JPH0731436B2 - Development device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to a developing device that can be suitably used for a color recording device that constitutes an output part of a color electrophotographic copying device, a computer, a facsimile, or the like. In particular, in the image forming apparatus as described above, a plurality of developing devices are mounted on a transporting device, and a desired developing device is moved to a position facing a latent image carrier, that is, an object to be developed to perform development. The present invention relates to a developing device capable of preventing the developer from scattering and color mixture due to movement and stop of the developing device.

The developing device according to the present invention can also be used with a rotary developing device in which the conveying device is a rotating body and each developing device is moved along a circular orbit, and the conveying device is an endless circulating movement other than the rotating body. It is also suitably used with a developing device which is a body and in which each developing device moves along a non-circular orbit such as an elliptical orbit. However, since the conventional rotary developing device is widely used, the present invention is not limited thereto. However, in the present specification, the developing device according to the present invention will be described in relation to the rotary developing device.

2. Description of the Related Art Conventionally, a color electrophotographic copying apparatus forms a latent image of each color with a color separation filter, and usually develops the latent image of each color individually using 3 to 4 developing devices to obtain a developed image. Then, a method is generally used in which a color image is obtained by sequentially transferring the developed image to the same transfer material.

As a developing device of such a color image forming apparatus, a side-by-side developing device in which a plurality of developing devices are arranged around an object to be developed, and a plurality of developing devices are typically mounted in a conveying device which is a rotating body. There has been proposed a rotary developing device of a type in which a desired developing device is moved to a developing position. Recently, a rotary developing device is frequently used because the developing device, and thus the color image forming apparatus, can be downsized.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, a rotary developing device having such an advantage also has a new problem that the developing device is rotated and stopped when the developing device of each color is rotated. The developer on the developing sleeve may spill, stain the screen on the object to be developed to deteriorate the image quality, or stain the inside of the machine.
More importantly, there is a drawback that the scattered developer is collected by another developing device, and a serious problem of color mixing of the developer occurs.

SUMMARY OF THE INVENTION Accordingly, the main object of the present invention is to improve the drawbacks of the conventional developing device as described above, and to prevent the developer scattered by the movement or stop of the developing device equipped with a plurality of developing devices. It is an object of the present invention to provide a developing device capable of collecting and collecting, preventing color mixture of a developer, and preventing stains inside the machine.

Means for Solving the Problems The above object is achieved by the present invention. In summary, the present invention mounts a plurality of developing devices having a developer carrying member that carries a developer by using magnetic force on a carrying device, and drives the carrying device to move a desired developing device to a developing position. Then, the developing device for developing the object to be developed is characterized in that it has a developer collecting magnet having the same polarity as the developing magnetic pole of the developer carrying member, the developing device being opposed to the conveying path of the developing device.

Next, the developing device according to the present invention will be described in more detail with reference to the drawings.

FIG. 1 illustrates a color electrophotographic copying apparatus to which the present invention is applied, which includes a photosensitive drum 1, a primary charger 2, an image exposure unit 3, a developing unit 4, a transfer charger 5, a cleaner 6, and the like.
A latent image is formed on the surface of the photosensitive drum 1 by a process well known to those skilled in the art, then visualized, and finally a developed image is transferred onto the transfer material P. The photosensitive drum 1 is then removed of the residual developed image and starts the next process.

In the present embodiment, the developing device is composed of a plurality of developing devices, for example, four developing devices 8Y respectively accommodating toner particles colored in respective colors of yellow Y, magenta M, cyan C and black BK.
8M, 8C, and 8BK, and the developing device is supported and suspended by the transport device 8 which is a rotating device that rotates around the axis O in this embodiment. Accordingly, each developing device is rotationally moved in a turret type by the rotating device 8, and one selected developing device is faced to the developing portion 4 of the photosensitive drum 1 to perform the developing action.

Each developing unit may have any structure having the developing roller 9, but in one example, the developing roller 9 is the developing sleeve 9a.
And a fixed magnet 9 arranged inside the developing sleeve 9a.
It consists of b, 9c and 9d. Further, among the fixed magnets in the developing sleeve 9a, the magnet 9c that opposes the photosensitive drum 1 is an N pole in this embodiment, and the other magnets 9b and 9d are S poles. At this time, in this embodiment, the magnetic flux density on the developing sleeve 9a is 850 gauss. Further, each developing device has a toner replenishing bottle 10, developer agitating and conveying screens 11, 12 like the conventional developing device.
Have.

In the above configuration, one of the developing devices 8Y to 8BK selected by the copy operation command is stopped at the developing unit 4 and the developing sleeve 9
a rotates to perform the developing action. In the case of a single-color command, the developing device waits as it is for the next development, but in the case of a color copy of two or more colors, the other developing device selected stops moving to the developing section 4.

As illustrated in FIG. 1, the developing device 20 according to the present invention is located above the photosensitive drum 1 and in the rotation direction X of the rotating device 8.
The developer collecting magnet sleeve 22 and the collecting device 24 are provided on the downstream side of the developing device 8Y to 8BK and at positions that can face the developing devices 8Y to 8BK. In this embodiment, the developer collecting magnet sleeve 22 includes a collecting sleeve 26, and the collecting sleeve 26.
26 has a collection magnet 28 fixed inside, and the collection magnet 28 is located opposite to the magnet 28a facing the developing device, and is located opposite to the magnet 28a, that is, at a angle of 180 °. 28b and. In addition, the two magnets in this sleeve 2
8a and 28b are independent of the rotation of the sleeve 22, and are arranged and fixed so as to be aligned in the direction of the rotation center O of the rotation device 8. Further, in the present invention, the magnetic pole of the magnet 28a is the same as the magnetic pole of the magnet 9c provided in the developing device and facing the object to be developed. In other words, in this embodiment, it is the N pole.

