JP2000181244A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device which can be more efficiently used, is excellent in economicity and further is outstanding in terms of repairability concerning image irregularity by restraining the deterioration of the surface of a photoreceptor drum. SOLUTION: In this image forming device, a transfer carrying belt 216 abuts on the photoreceptor drums 222a to 222d driven to be rotated and paper P is made to pass between the belt 216 and the photoreceptor drum abutting on each other, so that a toner image formed on the photoreceptor drum is transferred to the paper P. Then, an abutting stop position on the surface of the photoreceptor drum abutting on the belt 216 when the photoreceptor drum starts rotation is made different from an abutting stop position on the surface of the photoreceptor drum abutting on the belt 216 when the photoreceptor drum stops the rotation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image transfer apparatus in which a transfer material is supported and conveyed by a transfer conveyance belt which comes into contact with a surface of a transfer portion of a rotating image carrier (photosensitive drum) in a predetermined positional relationship. The present invention relates to an image forming apparatus that transfers and reproduces a toner image formed on a carrier on a transfer material.

[0002]

2. Description of the Related Art Conventionally, there is a color image forming apparatus which transfers a color image as YMCK image data to a recording unit and sequentially superimposes and reproduces a color image while reproducing each color image. In such a color image forming apparatus, there is a problem that a color image cannot be faithfully reproduced unless images of respective colors are accurately superimposed, and how to solve this problem is a major issue in technical development. Has become.

In an image forming apparatus having an infinite number of components, there is a small variation in the component accuracy of each component, and the variation varies in each image forming device due to the assembling accuracy when assembling these components. appear. Therefore, conventionally, a pattern adjustment of each color is performed by trially forming a pattern image of each color, and confirming a positional relationship between the pattern images of each color, and performing an image forming position adjustment for each image forming unit of each color. Registered Patent No. 2643511).

However, by performing the above-described registration adjustment, the "color misregistration" due to the "deviation of the image writing start position" can be corrected, but the periodicity of a driving system such as a driving gear for driving the photosensitive drum can be corrected. It was not possible to correct color misregistration caused by irregular fluctuations in the speed of the photosensitive drum caused by uneven driving. That is, in such an image forming apparatus, periodic driving unevenness in each recording unit has conventionally been a problem, and the periodic driving unevenness occurs in each recording unit, so that the color of each color is reduced. When images recorded on materials are sequentially superimposed and reproduced as a color image, there is a problem that a color shift occurs and a faithful color image cannot be reproduced.

Therefore, in the conventional color image forming apparatus, when the image formed on the photosensitive member in each recording unit is transferred in the transfer unit, the condition of the drive unevenness that occurs periodically becomes the same. In addition, it is considered to arrange the relationship between the distance (time) from the image writing position to the transfer position to the transfer position and the drive fluctuation period of the drive mechanism to be N times as large (see Japanese Patent Publication No. 7-31446). Gazette, Tokuhei 8-
No. 14731).

FIG. 7 shows a configuration of a conventional color image forming apparatus employing the above-described technique, in which each image forming section and a transfer conveyance belt which conveys a transfer material for transferring an image formed in each image forming section. Is shown. In FIG. 7, photosensitive drums 322a, 322b, 322c, and 3 constituting black, cyan, magenta, and yellow recording units are arranged in order from the left.
22d. These photosensitive drums 322a to 322d
The images of the respective colors formed in the steps (a) and (b) move along with the movement of the transfer conveyance belt 316, and the photosensitive drums 322a to 322d and the transfer conveyance belt 316 approach each other on the transfer material supported and conveyed by the transfer conveyance belt 316. In the transfer section, the transfer is performed in a superimposed order from black. Here, the photoconductor drums 322a to 322d are configured to start rotating at the same time, and the photoconductor drums 322a to 322d are mounted such that the rotational drive unevenness is the same.

As a specific example, each photosensitive drum 322
The drive gears (not shown) to which the shafts a to 322d are fitted are all aligned in the same direction with a certain reference (for example, a key-shaped (convex) hole ha as shown in FIG. 7) indicating the period of the drive unevenness. To be mounted. Thus, at the same time, the photosensitive drums 322a to 322d always rotate with the same drive unevenness (the drive unevenness has the same phase). Therefore, each distance L 'between the transfer portions A-A of the photosensitive drums 322a to 322d is set to be equal to the photosensitive drum 322a.
By setting L ′ = Nπd (where N is an integer), where d is the diameter of 〜322d, transfer of an image at each transfer portion A of the four photosensitive drums 322a〜322d arranged in parallel is performed. In the process, images formed of the color materials of the respective colors are sequentially superimposed on the transfer material at the same drive unevenness cycle at all times, and as a result, color shift caused by drive unevenness is eliminated. Could be done.

[0008]

In the above-mentioned conventional configuration,
In order to further reduce the friction between the photosensitive drum and the transfer conveyance belt, each of the photosensitive drums 322a to 322d starts rotating at the same time and stops rotating at the same time. Further, in order to prevent drive unevenness caused by the drive system of the photosensitive drums, the drive unevenness start position of each photosensitive drum and the phase with respect to the transfer conveyance belt 316 are maintained at the same phase, so that the photosensitive drums 322a to 322d are always maintained. The rotation starts from a reference position where the relative positional relationship between the transfer belt 316 and the transfer conveyance belt 316 is constant, and ends.

