JP3189097B2 - Color image forming equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus in which a toner image is formed on an image forming body by an electrophotographic method and is transferred onto a transfer material to obtain an image.

[0002]

2. Description of the Related Art As an image forming method for obtaining a color image by using an electrophotographic method, for example, JP-A-60-75850 and JP-A-60-767
No. 66, No. 60-95456, No. 60-95458, No. 60-158475, the latent image formation and development according to the number of separation colors of the original image on the image forming body are performed. There is a method in which a color toner image is repeatedly obtained by superimposing a color toner image on an image forming body and then transferring the same.

A color image forming apparatus to which an image forming method in which a latent image is repeatedly formed and developed in accordance with the number of separated colors of a document image read by a color scanner on the image forming body is applied. An exposure apparatus and a development apparatus corresponding to the number of separation colors (for example, three colors of yellow, magenta, and cyan or four colors including black) are arranged around a formed body. As a second example, a drum-shaped image formed body Are provided with an exposure device and a development device according to the number of colors.
Next, a color image forming apparatus including a belt-shaped image forming body will be described.

In a color image forming apparatus, a tension roller is attached to a belt-shaped image forming body in which a photoconductor is applied or vapor-deposited on a flexible belt. By rotating while maintaining the contact state, the belt-shaped image forming body is always conveyed while being kept at a constant position.Around the belt-shaped image forming body, a charger, an exposure device, and color toners of different colors are provided. (Yellow, magenta, cyan, black), and an image forming means comprising a plurality of developing units, and these image forming means are arranged at a fixed interval on a belt-shaped image forming body which rotates.

[0005]

In the color image forming apparatus, the speed of the photoconductor is controlled by a generally known servo technique so that the speed of the photoconductor drive motor is a predetermined constant speed. ing.

However, even if the photoconductor drive motor is controlled to a predetermined constant speed, the surface speed of the photoconductor itself does not always reach the predetermined speed. For example, when a drum is used as the photoconductor, the speed of the photoconductor surface changes due to a change in the drum diameter even if the rotation speed of the photoconductor drive motor is constant. Further, when the photoconductor belt is used, the photoconductor moving speed changes due to a change in the driving roller diameter of the belt, and when the belt is used, a change in the driving roller diameter of the belt or an error in the thickness of the belt itself.

That is, when the photosensitive drum, the photosensitive belt, and the belt driving roller are replaced for maintenance or the like, the photosensitive member surface speed is reduced due to manufacturing variations.
It has changed.

When the photosensitive drum is used or in the case of the multi-rotation system, there is no problem. However, when the photosensitive belt is used, the change in the belt thickness or the diameter of the belt driving roller does not occur in the sub-scanning direction. There is a problem that the superimposed image is shifted.

That is, the plurality of image writing apparatuses are arranged at a predetermined interval, and the start of image writing is shifted by a predetermined time as the image position moves from the upstream of the photosensitive belt. However, when the moving speed of the photoreceptor belt changes, the moving time of the image position changes, and the start of image writing of each image writing device is shifted by a predetermined time. Therefore, even when the image writing is started, at that time, the image writing start position on the photoreceptor belt may have already passed the exposure position or may not have reached yet.

In a conventional image forming apparatus, a driving motor of a feeding system is so arranged that the speed of the transfer paper and the speed of the photosensitive member coincide with each other so that the image is not disturbed during the transfer to the transfer paper. Although the number of rotations is also controlled, if the moving speed of the photoconductor changes, a speed difference occurs and the image is disturbed (so-called transfer deviation occurs).

As a solution to this problem, a conventionally known method is to provide a large number of slits in the circumferential direction of the photoreceptor belt itself and use a photocoupler or the like to form the slits.
It is conceivable to control the speed of the photoreceptor belt itself at a constant speed based on the read signal and the read signal. However, in this case, a dedicated photocoupler is required, which is disadvantageous in terms of space and cost.

In addition, from the viewpoint of the image writing apparatus, if the arrangement intervals are set in advance, the intervals change due to a temperature change. This is due to the thermal expansion of the mounting plate, etc. For example, if this arrangement interval is set to 15 mm, the distance between the first color and the fourth color becomes 450 mm, and a change of 20 ° C. causes a change of about 0.1 mm. Occurs.

[0013] Similarly, if the start of writing of each image is similarly shifted and controlled by a predetermined time, the image of each color is shifted by a change of 20 ° C.

In a color image forming apparatus which forms a color toner image by superposing a plurality of toner images (Y, M, C, K) on an image forming body as described above, a plurality of If the exposure start position on the belt-shaped image forming body from the exposure device cannot be set to a displacement of one pixel unit or less, for example, about 80 μm or less, there is a problem that the image quality of the color toner image is deteriorated. In particular, when a belt-shaped image forming body was used, it was difficult to control the alignment as compared with a drum-shaped image forming body.

