JPH0245190B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention enables development by coating a one-component magnetic developer as a thin layer on a developer carrier and bringing the surface of the thin developer layer close to the surface of a member to be developed having an electrostatic latent image. The present invention relates to an improvement in a so-called jumping developing device which is based on the principle of making the latent image visible by causing the developer to jump from a thin layer of developer toward the surface of a member to be developed using the electric force of the latent image.

Conventionally, as a means for forming a thin layer of developer, a non-magnetic sleeve is used as a developer carrier, and a thin layer of one-component developer is formed on the sleeve using a strong magnetic field created by a magnetic blade and a magnetic pole in the sleeve. However, as a means to improve this, the applicant first formed and held a magnetic brush of developer on a first magnetic roller serving as a first developer carrier, and the magnetic brush of the developer was A developing device has been proposed in which a brush is brought into contact with a developing roller serving as a second developer carrier, thereby coating a thin layer of a one-component developer on the surface of the developing roller.

FIG. 1 shows an outline of the developing device. 1 is the first
2 is a magnetic brush sleeve roller (hereinafter referred to as a coater sleeve) which is a developer carrier; 2 is a developing sleeve roller (hereinafter referred to as a developing sleeve) which is a second developer carrier; 3 is a first fixing member provided in the coater sleeve 1; Magnet (hereinafter referred to as coated electrode), 4
5 is an insulating magnetic one-component developer (hereinafter referred to as toner); 6 is a developer coated in a thin layer on two surfaces of the developing sleeve; Reference numeral 7 designates a developer hopper, and reference numeral 8 designates a second fixed magnet (hereinafter referred to as a counter pole) provided within the developing sleeve 2 opposite to the coater sleeve 1. Note that both the coater sleeve 1 and the developing sleeve 2 include magnets in addition to those shown in the drawings, but these are omitted for convenience of explanation.

By rotating the coater sleeve 1 in the same counterclockwise direction as the developing sleeve 2, the magnetic brush 9 formed and held on the surface of the sleeve comes into contact with the developing sleeve 2 at a portion where the coater sleeve 1 and the developing sleeve 2 face each other. At this time, toner having a sufficiently large charge in the magnetic brush is transferred onto the developing sleeve 2 by electric force or the like, and a thin toner layer 6 is formed on the developing sleeve 2.

Hereinafter, how the toner is applied to the end portion of the developing sleeve 2 will be explained. First, the longitudinal direction of the magnetic brush 9 formed on the surface of the coater sleeve 1 is restricted by a seal member between the coater sleeve 1 and the doctor blade 4 at both ends of the coater sleeve 1, as shown in FIG. 10
This is achieved by intervening. The sealing member 10 is made of Moltoprene, Teflon cloth, NOmax cloth, etc., and one end is fixed to the inner surface of the hopper 7 and the other end is fixed to the doctor blade 4. In this manner, the end surface of the coater sleeve 1 is covered with the seal member 10 and no toner is applied thereto. That is, as shown in FIG. 4, which is a longitudinal section taken along the line of FIG. By providing an overlapping width l4 so as to cover a portion of the magnet 11, the magnetic brush 9, which eliminates unevenness of the magnetic brush at the end of the magnet 11, has a doctor part magnetic brush length regulated by the end seal width l3. It is formed with a length L2'.

Next, toner regulation on the developing sleeve 2 will be explained with reference to FIG. 2, which is a longitudinal section taken along the line AA in FIG. 1. As shown in FIG. 2, in the opposing portion of the coater sleeve 1 and the developing sleeve 2, the length L2 of the magnetic brush 9 in the longitudinal direction is longer than the length L1 of the opposing pole 8 in the longitudinal direction. .
In this way, complete formation of a thin toner layer on the developing sleeve 2 corresponding to the length L1 of the opposing pole 8 is ensured.

However, as described above, since the length L1 of the opposing pole 8 in the longitudinal direction is shorter than the length L2 of the magnetic brush 9 in the longitudinal direction, the area where the opposing pole 8 does not exist at the end (the end l1 in FIG. , l2), the magnetic brush 9 comes into contact with the developing sleeve 2, and an abnormally thick toner layer 6' is formed at the end of the developing sleeve 2, as shown in FIG. That is, while the normal coating 6 has a thickness of 50 to 100μ, the toner layer 6' has a thickness of 50 to 100μ.
It may exceed 200μ.

This is because, in the case of FIG. 2, at the ends l1 and l2, there is no magnetic pole opposing the application pole 3, so the magnetic brush 9 can only form weak spikes, and as a result, the surface of the developing sleeve 2 is sufficiently strongly rubbed. Because it cannot be rubbed,
It is considered that the effect of scraping off the toner from the surface of the developing sleeve 2 by the magnetic brush 9 is weakened, resulting in a thick coating.

