JP2007067500A - Ultrasonic transceiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic transceiver ensuring high sensitivity, wideband transmission/reception of ultrasonic wave stably regardless of variation in ambient temperature, or the like. <P>SOLUTION: The ultrasonic transceiver 1 for transmitting/receiving ultrasonic wave to/from the surrounding space filled with environmental fluid comprises an ultrasonic vibrator 2, and a propagation medium portion 3 filling the gap between the ultrasonic vibrator and the environmental fluid 4 to form a propagation path of ultrasonic wave wherein the density ρ<SB>1</SB>and sound velocity C<SB>1</SB>of the propagation medium portion and the density ρ<SB>2</SB>and sound velocity C<SB>2</SB>of the environmental fluid satisfy a relation (ρ<SB>2</SB>/ρ<SB>1</SB>)<(C<SB>1</SB>/C<SB>2</SB>)<1, and the ultrasonic vibrator controls directivity of transmitting or receiving ultrasonic wave. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ultrasonic wave transmitter that transmits ultrasonic waves, an ultrasonic wave receiver that receives ultrasonic waves, or an ultrasonic wave transmitter that performs either or both of them. The present invention relates to an ultrasonic sensor capable of transmitting and / or receiving ultrasonic waves with high sensitivity.

  Inventor of the present application discloses an invention capable of transmitting and receiving ultrasonic waves with high sensitivity and broadband using the refraction of ultrasonic waves in Patent Document 1. The invention of Patent Document 1 is an ultrasonic transducer capable of transmitting and receiving ultrasonic waves with high sensitivity while refracting ultrasonic waves to a medium with extremely low acoustic impedance such as air, and uses a special material. This is an ultrasonic transducer that has a propagating medium portion and uses a refraction phenomenon.

  The invention disclosed in Patent Document 1 is shown in FIG. As shown in FIG. 11, the ultrasonic transducer 101 of the invention of Patent Document 1 is provided at least on the ultrasonic transducer 102 and the front surface of the ultrasonic transducer 102, and includes the environmental fluid 104 and the ultrasonic transducer 102. It has a propagation medium portion 103 that fills the gap. Here, in order to facilitate the following description, the interface between the ultrasonic transducer 102 and the propagation medium portion 103 is defined as a first surface region 131, and the interface between the propagation medium portion 103 and the environmental fluid 104 is defined as a second surface region 132. Define as

In such an ultrasonic transducer 101, the material (density, sound speed) of the propagation medium portion 103, the normal direction and the ultrasonic propagation direction in the second surface region 132 in the propagation medium portion 103 shown in FIG. By appropriately selecting the angle θ _{1 to be} formed and the angle θ ₂ inside the environmental fluid, the reflection of the ultrasonic wave at the interface between the propagation medium portion 103 and the environmental fluid 104 is substantially zero, and the transmission efficiency is substantially 1. Is something that can be done.

WO2004 / 098234

  The ultrasonic transmitter / receiver of Patent Document 1 having such advantageous effects has a problem that the transmission / reception sensitivity greatly changes due to environmental changes such as temperature. Hereinafter, this problem will be described in detail.

  The transmission / reception sensitivity in the ultrasonic transducer of Patent Document 1 varies greatly depending on the transmission efficiency of ultrasonic waves at the interface between the propagation medium portion and the environmental fluid.

  The same can be said for the conventional ultrasonic transducer using the acoustic matching layer in terms of ultrasonic transmission efficiency at the interface between the acoustic matching layer and the environmental fluid.

The ultrasonic transmission efficiency at the interface between the acoustic matching layer and the environmental fluid is determined by the acoustic impedance of the environmental fluid, the acoustic matching layer, and the ultrasonic transducer. However, the transmission efficiency is not determined by the relationship between the propagation medium portion, the environmental fluid, and the acoustic impedance of the ultrasonic transducer, but mainly the sound velocity of the propagation medium portion, the sound velocity of the environmental fluid, and the angle θ shown in FIG. _The transmission efficiency is determined with ₁ as a parameter.

  Here, the transmission efficiency of ultrasonic waves at the interface between the propagation medium part and the environmental fluid, which is a factor that greatly changes the sensitivity of the ultrasonic transducer, will be considered separately for transmission and reception. Here, description will be made using the reflectance at the interface as the transmission efficiency. This means that the lower the reflectance, the higher the transmission efficiency.

  Here, what is considered separately at the time of transmission and reception is that the sensitivity change of the ultrasonic transmitter / receiver of Patent Document 1 is different in the mechanism at the time of transmission and reception, and needs to be considered separately. Because there is.

The main factors of the sensitivity change during transmission and reception are as follows. That is, at the time of wave transmission, the main factor is that the transmission efficiency of the ultrasonic wave changes at the interface between the propagation medium part 103 and the environmental fluid 104 and the wave transmission sensitivity changes. On the other hand, during reception, the direction of the ultrasonic wave propagating through the propagation medium portion 103, i.e. it is the main cause of the sensitivity change the angle theta ₁ is changed.

  Changes in transmission / reception sensitivity at the time of transmission and reception will be described in detail below.

The time of wave transmission is a case where the ultrasonic wave transmitted from the ultrasonic transducer 102 is further radiated to the environmental fluid 104 through the propagation medium unit 103. In ultrasonic construction of the transducer 101 shown in FIG. 11, the traveling direction of the ultrasonic wave in the propagation medium portion 103 is a direction indicated by solid arrows 106, the angle theta ₁ is always constant.

This is because the ultrasonic transducer 102 does not have a mechanism for changing the direction of the ultrasonic wave and does not have a mechanism for changing the inclination angle of the second surface region 132. That is, a function of changing the angle theta ₁ ultrasonic transducer 101 does not have 11.

  In FIG. 11, a dotted line 107 inside the propagation medium portion 103 indicates the same phase wavefront of the ultrasonic wave 105 transmitted from the ultrasonic transducer 102. As described above, the ultrasonic wave transmitted from the ultrasonic transducer 2 has a wavefront having the same phase perpendicular to the traveling direction of the ultrasonic wave 105 as indicated by an arrow.

  When the ultrasonic transducer 102 is single as shown in FIG. 11, the interface formed by the ultrasonic transducer 102 and the propagation medium portion 103, that is, the first surface region 131 and the ultrasonic wavefront 107 are substantially parallel.

The ultrasonic wave generated by the ultrasonic vibrator 102 reaches the second surface region 132 through the propagation medium part 103. Usually, at such an interface, a part of the ultrasonic wave is reflected and returned to the propagation medium part 103, or a part is refracted and propagates to the environmental fluid 104. The ratio of reflected or refracted ultrasonic waves varies greatly depending on the angle θ ₁ .

  The reflectance R of the ultrasonic velocity potential in the second surface region is expressed by (Equation 1).

