JPS6015068B2 - Developer triboelectric charging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In a static exposure latent image development method using a one-component developer, the developer held between the developing rollers and conveyed to the developing section is The present invention relates to a device for charging to a polarity opposite to that of a latent image.

A developer in which a one-component developer is held between the developing rollers and transported by the rotation of the developing rollers, and frictionally charged in a reverse gutter manner with the electrostatic solution to develop the electrostatic latent image. The method is known.

An outline of this developing method and its problems will now be described with reference to FIGS. 1 and 2.

In FIG. 1, the developing roller 1 is formed by covering the circumferential surface of a metal cylinder 11 with a conductive rubber layer 12, and is provided so as to be rotatable around a shaft 13 in the direction of the arrow. .

A hopper 2 in which developer D is stored is provided above the developing roller 1.

The lower part of the hopper 2 is a gate for replenishing the developer. are doing.

The developer D is a powder and is a one-component system composed only of non-magnetic toner. When the developer D is supplied from the opening of the hopper 2 to the circumferential surface of the developing roller 1, it is affected by microscopic irregularities on the surface of the conductive rubber layer 12, adhesion force due to surface energy, and adhesion force between toner particles. A portion thereof is held on the circumferential surface by, for example, the following.

Therefore, when the developing roller 1 is rotated in the direction of the arrow, the developer D held on its circumferential surface is transported by moving together with the circumferential surface, and when the developing roller 1 rotates once, the developer D is D covers the circumferential surface of the developing roller 1 in a layered manner. The thickness of the developer layer held on the circumferential surface of the developing roller 1 is determined by the thickness of the side plate edge forming the opening of the hopper 2, especially the edge of the side plate on the side from which the developer D is sent out, and the circumferential surface of the developing roller 1. It is regulated by the size of the gap.

That is, by keeping the gap between the lower end of the side plate 21 and the circumferential surface of the developing roller constant, the layer thickness can be kept constant. In this example, the lower edge of the side plate 21 is also provided with a function of triboelectrically charging the developer D inversely to the electrostatic latent image.

That is, at least the portion near the lower edge of the side plate 21 is formed of a material that can triboelectrically charge the developer D in a manner opposite to the electrostatic latent image. Therefore, the developing roller 1
The toner on at least the surface portion of the developer layer held on the peripheral surface of the developer layer is electrically charged.

Incidentally, a potential having the same polarity as the static latent image is applied to the developing roller 1, so that a developing bias voltage is generated in the developing section.

The latent image carrier 3 on which the electrostatic latent image to be developed is formed is conveyed in the direction of the arrow, and in the developing section, the surface on which the electrostatic latent image is formed is exposed to the developing surface of the developing roller 1. The surface of the toner layer is brought into close proximity or lightly abutted, and development is performed by electrical interaction between the charge of the toner and the electrostatic latent image, and powder is deposited on the latent image carrier 3. Visible image of the bodyV. 1 is formed.

Now, what is important in such a developing method is to hold the developer D uniformly and in a layer thickness as small as possible on the circumferential surface of the developing roller 1.

That is, as described above, the force that keeps the developer D on the circumferential surface of the developing roller 1 is
These forces include the trapping force due to microscopic irregularities on the surface, the adhesion force due to surface energy, the adhesion force between toner particles, and the electrical attraction between the developing roller 1 and the charged toner, and these forces are not very large when taken together. However, if the thickness of the developer layer on the circumferential surface of the developing roller becomes large, the retention of the developer D will deteriorate, and the developer D will easily separate from the developing roller 1, making it more likely that background stains will occur. , replenishment of the developer D also deteriorates. Also, if the layer of developer D is not uniform, the developed visible image V. 1, density unevenness may occur. By the way, in the apparatus shown in FIG. 1, in order to form a very thin and uniform developer layer on the circumferential surface of the developing roller 1, it is necessary to The size of the gap with the surrounding surface,
It is necessary to keep the size of the upper vertical gap extremely small and uniform across the circumferential direction of the developing roller 1, which is technically extremely difficult. There was a drawback that the above-mentioned peripheral surface was damaged due to contact between the two.

