JP2683102B2 - Developing device - Google Patents

Description

The present invention relates to a developing device for developing a latent image formed by an electrophotographic method or an electrostatic recording method.

[Conventional technology]

Heretofore, various dry developing methods or apparatuses have been known for various principles and methods, and among them, various methods based on the so-called magnetic bra developing method are mainly put into practical use.

This is a so-called two-component developer composed of a mixture of toner particles having a particle size of about 1 to 20 μm and magnetic particles (carriers) having a particle size of about 20 to 200 μm as a developer, or a magnetic particle of several tens of particles. % So-called one-component type developer composed of magnetic toner is used, and the developer is held as a layer by a magnetic binding force on the surface of a developer carrying member which has a magnetic field generating means inside or which itself has magnetism. Then, the latent image is toner-developed by transporting the latent image bearing member to a developing unit facing the latent image carrier.

FIG. 4 is a lateral cross-sectional view of the main part of an example of a conventional developing device, in which the electrostatic latent image carrier 1 is rotated in the direction of arrow a. Reference numeral 21 is a non-magnetic rotating sleeve as a developer carrying member, 22 is a fixed (non-rotating) magnet roller as a magnetic field generating means inserted and built in the sleeve, and magnetic poles 22a, 22b, 22c and 22d are at predetermined positions. Are alternately magnetized.

The two-component developer 41 mixed with the toner 40 is constrained on the sleeve, and the sleeve 21 rotates in the direction of arrow b so that the developing unit
It is conveyed to 101, developed, and further collected in the developing container by the rotation of the sleeve. Further, in the developing device of the present example, an elastic seal member 31 for contacting and sealing the developer on the sleeve 21 is provided as shown in the figure in order to prevent the backflow of the developer 41 in the lower region, and further the scattering prevention member 30 is arranged. Has been done.

FIG. 5 is a cross-sectional view of the essential part of another example of the conventional developing device, and the same parts as those in FIG. 4 are designated by the same reference numerals and symbols. In FIG. 5, the developer carrier sleeve 21
The magnetic roller 22 built in the magnetic pole 22a, 22b, 22c, 22d
Are alternately magnetized in place, but the magnetic pole 22e
It is magnetized in the same pole as 2d, forms a repulsive magnetic field between the magnetic poles 22d and 22e, and has a structure for stripping off the developer 41 magnetically restrained on the sleeve 21. Further, in the developing device of this example, an elastic seal is provided in order to prevent toner scattering when the developer 41 stands up along the lines of magnetic force at the magnetic pole 22d and to prevent the developer 41 from flowing back toward the developing magnetic pole 22c. One end of the member 31 is fixed to the free end and the other end is fixed to the developing container, and the free end is partially contacted with the developer.

[Problems to be solved by the invention]

However, in the configuration of FIG. 4 of the above conventional example,
The developer, which is constrained by the developer carrier sleeve 21 and is rotating, collides with the elastic seal member 31, and the impact causes the toner particles constrained by the carrier particles of the developer to be scattered or scattered, or the elastic seal member. The elastic seal member 31 is triboelectrically charged by the friction with 31 and the toner particles are positively attached and deposited on the elastic seal member to form toner aggregates, which scatter for the reason or due to the pressure of the backflow blowing developer in the developing container. The elastic seal member 31 deforms and acts as a non-uniform barrier against the developer that is about to be collected in the developing container from the developing unit 101, increasing toner scattering and causing the developer itself to overflow to the outside of the developing device. Defects such as falling, elastic seal member
There was a problem of low durability due to deformation of 31.

Further, also in the configuration of FIG. 5 of the above-mentioned conventional example, the circumferentially bound developer constrained by the developer carrier sleeve 21 collides with the elastic seal member 31, and the impact thereof constrains the carrier particles of the developer. Toner particles are scattered and scattered, or due to friction with the elastic seal member 31, the elastic seal member 31
Are triboelectrically charged and the toner particles are positively deposited and deposited on the elastic seal member, forming toner aggregates and flying apart, or due to the repulsive magnetic field caused by the magnetic poles 22d and 22e, the magnetic flux line direction to the magnetic pole 22c is the opposite pole. Since the magnetic flux is dense, the spikes of the developer formed on the sleeve 21 near the position of the magnetic pole 22d are greatly extended in the direction of the magnetic pole 22c and become denser. It acts as a barrier against the developer that is about to be collected in the container, increases the scattering of toner, deteriorates the intake of the developer into the developing container, and the deformation of the elastic seal member 31. There was a problem such as low durability due to.

