JPH0225876A - Developing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is applicable to copying devices, image display devices, image recording devices, printers, facsimile machines, etc. The present invention relates to a developing device that develops a latent image formed on a holder surface.

More specifically, it relates to a developing device in which a so-called two-component developer consisting of a mixture of toner particles and carrier particles is carried on a developer carrier and applied to the surface of the latent image carrier to develop the latent image on the surface of the latent image carrier. .

[Prior Art] In a developing device that uses a two-component developer consisting of a mixture of toner particles and carrier particles, the toner in the developer adheres to the surface of a latent image carrier to develop the latent image. On the other hand, since the carrier is not consumed, as the toner in the developer is consumed to develop the latent image, the toner concentration (=toner content,
Fluctuations such as a gradual decrease in the mixture ratio of toner and carrier, developer concentration, and a decrease in the toner content of the developer appear as fluctuations in the image density and image quality of the output image.

Therefore, in this type of developing device, it is extremely important to maintain and manage the toner content of the developer at a predetermined tolerance level at all times in order to stabilize the image quality.

Therefore, the present applicant has realized that it is possible to naturally maintain the toner content of the developer at a predetermined tolerance level at all times in a self-controlled manner without using a complicated developer concentration control mechanism including a sensor, etc. A developing device has already been proposed (Japanese Patent Application No. 60-217557, etc.) that enables the development device configuration to be simplified, downsized, and reduced in cost.

FIG. 5 shows a cross-sectional view of essential parts of an example of such a developing device. 1 is a developing container, 2 is a developing sleeve made of a non-magnetic material as a developer carrier, and is located halfway around the right side of the sleeve with respect to the oblong opening formed in the longitudinal direction at the bottom of the left side wall of the developing container 1 in the drawing. The surface protrudes into the inside of the container, and the left side half-circumferential surface is exposed outside the container so as to face the latent image carrier 100 with a gap, and is horizontally installed so as to be freely rotatable by bearings.
It is rotationally driven in the counterclockwise direction indicated by the arrow at a predetermined circumferential speed by a drive system (not shown).

A magnet roll (permanent magnet roll) 3 having magnetic poles N1, S, . . . N2°S2 is built into the developing sleeve 2 which is rotated and serves as a stationary magnetic field generating means. Thus, the magnetic force generated on the outer surface of the rotating developing sleeve 2 attracts the carrier to the outer surface, and the toner particles are attached to the circumferential surface of the carrier and transported.

A non-magnetic regulating blade 4 made of stainless steel or the like as a developer regulating member is provided at the horizontally elongated opening that serves as the outlet of the developing container l, and the blade 4 is provided with a non-magnetic regulating blade 4 made of stainless steel or the like as a developer regulating member. A gap is formed facing each other, and the layer thickness of the developer carried on the circumferential surface of the developing sleeve and conveyed to the developing section A is regulated to a predetermined thickness.

A developer (magnetic particle) circulation limiting member 5 is disposed on the inner side of the regulation plate 4 (inner side of the developer container).

A developer T is contained in the developer container l.

The developer T is a two-component developer consisting of a mixture of toner particles t and magnetic particles C as a carrier. The magnetic particles C as a carrier have a particle size of 30 to 100%, for example.
Preferably, it has a resistance value of 40 to 80 ohms and a resistance value of 107 Ω.01 or more, preferably 10' ohm. obtain.

Reference numeral 9 designates a part of the toner storage container, in which replenishment toner t is stored. The toner storage container 9 communicates with the developer container 1 through a communication opening 9a.

The toner t in the developer container 1 is successively moved toward the developer sleeve 2 by a toner particle replenishing means 10 provided in the developer container 1 and driven to rotate in the clockwise direction of the arrow around a support shaft 10a. Ru.

The developer T held by the developing sleeve 2 is conveyed in the direction of the developer circulation limiting member 5 as the developing sleeve 2 rotates, and is conveyed by the lower surface 5a of the member 5 toward the regulating blade 4 and in the opposite direction. The amount will be distributed according to the proportion of the amount going to the destination. Then, the layer toward the regulating plate 4 side is subjected to layer thickness regulation in the process of passing under the lower side of the regulating plate 4, and is carried out of the developing container l while being magnetically supported on the developing sleeve 2 surface, and retains the latent image. It passes through the developing section A facing the body 100 and is subjected to development.

On the other hand, due to the rotation of the developing sleeve, the developer T, which has been directed to the opposite side from the aforementioned regulating blade 4, cyclically moves back toward the magnetic thin plate 6 provided at the bottom of the developer container, such as a flow process. The toner is sufficiently charged to a predetermined polarity by contact friction with the developing sleeve 2 and the lower surface 5a of the member 5, and fluid mixing friction of the developer amount V.

As the developer T in the developer container L is used to develop the latent image on the latent image holding member 100, the toner content decreases, but this decrease is self-controlled by the mechanism described above. Once replenished, the toner content is naturally maintained at a predetermined tolerance level at all times.

