JPH10171246A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel developing device capable of reducing the density unevenness of an image caused by vibration in a direction perpendicular to the axial directions of an image carrier and a developer carrier. SOLUTION: An elastic layer is formed on the surface of a developing sleeve 4 and reaction against the restoring force of the elastic layer accompanying the deformation of the elastic layer is exerted thereon, at a position where the elastic layer is deformed by contact with a photoreceptor drum 1, by using fixing members 11 having bearing parts 12 freely rotatably supporting the shaft parts 4a of the developing sleeve 4. Thus, this sleeve 4 is positioned against the drum 1 and the position of the sleeve 4 with respect to the drum 1 is maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used in an image forming apparatus such as a copying machine, a facsimile, a printer, etc., and more particularly, it includes a toner and a magnetic carrier carried on the surface of a developer carrying member. The present invention relates to a developing device for developing a latent image on an image carrier by transporting a two-component developer to a development area facing the image carrier.

[0002]

2. Description of the Related Art Conventionally, various methods have been proposed for maintaining a distance between an image carrier and a developer carrier that affect image quality. Among them, a rotary rigid body (hereinafter, referred to as a spacer roller) coaxially supported by a developer carrier is generally known in contact with an image carrier.

However, in the developing device provided with the spacer rollers, the developer that is released or scattered from the developer carrier at the time of development or from the surface of the image carrier after development is generated at the contact surface between the image carrier and the spacer rollers. It was melted by pressurization, forming fine projections on the contact surface between the two. Accordingly, the distance between the axes of the image carrier and the developer carrier fluctuates, and when the image carrier and the spacer roller rotate while being in contact with each other, the image carrier moves along the axis of the image carrier and the developer carrier. There is a problem in that the image vibrates in a direction perpendicular to the direction, and image density unevenness occurs.

In order to solve the above problem, Japanese Patent Laid-Open No.
Japanese Patent Application Laid-Open No. 975-975 discloses an image forming apparatus in which a developer carrier is arranged so as not to contact an image carrier, and a laser spot diameter and an exposure intensity distribution of a laser exposure apparatus are configured to satisfy predetermined conditions. Is disclosed.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above background, and has as its object to provide a direction perpendicular to the axial direction of an image carrier and a developer carrier. It is an object of the present invention to provide a novel developing device capable of reducing image density unevenness caused by vibration of the image.

[0006]

In order to achieve the above-mentioned object, according to the present invention, a two-component developer containing a toner carried on the surface of a developer carrier and a magnetic carrier is provided on an image carrier. A developing device that develops a latent image on the image carrier by transporting the developer to a developing area opposite to the developing device, and an elastic layer formed on the surface of the developer carrier and a two-component developing device that carries the elastic layer. At a position where the elastic layer is deformed by contact with the surface of the image carrier via an agent, the developer carrier is moved with respect to the image carrier against the restoring force of the elastic layer accompanying the deformation. It is characterized by comprising positioning means for positioning.

According to the first aspect of the present invention, the elastic layer formed on the surface of the developer carrier is deformed by contacting the surface of the image carrier via the two-component developer carried by the elastic layer. I do. At a position where the elastic body is deformed, the positioning means opposes the restoring force of the elastic body caused by the deformation, thereby positioning the developer carrier with respect to the image carrier, and the developer carrier with respect to the image carrier. Maintain position.

According to a second aspect of the present invention, in the developing device of the first aspect, a portion of the latent image formed on the image carrier to which toner is to be adhered passes through the development area on the elastic layer of the developer carrier. Sometimes, a developer layer of about one carrier is formed such that most of the toner in the developer on the developer carrier passing through the developing area is used for developing the portion where the toner is to be attached. It is characterized by the following.

According to the second aspect of the present invention, when the portion of the latent image formed on the image carrier to which the toner is to be attached passes through the development area, the latent image formed on the developer carrier passing through the development area is removed. Since most of the toner in the developer is used for developing the portion where the toner is to be attached, even when the developing potentials of the portions where the toner is to be attached are different from each other, a fixed amount of toner always adheres to the portion where the toner is to be attached.

