JP2019158675A - Clamp-on type ultrasonic flow sensor - Google Patents

Abstract

To provide a clamp-on type ultrasonic flow sensor that can calculate a flow rate of fluid flowing in metallic piping with a small diameter.SOLUTION: An ultrasonic wave transmitted from a transmission/reception surface A1 of an ultrasonic wave element 112 is propagated to piping P by a propagation route. The propagation route is supported by the piping P by a clamp member 130 in such a manner that a piping contact surface E1 contacts with the piping P and is arranged along an axial center direction of the piping P. The propagation route includes at least one of a wedge material 113, resilient couplant 114 and dumping material 116, and is provided in such a manner that an angle of incidence of a shear wave of the ultrasonic wave with respect to the axial center direction is a critical angle or more. A width change part is provided in the propagation route in such a manner that a width of the piping contact surface E1 is smaller than that of the transmission/reception surface A1 of the ultrasonic wave element 112. A flow rate of fluid flowing in the piping P is calculated based on the ultrasonic wave transmitted/received between an ultrasonic wave element 112 and an ultrasonic wave element 122.SELECTED DRAWING: Figure 2

Description

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

  There is known a clamp-on type ultrasonic flow sensor capable of calculating a flow rate of a fluid flowing in a pipe while being attached to the pipe by a clamp member (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 that have passed 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.

JP, 2006-217733, A

  In the clamp-on type ultrasonic flow sensor, a component that propagates in the peripheral wall of the pipe without passing through the fluid exists in the ultrasonic waves that reach the other ultrasonic element from one ultrasonic element. Such a component is an unnecessary component that does not have information on the flow rate of the fluid. When the unnecessary component of the ultrasonic wave is large, it is difficult to accurately calculate the fluid flow rate. Therefore, it is necessary to receive the component of the ultrasonic wave passing through the fluid separately from the unnecessary component.

  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 the resin material is smaller than the propagation speed of ultrasonic waves in the metal material. Furthermore, the attenuation rate of the ultrasonic wave in the resin material is larger than the attenuation rate of the ultrasonic wave in the metal material. Therefore, when the pipe diameter is large or the pipe is formed of a resin material, it is easy to receive the ultrasonic component passing through the fluid separated from unnecessary components in time or space. A pair of ultrasonic elements can be disposed on the surface.

  However, when the diameter of the pipe is small and the pipe is formed of a metal material, a pair of ultrasonic elements should be arranged so that the ultrasonic component passing through the fluid is received separately from unnecessary components. Is not easy. Therefore, the flow rate of the fluid flowing through the metal pipe having a small diameter cannot be calculated.

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

  (1) A 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 transmission / reception surface capable of transmitting and receiving ultrasonic waves. An ultrasonic element and a pipe contact surface in contact with the pipe, a propagation path for propagating ultrasonic waves transmitted from the transmission / reception surface of the first ultrasonic element to the pipe, the pipe, and the pipe contact surface A clamp member that supports the propagation path so as to be arranged along the axial direction of the pipe, and a second ultrasonic element that can transmit and receive ultrasonic waves between the first ultrasonic element across the pipe, A flow rate calculation unit that calculates a flow rate of fluid flowing in the pipe based on ultrasonic waves transmitted and received between the first ultrasonic element and the second ultrasonic element, and the propagation path is in the axial direction Wedge material that propagates ultrasonic waves in the inclined direction Including at least one of an elastic coplanar that matches the acoustic impedance of the die material and the pipe and a damping material that attenuates the ultrasonic wave in the peripheral wall of the pipe, and the incident angle of the ultrasonic shear wave with respect to the axial direction is greater than the critical angle The transmission / reception surface of the first ultrasonic element has a first width in the width direction orthogonal to the axial direction and the inclination direction, and the pipe contact surface of the propagation path is in the width direction. The propagation path has a second width smaller than the first width, and the propagation path extends from a third width different from the second width to the second width between the transmission / reception surface of the first ultrasonic element and the pipe contact surface. It has a width changing portion that changes to a width.

  In this clamp-on type ultrasonic flow sensor, the ultrasonic wave transmitted from the transmission / reception surface of the first ultrasonic element is propagated to the pipe through the 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 at least one of a wedge material, an elastic coplanar, and a damping material, and is provided so that the incident angle of the ultrasonic shear wave with respect to the axial direction is not less than the critical angle. Therefore, the ultrasonic wave emitted from the pipe contact surface is totally reflected by the pipe and hardly enters the peripheral wall of the pipe.

  According to said structure, an ultrasonic wave is excited in the surrounding wall of piping by vibration, and piping is pinched between the 1st ultrasonic element and the 2nd ultrasonic element using the excited ultrasonic wave. Ultrasound can be transmitted and received. In this case, unnecessary components of ultrasonic waves that are transmitted and received between the first ultrasonic element and the second ultrasonic element through the inside of the peripheral wall of the pipe without passing through the fluid are reduced. 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 tilt direction can be increased. On the other hand, when the width of the portion of the pipe that is irradiated with ultrasonic waves increases, the unnecessary components of the ultrasonic waves increase. Therefore, the propagation path is provided with a width changing portion such that the width of the pipe contact surface is smaller than the width of the transmission / reception surface of the first ultrasonic element. Thereby, unnecessary components of the ultrasonic wave can be reduced while increasing the intensity of the ultrasonic wave transmitted in the tilt direction. As a result, the flow rate of the fluid flowing through the metal pipe having a small diameter can be calculated.

  (2) The third width may coincide with the first width. In this case, even when an ultrasonic wave having a large first width is transmitted from the transmission / reception surface of the first ultrasonic element, it is possible to irradiate the pipe with an ultrasonic wave having a small second width.

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

  (4) 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 the ultrasonic wave that is transmitted and received between the first ultrasonic element and the second ultrasonic element by propagating through the peripheral wall of the pipe without passing through the fluid. it can.

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

  (6) The first ultrasonic element may be formed such that the product of the frequency of the ultrasonic wave displayed in megahertz 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 vibration is prevented. As a result, the fluid flow rate can be calculated more accurately.

  (7) The first ultrasonic element may be formed such that the product of the frequency of the ultrasonic wave displayed in megahertz and the thickness of the peripheral wall of the pipe displayed in millimeter 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 by vibration becomes dominant. Thereby, the intensity | strength of the ultrasonic wave transmitted / received between a 1st ultrasonic element and a 2nd ultrasonic element can be increased.

  (8) The peripheral wall of the pipe includes an excitation region in which a longitudinal wave of ultrasonic waves emitted from the pipe contact surface of the propagation path collides, and the excitation region of the pipe passes through the fluid flowing in the pipe and is second You may excite the ultrasonic wave which goes to an ultrasonic element. In this case, the flow rate of the fluid flowing in the pipe can be calculated based on the ultrasonic wave generated from the excitation region of the pipe.

