JP3533941B2 - Ultrasonic flow meter - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to relates to ultrasonic wave flow rate measuring apparatus to measure the gas and liquid flow and a flow rate by ultrasonic waves.

[0002]

2. Description of the Related Art Conventionally, as an ultrasonic transducer used in an ultrasonic flow rate measuring apparatus of this type, for example, Japanese Patent Laid-Open No. 4-309817 is known. As shown in FIG. The metal vibrating plate 2 was brazed to the metal housing 3 and welded to the metal housing 3. In addition, actual Kaihei 6-7
No. 8821 is known, and as shown in FIG. 11, the piezoelectric ceramic 1 is joined to the bottom surface 4a of the inner surface of the metal housing 4 that shields it from the measurement fluid by the pressing means 5 or the like.
The metal housing 4 was attached by welding or the like in a state of being inclined with respect to the pipe axis of the pipe line 6 through which the measurement fluid flows.

[0003]

However, in the conventional structure, since the metal housing is not provided with the antivibration measures, the vibration of the piezoelectric ceramic transmitted to the metal housing is returned to the piezoelectric ceramic without being damped, and the vibration of the piezoelectric ceramic is reduced. However, the ultrasonic pulse has a long reverberation. This reverberation causes a noise factor, which deteriorates the S / N, and thus has a problem that the measurement accuracy of the flow rate and the flow velocity decreases. In other conventional configurations, the ultrasonic transducer is directly attached to the conduit through which the measurement fluid flows, so when the piezoelectric ceramic is vibrated on the transmitting side, this vibration propagates through the measurement fluid and the receiving side. The vibration transmitted to the metal housing through the metal diaphragm or the bottom surface is also transmitted to the receiving side through the pipe wall, and the vibration propagating through this pipe wall interferes with the signal propagating in the measurement fluid and becomes noise. , S / N is deteriorated and the measurement range of the flow rate and the flow velocity cannot be expanded.

The present invention solves the above problems and realizes a highly reliable ultrasonic transducer capable of transmitting and receiving ultrasonic pulses with short reverberation and reducing the propagation of vibration to the conduit wall. The object is to improve the measurement characteristics of a sound wave flow rate measuring device.

[0005]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention has a ceiling-like cylindrical shape having a top portion, a side wall portion and an opening.
A case and a piezoelectric body fixed to the inner wall surface of the top,
An acoustic matching layer provided on the outer wall surface of the storage part and the side wall part
Provided at the end of the flange, the flange and the opening
And a sealing body for closing the
The thickness should be thicker than the flange.
Mounting hole on the fluid passage wall where the fluid to be measured flows
An ultrasonic flow rate measuring device attached to
The vibration of the ultrasonic transducers is
Through the vibration transmission suppression body that reduces the transmission to the wall side
It is an ultrasonic flow rate measuring device to be mounted in the mounting hole .

According to the above invention, the supporting portion is formed by the sealing body.
Since it can be reinforced, the thickness of the case can be made even thinner
The sensitivity of the vibrator can be increased .

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention provides a case-like 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, and an outer wall surface of the top portion. an acoustic matching layer provided, and a support portion provided on the side wall portion, supporting lifting unit which was a configuration of repeating a sealing member for closing the flange and the opening portion provided at an end portion of the side wall portion is there. Further, since the supporting portion can be reinforced by the sealing body, the plate thickness of the case can be further reduced, and the sensitivity of the ultrasonic transducer can be increased. In addition, the sealing body that houses the piezoelectric body in an airtight manner can be shared with the rigidity-enhancing member of the support section to improve productivity, and the case-side flange can be easily molded and sealed with a flange with a wide joint surface. Since the body is joined, the airtightness can be improved and the reliability can be improved.

Further, the thickness of the sealing body of the supporting portion is thicker than that of the flange. Further, by increasing the thickness of the sealing body, it is possible to prevent the support portion from being deformed, and to secure a seal portion in the support portion that seals the fluid to be measured so as not to leak from the mounting portion of the ultrasonic transducer to the outside. Furthermore, since the thickness of the sealing body can be increased, the terminals electrically connected to the piezoelectric body and the insulating portion that insulates the terminals can be easily molded, so that the productivity can be improved.

Further, a vibration transmission restraining member for reducing the transmission of the vibration of the ultrasonic transducer to the fluid passage wall side is provided, and the ultrasonic transducer is provided in a mounting hole provided in the fluid passage wall via the vibration transmission restraining member. Is attached. Then, by providing the acoustic impedance mismatch, it is possible to make it difficult for the vibration of the ultrasonic transducer to be transmitted to the mounting side, and to improve the measurement accuracy. In addition, a projection is provided at least on the fluid passage wall side of the vibration transmission suppressing body, and the vibration transmission suppressing body and the fluid passage wall are in partial contact. The partial contact makes it more difficult for the vibration of the ultrasonic transducer to be transmitted to the mounting side, and the measurement accuracy can be further improved.

Further, the vibration transmission restraining body is made of an elastic body,
A deformation preventing body for preventing the deformation of the elastic body is provided in contact with the vibration transmission suppressing body. And, the vibration transmission suppressing body not only reduces the transmission of vibration but also prevents leakage of the fluid to be measured and can be hermetically sealed, and the deformation preventing body prevents deformation of the elastic body and can maintain the hermetic sealing for a long time, The reliability of the airtight seal can be improved.

Further, the deformation preventing body is made of a material having a lower acoustic impedance than that of the cold sealing body at least in the case or the opening of the case. Even if the deformation preventive body and the ultrasonic transducer come into contact with each other, the vibration is hard to be transmitted to the mounting side. Therefore, the deformation preventive body is placed in contact with the ultrasonic transducer to ensure that the entire vibration suppression body is deformed. It can be prevented and the reliability of the airtight seal can be further improved.

Further, the mounting hole is a stepped mounting hole provided with a stepped portion for hitting the vibration transmission suppressing body, and the vibration transmission suppressing body having the ultrasonic vibrator mounted therein is inserted into the stepped mounting hole to form the stepped mounting hole. Fix the vibration transmission suppression body with the fixed body provided outside the mounting hole,
The ultrasonic transducer is not in contact with the fluid passage wall and the fixed body. The ultrasonic vibrator can be mounted on the mounting side in a non-contact manner, and the mounting position can be set reliably with high accuracy, so that the measurement accuracy can be improved by reducing the propagation of vibration and ensuring the mounting position accuracy.

