JPH0625880B2 - Color copier development device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention is a developing device for a color copying machine capable of preventing color mixing caused by the developer adhering to the photoconductor from the surface of a non-developing mode magnetic roll. Regarding

(Prior Art) Color copiers include full-color copiers that can faithfully reproduce the colors of originals and so-called flat color copiers that can reproduce originals in colors other than black (for example, red and blue) in a single color. . In the case of any copying machine, a plurality of developing machines are provided, and while one developing machine (one color) is operating, the other developing machines must be deactivated to prevent color mixture.

A conventional developing machine for preventing this color mixing is disclosed in, for example, Japanese Patent Publication No.
It is disclosed in Japanese Patent Publication No. 5-3707 and Japanese Patent Publication No. 58-10748. In the former, the entire developing machine including a developing machine roll, a toner donor, and the like is brought close to the photosensitive drum only during development, and is retracted when another developing machine is developing. The latter is provided with a scraping member that comes into contact with the surface of the magnetic roller that applies the developer to the latent image surface only during development and separates from the surface of the magnetic roller during non-development. With such a configuration, by eliminating the adhesion of the developer to the surface of the developing roll (or the magnetic roller) of the developing machine that is not developing, facing the photosensitive drum, or by preventing the developer from adhering to the photosensitive drum, This is to prevent color mixing.

(Problems to be Solved by the Invention) However, in the case of the conventional developing device, in the former case, it is necessary to have a structure for moving the developing device as a whole closer to and further away from the photoconductor drum, so that the size is increased and the cost is increased. There was a problem that caused up. In the latter case, the scraping member needs to be movable according to the developing mode and the non-developing mode, and has the same problem as the former case.

In particular, recently, flat color copying machines, which are capable of producing copies of various colors, although they are monochromatic, have begun to spread, and there is a demand for their miniaturization and low cost. Therefore, the present invention provides a developing device for a color copying machine which solves the problems of the prior art and is economical and compact.

(Means for Solving Problems) The developing device of the color copying machine of the present invention is made in view of the above, and at least one developing device containing a magnetic developer has magnetic poles of different polarities on the surface. Has a fixed magnet composed of a first area adjacent to the second area and a second area having the same polarity of the adjacent magnetic poles, and a magnetic roll formed of a sleeve rotatable around the outer circumference of the fixed magnet in forward and reverse directions, The second region is disposed downstream of the developing position in the developing mode in the forward direction of the sleeve and upstream of the magnetic developer supply position to the magnetic roll, and the sleeve is not developed. In the mode, the sleeve is rotated in the direction opposite to that in the developing mode until the position of the sleeve that has passed at least the second region reaches the developing position.

(Operation) In the developing device of the color copying machine of the present invention, the developer adheres to the surface of the sleeve in the range of the first area and the area where the developer does not adhere to the surface of the sleeve in the range of the second area. To do. Then, in the non-development mode, the sleeve is rotated in the direction opposite to that in the development mode, and the sleeve on which the developer has not adhered to the surface that has passed through the second region is positioned at the development position.

(Example) Hereinafter, the developing device of the color copying machine according to the present invention will be described in detail.

FIG. 1 is an explanatory view showing an embodiment of the developing device of the present invention. For convenience of explanation, only one developing machine is shown, but normally,
In the case of a flat color copying machine, three units of black, red, or black, red, and blue are provided, and in the case of a full color copying machine, three units of cyan, magenta, and yellow, and further four units with black added are provided. To be

The developing machine is disposed so as to face the photoconductor drum 20 on which a latent image is formed by exposure by a scanning optical system (not shown), and contains a magnetic roll 1, a paddle 2, a developer 4 and the like.
As the developer, a mixture of a non-magnetic toner and a magnetic carrier, or a magnetic toner is used. The magnetic roll 1 is provided with a fixed magnet 1a and a rotating sleeve 1b formed on the outer circumference of the fixed magnet 1a and rotating around the outer circumference of the fixed magnet 1a. The paddles 2 are arranged in close proximity to the magnetic roll 1 and are rotated together with the magnetic roll 1 to adhere the developer 4 attached to the surface to the surface of the magnetic roll 1. The magnetic roll 1 and the paddle 2 are housed in the housing 5 so as to be rotatable in the forward and reverse directions in synchronization with each other. The housing 5 is provided with an opening on the surface of the magnetic roll 1 facing the photosensitive drum 20, and a fixed amount of the developer 4 is supplied to the bottom. Inside the housing 5, a trimmer 3 for arranging the developer adhering to the surface of the magnetic roll 1 to a uniform thickness is arranged.

The fixed magnet 1a is a first region in which rod-shaped magnets having different polarities (N, S) are alternately arranged at a predetermined interval in the vicinity of the circumferential surface. Then, two adjacent bar-shaped magnets at one of them have the same polarity, and, for example, as shown in FIG. 2, a bar-shaped magnet S ₄ having a polarity S and a bar-shaped magnet S ₁ having a magnetic S are arranged adjacent to each other. The second area. This second area is the sleeve 1
When b is rotated in the forward direction (direction A) in the developing mode, it is located on the downstream side of the developing position and between the developer supplying position, the two magnetic forces repel each other, and no magnetic field is formed. . Then, the rod-shaped magnet S ₄ and the pole-shaped magnet S ₁ which are the second region
Between the angle θ and the angle θ (90 ° in this example), a region where the developer 4 does not adhere is formed on the surface of the sleeve 1b of the magnetic roll 1.

