JPH0375807B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ultrasonic sensor device, and more particularly to an ultrasonic sensor device that can remotely measure the sound speed of a fluid, etc. using leaky waves. .

[Conventional technology]

When measuring the speed of sound or the temperature of an object using ultrasonic waves, a configuration is adopted in which longitudinal ultrasonic waves output from one ultrasonic sensor are directly propagated through the object to be measured to the other ultrasonic sensor. There is. The majority of methods attempt to measure the sound velocity or temperature and changes thereof based on the propagation time and changes thereof of the ultrasonic waves that are repeatedly transmitted and received during this period.

[Problem that the invention seeks to solve]

Ultrasonic sensors used for monitoring high-temperature fluids or fluids under dangerous conditions, or for monitoring temperature changes in liquid hazardous materials, are required to withstand sufficiently even under these harsh environments.

However, general ultrasonic sensors consist of a composite body of a vibrator and a protector, and these are integrated with a bonding material, so there is an upper limit to the operating temperature (approximately
400 [°C]), making it nearly impossible to regularly and continuously measure temperatures between 500 and 800 [°C]. In addition, many vibrators and protectors are easily contaminated chemically, and there is a disadvantage that their deterioration progresses extremely quickly, especially in environments with rapid temperature changes.

[Purpose of the invention]

The present invention improves the disadvantages of the prior art, and specifically targets fluids and soft materials, even if they are harmful or constantly exposed to high temperatures. An ultrasonic sensor device that can remotely measure the speed of sound and its changes in a measured object with high precision, thereby making it possible to identify the temperature and viscosity of the measured object and their changes with high precision. to provide
That purpose.

[Means for solving problems]

Therefore, the present invention includes certain ultrasonic waveguides made of elastic bodies arranged at a certain distance apart, and an ultrasonic transducer installed at one end of each of the pair of ultrasonic waveguides. and adopting a configuration such as providing an ultrasonic reflecting means at the other end of each of the ultrasonic waveguides,
This aims to achieve the above objective.

[First Embodiment of the Invention] The first embodiment of the present invention will be described below with reference to FIGS. 1 to 4.
This will be explained based on the diagram.

In FIG. 1, the ultrasonic sensor device includes a pair of plate-shaped (or band-shaped) ultrasonic waveguides (hereinafter simply referred to as "waveguides") 1 and 2 arranged at a certain distance D apart, Ultrasonic transducers 3 and 4 are provided at one end of each of the waveguides 1 and 2.

In this embodiment, the waveguides 1 and 2 are made of stainless steel and have the same length. The other ends of the waveguides 1 and 2 are connected to a medium to be measured 5 as shown in the figure.
It is designed to be placed inside.

In this embodiment, one of the ultrasonic transducers 3 and 4 is used as a transmitter, and the other ultrasonic transducer 4 is used as a receiver. Each of the wave transmitter 3 and the wave receiver 4 is attached to the side surface of one end of the waveguides 1 and 2. Ultrasonic waves (longitudinal waves) are obliquely incident on the waveguide 1 from the transmitter 3. Receiver 4
can receive ultrasonic waves from the waveguide 2 under substantially the same conditions as the transmission action of the wave transmitter 3.

1A and 2A indicate end faces of waveguides 1 and 2 as ultrasonic wave reflecting means, respectively.

Here, the waves propagating in the waveguides 1 and 2 and the propagation situation in the medium to be measured 5 will be explained.

When a waveguide is brought into contact with a liquid or solid, a portion of the acoustic wave energy propagating in the waveguide tends to leak into the contact medium. Taking advantage of this property, when a pair of waveguides is arranged with the above-mentioned contact medium interposed, a part of the energy of the sound wave propagating in one waveguide will propagate to the other waveguide via the contact medium. At this time, the speed of sound in the contact medium can be detected by measuring the time required for the sound to propagate through the contact medium.

