JP2008286521A - Rotational speed detecting unit, and rotational speed sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a means to achieve a rotational speed detecting unit that is small, low-profile and inexpensive by applying SAW device technology. <P>SOLUTION: The rotational speed detecting unit comprises a rotational speed sensing element having: a piezoelectric substrate in which a protrusion portion is formed almost in the center part of the one major surface and uniform thin portions are formed on the both sides; and an IDT electrode consisting of a pair of comb-shaped electrodes one of which is formed almost in the center part of the other major surface of the piezoelectric substrate and the other of which is formed near the both ends respectively, and a support substrate bonding and holding the protrusion portion of the rotational speed sensing element by an adhesive, wherein, the IDT electrode arranged almost in the center part is set as input, and the comb-shaped electrodes of the IDT electrode which are arranged near the both ends respectively and have different polarities are connected with each other in parallel and are set as output. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a rotational speed detection unit and a rotational speed sensor, and more particularly, to a rotational speed detection unit and a rotational speed sensor that use a frequency change of a surface acoustic wave due to the rotational speed.

Conventionally, the rotational speed detection unit and the force detection unit are widely used for monitoring abnormal vibrations of various plants from VTRs, engines, motors, automobiles, and aircrafts.
Patent Document 1 discloses an external force sensor using surface acoustic waves. FIG. 16 is a front view showing the configuration of the external force sensor. A long plate-like beam 101 made of a piezoelectric material is sandwiched between two rectangular parallelepiped support portions 108 on the front and back surfaces of the base end portion, and is cantilevered. It is glued to. An adhesive surface acoustic wave absorber 107 is used for adhesion. The beam 101 is sandwiched and bonded by two rectangular parallelepiped weights 109 on both sides of the tip. The weight 109 is for efficiently converting external force into strain. On both surfaces of the beam 101 between the support unit 108 and the weight 109, a pair of IDT electrodes 103 for transmission are provided at positions facing each other across the beam. On both surfaces of the beam 101 between the transmission IDT electrode 103 and the support unit 108, a pair of reception IDT electrodes 104 are provided at positions facing each other with the beam 101 interposed therebetween.

  The reception IDT electrodes 104 are connected to the corresponding amplifiers 105, and each amplifier 105 is connected to the corresponding transmission IDT electrode 103 and the oscillator output buffer amplifier 113. The oscillator output buffer amplifier 113 is connected to the mixer 106. The pair of IDT electrodes 103 for transmission, the IDT electrode 104 for reception, and the amplifier 105 constitute a pair of front and back oscillators. The oscillator output buffer amplifier 113 is for preventing the pair of front and back oscillators from being affected by the load fluctuation of the mixer 106.

When the external force 102 acts on the weight 109 attached to the tip of the beam 101, the surface of the beam 101 is distorted. This distortion changes the propagation time of the surface acoustic wave propagating on the surface of the beam 101. When the propagation time of the surface acoustic wave between the transmitting IDT electrode 103 and the receiving IDT electrode 104 changes, the oscillation frequency of the oscillator constituted by the IDT electrode 103, the IDT electrode 104, and the amplifier 105 changes. . The mixer 106 performs signal processing on the oscillation frequency of the pair of front and back oscillators and outputs a difference frequency component, and the zero-cross comparator 114 extracts this output as a rectangular wave output. By processing this output, the magnitude of the external force 102 is obtained.
JP-A-2-228530

However, the conventional commercially available rotational speed detection unit has a problem that it is too large for use in a small device, and, like the external force sensor disclosed in Patent Document 1, the long plate-like beam 101 has a problem. Forming a pair of IDT electrodes for transmission and reception on the front and back increases the man-hours of the photolithography process, and the problem that the pattern accuracy of the IDT electrodes formed on the front and back is slightly different, degrading the measurement accuracy of the external force sensor was there.
The present invention has been made to solve the above-mentioned problems, and provides a small, low-profile, low-cost rotational speed detection unit and rotational speed sensor for forming a rotational speed by forming an IDT electrode on a piezoelectric substrate. It is in.

In order to obtain a small-sized, low-profile and low-cost rotational speed detection unit and rotational speed sensor, the present invention has a protrusion at a substantially central portion of one main surface and uniform thin portions on both sides of the protrusion. A rotational speed sensitive element comprising: a piezoelectric substrate having at least one IDT electrode formed on the other principal surface of the piezoelectric substrate, and at least one IDT electrode near both ends. A rotation speed detection unit including a support substrate that holds and holds the protrusion portion by a holding member, and one of the IDT electrode disposed at the substantially central portion and the IDT electrode disposed at positions near the both end portions. The phase transition between the IDT electrode disposed near the end of the IDT electrode, the IDT electrode disposed substantially at the center, and the position near the other end of the IDT electrodes disposed near the both ends. Placed ID Configuring the phase shift between the electrodes, a rotational speed detection unit but are different from each other by 180 °.
If comprised as mentioned above, the rotational speed detection unit which generate | occur | produces the voltage according to rotational speed with the piezoelectric substrate which formed three IDT electrodes on one main surface, and the support substrate which supports this piezoelectric substrate. Since it can be configured, the SAW device manufacturing technology can be used, and there is an effect that a small, low profile, and low cost unit can be obtained.

