JPH0743973A - Developing bias impressing system for multicolor developing device - Google Patents

Abstract

PURPOSE:To reduce the developer sticking of an electrostatic latent image carrier on the outside of a latent image area by simple constitution and to prevent electric noise from being generated. CONSTITUTION:As for a multicolor developing device executing multicolor developing by using plural developing units attached on a rotating body 5, a developing bias feeding part 15 disposed on a device main body 17 side and developing bias feeding parts 13a-13d which are provided on the rotating body 5 side, and which impress a developing bias on the developing rolls of the respective developing units by being attached and detached to/from the feeding part 15 are provided. Then, when the developing units are faced to the electrostatic latent image carrier at a developing position, the developing bias is impressed after the feeding parts and a power receiving part abut on one another. Thereafter, a developer layer is brought into contact with the electrostatic latent image carrier. When the developing unit are separated from the developing position, the impressing of the developing bias is released after the developer layer is separated from the electrostatic latent image carrier. Thereafter, the feeding parts and the power receiving part are separated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multicolor image forming apparatus such as a copying machine, a facsimile, a printer, etc., which uses electrophotography, and more particularly to a multicolor image forming apparatus having a plurality of developing devices mounted on a rotary member. The present invention relates to a developing bias applying method in a multicolor developing device of a developing type.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for downsizing and cost reduction in multicolor image forming apparatuses using electrophotography. For example, after uniformly charging a photoreceptor, Sequentially, electrostatic latent images of black, yellow, magenta, and cyan are formed, and each latent image is developed by a developing device for black, yellow, magenta, and cyan mounted on a rotating body, and the developed toner image is formed. A method of transferring to a transfer paper on a transfer drum that rotates in contact with the image carrier and rotating the transfer drum four times to transfer the toner images of four colors on the paper in an overlapping manner to obtain a four-color full-color copy (for example, JP-A-6
No. 3-128375) is known.

This will be described with reference to FIG. FIG. 7 shows, for example, only the yellow developing device 4Y of the plurality of developing devices mounted on the rotating body 4. The developing device 4Y is equipped with a developing roll 17 that closely faces and opposes the photoconductor 1.
The developer roll 17 includes a magnet roll 17a for forming a plurality of magnetic patterns, and a developing sleeve 17b rotatably supported on the outer circumference of the magnet roll 17a. An electrode 54 having a predetermined length is fixed to the fixed central axis 4b of the rotating body 4, a contact 55 provided in the developing housing 11 is brought into contact with the electrode 54, and the developing sleeve 17b is connected to the electrode 54 from the power source 51. A developing bias is applied via the contactor 55 and the like.

The developer is attracted to the surface of the developing sleeve 17b by the magnetic force of the magnet roll 17a, a magnetic brush in which magnetic carriers are connected in a spike shape is formed, and the developing sleeve 17b rotates. The developing sleeve 17b and the photoconductor 1 are conveyed to a developing area where they face each other, and the magnetic brush is brought into proximity with or in contact with the photoconductor 1. At this time, a developing bias voltage is applied between the developing sleeve 17b and the photoconductor 1, so that the charged toner is attracted to the photoconductor 1 between the latent image area on the photoconductor 1 and the developing sleeve 17b. Potential is set to
On the other hand, a potential is set between the non-latent image area and the developing sleeve 17b so as to attract the toner to the surface of the developing sleeve 17b. At this time, the contact 55 is the developing device 4Y.
Along with the movement of, the contact 54 starts to contact the electrode 54 from θ ₁ before reaching the developing position, and after the development, the contact 55 separates from the electrode 54 at the θ ₂ position. Therefore, by applying the developing bias to the developing sleeve 17b before and after the developing position,
The developer on the developing sleeve 17b is prevented from adhering to the non-latent image forming area on the photoconductor 1.

[0005]

However, in the above-mentioned conventional developing bias system, the specified voltage value is output from the power source 51 side and the contact between the main body side power feeding section 54 and the developing side power receiving section 55 is opened and closed. Since the application timing will be set, electrical noise will occur when the contacts are opened and closed, and this noise has a problem of not only affecting the main body but also various external equipment, which increases the cost. I have a problem.

The present invention is to solve the above-mentioned problems. In a multi-color developing apparatus of the type which performs multi-color development by a plurality of developing units mounted on a rotating body, the multi-color developing apparatus has a simple structure and is outside the latent image area. SUMMARY OF THE INVENTION It is an object of the present invention to provide a developing bias applying method capable of reducing the adherence of the developer of the electrostatic latent image carrier to the toner and preventing the generation of electrical noise.

