JPH0210537Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a developing device that visualizes an electrostatic latent image, and more particularly to a developing device suitable for an image forming apparatus using magnetic toner.

Prior Art In general, developing devices used in electrophotographic devices, particularly those using high-resistance single-component toner, form an extremely thin toner layer in order to uniformly impart sufficient charge to the developer. There is a need to.

Conventionally, as a developing device for meeting the above requirements, a developing device using a doctor blade as shown in FIG. 1 is well known. In FIG. 1, magnetic toner 1 supplied from a hopper 2 to a toner carrier 3 is supported on the surface of the toner carrier 3 by the magnetic force of an internally installed magnetic roller 4, and is conveyed in the same direction as the rollers rotate. Now we reach the location where the doctor blade 5 as a layer thickness regulating member is provided. Here, the toner 1 is clamped between the doctor blade 5 and the surface of the toner carrier 3, is frictionally charged, and is regulated to a predetermined layer thickness to form a thin toner layer 1a. In this case, the pressure contact force of the doctor blade 5 against the toner carrier 3 greatly affects the uniformity of the formed toner thin layer, but the doctor blade 5 is made of a magnetic material, and the magnetic force from the internal magnet roller 4 is used as the pressure contact force. Its optimization has been achieved through its use.

However, even in the above method, unexpected variations may occur in the thickness of the thin toner layer 1a. The inventors of the present invention have studied this phenomenon in detail and have obtained the knowledge described below. That is, as shown in FIG. 2, the doctor blade 5 is attracted to the surface of the toner carrier 3 by a force called FM caused by magnetic force. On the other hand, the contact point C of the doctor blade 5 with the surface of the toner carrier 3
As the toner carrier 3 rotates, the toner 1 is packed into a wedge-shaped region Z defined by the protruding portion 5P from the tip to the tip and the surface of the toner carrier 3, and a push-up force FP is thereby generated. This pushing up force FP acts in the direction of pushing up the doctor blade 5 against the above-mentioned magnetic force FM, and therefore, the toner layer thickness is regulated to a predetermined thickness in a state where both are balanced. In this case, the magnetic force FM is determined by the configuration of the magnet roll 4 and the material and thickness of the doctor blade 5 and does not vary, but the other pushing force FP is
Unstable protruding part 5P that changes depending on the installation condition etc.
It is easy to fluctuate because it depends on the size of. Therefore, it is very important to control the size of the protrusion 5P in order to keep the thickness of the thin toner layer 1a constant. In this case, with the conventional method of holding the doctor blade 5 with the holding member 5a or the like, it is difficult to always set the holding manner constant, and therefore it is also difficult to keep the protrusion amount Δ within an appropriate allowable range.

Purpose The present invention has been made in view of the above points, and is a development method that facilitates the management of the installation mode of the layer thickness regulating member and that enables stable formation of a thin layer of developer with a uniform layer thickness. The purpose is to provide equipment.

Configuration The configuration of the present invention will be described below based on specific examples. FIG. 3 is a schematic diagram showing a developing device applied to the electrophotographic copying machine of the present invention. In FIG. 3, a cylindrical toner carrier 7 is rotatably supported, and is rotated counterclockwise at a predetermined speed to carry and convey toner 6 on its circumferential surface. In the toner carrier 7, a dielectric layer 7b made of a dielectric material such as epoxy resin or polyester resin is adhered to the outer peripheral surface of a cylindrical conductive base 7a, and the surface of the dielectric layer 7b is formed in the width direction and As shown in FIG. 4, a large number of minute electrodes 7c are scattered over substantially the entire circumferential area. The electrodes 7c are made of hemispherical metal grains such as copper, and are held in a floating state on the surface of the dielectric layer 7b at appropriate distances from each other. And the toner carrier 7
A cylindrical magnetic roller 8 is rotatably disposed coaxially with the toner carrier 7 inside the toner carrier 7 and is rotated in the same direction as the rotation direction of the toner carrier 7 .
In this embodiment, the toner carrier 7 having an outer diameter of 30 mm is rotated at a speed of 300 rpm, and a magnetic roller 8 having eight isotropic poles and a surface magnetic force of about 700 Gauss is rotated.
It is configured to rotate in the same direction at 1500 rpm.

