JP2011080844A - Fluid measuring sensor and fluid measuring instrument - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simple and inexpensive fluid measuring sensor. <P>SOLUTION: The fluid measuring sensor 10 comprises: a piezoelectric element section 2; and a protrusion member 1 provided on one surface of the piezoelectric element section 2. The piezoelectric element section 2 has: a piezoelectric member 3; a first electrode pair comprising a pair of first electrodes formed at a position at which the first electrodes face each other through the piezoelectric member 3; and a second electrode pair comprising a pair of second electrodes formed at a position at which the second electrodes face each other through the piezoelectric member 3, and formed so as to be separated from the first electrode pair by a predetermined distance in the first direction. The width of a surface in the first direction of the protrusion member 1 on the side of piezoelectric element section 2 in the first direction is larger than the predetermined distance. A center of the surface of the protrusion member 1 on the side of piezoelectric element section 2 is coaxially positioned in the center between the first and second electrode pairs. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fluid measurement sensor that measures, for example, a flow velocity, a flow direction, a flow rate, and the like of a fluid, and a fluid measuring instrument including the fluid measurement sensor.

  Conventionally, for example, various fluid measuring instruments for measuring the flow velocity, the flow direction (hereinafter referred to as the flow direction) and / or the flow rate of a fluid such as gas, liquid, and vapor have been developed and applied in various technical fields. . For example, various velocimeters, flow meters, and flow direction meters are used for monitoring systems such as rivers. Various anemometers, anemometers, anemometers, and the like are used in, for example, weather observation systems.

  If these fluid measuring instruments are classified according to their measurement principles, they can be classified into mechanical and electrical types. As a mechanical fluid measuring device, one using a rotor such as a propeller has been proposed (for example, see Patent Document 1). In this type of fluid measuring device, the flow velocity or the like is converted by the rotation speed of the propeller and measured.

  On the other hand, for example, a hot wire type fluid measuring device has been conventionally proposed as an electric fluid measuring device (see, for example, Patent Document 2). This type of fluid measuring instrument includes a temperature-dependent resistance element, and measures the flow velocity of the fluid by monitoring the temperature of the resistance element when a current is passed through the resistance element. Specifically, if a fluid such as wind hits the heated resistance element, the heat of the resistance element is taken away by the fluid, and the temperature of the resistance element decreases. In a hot wire type fluid measuring instrument, such a temperature change of the resistance element is converted into a flow velocity or the like.

  Conventionally, a sensor that measures the direction and strength of wind using a piezoelectric element has been proposed as an electric fluid measuring instrument (see, for example, Patent Document 3).

JP 2001-159638 A JP 2003-75461 A US Pat. No. 4,615,214

  As described above, conventionally, various fluid measuring instruments have been applied in various fields. However, fluid measuring instruments in practical use are generally large and expensive.

  The present invention has been made in view of the above situation, and an object of the present invention is to provide a fluid measurement sensor having a simpler configuration and at a low cost, and a fluid measurement instrument including the same.

  In order to solve the above problems, the fluid measurement sensor of the present invention is configured to include a piezoelectric element portion and a protruding member provided on one surface of the piezoelectric element portion. In addition, the piezoelectric element portion is formed at a position facing the piezoelectric member, a first electrode pair including a pair of first electrodes formed at positions facing each other with the piezoelectric member interposed therebetween, and a position facing the piezoelectric member. The second electrode pair is formed of a pair of second electrodes and formed at a predetermined distance from the first electrode pair in the first direction. The width in the first direction of the surface of the protruding member on the piezoelectric element portion side is larger than a predetermined distance, and the center of the surface of the protruding member on the piezoelectric element portion side is coaxial with the center between the first and second electrode pairs. It is set as the structure located in.

  The first fluid measuring instrument of the present invention is configured to include the fluid measuring sensor of the present invention, a differential circuit unit, and a calculating unit, and the function of each unit is as follows. The differential circuit unit generates a first difference signal between a first voltage signal generated in the first electrode pair and a second voltage signal generated in the second electrode pair by pressure applied to the protruding member from the fluid. . The calculation unit calculates at least one of the flow velocity and the flow direction of the fluid based on the first difference signal generated by the differential circuit unit.

  Moreover, the 2nd fluid measuring device of this invention is set as the structure provided with the fluid measurement sensor of the said this invention, an addition circuit part, and a calculation part, and the function of each part is as follows. The adding circuit unit generates a sum signal of the first voltage signal generated in the first electrode pair and the second voltage signal generated in the second electrode pair by the pressure applied from the fluid to the protruding member. The calculation unit calculates the fluid flow rate based on the sum signal generated by the addition circuit unit.

  Furthermore, a third fluid measuring instrument of the present invention is configured to include the fluid measuring sensor of the present invention, a differential circuit unit, a first calculation unit, an addition circuit unit, and a second calculation unit, and each unit The functions are as follows. The differential circuit unit generates a first difference signal between a first voltage signal generated in the first electrode pair and a second voltage signal generated in the second electrode pair by pressure applied to the protruding member from the fluid. . The first calculation unit calculates at least one of the fluid flow velocity and the flow direction based on the first difference signal generated by the differential circuit unit. The adder circuit unit generates a sum signal of the first voltage signal and the second voltage signal. The second calculation unit calculates the fluid flow rate based on the sum signal generated by the addition circuit unit.

  As described above, since the fluid measurement sensor of the present invention has a configuration in which a protruding member is provided on the piezoelectric element portion, the configuration is simpler and can be manufactured at low cost. Therefore, according to the present invention, it is possible to provide a fluid measurement sensor that has a simpler configuration and is inexpensive and a fluid measurement instrument including the fluid measurement sensor.

FIG. 1 is a schematic perspective view of a fluid measurement sensor according to the first embodiment of the present invention. 2A is a schematic top view of the piezoelectric element portion of the first embodiment, FIG. 2B is a schematic side view of the piezoelectric element portion, and FIG. 2C is a piezoelectric element portion. FIG. FIG. 3 is a diagram for explaining the operation of the fluid measurement sensor according to the first embodiment. FIG. 4 is a diagram for explaining the operation of the fluid measurement sensor according to the first embodiment. FIG. 5 is a schematic configuration diagram of a flow velocity direction meter using the fluid measurement sensor of the first embodiment. FIG. 6 is an equivalent circuit diagram of a flow velocity direction meter using the fluid measurement sensor of the first embodiment. FIG. 7 is a schematic configuration diagram of a flow meter using the fluid measurement sensor of the first embodiment. FIG. 8 is an equivalent circuit diagram of a flowmeter using the fluid measurement sensor of the first embodiment. FIG. 9 is a diagram for explaining the flow rate measurement principle. FIG. 10 is an equivalent circuit diagram of another fluid measuring instrument using the fluid measuring sensor of the first embodiment. FIG. 11 is an electrode configuration diagram of the fluid measurement sensor of the first modification. FIG. 12 is an electrode configuration diagram of the fluid measurement sensor of Modification 2. FIG. 13 is a schematic perspective view of a fluid measurement sensor according to the second embodiment of the present invention. FIG. 14A is a schematic side view of the fluid measurement sensor of the second embodiment, and FIG. 14B is a schematic top view of the fluid measurement sensor. FIG. 15 is a schematic configuration diagram of a fluid measurement meter using the fluid measurement sensor of the second embodiment. FIG. 16 is a schematic configuration diagram of a protrusion sheet used in the fluid measurement sensor of Modification 3.

Embodiments of the present invention will be described below in the following order with reference to the accompanying drawings. In addition, this invention is not limited to the following examples.
1. 1. First embodiment: Basic configuration example of fluid measurement sensor and fluid measurement device Second embodiment: configuration example of fluid measuring sensor and fluid measuring instrument in which a plurality of protrusions are two-dimensionally arranged

<1. First Embodiment>
[Configuration of fluid measurement sensor]
FIG. 1 is a schematic perspective view of a fluid measurement sensor (hereinafter referred to as a fluid sensor) according to a first embodiment of the present invention. The fluid sensor 10 of the present embodiment is mainly composed of a protrusion 1 (protrusion member) and a piezoelectric element portion 2 provided on the bottom surface side thereof. The protruding portion 1 is bonded and fixed to the piezoelectric element portion 2 by a fixing means (not shown) such as an adhesive member.

  In the fluid sensor 10 of the present embodiment, when a fluid hits the protrusion 1, the pressure applied to the protrusion 1 by the fluid is converted into a voltage signal in the piezoelectric element portion 2. Then, the fluid measuring instrument (flow velocity direction meter and / or flow meter) of the present embodiment, which will be described later, measures the state of the fluid (flow rate, flow direction, and flow rate) based on the voltage signal generated by the fluid sensor 10.

  First, the configuration of the protrusion 1 will be described. The protruding portion 1 is formed of a quadrangular pyramid-shaped protruding member, and the extending direction thereof is the normal direction of the surface of the piezoelectric element portion 2 (z direction in FIG. 1). In the present embodiment, the bottom surface of the protrusion 1 (the surface on the piezoelectric element portion 2 side) is a square. In addition, the shape of the protrusion part 1 is not limited to a square weight, For example, it can change suitably according to a use etc.