[0015]

SUMMARY OF THE INVENTION In view of the above-mentioned conventional problems, the present invention provides a writing unit for a color image forming apparatus, which has a writing position shift due to a temperature change and a speed fluctuation at the time of rotation of an image forming body. An object of the present invention is to correct a color shift of a laser beam in a sub-scanning direction and prevent a shift of an exposure start point for forming a latent image when a plurality of latent images are repeatedly formed, thereby preventing a color shift. An object of the present invention is to provide a color image forming apparatus.

According to the color image forming apparatus of the present invention which achieves the above object, an image forming body which moves in the sub-scanning direction, a plurality of charging means for uniformly charging the image forming body, and a charging means for charging the image forming body. A plurality of scanning exposure devices that form an image latent image by main scanning exposure on the image forming body; and a plurality of developing units that form a toner image by developing the image latent image formed by the scanning exposure device, A transfer unit for transferring a toner image formed on the image forming body to a transfer material that is separately moved in the sub-scanning direction; and a color image forming apparatus that forms a color image. A pre-pattern is formed outside the image area, a plurality of light-receiving sensors are provided which emit light by the scanning exposure device and receive light transmitted or reflected by the pre-pattern and generate a detection signal. The speed control of the image forming body is performed based on detection signals detected by at least two light receiving sensors, and at the time of image formation, the scanning exposure is performed based on the detection signals detected by at least two light receiving sensors. The writing start timing in the sub-scanning direction in the apparatus is corrected.

Further, the color image forming apparatus according to the present invention comprises:
An image forming body that moves in the sub-scanning direction; a plurality of charging units that uniformly charge the image forming body; and a main scanning exposure on the image forming body charged by the charging unit to form an image latent image. A plurality of scanning exposure devices, a plurality of developing means for developing a latent image formed by the scanning exposure device to form a toner image, and a toner image formed on the image forming body separately in a sub-scanning direction. Transfer means for transferring to a transfer material to be moved, wherein a color image forming apparatus for forming a color image, wherein the scanning exposure device irradiates light outside the image area on the image forming body, and the developing means To form a development pattern, and a plurality of light receiving sensors that receive light that is irradiated with light by the scanning exposure device and that transmits or reflects the development pattern and generates a detection signal are provided. The image forming apparatus controls the speed of the image forming body based on the detection signals detected by the two light receiving sensors, and at the time of image formation, the scanning exposure apparatus based on the detection signals detected by the at least two light receiving sensors. , The writing start timing in the sub-scanning direction is corrected.

Further, in the color image forming apparatus according to the present invention, the image forming body moving in the sub-scanning direction, a plurality of charging means for uniformly charging the image forming body, and the image forming body charged by the charging means A plurality of scanning exposure devices for forming an image latent image by main scanning exposure on a body; a plurality of developing means for developing an image latent image formed by the scanning exposure device to form a toner image; A transfer unit for transferring a toner image formed on the body to a transfer material that is separately moved in the sub-scanning direction, wherein a color image forming apparatus for forming a color image is provided outside the image area on the image forming body. A plurality of surface potential sensors that form a latent image pattern by irradiating light with the scanning exposure device and detect a potential change of the latent image pattern to generate a detection signal; surface Position based on the detection signal detected by the sensor respectively, with the speed control of the image forming body,
At the time of image formation, the writing start timing in the sub-scanning direction in the scanning exposure apparatus is corrected based on detection signals detected by at least two surface potential sensors.

[0019]

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is an overall configuration diagram of a color printer as an example of a color image forming apparatus provided with a belt-shaped image forming body as one embodiment of the present invention, and FIG. 2 is a diagram showing the belt-shaped image forming body and laser scanning exposure. FIG. 2 is a perspective view showing an optical path of the device.

In FIG. 1, a color image forming apparatus according to the present embodiment includes a plurality of chargers 11 around a belt-shaped image forming body 1.
0, 210, 310, 410, exposure main scanning lines L1, L2, L
An image forming means comprising developing units 130, 230, 330, and 430 loaded with toners of different colors of 3, L4 and four colors is arranged, and yellow, magenta, cyan and black toners are rotated by one rotation of the image forming body 1. A color image is formed by superimposing images.

The belt-shaped image forming body 1 is a belt-shaped photoconductor (hereinafter referred to as a photoconductor belt) in which a photoconductor is applied or deposited on a flexible belt.
A tension roller 5 is attached to the photoreceptor belt 1 and stretched between the guide member 3 and a guide member 4 having a curvature. By rotating, the photosensitive belt 1 is always conveyed while keeping the surface thereof at a fixed position. With the above-described configuration, the photosensitive member on the outer peripheral surface of the photosensitive belt 1 is always maintained at a fixed position with respect to the surface of the guide member 4 even during conveyance, and a stable image forming surface having a large curvature is formed with a long width. Therefore, a large number of image forming means having the same shape can be arranged in parallel at a constant interval.

