JPS6055274A - Surface potential sensor - Google Patents

Abstract

PURPOSE:To make special parts such as a chopper electrode to be provided between the opening of a shield member and a measuring electrode unnecessary and to reduce the thickness of the whole sensor and to reduce the number of parts by vibrating directly the opening of shield members. CONSTITUTION:Electric line of force E of which potential is to be measured are made incident into a shield case 10 through an opening 12, received by the measuring electrode 11 and converted into a signal indicating the surface potential by a potential detecting circuit 15. The shield member 10C, 10D are vibrated by the action of a piezoelectric element 13 energized by a driving circuit 14, the opening part 12 is vibrated as shown by the arrow A and the area of the opening 12 is periodically changed. The number of electric line of force received by the measuring electrode 11 is also changed similarly and converted into an AC signal. The potential detecting circuit 15 processes these AC signals and outputs a signal indicating the measuring potential, so that the thickness of the sensor and the number of parts are reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a surface potential sensor for detecting and measuring the surface potential of conductors, insulators, etc. in a non-contact manner.

Conventionally, it has often been necessary to detect and measure the surface potential of objects in various fields, and in particular, in electrophotographic copying machines, it has been necessary to measure the surface potential of the photoreceptor drum in order to control the process to ensure good image formation. ing. There are various conventional surface electrometers that measure these surface potentials in a non-contact manner.

As an example, a configuration as shown schematically in FIG. 1 of the accompanying drawings has been proposed. This conventional surface electrometer is
Lines of electric force E received from the surface whose potential is to be measured through the opening 2 of the shield member 1 to the measuring electrode B are chopped by the chopper electrode 5 provided on the tuning fork vibrating piece 4 and converted into an alternating current signal for measurement. The potential detection circuit 6 connected to the electrode 8 is used as the output of an electrometer. This conventional surface electrometer uses a tuning fork as a chopper to extract the surface potential of the surface to be measured as an alternating current signal, which stabilizes the chopping frequency, reduces the power consumption of the drive source, simplifies the drive mechanism, and lowers the price. However, since a chopper electrode and a tuning fork vibrating piece are provided between the shield member and the measurement electrode, the overall thickness of the surface electrometer increases accordingly, and the number of parts also increases accordingly. Put it away.

An object of the present invention is to solve the above-mentioned problems and provide a thin and inexpensive surface potential sensor with a small number of parts.

The surface potential sensor according to the present invention includes a shield member having an opening formed therein, a measuring electrode that receives lines of electric force incident through the opening, and an electric force that the measuring electrode receives by changing the opening area of the opening. The apparatus is characterized by comprising a driving means for vibrating the opening so that the number of lines changes.

Next, the present invention will be explained in more detail with regard to embodiments of the present invention based on FIGS. 2, 3, and V of the accompanying drawings.

1 is a perspective view schematically showing a surface potential sensor as an embodiment of the present invention, and FIG. 3 is a schematic diagram for explaining the operation of the surface potential sensor shown in FIG. 2. The surface potential sensor of this embodiment includes a shield member 710 and a measurement electrode 11 disposed within the shield case 10. The shield case 10 includes a front plate 10A, a back plate 10B, and a pair of side members 10C and IO that can vibrate.
C, and an opening 12 is created between the side member 10c and the top surface of the IOD.

This surface potential sensor further includes a piezoelectric element 18 that acts on the side member 10G, which is a shield member, and the IOC to vibrate them. These piezoelectric elements 1B are energized by a suitable drive circuit 14 to vibrate the side member 10G and IOD, and vibrate the B mouth part 1!2 at a predetermined repetition period as shown by arrow A in FIG. . Instead of such a piezoelectric element, an electromagnetic coil may be used to cause the opening to vibrate by electromagnetic action.

These embodiments will be described with particular reference to FIG. 3 regarding the operation of the surface potential sensor. Lines of electric force Eij from the surface whose potential is to be measured, shield members 10C and 100
The light enters the shield case 1o through the opening 12 between the two, and is applied to the measuring electrode 11, which is converted into a signal representing the surface potential by the potential detection circuit 15 connected to the measuring electrode 11. Here, the opening 12 is opened to the shield member 10C by the action of the piezoelectric element 18 energized by the drive circuit 14.
and by 100 being made to vibrate.

It is repeatedly vibrated as shown by the arrows, and its opening area is changed periodically. Therefore, even if the electric lines of force from the surface to be measured are constant, they are incident through the entire aperture 12, and the number of electric lines of force (1-11) changes according to periodic changes in the aperture area due to the vibration of the aperture. , the number of lines of electric force received by the measuring electrode 11 changes similarly and is converted into an alternating current signal. The potential detection circuit 15 processes such an alternating current signal and outputs a signal representing the measured potential.

FIG. 3 is a diagram similar to FIG. 3 showing a surface potential sensor as another embodiment of the present invention. In the surface potential sensor of this embodiment, the side plate 10G and IOC as shield members in the embodiments shown in FIGS. The structure is similar to that of the embodiment shown in FIGS. 2 and 3, except that the side plates 10C' and 100' serving as shield members are bent in a V-shape. It works similarly.

As mentioned above, the surface potential sensor of the present invention directly vibrates the opening of the shield member, so there is no need for any special parts such as chopper electrodes to be placed between the opening of the shield member and the measurement electrode. Because of this, the overall thickness of the sensor can be reduced and the number of parts can be reduced, making it inexpensive. ,

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing an example of a conventionally proposed surface potential sensor, Fig. 2 is a schematic perspective view of a surface potential sensor as an embodiment of the present invention, and Fig. 3 is a surface diagram of the surface potential sensor. FIG. 3 is a schematic diagram for explaining the operation of a potential sensor. FIG. 3 is a view similar to FIG. 3 showing a surface position sensor as another embodiment of the present invention. IO... Shield case, IOC, IOC... Side member, 11... Measurement electrode, 12... Opening, 18.
... Piezoelectric element, 14... Piezoelectric element drive circuit, 15...
・Potential detection circuit.

Claims (1)

[Scope of Claims] (1) A shield member in which an opening is formed, a measurement electrode that receives lines of electric force incident through the opening, and an electric current that the measurement electrode receives when the opening area of the opening changes. A surface potential sensor comprising: driving means for vibrating the opening so that the number of lines of force changes. (21) The driving means is a surface potential sensor according to claim (1), which includes a pressure element acting on the shielding member. A surface potential sensor according to claim 1.