JP3825184B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as a color copying machine, a color printer, and a color facsimile.
[0002]
[Prior art]
Conventionally, in an image forming apparatus such as a color copying machine, a color printer, or a color facsimile that performs an electrophotographic process, exposure is performed after a photosensitive member as an image carrier is uniformly charged by a charger while moving in the sub-scanning direction. An electrostatic latent image is formed by exposure by means, and the electrostatic latent image on the photosensitive member is developed by a developing device and transferred to paper or the like by a transfer device.
[0003]
The developing device includes a developing roller. The developing roller is applied with a developing bias from a developing bias power source and is rotationally driven by a driving unit. The developing roller magnetically attracts and carries the developer in the apparatus by an internal magnet, and the developer on the developing roller is conveyed along with the rotation of the developing roller to be between the developing roller and the photosensitive member. The electrostatic latent image on the photosensitive member is developed in the developing area.
[0004]
[Problems to be solved by the invention]
  In the image forming apparatus, unevenness in the sub-scanning direction occurs in the toner image on the photosensitive member due to uneven resistance in the circumferential direction (rotating direction) of the developing roller.
  The present inventionAn object of the present invention is to provide an image forming apparatus capable of reducing uneven image density in the sub-scanning direction.
[0005]
  The present inventionAn object of the present invention is to provide an image forming apparatus capable of reducing the uneven image density in the sub-scanning direction by detecting the rotation period of the developing roller.
  The present inventionAn object of the present invention is to provide an image forming apparatus capable of reducing image density unevenness by detecting the amount of image density unevenness.
[0006]
  The present inventionAn object of the present invention is to provide an image forming apparatus that can reduce unevenness in image density in the sub-scanning direction by changing the developing bias.
  The present inventionAn object of the present invention is to provide an image forming apparatus capable of reducing image density unevenness in the sub-scanning direction by performing phase matching by using an output signal of the developing roller rotation period detecting device and an output signal of the uneven density detecting device. .
[0007]
[Means for Solving the Problems]
  In order to achieve the above object, an invention according to claim 1 is a development device having a developing roller that forms an electrostatic latent image on an image carrier and rotates at a predetermined cycle. Control means for changing a process condition in accordance with a rotation period of the developing roller in an image forming apparatus that develops an image into a toner imageA developing roller rotation period detecting device for detecting the rotation period of the developing roller, a density unevenness detecting device for detecting the density unevenness amount of the toner image on the image carrier, and an output signal of the density unevenness detecting device And a pattern generator for forming on the image carrier a pattern for phase matching of the output signal of the developing roller rotation period detector, and the density unevenness with respect to the pattern on the image carrier Phase matching is performed by the output signal of the detection device and the output signal of the developing roller rotation period detection device.Is.
[0008]
  The invention according to claim 2 is the image forming apparatus according to claim 1,The control means changes the developing bias of the developing device according to the rotation period of the developing roller as the process condition.Is.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 2 shows an embodiment of the present invention. This embodiment is an embodiment of a color printer as a color image forming apparatus. In FIG. 2, reference numeral 1 denotes a belt-like image carrier made of a flexible belt-like photoreceptor, and this belt-like photoreceptor 1 is constructed between the rotation rollers 2 and 3 and is driven by the rotation roller 2. And conveyed in the sub-scanning direction (clockwise). The belt-like photoreceptor 1 may be a drum-like photoreceptor.
[0013]
4 is a charging member composed of a charging roller as a charging means, 5 is a laser writing system unit as an image exposure means, and 6 to 9 are a plurality of developing means each containing developers of different specific colors in a rotary developing unit. Development unit. The laser writing system unit 5 is housed in a holding housing having a slit-shaped exposure opening on the upper surface and is incorporated in the apparatus main body. The charging member 4 as the charging means and the laser writing system unit 5 as the image exposure means constitute a latent image forming means.
[0014]
In addition to the optical system shown in the drawing, the laser writing system unit 5 may be an optical system in which a light emitting unit and a convergent light transmission body are integrated. The charging roller 4, the portion of the laser writing system unit 5 that irradiates the belt-shaped photoconductor 1 with the laser writing light 5D, and the photoconductor cleaning device 15 includes a plurality of rollers 2 and 3 on which the belt-shaped photoconductor 1 is installed. Is provided in the vicinity of one roller 2.
