JPS63225254A - Multicolor developing device - Google Patents

Abstract

PURPOSE:To prevent intrusion of different color toners by operating an upper stream side developing device together with a down stream side developing device at the time of changing over a recovering device for recovering the toner on a developing sleeve of the down stream side developing device from the upper stream side developing device to the down stream side developing device. CONSTITUTION:A photosensitive drum 1 rotates and the 2nd developing device 3b operates for the prescribed time, then a shutter 18 is closed simultaneously therewith and the developer on the developing sleeve 9 of the 2nd developing device 3b is recovered when a print SW is turned on at the time of changing over black development to color development to 1-scan 2-color development to execute the development in a two-color state of a color region and black region. The 1st developing device 3a operates in succession thereof and after the color development is executed, the 2nd developing device 3b on the down stream side operates and the black development is executed, but there is the possibility that the color toner on the developing sleeve 9 of the 1st developing device 3a intrudes into the developer of the 2nd developing device 3b right after the operation of the 2nd developing device 3b and, therefore, the recovering device 19 is operated simultaneously when the 2nd recovering device 3b is operated. The intrusion of the different color toner of the upper stream side developing device into the toner of the down stream side developing device is thereby prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a multicolor developing device used in an image forming apparatus such as a copying machine, a printer, a link, etc.

(Prior Art) A multicolor developing device arranges each developing sleeve of a plurality of developing devices close to an electrostatic latent image carrier, each containing a developer containing toners of different colors. Multi-color development can be performed by switching the operation appropriately. In order to prevent color mixture from occurring in an image, various methods for switching the developing device have been proposed.

For example, is the developer body or its developer sleeve static? ltM
The developing device is provided so as to be able to move forward and backward relative to the image carrier, so that a developing device used for development can be brought close to the electrostatic latent image carrier so that it can be developed, while a developing device that is not used for development is kept away from the electrostatic latent image carrier. There are some that cannot be developed.

There is also a device in which a shutter is provided between the developing device and the electrostatic latent image carrier so that it can be opened and closed, so that the shutter of the developing device not used for development is closed and the shutter of the developing device used for development is opened.

Further, there have been proposed methods for recovering the developer on the developing sleeve of a developing device that is not used for development.

(Problems to be Solved by the Invention) However, in any of the conventional developing devices, it is necessary to provide a retracting mechanism, a shutter opening/closing mechanism, etc. for each developing device, making the structure complicated and increasing the size of the entire device. do.

In addition, in a device that collects developer on a developing sleeve that is not used for development, the developing sleeve is not retracted or blocked by a shutter, and is always in close proximity to the electrostatic latent image carrier. Therefore, there is a possibility that the toner of the developer from the upstream developing device may get mixed into the downstream developing device due to the generation of powder smoke or the like. As the contamination of toners of different colors accumulates, the color tone of the toner changes or its properties deteriorate, resulting in problems such as the need to replace the developer as needed.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a multicolor developing device that has a simple structure and does not cause the mixing of different color toners.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a system in which each developing sleeve of a plurality of developing devices containing developers containing toners of different colors is placed close to the electrostatic latent image carrier. In a multi-color developing device that performs multi-color development by arranging the developing device and operating the developing device by switching the developing device appropriately, the device includes a collecting device that collects the toner on the developing sleeve of the downstream developing device; At least a control means is provided for operating the downstream developing device together with the downstream developing device for a predetermined period of time when switching from the upstream developing device to the downstream developing device.

(Example) Next, one embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows a developing section of a two-color copying machine, which is an embodiment of a multicolor image forming apparatus. 2) are placed in close proximity.

