JP2012018030A - Ultrasonic sensor attachment structure and ultrasonic flow measuring device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic sensor attachment structure having short reverberations by absorbing unnecessary vibration of a casing of an ultrasonic sensor and preventing vibration propagation into a flow channel.SOLUTION: The ultrasonic sensor attachment structure includes: an ultrasonic sensor 18 having a topped cylindrical case 7 provided with a top part 8, a side wall part 9 and an opening 10, a piezoelectric body 12 fixed on the internal surface of the top part 8, a flange part 13 provided on the edge of the side wall part 9, and a terminal plate 14 that closes the flange part 13 and the opening 10; a vibration propagation suppressing body 19 installed on the side wall part 9; and a sealing body 20 that is closely contacted with the flange part 13. The ultrasonic sensor 18 is attached to an attaching part 6 for the ultrasonic sensor via the sealing body 20. In this way, propagation of vibration to the case side wall surface due to the vibration of the piezoelectric body is cut off by the vibration propagation suppressing body, and at the same time unnecessary vibration propagation to the attaching part is prevented, thereby transmission and reception of signals necessary for measuring are made possible without being affected by unnecessary signals.

Description

  The present invention relates to an attachment structure of an ultrasonic transmission sensor that transmits and receives ultrasonic pulses and an ultrasonic flow rate measuring apparatus that measures the flow rate and flow velocity of gas and liquid using the ultrasonic sensor.

  Conventionally, an attachment structure for attaching this type of ultrasonic sensor to the flow path of an ultrasonic flow measuring device is, for example, an ultrasonic sensor in which a piezoelectric body is arranged on the inner surface of the top of a celestial cylindrical case. A support provided is formed by overlapping a flange provided on the outer periphery of the opening and a sealing body that closes the opening, and a damping body that reduces vibration is installed on the outer surface of the side wall of the case. An ultrasonic sensor is installed in the flow path via a vibration transmission suppressing body having a holding part for holding a part of the filter (for example, see Patent Document 1).

  FIG. 5 shows a cross-sectional view of a conventional ultrasonic sensor mounting structure. As shown in FIG. 5, the ultrasonic sensor 1 has a top 2a, a side wall 2b, an opening 2c, and a flange 2d on the outer periphery of the opening. Are integrally formed, and a piezoelectric body 3 installed on the inner surface of the top portion 2a. A vibration damping body 4 is wound around the side wall 2b of the case 2, the opening 2c is sealed with a sealing body 2e, and the support 1a of the ultrasonic sensor 1 is supported by the sealing body 2e and the flange 2d. The support portion 1a is held by the holding portion 5a of the vibration transmission restraining body 5, and the vibration transmission restraining body 5 is installed in the attached portion 6 of the ultrasonic flow measuring device.

Japanese Patent No. 3528726

  However, in the conventional configuration for attaching the ultrasonic sensor 1 to the attached portion 6, the vibration damping body 4 and the vibration transmission suppressing body 5 are provided as a vibration-proof measure for the case 2 of the ultrasonic sensor 1. Since the vibration damping body 4 and the vibration transmission restraining body 5 are in close contact with each other and the vibration transmission restraining body 5 has a holding portion 5a, the vibration transmission restraining body 5 is It is attached in close contact with the attachment portion 6. In this configuration, the vibration of the piezoelectric body 3 of the ultrasonic sensor 1 on the transmission side is transmitted to the vibration damping body 4 through the side wall portion 2b of the case 2, and therefore, the vibration transmission suppressing body 5 that is in close contact therewith also transmits the vibration. The vibration is transmitted and the reverberation vibration that has not been completely wiped out by the vibration transmission suppressing body 5 is transmitted to the receiving side through the wall of the attached portion 6 in close contact, and the vibration due to the reverberation propagated through the flow path wall. There has been a problem that there is a possibility that the measurement of the flow rate is deteriorated by interference with the signal propagated through the measurement fluid to become noise.

  Further, the vibration damping body 4 and the vibration transmission restraining body 5 of the conventional ultrasonic sensor are configured to fit each other, and the vibration transmission restraining body 5 is provided so as to sandwich the support portion 1 a of the ultrasonic sensor 1. Therefore, it takes time to incorporate the ultrasonic sensor 1. Further, the vibration transmission deterring body 5 must be provided with a recess in order to sandwich the sensor support portion 1a. However, since the material is often an elastic body such as rubber, the vibration transmission deterring body 5 is an elastic body. There is a problem that the holding portion 5a cannot be securely clamped by the holding portion 5a and may come off.