According to a third aspect of the present invention, in the developing device of the first aspect, the positioning means is a fixed member provided with a bearing for rotatably bearing a shaft of the developer carrier. It is a feature.

According to a third aspect of the present invention, a fixing member rotatably bearing a shaft portion of the developer carrying member by a bearing portion causes the elastic body to act as a resistance against the restoring force, thereby causing the developer carrying member to move. It is positioned with respect to the image carrier.

According to a fourth aspect of the present invention, in the developing device of the third aspect, the bearing portion is formed of an elastic body.

According to a fourth aspect of the present invention, the bearing of the fixed member is formed of an elastic body. Therefore, even if vibration generated from a drive system or the like other than between the image carrier and the developer carrier is transmitted to the fixed member, the vibration is absorbed by the bearing portion, and the vibration is applied to the image carrier and the developer carrier. Not easily transmitted. Since the bearing portion needs to rotatably support the shaft portion of the developer carrier, the bearing portion is formed of an elastic body such as Teflon having a relatively small friction coefficient.

According to a fifth aspect of the present invention, in the developing device of the fourth aspect, a bearing is provided inside the elastic portion made of an elastic body in the bearing portion.

In the developing device according to the fifth aspect, a bearing is provided inside the bearing portion made of an elastic body in the bearing portion. Therefore, the shaft of the developer carrying member is easily rotated, and the friction during rotation is reduced as compared with a case where no bearing is provided.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a developing device used in an electrophotographic image forming apparatus will be described below. FIG. 1 is a partial cross-sectional view illustrating a schematic configuration of a developing device according to the present embodiment. The developing device is provided on a side of a cylindrical photosensitive drum 1 used as an image carrier of a copying machine, and has a support case 2 having an opening formed toward the photosensitive drum 1. A developing sleeve 4 serving as a developer carrying member having on its surface a developer 3 composed of a toner and a magnetic carrier (hereinafter, simply referred to as a “carrier”) having exposed portions, and a layer of the developer 3 on the developing sleeve 4 A doctor 6 as a developer regulating member for regulating the thickness,
A power supply 7 for applying a DC developing bias voltage to the developing sleeve 4 is provided.

The support case 2 forms a developer accommodating portion A for accommodating a developer, and an upper end of the support case 2 is a doctor support portion 2a for supporting the doctor 6.

The photosensitive drum 1 and the developing sleeve 4 are rotationally driven such that the surfaces thereof move in the same direction in the developing area.

The developing sleeve 4 comprises a magnet roller 5a comprising a group of fixed magnets, a non-magnetic rigid layer 5b and an elastic layer 5c.

FIG. 1 shows the polarities of the magnetic poles on the surface of the magnet roller 5. Further, as the material of the non-magnetic rigid layer 5b, Al, non-magnetic SUS, or the like can be used, and as the material of the elastic layer 5c, sponge rubber is preferable. In addition, the surface of the elastic layer 5c has a surface roughness Rz (for example, 10 to several tens μm of the same order as the average particle diameter of the carrier) such that the surface of the elastic layer 5c has a concave portion in which a part of the carrier of the developer is embedded.
m). More specifically, when a sponge is used as the material of the elastic layer 5c, a single-cell foam type in which the average diameter of the cells of the sponge is equal to or less than the average particle diameter of the carrier is preferable. When a non-foamed rubber is used, it is preferable that the average interval between the convex portions in the axial direction of the developing sleeve 4 is equal to or less than the average particle size of the carrier. A particle size equal to or less than the particle size is preferred.

