JPH05100544A - Conductive brush electrifier - Google Patents

Abstract

PURPOSE:To prevent the generation of an unelectrified region on the end part of a conductive brush and further the short circuit of a conductive fiber having the application of a voltage and a recording medium substrate as a conductor, in a conductive brush electrifier used for the electrification of the electrostatic recording medium of an image forming device such as an electrophotographic printer. CONSTITUTION:This conductive brush electrifier 11 is provided with the conductive brush 12 constituted by holding a brush-like conductive fiber 13 on a conductive base part 14, and an insulation member 15. The top end part of the conductive fiber 13 is in contact with the surface of electrostatic recording medium 1. Then, the conductive brush 12 is connected to a power source 3 and has the application of the voltage. The insulation member 15 is provided on the conductive base part 14, and plays a part for regulating the spread of the conductive fiber 13 in the axial direction of the electrostatic recording medium.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive brush charger used for charging an electrostatic recording medium of an image forming apparatus such as an electrophotographic machine or an electrophotographic printer.

In this type of image forming apparatus, downsizing,
With the demand for simplification and cost reduction, there is a demand for a charger that is small in size, has a simple structure, and can be charged at a low voltage.

[0003]

2. Description of the Related Art Conventionally, in an image forming apparatus such as an electrophotographic copying machine or an electrophotographic printer, a corona charger is often used as an apparatus for uniformly charging an image on an electrostatic recording medium. ing.

However, the corona charger requires a high voltage of several kilovolts for corona discharge, which increases the cost of the device, and ozone generated by the discharge damages the components of the device, especially the recording medium. There was a problem of shortening the life of the. Further, ozone causes discomfort to a person who uses the device, and there is also a problem that when the concentration is high, it is harmful to the human body.

In order to solve this problem, as shown in FIG. 7, a charger using a conductive brush (conductive brush charger)
Is proposed. The charging device is configured to contact and rotate the electrostatic brush 2 (photosensitive drum) 1 such as a photoconductor or a dielectric to which the conductive brush 2 to which a voltage is applied by the power source 3 is charged to charge the conductive brush 2. The recording medium 1 can be charged to a required potential by applying a voltage of up to 1.5 KV. Moreover, this charger does not have a problem of ozone generation. In addition,
The conductive brush 2 is configured such that the conductive base 4 holds the brush-shaped conductive fibers 5.

[0006]

However, at the end of the conductive brush, as shown in FIG. 8, the conductive fiber 5 is pressed by the pressing force for bringing the conductive brush 2 into contact with the recording medium 1.
Are extruded in the axial direction of the recording medium 1, and a portion where the conductive fiber 5 and the recording medium 1 are not sufficiently contacted is generated. For this reason,
Insufficient charging occurs in this portion, the entire recording medium cannot be charged, and an uncharged area having no charge is generated.

When there is an uncharged area as described above, in the developing method (reverse developing method) which is used in a laser printer and which obtains a record by adhering toner to an area having no electric charge,
Toner adheres to the non-charged area and stains the image.

Further, in a developing system (positive developing system), which is often used in copying machines, in which an image of electric charge corresponding to an image is formed and toner is attached to the electric charge image, a missing image may occur if an uncharged area exists. Occur.

To prevent these problems, the effective width of the recording medium is set to be sufficiently wide so that the charged area is sufficiently wider than the developing area that defines the recordable area, and the uncharged area is outside the developing area. Should be However, in this method, the photosensitive member area that is not used for recording increases, which is a waste, and the recording medium required for a desired recording width becomes long, which becomes a factor that hinders downsizing of the apparatus.

Further, when the conductive fibers which are pushed out in the axial direction as described above come into contact with the conductor portion which is the base material of the recording medium, an excessive current flows through the portion when the voltage is applied to the conductive brush, so that the conductivity is increased. There is a problem that fiber damage occurs. Therefore, the length of the conductive brush (the length in the axial direction of the recording medium) is set shorter than the effective width of the recording medium so that the conductive fibers do not come into contact with the exposed portions of the conductors at both ends of the recording medium. It is necessary.

The present invention eliminates the generation of an uncharged region at the end of the conductive brush, and further, prevents the conductive fiber to which a voltage is applied from being short-circuited with the recording medium substrate which is a conductor. The purpose is to provide a vessel.

[0012]

FIG. 1 is a diagram for explaining the principle of the present invention. FIG. 1 (A) shows a fixed type conductive brush charger 11.
FIG. 1B shows each of the rotary conductive brush chargers 31.

