JP2002214911A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device provided with the conventional simplicity and low cost, where stored quantity of the developer can be increased, the service life of developer is long and toner filming is prevented. SOLUTION: A second developing sleeve 4b which is a second developer carrier is provided. Furthermore, differing magnetic poles are installed in the upstream and downstream sides of the proximal position between a first developing sleeve 4a and the second developing sleeve 4b to be faced to each other. Moreover, the potential of the first developing sleeve 4a and the potential of the second developing sleeve 4b are made the same.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device applicable to an image forming apparatus such as a copying machine, a facsimile, a printer, and the like. More specifically, the present invention relates to a developing device for storing a two-component developer composed of a toner and a magnetic carrier. A developer carrier having a magnet therein, a developer holding body that holds the developer in the developer housing chamber by magnetic force and conveys the developer by rotation, and a toner housing chamber that houses toner. The present invention relates to a developing device that takes in toner stored so as to come into contact with a developer by moving a developer.

[0002]

2. Description of the Related Art Hitherto, there has been known a developing apparatus of a type which does not require a toner density detecting means and takes in toner by movement of a developer. However, in this conventional method, the amount of toner taken in is different between a portion where the developer is active and a portion where the developer is not active, or a portion where the amount of the developer is large and a portion where the amount of the developer is small. Density unevenness and background contamination are likely to occur. Therefore, by disposing two toner supply members in the toner hopper and passing the developer through a path formed by each toner supply member,
Japanese Patent Application Laid-Open No. 63-4282 discloses a technique for solving density unevenness and background contamination in the longitudinal direction of the apparatus.

[0003]

However, in the conventional developing device, the developer is adsorbed only around the developing sleeve which is a single developer carrier, and the amount of developer stored is limited. Was. The developer is stressed by the photoreceptor drum and the developing doctor as a regulating member. Especially when the amount of the developer is small, the stress increases, and the abrasion of the carrier surface and the filming in which the toner and the third additive adhere to the surface are caused. It easily occurred at an early stage, and the life of the developer was short.

[0004] In view of the above problems, the present invention provides a developing device which has the conventional simplicity and low cost, can increase the amount of developer contained, has a long life of the developer, and can prevent toner filming. The purpose is to provide.

[0005]

In order to solve the above problems, the present invention according to claim 1 has a magnetic field generating means inside,
A first developer carrier that carries and transports a two-component developer including a toner and a magnetic carrier; a regulating member that regulates the amount of developer carried and transported by the developer carrier; and a regulating member. A developer accommodating portion for accommodating the developer scraped off by the first developer carrier, and a toner accommodating portion adjacent to the developer accommodating portion for supplying toner to the developer carrier. A developing device that changes the contact state between the developer and the toner by changing the toner concentration of the developer, thereby changing the state of taking in the toner on the developer carrier, characterized by having a second developer carrier. Storage. According to a second aspect of the present invention, in the developing device according to the first aspect,
A developing device is characterized in that different magnetic poles are arranged at opposing portions on the upstream and downstream sides of the closest positions of the two developer carriers. According to a third aspect of the present invention, there is provided the developing device according to the first aspect, wherein the potentials of the two developer carrying members are equalized.

[0006]

FIG. 1 is a schematic configuration diagram of a developing device in an image forming apparatus employing an embodiment of the present invention. The developing device (2) disposed on the side of the photosensitive drum (1) as a latent image carrier includes a support case (3), developing sleeves (4a) and (4b) as a developer carrier, and a developing device. It mainly comprises a developer container (5) and developing doctors (6a) and (6b) as developer regulating members.