ここで、ρ_１は伝搬媒質部１０３の密度、ρ_２は環境流体１０４の密度、θ_１は伝搬媒質部１０３内における第２表面領域１３２の垂線と超音波伝搬方向のなす角度、θ_２は環境流体１０４内における第２表面領域１３２の垂線と超音波伝搬方向のなす角度である。

Here, ρ ₁ is the density of the propagation medium portion 103, ρ ₂ is the density of the environmental fluid 104, θ ₁ is the angle between the perpendicular of the second surface region 132 in the propagation medium portion 103 and the ultrasonic wave propagation direction, and θ ₂ is This is an angle formed by the perpendicular of the second surface region 132 in the environmental fluid 104 and the ultrasonic wave propagation direction.

（数１）に示した反射率Ｒは（数２）を満たすとき、反射率Ｒが０となる角度θ_１、θ_２が必ず存在する。

When the reflectance R shown in (Equation 1) satisfies (Equation 2), there are always angles θ ₁ and θ _{2 at} which the reflectance R becomes 0.

  When such a reflectance R becomes 0, all ultrasonic waves are transmitted through the interface between the propagation medium part and the environmental fluid, so that the sensitivity is highest.

Meanwhile, between the angle theta ₁ and theta ₂ is related applicable is the law of refraction, the sound velocity of the propagation medium portion C _1, when the acoustic velocity of the environmental fluid was C _2, is shown by the equation (3) To establish.

すなわち、角度θ_１とθ_２をそれぞれ独立に設定する事は出来ず、送波の場合には角度θ_１が決まれば、角度θ_２は（数３）に示す関係より一意に決まる。

That is, the angles θ ₁ and θ ₂ cannot be set independently. In the case of transmission, if the angle θ ₁ is determined, the angle θ ₂ is uniquely determined from the relationship shown in (Equation 3).

The reflectivity R shown in (Equation 1) is a parameter for changing the reflectivity, ie, the density ρ ₁ of the propagation medium part, the sound speed C ₁ , the density ρ _{2 of the} environmental fluid, the sound speed C ₂ , the second surface region, and the ultrasonic wave. The angles θ ₁ and θ ₂ with respect to the propagation direction are related.

The density ρ ₂ of the environmental fluid and the sound velocity C ₂ of this parameter vary greatly depending on the environmental temperature. That is, when this parameter value changes, the reflectance R also changes. This is the reason why the sensitivity of the ultrasonic transducer disclosed in Patent Document 1 changes due to environmental changes.

Further, the influence of the density ρ ₁ and the sound velocity C ₁ of the environmental fluid will be estimated below, and this problem will be described more specifically.

When the ultrasonic transducer is used in the air, such as obstacle detection of a robot or back sonar of an automobile, that is, the reflectance R when air is considered as an environmental fluid, the propagation medium, and the environmental fluid. The relationship among the density, sound velocity, and ultrasonic propagation angles θ ₁ and θ ₂ will be described.

Normally, when the sound speed of air is C ₂ , the sound speed C ₂ is a function of the temperature t, and it is known that the temperature t can be expressed as (Equation 4). That is, when the temperature of the environmental fluid changes by 1 ° C., the sound speed of air changes by 0.6 m / s.

また、温度に対する空気の密度の変化について述べる。０℃での空気の密度は約１．２９３ｋｇ／ｍ^３であり、空気を理想気体として考えると、温度ｔにおける密度ρ_２は（数５）のように表す事が出来る。

In addition, the change in air density with respect to temperature will be described. The density of air at 0 ° C. is about 1.293 kg / m ³ , and considering air as an ideal gas, the density ρ _{2 at the} temperature t can be expressed as (Equation 5).

仮に超音波送受波器の使用環境として０〜６０℃を設定すると、０℃及び６０℃における空気の密度ρ_２及び音速Ｃ_２は、（数４）及び（数５）より、次のようになる。また、気圧によって空気の音速Ｃ_２は殆ど変化しない事が知られている。

If 0 to 60 ° C. is set as the usage environment of the ultrasonic transducer, the air density ρ ₂ and sound velocity C _{2 at} 0 ° C. and 60 ° C. are as follows from (Equation 4) and (Equation 5): Become. Further, it is known acoustic velocity C ₂ of the air is hardly changed by the pressure.

0 ° C., density ρ ₂ : 1.293 kg / m ³ , speed of sound C ₂ : 331.5 m / s
60 ° C., density ρ ₂ : 1.060 kg / m ³ , speed of sound C ₂ : 367.5 m / s
Here, the case where the dry gel currently disclosed by patent document 1 is used as the propagation medium part 103 is considered. The dried gel is a material having a density higher than that of air and a sound velocity lower than that of air, and satisfying the condition for setting the reflectance R shown in (Equation 2) to zero.

The dry gel of Patent Document 1 has a density ρ ₁ of 200 kg / m ³ and a sound velocity C ₁ of 180 m / s. Here, the change of the characteristic with respect to the temperature of dry gel is estimated.

The dry gel has various characteristics depending on the material constituting the skeleton, and a dry gel having a silica skeleton is considered as an example. The coefficient of linear expansion, defined as the dimensional change with temperature of the silica dry gel, is about 10 ⁻⁶ (1 / ° C.).

Thus, the volume change can be defined as the cube of the length change. Therefore, the volume change is as small as about 10 ⁻¹⁸ (1 / ° C.).

Thus, even when there is a temperature change of 0 to 60 ° C. set as the usage environment of the ultrasonic transducer, the volume change of the dry gel is about ^6-16 level change, and the environmental fluid such as air Compared to the change, it is considered that there is almost no change, and it can be regarded as a constant value with respect to the temperature change.

  Further, since the hardness of the dried gel hardly changes, the sound speed hardly changes and can be regarded as a constant value. Furthermore, since the dry gel has a very low thermal conductivity, the density and sound speed can be considered to be constant values because the temperature change itself hardly occurs with respect to the external temperature change.

Under such conditions, the propagation efficiency of ultrasonic waves from the propagation medium portion to the environmental fluid will be considered. FIG. 11 is a graph showing the relationship between the angle θ ₁ calculated based on (Equation 1) and the reflectance R of the ultrasonic wave.

  In the graph of FIG. 12, the amplitude of the ultrasonic wave toward the second surface region in the propagation medium part is 1, and is represented by the ratio of the amplitude of the ultrasonic wave reflected at the interface between the propagation medium part and the environmental fluid. That is, when all the ultrasonic waves are reflected, the reflectance is −1. When the reflectance is 0, all the ultrasonic waves are transmitted to the environmental fluid, and when the reflectance R is 1, the second surface. The case where the ultrasonic wave of the same phase as the ultrasonic wave incident on the region is totally reflected is shown.

As can be seen from FIG. 12, the reflectance R of the ultrasonic wave is extremely sensitive to changes in the angle θ ₁ . Therefore, the changes in the angle theta ₁ slightly, and the reflectance greatly changes, and that the transmitting sensitivity is greatly changed. In addition, the angle at which the sensitivity is maximum varies greatly depending on the temperature of the environmental fluid. When the angle θ ₁ is deviated by about 1 degree from the state where the reflectance R is almost 0, the reflectance rapidly increases to 0.9 or more.

