JP2010060359A - Piezoelectric vibrator and angular velocity sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric vibrator having the higher sensitivity of detecting an angular velocity. <P>SOLUTION: A tuning fork type piezoelectric vibrator 70 comprises a base 74 having a substancially-rectangular shape and two columnar legs 76a, 76b. The tuning fork type piezoelectric vibrator 70 comprises two piezoelectric body substrates 80, 82. An internal electrode 84 is formed between the piezoelectric body substrates 80, 82. Three drive detection electrodes 86, 88, 90 are formed to face the internal electrode 84 at surface of the piezoelectric body substrate 80. The thickness of the piezoelectric body substrate 80 is made as one forth of the thickness of the piezoelectric body substrate 82, namely as one fifth of the thickness of each piezoelectric body substrate 80, 82. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to piezoelectric vibrators and angular velocity sensors, and in particular, a plurality of stacked piezoelectric substrates, internal electrodes formed between the piezoelectric substrates, and formed on the surface of the piezoelectric substrate so as to face the internal electrodes. For example, the present invention relates to a piezoelectric vibrator such as a tuning fork type piezoelectric vibrator or a sound piece type piezoelectric vibrator that can be used for an angular velocity sensor or the like.

  FIG. 16 is a plan view showing an example of a conventional tuning fork type piezoelectric vibrator as a background of the present invention, and FIG. 17 is an illustrative view of the tuning fork type piezoelectric vibrator. The tuning fork type piezoelectric vibrator 1 shown in FIGS. 16 and 17 includes a substantially rectangular base 2, and two columnar legs 3 a and 3 b extend in parallel from one end in the longitudinal direction of the base 2. Formed as follows. The tuning fork type piezoelectric vibrator 1 includes two tuning fork type piezoelectric substrates 4 and 5 which are stacked. The piezoelectric substrates 4 and 5 are formed to have the same thickness and are polarized in opposite thickness directions. An internal electrode 6 is formed between the piezoelectric substrates 4 and 5. Therefore, the internal electrode 6 is positioned at the center in the thickness direction of the piezoelectric substrates 4 and 5. In addition, three drive detection electrodes 7 a, 7 b, 7 c are formed on the surface of one piezoelectric substrate 4 so as to face the internal electrode 6 at intervals in the width direction. In this case, the three drive detection electrodes 7a, 7b, 7c are provided on the surface side of one piezoelectric substrate 4 at the groove 4a extending in the center in the width direction of the leg 3a and in the center in the width direction of the leg 3b. They are separated from each other by the extending grooves 4b. Further, a full-surface electrode 8 is formed on the surface of the other piezoelectric substrate 5.

  In the tuning fork type piezoelectric vibrator 1 described above, if a drive signal is similarly applied between the drive detection electrode 7b at the center and the drive detection electrodes 7a, 7c on both sides, the legs 3a, 3b are shown in FIG. As shown, it vibrates with basic vibrations so as to open and close each other. In the state where the legs 3a and 3b are open to each other (the state shown by the solid line in FIG. 18), the portion where the central drive detection electrode 7b is formed is extended, and the portions where the drive detection electrodes 7a and 7c are formed on both sides Is shrinking. Conversely, in a state where the legs 3a and 3b are closed, the portion where the central drive detection electrode 7b is formed contracts, and the portions where the drive detection electrodes 7a and 7c on both sides are formed extend. During this basic vibration, the two legs 3a and 3b vibrate symmetrically in the same state with respect to the polarization direction, so the same signal is output from the drive detection electrodes 7a and 7c on both sides. Therefore, if the difference between these signals is taken, a signal of “0” is obtained.

  In this basic vibration state, when a rotational angular velocity is applied to the tuning fork type piezoelectric vibrator 1 about an axis parallel to the longitudinal direction, the legs 3a and 3b are mutually connected in a direction perpendicular to the direction of the basic vibration. Reverse Coriolis force works. Therefore, the two leg portions 3a and 3b are displaced in directions opposite to each other as shown in FIG. 19, for example. In the displacement state shown by the solid line in FIG. 19, in one leg portion 3a on which the drive detection electrode 7a is formed, one piezoelectric substrate 4 is contracted and the other piezoelectric substrate 5 is extended. In the other leg 3b on which the electrode 7c is formed, one piezoelectric substrate 4 is extended and the other piezoelectric substrate 5 is contracted. In the displacement state opposite to the displacement state shown by the solid line in FIG. 19, in one leg portion 3a, one piezoelectric substrate 4 is extended, and the other piezoelectric substrate 5 is contracted. In the other leg 3b, one piezoelectric substrate 4 is contracted and the other piezoelectric substrate 5 is extended. Due to this displacement, opposite-phase signals are output from the drive detection electrodes 7a and 7c on both sides, and if the difference between these signals is taken, it has a magnitude and polarity corresponding to the magnitude of the rotational angular velocity and the rotational direction. A signal is obtained, and the rotational angular velocity can be detected from the obtained signal.

  The tuning fork type piezoelectric vibrator 1 shown in FIGS. 16 and 17 includes two piezoelectric substrates 4 and 5 having the same thickness, which are stacked. In this way, the piezoelectric vibrator including two piezoelectric substrates having the same thickness is used. For example, it is disclosed by Unexamined-Japanese-Patent No. 2003-57035 (refer patent document 1).

JP 2003-57035 A

In the tuning fork type piezoelectric vibrator 1 described above, the one that uses the positive piezoelectric effect at the time of driving and detecting the angular velocity is one piezoelectric body between the internal electrode 6 and the drive detection electrodes 7a, 7b, 7c. Only the substrate 4 is present. The other piezoelectric substrate 5 is a mechanical load for converting bending vibration in the thickness direction into expansion and contraction of the one piezoelectric substrate 4 at the time of detection.
At the time of detection, the expansion and contraction of one piezoelectric substrate 4 is different at each location in the thickness direction, and the position close to the electrodes 7a, 7b, and 7c expands and contracts the most, and the position close to the internal electrode 6 hardly expands or contracts. At the time of detection, the electric charge generated in one piezoelectric substrate 4 due to the positive piezoelectric effect is proportional to the average of expansion and contraction in one piezoelectric substrate 4. Therefore, when the internal electrode 6 is positioned at the center in the thickness direction of the vibrator 1 (piezoelectric substrates 4 and 5) as in the tuning fork type piezoelectric vibrator 1 described above, one piezoelectric element is detected at the time of angular velocity detection. The positive piezoelectric effect of the body substrate 4 cannot be used efficiently, so that the angular velocity cannot be detected efficiently, and the sensitivity for detecting the angular velocity is low.

Therefore, a main object of the present invention is to provide a piezoelectric vibrator having high sensitivity for detecting angular velocity.
Another object of the present invention is to provide an angular velocity sensor using a piezoelectric vibrator having high sensitivity for detecting angular velocity.

