JP2008145798A - Developing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device capable of regulating a layer thickness of a developer on a developing sleeve by more simple configuration in order to stably form a fine image, and even after the lapse of time, capable of uniformly supplying the developer passed through a regulation member. <P>SOLUTION: The developing device 1 is provided with: a photoreceptor 2; a developing roller 10 opposed to the photoreceptor 2 to carry a developer 4 to a developing part opposed to the photoreceptor 2 by rotation; a magnet 11 having a plurality of magnetic poles arranged in the developing roller 10 in a non-rotational state; and a regulation roller 12 arranged opposite to the developing roller 10 to regulate the layer thickness of the developer 4 carried on the developing roller 10, wherein the regulation roller 12 is movable and a moving direction of the regulation roller 12 is a direction other than a normal direction observed from the developing roller 10. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a developing device using a dry two-component developer composed of a magnetic carrier and a non-magnetic toner, which is used in an image forming apparatus using electrophotography such as a copying machine or a printer.

In general, in a developing device used in various image forming apparatuses such as a copying machine, an electrostatic latent image corresponding to an image is formed on a latent image carrier made of a photoconductor and the like, and is provided in the developing device. A two-component developer consisting of a carrier and a toner is spiked and held on the developer carrying member, and the magnetic brush developer on the developer carrying member is carried into the development area by the transporting action of the developer carrying member. A developing operation is performed by supplying toner to the electrostatic latent image, and a visible image is obtained.
The developer carrying member is provided with a developing sleeve that is generally formed in a cylindrical shape, and a magnet body that forms a magnetic field in the developing sleeve so as to cause the developer to stand on the surface of the developing sleeve. ing. At this time, the carrier constituting the developer is spiked on the developing sleeve along the lines of magnetic force emitted from the magnet body, and the charged toner is attached to the spiked carrier. . The magnet body is formed in a roller shape having a plurality of magnetic poles, etc., and at least one of the developing sleeve and the magnet body is transferred, so that the developer spiked as a magnetic brush on the surface of the developing sleeve is formed. It has been moved. The developer carried into the development area is brought into contact with the surface of the latent image carrier so that the magnetic brush of the developer is bent, and the magnetic brush of the contact developer has a relative linear velocity difference from the latent image carrier. Based on this, toner is supplied while rubbing against the electrostatic latent image.

In the developing device as described above, in order to obtain a good image, it is necessary to make the developer layer thickness on the developing sleeve thin and uniform. Conventionally, the layer thickness on the developing sleeve has been regulated by the fixing regulation plate that has been used for a long time, but the interval between the fixing regulation plate and the development sleeve is constant during long-term use (hereinafter referred to as time). Even in this case, there was a problem that the layer thickness of the developer was lowered. The reason for this is that if the developing sleeve is used for a long period of time, the developing sleeve surface wears, the frictional force between the developing sleeve surface and the developer decreases, and the developer slips at the agent regulating portion where a heavy load is applied. This is thought to be due to a decrease in extrusion force.

  As a method for stably regulating the layer thickness of the developer by changing the pressing force applied to the developer in the agent regulating unit, for example, as in Patent Document 1, the surface is perpendicular to the surface of the developer carrying member. The layer thickness of the developer can be controlled by moving the layer thickness regulating member. However, this method has a problem that a plurality of detection means are required and the apparatus becomes large. In addition, since control is performed after detecting a change in the amount of developer supplied to the regulating roller, there is a time lag from detection to control.

Japanese Patent Application Laid-Open No. 07-234585

  Therefore, in order to solve these problems and stably form a good image, the present invention regulates the layer thickness of the developer on the developing sleeve with a simpler configuration, and passes the regulating member even over time. An object of the present invention is to propose a developing device capable of uniformly supplying the developer amount after the above.