In the above configuration, the photoconductor drum 20 that is precharged
By exposing the contents of the document on the surface of the
It is formed continuously as the drum 20 rotates. The photosensitive drum 20 on which the latent image is formed reaches the arrangement position of the first developing machine. In synchronization with the arrival of this latent image, the sleeve 1b of the magnetic roll 1 and the paddle 2 are both in the forward direction A
Rotate in the direction. The developer 4 adheres to the surface of the paddle 2,
The magnetic attraction force of the magnetic roll 1 rotating closer to each other causes the magnetic roll 1 to fly in the direction of the developer supply position on the surface of the sleeve 1b as shown by an arrow C. At this time, the developer 4 is attached to the surface of the sleeve 1b by the magnetic attraction force between the magnet S ₁ and the magnet S ₄ in the range of the first area where the fixed magnets are provided along with S ₁ , N ₁ , S ₂ , and N _2. However, the developer 4 is not adsorbed on the surface of the sleeve 1b between the magnet S ₄ and the magnet S ₁ , which is the second area.

With the rotation of the sleeve 1b in the rotation direction A (forward direction),
The developer adhering to the surface of the sleeve 1b is regulated to a certain thickness by the trimmer 3 while being attracted like a magnetic brush due to its magnetic absorption force, and then the surface of the photosensitive drum 20 facing the photosensitive drum 20 which is the opening of the housing 5. To reach. Here, the magnetic brush 6 of the developer comes into contact with the latent image surface of the photoconductor drum 20 and adheres to the latent image surface by the charged electric charge.

The rotation of the magnetic roll 1 and the paddle 2 is stopped when the rotation corresponding to one original has elapsed. At this stage as well, the photosensitive drum 20 continues to rotate, transfers the first color onto the recording paper, and then stops after the steps of cleaning, charge removal, and charging. As a result, a copy of the first color can be obtained.

Next, when a copy of the second color is obtained from the same original or another original, a copy button (not shown) provided in the copying machine is pressed to switch the developing machine containing the developer of the second color to operate the copying. To start. The process is the same as described above until the electrostatic latent image is formed. The electrostatic latent image formed on the photoconductor drum 20 is rotationally moved to the installation position of the second developing machine to be developed. A copy of the second color is obtained through the same steps as described above.

By the way, the magnetic roll 1 and the paddle 2 rotate in the B direction (reverse direction) at the same time when the development of the first color is completed. At this time, the developer attached to the paddle 2 flies in the direction downstream of the developing position of the sleeve 1b as indicated by arrow D. However, the fixed magnets 1a of the direction of the magnetic roller 1 is present a second region in which the polarity of the magnetic pole the same (range of S ₄ to S _1), the developer because there is no magnetic field in this range Does not adhere. Therefore, the sleeve 1 on which the developer is not attached
Even when b is rotated in the B direction in the reverse direction and reaches the developing position corresponding to the photoconductor 20, the developer does not fly from the developing machine.

The magnetic roll 1 and the paddle 2 of the first developing machine are rotated at a predetermined rotational speed until the position of the sleeve 1b that has passed at least the second region of the fixed magnet 1a reaches the developing position. The rotation is stopped and the state is maintained until the next development (until the operator selects it). At this time, since the developer is not attached to the peripheral surface of the magnetic roll 1 at the developing position (the magnetic brush is not formed), the developer of the first color is attached to the production of the second color. Does not occur, and color mixing cannot occur.

In the above-described embodiment, the case of the developing device of the flat color copying machine was described, but also in the developing device of the full color copying machine, a magnetic brush is provided on the sleeve of the magnetic roll of the developing machine other than the operating developing machine. It is exactly the same in that it is not formed.

Further, in the above-mentioned embodiment, the angle θ from the roll center between S _{1 and} S ₄ in the second region is 90 degrees, but this angle can be changed according to the configuration of the developing machine.

As described above, according to the developing device of the color copying machine of the present invention, in the developing mode, the rotating sleeve of the magnetic roll is rotated in the forward direction, and the magnetic field forming range of the fixed magnet is the first range. The sleeve with the developer attached to the surface after passing through the area causes the developer to fly toward the photoconductor at the developing position to perform the development, and at the time of non-development, the sleeve of the magnetic roll is rotated in the opposite direction to that at the time of development. Since the sleeve, which has passed through the second region of the fixed magnet in which the magnetic field is not formed and which does not have the developer attached, is positioned at the developing position, the developer does not attach to the photoconductor, so that the color developing process is performed. Generation of color mixture can be completely prevented.

Further, the developing device according to the present invention can be achieved without providing a special structure, and the size of the device can be reduced.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG.
The magnetic pole array explanatory drawing of the magnetic roll shown in the figure. DESCRIPTION OF SYMBOLS 1 ... Magnetic roll, 1a ... Fixed magnet, 1b ... Sleeve, 2 ... Paddle, 3 ... Trimmer, 5 ... Casing, 6 ... Magnetic brush, 20 ... Photoconductor drum.

Claims (1)

[Claims] 1. A developing device for a color copying machine, comprising a plurality of developing machines containing magnetic developers of different colors, and flying the developing agents toward a photoconductor at a developing position in a developing mode, at least one developing machine. Is a sleeve having a fixed magnet composed of a first region in which magnetic poles of different polarities are adjacent to the surface and a second region in which adjacent magnetic poles have the same polarity, and a sleeve rotatable around the outer periphery of the fixed magnet in forward and reverse directions. The second region is arranged downstream of the developing position in the developing mode in the forward direction of the sleeve and upstream of the magnetic developer supply position to the magnetic roll. At the same time, in the non-developing mode, the sleeve is rotated in a direction opposite to that in the developing mode until at least the position of the sleeve that has passed through the second region reaches the developing position. A developing device of a color copying machine, wherein.