In this embodiment, the photoreceptor belt 1 is used as an image forming member. However, the present invention is not limited to this, and may be applied to an existing image forming member having a photosensitive layer such as a photoreceptor drum. Applicable.

Around the photoreceptor belt 1, there are provided a plurality of charging means, a plurality of exposing means, a developing means loaded with toners of four different colors, a transferring means, and a cleaning means.

The charging means is provided to uniformly charge the photosensitive layer on the surface of the photoreceptor belt 1 with a predetermined polarity, and is provided with existing chargers 110, 210, 310, such as a corona charger and a scorotron charger. 410.

Exposure means are semiconductor laser writing units (laser scanning exposure devices) 120, 220, 320, and 420.
The surface of the photoreceptor belt 1 charged by the chargers 110, 210, 310, 410 is exposed to form an electrostatic latent image.

The developing means includes four developing devices 130 containing developers of different colors, for example, toners (developers) of yellow (Y), magenta (M), cyan (C) and black (K), respectively. , 230, 330, 430. Each of these developing units 130 to 430 has a function of visualizing the electrostatic latent image on the photosensitive belt 1 into a toner image by a non-contact developing method.
The non-contact developing method is different from the contact developing method in that the previous toner image formed on the photosensitive belt 1 is not damaged.
Since the movement of the photosensitive belt 1 is not hindered, a good color image can be obtained.

The transfer means transfers the toner image formed on the photosensitive belt 1 onto a transfer material by a transfer device 14 such as a transfer corona discharger. As this transfer means, an existing transfer member such as a transfer drum may be used instead of the transfer device 14.

The cleaning means 15 has a cleaning blade 151 and a cleaning roller 152.
The photoconductor belt 1 is provided so as to be in pressure contact with the surface thereof to clean the photoconductor belt 1.

The process of forming a color image by the image forming apparatus having the above configuration is performed as follows.

First, when an image signal of a first color output from an image reading device separate from the apparatus main body is input to the laser scanning exposure device 120, the laser scanning exposure device 120
A laser beam is generated by the laser light source 121 at.
A polygon mirror 124 whose laser beam is rotated by a drive motor 123 via a collimation lens 122
, And is projected through the fθ lens 125 and the cylindrical lens 126 onto the peripheral surface of the photoreceptor belt 1 which has been uniformly charged in advance to a predetermined charge by the chargers 110 to 410 to form a bright line.

On the other hand, in the sub-scanning direction, which will be described later in detail, a photo sensor detects a registration mark 1A corresponding to a specific position of the photoreceptor belt 1, and a laser based on an image signal based on the detection signal. The modulation of the light source 121 is started, and the main scanning line in the sub-scanning direction is determined. When scanning is started, the first laser light source 12 is moved in the main scanning direction.
The home position is detected by the first laser light, and the modulation of the laser light source 121 by the image signal of the first color is started based on the detected signal, and the modulated laser beam is applied to the surface of the photoreceptor belt 1. Is scanned. Accordingly, a latent image corresponding to the first color is formed on the surface of the photosensitive belt 1 uniformly charged by the main scanning by the laser beam and the sub-scanning by the conveyance of the photosensitive belt 1. This latent image is developed by the developing device 130 containing the yellow toner, and a yellow toner image is formed on the surface of the photoreceptor belt 1. Thereafter, the photoreceptor belt 1 is conveyed while holding the yellow toner image on the surface thereof, and subsequently enters the second color image formation.

That is, when the photosensitive belt 1 on which the yellow toner image is formed is conveyed to the next position of the charger 210, as in the case of the image signal of the first color, the charger is recharged again. After a predetermined time is counted by a timer from the start of modulation of the first laser light source, the modulation of the semiconductor laser of the laser scanning exposure device 220 by the second image signal is started, and the semiconductor laser is charged. Is rotated by a polygon mirror rotated by a drive motor through a collimation lens, passes through an fθ lens, a cylindrical lens, and is uniformly charged to a predetermined charge by a charger 210. A latent image is formed on the peripheral surface of the belt 1 by projection. The latent image is developed by a developing device 230 containing magenta toner as a second color. The magenta toner image
It is formed in the presence of the already formed yellow toner image.

Similarly, the photoreceptor belt 1 on which the magenta toner image of the second color is formed is further conveyed, and the charging device 310 continues to perform the same operation as in the case of the image signal of the second color. And a latent image is formed by the laser scanning exposure device 320, and a developing device 330 containing cyan toner
And a cyan toner image is formed. Further, the photoreceptor belt 1 on which the cyan toner image of the third color is formed is further conveyed and uniformly charged by the charger 410 as in the case of the image signals of the second and third colors. Then, a latent image is formed by the laser scanning exposure device 420, developed by the developing device 430 containing black toner, and superimposed on the black toner image, so that a color toner image is formed on the surface of the photoreceptor belt 1. That is, a color toner image is formed while the photosensitive belt 1 makes one rotation.

