JPH05134517A - Contact electrostatic charging device - Google Patents

Abstract

PURPOSE:To accomplish the uniformity of electrostatic charging and to prolong the life of an electrostatic charging device by comparatively simple constitution. CONSTITUTION:Magnetic particles Mgp are attracted and held on the outer peripheral surface 2a of a non-magnetic sleeve 2 by magnetic force of fixed magnets 5A-5D in the sleeve, and rotated in a direction shown by an arrow A in such a state. Then, the magnetic particles Mgp are carried to an opposed area 4 to a photosensitive body 3(electrostatic latent image carrier), and voltage is supplied from a power source 6 to the sleeve 2 in a state where the particles Mgp are uniformly brought into contact with the photosensitive body 3 by small contact force, thereby uniformly electrostatically charging the photosensitive body 3. It is also good to make it possible to rotate the magnet by which the particles Mgp are attracted in the sleeve 2 or to directly magnetize the outer peripheral surface of the sleeve. In the case that it is made possible to exchange the magnetic particles, the life is prolonged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact charging device for charging a contact by bringing a contact into contact with an electrostatic latent image carrier of an electrophotographic system such as a copying machine, a facsimile and a printer.

[0002]

2. Description of the Related Art Conventionally, as a contact charging device in which a contactor is brought into contact with a photosensitive member (electrostatic latent image bearing member) to be charged and a voltage is applied to the contactor to charge it For example, as described in Japanese Utility Model Application Laid-Open No. 57-205159, a brush is used as a contactor, or as disclosed in Japanese Patent Application Laid-Open No. 1-211779, it is composed of a plurality of layers. The elastic roller is used as a contactor, and further, a blade type contactor is used.

[0003]

However, in most of the conventional contact charging devices as described above, the same portion of the contactor is in direct contact with the photosensitive member, so that the portion has a short service life. However, the life of the entire charging device was determined by the life of the parts. The contactor changes its charging performance due to changes in surface roughness, wear, filming of a substance on the surface, and the like, resulting in poor charging uniformity. It was time. for that reason,
There are many restrictions on the selection of the material, which also restricts the degree of freedom of the entire device, making it difficult to extend the service life.

Therefore, the above-mentioned Japanese Utility Model Laid-Open No. 57-205159 is used.
In the contact charging device according to the publication, the brush is coated, and in the contact charging device according to the publication of JP-A 1-211779, the life is extended by forming the roller with a plurality of layers so that the roller has elasticity. While the stable air gap is maintained to prevent the charging unevenness, the structure tends to be complicated in any case. The present invention has been made in view of the above problems, and an object of the present invention is to make it possible to achieve uniform charging with a relatively simple configuration. Another object is to extend the life of the charging device.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a magnetic particle and an electrostatic latent image of the magnetic particle by rotating the magnetic particle while holding the magnetic particle on the outer peripheral surface. A conductive non-magnetic sleeve that conveys the electrostatic latent image carrier to the area opposite the image carrier and contacts the electrostatic latent image carrier, and a non-rotatably provided inside the sleeve that attracts and holds magnetic particles on the outer peripheral surface of the sleeve. The contact charging device is configured by providing a fixed magnet for the above and a power source for supplying a voltage to the non-magnetic sleeve to charge the electrostatic latent image carrier through the magnetic particles.

Further, by rotating the magnetic particles and the magnetic particles held on the outer peripheral surface thereof, the magnetic particles are conveyed to a region facing the electrostatic latent image carrier and the electrostatic latent image carrier is carried. A conductive non-magnetic sleeve that comes into contact with the body, a magnet that is independently rotatably provided inside the sleeve, and that holds the magnetic particles by adsorption on the outer peripheral surface of the sleeve, and supplies voltage to the non-magnetic sleeve. And a power source for charging the electrostatic latent image carrier via the magnetic particles to provide a contact charging device.

Further, the magnetic particles and the magnetic particles are rotated while being held on the magnetized outer peripheral surface by magnetic force, and the magnetic particles are conveyed to a region opposite to the electrostatic latent image carrier. A contact charging device is configured by providing a rotating body that comes into contact with the electrostatic latent image carrier and a power supply that supplies a voltage to the rotating body to charge the electrostatic latent image carrier through the magnetic particles. Good. Further, in each of the contact charging devices described above, a magnetic particle recovery container for recovering the magnetic particles may be provided so that the magnetic particles can be exchanged, or the magnetic particles can be a high resistance element.

