Claims
- 1. An image forming apparatus, comprising a photosensitive body, an electrostatic charger adjacent the photosensitive body, an image exposure means for forming on a charged surface of the photosensitive body an electrostatic image corresponding to signals representing a particular image, multiple developing means having respective multiple color toners to produce a toner image for the electrostatic image obtained with the image exposure means for at least one color of the multiple color toners, and a transfer means for transferring the toner image onto a transfer material; said multiple developing means comprising a plurality of first developing means placed in an installed position for respectively storing the multiple color toners, second developing means for storing a black toner, and means for selectively placing the second developing means in the installed position of at least one of said plurality of first developing means.
- 2. An image forming apparatus as recited in claim 1, wherein said plurality of first developing means are individual units that respectively store toners Y, M, and C, and one of which is replaceable in its installed position with the second developing means containing black toner.
- 3. An image forming apparatus as recited in claim 1, wherein said plurality of first developing means respectively storing the toners Y, M, and C are integrated into a unit, said unit being replaceable with the second developing means containing black toner.
- 4. An image forming apparatus recited in claim 1, wherein said photosensitive body and at least one of the plurality of first developing means are integrated into a unit, said unit being replaceable with another unit integrating another such photosensitive body and the second developing means storing black toner.
- 5. An image forming apparatus as recited in claim 1, further comprising means for automatically selecting a specific image forming mode set in advance for each of the first and second developing means to be actuated with placement of the respective first and second developing means in the installed position.
- 6. An image forming apparatus as recited in claim (5), further comprising means, actuated when power is applied to the image forming apparatus to turn it on, for setting a specific image forming mode which is the most frequency used mode for whichever one of the first and second developing means is being used.
- 7. An image forming apparatus as recited in claim (5), wherein said means for automatically selecting specific image forming mode changes to a color mode when the second developing means is replaced in the installed position with the first developing means containing yellow, magenta, and cyan toner.
- 8. An image forming apparatus as recited in claim (5), wherein said means for automatically selecting a specific image forming mode changes to a mono-color image forming mode when the first developing means is replaced with the second developing means containing black toner.
- 9. An image forming apparatus as recited in claim 1, wherein a unit comprising at least said plurality of the first developing means for developing an electro-static image on the photosensitive body and is exchangeable with the second developing means containing only black toner, and means for inhibiting the selection of the color image forming mode being actuated with a setting motion of the second developing means containing the black toner.
- 10. An image forming apparatus comprising an image reading means for reading an original image through a filter means for color separation and for converting the thus filtered image to image information to produce output data, and a plurality of units each of which includes a developing means for developing an electro-static image formed on a photosensitive body by the output data of the image reading means, the developing means of one of said plurality of unit shaving a black toner, and the developing means of another of said plurality of units having at least one color toner, means to produce motion for installing said one unit in place of said another unit, means for determining when said one unit having the developing means including the black toner is installed in place of said another unit, and means for setting a green or a neutral portion of said filter by the motion that installs said one unit in place of said another unit.
- 11. An image forming apparatus as recited in claim 1, wherein said apparatus further comprises means for selecting green or neutral data of said signals to produce said electrostatic image when said second developing means is installed.
- 12. An image forming apparatus comprising a color image reading means for reading an original image through a filter means for color separation and for converting the thus filtered image to image information to produce color output data, and a plurality of units each of which includes a developing means for developing an electro-static image formed on a photosensitive body by the color output data of the color image reading means, the developing means of one of said plurality of units having a black toner, and the developing means of another of said plurality of units having at least one color toner, means to produce motion for installing said one unit in place of said another unit, means for determining when said one unit having the developing means including the black toner is installed in place of said another unit, and means for selecting green or neutral data of said image information by the motion that installs said one unit in place of said another unit.
BACKGROUND OF THE INVENTION
This application is a continuation of application Ser. No. 07/268,160, filed Nov. 7, 1988, now abandoned.
This invention is related to an image forming technique of the electrophotographic type and, in particular, to providing color images and a sharp black image made separately by developers with a simple, compact image forming apparatus.
