JPH1039635A - Two component developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent developing unevenness with a simple construction and improve image quality in a two component developing device. SOLUTION: A static latent image carrier 1 for attracting and holding two component developing agent 2 by magnetic force and a developing agent carrier 4 for carrying the developing agent to an opposite developing area are formed with a magnet 8 positioned and fixed in its inside and a conductive cylinder 9a turnable around the magnet 8 and an elastic layer 9b having volume characteristic resistance of 10<2> -10<12> Ω/cm, same extent as the magnetic carrier and covering outer periphery of the cylinder 9a and a developing gap between the developing agent carrier 4 and the static latent image carrier 1 is set 0. Production cost can be reduced without mounting a mechanism for controlling the developing gap to a proper value. A magnetic member prepared by mixing magnetic power into the elastic layer 9b is not required and the layer can be formed soft and there is not obstacle if the static latent image carrier 1 and the developing agent carrier 4 are contacted at developing and developing unevenness can be prevented. Developing bias can be applied through the elastic layer 9b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-component developing apparatus using a two-component developer composed of a toner and a magnetic carrier.

[0002]

2. Description of the Related Art Conventionally, as a two-component developing apparatus using a two-component developer, a sleeveless developing roll having a plurality of magnetic poles on its surface has been used, for example, as described in JP-A-7-319277. What was known is known.

[0003]

Problems to be Solved by the Invention Japanese Patent Laid-Open No. 7-31927
In the two-component developing device described in Japanese Patent Application Publication No. 7 (1995) -1995, since the two-component developer hangs only at the location where the magnetic pole is present, the degree of contact of the two-component developer with the photoconductor changes according to the pitch of the magnetic pole. There is a disadvantage that development unevenness corresponding to the pitch is generated.

Further, since there are gaps (developing gaps, doctor gaps) of predetermined dimensions between the sleeveless developing roll and the photosensitive member and between the sleeveless developing roll and the doctor blade, these gaps are adjusted to appropriate values. A gap adjusting mechanism to manage is required, which increases the manufacturing cost.

Further, since there is a gap between the sleeveless developing roll and the doctor blade, when the sleeveless developing roll whirls, the layer thickness of the two-component developer changes, and density unevenness occurs.

Accordingly, an object of the present invention is to provide a two-component developing apparatus which can prevent development unevenness and density unevenness with a simple structure.

[0007]

According to the first aspect of the present invention,
Development in which a two-component developer composed of an electrostatic latent image carrier on which an electrostatic latent image is formed, and a toner and a magnetic carrier is attracted and held by magnetic force and transported to a development area facing the electrostatic latent image carrier. In a two-component developing device having a developer carrier and a doctor blade for regulating the layer thickness of the two-component developer on the developer carrier, the developer carrier is provided with a magnet provided in a fixed position therein. a conductive cylindrical body rotatably provided around the magnet, the magnetic carrier and comparable 10 ² -
An elastic layer having a volume resistivity of 10 ¹² Ω · cm and covering the outer periphery of the cylindrical body, and a developing gap between the developer carrier and the electrostatic latent image carrier is set to “0”. I made it.
Therefore, it is not necessary to mix magnetic powder into the elastic layer to form a magnetic material, and the elastic layer can be formed softly by not mixing magnetic powder. And, since the elastic layer is formed softly, even if the elastic layer is brought into contact with the electrostatic latent image carrier and developed, the electrostatic carrier is not damaged and stress is applied to the magnetic carrier. The life of the magnetic carrier is not shortened. Further, the two-component developer can be uniformly pressed against the electrostatic latent image carrier at the time of development, so that development unevenness does not occur. In addition, the volume resistivity of the elastic layer is almost the same as that of the magnetic carrier, and a developing bias can be applied through the elastic layer. There is no need for a developing gap adjusting mechanism for controlling the developing gap between the electrostatic latent image carrier and the developer carrier to an appropriate value, and the manufacturing cost is reduced.

According to a second aspect of the present invention, in the first aspect, the doctor gap between the developer carrier and the doctor blade is set to “0”. Accordingly, since the elastic layer located on the outer peripheral portion of the developer carrier is soft, a two-component developer can be formed even when the doctor gap is set to “0”, and the layer thickness of the two-component developer becomes uniform. And no density unevenness occurs. Further, a doctor gap adjusting mechanism for managing the doctor gap to an appropriate value is not required, and the manufacturing cost is reduced.