When ultrasonic waves are transmitted from the wave transmitter 3 to the waveguide 1, the waves propagate within the waveguide 1 toward the medium 5 to be measured. In this case, the ultrasonic wave passes through the waveguide 1
Of the velocities propagating inside, let the phase velocity be V _p and the group velocity V _g . The waveguide 1 is in contact with the medium 5 to be measured,
If the sound velocity V of the medium to be measured at this time is smaller than the phase velocity V _p of the waveguide 1 , a part of the ultrasonic energy propagating in the waveguide 1 is irradiated into the medium to be measured 5 . The incident angle θ at this time is determined by the following equation.

θ=sin ^-1 (V/V _p ) The ultrasonic wave that entered the medium 5 to be measured reaches the waveguide 2, and the wave that propagates along the waveguide 2 and the wave that is reflected here and go to the medium 5 side. There is a wave that returns. In this way, there is a wave that travels along the waveguide 2, is reflected at its tip 2A, and reaches the wave receiver 4.

Now, if the lengths of the two waveguides 1 and 2 are equal,
When the distance between the waveguides is D, the arrival time of the received wave whose path in the medium to be measured is N steps is t _N = [(2L−ND tanθ)/V _g ] + [ND/V cosθ] + τ ₁ + τ ₂ ... Here, τ ₁ and τ ₂ are fixed delay amounts during transmission and reception.

Next, when calculating the difference for N=1 and 3, Δt=2D [(1/V cosθ)−(tanθ/V _g )]... Therefore, the sound velocity V of the medium to be measured is given by the following formula. Determined from.

(4D ² +V _g ² Δt ² )V ⁴ −(8D ² V _p V _g +V _p ² V _g ² Δt ² )V ² +4D ² V _p ² V _g ² =0... Therefore, if we measure Δt, , immediate knowledge D, V _g , V _p
The sound velocity V of the medium to be measured 5 can be determined from the formula.

These series of calculations are performed in a calculation section (not shown) of the main body that has a display function.

Next, specific experimental results in the first example will be explained.

A steel plate with a thickness of 0.95 [mm] is used as the waveguides 1 and 2, and a frequency of 1 [MHz] is used as the transducer 3 and 4.
A variable angle probe was used. The wedge of the variable angle probe was made of acrylic, and the incident angle was fixed at 31.5 degrees, so that the S _p mode plate wave was guided. Tap water (21 [°C]) was used as the measurement medium. Therefore, in this case, the group velocity V _g and phase velocity V _p of the guided wave are:
It can be considered that it is almost equal to S _p mode even in the medium 5 to be measured (IAViktrov. “Rayleigh and Lamb
Waves” p. 117).

The applied electric pulse was a two-sine wave of 200 [V _pp ]. An example of the observed received waveform is shown in FIG. In the figure, T indicates the waveform of the transmitter, and P indicates the received waveform of the receiver. N=1 and 3 indicate waves whose underwater paths are one stroke and three strokes, respectively. *mark is N
1 shows the received waveform of a wave in which the wave =1 has made one round trip through the waveguide 2. In this example, Δt=75.1 [μs].
The group velocity of the guided wave can be experimentally determined from the arrival time difference between the wave marked with * and the wave with N=1, and becomes V _g ≈5200 [m/s]. Furthermore, the phase velocity could be calculated from the acoustic velocity of the acrylic material, 2720 [m/s], and the set incident angle of 31.5 degrees for the variable angle probe, and it was found that V _p ≈5300 [m/s].

On the other hand, FIG. 3 shows the results of confirming the relationship in the equation through actual measurements while changing the waveguide spacing D. From this, it was possible to obtain Δt/D=1.26 [μs/mm].
The sound speed of water can be calculated from the formula using V _g and V _p found earlier. The results are shown in FIG. The temperature is 3
The points were measured. The results are in very good agreement with publicly available values.

In this way, according to the first embodiment, the sound velocity V of the medium to be measured can be effectively determined regardless of the lengths of the waveguides 1 and 2, and The sound velocity V of the medium to be measured can be determined by simply detecting the time difference between the received waves of On the other hand, there is an advantage that remote measurement can be performed from a distance, and therefore sufficient durability can be ensured even if ordinary transmitters 3 and receivers 4 are used.
Furthermore, if the insertion dimensions of the waveguides 1 and 2 into the medium to be measured 5 are set large, the reception sensitivity will increase, but this has no direct relationship to the measurement accuracy. The dimensions of the ultrasonic sensor device to be inserted into the ultrasonic sensor device are not required to be particularly precise, and therefore, it is possible to obtain an ultrasonic sensor device that has excellent properties for remote measurement, such as being easy to handle.

