JPH09329936A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an image with an excellent quality without position-shifting in several color of the image by directly setting a rotary reference position corresponding to the image carrier, and forming a latent image on the latent image carrier based on the rotary reference position. SOLUTION: In this device, an intermediate transferring body 17 is provided with markers 30 such as a several slit in the peripheral direction with a specified space on a surface, and a marker sensor 31 placed opposite to the marker 30 outputs a digital signal '1' at the time of facing the slit and outputs '0' at the time of facing the space between slits. Reference setting means of a timing controller 16 makes the count reset by the signal on detection of a seam being output from the seam sensor 15, and thereafter performs count up in synchronism with the marker pulse signal. Then, the reference setting means starts the count up making a reference pulse as the start point, and each time when the counting value reaches a specific number, writes on the same position while generates the reference pulse, and a LSU 6 starts write-in of the latent image on a photoreceptor 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a page printer for printing color image data by using dots.

[0002]

2. Description of the Related Art Conventionally, printers based on various principles have been proposed as output terminals of personal computers, workstations, and the like. In particular, a laser beam printer (hereinafter abbreviated as LBP) using an electrophotographic process and laser technology. Are superior in terms of recording speed and print quality, and are rapidly spreading.

In the market, there is an increasing demand for colorization of LBP. In case of color LBP, printing 3
It is necessary to print by superimposing four color toners, which are black, in addition to the primary colors cyan, magenta, and yellow.
Image data for four colors cannot be formed at one time on the latent image carrier (hereinafter referred to as a photoconductor) used for P. Therefore, when the image data for one color is written on the photoconductor and developed by the toner, the toner image is temporarily transferred onto the image carrier (hereinafter referred to as an intermediate transfer member), and Write the image data of the next color,
After developing with the toner of the next color, the image is transferred onto the intermediate transfer member in an overlapping manner on the previous color. Then, when this cycle is completed for four colors, finally, the images for four colors are collectively transferred from the intermediate transfer member onto the recording paper. The recording paper on which the toner composite image is transferred has a color image formed through a fixing process in which the toner on the surface is melted and fixed on the recording paper.

The operation of the conventional image forming apparatus will be described below in detail with reference to the drawings.

FIG. 9 is a block diagram of an image forming apparatus in the prior art. In FIG. 9, the photosensitive member 1 is formed by applying a photosensitive layer such as an organic photoconductor (OPC) in a thin film on the outer peripheral surface of a Ni (nickel) belt base material having a closed loop shape. This photosensitive member 1 is supported by three photosensitive member conveying rollers 2, 3 and 4 and is driven by a drive motor (not shown).
Is rotated in the direction of arrow A.

On the peripheral surface of the belt-shaped photoconductor 1, a charger 5, an exposure optical system (hereinafter abbreviated as LSU) 6, black (K), and yellow (Y) are arranged in this order in the photoconductor rotation direction indicated by arrow A. , Developing devices 7, 8, 9 and 10 for each color of magenta (M) and cyan (C), an intermediate transfer unit 11, a photoconductor cleaning unit 12, and a charge eliminator 13.

A high voltage of about -4 to 5 kV is applied to the charger 5, and a uniform charging potential is applied to the portion of the photoconductor 1 facing the charger 5. The exposure light beam 14 is obtained by subjecting an image signal from a gradation converting means (not shown) to light intensity modulation or pulse width modulation by a laser driving circuit (not shown), and a static image corresponding to a specific color on the photoconductor 1. Form a latent image. The seam sensor 15 detects a seam of the photoconductor 1 formed in a loop shape. When the seam sensor 15 detects the seam of the photoconductor 1, the seam position is avoided and the latent image of each color is formed. The timing controller 16 controls the light emission timing of the LSU 6 so that the formation positions are the same.

