Sensor element, angular velocity sensor, and multi-axis angular velocity sensor

A sensor element includes a piezoelectric body, a plurality of excitation electrodes, and a plurality of detecting electrodes. The piezoelectric body includes a frame and a driving arm and detecting arm which extend from the frame within a predetermined plane parallel to an xy plane in an orthogonal coordinate system xyz. The excitation electrodes are located on the driving arm. The detecting electrodes are located on the detecting arm enabling detection of a signal generated by bending deformation of the detecting arm in a z-axis direction. The detecting arm includes first and second arms. The first arm extends from the frame in the predetermined plane. The second arm extends from a front end side of the first arm toward a frame side within the predetermined plane. An end part of the second arm on the frame side is formed as a free end.

TECHNICAL FIELD

The present disclosure relates to a sensor element, an angular velocity sensor including the sensor element, and a multi-axis angular velocity sensor including the angular velocity sensor.

BACKGROUND ART

Known in the art (for example Patent Literature 1) is a so-called piezoelectric vibration type angular velocity sensor. In this sensor, an AC voltage is supplied to a piezoelectric body to excite the piezoelectric body. When this excited piezoelectric body is rotated, a Coriolis force having a magnitude in accordance with the rotation speed (angular velocity) is generated in a direction perpendicular to the direction of excitation. The piezoelectric body vibrates by this Coriolis force. Further, by detecting an electrical signal generated in accordance with the deformation of the piezoelectric body caused by this Coriolis force, the angular velocity of the piezoelectric body can be detected.

CITATION LIST

Patent Literature

Patent Literature 1: Japanese Patent Publication No. 2005-037235

SUMMARY OF INVENTION

A sensor element according to one aspect of the present disclosure includes a piezoelectric body, a plurality of excitation electrodes, and a plurality of detecting electrodes. The piezoelectric body includes abase part and a driving arm and detecting arm which extend from the base part within a predetermined plane parallel to an xy plane in an orthogonal coordinate system xyz. The plurality of excitation electrodes are located on the driving arm. The plurality of detecting electrodes are located on the detecting arm in an arrangement enabling detection of a signal generated by bending deformation of the detecting arm in a z-axis direction. The detecting arm includes a first arm and second arm. The first arm extends from the base part in the predetermined plane. The second arm is connected to a front end side portion of the first arm and extend from a front end side of the first arm toward a base part side within the predetermined plane. An end part of the second arm on the base part side is formed as a free end.

An angular velocity sensor according to one aspect of the present disclosure includes a sensor element described above, a driving circuit supplying voltages to the plurality of excitation electrodes, and a detecting circuit detecting the signals from the plurality of detecting electrodes.

A multi-axis angular velocity sensor according to one aspect of the present disclosure includes an x-axis sensor detecting an angular velocity around an x-axis in an orthogonal coordinate system xyz, a y-axis sensor detecting an angular velocity around a y-axis, and a z-axis sensor detecting an angular velocity around a z-axis. The x-axis sensor is the angular velocity sensor described above. The driving arm, the first arm, and the second arm extend in the y-axis direction. The driving circuit supplies voltages to the plurality of excitation electrodes so that the driving arm vibrates in the x-axis direction. The y-axis sensor includes a piezoelectric body, a y-axis driving circuit, and a y-axis detecting circuit. The piezoelectric body in the y-axis sensor includes a y-axis driving arm and y-axis detecting arm which extend in the y-axis direction. The y-axis driving circuit supplies voltages to the y-axis driving arm so that the y-axis driving arm vibrates in the x-axis direction. The y-axis detecting circuit detects signals generated by bending deformation of the y-axis detecting arm in the z-axis direction. The z-axis sensor includes a piezoelectric body, a z-axis driving circuit, and a z-axis detecting circuit. The piezoelectric body in the z-axis sensor includes a z-axis driving arm and z-axis detecting arm which extend in the y-axis direction. The z-axis driving circuit supplies voltages to the z-axis driving arm so that the z-axis driving arm vibrates in the x-axis direction. The z-axis detecting circuit detects signals generated by bending deformation of the z-axis detecting arm in the x-axis direction.

DESCRIPTION OF EMBODIMENTS

Below, embodiments according to the present disclosure will be explained with reference to the drawings. Note that, the following drawings are schematic ones. Therefore, details will be sometimes omitted. Further, size ratios etc. do not always coincide with the actual ones. Further, size ratios in the plurality of drawings do not always coincide with each other.

Further, to each of the drawings, for convenience of explanation, an orthogonal coordinate system xyz is attached. Note that, the orthogonal coordinate system xyz is defined based on the shape of the sensor element (piezoelectric body). That is, the x-axis, y-axis, and z-axis do not always indicate an electrical axis, mechanical axis, and optical axis of a crystal. In the sensor element, any direction may be defined as “above” or “below”. In the following explanation, however, for convenience, sometimes the “upper surface” or “lower surface” and other terms will be used where the positive side in the z-axis direction is the upper part. Further, when simply referred to as “viewed on a plane”, it means “viewed in the z-axis direction” unless particularly explained otherwise.

For the same or similar configurations, sometimes additional notations of alphabetic letters which are different from each other will be attached such as with the “driving arm7A” and “driving arm7B”. Further, in this case, sometimes the configurations will be simply referred to as the “driving arms7” and will not be differentiated.

In the second and following embodiments, for the configurations which are common or similar to the configurations in the already explained embodiments, the notations which were attached to the configurations in the already explained embodiments will be used. Further, sometimes illustration and explanations will be omitted. Note that, for configurations corresponding (similar) to the configurations in the already explained embodiments, even in a case where notations which are different from those for the configurations in the already explained embodiments are attached, the matters not particularly described are the same as those of the configurations in the already explained embodiments.

First Embodiment

FIG.1is a perspective view showing the configuration of a sensor element1according to a first embodiment. However, in this view, basically illustration of a conductive layer which is provided on the surface of the sensor element1is omitted.

The sensor element1for example configures a piezoelectric vibration type angular velocity sensor51(notation is shown inFIG.3) which detects the angular velocity around the x-axis. The sensor element1has a piezoelectric body3. When the piezoelectric body3is rotated in a state where voltage is supplied to the piezoelectric body3and the piezoelectric body3is vibrating, vibration is generated by a Coriolis force in the piezoelectric body3. By detecting the voltage generated due to the vibration by this Coriolis force, the angular velocity is detected. Specifically, this is as follows.

The piezoelectric body3is for example formed integrally as a whole. The piezoelectric body3may be a single crystal or polycrystal. Further, the material for the piezoelectric body3may be suitably selected. For example, it is a quartz crystal (SiO2), LiTaO3, LiNbO3, PZT, or silicon.

In the piezoelectric body3, the electrical axis or polarization axis (below, sometimes only the polarization axis will be referred to as representative of the two) are set so as to coincide with the x-axis. Note that, the polarization axis may be inclined relative to the x-axis within a predetermined range (for example 15° or less) as well. Further, in a case where the piezoelectric body3is a single crystal, the mechanical axis and optical axis may be made suitable directions. For example, the mechanical axis is made the y-axis direction and the optical axis is made the z-axis direction.

The piezoelectric body3is for example made constant in thickness (z-axis direction) as a whole. Further, the piezoelectric body3is formed in a line symmetrical shape relative to a not shown symmetrical axis parallel to the y-axis.

The piezoelectric body3for example has a frame5, a pair of driving arms7A and7B and a detecting arm9which extend from the frame5, and a pair of mounting parts11supporting the frame5. The frame5, pair of driving arms7, detecting arm9, and pair of mounting parts11for example extend within the same plane parallel to the xy plane.

The pair of driving arms7are portions which are excited by supply of voltage (electric field). The detecting arm9is a portion which vibrates due to the Coriolis force and generates an electrical signal (for example voltage) in accordance with the angular velocity. The frame5is a portion which contributes to support of the driving arms7and detecting arm9and transfer of vibration from the driving arms7to the detecting arm9. The mounting parts11are portions contributing to mounting of the sensor element1on a not shown mounting body (for example a portion of a package or a circuit board).

The frame5for example has a long shape having two ends separated from each other in the x-axis direction. Specifically, for example, the frame5linearly extends in the x-axis direction. The two ends of the frame5become supported parts5awhich are supported by the pair of mounting parts11. Accordingly, the frame5becomes able to flexurally deform like a beam supported at its two ends.

The cross-sectional shape of the frame5is for example schematically rectangular. Either of the width (y-axis direction) or thickness (z-axis direction) of the frame5may be larger than the other. However, the frame5, as will be explained later, is designed to flexurally deform when viewed on a plane. Accordingly, the width of the frame5may be made relatively small. For example, the width of the frame5may be made 2 times or less or made 1 time or less of the thickness of the frame5. Further, for example, the length and width of the frame5may be adjusted so that the natural frequency of the flexural deformation becomes closer to the natural frequency of the driving arms7in a direction in which they are excited by application of voltage and/or the natural frequency of the detecting arm9in a direction in which it vibrates due to the Coriolis force.

The driving arms7extend from the frame5in the y-axis direction. Their front ends are formed as free ends. Accordingly, the driving arms7become able to flexurally deform like a cantilever. The pair of driving arms7extend alongside each other (for example in parallel) at positions separated from each other in the x-axis direction. The pair of driving arms7are for example provided line symmetrical relative to a not shown symmetrical axis which passes through the center between the pair of supported parts5aand is parallel to the y-axis.

The specific shapes etc. of the driving arms7may be suitably set. For example, the driving arms7are long rectangular cuboid shaped. That is, the cross-sectional shape (xz plane) is rectangular. Although not particularly shown, the driving arm7may be hammer shaped with the width (x-axis direction) becoming broader at the front end side portion as well. The pair of driving arms7are for example substantially mutually symmetrically shaped and sized. Accordingly, the vibration characteristics of the two are equal to each other.

