JPH0594076A - Image forming device - Google Patents

Abstract

(57) [Abstract] [Purpose] An object of the present invention is to provide an image forming apparatus having a charger capable of performing efficient and stable corona discharge on a photoreceptor and smoothly disposing of ozone. [Structure] The grid plate 32 is configured such that the widths of the crosspieces 32b between the grid holes 32a are equalized, and the opening area of the grid holes 32a becomes narrower toward the downstream side in the moving direction of the photoconductor 1. [Effect] It is possible to efficiently control the potential of the photoconductor and to exhibit a sufficient ozone discharging effect with a low air flow resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention visualizes an electrostatic latent image formed on a photoconductor with toner particles, transfers the toner image onto a sheet as a transfer material, and heats the toner image onto the sheet. The present invention relates to an image forming apparatus that is fixed by pressure or the like.

[0002]

2. Description of the Related Art In a conventional image forming apparatus, a device using corona discharge as a charging device in order to uniformly charge a photosensitive member is predominant. In this charger, a grid is provided to control the electric potential of the photoconductor, and this grid uses several metal wires having a wire diameter of about 0.1 mm, which are perpendicular to the moving direction of the photoconductor. There are used those formed by stretching in parallel, and those formed by etching a metal plate having a plate thickness of about 0.3 mm to form grid-shaped or stitch-shaped grid holes.

A conventional image forming apparatus will be described below with reference to FIGS.
This will be described with reference to FIG.

FIG. 8 is a cross-sectional view of a conventional image forming apparatus. Reference numeral 1 is a photosensitive material in which a photosensitive layer such as selenium (Se) or an organic photoconductor (OPC) is applied in a thin film on the outer peripheral surface of an aluminum tube. A body 2 is a charger, and the charger 2 is a charging wire 3 made of a tungsten wire or the like and a metal plate formed in a U shape as shown in more detail in FIG. 1 and a shield plate 4 having a hole 4b in a U-shaped bottom 4a and a corona discharge electron having holes formed in a lattice shape, and rectifying electrons to control the potential of the photoconductor 1. It is composed of a grid plate 5. As shown in FIG. 10, the grid plate 5 is formed by integrally forming a conductive plate-like member by etching or electroforming molding means, and is composed of several strip-shaped grids in a direction perpendicular to the moving direction of the photoconductor 1. The holes 5a are separated by the bars 5b of the grid. The opening area of this grid hole 5a is the same in each grid hole. Reference numeral 6 denotes an exposure light beam emitted from the optical device, which is image data light in the case of a printer. The exposure light beam 6 is controlled by a signal from a host computer (not shown),
As a result, an electrostatic latent image is formed on the photoconductor 1.

Reference numeral 8 is a developing device for two-component development.
Is a toner hopper 10 that stores the toner 9, and the toner 9
And a carrier 11 which is a magnetic particle such as iron powder, and a developing roller 12 having a magnet inside after mixing and stirring.
And a developing butt 13 which is conveyed to form a magnetic brush. A transfer material cassette 14 stores a transfer material 15. From the transfer material cassette 14, a half-moon-shaped paper feed roller 16 sends the transfer materials 15 one by one to a transfer material transport path 17. Reference numeral 18 denotes a pair of conveying rollers for conveying the transfer material 15 along the transfer material conveying path 17. Reference numeral 19 is a registration roller for temporarily stopping and waiting the transfer material 15 in order to make the positions of the transfer material 15 and the toner image formed on the photoconductor 1 coincide with each other.
It is in pressure contact with 0.

