JP2001356575A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of reproducing a faithful image by restraining the uneven elongation and contraction of the image outputted to image forming paper. SOLUTION: A digital color copying machine is provided with an image reading part 110 and an image forming part 210 inside a copying machine main body 1. Image stations Pa to Pd have the same constitution substantially, and include photoreceptor drums 222a to 222d driven to rotate in a direction shown by an arrow F respectively. The four drums 222a to 222d have the same outside diameter and Length each other. The outside diameter D of the parts 119a and 119a of driving pulleys 119 and 119 around which a wire 118 is wound and the outside diameter(d) of the drums 222a to 222d in the image forming part 210 are formed nearly with the same dimension.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading section for reading image data from an original by driving a scanning optical system with a wire, and an image forming section for forming an image by a photosensitive drum which is driven to rotate. And an image forming apparatus having the same.

[0002]

2. Description of the Related Art Conventionally, as a color image forming apparatus, a color image is formed by transferring a color image as YMCK image data to a recording unit and sequentially superimposing the color images while reproducing each color image. There is a device.

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 problem in technical development. It has become.

[0004] In an image forming apparatus having an infinite number of components, there is a small variation in the component accuracy of each type of component, and the variation varies in each image forming device due to the assembling accuracy when assembling these components. Or occur.

Therefore, conventionally, a pattern image of each color is formed on a trial basis, the positional relationship between the pattern images of each color is confirmed with each other, and a registration adjustment for adjusting the image forming position for each image forming unit of each color is performed. (Japanese Patent No. 2642)
351).

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 periodic drive of a drive system such as a drive gear for driving the photosensitive drum can be performed. It is not possible to correct color misregistration caused by irregular speed fluctuations of the photosensitive drum due to unevenness.

That is, in such an image forming apparatus, there has conventionally been a problem of periodic driving unevenness in each recording section, and the periodic driving unevenness occurs in each of the recording sections, so that each color has a problem. When images recorded with color materials are sequentially superimposed and reproduced as a color image, a color shift occurs, so that there is a problem that a faithful color image cannot be reproduced.

Therefore, in the conventional color image forming apparatus, when the image formed on the photoreceptor in each recording section is transferred in the transfer section, the condition of the drive unevenness that occurs periodically becomes the same. In addition, it is considered that the relationship between the distance (time) from the image writing position to the transfer position to the transfer position and the drive fluctuation cycle of the drive mechanism is N times (N is an integer). (Tokuhei 7-314
No. 46, Japanese Patent Publication No. 8-14731, etc.).

FIG. 12 shows the structure of each image forming section in a conventional color image forming apparatus employing the above-described technique, and the vicinity of a transfer / conveying belt for conveying a transfer material for transferring an image formed in each image forming section. Is shown.

In FIG. 12, four photosensitive drums are
Photosensitive drums 322a... Constituting black, cyan, magenta, and yellow recording sections in order from the right. 322b.
322c. 322d. These photosensitive drums 32
The images of the respective colors formed in 2a to 322d are transferred with the transfer / transport belt 316 as the transfer / transport belt 316 moves.
The photosensitive drums 322a to 322d and the transfer / transport belt are transferred in a superimposed order from black on a transfer material (not shown) supported and conveyed in the order from black.

Here, each photosensitive drum 322a-322
The drive d is connected so that the rotation is started at the same time, and is attached so that the rotation drive unevenness has the same phase.

As a specific example, each photosensitive drum 322
The drive gears to which the shafts a to 322d are fitted are mounted such that all the references (for example, a key-shaped hole ha as shown in the drawing) indicating the period of the drive unevenness are aligned in the same direction.
Thereby, at the same time, each photosensitive drum 32
2a to 322d always rotate with the same drive unevenness.

Therefore, the adjacent photosensitive drums 322
The distance L 'between the transfer portions a through 322d is defined as L' = Nπd, where d is the diameter of the photosensitive drums 322a through 322d.
(N is an integer), the image formed by the color material of each color is transferred to the transfer material in the image transfer process in each transfer unit of the four photosensitive drums 322a to 322d arranged in parallel. It is always superimposed on the upper part at the same drive unevenness cycle, and as a result, it is possible to eliminate color shift caused by drive unevenness.

[0014]

However, in the above-described conventional configuration, the purpose of improving the faithful image formation at the time of image formation by matching the phases of the respective portions in the image forming section is to improve the image data itself. If the image has unevenness in expansion and contraction, no matter how much the phases of the operations of the respective parts of the image forming apparatus are matched, the image does not become faithful to the image of the original before being read.

That is, unless unevenness is generated in image data generation by the reading device, image unevenness occurs during reading, and even if the image forming apparatus is controlled with high precision, the same duplication without expansion and contraction unevenness as that of the original is generated. Images cannot be formed. In order to reduce the image unevenness at the time of reading, it is necessary to make the dimensional accuracy of the driving pulley for scanning the optical system of the reading device and the dimensional accuracy of the transmission mechanism extremely high, thereby increasing the manufacturing cost. .