The driving arms7are excited in the x-axis direction as will be explained later. Accordingly, in the driving arms7, the larger the width (x-axis direction), the higher the natural frequency in the excitation direction (x-axis direction). Further, the larger the length (mass from another viewpoint), the lower the natural frequency in the excitation direction. The various dimensions of the driving arms7are for example set so that the natural frequency in the excitation direction of the driving arms7becomes close to the frequency at which excitation is desired be caused.

The detecting arm9has a first arm21extending from the frame5and has second arms23A and23B extending from the front end side and lateral sides of the first arm21toward the frame5side. The front ends of the second arms23are not connected to the frame5, but become free ends. Accordingly, in the detecting arm9, the first arm21can flexurally deform with the frame5as the fixed end side and with its front end side as the free end side. Further, the second arms23can flexurally deform with respect to the first arm21as the standard by making the sides of connection with the first arm21the fixed end sides and make the frame5sides the free end sides. Note that, the “front end side of the first arm21” for example designates a further front end side from the center in the long direction of the first arm21. The first arm21and pair of second arms23for example extend within the same plane parallel to the xy plane.

The first arm21for example extends from the frame5in the y-axis direction at a position between the pair of driving arms7in the x-axis direction. Further, the first arm21for example extends toward the same side (positive side in the y-axis direction) as the side of extension of the pair of driving arms7. From another viewpoint, the first arm21extends alongside (for example in parallel to) the pair of driving arms7. The first arm21is for example positioned at the center between the pair of supported parts5aand/or positioned at the center between the pair of driving arms7. The length of the first arm21is for example about the same as the lengths of the driving arms7.

The pair of second arms23are for example made line symmetrical positions and shapes relative to the first arm21. The second arms23for example extend in the y-axis direction and in turn extend alongside (for example in parallel to) the first arm21. The second arms23are for example connected at their end parts to the front end part of the first arm21. Specifically, between the side surfaces of the first arm21and the side surfaces of the second arms23which face them, connection parts (notation is omitted) having the same thicknesses (z-axis direction) as those of these arms are interposed. The lengths of the second arms23are for example lengths which are obtained by subtracting gaps between the second arms23and the frame5from the lengths of the driving arms7and first arm21. The gaps are for example made relatively small.

The specific shapes etc. of the first arm21and second arms23may be suitably set. For example, each of the first arm21and second arms23is made long rectangular cuboid shaped. That is, the cross-sectional shape (xz plane) is rectangular. Although not particularly shown, the second arms23may be hammer shaped with widths (x-axis direction) becoming broader at the end parts on the frame5side as well. Further, the second arms23may be hammer shaped so that the widths becomes broader toward the sides opposite to the first arm21in the end parts on the sides where they are connected to the first arm21.

The detecting arm9(first arm21and second arms23), as will be explained later, vibrates in the z-axis direction due to the Coriolis force in the present embodiment. Accordingly, in the detecting arm9, the larger the thickness (z-axis direction), the higher the natural frequency in the vibration direction (z-axis direction). Further, the larger the length (from another viewpoint, mass), the lower the natural frequency in the vibration direction. The various dimensions of the detecting arm9for example may be set so that the natural frequency in the vibration direction of the detecting arm9becomes closer to the natural frequency in the excitation direction of the driving arms7.

Further, the intervals between the first arm21and the second arms23, the intervals between the second arms23and the frame5, and the dimensions of the connection portions of the first arm21and the second arms23may also be suitably set. For example, the above intervals are set so that the portions seldom abut against each other. Further, for example, the areas of the yz cross-sections of the connection portions of the first arm21and the second arms23may be smaller than, equal to, or larger than the area of the xz cross-sections of the first arm21or second arms23. Note that, when the areas of the yz cross-sections of the connection portions are made larger, for example, it becomes easier to transfer a moment about the x-axis from the second arms23to the first arm21.

The pair of mounting parts11are for example formed in shapes having the y-axis direction as the long directions. More specifically, for example, the mounting parts11are plate shaped having rectangular planar shapes so that the z-axis direction becomes the thickness direction. The widths (x-axis direction) of the mounting parts11are for example broader than the width (y-axis direction) of the frame5, widths (x-axis direction) of the driving arms7, and the width (x-axis direction) of the detecting arm9(first arm21or second arms23in that). Accordingly, the mounting parts11become harder to flexurally deform (vibration) when viewed on a plane compared with the other portions (5,7,21, and23). However, the mounting parts11, in part or whole, may be made narrower in width compared with the other portions (5,7,21, or23) as well. The lengths of the mounting parts11may be suitably set. For example, the length from the frame5up to single ends of the mounting parts11may be shorter than (example shown), equal to, or longer than the lengths of the driving arms7or detecting arm9.

The frame5, as already explained, is fixed at its two ends (supported portions5a) to the pair of mounting parts11. The positions of the supported portions5ain the y-axis direction relative to the mounting parts11may be suitable ones. In the example shown, the supported portions5aare positioned at the center in the y-axis direction of the mounting parts11.

The lower surfaces of the pair of mounting parts11are provided with at least four pads13. The pads13face pads provided on a not shown mounting body and are bonded with the pads on the mounting body by bumps made of solder or conductive adhesive. Due to this, electrical connection of the sensor element1and the mounting body is achieved. Further, the frame5, driving arms7, and detecting arm9are supported in a state where they float above the mounting body and become able to vibrate. Note that, the frame5ends up being supported upon the pads13through the mounting parts11in the portions closer to the two sides of the x-axis direction (supported portions5a) than the pair of driving arms7. The four pads13are for example provided on the two ends in the pair of mounting parts11.

FIG.2is a perspective view showing a portion of the sensor element1in an enlarged manner. Further,FIG.3is a cross-sectional view taken along the III-III line inFIG.2.

The sensor element1has, as conductors which are provided on the surface etc. of the piezoelectric body3other than the pads13described above, excitation electrodes15A and15B for supplying voltages to the driving arms7, detecting electrodes17A and17B for extracting signals generated in the detecting arm9, and a plurality of wirings19connecting these electrodes. These conductors are configured by conductor layers formed on the surface of the piezoelectric body3. The materials for the conductor layers are for example Cu, Al, or another metal.

Note that, the additional notations A and B of the excitation electrodes15and detecting electrodes17are attached based on the orthogonal coordinate system xyz. Accordingly, as will be explained later, the excitation electrode15A on one driving arm7and the excitation electrode15A on the other driving arm7do not always have the same potential. The same is true for the excitation electrodes15B and detecting electrodes17A and17B.

At each of the driving arms7, the excitation electrode15A is provided at each of the upper surface and lower surface (a pair of surfaces facing the two sides in the z-axis direction). Further, at each of the driving arms7, the excitation electrode15B is provided at each of the pair of side surfaces (a pair of surfaces facing the two sides in the x-axis direction).

Note that, in the embodiments which will be explained later, sometimes provision is made of driving arms7which extend from the frame5toward the negative side in the y-axis direction. In such driving arms7as well, the additional notations “A” of the excitation electrodes15correspond to the upper surfaces and lower surfaces, and the additional notations “B” of the excitation electrodes15correspond to the side surfaces.

On each of the upper, lower, left, and right surfaces of each of the driving arms7, the excitation electrode15is for example formed so as to cover most of the surface. However, at least one of each two excitation electrodes15A and15B (excitation electrodes15A in the present embodiment) is formed smaller in the width direction than the surface so that the electrodes are not short-circuited with each other. Further, parts of the root sides and front end sides of the driving arms7may be made positions where no excitation electrodes15are arranged.

At each of the driving arms7, the two excitation electrodes15A are for example given the same potential as each other. For example, the two excitation electrodes15A are connected to each other by the wiring19. Further, at each of the driving arms7, the two excitation electrodes15B are for example given the same potential as each other. For example, the two excitation electrodes15B are connected to each other by the wiring19.

In such arrangement and connection relationships of the excitation electrodes15, if voltage is supplied between the excitation electrodes15A and the excitation electrodes15B, for example, in the driving arms7, an electric field going from the upper surface toward the pair of side surfaces (two sides in the x-axis direction) and an electric field going from the lower surface toward the pair of side surfaces are generated. On the other hand, the polarization axis matches with the x-axis direction. Accordingly, when focusing on the components in the x-axis direction of the electric fields, in the driving arm7, the orientation of the electric field and the orientation of the polarization axis match in one side portion of the x-axis direction, while the orientation of the electric field and the orientation of the polarization axis become inverse to each other in the other side portion.

As a result, single side portions of the driving arms7in the x-axis direction contract in the y-axis direction, and the other side portions extend in the y-axis direction. Further, the driving arms7flex to one side in the x-axis direction like a bimetal. If the voltages supplied to the excitation electrodes15A and15B are inverted, the driving arms7flex to an inverse direction. According to such a principle, if an AC voltage is supplied to the excitation electrodes15A and15B, the driving arms7vibrate in the x-axis direction.

Note that, although particularly not shown, one or more recessed grooves extending along the long directions of the driving arms7(a recessed groove may be configured by a plurality of recessed parts arranged in the long direction of the driving arm7as well) may be provided in the upper surfaces and/or lower surfaces of the driving arms7, and the excitation electrodes15A may be provided over the interiors of the recessed grooves. In this case, the excitation electrodes15A and the excitation electrodes15B face each other in the x-axis direction while sandwiching the wall portions of the recessed grooves therebetween, therefore the efficiency of excitation is improved.

Between the pair of driving arms7, the excitation electrodes15A on the driving arm7A and the excitation electrodes15B on the driving arm7B are given the same potential, while the excitation electrodes15B on the driving arm7A and the excitation electrodes15A on the driving arm7B are given the same potential. The excitation electrodes15which must be given the same potential are for example connected to each other by the wiring19.