Further, the opening of the mounting hole to the fluid passage has a smaller cross-sectional area than the accommodating portion for accommodating the side wall of the ultrasonic transducer. By reducing the area of the opening, the turbulence of the flow of the fluid to be measured due to the opening can be reduced and the measurement accuracy can be improved.

A measuring unit through which the fluid to be measured flows, a pair of ultrasonic transducers according to any one of claims 1 to 3 for transmitting and receiving ultrasonic waves provided in the measuring unit, and between the ultrasonic transducers. 10. A measurement control unit that measures the propagation time of the ultrasonic wave, and a calculation unit that calculates the flow rate based on a signal from the measurement control unit, and the ultrasonic transducer is any one of claims 4 to 9. The support structure is as described in (1). Then, an ultrasonic transducer having a case that shields the piezoelectric body from the fluid to be measured and capable of transmitting and receiving ultrasonic pulses with short reverberation,
A flow rate measurement device that can maintain measurement characteristics over a long period of time by increasing the measurement accuracy and expanding the measurement range with the ultrasonic transducer support structure that can reduce vibration propagation to the mounting side and the airtight seal structure that prevents leakage of measured fluid Can be realized.

Further, the cross section in the direction orthogonal to the flow of the measuring section is rectangular, and the shape of the opening on the fluid passage side of the mounting hole for mounting the ultrasonic transducer is rectangular. And since the opening area is constant in the height direction of the measurement part, it is possible to receive and transmit ultrasonic waves evenly in the height direction of the fluid passage, and to average by ultrasonic wave propagation according to the flow distribution in the height direction. The flow velocity can be detected accurately.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a sectional view of an ultrasonic transducer showing Embodiment 1 of the present invention. In FIG. 1, 7 is a case, 8 is a top part of the case 7, 9 is a side wall part of the case 7, 10 is an opening part of the case 7, and the case 7 has a top part 8, a side wall part 9 and an opening part 10. It has the shape of a hollow cylinder. Reference numeral 11 denotes an acoustic matching layer fixed to the outer wall surface of the top portion 8 of the case 7, 12 is a piezoelectric body fixed to the inner wall surface of the top portion 8, and 13 is a support portion provided on the outer wall of the side wall portion 9. The portion 13 is provided with a bent portion 14 and is folded and folded to increase the thickness to increase the rigidity.
Reference numeral 15 is a sealing body that closes the opening 10, 16a and 16b are terminals provided in the sealing body 15, and 17 is a terminal 16a and a terminal 16.
Insulating part for insulating b, 18 is piezoelectric body 12 and terminal 1
A lead wire for electrically connecting 6 a and a groove 19 provided in the piezoelectric body 12 are provided. As described above, the ultrasonic transducer 20 is provided with the piezoelectric body 12 inside the ceiling-shaped case 7 and sealed with the sealing body 15, and the acoustic matching layer 11 and the support portion 13 are provided outside the case 7. There is.

An example of a method of manufacturing the ultrasonic vibrator configured as above will be described. Ultrasonic transducer 20 is LP
Case 7 assuming use in gas or natural gas
For the acoustic matching layer 11, a material made of a mixture of epoxy resin and hollow glass spheres is selected. Case 7
Considering mass productivity, the forming method such as drawing is selected instead of cutting. Further, the thickness of the stainless steel of the case 7 is selected to be about 0.1 to 0.5 mm from the viewpoint of the sensitivity, structural strength, and moldability of the ultrasonic vibrator 20. In order to form the case 7 with such a thin material, the support portion 13 is formed from the side wall portion 9 of the case 7 to the bent portion 14
Is projected and folded to have a plurality of plate thicknesses to enhance rigidity. Further, since the piezoelectric body 12 is adhesively fixed to the top portion 8 made of stainless steel, vibration in the spreading direction is hindered. In order to increase the sensitivity of the ultrasonic vibrator 20, it is more advantageous to use the thickness longitudinal vibration as the main mode than the spreading vibration. However, the main mode of vibration of the piezoelectric body 12 is determined by the shape, and the allowable range for the shape of the piezoelectric body 12 and the operating frequency is narrow. Therefore, it is possible to set thickness vibration to the main mode with a practically small size as a structure in which grooves 19 are provided in the piezoelectric body 12 in a cross shape, for example.

As a concrete manufacturing procedure for such materials and shapes, first, a case 7 having a circular shape and having a circular top 8 is formed from a stainless steel plate having a thickness of 0.2 mm, and then the case 7 is formed. An annular bead is formed on the side wall portion 9 of the above, and the support portion 13 is formed by compressing the bead in the axial direction of the cylinder and compressing the bead. In addition, the thickness of the support portion 13 can be arbitrarily increased by forming a plurality of beads and compressing the beads. Next, the disk-shaped acoustic matching layer 11 is adhered to the outer wall surface of the top portion 8, and the piezoelectric body 12 is adhered and fixed to the inner wall surface using an epoxy adhesive. At this time, the electrodes (not shown) divided by the groove 19 and the top 8 are bonded and fixed via a thin adhesive layer of 10 μm or less, so that the divided electrodes (not shown) and the top 8 are electrically connected. The continuity can be taken. The lead wires 18 are soldered to the electrodes (not shown) of the piezoelectric body 12 and the terminals 16a, respectively. Finally,
A sealing body 15 made of a stainless steel plate of about 1 mm is fixed to the opening 10 by electric resistance welding or the like, and sealing and electrical conduction are performed at the same time. Since the piezoelectric body 12 shares the case 7 as a ground and is covered with the case 7 and the sealing body 15, the influence of noise can be reduced. Further, by substituting dry nitrogen or an inert gas in the case 7 for sealing, it is possible to prevent deterioration of the electrode of the piezoelectric body 12, the adhesive layer between the piezoelectric body 12 and the case 7, etc. due to long-term use. .