A support case (3) having an opening on the photosensitive drum (1) side forms a toner hopper (8) as a toner storage section for storing a toner (7) therein. A developer accommodating part (5a) for accommodating a developer (11) comprising a toner (7) and a carrier as magnetic particles is provided near the photosensitive drum (1) of the toner hopper (8). The member (5) is provided integrally with or separately from the support case (3). Further, a protruding portion (3a) having an opposing surface (3b) is formed in the support case (3) located below the developer accommodating member (5), and is opposed to a lower portion of the developer accommodating member (5). The space between the surface (3b) and the surface (3b) forms a toner supply opening (9) for supplying the toner (7).

Inside the toner hopper (8), there is provided a toner agitator (10) as toner supply means which is rotated by a driving means (not shown). The toner agitator (10) sends out the toner (7) in the toner hopper (8) toward the toner supply opening (9) with stirring. On the side of the toner hopper (8) facing the photosensitive drum (1), a toner end detecting means (12) for detecting when the amount of the toner (7) in the toner hopper (8) becomes small is arranged. Has been established.

Photosensitive drum (1) and toner hopper (8)
The first developing sleeve (4a) and the second developing sleeve (4b) are disposed in the space between the first developing sleeve (4a) and the second developing sleeve (4b). A first developing sleeve (4a) and a second developing sleeve (4b), which are driven to rotate in a direction indicated by an arrow in the drawing by driving means (not shown), are disposed inside each of the developing devices (2) so as not to change relative to the developing device (2). Was
It has a magnet (not shown) as a magnetic field generating means.

A first developer doctor (6a) as a developer regulating means is integrally attached to a side of the developer accommodating member (5) facing the support case (3) side. The first developing doctor (6a) is disposed with a relatively small gap kept between its tip and the outer peripheral surface of the first developing sleeve (4a).

Further, a pre-doctor (1) serving as a regulating member in a previous stage is provided at a portion located near the developer accommodating member (5).
3) is disposed with a relatively small gap kept between its tip and the outer peripheral surface of the first developing sleeve (4a). In the embodiment of the present invention, the predoctor (13) extends the developer accommodating member (5) and is integrally formed.
Similarly, a second developing doctor (6b), which is a means for regulating the developer, is disposed near the second developing sleeve (4b).
The second developing sleeve (4b) is provided with a relatively small gap between the tip and the outer peripheral surface of the second developing sleeve (4b).

The developer accommodating portion (5a) has a sufficient space for circulating the developer (11) within a range where the magnetic force of the first developing sleeve (4a) can reach. The facing surface (3b) is formed over a predetermined length so as to be inclined downward from the toner hopper (8) side toward the first developing sleeve (4a) side. With the above configuration,
From inside the toner hopper (8), the toner agitator (1)
The toner (7) sent out by (0) is supplied to the developer (11) carried on the first developing sleeve (4a) through the toner supply opening (9), and is supplied to the developer container (5).
transported to a). The developer (11) in the developer accommodating portion (5a) is carried on the first developing sleeve (4a) and passes through the second developing sleeve (4b) to the outer peripheral surface of the photosensitive drum (1). The toner image is formed on the photosensitive drum (1) by being conveyed to a position opposite to the photosensitive drum (1), and only the toner (7) is electrostatically combined with the electrostatic latent image formed on the photosensitive drum (1). Is done. Developer (1)
1) returns to the first developing sleeve (4a) again, replenishes the toner (7) as needed, agitates it, and prepares for the next development.

Here, the behavior of the developer (11) when forming a toner image will be described with reference to FIG. The first developing sleeve (4a) and the second developing sleeve (4b) have a magnet (not shown) as a magnetic field generating means disposed in the interior thereof at a position relative to the developing device. As described above, the magnet is composed of four magnetic poles P1, P2, P3, and P4, and the respective polarities are alternately arranged as N, S, N, S (the opposite is also possible). A so-called starting agent in which the magnetic carrier and the toner (7) are mixed in a predetermined ratio in advance is set in the developing device (2), and when the first developing sleeve (4a) rotates, as shown in FIG.
The transport of the developer (11) is regulated by a relatively narrow gap between the first developing doctor (6a) and the pre-doctor (13) and is magnetically attached to the surface of the first developing sleeve (4a) (A).
There are two types: a type (B) that is accommodated in the developer accommodating part (5a) and circulates, and a type (C) that stays upstream of the pre-doctor (13).