[0008]

According to the contact charging device having such a structure, the magnetic particles are conveyed to the area facing the electrostatic latent image carrier while being attracted and held by the magnetic force on the outer peripheral surface of the non-magnetic sleeve.
When it stands, it makes uniform contact with the electrostatic latent image carrier with a small contact force, and charging is performed in that state, resulting in uniform charging, and only the same part as the electrostatic latent image carrier always contacts. Since it does not occur, the problem of wear is improved.

If a magnet for adsorbing and holding the magnetic particles on the outer peripheral surface of the non-magnetic sleeve is rotatably provided independently in the sleeve, the magnet and the electrostatic particles can be electrostatically moved by rotating the magnet. Since the contact area and contact density with the latent image carrier can be adjusted, charging unevenness can be reduced and charging uniformity can be further improved, and the outer peripheral surface of the rotating body itself can be magnetized. If so, it is not necessary to provide a magnet inside the rotating body, and thus the structure becomes simpler.

Further, if a magnetic particle recovery container for recovering the magnetic particles is provided so that the magnetic particles can be replaced, the magnetic particles can be replaced without replacing the charging device in a unit state. It is possible to easily extend the life, and if the magnetic particles are made of a high resistance material, it is possible to prevent leakage due to defects of the electrostatic latent image carrier and to perform stable charging.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a block diagram showing a contact charging device according to an embodiment of the present invention. This contact charging device 1 is
For example, the magnetic particles Mgp using a coating of silicon (Si), and the magnetic particles Mgp held by the outer peripheral surface 2a are rotated in the direction of arrow A to rotate the magnetic particles Mgp.
A photoconductor 3 that rotates in the direction of arrow B, which is an electrostatic latent image carrier.
And a conductive non-magnetic sleeve 2 which is conveyed to a region 4 facing the photosensitive member 3 and is brought into contact with the photosensitive member 3, and a non-rotatably provided inside the non-magnetic sleeve 2, the magnetic particle Mgp is provided on the outer peripheral surface 2a of the sleeve. Fixed magnet 5A to attract and hold
5D and the magnetic particles M by supplying voltage to the non-magnetic sleeve 2
A power source 6 for charging the photoconductor 3 via gp is provided.

In this embodiment, for example, the speed Vp of the photoconductor 3 is 36 to 150 mm / sec, and the speed Vs of the non-magnetic sleeve 2 is about 1 to 1.
Set to 5 times speed ratio. The non-magnetic sleeve 2 is installed at a position closest to the photoconductor 3 with a space S, and the fixed magnets 5A to 5D are arranged in the non-magnetic sleeve 2 at a predetermined distance from the inner surface of the sleeve in the circumferential direction. In the state where they are aligned and arranged at substantially equal intervals, they are fixed to a fixing portion (not shown) of the charging device. And the fixed magnet 5A ~
In 5D, the distance between the fixed magnets 5A and 5D is made wider than the distance between other magnets.

To the right of the non-magnetic sleeve 2 in FIG.
An area 4 for accommodating the magnetic particles Mgp and facing the photoconductor 3
A case 7 which is a magnetic particle recovery container for recovering the magnetic particles Mgp returned after being transported to is provided, and a rectifying plate 9 is disposed in the case 7 in proximity to the outer peripheral surface 2a of the non-magnetic sleeve 2. A stirring supply member 11 for stirring the magnetic particles Mgp in the case 7 is provided below it so as to be rotatable in the arrow C direction.

Further, a doctor 12 is attached to the bottom of the case 7 at the open portion on the non-magnetic sleeve 2 side, and the doctor 12 is conveyed from inside the case 7 toward the area 4 facing the photoconductor 3 by the non-magnetic sleeve 2. Amount of magnetic particles Mgp (thickness)
Are regulated. The contact charging device 1 agitates and replenishes the magnetic particles Mgp stored in the case 7 with a stirring supply member 11.
The magnetic particles Mgp are agitated by the doctor 12, the particle thickness is regulated by the doctor 12, and the magnetic particles Mgp are adsorbed and held on the outer peripheral surface 2a of the non-magnetic sleeve 2 by the attraction force of the fixed magnets 5A to 5D therein, which is then held. By rotating the non-magnetic sleeve 2 in the direction of arrow A, a region 4 facing the photoconductor 3 is formed.
Transport to.

