JP2646629B2 - Developing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for developing an electrostatic latent image formed on an electrostatic latent image carrier.

2. Description of the Related Art A developing device of this type is applied to an image forming apparatus such as a copying machine or a printer, and a colored fine powder called a toner having a charged charge is electrostatically applied to a latent image by a potential difference between the electrostatic latent image and the developing device. The latent image is developed by being sucked in. As a developer used in such a device,
There are a one-component developer composed of only a powder toner and a two-component developer composed of a powder toner mixed with a fine powder such as a magnetic powder, resin, or glass called a carrier. In a developing device using this two-component developer,
Since the toner is charged by friction with the carrier, the toner can be charged reliably.However, in order to keep the developer concentration constant, the mixing ratio between the toner and the carrier, that is, the toner concentration is always kept constant. Therefore, there is a problem that the toner concentration needs to be controlled, and the carrier needs to be periodically replaced because its characteristics are deteriorated. On the other hand, in a developing device using a one-component developer, such control of the toner concentration is unnecessary, and in this point, it is superior to a device using a two-component developer.

Therefore, recently, a developing device using a one-component developer has been actively proposed. This developing device, for example, stirs a non-magnetic one-component developer housed in a hopper between a developer carrier and an elastic blade that is cantilevered and in contact with the developer carrier. The developer is frictionally charged between the two to form a thin layer of the developer on the surface of the developer carrier, and the developer on the developer carrier holds an electrostatic latent image in a nip area (development area). The electrostatic latent image on the body is electrostatically attracted and developed. The elastic blade is generally mounted such that its free end is located downstream of the fixed end in the moving direction of the developer carrier. However, in such a configuration, since the force of the developer contained in the hopper to push the elastic blade is different depending on the amount of the contained developer, the amount of the developer in the hopper is full. When the distance is close to that, the amount of the developer supplied between the elastic blade and the surface of the developer carrier becomes large, which causes problems such as fog of a latent image, an increase in development density, and scattering of excess developer. I was

To solve this problem, JP-A-61-52664 discloses
A developing device is disclosed in which an elastic blade is attached such that a free end of the developer carrier is located upstream of a fixed end with respect to a moving direction of the developer carrier. This developing device will be described with reference to FIG. In the figure, reference numeral 6 denotes a rotatable photosensitive drum.
The image exposure unit 11 forms an electrostatic latent image corresponding to the original on the photosensitive drum 6. This electrostatic latent image is developed by the developing device 5. The developing device 5 has a hopper 13 containing a nonmagnetic insulating toner 12, and a toner supply port is formed at one end 14 of the hopper 13. Reference numeral 15 denotes a developing roller which is a developer carrier, for example, a surface 15a of a metal roller such as SUS or Al is formed in an uneven shape,
It is configured to be driven to rotate in the direction of the arrow. The developing roll 15 is provided at the toner supply port 14 of the hopper 13 and is mounted at a position facing the photosensitive drum 6 with a certain gap.

Reference numeral 16 denotes an elastic blade, which is formed of, for example, a material such as rubber, resin, or metal. The elastic blade 16 moves the photosensitive drum 6 and the developing roll in the moving direction of the developing roll 15.
It is provided so as to be in pressure contact with the developing roll surface 15a on the upstream side of the position facing the developing roller 15 and on the downstream side of the toner supply port 14. Further, the free end 16a of the elastic blade 16 is located upstream of the fixed end with respect to the moving direction of the developing roll 15 as shown in the drawing, and the free end 16a is provided so as to face downward. . Reference numeral 17 denotes a protective plate for keeping the pressing force of the elastic blade 16 against the developing roll 15 constant.

