JPH0538361Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a scorotron type corona charging device used in electrostatic transfer copying machines, laser printers, and the like.

[Conventional technology]

The conventional scorotron type corona charging device has a fourth
As shown in Figures a and b, a grid 31 made of a conductive material is arranged in parallel close to the surface of the photoreceptor 30, and a discharge electrode wire 33 connected to a DC high voltage power source 32 is connected to the discharge electrode wire 33. The grid 31, the discharge electrode wire 33, and the shield case 34 have a U-shaped cross section and cover the grid 31, the discharge electrode wire 33, and the shield case 34
A pair of left and right holders 35 made of insulating material,
The structure is such that it is held at 35. The shield case 34 may be electrically connected to the grid 31 to have the same potential, or may be electrically insulated from both.

Thereby, the surface of the photoreceptor 30 is always charged to a constant potential.

[Problem that the invention attempts to solve]

However, in order to avoid uneven charging, it is necessary to place the grid 31 at a constant distance of about 1 mm from the surface of the photoreceptor 30, but this grid 31 is made of a thin metal conductor plate with a thickness of about 0.1 mm. Because of the shape, the grid 31 may be curved or
Distortion such as waving is likely to occur, and it is difficult to maintain the grid 31 at a uniform distance from the surface of the photoreceptor 30.

Therefore, as shown in Japanese Utility Model Application Publication No. 62-26760, a structure has been proposed in which a spring or the like is provided to apply tension to the grid 31 in the longitudinal direction thereof.

However, this method requires springs and many other parts, which not only complicates the structure, but also increases the number of parts, resulting in higher costs.In addition, cleaning and replacing the discharge electrode wire 33 is difficult. Although the frequency is relatively high, there is a problem in that the structure makes it extremely difficult to attach and detach the grid 31, which is required at that time. Furthermore, since the shield case 34 has a U-shaped cross section, the distance from the discharge electrode wire 33 arranged inside the shield case 34 to the shield case 34 is not constant, and as a result, stable discharge characteristics cannot be obtained. This also caused the problem.

[Means for solving problems]

In order to solve the above-mentioned problems, the corona charging device according to the present invention has a tunnel-shaped upper surface curved into a cylindrical shape, and has a longitudinal section at the lower end of each opposing side wall of a shield case made of an elastic conductive material. A plurality of locking claws are formed along the direction, a holder is provided supported at each of the longitudinal ends of the shield case, and the grid formed of a thin metal conductor plate has a plurality of locking claws formed therein. Engagement holes are formed at respective positions facing the shield case, and the respective locking claws are respectively engaged with the corresponding respective engagement holes on the grid side with both side walls of the shield case being bent inward. and passing through a center line equidistant from the cylindrical curved upper surface of the shield case,
The present invention is characterized in that a discharge electrode wire is constructed using the above-mentioned holder.

The plurality of engagement holes formed on the grid side may be provided in the grid itself, or may be provided in an insulating grid substrate fixed to the grid.

[Effect]

According to the above configuration, since the shield case itself has elasticity, when both side walls of the tunnel-shaped shield case are bent inward, the shield case tends to expand outward and return. Because the grid is forcibly expanded in the width direction by the elastic restoring force generated in the shield case itself, distortions such as curving and waving in the width direction of the grid are eliminated. In addition, a plurality of locking claws of the shield case are formed along the longitudinal direction at the lower ends of both side walls, so by engaging each of the locking claws with the engagement holes on the grid side, the grid can be fixed. Distortions such as longitudinal curvature and waving are also removed at the same time. Therefore, even though the grid is formed of a thin metal conductor plate, it is held in a flat state spread out over the whole by the shield case, so the distance from the photoreceptor surface can be set uniformly with high precision. becomes possible. Furthermore, since the discharge electrode wire installed inside the shield case using a holder passes through a center line that is equidistant from the cylindrical curved top surface, the distance from the discharge electrode wire to the top surface of the shield case can be determined in any direction. It also becomes constant, and stabilization of discharge can be obtained.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