Therefore, in order to eliminate such drawbacks, a developer triboelectric charging device as shown in FIG. 2 was proposed.

That is, the main part of the device is composed of a frictional charging member 4 and a compressible spring 5.

The frictional charging member 4 is an elongated plate in the direction perpendicular to the drawing, and one side twill along its length is smoothly rounded as shown in the drawing. One end of a compressible spring 5 is fixed to the other longitudinal side edge of the frictional charging member 4, and the other end of the spring 5 is in contact with the immovable member 6. The frictional charging member 4 is maintained in the position shown in the figure by a holding means (not shown) with the smoothly rounded side twill abutting against the upper circumferential surface of the developing roller. Then, the smoothly rounded side edges come into pressure contact with the circumferential surface of the developing roller in the length direction due to the elastic force of the spring 5. The developer D is appropriately supplied to the base of the triboelectric charging member and the upper part of the pressing portion of the developing roller 1. When the developing roller 1 rotates in the direction of the arrow, the developer D moves along with the circumferential surface of the developing roller 1 while being triboelectrically charged by the triboelectrically charging member 4 to form a layer on the curved surface.

This thickness is regulated by the strength of the pressure applied by the frictional charging member 4 to the developing roller 1, that is, by the elastic force of the spring 6. However, this device has the following problems.

That is, since the side edges of the frictional charging member 4 are smoothly rounded, the developing agent D easily passes through the gap between the side twill portion and the circumferential surface of the developing roller.
The thickness of the developer layer held on the circumferential surface of the developer tends to be large. Therefore, in order to keep this layer thickness small, it is necessary to increase the pressing force of the frictional charging member 4 on the developing roller 1. However, when the pressing force is increased, the developer D tends to aggregate or solidify on the circumferential surface of the development loaf 1. If the developer D aggregates or solidifies, the developing function will be significantly impaired and the quality of the visible image will deteriorate. The aggregation and solidification of the developer D occur because the developer moving along with the circumferential surface of the developing roller 1 is continuously compressed as it advances due to the curvature of the side edge of the triboelectric charger 4. .

SUMMARY OF THE INVENTION An object of the present invention is to improve a developer triboelectric charging device in order to eliminate the above-mentioned disadvantages.

EMBODIMENT OF THE INVENTION Hereinafter, the present invention will be explained separately with reference to illustrated embodiments. However, in order to reduce complexity, the same reference numerals as in FIGS. 1 and 2 are used in FIGS. 3 and below for items that are unlikely to be confused. FIG. 3 schematically shows an embodiment of the invention. The developer tribo-charging device according to the present invention is comprised of a tribo-charging member 7, a compressible spring 8, and means (not shown) for maintaining the disposed position of the tribo-charging member 7.

That is, in terms of construction, the developer frictional charging device according to the present invention and the frictional charging device shown in FIG. 2 are almost the same. The characteristics of the present invention reside in the shape of the frictional charging member 7 and its arrangement. That is, the frictional charging member 7 is a plate whose longitudinal direction is the direction perpendicular to the drawing in FIG. As shown in FIG. 4, the base surface 71 and the slope 72 make the tip end 0. It is formed into a green leaf below the peak.

The angle between the base surface 71 and the slope 72 is assumed to be 8. The frictional charging member 7 may be formed of a material that can be frictionally charged with the developer D to reverse the electrostatic port image to be developed, or may be formed of any hard material as shown in the figure. It may also be used by forming a ring and covering the pointed portion with the above-mentioned material.

Adjust the roundness of the cusps from 0 to 0. The value of the wave length is determined by the coefficient of friction between the roller and toner, the toner and blade material, and the blade pressure. The frictional charging part 7 has its pointed green surface on the circumferential surface of the developing roller 1.
It is disposed so as to be in contact with the developing roller 1 in all directions of its axis, and to oppose the rotation of the developing roller 1 .

At this time, the base surface 71 of the frictional charging member 7 is made to face the side that receives the moving developer D. Now, developing roller 1
A surface that perpendicularly intersects with the circumferential surface is called a slope, and the slope erected at the rear of the point line of the friction charging section 7 and the circumferential surface is indicated by the symbol n in FIG.

