JP2002178561A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can output a high quality image and can be reduced in cost. SOLUTION: The image forming apparatus obtains a color image by superposing toner images of plural colors. The image forming apparatus comprises a photosensitive body on which a latent image or a toner image obtained by developing the latent image are formed, an image carrier body that rotates by contacting with the photosensitive body and holds a synthesized image obtained by superposing the toner images in plural colors which are sequentially transferred thereto from the photosensitive body, an optical patterns which are arranged on the surface of the photosensitive body in the rotational direction at equal intervals, a pattern detecting means that detects the rotational condition of the photosensitive body by reading the plurality of optical patterns at the same time, an image signal generating means that generates an image signal based on an image to be formed, and a latent image forming means that forms the latent image by emitting to the photosensitive body a light beam in relation to the image from a rotary polygon mirror according to the image signal generated by the image signal generating means. The image signal generating means controls the timing of generating the image signal based on one or more synchronizing signals generated according to the optical patterns detected by the pattern detecting means by each one rotation of the rotary polygon mirror. There are other eight items.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and more particularly to a color image forming apparatus.

[0002]

2. Description of the Related Art In general, when fluctuations in the surface speed of a belt are measured, periodic fluctuations are observed as shown in FIG. This cycle T appears as a belt surface speed variation if the drive roll is eccentric, even if the rotation speed of the drive roll shaft is constant. When the surface speed of the belt is detected by this technique, the speed fluctuation due to the eccentricity of the detection roll is combined with the speed fluctuation of the belt and measured. Therefore, if the speed control is performed based on this, the speed fluctuation of the detection roll cycle occurs.

There is also a method of providing marks at regular intervals on a belt, detecting the marks with a sensor, and calculating a speed from a measurement time interval. In this method, since there is no detection roll, the drive roll frequency can be detected. However, if the detection is erroneously performed due to stains, scratches, or the like on the mark, a large speed fluctuation occurs.
In addition, it is necessary to make marks at regular intervals accurately on the belt.

In order to solve the above problem, Japanese Patent Laid-Open Publication No.
No. 81, a belt transport device has been devised. In this method, a mark (or hole) is provided at one place on a belt, and an optical sensor that detects the mark and generates a sensor signal and an encoder on a drive roll shaft that generates an index signal once per rotation. And the surface velocity is detected by Fourier transform of the ON time of the sensor signal and the Fourier transform of the count value by counting encoder pulses of the driving roll at this time. In addition, the speed data is stored in a memory, and the speed variation of the belt is not dared to be suppressed. Instead, the second and subsequent colors are controlled based on the speed variation value measured for the first color. This has the effect of reducing the influence of measurement errors on flaws.

[0005]

However, in the method disclosed in JP-A-6-263281, since the Fourier transform is speed data based on data of a plurality of mark signals, it is not a real-time speed but a delay and an average. The response becomes slow and high-speed control cannot be performed. Also, in the method of storing data in the memory, if dirt or scratches are made after the first round, an abnormal signal is generated and the operation becomes unstable.

An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide an image forming apparatus capable of achieving high image quality output and low cost.

[0007]

The above object of the present invention is achieved by the following means. An image forming apparatus according to a first aspect of the present invention is an image forming apparatus that obtains a color image by superimposing toner images of a plurality of colors, and comprises a latent image and a toner image formed by developing the latent image. A body, an image carrier that rotates in contact with the photoconductor, and holds a composite image in which the plurality of color toner images sequentially transferred from the photoconductor are superimposed; and a rotation direction on the photoconductor surface. Optical patterns arranged at equal intervals, a pattern detection unit that detects the rotation state of the photoconductor by simultaneously reading a plurality of the optical patterns, and an image signal generation unit that generates an image signal based on an image to be formed. A latent image forming means for forming a latent image by scanning a light beam related to an image on the photoreceptor with a rotating polygon mirror from the image signal generated by the image signal generating means; Signal generating means, and adjusts the timing of the image signal generated based on the rotating polygon mirror eleven times or more synchronization signals per rotation generated on the basis of the light pattern detected by the pattern detection means.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, a cleaning member is supplied to the photosensitive member and a contact portion which is a structure contacting the photosensitive member. It is characterized by doing.

According to a third aspect of the present invention, there is provided the image forming apparatus according to any one of the first to third aspects, wherein the static elimination member is disposed on the surface of the photosensitive member. Features.

