JPH10171252A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of preventing a scavenging phenomenon where carriers in a developer scrape an image, while improving developability and preventing the problems of a void, etc., by a multistage developing system. SOLUTION: A developing device 40 is provided with two developing chambers 42A and 43A in the rotational direction of a photoreceptor drum 39. The developing chamber 42A on the upstream side is provided with a developing sleeve 42 incorporating a magnet 42a, a stirring screw, etc., houses a two-component developer and develops an electrostatic latent image formed on the drum 39 by a two-component magnetic brush developing system. The developing chamber 43A on the downstream side adopts a nonmagnetic one- component developing system, for preventing the scavenging phenomenon. Further, the developing chamber 43A is provided with a developing sleeve 43, an elastic roller as a toner supplying member, etc., houses nonmagnetic toner of a one-component developer and superimposes/develops the same latent image on the drum 39 by the nonmagnetic one-component developing system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine, an image recording apparatus, a printer, a facsimile, etc. The present invention relates to an image forming apparatus employing a developing method.

[0002]

2. Description of the Related Art Conventionally, a two-component developer composed of a magnetic carrier and a non-magnetic toner has been magnetically carried on a developing sleeve in which a magnet is fixedly arranged, and the photosensitive drum and the developing sleeve are rotated by rotation of the developing sleeve. A so-called two-component magnetic brush developing device is known in which an electrostatic latent image on a photosensitive drum is developed and visualized by passing through a developing area between the two.

In such a two-component magnetic brush developing device,
A first developing step using the upstream developing sleeve, and a second developing using the downstream developing sleeve, in which two developing sleeves are provided on the upstream side and the downstream side along the rotation direction of the photosensitive drum. An image forming apparatus adopting a multi-stage developing method, in which the same electrostatic latent image on the photosensitive drum is overlaid and developed depending on the process, to improve developability, to prevent white spots at the rear end of the image, and the like. Has been proposed.

[0004]

However, in such a developing method, in the toner image on the photosensitive drum developed by the upstream developing sleeve, a portion having a small amount of toner, such as a halftone portion, is formed on the downstream side. When the image is developed again by the developing sleeve, a so-called scavenging phenomenon of the image by the carrier, that is, a phenomenon that the carrier mechanically or electrostatically scrapes the image and disturbs the image sometimes occurs.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus capable of preventing a scavenging phenomenon while improving a developing property and preventing problems such as white spots by a multi-stage developing method.

[0006]

The above object is achieved by an image forming apparatus according to the present invention. In summary, according to the present invention, the developing device has two developing chambers provided with a developer carrier along the moving direction of the image carrier, and the electrostatic latent image formed on the image carrier is developed by one of the developing chambers. In an image forming apparatus in which the same electrostatic latent image is further developed in the other developing chamber, the development in the one developing chamber is performed by a two-component developer in which a non-magnetic toner and a magnetic carrier are mixed. It is a component magnetic brush development method, and the development by the other developing chamber is
Non-magnetic 1 by one-component developer consisting of only non-magnetic toner
An image forming apparatus using a component developing method.

According to the present invention, the other developing chamber contains a one-component developer consisting of only non-magnetic toner, and the other developing chamber has a developer supply elastic member, and the elastic member is The non-magnetic toner is carried on the developer carrier by moving while contacting the carrier. Alternatively, a two-component developer in which a non-magnetic toner and a magnetic carrier are mixed is accommodated in the other developing chamber, and the other developing chamber has a developer supply member having a built-in magnet. The developer supply member carries the developer, and the non-magnetic toner in the developer is carried on the developer carrying member of the other developing chamber by a magnetic brush method. Alternatively, a two-component developer in which a nonmagnetic toner and a magnetic carrier are mixed is stored in the other developing chamber, and a developer carrier of the other developing chamber is
A magnet having at least a repelling magnetic pole is built in a portion of the one developing chamber facing the developer carrying member, and the developer carrying body of the other developing chamber carries the developer, and the developing of the one developing chamber is carried out. By weakening the magnetic binding force on the carrier in the developer at the portion facing the developer carrier, leaving only the non-magnetic toner in the developer and transferring the carrier to the developer carrier in the one developing chamber, The developer carrier in the other developing chamber carries the non-magnetic toner.

Preferably, the one developing chamber is provided on the upstream side in the moving direction of the image carrier, and the other developing chamber is provided on the downstream side in the moving direction of the image carrier. Further, at the time of development by the one developing chamber, a developing bias in which an AC bias is superimposed on a DC bias is applied to the developer carrier, and at the time of development of the other developing chamber, an AC bias is applied to the developer carrier by the DC bias. A developing bias on which a bias is superimposed is applied.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings.

