JPH08137255A - Developing device - Google Patents

Abstract

PURPOSE: To stably apply only sufficiently electrified toner on a developer carrier by combining the magnetic pole of a permanent magnet in the developer carrier with a rotatable developer regulating member in a device for returning the defectively electrified toner on the developer carrier to a container by the developer regulating member and stabilizing the electrification of the toner. CONSTITUTION: In the developing device provided with the developer carrier 1 carrying a developer including magnetic toner, the permanent magnet and the rotatable developer regulating member 2 regulating coating with the developer and consisting of at least a magnetic material, the regulating member 2 is arranged so that an angle θ formed by straight lines that link the center of the developer carrier and at least a magnetic pole P of the permanent magnet and the center of the developer carrier and a closest proximity position to the developer regulating member, by using the center of the developer carrier as an origin satisfies conditions of 0 deg.<=θ<=(the half-width of the magnetic pole P/2) deg., and in a position nearer to the downstream side than the magnetic pole P or the same position as the magnetic pole P, in the rotational direction of the developer carrier.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used in an electrophotographic image forming apparatus, an electrostatic recording device and the like.

[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, 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. In this method, a magnetic toner is applied very thinly on a developing sleeve, frictionally charged, and then brought close to an electrostatic latent image under the action of a magnetic field, and opposed to the electrostatic latent image without contact, thereby performing development. . That is, the purpose is to increase the chances of contact between the toner and the developing sleeve and to provide the toner with a triboelectric charge amount required for development by adopting a configuration in which the toner is applied extremely thinly.

As a conventional example using the above-mentioned developing system, a developing device using a magnetic one-component toner is shown in FIG. The present developing device includes a developing sleeve 1 that supplies toner to an electrostatic latent image, a blade 2 that is a magnetic member that regulates a toner layer thickness, and a toner container 4 that includes a toner stirring and conveying member 3 inside. It consists of

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. Further, the blade 2 is arranged so that the distance from the developing sleeve 1 is a constant value W, and the distance is generally set to a value within the range of 100 μm to 1 mm in many cases.

[0006] The charge application in the developing system will be briefly described in accordance with the conventional example. By the permanent magnet 1a and the blade 2 made of a magnetic member arranged so as to face the magnetic pole, a region G where the magnetic flux density is concentrated is formed in the vicinity of the vicinity of the developing sleeve 1 and the blade 2 as shown in FIG. To be done.

FIG. 8 shows an enlarged view of the area G. The magnetic toner T supplied from the toner container 4 forms a bristle (state B) from the developing sleeve 1 toward the blade 2 by the magnetic field generated by the permanent magnet 1a, and then reaches the area G and is magnetically restrained. . That is, the area G is a toner constrained area. Rotating developing sleeve 1 is attached to the restrained toner T.
It is known that charge is applied by frictional charging with.

[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 image power from. This serves as a conveying force for the toner, and the toner is conveyed as the developing sleeve 1 rotates.
Where the carrying force acting on the charged magnetic toner T overcomes the restraining force due to the magnetic force, that is, at the cut line L, the ears of the toner are torn off, and the toner remaining on the developing sleeve 1 is removed. Is conveyed in the direction of rotation.

However, in the above-mentioned conventional example, an insufficiently charged toner pool C is generated in the vicinity of the blade 2. When the toner pool C becomes large, the permanent magnet 1a
The magnetic restraining force in the area G due to the magnetic field is weakened, and a part of the toner in the toner pool C is conveyed in the rotation direction of the developing sleeve 1. As a result, a part of the toner conveyed on the developing sleeve 1 is charged. However, there is a problem that the toner is not provided with the toner, and a phenomenon associated with unstable charging is likely to occur.

In order to solve the above problems, the inventors of the present invention have devised a developing device for returning the insufficiently charged magnetic toner to the toner container by means of a developer regulating member to stabilize the charging of the magnetic toner. .

