JP2584153B2 - Electrophotographic equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus for forming a color image on a transfer material by superposing a plurality of single-color toner images.

[0002]

2. Description of the Related Art In recent years, devices using dry toner occupy the mainstream of electrophotographic apparatuses, and have been practically used as copiers, laser printers and the like, and have achieved remarkable development. In recent years, the demand for colorization has been increasing from the market in addition to monochrome, and color copying machines have been put on the market.

An electrophotographic apparatus that forms a color image by applying an electrophotographic process technology selectively forms an image by irradiating an exposure light beam corresponding to each color onto a photosensitive member having a photosensitive layer.
A plurality of electrostatic latent images respectively corresponding to a specific component among a plurality of predetermined color components are developed with respective predetermined toners, and the single-color toner images are superimposed to form a color image on a single transfer material. A method of forming an image has been adopted.

For example, US Pat. No. 4,652,115
In Japanese Patent Application Laid-Open No. 63-292156, an intermediate transfer material is provided between a photosensitive member and a transfer material conveying path, and toner images of different colors individually formed on the photosensitive member are optionally placed on the intermediate transfer member. A method has been proposed in which a composite image is obtained by superimposing and transferring the composite image, and the composite image is collectively transferred to one transfer material. However, when a single-color toner image is superimposed on an intermediate transfer member, it is superimposed. If the positions are displaced from each other, color unevenness occurs and the image deteriorates. Therefore, various attempts have been made to align the colors.

Hereinafter, a conventional electrophotographic apparatus will be described with reference to FIGS.
This will be described with reference to FIG.

In FIG. 5, reference numeral 1 denotes a photosensitive layer such as selenium (Se) or an organic photoconductor (OPC) on an outer peripheral surface of a belt base made of a synthetic resin material or a metal material in a closed loop shape having a seam 1a. A photosensitive member coated in a thin film form, and as shown in FIGS.
Therefore, an image formation prohibited area exists near the seam 1a. The area outside this area is the image formation allowable area, and the transfer material 2
The image forming area is determined by the four types. As shown in FIG. 5, the photoreceptor 1 is supported in a vertical plane by two photoreceptor transport rollers 2 and 3 and is driven by a drive motor (not shown) along the photoreceptor transport rollers 2 and 3 along an arrow A. Orbit in the direction. An arrow A is displayed on the peripheral surface of the belt-shaped photoconductor 1.
The charging device 4, the exposure optical system 5,
Developing devices 6B and 6 for storing developers of black (B), cyan (C), magenta (M), and yellow (Y), respectively.
C, 6M, 6Y, an intermediate transfer member unit 7, a photoconductor cleaning device 8, a static eliminator 9, and a photoconductor reference detection sensor 10 are provided. The charger 4 includes a charging wire 11 made of a tungsten wire or the like and a shield plate 12 made of a metal plate.
And the grid plate 13. Charged wire 1
When a high voltage is applied to the photosensitive drum 1, the charged wire 11 causes a corona discharge to uniformly charge the photosensitive member 1 via the grid plate 13. Reference numeral 14 denotes an exposure light beam of image data emitted from the exposure optical system 5. In the case of a laser printer, the exposure light beam 14 is controlled by a signal from a host computer (not shown) to form a plurality of electrostatic latent images on the photoconductor 1 corresponding to a plurality of predetermined color components, respectively. I do. As shown in FIG. 6, the photoconductor reference detection sensor 10
Is for detecting the position of the seam 1a of the photoconductor 1,
At one end of the photoconductor 1 and at a position close to the seam of the photoconductor 1, a photoconductor reference mark 1b such as a slit disposed at an upstream portion in the moving direction of the photoconductor 1 is detected. Each color developing device stores a toner corresponding to each color. The selection of the color of the toner can be performed by selecting the separation / contact cams 15B, 15C, 15M, and 15 whose both ends are rotatably supported by the body of the body corresponding to the respective colors.
Y is performed by rotating in response to a color selection signal from a host computer (not shown) and bringing a selected developing device, for example, 6B, into contact with the photosensitive member 1. The remaining unselected developing units 6C, 6M, and 6Y are separated from the photosensitive member 1. The intermediate transfer body unit 7 is a seamless loop belt-like intermediate transfer body 16 made of a conductive synthetic resin material or the like.
And two intermediate transfer body transport rollers 17 and 18 supporting the intermediate transfer body 16, and a photosensitive member with the intermediate transfer body 16 interposed therebetween to transfer the toner image on the photoconductor 1 to the intermediate transfer body 16. And an intermediate transfer roller 19 disposed opposite to the body 1. Here, the outer peripheral length L1 of the photoreceptor 1 is
6 is nominally equal to the outer peripheral length L2, but L1 ≦ L2 in consideration of dimensional tolerances due to mechanical manufacturing and variations such as aging.
(That is, one cycle of the photoconductor 1 is shorter than one cycle of the intermediate transfer body 16) or L1 ≧ L2 (that is, one cycle of the photoconductor 1 is longer than one cycle of the intermediate transfer body 16). It is set to hold. Further, the photoconductor 1 and the intermediate transfer body 16 are each driven by a driving source (not shown).
And are controlled so that their peripheral speeds become the same constant speed.

