JPH09160377A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an image forming device capable of high-speed output by dividing developing devices into two groups so as to correspond with developing positions, and alternately carrying out image formation in the two developing positions. SOLUTION: A first developing device 31 and a second developing device 32 form a first group, and develop electrostatic latent images formed on a photoreceptor in a first developing position 11. Similarly, a third developing device 33 and a fourth developing device 34 form a second group, and develop electrostatic latent images formed on the photoreceptor in a second developing position 12. By separating the developing devices into two groups so as to correspond with the developing positions, and by alternately carrying out development in the two developing positions, output speed can become high in comparison with the case of a single developing position because time required for a preliminary operation for development is eliminated. Also, by dividing a plurality of developing devices into groups, the developing devices similar in development characteristic, such as an amount of electrification of toner in the developing device and an amount of carrying, can be controlled in the same group, therefore, this contributes to a reduction in the wasteful occupation of space by the arrangement of the developing devices.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus having a plurality of developing devices for visualizing a latent image on a latent image carrier with a developer.

[0002]

2. Description of the Related Art Conventionally, as a color image forming apparatus utilizing an electrophotographic process, a plurality of developing devices are provided in the device, a developing device of a desired color is selected, and a developing path is moved to a developing position. An image forming apparatus that moves and develops has been proposed.

For example, as a conventional image forming apparatus, there is Japanese Patent Laid-Open No. 63-220267, which has a plurality of developing devices and two developing positions dedicated to a black developing device and a color developing device. When the selected developing device is moved to the developing position via the moving path, the developing device closer to the moving path is sequentially operated.

[0004]

However, in the image forming apparatus as disclosed in the above-mentioned Japanese Patent Laid-Open No. 63-220267, there are black and a color peculiar to the developer (for example, cyan, magenta, yellow). In two-color image formation,
High-speed output is possible, but in full-color image formation,
When replacing the developing device at the developing position, there is only one movement path from the developing position to the standby position, so move the next developing device to the developing position until the developing device that was at the developing position moves to the standby position. However, there is a problem in that it takes a long time to switch the developing device and high-speed output cannot be performed. When a full-color image is formed using the electrophotographic process, a developing device equipped with cyan, magenta, yellow, and black toners is used, and the image formation is performed four times on the photosensitive member. In comparison, the time required for output is four times as long. However, in reality, since the time for switching the developing device is added, time is required for further output, which hinders high-speed output.

The present invention has been made in view of the above-mentioned conventional technique, and has a plurality of developing devices and two developing positions for visualizing the latent image on the latent image carrier, and The time required to move the developing device from the standby position to the developing position is included in the time required for image output by dividing the image into two groups corresponding to the developing positions and alternately performing image formation at two developing positions. It is an object of the present invention to provide an image forming apparatus which is capable of high speed output.

[0006]

In order to achieve the above object, an image forming apparatus according to claim 1 of the present invention visualizes a latent image on a plurality of developing devices and a latent image carrier. In the image forming apparatus having the developing positions at the positions, the developing devices are divided into two groups corresponding to the developing positions, and the images are alternately formed at the developing positions at the two positions.

Further, the image forming apparatus according to claim 2 is
While the image is being formed at the first developing position, the developing device is replaced at the second developing position, and while the image is being formed at the second developing position, the developing device is replaced at the first developing position. It is characterized by

[0008]

According to the first aspect of the invention, the developing device is divided into two groups corresponding to the developing positions, and images are alternately formed at the two developing positions to form the first developing position. While developing, the developing device at the second developing position prepares for the development and performs a preliminary operation, and immediately after the completion of the developing at the first developing position, the developing at the second developing position is started. can do. Therefore, as compared with the case where there is only one development position, the time for the preliminary operation of development is saved, and high-speed output is possible. Further, by grouping a plurality of developing devices, it is possible to manage developing devices having similar developing characteristics such as the charge amount and the transport amount of toner in the developing devices in the same group. For example, for a developing device for a color that consumes a large amount of developer, if you want to increase the capacity of the developer in order to obtain the same usage period as a developing device that consumes less, the developing device becomes larger, but the developing device that consumes more It is only necessary to ensure that a larger developing device can exist only for the developing positions of the developing devices by making the same group, and it is necessary to secure a space where a large developing device can exist for both developing positions. There is no.