Accordingly, if applying AC voltage between the excitation electrodes15A and the excitation electrodes15B, voltages having inverse phases from each other are supplied to the pair of driving arms7, therefore the arms vibrate so as to flexurally deform in reverse orientations to each other in the x-axis direction.

In each of the first arm21and second arms23, the detecting electrodes17A are provided in the region on the positive side in the z-axis direction (for example, the side more positive than the center of the surface) in the surface facing the negative side in the x-axis direction and in the region on the negative side in the z-axis direction (for example, the side more negative than the center of the surface) in the surface facing the positive side in the x-axis direction. In each of the detecting arm9, the detecting electrodes17B are provided in the region on the negative side in the z-axis direction (for example, the side more negative than the center of the surface) in the surface facing the negative side in the x-axis direction and in the region on the positive side in the z-axis direction (for example, the side more positive than the center of the surface) in the surface facing the positive side in the x-axis direction.

Note that, in the embodiments which will be explained later, sometimes provision is made of a detecting arm9which is positioned on the negative side in the y-axis direction relative to the frame5. In such a detecting arm9as well, the additional notations “A” of the detecting electrodes17show the regions of +z in the side surfaces of −x and the regions of −z in the side surfaces of +x, while the additional notations “B” of the detecting electrodes17show the regions of −z in the side surfaces of −x and the regions of +z in the side surfaces of +x.

At each of the side surfaces of the first arm21and second arms23, the detecting electrode17A and the detecting electrode17B extend along the arm so that they are separated by a suitable interval so as not to short-circuit with each other. In each of arms, two detecting electrodes17A are for example connected with each other by the wiring19. Further, in each of arms, two detecting electrodes17B are connected with each other by for example the wiring19.

In such an arrangement and connection relationships of the detecting electrodes17, if the first arm21or second arms23flexurally deform in the z-axis direction, for example, an electric field parallel to the z-axis direction is generated. That is, on each of the side surfaces of the arms, voltage is generated between the detecting electrode17A and the detecting electrode17B. The orientations of the electric fields are determined by the orientation of the polarization axes and the orientation of the flexes (positive side or negative side in the z-axis direction). They are inverse to each other between the positive side portions and the negative side portions in the x-axis direction. These voltages (electric fields) are output to the detecting electrodes17A and detecting electrodes17B. When each of the arms (21or23) vibrates in the z-axis direction, the voltage is detected as AC voltage. Note that, among the electric fields, electric fields parallel to the z-axis direction may be dominant as described above or a ratio of the electric fields which are parallel to the x-axis direction and have inverse orientations to each other between the positive side portions and the negative side portions in the z-axis direction may be larger. In any case, voltage in accordance with the flexural deformation of each of the arms (21or23) in the z-axis direction is generated between the detecting electrodes17A and the detecting electrodes17B.

Between the pair of second arms23, the detecting electrodes17A are connected with each other and, further, the detecting electrodes17B are connected with each other. In such connection relationships, if the pair of second arms23flexurally deform to the same sides as each other in the z-axis direction, potentials having the same polarities as each other are generated in the detecting electrodes17which are connected with each other. In turn, signals generated in the pair of second arms23are added.

Further, between the first arm21and the second arms23, the detecting electrodes17A and the detecting electrodes17B are connected. In such connection relationships, if the first arm21and the second arms23flexurally deform to inverse sides from each other in the z-axis direction, potentials having the same polarities as each other are generated in the detecting electrodes17which are connected to each other. In turn, signals generated in the first arm21and the second arms23are added.

The wirings19for example are responsible for mutual connection of the excitation electrodes15and mutual connection of the detecting electrodes17as explained above. Further, the wirings19connect four sets of electrodes in total and the four pads13. The four sets of electrodes are comprised of the excitation electrodes15which are divided into two sets from a viewpoint of potentials and the detecting electrodes17divided into two sets from a viewpoint of potentials.

By suitable arrangement of the plurality of wirings19on the upper surfaces, lower surfaces, and/or side surfaces of various parts in the piezoelectric body3, the connections explained above can be realized without short-circuiting with each other in a mode where the entireties thereof are provided on the surfaces of the piezoelectric body3. However, three-dimensional wiring portions in which the wirings19intersect the other wirings19positioned on the piezoelectric body3above the same through insulation layers may be formed as well.

(Driving Circuit and Detecting Circuit)

As shown inFIG.3, the angular velocity sensor51has a driving circuit103supplying voltages to the excitation electrodes15and a detecting circuit105detecting electrical signals from the detecting electrodes17.

The driving circuit103is for example connected through two among the four pads13to the excitation electrodes15. The driving circuit103is configured including for example an oscillation circuit and amplifier and supplies an AC voltage having a predetermined frequency between the excitation electrodes15A and the excitation electrodes15B. Note that, the frequency may be determined in advance in the angular velocity sensor51or may be designated from an external apparatus or the like.

The detecting circuit105, for example, is connected through the two among the four pads13to the detecting electrodes17. The detecting circuit105, for example, is configured including an amplifier and wave detecting circuit, detects a potential difference between the detecting electrode17A and the detecting electrode17B, and outputs an electrical signal in accordance with the detection result to an external apparatus or the like. More specifically, for example, the potential difference described above is detected as the AC voltage, and the detecting circuit105outputs a signal in accordance with the amplitude of the detected AC voltage. The angular velocity is identified based on this amplitude. Further, the detecting circuit105outputs a signal in accordance with a phase difference between the applied voltage of the driving circuit103and the electrical signal which was detected. The orientation (positive/negative) of rotation is identified based on this phase difference.

Note that, the driving circuit103and detecting circuit105configure a control circuit107as a whole. The control circuit107is for example configured by a chip type IC (integrated circuit) and is mounted on a circuit board or a mounting body having a suitable shape with the sensor element1.

(Operation of Angular Velocity Sensor)

FIG.4AandFIG.4Bare schematic plan views for explaining excitation of the piezoelectric body3. In these views, the detecting arm9is schematically shown as one arm as a whole without differentiating between the first arm21and second arms23.

BetweenFIG.4AandFIG.4B, phases of AC voltages supplied to the excitation electrodes15are offset by 180° from each other. As explained above, the driving arms7A and7B are excited with inverse phases from each other so as to deform in inverse orientations to each other in the x-axis direction by application of AV voltage to the excitation electrodes15.

At this time, as shown inFIG.4A, if the pair of driving arms7warp to the outer side in the x-axis direction relative to each other, the bending moments thereof are transferred to the frame5, and the frame5warps to the positive side in the y-axis direction. As a result, the detecting arm9displaces to the positive side in the y-axis direction.

Conversely, as shown inFIG.4B, if the pair of driving arms7warp to the inner sides in the x-axis direction relative to each other, bending moments thereof are transferred to the frame5, and the frame5warps to the negative side in the y-axis direction. As a result, the detecting arm9displaces to the negative side in the y-axis direction.

Accordingly, due to excitation of the pair of driving arms7, the detecting arm9vibrates (displaces) in the y-axis direction.

FIG.4CandFIG.4Dare schematic perspective views for explaining the vibration of the detecting arm9due to the Coriolis force. In these views, however, in the same way asFIG.4AandFIG.4B, the first arm21and the second arms23in the detecting arm9are not differentiated. The entirety thereof is schematically shown as one arm. Further, in these views, illustration of deformation of the driving arms7and frame5is omitted. Parts of the other schematic views for explaining the vibration of the detecting arm are similarly omitted.

FIG.4CandFIG.4Dcorrespond to the states ofFIG.4AandFIG.4B. If the sensor element1is rotated around the x-axis in the state where vibration explained with reference toFIG.4AandFIG.4Bis generated, the detecting arm9vibrates (is deformed) in the direction (z-axis direction) perpendicular to the rotation axis (x-axis) and to the vibration direction (y-axis direction) due to the Coriolis force since it is vibrating (displaced) in the y-axis direction.

FIG.5AandFIG.5Bare schematic perspective views for explaining the vibration of the detecting arm9due to the Coriolis force in more detail thanFIG.4CandFIG.4D. In these views, the first arm21and second arms23are also schematically shown.

FIG.5AandFIG.5Bcorrespond toFIG.4CandFIG.4D. As explained with reference toFIG.4CandFIG.4D, the detecting arm9receives the Coriolis force in the z-axis direction.

As a result, the second arms23flexurally deform so as to bend in the direction of the Coriolis force indicated by an arrow y1. Further, the bending moments acting to make the second arms23flexurally deform act upon the first arm21so that they are transferred through the connection portions of the second arms23and the first arm21to the first arm21as indicated by an arrow y2to make the first arm21flexurally deform to bend to the side opposite to the direction of the Coriolis force. Accordingly, the first arm21and the second arms23end up flexurally deforming to inverse sides from each other in the z-axis direction.

The signals (voltages) generated due to the flexural deformation in the first arm21and second arms23in the z-axis direction are extracted by the detecting electrodes17. Further, the signals generated in the first arm21and second arms23are added. The larger the angular velocity, the larger the Coriolis force (in turn the voltage of the signal detected). Due to this, the angular velocity is detected.

As described above, in the present embodiment, the sensor element1has a piezoelectric body3, a plurality of excitation electrodes15, and a plurality of detecting electrodes17. The piezoelectric body3has a frame5(base part) and has driving arms7and a detecting arm9which extend from the frame5within a predetermined plane parallel to the xy plane in an orthogonal coordinate system xyz. The plurality of excitation electrodes15are positioned on the driving arms7. The plurality of detecting electrodes17are positioned on the detecting arm9in an arrangement enabling detection of signals generated due to the bending deformation in the z-axis direction of the detecting arm9. The detecting arm9has a first arm21and second arms23. The first arm21extends from the frame5within the predetermined plane. The second arms23are connected to the front end side portions of the first arm21and extend from the front end side of the first arm21toward the frame5in the predetermined plane. The end parts of the second arms23on the frame5side are formed as free ends.

