JP2000293005A - Image forming device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To be able to faithfully reproduce as a single color image in response to periodic drive fluctuations, to reduce the size of the device itself and to minimize the installation area in an office environment. To provide an image forming apparatus capable of performing such operations. SOLUTION: Photoconductor drums 222a to 222d, a motor M for rotating the photoconductor drums 222a to 222d, and sensors S1 to S4 for detecting the position of the photoconductor drum when the photoconductor drum is rotating. And a control unit CON that controls the motor M based on the detection signals of the sensors S1 to S4 to stop the rotation phase state of each photosensitive drum in accordance with a predetermined rotation phase state.
Control unit CO when the detection signal of each sensor deviates from a predetermined timing by a predetermined allowable value or more.
The phase adjustment by N is executed, and if the deviation does not exceed the allowable value, the phase adjustment by the control unit CON is not executed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer material such as paper by a transfer conveyance belt which abuts on a transfer portion surface of a rotatable image carrier such as a photosensitive drum in a predetermined positional relationship. The present invention relates to an image forming apparatus that supports and conveys and transfers and reproduces a toner image formed on an image carrier onto a transfer material. Specifically, the positional relationship when the image carrier stops is a predetermined positional relationship. The present invention relates to an image forming apparatus that controls so as to stop the image forming apparatus so that subsequent image forming is performed with high accuracy.

[0002]

2. Description of the Related Art Conventionally, a color image forming apparatus for transferring a color image as YMCK image data to a recording unit and sequentially superimposing the color images of each color while reproducing them in a transfer unit for each color to reproduce a color image. There is. In such a color image forming apparatus, there is a problem that a color image cannot be faithfully reproduced unless images of the respective colors are accurately superimposed on each transfer unit. This is a major development challenge.

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 image of each color is experimentally formed,
A registration adjustment is performed in which the positional relationship between the pattern images of the respective colors is mutually confirmed, and the image forming position is adjusted for each image forming unit of the respective colors (see Japanese Patent No. 2642351).

However, even if the above-described registration adjustment is performed, the "color shift" due to the "shift of the image writing start position" can be corrected, but the period of the drive system such as the drive gear for driving the photosensitive drum can be corrected. It has been impossible to correct the color misregistration caused by irregular speed fluctuations of the photosensitive drum caused by irregular driving. In other words, in such an image forming apparatus, there has conventionally been a problem of driving unevenness that periodically occurs in each recording unit of an image. When the images recorded with the color materials are sequentially superimposed and reproduced as a color image, there is a problem that 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 drum in each recording section is transferred in the transfer section, the condition of the drive unevenness that occurs periodically becomes the same. In this way, it is considered that the relationship between the distance (time) from the position where the image is written to the photosensitive drum to the transfer position and the drive fluctuation cycle of the drive mechanism is N times as large as the relationship (Japanese Patent Publication No. Hei 7 (1994)). -31446
And Japanese Patent Publication No. 8-14731.

FIG. 9 shows a configuration of a conventional color image forming apparatus employing the above-described method, around each image forming section and a transfer conveyance belt for conveying a transfer material for transferring an image formed by each image forming section. Is shown. In FIG. 9, the photosensitive drums 322a, 322b, 322c, 322 constituting black, cyan, magenta, and yellow recording units in order from the right.
d. The images of the respective colors formed by the photosensitive drums 322a to 322d are transferred to a transfer material (not shown) supported and transported by the transfer and transport belt 316 as the transfer and transport belt 316 moves. At the transfer portion A where the conveyance belt is close to the transfer belt, the transfer is performed in a superimposed order from black ink. Here, each photosensitive drum 322a
Drives 322d to 322d are connected so that rotation starts at the same time, and each photosensitive drum is mounted such that the rotation drive unevenness is the same.

As a specific example, each photosensitive drum 322
The drive gears (not shown) into which the drive shafts a to 322d (not shown) are fitted are arranged such that all the reference (for example, a key-shaped hole as shown) indicating the period of the drive unevenness are aligned in the same direction. Attached to. Thus, at the same time, each photosensitive drum always rotates with the same drive unevenness. Therefore, by setting each distance L ′ between the transfer portions of the respective photosensitive drums such that L ′ = Nπd (where N is an integer), where D is the diameter of the photosensitive drum, as shown in FIG. In the image transfer process in each transfer section A of the four photosensitive drums 322a to 322d arranged in parallel, images formed of color materials of each color are sequentially sequentially formed on the transfer material at the same drive unevenness cycle. As a result, they are superposed, and as a result, color shift caused by driving unevenness is eliminated.

