JPH04221974A - Color image forming device - Google Patents

Abstract

PURPOSE:To obtain a high-speed color image forming device which is small-sized and inexpensive, whose constitution is simple, where positional deviation is little, and whose image quality is high. CONSTITUTION:This device is a color image forming device where the toner images of respective colors formed on photosensitive bodies 1a and 1b are successively aligned and superposed on a belt-like intermediate transfer body 7 so as to form an image and finally transferred and fixed to a paper altogether so as to form a color image. A fly-wheel having large inertia is provided at one end of a driving roller 8 for driving the transfer body 7, and the transfer body 7 can stationarily travel without irregular speed change, and the toner images of the respective colors are superposed at an accurate position. By making a distance between transfer parts Ta and Tb and the length of the periphery of the intermediate transfer body about n times (n: integer) as long as the length of the outer periphery of a driving roller 6, color slurring caused by the unevenness of speed of every rotation of driving roller is eliminated.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to color image forming apparatuses such as color copying machines and color printers that utilize electrophotography.

0002

2. Description of the Related Art Generally, in order to form a color image using electrophotography, a method is used in which toner images of yellow, magenta, cyan, and black are superimposed to form a color image. A general method for superimposing this toner image on a transfer material is JP-A-1-1-2.
An example of a color image forming apparatus is disclosed in Japanese Patent No. 52982.

FIG. 5 shows an overview of the overall configuration of this conventional example, and the configuration and operation will be briefly explained below. In FIG. 5, reference numeral 101 denotes a photoreceptor, and a charger 1 is placed opposite the photoreceptor.
02, a developing section 103, a transfer drum 104, and a cleaner 105. The developing section 103 includes a Y developer 106 for creating a yellow toner image, an M developer 107 for magenta, and a C developer 10 for cyan.
8 and a K developing device 109 for black color, and the entire device rotates so that each developing device faces the photoreceptor 101 one after another and becomes ready for development.

During operation, the transfer drum 112 and the photoreceptor rotate at a constant speed in the directions of arrows while facing each other.

First, when the operation starts, the photoreceptor 101 rotates in the direction of the arrow, and its surface is uniformly charged by the charger 102.

Thereafter, the surface of the photoreceptor is exposed to a laser beam 110 modulated with a signal to form an image of the first color, yellow.
is irradiated to form a latent image. Further, this latent image is first developed in a yellow developing device 106 facing the photoreceptor, thereby forming a yellow toner image. By the time the formed yellow toner image comes to a position facing the transfer drum 104, a sheet of paper fed from the paper feed section 111 is already on the outer periphery of the transfer drum 104, the leading edge of which is gripped by the claw section 112. The toner image is formed at a timing such that the yellow toner image on the photoreceptor faces and meets a predetermined position on the paper.

After the yellow toner image on the photoreceptor is transferred to paper by the action of the transfer charger 113, the surface of the photoreceptor is cleaned by a cleaner 105 to prepare for the formation of the next color image. Subsequently, magenta, cyan, and black toner images are formed in the same manner, but at this time, the developing section 103 brings each developing device used according to the color to face the photoreceptor so as to be ready for development. The diameter of the transfer drum is large enough so that this switching of the developing device can be done in time and the toner image of the previous color and the toner image of the next color can be superimposed.

Laser beam 110 for image formation of each color
The irradiation is performed at a timing such that the toner image of each color on the photoreceptor and the toner image already transferred to the paper on the transfer drum are aligned and face each other as the photoreceptor rotates. In this way, the four-color toner image is transferred to the transfer drum 10.
The color image is transferred onto the paper on the paper 4 in an overlapping manner, and a color image is formed on the paper. After the toner images of all colors have been transferred, the paper is peeled off from the transfer drum 104 by a peeling claw 114.
The upper toner image is fixed by the fixing device 116 via the conveyance section 115, and then discharged to the outside of the apparatus. The above is a brief explanation of the configuration and operation of the conventional example.

[0009]

However, in the conventional apparatus described above, a transfer drum is used to align and overlap toner images of different colors. By rotating this transfer drum at a precise speed relative to the photoreceptor, the toner images of each color are aligned with each other. However, in the above configuration, the transfer drum needs to wrap the paper once and transfer the four color toner images in an overlapping manner, so the configuration is very complicated, and the size of the transfer drum is such that the outer circumference is the maximum length of the paper. Since it requires a larger size, it becomes larger overall. Additionally, since the paper must be wrapped around the transfer drum, there are limitations such as the inability to use thick or stiff paper.