Accordingly, for example, vibration energy escaping to the frame5can be reduced. Specifically, this is as follows.

InFIG.4CandFIG.4D, the detecting arm9was schematically shown as if it were one arm. Here, it is assumed that the detecting arm9is actually configured by one arm. In this case, as indicated by an arrow y3inFIG.4CandFIG.4D, the Coriolis force received by the detecting arm9acts as a moment acting to make the frame5deform (torsional deformation in the present embodiment). As a result, for example, energy making the detecting arm9vibrate will escape to the frame5, so the detection sensitivity is lowered.

On the other hand, in a case where the detecting arm9has the first arm21and second arms23, as explained with reference toFIG.5AandFIG.5B, moments acting to make the first arm21warp to the inverse direction to the direction of the Coriolis force indicated by the arrow y1are generated. Accordingly, due to the moments in the first arm21, the moment acting to cause deformation in the frame5as described above is reduced. As a result, for example, leakage of vibration energy from the detecting arm9to the frame5is reduced, so the detection sensitivity is improved.

Further, in the present embodiment, at least part of the plurality of detecting electrodes17are positioned on the second arms23.

Here, when comparing the first arm21and the second arms23, bending tends to become larger in the second arms23in which the direction of the Coriolis force and the direction of bending coincide. Accordingly, at least by providing the detecting electrodes17on the second arms23, the detection sensitivity can be made higher.

Further, in the present embodiment, the plurality of detecting electrodes17are positioned on the first arm21and second arms23. The wirings19connect the plurality of detecting electrodes17on the first arm21and the plurality of detecting electrodes17on the second arms23in connection relationships whereby the detecting electrodes17generating potentials having the same polarities as each other at the time when the first arm21and the second arms23bend to inverse sides from each other in the z-axis direction are connected to each other.

Accordingly, for example, the signals accompanying deformation of the piezoelectric body can respectively be detected in the first arm21and second arms23and these signals can be totaled up. As a result, for example, the detection sensitivity is improved compared with a mode in which the detecting electrodes17are provided on only either of the first arm21or the second arms23(this mode also included in the art according to the present disclosure).

Further, in the present embodiment, the detecting arm9has only one first arm21and only two second arms23which are positioned on the two lateral sides of the first arm21.

Accordingly, for example, it is easy to increase the mass of the detecting arm9while maintaining the balance of the detecting arm9. As a result, for example, entry of noise can be reduced. Further, for example, the two second arms23worth of mass is added to the front end of the single first arm21, therefore the moment applied from the second arms23to the first arm21tends to become larger. As a result, for example, the vibration energy escaping to the frame5is easily reduced.

Further, in the present embodiment, the base part (frame5) has a long shape in which the two ends are separated from each other in the x-axis direction. The piezoelectric body3has the pair of driving arms7which extend from the frame5alongside each other in the y-axis direction at positions where they are separated from each other in the x-axis direction. The first arm21extends from the frame5in the y-axis direction at a position between the pair of driving arms7in the x-axis direction. The plurality of excitation electrodes15are provided in an arrangement enabling supply of voltage for exciting the pair of driving arms7in the x-axis direction. The plurality of pads13are positioned in the piezoelectric body3so as to be able to support portions in the frame5(supported portions5a) which are closer to the two sides in the x-axis direction than the pair of driving arms7. The plurality of wirings19connect the plurality of excitation electrodes15in a connection relationships whereby voltages having inverse phases from each other making the pair of driving arms7vibrate to inverse sides from each other in the x-axis direction are supplied from the plurality of excitation electrodes15to the pair of driving arms7.

Accordingly, detection by a new mode of vibration of using excitation of the pair of driving arms7to make the frame5flex (vibrate) and make the detecting arm9displace (vibrate) and using the Coriolis force acting upon this displacing detecting arm9to detect the angular velocity becomes possible.

As another mode of vibration which is different from such a mode of vibration, for example, there can be mentioned the mode of making the Coriolis force act upon the excited driving arm to cause vibration and transferring the vibration due to the Coriolis force to the detecting arm. In the new mode of vibration of the present embodiment, unlike the other modes of vibration, the Coriolis force directly acts upon the detecting arm. As a result, for example, the detection sensitivity is improved. Note that, the other modes of vibration described above may be applied to the art of the present disclosure (detecting arm having the first arm and second arm).

Further, as another mode of vibration, for example, there can be mentioned a mode in which the detecting arm is made to deform by bending (vibrate) in the same direction as the vibration direction of the driving arms (x-axis direction) and in which the Coriolis force is made to act upon this vibrating detecting arm. In the new mode of vibration of the present embodiment, the vibration direction of the detecting arm is different from that in the other mode, so it becomes possible to detect the angular velocity for the rotation axis (x-axis) for which the angular velocity could not be detected in the other mode of vibration. Note that, the other mode of vibration may also be applied to the art of the present disclosure (detecting arm having the first arm and second arm).

In the new mode of vibration in the present embodiment, the frame5is made relatively thin so that flexural deformation to the y-axis direction can occur. Accordingly, in the frame5, torsional deformation is easily caused due to the Coriolis force acting upon the driving arms7and detecting arm9. In the present embodiment, however, due to the mode of operation explained above resulting from the provision of the first arm21and second arms23in the detecting arm9, this torsional deformation can be reduced. As a result, for example, the vibration energy becomes easier to seal in at the internal portion of the piezoelectric body3, therefore the detection sensitivity can be improved.

Further, in the present embodiment, the detecting arm9is positioned at the center between the pair of driving arms7.

In the new mode of vibration described above, the flexural deformation of the frame5tends to become larger at the center between the pair of driving arms7. Due to the detecting arm9being positioned at such a position, the amplitude of the detecting arm9can be larger to make the detection sensitivity larger. Note that, in the art referred to as “the other mode of vibration” in which the detecting arm is made to deform by bending (vibrate) in the vibration direction of the driving arms and the Coriolis force is made to act upon that vibrating detecting arm, in principle, for example, a pair of detecting arms are arranged line symmetrical relative to the center between the pair of driving arms or one driving arm and one detecting arm are arranged like a tuning fork.

Further, in the present embodiment, the piezoelectric body3has only one pair of driving arms7as arms extending from the frame5and vibrating by application of voltage (as will be explained later, it is also possible to provide another driving arm7extending alongside the pair of driving arms7). That is, no other driving arm which extends from the frame5to the side opposite to the driving arms7(negative side in the y-axis direction in the example shown) is provided.

Accordingly, for example, flexural deformation can be reliably caused in the frame5by the pair of driving arms7. Note that, in a comparative example in which the detecting arm is positioned at the center of the pair of driving arms (see Patent Literature 1), for example, provision is made of another pair of driving arms which extend to the side opposite to the pair of driving arms so as not to cause flexing as in the present embodiment in the part corresponding to the frame5, and the other pair of driving arms are excited with the same phase as that of the pair of driving arms.

Second Embodiment

FIG.6is a view, similar toFIG.1, showing the configuration of a sensor element201according to a second embodiment.

The sensor element210(piezoelectric body203) differs from the sensor element1(piezoelectric body3) in the first embodiment in the configuration of the detecting arm. Further, along with the difference, the connection relationships of the detecting electrodes17by the wirings19also differ. The rest of the configuration is the same as in the first embodiment. Specifically, this is as follows.

A detecting arm209in the present embodiment, in the same way as the detecting arm9in the first embodiment, has first arms21extending from a frame5and a second arm23connected to the front end side portions of the first arms21and extending from the front end sides of the first arms21toward the frame5. However, in contrast to the first embodiment in which one first arm21and two second arms23were provided, in the present embodiment, two first arms21(21A and21B) and one second arm23are provided.

The pair of first arms21are for example provided with line symmetrical positions and shapes relative to a not shown symmetrical axis which passes through the center of the pair of driving arms7and is parallel to the y-axis. The second arm23is for example positioned between the pair of first arms21and is connected to the front end side portions of the both of the pair of first arms21. Note that, the detecting arm209having such first arms21and second arm23is one example of a detecting arm which is positioned at the center between a pair of driving arms7in the same way as the detecting arm9in the first embodiment.

The configurations of the first arms21and second arm23and the configurations of the connection portions connecting them may be the same as those in the first embodiment. Naturally, specific dimensions may be different from those in the first embodiment in accordance with differences of the numbers and arrangement of the first arms21and second arms23.

The shapes, arrangement, and connection relationships of the plurality of detecting electrodes17in each of the first arms21and second arm23may be the same as those in the first embodiment. In the present embodiment, however, corresponding to the fact that there are two first arms21, between the two first arms21, the detecting electrodes17A are connected to each other, and the detecting electrodes17B are connected to each other. The connections are for example carried out by wirings19. Note that, between the first arms21and the second arm23, in the same way as the first embodiment, the detecting electrodes17A and the detecting electrodes17B are connected by wirings19. Also, the connection of the plurality of detecting electrodes17divided into two sets with two pads13by the wirings19is the same as that in the first embodiment.

As apparent from the explanation of the configuration described above, the operations of the sensor element201and the angular velocity sensor including the sensor element201are basically the same as the operations of the sensor element1and angular velocity sensor51in the first embodiment. For example, a new mode of vibration in which the detecting arm209displaces in the y-axis direction due to vibration in the x-axis direction of the pair of driving arms7and the Coriolis force in the z-axis direction acts upon the detecting arm209according to the rotation around the x-axis is realized. Further, for example, the second arm23flexurally deforms so as to bend to the direction of the Coriolis force, and a moment acting to bend the first arms21to the side opposite from the direction of the Coriolis force acts from the second arm23to the first arms21.