However, the photosensitive drums 322a to 322a-3
It is not possible to completely start and stop the transfer of the transfer belt 316 with the transfer of the transfer belt 22d, and the rotation and stoppage of the transfer belt 316 causes a large contact resistance near the reference position on the delicate photosensitive drum surface. The accumulation of the contact resistance accelerates the damage of the reference position on the surface of the photosensitive drum, resulting in a disturbed copy image, and the replacement of the photosensitive drum is unavoidable despite the partial damage.

Incidentally, since the partial damage near the reference position is accumulated with time and gradually appears as periodic image unevenness in the transferred image, it is difficult to distinguish it from the drive unevenness described above. In particular, when the position appearing as the unevenness overlaps with the reference position of the drive unevenness, it is very difficult to pursue the cause of the image unevenness.

Accordingly, the present invention has been made to solve the above-mentioned problems, and it is possible to suppress deterioration of the surface of a photosensitive drum, to use the photosensitive drum more efficiently, to be economically excellent, and to maintain the image unevenness. It is an object of the present invention to provide an image forming apparatus that excels in.

[0012]

The present invention has the following configuration to achieve the above object. The invention of claim 1 is
The transfer material transporting means abuts the image carrier that is driven to rotate, and the transfer material passes between the transfer material transporting means and the image carrier that are in contact with each other, so that the developing material image formed on the image carrier is removed. In an image forming apparatus for transferring an image on a transfer material, a first contact position on a surface of the image carrier with which a transfer material conveying unit contacts when the image carrier starts rotating, and the image carrier rotates. The image forming apparatus is characterized in that a second contact position on the surface of the image carrier with which the transfer material conveying means contacts when stopped is different.

According to a second aspect of the present invention, there is provided a developing material image formed on each image carrier on a transfer material passing through a transfer section where a plurality of image carriers rotatably driven and a transfer material transporting means come into contact with each other. In the image forming apparatus, the rotational driving unevenness is shifted in phase so that the periodic rotational driving unevenness of the image carrier becomes the same condition with respect to the transfer material passing through each transfer unit. A first contact position on the surface of the image carrier with which the transfer material conveying means contacts when the image carrier starts rotating, and a transfer when the image carrier stops rotating. An image forming apparatus is characterized in that a second contact position on the surface of the image carrier with which the material conveying means contacts is different.

According to a third aspect of the present invention, the first of the plurality of image carriers has the most surface deterioration condition.
And the second contact position is different from the second contact position.
The image forming apparatus according to claim 2, wherein the remaining image carriers are stopped in a relationship in which rotational driving unevenness is shifted from each other.

According to a fourth aspect of the present invention, the first contact position is different from the second contact position every time the driving of the plurality of image carriers is stopped or started a predetermined number of times. The image forming apparatus according to claim 1, wherein:

According to a fifth aspect of the present invention, the transfer member is brought into contact with the image carrier which is driven to rotate, and the transfer material is passed between the transfer member and the image carrier in contact with the transfer member. In an image forming apparatus that transfers a developing material image formed on a body onto a transfer material, the image carrier is transferred when the rotation of the image carrier starts every time the driving of the image carrier is stopped or started a predetermined number of times. The contact position on the surface of the image carrier where the material conveying means contacts is different from the contact position on the image carrier surface where the transfer material conveying means contacts the next time the image carrier starts rotating. An image forming apparatus having control means for controlling rotation of an image carrier.

According to the first aspect of the present invention, monochrome copying,
Regardless of color copying, the contact position of the surface of the image carrier that comes into contact with the transfer material conveying means is different between when the image carrier is started to drive and when the drive is stopped. Rubbing of the specific surface between the image carrier and the transfer material transporting means caused by the timing shift does not concentrate at one point. Therefore, damage to the surface of the image carrier due to contact with the transfer material transporting unit does not concentrate on a part, and a significant partial decrease in performance can be prevented in advance. Further, since the first contact position and the second contact position are made different in accordance with the rotation of the image carrier, the contact position can be changed efficiently.

According to the second aspect of the present invention, each image carrier is
Since the rotation of the driving unevenness is shifted with respect to the above-described transfer material passing through each transfer portion so that the periodic rotation driving unevenness of the image carrier becomes the same condition, the rotation is performed by each image carrier. The images are sequentially superimposed under the same conditions without being affected by the periodic driving unevenness of the image carrier,
As in the prior art, the finally output image is faithfully reproduced without color shift. Since the contact positions of the surfaces of the image carriers that come into contact with the transfer material conveying means are different between when the driving of the image carriers is started and when the driving is stopped, the driving of each image carrier and the transfer material conveying means is stopped or the driving is started. The rubbing of the surface caused by the difference in the timing of driving and stopping at the time does not concentrate on one point. Therefore, the damage on the surface of the image carrier due to the contact with the transfer material transporting means is not partially concentrated, and significant partial performance deterioration can be prevented in advance. Further, since the first contact position and the second contact position are made different in accordance with the rotation of the image carrier, the contact position can be changed efficiently.

According to the third aspect of the present invention, the stop position of the image carrier having the greatest deterioration condition among the image carriers in the plurality of recording units arranged in series in the transport direction of the transfer material is changed. Since the remaining image carriers are stopped in a relationship in which the rotational driving unevenness is shifted from each other, the stop positions of the other image carriers are corrected according to the image carrier having the largest degree of deterioration due to the difference in the image forming mode. Thus, it is possible to prevent only the image carrier having the most deterioration condition from being extremely deteriorated, and to reduce the chance of maintenance since the deterioration is averaged.