[0007]

To this end, the developing bias applying system in the multicolor developing apparatus of the present invention is a multicolor developing apparatus of a system in which a plurality of developing devices mounted on a rotary member perform multicolor development. A developing bias power supply unit disposed on the main body side, a developing bias power supply unit provided on the rotating body side, for applying a developing bias to the developing roll of each developing device by being brought into contact with and separated from the power supply unit, and the developing unit. Is opposed to the electrostatic latent image carrier at the developing position, a developing bias is applied after the power supply unit and the power receiving unit are in contact with each other.
When the developer layer is brought into contact with the electrostatic latent image carrier and the developing device is separated from the developing position, the application of the developing bias is released after the developer layer is separated from the electrostatic latent image carrier. After that, the power feeding unit and the power receiving unit are separated from each other.

[0008]

In the present invention, as the developing device approaches the latent image carrier, the developing bias power source is in the grounded state or in the low voltage output state below the specified value, and the developer layer contacts the latent image carrier. The bias power receiving unit on the developing device side comes into contact with the power feeding unit on the main body side that is grounded or in the low voltage application state before it is started up at the regular voltage applied during development, and then moved to the development position. However, since the length of the power supply section in the developing movement direction is set to be sufficiently long, the developer layer contacts the latent image carrier with a margin after the developing bias is raised to the normal voltage, and the developing device After reaching the developing position, the driving force is transmitted to the developing roll, and the latent image is visualized. When the developing device separates from the latent image carrier, the developing device starts to move after the developing roll stops, the developer layer is separated from the latent image carrier, and before the contact between the developing bias power receiving unit and the power supplying unit opens, The developing bias is switched from the voltage applied at the time of developing to the grounded state or a low voltage output state below a specified value, and finally the contact is opened.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 4 is a configuration diagram showing an example of a multicolor image forming apparatus using a multicolor developing device to which the present invention is applied. The color electrophotographic copying machine 50 includes an automatic document feeder 51, an image input section 52, an image output section 53, and a sheet supply section 54. The color original document is placed on the platen glass 55 by the automatic original document feeder 51. The image input unit 52 includes an imaging unit 56, a wire 57 for driving the unit 56, a drive pulley 58, and the like. A CCD line sensor and a color filter in the imaging unit 56 are used, and in the case of four-color full color, , A color original is read for each of the primary colors of light B (blue), G (green), and R (red), and after being converted into a digital image signal, this signal is the primary colors of toner K (black), Y ( Yellow), M
(Magenta), C (cyan), and further, in order to enhance reproducibility of color, gradation, definition, etc., various data processing is performed to turn on / off the color gradation toner signal. The converted signal is converted and output to the image output unit 53.

The image output section 53 has a scanner 59 and a drum-shaped electrostatic latent image carrier 7 made of an organic photoconductor. Around the electrostatic latent image carrier 7, a charging device 61 and a multicolor developing device. The device 1, the transfer device 63, and the cleaning device 64 are arranged,
The electrostatic latent image carrier 7 is rotationally driven by an electric motor as shown by an arrow. In the laser output section 59a of the scanner 59, for example, a black image signal from the image input section 52 is converted into an optical signal, and the polygon mirrors 59b, f / θ.
A latent image corresponding to the original image is formed on the electrostatic latent image carrier 7 via the lens 59c and the reflection mirror 59d. When this black latent image is transferred to the sheet through development, the electrostatic latent image carrier 7 is charged by the charging device 61 again after the residual toner is removed by the cleaner 64, and the laser output section 59a is yellow. The image signal of is output. Hereinafter, latent images of magenta and cyan image signals are sequentially formed.

The multicolor developing device 1 includes a developing device 2a for cyan,
It has a magenta developing device 2b, a yellow developing device 2c, and a black developing device 2d. Each developing device is arranged around a rotating body 5, and the rotating body 5 can be rotated in a direction indicated by an arrow by a motor (not shown). Has been done. Then, by the time the leading edge of the latent image of the first color reaches the development point, for example, the rotator 5 causes the cyan developing device 2a to reach the development point and drives the developing roll to perform development. The visualized image is transferred to the sheet on the transfer film at the transfer point, and the toner on the electrostatic latent image carrier 11 that is not transferred is cleaned by the cleaning device 64, and then a second color latent image is created. By the time the leading edge of the second color latent image reaches the development point, the rotator 13a rotates 90 degrees clockwise and reaches the magenta developing device 2b to develop. The same cycle is carried out for the third and fourth colors.

