JPH04358174A - Color electrophotographic device - Google Patents

Abstract

PURPOSE:To prevent the scattering of fine grain toner and to attain stable development by providing a means holding a developer having the mixture of a carrier and the fine grain toner on the outside of a developing means and connecting/separating it to/from the developing means. CONSTITUTION:Four sets of image forming units 9Bk 9C, 9M and 9Y parallely disposed on a printer part can be moved in the horizontal direction, as the whole and developer hoppers 23Bk, 23C, 23M. and 23Y holding respective developers and toner hoppers 24Bk, 24C, 24M and 24Y are fixedly provided on a main body, on the upper parts of respective image forming units. As the developer, a two-component developer having the mixture of a ferrite powder carrier whose surface is coated with silicone resin, and the toner whose average diameter is <=10mum is used and a connecting path for supplying the developers adjusted on the developer hoppers 23Bk, 23C, 23M and 23Y, respectively, to the image forming units 9Bk, 9C, 9M, and 9Y is provided. Moreover, the image forming units 9Bk, 9C, 9M and 9Y can be separated from the developer hoppers.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color electrophotographic apparatus applicable to printers, facsimile machines, and the like.

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. An example of a color image forming apparatus disclosed in Japanese Unexamined Patent Publication No. 1-252982 is a general method for superimposing toner images on a transfer material.

FIG. 3 shows an overview of the overall configuration of this conventional example, and the configuration and operation will be briefly explained below. In FIG. 3, 101 is a photoreceptor, and a charger 1 is located opposite to it.
02, a developing section 103, a transfer drum 104, and a cleaner 105. The developing section 103 is composed of a plurality of developing devices that perform development using a two-component developer that is a mixture of toner and carrier of different colors. It consists of a developing device 107, a C developing device 108 for cyan color, and a K developing device 109 for black color, and the entire device rotates so that each developing device faces the photoreceptor 101 in turn and becomes ready for development. It is now possible to do so. A toner hopper 118 is provided above the developing section 103, and is replenished with toner whenever the toner in the developer in each developing device is consumed and reduced.

During operation, the transfer drum 104 and the photoreceptor rotate at a constant speed in the directions of the 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.
4 and are superimposed on the paper and transferred to form a color image 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, passes through a conveyance section 115, the upper toner image is fixed by a fixing device 116, and is discharged out of the apparatus. The above is a brief explanation of the configuration and operation of the conventional example.

[0009]

[Problems to be Solved by the Invention] In the conventional apparatus described above, in order to sequentially form toner images of different colors on the photoreceptor, four color developing devices are sequentially moved to face the photoreceptor. The four color toner images are superimposed on the transfer drum.

[0010] Therefore, in such a configuration, since each developer moves, a connection part for supplying toner is required between the toner hopper that does not move, and this connection is necessary to connect the hopper that does not move and the developer that moves. Separation is necessary because it is performed in between. Therefore, as the average particle diameter of toner is reduced in line with recent demands for higher image quality, toner scattering at this connection becomes a serious problem.

Furthermore, as the toner particle size becomes smaller, it becomes necessary to delicately adjust the toner concentration and agitation control of the developer. In the conventional configuration, the entire device becomes large and the configuration for movement becomes complicated.

As the toner particle size becomes smaller, the influence of gravity among external forces acting on the toner decreases, whereas the influence of electrostatic force and adhesion force increases.

In experiments conducted by the inventors, it has been found that when toner is moved alone from a hopper in a supply section or the like, the degree of toner scattering increases dramatically when the toner average particle diameter is 10 μm or less. Furthermore, it was found that when the thickness is less than 10 μm, the characteristics of the developer tend to become very unstable, and in order to keep this stable, precise concentration control and sufficient stirring of the developer are necessary.

[0014]

[Means for Solving the Problems] In order to solve the above problems, the electrophotographic apparatus of the present invention includes a carrier and an average particle size of 1.
Contains a developer mixed with toner of 0 μm or less,
a plurality of movable developing means that face the photoreceptor and develop an electrostatic latent image on the surface of the photoreceptor; and a plurality of movable developing means that are located outside the developing means and hold the developer corresponding to each developing means. The electrophotographic apparatus has a developer hopper, and further includes a connecting means that can be connected and separated for supplying the developer between the developing means and the developer hopper.

