JP3270663B2 - Developing device - Google Patents

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 a developing apparatus used for an electrostatic recording apparatus.

[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 to practical use. This involves applying a very thin magnetic toner on the developing sleeve, frictionally charging it, and bringing it very close to the electrostatic latent image under the action of a magnetic field.
In addition, development is carried out by facing without contact. That is, by adopting a configuration 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 a toner with a triboelectric charge amount necessary for development.

FIG. 9 shows a developing device using a magnetic one-component toner as a conventional example using the above developing method. The developing device includes a developing sleeve 1, which is a developer carrier that carries a magnetic toner on the surface thereof and is opposed to the photosensitive drum 15, a blade 2 made of a magnetic member that is a developer regulating member that regulates a toner layer thickness, Stirring and developing sleeve 1
And a developer container 4 having therein conveying members 3a and 3b for supplying toner to the developer container.

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

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

FIG. 11 is an enlarged view of a region G. The magnetic toner T is supplied from the developer container 4 onto the developing sleeve 1 by the transport members 3a and 3b. The toner T on the developing sleeve 1 is magnetized by the magnetic field generated by the permanent magnet 1 a inside the developing sleeve 1, is formed as spikes (state B) by magnetic interaction between adjacent toners, and is conveyed. Subject to magnetic constraints. That is, the area G is a toner restricted area. It is known that 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.
Receive the mirror power from This toner is applied to the developing sleeve 1
With the rotation of the developing sleeve 1, a conveying force in the same direction as the rotating direction of the developing sleeve 1 is received. Where the conveying force acting on the charged magnetic toner T overcomes the magnetic restraining force in the restraining area G, that is, the toner spikes are separated at the position indicated by the cut line L, and the toner remaining on the developing sleeve 1 is The toner is applied by being conveyed in the rotation 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, the magnetization per toner decreases in reducing the toner particle size. The acting magnetic binding force may be weakened. As a result, the insufficiently charged toner may escape from the constraint in the area G and leak onto the developing sleeve 1. Further, when the pool C of the insufficiently charged toner generated near the blade 2 becomes large, the magnetic binding force to the area G is weakened, and the partially charged toner of the toner pool C leaks onto the developing sleeve 1. There was a thing.

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

In order to solve the above problem, the inventors of the present invention return the undercharged magnetic toner to the developer container by the developer regulating member and stably store the sufficiently charged magnetic toner in the developer container. We have created a developing device for coating on the body.

That is, as shown in FIG. 12, a 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 disposed inside, a developing sleeve 1 carrying a magnetic toner on the surface, a developer regulating member 2 composed of a magnetic member for regulating the amount of applied toner, and a developer regulating member. A scraper 5 arranged in contact with the member, toner agitation, and transport members 3a and 3b for supplying toner to the developing sleeve 1 are provided inside.
It comprises a developer container 4.

The developer regulating member 2 made of a magnetic member is opposed to the magnetic pole P of the permanent magnet 1a in the developing sleeve 1 through a gap spaced by a predetermined distance W, so that the developing member 2 can be developed. A toner confined region G where the magnetic flux density is concentrated is formed near the vicinity of the sleeve 1 and the developer regulating member 2. 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 conveying members 3a, 3b which rotate in the direction of the arrow shown in FIG.
To the developing sleeve 1. Developing sleeve 1
The magnetic toner supplied upward reaches the above-described region G,
In a magnetically constrained state, electric charges are applied by frictional charging with the rotating developing sleeve 1. The magnetic toner T charged by the above-described frictional charging receives the mirror force from the developing sleeve 1 by the charge obtained by itself.
This becomes a conveying force to the toner, and the toner is conveyed as the developing sleeve 1 rotates.

The developer regulating member 2 made of a magnetic member is arranged near the magnetic pole P, and is magnetized by receiving a magnetic field from the magnetic pole P. Therefore, the toner constrained 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 a direction of returning into the developer container.

On the other hand, in the toner constraint area G,
As described above, the magnetic toner that has been given a charge by frictional charging with the developing sleeve receives the mirror force from the developing sleeve 1 by the charge obtained by itself, and the developing sleeve 1 rotates with the rotation of the developing sleeve 1. It receives the transport force in the rotation direction.

