JPH0210423B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a corona discharger, and more particularly, to a corona discharger that makes it possible to easily maintain a constant distance between a corona discharge wire and a charged member.

Conventionally, corona dischargers that apply corona discharge to a charged member have adjustable fixed mounting positions of the discharge wire in order to uniformize the corona discharge action on the charged member, and the distance between the discharge wire and the charged member can be adjusted. The common method was to keep it constant. In this type of corona discharger, it is essential to adjust the attachment position of the discharge wire before attaching it to the member to be charged. In addition, for example, in a corona discharge device used in an image forming device such as an electrophotographic device, if the installation position of the discharge wire is not properly adjusted, there is an inconvenience that becomes noticeable as a gradient or uneven density on the image. .
Therefore, it was necessary to make further adjustments depending on the image forming apparatus to which the corona discharger is installed.

Therefore, this type of corona discharger requires the above-mentioned adjustment process, which lengthens the manufacturing process and poses an obstacle to automatic assembly.

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a corona discharger that enables a desired uniform corona discharge effect without requiring extra adjustment process work.

Hereinafter, details of the present invention will be explained using specific examples with reference to the drawings.

FIG. 1 is a side sectional view of a specific example image forming apparatus to which the corona discharger of the present invention is applied.

Reference numeral 1 denotes a document mounting table made of a transparent member, which moves back and forth in the direction of the arrow. 2 is an imaging element array that converts the optical image of the original on the original platen 1 into an OPC photosensitive drum 3.
Slit exposure on top. Note that the photosensitive drum 3 rotates in the direction of the arrow. 4 is a corona discharger which uniformly charges the photosensitive drum. A developing device 5 develops an electrostatic latent image formed by exposing a uniformly charged photosensitive drum to light using the array 2 with toner.

On the other hand, the transfer sheet P is fed onto the surface of the drum 3 by a feeding roller 6 and a register roller 7, and the toner image on the drum is transferred by a transfer corona discharger 8. Thereafter, the sheet is separated by the separating means 13
The fuser 1 is separated from the drum by the roller 9a located at the end of the conveyance path after passing over the guide 9.
Sent to 0. The toner image on the sheet is fixed by a fixing device 10, and the sheet is conveyed onto a tray 12 by a discharge roller 11. On the other hand, the toner remaining on the photosensitive drum 3 without being transferred is removed by a cleaning device 1.
It is recovered by 4. Furthermore, 15 is an illumination system for exposing the original, and 16 is a filter such as a heat ray absorption filter.

In this image forming apparatus, the upper housing 17
and a lower casing 18 are separably connected to each other by a support shaft 19, and the upper casing 17 is configured to rotate upward about this support shaft 19. Image forming means such as illumination optical systems 2 and 15, photosensitive drum 3, corona discharger 4, developing means 5, and cleaning device 14 are arranged in this upper housing 17. In addition, the lower housing 1
8, a feeding roller 6, a transfer corona discharger, a separating means 13, a guide 9, a fixing device 10, and the like are arranged on the sheet conveyance path.

A specific example of a corona discharger based on the present invention used for a photosensitive drum as a charged member of such an image forming apparatus will be described below.

FIG. 2 is a front cross-sectional view of a corona discharger according to an embodiment of the present invention, and FIG. 3 is a side cross-sectional view thereof.

The corona discharger 4 mainly consists of a shield case 20, a discharge wire 21, and block parts 23 and 24 to which the discharge wire 21 is attached.

Specifically, the discharge wire 21 is stretched closer to the member to be charged (photosensitive drum) 2 than a predetermined height equal to or more than the accumulation of dimensional tolerances of its component parts, and is connected to the block 2 with rivets 25 and 26 at both ends.
It is fixed at 3,24.

Each block is provided with pieces 27 and 28, which serve as discharge wire position setting means and are supported movably in a direction perpendicular to the member to be charged. Frame 2
A V-shaped groove is provided on the upper surface of each of the discharge wires 7 and 28, into which the discharge wire 21 is inserted.

Rollers 29 and 30 rotatably supported by shafts 31 and 32 are provided at the lower ends of the pieces 27 and 28, and are configured to contact and follow the charged member. As shown in FIG. 3, the pieces 27 and 28 are supported so as to be able to slide on the inner walls 23a and 23b of the block, that is, to be movable relative to the shield case 20, so that they move approximately perpendicularly to the member to be charged.

