JPS627546B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for developing an electrostatic image by applying a developer thereto.

As a device for developing an electrostatic latent image, for example, in the dry developing process of an electrophotographic copying device, a plurality of magnetic poles are arranged in a cylindrical shape, and a non-magnetic sleeve close to the outer periphery is rotated. A developer containing a magnetic carrier and toner is conveyed to a developing magnetic pole, and the developing agent is made to stand up like a brush at the developing magnetic pole, and the electrostatic latent image on the latent image carrier is lightly rubbed and developed. Sleeve development methods are widely used. In a developing device employing the sleeve developing method described above, for example, as shown in FIG. 1, the developer separated from the sleeve 4 after development is once stirred and sent into a developer reservoir. Then, in order to transport the developer while holding it on the sleeve 4 again from the developer reservoir to the developing magnetic pole position, a magnetic field is created by the magnetic pole inside the sleeve between the developing magnetic pole and the developer reservoir, and the magnetic field reaches the developing magnetic pole. A method is used in which the developer is attached to the sleeve 4 and conveyed.

Therefore, it is necessary to temporarily separate the developer that is magnetically attached onto the sleeve from above the sleeve 4 and stir it.

Particularly in a developing device in which two or more sleeves are lined up as shown in FIG. The spikes at some positions become larger than those at other sleeves, which can cause deterioration in image quality and poor flow of developer. Therefore, among the plurality of developing sleeves, for the sleeve at the last stage where the doctor member for regulating the thickness of the developer is not disposed facing each other, the developer on this sleeve is reliably separated from the sleeve. There is a strong need.

1 and 2, 1 and 8 are electrostatic latent image holding means, 2 and 9 are developing devices, 3 and 10 are magnets in sleeves 4 and 11, and 4 and 11 are non-magnetic sleeves;
5 and 12 are doctor blades that regulate the thickness of the developer on the sleeve; 6 and 13 are developer stirring members in the developing device housing; and 7 and 14 are developer.

Conventionally, to separate the developer from the sleeve surface,
The magnetic field of the part to be separated is made as small as possible to separate the sleeve, or a repelling magnetic field is used to separate the developer, but these methods do not necessarily separate all the developer from the sleeve surface.

Another method is to separate the developer from the sleeve surface by placing a peeling plate parallel to the sleeve in the area where the magnetic field has weakened, but the distance between the plate and the sleeve must be accurate. The drawback was that it required a large amount of developer to be removed from the sleeve, and it was difficult to separate all the developer from the sleeve. Further, the excess friction also accelerates deterioration of the developer.

Therefore, by providing special magnetic poles as mentioned above,
There is a need for a method for easily peeling off the developer at a portion of the sleeve where the magnetic field is weakened without providing a plate parallel to the sleeve.

The present invention aims to solve such conventional problems and to easily and reliably separate the developer from the sleeve surface. Furthermore, it is an object of the present invention to prevent other parts of development from being adversely affected.

Specifically, the lubricant is partially applied to the sleeve surface without changing the contact resistance between the sleeve surface and the developer.

Although it is easy to make the sleeve surface slippery by partially applying lubricant to the sleeve surface, on the other hand, the developer may slip too much on the sleeve and the developer may leak from the developer reservoir to the sleeve. Lifting becomes unstable, and since the sleeve surface is coated with an insulating lubricant, the contact resistance between the sleeve surface and the developer increases, resulting in adverse effects.

The present invention eliminates these drawbacks and provides a developing device that employs a method that reliably separates the developer from the sleeve.

FIGS. 3A and 3B show the surface of a sleeve applied to the developing device according to the present invention. This consists in partially applying a known lubricant to the sleeve surface. This portion not coated with lubricant prevents the developer on the sleeve from sliding excessively on the sleeve, and also prevents the contact resistance between the sleeve surface and the developer from increasing. Therefore, the size of one portion to which the lubricant is applied must be sufficiently smaller than the width of the spikes of developer (width contributing to development).