Thus, at the time of transmitting, the propagation efficiency from the propagation medium to the environment fluids, highly dependent ultrasonic angle theta ₁ in the second surface region, larger angles theta ₁ of the propagation efficiency is a function of the temperature If the temperature of the environmental fluid changes, the wave transmission sensitivity will change greatly. That is, the ultrasonic transmitter / receiver disclosed in Patent Document 1 has a problem that high-precision measurement is difficult due to temperature changes.

Further, from FIG. 12, when the use environment of the ultrasonic transducer was used in the condition as shown in above, if the correction angle theta ₁ at 4 ° about the width, always sensitive ultrasonic It is understood that can be transmitted and received.

Temperature range of using ultrasonic transducer, the type of environmental fluid, when the material of the propagation medium portion is changed, of course, also change the range of variation of the angle theta _1. With high sensitivity in accordance with the use environment to transmit the ultrasonic waves, the angle theta ₁ to be controlled may vary.

Next, the sensitivity change of the ultrasonic transducer that occurs during reception will be described. FIG. 13 shows a graph similar to FIG. 12 regarding the angle θ ₂ and the reflectance R of the ultrasonic wave.

As can be seen from FIG. 13, there is almost no difference in the relationship between the angle and the transmission efficiency when the ambient fluid temperature is 0 ° C. and 60 ° C. That is, the ultrasonic wave propagating from the environmental fluid to the propagation medium portion has the reflectance R of 0 and the maximum transmission efficiency when the angle θ ₂ is around 89 degrees regardless of the temperature of the environmental fluid.

  In other words, at the time of wave reception, regardless of the temperature of the environmental fluid, only the ultrasonic waves from the direction around 89 ° with respect to the second surface region are always transmitted into the propagation medium. There is a possibility of becoming a high ultrasonic receiver.

As described above, the angle θ ₂ at which the ultrasonic wave is efficiently transmitted from the environmental fluid to the propagation medium part is constant around 89 degrees regardless of the temperature, but is transmitted from the environmental fluid to the propagation medium part and further propagated. The direction of the ultrasonic wave propagating in the medium part changes depending on the temperature of the environmental fluid. The fact that the propagation direction of the ultrasonic wave in the propagation medium part changes depending on the temperature of the environmental fluid is a cause of the sensitivity change of the ultrasonic transducer during reception.

  In general, in an ultrasonic vibrator using a piezoelectric body or the like, the sensitivity varies depending on the incident angle of the ultrasonic wave to the ultrasonic vibrator. When the incident angle changes, the phase of the ultrasonic wave incident on the ultrasonic transducer changes depending on the ultrasonic incident position of the ultrasonic transducer, and the difference in the phase cancels out the charge generated in the piezoelectric body. is there.

  That is, even when ultrasonic waves of the same intensity propagate in the propagation medium part, the generated voltage to be evaluated as the receiving sensitivity decreases depending on the incident angle to the ultrasonic transducer, and the level to be decreased depends on the incident angle of the ultrasonic wave. Due to the difference, there is a problem that the received wave sensitivity cannot be increased or the received wave sensitivity according to the intensity of the ultrasonic wave cannot be obtained.

  In addition, when the temperature change increases and the refraction angle changes greatly and enters the propagation medium part, the ultrasonic wave incident on the propagation medium part does not directly reach the ultrasonic transducer, and the propagation medium part In some cases, multiple reflections may occur on the side wall. In such a case, there is a problem that ultrasonic waves that have propagated correctly cannot be received and correct ultrasonic measurement cannot be performed.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an ultrasonic transducer capable of stably obtaining high sensitivity to changes in environmental fluid such as temperature. It is.

  In order to achieve the above object, the present invention is configured as follows.

The ultrasonic transducer according to the first aspect of the present invention is an ultrasonic transducer that transmits or receives ultrasonic waves to a surrounding space filled with an environmental fluid,
At least an ultrasonic transducer,
A propagation medium that is filled between the ultrasonic transducer and the environmental fluid and forms a propagation path of the ultrasonic wave; and
The density ρ _{1 of} the propagation medium part, the sound speed C ₁ in the propagation medium part, the density ρ _{2 of the} environmental fluid filling the surrounding space, and the sound speed C ₂ in the environmental fluid are (ρ ₂ / ρ ₁ ) <(C ₁ / C ₂ ) <1 to form the propagation medium portion from a material satisfying the relationship:
The ultrasonic transducer is configured to further include a directivity control unit that controls directivity of ultrasonic wave transmission or reception.

An ultrasonic transducer according to a fifth aspect of the present invention is an ultrasonic transducer that transmits or receives ultrasonic waves to a surrounding space filled with an environmental fluid,
At least an ultrasonic transducer,
A propagation medium that is filled between the ultrasonic transducer and the environmental fluid and forms a propagation path of the ultrasonic wave; and
The density ρ _{1 of} the propagation medium part, the sound speed C ₁ in the propagation medium part, the density ρ _{2 of} the fluid filling the surrounding space, and the sound speed C ₂ in the environmental fluid are (ρ ₂ / ρ ₁ ) <(C ₁ / C ₂ ) The propagation medium portion is made of a material that satisfies the relationship of <1.
A sound speed control unit for changing the sound speed of the propagation medium unit is further provided.

An ultrasonic transducer according to an eleventh aspect of the present invention is an ultrasonic transducer that transmits or receives ultrasonic waves to a surrounding space filled with an environmental fluid,
At least an ultrasonic transducer,
A propagation medium that is filled between the ultrasonic transducer and the environmental fluid and forms a propagation path of the ultrasonic wave; and
The density ρ _{1 of} the propagation medium part, the sound speed C ₁ in the propagation medium part, the density ρ _{2 of} the fluid filling the surrounding space, and the sound speed C ₂ in the environmental fluid are (ρ ₂ / ρ ₁ ) <(C ₁ / C ₂ ) The propagation medium portion is made of a material satisfying the relationship of <1, and the ultrasonic transmission / reception surface of the ultrasonic transducer is a convex surface or a concave surface.

An ultrasonic transducer according to a twelfth aspect of the present invention is an ultrasonic transducer that transmits or receives ultrasonic waves to a surrounding space filled with an environmental fluid,
At least an ultrasonic transducer,
A propagation medium that is filled between the ultrasonic transducer and the environmental fluid and forms a propagation path of the ultrasonic wave; and
The density ρ _{1 of} the propagation medium part, the sound speed C ₁ in the propagation medium part, the density ρ _{2 of} the fluid filling the surrounding space, and the sound speed C ₂ in the environmental fluid are (ρ ₂ / ρ ₁ ) <(C ₁ / C ₂ ) The propagation medium portion is made of a material satisfying the relationship of <1, and the interface between the propagation medium portion and the environmental fluid is a convex surface or a concave surface.

