JP3267009B2 - 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 for forming a color image by multiply transferring a toner image for each color component constituting a color image onto a recording sheet.
The present invention relates to an improvement of a color image forming apparatus provided with a unit for correcting a transfer position shift of a multiply transferred toner image.

[0002]

2. Description of the Related Art Generally, in a color image forming apparatus such as a color copying machine or a color printer, a color image is formed by multiply transferring toner images of a plurality of colors such as magenta, yellow, and cyan onto a recording sheet. As a specific device,
One of the image forming stations that repeatedly transfers a toner image to a rotating recording sheet held by a sheet conveying drum (hereinafter referred to as a transfer drum method) or a plurality of recording sheets arranged along a recording sheet conveying path. 2. Description of the Related Art There is known an image forming station that continuously transfers a toner image to a recording sheet (hereinafter, a tandem method).

However, in any of the apparatuses, it is a condition for forming a good color image that the transfer positions of the toner images of the respective colors on the recording sheet are exactly coincident with each other. Otherwise, a subtle color shift occurs in the formed color image, and it is impossible to reproduce a color image faithful to image information.

Conventionally, as a means for addressing this problem, a transfer position shift amount of a toner image is detected from a test pattern image formed on a trial basis, and an electrostatic latent position with respect to the photosensitive member is determined based on the detected position shift amount. A method of correcting the image writing timing has been adopted. Specifically, when exposing and scanning the photoreceptor with a light beam emitted from the laser scanning unit, the timing of transferring image data to the laser scanning unit according to the detected amount of misalignment of the toner image is set to several scan lines. This is delayed or advanced by several scanning lines, thereby shifting the toner image formation position on the photoreceptor back and forth in the image forming direction.

In the color image forming apparatuses disclosed in JP-A-1-183676 and JP-A-2-291573, a light beam is reflected toward a photoreceptor in accordance with a detected positional shift of a toner image. The position of the toner image on the photosensitive member is shifted by shifting the optical path of the light beam by changing the attitude of the reflecting mirror or the attitude of the laser scanning unit itself.

[0006]

However, in the former method of changing the transfer timing of the image data to the laser scanning unit, the writing timing of the electrostatic latent image can be corrected only for each scanning line of the light beam. However, among the detected positional deviation amounts of the toner image, the positional deviation amount smaller than one scanning line cannot be corrected.

Particularly, in an image forming apparatus in which the number of scanning lines per unit length is small, that is, in an apparatus having a low resolution, the interval between scanning lines is large. The deviation was remarkable. On the other hand, in an image forming apparatus having a large number of scanning lines per unit length, that is, an apparatus having a high resolution, it is possible to substantially eliminate the transfer position shift of the toner image because the interval between the scanning lines is small. In order to realize the resolution, a high performance laser scanning unit or the like is required, and there is a problem that the production cost increases.

In the latter method of changing the attitude of the reflecting mirror or the laser scanning unit, since the irradiation angle of the light beam on the photoreceptor is changed, the light beam is scanned on the photoreceptor even if the posture is slightly changed. The position is greatly shifted, and there is a problem that the attitude control of the reflecting mirror or the like must be performed extremely precisely in order to correct the minute amount of the positional shift of the toner image. In particular, this problem is remarkable in an apparatus having a long optical path length from the reflecting mirror to the photosensitive member.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to correct the transfer position of a toner image on a recording sheet with high accuracy and to eliminate color shift. An object of the present invention is to provide a color image forming apparatus capable of forming a high-quality color image.

[0010]

In order to achieve the above object, a color image forming apparatus of the present invention forms an electrostatic latent image on a photoreceptor using a light beam for each color component constituting a color image. In addition, in a color image forming apparatus that develops the electrostatic latent image to form a toner image, and transfers a toner image of each color component onto a recording sheet in a multiplex manner to form a color image, And a driving means for changing the arrangement angle of the plate member with respect to the optical path of the light beam, and the displacement amount of the toner image multiple-transferred onto the recording sheet is reduced. A plate member controlling means for controlling the driving means based on the driving means is provided.

[0011]

Since a light-transmitting plate member is provided on the optical path of the light beam, the light beam passes through the plate member to expose the photosensitive member. As shown in FIG. 7, the light beam 101 incident on the plate member 100 at an incident angle θ is refracted on the front and back surfaces of the plate member 100 and transmitted through the plate member 100 at a transmission angle ω. If the front and back surfaces are parallel surfaces, θ = ω, and the incident light beam 101 and the transmitted light beam 102 become parallel light whose optical path is displaced by the distance d. This displacement amount d can be freely adjusted by appropriately changing the arrangement angle of the plate member with respect to the optical path of the light beam. That is, by appropriately changing the arrangement angle of the plate member using the driving unit, the formation position of the toner image on the photoconductor can be arbitrarily corrected.

