JPH019957Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention relates to a self-exhaust type charging device, and more particularly to a charging device that performs scronona discharge and that self-exhausts ozone or ion wind formed around a photoreceptor drum. In general, copying machines use various charging devices such as a main charging device that applies a certain static charge to the surface of the photoreceptor drum prior to exposure, and a static eliminator that applies an opposite charge to eliminate the residual charge on the photoreceptor drum. A static elimination mechanism is provided. As the surrounding air becomes ionized due to this charging, a harmful ionic wind that causes deterioration of the photoreceptor and the like is generated upon charging. For example, when ZnO, CdS, etc. are used as the photoreceptor drum, negative corona discharge is performed as the main charging to negatively charge the surface of the photoreceptor drum, and then exposure and development operations are performed. In addition, when a positively charged type photosensitive drum such as Se is used, a negative or Ac corona discharge operation is applied to remove static electricity. However, since such corona discharge contains a negative component as a discharge component, ozone gas is generated, and the oxidation effect of this ozone gas not only causes deterioration of the photoreceptor layer, but also causes negative corona discharge as the main charge. In some cases, developer,
In particular, there is a disadvantage that the toner component in which the pigment is dispersed in the resin is oxidized, resulting in deterioration of the developing characteristics. That is, an object of the present invention is to provide a corona discharge type charging device that can prevent the disadvantages caused by such corona discharge, that is, the deterioration of the photoreceptor layer and developer due to harmful air currents typified by ozone gas. Another object of the present invention is to provide a charging device that self-exhausts ozone gas generated by negative corona discharge. According to the present invention, there is provided a charging device for a copying machine comprising a U-shaped metal shield and a corona wire stretched in the longitudinal direction inside the U-shaped metal shield. In the charging device that applies an electric charge, at least a portion of the U-shaped metal shield is provided with an opening, and a shield wall on the downstream side in the rotational direction of the photoreceptor drum has an air flow blocking protrusion extending toward the surface of the photoreceptor drum. A self-exhaust type charging device is provided, which is characterized in that an ozone gas-containing airflow formed around the periphery of the photoreceptor drum is discharged from the opening. Generally, when corona discharge is performed, charged particles generated by corona discharge collide with electrically neutral gas particles as they drift along the electric field, creating a directional flow of neutral gas particles, the so-called ion wind. It is well known that this occurs. As is well known, in the case of negative corona discharge, ozone gas is generated, and therefore the ion wind contains a large amount of ozone gas, which has an adverse effect on the photoreceptor layer and developer as described above. For example, as shown in FIG.
At the same time, an air flow is formed that moves in the direction of arrow A, and therefore, the ion wind containing ozone gas also forms a fluid layer around the photoreceptor drum along the rotational direction of the drum. This fact can be easily confirmed by the fact that when cigarette smoke or the like is lightly blown onto the rotating photoreceptor drum, the smoke forms a layer around the drum that flows along the rotational direction of the drum. The present invention aims to self-exhaust ion wind containing ozone gas (hereinafter sometimes simply referred to as ozone wind) by utilizing the flow of this fluid layer. The present invention will be described in detail below based on specific examples shown in the accompanying drawings. In FIG. 2 showing the charger according to the present invention, the charger 2 consists of a U-shaped metal shield 3, and therefore a discharge opening B is formed at the lower side of the figure. It is provided in the main body of the copying machine so as to face the surface of the photosensitive drum 10. Inside this charger 2, corona wires 5, 5 are inserted through an insulating block 4 in the longitudinal direction.
is stretched, and one end of the corona wires 5, 5 is electrically connected to the plug 6. Furthermore, on the upper wall of shield 3 is this charger 2.
A handle 8 is provided at the end opposite to the shield 3 and the plug 6. An important feature of the present invention is that the shield 3
An opening 9 is provided in the upper wall of the shield 3, and an air flow blocking protrusion 12 is provided in one side wall 11 of the shield 3 on the downstream side in the rotational direction C of the photosensitive drum 10. That is, this charger 2 is connected to the photosensitive drum 10.
In FIG. 3, which shows the entire state in which the photoreceptor drum is provided facing the surface of the photoreceptor drum, the airflow A formed on the surface of the photoreceptor drum contains a large amount of ozone due to the negative discharge of the corona wire 5, and becomes a so-called ozone wind. , is discharged to the outside of the shield case 3 of the charger 2 through the opening 9 upon contact with the blocking protrusion 12;
Furthermore, it is discharged to the outside of the copying machine by a fan 13 or the like. This opening 9 is most preferably provided in the upper wall of the shield 3 on the downstream side with respect to the airflow A (that is, with respect to the rotational direction of the photoreceptor drum 10), but is located above the corona wire 5. If so, it may be provided at any arbitrary position and at a plurality of locations. Here, the upper part with respect to the corona wire 5 means the position opposite to the photoreceptor drum 10 with respect to the corona wire 5. The opening 9 is preferably an elongated hole extending in the longitudinal direction of the shield 3, but may also be, for example, a plurality of small holes arranged in the longitudinal direction. Since the airflow blocking protrusion 12 is for completely blocking the airflow A containing ozone, the airflow blocking protrusion 12 is provided on the shield side wall 1 on the downstream side of the airflow A.
1, and it also needs to be in the form of a sheet extending in the longitudinal direction. The blocking protrusion 12 is provided so as to be in close contact with the surface of the photoreceptor drum 10, either lightly or not. As mentioned above, the photoreceptor 1
The airflow A containing ozone that moves as the 0 rotates collides with the blocking protrusion 12, becomes an airflow D, and is discharged to the outside of the charger 2 through holes 9, 9 provided in the upper wall of the charger 2. However, when the airflow A collides with the blocking protrusion 12, the airflow A
A part of the flow becomes a spiral flow A. As a result, due to this flow A, even when the blocking protrusion 12 is not in complete contact with the photoreceptor drum 10, that is, in a state in which the blocking protrusion 12 is close to the photoreceptor drum 10 to the extent that it does not contact, the air flow A containing ozone is transferred to the blocking protruding piece 10. This makes it possible to prevent leakage. Furthermore, it is a noteworthy feature that even when the blocking protrusion 12 is in complete contact with the photosensitive drum 10, the contact force is softened by the collision of the air flow A. The above-mentioned ozone discharge and reduction of the contact force, as well as the leakage prevention effect in the close state, become more pronounced as the moving speed of the photoreceptor increases. Further, as shown in FIG. 3, a wall member 1 is provided to prevent the ozone-containing airflow discharged from the charger 2 from flowing back to the photoreceptor.
4 is also an effective means. As this blocking protrusion 12, a rubber-like elastic body,
It is preferable to use an insulating material such as felt, various films, or sponge. As described above, in the charging device of the present invention, harmful air currents such as ozone wind generated during charging are self-exhausted, and as a result, deterioration of the photoreceptor layer and developer is effectively prevented. Therefore, the charging device of the present invention is particularly effective as a negative charging type charging device that generates a large amount of ozone. Furthermore, when the charging device of the present invention is used in a negative charging type main charging device, since the developing device is provided in an adjacent position, deterioration of the developer due to ozone is particularly effectively prevented. be. The excellent effects of the charger of the present invention will be explained with the following example. Example Using the apparatus shown in Figures 3 to 5, using various chargers at 30 revolutions per minute and an applied voltage (-) of 8 KV, the photoreceptor was pasted on an aluminum drum for 5,000 consecutive cycles.
The discharge treatment was repeated several times, and the deterioration state of the photoreceptor was compared in terms of surface potential before and after treatment. As a charger, holes with a diameter of 6 mm are arranged in a row on both shoulders of the U-shaped metal shield, and a thin rubber blade for blocking airflow is installed on the shield wall on the downstream side in the drum rotation direction toward the drum surface. A device that is placed in contact with the surface of the photoreceptor. However, instead of providing a protruding piece for blocking airflow, only the metal shield on the downstream side is provided longer, so that the gap between the photoreceptor surface and the end of the metal shield is _d1 on the upstream side. It is about 6 mm, while on the downstream side d ₂ it is about 1.5 mm.
It was placed close to the surface of the photoreceptor so that the distance was 1 mm. (4th
(See figure) A charger used with a regular U-shaped metal shield charger, without holes in the shoulder of the shield, and with the downstream metal shield having the same length as the upstream shield. The experiment was carried out on three types: 1, 2 and 3, and 3 types that are not particularly close to the photoreceptor (see Fig. 5). A single-layer cadmium sulfide photoreceptor was used as the photoreceptor. In addition,
For surface potential measurement, an electrostatic paper analyzer manufactured by Kawaguchi Electric Manufacturing Co., Ltd. was used.
The measurement results are shown in the table below.

[Table] When using the charger from the above results, no difference was observed between the surface potential before repeated processing and the surface potential after 5000 (-) cycles of charging, indicating that deterioration of the photoreceptor due to ozone occurs. I wasn't there. When using a charger, the surface potential is
The voltage dropped by about 70V, indicating some deterioration of the photoreceptor. When a charger was used, the surface potential decreased by 275V compared to before treatment, and significant deterioration of the photoreceptor due to ozone was observed. Therefore, it was found that the charger of the present invention is very effective against deterioration caused by ozone gas and ionic wind.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the formation of airflow, FIG. 2 is a partially sectional perspective view showing the charging device of the present invention, and FIG. 3 is an explanatory diagram showing the function of the charging device of the present invention.
FIG. 4 is a diagram showing one embodiment of the charging device of the present invention, and FIG. 5 is a diagram showing a conventional type of charging device, in which reference numeral 2 is a charger, 3 is a metal shield, and 4 is an insulator. Block, 5 is corona wire, 6
is the plug, 7 is the rail, 8 is the handle, 9 is the opening, 1
0 is a photoreceptor drum, 12 is an airflow blocking protrusion, 13
indicates Juan respectively.

Claims (1)

[Claims for Utility Model Registration] A charging device for a copying machine consisting of a U-shaped metal shield and a corona wire stretched in the longitudinal direction inside the U-shaped metal shield, which is provided near the surface of a photoreceptor drum, and which is provided near the surface of a photoreceptor drum. In the charging device that applies an electric charge to the surface, at least a portion of the U-shaped metal shield is provided with an opening, and an air flow blocker is provided on the shield wall on the downstream side in the rotational direction of the photoreceptor drum and extends toward the surface of the photoreceptor drum. 1. A self-exhausting charging device, characterized in that a protruding piece is provided to exhaust airflow formed around the periphery of the photoreceptor drum through the opening.