Angular velocity detection element and angular velocity sensor

Abstract

To provide an angular velocity detection element and an angular velocity sensor that make it easier to increase the sensitivity of angular velocity detection. [Solution] The angular velocity detection element has a drive vibration arm that bends and vibrates in response to an applied drive signal, and a detection vibration arm that bends and vibrates in response to an applied angular velocity. The drive vibration arm and the detection vibration arm each have a bottomed groove along the extending direction. When the thickness of the drive vibration arm is t1 and the depth of the groove of the drive vibration arm is d1, and the thickness of the detection vibration arm is t2 and the depth of the groove of the detection vibration arm is d2, then d2 / t2 > d1 / t1.

Description

Technical Field

[0001] The present invention relates to an angular velocity detection element and an angular velocity sensor.

Background Art

[0002] The vibrator described in Patent Document 1 has a base portion located at its center, a pair of detection vibrating arms extending from the base portion to both sides in the Y-axis direction, a pair of connecting arms extending from the base portion to both sides in the X-axis direction, a pair of driving vibrating arms extending from the tip of one connecting arm to both sides in the Y-axis direction, and a pair of driving vibrating arms extending from the tip of the other connecting arm to both sides in the Y-axis direction. Further, grooves are formed on the upper and lower surfaces of each detection vibrating arm and each driving vibrating arm. Thus, by forming grooves on the upper and lower surfaces of each detection vibrating arm and each driving vibrating arm, the detection sensitivity of the angular velocity can be improved.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the vibrator of Patent Document 1, the groove depth of each detection vibrating arm is the same as the groove depth of each driving vibrating arm. Thus, when the groove depth of each detection vibrating arm is the same as the groove depth of each driving vibrating arm, there is a problem that it is difficult to increase the detection sensitivity of the angular velocity even if each groove is deepened.

Means for Solving the Problems

[0005] The angular velocity detection element of the present invention has a driving vibrating arm that flexurally vibrates in response to an applied driving signal, and a detection vibrating arm that flexurally vibrates in response to an applied angular velocity. The drive vibration arm and the detection vibration arm each have a bottomed groove along the extending direction, Let t1 be the thickness of the drive vibrating arm and d1 be the depth of the groove of the drive vibrating arm. When the thickness of the detection vibration arm is t2 and the depth of the groove portion of the detection vibration arm is d2, d2 / t2 > d1 / t1.

[0006] The angular velocity sensor of the present invention comprises the above-mentioned angular velocity detection element, The system includes a control circuit that is electrically connected to the angular velocity detection element, supplies the drive signal to the angular velocity detection element, and detects the angular velocity based on the bending vibration. [Brief explanation of the drawing]

[0007] [Figure 1] This is a cross-sectional view showing an angular velocity sensor according to the first embodiment. [Figure 2] This is a plan view of the angular velocity detection element of the angular velocity sensor shown in Figure 1. [Figure 3] This is a cross-sectional view along line AA in Figure 2. [Figure 4] This is a cross-sectional view along line BB in Figure 2. [Figure 5] Figure 2 is a schematic diagram showing the driving state of the angular velocity detection element. [Figure 6] Figure 2 is a schematic diagram showing the driving state of the angular velocity detection element. [Figure 7] This graph shows the relationship between d1 and sensitivity when d1 = d2. [Figure 8] This graph shows the relationship between d2 / d1 and sensitivity. [Figure 9] This graph shows the relationship between d2 and sensitivity when d2 / d1=1 and d2 / d1=2. [Figure 10] This graph shows the relationship between d2 and sensitivity for the following cases: d1=d2, d1=20μm, d1=40μm, d1=60μm, and d1=80μm. [Figure 11] This graph shows the relationship between d1 / t1 and d2 / t2. [Figure 12] It is a cross-sectional view showing a modified example of the angular velocity detection element, corresponding to the cross-sectional view taken along line A-A in FIG. 2. [Figure 13] It is a cross-sectional view showing a modified example of the angular velocity detection element, corresponding to the cross-sectional view taken along line B-B in FIG. 2. [Figure 14] It is a plan view showing the angular velocity detection element according to the second embodiment. [Figure 15] It is a cross-sectional view taken along line C-C in FIG. 14. [Figure 16] It is a cross-sectional view taken along line D-D in FIG. 14. [Figure 17] It is a schematic view showing the driving state of the angular velocity detection element shown in FIG. 14. [Figure 18] It is a schematic view showing the driving state of the angular velocity detection element shown in FIG. 14.

Embodiments for Carrying Out the Invention

[0008] Hereinafter, the angular velocity detection element and the angular velocity sensor of the present invention will be described in detail based on the embodiments shown in the accompanying drawings.

[0009] <First Embodiment> FIG. 1 is a cross-sectional view showing an angular velocity sensor according to the first embodiment. FIG. 2 is a plan view of the angular velocity detection element included in the angular velocity sensor of FIG. 1. FIG. 3 is a cross-sectional view taken along line A-A in FIG. 2. FIG. 4 is a cross-sectional view taken along line B-B in FIG. 2. FIGS. 5 and 6 are schematic views showing the driving states of the angular velocity detection element shown in FIG. 2, respectively. FIG. 7 is a graph showing the relationship between d1 and sensitivity when d1 = d2. FIG. 8 is a graph showing the relationship between d2 / d1 and sensitivity. FIG. 9 is a graph showing the relationship between d2 and sensitivity in the cases of d2 / d1 = 1 and d2 / d1 = 2. FIG. 10 is a graph showing the relationship between d2 and sensitivity in the cases of d1 = d2, d1 = 20 μm, d1 = 40 μm, d1 = 60 μm, and d1 = 80 μm. FIG. 11 is a graph showing the relationship between d1 / t1 and d2 / t2. FIG. 12 is a cross-sectional view showing a modified example of the angular velocity detection element, corresponding to the cross-sectional view taken along line A-A in FIG. 2. FIG. 13 is a cross-sectional view showing a modified example of the angular velocity detection element, corresponding to the cross-sectional view taken along line B-B in FIG. 2.

