JPH01298382A - Electrophotographic copying machine - Google Patents

Abstract

PURPOSE:To prevent a clogging phenomenon caused by the blocking of developer and to obtain stable images for a long time by constituting the title machine so that a sleeve is made to rotate in a direction opposed at the time of development. CONSTITUTION:The title machine is provided with the turnable sleeve 2 for conveying the developer 11a and 11b and a developer regulating part 4 for regulating the quantities of the developer 11a and 11b supplied to the sleeve and the sleeve 2 is made to rotate in the direction opposed at the time of development. Therefore, even if magnetic restraint of magnetic poles 3a-3f in the sleeve to the developer 11a and 11b is small as well as in one-component development system, even if a BSD is narrow and the developer conveying power of the sleeve 2 is weak, the blocking action of the developer caused by the compressing action, etc., of the developer 11a and 11b which occurs on the upstream side of the developer regulating member 4 can be prevented because of stir by making the sleeve 2 reversely rotate. Thus, the clogging and the unevenness of development can be prevented from occurring.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electrophotographic copying apparatus such as a laser beam printer.

BACKGROUND ART Conventionally, as a method for visualizing an electrostatic latent image, for example, in the dry development process of an electrophotographic device, a plurality of magnetic poles are arranged in a cylindrical shape, and a non-magnetic sleeve is placed close to the outer circumference of the magnetic pole. By rotating the developer, the developer is transported from the developer reservoir to a developing magnetic pole located opposite to a latent image carrier such as a photoreceptor, and at this developing magnetic pole, the developer is made to stand up like a brush and is applied onto the latent image carrier. A sleeve developing method is widely used in which development is performed by lightly rubbing an electrostatic latent image. In a developing device that employs the above-mentioned sleeve development method, in order to create uniform spikes of developer on the sleeve with a constant height and developer density at the developing magnetic pole position, the developer is transferred from the developer reservoir to the developing magnetic pole. A developer regulating member is used to regulate the amount of developer on the sleeve during conveyance.

In a developing method using such a sleeve developing device using a magnetic component developer, for example, one made mainly of synthetic resin and containing 25% to 50% magnetic powder, the developer is attached to the sleeve by the magnetic force of the magnet inside the sleeve. Then, the amount of developer regulated by the developer regulating member is conveyed from the developer reservoir to the developing magnetic pole by the rotational force of the sleeve, and after development, the developer separated from the sleeve is stirred once and sent to the developer reservoir again. It will be done. In the one-component development method described above, compared to the two-component development method, for example, in which iron powder or ferrite is used as a carrier, the proportion of magnetic material in the developer is smaller and the magnetic binding force on the developer is smaller, so a magnetic brush is used. Therefore, the distance between the developer regulating member and the sleeve (hereinafter referred to as BSD) and the distance between the photoreceptor and the sleeve (hereinafter referred to as DSD) are set with high accuracy and narrowly. Ta.

Problems to be Solved by the Invention However, in the above configuration, the magnetic restraining force of the magnetic poles in the sleeve on the developer is small, the BSD is narrow, and the developer conveying force of the sleeve is small, so that the upstream side of the developer regulating member In this case, clogging due to blocking of the developer due to the compressive action of the developer is likely to occur, often resulting in image defects. One way to prevent this phenomenon is to agitate the developer by rotating the magnetic poles inside the sleeve in addition to rotating the sleeve, but this method complicates the mechanism and increases the number of rotations of the magnet. If it is too low, uneven development is likely to occur, and if the rotational speed of the magnet is increased to the point where uneven development can be prevented, noise and vibrations are generated, resulting in large power losses.

Another method is to use a small plate-like piece with a thickness smaller than the BSD size to clean the space between the developer regulating member and the sleeve, but cleaning is necessary every time a clogging phenomenon occurs. In addition to having poor serviceability, such as the need to carry out the process, there were also problems in that a dedicated jig had to be prepared in advance.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide an electrophotographic apparatus that is structurally simple and has excellent performance in preventing clogging of a developing device.

Means for Solving the Problems In order to solve the above problems, an electrophotographic apparatus of the present invention includes a rotatable sleeve for conveying a developer, and a developer for regulating the amount of the developer supplied to the sleeve. The sleeve is configured to rotate in a direction opposite to that during development.

Operation The present invention has the above-described configuration, and unlike the -S development method, the magnetic binding force of the magnetic pole in the sleeve to the developer is small.
Even if the BSD is narrow and the developer conveyance force of the sleeve is small, the blocking effect of the developer due to the compressive action of the developer on the upstream side of the developer regulating member can be disturbed by reversing the sleeve, thereby preventing clogging. It is possible to prevent the occurrence of uneven development.