According to a third aspect of the present invention, in the first aspect of the present invention, the developed two-component developer which has been adsorbed and held on the developer carrier and once passed through the developing area is peeled off from the developer carrier. A peeling means was provided. Therefore, the developed two-component developer, in which the ratio of the toner is reduced by passing through the developing area, is prevented from being transported again to the developing area as it is, and is absorbed and held by the developer carrier and transported to the developing area. Since the ratio of the toner contained in the two-component developer is always constant, stable developing ability can be maintained.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIG. A photosensitive member 1 serving as an electrostatic latent image holding member is rotatably provided in a direction of an arrow a, and a developer storage housing a two-component developer 2 including a toner and a magnetic carrier at a position close to the photosensitive member 1. The tank 3 is arranged. In the developer storage tank 3, a developer carrier 4 that attracts and holds the two-component developer 2 by magnetic force and transports the developer to a development area opposed to the photoconductor 1, A doctor blade 5 for regulating the layer thickness of the two-component developer 2 and a developer carrier before the two-component developer 2 adsorbed and held by the developer carrier 4 and once passed through the development area is transported to the development area again. A non-magnetic wire 6 as a peeling means for peeling from the body 4 is provided.

The developer carrier 4 is provided with a shaft 7 fixed in position, a cylindrical magnet 8 fixed to the outside of the shaft 7, and rotatable around the magnet 8 in the direction of arrow b. It is formed by the developing sleeve 9 arranged. The developing sleeve 9 is made of a rigid conductive cylinder 9.
a and a nonmagnetic elastic layer 9b covering the outer periphery of the cylindrical body 9a. The elastic layer 9b is formed by using a sponge-like rubber, for example, urethane foam rubber or foam rubber, and is formed softly therein without mixing magnetic powder or the like. The volume-specific low effect of the elastic layer 9b is about 10 ² to 10 ¹² Ω · cm, which is almost the same as that of the magnetic carrier.
It can be energized. The rotational speed of the photoconductor 1 and the developing sleeve 9 is set so that the peripheral speed ratio is in the range of 1-2.

The developer carrier 4 is arranged such that the photoconductor 1 bites into the elastic layer 9b so that the development gap between the photoconductor 1 and the photoconductor 1 becomes "0". The doctor blade 5 holds the surface of the developer carrier 4 (the elastic layer 9) when the two-component developer 2 is not held by suction.
(b surface) so that the doctor gap between the developer carrier 4 and the developer carrier 4 is "0". A developing bias power source 1 is provided between the photoreceptor 1 and the cylinder 9a.
0 is connected.

In such a configuration, the developer storage tank 3
The two-component developer 2 inside the elastic layer 9 b is moved by the magnetic force of the magnet 8.
Is adsorbed and held on the outer peripheral surface. When the development operation starts,
The photoconductor 1 is driven to rotate in the direction of arrow a, and the developing sleeve 9 is rotated.
Is driven to rotate in the direction of arrow b.

When the developing sleeve 9 holding and holding the two-component developer 2 rotates in the direction of the arrow b, the two-component developer 2 held and held by the doctor blade 5 is regulated to a uniform layer thickness. The elastic layer 9 b is formed to be very soft, and the two-component developer 2 adsorbed and held on the developing sleeve 9 is formed.
When passes through the place facing the doctor blade 5,
The elastic layer 9b is compressed in a concave shape. For this reason, no stress acts on the two-component developer 2 between the doctor blade 5 and the developing sleeve 9, and the deterioration of the magnetic carrier caused by the carrier coat film shaving caused by such stress is prevented. Is done.

The two-component developer 2 controlled to have a uniform layer thickness by the doctor blade 5 includes the photosensitive member 1 and the developer carrier 4.
Is transported to a development area where the toner image and the toner image are opposed to each other, and the electrostatic latent image is developed by attaching the toner to the electrostatic latent image on the photoconductor 1. At the time of this development, since the layer thickness of the two-component developer 2 on the developing sleeve 9 is regulated to be constant, no density unevenness occurs.

At the time of this development, even if the developer carrier 4 and the photoconductor 1 are pressed so that the development gap between the developer carrier 4 and the photoconductor 1 becomes "0",
Since the elastic layer 9b is formed softly, the surface of the photoconductor 1 is not damaged. In addition, no stress acts on the two-component developer 2, and the deterioration of the magnetic carrier due to abrasion of the carrier coat film due to such stress is prevented. Further, by bringing the photoconductor 1 into contact with the developing sleeve 9, the contact of the two-component developer 2 with the photoconductor 1 becomes uniform, and no development unevenness occurs.