The developing device (2) includes a first developing device (3a) and a second developing device (
3b), which have almost the same configuration, but the first developing device (3a) has a larger photoreceptor drum (3b).
1) It is arranged so as to be located upstream with respect to the rotation direction (arrow (a) direction). Then, the first developing device (3a
) stores a first developer made of a mixture of color toner and a magnetic carrier, and a second developer (3b) stores a second developer made of a black toner and a magnetic carrier. In this embodiment, the toner and the carrier are charged to a positive polarity and the carrier to a negative polarity when the toner and the carrier come into frictional contact with each other.

1st. The second developing device (3a), (3b) is a developing tank (4).
and a tank of tona (5).

Inside the developer tank (4), from the photoreceptor drum (1) side to the rear, there is a developer sleeve housing section (6) and a conveyance path (7).
), (8) are formed, and a developing sleeve (9) is formed on each.
, a packet roller (10), and a conveyance roller (11). Note that the transport paths (7) and (8) are connected to the developer tank (
4) is partitioned by a partition plate (12) that rises from the bottom of the screen, but there is a passageway (not shown) formed at the back and front ends.
A circulation conveyance path is formed.

The developing sleeve (9) is made of a conductive non-magnetic material formed into a cylindrical shape, and minute irregularities are formed on the outer peripheral surface, as shown by the arrow (b).
) direction, and is partially exposed from the opening of the developing sleeve housing section (6) and is close to the photosensitive drum (1).

Inside this developing sleeve (9), magnetic poles extending in the axial direction are alternately arranged in the circumferential direction as S poles and N poles, and only a portion of the magnetic roller (13) with the same poles adjacent to each other is fixed. A predetermined magnetic pole faces the photoreceptor drum (1) via the developing sleeve (9), and an adjacent portion of the same pole faces the packet roller (10) via a guide plate (14) to be described later.
It is designed to face.

Further, a brush height regulating plate (15) attached to the developer tank (4) is opposed to the rear obliquely upper part of the developing sleeve (9) with a predetermined brush height regulating gap.

Further, a developing bias voltage is applied to the developing sleeve (9) of the first developing device (3a), and its value is -150V during development, and when not developing, and -aoov during operation 3b).

This allows the second developing device (3b) to be disconnected from a developing bias power source (not shown) when it is not in operation. on the other hand,
A developing bias voltage is also applied to the developing sleeve (9) of the second developing device (3b), and its value is -150V during development, and the connection to the developing bias power source can be disconnected when not developing. That's how it is.

The packet roller (10) is rotatably driven in the direction of the arrow (c), and mixes and stirs the developer in the conveyance path (7) while conveying it from the back side to the plane side, while passing a part of the developer onto the guide plate (14). ) to the surface of the developing sleeve (9).

This guide plate (14) is provided between the developing sleeve (9) and the packet roller (10), and is provided between the magnetic roller (I
The developing tank (4) is partitioned into upper and lower parts with the same-polarity adjacent parts (3) as the border.

The conveyance roller (11) is rotatably driven in the direction of arrow (d), and carries the developer sent from the conveyance path (7) to the conveyance path (8) via a path (not shown) on the plane side. It is conveyed from the front side to the rear side while mixing and stirring, and when it reaches the rear end, it passes through the rear passage (not shown) to the conveyance path (
7).

On the other hand, toner is stored in the toner tank (5), and an agitator (16) for preventing crosslinking of the toner is provided so as to be rotatable or swingable in the direction of arrow (e). 4] The screw roller (17) that replenishes is indicated by arrow Cf.
) direction.

Although not specifically shown, a toner tank (5) is also provided in the second developing device (3b).

The first developing device (3a) and the second developing device (3b) have a glosser (1g) only in the second developing device (3b) and a recovery device (
19) is different in that it is a provision.

This shutter (18) is provided between the developing sleeve (9) and the packet roller (10) so as to be rotatable approximately 90 degrees around a support shaft (20), and is driven by a drive mechanism such as a solenoid (not shown). , as shown in FIG.
4), and a state in which it rotates counterclockwise in FIG. 1 from this state to face the developing sleeve (9) and prevent the supply of developer to the developing sleeve (9) as appropriate. It is possible to switch.

