JPH049987A - Developing device for electrophotographing recording device - Google Patents

Abstract

PURPOSE:To make it possible to form a thin and uniform toner layer by a simple constitution even when a gap between a sleeve nd a blade is wide by forming a gap part on a fixed magnetic field generating means in a developing sleeve and preventing magnetic pole plates constituting a doctor blade from being affected by magnetic flux. CONSTITUTION:Magnetic toner 1a is stored in the container 2 of a toner feeding means 1 and supplied to a photosensitive drum 6 through the rotational developing sleeve 3 including the fixed magnetic field generating means 4. The layer thickness or the like of the toner layer is controlled by a doctor blade means 5 formed by the magnetic pole plates 5a, 5b or the like opposed to the sleeve 3. The gap 4a is formed in the area of the means 4 opposed to the means 5, and since magnetic flux from the means 4 does not exert influence upon the magnetic pole plates 5a, 5b due to the gap 4a, the toner layer on the sleeve can be thinly and uniformly formed by the simple constitution even when the gap between the sleeve and the blade is comparatively wide.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a developing device used in an electrophotographic recording apparatus.

[Prior Art] In the prior art, inside a moving toner support means,
A fixed magnetic field generating means is disposed, a magnetic member for regulating the layer thickness of the magnetic toner is disposed outside the toner supporting means, that is, on the opposite side of the magnetic field generating means, and the toner supporting means is controlled by the fixed magnetic field generating means and the magnetic member. There are 9 examples (I Japanese Patent Publication No. Sho 59 8831) in which a static magnetic field is created by sandwiching the magnetic toner. form a layer.

Further, a developing magnetic pole corresponding to the above-mentioned fixed magnetic field generating means,
A member corresponding to the toner supporting means, a means for replenishing the peripheral surface of this member with toner, a doctor blade for controlling the amount of replenished toner, and a pair made of a magnetic material between the doctor blade and the developing section. A magnetic pole plate is provided, and a curtain of magnetic lines of force is formed between the developing magnetic pole and the counter magnetic pole plate 1
For example, there is Special Publication No. 61-48157.

[Problem to be Solved] In the first conventional technique described above, the stationary magnetic field constituted by the fixed magnetic field generating means and the magnetic member is strong, and the magnetic toner can easily reach the stationary magnetic field by moving the toner supporting means. However, only a small amount of magnetic toner is pulled out from the stationary magnetic field because the force of trying to stop it in the static magnetic field is strong. Therefore, although it is effective in forming a thin layer of magnetic toner, the amount of magnetic toner that remains in the static magnetic field increases, resulting in toner aggregation. If the magnetic toner is drawn out in this state, there is a problem in that the density of the drawn magnetic toner becomes unstable, causing unevenness in printed characters.

In addition, in the second prior art described above, since the gap between the doctor blade and the sleeve is small, if foreign matter such as dust contained in the toner gets into this gap and clogging occurs, this gap will be damaged. Since toner replenishment is blocked, there are areas on the sleeve where there is no toner, and if development is carried out under such conditions, a phenomenon occurs in which white lines appear on the image in those areas.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to make it possible to form a very thin and uniform toner layer even if the gap between the sleeve and the doctor blade is relatively wide, and to provide this with a simple structure. be.

[Means for Solving the Problems] In order to achieve the above object, the developing device of the electrophotographic recording device of the present invention has a non-magnetic cylinder that supports magnetic toner on its surface and is rotated to convey the toner. a developing sleeve, a toner supplying means for supplying magnetic toner onto the developing sleeve, and a fixed magnetic field generating means disposed within the developing sleeve;
It consists of a doctor blade means disposed opposite to the surface of the developing sleeve to regulate the layer thickness of the magnetic toner. This doctor blade means is constituted by a silk magnetic pole plate whose tips are magnetized with different polarities at predetermined intervals, and the magnetic flux from the fixed magnetic field generating means is substantially absorbed by the fixed magnetic field generating means. A gap is formed in a region facing the magnetic pole plate so as not to act on the magnetic pole plate.

[Since the region of the fixed magnetic field generating means facing the working magnetic pole plates is made into an air gap, the magnetic flux from the fixed magnetic field generating means does not act on the set of magnetic pole plates. By configuring the doctor radar means with a pair of magnetic pole plates whose tips are magnetized with different polarities at a predetermined interval, a magnetic field is formed by the leakage magnetic flux of the pair of magnetic poles, and this magnetic field causes the toner to be magnetically to shield. Then, only the toner that is near the surface of the sleeve and is frictionally charged with the sleeve forms a thin layer on the sleeve and is transported.

[Example] An embodiment of the present invention will be described based on the drawings.

As shown in FIG.
A is housed in a container 2, and a non-magnetic cylindrical developing sleeve 3 is rotatably provided in the container, and a part of the outer peripheral surface of this sleeve is exposed. The magnetic toner 1a is supported on the surface of the cylindrical developing sleeve 3, and is carried out from the outlet 2a of the container 2 by its rotation.

A fixed magnetic field generating means 4 is built in the cylindrical developing sleeve 3. The fixed magnetic field generating means 4 is a magnet in which a gap 4a extending in the axial direction is formed in a portion of a cylindrical outer peripheral surface facing magnetic pole plates 5a and 5b, which will be described later.
On the circumferential surface of , a large number of magnetic poles are alternately magnetized in N and S directions. No magnetic pole exists in the gap 4a.

