JP2002108169A - Image forming device - Google Patents

Abstract

(57) [Problem] To solve the problem that it is difficult to directly and accurately detect the amount of movement of a rotary moving part of a rotating body. The present invention provides a drive motor for rotating an endless rotary body, and a rotary body on a surface of the rotary body.
Markers are provided at a constant cycle in the moving direction, and the number of markers provided by the number equal to the number of markers determined by one rotation of the rotating body 14 does not change in the cycle over one rotation of the rotating body 14 when the rotating body 14 rotates at a constant speed. And means 18 for detecting the marker to obtain the speed and position information of the rotating body 14, and a drive control unit for controlling the drive motor 16 based on the information from the means 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an endless rotary member to which a toner image on an image carrier is transferred, or an endless rotary member for conveying a transfer material and transferring the toner image on the image carrier to the transfer material. The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile having a body, and an image forming apparatus such as a copying machine, a printer, and a facsimile that form a color image by superimposing toner images of a plurality of colors.

[0002]

2. Description of the Related Art In an image forming apparatus having a rotating body such as a photoreceptor belt, an intermediate transfer belt, a transfer material conveying belt, a photoreceptor drum, and an intermediate transfer drum, which are used for image formation, a rotating unit of the rotating body is used. In order to perform high-accuracy alignment of an image or an image on a transfer material conveyed by a rotating unit of a rotating body, it is necessary to accurately control the amount and position of the rotating unit. However, if the rotational speed of the rotating body fluctuates for some reason, the moving amount and the moving position of the rotating moving section of the rotating body fluctuate, and the image on the rotating moving section and the image on the transfer material conveyed by the rotating moving section are changed. It was difficult to suppress the position error with high accuracy.

Conventionally, in order to suppress a position error of an image due to a fluctuation in a moving speed of a rotary moving portion of the rotating body with high accuracy,
A rotary encoder is directly connected to the rotating shaft of the driving roller of the endless rotating body or the rotating shaft of the drum-shaped rotating body. Based on the rotating speed of the rotating body detected by the encoder, the drive as the driving means of the rotating body is performed. An image forming apparatus for controlling the rotation speed of a motor is described in JP-A-6-175427. In this image forming apparatus, the amount of movement (movement position) of a rotating part of a rotator is indirectly controlled by controlling the rotational angular velocity of the rotator.

[0004] Generally, when the surface speed of a belt as an image carrier used in an image forming apparatus is measured, FIG.
A periodic fluctuation (T: period) as shown in FIG. 3 is observed.
The fluctuation in the surface speed of the belt appears as a fluctuation in the speed of the belt if the driving roll is eccentric, even if the rotation speed of the shaft of the driving roll that drives the belt is constant. When the surface speed of the belt is measured, a value obtained by combining the fluctuation of the surface speed of the belt with the speed fluctuation due to the eccentricity of the driving roll is measured. Therefore, when the belt speed is controlled based on the measurement result of the belt surface speed, the belt fluctuates due to the eccentricity of the driving roll.

[0005] JP-A-6-263281 discloses a belt transport device. The belt conveying device is provided with a mark (or hole) at one place on the belt, and an optical sensor that detects the mark and generates a sensor signal;
An encoder mounted on the shaft of a driving roll for rotating the belt and generating an index signal once per rotation of the belt is provided. Fourier transform of the ON time of the sensor signal and counting of the index signal from the encoder at this time The surface speed of the belt is detected by the Fourier transform of the value, and the speed data is stored in a memory, and the speed of the second color is determined based on the speed fluctuation of the belt measured in the first color without intentionally suppressing the speed fluctuation of the belt. Thereafter, fluctuation of the belt speed is suppressed, and the effect of measurement error of the belt surface speed due to dirt or scratches on the belt is reduced.

[0006]

SUMMARY OF THE INVENTION The above-mentioned JP-A-6-175
In the image forming apparatus described in Japanese Patent No. 427, the rotational angular velocity of the rotary body is detected by using the rotary shaft of the drive roller of the endless rotary body or the rotary encoder directly connected to the rotary axis of the drum-shaped rotary body. (Including the expansion and contraction in the case of a belt-shaped rotating body), the eccentricity of the rotating shaft and its bearing, and the misalignment of the bearing cannot be detected. However, it has been difficult to stably control the amount of movement of the rotary moving unit.

In the belt conveying device described in Japanese Patent Application Laid-Open No. 6-263281, the belt surface speed detected by the Fourier transform of the ON time of the sensor signal and the Fourier transform of the count value of the index signal from the encoder at this time. Is speed data based on a plurality of mark signals, and is not a real-time speed, but is delayed and averaged, resulting in a slow response and a high-speed belt surface speed control. Further, since the speed data is stored in the memory, if the mark becomes dirty or scratched after the first rotation of the belt, an abnormal signal is generated and the operation becomes unstable.

According to the present invention, there is provided an image forming apparatus capable of directly and accurately detecting a moving amount of a rotary moving portion of a rotating body used for image formation and stably controlling a moving amount of the rotary moving portion. The purpose is to provide. Further, the present invention has a less influence on the detection of the optical pattern even if there are defects, scratches, and attachments in the optical patterns arranged at equal intervals in the rotation direction on the surface of the image carrier, and the image carrier is more stably formed. An object of the present invention is to provide an image forming apparatus capable of performing body position control.

[0009]

According to one aspect of the present invention, there is provided an image bearing member, a toner image forming means for forming a toner image on the image bearing member, and the image bearing member. An endless rotator on which the toner image is transferred or which transfers a transfer material and transfers the toner image on the image carrier to the transfer material; a first drive motor for rotating the rotator; An image forming apparatus having a second drive motor for rotating the image carrier, wherein a surface of the rotator includes:
A marker is provided at a constant period in the moving direction of the rotating body, and the period does not change over one rotation of the rotating body when the rotating body rotates at a constant speed. A first marker detecting means for detecting a marker on the rotating body to obtain speed and position information of the rotating body;
Based on the information obtained from the marker detecting means of
And a first drive control unit for controlling the drive motor.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the first marker section has a pattern in which the reflectance changes at a constant cycle by a predetermined number of reflectance changes. It is formed on a certain tape-shaped member, and the member is continuously bonded to the rotating body.

According to a third aspect of the present invention, in the image forming apparatus of the second aspect, a flexible member is inserted as an intermediate layer between the member and the rotating body, and the member is attached to the rotating body. Adhered seamlessly.

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 toner image forming means includes the step of forming a toner image on the image carrier by one or more lines. A start pulse output unit for outputting a start pulse at a timing of starting one toner image formation, wherein the first drive control unit is configured to perform a marker detection cycle of the first marker detection unit. Controls the first drive motor so as to synchronize with an integral multiple of the start pulse.

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 surface of the image carrier is provided at a constant period in a moving direction of the image carrier. Markers are provided, and the period is not changed over one rotation of the image carrier when the image carrier is rotated at a constant speed, and the number of the markers is determined by one rotation of the image carrier. A second marker detecting means for detecting a marker on the image carrier and obtaining speed and position information of the image carrier; and a second marker detecting means for detecting the marker on the image carrier. A second controlling the second drive motor based on the information;
And a drive control unit.

According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the first marker detecting means, or the first marker detecting means and the second marker detecting means are provided. Is configured to detect a plurality of markers simultaneously.

According to a seventh aspect of the present invention, in the image forming apparatus for forming a color image by superimposing a plurality of color toner images, a latent image is formed and the latent image is developed to form a toner image. A latent image carrier, a toner image forming means for forming a latent image on the latent image carrier and developing the latent image,
An image carrier that rotates in contact with the latent image carrier, a plurality of color toner images are sequentially transferred from the latent image carrier to be superimposed and transferred to form a color image, and a rotation state of the image carrier. Detecting means for detecting, and control means for controlling the rotational position of the surface of the image carrier based on a detection signal from the detecting means, wherein the image carrier is optically arranged on the surface at regular intervals in the rotational direction. A detection unit for detecting a rotation state of the image carrier by simultaneously reading a plurality of the optical patterns.

[0016]

FIG. 1 schematically shows a first embodiment of the present invention. The first embodiment is an example of a color laser printer as a color electrophotographic machine. In this color laser printer, a photosensitive member as an image bearing member includes a cylindrical photosensitive drum 11 which is one of rotating members used for image formation.
Is driven to rotate.

After the photosensitive drum 11 is uniformly charged by a charging device (not shown), image signals of a plurality of colors, for example, black, yellow, magenta, and cyan, are sequentially output by an optical writing device (not shown) as exposure means. A plurality of electrostatic latent images corresponding to image signals of cyan, magenta, yellow, and black are sequentially formed by being converted into light signals and exposed with the light signals.

A plurality of electrostatic latent images corresponding to image signals of cyan, magenta, yellow, and black on the photosensitive drum 11 are supplied to a cyan developing unit 13C of the developing device 13,
The toner is developed by a magenta developing unit 13M, a yellow developing unit 13Y, and a black developing unit 13K to form a cyan toner image, a magenta toner image, a yellow toner image, and a black toner image. Therefore, the charging device and the optical writing device constitute a latent image forming unit, and the latent image forming unit and the developing device 1
Reference numeral 3 denotes a toner image forming unit.

An intermediate transfer belt 14 as an intermediate transfer member, which is another rotating member used for image formation, is supported by being stretched over a plurality of rollers 15. When the shaft is coupled to the drive motor 16, the intermediate transfer belt 14 is driven to rotate at the same peripheral speed as the photosensitive drum 11 by the drive motor 16. An outer peripheral surface of the intermediate transfer belt 14 is a transfer nip portion where the intermediate transfer belt 14 and the photosensitive drum 11 are in contact with each other, and a cyan toner image, a magenta toner image, a yellow toner image, which are sequentially formed on the photosensitive drum 11. The black toner images are sequentially superimposedly transferred by a transfer unit (not shown) to form a full-color image.

On the other hand, a transfer sheet as a transfer material is fed from a sheet feeder (not shown), and the transfer sheet is transferred to a full-color image on the intermediate transfer belt 14 by transfer means (not shown). The image is fixed and discharged out of the apparatus. After the transfer of the toner image, the photosensitive drum 11 is cleaned by a cleaning device (not shown) and can be reused.
No. 4 is cleaned by a cleaning device (not shown) after the transfer of the full-color image.

In the image forming process for forming an image on a transfer material, the photosensitive drum 11, the intermediate transfer belt 1
If the rotation speed (movement speed in the running direction) of the photoconductor drum 4 changes, the toner image on the intermediate transfer belt 14 or the transfer paper is disturbed.
No. 4 requires very precise rotational drive.

In general, an endless belt-shaped rotating body such as a photoreceptor belt, an intermediate transfer belt, and a transfer material conveying belt used in an image forming apparatus such as a color electronic copying machine or a color printer is supported by a plurality of rollers. The driving motor is connected to the rotating shaft of one of the supporting rollers, and the rotating body is driven to rotate by the driving motor. As the drive motor, a servo motor or a step motor having a built-in rotary encoder is used.

In driving such an endless belt-shaped rotating member, the moving amount (rotating position) of the rotating member is not directly detected, but the rotational moving amount (rotating position) of a driving motor as a driving source is detected. ), And the feedback control of the drive motor is performed based on the detection result. Therefore, even if the rotation position and the rotation angular velocity of the drive motor are controlled, the movement amount (rotation position) and the rotation movement speed of the rotating body are controlled. Is not precisely controlled. Therefore, since the speed reduction gear precision of the drive motor, the diameter of the drive roller, and the deformation of the rotating body directly affect the speed of the rotating body, it is impossible to position the rotating body beyond these precisions, and the upper limit of the image quality is also limited. It is naturally restricted.

Therefore, in the color laser printer according to the present embodiment, fine and precise graduations (markers) are formed at regular intervals on the non-image forming area (toner image non-transfer area) on the surface or the inner surface of the intermediate transfer belt 14. In addition to providing the formed marker portion 17, an optical detector 18 as a marker detecting means for detecting the marker is provided, and the rotational position and the moving amount of the intermediate transfer belt 14 are directly and accurately detected to detect the intermediate transfer belt 14. 14 can be positioned with high accuracy. A drive control unit (not shown) is a detector 18
The drive motor 16 is controlled based on the detection result.