That is, as shown in FIG. 1, the developer regulating member 2
Is rotatably provided near the developing sleeve 1. The developer regulating member 2 is made of a magnetic material, is disposed in the developing sleeve 1 in the vicinity of the magnetic pole P of the permanent magnet 1 a so as to face the same, and rotates in the same direction as the developing sleeve 1 rotates. Further, since the developer regulating member 2 is near the magnetic pole P, it is magnetized by the magnetic field formed by the magnetic pole P. Therefore, the magnetic toner in the toner restraining area G receives the magnetic force from the developer regulating member 2 and receives the conveying force in the direction to be returned into the toner container as the magnetic toner rotates. In the toner constrained area G, the magnetic toner, which has been charged by frictional charging with the sleeve, as described above, receives the image force from the developing sleeve 1 by the charge obtained by itself, and the developing sleeve 1
Along with the rotation, the carrying force in the rotation direction of the developing sleeve is received. Therefore, only the sufficiently charged magnetic toner overcomes the carrying force in the direction of returning from the developer regulating member 2 into the toner container, is applied onto the developing sleeve 1 and is carried to the developing area.

Moreover, the rotation of the developer regulating member improves the circulation of the developer in the toner constrained area G, and suppresses the formation of the insufficiently charged toner pool C which occurs in the conventional example. I was able to.

As described above, it is possible to stabilize the charging of the magnetic toner.

[0014]

As described above, the developer regulating member 2 made of a magnetic material is disposed in the developing sleeve 1 in the vicinity of the magnetic pole P of the permanent magnet 1a so as to face the developing sleeve 1. By rotating in the same direction as the rotating direction, it becomes possible to stabilize the charging of the magnetic toner.

However, even in the above-mentioned conventional example, depending on the combination or position of the magnetic pole P of the permanent magnet 1a in the developing sleeve 1 and the developer regulating member 2 made of a magnetic material, only the toner sufficiently charged is developed. In some cases, it could not be applied on top of 1. Further, in recent years, the particle size of the toner used in the developer has been reduced in order to obtain high image quality, but with the decrease in the particle size of the toner, the charge amount per toner particle increases, and the toner particles are statically separated from each other. In some cases, this may cause electrocoagulation, which may prevent uniform charging or uniform and thin layer coating on the developing sleeve.

Therefore, the object of the present invention is to stably
It is an object of the present invention to provide a developing device having a wide degree of freedom of design, which is capable of uniformly coating a developing sleeve with a sufficiently charged magnetic toner in a thin layer and supplying the toner to a developing region.

[0017]

The above object can be achieved by the developing device according to the present invention.

In summary, the present invention comprises a rotatably arranged developer carrier for carrying a developer containing a magnetic toner on its surface, and a permanent magnet arranged inside the developer carrier. In a developing device including a rotatably arranged developer regulating member, which is composed of a magnetic material and regulates application of the developer on the developer carrying member, the developer regulating member includes the developer carrying member. A straight line connecting the center of the developer carrier to the at least one magnetic pole P of the permanent magnet and a straight line connecting the center of the developer carrier and the closest position of the developer regulating member. , The angle θ (see FIG. 2) is 0 ° ≦ θ ≦ (half-value width of the magnetic pole P /
It is characterized in that it is disposed at 2) ° and is arranged at the downstream side or the same position as the magnetic pole P with respect to the rotation direction of the developer carrying material.

[0019]

EXAMPLES In the present invention, by the developer regulating member,
Since the toner constrained area is formed and the conveying force for returning the magnetic toner to the inside of the toner container is given, the arrangement configuration thereof is important.

According to the study by the present inventors, the arrangement position of the developer regulating member, which is a constitution for favorably embodying the present invention, is determined by the half-value width of the magnetic pole P in the vicinity thereof and the relative position with respect to the magnetic pole P. It was found that it is limited by such a positional relationship.

First, using the developing device shown in FIG. 1, using a commercially available magnetic toner having a weight average diameter of 6.5 μm,
The angle θ formed by the magnetic pole P and the developer regulating member was changed.
The magnetic pole P has a magnetic flux density of 1000 gauss and a range in which the absolute value of the extreme value of the magnetic flux density shows a value of 50% or more, that is, three kinds of half widths of 35 °, 45 °, and 60 ° are used. I examined it. The results are shown in FIGS. 9 and 10.

