JPS63264781A - Dry developing device - Google Patents

Abstract

PURPOSE:To form a uniform toner layer on a developing roller and to realize favorable development, by bringing the edge of an elastic triboelectrifying member into contact with the developing roller under pressure. CONSTITUTION:This dry developing device is provided with a movable developing agent holding body 21 which is opposed to an electrostatic latent image carrying surface at a prescribed interval in a developing section and is constituted of a nonmagnetic cylindrical body with a built-in magnet and a means which supplies a developing agent 22 to the developing agent holding body 21. In addition, the elastic triboelectrifying member 24 which is brought into contact with the surface of the developing agent holding body 21 and is provided so that a wedge-shaped space opened toward a developing agent supplying means 23 from the point of contact of the member 24 with the holding body 21, is provided between the developing agent supplying means and developing section. By bringing the edge section 24a at one end of the member 24 into contact with the developing agent holding body 21 under pressure, the thickness of the layer of the developing agent 22 is controlled. Therefore, scattering and aggregation of toner can be prevented and the thickness of the toner layer can be controlled to a constant and uniform and sufficient triboelectrification can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dry developing device for an electronic copying machine such as an electrophotographic copying machine or an electrostatic recording device. There are two types of developing devices for electronic copying machines: those that use a so-called two-component developer consisting of toner and carrier, and those that use a so-called one-component developer that does not have a carrier and consists only of toner. There is. The former method requires a toner concentration control device to maintain a constant mixing ratio of tote and carrier, which has the drawback of making the device complicated, large-sized, and expensive. The present invention relates to a developing device for a copying machine that uses a one-component developer.

Examples of the five-IL component developer include a non-magnetic toner made of a resin and a pigment, a mixture of a resin and magnetic iron powder, and a magnetic toner having magnetic iron powder as a core in the resin. Conventionally, in a developing device using such a one-component developer, a friction TI of a rigid body having an edge is applied to the developing roller.
The electrical group members are placed close to each other with a gap on the order of 10μ or less,
The developer passing through the gap was rubbed to generate a frictional current.

However, maintaining the gap between the developing roller and the frictional charging member on the order of several micrometers requires extremely sophisticated technology, and has drawbacks such as an expensive and complicated mechanism.

Therefore, even if the gap between the developing roller and the triboelectric charging member as described above is not determined accurately, the amount of developer on the developing roller can be controlled by using a flexible tribocharging member and adjusting its suppressing force against the developing roller. It was thought to determine the thickness of the layers. Such a developing device has a structure as shown in FIG. That is, this developing device includes a developing roller 1 that rotates in the direction of the arrow in the figure, and a hopper 3 above the developing roller 1 that supplies a one-component developer 2 to the surface of the developing roller 1. The one-component developer adhered to or absorbed on the surface of the developing roller 1 and transported is triboelectrically charged to a predetermined polarity by a triboelectric charging member 4 provided in pressure contact with the developing roller 1 . The developing roller 1 is provided close to the photoconductor or recording medium 5, and selectively supplies a charged l-component developer to the static FFI latent image formed on the photoconductor or recording medium 5. and visualize this.

However, in order to triboelectrically charge the toner sufficiently, the triboelectric charging member 4 is in pressure contact with the developing roller 1 in a state that extends beyond the point of contact with the developing roller 1, that is, in a shape that brings it into surface contact with the developing roller 1. Toner scatters from the contact area between the roller 1 and the frictional charging member 4, falls downward, and adheres to the photoconductor or recording medium 4, causing background stains and contaminating other parts of the machine. There are drawbacks such as.

SUMMARY OF THE INVENTION An object of the present invention is to provide a dry developing device for an electronic copying machine that eliminates the above-mentioned drawbacks and also forms a uniform layer of toner on a developing roller to perform good development. be.

An embodiment of the developing device of the present invention will be described below with reference to one drawing.