Next, the operation of this ultrasonic transducer will be described. First, on the transmission side, a driving electric input is applied to vibrate the piezoelectric body 12, and this vibration is not only emitted as ultrasonic pulses to the fluid to be measured via the acoustic matching layer 11 but also vibrates the case 7. And On the receiving side, the received ultrasonic pulse is converted into an electric signal by the piezoelectric body 12 and at the same time tries to vibrate the case 7. If the case 7 vibrates here, long reverberations of the piezoelectric body 12 are observed on both the transmitting side and the receiving side, and the reverberations on the transmitting side become electrical noise to a measuring circuit (not shown). Since the reverberation on the receiving side is combined with the received ultrasonic pulse, it affects the amplitude and the phase and causes an error in the measurement. Further, when the case 7 vibrates, the vibration of the case 7 is transmitted to the ultrasonic transducer on the receiving side via the fluid passage wall, and on the receiving side, the vibration via the fluid passage wall is combined with the received ultrasonic pulse. As a result, the amplitude and phase are affected, which causes a measurement error.

In the present embodiment, the case 7 is provided with the bent portion 14, and the rigidity of the side wall portion 9 is increased by the support portion 13 which is folded and thickened to increase the rigidity of the side wall portion 9 and the support portion 13. Has become. Therefore, the vibration of the case 7 can be suppressed, and the propagation of the vibration from the support portion 13 to the mounting side can be reduced. Further, since the vibration of the support portion 13 is small, it is possible to make it difficult to cause a deviation from the mounting side, a change in the propagation method of the vibration, and the like for a long period of time.
Therefore, it is possible to obtain an ultrasonic transducer capable of transmitting and receiving ultrasonic pulses with short reverberation and reducing the vibration propagation to the mounting side, and reducing the generation of noise due to reverberation and the vibration propagation to the mounting side. The measurement characteristics such as the flow rate of the fluid to be measured, the measurement accuracy of the flow velocity, and the expansion of the measurement range can be improved because the S / N can be reduced. In addition, the vibration-reduced support portion makes it possible to stabilize the attachment state over a long period of time and improve the measurement reliability.

Further, since the ultrasonic transducer of this embodiment is detachable from the mounting side, it is possible to improve the maintainability of the ultrasonic welding to the mounting side, and to dispose of it when it reaches the end of its service life. Since the ultrasonic vibrator can be easily separated from the fluid passage, recyclability can be secured.

The supporting portion 13 is not limited to the shape shown in the figure, and may be constituted by providing, for example, a vertically extending ridge rib on the wall portion 9, and various forms are possible. .

Example 2 FIG. 2 is a sectional view of an ultrasonic transducer showing Example 2 of the present invention. 2, the same members and functions as those of the embodiment of FIG. 1 are designated by the same reference numerals, detailed description thereof will be omitted, and different points will be mainly described. Reference numeral 21 denotes a ring-shaped flange provided at an end portion of the side wall portion 9 of the case 7 on the opening 10 side, and the support portion 13 is configured by stacking and joining the flange 21 and the sealing body 15 that closes the opening 10. is doing.

Here, the flange 21 is formed by drawing the case 7. By stacking the sealing bodies 15, it is possible to obtain the supporting portion 13 having an increased structural strength. Further, since the supporting portion 13 is reinforced by the sealing body 15, the case 7 can be molded with a material having a thinner thickness, and the ultrasonic transducer can have higher sensitivity. Further, the sealing body 15 can be used for both the sealing member of the case 7 and the rigidity enhancing member of the supporting portion 13 to enhance the productivity, and the flange 21 can be easily formed at the same time as the case 7 is formed. Flange 21
Since the joining surface of the sealing body 15 and the sealing body 15 are joined to each other with a wide annular surface, sealing with enhanced airtightness can be achieved, and the reliability of the members housed inside can be improved.

The thickness T1 of the sealing body 15 is equal to that of the flange 2
The thickness is larger than the thickness T2 of 1 (T1> T2). Deformation of the support portion 13 can be prevented by increasing the thickness of the sealing body 15, and the sealing portion 15 and the flange 21 can be deformed toward the flange 21 side of the thin plate when they are joined by electric resistance welding or the like. Since the sealing body 15 on the thick plate side is not deformed even if occurs, it is possible to secure a seal portion in the support portion 13 that seals the fluid to be measured from the mounting portion of the ultrasonic transducer to the outside. Further, since the thickness of the sealing body 15 can be increased, the terminal 1 electrically connected to the piezoelectric body 12
Insulating portion 1 for insulating 6a, 16b and this terminal 16a
Since the molding of No. 7 can be easily performed, the productivity can be improved (Example 3). FIG. 3 is a cross-sectional view showing an attached state of the ultrasonic transducer according to Example 3 of the present invention. 3, the same members and functions as those of the embodiment of FIGS. 1 and 2 are designated by the same reference numerals, detailed description thereof will be omitted, and different points will be mainly described.

Reference numeral 22 denotes a vibration transmission restraining member which abuts and holds the supporting portion 13 of the ultrasonic vibrator 20.
No. 0 is mounted in a mounting hole 24 provided in the fluid passage wall 23 through which the fluid to be measured flows, and is opened to the fluid to be measured side. The reference numeral 25 designates a vibration transmission suppressing body 22 and a fluid passage wall 23.
The positioning body 25 is detachably fixed to the fluid passage wall 23 by a coupling means such as a screw (not shown). 26 is an airtight packing provided between the fluid passage wall 23 and the positioning body 25 for airtightly sealing, 27a,
27b is a connection terminal connected to the terminals 16a and 16b of the ultrasonic transducer 20, and 28 is an insulating portion that insulates the connection terminals 27a and 27b from each other. In addition, the vibration transmission suppressing body 22 is divided in the supporting portion 13 into a pressing side 22a on the sealing body 15 side and a supporting side 22b on the flange 21 side, and the supporting portion 1 is divided.
3 outer peripheral surface and both planes (upper and lower surfaces of the support portion 13 in the figure)
Holding

Here, the vibration transmission restraining body 22 has the supporting portion 13
The acoustic impedance is made of a material smaller than the acoustic impedance of the material forming the case 7 or the sealing body 15 so that the vibration becomes a non-matching portion that is difficult to be acoustically transmitted to the fluid passage wall 23. As a material for the case 7, a metal such as stainless steel (acoustic impedance 30 to 50
In the case of using (× 103 kg / m2 s), a resin (acoustic impedance 3 to
5 × 10 3 kg / m 2 s) or an elastic body (acoustic impedance 1 to 2 × 10 3 kg / m 2 s) can be used. The ultrasonic transducer 20 is positioned by the vibration transmission suppressing body 22 and the positioning body 25 so that the side wall portion 9 does not come into contact with the wall surface of the mounting hole 24, and by the airtight packing 26 provided on the positioning body 25. The fluid to be measured is prevented from leaking to the outside.