Accordingly, only the sufficiently charged magnetic toner overcomes the conveying force received from the developer regulating member 2 in the direction of returning to the inside of the developer container, is applied on the developing sleeve 1, and is conveyed to the developing area to be charged. Insufficient magnetic toner
The developer is returned into the developer container 4.

Thus, there has been provided a developing apparatus for stably applying a sufficiently charged magnetic toner onto a developer carrying member.

[0020]

However, it has a developer container for storing a developer containing a magnetic toner, and a magnetic field generating means which is statically disposed inside, and is rotatably arranged to carry the developer on the surface thereof. A developer carrying member, a conveying member for supplying the developer from the developer container to the developer carrying member, and a developer regulating member having magnetism and having a gap with the developer carrying member and rotatably disposed. A developing device having a configuration in which the developer is regulated by a magnetic field formed in cooperation with the magnetic field generating means and the developer regulating member, and receives a conveying force from each of the developer regulating member and the developer carrier At
Depending on the position of the conveying member that supplies the developer to the developer carrier, the amount of the developer applied on the developer carrier may be non-uniform, or the toner may be insufficiently charged, and may be uniform and stable. In some cases, it is difficult to form an image.

The cause is that the position of the conveying member and the driving state thereof change the toner constrained state in the toner constrained area G.

According to the study by the present inventors, it has been obtained that the toner density in the toner constrained area G may change depending on the arrangement 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, the insufficiently charged toner is returned to the developer container, so that the amount of applied toner on the developing sleeve is significantly reduced, or the transport amount returned to the developer container is reduced. Catch-up may occur and insufficiently charged toner may leak.

Conversely, when the toner density in the constrained area G increases, the rotational torque of the developing sleeve 1 increases, causing driving unevenness of the developing sleeve or causing excessively charged toner to form aggregates on the developing sleeve. To do that.

Accordingly, it is an object of the present invention to provide a developing device capable of forming a uniform and stable image by applying a good developer on a developer carrying member.

[0026]

SUMMARY OF THE INVENTION The above objects are attained by the present invention.
This is achieved with a developing device . In summary, the present invention has a developer container containing a developer containing a magnetic toner, and a magnetic field generating means which is arranged stationary inside, and carries the developer on its surface, and is rotatably arranged. a developer carrying member, rotating and supplies the developer from the developer container to the developer carrying member
Rollable transport member, having a gap with the developer carrier,
A developer regulating member having magnetism rotatably arranged, and
Comprising, the developer is regulated by a magnetic field formed in cooperation with the magnetic field generating means and the developer regulating member, and,
In the developing device having a structure for receiving a conveying force from each of the developer regulating member and said developer carrying member, wherein
The closest distance L1 between the conveying member and the developer regulating member,
When the closest distance L2 to the developer carrier is L2, L1
.Gtoreq.L2, and the developer carrier and the developer
In the region where the rate of change of magnetic flux density between the imaging agent containers is within 20%
The rotation locus of the transport member is included.
It is a developing device.

[0027]

[0028]

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

Referring to FIG. 8, the electrophotographic image forming apparatus comprises:
A photosensitive drum 15 as an electrostatic latent image carrier is rotatably provided, and the photosensitive drum 15 is uniformly charged by the charger 12.
Next, for example, by 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, the toner image is transferred to the transfer material 16 by the transfer charger 14 and further fixed by the fixing device 17. The transfer residual toner on the photosensitive drum 15 is removed by the cleaning device 11.

Embodiment 1 As shown in FIG. 1, a developing device 10 according to the present embodiment rotates in the direction of the arrow in FIG. 1 and includes therein a permanent magnet 1a as a magnetic field generating means. A developing sleeve 1 serving as a developer carrier for supplying magnetic toner to the developing sleeve 1, and a magnetic material serving as a developer regulating member disposed at a certain distance from the developing sleeve 1 and rotatably arranged in the same direction as the developing sleeve 1. It comprises a round bar 2, a scraper 5 disposed in contact with the round bar, conveying members 3 a and 3 b for stirring the developer and supplying toner to the developing sleeve 1, and a developer container 4.

The developing sleeve 1 used in this embodiment has a diameter of φ
A cylinder 1b made of a nonmagnetic material having an outer diameter of 20 and a permanent magnet 1a having four poles
Used a magnetic member having a diameter of φ10. Since the round bar 2 is arranged at a fixed distance W from the developing sleeve 1 in the vicinity of the magnetic pole S1 of the permanent magnet fixed in the developing sleeve 1, the lines of magnetic force from the magnetic pole S1 to the round bar 2 concentrate. , A 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 magnetic lines of force 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. FIG. 2 shows the magnetic field analysis software “MAX”
WELL "(Ansoft Corporation: Ansof
t corporation).