[0008]

However, in the above-described conventional configuration, the distance relationship between the recording units arranged in parallel must be arranged in accordance with the periodic drive fluctuation. When the distance between the recording units is determined in accordance with the periodic drive fluctuation, even if the integer N is 1, a distance corresponding to the peripheral length of the photosensitive drum is necessarily required. As a result, the size of the image forming apparatus itself becomes large, so that not only can the size of the image forming apparatus desired by the user not be reduced, but also the assembling work of each part requires a long time and each part has a high precision. Is required and the production cost increases.

On the other hand, a color shift of each component color image or a rotational position shift of each of the photosensitive drums 322a to 322d is detected.
In an apparatus that always corrects the phase of each recording unit, the phase of the photosensitive drum of each recording unit is constantly controlled to adjust the phase with respect to the generated shift. In this case, the phase adjustment control is also performed for a minute phase shift of each photosensitive drum that does not significantly affect the color shift of the image. In order to match the phase of the photosensitive drum, rubbing occurs between the photosensitive drum and the recording medium or the transfer carrier, which damages the photosensitive drum, greatly affects the life of the photosensitive drum, and significantly shortens the life cycle. There was a problem.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and it has been proposed that, as in the prior art, periodic drive fluctuations in the recording units arranged in parallel (perpendicular to the direction of flow of the transfer and conveyance belt). Image formation that can be faithfully reproduced as a single color image correspondingly, yet the size of the device itself can be made compact even with the same diameter image carrier, and the installation area in an office environment can be minimized. It is intended to provide a device.

Further, the timing shift and the phase matching control of the start and stop of the driving of the image carrier such as the photosensitive drum and the contact portion of the transfer conveyance belt contacting the transfer portion of the image carrier are performed. An image forming apparatus capable of minimizing deterioration of the image carrier and the transfer carrier due to abrasion of the image carrier and the transfer carrier caused thereby, and reproducing a faithful image over the entire circumference of the image carrier. The purpose is to provide.

[0012]

The present invention has the following configuration to achieve the above object. According to the first aspect of the present invention, a plurality of image carriers, a driving unit for driving the image carriers to rotate, and detecting a rotation state of each of the image carriers when the image carriers are rotating. Detecting means for controlling the driving means based on a detection signal of the detecting means to stop the image carrier at a preset rotational phase state; If the signal has a deviation greater than or equal to a predetermined allowable value with respect to a predetermined timing, the phase matching means is executed, and if the deviation does not exceed the allowable value, the phase matching means is not executed. An image forming apparatus characterized in that:

According to a second aspect of the present invention, when the detection signal of the detection means does not exceed a predetermined allowable value with respect to a predetermined timing, the phase adjustment means is not executed, and 2. The image forming apparatus according to claim 1, wherein the rotation of the image carrier is stopped at the same time.

According to a third aspect of the present invention, when a plurality of image carriers are simultaneously stopped, all the image carriers are stopped based on a predetermined image carrier detection signal. Item 3. An image forming apparatus according to Item 2.

According to a fourth aspect of the present invention, the permissible value serving as a criterion for judging execution of the phase adjustment stop control is provided separately from a phase adjustment unit amount for presetting a stop position of each image carrier. 2. The image forming apparatus according to claim 1, wherein said phase adjustment unit amount is smaller than said phase adjustment unit amount.

According to a fifth aspect of the present invention, there is provided the image forming apparatus according to the first aspect, wherein the allowable value serving as a criterion for judging execution of the phase adjustment stop control can be changed.

According to the first aspect of the present invention, the rotational phase state between the image carriers is set in advance only when the rotational phase of any one of the plurality of image carriers deviates from the predetermined rotational phase state. The stop position of the image carrier is controlled by performing phase matching control so as to reset the set rotation phase state, but when any of the image carriers has a rotation phase within a predetermined deviation, Does not execute the phase matching means.

Therefore, the phase adjustment is performed only when the magnitude of the deviation of the rotational phase state actually exceeds the allowable value regardless of the large number of copies, the long-time operation of the apparatus, and other environmental changes or troubles. Since the control is performed and the phase adjustment control is not performed if the value does not exceed the allowable value, the phase control is always performed, the image is held after a predetermined number of copies, after a predetermined time of operation, or after a predetermined environmental change or trouble occurs. The rotation operation for performing unnecessary phase adjustment control of the body and the accompanying rubbing and abrasion of the image carrier can be prevented as much as possible, so that the service life of the image carrier can be prolonged and energy can be saved.

According to the second aspect of the present invention, when the rotational phase relationship between the plurality of image carriers is within a predetermined range, the rotational phase state between the image carriers is changed to a preset rotational phase state. All the image carriers are simply stopped at the same time without performing the phase adjustment control to reset the image carrier. In other words, even if the rotational phase state between the plurality of image carriers does not completely match the preset state, if the color misregistration is less than a preset allowable value that is not conspicuous, the phase adjustment stop control is not performed. ,
The stop position does not need to be stopped at a preset stop position. If the stop is performed at any point, the shift of the rotational phase state of all image carriers remains within the allowable range.