  (9) The damping material may be configured to maintain the position and posture of the elastic coplant. According to this configuration, even when the width changing portion is formed in the elastic coplant and the portion having the second width in the elastic coplant is brought into contact with the pipe, the change in the width of the portion is restricted. Therefore, it is possible to easily irradiate the pipe with ultrasonic waves having a small width. Further, bending, meandering and deformation of the part are prevented. Thereby, the flow rate of the fluid flowing through the metal pipe having a small diameter can be accurately calculated.

  (10) The clamp-on ultrasonic flow sensor may further include a pressing member that presses the damping material against the pipe. In this case, when the damping material is sufficiently pressed against the pipe, the ultrasonic wave propagating in the peripheral wall of the pipe is sufficiently attenuated. Thereby, the flow rate of the fluid can be calculated more accurately.

  (11) The pressing member may be configured to hold the position and posture of the elastic coplant. According to this configuration, even when the width changing portion is formed in the elastic coplant and the portion having the second width in the elastic coplant is brought into contact with the pipe, the change in the width of the portion is restricted. Therefore, it is possible to easily irradiate the pipe with ultrasonic waves having a small width. Further, bending, meandering and deformation of the part are prevented. Thereby, the flow rate of the fluid flowing through the metal pipe having a small diameter can be accurately calculated.

  (12) The pressing member may be formed of a metal member and disposed so as to block the ultrasonic wave propagating from the portion of the propagation path excluding the pipe contact surface to the pipe. In this case, it is possible to more reliably irradiate the pipe with ultrasonic waves having a small width.

  (13) The transmission / reception surface of the first ultrasonic element has a 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. The second length may be greater than the second length. According to this configuration, even when an ultrasonic wave is transmitted in the tilt direction, it is possible to irradiate the pipe from the pipe contact surface over a sufficiently large area in the axial direction.

  (14) 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 a fluid flowing through a metal pipe having a small diameter.

1 is an external perspective view of a flow sensor according to an embodiment of the present invention. FIG. 2 is a transverse cross-sectional view showing an internal configuration of the head unit in FIG. 1. It is a figure for demonstrating the calculation method of the flow volume in the flow sensor of FIG. It is a typical cross-sectional view showing details of a sensor head. FIG. 5 is a cross-sectional view of the sensor head of FIG. 4 taken along line AA. It is a typical cross-sectional view which shows the internal structure of the head part in a modification. It is a figure for demonstrating the process of attaching a head part to piping. It is a figure for demonstrating the process of attaching a head part to piping. It is a typical sectional view showing the inside of a clamp member in the state where piping is not attached. It is a typical sectional view showing the inside of a clamp member in the state where piping was attached. It is a typical sectional view showing the inside of a clamp member in the state where piping was attached. It is a block diagram which shows the internal structure of the relay part of FIG. 1, and a main-body part. It is sectional drawing which shows the 1st-4th modification of a 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. In the following description, a direction along the central axis of the pipe is referred to as an axial direction. A direction along the peripheral wall of the pipe is called a circumferential direction. A direction inclined by a predetermined angle with respect to the axial direction is referred to as an inclination direction. The direction orthogonal to the axial direction and the tilt direction is called the width direction. A direction orthogonal to the inclination direction and the width direction is referred to as a length direction.

  FIG. 1 is an external perspective view of a flow sensor according to an embodiment of the present invention. As shown in FIG. 1, the flow sensor 1 according to the present embodiment includes a head unit 100, a relay unit 200, and a main body unit 300. The head unit 100 includes two sensor heads 110 and 120 and two clamp members 130 and 140. The head unit 100 further includes two attachment metal plates 150 and 160 for attaching a part of the sensor heads 110 and 120 to the clamp members 130 and 140. The clamp members 130 and 140 are made 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 while 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, not less than 2 mm and not more than 20 mm. A fluid flows in the pipe P.

  A head cable CA1 is connected between the sensor head 110 and the relay unit 200, and a 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 a main body cable CA4 is further connected to the main body 300. The other end of the main body cable CA4 is connected to an external device (not shown) of the flow 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 an internal configuration of the head unit 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 coplant 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 the present example, a substantially rectangular parallelepiped shape) extending along the axial direction. Hereinafter, in the casing 111, a direction facing the pipe P is defined as a downward direction, and the opposite direction is defined as an 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 H <b> 1 is formed in the lower part of the casing 111.

  The ultrasonic element 112 has a transmission / reception surface A1 capable of transmitting and receiving ultrasonic waves. The wedge material 113 is formed of a non-metallic material having high rigidity and high sound transmission. The wedge material 113 is preferably formed of a material having high environmental resistance. The wedge material 113 has a joint surface B1 facing in the inclined direction, and has an entrance / exit surface C1 facing downward in the lower part. 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 portion of the casing 111 so as to close the opening H1 through a seal member (not shown). Thereby, a space into which liquid such as water and oil cannot enter is formed in the casing 111, and the ultrasonic element 112 is accommodated in the casing 111. The entrance / exit surface C <b> 1 of the wedge material 113 slightly projects downward from the opening H <b> 1 of the casing 111. In this state, the casing 111 is attached to the attachment sheet metal 150 by two attachment screws 151. The casing 111 is filled with a resin member.

  The elastic coplanar 114 has a solid shape and is formed of a soft elastic material made of a polymer rubber or a gel material. The hardness of the elastic coplant 114 is, for example, 20 degrees to 40 degrees. A projecting portion T1 projecting downward so as to be in contact with the pipe P over a predetermined length in the axial direction is formed at the lower portion of the elastic coplant 114.

  The elastic coplant 114 is disposed so as to contact 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. A contact surface of the elastic coplant 114 with the wedge material 113 is referred to as a wedge contact surface D1. Further, a contact surface with the pipe P in the protruding portion T1 of the elastic coplant 114 is referred to as a pipe contact surface E1.

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

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

  In the present embodiment, the indicator lamp 117 is lit in green when the external device is in an on state, and is lit in red when the external device is in an 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. Conversely, the indicator lamp 117 may be turned off when the external device is in the on state, and the indicator lamp 117 may be lit up when the external device is in the off state.

  The indicator lamp 117 is disposed inside the casing 111 so as to be close to the window portion W. Thereby, the mode of operation of the indicator lamp 117 is visible from the outside of the casing 111 through the window portion W. The user can easily identify the on state and the off state of the external device by visually recognizing the color or 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 coplant 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, an opening H2 similar to the opening H1 is formed in the casing 121.