A piezoelectric substrate having a protrusion at a substantially central portion of one main surface and a uniform thin portion on both sides of the protrusion, and at least two IDT electrodes formed on the other main surface of the piezoelectric substrate And a plurality of reflectors, and a rotation speed detecting unit, and a support substrate that holds and holds the protrusion of the rotation speed sensitive element by a holding member, wherein the piezoelectric substrate At least one IDT electrode and reflectors on both sides of the IDT electrode are arranged on one thin part of the piezoelectric substrate, and at least one IDT electrode and the IDT are arranged on the other thin part of the piezoelectric substrate. A rotational speed detection unit is configured in which reflectors are arranged on both sides of the electrode.
When configured as described above, a rotational speed detection unit that causes a frequency change proportional to the rotational speed between the piezoelectric substrate having two SAW resonators formed on one main surface and the support substrate that supports the piezoelectric substrate. Therefore, the SAW device manufacturing technology can be used, and there is an effect that a small, low profile, and low cost unit can be obtained.

A piezoelectric substrate having a protrusion at a substantially central portion of one main surface and a uniform thin portion on both sides of the protrusion, and at least two IDT electrodes formed on the other main surface of the piezoelectric substrate And a plurality of reflectors, and a rotation speed detecting unit, and a support substrate that holds and holds the protrusion of the rotation speed sensitive element by a holding member, wherein the piezoelectric substrate At least one IDT electrode and a reflector are disposed outside the IDT electrode, and at least one IDT electrode and the IDT electrode are disposed on the other thin part of the piezoelectric substrate. A rotational speed detection unit is configured in which reflectors are arranged outside the IDT and reflectors are arranged close to each inside the IDT electrodes.
When configured as described above, a rotational speed detection unit that causes a frequency change proportional to the rotational speed between the piezoelectric substrate having two SAW resonators formed on one main surface and the support substrate that supports the piezoelectric substrate. Therefore, it is possible to use the SAW device manufacturing technology, and to obtain a compact, low-profile and low-cost unit.

The rotational speed detection unit described above is formed by depositing a metal film as a weight on one main surface and / or the other main surface of both thin portions of the piezoelectric substrate or by adhering a metal filler adhesive or a metal member. .
When configured as described above, in addition to the above effects, there is an advantage that the sensitivity of rotation speed detection is improved.

A piezoelectric substrate having two uniform thin portions each formed by forming two recessed portions at a predetermined interval on one main surface, and having thick portions at substantially the center and both ends. A rotational speed sensing element having at least one IDT electrode formed on the other main surface of the piezoelectric substrate and at least one IDT electrode near both ends, and the substantially central part of the rotational speed sensing element. A rotational speed detection unit comprising a support substrate for fixing and holding a thick portion by a holding member, and an IDT electrode disposed at the substantially central portion and an IDT electrode disposed at a position closer to both ends. Phase transition between the IDT electrode disposed at one end portion position, the IDT electrode disposed at the substantially central portion, and the other end portion position among the IDT electrodes disposed at the both end portion positions. IDT electrode arranged in And phase shift between, but constitutes a rotational speed detection unit which are different from each other by 180 °.
If comprised as mentioned above, the rotational speed detection unit which generate | occur | produces the voltage according to rotational speed with the piezoelectric substrate which formed three IDT electrodes on one main surface, and the support substrate which supports this piezoelectric substrate. Since it can be configured, it is possible to use a SAW device manufacturing technique and to obtain a small, low-profile, low-cost unit that improves the sensitivity of rotational speed detection.

A piezoelectric substrate having two thin portions formed by forming two recessed portions at a predetermined interval on one main surface and having thick portions at the center and both ends, A rotational speed sensitive element having at least two IDT electrodes and a plurality of reflectors on the other main surface of the piezoelectric substrate; a support substrate for fixing and holding the protrusion of the rotational speed sensitive element by a holding member; A rotational speed detection unit comprising: at least one IDT electrode on one thin portion of the piezoelectric substrate, and reflectors on both sides of the IDT electrode, and the other thin portion of the piezoelectric substrate. Includes a rotational speed detection unit in which at least one IDT electrode and reflectors formed on both sides of the IDT electrode are arranged.
When configured as described above, a rotational speed detection unit that causes a frequency change proportional to the rotational speed between the piezoelectric substrate having two SAW resonators formed on one main surface and the support substrate that supports the piezoelectric substrate. Therefore, it is possible to use a SAW device manufacturing technique and to obtain a small, low-profile, low-cost unit with improved rotational speed detection sensitivity.