  For example, you may form the shape of the projection part 1 with a cone, a cylinder, polygonal pyramids other than a square. Moreover, you may make the bottom face of the projection part 1 into a rectangle, for example. Furthermore, for applications in which the fluid flow direction is one direction, the protrusion 1 may be formed of a plate-like member. Moreover, you may comprise the side surface of the projection part 1 by a curved surface. Further, the inside of the protrusion 1 may be a cavity or may not be a cavity.

  In the fluid sensor 10 of the present embodiment, the pressure when the fluid hits the side surface of the protrusion 1 is transmitted to the piezoelectric element portion 2 via the bottom surface of the protrusion 1, so that the shape of the protrusion 1 is determined by the fluid. It is preferable that the applied pressure has a shape that can easily be transmitted to the piezoelectric element portion 2. From such a point of view, it is preferable that the shape of the protrusion 1 is such that the diameter decreases from the bottom surface toward the tip as in the present embodiment. Note that the dimensions of the bottom surface of the protrusion 1 and the height of the protrusion 1 (the length in the z direction in FIG. 1) are appropriately set according to, for example, the application.

  Further, the protruding portion 1 can be formed of any insulating material, for example, an insulating resin material (plastic). Further, when an insulating layer or the like is provided between the protruding portion 1 and the piezoelectric element portion 2, the protruding portion 1 may be formed of a conductive material. However, when the cost and mass productivity of the fluid sensor 10 are taken into consideration, it is preferable to form the protrusion 1 with a resin material that can be molded.

  Next, the configuration of the piezoelectric element unit 2 will be described. The piezoelectric element portion 2 is composed of a piezoelectric sheet 3 (piezoelectric member) and an electrode pair group 4 composed of four electrode pairs. Each electrode pair is composed of a pair of electrodes arranged at positions facing each other across the piezoelectric sheet 3. That is, in this embodiment, four piezoelectric elements are formed in the piezoelectric element portion 2. And in the piezoelectric element part 2 of this embodiment, the pressure applied when a fluid hits the projection part 1 is converted into a voltage signal by each piezoelectric element.

  Here, the configuration of the piezoelectric element portion 2 will be described in more detail with reference to FIGS. 2A is a schematic top view of the piezoelectric element portion 2, FIG. 2B is a schematic side view of the piezoelectric element portion 2, and FIG. 2C is a piezoelectric element portion. 2 is a schematic bottom view of FIG.

  As shown in FIG. 2B, the piezoelectric element portion 2 mainly includes a piezoelectric sheet 3 and an upper electrode group 41 formed on a surface (hereinafter referred to as an upper surface) on the protruding portion 1 side of the piezoelectric sheet 3; The piezoelectric sheet 3 includes a lower electrode group 42 formed on the surface opposite to the protrusion 1 side (hereinafter referred to as a lower surface). Moreover, the surface shape of the piezoelectric element portion 2 is a square, and the length of each side is substantially the same as one side of the bottom surface of the protrusion 1. Then, the protruding portion 1 is attached on the piezoelectric element portion 2 so that each side of the piezoelectric element portion 2 coincides with each corresponding side of the bottom surface of the protruding portion 1.

  The piezoelectric sheet 3 is a sheet-like (film-like) member made of a piezoelectric material capable of converting an applied pressure into a voltage signal. The surface of the piezoelectric sheet 3 is square, and the length of each side is substantially the same as one side of the bottom surface of the protrusion 1.

  As a material for forming the piezoelectric sheet 3, a piezoelectric material used for a conventional piezoelectric sensor or the like can be used. For example, a piezo film or a piezoelectric ceramic used for a PVDF (Polyvinylidene Difluoride) film sensor or the like can be used as a material for forming the piezoelectric sheet 3. Moreover, the thickness of the piezoelectric sheet 3 can be about 20-200 micrometers, for example. The configuration of the piezoelectric sheet 3 such as the material and thickness is not limited to this, and can be set as appropriate depending on the application and the required detection sensitivity, for example.

  As shown in FIG. 2A, the upper electrode group 41 includes four isosceles triangular upper electrodes 41A to 41D (hereinafter referred to as first upper electrode 41A to fourth upper electrode 41D, respectively). In the present embodiment, the first upper electrode 41A to the fourth upper electrode 41D (first to fourth electrodes) all have the same shape. In addition, the length of each bottom side of the first upper electrode 41 </ b> A to the fourth upper electrode 41 </ b> D is shorter than the length of the side of the piezoelectric sheet 3, and the height is shorter than half the length of the side of the piezoelectric sheet 3.

  In the present embodiment, the first upper electrode 41A and the second upper electrode 41B are arranged in one opposite side direction (x direction in FIG. 2A: first direction) of the piezoelectric sheet 3 (the bottom surface of the protrusion 1). It arrange | positions so that it may mutually oppose at predetermined intervals. At this time, the first upper electrode 41 </ b> A and the second upper electrode 41 </ b> B are arranged so that the apex portions of both face each other and are symmetrical with respect to the center of the piezoelectric sheet 3. . In addition, although the space | interval in the opposing direction of 41 A of 1st upper electrodes and the 2nd upper electrode 41B can be about 1 mm, for example, this invention is not limited to this, For example, it sets suitably according to a use etc. Can do.

  In the present embodiment, the third upper electrode 41C and the fourth upper electrode 41D are in a direction orthogonal to the opposing direction of the first upper electrode 41A and the second upper electrode 41B (the y direction in FIG. 2A). : In the second direction) to be opposed to each other at a predetermined interval. Further, at this time, the third upper electrode 41C and the fourth upper electrode 41D are disposed so that the apex portions of both face each other and are symmetrical with respect to the center of the piezoelectric sheet 3. . In the present embodiment, the distance between the third upper electrode 41C and the fourth upper electrode 41D in the facing direction is the same as that of the first upper electrode 41A and the second upper electrode 41B.

  Further, in the present embodiment, the first upper electrode 41A to the fourth upper electrode 41D are arranged so as not to contact each other. The distance between the upper electrodes adjacent to each other in the circumferential direction of the piezoelectric sheet 3 can be set to, for example, about 1 mm. However, the present invention is not limited to this, and can be appropriately set according to, for example, the application. .

  By arranging each upper electrode on the upper surface of the piezoelectric sheet 3 as described above, the electrode pattern of the upper electrode group 41 including the first upper electrode 41A to the fourth upper electrode 41D is as shown in FIG. When viewed from the center of the piezoelectric sheet 3, it is symmetric in both the x direction and the y direction.

  Each upper electrode can be formed of an arbitrary metal material, and can be formed of, for example, silver or gold. Note that the material for forming each electrode is appropriately set in consideration of, for example, the application and the usage environment of the fluid sensor 10. The thicknesses of the upper electrodes are all the same, and can be about 100 μm, for example. However, this invention is not limited to this, The thickness of each upper electrode can be suitably set, for example according to a use etc.

  As shown in FIG. 2C, the lower electrode group 42 includes four isosceles triangular lower electrodes 42A to 42D (hereinafter, referred to as first lower electrode 42A to fourth lower electrode 42D, respectively). In the present embodiment, the first lower electrode 42A to the fourth lower electrode 42D (first to fourth electrodes) all have the same shape. In the present embodiment, the configurations (shape, dimensions, forming material, etc.) of the first lower electrode 42A to the fourth lower electrode 42D are the same as the configurations of the first upper electrode 41A to the fourth upper electrode 41D.

  In the present embodiment, the first lower electrode 42A and the second lower electrode 42B are separated from each other by a predetermined distance in one opposite side direction (the x direction in FIG. 2C) of the piezoelectric sheet 3 (the bottom surface of the protrusion 1). Are arranged to face each other. The interval in the facing direction of the first lower electrode 42A and the second lower electrode 42B is the same as that of the first upper electrode 41A and the second upper electrode 41B. At this time, the first lower electrode 42 </ b> A and the second lower electrode 42 </ b> B are arranged so that the apex portions of both face each other and are symmetrical with respect to the center of the piezoelectric sheet 3. .

  In the present embodiment, the third lower electrode 42C and the fourth lower electrode 42D are orthogonal to the opposing direction of the first lower electrode 42A and the second lower electrode 42B (the y direction in FIG. 2C). ) Are arranged so as to face each other at a predetermined interval. Note that the distance between the third lower electrode 42C and the fourth lower electrode 42D in the facing direction is the same as that of the third upper electrode 41C and the fourth upper electrode 41D. At this time, the third lower electrode 42 </ b> C and the fourth lower electrode 42 </ b> D are arranged so that the apex portions of both face each other and are symmetrical with respect to the center of the piezoelectric sheet 3. .

  Furthermore, in the present embodiment, the first lower electrode 42A to the fourth lower electrode 42D are arranged so as not to contact each other.

  By arranging the lower electrodes on the lower surface of the piezoelectric sheet 3 as described above, the electrode pattern of the lower electrode group 42 including the first lower electrode 42A to the fourth lower electrode 42D is as shown in FIG. When viewed from the center of the piezoelectric sheet 3, it is symmetric in both the x direction and the y direction. The first lower electrode 42A to the fourth lower electrode 42D are disposed at positions facing the first upper electrode 41A to the fourth upper electrode 41D, respectively, with the piezoelectric sheet 3 interposed therebetween.

  As described above, by arranging the upper electrode group 41 and the lower electrode group 42 with the piezoelectric sheet 3 interposed therebetween, four piezoelectric elements PA to PD are configured in the piezoelectric element portion 2. Specifically, between the first upper electrode 41A and the first lower electrode 42A (first electrode pair), between the second upper electrode 41B and the second lower electrode 42B (second electrode pair), the third upper electrode 41C and the first Piezoelectric elements PA to PD are formed between the three lower electrodes 42C (third electrode pair) and between the fourth upper electrode 41D and the fourth lower electrode 42D (fourth electrode pair).

