JPS6325667A - Multi-color developing device - Google Patents

Abstract

PURPOSE:To adjust the intensity of a magnetic field for forming a magnetic brush, to surely interrupt toner feeding to a stopped developing device and to prevent the generation of color mixing by arranging a magnetic plate for shielding the magnetic field in a developer carrier so as to reciprocate it. CONSTITUTION:After a start input, the developing operation of a 1st developing device 2 is executed. At that time, the magnetic plate 16 of the 1st developing device 2 is located on a position shown by a full line, toner is stuck to a developing roller 5 by a magnetic field formed by both magnetic poles P4, P5 and residual toner after development is dropped downward by a magnetic plate 16, i.e., a magnetic pole P3. In the magnetic field distribution of a 2nd developing device 3, the magnetic plate 16 is located on a position shown by a broken line and a magnetic field formed by the magnetic poles P4, P5 is shielded to suppress the sticking of toner. Consequently, the 1st developing device 2 executes normal developing operation and the 2nd developing device 3 executes no developing operation, so that color mixing can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a multicolor developing device, and more particularly to a multicolor developing device equipped with a plurality of developing devices that perform magnetic brush development.

(Prior Art) In a multicolor developing device that performs multicolor development such as twin color, multicolor, and full color, a plurality of developing devices storing toner of each color are arranged close to a latent image carrier. Then, the final color image is obtained by repeating development multiple times for each color toner.

Among such multicolor developing devices, in those that perform magnetic brush development, a developer carrier formed by a magnetic brush is installed inside each developing device.

A developing roller is widely used as a developer carrier for forming this magnetic brush. The developing roller is equipped with a group of magnets for generating a magnetic field inside a cylindrical sleeve, and by rotating at least one of the cylindrical sleeve or the group of magnets, the magnetic brush is divided into a toner supply area, a developing area, and a toner separation area. The farm is rotated between the two.

Thus, each developing device in the multicolor developing device repeats the developing operation selectively for each color, and when one developing device is in the developing operation, the other developing devices are stopped,
Toner is not supplied from the currently stopped machine.

However, even if a developing device that is not performing a developing operation is stopped, the toner attached to the developing roller of the stopped developing device comes into contact with the latent image side, resulting in unnecessary toner supply. Sometimes.

If this happens, the color reproduction of the image will be modulated, resulting in so-called color mixture.

Various proposals have been made to solve this problem. For example, one in which each developing unit independently contacts and separates from the latent image carrier (Japanese Patent Laid-Open No. 49-5195
No. 3, JP-A-52-188332, JP-A-51-11
No. 456, etc.), those in which only the developer carrier moves back and forth (Japanese Patent Laid-Open No. 50-151532, etc.), and those in which the blade comes into contact with and detaches from the developer carrier (Japanese Patent Laid-Open No. 50-151530, etc.) etc.), those in which the developing sleeve can be rotated forward and backward (Japanese Patent Application Laid-Open No. 50-93438, etc.), and those in which the group of magnets in the developer carrier are rotated (Japanese Patent Application Laid-open No. 105832-1987, etc.) Alternatively, a method has been proposed in which a shutter device is provided between the developer carrier and the latent carrier (such as Utility Model Application No. 52-152742). However, each proposal has the problem of lacking simplicity and certainty.

(Purpose) Therefore, the present invention is a multi-color printer that allows the intensity of the magnetic field generated from a group of magnets to form a magnetic brush to be increased/decreased and adjusted reliably with a simple structure.
The purpose is to provide equipment.

(Structure) In order to achieve the above object, the multi-color developing device according to the present invention has a structure in which between the cylindrical sleeve of each developing device and the magnet group,
A magnetic plate is installed to shield a part of the magnetic field, and the magnetic plate is provided so as to be able to be transported back and forth between a position where the developer starts adhering to the cylindrical sleeve and a position where the developer falls. There is.