The features of the present invention, which is a means for solving the above problems, are listed below.
The present invention relates to a latent image carrier, a developer carrier that is opposed to the latent image carrier and rotates to convey the developer to a developing unit opposed to the latent image carrier, and the developer carrier. A magnet having a plurality of magnetic poles arranged in a non-rotating manner inside, and a layer thickness regulation for regulating the layer thickness of the developer arranged on the developer carrying body and opposed to the developer carrying body In the developing device including the member, the layer thickness regulating member is movable, and the movable direction is other than the normal direction when viewed from the developer carrier.
According to the present invention, when the layer thickness regulating member moves to the upstream side in the rotation direction of the developer carrier, the interval between the closest point of the developer carrier and the layer thickness regulating member is minimized. It is characterized by that.
The present invention is further characterized in that the distance between the developer carrying member and the closest contact point between the layer thickness regulating member does not change when the layer thickness regulating member moves.
The present invention further provides a simple reduction in the distance between the closest point of contact between the developer carrying member and the layer thickness regulating member when the layer thickness regulating member moves upstream in the rotation direction of the developer carrying member. It is characterized by doing.
The present invention is further characterized in that the magnetic flux density is uniform in the movable region of the layer thickness regulating member.
The present invention is further characterized in that the layer thickness regulating member simply increases the magnetic flux density in the normal direction from the downstream side to the upstream side in the rotation direction of the developer carrier.
The present invention is further characterized in that the position of the layer thickness regulating member can be adjusted by pressing an elastic body.

  As described above, according to the present invention, even when the frictional force between the surface of the developing roller and the developer is lowered during long-time use, and the developer amount regulated by the regulating roller is reduced, the regulating roller Detects a decrease in the developer amount and widens the gap between the regulating roller and the developing roller, or moves the regulating roller in a direction where the magnetic flux density in the normal spring direction is strong, so that the developer is always stable in the developing area. The amount can be supplied and a good image can be obtained.

The best mode for carrying out the present invention will be described below with reference to the drawings. In order to achieve the above object, the present invention proposes a developing device characterized in that the position of the layer thickness regulating member is changed according to fluctuations in the amount of developer supplied to the layer thickness regulating member.
That is, it is achieved by the following developing device. A latent image carrier, a developer carrier that opposes the latent image carrier and rotates to convey the developer to a developing unit opposed to the latent image carrier, and a non-developer inside the developer carrier. Development comprising a magnet having a plurality of magnetic poles arranged in rotation and a layer thickness regulating member arranged in parallel with the developer carrier and regulating the layer thickness of the developer carried on the developer carrier In the apparatus, the arrangement of the layer thickness regulating member is movable, and the movable direction is determined by a straight line passing through the developer carrying member, the closest point of the layer thickness regulating member, and the center of the developer carrying member. The restriction member does not overlap before and after the movement.

FIG. 1 is a sectional view showing an example of a developing device according to the present invention.
First, it clarifies from the whole structure. The developing device 1 is disposed opposite to a drum-shaped photoconductor 2 which is an example of a latent image carrier, and the photoconductor 2 is rotationally driven in a clockwise direction in the drawing as indicated by an arrow A in FIG. A developing container 3 of the developing device 1 contains a powdery two-component developer 4 having a magnetic carrier and magnetic or non-magnetic toner. The concentration of the developer 4 is kept uniform by the toner and the carrier being stirred and mixed by the first stirring screw 5 and the second stirring screw 6. The developer 4 present in the first stirring screw is pumped up to the developing roller 10 by the magnetic force of the magnet 11 included in the developing roller 10.

  As described above, the developer supplied to the developing roller 10 by the first stirring screw 5 is carried on the developing roller 10 by the rotation of the developing roller 10 and the magnetic force of the magnet 11 provided therein. , And conveyed in the direction of arrow B. That is, first, the developer supplied and carried on the developing roller 10 passes through the regulating roller 12 as shown by the arrow B while being carried on the developing roller 10, and at this time, the excess developer is scraped off as shown by the arrow B1. Taken. The appropriate amount of developer that has passed through the regulating roller 12 passes through the developing region D between the first developing roller 10 and the photosensitive member 2 as indicated by an arrow B2, and then leaves the developing roller 10 and moves into the developing container 3. It flows to the bottom and is stirred again by the first stirring screw 5. When the developer 4 is conveyed and agitated as described above, the toner and the carrier are triboelectrically charged in opposite polarities, and when the developer passes through the development region D as described above, the toner in the developer Is electrostatically transferred to the electrostatic latent image formed on the photosensitive member 2, and the latent image is visualized.