As shown in Fig. 1, the shield case 1 has a tunnel-shaped upper surface curved into a cylindrical shape, and is made of a thin elastic conductive material so that it can be appropriately bent. has been done. Examples of the material of the shield case 1 include conductive materials having spring characteristics such as stainless steel and phosphor bronze. The lower end portions 1a, 1a of the opposite side walls of the shield case 1 have edges parallel to each other, and a plurality of locking claws 1b, which are bent outward at a substantially right angle, are connected to the lower end portions 1a, 1a. 1a
They are formed at equal intervals along the longitudinal direction.

On the other hand, the grid 2 is a thin plate with a thickness of about 0.1 mm, and a rectangular mesh part 2a is formed in the center of the grid 2. On both sides of the mesh part 2a, the shield cases 1 A plurality of engagement holes 2 are provided so as to correspond to each of the locking claws 1b...
b... are formed at equal intervals.

Each of the locking claws 1b of the shield case 1 is
It is engaged with each engagement hole 2b of the grid 2, but
In this case, the interval width between the opposing locking claws 1b, 1b formed on both side walls of the shield case 1 is as follows:
Since the spacing between the opposing engagement holes 2b and 2b formed on both sides of the grid 2 is set to be slightly larger, as shown in FIG. With each wall bent inward (in the direction of arrow A), each locking claw 1b of the shield case 1 can be engaged with each corresponding engagement hole 2b of the grid 2. It is something.

When the grid 2 is fixed to the shield case 1 in the above-mentioned engaged state, an elastic restoring force always acts on the shield case 1, so the grid 2 is affected by the shield case 1 as shown in Fig. 2b. An acting force is generated that tries to spread the paper in the width direction (arrow B-B direction). Therefore, even if the grid 2 is formed of a thin metal conductor plate, distortions such as curvature and waving that tend to occur in the width direction of the grid 2 are forcibly removed. In addition, each locking claw 1b on both side walls of the shield case 1 is connected to each engaging hole 2 of the grid 2.
By engaging with b..., the grid 2 is regulated in a stretched state in the longitudinal direction, and distortions such as curvature and waving in the longitudinal direction of the grid 2 are forcibly removed. Therefore, grid 2
are formed into a planar shape with high precision, and can be placed parallel to a photoreceptor (not shown) at a constant distance.

The above-mentioned shield case 1 is supported by fitting both longitudinal ends thereof into shield case holding parts 3a, 3a of a pair of insulating holders 3, 3 made of resin or the like as shown in FIG. Then, the shield case 1 and the holders 3, 3 are fixed with screws (not shown) or the like. As shown in FIG. 2b, the discharge electrode wire 4 connected between the pair of holders 3 and 3 and further connected to the DC high voltage power supply is inside the shield case 1 and has a curved upper surface in the shape of a cylindrical surface. It is constructed so as to pass through the center of the shape. As a result, the distance from the discharge electrode wire 4 to the shield case 1 is constant in all directions, so that stable discharge characteristics can be obtained.

As described above, once the relative arrangement of the shield case 1, the grid 2, and the discharge electrode wire 4 is determined, the distance between the photoreceptor and the grid 2 (not shown) and the distance between the photoreceptor and the discharge electrode wire 4 are determined. Since the distance between the two is inevitably set with high precision, the charging characteristics are improved.

In addition, in the engagement structure between the shield case 1 and the grid 2, the tensile force in the width direction that the shield case 1 applies to the grid 2 depends on the material and thickness of the elastic conductive material of the shield case 1, and the thickness of the shield case 1. It is affected by the shape of both side walls when molded into a tunnel shape. Therefore, it is necessary to take the above-mentioned factors into account when designing the shield case 1 so that it can apply the most appropriate tensile force to the grid 2 in its width direction.

