JPH03251880A - Developing device - Google Patents

Abstract

PURPOSE:To remove the toner fixed to a blade with the device consisting of a sleeve for carrying a developer fitted onto a driving roller by magnetizing the sleeve and holding ferromagnetic fine particles of the polarity reverse from the polarity of a toner and of nearly the same size as the size of the toner or the size slightly larger than the same on the sleeve. CONSTITUTION:The sleeve 2 is formed by dispersing and incorporating a magnetic material having a large coercive force into a resin and holding the magnetic fine particles C of nearly the same size as the particle size of the toner or the size slightly larger than the same on the surface thereof. The particles C are electrified to the polarity reverse from the polarity of the toner T by the friction with the toner T. The toner T is taken into a toner taking-in region S formed between a regulating blade 42 and the sleeve 2 as the sleeve 2 revolves. A prescribed amt. of the toner sticks to the sleeve 2 surface and is carried to a developing region. The surface is softened or melted by the friction heat of the toner against each other in the region S and the toner tending to stick to the blade 42 is rubbed and removed by the particles C. The sticking of the toner to the blade is, therefore, prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a developing device in an image forming apparatus such as an electrophotographic printer or a copying machine.

[Conventional technology]

In one of the developing devices in this type of image forming apparatus, a flexible thin film sleeve for carrying developer having an inner diameter slightly larger than the outer diameter of the drive roller is fitted onto the drive roller, and the sleeve is inserted from one side to the above-mentioned side. There is a developing device in which a driving roller is pressed to form a slack portion on the other side, the slack portion is brought into contact with the electrostatic latent image carrier, and a developing toner regulating blade is exposed to the sleeve surface from the one side. .

As shown in FIG. 6, the sleeve 2a is connected to the drive roller 1.
The rotation of the drive roller 1 is followed by the frictional force of the pressure contact, and the drive roller rotates in the same direction as the drive roller. In addition, the regulation blade 42
1, its tip and sleeve 2a as shown in FIG.
As the sleeve 2a rotates, the toner T is taken into the tree-shaped space S formed by the sleeve 2a, and a predetermined amount of the toner T is deposited on the sleeve 2a, and the toner is triboelectrically charged. Toner adhesion on the sleeve is usually one or two layers.
It's about a layer. FIG. 6 shows an example in which two layers are attached.

[Problem to be solved by the invention]

However, according to the conventional developing device, the Flede 4
In the toner intake area S below 2, the toner adhering to the sleeve and traveling together with the sleeve and the blade 4
Frictional heat is generated between the toner and the toner that is blocked by the toner and remains in the area S, and the surface of the toner is softened or melted by the nuclear heat, and this adheres to the tip 421 of the blade 42. Decrease in the amount of toner adhering to the sleeve 2a, uneven toner adhesion, insufficient toner charge amount, etc.
As a result, problems such as decreased followability of solid black images, image loss, increased fogging, and decreased reproducibility of halftones occur.

Therefore, it is an object of the present invention to solve these problems in the conventional developing device described above.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention includes a developer carrying sleeve having an inner diameter slightly larger than the outer diameter of the roller, which is fitted around the drive roller, and which is pressed against the drive roller from one side and sag on the other side. In the developing device, in which the slack portion is brought into contact with the electrostatic latent image carrier while forming the sleeve, and the developing toner regulating blade is exposed to the sleeve surface according to the above-mentioned example, the sleeve is magnetized and the sleeve is magnetized. Magnetic fine particles are held by magnetization, and the magnetic fine particles are triboelectrically charged to have a polarity opposite to that of the toner.
The object of the present invention is to provide a developing device characterized in that the toner particles have approximately the same size or a slightly larger size.

[For production]

According to the developing device of the present invention, in the wedge-shaped toner intake region formed by the toner regulating blade and the sleeve, the toner whose surface is softened or melted by frictional heat between the toners and tends to stick to the blade is retained on the sleeve. It is removed by rubbing with magnetic fine particles.

Further, since the toner is triboelectrically charged to have a polarity opposite to that of the magnetic fine particles, the toner electrostatically adheres to the magnetic fine particles, and a predetermined amount of toner adheres to the sleeve more reliably.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

The developing device shown in FIG. 1 is provided with a drive roller 1 rotated by a drive means (not shown) in a casing 4 containing a monocomponent developer consisting of toner T for development, and a drive roller 1 for carrying a thin developer. A sleeve 2 is fitted onto the outside.

The sleeve 2 is pressed against the drive roller 1 from inside the casing 4 by guide members 3 (only one shown) that abut semicircularly on the outer circumferential surface of both ends in the direction of the rotational axis, thereby creating a slack portion 20 on the outside of the casing. is formed, and this slack portion is in contact with the photosensitive drum PC, which is an electrostatic latent image carrier.

The developer in the casing 4 is fed onto the sleeve 2 while being stirred by the stirring rotary blade 41. In addition, within the casing, a blade 42 that is a regulating member is in contact with the surface of the sleeve 2, and this regulating member slightly contributes to pressing the sleeve 2 and also regulates the amount of charge of the toner T and the amount of adhesion to the surface of the sleeve 2. do.

When the drive roller l is rotated in the direction of the upper arrow in FIG. 1 by a drive means (not shown), the sleeve 2 is also rotated in the same direction due to friction between the surface of the drive roller 1 and the inner surface of the sleeve 2, which is mainly caused by the pressing force of the guide member 3. do.