Embodiment 1 First, an embodiment of the present invention will be described with reference to FIG. 1 and FIG. FIG. 1 is a sectional view showing a schematic configuration of an embodiment of the image forming apparatus of the present invention. The image forming apparatus of this embodiment is a transfer type electrophotographic copying apparatus of a fixed original platen, moving optical system, and rotating drum type.

In this embodiment, a fixed platen glass 2
When the copy 19 is pressed after the original 19 is placed on the document 0 and the necessary copy conditions are set, the photosensitive drum 39 is driven to rotate at a predetermined peripheral speed in a clockwise direction indicated by an arrow. Further, the light source 21 (which covers the reflection shade 22) and the first mirror 23, which are reciprocally movable, move at a predetermined speed V from the home position on the left side of the glass to the right side of the glass along the lower surface of the platen glass 20. To move (forward) and the second mirror 2
4. When the third mirror 25 moves in the same direction at a speed of V / 2, the image surface of the original 19 placed on the original platen glass 20 facing downward is illuminated and scanned from the left side to the right side. ,
The reflected light of the illumination scanning light from the document surface is imaged on the surface of the photosensitive drum 39 via the imaging lens 29, the fixed fourth mirror 26, the fixed fifth unmirror 27, and the fixed sixth mirror 28 (slit exposure). Is done.

The rotating photosensitive drum 39 is uniformly charged to a predetermined positive or negative potential by the primary charger 30 before the above-described exposure, and the above-described exposure is performed on this charged surface. Then, an electrostatic latent image having a pattern corresponding to the original image is sequentially formed on the surface of the photosensitive drum 39. The electrostatic latent image formed on the photosensitive drum 39 is developed by the developing sleeves 42 and 43 of the developing device 40 and is visualized as a toner image.

On the other hand, a recording material sheet P is fed toward a photosensitive drum 39 by a paper supply means (not shown), and the recording material sheet P passes through a guide 33 and a photosensitive drum 39 and a transfer charger 34 at a predetermined timing. And is introduced into the transfer section between them. The recording material sheet P introduced into the transfer unit receives the transfer corona from the transfer charger 34, and the photosensitive drum 3
9, the toner image on the surface of the photosensitive drum 39 is sequentially transferred to the surface of the recording material sheet P while passing through the transfer portion.

The recording material sheet P on which the toner image has been transferred by passing through the transfer section is sequentially separated from the surface of the photosensitive drum 39 by separation means, for example, a separation belt (not shown) provided at the end of the drum. After the charge on the back surface is removed by the charge removing needle 35, the toner is introduced into the fixing device 60 by the transport guide 38 and the guide 18, and is fixed to the toner image to form an image-formed product, that is, a print image, out of the image forming apparatus. Is discharged.

The surface of the photosensitive drum 39 on which the transfer has been completed is cleaned and removed by the cleaning blade 37 of the cleaning device 36, and is repeatedly used for image formation. The moving optical unit that has moved forward as described above,
That is, the light source 21, the reflection shade 22, the first mirror 23, the second
When the mirror 24 and the third mirror 25 reach the predetermined forward movement end point, they are turned backward, return to the initial home position, and wait for the start of the next copy cycle (optical system back process).

The developing device 40 installed in the image forming apparatus shown in FIG. 1 will be described with reference to FIG. In this embodiment, the developing device 40 has two upper and lower developing chambers 40A and 40B along the rotation direction of the photosensitive drum 39, and the developing chambers 40A and 40B, respectively, for developing circulation and stirring. And the upstream developing chamber 40 is provided.
A, a stirring screw 44 is provided in the space A, and a transport roller 45 and an elastic roller 4 are provided in the space of the developing chamber 40B on the downstream side.
8 are installed.

In the upstream developing chamber 40A, a two-component developer 4 in which a negative toner having a particle diameter of 8 μm and a ferrite carrier having a particle diameter of 50 μm are mixed is accommodated, and two-component magnetic brush development is performed. At 40B, a non-magnetic one-component developer 5 containing a negative toner having a particle diameter of 8 μm is accommodated, and non-magnetic one-component development is performed.

The respective developing steps will be described below. First, in the upstream developing chamber 40A, the developer 4 is stirred by the stirring screw 44 and supplied to the developing sleeve 42 in which the magnet 42a is fixedly arranged, and the developer 4 is carried on the surface of the developing sleeve 42. Then, the developer is conveyed toward the photosensitive drum 39, and the amount of the developer is regulated to an appropriate amount by the doctor blade 46 during the conveyance. The developer 4 conveyed toward the photosensitive drum 39 is applied to the developing sleeve 42 by applying a developing bias in which an AC bias is superimposed on a DC bias in the vicinity of a position facing the photosensitive drum 39, thereby forming a known two-component magnetic brush. The electrostatic latent image on the photosensitive drum 39 is developed by a developing method. As a result, the non-magnetic toner in the developer 4 adheres to the latent image, and the latent image is visualized as a toner image.