Next, the operation will be described. First, on the transmitting side, a driving electric input is applied, and the piezoelectric body 12 vibrates,
This vibration is not only emitted as ultrasonic pulses to the fluid to be measured via the acoustic matching layer 11, but also attempts to vibrate the case 7. However, since the case 7 is reduced in vibration by the support portion 13 having increased rigidity, and is attached to the attachment hole 24 provided in the fluid passage wall 23 via the vibration transmission restraining body 22, the case 7 is not affected. Vibration is reduced from being transmitted to the fluid passage wall 23 side.

Therefore, on the receiving side, the influence on the amplitude and the phase due to the combination of the vibration through the fluid passage wall 23 and the received ultrasonic pulse is prevented, the factor that gives the error in the measurement can be eliminated, and the measurement accuracy is improved. be able to.

Although the vibration transmission suppressing member 22 is mounted on the ultrasonic vibrator 20 by utilizing the supporting portion 13, the present invention is not limited to this. For example, a protrusion that does not increase the rigidity of the case 7. May be provided and attached to this, as long as the ultrasonic transducer 20 is held so that the vibration of the case 7 is not transmitted to the outer wall 23 of the fluid surface, the same applies to the embodiments described below. Is.

(Embodiment 4) FIG. 4 is a cross-sectional view showing an attached state of an ultrasonic transducer showing Embodiment 4 of the invention. 4, the same members and functions as those of the embodiment of FIGS. 1 to 3 are designated by the same reference numerals, detailed description thereof will be omitted, and different points will be mainly described.

Reference numeral 29 denotes a protrusion provided on the vibration transmission suppressing body 22, and the protrusion 29 is provided not only on the fluid passage wall 23 side but also on the positioning body 25 side. Therefore, the vibration transmission suppressing member 22 is in partial contact with the fluid passage wall 23 in a reduced contact area due to at least the projection 29 provided on the fluid passage wall 23.

Here, when the driving electric input is applied and the piezoelectric body 12 vibrates, this vibration is radiated to the fluid to be measured as an ultrasonic pulse through the acoustic matching layer 11. At this time, since the vibration of the case 7 is reduced by the support portion 13 having increased rigidity, and is attached to the attachment hole 24 provided in the fluid passage wall 23 through the vibration transmission suppressing body 22 with partial contact, Propagation of vibration of the ultrasonic transducer 20 to the fluid passage wall 23 side is further reduced.

Therefore, on the receiving side, the vibration propagating through the fluid passage wall 23 can be greatly reduced, so that the influence on the amplitude and phase due to the combination with the received ultrasonic pulse can be prevented and the factor that gives an error to the measurement can be eliminated. The measurement accuracy can be further improved. By providing the protrusions 29 not only on the fluid passage wall 23 side but also on the positioning body 25 side, it is possible to prevent vibration from propagating along the positioning body 25 to the fluid passage wall 23 side, and thus the vibration fluid passage wall. It is possible to further reduce the propagation to the 23 side.

(Embodiment 5) FIG. 5 is a cross-sectional view showing a mounted state of an ultrasonic transducer according to a fifth embodiment of the present invention. 5, the same members and functions as those of the embodiment of FIGS. 1 to 4 are designated by the same reference numerals, detailed description thereof will be omitted, and different points will be mainly described.

Reference numeral 30 is a vibration transmission suppressing member formed of an elastic material such as rubber and having an annular inner peripheral groove 30a for holding the support portion 13 of the ultrasonic vibrator 20 on the inner peripheral side. This is a deformation preventing body that is provided in contact with the inner circumferential side of the transmission suppressing body 30 to prevent the vibration transmission suppressing body 30 from deforming in the inner diameter direction. The deformation preventing body 31 has an annular shape so that the inner peripheral side thereof does not come into contact with the side wall portion 9 of the case 7 and has a gap, and also has a gap in the axial direction (up and down direction in the drawing) of the support portion 13. I try not to apply force to. Further, the deformation preventing body 32 has an annular shape so as not to contact the terminals 16a and 16b. Reference numeral 33 is an annular projection provided on the lower surface of the vibration transmission suppressing body 30, and 34 is an annular projection provided on the outer peripheral surface of the vibration transmission suppressing body 30. Reference numeral 35 is a vibration transmission suppressing body 30.
It is a stepped mounting hole provided with a stepped portion 36 that serves as a contact portion, and has a flat surface 33a with which the annular lower surface side projection 33 abuts and a cylindrical surface 33b with which the annular outer peripheral surface side projection 34 abuts. ing. Reference numeral 37 is a fixed body that is provided outside the stepped mounting hole 35 and holds down the vibration transmission restraining body 30.
A take-out hole 38 is provided through which a and 16b penetrate without coming into contact with each other and is fixed to the fluid passage wall 23 by a connecting means such as a screw.

Here, the mounting method will be described. The vibration transmission suppressing body 30 formed of an elastic body such as rubber is stretched to fit the support portion 13 of the ultrasonic transducer 20 into the inner circumferential groove 30a to hold the support portion 13 without a gap, and the deformation preventing body 3
1 and 32 are inserted into the inner circumference of the vibration transmission suppressing body 30. In this assembled state, the vibration transmission suppressing body 30 is inserted into the step portion 36 of the stepped mounting hole 35, and the vibration transmission suppressing body 30 is pressed by the fixed body 37 to mount the ultrasonic transducer 20. Here, the outer dimensions (including the protrusions 33 and 34) such as the height and the length of the vibration transmission suppressing body 30 are set to be slightly larger than the step portion 36, so that the vibration transmission suppressing body 30 can be inserted into the step portion 36 or the fixed body 37. The airtight sealing property can be ensured so that the vibration transmission suppressing body 30 of the elastic body is bent during pressing and the measured fluid does not leak from the mounting hole. By the way, when the deformation preventing bodies 31 and 32 are mounted without being provided, the vibration transmission suppressing body 30 tends to deform toward the inner peripheral side with the passage of time because the outer peripheral side is constrained by the mounting holes and the fixed body. However, here, since the deformation preventing bodies 31 and 32 are inserted on the inner peripheral side and constrained so as not to be deformed, the inward deformation is prevented and the airtight sealing property can be secured for a long period of time. Further, since the elastic body has a sufficiently smaller acoustic impedance than the metal material of the case 7 of the ultrasonic transducer 20 as described above, it is possible to reduce the propagation of vibration to the fluid passage.