[0015]
Each of the developing units 6 to 9 contains a developer having toners of, for example, yellow, magenta, cyan, and black, respectively, and is in the vicinity of or in contact with the belt-like photoreceptor 1 at a predetermined position. And a developer carrying member having a function of developing an electrostatic latent image on the photosensitive belt 1 by a non-contact developing method or a contact developing method. Reference numeral 10 denotes an intermediate transfer member as a transfer image carrier. The intermediate transfer member 10 is provided between the rotation rollers 11 and 12 and is driven by one of the rotation rollers to rotate counterclockwise. Consists of a transfer belt.
[0016]
The belt-like photosensitive member 1 and the intermediate transfer belt 10 are in contact with each other at the rotating roller 3, and a transfer bias is applied from a high-voltage power source to a bias roller 13 serving as a transfer unit that is in contact with the inside of the intermediate transfer belt 10. Then, the single color image of one color plate formed on the belt-shaped photosensitive member 1 for the first time is transferred onto the intermediate transfer belt 10. Similarly, a single color image of each of the other color plates formed on the belt-shaped photoreceptor 1 for the second time to the fourth time is displayed on the intermediate transfer belt 10 as a single color image of one color plate formed on the first time. The images are transferred so as not to be misaligned.
[0017]
The transfer roller 14 constituting the transfer unit is provided so as to be in contact with and separated from the intermediate transfer belt 10 by a contact and separation mechanism. Reference numeral 15 denotes a photoconductor cleaning device for cleaning the belt-like photoconductor 1, and 16 denotes an intermediate transfer belt cleaning device for cleaning the intermediate transfer belt 10. The blade 16 A of the cleaning device 16 is in contact with the separation mechanism during image formation. Is kept at a position spaced from the surface of the intermediate transfer belt 10 and is pressed against the surface of the intermediate transfer belt 10 as shown in the figure only during cleaning after image transfer.
[0018]
The formation of a multicolor image in this color printer is performed as follows. That is, an image reading apparatus separate from the color printer scans an original image and reads it with an image sensor, and performs an arithmetic process on the read color image data in an image data processing unit, that is, yellow, Magenta, cyan, and black image data are created and stored once in the image memory.
[0019]
Next, the image data of each color is extracted from the image memory at the time of image formation and is input to the laser writing system unit 5 in the color printer. That is, image data of each color output from an image reading device separate from the color printer is sequentially input to the laser writing system unit 5 via the image data processing unit.
[0020]
In the laser writing system unit 5, the rotary polygon mirror 5B is rotationally driven by a rotary polygon mirror drive device 5A composed of a drive motor, and the semiconductor lasers sequentially input images of respective colors from the image reading device via the image data processing unit. A laser beam whose intensity is changed in accordance with image data of each color is generated by being modulated and driven by the semiconductor laser driving circuit based on the data. This laser beam is deflected and scanned by the rotary polygon mirror 5B, and the optical path is bent by the mirror 5G through the fθ lens 5C and irradiated onto the peripheral surface of the belt-shaped photosensitive member 1.
[0021]
The belt-like photosensitive member 1 is discharged by the charge removing lamp 21 and uniformly charged by the charging roller 4, and then exposed by the laser beam 5D from the mirror 5G, and electrostatic latent images corresponding to the image signals of the respective colors are sequentially formed. It is formed. Here, a bias is applied to the charging roller 4 from a high-voltage power supply to uniformly charge the belt-shaped photoreceptor 1, and an image pattern exposed to the belt-shaped photoreceptor 1 by the laser writing system unit 5 is a desired full-color image that is yellow. , Magenta, cyan, and black.
[0022]
The electrostatic latent images corresponding to the image signals of the respective colors sequentially formed on the belt-shaped photosensitive member 1 are developed by developing with yellow, magenta, cyan and black developing units 6 to 9 in the rotary developing unit. As a result, each color becomes a single color image. When the electrostatic latent image corresponding to the yellow image signal is formed on the belt-like photoreceptor 1, the developing device 6 moves to the developing position by rotation and develops the electrostatic latent image into a yellow single color image, Similarly, when the electrostatic latent images corresponding to the magenta, cyan, and black image signals are formed on the belt-like photosensitive member 1, the other developing devices 7 to 9 move to the developing position by rotation and move to the magenta, The cyan and black electrostatic latent images are respectively developed to form magenta, cyan, and black single color images.