In the preferred embodiment, the collecting sleeve 26 installed between the rotating device 9 and the photosensitive drum 1 is a cylindrical body made of aluminum with an outer diameter of about 20φ, and has a wall thickness of 0.8 mm. This causes rotation in the direction of arrow Y in FIG.
The distance between the developing sleeve 9a and the collecting sleeve 26 is about 12 mm in the embodiment. The collecting sleeve 26 does not have to be cylindrical, and it is also possible to use, for example, an endless belt.

In the above structure, the magnetic lines of force on the collecting sleeve 26 are as shown by the broken lines in FIG. The magnetic flux density on the collecting sleeve 26 is about 800 gauss at the position of the magnet 28a and about 700 gauss at the position of the magnet 28b. Both magnetic poles are N poles. It is preferable that the surface of the collecting sleeve 26 is roughened by spraying non-magnetic stainless steel on the surface thereof in order to improve the transportability of the collected developer.

According to a preferred embodiment of the present invention, the collecting device 24 includes a scraper 24a pressed against the collecting sleeve 22 to collect the developer conveyed on the collecting sleeve 26,
The scraper 24a comprises a transport roller 24b for transporting the developer stripped from the surface of the collecting sleeve to a recovery box (not shown). The scraper 24a is made of a polyethylene terephthalate material and preferably has a thickness of about 200 μm. The contact position of the scraper 24 with the collection sleeve 26 is set in the vicinity of the position where the magnetic line of force on the sleeve 22 is cut. Further, although this scraper 24a is pressed against the collecting sleeve 26 in this embodiment, it may be installed with a minute gap.

The developer transported on the collecting sleeve 26 is scraped off by the scraper 24a at this position, and is transported to a recovery box (not shown) by the transport roller 24b therebelow and is recovered. The transport roller 24b has a spiral groove, and the developer in the groove can be moved and collected in a certain direction by rotation.

The operation of the developer collecting device configured as described above will be described. Now, the developing device 8Y which has completed the developing process is rotated by the rotating device to rotate the magnet sleeve 22 as shown in FIG.
Consider the case of passing the position. In this case, the magnetic lines of force between the developing sleeve 9a and the collecting sleeve 26 have the same polarity as the magnetic poles facing each other, so that the magnetic lines have a shape as shown by the broken line in FIG. 2, and there are portions where no magnetic lines of force exist (A in FIG. 2). Part indicated by). Therefore, the developer on the developing sleeve 9a passes through this position without moving on the collecting sleeve 26.

On the other hand, the developer scattered to the outside of the developing sleeve 9a, for example, the developer T scattered to the lower part of the developing device is collected by the collecting sleeve 26 as shown in FIG. 3, and passes through the scraper 24a and the conveying roller 24b. Will be collected. Similarly, each developing device passes in front of the collecting sleeve 26, and the scattered developer is repeatedly collected.

According to the embodiments of the present invention described above, the scattered developer was collected and recovered, and a good collecting effect was exhibited. In this example, no color mixing occurred between the developers even in the result of the copy test of about 10,000 copies.

FIG. 4 shows another embodiment of the present invention, in which the collecting sleeve 26 is rotated in the direction of arrow Z, which is the reverse of the embodiment, and three magnets 28a are provided inside the collecting sleeve 26. , 28b, 28
c is provided, the magnet 28a has a north pole, and the other magnets have a south pole. Further, the scraper 24a is arranged above the collecting sleeve 26, the magnetic poles of the magnets 28b and 28c are also repelled at this position, and the collected developer is spontaneously dropped into the collection box 24c as shown in the figure.

In this embodiment, the carrying roller 24b in the embodiment described with reference to FIG. 1 is not necessary, and it can be suitably used when the amount of scattering is small and therefore the amount of collection is also small. This is an effective configuration.

As described above, at the developing sleeve passing position of the developing device arranged in the conveying device, the collecting magnet sleeve having the magnet of the same polarity as the magnetic pole of the magnet in the developing sleeve is arranged, and the position thereof is provided. The developer on the developing sleeve is not collected from each developing device that passes through, but only the developer scattered outside the developing sleeve is collected, and the developer is collected from the collecting magnet sleeve. Therefore, it is possible to prevent the most serious color mixture between the developers in the color image forming apparatus.

It was also confirmed that making the magnetic poles between the developing sleeve and the collecting magnet sleeve to be the same magnetic pole has the effect of compressing the developer on the developing sleeve when passing through, thus contributing to the prevention of scattering.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view for explaining the developing device according to the present invention and the main components of a color copying machine to which the developing device can be applied. FIG. 2 is a vertical cross-sectional view illustrating how the developing sleeve passes through the developer collecting device. FIG. 3 is a vertical cross-sectional view illustrating the situation when the developer scattered outside the developing sleeve is collected. FIG. 4 is a longitudinal sectional view showing another embodiment of the developing device according to the present invention. 1: Developing object (photosensitive drum) 8: Rotating device 9: Developing roller 9a: Developing sleeves 9b, 9c, 9d: Magnet 20: Developer collecting device 22: Collecting magnet sleeve 24: Collecting device 24a: Scraper 26 : Collection sleeve 28a, 28b, 28c: Magnet

Claims (1)

[Claims] 1. A plurality of developing devices each having a developer carrying member for carrying a developer by using magnetic force are mounted on a carrying device, and the carrying device is driven to move a desired developing device to a developing position. A developing device for developing a developer, characterized in that it has a developer collecting magnet having the same polarity as the developing magnetic pole of the developer carrying member, the developer collecting magnet being opposed to the transport path of the developing device.