As described above, in the present embodiment as well, the detecting arm209has the first arms21and the second arm23. Accordingly, the same effects as those by the first embodiment are exhibited. For example, by the moment acting to bend the first arms21to the inverse side from the direction of the Coriolis force acting from the second arm23to the first arms21, a moment acting to cause deformation in the frame5(see the arrow y3inFIG.4) is reduced.

Further, in the present embodiment, the detecting arm209has only two first arms21and only one second arm23which is positioned between the two first arms21.

Accordingly, for example, it is easy to increase the mass of the detecting arm209while maintaining the balance of the detecting arm209. As a result, for example, entry of noise can be reduced. Further, for example, the moment acting to bend the first arms21to the inverse side from the direction of the Coriolis force is reliably transferred to the frame5by the two first arms21while the possibility of occurrence of stress concentration can be reduced.

Third Embodiment

FIG.7Ais a plan view showing the configuration of a sensor element301according to a third embodiment. However, in this view, illustration of the conductive layer provided on the surface of the sensor element301is basically omitted.

The piezoelectric body303in the sensor element301is shaped as if two piezoelectric bodies3in the first embodiment were combined. That is, the piezoelectric body303has two units304A and304B. Each unit304has a frame5, at least one pair of (two pairs in the present embodiment) driving arms7(7C to7J) which extend from the frame5alongside each other in the y-axis direction, and a detecting arm309(309A and309B).

The two units304are arranged so as to make the sides opposite from the directions of extension of the driving arms7and detecting arms309face each other and are supported upon a common pair of mounting parts11. The distance between the two units304for example may be suitably set so that the frames5A and5B do not contact each other. The two units304are for example the same shape and size (have line symmetrically shapes and sizes relative to a not shown symmetrical axis parallel to the x-axis).

Further, the piezoelectric body3in the first embodiment had one pair of driving arms7with respect to one frame5. However, each of the units304in the piezoelectric body303has two pairs of driving arms7with respect to one frame5. As will be explained later (FIG.8AandFIG.8B), two mutually neighboring driving arms7(two of7C and7D, two of7E and7F, two of7G and7H, and two of7I and7J) are supplied with voltages with the same phase so as to bend together to the same sides of the x-axis direction relative to each other. Accordingly, the two mutually neighboring driving arms7may be interpreted as corresponding to one driving arm7in the first embodiment. By dividing the driving arm7in the first embodiment into two in this way, for example, even if the length of the driving arms7is made short, the mass of the driving arms7as a whole can be secured and in turn both reduction of size and improvement of the detection sensitivity can be made achieved.

The position at the center between the two mutually neighboring driving arms7(or position of each of the driving arms7) may be for example made the same as the positions of the driving arms7explained in the first embodiment. The distance between the two mutually neighboring driving arms7may be suitably set. The configurations of the two mutually neighboring driving arms7are for example the same as each other. However, they may be different from each other as well. The piezoelectric body303for example has a line symmetrical shape relative to a not shown symmetrical axis (detecting arms309). The shapes and arrangement of the plurality of driving arms7are line symmetrical.

Each of the detecting arms309, in the same way as the detecting arm9in the first embodiment, has the first arm321extending from the frame5and the second arms323(323A and323B) which are connected to the front end side portions of the first arm321and extend from the front end side of the first arms321toward the frame5side. However, at least one (both in the present embodiment) of the first arm321and the second arms323have one or more via grooves (notation is omitted) which penetrate through in the z-axis direction and extend along each of the arms. From another viewpoint, each of the first arm321and second arms323has a plurality of divided arms324which extend alongside each other and are connected to each other at their roots and front ends.

The configurations of the detecting arms309, first arms321, and second arms323may be the same as the configurations of the detecting arm9, first arm21, and second arms23in the first embodiment except that the via grooves are provided. However, specific dimensions etc. may be different from those in the first embodiment due to the provision of the via grooves.

The number, widths, and intervals of the divided arms324in each of the first arms321and second arms323may be suitably set. The widths of the plurality of divided arms324may be the same as each other among the plurality of divided arms324(example shown) or may be different. If there are a plurality of intervals of the plurality of divided arms324, the plurality of intervals may be the same as each other among the plurality of divided arms324(first arm321in the example shown) or may be different.

Although not particularly shown, in each of the driving arms7, for example, in the same way as the driving arms7in the first embodiment, two excitation electrodes15A and two excitation electrodes15B are provided. Also, the connection relationships of the excitation electrodes15in each of the driving arms7by the wirings19are the same as those in the first embodiment.

The two mutually neighboring driving arms7correspond to one driving arm7in the first embodiment and are supplied with voltages with the same phases as each other. Therefore, between these two driving arms7, the excitation electrodes15A are rendered the same potentials as each other, and the excitation electrodes15B are rendered the same potentials as each other.

In each of the units304, the two driving arms7which are arranged line symmetrically while sandwiching the detecting arm309therebetween correspond to the pair of driving arms7in the first embodiment. Therefore, between these two driving arms7, the excitation electrodes15A and the excitation electrodes15B are rendered the same potential.

When focusing on the two units304, in the driving arms7(7C,7D,7G, and7H, or7E,7F,7I, and7J) which are positioned on the same sides of the detecting arms309in the x-axis direction, the excitation electrodes15A are rendered the same potentials as each other, and the excitation electrodes15B are rendered the same potentials as each other. Accordingly, if AC voltage is supplied to the plurality of excitation electrodes15, the driving arms7which are positioned on the same side of the detecting arms309in the x-axis direction vibrate so as to bend to the same sides as each other in the x-axis direction.

The excitation electrodes15to be rendered the same potentials as each other are for example connected to each other by the wirings19. Further, all excitation electrodes15divided into two sets are connected through the wirings19to two among the four pads13and in turn connected to the driving circuit103.

FIG.7Bis a cross-sectional view taken along the VIIb-VIIb line inFIG.7A.

In the detecting arms309, the detecting electrodes17are provided on each of the divided arms324in the same arrangement as the arrangement of the detecting electrodes17in the first arm21and second arms23in the first embodiment. That is, the detecting electrodes17A on each of the divided arms324are provided in the region of +z in the side surface of −x and the region of −z in the side surface of +x. The detecting electrodes17B on each of the divided arms324are provided in the region of −z in the side surface of −x and the region of +z in the side surface of +x.

Although not particularly shown, the connection relationships of the detecting electrodes17on each of the divided arms324is the same as the connection relationships of the detecting electrodes17in each of the first arm21and second arms23in the first embodiment. That is, the detecting electrodes17A are connected to each other, and the detecting electrodes17B are connected to each other. Due to this, each of the divided arms324, in the same way as the first arm21and second arms23, can output signal in accordance with the bending deformation to the z-axis direction.

Further, although not particularly shown, in each of the first arms321, the plurality of detecting electrodes17are connected so that the entirety including the plurality of divided arms324function in the same way as the first arm21in the first embodiment. That is, among the plurality of divided arms324, the detecting electrodes17A are connected to each other, and the detecting electrodes17B are connected to each other. The same is true for the second arms323.

In each of the detecting arms309, the first arm321and second arms323correspond to the first arm21and second arms23in the first embodiment. Therefore, although not particularly shown, between the first arm321and the second arms323, the detecting electrodes17A and the detecting electrodes17B are connected. That is, when the first arm321and the second arms323flexurally deform so as to bend to inverse sides from each other in the z-axis direction, the detection signals are added.

Between the detecting arm309A and the detecting arm309B, the detecting electrodes17A and the detecting electrodes17B are connected. In such connection relationships, at the time when the detecting arms309A and309B receive Coriolis forces to inverse sides from each other in the z-axis direction and flexurally deform, the signals generated in the two are added.

The plurality of detecting electrodes17are for example connected by the wirings19. All of the detecting electrodes17divided into the two sets are connected to two among the four pads13by the wirings19and in turn connected to the detecting circuit105.

(Operation of Angular Velocity Sensor)

FIG.8AandFIG.8Bare schematic plan views showing the excitation state of the piezoelectric body303and correspond toFIG.4AandFIG.4Bin the first embodiment. In these views, the detecting arms309, for convenience of explanation, are schematically shown as if they were a single arm.

The excitation in each of the units304is basically the same as the excitation of the piezoelectric body3in the first embodiment. However, as already explained, in each of the units304, two driving arms7neighboring each other are supplied with voltages with the same phase so as to bend to the same sides relative to each other together, therefore correspond to one driving arm7in the piezoelectric body3.

As described above, when focusing on the two units304, between the driving arms7which are positioned on the same sides of the detecting arms309in the x-axis direction (positive side or negative side), the excitation electrodes15A are connected to each other and the excitation electrodes15B are connected to each other. Therefore, the driving arms7positioned on the same side are supplied with voltages with the same phase, so bend to the same side in the x-axis direction. Accordingly, the frames5A and5B warp to inverse sides from each other. Further, the detecting arms309A and309B displace to inverse sides from each other.

FIG.8CandFIG.8Dare schematic perspective views for explaining vibrations of the detecting arms309due to the Coriolis force and correspond to the states inFIG.8AandFIG.8B. Here, for convenience of explanation, the detecting arms309are schematically shown as if they were a single arm as well.

When the sensor element301is rotated around the x-axis in the state where vibrations explained with reference toFIG.8AandFIG.8Boccur, in each of the units304, in the same way as the first embodiment, the detecting arm309vibrates in the z-axis direction due to the Coriolis force. At this time, the detecting arms309A and309B vibrate with phases displacing to inverse sides from each other in the y-axis direction, therefore they receive the Coriolis force on the same side relative to the rotation direction around the x-axis. From another viewpoint, the detecting arms309A and309B vibrate so as to bend to inverse sides from each other in the z-axis direction.

Further, the signal (voltages) generated due to deformation of each of the detecting arms309is extracted by the detecting electrodes17. The signals extracted in the pair of detecting arms309are added and output from the pads13.

