JP7032189B2 - Clamp-on type ultrasonic flow sensor - Google Patents

Description

The present invention relates to a clamp-on type ultrasonic flow rate sensor that calculates the flow rate of a fluid flowing in a pipe.

A clamp-on type ultrasonic flow sensor capable of calculating the flow rate of a fluid flowing in a pipe while being attached to the pipe by a clamp member is known (see, for example, Patent Document 1). The clamp-on type ultrasonic flow sensor (ultrasonic flow switch) of Patent Document 1 includes a pair of ultrasonic elements that transmit and receive ultrasonic waves. One ultrasonic element transmits ultrasonic waves to the fluid flowing in the pipe, and the other ultrasonic element receives ultrasonic waves passing through the fluid. The flow rate of the fluid is calculated based on the ultrasonic waves transmitted and received by the pair of ultrasonic elements.

Japanese Unexamined Patent Publication No. 2016-217733

In the clamp-on type ultrasonic flow sensor, the ultrasonic wave that reaches from one ultrasonic element to the other ultrasonic element contains a component that propagates in the peripheral wall of the pipe without passing through the fluid. Such components are unnecessary components that do not have information about the flow rate of the fluid. When the unnecessary component of ultrasonic waves is large, it becomes difficult to accurately calculate the flow rate of the fluid. Therefore, it is necessary to separate the ultrasonic component passing through the fluid from the unnecessary component and receive it.

Here, when the diameter of the pipe is large, the pair of ultrasonic elements can be arranged apart from each other. Further, the propagation speed of ultrasonic waves in a resin material is smaller than the propagation speed of ultrasonic waves in a metal material. Further, the attenuation rate of ultrasonic waves in the resin material is larger than the attenuation rate of ultrasonic waves in the metal material. Therefore, when the diameter of the pipe is large or the pipe is made of a resin material, it is easy to receive the ultrasonic component passing through the fluid separately from the unnecessary component temporally or spatially. A pair of ultrasonic elements can be arranged in the space.

However, when the diameter of the pipe is small and the pipe is made of a metal material, a pair of ultrasonic elements should be arranged so that the ultrasonic component passing through the fluid is separated from the unnecessary component and received. Is not easy. Therefore, it is not possible to calculate the flow rate of the fluid flowing in the metal pipe having a small diameter.

An object of the present invention is to provide a clamp-on type ultrasonic flow rate sensor capable of calculating the flow rate of a fluid flowing in a metal pipe having a small diameter.

(1) The clamp-on type ultrasonic flow sensor according to the present invention is a clamp-on type ultrasonic flow sensor that measures the flow rate of a fluid flowing in a pipe, and has a first transmission / reception surface capable of transmitting and receiving ultrasonic waves. It has an ultrasonic element and a pipe contact surface that contacts the pipe, and has a propagation path that propagates ultrasonic waves transmitted from the transmission / reception surface of the first ultrasonic element to the pipe, supports the pipe, and has a pipe contact surface. A clamp member that supports a propagation path so as to be arranged along the axial direction of the pipe, a second ultrasonic element capable of transmitting and receiving ultrasonic waves between the first ultrasonic element across the pipe, and a second ultrasonic element. A flow rate calculation unit that calculates the flow rate of the fluid flowing in the pipe based on the ultrasonic waves transmitted and received between the first ultrasonic element and the second ultrasonic element, and the ultrasonic wave in the peripheral wall of the pipe is attenuated. It is formed of an elastic body and has a damping material that surrounds the pipe contact surface in the circumferential direction and the axial direction of the pipe. It is provided so that the incident angle of the ultrasonic shear wave with respect to the axial center direction is equal to or higher than the critical angle, and the transmission / reception surface of the first ultrasonic element is provided in the axial center direction. A second width smaller than the first width in the width direction, having a first width in the width direction orthogonal to the inclination direction and having a substantially rectangular shape in the pipe contact surface of the elastic fluid included in the propagation path. The length of the pipe contact surface in the axial direction is larger than the length of the transmission / reception surface in the direction orthogonal to the width direction.

In this clamp-on type ultrasonic flow sensor, ultrasonic waves transmitted from the transmission / reception surface of the first ultrasonic element are propagated to the pipe by a propagation path. The propagation path is supported by the pipe by the clamp member so that the pipe contact surface is in contact with the pipe and is arranged along the axial direction of the pipe. The propagation path includes the wedge material and the elastic couplant , and is provided so that the incident angle of the ultrasonic shear wave in the axial direction is equal to or higher than the critical angle. Therefore, the ultrasonic waves emitted from the contact surface of the pipe are totally reflected by the pipe and hardly penetrate into the peripheral wall of the pipe.

According to the above configuration, ultrasonic waves are excited in the peripheral wall of the pipe by vibration, and the excited ultrasonic waves are used to sandwich the pipe between the first ultrasonic element and the second ultrasonic element. Can send and receive ultrasonic waves. In this case, unnecessary components of ultrasonic waves transmitted and received between the first ultrasonic element and the second ultrasonic element are reduced by propagating in the peripheral wall of the pipe without passing through the fluid. Therefore, it becomes easy to calculate the flow rate of the fluid flowing in the pipe based on the ultrasonic waves transmitted and received between the first ultrasonic element and the second ultrasonic element.

Here, when the width of the transmission / reception surface of the first ultrasonic element is large, the intensity of the ultrasonic wave transmitted in the inclined direction can be increased. On the other hand, as the width of the portion of the pipe irradiated with ultrasonic waves increases, the unnecessary components of the ultrasonic waves increase. Therefore, a width changing portion is provided in the propagation path so that the width of the pipe contact surface is smaller than the width of the transmission / reception surface of the first ultrasonic element. As a result, it is possible to reduce unnecessary components of the ultrasonic wave while increasing the intensity of the ultrasonic wave transmitted in the inclined direction. As a result, the flow rate of the fluid flowing in the metal pipe having a small diameter can be calculated.

( 2 ) The first width may be 5 times or more the thickness of the first ultrasonic element in the tilting direction. In this case, the intensity of the ultrasonic wave transmitted from the first ultrasonic element in the inclined direction can be sufficiently increased.

( 3 ) The second width may be one-third or less of the outer diameter of the pipe. In this case, it is possible to sufficiently reduce unnecessary components of ultrasonic waves transmitted and received between the first ultrasonic element and the second ultrasonic element by propagating in the peripheral wall of the pipe without passing through the fluid. can.

( 4 ) The first ultrasonic element may be configured to transmit ultrasonic waves by vibrating at a unique resonance frequency. In this case, the intensity of the ultrasonic wave transmitted from the first ultrasonic element can be easily increased.

( 5 ) The first ultrasonic element may be formed so that the product of the ultrasonic frequency displayed in megahertz units and the thickness of the peripheral wall of the pipe displayed in millimeters is 2 or more. .. In this case, the fluctuation of the phase velocity of the ultrasonic wave excited in the peripheral wall of the pipe by the vibration is prevented. This makes it possible to calculate the flow rate of the fluid more accurately.

( 6 ) The first ultrasonic element may be formed so that the product of the ultrasonic frequency displayed in megahertz units and the thickness of the peripheral wall of the pipe displayed in millimeters is 6 or less. .. In this case, it is prevented that the surface wave of the ultrasonic wave excited in the peripheral wall of the pipe becomes dominant due to the vibration. This makes it possible to increase the intensity of the ultrasonic waves transmitted and received between the first ultrasonic element and the second ultrasonic element.

( 7 ) The peripheral wall of the pipe contains an excited region where the longitudinal waves of ultrasonic waves emitted from the pipe contact surface of the propagation path collide, and the excited region of the pipe passes through the fluid flowing in the pipe and is a second. The ultrasonic waves directed toward the ultrasonic element may be excited. In this case, the flow rate of the fluid flowing in the pipe can be calculated based on the ultrasonic waves generated from the excited region of the pipe.

( 8 ) The damping material may be configured to hold the position and orientation of the elastic coplant. According to this configuration, even when the width change portion is formed in the elastic coplant and the portion having the second width in the elastic coplant is in contact with the pipe, the change in the width of the portion is restricted. Therefore, the pipe can be easily irradiated with ultrasonic waves having a small width. In addition, bending, meandering and deformation of the portion are prevented. This makes it possible to accurately calculate the flow rate of the fluid flowing in the metal pipe having a small diameter.

( 9 ) The clamp-on type ultrasonic flow sensor may further include a pressing member that presses the damping material against the pipe. In this case, the damping material is sufficiently pressed against the pipe, so that the ultrasonic waves propagating in the peripheral wall of the pipe are sufficiently attenuated. This makes it possible to calculate the flow rate of the fluid more accurately.

( 10 ) The pressing member may be configured to hold the position and orientation of the elastic coplant. According to this configuration, even when a width change portion is formed in the elastic coplant and a portion having a second width in the elastic coplant is in contact with the pipe, the change in the width of the portion is restricted. Therefore, the pipe can be easily irradiated with ultrasonic waves having a small width. In addition, bending, meandering and deformation of the portion are prevented. This makes it possible to accurately calculate the flow rate of the fluid flowing in the metal pipe having a small diameter.

( 11 ) The pressing member may be formed of a metal member and may be arranged between the pipe and a portion of the surface of the elastic couplant facing the pipe, excluding the pipe contact surface, in the inclined direction. In this case, ultrasonic waves having a small width can be more reliably applied to the pipe.

