JP2000352854A - Color image forming equipment - Google Patents

Abstract

(57) [Problem] To reduce the size of a color image forming apparatus having two photoconductors. SOLUTION: A rotary developing device 1 having a plurality of developing units 50 in proximity to two photoconductors 11 and 12 is provided.
7 is provided. Two of the developing units 50 face the photoconductors 11 and 12, respectively. Rotary developing device 1
By rotating the developing unit 7, the developing unit 50 facing the photoconductors 11 and 12 is changed. Rotary developing device 1
The developing is performed on the photoconductors 11 and 12 by 7 to form a toner image. Each toner image is superimposed on the intermediate transfer belt 10 and transferred to the paper 39 to form an image.

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 an image based on image information, and more particularly to a color image forming apparatus having two photosensitive members.

[0002]

2. Description of the Related Art Conventionally, in a color image forming apparatus such as a color copying machine and a color printer, a multi-rotation process color image forming apparatus and a tandem type color image forming apparatus have been mainly used.

The former has one photoreceptor, and four developing devices of yellow, magenta, cyan, and black are sequentially operated on this one photoreceptor, and an image forming process for each color is repeated four times. Thus, a color image is formed. Although this color image forming apparatus is small, it has a problem that the number of prints per unit time is small.

The latter is provided with an image forming station including a photoreceptor and a developing device for each of yellow, magenta, cyan, and black, that is, a total of four image forming stations. In this case, although the number of prints per unit time is large, since each image forming station requires an image forming process device such as a charger and an exposure device, there is a problem that the size of the device and the cost are increased. Have.

Therefore, conventionally, a color image forming apparatus having a larger number of prints per unit time than a multi-rotation process color image forming apparatus and capable of achieving downsizing and cost reduction as compared with a tandem type apparatus has been proposed. A two-photoconductor type color image forming apparatus having two photoconductors has been developed. For such a color image forming apparatus, for example, a technique disclosed in the following publication is known.

In the technique disclosed in Japanese Patent Application Laid-Open No. 2-1273, first, images of a first color and a second color are formed on two photosensitive members, respectively, and are sequentially transferred to a sheet on a transfer drum. This is a technique of forming a color image by forming a third color image and a fourth color image on each of the photoconductors and similarly transferring the images to a sheet on a transfer drum.

The technology disclosed in Japanese Patent Application Laid-Open Nos. 4-204871 and 10-177286 is to first form an image of a first color and a second color on two photoconductors, respectively, and to form an intermediate transfer belt. The images are sequentially transferred to the respective photoreceptors, and then the images of the third and fourth colors are formed on the respective photoconductors, similarly transferred to the intermediate transfer belt, and the images stacked on the intermediate transfer belt are transferred to paper. This is a technique for forming a color image.

As described above, while improvements have been made to the image forming process, techniques for achieving higher resolution have been developed, for example, as disclosed in the following publication.
Also in this case, there is a close relationship with the above-described image forming process.

The technique disclosed in Japanese Patent Application Laid-Open No. 8-169140 discloses a technique in which high-resolution image data is divided into a plurality of low-resolution image data, and latent images are individually hidden on a photoconductor based on each image data. This is a technique for obtaining an initial high-resolution image by forming an image and then performing transfer synthesis.

[0010]

However, in a color image forming apparatus having two photoconductors as in the above and the above techniques, it is necessary to face a plurality of developing devices for each photoconductor. . Therefore, in each photoconductor, it is necessary to secure the size of the photoconductor itself and the space around the photoconductor so that the developing device can be installed on the outer periphery. For this reason, the space occupied by the photoconductor in the color image forming apparatus becomes large regardless of whether the photoconductor is in a drum shape or a belt shape. This leads to an increase in the size of the entire color image forming apparatus.

In the case where a plurality of developing devices are provided for each photoconductor, the efficiency of space utilization in the color image forming apparatus is poor because the developing devices are arranged separately. In addition, the shape of each developing device often differs depending on the arrangement position and the like, which is disadvantageous for downsizing the color image forming apparatus from these points. In addition, when the shape of the developing tank in the developing device is not uniform, it is difficult to handle the toner when replacing the toner or when replacing the unit.

On the other hand, in a color image recording apparatus having the above-mentioned or two photoconductors, when the above technique is employed to form a black monochrome image, for example, four colors of yellow, magenta, cyan and black are used. In the case of a color image forming apparatus that forms an image using a color, a developing device for one color of black and one color is arranged around one photoconductor, and a total of 3 colors of black and the remaining color is arranged around the other photoconductor. It is necessary to arrange a developing device for each color. Therefore, the above problems of the color image forming apparatus having the above two photoreceptors become more serious.

Further, when there are a plurality of developing positions, the distance from the charging position and the exposing position differs for each developing position, and the time required for the photosensitive member to move the distance differs. The amount of charge decay of the body will be different. As a result, the optimum conditions for the image forming process differ at each developing position.

Therefore, it is very difficult to determine the process conditions for obtaining the optimum image quality at each developing position.
Therefore, the simulation for obtaining this is complicated, and an extremely large number of experiments are required. As a result, there is a problem that the development period is lengthened.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and has a large number of prints per unit time as compared with a multi-rotation process color image forming apparatus.
An object of the present invention is to provide a color image forming apparatus which is smaller and cheaper than a conventional two-photoconductor color image forming apparatus while maintaining the features of the photoreceptor type color image forming apparatus.

[0016]

SUMMARY OF THE INVENTION A color image forming apparatus according to the present invention includes two photoconductors that carry a toner image formed by development, and forms an image by superimposing the toner images. Wherein the developing unit includes a plurality of developing units that perform development in opposition to the photoreceptor, and includes a rotating developing device, and each of the developing units is configured such that two of the developing units respectively face the respective photoreceptors at the same time. The developing unit is provided so that the developing unit facing each of the photoconductors is changed by the rotation of the developing device.

According to the above arrangement, the developing device close to the two photoconductors performs development on each photoconductor. The developing device has a plurality of (for example, a plurality of colors) developing units. By rotating the developing device, it is possible to change a developing unit that develops each photoconductor.

In the above configuration, since the developing position of each photosensitive member is only one position facing the developing device, the above-mentioned problems of the technique due to the presence of a plurality of developing positions can be solved. Therefore, if the photosensitive member is in the form of a drum, the drum diameter can be reduced, and if the photosensitive member is in the form of a belt, the belt length can be reduced.

As a result, since the space occupied by the photoconductor can be reduced, the size of the color image forming apparatus incorporating the photoconductor can be reduced.

Further, since the development position on each photoconductor is one, the time from exposure to development (moving distance of the photoconductor from the exposure position to the development position) is reduced in each development unit. Matches when developing. Therefore, even if the images are developed by separate developing units,
The development is performed under the same conditions.

