JPH03263065A - charging device - Google Patents

Abstract

PURPOSE:To excellently hold image quality for a long time by providing a supporting mechanism which supports a casing so that it can rotate with a charging wire as center and a driving mechanism which drives to rotate the supported casing. CONSTITUTION:Cylindrical shafts 35, 35 are protrusively formed at both ends in the axial direction of the casing 29 and rotatably supported by bearings 37 and 37 functioning as the supporting mechanism provided to a device main body 3. A gear 39 is coaxially fixed to one end in the axial direction of the casing 29 and linked with the driving shaft of a servomotor 43 functioning as the driving mechanism through an idle gear 41. Therefore, the casing 29 which drives the servomotor 43 rotates with the charging wire 31 as center and a position opposed to an aperture 33 is allowed to move with the rotation of the casing 29. Thus, the secular image quality is excellently held.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to, for example, a charging device, and more particularly to an improvement for preventing deterioration of a photoreceptor used in an image forming process.

(Prior Art) An image forming apparatus using a conventional electrophotographic process, such as a laser printer, includes a photoreceptor, a charger that charges the surface of the photoreceptor to a predetermined potential by corona discharge, and a host attached to the photoreceptor after being charged. An optical system that forms an electrostatic latent image by guiding laser light based on image data from the machine onto a photoreceptor, a developing device that uses a developer to visualize the electrostatic latent image, and records a visible image. It includes a transfer device that transfers the image onto paper, and a fixing device that fixes the visible image on the recording paper after the transfer.

By the way, the air near the charger is ionized by corona discharge, producing ozone (0,) and nitrogen oxides (NOx).
), and nitrogen oxides in particular have a higher specific gravity than air, so if these harmful substances adhere to the photoreceptor located below the charger, sensitivity will decrease over time and image quality will deteriorate. There was an in-between layer.

In response to this, an image forming apparatus has been disclosed in which harmful substances are removed and the influence on the photoreceptor is suppressed by providing an exhaust means for forcibly exhausting the air around the charger (
(Refer to Japanese Unexamined Patent Publication No. 61-50165), a charging device is also disclosed in which nitrogen oxides generated by corona discharge are neutralized by applying a thin layer of lead plating to the surface of the conductive shield portion of the charging device. (Unexamined Japanese Patent Publication No. 61-144671
(see publication).

However, nitrogen oxides remain attached to the inner wall of the charger's casing, so even when the image forming unit centered on the photoreceptor is not operating, the harmful substances remaining on the casing are gradually released onto the photoreceptor. Therefore, in order to reliably remove nitrogen oxides in the equipment of ##, it is necessary to operate the exhaust means at all times. Also,
The latter device has a problem in that it is difficult to maintain a stable neutralizing effect because the plating wears out over time.

(Purpose of the Invention) This invention has been made by focusing on the above-mentioned problem, and by adding a simple configuration, it is possible to prevent harmful substances generated from the charging device from adhering to the photoreceptor and reducing the sensitivity. The present invention aims to provide a charging device that can maintain good image quality over time.

(Structure of the Invention) In order to achieve the above object, the present invention includes five charge wires provided along the axial direction of the photoreceptor for charging the surface of the photoreceptor, and one charge wire that covers the outside of the charge wire. A charging device comprising a casing facing the surface of the photoreceptor and having an opening formed therein, a support mechanism that rotatably supports the casing around a chassis wire, and a casing supported by the support mechanism. and a drive mechanism for rotationally driving the.

Further, when the photoreceptor is rotationally driven, the driving means is driven so that the opening of the casing faces the photoreceptor, and when the photoreceptor is stopped, the driving means is driven so that the opening is retracted from the surface facing the photoreceptor. It is characterized in that it is provided with a control means.

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 shows an embodiment in which the charging device according to the present invention is applied to a laser printer. It includes a laser optical system 5 that emits laser light, and an endless belt-shaped photoreceptor 7 on which an electrostatic latent image is formed according to image data by being irradiated with laser light from the laser optical system 5. Also,
The laser printer l includes a paper feed cassette II which is detachably attached to the apparatus main body 3 and stores a plurality of recording sheets 9, and a paper feed roller for conveying the recording sheets 9 from the paper feed cassette 11 in the direction of arrow A in the figure. 13, and registration rollers 15 for timing the conveyance of the recording paper 9 onto the photoreceptor belt 7.