As shown in FIG. 2, the developing roller 21 is rotating in the direction of the arrow in the figure, and a hopper 23 containing a one-component developer 22 is provided above the developing roller 21. As the developing roller 21, an elastic rubber roller is used. It is desirable that the surface roughness of the elastic rubber roller is smaller than the particle size of the developer, that is, if the particle size of the developer is 10 microns, the surface roughness is 3 to 10 microns. By using the developing roller 21 having such a surface roughness and a coefficient of friction with respect to the developer of 0°5 or more, the ability to attach and convey the developer from the hopper 23 to the surface of the developing roller 21 increases. The triboelectric charging effect of the developer can also be improved during triboelectrification, which will be described later. A free end edge 24a of a plate-shaped frictional charging member 24 whose one end is supported on another member (not shown) on the surface of the developing roller 21 is pressed against the developing roller 21. This frictional charging member is arranged so that a wedge-shaped space opens toward the hopper 23 from the point of contact of its leading edge 24a with the developing roller. Friction: By using an elastic material as the jfi 11 member 24, it is brought into pressure contact with the developing roller 21 by utilizing its flexibility. At least the portion of the triboelectric charging member 24 that comes into contact with the developer 22 needs to be separated from the triboelectrification order of the developer 22, and is made of, for example, Teflon. Hopper 23
The developer 22 supplied by the developer 22 is triboelectrically charged by the triboelectric charging member 24, and the thickness of the layer of the developer 22 on the developing roller 21 that has passed through that portion is set to a predetermined layer thickness and uniformly. There is a need to. That is, a photoreceptor or recording medium 25 on which an electrostatic latent image is formed, and a developing roller 2.
1 is adjusted so that the gap is constant, so if the layer thickness of the developer 22 on the developing roller 21 is not constant or uniform, uneven development will occur. .

In order to increase the developing effect, it is necessary to sufficiently triboelectrically charge the developer, but for this reason, if the triboelectric charging member is strongly pressed against the developing roller, the developer may aggregate and solidify, or the developer may scatter. It turns out. Therefore, in order to triboelectrically charge the developer to a sufficient degree for development without applying much pressure, a plate-shaped triboelectric charging member 24 is used.
I realized that I should use Edge 24a. Therefore, since the pressure on the frictional charging member 24 is reduced, deformation of the developing roller 21 is suppressed, and scattering of the GL developer and non-uniformity of the developer layer can be prevented. That is, the triboelectric charging member 24 is extended in the rotational direction of the developing roller 21 from the portion where it is supported, so that the edge 24a at one end of the triboelectric charging member 24 in the so-called forward direction is T!
The frictional charging sequence 24 is in pressure contact with the hopper 21. Although the frictional charging sequence 24 is separate from the hopper 23, it may also serve as the outlet end of the hopper. It is necessary to select a triboelectrification order with the triboelectrification member so that charging is possible, and it is also necessary to have electrical insulation of 10' Ω mark or more as a volume-specific low resistance value.

In the embodiment of the present invention, when non-magnetic toner is used as the one-component developer, an elastic rubber roller is sufficient as the developing roller 21, but it is necessary to prevent background smearing in non-image areas during development. Therefore, the developing roller 21 is designed to apply static electricity with the same polarity as the electrostatic latent image and higher than the background potential.
A conductive rubber roller can also be used.

In addition, when using a one-component magnetic toner, in order to hold the toner on the developing roller 21 using magnetic attraction force, a magnet with mtb arranged alternately is provided in a non-magnetic sleeve. The magnetic toner is conveyed by relatively moving the sleeve and the magnet.

At the time of development, it is preferable to set the Gaussian amount of the magnet so that the magnetic attraction force of the magnet is larger than the 1-ner electrostatic attraction force due to the electric charge in the background area in the background area.

Furthermore, in this case, even if the uppermost toner on the million-am sleeve is rubbed by the frictional charging member 24 and is likely to scatter, this can be prevented to a minimum by the magnetic attraction force.

Note that the rotational speed of the developing roller 21 is the same as that of the photosensitive drum 2.
At the contact area with photoreceptor drum 1% 25, the speed is the same as that of 25 or up to twice that speed, and the image is free from background stains and the image density is sufficiently high. ; One image can be performed.

As described above, according to the present invention, since the edge of the F-shaped member is brought into pressure contact with the developing roller by elastic friction, toner scattering and agglomeration can be eliminated, and the toner layer thickness can be kept constant. It can be made uniform and can be triboelectrified sufficiently. Furthermore, it is possible to provide a simple and inexpensive dry type 7tUQ device.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of a conventional developing device, and FIG. 2 is a schematic diagram of a developing device showing an embodiment of the present invention.

Claims (1)

[Scope of Claims] A movable developer holder made of a non-magnetic cylindrical body that is disposed facing an electrostatic latent image bearing surface at a predetermined distance from an electrostatic latent image bearing surface in a developing section and has a magnet inside, and this developer. a means for supplying developer to the holder, which is located between the developer supply means and the developing section, contacts the surface of the developer holder, and extends from the contact point in the direction of the developer supply means. It has an elastic triboelectric charging member arranged to form an open wedge-shaped space, and the layer thickness of the developer is regulated by bringing an edge portion of one end of the tribocharging member into pressure contact with the developer holder. A dry developing device characterized by