JPS58168068A - Magnetic toner development device - Google Patents

Abstract

PURPOSE:To efficiently attach a charged toner to an electrostatic latent image, by using a developing roll formed by alternately arranged magnetic and nonmagnetic metallic cylinders in the peripheral direction. CONSTITUTION:Magnetic and nonmagnetic metallic cylinders 7, 8 are alternately arranged in the peripheral direction to form a metallic cylinder 9 joined in one body, and columnar permanent magnets 4 are arranged in the cylinder 9. The region in which toner is present is reduced by using such a developing roll, a toner brush is prevented from overlapping during rotation and its rotation can be sufficiently executed, therefore, even if a high resistance magnetic toner is used, the charged toner can be efficiently attached to an electrostatic latent image.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic toner developing device used in copying machines, printers, etc. that utilize an electrophotographic process.

FIG. 1 is a side sectional view showing a conventional magnetic toner developing device of this type. In the figure, 1 is a magnetic toner, 2 is a toner hopper for storing the magnetic toner 1, and 3 is a non-magnetic toner made of aluminum or the like. The metal cylinder 4 is a cylindrical permanent magnet arranged concentrically within this non-magnetic metal cylinder 3, and this permanent magnet 4 has a structure in which north poles and south poles are arranged alternately in the circumferential direction. It is usually called a magnetic roll.

The non-magnetic metal cylinder 3 and the permanent magnet 4 are each rotatable, and the two are usually referred to as a developing roll as an integral component.In this developing roll, the permanent magnet 4 has its magnetic attraction force. The magnetic toner 1 in the toner hopper 2 is attracted onto the non-magnetic metal cylinder 3. The magnetic toner 1 usually has a particle size of 5 to 20 μm, and a plurality of magnetic toner particles are arranged in a row along the lines of magnetic force to form a toner brush on the non-magnetic metal cylinder 3.

5 is a doctor blade that regulates the height of the toner brush.

Reference numeral 6 denotes a rotatable developing object such as an electrostatic drum or a photosensitive drum, the surface of which is coated with a dielectric material, and an electrostatic latent image is formed by an optical system (not shown) at a position before the developing area. It will be sent to. The conductive base material of the object to be developed 6 and the non-magnetic metal cylinder 3 are electrically connected, or in the case of reversal development, a developing bias voltage is applied. and permanent magnet 4
The magnetic toner 1 is conveyed to the development area between the non-magnetic metal cylinder 3 and the object to be developed 6 by rotating each of the magnetic toners 1 and 2 to carry out development. There is a potential difference between the cylinder 3 and the object to be developed 6, and when the toner brush is moved from the state where the toner brush is sandwiched between the surfaces of both, the toner that was in contact with the non-magnetic metal cylinder 3 becomes non-magnetic. It receives an electric charge from the magnetic metal cylinder 3 and is charged. This phenomenon is called contact charging, and due to the electrical charge, the magnetic toner 1 is attracted to and adheres to the electrostatic latent image formed on the object to be developed 6, resulting in development.

Here, when the magnetic toner 1 has a high resistance, the above-mentioned charging is a factor that determines the image quality of development, and this will be explained below. Fig. 2 shows the magnetic flux density in the vertical direction (solid line) and the circumferential direction (dashed line) due to the permanent magnet 4 at a certain position X along the circumferential direction of the non-magnetic metal cylinder 3, and Fig. 3 shows the magnetic flux density of the toner. It is an explanatory view showing how a brush rotates.

As seen in this figure, the position of a is on the N pole,
The toner brush made up of a plurality of connected magnetic toners 1 is in the 0-order standing position, and when it reaches the position b between the N and S poles, the horizontal component becomes strong and the toner brush takes a lying shape. At the highest position C, the toner brush assumes an upright shape again.

Now, if the permanent magnet 4 is rotated to rotate the toner brush, the toner brushes will collapse from the position a to the position b, and furthermore, the rearranged toner brush will fall to the position C. stand up Therefore, when the toner brush is in the development area, the charged toner that comes into contact with the non-magnetic metal cylinder 3 cannot reach the tip of the toner brush because the toner brush does not rotate sufficiently and is rearranged midway through. As a result, the charged toner cannot efficiently adhere to the electrostatic latent image because other toners get in the way, making it impossible to perform efficient development.