Another invention provides a carrier and an average particle size of 10
a plurality of movable developing means which contain a developer mixed with a toner of .mu.m or less and develop an electrostatic latent image on the surface of the photoreceptor while facing the photoreceptor;
an electronic device comprising a plurality of stationary developer hoppers holding the developer corresponding to each developing means, and further comprising a connecting means for supplying the developer between the developing means and the developer hopper; It is a photographic device.

[0016]

[Operation] According to the above-described structure, the present invention has a means for holding a developer mixed with a carrier and a toner of 10 μm or less outside the developing means and maintaining its developing characteristics, thereby forming a color image. When the developing means is moved, there is almost no toner scattering at the connecting portion for supplying developer, and a high-quality color electrophotographic device with excellent stability and maintainability can be provided.

Furthermore, since it is possible to precisely control the developer using a developer hopper that does not move, the developing means that must be moved is small and has a simple structure. This enables a stable and excellent color electrophotographic device.

[0018]

Embodiments Examples of the present invention will be described below with reference to the drawings. An example of such a device will be explained using FIG. 1.

FIG. 1 shows only a printer section for forming an image in a color electrophotographic apparatus according to an embodiment of the present invention.

First, in the printer section, four sets of image forming units 9Bk, 9C, 9M, and 9Y are arranged side by side. Each image forming unit as a whole is movable in the lateral direction, and FIG. 1 shows the state during black development, which will be described later. Developer hoppers 23BK and 23C are located above each image forming unit in the state shown in FIG. 1 and hold respective developers.
, 23M, and 23Y are fixed to the main body. Furthermore, toner hoppers 24BK, 24C, 24M, and 24Y holding toner are provided at the upper part of each of the toner hoppers, fixed to the main body.

Each of the image forming units is composed of the same components except for the developer contained therein, so to simplify the explanation, the image forming unit for black will be explained, and explanations for other colors will be omitted. FIG. 2 shows the black image forming unit 9Bk and a part of its surroundings in detail.

In FIG. 2, 10 is an organic photoreceptor drum in which phthalocyanine is dispersed in a polyester binder resin, 11 is a magnet consisting of three magnetic poles fixed coaxially with the photoreceptor 10, and 12 is a negative charger for the photoreceptor. 13 is a grid electrode for controlling the charging potential of the photoreceptor, 14 is a laser beam scanning light, and 15 is a developer supply section.

The developer is a two-component developer consisting of a mixture of toner and a ferrite powder carrier with a particle size of 45 μm whose surface is coated with a silicone resin, and is dropped into the developer supply section 15 from the developer supply port 17 and is then dropped. The developer 16 is attached to the surface of the photoreceptor 10 by magnetic force. The toner used is a styrene acrylic resin mixed with 5% carbon black and 2% oxycarboxylic acid metal complex, melted, and crushed toner with an average particle size of 4.7 μm, and 0.5 μm of colloidal silica.
It was used with 1% external addition (all percentages by weight).

18 is a toner amount regulating blade made of nickel, which is a magnetic material; 19 is an electrode roller made of aluminum;
It has a fixed magnet 20 inside which is only partially magnetized, and is rotatable around it. 21 is a polyester film scraper that scrapes off the toner on the electrode roller. The magnetic flux density on the surface of the photoreceptor 10 is 800 Gs. The diameter of the photoreceptor 10 is 30 mm, and the peripheral speed is 180 mm.
/s to rotate in the direction of the arrow. 22 is a cleaner for cleaning the surface of the photoreceptor.

A developer hopper 23Bk storing black developer is shown above the black image forming unit 9Bk, and a toner hopper 24BK is further above that. FIG. 2 shows the respective positional relationships when the apparatus is in the state shown in FIG. 1, and as described later, among these, only the image forming unit group is movable as a whole in the direction of arrow 25. . In the state shown in FIG. 2, a certain amount of developer is dropped from the developer hopper 23Bk and is supplied into the image forming unit 9Bk through the supply port 16 of the developer supply section 15. Of the dropped developer, a large amount of developer still remains in the developer supply section and overflows into the overflow section 26.
It is then dropped into the drain 27. In the drain 27, a screw 28 is always operated during a developing operation, which will be described later, to send the developer to the front side in the depth direction of the paper. Therefore, this overflow developer and the developer used in the later-described developing operation are accumulated in the front part of the drain 27, and in the state shown in FIG. will be returned to.

These operations are repeated every time the developer hopper 23Bk and the image forming unit 9Bk are in the positional relationship as shown in FIG. Therefore, although the amount of developer in the image forming unit 19Bk is small, the developer in the developer hopper is always supplied.