However, the toner 12 in the hopper 13 is triboelectrically charged by gravity and friction between the developing roll 15 and friction between the elastic blade 16 and the developing roll 15 by pressure, and the surface 15 of the developing roll 15 is charged.
A thin layer of toner is formed on a. At this time, the toner 12 is restrained on the surface 15a of the developing roll 15 by physical adhesion and electrostatic attraction of the charge of the toner 12. Photosensitive drum 6
The upper electrostatic latent image is developed by the toner adhering to the surface of the developing roll 15 flying by electrostatic attraction. In this conventional apparatus, since the elastic blade 16 is attached as shown in FIG.
There is an advantage that the amount of toner conveyed between the developing roll 15 and the elastic blade 16 does not vary so much depending on the amount of the toner. This is due to the protection plate 17
This is further ensured by keeping the pressing force of the elastic blade 16 against the developing roll 15 constant.

However, in the developing device having the above-described configuration, the developer (toner) stored in the hopper is moved in the direction of the developer carrier (developing roll) by the rotating developer conveying member (agitator). When actively trying to convey, the pressing force of the developer acts on the elastic blade, causing poor charging of the developer, or transferring foreign matter between the elastic blade and the developer carrier. Thus, there has been a problem that the developer thin layer on the developer carrier may be disturbed.

The present invention has been made in view of such a point, and the object thereof is to always uniformly regulate the amount of the developer conveyed between the developer carrier and the elastic blade,
An object of the present invention is to provide a developing device that does not scratch foreign matter between the two.

Means for Solving the Problems There is provided a developer carrying member which carries the developer on the surface thereof and conveys the developer to face the electrostatic latent image carrying member. An elastic member that presses the developer against the developer carrier to form a thin developer layer is provided in pressure contact with the developer carrier so as to be on the upstream side of the fixed end. Further, a transport member for transporting the developer in the direction of the developer carrier is provided in the hopper, and the free end of the elastic member is 90 ° with respect to a line connecting the center of the transport member and the center of the developer carrier. Attach the elastic member so that it becomes {± 15}. Further, a partition portion is provided between the transport member and the developer carrier, and the leading end of the partition portion is located downstream of a line connecting the distal end of the elastic member and the center of the developer carrier in the developer transport direction. So that it is on the side.

Action As described above, the elastic member is attached such that the free end of the elastic member is substantially perpendicular to the line connecting the center of the conveying member and the center of the developer carrier, and The developer contained in the hopper is transported to the developer carrier by the transport member because it is configured to protrude downstream from the line connecting the tip of the elastic member and the center of the developer carrier in the developer transport direction. When the developer is conveyed, the pressing force of the developer is blocked by the partition portion, so that a large pressing force of the toner does not act on the distal end portion of the elastic member.
As a result, a uniform thin developer layer can be formed on the developer carrying member, and poor charging of the developer can be prevented. Furthermore, by regulating the amount of the developer before transporting the foreign matter between the elastic member and the developer carrier, a uniform thin layer can be formed without disturbing the developer layer on the developer carrier. Formation is possible.

EXAMPLES Hereinafter, the present invention will be described in detail based on examples shown in the drawings.

Reference numeral 20 denotes a photosensitive drum that constitutes an electrostatic latent image carrier. It is formed on the photosensitive drum 20. Reference numeral 26 denotes a developing device of the present embodiment for developing the electrostatic latent image, and has a hopper 28 containing a magnetic toner 30. Magnetic toner 30
For example, an insulating toner having a diameter of about 5 to 20 μm
It is composed of a mixture of 0.2 μm magnetite fine particles, and contains about 50% by weight of the magnetite fine particles.
At the bottom of the hopper 28, a developer conveying member (agitator) that rotates in the direction of the arrow shown in the figure is provided. Reference numeral 34 denotes a developing roll housing, which is formed integrally with the hopper 28. A magnetic developing roll 38 is provided in the developing roll housing 34.
Are provided to be rotationally driven in the direction of the arrow shown in the figure. The magnetic developing roll 38 includes, for example, a SU around a fixed magnet.
It is configured to rotationally drive a metal sleeve such as S or Al.