Further, the rotational speed of the photosensitive member 1 and the developing sleeve 9 is set so that the peripheral speed ratio is in the range of 1 to 2. Since the difference in speed is small, the rotational speed of the photosensitive member 1 and the developing sleeve 9 is small. Abrasion of the surface of the photoreceptor 1 due to the rubbing of the surfaces is prevented.

The developed two-component developer 2 which has been sucked and held on the outer peripheral surface of the developing sleeve 9 and once passed through the developing area is
The toner is consumed by the development, and the ratio of the toner decreases. For this reason, if the developed two-component developer 2 is transported to the development area as it is and used again for development, the developing capacity is reduced due to a decrease in the proportion of toner. However, the developed two-component developer 2 in which the ratio of the toner is reduced by passing through the development area is scraped off the surface of the developing sleeve 9 by the wire 6, and the developed two-component developer 2 is scraped off. After that, the two-component developer 2 containing a predetermined ratio of toner is sucked and held. Therefore,
The ratio of the toner contained in the two-component developer 2 that is adsorbed and held on the outer peripheral surface of the developing sleeve 9 and conveyed to the developing area is always constant, and a stable developing ability can be maintained.

[0019]

According to the first aspect of the present invention, it is not necessary to mix a magnetic powder into a magnetic material in the elastic layer provided on the outer peripheral portion of the developer carrier, and the magnetic layer has a low volume resistivity. The elastic layer can be sufficiently softened because it is 10 ² to 10 ¹² Ω · cm, which is almost the same as that of the carrier, and the developing gap between the developer carrier and the electrostatic latent image carrier is set to “0”. The electrostatic latent image carrier can be developed without being damaged, a developing bias can be applied via an elastic layer during this development, and the electrostatic latent image carrier and the developer carrier can be contacted. By doing so, the two-component developer can be evenly pressed against the electrostatic latent image carrier to prevent uneven development, and even if the electrostatic latent image carrier and the developer carrier are brought into contact, Stress does not act and the life of the magnetic carrier can be extended. Furthermore, it cheaper manufacturing costs since there is no need to provide a mechanism for managing the appropriate value development gap between the electrostatic latent image bearing member and the developer carrying member.

According to the second aspect of the present invention, since the doctor gap between the developer carrier and the doctor blade is set to "0", there is no need to provide a mechanism for managing the doctor gap to an appropriate value. Therefore, the production cost can be reduced, and the layer thickness of the two-component developer can always be kept constant, thereby preventing density unevenness.

According to the third aspect of the present invention, the peeling means is provided for peeling off the developed two-component developer which has been sucked and held by the developer carrier and once passed through the developing area from the developer carrier. The developed two-component developer, in which the proportion of the toner is reduced by passing through the developing area, can be prevented from being transported to the developing area again as it is, and is sucked and held by the developer carrier and transported to the developing area. A stable developing ability can be maintained by always keeping the ratio of the toner contained in the two-component developer constant.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional front view showing an embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 electrostatic latent image carrier 2 two-component developer 4 developer carrier 5 doctor blade 6 peeling means 8 magnet 9a cylinder 9b elastic layer

Claims (3)

[Claims] An image forming apparatus, comprising: an electrostatic latent image carrier on which an electrostatic latent image is formed; and a two-component developer including a toner and a magnetic carrier, which is attracted and held by magnetic force to face the electrostatic latent image carrier. In a two-component developing device having a developer carrier to be transported to an area and a doctor blade that regulates a layer thickness of the two-component developer on the developer carrier, the developer carrier is
A magnet provided in a fixed position therein, a conductive cylinder rotatably provided around the magnet, and a volume resistivity of 10 ² to 10 ¹² Ω · cm, which is almost the same as that of the magnetic carrier. A developing gap between the developer carrier and the electrostatic latent image carrier is set to "0". 2. The two-component developing device according to claim 1, wherein a doctor gap between the developer carrier and the doctor blade is set to “0”. 3. The developing device according to claim 1, further comprising a peeling means for peeling off the developed two-component developer which has been sucked and held by the developer carrier and once passed through the developing area from the developer carrier. Two-component developing device.