( 12 ) The transmission / reception surface of the first ultrasonic element has the first length in the length direction orthogonal to the inclination direction and the width direction, and the pipe contact surface of the propagation path is the first in the axial direction. May have a second length greater than the length of. According to this configuration, even when the ultrasonic wave is transmitted in the inclined direction, the ultrasonic wave can be applied to the pipe from the pipe contact surface over a sufficiently large region in the axial direction.

( 13 ) The outer diameter of the pipe may be 2 mm or more and 20 mm or less. According to this configuration, the flow rate of the fluid can be calculated even when the outer diameter of the metal pipe is sufficiently small.

According to the present invention, it is possible to calculate the flow rate of the fluid flowing in the metal pipe having a small diameter.

It is external perspective view of the flow rate sensor which concerns on one Embodiment of this invention. It is sectional drawing which shows the internal structure of the head part of FIG. It is a figure for demonstrating the calculation method of the flow rate in the flow rate sensor of FIG. It is a schematic cross-sectional view which shows the detail of a sensor head. 4 is a cross-sectional view taken along the line AA of the sensor head of FIG. It is a schematic cross-sectional view which shows the internal structure of the head part in the modification. It is a figure for demonstrating the process of attaching a head part to a pipe. It is a figure for demonstrating the process of attaching a head part to a pipe. It is a schematic cross-sectional view which shows the inside of the clamp member in the state which a pipe is not attached. It is a schematic cross-sectional view which shows the inside of the clamp member in the state which a pipe is attached. It is a schematic cross-sectional view which shows the inside of the clamp member in the state which a pipe is attached. It is a block diagram which shows the internal structure of the relay part and the main body part of FIG. It is sectional drawing which shows the 1st to 4th modification of the sensor head.

(1) Schematic Configuration of Clamp-On Type Ultrasonic Flow Sensor A clamp-on type ultrasonic flow sensor (hereinafter abbreviated as a flow sensor) according to an embodiment of the present invention will be described with reference to the drawings. Further, in the following description, the direction along the central axis of the pipe is referred to as the axial center direction. The direction along the peripheral wall of the pipe is called the circumferential direction. The direction tilted by a predetermined angle with respect to the axial center direction is called the tilt direction. The direction orthogonal to the axial direction and the tilt direction is called the width direction. The direction orthogonal to the inclination direction and the width direction is called the length direction.

FIG. 1 is an external perspective view of a flow rate sensor according to an embodiment of the present invention. As shown in FIG. 1, the flow rate sensor 1 according to the present embodiment is composed of a head portion 100, a relay portion 200, and a main body portion 300. The head portion 100 includes two sensor heads 110 and 120 and two clamp members 130 and 140. Further, the head portion 100 further includes two mounting sheet metals 150 and 160 for mounting a part of the sensor heads 110 and 120 to the clamp members 130 and 140. The clamp members 130 and 140 are formed of, for example, a metal material.

The sensor heads 110 and 120 are attached to the outer peripheral surface of the peripheral wall of the pipe P in a state of being held by the clamp members 130 and 140, respectively. In the present embodiment, the pipe P is a metal pipe having a relatively small diameter. The diameter (outer diameter) of the pipe P is, for example, 2 mm or more and 20 mm or less. A fluid flows in the pipe P.

The head cable CA1 is connected between the sensor head 110 and the relay unit 200, and the head cable CA2 is connected between the sensor head 120 and the relay unit 200. A relay cable CA3 is connected between the relay unit 200 and the main body unit 300. One end of the main body cable CA4 is further connected to the main body portion 300. The other end of the main body cable CA4 is connected to an external device (not shown) of the flow rate sensor 1. The external device is, for example, a personal computer or a programmable logic controller. Details of the relay unit 200 and the main body unit 300 will be described later.

FIG. 2 is a cross-sectional view showing the internal configuration of the head portion 100 of FIG. As shown in FIG. 2, the sensor head 110 includes a casing 111, an ultrasonic element 112, a wedge material 113, an elastic pumpplant 114, a leaf spring 115, a damping material 116, and an indicator lamp 117.

The casing 111 is formed of, for example, a resin material and has an elongated shape (in this example, a substantially rectangular parallelepiped shape) extending along the axial direction. Hereinafter, in the casing 111, the direction facing the pipe P is defined as the downward direction, and the opposite direction is defined as the upward direction. The vertical direction of the casing 111 is orthogonal to the axial direction and the width direction. A window portion W formed of a transparent member is formed on the upper surface of the casing 111. An opening H1 is formed in the lower part of the casing 111.

The ultrasonic element 112 has a transmission / reception surface A1 capable of transmitting / receiving ultrasonic waves. The wedge material 113 is made of a material that is non-metal and has high rigidity and high acoustic permeability. The wedge material 113 is preferably formed of a material having high environmental resistance. The wedge material 113 has a joint surface B1 that faces in an inclined direction, and has an entrance / exit surface C1 that faces downward at the bottom. The transmission / reception surface A1 of the ultrasonic element 112 is bonded to the bonding surface B1 of the wedge material 113 by an acoustic bonding agent (not shown).

The wedge material 113 is attached to the lower part of the casing 111 so as to close the opening H1 via a sealing member (not shown). As a result, a space in which liquids such as water and oil cannot enter is formed inside the casing 111, and the ultrasonic element 112 is housed inside the casing 111. The entrance / exit surface C1 of the wedge material 113 slightly protrudes downward from the opening H1 of the casing 111. In this state, the casing 111 is attached to the mounting sheet metal 150 by the two mounting screws 151. The inside of the casing 111 is filled with a resin member.

The elastic coplant 114 has a solid shape and is formed of a soft elastic material such as a polymer rubber or a gel-like substance. The hardness of the elastic couplant 114 is, for example, 20 to 40 degrees. At the lower part of the elastic couplant 114, a protrusion T1 is formed so as to project downward so as to be in contact with the pipe P over a predetermined length in the axial direction.

The elastic coplant 114 is arranged so as to be in contact with the entrance / exit surface C1 of the wedge material 113 and the pipe P, thereby matching the acoustic impedance of the wedge material 113 and the pipe P. The contact surface with the wedge material 113 in the elastic couplant 114 is called the wedge contact surface D1. Further, the contact surface with the pipe P in the protruding portion T1 of the elastic couplant 114 is referred to as a pipe contact surface E1.

The leaf spring 115 is arranged so as to surround the protrusion T1 in the circumferential direction and the axial direction, and is attached to the clamp member 130 together with the elastic pumpplant 114 by two mounting screws 134. The damping material 116 is formed of, for example, an elastic body that attenuates ultrasonic waves in the pipe P, and is arranged between the leaf spring 115 and the pipe P so as to surround the protrusion T1 in the circumferential direction and the axial direction.

As will be described later, the flow rate sensor 1 operates as a flow rate switch that changes the state of the switching signal (on / off signal) to the external device based on whether or not the fluid is flowing in the pipe P at a flow rate equal to or higher than the threshold value. It is also possible. The indicator lamp 117 includes, for example, a plurality of light emitting diodes that emit light in different colors, and is lit or blinks in a plurality of types depending on the operating state of the flow rate switch, based on the control by the relay unit 200 of FIG.

In the present embodiment, the indicator lamp 117 lights up in green when the external device is on, and lights up in red when the external device is in the off state. The indicator lamp 117 may be turned on when the external device is on, and the indicator lamp 117 may be turned off when the external device is off. On the contrary, when the external device is in the on state, the indicator lamp 117 may be turned off, and when the external device is in the off state, the indicator lamp 117 may be turned on.

The indicator lamp 117 is arranged inside the casing 111 so as to be close to the window portion W. Thereby, the mode of operation of the indicator lamp 117 can be visually recognized from the outside of the casing 111 through the window portion W. The user can easily distinguish between the on state and the off state of the external device by visually recognizing the color or the lighting state of the indicator lamp 117.

The sensor head 120 includes a casing 121, an ultrasonic element 122, a wedge material 123, an elastic pumpplant 124, a leaf spring 125 and a damping material 126. The casing 121 has the same configuration as the casing 111 except that the window portion W is not formed. Therefore, the casing 121 is formed with an opening H2 similar to the opening H1.

The ultrasonic element 122 and the wedge material 123 have the same configurations as the ultrasonic element 112 and the wedge material 113, respectively. Therefore, the ultrasonic element 122 has a transmission / reception surface A2 similar to the transmission / reception surface A1. Further, the wedge material 123 has a joint surface B2 and an entrance / exit surface C2 similar to the joint surface B1 and the entrance / exit surface C1, respectively. The transmission / reception surface A2 of the ultrasonic element 122 is joined to the joint surface B2 of the wedge material 123. The casing 121 is attached to the mounting sheet metal 160 by two mounting screws 161 with the wedge material 123 attached.

The elastic coplant 124 has the same configuration as the elastic coplant 114. Therefore, the elastic couplant 124 has a protrusion T2, a wedge contact surface D2, and a pipe contact surface E2, which are similar to the protrusion T1, the wedge contact surface D1, and the pipe contact surface E1, respectively. The elastic coplant 124 is arranged so as to be in contact with the entrance / exit surface C2 of the wedge material 123 and the pipe P, thereby matching the acoustic impedance of the wedge material 123 and the pipe P.