Next, in FIG. 7, reference numeral 20 denotes the intermediate transfer member 16.
Is a reference sensor for detecting the reference position of the intermediate transfer member, and detects the reference position with an intermediate transfer member reference mark 16a such as a slit disposed at one end of the intermediate transfer member 16. 2
Reference numeral 1 denotes a clutch mechanism provided for the photosensitive member transport rollers 2 or 3 or the intermediate transfer member transport rollers 17 and 18, which turns on / off the power from a drive source (not shown) to turn the photosensitive member 1 or the intermediate transfer member on or off. 16 is controlled. Reference numeral 22 denotes an intermediate transfer member cleaning device for scraping residual toner on the intermediate transfer member 16 after transferring the color composite image to the transfer material 24, and while the color composite image is being formed on the intermediate transfer member 16. Is separated from the intermediate transfer member 16 and comes into contact with the intermediate transfer member 16 only when it is subjected to cleaning. Reference numeral 23 denotes a transfer material cassette containing the transfer material 24. The transfer materials 24 are sent out one by one from a transfer material cassette 23 to a transfer material transport path 26 by a half-moon shaped paper feed roller 25. Reference numeral 27 denotes a registration roller for temporarily stopping the transfer material 24 to make the transfer material 24 coincide with the position of the color composite image formed on the intermediate transfer body 16, and is in pressure contact with a driven roller 28. 2
Reference numeral 9 denotes a transfer roller for transferring the color composite image formed on the intermediate transfer member 16 to the transfer material 24. The transfer roller 9 rotates in contact with the intermediate transfer member 16 only when the color composite image is transferred to the transfer material 24. 30 is a heat roller 3 having a heat source inside.
1 and a pressure roller 32, and a transfer material 2
4 is fixed on the thermal transfer material 24 by pressure and heat with the rotation of the heat roller 31 and the pressure roller 32 to form a color image.

The operation of the electrophotographic apparatus configured as described above will be described below.

When an image forming operation command is issued, first, a high voltage is applied to the charging line 11 in the charger 4 connected to the high voltage power supply to cause corona discharge, and the surface of the photoconductor 1 is uniformly reduced.
It is charged to about 700v to -800v. Next, photoconductor 1
Is rotated in the direction of arrow A to irradiate the uniformly charged surface of the photoconductor 1 with an exposure light beam 14 such as a laser beam corresponding to a predetermined black (B) image forming signal among a plurality of color components, for example. Then, the irradiated portion on the photoreceptor 1 loses its charge, and an electrostatic latent image is formed. This electrostatic latent image is shown in FIG.
As shown in FIG. 0, after a predetermined image formation start time U has elapsed since the intermediate transfer member reference detection sensor 20 that detects the reference position of the intermediate transfer member 16 has detected the intermediate transfer member reference mark 16a (this time U Is constant for each color in order to accurately overlap the toner images of each color on the intermediate transfer member 16)
Then, a seam 1 a of the photoconductor 1 is formed in an image formation allowable area on the photoconductor 1, avoiding the image formation prohibited area. As shown in FIG. 10, this image formation start position is Z hours after the photoconductor reference detection sensor 10 detects the photoconductor reference mark 1b when viewed from the photoconductor side. Here, Z1 and Z2 are image formation allowable start times. That is, the photoconductor reference detection sensor 10 detects the photoconductor reference mark 1
When the image formation is started after a lapse of time shorter than Z1 time from the detection of “b”, the image start position enters the image formation prohibition area, and Z2 hours after the photoconductor reference detection sensor 10 detects the photoconductor reference mark 1b. If the image formation is started after a longer time, the image end position of the image formation area enters the image formation prohibited area, causing image deterioration. Therefore, when viewed from the photoconductor 1 side, the photoconductor reference detection sensor 10 detects the photoconductor reference mark 1b and is longer than the Z1 time.
The intermediate transfer member is set to the reference sensor 20 within a range shorter than 2 hours.
Has to set the image forming start time after detecting the intermediate transfer member reference mark 16a.