As described above, the sensor element301according to the third embodiment includes the units304corresponding to the sensor element1in the first embodiment. Accordingly, the same effects as those by the first embodiment are exhibited. For example, by the moment acting to bend the first arms321to the inverse side from the direction of the Coriolis force acting from the second arms323to the first arms321, the moment acting to make the frames5torsionally deform (see the arrow y3inFIG.4) is reduced.

Further, in the present embodiment, the piezoelectric body303has two sets of the combinations (has the two units304) each having a frame5, (at least) one pair of driving arms7, and a detecting arm309so that the sides of the frames5opposite to the sides where the pairs of driving arms7extend outward are made to face each other.

Accordingly, for example, by adding the signals detected in the two detecting arms309, the detection sensitivity can be improved. Further, for example, in the first embodiment, the region between the pair of mounting parts11and on the negative side in the y-axis direction becomes a dead space. However, such a space is effectively utilized. As a result, improvement of sensitivity and reduction of size are both realized.

Fourth Embodiment

FIG.9is a perspective view showing the configuration of an angular velocity sensor451(particularly sensor element401) according to a fourth embodiment. However, in this view, illustration of the conductive layer provided on the surface of the sensor element401is basically omitted.

The sensor element401, in the same way as the sensor element301in the third embodiment, can be grasped as one having two sensor elements1of the first embodiment. However, the sensor element301is configured so that the sides of the sensor elements1(units304) opposite to the sides where the driving arms7extend outward are made to face each other. In contrast to this, the sensor element401is configured so that the sides of the sensor elements1where the driving arms7extend outward are made to face each other. Further, in the sensor element401, no mounting part11is provided. The configuration of the sensor element401(angular velocity sensor451) is specifically as follows.

The angular velocity sensor451for example has a sensor element401and a plurality of (four in the example shown) terminals402which support the sensor element401. The sensor element401has a piezoelectric body403.

The material and polarization direction of the piezoelectric body403are the same as those of the piezoelectric body3in the first embodiment. Further, the piezoelectric body403, for example, in the same way as the piezoelectric body3, is integrally formed as a whole, and its thickness (z-axis direction) is constant. Further, the piezoelectric body403, for example, is formed in a shape line symmetrical relative to a not shown symmetrical axis parallel to the y-axis and line symmetrical relative to a not shown symmetrical axis parallel to the x-axis.

The piezoelectric body403for example has a pair of frames5(5A and5B), a pair of driving arms407(407A and407B) which are arranged bridging the pair of frames5, and a pair of detecting arms9(9A and9B) extending from the pair of frames5.

The pair of frames5face each other in the y-axis direction. The configuration of each of the frames5may be the same as the first embodiment. The natural frequency of the flexural deformation of the frames5may be adjusted so as to become closer to the natural frequency of the driving arms407in the direction of excitation by application of voltage and/or the natural frequency of the detecting arms9in the direction of vibration due to the Coriolis force in the same way as in the first embodiment.

The pair of driving arms407are arranged bridging the pair of frames5and face each other in the x-axis direction. Accordingly, the pair of frames5and pair of driving arms407configure a frame shape (annular shape) surrounding an opening as a whole. The driving arms407are for example long shapes linearly extending in the y-axis direction. The pair of frames5and the pair of driving arms407are for example connected to each other at their two ends and configure a rectangle.

Note that, each of the driving arms407can be grasped as vertically connected driving arms7of the first embodiment. That is, it can be grasped that the driving arms7K and7L extending from the frame5A correspond to the driving arms7A and7B. In the same way, it can be grasped that the driving arms7M and7N extending from the frame5B correspond to the driving arms7A and7B. Further, the front end of the driving arm7K and the front end of the driving arm7M are connected, and the front end of the driving arm7L and the front end of the driving arm7N are connected.

The configuration of each of the driving arms7may be the same as the first embodiment. Further, as illustrated, the portions connecting the front ends of the driving arms7to each other are formed as broad width portions407dwhich are broader in widths than the driving arms7. Note that, such broad width portions407dneed not be provided either.

The pair of detecting arms9are for example positioned on the inner side of the pair of frames5(between the pair of frames5). The configuration of each of the detecting arms9may be the same as the first embodiment.

The plurality of terminals402are for mounting the sensor element401on a not shown mounting body (for example a portion of a package or a circuit board). The plurality of terminals402are for example configured so as to resiliently support the sensor element401to permit parallel movement and/or rotational movement of the joined positions of the plurality of terminals402and the sensor element401and in turn so that vibration of the piezoelectric body403which will be explained later is enabled. In the example shown, the terminals402are formed by long pieces of sheet metal having relatively small thicknesses and widths and having suitable bending portions.

The sensor element401is for example arranged with its lower surface facing a not shown mounting body. The plurality of terminals402are for example joined at one end side portions with the plurality of pads13which are provided on the surface (for example lower surface) of the piezoelectric body403and are joined at the other end side portions with pads on the not shown mounting body. Due to this, the sensor element401and the mounting body are electrically connected, and the sensor element401(piezoelectric body403) is supported in a state enabling vibration.

The positions of the plurality of pads13on the piezoelectric body403may be suitably set. In the example shown, a mode where the four pads13are provided on the pair of frames (two sides) is shown. Other than this, for example, four pads13may be provided on the pair of driving arms407(two sides), four pads13may be provided on the pair of frames5and pair of driving arms407(four sides), or four pads13may be provided at the four corner portions formed by the pair of frames5and pair of driving arms407.

As explained above, the driving arms7K and7L correspond to the driving arms7A and7B in the first embodiment. Accordingly, although not particularly shown, on the driving arms7K and7L, in the same way as the driving arms7A and7B in the first embodiment, a plurality of excitation electrodes15are arranged and are connected. The same is true for the driving arms7M and7N.

When focusing on each of the driving arms407, between the two driving arms7(7K and7M, or7L and7N) which are connected at the front ends to each other, the excitation electrodes15A are rendered the same potentials as each other, and the excitation electrodes15B are rendered the same potentials as each other. Accordingly, when AC voltages are supplied to the plurality of excitation electrodes15, in each of the driving arms407, the two driving arms7flexurally deform so as to bend to the same sides in the x-axis direction as each other.

Although not particularly shown, in each of the driving arms407, over substantially the entirety of its long direction (without differentiating between the two driving arms7), a pair of excitation electrodes15A and/or a pair of excitation electrodes15B may be provided as well. For example, four excitation electrodes15may be provided for one driving arm407. In particular, in a mode where no broad width portions407dare provided, formation of excitation electrodes15covering the entirety of the long direction of each of the driving arms407is easy.

As will be understood from the above description, in the explanation of the excitation electrodes15, it is not always necessary to differentiate whether the excitation electrodes15are provided for each of the driving arms7in the driving arms407. In the following description, even if the pair of excitation electrodes15A and pair of excitation electrodes15B are provided for each of the driving arms7, sometimes it will be expressed that the pair of excitation electrodes15A and the pair of excitation electrodes15B are provided on one driving arm407.

The excitation electrodes15which must be given the same potential are for example connected to each other by the wirings19. Further, all of the excitation electrodes15divided into two sets are connected through the wirings19to two among the four pads13and in turn connected to the driving circuit103.

The detecting arms9(9A and9B) are the same as the detecting arm9in the first embodiment. Accordingly, the arrangement and connection relationships of the detecting electrodes17in each of the detecting arms9are the same as those in the first embodiment.

Between the pair of detecting arms9, in the same way as the third embodiment, the detecting electrode17A and the detecting electrodes17B are connected. Accordingly, when the pair of detecting arms9vibrate so as to be deformed to inverse sides from each other about the z-axis direction, the signals generated in the two are added.

The plurality of detecting electrodes17are for example connected by the wirings19. All of the detecting electrodes17divided into the two sets are connected to two among the four pads13by the wirings19and in turn connected to the detecting circuit105.

(Operation of Angular Velocity Sensor)

FIG.10AandFIG.10Bare schematic plan views for explaining excitation of the piezoelectric body403. In these views, the entireties of the detecting arms9are schematically shown as single arms without differentiating between the first arms21and the second arms23. BetweenFIG.10AandFIG.10B, the phases of the AC voltages supplied to the excitation electrodes15are offset by 180° from each other.

Between the pair of driving arms407, the excitation electrode15A and the excitation electrode15B are rendered the same potential. Therefore, when the AC voltages are supplied to the excitation electrodes15, the pair of driving arms407are excited with inverse phases from each other so as to flexurally deform to inverse sides from each other in the x-axis direction.

At this time, as shown inFIG.10A, when a pair of driving arms407warp to the inner side of the pair of driving arms407in the x-axis direction, the bending moments thereof are transferred to the pair of frames5, and the pair of frames5warp to the outer sides of the pair of frames5in the y-axis direction. As a result, the pair of detecting arms9displace to the outer sides of the pair of frames5in the y-axis direction.

Conversely, as shown inFIG.10B, when a pair of driving arms407warp to the outer sides of the pair of driving arms407in the x-axis direction, the bending moments thereof are transferred to the pair of frames5, and the pair of frames5warp to the inner sides of the pair of frames5in the y-axis direction. As a result, the pair of detecting arms9displace to the inner sides of the pair of frames5in the y-axis direction.

Accordingly, by excitation of the pair of driving arms407, the pair of detecting arms9vibrate in the y-axis direction. Note that, in the first embodiment, the driving arms7were cantilever shaped. Therefore, in the x-axis direction, the front ends (free ends) displaced toward the sides being bent. In the present embodiment, however, the driving arms407are beam shaped with the two ends supported, therefore the center parts displace to the sides opposite to the sides of bending in the x-axis direction. Further, the relationships between the directions of bending of the driving arms7and the directions of bending of the frames5are inverse in the present embodiment relative to those in the first embodiment.

