Vibrating element, vibrating device, electronic apparatus, and moving object

A vibrating element includes a base part, drive arms containing first surfaces and second surfaces having front-back relations with the first surfaces, having groove portions provided on the first surface sides, and extended from the base part in extension directions, and drive parts provided to contain piezoelectric layers on the second surfaces, and section shapes of the drive arms orthogonal to the extension directions contain asymmetric section shapes with respect to virtual center lines passing through centers of widths in directions orthogonal to the extension directions.

BACKGROUND

1. Technical Field

The present invention relates to a vibrating element and a vibrating device, an electronic apparatus, and a moving object using the vibrating element.

2. Related Art

Recently, as crystal oscillators used for electronic apparatuses and automobile as moving objects or vibrating elements used for vibrating devices including angular velocity sensors, the following elements have been known.

For example, a vibrating element disclosed in Patent Document 1 (JP-A-2011-216924) is a tuning-fork vibrating element including a plurality of vibrating arms, and has a base part having a thickness in a Z-axis direction and two vibrating arms extending from the base part in a Y-axis direction and provided in parallel in an X-axis direction, with groove portions respectively dug into front surfaces and rear surfaces for improvement in vibration efficiency. Further, excitation electrodes are formed on the respective vibrating arms (drive arms). In the vibrating element, the two vibrating arms are vibrated in plane in the X-axis directions when voltages are applied to the above described electrodes formed on the vibrating arms.

Further, a vibrating element disclosed in Patent Document 2 (WO 2010/047115) is a tuning-fork vibrating element that detects an angular velocity and has a plurality of vibrating arms (drive arms). The vibrating element has a base part and two vibrating arms extending from the base part in a Y-axis direction in parallel to each other and provided in parallel in an X-axis direction. The respective vibrating arms have grooves respectively formed on front surfaces and rear surfaces opposed in a Z-axis direction, and their section shapes are “S”-shapes. The respective vibrating arms are formed in the shapes, and thereby, fluctuations of the Q-value may be suppressed while the mechanical strength is maintained.

The above described vibrating element may be formed by processing a plate-like substrate of e.g., crystal or silicon in a desired shape. Specifically, masks corresponding to the shapes in the plan view of the vibrating element are formed on both sides of the substrate and the substrate is etched via the masks, and thereby, the vibrating element may be obtained.

However, in the above described vibrating element disclosed in Patent Document 1, it is necessary to dig the grooves from the respective front surfaces and rear surfaces of the vibrating arms (drive arms). Further, in the vibrating element disclosed in Patent Document 2, it is necessary to form the grooves on the front surfaces and the rear surfaces so that the shapes of the vibrating arms (drive arms) may have the “S”-shaped cross sections. Particularly, in order to form the “S”-shaped cross sections of the vibrating arms like those of the vibrating element disclosed in Patent Document 2, the grooves should be formed deeper and the groove widths should be suppressed for downsizing of the vibrating arms (vibrating element). It is difficult to process the grooves deeper while suppressing their widths and, for example, the grooves formed on the front surfaces may penetrate to the rear surfaces or open to the side surfaces to chip the side surfaces. Further, for digging the grooves from the respective front surfaces and rear surfaces and forming electrodes or piezoelectric members on the front surfaces and the rear surfaces, the processing process becomes complex and the number of steps of the processing increases. As described above, the vibrating element in related art has a problem that the larger number of steps are taken for formation of the vibrating arms having the grooves from the front and rear surfaces and processing is harder.

Here, the inventor of the application focuses on oblique vibration of the vibrating arms in a direction in which both vibration components in the Z-axis direction and the X-axis direction are synthesized by asymmetric cross section shapes of the vibrating arms (asymmetric with respect to the center line in the X-axis direction as the width direction of the vibrating arms) and proposes a vibrating element using the oblique vibration. Even in the vibrating element using the oblique vibration, for example, when the grooves are formed from the front and rear surfaces of the vibrating arms as in Patent Document 1 or Patent document 2, there is the above described problem that the larger number of steps are taken and processing is harder.

SUMMARY

Application Example 1

A vibrating element according to this application example includes a base part, a drive arm containing a first surface and a second surface having a front-back relation with the first surface, having a recessed portion on the first surface side, and extended from the base part in an extension direction, and a drive part on the second surface, wherein a section shape of the drive arm orthogonal to the extension direction contains an asymmetric section shape with respect to a virtual center line passing through a center of a width in a direction orthogonal to the extension direction.

According to this application example, the vibrating element having the drive arm (vibrating arm) that can be obliquely vibrated may be obtained by simple processing. The oblique vibration is a vibration having vibration components in two axis directions of a first axis and a second axis intersecting with each other in a plane containing the extension direction of the drive arm and a third axis intersecting with the two axes. The obliquely vibrating drive arm is provided, and thereby, vibration leakage is reduced and the vibrating element according to the application example is advantageous in vibration characteristics. Further, processing is simple and yield is improved. Furthermore, the drive arm may be obliquely vibrated with low impedance. Specifically, the recessed portion of the drive arm forming the vibrating element is provided on the first surface. That is, the recessed portion may be formed by digging from one surface, and thereby, the recessed portion containing the asymmetric section shape with respect to the virtual center line may be easily formed. In addition, the drive part is provided on the second surface as the rear surface for the first surface. Therefore, according to the configuration, the drive arm in which the recessed portion is provided on one surface (first surface) and the drive part is provided on the rear surface (second surface) may be easily formed, and the vibrating element that can continue stable oblique vibration may be inexpensively provided.

Application Example 2

In the vibrating element according to the application example described above, it is preferable that the drive part includes a piezoelectric member and a plurality of electrodes provided in parallel in a width direction orthogonal to the extension direction.

According to this application example, the impedance of the so-called in-plane vibration that the drive arm vibrates in a plane direction containing the extension direction of the drive arm may be reduced, and the in-plane vibration may be easily obtained.

Application Example 3

In the vibrating element according to the application example described above, it is preferable that the recessed portion is provided on the drive arm along the extension direction, but does not reach the base part.

According to this application example, when an impact or the like is externally applied, large stress is generated in the connecting part between the drive arm and the base part, however, in the configuration of the example, the part having the smaller section area of the drive arm produced by the recessed portion does not exist in the connecting part to the base part. Therefore, the vibrating element with improved impact resistance may be obtained.

Application Example 4

In the vibrating element according to the application example described above, it is preferable that the recessed portion is provided on the drive arm along the extension direction and reaches the base part.

According to this application example, the drive arm may be obliquely vibrated with low impedance.

Application Example 5

In the vibrating element according to the application example described above, it is preferable that the recessed portion is a groove portion.

According to this application example, the recessed portion is the groove portion and wall parts exist on both sides and the shape of the drive arm is more stable and stiffness is higher, and thereby, more stable vibration of the drive arm may be obtained.

Application Example 6

In the vibrating element according to the application example described above, it is preferable that a detection arm connected to the base part is provided.

According to this application example, changes of the vibration components in the two axis directions of the drive arm are detected by the detection arm, and thereby, angular velocities around the respective axes of the two axes intersecting with each other may be detected. In other words, the angular velocities around the respective axes of the axes intersecting with one another may be detected by one vibrating element.

Application Example 7

In the vibrating element according to the application example described above, it is preferable that the drive arm includes a first drive arm and a second drive arm provided in parallel, the recessed portion of the first drive arm is provided to deviate in a first direction with respect to the virtual center line of the first drive arm, and the recessed portion of the second drive arm is provided to deviate in an opposite direction to the first direction with respect to the virtual center line of the second drive arm.

According to this application example, the vibrations of the width direction components of the respective oblique vibrations of the first drive arm and the second drive arm are in opposite directions to each other, in other words, in opposite phase to each other, and vibration leakage may be reduced. Thereby, the vibrating element with improved vibration characteristics may be obtained.

Application Example 8

In the vibrating element according to the application example described above, it is preferable that the drive arm includes a first drive arm and a second drive arm provided in parallel, and an adjustment arm extended from the base part is provided between the first drive arm and the second drive arm.

According to this application example, the first and second drive arms and the adjustment arm flexurally vibrate in opposite directions to each other with respect to the Z-axis directions, in other words, flexurally vibrate in opposite phase to each other, and thereby, at least part of the vibrations of the Z-axis direction components of the flexural vibrations of the first and second drive arms and at least part of the vibration in the Z-axis directions of the adjustment arm are cancelled out. Accordingly, vibration leakage may be reduced by providing the adjustment arm.