Each of the developing units 7, 8, 9 and 10 stores toner corresponding to each color, and contacts the photoconductor 1 at a timing corresponding to each color, so that the electrostatic charges formed on the photoconductor 1 are formed. The latent image is developed with toner. Intermediate transfer unit 11
Is an intermediate transfer member 17 in which a belt-shaped sheet made of a conductive resin or the like is wrapped around a metal tube of aluminum or the like, and an intermediate transfer member cleaning unit 18 in which rubber or the like is formed into a blade shape. While the composite image is formed on the intermediate transfer member 17, the intermediate transfer member cleaning unit 18 is separated from the intermediate transfer member 17 and abuts only during cleaning, and is not transferred from the intermediate transfer member 17 to the recording paper 19. Remove the toner remaining in. The recording paper 19 is conveyed one by one from the recording paper cassette 20 by the paper feed roller 21.
Will be sent to

The transfer unit 23 transfers the composite image on the intermediate transfer body 17 onto the recording paper 19, and includes a transfer belt 24 formed of a conductive rubber in a belt shape and the composite image on the intermediate transfer body 17. A transfer device 25 for applying a transfer bias to transfer the recording paper 19 to the recording paper 19 and to prevent the recording paper 19 from electrostatically sticking to the intermediate transfer body 17 after the composite image is transferred to the recording paper 19. And a separator 26 for applying a different bias.

The fixing device 27 is composed of a heat roller 28 having a heat source inside and a pressure roller 29. The composite image transferred onto the recording paper 19 is nipped and rotated by the heat roller 28 and the pressure roller 29. Recording paper 1 by applying pressure and heat with
The toner is fixed on 9 and a color image is formed.

The operation of the image forming apparatus constructed as above will be described below. Here, description will be made on the assumption that image development is performed in the order of black, cyan, magenta, and yellow.

The photosensitive member 1 and the intermediate transfer member 17 are driven in the directions of arrow A and arrow B by respective drive sources (not shown). At this time, in the timing controller 16, the encoder pulse output from the drive source is compared with a preset reference clock having a cycle determined from the time taken for the intermediate transfer body 17 to make one revolution, and the encoder output from the drive source is compared. By controlling the rotation speed of the driving source by PLL so that the pulse cycle and the reference clock cycle match, the peripheral speeds of the photoconductor 1 and the intermediate transfer member 17 are controlled to be the same constant speed. To be done.

In this state, first, the charger 5 is supplied with −4 to 5 kV.
By applying a high voltage of about -700, the surface of the photoconductor 1 is uniformly made -700.
It is charged to about V. Next, the photoconductor 1 is rotated in the direction of arrow A, and a laser beam corresponding to the data of a predetermined color of a plurality of color components, for example, black (K) is formed on the surface of the photoconductor 1 that is uniformly charged. When the exposure light beam 14 is irradiated after a certain time elapses after the seam sensor 15 detects the seam of the photoconductor 1 so as to avoid the seam of the photoconductor 1, the irradiated portion of the surface of the photoconductor 1 is charged. It disappears and an electrostatic latent image is formed.

On the other hand, the black developing device 7 is brought into contact with the photoconductor 1 at a predetermined timing. The toner in the developing unit is given a negative charge in advance, and the toner adheres only to the portion (electrostatic latent image portion) on the photoconductor 1 where the charge is lost by the irradiation of the exposure light beam 14, and the so-called negative-positive process is used. Development is performed. The toner image formed on the surface of the photoconductor 1 by the black developing device 7 is transferred to the intermediate transfer body 17 for each color. Residual toner that has not been transferred from the photoconductor 1 to the intermediate transfer body 17 is removed by the photoconductor cleaning means 12, and the charge on the photoconductor 1 from which the residual toner has been scraped off is removed by the static eliminator 13.

Thereafter, similar development is performed in the order of cyan, magenta, and yellow, and four color toner images are superposed on the intermediate transfer member 17 to form a composite image. In the composite image formed in this way, the transfer unit 23, which has been separated so far, comes into contact with the intermediate transfer body 1, and a high voltage of about +1 kV is applied to the transfer device 25, so that the paper is transferred from the recording paper cassette 20. It is collectively transferred onto the recording paper 19 sent along the carrying path 22.

Further, a voltage is applied to the separator 26 so that an electrostatic force that attracts the recording paper 19 is applied, and the recording paper 19 on which the transfer of the composite image is finished is peeled from the intermediate transfer body 17. Then, the recording paper 19 on which the toner image is transferred is sent to the fixing device 27, where it is fixed by the heat of the heat roller 28 and the holding pressure of the pressure roller 29, and is output as a color image. Further, the transfer unit 23 causes the recording paper 19
Residual toner on the intermediate transfer member 1 that has not been completely transferred onto the intermediate transfer member 1 is removed by the intermediate transfer member cleaning unit 18. The intermediate transfer member cleaning unit 18 is in a separated position until one synthetic image image is obtained, and after the synthetic image is transferred to the recording paper 19, it is brought into contact with it to remove residual toner.