  The ultrasonic element 122 and the wedge material 123 have the same configuration 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. Moreover, the wedge material 123 has the joint surface B2 and the incident / exit surface C2 similar to the joint surface B1 and the incident / exit surface C1, respectively. The transmission / reception surface A <b> 2 of the ultrasonic element 122 is bonded to the bonding surface B <b> 2 of the wedge material 123. The casing 121 is attached to the attachment metal plate 160 with two attachment screws 161 in a state where the wedge material 123 is attached.

  The elastic coplant 124 has the same configuration as the elastic coplant 114. Therefore, the elastic coplant 124 has the protrusion T2, the wedge contact surface D2, and the pipe contact surface E2 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 contact 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 configuration as the leaf spring 115 and the damping material 116, respectively. The leaf spring 125 is disposed so as to surround the projecting portion T2 in the circumferential direction and the axial direction, and is attached to the clamp member 140 together with the elastic coplant 124 by two attachment screws 144. The damping material 126 is disposed between the leaf spring 125 and the pipe P so as to surround the protruding portion T2 in the circumferential direction and the axial direction.

  The attachment sheet metal 150 and the attachment sheet metal 160 are coupled to each other by the four coupling screws 101 with the clamp member 130, the pipe P, and the clamp member 140 interposed therebetween. Thereby, the sensor head 110 is attached to the clamp member 130 in a state where the elastic coplant 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 in a state where the elastic coplant 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 sensor 1 of FIG. In FIG. 3, illustration of the clamp members 130 and 140 and the attachment metal plates 150 and 160 is omitted. 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 enters the wedge material 113 from the bonding surface B1. Thereafter, the ultrasonic wave propagates through the wedge material 113 and is transmitted from the incident / exit surface C1. The ultrasonic wave transmitted from the entrance / exit surface C1 enters the elastic coplanar 114 from the wedge contact surface D1, propagates through the elastic coplanar 114, and then exits from the pipe contact surface E1 of the protruding portion T1 toward the pipe P. The

  In the present embodiment, the wedge surface 113 is formed with the bonding surface B1 and the incident / exit surface C1 so that the incident angle of the ultrasonic transverse wave (shear wave) with respect to the axial direction is not less than the critical angle. In this case, the longitudinal wave and the transverse wave of the ultrasonic wave emitted from the pipe contact surface E1 are totally reflected by the peripheral wall P1 of the pipe P, and hardly enter the peripheral wall P1. On the other hand, a longitudinal wave of ultrasonic waves collides with the outer peripheral surface of the peripheral wall P1, whereby a guide wave is excited in the peripheral wall P1. The guide wave is an ultrasonic wave propagating through the pipe P in a direction parallel to the axial direction, and there is a plate wave or a surface wave. 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 state of vibration varies depending on the product of the ultrasonic frequency 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, ultrasonic waves are excited so as to pass through the fluid toward the opposing peripheral wall P2 at a predetermined incident angle θ. When the longitudinal wave of the ultrasonic wave that has passed through the fluid collides with the inner peripheral surface of the peripheral wall P2, a 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, an ultrasonic longitudinal wave from the pipe P toward the pipe contact surface E2 of the elastic coplant 124 is excited.

  The ultrasonic wave from the pipe P enters the projecting portion T2 from the pipe contact surface E2, propagates through the elastic coplant 124, and is emitted from the wedge contact surface D2. The ultrasonic wave emitted from the wedge contact surface D2 enters the wedge material 123 from the incident / exit surface C2, and then propagates through the wedge material 123 and is emitted from the bonding surface B2. Thereafter, the ultrasonic wave is received from the transmission / reception surface A <b> 2 of the ultrasonic element 122 based on the control by the relay unit 200.

  In this manner, the peripheral wall P1 is provided with the excitation region R1 in which the longitudinal wave of the ultrasonic wave emitted from the ultrasonic element 112 collides. The excitation region R <b> 1 is a region that mainly excites ultrasonic waves that pass through the fluid flowing in the pipe P and travel toward the ultrasonic element 122. In FIG. 3, the excitation region R1 is illustrated by a hatching pattern.

  Next, the ultrasonic element 122 transmits ultrasonic waves in the inclined direction from the transmission / reception surface A <b> 2 based on the control by the relay unit 200. The transmitted ultrasonic wave enters the wedge material 123 from the bonding surface B2. Thereafter, the ultrasonic wave propagates through the wedge material 123 and is transmitted from the incident / exit surface C2. The ultrasonic wave transmitted from the incident / exit surface C2 enters the elastic coplant 124 from the wedge contact surface D2, propagates through the elastic coplanar 124, and then exits from the pipe contact surface E2 of the protrusion T2 toward the pipe P. The

  In the present embodiment, the wedge material 123 is formed with the bonding surface B2 and the incident / exit surface C2 so that the incident angle of the ultrasonic transverse wave with respect to the axial direction is equal to or greater than the critical angle. In this case, the longitudinal wave and the transverse wave of the ultrasonic wave emitted from the pipe contact surface E2 are totally reflected by the peripheral wall P2 of the pipe P, and hardly enter the peripheral wall P2. On the other hand, a longitudinal wave of ultrasonic waves collides with the outer peripheral surface of the peripheral wall P2, whereby a 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 toward the opposing peripheral wall P1 at a predetermined incident angle θ. When the longitudinal wave of the ultrasonic wave that has passed through the fluid collides with the inner peripheral surface of the peripheral wall P1, a 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, an ultrasonic longitudinal wave from the pipe P toward the pipe contact surface E1 of the elastic coplant 114 is excited.

  The ultrasonic wave from the pipe P enters the protruding portion T1 from the pipe contact surface E1, propagates through the elastic coplanar 114, and is emitted from the wedge contact surface D1. The ultrasonic wave emitted from the wedge contact surface D1 enters the wedge material 113 from the incident / exit surface C1, then propagates through the wedge material 113 and is emitted from the bonding surface B1. Thereafter, 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 excitation region R2 in which the longitudinal wave of the ultrasonic wave emitted from the ultrasonic element 122 collides is provided on the peripheral wall P2. The excitation region R <b> 2 is a region that mainly excites ultrasonic waves that pass through the fluid flowing in the pipe P and travel toward the ultrasonic element 112. In FIG. 3, the excitation region R2 is illustrated by a dot pattern.

The difference between the ultrasonic wave propagation time from the ultrasonic element 112 to the ultrasonic element 122 and the ultrasonic wave propagation time from the ultrasonic element 122 to the ultrasonic element 112 is referred to as 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 ultrasonic waves in the fluid, and θ is the incident angle of ultrasonic waves 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 incident angle θ, and the flow rate correction coefficient K are known. The user can by operating the main body 300 of FIG. 1, to set the inner diameter d ₁ of the pipe P.

  The flow sensor 1 can also operate as a flow 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 a 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 an on state and an off state of an external device connected to the main body unit 300 through the main body cable CA of FIG. The indicator lamp 117 in FIG. 2 lights up so that the ON state and the OFF state of the external device can be distinguished.