According to the fourth aspect of the present invention, the first contact position and the second contact position are different each time the driving of the plurality of image carriers is stopped or started a predetermined number of times. Therefore, by selecting the predetermined number of times according to various use conditions and the like, it is possible to efficiently prevent the deterioration of the surface of the image carrier.

According to the invention of claim 5, monochrome copying,
Stop driving the image carrier regardless of color copying,
Alternatively, each time the start is performed a predetermined number of times, the contact position on the surface of the image carrier that contacts the transfer material transporting unit can be changed by the control unit, so that the specific surfaces of the image carrier and the transfer material transporting unit are The rubbing of the surface caused by the difference between the drive and stop timings at the start of driving does not concentrate on one point. Therefore, damage to the surface of the image carrier due to contact with the transfer material transporting unit does not concentrate on a part, and a significant partial decrease in performance can be prevented in advance.

[0022]

Embodiments of the present invention will be described below in detail with reference to the drawings. One embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a schematic front sectional view showing a configuration of a digital color copying machine 1 which is an image forming apparatus according to an embodiment of the present invention. A document table 111 and an operation panel (not shown) are provided on the upper surface of the copying machine main body 1, and an image reading section 110 and an image forming section 210 are provided inside the copying machine main body 1. On the upper surface of the platen 111, the platen 1
11 is supported so as to be openable and closable with respect to the platen 111.
Reversing Automatic Document Feeder (RADF)
er) 112 is mounted.

The double-sided automatic document feeder 112 first conveys the document such that one side of the document faces the image reading section 110 at a predetermined position on the document table 111, and the image reading on this one side is completed. Later, when the other surface is at a predetermined position on the
The document is inverted and conveyed toward the document table 111 so as to face the document table 111. Then, after the two-sided image reading for one document is completed, the double-sided automatic document feeder 112 discharges this document and performs a double-sided conveyance operation for the next document. The above-described operation of conveying the document and reversing the front and back is controlled in relation to the operation of the entire copying machine 1.

The image reading unit 110 is arranged below the document table 111 for reading an image of a document conveyed onto the document table 111 by the automatic duplex document feeder 112. The image reading unit 110 includes the platen 111
A document scanning body 113 that reciprocates in parallel along the lower surface of
114, an optical lens 115, and a photoelectric conversion element C
And a CD line sensor 116.

The original scanning bodies 113 and 114 are composed of a first scanning unit 113 and a second scanning unit 114. The first scanning unit 114 has an exposure lamp for exposing the surface of the document image and a first mirror for deflecting a reflected light image from the document in a predetermined direction. It reciprocates in parallel at a predetermined scanning speed while maintaining the distance.

The second scanning unit 114 further deflects the reflected light image from the document deflected by the first mirror of the first scanning unit 113 in a predetermined direction.
And a third mirror, and the first scanning unit 113
And reciprocate in parallel while maintaining a constant speed relationship.

The optical lens 115 reduces the reflected light image from the document deflected by the third mirror of the second scanning unit, and forms the reduced light image at a predetermined position on the CCD line sensor 116. It is.

The CCD line sensor 116 photoelectrically converts the formed light image sequentially and outputs it as an electric signal. The CCD line sensor 116 reads a black-and-white image or a color image, and outputs R (red), G (green), and B (blue).
This is a three-line color CCD capable of outputting line data color-separated into each color component. The document image information converted into an electric signal by the CCD line sensor 116 is further transferred to an image processing unit (not shown) and subjected to predetermined image data processing.

Next, the configuration of the image forming unit 210 and the configuration of each unit related to the image forming unit 210 will be described.
Below the image forming unit 210, paper (for example, paper, transfer material such as OHP paper) P stacked and housed in the paper tray TR is separated one by one and supplied to the image forming unit 210. A mechanism 211 is provided. Then, the sheets P separated and supplied one by one are conveyed to the image forming unit 210 at a controlled timing by a pair of registration rollers 212 disposed in front of the image forming unit 210. Further, the sheet P on which an image is formed on one side is transferred to the image forming unit 21.
0 and the image forming unit 210
Transported again.

Below the image forming section 210, a transfer and transport belt mechanism 213 is disposed. The transfer / transport belt mechanism 213 is provided between the drive roller 214 and the driven roller 215 to extend substantially in parallel with the transfer / transport belt 21.
6, the paper P is electrostatically attracted and transported. The pattern image detection unit 300 is provided near the lower side of the rotation orbit of the transfer conveyance belt 216. The pattern image detection unit 300 detects and recognizes a test pattern formed on the transfer conveyance belt 216 by a sensor (not shown), and adjusts an image forming position of an image forming unit based on the result. The means for conveying the paper P is not limited to the transfer / conveyance belt 216, and may be any means capable of transferring a toner image onto the paper P between the transfer belt and a photosensitive drum, which will be described later. Good.

Further, on the downstream side of the transfer conveyance belt machine side 213 in the paper conveyance path, close to the drive roller 214,
A fixing device 217 for fixing the toner image transferred and formed on the sheet P to the sheet P is provided. The sheet P passing through the nip between the pair of fixing rollers of the fixing device 217 passes through a conveyance direction switching gate 218 and is discharged by a discharge roller 219 onto a discharge tray 220 attached to the outer wall of the copying machine main body 1. Is done.

The switching gate 218 is connected to the sheet P after fixing.
Is selectively switched between a path for discharging the sheet P to the copying machine main body 1 and a path for re-supplying the sheet P toward the image forming unit 210. The sheet P whose transport direction has been switched again toward the image forming unit 210 by the switching gate 218 is turned upside down via the switchback transport path 221, and then the image forming unit 210 is turned over.
Is supplied again.