A piezoelectric substrate having two thin portions formed by forming two recessed portions at a predetermined interval on one main surface and having thick portions at the center and both ends, A rotational speed sensitive element having at least two IDT electrodes and a plurality of reflectors on the other main surface of the piezoelectric substrate; a support substrate for fixing and holding the protrusion of the rotational speed sensitive element by a holding member; A rotational speed detection unit comprising: at least one IDT electrode on one thin portion of the piezoelectric substrate; and a reflector on the outside of the IDT electrode, and the other thin portion of the piezoelectric substrate. Comprises a rotational speed detection unit in which at least one IDT electrode and a reflector are arranged outside the IDT electrode, and a reflector is arranged close to the center of the piezoelectric substrate of each IDT electrode.
When configured as described above, a rotational speed detection unit that causes a frequency change proportional to the rotational speed between the piezoelectric substrate having two SAW resonators formed on one main surface and the support substrate that supports the piezoelectric substrate. Therefore, the SAW device manufacturing technology can be used, the rotational speed detection sensitivity can be improved, and a small, low-profile, low-cost unit can be obtained.

A rotational speed sensor including the rotational speed detection unit, an oscillation circuit, and a signal processing circuit is configured.
When configured as described above, the SAW device manufacturing technology can be used, and there is an effect that a small, low-profile, low-cost rotational speed sensor can be obtained.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a configuration example of a rotation speed detection unit as an embodiment of the present invention, where FIG. 1 (a) is a plan view and FIG. 1 (b) is a cross-sectional view at QQ.
The rotational speed detection unit 1 according to the present invention has a protruding portion 6a at a substantially central portion of one main surface (lower surface), and a piezoelectric substrate 6 having a uniform thin portion 6b formed on both sides of the protruding portion 6a. And IDT electrodes 10, 11, 12 made of a pair of comb-shaped electrodes formed one by one on the other principal surface (upper surface) of the piezoelectric substrate 6 at a position near the center and both ends. A speed-sensitive element S and a support substrate P that holds the protrusion 6a of the rotational speed-sensitive element S by an adhesive (not shown) are provided. Phase transition between the IDT electrode 10 disposed in the substantially central portion and the IDT electrode 11 disposed in the position closer to one end of the IDT electrodes disposed in the positions closer to both ends, and disposed in the substantially central portion. The phase transition between the IDT electrode 10 and the IDT electrode 12 disposed near the other end of the IDT electrodes disposed near the both ends is set to be 180 ° different from each other. The IDT electrode 10 is used as an input or output, and the IDT electrodes 11 and 12 are connected in parallel to form the rotational speed detection unit 1 as an output or input.
In FIG. 1, when the number of electrode fingers of the IDT electrode 10 at the center is an even number, the IDT electrodes 11 and 12 near both ends are arranged symmetrically with respect to the central axis of the IDT electrode 10, When the number of electrode fingers of the IDT electrode 10 is an odd number, the phase difference between the IDT electrodes 11 and 12 is 180 ° if they are arranged point-symmetrically with respect to the central axis of the IDT electrode 10. A sound absorbing material 20 is applied to both ends of the main surface of the piezoelectric substrate.

Each IDT electrode 10, 11, 12 is composed of a pair of electrode fingers that are interleaved with each other, and an aluminum alloy or the like is used as the electrode material. The distances L1 and L2 between the center portion of the IDT electrode 10 and the center portions of the IDT electrodes 11 and 12 are made equal. As shown in FIG. 1A, one (lower) bus bar of the IDT electrode 10 and the other (upper) bus bar of the IDT electrodes 11 and 12 are connected by lead electrodes, and the IDT electrodes 11 and 12 are connected. Each one (lower) bus bar and the bonding pad 16 formed on the piezoelectric substrate 6 are connected by lead electrodes. Further, the other (upper) bus bar and one (lower) bus bar of the IDT electrode 10 are connected to the terminal electrodes 30 and 31 on the support substrate P by bonding wires, respectively, and the bonding pad 16 and the support substrate P on the support substrate P are connected. The rotational speed detection unit 1 is configured by connecting the terminal electrode 32 with a bonding wire. The terminal electrode 31 is grounded.
In the above description, an example is described in which one IDT electrode is arranged near the center and both ends on the main surface of the piezoelectric substrate 6, but a plurality of IDT electrodes may be arranged. Good. Moreover, although it demonstrated that the projection part 6a and the support substrate P were adhere | attached and hold | maintained with the adhesive agent, a solder bump, a gold bump, a glass material etc. may be sufficient.

  FIG. 2 shows an example in which a ceramic package is used as the support substrate P, and a protrusion 6a formed on the back surface of the rotational speed sensing element S shown in FIG. The rotational speed detection unit 1 is configured by connecting the bus bars and bonding pads of the IDT electrodes and the terminal electrodes 30 to 32 formed on the peripheral edge of the ceramic package with bonding wires 35. It is. Since the terminal electrodes formed at the peripheral edge portions of the four corners inside the ceramic package are formed to be inclined with respect to the central portion, a large piezoelectric substrate can be accommodated.

