JPS6088973A - Developing device - Google Patents

Abstract

PURPOSE:To coat a developer carrier with a single-component nonmagnetic developer uniformly while triboelectrifying it sufficiently by providing numbers of magnetic particles which are chained in a brush shape while being restrained by a magnetic field and circulates being stirred by the motion of the toner carrier. CONSTITUTION:A developer 2 contains the powdery single-component nonmagnetic developer (toner) 3. Magnetic particles 6 consisting of iron powder and ferrite are put in the container 2 closely to a magnet 4 and forms a brush at the upstream side of a specifying blade 5 with the magnetic field of the magnet 4, and they are circulated near the specifying blade 5 according to the rotation of a sleeve 1. This circulation mixes the toner 3 with the brush, and they are circulated and stirred to triboelectrify the toner 3 and magnetic particle brush. The toner 3 sticking to the brush 6 is applied over the sleeve 1 uniformly and conveyed according to the rotation of the sleeve. The magnetic particles 6 forming the brush, on the other hand, are given restraint by the magnetic field of the magnet 4 larger than conveyance force depending upon the electrostatic sticking force and mechanical frictional force of the sleeve 1 and magnetic particles 6, so the particles are applied over the sleeve 1 together with the toner 3 and stay in the container 2 without being conveyed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an image forming apparatus using a powder developer, such as an electrophotographic copying machine, in which a developer, particularly a -component, is placed on a developer carrier that supplies the developer to a latent image carrier. The present invention relates to a developing device that applies a non-magnetic developer.

In an image forming apparatus that uses a powder developer, such as an electrophotographic copying machine, a method is used to supply developer to the surface of a latent image carrier (photosensitive drum) in order to develop a latent image formed on the surface of the photosensitive drum. , a developer is applied to an endlessly rotating developer carrier (developing roller) disposed close to the developer carrier.

Conventionally, a development method using magnetic toner as a -component developer has been put into practical use, but the fixing performance when thermally fixing the toner image transferred to transfer paper after development is problematic, and the toner itself has to be completely internally loaded with magnetic material. Because of this, there are drawbacks such as poor color toner.

For this reason, a development method using non-magnetic toner has been considered, and in the 7ζ step, the developer is coated with a non-magnetic toner, and the developer is developed using a cylindrical brush made of soft bristles like beaver's hair. A method in which the developer is applied by adhesion, and a method in which the developer is applied using a doctor blade or the like to a developing roller whose surface is made of a fiber brush made of velvet or the like have been proposed.

However, when an elastic blade is used as a doctor blade for the above-mentioned fiber brush, it is possible to control the amount of toner, but uniform application is not achieved, and the fiber brush on the current roller is rubbed. However, since the toner existing between the fibers of the brush is not triboelectrically charged, ghosts and the like are likely to occur.

It is an object of the present invention to eliminate the drawbacks of the above-mentioned conventional methods and to provide a novel apparatus for applying a -component non-magnetic developer to a developer carrier uniformly and while imparting sufficient triboelectric charging.

The developing device of the present invention includes a container containing all the toner, a toner carrier (preferably a non-magnetic toner carrier) that moves (preferably moves endlessly) in contact with the toner, and the toner carrier A magnetic field generating means disposed inside the container, which is in contact with the toner in the container, is chained in a brush shape by being restrained by the magnetic field generated by the magnetic field generating means, and has a circular agitation movement due to the movement of the toner carrier. It is characterized by comprising a large number of magnetic particles such as a mixture of iron powder and ferrite powder that have the following properties.

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

In FIG. 1, reference numeral 1 denotes a developing sleeve (developing roller) as a developer carrier, which is made of a non-magnetic material, and is indicated by the arrow a.
Rotate in the direction. A developer container 2 has an open bottom and is partially surrounded by the developing sleeve l', and a powdered one-component non-magnetic developer (toner) 3 is contained therein. 4
5 is a stationary magnet disposed inside the developing sleeve 1, and 5 is a regulating blade made of a magnetic material screwed onto one side of the container 2. Magnetic particles 6 are placed in the container 2 near the magnet 4, and the magnetic particles 6 are placed in the vicinity of the magnet 4.
Magnetic particles 6 gather on the upstream side of the regulating blade 5 to form a brush. This magnetic particle brush moves in a circular motion near the regulation blade 5 due to the rotation of the sleeve 1, and due to this circulating motion, the toner 3 is mixed with the brush, circulated and agitated, and the toner 3 and the magnetic particle brush are triboelectrically charged. do. The toner 3 adhering to the brush 6 is uniformly applied onto the sleeve 1 by the reflection force with the sleeve 1, and is conveyed through the gap below the regulating blade 5 as the sleeve rotates. On the other hand, the magnetic particles 6 constituting the brush are arranged in such a way that the restraining force due to the magnetic field of the magnet 4 is greater than the conveying force that depends on the electrostatic adhesion force and mechanical friction force between the sleeve 1 and the magnetic particles 6. Because of this setting, the toner 3 remains in the container 2 without being applied onto the sleeve 1 and transported together with the toner 3.