Reference numeral 21 is a positive high voltage applied to the photosensitive member 1.
A transfer device for transferring the toner image formed on the transfer material 15. 22 is a heat roller 23 having a heat source inside
And a pressure roller 24.
Transfers the toner image transferred on the transfer material 15 to the heat roller 2
3 and the pressure roller 24 are rotated while being nipped, the toner is fixed on the transfer material 15 by pressure and heat to form an image. 25 is a cleaning device for scraping off the residual toner remaining on the photoconductor 1 without being transferred, and 26 is a static eliminator for removing charges on the cleaned photoconductor 1. Reference numeral 27 denotes a process cartridge in which the photoconductor 1, the charger 2 and the cleaning device 25 are integrated, and the process cartridge 27 has an ozone discharge hole 27a at a portion facing the hole 4b of the shield plate 4 of the charger 2.
Is opened. Reference numeral 28 denotes an ozone filter which is detachably attached to the machine body 29 through an opening provided in a side plate of the machine body 29 and which adsorbs and decomposes ozone generated in the charger 2. Reference numeral 30 denotes an ozone discharge fan that discharges ozone generated in the charger 2 to the outside of the machine together with the air flow.

The operation of the conventional image forming apparatus configured as described above will be described below.

When an image forming operation signal is issued, the photosensitive member 1 starts to rotate in the direction indicated by arrow A, and a high voltage is first applied to the charging wire 3 in the charger 2 connected to the high voltage power source to cause corona discharge. Then, the surface of the photoconductor 1 is uniformly charged to about −600V. Next, the uniformly charged surface of the photoconductor 1 is irradiated with an exposure light beam 6 which is a laser beam according to image data. The electric charge disappears in the portion of the photoconductor 1 irradiated with the exposure light beam 6, and an electrostatic latent image is formed.

On the other hand, the carrier 11 and the toner 9 in the developing butt 13 are triboelectrically charged, adsorbed on the surface of the developing roller 12 having a magnet inside, and conveyed to the developing section 31 by the rotation of the developing roller 12. .. In this developing unit 31, the carrier 11 and the toner 9 form a magnetic brush,
Contact with. At this time, by applying a potential difference between the developing roller 12 and the photoconductor 1, the toner 9 adheres to the electrostatic latent image on the photoconductor 1 to form a visible image, and the development is completed. By applying a high voltage to the transfer device 21, the toner images formed on the photoconductor 1 are sequentially transferred to the transfer material 15 sent from the transfer material cassette 14 along the transfer material transport path 17. Then, the transfer material 15 to which the toner image is transferred is sent to the fixing device 22, where it is fixed by the heat of the heat roller 23 and the nip rotation of the pressure roller 24, and is output as an image.

FIG. 11 is a perspective view of an essential part of another conventional image forming apparatus. Reference numeral 50 is a grid plate having hexagonal grid holes 50a and bars 50b having the same area.

[0011]

However, in the conventional image forming apparatus described above, the opening areas of the grid holes 5a are evenly formed in the moving direction of the photoconductor 1 as shown in FIG. When the transition of the surface potential on the body 1 is measured, the central portion of the charger 2 is already saturated. Therefore, the corona ion flow after passing through the central portion becomes excessive and inefficient. For this reason, the actual development 59-156257 and the actual development 59-184488.
In the above method, the crosspiece 5b of the grid is made thicker toward the downstream side in the moving direction of the photoconductor 1 to increase the efficiency of potential control of the photoconductor 1, but the crosspiece 5b of the grid becomes thicker so that the charger 2 It becomes a resistance to the air flow that flows into the inside, and ozone cannot be exhausted to the outside sufficiently and stays inside the charging unit 2,
After the printing operation of the machine body is completed, it flows toward the photoconductor 1 to deteriorate the photoconductor 1, and an image defect occurs at the beginning of printing again.

Therefore, the present invention solves the above problems and provides an image forming apparatus having a charger capable of efficiently and stably performing corona discharge on a photoconductor and smoothly disposing of ozone. The purpose is to provide.

[0013]

According to the present invention, the widths of the crosspieces between the grid holes in the moving direction of the photosensitive member are made equal, and
At least one of the opening area and the width of the grid hole is formed so as to become narrower toward the downstream side in the moving direction of the photoconductor.

[0014]

According to the above construction, the potential can be efficiently controlled by changing the opening area and / or width of the grid holes without increasing the resistance of the air flow.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An image forming apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of an image forming apparatus according to an embodiment of the present invention, and FIG. 2 is a partially enlarged view of the image forming apparatus. The same components as those of the conventional image forming apparatus are designated by the same reference numerals. The description is omitted.