[Operation of fluid sensor]
Next, the operation of the fluid sensor of the present embodiment will be specifically described with reference to FIGS. 3 shows that the fluid 100 moves (flows) from the piezoelectric element PB side to the piezoelectric element PA side in the opposing direction of the piezoelectric elements PA and PB in the piezoelectric element portion 2 (the x direction in FIG. 3). It is a figure which shows the mode of a case. FIG. 4 shows a state in which the fluid 100 moves from the piezoelectric element PD side to the piezoelectric element PC side in the facing direction of the piezoelectric elements PC and PD in the piezoelectric element portion 2 (y direction in FIG. 4). FIG.

  When the fluid 100 moves from the piezoelectric element PB side toward the piezoelectric element PA side (in the case of FIG. 3), among the four side surfaces (hereinafter referred to as opposing side surfaces) of the protrusion 1 facing the piezoelectric elements PA to PD, Since the opposing side surfaces of the piezoelectric elements PC and PD are parallel to the flow direction of the fluid 100 (the x direction in FIG. 4), the pressure applied to these side surfaces is the same. Therefore, the voltage signals VC and VD (third and fourth voltage signals) generated in the piezoelectric elements PC and PD respectively have the same value.

  On the other hand, since the in-plane direction of each opposing side surface of the piezoelectric elements PA and PB intersects the flow direction of the fluid 100, the pressure applied to each opposing side surface of the piezoelectric elements PA and PB is different from each opposing side of the piezoelectric elements PC and PD. Different from the pressure applied to the side. As a result, the voltage signals VA and VB (first and second voltage signals) generated in the piezoelectric elements PA and PB are different from the voltage signals VC and VD generated in the piezoelectric elements PC and PD, respectively.

  Further, since the opposing side surface of the piezoelectric element PB is positioned upstream of the opposing side surface of the piezoelectric element PA in the flow direction of the fluid 100, the pressure applied to the opposing side surface of the piezoelectric element PB is that of the opposing side surface of the piezoelectric element PA. Become bigger. As a result, the voltage signal VA generated in the piezoelectric element PA is different from the voltage signal VB generated in the piezoelectric element PB.

  That is, as shown in FIG. 3, when the fluid 100 moves from the piezoelectric element PB side toward the piezoelectric element PA side, the voltage signal VA to VD generated by the piezoelectric elements PA to PD, respectively, A relationship of ≠ VB ≠ VC = VD occurs.

  When the fluid 100 moves from the piezoelectric element PD side toward the piezoelectric element PC side (in the case of FIG. 4), the opposing side surfaces of the piezoelectric elements PA and PB are in the flow direction of the fluid 100 (the y direction in FIG. 4). ), The pressure applied to these sides is the same. Therefore, the voltage signals VA and VB generated in the piezoelectric elements PA and PB, respectively, have the same value.

  On the other hand, since the in-plane direction of each opposing side surface of the piezoelectric elements PC and PD intersects the flow direction of the fluid 100, the pressure applied to each opposing side surface of the piezoelectric elements PC and PD is opposite to each of the piezoelectric elements PA and PB. Different from the pressure applied to the side. As a result, the voltage signals VC and VB generated at the piezoelectric elements PC and PD, respectively, have different values from the voltage signals VA and VB generated at the piezoelectric elements PA and PB, respectively.

  Further, since the opposing side surface of the piezoelectric element PD is located upstream of the opposing side surface of the piezoelectric element PC in the flow direction of the fluid 100, the pressure applied to the opposing side surface of the piezoelectric element PD is that of the opposing side surface of the piezoelectric element PC. Become bigger. As a result, the voltage signal VC generated in the piezoelectric element PC is different from the voltage signal VD generated in the piezoelectric element PD.

  That is, as shown in FIG. 4, when the fluid 100 moves from the piezoelectric element PD side toward the piezoelectric element PC side, the voltage signals VA to VD generated by the piezoelectric elements PA to PD are VA. = VB ≠ VC ≠ VD.

  As described above, the magnitude relationship between the voltage signals VA to VD (first to fourth voltage signals) changes depending on the relative flow direction of the fluid 100 with respect to the fluid sensor 10 in the plane of the piezoelectric sheet 3. . In addition, the magnitude | size of each voltage signal VA-VD changes with the pressure applied to the fluid sensor 10 from the fluid 100, ie, the flow velocity or flow volume of the fluid 100. FIG.

  In the fluid sensor 10 of the present embodiment, as described above, the voltage signals VA to VD generated in the piezoelectric elements PA to PD according to the flow state (flow velocity, flow direction, flow rate, etc.) of the fluid 100 that hits the fluid sensor 10, respectively. Changes. Therefore, in the present embodiment, the flow state of the fluid 100 can be measured (detected) by detecting the voltage signals VA to VD generated by the four piezoelectric elements PA to PD in the fluid sensor 10. .

[Configuration of flow velocity direction meter]
Next, a configuration example of a fluid measuring device (hereinafter referred to as a flow velocity direction meter) that measures the fluid flow velocity and flow direction using the fluid sensor 10 of the present embodiment will be described. FIG. 5 shows a schematic configuration of the flow velocity direction meter of the present embodiment. FIG. 5 shows only components necessary for detecting the fluid velocity and flow direction for the sake of simplicity.

  The flow velocity direction meter 20 includes a fluid sensor 10, a differential circuit unit 21, and a flow velocity flow direction calculation unit 24 (calculation unit). Since the fluid sensor 10 is the fluid sensor 10 of the present embodiment described with reference to FIG. 1, the description thereof is omitted here. In FIG. 5, only the piezoelectric element portion 2 is shown as the fluid sensor 10 in order to simplify the description. In FIG. 5, the wiring between the first upper electrode 41A to the fourth upper electrode 41D of the piezoelectric element portion 2 and the differential circuit portion 21 is indicated by a solid line, and the first lower electrode 42A to the fourth lower electrode 42D ( The wiring between the differential circuit unit 21 and the differential circuit unit 21 is indicated by a dotted line.

  The differential circuit unit 21 is mainly composed of two differential amplifiers 22 and 23 (hereinafter referred to as a first differential amplifier 22 and a second differential amplifier 23, respectively).

  In the present embodiment, the “−” polarity input terminal of the first differential amplifier 22 is connected to the first upper electrode 41A and the fourth lower electrode 42D. Further, the “+” polarity input terminal of the first differential amplifier 22 is connected to the second upper electrode 41B and the third lower electrode 42C. Note that the present invention is not limited to this, and the second upper electrode 41B and the third lower electrode 42C are connected to the “−” polarity input terminal of the first differential amplifier 22, and the “+” polarity input terminal is connected to the first differential amplifier 22. The first upper electrode 41A and the fourth lower electrode 42D may be connected.

  The first differential amplifier 22 generates a difference signal X_out (first difference signal) between the voltage signal VA generated at the piezoelectric element PA and the voltage signal VB generated at the piezoelectric element PB. That is, the first differential amplifier 22 generates a differential signal of each voltage signal generated by two piezoelectric elements arranged along the x direction in FIG. The output terminal of the first differential amplifier 22 is connected to the flow velocity flow direction calculation unit 24, and the first differential amplifier 22 outputs the generated differential signal X_out to the flow velocity flow direction calculation unit 24.

  On the other hand, the “−” polarity input terminal of the second differential amplifier 23 is connected to the third upper electrode 41C and the first lower electrode 42A. The input terminal of “+” polarity of the second differential amplifier 23 is connected to the fourth upper electrode 41D and the second lower electrode 42B. Note that the present invention is not limited to this, and the fourth upper electrode 41D and the second lower electrode 42B are connected to the “−” polarity input terminal of the second differential amplifier 23, and the “+” polarity input terminal is connected to the second differential amplifier 23. 3 The upper electrode 41C and the first lower electrode 42A may be connected.

  The second differential amplifier 23 generates a difference signal Y_out (second difference signal) between the voltage signal VC generated by the piezoelectric element PC and the voltage signal VD generated by the piezoelectric element PD. That is, the second differential amplifier 23 generates a differential signal between the voltage signals generated by the two piezoelectric elements arranged along the y direction in FIG. The output terminal of the second differential amplifier 23 is connected to the flow velocity / flow direction calculating unit 24, and the second differential amplifier 23 outputs the generated differential signal Y_out to the flow velocity / flow direction calculating unit 24.

  The flow velocity flow direction calculation unit 24 is configured by, for example, a microcomputer (not shown), and calculates the flow velocity and flow direction of the fluid based on the two differential signals X_out and Y_out output from the differential circuit unit 21. To do. A specific method for calculating the fluid flow velocity and flow direction will be described later.

  In the flow velocity / direction meter 20 of the present embodiment, the display of the fluid flow velocity and the flow direction calculated by the flow velocity flow direction calculator 24 and the data storage of the fluid flow velocity and the flow direction may be performed by an external device. In addition, the flow velocity / direction meter 20 may include a display unit that displays the flow velocity and flow direction of the fluid calculated by the flow velocity / flow direction calculation unit 24 and / or a memory unit that stores data on the flow velocity and flow direction of the fluid.