That is, as described above, the developer T in the developing container 1 forms a moving layer (fluidized layer) near the developing sleeve that moves in the same direction as the developing sleeve as the developing sleeve 1 rotates. As the magnetic binding force decreases as the distance from 2 increases, a stationary layer that hardly moves is formed on the moving layer.

The toner t, which is sequentially replenished from the toner storage container 9 side to the developer container 1 side, is taken into the developer T in the developer container l by the above-mentioned moving layer. It is controlled by changing the volume of the static layer developer by increasing or decreasing the toner content in the static layer developer present above the agent. That is, as the toner content of the developer increases, the volume (amount) of the stationary layer developer increases and covers the moving layer developer, reducing the uptake of toner t into the moving layer. Further, when the toner content of the developer T decreases, the volume of the stationary layer developer decreases and the area covering the moving layer developer decreases, making it easier to take in toner.

Such a self-regulating cycle of increasing and decreasing the amount of toner taken in naturally maintains the toner content of the developer T in the developer container 1 at a predetermined tolerance level at all times.

[Problems to be Solved by the Invention] In this way, the developer that is magnetically held in the form of a magnetic brush on the surface of the rotating developing sleeve, which is the developer carrier, in the developing container is transferred! Self-regulating toner content maintenance control that utilizes volume changes of the LIy layer and the stationary layer above it maintains a state in which the developer in the developer container is magnetically held uniformly at each location along the length of the developer sleeve. It is kept stable by

However, even if the developer is held approximately evenly in the longitudinal direction of the developing sleeve when the developing device is installed in the initial stage of image production, as the developing sleeve continues to rotate, the inner wall of the developing container (both ends in the longitudinal direction) ) The developer held in the developing sleeve near the developing sleeve moves faster than that in the center, and as the amount of developer in the center gradually increases, its movement slows down, and toner uptake becomes worse. The problem was that the concentration was too low.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a developing device that can always maintain a uniform concentration of developer in the longitudinal direction of a developing sleeve and obtain good images.

[Means to solve the problem] According to the invention, the above objects are achieved.

A developing section that faces the surface of the latent image carrier and magnetically holds a developer containing a mixture of toner particles and magnetic particles as a carrier on the surface of the developer carrier, which has a rotating section that has a built-in magnetic field generating means for making it stationary. A developing device for developing a latent image on a surface of a latent image carrier, the developing device comprising: a developer container storing a developer for the developer carrier; and a toner particle replenishing means part for replenishing toner particles into the developer container. .

a developer regulating member disposed facing the developer carrier with a gap in order to regulate the amount of developer applied to the surface of the developer carrier, and a developer container inner side with respect to the developer regulating member. a developer circulation limiting member disposed at a position, and a developer circulation space surrounded by the developer circulation limiting member, the developer regulating member, and the developer carrier is arranged in a longitudinal direction of the developer carrier. This is achieved by being wide at the center and narrow at the ends.

[Function] According to the present invention as described above, since the circulation space in the center of the developing sleeve in the longitudinal direction is widened, the flow of the developer is improved and a predetermined amount of toner is deposited. As a result, the developer maintains a predetermined toner content, and as a result, each image is uniform and of good quality in the longitudinal direction.

[Example] Hereinafter, the present invention will be described in detail based on the accompanying drawings.
Prior to that, let me explain the circumstances that led to the present invention.

The movement of the developer at the central portion in the longitudinal direction of the developing sleeve is slower than that near the inner wall of the developer container (both ends in the longitudinal direction), and the developing agent tends to become clogged (hereinafter referred to as a "backing state").

Therefore, in order to find out whether this phenomenon is caused by the inner wall of the developing container itself or by the end of the magnet roll inside the developing sleeve, the following experiment was conducted.

A non-magnetic thin plate is placed on the developer surface area (the area where the developer moving layer and stationary layer are located) from the surface of the developer circulation limiting member (hereinafter referred to as "carrier return") facing the developing sleeve. are arranged at several locations in the longitudinal direction of the sleeve, as if it were on the inner wall of the developer container, and when an image is produced, the image density at 2 to 3 C■ on both sides of the thin plate or the gap between the thin plates. It turned out that it was darker than the center, and the developer was moving faster. From this, it can be said that the reason why the density is higher near the inner wall of the sleeve than at the center is not because it is at the end of the magnet in the sleeve, but because it is close to the wall. So, when we observed the movement of the developer near the wall, we found that
It can be seen that the developer moves downstream along the wall, and as it approaches the regulating blade, it gradually approaches the center in the longitudinal direction of the sleeve. As a result, it became clear that the amount of developer in the center gradually increased and its movement became slow, resulting in poor toner uptake and low density.

Therefore, the present invention has been made based on the results of the above experiments.

FIG. 1 is a sectional view showing one embodiment of the present invention. In this figure, the same reference numerals are given to the same components as those of the apparatus shown in FIG.