Therefore, even after a large amount of copying, a long-time operation of the apparatus, a change in the surrounding environment, or the occurrence of a minor trouble, the deviation of the image carriers from the preset rotational phase state is within an allowable value range. Then, all the image carriers are stopped at the same time irrespective of the set stop position of each image carrier without performing the phase adjustment control at all,
All the image carrier rotation operations become the same, so that rubbing of the transfer carrier in contact with the image carrier is reduced, and mutual wear is reduced. Further, as compared with a conventional apparatus that always performs phase adjustment control, useless rotation of the image carrier can be prevented as much as possible, and not only can the rotation time of the image carrier be shortened, but the life of the image carrier can be prolonged. It is also very useful for energy saving.

According to the third aspect of the present invention, the rotation of all the image carriers can be stopped by the same operation using the control program for any one image carrier serving as a reference. All the image carriers can be stopped while maintaining the rotational phase state between the carriers. Therefore, since it is not necessary to perform different control for each image carrier, not only the control is simplified, but also unnecessary rotation operation of the image carrier can be prevented as much as possible in comparison with a conventional apparatus that always performs phase adjustment control. Not only can the rotation time of the image carrier be shortened and the life of the image carrier can be prolonged, but it is also very useful for saving energy.

According to the fourth aspect of the present invention, whether or not to execute the phase adjustment control separately from the unit amount of the phase adjustment for setting the stop position of each image carrier for setting the rotational phase state of the image carrier. By separately providing an allowable value of the phase shift amount as a reference for judging, the allowable value of the phase shift amount can be changed when the occurrence of color shift is conspicuous, and the allowable value of the phase shift amount is made smaller than the phase adjustment unit amount (preferably 1 / 2 or less), it is possible to prevent a large shift in the rotational phase state, and it is possible to set phase matching control according to the state of the apparatus.

According to the fifth aspect of the present invention, the allowable value for judging whether or not to execute the phase matching control can be changed, so that the color shift is conspicuous at the set allowable value. By changing the allowable value in the case where the color shift occurs, the criterion for judging the phase shift can be made strict and a color shift occurrence trouble can be prevented. In addition, the allowable value can be increased in a range where the occurrence of color shift is not conspicuous, the criterion for determining the phase shift can be lowered, the phase adjustment control of the image holder can be reduced as much as possible, and the useless rotation of the image carrier can be performed. Can be prevented.

[0024]

Embodiments of the present invention will be described below in detail with reference to the drawings. An embodiment according to 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 11
1 is supported in an openable and closable manner, and has a predetermined positional relationship with respect to the surface of the document table 111, and a two-sided automatic document feeder (RADF;
Document Feeder) 112 is mounted.

The double-sided automatic document feeder 112 first conveys the document so that one side of the document faces the image reading unit 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 section 110 is disposed 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 1
Document scanning body 11 reciprocating in parallel along the lower surface of 11
3, 114, an optical lens 115, and a CCD line sensor 116 as a photoelectric conversion element.

The original scanning members 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 has second and third mirrors for further deflecting the reflected light image from the document deflected by the first mirror of the first scanning unit 113 in a predetermined direction. It reciprocates in parallel with one scanning unit 113 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), B
(Blue), which is a three-line color CCD capable of outputting line data that is color-separated into the respective color components of (blue). This C
The document image information converted into an electric signal by the CD 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, a recording medium such as paper or OHP paper) P stored and stored in the paper tray TR is separated one by one and supplied to the image forming unit 210. A paper 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 2 in synchronization with the image forming of the image forming unit 210.
10 and re-conveyed.

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. Further, a pattern image detection unit 300 that detects a test pattern formed on the transfer / transport belt 216 is provided near the lower side of the rotation orbit of the transfer / transport belt 216.

Further, on the downstream side of the transfer transport belt mechanism 213 in the paper transport 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 that has passed 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 discharged.

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.

Above the transfer belt 216 in the image forming section 210, a first image forming station Pa, a second image forming station Pb, and a third image forming station are disposed adjacent to the transfer belt 216. P
c, and a fourth image forming station Pd are provided in order from the upstream side of the paper transport path.

The transfer conveyance belt 216 is driven by the driving roller 21.
4, the sheet P is frictionally driven in the direction indicated by the arrow Z in FIG. 1, grips the sheet P fed through the sheet feeding mechanism 211 as described above, and transfers the sheet P to the image forming station Pa.
To Pd. Each image station Pa-P
d has substantially the same configuration. Each of the image stations Pa, Pb, Pc, and Pd has a photosensitive drum 222a, 222b, which is rotationally driven in the direction of arrow F shown in FIG.
222c and 222d, respectively.