The conductive brush charger of the present invention comprises a conductive brush having brush-shaped conductive fibers held on a conductive base, and the tip of the conductive fibers of the conductive brush is placed on the surface of the electrostatic recording medium. Charging is performed by bringing the conductive brushes into contact with each other and printing a voltage on the conductive brush. An insulating member is provided at an end portion of the conductive base portion to restrict spreading of the conductive fibers in the recording medium axial direction. (First configuration).

In the conductive brush charger of the first structure, the conductive base portion has a fixed plate shape or a block shape (second structure). The conductive brush charger 11 of FIG. 1 (A) has this configuration,
Reference numeral 12 is a conductive brush formed by holding a conductive fiber 13 on a conductive base portion 14, and reference numeral 15 is an insulating member. The power source 3 is a power source for applying a voltage to the conductive brush 12, and the tip of the conductive fiber 13 is an organic photosensitive layer (a charge generation layer and a charge transport layer) formed on the surface of the conductive substrate 1a of the recording medium 1. It is formed by sequentially coating and laminating) 1b.

Further, in the conductive brush charger of the first structure, the conductive brush is of a rotary type in which a conductive shaft formed in a roll shape is held by a conductive base portion having a rotary shaft shape. (3rd structure) characterized by this.
The conductive brush charger 31 of FIG. 1B has this configuration, and 32 is a roll-shaped conductive fiber 33 and a conductive base portion 34.
Is a conductive brush, and 35 is an insulating member. The conductive brush 32 is driven by a drive source (not shown) to rotate in the arrow direction.

In the conductive brush charger of the first structure, the insulating member is formed of a porous member and is provided so as to be in contact with the surface of the electrostatic recording medium (first structure). 4 configuration).

Further, in the conductive brush charger of the first structure, the insulating member is formed in a brush shape and provided so as to be in contact with the surface of the electrostatic recording medium (fifth structure). Configuration).

Further, in the conductive brush charger of the first structure, the insulating member is provided in a non-contact manner and in proximity to the electrostatic recording medium (sixth structure).
And

Further, in the conductive brush charger of the first structure, the shape of the insulating member is set so that the density of the leading end portion of the conductive fiber is higher than the density of the conductive base portion side. The configuration (seventh configuration) is adopted.

Further, in the conductive brush charger of the third structure, the insulating member 35 is rotatably supported by the conductive base portion 34 which is the rotating shaft of the conductive brush 32 (first structure). 8 configuration).

Further, a structure (a ninth structure) is characterized in that a layer for reducing a friction coefficient is added to a surface of the insulating member of the conductive brush charger of the fourth structure which is in contact with the electrostatic recording medium. To do.

[0022]

In the conductive brush charger of the present invention, the insulating member can prevent the conductive fibers from spreading in the axial direction of the recording medium and reduce the defective charging area. further,
The conductive fiber does not come into contact with the substrate of the recording medium to cause a short circuit.

Further, in the case of the conductive brush rotary type of the third structure, the unevenness of the charge amount can be reduced and the life is long as compared with the case of the conductive brush fixed type of the second structure.

Further, in the case of the fifth structure in which the insulating member is in the shape of a brush, the contact with the electrostatic recording medium becomes softer than in the fourth structure in which the insulating member is a porous material, and the rotation load is increased. Can be reduced, and the amount of toner adhered to the electrostatic recording medium can be reduced.

In the case of the seventh structure, the fiber density at the tip of the conductive fiber at the brush end can be substantially increased, which is more effective.

Further, in the case of the eighth structure, there is no fear of damaging the electrostatic recording medium side.

Further, in the case of the ninth configuration, as compared with the case of the fourth configuration, the frictional resistance with the electrostatic recording medium is reduced and the rotational load is reduced.

[0028]

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

FIG. 2 and FIG. 3 show the first embodiment.

FIG. 2 is a side view showing the outline of an electrophotographic printer to which the present invention is applied, and FIG. 3 is a structural explanatory view of a conductive brush charger. The conductive brush charger 11 of FIG.
It is similar to that shown in FIG. The base body 1a of the electrostatic recording medium 1 is made of an aluminum tube. The output voltage range of the DC power supply 3 is 0 to -2 KV.

The conductive brush charger 11 fixes a brush-shaped conductive fiber 13 on a plate-shaped or block-shaped conductive base 14 made of aluminum by means of a conductive adhesive layer, and also has an insulating member. 15 are provided and configured. The conductive fiber is one in which carbon particles are uniformly dispersed in the rayon fiber to impart conductivity. The thickness of the fiber is 10 to 15 μm, and the resistance value is 10 ⁹ Ω per brush-shaped fiber. The fiber length is 5 mm, the fiber density is 155 fibers / mm ² , and the brush width is 15 mm. The conductive brush charger 11 is arranged parallel to the axis of the electrostatic recording medium 1 which is an organic photosensitive drum, and the tip of the conductive fiber 13 contacts the surface of the recording medium 1 at a depth of about 0.5 mm. ing.