Also in the device of this embodiment, the bottom surface of the carrier returner 5 is crowned in a concave shape, as clearly shown in FIG. 2, and the surface of the carrier returner 5 facing the developing sleeve,
The circulation space surrounded by the thin plate member 12, the magnetic force line concentrating member 6, and the developing sleeve 3 provided in the carrier return is the same as the carrier return 5 when viewed in the longitudinal direction of the developing sleeve 3.
The center portion 5b is wider than the end portions 5a due to the crowned portion.

By doing this, it became possible to make the movement of the developer magnetically held in the developing sleeve 3 uniform in the longitudinal direction. The reasons for this are as follows.

The movement of the developer held in the developing sleeve is approximately determined by the circulation space, the amount (volume) of the developer, the magnetic force of the magnet in the developing sleeve, the magnetic pole position, the circumferential speed of the developing sleeve, and the surface properties of the developing sleeve. . Among the above conditions, focusing on the volume of the circulation space and the amount of developer, and assuming that the other conditions are approximately equal in the longitudinal direction of the developing sleeve,
When the volume of the circulation space is small, the backing state of the developer therein is strong and the movement of the developer is poor. Conversely, when the volume is large, the backing state of the developer therein is weak and the movement of the developer is good. As described above, when the surface of the carrier return facing the developing sleeve is uniform in the longitudinal direction as in the conventional case, the developer moves more easily near the inner wall of the developer container than at the center. Therefore, as in this embodiment, by bringing the surface of the carrier return facing the developing sleeve near the side wall closer to the developing sleeve, the volume of the surrounding area A is narrowed to reduce the movement of the developer, thereby reducing the difference in movement with the central part. Then, a uniform image is drawn in the longitudinal direction.

Next, in order to widen the circulation space at the center, the configurations shown in FIGS. 2 and 3 are also possible. That is, in FIG. 3, the bottom surface of the carrier returner 5 is stepped so that both ends approach the developing sleeve. this is,
Although the shape is simpler than in the case of FIG. 1, the same effect can be obtained.

In FIG. 3, four parts are provided at the center of the free edge of the thin plate member 12 provided on the carrier returner 5, thereby widening the gap for taking in the developer and substantially expanding the circulation space. It is.

Even in this case, the same effect as in the case of FIGS. 1 and 2 can be obtained.

Furthermore, the invention can also be applied to those in which the stationary layer described above is not formed.

[Effects of the Invention] As described above, according to the present invention, the movement of the developer near the inner wall of the developer container is controlled by changing the shape of the developer circulation IEI shading member at the center in the longitudinal direction of the developer sleeve. The movement of the developer in the center can be made almost equal to the movement of the developer in the center.
Approximately uniform toner content can be maintained in the longitudinal direction of the developing sleeve.

In addition, by providing four sections in the center of the free end of the thin plate attached to the carrier returner, toner can be taken in better at the center than at both ends, even if the developer movement is different between the center and the edges. Approximately uniform density can be achieved in the longitudinal direction.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an apparatus according to an embodiment of the present invention, and FIG.
FIG. 3 is a perspective view showing a modified example of the developer circulation limiting member in the device shown in FIG. 1, and FIG. 4 is a perspective view showing a modification of the developer circulation limiting member in the device shown in FIG. FIG. 5 is a perspective view showing a modification, and FIG. 5 is a sectional view showing a conventional device. 1......Developer container 2...Developer carrier (developing sleeve) 3...Magnetic field Generating means (magnet roll) 4-------Developer regulating member (regulating blade) 5------Developer circulation limiting member 10------ --------...1 henna particle replenishment means 12... Thin plate member C"
'''...Magnetic particle 1-...Toner particle T-...
...Developer

Claims (3)

[Claims] (1) The developer, which is a mixture of toner particles and magnetic particles as a carrier, is magnetically retained on the surface of the developer carrier, which has a rotating part that has a built-in magnetic field generating means for making it stationary, so that it faces the surface of the latent image carrier. A developing device that develops a latent image on the surface of a latent image carrier by transporting the latent image to a developing section, the developing device includes a developer container containing a developer for the developer carrier, and a toner particle replenisher that replenishes toner particles into the developer container. a means portion; a developer regulating member disposed facing the developer carrier with a gap therebetween in order to regulate the amount of developer applied to the surface of the developer carrier; and a developer regulating member arranged to face the developer carrier with a gap therebetween; and a developer circulation limiting member disposed on the inner side of the container, and a developer circulation space surrounded by the developer circulation limiting member, the developer regulating member, and the developer carrier is configured to support the developer. A developing device characterized by being wide at the center in the longitudinal direction of the body and narrowing at the ends. (2) The circulation space is formed such that the gap between the opposing surfaces of the developer circulation limiting member and the developer carrier is wide at the center in the longitudinal direction and becomes narrower as it approaches the ends. The developing device according to item (1). (3) The developer circulation limiting member is provided with a thin plate member extending toward the upstream side of the surface area on the side opposite to the developer regulating member. (
2) The developing device according to item 2).