In order to solve the above-described conventional problems, the ultrasonic sensor mounting structure of the present invention has the following structure:
A cylindrical case having a top, a side wall, and an opening, a piezoelectric body fixed to the inner wall surface of the top, a flange provided at the end of the side, a terminal plate that closes the flange and the opening An ultrasonic sensor having at least a part of the side wall, a vibration transmission deterrence body that prevents housing vibration of the side wall part, and a sealing body that is in close contact with at least a part of the flange part. The acoustic wave sensor is attached to the attachment portion of the ultrasonic sensor via a sealing body.

  As a result, the vibration transmission to the case side wall due to the vibration of the piezoelectric body is blocked by the vibration transmission suppressing body, and at the same time, the unnecessary vibration propagation to the flow path is prevented, so that the ultrasonic sensor on the transmission / reception side can It is possible to transmit and receive signals necessary for measurement without receiving the signal.

  The ultrasonic sensor mounting structure of the present invention enables highly accurate measurement.

Sectional drawing of the attachment structure of the ultrasonic sensor in Embodiment 1 of this invention Sectional drawing of the attachment structure of the ultrasonic sensor in Embodiment 2 of this invention Sectional drawing of the side wall part of the ultrasonic sensor in Embodiment 2 of this invention Sectional drawing of the ultrasonic flow measuring device in Embodiment 3 of this invention Sectional view of conventional ultrasonic sensor mounting structure

  According to a first aspect of the present invention, there is provided a cylindrical case having a top portion, a side wall portion, and an opening, a piezoelectric body fixed to an inner wall surface of the top portion, a flange portion provided at an end portion of the side wall portion, An ultrasonic sensor having a flange portion and a terminal plate that closes the opening; a vibration transmission restrainer that is installed on at least a part of the side wall portion to prevent housing vibration of the side wall portion; and at least the flange portion The ultrasonic sensor is attached to a portion to which the ultrasonic sensor is attached via the sealing body.

  As a result, since the vibration transmission suppressing body is provided on the case side wall surface of the ultrasonic sensor without contacting the attached portion, vibration from the piezoelectric body is prevented from propagating along the case side wall surface to the flow path side. In addition, since the sealing body and the vibration transmission suppressing body are configured in a non-contact manner, an ultrasonic pulse signal with a short reverberation can be transmitted and received, so that highly accurate measurement is possible.

  According to a second aspect of the invention, particularly in the first aspect of the invention, the molding layer is formed of an electrically insulating material that covers the surface of the side wall portion, and the vibration transmission suppressing body is installed on the surface of the molding layer. Is.

  Thereby, an electrical insulation distance can be ensured between the ultrasonic sensor and the attached portion, voltage resistance is improved, and lightning surge is improved. Furthermore, the generation of noise due to the reverberation of the ultrasonic sensor can be prevented, and the S / N ratio can be improved to improve the measurement characteristics such as the measurement accuracy of the flow rate and flow velocity of the fluid to be measured.

  According to a third aspect of the present invention, there is provided a pair of the ultrasonic sensors, a measurement channel through which a fluid to be measured flows, a pair of the attached portions disposed to face the measurement channel, and an ultrasonic wave between the ultrasonic sensors. A measurement circuit unit that measures a sound wave propagation time; and a calculation unit that calculates a flow rate based on a signal from the measurement circuit unit, and the ultrasonic sensor is configured to measure the measurement channel by a first or second mounting structure. It is the ultrasonic flow measuring device attached facing the to-be-attached part.

  Thereby, an ultrasonic flow measuring device with high measurement accuracy and excellent measurement characteristics can be provided.

  Hereinafter, a seal structure of an ultrasonic sensor according to an embodiment of the present invention and an ultrasonic flow rate measuring apparatus using the same will be described with reference to the drawings. In addition, what attaches | subjects the same code | symbol in drawing is the same thing, and abbreviate | omits detailed description.

(Embodiment 1)
FIG. 1 is a cross-sectional view showing an ultrasonic sensor mounting structure according to Embodiment 1 of the present invention.

  The case 7 of the ultrasonic sensor has a ceiling-like shape having a top 8, a side wall 9, and an opening 10. A matching layer 11 is fixed to the outer wall surface of the top portion 8 of the case 7, and a piezoelectric body 12 is bonded and fixed to the inner wall surface of the top portion 8. The piezoelectric body 12 is made of, for example, PZT (lead zirconate titanate) with silver electrodes (not shown) at both ends, and an epoxy adhesive (not shown) whose upper electrode is a bonding material. It is fixed.