The toner that has been applied and transported is transferred to the developing sleeve 1 as is well known.
It adheres to a photosensitive drum (not shown) that faces closely to the photosensitive drum (not shown) for development, and is consumed. However, if there is a sufficient amount of toner 3 above the brush of magnetic particles in the container 2, the ratio of toner particles 3 to magnetic particles 6 in the brush portion will always be approximately constant, so that the toner will be used and consumed for development. Since the toner 3 is automatically supplied to the brush portion as time passes, it is possible to always apply a constant amount of toner.

The conditions under which the above-mentioned effects must be carried out stably will be further explained below.

As shown in FIG. 1, the pole position of a magnet 4 serving as a magnetic field generating means is tilted by an angle θ with respect to a regulating plate 5. A value of 0 means that there is no magnetic material such as magnetic particles 6 or magnetic regulation blade 5 near the magnet 4. It is preferable to choose such that the magnetic flux density by the magnet 4 at the position facing the regulating blade on the surface is 30 to 90 degrees of the maximum magnetic flux density at the sleeve surface (at the position facing the magnetic pole).

When the positional relationship between the regulating blade 5 and the magnet 4 is selected to the above value, the shape of the brush of the magnetic particles 6 in the blade 5 part is as shown in FIG. ) are magnetic particles because most of them exist on the upstream side of the regulating blade 5.

6 is bound there.

If the pole position of the magnet 4 is on the downstream side of the regulating blade 5 as shown in Figure 2 (,), the polar particles will not be restrained, and the circulating movement of the magnetic particle brush downstream of the regulating blade will also be difficult to occur. Become.

The magnetic field for restraining the magnetic particles 6 is 400° at the position where the magnetic poles face each other on the sleeve surface (maximum position of magnetic flux density distribution).
It is desirable that it be Gauss or higher.

Further, it is desirable that the surface of the sleeve 10 has a surface roughness Rz of about 0.5 to 5 μm so that the toner can easily come into contact with it and be easily conveyed.

In addition, the sleeve 1 and the regulating blade 5 marked d in FIG.
It is desirable that the distance between the
．． If it is less than 9 times, magnetic particles will easily get caught between the sleeve and the regulating blade, and if it is significantly larger than 20 times, it will be impossible to hold the magnetic particles.

As the magnetic particles in the present invention, a mixture of iron powder and ferrite powder is used. The mixing ratio, expressed in terms of weight ratio, is as follows:

Iron powder/ferrite = 10/90 to 90/10 The magnetic particles form a brush on the developing sleeve 1 and circulate as the sleeve rotates to sufficiently engulf and stir the toner. The toner is restrained on the sleeve by the magnetic field and has the role of pressing the toner 1 against the sleeve to cause frictional charging between the sleeve surface and the developer, and it is necessary to satisfy both of these requirements at the same time. For the latter role, it is desirable that the magnetic particles uniformly cover the sleeve surface without any gaps, and that they press the toner equally at any point on the sleeve. In addition, for the former role, saturation magnetization is large and fluidity (see1
50. ! It is desirable that i') be small, and for the latter role, it is desirable that the saturation magnetization be small and the fluidity be large.

Therefore, it is difficult to satisfy all of these requirements using only one type of magnetic particles, and it is appropriate to individually achieve each of these requirements using one or more types of magnetic particles.

Therefore, in the present invention, the above problem is solved by using a mixture of iron powder and ferrite.

To explain this point in more detail with reference to Figure 3,
In the figure, it is assumed that the sleeve 1 rotates in the direction a.

The iron powder 6-1 has a large saturation magnetization and forms a brush with long spikes along the lines of magnetic force, and the ferrite 6-11 has a small saturation magnetization and forms a brush with short spikes.