The recovery device (I9) is a developer tank (4) of the second developer (3b).
), and a collection roller (22) and a conveyance roller (23) are provided in the collection tank (21) (g), respectively.
A scraper (24) is provided so as to be rotatably driven in the (h) direction, and whose tip is pressed against the collection roller (22) from a tangential direction. Then, the collection roller (2
2) is partially exposed through the opening (25) formed in the developer tank (4) and is placed close to the developer sleeve (9).
13), and a bias voltage is applied thereto.

This bias voltage is between -600V and -150V during recovery.
It can be adjusted to 0V, and to 150V, which is the same as the developing bias voltage of the developing sleeve, when not being collected. Note that the reason why Ov is not set when the developer is not collected is that carrier adhesion of the developer may occur.

Further, as an operating means of this recovery device (19), a recovery roller (22) and a conveyance roller (23) are connected to the second developing device (3).
b) to adjust the gap between the collection roller (22) and the developing sleeve (9), or to turn off the bias voltage applied to the collection roller (22); Various means can be used, such as using a clutch to intermittent the rotation of 22).

The general operation of the developing device (2) having the above configuration is explained in the first section.
A case in which color development is performed using the developing device (3a) will be explained.

While the photoreceptor drum (1) is being rotated at a constant speed in the direction of arrow (a), the photoreceptor! - The surface of the ram (1) is uniformly charged (-6° OV) by a charging charger (not shown), and is exposed to image light from an optical system (not shown) to form an electrostatic latent image.

As a result, the surface type of the electrostatic latent image area (ke is approximately -60
Although maintained at 0V, the surface potential of the non-image area of the electrostatic latent image is reduced to approximately OV.

In the first developing device (3a), the developer is transported through a transport path (7) by a packet roller (10) and a transport roller (11).
), (8) while being mixed and stirred and circulated through passages (not shown) formed at both ends of the partition plate (12), and the toner is charged to a positive polarity and the carrier to a negative polarity. A portion of the developer charged in this way is transferred from the guide plate (14) to the developing sleeve (
9).

The developer supplied onto the developing sleeve (9) is conveyed in the direction of the arrow (b) in the form of a magnetic brush along the lines of magnetic force generated by the magnetic roller (13), and then passes through the height regulating plate (15).
The head height is regulated at , and the sheet is conveyed to the development area (P, ).

The developer conveyed to the development area (Pυ), of which color toner is mixed with the surface potential (about -600V) of the electrostatic latent image area formed on the surface of the photoreceptor drum (1) and the development bias voltage (-150V), the toner image is supplied to the electrostatic latent image area, and a toner image corresponding to the developed image is formed.

The developer remaining on the developing sleeve (9) is conveyed in the direction of arrow (b) according to the rotation of the developing sleeve (9), and is transported to a portion facing the packet roller (10) and placed on the magnetic roller (13). When the same polarity reaches the adjacent portion, it is released from the magnetic force of the magnetic roller (13) and falls toward the packet roller (10), where it is taken up by the developer in the conveyance path (7) and circulated.

Next, the control operation when switching between the first developing device (3a) and the second developing device (3b) by the developing device (2) in this embodiment will be described as follows: (i) during black development, (ii) during color development. (iii) Three cases during two-color development will be explained separately.

(i) At the time of black development FIG. 2 shows a time chart when switching from the previous color development state to black development by selecting the color selection key.

When the print SW is turned on, the main motor is driven to rotate the photosensitive drum (1), the second developing device (3b) is activated, and at the same time, the recovery device (19) is activated for about 1 second.

Further, the solenoid of the shutter (18) of the second developing device (3b) does not operate, and the toner is ready to be supplied as shown in FIG. only possible.

