JP2577220B2 - Image forming device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to an image forming apparatus, and more particularly to an image forming apparatus in which a plurality of image carriers such as electrophotographic photoconductors are juxtaposed, and electrophotographic images are formed on these photoconductors. A forming process is performed to obtain a plurality of images or a plurality of colors of developed images, and the developed images are sequentially transferred to a transfer material carried and transported by a transfer material transport device, or to an image receiving body such as an intermediate transfer body or continuous paper, and multiplexed. The present invention relates to a multiplex (multicolor) electrophotographic image forming apparatus for obtaining an image or a color image. The present invention can be embodied not only in an electrophotographic copying machine but also in various printers, facsimile machines, etc., but in this specification, a light scanning means for scanning a light beam from a light source and irradiating image information to an image carrier is described. A description will be given in relation to an electrophotographic color laser beam printer in which a plurality is arranged. The image carrier used in the present invention may be in any form, such as a belt or a drum, as long as it is an image carrier that moves endlessly. .

2. Description of the Related Art Conventionally, several types of laser beam color printers using an electrophotographic method have been proposed. A laser beam printer having a plurality of optical scanning units includes a laser device as a light source and a laser device. , A fθ lens for condensing the scanning beam on the generatrix of the surface of the photosensitive drum, a reflecting mirror for deflecting a light beam, and a beam detecting device for detecting a specific position of the scanning beam. ing.

An example of a laser beam printer having a plurality of such optical scanning means is shown in FIG. In this example,
The image forming medium, that is, the image bearing member is an electrophotographic photosensitive drum 1, which rotates in the direction of the arrow, and has image forming means, namely, a charger 2, an optical scanning means 3, a developing device 4, around the photosensitive drum 1. A cleaner 5 is provided. These photosensitive drums 1,
An image forming section having a charger 2, an optical scanning unit 3, a developing unit 4, and a cleaner 5 is arranged for each station of yellow, magenta, cyan, and black. The transfer section 6 as a moving body has a transfer belt 6a and a transfer charger 6b. A full-color image is formed by sequentially transferring color toner on a transfer material supported on the transfer belt 6a. Is done. The transfer material is supplied from a paper supply cassette 7, and the transfer material having undergone the transfer process is separated and reaches a tray 9 via a fixing device 8.

In the four-drum full-color printer having the above-described configuration, for example, in the case of the single-color mode, the transfer material supported on the transfer belt 6a sequentially passes through a yellow station, a magenta station, a cyan station, and a black station. The forming unit may be any image forming unit of a desired station, for example, only a yellow station, that is, the photosensitive drum 1, the charger 2, the optical scanning unit 3, the developing unit 4, the cleaner 5, and the transfer charger 6b are operated. However, as described above, the transfer material is sequentially sent to yellow, magenta, cyan, and black stations and passes through the gap between the transfer belt and the photosensitive drum.
When all the operations of the image forming process of the undesired stations, in this case, magenta, cyan, and black stations, are stopped, as described above, the transfer material is transferred when passing through the gap between the drum and the belt of each station other than yellow. Yellow image already formed on the material is magenta,
There is a problem that the photosensitive drums of cyan and black are rubbed, and the image is significantly damaged.

Further, at this time, the yellow toner transferred onto the transfer material is electrostatically attracted to the transfer material, so that the transfer material passes through the gaps between the magenta, cyan, and black photosensitive drums and the belt. In such a case, if there is an electrostatic charge of a different polarity from the yellow toner forming the yellow image on these photosensitive drums, the yellow toner on the yellow image is adsorbed onto the photosensitive drum. Also, there is a problem that the image is significantly deteriorated. Further, in such a case, when the transfer material passes through the gap between the drum and the belt, clogging of the transfer material (hereinafter referred to as “jam”) tends to occur.

7 and 8 show a conventional example of FIG. 2 proposed to improve image rubbing in the single color mode. In this conventional example, a back-up member 10 is disposed in the vicinity of the transfer charger 6b for each of the yellow, magenta, cyan, and black photosensitive drums 1. Each back-up member 10
A lever 12 rotatably instructed by a fulcrum 11, a roller 13 rotatably supported at an end of the lever 12 on the transfer belt 6a side, and pressing the roller 13 against the transfer belt 6a to transfer the transfer belt 6a And a spring 15 for urging a force to move the lever 12 to the standby position.