[0010] Hereinafter, for convenience of explanation, the X-axis, Y-axis, and Z-axis, which are three mutually orthogonal axes, are illustrated. Also, the direction along the X-axis is also referred to as the X-axis direction, the direction along the Y-axis is also referred to as the Y-axis direction, and the direction along the Z-axis is also referred to as the Z-axis direction. Also, the arrow side of each axis is also referred to as the "plus side", and the opposite side is also referred to as the "minus side". Also, the plus side in the Z-axis direction is also referred to as "up", and the minus side is also referred to as "down". Also, a plan view from the Z-axis direction is simply referred to as a "plan view".

[0011] The angular velocity sensor 100 shown in FIG. 1 includes a package 200, an angular velocity detection element 300 housed in the package 200, a support substrate 500 that supports the angular velocity detection element 300, and a control circuit 400.

[0012] The package 200 has a box-shaped base 210 provided with a recess 211 that opens on the upper surface, and a plate-shaped lid 220 joined to the upper surface of the base 210 via a joining member 230 so as to close the opening of the recess 211. An airtight internal space S is formed inside the package 200 by the recess 211, and the angular velocity detection element 300, the support substrate 500, and the control circuit 400 are housed in this internal space S.

[0013] Also, the recess 211 has a first recess 211a that opens on the upper surface of the base 210, a second recess 211b that opens on the bottom surface of the first recess 211a and has a smaller opening than the first recess 211a, and a third recess 211c that opens on the bottom surface of the second recess 211b and has a smaller opening than the second recess 2llb. A plurality of internal terminals 241 are arranged on the bottom surface of the first recess 211a, a plurality of internal terminals 242 are arranged on the bottom surface of the second recess 211b, and a plurality of external terminals 243 are arranged on the lower surface of the base 210. Each internal terminal 242 is electrically connected to the internal terminal 241 or the external terminal 243 via an internal wiring (not shown) formed inside the base 210.

[0014] Furthermore, an angular velocity detection element 300 is mounted on the bottom surface of the first recess 211a via a mounting support substrate 500 called TAB (Tape Automated Bonding). The angular velocity detection element 300 is electrically connected to each internal terminal 241 via the support substrate 500. In addition, a control circuit 400 is mounted on the bottom surface of the third recess 211c. The control circuit 400 is electrically connected to the internal terminal 242 via a conductive wire W. As a result, the control circuit 400 is electrically connected to the angular velocity detection element 300 and the external terminal 243.

[0015] For example, the base 210 is made of a ceramic such as alumina, and the lid 220 is made of a metallic material such as Kovar. This results in a package 200 with excellent mechanical strength. Furthermore, the difference in their coefficients of thermal expansion can be kept small, thereby suppressing the generation of thermal stress. However, the constituent materials of the base 210 and the lid 220 are not particularly limited. In addition, the internal space S is in a reduced pressure state, preferably a state closer to a vacuum. This reduces viscous resistance and improves the vibration characteristics of the angular velocity detection element 300. However, the atmosphere of the internal space S is not particularly limited.

[0016] The above describes package 200. However, the configuration of package 200 is not particularly limited.

[0017] The control circuit 400 is electrically connected to the angular velocity detection element 300 and includes, for example, a drive circuit 410 that supplies a drive signal (described later) to the angular velocity detection element 300 to drive and vibrate the angular velocity detection element 300, and a detection circuit 420 that detects the angular velocity ωz based on a detection signal output by the angular velocity detection element 300 in accordance with the applied angular velocity.

[0018] Such a control circuit 400 may be placed outside the package 200. Alternatively, the control circuit 400 may be omitted.

[0019] The angular velocity detection element 300 can detect the angular velocity ωz about the Z axis. As shown in Figures 2 to 4, such an angular velocity detection element 300 has a vibrating substrate 310 made by patterning a Z-cut quartz substrate, and electrodes 320 formed on the surface of the vibrating substrate 310.

[0020] However, the constituent material of the vibrating substrate 310 is not limited to quartz, but can also be, for example, lithium niobate (LiNbO3), lithium tantalate (LiTaO3), or lead zirconate titanate. (PZT), lithium tetraborate (Li2B4O7), langasite (La3Ga5SiO2) 14 Various piezoelectric materials such as ) can be used.

[0021] Furthermore, the vibrating substrate 310 is plate-shaped and has an upper surface 310a as a first surface and a lower surface 310b as a second surface, which are in a front-back relationship with each other. The vibrating substrate 310 also has a base 311 located in its center, a pair of detection vibrating arms 312 and 313 extending from the base 311 in both directions along the Y-axis, a pair of support arms 314 and 315 extending from the base 311 in both directions along the X-axis, a pair of drive vibrating arms 316 and 317 extending from the tip of one support arm 314 in both directions along the Y-axis, and a pair of drive vibrating arms 318 and 319 extending from the tip of the other support arm 315 in both directions along the Y-axis. The base 311 is joined to the support substrate 500. With an angular velocity detection element 300 of this shape, as will be described later, the drive vibrating arms 316, 317, 318 and 319 bend and vibrate in a balanced manner, so the angular velocity ωz can be detected with high accuracy. In the following, the detection vibration arm and the drive vibration arm will be collectively referred to simply as the vibration arm.