According to the ultrasonic transducer of the present invention, the density ρ _{1 of} the propagation medium part, the sound speed C ₁ in the propagation medium part, the density ρ _{2 of the} environmental fluid filling the surrounding space, and the sound speed C ₂ in the environmental fluid. However, in the state where the propagation medium portion is made of a material satisfying the relationship of (ρ ₂ / ρ ₁ ) <(C ₁ / C ₂ ) <1, the ultrasonic transducer transmits or receives ultrasonic waves. The directivity of the ultrasonic wave is controlled, the sound velocity of the propagation medium portion is changed, or the ultrasonic wave transmitting / receiving surface of the ultrasonic transducer is formed in a convex or concave curved surface, or the propagation By forming the interface between the medium part and the environmental fluid as a convex or concave curved surface, ultrasonic transmission / reception that can transmit and receive ultrasonic waves with high sensitivity in a stable manner even when the temperature of the environmental fluid changes. Implements the vessel.

  Hereinafter, before describing embodiments of the present invention, various aspects of the present invention will be described.

According to the first aspect of the present invention, there is provided an ultrasonic transducer that transmits or receives ultrasonic waves to a surrounding space filled with an environmental fluid,
At least an ultrasonic transducer,
A propagation medium that is filled between the ultrasonic transducer and the environmental fluid and forms a propagation path of the ultrasonic wave; and
The density ρ _{1 of} the propagation medium part, the sound speed C ₁ in the propagation medium part, the density ρ _{2 of the} environmental fluid filling the surrounding space, and the sound speed C ₂ in the environmental fluid are (ρ ₂ / ρ ₁ ) <(C ₁ / C ₂ ) <1 to form the propagation medium portion from a material satisfying the relationship:
The ultrasonic transducer provides an ultrasonic transducer further including a directivity control unit that controls directivity of ultrasonic transmission or reception.

According to the second aspect of the present invention, a plurality of the ultrasonic transducers are provided,
The directivity control unit shifts the drive timing of adjacent ultrasonic transducers among the plurality of ultrasonic transducers in the case of transmission, and the plurality of ultrasonic transducers in the case of reception. By shifting the addition timing of the reception signals of the adjacent ultrasonic transducers of the two, by controlling the phase of the ultrasonic wave front in the case of transmission and reception, the transmission of the ultrasonic wave or The ultrasonic transducer according to the first aspect for controlling the directivity of reception is provided.

According to the third aspect of the present invention, further comprising a thermometer for measuring the temperature of the environmental fluid,
The directivity control unit provides the ultrasonic transducer according to the second aspect, which controls the phase of the wavefront of the ultrasonic wave based on the temperature information of the environmental fluid measured by the thermometer. .

According to the fourth aspect of the present invention, the apparatus further comprises a reflected ultrasonic wave receiving device that receives the ultrasonic wave reflected at the interface between the propagation medium part and the environmental fluid,
The directivity control unit controls the phase of the wavefront of the ultrasonic wave based on information of the reflected ultrasonic wave reflected at the interface between the propagation medium unit and the environmental fluid and received by the reflected ultrasonic wave receiving device. An ultrasonic transducer according to the second aspect is provided.

According to the fifth aspect of the present invention, there is provided an ultrasonic transducer that transmits or receives ultrasonic waves to a surrounding space filled with an environmental fluid,
At least an ultrasonic transducer,
A propagation medium that is filled between the ultrasonic transducer and the environmental fluid and forms a propagation path of the ultrasonic wave; and
The density ρ _{1 of} the propagation medium part, the sound speed C ₁ in the propagation medium part, the density ρ _{2 of the} environmental fluid filling the surrounding space, and the sound speed C ₂ in the environmental fluid are (ρ ₂ / ρ ₁ ) <(C ₁ / C ₂ ) <1 to form the propagation medium portion from a material satisfying the relationship:
An ultrasonic transducer further comprising a sound speed control unit that changes the sound speed of the propagation medium unit is provided.

  According to a sixth aspect of the present invention, the sound speed control unit is configured by a temperature adjustment unit that adjusts the temperature of the propagation medium unit, and the temperature adjustment unit changes the temperature of the propagation medium unit to change the propagation. The ultrasonic transducer according to the fifth aspect for changing the sound speed of the medium portion is provided.

  According to a seventh aspect of the present invention, the sound velocity control unit is configured by an actuator that compresses or expands the propagation medium unit, and the propagation is performed by applying an applied pressure or an extension force to the propagation medium by the actuator. The ultrasonic transducer according to the fifth aspect for changing the sound speed of the medium portion is provided.

  According to an eighth aspect of the present invention, there is provided the ultrasonic transducer according to the seventh aspect, wherein the actuator is disposed so as to be in contact with a side surface of the propagation medium portion.

According to the ninth aspect of the present invention, further comprising a thermometer for measuring the temperature of the environmental fluid,
The ultrasonic transducer according to any one of the fifth to eighth aspects, wherein the sound velocity control unit changes the sound velocity of the propagation medium unit based on information on the temperature of the environmental fluid measured by the thermometer. I will provide a.

According to the tenth aspect of the present invention, the apparatus further comprises a reflected ultrasonic receiving device that receives the ultrasonic wave reflected at the interface between the propagation medium portion and the environmental fluid,
The sound velocity control unit changes the sound velocity of the propagation medium portion based on information of the reflected ultrasonic wave reflected at the interface between the propagation medium portion and the environmental fluid and received by the reflected ultrasonic wave receiving device. The ultrasonic transducer according to any one of the fifth to eighth aspects is provided.

According to an eleventh aspect of the present invention, there is provided an ultrasonic transducer that transmits or receives ultrasonic waves to a surrounding space filled with an environmental fluid,
At least an ultrasonic transducer,
A propagation medium that is filled between the ultrasonic transducer and the environmental fluid and forms a propagation path of the ultrasonic wave; and
The density ρ _{1 of} the propagation medium part, the sound speed C ₁ in the propagation medium part, the density ρ _{2 of the} environmental fluid filling the surrounding space, and the sound speed C ₂ in the environmental fluid are (ρ ₂ / ρ ₁ ) <(C ₁ / C ₂ ) <1 is used to construct the propagation medium section, and the ultrasonic transducer of the ultrasonic transducer is a convex or concave curved surface. provide.

According to a twelfth aspect of the present invention, there is provided an ultrasonic transducer that transmits or receives ultrasonic waves to a surrounding space filled with an environmental fluid,
At least an ultrasonic transducer,
A propagation medium that is filled between the ultrasonic transducer and the environmental fluid and forms a propagation path of the ultrasonic wave; and
Density [rho ₁ of the propagation medium _portion, sound velocity C ₁ in the propagation medium _portion, the density [rho ₂ of the environmental fluid filling the surrounding _space, the sound velocity C ₂ in the environmental _{fluid, (ρ 2 / ρ 1)} <(C ₁ / C ₂ ) <1 An ultrasonic transducer in which the propagation medium portion is made of a material satisfying a relationship of 1 and the interface between the propagation medium portion and the environmental fluid is a convex or concave curved surface. provide.

