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EP-3385668-B1 - MICRO-MECHANICAL SENSOR ELEMENT OF ANGULAR VELOCITY

EP3385668B1EP 3385668 B1EP3385668 B1EP 3385668B1EP-3385668-B1

Inventors

  • KATO, YOSHITAKA

Dates

Publication Date
20260506
Application Date
20180328

Claims (15)

  1. A vibrating angular velocity sensor element configured to detect angular velocity about a single detection axis perpendicular to a reference plane of the essentially planar sensor element, the sensor element comprising: a supporting body; at least two primary masses (101, 102) and at least two Coriolis masses (103, 104) suspended to vibrate in respect of the supporting body, the primary masses (101, 102) and the Coriolis masses (103, 104) in a stationary suspended state forming the reference plane of the sensor element; at least two coupling lever structures (108, 118, 119, 113; 109, 118, 119, 113), each of the coupling lever structures being coupled to the two primary masses (101, 102) and to one of the two Coriolis masses (103; 104); wherein the two primary masses (101, 102) are suspended to the supporting body by a spring structure (110) having a relatively low spring constant in a first direction along the reference plane, so that the spring structure (110) enables a linear primary oscillation motion of the two primary masses (101, 102) in the first direction along the reference plane, and having a relatively high spring constant in other directions, so that the spring structure (110) disables motion of the two primary masses (101, 102) in other directions; each of the two coupling lever structures (108, 118, 119, 113; 109, 118, 119, 113) is configured to relay an anti-phase primary motion of the two primary masses (101, 102) to a linear primary motion of the one coupled Coriolis mass (103; 104), which linear primary oscillation motion of the one coupled Coriolis mass (103; 104) occurs in a second direction along the reference plane, and which second direction is perpendicular to the first direction, whereby the anti-phase primary motion of the two primary masses (101, 102) is relayed to an anti-phase primary motion of the two Coriolis masses (103, 104).
  2. The angular velocity sensor element of claim 1, wherein the two coupling lever structures (108, 118, 119, 113; 109, 118, 119, 113) are disposed symmetrically on opposite sides of a first symmetry axis of the sensor element traversing through the geometrical centroid of the sensor element.
  3. The angular velocity sensor element of any of claims 1 to 2, wherein the primary masses (101, 102) are disposed symmetrically on opposite sides of a second symmetry axis of the sensor element traversing through the geometrical centroid of the sensor element, the second symmetry axis being orthogonal to the first symmetry axis.
  4. The angular velocity sensor element of any of claims 1 to 3, wherein: - the sensor element further comprises means for exciting the two primary masses (101, 102) into the linear primary oscillation motions within the plane of the essentially planar sensor element along two parallel first axes having a non-zero distance from each other; - the two coupling lever structures are coupled with first springs (118; 119) to the two primary masses (101, 102) and configured to mutually couple the linear primary oscillation motions of the primary masses (101, 102), causing the linear primary oscillation motions of the primary masses (101, 102) to have mutually opposite phases at a first nominal frequency; and - the two coupling lever structures are further coupled with second springs (113) to the two Coriolis masses (103; 104) and configured to relay the anti-phase primary oscillation motion of the primary masses (101, 102) into the anti-phase primary motions of the Coriolis masses (103, 104) at the first nominal frequency within the plane of the essentially planar sensor element along two parallel second axes having a non-zero distance from each other, wherein the second axes of the anti-phase primary motions of the Coriolis masses (103, 104) are orthogonal to the first axes of the anti-phase primary motions of the primary masses (101, 102), and wherein the anti-phase primary motions of the Coriolis masses (103, 104) have mutually opposite phases at the first nominal frequency.
  5. The angular velocity sensor element of any of claims 1 to 4, wherein - the ends of the coupling levers (108, 109) coupled to the primary masses (101, 102) and the Coriolis masses (103, 104) form an isosceles triangle; and/or - each coupling lever (108, 109) comprises a second lever (202) attached to a first lever (201) in approximately middle of the length of the first lever (201); and - the second lever (202) and the first lever (201) are attached in an angle of 90 degrees.
  6. The angular velocity sensor element of any of claims 1 to 5, wherein the combined primary mode has a total angular momentum that is less than 5% of the sum of the absolute values of the angular momenta of the two primary masses (101, 102), the two coupling levers (108, 109) and the two Coriolis masses (103, 104).
  7. The angular velocity sensor element of any of claims 1 to 6, wherein the Coriolis masses (103, 104) are further configured to be excited by the Coriolis force into first anti-phase linear secondary motions within the plane of the essentially planar sensor element along a third axis orthogonal to the second axes of the anti-phase primary motions of the Coriolis masses (103, 104), when the sensor is subject to angular velocity about the detection axis during operation.
