JP2009282496A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which is capable of performing stable image forming processing, without affecting the number of prints per unit time and toner consumption. <P>SOLUTION: A control circuit 30 temporarily transfers the patterns for adjusting image density of each color of developing devices 9 except the most downstream one in the rotational direction of an intermediate transfer belt 8 to the intermediate transfer belt 8, then, transfers the patterns to a photoreceptor 18(K) by applying a bias having a polarity opposite to that of a normal transfer bias to a transfer device 19(K), and then, measures the pattern density of the photoreceptor 18(K) by an optical sensor 33, to adjust the image density, in such a state that the pattern for adjusting the image density of color by the most downstream developing device 9(K) is held on the most downstream photoreceptor 18(K), without transferring the pattern onto the intermediate transfer belt 8, by applying the bias having a polarity opposite to that of the normal transfer bias to the most downstream transfer device 19(K). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention sequentially transfers a toner image formed on each image carrier by each developing device corresponding to a plurality of colors arranged in a tandem manner in the transfer paper conveyance direction, and optically transmits an image signal of the toner image. The present invention relates to an image forming apparatus that performs image density adjustment and color misregistration correction by detecting with a sensor.

  Conventionally, color detection is performed by printing a detection pattern and controlling the toner adhesion amount of the printed image based on the detection result of the detection pattern, or setting a correction amount for the driving speed of the photosensitive member or intermediate transfer member. A technique for performing correction is known (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 08-190244

  However, since the image forming apparatus configured as described above uses a detection pattern for image density adjustment or image color misregistration correction when performing such control, the number of printed sheets per unit time is used. There have been problems such as a decrease in toner and an increase in toner consumption.

  Further, for example, in the case of an image forming apparatus in which an intermediate transfer member is arranged, an untransferred toner image directly contacts the secondary transfer roller without being provided with a mechanism for bringing the secondary transfer roller into contact with or separated from the intermediate transfer member. This was the cause of back dirt that would cause the next transfer roller to become dirty.

  Furthermore, since the untransferred toner needs to be collected by the cleaning device, the burden on the cleaning device is heavy, and there are a plurality of cases where the untransferred toner cannot be collected by one cleaning operation (one rotation / one cycle). It is necessary to execute cleaning operations one time, and the number of printed sheets per unit time is also reduced.

  In addition, when detecting the detection pattern on the intermediate transfer member, the surface state of the intermediate transfer member changes depending on the frequency of use (durability), variation in solids, etc., and therefore the influence of each image forming apparatus is corrected. Therefore, it is difficult to measure the toner amount with high accuracy.

  Further, when the intermediate transfer member has a belt shape, there is a problem that the distance to the sensor for detecting the position and density of the detection pattern changes due to the flutter of the belt.

  In view of the above circumstances, an object of the present invention is to provide an image forming apparatus capable of performing stable image forming processing without affecting the number of printed sheets per unit time and toner consumption. .

  The image forming apparatus according to the present invention includes an intermediate transfer body that can be rotated in the transfer material conveyance direction, and each development corresponding to a plurality of colors arranged in a tandem manner along the rotation movement direction of the intermediate transfer body. A transfer device for transferring a toner image formed on each image carrier by the apparatus onto the intermediate transfer member, and a toner image formed on the image carrier disposed on the most downstream side in the rotational movement direction of the intermediate transfer member. In the image forming apparatus, comprising: an optical sensor that outputs an image density signal of the image; and a control circuit that adjusts the image density of the developing device based on the image density signal output from the optical sensor. Is a pattern for adjusting the image density of each color by the developing device arranged at a position other than the most downstream in the rotational movement direction of the intermediate transfer member, and is transferred to the intermediate transfer member and then the image density adjustment pattern. The above The image arranged at the most downstream side in the rotational movement direction of the intermediate transfer body by applying a bias having a polarity opposite to a normal transfer bias to the transfer device arranged at the most downstream side in the rotational movement direction of the intermediate transfer body. In the pattern for adjusting the image density of the color by the developing device disposed downstream of the intermediate transfer member in the rotational movement direction after being transferred to the carrier, the intermediate transfer member is moved to the maximum in the rotational movement direction. By applying a bias having a polarity opposite to that of a normal transfer bias to the transfer device disposed downstream, the image density adjustment pattern is transferred to the maximum in the rotational movement direction of the intermediate transfer member without being transferred onto the intermediate transfer member. The image density adjusting pattern density on the image carrier disposed on the most downstream side in the rotational movement direction of the intermediate transfer member is held in the image carrier disposed downstream. And performs image density adjustment as determined by the formula sensor.

  The image forming apparatus according to the present invention includes an intermediate transfer body that can be rotated in the transfer material conveyance direction, and each development corresponding to a plurality of colors arranged in a tandem manner along the rotation movement direction of the intermediate transfer body. A transfer device for transferring a toner image formed on each image carrier by the apparatus onto the intermediate transfer member, and a toner image formed on the image carrier disposed on the most downstream side in the rotational movement direction of the intermediate transfer member. An image forming apparatus comprising: an optical sensor that outputs an image position signal; and a control circuit that performs color misregistration correction based on the image position signal output from the optical sensor. In the color misregistration correction pattern for each color by the developing device arranged at a position other than the most downstream in the rotational movement direction of the body, the color misregistration correction pattern is temporarily transferred onto the intermediate transfer body and then the color misregistration correction pattern is transferred to the intermediate transfer body. Rotation direction of After transferring the image to the image carrier disposed downstream in the rotational movement direction of the intermediate transfer member by applying a bias having a polarity opposite to a normal transfer bias to the transfer device disposed downstream, and In the color misregistration correction pattern by the developing device arranged on the most downstream side in the rotational movement direction of the intermediate transfer member, the transfer device arranged on the most downstream side in the rotational movement direction of the intermediate transfer member. The image carrier in which a color misregistration correction pattern is arranged on the most downstream side in the rotational movement direction of the intermediate transfer member without applying a bias having a polarity opposite to that of a normal transfer bias without being transferred onto the intermediate transfer member. In this state, the color misregistration correction pattern position on the image carrier disposed on the most downstream side in the rotational movement direction of the intermediate transfer member is measured by the optical sensor, thereby correcting the color misregistration. And performing.

  The image forming apparatus according to the present invention includes an intermediate transfer body that can be rotated in the transfer material conveyance direction, and each development corresponding to a plurality of colors arranged in a tandem manner along the rotation movement direction of the intermediate transfer body. A transfer device for transferring a toner image formed on each image carrier by the apparatus onto the intermediate transfer member, and a toner image formed on the image carrier disposed on the most downstream side in the rotational movement direction of the intermediate transfer member. An image forming apparatus comprising: an optical sensor that outputs an image position signal; and a control circuit that performs color misregistration correction based on the image position signal output from the optical sensor. Then, a toner discharge mode for discharging toner from each of the developing devices is activated, and toner discharged from the developing device arranged at a position other than the most downstream in the rotational movement direction of the intermediate transfer member is temporarily used for the intermediate transfer. After transferring the toner onto the body, the discharge toner is applied to the transfer device arranged at the most downstream in the rotational movement direction of the intermediate transfer body by applying a bias having a polarity opposite to that of a normal transfer bias. After the toner image is transferred to the image carrier disposed on the most downstream side in the rotational movement direction, and the toner discharged from the developing device disposed on the most downstream side in the rotational movement direction of the intermediate transfer body is the intermediate. By applying a bias having a polarity opposite to that of a normal transfer bias to the transfer device arranged on the most downstream side in the rotational movement direction of the transfer body, the discharged toner is transferred onto the intermediate transfer body without being transferred onto the intermediate transfer body. While being held by the image carrier arranged at the most downstream side in the rotational movement direction, the discharge toner position on the image carrier arranged at the most downstream side in the rotational movement direction of the intermediate transfer member And performing color misregistration correction, as measured by Manabu sensor.

