JPH0934258A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device capable of coating toner on a developing sleeve in a good manner and uniformly and stably forming images. SOLUTION: A developer control member 2 composed of round bars as magnetic bodies place as specified intervals W is arranged in a developing sleeve 1a having a permanent magnet 1a fixed inside and developer carrying means 3a and 3b are provided in a developer canister 4. The carrying means 3a is arranged in a position in a magnetic field formed between the permanent magnet 1a and the round bar 2 by a equal distance from these where the density of magnetic toner is nearly constant and the density of a magnetic line is rough.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a printer or a copying machine, or an electrostatic recording apparatus, and is characterized by a developing device.

[0002]

2. Description of the Related Art A number of developing methods have been proposed as a developing method used in an electrophotographic image forming apparatus, such as a magnetic brush developing method described in US Pat. No. 2,870,063.

For example, as a developing method using a developer containing a magnetic toner, a developing method known as a so-called "jumping developing method" described in JP-A-54-43036 has been proposed and put into practical use. This is because the magnetic toner is applied very thinly on the developing sleeve, and after triboelectrifying it, it is brought very close to the electrostatic latent image under the action of a magnetic field.
In addition, the development is performed by making them face each other without contacting each other. That is, by adopting a structure in which the toner is applied extremely thinly, the chance of contact between the toner and the developing sleeve is increased,
The purpose is to provide the toner with a triboelectric charge amount required for development.

As a conventional example using the above-mentioned developing system, a developing device using a magnetic one-component toner is shown in FIG. This developing device is arranged so as to face the photosensitive drum 15, and is a developing sleeve 1 that is a developer carrying member that carries a magnetic toner on its surface, a blade 2 that is a magnetic member that is a developer regulating member that regulates the toner layer thickness, and a toner. Stirring and developing sleeve 1
The developer container 4 is provided with the conveying members 3a and 3b for supplying toner to the inside.

The developing sleeve 1 comprises a permanent magnet 1a fixed therein and a cylinder 1b made of a non-magnetic member and rotatably arranged in the direction of the arrow shown in FIG. The blade 2 is arranged so that the gap between the blade 2 and the developing sleeve 1 is constant, and the distance W is
Generally, it is often set to a value within the range of 100 μm to 1 mm.

The charge application in the developing system will be briefly described with reference to the conventional example shown in FIG. The magnetic field P formed by the magnetic pole P of the permanent magnet 1a and the blade 2 made of a magnetic member and arranged in the vicinity of the permanent magnet 1a in cooperation with each other is shown in FIG. 10 in the vicinity of the developing sleeve 1 and the blade 2. As a result, a region G where the magnetic flux density is concentrated is formed.

FIG. 11 shows an enlarged view of the area G. The magnetic toner T is supplied from the developer container 4 onto the developing sleeve 1 by the conveying members 3a and 3b. The toner T on the developing sleeve 1 is magnetized by the magnetic field created by the permanent magnet 1 a inside the developing sleeve 1, and is conveyed by forming a brush (state B) by the magnetic interaction between the adjacent toners, and in the area G. Be magnetically restrained. That is, the area G is a toner constrained area. It is known that a charge is applied to the restrained toner T by frictional charging with the rotating developing sleeve 1.

[0008] The magnetic toner T charged by the above-mentioned frictional charging is charged in the developing sleeve 1 by the charge obtained by itself.
Receives the mirroring power from. This toner is applied to the developing sleeve 1
With the rotation of, the carrying force in the same direction as the rotating direction of the developing sleeve 1 is received. Where the carrying force acting on the charged magnetic toner T overcomes the magnetic restraining force in the restraining region G, that is, at the cut line L, the spikes of the toner are torn off and the toner remaining on the developing sleeve 1 is The toner is applied by being conveyed in the rotating direction of the developing sleeve 1.

However, in the above-mentioned conventional example, in order to meet the recent demand for high-quality image formation, in order to reduce the particle diameter of the toner, the magnetization per toner is reduced, so The magnetic restraining force acting may be weakened. As a result, the insufficiently charged toner may escape the restraint in the area G and leak onto the developing sleeve 1. Further, if the insufficiently charged toner pool C generated in the vicinity of the blade 2 becomes large, the magnetic restraining force to the region G weakens, and a part of the toner pool C undercharged toner leaks onto the developing sleeve 1. There were times when it happened.

As described above, in the above-described conventional example, the insufficiently charged toner leaks onto the developing sleeve which is the developer carrying member, which may interfere with good image formation. .

