JPS63249162A - Color image forming device - Google Patents

Abstract

PURPOSE:To extend the life of a distributor and to reduce noises by differentiating the turning-on/off timing of a bias voltage and the distribution timing to the distributor from each other. CONSTITUTION:A bias power source 430 common to plural developing devices 123-125 and a distributor 432 which distributes the bias voltage to developing devices are provided, and the turning-on/off timing of the bias voltage of the bias power source and the distribution timing to the distributor are made different from each other. The distributor 432 is switched a prescribed time Ta after the bias voltage is turned off, and the bias power source 430 is turned on a prescribed time Tb after the distributor 432 is switched. Since the distributor 432 is switched when the bias voltage as a high voltage is not applied, a contact part is not burnt and harmful high frequency noise is not generated.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is suitable for application to an electrophotographic color copying machine, etc., which develops a predetermined color image by switching between a plurality of developing units. The present invention relates to a color image forming apparatus.

[Background of the Invention] In an electrophotographic color copying machine that forms a predetermined color image by overlapping colors on an image forming body such as a photosensitive drum, as shown in FIG. A plurality of developing devices are arranged at 11 predetermined positions.

For example, when recording a color image using three colors of red, blue, and black, developing units 123 to 125 containing red, blue, and black toners are connected to the image forming body in the relationship shown in the figure. 11 while maintaining a predetermined interval in the direction of rotation.

In this case, one color is developed for one rotation of the image forming body 11, and in subsequent rotations, the next development must be formed one on top of the other without disturbing the previously formed development. The processing must be non-contact development as described below. Bias power supplies 430A to 430C are connected to each of the developing units 123 to 125 to obtain a predetermined developing bias, respectively.

The bias power supplies 430A to 430C are required because, in the case of non-contact development, toner particles must be flown from the surface of the developing sleeve provided in the developing units 123 to 125 onto the image forming body 11 or in the opposite direction. This is because it is necessary to provide a flight electric field for this purpose.

Further, the developing bias used in the developing devices 123 to 125 is generally a bias voltage obtained by superimposing a DC voltage on a high voltage AC voltage.

For example, as an AC voltage, 3 K VP-P, 3
A high voltage on the order of KHz is used, and a DC voltage on the order of -500 volts is used.

The bias power supply that generates this bias voltage is
Since it is very expensive, development N123 ~ as shown in Figure 4 is used.
Providing bias power supplies 430A to 430C for each 125 would increase the cost of the device.
It's hard to say that it's a very good idea.

Therefore, as shown in FIG.
0, and by providing a distributor 432 and controlling it in a time-sharing manner to supply bias voltage to predetermined developing units 123 to 125 while distributing it, costs can be reduced by that amount. It will be possible.

The relationship between the bias power supply 430 and the switching signal applied to the distributor 432 is shown in FIG.

A bias voltage is applied to the blue developing device 123 by the switching signal (B in the same figure), and after a predetermined period of time has elapsed,
The same bias voltage is applied to the red developing device 124 (C in the same figure).

In FIG. 4, 121 is a charger, 130 is a transfer electrode, 131 is a separation electrode, and 126 is a cleaning device.

[Problems to be Solved by the Invention] By the way, in the case where the bias power supply is configured to be used in common as described above, as shown in FIG. is continuously supplied, so the distributor 432 only switches it at predetermined time intervals.

However, if the distributor 432 is used with a high voltage applied, the following drawbacks will occur.

First, since a large current flows through the contact portions of the distributor 432 during switching, the contact portions may oxidize, deteriorate, or adhere to each other. This causes the distributor 432 to be damaged.

Second, when switching, noise is generated, which jumps into the microcomputer that controls the system of the device.
The system may malfunction. Alternatively, instantaneous leakage from the developing sleeve to the image forming body 11 also generates high frequency noise, which can also cause the microcomputer to malfunction.

Recorded images may be disturbed by high-frequency noise. This is because, especially when a laser or the like is modulated with a digital signal as in a digital color copying machine, the digital data may be disturbed by noise.

Therefore, the present invention proposes a color image forming apparatus that solves these problems with a simple structure, and achieves longer service life of the distributor and reduced noise.

