation of a toner adhesion pattern is started immediately after the rear edge of the print image toward (black), the toner adhesion pattern of each color is formed on the intermediate transfer belt 8 in the state where the head position is aligned in the same manner as the print image. Is done. Therefore, the above loss time does not occur.
The separation operation of the secondary transfer roller does not transfer the toner adhering pattern image if the trailing edge of the printed image is separated immediately after passing the secondary transfer step. Even if an impact occurs during the separation operation, the toner is not transferred. The effect on the adhesion pattern is only a moment during the secondary transfer separation operation. Therefore, by removing only the toner adhesion pattern imaged at that timing from the detection target, it can be executed in a short time without greatly affecting the halftone correction control. Alternatively, the toner adhesion pattern for each color may not be created at the secondary transfer roller separation timing.
As described above, when parallel processing by a plurality of photosensors 40Y, 40M, 40C, and 40K as in the case of the array [A] is performed, the upstream side in the rotation direction (surface movement direction) of the intermediate transfer belt 8 By sequentially forming images from the downstream side to the downstream side, it is possible to reduce the loss time for detecting a plurality of toner adhesion patterns and shorten the execution time.

Creation and detection of the toner adhesion pattern in the case of the arrangement [C] are performed as follows (steps 3C and 4C).
In this case, since there is only one photosensor, a plurality of toner adhesion patterns cannot be created simultaneously in the main scanning direction. Accordingly, the toner adhesion patterns for each color are aligned on the straight line in the sub-scanning direction, but the toner adhesion pattern for one color is the same regardless of whether the image formation order is the same as the array [A] or vice versa. There is no loss time by timing the image formation so that the next color toner adhesion pattern is formed immediately after the formation on the primary transfer belt.
However, in order to avoid the influence of the impact at the time of separation of the secondary transfer roller, the secondary transfer roller is separated from the primary transfer belt immediately after the rear end of the image of the final print passes the secondary transfer process, and the toner adheres immediately after that. An operation order of creating and detecting a pattern is essential.
In this case, when the toner adhesion pattern creation is started from the most upstream side (yellow), a loss time is generated by the distance movement to the image formation position on the most downstream side (black).
On the other hand, when the toner adhesion pattern is created from the most downstream side (black), the formation and detection of the toner adhesion pattern is started from the position closest to the secondary transfer process, so that the loss time is eliminated.
As described above, when creating and detecting a serial pattern by one photosensor such as the array [C], [black → magenta → cyan → c] from the downstream side to the upstream side in the rotation direction of the intermediate transfer belt 8. yellow] sequentially imaging to a Ikuko and, by reducing the loss time of the plurality of toner adhesion pattern detection, it is possible to shorten the execution time.
In addition, when the image formation of the next color toner adhesion pattern is started after the image formation of the tenth toner adhesion pattern of one color is completed, a loss time is generated for the moving time of the distance between the image forming stations. In order to suppress the occurrence of this loss time, it is necessary to advance the movement time corresponding to the distance between the image forming stations and start the toner adhesion pattern image forming operation for the next color.

Creation and detection of the toner adhesion pattern in the case of the arrangement [B] are performed as follows (steps 3B and 4B).
In the case of this array [B], [magenta], [cyan], and [yellow] are imaged in the order from the most downstream side (magenta) to the most upstream side (yellow) in the same manner as the array [C]. Since only one color is detected by the black-dedicated photo sensor 40K, the timing for starting the creation of the toner adhesion pattern is the same as that of the magenta toner adhesion pattern on the primary transfer belt immediately after the rear edge of the image of the final print. Any position may be used as long as the image forming timings are aligned in the main scanning direction.
In this case, the separation timing of the secondary transfer roller 19 from the intermediate transfer belt 8 is such that the [ yellow ] toner adhesion pattern passes through the secondary transfer position immediately after the image trailing edge of the final print passes through the secondary transfer position. Until just before.