Therefore, in order to solve the above problems, the inventors of the present invention return the insufficiently charged magnetic toner to the developer container by the developer regulating member and stably carry the sufficiently charged magnetic toner in the developer. We created a developing device for applying onto the body.

That is, as shown in FIG. 12, the developer regulating member 2 made of a magnetic member is rotatably provided near the developing sleeve 1. This will be described in detail below.

This developing device has a permanent magnet 1a fixedly arranged therein, a developing sleeve 1 for carrying a magnetic toner on the surface thereof, a developer regulating member 2 comprising a magnetic member for regulating the toner application amount, and a developer regulating member. A scraper 5 arranged in contact with the member, a stirring member for the toner, and conveying members 3a, 3b for supplying the toner to the developing sleeve 1 are provided inside.
It is composed of a developer container 4.

The developer regulating member 2 made of a magnetic member is disposed in the vicinity of the magnetic pole P of the permanent magnet 1a in the developing sleeve 1 with a gap of a certain distance W between them so as to face each other, thereby developing In the vicinity of the vicinity of the sleeve 1 and the developer regulating member 2, a toner constrained area G where the magnetic flux density is concentrated is formed. Further, the developer regulating member 2 rotates in the same direction as the rotation direction of the developing sleeve 1, as shown in FIG.

The magnetic toner in the developer container 4 is conveyed by the conveying members 3a, 3b which rotate in the direction of the arrow shown in FIG.
Is supplied to the developing sleeve 1. Developing sleeve 1
In the magnetic toner supplied upward, the area G is reached,
In the magnetically restrained state, an electric charge is applied by frictional charging with the rotating developing sleeve 1. The magnetic toner T, which is charged by the above frictional charging, receives a mirroring force from the developing sleeve 1 by the charge obtained by itself.
This serves as a conveying force for the toner, and the toner is conveyed as the developing sleeve 1 rotates.

By the way, the developer regulating member 2 made of a magnetic member is magnetized by receiving a magnetic field from the magnetic pole P by being arranged in the vicinity of the magnetic pole P. Therefore, the toner restraint area G
The magnetic toner inside receives the magnetic force from the developer regulating member 2,
Along with the rotation, it receives a conveying force in the direction of returning it into the developer container.

On the other hand, in the toner restraint area G,
As described above, the magnetic toner that has been given an electric charge by frictional charging with the developing sleeve receives a mirroring force from the developing sleeve 1 due to its own charge, and the developing sleeve 1 rotates as the developing sleeve 1 rotates. It receives the conveying force in the rotating direction.

Therefore, only the sufficiently charged magnetic toner overcomes the carrying force in the direction of returning from the developer regulating member 2 into the developer container, is applied onto the developing sleeve 1, is carried to the developing area, and is charged. Insufficient magnetic toner
It is returned to the developer container 4.

As described above, the developing device for stably applying the sufficiently charged magnetic toner onto the developer carrying member is provided.

[0020]

However, it has a developer container containing a developer containing magnetic toner and a magnetic field generating means arranged stationary inside, and is rotatably arranged to carry the developer on its surface. And a developer carrying member for supplying the developer from the developer container to the developer carrying member, and a developer restricting member having magnetism and having a gap with the developer carrying member and being rotatably arranged. A developing device having a configuration in which the developer is regulated by a magnetic field formed by the magnetic field generation means and the developer regulating member in cooperation with each other, and receives a conveying force from each of the developer regulating member and the developer carrier. At
Depending on the position of the transport member that supplies the developer to the developer carrier, the amount of developer applied on the developer carrier may become uneven, or the toner may leak insufficiently, resulting in uniform and stable In some cases, it may be difficult to form an image.

One of the causes is that the conveying member changes the arrangement position and the toner restraining state in the toner restraining region G due to the driving thereof.

According to the study by the present inventors, the result has been obtained that the toner density in the toner constrained area G may change depending on the position of the conveying member and its driving.

For example, when the toner density in the constrained area G decreases, the pressure of the toner pressed against the developing sleeve decreases, and the triboelectric charging of the toner becomes insufficient. Therefore, in the developing device having the above-described configuration, when the insufficiently charged toner is returned to the developer container, the amount of toner applied on the developing sleeve is significantly reduced, or the amount of the toner to be returned to the developer container is reduced. It may not catch up with the toner, resulting in leakage of insufficiently charged toner.