A DC or further AC bias is applied to each of these developing units 130 to 430, and reversal development (jumping development) is performed without contact with the photosensitive belt 1 whose base is grounded. . Incidentally, for the non-contact development, either a one-component developer or a two-component developer can be used. When a one-component developer is used, there is no need to provide a toner concentration control means, and the size can be reduced. However, the development method using a two-component developer is superior in terms of development stability, so that color reproduction is improved. preferable.

The color toner image formed on the surface of the photoreceptor belt 1 as described above is supplied from a paper supply cassette 161 by a paper supply roller 162, and is transferred by a timing roller 163 to a transfer material synchronized with the color toner image. Is transferred to The transfer device 14 performs transfer by applying a high-voltage power supply having a polarity opposite to that of the toner.

Thus, the transfer material on which the color toner image has been transferred is reliably separated by the photoreceptor belt 1 which changes direction rapidly (small diameter curvature) along the rotating roller 2,
After the toner is fused and fixed by the fixing unit 17, the toner is discharged from the apparatus main body by the discharge roller 18.

On the other hand, the photosensitive belt 1 after the transfer of the color toner image to the transfer material is further conveyed clockwise,
Cleaning blade 151 and cleaning roller 152
The remaining toner is removed and cleaned by the cleaning means 15 in a state of pressing the toner. After the cleaning is completed, a new image forming process is started again.

The color image forming apparatus according to the present embodiment
Around the photoreceptor belt 1, image forming means including a plurality of chargers 110 to 410, exposure devices 120 to 420, and developing units 130 to 430 loaded with four different color toners are arranged. Is a so-called one-pass method in which a yellow, magenta, cyan and black toner image is superimposed to form a color image in one rotation. Note that the present invention is not limited to the one-pass system, and it goes without saying that a multi-rotation system in which a latent image is formed and developed each time the image forming body makes one rotation may be used.

Further, the color printer of FIG. 1 has a compact design of a refraction optical system using a plurality of mirrors in order to arrange four series of exposure devices.

Next, the correction operation of detecting the position of the photoreceptor belt 1 in the sub-scanning direction, correcting these deviations and registering a plurality of images according to the present invention will be described in more detail.

As shown in FIG. 2, a plurality of pre-patterns (registration marks) of the present invention formed in advance by printing or the like near the side edge of the photosensitive surface of the photosensitive belt 1 outside the image area, as shown in FIG. 1A is provided in parallel with the sub-scanning direction X. The pre-pattern 1A serves as a reference in the sub-scanning direction that determines the exposure start timing of each of the main scanning lines L1, L2, L3, and L4 in the main scanning direction by a laser beam described later.

Above the vicinity of the position where the main scanning line L1 and the moving pre-pattern 1A coincide (see FIG. 2).
, A light receiving sensor PS1 is fixedly mounted, and the reflected light of the pre-pattern 1A by the main scanning line L1 of the laser beam is received by the light receiving sensor PS1.

FIG. 3 is a block diagram of the scanning exposure correction for preventing the deviation of the laser beam in the main scanning direction and the sub scanning direction. Here, the sub-area counter is a counter for shifting the sub-scanning direction, the sub-count setting unit is a unit for setting the timing from the reference detection value of the pre-pattern 1A to the start of image writing in the sub-scanning direction, and the sub-count correction unit is A part for correcting a predetermined count number, a main area counter is a counter for moving in the main scanning direction, and a main count setting unit sets a timing from an end point reference detection value of the pre-pattern 1A to the start of image writing in the main scanning direction. Part.

First, the speed correction control of the photosensitive belt will be described. FIG. 8 is a block diagram thereof.

Before writing an image, the photosensitive belt is rotated, and the image writing device turns on the laser beam to start scanning exposure.

The image writing laser beam on the main scanning line L1 irradiates the pre-pattern 1A formed on the non-image area of the rotating photosensitive belt 1, and its reflected light is received by the light receiving sensor PS1. The pre-pattern 1A is irradiated, the reflected light is received by the light receiving sensor PS1, and a detection signal of the pre-pattern 1A is generated.

Subsequently, similarly, in the main scanning line L2, the pre-pattern 1A on the photosensitive belt 1 is irradiated with the image writing laser light on the main scanning line L2, and the reflected light is received by the sensor PS2. Obtain a detection signal.

The detection of each passing time of the main scanning lines L3 and L4 and the belt speed between the line intervals A3 to L3 and L4 are detected.