That is, the effects of the deformation and eccentricity of the support roller 15 appearing in the rotational movement of the intermediate transfer belt 14, the eccentricity of the shaft of each support roller 15 and the speed fluctuation of the drive motor 16 are all included. It is possible to accurately detect the amount of movement (rotational position). Further, even if the rotational movement of the intermediate transfer belt 14 itself is slipped, a fine and precise marker is provided on the intermediate transfer belt 14 and the marker 18 is detected by the detector 18, so that the intermediate transfer belt 14 includes the slip. It is possible to accurately detect the amount of movement (rotational position).

Further, in this embodiment, the intermediate transfer belt 1
4, the marker section 17 is formed without a gap, so that if the intermediate transfer belt 14 is moving at a constant speed, the detection signal cycle of the detector 18 does not fluctuate.
Since the number of detection signals of the detector 18 for one rotation (for one rotation) of the intermediate transfer belt 14 is constant, the position of the intermediate transfer belt 14 can be detected with high accuracy. The above is very important when controlling the speed and position of the intermediate transfer belt 14.

For example, when the tape-shaped marker 17 is used, the tape-shaped marker can be created with high accuracy.
The intermediate transfer belt usually has a production error of about ± 1 to 2 mm. Therefore, when the tape-shaped marker portion 17 is adhered to the intermediate transfer belt 14, a gap or overlap occurs in the tape-shaped marker portion 17 within a tolerance range. If a gap is formed in the tape-shaped marker section 17 as described above, the detector 18 changes not in a fixed cycle but in a partial cycle when the intermediate transfer belt 14 rotates at a constant speed. For this reason, if the detection signal from the detector 18 is used as it is for controlling the speed and position of the intermediate transfer belt, the speed and position control of the intermediate transfer belt becomes unstable in the period variation portion of the detection signal.

Also, as described above, the tape-shaped marker 17
When the marker is formed by a method of adhering the intermediate transfer belt 14 to the intermediate transfer belt 14, if the gap is eliminated in the marker section 17, the number of markers in one circumference varies depending on the circumference of the intermediate transfer belt. When it is desired to perform positioning in each circumference of the intermediate transfer belt, a process such as storing the number of markers in one circumference in a memory in advance is required.

However, if the number of markers in one round of the intermediate transfer belt is fixed as in this embodiment, the number of markers can be set in advance on a counter or the like, so that the number of markers can be accurately adjusted for each rotation of the intermediate transfer belt. The positioning control of the transfer belt can be performed. In the present embodiment, although the creation of the marker is not particularly mentioned, a method using a marker portion 17 made of a flexible member as described later, and a method of directly measuring the circumferential length of the intermediate transfer belt 14 beforehand and then directly performing ink jet printing are described. For example, a method of forming a marker on the intermediate transfer belt 14 by using a printing method such as a printing method can be considered.

According to the first embodiment, a marker is provided on the surface of the rotating member 14 at a constant period in the moving direction of the intermediate transfer belt 14 as the rotating member.
4 has no change in the period over one rotation of the intermediate transfer belt 14 at a constant speed, and has a marker portion 17 provided with a number of markers determined by one rotation of the intermediate transfer belt 14. A detector 18 serving as a marker detecting means for detecting a marker on the belt 14 and obtaining speed and position information of the intermediate transfer belt 14, and rotates the intermediate transfer belt 14 based on information obtained from the detector 18. Since a drive control unit for controlling the drive motor 16 is provided, the position of the surface relating to image quality on the intermediate transfer belt can be accurately controlled, and there is no portion having a different cycle in one rotation of the intermediate transfer belt 14. There is no sudden change in the data fed back from the detector 18 to the drive control unit, and continuous stable control of the intermediate transfer belt 14 is possible. Therefore, the amount of movement of the rotary moving part of the intermediate transfer belt 14 can be directly and accurately detected, and the amount of movement of the rotary moving part can be stably controlled. In addition, since the number of markers for one rotation of the intermediate transfer belt 14 is determined, it is possible to detect that the intermediate transfer belt 14 has made one rotation by using a counter, and an origin sensor for detecting the origin on the intermediate transfer belt 14 is provided. No need.

In the second embodiment of the present invention, in the first embodiment, the marker portion 17 is provided on a stretchable tape-like member so that the reflectances T and D have a constant period d and a rotational direction as shown in FIG. A pattern in which a pattern that changes according to the position x is formed for a predetermined number of changes in the reflectance, for example, a pattern in which the reflecting portions 17a and the transparent portions 17b are alternately arranged in the rotation direction as shown in FIG. 2 is used. The member 17 is adhered to the intermediate transfer belt 14 without a break as shown in FIGS. In FIG. 5, reference numeral 17c denotes a joint of the marker unit 17. The method for creating the pattern is not particularly specified, but the pattern can be created by a generally well-known method.

For example, as one method, a pattern in which the reflectance changes at a constant cycle can be obtained by exposing and developing the photoemulsion film at a constant cycle. Since the photoemulsion film is formed by applying a photosensitive material on the film, it is possible to impart flexibility by using a thin film of PET or the like as a film to be a substrate. Alternatively, since the polymer film can be provided with a concavo-convex pattern by laser ablation processing, it is also possible to obtain the above pattern by, for example, processing a polymer film containing a dye so as to have a concentration fluctuation.

Although the marker tape as the marker portion 17 can be prepared by various methods as described above, the marker portion 17 is characterized by being a member having elasticity in the second embodiment. It may be created by a method. The feature of the second embodiment is to use the marker portion 17 configured by adhering the elastic marker tape to the intermediate transfer belt 14 without any seam as described above. In the second embodiment,
With such a configuration, if the speed and the position of the intermediate transfer belt 14 are detected by detecting the marker of the marker unit 17 with the detector 18, the position control of the intermediate transfer belt 14 can be performed with high accuracy as in the first embodiment. Becomes possible.

As described above, according to the second embodiment, in the above-described first embodiment, the first marker section 17 is provided with a pattern in which the reflectance changes at a fixed cycle by the predetermined number of reflectance changes. Is formed on a tape-shaped member having the following, and the member is seamlessly adhered to the intermediate transfer belt 14 as a rotating body, so that it can be processed on a flat surface at the time of pattern formation, and an existing processing machine can be used, and the pattern can be used. Can be created with high precision. In addition, since the marker section 17 has elasticity, it is easy to match the seam.

According to the third embodiment of the present invention, when the marker tape 17 is formed in the above-described second embodiment, the bonding intermediate between the marker tape 17 having the marker pattern 17d and the intermediate transfer belt 14 as shown in FIG. A flexible member 19 is used as a layer. The marker tape 17 is adhered to the intermediate transfer belt 14 with a flexible member 19 interposed between the intermediate transfer belt 14 to which the marker tape 17 is adhered and the marker tape 17. Such a load can be reduced, and the marker tape 1
7 can be partially reduced. Therefore,
The reflectance fluctuation cycle of the marker tape 17 is stabilized, and more accurate speed / positioning control of the intermediate transfer belt 14 becomes possible. The adhesive intermediate layer 19 may be selected according to the tolerance between the adhesive object 14 and the marker tape 17, and various materials such as a rubber-based material and urethane can be used.

According to the third embodiment, in the second embodiment, a flexible member 19 as an intermediate layer is provided between the member 17 and the intermediate transfer belt 14 as a rotating body.
Is inserted, and the member 19 is continuously bonded to the intermediate transfer belt 14, so that the load on the member can be reduced.
Peeling and partial elongation of the member can be prevented, and the accuracy of the marker can be maintained even after the member is adhered to the intermediate transfer belt.

In the fourth embodiment of the present invention, in each of the first to third embodiments, a charging device for uniformly charging the photosensitive drum 11 is provided as a latent image forming means. An optical writing means for forming an electrostatic latent image by sequentially performing optical writing on one line or a plurality of lines of an image is used. As the optical writing means, for example, there is known a laser scanning writing means for sequentially writing light on the photosensitive drum 11 one by one or a plurality of lines while scanning a laser beam using a polygon mirror. The LED writing means that has been used is actually being used. Here, for example, a laser scanning writing unit is used as the optical writing unit.

Further, a write start pulse output means for outputting a start pulse at the timing of starting one latent image formation is provided, and the reflectance variation cycle of the marker section 17 is an integral multiple of the write position cycle of the latent image formation means. Is set to FIG. 7 shows an outline of the fourth embodiment. The laser scanning writing means includes a beam shaping lens (not shown), fθ
It has an optical system such as a lens. In this laser scanning writing means, a laser light source 20 is driven by an image signal by a light beam modulation circuit as a modulation means to be described later and emits a light beam (laser beam). Polygon mirror 21 through
Incident on. The polygon mirror 21 is rotationally driven at a high speed by a polygon motor (not shown) to deflect and scan the laser beam.

The laser beam from the polygon mirror 20 is applied to the photosensitive drum 11 via an optical system such as an fθ lens and a return mirror 22. Polygon mirror 20
One scanning of the laser beam is performed on one surface of the polygon mirror 20, and the scanning of the photosensitive drum 11 by one surface of the polygon mirror 20 in the main scanning direction is performed by one scanning of the laser beam. By rotating at such a speed as to move in the direction, an electrostatic latent image is formed without a gap.

In the laser scanning writing means, since it is necessary to control the rotation speed of the polygon mirror 20 with high accuracy, a beam detector 23 as a rotation speed detector for detecting the rotation speed of the polygon mirror 20 is provided. The laser beam from the polygon mirror 20 is detected by the detector 23. The detection signal from the beam detector 23 can be used as a write start pulse, and the beam detector 23 constitutes a write start pulse output unit. When an LED array is used, it is necessary to separately provide a means for outputting a write start pulse. Since the beam detector 23 is normally set to receive the laser beam immediately before the writing area, the pulse signal from the beam detector 23 can be regarded as a signal indicating the head position in the main scanning direction.

FIG. 8 shows a part of the fourth embodiment. In the fourth embodiment, an intermediate transfer motor driver 24 serving as a motor drive unit drives the drive motor 16, and a motor control circuit 25 serving as a motor control unit includes a beam detector 23.
Cycle of an integer multiple of the pulse (light beam scanning pulse) from the detector and the pulse from the detector 18 (intermediate transfer marker output pulse)
The intermediate transfer motor driver 24 is synchronized with the cycle of
Control. In other words, as shown in FIG. 9, the motor control circuit 25 outputs the edges of the plurality of pulses (light beam scanning pulses) from the beam detector (BD) 23 and the pulses (intermediate transfer marker output pulses) from the detector 18. In comparison with the edge, the detector 1 is located closer to the edge of each pulse (light beam scanning pulse) from the beam detector (BD) 23.
Drive motor 16 (transfer M) via intermediate transfer motor driver 24 such that if the edge of the pulse (intermediate transfer marker output pulse) from pulse 8 is late, the edge of the pulse (intermediate transfer marker output pulse) from detector 18 will be early. ), If the edge of the pulse (intermediate transfer marker output pulse) from the detector 18 is earlier than the edge of the pulse (light beam scanning pulse) for each of the plurality of pulses from the beam detector (BD) 23, The drive motor 16 (transfer M) is controlled via the intermediate transfer motor driver 24 so that the edge of the pulse (intermediate transfer marker output pulse) is delayed.

The pulse counter 26 repeatedly counts the pulses (intermediate transfer marker output pulses) from the detector 18 by a predetermined number, and the light beam modulation circuit 27 outputs the pulses from the detector 18 based on the output signal of the pulse counter 26. The laser light source 20 is modulated by an image signal at a cycle that is an integral multiple of the cycle of the (intermediate transfer marker output pulse).

The general control of the drive motor 16 is as follows.
An origin signal is detected by detecting one origin mark provided on the intermediate transfer member, and the first laser beam scanning after the origin signal detection is used as the first line laser beam scanning of the color using the origin signal. Writing is in progress. However, since the head of the laser beam scanning and the origin signal by the origin mark on the intermediate transfer body are not always synchronized, the laser beam is emitted from the beam detector 2 at the moment when the origin signal is generated.
Immediately after passing through 3, the writing of the color (writing of one line) starts from the scanning of the next laser beam, and a start position shift of at most one scanning occurs.

In the fourth embodiment, the intermediate transfer motor driver 24 is controlled in synchronization with the write start pulse signal obtained by the beam detector 23 as described above. Even during the rotation, the head of writing and the position of the surface of the intermediate transfer belt 14 can be accurately matched, and a high-precision color image without color shift can be obtained.