  8. The angular velocity sensor element of any of claims 1 to 7, wherein the sensor element further comprises two sensing cells (105, 106) and the Coriolis masses (103, 104) are coupled to the sensing cells (105, 106) with third springs (125), the third springs (125) causing the sensing cells (105, 106) to be excited into second anti-phase linear secondary motions along an axis aligned with the third axis of the first linear secondary motions of the Coriolis masses (103, 104).
  9. The angular velocity sensor element of claim 8, wherein the sensing cells are mutually coupled with a second coupling arrangement (115, 116) disposed symmetrically on the first symmetry axis so that the second coupling arrangement (115, 116) extends an equal amount on both sides of the first symmetry axis, the second coupling arrangement (115, 116) causing the second anti-phase linear secondary motions of the sensing cells (105, 106) to have a second nominal frequency and the sensing cells (105, 106) to move in mutually opposite phases at the second nominal frequency.
  10. A method for operating a vibrating sensor element configured to detect angular velocity about a single detection axis perpendicular to a reference plane of the essentially planar sensor element, the sensor element comprising a supporting body, at least two primary masses (101, 102) and at least two Coriolis masses (103, 104) suspended to vibrate in respect of the supporting body, the primary masses (101, 102) and the Coriolis masses (103, 104) in a stationary suspended state forming the reference plane of the sensor element, and at least two coupling lever structures, each of the coupling lever structures (108, 118, 119, 113; 109, 118, 119, 113) being coupled to the two primary masses (101, 102) and to one of the two Coriolis masses (103, 104), the method comprising: - suspending the two primary masses (101, 102) to the supporting body by a spring structure (110) having a relatively low spring constant in a first direction along the reference plane, so that the spring structure (110) enables a linear primary oscillation motion of the two primary masses (101, 102) in a first direction along the reference plane, and having a relatively high spring constant in other directions, so that the spring structure (110) disables motion of the two primary masses (101, 102) in other directions; - relaying, by each of the two coupling lever structures (108, 118, 119, 113; 109, 118, 119, 113), an anti-phase primary motion of the two primary masses (101, 102) to a linear primary motion of the one coupled Coriolis mass (103; 104), which linear primary oscillation motion of the one coupled Coriolis mass (103, 104) occurs in a second direction along the reference plane, and which second direction is perpendicular to the first direction, whereby the anti-phase primary motion of the two primary masses (101, 102) is relayed to an anti-phase primary motion of the two Coriolis masses (103, 104).
  11. The method according to claim 10, further comprising: - exciting the two primary masses (101, 102) into the linear primary oscillation motions within the plane of the essentially planar sensor element along two parallel first axes having a non-zero distance from each other; - coupling the two coupling lever structures (108, 118, 119, 113; 109, 118, 119, 113) with first springs (118) to the two primary masses (101, 102) for mutually coupling the linear primary oscillation motions of the primary masses (101, 102), causing the linear primary oscillation motions of the primary masses (101, 102) to have mutually opposite phases at the first nominal frequency; and - coupling the two coupling lever structures with second springs (113) to the two Coriolis masses (103, 104) for relaying the anti-phase primary motion of the primary masses (101, 102) into the anti-phase primary motions of the Coriolis masses (103, 104) at the first nominal frequency, wherein the anti-phase primary oscillation motions of the Coriolis masses (103, 104) are configured to occur within the plane of the essentially planar sensor element along two parallel second axes having a non-zero distance from each other, wherein the second axes of the anti-phase primary motions of the Coriolis masses (103, 104) are orthogonal to the first axes of the anti-phase primary motions of the primary masses (101, 102), and wherein the anti-phase primary motions of the Coriolis masses (103, 104) have mutually opposite phases at the first nominal frequency.
  12. The method of claims 10, further comprising: - exciting the Coriolis masses (103, 104) into the first anti-phase linear secondary motions within the plane of the essentially planar sensor element along a third axis orthogonal to the second axes of the anti-phase primary motions of the Coriolis masses (103, 104), when the sensor is subject to angular velocity about the detection axis during operation.
  13. The method of any of claims 10 to 12, further comprising: - coupling the Coriolis masses (103, 104) to sensing cells (105, 106) with third springs (125), the third springs (125) causing the sensing cells to be excited into the second anti-phase linear secondary motions along an axis aligned with the third axis of the first linear secondary motions of the Coriolis masses (103, 104).
  14. The method of claim 13, further comprising: - mutually coupling the sensing cells (105, 106) with a second coupling arrangement (115, 116) disposed symmetrically on the first symmetry axis, wherein the second coupling arrangement (115, 116) extends an equal amount on both sides of the first symmetry axis, the second coupling arrangement (115, 116) causing the second anti-phase linear secondary motions of the sensing cells (105, 106) to have a second nominal frequency and the sensing cells (105, 106) to move in mutually opposite phases at the second nominal frequency.
  15. A sensor device comprising the sensor element of any of claims 1 to 9.

