JPH0317314Y2 - - Google Patents

Description

[Detailed explanation of the invention] (a) Industrial application field This invention is a developing method in which an electrostatic latent image formed on a recording medium is developed with a two-component developer consisting of a magnetic carrier and a non-magnetic toner. In particular, the present invention relates to an improvement in the structure of a carrier recovery section for removing and recovering magnetic carriers attached to a developed recording medium in an electrophotographic copying apparatus.

(B) Prior art A developer for developing an electrostatic latent image formed on electrostatic recording paper or a photoreceptor by exposure to a light image to be copied, such as a still image on a cathode ray tube, contains iron powder in a colored resin powder toner. There are two-component developers: one is a one-component developer in which a magnetic carrier such as iron powder is mixed with a toner in the form of a colored resin powder, and the other is a two-component developer in which a magnetic carrier such as iron powder is mixed with a colored resin powder toner. The former developer is sometimes used for monochromatic copying such as black-and-white copying, but it is not common, and it is rarely used especially for color copying because the magnetic powder in the ingredients may interfere with color reproducibility. The latter two-component developer is used for most color copying and general monochrome copying. This two-component developer magnetic carrier is used to convey non-magnetic toner to a recording medium (electrostatic recording paper, photoreceptor), and the carrier attached to the recording medium along with the toner is selectively removed before toner fixation. be done.

A conventional example of a color electrophotographic copying apparatus using the above-mentioned two-component developer is explained from FIG. 1. Reference numeral 1 denotes electrostatic recording paper as a recording medium;
These are an electrostatic latent image forming section, a developing section, a carrier removing section, a fixing section, and a static eliminating section arranged in series along the conveyance path 7. In the case of color copying, the electrostatic recording paper 1 reciprocates on the conveyance path 7 at least three times, and the series of steps of exposure, development, carrier recovery, fixing, and static elimination are repeated three times.

The electrostatic latent image forming section 2 has a photosensitive plate 8 and a back electrode plate 9 that sandwich the electrostatic recording paper 1 in a fixed position in a sandwich manner, and forms an optical image to be copied, such as a still image of a cathode ray tube 10, on the photosensitive member 8. When projected through the lens system 11 and exposed, a desired electrostatic latent image is formed on the electrostatic recording paper 1.

The developing section 3 is located behind the electrostatic latent image forming section 2,
For example, the first to fourth developing units 12a to 12d are arranged in series along the conveyance path 7. Each of the developing units 12a to 12d has a two-component developer 13 in which cyan, magenta, yellow, and black colored toners are mixed separately for each color in a magnetic carrier.
Magnetic brush type developing rollers 15a to 1 are installed in the upper openings of the boxes 14a to 14d that house the developing rollers 15a to 13d.
5d was installed. Each developing roller 15a
~15d are located at a sufficient distance from the conveyance path 7, and each time one development is performed, one selectively rises to bring the magnetic brush developer formed on the outer peripheral surface into contact with the electrostatic recording paper 1. Let it develop.

The carrier recovery section 4 is disposed between the developing section 3 and the fixing section 5, and collects developers 13a to 13a of desired colors in the developing section 3.
Only the carrier is removed and recovered from the electrostatic recording paper 1 developed in step 13d, and has a structure in which a magnet 16 is fixedly arranged near the conveyance path 7. In other words, when the electrostatic recording paper 1 is developed with any one of the two-component developers 13a to 13d, the toner in the components adheres by electrostatic adsorption, while a portion of the magnetic carrier also adheres mechanically. If the electrostatic recording paper 1 is sent to the fixing section 5 with this carrier attached to it for fixing, the color of the carrier may be mixed with the toner, resulting in poor copy colors. Therefore, for each development, the electrostatic recording paper 1 is passed over a magnet 16 before being sent to the fixing section 5, and only the carrier adhering during this passing is magnetically attracted to the magnet 16 and removed.

The fixing section 5 heats the toner adhering to the electrostatic recording paper 1 to firmly fix it, and the static eliminating section 6 discharges the charge of the toner after fixing to enable the formation of the next electrostatic latent image. It is.

By the way, the carrier collection section 4 has a structure in which the magnet 16 directly attracts and removes the carrier on the electrostatic recording paper 1, so as the number of copies increases, the carrier accumulates on the magnet 16 and the magnetic force decreases, causing the carrier to be removed. There have been problems in that the collection ability is reduced and that the carrier accumulated on the magnet 16 comes into contact with the electrostatic recording paper 1 and damages or stains the developing device. Therefore, the carriers attached to the magnets 16 are cleaned and removed periodically, but this makes maintenance cumbersome and also requires arranging multiple magnets in series to reduce the number of times the fixed points are damaged. However, this makes the structure complicated and does not solve the problem of temporal deterioration of carrier collection ability due to carrier adhesion.

(c) Purpose of the invention The purpose of the invention is to solve the above-mentioned problems in carrier recovery.

(d) Structure of the invention The present invention includes a carrier collecting section that is located below the conveyance path of the recording medium and rotates so that its rotation locus is close to the recording medium, and a magnet that is suspended and held by the magnet. and an endless non-magnetic belt that rotates as a result of the rotation.

In this carrier collection section, when the magnetic pole of the magnet rotates close to the electrostatic recording medium, the magnetic carrier on the electrostatic recording medium is attracted to the magnetic pole of the magnet and transferred onto the belt, and the attached carrier is transferred to the belt. rotates with the magnet, and as it moves away from the magnetic poles of the magnet, it naturally falls and is collected outside. With this type of carrier recovery unit, the carrier does not stick to the rotating magnet, and since the belt is suspended from the rotating magnet and rotates, it vibrates in the lateral direction, and this vibration shakes off the carrier that has stuck to it. Since the portion without carrier always comes close to the electrostatic recording medium, the carrier collection ability is not reduced and a stable carrier collection operation is always performed.