[0023]
A transfer bias is applied to the intermediate transfer belt 10 from a high-voltage power source via a bias roller 13, and yellow, magenta, cyan, and black single-color images sequentially formed on the belt-like photoreceptor 1 are applied to the belt-like photoreceptor 1. The images are sequentially superimposed and transferred onto the intermediate transfer belt 10 that rotates counterclockwise while contacting. A full-color image is formed by superimposing and transferring yellow, magenta, cyan, and black single-color images on the intermediate transfer belt 10, and this full-color image is fed from a paper feed stand 17 by a paper feed roller 18. Then, the toner image is transferred by the transfer roller 14 to the transfer paper that has been conveyed to the transfer portion via the registration roller 19.
[0024]
The transfer paper is fixed by the fixing device 20 to complete a full color image, and is discharged to the tray 23. The intermediate transfer belt 10 and the belt-like photoreceptor 1 are seamless. The belt-like photoreceptor 1 is cleaned by a photoreceptor cleaning device 15 after each monochrome image of yellow, magenta, cyan, and black is transferred to the intermediate transfer belt 10, and the intermediate transfer belt 10 after the image is transferred to the transfer paper. Cleaning is performed by the intermediate transfer belt cleaning device 16.
[0025]
FIG. 3 is an enlarged view showing a part of the color printer.
Six marks 41 </ b> A to 41 </ b> F are provided at predetermined intervals at the end of the intermediate transfer belt 10, and the mark detection means including the mark detection sensor 40 moves the marks 41 </ b> A to 41 </ b> F on the intermediate transfer belt 10 to a rotation roller. It is detected downstream of the intermediate transfer belt 10 in the rotational direction with respect to 12.
[0026]
When the mark detection sensor 40 detects any one of the six marks 41A to 41F, for example, the mark 41A, the laser writing system unit 5 writes the first color image on the belt-shaped photoreceptor 1 (yellow image signal). When the mark 41A goes around once and the mark detection sensor 40 detects the mark 41A again, the second color image is written (exposure with the laser beam corresponding to the magenta image signal). To start.
[0027]
At this time, the detection signals for the marks 41B to 41F of the mark detection sensor 40 are masked so that they cannot be used as the image writing timing by managing the number of marks detected by the mark detection sensor 40. A density unevenness detection device comprising a photo sensor (hereinafter referred to as P sensor) 22 is installed opposite to a portion on the photosensitive belt 1 upstream of the rotation direction of the photosensitive belt 1 with respect to the portion in contact with the intermediate transfer belt 10. The amount of uneven density of the toner image on the photoreceptor belt 1 is optically detected.
[0028]
FIG. 4 shows a part of the rotary developing unit. In the developing device 6, a detection plate 31 with one missing portion for detecting the rotation of the developing roller 6a is directly connected to the shaft of the developing roller 6a. The detecting plate 31 rotates in conjunction with the developing roller 6a. . By detecting the chipping of the detection plate 31 by the transmissive photo interrupter 32 every rotation of the detection plate 31, the rotation position (rotation period) of the developing roller 6a is detected. The detection plate 31 and the photo interrupter 32 constitute a developing roller rotation position (rotation cycle) detector that detects the rotation position (rotation cycle) of the developing roller 6a.
[0029]
FIG. 1 shows a density unevenness control unit of this embodiment. A high voltage power pack (PP) 33 as a developing bias power source applies a developing bias as a process condition to the developing roller 6a, and a control signal generator 34 as a control means detects from a developing roller rotation position (rotation cycle) detector. Image density unevenness is reduced by controlling the development bias by controlling the high-pressure PP 33 based on the signal (development roller signal) and phase information described later.
[0030]
FIG. 5 shows a pattern for performing phase matching between the detection signal from the developing roller rotation position detection device and the detection signal from the P sensor 22. When forming an electrostatic latent image corresponding to a yellow image signal, a pattern generator (not shown) generates a yellow pattern signal for forming a rectangular pattern of an arbitrary size on the photosensitive belt 1 and laser writing. Output to the system unit 5.
[0031]
The laser writing system unit 5 modulates and drives a semiconductor laser by a semiconductor laser driving circuit with a yellow pattern signal from a pattern generator, and exposes the photosensitive belt 1 with a laser beam from the semiconductor laser as described above. The photosensitive belt 1 is uniformly charged by the charging roller 4 and then exposed by the laser writing system unit 5 to form an electrostatic latent image 35 having a rectangular pattern as shown in FIG. When the intermediate portion of the electrostatic latent image 35 in the sub-scanning direction moves from the exposure position to the development position, the development bias applied from the high voltage PP 33 to the development roller 6a is temporarily turned off by a control device (not shown) and again. Turn on. The developing device 6 develops the electrostatic latent image 35 into yellow toner images 36 and 37 as shown in FIG.