FIG. 2 is a diagram illustrating in detail the movement of the regulating roller shown in FIG.
The developer 4 carried on the developing roller 10 from the stirring screw 5 is conveyed to a region C in front of the regulating roller by the magnetic force of the magnet 11 included in the developing roller 10 and the rotation of the developing roller 10. Since the amount of developer carried on the developing roller 10 from the stirring screw 5 is larger than the amount of developer that can pass through the regulating roller 12, the passing amount is regulated by the regulating roller 12. For this reason, the developer that could not pass through the regulating roller repeats recirculation until it passes through the regulating roller while being held in the region C before the regulating roller. When the amount of the refluxing agent increases, the developer gradually accumulates and is compressed in the area C before the regulating roller, so that the load applied to the regulating roller 12 or the developing roller 10 also increases. When the amount of developer after passing through the regulating roller 12 decreases with time, the amount of developer carried on the developing roller 10 from the stirring screw 5 is constant, whereas the amount of developer passing through the regulating roller 12 Therefore, the amount of developer that recirculates in the area C before the regulating roller increases. As a result, the load applied to the regulating roller 12 also increases.

  At this time, the present invention is configured to increase the amount of developer after passing through the regulating roller 12 in accordance with the pressure applied to the regulating roller 12 and to supply a constant amount of developer as a result. The mechanism is as follows. The distance (hereinafter referred to as “regulation gap”) between the restriction roller 12 and the developing roller 10 is the longest when the restriction roller takes G2 which is the most upstream in the developing roller rotation direction E and takes G1 which is the most downstream. The movable region of the regulating roller 10 is configured so as to be the shortest. Further, the restriction gap is configured to simply become longer as the restriction roller moves from the upstream side to the downstream side. Consider a case where an elastic body is used as the operating means of the regulating roller 10. In the initial state where the developer amount does not decrease after passing through the regulating roller, development is performed from the load pressing the regulating roller 10 downstream with respect to the developing roller rotation direction E by the elastic body and the developer existing in the region C before the regulating roller. The load applied to the regulating roller on the upstream side with respect to the roller rotation direction is balanced. When the amount of developer after passing through the regulating roller decreases, the amount of developer that flows back in the region C before the regulating roller increases, and the load applied to the regulating roller 12 increases, the regulating roller 12 develops. It moves upstream with respect to the roller rotation direction E. Since the restriction gap is the shortest distance when it is on the downstream side with respect to the developing roller rotation direction E, the restriction gap widens according to the moving distance, and the amount of developer that can pass through the restriction roller 12 increases.

That is, as shown in FIG. 3, even when the frictional force between the developing roller surface and the developer decreases and the developer becomes slippery in the agent restricting portion, the development that can pass through the agent restricting portion F if the restricting gap is widened. It can be seen that the amount of the agent can be the same, and a configuration in which the amount of variation in the interval at this time can be controlled by the load applied to the regulating roller.
At this time, it is desirable to configure the magnet so that the magnetic flux density is uniform in the region where the regulating roller 12 fluctuates. The amount of developer that passes through the regulating roller 12 is influenced by the magnitude of the magnetic flux density in the agent regulating section in addition to the regulation gap. Therefore, if the magnetic flux density is uniform in the fluctuation region of the regulating roller 12, in order to always make the developer amount after passing the regulating roller uniform, only the regulating gap needs to be considered, and the design is simpler. Can do.