The vertical axis in FIG. 9 indicates, among the toners coated on the developing sleeve 1, toner which is not charged to a desired polarity (reversed toner) when the conventional developing device shown in FIG. 6 is used. And the ratio of the toner charged to a desired polarity (regular toner) to 1, the ratio of the reversal toner is shown. The horizontal axis represents an angle θ that is positive when the developer regulating member is located downstream of the magnetic pole P with respect to the rotation direction of the developing sleeve 1.

That is, as shown in FIG. 9, the developer regulating member is located downstream of the magnetic pole P in the rotational direction of the developing sleeve 1 or at the same position, and O ° ≤θ≤.
The toner applied on the developing sleeve 1 by the present developing device in the region satisfying the (half-value width of the magnetic pole P / 2) ° has a reversal toner ratio equal to or less than that of the conventional example.

Further, FIG. 10 shows a comparison of the image quality of output images when the same electrophotographic image forming apparatus is used and each developing apparatus is used.

That is, what is shown in FIG. 10 is that if the reversal toner ratio is 1 or less, the image quality equal to or higher than that of the conventional example can be obtained.

Examples of the present invention will be described below.

(First Embodiment) The developing device in this embodiment is shown in FIG. The developing device includes a developing sleeve 1 as a developer carrying member for supplying magnetic toner to an electrostatic latent image, a round bar 2 made of a magnetic material as a developer regulating member,
It is composed of a scraper 3 arranged in contact with a round bar, a developer stirring member 4 and a conveying member 4, and a developer container 5.

As the developing sleeve 1, one having a diameter of φ20, in which the permanent magnet 10 having a plurality of magnetic poles is fixed, is used. Also, round bar 2
The diameter of the developing sleeve 1 and the diameter of the round bar 2 and the rotation speed of the developing sleeve 1 are not limited thereto. . Further, the stirring / conveying member 4 is adapted to rotate in the opposite direction with respect to the developing sleeve.

Further, the magnetic pole S used in this embodiment.
Although 1 has a magnetic flux density of 800 gauss and a half-value width of 35 °, it goes without saying that not only this but an appropriate one can be used depending on the conditions such as the magnetic toner used.

The round bar 2 has a fixed distance W from the developing sleeve 1.
And the angle θ is formed with respect to the straight line connecting the center of the developing sleeve 1 and the magnetic pole S1. When the angle θ is changed, the conditional expression 0 ° ≦ θ ≦
Satisfying (half width of magnetic pole S1 / 2) °, 0 ° ≦ θ ≦ 1
At 5 °, it was possible to obtain a uniformly good image output, so the magnetic pole S1 is fixed at the position where θ = 0 °.

A round bar 2 serving as a developer regulating member is arranged at the above-mentioned arrangement position.
The magnetic flux density from the magnetic pole S1 to the round bar 2 is sufficiently concentrated and the toner constrained area G is formed.

The magnetic toner in the constrained area G receives the magnetic force from the round bar 2 magnetized by the magnetic field formed by the magnetic pole S1, and as the rotation thereof, receives the carrying force in the direction of returning to the toner container.

The magnetic toner conveyed to the area G is
By being sufficiently restrained by the magnetic field, the developing sleeve 1
An electric charge is given by frictional charging with. Further, since the developer regulating member is arranged at the optimum position, even if the toner agglomerates due to electrostatic agglomeration or the like, the agglomeration can be broken and a sufficient restrained state for uniform charging can be created. The magnetic toner receives a mirror image force from the developing sleeve 1 due to the electric charge obtained by itself, and receives a conveying force in the developing sleeve rotation direction as the developing sleeve 1 rotates.

Therefore, only the sufficiently charged magnetic toner overcomes the carrying force in the direction of returning from the round bar 2 into the toner container and is applied onto the developing sleeve 1.

As described above, the present invention makes it possible to stabilize the charging of the magnetic toner.