In the figure, reference numeral 32 denotes a grid plate of the charger 2, which is a conductive plate member integrally formed by etching or electroforming, as shown in FIG. Several strip-shaped grid holes 32a are divided at right angles with respect to the moving direction by grid bars 32b. The opening area of the grid holes 32a is formed so as to become narrower in the moving direction of the photoconductor 1 (S).
1> S2 ... S4> S5). The widths of the crosspieces and 32b are all formed to be substantially equal.

As shown in FIG. 4, since the photosensitive member 1 is not charged near the upstream side of the moving direction of the photosensitive member 1 of the grid plate 32, the grid holes are formed in order to strengthen the action of corona ions on the photosensitive member 1 due to corona discharge. While the opening area of 32a is widened to promote the flow of corona ions, on the downstream side in the moving direction of the photosensitive member, the opening area of the grid hole 32a is narrowed toward the end of the grid plate 32 to reduce the surface potential of the photosensitive member 1. Are in control. Further, if the width of the grid rails 32b is set to be twice the plate thickness or less, the effect of charging control including ozone disposal is great. FIG. 4B shows a time change of the surface potential of the photoconductor.

The operation of the image forming apparatus of the present invention configured as described above will be described below.

Since a negative high voltage is applied to the charging wire 3 in the charger 2, ozone is generated around the charging wire 3.
This ozone is supplied to the fan 30 for ozone discharge as shown in FIG.
Flow through the hole 4b of the shield plate 4 and the ozone discharge hole 27a of the process cartridge 27 together with the air flowing into the charger 2 due to
It is adsorbed and decomposed by the ozone filter 28, the concentration is diluted, and the product is discharged to the outside of the machine body. When the air flows into the charger 2, since the widths of the bars 32b of the grid are all formed to be substantially equal, the air flows smoothly without resistance.

FIG. 5 is a perspective view of an essential part of the image forming apparatus of the second embodiment, in which the grid holes 33a of the grid plate 33 are divided by the grid bars 33b. This grid hole 3
The width of 3a is formed so as to become narrower in the moving direction of the photoconductor 1 (L1> L2 ... L6> L7).
Further, the widths of the grid bars 33b are all formed to be substantially equal.

FIG. 6 is a perspective view of an essential part of the image forming apparatus of the third embodiment. 34 is a grid plate, and 34a is narrower in width and area in the moving direction of the photoconductor 1 (M1> M2).
>>>M6> M7) Hexagonal grid hole, and 34b is a bar having a constant width.

FIG. 7 is a perspective view of an essential part of the image forming apparatus of the fourth embodiment. 35 is a grid plate, and 35a is the width as it goes in the moving direction of the photoconductor 1 as in the third embodiment. Area becomes smaller (L1>L2>...>L5> L6, S1> S
2 >> ... >>S5> S6) Lattice-like grid holes, 35b
Is a bar of constant width.

[0024]

As described above, according to the present invention, the widths of the crosspieces between the grid holes are formed to be equal, and at least one of the opening area and the width of the grid holes is narrowed toward the downstream side in the moving direction of the photoconductor. Therefore, the potential of the photoconductor can be efficiently controlled, and the resistance of the air flow is small, and a sufficient ozone discharging effect can be exhibited. As a result, it is possible to provide an image forming apparatus which is always reliable and has high printing quality.

[Brief description of drawings]

FIG. 1 is a sectional view of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a sectional view of the same main part.

FIG. 3 is a perspective view of the same main part.

FIG. 4A is a cross-sectional view of the same main part. FIG. 4B is a graph showing the time variation of the surface potential on the photoconductor.

FIG. 5 is a perspective view of a main part of an image forming apparatus according to a second embodiment of the present invention.

FIG. 6 is a perspective view of essential parts of an image forming apparatus according to a third embodiment of the present invention.

FIG. 7 is a perspective view of a main part of an image forming apparatus according to a fourth embodiment of the present invention.