In a multicolor developing device having such a configuration, when the magnetic plate of each developing device is conveyed to the developer adhesion starting position, the magnetic field that causes the developer to adhere is shielded, and the developer adhesion is interrupted. Ru. On the other hand, when the magnetic plate is conveyed to the image agent falling position, the magnetic field for adhering the developer is returned to its original state, the adhesion of the developer is resumed, and the developing operation is performed.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows twin color copying to which the present invention is applied. Around the photoreceptor drum 1 as an electrostatic latent image carrier, two first imagers 2 are arranged adjacent to the photoreceptor drum 1.
and a second developing device 3 are arranged. Both developing units 2 and 3
have the same configuration, but each developing unit 2, 3 has the following:
Toners of different colors are used.

To explain the developing device 2, a developing roller 5 serving as a developer carrying member is installed so as to close the front end opening of the casing 4.
is pivoted. A paddle roller 6 is installed at the rear of the roller 6 to draw up and supply the toner to the developing roller 5 while agitating the toner. Further, a doctor blade 7 is disposed above the developing roller 5 to form a uniform layer of toner adhered to the developing roller 5, and near the doctor blade 7, a doctor blade 7 is disposed to form a uniform layer of toner adhering to the developing roller 5. A separator 8 and a conveying screw 9 are provided for stirring the toner again.

Furthermore, a toner hopper 1 is provided at the rear of the casing 4.
1 are connected to each other, and a cartridge 12 is removably attached to this toner hopper 11. Inside the toner cartridge 12, an agitator 13 is installed which stores toner and transports the toner to the toner hopper 11 while agitating the toner. Also,
A toner supply roller 13 is provided within the small toner collar 11 .

The developing roller 5 includes a cylindrical sleeve 14 and a group of magnets 15 circumferentially arranged inside the cylindrical sleeve 14. A magnetic brush is formed on the outer surface of the cylindrical sleeve 14 by the magnetic field generated by the magnet group 15. This magnet group 15 includes a plurality of magnetic pole bodies P1. P2. P4.
P5 and P6 are arranged counterclockwise in order from the developing area side. Each of these magnetic pole bodies P1. P2゜P4.
P5. P6 is set in an angular arrangement as shown in FIG. 2, for example.

Further, a magnetic plate 16 is provided between the magnet group 15 and the cylindrical sleeve 14 for shielding the magnetic field. This magnetic plate 16 is formed from a magnetic plate member curved to a predetermined arcuate curvature, and extends in the axial direction of the cylindrical sleeve 14 . As will be described later, it is coaxially supported with the cylindrical sleeve 14,
It is adapted to be rotatably conveyed along the inside of the cylindrical sleeve 14.

This magnetic plate 16 is basically located at the position where the toner remaining on the magnetic brush after development falls, the magnetic pole body P2. P
4 (shown in solid line in FIG. 1), and has the function of a magnetic pole P3 that causes the toner to fall. In other words, the current 1tit& toner is
When the toner reaches the area directly below the magnetic plate 16 serving as the rpt polar body P, the toner falls under its own weight. Further, as shown by the broken line in FIG. 1, the magnetic plate 16 is located at the magnetic pole P4, which is the position where toner starts adhering. It is provided so as to be rotated and conveyed to a position covering P5.

When the magnetic plate 16 is conveyed to this position, both magnetic pole bodies P4.
The magnetic field caused by P5 is shielded, and toner does not adhere.

As shown in FIG. 3, the cylindrical sleeve 14 and the like are provided between both side plates 17, 17 of the casing 4 so as to be coaxially rotated or rotated. That is, one hollow tubular first drive shaft and a second drive shaft 20 are rotatably supported on the side plates 17.17 via bearings 18.18, and the first drive shaft 19 and the second drive shaft 20 are rotatably supported on the side plates 17.17. 2
Within the drive shaft 20, shaft portions 21, 21 of a magnet holder that holds the magnet group 15 are rotatably supported. Both shaft parts 21, 21 of the magnet holder are attached to the rear side plate 23.
and is fixed to the face plate 24.