Therefore, since the operation of the developing device (for example, the operation timing of the developing device) can be designed under the same conditions, the development period of the control system (including software) can be shortened, and the sensitivity of the photosensitive member can be shortened. Since the optimization of the process conditions such as the charge amount and the developing bias can be simplified, the time (development period) required for a simulation or an experiment for obtaining the same can be shortened. As a result, it is possible to suppress an increase in the cost of the device.

In the above configuration, since a plurality of developing units are housed in one developing device, the space utilization efficiency (space efficiency) can be improved. That is, in each of the developing units, the developing device accommodating the plurality of developing units can be miniaturized while securing the capacity of the developing tank containing the developer.
If the shape of the developing device is, for example, cylindrical, space efficiency is particularly improved.

As a result, since the space occupied by the developing device can be reduced, the size of the color image forming apparatus can be further reduced.

Further, since each developing unit of the developing device can be formed in the same shape, the cost of the device can be reduced as compared with a case where a plurality of developing devices having different shapes are manufactured and designed. Becomes

In the above-described color image forming apparatus, the developing device further includes four developing units, and the two developing units facing each of the photosensitive members at the same time are arranged adjacent to each other. Is preferred.

According to the above configuration, the developing device includes four developing units (for example, the developing device is formed by equally dividing the developing device into four). Of these, two adjacent developing units are used. By facing the photoconductor at the same time,
The development is performed on each photoconductor.

Of the four developing units, two that are not adjacent
In a configuration where two developing units face the photoconductor at the same time,
The angle formed by the direction connecting the center of the developing device to each of the opposing positions is approximately 180 degrees.

In this case, since the developing device is located between the photosensitive members, the distance between the photosensitive members is increased, and the space efficiency is reduced. Further, it becomes difficult to install an exposure device or the like between the photoconductors. Further, if the distance between the photoconductors is to be reduced, it is necessary to limit the size of the developing device, and it becomes difficult to secure a sufficient accommodation space for the developer.

On the other hand, in the above configuration, the angle formed by the direction connecting the center of the developing device to each of the opposing positions is close to 90 °. In this case, since the developing device is not disposed between the photoconductors, a cleaning device is provided between the photoconductors arranged in parallel,
Space for installing a charger, an exposure device, and the like can be secured. Further, since the size of the developing device is not limited by the distance between the photoconductors, it is possible to sufficiently secure the amount of developer stored in each developing unit.

As a result, the space efficiency inside the color image forming apparatus is improved, and it is possible to reduce the size of the entire apparatus while securing a sufficient space such as the capacity of the developer.

Alternatively, in the above-mentioned color image forming apparatus, the developing device further includes five or more developing units, and the two developing units facing each of the photoconductors at the same time are located between each other. It is preferable that one of the developing units is interposed therebetween.

According to the above arrangement, the developing device is provided with five or more developing units. Of these, two developing units separated by one face the photoconductor at the same time, so that each photoconductor is The development is carried out.

In a configuration in which two adjacent developing units of the five or more developing units face the photosensitive member at the same time, the angle formed by the direction connecting the center of the developing device and each facing position becomes small.

In this case, in the developing device, the positions facing the respective photoconductors come closer to each other, and accordingly, the respective photoconductors also need to be arranged closer to each other. Therefore, in order to secure a space for disposing an exposure device and the like between the photoconductors, it is necessary to increase the size of the developing device.

On the other hand, in the above configuration, two developing units separated by one face the photoreceptor at the same time. In addition, a space for installing a cleaning device, a charger, an exposure device, and the like can be secured.

Further, as compared with a configuration in which two adjacent developing units face each photosensitive member, the number of developing units required for changing the developing unit facing each photosensitive member when switching the image forming process is different. The rotation angle can be small. Therefore, the switching of the image forming process can be completed in a short time.

As a result, it is possible to reduce the size of the color image forming apparatus and to shorten the image forming time.

In the color image forming apparatus having five or more developing units, it is preferable that the developing device rotates in both directions.

According to the above configuration, when the stop position of the developing device is changed, the relationship between the arrangement of the developing units of each color used for color image formation and the stop positions before and after the change of the developing device is changed. Based on this, the developing device can be rotated in a direction in which the rotation angle is minimized.

For example, in a case where the developing units in the developing device are arranged at equal intervals, when forming a color image continuously, the developing device is alternately rotated in a different direction at a rotation angle of 72 degrees. Thereby, an image can be formed.

Therefore, the switching of the image forming process can be performed in the shortest time, and the image forming time can be reduced as compared with the configuration in which the rotation direction of the developing device is fixed in one direction.

In the color image forming apparatus having five or more developing units, it is preferable that the developing device further includes at least two developing units for storing a developer of a specific color.

According to the above configuration, one of the developing units for storing the developer of the color (for example, black) used in forming a monochrome image is dedicated to monochrome image formation, and the other is dedicated to color image formation. be able to.
As a result, the storage amount of the developer of the color used when forming a frequently used monochrome image is increased, and the consumption balance of the developer of each color stored in the developing device can be improved.

As a result, it is possible to suppress the variation in the timing of replenishing the developer, and to improve the maintainability of the color image forming apparatus.

In the color image forming apparatus having five or more developing units and having at least two developing units of a specific color, the developing units accommodating the developing agent of the specific color may further include: It is preferable that they are arranged so as to be able to face the photoconductor at the same time.

According to the above arrangement, for each photosensitive member,
Development can be performed in parallel with a developer of a color (for example, black) used when forming a monochrome image.

Therefore, the image data is divided into two pieces of low-resolution data (for example, divided so that pixels adjacent to each other in the main scanning direction do not exist), and each piece of low-resolution data is formed on each photosensitive member. By forming toner images corresponding to each other in parallel and superimposing them on each other, a high-resolution image can be formed in one image forming process.

In the above-described configuration, due to the above-described effect of improving the space efficiency by the developing device, the apparatus is compared with a conventional two-photoreceptor type image forming apparatus in which a developing unit for accommodating a developer used for monochrome image formation is provided on each photoreceptor. Can be reduced in size.

As a result, the present color image forming apparatus can form a high-speed and high-resolution image while avoiding an increase in the size of the apparatus.

The above color image forming apparatus is a color image forming apparatus in which the toner image is transferred to a recording medium, and the toner image carried by each of the photoconductors is exposed after each of the photoconductors is exposed. It is preferable that a monochrome image is formed on the photoconductor having a shorter time required to be transferred to the recording medium.

According to the above arrangement, a monochrome image is formed on the photosensitive member having a shorter required time from the exposure to the transfer of the carried toner image to the recording medium. In this case, a monochrome image can be formed in the shortest time.

By setting the stop position of the developing device at the time of forming the monochrome image to the default position (initial state), in particular, the time for forming the monochrome image can be reduced.

Further, in the above configuration, the toner image carried by the monochrome image formation does not come into contact with the photosensitive member not used at the time of the monochrome image formation. Therefore, it is possible to form a monochrome image with good transfer efficiency and little image quality deterioration without providing a separation / contact mechanism or the like for avoiding contact between the toner image and a photoreceptor not used at the time of monochrome image formation.