Around the photosensitive drums 222a to 222d, chargers 223a, 223b, 223c, 22 for uniformly charging the photosensitive drums 222a to 222d, respectively.
3d and developing devices 224a and 224 for developing electrostatic latent images formed on the photosensitive drums 222a to 222d, respectively.
4b, 224c, 224d and transfer dischargers 225a, 225b, 225c, 225d for transferring the developed toner images on the photosensitive drums 222a to 222d to the paper P.
Cleaning devices 226a, 226b, and 2 for removing toner remaining on photoconductor drums 222a to 222d.
26e and 226d are photosensitive drums 222a to 222d
Are sequentially arranged along the rotation direction.

Each of the photosensitive drums 222a to 222d
Above the laser beam scanner unit 227
a, 227b, 227c, and 227d are provided, respectively. Each laser beam scanner unit 227a-
Reference numeral 227d denotes a semiconductor laser device (not shown) for emitting dot light modulated according to image data, a polygon mirror (deflecting device) 240 for deflecting a laser beam from the semiconductor laser device in the main scanning direction, and a polygon. It is composed of an fθ lens 241 and mirrors 242 and 243 for imaging the laser beam deflected by the mirror 240 on the surfaces of the photosensitive drums 222a to 222d.

The laser beam scanner 227a receives a pixel signal corresponding to a black component image of a color original image, the laser beam scanner 227b receives a pixel signal corresponding to a cyan component image of a color original image, and the laser beam scanner 227c. The pixel signal corresponding to the magenta color component image of the color original image is output to the laser beam scanner 2
A pixel signal corresponding to the yellow component image of the color document image is input to 27d.

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. The developing device 227a receives the black toner, the developing device 227b receives the cyan toner, the developing device 227c receives the magenta toner, and the developing device 227c.
27d contains yellow toner, respectively, and the electrostatic latent images on the photosensitive drums 222a to 222d are:
The image is developed with the toner of each color. 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, between the fourth image station Pd and the fixing device 217, a cathode (not shown) is provided almost directly above the drive roller 214. 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. The paper P is transferred to the transfer conveyor belt 2 rotating in the direction of arrow Z 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 / conveying belt 216 by the negative discharger.
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 scanner unit 2
Optical writing to the photoreceptor is performed by exposing the laser beam by scanning with the laser beams 27a to 227d.

Note that a writing optical system (LED head) composed of 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.

Next, the control of the rotational phase of each photosensitive drum, which is a feature of the present embodiment, will be described. In the digital color copying machine of this embodiment, as shown in FIG. 2, unlike the conventional image forming apparatus shown in FIG. 9, the four photoconductor drums 222a to 222d of the image forming stations Pa to Pd are provided. , Rotation of the photoconductor drum rotation drive unevenness (common to each photoconductor drum if the phase is the same), the phase is shifted by a predetermined amount (in the image, the expansion / contraction phase of each color component image matches) Driven. More specifically, the photosensitive drums start rotating at the same time and stop rotating at the same time. Therefore, the stop positions (rotation start positions) are shifted and stopped. In the future, each photoconductor drum will be rotated with its phase shifted so that the expansion and contraction of each color component image on the image will match, but the rotation phase status of each photoconductor drum will be The description will be made with the description that the state is the predetermined state.

In FIG. 2, similarly to FIG. 9, in order to correct the phase shift in each photosensitive drum, a predetermined positional relationship with respect to the rotationally driven shaft (condition where periodic driving unevenness is constant). Each photoconductor drum is shifted by a predetermined angle (the difference between the circumference of the photoconductor drum and the distance between the transfer sections of adjacent photoconductors) by taking into consideration that the photoconductor drums are attached in the following manner. To stop in a state where
A key-shaped hole (or convex portion) ha of a drive gear attached to a shaft is shown as a reference.

Now, with reference to the black photosensitive drum 222a, the cyan photosensitive drum 222b
Is advanced by about 60 degrees. Similarly, the phase of the magenta photosensitive drum 222c is advanced by 120 degrees, and the phase of the yellow photosensitive drum 222d is advanced by 180 degrees. As described above, the phase of the drive unevenness in each photosensitive drum is shifted, so that each image forming station P
Even if the distance between the transfer portions A-A corresponding to a to Pd is made smaller than the peripheral length of the photosensitive drum, the drive unevenness between the respective photosensitive drums can be the same for the transfer material passing through the transfer portion A. .
In addition, by shifting in the opposite direction, the distance between A and A can be made longer than the circumference of the photosensitive drum.