According to the invention described in claim 2, the first
While the image is being formed at the developing position, the developing device is replaced at the second developing position so that the developing at the second developing position is started immediately after the completion of the developing at the first developing position. You can Therefore, the time for switching the developing device is not added to the time for image formation, and high-speed output is possible.

(First Embodiment) FIG. 1 is a schematic cross-sectional view of switching of a plurality of developing devices of a full color printer which is one mode of an image forming apparatus according to the present invention.

The photoconductor, which is the latent image carrier 1, is rotated in the direction of the arrow. A charging member, a developing device, a transfer device including an intermediate transfer medium, a cleaning device, and a charge eliminating device are arranged from the upstream side in the rotation direction of the photoconductor (not shown except the developing device).

The optical system is constructed so as to project a desired image on the photoconductor at the exposure section located between the charging member and the developing device.

Further, a fixing device and a paper feeding device are arranged in the printer, and a paper carrying system is arranged between the transfer device and the fixing device and the paper feeding device.

With the above structure, the photosensitive member is subjected to the charging, exposing, developing, transferring and cleaning processes for each color by the charging member, the developing device, the transferring device and the cleaning device.

The developing device includes a first developing device, a second developing device, a third developing device, and a fourth developing device, and includes yellow, cyan, magenta, and black color developing agents, and color separation is performed. The developed latent image of each color is visualized by a corresponding developing device. Each developing device conveys toner, which is a developer, to develop the electrostatic latent image formed on the photoconductor. The developing roller, which is the developer carrying member 311 that conveys toner, has a conductive elastic body arranged concentrically on the outer periphery of the shaft, and is pressed against the photoconductor at a predetermined pressure during development. A potential difference is provided between the photoconductor and the developing roller. The supply roller, which is the supply member 313, is pressed against the developing roller and is rotated to press the toner against the developer roller to rub and charge the toner to supply it to the developing roller. The regulating member 312 is made of a plate-like non-magnetic or magnetic metal or resin, has a fixed end on the upstream side in the toner conveying direction, and has an arc portion or the vicinity thereof in pressure contact with the developing roller, thereby forming a toner layer thickness. Regulate to an appropriate amount. Through the above steps, the developing device rotates the developing roller to convey the thin layer toner to the developing position to visualize the electrostatic latent image.

The transfer device is composed of a belt-shaped intermediate transfer medium, a primary transfer roller and a secondary transfer roller which are pressed against the photosensitive member. The intermediate transfer medium is rotatably transported, and a visible image for each color on the photoconductor is transferred in the primary transfer area where the primary transfer roller and the photoconductor face each other. The visible image of each color, that is, the intermediate transfer medium to which the toner image is sequentially transferred is transferred to the transfer paper in the secondary transfer area, which is a position facing the secondary transfer roller. Then, the transfer paper is sent to the fixing device by the paper conveying system. The toner image on the transfer paper is fixed on the transfer paper by the fixing device.

Next, the developing device will be described. The first developing device 31 and the second developing device 32 form a first group to visualize the electrostatic latent image formed on the photoconductor at the first developing position 11, and similarly to the third developing device. Developing device 33 and fourth developing device 34 form a second group, and second developing position 1
In step 2, the electrostatic latent image formed on the photoconductor is visualized. Less than,
I will describe the situation. First, the first electrostatic latent image formed on the photoconductor by the charging member and the optical system is transferred to the first developing position 11
Then, the image is visualized by the first developing device 31 which is brought into contact with the photoconductor. At that time, at the second developing position 12, the third developing device 33 faces the photoconductor in a non-contact manner and starts a preliminary operation if necessary. The preliminary operation is an operation of rotating the developing roller and the supplying roller to adjust the amount of toner conveyed on the developing roller and the amount of charge. The first developing device 31 that visualizes the first electrostatic latent image separates from and contacts the photoconductor. Next, the second electrostatic latent image formed on the photoconductor by the charging member and the optical system in the same manner as the first latent image is applied to the photoconductor by the third developing device 33 at the second developing position 12. Contact and visualize. During this visualization, at the first developing position 11, the first developing device 31 moves to the first standby position 314 (upward of A), and the second developing device 32 moves to the first developing position. 11 (to the left of B), the photoconductor is opposed to the photoconductor in a non-contact manner, and the preliminary operation is started if necessary. Similarly, at the first developing position 11, the third electrostatic latent image is visualized by the second developing device 32, while the third developing device 33 waits at the third standby position at the second developing position 12. To the position 334 (to the right of C), and the fourth developing device 3
4 is opposed to the photoconductor (upward direction of D). And the fourth
The electrostatic latent image is visualized by the fourth developing device 34, and a full color image is formed on the intermediate transfer medium onto which the visualized image of each color is transferred from the photoconductor. Table 1 shows the flow of image formation described above.