The piezoelectric vibrator according to the present invention includes a plurality of piezoelectric substrates to be stacked, an internal electrode formed between the piezoelectric substrates, and a drive detection surface formed on the surface of the piezoelectric substrate so as to face the internal electrode. A piezoelectric vibrator in which at least a portion between the internal electrode and the drive detection electrode is polarized in a direction in which the internal electrode and the drive detection electrode face each other in the plurality of piezoelectric substrates. In the piezoelectric vibrator, the thickness in the polarization direction of the portion between the internal electrode and the drive detection electrode is thinner than the thickness in the same direction as the polarization direction of the portion other than the portion.
In the piezoelectric vibrator according to the present invention, the thickness in the polarization direction of the portion between the internal electrode and the drive detection electrode is 1/6 to 1/4 of the thickness in the same direction as the polarization direction of the plurality of piezoelectric substrates. It is preferable to be formed.
In the piezoelectric vibrator according to the present invention, for example, the plurality of piezoelectric substrates are composed of three or more layers, and the internal electrode is formed between two piezoelectric substrates of different combinations among the piezoelectric substrates having three or more layers. Thus, at least two may be formed, and the drive detection electrodes may be formed on the front and back surfaces of the plurality of stacked piezoelectric substrates.
The angular velocity sensor according to the present invention is an angular velocity sensor including the piezoelectric vibrator according to the present invention.

In the piezoelectric vibrator according to the present invention, the portion between the internal electrode and the drive detection electrode is formed thinner than the other portions in the plurality of piezoelectric substrates, so that the internal electrode and the drive detection are detected at the time of angular velocity detection. The positive piezoelectric effect in the portion between the electrodes for use can be used efficiently. Therefore, in the piezoelectric vibrator according to the present invention, the angular velocity can be detected efficiently, and the sensitivity for detecting the angular velocity is increased.
In the piezoelectric vibrator according to the present invention, the thickness in the polarization direction of the portion between the internal electrode and the drive detection electrode is 1/6 to 1/4 of the thickness in the same direction as the polarization direction of the plurality of piezoelectric substrates. If formed, the angular velocity can be detected particularly efficiently, and the sensitivity for detecting the angular velocity is particularly high.
In the piezoelectric vibrator according to the present invention, a plurality of piezoelectric substrates are formed of three or more layers, and the internal electrode is formed between two piezoelectric substrates of different combinations among the piezoelectric substrates having three or more layers. If at least two drive detection electrodes are formed on the front and back surfaces of a plurality of stacked piezoelectric substrates, the portion that uses the positive piezoelectric effect increases when detecting the angular velocity, so the angular velocity is detected. Sensitivity to be further increased.

According to the present invention, a piezoelectric vibrator having high sensitivity for detecting angular velocity can be obtained.
In addition, according to the present invention, an angular velocity sensor using a piezoelectric vibrator having high sensitivity for detecting angular velocity can be obtained.

  The above-described object, other objects, features, and advantages of the present invention will become more apparent from the following description of the best mode for carrying out the invention with reference to the drawings.

  FIG. 1 is an internal perspective view showing an example of an angular velocity sensor according to the present invention, and FIG. 2 is an exploded perspective view of the angular velocity sensor. The angular velocity sensor 10 shown in FIGS. 1 and 2 includes a circuit board 20. The circuit board 20 is formed in a shape such as a rectangular plate. A recess 22 is formed on one surface of the circuit board 20. For example, the recess 22 is formed at a position that is offset toward one corner of the circuit board 20. In FIG. 2, the recess 22 is formed in a bowl shape, but may be any shape as long as an IC described later can be mounted, and may be formed in other shapes such as a square shape.

  In the recess 22 of the circuit board 20, a plurality of electrodes 24 are formed so as to be arranged in a square shape, for example. In addition, on the outside of the recess 22 of the circuit board 20, three rectangular electrodes 26a, 26b, and 26c are formed side by side in the vicinity of the short side close to the recess 22. These electrodes 26 a to 26 c are arranged so that the longitudinal direction thereof is in the same direction as the short side of the circuit board 20 close to the recess 22. Further, three rectangular electrodes 28 a, 28 b, and 28 c are formed side by side on the outside of the recess 22 of the circuit board 20 in the vicinity of the long side close to the recess 22. These electrodes 28 a to 28 c are arranged so that the longitudinal direction thereof is in the same direction as the long side of the circuit board 20 close to the recess 22.

  A plurality of pairs of counter electrodes 30 are formed between the recess 22 and the short side of the circuit board 20 located away from the recess 22. Each counter electrode 30 is formed so as to face each other in the longitudinal direction of the circuit board 20. A plurality of pairs of counter electrodes 30 are arranged along the short side of the circuit board 20. Further, a plurality of electrodes 32 are formed between the counter electrode 30 and the short side of the circuit board 20. A plurality of electrodes 34 are formed adjacent to the electrodes 26 a to 26 c formed in the vicinity of the short side of the circuit board 20 close to the recess 22. These electrodes 34 are arranged along the long side of the circuit board 20 away from the recess 22.

  As shown in FIG. 3, a plurality of external electrodes 40 and eight inspection electrodes 42 a to 42 h are formed on the other surface of the circuit board 20. The external electrodes 40 are formed side by side along the opposing long sides of the circuit board 20. Further, the inspection electrodes 42 a to 42 h are formed side by side inside the external electrode 40. The four inspection electrodes 42 a to 42 d and the other four inspection electrodes 42 e to 42 h are formed along each of the opposing long sides of the circuit board 20. Center points C of the eight inspection electrodes 42 a to 42 h are arranged on the other surface of the circuit board 20 so as to coincide with a position G corresponding to the center of gravity of the angular velocity sensor 10 as a whole.

  The circuit board 20 is made of alumina, for example. Further, the electrodes 24, 26a to 26c, 28a to 28c, 30, 32, 34, 40, 42a to 42h, etc. formed on the circuit board 20 are made of, for example, nickel and gold sequentially on the electrodes formed of tungsten. It is formed by plating. The circuit board 20 is formed with a number of conductive wiring members (not shown) such as via holes and patterns.

  The IC 50 is fitted into the recess 22 of the circuit board 20. The IC 50 is used for driving a tuning fork type piezoelectric vibrator described later and processing an output signal of the tuning fork type piezoelectric vibrator. A plurality of external electrodes (not shown) are formed on the IC 50, and the external electrodes of the IC 50 are connected to the electrodes 24 in the recess 22, respectively. At this time, for example, a gold bump 52 is formed on the electrode 24, and the electrode 24 and the external electrode of the IC 50 are connected by the gold bump 52. The IC 50 is fixed to the circuit board 20 by an underfill 54 made of an epoxy adhesive or the like.

  A chip capacitor 60 is connected to the counter electrode 30 formed on the circuit board 20. As the chip capacitor 60, for example, a multilayer ceramic capacitor is used, and external electrodes formed at both ends thereof are connected to the counter electrode 30 by solder 62 or the like.

  Further, the first tuning fork type piezoelectric vibrator 70 and the second tuning fork type piezoelectric vibrator 72 are respectively attached to the electrodes 26 a to 26 c and 28 a to 28 c formed on the outer side of the recess 22. Each of the first tuning fork type piezoelectric vibrator 70 and the second tuning fork type piezoelectric vibrator 72 includes a substantially rectangular base part 74, and two columnar leg parts from one end in the longitudinal direction of the base part 74. 76a and 76b are formed to extend. These leg portions 76 a and 76 b are formed so as to extend in parallel with each other on the inner side from both ends of the base portion 74 in the width direction.