A transfer film made of a dielectric film is stretched around the outer periphery of the transfer drum 64 which constitutes the transfer device 63. The transfer drum 64 has a dedicated electric motor or electrostatic latent image carrier 7 and a gear. And are driven to rotate as indicated by arrows. A transfer corotron 65, a pressing member 66, a separation corotron 67, a peeling claw 68, and a charge eliminating corotron 69 are provided inside and outside the transfer drum 64.
A cleaner 70, a suction roll 71, and a suction corotron 72 are arranged.

Then, the paper feed tray 54 of the paper supply unit 54.
The sheet conveyed and fed from a to 54d through the conveying roller 73, the sheet feeding guide 74 and the registration roller 75 is attracted to the transfer film by the pressing action of the suction roll 71 and the corona discharge of the suction corotron 72. The transfer drum 64 rotates in synchronization with the electrostatic latent image carrier 7. For example, when the toner image developed with cyan is transferred onto the sheet by the transfer corotron 65, after one rotation of the transfer drum 64, The toner image developed with magenta is transferred to the paper by the transfer corotron 65, and then yellow,
The toner images developed in black are superimposed and transferred. When the transfer drum 64 makes four rotations and the transfer of the four colors is completed, the paper is neutralized by the separating corotron 67, and then the paper is separated by the peeling claw 68 and sent to the fixing device 77 through the conveying path 76 and the transferred toner image. Is fused and fixed, and this series of copy cycles is repeated thereafter.

5 and 6 show the details of the multicolor developing device shown in FIG. 4, and FIG. 5 is a view seen from the front side of the device shown in FIG.
[Fig. 5] is a view seen from the back side of the device of Fig. 4.

In FIG. 5, a cyan developing roller 2a, a magenta developing roller 2b, a yellow developing roller 2c and a black developing roller 2d are a cyan developing roller 3a, a magenta developing roller 3b and a yellow developing roller 3c, respectively. , A developing roller 3d for black, and each of the developing devices 2a to 2d are arranged around a rotating body 5. The rotating body 5 is rotatably supported by an unillustrated apparatus main body by a rotating shaft 5a at the center thereof. There is. As shown in FIG. 6, each developing device 2a to 2d
Respectively have driven gears 4a, 4b, 4c, 4d,
These driven gears 4a to 4d are connected to the developing rollers 3a to 3 via gear transmission mechanisms 8a, 8b, 8c and 8d, respectively.
It is connected to d. Furthermore, each driven gear 4a-4d
Is a developer agitating and conveying auger 10a, 10 of each of the developing devices 2a to 2d via the gear transmission mechanism 9a, 9b, 9c, 9d.
a '; 10b, 10b'; 10c, 10c '; 10d,
It is connected to 10d '. On the back side of the multi-color developing device 1, a drive gear 6 is arranged on the main body side of the device, and by the rotation of the rotating body 5, a developing device, for example, a developing device 2 for cyan.
When a is located at the developing position A facing the electrostatic latent image carrier 7, the driven gear 4a of the cyan developing device 2a is driven by the drive gear 6
It is designed to mesh with.

Next, one embodiment of the developing bias applying system in the multicolor developing apparatus of the present invention will be described with reference to FIGS. 1 to 3. 1A is a perspective view showing a developing bias applying mechanism, FIG. 1B is a sectional view of FIG. 1A, FIG. 2 is a configuration diagram of a control system, and FIG. 3 is a timing chart.

In FIG. 1, the drive gear 6 described with reference to FIG.
Is connected to a developing roll drive motor 12 via a belt transmission mechanism 11. Further, in the rotating body 5, at the positions near the driven gears 4a to 4d of the developing devices 2a to 2d, the developing bias power receiving units 13a made of conductive brushes,
13b, 13c and 13d are fixed. On the other hand, on the apparatus main body 17 side, a developing bias power feeding unit 15 made of a conductive plate is fixed so as to be able to contact the power receiving units 13a to 13d, and this power feeding unit 15 is connected to a developing bias power source (not shown) via a power feeding cord 16. It is connected. The length of the developing bias power supply unit 15 is set so that the developing bias can be applied to the developing roll with a margin before and after the developing position.

In FIG. 2, the reference signal 19 generated by detecting the predetermined position of the transfer drum is the control device 2
It is input to 0 and various development timings are calculated here,
Based on this, the rotating body driving motor 21, the developing bias power source 22, and the developing roll driving motor 12 are controlled as shown in FIG.