FIG.10CandFIG.10Dare schematic perspective views for explaining vibrations of the pair of detecting arms9due to the Coriolis forces. In these views, the detecting arms9are schematically shown as single arms in their entireties without differentiating between the first arms21and the second arms23.FIG.10CandFIG.10Dcorrespond to the states inFIG.10AandFIG.10B.

When the sensor element1is rotated around the x-axis in the state where the piezoelectric body403is vibrating as explained with reference toFIG.10AandFIG.10B, the pair of detecting arms9vibrate (are deformed) in the direction (z-axis direction) perpendicular to the rotation axis (x-axis) and to the vibration direction (y-axis) due to the Coriolis forces since they are vibrating (displaced) in the y-axis direction.

Further, the pair of detecting arms9vibrate so as to displace to inverse sides from each other in the y-axis direction, therefore they displace to the same sides as each other about the rotation direction around the x-axis due to the Coriolis forces. From another viewpoint, the pair of detecting arms9displace to inverse sides from each other in the z-axis direction.

Further, the signal (voltages) generated due to deformation of each of the detecting arms9is extracted by the detecting electrodes17. The signals extracted in the pair of detecting arms9are added and output from the pads13.

As described above, in the fourth embodiment as well, the sensor element401has detecting arms9including the first arms21and second arms23. Accordingly, the same effects as those by the first embodiment are exhibited. For example, by the moments acting to bend the first arms21to the inverse sides from the directions of the Coriolis forces acting from the second arms23to the first arms21, the moments acting to cause deformation in the frames5(see the arrow y3inFIG.4) are reduced.

Further, in the present embodiment, the piezoelectric body403has the pair of frames5, pair of driving arms407, and pair of detecting arms9. The pair of frames5have long shapes so that the two ends are separated in the x-axis direction and face each other in the y-axis direction. The pair of driving arms407are respectively arranged bridging the pair of frames5and face each other in the x-axis direction. The pair of detecting arms9extend from the pair of frames5in the y-axis direction at positions between the pair of driving arms407in the x-axis direction. The plurality of excitation electrodes15are provided in an arrangement capable of supplying voltages exciting the pair of driving arms407in the x-axis direction. The wirings19connect the plurality of excitation electrodes15in such connection relationships where voltages having inverse phases from each other vibrating the pair of driving arms407to inverse sides from each other in the x-axis direction are supplied from the plurality of excitation electrodes15to the pair of driving arms407.

Accordingly, in the same way as the first to third embodiments, it becomes possible to perform new detection by a new mode of vibration of making the frames5flex (vibrate) by excitation of the pair of driving arms407, making the detecting arms9displace (vibrate), and detecting the angular velocity due to the Coriolis forces acting upon these displacing detecting arms9.

Further, when compared with the first to third embodiments, in the present embodiment, the two ends of each of the pair of driving arms407are connected to the pair of frames5, and the detecting arm9is provided at each of the frames5, therefore vibrations of the pair of driving arms407are efficiently transferred to the pair of detecting arms9. As a result, for example, the detection sensitivity is improved.

Further, in the present embodiment, the pair of detecting arms9extend to the inner side of the pair of frames5.

That is, the pair of detecting arms9are positioned within the opening configured by the pair of frames5and pair of driving arms407. Accordingly, for example, compared with the mode in which the detecting arms9extend to the outer sides of the pair of frames5(this mode also included in the present disclosure), the sensor element1is reduced in size.

Multi-Axis Angular Velocity Sensor

FIG.11is a plan view showing the configuration of a multi-axis angular velocity sensor550including an angular velocity sensor explained above.

The multi-axis angular velocity sensor550for example has an x-axis sensor351which detects the angular velocity around the x-axis, a y-axis sensor651which detects the angular velocity around the y-axis, and a z-axis sensor751which detects the angular velocity around the z-axis. Note that, in the example shown, the angular velocity sensor according to the third embodiment is shown as the x-axis sensor351. However, the x-axis sensor351may be replaced by an angular velocity sensor in the other embodiments explained above as well.

The x-axis sensor351for example has a sensor element301, a driving circuit103(FIG.3) supplying voltage to the sensor element301, and a detecting circuit105(FIG.3) detecting the signal from the sensor element301. The configurations and operations of them are as already explained.

The y-axis sensor651for example has a sensor element601, a driving circuit103(FIG.3) supplying voltage to the sensor element601, and a detecting circuit105(FIG.3) detecting the signal from the sensor element601.

The y-axis sensor651is for example a piezoelectric vibration type in the same way as the x-axis sensor351. The sensor element601has a piezoelectric body603. The piezoelectric body603for example has a base part605, one or more driving arms7(7O to7R) and one or more detecting arms609(609A and609B) which are all supported upon the base part605, and a pair of mounting parts11supporting the base part605.

The z-axis sensor751for example has a sensor element701, a driving circuit103(FIG.3) supplying voltage to the sensor element701, and a detecting circuit105(FIG.3) detecting the signal from the sensor element701.

The z-axis sensor751, for example, in the same way as the x-axis sensor351, is a piezoelectric vibration type. The sensor element701has a piezoelectric body703. The piezoelectric body703is for example obtained by providing detecting arms609C and609D in place of the detecting arms309A and309B in the piezoelectric body303in the x-axis sensor351.

The detecting arms609in the y-axis sensor651and z-axis sensor751are ones without the first arms21and second arms23unlike the detecting arms9. That is, the detecting arms609are shaped to extend in single directions from the base parts605.

The sensor element301, sensor element601, and sensor element701are for example arranged in the x-axis direction. Note that, the order of arrangement of the three sensor elements may be one other than the one shown as well. The piezoelectric bodies in these sensor elements are for example integrally formed and are fixed to each other. That is, the multi-axis angular velocity sensor550has a piezoelectric body502including the piezoelectric body303in the sensor element301, the piezoelectric body603in the sensor element601, and the piezoelectric body703in the sensor element701. Specifically, for example, these piezoelectric bodies are fixed so that mutually neighboring ones share the mounting part11. The piezoelectric body502has four mounting parts11in total.

Via holes11aare formed in the mounting parts11which are shared by the piezoelectric bodies in two mutually neighboring sensor elements. The via holes11aare for example slit-shaped so as to penetrate in the z-axis direction and extend in the y-axis direction (directions along the mounting parts11) with substantially constant widths. The pads13are for example positioned on the outer sides of the via holes11ain the y-axis direction. By formation of the via holes11a, for example, mutual influences of vibrations of the sensor elements are mitigated.

Among the x-axis sensor351, y-axis sensor651, and z-axis sensor751, the driving circuit103may be shared. From another viewpoint, the frequencies when exciting the piezoelectric bodies in these three angular velocity sensors may be made the same. At this time, the excitation-use pair of pads13may be shared among the three angular velocity sensors. Accordingly, the multi-axis angular velocity sensor550only has to include eight pads13in total including two detection-use pads13in each of the angular velocity sensors and the two excitation-use pads13. In the example shown, the eight pads13are respectively provided at the end parts of the four mounting parts11which are shared as explained above. Note that, the driving circuit103need not be shared at part or all of the three angular velocity sensors either. In this case, over eight pads13may be positioned at suitable positions of the mounting parts11. Further, in this case, the frequencies when exciting the piezoelectric bodies in the three angular velocity sensors may be different from each other or may be the same as each other.

The y-axis sensor651may be configured in various ways including known ones. In the following description, one example thereof will be explained.

The piezoelectric body603has a base part605, four (two pairs of) driving arms7O,7P,7Q, and7R, and two detecting arms609A and609B. The four driving arms7extend from the base part605toward one side (positive side in the example shown) in the y-axis direction. Further, they are configured line symmetrically relative to a not shown symmetrical axis parallel to the y-axis. The two detecting arms609extend from the base part605toward the side opposite to the driving arms7.

FIG.12AandFIG.12Bare schematic plan views for explaining the excitation states of the piezoelectric body603.

The four driving arms7O,7P,7Q, and7R, for example, in the same way as the driving arms7C,7D,7E, and7F in the third embodiment, are excited so that the two positioned on the same side (positive side or negative side) in the x-axis direction bend to the same sides as each other in the x-axis direction, and the two positioned on the positive side in the x-axis direction and the two positioned on the negative side in the x-axis direction bend to inverse sides from each other in the x-axis direction. Note that, due to the excitations of these driving arms7, the base part605need not flex. Further, the detecting arms609A and609B need not vibrate.

As will be understood from the operation described above, the arrangement and connection of the excitation electrodes15in the piezoelectric body603may be the same as those in the third embodiment. Further, all of the excitation electrodes15which were divided into the two sets are connected to two pads13by the wirings19and in turn connected to the driving circuit103.

FIG.12CandFIG.12Dare schematic perspective views for explaining vibrations due to the Coriolis forces of the piezoelectric body603.

When the piezoelectric body603is rotated around the y-axis in the state where the driving arms7are made to vibrate as described above, upon the driving arms7, the Coriolis force acts in the direction (z-axis direction) perpendicular to the vibration direction (x-axis direction) and to the rotation axis (y-axis). As a result, the driving arms7vibrate so as to flexurally deform in the z-axis direction. The driving arms7O and7P positioned on the negative side in the x-axis direction and the driving arms7Q and7R positioned on the positive side in the x-axis direction vibrate to inverse sides from each other in the x-axis direction, therefore they vibrate so as to bend to the same side around the rotation axis (around the y-axis). That is, the two vibrate so as to bend to inverse sides relative to each other in the z-axis direction.

The vibrations of these driving arms7in the z-axis direction are transferred through the base part605to the detecting arms609A and609B. Further, the detecting arms609vibrate so as to bend to the inverse side of the z-axis direction relative to the driving arms7positioned on the same side in the x-axis direction. Further, the two detecting arms609vibrate so as to bend to inverse sides from each other in the z-axis direction.