[Means for solving the problem]

The present invention which solves the above-mentioned problems, a developer container for containing a developer having toner particles and carrier particles, and a carrier particle in the container which forms a developing portion facing the electrostatic latent image carrier. In a developing device having a developer carrying member carrying and transporting toner particles to a developing unit, a first magnetic pole provided in the developer carrying member for collecting in a container and a first magnetic pole in the developer carrying member. Second magnetic pole which is provided on the downstream side in the moving direction of the developer carrying member and which forms a repulsive magnetic field with the first magnetic pole, and the first magnetic pole which is provided on the downstream side of the first magnetic pole in the moving direction of the developer carrying member with respect to the developer container. A magnetic member that forms a seal of the carrier particles with a brush, and the first and second rotation centers of the developer carrying member.
The angle formed by each straight line connecting the magnetic poles is θ ₁ , and the angle formed by each straight line connecting the rotation center of the developer carrying member and the closest point of contact between the first magnetic pole and the developer carrying member of the magnetic member is θ ₂ . In this case, 5 ° ≦ θ ₂ ≦ 1 / 3θ ₁ is satisfied.

〔Example〕

An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a sectional view of a first embodiment in which the present invention is applied to a copying machine using a drum type photosensitive member. Although not shown in the figure, a charging mechanism, an image exposure mechanism, a transfer mechanism, a cleaning mechanism, a charge eliminating mechanism, which are well-known electrophotographic processes, are arranged around the photosensitive drum 1.

The developing device is, for example, a device for developing a latent image formed on a latent image carrier 1 such as a photoconductor or a dielectric by an electrophotographic method, an electrostatic recording method, or the like. A developing sleeve 21 as a developer carrier, a blade 23 as a developer layer regulating member, and the like are included. That is, an opening is formed in the developing container 2 at a position close to the latent image carrier 1, the developing sleeve 21 is rotatably provided in the opening, and the developing sleeve 21 is provided above the developing sleeve 21. The blade 23 is attached with a predetermined gap, and the magnetic member 10 is attached below the developing sleeve 21 with a predetermined gap.

Incidentally, the developing sleeve 21 is made of a non-magnetic material, rotates in the direction of the arrow b in the drawing during the developing operation, and a magnet 22 which is a magnetic field generating means is fixed inside the developing sleeve 21. Pole) and a magnetic pole 22a that carries a developer 41 described later.
It has (S pole), 22b (N pole), 22d (N pole), and 22e (N pole). Here, the polarities of the magnetic poles may be the opposite combinations.

The blade 23 is made of a non-magnetic material such as aluminum (Al) or non-magnetic stainless steel (SUS) or a magnetic material such as iron (Fe) or magnetic stainless steel (SUS), which is the surface of the developing sleeve 21 as described above. A predetermined gap is provided between the developing sleeve 21 and the developing sleeve 21, and this gap is the amount of the developer 41 conveyed to the developing portion on the developing sleeve 21, specifically, the developing sleeve 21.
The thickness of the upper developer 41 is regulated. Therefore, in this embodiment, both the non-magnetic toner and the magnetic particles pass between the tip of the blade 23 and the surface of the developing sleeve 21 and are sent to the developing section.

The developer 41 is a two-component developer composed of the non-magnetic toner 40 and magnetic particles (carriers). The non-magnetic toner 40 has a volume average particle size of 10 μm or less (8 μm in this embodiment).
The toner for a color copying machine using the polyester resin or the styrene-acrylic acid ester resin as described above as a base was used.

The magnetic particles (carrier) have a weight average particle diameter of 30 to 80μ.
m, preferably 40 to 70 μm, and a resistance value of 10 ⁷ Ωcm or more,
Preferable ferrite particles of 10 ⁸ Ωcm or more (maximum magnetization 60e
Resin coated to mu / g) can be used, and in this example, the one having a weight average particle diameter of 50 μm was used.

The developer 41 is conveyed to the developing unit 101, and the sleeve 21
Is conveyed to the magnetic pole 22d while being held by the magnetic poles 22d and 22e.
Have the same polarity (N pole), a repulsive magnetic field is generated between them. Therefore, the developer carried to the magnetic pole 22d while being held by the sleeve 21 is removed from the sleeve 21 by the action of this repulsive magnetic field, and the first agitating and carrying means.
The toner is agitated and mixed by 51, and a developer is newly supplied to the developing sleeve 21 near the magnetic pole 22e.

That is, the developer that has received the development history on the sleeve 21 is peeled off and sufficiently mixed, and new developer is constantly supplied to the sleeve 21, so that a good image can be stably obtained.