[0022] The detection vibration arm 312 has an arm portion 312a extending from the base portion 311 in the positive direction in the Y-axis direction, and a weight portion 312b located at the tip of the arm portion 312a and wider in width (length in the X-axis direction) than the arm portion 312a. The detection vibration arm 312 also has a bottomed groove portion 312c formed on the upper surface 310a of the arm portion 312a, and a bottomed groove portion 312d formed on the lower surface 310b of the arm portion 312a. The groove portions 312c and 312d are formed along the arm portion 312a and cover almost the entire longitudinal area of ​​the arm portion 312a. Furthermore, the groove portions 312c and 312d are formed symmetrically.

[0023] Furthermore, the detection vibration arm 313 has an arm portion 313a extending from the base portion 311 in the negative direction in the Y-axis direction, and a weight portion 313b located at the tip of the arm portion 313a and wider than the arm portion 313a. The detection vibration arm 313 also has a bottomed groove portion 313c formed on the upper surface 310a of the arm portion 313a, and a bottomed groove portion 313d formed on the lower surface 310b of the arm portion 313a. The groove portions 313c and 313d are formed along the arm portion 313a and cover almost the entire longitudinal area of ​​the arm portion 313a. Furthermore, the groove portions 313c and 313d are formed symmetrically.

[0024] Furthermore, the drive vibrating arm 316 has an arm portion 316a extending from the support arm 314 in the positive direction in the Y-axis direction, and a weight portion 316b located at the tip of the arm portion 316a and wider than the arm portion 316a. The drive vibrating arm 316 also has a bottomed groove portion 316c formed on the upper surface 310a of the arm portion 316a, and a bottomed groove portion 316d formed on the lower surface 310b of the arm portion 316a. The groove portions 316c and 316d are formed along the arm portion 316a and cover almost the entire longitudinal area of ​​the arm portion 316a. The groove portions 316c and 316d are formed symmetrically.

[0025] Furthermore, the drive vibrating arm 317 has an arm portion 317a extending from the support arm 314 in the negative direction in the Y-axis direction, and a weight portion 317b located at the tip of the arm portion 317a and wider than the arm portion 317a. The drive vibrating arm 317 also has a bottomed groove portion 317c formed on the upper surface 310a of the arm portion 317a, and a bottomed groove portion 317d formed on the lower surface 310b of the arm portion 317a. The groove portions 317c and 317d are formed along the arm portion 317a and cover almost the entire longitudinal area of ​​the arm portion 317a. Furthermore, the groove portions 317c and 317d are formed symmetrically.

[0026] Furthermore, the drive vibrating arm 318 has an arm portion 318a extending from the support arm 315 in the positive direction in the Y-axis direction, and a weight portion 318b located at the tip of the arm portion 318a and wider than the arm portion 318a. The drive vibrating arm 318 also has a bottomed groove portion 318c formed on the upper surface 310a of the arm portion 318a, and a bottomed groove portion 318d formed on the lower surface 310b of the arm portion 318a. The groove portions 318c and 318d are formed along the arm portion 318a and cover almost the entire longitudinal area of ​​the arm portion 318a. Furthermore, the groove portions 318c and 318d are formed symmetrically.

[0027] Furthermore, the drive vibrating arm 319 has an arm portion 319a extending from the support arm 315 in the negative direction of the Y-axis, and a weight portion 319b located at the tip of the arm portion 319a and wider than the arm portion 319a. The drive vibrating arm 319 also has a bottomed groove portion 319c formed on the upper surface 310a of the arm portion 319a, and a bottomed groove portion 319d formed on the lower surface 310b of the arm portion 319a. The groove portions 319c and 319d are formed along the arm portion 319a and cover almost the entire longitudinal area of ​​the arm portion 319a. Furthermore, the groove portions 319c and 319d are formed symmetrically.

[0028] In this way, by arranging weights 312b, 313b, 316b, 317b, 318b, and 319b on each of the vibrating arms 312, 313, 316, 317, 318, and 319, the mass effect makes it possible to shorten each of the vibrating arms 312, 313, 316, 317, 318, and 319, thereby miniaturizing the angular velocity detection element 300 or lowering the resonant frequency of the angular velocity detection element 300. Furthermore, if the lengths of each vibrating arm 312, 313, 316, 317, 318, and 319 are the same, the arms 312a, 313a, 316a, 317a, 318a, and 319a can be made thicker compared to a configuration without the weights 312b, 313b, 316b, 317b, 318b, and 319b, thereby reducing the thermoelastic loss during bending vibration and increasing the Q value. In addition, a metal film for mass adjustment can be placed on the weights 312b, 313b, 316b, 317b, 318b, and 319b, and the resonance frequency can be finely adjusted by removing a portion of this metal film by laser irradiation or the like. However, the weights 312b, 313b, 316b, 317b, 318b, and 319b may be omitted.