For the sleeve 2, a magnetic material (FeCo powder, Co powder, 7-Fe2O3, Co7x light, etc.) with a large coercive force (residual magnetic field when magnetized) is dispersed and mixed into a resin such as polycarbonate, nylon, or fluorocarbon resin. and magnetized after forming it into a thin film sleeve, or by laminating a sheet of resin containing the magnet material dispersed on a metal thin film sleeve such as Ni, and then magnetizing the resin layer in the same way. Alternatively, a metal thin film sleeve may be directly magnetized, but in this embodiment, it is made of resin in which magnet material is dispersed.

Although various magnetization patterns can be considered for the sleeve 2, examples thereof are shown in FIGS. 2 to 4.

The pattern shown in FIG. 2 is a pattern in which north poles and south poles are alternately arranged in the thickness direction of the sleeve 2. The pattern shown in FIG. 3 is a pattern in which north poles and south poles are alternately arranged in the circumferential direction of the sleeve 2. The pattern shown in FIG. 4 is a pattern in which north poles and south poles are alternately arranged on the sleeve in the rotational axis direction and the circumferential direction, respectively.

As shown in FIG. 5, the sleeve 2 holds magnetic fine particles C on its surface by magnetic force.

The magnetic fine particles C are made of a ferromagnetic material (Fe, Co, Ni, etc.), and when the toner particle diameter is approximately 10 μm,
The diameter of this magnetic fine particle is also approximately 10 μm. The magnetic particles may have a slightly larger diameter as long as they do not cause defects in the final image. However, if the diameter of the magnetic particles is larger than the desired toner layer thickness, the desired toner layer thickness cannot be obtained and the regulating blade cannot be brought into contact with the toner on the sleeve, making it difficult to apply sufficient charge to the toner. I won't be able to do that. Although the diameter of the magnetic particles to be used cannot be guaranteed depending on various conditions, it is preferably 3 times or less, more preferably 2 times or less, the diameter of the toner particles used. On the other hand, if the diameter of the magnetic particles is too small compared to the toner particle diameter, the effect of rubbing off the toner that tries to stick to the blade will decrease, and the magnetic adsorption force with the sleeve will decrease, causing the toner to separate from the sleeve surface. It ends up.

Further, the particles C are charged with a polarity opposite to that of the toner T due to friction with the toner T.

The state of distribution of the particles C on the sleeve 2 can range from a state in which a small amount is evenly distributed to a state in which they are uniformly spread over almost the entire surface of the sleeve 2. In other words, the toner T adhering to the sleeve 2 and the particles Approximately 50vol in the total amount with C
．． %~3νo1. %, it is sufficient to distribute it evenly without any bias. Furthermore, since the toner T is usually deposited in one or two layers on the sleeve, it is desirable that the particles C be deposited in one layer. In the example shown in FIG. 5, particles C are held in one layer.

According to the developing device of the present invention, as the sleeve 2 rotates, the toner T is taken into the toner intake area S formed between the regulating blade 42 and the sleeve 2, and is charged to a predetermined state under the regulation of the blade 42. At the same time, a predetermined amount adheres to the surface of the sleeve 2. This adhered toner T is carried to a development area facing the photoreceptor drum PC, where the electrostatic latent image on the photoreceptor drum PC is developed.

In the toner intake area S, the surface of the toner is softened or melted by the frictional heat between the toners, and the toner that tends to stick to the blade is rubbed off by the magnetic fine particles C held on the sleeve 2.

Further, since the toner is triboelectrically charged to have a polarity opposite to that of the magnetic fine particles, the toner electrostatically adheres to the magnetic fine particles, and a predetermined amount of toner adheres to the sleeve more reliably.

Note that the present invention is not limited to the above embodiments,
Of course, it can be implemented in various other ways.

〔Effect of the invention〕

As explained above, according to the present invention, a developer carrying sleeve having an inner diameter slightly larger than the outer diameter of the roller is fitted around the drive roller, and the sleeve is pressed against the drive roller from one side so that the sleeve sag on the other side. In a developing device in which a slack portion is brought into contact with an electrostatic latent image carrier while forming a portion, and a regulating blade for developing toner is exposed to the sleeve surface from the other side, toner adhesion to the regulating blur can be prevented. Furthermore, the toner can be supplied onto the sleeve more reliably due to the electrostatic adhesion of the toner to the magnetic fine particles on the sleeve. Therefore, it is possible to ensure that a predetermined amount of toner adheres to the sleeve and to ensure uniformity of the adhesion. At the same time, a predetermined amount of toner charge can be obtained, and thereby good image quality can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of one embodiment of the present invention, and FIGS. 2 to 4 are explanatory views of the magnetization pattern of the sleeve, respectively. FIG. 5 is an explanatory diagram showing the magnetic particles and toner on the sleeve in the embodiment shown in FIG. 1, and the toner regulation state by the regulation blade. FIG. 6 is an explanatory diagram of a conventional example. l... Drive roller 2... Sleeve 2... Regulating blade T... Toner C... Magnetic fine particles PC... Photosensitive drum Applicant: Minolta Camera Co., Ltd. Diagram T... Toner diagram Figure Figure

Claims (1)

[Claims] (1) A developer carrying sleeve having an inner diameter slightly larger than the outer diameter of the roller is fitted onto the drive roller, and the sleeve is pressed against the drive roller from one side to form a slack portion on the other side. In the developing device, the sleeve is magnetized and holds magnetic fine particles due to the magnetization. A developing device characterized in that the magnetic fine particles are triboelectrically charged with a polarity opposite to that of the toner particles, and are approximately the same size as or slightly larger than the toner particles.