[Technical Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention has a plurality of developing devices, and the toner contained in each developing device is made to fly onto the image forming body. In a color image forming apparatus that develops a predetermined color image by increasing the voltage, a common bias power source is provided for a plurality of developing devices, and a distributor is provided to distribute the bias voltage to the developing devices. The present invention is characterized in that the on/off timing of the bias voltage and the timing of distribution to the distributor are different.

[Function] The on/off timing of the bias voltage of the bias power supply 430 and the timing of distribution to the distributor 432 are different as follows.

First, after turning off the bias voltage, the distribution M432 is switched after a predetermined time Ta has elapsed.

Then, the bias power supply 430 is turned on after a predetermined time Tb has passed since the distributor 432 is switched.

In this way, the distributor 432 is switched when no high bias voltage is applied, so that the contacts will not burn out or harmful high-frequency noise will be generated.

[Embodiment] Next, a case in which an example of the color image forming apparatus according to the present invention is applied to the above-mentioned color copying machine will be described in detail with reference to FIG. 1 and subsequent figures.

First, an I-shaped color copying machine suitable for application to the present invention will be described with reference to FIG.

A simple color copying machine attempts to record a color image by separating color information into about three types of color information. As described above, black BK, red R, and blue B are exemplified as the three types of color information to be separated.

By turning on the copy button on the device, the document reading section A
is driven, and the original 82 on the original table 81 is optically scanned by the optical system.

This optical system consists of a carriage 84. (2) Consists of a movable mirror unit 88 provided with mirrors 89 and 89°.

The carriage 84 and the movable unit 88 are caused to travel on the slide rail 83 at predetermined speeds and directions, respectively, by a stepping motor 90.

Optical information (image information) obtained by irradiating the document 82 with fluorescent lamps 85 and 86 is reflected on the reflecting mirror 87 and the mirror 89 .
89' to an optical information conversion unit 100.

When optically scanning color originals, commercially available warm white fluorescent lamps are used as the fluorescent lamps 85 and 86 to prevent optical enhancement or attenuation of specific colors, and these fluorescent lamps are used to prevent flickering. Lights 85 and 86 are approximately 40kHz
Can be lit and driven by high frequency power source. In addition, in order to maintain a constant temperature of the tube wall or to promote warm-up, the tube wall is kept warm by a heater using a POSISTOR.

A standard white plate 97 is placed on the back side of the left end of the platen glass 81.
is provided. This is because the image signal is normalized to a white signal by optically scanning the standard white plate 97.

The optical information conversion unit 100 includes a lens 101, a prism 102, a dichroic mirror 103, a CCD 104 that projects a red color-separated image, and a CCD 105 that projects a cyan color-separated image.

Optical signals obtained from the optical system are collected by a lens 101 and separated into red optical information and cyan optical information by a dichroic mirror provided in the prism 102 described above.

Each color separation image is formed on the light receiving surface of each COD, thereby obtaining an image signal converted into an electrical signal.

After the image signal is processed by the signal processing system, each color signal is output to the writing section B.

The signal processing system includes signal processing circuits such as color separation means and binarization means in addition to A/D conversion means.

The writing section B has a deflector 935. As the deflector 935, in addition to a galvanometer mirror or a rotating polygon mirror, a deflector made of an optical deflector using crystal or the like may be used.

The laser beam modulated by the color (= sign) passes through this deflector 9.
Deflection scanning can be completed by 35.

When the deflection scan is started, the beam scan is detected by a laser beam index sensor (not shown), and beam modulation using a first color signal (for example, a blue signal) is started. The modulated beam is caused to scan by a charger 121 over the image forming member (photosensitive drum) 11 which has been uniformly charged.

Here, an electrostatic image corresponding to the first color signal is formed on the image forming body 11 by the main scanning by the laser beam and the sub scanning by the rotation of the image forming body 11.

This electrostatic image is developed by a developer 123 containing blue toner. A predetermined bias voltage is applied to the developing device 123 from a bias power supply 430, which will be described later. A blue toner image is formed by development.

Note that toner supply to the developing device 123 is performed by the system control a-
A toner replenishing means (not shown) is controlled based on instruction No. 43 from the CPIJ (lffl not shown) for the main unit, so that toner is replenished when necessary.

