Piezoelectric relay with oppositely bending bimorphs

Details Piezoelectric relay with oppositely bending bimorphs Piezoelectric relay with oppositely bending bimorphs

1982-08-19

1983-09-06

Shoop, William M.

Electrical generator or motor structure

Non-dynamoelectric

Piezoelectric elements and devices

200181, 200246, 200283, H01L 4108

Patent

active

044031661

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to a piezoelectric relay using as a flexible element a piezoelectric porcelain plate having a bimorph structure.


BACKGROUND ART

FIG. 1 shows a fundamental arrangement of a flexible element as a principal element of the piezoelectric relay, and the mode of operation thereof. Referring to FIG. 1, reference numerals 1 and 1' are piezoelectric porcelain plates which are adhered to each other to constitute a flexible member 2 having a bimorph structure. One end of the flexible member 2 is supported as a cantilever by a support portion 3, and the other end thereof has a relay contact 5 through an insulating member 4. The piezoelectric porcelain plates 1 and 1' are respectively polarized in such a manner that electric fields applied to the piezoelectric porcelain plates 1 and 1' oppose to each other when a voltage is applied thereacross through input electrode lead wires 6 and 6'. Therefore, when the piezoelectric porcelain plate 1 (or 1') is straight, the piezoelectric porcelain plate 1' (or 1) is curved. As a result, the flexible member 2 is displaced as indicated by the broken lines.
In general, since flexible elements have a small displacement, two flexible members are used and displaced in opposite directions so as to double the total displacement, as described in U.S. Pat. No. 4,093,883. Furthermore, since a piezoelectric relay is generally turned on or off when input power is applied thereto, a combination of flexible members which are set from OFF to ON and from ON to OFF, respectively, is required for switching a circuit when power is supplied to the piezoelectric relay.
Known piezoelectric relays which provide a switching operation are described in U.S. Pat. No. 2,471,967 and U.S. Pat. No. 2,835,761. In these piezoelectric relays, the stroke of the movable contact is increased utilizing the principle of the "lever". However, the above-mentioned piezoelectric relays have drawbacks in that their structure is complex and pressure acting on the contact is decreased due to the principle of the "lever". Further, piezoelectric relays which do not utilize the principle of the "lever" are described in U.S. Pat. No. 2,166,763 and U.S. Pat. No. 2,182,340. In these relays, however, opposing contacts are fixed, so that a complex mechanism is required to control a small stroke. Further, the stroke must be increased by increasing drive input electric field.


DISCLOSURE OF INVENTION

It is an object of the present invention to provide a simple and multifunctional piezoelectric relay having first and second flexible members, each of which supports piezoelectric porcelain plates of a bimorph structure as a cantilever, and first, second and third relay contacts which are respectively electrically independent of each other so as to displace said first and second flexible members in opposite directions upon application of an electric field, wherein said first and second relay contacts are simultaneously displaced in the same direction within a single plane upon displacement of said first flexible member, and said third relay contact is displaced within the plane of displacement of said first and second relay contacts in the direction opposite to the direction of displacement of said first and second relay contacts, so that a switching operation of a circuit by a low drive input can be performed without utilizing the principle of the "lever", and multifunctionality is provided in accordance with the different polarities of the applied electric field.


BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view for explaining the mode of operation of a basic piezoelectric relay;
FIG. 2 is a view for explaining the mode of operation of a piezoelectric relay according to an embodiment of the present invention;
FIG. 3 is a view for explaining the mode of operation of a piezoelectric relay according to another embodiment of the present invention; and
FIGS. 4a and 4b are timing charts of input and output signals of the piezoelectric relay shown in FIG. 3.


BEST MODE OF CARRYING OUT THE INVE

REFERENCES:
patent: 2166763 (1939-07-01), Mason
patent: 2182340 (1939-12-01), Hearn
patent: 2471967 (1949-05-01), Mason
patent: 4093883 (1978-06-01), Yamamoto

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