JP2003263028A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-sized developing unit at a low cost. <P>SOLUTION: A system wherein a developing sleeve is fixed, and developer is carried by the rotation of a magnet, is provided with a carrying guide plate for carrying the developer in the axial direction of the sleeve after finishing a developing process on the sleeve, and only one screw is arranged to carry the developer in the opposite direction. <P>COPYRIGHT: (C)2003,JPO

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 such as a copying machine or a printer.

[0002]

2. Description of the Related Art In a conventional electrophotographic image forming apparatus, especially an image forming apparatus for forming a chromatic image, a two-component developing method in which a non-magnetic toner and a magnetic carrier are mixed and used as a developer is known. Widely used. Two
The component development method has advantages over other currently proposed development methods such as image quality stability and device durability, while keeping the state of the developer as constant as possible after development. In addition, there is a tendency for the apparatus to become large in size because it requires a step of constantly peeling the developer from the developer carrier after completion of the development, stirring with the developer not used for development, and supplying the developer to the developer carrier after completion of the stirring. It was

Several solutions to this problem have been proposed in the past. For example, a 5-pole sleeve provided with a repulsive pole as shown in FIG. 5 is used, and a screw for transporting the developer in the axial direction of the sleeve is provided at the dropping point of the developer. By providing a screw to be conveyed separately from the screw in the vicinity of the developing section, the circulation of the developer conveyed in the axial direction is balanced, and the developer dropped from the developing sleeve is conveyed by the screw in the vicinity of the developing section. There is proposed a developing device which is circulated so as to be stirred and then supplied to the developing sleeve and conveyed again to the developing section. In this way, the developer can be agitated and conveyed stably with a simple structure with one sleeve and two screws, so most of the developing devices of small-sized full-color copying machines are currently used. ing.

[0004]

On the other hand, while the market for full-color copying machines / printers has expanded in recent years and various functions are required, for example, in order to provide high productivity, a plurality of photosensitive drums are arranged and multiple transfer is performed. Many tandem type image forming apparatuses that perform the above have been commercialized, and it seems that they will continue to be one of the mainstream of the market.

However, the tandem system has a problem that the cost of the main body cannot be easily reduced because the number of used parts including the photoconductor is increased as compared with the conventional one-drum system. Therefore, in the tandem system, the cost reduction of the developing device alone has become more and more important. Further, the cost reduction is the same not only in tandem but also in an image forming apparatus that forms a monochrome image. In addition, downsizing of the device is also an important factor to reduce the cost of the main body. If the device can be made smaller, the cost of the main unit can be reduced as a result. Particularly in the case of the tandem system, since the developing device is arranged for each station, downsizing of the developing device is important.

Therefore, an object of the present invention is to provide a developing device having a small size and a simple structure in a single color image forming apparatus or a full color image forming apparatus having various structures such as a tandem system, thereby making it possible to reduce the cost. It is to realize and provide a small-sized image forming apparatus.

[0007]

The above object is achieved by an image forming apparatus according to the present invention as described below.

According to the present invention, an image carrier, charging means for charging the image carrier, exposing means for exposing the charged image carrier, and a static image formed on the image carrier by the exposing means. An image forming apparatus, comprising: a developing unit containing a two-component developer for developing an electrostatic latent image; and a transfer unit for transferring the developed image developed by the developing unit onto a recording material. Is composed of a fixed developer carrier having a magnet roll magnetized in multiple poles that rotate inside. The developer is conveyed by the rotation of the magnet roll, and the developer is located downstream of the developing section in the developer conveying direction. Is provided with a conveyance guide peeling plate for giving a force for feeding the developer in the axial direction of the image carrier and peeling the developer from the developer carrier.
A means for agitating and transporting the developer in a direction opposite to the direction in which the transport guide peeling plate is disposed in the vicinity of the developer carrier and parallel to the axial direction of the developer carrier is provided. The image forming apparatus.

As a result, it is possible to realize and provide a low-priced and small-sized image forming apparatus in a single-color image forming apparatus and a full-color image forming apparatus having various configurations such as a tandem system.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 is a diagram for explaining a developing device of this embodiment, FIG. 2 is a diagram for explaining an image forming device using this developing device, and FIG. It is explanatory drawing seen from.

First, the operation of the entire image forming apparatus will be described. In FIG. 2, first, the surface of the photosensitive drum 28 charged by the charger 21 is exposed by the laser 22 to form an electrostatic latent image on the photosensitive drum 28, and the latent image is developed by the developing device 1 to expose the latent image. A toner image is formed on the drum 28. This toner image is transferred to the recording paper 27 conveyed by the transfer belt 24 by the transfer bias of the transfer charger 23, and then the recording paper 27 is separated from the transfer belt 24 and pressed / heated by the fixing device 25. Get a permanent image. Also, after the transfer, the photosensitive drum 2
The residual toner remaining on the sheet 8 is removed by the cleaner 26 to prepare for the next image formation. The cleaner 26 is
It has a carrying screw 29 and carries the developer removed by the cleaner from the image forming unit into the main body apparatus. The developer is conveyed to one location (not shown) in the main body and is collected by a service person or the like at an appropriate timing.