  The first tuning fork type piezoelectric vibrator 70 and the second tuning fork type piezoelectric vibrator 72 include two tuning fork type piezoelectric substrates 80 and 82 which are stacked as shown in FIGS. 4 and 5, respectively. The piezoelectric substrates 80 and 82 are formed of a piezoelectric material such as lead zirconate titanate (PZT), for example, and are polarized in opposite thickness directions, for example. Further, the thickness of one piezoelectric substrate 80 is formed to be ¼ of the thickness of the other piezoelectric substrate 82, that is, 1/5 of the thickness of the piezoelectric substrates 80 and 82.

  In the first tuning fork type piezoelectric vibrator 70 and the second tuning fork type piezoelectric vibrator 72, internal electrodes 84 are formed between the piezoelectric substrates 80 and 82, respectively.

  In the first tuning-fork type piezoelectric vibrator 70 and the second tuning-fork type piezoelectric vibrator 72, three drive detection electrodes 86, 88, 90 are provided in the width direction on the surface of one piezoelectric substrate 80. They are formed so as to be opposed to the internal electrode 84 at intervals. In this case, on the surface side of the piezoelectric substrate 80, for example, one linear groove 80a is formed to extend in the center in the width direction of one leg 76a, and the other linear groove 80b is formed on the other side, for example. The leg portion 76b is formed to extend to the center in the width direction. The drive detection electrodes 86 and 88 are divided from each other by one groove 80a. The drive detection electrodes 88 and 90 are divided from each other by the other groove 80b. Therefore, the end-side drive detection electrode 86 is formed so as to extend from the base portion 74 to the leg portion 76a. Further, the end-side drive detection electrode 90 is formed so as to extend from the base portion 74 to the leg portion 76b. Further, the center drive detection electrode 88 is formed so as to extend from the base portion 74 to both the leg portions 76a and 76b. Here, the depths of the grooves 80a and 80b formed in the piezoelectric substrate 80 are respectively half the thickness of the piezoelectric substrate 80, that is, 1 / th of the thickness of the piezoelectric substrates 80 and 82. It is formed to a depth of 10. The widths of the grooves 80a and 80b between the drive detection electrodes 86, 88, and 90 are formed wide at the base portion 74 to prevent a short circuit between the drive detection electrodes 86, 88, and 90. In order to increase the efficiency of the drive detection electrodes 86, 88, 90, the leg portions 76a, 76b may be formed to be narrow.

  Further, in the first tuning-fork type piezoelectric vibrator 70 and the second tuning-fork type piezoelectric vibrator 72, a full surface electrode 92 is formed on the surface of the other piezoelectric substrate 82. The full-surface electrode 92 is used when the piezoelectric substrate 82 is polarized. For this reason, the entire surface electrode 92 may not be formed when the piezoelectric substrate 82 is not polarized or not necessary.

  The first tuning fork type piezoelectric vibrator 70 and the second tuning fork type piezoelectric vibrator 72 are attached to the electrodes 26 a to 26 c and the electrodes 28 a to 28 c formed outside the recess 22 of the circuit board 20. At this time, using the bonding material 100, the drive detection electrodes 86, 88, 90 of the two tuning fork type piezoelectric vibrators 70, 72 are connected to the electrodes 26a, 26b, 26c and the electrodes 28a, 28b, 28c, respectively. The As the bonding material 100, for example, an anisotropic conductive adhesive, a conductive adhesive, a resin-metal composite material, a gold bump, or the like is used. Since it is necessary to ensure insulation between the drive detection electrodes 86, 88, 90, when using an anisotropic conductive adhesive or a resin-metal composite material as the bonding material 100, The bonding material 100 can be applied to the entire surface of the three drive detection electrodes 86, 88, 90, but when other materials are used, they are divided into the respective drive detection electrodes 86, 88, 90. Thus, it is necessary to apply the bonding material 100.

  The first tuning fork type piezoelectric vibrator 70 and the second tuning fork type piezoelectric vibrator 72 are arranged in directions almost orthogonal to each other, but different resonances are used so that each vibration does not affect the other piezoelectric vibrators. Those having a frequency are used. The leg portions 76 a and 76 b of the first tuning fork type piezoelectric vibrator 70 are formed longer than the leg portions 76 a and 76 b of the second tuning fork type piezoelectric vibrator 72. Thereby, the first tuning fork type piezoelectric vibrator 70 has a lower resonance frequency than the second tuning fork type piezoelectric vibrator 72.

  The first tuning-fork type piezoelectric vibrator 70 having a low resonance frequency is connected to electrodes 26 a to 26 c formed in the vicinity of the short side of the circuit board 20. The second tuning-fork type piezoelectric vibrator 72 having a high resonance frequency is connected to electrodes 28 a to 28 c formed in the vicinity of the long side of the circuit board 20. The leg portions 76a and 76b of the first tuning fork type piezoelectric vibrator 70 and the second tuning fork type piezoelectric vibrator 72 extend along the short side and the long side of the circuit board 20 toward the recess 24 side. Placed in.

  A necessary part of the circuit formed by the IC 50 and the chip capacitor 60 is connected to the external electrode 40 formed on the other surface of the circuit board 20 via the electrode 24, the counter electrode 30 and a wiring member (not shown). Is done. Further, the drive detection electrodes 86, 88, 90 of the first tuning fork type piezoelectric vibrator 70 and the second tuning fork type piezoelectric vibrator 72 include electrodes 26a to 26c, 28a to 28c and a wiring member (not shown). In addition to being connected to the circuit of the IC 50, it is connected to the inspection electrodes 42 a to 42 h formed on the other surface of the circuit board 20. At this time, the drive detection electrodes 86, 88, and 90 of the first tuning fork type piezoelectric vibrator 70 and the second tuning fork type piezoelectric vibrator 72 are respectively four inspection electrodes 42a to 42d arranged in two rows. And four inspection electrodes 42e to 42h.

  Here, the drive detection electrode 88 at the center of the first tuning-fork type piezoelectric vibrator 70 is connected to the two inspection electrodes 42a and 42d on the outer sides of the four inspection electrodes 42a to 42d arranged side by side. The drive detection electrodes 86 and 90 on both sides of the first tuning-fork type piezoelectric vibrator 70 are connected to the two inner inspection electrodes 42b and 42c. The drive detection electrode 88 in the center of the second tuning-fork type piezoelectric vibrator 72 is connected to the two inspection electrodes 42e and 42h on the outer sides of the other four inspection electrodes 42e to 42h, The drive detection electrodes 86 and 90 on both sides of the second tuning-fork type piezoelectric vibrator 72 are connected to the two inner inspection electrodes 42f and 42g.

  On one surface of the circuit board 20, a cap 110 is attached so as to cover the IC 50, the chip capacitor 60, the first tuning fork type piezoelectric vibrator 70 and the second tuning fork type piezoelectric vibrator 72. The cap 110 is made of, for example, a material such as alumina or white and white, and is formed in a rectangular container shape that matches the outer shape of the circuit board 20.

  In order to attach the cap 110 to the circuit board 20, a cap adhesive 112 is applied between the end of the cap 110 and the circuit board 20. As the cap adhesive 112, for example, an epoxy adhesive or the like is used when an insulating cap 110 such as alumina is attached, and an epoxy adhesive is used when a conductive cap 110 such as white is attached. In addition, an epoxy conductive adhesive or the like is used.