Furthermore, in such a configuration, since latent image formation for four-color development is performed sequentially for each color on one photoreceptor, it takes a very long time to obtain one color image. It will take a while.

In view of the above-mentioned problems, the present invention provides an excellent color image forming apparatus that is small, inexpensive, and has a simple configuration, is capable of mutually aligning toner images of each color, and can be used with a wide range of paper. It is something to do. The present invention also provides a high-speed color image forming apparatus that can provide high-speed and high-quality images.

0012

Means for Solving the Problems In order to solve the above problems, the color image forming apparatus of the present invention includes a rotating electrostatic image carrier, and a plurality of different electrostatic image carriers disposed near the electrostatic image carrier. a developing means for developing with colored toners; an intermediate transfer member comprising an endless belt that sequentially transfers toner images of different colors on the electrostatic image carrier to form a multilayer color image; and transfer from the intermediate transfer member. The apparatus has a transfer means for transferring a toner image onto a material, and a drive roller having a flywheel at one end, which winds and drives the intermediate transfer body.

[0013] Still another color image forming apparatus according to the invention includes:
a plurality of rotating electrostatic image carriers; a plurality of developing means arranged around at least one of the electrostatic image carriers and developing with toners of mutually different colors;
an intermediate transfer member comprising an endless belt that sequentially transfers toner images of different colors on the electrostatic image carrier to form a multilayer color image; and a drive roller that winds and drives the intermediate transfer member; Further, the distance between the plurality of electrostatic image carriers and the circumferential length of the intermediate transfer body are set to be approximately integral multiples of the outer circumferential length of the drive roller.

[0014]

[Operation] With the above-described structure, the present invention does not require a transfer drum with a complicated structure, making the entire device simple. Furthermore, there is no need to wrap the paper around the transfer drum and the paper can be conveyed almost in a straight line, so it can be used for a wide range of paper. is wide. In addition, since a flywheel is provided on the drive roller that drives the intermediate transfer body, the intermediate transfer body can run accurately and steadily without jitter or irregular speed fluctuations, and the accurate position of each color toner image on this body can be maintained. It is something that can be matched.

[0015] Furthermore, a plurality of electrostatic image carriers are used as required, and the distance between the plurality of electrostatic image carriers and the circumferential length of the intermediate transfer body are set to be equal to the outer circumferential length of the drive roller. Because the ratio is approximately an integer, the toner images on each electrostatic image carrier can be accurately aligned with each other, and when the intermediate transfer body rotates once and the toner image of the next color is superimposed, it is possible to accurately align the toner images on each electrostatic image carrier, and to achieve high image quality and high speed. This enables a color image forming apparatus.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a color image forming apparatus according to an embodiment of the present invention. In FIG. 1, 51
is a reading section, and its configuration and operation will be described later. The configuration and operation of the writing section 52 will be described below. 1a and 1b are photoreceptors, each of which is made of an Al base material with the same diameter and coated with an organic photoconductor, and rotates at the same constant speed in the direction of the arrow during operation. 2a, 2b
are chargers that uniformly charge the surfaces of the photoreceptors 1a and 1b, respectively. 3 is a laser optical system that illuminates the uniformly charged surface of the photoreceptor with two types of laser beams 3a and 3b modulated by separate color signals coming from an image processing unit (described later).
to form a latent image on each. 4M and 4C are an M developing device for developing with magenta toner and a C developing device for cyan, which are opposed to the photoreceptor 1a, and each has two states: a developing state and a non-developing state. can be removed. Similarly, 4Y and 4K are respectively a Y developing device for developing with yellow toner and a K developing device for developing with black toner, which are installed facing the photoreceptor 1b. Cleaners 6a and 6b clean residual toner on the surfaces of the photoreceptors 1a and 1b, respectively.

Among the above, photoreceptor 1a, charger 2a, M
The developing device 4M, the C developing device 4C, and the cleaner 6a constitute the first process section A, and can be integrally inserted into and removed from the main body of the apparatus. A second process section B is similarly configured.

An intermediate transfer member 7 is a wide endless belt made of polycarbonate and is supported by a drive roller 8 and support rollers 9 and 10. During operation, it is driven by the drive roller 8 and transfers the photoreceptor 1a, the photoreceptor 1a, It revolves at the same speed as the circumferential speed of 1b.

