JPH09106146A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of preventing the deterioration of an image caused by leaked toner, having simple structure, restraining operational noise and eliminating the need for special maintenance work. SOLUTION: This image forming device is provided with two developing devices for black and red on the periphery of a photoreceptor drum 10. The developing device is constituted of an electrifier, an exposure unit and a developing unit. In the 1st developing unit 17 for black and the 2nd developing unit 18 for red, a toner image is formed by sticking toner on an electrostatic latent image on the drum 10. The 2nd electrifier 14 recovers potential by electrification attenuated by forming the black image by corona discharge whose polarity is negative. The 2nd electrifier 14 is provided with a movable cover 19. The cover 19 is motor-driven to freely rotate around the 2nd electrifier 14 so as to open/close the aperture part 14a of the 2nd electrifier 14. Therefore, even when black toner is leaked from the 1st developing device 17, the black toner T1 does not adhere to a charge wire 14b by the cover 19 in the 2nd electrifier 14.

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 for developing image data with a plurality of colors in an electrophotographic system in a copying machine, a facsimile, a printer or the like, and more particularly, to prevent the charger from being soiled by the developer. It was done.

[0002]

2. Description of the Related Art Generally, a multi-color image forming apparatus is sequentially provided for each constituent color of a developing device in the rotational direction of a photosensitive drum. Each developing device is provided with a charging device for forming an electrostatic latent image. Toner leaking from the developing device in front of the developing device or floating in the device adheres to this charging device to form a photosensitive drum. Hinders the uniform charging of the image, disturbs the developed image, and this develops as aged deterioration of the image. In order to prevent this, conventionally, a developing device is provided with a suction port in the vicinity of the photosensitive drum, and an orifice portion is provided between the suction port and the suction source to suck the developer leaked from the developing device at the front position. There is a device provided with a suction device (Japanese Patent Laid-Open No. 63-298269). Further, there is a device in which an electrode roller charged to the same polarity as the charging device of the developing device at the front position is provided and a scraper for removing the developer is brought into contact with the electrode roller (special opening and closing 2-2500
75).

[0003]

In the former of the above-mentioned conventional image forming apparatuses, the operation noise of the suction device is large, the filter needs to be replaced, and the size of the apparatus becomes large, resulting in cost reduction. It becomes high. Even in the latter case, the size of the device becomes large, the installation space is taken, the miniaturization is hindered, and the cost becomes high. Therefore, the present invention can prevent the deterioration of the image due to the leaked toner,
It is an object of the present invention to provide an image forming apparatus having a simple structure, which has a low operation sound, does not require special maintenance work.

[0004]

In order to solve the above problems, in the first invention, an electrophotographic photosensitive member 10 on which an electrostatic latent image and a developer image are formed, and this photosensitive member 1
A plurality of developing devices 11, 1 which are sequentially arranged in the displacement direction of 0 and form an electrostatic latent image and a developer image for each different constituent color.
2 and a transfer device 9 that transfers the developer image on the photoconductor 10 onto the image carrier P, and the developing devices 11 and 12 charge the photoconductor 10 with charging devices 13 and 14 and electrostatic charges. In the image forming apparatus 8 having the exposing devices 15 and 16 for forming a latent image and the developing devices 17 and 18 for forming a developer image by attaching a developer to the electrostatic latent image, the charger 1 of the developing device 12 is used.
4 is provided with a movable cover which can be closed and exposed to prevent the leaked developer T1 from adhering to the charger 14. In the second invention, the charger 2
4 is rotatably provided so as to face in a direction different from the direction in which the photoconductor 10 is charged. In the third invention, the charger 25 of the developing device 12 is provided so as to be movable back and forth with respect to the photoconductor 10. In the fourth invention, the charging device 25 and the developing device 27 are integrally formed, and are provided so as to be movable back and forth with respect to the photoconductor 10.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a copying machine will be described with reference to the drawings. In FIG. 1, a copying machine 1 includes a main body 2, an automatic document feeder 3 provided at an upper portion thereof, a manual feed tray 4 provided at a rear portion, and a paper discharge unit having a sorting function provided at a front portion. 5 and a sheet feeding unit 6 provided at the bottom. Body 2
Has an optical scanning system 7 for reading a document image and outputting the laser, an image forming apparatus 8, and a fixing apparatus 9.

As shown in FIG. 2, the image forming apparatus 8 is provided with a photosensitive drum 10 which is an electrophotographic photosensitive member substantially at the center thereof. The photosensitive drum 10 is adapted to rotate clockwise in the drawing. The photosensitive drum 10 has two peripheral portions so that an image is composed of two colors, black and red (or blue).
Two developing devices 11 and 12 are facing. Each developing device 1
1 and 12 include a charger 13, 14 and an exposure device 15, 1 in order.
6 and developing devices 17 and 18, respectively.

