JPS63180982A - Developing device - Google Patents

Abstract

PURPOSE:To develop an electrostatic latent image formed on the surface of a lower image formation body by partitioning a developer chamber and a developing roller chamber with a layer thickness control plate which controls the layer thickness of a developer and a reduction gate plate which contacts a developing roller elastically. CONSTITUTION:The upper developer chamber 1 and lower developing roller chamber 5 are partitioned with the layer thickness control plate 7, developing roller 6, and reduction gate plate 8. Therefore, there is no developer falling except a developer which is carried from the developer chamber 1 by being stuck on the developing roller 6, and the electrostatic latent image formed on the image carrier 13 is developed in a development area where the developing roller 6 projects from an opening A by using the developer layer carried stuck on the developing roller 6. When the image is developed, a developing bias voltage is applied to the sleeve 6a of the developing roller 6 from a bias power source so as to develop a sharp image. Consequently, the electrostatic latent image formed on the surface of the lower image formation body arranged by the arrangement above the image formation body to develop the electrostatic latent image without staining the image formation body surface.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a developing device used in an electrophotographic copying machine and the like. The present invention relates to a developing device that develops an electrostatic latent image on an image forming body into a toner image.

[Background of the invention]

The conventional developing device as described above has a developing roller chamber equipped with a developing roller, a developer chamber equipped with an agitating means for supplying developer to the developing roller, and a developer chamber in which the developer carried by the developing roller is sent to the developer chamber. They communicated with each other on the return side and were not partitioned, and the developing roller chamber was located next to or above the developer chamber. In such a developing device, since the surface of the developing roller that protrudes outward from the developing roller chamber faces sideways or upwards, the surface of the image forming body on which the electrostatic latent image is developed must face sideways or upwardly. Therefore, there is a problem in that the developing device cannot be disposed above the drum-shaped or flat-shaped image forming body. Particularly in color image forming apparatuses, three or four developing apparatuses are installed, which poses a problem in that the apparatus becomes extremely large.

[Purpose of the invention]

The present invention has been made to solve the above-mentioned problems, and is arranged above a drum-shaped or flat-shaped image forming body.
An object of the present invention is to provide a developing device capable of developing an electrostatic latent image formed on a lower surface of an image forming body.

[Structure of the invention]

In the present invention, a developing roller is provided below a developer chamber equipped with an agitating means, and a developing roller chamber having an opening at the bottom through which the developing roller projects outward is connected, and the developer chamber and the developing roller chamber are connected to each other. Developing roller and a layer thickness regulation plate that regulates the layer thickness of the developer that rides on the developing roller and the developer leaves the developer chamber, and a layer thickness regulating plate that is elastic in the same direction as the developer that rides on the developing roller and returns to the developer chamber. The developing device is characterized in that it is partitioned off by a reduction gate plate that is in contact with the developing roller, and this configuration achieves the above object.

〔Example〕

The present invention will be explained below using illustrated examples.

1 and 2 are schematic cross-sectional views showing examples of the developing device of the present invention, respectively.

In the figure, 1.1 is a developer chamber equipped with stirring rollers 2 and 3 each having stirring blades that rotate in the direction of the arrow, and a scraping roller 4 that has a sponge layer on its surface, and 5 is a developer chamber that rotates in the direction of the arrow. A sleeve 6a made of a non-magnetic material such as aluminum or stainless steel, and a magnet body 6b held stationary inside the sleeve 6a and having magnetic poles distributed on the surface as shown in the figure and exerting magnetic force on the surface of the sleeve 6a. A developing roller chamber 7 is provided with a developing roller 6 and has an opening A at the bottom through which the developing roller 6 protrudes outward.
The developer is attracted to the surface of the sleeve 6a by the magnetic force of the magnet body 6b, and as the sleeve 6a rotates in the direction of the arrow, the developer is transported from the developer chamber 1 to the developing roller chamber 5 using a non-magnetic or magnetic material. Layer thickness regulating plate made of material, 8
9 is a reduction gate plate, such as a thin polyester plate, which elastically contacts the surface of the sleeve 6a in the same direction as the developer layer carried as the sleeve 6a rotates in the direction of the arrow returns to the developer chamber 1; , a donor chamber provided with a means for replenishing the developer chamber 1 with toner.