  Hereinafter, an ultrasonic transducer according to an embodiment of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a perspective view showing a configuration of an ultrasonic transducer according to the first embodiment of the present invention. The ultrasonic transducer 1 in the first embodiment includes a plurality of ultrasonic transducers 2 and a propagation medium unit 3. The area around the ultrasonic transducer 1 is filled with an environmental fluid 4. The propagation medium part 3 has a surface (first surface region 31) parallel to the vibration surface of the ultrasonic transducer 2 and a surface (second surface region 32) in contact with the environmental fluid 4 filling the surrounding space. The ultrasonic transducer 2 is bonded to the vibration surface at the first surface region 31. As shown in FIG. 1, the first surface region 31 and the second surface region 32 are formed with a predetermined angle that is not parallel. As an example, each ultrasonic transducer 2 is a thin rectangular plate, and the propagation medium 3 is a prism having a trapezoidal side surface. In the first surface region 31 which is the bottom surface of the propagation medium unit 3, the ultrasonic transducers 2 are arranged from one end to the other end at equal intervals. As will be described in detail later, 5 indicates the propagation direction of the ultrasonic wave 5 to be transmitted / received. In the first embodiment, the ultrasonic wave 5 in the direction as shown in FIG. 1 is transmitted / received.

  Further, as shown in FIG. 1, XYZ directions orthogonal to each other are set. That is, the X direction is the arrangement direction (width direction) of the ultrasonic transducers 2, the Y direction is the longitudinal direction of the ultrasonic transducers 2, that is, the length direction, and the Z direction is the thickness direction of the ultrasonic transducers 2. .

  FIG. 2 is a cross-sectional view taken along the XZ plane for easy understanding of the configuration and operation of the ultrasonic transducer 1 shown in FIG. 2 includes a transmission / reception circuit 7 that is not shown in FIG. 1, a thermometer 8, a control circuit 9 that functions as an example of a directivity control unit, and a signal line 6 that connects the components. Show. All the ultrasonic transducers 2 are connected to the transmission / reception circuit 7, and the transmission / reception circuit 7 and the thermometer 8 are connected to the control circuit 9. As will be described in detail later, this directivity control unit controls the transmission direction of the ultrasonic wave at the time of wave transmission according to the temperature of the environmental fluid 4, and controls the directivity of the wave reception direction at the time of wave reception. It is something to control.

  In the specification and claims of this application, “environmental fluid that fills the surrounding space” means a fluid that is in contact with the second surface region 32, which is an interface formed by at least the propagation medium portion 3 and the environmental fluid 4. However, it does not necessarily mean a fluid that fills the entire periphery of the ultrasonic transducer 1, but a fluid that fills a part of the surroundings.

  The ultrasonic transducer 1 according to the first embodiment will be described in more detail with reference to FIG.

  Each ultrasonic transducer 2 plays a role of converting an electrical signal into ultrasonic vibration or converting ultrasonic vibration into an electric signal, and is formed of a material having piezoelectricity. Electrodes (not shown) are provided on the upper and lower surfaces of each ultrasonic transducer 2 in the Z direction, and polarization processing is performed in this direction. Each ultrasonic transducer 2 radiates an ultrasonic wave based on a signal applied between the electrodes, and when receiving the ultrasonic wave, detects the ultrasonic wave by generating a voltage signal between the electrodes. is there.

  In the first embodiment, a piezoelectric material used as an example for the ultrasonic transducer 2 is arbitrary, and a known material can be used. The piezoelectric body is made of a material having piezoelectricity, and a material having high piezoelectric performance is desirable because it can increase the transmission / reception efficiency of ultrasonic waves. As the piezoelectric material, a piezoelectric ceramic, a piezoelectric single crystal, a piezoelectric polymer, or the like is effectively used. In one example of the first embodiment, lead zirconate titanate ceramics which are piezoelectric ceramics with high piezoelectricity are used. A common metal having a low electrical impedance is used as the electrode, but silver is used in one example of the first embodiment.

  In addition, an electrostrictive body can be used as the ultrasonic vibrator 2, and a known material can be used for the electrostrictive body. Also in the case of using an electrostrictive body, a material having a large electrostrictive effect is preferable, as in the case of a piezoelectric body, because the transmission and reception efficiency can be increased.

On the front surface of each ultrasonic transducer 2, the ultrasonic wave generated by each ultrasonic transducer 2 is propagated to the environmental fluid 4, or the ultrasonic wave propagated through the environmental fluid 4 is propagated to each ultrasonic transducer 2. Propagation medium part 3 is provided. As described in the prior art, the propagation medium unit 3 satisfies the conditions shown in (Expression 2), that is, the density ρ _{1 of} the propagation medium unit 3, the sound speed C ₁ in the propagation medium unit 3, and the surrounding space. The density ρ _{2 of} the environmental fluid 4 and the sound velocity C ₂ in the environmental fluid 4 need to be made of a material that satisfies (ρ ₂ / ρ ₁ ) <(C ₁ / C ₂ ) <1.

In the first embodiment, a case where a silica dry gel is used as the propagation medium portion 3 will be described as in Patent Document 1. The silica dry gel used for the propagation medium part 3 has a density ρ ₁ = 0.20 × 10 ³ kg / m ³ and a sound velocity C ₁ = 180 m / s.

The density [rho ₂ and the sound velocity C ₂ of environmental fluid 4, as mentioned in the column of "Problems that the Invention is to Solve" in "Disclosure of invention" previous, vary with the temperature of the environmental fluid 4 For example, in the range of 0 to 60 ° C., it varies between ρ ₂ = 1.060 to 1.293 kg / m ³ , C ₂ = 331.5 to 367.5 m / s, and the temperature range of 0 to 60 ° C. Satisfies the relationship of (Equation 2). That is, the second surface region 32 has a condition that satisfies an angle that satisfies the condition for completely transmitting ultrasonic waves.

  Even when other materials are used for the environmental fluid 4 and the propagation medium part 3, it is necessary to set so as to satisfy the relationship of (Equation 2) in all temperature ranges to be used.

As shown in FIGS. 1 to 2, the propagation medium portion 3 has a shape parallel to the vibration surface of the ultrasonic transducer 2 (first surface region 31) and a non-parallel surface (second surface region) facing the surface. 32). For vibration plane parallel to the plane of the ultrasonic transducer 2 (first surface region 31), the angle of the surface not parallel to the opposing (second surface region 32) determines the angle theta _1, as described above. Since the performance of the ultrasonic transducer 1 may vary greatly depending on this angle, the second surface region 32 needs to be precisely formed.

  In the first embodiment, the frequency of ultrasonic waves to be transmitted and received is about 50 kHz. The piezoelectric body used for the ultrasonic vibrator 2 is a piezoelectric body (bimorph type) in which two piezoelectric bodies polarized in the thickness direction (Z direction) are bonded with the polarization directions reversed. ing. A bimorph type piezoelectric body transmits and receives ultrasonic waves by changing the difference in length between two piezoelectric bodies generated when an electric field is received into vibration that changes the deflection.