On the other hand, the developing device 6B containing the black toner contributing to the development is pushed in the direction of arrow D by the rotation of the separation / contact cam 15B by the color selection signal from the host computer (not shown), and is pressed by the photosensitive member 1. Abut With this contact, toner adheres to the electrostatic latent image portion formed on the photoreceptor 1 to form a toner image and development is completed. The developing device 6B that has completed the development is rotated by 180 degrees of the separation / contact cam 15B,
It moves from a contact position with the photoconductor 1 to a separation position. The toner image formed on the photosensitive member 1 by the developing device 6B is transferred to the intermediate transfer member 16 by applying a high pressure to an intermediate transfer roller 19 arranged in contact with the photosensitive member 1 for each color. The residual toner that has not been transferred from the photoconductor 1 to the intermediate transfer body 16 is removed by the photoconductor cleaning device 8, and the charge on the photoconductor 1 from which the residual toner has been scraped off by the static eliminator 9 is removed.

Next, for example, when the color of cyan (C) is selected, an image is formed on the photosensitive member 1 after an image forming start time U has elapsed after the intermediate transfer member reference detection sensor 20 detects the intermediate transfer member reference mark 16a. The formation is started, and an electrostatic latent image is formed on the photoconductor. At about the same time, the contact / disengagement cam 15C rotates, and this time pushes the developing device 6C in the direction of the photoconductor 1, and the
And development of cyan (C) is started. In the case of a copying machine or a printer using four colors, the above-described image forming operation is sequentially repeated four times, and the four colors B,
The C, M, and Y toner images are superimposed to form a color composite image.
In this manner, the color composite image formed on the intermediate transfer body 16 rotates the transfer material transfer roller 29, which has been separated so far, in contact with the intermediate transfer body 16, applies a high pressure to the transfer material transfer roller 29, and Is transferred onto the transfer material 24 sent from the transfer material cassette 23 along the transfer material transport path 26 at a time. Subsequently, the transfer material 2 on which the toner image has been transferred
4 is sent to a fixing device 30, where it is fixed by the heat of the heat roller 31 and the clamping pressure between the pressure roller 32 and is output as a color image. The residual toner on the intermediate transfer body 16 that has not been completely transferred onto the transfer material 24 by the transfer material transfer roller 29 is removed by the intermediate transfer body cleaning device 22. The intermediate transfer member cleaning device 22 is separated from the intermediate transfer member 16 until one color composite image is obtained, and after the color composite image is transferred to the transfer material 24 by the transfer material transfer roller 29, State and the residual toner is removed.

With the above operation, one image forming operation is completed. In this series of image forming operations, the image shift on the intermediate transfer member 16 is not started unless the image formation of each color is started after a lapse of a predetermined time U from the detection of the intermediate transfer member reference mark 16a by the intermediate transfer member reference detection sensor 20. Occurs. However, since there is always a period difference between the photoconductor 1 and the intermediate transfer body 16, if the image forming operation is continued, one cycle of the photoconductor 1 is longer than one cycle of the intermediate transfer body 16 (FIG. 1).
0 (b)) is the start position of image formation on the photoconductor 1, and if one cycle of the photoconductor 1 is shorter than one cycle of the intermediate transfer body 16 (FIG. 10 (c)), it is onto the photoconductor 1. The image formation end position comes into the image formation prohibited area. Therefore, it is necessary to control the image formation start position.

Here, the conventional image forming start position control when the period of the photosensitive member 1 is shorter than the period of the intermediate transfer member 16 will be described.

