JPS59133569A - Magnetic brush charging device - Google Patents

Abstract

PURPOSE:To eliminate gas discharge and prevent mechanical damage by forming a magnetic brush made of magnetic particles on a conductive cylinder and making charging by rubbing an electrostatic charge carrier with this magnetic brush. CONSTITUTION:When the conductive cylinder 2 is rotated in the direction of arrow (b) while rotating the electrostatic charge carrier 4 in the diection of arrow (a), magnetic particles 1 are connected magnetically on the conductive cylinder 2 along the magnetic line of force generated from a magnet roll 3 and a magnetic brush is formed. This magnetic brush is carried in the direction of rotation of the conductive cylinder 2 and rubs successively the surface of the electrostatic charge carrier 4 to cause charging. Thus, as high voltage is not necessary, gas discharge is eliminated and mechanical damage can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a charging device for uniformly charging electrostatic charge carriers in an electrophotographic apparatus.

[Prior art]

Electrophotographic devices have the advantage of being able to print high-quality images and characters at high speed, and are currently widely used as copying machines and printers.

Charging is the operating process of this electrophotographic device.

It is well known that there are various processes such as exposure, development, transfer, cleaning, and fixing, and when performing charging, which is the first process, in conventional electrophotographic equipment, a corona charger is generally used to charge the electrostatic drum, etc. The charge carriers are uniformly charged. This corona charger has 5
By applying a high voltage of KV or more to the wire, a strong electric field is created around the wire to generate a gas discharge, and charging is performed by adsorbing the electrons and charged ions generated at this time to an electrostatic charge carrier.

The corona charger used in such conventional electrophotographic devices can charge the electrostatic charge carrier without mechanically contacting it, so it has the advantage of not damaging the electrostatic charge carrier during charging. are doing. however,
As mentioned above, this corona charger uses high voltage, so there is a risk of electric shock and leakage, and there is a strong odor from ozone generated with gas discharge, which is harmful to the human body. had. Furthermore, the charging potential by a corona charger is unstable as it is strongly affected by temperature and humidity, and furthermore, with a corona charger, it takes about 5 seconds or more to obtain a stable charging potential after inputting a high voltage. This is a major obstacle when using electrophotographic devices as communication terminals or information processing devices.

Many drawbacks of such corona chargers are that charging 3- This is due to the fact that it involves gas discharge.

[Purpose of the invention]

The present invention was made in order to solve the above-mentioned drawbacks of the prior art, and does not use gas discharge like a corona charger.
Moreover, the object is to obtain a charging device that can charge an electrostatic charge carrier without mechanically damaging the electrostatic charge carrier. [Structure of the Invention] In order to achieve the above object, a magnet A magnetic brush is formed by adsorbing magnetic particles onto a conductive cylinder completely enclosed in the roll, and charging is performed by rubbing the surface of an electrostatic charge carrier with this magnetic brush.

〔Example〕

Examples will be described below based on the drawings. FIG. 1 is a side sectional view showing one embodiment of the magnetic brush charging device according to the present invention. In the figure, 1 is a conductive magnetic particle made of a magnetic material, for example, particles obtained by treating iron powder with coach ink, or magnetic These are magnetic resin particles etc. which are obtained by pulverizing the four main components after forming them with heat rays. However, as will be explained in detail later, this magnetic particle 1 is made of a non-magnetic metal in order to prevent it from adhering to electrostatic charge carriers as much as possible by taking into consideration its conductivity, magnetic properties, and particle size. The conductive cylinder 3 is a magnet roll disposed inside the conductive cylinder 2, and this magnet roll 3 has a structure in which N poles and S poles are alternately arranged on the circumference. The cylinder 2 and the magnet roll 3 are rotatable with respect to each other.

Reference numeral 4 denotes an electrostatic charge carrier such as an electrostatic drum or a photosensitive drum, which is formed of a conductive base material 5 and a dielectric layer (photoreceptor layer) 6 covering its surface. Grounded.

I is a constant voltage power supply that applies a voltage between the conductive cylinder 2 and the conductive base material 5, and the conductive cylinder 2 is grounded via this constant voltage power supply 7.

Reference numeral 8 denotes a cover constituting a storage section for the magnetic particles 1. The conductive cylinder 2 and the tag net roll 3 are disposed within the cover 8, and a regulating plate (not shown) is provided at the outlet of the cover 8. The blade 9 is made of a rubber plate with low hardness and has an electrically insulating property, and is adapted to regulate the thickness of the magnetic particles 1 to be carried out. It is provided so that its tip abuts against the electrostatic charge carrier 4 at a position near the cylinder 2 .