  The operation of the rotation speed detection unit 1 shown in FIG. 1 will be described using the IDT electrodes 10, 11, and 12 shown in FIG. The electrode patterns of the IDT electrodes 11 and 12 are the same, and the distances L1 and L2 from the central portion of the IDT electrode 10 to the central portions of the IDT electrodes 11 and 12 are both set equal. Since the electrode patterns of the IDT electrodes 11 and 12 are the same, one IDT electrode 11 is alternately connected from the innermost electrode finger to the outer electrode finger with the lower bus bar and the upper bus bar. The other IDT electrode 12 is alternately connected with the upper bus bar and the lower bus bar from the innermost electrode finger to the outer electrode finger. That is, when viewed from the IDT electrode 10 in the center, the order of connection of the electrode fingers of the IDT electrodes 11 and 12 on both sides to the bus bar is different.

  First, the case where the rotational speed detection unit 1 is in a stationary state will be described. When a high frequency voltage is applied to the IDT electrode 10 to excite the surface acoustic wave, the surface acoustic wave travels left and right on the piezoelectric substrate (not shown) at the same propagation speed, reaches the IDT electrodes 11 and 12, Electric charges are generated on the electrode fingers. FIG. 3 illustrates the state of charge generation at a certain moment. Charges indicated by signs +, −, +, and − are generated from the electrode fingers inside the IDT electrodes 11 and 12, respectively. The lower comb electrodes of the IDT electrodes 11 and 12 are connected, and the upper comb electrodes are grounded together and connected in parallel. Since charges having opposite polarities are generated in the comb electrodes on the lower side of the IDT electrodes 11 and 12, the generated charges are canceled when connected in parallel, and no charge (voltage) is generated in the output terminal OUT. However, the difference is slightly due to slight errors in the distances L1 and L2 from the central portion of the IDT electrode 10 to the central portions of the IDT electrodes 11 and 12, the etching error of the electrode pattern of the IDT electrodes 11 and 12, the processing error of the piezoelectric substrate, etc. Output voltage is generated.

  Next, FIG. 4A is a front view showing a state in which a rotational force is applied around the central portion of the rotational speed detection unit 1, and the support substrate P is omitted. As shown in FIG. 4A, the displacement in the rotational direction of both ends of the piezoelectric substrate 6 of the rotational speed detection unit 1 is delayed by inertia and deformed in the direction opposite to the rotational direction. When the thin-walled portion 6b is deformed as shown in FIG. 4A, the left thin-walled portion 6b is stretched and the right-side thin-walled portion 6b is compressed, and the propagation speeds of the surface acoustic waves to the left and right are different from each other. Come. In addition to this, the distance L1 increases and the distance L2 decreases. Unlike the stationary state, the generation state of charges generated in the IDT electrodes 11 and 12 due to these two phenomena generates charges (voltage) at the output OUT. The amount (voltage magnitude) of electric charges (voltage) generated at the output OUT changes according to the angular velocity. By measuring the voltage generated at the output OUT, the rotational speed of the rotational speed detection unit 1 can be measured.

  FIG. 5A shows an output frequency response when a high frequency voltage is applied to the input of the rotational speed detection unit 1 in a stationary state. The output response is very small. FIG. 5B shows a frequency response when rotation is applied to the rotation speed detection unit 1 with a high frequency voltage applied to the input of the rotation speed detection unit 1, and the output response is as shown in FIG. It can be seen that it is extremely large. The rotational speed is obtained from the generated voltage.

  FIG. 6 is a view showing a deformation of the thin portion 6b when an external force in the vertical direction is applied to the rotational speed detection unit 1 in a state where a high frequency voltage is applied to the input of the rotational speed detection unit 1. FIG. The thin portions 6b located at the left and right ends are both deformed in the direction opposite to the external force, and both the left and right thin portions 6b are stretched. In this case, each of the IDT electrodes 11, 12 is charged with +, −, +, − charges in order from the inner electrode finger to the outer electrode finger, and the lower comb electrodes are connected in parallel. In 11 and 12, the charges cancel each other, and no charge (voltage) is generated in the output section.

  FIG. 7 is a diagram showing the configuration of the second embodiment of the rotational speed detection unit, and is a diagram showing only the configuration of the IDT electrodes 10, 11, and 12. The piezoelectric substrate 6 and the support substrate P are configured in the same manner as in FIG. The IDT electrodes 11 and 12 are arranged symmetrically with respect to the IDT electrode 10, and one (lower) bus bar of one IDT electrode 11 is grounded, and the other (upper) bus bar of the other IDT electrode 12 is grounded. Then, the other (upper) bus bar of the IDT electrode 11 and one (lower) bus bar of the IDT electrode 12 are connected, and the IDT electrodes 11 and 12 are connected in parallel. When a high frequency voltage is applied to the IDT electrode 10 of the rotational speed detection unit of the second embodiment shown in FIG. 7, the charges generated in the comb electrode above the IDT electrode 11 and the comb electrode below the IDT electrode 12 are reversed. The polarity of the output OUT connected in parallel is zero. Since the operation when the rotation speed detection unit of the second embodiment is rotated is as described with reference to FIG.