(Second Embodiment) The present invention is also suitably implemented in the embodiment shown in FIG.

The developing device of this embodiment is the same as the first embodiment except that the developer regulating member 2 and its arrangement position are different.
Since it is the same as the developing device in 1), detailed description is omitted.

The developer regulating member 2 in this embodiment comprises a fixed shaft 21 made of a magnetic material, an endless belt 22 made of a non-magnetic material, and a drive shaft 23 for driving the endless belt 22 in the arrow direction. In this, the fixed shaft 21 magnetized by the magnetic pole S1 is provided with a conveying force inwardly of the toner container by the driving endless belt 22 for the insufficiently charged toner that is constrained via the endless belt 22 by the magnetic force. Thus, the insufficiently charged toner conveyed by the endless belt 22 made of a non-magnetic material loses its restraining force as it moves away from the fixed shaft 21, and naturally falls into the toner container due to gravity, which is seen in Conventional Example 1. It does not require such a scraper.

Further, the magnetic pole S used in this embodiment.
Although 1 has a magnetic flux density of 1000 gauss and a half value width of 60 °, it goes without saying that not only this but also an appropriate one can be used depending on the conditions of the magnetic toner used and the like.

The developer regulating member 2 is a straight line connecting the center of the developing sleeve 1 and the magnetic pole S1 at a certain distance W from the developing sleeve 1 and downstream of the magnetic pole S1 in the rotational direction of the developing sleeve 1. And the center of the developing sleeve 1 and the fixed shaft 2.
They are arranged at an angle θ formed by a straight line connecting the centers of 1. When the angle θ formed is changed, the conditional expression 0 ° ≦ θ ≦ (half-value width / 2 of the magnetic pole S1) ° is satisfied.
In the case of ° ≦ θ ≦ 30 °, a uniformly good image output could be obtained, so the magnetic pole S1 is fixed at the position of θ = 15 °.

By adopting the above structure, it is possible to stabilize the charging of the magnetic toner.

Further, the angle θ formed on the downstream side of the magnetic pole P with respect to the rotation direction of the developing sleeve 1 and the above-described angle θ is expressed by a conditional expression: O ° ≦ θ ≦ (half-value width of magnetic pole S1 = 60 ° / 2. By disposing the developer regulating member 2 at a position of θ = 15 °, which is almost an intermediate value of), even if the position of the magnetic pole S1 slightly fluctuates during the manufacture of the permanent magnet 1a, stable charging of the magnetic toner can be achieved. Can be granted.

(Third Embodiment) The present invention is also suitably implemented in the embodiment shown in FIG.

The developing device of this embodiment has the same structure as that of the developing device of the first embodiment except that the permanent magnet 10 used and the developer regulating member 2 are different.
Detailed explanation is omitted.

The developer regulating member 2 in the present embodiment is a rotatably arranged cylinder 25 made of a non-magnetic material, and a blade 26 made of a magnetic material fixed in the cylinder 25.
Consists of This is to give the blade 26 magnetized by the magnetic pole S1 a conveyance force inwardly of the toner container due to the rotation of the cylinder 25 for the insufficiently charged toner that is constrained via the cylinder 25 by the magnetic force. Insufficiently charged toner conveyed by the cylinder 25 made of a magnetic material rapidly loses its restraining force to the cylinder 25 as it moves away from the blade 26, and thus the insufficiently charged toner is transferred to the toner container without applying substantial pressure. It is something that can be scraped inward.

Further, the magnetic pole S used in this embodiment.
Although 1 has a magnetic flux density of 1000 gauss and a half value width of 60 °, it goes without saying that not only this but also an appropriate one can be used depending on the conditions of the magnetic toner used and the like.

The developer regulating member 2 is located on the downstream side of the magnetic pole S1 with respect to the rotation direction of the developing sleeve 1, and further, the straight line connecting the center of the developing sleeve 1 and the magnetic pole S1 and the center of the developing sleeve 1. The blades 22 are arranged at an angle θ formed by a straight line connecting the tips of the blades 22. When the above-described angle θ is changed, when 0 ° ≦ θ ≦ 30 °, which satisfies the conditional expression 0 ° ≦ θ ≦ (half-value width / 2 of the magnetic pole S1) °, a uniformly good image is obtained. Because I was able to get the output,
The magnetic pole S1 is fixed at a position where θ = 5 °.