Next, the developing device 1 will be described in detail with reference to FIG.

The developing device 1 contains a two-component developer consisting of a non-magnetic toner and a magnetic carrier, and the mixing ratio thereof is about 1: 9 by weight. This ratio should be properly adjusted depending on the charge amount of the toner, the particle size of the carrier, the configuration of the image forming apparatus, and the like, and it is not always necessary to follow this value.

The developing device 1 has an opening in a developing area facing the photosensitive drum 28, and a developing sleeve 3 is fixedly arranged so as to be partially exposed in the opening. The developing sleeve 3 including the rotatable magnet 4 as a magnetic field generating means is made of a non-magnetic material, and the developing sleeve 3 fixed on the developing sleeve 3 is fixed by rotating the magnet 4 in the direction of arrow A in FIG. 1 during the developing operation. The agent is conveyed in the direction opposite to arrow A.

The two-component developer in the developing unit 1 is regulated by the regulating member 5, forms a thin layer and is conveyed to the developing area, and is electrostatically formed on the photosensitive drum 28 in the developing area facing the photosensitive drum 28. Develop the latent image. The developer after developing the electrostatic latent image is conveyed in accordance with the rotation of the magnet 4, is conveyed in the axial direction of the sleeve by passing through the conveyance guide peeling plate, and is then peeled off from the sleeve into the developing device 1. Be recovered. Further, the developer circulating screw 2 is provided in the developing device 1.
As a result, the developer is conveyed in a direction opposite to the axial direction of the conveying guide peeling plate and the sleeve, whereby circulation is formed and mixing and stirring are performed. In the present embodiment, the direction of developer circulation is the direction from the front side to the back side of FIG. 1 on the developer circulation screw 2 side,
On the side of the transport guide peeling plate, the direction is from the back side to the front side in FIG.

Here, a characteristic part of this embodiment,
The developer transport guide peeling plate will be described in detail with reference to FIG. FIG. 3 is a view of the developing device 1 from above, and the left side of FIG. 3 is the front side of the developing device.

As shown in FIG. 3, the transport guide peeling plate 6 is formed by a plurality of two types of plates, a transport guide plate 6a for transporting the developer in the axial direction and a peeling plate 6b for peeling the developer from the sleeve. . As shown in FIG. 3, the conveyance guide plate 6a is arranged with an inclination in the axial direction with respect to the rotation direction of the developing sleeve, so that the developer is conveyed in the circumferential direction by the rotation of the magnet 4 and at the same time along the conveyance guide plate 6a. Arrow B
Is conveyed in the axial direction of the sleeve from the inner side to the front side in the axial direction of the sleeve, and at the same time, the peeling plate 6 moves in the circumferential direction of the sleeve.
It is transported to b. The developer that has reached 6b falls on the stirring screw 2 by the action of gravity after staying on 6b. The broken line portion of the stirring screw 2 shown in FIG. 3 is a portion hidden by the peeling plate 6b and not visible when viewed from above. The transport speed of the stirring screw 2 is adjusted so as to be in circulation balance with the transport speed of the transport guide plate 6a.

The toner consumed by the image formation is replenished from above the front side 2 of the developing device 1 according to the rotation of a replenishing screw (not shown).

As described above, the developing device according to the first embodiment of the present invention uses one sleeve and one screw.
With a simple structure such as a book, the functions of peeling, stirring, conveying, and supplying the developer can be satisfied, and even in an image forming apparatus such as a single-color image forming apparatus in which a developing device is fixed to a photoconductor, The object of the present invention to realize and provide a low-priced and small-sized image forming apparatus can be achieved.

(Second Embodiment) Next, a full-color image forming apparatus according to a second embodiment of the present invention will be described.

As shown in FIG. 4, in the image forming apparatus of this embodiment, Y stations, M stations, C stations, and K stations for forming toner images of respective colors are laterally arranged. The toner images of yellow, magenta, cyan, and black formed at each station are sequentially transferred onto the intermediate transfer belt 24a by the transfer charger 23 of each station, and then transferred onto the transfer paper 27 by the secondary transfer charger. Will be transferred at once.

In the intermediate transfer body method as in this embodiment, troubles such as paper jams are less likely to occur because the transport mechanism for the transfer paper 27 is simplified, and various materials such as plain paper and OHP film are easily supported. There are features such as what you can do.