Further, one end side of the magnetic plate 16 is fixed to the inner flange portion 19a of the first drive shaft 19. on the other hand,
A driven gear 25 is fitted into the externally protruding portion of one of the first drive shafts, and a driving gear 26 is meshed with the driven gear 25. The driving gear 26 is driven by a drive motor (not shown). The magnetic plate 16 is rotated as a result. A stepping motor (pulse motor) is used as the drive motor, and by rotating this stepping motor in the forward or reverse direction, the magnetic plate 16 is moved to the toner falling position (the first
solid line position in the figure) and toner adhesion start position (dashed line position in Figure 1)
It is designed to be rotated and conveyed between the two. In this case, since the rotational positioning accuracy of the magnetic plate 16 can have a margin of several degrees, sufficient positioning accuracy can be obtained using only the stepping motor.

In addition, the (l!2 end (right end in Fig. 2) of the above-mentioned adult root 16
is rotatably supported by the shaft portion 21 of the magnet holder via a bearing 27.

Further, one end portion of the cylindrical sleeve 14 is fixed to a flange portion 20a on the second drive shaft 20 side, and the other end portion is supported by the first drive shaft 19 via a bearing 28. The cylindrical sleeve 14 is constantly rotationally driven through the driven gear 3Q provided on the second drive shaft 20 side and the drive gear 31 that meshes with the driven gear 3Q.

The developing device in such an embodiment is operated as shown in FIG. 8, for example. That is, after the start input is input, first, a viewing operation of the first developing device 2 is performed. At this time, the second developing device 3 is stopped. Then, the first developing device 2
The magnetic plate 16 of (
On the other hand, the magnetic plate 16 of the second imager 3 is being conveyed to the toner adhesion starting position (the state shown by the broken line in the first developing device 2 in FIG. 1). In this case, the magnetic field strength distribution of the first developing device 2 is, for example, as shown by the solid line in FIG. That is, both magnetic pole bodies P4. The toner is adhered to the developing roller 5 by the magnetic field P5, and the residual toner after development falls downward to the magnetic plate 16, that is, the magnetic pole P3. On the other hand, the magnetic field distribution of the second current device 3 is as shown by the broken line in FIG. The magnetic field of P5 is shielded to prevent toner from adhering. As a result, the first developing device 2 performs the developing operation normally, and the -cut toner does not adhere to the developing roller in the second developing device 3. Therefore, toner is not supplied from the second developing device 3 to the latent image side.

When the developing operation by the first developing device 2 is completed and the first developing device 2 is stopped, at the same time, the first developing device 2 and the second developing device 2 are stopped.
Each magnetic plate 16 of the developing device 3 is transported to a toner adhesion start position and a toner fall position, respectively. As a result, toner supply from the first developing device 2 is completely stopped, and the second developing device 3 is placed in a state in which development can be started. Then, the second developing device 3 starts operating, and development with the different color toner is continued.

In this case, the operation of each sleeve 14, paddle roller 6, conveyance screw 9, etc. of the first developing device 2 and the second developing device 3 is started immediately before (for example, 2 seconds before) the first developing device 2 starts developing. . Immediately thereafter, the stepping motor that drives the magnetic plate 16 is activated, and the magnetic plate 16 is conveyed to a predetermined position. In addition, magnetic plate 1
Since the toner removal process by the transfer 6 can be sufficiently performed within 0.5 seconds, the magnetic plate 16 can be driven at a relatively low speed. Setting the speed to be as low as possible is advantageous because durability can be improved and driving load can be reduced.

Furthermore, simply transferring the magnetic plate would not allow the magnetic pole body P2 of the magnet group 15 to move. If the magnetic field due to P3 is significantly increased, it is effective to form the magnetic plate into a double structure as shown in FIG. That is, if a small magnetic plate 37 is provided between the magnetic pole bodies P2 and P4 in the inner region of the magnetic plate 36 to be transferred, both magnetic pole bodies P4. When P5 is shielded, the magnetic pole body P2
There is no problem even if the magnetic force of ゜P becomes stronger.

