JPH083688B2 - Magnetic developing device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic developing device for developing an electrostatic latent image formed on the surface of a photosensitive member with toner particles in an electrophotographic apparatus.

2. Description of the Related Art A magnetic brush developing device that has been conventionally used in a magnetic developing device has a developing sleeve (hereinafter referred to as a sleeve) formed of a non-magnetic material such as aluminum around a fixed permanent magnet so as to be rotatable. By covering and rotating this sleeve, a magnetic brush is formed on the outer circumference of the sleeve, and the electrostatic latent image on the outer circumference of the photosensitive drum is developed by this magnetic brush. Although it is guided into the stirrer in synchronization, a wall for preventing toner outflow is provided between the magnetic poles above the sleeve or on the magnetic poles in order to prevent the developer and the raw toner from coming into contact with the photoconductor.

Hereinafter, a conventional example of the above-described magnetic developing device will be described with reference to FIGS. 3 and 4.

In the figure, the photoconductor 1 having the electrostatic latent image formed on its outer periphery rotates in the direction of arrow A. The sleeve 2 is rotatably arranged near the surface of the photoconductor and rotates in the direction of arrow B. First to third rod-shaped members arranged in this sleeve
A magnetic brush is formed by the magnets 3, 4, and 5. As is well known, among the magnets 3, 4 and 5, the magnetic poles of the surfaces of the magnets 3 and 5 facing the sleeve 2 are installed so as to have the same pole.
And the surface of the magnets 3 and 5 facing the sleeve 2 is the S pole, and the surface of the magnet 4 facing the sleeve 2 is the N pole. Is located in). In addition, 6 is a developer agitator, 7 is a developing box, 8 is a developer scraping plate, 9 is a developer in which carrier and toner are mixed, and 11 is a toner outflow preventing plate.

In the magnetic developing device configured as described above, the developer 9 in the developing box is sufficiently agitated by rotating the agitator 6, and the magnetic force of the three magnets 3, 4, 5 is provided on the outer circumference of the sleeve 2. Attracted to form a magnetic brush. By passing a gap between the magnetic brush adjusting plate 10 and the outer periphery of the sleeve 2 in a state where the developer is in a state of standing in the vicinity of the portion facing the magnet 3, the amount of the developer passing through can be reduced to some extent. adjust. After that, the developer, which is in the state of the spikes again in the vicinity of the portion facing the magnet 4, comes into contact with the outer periphery of the photosensitive drum having the electrostatic latent image, so that the development is performed. Then, the developer which has completed the developing work passes between the toner outflow prevention plate 11 and the sleeve 2 as the sleeve 2 rotates, and is scraped off from the sleeve 2 by the scraping plate 8. Then, the developer is agitated sufficiently by the developer agitator 6 to be used for the development again.

Problems to be Solved by the Invention However, in the conventional magnetic developing device having the above-described structure, the toner outflow prevention plate 11 is provided between the magnets 4 and 5 or between the magnet 5 and the scraped plate 8. , The amount of the developer attracted to the outer circumference of the sleeve 2 varies depending on the magnetic strength of the magnet 3, the position of the magnetic brush, the roughness of the surface of the sleeve 2, and the like. Gap regulation is very difficult. Further, as shown in FIG. 5, when the toner outflow prevention plate 11a is provided above the magnet 5, it is not difficult to regulate the above-mentioned gap, but the sleeve is rotated due to the friction between the developer and the toner outflow prevention plate. There arises a problem that the torque required for the operation must be increased.

Means for Solving the Problems In order to solve the above problems, the magnetic developing device of the present invention is
An enclosure having an opening at a position facing the photoconductor drum and containing a developer in which carrier and toner are mixed, and an electrostatic charge formed on the surface of the photoconductor drum rotatably instructed to the opening of the casing. And a developing sleeve formed of a non-magnetic material for developing the latent image with a developer, in which the first magnet is arranged at the developing position of the photosensitive drum, and with respect to the first magnet 2nd to the direction of rotation of the developing sleeve
A third magnet is arranged, and the poles of the surfaces of the first, second and third magnets facing the inner peripheral surface of the developing sleeve are the first magnet with the second and third magnets having the same pole. And a toner outflow prevention plate is arranged on the outer peripheral side of the developing sleeve and inside the housing near the portion facing the second magnet.

Operation With the above-mentioned configuration, the developer that has spiked at the portion facing the first magnet and has been used for development passes between the toner outflow prevention plate and the sleeve in a state where spike development has disappeared as the developing sleeve rotates. The repulsive magnetic forces of the rear second magnet and the third magnet cause the toner to flow toward the toner outflow prevention plate and prevent the outflow of toner.

Example Hereinafter, an example of the present invention will be described with reference to the drawings.

The same parts as those in the conventional example described above are designated by the same reference numerals and the description thereof will be omitted.

