JP3136863B2 - Charger - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charger, and more particularly, to a charger used in an image forming apparatus such as a printer, a facsimile, a copying machine, etc. using an electrophotographic process.

[0002]

2. Description of the Related Art A conventional charger will be described with reference to the drawings. FIG. 5 is a vertical cross-sectional view of a configuration example of a conventional charger using a well-known scorotron system. The charger includes a shield plate 101, a wire 102, and a grid 103. Is held at a distance of. Wire 1 made of tungsten etc.
02 is connected to a means for supplying a high voltage of about 4 to 7 kv. A grid 103 made of stainless steel or the like having a mesh shape is provided with a means for supplying a constant potential by a varistor, a Zener diode, or the like. It is connected.

When a high voltage of several kv is applied to the wire 102, corona discharge occurs in the air, and the photosensitive member 104 starts to be charged. Since a fixed potential is applied to the grid 103, the charging potential of the photoconductor 104 is regulated by the potential applied to the grid 103, does not rise above this potential, and the charging potential of the photoconductor 104 is a desired value. To obtain a stable potential.

[0004]

The above-mentioned conventional charger requires a high voltage to apply a high voltage to the wire to generate corona discharge. Therefore, a large-sized high-voltage power supply is required, and a large amount of ozone is generated. In addition, since the atmosphere is contaminated, a filter for absorbing the atmosphere is required, which results in an increase in the size of the apparatus and an increase in cost.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems. It is an object of the present invention to provide a charger capable of miniaturizing a power supply and generating almost no ozone, and providing a high quality image. It is to obtain the use conditions for forming.

[0006]

The charger of the present invention charges a photoreceptor by holding a brush-like charger composed of bristles and a plate in contact with the photoreceptor. .

[0007] hair, acrylic, rayon, nylon, polyester, polypropylene, synthetic fibers such as polycarbonate, length 2 mm to 10 mm, 1.5 denier to 15 denier thickness, resistance 1 × 10 ² Ωcm~1 × 1
0 ⁸ used as the ^{Ωcm, 1 × 10 4 ~5 ×} 10 5 pieces /
The plate is held at a density of ² inches. The plate is made of a conductive metal such as stainless steel, a semiconductive engineering plastic, or an organic material.

In order to prevent the hair held on the plate from falling down due to the rotation of the photoconductor, an engineering plastic, PET, and the like are provided downstream of the plate in the rotation direction of the photoconductor.
A guard made of a film, a urethane sheet, a foam, or the like may be provided. The above charger has a width of 3 mm to 20 mm.
The length in the longitudinal direction is determined by the size of the recording medium.

[0009] As the above-mentioned holding condition of the charger, it is preferable that the hair is held in a state of being 0.5 mm to 2 mm longer than the contact with the photosensitive member. In order to stably charge the photoreceptor, the plate has a peak-to-peak voltage Vpp of 0.5 kv to 2 kv, and a direct current having an absolute value of 0.5 kv to 1.2 kv for an AC component having an arbitrary frequency. Voltage Vdc
It was found that it is sufficient to apply a voltage on which

Here, the frequency is a factor for uniformly charging the photosensitive member. If the value is too small, the photosensitive member cannot be charged uniformly. And the moire image is generated. On the other hand, if the frequency is too high, white vertical streaks occur in the halftone dot image. Therefore, high-quality images cannot be formed unless the optimum frequency is applied. In the halftone dot image, the optimal value f (Hz) of the frequency at which no moire image is generated and no white vertical streak is generated depends on the resolution R (dpi) of the image forming apparatus and the process speed S (mm / s).
F = RS / 25.4 (Hz)
Was found to be required. This can be explained as follows. Distance L of one dot in the sub-scanning direction
Is the time T corresponding to L, where L = 25.4 / R (mm).
Is T = L / S (s). Unless the photoreceptor is charged in synchronization with the time T by the charger, moire images may be generated due to uncharged portions, or moire images may be generated, and white vertical stripes may be generated. I do. f
= 1 / T = RS / 25.4, and as a result of the experiment, f
When the value was ± 100 Hz, the moiré image and the white vertical streak could not be recognized by the subjective evaluation, so that a good range was obtained.