The present invention has been made in view of such circumstances, and provides an image forming apparatus capable of suppressing unevenness in expansion and contraction of an image output on image forming paper and reproducing a faithful image. It is an object.

[0017]

According to the present invention, there is provided a scanning optical system for scanning a document, a driving pulley for driving the scanning optical system by a wire, and a power transmission system for transmitting power to the driving pulley. An image reading unit for reading image data from the original, and writing the image data read by the image reading unit as an electrostatic latent image on a photosensitive drum, developing the written electrostatic latent image, and developing And an image forming unit for transferring the toner image on the photoconductive drum onto the image forming paper. The outer diameter of a portion of the drive pulley of the image reading unit around which the wire is wound and the photoconductive drum of the image forming unit. The outer diameter is formed to almost the same dimensions,
Further, there is provided an image forming apparatus including a control unit that controls so that the phase of rotation unevenness caused by the driving pulley of the image reading unit and the phase of rotation unevenness caused by the photosensitive drum of the image forming unit match each other.

An image forming apparatus according to the present invention includes an image reading unit and an image forming unit. The image reading unit is a part for reading image data from a document, and includes a scanning optical system that scans the document, a driving pulley that drives the scanning optical system with a wire, and a power transmission system that transmits power to the driving pulley. Have. The image forming unit writes the image data read by the image reading unit as an electrostatic latent image on the photosensitive drum, develops the written electrostatic latent image, and converts the developed toner image on the photosensitive drum into an image. It is a part for transferring to a forming paper, and has a photosensitive drum.

In this image forming apparatus, the outer diameter of a portion of the drive pulley of the image reading section around which the wire is wound is substantially the same as the outer diameter of the photosensitive drum of the image forming section. Here, the “substantially the same size” is set to enhance the effect of control by the control unit described below, and the dimensional difference between the two is about 5.0 to about 6.
0% or less, and more preferably about 3.0 to about 4.0.
0% or less, most preferably from about 1.0 to about 2.
It means 0% or less.

The image forming apparatus further includes a characteristic control unit. The control unit controls the phase of the rotation unevenness caused by the driving pulley of the image reading unit to coincide with the phase of the rotation unevenness caused by the photosensitive drum of the image forming unit. With such a control, and since the outer diameter of the portion of the drive pulley around which the wire is wound and the outer diameter of the photosensitive drum are formed to be substantially the same size, unevenness in the expansion and contraction of the read image data is reduced. The phase can be matched with the phase of the rotation unevenness of the photoconductor drum,
A faithful image without unevenness in expansion and contraction can be formed.

In the image forming apparatus according to the present invention, the control unit further controls the phase of the unevenness of expansion and contraction of the image data and the phase of the unevenness of the rotation of the image forming unit due to the photosensitive drum so as to be opposite to each other. It is preferred that

With this configuration, it is possible to reduce the unevenness in expansion and contraction of the image data generated at the time of image reading by the image reading unit at the time of image formation, and it is possible to form a faithful image. .

In the image forming apparatus according to the present invention, the control unit may further cause the phase of the rotation unevenness of the photosensitive drum of the image forming unit to coincide with the phase of the rotation unevenness of the drive pulley of the image reading unit at a predetermined phase. Preferably, it is configured to control.

With this configuration, it is not necessary to store image data in a page memory or the like, and a faithful image formation with less unevenness in expansion and contraction can be realized in real time.

In the image forming apparatus according to the present invention, it is preferable that the control unit further controls writing of image data in accordance with the phase of the rotation unevenness of the photosensitive drum of the image forming unit.

With this configuration, it is possible to reliably form an image in accordance with the rotation non-uniformity of the photosensitive drum so as to reduce the non-uniform expansion and contraction of the image data, and to obtain a faithful image with less non-uniform expansion and contraction. Formation is possible.

In the image forming apparatus according to the present invention, the power transmission system of the image reading unit is provided so as to be position-adjustable, the position of the power transmission system is adjusted, and the control unit is further provided with the image forming unit. It is preferable that the phase of the image data is made to coincide with the phase of the rotation unevenness caused by the photosensitive drum.

With this configuration, the phase of the driving unevenness of the driving pulley of the image reading unit can be matched to the phase of the rotation unevenness of the photosensitive drum, and the expansion / contraction unevenness during image formation is reduced. Image formation becomes possible.

In the image forming apparatus according to the present invention, the photosensitive drums in the image forming section are a plurality of photosensitive drums for forming a color image on which electrostatic latent images corresponding to a plurality of predetermined colors are formed. preferable.