As a result, the present color image forming apparatus can form a monochrome image with good image quality at high speed.

[0055]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] The first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is an overall configuration diagram of a digital color copier 1 as a color image forming apparatus according to an embodiment of the present invention, and shows a schematic configuration inside the copier as viewed from the front of the apparatus. Digital color copier 1
Is mainly composed of a main unit 2 and a scanner unit 3 arranged above the main unit 2.

First, the configuration of the scanner unit 3 will be described.
The scanner unit 3 has a document table 4 on which a document is placed. The image of the document placed on the document table 4 is read by a reading optical system 5 installed below the document table 4 and converted into an electric signal. The reading optical system 5 includes a first scanning unit 5a and a second scanning unit 5b which reciprocate in parallel along the original placing surface of the original table 4, an optical lens 5c, and a CCD line sensor 5d as a photoelectric conversion element. are doing.

The first scanning unit 5a has an exposure lamp for exposing the surface of the original image and a first mirror for reflecting the reflected light image from the original in a predetermined direction. It reciprocates in parallel at a predetermined scanning speed while maintaining a constant distance from the mounting surface.

The second scanning unit 5b has second and third mirrors for further reflecting the reflected light image from the document reflected by the first mirror of the first scanning unit 5a in a predetermined direction. , Reciprocating in parallel with the first scanning unit 5a while maintaining a constant speed relationship.

The optical lens 5c includes a second scanning unit 5b
Is reduced by condensing the reflected light image from the document reflected by the third mirror, and the reduced light image is formed at a predetermined position on the CCD line sensor 5d.

The CCD line sensor 5d sequentially photoelectrically converts the formed light image and outputs it as an electric signal. The CCD line sensor 5d is a three-line color CCD capable of reading a black-and-white image or a color image and outputting line data separated into R (red), G (green), and B (blue) color components. . Original image data converted into an electric signal by the CCD line sensor 5d is
Further, the image data is transferred to an image processing unit described later and subjected to predetermined image data processing.

In the digital color copying machine 1, the scanner 3 is provided with a two-sided automatic document feeder (RADF: Reversin).
g Automatic Document Feeder) 6 is installed. The RADF 6 is mounted on the document table 4 with a predetermined positional relationship with respect to the document mounting surface of the document table 4 so as to be openable and closable with respect to the document table 4.

The operation of the RADF 6 first conveys the document to a position where one surface of the document faces the reading optical system 5 at a predetermined position on the document table 4. Subsequently, after the image reading on this one side is completed, the document is turned over,
Similarly, the document is conveyed to a position where the other surface faces the reading optical system 5 at a predetermined position on the document table 4.

After the reading of the image on both sides of one document is completed, the document is discharged and the double-sided conveyance operation for the next document is executed. The operation of the RADF 6 for transporting the original and reversing the original is controlled in relation to the operation of the digital color copying machine 1 as a whole.

Next, the main body 2 will be described. The main body 2 includes an image forming unit 7 therein, and an operation panel (not shown) is provided on an upper surface thereof.

The image forming section 7 is provided with a belt unit 8 inclined. The belt unit 8 includes a pair of stretching rollers 9a and 9b, and the stretching rollers 9a and 9b.
b, and the intermediate transfer belt 10 rotates in a direction indicated by an arrow A. Two photoconductors 11 and 12 are installed diagonally above the belt unit 8 that is arranged obliquely. Each of the photoconductors 11 and 12 has a drum shape.

The photoreceptor 11 disposed on the upstream side of the intermediate transfer belt 10 constitutes an image forming process section for forming two-color toner images of yellow (Y) and magenta (M). And rotates in the direction of arrow B in the figure. Around the photoconductor 11, a charger 13, an LED array device 15, a cleaning device 21, and the like are provided.

The charger 13 charges the entire surface of the photoconductor 11. The LED array device 15
The surface of the photoconductor 11 charged by the charger 13 is exposed based on an image signal sent from an image processing unit (FIG. 2) described later to form an electrostatic latent image. In this case, the LED array exposure device 15 forms a yellow electrostatic latent image and a magenta electrostatic latent image.

The cleaning device 21 scrapes off the toner remaining on the surface of the photoconductor 11 after the toner image formed by the rotary developing device (developing device) 17 described later is transferred to the intermediate transfer belt 10.

On the other hand, the photoreceptor 12 disposed downstream of the intermediate transfer belt 10 is responsible for forming two color toner images of black (Bk) and cyan (C) in the direction of arrow C in FIG. Rotate. Around the photoreceptor 12, similarly to the photoreceptor 11, the charger 14 and the LED array exposure apparatus 1 for forming an electrostatic latent image of two colors of black and cyan.
6 and a cleaning device 22 are provided.

A rotary developing device 17 which is a common developing device for the two photoconductors 11 and 12 is provided between the two photoconductors 11 and 12. The rotary developing device 17 has a drum shape extending coaxially with the photoconductors 11 and 12, and has a cylinder 51 that is intermittently driven to rotate about a shaft 17a.

The cylinder 51 has four developing tanks (developing units) 50 (developing tanks 50a, 50b, 50c, and 50d) formed by dividing the circumferential direction into four parts. Each of the developing tanks 50a, 50b, 50c, and 50d carries a toner (developer), and the photosensitive members 11 and
Developing rollers (developing units) 52 to be supplied to the developing roller 12 are provided.

Here, the developing tank 50a contains yellow toner, the developing tank 50b is black, and the developing tank 5
0c contains magenta toner, and the developing tank 50d contains cyan toner. And four developing tanks 50a, 50b, 5
0c and 50d are arranged in the order of yellow, black, magenta, and cyan.
The photoconductors 11 and 12 are arranged so as to face the respective photoconductors 11 and 12 for development. Further, each developing tank 50a / 50b
50c and 50d have the same shape. Details of the developing operation will be described later.

The rotary developing device 17 employs a contact developing method in which development is performed by contacting the photosensitive members 11 and 12 or a non-contact developing method in which development is performed without contacting the photosensitive members 11 and 12. Any of these may be used. However, in the case of the contact developing method, the rotary developing device 17
And a mechanism such as a shutter for taking toner in and out of the rotary developing device 17 is required. Therefore, a non-contact mechanism is required in terms of cost and design flexibility. A development method is desirable.

On the inner side of the intermediate transfer belt 10, first transfer units 23 and 24 are provided at positions where the intermediate transfer belt 10 faces the respective photoconductors 11 and 12. The first transfer devices 23 and 24 transfer the toner images formed on the photoconductors 11 and 12 to the intermediate transfer belt 10.

Also, below the belt unit 8,
A transfer / transport member 37 for transferring the toner image on the surface of the intermediate transfer belt 10 to a sheet 39 conveyed from a sheet cassette 38 described later and for conveying the sheet 39 is disposed at a position facing the tension roller 9b. Has been established.