In order to extract the signals generated in such detecting arms609, for example, in the detecting arms609, provision is made of the detecting electrodes17(FIG.3) provided on the first arm21or second arms23in the first embodiment. The arrangement and connection relationships of the detecting electrodes17on each of the detecting arms609are the same as those on the first arm21or second arms23. Further, in order to add the signals of the two detecting arms609which bend to inverse sides from each other, between two detecting arms609, the detecting electrodes17A and the detecting electrodes17B are connected by the wirings19. Further, all of the detecting electrodes17divided into the two sets are connected to the two pads13by the wirings19and in turn connected to the detecting circuit105.

The y-axis sensor, other than the configuration described above, for example, may be given various configurations such as the one disclosed in Japanese Patent Publication No. 2015-99130 having eight driving arms and two detecting arms, a tuning fork-shaped one having one driving arm and one detecting arm, and one having a pair of driving arms and pair of detecting arms which extend toward the same side of the y-axis direction. It may be one which does not have a mounting part and is mounted in the base part as well.

The z-axis sensor751, for example, in the same way as the x-axis sensor351, utilizes a new mode of vibration of making the frames5flexurally deform in the y-axis direction due to the vibrations of the driving arms7in the x-axis direction, and making the detecting arms609vibrate (displace) in the y-axis direction by this. Accordingly, in the z-axis sensor751, the arrangement and connection relationships of the excitation electrodes15may be the same as those in the x-axis sensor351.

FIG.13AandFIG.13Bare schematic plan views for explaining vibrations of the detecting arms609due to the Coriolis forces.FIG.13AandFIG.13Bcorrespond to the states inFIG.8AandFIG.8B.

When the sensor element701is rotated around the z-axis in the state where vibrations explained with reference toFIG.8AandFIG.8Bare caused, since the detecting arms609vibrate (are displaced) in the y-axis direction, they vibrate (displace) in the direction (x-axis direction) perpendicular to the rotation axis (z-axis) and to the vibration direction (y-axis direction) due to the Coriolis forces. Further, the pair of detecting arms609vibrate with phases for displacement to inverse sides from each other in the y-axis direction, therefore they receive the Coriolis forces on the same side relative to the rotation direction around the z-axis. From another viewpoint, the detecting arms609A and609B vibrate so as to bend to inverse sides from each other in the x-axis direction.

In order to extract the signals generated in such detecting arms609, for example, in each detecting arm609, although not particularly shown, provision is made of detecting electrodes having the same arrangement and connection relationships as those of the excitation electrodes15in the first embodiment (FIG.3). Further, in order to add the signals of the two detecting arms609which bend to inverse sides from each other, between the two detecting arms609, the detecting electrodes having the same arrangement as that of the excitation electrodes15A and the detecting electrodes having the same arrangement as that of the excitation electrodes15B are connected by the wirings19. Further, all of the detecting electrodes divided into the two sets are connected to the two pads13by the wirings19and in turn connected to the detecting circuit105.

Note that, the z-axis sensor751shown is based on the sensor in the third embodiment. However, it may be based on sensors in the other embodiments as well.

The present invention is not limited to the above embodiments and may be executed in various ways.

The sensor element (angular velocity sensor) is not limited to one detecting rotation around an axis perpendicular to the detecting arms (around the x-axis). The sensor element only have to be one generating a Coriolis force in a direction intersecting the plane including the first arms and second arms (plane parallel to the xy plane). For example, in the y-axis sensor651explained with reference toFIG.11andFIGS.12, in place of the detecting arms609, the detecting arms9having the first arm21and second arm23may be provided as well.

Further, as referred to also in the explanation of the embodiments, the sensor element is not limited to one utilizing the new mode of vibration of causing flexural deformation in the base part (frame5) and is not limited to one having a long shaped base part in which flexural deformation tends to occur. In any mode of vibration and any shape of the base part, the same effects as those in the embodiments (reduction of the vibration energy escaping to the base part) or other effects are exhibited.

The embodiments illustrated sensor elements in which the detecting arms extend from one frame5(base part) toward only one side in the y-axis direction and in which a moment acting to cause torsional deformation in the base part due to the Coriolis force acting upon the detecting arms is applied. However, the sensor element may be made one where the moment as described above is not applied to the base part by extension of the detecting arms from one base part to the two sides of the y-axis direction as well.

For example, in the first embodiment, pairs of driving arms7and single detecting arms9may extend from the same frame5toward the two sides in the y-axis direction, so four driving arms7and two detecting arms9in total may be provided. Further, the phase of the pair of driving arms7on the positive side in the y-axis direction and the phase of the pair of driving arms7on the negative side in the y-axis direction may be made different by 180° as well. In this case, the two detecting arms9vibrate to the same sides as each other in the y-axis direction. Further, when the sensor element rotates around the x-axis, the Coriolis force acts upon the same side of the two detecting arms9in the z-axis direction.

Further, for example, in the fourth embodiment (FIG.9), the detecting arms9may be provided not only on the inner side of the pair of frames5, but also on the outer sides (four detecting arms9in total may be provided). In this case, when the sensor element rotates around the x-axis, the Coriolis force acts upon the two detecting arms9positioned on the two sides of one frame5in the y-axis direction toward the same side in the z-axis direction.

The detecting arms are not limited to ones provided at the centers between pairs of driving arms. This is clear also from the fact that a detecting arm having the first arm and second arm may be applied to the y-axis sensor as already explained and as the y-axis sensor, a tuning-fork type one and one having an even number of detecting arms arranged line symmetrically are known.

In the detecting arms, the numbers of the first arms and second arms may be suitably set. For example, the detecting arm may have only one first arm and only one second arm as well. From another viewpoint, one detecting arm need not be line symmetrically shaped either. Note that, for example, when an even number of detecting arms are provided line symmetrically, the symmetry of the entirety of the sensor element is secured even if one detecting arm is not line symmetrically shaped.

The embodiments illustrated a mode in which the first arm bent to the inverse side from the direction of the Coriolis force due to the moment acting from the second arms to the first arm. However, the first arm may receive the moment acting to bend it to the inverse side from the direction of the Coriolis force from the second arm, but may bend to the direction of the Coriolis force due to the Coriolis force which directly acts upon the first arm and the like. Even in this case, for example, the effect of reduction of the vibration energy transferred to the base part is still exhibited. Note that, the direction of bending of the first arm relative to the direction of the Coriolis force can be set by for example adjusting the masses of the first arm and second arms. For example, if the masses of the second arms are made relatively larger, the operation as in the embodiment is exhibited.

The driving arms and the detecting arms need not be parallel to each other either. Further, the first arms and the second arms need not be parallel to each other either. That is, the first arms and the second arms may be inclined from each other. The detecting electrodes may be provided on only one of the first arms and second arms.

The plurality of embodiments may be suitably combined. For example, the configuration of the third embodiment in which two or more driving arms (for example7C and7D) which are adjacent to each other are excited with the same phase as if they were one driving arm may be applied to the first embodiment or second embodiment as well. Further, for example, the configuration of forming grooves in the first arm and/or second arms in the third embodiment may be applied to the first, second, or fourth embodiment as well. The detecting arm in the third or fourth embodiment need not be one having one first arm and two second arms as in the first embodiment, but may be one having two first arms and one second arm as in the second embodiment.

In the case where the new mode of vibration explained in the embodiments is utilized, it is suitable to combine the number of the driving arms and the number of the detecting arms which extend from one frame. For example, with respect to one pair of driving arms, a detecting arm extending to the positive side in the y-axis direction and a detecting arm extending to the negative side in the y-axis direction may be provided as well. Further, between the pair of driving arms, two or more detecting arms extending alongside each other may be provided as well.

In the first to third embodiments, the piezoelectric body need not have a mounting part extending in the y-axis direction as shown in the embodiments. For example, the piezoelectric body may be mounted by providing a plurality of pads on the two ends of the frame as well. That is, in the frame, the portions provided with the pads may be made the supported portions as well.

Further, in the first to third embodiments, the piezoelectric body may be configured having (at least) a pair of driving arms extending toward one side of the y-axis direction and only one detecting arm positioned on the other side of the y-axis direction (shape like a two-prong fork). That is, the pair of driving arms and the detecting arm need to extend toward the same direction (alongside each other). Further, in the fourth embodiment, only detecting arms positioned on the outer sides of the pair of frames may be provided as well.

In the third embodiment (FIG.7), the frame5sides of the two units304were made to face each other. However, conversely, the sides of the two units304opposite to the frames5may be made to face each other, and these two units304may be supported by a pair of mounting parts11. Further, in the third embodiment, the two units304were excited with the same phases as each other. However, they may be excited with inverse phases from each other. Further, in the case where the frames5of the two units304are made to face each other as in the third embodiment, the two frames5may be respectively configured by portions of annular shapes, and the end parts of the annular shapes may be directly or indirectly connected to the mounting parts11.

In the fourth embodiment (FIG.9), the pair of frames and the pair of driving arms configured a rectangle. However, they may configure a hexagonal or octagonal or other ring shape as well.

The sensor element or angular velocity sensor may be configured as a portion of an MEMS (micro electromechanical system). In this case, a piezoelectric body configuring the sensor element may be mounted on a substrate of MEMS or a substrate of MEMS may be configured by a piezoelectric body and the piezoelectric body in the sensor element may be configured by a portion thereof.

The multi-axis angular velocity sensor may be one having only any two among the x-axis sensor, y-axis sensor, and z-axis sensor as well. In the embodiments, the piezoelectric bodies in the three angular velocity sensors were arranged in the x-axis direction. However, they may be arranged in the y-axis direction or may be arranged in an L-shape. Further, among the piezoelectric bodies in the three angular velocity sensors, only two need be fixed to each other or all may be separately formed and mounted in the same package or substrate.

REFERENCE SIGNS LIST