Application Example 9

A vibrating device according to this application example includes the vibrating element according to any one of the application examples described above, and a housing container in which the vibrating element is housed.

According to this application example, the vibrating device that can continue stable oblique vibration and realize cost reduction may be obtained.

Application Example 10

An electronic apparatus according this application example includes the vibrating element according to any one of the application examples described above.

According to this application example, the vibrating element that can continue stable oblique vibration and realize cost reduction is provided, and the electronic apparatus in which more stable characteristics and lower cost are realized may be obtained.

Application Example 11

A moving object according this application example includes the vibrating element according to any one of the application examples described above.

According to this application example, the vibrating element that can continue stable oblique vibration and realize cost reduction is provided, and the moving object in which more stable characteristics and lower cost are realized may be obtained.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

As below, a vibrating element, a vibrating device, an electronic apparatus, and a moving object according to the invention will be explained in detail according to embodiments shown in accompanying drawings.

Vibrating Device

First Embodiment

A vibrator as a vibrating device according to a first embodiment of the invention will be explained usingFIGS. 1 to 5.FIG. 1is a sectional view showing the vibrating device according to the first embodiment of the invention,FIG. 2is a plan view (top view) showing a vibrating element provided in the vibrating device shown inFIG. 1,FIG. 3Ais a sectional view along line A-A inFIG. 2showing a configuration of drive parts, andFIG. 3Bis a similar sectional view showing a modified example of the drive parts. Further,FIGS. 4A and 4Bare sectional views for explanation of actions of the vibrating element shown inFIG. 2, andFIG. 4Acorresponds to the drive part inFIG. 3AandFIG. 4Bcorresponds to the drive part inFIG. 3B. Furthermore,FIGS. 5A and 5Bare sectional views showing a modified example of the vibrating element shown inFIG. 2. Note that, in the respective drawings, for convenience of explanation, an X-axis (first direction), a Y-axis (second direction), and a Z-axis (third direction) are shown as three axes orthogonal to one another. Further, as below, a direction in parallel to the X-axis is also referred to as “X-axis direction (first direction)”, a direction in parallel to the Y-axis is also referred to as “Y-axis direction (second direction)”, and a direction in parallel to the Z-axis is also referred to as “Z-axis direction (third direction)”. Furthermore, as below, a plane defined by the X-axis and the Y-axis is also referred to as “XY-plane”, a plane defined by the Y-axis and the Z-axis is also referred to as “YZ-plane”, and a plane defined by the X-axis and the Z-axis is also referred to as “XZ-plane”. In addition, in the following explanation, for convenience of explanation, the upside inFIG. 1is referred to as “upper” and the downside is referred to as “lower”.

As shown inFIG. 1, a vibrator1as the vibrating device has a vibrating element2and a package9that houses the vibrating element2. The package9has an internal space S formed by a base substrate91, a frame member92, and a lid member93, and the vibrating element2is housed in the internal space. The vibrating element2is connected and fixed to the base substrate91by a fixing material96. The vibrator1has a function of generating an electric signal that vibrates at a predetermined frequency (resonance frequency). As below, the respective parts forming the vibrator1will be sequentially explained in detail.

Vibrating Element

First, the vibrating element2will be explained with reference toFIGS. 2 and 3A. As shown inFIG. 2, the vibrating element2is a three-armed tuning-fork vibrating element. Further, the vibrating element2of the embodiment may generate an electric signal that vibrates at a predetermined frequency (resonance frequency). The vibrating element2has a base part4formed on an element substrate3, three vibrating arms (drive arms5,6and adjustment arm7) extended from the base part4, and a plurality of electrodes formed on the element substrate3.

The element substrate3is formed using a silicon substrate as a material, for example. Drive parts containing piezoelectric layers13(seeFIG. 3A) as piezoelectric members are provided on the element substrate3, and the arm parts (drive arms5,6) are vibrated using the drive parts. As described above, the silicon substrate or the like is used as the material for the element substrate3, and thereby, the element substrate3may be formed with high dimensional precision by etching. Note that the element substrate3may be formed using a piezoelectric material including crystal, lithium tantalate, lithium niobate, lithium borate, and barium titanate, for example. Also, in this case, the element substrate3may be formed with high dimensional precision by etching.

Base Part

As shown inFIG. 2, the base part4has a spread in the XY-plane and a plate shape with a thickness in the Z-axis direction. Further, the base part4is formed to have a thickness substantially equal to those of the vibrating arms (drive arms5,6and adjustment arm7). The three vibrating arms are connected to the base part4. Of the vibrating arms, the drive arms5,6function as driving arms for driving the vibrating element2and the adjustment arm7functions as an adjusting arm for cancelling out the vibrations of the drive arms5,6in the Z direction.

The adjustment arm7is provided at the center of the base part4in the X-axis direction, and extended in the Y-axis direction from an end portion4aof the base part4in the Y-axis direction. Further, the drive arm5and the drive arm6are provided at both end sides of the base part4in the X-axis direction so that the adjustment arm7may be located between the arms, and extended from the end portion4aof the base part4in the Y-axis direction in the Y-axis direction. The drive arms5,6and the adjustment arm7are respectively extended from the base part4in the Y-axis direction in parallel to each other. Further, the drive arms5,6and the adjustment arm7are provided apart at nearly equal intervals in parallel in the X-axis direction. Furthermore, the drive arms5,6and the adjustment arm7respectively have longitudinal shapes and their end portions are fixed ends and their distal end portions are free ends.

Drive Arms

As shown inFIGS. 2 and 3A, the drive arm5has a first surface (upper surface)10formed by the XY-plane and a second surface (lower surface)11formed by the XY-plane and having a front-back relation with the first surface, and has side surfaces20,21connecting the first surface10and the second surface11. A groove portion8ahaving a bottom as a recessed portion dug from the first surface10is provided on the drive arm5. One end16as an end of the groove portion8aat the base part4side is provided not to reach the end portion4aof the base part4. The one end16of the groove portion8ais provided as described above, and thereby, a part having a smaller section area of the drive arm5produced by providing the groove portion8adoes not exist in the connecting part between the drive arm5and the base part4, and strength reduction of the drive arm5in the connecting part between the drive arm5and the base part4is not caused. Thereby, impact resistance of the vibrating element2may be improved. Further, another end18as an end of the groove portion8aat the distal end portion side is provided in a location such that the end may not reach the distal end of the drive arm5, in other words, in a location having a distance from the distal end portion.

Furthermore, as another embodiment than the embodiment, the one end16as the end of the groove portion8aat the base part4side may be provided to reach the end portion4aof the base part4. In addition, as yet another embodiment than the embodiment, the one end16as the end of the groove portion8aat the base part4side is provided on the base part4and the other end18of the groove portion8ais provided on the base part4, and thereby, the groove portion8amay be formed over both the drive arm5and the base part4. The groove portion8ais formed as described above, and thereby, deformation at the base side of the drive arm5and deformation of the connecting part of the base part4to the drive arm5may be easily caused. As a result, the impedance of the drive arm5may be made smaller.

Further, the groove portion8ais provided so that the distance between one side wall of the groove portion8aand the side surface20may be smaller than the distance between the other side wall of the groove portion8aand the side surface21. That is, the groove portion8ais provided to deviate to the adjustment arm7side with respect to a first virtual center line P1passing through the center Q. Further, the drive arm5is provided to contain an asymmetric section shape with respect to the first virtual center line P1passing through the center Q of a width in a direction (X-axis direction) orthogonal to the extension direction (Y-axis direction) of the drive arm5. In other words, the virtual center line P1is a line that divides the maximum width of the drive arm5into two halves. That is, in the case where the side surfaces20,21of the drive arm5are not flat surfaces unlike those shown inFIG. 3A, but fins having irregular shapes (not shown) due to etching are formed on the side surfaces20,21, the line divides the maximum width of the drive arm5including the irregular shapes into two halves. Further, the drive arm5has an asymmetric section shape in the Y-axis direction with respect to a second virtual center line P2passing through the center Q of the thickness in the Z-axis direction (thickness direction). In other words, the virtual center line P2is a line that divides the maximum thickness of the drive arm5into two halves. Accordingly, as will be described later, when the drive arm5is vibrated in the X-axis directions (in-plane directions), a vibration in the Z-axis directions (out-of-plane directions) is newly excited by the vibration. As a result, the drive arm5may be flexurally vibrated (hereinafter, also simply referred to as “oblique vibration”) in directions having both direction components in the X-axis directions and the Z-axis directions, in other words, in directions oblique to both axes of the X-axis and the Z-axis.