The transfer / conveying member 37 is a roller-shaped second
The transfer belt 3 is attached to the transfer device 37a and the stretching roller 37b.
The second transfer unit 37a is provided so as to be detachable from the intermediate transfer belt 10 with the tension roller 37b serving as a fulcrum. Then, the transfer conveyance member 37
The second transfer device 37a is brought into contact with the surface of the intermediate transfer belt 10 only when the toner image is transferred from the intermediate transfer belt 10 to the paper 39.

Although not specifically shown in FIG. 1, the intermediate transfer belt after the transfer of the toner image is located downstream of the contact portion of the transfer / conveyance member 37 in the rotation direction of the intermediate transfer belt 10. A paper peeling claw for peeling the paper 39 adhered to the sheet 10, a cleaning device for cleaning the surface of the intermediate transfer belt 10, and the like are provided.

Below the image forming section 7, a paper cassette 38 for storing paper 39 as a material to be transferred is provided. The paper cassette 38 is provided with a pickup roller 36 and a paper feed roller pair 29 for feeding paper 39 in the cassette. The fed paper 39 is transported along the paper guide 34 by the transport roller pair 35. A pair of registration rollers 33 is provided at a stage preceding the transfer / conveying member 37 to adjust the timing for adjusting the position of the toner image on the intermediate transfer belt 10 to the position of the sheet 39.

A fixing device 32 for fixing the toner image transferred onto the paper 39 by the transfer / conveying member 37 is provided in front of the transfer / conveying member 37, and a fixing device 32.
Roller pair 31 for discharging paper 39 processed by
Is installed. Further, on the side surface of the main body 2, a paper discharge tray 30 for storing the paper 39 discharged by the paper discharge roller pair 31 is provided.

Next, the image processing section will be described with reference to FIG. FIG. 2 is a block diagram illustrating a configuration of the image processing unit. The image processing unit mainly includes an image data input unit 40, an image data processing unit 41, an image data output unit 42, a semiconductor memory 43 for delay, and a central processing unit (hereinafter referred to as a CPU).
44, and external interface units 46 and 47.

The image data input section 40 includes a CCD line sensor 5d, a shading correction circuit 40b, a line matching section 40c, a sensor color correction section 40d, and an MTF correction section 40.
e and a gamma correction unit 40f.

The CCD line sensor 5d reads a black-and-white original image or a color original image, and outputs line data of three lines that are separated into red (R), green (G), and blue (B) color components. Shading correction circuit 40b
Corrects the line image level of the line data output from the CCD line sensor 5d. Line matching unit 40
c is constituted by a line buffer or the like, and corrects a shift of line data. The sensor color correction unit 40d corrects the color data of the line data. The MTF correction unit 40e calculates C
The correction is performed so that the change in the signal in each pixel of the CD line sensor 5d has a sharp edge. And the γ correction unit 4
0f performs visibility correction by correcting the brightness of the image.

The image data processing section 41 includes a monochrome data generation section 41a (for monochrome original image), an input processing section 41b,
Region separation unit 41c, black generation unit 41d, color correction circuit 41
e, a zoom processing circuit 41f, a spatial filter 41g, a halftone processing section 41h, and a print data input section 41i.

The monochrome data generation section 41a generates monochrome data from the RGB signals which are color image signals input from the image data input section 40. The input processing unit 41b converts the RGB signals into YM signals corresponding to the image forming unit 7 (see FIG. 1) mounted on the digital color copying machine 1.
The signal is converted into a C (yellow / magenta / cyan) signal, and the clock is converted. The area separating section 41c determines whether the input image data is a character, a halftone picture, or a photographic paper picture, and separates each area. The black generation unit 41
d performs undercolor removal processing based on the YMC signal output from the input processing unit 41b to generate black in a color image.

The color correction circuit 41e adjusts each color of the color image signal based on each color conversion table. The zoom processing circuit 41f and the spatial filter 41g are:
The magnification of the input image information is converted based on the set magnification. The halftone processing section 41h expresses gradation such as multi-level error diffusion and multi-level dither. The print data input section 41i serves as an input section for print data input from an external interface section 47 described later.

Here, after the above-described color correction circuit 41e, a zoom processing circuit 41f, a spatial filter 41g, a print data input section 41i, and a halftone processing section 41h.
Are provided in two systems corresponding to the two LED array exposure devices 15 and 16. In the figure, the system on the left is LE
The second system corresponding to the D array exposure device 15 includes yellow and magenta lines, and the right system corresponds to the LED array exposure device 16 and includes the first system including cyan and black lines. is there.

The lines of the respective colors included in the first and second systems respectively correspond to the rotary developing device 1 described later.
7 is appropriately changed according to the arrangement of the developing tanks 50a, 50b, 50c, and 50d.

The image data output unit 42 includes two line memory buffers 42a and 42a and two LED controllers 42b and 42b corresponding to the first system and the second system in the image data processing unit 41, respectively. Corresponding two LED array exposure apparatuses 15.1
6 is comprised.

The line memory buffers 42a and 42a
Adjusts the output timing of the image data of each color sent from the halftone processing unit 41h. The LED controllers 42b and 42b perform pulse width modulation of the image data of each color sent from the halftone processing unit 41h. And
Each of the LED array exposure devices 15 and 16 is
Optical recording is performed on the photoconductors 11 and 12 based on a pulse width modulation signal corresponding to image data of each color output from the ED controllers 42b and 42b.

In the case of a color original, the second-system LED array exposure device 15 performs optical recording with a pulse modulation signal corresponding to yellow image data in the first scan in the image data input unit 40, and performs the second scan. In optical scan, optical recording is performed using a pulse modulation signal corresponding to magenta image data. On the other hand, the first-system LED array exposure apparatus 16 performs optical recording with a pulse modulation signal corresponding to black image data in the first scan in the image data input unit 40, and performs cyan recording in the second scan. Optical recording is performed using a pulse modulation signal corresponding to the image data.

The delay semiconductor memory 43 is provided to prevent the image forming position from being shifted between the two image forming process units of the first system and the second system. The image data of each color is temporarily stored in the delay semiconductor memory 43, the time is adjusted, and the image data is sent to the LED array exposure devices 15 and 16 to adjust the timing of the exposure start. Each photoconductor 11
The positional relationship between the images transferred from the position 12 is adjusted.

The CPU 44 controls the image data input section 40, the image data processing section 41, the image data output section 42, the external interface sections 46 and 47 described later, and the semiconductor memory 43 for delay based on a predetermined sequence. is there.

The external interface unit 46 is a communication interface means for receiving image data from an external image input processing device (communication portable terminal, digital camera, digital video camera, etc.) provided separately from the digital color copying machine 1. It is. Note that the image data input from the external interface unit 46 is also once input to the image data processing unit 41 to perform each processing, thereby achieving a data level that can be handled by the image forming unit 7 of the digital color copying machine 1. After the conversion, the image data is output to the image data output unit 42 in the same manner as described above.

