JP3057181B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for forming a latent image on a belt-like photosensitive member by an optical writing device or the like using a laser beam.

[0002]

2. Description of the Related Art Many methods and apparatuses have been proposed for obtaining a color image using electrophotography. For example, JP-A-61
As disclosed in JP-A-100770, a latent image is formed and developed in accordance with the number of color separations of a document image on a photosensitive drum as an image forming body, and transferred to a transfer drum each time development is performed. There is a method of obtaining a color copy by forming a multicolor image thereon and transferring it to a recording paper. The device according to this method is:
In addition to the photosensitive drum, it is necessary to provide a transfer drum having a size capable of transferring one image on the peripheral surface, and it is inevitable that the apparatus has a large and complicated structure.

Further, as disclosed in, for example, Japanese Patent Application Laid-Open No. 61-149972, a latent image is formed and developed on a photosensitive drum in accordance with the number of separated colors of an original image, and a latent image is formed on a transfer material each time development is performed. There is a method of transferring to obtain a multicolored color copy. In this method, it is difficult to accurately overlay multicolor images, and a high-quality color image cannot be obtained.

[0004] Further, the formation of a latent image in accordance with the number of colors of the original image on the photosensitive drum and the development with color toner are repeated,
There is a method of obtaining a color image by superimposing and transferring a color toner image on a photosensitive drum. The basic process of this multicolor image formation is described in Japanese Patent Application Laid-Open Nos. 60-75850 and 60-767 by the present applicant.
No. 66, No. 60-95456, No. 60-95458, No. 60-158475 and the like.

[0005] In a multicolor image forming apparatus in which a color image is obtained by such superposition, a plurality of developing devices accommodating color toners of different colors are arranged on the periphery of the photosensitive drum. Generally, the photosensitive drum is rotated a plurality of times to develop a latent image on the photosensitive drum to obtain a color image.

[0006] As described above, the image forming body is formed in a belt shape in which a photoconductor is coated or vapor-deposited on a flexible belt together with a photosensitive drum in which a photoconductor is coated or vapor-deposited on the drum peripheral surface as described above. Photoconductors have also been proposed.
A belt-shaped photoreceptor (hereinafter also referred to as a photoreceptor belt) is shaped by being stretched between rotating rollers including a driving roller, so that a compact color image forming apparatus is constructed by effectively utilizing space. It is effective when doing. In addition, since the photoreceptor belt can travel along a small curvature, the transfer material is separated by using a small-diameter rotating roller and utilizing the curvature portion, thereby preventing a transfer material separation failure and the like. it can.

[0007] The advantages of using the belt-shaped photoreceptor are the same for an image forming apparatus for a single color image.

[0008]

As a result of further study by the present inventor on a technique using a belt-shaped photoreceptor, the following problems became apparent.

(1) When writing or multiple writing by an optical writing device or the like using a laser beam as an exposure beam in order to form a latent image of a single color or multicolor image (images of each color are superimposed on a photosensitive member) In the case of writing, the belt is driven by a separate roller so that the roller and the belt slip or the belt naturally moves, so that the position shifts in the drive axis direction (main scanning direction) during the writing of the latent image (this is called a shift). )
This causes image distortion, and in the case of a multi-color image, there is a problem that color shift in the main scanning direction and a reduction in resolution due to the color shift occur.

(2) In order to solve the above-mentioned problems, it is necessary to improve the mechanical accuracy. However, it is difficult to take a sufficient countermeasure with this alone, and high-precision parts are used. As a result, cost increases also pose a problem, and there is a limit to mechanical measures alone.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-described problems, and has as its object to stop image formation when the deviation amount per rotation of the belt-shaped photoreceptor becomes equal to or more than a reference value, and to detect a defective image. The purpose is to prevent formation. Another object of the present invention is to provide an image forming apparatus which achieves the above object while minimizing the complexity of the apparatus.