The leaf spring 125 and the damping material 126 have the same configurations as the leaf spring 115 and the damping material 116, respectively. The leaf spring 125 is arranged so as to surround the protrusion T2 in the circumferential direction and the axial direction, and is attached to the clamp member 140 together with the elastic pumpplant 124 by two mounting screws 144. The damping material 126 is arranged between the leaf spring 125 and the pipe P so as to surround the protrusion T2 in the circumferential direction and the axial direction.

The mounting sheet metal 150 and the mounting sheet metal 160 are coupled to each other by four connecting screws 101 with the clamp member 130, the pipe P, and the clamp member 140 interposed therebetween. As a result, the sensor head 110 is attached to the clamp member 130 in a state where the elastic pumpplant 114 and the damping material 116 are pressed against the pipe P by the clamp member 130. Similarly, the sensor head 120 is attached to the clamp member 140 while the elastic pumpplant 124 and the damping material 126 are pressed against the pipe P by the clamp member 140.

(2) Flow rate calculation method FIG. 3 is a diagram for explaining a flow rate calculation method in the flow rate sensor 1 of FIG. In FIG. 3, the clamp members 130 and 140 and the mounting sheet metal 150 and 160 are not shown. As shown in FIG. 3, the ultrasonic element 112 and the ultrasonic element 122 are arranged in a state of being offset from each other in the axial direction.

The ultrasonic element 112 transmits ultrasonic waves in the inclined direction from the transmission / reception surface A1 based on the control by the relay unit 200 of FIG. The transmitted ultrasonic wave is incident on the wedge material 113 from the joint surface B1. After that, the ultrasonic wave propagates in the wedge material 113 and is transmitted from the entrance / exit surface C1. The ultrasonic waves transmitted from the input / exit surface C1 enter the elastic pumping 114 from the wedge contact surface D1, propagate in the elastic pumping 114, and then are emitted from the piping contact surface E1 of the protrusion T1 toward the piping P. To.

In the present embodiment, the wedge material 113 is formed with a joint surface B1 and an entrance / exit surface C1 so that the incident angle of the transverse wave (shear wave) of the ultrasonic wave in the axial direction is equal to or higher than the critical angle. In this case, the longitudinal and transverse waves of ultrasonic waves emitted from the pipe contact surface E1 are totally reflected by the peripheral wall P1 of the pipe P and hardly penetrate into the peripheral wall P1. On the other hand, the longitudinal wave of the ultrasonic wave collides with the outer peripheral surface of the peripheral wall P1, so that the guide wave is excited in the peripheral wall P1. The guide wave is an ultrasonic wave propagating in a direction parallel to the axial direction of the pipe P, and a plate wave, a surface wave, or the like exists. The guide wave has a plurality of resonance vibration modes, and the phase velocity and group velocity of the guide wave are characterized in that the vibration state differs depending on the product of the frequency of the ultrasonic wave and the thickness of the peripheral wall P1 and the resonance vibration mode.

When the guide wave in the peripheral wall P1 collides with the inner peripheral surface of the peripheral wall P1, the ultrasonic wave is excited so as to pass through the fluid and head toward the opposite peripheral wall P2 at a predetermined incident angle θ. The longitudinal wave of the ultrasonic wave that has passed through the fluid collides with the inner peripheral surface of the peripheral wall P2, so that the guide wave is excited in the peripheral wall P2. When the guide wave in the peripheral wall P2 collides with the outer peripheral surface of the peripheral wall P2, a longitudinal wave of ultrasonic waves directed from the pipe P to the pipe contact surface E2 of the elastic couplant 124 is excited.

The ultrasonic wave from the pipe P is incident on the protrusion T2 from the pipe contact surface E2, propagates in the elastic couplant 124, and is emitted from the wedge contact surface D2. The ultrasonic wave emitted from the wedge contact surface D2 is incident on the wedge material 123 from the inlet / output surface C2, then propagates in the wedge material 123, and is emitted from the joint surface B2. After that, the ultrasonic wave is received from the transmission / reception surface A2 of the ultrasonic element 122 based on the control by the relay unit 200.

As described above, the peripheral wall P1 is provided with an excited region R1 in which the longitudinal wave of the ultrasonic wave emitted from the ultrasonic element 112 collides with the peripheral wall P1. The excitation region R1 is a region that excites ultrasonic waves mainly passing through the fluid flowing in the pipe P and toward the ultrasonic element 122. In FIG. 3, the excited region R1 is illustrated by a hatch pattern.

Next, the ultrasonic element 122 transmits ultrasonic waves in the inclined direction from the transmission / reception surface A2 based on the control by the relay unit 200. The transmitted ultrasonic wave is incident on the wedge material 123 from the joint surface B2. After that, the ultrasonic wave propagates in the wedge material 123 and is transmitted from the entrance / exit surface C2. The ultrasonic waves transmitted from the input / output surface C2 enter the elastic pumping plant 124 from the wedge contact surface D2, propagate in the elastic pumping plant 124, and then are emitted from the piping contact surface E2 of the protrusion T2 toward the piping P. To.

In the present embodiment, the wedge material 123 is formed with a joint surface B2 and an entrance / exit surface C2 so that the incident angle of the transverse wave of the ultrasonic wave in the axial direction is equal to or higher than the critical angle. In this case, the longitudinal and transverse waves of ultrasonic waves emitted from the pipe contact surface E2 are totally reflected by the peripheral wall P2 of the pipe P and hardly penetrate into the peripheral wall P2. On the other hand, the longitudinal wave of the ultrasonic wave collides with the outer peripheral surface of the peripheral wall P2, so that the guide wave is excited in the peripheral wall P2.

When the guide wave in the peripheral wall P2 collides with the inner peripheral surface of the peripheral wall P2, ultrasonic waves are generated so as to pass through the fluid and head toward the opposite peripheral wall P1 at a predetermined incident angle θ. The longitudinal wave of the ultrasonic wave that has passed through the fluid collides with the inner peripheral surface of the peripheral wall P1, and the guide wave is excited in the peripheral wall P1. When the guide wave in the peripheral wall P1 collides with the outer peripheral surface of the peripheral wall P1, the longitudinal wave of ultrasonic waves directed from the pipe P to the pipe contact surface E1 of the elastic couplant 114 is excited.

The ultrasonic wave from the pipe P is incident on the protrusion T1 from the pipe contact surface E1, propagates in the elastic couplant 114, and is emitted from the wedge contact surface D1. The ultrasonic wave emitted from the wedge contact surface D1 is incident on the wedge material 113 from the inlet / outlet surface C1 and then propagates in the wedge material 113 and is emitted from the joint surface B1. After that, the ultrasonic wave is received from the transmission / reception surface A1 of the ultrasonic element 112 based on the control by the relay unit 200.

As described above, the peripheral wall P2 is provided with an excited region R2 in which the longitudinal wave of the ultrasonic wave emitted from the ultrasonic element 122 collides with the peripheral wall P2. The excitation region R2 is a region that mainly passes through the fluid flowing in the pipe P and excites ultrasonic waves toward the ultrasonic element 112. In FIG. 3, the excited region R2 is illustrated by a dot pattern.

The difference between the propagation time of the ultrasonic wave from the ultrasonic element 112 to the ultrasonic element 122 and the propagation time of the ultrasonic wave from the ultrasonic element 122 to the ultrasonic element 112 is called a time difference Δt. Based on the time difference Δt, the flow rate Q of the fluid flowing in the pipe P is calculated by the following equation (1). Here, d ₁ is the inner diameter of the pipe P, V _s is the velocity of the ultrasonic wave in the fluid, and θ is the incident angle of the ultrasonic wave in the fluid. K is a flow rate correction coefficient for converting the velocity of a fluid having a predetermined distribution in the cross section of the pipe P into an average velocity. The velocity V _s , the angle of incidence θ, and the flow rate correction coefficient K are known. _The user can set the inner diameter d1 of the pipe P by operating the main body portion 300 of FIG.

The flow rate sensor 1 can also operate as a flow rate switch. The user can set the flow rate threshold value by operating the main body 300. The main body 300 compares the flow rate Q calculated by the above equation (1) with the set threshold value, and outputs an on / off signal to the external device based on the comparison result. The on / off signal is a signal for switching between the on state and the off state of the external device connected to the main body 300 through the main body cable CA of FIG. The indicator lamp 117 of FIG. 2 is lit so that the on state and the off state of the external device can be discriminated from each other.

(3) Details of Head Unit FIG. 4 is a schematic cross-sectional view showing details of the sensor heads 110 and 120. FIG. 5 is a sectional view taken along line AA of the sensor heads 110 and 120 of FIG. In FIG. 4, the casings 111 and 121, the indicator lamp 117, the clamp members 130 and 140, and the mounting sheet metal 150 and 160 are not shown. In FIG. 5, the casings 111 and 121, the indicator lamps 117 and the mounting sheet metals 150 and 160 are not shown, and the sensor head 120 and the clamp members 130 and 140 are shown by dotted lines.