Similarly, the drive arm6has a first surface (upper surface)10formed by the XY-plane and a second surface (lower surface)11formed by the XY-plane and having a front-back relation with the first surface, and has side surfaces22,23connecting the first surface10and the second surface11. A groove portion8bhaving a bottom as a recessed portion dug from the first surface10is provided on the drive arm6. One end17as an end of the groove portion8bat the base part4side is provided not to reach the end portion4aof the base part4. The one end17of the groove portion8bis provided as described above, and thereby, apart having a smaller section area of the drive arm6produced by providing the groove portion8bdoes not exist in the connecting part between the drive arm6and the base part4, and strength reduction of the drive arm6in the connecting part between the drive arm6and the base part4is not caused. Thereby, impact resistance of the vibrating element2may be improved. Further, another end19as an end of the groove portion8bat the distal end portion side is provided in a location such that the end may not reach the distal end of the drive arm6, in other words, in a location having a distance from the distal end portion.

Furthermore, as another embodiment than the embodiment, the one end17as the end of the groove portion8bat the base part4side may be provided to reach the end portion4aof the base part4. In addition, as yet another embodiment than the embodiment, the one end17as the end of the groove portion8bat the base part4side is provided on the base part4and the other end19of the groove portion8bis provided on the base part4, and thereby, the groove portion8bmay be formed over both the drive arm6and the base part4. The groove portion8bis formed as described above, and thereby, deformation at the base side of the drive arm6and deformation of the connecting part of the base part4to the drive arm6may be easily caused. As a result, the impedance of the drive arm6may be made smaller.

Note that the other ends18,19of the groove portions8a,8bhave been explained in position examples that do not reach the distal ends of the drive arms5,6, however, not limited to those. The groove portions8a,8bmay reach the distal ends of the drive arms5,6and the other ends may be open ends.

Further, the groove portion8bis provided so that the distance between one side wall of the groove portion8band the side surface22may be smaller than the distance between the other side wall of the groove portion8band the side surface23. That is, the groove portion8bis provided to deviate to the adjustment arm7side with respect to a virtual center line P1passing through the center Q. Further, the drive arm6is provided to contain an asymmetric section shape with respect to the first virtual center line P1passing through the center Q of a width in a direction (X-axis direction) orthogonal to the extension direction (Y-axis direction) of the drive arm6. In other words, the virtual center line P1is a line that divides the maximum width of the drive arm6into two halves. That is, in the case where the side surfaces22,23of the drive arm6are not flat surfaces unlike those shown inFIG. 3A, but fins having irregular shapes (not shown) due to etching are formed on the side surfaces22,23, the line divides the maximum width of the drive arm6including the irregular shapes into two halves. Further, the drive arm6has an asymmetric section shape in the Y-axis direction with respect to a second virtual center line P2passing through the center Q of the thickness in the Z-axis direction. In other words, the virtual center line P2is a line that divides the maximum thickness of the drive arm6into two halves. Accordingly, as will be described later, when the drive arm6is vibrated in the X-axis directions (in-plane directions), a vibration in the Z-axis directions (out-of-plane directions) is newly excited by the vibration. As a result, the drive arm6may be flexurally vibrated (hereinafter, also simply referred to as “oblique vibration”) in directions having both direction components in the X-axis directions and the Z-axis directions, in other words, in directions oblique to both axes of the X-axis and the Z-axis.

As described above, the groove portion8ais provided to deviate in the +X-axis direction with respect to the virtual center line P1of the drive arm5and the groove portion8bis provided to deviate in the −X-axis direction opposite to the +X-axis direction with respect to the virtual center line P1of the drive arm6. As another embodiment than the embodiment, the groove portion8amay be provided to deviate in the −X-axis direction with respect to the virtual center line P1of the drive arm5and the groove portion8bmay be provided to deviate in the +X-axis direction opposite to the −X-axis direction with respect to the virtual center line P1of the drive arm6. Note that the above described groove portions8a,8bmay be formed by a simple method such as etching with high dimensional precision like the formation of the element substrate3.

As shown inFIG. 3A, in the vibrating element2of the embodiment, the drive parts containing the piezoelectric layers13as piezoelectric members are provided on the second surfaces11having the front-back relations with the first surfaces10of the drive arm5and the drive arm6. The drive part is formed by stacking a first electrode layer12, the piezoelectric layer (piezoelectric thin film)13as the piezoelectric member, and a second electrode layer14in this order on each second surface11of the drive arm5and the drive arm6. The drive parts containing the piezoelectric layers13have functions of expanding and contracting by energization and obliquely vibrating the drive arm5and the drive arm6. More specifically, the drive parts containing the piezoelectric layers13have functions of expanding and contracting and obliquely vibrating the drive arm5and the drive arm6by application of electric fields of alternating voltages between the first electrode layers12and the second electrode layers14. As described above, when the drive arm5and the drive arm6are vibrated using the drive parts containing the piezoelectric layers13, the element substrate3may be formed using a silicon substrate, for example.

As a constituent material of the first electrode layers12and the second electrode layers14, for example, a metal material including gold (Au), a gold alloy, platinum (Pt), aluminum (Al), an aluminum alloy, silver (Ag), a silver alloy, chromium (Cr), a chromium alloy, copper (Cu), molybdenum (Mo), niobium (Nb), tungsten (W), iron (Fe), titanium (Ti), cobalt (Co), zinc (Zn), and zirconium (Zr) or a conducting material including indium tin oxide (ITO) may be used.

Of the materials, as the constituent material of the first electrode layers12and the second electrode layers14, a metal consisting primarily of gold (gold, gold alloy) or platinum is preferably used, and a metal consisting primarily of gold (particularly, gold) is more preferably used. Au is advantageous in conductivity (lower electric resistance) and resistance to oxidation and preferable as an electrode material. Further, Au may be patterned by etching more easily than Pt.

Note that, for example, the first electrode layers12and the second electrode layers14are formed using gold and, when adhesion to the element substrate3is lower, it is preferable to provide foundation layers formed using Ti, Cr, or the like between the first electrode layers12and the second electrode layers14and the element substrate3. Thereby, adhesion between the foundation layers and the drive arms5,6and adhesion between the foundation layers and the first electrode layers12may be respectively made advantageous. As a result, separation of the first electrode layers12from the drive arms5,6may be reduced and reliability of the vibrating element2may be made advantageous.

As a constituent material of the piezoelectric layers13, for example, zinc oxide (ZnO), aluminum nitride (AlN), lithium tantalate (LiTaO3), lithium niobate (LiNbO3), potassium niobate (KNbO3), lithium tetraborate (Li2B4O7), barium titanate (BaTiO3), PZT (lead zirconate titanate), or the like may be used, and AlN or ZnO is preferably used.

Adjustment Arm

The adjustment arm7has constant thickness (length in the Z-axis direction) and width (length in the X-axis direction) over the entire region in its longitudinal direction (Y-axis direction as the extension direction). The adjustment arm7vibrates according to the vibrations of the drive arm5and the drive arm6.

Action of Drive Arms and Adjustment Arm

Also, with reference toFIG. 4A, the action of the drive arms5,6and the adjustment arm7will be explained.

In the above described configuration, when the alternating voltages are applied between the first electrode layers12and the second electrode layers14by a power source, the respective piezoelectric layers13expand or contract in the Y-axis directions and the drive arm5and the drive arm6flexurally vibrate in the Z-axis directions at a certain constant frequency (resonance frequency). In this regard, in the drive arm5and the drive arm6, new flexural vibrations in the X-axis directions due to their shapes are excited by the vibrations in the Z-axis directions. By the new flexural vibrations, the drive arm5and the drive arm6obliquely vibrate by synthesis of the flexural vibrations in the X-axis directions and the flexural vibrations in the Z-axis directions, and vibrate in directions oblique to the Z-axis and the X-axis as shown by arrows L1, L2inFIG. 4A(i.e., obliquely vibrate) because the section shapes of the drive arm5and the drive arm6are asymmetric with respect to the XY-plane and the YZ-plane. Further, the drive arm5and the drive arm6flexurally vibrate symmetrically with respect to the ZY-plane.

On the other hand, the adjustment arm7flexurally vibrates in the Z-axis directions as directions of an arrow L3shown inFIG. 4Aopposite to the vibrations of the drive arm5and the drive arm6in the Z-axis directions at the same time with the flexural vibrations of the drive arm5and the drive arm6.

