JPH0263073A - Electrifier for image carrier - Google Patents

Abstract

PURPOSE:To obtain a stable surface potential without reducing the moving speed of an image carrier and to obtain a stable image as a result by setting the bending of the grid of the electrifier in the rotating direction of the image carrier to the direction of the image carrier on an upstream side. CONSTITUTION:The width of the grid 1 facing the photosensitive body is set relatively to the width of the opening part of an earth plate 5 so as to form a gap on the upstream side in the moving direction of the photosensitive body 7. Consequently, saturation is attained with the fast rise in the surface potential of the photosensitive body and the grid potential as shown by graph solid lines in graphs. For the purpose, the grid 1 is bent toward the photosensitive body 7 on the upstream side of the photosensitive body 7 to obtain characteristics as shown in the graphs. Consequently, an electrifying potential is stabilized and the image carrier with good sensitivity can be selected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the structure of a charger for an image carrier used in an electrophotographic apparatus.

[Conventional technology]

Conventionally, in this type of charger, the end of a grid that controls the potential to be charged on the surface of the image carrier is bent in the opposite direction to the image carrier.

[Invention or problem to be solved]

In the conventional charger mentioned above, the curve of the charging potential control grid was in the opposite direction to the image carrier (because it was facing the charger side), so the width of the grid was made smaller than the width of the ground plate of the charger. (due to leakage), and ions can only be emitted to the image bearing member within the range of the bend.In order to obtain a stable charging potential, the high voltage power supply power of the image forming apparatus must be boosted. Alternatively, it is necessary to take measures such as selecting an image carrier with good sensitivity or reducing the speed of the apparatus, which is disadvantageous in that it is not desirable in terms of the specifications of the apparatus.

An object of the present invention is to provide a charger for an image carrier that solves the above problems.

[Means to solve the problem]

To achieve the above object, the present invention provides a scorotron charger for charging the surface of an image carrier to a predetermined potential, including a grid for controlling the charging potential, and a ground plate of the scorotron charger facing the image carrier. A gap is provided between the grid and the opening on the upstream side in the moving direction of the image carrier, and an end of the grid in the axial direction of the image carrier is bent toward the image carrier on the upstream side. It is.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a perspective view of one embodiment of the present invention.

In the figure, an electrode wire 4, a grid 1, and a ground plate 5 are set in a predetermined positional relationship by an insulating block 2.3 to form a charger 6.

This charger 6 is set on the photoreceptor 7 as shown in FIG. High voltage is applied to the electrode wire 4 from the high voltage power supply 9, and air breakdown occurs near the electrode wire 4.
Ions flow towards the grid 1 and ground plate 5. When these ions pass through the holes in the grid 1 and collide with the surface of the photoreceptor 7, the surface of the photoreceptor 7 is charged due to the discharge of charge at that time.

This charge amount V. is a function of the grid potential Vo determined by the Zener diode 8. In addition, it is affected by the moving speed and sensitivity of the photoreceptor 7, the shape of the grounding plate 5 of the charger, the current flowing through the wire 4, and even the state of the atmosphere.

However, in consideration of electrostatic latent images and development with toner, the value of Vo needs to be stable. However, as mentioned above, due to instability factors, in order to keep the value of Vo constant, V must be balanced with a certain level of Vo value. The time it takes for the surface potential of the photoreceptor to rise to this value must be shortened, and the device cannot afford to reduce its moving speed. Therefore, by forming the grid 1 facing the photoreceptor 7 so that it has a gap on the upstream side in the moving direction of the photoreceptor 7 with respect to the width of the opening of the ground plate 5, the solid line in the graph shown in FIG. As shown in , the photoreceptor surface potential rises quickly and ■. Saturation at slightly higher values can be obtained. Here, if the grid 1 has a planar shape with no bending, it is necessary to apply appropriate tension to the grid 1 using a spring or other method in order to achieve parallelism with the image carrier 7. In addition, if the grid 1 is to have a bend so that it is not necessary to apply tension, if the grid 1 is bent on the charger 6 side and the width of the grid 1 is smaller than the width of the ground plate 5, the wire 4 This causes a problem because leakage occurs more toward grid 1. Therefore, on the photoreceptor 7:
By bending the grid 1 toward the photoreceptor 7 using aIPI, the characteristics shown in FIG. 2 can be obtained.

On the other hand, if the bending direction of the grid 1 is on the side of the charger 6 (the width of the grid 1 must be made equal to the opening of the charger 6), the number of ion collisions will be indicated by the dotted line in the graph in Figure 2. As shown in the figure, the surface potential increases only to a value that does not reach Vo, that is, to an unsaturated value, and charging ends, and the value of Vo becomes unstable.

〔Effect of the invention〕

As explained above, the present invention makes it possible to obtain a stable surface potential without reducing the moving speed of the image carrier by setting the bending of the grid of the charger in the rotation direction of the image carrier on the upstream side toward the image carrier. As a result, a stable image can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing one embodiment of the present invention, and FIG. 2 is a longitudinal sectional view thereof. ■...Grid 2.3...Insulating block 4...Wire 5...Grounding plate 6...Charger 7...Photoreceptor 8...High voltage Zener diode 9...High voltage power supply patent Applicant Niigata NEC Co., Ltd. Agent Patent attorney Naka Kanno Figure 2

Claims (1)

[Claims] (1) In a scorotron charger that charges the surface of an image carrier to a predetermined potential, a grid for controlling the charging potential;
A gap is provided on the upstream side in the moving direction of the image carrier between the opening of the ground plate facing the image carrier of the scorotron charger, and the end of the grid in the axial direction of the image carrier is A charger for an image carrier, characterized in that an upstream side thereof is bent toward the image carrier.