  FIG. 8 is a diagram showing an example of a processing method for obtaining the magnitude of the applied rotation speed from the voltage generated on the output side of the rotation speed detection unit. When the high-frequency voltage signal (a) is input to the input side of the rotational speed detection unit, the output voltage (b) is obtained from the output side according to the rotational speed. When this output voltage is full-wave rectified, a voltage having a waveform (c) is obtained. When this voltage is input to the integration circuit of (d), a DC voltage shown in (e) is obtained. The magnitude of the rotational speed applied is determined from the magnitude of the DC voltage.

FIG. 9 is a diagram showing a configuration of a third embodiment of the rotational speed detection unit, where FIG. 9A is a plan view and FIG. 9B is a cross-sectional view taken along QQ. The rotational speed detection unit 2 includes two piezoelectric substrates 6 formed with a protrusion 6a at a substantially central portion of one main surface and a uniform thin portion 6b on both sides thereof, on the other main surface of the piezoelectric substrate 6. A rotation speed sensitive element S having IDT electrodes 13 and 14 and a plurality of reflectors 15; and a support substrate P that holds the protrusion 6a of the rotation speed sensitive element S by an adhesive (not shown). , A rotation speed detection unit 2. One IDT electrode 13 and a reflector 15 are disposed adjacent to both sides of the thin-walled portion 6b on one left side of the piezoelectric substrate 6, and the other IDT electrode 14 and its side are disposed on the other thin-walled portion 6b on the right side. The rotational speed detection unit 2 is configured by arranging the reflectors 15 adjacent to both sides.
In the above description, the case where one IDT electrode and reflectors are disposed on the left and right thin portions 6b of the piezoelectric substrate 6 has been described. However, a plurality of IDT electrodes are disposed on the left and right thin portions 6b. May be. Moreover, although it demonstrated that the projection part 6a and the support substrate P were adhere | attached and hold | maintained with the adhesive agent, a solder bump, a gold bump, a glass material etc. may be sufficient.

  Two bonding pads provided above and below the IDT electrode 13 and terminal electrodes 30 and 31 formed on the support substrate P are connected by bonding wires, and two bonding pads provided above and below the IDT electrode 14 are connected. The pads and the terminal electrodes 32 and 33 formed on the support base P are connected by bonding wires. The SAW resonator S1 is formed by the IDT electrode 13 disposed on the left side of the piezoelectric substrate 6 and the reflectors 15 on both sides thereof, and the SAW resonance is formed by the IDT electrode 14 disposed on the right side of the piezoelectric substrate 6 and the reflectors 15 on both sides thereof. Construct child S2. The SAW resonators S1 and S2 are each connected to an oscillation circuit (not shown). The operation of the rotation speed detection unit 2 shown in FIG. 9 will be described. First, when the rotation speed detection unit 2 is in a stationary state, it is assumed that the SAW resonators S1 and S2 oscillate at frequencies f1 and f2, respectively.

  Next, the state where the rotation is applied around the center of the rotation speed detection unit 2 shown in FIG. 9 is the same as the front view shown in FIG. As in FIG. 4, when the central portion of the rotational speed detection unit 2 is rotated in one direction, the displacement of the thin portions 6b located at both ends in the rotational direction is delayed by inertia and deforms in the direction opposite to the rotational direction. . When the thin-walled portion 6b is deformed as shown in FIG. 4, a tensile strain is generated in the left-side thin portion 6b and a compressive strain is generated in the right-side thin-walled portion 6b, and the propagation speeds of the surface acoustic waves to the left and right are different from each other. . In addition to this, the left thin portion 6b extends and the right thin portion 6b contracts. When the thin portion 6b is stretched, compressed, or stretched or contracted, the propagation speed and propagation time of the surface acoustic wave are changed, the resonant frequencies of the SAW resonators S1 and S2 are changed, and the oscillation frequency is f′1, f Change to '2. The change amounts (f1-f'1) and (f2-f'2) of the resonance frequencies of the SAW resonators S1 and S2 are approximately proportional to the rotational speed applied to the rotational speed detection unit 2. Since the distortion applied to the left and right thin portions 6b is opposite to the expansion distortion and the compression distortion, the signs of the frequency differences (f1-f'1) and (f2-f'2) are the opposite signs. Become.

FIG. 10 is a diagram showing the configuration of a fourth embodiment of the rotation speed detection unit, where FIG. 10 (a) is a plan view and FIG. 10 (b) is a cross-sectional view taken along QQ. Two rotation speed detection units 2 are provided on the other main surface of the piezoelectric substrate 6 and the piezoelectric substrate 6 in which a protrusion 6a and a thin portion 6b having a uniform thickness are formed on both sides of the protrusion 6a. A rotation speed sensitive element S having IDT electrodes 13 and 14 and a plurality of reflectors 15; and a support substrate P that holds the protrusion 6a of the rotation speed sensitive element S by an adhesive (not shown). It is equipped with. An IDT electrode 13 is disposed on one left thin portion 6b of the piezoelectric substrate 6, one reflector 15 is disposed outside the IDT electrode 3, and the other IDT electrode 14 is disposed on the other right thin portion 6b. At the same time, one reflector 15 is arranged outside the IDT electrode 14. Further, the other two reflectors 15 are arranged close to the inner positions of the IDT electrodes 13 and 14 to constitute the rotational speed detection unit 2.
In the above description, the case where one IDT electrode and reflectors are disposed on the left and right thin portions 6b of the piezoelectric substrate 6 has been described. However, a plurality of IDT electrodes are disposed on the left and right thin portions 6b. May be. Moreover, although it demonstrated that the projection part 6a and the support substrate P were adhere | attached and hold | maintained with the adhesive agent, a solder bump, a gold bump, a glass material etc. may be sufficient.