In the vibrations, the drive arm5and the drive arm6symmetrically vibrate with respect to the YZ-plane, and thus, the vibration of the X-axis direction component of the flexural vibration of the drive arm5and the vibration of the X-axis direction component of the flexural vibration of the drive arm6are balanced and cancelled out. Accordingly, the vibration in the X-axis directions is not transmitted to the adjustment arm7and the adjustment arm7hardly vibrates in the X-axis directions. Further, the drive arm5and the drive arm6and the adjustment arm7flexurally vibrate in the opposite directions in the Z-axis directions, and the vibrations of the Z-axis direction components of the flexural vibrations of the drive arm5and the drive arm6and the vibration of the Z-axis direction component of the flexural vibration of the adjustment arm7are balanced and cancelled out. Thus, according to the vibrating element2, vibration leakage may be effectively reduced.

Particularly, in the embodiment, the two obliquely vibrating drive arm5and drive arm6are located at both ends of the base part4(near both ends in the X-axis directions) and the vibrations in the out-of-plane directions (Z-axis directions) and the in-plane directions (X-axis directions) may be balanced (driven with balance), and thereby, the drive arm5, the drive arm6, and the adjustment arm7may be vibrated more stably. Accordingly, the vibration leakage may be reduced more effectively. Further, in the vibrating element2, the adjustment arm7is provided and the vibrations in the Z-axis directions (translation) of the drive arm5and the drive arm6may be automatically cancelled out, and thereby, the moment of rotation may be cancelled to be smaller.

Modified Examples of Drive Parts

Note that, in the above description, the configuration of the drive part formed by stacking the first electrode layer12, the piezoelectric layer (piezoelectric thin film)13as the piezoelectric member, and the second electrode layer14in this order on each second surface11of the drive arm5and the drive arm6has been explained, however, a configuration of the drive part shown inFIG. 3Bmay be employed. The detailed explanation will be made as below.

The drive part shown inFIG. 3Bhas a configuration in which a third electrode12aand a fourth electrode12bas a first electrode layer divided into two, a piezoelectric layer (piezoelectric thin film)13as a piezoelectric member, and a fifth electrode14aand a sixth electrode14bas a second electrode layer divided into two are stacked in this order on each second surface11of the drive arm5and the drive arm6. More specifically, the third electrode12aand the fourth electrode12bas the first electrode layer are provided in parallel in the width direction (X-axis direction) of the drive arm5and the fifth electrode14aand the sixth electrode14bas the second electrode layer are provided in parallel in the width direction (X-axis direction) of the drive arm5. In the drive part having the configuration, when alternating voltages are applied to the drive part containing the third electrode12a, the piezoelectric layer13, and the fifth electrode14aand the drive part containing the fourth electrode12b, the piezoelectric layer13, and the sixth electrode14bby a power source, the piezoelectric layer13corresponding to the third electrode12aand the piezoelectric layer13corresponding to the fourth electrode12bexpand or contract in the Y-axis directions and the drive arm5and the drive arm6flexurally vibrate in the X-axis directions at a certain constant frequency (resonance frequency). Note that the drive arms vibrate in directions oblique to the Z-axis and the X-axis as shown by arrows L4, L5inFIG. 4B(i.e., obliquely vibrate) because the section shapes of the drive arm5and the drive arm6are asymmetric with respect to the XY-plane and the YZ-plane like the above described embodiment. Further, the drive arm5and the drive arm6flexurally vibrate symmetrically with respect to the ZY-plane.

The above described drive arm5and the drive arm6may be vibrated both in the in-plane directions (X-axis directions) and the out-of-plane directions (Z-axis directions) as shown inFIGS. 4A and 4B. In this regard, the impedance is lower as the drive direction and the vibration direction are closer, and the drive direction may be selected. That is, the impedance is lower in the configuration ofFIG. 4Ain the case of vibration in directions closer to the Z-axis directions and in the configuration ofFIG. 4Bin the case of vibration in directions closer to the X-axis directions.

Note that, in the above described embodiment, the configuration in which no piezoelectric element (drive part) is provided on the adjustment arm7and the adjustment arm7vibrates with the vibrations of the drive arm5and the drive arm6has been explained, however, a piezoelectric element (drive part) may be provided on the adjustment arm7and the adjustment arm7may be vibrated in the Z-axis directions by the expansion and contraction of the piezoelectric element.

Further, in the above described embodiment, the example in which the thicknesses (lengths in the Z-axis direction) and the widths (lengths in the X-axis direction) are constant over the entire region in the longitudinal direction of the drive arm5, the drive arm6, and the adjustment arm has been explained, however, as shown inFIGS. 5A and 5B, wider parts (hammer heads)55wider than the drive arm5may be provided on the respective distal end portions. Note that, inFIGS. 5A and 5B, the drive arm5is shown as a representative example, and the same applies to a configuration in which the wider part (hammer head) is provided on the other drive arm or the adjustment arm. The groove portion8ahas an open end55band an end55aat the base part side. Another end50bof the groove portion8amay be closer to the open end55bside than the end55aof the wider part55at the base part4(seeFIG. 2) side, i.e., within the wider part55or may be in a location not reaching the end55aat the base part4side, i.e., within the drive arm5as shown inFIG. 5B.

Package

Next, returning toFIG. 1, the package9as a housing container that houses and fixes the vibrating element2will be explained. As shown inFIG. 1, the package9has the plate-like base substrate91, the frame-like frame member92, and the plate-like lid member93. The base substrate91, the frame member92, and the lid member93are stacked in this order from the downside to the upside (in the +Z direction). The base substrate91and the frame member92are formed using a ceramics material, which will be described later, or the like, and integrally baked with each other and joined. The frame member92and the lid member93are joined by an adhesive, a brazing filler metal, or the like. Further, the package9houses the vibrating element2in the internal space S defined by the base substrate91, the frame member92, and the lid member93. Note that, in addition to the vibrating element2, electronic components (oscillator circuit) that drive the vibrating element2etc. may be housed within the package9.

As a constituent material of the base substrate91, an insulating (non-conducting) material is preferable. For example, various kinds of glass, various kinds of ceramics materials including oxide ceramics, nitride ceramics, carbide-based ceramics, various kinds of resin materials including polyimide, or the like may be used.

Further, as a constituent material of the frame member92and the lid member93, for example, the same constituent material as the base substrate91, various kinds of metal materials including Al, Cu, and kovar, various kinds of glass, or the like may be used.

To the upper surface of the base substrate91, the above described vibrating element2is fixed via the fixing material96. The fixing material96includes an epoxy-based, polyimide-based, or silicone-based adhesive, for example. The fixing material96is formed by applying an uncured (unsolidified) adhesive onto the base substrate91, further, mounting the vibrating element2on the adhesive, and curing and solidifying the adhesive. Thereby, the vibrating element2is reliably fixed to the base substrate91. Note that the fixation may be performed using an epoxy-based, polyimide-based, or silicone-based conducting adhesive containing conducting particles.

According to the above explained first embodiment, the vibrating element2having the drive arms5,6that can be obliquely vibrated may be obtained by simple processing including etching. The obliquely vibrated drive arms5,6are provided, and thereby, the vibrating element2with suppressed vibration leakage and advantageous vibration characteristics may be obtained. In addition, the processing is simple and the yield is improved. Further, the groove portions8a,8bas the recessed portions are provided on the first surfaces10in the drive arms5,6. That is, the groove portions8a,8bmay be formed by digging from one surfaces (first surfaces10) by etching or the like, and thereby, the groove portions8a,8bcontaining the asymmetric section shapes with respect to the first virtual center lines P1may be easily formed. Furthermore, the drive parts containing the piezoelectric layers13are provided on the second surfaces11as the rear surfaces for the first surfaces10. The second surfaces11are flat surfaces without the groove portions8a,8band the drive parts may be easily formed thereon. Therefore, according to the configuration, the drive arms5,6in which the groove portions8a,8bare formed on the one surfaces (first surfaces10) and the drive parts are provided on the rear surfaces (second surfaces11) may be easily formed, and the vibrating element2that can continue stable oblique vibrations, i.e., the vibrator1may be inexpensively provided.