  The resonance frequency of the bimorph resonator is determined mainly by the lengths in the Z direction and the Y direction. The lead zirconate titanate used in the example of the first embodiment has a resonance frequency of about 50 kHz when the length in the Z direction is 1 mm and the length in the Y direction is 5 mm. Since the conversion efficiency of ultrasonic waves is increased, such a shape is adopted.

  The plurality of ultrasonic transducers 2 shown in FIG. 1 and FIG. 2 can control the direction of ultrasonic waves to be transmitted and received, or can receive received ultrasonic waves with high sensitivity regardless of the direction. However, the arrangement pitch of the ultrasonic transducers 2, that is, the length in the X direction and the length obtained by adding the interval between the ultrasonic transducers 2 is a direction in which ultrasonic waves can be transmitted or received. Is related.

Here, in FIG. 3A, when a plurality of ultrasonic transducers 2 are used, ultrasonic waves having different directions by an angle θ _{3 with} respect to the vibration surface (first surface region 31) of the ultrasonic transducer 2 are transmitted and received. Is shown schematically.

  A dotted line 37 shown in FIG. 3A indicates that ultrasonic waves parallel to the ultrasonic wave front or the vibration surface of the ultrasonic vibrator 2 when a plurality of ultrasonic vibrators 2 are driven by electric signals having the same phase are incident. Shows the case. An arrow 5A indicated by a dotted line indicates the traveling direction of this ultrasonic wave.

Similarly, the same wavefront of the ultrasonic wave having the wavefront inclined by the angle θ _{3 with} respect to the vibration surface (first surface region 31) of the ultrasonic transducer 2 is indicated by a one-dot chain line 38. Similarly, a dashed-dotted arrow 5B indicates the traveling direction of the ultrasonic wave in this direction. A case where ultrasonic waves in a direction inclined with respect to the vibration surface (first surface region 31) of the ultrasonic transducer 2 are transmitted and received will be described.

  In the case of transmission, the basis of measurement is to shift the drive timing of adjacent ultrasonic transducers 2 and in the case of reception, shift the addition timing of reception signals of adjacent ultrasonic transducers 2. . First, the case of transmission will be described.

In the case of transmission, a method of shifting the driving timing of the ultrasonic transducer 2 between the adjacent ultrasonic transducers 2 is used. That is, the wavefronts of the ultrasonic waves transmitted from the adjacent ultrasonic transducers 2 are made to coincide with each other in a direction inclined by an angle θ ₃ from the vibration surface of the ultrasonic transducers 2. As shown in FIG. 3A, in order for the ultrasonic waves transmitted from the adjacent ultrasonic transducers 2 to be in phase in the direction of the angle θ ₃ with respect to the vibration surface of the ultrasonic transducer 2, It is necessary to satisfy the relationship of (Equation 6).

ここで、ｄは隣り合う超音波振動子２のｘ方向における中心間の距離であり、すなわち超音波振動子２の配列ピッチである。ここで、伝搬媒質部３内における音速をＣ_１とすると、（数６）に示した距離Ｌを超音波が伝搬するのにかかる時間Ｔ_１は（数７）で表す事が出来る。よって、この時間Ｔ_１の分だけ、駆動タイミングをずらして駆動する事で、振動面に対して角度θ_３だけ傾いた波面を持つ超音波を送波出来るものである。

Here, d is the distance between the centers of adjacent ultrasonic transducers 2 in the x direction, that is, the arrangement pitch of the ultrasonic transducers 2. Here, the speed of sound in the propagation medium portion 3 When C _1, the time T ₁ to the distance L shown in (6) is an ultrasonic propagation can be represented by (Equation 7). Therefore, the amount corresponding to the time T _1, by driving and shifting the driving timing, in which it transmits an ultrasonic wave having a wavefront which is inclined by an angle theta ₃ to the vibration surface.

一方、受波の場合について説明する。送波の場合とは逆に、伝搬媒質部３を伝搬してきた超音波が超音波振動子２の一例である圧電体の表面まで到達し、超音波振動子２で受波された超音波振動が圧電体の圧電効果によって電気信号に変換され、送受波回路７で電気信号が加算されて計測が行われる。この電気信号を加算する際に、隣接する超音波振動子２からの電気信号を時間Ｔ_１だけ、時間的にずらして加算する事で、角度θ_３だけ傾いた方向の超音波を選択的に受波した事と同一となる。

On the other hand, the case of wave reception will be described. Contrary to the case of the transmission, the ultrasonic wave propagating through the propagation medium unit 3 reaches the surface of the piezoelectric body as an example of the ultrasonic vibrator 2 and is received by the ultrasonic vibrator 2. Is converted into an electrical signal by the piezoelectric effect of the piezoelectric body, and the electrical signal is added by the transmission / reception circuit 7 to perform measurement. When adding this electric signal, by the time T ₁ the electrical signal from the ultrasonic transducer 2 adjacent, by adding chronologically staggered, the direction of the ultrasound inclined by an angle theta ₃ selectively It is the same as that received.

As described above, for example, when the temperature of the environmental fluid 4 is assumed to be between about 0 ° C. and 60 ° C., the use environment of the ultrasonic transducer 2 in the first embodiment is super angle theta _1, i.e. the angle theta ₁ which the most transmittance increases reflectance R is the smallest of the waves, as shown in FIG. 12, between about 29 to 33 °, varies with a width of about 4 ° It will be.

That is, the angle at which the reflectance R is lowest is changed according to the temperature of the environmental fluid 4, if the set the conditions of the first embodiment (air, 0 to 60 ° C.) in the angle theta ₁ is about 31 ° As a center, both the plus and minus sides change within a width of about 2 °.

In order to perform stable ultrasonic wave transmission / reception, the reflectivity increases abruptly when the optimum angle θ ₁ slightly changes due to the temperature change of the environmental fluid 4 from the appropriate angle θ _{1 at} which the reflectivity decreases. It is necessary to change the transmission / reception direction according to the temperature.

  Here, a method for setting the length of the ultrasonic transducer 2 in the X direction will be described. There are a plurality of ultrasonic transducers 2 in the first embodiment, and the ultrasonic wave is changed by utilizing the phase difference of the ultrasonic waves transmitted from each of them. In this case, adjacent ultrasonic waves are used. A certain restriction is required on the arrangement interval of the vibrators. This is to prevent the directions of the ultrasonic waves from the ultrasonic transducers 2 from being aligned in directions other than the intended direction so that there is no intensifying direction.

  When it is necessary to change the direction of the ultrasonic wave to −90 to + 90 ° with respect to the normal direction of the vibration surface (first surface region 31) of the ultrasonic vibrator, the ultrasonic vibrator 2 However, since the angle to be changed is small in the case of the first embodiment, the arrangement interval of the ultrasonic transducers 2 may be about one wavelength or less. .

  When the angle to be redirected is large, it is desirable that the arrangement pitch of the ultrasonic transducers is ½ wavelength or less.