Such coating abnormality at the edge spreads to the normally coated thin layer 6 and appears as an abnormal density even on the image. This causes staining of the surface of the photoreceptor outside the image area, wasteful consumption of toner, and staining of the interior of the copying machine. In particular, when separating the transfer paper using a separation belt, there are inconveniences such as toner getting caught between the separation belt and the photoreceptor and damaging the photoreceptor. This requires some ingenuity. The technique for regulating the edge region of the thin layer of toner applied onto the developing sleeve (hereinafter referred to as sharp cut technique) is an indispensable technique for copying machines that requires high quality.

The present invention has been proposed in view of the above, and is intended to accurately control the thin layer of toner applied on the developing sleeve at the end region of the developing sleeve, thereby avoiding wasted toner consumption in areas other than the effective image area. It is an object of the present invention to provide a developing device that does not cause toner contamination caused by the toner contamination.

The above purpose is to form a first developer carrier that forms a magnetic brush of one-component developer, and to form a thin layer of one-component developer on the surface of the first developer carrier that comes into contact with the magnetic brush of the first developer carrier. a second developer carrier for developing an electrostatic latent image on a member to be developed, and a first developer carrier for forming the magnetic brush on an opposing portion of the first and second developer carriers.
a magnet or magnetic body disposed within the second developer carrier, and a magnet or magnetic body disposed within the second developer carrier. This is achieved by a developing device whose length in the longitudinal direction is greater than or equal to the length in the longitudinal direction of the magnetic brush formed on the first developer carrier.

The embodiments shown in the drawings will be described below. FIG. 6 shows an embodiment of the present invention in which the same parts as in FIG. 2 are given the same reference numerals, and like FIG. 2, it is a longitudinal sectional view taken along the line AA in FIG. 1. This embodiment is characterized in that the opposing pole length L1 is longer than the magnetic brush L2 (L1≧L2). Here, the magnetic brush length L2 is regulated by the end seal member 10 shown in FIG. At the opposing portion between the magnetic brush 9 and the developing sleeve 2, a certain amount of toner is held by the action of the mutually attracting magnetic fields of the application pole 3 and the opposing pole 8, and the end of the opposing pole 8, which is longer than the length of the magnetic brush 9 itself, is The toner also flows around and is supplied to the surface of the developing sleeve 2 corresponding to the area. The magnetic brush 9 comes to rub the developing sleeve 2 over the entire area of the opposing pole 8, and due to the toner scraping effect of the magnetic brush 9, the area in contact with the magnetic brush 9 is shown in FIG. As shown, a uniform toner thin layer 6 is formed, and the abnormal toner application 6' at the end of the developing sleeve as shown in FIG. 5 does not occur.

In addition, in order to perform coating stably, the coating maximum length L3
is equal to or longer than the opposing pole length L1 (L3
≧L1). In this way, the magnetic brush 9 can rub the surface of the developing sleeve 2 more stably. That is, the coating pole length L3 is the opposite pole length L1.
If the length is too short, the magnetic field at the end will be weakened, and as a result, the rubbing effect and scraping effect of the magnetic brush 9 will also be weakened.

As described above, the longitudinal length of the magnet or magnetic body disposed within the second developer carrier is equal to the longitudinal length of the magnetic brush formed on the first developer carrier. As described above, it is possible to form a thin developer layer with a uniform layer thickness over the entire region with a simple configuration. As a result, when developing the latent image on the photoreceptor with the developer formed in a uniform thin layer on the second developer carrier, the surface of the photoreceptor outside the image area may be smeared, and toner may be wasted. This provides remarkable effects as a developing device, such as no toner contamination.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a developing device, FIG. 2 is a vertical cross-sectional view of the facing portion of the first and second developer carriers in a conventional developing device, and FIG. 3 is a schematic diagram of the first developer carrier. 4 is a longitudinal sectional view of one end of the first developer carrier, and FIG. 5 is an explanatory diagram of the state of developer application on the second developer carrier in a conventional developing device. FIG. 6 is a vertical cross-sectional view of the opposing portions of the first and second developer carriers in an embodiment of the developing device of the present invention, and FIG. 7 is a diagram showing developer application on the second developer carrier in the developing device of the present invention. It is an explanatory diagram of a state. 1 is a coater sleeve which is a first developer carrier; 2 is a developing sleeve which is a second developer carrier;
3 and 8 are first and second fixed magnets, 4 is a magnetic brush regulating plate, 5 is a developer, 6 is a thin layer of developer applied to the surface of the developing sleeve, and 7 is a hopper.

Claims (1)

[Scope of Claims] 1. A first developer carrier forming a magnetic brush of one-component developer, and a thin layer of one-component developer on the surface of the first developer carrier in contact with the magnetic brush. a second developer carrier for developing the electrostatic latent image on the member to be developed, and a first developer to form the magnetic brush on the opposing portion of the first and second developer carriers. A magnet disposed within the developer carrier, and a magnet or magnetic body disposed within the second developer carrier, the magnet or magnetic body disposed within the second developer carrier in the longitudinal direction. A developing device characterized in that the length is equal to or longer than the longitudinal length of a magnetic brush formed on a first developer carrier.