From these belt speeds, an average speed is calculated and compared with a predetermined speed.
to correct.

That is, when it is determined that the belt speed is low, a command is issued to the belt drive control unit so as to increase the speed by the difference, and the speed is corrected.

In this manner, a change in belt speed caused by a manufacturing error in the diameter of the belt driving roller or the belt thickness is adjusted to the set value, thereby eliminating problems such as transfer deviation.

In this embodiment, between L1 and L2, L2 and L3
The average of the speeds between L3 and L4 was compared with the set belt speed, but this is to improve the accuracy by averaging. Of course, even if the comparison and correction are performed only between L1 and L2 good. Further, the speed may be calculated, compared, and corrected at a long distance between L1 and L4.

The photoconductor speed at the time of this speed correction need not be the same as that at the time of image formation. The purpose is to correct the belt speed caused by an error in the belt drive roller diameter and the belt thickness, so that the belt drive control unit calculates the set speed calculated based on the motor rotation speed, and actually measures and calculates the speed. It suffices if the speed deviation can be corrected. In order to increase the accuracy, it is conceivable that the speed during image formation is set to 1/2 to 1/5 only during this correction.

The distance A1 between the main scanning lines L1 and L2
Are predetermined and both main scanning lines L1, L2
Pre-pattern passing time between the light receiving sensors PS1, P
Since it is determined from the detection signal and the clock by S2,
The average speed between the two main scanning lines L1 and L2 is immediately calculated by the CPU.

Similarly, the speed between the L2 and L3 lines of the photoreceptor belt 1 is detected from the detection of the passage times of the main scanning lines L2 and L3 of the pre-pattern 1A and the line interval A2.

The image writing laser light on the main scanning line L1 irradiates the pre-pattern 1A formed on the non-image area of the rotating photosensitive belt 1, and its reflected light is received by the light receiving sensor PS1. after the detection signal generated in the pre-patterns 1A, at a constant timing sub-scanning direction, after dT _H, mainly after a certain time dT _V passed the scanning direction, the main scanning lines L1 of the first image (e.g., yellow image)
Start writing.

Subsequently, the first latent image is formed by the main scanning line L1 by the sub-scanning by the rotation of the photosensitive belt 1 and the main scanning light by the exposure device 120, and then the image is visualized by the developing device 130 and proceeds. .

Further, when the photosensitive belt 1 is rotated, the pre-pattern 1A is irradiated by the writing laser beam immediately before the second main scanning line L2, and the reflected light thereof is received by the light receiving sensor PS2. 1A is generated.

The second writing device is supposed to start image writing after a predetermined time elapses according to a timer count from the start of writing by the first writing device. The measured passing time of the pre-pattern 1A between L1 and L2 is compared with the predetermined time.

There should be no difference between the distance A1 between L1 and L2 if there is no error in mechanical assembly and there is no fluctuation due to temperature change. When a difference larger than one line of the exposure scan is calculated, the second write start timing is corrected by the difference.

Similarly, the detection of the passing time of each of the main scanning lines L2 and L3 of the pre-pattern 1A is compared with a predetermined time, and the third image writing is performed by the sub-count corrected by the sub-count correcting unit. A temporal control of the start is performed, and a temporal control of the writing start of the third image (for example, a cyan image) is performed by comparing each detection of the passing time of the main scanning lines L3 and L4 with a predetermined time, The fourth image (for example, a black color image) is continuously written.

In FIG. 2, one pre-pattern 1A is formed on the photoreceptor belt 1, but a plurality of pre-patterns are provided at regular intervals, and control is performed by detecting lightly by the light receiving sensors PS1 to PS4. It is also possible.

In this case as well, the scanning line transit time is not limited to between L1 and L2, between L2 and L3, and between L3 and L4, but also between L1 and L3 and between L1 and L4. Needless to say, the correction may be made.

Further, since the light receiving sensors PS1 to PS4 can be installed at a position close to the surface of the photoreceptor belt 1, the writing start control detection accuracy in the sub-scanning direction is high, and only on one end side of the photoreceptor belt 1. The space for the light receiving sensor can be minimized because it may be installed. The pre-pattern 1A and the light receiving sensor are not limited to the detection of reflected light of laser light, but can be applied to the detection of reflected light of main scanning exposure using an LED array. Thereafter, image formation is started.

FIG. 4 is an overall structural view of a color copying machine according to a second embodiment of the present invention, which has a photosensitive belt 11 on which a translucent pre-pattern is formed, and has an image reading system A on the upper part. .

FIG. 5 is a perspective view showing an optical path of the photosensitive belt 11 and a laser scanning exposure apparatus. In the drawings, parts having the same functions as those of the above embodiment are denoted by the same reference numerals. Further, points different from the above embodiment will be described.