FIG. 2 is an enlarged view showing a schematic configuration around the doctor 6. In the present embodiment, when the portion of the latent image formed on the photosensitive drum 1 where the toner is to be adhered passes on the elastic layer 5c of the developing sleeve 4 and passes through the developing region, the toner passing through the developing region is not used. Most of the toner in the developer on the developer sleeve 4 forms a thin developer layer having a thickness of about one carrier, which is used for developing the portion where the toner is to be attached. For this purpose, the doctor 6 is elastically pressed against the developing sleeve 4. In FIG. 2, the stepped screw 8 penetrates a long hole 6a formed in the doctor 6 and is attached to the doctor support portion 2a of the support case, so that the doctor 6 is positioned inside the doctor support portion 2a in the vertical direction (arrow in the drawing). B direction). The spring 9 is attached between the upper end surface of the doctor 6 and the inner wall surface of the doctor support 2a in a compressed state, and the elastic repulsive force of the spring 9 presses the doctor 6 against the developing sleeve 4. . Even when the doctor 6 is brought into contact with the surface of the developing sleeve 4 when the initial setting of the doctor 6 is performed without the developer, the surface roughness of the developing sleeve 4 has the same roughness as the particle size of the magnetic carrier. If so, the developer 3 enters under the doctor 6 and a uniform thin layer can be formed. The layer thickness and uniformity of the thin layer change depending on the surface roughness of the developing sleeve 4. However, if the surface of the developing sleeve 4 is too smooth, it is difficult to form a uniform thin layer. Since the thickness is increased, a surface roughness equivalent to the carrier particle size is preferable. The pressure of the doctor 6 against the developing sleeve 4 can be adjusted by changing the degree of compression of the spring 9 with a doctor pressure adjusting screw 10 attached to the doctor support 2a so as to contact the upper end of the spring 9.
Since the doctor 6 is movable in the vertical direction as described above, even if an excessive force is applied to the doctor 6, the force can be absorbed by the spring 9. The spring 9 is not limited to a wire, and may be an elastic body such as rubber.

By using the developing sleeve 4 in which the elastic layer 5c carrying the developer 3 is made of an elastic material, the elastic layer 5c of the developing sleeve 4 is compressed by the doctor 6 to form a thin layer of the developer at a predetermined level. Can be easily obtained. Also, the developer 3 is not subjected to a large stress,
The toner can be prevented from sticking to the doctor 6. Further, the developer thin layer on the developing sleeve 4 is transported to the developing area, and the developer thin layer is stably pressed against the surface of the photosensitive drum 1 (rigid body) that carries the electrostatic latent image, and the electrostatic latent image is stuck. Development faithful to an image can be performed without unevenness.

In the developing device having the above structure, the developer 3 on the developing sleeve 4 is conveyed with the rotation of the sleeve 4 in the direction of the arrow, regulated by the doctor 6 and
It is thinned to about a layer. This thinned developer 3 is
The photosensitive drum 1 is transported to a developing area facing the photosensitive drum 1 rotating in the direction of the arrow. In the developing area, a magnetic brush made of the developer 3 on the developing sleeve 4 is applied to the photosensitive drum 1.
Most of the toner in the developer is supplied to the electrostatic latent image formed on the drum 1 while being in contact with the surface, and the electrostatic latent image is visualized.

Here, as described above, in order to maintain the position of the developing sleeve with respect to the photosensitive drum, in a developing device in which a rotating rigid body such as a spacer roller is brought into contact with the photosensitive drum, the spacer roller and the photosensitive drum are used. Due to the projection formed on the contact surface with the photosensitive drum 1, the distance between the axes of the photosensitive drum and the developing sleeve fluctuates.
Vibration in the direction perpendicular to the axial direction of the drum and the developing sleeve caused uneven image density. Therefore,
The present embodiment includes a positioning unit that positions the developing sleeve 4 with respect to the photosensitive drum 1 without using a rotating rigid body that is in contact with the photosensitive drum 1 that causes the vibration.