  The cap 110 is formed with an explosion-proof through hole 114. The through hole 114 is formed in the vicinity of the corner portion of the cap 110 at a position corresponding to the base portion 74 of the first tuning fork type piezoelectric vibrator 70. The through hole 114 may be formed in the vicinity of the corner portion of the cap 110 at a position corresponding to the base portion 74 of the second tuning fork type piezoelectric vibrator 72. That is, the through hole 114 is preferably formed at a position where the cap 110 is not disposed on the IC 50 even when the cap 110 is rotated 180 ° and attached to the circuit board 20.

  Next, the circuit configuration of the angular velocity sensor 10 will be described with reference to FIG. Here, in the angular velocity sensor 10, the circuit configuration related to the first tuning fork type piezoelectric vibrator 70 and the circuit configuration related to the second tuning fork type piezoelectric vibrator 72 are the same circuit configuration. A circuit configuration related to the first tuning fork type piezoelectric vibrator 70 will be described in detail, and then a circuit configuration related to the second tuning fork type piezoelectric vibrator 72 will be briefly described.

  In the angular velocity sensor 10, the drive detection electrodes 86 and 90 of the first tuning fork type piezoelectric vibrator 70 are connected to the input buffer 200 included in the IC 50 via the electrodes 24, 26 a and 26 c and a wiring member (not shown). Connected to two inputs. This input buffer 200 has one output end and the other two output ends, and one output end is for outputting a signal that is the sum of the signals input to the two input ends. These two output terminals are for outputting signals input to the two input terminals. In the IC 50, one output terminal of the input buffer 200 is connected to an input terminal of an amplitude control circuit 202 for controlling the amplitude of the signal, and the output terminal of the amplitude control circuit 202 is used to make the phase of the signal appropriate. Connected to the input terminal of the phase shift circuit 204. The output terminal of the phase shift circuit 204 in the IC 50 is connected to the drive detection electrode 88 of the first tuning-fork type piezoelectric vibrator 70 via the electrodes 24 and 26b and a wiring member (not shown). Thus, a driving feedback loop is formed in the first tuning-fork type piezoelectric vibrator 70. The drive detection electrodes 86, 88, 90 of the first tuning fork type piezoelectric vibrator 70 are connected to predetermined ones of the four inspection electrodes 42a to 42d as described above.

  In the IC 50, the other two output terminals of the input buffer 200 are connected to two input terminals of the differential amplifier circuit 206, and the output terminal of the differential amplifier circuit 206 is synchronously detected via the amplitude adjustment circuit 208. The circuit 210 is connected to one input terminal, and one output terminal of the input buffer 200 is connected to the other input terminal of the synchronous detection circuit 210 via the detection clock generation circuit 212. The synchronous detection circuit 210 detects a signal input to one input terminal thereof in synchronization with a signal (detection clock) input to the other input terminal. The output terminal of the synchronous detection circuit 210 is connected to one external electrode (electrode 24) of the IC 50, and this external electrode and another external electrode (another electrode 24, external electrode 40 (REF) of the IC 50 to which a reference voltage is applied. )) Is connected to a capacitor C1 (chip capacitor 60) via an electrode 30 and a wiring member (not shown).

  Further, in the IC 50, the output terminal of the synchronous detection circuit 210 is connected to one input terminal of the adjustment circuit 214. This adjustment circuit 214 is for temperature compensation of the output signal of the synchronous detection circuit 210. Therefore, a serial interface 216, a logic circuit 218, a memory 220, and a temperature sensor 222 are provided in the IC 50. The serial interface 216 has three input terminals connected to three external electrodes (three electrodes 24) and three external electrodes 40 (ACS, ACLK, and ASDIO) of the IC 50, respectively, and an output terminal connected to the input of the logic circuit 218. Connected to the end. The input / output terminal of the logic circuit 218 is connected to the input / output terminal of the memory 220. Further, the VPP voltage terminal of the memory 220 is connected to the external electrode (electrode 24) and the external electrode 40 (VPP) of the IC 50. Therefore, various data such as data relating to impedance change characteristics with respect to temperature changes of the first tuning-fork type piezoelectric vibrator 70 actually measured are transferred from the external electrode 40 through the serial interface 216 and the logic circuit 218 to the memory 220. Can be memorized. The output terminal of the logic circuit 218 is connected to another input terminal of the adjustment circuit 214. Therefore, data stored in the memory 220 can be supplied to the adjustment circuit 214 via the logic circuit 218. Further, the output terminal of the temperature sensor 222 is connected to another input terminal of the adjustment circuit 214. Therefore, the adjustment circuit 214 can compensate the temperature of the input signal, that is, the output signal of the synchronous detection circuit 210 based on the data stored in the memory 220 and the output signal of the temperature sensor 222.

  Although not shown, the memory 220 is also connected to the amplitude adjustment circuit 208 described above. Based on the gain-related data stored in the memory 220, the amplitude adjustment circuit 208 outputs an output signal of the differential amplifier circuit 206. Can be adjusted.

  In the IC 50, the output terminal of the adjustment circuit 214 is connected to the input terminal of the low-pass filter 224. The low-pass filter 224 is for passing a low frequency band including an angular velocity frequency detected by the angular velocity sensor 10, for example, 10 Hz to 50 Hz. The output end of the low-pass filter 224 is connected to the external electrode (electrode 24), electrode 30 and external electrode 40 (OUTx) of the IC 50. The low-pass filter 224 also has another output terminal that passes and outputs the input signal, and the other output terminal is connected to another external electrode (electrode 24) and another electrode 30 of the IC 50. A capacitor C2 (chip capacitor 60) is connected between the output end of the low-pass filter 224 and another output end (between the electrodes 30).

  The output end of the low-pass filter 224, that is, the external electrode 40 (OUTx) is connected to the input end of a high-pass filter 226 provided outside. The high pass filter 226 is for cutting a DC component in the signal. The high pass filter 226 includes a capacitor C3 and a resistor R1, and the capacitor C3 is connected between the input terminal and the output terminal thereof, and another external electrode 40 (REF) to which the reference voltage of the IC 50 is applied. Is connected to the resistor R1.

  The output end of the high-pass filter 226, that is, the connection point between the capacitor C3 and the resistor R1 is connected to the external electrode 40 (AINx). The external electrode 40 (AINx) is connected to the positive input terminal of the operational amplifier 228 used for the subsequent amplifier in the IC 50 through the electrode 24 and the like. The post-stage amplifier is for amplifying the amplitude of the signal input to the external electrode 40 (AINx) by about 50 times, for example. The operational amplifier 228 has a negative input terminal connected to the external electrode 40 (AFBx) via the electrode 24 and the like, and an output terminal connected to another external electrode 40 (APOx) via the other electrode 24 and the like. Further, a low-pass filter 230 provided outside is connected to these external electrodes 40 (AFBx, APOx). The low-pass filter 230 includes a resistor R2 and a capacitor C4, and the resistor R2 and the capacitor C4 are connected in parallel between the external electrodes 40 (AFBx, APOx). A resistor R3 is connected between the external electrode 40 (AFBx) and another external electrode 40 (REF) to which the reference voltage is applied. Therefore, the amplitude of the signal input to the external electrode 40 (AINx) is amplified by, for example, about 50 times by a post-stage amplifier including the operational amplifier 228, and output from the output terminal of the op amp 228, that is, the external electrode 40 (APOx). it can.