[0012]

The object of the present invention is to provide a belt-shaped photoreceptor, charging means for charging the belt-shaped photoreceptor,
An exposure unit that forms a latent image on the belt-shaped photoconductor charged by the charging unit; a developing unit that develops the latent image formed by the exposure unit to form a toner image; and a developing unit that is formed by the developing unit. Transfer means for transferring the transferred toner image to a transfer material, the developing means comprising two or more developing devices containing developers composed of toners of different colors, and developing each time the belt-shaped photoreceptor rotates. The charging, exposing, and developing are performed by switching the image forming apparatus, and a multi-color toner image is formed by superimposing toner images of different colors on the belt-shaped photoreceptor. In a color image forming apparatus that obtains a color image of a color, the color image forming apparatus detects a position of the driving roller of the belt-shaped photosensitive member in an axial direction, and receives a signal from the detecting unit, and receives the signal from the detecting unit. Photoconductor A shift amount detecting means for detecting a shift amount of the drive roller in the axial direction per rotation, wherein the image formation is stopped when the shift amount exceeds a reference value. You.

The image forming apparatus includes a belt-shaped photosensitive member, charging means for charging the belt-shaped photosensitive member, exposing means for forming a latent image on the belt-shaped photosensitive member charged by the charging means, An image forming apparatus including a developing unit that develops a latent image formed by the unit to form a toner image, and a transfer unit that transfers the toner image formed by the developing unit to a transfer material. Detecting means for detecting the axial position of the drive roller of the belt-shaped photoreceptor, and control means for receiving a signal from the detection means and calculating a shift amount in the drive roller axial direction per one rotation of the belt-shaped photoreceptor Wherein the detection unit performs detection using exposure light emitted from the exposure unit, and the detection unit is also applied to the image forming apparatus. Stage is mentioned as the color image forming apparatus preferred embodiment and performing detection by using an exposure light emitted from the exposing unit.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention detects a shift amount, which is a positional shift of a belt-shaped photosensitive member in the drive axis direction, and detects that the shift amount per rotation of the belt-shaped photosensitive member has exceeded a reference value. This is an image forming apparatus that controls an optical writing device using a laser beam as an exposure beam so as to stop the image formation at times. The control of the optical writing device is performed by (A) an image forming apparatus that forms a single color image during one rotation of the belt-shaped photosensitive member, and (B) a color image in which the toner image is overlapped by a plurality of rotations of the belt-shaped photosensitive member. The image forming apparatus is also applied to (C) a color image forming apparatus that forms a color image by superimposing a toner image during one rotation of a belt-shaped photoconductor, but the description is duplicated.
A description will be given of a color image forming apparatus in which a toner image is superimposed by a plurality of rotations.

FIG. 1 shows a color image forming apparatus according to an embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a photosensitive belt, which is a flexible belt-shaped photosensitive member coated or deposited with a photoconductor, and the photosensitive belt 1 is bridged between rotating rollers 2 and 3. The paper is conveyed clockwise by the rotation of the rotation roller 2. Reference numeral 1A denotes a reflection type mark provided on a predetermined portion of the photoreceptor belt 1 for reflecting a laser beam. Reference numeral 4 denotes a guide member fixed to the apparatus main body so as to be in contact with the photoreceptor belt 1. The photoreceptor belt 1 is tensioned by the action of a tension roller 5 so that its inner peripheral surface slides on the guide member 4. Rub.

Reference numeral 6 denotes a scorotron-type charger as charging means, 7 denotes an optical writing device for exposing (writing) with a laser beam L as an exposure beam in an exposure section between the charger 6 and the developing device, and 8 to 11 Reference numeral denotes a developing device which is a plurality of developing units each containing a developer composed of a toner of a different color. These image forming units are disposed in a portion of the photosensitive belt 1 in contact with the guide member 4. Each of the developing units 8, 9, 10, and 11 accommodates, for example, each of yellow, magenta, cyan, and black developers, and each of the developing sleeves 8A, 9A, 10A, which keeps a predetermined gap from the photosensitive belt 1. 11A
And has a function of visualizing the latent image on the photosensitive belt 1 by a non-contact reversal developing method. Unlike the contact development, the non-contact development has an advantage of not hindering the movement of the photosensitive belt.