The recording of one image is completed by the above series of operations.

[0018]

In the above conventional structure, when forming a latent image on the photoconductor 1, the seam of the photoconductor 1 is detected by the seam sensor 15, and the timing controller 16 starts horizontal synchronization from that point. The signal counting is started, and the writing of the latent image is controlled to start at the time when a certain number is counted. Therefore, when there is a subtle difference in the circumferential lengths of the photoconductor 1 and the intermediate transfer body 17, when writing is started with a fixed position as a reference from the seam on the photoconductor 1, the intermediate transfer body is caused by the difference in the circumferential lengths of the two. The transfer position of No. 1 is shifted for each color, and the image quality is deteriorated due to the positional shift of the image of each color.

Further, in the conventional configuration, when controlling the rotational speed of the intermediate transfer member 17, the encoder pulse output from the drive source is compared with the reference clock so that the two cycles are controlled to match. . In the transmission system that transmits the driving force from the driving source to the intermediate transfer body 17, the transmission speed may change due to the influence of, for example, the stretching of the belt. In addition, conventionally, since the image forming timing is independently controlled without recognizing the influence of the speed fluctuation of the transmission system, the position of the image of each color formed on the intermediate transfer body 17 is displaced, and the image quality is deteriorated. It was causing deterioration.

The present invention solves the above problems,
An object of the present invention is to provide an image forming apparatus capable of accurately synthesizing toner images of a plurality of colors on an image carrier.

[0021]

An image forming apparatus according to the present invention is an image forming apparatus that obtains a color image by superposing toner images of a plurality of colors, and a latent image and a toner on which the latent image is developed. A latent image carrier on which an image is formed, a latent image forming means for forming a latent image on the latent image carrier, and a plurality of colors which are sequentially transferred from the latent image carrier and rotate in contact with the latent image carrier. An image carrier that holds the composite image by superposing the toner images, and a detection unit that detects the rotation state of the image carrier,
The control means controls the timing at which the latent image forming means forms a latent image on the latent image carrier based on the detection signal from the detection means.

In the image forming apparatus according to the present invention, since the formation of the latent image on the latent image carrier is started based on the timing when the image carrier is always rotated to a constant position, a plurality of latent image carriers are formed. It is possible to accurately align the positions on the image carrier on which the toner images of colors are superimposed, and it is possible to output a high-quality image.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image forming apparatus according to the invention of claim 1 is an image forming apparatus for obtaining a color image by superposing toner images of a plurality of colors, and a latent image and a latent image are developed. A latent image carrier on which a toner image is formed, a latent image forming means for forming a latent image on the latent image carrier, a plurality of colors that rotate in contact with the latent image carrier and are sequentially transferred from the latent image carrier. An image carrier that holds the composite image by superposing the toner images of, and a detection unit that detects the rotation state of the image carrier,
The control means controls the timing at which the latent image forming means forms a latent image on the latent image carrier based on the detection signal from the detection means.

As a result, since the latent image is formed with reference to the position on the image carrier on which the toner images of a plurality of colors are superposed, the formation positions of the toner images of the respective colors can be accurately adjusted, and high quality is achieved. It is possible to output various images.

An image forming apparatus according to a second aspect of the present invention is the image forming apparatus according to the first aspect of the invention, in which the detecting means has a marker formed on the surface of the image carrier and a position facing the marker. And a marker detection means disposed in the control means, the control means sets the rotation reference position of the image carrier according to the output signal from the marker detection means, and the timing when the rotation reference position of the image carrier passes a predetermined position. Then, the latent image forming means controls to start the formation of the latent image.

Thus, the rotational position of the image carrier can be recognized based on the output signal from the marker detecting means, and the superimposed positions of the toner images of the respective colors on the image carrier can be accurately matched. .

An image forming apparatus according to a third aspect of the present invention is the image forming apparatus according to the first or second aspect of the present invention, which has a plurality of sets of markers and marker detecting means, and the control means includes a plurality of sets. The timing for forming a latent image on the latent image carrier is controlled based on the regular output signal obtained by logically calculating the output signal from the marker detecting means.

As a result, it is possible to prevent noise from being mixed into the output signal of the marker detecting means and erroneous control of the latent image forming timing due to detection omission or the like.