The insulating member 15 is made of a porous urethane resin having a relatively small friction coefficient and excellent wear resistance,
The brush-like conductive fibers 13 are bonded to the conductive base portion 14 so as to sandwich the brush-like conductive fibers 13 from both sides in the axial direction. Therefore, the conductive fiber 13 is restricted within the organic photosensitive layer 1b. The insulating member 15 has a thickness of 5 mm, which is the same as the length of the conductive fiber, and a hardness of 20 to 40 degrees (Asker C), and the conductive brush 12 is pressed against the recording medium 1 so that the recording medium is pressed. Deform along the surface of 1.

By connecting the conductive brush 12 of the conductive brush charger 11 having such a structure to the power source 3 and applying a voltage from the power source 3 while rotating the recording medium 1 at a constant peripheral speed (60 mm / s), The surface of the recording medium 1 is charged to a constant potential. Thereafter, the surface is imagewise exposed by a laser exposure system 52 to form an electrostatic latent image. This electrostatic latent image is developed by the developing device 53.
Is developed (toner is attached to the electrostatic latent image) to form a visible image.

On the other hand, the recording paper 55 of the paper supply section 54 is picked up by the pick roller 5 at a predetermined timing with the rotation of the recording medium 1.
6 and is sent to the transfer position P, where the recording paper 55 by the belt transfer device 57 provided with the transfer device 57a.
Transfer of the visible image to. The transferred visible image is fixed by the fixing device 58, and the recording paper on which the fixing is completed is discharged to the stacker 60 by the discharging roller 59.

The charges and toner remaining on the recording medium 1 at the time of the transfer are removed by the static eliminator 50 and the cleaner 51.

In the above description, an example in which the insulating member 15 is pressed against the surface of the recording medium 1 of the recording medium 1 has been described, but the insulating member may be provided in the recording medium 1 in a non-contact manner and in close proximity thereto. .. In this case, the rotational load is small. The same effect can be obtained by adding a layer for reducing the friction coefficient between the insulating member and the recording medium.

As shown in FIG. 3B, the inclined surface 1
If the insulating member 16 having 6a is used, the fiber density at the tip of the conductive fiber 13 at the brush end can be substantially increased, which is more effective.

FIG. 4 shows a second embodiment.

The conductive brush charger 31 of FIG. 4 (A) is the same as that shown in FIG. 1 (B).

The conductive brush 32 is formed in a cylindrical shape by winding a brush-shaped conductive fiber 33 around a conductive base portion 34 which is a rotating shaft. The unevenness of charging can be reduced and the service life can be shortened as compared with the fixed type of the previous example. It has the advantage of being good. When forming the conductive brush 32, the same brush-shaped fibers as in the previous example are wound around the conductive base portion 34 made of a stainless steel rod having a diameter of 6 mm, and then the fiber length is cut to 5 mm to make the conductive brush 32 having a diameter of 16 mm. I made it. The positional relationship between the conductive brush 32 and the recording medium 1 is the same as in the previous example.

The insulating member 35 is formed into a cylindrical shape using the same porous urethane as in the previous example, and is fixed to the conductive base portion 34 by adhesion. The insulating member 35 has a diameter of 15 mm and rotates while contacting the surface of the recording medium 1.

The insulating member 35 is connected to the conductive base 34.
If it is rotatably supported without being fixed to the recording medium, the recording medium side will not be damaged.

Further, as shown in FIG. 4 (B), the inclined surface 3
If the insulating member 36 having 6a is used, the fiber density at the tip of the conductive fiber 33 at the brush end can be substantially increased, which is more efficient.

FIG. 5 shows a third embodiment.

In this example, instead of the porous urethane insulating member, a brush-like insulating member 37 made of insulating fiber is used. Specifically, the insulating member 37 is configured by winding a brush made by pile-weaving fluororesin fibers around both ends of the conductive base portion 34 of the conductive brush 32. The fiber length was 5 mm, which is the same as the conductive fiber 33. According to this example, since a flexible brush is used for the insulating member,
The contact with the recording medium becomes soft, the rotational load can be reduced, and the adhesion of toner to the recording medium 1 can be reduced.

FIG. 6 shows a fourth embodiment.