In addition, in the above embodiment, the case where the entire grid 2 is formed of a thin conductive material and the shield case 1 and the grid 2 are at the same potential is explained, but the case where the shield case 1 and the grid 2 are insulated is explained. Of course, it can also be applied when used in In this case, as shown in FIG. 3, for example, both ends of the mesh portion 2a in the grid 2 in the width direction are fixed to the grid substrates 2c, 2c made of thin plates or sheets of insulating material with adhesive or the like, and the shield case is Each locking claw 1b of 1
The engaging holes 2b... of the grid 2 corresponding to... are provided in the grid boards 2c, 2c, and the respective locking claws 1b... of the shield case 1 are inserted into the engaging holes 2b... of the grid boards 2c, 2c. While engaging the shield case 1 and the grid 2, a potential difference may be created between the shield case 1 and the grid 2 using a constant voltage element such as a varistor.

[Effect of idea]

As described above, the scorotron-type corona charging device according to the present invention has a tunnel-shaped upper surface curved into a cylindrical shape, and has a shield case made of an elastic conductive material. A plurality of locking pawls are formed along the shield case, and a holder supported at each of the longitudinal ends of the shield case is provided. An engaging hole is formed at each position, and each of the locking pawls is engaged with each of the corresponding engaging holes on the grid side with both side walls of the shield case being bent inward. , passing through a center line equidistant from the cylindrical curved upper surface of the shield case,
This is a configuration in which the discharge electrode wire is constructed using the above-mentioned holder.

With this structure, the shield case has an elastic restoring force directed outward in the width direction, and the locking claw of the shield case engages with the engagement hole of the grid. Since it is possible to restrict the grid to spread out in the longitudinal direction, distortions such as curvature and undulation of the grid can be eliminated, and the grid can be formed into a planar shape as a whole. Therefore, the grid can be held close to and parallel to the photoreceptor surface with high accuracy.

Further, the above-mentioned grid is extremely easy to attach and detach, and the attachment position of the grid can always be determined with high precision. Therefore, the discharge electrode wire can be easily cleaned and replaced.

Furthermore, since no springs or other members are required to apply tensile force to the grid, the structure is simple and the number of parts can be reduced, resulting in cost reduction.

Furthermore, since the top surface of the shield case is curved into a cylindrical shape, the distance from the discharge electrode wire passing through the center to the top surface of the shield case is constant in all directions, resulting in significantly improved discharge characteristics. Then, the same effect will be produced as well.

[Brief explanation of the drawing]

Figures 1 and 2 show one embodiment of the present invention, in which Figure 1 is an exploded perspective view showing the structure of the corona charging device, and Figure 2a is before the shield case and grid are engaged. Fig. 2b is a longitudinal sectional view showing a state in which the shield case and the grid are engaged and assembled, Fig. 3 is a longitudinal sectional view showing another embodiment of the present invention, Fig. 4 4A and 4B are explanatory diagrams showing a schematic configuration of a conventional corona charging device, in which FIG. 4a is a front view and FIG. 4b is a longitudinal sectional view. 1 is a shield case, 1a is a lower end, 1b is a locking claw, 2 is a grid, 2a is a mesh portion, 2b is an engagement hole, 3 is a holder, and 4 is a discharge electrode wire.

Claims (1)

[Scope of utility model registration request] A plurality of locking pawls are formed along the longitudinal direction at the lower ends of the opposite side walls of the shield case, which has a tunnel-shaped upper surface curved into a cylindrical shape and is made of an elastic conductive material. A holder is provided at each end of the grid, and a grid made of a thin metal conductor plate has engaging holes formed at respective positions facing the locking claws. are respectively engaged with the corresponding engagement holes of the grid with both side walls of the shield case bent inward, and from the inside of the shield case from the cylindrical curved upper surface. A corona charging device characterized in that a discharge electrode wire is installed using the above-mentioned holder so as to pass through a center line that forms a distance.