[0029] The electrode 320 includes a first detection signal electrode 321, a first detection ground electrode 322, a second detection signal electrode 323, a second detection ground electrode 324, a drive signal electrode 325, and a drive ground electrode 326. Of these, the first detection signal electrode 321 is positioned on the upper surface 310a and lower surface 310b of the detection vibration arm 312, and the first detection ground electrode 322 is positioned on both sides of the detection vibration arm 312. The second detection signal electrode 323 is positioned on the upper surface 310a and lower surface 310b of the detection vibration arm 313, and the second detection ground electrode 324 is positioned on both sides of the detection vibration arm 313. The drive signal electrode 325 is positioned on the upper surface 310a and lower surface 310b of the drive vibration arms 316 and 317, and on both sides of the drive vibration arms 318 and 319. Furthermore, the drive ground electrode 326 is positioned on both sides of the drive vibrating arms 316 and 317, and on the upper surface 310a and lower surface 310b of the drive vibrating arms 318 and 319. Although not shown in the figures, each of these electrodes 321, 322, 323, 324, 325, and 326 is extended to the lower surface of the base 311 and electrically connected to the support substrate 500 at the lower surface of the base 311.

[0030] The configuration of the angular velocity detection element 300 has been briefly explained above. The angular velocity detection element 300 with this configuration detects the angular velocity ωz around the Z axis as follows.

[0031] When a drive signal is applied between the drive signal electrode 325 and the drive ground electrode 326, the drive vibration arms 316, 317 and 318, 319 flex in opposite phases in the X-axis direction, as shown in Figure 5 (this state is also called the "drive vibration mode"). In this state, the vibrations of the drive vibration arms 316, 317, 318, and 319 are canceled out, and the detection vibration arms 312 and 313 do not vibrate. In this state, when an angular velocity ωz is applied to the angular velocity detection element 300, as shown in Figure 6, the Coriolis force acts on the drive vibration arms 316, 317, 318, and 319, exciting flex vibration in the Y-axis direction, and the detection vibration arms 312 and 313 flex in the X-axis direction in response to this flex vibration (this state is also called the "detection vibration mode"). The charge generated on the detection vibration arm 312 by this bending vibration is extracted as a first detection signal from the first detection signal electrode 321, and the charge generated on the detection vibration arm 313 is extracted as a second detection signal from the second detection signal electrode 323. Based on these first and second detection signals, the angular velocity ωz is determined. Since the first and second detection signals are signals with opposite phases, the angular velocity ωz can be detected with greater accuracy by using a differential detection method.

[0032] Next, the configuration of the grooves formed on each of the vibrating arms 312, 313, 316, 317, 318, and 319 will be described in detail. Note that the detection vibrating arms 312 and 313 have similar configurations, and the driving vibrating arms 316, 317, 318, and 319 have similar configurations. Therefore, for the sake of explanation, the detection vibrating arms 312 and 313 will be described using the detection vibrating arm 312 as a representative, and the driving vibrating arms 316, 317, 318, and 319 will be described using the driving vibrating arm 316 as a representative.

[0033] As mentioned above, the detection vibrating arm 312 has a pair of grooves 312c and 312d, and the drive vibrating arm 316 has a pair of grooves 316c and 316d. Therefore, the heat transfer path during bending vibration of each vibrating arm 312 and 316 can be lengthened, reducing thermoelastic loss and increasing the Q value. Furthermore, each vibrating arm 312 and 316 becomes more flexible and more easily deformed by bending in the X-axis direction. Therefore, the amplitude of the drive vibrating arm 316 in drive vibration mode can be increased. The larger the amplitude of the drive vibrating arm 316, the greater the Coriolis force, and the larger the amplitude of the detection vibrating arm 312 in detection vibration mode. Therefore, a larger detection signal can be obtained, and the detection sensitivity of angular velocity ωz is increased.

[0034] Below, as shown in Figure 3, the relationship between d2 / t2 and d1 / t1 will be explained in detail, with t1 being the thickness of the drive vibrating arm 316, d1 being the depth of the grooves 316c and 316d of the drive vibrating arm 316, t2 being the thickness of the detection vibrating arm 312, and d2 being the depth of the grooves 312c and 312d of the detection vibrating arm 312. Note that d1 is the sum of the depths of the grooves 316c and 316d. Since the grooves 316c and 316d are formed symmetrically, the depths of the grooves 316c and 316d are d1 / 2, respectively. Similarly, d2 is the sum of the depths of the grooves 312c and 312d. Since the grooves 312c and 312d are formed symmetrically, the depths of the grooves 312c and 312d are d2 / 2, respectively.

[0035] Furthermore, for example, when the vibration substrate 310 is patterned by wet etching, the crystal angles of the quartz may become visible, resulting in grooves 312c, 312d, 316c, and 316d having shapes that are not of a constant depth. In such cases, the depth of grooves 312c, 312d, 316c, and 316d refers to the depth at the deepest point. Also, in this embodiment, t1 and t2 correspond to the plate thickness of the vibration substrate 310, and t1 = t2. However, it is not limited to this, and t1 ≠ t2.

[0036] Figure 7 shows the relationship between d1, d2 (where d1=d2) and the detection sensitivity (sensitivity) of the angular velocity ωz. The thickness of the vibrating substrate 310, i.e., t1 and t2, is 100 μm. The detection sensitivity is expressed as a ratio with the detection sensitivity when d1 and d2 are 60 μm set to 1. As can be seen from the figure, the detection sensitivity increases as d1 and d2 increase. However, even when d1 and d2 are set to 90 μm (90% of the plate thickness), the detection sensitivity only increases by 1.09 times compared to when d1 and d2 are 60 μm (60% of the plate thickness). From this, it can be seen that when d1=d2, increasing d1 and d2 does not significantly increase the detection sensitivity.