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

The ultrasonic element 112 is formed of a thin plate-like 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 sizes in the inclination direction and the width direction, respectively. The size of the transmitting and receiving surface A1 in the length direction (length) is L ₁ (FIG. 4). The length L ₁ may be substantially equal to the width w _1, may be greater than the width w _1. In FIG. 4, the thickness of the ultrasonic element 112 is shown larger than the actual thickness. The outer diameter of the pipe P is d _2, the circumferential wall has a thickness of t _2.

An alternating voltage (pulse voltage) near the natural frequency is applied to the ultrasonic element 112. Thereby, the ultrasonic element 112 vibrates at the natural frequency (resonance frequency f _r ), and transmits an ultrasonic wave having high intensity. Hereinafter referred MHz the product of the thickness t ₂ of the peripheral wall which is in units of the resonance frequency f _r and mm ultrasonic displayed (millimeters) in units of (MHz) and f · t product.

The ultrasonic element 112 is preferably formed so as to vibrate at a resonance frequency _fr at which the f · t product is 2 or more and 6 or less. By setting the f · t product to 2 or more, fluctuations in the phase velocity of the guide wave in the peripheral wall are prevented. As a result, the fluid flow rate can be calculated more accurately. In addition, by setting the f · t product to 6 or less, the surface wave of the guide wave in the peripheral wall is prevented from becoming dominant. Thereby, the ultrasonic wave which has high intensity | strength in a fluid can be generated.

In addition, the ultrasonic element 112 is preferably formed so that the width w ₁ is not less than 5 times the thickness t ₁ . In this case, the intensity of double resonance in the width direction with respect to resonance in the tilt direction, which is the transmission direction of the ultrasonic waves, is reduced. Thereby, the resonance characteristics in the tilt direction can be improved. A preferable configuration of the ultrasonic element 122 is the same as the preferable configuration of the ultrasonic element 112.

The width of the portion irradiated with ultrasonic waves on the peripheral wall of the pipe P (hereinafter referred to as the irradiation width) is preferably equal to or less than one third of the outer diameter d ₂ of the pipe P. In this case, it is possible to further reduce the ultrasonic component that is transmitted and received between the sensor heads 110 and 120 by propagating through the peripheral wall without passing through the fluid. As a result, the fluid flow rate can be calculated more accurately.

Here, as described above, the width w ₁ of the ultrasonic element 112 is preferably not less than 5 times the thickness t ₁ . In addition, 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 greater than a predetermined thickness. Therefore, the width _{w 1} of the ultrasonic element 112 (transmission and reception surface A1) is larger than the predetermined width.

On the other hand, as described above, the ultrasonic irradiation width is preferably equal to or less than one third of the outer diameter d ₂ of the pipe P. In this embodiment, the outer diameter d ₂ of the pipe P is (is, for example 2mm or more 20mm or less) smaller for the irradiation width of the ultrasonic wave becomes smaller than the predetermined width. Thus, when irradiating the pipe P with ultrasonic waves transmitted from the entire region of the width w ₁ of the transmission / reception surface A1, the above two preferable conditions cannot be satisfied.

Therefore, a propagation path for propagating ultrasonic waves transmitted from the transmission / reception surface A <b> 1 of the ultrasonic element 112 to the pipe P is provided in the elastic coplant 114. 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 this embodiment, the wedge contact surface D1 of the elastic couplant 114 is formed so that the width becomes w _1. On the other hand, the protrusion T1 and the pipe contact surface E1 is formed so that the width becomes w ₁ is smaller than w _2. Specifically, the width w ₂ is equal to or less than one third of the outer diameter d ₂ of the pipe P. That is, the width varying portions V1 of the propagation path, between the wedge contact surface D1 and a pipe contact surface E1, width varies from w ₁ to w _2.

In this configuration, an ultrasonic wave having a large width w ₁ enters the elastic coplanar 114 from the wedge contact surface D1. Thereafter, the ultrasonic wave propagates through the elastic coplanar 114 and is emitted from the lower surface (exiting surface) of the elastic coplant 114. Here, since the ultrasonic wave emission surface excluding 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 hardly irradiated to the pipe P. On the other hand, since the pipe contact surface E1 is in contact with the pipe P, the ultrasonic wave emitted from the pipe contact surface E1 is 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 disposed between the ultrasonic wave emission surface excluding the pipe contact surface E1 and the pipe P. In this case, the ultrasonic wave emitted from the emission surface is blocked by the leaf spring 115. Thereby, it can prevent more reliably that an ultrasonic wave is irradiated to the piping P from the output surface except the piping contact surface E1.

Thus, it is possible to irradiate the receiving surface A1 of the ultrasonic element 112 having a larger width w ₁ even when the ultrasonic wave is transmitted, the ultrasonic wave having a smaller width w ₂ in the pipe P. Thereby, said two preferable conditions can be made compatible. In the present embodiment, the width of the width varying portions V1 varies from w ₁ to w _2, the present invention is not limited thereto. The width of the width changing portion V1 may change from w ₃ to w ₂ different from w ₁ and w ₂ . Width _{w 3} may be larger than _{w 1,} it may be smaller than _{w 1.}

The ultrasonic element 112 is arranged to transmit ultrasonic waves in the tilt direction. Therefore, the spread area of the ultrasonic wave in the axial direction is larger than the spread area of the ultrasonic wave transmitted from the ultrasonic element 112 in the direction orthogonal to the axial direction. Therefore, the pipe contact surface E1 of the protrusion T1 of the elastic couplant 114 is preferably a length in the axial direction is formed to be L ₁ greater than L _2. Thereby, an ultrasonic wave can be irradiated from the pipe contact surface E1 to the pipe P over a sufficiently large region in the axial direction.

The configuration of the elastic coplant 124 is the same as the configuration of the elastic coplant 114. Therefore, a width change portion V2 similar to the width change portion V1 is formed in the propagation path of the elastic coplant 124. Further, the pipe contact surface E2 of the protrusion T2 of elastic couplant 124 is preferably a length in the axial direction is formed to be L ₁ greater than L _2.

  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 protruding portion T1 of the elastic coplant 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 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 protruding portion T <b> 1 while being attached to the clamp member 130. Thus, even when the protrusions T1 has a smaller width w ₂ is pressed to the pipe P, a change in the width of the protrusion T1 is regulated. Therefore, it is possible to irradiate ultrasonic waves having a smaller width w ₂ easily piping. Further, bending, meandering and deformation of the protruding portion T1 are prevented while maintaining the width of the protruding portion T1. As a result, the flow rate of the fluid flowing in the pipe P can be accurately calculated.