Further, the external interface unit 47
A printer interface for inputting image data created by a personal computer or the like.
A black-and-white or color FAX interface for receiving AX-received image data. Since the image data input from the external interface unit 47 is already a CMYK (cyan / magenta / yellow / black) signal, the image data is processed by the halftone processing unit 41h from the middle of the image data processing unit 41, It is output to the output unit 42.

Next, the operation of the digital color copying machine 1 for forming a color image in the above configuration will be described with reference to FIGS. FIG. 3 is a partial configuration diagram showing the periphery of the rotary developing device 17 of the digital color copying machine 1. FIG. 3A shows a stop position (default stop position) during yellow and black development.
(B) shows a stop position at the time of developing magenta and cyan.

Before the start of the color image forming operation,
As shown in FIG. 3A, the rotary developing device 17 is stopped at a position where the yellow developing tank 50a faces the photoconductor 11 and the black developing tank 50b faces the photoconductor 12 at the same time. This position is the default stop position of the rotary developing device 17.

The reading optical system 5 performs a total of two scans when reading a document. When the color image forming operation is started, first, the original image read in the first scan is formed as an optical image on the CCD line sensor 5d via the optical lens 5c. CCD line sensor 5
d photoelectrically converts this into an image signal corresponding to each of the R, G, and B colors, and sends it to the image processing unit in FIG.

The image processing section performs the above-described image processing on the original image data, and emits light modulated based on the yellow image data from the second-system LED array exposure device 15 in the image data output section 42. Then, light modulated based on black image data is emitted from the first-system LED array exposure device 16. These LE
Each writing of the D array exposure devices 15 and 16
When each image is transferred to the surface of the intermediate transfer belt 10, the transfer is performed at a timing determined so that the transfer positions coincide with each other.

The surfaces of the photoconductors 11 and 12 are:
Each of the chargers 13 is rotated with rotation in the directions B and C, respectively.
14 and is uniformly charged when passing through. By irradiating the charged surface with light from each of the LED array exposure devices 15 and 16, a yellow electrostatic latent image is formed on the photoconductor 11 and a black electrostatic latent image is formed on the other photoconductor 12, respectively. It is formed.

The yellow electrostatic latent image on the photoreceptor 11 is provided with yellow toner when passing through the position of the yellow developing tank 50a facing the developing roller 52 in the rotary developing device 17. Thus, the toner image is visualized to form a yellow toner image. This toner image is the first
The image is transferred to the intermediate transfer belt 10 by the operation of the transfer device 23.

On the other hand, the black electrostatic latent image on the photoreceptor 12 also passes through the black developing tank 50a of the rotary developing device 17 in a position facing the developing roller 52 in the same manner as described above. Is applied to make the toner image visible and a black toner image is transferred to the intermediate transfer belt 10 by the operation of the first transfer device 24.

Here, as described above, the L and L are applied to the photoconductors 11 and 12 so that the yellow toner image and the black toner image on the intermediate transfer belt 10 coincide with each other.
The timing of image writing by the ED array exposure devices 15 and 16 is controlled using the delay semiconductor memory 43. Therefore, the black toner image transferred from the photoconductor 12 is transferred without displacement to the yellow toner image previously transferred to the intermediate transfer belt 10.

When the first scanning is completed, the reading optical system 5 returns to the original position and prepares for the second scanning. When the development of the toner image by the first scan is completed, the rotary developing device 17
From the position shown in (a), the photosensitive drum 11 is rotated by 180 degrees in a predetermined direction, either leftward or rightward, so that the magenta developing tank 50c faces the photoconductor 11 as shown in FIG. And the cyan developing tank 50d is the photosensitive member 1
Stop at a position opposite to 2.

Next, the reading optical system 5 performs a second scan. In the second scan, the LED array exposure device 15 outputs magenta image data based on the read image information. The modulated light is emitted, and the LED array exposure device 16 emits light modulated based on cyan image data. Each of these LEs
The writing timing of each of the D array exposure devices 15 and 16 is controlled in the same manner as in the first scan.

Each of the surfaces of the photoconductors 11 and 12 has a B
And the rotation in the C direction, the toner is uniformly charged when passing through the position facing each of the chargers 13 and 14. By irradiating the charged surface with light from each of the LED array exposure devices 15 and 16, a magenta electrostatic latent image is formed on the photoconductor 11 and a cyan electrostatic latent image is formed on the photoconductor 12. .

The magenta electrostatic latent image on the photoreceptor 11 is visualized when passing through a position facing the developing tank 50c of the rotary developing device 17, and becomes a magenta toner image. When passing through the position facing the first transfer unit 23, the image is transferred to the intermediate transfer belt 10 by the operation of the first transfer unit 23. Here, the magenta toner image is transferred so as to be superimposed on the yellow and black toner images which have been previously transferred.

Similarly, the electrostatic latent image of cyan on the photosensitive member 12 is also visualized when passing through the position facing the developing tank 50d of the rotary developing device 17, and becomes a cyan toner image. When passing through the position facing the first transfer unit 24, the image is transferred to the intermediate transfer belt 10 by the operation of the first transfer unit 24.

At this time, the cyan toner image is further transferred onto the yellow, black and magenta toner images. As a result, a four-layered laminated image in which the four color toner images are laminated is formed on the surface of the intermediate transfer belt 10.

Each time the toner images of the respective colors formed on the surfaces of the photoconductors 11 and 12 are transferred to the intermediate transfer belt 10, the residual toner is removed by the cleaning devices 21 and 22. The electricity is removed by an electric device (not shown).

In this way, the four-layered laminated image transferred on the intermediate transfer belt 10 is conveyed to the vicinity of the transfer conveying member 37 as the intermediate transfer belt 10 rotates. Then, when passing through the position facing the transfer / conveying member 37, the image is transferred to the sheet 39 fed from the sheet cassette 38 by the operation of the second transfer unit 37a. The transfer / conveying member 37 normally holds the intermediate transfer belt 10
When the intermediate transfer belt 10 makes two rotations to complete the stacked toner image on the intermediate transfer belt 10, the intermediate transfer belt 10 is transferred to the paper 39. Contacted.

Subsequently, the sheet 3 on which the above-mentioned laminated image has been transferred
9 is transported to the fixing device 32 by the transport action of the transfer transport member 37. The image transferred to the paper 39 is transferred to the fixing device 32.
Is fixed on the paper 39 to form a color image. afterwards,
The paper 39 is discharged to the discharge tray 30 by the discharge roller pair 31.

When the development of the toner image by the second scan is completed, the rotary developing device 17 shown in FIG.
From the stop position shown in (b), the image is rotated 180 degrees in a predetermined direction, either clockwise or counterclockwise, to return to the default stop position shown in FIG.

Here, the rotary developing device 1
The rotation of 7 may be a rotational movement every 180 degrees in a fixed direction, or a 180 degree swing (alternating left and right rotation) by being configured to be reversible. Good.

On the other hand, when forming a monochrome image, the rotary developing device 17 does not rotate because the monochrome printing position shown in FIG. 3A is set as the default stop position.