Further, above the transfer belt 216 in the image forming section 210, the first image forming station Pa, the second image forming station Pb, and the third image forming station are located close to the transfer belt 216. Station P
c and a fourth image forming station Pd are provided in order from the upstream side of the sheet transport path.

The transfer conveyance belt 216 is driven by a driving roller 214.
As a result, the sheet P is frictionally driven in the direction indicated by the arrow Z in FIG. 1 and is gripped by the sheet P fed through the sheet feeding mechanism 211 as described above.
Conveyed sequentially to Pd.

Each of the image stations Pa to Pd has substantially the same configuration. Each image station Pa,
Pb, Pc, and Pd respectively include the photosensitive drums 222a to 222d that are driven to rotate in the direction of arrow F shown in FIG.

Around the photosensitive drums 222a to 222d, a charger 2 for uniformly charging each photosensitive drum is provided.
23a, 223b, 223c, and 223d and developing devices 224a, 224b, 224c, and 224d for developing electrostatic latent images formed on the respective photosensitive drums
And the transfer dischargers 225a and 225 for transferring the developed toner images (developing material images) on the photosensitive drums to the paper P.
b, 225c and 225d and cleaning devices 226a and 226 for removing toner remaining on each photosensitive drum.
26b, 226c, and 226d are sequentially arranged along the rotation direction of the corresponding photosensitive drums 222a to 222d.

Each of the photosensitive drums 222a to 222d
Above the laser beam scanner unit 227
a, 227b, 227c, and 227d are provided, respectively. Laser beam scanner unit 227a
To 227d, a semiconductor laser element (not shown) for emitting dot light modulated in accordance with image data, a polygon mirror (deflecting device) 240 for deflecting a laser beam from the semiconductor laser element in the main scanning direction, It comprises an f-θ lens 241 and mirrors 242 and 243 for forming an image of the laser beam deflected by the polygon mirror 240 on the surfaces of the photosensitive drums 222a to 222d.

The laser beam scanner 227a receives pixel signals corresponding to the black component (Bk) image of the color original image, and the laser beam scanner 227b receives the pixel signals corresponding to the cyan (C) color component image of the color original image. The laser beam scanner 227c receives pixel signals corresponding to the magenta (M) color component image of the color original image, and the laser beam scanner 227d receives the pixel signals corresponding to the yellow (Y) color component image of the color original image. Is entered. As a result, an electrostatic latent image corresponding to the color-converted document image information is formed on each of the photosensitive drums 222a to 222d. Then, black (B
k) toner (developing material), cyan (C) toner (developing material) in developing device 227b, magenta (M) toner (developing material) in developing device 227c, and developing device 2
27d contains yellow (Y) toner (developer), respectively, and is a photosensitive drum 222a to 222d.
The upper electrostatic latent image is developed with each of these color toners. As a result, the document image information color-converted by the image forming unit 210 is reproduced as a toner image of each color.

A paper-suction (brush) charger 228 is provided between the first image forming station Pa and the paper feeding mechanism 211. And the sheet feeding mechanism 211
The sheet P supplied from the first image forming station Pa is securely sucked onto the transfer / conveying belt 216.
To the fourth image forming station Pd without shifting.

On the other hand, a static eliminator (not shown) is provided almost directly above the drive roller 214 between the fourth image station Pd and the fixing device 217. An AC current is applied to the static eliminator to separate the paper P electrostatically attracted to the conveyor belt 216 from the transfer conveyor belt 216.

In the digital color copying machine having the above configuration, cut sheet-shaped paper is used as the paper P. The sheet P is sent out from the sheet cassette and fed to the sheet feeding mechanism 2.
When the paper P is fed into the guide of the paper feed conveyance path 11, the leading end of the paper P is detected by a sensor (not shown),
It is temporarily stopped by the pair of registration rollers 212 based on a detection signal output from this sensor. Then, the paper P is transferred to the transfer conveying belt 2 rotating in the arrow z direction in FIG.
16 is sent. At this time, since the transfer conveyor belt 216 has been given a predetermined charge by the attraction charger 228 as described above, the paper P is transferred to each image station Pa.
ＰPd is stably conveyed and supplied.

In each of the image stations Pa to Pd, a toner image of each color is formed, and is superposed on the support surface of the paper P conveyed by being electrostatically attracted and conveyed by the transfer conveyance belt 216. Fourth image station Pd
Is completed, the paper P is sequentially transferred from the leading end portion thereof to the transfer conveyance belt 216 by the discharger for static elimination.
It is peeled off from above and guided to the fixing device 217. Finally, the paper P on which the toner image has been fixed is discharged onto a paper discharge tray 220 from a paper discharge port (not shown).

In the above description, the laser beam is scanned and exposed by the laser beam scanner units 227a to 227d, thereby performing optical writing on the photosensitive member. However, a writing optical system (LED head) including a light emitting diode array and an imaging lens array may be used instead of the laser beam scanner unit. The LED head is smaller in size than the laser beam scanner unit, and has no moving parts and is silent. Therefore, it can be suitably used in an image forming apparatus such as a tandem type digital color copying machine which requires a plurality of optical writing units.