Furthermore, since the insertion dimensions into the medium 5 to be measured are directly related to the level of the ultrasonic waves received by the receiver 4, there is also the advantage that the liquid level of the medium 5 to be measured can be detected at the same time. be.

Furthermore, in the first embodiment, the waveguide is formed of a plate-like member, but other members,
For example, the waveguide may be formed of a round bar member, a suitable wire-like member, a pipe-like member, or the like.

[Second Embodiment] Next, a second embodiment will be described based on FIG. 5.

Here, the same reference numerals are used for the same constituent members as in the conventional example described above.

In FIG. 5, the ultrasonic sensor device includes a pair of waveguides 1 and 2 made of stainless steel plate members arranged at a constant distance D, and one end of each waveguide 1 and 2. Transducer/receiver 3, 4 attached to
and a spacer 10 inserted between one end of the waveguides 1 and 2.

The transducer 3 is used as a wave transmitter in this embodiment and includes a piezoelectric vibrator 3A and a wedge 3B made of organic glass.
An oblique probe type is used.

Further, the transducer 4 which acts as a receiver is configured in exactly the same way as the transmitter 3. Each of these transducers 3 and 4 is fixed to one end of the corresponding waveguide 1 and 2, as shown in FIG.

The spacer 10 is a block 10 made of an insulating material.
A and sound insulating members 10B fixed to both ends of the block 10A. As the sound insulation member 10B, a member having an acoustic impedance significantly different from that of the waveguides 1 and 2 is used. Further, this spacer 10 is sandwiched between the waveguides 1 and 2 so as to be located on the opposite side of the above-mentioned wave transducers 3 and 4.

Sound absorbing members 11, 1 are provided on the outside of the transducers 3, 4.
2 are provided respectively. Then, the above-mentioned wave transducers 3 and 4, waveguides 1 and 2, and spacer 10 are all clamped by the clamp mechanism 15 via the sound absorbing members 11 and 12, and the clamp mechanism 1
5 by the set screws 15A, 15B of
It is fixed as shown in the figure.

In this case, the sound insulation members 11 and 12 of the spacer 10
The entire structure is made of a sound insulating material such as asbestos or foamed plastic.
The difference in acoustic impedance of this foamed plastic to the waveguides 1 and 2 is 1000 to 10000.
It has doubled. Therefore, the ultrasonic energy propagating to the block 6 side is almost negligible.

Even in this case, the same working effect as in the first embodiment described above is obtained, and furthermore, due to the effect of the spacer 10, the waveguides 1 and 2 can be connected without interfering with the propagation of elastic waves.
This has the advantage that the mutual dimensions of the two can be effectively maintained.

[Third Example] Next, a third example will be described based on FIG. 6.

In this embodiment, in the second embodiment described above,
The waveguide 2 on the receiver 4 side is set to be shorter than the waveguide 1 on the transmitter 3 side by ΔL. The other configurations are completely the same as the second embodiment described above.

Here, the propagation situation of ultrasonic waves in this third embodiment will be explained.

In the case of this embodiment as well, the arrival time of the received wave whose length is L and is reflected at the tip of the waveguide 1 and whose path through the medium to be measured is N steps can be expressed by the equation.
Next, the arrival time t ₂ ' of the received wave that is reflected at the tip of the other waveguide 2 and whose path through the medium to be measured is three steps is determined by the following equation.

t ₂ ′ = [2(L-ΔL)−3D tanθ)/V _g + [(3D/V cosθ)/V] + τ ₁ + τ ₂ …… The time difference Δt′ between tτ ₁ and t ₂ ′ is as follows: .

Δt'=2ΔL/V _g ... Therefore, in this case, the group velocity of the waveguide itself can be obtained from the equation.