[0018]

[Table 1]

As shown in Table 1, the first developing device 31
However, when the fourth developing device 34 is performing the fourth development,
By moving to the first development position 11, the first development is immediately performed without moving at the start of image formation next time,
It is possible to shorten the start-up time until the start of printing.
However, it goes without saying that this movement of the first developing device 31 may be performed at the start-up until the start of printing. Further, after the fourth developing device 34 has performed the fourth development, it may move to the fourth standby position 344 before stopping the movement of the printer, or the first development for the next image formation may be performed. When I was going,
You may move to the 4th standby position 344.

The plurality of developing devices are divided into two groups, and while the first developing is being performed at one developing position, the developing devices are exchanged in preparation for the next second developing at the other developing position. The second development can be performed immediately after the first development. Therefore, compared to the case where a plurality of developing devices are exchanged at one developing position to form an image, the time for exchanging the developing devices is not added to the image forming time, and high-speed output is possible. .

There are several possible methods for dividing a plurality of developing devices into two groups.

Depending on the characteristics of the photoconductor, the attenuation of the potential of the photoconductor due to the exposure is not sufficient at the first developing position and the potential of the photoconductor is attenuated at the second developing position depending on the characteristics of the photoconductor. However, in such a case, a developing device for which stable development is desired should be arranged at the second developing position. If a black, magenta, or cyan developing device that is frequently used or that is easily recognized in the formed image is placed in the second developing position, the image deteriorates when unnecessary toner adheres to the non-image area. Become. Therefore, by disposing these developing devices at the second developing position, it is possible to develop a stable electrostatic latent image, and it is possible to prevent unnecessary adhesion of toner to a non-image portion.

Further, the toner consumption amount with respect to the number of printed sheets determines the size of the toner storage unit to be prepared, and for a color with a large toner consumption amount, a large developing unit for the toner storage unit is required. If there is a difference, the developing devices having similar toner consumption amounts are arranged at the same developing position, so that the space to be secured for disposing the developing device at the developing position can be used without waste.

Further, conventionally, there has been a problem that toner is leaked by driving the developing device and the inside of the printer is soiled. By moving a plurality of developing devices and switching them to perform development, the problem becomes more likely to occur. When a plurality of developing devices are arranged in the vertical direction as shown in FIG. 1, there is also a problem that toner leaked from the upper developing device is mixed in the lower developing device and the output image is deteriorated. Therefore, by making the developing device arranged at the lower second developing position a dark color system and the developing device arranged at the upper first developing position a light color system, toner leaks from the upper developing device. , Even if mixed in the developing device below, it is hardly recognizable in the output image.

As described above, there are various advantages by dividing the developing device into two groups.

The method for replacing the developing devices is not limited to the example in which the first and fourth developing devices move vertically and the second and third developing devices move horizontally as shown in FIG. , Various examples are possible.

(Second Embodiment) FIG. 2 is a schematic cross-sectional view of another switching of a plurality of developing devices of the image forming apparatus according to the present invention.

The first developing device 31 and the second developing device 3
The second developing device 33 and the fourth developing device 34 are housed in the first rotating body 41 having the center of rotation 2 and the second rotating body 42 having the center of rotation, respectively. The first electrostatic latent image is visualized by the first developing device 31, and the second electrostatic latent image is visualized by the third developing device 33. During the visualization of the second electrostatic latent image, the first rotating body 41 rotates, and the second developing device 3
2 faces the photoconductor. During visualization of the third electrostatic latent image by the second developing device 32, the second rotating body 42 rotates and
Developing device 34 faces the photoconductor.