The monochrome image forming operation is as follows. First, the reading optical system 5 scans and reads image information, and an electrostatic latent image is written on the photoconductor 12 based on the image information. A rotary developing device 17 is attached to the electrostatic latent image.
The toner is applied to the black developing layer 50b of
The image is transferred to the surface of the intermediate transfer belt 10 on the surface facing the first transfer unit 24. Thereafter, when the sheet passes through a position facing the second transfer unit 37a, the image is transferred onto the sheet 39, and thereafter, is the same as a color image.

As described above, the digital color copying machine 1 according to the present embodiment is configured to include one rotary developing device 17 acting on each of the photoconductors 11 and 12 in common.

The rotary developing device 17 divides the inside of a cylinder 51 that is intermittently driven into rotation into a plurality of chambers in the circumferential direction, and has a developing roller 52 of each color for each chamber. The shaft 17a rotatably supports the cylinder 51. According to this rotation, the developing roller 52 in each chamber is sequentially opposed to each of the photoconductors 11 and 12 to perform development.

Therefore, since the position of the developing roller 52 opposed to each of the photoconductors 11 and 12 is one, if the photoconductors 11 and 12 have the drum shape as described above, the drum diameter can be reduced, and The space occupied by the photoconductors 11 and 12 in the digital color copying machine 1 can be reduced. As a result, the size of the entire digital color copying machine 1 can be reduced.

Further, since the developing roller 52 faces each of the photoconductors 11 and 12 at one position, the distance between the exposure point and the developing position is constant even when the color of the toner to be developed is changed. Therefore, since the operation of the developing device (for example, the operation timing of the developing device) can be designed under the same conditions, the development period of the control system (including software) can be shortened, and the process conditions can be optimized. Because of simplicity, the development period for finding this can be shortened. As a result, the cost of the device can be reduced.

Further, since the plurality of developing tanks 50 are housed in one rotary developing device 17, the space utilization efficiency is high and the digital color copier 1 can be used without lowering the toner storage capacity in the developing tank 50. The overall size can be reduced.

In addition, the developing tanks 50a, 50b, 5
Since 0c and 50d have the same shape, the cost merit is high as compared with the case where developing devices having different shapes are manufactured and designed.

Here, in the case where the rotary developing device 17 is divided into four parts as described above, the two photosensitive members 11.
2 and two developing tanks 50 facing each other are separated from each other by two, and the rotary developing device 1
7 must be arranged so as to be sandwiched between the photoconductors 11 and 12.

In this case, the size itself of the rotary developing device 17 becomes inevitably small, so that a sufficient amount of toner can not be secured, and the charger 13 and the like are arranged between the photoconductor 11 and the photoconductor 12. Space becomes difficult to secure.

On the other hand, in the above configuration, two adjacent
In this configuration, two developing tanks 50 are simultaneously opposed to the photoconductors 11 and 12. Thus, a space for disposing the charger 13, the LED array exposure device 15, the cleaning device 21 and the like can be secured between the photoconductors 11 and 12 arranged side by side, and the size of the rotary developing device 17, That is, the amount of toner stored in the developing tank 50 can be secured.

Further, in the above configuration, the default stop position of the rotary developing device 17 is
The black developing tank 50b is set so as to face the photoreceptor 12 located on the downstream side of 12. Therefore, the time required from the exposure to the transfer to the recording paper for the black toner image can be minimized without changing the position of the rotary developing device 17 from the default stop position during monochrome image formation. Therefore, the formation time per sheet when forming a monochrome image is shortened,
High-speed monochrome image formation can be achieved.

In forming a monochrome image, the black toner image formed on the intermediate transfer belt 10 does not come into contact with the other photosensitive member 11 which is not involved in image formation. Even without such an arrangement, it is possible to obtain an image with good transfer efficiency and no image quality deterioration.

Although the above description has been given of the case where the monochrome image is a black monochrome image, a monochrome image of another single color may be used.

[Embodiment 2] Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 4 is an overall configuration diagram of a digital color copying machine 60 as a color image forming apparatus according to a second embodiment of the present invention, and shows a schematic configuration inside the copying machine viewed from the front of the apparatus. Embodiment 1
The components having the same functions as those described in are described by the same reference numerals, and the description thereof is omitted.

The digital color copying machine 60 according to the present embodiment differs from the digital color copying machine 1 according to the first embodiment in the configuration of the built-in rotary developing device 18.

[0130] The rotary developing device 18
· Five developing tanks (developing units) formed in a cylinder 51 which is coaxial with the drum 12 and is driven to rotate intermittently about the shaft 18a by dividing the circumferential direction into five parts.
50a, 50b, 50e, 50c, and 50d. Each of the developing tanks 50a, 50b, 50e, 50c
A developing roller 52 is provided at 50d.

Here, the developing tanks 50a, 50c, 50d
Contains yellow, magenta, and cyan toners, respectively, as described above. The developing tanks 50b and 50
e contains black toner.

The five developing tanks 50 are arranged in the order of yellow, cyan, black, black, and magenta. In this case, two adjacent developing tanks 50 are separated by one developing tank 50, respectively. It is configured so that development is performed facing the bodies 11 and 12.

Next, the developing operation will be described with reference to FIG. FIG. 5 is a partial configuration diagram showing the periphery of the rotary developing device 18 of the digital color copying machine 60. FIG. 5A shows the rotary developing device 18 during the first image forming process in color image formation. The stop position is shown in FIG.
FIG. 5B shows the stop position of the rotary developing device 18 at the time of the second image forming process in color image formation.
(C) represents a stop position (default stop position) of the rotary developing device 18 in monochrome image formation.

At the time of the first image forming process in color image formation (FIG. 5A), the yellow developing tank 50a faces the photoconductor 11, and the black developing tank 50b faces the photoconductor 12. I have. Subsequently, at the time of the second image forming process (FIG. 5B), the magenta developing tank 50c faces the photoconductor 11, and the cyan developing tank 50d faces the photoconductor 12.
Are facing each other.

When the second image forming process is completed, if the next color image formation is to be continued, the rotary developing device 1
8 returns to the stop position shown in FIG. on the other hand,
When there is no instruction for the next color image formation, FIG.
It returns to the stop position for monochrome printing shown in (c). The stop position shown in FIG. 5C is also a default stop position, in which the cyan developing tank 50 d faces the photoconductor 11, and the black developing tank 5 dedicated to monochrome image formation faces the photoconductor 12.
0e is facing.

The rotary developing device 18 according to the present embodiment shifts from the first image forming process to the second image forming process at the time of color image formation (ie, FIG. 5).
At the time of shifting from the stop position of (a) to the stop position of FIG. 5B), it is rotated by 72 degrees in the direction of arrow D in the figure. In the reverse case (ie, from the stop position in FIG.
At the time of shifting to the stop position (a)), the rotation is performed by 72 degrees in the direction opposite to the direction D.