In addition, when the sleeve 1 moves in the direction a, the iron powder 6-1
has a low flow rate, so it flows smoothly on the sleeve and
6-+1 has a high flow rate and has sufficient regulating force to press the toner against the sleeve and cause uniform charging.

Here, it is desirable that the magnetic particles have an average particle size of 1 to 30 times the average particle size of the toner particles.

If the particle size of the magnetic particles is significantly smaller than that of the toner particles, the toner and the magnetic particles tend to be coated onto the sleeve while adhering to each other, and conversely, if the magnetic particles are significantly larger than the toner particles, the toner particles that enter the plunger part may be easily coated onto the sleeve. If the amount is too small, stirring of the toner and magnetic particles at the brush part will be poor, and streaks will easily occur in the resulting toner coating. Preferably, the amount is sufficient to be retained by the magnet and to generate circular motion.

A specific embodiment of the present invention will be explained with reference to FIG.

In Fig. 4, 1 is a developing sleeve made of SUS 304 with a diameter of 30mm, and the surface is subjected to cine sandblasting with ÷600 Aranmem abrasive grains to obtain a surface roughness of Rz = 0.8.
It is set to μm. Inside the developing sleeve 1, a regulating blade 5 of a roll-shaped magnet of the ferrite sintered type is made of iron and has a surface coated with nickel metal. The maximum magnetic flux on the sleeve surface of the magnet is 800 Gauss, and at the position of the regulating blade 5, it is 600 Gauss when the regulating blade is removed. The magnetic particles 6 were made by mixing spherical ferrite with an average particle size of 80 μm and spherical iron powder with an average particle size of 90 μm in a weight ratio of 1:4, and the distance d between the sleeve 1 and the regulating blade 5 was 300 μm. Coated with toner.

As toner 3, a negative cyan toner in which copper phthalo, 3 parts of cyani pigment, and 5 parts of negative charge control agent were internally added to 100 parts of polyester resin was used, and 2,009 parts of the toner was replenished into container 2. When the sleeve 1 was rotated in this state, a thick toner was stirred and circulated together with the magnetic particle brush every 10 rotations of the sleeve, and a uniform charge of 17 μC/11 was deposited on the sleeve to a thickness of about 120 μm.1 as measured by the blow-off method. There are products that completely prevent toner coatiner from falling or spilling.

In order to subject the toner coating layer thus obtained on the sleeve l to a block imaging effect, the photosensitive drum 1 has a dark part of -500cm and a light part of -5QV as an electrostatic latent image.
0 and the sleeve l, the photosensitive drum 10 is grounded, the power supply 7 is connected to the sleeve 1, and the frequency is 800 Hz 1 peak-to-peak value 1
．． When a voltage of 6 kV and a center value of -200 V was applied, a good developed image without ghost fog was obtained, with a voltage of about 30
After copying 00 sheets, there was no change in image density until the toner was almost consumed, and the magnetic particles 6 were not supplied to the photosensitive drum.

As described above, according to the present invention, a one-component non-magnetic toner can be used without using a magnetic toner without adversely affecting the heat fixability of a transferred toner image or the color of the obtained image, and furthermore, the toner can be used without using a magnetic toner. It is possible to apply and convey the developer carrier (developing sleeve) uniformly and with a constant supply amount while giving a sufficient amount of static electricity, and it is possible to form a good image.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an embodiment of the present invention, Fig. 2(a)
, (b) is an explanatory diagram of the effect, FIG. 3 is an explanatory diagram of the effect of an embodiment of the present invention using iron powder and ferrite powder as magnetic particles, and FIG. 4 is a cross-sectional view of a specific embodiment of the present invention. It is. 1...Developing sleeve 2...Toner container 3...Toner 4...Magnet 5...i Control blade 6...Magnetic particles 9...Falling prevention sheet 10...Photosensitive drum . 6. ) Figure 2 (b Figure 3 Figure 4

Claims (1)

[Claims] A container containing all the toner, a toner carrier that moves in contact with the toner, a magnetic field generating means disposed inside the toner carrier, and a magnetic field generated by the magnetic field generating means in contact with the toner in the container. A developing device comprising a large number of magnetic particles made of a mixture of iron powder and ferrite powder, which are chained together in a brush-like manner and are made of a mixture of iron powder and ferrite powder, and which perform a circular agitation motion due to the movement of the toner carrier. .