In this example, as shown in FIG. 6A, a cylindrical resin member with a flange is used as the insulating member 38. The conductive brush 32 is the same as the previous example. The insulating member 38 has a maximum outer diameter of 13 mm, is supported by the conductive base 34, and can rotate independently. The gap between the conductive member 38 and the recording medium 1 is 0.5 mm. However, even if foreign matter such as toner or a piece of paper is clogged in this gap, the insulating member 38 can rotate independently. It does not scratch 1.

Further, as shown in FIG. 6B, if the insulating member 39 having the protrusion 39a on the flange portion is used, the fiber density at the tip of the conductive fiber 33 at the brush end can be substantially increased. Can be more effective.

In the above description, the example in which the electrostatic recording medium of the organic photoconductor is used has been described, but the selenium photoconductor, a-
It is similarly effective to use a Si-based photoconductor. Further, the shape of the recording medium is not limited to the drum, but it is also effective if it has a film shape or a belt shape.

[0050]

As described above, according to the present invention, the insulating member is provided at the end portion of the conductive brush so that the brush-shaped conductive fibers to which a voltage is applied are prevented from spreading in the axial direction of the recording medium. Therefore, it is possible to narrow the charging failure area of the recording medium and eliminate the contact between the conductive portion of the recording medium portion and the conductive fiber.

If the insulating member is provided with an inclined surface or the like so that the density of the leading end of the conductive fiber is higher than that on the conductive base side, the above effect is further improved.

[Brief description of drawings]

1A and 1B are explanatory views of the principle of the present invention. FIG. 1A shows a fixed conductive brush charger and FIG. 1B shows a rotary conductive brush charger.

FIG. 2 is a side view showing an outline of an electrophotographic printer to which the present invention is applied.

FIG. 3 is a structural explanatory view of a conductive brush charger according to a first embodiment of the present invention, FIG. 3 (A) shows a case where the insulating member has no inclined surface, and FIG. 3 (B) shows an insulating member. If there is an inclined surface,
Shown respectively.

FIG. 4 is a structural explanatory view of a conductive brush charger according to a second embodiment of the present invention, FIG. 4 (A) shows a case where the insulating member has no inclined surface, and FIG. 4 (B) shows an insulating member. If there is an inclined surface,
Shown respectively.

FIG. 5 is a front view showing the structure of a conductive brush charger according to a third embodiment of the present invention.

6A and 6B are structural explanatory views of a conductive brush charger according to a fourth embodiment of the present invention. FIG. 6A shows a case where the insulating member has no protrusion, and FIG. 6B shows a protrusion on the insulating member. In each case, there is a case.

FIG. 7 is a perspective view of a conventional conductive brush charger.

FIG. 8 is a diagram illustrating a problem of a conventional conductive brush charger.

[Explanation of symbols]

1 Electrostatic Recording Medium 11 Fixed Conductive Brush Charger 12,32 Conductive Brush 13,33 Conductive Fiber 14,34 Conductive Base 15,16,35,36,37,38,39 Insulating Member 16a, 36a Inclined Surface 31 Rotating Conductive Brush Charger 39a Protrusion

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukio Nishio 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited

Claims (9)

[Claims] 1. A conductive brush comprising a brush-shaped conductive fiber held on a conductive base portion, wherein the tip of the conductive fiber of the conductive brush is brought into contact with the surface of an electrostatic recording medium, and the conductive brush is also provided. In a conductive brush charger that charges by applying a voltage to the end of the conductive base portion, an insulating member for restricting the spread of the conductive fiber in the electrostatic recording medium axial direction is provided. Characteristic conductive brush charger. 2. The conductive brush charger according to claim 1, wherein the conductive base has a plate-like shape or a block-like shape that is fixedly installed. 3. The conductive brush charger according to claim 1, wherein the conductive brush is a rotary type in which a conductive base formed in a roll shape is held by a conductive base portion having a rotary shaft shape. .. 4. The insulating member is formed of a porous member,
The conductive brush charger according to claim 1, wherein the conductive brush charger is provided so as to be in contact with the surface of the electrostatic recording medium. 5. The conductive brush charger according to claim 1, wherein the insulating member is formed in a brush shape and is provided so as to be in contact with the surface of the electrostatic recording medium. 6. The conductive brush charger according to claim 1, wherein the insulating member is provided in non-contact with and in proximity to the electrostatic recording medium. 7. The conductive brush charger according to claim 1, wherein the shape of the insulating member is set such that the density of the leading end portion of the conductive fiber is higher than the density of the conductive base portion side. 8. The conductive brush charger according to claim 3, wherein the insulating member is rotatably supported by a conductive base portion which is a rotating shaft of the conductive brush. 9. A conductive brush charger according to claim 4, wherein a layer for reducing a friction coefficient is added to a surface of the insulating member of the conductive brush charger in contact with the electrostatic recording medium.