Then, the arrangement position of the frictional charging member 7 changes to the position of the developing roller 1.
The term ``determined so as to oppose the rotation'' means that the base surface 71 is tilted clockwise by more than oo with respect to the slope n, with the apical edge as the center.

The angle formed by the slope n and the base surface 71 is assumed to be 02.

Corner 8 and angle a2 must satisfy the following conditions.

That is, the condition is oo<8, S90o o0
S82<900 and 00<8,182 S900
It is.

This is the content of determining the shape and disposition of the frictional charging member 7. In this example, the developer D is appropriately supplied to the upper part of the saddle between the frictional charging section 7 and the developing roller 1. In some cases, the frictional charging member 7 may be used as the side plate 21 of the hopper 2 shown in FIG. Now, one end of a compressible spring 8 is fixed to the side end surface of the frictional charging member 7 on the opposite side to the pointed green. Due to the elastic force of the triboelectric charging member 8, the green point of the frictional charging member 8 is pressed against the cylindrical surface of the developing roller 1.
Now, when the triangular shape and arrangement position of the triboelectric charging member 7 are determined to satisfy the above-mentioned conditions, the developer D moving together with the circumferential surface of the developing roller is
As a result, the developer is less likely to be compressed, and therefore the developer is kept in a state where aggregation and solidification are less likely to occur.

Furthermore, since the portion of the frictional charging member 7 that is pressed against the developing roller 1 has a pointed green shape, the pressing force is effectively concentrated on the pressing portion, and therefore, even if the elastic force of the spring 8 is relatively small, A sufficiently thin and uniform developer layer can be formed on the circumferential surface of the developing roller 1.

Of course, if the elastic force of the spring 8 is too strong, the developer D will
Since agglomeration and solidification may occur, the strength of the spring 8 must be set to a value that prevents this from occurring.

Note that the developing conditions, such as the rotational speed of the developing roller 1, may be the same as conventional ones.

As described above, according to the present invention, it is possible to provide a developer triboelectric charging device that can improve the developing function in a developing system using a one-component developer.

[Brief explanation of the drawing]

1 and 2 are explanatory diagrams showing an example of a developing device using a conventionally known one-component developer, and FIG. 3 is an explanatory diagram showing only the essential parts of an embodiment of the present invention. Front view, 4th
The figure is a partial perspective view for explaining the shape of the frictional charging member. DESCRIPTION OF SYMBOLS 1...Development roller, 12...Conductive rubber layer, 7...Frictional charging member, 71...Base surface, 72...Slope, 8... Compressible spring, D... Developer. Rare illustration of boar, 2 figures of sticks, 3 figures, 4th figure

Claims (1)

[Claims] 1 A thin layer of a one-component developer made only of powdered non-magnetic toner is held on the circumferential surface of a developing roller whose circumferential surface is made of conductive rubber, and is transported by the rotation of the developing roller. However, in a development method in which the electrostatic latent image is charged to a polarity opposite to that of the electrostatic latent image to be developed, the electrostatic latent image is developed.
A device for triboelectrically charging a developer, wherein the triboelectric charging member is formed by forming a tip of the edge of a plate having a straight edge into a sharp edge, and the sharp edge is arranged in an apparatus space. means for maintaining the position of the triboelectric charging member so as to be in contact with the circumferential surface of the developing roller in the longitudinal direction at a fixed position, the tip of the triboelectric charging member being brought into contact with the base surface. is brought into pressure contact with the developing roller so that it faces the side that receives the developer and opposes the rotation of the developing roller, and the angle θ_1 between the base surface and the slope at the tip and the angle θ_1 at the pressure contact portion are The angle θ_2 between the slope of the circumferential surface of the developing roller and the base surface meets the conditions 0°<θ_1≦90°, 0°
The shape of the pointed edge and the arrangement position of the frictional charging member are determined so as to satisfy ≦θ_2<90°, 0°<θ_1+θ_2≦90°, and the toner is prevented from coagulating and solidifying. A developer triboelectric charging device.