As described above, according to the present embodiment, a plurality of color toner adhesion pattern arrays A, B, and C are selected according to information on the recognition result of the apparatus state including at least one of the use state and the use history of the apparatus body. Switch to the optimal array. This makes it possible to create an appropriate toner adhesion pattern and detect its image density according to the state of the apparatus. Therefore, image forming condition control can be executed by forming an optimum toner adhesion pattern according to the apparatus state of the image forming apparatus.
In addition, the order of the image forming timings of the toner adhesion patterns of a plurality of colors is switched in accordance with each of the arrangements A, B and C of the toner adhesion patterns. By switching the order of the image formation timings of the toner adhesion patterns, the toner adhesion patterns of each array can be created and detected in the minimum necessary time according to the arrangement of the toner adhesion patterns. Accordingly, it is possible to shorten the execution time of the creation and detection of the toner adhesion pattern used for the image forming condition control.

  In the above-described embodiment, the toner images of the respective colors on the plurality of photoreceptors 1 are superimposed on the intermediate transfer belt 8 and primarily transferred, and then the color images on the intermediate transfer belt 8 are collectively transferred onto the transfer paper. The case of the so-called indirect transfer type color image forming apparatus has been described. The present invention is not limited to such an indirect transfer type color image forming apparatus, but directly to superimpose toner images of respective colors on a plurality of photosensitive members 1 on transfer paper conveyed by a transfer conveyance belt as a transfer member. The present invention can also be applied to a so-called direct transfer color image forming apparatus.

1 is a front view showing a schematic configuration of an image forming apparatus (laser copying machine) according to an embodiment of the present invention. FIG. 2 is a block diagram showing an example of a main part of a control system in the copier. FIG. 6 is an explanatory diagram showing types of arrangement of toner detection patterns. 6 is a flowchart illustrating an example of image forming condition control.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 6 Image forming station 8 Intermediate transfer belt 19 Secondary transfer roller 30 Main control part 40K, 40Y, 40C, 40M Reflective type photo sensor P Transfer paper

Claims (4)