FIG. 3 is a plan view for explaining the positioning means according to this embodiment. At the axial ends of the photosensitive drum 1 and the developing sleeve 4, there is provided a fixing member 11 for rotatably bearing both shafts 1 a, 4 a by bearings 12 thereof. The fixing member 11 is provided on the elastic layer 5 c of the developing sleeve 4.
At the position where the elastic layer 5c is deformed due to contact with the photosensitive drum 1 via the two-component developer, a resistance to the restoring force of the elastic layer 5c due to the deformation is exerted on the elastic layer 5c. As a result, the developing sleeve 4 is positioned with respect to the photosensitive drum 1. In the present embodiment, the elastic layer 5c of the developing sleeve 4 and the photosensitive drum 1 are brought into contact with each other via the two-component developer carried by the elastic layer 5c, so that the photosensitive member is brought into contact with the elastic layer 5c. The amount of penetration of the drum 1 is 0.1m
m or less.

FIG. 4A is a partial sectional view showing the structure of the fixing member 11. The bearing portion 12 of the fixing member 11
Is formed of an elastic body such as Teflon having a small friction coefficient. Therefore, vibration generated from, for example, a drive system or the like other than between the photosensitive drum 1 and the developing sleeve 4 causes the fixed member 1
1 is transmitted to the photosensitive drum 1 and the developing sleeve 4 because the vibration is absorbed by the bearing portion 12.

FIG. 4B is a partial sectional view showing a modification of the fixing member 11. The fixed member 11 has a bearing 12b as a bearing 12 inside an elastic portion 12a made of an elastic body. Therefore, the friction during rotation of the shaft portion 4a of the developing sleeve 4 is reduced as compared with the case where the bearing shown in FIG. 4A is not provided.

As described above, in the present embodiment, the elastic member 5c is formed on the surface of the developing sleeve 4, and the fixing member 11 having the bearing portion 12 for rotatably bearing the shaft portion 4a of the developing sleeve 4 is used. At a position where the elastic layer 5c is deformed by the contact with the photosensitive drum 1, a reaction force against the restoring force of the elastic layer 5c due to the deformation is applied to the elastic layer 5c, so that the developing sleeve 4 is moved to the photosensitive drum 1. , And the position of the developing sleeve 4 with respect to the photosensitive drum 1 is maintained. This positioning means causes the vibration of the photosensitive drum 1 and the developing sleeve 4 in the direction perpendicular to the axial direction of the photosensitive drum 1 to be generated with respect to the photosensitive drum 1 without providing a rotating rigid body in contact with the photosensitive drum 1. Developing sleeve 4
, The occurrence of the vibration is suppressed, and the image density unevenness can be reduced.

Further, in the present embodiment, even when the developing potentials of the toner adhering portions of the latent image formed on the photosensitive drum 1 are different from each other, a fixed amount of toner always adheres to the toner adhering portions. Even when the development potential of the portion where the toner is to be adhered fluctuates, a stable amount of toner can be obtained. Therefore, it is possible to provide a developing device suitable for a digital image forming apparatus capable of maintaining stable image quality without variation in dot image density and size.

Further, by forming the bearing portion 12 of the fixing member 11 from an elastic body, even if vibration generated from a drive system or the like is transmitted to the fixing member 11, the vibration is transmitted to the bearing portion 1.
2, the vibration is hardly transmitted to the photosensitive drum 1 and the developing sleeve 4, so that the influence of the vibration can be avoided.

Further, by using a bearing for the bearing portion 12 of the fixing member 11, friction during rotation of the shaft portion 4a of the developing sleeve 4 is reduced, so that frictional heat is less likely to be generated. Therefore, deterioration of the material can be suppressed. Further, the torque at the time of rotationally driving the developing sleeve 4 can be reduced by the reduction of the friction, so that the driving motor can be downsized. Therefore, the space efficiency can be increased, and the cost of the entire apparatus can be reduced.