As described above, the vibration transmission suppressing member 30 not only reduces the transmission of vibration but also prevents the fluid to be measured from leaking and can be hermetically sealed, and the deformation preventing member prevents the deformation of the elastic body for a long period of time. The hermetic seal can be maintained and the reliability of the hermetic seal can be improved.

(Embodiment 6) FIG. 6 is a cross-sectional view showing an attached state of an ultrasonic transducer showing Embodiment 6 of the invention. 6, the same members and functions as those of the embodiment of FIGS. 1 to 5 are designated by the same reference numerals, detailed description thereof will be omitted, and different points will be mainly described.

Reference numeral 39 is a deformation preventing body which is provided in contact with the inner peripheral side of the vibration transmission suppressing body 30 to prevent the case 7 side of the vibration transmission suppressing body 30 from being deformed in the inner diameter direction. The inner peripheral side is arranged without any gap so as to come into contact with the side wall portion 9 of the case 7, and is brought into contact with the support portion 13 and the stepped portion 36 of the stepped mounting hole 35 in the axial direction (vertical direction in the drawing). The vibration transmission suppressing body 30 is prevented from being deformed inward over the entire area in the vertical direction in the figure. Reference numeral 40 denotes a deformation preventing body which is provided in contact with the inner peripheral side of the vibration transmission suppressing body 30 to prevent the sealing body 15 side of the vibration transmission suppressing body 30 from being deformed in the inner diameter direction. The inner peripheral side is annular so as to have a gap without contacting the terminals 16a and 16b, and contacts the sealing body 15 and the fixed body 37 in the axial direction (vertical direction in the drawing). The vibration transmission suppressing body 30 is arranged without gaps to prevent the vibration transmitting body 30 from being deformed inward over the entire area in the vertical direction in the drawing. Here, the deformation preventive body 39 or the deformation preventive body 40 is made of a material smaller than the acoustic impedance of the material of the case 7 or the sealing body 15 forming the support portion 13 of the ultrasonic transducer 20. Even if the passage 23 is in contact with the deformation preventive body 39, the vibration of the case 7 is prevented from propagating to the fluid passage 23 side, and the support portion 13 and the sealing body 1 are prevented.
The vibration of the case 7 is prevented from propagating to the fluid passage 23 side even when the case 7 and the fixed body 37 are in contact with each other. Here, as the material of the deformation preventing bodies 39 and 40, by using a resin having acoustic impedance sufficiently smaller than that of the metal material of the case 7 of the ultrasonic transducer 20 as described above, an elastic body such as rubber (deformation preventing body) is used. It is possible to prevent the deformation by constraining the entire inner circumference of the vibration transmission suppressing body 30 formed of the resin of the bodies 39 and 40 having an acoustic impedance smaller than that of the resin.

As described above, even if the deformation preventing body and the ultrasonic transducer are in contact with each other, it is difficult for the vibration to be transmitted to the mounting side. Therefore, the deformation preventing body is placed in contact with the ultrasonic transducer, and the entire area of the vibration transmission suppressing body is arranged. Therefore, the deformation can be reliably prevented, and the reliability of the airtight seal can be further improved.

(Seventh Embodiment) A seventh embodiment of the present invention will be described with reference to FIG. A method of attaching the ultrasonic transducer 20 will be described with reference to FIG. First, the vibration transmission suppressing body 30 is mounted on the support portion 13 of the ultrasonic transducer 20, and the mounted vibration transmission suppressing body 30 is inserted into the stepped mounting hole 35 provided in the fluid passage wall 23. At this time, the end surface of the vibration transmission suppressing body 30 is brought into contact with the flat surface 33a of the step portion 36 for axial positioning, and the outer peripheral portion of the vibration transmission suppressing body 30 is brought into contact with the cylindrical surface 33b of the step portion 36 so as to have a diameter. Directional positioning. After that, the fixed body 37 provided outside the stepped mounting hole 35 is screwed to the fluid passage wall 23 to hold down the vibration transmission restraining body 30 to prevent it from coming off and to ensure the axial positioning. By mounting in this way, the ultrasonic transducer 20 is supported by the vibration transmission restraining body 30 without contacting the fluid passage wall 23 and the fixed body 37.

Therefore, the ultrasonic transducer 20 is installed in the fluid passage wall 2
When the pair of ultrasonic transducers on the receiving side and the transmitting side is attached to the flow path, the distance between the ultrasonic transducers is fixed and the accurate fluid is determined. The speed of can be detected, and by aligning the centers of the central axes of the pair of ultrasonic transducers, it is possible to prevent the sensitivity from degrading due to misalignment and to perform highly sensitive measurement. Further, since the ultrasonic transducer and the fluid passage wall are kept in non-contact with each other, it is possible to improve the measurement accuracy or extend the measurement range by preventing the vibration propagation to the fluid passage wall and increasing the S / N.

Therefore, the ultrasonic vibrator can be mounted on the mounting side in a contacted manner, and the mounting position can be set reliably with high accuracy both in the radial direction and the axial direction, so that the propagation of vibration is reduced and the mounting position accuracy is ensured. Can improve the measurement accuracy.

(Embodiment 8) Embodiment 8 of the present invention will be described based on FIG. 5 described above. In FIG. 5, 41 is an opening of the mounting hole 24 to the fluid passage, 42 is a housing provided in the mounting hole 24 for housing the side wall 9 of the ultrasonic transducer 20, and the length of the opening 41 in the cross-sectional direction. The length D1 is smaller than the length D2 of the storage portion 42 in the cross-sectional direction (D1 <D
2) Then, the cross-sectional area of the opening 41 is smaller than the cross-sectional area of the storage portion 42.