According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the optical pattern is a pattern formed on the photosensitive member. Wherein slits having a plurality of optical patterns are formed at least at two or more positions on the photoreceptor.

According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the arrangement period of the optical pattern is an integer ratio of a writing resolution. It is characterized by being.

According to a fifth aspect of the present invention, there is provided the image forming apparatus according to any one of the first to fifth aspects, wherein the pattern detecting means includes the photosensitive member and the image bearing member. It is characterized by being arranged in the vicinity of a contact part with the body.

According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the first to sixth aspects, the control means includes a signal pulse from the pattern detector. And a signal interpolating circuit for temporally interpolating between the pulse edges with a fixed interval clock having a shorter cycle than the signal pulse.

According to an eighth aspect of the present invention, in the image forming apparatus according to any one of the first to seventh aspects, the pattern detecting unit is configured to vibrate in the moving direction of the photosensitive member. It is characterized in that it is arranged in a position where there is little.

According to a ninth aspect of the present invention, there is provided the image forming apparatus according to any one of the first to seventh aspects, wherein a means for reducing vibration of the pattern detecting means is added. It is characterized by the following.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of an image forming unit, which is a main part of a color copying machine according to this embodiment. The color copying machine includes, in addition to the image forming unit shown in FIG. 1, a color image reading unit (hereinafter, referred to as a “color scanner”), a paper feeding unit, and a control unit that drives and controls these units.

The color scanner reads color image information of a document for each color separation light of, for example, red, green, and blue (hereinafter, referred to as "R", "G", and "B", respectively) and outputs an electrical image. Convert to a signal. Then, based on the intensity levels of the R, G, and B color separation image signals obtained by this color scanner, a color conversion process is performed by an image processing unit (not shown), and black, cyan, magenta, and yellow (hereinafter, respectively) “Bk”, “C”, “M”, “Y”) are obtained.

The image forming unit shown in FIG. 1 includes a photosensitive drum 100 as an image carrier, and a charger 2 as a charging unit.
00, a photoconductor cleaning device 300 including a cleaning blade and a fur brush, a writing optical unit (not shown) as an exposure unit, a revolver developing device 400 as a developing unit, an intermediate transfer belt 500, a secondary transfer roll 600, and a fixing unit (not shown) It is composed of

The photosensitive drum 100 rotates in a counterclockwise direction as indicated by an arrow in the drawing, and the surroundings of the photosensitive drum 100 are selected from the selected color toner of the charging charger 200, the photosensitive member cleaning device 300, and the revolver developing device 400. Developing device,
An intermediate transfer belt 500 and the like are arranged.

The writing optical unit converts the color image data from the color scanner into an optical signal, and applies a laser beam corresponding to the image of the document on the surface of the photosensitive drum 100 uniformly charged by the charger 200. Light L
To perform optical writing to form an electrostatic latent image on the surface of the photosensitive drum 100. The writing optical unit includes, for example, a semiconductor laser as a light source, a laser emission drive control unit, a polygon mirror and its rotation motor, f / θ
It can be constituted by a lens, a reflection mirror or the like.

The revolver developing device 400 includes a Bk developing device 401 using Bk toner, a C developing device 402 using C toner, an M developing device 403 using M toner, a Y developing device 404 using Y toner, and the entire unit. It is constituted by a developing revolver driving unit which rotates counterclockwise. Each of the developing devices 401 to 404 installed in the revolver developing unit 400 is a developing device as a developing material carrier that rotates by contacting the ears of the developing material with the surface of the photosensitive drum 100 in order to develop an electrostatic latent image. It comprises a sleeve, a developer paddle that rotates to pump up and agitate the developer, and a developing sleeve drive unit that rotates the developing sleeve clockwise as indicated by the arrow.

In this embodiment, each of the developing devices 401 to 404
The toner inside is charged negatively by agitation with the ferrite carrier, and a developing bias power supply (not shown) as a developing bias applying means (not shown) supplies a negative DC voltage Vdc (DC component) to each developing sleeve with an AC voltage Vac (DC component). A developing bias voltage on which an AC component is superimposed is applied, and each developing sleeve is biased to a predetermined voltage with respect to the metal base layer of the photosensitive drum 100.

In the standby state of the main body of the color copying machine, the revolver developing unit 400 is stopped at the home position where the Bk developing unit 401 is located at the developing position, and when the copy start key is pressed, the original starts reading image data. Then, based on the color image data, the optical writing by the laser beam L, that is, the formation of the electrostatic latent image starts (hereinafter, referred to as an electrostatic latent image).
The electrostatic latent image based on the Bk image data is called “Bk electrostatic latent image”. The same applies to C, M, and Y).