In such a configuration, the rotation phase of each photosensitive drum can be matched with the rotation phase of the drive pulley of the image reading unit so that expansion and contraction can be reduced, and only the expansion and contraction of the image can be achieved. A color image forming apparatus with little color misregistration can be provided at low cost.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment according to the present invention will be described below with reference to the drawings. The present invention is not limited by this.

As shown in FIG. 1, a digital color copying machine, which is an image forming apparatus according to the present invention, has a platen 111 and an operation panel (not shown) provided on the upper surface of a copying machine main body 1. The image reading unit 110 and the image forming unit 210 are provided inside the printer. The upper surface of the platen 111 is supported in an openable and closable manner with respect to the platen 111, while maintaining a predetermined positional relationship with the upper surface of the platen 111, and a duplex automatic document feeder (RADF;
ng Automatic DocumentFeed
er) 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. Then, the document is turned over so that the other surface faces the image reading unit 110 at a predetermined position on the document table 111, and is conveyed toward the document table 111. Then, the double-sided automatic document feeder 112 performs a double-sided conveyance operation for one document. The operation of transporting the original and turning over the original is controlled in relation to the operation of the entire copying machine.

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. As shown in FIGS. 1 and 6, the image reading unit 110
Is a scanning optical system 117 for scanning a document, a driving pulley 119 for driving the scanning optical system 117 by a wire 118, and a power transmission system 1 for transmitting power to the driving pulley 119.
20. The scanning optical system 117 includes the document table 111
Scanning body 113 reciprocating 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 front surface of the document and a first mirror for deflecting a reflected light image from the document in a predetermined direction. Platen 11 at a predetermined scanning speed
Reciprocate in parallel with 1. The second scanning unit 114
A second mirror 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;
A first scanning unit 113 having a mirror and a third mirror;
, And reciprocates in parallel with the document table 111 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. is there.

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
This is a three-line color CCD that can output line data that is color-separated into each color component of (blue). This CC
The document image information converted into an electric signal by the D line sensor 116 is transferred to an image processing unit (not shown), and the image processing unit performs predetermined image data processing.

Below the image forming unit 210, image forming papers (for example, recording media such as plain paper and OHP paper) P stored and housed in the paper tray TR are separated one by one, and are separated into the image forming unit 210. A paper feed mechanism 211 that supplies the paper to the apparatus is provided. Then, the paper P separated and supplied one by one
The sheet is conveyed to the image forming unit 210 with the timing controlled 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 again supplied and conveyed to the image forming unit 210 in synchronization with the image formation of the image forming unit 210.

Below the image forming section 210, a transfer and transport belt mechanism 213 is disposed. The transfer and transport belt mechanism 213 transports the paper P by electrostatically attracting the paper P to a transfer and transport belt 216 stretched so as to extend substantially in parallel between the drive roller 214 and the driven roller 215. The pattern image detection unit 30 detects a test pattern formed on the transfer conveyance belt 216 in the vicinity of the lower side of the rotation trajectory of the transfer conveyance belt 216.
0 is provided.

Further, a fixing device 217 for fixing the toner image transferred and formed on the sheet P on the sheet P, in the vicinity of the driving roller 214, on the downstream side of the transfer and conveying belt mechanism 213 in the sheet conveying path. Is arranged. The sheet P that has passed through the nip between the pair of rollers of the fixing device 217 passes through a conveyance direction switching gate 218 and is connected to a discharge tray 22 attached to a side wall of the copying machine main body 1.
The sheet is discharged by the discharge roller 219 onto the “0”.

The switching gate 218 has a path for discharging the paper P to the copying machine main body 1 and a paper P for the image forming section 210.
Is selectively switched between the feeding route and the feeding route of the sheet P after fixing. 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 is again supplied to the image forming unit 210.

In addition, above the transfer belt 216 in the image forming section 210, the first image forming station Pa, the second image forming station Pb, the third image forming station Pc, and the vicinity of the transfer belt 216. Fourth image forming stations Pd are provided in order from the upstream side to the downstream side of the sheet transport path.

The transfer conveying belt 216 is
4, the sheet P is frictionally driven in the direction indicated by the arrow Z in FIG. 1 and grips the sheet P fed through the sheet feeding mechanism 211 as described above.
To Pd. Each image station Pa-P
d has substantially the same configuration. The image stations Pa, Pb, Pc, and Pd are photosensitive drums 222a, 222b, and 2 that are driven to rotate in the direction of arrow F shown in FIG.
22c and 222d. These four photosensitive drums 222a to 222d have the same outer diameter and length.