  The image forming apparatus according to the present invention includes an intermediate transfer body that can be rotated in the transfer material conveyance direction, and each development corresponding to a plurality of colors arranged in a tandem manner along the rotation movement direction of the intermediate transfer body. A transfer device for transferring a toner image formed on each image carrier by the apparatus onto the intermediate transfer member, and a toner image formed on the image carrier disposed on the most downstream side in the rotational movement direction of the intermediate transfer member. An image forming apparatus comprising: an optical sensor that outputs an image density signal; and a control circuit that adjusts the image density of the developing device based on the image density signal output from the optical sensor. The toner discharge mode for discharging the toner from the developing device at a predetermined timing is activated, and the toner discharged from the developing device arranged at a position other than the most downstream in the rotational movement direction of the intermediate transfer member is First, the toner is transferred onto the intermediate transfer member, and the discharged toner is applied to the transfer device disposed on the most downstream side in the rotational movement direction of the intermediate transfer member by applying a bias having a polarity opposite to that of a normal transfer bias. After the toner image is transferred to the image carrier disposed at the most downstream side in the rotational movement direction of the intermediate transfer member, the toner is discharged from the developing device disposed at the most downstream side in the rotational movement direction of the intermediate transfer member. In other words, by applying a bias having a polarity opposite to a normal transfer bias to the transfer device arranged on the most downstream side in the rotational movement direction of the intermediate transfer member, the discharged toner is transferred without being transferred onto the intermediate transfer member. While being held by the image carrier disposed at the most downstream side in the rotational movement direction of the intermediate transfer member, the discharge tray on the image carrier disposed at the most downstream side in the rotational movement direction of the intermediate transfer member, respectively. And performs image density adjustment by measuring the over concentration by the optical sensor.

  In this case, a second optical sensor that measures the toner density on the image carrier on the downstream side in the rotational movement direction of the intermediate transfer member with respect to the optical sensor is provided, and the control circuit is disposed on the most downstream side. The density of the image density adjustment pattern on the image carrier thus measured is measured by the optical sensor, and the density of the toner remaining on or transferred to the intermediate transfer body is measured by the second optical sensor. It is also possible to perform image density adjustment based on the measurement results from these sensors.

  Moreover, it is preferable that the sensitivity of the second optical sensor is higher than the sensitivity of the optical sensor.

  The image forming apparatus according to the present invention includes a transfer body that can be rotated in the transfer material conveyance direction, and developing devices that support a plurality of colors arranged in a tandem manner along the rotation movement direction of the transfer body. A transfer device for transferring a toner image formed on each image carrier onto a transfer material conveyed by the transfer member, and a toner formed on the image carrier disposed on the most downstream side in the rotational movement direction of the transfer member An image forming apparatus comprising: an optical sensor that outputs an image density signal of an image; and a control circuit that adjusts the image density of the developing device based on the image density signal output from the optical sensor. The circuit temporarily transfers the image density adjustment pattern for each color by the developing device arranged at a position other than the most downstream in the rotational movement direction of the transfer body onto the transfer body, and then transfers the image density adjustment pattern to the transfer body. The transfer body By applying a bias having a polarity opposite to that of a normal transfer bias to the transfer device arranged on the most downstream side in the rotational movement direction, the transfer device is transferred to the image carrier arranged on the most downstream side in the rotational movement direction of the transfer body. After that, in the color image density adjustment pattern by the developing device arranged at the most downstream side in the rotational movement direction of the transfer body, the transfer arranged at the most downstream side in the rotational movement direction of the transfer body. The image carrier in which an image density adjustment pattern is arranged on the most downstream side in the rotational movement direction of the transfer body without transferring the image onto the transfer body by applying a bias having a polarity opposite to a normal transfer bias to the device. In this state, the image density adjustment pattern density on the image carrier disposed on the most downstream side in the rotational movement direction of the transfer body is measured by the optical sensor to adjust the image density. And wherein the Ukoto.

  The image forming apparatus according to the present invention includes a transfer body that can be rotated in the transfer material conveyance direction, and developing devices that support a plurality of colors arranged in a tandem manner along the rotation movement direction of the transfer body. A transfer device for transferring a toner image formed on each image carrier onto a transfer material conveyed by the transfer member, and a toner formed on the image carrier disposed on the most downstream side in the rotational movement direction of the transfer member An image forming apparatus comprising: an optical sensor that outputs an image position signal of an image; and a control circuit that performs color misregistration correction based on the image position signal output from the optical sensor. In the color misregistration correction pattern of each color by the developing device arranged at a position other than the most downstream in the rotational movement direction of the transfer body, the color misregistration correction pattern is temporarily transferred onto the transfer body and then the color misregistration correction pattern of the transfer body. The most downstream direction of rotation The transfer device is transferred to the image carrier disposed downstream in the rotational movement direction of the transfer body by applying a bias having a polarity opposite to a normal transfer bias to the disposed transfer device, and then the transfer device In the color misregistration correction pattern by the developing device arranged at the most downstream in the rotational movement direction of the body, a normal transfer bias is applied to the transfer device arranged at the most downstream in the rotational movement direction of the transfer body. Is a state in which a color misregistration correction pattern is held on the image carrier disposed on the most downstream side in the rotational movement direction of the transfer body without being transferred onto the transfer body by applying a reverse polarity bias, The color misregistration correction is performed by measuring the color misregistration correction pattern position on the image carrier disposed on the most downstream side in the rotational movement direction of the transfer body by the optical sensor.

  The image forming apparatus according to the present invention includes a transfer body that can be rotated in the transfer material conveyance direction, and developing devices that support a plurality of colors arranged in a tandem manner along the rotation movement direction of the transfer body. A transfer device for transferring a toner image formed on each image carrier onto a transfer material conveyed by the transfer member, and a toner formed on the image carrier disposed on the most downstream side in the rotational movement direction of the transfer member An image forming apparatus comprising: an optical sensor that outputs an image position signal of an image; and a control circuit that performs color misregistration correction based on the image position signal output from the optical sensor. The toner discharge mode for discharging the toner from each of the developing devices is started at the same timing, and the toner discharged from the developing device arranged at a position other than the most downstream in the rotational movement direction of the transfer body is temporarily transferred. After the transfer toner is transferred onto the transfer device, the transfer device disposed on the most downstream side in the rotational movement direction of the transfer body is applied with a bias having a polarity opposite to that of a normal transfer bias. After the toner image is transferred to the image bearing member arranged on the most downstream side in the direction, and the toner discharged from the developing device arranged on the most downstream side in the rotational movement direction of the transfer member, the transfer member rotates. By applying a bias having a polarity opposite to that of a normal transfer bias to the transfer device arranged on the most downstream side in the movement direction, the discharged toner is moved to the most downstream side in the rotational movement direction of the transfer body without being transferred onto the transfer body. While being held by the arranged image carrier, the discharge toner position on the image carrier arranged on the most downstream side in the rotational movement direction of the transfer member is measured by the optical sensor to compensate for color misregistration. And performing.