The ultrasonic element 112 is formed by a thin plate-shaped piezoelectric element. The thickness of the ultrasonic element 112 is t ₁ (FIG. 4). The width of the ultrasonic element 112 (transmission / reception surface A1) is w ₁ (FIG. 5). Here, the thickness and the width mean the sizes in the inclination direction and the width direction, respectively. The size (length) of the transmission / reception surface A1 in the length direction is L ₁ (FIG. 4). The length L ₁ may be substantially equal to the width w ₁ or may be larger than the width w ₁ . In FIG. 4, the thickness of the ultrasonic element 112 is shown to be larger than the actual thickness. The outer diameter of the pipe P is d ₂ , and the thickness of the peripheral wall is t ₂ .

An AC voltage (pulse voltage) near the natural frequency is applied to the ultrasonic element 112. As a result, the ultrasonic element 112 vibrates at a natural frequency (resonance frequency _fr ) and transmits ultrasonic waves having high intensity. Hereinafter, the product of the resonance frequency fr of the ultrasonic wave displayed in the unit of MHz (megahertz) and the thickness t ₂ of the peripheral wall displayed in the unit of mm (millimeter) is referred to as an f · _t product.

The ultrasonic element 112 is preferably formed so as to vibrate at a resonance frequency fr such that the f · _t product is 2 or more and 6 or less. By setting the f · t product to 2 or more, the fluctuation of the phase velocity of the guide wave in the peripheral wall is prevented. This makes it possible to calculate the flow rate of the fluid more accurately. Further, by setting the f · t product to 6 or less, it is possible to prevent the surface wave of the guide wave in the peripheral wall from becoming dominant. This makes it possible to generate ultrasonic waves having high intensity in the fluid.

Further, the ultrasonic element 112 is preferably formed so that the width w ₁ is 5 times or more the thickness t ₁ . In this case, the strength of the double resonance in the width direction with respect to the resonance in the tilt direction, which is the transmission direction of the ultrasonic wave, decreases. Thereby, the resonance characteristic in the inclination direction can be improved. The preferred configuration of the ultrasonic element 122 is the same as the preferred configuration of the ultrasonic element 112.

The width of the portion of the peripheral wall of the pipe P to be irradiated with ultrasonic waves (hereinafter referred to as the irradiation width) is preferably one-third or less of the outer diameter d ₂ of the pipe P. In this case, it is possible to further reduce the components of ultrasonic waves that propagate in the peripheral wall without passing through the fluid and are transmitted and received between the sensor heads 110 and 120. This makes it possible to calculate the flow rate of the fluid more accurately.

Here, as described above, the width w ₁ of the ultrasonic element 112 is preferably 5 times or more the thickness t ₁ . Further, in order to prevent the ultrasonic element 112 from being damaged, it is necessary to make the thickness t ₁ of the ultrasonic element 112 equal to or larger than a predetermined thickness. Therefore, the width w ₁ of the ultrasonic element 112 (transmission / reception surface A1) is larger than a predetermined width.

On the other hand, as described above, the irradiation width of the ultrasonic wave is preferably one-third or less of the outer diameter d ₂ of the pipe P. In the present embodiment, since the outer diameter d ₂ of the pipe P is relatively small (for example, 2 mm or more and 20 mm or less), the irradiation width of the ultrasonic wave is smaller than a predetermined width. As described above, when the pipe P is irradiated with ultrasonic waves transmitted from the _entire region of the width w1 of the transmission / reception surface A1, the above two preferable conditions cannot be compatible with each other.

Therefore, the elastic coplant 114 is provided with a propagation path for propagating the ultrasonic waves transmitted from the transmission / reception surface A1 of the ultrasonic element 112 to the pipe P. In the propagation path, a width changing portion V1 whose width changes between the wedge contact surface D1 and the pipe contact surface E1 is formed. In the present embodiment, the wedge contact surface D1 of the elastic coplant ₁₁₄ is formed so that the width is w1. On the other hand, the protrusion T1 and the pipe contact surface E1 are formed so that the width is w ₂ smaller than w ₁ . Specifically, the width w ₂ is one-third or less of the outer diameter d ₂ of the pipe P. That is, the width of the width changing portion V1 of the propagation path changes from _w1 to _w2 between the wedge contact surface D1 and the pipe contact surface E1.

In this configuration, ultrasonic waves having a large width w1 are incident on the elastic couplant ₁₁₄ from the wedge contact surface D1. After that, the ultrasonic wave propagates in the elastic coplant 114 and is emitted from the lower surface (emission surface) of the elastic coplant 114. Here, since the emission surface of the ultrasonic wave other than the pipe contact surface E1 is not in contact with the pipe P, the ultrasonic wave emitted from the emission surface is gradually attenuated and the pipe P is hardly irradiated. On the other hand, since the pipe contact surface E1 is in contact with the pipe P, the ultrasonic waves emitted from the pipe contact surface E1 are irradiated to the pipe P with almost no attenuation.

In particular, in the present embodiment, a leaf spring 115 formed of a metal member is arranged between the emission surface of ultrasonic waves excluding the pipe contact surface E1 and the pipe P. In this case, the ultrasonic waves emitted from the exit surface are blocked by the leaf spring 115. As a result, it is possible to more reliably prevent the pipe P from being irradiated with ultrasonic waves from the exit surface other than the pipe contact surface E1.

As described above, even when the ultrasonic wave is transmitted from the transmission / reception surface A1 of the ultrasonic element 112 having the large width w ₁ , the ultrasonic wave having the small width w ₂ can be irradiated to the pipe P. This makes it possible to achieve both of the above two preferable conditions. In the present embodiment, the width of the width changing portion V1 changes from w ₁ to w ₂ , but the present invention is not limited to this. _The width of the width changing portion V1 may change from _w3 to _w2 , which is different from w1 and _w2 . The width w ₃ may be larger than w ₁ or smaller than w ₁ .

The ultrasonic element 112 is arranged so as to transmit ultrasonic waves in the tilt direction. Therefore, the spread region of the ultrasonic wave in the axial direction is larger than the spread region of the ultrasonic wave transmitted in the direction orthogonal to the axial direction by the ultrasonic element 112. Therefore, it is preferable that the pipe contact surface E1 of the protruding portion T1 of the elastic couplant 114 is formed so that the length is L ₂ larger than L ₁ in the axial direction. As a result, ultrasonic waves can be applied to the pipe P from the pipe contact surface E1 over a sufficiently large area in the axial direction.

The configuration of the elastic coplant 124 is similar to that of the elastic coplant 114. Therefore, a width changing portion V2 similar to the width changing portion V1 is formed in the propagation path of the elastic coplant 124. Further, it is preferable that the pipe contact surface E2 of the protruding portion T2 of the elastic coplant 124 is formed so that the length is L ₂ larger than L ₁ in the axial direction.

The leaf spring 115 is formed with a rectangular slit S3 extending along the axial direction. The damping material 116 is formed with a rectangular slit S1 extending along the axial direction and overlapping the slit S3. The protrusion T1 of the elastic couplant 114 is fitted into the slit S3 of the leaf spring 115 and the slit S1 of the damping material 116. In this case, the protruding portion T1 is surrounded by the leaf spring 115 and the damping material 116 in the circumferential direction and the axial center direction while being in contact with the pipe P.

The leaf spring 115 holds the position and posture of the elastic coplant 114 with respect to the clamp member 130 by surrounding the protrusion T1 in a state of being attached to the clamp member 130. As a result, even when the protruding portion T1 having the small width w ₂ is pressed against the pipe P, the change in the width of the protruding portion T1 is restricted. Therefore, the pipe can be easily irradiated with ultrasonic waves having a small width _w2 . Further, while maintaining the width of the protruding portion T1, bending, meandering and deformation of the protruding portion T1 are prevented. This makes it possible to accurately calculate the flow rate of the fluid flowing in the pipe P.

The damping material 116 is attached to the pipe P in a state of surrounding the protrusion T1 and the excited region R1 in the circumferential direction, and is pressed against the pipe P. In this case, the vibration of the portion of the pipe P excluding the excitation region R1 is suppressed, and the ultrasonic waves propagating in the circumferential direction in the peripheral wall are attenuated by the damping material 116. As a result, it is possible to further reduce the components of ultrasonic waves that propagate in the peripheral wall without passing through the fluid and are transmitted and received between the sensor heads 110 and 120.

Further, the damping material 116 is attached to the pipe P in a state of surrounding the protrusion T1 and the excited region R1 in the axial direction, and is pressed against the pipe P. In this case, the vibration of the portion of the pipe P excluding the excitation region R1 is suppressed, and the ultrasonic wave propagating in the circumferential wall of the pipe P is attenuated by the damping material 116. Therefore, the guide wave propagating in the axial direction is prevented from being reflected by the end face of the peripheral wall in the axial direction and returning. Therefore, the returned guide wave does not excite the ultrasonic wave at an unnecessary timing. This makes it possible to calculate the flow rate of the fluid more accurately.

The configurations of the leaf spring 125 and the damping material 126 are the same as the configurations of the leaf spring 115 and the damping material 116, respectively. Therefore, the leaf spring 125 is formed with the slit S4 similar to the slit S3, and the damping material 126 is formed with the slit S2 similar to the slit S1. The protrusion T2 of the elastic pumpplant 124 is fitted into the slit S4 of the leaf spring 125 and the slit S2 of the damping material 126. As a result, the protruding portion T2 is surrounded by the leaf spring 125 and the damping material 126 in the circumferential direction and the axial center direction while being in contact with the pipe P. Further, the damping material 126 is attached to the pipe P in a state of surrounding the excited region R2 in the circumferential direction and the axial center direction, and is pressed against the pipe P.