The layer thickness regulating plate 7 shown in FIG. 1 has its tip opposed to the surface of the sleeve 6a with a narrow gap so as to allow the developer to pass through with an appropriate layer thickness when the sleeve 6a rotates in the direction of the arrow. The thickness of the developer layer is adjusted by adjusting the gap within a range where the developer does not pass through when the sleeve 6a is not rotating. The layer thickness regulating plate 7 shown in FIG. 2 is made of an elastic body that elastically contacts the surface of the sleeve 6a with its tip facing in a direction opposite to the developer transport direction so as to prevent excess developer from passing through. The thickness of the developer layer is adjusted by adjusting the contact pressure on the sleeve 6a and the distance from the contact point to the tip.

In both the developing devices shown in FIGS. 1 and 2, the upper developer chamber 1 and the lower developer roller chamber 5 are partitioned by the layer thickness regulating plate 7, the developing roller 6, and the reduction gate plate 8. Therefore, no developer other than the developer carried from the developer chamber 1 by adhering to the developing roller 6 is spilled, and the developing roller 6 protrudes from the opening A due to the developer layer carried by adhering to the developing roller 6. The electrostatic latent image formed on the image forming member 13 is developed into a toner image in the developing area.

During development, a developing bias voltage is applied to the sleeve 6a of the developing roller 6 from a bias power source to ensure clear development without fogging. The developer layer conveyed through the development area by the development roller 6 pushes up the reduction gate plate 8 and is returned to the developer chamber 1.

It is most likely that the developer will fall from the developer layer carried by the developing roller 6 regardless of the development process, when the developer passes through the layer thickness regulating plate 7 or when it pushes up and passes through the reduction gate plate 8. As shown in the figure, the edge Al+Ax of the opening A parallel to the developing roller axis is located near the developing roller 6.
It is inside the vertical plane Bl+ th that is in contact with
It is preferable that the distance between A+ and At be narrower than the outer diameter of the developing roller 6, and furthermore, the distance between the edges ^1. It is more preferable that A2 has an upwardly bent portion.
As a result, most of the developer falling from the developer layer is stopped by the lower plate of the developing roller chamber 5 having the opening A.
The developer is collected at the bent portion, and it is possible to stably prevent the surface of the image forming body 13 from being contaminated by the developer falling from the developer layer. In addition, if a DC voltage with a polarity opposite to the charging of the toner in the developer is applied to the inner wall of the developing roller chamber 5 by a DC power source as shown in the figure, the toner falling from the developer layer will be applied to the inner wall of the developing roller chamber. was captured,
It is possible to further prevent the surface of the image forming member 13 from being contaminated by falling toner.

The developer layer with reduced toner concentration returned to the developer chamber 1 is removed from the surface of the developing roller 6 by a scraping roller 4 having a sponge layer, and is removed by the developer in the developer chamber 1 and the stirring rollers 2 and 3. Mixed evenly.

The toner chamber 9 includes a pushing rotary body 10 that rotates in the direction of the arrow and has an elastic plate 10a such as a thin polyester plate at its tip, and a rotating body 10 that rotates in the direction of the arrow and has a sponge layer on its surface in FIG. The toner replenishing means is provided with a toner replenishing means constituted by a delivery roller 11 and a scraping delivery gate 12 made of an elastic plate such as a polyester plate in FIG. Replenish toner equivalent to .

In the developing device of the present invention, development is performed by forming the developer layer to a thickness that is in contact with or non-contact with the image forming body using the layer thickness regulating plate 7. During development, a DC or AC bias is applied to the sleeve 6a in a superimposed manner.

