JPH08286480A - Developing device - Google Patents

Abstract

PURPOSE: To prevent the generation of an abnormal image caused by surface staining, etc., by arranging a magnetic body in parallel with a stirring/carrying member in its axial direction. CONSTITUTION: This developing device is provided with a developing sleeve 2 incorporating a developing roller 3 and first and second stirring/carrying screws 4 and 5 as the stirring/carrying member, in a housing 8 formed to be flat, that is, to a rectangular parallelepiped shape. A stirring magnet 12 as the magnetic body is provided in the axial direction of the screw in the part of the housing 8 located in the lower part of the second stirring/carrying screw 5. Thus, a developer therearound is attracted by the magnetic work of the magnet 12 and the attracted developer is carried in a fixed direction by the rotation of the screw 5. Therefore, at the time of stirring/carrying the developer, stress can be applied thereto, so that even if toner is supplied, the toner can be sufficiently electrified and then, supplied to the developing roller 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device mounted on an image forming apparatus such as a copying machine or a laser printer.

[0002]

2. Description of the Related Art Generally, an electrophotographic image forming apparatus prints by the following process. That is, the surface of the photoconductor is uniformly charged by the charger, and image information is formed on the surface as an electrostatic latent image by light irradiation by the optical system. Then, when the electrostatic latent image passes through a position opposite to the developing device, the latent image is visualized by toner adhesion, and the latent image is superposed on the recording paper conveyed at a timing, using a transfer device.
Transfer the toner image to the recording paper. The transferred toner image is fixed on the recording paper by passing through the fixing device.
On the other hand, the residual toner on the photoconductor after the transfer processing is removed by the cleaning device, and the residual charge on the photoconductor is removed by the charge removing device.

In recent years, image forming apparatuses that perform such a series of processes have been downsized and reduced in price.
Needless to say, it is also necessary to reduce the size and cost of the developing unit. Therefore, the diameter of the developing roller is reduced, or, as disclosed in, for example, JP-A-1-134483, the developer is circulated bidirectionally along the longitudinal direction of the developing roller by using two screw-shaped members. Therefore, simplification of stirring and conveying has been put into practical use.

For example, in the case of the two-component developing system, if the developer is not sufficiently triboelectrically charged and supplied to the developing roller, the image quality such as toner scattering and scumming will be adversely affected, so the toner is stored in the developing device. Chargeability to the developer is very important. Nevertheless, due to the miniaturization of each member, it is very difficult to apply a stress sufficient to obtain a necessary and sufficient charge amount to the developer after replenishing the toner. In addition to the downsizing of the developing roller and the agitating / conveying member, the developing roller and the agitating / conveying member are arranged close to each other, so that the distance and time from the replenishment of the toner to the arrival of the toner on the developing roller are shortened and the agitating action The situation is also disadvantageous.

[0005]

Therefore, for example, Japanese Patent Laid-Open No. Hei 5
In Japanese Patent No. 127519, it is proposed to provide a plurality of auxiliary stirring members for moving and stirring the developer in the circumferential direction of the stirring and conveying roller. With such a structure, the agitation property is improved, and the auxiliary agitation member applies stress to the developer to charge it, but the number of parts for agitation increases, and the mechanism becomes complicated. By providing the member, the amount of developer that can be stored in the developing tank is limited. Further, according to the test conducted by the present inventors, the effect of stirring is not improved as expected.

Therefore, the present invention provides a developing device which can sufficiently agitate the replenished toner and developer by the time they reach the developing roller without increasing the complexity of the agitating mechanism to secure a necessary charge amount. This is an issue.

[0007]

In order to solve the above problems, according to the present invention, a developing roller for applying a developer to the surface of an image bearing member, and one end side to the other end side in the axial direction of the developing roller. In a developing device having a stirring / transporting member having a blade portion for transporting and stirring the developer, a magnetized body is arranged in parallel along the axial direction of the stirring / transporting member.