  The image forming apparatus according to the present invention includes a transfer body that can be rotated in the transfer material conveyance direction, and developing devices that support a plurality of colors arranged in a tandem manner along the rotation movement direction of the transfer body. A transfer device for transferring a toner image formed on each image carrier onto a transfer material conveyed by the transfer member, and a toner formed on the image carrier disposed on the most downstream side in the rotational movement direction of the transfer member An image forming apparatus comprising: an optical sensor that outputs an image density signal of an image; and a control circuit that adjusts the image density of the developing device based on the image density signal output from the optical sensor. The circuit activates a toner discharge mode that discharges toner from the developing device at a predetermined timing, and includes a discharge toner from the developing device arranged at a position other than the most downstream in the rotational movement direction of the transfer body. Once the transfer toner is transferred onto the transfer body, a bias having a polarity opposite to that of a normal transfer bias is applied to the transfer device disposed downstream of the transfer body in the rotational movement direction. The toner transferred from the developing device disposed at the most downstream side in the rotational movement direction of the transfer body is transferred to the image carrier after being transferred to the downstream side in the rotational movement direction of the transfer body. By applying a bias having a polarity opposite to that of a normal transfer bias to the transfer device disposed on the most downstream side in the rotation movement direction of the body, the transfer toner is rotated without being transferred onto the transfer body. With the optical sensor, the optical sensor measures the discharged toner density on the image carrier disposed at the most downstream side in the rotational movement direction of the transfer body while being held by the image carrier disposed at the most downstream in the direction. And performs image density adjustment by.

  In this case, a second optical sensor that measures the toner concentration on the transfer body downstream of the optical sensor in the rotational movement direction of the transfer body is provided, and the control circuit is disposed on the most downstream side. The density of the image density adjustment pattern on the image carrier is measured by the optical sensor, and the density of the toner remaining on or transferred to the transfer body is measured by the second optical sensor. It is also possible to adjust the image density based on the measurement result from each sensor.

  Moreover, it is preferable that the sensitivity of the second optical sensor is higher than the sensitivity of the optical sensor.

  The image forming apparatus of the present invention can perform stable image forming processing without affecting the number of printed sheets per unit time and toner consumption.

1 illustrates an image forming apparatus according to an embodiment of the present invention, and is an explanatory diagram of a tandem color printer as an image forming apparatus according to Embodiment 1. FIG. 1 illustrates an image forming apparatus according to an embodiment of the present invention, and is an enlarged explanatory view of a main part of the image forming apparatus according to Embodiment 1. FIG. FIG. 2 illustrates an image forming apparatus according to an embodiment of the present invention, and is an explanatory diagram of a tandem color printer as an image forming apparatus according to a modification of the first embodiment. FIG. 2 is an enlarged explanatory diagram of a main part of an image forming apparatus according to a modification of the first embodiment, showing an image forming apparatus according to an embodiment of the present invention. FIG. 3 illustrates an image forming apparatus according to an embodiment of the present invention, and is an explanatory diagram of a tandem color printer as an image forming apparatus according to a second embodiment. FIG. 3 is an enlarged explanatory diagram of a main part of an image forming apparatus according to a second embodiment, showing an image forming apparatus according to an embodiment of the present invention. FIG. 9 is an explanatory diagram of a tandem color printer as an image forming apparatus according to a modification of the second embodiment, showing an image forming apparatus according to an embodiment of the present invention. FIG. 9 is an enlarged explanatory diagram of a main part of an image forming apparatus according to a modification of the second embodiment, showing an image forming apparatus according to an embodiment of the present invention.

  Next, an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 illustrates an image forming apparatus according to an embodiment of the present invention, and is an explanatory diagram of a tandem color printer as the image forming apparatus according to the first embodiment. FIG. 2 shows an image forming apparatus according to an embodiment of the present invention, and is an enlarged explanatory view of a main part of the image forming apparatus according to the first embodiment.

(Overall configuration of color printer 1)
In FIG. 1, a color printer 1 as an image forming apparatus according to an embodiment of the present invention is turned upside down on a paper feed cassette 3 that can be pulled out from one surface (for example, the front surface) of a printer main body 2 and one surface of the printer main body 2. A manually feed tray 4 that can be provided, a transport path 5 that transports transfer paper (not shown) set in the paper feed cassette 3 or the manual feed tray 4, and an upstream end of the transport path 5 are configured. A sheet feeding unit 6, a secondary transfer roller 7 disposed in the middle of the conveyance path 5, and an endless belt-shaped intermediate for forming a toner transfer image on the surface of the transfer paper in cooperation with the secondary transfer roller 7 Each color (for example, yellow (Y), magenta (M), cyan (C), etc.) arranged in a tandem manner above the transfer belt 8 and along the rotational movement direction of the intermediate transfer belt 8 above the intermediate transfer belt 8. Black (K)) A developing unit 9, a fixing unit 10 that is arranged near the end of the transport path 5 and fixes a toner transfer image formed on the surface of the transfer paper, and a fixed transfer paper from the downstream end of the transport path 5 to the printer A discharge unit 12 that discharges to the discharge tray unit 11 of the main body 2 is provided.

  The intermediate transfer belt 8 as an intermediate transfer member employs an elastic intermediate transfer belt using at least one elastic layer as a layer structure, and rotates between a driving roller 13, a driven roller (tension roller) 14, and a pressure roller 15. Move and move (see arrow in the figure).

  The pressure roller 15 is disposed opposite to the secondary transfer roller 7 with the intermediate transfer belt 8 interposed therebetween, and the toner is applied to the surface of the transfer paper conveyed to the conveyance path 5 by applying a transfer bias to the secondary transfer roller 7. The image is transferred to form a toner transfer image.

(Configuration of developing device 9)
The developing devices 9 are arranged at four locations in a tandem manner along the rotational movement direction of the intermediate transfer belt 8 along the transfer paper conveyance direction, and those having substantially the same configuration are arranged. Further, the developing device 9 includes a toner container 16 that stores toner of each color, a supply unit 17 that supplies the toner stored in the toner container 16 to the surface of a photosensitive member 18 as a drum-shaped image carrier, and an intermediate transfer belt. A primary transfer device 19 disposed opposite to the photoconductor 18 across 8, a cleaning device 20 that removes residual toner and the like attached to the surface of the photoconductor 18, a static elimination device 21 that removes the charge on the photoconductor 18, A charging device 22 for charging the surface of the photoconductor 18 and an exposure device 23 for forming a predetermined electrostatic latent image on the surface of the photoconductor 18 are provided.