  The damping material 116 is attached to the pipe P so as to surround the protruding portion T1 and the excitation 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 wave propagating in the circumferential direction in the peripheral wall is attenuated by the damping material 116. Thereby, the component of the ultrasonic wave which propagates in the surrounding wall without passing through the fluid and is transmitted and received between the sensor heads 110 and 120 can be further reduced.

  The damping material 116 is attached to the pipe P in a state of surrounding the protruding portion T1 and the excitation 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 R <b> 1 is suppressed, and the ultrasonic wave propagating in the axial direction in the peripheral wall of the pipe P is attenuated by the damping material 116. For this reason, the guide wave propagating in the axial direction is prevented from being reflected and returned by the end face of the peripheral wall in the axial direction. Therefore, the ultrasonic wave is not excited at a timing when the returned guide wave is unnecessary. As a result, the fluid flow rate can be calculated 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. Accordingly, a slit S4 similar to the slit S3 is formed in the leaf spring 125, and a slit S2 similar to the slit S1 is formed in the damping material 126. The protruding portion T2 of the elastic coplant 124 is fitted into the slit S4 of the leaf spring 125 and the slit S2 of the damping material 126. Accordingly, the protruding portion T2 is surrounded by the leaf spring 125 and the damping material 126 in the circumferential direction and the axial direction while being in contact with the pipe P. The damping material 126 is attached to the pipe P in a state of surrounding the excitation region R2 in the circumferential direction and the axial direction, and is pressed against the pipe P.

  FIG. 6 is a schematic cross-sectional view showing the internal configuration of the head unit 100 in a modified example. As shown in FIG. 6, the leaf spring 115 in the modified example is formed with a standing wall portion W <b> 1 that surrounds the edge of the slit S <b> 3 and extends toward the pipe P. The standing wall portion W1 surrounds the protruding portion T1 of the elastic coplant 114 while being fitted into the slit S1 of the damping material 116. In this case, the leaf spring 115 holds the position and posture of the elastic coplant 114 with respect to the clamp member 130 more firmly. Thereby, the bending, meandering and deformation of the protruding portion T1 are more reliably prevented.

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

(4) Attaching the Head Part to the Pipe FIGS. 7 and 8 are diagrams for explaining a process of attaching the head part 100 to the pipe P. FIG. As shown in FIG. 7, the elastic coplant 114 is disposed between the clamp member 130 and the leaf spring 115. Next, the leaf spring 115 is attached to the clamp member 130 by the two attachment screws 134 in a state where the protruding portion T1 (FIGS. 4 and 5) of the elastic coplant 114 is fitted in 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 disposed so that the tip of the protruding portion T1 is fitted into the slit S1. The damping material 116 may be bonded to the leaf spring 115 with an adhesive or the like. In this case, the elastic coplant 114, the leaf spring 115, and the damping material 116 can be easily handled together with the clamp member 130.

  Similarly, an elastic coplant 124 is disposed 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 attachment screws 144 in a state where the protruding portion T2 of the elastic coplant 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 disposed so that the tip of the protruding portion T2 is fitted into the slit S2 (FIGS. 4 and 5). The damping material 126 may be bonded to the leaf spring 125 with an adhesive or the like. In this case, it becomes easy to handle the elastic coplant 124, the leaf spring 125 and the damping material 126 together with the clamp member 140.

  The clamp member 140 has a pair of vertical walls 141 extending in the axial direction and facing in the width direction, and a pair of vertical walls 142 facing in the axial direction. In addition, the clamp member 140 has a support portion 143 formed so as to be able to support the pipe P by contacting the pipe P. A pair of temporary fixing members 145 for temporarily fixing the clamp member 140 to the pipe P are provided on the mutually opposing surfaces (inner surfaces) of the pair of vertical walls 141. 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 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. In addition, the clamp member 130 has a support portion 133 formed so as to be able to support the pipe P by contacting 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 clamp members 130 and 140 are guided 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.

  The inner surface of the pair of vertical walls 131 and the outer surface of the pair of vertical walls 141 are movable in parallel with each other when they face each other, and a clearance is formed that restricts the inclination of the pipe P around a predetermined angle around the axial center direction. The dimensional relationship is as follows. Similarly, the inner surfaces of the pair of vertical walls 132 and the outer surfaces of the pair of vertical walls 142 are movable in parallel to each other when they face each other, and are inclined at 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 for regulating this is formed.

  The clamp member 140 is disposed 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. In addition, the clamp member 130 is disposed so that the pair of vertical walls 141 is positioned between the inner surfaces of the pair of vertical walls 131 and the pair of vertical walls 142 is positioned between the inner surfaces of the pair of vertical walls 132. Thereafter, the clamp member 130 and the clamp member 140 are sandwiched with respect to the pipe P with a predetermined pressing force or more. In this state, the 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.

  The clamp members 130 and 140 are temporarily fixed to the pipe P together with the elastic coplants 114 and 124, the leaf springs 115 and 125, and the damping materials 116 and 126 by the above procedure. 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. This prevents the clamp members 130 and 140 from falling off 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 sliding 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 screw portion of the corresponding temporary fixing screw 135. When the clamp members 130 and 140 are sandwiched between the pipes P with a predetermined pressing force or more, the temporary fixing screws 135 are inserted into the temporary fixing members 145 while expanding the screw holes of the corresponding temporary fixing members 145. . In this case, due to the frictional force generated between the temporary fixing screw 135 and the temporary fixing member 145, the temporary fixing screw 135 is difficult to come off from the temporary fixing member 145. Thereby, it is possible to maintain the state in which the clamp members 130 and 140 are sandwiched with respect to the pipe P with a predetermined pressing force or more.

  Note that the length of the screw portion of the temporary fixing screw 135 inserted into the screw hole of the temporary fixing member 145 varies 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 fixing member 145 can generate a sufficient frictional force even when the insertion portion of the temporary fixing screw 135 is the shortest, and the tip of the temporary fixing screw 135 even when the insertion portion of the temporary fixing 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. Thereby, the clamp members 130 and 140 can be temporarily fixed to the pipes P having various outer diameters.

  Thereafter, as shown in FIG. 8, the attachment metal plates 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 attachment metal plate 150 by two attachment screws 151. The casing 121 is attached to the attachment sheet metal 160 by two attachment screws 161.

  In this state, the attachment sheet metal 150 and the attachment sheet metal 160 are coupled to each other by the four coupling screws 101 so that the attachment sheet metal 150 is attached to the clamp member 130 and the attachment sheet metal 160 is attached to the clamp member 140. Is done. Thus, 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 a state where the sensor head 110 is attached to the pipe P, the elastic coplant 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 coplant 114 is disposed along the axial direction while being in contact with the pipe P. When the support part 133 of the clamp member 130 contacts the pipe P, the amount of crushing of the elastic coplant 114 (projection part T1) is regulated. Therefore, it is possible to press the elastic coplanar 114 uniformly regardless of individual differences among the workers who install the clamp members 130.