EXAMPLE Hereinafter, an electrophotographic apparatus according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of a main part of a developing device of an electrophotographic apparatus according to a first embodiment of the present invention.

In FIG. 1, 1 is a photoreceptor, 2 is a non-magnetic sleeve,
3a to 3f are fixed magnets, 4 is a developer regulating member, 5 is a scraper, 6 is a holding table, 7 is a developer car 1 cartridge, 8 is a stirring blade, 9 is a holding metal fitting, 10 is a shaft, 11a and 11b are developing devices 12 is a developing container, and 13 is a developing bias power source.

Regarding the electrophotographic apparatus configured as above, the following is the first part.
The operation will be explained using diagrams. The drum-shaped photoreceptor 1 is an organic photoreceptor, and rotates at a speed of 120 mm/sec in the direction indicated by the arrow in the figure. The sleeve 2 is made of non-magnetic stainless steel and rotates in the direction of arrow B in the figure at a speed of 115 rpm. The surface magnetic flux densities of the fixed magnets 3a to 3f in the sleeve 2 are respectively 750G to 950G. The DSD between the photoreceptor 1 and the sleeve 2 is 0.3ff1m, and an output in which 5C and DC voltage are superimposed is applied to the sleeve 2 from the developing bias power supply 13. The developer regulating member 4 is a non-magnetic member that maintains a BSD of 0.15ffIm with respect to the sleeve 2 and the fixed magnet 3! It is installed in a position opposite to L so that it can be adjusted. The scraper 5 is made of phosphor bronze with a thickness of 0.15[111+1] and has an opening in the longitudinal direction at the center, is held in contact with the sleeve 2, and has the function of scraping off the developer on the sleeve 2. are doing.

The developer cartridge 7 is installed at a position where the opening faces the fixed magnet 3f. A stirring blade 8 is provided inside the developer cartridge 7 and rotates in the direction of arrow C around a shaft 1o, and serves to supply the developer to the developing sleeve. The holding fitting 9 holds the stirring blade 8 with respect to the shaft 1o. The developer 111L is an insulating component developer having an average particle size of 1 μm and having synthetic resin and magnetic powder as basic materials and externally adding silica.

The photoreceptor 1 first receives a negative charge (for example, negative) with a DC corona discharger (not shown), and then receives a light image projected by a laser beam or the like (not shown). A high-contrast electrostatic image corresponding to the image information is created. On the other hand, the developer 11b in the developer reservoir is attracted to the sleeve by the magnetic force of the fixed magnet in the sleeve 2, and is conveyed in the direction of rotation of the sleeve 20. On the way, the developer 11b is regulated in flow by the developer regulating member 4, and the spike height is Sleeve 2 has a uniform developer layer.
formed on top. The developer is well charged (for example, negatively) by the above action and the action of the developing bias. This developer layer is conveyed by the sleeve 2, and the electrostatic latent image on the photoreceptor 1 is reversely developed at the position of the fixed magnet 3b, and the remaining toner is further conveyed and scraped off by the scraper 6. The developer is transported through the opening to the developer reservoir and collected.

Among these actions, the actions that the developer in the developer reservoir receives will be explained in detail with reference to FIGS. 2 and 3.

FIG. 2 is an enlarged sectional view of main parts for explaining the action of the developer during printing operation in the electrophotographic apparatus according to the present invention, and FIG. FIG. 3 is an enlarged sectional view of a main part for explaining the action of a developer.

In FIG. 2, the developer 11b in the developer reservoir is attached to the fixed magnet 3.
The magnetic brush formed by the magnetic force of the stationary magnet 3a hits the developer regulating member 4 and receives a force that prevents the developer from being conveyed. In this manner, the developer 11b is subjected to a strong compressive force when passing through the developer regulating member 4, so that a blocking phenomenon occurs partially. When the degree of blocking is weak, the conveying force of the fixed magnet 31L and the sleeve 2, which are constantly working, may act to loosen the blocked developer 11b, but as the developer continues to operate for a long time, the blocking phenomenon occurs. As this progresses, the developer regulating member 4 will eventually become clogged, resulting in image defects.

Therefore, in the electrophotographic apparatus according to the present invention, the sleeve 2 is rotated 80' in the direction opposite to the direction of arrow B after printing is completed. The action of the developer at this time will be explained using FIG.