Accordingly, the rotary developing device 18 is configured to rotate only in one direction, and the movement when shifting from the stop position in FIG. 5B to the stop position in FIG.
In the above configuration, as compared with the configuration of rotating 288 degrees in the direction,
The switching operation of the rotary developing device 18 at the time of switching the image forming process can be speeded up.

Further, the rotary developing device 18 shown in FIG.
The transition from the stop position shown in (b) to the default stop position shown in FIG. 5 (c) is configured to rotate 144 degrees in the direction opposite to the D direction, whereby 21
The switching operation of the rotary developing device 18 at the time of switching the image forming process can be performed faster than in the configuration in which the image forming process is rotated six degrees.

Further, the rotary developing device 18 is configured to rotate from the default stop position shown in FIG. 5C to the stop position in FIG. 5A by 72 degrees in the direction D. Accordingly, the switching operation of the rotary developing device 18 at the time of switching the image forming process can be performed faster than when the image forming process is rotated by 288 degrees in the direction opposite to the direction D.

For black which is frequently used,
By providing two developing tanks 50 (developing tanks 50c and 50e), it is possible to improve the consumption balance of the developers of each color housed in the developing device.

Although the rotary developing device 18 having five developing tanks 50 has been described above, the rotary developing device 18 may have more developing tanks 50.

[Embodiment 3] Next, a third embodiment of the present invention will be described with reference to FIGS.
It is as follows. FIG. 6 is an overall configuration diagram of a digital color copying machine 61 as a color image forming apparatus according to a third embodiment of the present invention, and shows a schematic configuration inside the copying machine viewed from the front of the apparatus. Note that components having the same functions as those described in the first and second embodiments are denoted by the same reference numerals, and description thereof is omitted.

The digital color copying machine 61 is intended to increase the resolution of an image to be formed in monochrome image formation. The digital color copying machine 61 is different from the digital color copying machine 60 in that the rotary developing device 19 has a black developing tank 50b.
50e is different in that they are arranged so as to be adjacent to each other with one space therebetween. Thus, the two black developing tanks 50
b and 50e can be simultaneously opposed to the photoconductors 11 and 12, respectively. In order to realize high resolution, it is necessary to reduce the beam spot diameter for forming an electrostatic latent image by exposing the photoconductors 11 and 12 and to reproduce it as a toner image in development.

However, even when the beam spot diameter is reduced, the resolution of the toner image is reduced in the development stage in the ordinary developing method.

Therefore, in the digital color copying machine 61 according to the present embodiment, high-resolution image data is transferred in the main scanning direction (a direction orthogonal to the scanning direction of the reading optical system 5).
Are divided into two pieces of low-resolution data so that no adjacent pixel exists. Then, based on the low-resolution data obtained by the division, the two photoconductors 11 and 12 are used.
A single high-resolution image is obtained by forming low-resolution toner images thereon, superimposing them on the intermediate transfer belt 10, and then transferring them onto the paper 39.

The image processing section for increasing the resolution will be described with reference to FIG. FIG. 7 is a block diagram showing the configuration of the image processing unit of the digital color copying machine 61.

When the high resolution mode is selected during monochrome image formation, the high resolution monochrome image data is subjected to halftone processing by the halftone processing unit 41h in the first system, and then by the image division unit 41j. The image data is divided into two types of low-resolution monochrome image data.

The division method by the image division section 41j is, for example, such that data read from an odd-numbered pixel group in the CCD line sensor 5d is used so that there is no adjacent pixel in the main scanning direction. The data is divided into data read from the even-numbered pixel groups.

Then, one of the monochrome image data is processed as it is in the first system, and the other monochrome image data is transferred to the second system, and the subsequent processing is performed. Then, electrostatic latent images are formed on the photoconductors 11 and 12 by the LED array exposure devices 15 and 16, respectively.

The developing operation of the digital color copying machine 61 having the above configuration will be described with reference to FIG. FIG.
FIG. 8 is a partial configuration diagram showing the periphery of the rotary developing device 19 of the digital color copying machine 61. FIG.
FIG. 8B shows the stop position (default stop position) of the rotary developing device 19 in monochrome image formation, and FIG. 8B shows the stop position of the rotary developing device 19 in the first image forming process in color image formation. (C) shows the stop position of the rotary developing device 19 at the time of the second image forming process in color image formation.

In the case of the high resolution mode when forming a monochrome image, the rotary developing device 19 performs development at the default stop position shown in FIG. 8A. In this state, the black developing tanks 50b and 50e face the photoconductors 11 and 12, respectively.

The electrostatic latent images formed on the photoconductors 11 and 12 are developed by the developing tanks 50b and 50e based on the divided low-resolution monochrome image data to form toner images.

Thereafter, a high-resolution monochrome image is formed on the paper 39 in the same manner as in the first embodiment.

Therefore, in the above case, the resolution can be increased by dividing the image without increasing the size of the apparatus and prolonging the time required for the image forming process as compared with the case of forming a normal monochrome image. Can be.

If the high-resolution mode is not selected during monochrome image formation, the electrostatic latent image formed on the photosensitive member 12 is developed in the developing tank 50e in the state shown in FIG. 5C.

Further, at the time of the first image forming process (FIG. 8B) during the formation of a color image, the yellow developing tank 50a faces the photosensitive member 11 and the cyan developing tank 50d faces the photosensitive member 12. Are facing each other. Subsequently, at the time of the second image forming process (FIG. 8C), the magenta developing tank 50c faces the photoconductor 11, and the black developing tank 50b faces the photoconductor 12.

When the second image forming process is completed, if the next color image formation is to be continued, the rotary developing device 1
9 returns to the stop position shown in FIG. on the other hand,
When there is no instruction to form a subsequent color image, FIG.
It returns to the stop position for monochrome printing shown in FIG. The stop position shown in FIG. 8A is also a default stop position.

When shifting from the first image forming process to the second image forming process in forming a color image (ie, shifting from the stop position in FIG. 8B to the stop position in FIG. 8C). Then, it rotates 72 degrees in the direction of arrow D in the figure. In the opposite case (that is, when shifting from the stop position in FIG. 8C to the stop position in FIG. 8B), the motor rotates 72 degrees in the direction opposite to the direction D.

Accordingly, the rotary developing device 19 is configured to rotate only in one direction, and the movement when shifting from the stop position in FIG. 8C to the stop position in FIG.
In the above configuration, as compared with the configuration of rotating 288 degrees in the direction,
The switching operation of the rotary developing device 19 at the time of switching the image forming process can be speeded up.

Further, the rotary developing device 19 shown in FIG.
The transition from the stop position illustrated in FIG. 8C to the default stop position illustrated in FIG. 8A is configured to rotate 144 degrees in the direction opposite to the D direction, and as a result, 21 degrees in the D direction.
The switching operation of the rotary developing device 19 at the time of switching the image forming process can be performed faster than the configuration in which the image forming process is rotated six degrees.