Next, as the magnetic member 10 provided below the sleeve 21 which is the main point of the present invention, a member having weak magnetism by deforming a magnetic material such as iron or a magnet or a non-magnetic material can be applied.

In this example, an iron member having a thickness of 0.5 mm and a width of 5 mm was used. In the developing device using the repulsive magnetic field with the magnetic poles 22d and 22e having the same polarity as in the present invention, the magnetic line of force by the magnetic pole 22d does not wrap around in the direction of the magnetic pole 22e, and is largely concentrated on the magnetic pole 22c having a different polarity. , The magnetic flux density from the magnetic poles 22d to 22c increases.

Therefore, in the configuration (FIG. 3) in which the magnetic member 10 is not provided as in this embodiment, the sleeve 21 is located near the magnetic pole 22d.
The spikes of the developer 41 formed on the top of the magnetic pole 22c are large and long.
Direction, and becomes denser, acts as a barrier against the developer that is restrained and conveyed from the developing unit 101 to the sleeve 21 and is collected in the developing container. It was confirmed by an experiment that the uptake of the developer 41 into the developing container deteriorates. Further, in an experiment using the above-described color toner, particularly a polyester-based toner that is easily made into a streak, a dense, long and long spike of developer near the magnetic pole 22d causes a developer container lower sealing member.
It was also experimentally confirmed that the toner was loosely rubbed against 11, and the toner was released, melted and agglomerated, and the agglomerates were sequentially mixed in the developing container and appeared as an abnormal image on the actual image. Therefore, when the magnetic member 10 is provided as in the present embodiment of the present invention, the magnetic pole 22d
The magnetic force line due to does not concentrate greatly on the magnetic pole 22c,
A large magnetic flux is not formed from the magnetic poles 22d to 22c because a part of the magnetic force lines concentrates on the magnetic member 10 and then forms a large arc toward the magnetic pole 22c.

Therefore, the spikes of the developer 41 formed on the sleeve 21 near the position of the magnetic pole 22d are concentrated on the magnetic member 10 to bring about the magnetic sealing effect by the magnetic brush, and the spike of the developer from the magnetic pole 22d to the magnetic pole 22c is small. As a result, the developer that is restrained and conveyed from the developing unit 101 to the sleeve 21 and is about to be collected in the developing device does not increase the layer thickness, and the spikes of the developer do not come into contact with the developing container lower seal member 11. I was able to confirm that.

Here, a part of the magnetic brush formed between the magnetic member 10 and the magnetic pole 22d is retained in the magnetic member due to the balance of the static restraining force such as magnetic restraining force and mirroring force and the frictional force due to the rotation of the sleeve 21, and the like. Are sequentially taken into the developing container and fall into the container due to the repulsive magnetic field.

Further, since the magnetic brush formed between the magnetic pole 22d and the magnetic member 10 acts as a seal member by the developer itself which sequentially rotates, it is constrained and conveyed from the developing unit 101 to the sleeve 21,
Acts as a soft seal member against the developer that is about to be collected in the developing container, and is free from the fact that the toner is not scattered and scattered by the impact, and the intake of the developer 41 into the developing container is not deteriorated. It has been confirmed by experiments that the sealing effect is exhibited.

Therefore, even in the experiment using the color toner as described above, particularly the polyester-based toner that is easily made into a streak, the free agglomerates of the toner are formed or the agglomerates are formed in the developing container as in the comparative example (FIG. 3). It was also confirmed that they were sequentially mixed and did not appear as an abnormal image on the actual image.

Next, the present invention will be described with respect to the positional relationship between the magnetic member 10 and the developing sleeve 21.

In FIG. 2, the rotation center of the sleeve 21 and the magnetic poles 22d, 2
The angle formed by each straight line connecting the pole centers of 2e is θ ₁ , the rotation center of the sleeve 21, the pole center of the magnetic pole 22d, and the magnetic member 10
Let θ ₂ be the angle formed by each straight line connecting the sleeve 21 and the closest point to the sleeve 21. First, θ ₂ = 0 or minus (here, minus means that the position of the magnetic member 10 is relative to the magnetic pole 22d in the rotational direction of the sleeve 21). In the case of (on the upstream side), the magnetic lines of force by the magnetic pole 22d are strongly concentrated on the magnetic member 10. Therefore, the ears of the developer 41 formed on the sleeve 21 near the position of the magnetic pole 22d become large, strong and dense, and the developing unit 10
It becomes a complete barrier against the developer that is constrained from 1 to the sleeve 21 and is about to be collected in the developing container, and the developer overflows outside the container without being taken in, contrary to the intention of the present invention.