  Moreover, although the example shown in FIG. 5 demonstrated the example of the fluid measuring device which measures both the flow velocity and flow direction of a fluid, this invention is not limited to this. The fluid measuring instrument 20 shown in FIG. 5 may be used as a fluid measuring instrument that measures only one of the flow velocity and the flow direction of the fluid.

  Here, FIG. 6 shows an equivalent circuit of the flow velocity direction meter 20 of the present embodiment. Each piezoelectric element formed in the fluid sensor 10 is represented by a voltage source in the equivalent circuit, and the polarities “+” and “−” of each voltage source shown in FIG. It corresponds to the terminal of the upper electrode and lower electrode of the element.

  In the equivalent circuit of the flow velocity direction meter 20, as shown in FIG. 6, the fluid sensor 10 has a configuration in which four voltage sources corresponding to the piezoelectric elements PA to PD are connected to a bridge circuit. The connection point between the “+” side terminal of the voltage source of the piezoelectric element PA and the “−” side terminal of the voltage source of the piezoelectric element PD is connected to the input terminal of the “−” polarity of the first differential amplifier 22. The The connection point between the “+” side terminal of the voltage source of the piezoelectric element PB and the “−” side terminal of the voltage source of the piezoelectric element PC is connected to the “+” polarity input terminal of the first differential amplifier 22. The Further, the connection point between the “+” side terminal of the voltage source of the piezoelectric element PC and the “−” side terminal of the voltage source of the piezoelectric element PA is connected to the “−” polarity input terminal of the second differential amplifier 23. The The connection point between the “+” side terminal of the voltage source of the piezoelectric element PD and the “−” side terminal of the voltage source of the piezoelectric element PB is connected to the “+” polarity input terminal of the second differential amplifier 23. The

[Calculation method of flow velocity and flow direction]
Next, a method of calculating the flow velocity and the flow direction in the flow velocity flow direction calculation unit 24 of the flow velocity flow direction meter 20 of the present embodiment will be briefly described.

  First, based on the two difference signals X_out and Y_out output from the differential circuit unit 21, the flow velocity / flow direction calculation unit 24 obtains parameters relating to the fluid flow velocity and the flow direction by the following two equations.

  Note that Y_out / X_out in parentheses in the above equation 2 may be X_out / Y_out.

  As described above, in the fluid sensor 10 of the present embodiment, the magnitudes and magnitude relationships of the voltage signals VA to VD generated by the piezoelectric elements PA to PD, respectively, according to the relative flow direction and flow velocity of the fluid hitting the fluid sensor 10. Changes. Therefore, the flow velocity parameter and the flow direction parameter shown by the above-described Equation 1 and Equation 2 also change according to the relative flow direction and the flow velocity of the fluid that strikes the fluid sensor 10.

  Next, the flow velocity flow direction calculation unit 24 refers to the flow velocity parameter and flow direction calculated with reference to the previously prepared flow velocity parameter and the information table showing the correspondence between the flow direction parameter and the fluid flow state (flow velocity, flow direction, etc.). The fluid flow velocity and flow direction corresponding to the parameters are obtained. In this way, the flow velocity direction meter 20 of the present embodiment calculates the flow velocity and the flow direction of the fluid.

  As for a data reference method such as an information table indicating a correspondence relationship between the actual flow state of the fluid and the flow parameters (flow velocity parameter and flow direction parameter), the flow velocity flow direction calculation unit 24 may The data may be read from an external device in which data is stored in advance. Further, the flow velocity flow direction calculation unit 24 may include a memory unit, and an information table or the like indicating a correspondence relationship between a fluid flow state and a flow parameter may be stored in the memory unit.

[Configuration of flow meter]
In the example shown in FIGS. 5 and 6, the example in which the fluid sensor 10 of the present embodiment is applied to the flow velocity direction meter 20 has been described, but the present invention is not limited to this. The fluid sensor 10 according to the present embodiment includes, for example, a flow meter (for example, a flow rate of solid fine particles in a slurry (a fluid containing solid fine particles), a flow rate of fluid that discontinuously flows (for example, rainfall), and the like. (Fluid measuring instrument).

  In FIG. 7, schematic structure of the flowmeter of this embodiment is shown. FIG. 7 shows only components necessary for detecting the flow rate for the sake of simplicity. In FIG. 7, the same components as those in the flow velocity direction meter 20 shown in FIG.

  The flow meter 30 includes the fluid sensor 10, an addition circuit unit 31, and a flow rate calculation unit 34 (calculation unit). Since the fluid sensor 10 is the fluid sensor 10 of the present embodiment described with reference to FIG. 1, the description thereof is omitted here. In FIG. 7, only the piezoelectric element portion 2 is shown as the fluid sensor 10 in order to simplify the description. In FIG. 7, the wiring between the first upper electrode 41A to the fourth upper electrode 41D of the piezoelectric element portion 2 and the addition circuit portion 31 is indicated by a solid line, and the first lower electrode 42A to the fourth lower electrode 42D (see FIG. 7). (Not shown in FIG. 7) and the wiring between the addition circuit unit 31 are indicated by dotted lines.

  The adder circuit unit 31 includes a filter circuit unit 32 and an adder 33.

  The filter circuit unit 32 includes a plurality of high-pass filters including capacitors 32a and resistors 32b. Specifically, the filter circuit unit 32 includes the same number (four) of high-pass filters as the input terminals of the adder circuit unit 31.

  The input terminal of the capacitor 32a (input terminal of the filter circuit unit 32) in each high-pass filter is connected to a corresponding output terminal among the four output terminals (output terminals of the voltage signals VA to VD) of the fluid sensor 10. . The output terminal of the capacitor 32 a is connected to one terminal of the resistor 32 b and to the corresponding input terminal of the adder 33. Further, the other terminal of the resistor 32b is grounded.

  As will be described later, for example, the flow rate of the solid fine particles in the slurry and the fluid that discontinuously flows in time (hereinafter referred to as discontinuous fluid) is based on the pulsed voltage signal output from the fluid sensor 10. To calculate. Therefore, in the present embodiment, the filter circuit unit 32 including a plurality of high-pass filters is provided in the previous stage of the adder 33 to remove the influence of low-frequency noise on the pulse voltage signal.

  The adder 33 adds the voltage signals VA to VD (first to fourth voltage signals) input via the filter circuit unit 32. The output terminal of the adder 33 is connected to the flow rate calculation unit 34, and the adder 33 outputs the generated addition signal (sum signal) to the flow rate calculation unit 34.

  The flow rate calculation unit 34 is composed of, for example, a microcomputer (not shown), and calculates the fluid flow rate based on the addition signals of the voltage signals VA to VD output from the addition circuit unit 31. A specific method for calculating the fluid flow rate will be described later.

  In the flow meter 30 of the present embodiment, the display of the flow rate calculated by the flow rate calculation unit 34 and the data storage of the flow rate may be performed by an external device, or the flow meter 30 is calculated by the flow rate calculation unit 34. You may provide the display part which displays the flow volume of a fluid, and / or the memory part which memorize | stores the flow volume data of a fluid.

  Here, FIG. 8 shows an equivalent circuit of the flow meter 30 of the present embodiment. Each piezoelectric element formed in the fluid sensor 10 is represented by a voltage source in an equivalent circuit, and the polarity “+” and “−” of each voltage source shown in FIG. It corresponds to the terminal of the upper electrode and lower electrode of the element.

  As shown in FIG. 8, the equivalent circuit of the flow meter 30 has a configuration in which four voltage sources corresponding to the piezoelectric elements PA to PD are connected to a bridge circuit. The connection point between the “+” side terminal of the voltage source of the piezoelectric element PA and the “−” side terminal of the voltage source of the piezoelectric element PD is connected to the input terminal of the voltage signal VA of the adder circuit unit 31. Further, the connection point between the “+” side terminal of the voltage source of the piezoelectric element PB and the “−” side terminal of the voltage source of the piezoelectric element PC is connected to the input terminal of the voltage signal VB of the adding circuit unit 31. Further, the connection point between the “+” side terminal of the voltage source of the piezoelectric element PC and the “−” side terminal of the voltage source of the piezoelectric element PA is connected to the input terminal of the voltage signal VC of the adding circuit unit 31. Further, the connection point between the “+” side terminal of the voltage source of the piezoelectric element PD and the “−” side terminal of the voltage source of the piezoelectric element PB is connected to the input terminal of the voltage signal VD of the adding circuit unit 31.

[Flow rate calculation method]
Next, a flow rate calculation method in the flow rate calculation unit 34 of the flow meter 30 of the present embodiment will be briefly described.

  When the discontinuous fluid hits the protrusion 1 of the fluid sensor 10, pressure is applied to the fluid sensor 10 only during that time zone, so that the voltage signal output from each piezoelectric element of the fluid sensor 10 also increases during that time zone. That is, when the discontinuous fluid hits the protrusion 1 of the fluid sensor 10, a pulsed voltage signal is output from each piezoelectric element of the fluid sensor 10. Therefore, in this case, the addition signal (sum signal) of the voltage signals VA to VD output from the addition circuit unit 31 is also a pulse-like discontinuous voltage signal.

  FIG. 9 shows a signal waveform example of the addition signal output from the addition circuit unit 31 when the discontinuous fluid hits the protrusion 1 of the fluid sensor 10. In FIG. 9, the horizontal axis represents time, and the vertical axis represents the signal level of the added signal.