Further, since the light beams before and after the plate member are parallel to each other, even if the arrangement angle of the plate member is largely changed, the displacement d of the light beam incident on the photoreceptor is small, and The formation position of the toner image can be finely corrected.

Therefore, the amount of positional deviation of the toner image multiplex-transferred onto the recording sheet is detected in advance, and the driving means is controlled by the plate member control means to which the detected amount is input, so that the amount of positional deviation of the toner image is increased. It can be corrected to accuracy.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a color image forming apparatus according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a first embodiment of a color laser printer to which the present invention is applied. In the figure, reference numeral 10 denotes a photosensitive drum, and reference numeral 11 denotes a photosensitive drum.
Is a charging corotron for pre-charging the surface of the photoconductor drum 10, reference numeral 12 is a laser scanning unit for exposing and scanning the charged photoconductor drum 10 with a light beam to write an electrostatic latent image, and reference numeral 13 is black, cyan, Four developing devices 13B, 13C, each containing magenta and yellow toners,
Rotary developing units 13M and 13Y are rotatably disposed and selectively selected. Reference numeral 14 denotes a pre-transfer treatment corotron for removing the potential on the photosensitive drum 10, and reference numeral 15 denotes a residual toner on the photosensitive drum 10. Reference numeral 16 denotes a cleaner for removing toner, and an erase lamp for removing residual charges on the photosensitive drum 10.

Reference numeral 21 denotes a transfer drum which rotates by electrostatically adsorbing the recording sheet 20 on the peripheral surface, reference numeral 22 denotes an adsorption corotron which applies electric charge to the transfer drum 21 to adsorb the recording sheet 20, and reference numeral 23 denotes A transfer corotron for transferring the toner image on the photosensitive drum 20 to the recording sheet 20 side, a reference numeral 24 denotes a charge removing corotron for discharging the recording sheet 20 after the final color transfer step is completed, and a reference numeral 25 denotes a transfer after the final color transfer step is completed. A neutralizing corotron for neutralizing the drum 21;
Reference numeral 26 denotes a cleaning brush for cleaning paper dust and the like adhering to the transfer drum 21, and reference numeral 27 denotes a separation finger for separating the recording sheet 20 from the transfer drum 21. Reference numeral 28 denotes a sheet transport system that transports the recording sheet 20 to the suction corotron 22.

Reference numeral 30 denotes a fixing device comprising a pair of a heating roll 31 and a pressure roll 32, through which the recording sheet 20 having undergone the transfer step is inserted. Reference numeral 33 denotes a recording sheet passing through the fixing device 30. A fuser exit roll to be conveyed, reference numeral 34 denotes a discharge tray for accommodating the fixed recording sheet 20, and reference numeral 35 denotes a recording sheet 2 to the discharge tray 34.
Exit roll for sending 0.

With the above configuration, in the color laser printer of this embodiment, a toner image is formed on the photosensitive drum 10 for each color component constituting a color image, and the formed toner image is transferred to the transfer drum 21. Are sequentially transferred to the recording sheet 20 held by the printer, and a color image in which the toner images of the respective color components overlap each other is formed on the recording sheet 20. Thereafter, the recording sheet 20 peeled from the transfer drum 31 is discharged to the discharge tray 34 via the fixing device 30, and
The color image is fixed on the recording sheet 20.

Next, a configuration for realizing the present invention in the above-described apparatus will be described. FIG. 2 shows a schematic configuration of the laser scanning unit of the present embodiment. In the figure, reference numeral 40 denotes a laser light source, reference numeral 41 denotes a collimator lens,
Reference numeral 42 denotes a polygon mirror for deflecting the light beam 51 to scan the photosensitive drum 10, reference numeral 43 denotes an f-θ lens, and reference numeral 44 denotes a reference sensor for detecting the start of scanning of the light beam 51 for each line. . The light beam 51 emitted from the laser light source 40 passes through the collimator lens 41 and is incident on and reflected by the polygon mirror 42. The reflected light beam is deflected by the rotation of the polygon mirror 42, Is repeatedly scanned for each line. At this time, the reference sensor 44 outputs a scan start timing signal for each line scan, and the data transfer means (not shown) transfers image data to the laser scanning unit at a predetermined timing synchronized with the input of the scan start timing signal. Run.