Next, the operation of the above-described configuration will be explained. First, when the electrostatic charge carrier 1 body 4 is rotated in the direction of arrow a and the conductive cylinder 2 is rotated in the direction indicated by the arrow, the magnetic particles 1 are moved on the conductive cylinder 2 along the lines of magnetic force generated from the magnet roll 3. They are magnetically connected to form a kind of brush-like shape, a so-called magnetic brush. This magnetic brush is conveyed in the direction of rotation of the conductive cylinder 20 and sequentially rubs the surface of the electrostatic charge carrier 40, that is, the dielectric layer 6, thereby charging the conductive cylinder 2 and the electrostatic charge carrier. 4 conductive base material 5
A constant voltage is applied between 0.0 and 0.0. The dielectric layer 6 of the carrier 4 can be viewed as a capacitor of capacitance C0 However, since the electrostatic charge carrier 4 is rotating in the direction of the arrow a, it is interpreted as being updated at a constant rate into an uncharged capacitor. ○E is the step voltage of the constant voltage power supply 1.

FIG. 3 is an explanatory diagram of the charging curve in this example, where the horizontal axis shows the contact time tf between the magnetic brush formed by the magnetic particles 1 and the dielectric layer 6 of the electrostatic charge carrier 4, and the vertical axis shows the dielectric layer 6. Here, the charging potential can be seen as a transient response of the step voltage E in the equivalent circuit of FIG. 2, so it is expressed as follows.

As is clear from FIG. 3, if the contact time t is sufficiently long compared to the time constant CR, it becomes approximately equal to the charging potential E. However, in reality, it is difficult to increase the contact time of the magnetic brush, so it is desirable to set the value of the time constant CR, especially R, to a small value. If the conductivity of the magnetic particles 1 is made sufficiently high, a constant charging potential can be obtained.

Note that when the conductive cylinder is rotated, if the magnet roll 3 is also rotated, the magnetic brush rubs the electrostatic charge carrier 4 evenly and uniformly, so that uniform charging can be performed.

Next, the attachment of the magnetic particles 1 to the electrostatic charge carrier 4 during the above-mentioned charging will be explained. FIG. 4 is an enlarged view of the main part of FIG. 1. As seen in this figure, the magnetic particles 1 are connected to form a magnetic brush, and the electric field of the constant voltage power supply 7 causes the magnetic particles 1 at the tip of the magnetic brush to A charge is injected from the conductive cylinder 2 into the conductive cylinder 2.

A part of the injected charge moves onto the dielectric layer 6 of the electrostatic charge carrier 4, but the charge also remains on the magnetic particle 1. Therefore, the magnetic particles 1 are subjected to an opposite charge and a Coulomb force f induced on the back surface of the dielectric layer 6. acts, and this Coulomb force, fo is the magnetic binding force of the magnet roll 3 on the magnetic particles 1, f
When m is overcome, the magnetic particles 1 will adhere to the electrostatic charge carrier 4.

8- In order to prevent such adhesion, it is desirable to make the conductivity of the magnetic particles 1 sufficiently high to reduce the charge remaining on the magnetic particles 1. On the other hand, it is also effective to increase the magnetic binding force fm by the magnet roll 3, and to increase this magnetic binding force fm, increasing the magnetic flux density of the magnet roll 3, increasing the amount of magnetization of the magnetic particles 1, Another possibility is to increase the diameter of the magnetic particles 1.

However, there is still a possibility that the magnetic particles 1 actually adhere to the electrostatic charge carrier 4, so in this embodiment, the tip of the blade 9 is brought into contact with the surface of the electrostatic charge carrier 40, and the blade 9
The magnetic particles 1 adhering to the electrostatic charge carrier 4 are mechanically blocked, and only the remaining charges flow to the electrostatic charge carrier 4 side. As a result, the magnetic particles 1 whose adhesion force has weakened are recovered onto the conductive cylinder 2 by the magnetic attraction force of the magnet roll 3. Since the magnetic particles 1 are collected in this way, their loss can be prevented, and at the same time, it is possible to prevent the electrostatic charge carriers 4 from proceeding to the primary process with unnecessary magnetic particles 1fa attached. As described above, it is desirable that the magnetic particles 1 have high electrical conductivity and high saturation magnetization so that the magnetic attraction force is strong. Regarding the particle size, the larger the particle size, the stronger the magnetic attraction force will be, but if it is too large, the magnetic brush will lose its uniformity, so from this point on, from 20 μm to 10 μm.
Approximately 0 μm is suitable.

Incidentally, if magnetic particles 1 are made of magnetic particles with a particle size of about 0.5 μm and resin as main components, and are pulverized after hot ray formation, the dielectric layer 6 of the electrostatic charge carrier 4 can be
This is convenient because it can be rubbed without damaging the surface.