In order to enable development from the front end of the Bk electrostatic latent image, before the front end of the electrostatic latent image reaches the Bk development position, the rotation of the Bk developing sleeve is started and the Bk electrostatic latent image is started. Is developed with Bk toner. Thereafter, the developing operation of the Bk electrostatic latent image is continued. When the trailing end of the Bk electrostatic latent image passes the Bk developing position, the revolver is immediately moved until the developing device of the next color comes to the developing position. The developing unit 400 rotates. This is completed at least before the leading end of the electrostatic latent image based on the next image data reaches the developing position.

The intermediate transfer unit 500 includes an intermediate transfer belt 501 which is an intermediate transfer member stretched over a plurality of rollers described later. This intermediate transfer belt 50
1, a secondary transfer belt 601 as a transfer material carrier of the secondary transfer unit 600, a secondary transfer bias roller 605 as a secondary transfer charge applying unit, and a belt cleaning blade 504 as an intermediate transfer body cleaning unit. ,
A lubricant application brush 505 serving as a lubricant application means is disposed so as to face the lubricant application brush 505.

The intermediate transfer belt 501 includes a primary transfer bias applying roller 507, a belt driving roller 508, a belt tension roller 509, and a primary transfer charge applying means.
Secondary transfer opposed roller 510, cleaning opposed roller 5
11 and an earth roller 512. Each roller is formed of a conductive material, and each roller other than the primary transfer bias roller 507 is grounded. A transfer bias controlled to a predetermined magnitude of current or voltage in accordance with the number of superimposed toner images is applied to the primary transfer bias roller 507 by a primary transfer power supply 801 controlled by a constant current or a constant voltage. ing. Also, the intermediate transfer belt 501
Is driven in the direction of the arrow by a belt drive roller 508 that is driven to rotate in the direction of the arrow by a drive motor (not shown). The intermediate transfer belt 501 is made of a semiconductor,
Alternatively, it is an insulator and has a single-layer or multilayer structure. The toner image on the photosensitive drum 100 is transferred to the intermediate transfer belt 501.
Transfer section (hereinafter referred to as “primary transfer section”)
Primary transfer bias roller 507 and ground roller 512
The intermediate transfer belt 501 is stretched so as to be pressed against the photosensitive drum 100 side.
A nip portion having a predetermined width is formed between the intermediate transfer belt 501 and the intermediate transfer belt 501.

The lubricant applying brush 505 grinds the zinc stearate 506 as a lubricant formed in a plate shape,
The polished fine particles are applied to the intermediate transfer belt 501. The lubricant application brush 505 is also configured to be adjacent to the intermediate transfer belt 501, and is controlled so as to contact the intermediate transfer belt 501 at a predetermined timing.

The secondary transfer unit 600 includes a secondary transfer belt 601 stretched around three support rollers 602, 603, and 604, and a stretched portion between the support rollers 602 and 603 of the intermediate transfer belt 501 is formed. The secondary transfer opposing roller 510 can be pressed against the roller. One of the three support rollers 602, 603, and 604 is a driving roller that is rotationally driven by a driving unit (not shown), and the driving roller drives the secondary transfer belt 601 in a direction indicated by an arrow in the drawing.

The secondary transfer bias roller 605 is a secondary transfer means, and is disposed so as to sandwich the intermediate transfer belt 501 and the secondary transfer belt 601 between the secondary transfer opposing roller 510 and a constant current control. A transfer bias of a predetermined current is applied by a secondary transfer power supply 802 to be performed. Further, the support roller 602 and the secondary transfer bias roller 605 are arranged such that the secondary transfer belt 601 and the secondary transfer bias roller 605 can take a position where the secondary transfer belt 601 is pressed against the secondary transfer opposing roller 510 and a position where the secondary transfer belt 601 and the secondary transfer bias roller 605 are separated. Is provided in the direction of the arrow. The secondary transfer belt 601 and the support roller 602 at the separated position are shown by two-dot chain lines in FIG. The registration rollers 650 are a pair, and the secondary transfer bias rollers 60
Transfer paper P, which is a transfer material, is fed at a predetermined timing between the intermediate transfer belt 501 and the secondary transfer belt 601 held between the transfer belt 5 and the secondary transfer facing roller 510. The supporting roller 60 on the fixing roller pair 701 side of the secondary transfer belt 601
A transfer sheet static eliminator 606 as a transfer material static eliminator and a belt static eliminator 607 as a transfer material carrier static eliminator are opposed to the portion stretched over the sheet 3. Further, the support roller 60 on the lower side of the secondary transfer belt 601 in the drawing is illustrated.
A cleaning blade 608, which is a transfer material carrier cleaning unit, is in contact with the portion that is stretched over the transfer member 4.