The IDT electrode 13 arranged on the left side of the piezoelectric substrate 6 shown in FIG. 10 and the reflectors 15 on both sides thereof constitute a SAW resonator S1, and the IDT electrode 14 arranged on the right side of the piezoelectric substrate 6 and the reflectors on both sides thereof. The SAW resonator S2 is composed of 15 as in the case of FIG. A difference from the rotational speed detection unit of the third embodiment shown in FIG. 9 is that a part or all of the reflectors 15 inside the two SAW resonators S1 and S2 are protruded from the piezoelectric substrate 6. It is a point formed on the main surface facing the portion 6a. The operation of the rotational speed detection unit 2 shown in FIG. 10 is as described in the example of FIG.
In the rotational speed detection unit of the fourth embodiment shown in FIG. 10, the reflector 15 can be formed on the main surface of the projecting portion 6a facing, so that the size of the piezoelectric substrate can be reduced, and the rotational speed detection unit can be downsized. There is an advantage that it can be planned.

  FIGS. 11A and 11B are diagrams showing the configuration of the fifth embodiment of the rotational speed detection unit, where FIG. 11A is a plan view and FIG. 11B is a cross-sectional view taken along QQ. The rotational speed detection unit 2 of the fifth embodiment is different from the embodiment shown in FIG. 10 in that one main surface and / or the other main surface of both thin portions 6b of the piezoelectric substrate 6 are weighted. The rotational speed detection unit 2 is configured by depositing the metal film 40 or bonding the metal filler adhesive or the metal member 40. The operation of the rotational speed detection unit 2 shown in FIG. 11 is the same as described in the example of FIG. 9 and is omitted. However, due to the weight added to the thin portion 6b of the piezoelectric substrate 6, the rotational speed detection unit 2 rotates. When added, the amount of change in the frequency of the SAW resonator is increased, and the sensitivity of the rotational speed detection unit 2 is improved.

FIG. 12 is a diagram showing the configuration of the sixth embodiment of the rotational speed detection unit, where FIG. 12 (a) is a plan view and FIG. 12 (b) is a cross-sectional view taken along QQ. The rotational speed detection unit 3 of the sixth embodiment has two uniform thin portions formed by forming two concave portions 7b on one main surface at a predetermined interval, and is substantially in the center. And a pair of comb-shaped electrodes formed on the other main surface of the piezoelectric substrate 7 and one near the both ends, respectively, on the piezoelectric substrate 7 having thick portions 7a, 7c, and 7c on both sides. A rotational speed sensitive element S having IDT electrodes 10, 11, and 12, and a support substrate P that adheres and holds the thick portion 7 a of the rotational speed sensitive element S with an adhesive (not shown). I have. The rotational speed detection unit 3 is configured with the IDT electrode 10 arranged in the center as an input part, and comb-shaped electrodes having different polarities of the IDT electrodes 11 and 12 arranged near both ends are connected in parallel.
The operation of the rotational speed detection unit 3 shown in FIG. 12 is the same as described in the embodiment of FIG. Since the thick portions 7c and 7c are provided at both ends of the piezoelectric substrate 7, if rotation is applied to the rotation speed detection unit 3 due to this mass, the amount of charge generated in the IDT electrodes 11 and 12 increases, and rotation occurs. The sensitivity of the speed detection unit 2 is improved.
The piezoelectric substrate 7 having thick portions at the substantially central portion and both end portions shown in FIG. 12 can be applied to the second to fifth embodiments of FIGS. 7, 9, 10, and 11.

  FIG. 13 is a flowchart for explaining a method of manufacturing the piezoelectric substrate 6 having the protrusion 6a at the substantially central portion as shown in FIG. This flowchart shows a method of manufacturing the piezoelectric substrate 6 shown in the upper left corner of FIG. After cleaning and drying the flat rectangular quartz substrate 51 as shown in FIG. 13A, it is placed in a vacuum device (not shown) as shown in FIG. In this manner, chromium is vapor-deposited on both main surfaces of the quartz substrate 51, and then gold is vapor-deposited to form a thin film of chromium 52 and gold 53. Next, as shown in FIG. 13C, a resist film 54 is applied on the chromium and gold thin films 52 and 53 and dried. When the resist film 54 is exposed and developed through a mask and the exposed portion of the resist film 54 is peeled off, the resist film 54 is processed into a desired shape as shown in FIG. Next, when the exposed metal film is soaked in an etching solution of gold and chromium, respectively, the gold and chromium thin films to be etched are removed as shown in FIG. When this is etched for a predetermined time in a crystal etching solution, it is etched into a desired shape as shown in FIG. The resist film 54, the gold thin film 53, and the chromium film 52 are peeled off to obtain the piezoelectric substrate 6 having the protrusion 6a at the substantially central portion as shown in FIG. When the quartz substrate is etched, the etching rate varies depending on the axial direction due to the anisotropy of the crystal, which may deviate from a desired shape. In the case of dry etching, there is an advantage that it can be processed into a desired shape which takes time.