In this laser scanning unit, a light transmissive plate glass 45 is disposed between the collimator lens 41 and the polygon mirror 42, and the laser light source 4
The light beam 51 emitted from 0 passes through the plate glass 45 and enters the polygon mirror 42. Further, a stepping motor 46 for changing the arrangement angle of the plate glass 45 with respect to the optical path of the light beam 51 is connected to the plate glass 45. Accordingly, when a drive control signal based on the toner image transfer position shift amount is given to the stepping motor 46 to change the arrangement angle of the plate glass 45 with respect to the optical path of the light beam 51, the light beam 51 transmitted through the plate glass is not changed before the angle change. Is displaced in parallel to the optical path of the photosensitive drum, and the writing position of the electrostatic latent image on the photosensitive drum is corrected.

As shown in FIG. 3, a sheet glass control means 47 is connected to the stepping motor 46, and generates a drive control signal for the stepping motor 46 based on the input displacement amount of the toner image. Is sent to the stepping motor 46. This control means 47 includes a storage circuit 48 for storing the transfer position deviation amount by replacing it with the corresponding number of pulse signals, a pulse generation circuit 49 for continuously generating pulse signals at predetermined intervals for the stepping motor 43, and The counter circuit counts the number of pulse signals generated by the pulse generation circuit 49 and stops the pulse generation circuit 49 when the number of pulse signals becomes equal to the number of pulse signals set in the recording circuit. The input of the transfer position shift amount to the sheet glass control means 47 is performed by inputting the position shift amounts of the remaining three color toner images with respect to the reference toner image, respectively, and the sheet glass control means 47 drives each color component. The control signal is sent to the stepping motor 46 before the formation of the corresponding toner image. Further, the plate glass control means 47 sends a drive control signal for resetting the plate glass 45 to the reference position to the stepping motor 46 before forming the reference toner image.

In the color laser printer of the present embodiment having the above-described configuration, for example, at the time of shipment or maintenance at the installation site, the engineer can use the color image of the test pattern output in advance by the engineer as a reference toner image (for example, The transfer position deviation amounts of the toner images of the other three colors with respect to the yellow toner image) are read, and these values are input to the plate glass control means 47 and used. Thus, after the transfer position shift amount is input, the arrangement angle of the plate glass 45 is changed based on the input value every time a color toner image is formed, and the toner image formation position on the photosensitive drum 10 is corrected. Therefore, the transfer position of the toner image of each color component on the recording sheet 20 is also corrected, and a high-quality color image without color shift can be obtained.

In this embodiment, the entire transfer position deviation of the toner image is corrected by changing the arrangement angle of the plate glass 45. However, the transfer position deviation amount becomes large. When the arrangement angle of the plate glass 45 with respect to the optical path of the light beam becomes large, the light beam may be totally reflected on the surface of the plate glass 45. For this reason, it is preferable that the large transfer position shift amount is corrected at the timing of sending image data to the laser scanning unit 12, and only the small transfer position shift amount is corrected by the arrangement angle of the plate glass 45.

Next, a second embodiment of the color laser printer to which the present invention is applied will be described. FIG. 4 shows a color laser printer according to the second embodiment. This apparatus is a so-called tandem type, and has four image forming stations 60Y, 60M, 60C, 60 corresponding to respective colors of yellow, magenta, cyan, and black.
B, and the image forming stations 60Y to 60B
Transfer and transfer the toner image for each color component formed by
Are sequentially transferred to a recording sheet 80 held and conveyed to form a color image.

Each image forming station 60Y-60B
Are provided with a charger 62, a laser scanning unit 63, a developing device 64, and a cleaner 65 around a photosensitive drum 61, respectively, and form a toner image for each color component through respective steps of charging, exposure, and development. Formed on the photosensitive drum 61,
This toner image is electrostatically transferred to a recording sheet 80 carried on the transfer / conveying belt 70.

On the other hand, the transfer / conveying belt 70 is wound around a plurality of roll groups including a driving roll, and inside the recording sheet 80 sent from a supply tray (not shown) is electrostatically attracted to the surface of the belt 70. Charging unit 71, a transfer corotron 72 for electrostatically transferring the toner images formed in the image forming stations 60Y to 60B to the recording sheet 80, and the recording sheet 80 electrostatically attracted to the belt
And a neutralizing corotron 74 for neutralizing the belt 70 after the recording sheet 80 is peeled off. A sheet detection sensor 75 for detecting the recording sheet 80 is provided near the position where the recording sheet 80 is attracted to the belt 70, and the detection signal is input to a data transfer unit described later.