Then, the length from the V-shaped groove of the pieces 27 and 28 to the tip of the roller of the piece is set to be the same as the distance between the discharge wire and the charged member.

With this configuration, when the corona discharger 4 is set on the charged member, the rollers 29 and 30 come into contact with the charged member, and the pieces 27 and 28 push up the discharge wire 21, allowing accurate positioning. .

Further, as shown in FIG. 2, the discharge wire 21 is inclined from the portion supported by the pieces 27 and 28 toward the portion where the wire 21 is fixed to the blocks 23 and 24. Therefore, while the discharge wire 21 is pushed up by the pieces 27 and 28, on the other hand, the discharge wire 21 presses the pieces 27 and 28 against the photosensitive drum 3 due to its tension.
As a result, the rollers 29 and 30 come into contact with the photosensitive drum 3, and the distance between the discharge wire 21 and the photosensitive drum 3 is kept constant.

FIG. 4 shows an enlarged cross-sectional view of a block at the end of the corona discharger. Reference numeral 31 in the figure indicates the rotation axis of the roller 29, which is provided integrally with the top 27.

The discharge wire 21 of the corona discharger shown in this way
The height accuracy with respect to the three surfaces of the charged member (photosensitive drum) is achieved by using rollers 29 and 30 that come into contact with the drum surface.

FIG. 5 is a side sectional view showing a modification of the discharge wire position setting means.

In the above example, the pieces 27 and 28 were guided by the inner wall of the block and moved, but in this embodiment, the pieces 27' and 28' are provided with arm portions 33 and 34, and are swung on support shafts 35 and 36. It is supported so that it can move freely. In this embodiment, the V-shaped groove portion that regulates the spatial position of the discharge wire 21 and the charged member (photosensitive drum)
The distance to the rollers 29 and 30 that come into contact with the roller 3 is determined by setting the length of the block body and the roller support position.
As a result, the distance between the discharge wire and the charged member can be set to a predetermined value without adjustment by setting the corona discharger, as in the previous embodiment.

In each of the above-mentioned embodiments, an example was shown in which a separately movable roller was used for the contact portion with the member to be charged, but if the roller is made of a material with good sliding properties, it may be fixed. In this case, the contact portion may be integrated with the top body. On the other hand, although a V-shaped groove is shown as a part that defines the discharge wire, any structure may be used as long as the spatial position of the discharge wire can be defined according to the movement of the top body. It goes without saying that the spatial position regulating portion of the discharge wire may be made separate from the top body.

In addition, if the amount of pushing up of the pieces 27 and 28 is large and the wire tension changes greatly, one end of the discharge wire 21 may be fixed via a spring.
If the amount of push-up can be absorbed by the tension caused by the stretching of the wire, a spring is not necessary and assembly becomes simple.

As described above in detail using specific examples, the corona discharger of the present invention can be set at a fixed distance between the discharge wire and the charged member by simply setting it on the charged member. This is an excellent feature that does not require adjustment operations.

Furthermore, since the corona discharger of the present invention can directly define the spatial position of the discharge wire itself, it is possible to regulate the desired position regardless of the accuracy error of the attachment part of the device such as an image forming apparatus to which the corona discharger is attached. It is.

[Brief explanation of drawings]

FIG. 1 is a side sectional view of a specific example image forming apparatus to which the corona discharger of the present invention is applied, FIG. 2 is a front sectional view of a specific example of the corona discharger based on the present invention, and FIG. 3 is the same side. 4 is an enlarged front sectional view of the same portion, and FIG. 5 is a side sectional view of a corona discharger according to a modified example of the present invention. In the figure, 1: document mounting table, 2: imaging element array,
3: Charged member (photosensitive drum), 4: Corona discharger.

Claims (1)

[Scope of Claims] 1. A corona discharger that applies corona discharge to a charged member, comprising a corona discharge wire, a shield case, and a support member that supports the corona discharge wire and that contacts the charged member. a support member movable with respect to the shield case, having a contact portion and having a constant distance between the contact portion and the support portion of the wire;
The supporting member supports the corona discharge wire near the end of the corona discharge wire, thereby maintaining a constant distance between the corona discharge wire and the member to be charged. corona discharger.