The transfer paper discharging charger 606 discharges the electric charges held in the transfer paper so that the transfer paper can be separated from the secondary transfer belt 601 by the strength of the transfer paper itself. is there. The belt static elimination charger 607 eliminates electric charges remaining on the secondary transfer belt 601. Further, the cleaning blade 608 is for removing the adhered matter adhered to the surface of the secondary transfer belt 601 for cleaning.

When the image forming cycle is started in the color copying machine having the above-described configuration, the photosensitive drum 1
Reference numeral 00 denotes a counterclockwise rotation indicated by an arrow by a drive motor (not shown), and the intermediate transfer belt 501 is rotated clockwise by an arrow by a belt driving roller 508. As the intermediate transfer belt 501 rotates, primary transfer is performed by a transfer bias by a voltage applied to a primary transfer bias roller 507 to form a Bk toner image, a C toner image, a M toner image, and a Y toner image. Then, a toner image is finally formed on the intermediate transfer belt 501 in the order of Bk, C, M, and Y.

For example, a Bk toner image is formed as follows. The charging charger 200 uniformly charges the surface of the photosensitive drum 100 to a predetermined potential with negative charges by corona discharge. Then, raster exposure using laser light is performed by a writing optical unit (not shown) based on the Bk color image signal. When this raster image is exposed, in the exposed portion of the surface of the photosensitive drum 100 that is initially uniformly charged, the charge proportional to the amount of exposure light disappears, and a Bk electrostatic latent image is formed.

When the negatively charged Bk toner on the Bk developing roller of the Bk developing unit 401 comes into contact with the Bk electrostatic latent image, the toner adheres to a portion of the photosensitive drum 100 where the charge remains. Instead, the toner is attracted to a portion having no charge, that is, an exposed portion, and a Bk toner image similar to the electrostatic latent image is formed. The Bk toner image formed on the photosensitive drum 100 is transferred onto the surface of the intermediate transfer belt 501 that is driven at a constant speed in a state of contact with the photosensitive drum 100. Hereinafter, the transfer of the toner image from the photosensitive drum 100 to the intermediate transfer belt 501 is referred to as “belt transfer”.

A small amount of untransferred residual toner remaining on the surface of the photosensitive drum 100 after the belt transfer is cleaned by the photosensitive member cleaning device 300 in preparation for reusing the photosensitive drum 100. On the photosensitive drum 100 side, B
After the k-image forming process, the process proceeds to the C-image forming process. At a predetermined timing, reading of C-image data by a color scanner starts, and writing of laser light based on the C-image data causes a C electrostatic latent on the surface of the photosensitive drum 100. Form an image. Then, after the rear end of the previous Bk electrostatic latent image has passed and before the front end of the C electrostatic latent image has arrived, the rotating operation of the revolver developing unit 400 is performed, and the C developing device 4
02 is set at the development position, and the C electrostatic latent image is developed with the C toner.

Thereafter, the development of the C electrostatic latent image area is continued.
When the rear end of the C electrostatic latent image has passed, the revolver developing unit is rotated in the same manner as in the case of the Bk developing device 401, and the next M developing device 403 is moved to the developing position.
This is also completed before the leading end of the next M electrostatic latent image reaches the developing position. Regarding the M and Y image forming processes, the respective operations of reading the color image data, forming the electrostatic latent image, and developing are the same as those of the above-described Bk and C processes, and thus the description is omitted.

On the intermediate transfer belt 501, Bk, C, M, and Y toner images sequentially formed on the photosensitive drum 100 are transferred onto the same surface while being sequentially aligned. As a result, a toner image in which a maximum of four colors are superimposed on the intermediate transfer belt 501 is formed. At the time when the image forming operation is started, the transfer paper P is fed from a paper supply unit such as a transfer paper cassette (not shown) or a manual feed tray, and stands by at the nip of the registration roller pair 650. An intermediate transfer belt 501 is attached to a secondary transfer portion where a nip is formed by a secondary transfer facing roller 510 and a secondary transfer bias roller.
When the leading edge of the upper toner image is approaching, the registration roller pair 650 is driven such that the leading edge of the transfer paper P coincides with the leading edge of the toner image, and registration of the transfer paper P with the toner image is performed.