Next, in the downstream developing chamber 40B, the non-magnetic one-component developer, that is, the non-magnetic toner 5 is conveyed toward the elastic roller 48 by the conveying roller 45, and the non-magnetic toner 5 is adhered and stripped. It is carried on the surface of the non-magnetic developing sleeve 43 by the elastic roller 48 which also serves as a carrier, and is conveyed toward the photosensitive drum 39 by the developing sleeve 43. The toner 5 is regulated to an appropriate amount by the elastic blade 47 during the conveyance. The non-magnetic toner 5 conveyed toward the photosensitive drum 39 is applied to the developing sleeve 43 by applying a developing bias in which an AC bias is superimposed on a DC bias in the vicinity of a position facing the photosensitive drum 39, thereby obtaining a known non-magnetic toner 5. The electrostatic latent image once developed on the photosensitive drum 39 is developed by the component developing method. As a result, the toner 5 adheres to the latent image, and the latent image is further developed.

As described above, in the present embodiment, since the second developing step in the downstream developing chamber 40B is a non-magnetic one-component developing method, the scavenging phenomenon which has conventionally occurred in the second developing step can be achieved. That is, mechanical and electrostatic scraping of the image itself by the carrier does not occur. Therefore, it is possible to obtain a high-quality image by preventing image disorder while maintaining the effect of improving the developability by the multi-stage developing method and preventing the occurrence of white spots at the rear end of the image.

Embodiment 2 Another embodiment of the present invention will be described with reference to FIG. Figure 1
In the first embodiment shown in FIG.
Although two types of developers were used, such as a two-component developer 4 for A and a one-component developer 5 for the developing chamber 40B, the two-component developer 4 was also used for the developing chamber 40B in this embodiment. In the downstream developing chamber 40B, instead of the elastic roller 48 of the first embodiment, a toner supply sleeve 50 in which a magnet (not shown) is fixedly provided is installed. Further, instead of the elastic blade 47 for the developing sleeve 43, a toner supply sleeve 50 is provided. A magnetic doctor blade 49 for the toner supply sleeve 50 is provided.

In this embodiment, the upstream developing chamber 40A
Is performed through the same process as in the first embodiment.

The second developing step in the downstream developing chamber 40B is performed as follows. That is, in the downstream developing chamber 40 </ b> B, the two-component developer 4
Is transported to the toner supply sleeve 50, and the developer 4 is carried on the surface of the toner supply sleeve 50 having a built-in magnet, and is transported toward the developing sleeve 43. After regulating the developer 4 to an appropriate amount by the doctor blade 49 during the conveyance, the non-magnetic toner 5 in the developer 4 is supplied to the non-magnetic developing sleeve 43 by a well-known two-component magnetic brush method. And carry it. The non-magnetic toner 5 carried on the developing sleeve 43 is conveyed toward the photosensitive drum 39, and a developing bias in which an AC bias is superimposed on a DC bias is applied to the developing sleeve 43 in the vicinity of a position facing the photosensitive drum 39. The electrostatic latent image once developed on the photosensitive drum 39 is developed by a non-magnetic one-component developing method. As a result, the toner 5 adheres to the latent image, and the latent image is further developed.

As described above, in this embodiment, the two-component developer 4 is used in the downstream developing chamber 40B, but the non-magnetic toner is supplied to the developing sleeve 43 from the two-component developer.
Since the second developing step was performed by the non-magnetic one-component developing method, there was no scavenging phenomenon due to the carrier, as in the case of Example 1, and the multi-stage developing method improved the developability and caused a white spot at the rear end of the image. It is possible to obtain a high-quality image by preventing image disturbance while maintaining the effect of preventing the image. In this embodiment, since only the two-component developer was used,
The mechanism for supplying the developer to the developing device 40 can be simplified, and the above effects can be achieved at lower cost than in the first embodiment.

Embodiment 3 FIG. 4 is a schematic structural view showing a developing device according to another embodiment of the present invention. In the present embodiment, the toner supply sleeve 50 is omitted in the developing device of FIG.
As shown in FIG. 4, a magnet 43a is fixedly arranged inside the developing sleeve 43 of the downstream developing chamber 40B, and the facing position of the magnet 43a facing the magnet 42a in the developing sleeve 42 of the upstream developing chamber 40A. Is characterized by providing repelling magnetic poles (magnetic poles S, S in this example) in the vicinity of. The doctor blade 49 was provided for the developing sleeve 43. Further, the surface of the developing sleeve 43 is a rough surface having a surface roughness Rz of about 3 μm so as to easily carry the toner.