[0032]
Since the electrostatic latent image 35 is formed by writing with the laser beam having the maximum power by the laser writing system unit 5, the electrostatic latent image 35 is developed by the developing device 6 and becomes the toner images 36 and 37 firmly when the developing bias is turned on. When the developing bias is off, a toner image is not formed even if the electrostatic latent image 35 is developed by the developing device 6.
[0033]
The toner images 36 and 37 on the photosensitive belt 1 are detected by the P sensor 22 for the amount of density unevenness. The control device measures the timing for turning on / off the developing bias of the developing roller 6a and the rotation angle from the detection position of the developing roller 6a (hereinafter referred to as home) (elapsed time since passing through the home) and responds to them. Each position is set as a reference position.
[0034]
FIG. 6 shows the operation timing of this embodiment. Phase (time) a based on a detection signal (development roller signal from the photo interrupter 32) from the development roller rotation position detection device at the time of development bias on / off for turning on / off the development bias of the development roller 6a, development The time t from when the bias is turned on / off until the toner images 36 and 37 of the above pattern are detected by the P sensor 22 is measured by the control device, and the result is input to the control signal generator 34 as phase information and developed. The detection signal from the P sensor 22 is matched with the phase corresponding to the ON / OFF state of the developing bias so that the developing position of the developing device 6 and the detecting position of the developing roller rotation position detecting device match.
[0035]
FIG. 7 shows the operation timing at the time of density detection of the present embodiment. When density unevenness is detected, a pattern generator (not shown) generates a yellow pattern signal for forming a pattern having a writing level of about 20% on the photosensitive belt 1 and outputs it to the laser writing system unit 5. The laser writing system unit 5 modulates and drives a semiconductor laser by a semiconductor laser driving circuit with a yellow pattern signal from a pattern generator, and exposes the photosensitive belt 1 with a laser beam from the semiconductor laser as described above.
[0036]
The photosensitive belt 1 is uniformly charged by the charging roller 4 and then exposed by the laser writing system unit 5 to form an electrostatic latent image having a rectangular pattern. The electrostatic latent image is developed by the developing device 6 to become a yellow toner image, and the yellow toner image is detected by the P sensor 22 for uneven density.
[0037]
Here, the rectangular pattern has a length of about five cycles (five rotations) of the developing row 6a in the rotation direction of the photosensitive belt 1, and the control signal generator 34 develops from the developing roller rotation position detecting device. Based on the roller signal and the phase information, the developing position of the developing device 6 and the detection position of the developing roller rotation position detecting device are matched (when the detection signal from the P sensor 22 is on / off of the developing bias). The yellow toner image on the photosensitive belt 1 is repeatedly detected by the P sensor 22 (so that the detection signal of the developing roller rotational position detection device and the detection signal of the P sensor 22 are phase-matched). The detection result of the P sensor 22 is averaged with the period of the developing roller signal from the developing roller rotation position detecting device to obtain a density unevenness correction profile.
[0038]
Thereafter, the control signal generator 34 smoothes the density unevenness correction profile by taking a weighted average of the density unevenness correction profile with the preceding and subsequent density unevenness correction profiles. Then, the control signal generator 34 outputs an analog signal corresponding to the smoothed density unevenness correction profile to the high-pressure PP 33 based on the developing roller signal from the developing roller rotation position detector and the phase information.
[0039]
That is, the control signal generator 34 outputs an analog signal corresponding to the density unevenness correction profile after the smoothing, and at the same time, this analog signal reduces density unevenness in the sub-scanning direction of the toner image on the photosensitive belt 1. As described above, the developing roller signal from the developing roller rotation position detecting device and the phase information change the resistance in the circumferential direction (rotating direction) of the developing roller 6a.
[0040]
Accordingly, the developing bias of the developing roller 6a changes to a developing bias that lowers the density of the toner image during the period in which the density of the toner image on the photosensitive belt 1 is high (the period of the developing roller 6a). In the period when the density of the toner image on the photosensitive belt 1 is low (the period of the developing roller 6a), the developing bias is changed so as to increase the density of the toner image.
[0041]
Since the effect of varying the developing bias varies depending on the control gain, the control signal generator 34 varies the developing bias with a constant gain when the first developing bias is varied, and increases the gain when the second developing bias is varied. Variable development bias. The control signal generator 34 ends the operation when the density of the toner image on the photosensitive belt 1 falls within the determined density unevenness.
Such a developing bias control operation is repeatedly performed at predetermined timings.