In FIG. 8 and FIG. 10A, in the first image formation, a predetermined image formation start time U elapses after the intermediate transfer member reference detection sensor 20 detects the intermediate transfer member reference mark 16a. Later (this time U is constant for each color in order to accurately overlap the toner images of each color on the intermediate transfer body 16), and the image avoiding the image formation prohibited area on the photosensitive body 1 where the seam 1a of the photosensitive body 1 is present It is formed in the formation allowable area. This image formation start position is Z time after the photosensitive member reference detection sensor 10 detects the photosensitive member reference mark 1b when viewed from the photosensitive member 1 side. When the image forming operation is continued, the period difference between the photosensitive member 1 and the intermediate transfer member 16 is added to the n-th sheet as shown in FIGS. When the image forming start position gradually shifts from the photosensitive member 1 side, the photosensitive member reference detection sensor 1
0 is equal to the ZL time after the detection of the photoconductor reference mark 1a, approaches the image formation allowable time Z2, and eventually enters the image formation prohibited area. 8 and 10 (a) by stopping the power for a predetermined time by a clutch mechanism 21 provided on the drive shaft of the photoconductor transport roller 3 of the photoconductor 1 and decelerating or stopping only the rotation of the photoconductor 1. Thus, the image forming start position is adjusted by connecting the power from the drive source again by the clutch mechanism 21 and restarting the rotation.

[0015]

However, in the above configuration, fine adjustment for each color shorter than the pressing time of the clutch mechanism is impossible, and accurate adjustment corresponding to the temporal change of the photosensitive member or the intermediate transfer member is impossible. Positioning could not be performed for each color. Also, when the image forming start position or the image forming end position of the photoconductor is likely to enter the image forming prohibited area, the image forming operation was stopped and the adjustment was performed.
There is a problem that a time is required for stopping the temporary image forming operation during the image forming operation and performing the reference position alignment of the photosensitive member and the intermediate transfer member, and the image forming speed is reduced.
In addition, a complicated position adjusting mechanism between the photosensitive member such as a clutch and the intermediate transfer member is required, and the manufacturing cost is greatly increased. Furthermore, the slippage occurs in the intermediate transfer section where the photoconductor and the intermediate transfer body are in contact and rotation with the position adjustment, and this slippage damages the surfaces of the photoconductor and the intermediate transfer body, thereby pulling the image. The problem of deterioration has also occurred.

An object of the present invention is to provide a long-life, high-reliability electrophotographic apparatus in which the number of parts is small, fine color matching is possible, and the photosensitive member and the intermediate transfer member are not damaged. The purpose is.

[0017]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention has a joint and sequentially carries a plurality of colors of electrostatic latent images.
Loop and a belt-shaped photoreceptor rotatable to, responsible to the photosensitive member
The held electrostatic latent images of multiple colors are visualized with toner of a predetermined color.
Fractionated by a developing means for forming a toner image, et al provided in the photosensitive member
A photoreceptor reference mark, a photoreceptor reference detecting sensor for detecting a reference position of the photosensitive member by detecting a photoreceptor reference mark, the toner images of plural colors formed on the photosensitive member
The images are sequentially transferred and superimposed to form a color toner image.
And the intermediate transfer member rotatable be made, et al provided an intermediate transfer member
The intermediate transfer member reference mark and the intermediate transfer member reference sensor that detect the reference position of the intermediate transfer member by detecting the intermediate transfer member reference mark, and the intermediate transfer member reference detection sensor detects the intermediate transfer member reference mark photoreceptor reference detecting sensor after having a time difference measuring means for measuring a time difference T until detecting a photoreceptor reference mark, the electrostatic to the photoconductor
Feeling that the latent image forming area does not include the seam of this photoconductor
The photoconductor reference detection sensor detects the photoconductor reference mark and exposes it.
When the time between the start of the image recording on the body is Z, the intermediate transfer body reference mark is detected by the intermediate transfer body reference detection sensor, and after T + Z time has elapsed , the image recording of each color on the photoreceptor is performed.
It is obtained so as to control the timing of the image recording start to perform.