In this state, the first developing device (3a) does not operate, and the developing bias voltage of its developing sleeve (9) is -300.
Due to the high voltage of v, the toner photoreceptor drum (
No electrostatic adsorption to 1) takes place. However, since the ears of the first color developer remaining in the developing sleeve (9) due to the previous developing operation are in contact with the photoreceptor drum (1), powder smoke is generated due to frictional contact or disturbance. Some of the color toner adheres to the photoreceptor drum (1) and is transported to the developing area (P) of the second developing device (3b), where it is transported to the developing tank (4) of the second developing device (3b). may be mixed in.

In this way, when the color toner in the first developing device (3a) mixes with the black toner in the second developing device (3b) and accumulates, the color tone of the black toner changes or the properties deteriorate. Therefore, the entire black toner must be replaced.

In the present invention, since the recovery device (19) operates for approximately 1 second at the same time as the second developing device (3b) operates, the black toner on the developing sleeve (9) that may contain color toner is removed. It will be collected by the collection device (19).

That is, when the recovery device (19) operates, the recovery roller (22) receives a voltage higher than the photoreceptor drum (-600V).
Since a bias voltage of 600 to -1500 V is applied, black toner that may be mixed with color toner on the developing sleeve (9) is removed based on the potential difference with the bias voltage (-150 V) of the developing sleeve (9). All are electrostatically attracted to the collection roller (22) in the collection area (P3). This collection roller (22) is operated at a high bias voltage (-600 to -1
500V) may be stopped while the bias voltage is being applied, and after lowering the bias voltage to -150V, it may be rotated in the direction of arrow (g), or it may be rotated at the same time. The black toner collected by the collection roller (22) is conveyed in the direction of arrow (g), scraped off by the scraper (24), and collected by the conveyance roller (23) into a waste box (not shown).

It should be noted that the operation time of this collection device (19) is determined by applying a high bias voltage (-600 to -15
00V) should be kept to a minimum to avoid unnecessary recovery and increase in black toner consumption. That is, in FIG. 1, the packet roller (10)
The time from when new developer is supplied onto the developing sleeve (9) until it reaches the collecting area (P3) via the developing area (P,) may be set to approximately 3/4 rotation. In the example, it is about 1 second.

Furthermore, the recovery device (19) only needs to be activated once when switching from color to black, and does not necessarily need to be activated when black development is performed continuously.

(11) Color development FIG. 3 shows a time chart when the color selection key is selected to switch from the previous black development to color development.

When the print switch is turned on, the main motor is driven to rotate the photoreceptor drum (1), and the second developer (3b) is turned on for a predetermined period of time.
) is activated, the shutter (18) closes, while the recovery device (19) is activated for about 1 second.

In this state, the shutter (18) is closed and the supply of developer from the packet roller (10) to the developing sleeve (9) is cut off, so the second developing device (3b) is operated and the developing sleeve (9) is closed. ) rotates, then remove the developing sleeve (
9) Only the upper developer will be collected. This developer recovery operation is performed at IJ when the developing sleeve (9) rotates at least once. Therefore, there is no developer spike in the second developing device (3b)l.

The collection device (19) is operated together with the second developing device (3b) to assist in collecting the developer, especially toner, on the developing sleeve (9), thereby shortening the developer collection time and increasing collection efficiency. At the same time, this is to remove black toner that may have been mixed with color toner from the first developing device (3a) during this developer collection operation.

When the color developer collecting operation is completed, the first developing device (3a) is activated and becomes ready for color development. During color development using the first developing device (3a), the second developing device (3a)
3b) Since the developer above is recovered by the above operation, color mixing does not occur.

(iii) I-scan 2-color development FIG. 4 shows a time chart when switching from conventional black development or color development to 1-scan 2-color development by selecting the color selection key. Here, 1 scan 2 color development means that the first developer (3a) and the second developer (3b) are switched during one scan operation of an optical system (not shown) to develop the electrostatic latent image area in color. This refers to developing in two colors: a black area and a black area.