A translucent pre-pattern (registration mark) 11A is formed near the side end face of the photoreceptor belt 11 outside the image area and substantially at the same position as the pre-pattern 1A so as to be translucent. On the other hand, the guide member 4 has a concave portion formed at a position where the pre-pattern 11A and each main scanning line L1 coincide with each other, and a light receiving sensor PS11 is fixedly disposed in the concave portion as light detecting means. The light receiving sensor PS11
To PS14 detect the passage of the exposure scanning laser beam from the exposure device 120 through the translucent pre-pattern 11A, generate a reference position signal in the sub-scanning direction, and generate L2 in the next step.
.. L4.

Also in this embodiment, similarly to the above, at least two laser beams are used to irradiate the pre-pattern 11A provided on the photoreceptor belt 1, and the reflected light is pre-pressed using each light-electric sensor. The passage of the pattern 11A is detected, the speed change is detected based on the passage time and the distance between the two points, and the drive control of the photosensitive belt 11 is fed back. Further, temporal control of the start of writing of each image is performed based on the passing time between two points. As a result, the timing can be matched in the writing line corresponding to each color.

FIG. 6 shows a third embodiment of the present invention and is a perspective view showing the optical path of the belt-shaped image forming body and the laser scanning exposure apparatus.

The latent image of the exposure main scanning line L1 is formed on the surface of the photoreceptor belt 12 charged in advance by the laser beam of the laser scanning exposure device 120. Prior to this, a reference line (near the side edge of the non-image area) is formed. The latent images of the registration marks 12A and 12B are formed. The reference lines 12A and 12B are the first developing devices.
Developed by 130 to form visible image reference lines 12A, 12B. PS1 is a beam detector (light receiving sensor),
The laser beam incident from the rotating polygon mirror 124 via the fθ lens 125 is received, an output signal is generated, and a beam detection signal of a rectangular wave based on an arbitrary set value is output by a beam detection detection circuit.

The latent images are formed on the reference lines 12A and 12B by laser light exposure after the time set by the reference line count setting section has elapsed after the generation of the beam detect signal.

FIG. 7 is a block diagram of the scanning exposure correction for preventing the deviation of the laser beam in the main scanning direction and the sub scanning direction. Here, the sub-area counter is a counter for shifting the sub-scanning direction, and the sub-count setting section is for the first image exposure (by the laser scanning exposure apparatus 120) after the writing of the reference line 12A. Image exposure (laser scanning exposure equipment
220, 320, 420) for setting the timing from the reference detection value of the reference line 12A to the start of image writing in the sub-scanning direction, the main area counter is a counter for moving in the main scanning direction, and the main count setting unit is For image exposure 1 (by laser scanning exposure apparatus 120), reference line 1
After the 2A writing, the reference line 12 is used for the second to fourth image exposures (by the laser scanning exposure devices 220, 320, and 420).
This part sets the timing from the end point reference detection value of A to the start of image writing in the main scanning direction.

A plurality of (usually three) main scanning exposure beams downstream of the main scanning line L1 irradiate the visualized sub-scanning reference line 12B during scanning, respectively, and reflect the reflected light respectively to the light receiving sensors. By receiving light at PS22, PS23, and PS24, the speed control of the photosensitive belt 12 and the sub-scanning direction start time are controlled.

That is, before the image formation, the sub-scanning reference line 12B
By but be measured by using a light receiving sensor PS22, PS23, PS24 a time through the Shuhashi line spacing A _2, A _3,
The average speed of the photoconductor surface is calculated and corrected and corrected to a predetermined value.

During image formation, the first main scanning line L1 is positioned in the sub-scanning direction by the light-receiving sensor PS1 in a well-known manner, after the sub area counter counts dT _V ′, and then in the main scanning direction. DT at area counter
_{After H} ′ count, image exposure is performed, and the first
(For example, a yellow color image).

Next, the laser light for writing on the main scanning line L2 is applied to the rotating photosensitive belt 12 in the sub-scanning direction from the writing start time of the first scanning laser on the sub-scanning reference line 12B. The light reflected by the second writing laser beam is received by the light receiving sensor PS22, the time until the detection signal of the sub-scanning reference line 12B is generated is measured, and the measured value is compared with a predetermined value. Correct the start of writing.

[0079] In the main scanning direction, the reflected light of the second writing laser beam received by the light receiving sensor PS22, after a certain time dT _H elapses a predetermined after the detection signal generated in the reference line 12A, the main scanning line L2 Starts writing of a second image (for example, a magenta image).

Next, the reference lines 12A and 12B are irradiated by the main scanning line L3, a position detection signal is generated, and the passing time between the main scanning lines L2 and L3 is counted. The image writing time is controlled.

In the present embodiment, the arrangement order of the toner colors of the developing units 130 to 430 is not limited to Y, M, C, and K. For example, it is easy to detect the first development reference line 1A. Therefore, the first developing device 130 may be loaded with black (K) toner.