Monochromatic image forming apparatus which use the latest electrophotographic technology is described in Japanese Patent Publication Open to Public Inspection (hereinafter referred to as Japanese Patent O.P.I. Publication) No. 2433/1976 as having an electro-static charger, a photosensitive body and cleaning devices integrated into a replaceable process unit. This has contributed to making image forming apparatus compact, and has improved its reliability.
Also by exchanging developing devices having different color toners (U.S. Pat. No. 4,097,139) with the use of the above mentioned process units, a technique has been developed to enable one image forming apparatus to make copies in a selected mono-color.
As an extension of this concept, the application of the above mentioned method to a color image formation may be considered. According to the concept expressed in Japanese Patent O.P.I., Publication No. 72159/1983, processing components other than those which are a part of the transfer means of a conventional analog color image forming apparatus are integrated into a unit. By exchanging a process unit having a color toner with one having a black toner, a black image forming process is converted to a color image forming process.
However, in a color image forming apparatus, as indicated in Japanese Patent O.P.I. Publication No. 72159/1983, where a transfer means performs, transfer process for each of several colors, since a high degree of accuracy is required between the transfer means and a photosensitive drum, it is thought that a process unit having no transfer means has reliability problems. Consequently, the present development is moving in the direction of unitizing and miniaturizing individual processing components as shown by a rotary-type developing device (Japanese Patent O.P.I. Publication No. 2600073/1985).
In contrast to the above, it is known that a full-color electro-photographic image forming apparatus that does not use such an elaborate transfer means or rotary type developing device as stated above comprises a charger, image exposure means, three units of adjacently arranged developing devices respectively accommodating yellow(Y), magenta(M), and cyan(C) toners, and transfer means adjacent a photosensitive drum. While the photosensitive drum makes three turns, a color image is formed with sequential Y, M, and C toner images each of which is transferred to a transfer material.
If one tries to form a black image using such an image forming apparatus, however, dislocation occurs at exposure, or color imbalance occurs in the development process caused by the preceding toner image, eventually producing a redish or bluish black, and failing to produce a sharp black image
Likewise, it is difficult to obtain a sharp image in black in a transfer method (Japanese Patent O.P.I. Publication No. 2600073/1985.) that develops a same latent image using toners Y, M, and C while a photosensitive drum makes one turn. This is primarily due to the fact that a toner image adhering to a photosensitive drum, in turn, influences exposure transmissivity when a following toner image is to be formed, or affects a potential in a development process.
To cope with this problem, a developing device accommodating black toner is added for forming a black image. This, however, causes the image forming apparatus to become larger. In addition to this, if developing devices containing Y, M, C and black are used, the black toner consumption becomes generally greater, posing the problem of frequent toner replenishment.
Moreover, there is a growing need for easy and sure conversion from mono-color such as black color image development to full color image development using yellow, magenta, and cyan toners. Subsequently, some modifications on a drive system in a main body of an image forming apparatus, bias and other electric input/output signal connections and their improvement have become necessary.
The present invention is made on the basis of the above mentioned background to provide a compact image forming apparatus capable of forming full color and sharp black images. This invention has achieved a configuration which is much smaller than the transfer drum system, whose mechanism is more complex and transfer registration is difficult, by repeating development in individual colors on a image forming means, and by summarily transferring a superimposed color toner image to a transfer material.
In addition to miniaturization, this invention has unitized at least a section including a developing device to simplify and ensure conversion between a configuration for forming a full color image and another one for forming a black image, while at the same time maintaining a proper image quality. The present invention has also been designed to replace a group of developing devices for multiple color toners with a developing device having a large amount of black toner or to replace only a specified color developing device of the above mentioned color developer group with a black toner developing device, giving them good interchangeability. This invention has effective developed the commonly used drive and electrical input/output terminals by matching a sleeve position of the black toner developing devices to that of any one of multiple color toner developing devices to be replaced with the former.