Then, the transfer paper P is transferred to the intermediate transfer belt 501.
The sheet passes through the secondary transfer portion while being superposed on the upper toner image. At this time, the four-color superimposed toner image on the intermediate transfer belt 501 is collectively transferred onto the transfer paper by the transfer bias by the voltage applied to the secondary transfer bias roller 605 by the secondary transfer power supply 802.

When the paper P passes through a portion facing the transfer paper discharging charger 606 disposed downstream of the secondary transfer portion in the moving direction of the secondary transfer belt 601, the transfer paper P is discharged, and the secondary transfer belt 601 is discharged. And is sent to a fixing unit (not shown). The toner image is fused and fixed by the fixing unit, sent out of the apparatus body by a discharge roller pair (not shown), and stacked face-up on a copy tray (not shown) to obtain a full-color copy.

On the other hand, the photosensitive drum 1 after the belt transfer
The surface of No. 00 is cleaned by the photoconductor cleaning device 300 and is uniformly discharged by a discharge lamp (not shown). Further, the toner remaining on the surface of the intermediate transfer belt 501 after the transfer of the toner image onto the transfer paper P is cleaned by a belt cleaning blade 504 pressed against the intermediate transfer belt 501 by a separation / contact mechanism (not shown). Here, in the case of the repeat copy, the operation of the color scanner and the image formation on the photosensitive drum 100 are performed in one copy.
After the fourth color (Y) image forming process of the sheet, the process proceeds to the second color (Bk) image forming process at a predetermined timing. In addition, the intermediate transfer belt 501 is
Following the batch transfer process of color superimposed toner image to transfer paper,
The second Bk toner image is belt-transferred to an area of the front surface cleaned by the belt cleaning blade 504. Thereafter, the operation is the same as that of the first sheet.

The above is the copy mode for obtaining a four-color full-color copy. However, in the three-color copy mode and the two-color copy mode, the same operation as described above is performed for the designated color and the number of times. Become. In the case of the single-color copy mode, only the developing device of the predetermined color of the revolver developing unit 400 is in the developing operation state until the predetermined number of sheets is completed, and the belt cleaning blade 504 is pressed against the intermediate transfer belt 501. The copy operation is performed with the position as it is.

Hereinafter, an example in which the present invention is applied to a color copying machine will be described. FIG. 2 is a schematic structural perspective view of a main part in which the present invention is applied to a color image forming apparatus requiring a photosensitive drum and an intermediate transfer belt.

The present invention relates to the photosensitive drum 100, the latent image forming means and the periphery thereof in the above color image forming apparatus, and has a fine and precise scale on the surface or the inner surface of the photosensitive drum 100. Is formed, and an optical pattern detector 12 as reading means for reading the optical pattern 110
0, and an image signal generating means for forming a latent image, and a signal from the pattern detector 120 is inputted to the image signal generating means.

The optical pattern 110 and the pattern detector 120 will be described. Optical pattern 110
Is an optical pattern having a periodic change in reflectivity on the surface or the inner surface of the photosensitive drum 100, and is used as a scale line of a position. Optical pattern detector 1
Numeral 20 detects the optical pattern 110 and is configured as a detector that can simultaneously detect a plurality of periods of the optical pattern reflectance period. The optical pattern used is shown in FIG.
As shown in (a), the slit rows of the reflection section and the transmission section are generally easily available and easy to use. The pattern detector 120
This is an optical detector that detects a plurality of periods at the same time. One example is a method using a split beam as shown in FIG. The divided beams may have the same period as the period of the pattern. When the optical pattern is irradiated with the divided beam having the same period, the reflection and transmission of the beam having the same period are repeated with the movement of the optical pattern. By detecting this with a light receiving element such as a photodiode, a signal corresponding to the moving speed and position of the optical pattern can be obtained.