In this embodiment, the upstream developing chamber 40A
Is carried out through the same process as in Example 2 (accordingly, Example 1). Next, in the developing chamber 40B on the downstream side where the second developing step is performed, the transport rollers 4
The two-component developer 4 conveyed by 5 is carried on a developing sleeve 43 containing a magnet 43a. Developer 4
After the amount of the developer is regulated by the doctor blade 49, the magnet 43a in the developing sleeve 43 is located near the position where the upstream developing chamber 40A faces the developing sleeve 42.
Due to the repelling magnetic poles S, the carrier holding force in the developer 4 is relaxed, and the carrier is attracted to the upstream developing sleeve 42 and shifts. Therefore, only the non-magnetic toner 5 in the developer 4 remains on the downstream developing sleeve 43, and the latent image on the photosensitive drum 39 can be further developed by the non-magnetic one-component developing method.

As described above, in this embodiment, it is not necessary to use the toner supply roller 50 as in the second embodiment, so that the same effects as those of the second embodiment can be obtained, and the size of the apparatus can be reduced. The cost can be reduced.

[0028]

As described above, according to the present invention,
2 provided with a developer carrier along the moving direction of the image carrier.
When the same electrostatic latent image formed on the image bearing member is superimposed and developed by a developing device having two developing chambers, after the development using a two-component magnetic brush developing method using a two-component developer in one developing chamber, the other is performed. Since the development in the developing chamber was performed by the non-magnetic one-component developing method including only the non-magnetic toner,
The carrier generated during the development process does not cause scavenging itself, which mechanically and electrostatically scrapes the image, maintaining the effect of improving the developability by multi-stage development and preventing white spots at the trailing edge of the image As a result, a high-quality image can be obtained while preventing image disturbance.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view illustrating a schematic configuration of a developing device installed in the image forming apparatus of FIG.

FIG. 3 is a cross-sectional view illustrating a schematic configuration of a developing device according to another embodiment of the present invention.

FIG. 4 is a cross-sectional view illustrating a schematic configuration of a developing device according to still another embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 4 two-component developer 5 nonmagnetic toner 39 photosensitive drum 40 developing device 42, 43 developing sleeve 42a, 43a magnet 42A, 43A developing chamber 47 elastic blade 48 elastic roller 49 doctor blade 50 toner supply sleeve

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuhiro Hasegawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc.

Claims (6)

[Claims] A developing device has two developing chambers provided with a developer carrier along a moving direction of the image carrier, and develops an electrostatic latent image formed on the image carrier by one developing chamber. In the image forming apparatus for further developing the same electrostatic latent image by the other developing chamber, the developing by the one developing chamber may be performed by a two-component magnetic brush using a two-component developer obtained by mixing a non-magnetic toner and a magnetic carrier. An image forming apparatus, wherein the image forming apparatus is a non-magnetic one-component developing method using a one-component developer made of only a non-magnetic toner. 2. The one-component developer containing only non-magnetic toner is contained in the other developing chamber, and the other developing chamber has a developer supply member composed of an elastic member. The image forming apparatus according to claim 1, wherein the nonmagnetic toner is carried on the developer carrier by moving while contacting the developer carrier. 3. The other developing chamber contains a two-component developer in which a non-magnetic toner and a magnetic carrier are mixed, and the other developing chamber has a developer supply member having a built-in magnet. 2. The image forming apparatus according to claim 1, wherein a supply member carries the developer, and a non-magnetic toner in the developer is carried on a developer carrier of the other developing chamber by a magnetic brush method. 4. The two-component developer in which a non-magnetic toner and a magnetic carrier are mixed is accommodated in the other developing chamber, and the developer carrying member of the other developing chamber carries the developer carrying material of the one developing chamber. A magnet having at least a repelling magnetic pole is built in a portion facing the body, and the developer carrier of the other developing chamber carries the developer, and the developer is developed at the portion of the one developing chamber facing the developer carrier. By weakening the magnetic binding force on the carrier in the developer, leaving the non-magnetic toner in the developer and transferring only the carrier to the developer carrying member in the one developing chamber, the developer carrying in the other developing chamber is reduced. The image forming apparatus according to claim 1, wherein the body carries a non-magnetic toner. 5. The image forming apparatus according to claim 1, wherein said one developing chamber is installed on the upstream side in the moving direction of the image carrier, and the other developing chamber is installed on the downstream side in the moving direction of the image carrier. The image forming apparatus according to the item. 6. A developing bias in which an AC bias is superimposed on a DC bias is applied to the developer carrying member during development by the one developing chamber, and a DC bias is applied to the developer carrying member during development in the other developing chamber. The image forming apparatus according to claim 1, wherein a developing bias in which an AC bias is superimposed on the bias is applied.