  In the present embodiment, each developing device 9 includes a magenta developing device 9 (M), a cyan developing device 9 (C), and a yellow developing device along the rotational movement direction of the intermediate transfer belt 8. The developing device 9 (K) for black is arranged at the end portion on the right side in the drawing, which is arranged in the order of the apparatus 9 (Y) and is the most downstream in the rotational movement direction of the intermediate transfer belt 8.

(Configuration of supply unit 17)
As shown in FIG. 2, the supply unit 17 includes a stirring mixer 24 that stirs and charges the toner supplied from the toner container 16 together with a carrier, and a paddle mixer that stirs and conveys the two-component developer supplied from the stirring mixer 24. 25, a partition plate 26 interposed between the mixers 24, 25, and a magnetic roller 27 as a sleeve-like developer carrier having a plurality of fixed magnets arranged therein and rotatable around the periphery. A developing roller 28 as a toner carrier that forms a toner layer (not shown) by a magnetic brush (not shown) formed on the magnetic roller 27; and the height of the magnetic brush formed on the magnetic roller 27. A control blade 30 for controlling the transfer bias applied to the transfer device 19, and a control circuit 30 for controlling the transfer bias applied to the transfer device 19. Includes a ROM31 the control data stored relating to the image forming process in general, including, a RAM (or HDD) 32 as a temporary storage means.

  The ROM 31 also stores control data relating to image density correction and color misregistration correction according to the present invention. Thus, the ROM 31 and the control circuit 30 constitute a microcomputer that executes image density correction and color misregistration correction according to the present invention. Further, the control circuit 30 is formed on the photosensitive member 18 (K) from the optical sensor 33 disposed with respect to the black photosensitive member 18 (K) which is the most downstream in the rotational movement direction of the intermediate transfer belt 8. The image density signal of the toner image is input, and the image density correction control and the color shift correction control are performed based on the image density correction control data and the color shift correction control data according to the present invention stored in the ROM 31 based on the input result. Do.

(Image formation processing)
In the color printer 1 having such a configuration, when print data is output from a personal computer (not shown) or the like, the surface of the photoconductor 18 is charged by the charging device 22 (charging process), and then exposed by the exposure device 23. The surface of the body 18 is exposed to form an electrostatic latent image (exposure process).

  On the other hand, in the supply unit 17, the two-component developer is carried on the surface of the magnetic roller 27 to form a magnetic brush, and only the toner is transferred from the magnetic brush on the surface of the magnetic roller 27 to the surface of the developing roller 28. A toner layer is formed on the surface of the developing roller 28.

  Further, the toner is ejected from the toner layer of the developing roller 28, and the toner is attached to the electrostatic latent image on the photoreceptor 18 to develop the electrostatic latent image as a toner image (development process). The transfer device 19 performs primary transfer from the photoreceptor 18 to the intermediate transfer belt 8 (primary transfer process).

  Next, the toner image primarily transferred to the intermediate transfer belt 8 is conveyed to the secondary transfer roller 7 by the rotational movement of the intermediate transfer belt 8, and the transfer paper is applied by the transfer bias applied to the secondary transfer roller 7. (Secondary transfer process).

  The toner remaining on the surface of the intermediate transfer belt 8 after the toner image is secondarily transferred by the secondary transfer roller 7 is arranged downstream of the secondary transfer roller 7 in the rotational movement direction of the intermediate transfer belt 8. Removed by the cleaned cleaning device 38.

(Example)
Next, control examples (embodiments 1 to 4) of image density correction and color misregistration correction by the control circuit 30 will be described.

Example 1
The control circuit 30 prints an image density adjustment pattern on the photosensitive member 18 (K) by the developing device 9 (K) disposed on the most downstream side in the rotational movement direction of the intermediate transfer belt 8.

  Further, the control circuit 30 applies a reverse bias to the transfer device 19 (K) to prevent the toner from being transferred to the intermediate transfer belt 8, and the optical sensor 33 controls the toner density on the photoconductor 18 (K). Measure and adjust the toner density according to the result.

  On the other hand, for example, the control circuit 30 adjusts the image density on the photosensitive member 18 (Y) by the developing device 9 (for example, the developing device 9 (Y)) disposed at a position other than the most downstream in the rotational movement direction of the intermediate transfer belt 8. The pattern for printing is printed.

  In addition, the control circuit 30 transfers the image density adjustment pattern to the intermediate transfer belt 8 by applying a positive bias to the transfer device 19 (Y).

  Then, the control circuit 30 applies the reverse bias to the transfer device 19 (K) to transfer the image density adjustment pattern onto the photoconductor 18 (K).

  Thereafter, the control circuit 30 measures the toner density on the photoconductor 18 (K) with the optical sensor 33 and adjusts the toner density according to the result.

  As a method for adjusting the toner density, adjustment of the developing bias, adjustment of the exposure amount, adjustment of the charging voltage of the photosensitive member, adjustment of gamma correction, change of the toner density in the developer, and the like can be considered.

(Modification 1)
3 and 4 show a modification of the first embodiment of the present invention. The intermediate transfer belt 8 is located downstream of the optical sensor 33 in the rotational movement direction, in this example, facing the conveyor belt 46 and facing the conveyor belt 46. The toner density on the intermediate transfer belt 8 is measured between the transfer device 19 (K) disposed on the most downstream side in the rotational movement direction 46 and the secondary transfer roller 7 on the downstream side of the transfer device 19 (K). A second optical sensor 34 is arranged. Further, the toner density signal on the intermediate transfer belt 8 is input from the second optical sensor 34 to the control circuit 30.

  In such a configuration, the control circuit 30 prints an image density adjustment pattern on the photoreceptor 18 (K).

  Further, the control circuit 30 applies a reverse bias to the transfer device 19 (K) to prevent the toner from being transferred to the intermediate transfer belt 8, and the optical sensor 33 controls the toner density on the photoconductor 18 (K). taking measurement.

  At this time, since a part of the toner may be transferred onto the intermediate transfer belt 8, the control circuit 30 determines the density of the toner transferred onto the intermediate transfer belt 8 by the second optical sensor. Measure at 34.

  The control circuit 30 adjusts the toner density based on the result obtained by adding the densities detected by the sensors 33 and 34.

  On the other hand, for example, the control circuit 30 adjusts the image density on the photosensitive member 18 (Y) by the developing device 9 (for example, the developing device 9 (Y)) disposed at a position other than the most downstream in the rotational movement direction of the intermediate transfer belt 8. The pattern for printing is printed.

  In addition, the control circuit 30 transfers the image density adjustment pattern to the intermediate transfer belt 8 by applying a positive bias to the transfer device 19 (Y).

  Further, the control circuit 30 applies a reverse bias to the transfer device 19 (K) to transfer the image density adjustment pattern onto the photoconductor 18 (K), and the optical sensor 33 performs photoconductor 18 (K). Measure the toner density on the top.

  At this time, since some toner may remain on the intermediate transfer belt 8, the density of the toner remaining on the intermediate transfer belt 8 is measured by the second optical sensor 34.

  Then, the toner density is adjusted based on the result obtained by adding the densities detected by the sensors 33 and 34.

  As a method for adjusting the toner density, adjustment of the developing bias, adjustment of the exposure amount, adjustment of the charging voltage of the photosensitive member, adjustment of gamma correction, change of the toner density in the developer, and the like can be considered.

  The second optical sensor 34 may have the same sensitivity as that of the optical sensor 33. However, in order to increase the accuracy of density correction, the second optical sensor 34 has a smaller amount of toner to be measured than the optical sensor 33. The sensitivity of the two-optical sensor 34 is preferably increased. As a conversion method from the output value of the optical sensor 34 to the toner density value, a known calculation method can be used.

(Example 2)
The control circuit 30 prints a color misregistration correction pattern on the photoreceptor 18 (K).

  Further, the control circuit 30 applies a reverse bias to the transfer device 19 (K) to prevent the toner from being transferred to the intermediate transfer belt 8, and the optical sensor 33 sets the toner position on the photoconductor 18 (K). taking measurement. Then, color misregistration correction is performed based on the result.

  On the other hand, the control circuit 30 prints a color misregistration correction pattern on the photoreceptor 18 (Y).

  Further, the control circuit 30 transfers the color misregistration correction pattern to the intermediate transfer belt 8 by applying a positive bias to the transfer device 19 (Y). By applying a reverse bias to the transfer device 19 (K), the color misregistration correction pattern is transferred onto the photoreceptor 18 (K). The position of the toner on the photoreceptor 18 (K) is measured by the optical sensor 33, and the color shift is adjusted based on the result.

  The same color misregistration correction is performed on the photoconductors 18 (M) and 18 (C). At this time, color misregistration correction includes changing the rotation speed of the driving roller 4 or changing the exposure timing.

(Example 3)
The control circuit 30 discharges toner from the developing device 9 (K) onto the photosensitive member 18 (K) when the printing rate of the developing device 9 (K) is low.

  Further, the control circuit 30 applies a reverse bias to the transfer device 19 (K) so that the toner is not transferred to the intermediate transfer belt 8, and the position of the toner on the photoconductor 18 (K) is detected by the optical sensor 33. Is measured, and color misregistration correction is performed based on the result.

  On the other hand, when the printing rate of the developing device 9 (Y) is low, the control circuit 30 discharges toner from the developing device 9 (Y) onto the photoreceptor 18 (Y).

  In addition, the control circuit 30 transfers the discharged toner to the intermediate transfer belt 8 by applying a positive bias to the transfer device 19 (Y).

  Further, the control circuit 30 applies the reverse bias to the transfer device 19 (K) to transfer the discharged toner onto the photoreceptor 18 (K).

  Further, the control circuit 30 measures the position of the toner on the photoconductor 18 (K) with the optical sensor 33 and corrects the color misregistration based on the result.

  Note that color misregistration correction includes changing the rotation speed of the drive roller 13 and changing the exposure timing. Further, the color misregistration correction may be performed in combination with normal color misregistration correction as well as the discharged toner.

Example 4
The control circuit 30 discharges toner from the developing device 9 (K) onto the photosensitive member 18 (K) when the printing rate of the developing device 9 (K) is low (for example, 1% or less).

  Further, the control circuit 30 applies a reverse bias to the transfer device 19 (K) to prevent the toner from being transferred to the intermediate transfer belt 8, and the optical sensor 33 controls the toner density on the photoconductor 18 (K). Measure and adjust the toner density based on the result.

  Further, when the printing rate of the developing device 9 (Y) is low, the control circuit 30 discharges toner from the developing device 9 (Y) onto the photosensitive member 18 (Y). By applying a positive bias to the transfer device 19 (Y), the discharged toner is transferred to the intermediate transfer belt 8. By applying a reverse bias to the transfer device 19 (K), the discharged toner is transferred onto the photoreceptor 18 (K). The optical sensor 33 measures the toner density on the photoreceptor 18 (K), and adjusts the toner density based on the result.

  As a method for adjusting the toner density, adjustment of the developing bias, adjustment of the exposure amount, adjustment of the charging voltage of the photosensitive member, adjustment of gamma correction, change of the toner density in the developer, and the like can be considered. At this time, the image density adjustment may be performed in combination with not only the discharged toner but also the normal image density adjustment.

(Embodiment 2)
FIG. 5 shows an image forming apparatus according to an embodiment of the present invention, and is an explanatory diagram of a tandem type color printer as the image forming apparatus of the second embodiment. FIG. 6 shows an image forming apparatus according to an embodiment of the present invention, and is an enlarged explanatory view of a main part of the image forming apparatus according to the second embodiment.

(Overall configuration of the color printer 41)
As shown in FIG. 5, a tandem color printer 41 as an image forming apparatus according to an embodiment of the present invention is connected to a personal computer, a printer server, or the like (not shown) and is sent from the computer. A full-color image is transferred and fixed on transfer paper based on the image data.

  In addition, the same code | symbol is attached | subjected to the structure same as the color printer 1 shown in the said Embodiment 1, and the detailed description is abbreviate | omitted.

  Further, the printer 41 forms a part of the conveyance path 5 that conveys transfer paper (not shown) stored in a plurality of stages of paper feed cassettes 3 to the discharge unit 12 while transferring and fixing the photosensitive paper. A transport belt 48 is provided as a transfer body that can be rotated and moved in the arrangement direction of 18, that is, the transfer paper transport direction.

(Other examples)
Next, control examples (embodiments 5 to 8) of image density correction and color misregistration correction by the control circuit 30 will be described.

(Example 5)
The control circuit 30 prints an image density adjustment pattern on the photoreceptor 18 (K).

  In addition, the control circuit 30 applies a reverse bias to the transfer device 19 (K) so that the toner is not transferred to the transport belt 48, and the black photoconductor that is the most downstream in the rotational movement direction of the transport belt 48. The toner density on the photosensitive member 18 (K) is measured by the optical sensor 33 arranged for 18 (K), and the toner density is adjusted based on the result.

  On the other hand, the control circuit 30 prints an image density adjustment pattern on the photoreceptor 18 (Y).

  Further, the control circuit 30 transfers the image density adjustment pattern onto the conveyance belt 48 by applying a positive bias to the transfer device 19 (Y).

  Further, the control circuit 30 applies the reverse bias to the transfer device 19 (K) to transfer the image density adjustment pattern onto the photoreceptor 18 (K).

  As a result, the control circuit 30 measures the toner density on the photoconductor 18 (K) with the optical sensor 33 and adjusts the toner density based on the result.

  As a method for adjusting the toner density, adjustment of the developing bias, adjustment of the exposure amount, adjustment of the charging voltage of the photosensitive member, adjustment of gamma correction, change of the toner density in the developer, and the like can be considered.

