JPS6255155B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a static eliminator for a conveyor belt used in a transfer mechanism of an electrophotographic copying apparatus.

For example, in the above-mentioned transfer mechanism, as shown in FIG. 1, an insulating conveyor belt 1 is provided, and this conveyor belt 1 performs the operation of conveying the transfer paper P to the right in the drawing.

A photoreceptor 2 that carries a toner image on its circumferential surface and a transfer charger 3 that is in contact with the photoreceptor 1 are installed near the top and bottom of the rightward movement path of the belt 1, respectively. The toner image on the circumferential surface of the photoconductor 1 is transferred to the transfer paper P that comes into contact with the circumferential surface of the photoconductor 1 during the transfer due to electrostatic attraction based on the charging action of the charger 3 .

Further, after this transfer operation, the transfer paper P leaves the belt 1 by moving straight and is sent to the next process, but the belt 1 reverses and moves to the left and passes through the static eliminator charger 4.
It is guided by a counter electrode roller 5 that is in contact with.

By the way, the surface of the belt 1 entering the counter electrode roller 5 is charged with static charges generated when passing through the transfer charger 3, and this charge is useless for the next transfer operation of the belt 1. From, belt 1
When passing through the counter electrode roller 5, the AC charger 4
Static electricity is eliminated by the action of

As described above, the transfer mechanism of the electrophotographic copying apparatus includes an AC charger 4 as schematically shown in FIG.
A belt static eliminator formed of a counter electrode roller 5 and a counter electrode roller 5 is used, but in addition to the above-mentioned roller type counter electrode plate, a flat plate type counter electrode plate facing the AC charger 4 is used as shown in FIG. The electrode plate 6 is used, and its operation is the same as that of the counter electrode roller 5.

Here, no matter which type of return electrode plate is used, conventional static eliminators have their own drawbacks, and each type of return electrode plate will be specifically explained below.

(a) Device using electrode plate 6 (Fig. 3) Since the path distance of belt 1 on electrode plate 6 is long, belt 1 vibrates and dances up and down on electrode plate 6 while moving, resulting in , belt 1 is the return electrode 6
If the object rises from the surface, some parts remain that are not locally neutralized.

In addition, as the contact area of the belt 1 increases for the same reason, the electrostatic adhesion force of the belt 1 to the electrode plate 6 increases, which becomes movement resistance and unnecessarily increases the driving load of the belt 1. .

(b) Device using counter electrode roller 5 (Figures 2 and 4) This device has a characteristic defect that causes uneven charge removal on the belt 1, which will be explained in detail with reference to Figure 4. .

Now, as shown in Figure a, for example, when the belt 1 is negatively charged, the moment when the current potential of the charger 4 is at a positive peak is set as t=0,
The contact line of the belt 1 with the roller 5 at this time is defined as a local point A.

At this point, the local area A is completely neutralized and has no potential due to charging energization of the opposite polarity.

Next, as shown in Figure b, after half a cycle when the power supply potential reaches a negative peak, that is, at the moment of t = 1/f x 1/2, local B is charged with the same polarity. Therefore, the distance l between the local area A and the local area B is v/f×1/2, where v is the speed of the belt 1.

Thus, on the surface of the belt 1, static elimination unevenness with an interval l characteristically occurs, and as can be easily seen from the above values, the higher the speed v of the belt 1, the more uneven the unevenness becomes. For example, when f = 50 Hz and v = 400 mm/sec, stripes appear every 8 mm.

In addition, as a means to prevent this striped unevenness, it is possible to increase the power frequency, but in that case, a new leakage current failure occurs, and it is also necessary to increase the diameter of the roller 5 to increase the contact area. It is conceivable to widen it, but in that case, it would be accompanied by a problem that would increase the difficulty of layout, and in any case, it would be hard to say that it is an effective means.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a belt static eliminator that can provide a uniform static neutralizing effect and that does not impede the movement of the belt. It is about providing.

The present invention will be described below based on an illustrated embodiment. In the static eliminator of this embodiment, as shown in FIG. In addition to forming a plurality of rows (two rows in the illustration) of protrusions 7a in the width direction in a sawtooth shape,
The inter-row dimension D is v/f×2n+1/2, that is, v/f×(n+1/
2) [However, n is set to any integer].

In the static eliminator of the embodiment configured in this way,
Since the contact path length and contact area of the return electrode plate 7 with the belt 1 are small, there is no adverse effect on the movement of the belt, and the contact line, that is, the distance between the rows between the top edges of the protrusions 7a, is small. Since the length is shifted by half a period, the entire surface of the belt 1 is inevitably subjected to the opposite polarity charging action of the charger 4 when it comes into contact with one of the protrusions 7a. It is difficult for static elimination leakage or uneven static elimination to occur on the surface.

In addition, as shown in FIG. 7, the protrusion 8 of the return electrode plate 8
If multiple rows (5 rows in the figure) are formed by narrowing the pitch of a, the static elimination effect will be made even more uniform. If you do it like this,
When the entire surface of the belt 1 comes into contact with any of the protrusions 8a, the belt 1 receives an energizing charge close to the peak potential of the power source.

As described above, according to the belt static eliminator according to the present invention, multiple rows of protrusions are formed on the belt contacting surface of the return electrode based on the inter-row dimension corresponding to the power cycle and belt speed. Obstacles to belt movement are eliminated, and the static neutralization effect is evened out.
This has the effect of improving the practicality of the static eliminator.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a transfer mechanism of an electrophotographic copying machine, Fig. 2 is a schematic diagram of a conventional static eliminator using a counter electrode roller, and Fig. 3 is a schematic diagram of a static eliminator using a conventional electrode plate. 4 is an operational diagram of FIG. 2, FIG. 5 is a schematic diagram of a belt static eliminator showing an embodiment of the present invention, and FIG. 6 is a perspective view of the return electrode of FIG. 5. FIG. 7 is a sectional view of a return electrode plate showing another embodiment. 1...Belt, 4...Charger, 7, 8...Return electrode plate, 7a, 8a...Protrusion.

Claims (1)

[Claims] 1. An insulating belt whose surface is electrically charged is disposed on its movement path and passed over a counter electrode plate facing an AC charger, so that the electrical charge is dissipated. In the static eliminator for a belt, a plurality of rows of longitudinal protrusions in the width direction are formed to protrude in a sawtooth shape on the belt contacting surface of the return electrode, and the inter-row dimension between the two rows of protrusions is adjusted as appropriate depending on the movement of the belt. The speed (referred to as v) and the frequency of the charger power source (f
A static eliminator for a belt, characterized in that the voltage is set equal to the value of v/f×2n+1/2 (where n is an arbitrary integer).