  FIG. 14 is a flowchart for explaining a method of manufacturing the piezoelectric substrate 7 having thick portions at the substantially central portion and both end portions as shown in FIG. FIG. 14A is a rear view of the piezoelectric substrate 7 in the upper left corner of the figure, and FIG. 14B is a front view. As described in FIG. 13, a thin film of chrome and gold is formed on both surfaces of the piezoelectric substrate, a resist film is applied thereon, exposed through a mask, and the exposed resist film is peeled off. . The resist film in the portion to be etched of the piezoelectric substrate is peeled off from the gold and chromium thin film, and the portion that is not etched is left. FIG. 14C shows a state in which the piezoelectric substrate 7 is immersed in an etching solution and slightly etched. When this piezoelectric substrate is further etched in an etching solution, the etching proceeds through the state shown in FIG. 14 (d). After immersion for a predetermined time, the resist film and the gold / chromium thin film are peeled off to obtain FIG. 14 (e). A piezoelectric substrate having a substantially central portion and thick portions at both ends as shown in the drawing is obtained.

  FIG. 15 is an example of a rotational speed sensor, and a housing 60 that houses the rotational speed detection unit, the oscillation circuit 61, the signal processing circuits 62 and 63, the rotational speed detection unit, the oscillation circuit, and the signal processing circuit. And a rotational speed sensor comprising: Although the rotational speed detection unit 1 shown in FIG. 1 is used in FIG. 15, the other rotational speed detection units described above may be used. Since the rotational speed detection unit using the surface acoustic wave according to the present invention is small in size and low in height, there is an effect that a rotational speed sensor having a small thickness can be configured.

Although the rotation speed detection unit and the rotation speed sensor have been described above, they can also be used as an acceleration detection unit and an acceleration sensor.
In the above description, an unbalanced IDT electrode has been used. However, if a balanced terminal IDT electrode is used, a rotational speed detection unit and a rotational speed sensor with strong unnecessary signals can be configured.

It is a figure which shows the structure of the rotational speed detection unit which concerns on this invention, (a) is a top view, (b) is sectional drawing. It is the top view which accommodated the Example of FIG. 1 in the ceramic package. It is a figure which shows the IDT electrode structure for demonstrating operation | movement of the Example of FIG. FIG. 2A is a front view showing deformation of a piezoelectric substrate and FIG. 2B is a view showing electric charges generated on an IDT electrode when rotation is applied to the rotation speed detection unit of the embodiment of FIG. (A) of a rotational speed detection unit is a figure which shows the output frequency response of a stationary state, (b) is a figure which shows an output frequency response when rotation is added. (A) is a figure which shows the deformation | transformation state of a piezoelectric substrate when an external force is applied to a rotational speed detection unit, (b) is a figure which shows the electric charge generation state on an IDT electrode. It is a figure which shows the IDT electrode structure of the Example of FIG. 2, and the electric charge generation state of a certain moment. (A)-(e) is a figure explaining the processing method of the voltage which generate | occur | produces in a rotational speed detection unit. It is a figure which shows the structure of the 3rd Example of a rotational speed detection unit, (a) is a top view, (b) is sectional drawing. It is a figure which shows the structure of the 4th Example of a rotational speed detection unit, (a) is a top view, (b) is sectional drawing. It is a figure which shows the structure of the 5th Example of a rotational speed detection unit, (a) is a top view, (b) is sectional drawing. It is a figure which shows the structure of the 6th Example of a rotational speed detection unit, (a) is a top view, (b) is sectional drawing. (A)-(g) is a figure explaining the manufacturing flow of the piezoelectric substrate which has a projection part in the approximate center part. (A)-(e) is a figure explaining the manufacturing flow of the piezoelectric substrate which has a thick part in a substantially center part and both ends. It is a schematic perspective view which shows the structure of a rotational speed sensor. It is a front view which shows the conventional external force sensor.