FIG. 6 is a schematic cross-sectional view showing the internal configuration of the head portion 100 in the modified example. As shown in FIG. 6, the leaf spring 115 in the modified example is formed with a vertical wall portion W1 that surrounds the edge of the slit S3 and extends toward the pipe P. The vertical wall portion W1 surrounds the protruding portion T1 of the elastic pumpplant 114 while being fitted into the slit S1 of the damping material 116. In this case, the leaf spring 115 more firmly holds the position and orientation of the elastic coplant 114 with respect to the clamp member 130. This more reliably prevents bending, meandering and deformation of the protrusion T1.

Similarly, the leaf spring 125 in the modified example is formed with a vertical wall portion W2 that surrounds the edge of the slit S4 and extends toward the pipe P. The vertical wall portion W2 surrounds the protruding portion T2 of the elastic pumpplant 124 while being fitted into the slit S2 of the damping material 126.

(4) Attaching the head portion to the pipe FIG. 7 and FIG. 8 are diagrams for explaining a process of attaching the head portion 100 to the pipe P. As shown in FIG. 7, the elastic coplant 114 is arranged between the clamp member 130 and the leaf spring 115. Next, the leaf spring 115 is attached to the clamp member 130 by two mounting screws 134 in a state where the protruding portion T1 (FIGS. 4 and 5) of the elastic pumpplant 114 is fitted into the slit S3 of the leaf spring 115. The tip of the protruding portion T1 protrudes from the slit S3 of the leaf spring 115.

Subsequently, the damping material 116 is arranged so that the tip of the protruding portion T1 is fitted into the slit S1. The damping material 116 may be adhered to the leaf spring 115 with an adhesive or the like. In this case, the elastic capplant 114, the leaf spring 115 and the damping material 116 can be easily handled together with the clamp member 130.

Similarly, the elastic couplant 124 is arranged between the clamp member 140 and the leaf spring 125. Next, the leaf spring 125 is attached to the clamp member 140 by the two mounting screws 144 in a state where the protruding portion T2 of the elastic pumpplant 124 is fitted into the slit S4 (FIGS. 4 and 5) of the leaf spring 125. The tip of the protruding portion T2 protrudes from the slit S4 of the leaf spring 125.

Subsequently, the damping material 126 is arranged so that the tip of the protrusion T2 is fitted into the slit S2 (FIGS. 4 and 5). The damping material 126 may be adhered to the leaf spring 125 with an adhesive or the like. In this case, the elastic pumpplant 124, the leaf spring 125 and the damping material 126 can be easily handled integrally with the clamp member 140.

The clamp member 140 has a pair of vertical walls 141 extending in the axial direction and facing each other in the width direction, and a pair of vertical walls 142 facing the axial direction. Further, the clamp member 140 has a support portion 143 formed so as to be able to support the pipe P by coming into contact with the pipe P. On the surfaces (inner surfaces) of the pair of vertical walls 141 facing each other, a pair of temporary fixing members 145 for temporarily fixing the clamp member 140 to the pipe P is provided. The temporary fixing member 145 is formed of an elastic body such as a rubber member. In the present embodiment, the pair of temporary fixing members 145 are arranged so as to be offset from each other in the axial direction without facing each other in the width direction.

The clamp member 130 has a pair of vertical walls 131 extending in the axial direction and facing each other in the width direction, and a pair of vertical walls 132 facing in the axial direction. The pair of vertical walls 131 and the pair of vertical walls 141 correspond to each other. Similarly, the pair of vertical walls 132 and the pair of vertical walls 142 correspond to each other. Further, the clamp member 130 has a support portion 133 formed so as to be able to support the pipe P by coming into contact with the pipe P.

The pair of vertical walls 131 and the pair of vertical walls 132 guide the clamp member 130 when the clamp member 130 is attached to the pipe P. The pair of vertical walls 141 and the pair of vertical walls 142 guide the clamp member 140 when the clamp member 140 is attached to the pipe P. The guide of the clamp members 130 and 140 is performed by a pair of vertical walls 131 and 141 corresponding to each other and a pair of vertical walls 132 and 142 corresponding to each other.

A clearance is formed between the inner surface of the pair of vertical walls 131 and the outer surface of the pair of vertical walls 141 so that they can move in parallel with each other when facing each other and are restricted from tilting by a predetermined angle or more around the axial direction of the pipe P. It has a dimensional relationship as such. Similarly, the inner surface of the pair of vertical walls 132 and the outer surface of the pair of vertical walls 142 can move in parallel with each other when facing each other and are tilted by a predetermined angle or more in the pitching direction along the axial direction of the pipe P. It has a dimensional relationship such that a clearance is formed to regulate the fact.

The clamp member 140 is arranged so that the pipe P is located between the inner surfaces of the pair of vertical walls 141. In this case, the pair of temporary fixing members 145 come into contact with the pipe P. Further, the clamp member 130 is arranged so that the pair of vertical walls 141 are located between the inner surfaces of the pair of vertical walls 131 and the pair of vertical walls 142 are located between the inner surfaces of the pair of vertical walls 132. After that, the clamp member 130 and the clamp member 140 are sandwiched with respect to the pipe P by a pressing force equal to or higher than a predetermined value. In this state, a pair of temporary fixing screws 135 are screwed into the pair of temporary fixing members 145 of the clamp member 140 so as to penetrate the clamp member 130 in the vertical direction.

By the above procedure, the clamp members 130 and 140 are temporarily fixed to the pipe P together with the elastic pumpplants 114 and 124, the leaf springs 115 and 125 and the damping materials 116 and 126. In this case, the state in which the clamp member 130 and the clamp member 140 are pressed is maintained by the pair of temporary fixing members 145 and the pair of temporary fixing screws 135. As a result, the clamp members 130 and 140 are prevented from falling off from the pipe P. Further, the frictional force generated between the clamp members 130 and 140 and the pipe P prevents the clamp members 130 and 140 from slipping in the axial direction.

Each temporary fixing member 145 is formed with a screw hole having a diameter slightly smaller than the diameter of the threaded portion of the corresponding temporary fixing screw 135. When the clamp members 130 and 140 are clamped to the pipe P with a pressing force equal to or higher than a predetermined value, each temporary fixing screw 135 is inserted into the temporary fixing member 145 while expanding the screw hole of the corresponding temporary fixing member 145. .. In this case, the frictional force generated between the temporary fixing screw 135 and the temporary fixing member 145 makes it difficult for the temporary fixing screw 135 to come off from the temporary fixing member 145. As a result, it is possible to maintain the state in which the clamp members 130 and 140 are sandwiched between the pipes P with a predetermined or higher pressing force.

The length of the threaded portion of the temporary set screw 135 inserted into the screw hole of the temporary fixing member 145 differs depending on the outer diameter of the pipe P. Specifically, when the outer diameter of the pipe P is large, the insertion portion of the temporary set screw 135 is short, and when the outer diameter of the pipe P is small, the insertion portion of the temporary set screw 135 is long. Therefore, the screw hole of the temporary setting member 145 can generate a sufficient frictional force even when the insertion portion of the temporary setting screw 135 is the shortest, and the tip of the temporary setting screw 135 is provided even when the insertion portion of the temporary setting screw 135 is the longest. Is formed to a length that does not contact the bottom of the screw hole of the temporary fixing member 145. This makes it possible to temporarily fix the clamp members 130 and 140 to the pipes P having various outer diameters.

After that, as shown in FIG. 8, the mounting sheet metals 150 and 160 are arranged so as to sandwich the clamp members 130 and 140 temporarily fixed to the pipe P. Here, as shown in FIG. 2, the casing 111 is attached to the mounting sheet metal 150 by two mounting screws 151. Further, the casing 121 is attached to the mounting sheet metal 160 by two mounting screws 161.

In this state, the mounting sheet metal 150 and the mounting sheet metal 160 are connected to each other by four connecting screws 101 with the pipe P sandwiched so that the mounting sheet metal 150 is attached to the clamp member 130 and the mounting sheet metal 160 is attached to the clamp member 140. Will be done. As a result, the sensor head 110 is attached to the pipe P by the clamp member 130 while the pipe P is supported by the support portion 133 of the clamp member 130. Further, the sensor head 120 is attached to the clamp member 140 while the pipe P is supported by the support portion 143 of the clamp member 140.

In the state where the sensor head 110 is attached to the pipe P, the elastic pumpplant 114 and the damping material 116 are pressed against the pipe P by the clamp member 130. Further, the protruding portion T1 of the elastic couplant 114 is arranged along the axial direction while being in contact with the pipe P. When the support portion 133 of the clamp member 130 comes into contact with the pipe P, the amount of crushing of the elastic pumpplant 114 (protruding portion T1) is regulated. Therefore, the elastic couplant 114 can be uniformly pressed regardless of the individual difference of the person who installs the clamp member 130.

Similarly, when the sensor head 120 is attached to the pipe P, the elastic pumpplant 124 and the damping material 126 are pressed against the pipe P by the clamp member 140. Further, the protruding portion T2 of the elastic couplant 124 is arranged along the axial direction while being in contact with the pipe P. When the support portion 143 of the clamp member 140 comes into contact with the pipe P, the amount of crushing of the elastic pumpplant 124 (protruding portion T2) is regulated. Therefore, the elastic pumpplant 124 can be uniformly pressed regardless of the individual difference of the person who installs the clamp member 140.