Therefore, even when the size of the ultrasonic transducer 20 is large, the opening 41 to the fluid passage through which the non-measurement fluid flows is formed.
Can be made smaller, turbulence of the flow due to the opening 41 acting as a depression for the flow can be reduced, and more accurate flow velocity can be measured. In addition, by enlarging the storage portion 42 with respect to the side wall portion 9 of the ultrasonic transducer 20 and increasing the distance between the ultrasonic transducer 20 and the fluid passage wall 23, it is possible to improve lightning surge characteristics and improve reliability. Can be further enhanced.

Therefore, by reducing the area of the opening, it is possible to reduce the turbulence of the flow of the fluid to be measured due to the opening, improve the measurement accuracy, and improve the withstand voltage characteristics to improve the reliability.

(Embodiment 9) FIG. 7 is a block diagram of an ultrasonic flow rate measuring apparatus showing Embodiment 9 of the present invention. 7, the same members and functions as those of the embodiment of FIGS. 1 to 6 are designated by the same reference numerals and detailed description thereof will be omitted.
The different points will be mainly explained.

Reference numeral 43 is a measuring portion surrounded by the fluid passage wall 23, and reference numerals 44 and 45 are ultrasonic transducers attached to the attachment hole 24 of the fluid passage wall 23 via the vibration transmission restraining body 30 so as to face each other. The ultrasonic transducer 44 on the upstream side and the ultrasonic transducer 45 on the downstream side are installed at a distance L and at an angle θ with respect to the flow of the fluid to be measured at the velocity V. Reference numeral 46 is a measurement control unit that transmits and receives ultrasonic waves to and from the connected ultrasonic transducers 44 and 45, and 47 is a calculation unit that calculates a flow velocity based on a signal from the measurement control unit 46 and calculates a flow rate. is there.

Next, the operation of this ultrasonic flow rate measuring device will be described. When the fluid to be measured is flowing through the measurement unit 43, the ultrasonic wave is transmitted and received between the ultrasonic transducers 44 and 45 by the action of the measurement control unit 46 so as to cross the measurement unit 43.
That is, the elapsed time T1 until the ultrasonic wave emitted from the upstream ultrasonic transducer 44 is received by the downstream ultrasonic transducer 45 is measured. On the other hand, the ultrasonic wave emitted from the ultrasonic transducer 45 on the downstream side is transmitted to the ultrasonic transducer 4 on the upstream side.
The elapsed time T2 until it is received at 4 is measured. Based on the elapsed times T1 and T2 measured in this way, the flow rate is calculated by the calculation unit 47 by the following calculation formula.

Now, the angle formed by the flow of the fluid to be measured and the ultrasonic wave propagation path is θ, and the ultrasonic transducer 4 serving as the flow rate measuring unit
When the distance between 4 and 45 is L and the sound velocity of the fluid to be measured is C, the flow velocity V is calculated by the following formula.

T1 = L / (C + Vcosθ) T2 = L / (C-Vcosθ) V = (L / 2cosθ) ((1 / T1) by eliminating the sound velocity C from the equation of subtracting the inverse of T2 from the inverse of T1. -(1 / T2)) Since θ and L are known, the flow velocity V is calculated from the values of T1 and T2.
Can be calculated. Considering measuring the flow rate of air, angle θ = 45 degrees, distance L = 70 mm, sound velocity C = 340 m /
s and the flow velocity V = 8 m / s, T1 = 2.0 × 1
Since 0-4 seconds and T2 = 2.1 × 10-4 seconds, instantaneous measurement is possible.

Here, from the cross-sectional area s orthogonal to the flow direction of the measuring section 43, the flow rate Q is Q = kVs, where k is a conversion coefficient considering the flow velocity distribution in the cross-sectional area s.

In this way, the flow rate can be calculated by the calculation unit 47. In the flow rate measurement using ultrasonic waves, time T1,
It is important to measure T2 with high accuracy. That is,
On the transmitting side, it is important to generate ultrasonic vibrations with little reverberation only in the fluid to be measured.On the receiving side, ultrasonic vibrations propagating through the fluid passage wall should be eliminated and only ultrasonic vibrations propagating in the fluid to be measured should be eliminated. It is important to receive less reverberation.
In the ultrasonic flow rate measuring device of the present invention, in the ultrasonic transducer 20, the piezoelectric body 12 is shielded from the fluid to be measured by the case 7 to enhance reliability, and the shape of the supporting portion 13 having increased rigidity causes reverberation. It is possible to improve the measurement accuracy by reducing the sensitivity and improving the noise. Further, by mounting the support portion 13 for reducing the vibration to the fluid passage wall 23 through the vibration transmission restraining body 30 in a non-contact manner, the vibration transmitted through the fluid passage wall 23 is further reduced and the fluid to be measured is propagated. Since the signal detection accuracy can be improved, it is possible to detect a minute flow rate with a flow velocity of about 1 mm / s. Further, by separating the piezoelectric body 12 from the fluid to be measured by the case 7 and using the vibration transmission suppressing body 30 both as a vibration transmission suppressing body and as a seal member for holding the fluid to be measured airtight so as not to leak to the outside,
In addition to air, it can be applied to various fluids such as combustible gases such as city gas and LP gas, and its application range can be expanded. further,
By reducing the size of the opening, turbulence of the flow due to the opening can be reduced and the measurement range at large flow rate (high flow velocity) can be expanded, and rangeability (ratio of minimum flow velocity to maximum flow velocity) can be expanded to further enhance practicality. be able to.

As described above, the ultrasonic transducer having the case for shielding the piezoelectric body from the fluid to be measured and capable of transmitting and receiving the ultrasonic pulse with short reverberation, and the ultrasonic transducer capable of reducing the vibration propagation to the mounting side are supported. With the structure and the airtight seal structure that prevents the fluid to be measured from leaking, it is possible to realize a flow rate measuring device that can improve the measurement accuracy, expand the measurement range, and maintain the measurement characteristics for a long period of time.

The calculation unit 47 calculates the sound velocity C by the following formula obtained by adding the reciprocal of the elapsed time T1 and the reciprocal of T2, and C = L ((1 / T1) + (1 / T2)) / 2 It is possible to discriminate the type of the fluid to be measured from the calculated sound velocity C and set the measurement condition as the ultrasonic flow rate measuring device suitable for the sound velocity or the type of the fluid to be measured. The measurement conditions of the ultrasonic flow rate measuring device include the number of repetitions such as how many times the driving power such as the driving frequency and driving voltage of the ultrasonic transducer or the elapsed times T1 and T2 are measured to calculate the flow velocity. . It should be noted that by registering the fluid that is supposed to be used in advance, it is possible to improve the accuracy of determining the type of the fluid to be measured, and since the sonic velocity C changes depending on the temperature, the temperature of the fluid to be measured is detected. It goes without saying that the accuracy of determining the type of the fluid to be measured can be further improved by providing the temperature sensor (not shown).