A plurality of image carriers, toner image forming means for forming a plurality of color toner images composed of different color toners on each image carrier, and a surface of a transfer member that moves a transfer position facing each image carrier Or a transfer means for transferring a toner image formed on each image carrier to a recording material carried on the surface of the transfer member and moving, and a plurality of colors formed on each image carrier and transferred onto the transfer member. A plurality of image density detection means for detecting the toner adhesion amount of each toner adhesion pattern for image adjustment, and a process control and a toner for changing the image forming condition based on the detection result of the toner adhesion amount of the toner adhesion pattern of the plurality of colors Control means for performing at least one of toner density control for changing the replenishment amount,
The plurality of image carriers are arranged so as to be aligned in the surface movement direction of the transfer member,
The plurality of image density detection means are image forming apparatuses arranged so as to be aligned in a direction intersecting a surface movement direction of the transfer member,
Device state recognition means for recognizing a device state including at least one of a use state and a use history of the device body,
On the transfer member, when the apparatus state recognizing means recognizes the apparatus state giving priority to the image forming speed and when the apparatus state recognizing the apparatus state prioritizing high-precision image forming condition control is recognized on the transfer member. Switching between the arrangement of toner adhesion patterns of multiple colors formed by transfer and the order of image formation timing of the toner adhesion patterns of multiple colors ,
If it recognizes the priority device state imaging speed by the device state recognition unit, toner adhesion multiple rows formed by the different color toners together as a one-to-one correspondence with the plurality of image density detection means A pattern is formed,
When the apparatus state recognizing unit recognizes an apparatus state that prioritizes high-precision image forming condition control, the plurality of color toners are sequentially formed so as to correspond to one of the plurality of image density detecting units. image forming apparatus characterized by one column toner deposition pattern of that is formed. A plurality of image carriers, toner image forming means for forming a plurality of color toner images composed of different color toners on each image carrier, and an intermediate transfer member that moves a transfer position facing each image carrier. Transfer means for transferring a toner image formed on each image carrier on the surface, a secondary transfer member that can contact and separate from the surface of the intermediate transfer member, and the intermediate transfer member formed on each image carrier. Image formation based on a plurality of image density detection means for detecting the toner adhesion amount of each of the color adhesion toner adhesion patterns transferred onto the image, and the detection result of the toner adhesion amount of the toner adhesion pattern of the plurality of colors Control means for performing at least one of process control for changing conditions and toner density control for changing toner replenishment amount;
The plurality of image carriers are arranged so as to be aligned in the surface movement direction of the intermediate transfer member,
The plurality of image density detection means are arranged so as to be aligned in a direction intersecting the surface movement direction of the intermediate transfer member,
The secondary transfer member is separated from the intermediate transfer member after the toner image on the intermediate transfer member transferred to the recording material has passed the secondary transfer position, and the toner adhesion pattern is separated after the separation of the secondary transfer member. An image forming apparatus in which is formed,
Device state recognition means for recognizing a device state including at least one of a use state and a use history of the device body,
When the apparatus state recognizing unit recognizes the apparatus state giving priority to the image forming speed, and when the apparatus state recognizing unit recognizes the apparatus state giving priority to the high-precision image forming condition control. Switching between the arrangement of a plurality of color toner adhesion patterns formed by transferring to the image forming timing of the plurality of color toner adhesion patterns,
When the apparatus state recognizing unit recognizes the apparatus state giving priority to the image forming speed, a plurality of rows of toner adhesion patterns corresponding to the plurality of image density detecting units are formed, and the surface movement direction of the intermediate transfer member In order from the image carrier on the most upstream side to the image carrier on the downstream side thereof in order,
When the apparatus state recognizing unit recognizes an apparatus state that prioritizes highly accurate image forming condition control, a row of toner adhesion patterns corresponding to one of the plurality of image density detecting units is formed. An image forming apparatus starting image formation of a toner adhesion pattern in order from an image carrier on the most downstream side in the surface movement direction of the intermediate transfer member to an image carrier on the upstream side. A plurality of image carriers, toner image forming means for forming a plurality of color toner images composed of different color toners on each image carrier, and a surface of a transfer member that moves a transfer position facing each image carrier Or a transfer means for transferring a toner image formed on each image carrier to a recording material carried on the surface of the transfer member and moving, and a plurality of colors formed on each image carrier and transferred onto the transfer member. A plurality of image density detection means for detecting the toner adhesion amount of each toner adhesion pattern for image adjustment, and a process control and a toner for changing the image forming condition based on the detection result of the toner adhesion amount of the toner adhesion pattern of the plurality of colors Control means for performing at least one of toner density control for changing the replenishment amount,
The plurality of image carriers are arranged so as to be aligned in the surface movement direction of the transfer member,
The plurality of image density detection means are image forming apparatuses arranged so as to be aligned in a direction intersecting a surface movement direction of the transfer member,
Device state recognition means for recognizing a device state including at least one of a use state and a use history of the device body,
On the transfer member, when the apparatus state recognizing means recognizes the apparatus state giving priority to the image forming speed and when the apparatus state recognizing the apparatus state prioritizing high-precision image forming condition control is recognized on the transfer member. Switching between the arrangement of toner adhesion patterns of multiple colors formed by transfer and the order of image formation timing of the toner adhesion patterns of multiple colors,
The plurality of image carriers are composed of an image carrier on which a toner image of black toner is formed and a plurality of image carriers on which toner images of color toners having different colors other than black toner are formed,
The switchable toner adhesion pattern array is as follows:
A first array comprising a plurality of rows of toner adhesion patterns formed of different color toners so as to correspond one-to-one to the plurality of image density detection means;
One row of black toner adhesion patterns formed of black toner so as to correspond to one image density detection means dedicated to the black toner and a plurality of colors corresponding to one image density detection means for the color toner. A second array comprising a row of color toner adhesion patterns sequentially formed with color toners;
An image forming apparatus comprising: a third array composed of one row of toner adhesion patterns sequentially formed from the plurality of colors of toner so as to correspond to one image density detecting means. The image forming apparatus according to claim 3 .
When switched to the first arrangement, image formation of the toner adhesion pattern is started in order from the most upstream image carrier in the surface movement direction of the transfer member to the downstream image carrier.
When switching to the second arrangement, the toner adhesion pattern for the color is formed in order from the most downstream image carrier in the surface movement direction of the transfer member to the upstream image carrier. When the image is started and switched to the third arrangement, the image formation of the toner adhesion pattern is started in order from the most downstream image carrier in the surface movement direction of the transfer member to the upstream image carrier. An image forming apparatus.