As understood from FIG. 3, by reversing the sleeve 2 in the direction of arrow B', the developer 11b in the developer reservoir moves away from the developer regulating member 4 as the sleeve 2 moves. Fixed magnet 3! Sleeve 2 drawn to L
The developer is released from the strong compressive force caused by the force of the magnetic brush formed by the magnetic force of the fixed magnet 3a hitting the developer regulating member 4 and preventing the developer from being conveyed. Secondly, since the direction of the magnetic lines of force formed by the fixed magnet changes depending on the rotational position of the sleeve 20, the developer tends to be eaten in the direction of arrangement, and is therefore subjected to a strong disintegrating force. In this way, even if the blocking phenomenon progresses in the developer regulating member 4, the developer is decomposed and further disturbed by these first and second actions, so even if it continues to operate for a long time, the blocking phenomenon will not occur. Since the curing phenomenon does not proceed, clogging of the developer regulating member 4 can be prevented and uneven development will not occur.

FIG. 4 is a block diagram of a drive circuit according to the present invention.

In the figure, 15 is a motor, 16 is a control circuit, and 17 is a drive circuit.

The operation of the drive circuit according to the present invention configured as described above will be explained below using FIG. 4.

The motor 15 is a DC motor, and is equipped with a coil-type sensor that generates a pulse output according to the rotation angle of the motor in addition to a driving coil, and is connected to the sleeve of the developing device by a gear or the like. The control circuit 16 is equipped with a microprocessor, which monitors the rotation speed of the motor 150, controls 0N10FF, and forward/reverse rotation signals. The drive circuit 17 controls the motor 15CION (rotation), 10FF (stop), and normal/reverse rotation based on signals from the control circuit 16.

When the series of printing operations is completed and the motor 16 is turned off (stopped), the pulses from the coil sensor inside the motor are no longer output. Then, the control circuit 16 immediately turns the control signal OFF (stops) for 3 seconds, then changes the rotation direction switching signal to the reverse side and turns the control signal ON (rotation).

Then, the drive circuit 17 causes the motor 16 to rotate.

When the motor 15 enters the reverse rotation operation, the control circuit 1e continues to count the H/L/S generated from the coil type sensor of the motor 16, and when a preset prescribed pulse that adjusts to the reverse rotation angle is counted, the control circuit 1e outputs a control signal. oyy (stop), and the drive circuit 17 stops the motor 15. In this embodiment, after the sleeve 2 performs the reverse rotation, it remains stopped until the next operation starts, but of course, it may be returned to the normal direction after the reverse rotation and then stopped. Further, when the sleeve 2 is reversed, the flow rate cannot be regulated by the developer regulating member 4, so if the sleeve 2 is reversed too much, the developer will be caught between the sleeve 2 and the photoreceptor 1 and crushed, so the reverse angle of the sleeve 2 is 80°. '.

As described above, in the electrophotographic apparatus according to the present invention, by adding an operation of reversing the sleeve at the end of the printing operation, it is possible to obtain a stable image for a long time. Further, in this embodiment, a non-magnetic material is used as the developer regulating member 4, but of course it will also work effectively if a magnetic material is used.

Effects of the Invention As detailed above and as follows, according to the electrophotographic apparatus according to the present invention, by providing a configuration in which the rotation of the sleeve is rotated in the opposite direction to that during development, clogging phenomenon due to blocking of developer can be prevented and a long life can be achieved. It becomes possible to obtain time-stable images. Moreover, it is simple as a device, and can provide a device with excellent serviceability without any troublesome operation or maintenance.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part of an electrophotographic apparatus according to an embodiment of the present invention, and FIG. 2 is an enlarged sectional view of a main part for explaining the action of a developer during a printing operation in an electrophotographic apparatus according to the present invention.
FIG. 3 is an enlarged sectional view of main parts for explaining the action of the developer during the reverse rotation of the sleeve after printing in the electrophotographic apparatus according to the present invention, and FIG. 4 is a block diagram of the drive circuit according to the present invention. 1...Photoconductor, 2...Sleeve, 3&
~3f...Fixed magnet, 4...Developer regulating member, 5...Scraper, 6...
Holding stand, 7...Developer cartridge, 8...
... Stirring blade, 9... Holding fitting, 10...
...Shaft, 11&, 11b...Developer, 12.
...Development container, 13...Development bias power supply, 16...Motor, 16...Control circuit, 17...Drive circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 4
Figure ゝ

Claims (1)

[Claims] A rotatable sleeve for conveying developer, and a developer regulating section for regulating the amount of developer supplied to the sleeve, and for rotating the sleeve in a direction opposite to that during development. Characteristic electrophotographic equipment.