JPH0535430B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a thin film processing technology for one-component magnetic developer, and more particularly, to a method applicable to a developing device in a plain paper image forming apparatus such as a facsimile machine, an electrophotographic copying machine, and a printer. It relates to various improved techniques.

PRIOR ART A developing method using a one-component developer is advantageous in terms of compactness of the device and ease of maintenance, but there are various problems in putting it into practical use. For example, in order to sufficiently and uniformly impart a charge necessary for development to a one-component developer, it is first required to uniformly thin the one-component developer. For this purpose,
Although it is desirable that the particle size of the developer particles be small, it also tends to cause background stains and ghost images. Further, the particle size of the developer particles is also limited by the required image resolution. Therefore, various factors involved in forming a thin layer, such as a developing roller that carries the developer and transports it along a predetermined path, a doctor blade that regulates the thickness of the thin developer layer, and a developing roller that transfers the used developer It is necessary to have an optimal structure for the scraper etc. that removes the material.

Purpose The present invention has been made in view of the above points, and it is possible to easily form a thin layer of a monocomponent developer with uniform layer thickness and surface potential, and to stably obtain high image quality. The purpose of the present invention is to provide various improvements regarding a developing device.

Configuration Hereinafter, the configuration of the present invention will be described in detail based on specific examples. FIG. 1 is a schematic diagram showing a developing device as an embodiment of the present invention. 1st
In the figure, an endless dielectric belt 1 serving as a latent image carrier is rotatably stretched between an appropriate number of rollers 1a. In this example, the dielectric belt 1
A negative latent image is formed thereon according to input information using a multi-stylus (not shown) or the like.

In order to develop the formed latent image, a developing roller 2 as a developer conveying member is rotatably disposed so as to be able to roll into contact with a part of the dielectric belt 1. rotated in a clockwise direction. The developing roller 2 is formed into a cylindrical shape in this example, and a carbon-containing conductive silicone rubber 2a having a specific resistance value of 10 ⁵ Ω·cm or less is adhered to the circumferential surface of the developing roller 2 . In this case, the surface roughness of the silicone rubber 2a greatly affects the thickness of the thin layer of developer formed and the uniformity of the surface potential, causing background stains and the generation of ghost images, but this point will be discussed later. Explain in detail. The material for the surface layer of the roller 2 mentioned above is the carbon-containing conductive material used in this example in terms of toner thinning, chargeability, transportability, wear resistance, etc. Silicone rubber is preferred, but other materials such as neoprene rubber, nitrile rubber, or EPDM can also be used.

Inside the developing roller 2, six magnets 3a to 3f are arranged substantially evenly along the inner peripheral surface of the roller 2 in this example. In this case, the surface magnetic flux density of each magnet 3 is set to approximately 1000 Gauss for only the magnet 3c, and approximately 800 Gauss for all the other five magnets. The polarities of the respective magnets are arranged such that the polarities of the ends of the adjacent magnets 3 facing the inner circumferential surface of the roller 2 are different.

Near the circumferential surface of the developing roller 2 configured as described above, on the substantially opposite side of the developing position D where it rolls into contact with the dielectric belt 1, there is a freely rotatable replenishment roller 4 for replenishing the developing roller 2 with unused fresh toner. It is located in In this example, the replenishment roller 4 is formed into a cylindrical shape, and inside thereof, four magnets 5a to 5d are arranged substantially evenly along the inner circumferential surface of the roller 4, similar to the magnets 3 on the developing roller 2. ing. in this case,
The delivery of toner from the replenishing roller 4 to the developing roller 2 is mainly due to the magnetic force of the magnets 3b and 5d, which face each other with different polarities at the adjacent portion T while both rollers move in approximately the same direction. ,
In order to make this transfer operation proceed efficiently and smoothly, the distance C between both rollers 4 and 2, and the magnet 3
It is required to optimally set the arrangement of magnets b and 5d and the spread of the magnetic field from the magnet 5 on the replenishment roller 2 side in the circumferential direction of the replenishment roller 4. First, the roller interval C is preferably about 2 to 6 mm, and in this example,
It is set to 4.3mm. Furthermore, the arrangement of the magnet 5d with respect to the magnet 3b is such that the center line _D of the magnet 5d is at a rotation angle _α (preferably It should be set so that it is located within 15°).
However, in this case, the magnet 3b is positioned such that the rotation angle θ between its center line _B and the reference line _O is 15°. Furthermore, the magnetic properties of the magnet 5d are greatly involved in the transfer effect, which will be explained in detail later.

Returning to FIG. 1, a hopper 6 for storing fresh toner for replenishment is formed near the circumferential surface of the replenishment roller 4 configured as described above, on the substantially opposite side of the toner transfer position T close to the developing roller 2. has been done. The hopper 6 includes a supply port 6a for supplying fresh one-component magnetic toner, and a supply port 6b that opens near the circumferential surface of the supply roller 4. An agitator 7 for agitating the toner is rotatably disposed inside the supply port 6b in a portion thereof close to the supply port 6b. or,
Hopper supply port 6 in the rotational direction of the supply roller 4
On the downstream side of b, a toner regulating member 8 is disposed such that its tip is separated from the surface of the replenishing roller 4 by a gap D for regulating the amount of toner conveyed.
The preferred dimension of this gap D is about 0.3±0.2 mm, and the so-called spike cutting process is performed here to cut the chain state of the fresh toner supplied from the supply port 6b onto the circumferential surface of the supply roller 4. As a result, a toner layer having a substantially uniform thickness is formed on the surface of the replenishment roller 4.