(Modification 2)
7 and 8 show a modification of the second embodiment of the present invention. The downstream side of the optical sensor 33 in the rotational movement direction of the conveyance belt 48, in this example, the conveyance belt 46 is opposed to the conveyance belt 46. FIG. Between the transfer device 19 (K) arranged on the most downstream side in the rotational movement direction and the transfer device 19 (M) arranged on the most upstream side in the rotational movement direction downstream from the transfer device 19 (K). A second optical sensor 34 for measuring the toner density on the belt 48 is disposed. Further, the toner density signal on the conveyor belt 48 is input from the second optical sensor 34 to the control circuit 30.

  In such a configuration, the control circuit 30 prints an image density adjustment pattern on the photoreceptor 18 (K).

  Further, the control circuit 30 applies a reverse bias to the transfer device 19 (K) to prevent the toner from being transferred to the conveyance belt 48, and measures the toner density on the photoconductor 18 (K) with the optical sensor 33. To do.

  At this time, since a part of the toner may be transferred onto the conveyor belt 48, the control circuit 30 uses the second optical sensor 34 to determine the density of the toner transferred onto the conveyor belt 48. taking measurement.

  The control circuit 30 adjusts the toner density based on the result obtained by adding the densities detected by the sensors 33 and 34.

  On the other hand, the control circuit 30 prints an image density adjustment pattern on the photoreceptor 18 (Y).

  Further, the control circuit 30 transfers the image density adjustment pattern onto the conveyance belt 48 by applying a positive bias to the transfer device 19 (Y).

  Further, the control circuit 30 applies a reverse bias to the transfer device 19 (K) to transfer the image density adjustment pattern onto the photoconductor 18 (K), and the optical sensor 33 performs photoconductor 18 (K). Measure the toner density on the top.

  At this time, there is a possibility that a part of the toner may remain on the transport belt 48, and therefore the density of the toner remaining on the transport belt 48 is measured by the second optical sensor 34.

  Then, the toner density is adjusted based on the result obtained by adding the densities detected by the sensors 33 and 34.

  As a method for adjusting the toner density, adjustment of the developing bias, adjustment of the exposure amount, adjustment of the charging voltage of the photosensitive member, adjustment of gamma correction, change of the toner density in the developer, and the like can be considered.

  The second optical sensor 34 may have the same sensitivity as that of the optical sensor 33. However, in order to increase density correction accuracy, the amount of toner to be measured is smaller than that of the optical sensor 33. The sensitivity of the second optical sensor 34 is preferably increased. As a conversion method from the output value of the optical sensor 34 to the toner density value, a known calculation method can be used.

(Example 6)
The control circuit 30 prints a color misregistration correction pattern on the photoreceptor 18 (K).

  Further, the control circuit 30 applies a reverse bias to the transfer device 19 (K) so that the toner is not transferred to the conveyance belt 48, and the position of the toner on the photoconductor 18 (K) is detected by the optical sensor 33. Measure and correct color misregistration based on the result.

  On the other hand, the control circuit 30 prints a color misregistration correction pattern on the photoreceptor 18 (Y).

  In addition, the control circuit 30 applies a positive bias to the transfer device 19 (Y) to transfer the color misregistration correction pattern onto the transport belt 48.

  Further, the control circuit 30 applies a reverse bias to the transfer device 19 (K) to transfer the color misregistration correction pattern onto the photoreceptor 18 (K).

  As a result, the control circuit 30 measures the position of the toner on the photoreceptor 18 (K) with the optical sensor 33 and corrects the color misregistration based on the result.

  Note that color misregistration correction includes changing the rotation speed of the driving roller 4 and changing the exposure timing.

(Example 7)
The control circuit 30 discharges toner from the developing device 9 (K) onto the photosensitive member 18 (K) when the printing rate of the developing device 9 (K) is low.

  Further, the control circuit 30 applies a reverse bias to the transfer device 19 (K) so that the toner is not transferred to the conveyance belt 48, and the position of the toner on the photoconductor 18 (K) is detected by the optical sensor 33. Measure and correct color misregistration based on the result.

  On the other hand, when the printing rate of the developing device 9 (Y) is low, the control circuit 30 discharges toner from the developing device 9 (Y) onto the photoreceptor 18 (Y).

  In addition, the control circuit 30 applies the positive bias to the transfer device 19 (Y) to transfer the discharged toner to the transport belt 48.

  Further, the control circuit 30 applies the reverse bias to the transfer device 19 (K) to transfer the discharged toner onto the photoreceptor 18 (K).

  As a result, the control circuit 30 measures the position of the toner on the photoreceptor 18 (K) with the optical sensor 33 and corrects the color misregistration based on the result.

  Note that color misregistration correction includes changing the rotation speed of the driving roller 4 and changing the exposure timing. At this time, the color misregistration correction may be performed in combination with the normal color misregistration correction as well as the discharged toner.

(Example 8)
The control circuit 30 discharges toner from the developing device 9 (K) onto the photosensitive member 18 (K) when the printing rate of the developing device 9 (K) is low.

  Further, the control circuit 30 applies a reverse bias to the transfer device 19 (K) to prevent the toner from being transferred to the conveyance belt 48, and measures the toner density on the photoconductor 18 (K) with the optical sensor 33. The toner density is adjusted based on the result.

  On the other hand, when the printing rate of the developing device 9 (Y) is low, the control circuit 30 discharges toner from the developing device 9 (Y) onto the photoreceptor 18 (Y).

  In addition, the control circuit 30 applies the positive bias to the transfer device 19 (Y) to transfer the discharged toner to the transport belt 48.

  Further, the control circuit 30 applies the reverse bias to the transfer device 19 (K) to transfer the discharged toner onto the photoreceptor 18 (K).

  As a result, the control circuit 30 measures the toner density on the photoconductor 18 (K) with the optical sensor 33 and adjusts the toner density based on the result.

  As a method for adjusting the toner density, adjustment of the developing bias, adjustment of the exposure amount, adjustment of the charging voltage of the photosensitive member, adjustment of gamma correction, change of the toner density in the developer, and the like can be considered. At this time, the image density adjustment may be performed in combination with not only the discharged toner but also the normal image density adjustment.

  By the way, in the toner discharge mode described above, particularly when the toner printing rate is low, the replacement of the old toner with the new toner is reduced, and the toner is deteriorated.

  Accordingly, in such a case, the deteriorated toner in the developing device 9 is prevented from accumulating in the developing device 9 by controlling to discharge the deteriorated toner in the developing device 9 and supply new toner.

  The discharged toner is collected in the waste toner box as it is, but in the above-described embodiment, the discharged toner is effectively used for color misregistration correction.

  At this time, since the color misregistration correction is performed simultaneously with the toner ejection, the color misregistration correction can be performed without reducing the number of printed sheets per unit time.

  Further, particularly during low printing that is frequently used, color misregistration correction can be performed frequently without worrying about toner consumption, and an image with little color misregistration can always be output.

  In the above embodiment, the image forming apparatus of the present invention is applied to the tandem type color printers 1 and 41. However, the image forming apparatus can be applied to all image forming apparatuses such as a color multifunction peripheral. Of course.