By adopting the above structure, it is possible to stabilize the charging of the magnetic toner.

Further, the magnetic pole S1 in this embodiment is a magnetic field generating means for forming the toner constrained area G, and at the same time,
The magnetic force can also serve as auxiliary means for supplying the magnetic toner from the toner container 4 to the developing sleeve 1. As described above, by using the present invention, stable charging of the magnetic toner can be performed, and the degree of freedom in designing the developing device can be increased.

The present invention is not limited to the above-described embodiments, but can be widely applied to general developing devices.

[0051]

As described above, according to the present invention, the developer carrier rotatably disposed, the permanent magnet disposed inside the developer carrier, and the developer carrier above It regulates the application of the developer of
In a developing device including a rotatably arranged developer regulating member, the developer regulating member is set with the center of the developer carrying member as an origin, and the developer carrying member center and at least one magnetic pole P of the permanent magnet. The angle θ formed by the straight line connecting the line and the line connecting the center of the developer carrying member and the closest position of the developer regulating member is the following condition: O ° ≦ θ ≦ (half-value width of magnetic pole P / It is sufficient to impart sufficient electric charge to the magnetic toner by satisfying 2) ° and arranging it at the downstream side or the same position as the magnetic pole P with respect to the rotation direction of the developer carrying material. It has become possible to form a toner constrained area and to apply a conveying force to the magnetic toner in the toner constrained area in the direction of returning it to the inside of the toner container.

Further, by rotating the developer regulating member,
The circulation of the developer in the toner constrained region G is improved, and the insufficiently charged toner pool C generated in the above-mentioned conventional example.
It has become possible to suppress the formation of

As a result, only sufficiently charged toner, which has a mirror image force that overcomes the conveying force in the direction of returning it into the toner container, is selectively and stably applied onto the developing sleeve to reach the developing area. It was possible to provide a developing device that can be transported and has a wide degree of freedom in design.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a developing device having a basic configuration that embodies the present invention.

FIG. 2 is an explanatory diagram of an angle θ formed between the magnetic pole P and the arrangement position of the developer regulating member.

FIG. 3 is a schematic diagram of a developing device according to the first embodiment.

FIG. 4 is a schematic diagram of a developing device according to a second embodiment.

FIG. 5 is a schematic diagram of a developing device according to a third embodiment.

FIG. 6 is a schematic view of a conventional developing device.

FIG. 7 is an explanatory diagram of the toner restraint area G.

FIG. 8 is an enlarged explanatory diagram of the toner restraint area G.

FIG. 9 is a correlation diagram of the arrangement position of the developer regulating material and the reverse toner ratio

FIG. 10 is a comparison diagram of the reversal toner ratio and the image quality of an output image.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Developing sleeve 1a ... Permanent magnet 2 ... Developer regulating member 21 ... Fixed shaft 22 ... Endless belt P ... Magnetic pole

Front page continuation (72) Inventor Takeshi Yamamoto 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (1)

[Claims] 1. A rotatably arranged developer carrying member carrying a developer containing a magnetic toner on its surface, a permanent magnet arranged inside the developer carrying member, and a developer carrying member on the developer carrying member. In a developing device including a rotatably arranged developer regulating member that regulates the application of the developer of at least a magnetic body, the developer regulating member has the center of the developer carrier as an origin. An angle θ formed between a straight line connecting the center of the developer carrying member and at least one magnetic pole P of the permanent magnet and a straight line connecting the center of the developer carrying member and the closest position of the developer regulating member. , The following condition O
Satisfying the condition: ≦ θ ≦ (half-value width of the magnetic pole P / 2) °, and with respect to the rotation direction of the developer carrier, the magnetic pole P
A developing device, which is arranged on the downstream side or at the same position.