  When the discontinuous fluid hits the protrusion 1 of the fluid sensor 10, as described above, the pulse-like signal 35 appears only in the time zone when the discontinuous fluid hits the protrusion 1 of the fluid sensor 10. In such a signal waveform, the generation interval ΔT of the pulsed signal 35 and the signal width Δτ of the pulsed signal 35 change depending on the flow rate of the discontinuous fluid. Specifically, when the flow rate of the discontinuous fluid increases, the generation interval ΔT of the pulse-like signal 35 becomes narrower, and the signal width Δτ of the pulse-like signal 35 becomes larger.

  Therefore, the flow rate calculation unit 34 refers to an information table or the like that indicates a correspondence relationship between the generation interval ΔT and the signal width Δτ (waveform parameter) of the pulse-shaped signal 35 and the flow rate of the discontinuous fluid prepared in advance. The flow rate corresponding to the calculated waveform parameter of the addition signal is obtained. In the flow meter 30 of the present embodiment, the fluid flow rate is calculated in this manner.

  Note that a method for referring to data such as an information table indicating the correspondence between the actual flow rate of the fluid and the waveform parameters (the generation interval ΔT and the signal width Δτ of the pulse-like signal 35) is as follows. However, the data may be read from an external device in which data such as an information table is stored in advance. Further, the flow rate calculation unit 34 may include a memory unit, and an information table or the like indicating the correspondence between the flow rate of the fluid and the waveform parameter may be stored in the memory unit.

  As described above, in the example illustrated in FIG. 5, an example in which the fluid sensor 10 according to the present embodiment is applied to the flow velocity direction meter 20 will be described. In the example illustrated in FIG. 7, the fluid sensor 10 is applied to the flow meter 30. However, the present invention is not limited to this. The fluid sensor 10 of the present embodiment can also be applied to a fluid measuring instrument that can measure all of the fluid flow velocity, flow direction, and flow rate.

  In FIG. 10, the structural example of the fluid measuring device which measures the flow velocity, flow direction, and flow volume of a fluid using the fluid sensor 10 of this embodiment is shown. In FIG. 10, the same components as those of the flow velocity direction meter 20 shown in FIG. 5 and the flow meter 30 shown in FIG.

  The fluid measuring instrument 50 includes a fluid sensor 10, a differential circuit unit 21 connected to the output terminal of the fluid sensor 10, and a flow velocity flow direction calculation unit 24 (first calculation unit) connected to the output terminal of the differential circuit unit 21. ), An addition circuit unit 31 connected to the output terminal of the fluid sensor 10, and a flow rate calculation unit 34 (second calculation unit) connected to the output terminal of the addition circuit unit 31.

  The fluid sensor 10 has the same configuration as the fluid sensor 10 of the present embodiment described with reference to FIG. The differential circuit unit 21 and the flow velocity flow direction calculation unit 24 have the same configuration as those of the flow velocity flow direction meter 20 described in FIG. Further, the addition circuit unit 31 and the flow rate calculation unit 34 have the same configuration as those of the flow meter 30 described in FIG.

  In the fluid measuring instrument 50 shown in FIG. 10, the four input terminals of the differential circuit unit 21 and the four input terminals of the adding circuit unit 31 with respect to the four output terminals of the voltage signals VA to VC of the fluid sensor 10. Are connected in parallel. With such a circuit configuration, the flow rate and the flow direction of the fluid are output from the circuit system of the differential circuit unit 21 and the flow velocity / flow direction calculation unit 24 in the same manner as the above-described flow velocity and flow direction calculation method. On the other hand, the flow rate is output from the circuit system of the addition circuit unit 31 and the flow rate calculation unit 34 in the same manner as the above-described flow rate calculation method.

  In the fluid sensor 10 and various fluid measuring instruments of the present embodiment described above, the following effects can be obtained.

  Since the fluid sensor 10 of the present embodiment has a simple configuration in which the protruding portion 1 is simply provided on the piezoelectric element portion 2, it can be manufactured at low cost. Therefore, according to the present embodiment, it is possible to provide a fluid sensor 10 having a simpler configuration and at a lower cost, and a fluid measuring instrument including the fluid sensor 10.

  Furthermore, in the fluid sensor 10 of this embodiment, as is clear from the calculation principle (calculation method) of the fluid flow state (flow velocity, flow direction, flow rate, etc.) described above, the fluid flow regardless of the size of the protrusion 1. Since the state can be detected, a smaller fluid sensor can be provided.

  Further, in a conventional flow velocity meter using a rotor such as a propeller, for example, the fluid flow velocity and flow direction cannot be measured unless the rotor rotates once. Further, in the conventional flow meter, the flow rate is obtained by directly measuring the amount of fluid flowing within a predetermined time. That is, with these conventional fluid measuring instruments, it is difficult to measure the fluid state in real time. On the other hand, in the fluid measuring instrument of the present embodiment, the fluid flow velocity, flow direction, and flow rate can be obtained based on the voltage signal that is output from the fluid sensor 10 every moment (for example, at intervals of several milliseconds or less). Therefore, in the fluid measuring instrument of the present embodiment, it is possible to measure the fluid flow state in real time compared to the conventional case.

[Modification 1]
In the first embodiment, the configuration in which the size of the piezoelectric sheet 3 of the piezoelectric element portion 2 is substantially the same as that of the bottom surface of the protruding portion 1 and the entire upper electrode group 41 is covered with the protruding portion 1 has been described. In the first embodiment, the example in which the four electrodes constituting the upper electrode group 41 and the lower electrode group 42 are isosceles triangles has been described. However, the configuration of the piezoelectric sheet and the electrode (for example, shape, size, etc.) is not limited to this, and can be appropriately changed according to, for example, the application. Modification 1 shows a modification of the configuration of the piezoelectric sheet and the electrodes.

  FIG. 11 shows a schematic top view of the piezoelectric element portion of the fluid sensor of the first modification. Note that a dotted line 64 in FIG. 11 indicates a side portion of the bottom surface of the protruding portion disposed on the piezoelectric element portion 60. However, in this example, the protruding portion has the same configuration as the protruding portion 1 of the first embodiment. In the fluid sensor of this example, the protrusion 1 is disposed on the upper surface of the piezoelectric element portion 60 so that the center of the bottom surface 64 of the protrusion 1 and the center of the piezoelectric sheet 63 are coaxially disposed.

  The piezoelectric element unit 60 is mainly formed on the piezoelectric sheet 63, four upper electrodes 61 </ b> A to 61 </ b> D (first upper electrode to fourth upper electrode) formed on the upper surface of the piezoelectric sheet 63, and the lower surface of the piezoelectric sheet 63. And four lower electrodes (not shown).

  The piezoelectric sheet 63 is formed with the same material and thickness as the piezoelectric sheet 3 of the first embodiment. Further, in this example, the surface shape of the piezoelectric sheet 63 is a square, and the length of one side is equal to or longer than the diagonal length of the bottom surface 64 (square) of the protrusion 1.

  The first upper electrode 61A to the fourth upper electrode 61D are formed of a metal film having a square surface, and all have the same shape. Then, the length of each side of the first upper electrode 61 </ b> A to the fourth upper electrode 61 </ b> D is shorter than half the length of one side of the piezoelectric sheet 63.

  In this example, the first upper electrode 61A and the second upper electrode 61B are arranged so as to face each other at a predetermined interval in one diagonal direction of the piezoelectric sheet 63 (the x direction in FIG. 11). . At this time, the first upper electrode 61 </ b> A and the second upper electrode 61 </ b> B are disposed so that the corner portions thereof are opposed to each other and are symmetrical with respect to the center of the piezoelectric sheet 63.

  On the other hand, the third upper electrode 61C and the fourth upper electrode 61D are arranged so as to face each other with a predetermined distance in the other diagonal direction of the piezoelectric sheet 63 (y direction in FIG. 11). At this time, the third upper electrode 61 </ b> C and the fourth upper electrode 61 </ b> D are disposed so that the corner portions thereof are opposed to each other and are symmetrical with respect to the center of the piezoelectric sheet 63. Note that the distance between the third upper electrode 61C and the fourth upper electrode 61D in the facing direction is the same as that of the first upper electrode 61A and the second upper electrode 61B.

  Furthermore, in the example shown in FIG. 11, the first upper electrode 61A to the fourth upper electrode 61 are arranged so as not to contact each other. In the example shown in FIG. 11, the first upper electrode 61 </ b> A to the fourth upper electrode 61 </ b> D are arranged at four corners of the piezoelectric sheet 63, respectively.

  By disposing each upper electrode as described above, the electrode pattern of the upper electrode group including the first upper electrode 61A to the fourth upper electrode 61 is both in the x direction and the y direction when viewed from the center of the piezoelectric sheet 63. It becomes symmetrical.

  The four lower electrodes (not shown) formed on the lower surface of the piezoelectric sheet 63 have the same configuration as that of the first upper electrode 61A to the fourth upper electrode 61D, and the first upper electrode is sandwiched between the piezoelectric sheets 63. 61A to the fourth upper electrode 61D are arranged at positions facing each other.

  As described above, by arranging the first upper electrode 61A to the fourth upper electrode 61D and the four lower electrodes corresponding to the first upper electrode 61A to the fourth upper electrode 61D with the piezoelectric sheet 63 interposed therebetween, Similar to the embodiment, four piezoelectric elements PA to PD are configured.