Moreover, unlike the conventional color image forming apparatus using a transfer drum system, this invention by switching to the black image forming configuration (process), provides the device with a control that enables production of a longer black image (or a single mono-color) than that of a circumferential length of a photosensitive drum. This invention has improved user operabilities by unitizing not only the developing devices but photosensitive drum, cleaning device, and electro-static charger as well for mutual interchangeability.
In particular, this invention has enabled interchangeability between the black toner developing device, which has integrated (unitized) photosensitive drum and cleaning device, and the yellow toner developing device among yellow, magenta, and cyan which are all needed for full color development. The yellow toner developing device has also unitized the sensitized material and the cleaning device.
While black toner is used frequently, the photosensitive drum in the unit for yellow developing device is used less frequently. Therefore, the latter may be used separately, and the black toner unit may be abolished when black toner is used up.
Furthermore, as another embodiment, an image forming apparatus switches an image forming mode in response to an operation that each unit is inserted or removed, ensuring the production of flawless images. Moreover, when a power switch is turned ON, the most frequently used mode is set in accordance with a kind of the process unit currently being set on the device, thus improving usability.
The present invention has made it possible to inhibit the full color mode once the unit containing the black toner developing device is set on the device.
Furthermore, this image forming, apparatus automatically switches the filter installed in the optical path for image reading to neutral or to a green filter by the setting motion of black toner developing device or the unit containing it.
An image forming apparatus in accordance with one aspect of the present invention comprises a photosensitive body, an electro-static charger adjacent the photosensitive body, an image exposure means for detecting an original image and forming a corresponding electrostatic image on a charged surface of the photosensitive body, multiple developing means having respective multiple color toners to produce a toner image for the electrostatic image obtained with the image exposure means for at least one color of the multiple color toners, and a transfer means for transferring the toner image onto a transfer material. The multiple developing means comprises a plurality of first developing means respectively placed in an installed position for storing the multiple color toners, second developing means for storing a black toner, and means for selectively placing the second developing means in the installed position of at least one of the plurality of first developing means.
This invention is characterized by a capability for switching a configuration where there are provided developers for multiple color toners, for example, three developing devices containing yellow (Y), magenta(M), or cyan(C) toner, which forms a color image by synthesizing superimposing toner images of Y, M, and C while the photosensitive drum revolves three times, to another configuration where there is provided a developing device containing black toner in the position of the above mentioned three developing devices which forms and transfers a black toner image while a photosensitive drum revolves around once.
Another aim of this invention is to provide the device with a compact configuration through the switching of developing devices. Another, aim is to provide an easy way of mode selection after the developing devices are exchanged. To achieve these aims, the image forming apparatus wherein it is possible to exchange developing devices that develop static latent image on the photosensitive drum is configured so that the setting motion of the developing device after an exchange of developing device will automatically select a specific image forming mode which is set up with the individual developing devices in advance.
In addition to miniaturization of the device through the exchange of developing devices, it is a further aim of this invention to provide protection against an erroneous operation in mode selection after the exchange of developing device. To achieve this aim, the, image forming, apparatus which exchanger developing devices that develop static latent image on the photosensitive drum is configured to inhibit the selection of a mode for color-image formation by the setting motion of a developing device containing black toner, as it replaces a developing device containing another color toner.
In addition to miniaturization of the device through the exchange of developing devices, it is a further aim of this invention to provide a way for automatically exchanging color separation filters used on the image-reading device.
To achieve this aim, there is an image-forming apparatus which enables the exchange of developing devices which develop a static latent image formed on the photosensitive drum. The image reading device reads the original image through a filter and provides an output signal after changing the read image into image information. The signal image forming apparatus is configured to select a neutral filter in response to a setting motion of developing device containing black toner as it is set on the device as the result of the exchange of developing devices.
US Referenced Citations (6)
Foreign Referenced Citations (1)
| Number |
Date |
Country |
| 59-79264 |
May 1984 |
JPX |
Continuations (1)
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Number |
Date |
Country |
| Parent |
268160 |
Nov 1988 |
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Patent Grant
5036367