  Further, a switch SW is provided in the IC 50. The switch SW is connected to the external electrode (electrode 24) of the IC 50 connected to the external electrode 40 (AINx) and another external electrode of the IC 50 connected to another external electrode 40 (REF) to which the reference voltage of the IC 50 is applied. Connected to another electrode 24). The switch SW is connected to the external electrode (electrode 24) of the IC 50 connected to the external electrode 40 (SCT). Further, the switch SW is configured to be turned on or off by a control signal input to the external electrode 40 (SCT). If the capacitor C3 of the high-pass filter 226 is charged by turning on the switch SW for 0.2 seconds, for example, the output terminal of the low-pass filter 224, that is, the signal of the external electrode 40 (OUTx) can be transmitted in a short time to the positive input terminal of the operational amplifier 228. The rise time of the output signal at the output terminal of the operational amplifier 228, that is, the external electrode 40 (APOx) can be shortened.

  The external electrode 40 (VCC) is connected to the electrode 24 connected to VCC and VDD of the IC 50 via a wiring member (not shown), and the external electrode 40 (GND) is connected to the wiring member (not shown). To the electrode 24 connected to the GND of the IC 50. The external electrode 40 (SLP) is connected to the electrode 24 connected to the sleep control terminal of the IC 50 via a wiring member (not shown).

  In the angular velocity sensor 10, like the first tuning-fork type piezoelectric vibrator 70, the drive detection electrodes 86, 90 of the second tuning-fork type piezoelectric vibrator 72 are electrodes 24, 28a, 28c and a wiring member (not shown). ) To two input terminals of an input buffer 200 ′ similar to the input buffer 200 included in the IC 50. One output terminal of the input buffer 200 ′ includes an amplitude control circuit 202 ′ similar to the amplitude control circuit 202, a phase shift circuit 204 ′ similar to the phase shift circuit 204, electrodes 24 and 28 b and a wiring member (not shown). To the drive detection electrode 88 of the second tuning-fork type piezoelectric vibrator 72. In this manner, a feedback loop for driving is also formed in the second tuning fork type piezoelectric vibrator 72. However, the driving feedback loop is formed such that the driving frequency of the second tuning fork type piezoelectric vibrator 72 is higher than the driving frequency of the first tuning fork type piezoelectric vibrator 70.

  The other two output terminals of the input buffer 200 ′ are also synchronized with the synchronous detection circuit 210 through the differential amplification circuit 206 ′ and the amplitude adjustment circuit 208 ′ similar to the differential amplification circuit 206 and the amplitude adjustment circuit 208. It is connected to one input terminal of the detection circuit 210 ′, and one output terminal of the input buffer 200 ′ is connected to the synchronous detection circuit 210 ′ via a detection clock generation circuit 212 ′ similar to the detection clock generation circuit 212. Connected to the other input end. Although not shown, the memory 220 is also connected to the adjustment circuit 208 ′, and the amplitude of the output signal of the differential amplifier circuit 206 ′ is adjusted by the amplitude adjustment circuit 208 ′ based on the gain-related data stored in the memory 220. Can be adjusted. In addition, the detection clock generation circuit 212 ′ generates a detection clock having a shorter period corresponding to the higher drive frequency of the second tuning-fork type piezoelectric vibrator 72 than the detection clock generation circuit 212, and the synchronous detection circuit 210 ′. The detection cycle at is also shorter than the detection cycle at the synchronous detection circuit 210.

  The output terminal of the synchronous detection circuit 210 ′ is connected to one external electrode (electrode 24) and electrode 30 of the IC 50, and this electrode 30 and another external electrode (another electrode 24, external electrode) of the IC 50 to which a reference voltage is applied. A capacitor C5 (chip capacitor 60) is connected between the electrode 40 (REF)).

  Further, in the IC 50, the output terminal of the synchronous detection circuit 210 ′ is connected to one input terminal of an adjustment circuit 214 ′ similar to the adjustment circuit 214. Further, the memory 220 and the temperature sensor 222 are connected to another input terminal and further another input terminal of the adjustment circuit 214 ′, respectively. Therefore, the data stored in the memory 220 can be given to the adjustment circuit 214 ′. Further, the adjustment circuit 214 ′ compensates the temperature of the output signal of the synchronous detection circuit 210 ′ based on the data related to the second tuning-fork type piezoelectric vibrator 72 stored in the memory 220 and the output signal of the temperature sensor 222. Can do.

  In the IC 50, the output terminal of the adjustment circuit 214 ′ is connected to the input terminal of a low-pass filter 224 ′ that is similar to the low-pass filter 224. The output terminal of the low-pass filter 224 ′ is connected to the external electrode (electrode 24), the electrode 30 and the external electrode 40 (OUTy) of the IC 50, and another output terminal of the low-pass filter 224 ′ is connected to another external electrode (electrode) of the IC 50. 24) and another electrode 30. A capacitor C6 (chip capacitor 60) is connected between the output end of the low-pass filter 224 ′ and another output end (between the electrodes 30).

  The output end of the low-pass filter 224 ′, that is, the external electrode 40 (OUTy) is connected to the input end of a high-pass filter 226 ′ provided outside the same as the high-pass filter 226. The high-pass filter 226 ′ has a capacitor C7 connected between its input end and output end, and a resistor R4 between the output end and another external electrode 40 (REF) to which the reference voltage of the IC 50 is applied. Connected.

  The output terminal of the high-pass filter 226 ′, that is, the connection point between the capacitor C7 and the resistor R4 is connected to the external electrode 40 (AINy). The external electrode 40 (AINy) is connected to the positive input terminal of an operational amplifier 228 ′ used in another post-stage amplifier similar to the post-stage amplifier in the IC 50 via the electrode 24 and the like. This other post-stage amplifier is for amplifying the amplitude of the signal input to the external electrode 40 (AINy) by about 50 times, for example. The operational amplifier 228 ′ has a negative input terminal connected to the external electrode 40 (AFBy) via the electrode 24 and the like, and an output terminal connected to another external electrode 40 (APOy) via the other electrode 24 and the like. . The external electrodes 40 (AFBy, APOy) are connected to a low-pass filter 230 ′ provided outside the same as the low-pass filter 230. A resistor R5 and a capacitor C8 of the low-pass filter 230 ′ are connected in parallel between the external electrodes 40 (AFBy, APOy). A resistor R6 is connected between the external electrode 40 (AFBy) and another external electrode 40 (REF) to which the reference voltage is applied. Therefore, the amplitude of the signal input to the external electrode 40 (AINy) is amplified by, for example, about 50 times by another subsequent amplifier including the operational amplifier 228 ′, and the output terminal of the operational amplifier 228 ′, that is, the external electrode 40 (APOy) is amplified. Can be output.

  In addition, a switch SW ′ similar to the switch SW is provided in the IC 50. The switch SW ′ is another external electrode of the IC 50 connected to the external electrode (electrode 24) of the IC 50 connected to the external electrode 40 (AINy) and another external electrode 40 (REF) to which the reference voltage of the IC 50 is applied. It is connected between (another electrode 24). The switch SW ′ is also connected to the external electrode (electrode 24) and the external electrode 40 (SCT) of the IC 50. Further, the switch SW is also configured to be switched on or off by a control signal input to the external electrode 40 (SCT). Therefore, if the capacitor C7 of the high-pass filter 226 ′ is charged by turning on the switch SW ′ for 0.2 seconds, for example, the signal of the output terminal of the low-pass filter 224 ′, that is, the external electrode 40 (OUTy) can be obtained in a short time. It is transmitted to the positive input terminal of 228 ′, and the rise time of the output signal at the output terminal of the operational amplifier 228 ′, that is, the external electrode 40 (APOy) can be shortened.