  Similarly, in a state where the sensor head 120 is attached to the pipe P, the elastic coplant 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 coplant 124 is disposed along the axial direction while being in contact with the pipe P. When the support part 143 of the clamp member 140 contacts the pipe P, the amount of crushing of the elastic coplant 124 (projection part T2) is regulated. Therefore, the elastic coplanar 124 can be pressed uniformly regardless of individual differences among the workers who install the clamp members 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 in a state where the pipe P is 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 the present embodiment, the leaf springs 115 and 125 and the damping materials 116 and 126 have high elasticity. The plate springs 115 and 125 are semi-cylindrical thin plate springs, and are thin plate springs whose circular ends are cantilevered at fixed positions attached to the clamp members 130 and 140 by two mounting screws 134 and 144. It has become. Further, as shown in FIGS. 9 to 11, a space V that allows deformation of the leaf springs 115 and 125 and the damping materials 116 and 126 is secured inside the clamp members 130 and 140. Furthermore, as shown in FIG. 9, in the state where the pipe P is not attached to the leaf springs 115, 125, the diameter of the inner surface of the damping material 116, 126 is set slightly smaller than the outer diameter of the attachable pipe P. Has been.

  As shown in FIG. 10, the clamp members 130 and 140 are sandwiched between the pipes P, and the pipes P are attached to the leaf springs 115 and 125. At this time, as indicated by the white arrows, the opposing forces are generated in the leaf springs 115 and 125, and the opposing forces are generated in the damping materials 116 and 126, whereby the leaf springs 115 and 125 and the damping material 116, 126 is pushed into the space V. In this case, due to the elasticity of the arc-shaped cantilevered thin leaf springs of the leaf springs 115 and 125 that opposes the spreading, a direction (pipe) different from the clamping direction of the clamp members 130 and 140, as indicated by the dashed-dotted arrows. A pressing force is also generated in the direction toward the axis of P). Thus, simply by sandwiching the pipe P between the clamp members 130 and 140, the damping materials 116 and 126 are pressed against the pipe P toward the axial center of the pipe P by the leaf springs 115 and 125 that are semi-cylindrical thin plate springs. The As a result, an unnecessary component of the ultrasonic wave propagating in the peripheral wall of the pipe P can be surely attenuated.

  As shown in FIG. 11, even when 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 caused by the elasticity of the leaf springs 115 and 125 as in FIG. A pressing force is generated in a direction toward the axis center of P. Thereby, the damping materials 116 and 126 are pressed by the pipe P toward the axial center of the pipe P.

  Thus, by ensuring the space V inside the clamp members 130 and 140, the leaf springs 115 and 125 are allowed to be deformed even when 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, since the damping material 116 is deformed, the damping material 116 can be reliably pressed against the pipe P by the clamp member 130. Similarly, when the damping material 126 is deformed, the damping material 126 can be reliably pressed against the pipe P by the clamp member 140.

(5) Relay Unit and Main Body FIG. 12 is a block diagram showing an internal configuration of the relay unit 200 and the main body 300 of FIG. As illustrated in FIG. 12, the relay unit 200 includes a switching circuit 201, transmission circuits 202 and 203, an amplifier circuit 204, an A / D (analog / digital) converter 205, a relay control unit 206, a calibration information storage unit 207, and a communication circuit. 208, a power supply circuit 209, and an indicator lamp driving 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. 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 where 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 an ultrasonic wave, and outputs an analog ultrasonic signal corresponding to the received ultrasonic wave. The ultrasonic signal output from the ultrasonic element 122 is supplied 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 an ultrasonic wave and outputs an analog ultrasonic signal corresponding to the received ultrasonic wave. The ultrasonic signal output from the ultrasonic element 112 is supplied to the amplifier circuit 204.

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

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

  The relay control unit 206 includes, for example, a field-programmable gate array (FPGA) or a CPU (central processing unit) and a memory, and includes an ultrasonic control unit 206a, a measurement information generation unit 206b, and an indicator light control unit 206c as functional units. including. When the relay control unit 206 includes 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 an FPGA, and the remaining part is realized by the CPU executing a program. May be.

  The ultrasonic control unit 206 a 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 operates the transmission circuit 202 to generate the first drive signal while shifting the connection state between the ultrasonic elements 112 and 122 and the amplifier circuit 204 to the first state. Let In this case, an ultrasonic wave is transmitted by the ultrasonic element 112 and an ultrasonic wave is 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 provided to the measurement information generation unit 206b.

  Further, the ultrasonic control unit 206a operates the transmission circuit 203 so as to shift the connection state between the ultrasonic elements 112 and 122 and the amplifier circuit 204 to the second state and generate the second drive signal. Let In this case, an ultrasonic wave is transmitted by the ultrasonic element 122 and an ultrasonic wave is received by the ultrasonic element 112. 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 provided to the measurement information generation unit 206b.

  The measurement information generation unit 206b generates a 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 ultrasonic wave propagation time from the ultrasonic element 112 to the ultrasonic element 122 and the ultrasonic wave propagation time from the ultrasonic element 122 to the ultrasonic element 112, respectively. A time difference may be calculated as a time difference.

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

  The calibration information storage unit 207 is configured by, for example, a nonvolatile memory, and stores calibration information related to the ultrasonic elements 112 and 122, the switching circuit 201, the transmission circuits 202 and 203, the amplification circuit 204, and the A / D converter 205.

  Depending on the operational characteristics of each component of the head unit 100 and the relay unit 200, the relationship of the formula (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 There is. The calibration information is information for calibrating the equation (1) in order to accurately calculate a 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 the flow rate 0) to be added to a term including the time difference Δt in the equation (1).

  The communication circuit 208 is connected to one end of the relay cable CA3 in FIG. 1 and outputs the measurement information and calibration information in digital format generated by the measurement information generation unit 206b to the main body unit 300 through the relay cable CA3. In addition, the communication circuit 208 provides the relay control unit 206 with a transmission control signal and a display control signal input from the main body unit 300 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 driving circuit 210.

  The power supply circuit 209 receives power supplied from the main unit 300 through the relay cable CA3 and supplies the received 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 in FIG. 1 and supplies 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 a transmission control signal and a display control signal generated by the main body control unit 302 to the relay unit 200 through the relay cable CA3 as will be 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. The user can input the dimensions of the pipe P to which the head unit 100 is attached, the flow rate correction coefficient, and the like by operating the operation unit 304. Further, the user can input a flow rate threshold value by operating the operation unit 304. The storage unit 305 is configured by a nonvolatile 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 and 122 and the indicator lamp 117, respectively. Further, the main body control unit 302 sets information by causing the storage unit 305 to store information such as the dimensions of the pipe P, the flow rate correction coefficient, the flow rate threshold value, and the like input by the operation unit 304. As the dimensions of the pipe P, the inner diameter d ₁ of the pipe P may be set by the operation unit 304 to the pipe thickness t ₂ of the outer diameter d ₂ and the peripheral wall of P is input.