On the contrary, when the toner density in the constrained area G increases, the rotational torque of the developing sleeve 1 increases, driving unevenness of the developing sleeve occurs, and excessively charged toner forms agglomerates on the developing sleeve. I got the knowledge that.

Therefore, an object of the present invention is to provide an image forming apparatus equipped with a developing device capable of applying a good developer onto a developer carrying member and capable of forming a uniform and stable image.

[0026]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
A developer container containing a developer containing a magnetic toner, a magnetic field generating means statically arranged inside, and a developer carrier rotatably arranged to carry the developer on its surface,
A developer is provided which includes a conveying member that supplies the developer from the developer container to the developer carrying member, and a developer restricting member that has a magnetism and is rotatably arranged with a gap from the developer carrying member. Is regulated by a magnetic field formed by the magnetic field generating means and the developer regulating member in cooperation with each other, and receives a conveying force from each of the developer regulating member and the developer carrying member. In the image forming apparatus including the apparatus, the conveying member is arranged in a place where the developer density is uniform in the developer container.

The closest distance L1 between the conveying member and the developer regulating member and the closest distance L2 between the developer carrying member and the developer carrying member.
Then, it is preferable that L1 ≧ L2 is satisfied. Further, it is preferable that the transport member is made of a non-magnetic material.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image forming apparatus according to the present invention will be described below in more detail with reference to the drawings. The present invention is described as being embodied in, for example, an electrophotographic image forming apparatus as shown in FIG. 8, but is not limited to this. The same members as those described above are denoted by the same reference numerals.

In FIG. 8, the electrophotographic image forming apparatus is
A photosensitive drum 15 as an electrostatic latent image carrier is rotatably provided, and the photosensitive drum 15 is uniformly charged by a charger 12.
Then, with a light emitting element 13 such as a laser,
The information signal is exposed to form an electrostatic latent image, which is visualized by the developing device 10. Next, it is transferred to the transfer material 16 by the transfer charger 14 and further fixed by the fixing device 17. Further, the transfer residual toner on the photosensitive drum 15 is removed by the cleaning device 11.

First Embodiment As shown in FIG. 1, the developing device 10 according to the present embodiment rotates in the direction of the arrow in the drawing and has a permanent magnet 1a as a magnetic field generating means therein, and an electrostatic latent image. And a developing sleeve 1 which is a developer carrying body for supplying magnetic toner to the developing sleeve 1, and a magnetic body which is a developer regulating member which is rotatably arranged in the same direction as the developing sleeve 1 with a certain distance from the developing sleeve 1. It is composed of a round bar 2, a scraper 5 arranged in contact with the round bar, agitating developer, and conveying members 3a and 3b for supplying toner to the developing sleeve 1, and a developer container 4.

The developing sleeve 1 used in this embodiment is φ
A cylinder 1b made of a non-magnetic material having an outer diameter of 20 and a permanent magnet 1a having four poles inside the cylinder 1b.
Was a magnetic member having a diameter of φ10. The round bar 2 is arranged in the vicinity of the magnetic pole S1 of the permanent magnet fixed in the developing sleeve 1 with a certain distance W from the developing sleeve 1, so that the magnetic force lines from the magnetic pole S1 to the round bar 2 are concentrated. , The toner constrained area G is formed. The magnetic pole S1 has a magnetic flux density of 1000 gauss and a half value width of 30 °.

FIG. 2 shows a state of magnetic force lines of a magnetic field formed by the permanent magnet 1a and the round bar 2 in cooperation with each other in the developing device of this embodiment. 2 shows the magnetic field analysis software "MAX".
WELL "(Ansoft Corporation: Ansof
t corporation make).

In this embodiment, the conveying members 3a, 3b
As shown in FIG. 1, the conveying member 3a is arranged adjacent to the developing sleeve 1 and the conveying member 3b is arranged on the inner side of the developer container 4 (these are referred to as arrangement A). From the analysis diagram of the magnetic field shown in FIG. 2, this is because the density of magnetic field lines is coarse and the magnetic field lines are roughly evenly spaced so that the density of the magnetic toner becomes substantially uniform, and the magnetic flux on the trajectory of the rotation of the transport member 3a. The conveyance member 3a is arranged by selecting a region in which the change rate of the density in the rotation direction is within 20%.