In the facing area 4, the particle layer of the magnetic particles Mgp that rises in a spike shape contacts the surface of the photoconductor 3 as shown in FIG.
Bias voltage VT is applied to the photoconductor 3 by the power source 6
To the desired value. After that, the magnetic particles Mgp
Is returned to the inside of the case 7 while being held by the non-magnetic sleeve 2 which continues to rotate in the direction of arrow A, and the particle layer held by magnetic force on the outer peripheral surface 2a of the non-magnetic sleeve 2 is fixed magnets 5A and 5D.
When it reaches the part without the magnet, it is released from the magnetic attraction force and falls and is recovered.
Then, the magnetic particles Mgp are formed by the rectifying plate 9 and the stirring replenishment member 1.
It is mixed by 1 and returns to the initial state.

According to this contact charging device 1, the magnetic particles Mgp
Is conveyed to the region 4 facing the photoconductor 3 while being attracted and held by the outer peripheral surface 2a of the non-magnetic sleeve 2 to the photoconductor 3, and the ears of the nonmagnetic sleeve 2 uniformly contact the photoconductor 3 with a small contact force. Since charging is performed in that state, uniform charging is performed, and since the magnetic particles Mgp (which serves as a contact) contact the photoconductor 3, only the same portion of the contact always contacts the photoconductor 3. Since it does not occur, the problem of wear is improved.

In this embodiment, the fixed magnet 5 is used.
Regulation of the particle layer thickness of the magnetic particles Mgp by the magnetic force of A to 5D and the gap between the doctor 12 and the non-magnetic sleeve 2, and the distance S between the photoconductor 3 and the non-magnetic sleeve 2 is adjusted. As a result, the particle density between the photoconductor 3 and the non-magnetic sleeve 2, that is, the contact density can be changed.

FIG. 2 is a constitutional view similar to FIG. 1 showing an embodiment of a contact charging device in which a magnet which independently rotates is provided in a non-magnetic sleeve, and the portions corresponding to those in FIG. Is attached. The contact charging device 20 includes a large number (eight in this example) of magnets 25 for attracting and holding the magnetic particles Mgp on the outer peripheral surface 2a of the non-magnetic sleeve 2.
The non-magnetic sleeve 2 is circumferentially aligned at a predetermined distance from the inner surface of the sleeve so that the non-magnetic sleeve 2 can rotate independently in the arrow E direction opposite to the rotation direction of the non-magnetic sleeve 2.

A scraper 21 is provided in the case 7 for forcibly peeling off the magnetic particles Mgp held by the magnetic force on the outer peripheral surface 2a of the rotating non-magnetic sleeve 2 and dropping them into the case 7. ing. In this embodiment, the speed of the magnet 25 in the arrow E direction is set to the speed Vs of the non-magnetic sleeve 2 (the speed of the photoconductor 3 is 36 to 150 mm /
It is set to the same speed as about 1 to 1.5 times sec).

According to the contact charging device 20, like the contact charging device 1 of FIG. 1, the magnetic particles Mgp in the case 7 are agitated by the agitation replenishing member 11, and the doctor 12 regulates the particle thickness. Is attracted to the outer peripheral surface 2a of the non-magnetic sleeve 2 by the magnetic force of the magnet 25 and is held by being held in the vertical direction of the non-magnetic sleeve 2, which is exposed by the rotation of the non-magnetic sleeve 2 in the arrow A direction. Body 3
The particle layer contacts the surface of the photoconductor 3 by being conveyed to the area 4 facing the photoconductor 3, and the bias voltage VT from the power source 6 is applied to the nonmagnetic sleeve 2 to charge the photoconductor 3.

According to this embodiment, regulation of the particle layer thickness of the magnetic particles Mgp by adjusting the magnetic force of the magnet 25 and the gap between the doctor 12 and the non-magnetic sleeve 2, and further the photosensitive member 3
In addition to adjusting the distance S between the non-magnetic sleeve 2 and the non-magnetic sleeve 2, the magnetic particles in the facing region 4 can be changed by changing the number of magnetic poles and the rotational speed of the magnet 25 (the speed difference between the moving speed of the magnetic pole and the speed of the sleeve). Since the particle density of the body Mgp can be changed, it is possible to further improve the followability of the charging performance with respect to the linear velocity of the photoconductor 3 and reduce the charging unevenness.