  By configuring the fluid sensor as described above, each of the piezoelectric elements PA to PD is generated according to the flow state (for example, the flow velocity, the flow direction, and the flow rate) of the fluid that hits the fluid sensor, as in the first embodiment. The magnitudes and magnitude relationships of the voltage signals VA to VD to be changed change. Therefore, also in the fluid sensor of this example and the fluid measuring instrument using the fluid sensor, the same effect as in the first embodiment can be obtained.

  Furthermore, in this example, since the surface dimension of the piezoelectric element portion 60 is equal to or larger than the dimension of the bottom surface 64 of the protrusion portion 1, the protrusion portion 1 can be installed more easily.

[Modification 2]
In the first embodiment, the example in which four piezoelectric elements are formed in the piezoelectric element portion has been described. However, the present invention is not limited to this, and the number of piezoelectric elements provided in the piezoelectric element portion depends on, for example, the application. Can be set as appropriate. In the fluid measuring instrument (flow velocity direction meter) using the differential signal described above, the number of piezoelectric elements provided in the piezoelectric element section is preferably an even number. For applications where the fluid flow direction is mainly one direction, the number of piezoelectric elements provided in the piezoelectric element portion may be two. In the second modification, an example will be described.

  FIG. 12 shows a schematic top view of the piezoelectric element portion of the fluid sensor of the second modification. The piezoelectric element portion 65 is mainly formed on the piezoelectric sheet 68, two upper electrodes 66A and 66B (first upper electrode and second upper electrode) formed on the upper surface of the piezoelectric sheet 68, and the lower surface of the piezoelectric sheet 68. And two lower electrodes (not shown).

  In this example, the protrusion of the fluid sensor has the same configuration as the protrusion 1 (FIG. 1) of the first embodiment. In this example, the protrusion 1 is arranged on the upper surface of the piezoelectric element portion 65 so that the center of the bottom surface of the protrusion 1 and the center of the piezoelectric sheet 68 are coaxially arranged. Further, the protrusion 1 is disposed on the upper surface of the piezoelectric element portion 65 so that each side of the bottom surface of the protrusion 1 and each side of the piezoelectric element portion 65 corresponding thereto correspond to each other.

  The piezoelectric sheet 68 is formed with the same material and thickness as the piezoelectric sheet 3 of the first embodiment. Further, in this example, the surface shape of the piezoelectric sheet 68 is a square, and the length of one side thereof is substantially the same as the length of one side of the protrusion 1 disposed on the piezoelectric element portion 65.

  Both the first upper electrode 66A and the second upper electrode 66B are formed of a metal film having a rectangular surface, and have the same dimensions. In each of the first upper electrode 66A and the second upper electrode 66B, the length of the long side is the same as the length of one piece of the piezoelectric sheet 68, and the length of the short side is half the length of one side of the piezoelectric sheet 68. shorten.

  Further, in this example, the first upper electrode 66A and the second upper electrode 66B are arranged so as to face each other at a predetermined distance in one opposite side direction (the x direction in FIG. 12) of the piezoelectric sheet 68. At this time, the first upper electrode 66 </ b> A and the second upper electrode 66 </ b> B are disposed so that one of the long sides thereof is opposed to each other and is symmetric with respect to the center of the piezoelectric sheet 68. The distance between the first upper electrode 66A and the second upper electrode 66B in the facing direction can be, for example, about 1 mm. However, the present invention is not limited to this, and is appropriately set according to the application, for example. Can do.

  Further, two lower electrodes (not shown) formed on the lower surface of the piezoelectric sheet 68 have the same configuration as that of the first upper electrode 66A and the second upper electrode 66B, and the first upper electrode is sandwiched between the piezoelectric sheets 68. 66A and the second upper electrode 66B are disposed at positions facing each other.

  By arranging the first upper electrode 66A and the second upper electrode 66B and the two lower electrodes corresponding to the first upper electrode 66A and the second upper electrode 66B with the piezoelectric sheet 68 interposed therebetween as described above, two piezoelectric elements are provided in the piezoelectric element portion 65. Elements PA and PB are configured.

  The fluid sensor having such a configuration is applicable to an application in which the fluid flows only in the facing direction (the x direction in FIG. 12) of the first upper electrode 66A and the second upper electrode 66B. For such an application, as in the first embodiment, the voltage signal VA generated in each of the piezoelectric elements PA and PB according to the flow state (for example, the flow velocity, the flow direction, and the flow rate) of the fluid that hits the fluid sensor. And the magnitude and magnitude relationship of VB changes. Therefore, in the fluid sensor of this example and the fluid measuring instrument using the fluid sensor, the same effects as those of the first embodiment can be obtained in the above-described application.

<2. Second Embodiment>
In the first embodiment, the example of the fluid sensor in which one protrusion is provided on one sheet-like piezoelectric element has been described. However, the present invention is not limited to this, and one sheet-like piezoelectric element is provided. A plurality of protrusions may be provided on the element portion. In the second embodiment, an example of such a configuration will be described.

[Configuration of fluid measurement sensor]
FIG. 13 is a schematic perspective view of a fluid sensor according to the second embodiment of the present invention. The fluid sensor 70 of the present embodiment is mainly composed of a projection group 71 composed of a plurality of projections 71a (projection members) and a piezoelectric element portion 72 provided below the projection group 71.

  The plurality of protrusions 71 a are regularly arranged in a two-dimensional manner on one surface (the upper surface in FIG. 13) of the piezoelectric element portion 72. Under the present circumstances, it arrange | positions so that the edge | side where the bottom face of the adjacent protrusion part 71a opposes may contact | connect. Further, the plurality of protrusions 71 a provided at the outer peripheral end of the piezoelectric element portion 72 are arranged so that the sides on the outer peripheral end side of the piezoelectric element portion 72 on the bottom surface thereof coincide with the sides of the corresponding piezoelectric element portion 72. In other words, the fluid sensor 70 of this example has a configuration in which the plurality of protrusions 71 a are two-dimensionally spread over the entire surface of the piezoelectric element portion 72.

  Each of the protrusions 71a has the same configuration, and is the same configuration as the protrusion 1 used in the fluid sensor 10 (FIG. 1) of the first embodiment. Further, the protrusion 71a can be formed of the same material as that of the protrusion 1 of the first embodiment. In addition, the dimension of the bottom face and height of each protrusion part 71a is suitably set according to the dimension of the piezoelectric element part 72 and the number of arrangement | sequences of the protrusion part 1, for example. For example, when the outer peripheral dimension of the piezoelectric element portion 72 is 50 to 100 mm × 50 to 100 mm and the protrusions 71a are arranged in 10 × 10, the dimension of one side of the bottom surface of the protrusion 71a is, for example, about 5 to 5. 10 mm. In this case, the height of the protrusion 71a (the length in the z direction in FIG. 13) can also be set to about 5 to 10 mm, for example.

  In addition, although the shape of the projection part 71a is a square weight here as in the first embodiment, the present invention is not limited to this. The shape of the protrusion 71a can be appropriately changed according to, for example, the use.

  For example, the shape of the protrusion 71a may be formed of a cone, a cylinder, a polygonal pyramid other than a square, or the like. Further, the bottom surface of the protrusion 71a may be rectangular, for example. For applications in which the fluid flow direction is one direction, the protrusion 71a may be formed of a plate-like member. Moreover, you may comprise the side surface of the projection part 71a with a curved surface. Furthermore, the inside of the protrusion 71a may be a cavity or may not be a cavity.

  In the fluid sensor 70 of the present embodiment, the pressure when the fluid hits the side surface of the protrusion 71a is transmitted to the piezoelectric element portion 72 via the bottom surface of the protrusion 71a. It is preferable that the applied pressure has a shape that can easily be transmitted to the piezoelectric element portion 72. From such a viewpoint, it is preferable that the shape of the protruding portion 71a is such that the diameter decreases from the bottom surface toward the tip as in the present embodiment.

  Further, the number and arrangement of the protrusions 71a are appropriately set according to, for example, the application. For example, the number of the protrusions 71a arranged in one direction may be different from the number of the protrusions 71a arranged in the other direction, or the protrusions 71a may be arranged one-dimensionally. Further, the protrusions 71a may be arranged at random. Furthermore, you may arrange | position the projection part of a different structure (a shape, a dimension, etc.).

  Next, the configuration of the piezoelectric element portion 2 of the present embodiment will be described with reference to FIGS. 14 (a) and 14 (b). 14A is a schematic side view of the fluid sensor 70 of the present embodiment, and FIG. 14B is a schematic top view of the fluid sensor 70. However, in FIGS. 14A and 14B, only the configuration in the vicinity of one corner of the piezoelectric element portion 72 is shown to simplify the description.

  The piezoelectric element portion 72 is mainly formed on the piezoelectric sheet 73 (piezoelectric member), the upper electrode group 74 formed on the upper surface of the piezoelectric sheet 73 (surface on the protruding portion 71a side), and the lower surface of the piezoelectric sheet 73. A lower electrode group 75 is included.

  The piezoelectric sheet 73 is a sheet (film) made of a piezoelectric material capable of converting an applied pressure into a voltage signal, like the piezoelectric sheet 3 used in the fluid sensor 10 (FIG. 1) of the first embodiment. Shape). The surface of the piezoelectric sheet 73 is square, and the length of each side is substantially the same as (one side of the bottom surface of the protrusion 71a) × (the number of arrangement of the protrusions 71a in one direction). Moreover, the formation material and thickness of the piezoelectric sheet 73 can be formed with the same material and thickness as the piezoelectric sheet 3 of the first embodiment. The configuration of the piezoelectric sheet 73, such as the material and thickness, can be set as appropriate depending on, for example, the application and the required detection sensitivity.

