JPS6222147B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a powder developing device,
To provide a developing device that prevents powder developer from scattering and is free from stains.

There are also two-component development methods using a carrier and toner, such as magnetic brush development and cascade development, as well as one-component development methods using only toner containing ferromagnetic fine powder, such as the applicant's patent application Sho.
Also in No. 49-99385 (Japanese Unexamined Patent Publication No. 51-26046),
Contamination near the developing device due to toner scattering is a problem that must be solved.

Whether the toner is electrostatically attracted to the carrier by frictional electrification or attracted to the toner support member by magnetic force,
Their suction and holding power cannot be set to be so strong as to enable development. Therefore, it is necessary to prevent toner scattering during several processes associated with the development process, such as feeding the developer and bringing it into contact with the surface of the electrostatic support member, or scraping the developer from the surface of the feeding carrier. It is extremely difficult to escape.

Furthermore, in the case of a two-component developer, the scattering will further increase if the newly supplied toner is insufficiently mixed or the toner mixing ratio increases.

The present invention provides an effective means for preventing such toner scattering.

The invention will now be described with reference to the accompanying drawings.

FIG. 1 shows an embodiment of the present invention, in which a developing device has a rotating sleeve 1 made of a non-magnetic material arranged inside a housing 3, and a group of magnets 2 fixedly built into the rotating sleeve 1. . A developer 4 is stored in the housing 3, and when the sleeve 1 is rotated in the direction of the arrow, the developer 4 is transferred together, shaped by a doctor blade 6, passed through a developing section 7, and is deposited on a scraping plate 8. Development is continued in sequence. 9 is a toner supply section. An insulating layer 12 is provided on the housing 3 outside the opening 11 where the developer contacts the latent image support surface 10.
Toner collecting electrodes 14 and 15 are disposed with surfaces substantially parallel to the latent image support surface 10 via 13 and extending over the length of the opening in the axial direction of the sleeve 1.

On the other hand, FIG. 2 shows a corona discharge device built into a copying machine, in which a discharge wire 18 is surrounded by conductive shields 19 from three sides. Generally, this shield 19 is grounded. A charge absorbing plate 21 made of a conductive material is installed at a part of the shield 19 or outside the shield at a position where the corona charge reaches, with an insulating plate 20 interposed therebetween. Charge absorption plate 2
High voltage lead wires 16 and 17 are led out from 1 and connected to toner collecting electrode plates 14 and 15 via connectors 16' and 17'. Charge absorption plate 21
When the corona discharge charge is absorbed from the charge absorption plate 21 itself and the capacitance mainly composed of the collection electrodes 14 and 15, a potential is established, and when the potential gradient near the absorption plate 21 disappears, the charge is removed. absorption stops. These are done in an extremely short time. In order to effectively increase the potential with a small amount of charge and to maintain insulation, the thickness of the insulating layer is required to a certain extent, and in the embodiment of the present invention, the thickness is 2 mm.
with a thickness of In addition, toner collecting electrodes 14 and 15
Although it is arranged only in the longitudinal direction of the opening 11, it may be arranged on the remaining two sides of the opening along the traveling direction of the latent image support surface 10. A member may be provided to prevent toner scattering.

Generally, when the toner has positive polarity, the charger or transfer device has negative polarity, which is convenient for capturing floating toner. Furthermore, if the toner is in a floating state and the collection electrode is set at a high voltage and the gap between it and other low potential members is small, the toner can be captured even by polarization force. Furthermore, when a copying machine has a corona discharger with both positive and negative polarities, it is also possible to configure the collection electrode with a two-layer configuration of positive and negative polarities. These corona dischargers are those used for the operation of electrostatic latent images, as well as for latent image conversion, such as those used, for example, when transferring latent images to other supports.

There are many advantages to using corona discharge with the toner collecting electrode of the developing brush electrically insulated and floating. That is, (1) a dedicated power source for the collection electrode is not required;

(2) Since almost no current flows, there is no substantial burden on the corona power supply.

(3) Toner can be captured even when the corona discharger is not in the discharge cycle.

(4) Although it is rare to touch the discharger during corona discharge, there are relatively many opportunities to touch the developing device, to which no high voltage is normally applied, and in addition, there are many opportunities to touch the developing device. Since the operating cycles are different, the developer is not operating, but there is a high possibility that the collection electrode will be touched during corona discharge. However, according to the present invention, even if touched, there is no danger to the human body. As can be seen from FIG. 2, the space between the discharge wire 18 and the charge absorption plate 21 has a high resistance, so that only a very weak current flows. This is a person,
This is the most important of the above advantages, especially since the operator's life is at stake. Note that it is dangerous to place the charge absorption plate closer to the discharge wire than the usual shield plate position or to make the area of the charge absorption plate larger than necessary. In short, it is important to use a high resistance state between the discharge wire and the charge absorption plate.

In one embodiment of the present invention, the discharge voltage is 6KV,
When the distance between the discharge wire and the charge absorption plate was 8 mm, and the area of the charge absorption plate was approximately ^0.25cm2 , the collection electrode 1
The voltage obtained on 4.15 was 1.2KV.

FIG. 3 shows another preferred embodiment of the invention, in which the same reference numerals as in FIG. 1 indicate the same parts.

In FIG. 3, a conductive roller 22 is installed on the housing 3 and is rotatably fixed and electrically insulated from other parts of the developing device. The roller 22 rotates in the direction of the arrow, and a toner scraping plate 2 is provided on the circumferential surface of the roller.
3 is in contact. The high voltage lead wire 16 is connected to the charge absorbing plate (not shown in FIG. 3) of the corona discharger, as in the embodiment shown in FIGS. 1 and 2 above. In the embodiment described above, when toner accumulates on the toner collecting electrode 14, the toner collecting ability decreases, but in this embodiment, the collected toner is scraped off by the toner scraping plate 23. , is reduced into the developer, so the collection ability of the roller 22 is always good without deterioration. The toner scraping section 23 is preferably an insulating plate and preferably contacts the roller 22 at an angle that prevents it from touching the falling toner.

Note that a separate tray may be provided to receive the scraped toner.

As described above, according to the present invention, a developing device equipped with a toner collecting electrode that is simple in structure, inexpensive, and highly safe is provided.

[Brief explanation of the drawing]

FIG. 1 of the accompanying drawings is a schematic cross-sectional side view of one embodiment of the developing device according to the present invention, FIG. 2 is a schematic cross-sectional view of a charger using corona discharge shown in relation to FIG. 1, and FIG. FIG. 6 is a schematic cross-sectional side view of another embodiment of the main part of the present invention. 1... Rotating sleeve, 2... Magnet group, 3... Housing, 4... Developer, 6... Doctor blade, 7
...developing section, 8...scraping section, 9...toner capturing section, 10...latent image support surface, 11...opening section, 1
2, 13... Insulating layer, 14, 15... Toner collection electrode, 16, 17... High voltage lead wire, 16',
17'...Connector, 18...Discharge wire,
19... Shield, 20... Insulating plate, 21... Charge absorption plate, 22... Roller, 23... Toner scraping plate.

Claims (1)

[Claims] 1. A toner collecting electrode is disposed in the vicinity of the developing position of the developing device that visualizes the electrostatic latent image formed on the surface of the latent image support, in an electrically insulated state from the developing device, and 1. A developing device for an electrophotographic copying machine, characterized in that a toner collecting electrode is electrically connected to a charge absorbing member attached via an insulating member to a shield of a corona discharge device incorporated in the electrophotographic copying machine.