(Embodiment 10) FIGS. 8 and 9 are partial sectional views of an ultrasonic flow rate measuring apparatus showing Embodiment 10 of the present invention. FIG. 8 is a sectional view taken along line AA of FIG.
FIG. 9 is a sectional view taken along the line BB of FIG. In the drawing, the same members and the same functions as those in the embodiment of FIGS. 1 to 7 are designated by the same reference numerals, detailed description thereof will be omitted, and different points will be mainly described.

As shown in the drawing, the cross section of the measuring section 43 in the direction orthogonal to the flow is a rectangle having a width W and a height H, and a fluid passage wall 23a having a concave portion and a fluid passage wall 23b having a convex portion are fitted therein. In addition, the fluid passage wall 23 having the rectangular cross section forms the measuring portion 43. The shape of the opening 41 on the fluid passage side of the mounting hole 24 for mounting the ultrasonic transducer is a rectangle having a length D1 in the left-right direction and a length D3 in the up-down direction (the height direction of the measuring unit 43) in FIG. Yes, here, it is assumed that the square is D1 = D3. By making the cross section in the direction orthogonal to the flow of the measurement unit 43 rectangular, the flow in the measurement unit 43 is made into a two-dimensional flow, and ultrasonic waves can be transmitted throughout the height H direction of the flow. Furthermore, by making the shape of the opening 41 rectangular, the opening width becomes the dimension of D1 at any position in the height H direction, and ultrasonic waves are evenly transmitted and received in the height H direction of the measurement unit 43. You can In this way, the measurement unit 4 is determined by the rectangular cross section of the measurement unit 43 and the rectangular cross section of the opening.
The ultrasonic waves can be applied to the entire region of the flow No. 3, and the ultrasonic waves are evenly transmitted and received in the height H direction, so that the entire region of the flow is uniformly measured, and thus the flow velocity or the flow rate can be accurately measured.

As described above, since the opening area is constant in the height direction of the measuring portion, ultrasonic waves can be evenly transmitted and received in the height direction of the fluid passage, depending on the distribution of the flow in the height direction. The average velocity can be accurately detected by ultrasonic wave propagation.

The opening 41 is made uniform in the height direction of the fluid passage by making the length D1 in the left-right direction smaller than the length D3 in the up-down direction (height direction of the measuring section 43) (D1 <D3). In addition to transmitting and receiving ultrasonic waves, the occurrence of turbulence in the flow due to the depression of the opening 41 can be further reduced and the measurement accuracy can be further improved.

[0062] As will be apparent from the description on the following fruit of the present invention
According to the flow rate measuring device of the embodiment , the following effects can be obtained.

The piezoelectric body is enclosed in a case that shields it from the fluid to be measured, an acoustic matching layer is provided on the top of the case, and a supporting portion with increased rigidity is provided on the side wall of the case. There is an effect that it is possible to obtain an ultrasonic transducer that can send and receive short ultrasonic pulses and reduce the vibration propagation to the mounting side, and the measurement characteristics such as flow rate, flow velocity measurement accuracy, and measurement range expansion. There is an effect that it can be improved, and further, there is an effect that the mounting state can be stabilized over a long period of time by the supporting portion with reduced vibration and the reliability of measurement can be improved.

Further, since the support portion is formed by stacking the flange provided at the end of the side wall portion and the sealing body that closes the opening, the support portion is reinforced by the sealing body to further increase the plate thickness of the case. There is an effect that the sensitivity can be increased by thinning the ultrasonic vibrator, and there is an effect that productivity can be improved by sharing the sealing body with the rigidity reinforcing member of the supporting portion. Furthermore, there is an effect that the internal airtightness can be enhanced and the reliability can be improved by joining the sealing body to the flange having the widened joining surface.

Further, since the thickness of the sealing body of the supporting portion is larger than that of the flange, there is an effect that the deformation of the supporting portion can be prevented and the airtightness of the fluid to be measured can be secured to the outside. Since the thickness of the body can be increased and the terminal and the insulating portion of the terminal can be easily molded, the productivity can be improved.

Further, a vibration transmission suppressing member for reducing the transmission of the vibration of the ultrasonic vibrator to the fluid passage wall side is provided, and the ultrasonic vibrator is installed in the mounting hole provided in the fluid passage wall via the vibration transmission suppressing member. Since the acoustic wave is attached, it is possible to prevent the vibration of the ultrasonic transducer from being transmitted to the attachment side by providing the acoustic impedance mismatch, and to improve the measurement accuracy.

Further, since the projection is provided at least on the fluid passage wall side of the vibration transmission suppressing body and the vibration transmission suppressing body and the fluid passage wall are in partial contact, the vibration of the ultrasonic transducer is further transmitted to the mounting side. This has the effect of making it difficult and improving the measurement accuracy.

Further, the vibration transmission restraining body is made of an elastic body,
Since the deformation preventing body for preventing the deformation of the elastic body is provided in contact with the vibration transmission suppressing body, the vibration transmission suppressing body can be used not only for reducing the vibration transmission but also for airtight sealing of the fluid to be measured. In addition, there is an effect that the deformation preventing body prevents the elastic body from being deformed, maintains the airtight seal for a long period of time, and improves the reliability of the airtight seal.

Further, since at least the case or at least the opening of the case is made of a material having a smaller acoustic impedance than the cold sealing body, the deformation preventing body is mounted on the mounting side even if the deformation preventing body and the ultrasonic transducer come into contact with each other. Because it is difficult to transmit vibration to
By arranging the deformation preventing body in contact with the ultrasonic vibrator, there is an effect that the deformation is surely prevented over the entire area of the vibration transmission suppressing body and the reliability of the hermetic seal can be further improved.