  A flange portion 13 is integrally provided on the outside of the side wall portion 9, and includes a flange portion 13 that spreads in an annular shape on the opening 10 side of the case 7 and a terminal plate 14 that closes the opening portion 10 by welding or the like. The terminal plate 14 is provided with terminals 15 a and 15 b, and the terminals 15 a and 15 b are insulated by an insulating portion 17. The terminal 15a is electrically connected by being connected to the lower electrode of the piezoelectric body 12 via a conductive portion 16 containing nickel balls whose surface is gold-plated.

  As described above, the ultrasonic sensor 18 is provided with the piezoelectric body 12 inside the cased cylindrical case 7 and sealed with the terminal plate 14, and includes the matching layer 11 and the flange portion 13 outside the case 7. .

  Since the ultrasonic sensor 18 is used in a gas fluid (LP gas, natural gas) to be measured, the case 7 uses stainless steel having excellent corrosion resistance, and the matching layer 11 oscillates from the piezoelectric body 12 in the gas fluid. In order to efficiently emit the ultrasonic waves, a material made of a mixture of an epoxy resin and a hollow glass sphere is selected in consideration of acoustic impedance and durability. The flange portion 13 and the terminal plate 14 of the case 7 are fixed by electrical resistance welding or the like to ensure sealing and electrical continuity.

  A vibration transmission suppressing body 19 made of a material having excellent vibration damping properties is tightly wound around the side wall 9 of the case 7 so that the ultrasonic sensor 18 emits ultrasonic waves from the piezoelectric body 12 to the case. 7 to prevent vibration transmitted to the side wall portion 9.

  The ultrasonic sensor 18 is attached and fixed to the attachment portion 6 via a gas seal sealing body 20. The sealing body 20 is provided in an annular shape around the entire circumference of the flange portion 13, and is deformed and fixed along the wall surface of the attached portion 6 to be contacted.

  The vibration transmission suppressing body 19 fixes the ultrasonic sensor 18 so as not to come into contact with the attached portion 6 when being fixed to the attached portion 6 via the sealing body 20. This is to prevent unnecessary housing vibration generated at the side wall portion of the case 7 from propagating to the attached portion 6 via the vibration transmission suppressing body 19.

  The vibration transmission restraining body 19 has a certain flexibility because it is provided in an annular shape around the entire wall surface or a part of the side wall portion 9 of the case 7 and has a certain diameter that can be easily fixed on the side wall surface of the case 7. A 0 ring-shaped elastic body or elastomer is used.

The vibration transmission suppressing body 19 and the sealing body 20 for fluid seal are made of an electrically insulating material. Specific examples include rubbers mainly composed of acrylonitrile butadiene rubber (NBR), fluorosilicone rubber, fluorine rubber, and silicon rubber. The sealing body 20 is made of a material used for a zero ring-shaped elastic body or elastomer, for example, a vibration transmission suppressing body 19, which is excellent in gas sealing and has a small deformation amount after the ultrasonic sensor 18 is mounted on the mounted portion 6. It is done. If each purpose is achieved, the material is not particular, and the vibration transmission suppressing body 19 and the sealing body 20 may be the same material or different materials.

  By adopting the above-described configuration of the present embodiment, the vibration transmission suppressing body 19 causes the vibration from the piezoelectric body 12 to propagate to the side wall portion 9 of the case 7 and the attached portion 6 via the flange portion 13. And unnecessary vibration is prevented from propagating to the other ultrasonic sensor 18 through the wall surface of the attached portion 6.

  In addition, the case propagation of the side wall 9 of the case 7 is prevented from being combined with the ultrasonic pulse signal of the ultrasonic sensor 18 by vibrating to the terminal plate 14 and the terminals 15a and 15b via the flange 13.

  Further, since the sealing body 20 can be easily attached to the entire circumference on the flange portion 13 of the ultrasonic sensor 18 like an O-ring, the sealing body 20 is formed into a recess along the flange portion 13. There is no need to previously fit the molded product into the ultrasonic sensor, and the ultrasonic sensor 18 can be attached to the attached portion 6 through the sealing body 20 in a short time. Moreover, since it is not necessary to shape the sealing body 20 into the recess along the flange portion 13, the sealing body for gas sealing can be obtained at low cost.

(Embodiment 2)
FIG. 2 is a cross-sectional view showing an ultrasonic sensor mounting structure according to Embodiment 2 of the present invention.