FIG. 8 is a sectional view of a conventional image forming apparatus.

FIG. 9 is a sectional view of the same main part.

FIG. 10 is a perspective view of the same main part.

FIG. 11 is a perspective view of a main part of an image forming apparatus according to another conventional example.

FIG. 12A is a cross-sectional view of a main part of an image forming apparatus according to a first conventional example. FIG. 12B is a graph showing a time change of the surface potential on the photoconductor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging device (charging means) 3 Charging wire 4 Shield plate 32 Grid plate 32a Grid hole 32b Bar 7 Optical device (exposure means) 8 Developing device (developing means)

Claims (5)

[Claims] 1. A photosensitive member coated with a photosensitive layer, a charging unit for charging the photosensitive member, an exposing unit for exposing the surface of the charged photosensitive member to form an electrostatic latent image, and the photosensitive member. The electrostatic latent image formed on the developing unit is provided with a developing unit that visualizes the toner image to form a toner image, and a transfer unit that transfers the toner image onto a transfer material. The charging unit includes a charging line and the charging line. A shield plate having a U-shape and having an opening opposed to the photoconductor, and a grid plate having a plurality of grid holes and the surface of the photoconductor arranged through a slit, The width of the crosspiece between the grid holes in the moving direction of the photoconductor is formed to be equal, and at least one of the opening area and the width of the grid hole is formed to become narrower toward the downstream side in the moving direction of the photoconductor. Image forming apparatus. 2. The width of the crosspieces between the grid holes is 2 times the grid plate thickness.
The image forming apparatus according to claim 1, wherein the image forming apparatus has a size equal to or less than double. 3. A photosensitive member coated with a photosensitive layer, a charging unit for charging the photosensitive member, an exposing unit for exposing the surface of the charged photosensitive member to form an electrostatic latent image, and the photosensitive member. The electrostatic latent image formed on the developing unit is provided with a developing unit that visualizes the toner image to form a toner image, and a transfer unit that transfers the toner image onto a transfer material. The charging unit includes a charging line and the charging line. A shield plate having a U-shape and having an opening opposed to the photoconductor, and a grid plate having a plurality of grid holes and the surface of the photoconductor arranged through a slit, The image forming apparatus is characterized in that the width of the crosspiece between the grid holes in the moving direction of the photoconductor is formed to be equal, and the opening area of the grid hole becomes narrower toward the downstream side in the moving direction of the photoconductor. 4. A photosensitive member coated with a photosensitive layer, a charging unit for charging the photosensitive member, an exposing unit for exposing the surface of the charged photosensitive member to form an electrostatic latent image, and the photosensitive member. The electrostatic latent image formed on the developing unit is provided with a developing unit that visualizes the toner image to form a toner image, and a transfer unit that transfers the toner image onto a transfer material. The charging unit includes a charging line and the charging line. A shield plate having a U-shape and having an opening opposed to the photoconductor, and a grid plate having a plurality of grid holes and the surface of the photoconductor arranged through a slit, The image forming apparatus is characterized in that the crosspieces between the grid holes are formed to have the same width in the moving direction of the photoconductor, and the width of the grid holes is narrowed toward the downstream side in the moving direction of the photoconductor. 5. A photosensitive member coated with a photosensitive layer, a charging unit for charging the photosensitive member, an exposing unit for exposing the surface of the charged photosensitive member to form an electrostatic latent image, and the photosensitive member. The electrostatic latent image formed on the developing unit is provided with a developing unit that visualizes the toner image to form a toner image, and a transfer unit that transfers the toner image onto a transfer material. The charging unit includes a charging line and the charging line. A shield plate having a U-shape and having an opening opposed to the photoconductor, and a grid plate having a plurality of grid holes and the surface of the photoconductor arranged through a slit, The image forming apparatus is characterized in that the widths of the crosspieces between the grid holes in the moving direction of the photoconductor are made equal, and the opening area and width of the grid holes become narrower toward the downstream side in the moving direction of the photoconductor. ..