It is preferable that the magnetized body is arranged in a region other than the region in the vicinity of the attached concentration detecting means. Further, it is effective if the magnetic force of the magnetized body changes along the axial direction of the stirring and conveying member.

It is advantageous if the magnetized body is intermittently arranged along the axial direction of the stirring and conveying member. When there are two stirring and conveying members, the magnetized body may be arranged between these stirring and conveying members.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described based on the embodiments shown in the drawings. FIG. 1 schematically shows a main part of a developing device according to the present invention. This developing device is provided with a developing sleeve 2 having a developing roller 3 therein, a first stirring / conveying screw 4 and a second stirring / conveying screw 5 as a stirring / conveying member, in a housing 8 formed flat, that is, in a rectangular parallelepiped shape. Become. The developing sleeve 2 is opened at the front of the housing 8 (see FIG.
Photosensitive drum 1 of the image forming apparatus from the left side in FIG.
1 by a driving means (not shown).
It is rotated counterclockwise as viewed in (b). Further, the developing sleeve 6 has a developing blade 6 as a developer height regulating member for the developing sleeve 2.
Touches the tip.

The first stirring and conveying screw 4 is arranged on the opposite side of the photosensitive drum 1 behind the developing sleeve 2, and the second stirring and conveying screw 5 is arranged behind this first stirring and conveying screw 4, respectively. Sleeve 2, first,
The rotation axes of the second stirring and conveying screws 4 and 5 are parallel to each other. Similarly to the developing sleeve 2, the first and second stirring and conveying screws 4 and 5 are also rotationally driven by driving means (not shown). As can be seen in FIG. 1A, each stirring and conveying screw 4 and 5 has a spiral blade, but the direction of each spiral blade depends on the direction rotated by each drive means. Then, as a result, the conveying directions of the developer by both screws are set to be staggered. For example, when each screw rotates counterclockwise as viewed in FIG.
The second agitating / conveying screw 5 is set so as to convey the developer to the right as viewed in (a) so as to convey to the left.

The first stirring and conveying screw 4 and the second stirring and conveying screw 5 are almost partitioned by a partition plate 11. However, at both ends of the first agitating and conveying screw 4, for example, only a few millimeters are provided for partitioning the developer for delivery. As a result, the developer is circulated between the first and second stirring and feeding screws 4 over the length of the first stirring and feeding screw 4.

Regarding the control of the toner concentration, when the toner concentration detection sensor 10 provided in the housing 8 on the side of the second agitating and conveying screw 5 detects the concentration and it is judged that the toner concentration is lower than a predetermined value, 2 Toner supply port 9 provided in the vicinity of the end of the agitating and conveying screw 5 (see FIG.
From (a), toner is replenished by a toner replenishing device (not shown).

A stirring magnet 12 serving as a magnetized body is provided in a portion of the housing 8 located below the second stirring and conveying screw 5.
(FIG. 1B) is provided along the axial direction of the screw. As a result, the developer around the second agitating / conveying screw 5 is attracted by the magnetic action of the magnet, and the agitating and conveying screw 5 rotates to convey the adsorbed developer in a predetermined direction. In this embodiment, it is the right direction in FIG. As a result, the developer is stressed.

In the above example, the stirring magnet 12 is continuously provided along the axial direction of the screw, but the toner concentration detection sensor 10 is also arranged for the same second stirring and conveying screw 5 to detect the concentration. It is like this. Therefore, the detection sensor 10 is the stirring magnet 1
It may be affected by the magnetic force of 2. Therefore, FIG.
As can be seen in (a), the toner concentration detection sensor 10
The stirring magnet may not be present in the vicinity of, and the stirring magnet 12 may be attached to the other portion of the housing 8 along the screw axis direction. Even if it is arranged in this way, it is the same as that of FIG. 1B as seen in FIG.

In the first example, the stirring magnet 1 is provided along the axial direction of the second stirring and conveying screw 5.
No. 2 has a uniform magnetic force distribution, but as shown in FIG. 3, the magnetic force may have strength along the axial direction. Due to such strength, it is possible to apply stress to the developer in a portion having a strong magnetic force, and it is possible to mix the toner and the carrier well in a portion having a weak magnetic force.