An image forming apparatus according to a fourth aspect of the present invention is the image forming apparatus according to any one of the first to third aspects, in which the driving means for driving the image carrier and the image carrier are provided. A reference signal generating unit that generates a reference signal that serves as a reference for setting the rotation speed, and the control unit sets a predetermined image carrier based on the detection signal from the detecting unit and the reference signal from the reference signal generating unit. A control signal for rotating at a speed is output to the drive means.

As a result, the rotational state of the image carrier can be maintained in a predetermined state, fluctuations in the rotational state due to various factors in the transmission system of the driving force to the image carrier can be suppressed, and the image carrier can be prevented. It is possible to further improve the overlay accuracy of the toner images of the respective colors.

An image forming apparatus according to a fifth aspect of the present invention is an image forming apparatus that obtains a color image by superposing toner images of a plurality of colors, and a latent image and a toner image in which the latent image is developed are formed. And an image carrier that rotates in contact with the latent image carrier and that forms a composite image by superimposing toner images of a plurality of colors that are sequentially transferred from the latent image carrier, Drive means for driving the body, reference signal generating means for generating a reference signal serving as a reference for setting the rotational speed of the image carrier, detection means for detecting the rotational speed of the image carrier, and a detection signal from the detecting means. And a control means for outputting to the drive means a control signal for rotating the image carrier at a predetermined speed based on the reference signal from the reference signal generation means.

This makes it possible to directly recognize the rotation reference position and the rotation speed of the image carrier on which the toners of a plurality of colors are superposed, and therefore the influence of the transmission system for transmitting the driving force from the drive source to the image carrier. It is possible to accurately align the positions of image formation of the respective colors without receiving the image, and to output a high-quality image.

(Embodiment 1) Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an image forming apparatus according to the first embodiment of the present invention, in which the same components as those of the conventional image forming apparatus are designated by the same reference numerals and detailed description thereof will be given. The description is omitted.

First, with reference to FIG. 1, a general operation of the image forming apparatus according to the present embodiment will be described. Here, it is assumed that image development is performed in the order of black, cyan, magenta, and yellow.

The photosensitive member 1 and the intermediate transfer member 17 are driven in the directions of arrow A and arrow B by a driving source (not shown), respectively, and are controlled so that their peripheral speeds become the same constant speed. In this state, first, a high voltage of about -4 to 5 kV is applied to the charger 5 to uniformly charge the surface of the photoconductor 1 to about -700V. Next, the photoconductor 1 is rotated in the direction of arrow A, and a laser beam corresponding to the data of a predetermined color of a plurality of color components, for example, black (K) is formed on the surface of the photoconductor 1 that is uniformly charged. The exposure light beam 14 is emitted at a predetermined timing. Then, the electric charge disappears in the irradiated portion of the surface of the photoconductor 1 and an electrostatic latent image is formed.

On the other hand, the black developing device 7 is brought into contact with the photoconductor 1 at a predetermined timing. The toner in the developing device is given a negative charge in advance, and the exposure light beam 14 on the photoconductor 1 is exposed.
The toner adheres only to the portion (electrostatic latent image portion) where the electric charge has been lost by irradiation with, and development is performed by a so-called negative-positive process. The toner image formed on the surface of the photoconductor 1 by the black developing device 7 is transferred to the intermediate transfer body 17 for each color. Residual toner that has not been transferred from the photoconductor 1 to the intermediate transfer body 17 is removed by the photoconductor cleaning means 12, and the charge on the photoconductor 1 from which the residual toner has been scraped off is removed by the static eliminator 13.

Thereafter, similar development is performed in the order of cyan, magenta, and yellow, and four color toner images are superposed on the intermediate transfer member 17 to form a composite image. In the composite image formed in this manner, the transfer unit 23, which has been separated so far, comes into contact with the intermediate transfer member 17, and a high voltage of about +1 kV is applied to the transfer device 25, so that the paper is transferred from the recording paper cassette 20 to the paper. It is collectively transferred onto the recording paper 19 sent along the carrying path 22. Further, a voltage is applied to the separator 26 such that an electrostatic force that attracts the recording paper 19 is applied, and the recording paper 19 on which the transfer of the composite image is completed is peeled from the intermediate transfer body 17. Then, the recording paper 19 on which the toner image is transferred is sent to the fixing device 27, where it is fixed by the heat of the heat roller 28 and the holding pressure of the pressure roller 29, and is output as a color image. Residual toner on the intermediate transfer body 1 which has not been completely transferred onto the recording paper 19 by the transfer unit 23 is removed by the intermediate transfer body cleaning means 18. The intermediate transfer member cleaning unit 18 is in a separated position until one synthetic image image is obtained, and after the synthetic image is transferred to the recording paper 19, it is brought into contact with it to remove residual toner. The recording of one image is completed by the above series of operations.