Around the photosensitive drums 222a to 222d, chargers 223a, 223b, 223c, 223 for uniformly charging the photosensitive drums 222a to 222d, respectively.
d and developing devices 224a and 224 for developing the electrostatic latent images formed on the photosensitive drums 222a to 222d, respectively.
b, 224c, 224d and the developed photosensitive drum 2
Transfer dischargers 225a, 225b, 225c, 225d for transferring the toner images on the sheets P on the sheets 22a to 222d;
Cleaning devices 226a, 226b, 226 for removing toner remaining on photoconductor drums 222a to 222d
e and 226d are sequentially arranged along the rotation direction (arrow) of the photosensitive drums 222a to 222d.

Above the photosensitive drums 222a to 222d, a laser beam scanner unit 227a,
227b, 227c, and 227d are provided, respectively. Laser beam scanner units 227a to 227
d denotes a semiconductor laser element (not shown) that emits 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; Mirror 24
The laser beam deflected by 0 is applied to the photosensitive drum 22.
Fθ lens 2 for forming an image on the surfaces of 2a to 222d
41 and mirrors 242 and 243, respectively.

The laser beam scanner 227a receives a pixel signal corresponding to the black component image of the color original image, the laser beam scanner 227b receives a pixel signal corresponding to the cyan component image of the 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, the electrostatic latent image corresponding to the color-converted document image information is transferred to each of the photosensitive drums 222a to 222d.
Formed on top. Then, black toner is applied to the developing device 227a, cyan toner is applied to the developing device 227b,
The developing device 227c contains magenta toner, and the developing device 227d contains yellow toner. The electrostatic latent images on the photosensitive drums 222a to 222d are developed with the toners of these colors. As a result, the document image information color-converted by the image forming unit 210 is reproduced as a toner image of each color.

Further, between the first image forming station Pa and the paper feeding mechanism 211, a paper suction (brush) charger 228 is provided. The charger 228 charges the surface of the transfer conveyance belt 216, and the sheet P supplied from the paper feeding mechanism 211 is securely adsorbed on the transfer conveyance belt 216. The sheet is transported without shifting between the four image forming stations Pd.

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

In this digital color copier, cut sheets of plain paper are used as the paper P. The sheet P is sent out from the sheet cassette and fed to the sheet feeding mechanism 21.
When the sheet P is fed into the guide of the sheet feeding conveyance path, the leading end of the sheet P is detected by a sensor (not shown), and temporarily stopped by a pair of registration rollers 212 based on a detection signal output from the sensor. Is done.

Next, the paper P is stored in each image station Pa.
At a timing of .about.Pd, the sheet is fed onto the transfer / conveying belt 216 rotating in the direction of arrow Z in FIG. At this time, since the transfer conveyor belt 216 is charged by the charger 228 as described above, the paper P
Is transported and supplied stably while passing through the image stations Pa to Pd.

In the image stations Pa to Pd,
Each of the toner images of each color is formed,
The paper P is superposed on the support surface of the paper P which is electrostatically attracted and conveyed by 16. When the transfer of the image by the fourth image station Pd is completed, the sheet P is sequentially separated from the transfer conveyance belt 216 by the discharging device for discharging from the leading end thereof, and is guided to the fixing device 217.

Finally, the sheet P on which the toner image is fixed
Is discharged onto a paper discharge tray 220 from a paper discharge port (not shown). In the above description, the laser beams are scanned and exposed by the laser beam scanner units 227a to 227d, whereby the photosensitive drum 22 is exposed.
Optical writing to 2a to 222d is performed.

Incidentally, instead of the laser beam scanner unit, a writing optical system (LED head) comprising a light emitting diode array and an imaging lens array may be used. 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, each of the photosensitive drums 222a to 222d
Will be described. In this digital color copying machine, as shown in FIG. 2, four photosensitive drums 222a to 222d of image forming stations Pa to Pd are used.
However, the phase of the rotational drive unevenness of the photoconductor drums 222a to 222d (common to each photoconductor drum if the phase is matched) is shifted by a predetermined amount (on the image, the phases of expansion and contraction of each color component image are matched). State). More specifically, the photosensitive drums 222a to 222d start rotating at the same time and stop rotating at the same time. Therefore, the stop positions (rotation start positions) are shifted and stopped. Here, each of the photosensitive drums 222a to 222a-2 is actually set so that the expansion and contraction of each color component image on the image match.
The rotation of the photosensitive drums 222a to 222d is described as being in a predetermined state.

In FIG. 2, each photosensitive drum 222a
The photosensitive drums 222a to 222d are mounted with a predetermined positional relationship (a positional relationship where periodic driving unevenness is a constant condition) with respect to the shaft that is driven to rotate, in order to correct the phase shifts of 222d to 222d. In consideration of the above, the state in which each of the photosensitive drums 222a to 222d is stopped at a predetermined angle (difference between the circumferential length of the photosensitive drum and the distance between the transfer units of the adjacent photosensitive members) is stopped by the shaft. Key-shaped hole (or projection) ha of the drive gear to be mounted
It shows based on.

Here, the black photosensitive drum 222a
, The cyan photosensitive drum 22 adjacent thereto
The phase of 2b 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 photosensitive drums 222a to 222a-2
By shifting the phase of the drive unevenness in 22d, the distance between the transfer units A-A corresponding to the respective image forming stations Pa-Pd is changed by the amount of the phase shift.
Even if the photosensitive drums 222a
The drive unevenness of the transfer material passing through the transfer section A can be made the same between the drive unevenness of the transfer material and the transfer material of the transfer material. Further, the distance between the transfer units A-A can be reduced by shifting in the opposite direction.
It is also possible to extend it beyond the perimeter of 22d.

As described above, the adjacent photosensitive drum 22
Assuming that the diameter of the photosensitive drums 222a to 222d is d by advancing the drive unevenness cycle by 60 degrees between 2a to 222d, L corresponding to the distance between the transfer units A-A is L = photosensitive drum 222a to Perimeter of 222d = πd × ((360
−60) degrees / 360 degrees.

Here, for convenience of explanation, each photosensitive drum 2
Although it has been described that the distance between the transfer units A-A is set based on the phase shift in the regions 22a to 222d, in practice, the distance L between the transfer units A-A is determined, and based on that, What is necessary is just to set the phase shift of the body drums 222a to 222d. For example, when the distance L between the transfer units A and A is 105 mm using the photosensitive drums 222a to 222d having a drum diameter of 40 mm, the stop position is between the adjacent photosensitive drums 222a to 222d as described above. Is set so that each driving unevenness causes a phase shift of about 60 degrees.

Here, referring to FIG.
A description will be given of a state in which images for each of 2a to 222d are superimposed without color shift due to driving unevenness.

Now, it is assumed that the four photosensitive drums 222a to 222d are rotating in the state 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 line a for clarity) is the timing of (4) (the position of the photosensitive drum 222a). After the time required for 180 ° rotation has elapsed), the image is transferred onto the transfer / transport belt 216, 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 of (6). FIG. 3A shows (1) to (3).
Cyan photosensitive drum 22 at timing (6)
2b shows the position of line a in FIG.

As is apparent 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 with the image formed at the timing (14). Here, an image has already been formed on the magenta photosensitive drum 222c at the timing (11).

FIG. 3B shows the position of the line a on the magenta photosensitive drum 222c at the timings (1) to (11). As is clear from the figure, (1)
Line a at the timing of 1) is (1), (6)
Photosensitive drum 222 at the timing of
a, at the same position as the cyan photosensitive drum 222b.
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 with the image formed at the timing (19). Therefore, an image is already formed on the yellow photosensitive drum 222d at the timing of (16). FIG. 3C shows the position of the line a on the yellow photosensitive drum 222d at the timings (1) to (16).

As can be seen from the drawing, the line a at the timing (16) corresponds to the black photosensitive drum 222a at the timings (1), (6) and (11).
It is located at the same position as the cyan photosensitive drum 222b. Therefore, the superimposed images have the same driving unevenness,
There is no color shift due to the influence of driving unevenness.

The four photosensitive drums 222a-222
The rotation drive of the photosensitive drums 222 d
Based on the reference mark Q that can specify the 2d driving unevenness, FIG.
Is controlled by the control unit CON shown in FIG.

Hereinafter, based on FIGS. 4 and 5, the rotational drive control (phase matching control) of the photosensitive drums 222a to 222d will be described.
Will be described.

As shown in FIG. 4, a key-shaped mark (convex portion) ha is provided in a hole of a driving gear G1 to G4 for transmitting a rotational driving force to the photosensitive drums 222a to 222d in the digital color copying machine. ing. And the pin provided in the shaft will engage with this convex part ha. Therefore, all the shafts connected to the drive mechanism having the same configuration are rotationally driven with a constant periodic drive unevenness characteristic.

Since the photosensitive drums 222a to 222d are also supported in a predetermined positional relationship with respect to the shaft that is driven to rotate, the photosensitive drums 222a to 222d are periodically rotated. All the driving irregularities are almost the same.

Further, as shown in FIG.
ＧG4 are detected by detection sensors S1 to S4 including optical sensors and the like, respectively.

Each of the sensors S1 to S4 is mounted 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 of the photosensitive drums 222a to 222d independently to rotate.

The sensors S1 to S4 are connected to the drive gear G1.
It is described that the stop positions of the photosensitive drums 222a to 222d are controlled by detecting the reference marks Q attached to G4 to G4. However, the detection of the reference marks Q in another sequence may be performed. Each photosensitive drum 222
a to 222d (refer to Japanese Patent Application Laid-Open No. 6-55151 for details).
No. Gazette).

The control unit CON includes: first control means for controlling an image forming process for the photosensitive drums 222a to 222d based on detection results (signals) from the sensors S1 to S4 based on different sequences; 2
Second control means for controlling the stop positions of the stop positions of 22a to 222d to be surely stopped at the respective stop positions so as to have a predetermined positional relationship. Each control sequence is automatically performed when a predetermined condition and a predetermined timing (timing) are reached.

FIG. 5 shows photosensitive drums 222a to 222d.
4 shows a timing chart of the output of each of the sensors S1 to S4 when stopping the operation. The pattern Q is detected and turned on in order from the sensor S4 of the photosensitive drum 222d located on the downstream side, and the photosensitive drum 222a located on the most upstream side is detected.
Finally, the sensor S1 is turned ON.

The time from when the last sensor S1 is turned on until the pattern Q shown in FIG. 4 reaches the transfer portion A (here, the time for rotating about 90 degrees) is defined as a margin time (margin angle). After the lapse of the allowance time, the photosensitive drum 222
a is stopped.

With respect to the photosensitive drums 222b to 222d other than the reference photosensitive drum 222a, a 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 set aside. After adding to the time, stop 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 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 margin time, and the margin time is 89 degrees. As a minute, the sensor S1 is turned on and stopped after a lapse of a margin time of 89 degrees.

If the margin time is not set, if the correction amount is positive, the photosensitive drum 222b may be further rotated and stopped accordingly.
However, in the case of minus, it has already passed the stop position, so it is necessary to make another rotation to stop at the correct position. Then, the surface of the transfer / transport belt 216 or the surface of the photosensitive drum 222b may be damaged by contact. However, according to the above-described configuration, it is possible to suppress damage and the like and to record an ideal image in a short time. The image can be stopped, and the subsequent image recording can be smoothly performed.

Each of the photosensitive drums 222a to 222d
Is most suitable as the motor M for individually driving the stepping motors.

Further, no matter how precisely the dimension between the transfer portions A-A is set, the photosensitive drums 222a to 222a
If the mounting position of 2d is displaced and there is an error even if the dimension is only 100 μm, it will appear as a large color shift in a high-density recording image forming apparatus of 600 dpi (diameter of one dot: about 43 μm). Therefore, it is preferable that a means for adjusting the stop position of each of the photoconductor drums 222a to 222d be separately provided irrespective of the drive unevenness of the photoconductor drums 222a to 222d. Similarly,
An error is likely to occur in the mounting positions of the sensors S1 to S4, and 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 of the photosensitive drums 222a to 222d. That is, in the above description, the allowance time is set to 90 degrees for all four photosensitive drums 222a to 222d. However, according to the mounting error of the sensors S1 to S4 and the dimensional error between the transfer units A-A, respectively. It is sufficient that the correction is made in advance, and the correction amount at the time of stop is newly added (subtracted) to the corrected margin time.

Further, since it is difficult to correct these errors in advance, by outputting a specific test image in the adjustment process after the assembly is completed, the photosensitive members 222a to 222d can be automatically or manually stopped. The position may be adjusted.

As described above with reference to FIGS. 1 and 6, the image reading section 110 of the digital color copying machine according to the present invention includes a scanning optical system 117 for scanning an original, and the scanning optical system 117 is driven by a wire 118. Drive pulley 11
9 and a power transmission system 120 for transmitting power to the drive pulley 119.

In FIG. 6 to FIG.
Comprises a drive motor 131, a power transmission toothed belt 121 hung on a gear 132 attached to the rotating shaft of the motor 131, and a gear 122 hung on the toothed belt 121. The drive pulley 119 and the gear 122 are fixed to one end of a common rotating shaft 123. A driving pulley 119 is provided at the other end of the rotating shaft 123.
Has been fixed.

On one outer surface of the gear 122, four linear markings 124 are provided at intervals of 90 degrees from each other. Further, the power transmission system 120 is provided so as to be adjustable in position.

Then, portions 119a and 119 of the drive pulleys 119 and 119 around which the wire 118 is wound are described.
The outer diameter D of a and the outer diameter d of the four photosensitive drums 222a to 222d of the image forming unit 210 are formed to have substantially the same size. Here, “substantially the same size” means that the size difference between the two is about 1.0 to about 2.0% or less.

The control unit CON includes the drive pulleys 119 and 11
9 and the photoconductive drums 222a to 222a
Control is performed so as to match the phase of the rotation unevenness due to 2d. With such control, the phase of the unevenness of the read image data and the phase of the unevenness of the rotation of the photosensitive drums 222a to 222d can be matched with each other, so that a faithful image without the unevenness of the stretch can be formed. it can.

The control unit CON is further configured to control so that the phase of the unevenness of expansion and contraction of the image data and the phase of the unevenness of rotation by the photosensitive drums 222a to 222d are reversed.

That is, as shown in FIG. 9, if the phase of the unevenness of expansion and contraction of the image data read by the scanning optical system 117 (scanner) matches the phase of the unevenness of rotation by the photosensitive drums 222a to 222d. Photoconductor drum 22
The expansion and contraction of the image in 2a to 222d is enlarged. On the other hand, as shown in FIG.
17 (scanner), the phase of the unevenness of expansion and contraction of the image data read by the scanner 17 and the phase of the unevenness of rotation by the photosensitive drums 222a to 222d are controlled by the controller CON so that the photosensitive drum 222a ~ 222
The expansion and contraction of the image in d will cancel each other out and reduce. As a result, unevenness in expansion and contraction of image data can be reduced during image formation, and faithful image formation becomes possible.

In some cases, the control unit CON may be configured so that the phase of the rotation unevenness of the photosensitive drums 222a to 222d coincides with the phase of the rotation unevenness of the drive pulleys 119 at a predetermined phase. The writing of the image data may be controlled in accordance with the phase of the rotation unevenness caused by the photosensitive drums 222a to 222d. Also in these cases, it is possible to form a faithful image with less unevenness in expansion and contraction.

FIG. 11 shows four photosensitive drums 222a to 222 in the digital color copying machine according to the present invention.
2D is a flowchart showing a sequence in which a series of image forming operations starting from reading of a document and ending with transfer are performed simultaneously, and the respective photosensitive drums 222a to 222d are stopped at predetermined positions.

[0094]

According to the image forming apparatus of the present invention, a scanning optical system for scanning an original, a driving pulley for driving the scanning optical system by a wire, and transmitting power to the driving pulley. An image reading unit having a power transmission system for reading image data from the original; and writing the image data read by the image reading unit as an electrostatic latent image on a photosensitive drum, and writing the written electrostatic latent image on the photosensitive drum. An image forming section for developing an image and transferring the developed toner image on the photosensitive drum to an image forming sheet, and an outer diameter of a portion of the drive pulley of the image reading section around which the wire is wound and an image forming section. The outer diameter of the photosensitive drum of the image forming section is formed to be substantially the same size, and the phase of the rotation unevenness due to the driving pulley of the image reading section and the rotation unevenness due to the photosensitive drum of the image forming section are changed. Comprising a control unit for controlling so as to match the door. Therefore, the image read by the control of the control unit and the outer diameter of the portion of the drive pulley around which the wire is wound and the outer diameter of the photosensitive drum are formed to be substantially the same. The phase of the unevenness of the expansion and contraction of the data and the phase of the unevenness of the rotation of the photosensitive drum can be matched, and a faithful image without the unevenness of the expansion and contraction can be formed.

In the image forming apparatus according to the second aspect of the present invention, the control unit further reverses the phase of the unevenness of expansion and contraction of the image data and the phase of the rotation unevenness of the image forming unit due to the photosensitive drum. It is configured to control as follows. Accordingly, unevenness in expansion and contraction of image data generated at the time of image reading by the image reading unit can be reduced at the time of image formation, and faithful image formation becomes possible.

In the image forming apparatus according to the third aspect of the present invention, the control unit further sets the phase of the rotation unevenness caused by the photoconductor drum of the image forming unit to the phase of the rotation unevenness caused by the driving pulley of the image reading unit. It is configured to control to match at a predetermined phase. Therefore, it is not necessary to store the image data in a page memory or the like, and a faithful image formation with less unevenness in expansion and contraction can be realized in real time.

In the image forming apparatus according to a fourth aspect of the present invention, the control unit further controls the writing of the image data in accordance with the phase of the rotation unevenness of the photosensitive drum of the image forming unit. Have been. Therefore, it is possible to reliably form an image in accordance with the rotation unevenness of the photosensitive drum so as to reduce the expansion / contraction unevenness of the image data, and to form a faithful image with less expansion / contraction unevenness.

In the image forming apparatus according to the fifth aspect of the present invention, the power transmission system of the image reading unit is provided so as to be position-adjustable, and the position of the power transmission system is adjusted to control the power transmission system. Further, the phase of the image data is made to coincide with the phase of the rotation unevenness due to the photosensitive drum of the image forming section. Therefore, the phase of the driving unevenness of the drive pulley of the image reading unit can be matched with the phase of the rotation unevenness of the photosensitive drum, and a faithful image formation with reduced expansion / contraction unevenness during image formation can be performed.

In the image forming apparatus according to the sixth aspect of the present invention, the photosensitive drum of the image forming section is used for forming a color image on which electrostatic latent images corresponding to a plurality of predetermined colors are formed. There are multiple things. Therefore, the rotation phase of each photoconductor drum can be matched with the rotation phase of the drive pulley of the image reading unit so that expansion and contraction can be reduced, so that a color image forming apparatus with less color shift as well as image expansion and contraction can be manufactured at low cost. Can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration explanatory diagram illustrating an overall configuration of a digital color copying machine according to one embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating the phase adjustment of four photosensitive drums in the color copying machine of FIG.