On the other hand, if we use this fact inversely and measure and know the temperature dependence of the group velocity of this waveguide in advance, we can get
The temperature of the medium 5 to be measured is determined, and this sensor becomes a temperature sensor. This means that the temperature can be measured without knowing in advance the temperature dependence of the sound velocity of the medium to be measured.
Furthermore, since the speed of sound in the medium 5 to be measured can also be measured, it is convenient to know the relationship between the speed of sound and temperature.

[Fourth Example] Next, a fourth example will be described based on FIG. 7.

This fourth embodiment has waveguides 41 and 4 of the same length.
2 has a circular cross section, and sound collection guide portions 43A, 44 are provided at one end of each of these waveguides 41, 42.
A is provided respectively, and these sound collection guide parts 43A, 44A
Waveguides 41 and 42 are installed in the vicinity of the waveguides 43 and 44.
It has a structure in which a spacer 45 is provided between the two. This spacer 45 has sound insulating members 45A, 45B at the contact portions with the waveguides 41, 42.

The other ends of the waveguides 41, 42 are formed relatively sharply, and notches 41B, 42B as ultrasonic reflecting means are formed on the waveguides 41, 42 close to the sharp ends 41A, 42A. There is.

Therefore, in this fourth embodiment, the waveguide 41,
The waves propagated along the notches 41B,
42B and detected by the receiver 44. Therefore, the thigh of this fourth embodiment is suitable for measuring the sound velocity of a solid object using a soft member. Other configurations and effects are substantially the same as those of the first embodiment described above.

In each of the above embodiments, the spacers 10, 45 are provided at one end of the waveguides 1, 2 or 41, 42, or are not particularly used. It may be installed in multiple locations, such as at the tip (other end), as long as it does not cause any damage.

Furthermore, in each of the above embodiments, the waveguide 1, 2 or 4
Although the case where the waveguides 1 and 42 are each made into a pair is illustrated, for example, as shown in FIG. 8, there may be three waveguides, with both sides used for reception. If the medium to be measured is layered, for example, its phase velocity V, temperature, and group velocity can be detected simultaneously. In this FIG. 8, 55 and 65 indicate spacers, and 42 and 52 indicate waveguides on the reception side.
Further, 43 indicates a transmitter, and 44 and 54 each indicate a receiver. Furthermore, as long as it functions in the same manner as the spacers 10 and 45, a structure that supports each waveguide from the side opposite to the opposing side of each waveguide may be adopted, for example.

Furthermore, there is also an embodiment in which the shape of the waveguide pair is semi-cylindrical, facing each other, as shown in FIG. In this case, since the pair of waveguides each act as a lens, the efficiency in transferring sound wave energy from one waveguide to the other is extremely high, and at the same time, the width B of the waveguide is Since it has the effect of increasing the rigidity of the waveguide when it cannot be made too large, it is effective when measuring the sound velocity in soft tissue, etc.

In addition, until now, one of a pair of ultrasonic transducers was used as a transmitter and the other as a receiver, but it is also possible to use both transducers as transmitters and receivers. By using it as a receiver, it is expected that the transmitting and receiving sensitivity will improve.
As shown in Figure 1, it is possible to receive received waves not only from odd-numbered paths in the medium under test, but also from even-numbered paths, so it is possible to obtain a lot of reliable information and improve accuracy in signal processing. There is an advantage that it is possible to sufficiently achieve the following.

〔Effect of the invention〕

Since the present invention is configured and functions as described above,
According to this method, the sound speed of a medium to be measured can be measured with high precision regardless of the length of the waveguide, and therefore even if the medium to be measured is a high-temperature fluid or a highly dangerous fluid, it can be measured from a distance. This is an unprecedentedly easy-to-use and highly durable remote device that fully enables remote measurement and can ensure sufficient durability even when using a regular ultrasonic transducer. An ultrasonic sensor device suitable for measurement can be provided.