Among these development methods, a non-contact development method in which development is performed while the developer layer and the image forming body are kept in non-contact is particularly preferred. In the contact development method, the developer tends to scatter when it rubs against the image forming body, and it is more difficult to collect this against the force of gravity compared to a conventional developing device installed below the image forming body. For this reason, the contact development method tends to cause carrier adhesion and fogging. On the other hand, the non-contact development method does not have the above-mentioned problems caused by the contact development method because there is no rubbing with the image forming member, and is suitable for the development method of the developing device of the present invention provided above the image forming member.

A preferable developing method used in the developing apparatus of the present invention includes the method described in Japanese Patent Application Laid-open No. 181362/1983. That is, the average particle size is 5 to 50μ
Non-contact development uses a two-component developer consisting of a mixture of magnetic carrier particles of m and toner particles with an average particle size of 1 to 20 μm, and applies a developing bias voltage of a DC voltage and an AC voltage to the sleeve 6a. method is preferred. If the average particle diameter of the carrier particles is less than 5 μm, the magnetization becomes too weak,
If it exceeds .mu.m, the image will not be improved, and breakdown or discharge will likely occur, making it impossible to apply a high voltage. On the other hand, when the average particle size of toner particles is less than 1 μm, it becomes difficult to separate from the carrier even when vibration is applied by AC voltage, and 20 μm
If it exceeds m, the resolution of the image will decrease. The average charge amount of the toner is preferably 3 to 300 μc/g, particularly 1
0 to 100 μc/g is preferred.

Since a DC voltage to prevent fogging and an AC voltage to vibrate the developer layer are applied to the sleeve 6a to form an oscillating electric field between the image forming body and the sleeve 6a, the spacing between them becomes a problem. If this distance is made too narrow, electrical discharge will occur between the two, damaging the image forming body and preventing the developer layer from being conveyed between the two.

On the other hand, if the distance between the two is too wide, the opposing electrode effect will be reduced, sufficient development density will not be recorded, and the edge effect will also increase. According to experiments, preferable results are obtained when the distance between the two is 2000 μm or less, particularly in the range of 10 μl to 1000 μm. The DC bias voltage for preventing fogging is usually set at 50 to 500 V to keep the sleeve 6a at a higher potential than the non-image area, and at 100 to 10 kHz to vibrate the developer layer. Preferably an alternating voltage with a frequency of 1 to 5 kHz is used.

The DC voltage may be smaller than the above value if the toner has magnetism.

Naturally, when performing reversal development, a DC voltage higher than this is applied. The DC voltage in this case is for obtaining sufficient development density.

The higher the AC voltage value is, depending on the frequency, the more the developer layer is vibrated, but on the other hand, fogging and discharge are more likely to occur. As the frequency increases, the vibration of the developer layer cannot follow this change, and the developed density and sharpness tend to decrease, leading to a decrease in image quality.

As carrier particles for developer, apart from the average particle size,
The same particles as conventional magnetic carrier particles can be used. That is, metals such as iron, chromium, nickel, and cobalt, or compounds and alloys thereof, such as triiron tetroxide, γ-ferric oxide, chromium dioxide, manganese oxide,
Particles of ferromagnetic or paramagnetic substances such as ferrite, manganese-copper alloy, or the surface of these particles are coated with styrene resin, vinyl resin, ethyl resin, rosin modified resin, acrylic resin, polyamide resin, Epoxy resin,
Insulating particles coated with a resin such as polyester resin or a fatty acid wax such as balditic acid or stearic acid can be used.