When the print switch is turned on, the main motor is driven to rotate the photosensitive drum (1), and first, as in the case of color development, the second developing device (3b) is operated for a predetermined time, and at the same time the shutter (18) is activated. is closed and the second developing device (3b)
The developer on the developing sleeve (9) is collected. At this time, since the recovery device (19) will be activated later, it is not necessarily necessary to activate it here.

Subsequently, the first developing device (3a) is activated to perform color development, and then the second developing device (3b) is activated to perform black development.

Here, immediately after the operation of the second developing device (3b), the first developing device (3b) is activated.
There is a possibility that the color toner on the developing sleeve (9) of 3a) gets mixed into the developer of the second developing device (3b). Therefore, at the same time as the second developing device (3b) is activated, the recovery device (19) is activated, and the second developing device (3b) is activated! (3b) The toner on the developing sleeve (9) that may be mixed with the color toner is collected.

In the embodiment described above, the recovery device was operated according to the time chart of the copy control mode.
An activation switch exclusively for the recovery device may be provided so that the recovery device can be activated arbitrarily during maintenance by a service person or the like. The color toner in the first developing device on the upstream side or the black toner in the second developing device on the downstream side gets mixed in and accumulates, causing a change in the color tone and deterioration of the black toner after long periods of use (10,000 times or more). (after copying 30,000 times), it is effective even if the recovery device is activated by the activation switch at that time based on judgment by a service person or the like.

In addition, in the above embodiment, two
Although the example in which the 1st and 2nd developing units (3a) and (3b) of the stand are provided to form a two-color image is shown, the present invention is not limited to this. Even in the case where developing devices are arranged, a collection device may be provided for a plurality of developing devices on the downstream side.

Furthermore, in the embodiment described above, a cylindrical photoreceptor drum (1) is used as the electrostatic latent image carrier, but
Of course, the present invention is not limited to this, and a belt-type photoreceptor may be used.

(Effects of the Invention) As is clear from the above description, according to the present invention, the developing sleeve of each developing device is switched while being kept close to the electrostatic latent image carrier, and no evacuation mechanism or the like is provided. Therefore, the structure is simple and miniaturization can be achieved.

@1 Also, even if the toner in the upstream developer mixes with the toner in the downstream developer, the collection device is activated every time the developer switches to the downstream developer to collect the mixed color toner. This prevents the toner from the upstream developer from mixing with the developer from the downstream developer and accumulating, resulting in no change in color tone or property deterioration, and eliminating the need to replace the developer. have.

[Brief explanation of drawings]

Figure 1 is a sectional view of the main parts of a copying machine equipped with a developing device according to the present invention, and Figures 2, 3, and 4 are times for black development, color development, and scan 2 color development, respectively. It is a chart. 1°...photosensitive drum (electrostatic latent image carrier), 2...
Developing device, 3a... first developing device, 3b... second developing device, 9.
...Developing sleeve, 19...Recovery device. Patent applicant Minolta Camera Co., Ltd. Agent
People Patent attorney Aobai Ao and 2 others

Claims (2)

[Claims] (1) By arranging each developing sleeve of a plurality of developing devices containing developers containing toners of different colors in close proximity to the electrostatic latent image carrier, and operating the developing devices by switching them appropriately, multi-color In a multi-color developing device that performs development, the toner on the developing sleeve of the downstream developing device is collected, and the collecting device is connected to the downstream developing device at least when switching from the upstream developing device to the downstream developing device. 1. A multicolor developing device comprising: a control means for operating the developing device for a predetermined period of time together with the developing device. (2) The collecting device includes a collecting roller disposed close to the developing sleeve of the developing device and to which a bias voltage is applied during operation, a removing means for scraping off the toner on the collecting roller, and a removing means for scraping off the toner on the collecting roller; The multicolor developing device according to claim 1, further comprising a conveyance means for conveying the dropped toner to a waste box.