1. Color printer (image forming device)
8. Intermediate transfer belt (intermediate transfer member)
9 ... Developing device 18 ... Photoconductor (image carrier)
DESCRIPTION OF SYMBOLS 19 ... Transfer device 30 ... Control circuit 33 ... Optical sensor 34 ... 2nd optical sensor 48 ... Conveyance belt (transfer body)

Claims (12)

Formed on each image carrier by an intermediate transfer member that can be rotated and moved in the transfer material conveyance direction, and developing devices for multiple colors arranged in a tandem manner along the direction of rotation of the intermediate transfer member A transfer device that transfers the toner image formed on the intermediate transfer member, and an optical device that outputs an image density signal of the toner image formed on the image carrier disposed downstream in the rotational movement direction of the intermediate transfer member In an image forming apparatus comprising: an image sensor; and a control circuit that adjusts an image density of the developing device based on an image density signal output from the optical sensor,
The control circuit transfers the image density of the image density adjustment pattern for each color by the developing device arranged at a position other than the most downstream in the rotational movement direction of the intermediate transfer body after the image is once transferred onto the intermediate transfer body. By applying a bias having a polarity opposite to that of a normal transfer bias to the transfer device disposed at the most downstream side in the rotational movement direction of the intermediate transfer body, the adjustment pattern is placed on the downstream side in the rotational movement direction of the intermediate transfer body. In the pattern for adjusting the image density of the color by the developing device disposed at the most downstream side in the rotational movement direction of the intermediate transfer member after being transferred to the arranged image carrier, the intermediate transfer member By applying a bias having a polarity opposite to that of a normal transfer bias to the transfer device arranged on the most downstream side in the rotational movement direction, the image density adjusting pattern is not transferred onto the intermediate transfer member. On the image carrier disposed on the most downstream side in the rotational movement direction of the intermediate transfer member, respectively, in a state in which the toner image is held on the image carrier disposed on the most downstream side in the rotational movement direction of the intermediate transfer member. An image forming apparatus, wherein image density adjustment is performed by measuring a pattern density for image density adjustment with the optical sensor. Formed on each image carrier by an intermediate transfer member that can be rotated and moved in the transfer material conveyance direction, and developing devices for multiple colors arranged in a tandem manner along the direction of rotation of the intermediate transfer member A transfer device for transferring the toner image formed on the intermediate transfer member, and an optical type for outputting an image position signal of the toner image formed on the image carrier disposed downstream in the rotational movement direction of the intermediate transfer member In an image forming apparatus comprising: a sensor; and a control circuit that performs color misregistration correction based on an image position signal output from the optical sensor.
The control circuit is configured to transfer the color misregistration pattern of each color by the developing device arranged at a position other than the most downstream in the rotational movement direction of the intermediate transfer member, after transferring the color onto the intermediate transfer member. By applying a bias having a polarity opposite to that of a normal transfer bias to the transfer device disposed at the most downstream side in the rotational movement direction of the intermediate transfer body, the correction pattern is placed on the downstream side in the rotational movement direction of the intermediate transfer body. In the pattern for correcting color misregistration by the developing device arranged at the most downstream side in the rotational movement direction of the intermediate transfer body after being transferred to the arranged image carrier, the intermediate transfer body By applying a bias having a polarity opposite to that of a normal transfer bias to the transfer device arranged on the most downstream side in the rotational movement direction, a color misregistration correction pattern is transferred without being transferred onto the intermediate transfer body. The color misregistration on the image carrier disposed on the most downstream side in the rotational movement direction of the intermediate transfer member while being held by the image carrier disposed on the most downstream side in the rotational movement direction of the intermediate transfer member. An image forming apparatus, wherein a color misregistration correction is performed by measuring a correction pattern position with the optical sensor. Formed on each image carrier by an intermediate transfer member that can be rotated and moved in the transfer material conveyance direction, and developing devices for multiple colors arranged in a tandem manner along the direction of rotation of the intermediate transfer member A transfer device for transferring the toner image formed on the intermediate transfer member, and an optical type for outputting an image position signal of the toner image formed on the image carrier disposed downstream in the rotational movement direction of the intermediate transfer member In an image forming apparatus comprising: a sensor; and a control circuit that performs color misregistration correction based on an image position signal output from the optical sensor.
The control circuit activates a toner discharge mode for discharging toner from each of the developing devices at a predetermined timing, and detects the discharge toner from the developing device disposed at a position other than the most downstream in the rotational movement direction of the intermediate transfer member. First, after transferring the toner onto the intermediate transfer member, a bias having a polarity opposite to that of a normal transfer bias is applied to the transfer device disposed on the most downstream side in the rotational movement direction of the intermediate transfer member. The toner discharged from the developing device disposed on the most downstream side in the rotational movement direction of the intermediate transfer body after being transferred to the image carrier disposed on the most downstream side in the rotational movement direction of the intermediate transfer body. In this case, a bias having a polarity opposite to that of a normal transfer bias is applied to the transfer device disposed at the most downstream in the rotational movement direction of the intermediate transfer member. In the state where the discharged toner is held on the image carrier disposed on the most downstream side in the rotational movement direction of the intermediate transfer body without being transferred onto the intermediate transfer body, the downstream side in the rotational movement direction of the intermediate transfer body, respectively. An image forming apparatus, wherein a color misregistration correction is performed by measuring a position of a discharged toner on the image carrier disposed on the image carrier with the optical sensor. Formed on each image carrier by an intermediate transfer member that can be rotated and moved in the transfer material conveyance direction, and developing devices for multiple colors arranged in a tandem manner along the direction of rotation of the intermediate transfer member A transfer device for transferring the toner image formed on the intermediate transfer member, and an optical device for outputting an image density signal of the toner image formed on the image carrier disposed on the most downstream side in the rotational movement direction of the intermediate transfer member In an image forming apparatus comprising: a sensor; and a control circuit that performs image density adjustment of the developing device based on an image density signal output from the optical sensor.
The control circuit activates a toner discharge mode that discharges toner from the developing device at a predetermined timing, and is provided for toner discharged from the developing device disposed at a position other than the most downstream in the rotational movement direction of the intermediate transfer member. Is obtained by transferring the toner onto the intermediate transfer member and applying a bias having a polarity opposite to that of a normal transfer bias to the transfer device disposed on the most downstream side in the rotational movement direction of the intermediate transfer member. After the toner image is transferred to the image carrier disposed on the most downstream side in the rotational movement direction of the intermediate transfer member, the toner discharged from the developing device disposed on the most downstream side in the rotational movement direction of the intermediate transfer member is used. In this case, by applying a bias having a polarity opposite to that of a normal transfer bias to the transfer device arranged on the most downstream side in the rotational movement direction of the intermediate transfer member, The discharged toner is held on the image carrier disposed on the most downstream side in the rotational movement direction of the intermediate transfer body without being transferred onto the transfer body, and is respectively disposed on the downstream side in the rotational movement direction of the intermediate transfer body. An image forming apparatus comprising: adjusting an image density by measuring a density of a discharged toner on the arranged image carrier with the optical sensor. A second optical sensor for measuring the toner density on the image carrier on the downstream side in the rotational movement direction of the intermediate transfer member with respect to the optical sensor;