As described above, if the diameter of the photosensitive drum is d by advancing the period of the driving unevenness between adjacent photosensitive drums by 60 degrees, L corresponding to the distance between the transfer portions AA is obtained.
L is the circumference of the photosensitive drum πd × ((360−60) degrees /
360 degrees).

Here, for convenience of explanation, the distance between the transfer sections A-A is set based on the phase shift of each photosensitive drum. However, the distance between the transfer sections A-A is actually set. L may be determined, and the phase shift of each photoconductor drum may be set based on L. 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 10
In the case of 5 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.

The manner in which the images of the respective photosensitive drums are superimposed without any color shift due to driving unevenness will be described with reference to FIG. 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 drive unevenness is indicated by line a for clarity) is the timing of (4) (the timing of the photosensitive drum 222a). 1
After the time required for 80 ° rotation has elapsed),
6 and is superimposed on the image on the cyan photosensitive drum 222b at the timing of (9). Here, an image has already been formed on the cyan photosensitive drum 222b by the laser beam at the timing (6). FIG. 3 (a)
9 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 magenta photosensitive drum 222c 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). Therefore, 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 located at the same position as the black and cyan photosensitive drums at the timings (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. Such four photosensitive drums 222
The rotational drivings a to d are controlled by the control unit CON shown in FIG. 4 on the basis of the reference marks Q that can specify the driving unevenness of each photosensitive drum.

Hereinafter, the rotational drive control (phase matching control) of the photosensitive drum will be described with reference to FIGS.
As shown in FIG. 4, in the holes of the drive gears G1 to G4 for transmitting the rotational drive force to the photosensitive drums 222a to 222d in the digital color copying machine of the present embodiment, a key-shaped mark (convex portion) ha is provided.
And the pins provided on the shafts are engaged with the projections ha, so that any of the shafts connected to the drive mechanism having the same configuration is rotationally driven with a constant periodic drive unevenness characteristic. It will be. Since the image carrier (photosensitive drum) is also supported in a predetermined positional relationship with respect to the shaft that is rotationally driven, the periodic drive unevenness in each photosensitive drum is reduced. , All become almost identical.

Further, as shown in FIG.
G4 are detected by the detection sensors S1 to S4 including optical sensors and the like. Each of the sensors S1 to S4 is attached at the same position from each transfer portion A. The sensor output is sent to the control unit CON, and based on this, the control unit CON controls each motor M that drives each photoconductor drum independently and rotationally. The sensors S1 to S4 are connected to the drive gear G1.
It is described that the stop position of the photosensitive drum is controlled by detecting the reference mark Q attached to G4 to G4. However, in another sequence, the detection of the reference mark Q It is also used as a reference for correcting the conditions for forming an image formed on the body drum. (For details, refer to JP-A-6-51551)

The control unit CON includes first control means for controlling an image forming process on the photosensitive drum based on detection results (signals) from the respective sensors based on different sequences, and a stop position of each photosensitive drum is determined. And a second control means for controlling so as to surely stop at the respective stop positions so as to satisfy the following positional relationship. When the respective control sequences reach a predetermined condition and a predetermined timing (timing), the control sequence is automatically performed. Will be

FIG. 5 is a timing chart showing the outputs of the sensors S1 to S4 when the photosensitive drum is stopped.
The pattern Q is detected and turned on sequentially from the sensor S4 of the photosensitive drum 222d located on the downstream side, and the sensor Sl of the photosensitive drum 222a located on the most upstream side is turned on last.
I do. The time when the pattern Q shown in FIG. 4 reaches the transfer portion A (here, the time for rotating about 90 degrees) after the last sensor S1 is turned on is defined as a margin time and a margin angle. The photosensitive drum 222a is stopped. Then, the photosensitive drums 2 other than the reference photosensitive drum 222a
At 22b to 22d, the correction amount is detected from the detection results of the sensors S2 to S4 and the detection result of the sensor S1, and the correction amount is added to the margin time, and then stopped when the time has elapsed.

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
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, after the sensor S1 is turned ON, a margin time of 89 degrees elapses, and then the operation is stopped.

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.
In the case of minus, since the stop position has already been passed, it is necessary to make another rotation to stop at the correct position.
Although the surface or the surface of the photoconductor drum may be damaged by contact, the above-described configuration can stop the recording in a state where an ideal image can be recorded in a short time while suppressing damage and the like. Recording can be done smoothly.

A stepping motor is most suitable as a motor for individually driving the photosensitive drums.

Even if the dimension between the transfer portions A-A is set with high accuracy, if the mounting position of the photosensitive drum shifts and there is an error of only 100 μm in the dimension, 600 dpi (one dot of one dot) (Diameter: about 43μm)
In such an image forming apparatus for high-density recording, a large color shift appears. 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, an error is likely to occur in the mounting position of the above-described sensors S1 to S4. Therefore, it is desirable that the configuration be such that such an error can be corrected.