[0037] Figure 8 shows the relationship between d2 / d1 and detection sensitivity. The plate thickness of the vibration substrate 310, i.e., t1 and t2, is 100 μm. The detection sensitivity is expressed as a ratio with the detection sensitivity in the conventional configuration (d2 / d1=1) set to 1. As can be seen from the figure, the detection sensitivity increases as d2 / d1 increases. In other words, the detection sensitivity increases as the grooves 312c and 312d of the detection vibration arm 312 become deeper relative to the grooves 316c and 316d of the drive vibration arm 316. It can be seen that the detection sensitivity can be increased compared to the conventional configuration in the region where d2 / d1>1. Therefore, the angular velocity detection element 300 satisfies d2 / d1>1, i.e., d2 / t2>d1 / t1. This makes it possible to increase the detection sensitivity compared to the conventional configuration.

[0038] Figure 9 shows the relationship between d2 and detection sensitivity for the cases d2 / d1=1 and d2 / d1=2. The plate thickness of the vibrating substrate 310, i.e., t1 and t2, is 100 μm. As can be seen from the figure, the rate of increase in detection sensitivity is greater when d2 / d1=2 than when d2 / d1=1. Therefore, by satisfying d2 / d1>1, i.e., d2 / t2>d1 / t1, the detection sensitivity can be increased more significantly by increasing the depth of d1 and d2.

[0039] Figure 10 shows the relationship between d2 and detection sensitivity for the cases d1=d2(□), d1=20μm(▲), d1=40μm(△), d1=60μm(●), and d1=80μm(〇). The figure also shows approximation formulas (1) obtained by linearly approximating each point of d1=d2, approximation formula (2) obtained by linearly approximating each point of d1=20μm, approximation formula (3) obtained by linearly approximating each point of d1=40μm, approximation formula (4) obtained by linearly approximating each point of d1=60μm, and approximation formula (5) obtained by linearly approximating each point of d1=80μm. Furthermore, the value of approximation formula (1) at d2=100um, i.e., d2=t2 (=0.872), is calculated, and the intersection point p(■) of y=0.872 with each of the approximation formulas (2) to (5) is shown.

[0040] y=0.872 represents the limiting sensitivity ratio for conventional configurations. Figure 11 shows the relationship between d1 / t1 and d2 / t2, with the intersection point p in Figure 10 plotted. The figure also shows the approximation formula (6) obtained by linearly approximating each intersection point p. As mentioned above, since y=0.872 represents the limiting sensitivity ratio for conventional configurations, if d2 / t2 is greater than or equal to approximation formula (6), that is, if d2 / t2 is within the gray area in Figure 11, then the detection sensitivity is higher than that achievable with conventional configurations. Therefore, in this embodiment, d2 / t2≧0.8661×d1 / t1+0.1582 is satisfied, resulting in a detection sensitivity higher than that achievable with conventional configurations.

[0041] While there are no particular limitations on d1 / t1, it is preferable that d1 / t1 ≥ 0.2. This prevents the grooves 316c and 316d from becoming too shallow, and the stress applied to the drive vibration arm 316 can be sufficiently reduced. Therefore, damage to the drive vibration arm 316 can be effectively suppressed. Furthermore, while there are no particular limitations on d2 / t2, it is preferable that d2 / t2 ≤ 0.9. This prevents the grooves 312c and 312d from becoming too deep, and the mechanical strength of the detection vibration arm 312 can be sufficiently high.

[0042] In particular, in this embodiment, each detection vibration arm 312, 313 satisfies the above-mentioned relationship with all the drive vibration arms 316, 317, 318, 319, specifically d2 / t2 > d1 / t1 and d2 / t2 ≥ 0.8661 × d1 / t1 + 0.1582. This makes the above-mentioned effect more pronounced and allows for a higher detection sensitivity. However, it is not limited to this, and it is sufficient if at least one of the detection vibration arms 312, 313 satisfies the above-mentioned relationship with at least one of the drive vibration arms 316, 317, 318, 319.

[0043] The angular velocity sensor 100 has been described above. The angular velocity detection element 300 included in such an angular velocity sensor 100 has a drive vibration arm 316 that bends and vibrates in response to an applied drive signal, and a detection vibration arm 312 that bends and vibrates in response to an applied angular velocity ωz. The drive vibration arm 316 has bottomed grooves 316c and 316d along the extending direction, and the detection vibration arm 312 has bottomed grooves 312c and 312d along the extending direction. When the thickness of the drive vibration arm 316 is t1, the depth of the grooves 316c and 316d of the drive vibration arm 316 is d1, the thickness of the detection vibration arm 312 is t2, and the depth of the grooves 312c and 312d of the detection vibration arm 312 is d2, then d2 / t2 > d1 / t1. With this configuration, the detection sensitivity can be greatly increased by increasing the depth of d1 and d2 compared to a conventional configuration.

[0044] Furthermore, as mentioned above, in the angular velocity detection element 300, d2 / t2 ≥ 0.8661 × d1 / t1 + 0.1582. By satisfying this relationship, the detection sensitivity of angular velocity ωz can be increased to a level that cannot be reached with conventional configurations. Therefore, the angular velocity detection element 300 has excellent detection accuracy for angular velocity ωz.