As described above, according to the fourth embodiment, in the first to third embodiments, the toner image forming means applies the toner image to the photosensitive drum 11 as an image carrier on one line or a plurality of lines. A start pulse output unit for outputting a start pulse at a timing when one toner image formation is started, and a motor control circuit 25 as a drive control unit and an intermediate transfer motor driver 24 are provided with a marker. Since the drive motor 16 is controlled such that the marker detection cycle of the detector 18 as the detection means is synchronized with the integral multiple of the start pulse, the latent image writing timing and the marker detection signal of the marker detection means are generated in the same cycle, The writing of the latent image and the control of the drive motor 16 may be performed in synchronization with the same clock, which simplifies the system. In addition, it is possible to position the leading end of the image with high accuracy.

The fourth embodiment is an embodiment according to the fifth aspect of the present invention. In the fourth embodiment, a marker section 27 in which fine and precise graduations (markers) are formed in a non-image forming area on the surface or the inner surface of the photosensitive drum 11 at a constant period in the moving direction of the photosensitive drum 11 is provided. In addition to the above, an optical detector 28 as a marker detecting means for detecting the marker is provided, and the rotational position and the moving amount of the photosensitive drum 11 are directly and accurately detected to perform highly accurate positioning of the photosensitive drum 11. It is possible to do.

The marker section 27 is constructed in the same manner as the marker section 17, and the period of the detection signal from the detector 28 does not change during one rotation of the photosensitive drum 11 when the photosensitive drum 11 rotates at a constant speed. The marker unit 27 is provided with the number of markers determined by one rotation of the photoconductor drum 11, and detects the markers on the photoconductor drum 11 to obtain the speed and position information of the photoconductor drum 11.

As shown in FIG. 8, a photoreceptor motor driver 28 as a motor driving means drives the drive motor 12, and a motor control circuit 25 has a cycle of an integral multiple of a pulse (light beam scanning pulse) from the beam detector 23. And detector 2
The photoreceptor motor driver 28 is controlled so that the period of the pulse (photoreceptor marker output pulse) from step 8 is synchronized.
That is, as shown in FIG. 9, the motor control circuit 25 determines the number of pulses (light beam scanning pulses) from the beam detector (BD) 23 and the number of pulses (photoconductor marker output pulses) from the detector 28. If the edge of the pulse (photoconductor marker output pulse) from the detector 28 is later than the edge of the pulse (light beam scanning pulse) from the beam detector (BD) 23, the detector 28 The drive motor 12 (photoconductor M) is controlled via the photoconductor motor driver 28 so that the edge of the pulse (photoconductor marker output pulse) from the camera becomes earlier, and the pulse from the beam detector (BD) 23 If the edge of the pulse (photoconductor marker output pulse) from the detector 28 is earlier than the edge of the (light beam scanning pulse), the pulse (photoconductor marker) from the detector 28 Edge of the mosquito output pulse) via the photoreceptor motor driver 28 to be slower for controlling the driving motor 12 (the photoreceptor M).

As described above, by controlling the drive motor 12 and controlling the drive motor 16 in synchronization with the write start pulse signal obtained by the beam detector 23 as described above, a higher definition color image can be obtained. Can be obtained. Further, usually, the color shift due to eccentricity is reduced by setting the circumference of the photoconductor and the circumference of the intermediate transfer body to an integer ratio, but in the present embodiment, the surface positions of the photoconductor and the intermediate transfer body are directly adjusted. Since detection and control are performed, the surface positions of the photoconductor and the intermediate transfer member due to deformation and eccentricity are not changed, and the diameter and circumference of the photoconductor can be set freely. .

According to the fourth embodiment, a marker is provided on the surface of the photosensitive drum 11 as an image carrier at a constant period in the moving direction of the photosensitive drum 11 so that the constant speed of the photosensitive drum 11 is maintained. During rotation, the period does not change over one rotation of the photoconductor drum 11, and the marker portion 27 is provided with a predetermined number of the markers for one rotation of the photoconductor drum 11. And a drive control unit that controls the drive motor 12 based on information obtained from the detector 28. Since the motor control circuit 25 and the photoconductor motor driver 28 are provided, a higher quality color image can be obtained.

Next, a fifth embodiment of the present invention will be described. The fifth embodiment is similar to the first to fourth embodiments.
In the embodiment, when the detectors 18 and 28 detect the markers of the marker units 17 and 27, respectively, the marker unit 1
Instead of detecting only one period (one marker) of the reflectance periods of 7, 27, a plurality of periods (a plurality of markers) of the reflectance periods of the marker units 17, 27 are simultaneously detected. It is.

For simplicity of description, the marker sections 17, 2
The pattern of No. 7 has reflection portions 17a and 27 as shown in FIG.
It is assumed that the slit pattern is a pattern of a and the transmission portions 17b and 27b. The detectors 18 and 28 detect the patterns of the marker sections 17 and 27 using a split beam 29 as shown in FIG. 10, for example. In this case, the split beam 29 is, for example, as shown in FIG.
1 can be generated by using the slit 30 as shown in FIG. When the detectors 18 and 28 irradiate the pattern of the marker sections 17 and 27 with the divided beam 29 having the same cycle of the beam pattern, the reflection and transmission of the beam 29 having the same cycle as the pattern of the marker sections 17 and 27 are repeated. Yes,
By detecting this with a light receiving element such as a photodiode, the moving speed of the pattern of the marker portions 17 and 27 is determined.
A signal corresponding to the position can be obtained.

As a method for simultaneously detecting a plurality of cycles of the patterns of the marker sections 17 and 27, a method using slit projection may be employed. In this case, detector 18,
Reference numeral 28 irradiates light from the light source 31 to the marker units 17 and 27 through the lens 32 and the slit 30 as shown in FIG. With the movement of the rotating bodies 11 and 14, the marker section 17,
When the lens 27 moves, the light from the lens 32 is
Through the patterns 17d, 27d of the marker portions 17, 27
, The reflection and transmission are repeated, and this is received by the light receiving element 33, and a signal corresponding to the moving speed / position of the pattern of the marker sections 17, 27 is obtained.

As described above, the detectors 18 and 28 are connected to the marker 1
If a device that detects a large area of 7, 27 is used,
Marker part 1 even if there are defects, scratches, and attachments on the marker part
The influence on the detection operations 7 and 27 is reduced, and more stable position feedback on the photosensitive drum 11 and the intermediate transfer belt 14 can be performed.

According to the fifth embodiment, the detectors 18 and 28 as the marker detecting means are configured to detect a plurality of markers at the same time. be able to.

The present invention is applicable to, for example, a copying machine, a printer, a facsimile, etc. having an endless rotating body such as a photosensitive belt, an intermediate transfer belt, a transfer material conveying belt, a photosensitive drum, and an intermediate transfer drum used for image formation. The present invention can be applied to an image forming apparatus in the same manner as the above embodiment. Further, the present invention also provides a transfer material conveying belt on which a toner image of an image carrier is transferred, an endless rotating body such as an intermediate transfer drum, or a transfer material to transfer the toner image on the image carrier to the transfer material. The present invention can be applied to an image forming apparatus having an endless rotating body such as a transfer material conveying bell to be transferred in the same manner as the above-described embodiment, and not only an image forming apparatus for forming a color image but also an image forming apparatus for forming a monochrome image The present invention can also be applied to an image forming apparatus that forms a full-color image by superimposing toner images of three primary colors in the same manner as in the above embodiment.

FIG. 14 shows a sixth embodiment of the present invention.
The sixth embodiment is an embodiment of a color copying machine. The color copying machine includes a color image reading unit (hereinafter, referred to as a color scanner) 41, an image forming unit (hereinafter, referred to as a color printer) 42, a paper feeding unit 43, and the like.

The color scanner 41 illuminates the original 44 placed on the contact glass 101 with the illumination lamp 102, and reflects the reflected light on mirrors 103a, 103b, 103b.
A color sensor 105 via the lens 103c and the lens 104;
And the illumination lamp 102 and the mirror group 1
The original 44 is scanned by moving the reference numerals 03a, 103b, and 103c, and the color image information of the original 44 is read for each color separation light of, for example, red, green, and blue (hereinafter, referred to as R, G, and B, respectively). To an appropriate image signal. Here, the color sensor 105 includes R, G, B in this embodiment.
, And a color image information of three colors R, G and B obtained by color-separating the image of the document 44 at the same time.

An image processing unit (not shown) performs a color conversion process on the image signal decomposed into the R, G, and B colors from the color scanner 41 based on its intensity level, and outputs a black signal (hereinafter referred to as K). ), Cyan (hereinafter referred to as C), magenta (hereinafter referred to as M), and yellow (hereinafter referred to as Y) color image data are sequentially obtained. And
The color printer 42 receives K, C, M,
K, C, M, Y in order according to the color image data of each Y color
An image of each color is formed, and these images are superimposed to form a final four-color superimposed full-color image.

The color scanner 41 is a color printer 4
In response to the scanner start signal that is timed with the operation of Step 2, the illumination lamp 102 and the mirror groups 103a and 103a are received.
The original 44 is scanned by moving the optical system composed of 3b, 103c, etc. in the direction of the arrow, and color image data of R, G, B colors is output to the image processing unit, and a color image of one color is scanned each time. Data is obtained from the image processing unit. This operation is a total of 4
By repeating this process four times, color image data of four colors is sequentially obtained. Then, the color printer 42 sequentially forms images of each color of K, C, M, and Y based on the color image data of each color of K, C, M, and Y from the image processing unit, and superimposes these images to form a final image. To form a full four-color superimposed full-color image.

The color printer 42 includes a photosensitive member (here, a drum-shaped photosensitive member) 200 as a latent image carrier, a writing optical unit 220 as an exposure unit, a revolver developing unit 230 as a developing unit, and an intermediate transfer unit 50.
0, a secondary transfer unit 600, a fixing device 270, and the like.

The photoreceptor 200 is rotated by a drive motor (not shown) and rotates in a counterclockwise direction indicated by an arrow. Around the photoreceptor cleaning device 201, a part of which is shown in FIG. Lamp 202, charger 203 as charging means, surface potential sensor 204, selected developer of revolver developing unit 230, reflection density sensor 20
5, an intermediate transfer unit 500 and the like are arranged.

The charger 203 receives a voltage from a charging power supply (not shown) to uniformly charge the photosensitive member 200.
The surface potential sensor 204 detects the surface potential of the photoconductor 200, and the reflection density sensor 205 optically detects the reflection density of the photoconductor 200. The charging unit 203 and the writing optical unit 220 constitute an electrostatic latent image forming unit that forms an electrostatic latent image on the photoconductor 200. The electrostatic latent image forming unit and the revolver developing unit 230 include a toner on the photoconductor 200. It constitutes a toner image forming means for forming an image.

The writing optical unit 220 converts color image data input from the color scanner 41 via the image processing unit into an optical signal, and performs optical writing corresponding to the color image information of the original 44 on the photosensitive member 200. Done to
An electrostatic latent image is formed on the photoconductor 200. The writing optical unit 220 includes a semiconductor laser 22 as a light source.
1. Laser emission drive control unit (not shown), polygon mirror 222, motor 223 for rotating the polygon mirror, f / θ lens 2
24, a reflection mirror 225 and the like. The semiconductor laser 221 is driven and controlled by the laser emission drive control unit based on color image data input from the color scanner 41 via the image processing unit, and emits a laser beam modulated with the color image data. This laser beam
The light is repeatedly scanned in the main scanning direction by the polygon mirror 222, and is irradiated on the photoconductor 200 via the f / θ lens 224, the reflection mirror 225, and the like.

Further, the revolver developing unit 230
Developing device 231K, C developing device 231C, M developing device 231
M and Y developing units 231Y, these developing units 231K,
31C, 231M, and 231Y in a counterclockwise direction indicated by an arrow, and a revolver rotation driving unit;
1C, 231M, and 231Y are provided with K, C, M, and Y color toner replenishing units for replenishing K, C, M, and Y toners, respectively.