(E) Embodiment An embodiment in which the present invention is applied to the electrophotographic copying apparatus shown in FIG. 1 will be explained from FIG. 2. Components with the same reference numerals as in FIG. The only difference is the carrier collecting section 17 installed between the developing section 3 and the fixing section 5, which includes, for example, a total of four magnets 1.
8, 18..., a circular rotating drum 19 made of a non-magnetic material that integrally supports each magnet 18, 18... with one magnetic pole arranged at 90° intervals on the outer periphery; It consists of an endless non-magnetic belt 20 that is suspended, and 21 is the belt 20.
The carrier collection box is shown in position below. The rotating drum 19 has a rotation center shaft 22 located at a fixed position parallel to and orthogonal to the conveyance path 7 of the electrostatic recording paper 1.
The upper part of the outer circumference is located near the conveyance path 7. The belt 20 is flexible, and its entire length is sufficiently longer than the outer circumference of the rotating drum 19, and its lower part is suspended below the rotating drum 19. The rotating drum 19 rotates in one direction synchronously when the electrostatic recording paper 1 that has been developed is carried above it, and the belt 20 is also suspended from the rotating drum 19 as a result of this rotation. Rotate as it is.

Now, the operation of the carrier recovery section 17 will be explained using one point on the belt 20 as P. Rotating drum 1
The belt 20 is rotated by the rotation of 9, and the P of 20 is rotated.
When the point rises from the lower position shown in FIG. 3 and reaches the circumferential surface of the rotating drum 19, the point P is placed on or near the magnetic pole of one of the magnets 18, and the point P continues to rotate and rise together with the magnet 18. The carrier 23, which approaches the electrostatic recording paper 1 and is attached to the electrostatic recording paper 1, is magnetically attracted by the magnet 18 and is transferred and attached onto the point P.
As the rotating drum 19 continues to rotate, point P reaches the electrostatic recording paper 1.
The rotary drum 19 gradually moves away from and descends.
As the point P moves away from the point P, it gradually moves away from the magnet 1 that was magnetically attracting the carrier 23 to the point P, and the attraction force of the carrier 23 on the point P suddenly weakens.
From the point, the carrier 23 naturally falls under its own weight and is stored in the carrier collection box 21. On the other hand, the belt 2 hanging below the rotating drum 19
The lower part of 0 is unstable and continues to vibrate left and right due to its rotational movement, and due to this vibration, the carrier 23 at point P is thrown off and falls naturally.
More reliable carrier collection becomes possible. P is now in a state without its original carrier due to the fall of Carrier 23.
The point rises again and the above operation is repeated. Only the developed toner 24 adheres to the electrostatic recording paper 1 that has passed through the carrier collecting section 17 and is fixed in the next fixing section 5.

Next, other embodiments of the present invention will be explained with reference to FIGS. 4 to 6.

FIG. 4 shows a structure in which a swingable guide roller 25 is placed over the hanging lower part of the belt 20.
In this case, it is possible to forcibly vibrate the belt 20 in the left-right direction using the guide roller 25.

FIG. 5 shows each magnet 1 on the outer periphery of the rotating drum 19.
8, 18...The space between them is recessed. With such a substantially star-shaped rotating drum 19, the belt 20 is vibrated in the left-right direction with a larger amplitude, thereby increasing the effect of shaking off the carrier 23.

Figure 6 shows one plate magnet 26 with both ends magnetized.
In this case, the belt 20 has a horizontal spacing that changes greatly between the vertical state of the magnet 26 (solid line in Figure 6) and the horizontal state (dashed line in Figure 6), and the vibration in the left and right direction is further increased. carried out with large amplitude,
In addition, a large amount of vertical vibration is added, further increasing the effect of shaking off the carrier.

It should be noted that the present invention is not limited to the above-mentioned embodiment, but can be similarly applied to a monochrome electrophotographic copying apparatus using one color developer. It can also be applied to a copying apparatus that uses a photoreceptor as a recording medium, forms an electrostatic latent image on the photoreceptor, develops it, removes the carrier, and transfers and fixes the toner onto plain paper.

(F) Effect of the invention As explained above, according to the invention, the carrier recovery ability in the two-component developer from the recording medium is always maintained at its highest level, so that good electronic copying can always be achieved. This is particularly effective for color copying. Furthermore, the need for cleaning the carrier recovery section is reduced, making maintenance management easier and improving the operating rate of the device.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view showing an example of a conventional electrophotographic copying apparatus, FIG. 2 is a schematic side view showing an embodiment of the present invention, and FIG. 3 is an enlarged view of the carrier collecting section in FIG. 4 to 6 are side views of the carrier recovery section showing other embodiments of the present invention. 1... Recording medium, 2... Electrostatic latent image forming section, 3...
...Developing section, 7... Conveyance path, 13a-13d... Two-component developer, 17... Carrier recovery section, 18...
...Magnet, 20...Belt, 23...Carrier, 2
4...Toner, 26...Magnet.

Claims (1)

[Scope of utility model registration request] An electrostatic latent image forming section forms an electrostatic latent image on a recording medium, and a two-component developer consisting of a magnetic carrier and a non-magnetic toner is selectively applied to the recording medium on which the electrostatic latent image is formed. The device includes a developing section that causes the carrier to adhere, and a carrier collecting section that removes the carrier that has adhered from the developed recording medium, and the carrier collecting section is located below the conveying path of the recording medium so that the rotation locus circle reaches the recording medium. An electrophotographic copying apparatus comprising a magnet that rotates in close proximity to the magnet and an endless non-magnetic belt that rotates while suspended from the magnet.