[0018]

DETAILED DESCRIPTION OF THE INVENTION The present invention with the configuration described above, the intermediate transfer member reference
After the mark is detected by the intermediate transfer member reference detection sensor.
The timing for recording each color image on the photoconductor
Transfer body reference detection sensor detects intermediate transfer body reference mark
And then the photoconductor reference detection sensor
By changing according to the time difference until detection,
Exposure without adjusting relative position to intermediate transfer member
The electrostatic latent image forming area of the body does not include this photoconductor seam
The time required for adjusting the position of the photoconductor with respect to the intermediate transfer body is eliminated, the clutch mechanism can be eliminated, and fine adjustment of color matching becomes possible, and the life of the photoconductor and the intermediate transfer body becomes longer. Can be extended.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An electrophotographic apparatus according to one embodiment of the present invention will be described below with reference to FIGS.

The configuration and operation of each part of the electrophotographic apparatus for charging, exposure, and color development are the same as those of the conventional example shown in FIG. 5, and the description of FIG. 5 is diverted. And the description is omitted.

In the present invention, the outer peripheral length L1 of the photoreceptor 1 is nominally equal to the outer peripheral length L2 of the intermediate transfer body 16. However, in consideration of dimensional tolerances due to mechanical manufacturing and variations such as aging, L1 ≦ L.
L2 (that is, one cycle (E) of the photoconductor 1 is
6 is shorter than one cycle (F) or L1 ≧ L2 (that is, one cycle (E) of the photoconductor 1 is longer than one cycle (F) of the intermediate transfer body 16). Is set. Further, the photosensitive member 1 and the intermediate transfer member 16
Are driven by drive sources (not shown), and are controlled so that their peripheral speeds become the same constant speed.

An image forming start control method for forming an image on the photosensitive member 1 so as to avoid an image forming prohibited area including the seam 1a of the photosensitive member 1 will be described by taking continuous printing as an example. Here, FIG. 1 and FIG. 2A show a case where one cycle of the photoconductor 1 is shorter than one cycle of the intermediate transfer body 16.
This will be described with reference to FIG. Prior to image formation, the power of the apparatus main body is turned on (step 1). Then the variable n
Is set to 1 (step 1-1), and after the rotation of the photosensitive member 1 and the intermediate transfer member 16 is started and the intermediate transfer member reference detection sensor 20 detects the intermediate transfer member reference mark 16a, the photosensitive member reference detection sensor 10 The measurement of the time difference T1 until the detection of the photoconductor reference mark 1b is started. This measurement is always performed while the photosensitive member 1 and the intermediate transfer member 16 are rotating on a predetermined line.
02 has been updated. Then, the time difference T1 at the time of the normal rotation immediately before the end of the initialization rotation is stored in the memory (step 2).

In the first color image forming operation,
When an image formation start operation signal is issued (step 3),
As shown in FIG. 2 and FIG. 3, the time difference T1 stored in step 2 and the photoconductor reference detection sensor 10 detect the photoconductor reference mark 1b provided on the photoconductor 1, and Z time (image on the photoconductor 1) After a time U1 obtained by adding the elapsed time when the formation area does not overlap the image formation inhibition area, the exposure light beam 14 corresponding to the image formation signal of the first color of the fourth color, for example, black (B), is formed on the photosensitive member 1. Then, an initial setting image start time U1 set in the image formation start position designation register 103 so that the image is formed by irradiating the image is set in the timer 101 (step 4). The initial setting image formation start time U1 is set such that the image formation start position and the image formation end position do not come to the image formation prohibited area on the photosensitive member 1 described with reference to FIG. The change in the time difference between the photosensitive member 1 and the intermediate transfer member 16, that is, the period difference is a minute time as compared with the initial setting image start time U1, and the time from the first sheet to the first
The lengths of the photoconductor 1 and the intermediate transfer body 16 are set so that the image forming area of the last color of the sheet, for example, yellow (Y) does not enter the image forming prohibited area. Subsequently, the intermediate transfer member reference detection sensor 20 detects the intermediate transfer member reference mark 16a.
Is detected and an intermediate transfer reference detection signal is output (step 5), the timer 101 is started (step 6), and after an elapse of U1 time (step 7), an image forming signal is output (step 8), and black (B) is output. An exposure light beam 14 corresponding to an image forming signal is irradiated on the photoconductor 1 to start image formation, and an electrostatic latent image is formed on the photoconductor 1. The electrostatic latent image formed on the photoconductor 1 is visualized by the black toner of the developing device 6B to form a toner image. The toner image formed on the photoconductor 1 is transferred onto the intermediate transfer member 16 after a lapse of Q1 since the intermediate transfer member reference detection sensor 20 detects the intermediate transfer member reference mark 16a provided on the intermediate transfer member 16. Is done.