[0045] Furthermore, as mentioned above, it is preferable that d1 / t1 ≥ 0.2 in the angular velocity detection element 300. This prevents the grooves 316c and 316d from becoming too shallow, and sufficiently reduces the stress applied to the drive vibrating arm 316. As a result, damage to the drive vibrating arm 316 can be effectively suppressed.

[0046] Furthermore, as mentioned above, it is preferable that d2 / t2 ≤ 0.9 for the angular velocity detection element 300. This prevents the grooves 312c and 312d from becoming too deep, and ensures that the mechanical strength of the vibration detection arm 312 is sufficiently high.

[0047] Furthermore, as mentioned above, for the angular velocity detection element 300, d1 / t1 ≥ 0.2, d2 / t2 ≤ 0.9, and d2 / t2 ≥ 0.8661 × d1 / t1 + 0.1582. This effectively suppresses damage to the detection vibration arm 312 and the drive vibration arm 316, while increasing the detection sensitivity to a level that cannot be reached with conventional configurations.

[0048] Furthermore, as mentioned above, the angular velocity detection element 300 includes a base 311, a pair of detection vibration arms 312 and 313 extending from the base 311 in a first direction, the Y-axis direction, a pair of support arms 314 and 315 extending from the base 311 in a second direction, the X-axis direction, which intersects the Y-axis direction, a pair of drive vibration arms 316 and 317 extending from one support arm 314 in a Y-axis direction, and a pair of drive vibration arms 318 and 319 extending from the other support arm 315 in a Y-axis direction. With this configuration, the angular velocity detection element 300 can detect the angular velocity ωz about the Z-axis which is orthogonal to the X-axis and Y-axis.

[0049] Furthermore, as mentioned above, the detection vibration arm 312 has an arm portion 312a with grooves 312c and 312d, and a weight portion 312b located on the tip side of the arm portion 312a and wider than the arm portion 312a, and the drive vibration arm 316 has an arm portion 316a with grooves 316c and 316d, and a weight portion 316b located on the tip side of the arm portion 316a and wider than the arm portion 316a. As a result, the mass effect of the weight portions 312b and 316b makes it possible to shorten the detection vibration arm 312 and the drive vibration arm 316 to miniaturize the angular velocity detection element 300, or to lower the resonant frequency of the angular velocity detection element 300. Furthermore, if the lengths of each vibrating arm 312 and 316 are the same, the arms 312a and 316a can be made thicker compared to a configuration without the weights 312b and 316b, thereby reducing the thermoelastic loss during bending vibration and increasing the Q value.

[0050] Furthermore, as mentioned above, each detection vibration arm 312, 313 satisfies the relationship d2 / t2 > d1 / t1 for all drive vibration arms 316, 317, 318, 319. This makes it possible to more reliably increase the detection sensitivity by deepening d1 and d2 compared to the conventional configuration.

[0051] Furthermore, as mentioned above, the drive vibration arm 316 and the detection vibration arm 312 each have a first surface, the upper surface 310a, and a second surface, the lower surface 310b, which are in a front-back relationship with each other, and grooves 316c, 316d, 312c, and 312d are formed on the upper surface 310a and the lower surface 310b, respectively. As a result, the grooves 316c and 316d are formed symmetrically on the front and back surfaces of the drive vibration arm 316, and the grooves 312c and 312d are formed symmetrically on the front and back surfaces of the detection vibration arm 312. Therefore, out-of-plane bending vibration of the drive vibration arm 316 and the detection vibration arm 312 can be suppressed. Consequently, the generation of spurious signals is suppressed, and the angular velocity ωz can be detected with high accuracy.

[0052] Furthermore, as mentioned above, the angular velocity sensor 100 includes an angular velocity detection element 300 and a control circuit 400 that is electrically connected to the angular velocity detection element 300, supplies a drive signal to the angular velocity detection element 300, and detects the angular velocity ωz based on the bending vibration of the detection vibration arm 312. This allows the angular velocity sensor 100 to take advantage of the effects of the angular velocity detection element 300 described above and has excellent angular velocity detection accuracy.

[0053] The first embodiment has been described above. However, the configuration of the angular velocity detection element 300 is not particularly limited. For example, as shown in Figures 12 and 13, the grooves 312d, 313d, 316d, 317d, 318d, and 319d on the lower surface 310b side may be omitted from each vibrating arm 312, 313, 316, 317, 318, and 319. In this case, the depth of the grooves 312c and 313c becomes d2, and the depth of the grooves 316c, 317c, 318c, and 319c becomes d1.

[0054] <Second Embodiment> Figure 14 is a plan view showing the angular velocity detection element according to the second embodiment. Figure 15 is a cross-sectional view taken along the CC line in Figure 14. Figure 16 is a cross-sectional view taken along the DD line in Figure 14. Figures 17 and 18 are schematic diagrams showing the driving state of the angular velocity detection element shown in Figure 14, respectively.

[0055] The angular velocity sensor 100 according to this embodiment is the same as the angular velocity sensor 100 of the first embodiment described above, except that the configuration of the angular velocity detection element is different. In the following description, the angular velocity sensor 100 of this embodiment will be described mainly in terms of the differences from the first embodiment described above, and similar matters will be omitted from the description. In addition, in the figures of this embodiment, the same reference numerals are used for components that are the same as in the previously described embodiment.

[0056] In the angular velocity sensor 100 of this embodiment, an angular velocity detection element 600 is used instead of the angular velocity detection element 300. The angular velocity detection element 600 shown in Figures 14 to 16 can detect the angular velocity ωy around the Y axis. Such an angular velocity detection element 600 has a vibrating substrate 610 made by patterning a Z-cut quartz substrate, and an electrode 620 formed on the surface of the vibrating substrate 610.