FIG. 9 is a schematic cross-sectional view showing the inside of the clamp members 130 and 140 in a state where the pipe P is not attached. 10 and 11 are schematic cross-sectional views showing the inside of the clamp members 130 and 140 with the pipe P attached. The outer diameter of the pipe P in FIG. 11 is slightly larger than the outer diameter of the pipe P in FIG.

In this embodiment, the leaf springs 115, 125 and the damping materials 116, 126 have high elasticity. The leaf springs 115 and 125 are semi-cylindrical thin plate springs, and are cantilevered cantilevered at both ends in the circumferential direction with respect to the fixing points attached to the clamp members 130 and 140 by the two mounting screws 134 and 144. It has become. Further, as shown in FIGS. 9 to 11, a space V is secured inside the clamp members 130 and 140 to allow deformation of the leaf springs 115 and 125 and the damping materials 116 and 126. Further, as shown in FIG. 9, when the pipe P is not attached to the leaf springs 115 and 125, the diameter of the inner surface of the damping materials 116 and 126 is set to be slightly smaller than the outer diameter of the attachable pipe P. Has been done.

As shown in FIG. 10, the clamp members 130 and 140 are sandwiched with respect to the pipe P, and the pipe P is attached to the leaf springs 115 and 125. At this time, as shown by the white arrows, the leaf springs 115 and 125 generate forces facing each other, and the damping materials 116 and 126 generate forces facing each other, whereby the leaf springs 115 and 125 and the damping materials 116, 126 is pushed into space V. In this case, due to the elasticity of the arcuate cantilevered thin leaf springs of the leaf springs 115 and 125 that oppose the spreading, the direction (pipe) different from the sandwiching direction of the clamp members 130 and 140 is shown by the arrow of the alternate long and short dash line. Pushing pressure is also generated in the direction toward the center of the axis of P). As a result, the damping materials 116 and 126 are pressed against the pipe P toward the center of the axis of the pipe P by the leaf springs 115 and 125, which are semi-cylindrical thin plate springs, only by sandwiching the pipe P between the clamp members 130 and 140. To. As a result, unnecessary components of ultrasonic waves propagating in the peripheral wall of the pipe P can be reliably attenuated.

As shown in FIG. 11, even if the outer diameters of the pipes P are slightly different, when the clamp members 130 and 140 are sandwiched between the pipes P, the pipes are piped by the elasticity of the leaf springs 115 and 125 as in FIG. A pressing force is generated in the direction toward the center of the axis of P. As a result, the damping materials 116 and 126 are pressed against the pipe P toward the axis center of the pipe P.

By securing the space V inside the clamp members 130 and 140 in this way, the leaf springs 115 and 125 are allowed to be deformed even if there is an error or variation in the outer diameter of the pipe P. Thereby, the clamp members 130 and 140 can be easily attached to the pipe P. Further, by deforming the damping material 116, the damping material 116 can be reliably pressed against the pipe P by the clamp member 130. Similarly, by deforming the damping material 126, the damping material 126 can be reliably pressed against the pipe P by the clamp member 140.

(5) Relay section and main body section FIG. 12 is a block diagram showing an internal configuration of the relay section 200 and the main body section 300 of FIG. As shown in FIG. 12, the relay unit 200 includes a switching circuit 201, a transmission circuit 202, 203, an amplifier circuit 204, an A / D (analog-to-digital) converter 205, a relay control unit 206, a calibration information storage unit 207, and a communication circuit. It includes 208, a power supply circuit 209 and an indicator light drive circuit 210.

The switching circuit 201 is connected to the ultrasonic element 112 via the head cable CA1 of FIG. 1 and is connected to the ultrasonic element 122 via the head cable CA2 of FIG. Further, in the relay unit 200, the switching circuit 201 is connected to the amplifier circuit 204. The switching circuit 201 switches the connection state between the ultrasonic elements 112 and 122 and the amplifier circuit 204 between the first state and the second state based on the control of the relay control unit 206.

The first state is a state in which the ultrasonic element 122 and the amplifier circuit 204 are connected and the ultrasonic element 112 and the amplifier circuit 204 are not connected. In the first state, the ultrasonic element 122 receives the ultrasonic wave and outputs an analog-type ultrasonic signal corresponding to the received ultrasonic wave. The ultrasonic signal output from the ultrasonic element 122 is given to the amplifier circuit 204.

The second state is a state in which the ultrasonic element 112 and the amplifier circuit 204 are connected and the ultrasonic element 122 and the amplifier circuit 204 are not connected. In the second state, the ultrasonic element 112 receives the ultrasonic wave and outputs an analog-type ultrasonic signal corresponding to the received ultrasonic wave. The ultrasonic signal output from the ultrasonic element 112 is given to the amplifier circuit 204.

The transmission circuit 202 includes a tri-state driver. In the transmission circuit 202, the output state of the tri-state driver is switched between three states (H level state, L level state, and high impedance state) based on the control of the relay control unit 206, so that the first drive signal is obtained. Is generated. The ultrasonic element 112 transmits ultrasonic waves in response to the first drive signal generated by the transmission circuit 202.

Similarly, the transmit circuit 203 includes a tri-state driver. In the transmission circuit 203, a second drive signal is generated by switching the output state of the tri-state driver between the three states based on the control of the relay control unit 206. The ultrasonic element 122 transmits ultrasonic waves in response to a second drive signal generated by the transmission circuit 203.

The amplifier circuit 204 amplifies the ultrasonic signal given from the ultrasonic element 112 or the ultrasonic element 122 with a predetermined gain, and gives the amplified ultrasonic signal to the A / D converter 205. The A / D converter 205 performs A / D conversion of the given ultrasonic signal, and gives the converted digital ultrasonic signal to the relay control unit 206.

The relay control unit 206 is composed of, for example, an FPGA (Field-Programmable Gate Array), a CPU (Central Processing Unit), and a memory, and has ultrasonic control units 206a, measurement information generation units 206b, and indicator light control units 206c as functional units. including. When the relay control unit 206 is composed of a CPU and a memory, these functional units are realized by the CPU executing a program stored in the memory. A part of the ultrasonic control unit 206a, the measurement information generation unit 206b, and the indicator light control unit 206c is realized by an electronic circuit (hardware) such as FPGA, and the rest is realized by the CPU executing a program. You may.

The ultrasonic control unit 206a controls the switching circuit 201 and the transmission circuits 202 and 203 based on the control by the main body unit 300. For example, the ultrasonic control unit 206a shifts the connection state between the ultrasonic elements 112 and 122 and the amplifier circuit 204 to the first state, and operates the transmission circuit 202 so as to generate the first drive signal. Let me. In this case, ultrasonic waves are transmitted by the ultrasonic element 112, and ultrasonic waves are received by the ultrasonic element 122. The ultrasonic signal output from the ultrasonic element 122 is amplified by the amplifier circuit 204, A / D converted by the A / D converter 205, and then given to the measurement information generation unit 206b.

Further, the ultrasonic control unit 206a shifts the connection state between the ultrasonic elements 112 and 122 and the amplifier circuit 204 to the second state, and operates the transmission circuit 203 so as to generate the second drive signal. Let me. In this case, the ultrasonic element 122 transmits the ultrasonic wave, and the ultrasonic element 112 receives the ultrasonic wave. The ultrasonic signal output from the ultrasonic element 112 is amplified by the amplifier circuit 204, A / D converted by the A / D converter 205, and then given to the measurement information generation unit 206b.

The measurement information generation unit 206b generates the time difference as measurement information from the peak of the cross-correlation function of the signal waveforms of the two ultrasonic signals output from the ultrasonic elements 112 and 122. The measurement information generation unit 206b measures the propagation time of the ultrasonic wave from the ultrasonic element 112 to the ultrasonic element 122 and the propagation time of the ultrasonic wave from the ultrasonic element 122 to the ultrasonic element 112, respectively. The time difference may be calculated as the time difference.

The indicator light control unit 206c controls the indicator light drive circuit 210 based on the control by the main body unit 300. The indicator light drive circuit 210 is connected to the indicator light 117 via the head cable CA1 of FIG. 1, and generates a third drive signal for driving the indicator light 117 based on the control of the indicator light control unit 206c. ..

The calibration information storage unit 207 is configured by, for example, a non-volatile memory, and stores calibration information regarding the ultrasonic elements 112, 122, the switching circuit 201, the transmission circuits 202, 203, the amplifier circuit 204, and the A / D converter 205.

When the relationship of equation (1) is not satisfied between the time difference calculated by the measurement information generation unit 206b and the flow rate of the fluid flowing in the pipe P, depending on the operating characteristics of each component of the head unit 100 and the relay unit 200. There is. The calibration information is information for calibrating the equation (1) in order to accurately calculate the unique relationship between the time difference calculated by the measurement information generation unit 206b and the flow rate to be actually measured. The calibration information includes, for example, a value for adjusting the coefficient of the time difference Δt in the equation (1) and an offset value (adjustment value for a flow rate of 0) to be added to the term including the time difference Δt in the equation (1).

