JPH01172879A - Developing device - Google Patents

Abstract

PURPOSE:To prevent the generation of surface contamination of an image by constituting a toner replenishing roller, as a toner electrifying and replenishing roller for replenishing a toner, while bringing it to triboelectrification. CONSTITUTION:A toner replenishing roller which has been conventionally used is replaced with a toner electrifying and replenishing roller 23 for allowing a toner to pass through between the roller and a blade 22 which comes into contact therewith opposingly and replenishing it, while bringing it to triboelectrification. The blade 22 consists of a rigid body of, for instance, a metal, a synthetic resin, etc., and the toner electrifying and replenishing roller 23 consists of an elastic body of, for instance, rubber, etc., and this roller 23 is inserted and held by the blade 22 and a sponge member 24. Even if a replenishing toner which has passed through between the blade 22 and the roller 23 is brought to triboelectrification and drops down to a two component compound developer in a developing container 1, and carried toward to a developing sleeve 12 in a state that it is not stirred so much, its toner becomes a state that the electrification has risen. In such a way, it is prevented that the toner adheres carelessly to other part than a latent image on the surface of a photosensitive body, and the generation of surface contamination on an image is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developing device used in an image forming apparatus such as an electrophotographic copying apparatus.

Conventionally, in some types of image forming apparatuses such as antibiotic electrophotographic copying machines, an electrostatic latent image is formed on a latent image carrier such as a photoreceptor, and this electrostatic latent image is developed using a powder developer. It has become FIG. 2 shows a conventional example of a dry type developing device that achieves this function.

In the developing device of this example, a two-component developer containing carrier in addition to toner is stored in the developer container 1, and a toner concentration detection sensor 2 detects a decrease in the toner concentration of the developer. At this time, toner is supplied from the toner replenishing section 3 to the developer in the container 1 via the toner replenishing roller 4. The developer replenished with toner in this way is agitated immediately below the replenishment by the rotation of the agitator 5. At least a portion 1 of the developer, for example only the carrier, or both the carrier and the toner, is made of a magnetic material.

A developer stirring, transporting and pumping member 6 is provided adjacent to the agitator 5 in the developer container 1, and the developer stirring, transporting and pumping member 6 shown as an example in the figure is connected to a return auger 8. Paddle9. It consists of a supply auger 1o, etc. Of these, the return auger 8 and paddle 9 rotate in the direction of the arrow as a pair, with the return auger 8 transporting the developer from the back side to the front side in the figure, and the paddle 9 transporting the developer around the circumference. Pump up and transport in the direction. On the other hand, the supply auger 10 at the center rotates in the direction of the arrow to convey the developer from the front side to the back side.

In this way, the developer agitation conveyance pumping member 6 agitates the developer while conveying it in this axial direction, and also agitates the developer in a direction perpendicular to the axial direction while pumping up the developer with the paddle 9. During stirring in both directions, the carrier and toner are triboelectrically charged to opposite polarities. The developer stirring and conveying pumping member 6 stirs the developer in two directions: vertically (axially) and horizontally (perpendicular to the axial direction), and is also called a dual cross mixer. It also achieves the developer dispersion function of crushing the toner and mixing it into the developer.

A developing sleeve 12 is provided adjacent to the developer stirring, conveying and pumping member 6, and has five fixed magnets arranged in the circumferential direction inside, p2. p,, P4. The magnetic poles S and N of these magnets on the side facing the sleeve 12 are set as shown in the figure. Further, a magnetic shield plate 13 made of a magnetic material such as iron is provided inside the developing sleeve 12, and this can be moved between the solid line and the imaginary line position, and when the developing device performs development, it is moved to the solid line position It is located in

Magnet P1~. are hereinafter referred to as P1 to P5 poles, of which P3 pole faces the developer agitation conveyance pumping member 6, and magnetically develops the developer drawn up by the developer agitation conveyance pumping member 6. Pull it toward the sleeve 12. As the developing sleeve 12 is rotated in the direction of the arrow, the developer thus received on the developing sleeve 12 rotates as a magnetic brush along the curve in the same direction as the sleeve rotation direction.

When the developer is carried over the developing sleeve and reaches the part of the doctor blade 14 located between the P pole and the P pole, the excess developer is scraped off and the developer on the sleeve is removed from the developing sleeve. The thickness is set to suit. In this state, the developer on the sleeve comes into contact with a latent image carrier, for example, a drum-shaped photoreceptor 15 rotating in the direction of the arrow as shown in the figure, and the electrostatic latent image formed on the surface of the photoreceptor is transferred to the developer. Visualized by toner.

Next, when the developer on the developing sleeve 12 reaches the P2 pole, the developer on the sleeve reaches the magnetic shield plate 1.
Since the magnetic field of the P2 pole is shielded by the action of 3, the developer is released from the magnetic field, moves away from the sleeve, and is carried toward the developer stirring, conveying, and pumping member 6.