  Here, an example of a manufacturing method of the first (second) tuning-fork type piezoelectric vibrator 70 (72) used in the above-described angular velocity sensor 10 will be described.

  First, as shown in FIG. 7, a multilayer substrate 300 is formed. The multilayer substrate 300 is obtained by alternately stacking two piezoelectric substrates 310 and 312 and three electrodes 320, 322, and 324. One piezoelectric substrate 310 becomes a large number of piezoelectric substrates 80, and the other piezoelectric substrate 312 becomes a large number of piezoelectric substrates 82. Therefore, the thickness of one piezoelectric substrate 310 is formed thinner than the thickness of the other piezoelectric substrate 312. In this case, for example, the piezoelectric substrates 310 and 312 are each formed by laminating a plurality of piezoelectric sheets, and the thickness of the piezoelectric substrates 310 and 312 is adjusted by adjusting the number of laminated piezoelectric sheets. The The electrode 320 serves as a large number of internal electrodes 84, the electrode 322 serves as a large number of drive detection electrodes 86, 88, and 90, and the electrode 324 serves as a large number of full surface electrodes 92. .

  Then, as shown in FIG. 8, a DC voltage is applied between the electrodes 322 and 320 on both surfaces of the one piezoelectric substrate 310 and between the electrodes 324 and 320 on both surfaces of the other piezoelectric substrate 312 in the multilayer substrate 300. As a result, one piezoelectric substrate 310 and the other piezoelectric substrate 312 are polarized in opposite thickness directions.

  Then, one piezoelectric substrate 310 and the electrode 322 of the multilayer substrate 300 thus polarized are provided with grooves 80a between the drive detection electrodes 86 and 88 of the multiple tuning fork type piezoelectric vibrators 70 (72) and the drive detection. Grooves corresponding to the grooves 80b between the electrodes 88, 90 are formed.

  The multilayer substrate 300 in which grooves corresponding to the grooves 80a and 80b are formed is cut into individual piezoelectric vibrators 70 (72) along the outline of each tuning fork type piezoelectric vibrator 70 (72). In this way, a large number of tuning fork type piezoelectric vibrators 70 (72) are manufactured.

  Next, the operating state of the angular velocity sensor 10 described above will be described. In the angular velocity sensor 10, for example, the first tuning fork type piezoelectric vibrator 70 is used to detect the rotational angular velocity applied around the X axis parallel to the short side of the circuit board 20, and the second tuning fork type piezoelectric vibrator 70 is used. The vibrator 72 is used to detect a rotational angular velocity applied around the Y axis parallel to the long side of the circuit board 20.

  In the first tuning-fork type piezoelectric vibrator 70, a self-excited drive circuit is formed by a drive feedback loop including the input buffer 200, the amplitude control circuit 202, and the phase shift circuit 204. The leg portions 76a and 76b are, for example, shown in FIG. As shown in Fig. 2, the vibrations are caused by basic vibrations so as to open and close each other. In a state where the legs 76a and 76b are open to each other (indicated by a solid line in FIG. 9), the portion where the central drive detection electrode 88 is formed in the first tuning fork type piezoelectric vibrator 70 is extended. The portion where the drive detection electrodes 86 and 90 are formed is shrunk. On the other hand, in the state where the legs 76a and 76b are closed to each other, in the first tuning-fork type piezoelectric vibrator 70, the portion where the central drive detection electrode 88 is formed contracts, and the drive detection electrodes 86, The portion where 90 is formed extends. At the time of this basic vibration, the two legs 76a and 76b vibrate symmetrically in the same state with respect to the polarization direction, so the same signal is output from the drive detection electrodes 86 and 90 on both sides. Therefore, a signal “0” is output from the differential amplifier circuit 206 for the detection circuit, and thus from the external electrode 40 (APOx).

  In this basic vibration state, when a rotational angular velocity is applied to the first tuning fork type piezoelectric vibrator 70 around the X axis, Coriolis force is applied to the legs 76a and 76b in a direction perpendicular to the direction of the basic vibration. work. Since the Coriolis forces acting on the legs 76a and 76b are opposite to each other, the two legs 76a and 76b are displaced in opposite directions as shown in FIG. 10, for example. In the displacement state indicated by the solid line in FIG. 10, in one leg 76a on which the drive detection electrode 86 is formed, one piezoelectric substrate 80 is contracted and the other piezoelectric substrate 82 is expanded. In the other leg portion 76b on which the working electrode 90 is formed, one piezoelectric substrate 80 extends and the other piezoelectric substrate 82 contracts. Although not shown in the displacement state opposite to the displacement state shown by the solid line in FIG. 10, in one leg 76a, one piezoelectric substrate 80 extends and the other piezoelectric substrate 82 contracts, conversely, In the other leg portion 76b, one piezoelectric substrate 80 is contracted and the other piezoelectric substrate 82 is extended. Due to this displacement, opposite-phase signals are output from the drive detection electrodes 86 and 90 on both sides, and a large signal corresponding to the rotational angular velocity is output from the differential amplifier circuit 206. The magnitude and polarity of the signal output in this way correspond to the magnitude of the rotational angular velocity and the direction of rotation, respectively.

  The amplitude of the output signal of the differential amplifier circuit 206 is adjusted by the amplitude adjustment circuit 208 based on the data stored in the memory 220. The signal whose amplitude is adjusted in this way is detected by the synchronous detection circuit 210 in synchronization with the detection clock of the detection clock generation circuit 212. The detected signal is temperature compensated by the adjustment circuit 214 or the like. The necessary low frequency band of the temperature-compensated signal is passed by the low-pass filter 224, and the DC component is cut by the high-pass filter 226. Then, the signal from which the DC component is cut is amplified by a post-stage amplifier including the operational amplifier 228 and is output from the output terminal of the operational amplifier 228, that is, the external electrode 40 (APOx). Therefore, the magnitude and direction of the rotational angular velocity applied around the X axis can be detected based on the magnitude and polarity of the output signal from the external electrode 40 (APOx).

  In the second tuning-fork type piezoelectric vibrator 72 as well, like the first tuning-fork type piezoelectric vibrator 70, the leg portions 76a and 76b are vibrated by the fundamental vibration by the driving feedback loop including the input buffer 200 '. To do. However, in the second tuning fork type piezoelectric vibrator 72, the directions of the basic vibrations of the legs 76a and 76b are displaced according to the rotational angular velocity applied around the Y axis. Therefore, with respect to the second tuning-fork type piezoelectric vibrator 72, the magnitude of the rotational angular velocity applied around the Y axis is determined by the magnitude and polarity of the output signal from the differential amplifier circuit 206 ′ and thus the external electrode 40 (APOy). The direction of rotation can be detected.