Each of the developing units 231K, 231C, 231M,
231Y is a developing sleeve as a developer carrier which rotates by bringing a spike of developer into contact with the surface of the photoconductor 200 to develop an electrostatic latent image on the photoconductor 200, and draws up the developer. It is composed of a developer paddle or the like as a stirring means which rotates for stirring. The toner supply units of the respective colors are driven by toner supply motors (not shown), so that the developing units 231K, 231C, 231M, and 231Y are developed.
To the developing units 231K, 231C,
Reference numerals 231M and 231Y agitate the internal developer and the toner supplied from the toner supply unit with a developer paddle.

Each developing unit 231K, 231C, 231M,
231Y includes a two-component developer composed of a K toner and a ferrite carrier, a two-component developer composed of a C toner and a ferrite carrier, a two-component developer composed of an M toner and a ferrite carrier, a Y toner and a ferrite carrier. Are stored, respectively.
The toner of each color of K, C, M and Y is negatively charged by stirring with the ferrite carrier. Further, each developing unit 23
A developing bias in which an AC voltage is superimposed on a negative DC voltage is applied by a developing bias power supply (not shown) to a developing sleeve in each of 1K, 231C, 231M, and 231Y. Are biased to a predetermined potential.

In the standby state of the color copying machine, the revolver developing unit 230 has the K developing device 231K set at the home position of the developing position, and when the start key is pressed to start the copying operation, the color scanner 41 is started. The reading of the original image for obtaining the K image data is started at a predetermined timing, and the color image data from the color scanner 41 is input to the writing optical unit 220 via the image processing unit, and
0 starts optical writing with a laser beam based on K image data from the image processing unit and starts formation of an electrostatic latent image (hereinafter, an electrostatic latent image based on K image data is referred to as a K latent image. An image, an electrostatic latent image based on M image data, and an electrostatic latent image based on Y image data are similarly referred to as a C latent image, an M latent image, and a Y latent image).

The revolver developing unit 230 includes the photosensitive member 2
Before the leading end of the K electrostatic latent image arrives at the developing position to develop from the leading end of the K electrostatic latent image on 00, rotation of the K developing sleeve in the K developing device 231K is started, and the photosensitive member 200 is started. The above K electrostatic latent image is developed with K toner to form a K toner image.
Thereafter, the developing operation of the K electrostatic latent image on the photoconductor 200 is continued, but when the rear end portion of the K electrostatic latent image passes the developing position, the developing device for the next color is developed immediately. The revolver developing unit 230 rotates until it reaches the position. 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 is composed of an intermediate transfer member including an intermediate transfer belt 501 as an image carrier which is stretched over a plurality of rollers described later. Around the intermediate transfer belt 501, the secondary transfer unit 6
00, a secondary transfer belt 601 as a transfer material carrier, a secondary transfer bias roller 605 as a secondary transfer means, and a belt cleaning device 5 as an intermediate transfer body cleaning means.
04, a lubricant application brush 505 serving as a lubricant application means is disposed so as to face the intermediate transfer belt 501.

The intermediate transfer belt 501 is stretched around a primary transfer bias roller 507, a belt drive roller 508, a belt tension roller 509, a secondary transfer opposed roller 510, a cleaning opposed roller 511, and an earth roller 512 as primary transfer means. It is suspended. These rollers 5
Reference numerals 07 to 512 are formed of a conductive material, and the rollers 508 to 512 other than the primary transfer bias roller 507 are grounded.

The primary transfer power supply 801 applies to the primary transfer bias roller 507 a transfer bias controlled to a predetermined current or voltage in accordance with the number of superimposed toner images on the intermediate transfer belt 501. Is done. The intermediate transfer belt 501 is driven in a direction indicated by an arrow by a belt drive roller 508 that is rotated by a drive motor (not shown).

In a transfer section (hereinafter referred to as a primary transfer section) for transferring the toner image on the photosensitive member 200 to the intermediate transfer belt 501, a primary transfer bias roller 507 and an earth roller 5
At 12, the intermediate transfer belt 501 is stretched so as to be pressed against the photoconductor 200, thereby forming a nip portion having a predetermined width between the photoconductor 100 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 able to contact and separate from the intermediate transfer belt 501 by a contact and separation mechanism (not shown), and is controlled to contact the intermediate transfer belt 501 at a predetermined timing.

The secondary transfer unit 600 includes a secondary transfer belt 601 stretched over three support rollers 602, 603, and 604, and a portion between the support rollers 602 and 603 of the secondary transfer belt 601 is stretched. Secondary transfer opposing roller 5
10 can be pressed against. 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.

The secondary transfer bias roller 605 is provided between the intermediate transfer belts 501 and
The secondary transfer power supply 802 applies a transfer bias of a predetermined current to the secondary transfer belt 601 so as to sandwich the next transfer belt 601. Further, the supporting 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 and the secondary transfer bias roller 605 are pressed against the secondary transfer opposed roller 510 and a position where the secondary transfer bias roller 605 is separated. A not-shown contact / separation unit to be driven is provided. 15 of FIG.
The dotted line indicates the position where the secondary transfer belt 601 and the support roller 602 are separated from the secondary transfer opposing roller 510, and the solid line in FIG. 15 indicates that the secondary transfer belt 601 and the support roller 602 are connected to the secondary transfer opposing roller 510. Shows the position of the pressure contact.

The pair of registration rollers 650 includes an intermediate transfer belt 501 and a secondary transfer belt 6 sandwiched between a secondary transfer bias roller 605 and a secondary transfer opposing roller 510.
During the period 01, a transfer paper as a transfer material is fed at a predetermined timing. A portion of the secondary transfer belt 601 that is stretched around the support roller 603 on the side of the fixing device 270 includes a transfer paper charge remover 606 as a transfer material charge remover and a belt charge remover 607 as a transfer material carrier charge remover. Are arranged facing each other. Further, a cleaning blade 608 serving as a transfer material carrier cleaning unit is in contact with a portion stretched around the lower support roller 604 of the secondary transfer belt 601.

The transfer paper discharging charger 606 removes the charge held on the transfer paper on the secondary transfer belt 601 to separate the transfer paper from the secondary transfer belt 601 with the strength of the transfer paper itself. . The belt static elimination charger 607 eliminates electric charges remaining on the secondary transfer belt 601. In addition, the cleaning blade 608 removes substances attached to the surface of the secondary transfer belt 601 and performs cleaning.

In the color copier thus constructed, when the image forming cycle is started, the photosensitive member 100 and the intermediate transfer belt 501 are rotationally driven by a drive motor (not shown) in the direction shown by the arrow, and at the primary transfer position. Rotate at the same linear speed. With the rotation of the photoconductor 200 and the intermediate transfer belt 501, K toner image formation, C toner image formation, M toner image formation, and Y toner image formation are performed, and these K toner image, C toner image, M toner image, The Y toner image is transferred from the primary transfer power supply 801 to the primary transfer bias roller 50.
By the transfer bias applied to the transfer belt 7, primary transfer is sequentially performed from the photoconductor 200 to the intermediate transfer belt 501, and a full-color toner image of four colors is finally formed on the intermediate transfer belt 501.

The toner image is formed as follows. The charging charger 203 uses the photoconductor 100 by corona discharge.
Is uniformly charged to a predetermined potential with a negative charge. The writing optical unit 220 performs raster exposure on the photoconductor 200 based on the K image signal from the image processing unit. At this time,
In the exposed portion of the surface of the photoreceptor 100 that is initially uniformly charged, the charge proportional to the amount of exposure light disappears, and a K latent image is formed.

When the negatively charged K toner on the K developing roller of the K developing device 231K comes into contact with the K latent image, the toner does not adhere to the unexposed portion of the photoconductor 200, The toner adheres to the exposed portion, and a K toner image similar to the K latent image is formed. The K toner image formed on the photoconductor 200 is transferred to the surface of the intermediate transfer belt 501 that is driven at a constant speed in contact with the photoconductor 200 at the primary transfer position. Hereinafter, the photoconductor 20
The transfer of the toner image from 0 to the intermediate transfer belt 501 is called belt transfer. In the photoconductor 200 after the belt transfer, a small amount of untransferred residual toner remaining on the surface of the photoconductor 200 is cleaned by the photoconductor cleaning device 201 and uniformly discharged by the discharging lamp 202 in preparation for reuse of the photoconductor 200. .

On the photoconductor 200 side, the process proceeds to the C image forming process after the K image forming process described above. At a predetermined timing, reading of a document image for obtaining C image data by the color scanner 41 is started. R,
G and B color image data are output to the image processing unit, and the image processing unit outputs C image data to the writing optical unit 220. The writing optical unit 220
Optical writing is performed on the photoconductor 200 based on the C image data from the image processing unit to form a C latent image on the surface of the photoconductor 200.

After the rear end of the K latent image on the photosensitive member 200 has passed,
Before the leading end of the latent image reaches, the C developing device 231C is set to the developing position by performing a rotating operation, and the C latent image is
The toner image is developed at 1C to form a C toner image.

Thereafter, the C developing device 231C continues developing the C latent image area on the photoconductor 200, but when the rear end of the C latent image on the photoconductor 200 passes, the C developing device 231K starts. As in the case, the revolver developing unit 230 performs a rotating operation to move the next M developing device 231M to the developing position.
This is also completed before the leading end of the next M latent image reaches the developing position.

The C toner image formed on the photoreceptor 200 is superposed on the surface of the intermediate transfer belt 501 which is driven at a constant speed in a state of contact with the photoreceptor 200 at the primary transfer position and is superposed on the K toner image. Is done. Photoreceptor 200 after belt transfer
In order to prepare for re-use of the photoconductor 200, a small amount of untransferred residual toner remaining on the surface of the photoconductor 200 is cleaned by the photoconductor cleaning device 201, and is uniformly discharged by the discharge lamp 202.

On the photoconductor 200 side, the process proceeds to the M image forming process after the C image forming process. At a predetermined timing, reading of a document image for obtaining M image data by the color scanner 41 is started. G, B3
The color image data of the color is output to the image processing unit, and the M image data is output from the image processing unit to the writing optical unit 220. The writing optical unit 220 performs optical writing on the photoconductor 200 based on the M image data from the image processing unit to form an M latent image on the surface of the photoconductor 200.

Then, the revolver developing unit 400 operates after the rear end of the C latent image on the photosensitive member 200 has passed and
Before the leading end of the latent image arrives, the rotating operation is performed to set the M developing device 231M to the developing position.
The image is developed at 1M and becomes an M toner image. Thereafter, M developing device 2
31M continues development of the M latent image area on the photoconductor 200, but when the rear end of the M latent image on the photoconductor 200 has passed, the revolver developing unit 230 performs a rotation operation to execute the next Y developing unit. 231Y is moved to the developing position. This is also completed before the leading end of the next Y latent image reaches the developing position.

The M toner image formed on the photosensitive member 200 has a K toner image and a C toner image on the surface of the intermediate transfer belt 501 which is driven at a constant speed in contact with the photosensitive member 200 at the primary transfer position. The belt is transferred in an overlapping manner. The photoreceptor 200 after the belt transfer is cleaned by a photoreceptor cleaning device 201 with a small amount of untransferred residual toner remaining on the surface thereof in preparation for reuse of the photoreceptor 200, and the charge removing lamp 202.
The charge is removed evenly.

On the photoconductor 200 side, the process proceeds to the Y image forming process after the M image forming process. At a predetermined timing, reading of a document image for obtaining Y image data by the color scanner 41 is started. G, B3
The color image data of the color is output to the image processing unit, and the Y image data is output from the image processing unit to the writing optical unit 220. The writing optical unit 220 forms a Y latent image on the surface of the photoconductor 200 by performing laser beam writing on the photoconductor 200 based on the Y image data from the image processing unit.

Then, after the rear end of the M latent image on the photosensitive member 200 has passed,
Before the leading end of the latent image arrives, the rotating operation is performed to set the Y developing device 231Y at the developing position, and the Y latent image is
The image is developed at 1Y to form a Y toner image. Thereafter, the Y developing device 2
31Y continues development of the Y latent image area on the photoconductor 200, but when the rear end of the Y latent image on the photoconductor 200 has passed, the revolver developing unit 230 performs a rotation operation to execute the next K developing unit. 231K is moved to the development position.