There is also a method using slit projection. FIGS. 3C and 3D show an example of an optical system when slit projection is used. Light from a light source is applied to an optical pattern through a slit. When the optical pattern moves and is viewed through a slit, reflection and transmission are alternately repeated, and a signal similar to the above-mentioned split beam can be obtained.
Regarding the method of forming an optical pattern, etching, printing, and a pattern using a photoemulsion film can be performed. Examples of the material for the optical pattern include a method of bonding a slit pattern made of a flexible material, a method of bonding a tape-shaped pattern, and a method of directly printing on a belt or a drum. The shape of the pattern does not need to be a continuous rectangular pattern, and may be freely selected.

The image signal generating means will be described. The image signal generation means receives image data to be output (scan data from a scanner for a copying machine, image data sent from a computer for a printer),
Based on this, it is a portion that generates a signal for driving a latent image forming unit that forms a latent image on the photosensitive drum 100. In the present invention, the image signal generating means simultaneously receives the signal from the pattern detector 120 together with the image data, and generates a drive signal based on the pattern signal. The received signals are not only those two, but also normally transmit and receive control signals from the CPU and signals from various processes. Alternatively, the signal generation means can be constituted by a main control CPU. The feature of the present invention is that a signal from the pattern detector 120 is used. Therefore, only the use of a signal from the pattern detector will be described.

FIG. 3 shows a configuration example of the image signal generating means.
As the signal from the pattern detector 120, a sinusoidal signal having a pattern period is obtained according to the above-described principle. This signal is a signal having a cycle corresponding to one cycle of the optical pattern on the photosensitive member surface. This signal can be pulsed and integrated by a counter to obtain position data, and by measuring its period, speed data can also be obtained. When the latent image forming means is constituted by a polygon mirror, one line is written at a constant period in accordance with the rotation speed of the mirror, and writing is performed at a constant period in LED writing. If a speed change occurs, the change appears as a position shift of the latent image as it is.

Normally, in the image signal generating means, data for each line is generated in a data generating section and stored in a buffer, and a modulation circuit modulates data by using a trigger input signal as a trigger and outputs the modulated data to an LD driver or an LED driver. . Here, the pattern detector 12 according to the present invention is used.
The writing timing or the writing data is corrected by using the position measurement result of the photosensitive member surface obtained in step 0 to correct the position fluctuation, thereby obtaining a latent image without distortion. The correction of the write timing is performed by the pattern detector 12.
A method of using a signal edge from 0 as a trigger of the modulation circuit (FIG. 4A), a trigger output generated based on position data obtained from an optical pattern signal, and the like can be used. As a method of correcting the write data, there is a method of correcting the data generated by the data generating unit based on the position data and recreating the data (FIG. 4B).

The arrangement of the optical pattern 110 and the pattern detector 120 is preferably detected near the writing position for the above purpose. Further, it is desirable that the optical pattern is formed on the surface of the photoreceptor in order to capture positional fluctuation on the surface of the photoreceptor. From the above, it is preferable that a pattern is formed on the surface of the photoreceptor at a position excluding the portion where the latent image is to be formed, and a detector is arranged near the irradiation position of the latent image writing light to measure the pattern (see FIG. 2).

The pattern detector 120 is connected to the photosensitive member 10.
It can be placed in a position where there is little vibration in the direction of movement 0,
By adding a device for reducing vibration, a latent image free from positional displacement can always be obtained without lowering the pattern detection accuracy (see FIG. 2).

[0050]

As described above, according to the present invention, the following effects can be obtained. (1) A position signal of the photoconductor is detected by reading an optical pattern on the surface of the photoconductor, and a data writing timing is adjusted in accordance with the fluctuation to form a latent image on the photoconductor without displacement. As a result, high-quality color output can be obtained, and an expensive controller for driving the photosensitive drum with high accuracy is not required, so that the cost can be reduced. (2) By cleaning the surface of the photoreceptor, a latent image without any displacement can always be obtained without lowering the detection accuracy of the optical pattern. (3) By eliminating the charge on the photoconductor, a latent image without any positional displacement can always be obtained without lowering the detection accuracy of the optical pattern. (4) Since at least two or more slits having a plurality of optical patterns are formed on the surface of the photoreceptor, the detection accuracy of the optical patterns is improved, and a latent image without displacement is obtained. (5) Since the pattern arrangement period is set to an integer ratio of the writing resolution, the pattern detection accuracy is improved, and a latent image without positional displacement can be obtained. (6) Since the pattern detector is arranged near the contact portion between the photoconductor and the image carrier, the accuracy of pattern detection is improved, and a latent image without displacement is obtained. (7) Since a signal interpolating circuit for temporally interpolating between the pulse edges of the signal pulse from the pattern detector with a fixed-interval clock having a shorter cycle than the signal pulse is also provided, a latent image without positional displacement can be obtained. Since the pattern detector of (8) is arranged at a position where the vibration in the moving direction of the photoconductor is small, a latent image without any displacement can be always obtained without lowering the pattern detection accuracy.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a color image forming unit according to an embodiment of the present invention.

