JPH0625883B2 - Image forming device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus having a plurality of developing devices, and is preferably applied to a color image forming device in which each developing device contains a different developer. It can be applied to electrophotographic image recording devices, copying machines, printers, printing machines, facsimile machines and the like.

2. Description of the Related Art Recently, many multicolor image forming apparatuses have been proposed. However, such image forming apparatuses have a plurality of developing devices around an image carrier and selectively operate each developing device. This produces a multicolor image.

In such an apparatus, each developing device is generally movable between a developing position close to the image carrier and a developing inoperative position separated from the image carrier. It is conceivable that when it comes close to the body, color mixing of the developer occurs and the image is remarkably deteriorated. In particular, when a plurality of developing devices are arranged in close contact with each other in order to minimize the unnecessary space around the image bearing member due to downsizing of the device, the plurality of developing devices are simultaneously mounted on the image bearing member. If the developing devices are brought close to each other, problems such as damage to the developing devices due to contact between the developing devices, damage to the driving mechanism of the developing devices, and damage to the image carrier may occur.

Further, when the image forming apparatus has a driving means for moving each developing device closer to or away from the image carrier and a control means for controlling the driving means, (1) when the power source of the image forming apparatus is turned off, Or, when the control means is turned off when the power of the device is turned off due to a sudden power failure or a jam process, or (2) there is a problem in the part that stores the position information of the developing device. In the case where the device is generated and the device is stopped, there is a possibility that a plurality of developing devices come close to the image carrier at the same time when the power is turned on again, and the above-mentioned problems occur.

Further, the position of the developing device is controlled by an electric circuit, a microcomputer, etc., but a means for detecting the position is required to electrically feed back the position information, which is expensive. There was a flaw.

Object of the Invention An object of the present invention is to prevent a plurality of developing devices from approaching the image carrier at the same time when the power is turned on, thereby preventing color mixture of the developers, and further to prevent the developing devices from contacting each other. An object of the present invention is to provide an image forming apparatus that can solve problems such as damage, damage to a driving mechanism of a developing device, damage to an image carrier, and the like, and obtain a high-quality image.

Means for Solving Problems The above object is achieved by the image forming apparatus according to the present invention.
In summary, the present invention is directed to a plurality of developing devices arranged around the image carrier and accommodating developers of different colors, and a developing position for each developing device in the vicinity of the image carrier. And a plurality of developing device moving means for independently moving each developing device between a developing inoperative position of each developing device separated from the image carrier, and only a selected developing device is provided. In an image forming apparatus that develops an electrostatic latent image by moving it to the developing position, all the developing devices are temporarily placed in their respective development inoperative positions when the image forming apparatus is powered on, and then a black developer is stored. The image forming apparatus is characterized in that only the developing device is moved to the developing position.

Embodiment Hereinafter, the image forming apparatus according to the present invention will be described in more detail with reference to the drawings. In this embodiment, the present invention is embodied in a color electrophotographic copying machine having two developing devices.

Referring to FIG. 3, an original 2 placed on an original placing glass 1 is illuminated by a lamp 3, and its optical image is composed of reflecting mirrors 4, 5, 6, 7, 8, 9 and a lens 10. The optical system guides the image bearing member, that is, the electrophotographic photosensitive drum 11 in this embodiment. Lamp 3 and mirror 4,
Documents 5 and 6 scan the document 2 in the arrow direction at a predetermined speed. On the other hand, the photosensitive drum 11 rotating in the direction of the arrow is uniformly charged on its surface by the charger 12, and then is irradiated with a light image, and an electrostatic image corresponding to the original image is formed on the drum surface. Around the photosensitive drum 11, a color developing device 13 containing color toner (eg, red and blue) and a black developing device 14 containing black toner are arranged. Each of these developing devices is configured to move in the direction of the arrow so as to maintain a developing position close to the photosensitive drum 11 and a developing inoperative position separated from the photosensitive drum 11, and the photosensitive device is exposed in accordance with a desired color image. The electrostatic image on the drum is visualized by approaching the drum 11. In FIG. 3, the color developing device 13 is in the non-developing position, the black developing device 14 is held in the developing position, and the black image is formed on the drum. This image is transferred onto the transfer paper by the transfer charger 15. After that, the photosensitive drum 11 reaches the cleaner 16, the residual toner on the surface of the drum is removed, and the process goes to the next step again.