Since the light receiving sensors PS1 to PS4 can be installed at positions near the surface of the photosensitive belt 1, the detection accuracy of the write start control position in the sub-scanning direction is high, and the light receiving sensors PS1 to PS4 can be installed only on both sides of one end of the photosensitive belt 1. The space for the light receiving sensor can be minimized. The reference lines 12A, 12B and the light receiving sensors PS2, PS3,
The PS4 is not limited to detection of reflected light of laser light, but can be applied to detection of reflected light in main scanning exposure using an LED array.

Next, a color image formation of the fourth embodiment is shown in FIG.

In this embodiment, the transparent belt and the support near the position of the reference line 12A provided near the side edge of the non-image area of the photosensitive belt 12 are formed.
That is, the first developing device 13 corresponding to the first main scanning light L1
The toner color of the developer accommodated in 0 is made to be capable of transmitting the main scanning laser beam. The reference line (developed pattern) 12B visualized by the developing device 130 is transmitted by receiving the irradiation of the main scanning light L2, and the transmitted light is detected by the light receiving sensor PS12, as in the third embodiment. After a lapse of a predetermined timing dT by the detection signal, the image signal becomes a reference in the main scanning direction.

In the main scans L3 and L4, similarly, image writing is performed by the detected signal of the reference line 12B visualized.

FIG. 10 shows a fifth embodiment according to the present invention.
FIG. 2 is a perspective view showing a photoreceptor belt 11 that forms a potential change and an optical path of a scanning exposure device.

The photoreceptor belt 13 which has been charged in its entirety by the charger 110 has a linear latent image pattern 13B short in the main scanning direction at a predetermined position in the non-image forming area by the main scanning L1.
Are instantaneously formed. The formation of the latent image pattern 13B causes a change in the surface potential of the photosensitive belt 13.

Each main scanning light L in the traveling direction of the photosensitive belt 13
2, L3, L4 on the upstream side of the surface potential sensor SS2,
SS3 and SS4 are fixed respectively. When the latent image pattern 13B passes through the surface potential sensor SS2 immediately before the second main scanning light L2 due to the sub-scanning movement (X direction) of the photoreceptor belt 13, the surface potential sensor SS2 detects a potential change of the latent image pattern 13B. The main scanning lines L3 and L4, which detect and generate a reference position signal to correct the surface moving speed of the photoreceptor belt 13 and also correct the writing start timing, are similarly latent by the surface potential sensors SS3 and SS4. After the reference position of the image pattern 13B is detected, image writing is performed.

As described in the above embodiments, after the laser scanning exposure devices 120, 220, 320, and 420 are first provided, the focus of the laser beam is adjusted, and the drive roller diameter, belt thickness, and temperature are adjusted. Even if changes occur, the pre-pattern, toner pattern, and surface potential change pattern for each sub-scan line are detected and corrected for the speed change between sub-scan lines by sensor detection, and image writing timing control and drive control are performed. The image is formed by finely adjusting the fine color shift of one scanning width unit or one dot width unit with high precision, and forming an image.
It provides excellent effects and dramatically improves color image quality.

[0090]

As described above, in the color image forming apparatus of the present invention, in short, the present invention is directed to writing a pre-pattern, a developed pattern or a reference latent image on an image forming body in a sub-scanning direction in a scanning exposure apparatus. The cost can be reduced by using the control not only for the start control but also for the speed control of the image forming body. Further, by controlling the speed of the image forming body based on detection signals from at least two sensors, it is possible to prevent a transfer deviation when transferring the toner image formed on the image forming body. Furthermore, by correcting the write start timing based on the detection signals from at least two sensors , the
If there is an error in mechanical assembly or fluctuation due to temperature change
Also, when forming a color image , it is possible to easily and accurately realize the alignment of dots of multiple colors in the sub-scanning direction, which is one of the most important factors that determine the recording image quality, to prevent color misregistration and achieve high quality. An excellent effect of forming an image is produced. In particular, in the present invention, by controlling the speed of the image forming body prior to the image formation, and thereafter performing the writing start control also at the time of image formation, it is possible to realize more accurate alignment.

[Brief description of the drawings]

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

FIG. 2 is a perspective view showing a first embodiment of a laser scanning exposure apparatus of the color image forming apparatus of the present invention.

FIG. 3 is a control block diagram of the laser scanning exposure apparatus.

FIG. 4 is an overall configuration diagram of a second embodiment of the color image forming apparatus according to the present invention.

FIG. 5 is a perspective view of a laser scanning exposure apparatus according to the second embodiment.

FIG. 6 is a perspective view of an image forming body and a scanning exposure apparatus according to a third embodiment of the present invention.

FIG. 7 is a control block diagram of the scanning exposure apparatus of the third embodiment.