The first charger 13 provided on the photosensitive drum 10 for forming an electrostatic latent image for a black image is
In the dark, the photosensitive drum 10 is charged by negative corona discharge, and the grid is used to make the charged state uniform. A first exposure device 15 is provided on the front side of the first charging device 13 in the rotation direction of the photosensitive drum 10 so that a laser diode emits light to form an electrostatic latent image on the photosensitive drum 10 by charge erasing. There is. A first developing device 17 is provided on the front side of the first exposing device 15. The first developing unit 17 forms a black toner image on the photosensitive drum 10 by adhering the black toner T1 which is a developer charged to the negative polarity to the electrostatic latent image.
On the front side of the first developing device 17, the second charger 1 for red image is provided.
4 are provided. The second charger 14 restores the charging potential attenuated by the formation of the black image by negative corona discharge. In the second charger 14, as shown in FIG.
It is covered with a movable cover 19 for preventing the leaked black toner from adhering. This movable cover 19
Like the second charger 14, it has a substantially semi-cylindrical shape and is rotatable around the second charger 14 by a motor 19a via a gear 19b. As shown in FIGS. Two
The charge wire 1 is opened and closed by opening and closing the opening 14a of the charger 14.
4b is exposed and closed. On the front side of the second charger 14, the photosensitive drum 10 which is charged by the laser diode emitting light.
A second exposure device 16 that forms an electrostatic latent image by erasing the charge on the top
Is provided. A second developing device 18 is provided on the front side of the second exposing device 16. The second developing device 18 attaches a negatively charged red toner T2, which is a negatively charged developer, to the electrostatic latent image by non-magnetic one-component non-contact development without disturbing the already formed black image, and then the photosensitive drum. Form a red (or blue) visible image on 10. A transfer unit 20 is provided on the front side of the second developing device 18. The transfer unit 20 places the transfer paper P, which is an image carrier, on the transfer belt 20a applied with the positive polarity and moves it, and contacts the photosensitive drum 10 with the toner T1 and T2 charged with the negative polarity to the transfer paper P. The transfer paper P is adhered, and is reliably peeled off and separated from the photosensitive drum 10 by the separation claw 20b. A photo sensor 21 is provided on the front side of the transfer unit 20. The photo sensor 21 detects the shortage of the black toner T1 from the density of the black image developed on the photosensitive drum 10 and feeds back the black toner T1 so as to replenish it to control the first developing device 13. A cleaning unit 22 is provided on the front side of the photo sensor 21. The cleaning unit 22 scrapes off the toner T1 and T2 remaining on the photosensitive drum 10 with the cleaning blade 22a and collects them with the brush 22b. On the front side of the cleaning unit 22, there is provided a charge removing unit 23 that erases the negative charge remaining on the photosensitive drum 10 by front exposure of the LED and restores the photosensitive drum 10 to the initial state in preparation for the next transfer. .

In the image forming apparatus 8 according to this embodiment, the photosensitive drum 10 rotates clockwise in FIG. 2, and the first charger 13 uniformly charges the surface of the photosensitive drum 10.
Then, the first exposure device 15 forms an original image read by the optical scanning system 7 on the photosensitive drum 10 as an electrostatic latent image. Next, the first developing device 17 adheres the black toner T1 to the electrostatic latent image to form a black toner image on the photosensitive drum 10. At this time, even if the black toner leaks from the first developing device 17, the opening 14a of the second charger 14 is closed by the movable cover 19 as shown in FIG.
The black toner T1 does not adhere to the charge wire 14b. The second charger 14 restores the charging potential on the photosensitive drum 10 that has been reduced due to the formation of the black image because the second charger 14 forms the red image. Then, after the second exposure device 16 forms an electrostatic latent image for a red image on the photosensitive drum 10,
The second developing device 18 adheres the red toner T2 to the electrostatic latent image to form a red toner image on the photosensitive drum 10. Next, the transfer unit 20 moves the transfer paper P while transferring it, and the cleaning unit 22 scrapes off and collects the toners T1 and T2 remaining on the photosensitive drum 10. Finally, the charge eliminating portion 23 erases the negative charge remaining on the photosensitive drum 10 by front exposure of the LED to restore the initial state.

A second embodiment is shown in FIGS. 6 to 8. As shown in FIG. 6, the second charger 24 in this embodiment is rotatably provided via a gear 24d by driving a motor 24c, and its opening 24a is directed in a direction different from the photosensitive drum 10 side. It can be turned. Therefore, even if the black toner T1 leaks from the first developing device 13, the second charging device 24 is rotationally displaced when the first developing device 13 operates from the state shown in FIG. 7, and the opening thereof is opened as shown in FIG. If the portion 24a is turned to the opposite side, the charge wire 2
The black toner T1 does not adhere to 4b.