The transfer paper 17 is taken out of the paper feed table 18 by a pick-up roller 19, separated into only one sheet by a separation roller 20, and then guided by guides 21 and 22 to the register roller 2.
It is transported to 3. The register roller 23 is the photosensitive drum 1.
The transfer paper is fed to the drum surface through the transfer upper guide 31 and the transfer lower guide 32 at a timing so that the visible image on 1 and the transfer paper coincide with each other.

An image on the drum surface is transferred to the transfer paper by the transfer charger 15, and separated from the drum surface by the separation charger 33.
It is sent to the fixing device 35 via the transport unit 34. The image on the transfer paper is fixed as a permanent image by the fixing device 35, the transfer paper is sent to the first discharge roller 36, then reaches the second discharge roller 39, and is then discharged to the outside of the copying apparatus.

Next, the developing devices 13 and 14 will be described with reference to FIG.

The developing devices 13 and 14 are urged by the panels 18a and 18b in a direction away from the image carrier, that is, the photosensitive drum 11, and the developing device driving cams 50a and 50b rotate to push the developing devices against the spring force. When the pressure is applied, the developing devices 13 and 14 are moved toward the photosensitive drum 11,
The developing rollers 13a and 14a of each developing device are the photosensitive drum 1.
When the developing device drive cams 50a and 50b are further rotated and the pressing force is not applied to the developing devices, the developing devices 13 and 14 have springs 18 respectively.
The developing rollers 13a and 14a of the respective developing devices are moved away from the photosensitive drum 11 by a and 18b, so that the developing rollers 13a and 14a of the developing devices are separated from the surface of the photosensitive drum 11 and are in a non-developable state. The two developing devices 13 and 14 are controlled so that when one of them approaches the photosensitive drum 11, one of them separates from each other so that they do not simultaneously approach the photosensitive drum 11. Further, in this embodiment, the developing device 13 has the shutter 60 of the developing device 14 located below, and when the developing device 13 approaches the photosensitive drum 11, the developing roller 14a of the developing device 14 is shielded.
The developer leaked from the developing device 13 is prevented from entering the developing roller 14a.

FIG. 2 is a cross-sectional view of a drive unit having a spring clutch C for rotating the drive cams 50a and 50b for forcibly moving the developing device to the photosensitive drum side against the spring force.

The spring clutch C transmits the rotation transmitted to the input gear 53 to the driven drum 55 via the coil spring 54. A hook is formed on the spring 54, and the hook is engaged with one end of the control ring 56. The control ring has a claw 5 for engaging a lever 58 controlled by the solenoid 40.
There are 7a and 57b, and when the tab is pushed by the lever 58, the rotational torque is not transmitted. However, when the lever separates from the claw, the spring 5 presses the drum surface 55 of the input gear 53, and transmits the rotation on the input side to the driven side. The rotation transmitted to the driven drum 55 is transmitted to the cam shaft 59 which rotates integrally with the driven drum 55, and rotates the cam 50b. The cam 50a is similarly operated.

The cam must be stopped at two positions, that is, a position where the developing device is close to the drum and a position where the developing device is separated from the drum. Therefore, the claws that define the position are provided at two opposing positions that are separated by 180 degrees, and one claw can be engaged with the lever 58 when the solenoid is on, and the other claw can be engaged with the lever 58 when the solenoid is off. In this embodiment, the solenoid is on and 5
7a, and 57b when turned off, the tab 57a
Defines the separated position, and the claw 57b defines the close position.

As described above, according to the present embodiment, each developing device is provided with the driving means capable of defining the position of the developing device, and the position control thereof is performed by the electric circuit and the micro computer (not shown). .

With the above structure, during the image forming operation, one of the developing devices is positioned by the drive means to the position close to the drum (developing position) to perform the developing operation. In addition, when the image forming apparatus is normally energized and ready for the next operation (standby state), the number of developing apparatuses is the highest among the plurality of developing apparatuses in order to shorten the time required until the start of the next operation. Frequently used developing devices are often stopped at a position close to the drum. In this embodiment, in the standby state, as shown in FIG.
The black developing device 14 is controlled to stop at a position close to the drum, and the color developing device 13 is controlled to stop at a position separated from the drum.