The blue toner image is rotated with the cleaning blade 127 released, and an electrostatic image is formed based on a second color signal (for example, a red signal) in the same manner as in the case of the first color signal, and the red toner image is rotated. This is developed to form a red toner image using a developer 124 containing the toner.

Needless to say, a predetermined bias voltage is also applied to the developing device 124 from the high voltage bias power supply 430.

Similarly, an electrostatic image is formed based on the third color signal (black signal), and the developing device 125 is filled with black toner.
It is developed in the same way as before.

Therefore, a multicolor toner image is written on the image forming body 11.

Note that although the formation of a three-color multicolor toner image has been described here, it goes without saying that a two-color or single-color toner image can be formed.

The development process is a non-contact two-component jumping development process. As described above, this refers to a process in which each toner is ejected toward the image forming body 11 for development while AC and DC bias voltages from a high-voltage bias power source are applied.

Toner replenishment to the developing devices 124 and 125 is performed based on a command signal from the CPU as described above, and a predetermined amount of toner is replenished.

On the other hand, the recording paper P fed from the paper feeding device 141 via the feed roll 142 and the timing roll 143 is
The image forming member 11 is conveyed onto the surface of the image forming member 11 while being timed with the rotation of the image forming member 11 . Then, the multicolor toner image is transferred onto the recording paper P by the transfer pole 130 to which high voltage has been applied from the high voltage power supply, and separated by the separation pole 131.

The separated recording paper P is conveyed to the fixing device 132, where it undergoes a fixing process and a color image is obtained.

The image forming body 11 after the transfer is cleaned by a cleaning device 126 and is prepared for the next image forming process.

In the cleaning device 126, a predetermined DC voltage is applied to a metal roll 128 provided on the blade 127 in order to facilitate recovery of the toner cleaned by the blade 127. This metal roll 128 is the image forming body 1
1 and is placed in a non-contact state on the surface of

After the cleaning is completed, the blade 127 is released from the pressure bond, but in order to remove unnecessary toner that is left behind when the blade 127 is released, an auxiliary cleaning roller 129 is provided, and this roller 129 is rotated in the opposite direction to the image forming body 11 and the pressure bond is removed. By doing this, unnecessary toner is sufficiently cleaned and removed.

FIG. 1 shows an example of a bias supply means for such a developing device. Since the basic configurations of the developers M123 to M125 are almost the same, one of them, for example, bias supply means for the developer 123 is shown.

To explain the structure of the developing device 123, reference numeral 421 indicates a housing, and a cylindrical developing sleeve 422 is rotatably housed within the housing 421. Developing sleeve 4
A magnetic roll 423 having 8 N and S poles is provided inside the magnetic roll 22 . A layer regulating piece 42 is provided on the outer peripheral surface of the developing sleeve 422.
4 is completely pressed, and the layer thickness of the developer attached to the developing sleeve 422 can be regulated to a predetermined thickness. The predetermined thickness refers to a predetermined value from 10 to 500 μm.

Inside the housing 421, first and second stirring members 425, 426 are provided. The developer reservoir in the developer reservoir 429 is moved by the first stirring member 42 which rotates counterclockwise.
5 and a second stirring member 426 that rotates in the opposite direction to the first stirring member 425 so as to overlap each other. The developer adheres to the surface of the developing sleeve 422 and is conveyed by the rotational conveying force of the developing sleeve 422 and the magnetic roll 423 that rotate in the direction.

The static i! formed on the image forming body 11 by the developer deposited on the image forming body 11! The latent image is developed in a non-contact manner.

During development, a developing bias supplied from the bias power supply 430 is applied to the developing sleeve 422. As a result, only the toner T in the developer on the developing sleeve 422 is
By selectively transferring to the surface of the image forming body 11, which has been made into a latent image, it is completely attached to the surface and development processing is performed.

A two-component developer is used as the developer, and when no bias voltage is applied, the image forming body 11 and the developer do not come into contact with each other. The T is caused to fly and is selectively attached to the electrostatic image on the image forming body 11 for development.