FIG. 2 is a schematic perspective view of a main part in which the present invention is applied to a color image forming apparatus.

FIG. 3 is a diagram illustrating an optical pattern and a pattern detection method used in the present invention.

FIG. 4 is an explanatory diagram illustrating a configuration example of an image signal generation unit according to the present invention.

FIG. 5 is a diagram for explaining a position of a cleaning member of the photoconductor.

FIG. 6 is a diagram for explaining a setting position of an optical pattern.

FIG. 7 is a diagram for explaining a circuit for shortening an interval between signal pulses from a pattern detector.

FIG. 8 is a graph of the periodic variation of the surface speed of a prior art belt.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 photoconductor 110 optical pattern 120 pattern detector 200 charging charger 202 static elimination unit 300 photoconductor cleaning device 400 developing device 401 Bk developing device 402 C developing device 403 M developing device 404 Y developing device 500 Intermediate transfer unit 600 secondary transfer unit

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 1/04 H04N 1/04 D 5C072 1/113 104A 5C079 1/46 1/46 Z (72) Inventor Mitsuru Takahashi 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Takuro Kamiya 1-3-6, Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. 2C362 BA52 BA69 BA71 BA89 BB29 BB30 BB47 BB48 BB50 CA22 CA23 CA39 CB59 CB80 2H027 DA22 DE02 DE07 DE10 EC06 EC07 ED02 ED04 ED06 EE01 ZA07 2H030 AA01 AD11 AD17 BB02 BB16 BB24 BB42 BB63 2H034 AA12 AB12 A0212A02 QA17 RA07 UA14 UA18 XA01 5C079 HB01 HB02 HB12 KA02 KA09 KA17 KA18 KA20 LA01 NA01 NA04 NA25

Claims (9)

[Claims] An image forming apparatus for obtaining a color image by superimposing toner images of a plurality of colors, comprising: a photosensitive member on which a latent image and a toner image obtained by developing the latent image are formed; An image carrier that rotates in contact with the image carrier that holds a composite image obtained by superimposing the plurality of color toner images sequentially transferred from the photoconductor, and is arranged at equal intervals in the rotation direction on the photoconductor surface. An optical pattern, a pattern detection unit that detects a rotation state of the photoconductor by simultaneously reading a plurality of the optical patterns, an image signal generation unit that generates an image signal based on an image to be formed, and the image signal generation unit. A latent image forming means for forming a latent image by scanning a light beam related to an image on the photoreceptor with a rotating polygon mirror from the created image signal, and the image signal generating means comprises: An image forming apparatus, wherein the timing of generating an image signal is adjusted based on one or more synchronization signals for one rotation of the rotating polygon mirror generated based on the light pattern detected by the pattern detection means. 2. The image forming apparatus according to claim 1, wherein a cleaning member is supplied to the photosensitive member and a contact portion that is a structure that contacts the photosensitive member. 3. The image forming apparatus according to claim 1, wherein a static eliminator is disposed on the surface of the photoreceptor. 4. The image forming apparatus according to claim 1, wherein the optical pattern is a pattern formed on the photoconductor, and a plurality of optical patterns are formed on the photoconductor. An image forming apparatus, wherein slits having a pattern are formed in at least two or more places. 5. The image forming apparatus according to claim 1, wherein an arrangement period of the optical patterns is an integer ratio of a writing resolution. 6. The image forming apparatus according to claim 1, wherein the pattern detecting unit is disposed near a contact portion between the photoconductor and the image carrier. Characteristic image forming apparatus. 7. The image forming apparatus according to claim 1, wherein the control unit sets a period between pulse edges of a signal pulse from the pattern detector shorter than the signal pulse. An image forming apparatus having a signal interpolation circuit for temporally interpolating at a constant interval clock. 8. An image forming apparatus according to claim 1, wherein said pattern detecting means is arranged at a position where vibration in the moving direction of said photosensitive member is small. Forming equipment. 9. The image forming apparatus according to claim 1, further comprising: a unit for reducing vibration of said pattern detecting unit.