Note that when the developing device does not perform development, the magnetic shield plate 13 is displaced to the imaginary line position, thereby cutting off the supply of developer to the sleeve 12. Further, the sleeve 12 may be stopped by rotationally driving P1 to S poles, or both may be rotationally driven.

By the way, in FIG. 2, the developing sleeve 12 supports a developer on its surface and constitutes an example of the structure of a developer carrying member that visualizes the electrostatic latent image on the photoreceptor 15 with the carried developer. However, sufficient triboelectrically charged developer must be supplied to such a developer carrying member.

The developer stirring and conveying pumping member 6 pumps up the developer while conveying it, and triboelectrically charges the developer by stirring the developer at this time. For example, in a developing device with a small developer capacity, when toner is replenished and the toner concentration increases, the volume of the developer increases. If the toner is buried in the developer, when toner is replenished on top of the toner, the replenished toner will not be stirred and will float, and the toner will not be sufficiently charged.

If this kind of floating toner that has caused insufficient charging is conveyed to the developing sleeve 12 together with the developer and adheres to the surface of the photoreceptor 15, it will cause background stains on the image.

An object of the present invention is to provide a developing device that eliminates the above-mentioned conventional drawbacks.

In order to achieve the above object, the present invention includes a developer container containing a developer, a toner replenishing roller that replenishes toner from a toner replenishing section into the developer in the developer container, and a toner replenishing roller that replenishes the developer in the developer container. In a developing device comprising a developer carrying member that carries a frictionally charged developer and visualizes an electrostatic latent image formed on a latent image carrier with the carried developer, the toner replenishing roller comprises: This roller is characterized by being constructed as a toner charging replenishment roller that replenishes toner while frictionally charging it by passing the toner between opposing blades.

The present invention will be explained below based on one embodiment. In this description, the same reference numerals are used for the members that achieve the same functions as those in the conventional example for convenience.

FIG. 1 shows an embodiment of the present invention, and the feature of this embodiment is that the toner supply roller 4 (
2) is replaced by a toner charge replenishment roller 23 that replenishes the toner while being frictionally charged by passing the toner between the blades 22 that are in contact with each other.

The blade 22 is made of a rigid body such as metal or synthetic resin, and the toner charge supply roller 23 is made of an elastic body such as rubber.
and the sponge member 24.

The replenishment toner that has passed between the blade 22 and the roller 23 is triboelectrically charged during this passage and falls onto the two-component developer in the developer container 1 . Even if such fallen toner is conveyed to the developing sleeve 12 without being stirred very much, the toner will still be charged to some extent, so it will not actively develop the latent image. This prevents inadvertent adhesion to areas other than the latent image on the surface of the photoreceptor. Therefore, on the image,
It is possible to prevent the occurrence of skin stains.

By the way, as shown in the figure, the toner charge supply roller 23
Providing a roller 25 immediately below the toner for transporting and stirring the charged replenishment toner to the developer is effective in a developing device where the upper part of the developer stirring, transporting and pumping member 6 is easily buried in the developer. be.

Like the developing sleeve 12, this roller 25 is configured as a magnetic roller with a fixed magnet provided inside, and the roller 25 rotates counterclockwise to convey the developer supported on its surface in the direction of the solid line arrow. . Among these magnets, the magnetic poles of the two lower magnets on the side facing the roller 25 have the same polarity (N pole). First, the developer pumped up in the direction of the broken line arrow is carried along the curved surface of the roller 25 and merges with the charged and falling replenishment toner.

Thereafter, the replenishment toner and developer are mixed and conveyed toward the developer agitation conveyance pumping member 6, and are separated from the roller 25 by the repulsive magnetic field of two magnets of the same polarity located below, and are pumped up. Moving on to member 6.

As mentioned earlier, it is sufficient if the upper part of the developer agitation conveyance pumping member 6 is exposed from the upper surface of the developer, but in a developing device where the upper part is easily buried in developer, the toner to be replenished is , there is a risk that the developer may remain floating on the top surface and not be stirred.

The magnetic roller 25 transports such floating toner and incorporates it into the developer, thereby making the toner more fully chargeable and further improving the ability to prevent background stains. . In this way, the addition of the magnet roller 25 can effectively cope with a developing device in which the volume of developer tends to fluctuate.

As described above, according to the present invention, since the charge rise of the replenishing toner is improved, it is possible to prevent the occurrence of background stains.
Further, such functions can be realized with a relatively simple configuration.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of one embodiment of the present invention, and FIG. 2 is a sectional view of a conventional example.

Claims (1)

[Claims] a developer container that stores a developer; a toner replenishment roller that replenishes toner from a toner replenishment unit into the developer in the developer container; In a developing device comprising a developer carrying member that visualizes an electrostatic latent image formed on a latent image carrier with the carrying developer, the toner is passed between the toner replenishing roller and an opposing blade. 1. A developing device configured as a toner charging replenishment roller that replenishes toner while frictionally charging the toner.