Patent ID: 7124633

Claim:
An accelerometer micromachined in a plane plate having a base, comprising: a measurement cell including a moveable seismic mass connected to the base and capable of moving translationally along a sensitive Oy axis; of the accelerometer under the effect of an acceleration γ along this Oy axis, a resonator cell comprising a resonator that can vibrate and be subjected to a tensile or compressive force depending on the direction of acceleration γ and is placed symmetrically with respect to an axis of symmnetry S of a structure, the axis S being parallel to the Oy axis and passing through the center of gravity of the seismic mass; the measmrement cell furthermore including amplification means for amplifying an acceleration force that generates the translation, which include an anchoring foot for anchoring to the base, two rigid terminations of the resonator cell and two pairs of micromachined arms, the pairs of arms being symmetrical with respect to the axis S, each pair comprising a first arm connecting a first point of attachment to a termination and a second point of attachment to the seismic mass, and a second arm connecting a third point of attachment to the same termination and a fourth point of attachment to the anchoring foot, an angle α between an Ox axis perpendicular to the Oy axis and the line joining the first and second points of attachment being symmetrical with respect to the axis connecting the terminations via mid-points of the first and second arms, of the angle between the Ox axis and the line joining the third and fourth points of attachment and sufficiently small for the tensile or compressive force exerted on the resonator to be greater than the acceleration force exerted on the seismic mass, wherein the resonator cell comprises two rigid embedding elements for embedding the ends of the resonator and two pairs of secondary micromachined arms, the secondary pairs of arms being symmetrical with respect to the axis S, each pair comprising a first secondary arm connecting a first point of attachment to an embedding element and a second point of attachment to a termination of the cell, and a second secondary arm connecting a third point of attachment to the other embedding element and a fourth point of attachment to the same termination of the cell, an angle β between the Oy axis and the line joining the first and second points of attachment being symmetrical with respect to the axis passing through the mid-points of the embedding elements, of the angle between the Oy axis and the line joining the third and fourth points of attachment and low enough for the tensile or compressive force exerted on the resonator to be greater than the acceleration force exerted on the seismic mass.