FIG. 3 is a configuration diagram similar to FIG. 2 showing an embodiment of a contact charging device in which the outer peripheral surface of the rotating body is directly magnetized, and the same reference numerals are given to the portions corresponding to FIG. It is attached. The contact charging device 30 rotates in the direction of arrow A while holding the magnetic particles Mgp on the magnetized outer peripheral surface 32a by magnetic force, and conveys the magnetic particles Mgp to the area 4 facing the photoconductor 3. Then, a rotating body 32 is provided to be brought into contact with the photosensitive body 3, and a bias voltage VT from a power source 6 is supplied to the rotating body 32 to charge the photosensitive body 3 via the magnetic particles Mgp.

In this embodiment, for example, 85 parts of ferrite is mixed in EPDM (rubber material) to form a roller-shaped rotating body 32, and the surface of the rotating body 32 has a fine pitch, that is, a magnetizing pitch, for example. It is set to about 2 mm and magnetized to about 400 Gauss by magnetic flux measurement, and the magnetic particles Mgp housed in the case 7 are magnetically held along the magnetic lines of force between the magnetic poles.

Also in this embodiment, the magnetic particles Mgp contact the photoconductor 3 in the facing area 4, and the photoconductor 3 is charged by supplying the bias voltage VT to the rotary body 32. By rotating in the direction A, the magnetic particles Mgp are returned into the case 7, separated by the scraper 21, collected, and returned to the initial state. By doing so, it is not necessary to provide a magnet in the rotating body, and the structure is accordingly simplified.

FIG. 4 shows an embodiment of a contact charging device in which the recovered magnetic particles can be replaced.
The same reference numerals are given to the portions corresponding to. The contact charging device 40 includes a case 47, which is a magnetic particle recovery container for recovering the magnetic particles Mgp, an upper case 48, and a lower case 49.
In addition, the upper case 48 side can be replaced with the magnetic particle Mgp housed inside. In this embodiment, the magnetic particles Mgp used to charge the photoconductor 3 are collected in the upper case 48 by rotating the non-magnetic sleeve 2 in the direction of arrow A, which is usually shown in FIG. As shown in FIG. 5, the shutter 45 in the opened state drops into the lower case 49 through the opening 46 opened.

When the magnetic particles Mgp are used for a long period of time and the charging performance is expected to deteriorate due to a change with time, the shutter 45 is closed as shown by the phantom line in FIG. Granular Mgp upper case 48
Only the side should be collected and stored, and the case 48
Is replaced with a new upper case 48 in which a new magnetic particle Mgp is stored while the deteriorated magnetic particle Mgp is housed inside. By doing so, the life of the charging device can be extended by a simple operation of exchanging the magnetic particles Mgp together with the upper case 48. The case 47 which can be divided into the upper and lower parts can be similarly applied to the embodiments shown in FIGS. 2 and 3.

Although the respective embodiments of the contact charging device using the magnetic particles have been described above, the resistance of the magnetic particles Mgp used in each of the embodiments is actually from low resistance to high resistance. As a result of conducting experiments and confirming that any of them was used, the photoconductor 3 could be charged by applying a bias voltage to the non-magnetic sleeve 2 and the rotating body 32. However, it is more effective to use a high-resistor for it because leakage due to defects of the photoconductor 3 can be prevented and stable charging can be performed.

For example, the magnetic particles M in each of the above embodiments
The resistance value r of gp is 10 ⁶ to 10 ¹³ Ωcm (log 6.0 to log 1
3.0 Ωcm) and the saturation magnetic flux density as 40 to 50 emu /
g, the dielectric constant ε is 3.0 to 5.0, and the magnetic flux of the magnet is set to 600 to 800 (Ggauss) at a distance of 0.1 mm from the outer peripheral surface of the non-magnetic sleeve 2 or the rotating body 32. The particles Mgp can be reliably held by the magnetic force and can be conveyed, and the charging of the photoconductor 3 can be performed uniformly and stably.

Then, the resistance r of the magnetic particle Mgp is set to 10
^By setting the resistance to ¹⁰ Ωcm (log ¹⁰ Ωcm) or more, it is possible to reliably prevent the generation of black spots and the like due to a leak that occurs when the photoconductor 3 has a defect. Further, the bias voltage VT applied by the power source 6 can be controlled so that it is linearly increased with an increase in the voltage only after being charged from around -600V.