In the above image processing, the writing timing of the latent image formed on the photoconductor 1 by the LSU 6 is
The timing controller 16 controls as follows. Here, FIG. 2 is a perspective view of a main part of the intermediate transfer body 17, FIG. 3 is an enlarged sectional view of a main part of the intermediate transfer body 17, FIG. 4 is a block diagram of a part of the timing controller 16, and FIG. It is a timing chart which shows operation.

In FIGS. 2 and 3, 360 markers 30 such as slits are provided at regular intervals in the circumferential direction of the surface of the intermediate transfer member 17, and a marker sensor 31 is installed at a position facing the marker 30. ing. The marker sensor 31 is composed of a reflection type photo interrupter or the like, and outputs a digital signal "1" from the marker sensor 31 when the detection position faces the slit, and a "0" when the detection position faces the slit. ”
Is configured to be output.

In FIGS. 4 and 5, the timing controller 16 is provided with a joint avoiding means 32 and a reference setting means 33. The reference setting means 33 is composed of a counter or the like, and after the count is reset by the output signal indicating that the seam from the seam sensor 15 has been detected, the reference setting means 33 counts in synchronization with the marker pulse signal output from the marker sensor 31. Up. Then, in consideration of the relationship between the attachment position of the seam sensor 15 and the actual writing position of the LSU 6, a marker at a certain time point (160 in the present embodiment) so that the seam passes through the actual writing position of the LSU 6. The pulse signal is determined as the reference pulse.

The reference setting means 33 is composed of a counter or the like, and starts counting up with the reference pulse determined by the seam avoiding means 32 as a starting point, and the count value becomes 3
When it reaches 60 (that is, when the intermediate transfer body 17 rotates once), the write reference pulse is generated once at the same position, and the output reference signal for starting the output of data is output to the LSU 6. Starting from this output reference signal,
The LSU 6 starts writing a latent image on the photoconductor 1. Therefore, the LSU 6 receives the output reference signal from the reference setting means 33 every time the intermediate transfer member 17 makes one rotation, and forms an electrostatic latent image for each color on the surface of the photosensitive member 1. This allows
On the surface of the intermediate transfer body 17, toner images of respective colors are always transferred from the same position. Therefore, the intermediate transfer member 17
When toner images of a plurality of colors are superposed on each other, it is possible to obtain a high-quality image without positional deviation.

(Second Embodiment) A second embodiment of the present invention will be described below. Here, the configuration of the image forming apparatus according to the second embodiment is almost the same as the configuration of the image forming apparatus according to the first embodiment, and detailed description of the same portions will be omitted.

FIG. 6 is a perspective view of an essential part of the intermediate transfer member 17 of the image forming apparatus according to the second embodiment of the present invention, and FIG. 7 is a timing chart explaining the operation of the timing controller. In FIG. 6, on both end surfaces of the intermediate transfer body 17, first and second markers 3 each having 360 slits or the like provided at regular intervals in the circumferential direction are provided.
4, 35 are formed. In addition, first and second marker sensors 36 and 37 are installed at positions facing the first and second markers 34 and 35, respectively. First
The second marker sensors 36 and 37 are made of a reflection type photo interrupter or the like, and when the detection position faces the slit, "1" of the digital signal, and when the detection position faces between the slits, It is configured to output "0".

Marker pulses as shown in FIG. 7 are output from the first and second marker sensors 36 and 37 thus constructed. The first and second marker sensors 36 and 37 are provided so that regular pulses can be reliably obtained at predetermined intervals. That is, for example, if the marker pulse from the second marker sensor 37 is missed by one pulse for some reason,
If this configuration is not adopted, the count value in the timing controller 16 will be displaced, and thus the superimposed image on the intermediate transfer member 17 will be displaced.
On the other hand, in the configuration of the present embodiment, the timing controller 1 is used by using the result of the logical sum of the output of the first marker sensor 36 and the output of the second marker sensor 37.
It is configured to count at 6. Therefore, even when the marker pulse from one of the marker sensors is missing, the missing pulse is repaired as a result of the logical sum, and therefore the pulse can be correctly counted, and the image on the intermediate transfer body 17 can be counted. There is no misalignment.