FIGS. 6 and 7 show other embodiments of the magnetic plate conveyance system. A crank arm 41 is fixed to the rotating shaft 40 of the magnetic plate, and the rolled end of a connecting rod 42 connected to the tip of the crank arm 41 via a crank arm 43 is connected to a drive shaft 44. ing.

The drive shaft 44 is connected to mesh gears 47 and 48 via a sleeve clutch 45 and a spring clutch 46, and the gear 48 is fixed to the drive shaft of the paddle roller 6. Further, a solenoid 49 is disposed near the sleeve clutch 45, and two stoppers protruding from the sleeve clutch 45 approach the tips of the four solenoids to stop the rotation by half a rotation. The magnetic plate is moved back and forth. Note that when the rotation is stopped, the meshing gear 47 is slid inside the spring clutch 46.

If stricter positioning is required, it is also possible to install a positioning plate on the drive shaft 44 in addition to the two stoppers. According to such a drive system, toner scattering and drive torque can be reduced.

Furthermore, in the embodiment shown in FIG. 8, the rotational drive shaft portion of the magnetic plate 16 and the cylindrical sleeve 14 has a double structure,
The drive shaft portion of the magnetic plate 16 is connected to the middle of the drive gear of the cylindrical sleeve 14. In this case, a predetermined positioning can be performed by inserting the spring clutch 46 as described above in the middle of the drive gear.

Furthermore, it is also possible to obtain arcuate motion of the magnetic plate using a reversing electromagnetic clutch or the like.

(Effects) As described above, in the multicolor developing device according to the present invention, a magnetic plate for shielding a magnetic field is installed in a developer carrier so as to be reciprocally transportable, and the strength of a magnetic field for forming a magnetic brush is adjusted. Therefore, the toner supply operation from the stopped developing device can be shut off reliably with an extremely simple configuration, and color mixing can be completely prevented and image quality can be improved. In addition, in the device according to the present invention, since the toner on the developer carrier is completely removed at each development cycle, it is possible to prevent an increase in the internal pressure within the developing device and eliminate toner scattering. You can also do it.

[Brief explanation of drawings]

FIG. 1 is an explanatory longitudinal cross-sectional view of a multicolor phenomenon device according to an embodiment of the present invention, FIG. 2 is a diagram showing the arrangement of each magnetic pole body, and FIG. 3 is a diagram showing the drive system of the developer carrier portion. cross-sectional view, 4th
The figure is a diagram showing the intensity distribution of the magnetic field, FIG. 5 is a cross-sectional view of a developer carrier showing another embodiment of the present invention, and FIG. 6 is a diagram showing another embodiment of the drive system for the magnetic plate. FIG. 7 is a sectional view taken along arrow A in FIG. 6, and FIG. 8 is a longitudinal sectional view showing still another embodiment of the magnetic plate drive system.
B is the flow diagram for the image movement. 1... Photosensitive drum, 2.3... Developing device, 5...
Developing roller, 14... Cylindrical sleeve, 15... Magnet group, 16... Magnetic plate. Figure 1 Figure 2 Figure 3 Figure 5! 4 Figure 3.

Claims (1)

[Claims] Each of the plurality of developing devices arranged close to the latent image carrier is provided with a developer carrier forming a magnetic brush, and the developer carrier is provided with a magnetic field generating member inside a cylindrical sleeve. In the multi-color developing device equipped with a group of magnets, a magnetic plate is installed between the cylindrical sleeve and the group of magnets to shield a part of the magnetic field, and this magnetic plate has the following characteristics: A multicolor developing device characterized in that it is provided so as to be reciprocally transportable between a developer adhesion start position and a developer fall position on a cylindrical sleeve.