  In this angular velocity sensor 10, in the first tuning fork type piezoelectric vibrator 70 and the second tuning fork type piezoelectric vibrator 72, the internal electrodes 84 and the drive detection electrodes 86, 88, A portion between 90 (one piezoelectric substrate 80) is formed thinner than a portion other than that portion (the other piezoelectric substrate 82). Therefore, the positive piezoelectric effect of the portion between the internal electrode 84 and the drive detection electrodes 86, 88, 90 (one piezoelectric substrate 80) can be efficiently used when detecting the angular velocity. Therefore, the angular velocity sensor 10 can detect the angular velocity efficiently, and the sensitivity for detecting the angular velocity is increased. In this case, the thickness in the polarization direction of the portion between the internal electrode 84 and the drive detection electrodes 86, 88, 90 (one piezoelectric substrate 80) is in the same direction as the polarization direction of the two piezoelectric substrates 80, 82. Since the thickness is 1/6 to 1/4 of the thickness, the angular velocity can be detected particularly efficiently, and the sensitivity for detecting the angular velocity is particularly high.

Here, the reason why the angular velocity can be detected particularly efficiently in the above-described angular velocity sensor 10 and the sensitivity for detecting the angular velocity is particularly high will be described.
In the angular velocity sensor 10 described above, the sensitivity (voltage) is generated in the tuning fork type piezoelectric vibrator 70 (72) when the angular velocity is detected. One of the piezoelectric elements between the internal electrode 84 and the drive detection electrodes 86, 88, 90 is generated. This is the body substrate 80. The voltage generated in the piezoelectric substrate 80 monotonously increases as the average expansion / contraction increases in the piezoelectric substrate 80. The portions of the tuning fork type piezoelectric vibrator 70 (72) that expand and contract the most are the drive detection electrodes 86, 88, and 90 and the entire surface electrode 92 portion of the piezoelectric substrate 82. The largest expansion / contraction amount of each portion is ΔL, and from the drive detection electrodes 86, 88, 90 to the internal electrode 84 with respect to the thickness of the tuning fork type piezoelectric vibrator 70 (72), that is, the thickness of the piezoelectric substrate 80, 82. If the thickness ratio of the portion (one piezoelectric substrate 80) is α, the average expansion / contraction amount of the piezoelectric substrate 80 is ΔL * (α-1).
With respect to this average expansion / contraction amount, the amount of charge generated in the piezoelectric substrate 80 is g31 * ΔL * (α-1) = β * ΔL * k31 * (α-1). However, g31 is a piezoelectric constant, β is a coefficient, and k31 is an electromechanical coupling constant.
In the above formula, only the portion of k31 * (α-1) depends on the ratio α representing the position of the internal electrode 84, and this represents the detection efficiency.
Here, the graph obtained from the simulation is shown in FIG. The graph shown in FIG. 11 shows the relationship between the ratio α representing the position of the internal electrode 84 in the tuning fork type piezoelectric vibrator 70 (72) and the detection efficiency k31 * (α-1).
Explaining in principle, if the piezoelectric substrate 80 includes the central portion in the thickness direction of the tuning fork type piezoelectric vibrator 70 (72) that hardly expands or contracts, the average expansion / contraction amount of the piezoelectric substrate 80 is reduced. At the same time, there is almost no expansion and contraction near the center in the thickness direction. Therefore, the positive piezoelectric effect of the piezoelectric substrate 80 can be efficiently used when the internal electrode 84 is as close as possible to the drive detection electrodes 86, 88, 90.
However, if the internal electrode 80 is too close to the drive detection electrodes 86, 88, 90, the total amount of charges that can be picked up inside the piezoelectric substrate 80 is reduced.
Therefore, when the ratio α representing the position of the internal electrode 84 is smaller than ½, an excellent point exists, but a particularly excellent point exists in any range.
According to the graph shown in FIG. 11, the particularly excellent point is that the internal electrode 84 extends from the drive detection electrodes 86, 88, 90 in the thickness direction of the tuning fork type piezoelectric vibrator 70 (72). It was found that the thickness was 1/6 to 1/4 of the thickness of (72), that is, the ratio α was 1/6 to 1/4.

  Further, in the above-described method for manufacturing the tuning fork type piezoelectric vibrator 70 (72) shown in FIGS. 7 and 8, the multilayer substrate 300 is used as a material for the piezoelectric substrates 80 and 82 of the plurality of tuning fork type piezoelectric vibrators 70 (72). Therefore, the step of bonding the piezoelectric substrates 80, 82 and the like for each individual tuning fork piezoelectric substrate 70 (72) can be omitted, and the tuning fork type piezoelectric vibrator 70 (72) can be easily manufactured. In addition, there is an effect that the tuning fork type piezoelectric vibrator 70 (72) is excellent in mass productivity.

  Furthermore, in the above-described method for manufacturing the tuning fork type piezoelectric vibrator 70 (72) shown in FIGS. 7 and 8, since the piezoelectric substrates 310 and 312 are each a laminate of a plurality of piezoelectric sheets, By adjusting the number of stacked layers, the thickness of the piezoelectric substrates 310 and 312 can be adjusted, respectively, and the thickness of the piezoelectric substrates 80 and 82 can be adjusted.

In the tuning fork type piezoelectric vibrator 70 (72) described above, the piezoelectric substrates 80 and 82 are polarized in opposite thickness directions. However, the piezoelectric substrates 80 and 82 may be polarized in the same thickness direction. Good. In order to polarize in this way, for example, a DC voltage is applied between the electrodes 322 and 324 of the multilayer substrate 300 as shown in FIG. 12, or the electrodes 322 and 320 of the multilayer substrate 300 as shown in FIG. The piezoelectric substrates 310 and 312 to be a large number of piezoelectric substrates 80 and 82 are applied by applying a direct current voltage corresponding to each interval (thickness) between the electrodes 320 and 324. What is necessary is just to polarize in the same thickness direction.
Here, as shown in FIG. 12, when the piezoelectric substrates 310 and 312 are polarized in series, the DC voltage is divided due to variations in the insulation resistance of the piezoelectric substrates 310 and 312 and cannot be sufficiently polarized. In some cases, the sensitivity may decrease.
On the other hand, as shown in FIG. 13, when a DC voltage of each magnitude is applied to the piezoelectric substrates 310 and 312, it is possible to prevent the polarization and the sensitivity from being lowered as described above. be able to.

  Furthermore, in the tuning fork type piezoelectric vibrator 70 (72) described above, only the piezoelectric substrate 80 may be polarized in the thickness direction. In order to polarize in this way, for example, as shown in FIG. 14, a DC voltage is applied between the electrodes 322 and 324 of the multilayer substrate 300, and only the piezoelectric substrate 310 to be a large number of piezoelectric substrates 80 has a thickness. What is necessary is just to polarize in a direction.

  FIG. 15 is an illustrative view showing another example of a tuning fork type piezoelectric vibrator used in the angular velocity sensor according to the present invention. In the tuning fork type piezoelectric vibrator 70 shown in FIG. 15, compared to the tuning fork type piezoelectric vibrator 70 shown in FIGS. 4 and 5, the piezoelectric substrate 82 has a surface opposite to the surface on which the internal electrode 84 is formed. In contrast to the internal electrode 84, the piezoelectric substrate 80 having the grooves 80a and 80b, and the drive detection electrodes 86, 88, and 90 without forming the entire surface electrode 92, a further internal electrode 84 ', groove 80a', A piezoelectric substrate 80 'having 80b' and drive detection electrodes 86 ', 88', 90 'are formed. Moreover, the ratio of the thicknesses of the piezoelectric substrates 80, 82, and 80 ′ is, for example, 1: 3: 1. That is, the thickness of the piezoelectric substrate 80 is formed to be 1/5 of the thickness of the piezoelectric substrates 80, 82, and 80 '. Similarly, the thickness of the piezoelectric substrate 80' is also equal to the thickness of the piezoelectric substrates 80, 82, and 80 '. It is formed to a thickness of 1/5 of the thickness of 80 '.