Further, as shown in FIG. 3, the conveying member 3a
From the disposition position (broken line) shown in FIG. 1 to the developing sleeve 1 so that the density of magnetic force lines is high and the intervals are narrowed, and the rate of change of the magnetic flux density in the rotation direction on the trajectory of rotation of the conveying member 3a is increased. In the arrangement B in which the conveying member is arranged at a position over the area exceeding 20% and the conveying member 3a is arranged at the position of the distribution of magnetic field lines similar to the arrangement A, as shown by the dashed line in FIG. Arrangement C, which is located higher than Arrangement A so as to be closer to round bar 2 than 1, was also examined. The results are shown in Table 1 below.

[0035]

[Table 1]

As shown in Table 1, good toner application was performed in the arrangement A and the arrangement C, and in the arrangement B, the toner was applied onto the developing sleeve 1 at every rotation cycle of the conveying member 3a. The toner application amount fluctuated, and stable application could not be performed.

In the arrangement B, since the conveying member 3a is arranged at a position where the density of magnetic lines of force becomes dense from the rotation axis of the conveying member 3a to the developing sleeve 1, the developing sleeve 1 is moved to the developing sleeve 1 due to its rotation. It is considered that this is because the amount of toner supplied increases remarkably and the toner density in the constrained region G varies.

Further, the arrangement A provides better coating than the arrangement C is that the conveying member 3a in the arrangement C is
Since it is arranged close to the round bar 2, it interferes with the flow of the insufficiently charged toner that is returned to the developer container 4 due to the conveying force from the round bar 2, and affects the toner density in the constrained area G. It is thought to be for giving.

As described above, by disposing the transport member at a location where the developer density is uniform in the developer container, it becomes possible to satisfactorily apply the magnetic toner onto the developer carrying member. It was In the developing device,
It is desirable to dispose the transport member closer to the developer carrying member than the developer regulating member.

Second Embodiment Next, a second embodiment of the developing device according to the present invention will be described with reference to FIGS.
This will be described with reference to FIG.

As shown in FIG. 5, the developing device according to the present embodiment rotates in the direction of the arrow in the drawing, has a permanent magnet 1a therein, and supplies a magnetic toner to the electrostatic latent image. A developing sleeve 1 as a carrier, and a permanent magnet 2 inside thereof.
a regulating sleeve 2 which is a developer regulating member and which is disposed rotatably in the same direction as the developing sleeve 1 with a constant distance W from the developing sleeve 1, and a scraper 5 disposed in contact with the regulating sleeve 2. The developer container 4 is composed of conveying members 3a and 3b for stirring the developer and supplying the toner to the developing sleeve 1.

The developing sleeve 1 used in this embodiment is
a cylinder 1b made of a non-magnetic material having an outer diameter of φ20,
The regulating sleeve 2 was composed of a permanent magnet 1a having four poles inside, and the regulating sleeve 2 was composed of a cylinder 2b made of a nonmagnetic material having an outer diameter of φ20 and a permanent magnet 2a having two poles inside. Further, the magnetic pole S1 of the permanent magnet 1a fixed inside the developing sleeve 1 and the magnetic pole N of the permanent magnet 2a fixed inside the regulating sleeve 2 as a magnetic field generating means.
Due to the magnetic field formed by the cooperation of 1 with each other, the constrained region G is formed in the entire vicinity of the developing sleeve 1 and the regulating sleeve 2. The magnetic pole S1 has a magnetic flux density of 1000 gauss,
The half width is 60 °, the magnetic pole N1 has a magnetic flux density of 1000 gauss,
The full width at half maximum is 30 °.

Permanent magnet 1 in the developing device of this embodiment
FIG. 6 shows the state of magnetic force lines of the magnetic field formed by the cooperation of a and 2a.
Shown in FIG. 6 shows the magnetic field analysis software "MAXW".
ELL "(Ansoft Corporation: Ansoft
made by corporation).

In this embodiment, the transport members 3a, 3b
As shown in FIG. 5, the conveying member 3a is arranged adjacent to the developing sleeve 1, and the conveying member 3b is arranged on the inner side of the developer container 4 (these are referred to as arrangement D). From the analysis diagram of the magnetic field shown in FIG. 6, this is because the density of the magnetic lines of force is coarse and the magnetic field lines are roughly evenly spaced so that the density of the magnetic toner is almost uniform, and the magnetic flux on the trajectory of the rotation of the transport member 3a. The conveyance member 3a is arranged by selecting a region in which the change rate of the density in the rotation direction is within 20%.