The Y toner image formed on the photosensitive member 200 has a K toner image and a K toner image on the surface of the intermediate transfer belt 501 that is driven at a constant speed in a state of contact with the photosensitive member 200 at the primary transfer position.
The belt is transferred to be superimposed on the C toner image and the M toner image.
A full-color image of color superposition is formed. After the belt transfer, the photoreceptor 200 is cleaned by a photoreceptor cleaning device 201 to remove untransferred residual toner remaining on the surface of the photoreceptor 200 in preparation for reuse, and is uniformly discharged by a discharge lamp 202. You.

As described above, on the intermediate transfer belt 501, K, C, M, and Y sequentially formed on the photosensitive member 200.
The toner images of the respective colors are sequentially aligned and transferred on the same surface to form a four-color superimposed full-color image. At the time when the image forming operation is started, the transfer paper P is
3 or is fed from the manual feed tray 210 and is waiting at the nip of the registration roller 650.

When the leading edge of the full-color image on the intermediate transfer belt 501 reaches the secondary transfer portion where the nip is formed by the secondary transfer facing roller 510 and the secondary transfer bias roller 605, the leading edge of the transfer paper P is just The registration roller 65 is aligned with the end of the full-color image.
0 is driven, registration of the transfer sheet P with the full-color image is performed, and the transfer sheet P is sent out by the registration roller 650.

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

Thereafter, the transfer paper P is transferred to the secondary transfer belt 60.
When the sheet passes through an opposing portion of the transfer paper neutralization charger 606 and the secondary transfer belt 601 disposed on the downstream side of the secondary transfer section in the moving direction of the transfer paper 1, the transfer paper neutralization charger 606 is used.
, And is separated from the secondary transfer belt 601 and sent to the fixing device 270 by the transport device 211. The transfer sheet P is fused and fixed by a fixing device 270 and is stacked face up on a copy tray (not shown) by a pair of discharge rollers 212 to obtain a full-color copy. 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 device 504 pressed against the intermediate transfer belt 501 by a separation / contact mechanism (not shown).

At the time of repeat copying, the operation of the color scanner 41 and the formation of an image on the photosensitive member 200 are performed at a predetermined timing following the fourth color (Y) image forming process of the first sheet. To the first color (K) image forming process. In addition, the intermediate transfer belt 501 has a second K toner image in an area where the surface is cleaned by the belt cleaning device 504 following the batch transfer process of the first four-color superimposed full-color image onto transfer paper. Is transferred to the belt. After that, the operation becomes the same as that of the first sheet.

The above is the copy mode for obtaining a four-color full-color copy. 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. . In the case of the single color copy mode, only the developing device of the predetermined color of the revolver developing unit 230 is in the developing operation state until the predetermined number of copies are completed, and the belt cleaning device 504 is pressed against the intermediate transfer belt 501. The copying operation is performed while the state is maintained.

In the above image forming process, the photosensitive member 2
When the rotational movement speed (movement speed in the traveling direction) of the intermediate transfer belt 501 fluctuates, the color image on the intermediate transfer belt 501 or the transfer paper is disturbed.
The 0 and the intermediate transfer belt 501 require very precise rotational driving.

Generally, an endless belt-shaped rotating body used in an image forming apparatus such as a color electrophotographic copying machine or a color printer has a structure supported by a plurality of supporting rollers. A drive motor is connected to the rotation shafts of the two support rollers to rotationally drive the endless belt-shaped rotator. As the drive motor, a servo motor or a step motor having a built-in rotary encoder is used.
In driving such an endless belt-shaped rotating body, the moving amount (rotating position) of the rotating body is not directly detected, but the rotating movement amount (rotating position) of a driving motor as a driving source is detected. However, since the feedback control of the drive motor is performed based on the detection result, even if the rotational position and the rotational angular velocity of the drive motor can be precisely controlled, the moving amount (the rotational position) and the rotational movement speed of the rotating body are not. Not precisely controlled. Therefore, since the reduction gear precision of the drive motor, the diameter of the drive roller, and the deformation directly affect the speed fluctuation of the rotating body, it is impossible to perform positioning beyond these production precisions.
The upper limit of image quality is naturally limited.

Therefore, in the image forming apparatus of this embodiment, as shown in FIG. 16, fine and precise graduations are formed on the surface or the inner surface of the intermediate transfer belt 501 at regular intervals in the rotation direction of the intermediate transfer belt 501. The formed optical pattern 701 is provided.
An optical detector 702 is provided as detecting means for detecting the rotational position and the amount of movement of the intermediate transfer belt 501 directly and accurately. That is, the movement amount (rotational position) of the intermediate transfer belt 501 includes all the effects such as the deformation and eccentricity of the support roller appearing in the rotational movement of the intermediate transfer belt 501, the eccentricity of the shaft of each support roller, and the speed fluctuation of the drive motor 703. ) Can be accurately detected. Also, even if the rotational movement of the intermediate transfer belt 501 itself slips,
A fine and precise marker (optical pattern) 701 is provided on the intermediate transfer belt 501, and this marker 701 is
2, the amount of movement (rotational position) of the intermediate transfer belt 501 can be accurately detected, including the slippage. Here, the drive motor 703 is connected to the drive roller 508 to rotate the intermediate transfer belt 501 via the drive roller 508, and the drive motor 704 is connected to the shaft of the photoconductor 200 to rotate the photoconductor 200.

Further, this embodiment is characterized in that the optical pattern 7
01 is detected, it is not necessary to detect only one period of the reflectance period of the optical pattern 701.
The object of the present invention is to simultaneously detect a plurality of periods of one reflectance. For the sake of simplicity, it is assumed that the optical pattern 701 is a slit pattern in which a reflection section 701a and a transmission section 701b are arranged at regular intervals in the rotation direction of the intermediate transfer belt 501 as shown in FIG.

The detector 702 uses a split beam 705 as shown in FIG. 17, for example. At this time, the split beam 705
Is preferably the same as the cycle of the optical pattern 701.
As shown in FIG. 17, the detector 702 has an optical pattern 701.
Irradiation with a beam pattern 705 having the same period as the
Reflection and transmission of the beam 705 having the same period as the optical pattern 701 are repeated, and the reflected beam is detected by a light-receiving element such as a photodiode by the detector 702, so that the beam can be adjusted according to the moving speed and position of the optical pattern 701. Signal is obtained.

Similarly, the optical pattern 70 is detected by the detector 702.
To simultaneously detect a plurality of lines (for a plurality of periods), slit projection may be used. FIG. 18 shows a configuration example of a detector 702 using slit projection. The light from the light source 706 is converted into substantially parallel light by a lens 707, is divided into a plurality of slits of a slit plate 708 as shown in FIG. As the intermediate transfer belt 501 moves, the optical pattern 7
When 01 moves, when the optical pattern 701 is viewed by the detector 702 through a plurality of slits of the slit plate 708, the reflection and transmission of the divided beam 705 by the optical pattern 701 are alternately repeated, and as shown in FIG. The beam is detected by the light receiving element 709 through the plurality of slits of the slit plate 708, and a signal similar to the above is obtained.

Although the method of forming the optical pattern 701 is not particularly described in the present embodiment, the slit pattern 701 made of a flexible material is used for the intermediate transfer belt 5.
01, a method of bonding the tape-shaped pattern 701 to the intermediate transfer belt 501, and a method of bonding the intermediate transfer belt 501.
In this case, a method of directly printing the optical pattern 701 may be adopted. Also, the shape of the optical pattern 701 does not need to be a continuous rectangular pattern, and may be freely selected.

FIG. 21 shows a hardware configuration of an intermediate transfer belt drive control system used in this embodiment. The intermediate transfer belt drive control system is provided with a microcomputer 710 as control means for performing overall control. The microcomputer 710 includes a microprocessor (CPU) 711, a read only memory (ROM) 712, and a random access memory (RA).
M) 713 are connected via a bus 714, respectively.

The output signal of the detector (belt sensor) 702 is supplied to a state detection interface 715 and a bus 7.
14 to a microcomputer 710. Here, an interface 715 for state detection processes the output signal of the detector (belt sensor) 702 and converts it into a digital numerical value.
A counter for counting the number of pulses from 02 is provided.

The optical pattern 701 corresponds to the intermediate transfer belt 50.
The detector 702 detects the origin marker of the optical pattern 701 and outputs the origin information. The state detection interface 715 stores the origin information from the detector 702 and the initial position of the intermediate transfer belt 501 when the power is turned on in the RAM 713, thereby associating (correlation) with the movement position of the intermediate transfer belt 501. It has a function to take Therefore, in the present embodiment, the interface 715 for state detection is
1 has a function of managing the position. The microcomputer 710 calculates a position control amount of the drive motor 703 so that the rotational position of the intermediate transfer belt 501 becomes a target value by using an input signal from the state detection interface 715.

The drive motor 703 is connected to the microcomputer 710 via a bus 714, a drive interface 716, and a drive (driver) 717. The drive interface 716 converts the digital signal of the result of the position control amount calculation in the microcomputer 710 into an analog signal, and
The current and the voltage applied to the drive motor 703 from this motor drive amplifier are controlled. As a result, the intermediate transfer belt 501 is driven to follow a predetermined target position. At this time, the position of the intermediate transfer belt 501 is detected by the detector 702 and the state detection interface 715 and is taken into the microcomputer 710.

The drive control system for the intermediate transfer belt according to the present embodiment is realized by a microcomputer 710, a driving device 717 and the like. Note that, instead of the microcomputer 710, a DSP or RISC processor having a high arithmetic processing speed may be used.

In this embodiment, as shown in FIG.
An intermediate transfer belt drive control system that performs a control operation by a computer such as a CPU or a DSP may be used. In the intermediate transfer belt drive control system, the target speed is integrated by an integrating means 718 to create a target position in order to eliminate the positional shift of the intermediate transfer belt 501. Reset signal RE given to integrating means 718
In the SET, the origin information obtained by the detector 702 detecting the origin marker of the optical pattern 701 at the home position once per rotation is used as the state detection interface 7.
15 and resets the integrating means 718.

The position controller 719 is, for example, a PID
A controller is used, and a computer 720 such as a CPU or a DSP has a PID controller 719 as a position control controller. The belt system 72 includes an intermediate transfer unit 500, a drive motor 703, a detector 702, and a drive circuit for driving the drive motor 703. The drive motor 703 is controlled via a drive circuit by a control signal from a PID controller 719. The position of the intermediate transfer belt 501 is read by detecting the optical pattern 701 by the detector 702, and the output signal of the detector 702 is set to PLD.
(Programmable Logic Device) 721.

The PLD 721 electrically converts slits (markers) of the optical pattern 701 having a pitch of 100 μm with respect to an output signal of the detector 702 to a resolution of 0.5 μm to 100 μm.
The slit detection signal having a resolution of 0.5 μm and the slit detection signal having a resolution of 0.5 μm are input in parallel to the input units 722 and 723 of the computer 720. The slit detection signal of 100 μm resolution has 15 bits, and the slit detection signal of 0.5 μm resolution has 8 bits.

The PLD 721 inputs the origin signal home obtained by the detector 702 detecting the origin marker of the optical pattern 701 at the home position once per rotation to the input section 724 of the computer 720, and outputs the origin signal home. home is given to the integration means 718 via the interface 715 for state detection. Computer 720
From the target position obtained by the integration means 718, the input units 722, 7
23 is subtracted from the surface position of the intermediate transfer belt 501 fed back to the position control controller 23, and the position control controller 7
The position control amount of the intermediate transfer belt 501 is obtained by 19 and output to the drive circuit of the belt system 720 to control the surface position of the intermediate transfer belt 501.

FIG. 23 shows the deviation between the surface position of the intermediate transfer belt 501 and the target position. When the computer 720 uses the position signal from the input unit 722, the resolution of the position signal is 0.5 μm, so that the deviation between the surface position of the intermediate transfer belt 501 and the target position is within ± 10 μm. . FIG. 24 shows the deviation between the surface position of the intermediate transfer belt 501 and the target position. Since the computer 720 uses only the position signal from the input unit 723, the resolution of the position signal is 100 μm.
The deviation between the surface position and the target position is 100 μm.
23 and 24 show the case where the sampling cycle of the controller 720 is 1 ms and the linear velocity of the intermediate transfer belt 501 is 200 ms.
The results when mm / s and the cross frequency of the open loop transfer function are 50 Hz are shown.