In the embodiment shown in FIGS. 3A and 3B, there are a number of V-shaped grooves 16 in the axial direction on the surface of the sleeve 15, and these grooves prevent the developer on the sleeve from sliding on the sleeve surface. There is. Therefore, if the above-mentioned lubricant is applied to the sleeve surface other than the V-shaped groove to provide appropriate lubricity, the developer will not slip on the sleeve and the contact resistance between the sleeve surface and the developer will be reduced. It is possible to easily remove the developer from the sleeve without increasing the amount.

Any known method can be used to apply the lubricant onto the sleeve, such as dispersing fluororesin powder in a solvent and applying it by a known spray method. In this method, it is difficult to coat the V-shaped grooves on the sleeve surface, and furthermore, the sleeve surface has areas 17 where it is coated and areas 16 where it is not coated.
It is very good because it can be done.

In FIGS. 1 and 2, the developer on the sleeves 4, 11 passes the development position and passes the last magnetic pole, and reaches a portion on the sleeve where the magnetic field is weak. Since the magnetic field is weak in this part, there is not enough force to keep the developer on the sleeve on the sleeve, so the developer is shaken off from the sleeve by the centrifugal force caused by the rotation of the sleeve. Incidentally, even when the magnetic field weakens, the developer tends to continue to adhere to the sleeve due to mechanical adhesion, but in the present invention, the developer is intermittently coated with a slippery substance (lubricant) on the sleeve surface. Since the sleeve is coated to weaken the mechanical adhesion, it becomes possible to shake off all the developer on the sleeve at the position where the magnetic field is weakened.

FIG. 4 shows lubricant 19 intermittently applied on sleeve 18.
This is an example of trying to achieve the intended purpose by applying the same.

As described above, the present invention includes a rotating non-magnetic sleeve and a plurality of magnetic poles arranged within the sleeve along the direction of rotation of the sleeve, and a developer containing a magnetic carrier and toner in the sleeve. The electrostatic image on the electrostatic image holding means is developed by carrying the developer to the developing position, and at the same time, the magnetic field by the magnetic pole is weakened at the post-development position, and at this position, the developed developer is transferred to the sleeve. In a developing device that is separated from the sleeve and agitates the developer separated from the sleeve, the surface of the sleeve is intermittently coated with a material on which the developer is more slippery (i.e., lubricant) than the material of the sleeve. Since the developing device is characterized by It has the effect of Furthermore, when the well-known styrene-based toner used in an electrophotographic developing device is supported on a well-known sleeve made of aluminum or the like, the present invention makes it easy to remove the developer from the sleeve surface after development, and makes it possible to easily remove the developer from the sleeve surface and the development surface. This is particularly effective because the contact resistance of the agent can be prevented from increasing. The durability of such a lubricating effect is extremely good and can be maintained for a period equal to or longer than the life of the electrostatic image holder used.

[Brief explanation of the drawing]

1 and 2 are explanatory diagrams showing an example of an electrophotographic developing device to which the developing device according to the present invention can be applied, and FIG.
Figure A is a perspective view of an example of a sleeve applied to the developing device according to the present invention, Figure B is a cross-sectional view thereof, and Figure 4
The figure is a perspective view of another example of the sleeve applied to the developing device according to the present invention. 4, 11, 15, 18...developer supporting means,
1, 8... Electrostatic image holding means, 7, 14... Developer, 17, 19... Substance with good lubricity.

Claims (1)

[Claims] 1. It has a rotating non-magnetic sleeve and a plurality of magnetic poles arranged in the sleeve along the direction of rotation of the sleeve, and the sleeve supports a developer having a magnetic carrier and toner and transports it to a development position. to develop the electrostatic image on the electrostatic image holding means, and at the same time weaken the magnetic field by the magnetic pole at a position after development, and at this position, the developer after development is separated from the sleeve and separated from this sleeve. What is claimed is: 1. A developing device for agitating the developer, characterized in that the surface of the sleeve is intermittently coated with a material on which the developer is more slippery than the material of the sleeve.