The formation of one color image is completed (step 9).
If the image forming signal is not the signal of the final color, the process proceeds to the image formation of the next color, for example, cyan (C) as the second color (step 5). The cyan (C) toner image formed on the photoreceptor 1 is black unless the intermediate transfer member reference detection sensor 20 detects the intermediate transfer member reference mark 16a on the intermediate transfer member 16 after a lapse of Q1 time. This does not coincide with the start of the image formation in (B), causing an image shift. For this purpose, the intermediate transfer member reference mark 16a is attached to the intermediate transfer member reference detection sensor 2 as in the case of forming a black (B) image.
The image formation on the photoconductor 1 may be started after a lapse of U1 time from the detection of 0. Therefore, when the next intermediate transfer member reference detection signal is output (step 5), the timer 101
Is activated (step 6), and the time U1 has elapsed (step 7).
Thereafter, an image forming signal is output (step 8), and an exposure light beam 14 corresponding to the cyan (C) image forming signal is irradiated onto the photoconductor 1 to start image formation, and an electrostatic latent image is formed on the photoconductor 1. Form. The electrostatic latent image formed on the photoreceptor 1 is visualized by the cyan toner of the developing device 6C to form a toner image. Subsequently, the toner image formed on the photoreceptor 1 is blackened on the intermediate transfer body 16 after a lapse of Q1 after the intermediate transfer body reference detection sensor 20 detects the intermediate transfer body 16a provided on the intermediate transfer body 16. It will be accurately transferred onto the toner image.

Through the same process, magenta (M)
2 and the yellow (Y) image are formed after the intermediate transfer member reference mark 16a is detected by the intermediate transfer member reference detection sensor 20 for U1 time, respectively, thereby forming the intermediate image as shown in FIG. The toner image of each color is transferred onto the intermediate transfer body 16 after a lapse of Q1 time since the intermediate transfer body reference detection sensor 20 detects the transfer body reference mark 16a,
A color composite image without color shift can be obtained. The superposed color composite image is transferred to the transfer material 2 by the transfer material roller 29.
4 and are fixed to the transfer material 24 by the fixing device 30, and the first color image forming operation is completed. This is the final color. When the yellow (Y) image formation is completed, the process proceeds from step 10 to step 11. In step 11, the variable n is counted up by 1 (n = 2), and in step 12, the time difference T2 between the photosensitive body reference detection and the intermediate transfer body reference detection measured at the time of image formation of the final color is stored in the memory.
Then, if there is data for the next page in step 13, the process proceeds to the second color image forming operation (step 4).

Next, the operation of forming a color image on the twenty-first sheet will be described with reference to FIGS. 1 and 2B. First, in step 4, after the photoconductor reference detection sensor 10 detects the time difference T2 stored in the memory in step 12 and the photoconductor reference mark 1b provided on the photoconductor 1, Z time (the image forming area on the photoconductor 1 is The time U2 obtained by adding the elapsed time (the time not covering the image formation prohibited area) is set in the image formation start position designation register 103 and set in the timer 101. Subsequently, when the intermediate transfer member reference detection sensor 20 detects the intermediate transfer member reference mark 16a and outputs an intermediate transfer member reference signal (step 5), the timer 101 is started (step 6), and after a lapse of U2 time (step 7). An image forming signal is output (step 8), and an exposure light beam 14 corresponding to a black (B) image forming signal is irradiated onto the photosensitive member 1 to start image formation, and an electrostatic latent image is formed on the photosensitive member 1. I do. The electrostatic latent image formed on the photoconductor 1 is visualized by the black toner of the developing device 6B to form a toner image. The toner image formed on the photoreceptor 1 is transferred onto the intermediate transfer member 16 after a lapse of Q2 since the intermediate transfer member reference detection sensor 20 detects the intermediate transfer member reference mark 16a provided on the intermediate transfer member 16. Is done.