The agitator 32 and the developing roll 38 are mounted so that β = 0 ° ± 15 °, where β is an angle formed by a straight line connecting the center of the agitator 32 and the center of the developing roll 38 with the horizontal line. An elastic blade 40 provided with a silicone gum or the like at a contact portion thereof is in pressure contact with the developing roll 38, and the elastic blade 40 is fixed to a blade holder 42.
The elastic blade 40 is attached to the blade holder 42 such that its free end is located upstream of the fixed end in the rotation direction of the developing roll 38, and the center of the agitator 32 and the developing roll 38 Assuming that the angle between the free end of the elastic blade 40 and the straight line connecting the center is α, α = 90
The elastic blade 40 is fixed to the blade holder 42 so as to be {± 15}. The elastic blade 40 is 50 to 70 g /
The developing roll 38 is pressed against the surface at a pressure of cm.

A partition 36 is provided between the hopper 28 and the developing roll housing 34 over the entire length of the developing roll 38, and the tip of the partition 36 is connected to the tip of the elastic blade 40 and the developing roll.
The developing roller 38 is configured to protrude downstream from the straight line connecting the center of the developing roller 38 in the toner conveying direction by the developing roller 38. 28a
Is a toner supply port for supplying the toner 30 in the hopper 28 toward the developing roll 38.

The magnetic toner 30 in the hopper 28 is conveyed in the direction of the developing roll 38 by rotating the agitator 32 in the direction indicated by the arrow. As described above, the partition 36 is
Agitator since it projects between
The pressing force of the toner conveyed by the block 32 is blocked by the partition section 36, and is not directly applied to the tip of the elastic blade 40. Furthermore, the mounting angle α of the elastic blade 40 is
Since the angle is regulated to 90 ° ± 15 ° as described above, a constant pressure is always applied to the distal end of the elastic blade 40 regardless of the rotation of the agitator 32 in cooperation with the operation of the partitioning portion 36. Will be applied. As a result, a constant amount of toner is always conveyed between the developing roll 38 and the elastic blade 40, and the toner can be uniformly charged by the frictional force with the elastic blade 40. The thin layer of toner formed on the developing roller 38 adheres to the surface of the developing roller by magnetic force and electrostatic force, and is carried to a developing nip (development area) with the rotation of the developing roller 38, and the static layer on the photosensitive drum 20 The electrostatic latent image is electrostatically attracted and developed.

In the above-described embodiment, the case where the magnetic toner is used as the developer has been described. However, the present invention is not limited to this, and can be similarly applied to a developing device using a non-magnetic toner as the developer. Of course, it is.

Effect of the Invention Since the developing device of the present invention is configured as described above in detail, when the developer contained in the hopper is transported to the developer carrier by the transport member, the developer transport pressure is reduced by the elastic member. Is prevented from directly acting on the front end of the developer, so that a uniform amount of developer can always be transported between the developer carrier and the elastic member. This can prevent poor charging of the developer, prevent foreign substances from being squeezed between the elastic member and the developer carrier, and provide a uniform thickness without disturbing the developer layer on the developer carrier. It is possible to form a thin layer.

[Brief description of the drawings]

 FIG. 1 is a schematic configuration diagram of one embodiment of the present invention, and FIG. 2 is a schematic configuration diagram of a conventional apparatus. 20 photosensitive drum, 26 developing device, 28 hopper, 30 magnetic toner, 32 agitator, 36 partition part, 38 developing roll, 40 elastic blade.

Claims (1)

(57) [Claims] A developer carrying member provided opposite to the electrostatic latent image carrying member for carrying and transporting the developer on the surface; a hopper containing the developer; and a hopper in a moving direction of the developer carrying member. An elastic member which is provided in pressure contact with the developer carrier so that its free end is located upstream of the fixed end, and which presses the developer against the developer carrier to form a developer thin layer. In the developing device, a transport member that transports the developer in the direction of the developer carrier is provided in the hopper, and a line connecting the center of the transport member and the center of the developer carrier is provided. The elastic member is attached so that the free end of the elastic member is 90 ° ± 15 °, and a partition is provided between the transport member and the developer carrier. From the line connecting the tip of the body member and the center of the developer carrier, the developer carrier Developing apparatus is characterized in that is projected such that the developer conveying direction downstream side of that.