  Therefore, in the first embodiment, the length of the ultrasonic transducer 2 in the x direction is 3 mm, and the interval is 0.3 mm. That is, the arrangement pitch of the ultrasonic transducers 2 is 3.3 mm. This is because the frequency of ultrasonic waves to be transmitted and received is 50 kHz, and the speed of sound in the propagation medium section 3 is 180 m / s, so the wavelength in the propagation medium section 3 is about 3.6 mm, which is less than this one wavelength. Satisfy the array pitch.

  In the first embodiment, 16 ultrasonic transducers 2 are arranged. Therefore, the length of the ultrasonic transducer 1 in the X direction is approximately 24 mm. The number of the ultrasonic transducers 2 is determined based on the necessity that the ultrasonic waves transmitted from the ultrasonic transducers 2 interfere with each other and propagate as plane waves. Since it is close to a spherical wave, a certain number (about 10) is required at a minimum.

  In the first embodiment, an angle change is applied in the direction of the ultrasonic wave of 2 ° on the one side from the center at the maximum. In order to set an angle change of 2 ° or less, the control circuit 9 similarly uses (Equation 6). By setting the calculated drive timing corresponding to the distance L, it is possible to realize transmission of ultrasonic waves in a necessary angular direction.

The ultrasonic frequency, the angle θ ₁ , the shape of the ultrasonic transducer 2, the arrangement interval, and the like described above change as the type of the environmental fluid 4 and the material of the propagation medium unit 3 change. It is necessary to select and set an optimum design value according to the environment, and the present invention is not limited to the value of the first embodiment.

  As described above, there are a plurality of ultrasonic transducers 2 in the first embodiment, each of which is independently connected to the transmission / reception circuit 7 via the signal line 6, and the transmission / reception circuit 7 includes a plurality of ultrasonic waves. By being configured so that the drive voltage and drive timing of the vibrator 2 and the addition timing of the received signal can be controlled independently, it is possible to adjust the direction of ultrasonic waves to be transmitted and received. .

  Further, the transmission / reception circuit 7 is connected to a control circuit 9, and the control circuit 9 controls a driving voltage and driving timing for each ultrasonic transducer 2 or a method of processing an electric signal based on the received ultrasonic vibration. Can be ordered.

  A thermometer 8 that measures the temperature of the environmental fluid 4 is connected to the control circuit 9. By controlling the timing of transmission or reception based on the temperature from the thermometer, stable and highly sensitive transmission / reception can be performed.

  The feature of the ultrasonic handset 1 in the first embodiment is that the ultrasonic wave transmission direction is controlled at the time of wave transmission in accordance with the temperature of the environmental fluid 4, and the directivity of the wave receiving direction at the time of wave reception. It is in the point which is comprised so that control is possible.

  First, the ultrasonic transducer 1 of the first embodiment drives a plurality of ultrasonic transducers 2 without phase difference or adds received signals at a temperature of 30 ° C., which is the median value of the operating temperature environment. In this case, the transmission / reception sensitivity is set to be high.

More specifically, the density ρ ₁ and the sound speed C ₁ of air, which is an example of the environmental fluid 4 at a temperature of 30 ° C., are represented by ρ ₁ = 1.165 kg / m ³ from (Equation 4) and (Equation 5), respectively. Since C ₁ = 349.5 m / s, the angle θ ₁ for increasing the transmission / reception sensitivity calculated by the control circuit 9 from (Equation 8) is made to be about 31 °.

以下、本第１実施形態における超音波送受波器１の動作方法を、図３Ｂを用いてより具体的に説明する。

Hereinafter, the operation method of the ultrasonic transducer 1 in the first embodiment will be described more specifically with reference to FIG. 3B.

  In the case of wave transmission, first, the temperature t of air, which is an example of the environmental fluid 4, is measured by the thermometer 8 (step S 1), and information on the temperature t is sent to the control circuit 9. In the control circuit 9, after determining whether the temperature of the environmental fluid 4 is within the measurable range (step S2), if the temperature of the environmental fluid 4 is outside the measurable range, a measurement error (step S3) is performed again, and step S1 is repeated. The temperature t of air, which is an example of the environmental fluid 4, is measured by the thermometer 8. When the temperature of the environmental fluid 4 is outside the measurable range, the error display is repeated.

On the other hand, if the measurement range temperature environment fluid 4, based on the environmental temperature t is calculated sound velocity C ₂ of environmental fluid _4, the density [rho ₂ in the control circuit 9 (step S4), and the sound velocity C _2, density with [rho _2, further optimal incident angle theta ₁ to be Do the second surface region 32 is calculated by the control circuit 9 on the basis of the equation (8) (step S5).

In this way, using the angle θ ₁ calculated by the control circuit 9 in step S4, the control circuit 9 obtains the angle θ ₃ obtained by taking the difference from the incident angle 31 ° that does not require any delay in the ultrasonic transducer 2 (step S4). S6), using the angle θ ₃ , the arrangement pitch d of the ultrasonic transducers 2, and the sound velocity C ₁ of the propagation medium unit 3, the timing of driving the ultrasonic transducer 2 according to (Equation 6) and (Equation 7). The deviation time ΔT is calculated by the control circuit 9 (step S7).

Information on the deviation time ΔT is further sent from the control circuit 9 to the transmission / reception circuit 7, and the plurality of ultrasonic transducers 2 are driven under the control of the control circuit 9. By controlling the deviation time ΔT, the ultrasonic angle θ ₁ in the second surface region 32 is controlled by the control circuit 9 so that ultrasonic waves can be stably transmitted with high sensitivity (step S8). ). Thereafter, the operation from step S1 is started again, so that the transmission operation of the ultrasonic transducer 1 can be performed continuously.

  More specifically, the operation when the temperature of the environmental fluid 4 is 30 ° C. will be described.

  Since the ultrasonic transducer 1 of the first embodiment is created so that the vibration surface (first surface region 31) of the ultrasonic transducer 2 and the second surface region 32 have an angle of 31 °, When the ultrasonic wave propagates in a direction perpendicular to the first surface region 31, the sensitivity is maximized.

  In order to propagate ultrasonic waves in such a direction, the plurality of ultrasonic transducers 2 may be driven without a phase difference.

  Thus, when the propagation medium portion 3 of the ultrasonic transducer 1 in the first embodiment is driven to a plurality of ultrasonic transducers 2 without a phase difference when the temperature of the environmental fluid 4 is 30 ° C., it is efficient. The material and shape of the propagation medium portion 3 are formed so that ultrasonic waves can be transmitted to the environmental fluid 4.

On the contrary, when receiving the wave, only the ultrasonic wave having an angle θ ₂ formed with the second surface region 32 of approximately 89 ° among the ultrasonic waves propagating through the environmental fluid 4 is selectively transmitted through the propagation medium 3. It becomes transparent. The ultrasonic waves refracted in the second surface region 32 propagate through the propagation medium portion 3 with an angle θ ₁ of 31.0 ° and reach a plurality of ultrasonic transducers 2.