Second Embodiment

Next, a gyro sensor as a vibrating device according to a second embodiment of the invention will be explained.FIG. 6is a sectional view showing the gyro sensor as the vibrating device according to the second embodiment of the invention,FIG. 7is a plan view (top view) showing a gyro element as a vibrating element provided in the vibrating device shown inFIG. 6,FIG. 8Ais a sectional view along line B-B inFIG. 7,FIG. 8Bis a similar sectional view showing a modified example of drive parts, andFIGS. 9A and 9Bare sectional views showing a modified example of the gyro element shown inFIG. 7. Further,FIGS. 10A and 10Bare sectional views for explanation of actions of vibrating arm of the gyro element shown inFIG. 7, andFIG. 10Acorresponds to the drive parts inFIG. 8AandFIG. 10Bcorresponds to the drive parts inFIG. 8B. Furthermore,FIG. 11is a plan view showing a vibration of the gyro element when an angular velocity around a Z-axis is applied, andFIG. 12is a plan view showing a vibration of the gyro element when an angular velocity around a Y-axis is applied.

Note that the second embodiment will be explained as below with a focus on the differences from the above described embodiment and the explanation of the same items will be omitted. Further, as below, as shown inFIG. 1, three axes orthogonal to one another are an X-axis (first axis), a Y-axis (second axis) and a Z-axis (third axis). Furthermore, a direction in parallel to the X-axis is also referred to as “X-axis direction”, a direction in parallel to the Y-axis is also referred to as “Y-axis direction”, and a direction in parallel to the Z-axis is also referred to as “Z-axis direction”. In addition, a plane defined by the X-axis and the Y-axis is also referred to as “XY-plane”, a plane defined by the Y-axis and the Z-axis is also referred to as “YZ-plane”, and a plane defined by the X-axis and the Z-axis is also referred to as “XZ-plane”.

A gyro sensor1ashown inFIG. 6has a gyro element40as a vibrating element, and a package9athat houses the gyro element40. The package9ahas an internal space S formed by a base substrate91a, a frame member92a, and a lid member93a, and the gyro element40is housed in the internal space. The gyro element40is connected and fixed to the base substrate91by a fixing material96a. The gyro sensor1ahas a function of generating an electric signal that vibrates at a predetermined frequency (resonance frequency). The gyro sensor1ais a gyro sensor that may detect an angular velocity ωz around the Z-axis and an angular velocity ωy around the Y-axis. As below, the respective parts forming the gyro sensor1awill be sequentially explained in detail.

Gyro Element

First, the gyro element40will be explained with reference toFIGS. 7 and 8A. As shown inFIG. 7, the gyro element40is the so-called double-T-shaped gyro element. The gyro element40has an element substrate70, and drive parts containing piezoelectric layers63,66as a plurality of piezoelectric members formed on the element substrate70.

The element substrate70is formed using a silicon substrate as a material, for example. The drive parts and detection parts containing piezoelectric layers63,66(seeFIG. 8A) as piezoelectric members are provided on the element substrate70. Further, a first drive arm46and a third drive arm48as first drive arms and a second drive arm47and a fourth drive arm49as second drive arms are driven using the drive parts, and signals (output signals) are extracted from first, second detection arms42,43using the detection parts.

As described above, the silicon substrate or the like is used as the material for the element substrate70, and thereby, the element substrate70may be formed with high dimensional precision by etching. Note that the element substrate70may be formed using a piezoelectric material. The piezoelectric material includes crystal, lithium tantalate, lithium niobate, lithium borate, and barium titanate, for example. Specifically, as the piezoelectric material forming the element substrate70, crystal is preferable. When the element substrate70is formed using crystal, the vibration characteristics (particularly, frequency-temperature characteristics) of the element substrate70may be made advantageous. Further, the element substrate70may be formed with high dimensional precision by etching.

The element substrate70has a spread in the XY-plane and a thickness in the Z-axis direction, and has a center base part41, the first detection arm42, the second detection arm43, a first connecting arm44, a second connecting arm45, the first drive arm46, the second drive arm47, the third drive arm48, and the fourth drive arm49. Note that, in the following explanation, the first detection arm42and the second detection arm43may be collectively described as “first, second detection arms42,43”, the first connecting arm44and the second connecting arm45may be collectively described as “first, second connecting arms44,45”, the first drive arm46, the second drive arm47, the third drive arm48, and the fourth drive arm49may be collectively described as “first, second, third, fourth drive arms46,47,48,49”.

A base part58including the center base part41and the first connecting arm44and the second connecting arm45extended from the center base part41in opposite directions to each other in the X-axis directions is provided at the center of the element substrate70. Further, the first detection arm42and the second detection arm43are extended from the center base part41in opposite directions to each other in the Y-axis directions. Note that the first detection arm42and the second detection arm43are not necessarily directly extended from the base part41as long as they are integrally connected with the base part41. Further, the first drive arm46and the third drive arm48are extended from a distal end portion of the first connecting arm44in opposite directions to each other in the Y-axis directions. Furthermore, the second, fourth drive arms47,49are extended from a distal end portion of the second connecting arm45in opposite directions to each other in the Y-axis directions.

Note that, in the illustrated configuration, the widths of the first connecting arm44and the second connecting arm45are narrower than the width of the center base part41, however, they may be integrally formed with the center base part41in the same width. Further, the first, third drive arms46,48may be extended from the middle of the first connecting arm44in the extension direction, and similarly, the second, fourth drive arms47,49may be extended from the middle of the second connecting arm45in the extension direction.

Detection Arms

The first, second detection arms42,43are symmetrically provided with respect to the XZ-plane intersecting with the center of gravity (center) G. Further, the first, second detection arms42,43have nearly rectangular cross section shapes as shown inFIG. 8A. Two detection parts are formed in parallel in the X-axis direction on a second surface (lower surface)68of the first detection arm42. The two detection parts include a first detection part75in which a first electrode layer65a, a piezoelectric layer66, and a second electrode layer67aare stacked in this order, and a second detection part76in which a first electrode layer65b, a piezoelectric layer66, and a second electrode layer67bare stacked in this order. Note that the piezoelectric layers66in this example are integrally formed, however, they are not necessarily integrally formed. They may be individually formed. The second detection part76has a potential as the ground with respect to the first detection part75. Similarly, two detection parts are formed in parallel in the X-axis direction on a second surface (lower surface) of the second detection arm43, and their explanation will be omitted because they have the same configurations.

In the configuration, when the first, second detection arms42,43vibrate in a detection mode in which the arms are excited by application of at least one of the angular velocity ωy and the angular velocity ωz, the first detection part75and the second detection part76expand or contract. By the expansion or contraction, strain of the first, second detection arms42,43may be extracted as signals (output signals) from between the first electrode layer65aand the second electrode layer67a(first detection part75) and between the first electrode layer65band the second electrode layer67b(second detection part76).

Thus extracted signals from the two detection parts are processed in a manner, which will be described later, and thereby, the angular velocity ωy and the angular velocity ωz may be independently detected, respectively.

Note that the two detection parts are used, and thereby, strain of the first, second detection arms42,43may be extracted as the signals more reliably with the simple configuration.

In the illustrated configuration, the section shapes of the first detection arm42and the second detection arm43are rectangular shapes, however, grooves may be provided on at least one surfaces of the upper surfaces and the lower surfaces of the first, second detection arms42,43.

Drive Arms

Next, the configurations of the first, second, third, fourth drive arms46,47,48,49will be explained. Note that the first, second drive arms46,47and the third, fourth drive arms48,49are symmetrically provided with respect to the XZ-plane intersecting with the center of gravity (center) G. Therefore, in the explanation, the first, second drive arms46,47will be explained and the explanation of the third, fourth drive arms48,49will be omitted.

As shown inFIGS. 7 and 8A, the first drive arm46has a first surface (upper surface)60formed by the XY-plane and a second surface (lower surface)61formed by the XY-plane and having a front-back relation with the first surface, and has side surfaces71,72connecting the first surface60and the second surface61. A groove portion50having a bottom as a recessed portion dug from the first surface60is provided on the first drive arm46. One end50aas an end of the groove portion50at the first connecting arm44side is provided not to reach the first connecting arm44. The one end50aof the groove portion50is provided as described above, and thereby, a part having a smaller section area of the first drive arm46produced by providing the groove portion50does not exist in the connecting part between the first drive arm46and the first connecting arm44, and strength reduction of the first drive arm46is not caused. Thereby, impact resistance of the gyro element40may be improved. Further, another end50bas an end of the groove portion50at the distal end portion side is provided in a location such that the end may not reach the distal end of the first drive arm46, in other words, in a location having a distance from the distal end portion.