EXAMPLES Next, experimental examples of the present invention will be described. Capacity per unit area is 1
．． An electrostatic charge carrier (Se-based photosensitive drum) of 00 p F 7 cm is rotated at a speed of 100 m+n/sec, a conductive cylinder with a twisted diameter of 18 stones is rotated at 5 Orpm, and the magnetic flux density within this conductive cylinder is was 900 Gauss, and an 8-pole magnet roll was rotated at 11,000 rpm.

At this time, the gap between the conductive cylinder and the electrostatic charge carrier is 1 inch,
The contact width of the magnetic brush was approximately 3 brains.

With this configuration, the conductivity as magnetic particles is 10-7 V/c
m, saturation magnetization 60emu/? , particle size distribution 20-40μm
As a result of using magnetic resin particles, the applied voltage was 60
It was possible to stably obtain a surface charge (Q 500 V fzc) with respect to 0 V. At that time, the adhesion of magnetic resin particles to the electrostatic charge carrier was extremely small, and if the blade was installed, magnetic i = fat particle The reduction was completely prevented, and no feeding of magnetic resin particles was required even after long-term use.

〔Effect of the invention〕

As explained above, the present invention has a structure in which a magnetic brush made of magnetic particles is formed on a conductive cylinder, and charging is performed by rubbing the electrostatic charge carrier with this magnetic brush. Charging can be performed using only a voltage that is equal to or slightly higher than the surface potential of the corona charger, and safety can be improved because high voltage is not required as in conventional corona chargers.

Furthermore, since it does not involve gas discharge, it does not generate ozone, is odorless, and is harmless to the human body.

Furthermore, the charging potential obtained by the device of the present invention depends on the temperature,
The humidity level is so short that it does not cause any practical problems, making it advantageous when electrophotographic devices are used as communication terminals or information processing devices. Naru 0

[Brief explanation of the drawing]

FIG. 1 is a side sectional view showing an embodiment of the magnetic brush charging device according to the present invention, FIG. 2 is an equivalent circuit diagram of the embodiment of FIG. 1,
3 is an explanatory diagram of the charging curve in the embodiment of FIG. 1, and FIG. 4 is an explanatory diagram of charging in the embodiment of FIG. 1. DESCRIPTION OF SYMBOLS 1... Magnetic particle 2... Conductive cylinder 3... Magnet roll 4... Electrostatic charge carrier 5... Conductive base material 6... Dielectric layer 1... Constant voltage power supply 8...・Cover 9...Blade Patent Applicant Oki Electric Industry Co., Ltd. Agent Patent Attorney Takashi Kanakura 211II! Procedural amendment (spontaneous) November 1, 1980 Kazuo Wakasugi, Commissioner of the Patent Office ■, Indication of the case 1988 Patent Application No. 006711 2, Title of invention Magnetic brush charging device 3, Case made by the person making the amendment Relationship with Patent Applicant Address 1-7-12 Toranomon, Minato-ku, Tokyo Name (029) Oki Electric Industry Co., Ltd. Representative Nankai Hashimoto 4, Agent 6 Subject of amendment Description “Details of the Invention” "Explanation column". 7 Contents of amendment 1, Meiryo 1, page 6, line 2, the phrase “regulation plate” has been replaced with “
``Regulation board''. 2. In the 3rd line of page 6 of the Akiri book, the word ``regulation'' is amended to read ``all 1 regulation''. 3 In the first line of page 11 of the specification, it is written that “conductivity 10” V/c
m J is corrected to "conductivity ■0-7 U/cm".

Claims (1)

[Claims] 1. Conductive magnetic particles, a conductive cylinder formed of a non-magnetic metal and rotatably arranged near an electrostatic charge carrier, and an N pole and a S pole in the circumferential direction. and a constant voltage power supply that applies a voltage between the conductive cylinder and the conductive base material of the electrostatic charge carrier. The magnetic particles are magnetically connected on the entire conductive cylinder to form a magnetic brush, and the magnetic brush rubs the dielectric layer on the surface of the electrostatic charge carrier,
Magnetic brush charging device 02 characterized by charging the electrostatic charge carrier An insulating blade is disposed near the conductive cylinder with its tip in contact with the dielectric layer of the electrostatic charge carrier, and the electrostatic charge carrier is charged during charging. 2. The magnetic brush charging device according to claim 1, wherein the magnetic particles adhering to the electrostatic charge carrier are separated from the electrostatic charge carrier by the blade and collected onto a conductive cylinder. 3. The magnetic brush charging device according to claim 1, wherein the magnetic particles are magnetic resin particles whose main components are at least magnetic particles and resin.