Considering further such a structure for increasing the strength of the magnetic force, as shown in FIG. 4, the stirring magnets 12 may be intermittently arranged in the axial direction of the second stirring and conveying screw 5. With this arrangement, triboelectric charging is accelerated in a portion where the stirring magnet 12 exists and has a magnetic force, and the toner and the carrier are well mixed in a portion where the stirring magnet 12 is absent and the influence of the magnetic force is absent.

Further, in each of the above examples, the stirring magnet 12 exerts a magnetic action only on the second stirring / conveying screw 5, but as shown in FIG. The screw may be provided on a portion of the housing 8 located between the two agitating / conveying screws 5 to act on both screws 4 and 5. With such an arrangement, it becomes possible to apply a frictional force to the developer by both the first stirring and conveying screw 4 and the second stirring and conveying screw 5.

[0019]

According to the first aspect of the present invention, the developing roller for applying the developer to the surface of the image bearing member and the developer is conveyed from one end side to the other end side in the axial direction of the developing roller. In a developing device having a stirring and conveying member having a blade portion for stirring while stirring, since the magnetized body is arranged in parallel along the axial direction of the stirring and conveying member, stress is applied to the developer during stirring and conveying of the developer. Even when the toner is replenished, the toner is sufficiently charged and then supplied to the developing roller, so that the occurrence of an abnormal image such as background stain can be prevented.

According to the second aspect of the present invention, since the magnetized body is arranged in a region other than the area near the attached concentration detecting means, the influence of the magnetized body does not affect the concentration detecting means, and a false detection is made. Since this can be prevented and the frictional charging ability is secured, the effect of claim 1 of preventing the generation of an abnormal image such as background stain can be obtained.

According to the third aspect of the invention, the magnetic force of the magnetized body changes along the axial direction of the stirring and conveying member,
Further, according to the invention described in claim 4, since the magnetized body is arranged intermittently along the axial direction of the stirring and conveying member,
Both improved triboelectric charging ability and improved dispersibility ability are achieved.

According to the fifth aspect of the present invention, when there are two agitating / conveying members, the magnetized body is disposed between the agitating / conveying members, so that the triboelectrification of the developer is performed over a long distance. It becomes possible to do.

[Brief description of drawings]

FIG. 1 is a schematic view of a developing device according to the present invention, in which (a) is a plan view and (b) is a sectional view.

FIG. 2 is a schematic diagram illustrating an embodiment different from FIG.
(A) is a plan view and (b) is a sectional view.

FIG. 3 is a schematic diagram illustrating an embodiment different from FIG.
(A) is a plan view and (b) is a sectional view.

FIG. 4 is a schematic view for explaining still another embodiment, (a)
Is a plan view, and (b) is a sectional view.

FIG. 5 is a schematic view for explaining a further different embodiment, (a)
Is a plan view, and (b) is a sectional view.

[Explanation of symbols]

 2 developing sleeve 4 first stirring and conveying screw 5 second stirring and conveying screw 6 developing sleeve 8 housing 10 toner concentration detection sensor 12 stirring magnet

Claims (5)

[Claims] 1. An agitating / conveying roller having a developing roller for applying a developer to the surface of an image bearing member, and a blade portion for agitating the developing roller from one end side to the other end side in the axial direction of the developing roller. In a developing device having a member, a magnetic device is arranged in parallel along the axial direction of the stirring and conveying member. 2. The developing device according to claim 1, wherein the magnetized body is disposed in a region other than a region in the vicinity of the attached density detecting means. 3. The developing device according to claim 1, wherein the magnetic force of the magnetized body changes along the axial direction of the stirring and conveying member. 4. The magnetized body is intermittently arranged along the axial direction of the stirring and conveying member.
The developing device according to 1. 5. The developing device according to claim 1, wherein there are two agitating / conveying members, and the magnetized body is disposed between the agitating / conveying members.