A doctor blade means 5 is disposed at the outlet 2a of the container, facing the surface of the developing sleeve 3 and at a constant interval. The doctor blade means 5 carries the magnetic toner 1
A pair of magnetic pole plates 5a and 5b are opposed to each other at a predetermined interval, and a permanent magnet 5c is interposed in the gap between the bases of both magnetic pole plates.
The tip of 5b is magnetized with different polarities. A spacer 5d made of a non-magnetic material is provided in the gap between the tips of both magnetic pole plates.
is interposed.

The above-mentioned air gap 4a of the fixed magnetic field generating means 4 is formed in a region facing the tips of the two magnetic pole plates 5a and 5b, so that the magnetic flux from the fixed magnetic field generating means 4 is directed between the two magnetic pole plates 5a and 5b. It is designed so that it does not act on 5a and 5b.

Magnetic toner 1a or developing sleeve 3 whose layer thickness is regulated to be thin
A photoreceptor tram 6 is disposed facing the developing sleeve 3 while being conveyed with a predetermined gap therebetween.

Next, the operation of conveying the magnetic toner 1a to a position facing the photoreceptor tram 6 will be explained.

First, the magnetic toner 1a in the container 2 is transferred to the fixed magnetic field generating means 4.
The particles stand up along the magnetic field, adhere to the surface of the cylindrical developing sleeve 3 as it is rotated, and are transported to the vicinity of the doctor blade means 5. In the vicinity of the doctor blade means 5, there is no fixed magnetic field generating means 4 in the opposing position and there is an air gap 4a, so as shown in FIG. A magnetic field is formed, and the container 2 is in a magnetically shielded state. The magnetic toner 1a that has been conveyed to this position is now separated from the influence of the magnetic field produced by the fixed magnetic field generating means 4 and aligned along the magnetic field produced by the magnetic pole plates 5a and 5b. Since the cylindrical developing sleeve 3 continues to rotate, friction occurs between the surface of the sleeve and the magnetic toner 1a, causing the magnetic toner 1 in contact with the developing sleeve 3 to
a is triboelectrically charged and adheres to the surface of the sleeve in a thin layer thickness. Therefore, only the attached magnetic toner 1a passes through the shield portion as the developing sleeve 3 rotates, and reaches a developing position facing the photoreceptor tram 6.

The magnetic toner 1a that adheres to the surface of the cylindrical developing sleeve 30 in this manner is limited to that which has been triboelectrically charged due to friction with the sleeve, so that a thin and uniform layer thickness is formed. Furthermore, when increasing the distance between the doctor blade means 5 and the developing sleeve 3, the magnetic toner 1
It is possible to form a thin layer thickness of a.

Note that the spacer 5 is made of a paramagnetic metal such as a brass plate, plastic such as Mylar film, ceramic, glass, or the like.

Also, the magnetic toner 1a is generated by the magnetic field generated by the magnetic pole plates 5a and 5b.
If the chain breaks, the torque plate means 5.
In order to prevent electric discharge from occurring between the cylindrical developing sleeves 3, a doctor blade means 5. The cylindrical developing sleeve 3 is kept at the same potential.

In addition, the means for magnetizing a set of magnetic pole plates to different polarities is a permanent magnet 5.
It does not have to depend on C. That is, as shown in FIG. 3, a pair of opposing portions 15a and 15b are formed by one ferromagnetic material 15 (doctor blade means), and a coil 6 is wound around the ferromagnetic material 15. A drive circuit 7 is connected to the coil 6, and a voltage can be applied to this.

A gap spacer 15d, which is not made of ferromagnetic material, is provided between the opposing parts 15a and 15b.

By energizing the coil 6 by the drive circuit 7, a magnetic path is formed within the ferromagnetic body 15, the opposing portions 15a and 15b are magnetized with different polarities, and a magnetic field due to leakage magnetic flux can be formed during this time.

[Effects] As described above, the present invention uses a doctor blade to form a magnetic field due to leakage magnetic flux, and the friction between the magnetic toner and the cylindrical developing sleeve causes the magnetic toner to be triboelectrically charged and adhered to the sleeve. A thin and uniform layer of magnetic toner can be formed.

Furthermore, even if the gap between the doctor blade means and the sleeve surface is relatively wide, a very thin and uniform layer of magnetic toner can be formed. Stable, high-quality printing is always possible without clogging. Moreover, since the structure is simple, it can be provided at low cost.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention; FIG. 1 is a sectional view of the main part, FIG. 2 is a partially enlarged sectional view explaining the principle, and FIG. 3 is a sectional view of the main part showing another embodiment. be. 1. Toner supply means, 1a. Magnetic toner 3. Cylindrical developing sleeve, 4. Fixed magnetic field generation means, 4a. Gap, 5.15-φ.Doctor blade means, 5a, 5b.
15a, 1.5b...-Magnetic pole plate. Above Figure 5. One car and one door with two tarps and one door.

Claims (1)

[Scope of Claims] A non-magnetic cylindrical developing sleeve that supports magnetic toner on its surface and is rotationally driven to convey the magnetic toner, toner supply means that supplies the magnetic toner onto the developing sleeve, and the developing sleeve. a fixed magnetic field generating means disposed within the sleeve;
A doctor blade means is arranged to face the surface of the developing sleeve and regulates the layer thickness of the magnetic toner. The fixed magnetic field generating means is configured with a set of magnetic pole plates, and the fixed magnetic field generating means is configured such that magnetic flux from the fixed magnetic field generating means does not substantially act on the magnetic pole plates.
A developing unit for an electrophotographic recording apparatus, characterized in that a gap is formed in a region facing the magnetic pole plate.