As described above, according to this embodiment,
The object of the present invention to realize and provide a low-priced and compact image forming apparatus can be achieved, and the high productivity which is a characteristic of the tandem type full-color image forming apparatus and the transfer paper conveyance stability and the transfer which are a characteristic of the intermediate transfer method. It is also possible to downsize the entire device by taking advantage of material compatibility.

(Third Embodiment) As shown in FIG.
In addition to the developing device, the developer protecting member 7 is arranged over the entire surface of the sleeve on the downstream side of the developer transporting of the peeling member 6b.

The developer protect member 7 need only be non-magnetic and have an appropriate thickness. By disposing the developer protect member 7, the developer does not stay near the sleeve except in the vicinity of the regulating portion 5, Since the stress on the developer can be made extremely small, stable image formation can be obtained for a longer period of time.

(Fourth Embodiment) As shown in FIG.
It has the same configuration as that of the first embodiment except that the developer peeling guide auxiliary member 8 is arranged on the sleeve surface layer on the upstream side of the developer transport of the peeling member 6b.

The developer peeling guide auxiliary member 8 may be non-magnetic and has an appropriate thickness. By disposing the developer peeling guide auxiliary member 8, the developer may not stay near the sleeve of the peeling member 6b at all. Since it disappears and the stress on the developer can be made very small, stable image formation can be obtained for a longer period of time.

Although the image forming apparatus of the present invention has been described above with reference to the three embodiments, the present invention is not limited to the above-mentioned structure, and various structures can be adopted according to the proposal of the present invention.

[0029]

As described above, according to the present invention, the image carrier, the charging means for charging the image carrier, the exposing means for exposing the charged image carrier, and the exposing means are provided. A developing unit containing a two-component developer for developing the electrostatic latent image formed on the image carrier, and a transfer unit for transferring the developed image developed by the developing unit to a recording material. In an image forming apparatus having the developing device, the developing device is composed of a fixed developer carrier having a magnet roll magnetized in a multi-pole that rotates, and conveys the developer by the rotation of the magnet roll, Provided on the downstream side of the developer carrying direction is a carrying guide peeling plate that gives a force for carrying the developer in the axial direction of the image carrier and separates the developer from the developer carrying body, and develops in proximity to the developer carrying body. Axial direction of agent carrier An image forming apparatus, wherein said conveying guide peeling plate disposed in parallel to have a means for stirring and conveying the developer in a direction opposite to the direction for conveying the developer with. These are preferable because the cost and size of the apparatus can be reduced in a single-color image forming apparatus and a full-color image forming apparatus having various configurations such as a tandem system.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a developing device according to a first embodiment of the invention.

FIG. 2 is a diagram illustrating an image forming apparatus using the developing device according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating in detail developer circulation according to the first embodiment of the present invention.

FIG. 4 illustrates an image forming apparatus according to a second exemplary embodiment of the present invention.

FIG. 5 is a diagram illustrating a conventional example.

FIG. 6 is a diagram illustrating in detail developer circulation according to the third embodiment of the present invention.

FIG. 7 is a diagram illustrating in detail developer circulation according to a fourth embodiment of the present invention.

[Explanation of symbols]

1. Developer 2. Developer circulation screw 3. Development sleeve 4. magnet 5. Developer Control Department 21. Primary charger 22. laser 23. Transfer charger 24. Transfer paper conveyor belt 24a. Intermediate transfer belt 25. Fixing device 26. cleaner 27. Transfer paper 28. Photosensitive drum

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2H031 AA12 AB02 AB09 AC03 AC08                       AC19 AC23 AC29 BA04 EA03                       FA01                 2H077 AB02 AB06 AB14 AB15 AC02                       AC11 AC16 AD06 AD13 AD22                       AD32 BA08 BA09 EA03 GA13

Claims (3)

[Claims] 1. An image carrier, charging means for charging the image carrier, exposure means for exposing the charged image carrier, and electrostatic formed on the image carrier by the exposing means. An image forming apparatus comprising: a developing unit that contains a two-component developer for developing a latent image; and a transfer unit that transfers the developed image developed by the developing unit onto a recording material, wherein the developing unit is It consists of a fixed developer carrier with a magnet roll magnetized in a rotating multipole inside,
A carrier that conveys the developer by the rotation of the magnet roll, gives a force to convey the developer in the axial direction of the image carrier to the downstream side of the developer conveying direction from the developing unit, and separates the developer from the developer carrier. A guide peeling plate is provided, and means for stirring and carrying the developer is provided in the vicinity of the developer carrying member and in parallel with the axial direction of the developer carrying member, in a direction opposite to the direction in which the carrying guide peeling plate carries the developer. An image forming apparatus characterized by the above. 2. The image forming apparatus according to claim 1, wherein the stirring and conveying means is a screw. 3. The image forming apparatus according to claim 1, wherein the agitating and conveying unit is a single unit.