JPS59101678A - Developing device - Google Patents

Abstract

PURPOSE:To prevent a trimmer gap from being clogged with foreign matter, and accordingly, to slove a whitening problem of a copy by providing a repulsion magnetic pole part of the same polarity between a developer attraiting port of a developer carrying path and a trimming part. CONSTITUTION:A foreign matter removing part D is formed between a developer attracting part A and a trimming part C on which a trimmer 6 is arranged. In this foreign matter removing part D, adjacet fixed magnetic poles have the same polarity, and a magnetic field is not formed. Therefore, even in case of non-magnetic foreign matter such as a lump of paper powder, etc. contained in a developer carried from the attracting part A, or a magnetic material such as a metallic fragment, a lump of the developer, etc., that which has a large weight drops by receiving an action of gravity, and is removed from a developer carrying path, namely, the surface of a carrying roller 4. As for a normal developer, its weight is comparatively small, it is helped by inertia force, too, of a carrying motion by the carrying roller 4, jumps the foreign matter removing part D and is caught by the adjacent magnetic field, therefore, it does not get out of the developer carrying path.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developing device for a copying machine, and more particularly to a developing device having a developer conveying path for magnetically attracting magnetic developer, trimming it, and conveying it to a developing area.

In this O developing device, the developer is sucked in using a developer transport roll consisting of a fixed magnet and a non-magnetic rotating sleeve, and while the developer is being transported, the developer is trimmed by a trimmer means. A common method is to form spikes of magnetic brush or the like using an image roll and then use a cage to perform a +A image in the development axis area.

However, recently, developers have become one-component, or the carrier particle size in two-component developers has become smaller (10 to 40 μm).
), and because the formation of spikes is low, the developer layer attached to the developer roll surface is kept thin. There is a tendency to narrow the trimmer gap in order to form this thin layer, but a secondary problem is that foreign matter (paper dust, metal fragments, etc.) or developer particles that have solidified together can clog the trimmer gap. , the conveyance of the developer is obstructed at that location, and white spots may occur in the copy of the portion corresponding to this location.

The present invention has been made in view of the shortcomings in the prior art, and its purpose is to use a one-component or two-component magnetic developer. In an EJI image device, the purpose is to prevent a part of the trimmer from clogging due to foreign matter other than normal developer, developer clumps, etc.

That is, the present invention removes foreign objects, developer lumps, etc. by providing a same-polarity repelling magnetic pole part in the developer conveyance path between the developer suction part and the trimming part of the developing device.
This prevents these from clogging the trimmer gap. In this same-polarity repulsion magnetic pole section, magnetic poles of the same polarity are provided adjacently, so no magnetic field is formed, and therefore non-magnetic foreign matter such as paper dust particles or developer particle clumps can be detected. Objects that are heavy are removed from the development conveyance path.

However, normal developer particles are relatively light in weight, and with the help of the inertia of the conveying motion, they jump over the same-polarity repelling magnetic pole, are captured by the adjacent magnetic field, and continue to be conveyed.

In this manner, in the present invention, it is possible to remove foreign matter contained in the developer and agglomerates of developer particles while maintaining normal conveyance of the developer.

Embodiments of the present invention will be described below with reference to the drawings. Referring to Figure 1, a developing housing 2 is arranged adjacent to the photoreceptor drum 1, and within this developing housing, a developing wheel 3, a transport roll 4, and a developing roll 5 are indicated by arrows. It is provided in the rotating part in the direction of . /zodle wheel 3 supplies the magnetic developer accumulated at the bottom of the developing roller to the conveying roll 4, and the conveying roll 4 magnetically attracts the developer at its suction portion A and transfers it to the developing roller. 5, the developing roll 5 receives the developer from the transport roll 4, and passes the developer through the developing area B adjacent to the photoreceptor 1, thereby forming the developer on the surface of the photoreceptor. It is used to develop the electrostatic image that is present.

Both the conveying roll 4 and the developing roll 5 are composed of a fixed magnetic pole and a non-magnetic rotating sleeve that rotates around the fixed magnetic pole, and convey the developer while magnetically attracting it. As a result, a developer transport path is formed between the developer suction portion A and the development area B. A trimmer 6 is disposed in this developer transport path, and the trimmer 6 controls the height of the layer of developer deposited on the surface of the developing roll, so that an appropriate amount of developer is deposited in the developing area. can be supplied to the surface of the photoreceptor. In this developing device,
A foreign matter removal portion is formed between the developer suction portion A and the trimming portion C where the trimmer 6 is disposed.

In this foreign matter removal area, adjacent fixed magnetic poles have the same polarity and no magnetic field is formed. For this reason, non-magnetic foreign objects such as hardened paper powder contained in the developer conveyed from the suction part A, and magnetic objects such as metal fragments and developer clumps, which have a large weight, It falls under the action of gravity and is removed from the developer transport path, that is, the surface of the transport roller. However, normal developer has a relatively small weight, and with the help of the inertia of the transport movement by the transport roller 4, it jumps over the foreign object removal area and is captured by the adjacent magnetic field, so it does not come off the developer transport path. .

In the example shown in FIG. 2, the conveyance roller is omitted, and the developer supplied from the paddle wheel 3 is directly attracted to the suction part of the developing roll 4, trimmed at the trimming part C, and then removed from the developing area. B is supplied. In addition, in this embodiment, a box 7 is provided as a foreign object receptacle below the foreign object removal part, and the foreign object is stored in this box.
Compared to the embodiment shown in FIG. 1, foreign matter will not accumulate again at the bottom of the developer housing, increasing reliability.

The percentage characteristics common to the embodiments shown in FIGS. 1 and 2 are that the foreign matter removal part, that is, the repelling magnetic pole part is placed at the bottom of the magnetic roll, and non-magnetic foreign matter or heavy developer is solidified by gravity. This is the point where the stains and the like come off during the conveyance of the developer layer formed on the surface of the magnetic roll. In these embodiments, the greater the distance between the same poles of the repelling magnetic pole portions, the higher the foreign matter removal effect, but if this distance becomes too large, problems will occur in the conveyance of the developer. Therefore, this homopolar distance is
Although it cannot be made that large, by installing a barrier at the repulsion magnetic pole portion as shown in FIG. 3, a relatively high foreign matter removal effect can be obtained even with a narrow copolarity distance. In the example shown in FIG. 3, a developer conveying path A-*C->8 is formed on the surface of the developing roll 40, and a non-magnetic sleeve 4' for the developer is formed at a part of the path where foreign matter is removed.
A non-magnetic bar 8 having a thickness thinner than the developer layer is installed in contact with the developer layer in the axial direction. In this embodiment, the developer collides with this bar on its way over the foreign matter removal section and is more agitated, so that foreign matter is removed more effectively.

As described above, in the present invention, foreign matter can be removed by providing a Pl-polarity repelling magnetic pole section between the developer suction part and the trimming part of the developer transport path, so that the foreign matter can be prevented from sticking to the trimmer gap. Therefore, the problem of white spots on copies can also be eliminated.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a first embodiment of the developing device of the present invention;
FIG. 2 is a schematic diagram showing a second embodiment of the developing device of the present invention;
FIG. 3 is a schematic diagram showing a third embodiment of the developing device of the present invention.

Claims (1)

[Claims] A developing device characterized in that a same-polarity repelling magnetic pole portion is provided between the attracting portion and the trimming portion of a developer conveying path that magnetically attracts magnetic developer, trims it, and conveys it to a developing area. Equipment〇