[0057] However, the constituent material of the vibrating substrate 610 is not limited to quartz, but can also be, for example, lithium niobate (LiNbO3), lithium tantalate (LiTaO3), or lead zirconate titanate. (PZT), lithium tetraborate (Li2B4O7), langasite (La3Ga5SiO2) 14 Various piezoelectric materials such as ) can be used.

[0058] Furthermore, the vibrating substrate 610 is plate-shaped and has an upper surface 610a as a first surface and a lower surface 610b as a second surface, which are in a front-back relationship with each other. The vibrating substrate 610 also has a base 611 located in its center, a pair of detection vibration arms 612 and 613 extending from the base 611 in the positive Y-axis direction, and a pair of drive vibration arms 614 and 615 extending from the base 611 in the negative Y-axis direction. The pair of detection vibration arms 612 and 613 are arranged side by side in the X-axis direction, and the pair of drive vibration arms 614 and 615 are arranged side by side in the X-axis direction.

[0059] Furthermore, the detection vibration arm 612 has an arm portion 612a extending from the base portion 611 in the positive direction in the Y-axis direction, and a weight portion 612b located at the tip of the arm portion 612a and wider than the arm portion 612a. The detection vibration arm 612 also has a bottomed groove portion 612c formed on the upper surface 610a of the arm portion 612a, and a bottomed groove portion 612d formed on the lower surface 610b of the arm portion 612a. The groove portions 612c and 612d are formed along the arm portion 612a and cover almost the entire longitudinal area of ​​the arm portion 612a. Furthermore, the groove portions 612c and 612d are formed symmetrically.

[0060] Furthermore, the detection vibration arm 613 has an arm portion 613a extending from the base portion 611 in the positive direction in the Y-axis direction, and a weight portion 613b located at the tip of the arm portion 613a and wider than the arm portion 613a. The detection vibration arm 613 also has a bottomed groove portion 613c formed on the upper surface 610a of the arm portion 613a, and a bottomed groove portion 613d formed on the lower surface 610b of the arm portion 613a. The groove portions 613c and 613d are formed along the arm portion 613a and cover almost the entire longitudinal area of ​​the arm portion 613a. Furthermore, the groove portions 613c and 613d are formed symmetrically.

[0061] Furthermore, the drive vibrating arm 614 has an arm portion 614a extending from the base portion 611 in the negative direction in the Y-axis direction, and a weight portion 614b located at the tip of the arm portion 614a and wider than the arm portion 614a. The drive vibrating arm 614 also has a bottomed groove portion 614c formed on the upper surface 610a of the arm portion 614a, and a bottomed groove portion 614d formed on the lower surface 610b of the arm portion 614a. The groove portions 614c and 614d are formed along the arm portion 614a and cover almost the entire longitudinal area of ​​the arm portion 614a. Furthermore, the groove portions 614c and 614d are formed symmetrically.

[0062] Furthermore, the drive vibrating arm 615 has an arm portion 615a extending from the base portion 611 in the negative direction in the Y-axis direction, and a weight portion 615b located at the tip of the arm portion 615a and wider than the arm portion 615a. The drive vibrating arm 615 also has a bottomed groove portion 615c formed on the upper surface 610a of the arm portion 615a, and a bottomed groove portion 615d formed on the lower surface 610b of the arm portion 615a. The groove portions 615c and 615d are formed along the arm portion 615a and cover almost the entire longitudinal area of ​​the arm portion 615a. Furthermore, the groove portions 615c and 615d are formed symmetrically.

[0063] The relationship between d2 / t2 in the detection vibration arms 612 and 613 and d1 / t1 in the drive vibration arms 614 and 615 is the same as in the first embodiment described above.

[0064] The electrode 620 includes a first detection signal electrode 621, a first detection ground electrode 622, a second detection signal electrode 623, a second detection ground electrode 624, a drive signal electrode 625, and a drive ground electrode 626.

[0065] Of these, the first detection signal electrode 621 is positioned on the upper surface 610a and lower surface 610b of the detection vibration arm 612, and the first detection ground electrode 622 is positioned on both sides of the detection vibration arm 612. The second detection signal electrode 623 is positioned on the upper surface 610a and lower surface 610b of the detection vibration arm 613, and the second detection ground electrode 624 is positioned on both sides of the detection vibration arm 613. The drive signal electrode 625 is positioned on the upper surface 610a and lower surface 610b of the drive vibration arm 614 and on both sides of the drive vibration arm 615, and the drive ground electrode 626 is positioned on both sides of the drive vibration arm 614 and on the upper surface 610a and lower surface 610b of the drive vibration arm 615.

[0066] The angular velocity detection element 600 with this configuration detects the angular velocity ωy around the Y axis as follows. When a drive signal is applied between the drive signal electrode 625 and the drive ground electrode 626, the drive vibration arms 614 and 615 flex in opposite phases in the X-axis direction, as shown in Figure 17. In this state, the vibrations of the drive vibration arms 614 and 615 are canceled out, and the detection vibration arms 612 and 613 do not vibrate. In this state, when an angular velocity ωy is applied to the angular velocity detection element 600, as shown in Figure 18, a Coriolis force acts on the drive vibration arms 614 and 615, exciting flex vibration in the Z-axis direction, and the detection vibration arms 612 and 613 flex in the Z-axis direction in response to this flex vibration. The charge generated on the detection vibration arm 612 by this bending vibration is extracted as a first detection signal from the first detection signal electrode 621, and the charge generated on the detection vibration arm 613 is extracted as a second detection signal from the second detection signal electrode 623. Based on these first and second detection signals, the angular velocity ωy can be determined. Since the first and second detection signals are signals in opposite phases, the angular velocity ωy can be detected with greater accuracy by using a differential detection method.