  Further, the main body control unit 302 calibrates the expression (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 a comparison result between the calculated flow rate and a set flow rate threshold value. 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 sensor 1 through the main body cable CA4.

(6) Modification In the above embodiment, the head unit 100 includes the elastic coplants 114 and 115, but the present invention is not limited to this. The head unit 100 may not 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 protruding portion T2 and the width changing portion V2 are formed on at least one of the wedge material 123 and the damping material 126.

  FIGS. 13A to 13D are cross-sectional views showing first to fourth modifications of the sensor head 110, respectively. 13A to 13D, cross-sectional views corresponding to the cross-sectional view of the sensor head 110 in FIG. 5 are shown. Hereinafter, differences between the sensor head 110 of FIG. 5 and the first to fourth modifications of the sensor head 110 will be described. 13A to 13D, the sensor head 120 is not shown, but the sensor head 120 has the same configuration as the corresponding sensor head 110.

  As shown in FIG. 13A, in the first modified example of the sensor head 110, a protrusion that protrudes upward so as to come into contact with the wedge material 113 over a predetermined length in the axial direction on 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 in 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 surface of the damping material 116 that is in contact with the pipe P and that overlaps the protruding portion T1 in the vertical direction is the pipe contact surface E1. Joint surface B1 of the wedge member 113 is formed so that the width becomes _{w 1.} On the other hand, the protrusion T1 and the pipe contact surface E1 is formed so that the width becomes w ₁ is smaller than w _2. In other words, the wedge member 113 and damping member 116, the propagation path is provided between the joint surface B1 and the pipe contact surface E1, width varying portions V1 which width varies from w ₁ to w ₂ is formed.

  As shown in FIG. 13B, in the second modified example of the sensor head 110, a protrusion that protrudes downward at a lower portion of the wedge material 113 so as to be in contact with the damping material 116 over a predetermined length in the axial direction. Part T1 is formed. Further, the slit S <b> 1 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 surface of the damping material 116 that is in contact with the pipe P and that overlaps the protruding portion T1 in the vertical direction is the pipe contact surface E1. Joint surface B1 of the wedge member 113 is formed so that the width becomes _{w 1.} On the other hand, the protrusion T1 and the pipe contact surface E1 is formed so that the width becomes w ₁ is smaller than w _2. In other words, the wedge member 113 and damping member 116, the propagation path is provided between the joint surface B1 and the pipe contact surface E1, width varying portions V1 which width varies from w ₁ to w ₂ is formed.

  As shown in FIG. 13C, in the third modified example of the sensor head 110, a protrusion that protrudes downward so as to come into contact with the damping material 116 over a predetermined length in the axial direction is provided below the wedge material 113. Part T1 is formed. Further, the sensor head 110 does not include the leaf spring 115. Further, the slit S <b> 1 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 surface of the damping material 116 that is in contact with the pipe P and that overlaps the protruding portion T1 in the vertical direction is the pipe contact surface E1. Joint surface B1 of the wedge member 113 is formed so that the width becomes _{w 1.} On the other hand, the protrusion T1 and the pipe contact surface E1 is formed so that the width becomes w ₁ is smaller than w _2. In other words, the wedge member 113 and damping member 116, the propagation path is provided between the joint surface B1 and the pipe contact surface E1, width varying portions V1 which width varies from w ₁ to w ₂ is formed.

  As shown in FIG. 13 (d), in the fourth modified example of the sensor head 110, a protruding portion that protrudes downward at a lower portion of the wedge material 113 so as to be in contact with the pipe P over a predetermined length in the axial direction. T1 is formed. The protruding portion T1 of the wedge material 113 is in 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 with the pipe P in the protruding portion T1 of the wedge material 113 is the pipe contact surface E1. Grease for matching the acoustic impedance between the wedge material 113 and the pipe P may be applied to the pipe contact surface E1. Joint surface B1 of the wedge member 113 is formed so that the width becomes _{w 1.} On the other hand, the protrusion T1 and the pipe contact surface E1 is formed so that the width becomes w ₁ is smaller than w _2. In other words, the wedge member 113, propagation path is provided between the joint surface B1 and the pipe contact surface E1, width varying portions V1 which width varies from w ₁ to w ₂ is formed.

(7) Effect The flow sensor 1 according to the present embodiment includes sensor heads 110 and 120. In the sensor head 110, the ultrasonic wave transmitted from the transmission / reception surface A 1 of the ultrasonic element 112 is propagated to the pipe P through the wedge material 113 and the elastic coplanar 114. The elastic coplant 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 with respect to the axial direction is not less than the critical angle. Therefore, the ultrasonic wave emitted from the pipe contact surface E1 is totally reflected by the pipe P and hardly enters 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 an ultrasonic wave is sandwiched between the ultrasonic element 112 and the ultrasonic element 122 by using the excited guide wave. You can send and receive. In this case, unnecessary components of the ultrasonic wave transmitted and received between the ultrasonic element 112 and the ultrasonic element 122 by propagating through the peripheral wall of the pipe P without passing through the fluid are reduced. 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 wave transmitted in the tilt direction can be increased. On the other hand, when the width of the portion irradiated with the ultrasonic wave in the pipe P is increased, the unnecessary component of the ultrasonic wave is increased. Therefore, the elastic coplant 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. Thereby, unnecessary components of the ultrasonic wave can be reduced while increasing the intensity of the ultrasonic wave transmitted in the tilt direction. As a result, the flow rate of the fluid flowing through 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 separately and connected by the relay cable CA3, but the present invention is not limited to this. The relay unit 200 and the main body unit 300 may be provided integrally.

  (B) In the above embodiment, the damping material 116 is configured by one elastic body that surrounds the protrusion T1 of the elastic coplant 114 in the circumferential direction and the axial direction, but the present invention is not limited to this. The damping material 116 may be configured by a plurality of elastic bodies that surround the protruding portion T1 of the elastic coplant 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 configured by a plurality of elastic bodies that surround the protruding portion T2 of the elastic coplant 124 in the circumferential direction and the axial direction.

  (C) In the above embodiment, the damping material 116, 126 is provided in the head unit 100, but the present invention is not limited to this. When the portion of the pipe P excluding the excitation regions R1 and R2 hardly excites unnecessary ultrasonic waves, the damping materials 116 and 126 may not be provided in the head unit 100.