According to the sixth embodiment, since a plurality of cycles of the optical pattern 701 are detected at the same time, the influence on the detection of the optical pattern is reduced even if there is a defect, a scratch or an adhering matter in the optical pattern. More stable position control of the intermediate transfer belt 501 can be performed.

Generally, an endless belt-shaped rotating body used in an image forming apparatus such as a color electrophotographic copying machine or a color printer has a structure supported by a plurality of supporting rollers. A drive motor is connected to the rotation shafts of the two support rollers to rotationally drive the endless belt-shaped rotator. Further, the latent image carrier and the image carrier come into contact with each other to transfer the toner image.

In the seventh embodiment of the present invention, an optical pattern on which fine and precise graduations are formed is provided on the surface or the inner surface of the image carrier. The structure is such that the driving roller to be rotated, the supporting roller for supporting the image carrier, the latent image carrier, and the like avoid contact, and a gap is provided between the optical pattern and the rotating structure.

For example, when an optical pattern is formed on the back surface of the image carrier, it can be realized by providing a recess in a part of the driving roller and the supporting roller.
A similar effect can be achieved by forming a pattern in a region that does not come into contact with a latent image carrier or the like.

According to the configuration of the seventh embodiment, it is possible to prevent the optical pattern from being broken due to abrasion or the like, and to eliminate the influence of the rotation deviation or the speed fluctuation caused by the arrangement of the optical pattern. In addition, by providing a gap between the optical pattern and the rotating structure, even when toner, dust, etc. adhere to the optical pattern, contact between the optical pattern and another rotating body is less likely to occur, and water repellency to the optical pattern is obtained. It is not necessary to add functions such as oil repellency.

FIG. 25 shows an intermediate transfer unit according to the present embodiment, and FIG. 26 shows a part thereof. In the seventh embodiment, in the sixth embodiment, a recess 725 is provided in a part of the rotation shaft of the rollers 507 to 512 in order to avoid the contact between the optical pattern 701 and the supporting rollers 507 to 512 as a rotating body. An optical pattern 701 is formed on the inner surface of the intermediate transfer belt 501 by printing, exposing, laser processing, or the like, or is formed by printing, exposing, laser processing, etc. The optical pattern 701 is transferred to the intermediate transfer belt 501.
Place on the inner surface of. The optical pattern 701 can be formed on a non-snaking guide 726 formed on the inner surface end of the intermediate transfer belt 501, or can also have the function of the non-slip guide. With such a configuration, contact between the optical pattern 701 and the rollers 507 to 512 during rotation of the rollers 507 to 512 is avoided.

In an image forming apparatus, particularly in a color image forming apparatus, toner scattering is a problem. In particular, the toner scatters around the image carrier, and when the optical pattern 701 or the like is detected by the detector 702, a countermeasure against contamination is required. In the present embodiment, the cleaning member 727 is installed at a position corresponding to the optical pattern 701. Here, a fibrous brush is arranged as a cleaning member 727 so as to contact the optical pattern 701, and the optical pattern 701 is cleaned by the cleaning member 727 by rotating the intermediate transfer belt 501 as an image carrier. This prevents detection failure of the optical pattern 701. The cleaning member 727 may be a sponge, felt, or the like.

An image carrier in an image forming apparatus often has a layer having a relatively high resistance, and always retains electric charge by charging, transferring and the like. In some cases, the image carrier always has a potential of 1000 V or more. When the optical pattern 701 is detected by the detector 702 close to the optical pattern, it is necessary to prevent erroneous detection due to noise or the like.

In the present embodiment, a charge removing member is provided at a position corresponding to the optical pattern 701. Here, as the cleaning member 727, a fibrous brush is an optical pattern 70.
The brush 727 is grounded and serves as a charge removing member, and the rotation of the intermediate transfer belt 501 as an image carrier causes the brush 727 to remove charge from the optical pattern 701. Thereby, the optical pattern 70
1 is prevented from being detected.

In the eighth embodiment of the present invention, in the sixth embodiment, the intermediate transfer belt 501 as an image carrier is used.
An optical pattern 701 in which fine and precise graduations are formed on the surface or the inner surface is divided into a plurality of portions. For example, as shown in FIG. 27, another optical pattern slit 701b is arranged close to and parallel to one optical pattern slit 701a, or one optical pattern slit 701a is connected to the other optical pattern slit 701a. It is also possible to arrange continuously such as arranging continuously with the attached slit 701b. The same arrangement is possible for two or more slits with an optical pattern. Further, a plurality of slits with an optical pattern can be arranged on both sides of the intermediate transfer belt 501 as an image carrier, or can be arranged near the center of the image forming portion and the peripheral portion on the back surface of the intermediate transfer belt 501.

In this embodiment, one slit 701a with an optical pattern is connected to the other slit 701a with an optical pattern.
b and one or more detectors 7
By detecting the slits 701a and 701b with the optical pattern simultaneously by using 02a and 702b, it is possible to reduce the detection error. The plurality of detectors 702a, 7
By detecting the slits 701a and 701b with optical patterns at positions different from each other by 02b, it is possible to reduce a detection error at the positions of the slits 701a and 701b with optical patterns.

By arranging a plurality of slits with an optical pattern so as to complement the slit-unformed portion,
Slit detection can be performed over the entire circumference of the image carrier. The same effect can be expected by arranging a plurality of slits with an optical pattern in succession, so that a slit with an optical pattern shorter than the entire circumference of the image carrier can be used. This facilitates the creation of a slit with an optical pattern, and brings about an effect of cost reduction. Further, when the length of the slit with the optical pattern is shortened, the work of bonding the slit with the optical pattern becomes easy, and there is an advantage that the slit with the optical pattern can be formed with high accuracy.

Further, by detecting the difference in the slit depending on the position of the peripheral portion, the central portion, or the like of the image carrier, it is possible to detect the deviation of rotation due to the position of the image carrier, and to use it to adjust the balance of the image carrier. It can be used for speed control, speed adjustment, and the like, and is effective for highly accurate image carrier surface position control.

In this embodiment, for example, the intermediate transfer belt 5
Slit 701 with optical pattern formed in a part of 01
a and 701b are detected by the detectors 702a and 702b, respectively, and the position of the intermediate transfer belt 501 is detected. The detection signal of the detector 702b is switched at a portion where the detection signal of the detector 702a does not have the detection signal to generate the detection signal, so that the position can be detected over the entire circumference of the intermediate transfer belt 501. At this time, the detectors 702a, 702b
A circuit for calculating the position of the intermediate transfer belt 501 from the detection signal is provided, and the signal from this circuit is converted into an averaged signal or a signal complementing the other by the drive motor 703 by the intermediate transfer belt drive control system. Can be used for position control. In addition, the detector 702a is arranged in the middle of the slits 701a and 701b with an optical pattern. For example, a split photo-diad is used as the detector 702a to detect both the slits 701a and 701b with an optical pattern at the same time. Then, the slits 701a, 701a, 7
01b can be detected.

In general, an endless belt-shaped rotator used in an image forming apparatus such as a color electrophotographic copying machine or a color printer is supported by a plurality of support rollers and is driven to rotate by one rotation shaft. According to a ninth embodiment of the present invention, an optical pattern 701 in which fine and precise graduations are formed on a surface or an inner surface of an intermediate transfer belt 501 as an image carrier according to the sixth embodiment is provided. The pitch (period) 701 is an integer ratio of the image forming pitch. For example, in an electrophotographic copying machine or a printer having an optical resolution of 600 dpi, this is an integral multiple of the image forming pitch of about 40 microns.
This corresponds to creating the optical pattern 701 by selecting the pitch of the optical pattern 701 from microns, 80 microns, 120 microns, or the like.

At this time, the drive shaft of the endless intermediate transfer belt 501 is controlled by the intermediate transfer belt drive control system so that the signal based on the write timing and the detection signal of the detector 702 for the optical pattern 701 are synchronized. The speed and position of the intermediate transfer belt 501 are controlled. The deviation between the latent image forming position and the image forming position on the intermediate transfer belt 501 is, for example, temporarily storing a write timing signal in a memory and synchronizing with a write timing at the image forming position after a certain delay time or by signal processing. Thereby, high precision can be achieved.

This write timing signal uses, for example, a signal formed once on one surface or one rotation of the polygon mirror when writing is performed using a polygon mirror, or one pixel when writing using an LED. Can be used. In the present embodiment, the drive shaft of the intermediate transfer belt 501 is controlled so that the write timing and the position signal of the endless belt 501 (the output signal of the detector 702) are synchronized.

Conventionally, the control of the rotating body has been performed so as to keep the rotation speed of the drive shaft constant.
There has been a shift between the actual image forming position and the surface position of the rotating body due to a shift due to a processing error, an error in a transmission system such as a gear, or the like. In addition, since the rotation of the rotating body is independently controlled at the writing timing in the related art, it is difficult to remove the influence of the image deterioration due to the writing deviation.

According to the present embodiment, the image forming timing and the surface position of the intermediate transfer belt 501 are
01 can be synchronized at the image forming position.
It is not necessary to synchronize all the timings of writing with the surface position of the intermediate transfer belt 501. If necessary, a signal having an integer ratio of the rotation signal of the intermediate transfer belt 501 is selected, and the image forming timing and the intermediate transfer belt 501 are selected. Can be synchronized.

As a result, since the surface position of the intermediate transfer belt 501 can be synchronized with the image forming timing, the intermediate transfer belt 50 can be synchronized with the writing timing.
Positioning of one surface becomes possible. As a result, it is possible to eliminate many of the above-mentioned causes of image quality deterioration, and to configure an inexpensive system that does not require the use of high-precision parts.

FIG. 28 shows an intermediate transfer belt drive control system of this embodiment, and FIG. 29 is a timing chart thereof. In the present embodiment, in the sixth embodiment, a writing optical unit having a polygon mirror or a writing system having an LED is used as the writing system. This writing system uses a beam detector or a synchronization detector such as a sensor to write a write synchronization signal. It has occurred. If the optical pattern detection signal from the detector 702 and the write synchronization signal are in an integer ratio, the image forming pitch is maintained at a constant interval by controlling so that no phase difference occurs at the edges of both signals.

In detecting the phase difference between the optical pattern detection signal from the detector 702 and the write synchronization signal, the write synchronization signal is frequency-divided by a frequency dividing circuit 728 such as a counter so that the pulse frequency becomes the same, and a general PLL is used. The circuit 729 forms a motor control system. That is, the PLL circuit 729
Drives the drive motor (transfer M) 703 with an output signal whose phase is synchronized with the output signal of the frequency dividing circuit 728,
PLL circuit 72 based on the optical pattern detection signal
9, the surface position of the intermediate transfer belt 501 is controlled. Thereby, the intermediate transfer belt 501
The transfer position of the toner image becomes constant regardless of the deviation of the writing timing, the eccentricity of the rotating shaft, and the like, and a highly accurate image can be formed.

In general, an endless belt-shaped rotating body as an image carrier used in an image forming apparatus such as a color electrophotographic copying machine or a color printer is a latent image carrier such as a photosensitive drum or a photosensitive belt. The image is formed by transferring the toner image from the latent image carrier to the image carrier by electrostatic force or the like.

In the tenth embodiment of the present invention, fine and precise graduations are formed on the surface or the inner surface of the intermediate transfer belt (endless belt-shaped rotating body) 501 as the image carrier in the sixth embodiment. An optical pattern 701 is provided, and a detector 702 is arranged near a contact position between the photosensitive member 200 as a latent image carrier and the intermediate transfer belt 501, and the optical pattern is detected by the detector 702.

At this time, the detector 7 detects the fine-pitch optical pattern 701 formed on the intermediate transfer belt 501.
02 is used for controlling the drive shaft of the intermediate transfer belt 501 (control of the drive motor 703) by the intermediate transfer belt drive control system, and the photosensitive member 200 and the intermediate transfer belt 501 are controlled by the intermediate transfer belt drive control system. Is performed near the contact position. As a result, alignment control of the intermediate transfer belt 501 with respect to the photoconductor 200 near the toner image transfer position is performed.

Conventionally, the positioning between the photosensitive member and the image carrier has been performed by controlling the rotation of the drive shaft of the image carrier. However, in this method, the quality of the image is reduced due to the displacement of the endless belt, which is an image bearing member, due to elongation and slippage, and the toner transfer between the endless belt and the photosensitive member due to perturbation such as cleaning of the endless belt and paper contact. The position shift occurred.