With this configuration, in the single color mode, for example, in the single color mode of yellow, only the yellow backup member 10Y is operated as shown in FIG. In other words, the transfer belt 6a contacts only the photosensitive drum 1Y by operating the pressing member 14 of the yellow station, and the other photosensitive drums
1M, 1C, and 1BK do not come into contact with the transfer belt, and the problem of image rubbing described above does not occur.

As described above, in the second conventional example, the photosensitive drum of the undesired image forming station is used to separate the transfer belt from the photosensitive drum.
Although the problem of image rubbing is solved because pressure contact is possible, a pressure contact release mechanism for the transfer belt to the photosensitive drum is required for each station, and the pressure contact between the back-up member and the photosensitive drum is required. Transfer unevenness and transfer failure during image transfer are likely to occur due to the force, which is not satisfactory.

SUMMARY OF THE INVENTION An object of the present invention is to solve the problem of rubbing of an image even in a non-full-color mode such as a single color mode or a two-color or three-color mode, and to obtain an image capable of obtaining an image of good quality without image damage. It is to provide a forming device.

It is another object of the present invention to provide a low-cost image forming apparatus which has a simple structure and does not cause deterioration of an image, jam of a transfer material, and the like.

Another object of the present invention is to provide a multicolor image forming apparatus capable of favorably forming multicolor and monochromatic images.

Means for Solving the Problems The above objects are achieved by an image forming apparatus according to the present invention. In summary, the present invention provides a method for forming a latent image on an image carrier by an image forming means, developing the latent image with a developing device, and arranging a plurality of image forming members for visualization. In an image forming apparatus that sequentially transfers images formed in the image forming units to a moving body that passes through the transfer position of each image forming unit, in an image forming unit other than the image forming unit that is currently performing the transfer process. Is an image forming apparatus in which only the developing device is stopped from operating.

Next, an image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

FIG. 1 shows an embodiment in which the present invention is applied to a four-drum full-color printer similar to that described with reference to FIG. In this embodiment, the image forming apparatus has four color stations of yellow, magenta, cyan, and black, and an image forming unit of each station includes electrophotographic photosensitive drums 1Y, 1M, 1C, and 1B as image carriers. , Image forming means arranged therearound, that is, chargers 2Y, 2M, 2C, 2B, light traveling means 3Y, 3M, 3C, 3B, developing devices 4Y, 4M, 4C, 4B, cleaners 5Y, 5M, 5C, 5B is provided.

In this embodiment, the moving body located at the transfer portion is a transfer belt 6a, which supports the transfer material supplied from the paper supply cassette 7 on the transfer belt 6a, and sequentially transfers the transfer material to each station. The image is formed on the transfer material by being conveyed and the color toner is transferred onto the transfer material under the action of the transfer charger 6b. The transfer material is separated from the transfer material after the transfer process, and the fixing device 8
Through the tray 9.

In the above configuration, according to the present invention, a single color mode,
In the color or three-color mode, that is, yellow, magenta,
When all four colors of cyan and black are not used, image forming means in an image forming station outside a desired color;
That is, only the operation of the developing device 4 of the photosensitive drum 1, the charging device 2, the scanning optical device 3, the developing device 4, and the transfer charging device 6b is stopped, and the other process devices are normally operated as in the full color mode. You.

At this time, the transfer charger 6b is a charging device configured to apply a corona discharge having a polarity opposite to the charge polarity of the toner particles. In this embodiment, a corona charger as shown in FIG. 1 is used. If the requirements described above are satisfied, another charging device can be used.

Next, the operation of the image forming apparatus having the above-described configuration will be described with reference to, for example, a yellow single color mode.

Now, since the apparatus is in the yellow single-color mode, the process units other than the developing device 4 operate in the image forming sections of the magenta, cyan, and black stations in the same manner as in the normal full-color mode. Are all working as usual. The transfer material supplied from the paper supply cassette 7 first passes through a yellow station, and a yellow image is formed by a normal image forming process. Thereafter, the paper passes between the photosensitive drum 1M of the magenta station and the transfer belt 6a. At this time, the photosensitive drum 1M, the charger 2M,
3M, the transfer charger 6b is operating but the developing device 4 is stopped, so that even if a latent image is formed on the photosensitive drum 1M, the latent image is not developed. Therefore, the magenta image is not transferred onto the passing transfer material.