In FIG. 1, reference numeral 12 is a fourth magnet, which is magnetized so that the side facing the inner circumference of the sleeve 2 becomes the S pole.
Adjacent magnets 5 have the same pole arrangement. And
A toner outflow prevention plate 13 is arranged near the magnet 5 with the sleeve 2 interposed therebetween. FIG. 2 is a partially enlarged view of FIG. 1 and shows the peripheral portion of the sleeve 2. In the figure, reference numeral 13 is a developer ear, and 14 is a hollow portion.

In the magnetic developing device of the present embodiment having such a configuration, the developer 9 in the developing box is sufficiently agitated by the agitator 6 and attracted onto the outer circumference of the sleeve 2 by the magnetic force of the magnet in the sleeve to remove the magnetic brush. Form. The thickness of the magnetic brush is regulated by the magnetic brush adjusting plate 10 to be substantially uniform. Then, the magnetic brush contacts the outer circumference of the photosensitive drum 1 again while rising again by the magnetic force of the magnet 4 to develop the electrostatic latent image on the outer circumference of the photosensitive drum. Then, the developed developer passes through the gap between the toner outflow prevention plate 15 and the outer periphery of the sleeve 2 in a pulling contact state as the sleeve 2 rotates, and thereafter, due to the repulsive magnetic force between the magnet 5 and the magnet 12. The developer is pushed back in the direction opposite to the rotating direction of the sleeve 2, and the tip portion 1 of the brush 13 is formed on the back surface (the surface on the back side as viewed from the photosensitive drum 1) 15a of the toner outflow prevention plate 15.
3a abuts or approaches. When the sleeve 2 further rotates, the sleeve 2 passes over the cavity 14 and is attracted toward the magnet 12, and thereafter the developer is scraped off by the scraping plate 8. Then, it is agitated by the agitator 6 and again provided for development.

As described above, according to the present embodiment, the magnet 12 is arranged next to the magnet 5 and the opposite sides of the two magnets to the inner circumference of the sleeve have the same polarity, so that the repulsive magnetic force of the two magnets causes the developer to develop. Has an effect that the outflow of raw toner can be sufficiently prevented without increasing the mechanical torque because the ears stand on the back surface side of the toner outflow prevention plate and the tip portions of the ears extend to the toner outflow prevention plate side. In the present embodiment, the magnetic poles of the magnets 3, 4, 5 and 12 facing the sleeve 2 are S pole, N pole, S pole and S pole, respectively.
Needless to say, it may be a pole or an N pole.

As described above, the magnetic developing device of the present invention has an opening at a position facing the photosensitive drum, and a housing for accommodating the developer in which the carrier and the toner are mixed, and the opening of the housing. A developing sleeve formed of a non-magnetic material that develops the electrostatic latent image formed on the surface of the photoconductor drum by a developer, and is rotatably supported. The first magnet is placed and this first
Second and third magnets are arranged on the side of the developing sleeve in the direction of rotation with respect to the magnet, and the poles of the surfaces of the first, second, and third magnets facing the inner peripheral surface of the developing sleeve are included. , The surfaces of the second and third magnets have the same pole, and the surfaces of the first magnet have different polarities, and are on the outer peripheral side of the developing sleeve and in the vicinity of a portion facing the second magnet. By disposing the toner outflow prevention plate inside the housing, the effect that the outflow of the raw toner can be sufficiently prevented without increasing the mechanical torque for driving the sleeve is obtained, which is very effective in practice.

[Brief description of drawings]

1 is a side view of a magnetic developing apparatus according to an embodiment of the present invention, FIG. 2 is a partially enlarged view of FIG. 1, FIG. 3 is a side view of a conventional magnetic developing apparatus, and FIG. 4 is FIG. And FIG. 5 is a side view of another conventional example. 1 ... Photosensitive drum 2 ... Development sleeve 3,4,5,12 ... Magnet 6 ... Developer agitator 7 ... Development box 8 ... Developer scraping plate 9 ... Developer 10 ... Magnetic Brush adjustment plate 15 …… Toner outflow prevention plate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazunori Yukitake 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-58-160962 (JP, A)

Claims (1)

[Claims] 1. A housing which has an opening at a position facing the photoconductor drum and contains a developer in which a carrier and a toner are mixed, and a surface of the photoconductor drum which is rotatably supported by the opening of the housing. A developing sleeve formed of a non-magnetic material that develops the electrostatic latent image formed on the developer with a developer, and a first magnet disposed in the developing sleeve in the vicinity of a position facing the photosensitive drum, The second magnet and the third magnet, which are sequentially arranged in the rotation direction side of the developing sleeve with respect to the first magnet, and the outer peripheral side of the developing sleeve and near the facing portion of the second magnet. A toner outflow prevention plate disposed inside the housing, wherein the magnetic poles of the second and third magnets on the side opposite to the developing sleeve are the same pole, and the magnetic poles are different from the magnetic poles of the first magnet. A magnetic developing device characterized in that