On the other hand, a relatively large amount of developer is held in the developer hopper 9Bk, and the toner concentration of the developer is constantly detected by the toner concentration sensor 30, and when the toner concentration falls below a predetermined concentration, the toner hopper 24Bk in the upper part is Toner is supplied from. Therefore, the developer in the developer hopper 23Bk is always controlled to have optimal development characteristics, and is supplied to the image forming unit 9Bk.

The image forming operation of the black image forming unit 9Bk constructed as described above will be described below with reference to FIG. The photoreceptor 10 is charged with a corona charger 12 (applied voltage -4 kV, grid 13 voltage -500 V) to -50
Charge it to 0V. This photoreceptor 10 is irradiated with laser beam scanning light 14 to form an electrostatic latent image. At this time, the exposure potential of the photoreceptor is -100V.

When the developer 16 is passed through the photoreceptor 10 on which the electrostatic latent image is formed in this manner, the developer 16 is attracted by the magnet and moves together with the photoreceptor 10, and after passing the toner amount regulating blade 18, the developer 16 is , a uniform magnetic brush layer is formed on the photoreceptor 10.

Next, the photoreceptor 1 with this magnetic brush layer attached is
0 was passed in front of the electrode roller 19. Electrode roller 19
A high-voltage power supply (not shown) is used to generate 400V0-p (peak to peak 8
An alternating current voltage (frequency: 300 Hz) of 00 V) was applied. The magnetic brush layer on the photoconductor 10 moves between the photoconductor 10 and the toner collection electrode roller 19, and is attracted by the magnet 20 in the electrode roller 19 and moves toward the electrode roller, but at the same time, the magnetic brush layer moves between the photoconductor 10 and the toner collection electrode roller 19. Due to the action of the applied alternating current voltage, the toner in the non-image area gradually moves along with the carrier to the electrode roller 19.
The toner image remained on the photoreceptor 10 only in the image area, and a negative-positive toner image was formed. Electrode roller 2
As the developer rotates, the magnetic force of the magnet 20 ceases to act, and the developer is further scraped off by the scraper 21 and dropped into the drain 27. In this way, a black toner image is obtained on the photoreceptor 10. These image forming operations are performed when each image forming unit sequentially moves to an image forming position as described below.

Other image forming units 9C, 9M,
9Y also has a similar configuration and operates.

Referring again to FIG. 1, the overall configuration of the printer section will be explained first. The image forming units 9Bk, 9C, 9M, and 9Y arranged side by side are movable in the lateral direction as a whole, and each image forming unit can be sequentially located at an image forming position 50 facing the transfer drum 51.

3 is a laser exposure device which generates a laser beam scanning light 14 modulated by a signal input to the printer section, which is reflected by a mirror 4 and is directed onto the photoreceptor of the image forming unit at the image forming position 50. is irradiated to form a latent image.

Reference numeral 5 denotes a static elimination lamp fixed to the main body, and is located at a position to irradiate the surface of the photoreceptor of the image forming unit at the image forming position after transfer.

51 is a transfer drum which is basically composed of a cylindrical polyester film with a thickness of 100 μm, and the paper is attracted to the surface of the transfer drum, and four color toner images are transferred to the same position on the paper during four rotations. It has a transfer charger 52 at a position corresponding to the internal image forming position, and further includes static eliminators 53 and 54 for removing static from the toner image, paper, polyester film, etc. after transfer, and a cleaner 55 and paper It has an adsorption charger 56 etc. for adsorbing the polyester film to the polyester film. 57 is a separation charger used to peel off the paper from the polyester film after all transfers are completed.

Reference numeral 58 denotes a paper feed section from which paper is fed and supplied to the transfer drum via a paper feed path 59.

60 is a fixing device that fixes the toner image on the paper after transfer; 61 is a suction port (not shown) provided in each part of the device that sucks the scattered toner to prevent the inside of the device from becoming dirty; It is a cleaning device. The above is an explanation of the main structure of the electrophotographic apparatus of the present invention.

Next, the operation at this time will be explained. Paper (not shown) is fed from a paper feed section 58 , passes through a paper feed path 59 , and is wound around the transfer drum 51 by the action of an adsorption charger 56 . First of all, each image forming unit has moved to the left side in the drawing with respect to the position shown in FIG. Exposure is performed using beam scanning light 14.