More specifically, the above-mentioned margin time (margin angle)
Can be adjusted for each photosensitive drum.
That is, in the above description, the spare time is set to 90 degrees for all four photosensitive drums.
It is only necessary to correct each of them in advance in accordance with the dimensional error between the transfer units and to add (subtract) the correction amount at the time of stopping to the corrected margin time.

Further, since it is difficult to correct these errors in advance, the stop position of each photoconductor is automatically or manually adjusted by outputting a specific test image in an adjustment process after the assembly is completed. May be used.

FIG. 6 shows a method of adjusting the stop positions of the photosensitive drums 222a to 222d by manual setting.
This will be described with reference to FIGS. The apparatus is changed to the adjustment mode (simulation mode) by operating a plurality of predetermined keys from an operation panel (not shown), and the stop position of each photosensitive drum and the deviation from the set phase state are displayed on the touch display screen TP on the operation panel. Screens (FIGS. 6 and 7) for displaying the limit values (allowable values) of the above are set, and the values and the like are set and changed. Here, the limit value (permissible value) is the limit (permissible) phase shift amount (angle) serving as a criterion for determining whether to execute or not to perform the above-described photoconductor drum rotational drive control (phase matching stop position control). Or the number of driving steps of the driving means).

First, a photosensitive drum position setting screen 300
Is displayed and the cursor 306 is displayed using the selection keys 301 and 302.
To select a limit value or a recording color (the stop position of the photosensitive drum for forming an image of the described color is indicated by a color name display).

The set value of the stop position of the photosensitive drum is coded and a desired value is inputted by using a numeric key (not shown) on the operation panel. That is, the stop position of the photosensitive drum is [1] is 60 relative to the reference photosensitive drum.
Degrees, [2] is 120 degrees, [3] is 180 degrees, [4] is 2
40 degrees and [5] are positions advanced (or delayed) by 300 degrees, and these [1] to [5] are set in the setting window 3
By inputting to 05, the stop position of the photosensitive drum of each color except the reference color is set.

In the present embodiment, the reference color is black, and the photosensitive drum 222a for forming a black component image does not input the stop position. The photosensitive drum 222a for the black component is always at a predetermined position. Although the stop is performed, the stop position of the photosensitive drum 222a for the black component may be set, or may be automatically set according to the conditions.

In the present embodiment, the phase shift adjustment amount of the photosensitive drum is set to 60 degrees. However, the present invention is not limited to this, and a value such as 30 degrees or 90 degrees may be used.
Preferably, it is 90 degrees or less. The set value at the time of input setting is determined by pressing the OK key 303 after inputting the numerical value of the numeric keys, or by operating the selection keys 301 and 302 as it is.

To set a limit value (permissible value) as a criterion for determining whether or not to execute the phase adjustment stop position control of the photosensitive drum, select the uppermost LIMIT by operating the select keys 301 and 302. The value can be set by setting the value of the setting window 305 to one of [1] to [3] using the numeric keys on the operation panel. Here [1] is 10 degrees, [2]
Is set to 20 degrees and [3] is set to 30 degrees, and is set to a value smaller than the position (phase) adjustment unit amount of each photosensitive drum 60 degrees, but preferably 1/100 of the position (phase) adjustment unit amount.
It is a value of 2 or less. Further, in the present embodiment, the limit value (allowable value) is represented by an angle, but may be the number of driving steps of the driving means. The setting of the limit value (allowable value) is determined by the same operation as the setting of the stop position of the photosensitive drum.

The Execut key 304 is a key for executing a sample output of a test image in the set phase state of each photosensitive drum. The adjustment result can be viewed immediately after the setting, and if there is a problem, the setting is reset immediately. You can do it.

In this embodiment, the phase adjustment unit amount is 60
Although the case where the degree is fixed has been described, it is possible to select and perform a rough phase setting or a fine phase setting by changing the unit amount. In this case, the limit value (permissible value) of the phase shift is also automatically determined according to the selection of the phase adjustment unit amount, and the value is smaller than the phase adjustment unit amount, and preferably １ ／ or less of the phase adjustment unit amount. It is good to set to the value of.