[0067] The second embodiment described above can also achieve the same effects as the first embodiment described above.

[0068] Although the angular velocity detection element and angular velocity sensor of the present invention have been described above based on the illustrated embodiments, the present invention is not limited thereto, and the configuration of each part can be replaced with any configuration having a similar function. Furthermore, any other components may be added to the present invention. [Explanation of symbols]

[0069] 100…Angular velocity sensor, 200…Package, 210…Base, 211…Recess, 211a…First recess, 211b…Second recess, 211c…Third recess, 220…Lid, 230…Jointing member, 241…Internal terminal, 242…Internal terminal, 243…External terminal, 300…Angular velocity detection element, 310…Vibration substrate, 310a…Top surface, 310b…Bottom surface, 311…Base, 312…Detection vibration arm, 312a…Arm section, 312b…Weight section, 312c…Groove section, 312d…Groove section, 313…Detection vibration arm, 313a…Arm section, 313b…Weight section ,313c...groove, 313d...groove, 314...support arm, 315...support arm, 316...drive vibrating arm, 316a...arm, 316b...weight, 316c...groove, 316d...groove, 317...drive vibrating arm, 317a...arm, 317b...weight, 317c...groove, 317d...groove, 318...drive vibrating arm, 318a...arm, 318b...weight, 318c...groove, 318d...groove, 319...drive vibrating arm, 319a...arm, 319b...weight, 319c...groove, 319d...groove, 320...electrode, 321...first detection signal electrode, 3 22...First detection ground electrode, 323...Second detection signal electrode, 324...Second detection ground electrode, 325...Drive signal electrode, 326...Drive ground electrode, 400...Control circuit, 410...Drive circuit, 420...Detection circuit, 500...Support substrate, 600...Angular velocity detection element, 610...Vibration substrate, 610a...Top surface, 610b...Bottom surface, 611...Base, 612...Detection vibration arm, 612a...Arm part, 612b...Weight part, 612c...Groove part, 612d...Groove part, 613...Detection vibration arm, 613a...Arm part, 613b...Weight part, 613c...Groove part, 613d...Groove 614...Drive vibrating arm, 614a...Arm section, 614b...Weight section, 614c...Groove section, 614d...Groove section, 615...Drive vibrating arm, 615a...Arm section, 615b...Weight section, 615c...Groove section, 615d...Groove section, 620...Electrode, 621...First detection signal electrode, 622...First detection ground electrode, 623...Second detection signal electrode, 624...Second detection ground electrode, 625...Drive signal electrode, 626...Drive ground electrode, d1...Depth, d2...Depth, t1...Thickness, t2...Thickness, S...Internal space, W...Wire, p...Intersection, ωy...Angular velocity, ωz...Angular velocity

Claims

1. A drive vibrating arm that bends and vibrates in response to an applied drive signal, It has a detection vibrating arm that bends and vibrates in accordance with the applied angular velocity, The drive vibration arm and the detection vibration arm each have a bottomed groove along the extending direction, Let t1 be the thickness of the drive vibrating arm and d1 be the depth of the groove of the drive vibrating arm. When the thickness of the detection vibration arm is t2 and the depth of the groove portion of the detection vibration arm is d2, An angular velocity detection element characterized by d2 / t2 > d1 / t1.

2. The angular velocity detection element according to claim 1, wherein d² / t² ≥ 0.8661 × d¹ / t¹ + 0.1582.

3. The angular velocity detection element according to claim 1, wherein d1 / t1 ≥ 0.

2.

4. The angular velocity detection element according to claim 1, wherein d² / t² ≤ 0.

9.

5. d1 / t1 ≥ 0.2, d² / t² ≤ 0.9, The angular velocity detection element according to claim 1, wherein d² / t² ≥ 0.8661 × d¹ / t¹ + 0.1582.

6. The base and, A pair of detection vibration arms extending from the base in the first direction to both sides, A pair of support arms extending from the base in a second direction intersecting the first direction, A pair of drive vibrating arms extending from one of the support arms to both sides in the first direction, The angular velocity detection element according to claim 1, further comprising a pair of drive vibrating arms extending from the other support arm to both sides in the first direction.

7. The angular velocity detection element according to claim 6, wherein the detection vibrating arm and the driving vibrating arm each have an arm portion provided with the groove and a weight portion located on the tip side of the arm portion and wider than the arm portion.

8. The angular velocity detection element according to claim 6, wherein each of the detection vibration arms satisfies the relationship d2 / t2 > d1 / t1 for all of the drive vibration arms.

9. The angular velocity detection element according to claim 1 or 6, wherein the driving vibration arm and the detection vibration arm each have a first surface and a second surface that are in a front-back relationship with each other, and the groove portion is formed on each of the first surface and the second surface.

10. The angular velocity detection element according to claim 1, An angular velocity sensor comprising a control circuit that is electrically connected to the angular velocity detection element, supplies the drive signal to the angular velocity detection element, and detects the angular velocity based on the bending vibration.

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