  As shown in FIG. 2, a molding layer 21 made of an electrically insulating material is provided so as to be in close contact with the surface of the side wall 9 of the case 7 of the ultrasonic sensor 18. The vibration transmission suppressing body 19 is fixed in contact with the surface of the molding layer 21.

  By providing the molding layer 21, even when an abnormally high voltage is generated between the attached portion 6 and the case 7 of the ultrasonic sensor 18 due to lightning or the like, it is possible to increase the withstand voltage leading to leakage, and the ultrasonic sensor based on the leakage current. 18 damage can be prevented.

  The molding layer 21 may be an elastic body such as a rubber material or a resin molding such as polypropylene, and may be a resin sleeve that conforms to the shape of the side wall 9 of the case 7. When the molding layer 21 is a resin such as polypropylene, the guide 22 is provided on a part of the entire circumference on the surface of the molding layer 21, as shown in FIG. Can also be provided.

  As described above, when the surface of the side wall portion 9 of the case 7 of the ultrasonic sensor 18 is shielded by the insulator and attached to the attached portion 6, the electrical conduction distance between the ultrasonic sensor 18 and the attached portion 6 is increased. By taking lightning surges such as lightning, even if an abnormally high voltage occurs between the ultrasonic sensor and the flow path, it is possible to increase the withstand voltage leading to leakage and prevent damage to the ultrasonic sensor due to leakage current .

(Embodiment 3)
FIG. 4 is a cross-sectional view showing the configuration of the ultrasonic flow rate measuring apparatus according to Embodiment 3 of the present invention.

  As shown in the figure, a measurement channel 24 having a width W surrounded by the channel wall 24, and the two ultrasonic sensors 25 and 26 transmit vibration to the attachment portion 6 of the channel wall 24 so as to face each other. The restraining body 19 and the sealing body 20 are attached. The ultrasonic sensor 25 on the upstream side and the ultrasonic sensor 26 on the downstream side are separated from each other by a distance L and inclined at an angle θ with respect to the flow of the fluid to be measured at the velocity V. A measurement circuit unit 27 that transmits and receives ultrasonic waves is connected to the ultrasonic sensors 25 and 26. The measurement circuit unit 27 calculates a flow rate based on a signal from the measurement circuit unit 27 and calculates a flow rate. The unit 28 is connected.

  The fluid to be measured is city gas or LP gas. As the ultrasonic flow rate measuring device, for example, a household gas meter is conceivable, and the material constituting the measurement flow path 23 is aluminum die cast or the like.

  The operation and action of the ultrasonic flow rate measuring apparatus configured as described above will be described below.

  When the fluid to be measured flows through the measurement flow path 23, ultrasonic waves are transmitted and received across the measurement flow path 23 between the ultrasonic sensors 25 and 26 by the action of the measurement circuit unit 27. That is, the elapsed time T1 until the ultrasonic wave emitted from the upstream ultrasonic sensor 25 is received by the downstream ultrasonic sensor 26 is measured. On the other hand, the elapsed time T2 until the ultrasonic wave emitted from the downstream ultrasonic sensor 26 is received by the upstream ultrasonic sensor 25 is measured.

  Based on the elapsed times T1 and T2 measured in this way, the flow rate is calculated by the calculation unit 28 by the following calculation formula. Now, assuming that the angle between the flow of the fluid to be measured and the ultrasonic propagation path is θ, the distance between the ultrasonic sensors 25 and 26 as the flow rate measurement unit is L, and the sound velocity of the fluid to be measured is C, the flow velocity V is It is calculated by the following formula.

T1 = L / (C + V cos θ)
T2 = L / (C−Vcos θ)
The speed of sound C is eliminated from the equation for subtracting the reciprocal of T2 from the reciprocal of T1,
V = (L / 2 cos θ) {(1 / T1) − (1 / T2)}
Since θ and L are known, the flow velocity V can be calculated from the values of T1 and T2.
Here, from the cross-sectional area s orthogonal to the flow direction of the measurement channel 23, the flow rate Q is Q = kVs.
Here, k is a conversion coefficient considering the flow velocity distribution in the cross-sectional area s.
In this way, the flow rate can be obtained by the calculation unit 28.

  In ultrasonic flow rate measurement, it is important to measure the times T1 and T2 with high accuracy. In other words, it is important that the transmitter side emits ultrasonic vibrations with little reverberation due to the case vibration propagating from the piezoelectric body to the case only in the fluid to be measured, while the receiver side excludes ultrasonic vibrations that have propagated through the fluid passage walls. It is important to receive only the ultrasonic vibration that has propagated through the fluid to be measured with less reverberation.