When using such a non-contact developing method, when multicolor toner images consisting of a blue toner image, a red toner image, a black toner image, etc. are sequentially developed on the image forming body 11, the previous toner image is It has the advantage that it will not be damaged during subsequent development and can realize thin layer development.

Note that 427 is a replenishment toner container, and 428 is a toner replenishment roller. 431 indicates a development area.

A single bias power supply 430, which is commonly used in the present invention, is provided for the plurality of developing units 123 to 125 configured in this manner.

Then, a predetermined bias voltage is distributed by a distributor 432 and applied to the developing sleeves 422 provided in each of the developing devices 123 to 125. As the distributor 432, a high voltage relay or the like can be used.

The figure shows only the bias supply path to the blue developer 123.

The bias power supply 430 is supplied with power on/off power No. 8 from the control means 433, and the distributor 432 is supplied with a switching signal for switching the contact portions at predetermined intervals.

The control means 433 control the system II of the device as described above.
A microcomputer is used that controls IaI+.

FIG. 2 shows the timing relationship between the on/off signal and the switching signal.

In the present invention, a switching signal for the distributor 432 is generated after a predetermined time Ta has elapsed after the on/off signal (power supply control signal) for the bias power supply 430 is turned off and the bias voltage is cut off.

Then, a predetermined time Tb after switching the distributor 432
The respective timing relationships are selected such that after a period of time, the on/off signal is turned on and a predetermined bias voltage is applied to the distributor 432.

The predetermined time Ta is selected to be at least longer than the fall time of the bias voltage (usually about 50+sec. The same applies to the rise time).

This is because the bias voltage does not immediately become zero even if an on/off signal is supplied to the bias power supply 430.

Similarly, even if the distributor 432 is switched, it does not instantly return to the steady switching state, so this transient time must be taken into account. Therefore, the other predetermined time Tb is set to be at least longer than this transient time. The transient time is usually 1
It is about 00 to 150 seconds. In the embodiment, 'Ta=50 msec and Tb=150 msec are set.

If each time is set in this way and the on/off timing and switching timing are selected, the high bias voltage will be applied and distributed after the distributor 432 has transitioned to a completely stable steady state.

In the above description, three colors, red, blue, and black, are illustrated as examples of colors to be handled, but the present invention is not limited to this example. Of course,
The number of developing devices used is arbitrary.

[Effects of the Invention] As described above, according to the present invention, a predetermined bias voltage is applied after the contact portions of the distributor are completely switched and returned to a steady state.

According to this, there is no burnout of the contact portion, and no high frequency noise is generated when switching the contact.

Therefore, according to the present invention, it is possible to extend the life of the distributor, and also to eliminate adverse effects on microcomputers and the like. Of course, there is no effect on the image data either, so deterioration in recorded image quality can be avoided.

As a result of the above, the present invention is extremely suitable for application to the developing device of the electrophotographic color copying machine as described above.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration around the developing device, which is a main part of the color image forming apparatus according to the present invention, FIG. 2 is a waveform diagram for explaining its operation, and FIG. 3 is a color copying machine applicable to the present invention. Fig. 4 is a block diagram showing an overview of a conventional color image forming apparatus, Fig. 5 is an explanatory diagram of the developing bias, Fig. 6
The figure is a timing chart. 11...Image forming bodies 123-125...Developer 422...Developing sleeve 430...Bias power supply 432...Distributor 433...Control means patent applicant Konishiroku Photo Industry Co., Ltd. No. 1 Figure 123: Phenomenon X

Claims (4)

[Claims] (1) In a color image forming apparatus that has a plurality of developing devices and develops a predetermined color image by causing toner contained in each developing device to fly onto an image forming body, A common bias power source for the developing devices and a distributor for distributing the bias voltage to the developing devices are provided, and the on/off timing of the bias voltage of the bias power source and the timing of distribution to the distributor are different. Color image forming apparatus. (2) The color image forming apparatus according to claim 1, wherein the distributor is switched after a predetermined time has elapsed after the bias voltage is turned off. (3) The color image forming apparatus according to Claims 1 and 2, wherein the bias power source is turned on after a predetermined time has elapsed after switching the distributor. (4) The color image forming apparatus according to claim 1, wherein the distributor uses a high voltage relay.