By providing a plurality of markers 34 and 35 in this way, even if noise is mixed in the outputs from the marker sensors 36 and 37 or the marker detection omission occurs for some reason, the image writing timing Erroneous control can be prevented, and when toner images of a plurality of colors are superposed on the intermediate transfer body 17, it is possible to obtain a high-quality image without misalignment of the images for each color.

(Third Embodiment) The third embodiment of the present invention will be described below.

Here, since the configuration of the image forming apparatus in the third embodiment is almost the same as the configuration of the image forming apparatus in the first embodiment, detailed description of the same parts will be omitted and the first embodiment will be omitted. Only differences from the first embodiment will be described.

FIG. 8 is a block diagram of a part of the timing controller of the image forming apparatus according to the third embodiment of the present invention. In FIG. 8, the timing controller 16 includes a crystal oscillator 38, PL for generating a reference clock.
A PLL control unit 39 that performs L control and a driver 40 that drives a drive source of the intermediate transfer body 17 are provided.

The crystal oscillator 38 generates a reference clock having a cycle (Fref) obtained from the preset time taken for the intermediate transfer member 17 to rotate once, and the PLL control unit 3
Output to 9. The PLL control unit 39 compares the reference clock output from the crystal oscillator 38 with the marker pulse (cycle: Fenc) output from the marker sensor 31, and performs PLL control. The driver 40 rotates the drive source at a speed according to the control signal output from the PLL control unit 39.

Now, assuming that the set value of the time for the intermediate transfer body 17 to make one turn is 3 seconds and the number of markers 30 (see FIG. 2) such as slits provided on the intermediate transfer body 17 is 360, the crystal oscillator 38 is The frequency of the output reference clock is 360 /
3 = 120 Hz. Here, the intermediate transfer member 17 is actually
When is rotated, the marker 30 is detected by the marker sensor 31 (see FIG. 2), and a marker pulse having a cycle of Fenc is input to the PLL control unit 39. The PLL control unit 39 adjusts the control signal to the driver 40 so that the cycle of the marker pulse output from the marker sensor 31 matches the reference clock. For example, when the period of the marker pulse is longer than the reference clock (Fenc> Fr
Since ef) is when the rotation speed of the drive source is slow, a control signal for accelerating the rotation of the drive source is supplied when the marker pulse cycle is shorter than the reference clock (Fenc <Fr).
In ef), since the rotation speed of the drive source is high, a control signal for slowing the rotation of the drive source is output to the driver 40, and the rotation speed of the intermediate transfer body 17 is controlled to be constant.

As a result, the rotational speed of the intermediate transfer member 17 becomes constant in synchronization with the cycle of the reference clock, so that fluctuations in the rotational speed due to the driving force transmission system of the intermediate transfer member can be suppressed, and the intermediate transfer member 17 can be suppressed. An image of each color can be accurately combined on top.

The image forming apparatuses according to the first to third embodiments are preferably used in combination. Most preferably, all the configurations according to the first to third embodiments are combined. In this case, the intermediate transfer member 17 according to the third embodiment is used.
In addition to being able to make the rotation speed constant, the standard for controlling the timing of latent image formation on the photoconductor 1 according to the first embodiment uses the marker 30 of the intermediate transfer body 17 having the constant rotation speed. By using the marker pulse, the positions of the images of the respective colors on the intermediate transfer body 17 can be aligned more accurately. Further, the reliability of the marker pulse detection operation is improved by the second embodiment.

Further, the configurations according to the first and second embodiments or the configurations according to the first and third embodiments may be combined.

[0055]

As described above, according to the present invention, the rotation reference position is directly set with respect to the image carrier in the image forming apparatus which obtains a color image by superposing toners of a plurality of colors. By forming a latent image on the latent image bearing member based on the rotation reference position, when the toner images of a plurality of colors are superposed on the image bearing member from the latent image bearing member, the image of each color It is possible to obtain a high-quality image with no displacement.