Next, the toner (7) is added to the toner hopper (8).
Is set, the toner (7) is supplied from the toner supply opening (9) to the developer (11) carried on the first developing sleeve (4a). The developer (11) and the newly supplied toner (7) are stirred and charged in the circulating section (B) in the developer accommodating section (5a) to be uniform. Developer (1
As the ratio (toner density) of the toner (7) in 1) increases, the fluidity of the developer (11) decreases, and the amount of the developer (11) that can pass through the predoctor (13) decreases.
Grows greatly (C ′). Retention part at this time (C ')
Surface has no movement due to the decrease in fluidity, and toner (7)
Supply stops. As the photoreceptor-like electrostatic latent image is developed, the toner concentration decreases, the fluidity of the developer (11) increases, and the stagnant portion (C ′) decreases (C). Then, the supply of the toner is restarted.

Further, P1 (N) and P4 (S), and P2 (S) and P3 (N) have opposite polarities at a portion where the first developing sleeve (4a) and the second developing sleeve (4b) face each other. They are arranged so as to face each other. As a result, the developer (11) smoothly moves from the first developing sleeve (4a) to the second developing sleeve (4b) and vice versa from the second developing sleeve (4b) to the first developing sleeve (4a). During this transition, the developer (11) self-circulates, so that local unevenness in toner density is reduced.

In developing a photoreceptor-like electrostatic latent image,
In order to prevent background contamination, it is customary to apply a developing bias intermediate between a bright portion potential and a dark portion potential of the electrostatic latent image to the developing sleeve, but a first developing sleeve (4a) and a second developing sleeve are applied. If there is a potential difference in (4b), the toner (7) moves to one of them, and toner filming that becomes black with the toner (7) occurs. In the present invention, in order to prevent this, both are kept at the same potential by a power supply (not shown).

[0017]

As described above, by having the second developing sleeve as the second developing carrier, it is possible to increase the amount of stored developer and provide a developer storage having a long life of the developer. In addition, since different magnetic poles are arranged at opposing portions of the first developer sleeve and the second developer sleeve, which are the two developer carriers, on the upstream and downstream sides of the closest position, the developer is smoothly transferred, and The developer self-circulates, and a developing device capable of reducing toner filming can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a developing device in an image forming apparatus employing an embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating a behavior of a developer when forming a toner image.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photosensitive drum 2 developing device 3 support case 3a projecting portion 3b facing surface 4a first developing sleeve 4b second developing sleeve 5 developer accommodating member 6a first developing doctor 6b second developing doctor 7 toner 8 toner hopper 9 toner supply opening DESCRIPTION OF SYMBOLS 10 Toner agitator 11 Developer 12 Toner end detection means 13 Predoctor A Magnetically attached part B Circulation part C Retention part C 'Retention part

Claims (3)

[Claims] A first developer carrying member having a magnetic field generating means therein for carrying and transporting a two-component developer containing a toner and a magnetic carrier; and a first developer carrying member carried and transported by the developer carrying member. Regulating member for regulating the amount of developer to be supplied, a developer accommodating portion for accommodating the developer scraped off by the regulating member, and a toner accommodating portion which is adjacent to the developer accommodating portion and supplies toner to the developer carrier. A developing device that changes a contact state between the developer and the toner by changing a toner concentration of the developer on the first developer carrier, thereby changing a toner taking-in state on the developer carrier. A developer storage, comprising: a second developer carrier. 2. The developing device according to claim 1, wherein different magnetic poles are arranged at opposing portions on the upstream and downstream sides of the closest positions of the two developer carriers. 3. The developing device according to claim 1, wherein
A developing device, wherein the potentials of the two developer carrying members are made equal.