In the conventional countermeasure for preventing image displacement due to driving unevenness shown in FIG. 7, the distance relationship between the recording units arranged in parallel must be arranged in accordance with the periodic driving fluctuation. If the distance between the recording units is determined in accordance with the typical drive fluctuation, even if the integer N is 1,
A distance corresponding to the perimeter of the photoreceptor drum is always required, and as a result, the size of the image forming apparatus itself becomes large, and the miniaturization desired by the user cannot be achieved. In particular, as described above, this is a serious problem in an image forming apparatus provided with photoconductors for four colors of Y, M, C, and Bk.

Therefore, in the digital color copying machine of the present embodiment, as shown in FIG. 2, unlike the image forming apparatus having the conventional configuration shown in FIG. 7, the image forming stations Pa to Pd (see FIG. 1). Four photosensitive drums 222a
To 222d are rotation drive unevenness of the photosensitive drums 222a to 222d (common to each photosensitive drum if the phases are matched)
Are installed with their phases shifted by a predetermined amount, and are rotationally driven. Specifically, each of the photosensitive drums 222a to 222d
Is configured to start rotation at the same time and stop rotation at the same time. Therefore, the phase is set to be shifted by shifting the stop position (rotation start position) at the time of initial setting. In FIG. 2, similarly to FIG. 7, a drive gear attached to transmit a drive to the shaft of each of the photosensitive drums 222 a to 222 d to transfer the phase shift in each of the photosensitive drums 222 a to 222 d (see FIG. 4 described later). Key-shaped (convex) hole ha.

Now, the photosensitive drum 2 of black (Bk)
With reference to 22a, the phase of the photosensitive drum 222b of cyan (C) adjacent thereto is stopped in a state advanced by about 60 degrees. Similarly, the magenta (M) photosensitive drum 22
The phase of 2c is stopped by 120 degrees, and the phase of the photosensitive drum 222d of yellow (Y) is advanced by 180 degrees.
In this manner, by shifting the phase of the drive unevenness in each photoconductor drum, the distance between the transfer units A-A corresponding to the respective image forming stations Pa to Pd is reduced by the phase difference. Even if the transfer material is further reduced, the drive unevenness between the photosensitive drums can be made the same for the transfer material passing through the transfer portion A.

As described above, if the diameter of the photosensitive drum is d by advancing the period of the drive unevenness between adjacent photosensitive drums by 60 degrees, L corresponding to the distance between transfer portions A-A is obtained.
L = (360-60) degrees / 3 of the circumference d of the photosensitive drum
60 degrees. Here, for convenience of explanation, the distance between the transfer units A-A is set based on the phase shift amount in each photosensitive drum, but actually, the distance L between the transfer units A-A is set. The phase shift of each photosensitive drum may be set based on the determination. For example, using a photosensitive drum having a drum diameter of 40 mm, the distance L between the transfer portions A-A is set to 105
In the case of mm, the stop position between the adjacent photosensitive drums is set so as to shift the phase of each drive unevenness by about 60 degrees as described above.

Next, referring to FIG. 3, a description will be given of a state in which images of the respective photosensitive drums are superimposed without color shift due to driving unevenness. Now, it is assumed that four photosensitive drums are rotating in a state as shown in FIG. The image written at the timing of (1) at the position of “G” of the black photosensitive drum 222a (the reference of the drive unevenness is indicated by an arrow line a for clarity) at the timing of (4) (the photosensitive drum 222
a) after the time required for 180 ° rotation of a
The image is transferred onto the image 16 and is superimposed on the image on the cyan photosensitive drum 222b at the timing (9). Here, an image has already been formed on the cyan photosensitive drum 222b by the laser beam at the timing (6) (see FIG. 1).

FIG. 5A shows the position of the line a of the cyan photosensitive drum 222b at the timings (1) to (6). As is clear from the figure, the line a at the timing (9) is located at the same position as the black photosensitive drum 222a at the timing (4). Therefore, the driving unevenness of the superimposed images becomes the same, and there is no color shift due to the influence of the driving unevenness.

Similarly, the magenta photosensitive drum 222c
Is superimposed on the image formed at the timing (14). Here, the magenta photosensitive drum 222c has
An image has already been formed at the timing of (11). FIG.
(B) shows the position of the line a of the photosensitive drum 222c of aagenta at the timings (1) to (11). As is clear from the figure, the line a at the timing of (11) is
(1) It is at the same position as the black and cyan photosensitive drums at the timings of (6). Therefore, the superimposed images have the same driving unevenness, and there is no color shift due to the influence of the driving unevenness.

Similarly, the yellow photosensitive drum 222d
Is superimposed on the image formed at the timing (19). Here, the yellow photosensitive drum 222d has
An image has already been formed at the timing of (16). FIG.
(C) shows the position of the line a of the yellow photosensitive drum 222d at the timings (1) to (16). As is clear from the figure, the line a at the timing of (16) is
It is at the same position as the black, cyan, and magenta photosensitive drums at the timings of (1), (6), and (11). Therefore, the superimposed images have the same driving unevenness, and there is no color shift due to the influence of the driving unevenness.

The four photosensitive drums 222a-222
The rotational drive of 222d is based on a reference mark that can specify the drive unevenness of each photosensitive drum, and the control unit CON (see FIG. 4).
Is controlled by

Hereinafter, the rotational drive control of the photosensitive drums 222a to 222d will be described with reference to FIGS.
As shown in FIG. 4, the drive gears G1 to G4 for transmitting the rotational driving force to the photosensitive drums 222a to 222d have key-shaped protrusions in which the shafts of the respective photosensitive drums and the drive gears G1 to G4 are fitted. Together with a rectangular pattern Q as a reference mark
And a detection sensor S1 comprising an optical sensor or the like.
To S4. of course,
The detecting means is not limited to this.