Reference numeral 12 denotes a transfer device, and 13 denotes a cleaning device. A blade 13A of the cleaning device 13 and a toner conveying roller 13B
Is held at a position away from the surface of the photoreceptor belt 1 during image formation, and is brought into pressure contact with the surface of the photoreceptor belt 1 as shown in FIG.

Reference numeral 23 denotes an optical mark 1 using, for example, an LED as a light emitting element and a phototransistor as a light receiving element.
A mark sensor for detecting A. Mark sensor 2
The installation position of 3 is not limited to the position shown in FIG. 1 and may be anywhere as long as there is space. Reference numeral 24 denotes a belt edge which is a sensor (photosensitive member position detecting means) provided on the back side of the side end portion of the photosensitive belt 1 (opposite to the writing light source across the photosensitive member), for example, a shift amount detecting means comprising a photodiode or the like. Sensors,
Reference numeral 78 denotes an index sensor comprising a phototransistor or the like for receiving a beam at the scanning start point of the laser beam L and outputting a signal. The process of forming a color image by such a color image forming apparatus is performed as follows.

That is, when color-specific image data output from an image reading device separate from the color image forming device is input to the optical writing device 7, the optical writing device 7 uses a writing light source (not shown). A laser beam L generated by a certain laser diode passes through a collimator lens and a cylindrical lens, and is rotationally scanned by a rotating polygon mirror 74 rotated by a polygon mirror driving motor 79, and the fθ lens 75
The optical path is bent by the mirror 76 and the mirror 77 during that time, and is projected on the peripheral surface of the photoreceptor belt 1 to which a uniform charge is previously given by the charger 6 to perform main scanning, thereby forming a bright line. Form.

The timing of starting writing by scanning with the laser beam L is determined by a mark detection signal obtained by the mark sensor 23. The laser beam L modulated by the image data of the first color scans the peripheral surface of the photosensitive belt 1. Therefore, a latent image corresponding to the first color is formed on the peripheral surface of the photosensitive belt 1 by the main scanning by the laser beam L and the sub-scanning by the movement of the photosensitive belt 1. This latent image is developed by a developing unit 8 loaded with yellow (Y) toner (a visual medium) in the developing means.
A toner image is formed on the peripheral surface of the photoreceptor belt 1. The obtained toner image passes under the cleaning device 13 as a cleaning means separated from the peripheral surface of the photoreceptor belt 1 while being held on the peripheral surface of the belt, and enters the next image forming cycle.

That is, the photosensitive belt 1 is connected to the charger 6
, And then the second color image data output from the image data processing unit is input to the optical writing device 7 and is applied to the peripheral surface of the photosensitive belt 1 in the same manner as in the case of the first color described above. Is written to form a latent image. The latent image is developed as a second color by a developing device 9 loaded with magenta (M) toner.

The magenta (M) toner image is formed in the presence of the previously formed yellow (Y) toner image.

Reference numeral 10 denotes a developing device having a cyan (C) toner. The image data of the third color generated by the image data processing section is input to the optical writing device 7 and the third color image data is processed similarly to the previous color. Developing device 10 containing cyan (C) toner as the color
To form a cyan (C) toner image on the belt surface.

Further, reference numeral 11 denotes a developing device having black toner, which forms a black toner image on the belt surface by the same processing. These developing units 8, 9, 10 and
A DC or further AC bias is applied to each of the sleeves 8A, 9A, 10A and 11A, and non-contact development is performed by a two-component developer as a visualizing means. Are developed in a non-contact manner.

The color toner image thus formed on the peripheral surface of the photoreceptor belt 1 is fed from the paper feed cassette 14 through the paper feed guide 15 by applying a high voltage having a polarity opposite to that of the toner at the transfer section. Is transferred to the transfer material.

That is, one of the uppermost layers of the transfer material accommodated in the paper feed cassette 14 is carried out by the rotation of the paper feed roller 16, and the timing of image formation on the photosensitive belt 1 is adjusted via the timing roller 17. And is supplied to the transfer device 12.