In FIG. 3, the developing bias power supply unit 15 and the developing bias power receiving units 13a to 13d have their contacts at A only for a short time when the rotating body 5 is rotated and the developing devices 2a to 2d are switched. As shown, the contacts of the developing bias power feeding unit 15 and the developing bias power receiving units 13a to 13d are indicated by A before the rotating body 5 rotates and the developing devices 2a to 2d reach the developing position. After that, the developing bias is applied with a high voltage as shown in B, and therefore, as shown in C, even if the developer layer comes into contact with the electrostatic latent image carrier 7, the developer is electrostatically charged. Adhesion to the latent image carrier 7 is prevented. Thereafter, as shown by E, development is performed by rotation of the developing rolls 3a to 3d, and when the development is completed, the rotating body 5 rotates, but even if the developing position is separated, the developing bias power feeding unit 15 and the developing bias power receiving unit 13a to 13d
The contact of is closed and the developing bias is applied,
Similarly, even when the developer layer is in contact with the electrostatic latent image carrier 7, the developer is prevented from adhering to the electrostatic latent image carrier 7. Then, after the developing bias becomes a low voltage or the grounded state, the contacts of the developing bias power feeding unit 15 and the developing bias power receiving units 13a to 13d are opened. Therefore, the developing bias power feeding unit 15 and the developing bias power receiving units 13 a to 13
Since the developing bias is controlled in the state where the contact point of d is closed, the developer adhesion of the electrostatic latent image carrier to the outside of the latent image area can be reduced with a simple configuration, and the electrical noise Occurrence can be eliminated.

FIG. 3F shows a modified example of the control of the developing roll. If the relationship between the switching of the developing bias applied voltage and the opening / closing of the contact of the developing bias power feeding portion / power receiving portion is within the scope of the claims, the developing roll is controlled. The developer layer may be separated from the electrostatic latent image bearing member while it is still rotating. In the example of E, the toner adheres to the surface of the developing roll in a band shape due to the electric field working in the developing nip for a short time while facing the electrostatic latent image carrier with the developing roll stopped. When the strip-shaped portion next faces the electrostatic latent image carrier, a dark strip may appear at a position corresponding to the strip on the print sample, but in the modified example of F, the developing roll stopped. In this state, the time facing the latent image carrier is half that in the embodiment, which also improves the problem of copy quality.

[0021]

As is apparent from the above description, according to the present invention, in a multicolor developing device of a system for performing multicolor development by a plurality of developing devices mounted on a rotating body, the latent image area is simple in structure. It is possible to reduce the adhesion of the developer to the electrostatic latent image bearing member to the outside and prevent the generation of electrical noise.

[Brief description of drawings]

FIG. 1 shows an embodiment of a developing bias applying system in a multicolor developing apparatus of the present invention, FIG. 1 (A) is a perspective view showing a developing bias applying mechanism, and FIG. 1 (B) is a perspective view of FIG. 1 (A). FIG.

FIG. 2 is a configuration diagram of a control system in the present invention.

FIG. 3 is a diagram showing a timing chart for explaining the operation of the present invention.

FIG. 4 is a configuration diagram showing an example of a multicolor image forming apparatus using a multicolor developing device to which the present invention is applied.

5 is a diagram showing the details of the multi-color developing device of FIG. 4, as viewed from the front side of the device of FIG.

6 is a diagram showing the details of the multi-color developing device of FIG. 4, as viewed from the back side of the device of FIG. 4;

FIG. 7 is a diagram showing a developing bias applying system of a conventional multicolor developing device.

[Explanation of symbols]

1 ... Multicolor developing device, 2a-2d ... Developing device, 3a-3d ...
Developing rolls 4a to 4d ... Driven gear, 5 ... Rotating body, 6 ... Drive gear, 7
... electrostatic latent image carrier 12 ... developing roll driving motors 13a to 13d ... developing bias power receiving unit 15 ... developing bias power supplying unit 17 ... device body

Claims (1)

[Claims] 1. A multi-color developing device of a type for performing multi-color development by a plurality of developing devices mounted on a rotating body, a developing bias power supply section disposed on the apparatus main body side, and a developing bias feeding section provided on the rotating body side. A developing bias power feeding portion that applies a developing bias to the developing roll of each developing device by being brought into contact with and separated from the power feeding portion, and a power feeding portion when the developing device faces the electrostatic latent image carrier at the developing position. A developing bias is applied after the contact with the power receiving unit, and then the developer layer is brought into contact with the electrostatic latent image carrier, and when the developing unit is separated from the developing position, the developer layer is electrostatically charged. A developing bias applying system characterized in that the application of the developing bias is released after the developing device is separated from the latent image carrier, and then the power feeding unit and the power receiving unit are separated.