The formation of one color image is completed (step 9).
If the image forming signal is not the signal of the final color, the process proceeds to the image formation of the next color, for example, cyan (C) as the second color (step 5). The cyan (C) toner image formed on the photoreceptor 1 is black unless the intermediate transfer member reference detection sensor 20 detects the intermediate transfer member reference mark 16a on the intermediate transfer member 16 after a lapse of Q2 time. This does not coincide with the start of the image formation in (B), causing an image shift. For this purpose, the intermediate transfer member reference mark 16a is attached to the intermediate transfer member reference detection sensor 2 as in the case of forming a black (B) image.
Image formation on the photoconductor 1 may be started after a lapse of U2 time from the detection of 0. Therefore, when the next intermediate transfer member reference detection signal is output (step 5), the timer 101
Is activated (step 6), and the U2 time elapses (step 7).
Thereafter, an image forming signal is output (step 8), and an exposure light beam 14 corresponding to the cyan (C) image forming signal is irradiated onto the photoconductor 1 to start image formation, and an electrostatic latent image is formed on the photoconductor 1. Form. It is formed on the photoconductor 1. Subsequently, the photoconductor 1
The toner image formed on the intermediate transfer member 16a provided on the intermediate transfer member 16
Is transferred onto the black toner image on the intermediate transfer body 16 after a lapse of Q2 from the detection.

Through the same process, magenta (M)
2 and the yellow (Y) image are formed after a lapse of U2 time from the detection of the intermediate transfer member reference mark 16a by the intermediate transfer member reference detection sensor 20, respectively. After a lapse of Q2 time from the detection of the transfer body reference mark 16a by the intermediate transfer body reference detection sensor 20, the toner image of each color is transferred onto the intermediate transfer body 16;
A color composite image without color shift can be obtained. The superimposed color composite image is collectively transferred to the transfer material 24 by the transfer material transfer roller 29, and is fixed to the transfer material 24 by the fixing device 30, and the first color image forming operation is completed. When the image formation of the final color yellow (Y) is completed, the process proceeds from step 10 to step 11. In step 11, the variable n is counted up by 1 (n = 3), and in step 12, the time difference T3 between the photoconductor reference detection and the intermediate transfer body reference detection measured at the time of image formation of the final color is stored in the memory. Then, if there is data for the next page in step 13, the process proceeds to the third color image forming operation (step 4), and the image forming operation is similarly continued. If there is no data for the next page, the image forming operation ends (step 14).

As described above, the intermediate transfer member reference mark 16 is formed on the photosensitive member 1 based on the time difference between the photosensitive member reference detection and the intermediate transfer member reference detection during the rotation of the photosensitive member 1 and the intermediate transfer member 16 just before.
a after the intermediate transfer member reference detection sensor 20 detects
Since the image formation is started after elapse of n hours, the continuous image forming operation can be continued without the image forming area entering the image forming prohibited area on the photoconductor 1.

In the above, one cycle of the photosensitive member 1 corresponds to the intermediate transfer member 1
6 has been described, but one cycle (E) of the photoconductor 1 is one cycle (F) of the intermediate transfer body 16.
Even in the case where the length is longer, image formation may be performed according to a flowchart similar to that of FIG. 1 as shown in FIGS.

In one embodiment of the present invention, the initial time difference T1 is measured at the time of initialization, and the initial image forming time U1 (= T1 + Z) is set based on the measured time difference. However, the operation is performed after a color image forming start command is issued. Various methods can be considered without departing from the gist of the present invention.

[0032]