  As shown in FIG. 14B, the upper electrode group 74 includes a plurality of upper electrode portions 76, and each upper electrode portion 76 is provided for each protrusion 71a. Each upper electrode portion 76 includes four isosceles triangular first upper electrode 76A to fourth upper electrode 76D.

  The configurations of the first upper electrode 76A to the fourth upper electrode 76D (first to fourth electrodes) are the same as the first upper electrode 41A to the fourth upper electrode 41D used in the fluid sensor 10 of the first embodiment (FIG. 2 ( The configuration is the same as a)). Further, the arrangement relationship between these upper electrodes and the corresponding projections 71a is the same as the arrangement relationship between the first upper electrode 41A to the fourth upper electrode 41D and the projections 1 of the first embodiment (FIG. 1). It is the same. In the present embodiment, the first upper electrode 76A and the second upper electrode 76B are separated from each other by a predetermined distance along one opposite side direction of the piezoelectric element portion 72 (x direction: first direction in FIG. 14B). The third upper electrode 76C and the fourth upper electrode 76D are separated from each other by a predetermined distance along the other opposite side direction of the piezoelectric element portion 72 (y direction: second direction in FIG. 14B). Form.

  The lower electrode group 75 includes a plurality of lower electrode portions (not shown), and each lower electrode portion is provided for each protrusion 71a. The structure of each lower electrode part is the same structure (shape, dimension, forming material, etc.) as the upper electrode part 76. Each lower electrode portion is disposed at a position facing the corresponding upper electrode portion 76 with the piezoelectric sheet 73 interposed therebetween. That is, each lower electrode portion is composed of four isosceles triangular lower electrodes (not shown: first to fourth electrodes), and the four lower electrodes sandwich the piezoelectric sheet 73 with the first upper electrode 76A. To the fourth upper electrode 76D.

  As described above, by arranging the upper electrode group 74 and the lower electrode group 75 with the piezoelectric sheet 73 interposed therebetween, four piezoelectric elements PA to PD are provided in the piezoelectric element portion 72 for each protrusion 71a. Composed. Specifically, between the first upper electrode 76A and the lower electrode facing it (first electrode pair), between the second upper electrode 76B and the lower electrode facing it (second electrode pair), the third upper electrode Piezoelectric elements PA to PD are configured between the electrode 76C and the lower electrode facing it (third electrode pair) and between the fourth upper electrode 76D and the lower electrode facing it (fourth electrode pair), respectively. Is done.

  That is, in the fluid sensor 70 of this example, a sensor element 77 having the same configuration as that of the fluid sensor 10 of the first embodiment (FIG. 1) is formed for each protrusion 71a. Therefore, each sensor element 77 operates in the same manner as the fluid sensor 10 of the first embodiment, and configures each sensor element 77 according to the state (flow velocity, flow direction, and flow rate) of the fluid that hits each sensor element 77. Voltage signals VA to VD generated by the piezoelectric elements PA to PD change, respectively. The fluid sensor 70 of this example measures (detects) the fluid flow state (flow direction, flow velocity, flow rate, etc.) using the voltage signals VA to VD detected by the sensor elements 77.

[Configuration of fluid measuring instrument]
Next, the configuration of a fluid measuring instrument to which the fluid sensor 70 of the present embodiment is applied will be described. FIG. 15 shows a schematic configuration of the fluid measuring instrument of the present embodiment. FIG. 15 shows only components different from the various fluid measuring instruments (FIGS. 5, 7 and 10) described in the first embodiment.

  The fluid measuring instrument 80 of this embodiment includes a fluid sensor 70 and an averaging circuit unit 81. When the fluid meter 80 is used as a flow velocity meter, the fluid meter 80 further includes an averaging circuit unit 81 as in the flow velocity meter 20 (FIG. 5) described in the first embodiment. A differential circuit unit 21 and a flow velocity / flow direction calculating unit 24 (calculating unit) are provided on the output side. Further, in this case, the fluid measuring instrument 80 includes a display unit that displays the flow velocity and flow direction of the fluid calculated by the flow velocity / flow direction calculation unit 24 and / or a memory unit that stores data on the flow velocity and flow direction of the fluid. Also good.

  When the fluid measuring device 80 is used as a flow meter, the fluid measuring device 80 is further provided on the output side of the averaging circuit unit 81 as in the flow meter 30 (FIG. 7) described in the first embodiment. In addition, an addition circuit unit 31 and a flow rate calculation unit 34 (calculation unit) are provided. Further, in this case, the fluid measuring instrument 80 may include a display unit that displays the fluid flow rate calculated by the flow rate calculation unit 34 and / or a memory unit that stores fluid flow rate data.

  Further, when the fluid measuring device 80 is used as a fluid measuring device capable of measuring the flow velocity, flow direction, and flow rate of the fluid, the fluid measuring device is similar to the fluid measuring device 50 (FIG. 10) described in the first embodiment. Further, on the output side of the averaging circuit unit 81, the device 80 includes a differential circuit unit 21, a flow velocity flow direction calculation unit 24 (first calculation unit), an addition circuit unit 31, and a flow rate calculation unit 34 (second calculation). Part). In this case, the fluid measuring device 80 may include a display unit that displays the measured flow state (flow velocity, flow direction, and flow rate) and / or a memory unit that stores data on the fluid flow state.

  In the fluid sensor 70 of the present embodiment, four voltage signals VA to VD are output for each sensor element 77 as described above. Therefore, from the fluid sensor 70 including a plurality of sensor elements 77, the same number of voltage signals VA as the number of sensor elements 77 are output in parallel to the averaging circuit unit 81 as shown in FIG. Similarly, the fluid sensor 70 outputs the same number of voltage signals VB to VD as the number of sensor elements 77 to the averaging circuit unit 81 in parallel.

  The averaging circuit unit 81 calculates the average voltage signal VAm by averaging the same number of voltage signals VA output from the fluid sensor 70 as the number of sensor elements 77. Further, the averaging circuit unit 81 calculates the average voltage signal VBm by averaging the same number of voltage signals VB output from the fluid sensor 70 as the number of sensor elements 77. Further, the averaging circuit unit 81 calculates the average voltage signal VCm by averaging the same number of voltage signals VC output from the fluid sensor 70 as the number of sensor elements 77. Further, the averaging circuit unit 81 calculates the average voltage signal VDm by averaging the same number of voltage signals VD output from the fluid sensor 70 as the number of sensor elements 77. Then, the averaging circuit unit 81 outputs the calculated four average voltage signals VAm to VDm to the corresponding four input terminals of the differential circuit unit 21 and / or the addition circuit unit 31, respectively.

  Thereafter, the fluid measuring instrument 80 calculates the flow velocity, flow direction and / or flow rate of the fluid based on the four average voltage signals VAm to VDm output from the averaging circuit unit 81 in the same manner as in the first embodiment. To do. In this embodiment, the fluid flow velocity, flow direction, and / or flow rate are measured in this way.

  In the fluid sensor 70 and the fluid measuring instrument 80 of the present embodiment described above, the following effects are obtained.

  Since the fluid sensor 70 of this embodiment has a simple configuration in which a plurality of protrusions 71a are provided on the piezoelectric element portion 72, the fluid sensor 70 can be manufactured at low cost. Therefore, according to the present embodiment, similarly to the first embodiment, it is possible to provide a fluid sensor 70 having a simpler configuration and at a low cost, and a fluid measuring instrument including the fluid sensor 70.

  In the present embodiment, the size of each protrusion 71a arranged on the piezoelectric element portion 72 can be further reduced. Therefore, the thickness of the fluid sensor 70 can be further reduced (made into a sheet), and the fluid sensor 70 can be downsized.

  Further, in the fluid measuring instrument 80 of the present embodiment, as in the first embodiment, the fluid flow velocity and flow direction are based on the voltage signal output from the fluid sensor 70 every moment (for example, at intervals of several milliseconds or less). And the flow rate can be determined. Therefore, in the fluid measuring instrument of the present embodiment, it is possible to measure the fluid flow state in real time compared to the conventional case.

  Furthermore, in this embodiment, the voltage signals output from the plurality of sensor elements 77 are averaged to calculate the fluid state (flow velocity, flow direction, flow rate, etc.). Therefore, in this embodiment, the influence of disturbance (noise) can be further reduced, and the fluid state (flow velocity, flow direction, flow rate, etc.) can be measured with higher accuracy.

[Modification 3]
In the second embodiment, the configuration example in which the plurality of protrusions 71a are two-dimensionally arranged on one piezoelectric element portion 72 has been described. However, the present invention is not limited to this. For example, a plurality of fluid sensors 10 according to the first embodiment may be prepared, and the plurality of fluid sensors 10 may be arranged two-dimensionally. Further, for example, a single protruding sheet obtained by integrating a plurality of protruding portions may be arranged on one piezoelectric element portion 72. An example (Modification 3) is shown in FIG.

  FIG. 16 is a schematic cross-sectional view of a protruding sheet used in the fluid sensor of the third modification. In FIG. 16, a partial cross section of the protruding sheet 90 is shown to simplify the description.