[0042]
The operation of controlling the developing bias of the developing rollers 7a to 9a of the other developing devices 7 to 9 is performed in the same manner as the operation of controlling the developing bias of the developing roller 6a of the developing device 6 described above. That is, the rotation position (rotation cycle) of the developing rollers 7a to 9a is detected by the developing roller rotation position (rotation cycle) detection device. A developing bias is applied to each of the developing rollers 7a to 9a by a high-voltage power pack (PP) as a developing bias power source, and a control signal generator as a control means has a developing roller rotation position (rotation cycle) for each color as described above. Image density unevenness is reduced by controlling the development bias by controlling the high-pressure PP based on the detection signal (development roller signal) from the detection device and the phase information.
[0043]
On the photosensitive belt 1, a pattern is formed for each color to match the phase of the detection signal from each developing roller rotational position detection device and the detection signal from the P sensor 22. In this case, the pattern generator generates a magenta pattern signal, a cyan pattern signal, and a black pattern signal for forming a rectangular pattern of an arbitrary size on the photosensitive belt 1 and outputs them to the laser writing system unit 5. Then, the laser writing system unit 5 exposes the photosensitive belt 1 after the uniform charging by the charging roller 4 by a magenta pattern signal, a cyan pattern signal, and a black pattern signal from the pattern generation device, and exposes the static pattern of the rectangular pattern on the photosensitive belt 1. An electrostatic latent image is formed.
[0044]
When the intermediate portion of the electrostatic latent image in the sub-scanning direction is moved from the exposure position to the developing position, the developing bias applied from the high pressure PP to the developing rollers 7a to 9a is temporarily turned off by the control device and again. The developing units 7 to 9 develop the electrostatic latent image to form a magenta toner image, a cyan toner image, and a black toner image, respectively. The toner image on the photosensitive belt 1 is detected by the P sensor 22 in terms of density unevenness.
[0045]
For each color, the phase (time) based on the detection signal (development roller signal) from the development roller rotation position detection device when the development bias is on / off for turning on / off the development bias of the development rollers 7a to 9a, and development The time from when the bias is turned on / off until the toner image of the above pattern is detected by the P sensor 22 is measured by the control device, and the result is input as phase information to the control signal generator.
[0046]
When density unevenness is detected, the pattern generator generates a magenta pattern signal, a cyan pattern signal, and a black pattern signal for forming a pattern having a writing level of about 20% on the photosensitive belt 1 and outputs it to the laser writing system unit 5. Then, the laser writing system unit 5 exposes the photosensitive belt 1 after uniform charging by the charging roller 4 with a magenta pattern signal, a cyan pattern signal, and a black pattern signal from the pattern generator, and forms a rectangular pattern on the photosensitive belt 1. An electrostatic latent image is formed. The developing units 7 to 9 develop the electrostatic latent image on the photosensitive belt 1 corresponding to the magenta pattern signal, the cyan pattern signal, and the black pattern signal to form a magenta toner image, a cyan toner image, and a black toner image. The amount of density unevenness of the image is detected by the P sensor 22.
[0047]
For each color, the control signal generator matches the developing position of the developing units 7 to 9 with the detection position of the developing roller rotational position detector based on the developing roller signal from the developing roller rotational position detector and the phase information. (So that the detection signal from the P sensor 22 is matched to the phase corresponding to when the developing bias is turned on / off so that the detection signal of the developing roller rotational position detecting device and the detection signal of the P sensor 22 are phase matched) The toner image of each color on the photosensitive belt 1 is repeatedly detected by the P sensor 22, and the detection result of the P sensor 22 is averaged by the period of the developing roller signal from the developing roller rotation position detecting device for each color to obtain the density. Use a profile for unevenness correction.
[0048]
Thereafter, for each color, the control signal generator smoothes the density unevenness correction profile by taking a weighted average of the density unevenness correction profile with the previous and subsequent ones. Then, for each color, the control signal generator outputs an analog signal corresponding to the smoothed density unevenness correction profile to the high-pressure PP based on the developing roller signal from the developing roller rotational position detector and the phase information.
[0049]
That is, for each color, the control signal generator outputs an analog signal corresponding to the smoothed density unevenness correction profile to the high-pressure PP and simultaneously outputs the analog signal to the developing roller from the developing roller rotational position detecting device. Based on the signal and the phase information, the density unevenness in the sub-scanning direction of each color toner image on the photosensitive belt 1 is changed according to the resistance unevenness in the circumferential direction (rotation direction) of the developing rollers 7a to 9a.