FIG. 2 is a plan view showing the driving roller portion of this intermediate transfer body in detail. At one end of the rear side of the driving roller 8, there is a flywheel which has a larger rotational moment than the driving roller 8 and is integrated with the driving roller. 21 are provided. 22
, 23 is a gear, and 24 is an intermediate transfer member driving motor.

Returning to FIG. 1 again, the intermediate transfer member lightly contacts the photoreceptor 1a at the first transfer portion Ta, and has a transfer charger 11a on its back surface to transfer the toner image on the photoreceptor to the intermediate transfer member. In addition, the second transfer section T
It is in contact with the photoreceptor 1b at b, and the toner image on the photoreceptor can be transferred to the intermediate transfer member by the action of the transfer charger 11b.

At this time, the laser beam 3 on the circumference of the photoreceptor 1a
The distance La from the irradiation position of a to the first transfer portion Ta, and the distance La from the irradiation position of the laser beam 3b on the circumference of the photoreceptor 1b to the second
The distance Lb to the transfer portion Tb is set to be equal to the distance Lb.

Furthermore, the distance Lc between the first transfer portion Ta and the second transfer portion Tb is approximately twice the length of the outer circumference of the drive roller 8. Furthermore, the circumferential length of the intermediate transfer member 7 is set to be approximately eight times the outer circumferential length of the drive roller 8.

A transfer charger 12 is provided in the third transfer portion Tc of the support roller 10 portion in opposition thereto, and when the paper moves in contact with the intermediate transfer member 7 in this portion, the transfer charger 12 The toner image can be transferred to paper. Reference numerals 13 and 14 are static eliminators that remove an appropriate amount of residual charge from the intermediate transfer member. 15 is a cleaner which, after the toner image on the intermediate transfer body is transferred to paper at the third transfer section Tc,
Clean any residual toner left on the intermediate transfer body. Further, the cleaner 15 is designed to be able to move toward and away from the intermediate transfer body, and if necessary, it can be moved away from the intermediate transfer body to allow the toner image thereon to pass through without disturbing it.

Reference numerals 16 and 17 denote paper feed sections that feed sheets of desired size one by one to the third transfer section Tc.

A fixing device 18 fuses and fixes the toner image on the paper when the paper to which the toner image has been transferred passes.

The operation of the writing section of the color image forming apparatus configured as described above will be explained below.

In FIG. 1, when the operation starts, the photoreceptors 1a, 1b and the intermediate transfer member 7 start rotating and circulating in the directions of the arrows, and the surfaces of the photoreceptors 1a, 1b are charged approximately negative by chargers 2a, 2b, respectively. It is uniformly charged to about 600V.

The uniformly charged surface of the photoreceptor is then irradiated with laser beams 3a and 3b modulated with respective color signals, and a latent image is formed by lowering the potential of only the areas to be toned according to the image. Ru.

At this time, the laser beam 3a is modulated with an M signal for an image to be developed with magenta toner among the color signals input to the laser optical system. On the other hand, the laser beam 3b is modulated with a Y signal for yellow color, and the timing of the start of the irradiation is set so that the intermediate transfer body is first
It is set to lag behind the M signal by the time it takes to travel from the transfer section Ta to the second transfer section Tb.

The latent image formed on the photoreceptor 1a is first developed as a magenta toner image by the M developer 4M, which is set to a developable state. The magenta toner image on the photoreceptor 1a is sequentially transferred from the leading edge of the image to the intermediate transfer member 7 by the action of the transfer charger 11a as the photoreceptor 1a rotates.

On the other hand, the latent image on the photoreceptor 1b is similarly developed as a yellow toner image by the Y developer, and further transferred to the intermediate transfer member sequentially from the leading edge. However, at this time, the writing timings of both latent images coincide with each other at the same location, so that the magenta toner image and the yellow toner image are transferred onto the intermediate transfer member while being aligned in position.

After the transfer, the surface of the photoreceptor is cleaned of residual toner by cleaners 6a and 6b, respectively, to prepare for the next image formation.

That is, La=Lb=Lc On the other hand, the superimposed magenta and yellow toner images transferred to the intermediate transfer body are applied with the neutralizing chargers 13 and 14 according to the rotation thereof, and the toner images are transferred to the intermediate transfer body and thereon. The toner image is neutralized. It rotates further and comes to the position of the transfer charger 12, but at this time the transfer charger 11 is in a non-operating state and passes through as it is. Further, at the position of the cleaner 14, the cleaner is in a non-operating state at this time and passes through as is.