The transfer material to which the toner image has been transferred is transferred to the photoreceptor belt 1 which suddenly changes its direction along the rotating roller 2.
After the toner image is fused and fixed by the fixing roller 18, the toner image is discharged onto the tray 20 via the sheet discharging roller 19.

On the other hand, the photoreceptor belt 1 after the transfer to the transfer material is further moved to remove the residual toner in the cleaning device 13 in which the blade 13A and the toner conveying roller 13B are pressed against each other, and the process is completed. Then, the blade 13A is separated again, and a little later, the toner conveying roller 13B is separated to start a new image forming process.

In the color image forming apparatus shown in FIG. 1, according to the present invention, the shift amount of the photosensitive belt 1 per one time is calculated based on information from the index sensor 78, the belt edge sensor 24 and the mark sensor 23. When the hit amount exceeds a reference value, the process of forming a latent image is stopped.

FIG. 2 is a block diagram showing an example of a circuit for performing the deviation amount detection and write control, and FIG. 3 is a time chart of signals of the circuit of FIG.

In the circuit shown in FIG. 2, each time the mark 1A on the photosensitive belt 1 passes the detection position of the mark sensor 23, the mark sensor 23 sends a mark detection signal S3, which is a detection signal of the mark 1A, to the overall control unit 41. One-time deviation detection circuit 4
Send to 5. Index sensor 78 is laser beam L
Each time the laser beam L is incident at the scanning start point, the exposure control unit
The index signal S1 is sent to the belt 42 and the belt shift amount detection circuit 44. The laser beam L enters the belt edge sensor 24 immediately after the scanning start point of the laser beam L until it is interrupted by the side edge of the photoreceptor belt 1, and the signal shown in S2 in FIG. Send out. In the belt shift amount detecting circuit 44, the times ta, tb, from the rising portion of the index signal S1 to the falling portion of the signal S2, which is the time corresponding to the distance from the position of the index sensor 78 to the side end of the photosensitive belt 1. Are measured and sent to the shift amount detection circuit 45 per one time. The one-time deviation amount detection circuit 45 calculates the difference between the time ta proportional to the deviation amount immediately after the input of the first mark detection signal S3a and the time tn at the time when the next mark detection signal S3b is input. The shift amount (the change amount of the shift amount during one rotation of the photosensitive belt 1) or a count value proportional thereto is sent to the overall control unit 41. Since the deviation amount per operation is calculated by comparing the deviation amount immediately after the detection of the mark detection signal S3, the deviation amount per operation is calculated using the deviation amount of the same portion of the photosensitive belt 1. Therefore, even if the side end of the photoreceptor belt 1 has irregularities, it is possible to accurately obtain the deviation amount per one time.

When the deviation amount per one time exceeds the reference value, the overall control unit 41 displays a warning on the display unit of the operation panel, and sends a write stop signal to the exposure control unit 42 to transmit an image for forming the latent image or less. Stop the forming process. If the shift amount per one time is equal to or less than the reference value, the overall control unit 41 causes the exposure control unit 42 to proceed with the process of forming a latent image in accordance with the exposure start timing obtained by the detection signal of the mark 1A. The exposure control unit 42 reads out image data, which is a color signal stored in the image memory 43, modulates pulse width in the exposure control unit 42 for each scan by the index signal S1, and sends the pulse data to the laser diode 71 via the laser diode driver 46. Output to control the light emission. With such control, when the deviation amount per rotation of the photoreceptor belt 1 is large, the latent image is not formed, so that the formation of a defective image can be surely prevented.

The detection of the shift amount per one time and the control of the latent image forming process are performed when the power of the apparatus main body is turned on, during warm-up after the power is turned on, or when a latent image is formed to feed the transfer material. It may be performed before the image formation is performed, or before the image formation is performed. Alternatively, the photosensitive belt 1 may be rotationally moved during warm-up after the power is turned on, and image formation may be started when the movement of the photosensitive belt 1 is stabilized and the amount of deviation per operation is reduced.