The communication circuit 208 is connected to one end of the relay cable CA3 of FIG. 1, and outputs digital measurement information and calibration information generated by the measurement information generation unit 206b to the main body unit 300 through the relay cable CA3. Further, the communication circuit 208 gives a transmission control signal and a display control signal input from the main body unit 300 to the relay control unit 206 through the relay cable CA3. The transmission control signal is a control signal for controlling the transmission circuits 202 and 203, and the display control signal is a control signal for controlling the indicator lamp drive circuit 210.

The power supply circuit 209 receives the electric power supplied from the main body 300 through the relay cable CA3, and supplies the received electric power to other components provided in the relay unit 200.

The main body unit 300 includes a communication circuit 301, a main body control unit 302, a display unit 303, an operation unit 304, a storage unit 305, an output circuit 306, and a power supply circuit 307. The communication circuit 301 is connected to the other end of the relay cable CA3 of FIG. 1, and gives measurement information and calibration information output from the relay unit 200 through the relay cable CA3 to the main body control unit 302. Further, the communication circuit 301 outputs the transmission control signal and the display control signal generated in the main body control unit 302 to the relay unit 200 through the relay cable CA3 as described later.

The display unit 303 includes, for example, a segment display or a dot matrix display, and displays the flow rate of the fluid flowing in the pipe P based on the control of the main body control unit 302. The operation unit 304 includes a plurality of operation buttons. By operating the operation unit 304, the user can input the dimensions, the flow rate correction coefficient, and the like of the pipe P to be attached to the head unit 100. Further, the user can input the threshold value of the flow rate by operating the operation unit 304. The storage unit 305 is composed of a non-volatile memory or a hard disk drive.

The main body control unit 302 includes, for example, a CPU and a memory, and generates a transmission control signal and a display control signal to be given to the relay unit 200 in order to drive the ultrasonic elements 112, 122 and the indicator lamp 117, respectively. Further, the main body control unit 302 sets the information by storing information such as the dimensions of the pipe P, the flow rate correction coefficient, and the flow rate threshold value input by the operation unit 304 in the storage unit 305. The inner diameter d ₁ of the pipe P may be set by inputting the outer diameter d ₂ of the pipe P and the thickness t ₂ of the peripheral wall into the operation unit 304 as the dimensions of the pipe P.

Further, the main body control unit 302 calibrates the equation (1) based on the calibration information given from the communication circuit 301. Further, the main body control unit 302 calculates the flow rate of the fluid flowing in the pipe P based on the calibrated equation (1), the measurement information given from the communication circuit 301, and the set flow rate correction coefficient. Further, the main body control unit 302 generates an on / off signal based on the comparison result between the calculated flow rate and the set threshold value of the flow rate. The output circuit 306 is connected to one end of the main body cable CA4 of FIG. 1, and outputs an on / off signal generated by the main body control unit 302 to an external device of the flow rate sensor 1 through the main body cable CA4.

(6) Modification Example In the above embodiment, the head portion 100 includes elastic pumpplants 114 and 115, but the present invention is not limited thereto. The head portion 100 does not have to include the elastic coplants 114 and 115. In this case, the protruding portion T1 and the width changing portion V1 are formed on at least one of the wedge material 113 and the damping material 116. Similarly, the protrusion T2 and the width change portion V2 are formed on at least one of the wedge material 123 and the damping material 126.

13 (a) to 13 (d) are cross-sectional views showing first to fourth modified examples of the sensor head 110, respectively. 13 (a) to 13 (d) show a cross-sectional view corresponding to the cross-sectional view of the sensor head 110 of FIG. Hereinafter, the first to fourth modified examples of the sensor head 110 will be described as different from the sensor head 110 of FIG. Although the sensor head 120 is not shown in FIGS. 13 (a) to 13 (d), the sensor head 120 has the same configuration as the corresponding sensor head 110.

As shown in FIG. 13A, in the first modification of the sensor head 110, a protrusion protruding upward so as to be in contact with the wedge material 113 over a predetermined length in the axial direction is above the damping material 116. Part T1 is formed. Further, the slit S1 (FIG. 5) is not formed in the damping material 116. The protruding portion T1 of the damping material 116 is brought into contact with the wedge material 113 in a state of being fitted into the slit S3 of the leaf spring 115 from below.

In this example, the contact surface of the damping material 116 with the pipe P and overlapping with the protrusion T1 in the vertical direction is the pipe contact surface E1. The joint surface _B1 of the wedge material 113 is formed so that the width is w1. On the other hand, the protrusion T1 and the pipe contact surface E1 are formed so that the width is w ₂ smaller than w ₁ . That is, the wedge material 113 and the damping material 116 are provided with a propagation path, and a width changing portion V1 whose width changes from _w1 to w2 is formed between the joint surface _B1 and the pipe contact surface E1.

As shown in FIG. 13B, in the second modification of the sensor head 110, a protrusion below the wedge material 113 so as to contact the damping material 116 over a predetermined length in the axial direction. Part T1 is formed. Further, the slit S1 is not formed in the damping material 116. The protruding portion T1 of the wedge material 113 is brought into contact with the damping material 116 in a state of being fitted into the slit S3 of the leaf spring 115 from above.

In this example, the contact surface of the damping material 116 with the pipe P and overlapping with the protrusion T1 in the vertical direction is the pipe contact surface E1. The joint surface _B1 of the wedge material 113 is formed so that the width is w1. On the other hand, the protrusion T1 and the pipe contact surface E1 are formed so that the width is w ₂ smaller than w ₁ . That is, the wedge material 113 and the damping material 116 are provided with a propagation path, and a width changing portion V1 whose width changes from _w1 to w2 is formed between the joint surface _B1 and the pipe contact surface E1.

As shown in FIG. 13 (c), in the third modification of the sensor head 110, a protrusion below the wedge material 113 so as to contact the damping material 116 over a predetermined length in the axial direction. Part T1 is formed. Further, the sensor head 110 does not include the leaf spring 115. Further, the slit S1 is not formed in the damping material 116. The damping material 116 is attached to the clamp member 130 (FIG. 5) with an adhesive or the like. The protruding portion T1 of the wedge material 113 is in contact with the damping material 116 from above.

In this example, the contact surface of the damping material 116 with the pipe P and overlapping with the protrusion T1 in the vertical direction is the pipe contact surface E1. The joint surface _B1 of the wedge material 113 is formed so that the width is w1. On the other hand, the protrusion T1 and the pipe contact surface E1 are formed so that the width is w ₂ smaller than w ₁ . That is, the wedge material 113 and the damping material 116 are provided with a propagation path, and a width changing portion V1 whose width changes from _w1 to w2 is formed between the joint surface _B1 and the pipe contact surface E1.

As shown in FIG. 13 (d), in the fourth modification of the sensor head 110, a protruding portion protruding downward so as to be in contact with the pipe P over a predetermined length in the axial direction at the lower portion of the wedge material 113. T1 is formed. The protruding portion T1 of the wedge material 113 is brought into contact with the pipe P in a state of being fitted into the slit S3 of the leaf spring 115 and the slit S1 of the damping material 116 from above.

In this example, the contact surface of the wedge material 113 with the pipe P in the protruding portion T1 is the pipe contact surface E1. The pipe contact surface E1 may be coated with grease for matching the acoustic impedance between the wedge material 113 and the pipe P. The joint surface _B1 of the wedge material 113 is formed so that the width is w1. On the other hand, the protrusion T1 and the pipe contact surface E1 are formed so that the width is w ₂ smaller than w ₁ . That is, the wedge material 113 is provided with a propagation path, and a width changing portion V1 whose width changes from w ₁ to w ₂ is formed between the joint surface B1 and the pipe contact surface E1.

(7) Effect The flow rate sensor 1 according to the present embodiment includes sensor heads 110 and 120. In the sensor head 110, the ultrasonic waves transmitted from the transmission / reception surface A1 of the ultrasonic element 112 are propagated to the pipe P through the wedge material 113 and the elastic coplant 114. The elastic couplant 114 is supported by the pipe P by the clamp member 130 so that the pipe contact surface E1 is in contact with the pipe P and is arranged along the axial direction. The wedge material 113 is provided so that the incident angle of the ultrasonic shear wave in the axial direction is equal to or greater than the critical angle. Therefore, the ultrasonic waves emitted from the pipe contact surface E1 are totally reflected by the pipe P and hardly penetrate into the peripheral wall of the pipe P.

The sensor head 120 has the same configuration as the sensor head 110. According to this configuration, a guide wave is excited in the peripheral wall of the pipe P by vibration, and the excited guide wave is used to sandwich the pipe P between the ultrasonic element 112 and the ultrasonic element 122 to generate ultrasonic waves. You can send and receive. In this case, unnecessary components of ultrasonic waves transmitted and received between the ultrasonic element 112 and the ultrasonic element 122 are reduced by propagating in the peripheral wall of the pipe P without passing through the fluid. Therefore, it becomes easy to calculate the flow rate of the fluid flowing in the pipe P based on the ultrasonic waves transmitted and received between the ultrasonic element 112 and the ultrasonic element 122.

Here, when the width of the transmission / reception surface A1 of the ultrasonic element 112 is large, the intensity of the ultrasonic waves transmitted in the inclined direction can be increased. On the other hand, as the width of the portion of the pipe P to which the ultrasonic wave is irradiated increases, the unnecessary component of the ultrasonic wave increases. Therefore, the elastic couplant 114 is provided with a width changing portion V1 so that the width of the pipe contact surface E1 is smaller than the width of the transmission / reception surface A1 of the ultrasonic element 112. As a result, it is possible to reduce unnecessary components of the ultrasonic wave while increasing the intensity of the ultrasonic wave transmitted in the inclined direction. As a result, the flow rate of the fluid flowing in the metal pipe P having a small diameter can be calculated.