Explanation of symbols

  1, 2, 3 Rotational speed detection unit, 6, 7 Piezoelectric substrate, 6a Protruding part, 6b Thin part, 7a, 7c Thick part, 7b Concave part 10, 11, 12, 13, 14 IDT electrode, 15 reflector , 16 Bonding pad, 20 Sound absorbing material, 30, 31, 32, 33 Terminal electrode, 35 Bonding wire, 40 Weight, 51 Piezoelectric substrate, 52 Chrome thin film, 53 Gold thin film, 54 Resist film, 60 Housing, 61 Oscillator circuit, 62, 63 Signal processing circuit, P support substrate, S rotational speed sensing element, L1, L2 Distance between center of IDT electrode 10 and center of IDT electrodes 11, 12

Claims (8)

A piezoelectric substrate having a protrusion at a substantially central portion of one main surface and a uniform thin portion on both sides of the protrusion, and a substantially central portion on the other main surface of the piezoelectric substrate and close to both ends, respectively. A rotational speed sensitive element having at least one IDT electrode formed;
A support substrate that holds and holds the protrusion of the rotational speed sensing element by a holding member;
A rotational speed detection unit comprising:
Phase transition between the IDT electrode arranged at the substantially central portion and the IDT electrode arranged at one end portion of the IDT electrodes arranged at the positions near the both ends,
The phase transition between the IDT electrode arranged at the substantially central portion and the IDT electrode arranged at the other end portion of the IDT electrodes arranged at the positions near the both end portions is different from each other by 180 °. Rotational speed detection unit characterized by that. A piezoelectric substrate having a protrusion at a substantially central portion of one main surface and a uniform thin portion on both sides of the protrusion, and at least two IDT electrodes formed on the other main surface of the piezoelectric substrate And a rotational speed sensing element having a plurality of reflectors,
A support substrate that holds and holds the protrusion of the rotational speed sensing element by a holding member;
A rotational speed detection unit comprising:
At least one IDT electrode and reflectors on both sides of the IDT electrode are arranged on one thin part of the piezoelectric substrate,
At least one IDT electrode and reflectors on both sides of the IDT electrode are arranged on the other thin part of the piezoelectric substrate. A piezoelectric substrate having a protrusion at a substantially central portion of one main surface and a uniform thin portion on both sides of the protrusion, and at least two IDT electrodes formed on the other main surface of the piezoelectric substrate And a plurality of reflectors, a rotational speed sensitive element having,
A support substrate that holds and holds the protrusion of the rotational speed sensing element by a holding member;
A rotational speed detection unit comprising:
At least one IDT electrode and a reflector outside the IDT electrode are disposed on one thin portion of the piezoelectric substrate,
On the other thin part of the piezoelectric substrate, at least one IDT electrode and a reflector outside the IDT electrode,
A rotational speed detection unit, wherein reflectors are arranged close to each inside of each IDT electrode.   2. A metal film is vapor-deposited as a weight, or a metal filler adhesive or a metal member is bonded to one main surface and / or the other main surface of both thin portions of the piezoelectric substrate. The rotational speed detection unit as described in any one of thru | or 3. A piezoelectric substrate having two uniform thin portions each formed by forming two recessed portions at a predetermined interval on one main surface, and having thick portions at substantially the center and both ends. And a rotational speed sensitive element having at least one IDT electrode formed on the other principal surface of the piezoelectric substrate and at least one IDT electrode near both ends,
A support substrate that holds and holds the thick portion of the substantially central portion of the rotational speed sensing element by a holding member;
A rotational speed detection unit comprising:
Phase transition between the IDT electrode arranged at the substantially central portion and the IDT electrode arranged at one end portion of the IDT electrodes arranged at the positions near the both ends,
The phase transition between the IDT electrode arranged at the substantially central portion and the IDT electrode arranged at the other end portion of the IDT electrodes arranged at the positions near the both end portions is different from each other by 180 °. Rotational speed detection unit characterized by that. A piezoelectric substrate having two thin portions formed by forming two recessed portions at a predetermined interval on one main surface and having thick portions at the center and both ends, A rotational speed sensitive element having at least two IDT electrodes and a plurality of reflectors on the other main surface of the piezoelectric substrate;
A support substrate that holds and holds the protrusion of the rotational speed sensing element by a holding member;
A rotational speed detection unit comprising:
At least one IDT electrode and reflectors on both sides of the IDT electrode are disposed on one thin portion of the piezoelectric substrate,
At least one IDT electrode and reflectors formed on both sides of the IDT electrode are arranged on the other thin part of the piezoelectric substrate, respectively. A piezoelectric substrate having two thin portions formed by forming two recessed portions at a predetermined interval on one main surface and having thick portions at the center and both ends, A rotational speed sensitive element having at least two IDT electrodes and a plurality of reflectors on the other main surface of the piezoelectric substrate;
A support substrate that holds and holds the protrusion of the rotational speed sensing element by a holding member;
A rotational speed detection unit comprising:
At least one IDT electrode and a reflector outside the IDT electrode are disposed on one thin portion of the piezoelectric substrate,
On the other thin part of the piezoelectric substrate, at least one IDT electrode and a reflector outside the IDT electrode,
A rotational speed detection unit, wherein a reflector is arranged close to the center of the piezoelectric substrate of each IDT electrode.   A rotational speed sensor comprising the rotational speed detection unit according to claim 1, an oscillation circuit, and a signal processing circuit.

Images