With the above configuration, in the color laser printer according to the present embodiment, when the sheet detection sensor detects a recording sheet attracted to the transfer / transport belt, a sheet detection signal is output to the data transfer means, and the data transfer is performed. The means transfers the image data to the laser scanning unit 63 of each of the image forming stations 60Y to 60B at a predetermined timing synchronized with this signal. The transfer of the image data is first performed to the laser scanning unit 63 of the image forming station 60Y serving as a reference, and the other image forming stations 60M to 60B each have a predetermined timing from the transfer to the image forming station 60Y. And transferred. As a result, in each of the image forming stations 60Y to 60B, a toner image for each color component is formed on the photosensitive drum 61, and these toner images are recorded on the recording sheet 8 conveyed by the transfer conveyance belt 70.
0, and a color image in which the toner images of the respective color components overlap each other is formed on the recording sheet 80. Thereafter, the recording sheet 80 separated from the transfer conveyance belt 70
Is discharged to a discharge tray (not shown) via the fixing device 76.

Next, a configuration for embodying the present invention in the device of the second embodiment will be described. In this embodiment, it is required to correct the transfer position deviation of the toner images of other colors formed in the image forming stations 60M to 60B based on the yellow toner image formed in the image forming station 60Y. Therefore, the other image forming stations 60M except the image forming station 60Y serving as a reference
~ 60B, the laser scanning unit 63M ~
As 63B, the laser scanning unit with the plate glass 45 shown in the first embodiment was used. For the image forming station 60Y, a conventional laser scanning unit having no plate glass 45 is used.

In this embodiment, in order to periodically detect the transfer position shift amount of the toner image of another color with respect to the reference yellow toner image, a position shift detecting means as shown in FIG. 5 is provided. This displacement detecting means is provided by the laser scanning unit 63Y of each of the image forming stations 60Y to 60B.
And mark data transfer means 81 for sequentially transmitting the image data of the misregistration detection mark at predetermined timing with respect to .about.63B, and each image forming station 60Y provided downstream of the last image forming station 60B. ~ 6
0B, a detection sensor 82 for reading the misregistration detection marks sequentially transferred onto the transfer conveyance belt 70, and a mark detection signal output from the detection sensor 82 is used to determine the amount of misregistration of the transfer position of the toner image of another color with respect to the yellow toner image. And a displacement amount calculating means 83 for calculating each.

Accordingly, by periodically operating the position shift detecting means, data of the transfer position shift of the toner image of another color with respect to the yellow toner image can be obtained. The transfer timing of the image data to the laser scanning units 63Y to 63B or the arrangement angle of the plate glass 45 disposed in the laser scanning units 63M to 63B is determined.

FIG. 6 shows laser scanning units 63Y to 63B using data obtained by the above-mentioned displacement detecting means.
FIG. 3 is a block diagram showing a control system of FIG. First, in the positional deviation amount detection mode which is periodically performed, the positional deviation amount calculating means 83 calculates a transfer positional deviation amount of the other color toner image with respect to the yellow toner image for each color based on the mark detection signal. The correction data is distributed to the data rolling means 84 and the sheet glass control means 85. At this time, with respect to the positional deviation amount larger than one scanning line on the photosensitive drum, the correction data is sent to the data transfer means 84, and the data
The correction data for the positional deviation amount smaller than the scanning line is sent to the sheet glass control means 85. For example, if the amount of misalignment of the magenta toner image with respect to the yellow toner image is 2.5 scan lines, correction data for 2 scan lines is sent to the data transfer unit 84 and 0.5 mm to the plate glass control unit 85. The correction data for the scanning line is sent. Such correction data is transferred for each of the magenta, cyan, and black color toner images, and the data transfer unit 84 and the plate glass control unit 85 hold these correction data.

Next, when the normal print mode is started after the position shift amount detection mode is completed, first, the sheet glass control means 85 first executes the stepping motor 46 provided in the laser scanning unit 63M based on the held correction data. Is generated and transmitted to the stepping motor 46. Thereby, in the laser scanning unit 63M, the arrangement angle of the plate glass 45 located in the optical path of the light beam is changed based on the transfer position shift amount smaller than one scanning line. Then, a drive control signal is also sent to each of the stepping motors 46 of the laser scanning units 63C and 63B based on the correction data for each color, and the laser scanning units 63C and 63B are driven.
Also, the arrangement angle of the plate glass 45 is changed based on the transfer position deviation amount smaller than one scanning line.