Also, when the transfer material on which the image is formed by the yellow station passes through the gap between the photosensitive drum of the magenta station and the transport belt, the image on the transfer material is rotated because the drum rotates together with the transport belt. Does not damage the image due to rubbing against the photosensitive drum, and because the corona discharge of the opposite polarity to that of the toner is applied to the back surface of the transfer material by the transfer charger, the transfer material and the toner are attracted. The force is kept strong, and the yellow toner on the transfer material is not reversely transferred to the drum side. Further, the transfer material does not jam in the gap.

The transfer material that has completed the transfer process without passing through the yellow image formed on the transfer material is also separated when passing through the cyan and black stations in the same manner as when passing through the magenta station, and separated on the tray 9 via the fixing device 8. Leads to.

Also in the two-color mode and the three-color mode, an image of good quality can be obtained without disturbing the image on the transfer material as in the case of the single-color mode.

FIG. 2 and FIG. 3 show the operation state of each process device. FIG. 2 shows a normal operation state of each processing apparatus at the time of full-color image formation and an operation state of each processing apparatus at a station of a desired color in the single-color mode. FIG. 3 shows the operation state of the single-color mode or the non-full-color mode. 3 shows the operation state of each process device in an image forming station other than the desired one.

In the above embodiment, the moving body is the transfer material conveying means 6a such as a transfer belt for conveying the transfer material P for transferring the image formed on the image carrier, but the moving body is shown in FIG. Transfer member 16 for transferring the image formed on the image carrier as described above, and the image on the intermediate transfer member is again transferred to the transfer material P.
It is also possible to configure so that the image is transferred to As shown in FIG. 5, the moving body is a roll paper 17 which is continuously supplied, that is, a transfer material P, and the image on the photosensitive drum is transferred onto the roll paper.

Effects of the Invention The image forming apparatus according to the present invention has the above configuration and operation, and can provide the following effects.

(1) There is no effect on the image due to the rubbing of the image when passing through the image forming station outside the desired color in the single color mode or the non-full color mode.

(2) There is no paper jam (jam) of the transfer material when passing the image forming station outside the desired color in the single color mode or the non-full color mode.

(3) In the single color mode or the non-full color mode, the toner on the transfer material is not retransferred to the photoconductor side when passing through an image forming station other than the desired color.

(4) There is no unnecessary developer circulation or stirring in an undesired image forming station in the single color mode or the non-full color mode, so that deterioration of the developer is suppressed and the life of the developer is extended.

It is possible to obtain an image of excellent quality with a simple structure.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of an embodiment of the image forming apparatus according to the present invention. FIGS. 2 and 3 are timing charts showing the operation of the image forming apparatus according to the present invention. 4 and 5 are schematic longitudinal sectional views of another embodiment of the image forming apparatus according to the present invention. 6, 7, and 8 are schematic longitudinal sectional views of a conventional multicolor image forming apparatus. 1Y, 1M, 1C, 1B: Image carrier 2Y, 2M, 2C, 2B: Charger 3Y, 3M, 3C, 3B: Optical scanning means 4Y, 4M, 4C, 4B: Developing device 5Y, 5M, 5C, 5B: Cleaner 6: Transfer unit 6a: Transfer material transport means 16: Intermediate transfer body 17: Roll paper

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Setsu Uchida, Inventor 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Kunihiko Matsuzawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (56) References JP-A-63-8665 (JP, A) JP-A-63-8659 (JP, A) JP-A-63-249165 (JP, A) JP-A-63-249161 (JP, A) A) Tokiko Hei 7-107613 (JP, B2)

Claims (5)

(57) [Claims] An image forming means for forming a latent image on an image carrier, developing the latent image with a developing device to form a visible image, and arranging a plurality of image forming portions in parallel. In an image forming apparatus in which the formed image is sequentially transferred to a moving body passing through the transfer position of each image forming unit, the image forming units other than the image forming unit currently performing the transfer process are developed. An image forming apparatus, wherein only the device is stopped operating. 2. The image forming apparatus according to claim 1, wherein the moving body is a transfer material conveying unit that conveys a transfer material for transferring an image formed on the image carrier. 3. The image forming apparatus according to claim 1, wherein the moving body is a transfer material for transferring an image formed on the image carrier. 4. The image forming apparatus according to claim 3, wherein the transfer material is an intermediate transfer member. 5. The image forming apparatus according to claim 3, wherein the transfer material is a roll paper supplied continuously.