However, among these, insulating magnetic particles with a resistivity of 108Ω1 or more, particularly preferably 10''Ω or more are particularly preferred.If the resistivity is low, when a bias voltage is applied to the sleeve 6a, the carrier particles will be charged. There is a problem that carrier particles tend to adhere to the surface of the image forming body after being injected,
A problem arises in that a sufficient bias voltage is not applied. The resistivity was determined by placing the particles in a container with a cross-sectional area of 0.50C11", tapping them, applying a load of 1kg/cm" on the packed particles, and applying 100OV/cn between the load and the bottom electrode. This value is obtained by reading the current value when applying a voltage that generates an electric field. Insulating carrier particles are not limited to magnetic particles with a coating layer such as resin on the surface, but may also be magnetic particles dispersed in resin. The toner particles used in the developing device of the present invention are manufactured in the same manner as the carrier particles, and the average particle size is selected by a conventionally known average particle size selection means. Toner particles that have been sorted by a sorting means are used. Preferably, the toner particles are magnetic particles containing fine magnetic particles, particularly those in which the amount of fine magnetic particles does not exceed 30-t%. When the toner particles contain magnetic particles, the toner particles are influenced by the magnetic force of the magnet 6b, which further improves uniform formation of the developer layer and prevents fogging. Furthermore, scattering of toner particles becomes less likely to occur. However, if the amount of magnetic material contained is too large, not only will color clarity be impaired in the case of color toner, but the magnetic force between it and the carrier particles will become too large, making it difficult to obtain sufficient development density. Furthermore, fine magnetic particles appear on the surface of the toner particles, making it difficult to control triboelectrification, making the toner particles more likely to be damaged, and making them more likely to aggregate with the carrier particles. or

Toner particles as described above are produced by using fine particles of resin and magnetic material as described for carrier particles, adding coloring components such as pigments, dyes, and carbon, and charge control agents as necessary. It can be produced by a method similar to a known method for producing toner particles.

The ratio of carrier particles to toner particles in the developer may be the same as that in conventional two-component developers, and if necessary, other flow agents may be added to improve the fluidity and slippage of the particles, and the surface of the image forming member may be added. Cleaning agents etc. that are useful for cleaning are mixed.

The developing device of the present invention is not limited to one that uses a two-component developer as described above (nor is it limited to one that has a toner chamber integrated with the developer chamber. It goes without saying that even if there is only one agitating means, the scraping roller may be omitted, and the developing roller is not limited to the illustrated example. They may rotate in opposite directions or in the same direction.

〔Effect of the invention〕

The developing device of the present invention has the effect of being disposed above the image forming body and can develop the electrostatic latent image formed on the surface of the image forming body below without contaminating the surface of the image forming body. By using this device, it is possible to configure a compact image forming device that forms color images by arranging multiple developing devices for a drum-shaped image forming body, and it is also possible to configure a compact image forming device that forms color images. It is also possible to construct an image forming apparatus in which the forming body is placed horizontally and the electrostatic latent image is developed from the upper surface side.

[Brief explanation of the drawing]

1 and 2 are schematic cross-sectional views showing examples of the developing device of the present invention, respectively. 1... Developer chamber, 2.3... Stirring roller,
4...Scraping roller, 5...Developing roller chamber, 6
...Developing roller, 6a...Sleeve, 6b...
... Magnet body, 7... Layer thickness regulating plate, 8...
Reduction gate plate, 9... Toner chamber, 10... Push-feed rotary body, 11... Delivery roller, 12... Delivery gate, 13... Image forming body.

Claims (5)

[Claims] (1) A developing roller chamber is provided with a developing roller at the bottom of the developer chamber equipped with an agitating means, and a developing roller chamber is provided with an opening at the bottom through which the developing roller projects outward, and the developer chamber and the developing roller chamber are connected to each other. is a layer thickness regulating plate that regulates the layer thickness of the developer that rides on the developing roller and the developer leaves the developer chamber, and an elastic plate that runs in the same direction as the developer that rides on the developing roller and returns to the developer chamber. and a reduction gate plate in contact with the developing roller. (2) The developing device according to claim 1, wherein an edge of the opening in the lower part of the developing roller chamber, which is parallel to the developing roller axis, extends inside a vertical plane that contacts the developing roller. (3) The developing device according to claim 2, wherein an edge of the opening in the lower part of the developing roller chamber parallel to the developing roller axis has an upwardly bent portion. (4) The developing device according to claim 1 or 2, wherein a voltage having a polarity opposite to that of the toner charge of the developer is applied to the inner wall of the developing roller chamber. (5) The developing device according to claim 1, further comprising a toner chamber provided with a means for replenishing toner to the developer chamber along with the developer chamber.