Thereafter, the recording sheet 80 is attracted to the transfer / conveying belt 70, and the sheet detection signal is transmitted to the data rolling means 84.
The data transfer means 84 sends image data relating to the yellow toner image to the laser scanning unit 63Y at a predetermined timing synchronized with the sheet detection signal, and further transmits the image data relating to the magenta toner image at a predetermined timing from this transmission. Laser scanning unit 6 for image data
Send to 3M. At this time, the laser scanning unit 63
The transmission timing of the image data for M is changed based on the correction data held by the data transfer unit 84, that is, the transfer position deviation amount larger than one scan line. The image data is also transmitted to the laser scanning units 63C and 63B at a predetermined timing after the image data is transmitted to the laser scanning unit 63Y.
The transmission timing is changed based on the correction data for each color held in the data transfer unit 84.

As described above, in the present embodiment, the writing of the electrostatic latent image on the photosensitive drum is performed with respect to the displacement amount larger than one scanning line among the transfer positions of the toner image detected by the displacement detecting means. The shift is corrected by changing the timing, and the position shift amount smaller than one scanning line is corrected by shifting the incident position of the light beam on the photosensitive drum. As a result, it is possible to correct the transfer position shift of the toner image of each color on the recording sheet with high accuracy, and to effectively prevent the occurrence of the color shift.

[0034]

As described above, according to the color image forming apparatus of the present invention, the light transmittance provided on the optical path of the light beam based on the positional deviation of the toner image multiplex-transferred onto the recording sheet. Since the arrangement angle of the plate member is changed to correct the formation position of the toner image on the photosensitive member, a high-quality color image without color shift can be obtained.

Further, even if the arrangement angle of the light transmitting plate member is largely changed, the incident position of the light beam on the photoreceptor changes only slightly. Therefore, the formation position of the toner image on the photoreceptor is finely corrected. Thus, the toner image transfer position deviation can be corrected with higher accuracy.

Further, since the toner image transfer position deviation can be finely corrected with a simple configuration merely by changing the arrangement angle of the light transmitting plate member, a high quality color image forming apparatus is provided at low cost. It is possible.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a first embodiment of a color image forming apparatus of the present invention.

FIG. 2 is a perspective view illustrating a configuration of a laser scanning unit according to the first embodiment.

FIG. 3 is a block diagram illustrating a control system of the flat glass according to the first embodiment.

FIG. 4 is a schematic view showing a second embodiment of the color image forming apparatus of the present invention.

FIG. 5 is a schematic diagram illustrating a configuration of a displacement detection unit according to a second embodiment.

FIG. 6 is a block diagram illustrating a control system of a laser scanning unit according to a second embodiment.

FIG. 7 is a diagram illustrating the operation of the present invention.

[Explanation of symbols]

10 photoreceptor drum, 12 laser scanning unit, 2
0 ... recording sheet, 45 ... sheet glass, 46 ... stepping motor, 47 ... sheet glass control means

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Katsumi Sakamaki 2274 Hongo, Ebina City, Kanagawa Prefecture, within Fuji Xerox Co., Ltd. (72) Inventor Nobuyuki Nakayama 2274 Hongo, Ebina City, Kanagawa Prefecture, within Fuji Xerox Co., 72) Inventor Takeshi Noguchi 2274, Hongo, Ebina-shi, Kanagawa Prefecture, within Fuji Xerox Co., Ltd. (72) Inventor Minoru Minato Kasama 2274, Hongo, Ebina-shi, Kanagawa Prefecture, within Fuji Xerox Co., Ltd. 2274 Hongo, Ebina City, within Fuji Xerox Co., Ltd. (72) Inventor Satoshi Usui 2274, Hongo, Ebina City, Kanagawa Prefecture, within Fuji Xerox Co., Ltd. (56) References JP 50-3346 (JP, A) 60-4951 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41J 2/525 G03G 15/01

Claims (2)

(57) [Claims] 1. A method for exposing a photoreceptor using a light beam.
A plurality of laser scanning units for forming an electrostatic latent image on the photoreceptor using a light beam for each color component constituting a color image, and developing the electrostatic latent image to form a toner image In a color image forming apparatus that forms a color image by transferring a toner image of each color component onto a recording sheet in a multiplex manner, the laser scanning unit includes a laser light source and a laser light source.
Scans the photoconductor by deflecting the light beam emitted from the light source
A polygon mirror for arranging a light-transmitting plate member on an optical path of a light beam between the laser light source and the polygon mirror, and an arrangement angle of the plate member with respect to an optical path of the light beam. And a plate member control means for controlling the drive means based on the amount of positional deviation of the toner image multiplex-transferred onto the recording sheet. 2. The color image forming apparatus according to claim 1, further comprising: a misregistration detecting means for detecting a misregistration amount of the toner image for each color component when the respective color toner images are multiplex-transferred. Is input to the plate member control means.