  In the ultrasonic flow measuring device of the present embodiment, the vibration transmission suppressing body 19 provided on the side wall 9 of the ultrasonic sensor 18 moves the side wall 9 of the case 7 from the piezoelectric body 12 when the sensor emits ultrasonic vibration. Since the propagating casing vibration is prevented, an ultrasonic pulse signal with short reverberation can be oscillated.

Furthermore, since the vibration transmission restraining body 19 is attached so as not to contact the flow path wall 24 when being attached to a predetermined location of the flow path wall 24, an unnecessary casing when oscillating from the ultrasonic sensor on the transmission side is used. Vibration is not propagated to the flow path side.

  Further, in the ultrasonic sensor on the reception side, when the ultrasonic pulse signal oscillated from the transmission side is received, the vibration vibrates the piezoelectric body 12 through the matching layer 11, and at the same time, the side wall 9 also vibrates the casing. However, since the unnecessary vibration is not propagated to the terminal board 14 via the flange portion 13 by the vibration transmission restraining body 19, the ultrasonic pulse signal with short reverberation can be received. it can.

  From this, it is possible to reduce the variation in the vibration attenuation characteristics of the ultrasonic sensor and to improve the stability and reliability of the transmission / reception characteristics of the ultrasonic sensor.

  Further, when the transmission / reception ultrasonic sensor is attached to the flow path wall 24, the gas seal sealing body 20 on the flange portion 13 of the ultrasonic sensor 18 prevents the flange portion from being deformed, and the airtightness for a long period of time. Sex can be secured. Since the sealing body for gas sealing has a simple configuration that does not depend on the shape of the flange portion 13, when the ultrasonic sensor 18 is attached to the flow path wall 24, the sealing material can be easily fitted in a short time. .

  Further, since the sealing body 20 is used for the ultrasonic sensor independently of the vibration transmission suppressing body 19 for preventing the housing vibration on the side wall of the sensor, Since the housing vibration of the ultrasonic sensor 18 does not propagate the vibration to the sealing body 20 via the vibration transmission suppressing body 19, the vibration is propagated to the flow path wall 24 with which the sealing body 20 is in contact. Thus, the gas sealing property can be ensured without causing unnecessary vibration to propagate through the measurement channel to the other ultrasonic sensor.

  Furthermore, if the molding layer 21 provided on the side wall portion 9 of the ultrasonic sensor 18 is provided, an electrical insulation distance between the flow path wall 24 made of metal such as aluminum die casting and the ultrasonic sensor 18 is ensured. Therefore, it is possible to provide a reliable ultrasonic flow rate measuring device that can improve the lightning surge by improving the voltage resistance.

  Since the present invention can suppress the propagation of vibrations generated by the ultrasonic transducer to the attached portion, it can also be applied to various measuring apparatuses using the ultrasonic transducer.

6 Attached part 7 Case 8 Top part 9 Side wall part 10 Opening part 12 Piezoelectric body 13 Flange part 14 Terminal plate 18, 25, 26 Ultrasonic sensor 19 Vibration transmission inhibiting body 20 Sealing body 21 Molding layer 23 Measurement flow path 27 Measurement Circuit part 28 Calculation part

Claims (3)

A case having a ceiling, a side wall, and an opening, a piezoelectric body fixed to an inner wall surface of the top, a flange provided at an end of the side wall, and the flange An ultrasonic sensor having a terminal plate for closing the opening;
A vibration transmission deterrent body installed on at least a part of the side wall portion to prevent housing vibration of the side wall portion;
A sealing body closely contacting at least a part of the flange portion,
The ultrasonic sensor is installed on a mounting portion of the ultrasonic sensor via the sealing body,
Ultrasonic sensor mounting structure. Comprising a molding layer formed of an electrically insulating material covering the surface of the side wall,
The vibration transmission suppressing body is installed on the surface of the molding layer,
The ultrasonic sensor mounting structure according to claim 1. A pair of said ultrasonic sensors;
A measurement channel through which the fluid to be measured flows;
A pair of attached parts disposed opposite to the measurement channel;
A measurement circuit unit for measuring an ultrasonic propagation time between the ultrasonic sensors;
A calculation unit that calculates a flow rate based on a signal from the measurement circuit unit,
The ultrasonic sensor is attached to face the attached portion of the measurement channel by the attachment structure according to claim 1 or 2.
Ultrasonic flow measuring device.

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