Therefore, using the above charger, f
By applying a voltage obtained by superimposing a DC component on an AC component having a frequency of = RS / 25.4 ± 100, a moiré image or a white vertical line does not occur.

[0012]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a vertical sectional view of an image forming apparatus using the charger of the present invention. The charger 1, a photosensitive member 3, a toner carrier 4, a supply roller 5, a regulating blade 6, It comprises a toner 7, a stirring member 8, a toner hopper 9, a cleaner 10, and a shutter 11. OPC is applied to the charger 1 by applying a voltage in which a DC component is superimposed on an AC component.
(Organic Photoconductor), a photoconductor 3 of Se type or the like is uniformly charged, and an initial potential is applied to the outer peripheral surface thereof. The surface of the photoreceptor 3 is exposed to image data 2 from a light source such as a laser, LED, or liquid crystal (not shown) to form an electrostatic latent image. A toner 7 serving as a developer is guided by a stirring member 8 to a supply roller 5 made of a material such as conductive or insulating urethane, silicone foam, or aluminum.
Silicon rubber, urethane rubber, nitrile butylene rubber,
The toner is guided to the toner carrier 4 made of a flexible material such as natural rubber, urethane or silicone foam, or a member having a surface treated thereon.

The toner 7 guided to the toner carrier 4 is regulated by a regulating blade 6 made of a metal spring member such as stainless steel, phosphor bronze, nickel silver, etc., and is formed into a more uniform thin layer. At this time, the toner 7 is charged by friction. A voltage having a polarity different from that of the toner 7 is applied to the toner carrier 4. When the charged thin toner layer 7 on the toner carrier 4 faces the photoconductor 3, the electric field is applied to the photoconductor 3 by the electric field. The toner adheres to the upper electrostatic latent image, is developed, and a toner image is formed.

The toner image on the photoreceptor 3 is transferred to a recording medium such as paper, an OHP, a postcard, or the like by a transfer unit (not shown).
An image is obtained by fixing the toner image to a recording medium by a fixing unit (not shown).

FIG. 2 is a longitudinal sectional view of the charger according to the first embodiment of the present invention, which comprises brushes 1a, a plate 1b, and a guard 1c, and has a brush-like structure. Hair 1
a is made of acrylic fiber, has a length of 5 mm, a thickness of 6.2 denier, and a resistance of 1 × 10 ³ Ωcm to 1 × 1.
0 ⁴ Ωcm, and is held on the plate 1b at a density of 50,000 lines / inch ² . The plate 1b is made of a conductive stainless steel plate. Guard 1c has A
Use BS resin.

The charger of this embodiment, which is composed of the hair 1a, the plate 1b, and the guard 1c, holds the hair 1a 1 mm longer than the contact with the photosensitive member 3, and
b, a voltage obtained by superimposing a DC voltage Vdc = −700 V on an AC component having a peak-to-peak voltage Vpp = 1.2 kv is applied to change the frequency f of the AC component to obtain a resolution of 300 dp.
i. A dot image having an area ratio of 12.5% was printed by a printer having a process speed of 30 mm / s, and the print quality was subjectively evaluated. The results shown in Table 1 were obtained.

[0018]

[Table 1]

FIG. 3 is a longitudinal sectional view of a charger according to a second embodiment of the present invention, which comprises brushes 1a and a plate 1b and has a brush-like structure. The hair 1a is made of acrylic fiber, has a length of 5 mm, a thickness of 6.2 denier, a resistance of 1 × 10 ³ Ωcm to 1 × 10 ⁴ Ωcm, and a density of 50,000 hairs / inch ² . It is held on the plate 1b. The plate 1b is made of a conductive stainless steel plate.

The charging device of this embodiment, which is composed of the hair 1a and the plate 1b,
Is 1 mm longer, and the plate 1b has a peak t
o A voltage obtained by superimposing a DC voltage Vdc = −700 V on an AC component having a peak voltage Vpp = 1.2 kv is applied, and the frequency f of the AC component is changed. The area is determined by a printer device having a resolution of 240 dpi and a process speed of 33 mm / s. Rate 12.5
% Of the dot image was printed and the print quality was subjectively evaluated.
Was obtained.

