Monolithic accelerometric transducer

• US 5,962,786 A
• Filed: 02/23/1998
• Issued: 10/05/1999
• Est. Priority Date: 09/26/1995
• Status: Expired due to Term

• Current Assignee: Office National D'Etudes et de Recherches Aerospatiales
• Original Assignee: Office National D'Etudes et de Recherches Aerospatiales
• Inventors: Muller, Serge, Le Traon, Olivier, Janiaud, Denis
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): Kwok, Helen C.
• Application Number:
  US09/027,859
• Time in Patent Office: 589 Days
• Field of Search: 73/514.29, 73/514.15, 73/514.18, 73/514.16, 73/862.59, 310/321, 310/323, 310/338, 310/25
• US Class Current: 73/514.29
• CPC Class Codes: G01P 15/097 by vibratory elements
• CPC Class Codes: G01P 2015/0817 for pivoting movement of the mass, e.g. in-plane pendulum
• CPC Class Codes: G01P 2015/0828 the mass being of the paddle type being suspended at one of its longitudinal ends

Abstract

A monolithic accelerometric transducer comprises a fixed part, two mobile mass parts and a resonator having ends fastened to said mobile parts, a flexible frame around the two mobile parts, and two connecting members connecting the frame to the second mobile part and to the fixed part. The frame provides a mechanical filter between the resonator and the fixed part which is not affected by the vibrations of the resonator. The quality factor Q of the resonator is not degraded and the measurement provided by the transducer is more accurate. In a differential output accelerometer, the position of the transducer is deduced from that of another, identical transducer by rotation of 180° about an axis parallel to the resonator, the fixed parts of the transducers being fastened together.

Claims

1. A monolithic accelerometric transducer comprising

(a) a fixed part (1);

(b) first (2) and second (4) spaced mobile mass parts;

(c) a resonator (3) connected between said first and second mobile parts;

(d) a hollow flexible frame (5) arranged in spaced relation concentrically about said first and second mobile mass parts and said resonator;

(e) a first connecting member (6) connecting said second mobile mass part with a first part of said frame; and

(f) a second connecting member (7) connecting an opposite part of said frame with said fixed part.

2. The transducer according to claim 1, wherein said flexible frame (5) is rectangular and comprises a first pair of opposed sections (51, 52) extending substantially parallel to said resonator (3), and a second pair of opposed sections (53, 54) extending substantially perpendicular to said resonator (3) said second pair of sections being connected with said second mobile mass part (4) and with said fixed part (1) by said first and second connecting members (6, 7), respectively, said first connecting member (6) having a width (L6, L6a) less than the corresponding width (L4, L4a) of said second mobile mass part (4), and said second connecting member (7) having a width (L7, L7b) less than the length of said second pair of sections (53, 54), said widths (L6, L6a;

L4, L4a;

L7, L7b) being those in the lengthwise direction (L, 30 La, Lb) of said second pair of sections (53,

     54), at least one of said connecting members (6,

     7) having a cross-sectional area (L6.E;

L7.E) in the same order of magnitude as the cross-sectional areas (L51.E, H53.E, H54.E) of said first and second pairs of frame sections.

3. The transducer according to claim 2, wherein said frame lies in a first plane (PM);

and further wherein said mobile mass parts (2,

     3), said resonator (3), said flexible frame (5) and said connecting members (6,

     7) have a common plane of symmetry (PS) perpendicular to said plane (PM) of said frame, said connecting members (6,

     7) being located at respective intersections of said frame and said plane of symmetry.

4. A transducer according to claim 1, and further including a pair of coplanar parallel blades (81, 82) arranged on opposite sides of said resonator, said blades being connected between said first and second mobile mass parts.

5. The transducer according to claim 4, wherein said blades (81, 82) have a length (HB) between one tenth and one-half the length (H3) of said resonator.

6. The transducer according to claim 5, wherein said blades (81, 82) are positioned generally opposite the middle of the length (H3) of said resonator (3).

7. The transducer according to claim 4, wherein said blades (81, 82) are flush with a face common to said first and second mobile mass parts (2, 4), said resonator (3) is flush with another face common to the first and second mobile mass parts, and said blades and said resonator have a common width (E8=E3) in the direction of the thickness (E) of said mobile mass parts.

8. The transducer according to claim 1, wherein said fixed part (Id) is arranged inside said frame (5d).

9. The transducer according to claim 1, wherein said fixed part (1e) has a generally U-shaped configuration surrounding said second connecting member (7) and adjacent portions of said frame, said fixed part including an annular base section (10e) having a middle portion fastened to said second connecting member (7e) and two branches (11e, 12e) fastened to respective ends of said base section (10e) to fix said transducer (TAe) to a base (BAe).

10. A transducer according to claim 1, comprising two electrodes (31e, 32e) supported by said resonator (3e), two contact pads (33e, 34e) supported by said fixed part (1e);

and two conductor strips (35e, 36e) supported by said second mobile mass part (4e), said first connecting member (6e), said frame (5e), said second connecting member (7e), and said fixed part (1e) for respectively connecting said two electrodes (31e, 32e) with said two contact pads (33e, 34e).

11. An accelerometer, comprising:

(a) first (TAe₁ ;

TA₁ '"'"') and second (TAe₂ ;

TA₂ '"'"') accelerometric transducers each including;

(1) a fixed part;

(2) first and second spaced mobile mass parts;

(3) a resonator connected between said first and second mobile parts;

(4) a hollow flexible frame arranged in spaced relation concentrically about said first and second mobile mass parts and said resonator;

(5) a first connecting member connecting said mobile mass part with a first part of said frame; and

(6) a second connecting member connecting an opposite part of said second frame with said fixed part;

(b) said second transducer having a position that is deduced from that of said first transducer by a rotation of 180°

about an axis (Y'"'"'Y) parallel to an axis passing through the ends of said resonator (3e₁ ;

3₁) of said first transducer; and

(c) means for fastening together said fixed parts of said first and second transducers.

12. The accelerometer according to claim 11, wherein said transducers (TAe₁, TAe₁) are symmetrical to each other about a plane parallel to coplanar faces of said mobile mass parts (2e₁, 4e₁ ;

2e₂, 4e₂) of each of said transducers.

13. The accelerometer according to claim 11, wherein said mobile mass parts (2₁, 4₁, 2₂, 4₂), said frames (5₁, 5₂) and said fixed parts (1₁, 1₂) of said transducers (TA₁ '"'"';

TA₂ '"'"') have coplanar faces, said transducers being symmetrical to each other about an axis (Y'"'"'Y) parallel to said coplanar faces.