[Brief explanation of drawings]

FIG. 1 is a partially omitted front view showing the first embodiment of the present invention, FIG. 2 is an explanatory diagram showing waveforms of transmitted waves and received waves obtained through experiments based on the configuration of FIG. 1, and FIG. The figure is a diagram showing the experimental results in Figure 1, and Figure 4.
The figure is a diagram showing the sound speed of water obtained based on the experimental results shown in Figure 1, Figure 5 is a partially omitted front view showing the second embodiment, and Figure 6 is a partial diagram showing the third embodiment. 7 is a partially omitted front view showing the fourth embodiment, FIG. 8 is a right side view of FIG. 7, and FIG. 9 is a partially omitted front view showing the fourth embodiment.
FIG. 10 is an explanatory diagram showing another embodiment, FIG. 10 is a cross-sectional view of a waveguide portion showing another embodiment, and FIG. 11 is an explanatory diagram showing signal waveforms detected by another embodiment of a different method. It is. 1, 2, 41, 42... Waveguide, 3, 4, 4
3, 44... Ultrasonic transducer, 1A, 2A... End face as ultrasonic reflecting means, 41B, 42B...
Notch part as ultrasonic reflection means.

Claims (1)

[Claims] 1. A pair of ultrasonic waveguides made of elastic bodies arranged at a certain distance apart, and an ultrasonic transducer installed at one end of each of the pair of ultrasonic waveguides. An ultrasonic sensor device comprising: an ultrasonic reflecting means provided at the other end of each of the ultrasonic waveguides. 2. The ultrasonic sensor device according to claim 1, wherein the pair of ultrasonic waveguides are a pair of elastic plates. 3. The ultrasonic sensor device according to claim 1, wherein the pair of ultrasonic waveguides are formed by a pair of round bar-shaped members. 4. The ultrasonic sensor device according to claim 1, wherein the pair of ultrasonic waveguides are formed by a pair of pipe-shaped members. 5. Claim 1, wherein the pair of ultrasonic waveguides are formed by ultrasonic waveguides having the same length in the ultrasonic propagation direction.
The ultrasonic sensor device according to item 2, 3 or 4. 6. Claims 1, 2, 3, or 4, characterized in that the pair of ultrasonic waveguides are formed by ultrasonic waveguides with different lengths in the ultrasonic propagation direction. The ultrasonic sensor device described. 7. The ultrasonic sensor device according to claim 1, wherein the ultrasonic transducer is mounted on a side surface of each of the ultrasonic waveguides. 8. The ultrasonic sensor device according to claim 1, wherein the ultrasonic transducer is mounted perpendicular to the center line of each of the ultrasonic waveguides. 9 It has a pair of ultrasonic waveguides made of an elastic body arranged at a certain distance apart, and an ultrasonic transducer installed at one end of each of the pair of ultrasonic waveguides, and each of the ultrasonic waves An ultrasonic reflecting means is provided at the other end of each of the ultrasonic waveguides, a spacer is provided between one end of each of the ultrasonic waveguides, and a sound insulating member is provided at a portion of the spacer that contacts each of the ultrasonic waveguides. An ultrasonic sensor device characterized by being equipped with. 10. The ultrasonic sensor device according to claim 9, wherein the ultrasonic transducer is installed on the opposite side of the sound insulation member via each of the ultrasonic waveguides. 11 It has a pair of ultrasonic waveguides made of elastic bodies arranged at a certain distance apart, and an ultrasonic transducer installed at one end of each of the pair of ultrasonic waveguides, and each of the ultrasonic waves An ultrasonic reflecting means is provided at the other end of each of the ultrasonic waveguides, and a spacer is provided between both ends of each of the ultrasonic waveguides. Equipped with sound insulation materials,
An ultrasonic sensor device characterized in that an ultrasonic wave reflecting means is provided in the ultrasonic waveguide located inside the spacer at the other end. 12 It has a pair of ultrasonic waveguides made of an elastic body arranged at a certain distance apart, and an ultrasonic transducer installed at one end of each of the pair of ultrasonic waveguides, and each of the ultrasonic waves An ultrasonic reflecting means is provided at the other end of each of the ultrasonic waveguides, and the tip of the other end of each of the ultrasonic waveguides is formed relatively sharply, and the ultrasonic reflecting means is provided at an appropriate position close to this tip. An ultrasonic sensor device characterized by: