Angular speed measuring transducer

• US 20060130579A1
• Filed: 12/19/2005
• Published: 06/22/2006
• Est. Priority Date: 12/20/2004
• Status: Active Grant

• Current Assignee: ETA SA Manufacture Horlogere Suisse (The Swatch Group AG)
• Original Assignee: ETA SA Manufacture Horlogere Suisse (The Swatch Group AG)
• Inventors: Dalla Piazza, Silvio, Studer, Bruno
• Granted Patent: US 7,168,319 B2
• Time in Patent Office: Days
• US Class Current: 73/504.160
• CPC Class Codes: G01C 19/5607 using vibrating tuning forks double-ended tuning forks using planar vibrating masses suspended at opposite ends G01C19/5719

Abstract

The invention concerns a transducer for measuring an angular velocity formed by a single piezoelectric tuning fork (21) that rotates at said angular velocity, including first (23) and second (24) vibrating legs extending from a base (22), excitation means (25a, 25b, 26a, 26b) arranged on the excitation leg (23), detection means (27a, 27b, 28a, 28b), arranged on the detection leg (24), characterized in that the detection leg includes at least one first groove (33, 34) on the top face and at least one second groove (35, 36) on the bottom face, and in that the detection means include first and second detection electrodes arranged facing each other, the first (27a) respectively the second detection electrode (28a) being arranged on one lateral flank of the groove (33) respectively of the groove (34) such that the electrical field between the first and second detection electrodes is substantially rectilinear through the detection leg, and third and fourth detection electrodes arranged facing each other, the third (27b) respectively the fourth detection electrode (28b) being arranged on one lateral flank of the groove (36) respectively of the groove (35), such that the electrical field between the third and fourth detection electrodes is substantially rectilinear through the detection leg.

Claims

1. A transducer for measuring an angular velocity formed by:

a single piezoelectric tuning fork that rotates at said angular velocity,

said tuning fork including first and second vibrating legs extending from a base, each leg having two main top and bottom faces and two lateral faces,

means for exciting a first vibration of the tuning fork, arranged on one of the two legs, called the excitation leg,

means for detecting a second vibration of the tuning fork generated in response to said first vibration and to a rotation of the tuning fork, arranged on the other of the two legs, called the detection leg,

wherein said detection leg includes at least one first groove on said top face and at least one second groove on said bottom face, said first and second grooves each having lateral flanks, and

wherein said detection means include first and second detection electrodes arranged facing each other, the first detection electrode being arranged on one of the lateral flanks of said first groove, the second detection electrode being arranged such that the electrical field between the first and second detection electrodes is substantially rectilinear through the detection leg, and third and fourth detection electrodes arranged facing each other, the third detection electrode being arranged on one of the lateral flanks of said second groove, the fourth detection electrode being arranged such that the electrical field between the third and fourth detection electrodes is substantially rectilinear through the detection leg.

2. The transducer for measuring an angular velocity according to claim 1, wherein said detection leg includes a third groove on said top face and a fourth groove on said bottom face, said third and fourth grooves each having two lateral flanks,

wherein said first, respectively second detection electrode is arranged on one of the lateral flanks of the first, respectively third groove, such that the electrical field between the first and second detection electrodes is substantially rectilinear through the detection leg, and

wherein said third, respectively fourth detection electrode is arranged on one of the lateral flanks of the second respectively fourth groove such that the electrical field is substantially rectilinear between the third and fourth detection electrodes through the detection leg.

3. The transducer for measuring an angular velocity according to claim 2, wherein the excitation means include first, second, third and fourth excitation electrodes arranged respectively on the top, bottom and lateral faces of the excitation leg, wherein said excitation leg has at least one first groove on the top face, respectively one second groove on the bottom face of said excitation leg, and wherein said first excitation electrode is arranged so as to cover transversely the first groove, and said third excitation electrode is arranged so as to cover transversely said second groove.

4. The transducer for measuring an angular velocity according to claim 2, wherein the tuning fork is a tuning fork with crossed electrodes.

5. The transducer for measuring an angular velocity according to claim 3, wherein the turning fork is a turning fork with crossed electrodes.

6. The transducer for measuring an angular velocity according to claim 1, wherein the second detection electrode is arranged over the entire thickness of a first lateral face of the detection leg such that the electrical field between the first and second detection electrodes is substantially rectilinear through the detection leg, and

wherein the fourth detection electrode is arranged over the entire thickness of the second lateral face of the detection leg opposite the first lateral face, such that the electrical field between the third and fourth detection electrodes is substantially rectilinear through the detection leg.

7. The transducer for measuring an angular velocity according to claim 1, wherein the piezoelectric tuning fork is a quartz whose main top and bottom faces are substantially perpendicular to the optical axis (z) of the quartz and wherein the legs extend substantially along the mechanical axis (y) of the quartz.

8. The transducer for measuring an angular velocity according to claim 1, wherein the base is provided with mechanical uncoupling means between the part for securing the base and the legs of the tuning fork.