By adopting the form of FIG. 2, it is possible to move and retreat at the same time as described in Table 1.

(Third Embodiment) FIG. 3 is a schematic cross-sectional view of another switching of a plurality of developing devices of an image forming apparatus according to the present invention.

The first developing device 31 moves to the first developing position 11
Then, the third developing device 33 faces the photoconductor at the second developing position 12, the second developing device 32 is the first storing device 51, and the fourth developing device 34 is the second storing device. It is stored in 52. The third developing device 33 is held in non-contact with the photoconductor, and the first developing device 31 is brought into pressure contact with the photoconductor to visualize the first electrostatic latent image. Next, the third developing device 3
3 is brought into contact with the photoconductor to visualize the second electrostatic latent image.
Meanwhile, the first developing device 31 is stored in the first storage device 51 along the movement path. Then, the first storage device 5
1 moves up and down to move the second developing device 32 until it is located in the moving path, and then, through the moving path, the first
At the developing position 11 of the above, it faces the photoconductor in a noncontact manner. Then
The second developing device 32 is brought into contact with the photoconductor to visualize the third electrostatic latent image. Meanwhile, the third developing device 33 is stored in the second storing device 52 along the movement path. continue,
The second storage device moves up and down to move the fourth developing device 34.
Is moved to a position on the moving path, and the second developing position 12 faces the photoconductor in a non-contact manner via the moving path. Then, the fourth developing device 34 is brought into contact with the photoconductor,
The fourth electrostatic latent image is visualized.

By adopting the configuration of FIG. 3, it is possible to make the moving path common for each developing position, and it is not necessary to prepare the moving paths corresponding to the number of developing devices in the vicinity of the photosensitive member which is easily restricted by layout.

Although the image forming apparatus of the present invention has been described with respect to the embodiment provided with the developing device in which the developing roller is brought into contact with the photosensitive member to perform the pressure contact development, the present invention does not require the developing roller to be in contact with the photosensitive member. The present invention can be similarly applied to an image forming apparatus provided with a developing device that performs held non-contact development. Further, the transfer device is not limited to the intermediate transfer medium, but can be similarly applied to an image forming device including a transfer drum that holds a transfer sheet on a drum. Further, the image forming apparatus of the present invention is limited by the structure, material, driving direction, driving speed, etc. of the electrostatic latent image carrier, the developer carrier, the regulating member, the supplying member, the charging member, the transfer device and the like. Instead, it can be widely applied to an image forming apparatus for switching a plurality of developing devices to visualize a latent image.

[0034]

As described above, the developing devices are divided into two groups corresponding to the developing positions, and images are alternately formed at the two developing positions. The effect is that the time for the preliminary operation of development is omitted, and high-speed output is possible. In addition, by grouping a plurality of developing devices, it is possible to manage developing devices having similar developing characteristics such as toner charge amount and transport amount in the developing devices in the same group, and to improve space of the developing devices. This has the effect of reducing waste.

By changing the developing device at the second developing position while the image is being formed at the first developing position, the second developing position is immediately after the development at the first developing position is completed. Since the development can be started and the time for switching the developing device is not added to the time for image formation, there is an effect that high-speed output is possible.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of an image forming apparatus according to an exemplary embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of the image forming apparatus according to the exemplary embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view of the image forming apparatus according to the exemplary embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Latent image carrier 11 1st developing position 12 2nd developing position 31 1st developing device 32 2nd developing device 33 3rd developing device 34 4th developing device 41 1st rotary body 42 2nd Rotating body 51 First storage device 52 Second storage device 311 Developer carrier 312 Control member 313 Supply member 314 First standby position 324 Second standby position 334 Third standby position 344 Fourth standby position

Claims (2)

[Claims] 1. An image forming apparatus having a plurality of developing devices and two developing positions for visualizing a latent image on a latent image carrier, wherein the developing devices are divided into two groups corresponding to the developing positions. An image forming apparatus, wherein images are alternately formed at two developing positions. 2. A developing device is replaced at a second developing position while an image is being formed at the first developing position, and a first developing position is being formed while an image is being formed at the second developing position. 2. The image forming apparatus according to claim 1, wherein the developing device is replaced with the developing device.