FIG. 8 is a block diagram of speed correction according to the present invention.

FIG. 9 is a perspective view of a scanning exposure apparatus according to a fourth embodiment of the present invention.

FIG. 10 is a perspective view of a scanning exposure apparatus according to a fifth embodiment of the present invention.

[Explanation of symbols]

1, 11, 12, 13 Belt-shaped image forming body (photosensitive belt) 1A Pre-pattern (registration mark) 2, 3 Rotating roller 4 Guide member 11A Translucent pre-pattern (registration mark) 12A Main scanning reference line 12B Secondary Scanning reference line 13A Main scanning latent image pattern 13B Sub-scanning latent image pattern 14 Transfer unit (transfer unit) 110, 210, 310, 410 Charger 120, 220, 320, 420 Laser scanning exposure device (laser writing unit) 121 Laser light source (Semiconductor laser) 124 polygon mirror (rotating polygon mirror) 125 fθ lens 130, 230, 330, 430 developing unit L1, L2, L3, L4 exposure main scanning line PS1, PS2, PS3 light receiving sensor PS4, PS11, PS12 light receiving sensor PS13 , PS14, PS21 Photo sensor SS2, SS3, SS4 Surface potential sensor W Image area width

──────────────────────────────────────────────────の Continuing on the front page (72) Isao Matsuoka, Inventor Konica, Ltd., 2970, Ishikawa-cho, Hachioji-shi, Tokyo (72) Inventor Tadayoshi Inspector, Konica, 2970, Ishikawa-cho, Hachioji-shi, Tokyo ▲ Saki ▼ Junichi (56) References JP-A-3-174172 (JP, A) JP-A-3-233471 (JP, A) JP-A-3-120063 (JP, A) JP-A-63-66580 (JP) JP-A-64-13567 (JP, A) JP-A-2-76754 (JP, A) JP-A-63-170818 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB G03G 13/01 G03G 15/01-15/01 117 G03G 21/00 370-502 G03G 21/14

Claims (3)

(57) [Claims] An image forming body that moves in a sub-scanning direction; a plurality of charging units that uniformly charge the image forming body; and an image formed by performing main scanning exposure on the image forming body charged by the charging unit. A plurality of scanning exposure devices for forming a latent image, a plurality of developing means for developing a latent image formed by the scanning exposure device to form a toner image, and a toner image formed on the image forming body. A transfer means for transferring to a transfer material separately moved in the sub-scanning direction, wherein a pre-pattern is formed outside an image area on the image forming body, and the scanning is performed. A plurality of light receiving sensors are provided which generate light detection signals by receiving light transmitted or reflected by the pre-pattern and illuminated by an exposure device. Prior to image formation, at least two light receiving sensors detect light detected by each of the light receiving sensors. And performing speed control of the image forming body based on the detection signal detected by each of the at least two light receiving sensors, and correcting a writing start timing in the sub-scanning direction in the scanning exposure apparatus. A color image forming apparatus. 2. An image forming body that moves in a sub-scanning direction, a plurality of charging units that uniformly charge the image forming body, and an image formed by performing main scanning exposure on the image forming body charged by the charging unit. A plurality of scanning exposure devices for forming a latent image, a plurality of developing means for developing a latent image formed by the scanning exposure device to form a toner image, and a toner image formed on the image forming body. A transfer means for transferring to a transfer material separately moved in the sub-scanning direction, wherein a color image forming apparatus forms a color image. Forming a development pattern by developing by the developing means; providing a plurality of light receiving sensors for receiving light emitted by the scanning exposure device and transmitting or reflecting the development pattern to generate a detection signal; To Prior to performing speed control of the image forming body based on detection signals detected by at least two light receiving sensors, at the time of image formation, the scanning is performed based on detection signals detected by at least two light receiving sensors. A color image forming apparatus for correcting a writing start timing in a sub-scanning direction in an exposure device. 3. An image forming body that moves in a sub-scanning direction, a plurality of charging units that uniformly charge the image forming body, and an image formed by performing main scanning exposure on the image forming body charged by the charging unit. A plurality of scanning exposure devices for forming a latent image, a plurality of developing means for developing a latent image formed by the scanning exposure device to form a toner image, and a toner image formed on the image forming body. A transfer means for transferring to a transfer material separately moved in the sub-scanning direction, wherein a color image forming apparatus forms a color image. Forming a latent image pattern, and providing a plurality of surface potential sensors for detecting a potential change of the latent image pattern to generate a detection signal, and detecting a detection signal detected by each of at least two surface potential sensors prior to image formation. Based on And controlling the speed of the image forming body and correcting a writing start timing in the sub-scanning direction in the scanning exposure apparatus based on a detection signal detected by each of at least two surface potential sensors during image formation. A color image forming apparatus.