  (D) In the above embodiment, the leaf springs 115 and 125 are provided in the head unit 100, but the present invention is not limited to this. The leaf spring 115 may not be provided on the head unit 100. In this case, the damping material 116 is attached to the clamp member 130 with an adhesive or the like. The protruding portion T1 of the elastic coplant 114 is fitted into the slit S1 of the damping material 116. Thereby, the damping material 116 maintains the position and posture of the elastic coplant 114 with respect to the clamp member 130.

  Similarly, the leaf spring 125 may not be provided in the head unit 100. In this case, the damping material 126 is attached to the clamp member 140 with an adhesive or the like. The protruding portion T2 of the elastic coplant 124 is fitted into the slit S2 of the damping material 126. Thereby, the damping material 126 maintains the position and posture of the elastic coplant 124 with respect to the clamp member 140.

(9) Correspondence between each component of claim and each part of embodiment The following describes an example of the correspondence between each component of the claim and each part of the embodiment. It is not limited. As each constituent element in the claims, various other elements having configurations or functions described in the claims can 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 These are examples of 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 coplanar, 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 excitation region R1 is an example of an excitation region, and the leaf spring 115 is It is an example of a pressing member. In the example of FIG. 5, the elastic coplant 114 is an example of a propagation path, and in the examples of FIGS. 13A to 13C, the wedge material 113 and the damping material 116 are examples of the propagation path, and FIG. In the example, the wedge material 113 is an example of a propagation path.

  DESCRIPTION OF SYMBOLS 1 ... Flow sensor, 100 ... Head part, 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 lamp, 130, 140 ... clamp member, 131, 132, 141, 142 ... vertical wall, 133, 143 ... support, 134, 144, 151, 161 ... Mounting screw, 135, 146 ... Temporary fixing screw, 145 ... Temporary fixing member, 150, 160 ... Mounting sheet metal, 200 ... Relay part, 201 ... Switching circuit, 202, 203 ... Transmission circuit, 204 ... Amplifying 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 lamp drive circuit, 300 ... main unit, 302 ... main unit control unit, 303 ... display unit, 304 ... operation unit, 305 ... storage 306 ... Output circuit, A1, A2 ... Transmission / reception surface, B1, B2 ... Joint surface, C1, C2 ... I / O surface, CA1, CA2 ... Head cable, CA3 ... Relay cable, CA ... Main body cable, D1 ... Wedge Contact surface, E1, E2 ... piping contact surface, H1, H2 ... opening, P ... piping, P1, P2 ... peripheral wall, R1, R2 ... excitation region, S1-S4 ... slit, T1, T2 ... projection, V1, V2 ... width changing part, V ... space, W ... window part, W1, W2 ... standing wall part

Claims (14)

A clamp-on ultrasonic flow sensor that measures the flow rate of fluid flowing in a pipe,
A first ultrasonic element having a transmitting and receiving surface capable of transmitting and receiving ultrasonic waves;
A propagation path for propagating ultrasonic waves transmitted from the transmission / reception surface of the first ultrasonic element to the piping, having a piping contact surface in contact with the piping;
A clamp member that supports the pipe and supports the propagation path so that the pipe contact surface is disposed 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;
A flow rate calculation unit that calculates a flow rate of fluid flowing in the pipe based on ultrasonic waves transmitted and received between the first ultrasonic element and the second ultrasonic element;
The propagation path includes a wedge material that propagates ultrasonic waves in an inclined direction with respect to the axial direction, an elastic coplanar that matches the acoustic impedance between the wedge material and the pipe, and a damping that attenuates ultrasonic waves in the peripheral wall of the pipe Including at least one material, provided that the incident angle of the ultrasonic shear wave with respect to the axial direction is equal to or greater than the critical angle,
The transmitting / receiving surface of the first ultrasonic element has a first width in a width direction orthogonal to the axial direction and the tilt direction,
The pipe contact surface of the propagation path has a second width smaller than the first width in the width direction;
The propagation path includes a width changing portion that changes from a third width different from the second width to the second width between the transmission / reception surface and the pipe contact surface of the first ultrasonic element. A clamp-on ultrasonic flow sensor. The clamp-on ultrasonic flow sensor according to claim 1, wherein the third width coincides with the first width. The clamp-on type ultrasonic flow sensor according to claim 1 or 2, wherein the first width is five times or more the thickness of the first ultrasonic element in the tilt direction. The clamp-on ultrasonic flow sensor according to any one of claims 1 to 3, wherein the second width is equal to or less than one third of the outer diameter of the pipe. The clamp-on type ultrasonic flow sensor according to any one of claims 1 to 4, wherein the first ultrasonic element is configured to transmit an ultrasonic wave by vibrating at a specific resonance frequency. The said 1st ultrasonic element is formed so that the product of the frequency of the ultrasonic wave displayed by the unit of megahertz and the thickness of the surrounding wall of the said piping displayed by the unit of millimeter may be 2 or more. 5. A clamp-on type ultrasonic flow sensor according to 5. The said 1st ultrasonic element is formed so that the product of the frequency of the ultrasonic wave displayed in the unit of megahertz and the thickness of the surrounding wall of the said piping displayed in the unit of millimeter may be 6 or less. The clamp-on type ultrasonic flow sensor according to 5 or 6. The peripheral wall of the pipe includes an excitation region in which a longitudinal wave of ultrasonic waves emitted from the pipe contact surface of the propagation path collides,
The said excitation area | region of the said piping excites the ultrasonic wave which passes the fluid which flows through the said piping, and goes to a said 2nd ultrasonic element, The clamp-on type superposition | superposition as described in any one of Claims 1-7 Sonic flow sensor. The clamp-on type ultrasonic flow sensor according to any one of claims 1 to 8, wherein the damping material is configured to maintain a position and a posture of the elastic coplant. The clamp-on type ultrasonic flow sensor according to any one of claims 1 to 9, further comprising a pressing member that presses the damping material against the pipe. The clamp-on ultrasonic flow sensor according to claim 10, wherein the pressing member is configured to hold the position and posture of the elastic coplant. The clamp-on type ultrasonic wave according to claim 10 or 11, wherein the pressing member is formed of a metal member, and is arranged so as to block an ultrasonic wave propagating from the portion of the propagation path excluding the pipe contact surface to the pipe. Sonic flow sensor. The transmitting / receiving surface of the first ultrasonic element has a first length in a length direction orthogonal to the tilt direction and the width direction,
The clamp-on ultrasonic flow sensor according to any one of claims 1 to 12, wherein the pipe contact surface of the propagation path has a second length that is greater than the first length in the axial direction. . The clamp-on type ultrasonic flow sensor according to any one of claims 1 to 13, wherein an outer diameter of the pipe is 2 mm or more and 20 mm or less.

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