When the leading edge of the magenta and yellow multilayer toner image on the intermediate transfer member comes to the first transfer portion Ta, the cyan toner image, which is the third color, is placed on the photoreceptor 1a in the same way as the magenta one. The cyan toner image is formed at a timing such that the respective toner images match positionally and meet each other according to the rotation of the photoreceptor 1a and the rotation of the intermediate transfer member 7. . Furthermore, when the leading edge of the toner image on the intermediate transfer body reaches the second transfer section, the black toner image formed with a predetermined time delay relative to cyan, similar to the timing of yellow relative to magenta, matches positionally. and transcribed.

The four-color toner image formed in the above manner is transferred to the paper fed from the paper feed section 16 or 17 at the third transfer section Tc at the same timing after the black color is finally transferred. The image is transferred by the action of the charger 12 and fixed by the fixer 17 to complete a full-color image.

The residual toner remaining on the intermediate transfer member after the transfer is cleaned by the cleaner 15 which is in operation.
Prepared for transfer of a new toner image.

The overall operation of the writing section has been described above. Next, the relationship between the detailed running state on the intermediate transfer member and minute positioning between toner images will be explained using FIG.

FIG. 3 shows the elapsed time during operation on the horizontal axis and the traveling speed of the intermediate transfer member on the vertical axis.

As mentioned above, since the drive roller is provided with a flywheel with large inertia at one end, it rotates steadily with very little change, but mainly due to the eccentricity of the drive roller 8, the intermediate transfer body is As shown in Figure 3, there is a slight fluctuation with a period of one rotation of the drive roller.

However, the intermediate transfer body is
The time it takes to move Lc between a and the second transfer portion Tb is equal to the time it takes for the drive roller to rotate twice, as explained in the configuration. Therefore, the magenta toner image transferred at the first transfer section Ta and the yellow toner image transferred at the second transfer section are in an overlapping state, although each has slight positional changes as described above. Then the waves of change overlap and there is no deviation from each other.

Further, even when the intermediate transfer member rotates once and the magenta toner image and the cyan toner image overlap at the first transfer portion Ta, the waves of change overlap in the same way, and there is no mutual positional deviation.

Therefore, although the four-color toner images formed on the intermediate transfer body have slight positional changes as a whole, there is no mutual positional shift between the colors. As long as the overall change is gradual, there will be no visual problem. Since there is no mutual positional shift between colors, the color image formed has stable hue and no color shift and is of excellent quality.

The structure and operation of the writing section have been described above. Next, the structure and operation of the reading section 52 and the image processing section will be explained.

FIG. 4 is a diagram for explaining the general configuration of the reading section 52 and the signal flow of the image processing section 53.

In FIG. 4, the color original placed on the original platen 54 is illuminated by an illumination lamp 55, a lens,
The color sensor is configured to perform a reading operation by scanning from the left end of the figure to the right. When one reading is completed, these are returned to their original positions at high speed in preparation for the next reading. The output from the color sensor 57 is first input to the masking section 58 in the image processing section and then to the writing section 5.
The signals are converted into signals for the four colors used in 2008: magenta, cyan, yellow, and black. Of these, the magenta signal M' and the cyan signal C' are selectively input to the multi-value circuit 59 and input to the writing section almost in real time. On the other hand, yellow signal Y' and black signal K' are generated by halftone processor A60 and halftone processor B, respectively.
After being input to 61, its output is selectively entered into buffer memory 62. These signals are delayed by a predetermined time by a buffer memory and input to the writing section. The amount of time for this delay is determined by the amount of time that the photoreceptor 1
This amount corresponds to the amount of time required to delay the latent image to be formed on the photoreceptor 1b with respect to the latent image to be formed on the photoreceptor 1b.

Halftone processor A also processes signal Y'
is binarized by dither processing, and the output is Y'
compared to the amount of information. Furthermore, the halftone processor B performs error diffusion processing on the signal K' to binarize it, and its output is also small compared to the amount of information of K'.

The above is the general configuration of the reading section 51 and the signal flow of the image processing section.Next, these operations will be explained. When the device starts operating, the reading section 51 starts the first reading operation, and the M signal and Y signal are selected from the output from the masking section and input to the writing section 52 through the respective processing sections. be done. However, at this time, the magenta signal M is input almost in real time in parallel with the reading operation, whereas the yellow signal Y is input with a delay of a predetermined time. These signals are transmitted to the writing section by laser beams 3a and 3b, respectively.
This signal is used as a modulation signal to perform the operation of the writing section described above.