  Other embodiments include the following. As described above, the amount of developer passing through the regulating roller 12 is also affected by the magnitude of the magnetic flux density in the agent regulating section. In the case of the two-component developer, the magnetic spikes stand up or fall down as shown in FIG. 4 depending on the magnetic flux density of the magnet contained in the developing roller. In places where the magnetic flux density in the normal direction is high, the developer takes a standing state, and when the magnetic flux density in the normal direction is low, the magnetic spikes fall down. When the layer thickness of the developer is regulated, the amount of developer passing through the regulation roller is reduced as shown in FIG. 5 even when the regulation gap is the same. The amount of developer passing through increases. An embodiment using this relationship is proposed. As shown in FIG. 6, the restriction roller 12 is moved so that the restriction gap G3 is always kept constant.

  In the fluctuation region of the regulating roller 12, when the regulating roller 12 moves to the most upstream side, the normal direction magnetic flux density is maximized, and when the regulating roller 12 moves to the most downstream side, the normal direction magnetic flux density is increased. Arrange the magnets to be the lowest. Further, in the regulation roller fluctuation region, the magnets are arranged so that the magnetic flux density in the normal direction simply decreases from the upstream side toward the downstream side. When the amount of developer after passing through the regulating roller decreases, the amount of developer that recirculates in the area before the regulating roller increases, and the load applied to the regulating roller 12 increases, the same principle as in the first embodiment is used. The regulating roller 12 is configured to move downstream in the rotation direction of the developing roller. At this time, the magnetic flux density in the normal direction in the agent restricting portion is lowered and the magnetic spike is in a collapsed state, so that the amount of developer passing through the restricting roller 12 increases.

It is a figure showing sectional drawing of a developing device. It is a figure explaining the detail of how the regulation roller moves. 6 is a graph showing a relationship between a developer amount regulated by a regulation roller and a regulation gap. FIG. 6 is a diagram illustrating a state of rising of a developer due to a difference in magnetic flux density in a normal direction. 6 is a graph showing a relationship between a magnetic flux density in a normal direction and a developer amount regulated by a regulation roller. It is a figure explaining the detail of the way of movement of a control roller when the fluctuation area | region of a control roller is the same.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Developing apparatus 2 Photoconductor 3 Developing container 4 Developer 5 1st stirring screw 6 2nd stirring screw 10 Developing roller 11 Magnet 12 Control roller

Claims (7)

A latent image carrier, a developer carrier that opposes the latent image carrier and rotates to convey the developer to a developing unit opposed to the latent image carrier, and a non-developer inside the developer carrier. A magnet having a plurality of magnetic poles arranged in rotation and a layer thickness regulating member arranged to face the developer carrier and regulating the layer thickness of the developer carried on the developer carrier. In the developing device,
The developing device, wherein the layer thickness regulating member is movable, and a moving direction thereof is other than a normal direction when viewed from the developer carrier. The developing device according to claim 1,
When the layer thickness regulating member moves to the upstream side in the rotation direction of the developer carrying member, a distance connecting the closest contact point between the developer carrying member and the layer thickness regulating member is minimized. apparatus. The developing device according to claim 1,
The developing device, wherein the distance between the developer carrying member and the closest contact point of the layer thickness regulating member does not change when the layer thickness regulating member moves. The developing device according to claim 2,
When the layer thickness regulating member moves to the upstream side in the rotation direction of the developer carrying member, an interval between the closest point of contact between the developer carrying member and the layer thickness regulating member is simply reduced. Development device. The developing device according to claim 2 or 4,
The developing device, wherein a magnetic flux density in a movable region of the layer thickness regulating agent is uniform. The developing device according to claim 3,
The developing device, wherein the layer thickness regulating member simply increases the magnetic flux density in the normal direction from the downstream side to the upstream side in the rotation direction of the developer carrier. The developing device according to claim 1, 2, 3, 4, 5 or 6.
A developing device characterized in that the position of the layer thickness regulating member can be adjusted by pressing an elastic body.

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