Around the photoreceptor belt 7, there is a charger 17 which is disposed above the photoreceptor belt 7 and charges the front side of the laser beam LWA@ section to a predetermined potential, and an electrostatic latent formed by the laser beam. A developing device i19 that attaches toner as a developer to the photoreceptor belt 7 in order to visualize the image.
and a transfer charger 21 that transfers the visible image onto the recording paper 9.
and is provided.

Recording paper 9 onto which a visible image has been transferred by transfer charger 21
is separated from the photoreceptor belt 7, fixed by the fixing device fi23, and then discharged to the discharge section 25 in the direction of arrow B in FIG. On the other hand, residual toner is removed from the photoreceptor belt 7 after the visible image has been transferred onto the recording paper by a cleaning device i27 having a cleaning blade, and the removed toner is collected in the cleaning device 27. .

The charger 17 has a cylindrical casing 2 as shown in FIGS. 2(a), 2(b), and 2(cl).
9, and a charge wire 3 located on the central axis (indicated by a broken line in FIG. 2 ICL) in the casing 29 to cause corona discharge.
1, and an opening 33 (facing the surface of the photoreceptor belt 7 in FIG. 2(b)) extending along the longitudinal direction is formed on the lower side of the casing 29.

A cylindrical shaft 35.3 is provided at both axial ends of the casing 29.
5 is formed in a protruding manner, and both wheels 35.35 are rotatably supported by bearings 37.37 as a support mechanism provided on the main body 3 of the device.

A gear 39 is fixed coaxially to one axial end of the casing 29, and the gear 39 is connected to a drive shaft of a servo motor 43 as a drive mechanism via an idle gear 4I. Therefore, when the servo motor 43 is driven, the casing 29 rotates around the charge wire 31, and as the casing 29 rotates, the opposing position of the opening 33 moves.

A first photo sensor 45 and a second photo sensor 47 as photo interrupters are arranged along the outer circumferential surface of the casing 29 with the casing 29 in between. between the light emitting and light receiving elements in 45 or the second
A shutter portion 49 that passes between the light emitting and light receiving elements in the photo sensor 47 is formed in a protruding manner. The first or second photosensor 45.47 is configured to turn on when the shutter section 49 is located between the first or second photosensor 45.47 (see FIG.
In b), the second photo sensor 47 is on)6
The first and second photosensors 45 and 47
When the photo sensor 47 is turned on, the opening 33 faces downward and faces the photoreceptor belt 7, while when the first photo sensor 45 is turned on, the opening 33 faces upward and faces the photoreceptor belt 7. Each position has been determined so that they can be evacuated.

One end (the right end in FIG. 2(C)) of the charge wire 31 is fixed to an end block 51, and the other end is fixed to a terminal 53 provided within the shaft 45.

The terminal 53 is relatively rotatably connected to a contact 55 on the side of the device main body 3, thereby supplying charging current to the charging wire 31. Since the shaft of the casing 29 is made of a material with excellent insulation properties, such as polyacetal, the current supplied to the charge wire 31 will not leak from the bearing.

No.! and second photosensors 45 and 47 are control means C.
It is connected to the input side of the PU 57, and the servo motor 43 is connected to the output side of the CPU 57. A CPU constituting a control section (not shown) is configured to drive the servo motor 43 based on the time chart shown in diagram N3.

In an initial state where no print command is received from the host machine, the main motor (not shown) that executes the print operation, the servo motor 43, and the main charge are controlled to be off, and in this state, the III photo sensor 45 is on. The opening 33 of the cage casing 29 faces upward (see FIG. 4(a)).

When the print command is output, the main motor is turned on and at the same time, the servo motor 43 is turned on. When the servo motor 43 is turned on, the casing 29 rotates and the first photo sensor 45 is turned off (see FIG. 4 Tb))
, the second photo sensor 47 is turned on. When the second photo sensor 47 is turned on, an off signal is output to the servo motor 43 and the rotation of the casing 29 is stopped. In this state, the opening 33 of the casing 29 faces downward and faces the photoreceptor belt 7, and then the main charge is turned on and a printing operation is performed (see Figure J4 (c)).

Thereafter, when a print command is output several times, the main charge is turned on after a predetermined period of time has elapsed from each command, and a print operation is performed.

If there is no next print command after a predetermined period of time has elapsed, a signal is output so that the main motor is turned off and the servo motor 43 is turned on at the same time.

When the servo motor 43 is turned on, the casing 29 rotates and the second photo sensor 47 is turned off (see FIG. 4(d)), and then i! 17 Oto sensor 45 turns on 5
When the first photo sensor 45 is turned on, the servo motor 4
3, an off signal is output and the rotation of the casing 29 is stopped. 2 In this state, the opening 33 of the casing 29 faces upward and is retracted from the surface facing the photoreceptor belt 7 (
Figure 4 (see el).

As described above, when the main motor is driven (the second odometer 47 is on), the opening 33 faces the photoreceptor belt 7 and the charge wire 31 is able to charge the surface of the photoreceptor belt 7. It is in. On the other hand, when the main motor is stopped (the first photo sensor 45 is in the on state), the opening 33 faces upward and does not face the photoreceptor belt 7, so that nitrogen remaining on the inner wall of the casing 29 Even if the oxide gradually separates when the laser printer 1 is stopped, it will not fall from the opening 33 onto the photoreceptor belt 7, so deterioration of the sensitivity of the photoreceptor belt 7 over time can be suppressed, and it can be used for a long time. Good image quality can be maintained over a period of time.

It goes without saying that the present invention is not limited to the above-mentioned embodiment, and that similar effects can be obtained by using other configurations of the support mechanism and drive mechanism of the casing 29, for example.

Further, in the above embodiment, the time when the main motor stops is defined as the time when the drive of the photoreceptor belt 7 is stopped, but the time when the main power of the laser printer I is in an OFF state is defined as the time when the drive of the photoreceptor belt 7 is stopped. Accordingly, the opening 33 may be configured not to face the photoreceptor belt 7.

Further, instead of controlling the rotational drive of the casing 29 by the CPU, a configuration may be adopted in which the opening 33 of the casing 29 is rotated as appropriate by manual operation so as not to face the photoreceptor belt surface.

(Effects of the Invention) As explained above, according to the present invention, ozone and nitrogen oxides generated from the charging device can be removed by simply adding a support mechanism that rotatably supports the casing and a drive mechanism that rotationally drives the casing. It is possible to prevent the photoreceptor from having an adverse effect on the photoreceptor and causing a decrease in sensitivity, and to maintain good image quality even after a long period of time has passed.

[Brief explanation of drawings]

FIG. 1 is a schematic overall configuration diagram of a laser printer to which a charging device according to the present invention is applied, FIG. 2(a) is a perspective view of the charging device according to the main part of FIG. 1, and FIG. 2(b) is shown in Figure 2 (
2(c) is a side sectional view of FIG. 2(a), FIG. 3 is a time chart showing the action of the control means, and FIG. 4 is a front view of AT.
Figures (al, (b), (c), (di,
(El is an explanatory diagram of the action of the casing under control based on the time chart shown in FIG. 3.

Claims (2)

[Claims] (1) A charge wire is provided along the axial direction of the photoreceptor to charge the surface of the photoreceptor, and an opening is formed in a surface that covers the outside of the charge wire and faces the surface of the photoreceptor. A charging device comprising: a casing that is rotatably supported by the casing around a charge wire; and a drive mechanism that rotatably drives the casing supported by the support mechanism. A charging device that (2) In the charging device according to claim (1), the drive mechanism is driven such that the opening of the casing faces the photoreceptor when the photoreceptor is rotationally driven, and the opening is opposed to the photoreceptor when the photoreceptor is stopped. The charging device according to claim 1, further comprising a control means for driving the drive mechanism to retreat from the opposing surface of the charging device.