A third embodiment is shown in FIG. The second charger 25 in this embodiment is provided via a return spring 25c, and is movable back and forth with respect to the photosensitive drum 10 by a cam 25d that rotates in synchronization with the operation of the first developing device 13. Therefore, even if the black toner T1 leaks from the first developing device 13, the second charging device 2 is operated when the first developing device 13 operates.
Since the toner 5 is separated from the photosensitive drum 10, the black toner T1 hardly adheres to the charge wire.

A fourth embodiment is shown in FIGS. The second charger 26 in this embodiment is integral with the second developing device 27. The second developing device 27 is provided via a return spring 27a, and the photosensitive drum 10 is driven by a cam 27b that rotates in synchronization with the operation of the first developing device 13.
You can move forward and backward freely. Further, the base of the second charger 26 is provided with an opening 26c in the movable range of the laser so as not to interfere with the exposure operation of the second exposure device 14. Therefore, even if the black toner T1 leaks from the first developing device 13,
When the first developing device 13 is operating, the second charging device 26 and the second developing device 27 are separated from the photosensitive drum 10, so that the black toner T1 is less likely to adhere to the second charging device 26.

[0012]

As described above, according to the present invention, it is possible to prevent the image from being disturbed due to the developer leaking from another charging device to be attached to the charging device, and to maintain it for a long period of time. Noise due to the conventional suction device is avoided, no special maintenance work such as filter replacement is required, and the device is relatively simple, can be downsized, and can be provided at low cost. Has the effect.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a copying machine.

FIG. 2 is an explanatory diagram of an image forming apparatus.

FIG. 3 is a perspective view of a second charger according to the first exemplary embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of a second charger with a movable cover opened.

FIG. 5 is a schematic configuration diagram of a second charger with a movable cover closed.

FIG. 6 is a perspective view of a second charger according to the second exemplary embodiment.

FIG. 7 is a schematic configuration diagram of a second charger in a normal state.

FIG. 8 is a schematic configuration diagram of a second charger in a rotated state.

FIG. 9 is a schematic configuration diagram of a second charger in a retracted state in the third embodiment.

FIG. 10 is a schematic configuration diagram of a second charger in an approaching state according to a fourth embodiment.

FIG. 11 is a schematic configuration diagram of a second charger in a retracted state.

[Explanation of symbols]

 8 Image Forming Device 10 Photosensitive Drum 11 First Developing Device 12 Second Developing Device 13 First Charging Device 14 Second Charging Device 15 First Exposure Device 16 Second Exposure Device 17 First Developing Device 18 Second Developing Device 19 Movable Cover 24 Second Charger 25 Second Charger 25c Return Spring 25d Cam 26 Second Charger 27 Second Developer 27a Return Spring 27b Cam

Front page continuation (72) Inventor Naoshi Hayakawa 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (4)

[Claims] 1. An electrophotographic photosensitive member on which an electrostatic latent image and a developer image are formed, and an electrostatic latent image and a developer image which are sequentially arranged in the displacement direction of the photosensitive member, and which have different constituent colors. And a transfer device for transferring the developer image on the photoconductor onto the image carrier, the developing device charging the photoconductor and an electrostatic latent image. In an image forming apparatus having an exposing device for forming and a developing device for forming a developer image by adhering a developer to an electrostatic latent image, a movable cover capable of closing and exposing the charging device of the developing device. An image forming apparatus comprising: 2. An electrophotographic photosensitive member on which an electrostatic latent image and a developer image are formed, and an electrostatic latent image and a developer image which are sequentially arranged in the displacement direction of the photosensitive member and which have different constituent colors. And a transfer device for transferring the developer image on the photoconductor onto the image carrier, the developing device charging the photoconductor and an electrostatic latent image. In an image forming apparatus having an exposing device for forming a developer and a developing device for forming a developer image by adhering a developer to an electrostatic latent image, the charger of the developing device is An image forming apparatus, which is rotatably provided so as to face in a direction different from the direction. 3. An electrophotographic photosensitive member on which an electrostatic latent image and a developer image are formed, and an electrostatic latent image and a developer image which are sequentially arranged in the displacement direction of the photosensitive member and which are different in constituent colors. And a transfer device for transferring the developer image on the photoconductor onto the image carrier, the developing device charging the photoconductor and an electrostatic latent image. In an image forming apparatus having an exposing device for forming a toner image and a developing device for forming a developer image by adhering a developer to an electrostatic latent image, a charging device of the developing device is capable of advancing and retracting with respect to the photoconductor. An image forming apparatus provided in the. 4. An electrophotographic photosensitive member on which an electrostatic latent image and a developer image are formed, and an electrostatic latent image and a developer image, which are sequentially arranged in the displacement direction of the photosensitive member, for different constituent colors. And a transfer device for transferring the developer image on the photoconductor onto the image carrier, the developing device charging the photoconductor and an electrostatic latent image. In an image forming apparatus having an exposing device for forming an electrostatic latent image and a developing device for forming a developer image by adhering a developer to an electrostatic latent image, the charging device and the developing device are integrally formed, and An image forming apparatus, which is provided so as to be able to move forward and backward.