The formed latent image is visualized in the image forming unit 9Y as detailed above, and the toner image is transferred onto paper by the action of the transfer charger 52. Next, move each image forming unit to the right, and move the magenta image forming unit 9M to the right.
Image forming position 5 where the previous yellow image forming unit is placed
Move it to 0, replace it with yellow, and do the same image forming process. At this time, the transfer drum around which the paper is wound rotates once, and the magenta toner image is transferred to the same position as the yellow image on the paper.

This process was repeated using the cyan unit 9C and finally the black unit 9Y to obtain a beautiful full-color image on the transfer paper. Thereafter, the paper is separated from the transfer drum by a separation charger 57, and finally by a fixing device 6.
It was heat-fixed at 0. The result was a beautiful full-color image.

At the time of forming the final black image in this one color image forming operation, each image forming unit is in the position shown in FIG. At this time, each image forming unit 9Bk, 9C, 9M, 9
Y, developer hoppers 23Bk, 23C, 23M, 23Y
are positioned vertically corresponding to each other, and the developer is supplied from the developer hopper to the image forming unit as described in detail in the operation of the image forming unit described above. At the same time, the used developer in the image forming unit is collected into the developer hopper.

The above is an explanation of the main operations of the electrophotographic apparatus of this embodiment. As mentioned above, in this example, the average particle size was 4.
．． High-quality full-color images can be obtained using toner as small as 7 μm, but when the image forming units for each color are moved, the developer supply ports that are separated and connected carry developer containing carrier instead of toner alone. Due to handling, there is very little scattering.

Further, since the developer supply operation at this time is performed every time a color image is formed, it is sufficient that there is enough developer in the image forming unit for at least one image formation. Furthermore, since the supplied developer is sufficiently adjusted each time, stable image formation can be achieved.

Furthermore, since the developer hopper does not move, it can be made large enough to hold a sufficient amount of developer without requiring a complicated mechanism or extra space, and this ensures stable images over a long period of time. can.

In the above embodiment, the developer is supplied every time a color image is created, but it may be controlled to be supplied every time an appropriate number of images are produced.

On the other hand, when black monochromatic images are continuously formed, the black image forming unit 9Bk is located at the position shown in FIG. 1, so that developer is supplied and collected at any time during the continuous forming operation.

In this example, a method was used in which a magnetic brush was formed on the surface of the photoreceptor in advance and unnecessary developer and toner were removed from the developing method. It goes without saying that similar effects can be obtained by a two-component development method using a roller.

Furthermore, in this embodiment, the method of moving the image forming unit including the photoreceptor has been explained, but even in the conventional method of fixing the photoreceptor and moving only the developing device, two-component development is possible. A similar effect can be obtained using the law.

The above is a detailed description of the present invention.

[0050]

As described above, the present invention has a means for holding a developer mixed with a carrier and a toner of 10 μm or less outside the developing means and maintaining its developing characteristics, thereby forming a color image. Therefore, when the developing means is moved, there is almost no toner scattering at the connecting portion for supplying developer, and a color electrophotographic device with excellent stability and maintainability can be provided.

Furthermore, since it is possible to precisely control the developer using a developer hopper that does not move, the developing means that must be moved is small and has a simple structure. This enables a stable and excellent color electrophotographic device.

[Brief explanation of the drawing]

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

FIG. 2 is a detailed view of an image forming unit and a part of its surroundings according to an embodiment of the present invention.

FIG. 3 is a schematic diagram of a conventional electrophotographic developing device.

[Explanation of symbols]

3 Laser exposure device 9Bk, 9C, 9M, 9Y Image forming unit 10
Photoreceptor 17 Supply ports 23Bk, 23C, 23M, 23Y Developer hopper 2
4Bk, 24C, 24M, 24Y toner hopper 51
Transfer drum 52 Transfer charger

Claims (2)

[Claims] 1. A plurality of movable developing means that contain a developer containing a mixture of a carrier and a toner having an average particle size of 10 μm or less, and that face the photoreceptor and develop an electrostatic latent image on the surface of the photoreceptor. , a plurality of developer hoppers that are located outside the developing means and hold the developer corresponding to each developing means, and further supply the developer between the developing means and the developer hopper. An electrophotographic apparatus having connection means that can be connected and separated for the purpose of connecting and separating. 2. A plurality of movable developing means which contain a developer containing a mixture of a carrier and a toner having an average particle size of 10 μm or less, and which face the photoreceptor and develop an electrostatic latent image on the surface of the photoreceptor. , a plurality of stationary developer hoppers that are located outside the developing means and hold the developer corresponding to each developing means, and further have a plurality of stationary developer hoppers between the developing means and the developer hopper. an electrophotographic device having connection means for supplying