Description

Field of the invention The present invention relates to measuring devices used in measuring angular velocity and specially to vibrating sensor elements for detecting angular velocity as defined in independent claim 1. The present invention more particularly relates to a vibrating sensor element for detecting angular velocity about a single detection axis perpendicular to a plane of the essentially planar sensor element and to a sensor device comprising such sensor element. The present invention also relates to a method for operating a vibrating sensor element for detecting angular velocity as defined in independent claim 10. Background of the invention Measuring angular velocity or angular rate (absolute value of an angular velocity vector) with a vibrating sensor of angular velocity is known to be a simple and reliable concept. In a vibrating sensor of angular velocity, a primary motion of vibrating mass/es is produced and maintained in the sensor. The motion to be measured is then detected as deviation from the primary motion. International patent publication WO2010/100333 A1 discloses a micromechanical sensor of angular velocity comprising two masses coupled in the direction of a common axis. Published US patent application US 2016/0069682 discloses a rotation rate sensor with two pairs of seismic masses. Published US patent application US 2016/0334215 discloses a sensor of angular velocity with a rotor mass and two linearly moving masses. In a MEMS gyroscope, mechanical oscillation is used as the primary movement, referred also to as the primary motion or the primary mode. When an oscillating gyroscope is subjected to an angular motion orthogonal to the direction of the primary motion, an undulating Coriolis force results. This creates a secondary oscillation, also referred to as the secondary motion, the detection motion, the sense mode or the secondary mode, which is orthogonal to the primary motion and/or to the axis of the angular motion, and at the frequency of the primary oscillation. The amplitude of this coupled oscillation can be used as the measure of the angular rate, i.e. the absolute value of angular velocity. In a gyroscope device, combination of multiple moving masses may cause total angular momentum in addition to total linear momentum, both of which may cause some problems in the gyroscope device. For example, non-zero total momentum may cause instability of rate offset, rate signal noise, susceptibility to and/or interference with external mechanical shock and vibration. Brief description of the invention The object of the present invention is to provide a method and apparatus so as to overcome the prior art disadvantages and specifically to alleviate problems caused by non-zero total angular momentum. The objects of the present invention are achieved with a vibrating sensor element according to claim 1, and with a method according to claim 10. The preferred embodiments of the invention are disclosed in the dependent claims. All motions of the sensor element occur in the plane of the essentially planar sensor element, in other words, in the plane of the device. Thus, there are less dimensions to be taken into account in designing of the element if compared to a sensor element having more directions of motion enabled, and design of a well-balanced and low momentum sensor element is enabled. The present invention has the advantage that the sensor element with a sensor element according to the claims the enables reliable measurement of angular velocity with good performance. Low total angular momentum reduces detectable vibration of the sensor element. Thus, no or very little vibrational energy leaks outside of the sensor element, which improves stability of sensor device Q-value. Brief description of the figures In the following the invention will be described in greater detail, in connection with preferred embodiments, with reference to the attached drawings, in which: Figure 1a shows schematically the main structural parts of an exemplary sensor element.Figure 1b shows an exemplary embodiment of a sensor element design.Figure 2 shows an enlarged view to an exemplary coupling lever.Figure 3 shows an enlarged view of a second coupling arrangement.Figures 4a and 4b illustrate the primary motion of the Coriolis masses.Figure 5 illustrates secondary motion of the sensor element.Figure 6 illustrates a sensor device disposed inside a housing. Detailed description of the invention As known to a skilled person, a MEMS sensor element may be an essentially planar structure, and the structure of the functional, moving elements of the sensor device may be illustrated in a plane. Terms "plane of the device", "plane of the essentially planar sensor element" and "plane of the masses", refer to a plane formed by moveable masses of a sensor device or a sensor element of a sensor device in their initial position when not excited to any movement. In the coordinates in the figures of this document, this pl