Furthermore, the closer the magnetic member 10 is to the downstream side of the magnetic pole 22d with respect to the rotating direction of the sleeve 21 (the closer to the magnetic pole 22e), the weaker the concentration of the magnetic force lines of the magnetic pole 22d becomes, and the smaller the magnetic sealing effect becomes. According to the applicant's experiment, 0 <θ ₂ <5
It was found that, in the range of °, neither the magnetic sealing effect, the developer taking-in effect, nor the toner releasing and scattering effect described above was sufficient and not satisfactory. Also, 1 / 3θ ₁ <θ
It was found that the magnetic member had no effect in the range of _{2, and} the range in which the magnetic sealing effect, the developer uptake effect, and the toner release and scattering effect can be sufficiently exhibited is 5 ° ≦ θ ₂ ≦ 1 / 3θ
It was confirmed by experiment that it exists in ₁ .

Next, in FIG. ₂ showing the relationship between the gap between the magnetic member 10 and the developing sleeve 21 and the gap between the developer regulating member blade 23 and the developing sleeve 21, both gaps are indicated by g ₂ and g ₁ . Amount of developer 41 formed on sleeve 21 (thickness t)
Is regulated by g ₁ . When a magnetic member is used for the blade 23 and the developer is regulated by a so-called magnetic cutting method, the developer amount thickness t <g ₁ is generally satisfied.

Further, when a non-magnetic member is used for the blade 23, it is generally t to g ₁ .

Further, in the magnetic brush portion formed between the magnetic pole 22d and the magnetic member 10, as described above, a part of the developer accumulates on the magnetic member 10 side, so that the development that substantially passes between the sleeve 21 and the magnetic member 10 is performed. The agent thickness is smaller than g ₂ .

To do a good uptake of the developer in the experiments in the developing apparatus of the present invention configured thus, when using the magnetic blade 23, g ₁ ≦ g _2, when using a non-magnetic blade 23 g ₁ <g ₂ It turned out to be

Although the developing sleeve having five poles of magnetic field generating means is described in the present embodiment, the present invention is not limited to this and is applicable to all developing sleeves having a repulsive magnetic field.

Further, in the embodiment, as the toner, a two-component developer having a volume average particle diameter of 8 μ and a magnetic carrier particle diameter of 50 μm is used, but the invention is not limited to this, and the toner and the carrier having the particle diameters conventionally used are used. The present invention can also be applied to a developer using a toner and a so-called magnetic one-component toner containing magnetic particles.

〔The invention's effect〕

As described above, the above configuration provides a developing device with less toner scattering from the developing device, the developer itself does not overflow and fall from the developing device, good circulation intake of the developer, and high durability. In addition, it is possible to provide a developing device that can stably supply a good image without forming toner aggregates due to friction.

[Brief description of the drawings]

 FIG. 1 is a transverse sectional view of a developing device showing the present invention. FIG. 2 is a transverse sectional view of the developing device showing the present invention. FIG. 3 is a transverse sectional view of a developing device showing a comparative example. FIG. 4 is a transverse sectional view of a developing device showing a conventional example. FIG. 5 is a transverse sectional view of a developing device showing a conventional example. DESCRIPTION OF SYMBOLS 1 ... Photosensitive member 2 ... Developing container 10 ... Magnetic member 21 ... Developing sleeves 22a to 22e ... Magnetic field generating means 23 ... Developer regulating member 40 ... Toner 41 ... Developer

Claims (1)

(57) [Claims] 1. A developer container for accommodating a developer having toner particles and carrier particles, and a developing section facing a latent electrostatic image bearing member to form a developing section, and the carrier particles and toner particles in the container are developed in the developing section. In a developing device having a developer carrying member that carries and conveys the first magnetic pole to the developer carrying member, the first magnetic pole is provided in the developer carrying member for collecting the developer into the container, and the first magnetic pole is developed in the developer carrying member. A second magnetic pole that is provided on the downstream side in the moving direction of the agent carrying member and forms a repulsive magnetic field with the first magnetic pole; and a first magnetic pole that is provided on the downstream side of the first magnetic pole in the moving direction of the developer carrying member with respect to the developer container. And a magnetic member that forms a seal by a brush of carrier particles between them, and an angle between the rotation center of the developer carrying member and each straight line connecting the first and second magnetic poles is θ ₁ , The rotation center, the current of the first magnetic pole and the magnetic member The angle between the straight lines recently connecting the contact point between the carrying member θ
A developing device which is a _{5 ° ≦ θ 2 ≦ 1 /} 3θ 1 when _2.