Further, the groove portion50is provided so that the distance between one side wall of the groove portion50and the side surface71may be smaller than the distance between the other side wall of the groove portion50and the side surface72. That is, the groove portion50is provided to deviate to the first detection arm42side with respect to the center Q. In other words, the first drive arm46is provided to contain an asymmetric section shape with respect to a first virtual center line P1passing through the center Q in the width direction (X-axis direction) orthogonal to the extension direction (Y-axis direction) of the first drive arm46. Further, the first drive arm46has an asymmetric section shape in the Y-axis direction with respect to a second virtual center line P2passing through the center Q in the Z-axis direction. Accordingly, as will be described later, when the first drive arm46is vibrated in the X-axis directions (in-plane directions), a vibration in the Z-axis directions (out-of-plane directions) is newly excited by the vibration. As a result, the first drive arm46may be flexurally vibrated (hereinafter, also simply referred to as “oblique vibration”) in directions having both direction components in the X-axis directions and the Z-axis directions, in other words, in directions oblique to both axes of the X-axis and the Z-axis.

Similarly, the second drive arm47has a first surface (upper surface)60formed by the XY-plane and a second surface (lower surface)61formed by the XY-plane and having a front-back relation with the first surface, and has side surfaces73,74connecting the first surface60and the second surface61. A groove portion51having a bottom as a recessed portion dug from the first surface60is provided on the second drive arm47. One end51aas an end of the groove portion51at the second connecting arm45side is provided not to reach the second connecting arm45. The one end51aof the groove portion51is provided as described above, and thereby, a part having a smaller section area of the second drive arm47produced by providing the groove portion51does not exist in the connecting part between the second drive arm47and the second connecting arm45, and strength reduction of the second drive arm47is not caused. Thereby, impact resistance of the gyro element40may be improved. Further, another end51bas an end of the groove portion51at the distal end portion side is provided in a location such that the end may not reach the distal end of the second drive arm47, in other words, in a location having a distance from the distal end portion.

Note that the other ends50b,51bof the groove portions50,51have been explained in position examples that do not reach the distal ends of the first drive arm46, the second drive arm47, however, not limited to those. The groove portions50,51may reach the distal ends of the first drive arm46, the second drive arm47and the other ends may be open ends.

Further, the groove portion51is provided so that the distance between one side wall of the groove portion51and the side surface73may be smaller than the distance between the other side wall of the groove portion51and the side surface74. That is, the groove portion51is provided to deviate to the first detection arm42side with respect to the center Q. In other words, the second drive arm47is provided to contain an asymmetric section shape with respect to a first virtual center line P1passing through the center Q in the width direction (X-axis direction) orthogonal to the extension direction (Y-axis direction) of the second drive arm47. Further, the second drive arm47has an asymmetric section shape in the Y-axis direction with respect to a second virtual center line P2passing through the center Q in the Z-axis direction. Accordingly, as will be described later, when the second drive arm47is vibrated in the X-axis directions (in-plane directions), a vibration in the Z-axis directions (out-of-plane directions) is newly excited by the vibration. As a result, the second drive arm47may be flexurally vibrated (hereinafter, also simply referred to as “oblique vibration”) in directions having both direction components in the X-axis directions and the Z-axis directions, in other words, in directions oblique to both axes of the X-axis and the Z-axis.

As described above, the groove portions50,51are provided to deviate in the same direction with each other toward the virtual center lines passing through the centers in the thickness direction (Z-axis direction) of the first drive arm46and the second drive arm47. Note that the groove portions50,51may be formed by a simple method such as etching with high dimensional precision like the formation of the element substrate70.

As shown inFIG. 8A, in the gyro element40of the embodiment, the drive parts containing the piezoelectric layers63as piezoelectric members are provided on the second surfaces61having the front-back relations with the first surfaces60of the first drive arm46and the second drive arm47. The drive part is formed by stacking the first electrode layer62, the piezoelectric layer (piezoelectric thin film)63as the piezoelectric member, and the second electrode layer64in this order on each second surface61of the first drive arm46and the second drive arm47. The drive parts containing the piezoelectric layers63have functions of expanding and contracting by energization and obliquely vibrating the first drive arm46and the second drive arm47. As described above, when the first drive arm46and the second drive arm47are vibrated using the drive parts containing the piezoelectric layers63, the element substrate70may be formed using a silicon substrate, for example.

As a constituent material of the first electrode layers62and the second electrode layers64, for example, a metal material including gold (Au), a gold alloy, platinum (Pt), aluminum (Al), an aluminum alloy, silver (Ag), a silver alloy, chromium (Cr), a chromium alloy, copper (Cu), molybdenum (Mo), niobium (Nb), tungsten (W), iron (Fe), titanium (Ti), cobalt (Co), zinc (Zn), and zirconium (Zr) or a conducting material including indium tin oxide (ITO) may be used.

Of the materials, as the constituent material of the first electrode layers62and the second electrode layers64, a metal consisting primarily of gold (gold, gold alloy) or platinum is preferably used, and a metal consisting primarily of gold (particularly, gold) is more preferably used. Au is advantageous in conductivity (lower electric resistance) and resistance to oxidation and preferable as an electrode material. Further, Au may be patterned by etching more easily than Pt.

Note that, for example, the first electrode layers62and the second electrode layers64are formed using gold and, when adhesion to the element substrate70is lower, it is preferable to provide foundation layers formed using Ti, Cr, or the like between the first electrode layers62and the second electrode layers64and the element substrate70. Thereby, adhesion between the foundation layers and the first drive arm46and the second drive arm47and adhesion between the foundation layers and the first electrode layers62may be respectively made advantageous. As a result, separation of the first electrode layers62from the first drive arm46and the second drive arm47may be reduced and reliability of the gyro element40may be made advantageous.

As a constituent material of the piezoelectric layers13, for example, zinc oxide (ZnO), aluminum nitride (AlN), lithium tantalate (LiTaO3), lithium niobate (LiNbO3), potassium niobate (KNbO3), lithium tetraborate (Di2B4O7), barium titanate (BaTiO3), PZT (lead zirconate titanate), or the like may be used, and AlN or ZnO is preferably used.

Modified Examples of Drive Parts

In the drive parts shown inFIG. 8B, a third electrode62aand a fourth electrode62bas a first electrode layer divided into two, a piezoelectric layer (piezoelectric thin film)63as a piezoelectric member, and a fifth electrode64aand a sixth electrode64bas a second electrode layer divided into two are stacked in this order on each second surface61of the first drive arm46and the second drive arm47. In the drive parts having the configurations, when alternating voltages are applied to the drive part containing the third electrode62a, the piezoelectric layer63, and the fifth electrode64aand the drive part containing the fourth electrode62b, the piezoelectric layer63, and the sixth electrode64bby a power source, the piezoelectric layer63corresponding to the third electrode62aand the piezoelectric layer63corresponding to the fourth electrode62bexpand or contract in the Y-axis directions and the first drive arm46and the second drive arm47flexurally vibrate in the X-axis directions at a certain constant frequency (resonance frequency). Note that the drive arms vibrate in directions oblique to the Z-axis and the X-axis as shown by arrows L4, L5inFIG. 10B(i.e., obliquely vibrate) because the section shapes of the first drive arm46and the second drive arm47are asymmetric with respect to the XY-plane and the YZ-plane like the above described embodiment. Further, the first drive arm46and the second drive arm47flexurally vibrate symmetrically with respect to the ZY-plane.

Further, in the above described embodiment, the example in which the thicknesses (lengths in the Z-axis direction) and the widths (lengths in the X-axis direction) are constant over the entire region in the longitudinal direction (in the Y-axis direction as the extension direction) of the first drive arm46and the second drive arm47has been explained, however, as shown inFIGS. 9A and 9B, wider parts (hammer heads)55wider than the first drive arm46and the second drive arm47may be provided on the respective distal end portions. Note that, inFIGS. 9A and 9B, the first drive arm46is shown as a representative example. The groove portion50has an open end55band an end55aat the first connecting arm44(seeFIG. 7) side. Another end50bof the groove portion50may be closer to the open end55bside than the end55aof the wider part55at the first connecting arm44side, i.e., within the wider part55as shown inFIG. 9A, or may be in a location not reaching the end55aat the base part side, i.e., within the first drive arm46. A wider part corresponding to the above described wider part55may be also provided on the first detection arm42.