Further, by using the output signal of the same marker detection means for controlling both the timing of image formation on the latent image carrier and the rotational speed of the image carrier, the position on the image carrier and the image can be controlled. It is possible to directly recognize the rotation speed of the carrier and correct the influence of speed fluctuation in the transmission system that transmits the driving force from the drive source to the image carrier to control the timing of image formation on the latent image carrier. Therefore, it is possible to prevent the positional deviation of the image composition of the respective colors on the image carrier due to the influence of the speed fluctuation in the transmission system, thereby obtaining a high-quality image without the positional deviation of the images of the respective colors. be able to.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a perspective view of a main part of an intermediate transfer member of the image forming apparatus according to the first embodiment of the present invention.

FIG. 3 is an enlarged sectional view of an essential part of an intermediate transfer member of the image forming apparatus according to the first embodiment of the present invention.

FIG. 4 is a block diagram of a part of a timing controller of the image forming apparatus according to the first embodiment of the present invention.

FIG. 5 is a timing chart of the operation of the timing controller of the image forming apparatus according to the first embodiment of the present invention.

FIG. 6 is a perspective view of a main part of an intermediate transfer member of an image forming apparatus according to a second embodiment of the present invention.

FIG. 7 is a timing chart of the operation of the timing controller of the image forming apparatus according to the second embodiment of the present invention.

FIG. 8 is a block diagram of a part of a timing controller of the image forming apparatus according to the third embodiment of the present invention.

FIG. 9 is a configuration diagram of an image forming apparatus according to a conventional technique.

[Explanation of symbols]

 1 Photoreceptor 2, 3, 4 Photoreceptor Conveying Roller 5 Charging Device 6 LSU 7 Black Developing Device 8 Yellow Developing Device 9 Magenta Developing Device 10 Cyan Developing Device 11 Intermediate Transfer Unit 12 Photoreceptor Cleaning Means 13 Static Eliminator 15 Seam Sensor 16 Timing Controller 19 Recording paper 20 Recording paper cassette 23 Transfer unit 27 Fixing device 30, 34, 35 Marker 31, 36, 37 Marker sensor 32 Seam avoiding means 33 Reference setting means 38 Crystal oscillator 39 PLL control section 40 Driver

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroyoshi Kirihara 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (5)

[Claims] 1. An image forming apparatus for obtaining a color image by superposing toner images of a plurality of colors, wherein a latent image carrier and a latent image carrier on which the latent image is developed are formed. A latent image forming unit that forms the latent image on the latent image carrier and toner images of the plurality of colors that are rotated in contact with the latent image carrier and that are sequentially transferred from the latent image carrier are superimposed on each other. An image carrier that holds a composite image, a detection unit that detects a rotation state of the image carrier, and the latent image forming unit that detects the latent image on the latent image carrier based on a detection signal from the detection unit. An image forming apparatus, comprising: a control unit that controls the timing of forming the image. 2. The detection means includes a marker formed on the surface of the image carrier, and a marker detection means arranged at a position facing the marker, and the control means includes:
A rotation reference position of the image carrier is set by an output signal from the marker detection means, and the latent image forming means forms the latent image at a timing when the rotation reference position of the image carrier passes a predetermined position. The image forming apparatus according to claim 1, wherein the image forming apparatus is controlled so as to start. 3. A latent image based on a regular output signal obtained by logically calculating output signals from the plurality of marker detecting means, the plurality of sets of the marker and the marker detecting means being provided. The image forming apparatus according to claim 1, wherein the timing of forming the latent image on the carrier is controlled. 4. A driving means for driving the image carrier, and a reference signal generating means for generating a reference signal as a reference for setting the rotational speed of the image carrier, wherein the control means comprises the detecting means. 4. A control signal for rotating the image carrier at a predetermined speed is output to the drive means based on the detection signal from the reference signal and the reference signal from the reference signal generation means. The image forming apparatus according to any one of 1. 5. An image forming apparatus for obtaining a color image by superposing toner images of a plurality of colors, wherein a latent image carrier and a latent image carrier on which the latent image is developed are formed. An image carrier that rotates in contact with the latent image carrier and holds a composite image by superposing the toner images of the plurality of colors sequentially transferred from the latent image carrier, and a drive that drives the image carrier. Means, reference signal generating means for generating a reference signal as a reference for setting the rotation speed of the image carrier, detection means for detecting the rotation speed of the image carrier, detection signal from the detection means and the reference. An image forming apparatus comprising: a control unit that outputs a control signal for rotating the image carrier at a predetermined speed to the drive unit based on a reference signal from a signal generation unit.