A hopper 9 is provided at a suitable location near the circumferential surface of the toner carrier 7 to store the toner 6 and replenish the circumferential surface of the toner carrier 7 in an appropriate amount. Toner 6 is a so-called one-component high-resistance magnetic toner in which magnetic powder is mixed in resin, and for example, the average particle size is about 6 μm and the true specific gravity is about 6 μm.
Adjusted to 1.75.

A doctor blade 10 made of a magnetic material such as SK material and having a thickness of 0.1 mm is disposed on the downstream side of the hopper 9 in the direction in which the toner carrier 7 is guided. As shown in FIG. 3, the doctor blade 10 has one end held by the holding member 10b attached to the shaft 1.
0a, and is provided so that the other free end is in uniform pressure contact with substantially the entire widthwise circumferential surface of the toner carrier 7 due to the magnetic force of the magnet roller 8. The amount of toner 6 supported on the peripheral surface is regulated to form a thin toner layer 6a, and the friction at this time is used to triboelectrically charge the necessary charge. In this case, as described above, the amount of protrusion Δ of the doctor blade 10 from the pressure contact point C has a large influence on the thickness of the thin toner layer 6a, but the support side end can be freely rotated around the shaft 10a. By supporting the protrusion amount Δ, it is possible to easily maintain the protrusion amount Δ within an appropriate range.

This is because, as shown in FIG. 5, the length from the support point P of the doctor blade 10 to the tip +Δ
is clearly and easily determined by the dimensions of the holding member 10b and the length of the blade 10c. On the other hand, the distance L between the support point P and the center of rotation O of the toner carrier 7 can also be set with high precision by integrally forming the base for supporting both. Therefore, if the radius of the toner carrier 7 is R, the length from the support point P of the doctor blade 10 to the pressure contact point C is set as =√ ² − ² (1). In this case, doctor blade 1
0 is rotatably supported by the shaft 10a, so
Even without adjusting the mounting angle, etc., it can be installed in a substantially straight line without causing any deformation such as bending, and therefore, the length dimension is equal to the value set based on equation (1). There is no problem in considering it. Therefore, the protrusion amount Δ
is always maintained within an appropriate range with high precision.

By the way, as shown in FIG. 6, the doctor blade 10 may be bent beyond the allowable limit due to, for example, setting the magnetic force of the magnet roller 8 to be too strong or using a highly elastic material for the doctor blade 10. can also be considered. However, this deformation is
Since it is determined by the shape and magnitude of the magnetic field in that case and the material (magnetic properties) and shape of the doctor blade 10, by setting these factors constant, the protrusion amount Δ can be maintained within an appropriate range with high accuracy.

As an example, in this embodiment, for the doctor blade 10 whose length to the tip +Δ is 25 mm, a protrusion amount Δ of 1.0 mm is always stably ensured, and as a result, the adhesion density is 0.4 mg/cm ² It was possible to stably form a thin toner layer 6a.

Returning to FIG. 3 again, the doctor blade 10 configured as described above has the toner carrier 7.
After being connected to the same potential as the substrate 7a, it is connected to a bias power supply 11, and the effect of the applied bias voltage prevents background staining during development. In the above embodiment, the support point P of the doctor blade 10 is located on the extension of the tangent at the pressure contact point C, but no problem will occur even if the support point P is located off the tangent. Further, the entire blade 10c of the doctor blade 10 does not need to be made of a magnetic material, and as shown in FIG.
Only the vicinity 10'c may be selectively formed of a magnetic material. Furthermore, as shown in FIG. 8, the blade 10c of the doctor blade 10 is entirely made of non-magnetic material, and the pressing member 10'd made of magnetic material is secondarily fixed near the back side of the pressure contact point C. It's good as well.