The above described first drive arm46and second drive arm47may be vibrated both in the in-plane directions (X-axis directions) and the out-of-plane directions (Z-axis directions) as shown inFIGS. 10A and 10B. In this regard, the impedance is lower as the drive direction and the vibration direction are closer, and the drive direction may be selected. That is, the impedance is lower in the configuration ofFIG. 10Ain the case of vibration in directions closer to the Z-axis directions and in the configuration ofFIG. 10Bin the case of vibration in directions closer to the X-axis directions.

Package

Next, returning toFIG. 6, the package9aas a housing container that houses and fixes the gyro element40will be explained. As shown inFIG. 6, the package9ahas the plate-like base substrate91a, the frame-like frame member92a, and the plate-like lid member93a. The base substrate91a, the frame member92a, and the lid member93aare stacked in this order from the downside to the upside (in the +Z direction). The base substrate91aand the frame member92aare formed using a ceramics material, which will be described later, or the like, and integrally baked with each other and joined. The frame member92aand the lid member93aare joined by an adhesive, a brazing filler metal, or the like. Further, the package9ahouses the gyro element40in the internal space S defined by the base substrate91a, the frame member92a, and the lid member93a. Note that, in addition to the gyro element40, electronic components (oscillator circuit) that drive the gyro element40etc. may be housed within the package9a.

As a constituent material of the base substrate91a, an insulating (non-conducting) material is preferable. For example, various kinds of glass, various kinds of ceramics materials including oxide ceramics, nitride ceramics, carbide-based ceramics, various kinds of resin materials including polyimide, or the like may be used.

Further, as a constituent material of the frame member92aand the lid member93a, for example, the same constituent material as the base substrate91a, various kinds of metal materials including Al, Cu, and kovar, various kinds of glass, or the like may be used.

To the upper surface of the base substrate91a, the above described gyro element40is fixed via the fixing material96a. The fixing material96aincludes an epoxy-based, polyimide-based, or silicone-based adhesive, for example. The fixing material96ais formed by applying an uncured (unsolidified) adhesive onto the base substrate91a, further, mounting the gyro element40on the adhesive, and curing and solidifying the adhesive. Thereby, the gyro element40is reliably fixed to the base substrate91a. Note that the fixation may be performed using an epoxy-based, polyimide-based, or silicone-based conducting adhesive containing conducting particles.

Action of Gyro Sensor

The configuration of the gyro sensor1ahas been explained. The gyro sensor1adetects the angular velocity ωy around the Y-axis and the angular velocity ωz around the Z-axis in the following manner. As below, the explanation will be made usingFIG. 10A to 12, and illustration of the respective electrodes and groove portions will be omitted inFIGS. 11 and 12for convenience of explanation.

Without application of an angular velocity, when alternating voltages are applied between the drive part containing the third electrode62a, the fourth electrode62b, and the piezoelectric layer (piezoelectric film)63as the piezoelectric member and the drive part containing the fifth electrode64a, the sixth electrode64b, and the piezoelectric layer (piezoelectric film)63as the piezoelectric member, as shown inFIGS. 10A and 10B, the first, second drive arms46, and the third, fourth drive arms48,49(not shown) respectively obliquely vibrate because they have asymmetric parts. Further, the vibrations are plane-symmetric vibrations of the first, third drive arms46,48and the second, fourth drive arms47,49(seeFIG. 7) with respect to the YZ-plane intersecting with the center of gravity G.

In this regard, as described above, the first, third drive arms46,48and the second, fourth drive arms47,49vibrate plane-symmetrically with respect to the YZ-plane intersecting with the center of gravity G, and thus, the vibrations of the first, second, third, fourth drive arms46,47,48,49in the X-axis directions are cancelled. Accordingly, the first, second detection arms42,43hardly vibrate in the X-axis directions. On the other hand, the first, second, third, fourth drive arms46,47,48,49vibrate toward the same side in the Z-axis directions with each other, and the vibrations of the first, second, third, fourth drive arms46,47,48,49in the Z-axis directions are not cancelled. Accordingly, the first, second detection arms42,43flexurally vibrate in the Z-axis directions opposite to the first, second, third, fourth drive arms46,47,48,49to balance with the first, second, third, fourth drive arms46,47,48,49as shown inFIGS. 10Aand10B. Note that the vibration directions of the first, second, third, fourth drive arms46,47,48,49are not limited to the vibration directions shown inFIGS. 10A and 10B, but may be opposite to the vibration directions shown inFIGS. 10A and 10B, for example. The vibration directions may be appropriately selected depending on a desired frequency or a driving unit.

Under the condition, when the angular velocity ωz around the Z-axis is applied to the gyro sensor1a, Coriolis forces A act and vibrations shown by arrows B (angular velocity around Z-axis detection vibration mode) are excited by the Coriolis forces A as drive force as shown inFIG. 11. In this regard, deformation generated in the first, second detection arms42,43is in the opposite direction with respect to the X-axis. Further, it is preferable that the detection vibration mode is at a frequency within ±10% of the drive frequency. Note that, regarding the vibration directions of the first, second detection arms42,43, in other words, the first, second detection arms42,43vibrate in the same rotation direction with respect to the Z-axis. This is because the first, second, third, fourth drive arms46,47,48,49vibrate as shown inFIG. 11by the action of the Coriolis forces A and the first, second detection arms42,43respectively extend toward the upside and the downside with the center base part41in between, and thereby, the first detection arm42is deformed according to the first, second drive arms46,47and the second detection arm43is deformed according to the third, fourth drive arms48,49.

On the other hand, when the angular velocity ωy around the Y-axis is applied to the gyro sensor1a, Coriolis forces A act and vibrations shown by arrows B (angular velocity around Y-axis detection vibration mode) are excited by the Coriolis forces A as drive force as shown inFIG. 12. In this regard, deformation generated in the first, second detection arms42,43is in the same direction with respect to the X-axis. Further, it is preferable that the detection vibration mode is at a frequency within ±10% of the drive frequency. Note that, regarding the vibration directions of the first, second detection arms42,43, in other words, the first, second detection arms42,43vibrate in the same direction with respect to the X-axis. This is because the first, second, third, fourth drive arms46,47,48,49vibrate as shown inFIG. 12by the action of the Coriolis forces A and Coriolis forces in the same direction with respect to the X-axis direction and in the opposite directions to the first, second, third, fourth drive arms46,47,48,49act, and thereby, the first, second detection arms42,43vibrate in the same direction with respect to the X-axis direction.

In the gyro sensor1a, the angular velocity ωz and the angular velocity ωy may be respectively and independently detected using differences in the vibration directions of the first, second detection arms42,43when the angular velocity ωz around the Z-axis is applied and when the angular velocity ωy around the Y-axis is applied as described above. Note that the detection parts provided on the first detection arm42are the first detection part75and the second detection part76(seeFIGS. 8A and 8B) and the detection parts provided on the second detection arm43are a third detection part (not shown) and a fourth detection part (not shown).

In the specific explanation, when the angular velocity ωz is applied, signals (voltages) V1extracted from the first detection part75and the second detection part76are signals (voltages) +Vz due to the angular velocity ωz and signals (voltages) V2extracted from the third detection part and the fourth detection part are signals (voltages) −Vz due to the angular velocity ωz. That is, V1=+Vz, V2=−Vz.

On the other hand, when the angular velocity ωy is applied, signals V1extracted from the first detection part75and the second detection part76are signals +Vy due to the angular velocity ωy and signals V2extracted from the third detection part and the fourth detection part are signals +Vy due to the angular velocity ωy. That is, V1=+Vy, V2=+Vy. Note that the signs are the same between the signals V1, V2because a strain detection unit is adapted to produce signals with different signs for the angular velocity around the Z-axis as described above.

Accordingly, when an angular velocity ωyz around an axis having both direction components in the Y-axis direction and the Z-axis direction (i.e., an axis oblique with respect to both axis of the Y-axis and the Z-axis) is applied to the gyro sensor1a, signals V1extracted from the first detection part75and the second detection part76are (+Vy)+(+Vz) and signals V2extracted from the third detection part and the fourth detection part are (+Vy)+(−Vz). That is, V1=Vy+Vz, V2=Vy−Vz.

Thus obtained signals V1, V2are added or subtracted, and thereby, the angular velocity ωy around the Y-axis and the angular velocity ωz around the Z-axis of the angular velocity ωyz may be separated and the angular velocity Coy and the angular velocity ωz may be respectively and independently detected. Specifically, V1+V2=2Vy, and the signal Vz due to the angular velocity ωz may be removed. Thereby, the angular velocity ωy around the Y-axis is obtained. On the other hand, V1−V2=2Vz, and the signal Vy due to the angular velocity ωy may be removed. Thereby, the angular velocity ωz around the Z-axis is obtained. According to the gyro sensor1a, the angular velocity ωy around the Y-axis and the angular velocity ωz around the Z-axis may be respectively and independently detected in a simple manner.