Further, the rotary developing device 19 is configured so that the transition from the default stop position shown in FIG. 8A to the stop position in FIG. Accordingly, the switching operation of the rotary developing device 18 at the time of switching the image forming process can be performed faster than when the image forming process is rotated by 288 degrees in the direction opposite to the direction D.

[0162]

According to the color image forming apparatus of the present invention, two developing units of a rotary developing device having a plurality of developing units can simultaneously face two photoconductors at the same time, and the rotary developing device rotates. And the developing unit can be changed.

In the above configuration, since the developing position is one in each photosensitive member, the size of the photosensitive member can be reduced. In addition, since a plurality of developing units are housed in one rotary developing device, the space can be efficiently used, and the entire developing device can be downsized while securing the capacity of the developing tank for storing the developer. can do.

In addition, since the distance from the exposure position to the development position on each photosensitive member is equal regardless of the development unit, the control system and process conditions of the development device can be designed under the same conditions. Regarding the development unit,
Each developing unit can have the same shape. Therefore, costs required for development and design can be suppressed, and the cost of the entire apparatus can be reduced.

As a result, it is possible to provide a small and inexpensive color image forming apparatus.

In the above color image forming apparatus, the rotary developing device further includes four developing units.
It is preferable that two adjacent developing units are arranged so as to be able to face each photoconductor at the same time.

With the above configuration, the space utilization efficiency of the photosensitive member and the rotary developing device is improved. Further, a space for installing an exposure device or the like between the photoconductors can be secured.

As a result, it is possible to provide a more compact color image forming apparatus by effectively utilizing the space in the apparatus.

In the above color image forming apparatus, the rotary type developing device further comprises five or more developing units, and the two developing units separated by one are arranged so as to be able to face each photosensitive member at the same time. Is preferred.

With the above configuration, it is possible to secure a space required for installing an exposure device or the like between the photosensitive members without increasing the size of the rotary developing device more than necessary. Also, when changing the developing unit, it is possible to reduce the angle of rotation of the rotary developing device,
The switching time of the imaging process can be reduced.

As a result, it is possible to provide a color image forming apparatus which is small in size and requires a short time for image formation.

In the color image forming apparatus having five or more developing units, it is preferable that the rotary developing device rotates in both directions.

In the above configuration, when the image unit is changed, the rotary developing device can be rotated in a direction in which the rotation angle is small, and the switching time of the image forming process can be further reduced.

As a result, it is possible to provide a color image forming apparatus in which the time required for image formation is even shorter.

In the color image forming apparatus having five or more developing units, the rotary developing device may include at least two developing units for containing a developer of a specific color.
It is preferable to provide one.

In the above configuration, one of the two developing units can be dedicated to monochrome image formation, and the other can be dedicated to color image formation. Therefore, it is possible to improve the consumption balance of the developers of each color stored in the rotary developing device.

As a result, it is possible to provide a color image forming apparatus having good maintainability.

In the color image forming apparatus having five or more developing units and having at least two developing units of a specific color, the two developing units may be arranged so that each of the two developing units can simultaneously face each photosensitive member. It is preferred that

With the above configuration, a high-resolution image can be formed in one image forming process without increasing the size of the apparatus.

As a result, it is possible to provide a small-sized color image forming apparatus capable of forming a high-resolution image in a short time.

It is preferable that the color image forming apparatus forms a monochrome image on a photosensitive member having a shorter time from exposure to transfer to a recording medium.

With the above arrangement, a monochrome image can be formed in the shortest time. Further, since the toner image of the monochrome image does not come into contact with the photoreceptor which is not involved in the formation, the image formation with high transfer efficiency can be performed without complicating the apparatus configuration.

As a result, it is possible to provide a color image forming apparatus capable of forming a high quality image with a short image forming time in monochrome image formation.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a digital color copying machine as a color image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of an image processing unit in the digital color copying machine of FIG.

FIG. 3 shows the digital color copying machine of FIG.
At the time of yellow and black development, and (b)
FIG. 3 is a partial configuration diagram showing the periphery of a rotary developing device during magenta and cyan development.

FIG. 4 is an overall configuration diagram of a digital color copying machine as a color image forming apparatus according to another embodiment of the present invention.

FIG. 5A shows a digital color copying machine shown in FIG.
FIGS. 3A and 3B are partial configuration diagrams illustrating the periphery of a rotary developing device during yellow and black development, FIG. 3B during magenta and cyan development, and FIG. 3C during monochrome development.

FIG. 6 is an overall configuration diagram of a digital color copying machine as a color image forming apparatus according to still another embodiment of the present invention.

FIG. 7 is a block diagram illustrating a configuration of an image processing unit in the digital color copying machine of FIG. 6;

FIG. 8 shows a digital color copying machine shown in FIG.
FIGS. 4A and 4B are partial configuration diagrams showing the periphery of the rotary developing device during monochrome development, FIG. 4B during yellow and cyan development, and FIG. 4C during magenta and black development, respectively.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Digital color copier 10 Intermediate transfer belt 11 Photoconductor 12 Photoconductor 17 Rotary developing device (developing device) 18 Rotary developing device (developing device) 19 Rotary developing device (developing device) 41j Image dividing section 50 Developing tank ( Developing unit) 50a Developing tank (developing unit) 50b Developing tank (developing unit) 50c Developing tank (developing unit) 50d Developing tank (developing unit) 50e Developing tank (developing unit) 51 Cylinder 52 Developing roller (developing unit) 60 Digital color Copier

Claims (7)

[Claims] 1. A color image forming apparatus comprising two photoreceptors carrying a toner image formed by development and forming an image by superimposing the toner images, wherein a developing operation is performed in opposition to the photoreceptor. A developing device that has a plurality of units and that rotates, wherein each of the developing units is configured such that two of the developing units face the respective photoconductors at the same time, and each of the photosensitive units is rotated by rotation of the developing device. A color image forming apparatus, wherein the developing unit facing the body is provided so as to be changed. 2. The image forming apparatus according to claim 1, wherein said developing device includes four developing units, and said two developing units respectively facing said photosensitive members are arranged adjacent to each other. Item 2. A color image forming apparatus according to Item 1. 3. The developing device includes at least five developing units, and the two developing units facing each of the photoconductors are disposed with one of the developing units interposed therebetween. The color image forming apparatus according to claim 1, wherein 4. The color image forming apparatus according to claim 3, wherein said developing device rotates in both directions. 5. The color image forming apparatus according to claim 3, wherein said developing device includes at least two developing units for storing a developer of a specific color. 6. A color image forming apparatus according to claim 5, wherein said developing units for accommodating said specific color developer are arranged so as to be able to simultaneously face said respective photoconductors. 7. A color image forming apparatus in which the toner image is transferred to a recording medium, and after each of the photoconductors is exposed, a toner image carried by each of the photoconductors is transferred to the recording medium. The color image forming apparatus according to any one of claims 1 to 6, wherein a monochrome image is formed on the photosensitive member having a shorter required time.