Next, the control of stopping the photosensitive drum when the phase shift amount of the photosensitive drum according to the present invention is equal to or larger than the limit value (permissible value) will be described with reference to the flowchart of FIG. At the end of forming each color component image for color printing on paper (step (hereinafter abbreviated as “ST”) 1), reference mark Q attached to the surface of each photosensitive drum
Are respectively detected by the detection sensors S1 to S4 including an optical sensor or the like (ST2). These detection sensors S1 to S4
The phase corresponding to a preset stop position relationship with respect to the photosensitive drum 222a that forms a black component image based on the rotational phase state of all the photosensitive drums is checked based on the detection signal of Limit value (allowable value)
Is set to, for example, 30 degrees, it is determined whether or not the angle falls within a range of ± 30 degrees (ST3). If any of the determination results for the remaining photosensitive drums 222b to 222d excluding the reference photosensitive drum 222a has a phase shift of 30 degrees or more of the limit value (allowable value), the shift from the set value is performed. The phase adjustment stop control for controlling the stop timing is performed so that there is no stop, and all the photosensitive drums 222a to 222d are stopped at a preset stop position (ST4).

If the result of the phase shift determination with respect to the remaining photosensitive drums 222b to 222d excluding the reference photosensitive drum 222a is less than the limit value (allowable value) of 30 degrees, the above-mentioned phase matching is regarded as a range in which the color shift is inconspicuous. The stop control is not performed, and all the photosensitive drums 222a to 222d are simultaneously driven to stop at the stop timing based on the detection signal of the reference photosensitive drum 222a based on the detection signal of the detection sensor Sl by driving the stepping motor which is the driving means. (ST5). At this time, the rotational phase state of all the photosensitive drums is shifted from a phase state corresponding to a preset stop state within a limit value (allowable value). The stop position of the photosensitive drum 222a may or may not be a preset stop position. Naturally, the photosensitive drum serving as a reference need not be the photosensitive drum 222a for forming a black component image, and the number of photosensitive drums may be two, three, or more than four instead of four.

As described above, the detection sensors S2 to S
When the detection signal of No. 4 deviates by more than the limit value (permissible value), the phase adjustment control of the photosensitive drum is executed, but when the deviation of the detection signal does not exceed the permissible value where the color deviation is not conspicuous, Is not executed, the other photosensitive drums 222b to 222d are stopped simultaneously with the stop of the rotation of the photosensitive drum 222a simply as a reference, so that the phase control is always performed, or after a predetermined number of copies or after a predetermined time of operation. Rotation operation for performing unnecessary phase adjustment control of the image carrier after occurrence of a predetermined environmental change or trouble, and the accompanying rubbing wear of the image carrier can be prevented as much as possible, and the life of the image carrier is prolonged. Not only can you save money, but it can also help save energy.

By stopping the rotation of the other photosensitive drum by the same operation using the control program for any one of the photosensitive drums as a reference, the rotational phase between the photosensitive drums before the stop is stopped. By stopping all the photosensitive drums while maintaining the state, it is not necessary to perform different control for each of the photosensitive drums, so that not only the control is simplified,
As compared with a conventional apparatus that always performs phase matching control, useless rotation of the photosensitive drum can be prevented as much as possible. If the deviation is within the allowable value, the stop position of the photoconductor drum is not limited, and the photoconductor drum may be stopped in any rotational state, so that unnecessary rotation operation of the photoconductor drum can be prevented as much as possible.

Further, by providing an allowable value separately from the unit amount of the phase adjustment for setting the stop position of the photosensitive drum, the allowable value can be changed when the occurrence of color shift is conspicuous. (Preferably 1 /
2 or less), it is possible to prevent the deviation of the rotational phase state from being largely deviated, and it is possible to set the phase alignment control according to the state of the apparatus.

Further, since the allowable value for determining whether or not to execute the phase matching control can be changed, the allowable value can be changed when the set allowable value causes a state in which color misregistration is conspicuous. As a result, the criterion for judging the phase shift can be made strict, and the occurrence of a color shift can be prevented. In addition, the allowable value can be increased in a range where the occurrence of color misregistration is inconspicuous, the criteria for judging the phase misregistration can be reduced, the phase adjustment control of the photosensitive drum can be reduced as much as possible, and the useless rotation of the photosensitive drum Can be prevented.

When the stop position of each photosensitive drum is automatically set based on a preset phase adjustment unit amount, the allowable value does not have to be set every time. In addition, it is possible to prevent troubles such as the allowable position being larger than the phase adjustment unit amount.

[0078]

As described above, according to the first aspect of the present invention, the rotational phase state is actually shifted irrespective of the copying of a large number of sheets, the long-time operation of the apparatus, and other environmental changes or troubles. The phase adjustment control is performed only when the size exceeds the allowable value, and the phase adjustment control is not performed when the size does not exceed the allowable value. After the occurrence of a predetermined environmental change or trouble, etc., it is possible to minimize the rotation operation of performing unnecessary phase adjustment control of the image carrier and the accompanying rubbing wear of the image carrier, thereby extending the life of the image carrier. Not only is it possible, but it also helps save energy.

