JPH03204663A - Image forming device charger - Google Patents

Abstract

PURPOSE:To simplify construction and to facilitate electrifying potential adjustment by extending a charge wire in the position where the distance from a photosensitive body is different when this wire is mounted in a 1st direction and is mounted in a 2nd direction. CONSTITUTION:The charge wire 26 is extended to a charge casing 23, which can be mounted to an image forming body 10 in the 1st and 2nd directions reversed from each other, in the position where the distance from the photosensitive body 15 is different when the wire is mounted in the 1st direction and is mounted in the 2nd direction. Namely, the electrifying power is high while the photosensitive belt 15 is fresh and, therefore, the electrifying charger 16 is set in a printer body 10 in the direction where the charge wire 26 is apart from the photosensitive belt 15. The electrifying charger 16 is inverted upside down to set the charge wire 26 in the direction proximate to the photosensitive belt 15 when the electrifying power is degraded on aging of the photosensitive belt 15. The construction is simplified in this way and the electrifying potential adjustment is facilitated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a charger for charging a photoreceptor by corona discharge in an electrophotographic image forming apparatus such as a laser printer or a copying machine.

Conventional chargers capable of adjusting charging conditions for a photoreceptor have been described in the following publications.

(1) Japanese Unexamined Patent Publication No. 61-294467 A device in which charging conditions are electrically changed by switching the bias voltage of the grid section.

■ Publication of Utility Model Publication No. 61-20602 The height of the charge wire is adjusted by sliding a wedge-shaped charge adjuster.

(1) Japanese Unexamined Patent Publication No. 62-28774 A device in which the gap between the surface of the photoreceptor and the charger and/or the size of the opening of the charger is adjusted by a surface potential correction means.

It is an object of the present invention to provide a charger that has a simpler structure than any of these conventional chargers and can easily adjust the charging potential.

The charger according to the present invention has a charging wire that is attached in a first orientation to a charger casing that can be attached to an image forming body in first and second orientations that are opposite to each other. The distance from the photoreceptor is different when the photoreceptor is mounted in the second orientation.

By inverting the stopper plate charger casing and mounting it on the image forming apparatus, the distance between the photoreceptor and the charge wire can be adjusted in two stages.

L-Kenichi Next, embodiments of the present invention will be described based on the drawings.

FIG. 2 is a schematic configuration diagram of a laser printer equipped with an electrostatic charger according to the present invention, in which 10 is the main body of the printer, 11
is a paper tray that is removably loaded into the printer main body 10. From this paper tray 11 to the paper feed roller 12
The recording paper 13 fed in the direction of the arrow by is conveyed to the photoreceptor belt 15 at a timing determined by a pair of registration rollers 14 . The photoreceptor belt 15 is rotated clockwise, and the charger 1 according to the present invention is rotated at this time.
The surface of the photoreceptor belt 15 is electrically charged and irradiated with laser light from a laser optical unit 17 to form an electrostatic latent image on the photoreceptor belt 15 . This latent image is made visible by toner as it passes through the developing unit 18, and this visible image is transferred by the transfer charger 19. Thereafter, the recording paper 13 is conveyed to a fixing unit 20 to have the visible image fixed thereon, and then is discharged to a paper discharge section 21 in the direction of arrow B. On the other hand, the cleaning unit 22 removes residual toner from the photoreceptor belt 15 after the visible image has been transferred. The toner removed from the photoreceptor belt 15 is collected into the cleaning unit 22.

FIG. 3 is a perspective view of the charger 16, FIG. 4 is a partially cutaway side view thereof, and FIG. 5 is a front view thereof.

The charger 16 has a charge wire 26 stretched between end blocks 25 fixed to both ends of a charger casing 23 with screws 24. The charger casing 23 is vertically and horizontally symmetrical, except that both ends thereof are U-shaped.

Flanges 27 are provided on both upper and lower edges of the left and right side walls.

The charger casing 23 is made of SUS or plated to prevent it from being attacked by 03, NOx gas, etc.

The end block 25 is made of an insulating material such as meryl or polyacete.

A contact protrusion 28 is provided on the outer surface of one end block 25. This contact protrusion 28 is located at the vertical center and the horizontal center of the charger casing 23 so that it is in the same position even when the charger casing 23 is turned upside down. Namely.

As shown in FIG. 5, the contact protrusions 28 are located at an equal distance a from both left and right walls of the charger casing 23, and at an equal distance a from the upper and lower flanges 27. In FIG. 3, A is the center line in the horizontal direction, and B is the center line in the vertical direction.

On the other hand, the position of the charge wire 26 is on the center line A in the left-right direction, but on one side of the center line B in the vertical direction.
(for example, 0.5 to 2 m).

FIGS. 1(a) and 1(b) show examples of how the charger 16 is used. When the photoreceptor belt 15 is new, its own charging ability is high, so the charger 16 is set in the printer main body 10 with the charge wire 26 facing away from the photoreceptor belt 15 as shown in (a).

When the photoreceptor belt 15 becomes old and its charging ability decreases, the charger 16 is turned upside down so that the charge wire 26 is oriented closer to the photoreceptor belt 15 as shown in FIG. Charging by corona discharge requires shields in three directions, but the charger 16 itself has two shields on the left and right.
Since there is a shield part only in the direction, the upper part is shielded by the shield plate 29 on the printer main body 10 side.

Note that the present invention can also be used in an image forming apparatus using a photoreceptor drum.

(Sakugai Mika According to the present invention, there are the following effects.

■ Just flip the charger upside down to increase the charging potential by 2.
Since it can be adjusted in stages, there is no need for a special adjustment mechanism like in the past, making it highly reliable and inexpensive.

■ The charged potential of the photoconductor can be corrected over time, so
High quality images can be maintained for a long period of time.

[Brief explanation of drawings]

Figures 1 (a) and (b) are explanatory diagrams showing an example of how the charger is used upside down, Figure 2 is a schematic configuration diagram of a laser printer equipped with the charger, and Figure 3 is a perspective view of the charger. FIG. 4 is a partially cutaway side view, and FIG. 5 is a front view. 10...Printer body 15...Photoreceptor belt 16...Charger 23...
...Charger casing 26...Charge wire (G) 2nd (b)

Claims (1)

[Claims] In a charging charger that charges a photoreceptor of an image forming apparatus by corona discharge, a charge wire is placed in a charger casing that can be attached to the image forming body in first and second directions that are reversed to each other, and the charge wire is placed in the first direction. A charger for an image forming apparatus, characterized in that the charger is stretched at a position where the distance from the photoreceptor is different when the charger is mounted in a second direction and when it is mounted in a second direction.