An endless photoreceptor belt 12 is rotatable at a suitable position on the peripheral surface of the toner carrier 7 on the downstream side of the doctor blade 10 described above, for example, on the opposite side of the position where the doctor blade 10 is disposed as in this embodiment. It is located in A toner carrier 7 rotating in the opposite direction comes into rolling contact with this surface, and a thin toner layer 6 a supported on the surface of the toner carrier 7 is supplied to the surface of the photoreceptor belt 12 . The photoreceptor 12 has a photosensitive layer made of a photoconductive substance formed on a belt-shaped conductive substrate, and after an electrostatic latent image is formed through the steps of uniform charging and image exposure at appropriate locations, The developer reaches the development position D, which is the location of the development device according to the present invention, where the electrostatic latent image is made visible by being supplied with the thin toner layer 6a. Furthermore, the development position D
A static eliminating brush 13 is connected to the aforementioned bias power source 11 so as to have the same potential as the doctor blade 10 and the base 7a, and the static eliminating brush 13 remains on the surface of the toner carrier 7 without being subjected to development. The toner 6c has its electrical charge removed, and is returned to the hopper 9 as the toner carrier 7 rotates and is reused.

Note that, unlike the above embodiment, the layer thickness regulating member may be formed by magnetic field generating means such as a permanent magnet, or a portion thereof may be formed by magnetic field generating means. Further, the magnetic roller 8 may be fixedly installed, or the toner carrier 7 may be kept stationary and only the magnetic roller 8 may be rotated in the clockwise direction opposite to the toner conveying direction.

Effects As detailed above, according to the present invention, the developer layer thickness regulating member is configured to be magnetically attractable, and one end is rotatably supported and pressed against the developer carrier surface. As a result, the protrusion length from the pressure contact point to the tip can always be kept within the allowable range with high accuracy regardless of the mounting manner. Therefore, it is possible to stably form a thin layer of developer suitable for development using a layer thickness regulating member having a simple structure. still,
The present invention is not limited to the above-mentioned embodiments, and it goes without saying that various modifications can be made within the technical scope of the present invention. For example, the toner carrier 7 may be a normal non-magnetic metal sleeve,
It is also possible to provide a float electrode directly on the rubber magnet.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing the layer thickness regulating section of a conventional developing device, Fig. 2 is an explanatory diagram showing the action when regulating the layer thickness of the developer, and Fig. 3 is an explanatory diagram showing an embodiment of the present invention. FIG. 4 is an explanatory diagram showing the main parts of one embodiment of the present invention. FIG. 5 is an explanatory diagram explaining the configuration of the main parts of one embodiment of the present invention. FIGS. 7 and 8 are schematic diagrams of essential parts showing modified embodiments of the embodiment of the present invention, respectively. Explanation of symbols, 3, 7: Toner carrier, 4, 8:
Magnet roller, 5, 10: Doctor blade, Δ:
Protrusion amount.

Claims (1)

[Claims for Utility Model Registration] 1. In a developing device that supplies a thin layer of developer to the surface of an image carrier, a part of the surface of the developer carrier is disposed in contact with or in close proximity to the image carrier. ,
a magnetic field generating means for forming a magnetic field on the surface of the developer carrier; one end of which is rotatably supported; and a layer thickness regulating member on which a leading edge of the other end is located, and a surface near the leading edge of the other end of the layer thickness regulating member is caused by the magnetic field generated by the magnetic field generating means to cause the surface of the layer thickness regulating member near the leading edge of the other end to 1. A developing device characterized in that the layer thickness regulating member is configured to be attracted to a surface and not deformed by the attractive force of a magnetic field. 2 Utility Model Registration Claim Paragraph 1 provides that the layer thickness regulating member is arranged such that the amount of protrusion from the point of contact with the surface of the developer carrier to the tip is always maintained within a predetermined tolerance range. A developing device characterized by: