WO2010073576A1

WO2010073576A1 - Angular velocity sensor

Info

Publication number: WO2010073576A1
Application number: PCT/JP2009/007043
Authority: WO
Inventors: 相澤宏幸; 大内智
Original assignee: パナソニック株式会社
Priority date: 2008-12-26
Filing date: 2009-12-21
Publication date: 2010-07-01

Abstract

A first sense arm (24) has a first substrate (26), first and second lower electrodes (27, 28) formed on the first substrate, first and second piezoelectric bodies (29, 30) formed on the first and second lower electrodes, and first and second upper electrodes (31, 32) formed on the first and second piezoelectric bodies. A second sense arm (25) has a second substrate (33), third and fourth lower electrodes (34, 35) formed on the second substrate, third and fourth piezoelectric bodies (36, 37) formed on the third and fourth lower electrodes, and third and fourth upper electrodes (38, 39) formed on the third and fourth piezoelectric bodies. A calculating section calculates a difference between the sum of the voltages of the first and second lower electrodes (27, 28) and the sum of the voltages of the third and fourth lower electrodes (34, 35). Based on the obtained difference, an angular velocity around the axis can be obtained with the direction wherein the first and second sense arms (24, 25) extend from a base section as the axis.

Description

Angular velocity sensor

The present invention relates to an angular velocity sensor used for automobile control, a car navigation device, a digital camera, and the like.

8 and 9 are a perspective view and a cross-sectional view of the element of the conventional angular velocity sensor, respectively. This element has a base 1, a first drive arm 3A, a second drive arm 3B, a first sense arm 5A, and a second sense arm 5B. The first drive arm 3A and the second drive arm 3B are connected to the base 1 and formed symmetrically with each other. The first sense arm 5A is connected to the base 1 and extends in a direction substantially opposite to the first drive arm 3A. The second sense arm 5B is also connected to the base 1 and extends in a direction substantially opposite to the second drive arm 3B. The first drive arm 3A and the second drive arm 3B vibrate in a direction substantially perpendicular to their extending direction.

As shown in FIG. 9, the first sense arm 5A includes a first substrate 6, a first lower electrode 7, a second lower electrode 8, a first piezoelectric body 10A, and a second piezoelectric body 10B. The first upper electrode 11 and the second upper electrode 12 are provided. The

lower electrodes

7 and 8 are formed on the first substrate 6. The

piezoelectric bodies

10A and 10B are formed on the

lower electrodes

7 and 8, respectively. The

upper electrodes

11 and 12 are formed on the

piezoelectric bodies

10A and 10B, respectively.

The second sense arm 5B includes the second substrate 13, the third lower electrode 14, the fourth lower electrode 15, the third piezoelectric body 16A, the fourth piezoelectric body 16B, and the third upper electrode. 18 and a fourth upper electrode 19. The third lower electrode 14 and the fourth lower electrode 15 are formed on the second substrate 13. The third piezoelectric body 16 A is formed on the third lower electrode 14, and the fourth piezoelectric body 16 B is formed on the fourth lower electrode 15. The third upper electrode 18 is formed on the third piezoelectric body 16A, and the fourth upper electrode 19 is formed on the fourth piezoelectric body 16B.

In the first sense arm 5A, the second upper electrode 12 is disposed on the side close to the second sense arm 5B, and the first upper electrode 11 is disposed on the opposite side to the second sense arm 5B. In the second sense arm 5B, the third upper electrode 18 is disposed on the side close to the first sense arm 5A, and the fourth upper electrode 19 is disposed on the opposite side to the first sense arm 5A.

In the angular velocity sensor using this element, the angular velocity around the axis about the Z direction shown in FIG. 8 is detected as follows. When an AC voltage is applied to the pair of upper and lower electrodes provided on the

drive arms

3A and 3B, the

drive arms

3A and 3B vibrate so as to be parallel to the surface constituting the base 1 and to approach and separate from each other. . Along with this vibration, the

sense arms

5A and 5B also vibrate in synchronization. At this time, the drive arm 3A and the sense arm 5A vibrate in the same phase, and the drive arm 3B and the sense arm 5B vibrate in the same phase. The drive arm 3A and the drive arm 3B vibrate in opposite phases. As a result, a current (drive current) due to this vibration is generated in the electrodes provided on the

sense arms

5A and 5B.

In this state, when an angular velocity is generated around the Z axis, a Coriolis force is generated in a direction parallel to the surface constituting the base 1 and perpendicular to the vibration direction. Therefore, distortion due to the angular velocity around the Z axis occurs in the

sense arms

5A and 5B. Along with this, due to a change in the state of the

sense arms

5A and 5B which are bent due to the Coriolis force, a current corresponding to the angular velocity is generated on the electrodes provided on the

sense arms

5A and 5B in a manner superimposed on the drive current. . At this time, for example, the phase of the drive current component of the second upper electrode 12 and the phase of the drive current component of the fourth upper electrode 19 are reversed.

The current generated in the upper electrodes of the

sense arms

5A and 5B in this way is then converted into a voltage. Then, the sum of the voltage of the second upper electrode 12 and the voltage of the fourth upper electrode 19 is obtained. On the other hand, the sum of the voltage of the first upper electrode 11 and the sum of the voltage of the third upper electrode 18 is obtained. The angular velocity in the direction perpendicular to the plane forming the base 1 is detected from the difference between the two sums. Specifically, the voltage line from the second upper electrode 12 and the voltage line from the fourth upper electrode 19 are connected, and the voltage line of the first upper electrode 11 and the voltage line of the third upper electrode 18 are connected to each other. Connect. These outputs are input to the amplifier. Thus, in this calculation, the angular velocity around the axis about the Z direction can be detected.

However, the out-of-plane angular velocity cannot be accurately detected. That is, it is impossible to accurately detect the angular velocity around the axis with the

sense arm

5A, 5B extending from the base 1, that is, the Y direction in FIG. The reason will be briefly explained. As described above, the voltage line from the upper electrode is connected. Therefore, in order to obtain the angular velocity around the axis with the Y direction as an axis, it is necessary to input a voltage caused by the drive current to the amplifier. As a result, the S / N ratio decreases.

For example, Patent Document 1 is known as prior art document information relating to this application.

International Publication No. 2008/102537

The angular velocity sensor of the present invention has an element and a calculation unit. The element includes a base, first and second drive arms, and first and second sense arms. The first and second drive arms have portions connected to the base and extending parallel to each other from the base. The first and second sense arms are connected to the base and have portions extending from the base in opposite directions to the first and second drive arms and extending in parallel with each other from the base.

The first sense arm has a first substrate, first and second lower electrodes, first and second piezoelectric bodies, and first and second upper electrodes. The first and second lower electrodes are formed on the first substrate. The second lower electrode is formed closer to the second sense arm than the first lower electrode. The first and second piezoelectric bodies are respectively formed on the first and second lower electrodes, and the first and second upper electrodes are respectively formed on the first and second piezoelectric bodies.

The second sense arm has a second substrate, third and fourth lower electrodes, third and fourth piezoelectric bodies, and third and fourth upper electrodes. The third and fourth lower electrodes are formed on the second substrate. The fourth lower electrode is formed on the side farther from the first sense arm than the third lower electrode. The third and fourth piezoelectric bodies are respectively formed on the third and fourth lower electrodes, and the third and fourth upper electrodes are respectively formed on the third and fourth piezoelectric bodies.

The computing unit includes a sum of a voltage signal of the first lower electrode with respect to the first upper electrode and a voltage signal of the second lower electrode with respect to the second upper electrode, and the third lower electrode with respect to the third upper electrode. The difference between the voltage signal and the sum of the voltage signal of the fourth lower electrode with respect to the fourth upper electrode is calculated. Alternatively, the sum of the voltage signal of the first upper electrode for the first lower electrode and the voltage signal of the second upper electrode for the second lower electrode, and the voltage signal of the third upper electrode for the third lower electrode And the sum of the voltage signal of the fourth upper electrode with respect to the fourth lower electrode is calculated. With this configuration, it is possible to detect angular velocities around the axis about the direction in which the first and second sense arms extend from the base.

FIG. 1 is a perspective view of an element of an angular velocity sensor according to an embodiment of the present invention. 2 is a cross-sectional view taken along line 2-2 of the element shown in FIG. FIG. 3 is a block diagram showing the configuration of the angular velocity sensor according to the embodiment of the present invention. FIG. 4 is a conceptual diagram illustrating a voltage detection method in the calculation unit of the angular velocity sensor according to the embodiment of the present invention. FIG. 5A is a perspective view showing a driving state of the element shown in FIG. 5B is a perspective view showing a state in which an angular velocity around the Y axis is applied to the element shown in FIG. FIG. 5C is a perspective view showing a state in which an angular velocity around the Z-axis is applied to the element shown in FIG. FIG. 6 shows the voltage phase of each electrode in a state where an angular velocity around the Y axis is applied and an angular velocity around the Z axis is applied when the element shown in FIG. 1 is driven. FIG. 7A is a conceptual diagram illustrating a method of detecting an angular velocity around the Y axis by the calculation unit of the angular velocity sensor according to the embodiment of the present invention. FIG. 7B is a conceptual diagram illustrating a method of detecting an angular velocity around the Z axis by the calculation unit of the angular velocity sensor according to the embodiment of the present invention. FIG. 8 is a perspective view of an element of a conventional angular velocity sensor. FIG. 9 is a cross-sectional view of the element shown in FIG. 8 taken along line 9-9.

FIG. 1 is a perspective view of an element of an angular velocity sensor according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along line 2-2 of FIG. FIG. 3 is a block diagram showing the overall configuration of the angular velocity sensor according to the embodiment of the present invention.

As shown in FIG. 1, the element 20 has a base 21, a first drive arm 22, a second drive arm 23, a first sense arm 24, and a second sense arm 25. The first drive arm 22 has a U-shaped bent portion 22A and a weight portion 22B provided at the tip of the bent portion 22A. Similarly, the second drive arm 23 has a bending portion 23A and a weight portion 23B. The first sense arm 24 has a bent portion 24A and a weight portion 24B, and the second sense arm 25 has a bent portion 25A and a weight portion 25B. The bending

portions

22A, 23A, 24A, and 25A are connected to the base portion 21. The

bent portions

22A and 23A are parallel on the side connected to the base portion 21. Similarly, the bent portions 24 A and 25 A are parallel on the side connected to the base portion 21. That is, the

drive arms

22 and 23 have a portion connected to the base portion 21 and extending in parallel from the base portion 21. The

sense arms

24 and 25 are connected to the base 21 and extend in the opposite direction from the base 21 to the

drive arms

22 and 23 and have portions extending in parallel from the base 21.

The first sense arm 24 and the second sense arm 25 are formed in substantially opposite directions with respect to the first drive arm 22 and the second drive arm 23. That is, the first drive arm 22 and the second drive arm 23 are provided symmetrically with respect to the Y axis in the X axis direction, and the first drive arm 22 and the first sense arm 24 are in the X axis direction in the Y axis direction. With respect to the line symmetry. Similarly, the first sense arm 24 and the second sense arm 25 are provided symmetrically with respect to the Y axis in the X-axis direction, and the second drive arm 23 and the second sense arm 25 are X-directional in the Y-axis direction. It is provided in line symmetry with respect to the axis.

As shown in FIG. 2, the bending portion 24 A of the first sense arm 24 includes a first substrate 26, a first lower electrode 27, a second lower electrode 28, a first piezoelectric body 29, and a second piezoelectric element. Piezoelectric body 30, first upper electrode 31, and second upper electrode 32. The first lower electrode 27 and the second lower electrode 28 are formed on the first substrate 26. The second lower electrode 28 is formed closer to the second sense arm 25 than the first lower electrode 27. The first piezoelectric body 29 is formed on the first lower electrode 27, and the second piezoelectric body 30 is formed on the second lower electrode 28. The first upper electrode 31 is formed on the first piezoelectric body 29, and the second upper electrode 32 is formed on the second piezoelectric body 30.

Similarly, the flexible portion 25A of the second sense arm 25 includes a second substrate 33, a third lower electrode 34, a fourth lower electrode 35, a third piezoelectric body 36, and a fourth piezoelectric body 37. And a third upper electrode 38 and a fourth upper electrode 39. The

lower electrodes

34 and 35 are formed on the second substrate 33. The fourth lower electrode 35 is formed on the side farther from the first sense arm 24 than the third lower electrode 34. The

piezoelectric bodies

36 and 37 are formed on the

lower electrodes

34 and 35, respectively, and the

upper electrodes

38 and 39 are formed on the

piezoelectric bodies

36 and 37, respectively. Although not shown, the

bent portions

22A and 23A also have a similar laminated structure.

The base of the element 20, such as the base 21, the first substrate 26, and the second substrate 33, is formed of silicon or the like. The

piezoelectric bodies

29, 30, 36 and 37 are made of lead zirconate titanate (PZT) or the like. In addition, by using a piezoelectric material made of quartz, lithium niobate (LiNbO ₃ ), etc., the base portion 21, the first substrate 26, the second substrate 33, etc., the element 20 and the

piezoelectric materials

29, 30, 36, 37 are formed. You may form as one.

The element 20 configured as described above is connected to the drive unit 50 and the calculation unit 70 to form an angular velocity sensor as shown in FIG. The output of the drive part 50 is connected to each electrode formed in the

bending parts

22A and 23A. On the other hand, each electrode of the element 20 is connected to the calculation unit 70. That is, the first lower electrode 27, the second lower electrode 28, the first upper electrode 31, and the second upper electrode 32 are connected to the

output lines

27A, 28A, 31A, and 32A, respectively, and the third lower electrode 34 is connected. The fourth lower electrode 35, the third upper electrode 38, and the fourth upper electrode 39 are connected to

output lines

34A, 35A, 38A, and 39A, respectively.

Output lines

80 and 90 are provided on the output side of the arithmetic unit 70.

Next, the configuration for detecting the output voltage from each electrode in the calculation unit 70 will be described with reference to FIG. FIG. 4 is a conceptual diagram illustrating a voltage detection method in the calculation unit 70. Here, as an example, a set of the first lower electrode 27 and the first upper electrode 31 will be described as an example.

When the first piezoelectric body 29 is distorted, a current of Is is generated from the first upper electrode 31 and −Is is generated from the first lower electrode 27. The output line 31A of the first upper electrode 31 and the output line 27A of the first lower electrode 27 are connected to the resistor Rf, respectively, and a current signal is converted into a voltage signal. These voltage signals are respectively compared with the reference voltage Vref and converted into a voltage waveform based on the reference voltage Vref. At this time, since the converted waveforms in the

output lines

31A and 27A have the same amplitude in opposite phases, the amplitude of the difference signal between them is twice the amplitude of the original signal. Therefore, the detection sensitivity is improved.

Next, a method for detecting the angular velocity around the Y axis and the angular velocity around the Z axis in FIG. 1 will be described with reference to FIGS. 5A to 7B. 5A is a perspective view showing a driving state of the element 20, FIG. 5B is a perspective view showing a state where an angular velocity around the Y axis is applied to the element 20, and FIG. 5C is a state where an angular velocity around the Z axis is applied to the element 20 FIG. FIG. 6 shows the voltage phase of each electrode when the element 20 is driven in a state where an angular velocity around the Y axis is applied and in a state where an angular velocity around the Z axis is applied. FIG. 7A is a conceptual diagram illustrating a method for detecting an angular velocity around the Y axis by the calculation unit 70, and FIG. 7B is a conceptual diagram illustrating a method for detecting the angular velocity around the Z axis by the calculation unit 70.

First, the material constituting the substrate such as the first substrate 26 is combined with the pair of the lower electrode and the upper electrode provided on the first drive arm 22 and the second drive arm 23 from the drive unit 50 shown in FIG. An AC voltage with a unique resonance frequency is applied. Then, as shown in FIG. 5A, the

drive arms

22 and 23 vibrate in a direction substantially perpendicular to the direction in which the bent portions 22 A and 23 A extend from the base portion 21 in a direction parallel to the surface forming the base portion 21. Along with this vibration, the

sense arms

24 and 25 also vibrate in synchronization. That is, for example, the drive vibration 42 is generated in the sense arm 25 in synchronization with the drive vibration 41 of the drive arm 23.

At this time, the first drive arm 22 and the first sense arm 24 vibrate in the same phase, and the second drive arm 23 and the second sense arm 25 vibrate in the same phase. The first drive arm 22 and the second drive arm 23 vibrate in opposite phases. As a result, a current (drive current) due to this vibration is generated in the electrodes provided on the

sense arms

24 and 25.

In this state, when an angular velocity is generated around the Y axis as shown in FIG. 5B, for example, a Coriolis force 43 is generated in the drive arm 23 and a Coriolis force 44 is generated in the sense arm 25 in a direction orthogonal to the vibration direction. As a result, distortion due to the angular velocity around the Y axis occurs in the

sense arms

24 and 25. That is, the distortion resulting from the angular velocity around the axis about the direction in which the

bent portions

24A and 25A extend from the base 21 is generated. Along with this, due to a change in the state of the

sense arms

24 and 25 that are bent due to the Coriolis force, a current corresponding to the angular velocity is generated on the electrodes provided on the

sense arms

24 and 25 so as to be superimposed on the drive current. .

On the other hand, when an angular velocity is generated around the Z axis,

Coriolis forces

45 and 46 are generated in a direction orthogonal to the vibration direction. Therefore, as shown in FIG. 5C, the

sense arms

24 and 25 are caused by the angular velocity around the Z axis. Distortion occurs. That is, distortion due to the angular velocity around the axis about the direction perpendicular to the plane forming the base 21 occurs. Along with this, due to a change in the state of the

sense arms

24 and 25 so as to be superimposed on the drive current. .

The phase of the output signal in each of the above states is shown in FIG. For example, when the first sense arm 24 and the second sense arm 25 are driven in a direction away from each other, the first piezoelectric body 29 is compressed and the second piezoelectric body 30 is stretched. Therefore, the phase of the voltage signal of the first lower electrode 27 with respect to the first upper electrode 31 is +, and the phase of the voltage signal of the second lower electrode 28 with respect to the second upper electrode 32 is −. Similarly, + and-indicate whether the phase is the same or opposite.

In FIG. 6, for example, “lower 1” indicates a voltage signal of the first lower electrode 27 with respect to the first upper electrode 31. “Upper 4” indicates a voltage signal of the fourth upper electrode 39 with respect to the fourth lower electrode 35. Thus, the leftmost column indicates the voltage signal of the electrode with respect to the pair of electrodes in each pair of the upper electrode and the lower electrode.

Next, a method of calculating the angular velocity around the Y axis and the Z axis by the calculation unit 70 will be described with reference to FIGS. 7A and 7B. When calculating the angular velocity around the Y axis, as shown in FIG. 7A, the calculating unit 70 first obtains the sum of the voltage output 27B of “lower 1” and the voltage output 28B of “lower 2”. On the other hand, the sum of the voltage output 34B of the “lower 3” and the voltage output 35B of the “lower 4” is obtained. Then, the difference between the two is obtained. As apparent from FIG. 6, when the angular velocity is applied around the Y axis, “lower part 1” and “lower part 2” have the same phase, “lower part 3” and “lower part 4” have the same phase, and “lower part 1”. Is the opposite phase. Therefore, the difference signal 80B output to the output line 80 in FIG. 3 has an amplitude four times that of a single voltage output. Further, the signal component based on the drive current is canceled by these calculations, and only the component due to the angular velocity is obtained.

The calculation unit 70 outputs the difference signal 80B obtained in this way from the output line 80 to an external circuit. The external circuit calculates the angular velocity applied around the Y axis based on the amplitude of the difference signal 80B. Alternatively, the calculation unit 70 may include such a function and output an electrical signal corresponding to the angular velocity.

Coriolis force is proportional to the angular velocity. On the other hand, when an angular velocity is applied around the Y axis or around the Z axis, the magnitude of deflection of the

sense arms

24 and 25 changes according to the Coriolis force, and a current having a magnitude corresponding to the magnitude of the deflection. Are generated from each electrode. Therefore, the angular velocity can be calculated by knowing the magnitude of the amplitude of the voltage difference signal 80B.

That is, for example, when a clockwise angular velocity occurs around an axis with the Y direction as an axis, the first sense arm 24 moves to the negative side in the Z-axis direction, and the second sense arm 25 moves to the positive side in the Z-axis direction. Moving. Accordingly, the output amplitude of the sum of the voltage output of the first lower electrode 27 with respect to the first upper electrode 31 and the voltage output of the second lower electrode 28 with respect to the second upper electrode 32 decreases. On the other hand, the output amplitude of the sum of the voltage output of the third lower electrode 34 to the third upper electrode 38 and the voltage output of the fourth lower electrode 35 to the fourth upper electrode 39 increases. Therefore, by calculating the difference between them, the angular velocity around the axis about the direction in which the

flexures

24A and 24B, which are a part of the

sense arms

24 and 25, extend from the base 21, that is, the Y direction shown in FIG. can do.

Similarly, when calculating the angular velocity around the Z axis, the calculation unit 70 first obtains the sum of the voltage output 31B of the upper part 1 and the voltage output 38B of the upper part 3 as shown in FIG. 7B. On the other hand, the sum of the voltage output 32B of the upper part 2 and the voltage output 39B of the upper part 4 is obtained. Then, the difference between the two is obtained. As apparent from FIG. 6, when an angular velocity is applied around the Z axis, the upper part 1 and the upper part 3 are in phase, the upper part 2 and the upper part 4 are in phase, and the upper part 1 is in antiphase. Therefore, the difference signal 90B output to the output line 90 in FIG. 3 has an amplitude four times that of a single voltage output.

The calculation unit 70 outputs the difference signal 90B thus obtained to the external circuit, and the external circuit calculates the angular velocity around the Z axis based on the amplitude of the difference signal 90B. Alternatively, the calculation unit 70 may include such a function and output an electrical signal corresponding to the angular velocity.

That is, when, for example, a clockwise angular velocity is generated around an axis about the Z direction, the first and

second sense arms

24 and 25 move to the negative side in the X axis direction. Accordingly, the output amplitude of the sum of the voltage output of the second upper electrode 32 with respect to the second lower electrode 28 and the voltage output of the fourth upper electrode 39 with respect to the fourth lower electrode 35 increases. On the other hand, the output amplitude of the sum of the voltage output of the first upper electrode 31 with respect to the first lower electrode 27 and the voltage output of the third upper electrode 38 with respect to the third lower electrode 34 decreases. Therefore, by calculating the difference between them, it is possible to detect the angular velocity around the axis about the direction perpendicular to the plane forming the base 21, that is, the Z direction shown in FIG. Thus, the angular velocity sensor according to the present embodiment can perform multi-axis detection.

The angular velocity around the axis with the Z direction as the axis can also be obtained as follows. That is, the arithmetic unit 70 first obtains the sum of the voltage output 28B of the lower part 2 and the voltage output 35B of the lower part 4. On the other hand, the sum of the voltage output 27B of the lower part 1 and the voltage output 34B of the lower part 3 is obtained. Then, the difference between the two is obtained. However, in this case, since the angular velocity around the Y axis and the angular velocity around the Z axis are calculated using the same signal, it is necessary to perform all calculations using an amplifier. Therefore, many amplifiers are required for the arithmetic unit 70.

However, as described above, by using the voltage of the upper electrode for the angular velocity around the axis with the Z direction as the axis, the sum can be calculated only by connection without using an amplifier. Therefore, the calculating part 70 can be comprised simply. Drive current is 10 ⁶ times the current due to the angular velocity, because the driving current can be canceled before entering into the amplifier, this arrangement is effective from the viewpoint of S / N ratio.

In consideration of the orientation of the

piezoelectric bodies

29, 30, 36, and 37, the

lower electrodes

27, 28, 34, and 35 are preferably formed of platinum. When the piezoelectric body is formed of PZT, a platinum electrode is essential. On the other hand, in consideration of electrical connection reliability, the

upper electrodes

31, 32, 38, and 39 are preferably formed of gold. Thus, if the upper electrode and the lower electrode are formed of different materials, the specific resistances of the materials are different, and there is a concern that a phase shift may occur. However, as described above, in this embodiment, the angular velocity is detected by finally obtaining the difference in voltage output. Therefore, occurrence of phase shift can be suppressed. The material of the upper electrode and the lower electrode is not limited to this combination.

The

upper electrodes

31, 32, 38 and 39 are used for calculation in angular velocity detection around the axis with the Z direction as an axis shown in FIG. The

lower electrodes

27, 28, 34, and 35 are used for calculation in angular velocity detection around an axis with the Y direction shown in FIG. 1 as an axis. The

upper electrodes

31, 32, 38, and 39 can be formed using gold of the same material, and the

lower electrodes

27, 28, 34, and 35 can be formed of platinum of the same material. Thus, even when the

lower electrodes

27, 28, 34, and 35 and the

upper electrodes

31, 32, 38, and 39 are formed of different materials, the occurrence of phase shift can be suppressed.

Note that currents generated from the electrodes of the

sense arms

24 and 25 are led out from the base 21 to the end of the element 20 through a thin wiring portion. For this reason, when these currents are large, the voltage drop becomes large, and a phase shift tends to occur. In particular the drive current is 10 ⁶ times the current due to the angular velocity as described above. In order to suppress such a phase shift, the first lower electrode 27 and the second lower electrode 28 may be electrically connected on the first substrate 26. Further, the third lower electrode 34 and the fourth lower electrode 35 may be electrically connected on the second substrate 33. In particular, it is preferable that the first lower electrode 27 and the second lower electrode 28 are integrally formed, and the third lower electrode 34 and the fourth lower electrode 35 are integrally formed. With these configurations, a large current generated by driving the

sense arms

24 and 25 in synchronization with the

drive arms

22 and 23 is canceled on the

substrates

26 and 33. Therefore, the current flowing on the wiring is reduced, and the influence of phase shift can be reduced.

In the above description, the arithmetic unit 70 obtains the sum of the voltage signal of the first lower electrode 27 for the first upper electrode 31 and the voltage signal of the second lower electrode 28 for the second upper electrode 32. On the other hand, the sum of the voltage signal of the third lower electrode 34 for the third upper electrode 38 and the voltage signal of the fourth lower electrode 35 for the fourth upper electrode 39 is obtained. Then, the difference between the two sums is obtained. Based on this difference, it is possible to detect the angular velocity around the axis with the direction in which the

sense arms

24 and 25 extend from the base 21 as the axis. That is, the angular velocity around the axis with the Y direction shown in FIG. 1 as an axis can be detected. However, the angular velocity about the axis about the Y direction shown in FIG. 1 can be detected even if the same calculation is performed using the voltage signal of each corresponding upper electrode for each lower electrode.

That is, in this case, the arithmetic unit 70 obtains the sum of the voltage signal of the first upper electrode 31 for the first lower electrode 27 and the voltage signal of the second upper electrode 32 for the second lower electrode 28. On the other hand, the sum of the voltage signal of the third upper electrode 38 for the third lower electrode 34 and the voltage signal of the fourth upper electrode 38 for the fourth lower electrode 35 is obtained. Then, the difference between the two sums is obtained. Based on this difference, it is possible to detect the angular velocity around the axis with the direction in which the

sense arms

24 and 25 extend from the base 21 as the axis. The calculation unit 70 may be configured in this way.

At that time, the arithmetic unit 70 calculates the sum of the voltage signal of the second lower electrode 28 for the second upper electrode 31 and the voltage signal of the fourth lower electrode 35 for the fourth upper electrode 39, and the first upper electrode 31. The difference between the voltage signal of the first lower electrode 27 for the electrode 31 and the sum of the voltage signal of the third lower electrode 34 for the third upper electrode 38 may be calculated. From this difference, it is also possible to detect an angular velocity around an axis about the direction perpendicular to the plane forming the base 21, that is, the Z direction shown in FIG.

Thus, in this embodiment, the angular velocity around the axis with the Y direction as the axis and the angular velocity around the axis with the Z direction as the axis are obtained separately using the upper electrode for the lower electrode and the upper electrode for the lower electrode, respectively. . Therefore, it is possible to accurately detect the biaxial angular velocity while suppressing the influence of the drive current.

Even when the calculation unit 70 performs such calculation, the effects of the material configuration of the lower electrode and the upper electrode and the integration of the two lower electrodes provided on the same sense arm are the same as those described above.

3 may be configured not to be included in the angular velocity sensor but to provide a terminal electrically connected to each drive arm and to supply a drive signal from an external circuit to each drive arm.

The angular velocity sensor of the present invention can detect the angular velocity around the axis with the direction in which the first and second sense arms extend from the base as an axis. This angular velocity sensor is useful in automobile control, car navigation devices, digital cameras, and the like.

20 element 21 base 22 first drive arm 23

second drive arms

22A, 23A, 24A,

25A flexures

22B, 23B, 24B, 25B weight 24 first sense arm 25 second sense arm 26 first Substrate 27 First lower electrode 28 Second

lower electrode

27A, 28A, 31A, 32A, 34A, 35A, 38A, 39A, 80, 90

Output line

27B, 28B, 31B, 32B, 34B, 35B, 38B, 39B Voltage Output 29 First piezoelectric body 30 Second piezoelectric body 31 First upper electrode 32 Second upper electrode 33 Second substrate 34 Third lower electrode 35 Fourth lower electrode 36 Third piezoelectric body 37 Four piezoelectric bodies 38 Third upper electrode 39 Fourth

upper electrodes

41, 42

Drive vibrations

43, 44, 45, 46 Coriolis force 50 Drive unit 70

Calculation section

80B, 90B difference signal

Claims

An angular velocity sensor including an element and a calculation unit,
The element is
The base,
First and second drive arms having portions connected to the base and extending parallel to each other from the base;
First and second sense arms connected to the base and extending in opposite directions from the base to the first and second drive arms and having portions extending parallel to each other from the base;
The first sense arm includes: a first substrate; a first lower electrode formed on the first substrate; and the first sense arm on the first substrate rather than the first lower electrode. A second lower electrode formed on the side close to the second sense arm; a first piezoelectric body formed on the first lower electrode; and formed on the second lower electrode. A second piezoelectric body, a first upper electrode formed on the first piezoelectric body, and a second upper electrode formed on the second piezoelectric body,
The second sense arm includes a second substrate, a third lower electrode formed on the second substrate, and the second sense arm on the second substrate more than the third lower electrode. A fourth lower electrode formed on the side far from the first sense arm, a third piezoelectric body formed on the third lower electrode, and formed on the fourth lower electrode. A fourth piezoelectric body, a third upper electrode formed on the third piezoelectric body, and a fourth upper electrode formed on the fourth piezoelectric body,
The computing unit is
The sum of the voltage signal of the first lower electrode for the first upper electrode and the voltage signal of the second lower electrode for the second upper electrode, and the third lower electrode for the third upper electrode Calculating the difference between the voltage signal of the electrode and the sum of the voltage signal of the fourth lower electrode with respect to the fourth upper electrode;
Angular velocity sensor.
The arithmetic unit includes the sum of the voltage signal of the first lower electrode with respect to the first upper electrode and the voltage signal of the second lower electrode with respect to the second upper electrode, and the third upper electrode. From the difference between the sum of the voltage signal of the third lower electrode with respect to and the voltage signal of the fourth lower electrode with respect to the fourth upper electrode, the first and second sense arms from the base Detect angular velocity around the axis with the extending direction as the axis,
The angular velocity sensor according to claim 1.
The computing unit is
The sum of the voltage signal of the second upper electrode with respect to the second lower electrode and the voltage signal of the fourth upper electrode with respect to the fourth lower electrode, and the first upper electrode with respect to the first lower electrode And the difference between the voltage signal of the third upper electrode and the voltage signal of the third upper electrode with respect to the third lower electrode,
The angular velocity sensor according to claim 1.
The arithmetic unit includes the sum of the voltage signal of the second upper electrode with respect to the second lower electrode and the voltage signal of the fourth upper electrode with respect to the fourth lower electrode, and the first lower electrode. From the difference between the sum of the voltage signal of the first upper electrode to the third and the voltage signal of the third upper electrode to the third lower electrode, the direction perpendicular to the plane forming the base is the axis Detect angular velocity around the axis,
The angular velocity sensor according to claim 3.
The first, second, third and fourth upper electrodes are formed of the same material,
The first, second, third and fourth lower electrodes are formed of the same material,
The first, second, third, and fourth upper electrodes and the first, second, third, and fourth lower electrodes are formed of different materials.
The angular velocity sensor according to claim 1.
The first and second lower electrodes are electrically connected;
The angular velocity sensor according to claim 1.
The first and second lower electrodes are integrally formed;
The angular velocity sensor according to claim 1.
The third and fourth lower electrodes are electrically connected;
The angular velocity sensor according to claim 1.
The third and fourth lower electrodes are integrally formed;
The angular velocity sensor according to claim 1.
An angular velocity sensor including an element and a calculation unit,
The element is
The base,
First and second drive arms having portions connected to the base and extending parallel to each other from the base;
First and second sense arms connected to the base and extending in opposite directions from the base to the first and second drive arms and having portions extending parallel to each other from the base;
The first sense arm includes: a first substrate; a first lower electrode formed on the first substrate; and the first sense arm on the first substrate rather than the first lower electrode. A second lower electrode formed on the side close to the second sense arm; a first piezoelectric body formed on the first lower electrode; and formed on the second lower electrode. A second piezoelectric body, a first upper electrode formed on the first piezoelectric body, and a second upper electrode formed on the second piezoelectric body,
The second sense arm includes a second substrate, a third lower electrode formed on the second substrate, and the second sense arm on the second substrate more than the third lower electrode. A fourth lower electrode formed on the side far from the first sense arm, a third piezoelectric body formed on the third lower electrode, and formed on the fourth lower electrode. A fourth piezoelectric body, a third upper electrode formed on the third piezoelectric body, and a fourth upper electrode formed on the fourth piezoelectric body,
The computing unit is
The sum of the voltage signal of the first upper electrode for the first lower electrode and the voltage signal of the second upper electrode for the second lower electrode, and the third upper electrode for the third lower electrode Calculating the difference between the voltage signal of the electrode and the sum of the voltage signal of the fourth upper electrode with respect to the fourth lower electrode;
Angular velocity sensor.
The arithmetic unit includes the sum of the voltage signal of the first upper electrode with respect to the first lower electrode and the voltage signal of the second upper electrode with respect to the second lower electrode, and the third lower electrode. From the difference between the sum of the voltage signal of the third upper electrode with respect to the voltage signal of the fourth upper electrode with respect to the fourth lower electrode, the first and second sense arms from the base Detect angular velocity around the axis with the extending direction as the axis,
The angular velocity sensor according to claim 10.
The computing unit is
The sum of the voltage signal of the second lower electrode with respect to the second upper electrode and the voltage signal of the fourth lower electrode with respect to the fourth upper electrode, and the first lower electrode with respect to the first upper electrode Calculating the difference between the voltage signal and the sum of the voltage signal of the third lower electrode with respect to the third upper electrode;
The angular velocity sensor according to claim 10.
The arithmetic unit includes the sum of the voltage signal of the second lower electrode with respect to the second upper electrode and the voltage signal of the fourth lower electrode with respect to the fourth upper electrode, and the voltage with respect to the first upper electrode. An axis about the direction perpendicular to the plane forming the base from the difference between the voltage signal of the first lower electrode and the sum of the voltage signal of the third lower electrode with respect to the third upper electrode Detect the angular velocity around,
The angular velocity sensor according to claim 12.
The first, second, third and fourth upper electrodes are formed of the same material,
The first, second, third and fourth lower electrodes are formed of the same material,
The first, second, third, and fourth upper electrodes and the first, second, third, and fourth lower electrodes are formed of different materials.
The angular velocity sensor according to claim 10.