Further, as shown in FIG. 7, the developing member 1 is placed at the position of the distribution of the lines of magnetic force similar to the arrangement D in the conveying member 3a.
The arrangement E, which is higher than the arrangement D, is also considered so as to be closer to the restriction sleeve 2. At the same time, a transport member made of a magnetic member and a transport member made of a non-magnetic material were also examined. The results are shown in Table 2 below.

[0046]

[Table 2]

As shown in Table 2, good arrangement of toner was carried out only in the arrangement D. In the arrangement E, the toner coating amount on the developing sleeve 1 fluctuates remarkably, and when a conveying member made of a magnetic member is used, it may not be coated at all, and stable coating cannot be performed. .

In the arrangement E, the magnetic pole S1 and the magnetic pole N1
Region G formed by the magnetic field formed by
Has reached the immediate vicinity of the transport member 3a,
Since an increase in the driving torque of the developing sleeve 1 when ‘a’ passes near the restraint region G is observed, the conveying member 3 a
It is considered that the rotation of causes the fluctuation of the toner density in the constrained area G and affects the constrained state. Further, when the conveying member made of a magnetic material receives a magnetic field in the vicinity of the constraining region G and is magnetized, it exerts a new conveying force on the magnetic toner and makes the constrained state unstable. Conceivable.

Further, in the arrangement D, the difference in the material of the conveying member is not observed, because the density of the magnetic lines of force is coarse and the conveying members are arranged at substantially equal intervals, the influence of the magnetic field is negligible. It is thought that there will be no adverse effects due to its small or uniform action.

As described above, the magnetic toner can be satisfactorily applied onto the developer carrying member when the carrying member is arranged at a place where the developer density is uniform in the developer container. It was In the developing position,
It is desirable that the conveying member be composed of a non-magnetic member.

The present invention is not limited to the above-described embodiments, but can be applied to an image forming apparatus having a general developing device.

[0052]

As is clear from the above description, in the image forming apparatus according to the present invention, the transport member is arranged in the developer container at a location where the developer density is uniform.
A good developer can be applied on the developer carrying member, uniform and stable image formation can be realized, and therefore a high quality image can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of a developing device according to a first embodiment of the present invention and an arrangement A of conveying members.

FIG. 2 is an analysis diagram of a magnetic field formed in the developing device according to the first embodiment.

FIG. 3 is an arrangement B of the transport member in the developing device of Embodiment 1.
FIG.

FIG. 4 is an arrangement C of the transport member in the developing device of Example 1.
FIG.

FIG. 5 is an explanatory diagram showing an outline of a configuration and an arrangement D of a transport member in the developing device of Example 2.

FIG. 6 is an analysis diagram of a magnetic field formed in the developing device according to the second embodiment.

FIG. 7 is an arrangement E of the conveying member in the developing device of Embodiment 2.
FIG.

FIG. 8 is a schematic configuration diagram showing an example of an electrophotographic image forming apparatus in which this embodiment can be embodied.

FIG. 9 is a schematic configuration diagram illustrating an example of a conventional developing device.

10 is an explanatory diagram of a toner restraining area G of the developing device of FIG.

FIG. 11 is an enlarged explanatory diagram of the toner restraint area G of FIG.

FIG. 12 is a schematic configuration diagram showing another example of a conventional developing device and having a basic configuration in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Development sleeve (developer carrying body) 1a Permanent magnet (magnetic field generating means) 1b Cylinder 2 Round bar (developer regulating member) 2a Permanent magnet (magnetic field generating means) 3a, 3b Conveying means 4 Developer container 10 Developing device

Claims (3)

[Claims] 1. A developer container containing a developer containing a magnetic toner, and a magnetic field generating means disposed stationary inside thereof.
A rotatably arranged developer carrying member for carrying a developer on its surface, a conveying member for supplying the developer from the developer container to the developer carrying member, and a gap for the developer carrying member. A rotatably arranged developer controlling member having magnetism, wherein the developer is regulated by a magnetic field formed by the magnetic field generating means and the developer regulating member in cooperation with each other, and An image forming apparatus including a developing device configured to receive a conveying force from each of a developer regulating member and the developer carrying member, wherein the conveying member is arranged at a location where the developer density is uniform in the developer container. An image forming apparatus characterized by the following. 2. The closest distance L1 between the transport member and the developer regulating member, and the closest distance L between the developer carrying member.
2. The image forming apparatus according to claim 1, wherein when it is 2, L1 ≧ L2 is satisfied. 3. The image forming apparatus according to claim 1, wherein the conveying member is made of a non-magnetic material.