Next, when a power failure or a power cord is pulled out for some reason during the operation of the image forming apparatus, or a paper jam occurs during the operation, the copy operation is instantaneously stopped. Therefore, if the device stops due to such a cause,
There is a possibility that each developing device is in the process of moving, and it is possible that the position information of the developing device immediately before that is erroneously stored when the power is turned off.

Therefore, in the present invention, immediately after the power is turned on again, all the developing devices are once moved to positions separated from the photosensitive drum, and then the position control of each developing device is performed so as to be in the standby state. .

That is, the embodiment of the driving means of the developing device shown in FIG. 2 will be described. In this embodiment, the solenoid 40 is energized before the power is turned on again and the main motor begins to rotate, whereby the main motor rotates and at the same time the developing device is moved to the separated position. After the time required for separating all the developing devices has passed, the black developing device 14
Is controlled to move to a position close to the photosensitive drum 11, and the color developing device 13 is moved to a position separated from the photosensitive drum 11, to prepare for the next operation.

Further, as another example, when a service person or the like performs maintenance of the apparatus, or when connecting an option product, the lever 58 of the solenoid 40 is erroneously touched when connecting the connector of the drive portion. And the tab 57 may be disengaged, but even when the power is turned off from the standby state in this way, when the main motor starts to rotate when the power is turned on again, both developing devices are moved to a position separated from the drum. Control is performed to move each developing device to the standby position after a lapse of a time or more required to move the developing device to the separated position.

As is apparent from the above description, in the image forming apparatus according to the present invention, when the power is turned on to the apparatus, all the developing devices are always moved to the position separated from the drum and then moved to the standby position. Is performed.

EFFECTS OF THE INVENTION As described above, the image forming apparatus according to the present invention is capable of position control at the proximity position (development position) and the separation position (development inoperative) with respect to the image carrier when the power is turned on. By temporarily moving all the developing devices installed in the image forming apparatus to the separated positions and then controlling the positions of the developing devices so as to be in the standby state, it is possible to prevent a plurality of developing devices from approaching the image carrier at the same time. Therefore, it is possible to prevent deterioration of the image due to a mixture of a plurality of developers, and it is possible to avoid damage to the developing device and damage to the driving device due to contact between the developing devices.

Further, by controlling the image forming apparatus according to the configuration of the present invention, it is not necessary to detect the position of the developing device in the proximity position or the separation position, and the position detection sensor, its accompanying mechanism, and electric circuit are detected. It becomes possible to perform highly reliable position control with a cheaper device. Further, even if a service person or the like mistakenly touches the drive mechanism portion for repair or maintenance, it is possible to prevent the developing device from performing unnecessary operation and causing the damage as described above. Natsuta.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a developing device portion of an image forming apparatus according to the present invention. FIG. 2 is a sectional view showing an embodiment of the developing device driving means. FIG. 3 is a schematic sectional view of an embodiment of the image forming apparatus according to the present invention. 11: image carrier 13, 14: developing device 18a, 18b: spring 50a, 50b: developing device driving cam

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Akiyoshi Kimura 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Toshihiko Kusumoto 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (72) Inventor Takashi Ozawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Naoki Okuda 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. ( 72) Inventor Tatsuya Shiratori 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Michio Koike 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Atsushi Kubota 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Yasuyoshi Yamamoto 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Yasunori Maeda 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) Reference JP 61-201272 (JP, A) JP 58-40760 (JP, A)

Claims (1)

[Claims] 1. A plurality of developing devices, which are arranged around the image bearing member and which contain developers of different colors, and a developing position for each developing device, which is close to the image bearing member.
A plurality of developing device moving means for independently moving each developing device to and from a developing inoperative position of each developing device separated from the image bearing member, and developing only the selected developing device. In an image forming apparatus for moving an electrostatic latent image to a position to develop the electrostatic latent image, all developing devices are temporarily placed in respective development inoperative positions when the image forming apparatus is powered on, and then the developing device containing the black developer is developed. An image forming apparatus characterized in that only the apparatus is moved to the developing position.