In this embodiment, the transport members 3a, 3b
As shown in FIG. 1, the transport member 3a is disposed adjacent to the developing sleeve 1, and the transport member 3b is disposed behind the developer container 4 (these are referred to as arrangement A). This is because, from the analysis diagram of the magnetic field shown in FIG. 2, the density of the lines of magnetic force is coarse and almost equally spaced so that the density of the magnetic toner becomes almost uniform. A region where the rate of change of the density in the rotation direction falls within 20% is selected and the transport member 3a is arranged.

Further, as shown in FIG.
From the arrangement position (broken line) shown in FIG. 1 (dashed line) (arrangement A) , the density of the lines of magnetic force is dense, the intervals are narrowed, and the rotation direction of the magnetic flux density on the locus of rotation of the conveying member 3a. The transfer member is disposed at a position where the rate of change of the transfer member exceeds 20%. In the arrangement B, as shown by a dashed line in FIG. So that it is closer to the round bar 2 than the developing sleeve 1, that is, if the transport member 3 a and the round bar 2
The contact distance is L1 and the closest distance to the developing sleeve 1 is L2.
Then, the arrangement C, which is higher than the arrangement A, was also studied so that L1 <L2 . The results are shown in Table 1 below.

[0035]

[Table 1]

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

In the arrangement B, the conveying member 3a is arranged at a position where the density of the lines of magnetic force is high from the rotating shaft of the conveying member 3a to the developing sleeve 1, and the developing member 1 is moved to the developing sleeve 1 with the rotation. It is considered that the supplied toner is remarkably increased, and the toner density in the constrained area G fluctuates.

Further, in the arrangement A, better application is performed than in the arrangement C. In the arrangement C, the conveying member 3a
Since it is arranged close to the round bar 2, the flow of the insufficiently charged toner that is returned into the developer container 4 by receiving the conveying force from the round bar 2 becomes an obstacle to the toner density in the restricted area G. It is thought to give.

As described above, when the transporting member is disposed at a position where the developer density is uniform in the developer container, it becomes possible to perform good application of the magnetic toner on the developer carrying member. Was. Further, in the developing device,
It is desirable that the conveying member is disposed closer to the developer carrier 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 FIG. 5 and has a permanent magnet 1a therein to supply a magnetic toner to the electrostatic latent image. Developing sleeve 1 as a carrier, and permanent magnet 2 inside
a regulating sleeve 2, which is a developer regulating member disposed at a fixed distance W from the developing sleeve 1 and rotatable in the same direction as the developing sleeve 1, and a scraper 5 disposed in contact with the regulating sleeve 2. And a conveying member 3 a, 3 b for stirring the developer and supplying the toner to the developing sleeve 1, and a developer container 4.

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 is composed of a cylinder 2b made of a non-magnetic material having an outer diameter of φ20 and a permanent magnet 2a having two poles therein. A magnetic pole S1 of a permanent magnet 1a fixed inside the developing sleeve 1 and a magnetic pole N of a permanent magnet 2a as a magnetic field generating means fixed inside the regulating sleeve 2.
A constrained area G is formed in the vicinity of the developing sleeve 1 and the regulating sleeve 2 by a magnetic field formed by the cooperation 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 60 °, the magnetic pole N1 has a magnetic flux density of 1000 Gauss,
The half width is 30 °.

The permanent magnet 1 in the developing device of this embodiment
a and 2a show the state of the magnetic field lines of the magnetic field formed in cooperation with each other.
Shown in FIG. FIG. 6 shows the magnetic field analysis software “MAXW
ELL "(Ansoft Corporation: Ansoft
corporation).

In this embodiment, the transport members 3a, 3b
As shown in FIG. 5, the transport member 3a is disposed adjacent to the developing sleeve 1, and the transport member 3b is disposed behind the developer container 4 (these members are referred to as arrangement D). This is because, from the analysis diagram of the magnetic field shown in FIG. 6, the density of the lines of magnetic force is coarse and almost equally spaced so that the density of the magnetic toner is almost uniform. A region where the rate of change of the density in the rotation direction falls within 20% is selected and the transport member 3a is arranged.