Each of the sensors S1 to S4 is mounted at the same position with respect to each transfer portion A. This sensor output is sent to the control unit CON, and based on this, the control unit CON
Controls the rotation of each motor M for rotating the drive gears G1 to G4 in order to independently rotate each photosensitive drum.

The control unit CON controls the photosensitive drums 222a to 222d based on the detection results from the sensors S1 to S4.
Are surely stopped at the respective stop positions, and when copying is started, rotation is started at the same time.

FIG. 5 shows photosensitive drums 222a to 222d.
The relationship between the output timings of the sensors S1 to S4 when stopping the operation is shown. Photosensitive drum 222d located on the downstream side
The pattern Q is detected and turned on sequentially from the sensor S4 of
Sensor S of photosensitive drum 222a located at the most upstream side
1 is finally turned on. The time when the pattern Q shown in FIG. 4 reaches the transfer portion A (in this case, the time to rotate 90 degrees) after the last sensor S1 is turned on is defined as a margin time (margin angle). Body drum 222
Stop a.

In the photosensitive drums 222b to 222d other than the reference photosensitive drum 222a, a correction amount is detected based on the detection results of the sensors S2 to S4 and the detection result of the sensor S1, and the correction amount is set to a margin time. At the time when the time elapses after the sensor S1 is turned on. As a result, each photosensitive drum can be accurately set in a state where the phase is shifted by a predetermined amount.

For example, when the photosensitive drum 222b for cyan is considered, there is a shift of 60 degrees between the photosensitive drum 222b and the reference photosensitive drum 222a. Therefore, when the sensor S1 is turned on and the sensor S2 is
The correction amount of the photosensitive drum 222b is calculated from the timing of N. Here, if the interval is 61 degrees and is advanced by 1 degree, it is necessary to return it once. Therefore, the correction amount is set to −1, and this is added to 90 degrees of the extra time, and the extra time is 89. As a degree, the sensor S1 is turned on and stopped after a lapse of an extra time of 89 degrees. If the above-mentioned margin time is not set, if the correction amount is positive, the photosensitive drum 222b may be further rotated and stopped by that much, but if it is negative, the photosensitive drum 222b has already passed the stop position. It has to be turned one more turn to stop it in the right position,
Although the surface of the transfer conveyance belt 216 and the surface of the photoconductor drum may be damaged by contact, the above-described configuration can be stopped in a state where an ideal image can be recorded in a short time while suppressing damage and the like. The image recording to be performed can also be performed smoothly.

The reason why the stop position of the photosensitive member in each transfer section A fluctuates will be described. The transfer conveyance belt mechanism 213 illustrated in FIG. 1 includes a transfer conveyance belt 216 and image forming stations Pa to Pd that are close to each other, and a sheet conveyance position at which the sheet P can be conveyed, and a position lower than the sheet conveyance position. The image forming stations Pa to Pd can be switched to a jam processing position separated from each other. Transfer transfer belt mechanism 213 is moved to photosensitive drum 222a.
Factors that cause the transfer position to approach / separate from the transfer positions 222d to 222d include abnormal transfer of the transfer material in the transfer transfer path, periodic inspection, replacement of components, adjustment, and the like. It is conceivable that the stop position relationship changes. Therefore, after taking measures against such factors, for example, when the power is turned on or when the transfer / conveyance unit is returned to a predetermined position, the control of the stop position of each photosensitive drum is performed. Do.

Further, in the case where images are continuously output, the photosensitive drums initially having a fixed relationship with each other slightly change as time (continuous driving time) elapses. It is also possible. Therefore, the number of continuous output sheets, the continuous output time, and the like can be managed by an internal counter, an internal timer, and the like of the CPU, and the stop position of each photoconductor can be controlled when a predetermined level is reached. is there.

Further, the color image forming apparatus 1 according to the present embodiment is capable of forming a black image, a monochromatic color, or the like by one or a combination of a plurality of image forming units for forming images of black, yellow, magenta, and cyan. Some can record and reproduce images. At this time, depending on the device, an image forming unit that is not used for recording and reproduction of an image is stopped, and only a necessary image forming unit is operated. It is also possible to control the stop position on the photoconductor.

Further, no matter how precisely the dimensions between the transfer portions A-A are set, the photosensitive drums 222a through 222a
If the mounting position of 2d is shifted and there is an error of only 100 μm in the dimension, it will appear as a large color shift in a high-density recording image forming apparatus such as 600 dpi (diameter of one dot: about 43 μm). Therefore, it is preferable that a means for adjusting the stop position of each photoconductor drum be provided separately irrespective of the drive unevenness of the photoconductor drum.

Similarly, since errors tend to occur in the mounting positions of the above-mentioned sensors S1 to S4, it is desirable to have a configuration capable of correcting such errors. For example, in the above description, the allowance time is set to 90 degrees for all four photosensitive drums, but the mounting error of the sensor and the transfer section A-A
In accordance with the dimensional error between them, the respective corrections may be made in advance, and the correction amount at the time of stoppage may be newly added (subtracted) to the corrected margin time.

Next, the photosensitive drums 222a to 222d
The position control means will be described. As the motor used for controlling the position of each photosensitive drum, a motor for individually driving each photosensitive drum and a stepping motor or a servomotor capable of accurate position control are suitable. Can be adjusted for each photosensitive drum.