On the other hand, on the downstream side in the rotational direction of the developing roller 2 from the transfer position T, there are fresh toner transferred from the replenishment roller 4, carried on the surface of the developing roller 2, and conveyed along with its rotation, and toner that is once subjected to development. A doctor plate 9 is provided that regulates the layer thickness of the collected toner to form a thin toner layer suitable for development. In this case, the toner is, as mentioned above,
The toner is transferred from the supply roller 4 to the developing roller 2 by flying. As shown in FIGS. 3a and 3b, the doctor blade 9 has a tip 9a formed into an elongated shape with a notch 9c formed therein, and connects it to the surface of the silicone rubber layer 2a of the developing roller 2 via a compression spring 10 or the like. It is supported in uniform elastic contact over almost the entire width direction, and the toner being conveyed between these is mechanically clamped and pressed to regulate the layer thickness, and the frictional action at this time imparts the necessary charge to the toner. Charge. In this case, in order to obtain an appropriate layer thickness regulation effect, in this example, the end surface 9d of the tip portion 9a and the tip edge 9e are
The edge angle β between the contact point with the surface and the tangent line 9f is set to a suitable value of about 15°. Further, a notch 9c is formed on the downstream side of the elongated tip 9a, so that a large amount of toner is sandwiched between the doctor blade 9 and the roller 2, and the blade 9 is separated from the surface of the roller 2 against the force of the spring 10. is prevented. In order to more reliably prevent the blade 2 from floating up, the ceiling portion 9g of the cutout portion 9c may be inclined. In order to obtain a long-term stable and appropriate layer thickness regulating effect using the blade 9 formed as described above, the hardness of the blade tip 9a, the method of supporting the blade 9, and the arrangement position of the blade 9 are required. These points will be explained in detail later.

As shown in FIG. 1, a scraper 11 is disposed with its tip in contact with the surface of the developing roller 2 in a region facing the magnet 3c on the downstream side of the developing position D near the circumferential surface of the developing roller 2. The toner remaining on the surface of the developing roller 2 without being subjected to development is scraped off. The scraper 11 is formed of a magnetic material into a thin plate shape, and the supporting end is rotatably supported by a shaft 11a in a downstream region in the toner transport direction from the contact position of the tip. As a result, the leading end can be pressed with an appropriate force by the magnetic force of the magnet 3c, and a uniform pressed state can be stably maintained by flexibly responding to changes in the circumferential surface of the developing roller 2. The scraper 11 of this example is formed in a rectangular shape as shown in FIG.
A large number of windows 11c are located in the vicinity of b in the longitudinal direction L.
They are arranged in parallel along the developing roller 2, and the tip end surface 11b is brought into contact with substantially the entire circumferential surface of the developing roller 2 in the width direction to scrape off the remaining toner. A protrusion 11d is formed in each window 11c to prevent the passage of foreign substances. The scraping effect of the scraper 11 particularly affects the generation of ghost images among the resulting image quality.
Therefore, similarly to the doctor blade 9, it is required to optimally set its supporting method and placement position, which will be explained in detail later.

In FIG. 1, a scraper roller 12 is rotatably disposed near the upstream side of the scraper 11 where the scraped toner remains, and the scraper roller 12 is rotatably disposed to remove the toner scraped from the surface of the developing roller 2 through a window 11c. Transfer to the downstream side.

Here, the surface roughness of the developing roller 2 will be explained. Background stains and ghost images tend to be less likely to occur as the particle size of toner particles becomes larger.
However, as described above, the particle size is limited by considerations such as image resolution. Therefore, in this example, the prerequisite is to form a thin layer with a layer thickness of 20 to 30 μm using a one-component magnetic toner having an average particle diameter of about 12 μm, which is optimal considering various conditions. When the surface of the silicone rubber 2a adhered to the circumferential surface of the roller 2 is relatively rough, it is schematically shown in an exaggerated and enlarged manner as shown in FIG. It is presumed that the toner particles T _P are trapped in such recesses 2 _R on the surface, and as they are repeatedly subjected to triboelectric charging, the toner potential increases, causing background stains and the like. The relationships between the roller surface roughness and changes in image quality due to background stains and the occurrence of ghost images, which the inventors of the present application have determined through experiments, are shown in FIGS. 6 and 7, respectively. Here, "Surface roughness
4S'' in Fig. 5, an exceptionally high convex portion 1 _A that appears only once within a predetermined range Z, for example, 1 mm.

Claims (1)

[Claims] 1. A carrier made of a non-magnetic material that carries magnetic particles on the surface of a rubber layer, a magnetic pole disposed on the back side of the carrier, and a tip on the surface of the carrier. a layer thickness regulating member that regulates the layer thickness of the magnetic particles that are brought into pressure contact and conveyed;
A magnetic particle layer thickness control device, characterized in that the magnetic particle layer thickness control device is pressed into a unit region located at the most upstream side with respect to the transport direction of the magnetic particles among the equally divided unit regions. 2. In claim 1, the magnetic particle carrier is formed in a cylindrical shape and rotatably supported, and the magnetic flux density of the magnetic pole is about 800 Gauss,
The layer thickness regulating member is supported such that the center of rotation of the conveying body is on an extension of the side surface on the upstream side with respect to the conveying direction of the magnetic particles, and the center of rotation of the conveying body is located between the center of the magnetic pole and the rotation of the conveying body. A magnetic particle layer thickness control device characterized in that an angle formed between a straight line connecting the centers and the extension line is 5° to 10°.