FIG. 3 is an explanatory diagram for explaining an overlapping state of images on four photosensitive drums in the color copying machine of FIG. 1;

FIG. 4 is an explanatory diagram illustrating phase control of four photosensitive drums in the color copying machine of FIG. 1;

FIG. 5 is a time chart relating to output signals of a sensor for detecting a shift angle of four photosensitive drums in the color copying machine of FIG. 1;

FIG. 6 is an enlarged perspective view of a part of an image reading unit in the color copying machine of FIG. 1;

FIG. 7 is a plan view of an image reading unit in the color copying machine shown in FIG. 1;

FIG. 8 is a side view of an image reading unit in the color copying machine shown in FIG. 1;

FIG. 9 is a photoconductor drum when the phase of expansion and contraction unevenness of image data read by the scanning optical system matches the phase of rotation unevenness of the photoconductor drum in the color copying machine of FIG. 1; FIG. 4 is an explanatory diagram illustrating expansion and contraction of an image in FIG.

FIG. 10 is a diagram illustrating the light exposure when the phase of the unevenness of expansion and contraction of the image data read by the scanning optical system and the phase of the rotation unevenness of the photosensitive drum are opposite in the color copying machine of FIG. 1; FIG. 4 is an explanatory diagram illustrating expansion and contraction of an image on a body drum.

FIG. 11 is a flowchart when the color copying machine of FIG. 1 performs a series of image forming operations starting from reading of a document and ending with transfer.

FIG. 12 is a configuration explanatory view showing the configuration of each image forming unit and the periphery of a transfer conveyance belt in a conventional color image forming apparatus.

[Explanation of symbols]

 1 Digital Color Copier (Image Forming Apparatus) 110 Image Reading Unit 113 Document Scanning Unit 114 Document Scanning Unit 115 Optical Lens 116 CCD Line Sensor 117 Scanning Optical System 118 Wire 119 Drive Pulley 120 Power Transmission System 121 Toothed Belt 122 Gear 123 Rotation Shaft 210 Image forming unit 322a Photoconductor drum 322b Photoconductor drum 322c Photoconductor drum 322d Photoconductor drum) CON control unit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 1/29 H04N 1/29 F 5C074 F term (Reference) 2H030 AB02 AD16 BB04 BB07 BB16 2H076 AA22 AA24 AA58 AB02 AB48 EA01 2H108 AA01 BB01 CA01 CB01 DA01 DA06 FB22 FB33 5C062 AA05 AB17 AB22 AB33 AB40 AC13 AD06 AE03 AE15 5C072 AA05 BA15 DA02 EA05 JA08 JB07 SA06 XA01 5C074 AA10 BB03 BB04 BB26 CC15 DD26 GG12 BB26

Claims (6)

[Claims] 1. A scanning optical system for scanning a document, a driving pulley for driving the scanning optical system by a wire, and a power transmission system for transmitting power to the driving pulley, for reading image data from the document. An image reading unit, and a photosensitive drum, wherein the image data read by the image reading unit is written on the photosensitive drum as an electrostatic latent image, the written electrostatic latent image is developed, and the developed photosensitive member is developed. An image forming unit for transferring the toner image on the drum to the image forming paper, wherein the outer diameter of the portion of the drive pulley of the image reading unit around which the wire is wound and the outer diameter of the photosensitive drum of the image forming unit are The control unit is formed to have substantially the same dimensions. Further, a control unit that controls so that the phase of the rotation unevenness due to the drive pulley of the image reading unit and the phase of the rotation unevenness due to the photosensitive drum of the image forming unit match. Ete composed image forming apparatus. 2. The image forming apparatus according to claim 1, wherein the control unit further controls the phase of the unevenness of expansion and contraction of the image data and the phase of the unevenness of rotation of the image forming unit due to the photosensitive drum to be opposite to each other. 3. The control unit according to claim 1, wherein the control unit further controls the phase of the rotation unevenness of the photosensitive drum of the image forming unit to coincide with the phase of the rotation unevenness of the drive pulley of the image reading unit at a predetermined phase. Image forming device. 4. The image forming apparatus according to claim 1, wherein the control unit further controls writing of the image data in accordance with the phase of the rotation unevenness of the photosensitive drum of the image forming unit. 5. A power transmission system of the image reading unit is provided so as to be position-adjustable. The position of the power transmission system is adjusted, and the control unit further controls the rotation of the image forming unit caused by the photosensitive drum. 2. The image forming apparatus according to claim 1, wherein the phase of the image data is made to coincide with the phase. 6. The photoconductor drum in the image forming section is a plurality of photoconductor drums for forming a color image on which electrostatic latent images corresponding to a plurality of predetermined colors are formed. An image forming apparatus according to any one of the preceding claims.