As shown in FIG. 7, the transfer member 3a is placed at the position of the distribution of the lines of magnetic force similar to the arrangement D, and
An arrangement E higher than the arrangement D so as to be closer to the regulating sleeve 2 was also examined. At the same time, a transport member made of a magnetic material 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, only the arrangement D performed good toner application. In the arrangement E, the amount of toner applied to the developing sleeve 1 fluctuates remarkably, and when a transport member made of a magnetic member is used, the toner may not be applied at all, and stable application may not be performed. .

In the arrangement E, the magnetic pole S1 and the magnetic pole N1
Region G formed by a magnetic field formed by
Reaches the vicinity of the conveying member 3a, and the conveying member 3
Since the increase in the driving torque of the developing sleeve 1 when the “a” passes in the vicinity of the constraint area G is observed, the conveying member 3a
Is considered to cause a change in the toner density in the constrained area G and affect the constrained state. Furthermore, the conveying member made of a magnetic material receives a magnetic field in the vicinity of the constrained region G and is magnetized, so that a new conveying force acts on the magnetic toner, thereby making the constrained state unstable. Conceivable.

In the arrangement D, there is no difference in the material of the transport member because the density of the magnetic field lines is coarse and the transport members are arranged at substantially equal intervals, so that the influence of the magnetic field can be ignored. It is considered that no adverse effect is caused due to the small or uniform action.

As described above, when the conveying member is disposed at a place where the developer density is uniform in the developer container, it becomes possible to perform the good application of the magnetic toner on the developer carrier. Was. In the above-mentioned developing position,
It is desirable that the transport member be formed of a non-magnetic member.

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

[0052]

As is apparent from the above description, the present invention
Is the closest distance L1 between the conveying member and the developer regulating member,
Assuming that the closest distance L2 to the developer carrier is L1 ≧ L
2 and between the developer carrier and the developer container
In the area where the rate of change of magnetic flux density is within 20%
Since the rolling locus is included, the developer constrained area
Developer density can be maintained properly,
Good developer application on the developer carrier, uniform,
In addition, stable image formation can be achieved, and thus a high-quality image can be obtained.

[Brief description of the drawings]

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

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

FIG. 3 is a diagram illustrating an arrangement B of a conveying member in the developing device of the first embodiment
FIG.

FIG. 4 is a diagram illustrating an arrangement C of a conveying member in the developing device according to the first exemplary embodiment.
FIG.

FIG. 5 is an explanatory diagram showing an outline of a configuration and an arrangement D of a conveying member in a developing device according to a second embodiment.

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

FIG. 7 illustrates an arrangement E of a conveying member in the developing device according to the second exemplary embodiment.
FIG.

FIG. 8 is a schematic configuration diagram illustrating an example of an electrophotographic image forming apparatus in which the present 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 constrained area G of the developing device of FIG. 9;

FIG. 11 is an enlarged explanatory view of a toner constraint area G of FIG. 11;

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

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 developing sleeve (developer carrying member) 1a permanent magnet (magnetic field generating means) 1b cylinder 2 round bar (developer regulating member) 2a permanent magnet (magnetic field generating means) 3a, 3b transport means 4 developer container 10 developing device

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-7-152253 (JP, A) JP-A-7-152251 (JP, A) JP-A-7-168443 (JP, A) JP-A-7-152 152245 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 15/08-15/095

Claims (1)

(57) [Claims] A developer container that contains a developer containing a magnetic toner; and a magnetic field generating unit that is statically disposed inside the developer container.
A developer carrying member that carries a developer on its surface, is rotatably disposed, a rotatable transport member that supplies developer from the developer container to the developer carrying member, and the developer carrying member. A developer regulating member having magnetism and having a gap, which is rotatably disposed, the developer is regulated by a magnetic field formed in cooperation with the magnetic field generating means and the developer regulating member, and A developer receiving a transport force from each of the developer regulating member and the developer carrier.
In the apparatus , the closest distance L between the transport member and the developer regulating member
1. When the closest distance L2 to the developer carrier is defined as:
L1 ≧ L2 is satisfied, and the developer carrying member is
The rate of change of the magnetic flux density between the developer containers is within 20%.
Wherein the rotation locus of the transport member is included in the area.
Developing device.