  In the tuning fork type piezoelectric vibrator 70 shown in FIG. 15, compared to the tuning fork type piezoelectric vibrator 10 shown in FIGS. 4 and 5, the internal electrodes 84, 84 ′, the piezoelectric substrate 80, 80 'and drive detection electrodes 86, 88, 90, 86', 88 ', 90' are formed, respectively. That is, the internal electrodes 84 and 84 ′ are respectively formed between two different piezoelectric substrates (between the piezoelectric substrates 80 and 82 and the piezoelectric substrate 80 ′ 82), and further, drive detection electrodes 86, 88, 90. , 86 ', 88', 90 'are formed on the surfaces of two different piezoelectric substrates 80, 80', respectively. Therefore, in the tuning fork type piezoelectric vibrator 10 shown in FIG. 15, the positive piezoelectric effect of the portions between the internal electrodes and the drive detection electrodes (piezoelectric substrates 80, 80 ′) can be efficiently used on both sides. Since the portion using the positive piezoelectric effect at the time of detecting the angular velocity doubles, the sensitivity for detecting the angular velocity also doubles.

  In each tuning fork type piezoelectric vibrator 70 described above, grooves 80a, 80b, 80a ', 80b' having a predetermined depth are formed in the piezoelectric substrates 80, 80 '. The depths of these grooves are as follows. These grooves may be arbitrarily changed, or these grooves may not be formed when it is not necessary to form a groove, for example, when there is no short circuit between adjacent drive detection electrodes.

  Each of the tuning fork type piezoelectric vibrators 70 described above is formed in a tuning fork type as a whole. However, the present invention can be applied to a sound piece type piezoelectric vibrator having a cantilever structure such as a strip shape. Can also be applied. As such a sound piece type piezoelectric vibrator, for example, the above-mentioned tuning fork type piezoelectric vibrator 70 is divided into two at the center in the width direction and the base portion 74 is divided into two legs 76a (76b). be able to. In this case, the width of the base part 74 divided into two and the width of the leg part 76a (76b) may be formed to the same width.

  Further, each tuning fork type piezoelectric vibrator 70 described above has two or three piezoelectric substrates to be stacked, but the present invention is also applicable to a piezoelectric vibrator having four or more piezoelectric substrates to be stacked. Can be done.

  The piezoelectric vibrator according to the present invention is used for an angular velocity sensor or the like.

It is an internal see-through | perspective perspective view which shows an example of the angular velocity sensor concerning this invention. It is a disassembled perspective view of the angular velocity sensor shown in FIG. It is a perspective view which shows the other surface of the circuit board used for the angular velocity sensor shown in FIG. FIG. 2 is a perspective view showing a first (second) tuning-fork type piezoelectric vibrator used in the angular velocity sensor shown in FIG. 1. FIG. 5 is an illustrative view showing a first (second) tuning-fork type piezoelectric vibrator shown in FIG. 4. It is a block diagram which shows the circuit structure of the angular velocity sensor shown in FIG. FIG. 2 is a perspective view showing a multilayer substrate for manufacturing a first (second) tuning-fork type piezoelectric vibrator of the angular velocity sensor shown in FIG. 1. FIG. 8 is an illustrative view showing one example of a step of polarizing two piezoelectric substrates of the multilayer substrate shown in FIG. 7. FIG. 2 is an illustrative view showing a state in which a first (second) tuning-fork type piezoelectric vibrator of the angular velocity sensor shown in FIG. FIG. 10 is an illustrative view showing a state in which the first (second) tuning-fork type piezoelectric vibrator of the angular velocity sensor shown in FIG. 1 is displaced by applying a rotational angular velocity in a state where it is oscillating with the fundamental vibration shown in FIG. 9. is there. 2 is a graph showing a relationship between a ratio α representing the position of an internal electrode and a detection efficiency k31 * (α−1) in the first (second) tuning-fork type piezoelectric vibrator of the angular velocity sensor shown in FIG. 1. FIG. 8 is an illustrative view showing another example of a step of polarizing two piezoelectric substrates of the multilayer substrate shown in FIG. 7. FIG. 10 is an illustrative view showing still another example of a step of polarizing two piezoelectric substrates of the multilayer substrate shown in FIG. 7. FIG. 8 is an illustrative view showing one example of a step of polarizing one piezoelectric substrate of the multilayer substrate shown in FIG. 7. It is an illustration figure which shows the other example of the tuning fork type piezoelectric vibrator used for the angular velocity sensor concerning this invention. It is a top view which shows an example of the conventional tuning fork type piezoelectric vibrator used as the background of this invention. FIG. 17 is an illustrative view showing a tuning fork type piezoelectric vibrator shown in FIG. 16. FIG. 17 is an illustrative view showing a state in which the tuning fork type piezoelectric vibrator shown in FIG. FIG. 19 is an illustrative view showing a state in which the tuning fork type piezoelectric vibrator shown in FIG. 16 is displaced by applying a rotational angular velocity in a state where the tuning fork type piezoelectric vibrator is oscillating with a basic vibration shown in FIG. 18.

Explanation of symbols

10 Angular velocity sensor 20 Circuit board 50 IC
60 Tuning Fork Type Piezoelectric Vibrator for Chip Capacitors 70, 72 74 Base 76a, 76b Leg 80, 82, 80 ′ Piezoelectric Substrate 84, 84 ′ Internal Electrode 86, 88, 90, 86 ′, 88 ′, 90 ′ Drive detection electrode 110 Cap

Claims (4)

A plurality of piezoelectric substrates to be stacked;
An internal electrode formed between the piezoelectric substrates, and a drive detection electrode formed on the surface of the piezoelectric substrate so as to face the internal electrodes,
A piezoelectric vibrator in which at least a portion between the internal electrode and the drive detection electrode in the plurality of piezoelectric substrates is polarized in a direction opposite to the internal electrode and the drive detection electrode;
Piezoelectric vibrator in which the thickness in the polarization direction of the portion between the internal electrode and the drive detection electrode is thinner than the thickness in the same direction as the polarization direction of the portion other than the portion in the plurality of piezoelectric substrates. .   The thickness in the polarization direction of the portion between the internal electrode and the drive detection electrode is formed to be 1/6 to 1/4 of the thickness in the same direction as the polarization direction of the plurality of piezoelectric substrates. The piezoelectric vibrator according to claim 1. The plurality of piezoelectric substrates are composed of three or more layers,
The internal electrodes are formed between two piezoelectric substrates of different combinations among the piezoelectric substrates having three or more layers, and the drive detection electrodes are formed by laminating the plurality of stacked electrodes. The piezoelectric vibrator according to claim 1, wherein the piezoelectric vibrator is formed on front and back surfaces of the piezoelectric substrate.   An angular velocity sensor comprising the piezoelectric vibrator according to any one of claims 1 to 3.

Images