[0032]

According to the present invention, the elastic layer is formed on the surface of the developer carrier, and the elastic layer is deformed by the contact with the image carrier at the position where the elastic layer is deformed by contact with the image carrier. The position of the developer carrier relative to the image carrier is maintained by a novel developing device having positioning means for positioning the developer carrier with respect to the image carrier against the restoring force of the layer. This positioning means causes the developer with respect to the image carrier to be provided without providing a rotating rigid body in contact with the image carrier, which causes vibration in a direction perpendicular to the axial direction of the image carrier and the developer carrier. Since the position of the carrier is maintained, there is an excellent effect that generation of the vibration is suppressed and image density unevenness can be reduced.

In particular, according to the second aspect of the present invention, even when the developing potentials of the toner adhering portions of the latent image formed on the image carrier are different from each other, a constant amount of toner always adheres to the toner adhering portions. Accordingly, a stable amount of toner adhesion can be obtained even when the development potential of the portion where the toner is to be attached fluctuates. Therefore, there is an effect that it is possible to provide a developing device suitable for a digital image forming apparatus capable of maintaining stable image quality without variation in dot image density and size.

In particular, according to the third aspect of the present invention, a simple method of providing a fixing member having a bearing portion for rotatably bearing the shaft portion of the developer carrying member is provided by using a simple method. There is an excellent effect that the position can be maintained.

In particular, according to the fourth aspect of the invention, even if the vibration generated from the drive system or the like is transmitted to the fixed member, the vibration is absorbed by the bearing portion, and the vibration is applied to the image carrier and the developer carrier. Is not easily transmitted, so that there is an excellent effect that the influence of the vibration can be avoided.

In particular, according to the fifth aspect of the present invention, friction during rotation of the shaft of the developer carrying member is reduced, so that frictional heat is less likely to be generated. Therefore, there is an excellent effect that deterioration of the material can be suppressed. Further, the torque at the time of rotationally driving the developer carrying member can be reduced by the reduction of the friction, so that the driving motor can be downsized. Therefore, there is an excellent effect that the space efficiency can be increased and the cost of the entire apparatus can be reduced.

[Brief description of the drawings]

FIG. 1 is a front view showing a schematic configuration inside a developing device according to an embodiment of the present invention.

FIG. 2 is an enlarged view showing a schematic configuration around a doctor of the developing device.

FIG. 3 is a plan view illustrating a positioning unit.

FIG. 4A is an enlarged view around a fixing member. (B)
FIG. 10 is an enlarged view around a fixing member according to a modification.

[Explanation of symbols]

 Reference Signs List 1 photosensitive drum 2 support case 2a doctor support part 3 developer 4 developing sleeve 5a magnet roller 5b nonmagnetic rigid layer 5c surface layer 6 doctor 6a long hole 7 power supply 8 stepped screw 9 spring 10 doctor pressure adjusting screw 11 fixing member 12 Bearing part 12a Elastic part 12b Bearing

Claims (5)

[Claims] A two-component developer containing a toner and a magnetic carrier carried on the surface of a developer carrying member is conveyed to a developing area opposed to the image carrying member, whereby a latent image on the image carrying member is transferred. In the developing device for developing, the elastic layer formed on the surface of the developer carrier and the elastic layer are deformed by the contact between the elastic layer and the surface of the image carrier via the two-component developer carried by the elastic layer. And a positioning device for positioning the developer carrier with respect to the image carrier against a restoring force of the elastic layer caused by the deformation at a position where the developer is deformed. 2. The developing device according to claim 1, wherein when the portion of the latent image formed on the image carrier to which toner is to be attached passes through the development area, the elastic layer of the developer carrier. A developing method characterized in that almost all of the toner in the developer on the developer carrier passing through the region forms a developer layer of about one carrier so as to be used for developing the portion where the toner is to be attached. apparatus. 3. The developing device according to claim 1, wherein said positioning means is a fixed member provided with a bearing for rotatably bearing a shaft of said developer carrier. 4. The developing device according to claim 3, wherein said bearing portion is formed of an elastic body. 5. The developing device according to claim 4, wherein a bearing is provided inside the elastic portion made of an elastic body in the bearing portion.