According to the present embodiment, the endless intermediate transfer belt 501 serving as an image carrier is controlled using the intermediate transfer belt surface position detection signal from the detector 703, and the surface position of the intermediate transfer belt 501 is exposed. By observing in the vicinity of the contact position between the body 200 and the intermediate transfer belt 501, the positional shift at the time of transferring the toner from the photoconductor to the endless belt (here, the intermediate transfer belt 501), which has conventionally been a problem, is greatly reduced. It becomes possible.

The photosensitive member 200 and the intermediate transfer belt 50
By measuring the surface position of the intermediate transfer belt 501 near the position of contact with the intermediate transfer belt 501 by the optical pattern 701 and the detector 702, the arrangement of the rotation support shaft and the drive shaft of the intermediate transfer belt 501, the tension of the intermediate transfer belt 50, etc.
Even if there is a variation in the elongation of the surface within 1, the toner image transfer and image formation can be performed with high accuracy without changing the structure.

In the intermediate transfer device, in order to superpose images of a plurality of colors, a member that comes into contact with the intermediate transfer member needs to be separated from the intermediate transfer member when the images are superimposed. As the number of formed images increases, the linear velocity naturally increases, the distance between images also decreases, and it becomes difficult to take timing. It is desirable to control the timing in accordance with the rotation state of the intermediate transfer member calculated from the output signal of the detector with respect to the optical pattern, rather than the usual control over a fixed time. Furthermore, in the case of an image carrier using a material whose peripheral length changes due to heat or the like, if the distance from the primary transfer position to the member that comes into contact with or separates from the primary transfer position varies depending on the configuration, a detection signal of the optical pattern is used. It is desirable to control the timing based on the calculated distance.

In the eleventh embodiment of the present invention, in the sixth embodiment, the contact / separation means for bringing the belt cleaning device 50 into and out of contact with the intermediate transfer belt 501 is controlled by a control unit (not shown) as shown in FIG. After a predetermined time Tb has elapsed from the reference position image detection signal,
02 detects the origin marker of the optical pattern 701 and then the intermediate transfer belt 501 moves by a certain distance and the detector 702
Is turned on for a predetermined time after detecting a predetermined number of optical patterns 701 (for a predetermined period), and the belt cleaning device 50
Is brought into contact with the intermediate transfer belt 501. Optical pattern 7
If 01 is extended in synchronization with the extension of the intermediate transfer belt 501, the belt cleaning device 50 (here, a cleaning blade) is brought into contact with and separated from the intermediate transfer belt 501 by detecting a fixed number of optical patterns. Accurate control of the belt cleaning device 50 is possible in accordance with the rear end of the image on the intermediate transfer belt 501.

By accurately bringing the belt cleaning device 50 into and out of contact with the image on the intermediate transfer belt 501 as described above, it is possible to more accurately prevent toner scattering caused by each of the contact and separation shocks from affecting the preceding and following images. Can be prevented.

It has been conventionally known that the secondary transfer device has different transfer properties at the leading edge, the trailing edge, and the center of the transfer paper. This is because the leading edge of the transfer paper first comes into contact with the intermediate transfer member side and enters the secondary transfer entrance portion, and then the secondary paper stably enters the secondary transfer entrance portion.
This is a phenomenon that occurs when the transfer paper passes through the entrance guide plate when there is an entrance guide plate at the rear end of the transfer paper when the next transfer is performed. Therefore, different secondary transfer bias values are set for the leading end and the trailing end of the transfer paper. The boundary position for switching the secondary transfer bias value needs to be finely adjusted.

[0147] Therefore, by the usual control for a fixed time,
It is desirable to control the timing in accordance with the rotation state of the intermediate transfer member calculated from the optical pattern detection signal. Furthermore, in the case of an intermediate transfer member using a material whose circumferential length changes due to heat or the like, when the distance from the primary transfer position to the secondary transfer position changes depending on the configuration, it is calculated from the detection signal of the optical pattern. It is desirable to control timing by distance.

In this embodiment, the contacting / separating means for bringing the secondary transfer belt 601 and the support roller 602 into and out of contact with the secondary transfer opposing roller 510 is controlled by a control unit (not shown) in FIG.
As shown in the figure, after a predetermined time Ta has elapsed from the reference position image detection signal, that is, the detector 702
After the first origin marker is detected, the intermediate transfer belt 501 moves by a predetermined distance, and the detector 702 detects the optical pattern 701 for a predetermined number (for a predetermined period), and then is turned on for a predetermined time to support the secondary transfer belt 601 and the support. The roller 602 is brought into contact with the secondary transfer facing roller 510.

The optical pattern 701 corresponds to the intermediate transfer belt 50.
If it extends in synchronization with the extension of 1, the secondary transfer power supply 802 to the secondary transfer bias roller 605 from the secondary transfer power supply 802 by inputting a certain number of optical pattern detection signals from the detector 702 by a control unit (not shown) By switching the transfer bias, accurate secondary transfer bias control can be performed in accordance with the rear end of the image on the intermediate transfer belt 501. By accurately switching the secondary transfer bias to the image on the intermediate transfer belt 501, a good image can be obtained over the entire image.

It is necessary to align the registration of the leading edge of the image on the transfer paper with the intermediate transfer member. However, the time required for the image on the intermediate transfer member to pass through the image forming path and reach the secondary transfer portion after the output of the conventional reference signal varies depending on the speed of the intermediate transfer member, the expansion and contraction of the intermediate transfer member, and the circumference. Would. Therefore, it is desirable to control the timing in accordance with the rotation state of the intermediate transfer member calculated from the optical pattern detection signal by ordinary constant time control. Further, it is desirable to control the timing based on the distance calculated based on the optical pattern detection signal.

In this embodiment, the registration roller 650
As shown in FIG. 30, after a predetermined time Tc elapses from the reference position image detection signal by the control unit (not shown), that is, after the detector 702 detects the origin marker of the optical pattern 701, the intermediate transfer belt 501 is fixed. After being moved a distance, the detector 702 detects the optical pattern 701 for a predetermined number (for a predetermined period), and is controlled so as to be rotationally driven by the driving source for a predetermined time. If the optical pattern 701 is extended in synchronization with the extension of the intermediate transfer belt 501, a good number of images with no displacement with respect to the transfer paper can be obtained by turning on the registration roller 650 with a certain number of pattern detection signals. It is possible to get.

In general, a latent image carrier such as an endless belt-shaped rotating member, a photosensitive drum, or a photosensitive belt is used as an image carrier used in an image forming apparatus such as a color electrophotographic copying machine or a color printer. The image is formed by rotating in synchronization with the toner and transferring the toner from the latent image carrier to the endless belt-shaped rotator by electrostatic force or the like.

The twelfth embodiment of the present invention is the same as the sixth embodiment, except that the intermediate transfer belt 50 as an image carrier is used.
An optical pattern 701 on which fine and precise graduations are formed is provided on the surface or the inner surface of the intermediate transfer belt 1, and the detector 702 detects the optical pattern 701 on the flat portion of the intermediate transfer belt 501. The flat portion of the intermediate transfer belt 501 is provided by disposing the intermediate transfer belt 501 between the drive shaft and the rotation support shaft, between the rotation support shaft and the rotation support shaft, or
2 is formed by arranging a fixed belt support structure arranged so that the intermediate transfer belt 501 is flat. The length of the flat portion of the intermediate transfer belt 501 may be at least as long as the light irradiation width of the detector 702.

At this time, the detector 7 detects the fine pitch optical pattern 701 formed on the intermediate transfer belt 501.
The output signal 02 is used by the intermediate transfer belt drive control system to control the drive shaft of the intermediate transfer belt 501, and the intermediate transfer belt drive control system uses the photosensitive member 200 and the intermediate transfer belt 501.
The position of the intermediate transfer belt 501 is controlled in the vicinity of the contact position with the belt. As a result, the position of the intermediate transfer belt 501 is controlled based on a signal obtained by detecting the optical pattern 701 by the detector 702 on the flat portion of the intermediate transfer belt 501.

Conventionally, the alignment between the photosensitive member as the latent image carrier and the image carrier has been performed by controlling the rotation of the drive shaft of the image carrier. However, in this method, the image quality is reduced due to the influence of displacement due to elongation and slip of the endless intermediate transfer belt serving as the image carrier, and the intermediate transfer belt is cleaned and the intermediate transfer belt is contacted with the photoconductor by perturbation such as paper contact. A deviation of the toner transfer position from the belt has occurred.

According to the present embodiment, the intermediate transfer belt 501 serving as an image carrier is controlled using the intermediate transfer belt 501 surface position detection signal from the detector 702, and the surface position of the intermediate transfer belt 501 is detected. This is performed on the flat portion of the intermediate transfer belt 501 by the device 702. Accordingly, when the position of the intermediate transfer belt 501 is detected on the curved surface of the intermediate transfer belt 501, light reflection loss on the curved surface can be reduced, and the optical patterns 701 having the same pitch can be detected with high accuracy without changing the image. It becomes possible.

Also, depending on the structure, the intermediate transfer belt 501 may be used.
, The fluctuation of the surface position detection signal due to the vibration of the intermediate transfer belt 501 and the surface position measurement error caused by the fluctuation can be reduced. This also makes it possible to reduce the fluctuation of the surface position detection signal due to the displacement of the intermediate transfer belt 501 in the direction perpendicular to the rotation direction, and reduce the surface position measurement error due to the fluctuation. For this reason, the surface position of the intermediate transfer belt 501 as an image carrier can be controlled with high accuracy, and improvement in image quality and reduction in color shift can be expected.

In general, an endless belt-shaped rotating body as an image carrier used in an image forming apparatus such as a color electrophotographic copying machine or a color printer is a latent image carrier such as a photosensitive drum or a photosensitive belt. The image is formed by transferring the toner from the latent image carrier to the image carrier by electrostatic force or the like.

In the thirteenth embodiment of the present invention, the twelfth embodiment
In the embodiment, an intermediate transfer belt 5 as an image carrier
An optical pattern 701 on which fine and precise graduations are formed is provided on the surface or inner surface of the optical pattern 01, and a detector 702 for detecting the optical pattern is arranged at a position where the vibration is reduced, or the detector 702 is an optical pattern. A vibration reducing structure for reducing the vibration is added at the position where 701 is detected.

For example, the optimum position of the detector 702 is calculated by a vibration analysis simulation of the entire apparatus or the structure of the intermediate transfer belt 501 including a rotating mechanism, or the amount of vibration of the detector 702 is measured experimentally. This can be realized by disposing the detector 702 at the minimum vibration position or by fixing the detector 702 with a vibration reducing material.

At this time, the detector 7 detects the fine pitch optical pattern 701 formed on the intermediate transfer belt 501.
The detection signal 02 is used for controlling the drive shaft of the endless intermediate transfer belt 501 by the intermediate transfer belt drive control system, and when the intermediate transfer belt drive control system is in the vicinity of the contact position between the photoconductor 200 and the intermediate transfer belt 501. Of the intermediate transfer belt 501 is controlled. As a result, the detector 702 detects the optical pattern 701 with little vibration, and controls the alignment of the intermediate transfer belt 501 with respect to the photoconductor 200 based on the detection signal.

Conventionally, the positioning between the photosensitive member as the latent image carrier and the image carrier has been performed by controlling the rotation of the drive shaft of the image carrier. However, in this method, the image quality is reduced due to the influence of displacement due to elongation and slip of the endless intermediate transfer belt serving as the image carrier, and the intermediate transfer belt is cleaned and the intermediate transfer belt is contacted with the photoconductor by perturbation such as paper contact. A deviation of the toner transfer position from the belt has occurred.

According to the present embodiment, the surface position detection signal of the intermediate transfer belt 501 from the detector 702 is used to control the endless intermediate transfer belt 501 as an image carrier, and the surface position is detected by the intermediate transfer belt. This is performed on the flat portion 501. At this time, an arrangement and a structure are added so as to reduce the vibration of the detection signal of the detector 702. As a result, the error of the intermediate transfer belt surface position detection signal due to the vibration is reduced, the influence of the vibration is reduced, and the intermediate transfer belt position can be controlled with a signal resulting from the intrinsic behavior of the intermediate transfer belt surface. As a result, the surface position of the intermediate transfer belt can be controlled with high accuracy, and improvement in image quality and reduction in color shift can be expected.