  The protrusion sheet 90 has a plurality of protrusions 91 (protrusion members) formed continuously on one surface thereof. In this example, the vicinity of the bottoms of the side surfaces facing each other in the adjacent protrusions 91 are connected by the connection part 92 having a predetermined thickness t. Note that the thickness t of the connecting portion 92 is preferably as thin as possible. For example, the thickness Δt of the connecting portion 92 can be formed to be about 20 to 100 μm.

  In the configuration of this example, the protruding sheet 90 can be manufactured using a conventional molding method. In the configuration of this example, the plurality of protrusions 91 can be regularly arranged on the piezoelectric element portion simply by sticking the protrusion sheet 90 on the piezoelectric element portion. Therefore, in this example, the fluid sensor can be manufactured at a lower cost and more easily.

  DESCRIPTION OF SYMBOLS 1,71a ... Projection part, 2,72 ... Voltage element part, 3 ... Piezoelectric sheet, 4 ... Electrode pair group 10,70 ... Fluid sensor, 20 ... Flow velocity direction meter, 21 ... Differential circuit part, 22, 23 ... Differential amplifier, 24 ... flow velocity flow direction calculation unit, 30 ... flow meter, 31 ... addition circuit unit, 32 ... filter circuit unit, 33 ... adder, 34 ... flow rate calculation unit, 41,74 ... upper electrode group, 41A, 76A ... 1st upper electrode, 41B, 76B ... 2nd upper electrode, 41C, 76C ... 3rd upper electrode, 41D, 76D ... 4th upper electrode, 42, 75 ... lower electrode group, 42A ... 1st lower electrode, 42B ... 2nd lower electrode, 42C ... 3rd lower electrode, 42D ... 4th lower electrode, 50, 80 ... Fluid measuring instrument, 71 ... Projection group, 76 ... Upper electrode part, 77 ... Sensor element, 81 ... Averaging circuit, PA , PB, PC, PD ... Piezoelectric elements

Claims (12)

A piezoelectric member, a first electrode pair composed of a pair of first electrodes formed at positions facing each other across the piezoelectric member, and a pair of second electrodes formed at a position opposed to each other across the piezoelectric member A piezoelectric element having a second electrode pair formed at a predetermined distance from the first electrode pair in a first direction;
A protrusion member provided on one surface of the piezoelectric element portion,
The width of the surface of the protruding member on the piezoelectric element portion side in the first direction is larger than the predetermined distance, and the center of the surface of the protruding member on the piezoelectric element portion side is between the first and second electrode pairs. Fluid measurement sensor located on the same axis as the center. The piezoelectric element portion further includes a third electrode pair including a pair of third electrodes formed at positions facing each other across the piezoelectric member, and a pair formed at positions facing each other across the piezoelectric member. A fourth electrode pair comprising a fourth electrode and formed apart from the third electrode pair by a predetermined distance in a second direction orthogonal to the first direction;
The fluid measurement sensor according to claim 1, wherein the third electrode pair and the fourth electrode pair are formed at positions symmetrical with respect to a center between the first and second electrode pairs. A plurality of the protruding members;
A plurality of the protruding members are arranged on the one surface of the piezoelectric element portion,
The fluid measurement sensor according to claim 2, wherein the first to fourth electrode pairs are provided for each protrusion member. The fluid measurement sensor according to claim 3, wherein the plurality of protruding members are integrally formed. The shape of the protruding member is a square pyramid whose surface on the piezoelectric element portion side is a square,
The first direction coincides with one opposite side direction of the surface of the protruding member on the piezoelectric element portion side,
The fluid measurement sensor according to any one of claims 2 to 4, wherein the second direction coincides with the opposite side direction of the surface of the protruding member on the piezoelectric element portion side. A piezoelectric member, a first electrode pair composed of a pair of first electrodes formed at positions facing each other across the piezoelectric member, and a pair of second electrodes formed at a position opposed to each other across the piezoelectric member And a piezoelectric element portion having a second electrode pair formed at a predetermined distance in the first direction with respect to the first electrode pair, and a protruding member provided on one surface of the piezoelectric element portion. The width in the first direction of the surface of the protruding member on the piezoelectric element portion side is larger than the predetermined distance, and the center of the surface of the protruding member on the piezoelectric element portion side is the first and second electrode pairs. A fluid measurement sensor located coaxially with the center between,
A differential circuit that generates a first difference signal between a first voltage signal generated in the first electrode pair and a second voltage signal generated in the second electrode pair by pressure applied to the protruding member from the fluid. And
A fluid measuring instrument comprising: a calculation unit that calculates at least one of a flow velocity and a flow direction of the fluid based on the first difference signal generated by the differential circuit unit. The shape of the protruding member is a square pyramid whose surface on the piezoelectric element portion side is a square,
The piezoelectric element portion further includes a third electrode pair including a pair of third electrodes formed at positions facing each other across the piezoelectric member, and a pair formed at positions facing each other across the piezoelectric member. A fourth electrode pair comprising a fourth electrode and formed apart from the third electrode pair by a predetermined distance in a second direction orthogonal to the first direction;
The third electrode pair and the fourth electrode pair are formed at positions symmetrical with respect to the center between the first and second electrode pairs;
The first direction coincides with one opposite side direction of the surface of the protruding member on the piezoelectric element portion side, and the second direction is the other opposite side direction of the surface of the protruding member on the piezoelectric element portion side. Matches
The differential circuit section further includes a third voltage signal generated in the third electrode pair and a fourth voltage signal generated in the fourth electrode pair due to pressure applied from the fluid to the protruding member. Generating a second difference signal;
The fluid measuring device according to claim 6, wherein the calculation unit calculates at least one of a flow velocity and a flow direction of the fluid based on the first and second difference signals generated by the differential circuit unit. A plurality of the protruding members;
A plurality of the protruding members are arranged on the one surface of the piezoelectric element portion,
The fluid measuring instrument according to claim 7, wherein the first to fourth electrode pairs are provided for each protruding member. A piezoelectric member, a first electrode pair composed of a pair of first electrodes formed at positions facing each other across the piezoelectric member, and a pair of second electrodes formed at a position opposed to each other across the piezoelectric member And a piezoelectric element portion having a second electrode pair formed at a predetermined distance in the first direction with respect to the first electrode pair, and a protruding member provided on one surface of the piezoelectric element portion. The width in the first direction of the surface on the piezoelectric element portion side of the protruding member is larger than the predetermined distance, and the center of the surface on the piezoelectric element portion side of the protruding member is the first and second electrode pairs. A fluid measurement sensor located coaxially with the center between,
An adder circuit for generating a sum signal of a first voltage signal generated in the first electrode pair and a second voltage signal generated in the second electrode pair by a pressure applied to the protruding member from a fluid;
A fluid measuring instrument comprising: a calculating unit that calculates a flow rate of the fluid based on the sum signal generated by the adding circuit unit. The shape of the protruding member is a square pyramid whose surface on the piezoelectric element portion side is a square,
The piezoelectric element portion further includes a third electrode pair including a pair of third electrodes formed at positions facing each other across the piezoelectric member, and a pair formed at positions facing each other across the piezoelectric member. A fourth electrode pair comprising a fourth electrode and formed apart from the third electrode pair by a predetermined distance in a second direction orthogonal to the first direction;
The third electrode pair and the fourth electrode pair are formed at positions symmetrical with respect to the center between the first and second electrode pairs;
The first direction coincides with one opposite side direction of the surface of the protruding member on the piezoelectric element portion side, and the second direction is the other opposite side direction of the surface of the protruding member on the piezoelectric element portion side. Matches
The adding circuit unit is configured to generate the first voltage signal generated in the first electrode pair by the pressure applied to the projecting member from the fluid, the second voltage signal generated in the second electrode pair, Generating a sum signal of a third voltage signal generated at the third electrode pair and a fourth voltage signal generated at the fourth electrode pair;
The fluid measuring device according to claim 9, wherein the calculation unit calculates a flow rate of the fluid based on the sum signal generated by the addition circuit unit. A plurality of the protruding members;
A plurality of the protruding members are arranged on the one surface of the piezoelectric element portion,
The fluid measuring instrument according to claim 10, wherein the first to fourth electrode pairs are provided for each protruding member. A piezoelectric member, a first electrode pair composed of a pair of first electrodes formed at positions facing each other across the piezoelectric member, and a pair of second electrodes formed at a position opposed to each other across the piezoelectric member And a piezoelectric element portion having a second electrode pair formed at a predetermined distance in the first direction with respect to the first electrode pair, and a protrusion member provided on one surface of the piezoelectric element portion. The width in the first direction of the surface on the piezoelectric element portion side of the protruding member is larger than the predetermined distance, and the center of the surface on the piezoelectric element portion side of the protruding member is the first and second electrode pairs. A fluid measurement sensor located coaxially with the center between,
A differential circuit that generates a first difference signal between a first voltage signal generated in the first electrode pair and a second voltage signal generated in the second electrode pair by pressure applied to the protruding member from the fluid. And
A first calculation unit that calculates at least one of a flow velocity and a flow direction of the fluid based on the first difference signal generated by the differential circuit unit;
An adder circuit for generating a sum signal of the first voltage signal and the second voltage signal;
A fluid measuring instrument comprising: a second calculation unit that calculates a flow rate of the fluid based on the sum signal generated by the addition circuit unit.

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