[0050]
  This embodiment isThe present inventionThe image carrier 1 is formed by developing devices 6 to 9 having developing rollers 6a to 9a that form an electrostatic latent image on a photosensitive belt 1 serving as an image carrier and rotate at a predetermined cycle. In the image forming apparatus that develops the electrostatic latent image above into a toner image, the image forming apparatus includes a control signal generator 34 as a control unit that changes process conditions according to the rotation period of the developing rollers 6a to 9a. Image density unevenness in the sub-scanning direction can be reduced.
[0051]
  Also this embodimentSaidA developing roller rotation period detecting device for detecting the rotation period of the developing rollers 6a to 9a is provided, and a detection signal from the developing roller rotation period detecting device is input to the control means 34. Therefore, the rotation period of the developing roller is detected. Thus, image density unevenness in the sub-scanning direction can be reduced.
[0052]
  Also this embodimentSaidA P sensor 22 is provided as a density unevenness detecting device for detecting the density unevenness amount of the toner image on the image carrier 1, and the control means 34 controls the process condition by a detection signal from the density unevenness detection device 22. Therefore, it is possible to reduce the image density unevenness by detecting the image density unevenness amount.
[0053]
  Also this embodimentSaidThe control means 34 changes the developing bias of the developing devices 6-9 as the developing device as the process condition according to the rotation period of the developing rollers 6a-9a, so that the image density in the sub-scanning direction is changed by changing the developing bias. Unevenness can be reduced.
[0054]
  Also this embodimentSaidA developing roller rotation period detecting device for detecting the rotation period of the developing rollers 6a to 9a, a density unevenness detecting device 22 for detecting the density unevenness amount of the toner image on the image carrier 1, and the density unevenness detecting device 22 A pattern generator for forming on the image carrier 1 a pattern for performing phase matching between the output signal of the developing roller and the output signal of the developing roller rotation period detecting device, and the pattern on the image carrier 1 Since the phase matching is performed based on the output signal of the density unevenness detection device 22 and the output signal of the developing roller rotation cycle detection device, the phase matching is performed based on the output signal of the development roller rotation cycle detection device and the output signal of the density unevenness detection device. To reduce the uneven image density in the sub-scanning direction.
[0055]
The present invention is not limited to the above-described embodiment, and can also be applied to an image forming apparatus such as a color copying machine or a color facsimile.
[0056]
【The invention's effect】
  As described above, according to the first aspect of the invention, the image density unevenness in the sub-scanning direction can be reduced by the above configuration.In addition, phase matching can be performed by the output signal of the developing roller rotation period detection device and the output signal of the density unevenness detection device to reduce image density unevenness in the sub-scanning direction.
[0057]
  Claim2According to the invention relating to the above, with the above-described configuration, it is possible to reduce the uneven image density in the sub-scanning direction by changing the developing bias.it can.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a density unevenness control unit according to an embodiment of the present invention.
FIG. 2 is a sectional view showing the same embodiment;
FIG. 3 is an enlarged schematic view showing a part of the embodiment.
FIG. 4 is a schematic view showing a part of a rotary developing unit in the embodiment.
FIG. 5 is a diagram showing a pattern for performing phase matching between a detection signal from a developing roller rotation position detection device and a detection signal from a P sensor in the same embodiment;
FIG. 6 is a timing chart showing the operation timing of the embodiment.
FIG. 7 is a timing chart showing operation timing at the time of density detection of the same embodiment;
[Explanation of symbols]
1 Photoconductor belt
6-9 Development device
6a-9a developing roller
22 P sensor
34 Control signal generator

Claims (2)

An image forming apparatus that forms an electrostatic latent image on an image carrier and develops the electrostatic latent image on the image carrier with a developing device having a developing roller that rotates at a predetermined cycle to form a toner image. Control means for changing process conditions according to the rotation period of the developing roller, a developing roller rotation period detecting device for detecting the rotation period of the developing roller, and a density for detecting the amount of density unevenness of the toner image on the image carrier An uneven amount detecting device, and a pattern generating device for forming a pattern on the image carrier for phase matching between the output signal of the uneven density detecting device and the output signal of the developing roller rotation period detecting device. provided, the image formation and performing phase matching by the output signal and the output signal of the developing roller rotation cycle detecting device of the density unevenness quantity detecting device for said pattern on said image bearing member Location. The image forming apparatus according to claim 1, wherein the control means is an image type forming apparatus characterized by changing in accordance with a developing bias of the developing device as the process condition to the rotation period of the developing roller.

Images