As described above, the present invention has a seam
A rotatable loop belt that successively carries electrostatic latent images of several colors
Jo of the photosensitive member, an electrostatic latent image of a plurality of colors carried on the photosensitive member
The current state in which a toner image of a predetermined color is visualized to form a toner image
An image unit, a photoconductor reference mark provided on the photoconductor, a photoconductor reference detection sensor that detects a reference position of the photoconductor by detecting the photoconductor reference mark, and a plurality of colors formed on the photoconductor . The toner images are sequentially transferred and superimposed.
A rotatable intermediate transfer member on which a color toner image is formed, an intermediate transfer member reference mark provided on the intermediate transfer member, and a reference position of the intermediate transfer member are detected by detecting the intermediate transfer member reference mark. An intermediate transfer body reference detection sensor and a time difference measuring means for measuring a time difference T from when the intermediate transfer body reference detection sensor detects the intermediate transfer body reference mark to when the photoconductor reference detection sensor detects the photoconductor reference mark. The area where the electrostatic latent image is formed on the photoconductor is
Photoconductor reference detection sensor to eliminate the seam
Detects the optical body reference mark and starts image recording on the photoconductor
When the time between them is Z, the intermediate transfer member reference mark is detected by the intermediate transfer member reference detection sensor, and the image recording start timing is set so that the image recording of each color is performed on the photosensitive member after the elapse of T + Z time. Control of the intermediate transfer member
Sensed by the intermediate transfer member reference detection sensor
The timing for recording images of each color on the optical
The object reference detection sensor detects the intermediate transfer object reference mark.
The photoconductor reference detection sensor detects the photoconductor reference mark
By changing according to the time difference until the
Photoconductor without adjusting the relative position to the intermediary transfer body
The electrostatic latent image forming area does not include the seam of this photoconductor.
Thus , continuous printing can be performed without adjusting the position of the photosensitive member with respect to the intermediate transfer member. Accordingly, the time for adjusting the position of the photosensitive member with respect to the intermediate transfer member can be omitted, and the clutch mechanism can be eliminated. As a result, it is possible to significantly reduce the manufacturing cost and finely adjust the color matching. Further, since there is no need to generate a speed difference between the photosensitive member and the intermediate transfer member, damage to the photosensitive member and the intermediate transfer member can be prevented, and the life of the photosensitive member and the intermediate transfer member can be extended. A highly reliable electrophotographic apparatus can be provided.

[Brief description of the drawings]

FIG. 1 is a flowchart of an image forming operation of an electrophotographic apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating an image forming state of the photosensitive member and the intermediate transfer member when the period of the photosensitive member is shorter than the period of the intermediate transfer member.

FIG. 3 is a diagram illustrating an image forming state of the photosensitive member and the intermediate transfer member when the period of the photosensitive member is longer than the period of the intermediate transfer member.

FIG. 4 is a block diagram of the present invention.

FIG. 5 is a partial cross-sectional view of an electrophotographic apparatus according to a related art and an embodiment of the present invention.

FIG. 6 is an explanatory diagram of an operation of the photoconductor reference detection.

FIG. 7 is an explanatory diagram of an operation of the intermediate transfer member reference detection.

FIG. 8 is a partial cross-sectional view showing a state where image formation is started on a first photosensitive member of the image formation;

FIG. 9 is a partial cross-sectional view showing an image forming start state on the photoconductor after the photoconductor and the intermediate transfer body have passed a predetermined number of rotations;

FIG. 10 is a diagram showing a timing of starting image formation on the photoconductor.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoconductor 1 a photoconductor joint 1 b photoconductor reference mark 5 exposure optical system 6 developing device 10 photoconductor reference detection sensor 14 exposure light 16 intermediate transfer body 16 a intermediate transfer body reference mark 20 intermediate transfer body reference detection sensor 24 transfer material 101 Timer 102 CPU 103 Image formation start position designation register

Claims (1)

(57) [Claims] 1. An electrostatic latent image of a plurality of colors having a seam is sequentially carried.
Rotatable loop-belt-shaped photoconductor, and the photoconductor
The electrostatic latent images of a plurality of colors carried on the
A developing means for forming a image-forming of toner images Ri, the photosensitive drum reference mark provided on the photosensitive member, the photosensitive drum reference detection sensor for detecting the reference position of the photosensitive member by detecting the photoreceptor reference mark And toner images of a plurality of colors formed on the photoreceptor are sequentially transferred and superimposed, and
A rotatable intermediate transfer member on which a toner image is formed, an intermediate transfer member reference mark provided on the intermediate transfer member, and a reference position of the intermediate transfer member by detecting the intermediate transfer member reference mark. An intermediate transfer member reference detection sensor to detect, and a time difference T from when the intermediate transfer member reference detection sensor detects the intermediate transfer member reference mark to when the photoconductor reference detection sensor detects the photoconductor reference mark is measured. Time difference measuring means ,
The electrostatic latent image forming area does not include the seam of the photoconductor.
The photoconductor reference detection sensor detects the photoconductor reference mark.
The time between detection and the start of image recording on the photoconductor is Z
Is time, and wherein the intermediate transfer member reference mark the intermediate transfer member reference detection sensor to control the timing of the image recording start to record an image of each color onto the photosensitive member after lapse T + Z time detection in Electrophotographic equipment.