The fourteenth embodiment of the present invention is characterized in that a control circuit as control means is provided with a signal interpolating circuit for temporally interpolating at a constant interval clock. This signal interpolation circuit can be constituted by, for example, a counter that counts a reference clock having a cycle shorter than that of the optical pattern detection signal by using an edge of the optical pattern detection signal as a trigger. The control circuit captures the count value of the pattern detection signal and the count value of the signal interpolation circuit, calculates the position of the intermediate transfer belt 501 at the moment when the count value is captured, and compares the calculated value with the target value to calculate a feedback amount.
U, a microcomputer, and a controller such as a DSP.

A feedback system using a general encoder or the like employs a configuration in which an encoder counter is used, and a position and an angle are calculated from the count value at the time when the controller reads the count value, and are compared with target values. ing. However, the count value of the counter has uncertainty for the pulse period, for example, 0.
A pulse corresponding to a 1 mm cycle will cause an error of 0.1 mm at the maximum, which may cause unstable control.

In the present embodiment, interpolation is performed by regarding the optical pattern signal period as a constant speed using a clock corresponding to, for example, a period of 0.001 mm. By doing so, the position detection error can be suppressed to an error corresponding to the speed fluctuation, and the control system can be stabilized and higher-speed control can be performed.

In the present embodiment, as shown in FIG. 31, in the sixth embodiment, the counter 730 to which the optical pattern detection signal (pattern signal) from the detector 702 and the interpolation clock are input is a general GATE input. It is configured by a counter having a terminal and a SOUCE input terminal. The optical pattern signal counter 731 receives an origin signal generated once per rotation of the intermediate transfer belt 501 or a signal from the machine main body as an input to the GATE input terminal, and uses this signal to start counting. Optical pattern signal counter 731
Starts counting the optical pattern detection signal from the detector 702 by inputting the optical pattern detection signal from the detector 702 to the SOURCE input terminal and inputting the signal to the GATE input terminal.

The counter 730 starts counting the interpolation clock when the optical pattern detection signal is input from the detector 702 to the GATE input terminal, the interpolation clock is input to the SOURCE input terminal, and the optical pattern detection signal is input. . For example, the interval (period) of the optical pattern 701 is
0.1 mm, optical pattern detection signal from detector 702 is approximately 1
It is assumed that the frequency fluctuates around 1% at 1 kHz due to the speed fluctuation of the intermediate transfer belt 501, and the interpolation clock is 100 kHz. The motor controller 732 captures the data of the counters 730 and 731, calculates the position control amount of the drive motor 703 from the captured data and the target value, and a motor drive circuit that drives the drive motor (belt drive motor) 703. And the reading of the data of the counters 730 and 731 fluctuates depending on the processing speed.

Therefore, the motor controller 732
For example, when the value of the counter 731 is read,
If the value is 10 counts, the position is 1 mm
Can be ~ 1.1 mm. Then, the motor controller 732 reads the value of the counter 730, and if the value is 50 counts, the average speed of the intermediate transfer belt 501 is 100 (mm / s) × 50 (counts) / 100k (H) from 100 mm / s.
The clock count of z) is determined to be 0.05 mm, and it is calculated that the intermediate transfer belt 501 is located at a position of 1.05 mm as a whole. If the variation of the average speed is 1%, the error of the clock count is also within 0.0% from 0.0499 to 0.0501 mm,
Highly accurate position detection can be performed.

In the sixth to fourteenth embodiments, a belt-shaped photoconductor may be used instead of the drum-shaped photoconductor 200 as the latent image carrier, and the intermediate transfer belt may be used as the image carrier. An intermediate transfer drum or the like may be used instead of 501.

[0171]

As described above, according to the first aspect of the present invention, the position of the surface relating to the image quality on the rotating body can be controlled with high accuracy, and a portion having a different period in one rotation of the rotating body can be controlled. There is no sudden change in the data fed back from the marker detection means to the drive control unit, and continuous stable control of the rotating body is possible. Therefore, it is possible to directly and accurately detect the amount of movement of the rotary moving part of the rotating body, and to stably control the amount of movement of the rotary moving part. Further, since the number of markers for one rotation of the rotating body is determined, it is possible to detect that the rotating body has made one rotation by using the counter, and it is not necessary to provide an origin sensor for detecting the origin on the rotating body.

According to the second aspect of the present invention, a pattern can be formed on a plane at the time of pattern creation, an existing processing machine can be used, and a pattern can be created with high precision. Further, since the first marker portion has elasticity, it is easy to match the seam. According to the third aspect of the present invention, the load on the member can be reduced, the member can be prevented from being peeled and partially stretched, and the accuracy of the marker can be maintained even after the member is bonded to the rotating body.

According to the fourth aspect of the present invention, the latent image writing timing and the marker detection signal of the marker detecting means are generated in the same cycle, and the latent image writing and the control of the intermediate transfer body driving motor are synchronized by the same clock. All you have to do is simplify the system. In addition, it is possible to position the leading end of the image with high accuracy. According to the fifth aspect of the invention, a higher quality color image can be obtained. According to the invention according to claim 6, it is possible to make the marker resistant to the manufacturing error of each marker and the staining of the marker.

According to the seventh aspect of the present invention, even if there is a defect, a flaw or an adhering matter in the optical pattern, the influence on the detection of the optical pattern is reduced, and more stable position control of the image carrier can be performed. Can be.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing a first embodiment of the present invention.

FIG. 2 is a plan view illustrating a marker unit according to a second embodiment of the present invention.

FIG. 3 shows the reflectance T,
FIG. 6 is a diagram illustrating a relationship between D and a rotational direction position x.

FIG. 4 is a perspective view showing an intermediate transfer belt according to the second embodiment.

FIG. 5 is a plan view showing a marker unit according to the second embodiment.

FIG. 6 is a sectional view showing a marker tape, an adhesive intermediate layer, and an intermediate transfer belt according to a third embodiment of the present invention.

FIG. 7 is a perspective view schematically showing a fourth embodiment of the present invention.

FIG. 8 is a block diagram showing a part of the fourth embodiment.

FIG. 9 is a timing chart showing operation timings of the fourth embodiment.

FIG. 10 is a diagram illustrating a marker unit and a split beam according to a fifth embodiment of the present invention.

FIG. 11 is a plan view showing a slit used in the fifth embodiment.

FIG. 12 is a front view showing a marker detecting means used in the fifth embodiment.

FIG. 13 is a diagram showing a periodic variation of a belt surface speed.

FIG. 14 is a sectional view schematically showing a sixth embodiment of the present invention.

FIG. 15 is a sectional view showing a part of the sixth embodiment in an enlarged manner.

FIG. 16 is a perspective view showing a part of the sixth embodiment.

FIG. 17 is a diagram showing an optical pattern and split beams according to the sixth embodiment.

FIG. 18 is a schematic diagram showing a detector used in the sixth embodiment.

FIG. 19 is a plan view showing a slit plate used in the sixth embodiment.

FIG. 20 is a cross-sectional view illustrating a detector, an optical pattern, and an intermediate transfer belt used in the sixth embodiment.

FIG. 21 is a block diagram showing an intermediate transfer belt drive control system used in the sixth embodiment.

FIG. 22 is a block diagram showing another intermediate transfer belt drive control system used in the sixth embodiment.

FIG. 23 is a diagram showing a deviation between the surface position of the intermediate transfer belt and a target position in the sixth embodiment.

FIG. 24 is a diagram showing a deviation between the surface position of the intermediate transfer belt and a target position in the sixth embodiment.

FIG. 25 is a schematic view showing an intermediate transfer unit according to a seventh embodiment of the present invention.

FIG. 26 is a schematic view showing a part of the intermediate transfer unit.

FIG. 27 is a plan view illustrating an intermediate transfer belt, an optical pattern, and a detector according to an eighth embodiment of the present invention.

FIG. 28 is a block diagram illustrating an intermediate transfer belt drive control system according to a ninth embodiment of the present invention.

FIG. 29 is a timing chart showing the operation timing of the ninth embodiment.

FIG. 30 is a timing chart showing the operation timing of the eleventh embodiment of the present invention.

FIG. 31 is a block diagram illustrating an intermediate transfer belt drive control system according to a fourteenth embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 11 photoconductor drum 14 intermediate transfer belt 16 drive motor 17, 27 marker unit 18, 28 detector 19 adhesive intermediate layer 24 intermediate transfer motor driver 25 motor control circuit 28 photoconductor motor driver 200 photoconductor 203 charger 220 writing optical unit 230 Revolver developing unit 501 Intermediate transfer unit 507 Primary transfer bias roller 701 Optical pattern 702 Detector 703 Drive motor

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yasushi Yamada 1-3-6 Nakamagome, Ota-ku, Tokyo, Ricoh Co., Ltd. (72) Inventor Mitsuru Takahashi 1-3-6 Nakamagome, Ota-ku, Tokyo・ F-term in Ricoh Co., Ltd. (reference) 2H027 DA17 DE02 DE07 DE09 EB04 EC06 EC07 ED02 EE01 EE03 EE04 2H030 AA01 AD17 BB24 BB42 BB71 2H032 AA05 AA15 BA09 BA18 CA02 CA13

Claims (7)

[Claims] An image carrier, a toner image forming means for forming a toner image on the image carrier, and a toner image transferred onto the image carrier or a transfer material conveyed to the transfer material. An endless rotating body for transferring the toner image on the image carrier,
In an image forming apparatus having a first drive motor for rotating the rotator and a second drive motor for rotating the image carrier, the surface of the rotator has a fixed surface in a moving direction of the rotator. Markers are provided in a cycle, and there is no change in the cycle over one rotation of the rotating body when the rotating body is rotated at a constant speed, and the number of the markers provided in a predetermined number of rotations of the rotating body is provided. A first marker detecting means for detecting a marker on the rotating body to obtain speed and position information of the rotating body, based on information obtained from the first marker detecting means. And a first drive control unit for controlling the first drive motor. 2. The image forming apparatus according to claim 1, wherein the first marker section is provided on a tape-shaped member having an elasticity by a predetermined number of times of change of the reflectance. An image forming apparatus wherein the member is formed and the member is adhered to the rotating body without a break. 3. An image forming apparatus according to claim 2, wherein a flexible member is inserted as an intermediate layer between said member and said rotating body, and said member is continuously bonded to said rotating body. Characteristic image forming apparatus. 4. An image forming apparatus according to claim 1, wherein said toner image forming means forms a toner image on said image carrier in order of one line or a plurality of lines. And a start pulse output unit that outputs a start pulse at a timing of starting one toner image formation, wherein the first drive control unit sets the marker detection cycle of the first marker detection unit to an integer of the start pulse. An image forming apparatus, wherein the first drive motor is controlled so as to be doubled. 5. The image forming apparatus according to claim 1, wherein a marker is provided on the surface of the image carrier at a constant period in a moving direction of the image carrier. When the image carrier is rotated at a constant speed, there is no change in the period over one rotation of the image carrier, and a second marker portion provided with a predetermined number of the markers for one revolution of the image carrier is used. A second marker detecting means for detecting a marker on the image carrier to obtain speed and position information of the image carrier, and the second marker detecting means based on information obtained from the second marker detecting means. An image forming apparatus comprising: a second drive control unit that controls a second drive motor. 6. An image forming apparatus according to claim 1, wherein said first marker detecting means is provided.
The image forming apparatus according to claim 1, wherein said first marker detecting means and said second marker detecting means detect a plurality of markers simultaneously. 7. An image forming apparatus for forming a color image by superimposing toner images of a plurality of colors on a latent image carrier on which a latent image is formed and the toner image is formed by developing the latent image. A toner image forming unit that forms a latent image on the latent image carrier and develops the latent image, and a toner image forming unit that rotates in contact with the latent image carrier and a plurality of color toner images are sequentially output from the latent image carrier. An image carrier on which a color image is formed by being superimposed and transferred, and a detecting means for detecting a rotation state of the image carrier,
Control means for controlling the rotation position of the surface of the image carrier based on a detection signal from the detection means, wherein the image carrier has an optical pattern arranged on the surface at regular intervals in the rotation direction, An image forming apparatus, wherein the detecting means detects the rotation state of the image carrier by simultaneously reading a plurality of the optical patterns.