Further, the mounting hole is a stepped mounting hole provided with a stepped portion which hits the vibration transmission suppressing body, and the vibration transmission suppressing body having the ultrasonic vibrator mounted therein is inserted into the stepped mounting hole to form the stepped mounting hole. Fix the vibration transmission suppression body with the fixed body provided outside the mounting hole,
Since the ultrasonic vibrator is not in contact with the fluid passage wall and the fixed body, there is an effect that vibration propagation due to non-contact can be reduced, and measurement accuracy can be improved by securing the mounting position accuracy.

Further, since the cross-sectional area of the opening of the mounting hole to the fluid passage is smaller than that of the accommodating portion for accommodating the side wall of the ultrasonic transducer, the disturbance of the flow of the fluid to be measured due to the opening is reduced. This has the effect of improving the measurement accuracy.

Further, a measuring section through which the fluid to be measured flows, a pair of ultrasonic transducers according to any one of claims 1 to 3 for transmitting and receiving ultrasonic waves provided in the measuring section, and between the ultrasonic transducers. 10. A measurement control unit that measures the propagation time of the ultrasonic wave, and a calculation unit that calculates the flow rate based on a signal from the measurement control unit, and the ultrasonic transducer is any one of claims 4 to 9. The ultrasonic transducer has a case that shields the piezoelectric body from the fluid to be measured, and can transmit and receive ultrasonic pulses with short reverberation. There is an effect that the propagation can be reduced and the fluid to be measured can be prevented from leaking, the measurement accuracy can be improved, and the measurement range can be expanded. Furthermore, there is an effect that the measurement characteristics can be maintained for a long period of time.

Further, since the cross section in the direction orthogonal to the flow of the measuring section is rectangular and the shape of the opening on the fluid passage side of the mounting hole for mounting the ultrasonic transducer is rectangular, the opening area in the height direction of the measuring section is set. Since there is a constant value, there is an effect that ultrasonic waves can be evenly transmitted and received in the height direction of the fluid passage, and the average flow velocity can be accurately detected by ultrasonic wave propagation according to the flow distribution in the height direction. effective.

[0074]

As is apparent from the above description, the present invention
According to the flow rate measuring device, the support part can be reinforced by the sealing body.
Therefore, the plate thickness of the case can be further reduced, and the ultrasonic transducer
The sensitivity can be increased.

[Brief description of drawings]

FIG. 1 is a sectional view of an ultrasonic transducer according to a first embodiment of the present invention.

FIG. 2 is a sectional view of an ultrasonic transducer according to a second embodiment of the present invention.

FIG. 3 is a sectional view of a supporting structure of an ultrasonic transducer according to a third embodiment of the present invention.

FIG. 4 is a sectional view of a supporting structure of an ultrasonic transducer according to a fourth embodiment of the present invention.

FIG. 5 is a cross-sectional view of a supporting structure of an ultrasonic transducer according to embodiments 5, 7, and 8 of the present invention.

FIG. 6 is a sectional view of a supporting structure of an ultrasonic transducer according to a sixth embodiment of the present invention.

FIG. 7 is a configuration diagram of an ultrasonic flow rate measuring device according to a ninth embodiment of the present invention.

FIG. 8 is a cross-sectional view taken along line AA of the ultrasonic flow rate measuring device of FIG. 7 showing Example 10 of the present invention.

FIG. 9 is a cross-sectional view taken along line BB of the ultrasonic flow rate measurement device of FIG. 7 showing the tenth embodiment of the present invention.

FIG. 10 is a sectional view of a conventional ultrasonic transducer.

FIG. 11 is a sectional view of another conventional ultrasonic transducer.

[Explanation of symbols]

7 cases 8 Heaven 9 Side wall 10 openings 11 Acoustic matching layer 12 Piezoelectric body 13 Support 15 Sealed body 20, 44, 45 ultrasonic transducer 21 flange 22, 30 Vibration transmission suppression body 23 Fluid passage wall 24 mounting holes 29 Projection 31, 32, 39, 40 Anti-deformation body 35 stepped mounting holes 36 Step 37 Fixed body 41 opening 42 Storage 43 Measuring unit 46 Measurement control unit 47 Operation part

Continuation of the front page (56) References JP-A-58-174813 (JP, A) JP-A-59-190621 (JP, A) Actually open 59-46078 (JP, U) Actual-opening 4-53389 (JP , U) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01F 1/00-9/02

Claims (6)

(57) [Claims] 1. A cylindrical case having a ceiling, a side wall, and an opening, and a piezoelectric body fixed to an inner wall surface of the ceiling.
The sealing body as well as formed by stacking an acoustic matching layer provided on the outer wall surface of the top portion, and a flange provided at an end portion of the side wall portion, and a sealing member for closing said flange and said opening
Is an ultrasonic flow rate measuring device in which an ultrasonic transducer having a support thicker than a flange is attached to a mounting hole provided in a fluid passage wall through which a fluid to be measured flows. An ultrasonic flow rate measuring device, wherein a part is attached to the attachment hole via a vibration transmission suppressing body that reduces transmission of vibration of the ultrasonic transducer to a fluid passage wall side. 2. At least a fluid passage wall of the vibration transmission suppressing body.
The protrusion is provided on the side, and the vibration transmission suppressor and the fluid passage wall are
The ultrasonic flow rate measuring device according to claim 1, which is in minute contact . 3. The vibration transmission restraining body is made of an elastic body.
The deformation prevention body that prevents deformation of the elastic body suppresses the vibration transmission.
The ultrasonic flow rate measuring device according to claim 1, which is provided in contact with a body . 4. The deformation preventing body is at least a case or a deformation preventing body.
Is the acoustic impedance of the sealing body that closes the opening of the case.
The ultrasonic flow rate measuring device according to claim 3 , wherein the ultrasonic flow rate measuring device is made of a material having a small size . 5. A step in which the mounting hole comes into contact with the vibration transmission suppressing body.
A stepped mounting hole with a difference is made, and ultrasonic waves are placed in this stepped mounting hole.
Insert a vibration transmission suppression body with a vibrator and step mounting holes
The vibration transmission suppression body is fixed with a fixed body provided outside the
The wave oscillator is not in contact with the fluid passage wall and the fixed body.
The ultrasonic flow rate measuring device according to any one of claims 1 to 4 . 6. An ultrasonic vibration is applied to the opening of the mounting hole to the fluid passage.
Smaller cross-sectional area than the storage unit that stores the side wall of the pendulum
The ultrasonic flow rate measuring device according to any one of claims 1 to 5 .