The mark 1A is not limited to the reflection type, but may be a transmission type in which a slit-shaped hole is formed in the photosensitive belt 1, and in this case, a photocoupler is used as a sensor. Further, the belt edge sensor 24 may be provided at a place where a reflection or refraction means is provided between the belt edge sensor 24 and the photoreceptor belt 1 to bend the laser beam L so that the belt edge sensor 24 is easily installed in design.

[0036]

As described above, according to the present invention, the following effects can be obtained.

(1) In an image forming apparatus using a belt-shaped photoreceptor, a latent image is not formed if the shift amount of the photoreceptor per one time exceeds a reference value. It is possible to prevent the occurrence of an image or the like having a reduced resolution due to a shift.

(2) Since the writing light source is used in common as the light source of the belt edge sensor as the photosensitive member position detecting means, it is not necessary to adjust the mounting position of the photosensitive member position detecting means with strict accuracy without increasing the number of parts. The device can be small and inexpensive.

(3) Since it is not necessary to extremely improve the mechanical accuracy, an increase in the cost of the apparatus can be suppressed, and the size of the apparatus can be reduced.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a color image forming apparatus showing an embodiment of the present invention.

FIG. 2 is a block diagram illustrating an example of a circuit that performs deviation detection and write control according to the present invention.

FIG. 3 is a time chart of signals of the embodiment shown in FIG. 2;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoreceptor belt 1A mark 2 rotating roller 3 rotating roller 6 charger 7 optical writing device 8 developing unit 9 developing unit 10 developing unit 11 developing unit 23 mark sensor 24 belt edge sensor 41 overall control unit 42 exposure control unit 43 image Memory 44 Belt shift amount detection circuit 45 One time shift amount detection circuit 71 Laser diode 74 Rotating polygon mirror 78 Index sensor 79 Polygon mirror drive motor L Laser beam

Continuation of the front page (72) Inventor Tetsu Haneda 2970 Ishikawa-cho, Hachioji-shi, Tokyo Konica Co., Ltd. Examiner, Naoki Matsukawa (56) References JP-A-2-96774 (JP, A) JP-A-3-209285 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 21/00 370 G03G 21/00 350 B41J 2/525 G03G 15/01

Claims (3)

(57) [Claims] A belt-shaped photoconductor; a charging unit for charging the belt-shaped photoconductor; an exposure unit for forming a latent image on the belt-shaped photoconductor charged by the charging unit; Developing means for developing the formed latent image to form a toner image, and transfer means for transferring the toner image formed by the developing means to a transfer material, wherein the developing means is composed of toner of different colors The developing device is switched for each rotation of the belt-shaped photoconductor to perform charging, exposure, and development, and toner images of different colors are superimposed on the belt-shaped photoconductor. A color image forming apparatus that forms a color toner image, collectively transfers the toner image to a transfer material, and then fixes the toner image to obtain a multicolored color image, wherein the color image forming apparatus includes a driving roller for the belt-shaped photosensitive member. Axial position Detecting means for detecting the position, and receiving a signal from the detecting means,
A color image forming apparatus, comprising: a shift amount detecting means for detecting a shift amount of the drive roller in the axial direction per rotation, wherein the image forming is stopped when the shift amount exceeds a reference value. 2. A belt-shaped photoconductor, a charging unit for charging the belt-shaped photoconductor, an exposure unit for forming a latent image on the belt-shaped photoconductor charged by the charging unit, and a charging unit formed by the exposure unit An image forming apparatus including: a developing unit configured to develop the formed latent image to form a toner image; and a transfer unit configured to transfer the toner image formed by the developing unit to a transfer material. Detecting means for detecting an axial position of a body driving roller; and receiving a signal from the detecting means, the belt-shaped photoconductor 1
An image forming apparatus, comprising: control means for calculating a shift amount in the drive roller axial direction per rotation; wherein the detection means performs detection using exposure light emitted from the exposure means. . 3. The color image forming apparatus according to claim 1, wherein said detection means performs detection using exposure light emitted from said exposure means.