The calculation may be performed using an IC chip or the like (not shown) connected to the gyro sensor1a. Note that the signs of the above described signals “Vz”, “Vy” are reversed depending on the wiring configuration. That is, the “+Vz” may become “−Vz” and “−Vz” may become “+Vz”, and the “+Vy” may become “−Vy” and “−Vy” may become “+Vy”.

According to the above explained second embodiment, the gyro element40having the first, second, third, fourth drive arms46,47,48,49that can obliquely vibrate may be obtained by simple processing including etching. With the obliquely vibrated first, second, third, fourth drive arms46,47,48,49, the gyro element40that can respectively and independently detect the angular velocity ωy around the Y-axis and the angular velocity ωz around the Z-axis may be obtained. Further, the groove portions50,51,52,53provided on the first, second, third, fourth drive arms46,47,48,49may be formed by digging from the one surfaces (first surfaces10) by etching or the like, and thereby, the groove portions50,51,52,53containing the asymmetric section shapes with respect to the first virtual center lines P1may be easily formed. The groove portions50,51,52,53may be easily formed as described above, and thereby, the processing yield of the gyro element40is improved. Further, the drive parts containing the piezoelectric layers63are provided on the second surfaces61as the rear surfaces for the first surfaces60. The second surfaces61are flat surfaces without the groove portions50,51,52,53, and the drive parts may be easily formed thereon. Therefore, according to the configuration, the first, second, third, fourth drive arms46,47,48,49in which the groove portions50,51,52,53are provided on the one surfaces (first surfaces60) and the drive parts are provided on the rear surfaces (second surfaces61) may be easily formed, and the gyro element40that can continue stable oblique vibration, i.e., the gyro sensor1amay be inexpensively provided.

Referring toFIG. 13, a modified example of the recessed portions will be explained. In the above described embodiments, as the recessed portions, the configurations of the groove portions8a,8band the groove portions50,51,52,53dug from the one surfaces (first surfaces10,60) and opening to the one surfaces (first surfaces10,60) have been explained, however, as the configuration of the recessed portions that generate oblique vibration, the configuration shown inFIG. 13may be employed.FIG. 13is a sectional view showing the modified example of the recessed portions. A step portion8cas the recessed portion of the modified example is a step portion having a bottom opening to both the first surface10of the drive arm5and a side surface15aat the adjustment arm7side. The step portion8cis provided on the drive arm5to deviate in the direction in which the adjustment arm7is located. Further, a step portion8dis a step portion having a bottom opening to both the first surface10of the drive arm6and a side surface15bat the adjustment arm7side. The step portion8dis provided on the drive arm6to deviate in the direction in which the adjustment arm7is located.

The step portions are provided, and thereby, like the groove portions of the above described embodiments, the drive arms5,6have asymmetric section shapes with respect to the first virtual center lines passing through the center Q in the X-axis direction and the second virtual center lines passing through the center Q in the Z-axis direction. Accordingly, as will be described later, when the drive arms5,6are vibrated in the X-axis directions (in-plane directions), a vibration in the Z-axis directions (out-of-plane directions) is newly excited by the vibration. As a result, the drive arms5,6may be flexurally vibrated (hereinafter, also simply referred to as “oblique vibration”) in directions having both direction components in the X-axis directions and the Z-axis directions, in other words, in directions oblique to both axes of the X-axis and the Z-axis. Note that the same modified example may be applied to the configuration of the second embodiment.

Further, the example in which one adjustment arm7is provided has been explained in the first embodiment, however, any number of adjustment arms may be provided. Furthermore, regarding the drive arms5,6, any number of drive arms may be provided.

In addition, in the embodiment2, the configuration in which the first, second, third, fourth drive arms46,47,48,49and the first, second detection arms42,43are provided has been explained, however, any number of drive arms and detection arms may be provided.

Electronic Apparatuses

Next, as vibrating devices according to one embodiment of the invention, electronic apparatuses to which any one of the vibrator1using the vibrating element2or the gyro sensor1ausing the gyro element40is applied will be explained in detail with reference toFIGS. 14 to 16. Note that, in the explanation, examples of application of the gyro sensor1aare shown.

FIG. 14is a perspective view showing an outline of a configuration of a mobile (or notebook) personal computer as an electronic apparatus including the gyro sensor1aas an electronic device according to one embodiment of the invention. In the drawing, a personal computer1100includes a main body unit1104having a keyboard1102and a display unit1106having a display part1101, and the display unit1106is rotatably supported via a hinge structure part with respect to the main body unit1104. The personal computer1100contains the gyro sensor1ahaving a function of detecting an angular velocity.

FIG. 15is a perspective view showing an outline of a configuration of a cell phone (including a PHS) as the electronic apparatus including the gyro sensor1aas the electronic device according to one embodiment of the invention. In the drawing, a cell phone1200includes a plurality of operation buttons1202, an ear piece1204, and a mouthpiece1206, and a display part100is provided between the operation buttons1202and the ear piece1204. The cell phone1200contains the gyro sensor1ahaving a function of detecting an angular velocity.

FIG. 16is a perspective view showing an outline of a configuration of a digital still camera as the electronic apparatus including the gyro sensor1aas the electronic device according to one embodiment of the invention. Note that, in the drawing, connection to an external device is simply shown. Here, in a film camera in related art, a silver halide photographic film is exposed to light by an optical image of a subject and, on the other hand, a digital still camera1300photoelectrically converts an optical image of a subject using an image sensing device such as a CCD (Charge Coupled Device) and generates imaging signals (image signals).

On a back surface of a case (body)1302in the digital still camera1300, a display part100is provided and adapted to display based on the imaging signals by the CCD, and the display part100functions as a finder that displays the subject as an electronic image. Further, on the front side (the rear side in the drawing) of the case1302, a light receiving unit1304including an optical lens (imaging system), the CCD, etc. is provided.

When a photographer checks the subject image displayed on the display part100and presses down a shutter button1306, the imaging signals of the CCD at the time are transferred and stored into a memory1308. Further, in the digital still camera1300, a video signal output terminal1312and an input/output terminal for data communication1314are provided on the side surface of the case1302. Furthermore, as illustrated, a television monitor1430is connected to the video signal output terminal1312and a personal computer1440is connected to the input/output terminal for data communication1314, respectively, as appropriate. In addition, by predetermined operation, the imaging signals stored in the memory1308are output to the television monitor1430and the personal computer1440. The digital still camera1300contains the gyro sensor1ahaving a function of detecting an angular velocity.

Note that the gyro sensor1aas the electronic device according to one embodiment of the invention may be applied not only to the personal computer (mobile personal computer) inFIG. 14, the cell phone inFIG. 15, and the digital still camera inFIG. 16but also to an electronic apparatus including an inkjet ejection device (for example, an inkjet printer), a laptop personal computer, a television, a video camera, a video tape recorder, a car navigation system, a pager, a personal digital assistance (with or without communication function), an electronic dictionary, a calculator, an electronic game machine, a word processor, a work station, a videophone, a security television monitor, electronic binoculars, a POS terminal, a medical apparatus (for example, an electronic thermometer, a sphygmomanometer, a blood glucose meter, an electrocardiographic measurement system, an ultrasonic diagnostic system, or an electronic endoscope), a fish finder, various measurement instruments, meters and gauges (for example, meters for vehicles, airplanes, and ships), and a flight simulator, for example.

Moving Object

FIG. 17is a perspective view schematically showing an automobile as an example of a moving object. In an automobile506, the gyro sensor1aas the electronic device according to the invention is mounted. For example, as shown in the drawing, in the automobile506as the moving object, an electronic control unit508that contains the gyro sensor1aand controls tires509etc. is mounted on a vehicle body507. In addition, the gyro sensor1amay be widely applied to an electric control unit (ECU) including keyless entry, an immobilizer, a car navigation system, a car air-conditioner, an antilock brake system (ABS), an airbag, a tire pressure monitoring system (TPMS), engine control, a battery monitor of a hybrid car or an electric car, and a vehicle body attitude control unit.

The entire disclosure of Japanese Patent Application No. 2013-166004, filed Aug. 9, 2013 is expressly incorporated by reference herein.