Therefore, when a high-resistance magnetic toner is used in a conventional developing device, efficient development cannot be performed as described above, resulting in poor developed image quality.The present invention solves this drawback. Therefore, in place of the conventional non-magnetic metal cylinder, a metal cylinder with a structure in which magnetic and non-magnetic materials are arranged alternately in the circumferential direction is used to improve the area where the toner brush is present. The present invention is characterized in that the toner brushes are prevented from overlapping each other during rotation, and the toner brushes are sufficiently rotated to efficiently attach the charged toner to the electrostatic latent image. Embodiments of the invention will be explained with reference to FIGS. 4 and 5. First, FIG. 4 is a partially enlarged sectional view showing the first embodiment of the invention, in which the magnetic material 7 and the non-magnetic material 8 are shown in the circumferential direction. A metal cylinder 9 is formed by arranging the metal cylinders 9 and 9 alternately, and permanent magnets 4 are arranged in the metal cylinder 9 to form a developing roll. 2
It is a magnetic toner developing device in combination with a doctor blade 5, etc. 0 As the magnetic material T, metals and alloys such as iron, cobalt, nickel, various ferrites, etc. can be used, and non-magnetic materials can also be used. 8 can be made of metal such as aluminum or stainless steel. In this configuration, as in the conventional case, the permanent magnet 4 and the metal cylinder 9 are each rotated, thereby conveying the magnetic toner 1 to the developing area. Development is carried out by attracting and adhering the electrostatic latent image on the developing body 6. At this time, since the magnetic material T of the metal cylinder 9 has a high magnetic permeability, most of the lines of magnetic force coming out from the permanent magnet 4 are The lines of magnetic force that pass through the magnetic material 1 and the lines of magnetic force that pass through the non-magnetic material 8 become minute.

Therefore, the toner brush made of magnetic toner 1 is made of magnetic material T.
Therefore, if the interval between the magnetic materials 1 is set to be equal to or longer than the length of the toner brush regulated by the doctor blade 5, the toner brushes overlap each other when the toner brushes rotate. FIG. 5 is a partially enlarged sectional view showing a second embodiment of the present invention, in which a cylindrical non-magnetic material 10 A metal cylinder 12 is formed by disposing a magnetic material 11 at regular intervals along the circumferential surface thereof, and a permanent magnet 4 is arranged inside this metal cylinder 12 to constitute a developing roll. This is combined with the toner hopper 2, doctor blade 5, etc. shown in FIG. 1 to form a magnetic toner developing device.

Note that the non-magnetic material 10 and the magnetic material 11 are made of the same metal as in the first embodiment, and the metal cylinder 12 can be easily formed by etching technology.

Also in the second embodiment described above, the metal cylinder 12 is the non-magnetic material 10.
Since the magnetic material 11 is arranged alternately in the circumferential direction, the effect on the magnetic toner 1 is similar to that on the first ★ flow side.

As explained above, the present invention provides a cylindrical permanent magnet in which N poles and S poles are arranged alternately in the circumferential direction in a metal cylinder in which magnetic materials and non-magnetic materials are arranged alternately in the circumferential direction. Since the toner brush is formed on the magnetic material of the metal cylinder, the area where the toner brush exists is reduced compared to the conventional method, and the toner brush is It is possible to prevent the toner from overlapping each other when it rotates, and it is also possible to rotate sufficiently, so that the high-resistance magnetic toner contact-charged with the metal cylinder can be transferred to an electrostatic latent image on the object to be developed. It has the effect that it can be efficiently suctioned and adhered, and development can be performed with high image quality.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view showing a conventional magnetic toner developing device, Fig. 2 is a drawing showing its magnetic flux density, Fig. 3 is an explanatory diagram showing how the toner brush rotates on its axis in the conventional device, and Fig. 4 is a side sectional view showing a conventional magnetic toner developing device. FIG. 5 is a partially enlarged sectional view showing the first embodiment of the invention, and FIG. 5 is a partially enlarged sectional view showing the second embodiment of the invention. 1... Magnetic toner 2... Toner hopper 4...
Permanent magnet 5...Doctor blade 6...Object to be developed 7...Magnetic material Non-magnetic material 9...Metal cylinder 1 [i 1i124! ! 41111? Noodles 3-398

Claims (1)

[Claims] 1. A cylindrical permanent magnet with north poles and south poles arranged alternately in the circumferential direction is rotatably placed inside a rotatable metal cylinder in which magnetic and non-magnetic materials are arranged alternately in the circumferential direction. A magnetic toner developing device characterized by having a developing roll arranged and configured.