In the above-described operation of the writing section, after the transfer of the magenta image starts at the transfer section Ta, the intermediate transfer body 7 rotates approximately once, and the leading edge of the magenta and yellow superimposed images returns to the transfer section Ta. Before the vehicle is opened, the first reading operation has already been completed in the reading section 51, and the next second reading operation has started. Reading section 2
In the second reading, signals C' and K' are selected and input to the writing section with the same time difference as the previous relationship between M and Y. At this time, the second reading operation is started at the timing when the image based on the signal C matches the leading edge of the toner image on the intermediate transfer body. After this, the formation of a color image is completed by the operation of the writing section as described above. The above is the explanation of the configuration and operation of the reading section and the image processing section.

As described above, according to this embodiment, the use of the intermediate transfer member simplifies the device, and there is no need to wrap the paper around the transfer drum, allowing it to be conveyed almost in a straight line, so that a wide range of paper can be used. . Furthermore, by using two electrostatic image carriers, images of two colors are formed in parallel in one reading, thereby enabling a high-speed color image forming apparatus.

Furthermore, in this embodiment, since the drive roller of the intermediate transfer body is provided with a flywheel, the intermediate transfer body can run stably without irregular speed fluctuations. Furthermore, because the distance between the two photoreceptors is set to approximately an integral multiple of the outer circumferential length of the drive roller of the intermediate transfer member, periodic speed unevenness that occurs with each rotation of the drive roller is eliminated from the transfer from each photoreceptor. When the toner images are overlapped, the same unevenness occurs at the same position, and there are few positional deviations between the toner images on each photoreceptor. Furthermore, since the circumferential length of the intermediate transfer body is approximately an integral multiple of the outer circumference length of the drive roller, the speed unevenness that occurs each time the drive roller rotates becomes the same unevenness at the position where the intermediate transfer body rotates once. There is little positional deviation between the two color toner images transferred from the photoreceptor.

[0052]

As described above, the present invention does not require a transfer drum with a complicated structure, making the entire device simple, and also allows the paper to be conveyed in an almost straight line without having to wrap the paper around the transfer drum. The range is wide. Furthermore, stable running of the intermediate transfer body is possible, and high quality color images can be formed.

Further, according to the present invention, by using a plurality of electrostatic image carriers as many as necessary regardless of the number of colors, a small, simple, and high-speed color image forming apparatus can be realized. Furthermore, it is possible to accurately align toner images formed on each electrostatic image carrier, as well as between toner images of different colors formed on the same electrostatic image carrier, resulting in excellent image quality and high speed. This enables a color image forming apparatus.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of an embodiment of the present invention.

FIG. 2 is a detailed view of a drive roller portion of an intermediate transfer member in an embodiment of the present invention.

FIG. 3 is a chart diagram illustrating the running state of the intermediate transfer body in the embodiment of the present invention.

FIG. 4 is a block diagram illustrating a schematic configuration of a reading section and a signal flow of an image processing section in an embodiment of the present invention.

FIG. 5 is a schematic configuration diagram of a conventional color image forming apparatus.

[Explanation of symbols] 1a, 1b Photoreceptor 3 Laser optical system 4M M developer 4C C developer 4Y Y developing device 4K K developer 7 Intermediate transfer body 8 Drive roller 14 Cleaner 21 Flywheel

Claims (2)

[Claims] Claims: 1. A rotating electrostatic image carrier; a plurality of developing means disposed near the electrostatic image carrier for developing with toners of different colors; The intermediate transfer member includes an endless belt that sequentially transfers toner images to form a multilayer color image, and a transfer means that transfers the toner image from the intermediate transfer member to a transfer material, and the intermediate transfer member is wound. A color image forming apparatus having a drive roller with a flywheel at one end that is rotated and driven. 2. A plurality of rotating electrostatic image carriers, and a plurality of developing means arranged around at least one of the electrostatic image carriers and developing with toners of mutually different colors. an intermediate transfer member comprising an endless belt that sequentially transfers toner images of different colors on the electrostatic image carrier to form a multilayer color image; and a drive roller that winds and drives the intermediate transfer member. and a color image forming apparatus in which the distance between the plurality of electrostatic image carriers and the circumferential length of the intermediate transfer body are approximately an integral multiple of the outer circumferential length of the drive roller.