If the stop positions of the photosensitive drums 222a to 222d and the transfer / transport belt 216 are set to the same position each time by preventing the drive unevenness by the above configuration, deterioration due to partial wear of the surface of the photosensitive drum. Occurs, which leads to a decrease in the image quality of the recorded and reproduced image. This is caused by a frictional force due to a difference in timing between the start and stop of the drive when the drive of the photosensitive drum and the transfer conveyance belt 216 is started and when the drive is stopped.
Therefore, in the present embodiment, in addition to the above configuration, when the number of times of starting or stopping the driving reaches a predetermined number (one or more times), the photosensitive drums 222a to 222d (image carrier)
Stop position (contact position with the transfer conveyance belt 216 in the stop state) is stopped at a positional relationship shifted by a certain angle, and the same surface portion of the photosensitive drum is transferred to the transfer conveyance belt 21 every time.
6 so as not to stop in contact with the surface.

As means for managing that the number of times of starting or stopping of driving has reached a predetermined number (one or more times),
As a very commonly used method, the basic operation of the image forming apparatus is managed using an internal management counter or the like of a microcomputer, and the stop position is shifted by a predetermined amount (angle) when a predetermined number of times is reached. Then, a specific portion (area) on the surface of the photosensitive drum is not concentrated and deteriorated. This will be specifically described with reference to FIG.

FIG. 6 shows the photosensitive drums 222a to 222d.
Is shown in a flowchart.
First, when the photosensitive drum is mounted or replaced, the copy (transfer) rotation speed T of the counting means such as a memory device (not shown) in the control unit shown in FIG. Can be changed as appropriate), and the correction angle θ (changeable as appropriate) is input (step S).
1). When each photosensitive drum is mounted and a copy command is issued to an operation panel (not shown) of the digital color copying machine 1 shown in FIG. 1 (transfer switch is turned on: step S2), the number of copies T and the number of changes N of the counting means are determined. Compare (step S3). As a result of the comparison, if the number of copies T is smaller than the number of changes N (T <N), the process proceeds to step S4. If the number of copies T is equal to the number of changes N (T = N), the process proceeds to step S6. move on. In step S4, the number of copies T is incremented by 1 without correcting the margin time (angle) shown in FIG. 5 (step S5), and the copying process (step S8).
Execute If the process proceeds to step S6, the correction angle θ is added to the extra time (angle) to obtain a new extra time (angle).
The number of copies T is cleared to T = 1 (step S7), and the copying process (step S8) is executed. When the copying process is completed, each photosensitive drum stops with a margin time (angle), and waits for a copying command from the next operation panel (step S2).

According to the starting position control means for the photosensitive drums 222a to 222d according to the flowchart of FIG.
Since the position where the photosensitive drum comes into contact with the transfer / transport belt 216 while the photosensitive drum is stopped (copy standby state) changes every predetermined number of copies T, a specific portion (area) on the surface of the photosensitive drum concentrates and deteriorates. It can be prevented.
Note that the flowchart of FIG. 6 is merely an example of a control unit that changes the start position of the photosensitive drum, and the order of the processing steps may be efficiently changed as appropriate. For example, FIG.
Although the copying process (step S8) is a process after the control process (steps S3, S4, S5, S6 and S7), in order to speed up the processing process, the copying process and the control process are performed in parallel. Can be changed. The angle correction (steps S4 and S6) is not limited to the allowance time, but may be performed by adding a new variable, for example, a correction angle proportional to the number of copies T to the first reference position.

The start position of the photosensitive drum can be changed efficiently by changing the margin time at the end of copying of the photosensitive drum as described above. Is completed or before copying starts,
The start position may be changed by rotating the photoconductor drum by a predetermined angle independently of the photoconductor drum, or by synchronizing the photoconductor drum and the transfer conveyance belt and independently of the copying operation. When the photosensitive drum is rotated independently of the transfer / transport belt when changing the start position of the photosensitive drum, the photosensitive drum and the transfer / transport belt are separated from each other to prevent damage due to friction of the photosensitive drum. It is desirable.

In the image forming apparatus 1, a mode for recording and reproducing a color image by using a plurality of photosensitive drums and the transfer unit A, and a black image by using the photosensitive drum and the transfer unit A for reproducing a black image. The transfer frequency indicates that the photosensitive drum of the transfer unit A that reproduces a black image among the four photosensitive drums is most likely to deteriorate due to wear. Therefore, among the four photosensitive drums, the number of image formations of the recording unit that reproduces a black image is managed, and when the number of image formations of the recording unit that reproduces the black image reaches a predetermined number, four image formations are performed. The stop position of the photoconductor drum may be shifted by a predetermined amount (angle) so that a specific portion (area) of the photoconductor drum surface does not concentrate and deteriorate.

In the present embodiment, an image forming apparatus for forming a color image in which a plurality of photosensitive drums are arranged in parallel and a transfer conveyance belt 216 is brought into contact with the surfaces of the plurality of photosensitive drums is described. As explained as an example,
The transfer conveyance belt 216 is provided on the transfer area of the single photosensitive drum.
Can also be applied to an image forming apparatus in which the contact is made.

In the same manner, in the charging roller, the developing roller, the transfer roller and the like which are driven in a state of acting on the surface of the photosensitive drum in synchronization with the driving of the photosensitive drum, the influence on the surface of the photosensitive drum is also considered. Then, the stop position of the photoconductor can be shifted every time the predetermined number of times is reached.

[0073]

As described above, according to the first aspect of the present invention, damage to the surface of the image carrier is not concentrated on a predetermined area, so that the image carrier can be used more efficiently, and maintenance can be performed. And the product life of the image carrier can be extended.