[0021]

[Table 2]

FIG. 4 is a longitudinal sectional view of a charger according to a third embodiment of the present invention, which comprises brush 1a, plate 1b, and gart 1c, and has a brush-like configuration. Hair 1a
Is made of acrylic fiber, has a length of 5 mm, a thickness of 3 denier, and a resistance of 1 × 10 ³ Ωcm to 1 × 10 ^4.
Ωcm, and is held on the plate 1b at a density of 100,000 lines / inch ² . The plate 1b is made of a conductive stainless steel plate. Guard 1c has PE
A T film was used.

The charger of the present embodiment, which is composed of the hair 1a, the plate 1b, and the guard 1c, holds the hair 1a 1 mm longer than the contact with the photoreceptor 3, and holds the plate 1b.
Is applied with a voltage obtained by superimposing a DC voltage Vdc = −700 V on an AC component having a peak-to-peak voltage Vpp = 1.2 kV, and changing the frequency f of the AC component to obtain a resolution of 400 dp.
i. A dot image having an area ratio of 12.5% was printed by a printer device having a process speed of 33 mm / s, and the print quality was subjectively evaluated. The results shown in Table 3 were obtained.

[0024]

[Table 3]

[0025]

As described above, according to the present invention, a brush-shaped charger composed of bristles and a plate, or a charger provided with a guard, is held in contact with a photoreceptor, The frequency f is RS / 25.4 ± 100 on the plate
(Hz), by applying a voltage obtained by superimposing a DC voltage Vdc having an absolute value of 0.5 kv to 1.2 kv on an AC component having a Vpp of 0.5 kv to 2 kv, a moire image or a white vertical Good image quality can be obtained without streaks. In addition, the charger is held in contact with the photoreceptor, and the applied voltage is much smaller than in the prior art. Therefore, there is almost no generation of ozone, and the conventionally required filter is unnecessary. Further, since the power supply for supplying a voltage to the charger can be made smaller than before, there is an effect that the size and cost of the image forming apparatus can be reduced.

Further, in an image forming apparatus having only a different resolution, the frequency of the voltage applied to the charger has a range of 100 Hz up and down, and the same frequency can be used depending on the resolution. Also, there is an effect that cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an image forming apparatus using a charger of the present invention.

FIG. 2 is a longitudinal sectional view of the charger of the first embodiment of the present invention.

FIG. 3 is a longitudinal sectional view of a charger according to a second embodiment of the present invention.

FIG. 4 is a longitudinal sectional view of a charger according to a third embodiment of the present invention.

FIG. 5 is a longitudinal sectional view of a conventional charger.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Charger 1a Hair 1b Plate 1c Guard 2 Exposure 3,104 Photoconductor 4 Toner carrier 5 Supply roller 6 Regulator blade 7 Toner 8 Stirrer 9 Toner hopper 10 Cleaner 11 Shutter 101 Shield plate 102 Wire 103 Grid

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 15/02-15/02 102 A46B 15/00

Claims (2)

(57) [Claims] 1. A charger for charging a photoreceptor of an image forming apparatus used in an electrophotographic process, comprising a synthetic fiber of at least one of acrylic, rayon, nylon, polyester, polypropylene and polycarbonate, and having a length of 2 mm. 〜１０10 mm, thickness 1.5 denier ニ ー 15 denier, resistance 1 × 10 ² Ωcm〜1 × 10 ⁸
Ωcm, a conductive metal plate such as stainless steel, and a plate made of any of a semiconductive organic material, wherein the bristle is 1 × 10 ^{4 to} 5 × 1
0 at ⁵ / inch ² density on the plate,
With a width of 3 mm to 20 mm, the tip of the hair contacts the photoconductor,
When the process speed is S (mm / s) and the resolution of the image forming apparatus is R (dpi), the frequency is RS / 25.
A charger characterized by applying a voltage obtained by superimposing a DC voltage having an absolute value of 0.5 kv to 1.2 kv on an AC component having a peak voltage of 0.5 kv to 2 kv at 4 ± 100 Hz. 2. The charging device according to claim 1, wherein said bristle is held 0.5 to 2 mm longer than contact with a photoreceptor.