According to the second aspect of the present invention, even if a large amount of copying is performed, the apparatus is operated for a long time, the surrounding environment is changed, or a minor trouble occurs, the predetermined rotational phase state between the image carriers is maintained. If the deviation is within the allowable value range, all the image carriers are stopped at the same time irrespective of the set stop position of each image carrier without performing any phase adjustment control. The body rotation operation becomes the same, so that the rubbing of the transfer carrier in contact with the image carrier is reduced, and the mutual wear is reduced. Further, as compared with a conventional apparatus that always performs phase adjustment control, useless rotation of the image carrier can be prevented as much as possible, and not only can the rotation time of the image carrier be shortened, but the life of the image carrier can be prolonged. It is also very useful for energy saving.

According to the third aspect of the present invention, since different controls need not be performed for each image carrier, not only the control is simplified, but also the image carrier is controlled as compared with the conventional apparatus which always performs the phase adjustment control. Unnecessary rotation of the body can be prevented as much as possible, so that the rotation time of the image carrier can be shortened and the life of the image carrier can be prolonged.

According to the fourth aspect of the invention, when the occurrence of color shift is conspicuous, the allowable value of the phase shift amount can be changed, and it is made smaller than the phase adjustment unit amount (preferably に す る or less). As a result, it is possible to prevent the deviation of the rotation phase state from being largely deviated, and it is possible to set the phase adjustment control according to the state of the apparatus.

According to the fifth aspect of the present invention, the criterion for determining a phase shift is made strict by enabling the allowable value to be changed when a state in which the color shift is conspicuous occurs with the set allowable value. And the occurrence of color misregistration can be prevented. In addition, the allowable value can be increased in a range where the occurrence of color shift is not conspicuous, the criterion for determining the phase shift can be lowered, the phase adjustment control of the image holder can be reduced as much as possible, and the useless rotation of the image carrier can be performed. Can be prevented.

[Brief description of the drawings]

FIG. 1 is an operational explanatory diagram showing a side cross section of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is an operational explanatory diagram of a plurality of photosensitive drums arranged in parallel according to an embodiment of the present invention in a phase matching state;

FIG. 3 is an operational explanatory diagram illustrating an overlapping state of images on a plurality of photosensitive drums according to the embodiment of the present invention.

FIG. 4 is an explanatory diagram of phase control of a plurality of arranged photosensitive drums according to the embodiment of the present invention.

FIG. 5 is a time chart of an output signal of a sensor for detecting a shift angle of a plurality of photosensitive drums according to the embodiment of the present invention.

FIG. 6 is an explanatory diagram of an operation panel of the image forming apparatus according to the embodiment of the present invention.

FIG. 7 is an explanatory diagram of an operation panel of the image forming apparatus according to the embodiment of the present invention.

FIG. 8 is a flowchart for determining whether to perform phase control of the photosensitive drum according to the embodiment of the present invention.

FIG. 9 is an operational explanatory diagram of a conventional plurality of photosensitive drums arranged in parallel in a phase matching state.

[Explanation of symbols]

 1 Image Forming Apparatus 216 Transfer Belt 222a-222d Photoconductor Drum M Motor Q Reference Mark CON Control Unit G1-G4 Drive Gear S1-S4 Sensor

Continuation of the front page F term (reference) 2H027 DA22 DA38 DE02 DE07 ED02 EE04 HB06 ZA07 2H030 AA01 AB02 AD17 BB02 BB23 BB46 BB56

Claims (5)

[Claims] A plurality of image carriers; a driving unit configured to rotationally drive the image carriers; a detection unit configured to detect a rotation state of each of the image carriers when the image carriers are rotating; A phase matching unit that controls the driving unit based on a detection signal of the detection unit to stop the image carrier at a preset rotation phase state. The detection signal of the detection unit is a predetermined signal. An image characterized in that the phase matching means is executed when a deviation of the timing exceeds a predetermined allowable value, and the phase adjusting means is not executed when the deviation does not exceed the allowable value. Forming equipment. 2. When the detection signal of the detection means does not exceed a predetermined allowable value with respect to a predetermined timing, the rotation of all the image carriers is performed without executing the phase adjustment means. 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is stopped at the same time. 3. The image forming apparatus according to claim 2, wherein when stopping a plurality of image carriers at the same time, all the image carriers are stopped based on a detection signal of a predetermined image carrier. . 4. The above-mentioned permissible value serving as a criterion for judging execution of the phase adjustment stop control is provided separately from a phase adjustment unit amount for presetting a stop position of each image carrier, and is set based on the phase adjustment unit amount. The image forming apparatus according to claim 1, wherein the image forming apparatus is also small. 5. The image forming apparatus according to claim 1, wherein the allowable value serving as a criterion for determining execution of the phase adjustment stop control can be changed.