According to the second aspect of the present invention, even when a plurality of image carriers are used, the periodic rotation driving unevenness of each image carrier is synchronized, so that the sequentially superposed developer can be used. Since there is no shift, a color image or the like can be faithfully reproduced without color shift, and when the distance between the image carriers is smaller than the circumference of the image carriers, the apparatus can be downsized. In addition, since the contact positions of the surfaces of the image carriers that come into contact with the transfer material conveying means are made different, damage on the surface of the image carriers does not concentrate on a predetermined area, so that the image carriers can be more efficiently moved. It can be used, maintenance is improved,
Further, the product life of the image carrier can be extended.

According to the third aspect of the present invention, the first and second contact positions are changed with reference to the image carrier having the most deterioration conditions, so that the image carrier is used more efficiently. And the product life of a plurality of image carriers can be extended.

According to the fourth aspect of the present invention, each time the driving is stopped or started a predetermined number of times, the contact position of the surface of each image carrier that comes into contact with the transfer material conveying means is changed, so that the image carrier is Before the surface of the transfer material conveying means is deteriorated, the contact position is set in a state where the next area is in contact with the next area, and the driving of the image carrier and the transfer material conveying means is stopped, or the driving is stopped at the start of driving. The rubbing of the surface resulting from the timing deviation does not concentrate on one point. Therefore, the image carrier can be used appropriately and efficiently, and the product life of the image carrier can be extended.

According to the fifth aspect of the present invention, each time the driving is stopped or started a predetermined number of times, the contact position of the surface of each image carrier that comes into contact with the transfer material conveying means at the start of driving is made different. As a result, the image carrier is prevented from being concentrated on a predetermined area, the image carrier can be used more efficiently, the maintainability is improved, and the product of the image carrier is controlled. Life can be extended.

[Brief description of the drawings]

FIG. 1 is a front sectional view of a digital color copying machine 1 according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a relative positional relationship between a photosensitive drum and a transfer conveyance belt according to the embodiment of the present invention.

FIG. 3 is an explanatory diagram illustrating a relationship between an interval between four photosensitive drums and a transferred image according to the embodiment of the present invention.

FIG. 4 is an explanatory diagram of a method of controlling a photosensitive drum according to the embodiment of the present invention.

FIG. 5 is a time chart for stopping rotation of four photosensitive drums according to the embodiment of the present invention.

FIG. 6 is a flowchart for changing a stop position of a photosensitive drum according to the embodiment of the present invention.

FIG. 7 is an explanatory diagram of a relative positional relationship between a conventional photosensitive drum and a transfer conveyance belt.

[Explanation of symbols]

 1 Digital Color Copier 216 Transfer Conveying Belt 222a-222d Photoconductor Drum A Transfer Unit CON Control Unit d Photoconductor Drum Diameter T Number of Copies N Predetermined Number Q Rectangular Pattern S1-S4 Detection Sensor 2 θ Correction Angle

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Hidekazu Sakagami 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation F-term (for reference) in JAP Corporation 2H027 DA22 ED16 ED24 EF13 2H032 AA15 BA01 BA18 BA23 CA13

Claims (5)

[Claims] An image carrier is formed on an image carrier by bringing a transfer material into contact with the image carrier that is rotationally driven and passing the transfer material between the image carrier and the transfer material carrier that abuts. An image forming apparatus for transferring the developing material image onto a transfer material, wherein the first contact position on the surface of the image carrier with which the transfer material conveying means contacts when the image carrier starts rotating; An image forming apparatus, wherein a second contact position on a surface of an image carrier with which a transfer material conveying unit contacts when the carrier stops rotating is different. 2. An image forming apparatus, comprising: a developing material image formed on each image carrier is sequentially superimposed on a transfer material that passes through a transfer section where a plurality of image carriers that are rotationally driven are in contact with a transfer material transport unit; In the apparatus, each image carrier is rotationally driven by shifting the phase of the rotational drive unevenness such that the periodic rotational drive unevenness of the image carrier becomes the same condition with respect to the transfer material passing through each transfer unit. A first contact position on the surface of the image carrier with which the transfer material conveying means contacts when the image carrier starts to rotate, and a transfer material transport means when the image carrier stops rotating. An image forming apparatus, wherein the second contact position on the surface of the image carrier that is in contact is different. 3. The image bearing member having the largest condition of surface deterioration among the plurality of image bearing members, the first contact position and the second contact position of the image bearing member differ from each other, and the remaining image bearing members are different. The image forming apparatus according to claim 2, wherein the image forming apparatuses are stopped in a relationship in which rotational driving unevenness is shifted from each other. 4. The method according to claim 1, wherein the driving of the plurality of image carriers is stopped.
4. The image forming apparatus according to claim 1, wherein the first contact position and the second contact position are different each time the start is performed a predetermined number of times. 5. 5. The image forming apparatus according to claim 1, wherein the transfer material conveying means is in contact with the image carrier which is driven to rotate, and the transfer material is passed between the transfer material conveying means and the image carrier in contact with the image carrier. In the image forming apparatus for transferring the developed developer image onto the transfer material, the transfer material transporting means is activated when the image carrier starts rotating every time the driving of the image carrier is stopped or started a predetermined number of times. The rotation of the image carrier such that the contact position on the surface of the image carrier that comes into contact is different from the contact position on the surface of the image carrier that the transfer material conveying means contacts when the image carrier starts rotating next time. An image forming apparatus, comprising: a control unit for controlling the image forming apparatus.