The control circuit measures the density of the image density adjustment pattern on the image carrier disposed on the most downstream side with the optical sensor and detects the toner remaining or transferred on the intermediate transfer body. 5. The image forming apparatus according to claim 1, wherein the image density is measured by the second optical sensor, and image density adjustment is performed based on a measurement result from each of the sensors.   The image forming apparatus according to claim 5, wherein the sensitivity of the second optical sensor is higher than the sensitivity of the optical sensor. Formed on each image carrier by a transfer body that can be rotated and moved in the transfer material conveyance direction, and developing devices for multiple colors arranged in a tandem manner along the rotation and movement direction of the transfer body. A transfer device that transfers a toner image onto a transfer material conveyed by a transfer body, and an image density signal of the toner image formed on the image carrier disposed on the most downstream side in the rotational movement direction of the transfer body is output. In an image forming apparatus comprising: an optical sensor; and a control circuit that performs image density adjustment of the developing device based on an image density signal output from the optical sensor.
The control circuit temporarily transfers the image density adjustment pattern of each color by the developing device arranged at a position other than the most downstream in the rotational movement direction of the transfer body onto the transfer body and then adjusts the image density. The pattern disposed at the most downstream side in the rotational movement direction of the transfer body by applying a bias having a polarity opposite to a normal transfer bias to the transfer device disposed at the most downstream side in the rotational movement direction of the transfer body. After the image is transferred to the image carrier, and in the color image density adjustment pattern by the developing device arranged at the most downstream side in the rotational movement direction of the transfer body, the downstream side in the rotational movement direction of the transfer body. By applying a bias having a polarity opposite to that of a normal transfer bias to the transfer device arranged on the transfer device, an image density adjustment pattern is rotated and moved without being transferred onto the transfer member. The optical sensor detects the image density adjustment pattern density on the image carrier disposed on the most downstream side in the rotational movement direction of the transfer body while being held by the image carrier disposed on the most downstream side. An image forming apparatus characterized in that image density adjustment is performed by measuring with the above. Formed on each image carrier by a transfer body that can be rotated and moved in the transfer material conveyance direction, and developing devices for multiple colors arranged in a tandem manner along the rotation and movement direction of the transfer body. A transfer device for transferring a toner image onto a transfer material conveyed by a transfer body, and an image position signal of the toner image formed on the image carrier disposed on the most downstream side in the rotational movement direction of the transfer body are output. In an image forming apparatus comprising: an optical sensor; and a control circuit that performs color misregistration correction based on an image position signal output from the optical sensor.
The control circuit transfers the color misregistration correction pattern for each color by the developing device arranged at a position other than the most downstream in the rotational movement direction of the transfer body, after transferring the pattern onto the transfer body. The pattern disposed at the most downstream side in the rotational movement direction of the transfer body by applying a bias having a polarity opposite to a normal transfer bias to the transfer device disposed at the most downstream side in the rotational movement direction of the transfer body. In the pattern for correcting color misregistration of the color by the developing device disposed at the most downstream side in the rotational movement direction of the transfer body after being transferred to the image carrier, the transfer body in the rotational movement direction is the most. By applying a bias having a polarity opposite to that of a normal transfer bias to the transfer device disposed downstream, the color misregistration correction pattern is transferred to the bottom in the rotational movement direction of the transfer body without being transferred onto the transfer body. With the optical sensor, the optical sensor measures the color misalignment correction pattern position on the image carrier disposed at the most downstream side in the rotational movement direction of the transfer member. An image forming apparatus that performs color misregistration correction. Formed on each image carrier by a transfer body that can be rotated and moved in the transfer material conveyance direction, and developing devices for multiple colors arranged in a tandem manner along the rotation and movement direction of the transfer body. A transfer device for transferring a toner image onto a transfer material conveyed by a transfer body, and an image position signal of the toner image formed on the image carrier disposed on the most downstream side in the rotational movement direction of the transfer body are output. In an image forming apparatus comprising: an optical sensor; and a control circuit that performs color misregistration correction based on an image position signal output from the optical sensor.
The control circuit activates a toner discharge mode for discharging toner from each of the developing devices at a predetermined timing, and is provided for toner discharged from the developing device disposed at a position other than the most downstream in the rotational movement direction of the transfer body. Transfer the toner onto the transfer body by applying a bias having a polarity opposite to that of a normal transfer bias to the transfer device disposed on the most downstream side in the rotational movement direction of the transfer body. The toner discharged from the developing device disposed on the most downstream side in the rotational movement direction of the transfer body after being transferred to the image carrier disposed on the most downstream side in the rotational movement direction of the body The transfer device arranged at the most downstream in the rotational movement direction of the transfer body is not transferred onto the transfer body by applying a bias having a polarity opposite to that of a normal transfer bias. In the state where the discharged toner is held on the image carrier arranged at the most downstream side in the rotational movement direction of the transfer body, the discharge on the image carrier arranged at the most downstream side in the rotational movement direction of the transfer body, respectively. An image forming apparatus that performs color misregistration correction by measuring a toner position with the optical sensor. Formed on each image carrier by a transfer body that can be rotated and moved in the transfer material conveyance direction, and developing devices for multiple colors arranged in a tandem manner along the rotation and movement direction of the transfer body. A transfer device that transfers a toner image onto a transfer material conveyed by a transfer body, and an image density signal of the toner image formed on the image carrier disposed on the most downstream side in the rotational movement direction of the transfer body is output. In an image forming apparatus comprising: an optical sensor; and a control circuit that performs image density adjustment of the developing device based on an image density signal output from the optical sensor.
The control circuit activates a toner discharge mode for discharging toner from the developing device at a predetermined timing, and for the toner discharged from the developing device arranged at a position other than the most downstream in the rotational movement direction of the transfer body. Once the transfer toner is transferred onto the transfer body, a bias having a polarity opposite to that of a normal transfer bias is applied to the transfer device disposed downstream of the transfer body in the rotational movement direction. The toner transferred from the developing device disposed at the most downstream side in the rotational movement direction of the transfer body is transferred to the image carrier after being transferred to the downstream side in the rotational movement direction of the transfer body. By applying a bias having a polarity opposite to that of a normal transfer bias to the transfer device arranged on the most downstream side in the rotational movement direction of the body without transferring onto the transfer body The discharged toner is held on the image carrier disposed at the most downstream side in the rotational movement direction of the transfer body, and discharged on the image carrier disposed at the most downstream side in the rotational movement direction of the transfer body. An image forming apparatus, wherein toner density is measured by the optical sensor to adjust image density. A second optical sensor for measuring the toner density on the transfer body downstream of the optical sensor in the rotational movement direction of the transfer body;
The control circuit measures the density of the image density adjustment pattern on the image carrier disposed on the most downstream side with the optical sensor, and the density of the toner remaining or transferred on the transfer body. The image forming apparatus according to claim 7, wherein the image density is measured by the second optical sensor and image density adjustment is performed based on a measurement result from each of the sensors.   The image forming apparatus according to claim 11, wherein the sensitivity of the second optical sensor is higher than the sensitivity of the optical sensor.

Images