(8) Other Embodiments (a) In the above embodiment, the relay unit 200 and the main body unit 300 are provided as separate bodies and are connected by the relay cable CA3, but the present invention is not limited thereto. The relay unit 200 and the main body unit 300 may be provided integrally.

(B) In the above embodiment, the damping material 116 is composed of one elastic body that surrounds the protrusion T1 of the elastic pumpplant 114 in the circumferential direction and the axial direction, but the present invention is not limited thereto. The damping material 116 may be composed of a plurality of elastic bodies that surround the protrusion T1 of the elastic pumpplant 114 in the circumferential direction and the axial direction. In this case, the slit S1 may not be formed in the damping material 116. Similarly, the damping material 126 may be composed of a plurality of elastic bodies that surround the protrusion T2 of the elastic pumpplant 124 in the circumferential direction and the axial direction.

(C) In the above embodiment, the damping materials 116 and 126 are provided on the head portion 100, but the present invention is not limited thereto. When the portion of the pipe P other than the excited regions R1 and R2 hardly excites unnecessary ultrasonic waves, the damping materials 116 and 126 may not be provided in the head portion 100.

(D) In the above embodiment, the head portion 100 is provided with leaf springs 115 and 125, but the present invention is not limited thereto. The leaf spring 115 may not be provided on the head portion 100. In this case, the damping material 116 is attached to the clamp member 130 with an adhesive or the like. The protrusion T1 of the elastic couplant 114 is fitted into the slit S1 of the damping material 116. As a result, the damping material 116 holds the position and orientation of the elastic pumpplant 114 with respect to the clamp member 130.

Similarly, the leaf spring 125 may not be provided on the head portion 100. In this case, the damping material 126 is attached to the clamp member 140 by an adhesive or the like. The protrusion T2 of the elastic couplant 124 is fitted into the slit S2 of the damping material 126. As a result, the damping material 126 holds the position and orientation of the elastic pumpplant 124 with respect to the clamp member 140.

(9) Correspondence between each component of the claim and each part of the embodiment The example of correspondence between each component of the claim and each part of the embodiment will be described below. Not limited. As each component of the claim, various other components having the structure or function described in the claim can also be used.

In the above embodiment, the pipe P is an example of a pipe, the flow sensor 1 is an example of a clamp-on type ultrasonic flow sensor, the transmission / reception surface A1 is an example of a transmission / reception surface, and the ultrasonic elements 112 and 122 are. This is an example of the first and second ultrasonic elements, respectively. The pipe contact surface E1 is an example of a pipe contact surface, the clamp member 130 is an example of a clamp member, the main body control unit 302 is an example of a flow rate calculation unit, and the wedge material 113 is an example of a wedge material.

The elastic coplant 114 is an example of an elastic coplant, the damping material 116 is an example of a damping material, the width changing portion V1 is an example of a width changing portion, the excited region R1 is an example of an excited region, and the leaf spring 115 is an example. This is an example of a pressing member. In the example of FIG. 5, the elastic coplant 114 is an example of the propagation path, and in the examples of FIGS. 13 (a) to 13 (c), the wedge material 113 and the damping material 116 are examples of the propagation path, and FIG. 13 (d) is shown. In this example, the wedge material 113 is an example of the propagation path.

1 ... Flow sensor, 100 ... Head, 101 ... Coupling screw, 110, 120 ... Sensor head, 111 ... Casing, 112, 122 ... Ultrasonic element, 113, 123 ... Wedge material, 114, 124 ... Elastic coplant, 115, 125 ... Leaf spring, 116, 126 ... Damping material, 117 ... Indicator light, 130, 140 ... Clamp member, 131, 132, 141, 142 ... Vertical wall, 133, 143 ... Support part, 134, 144, 151, 161 ... Mounting screw, 135, 146 ... Temporary fixing screw, 145 ... Temporary fixing member, 150, 160 ... Mounting sheet metal, 200 ... Relay unit, 201 ... Switching circuit, 202, 203 ... Transmission circuit, 204 ... Amplifier circuit, 205 ... A / D converter, 206 ... relay control unit, 206a ... ultrasonic control unit, 206b ... measurement information generation unit, 206c ... indicator light control unit, 207 ... calibration information storage unit, 208, 301 ... communication circuit, 209, 307 ... power supply Circuit, 210 ... Indicator light drive circuit, 300 ... Main unit, 302 ... Main unit control unit, 303 ... Display unit, 304 ... Operation unit, 305 ... Storage unit, 306 ... Output circuit, A1, A2 ... Transmission / reception surface, B1, B2 ... Joint surface, C1, C2 ... Input / output surface, CA1, CA2 ... Head cable, CA3 ... Relay cable, CA ... Main body cable, D1 ... Wedge contact surface, E1, E2 ... Pipe contact surface, H1, H2 ... Opening, P ... Piping, P1, P2 ... Peripheral wall, R1, R2 ... Excitation region, S1 to S4 ... Slit, T1, T2 ... Projection, V1, V2 ... Width change, V ... Space, W ... Window, W1, W2 … Standing wall

Claims (13)

A clamp-on type ultrasonic flow sensor that measures the flow rate of fluid flowing in a pipe.
A first ultrasonic element having a transmission / reception surface capable of transmitting / receiving ultrasonic waves,
A propagation path having a pipe contact surface in contact with the pipe and propagating ultrasonic waves transmitted from the transmission / reception surface of the first ultrasonic element to the pipe.
A clamp member that supports the pipe and supports the propagation path so that the pipe contact surface is arranged along the axial direction of the pipe.
A second ultrasonic element capable of transmitting and receiving ultrasonic waves to and from the first ultrasonic element across the pipe, and a second ultrasonic element.
A flow rate calculation unit that calculates the flow rate of the fluid flowing in the pipe based on the ultrasonic waves transmitted and received between the first ultrasonic element and the second ultrasonic element .
It is formed by an elastic body that attenuates ultrasonic waves in the peripheral wall of the pipe, and is provided with a damping material that surrounds the pipe contact surface in the circumferential direction and the axial direction of the pipe .
The propagation path includes a wedge material that propagates ultrasonic waves in an inclined direction with respect to the axial center direction, and an elastic couplant that matches the acoustic impedance between the wedge material and the pipe, and shears the ultrasonic waves with respect to the axial center direction. It is provided so that the incident angle of the wave is equal to or higher than the critical angle.
The transmission / reception surface of the first ultrasonic element has a first width in a width direction orthogonal to the axial direction and the inclination direction.
The pipe contact surface of the elastic coplant included in the propagation path has a substantially rectangular shape and has a second width smaller than the first width in the width direction.
A clamp-on type ultrasonic flow sensor in which the length of the pipe contact surface in the axial direction is larger than the length of the transmission / reception surface in the direction orthogonal to the width direction. The clamp-on type ultrasonic flow sensor according to claim 1, wherein the first width is five times or more the thickness of the first ultrasonic element in the tilting direction. The clamp-on type ultrasonic flow sensor according to claim 1 or 2, wherein the second width is one-third or less of the outer diameter of the pipe. The clamp-on type ultrasonic flow sensor according to any one of claims 1 to 3, wherein the first ultrasonic element is configured to transmit ultrasonic waves by vibrating at a unique resonance frequency. The first ultrasonic element is formed so that the product of the ultrasonic frequency displayed in megahertz units and the thickness of the peripheral wall of the pipe displayed in millimeters is 2 or more. 4. The clamp-on type ultrasonic flow sensor according to 4. The first ultrasonic element is formed so that the product of the ultrasonic frequency displayed in megahertz units and the thickness of the peripheral wall of the pipe displayed in millimeters is 6 or less. 4. The clamp-on type ultrasonic flow sensor according to 4 or 5. The peripheral wall of the pipe includes an excited region where a longitudinal wave of ultrasonic waves emitted from the pipe contact surface of the propagation path collides.
The clamp-on type supermarket according to any one of claims 1 to 6, wherein the excited region of the pipe excites an ultrasonic wave passing through a fluid flowing in the pipe and toward the second ultrasonic element. Sound wave flow sensor . The clamp-on type ultrasonic flow sensor according to any one of claims 1 to 7 , wherein the damping material is configured to hold the position and posture of the elastic pumpplant. The clamp-on type ultrasonic flow sensor according to any one of claims 8 or 1 to 8 , further comprising a pressing member for pressing the damping material against the pipe. The clamp-on type ultrasonic flow sensor according to claim 9 , wherein the pressing member is configured to hold the position and posture of the elastic coplant. 9 . 10. The clamp-on type ultrasonic flow sensor according to 10. The transmission / reception surface of the first ultrasonic element has a first length in a length direction orthogonal to the inclination direction and the width direction.
The clamp-on type ultrasonic flow sensor according to any one of claims 1 to 11 , wherein the pipe contact surface of the propagation path has a second length larger than the first length in the axial direction. .. The clamp-on type ultrasonic flow sensor according to any one of claims 1 to 12 , wherein the outer diameter of the pipe is 2 mm or more and 20 mm or less.

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