[0030]

As described above, according to the present invention, the magnetic particles are conveyed to the area opposite to the electrostatic latent image bearing member while being attracted and held by the magnetic force on the outer peripheral surface of the non-magnetic sleeve. As a result of the ears standing, the electrostatic latent image carrier is uniformly contacted with a small contact force and charged in that state, so that uniform charging can be performed. Further, unlike the conventional case, only the same portion of the contact is not always in contact with the electrostatic latent image carrier, so that the life is extended.

If a magnet for adsorbing and holding magnetic particles on the outer peripheral surface of the non-magnetic sleeve is independently rotatably provided in the sleeve, the rotation speed of the non-magnetic sleeve can be increased by rotating the magnet. Since it is possible to adjust the contact area and the contact density between the magnetic particles and the electrostatic latent image bearing member, it is possible to reduce charging unevenness and further improve the charging uniformity. ..
If the outer peripheral surface of the rotating body that holds the magnetic particles is magnetized, it is not necessary to provide a magnet inside the rotating body, so that the structure can be simplified and the cost can be reduced and the magnetizing layer Leakage can also be prevented by selecting the material.

Further, if a magnetic particle recovery container for recovering the magnetic particles is provided and the magnetic particles can be exchanged, the magnetic particles can be replaced without replacing the charging device in a unit state. The life can be easily extended by simply doing this, and if the magnetic particles are made of high-resistivity, voltage drop due to current leakage caused by defects in the electrostatic latent image carrier and black spots on the image will occur. ， White spots can be prevented without treating the non-magnetic sleeve or the rotating body, and stable charging can be performed.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a contact charging device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram similar to FIG. 1, showing an embodiment of a contact charging device in which a magnet that rotates independently is provided in a non-magnetic sleeve.

FIG. 3 is a configuration diagram similar to FIG. 2, showing an embodiment of a contact charging device in which the outer peripheral surface of a rotating body is directly magnetized.

FIG. 4 is a configuration diagram showing an embodiment of a contact charging device in which collected magnetic particles can be replaced.

[Explanation of symbols]

1, 20, 30, 40 Contact charging device 2 Non-magnetic sleeve 2a, 32a Outer peripheral surface 3 Photoreceptor (electrostatic latent image carrier) 4 Opposing area 5A to 5D
Fixed magnet 6 Power supply 7,47 Case (Magnetic particle collection container) 25 Magnet 32 Rotating body Mgp Magnetic particle

Claims (5)

[Claims] 1. A magnetic particle, and by rotating the magnetic particle while holding the magnetic particle on the outer peripheral surface, the magnetic particle is conveyed to a region facing the electrostatic latent image carrier and the electrostatic latent image. A conductive non-magnetic sleeve that comes into contact with the carrier, a fixed magnet that is non-rotatably provided in the sleeve and that holds the magnetic particles on the outer peripheral surface of the sleeve by adsorption, and a voltage is supplied to the non-magnetic sleeve. And a power source for charging the electrostatic latent image carrier through the magnetic particles, the contact charging device. 2. A magnetic particle, and by rotating the magnetic particle while holding the magnetic particle on the outer peripheral surface, the magnetic particle is conveyed to a region facing the electrostatic latent image carrier, and the electrostatic latent image is transferred. A conductive non-magnetic sleeve that comes into contact with the carrier, a magnet that is rotatably provided independently in the sleeve, and that holds the magnetic particles on the outer peripheral surface of the sleeve by adsorption, and a voltage applied to the non-magnetic sleeve. And a power supply for charging the electrostatic latent image carrier via the magnetic particles. 3. The magnetic particles and the magnetic particles are rotated while being held on the magnetized outer peripheral surface by magnetic force, and the magnetic particles are conveyed to a region facing the electrostatic latent image carrier. A rotating body to be brought into contact with the electrostatic latent image carrier, and a power source for supplying a voltage to the rotating body to charge the electrostatic latent image carrier via the magnetic particles are provided. Contact charging device. 4. The contact charging device according to claim 1, further comprising a magnetic particle recovery container for recovering the magnetic particles, the magnetic particles being replaceable. And a contact charging device. 5. The contact charging device according to claim 1, wherein the magnetic particles are high resistance materials.