  At this time, since the ultrasonic waves reach the plural ultrasonic transducers 2 without a phase difference, the receiving circuit adds the electric signals obtained from the plural ultrasonic transducers 2 without any phase difference. In this way, highly sensitive ultrasonic waves are received.

The propagation medium portion 3 having the second surface region 32 in which the angle θ _{1 at} which the temperature is maximum at 30 ° C. is 31 ° is not limited to this angle, and the angle θ ₁ is the sound speed and density of the environmental fluid 4. Then, the angle of the second surface region 32 and the propagation direction of the ultrasonic wave may be controlled so as to satisfy the optimum angle θ ₁ determined by (Equation 8) from the sound speed and density of the propagation medium portion 3. The ultrasonic transducer 1 in the first embodiment is an example.

  Next, the operation of the ultrasonic transducer 1 when the temperature of the environmental fluid 4 is 0 ° C. and 60 ° C. will be described. By explaining the operation when the temperature is 0 ° C. and 60 ° C., the operation at the temperature during that time can be more easily understood than those operation methods by understanding the case where the turning angle of the ultrasonic wave is the largest.

  When the temperature t of the environmental fluid 4 is 0 ° C. is sent to the control circuit 9 by the thermometer 8 as in the case of the temperature 30 ° C., the control circuit 9 calculates the deviation time difference ΔT by the control circuit 9 and sends / receives it. The wave circuit 7 is sent out. In the transmission / reception circuit 7, the plurality of ultrasonic transducers 2 are driven based on the deviation time difference ΔT from the control circuit 9, and the transmitted ultrasonic waves have an angle of about 29.0 ° with respect to the second surface region 32. It will be controlled to reach at.

  That is, as indicated by the dotted line in FIG. 3A with respect to the first surface region 31, the wavefront ultrasonic wave having an angle of about 2 ° to the left propagates toward the second surface region 32. To do.

  More specifically, the value of the deviation time difference ΔT that shifts the drive timing of the ultrasonic transducer 2 in the first embodiment will be described.

  In order to make an angle of 2 ° with respect to the vertical direction of the ultrasonic vibration surface, the ultrasonic waves transmitted from the adjacent ultrasonic transducers 2 are arranged and changed in the arrangement interval between the ultrasonic transducers 2. It is calculated by the control circuit 9 that a distance difference of about 0.12 mm (3.3 mm × sin 2 °) can be obtained from the angle of 2 degrees.

  Since the sound speed of the propagation medium unit 3 is 180 m / s, the time difference of the drive signal actually applied to the ultrasonic transducer 2 is approximately calculated by dividing the distance L = 0.12 mm by the sound speed 180 m / s. 0.67 μs.

By providing such a time difference ΔT = 0.67 μs in the drive signal applied to the adjacent ultrasonic transducer 2, even when the temperature of the environmental fluid 4 is 0 ° C., an appropriate angle θ ₁ is ensured, High-efficiency ultrasonic transmission can be performed.

  This time difference ΔT = 0.67 μs is obtained when air is used as the environmental fluid 4 and when the second surface region 32 is formed at an angle of 31 ° with respect to the first surface region 31, the environmental fluid 4 is 0 ° C. It is a solution, and is changed as needed depending on other environmental fluids, the temperature environment to be used, the angle of the second surface region 32, and the like.

  On the other hand, in the case of wave reception, the ultrasonic wave incident from the second surface region 32 of the propagation medium portion 3 passes through the path opposite to that in the case of wave transmission and is directed to the vibration surface of the ultrasonic transducer 2. Then, the light is incident at an angle of about 2 ° inclined to the left side of FIG. 3A. By adding the ultrasonic waves received by each transducer 2 with the same time difference (about 0.67 μs) as described above, it is possible to receive ultrasonic waves with high sensitivity according to the intensity of the ultrasonic waves.

  Next, the case where the temperature of the environmental fluid 4 is 60 ° C. will be described. When the temperature is 60 ° C., similarly to the case of 0 ° C., when the thermometer 8 sends to the control circuit 9 that the temperature of the environmental fluid 4 is 60 ° C., the transmission / reception circuit 7 The sound wave is controlled to be incident on the second surface region 32 at an angle of 33 °. That is, in FIG. 2, control is performed so that the ultrasonic wave having a wavefront inclined to the right with respect to the first surface region 31 and having an angle of about 2 ° propagates toward the second surface region 32.

  In order to transmit an ultrasonic wave with an angle of 2 ° on the opposite side to the case where the temperature of the environmental fluid 4 is 0 degree, similarly, the ultrasonic wave transmitted from each ultrasonic transducer 2 is The time difference of the drive signals is set to about 0.67 μs so that the difference in distance in the propagation medium unit 3 is about 0.12 mm. However, it is necessary to add a phase difference opposite to that at 0 ° C.

  By doing so, an ultrasonic wavefront having an angle of about 2 ° from the first surface region 31 is formed and incident on the second surface region 32 with an angle of about 33 °. Highly sensitive ultrasonic waves can be transmitted to the environmental fluid 4.

  Also in the case of reception, similarly to the case of the temperature of 0 ° C., the ultrasonic wave received by each ultrasonic transducer 2 is added with the same time difference of 0.67 μs as in the case of transmission, thereby increasing the frequency. Sensitive ultrasonic waves can be received.

  As described above, the ultrasonic transducer 1 according to the first embodiment of the present invention uses the propagation medium unit 3 that can transmit and receive ultrasonic waves with high sensitivity to a medium such as gas. It is possible to provide an ultrasonic transducer 1 that can stably and highly sensitively transmit and receive ultrasonic waves in response to temperature changes in the environmental fluid 4.

  Further, when the temperature of the environmental fluid 4 is 0 to 30 ° C. or 30 to 60 ° C., the driving time difference between the above-described cases in the case of wave transmission and the wave reception in the case of wave reception depending on the temperature. By measuring with a predetermined time difference when the added signals are added, stable and highly sensitive measurement can be realized.

  The use environment in which the temperature of the environmental fluid 4 is 0 to 60 ° C. is set in order to understand the first embodiment more specifically, and the use of the ultrasonic transducer 1 of the first embodiment. The environment is not particularly limited to this range, and ultrasonic transmission / reception that can transmit and receive ultrasonic waves stably and with high sensitivity to temperature changes by changing the direction of ultrasonic waves according to the environment of use. The device 1 can be realized.

  Moreover, although the ultrasonic transducer 1 in the first embodiment shown in FIGS. 1 and 2 is composed of only the ultrasonic transducer 2 and the propagation medium portion 3, for example, as shown in FIG. 4A. Furthermore, it is good also as a form which has another member.

  That is, in order to increase the strength of the ultrasonic transducer 1, the filler 10 may be provided between the ultrasonic transducers 2 arranged adjacent to each other. The material to be filled as the filler 10 is preferably rubber or resin because the strength of the ultrasonic transducer 1 can be increased without lowering the electromechanical conversion efficiency of the ultrasonic transducer 2. Use of a hard material for the filler 10 is not preferable because the conversion efficiency of the ultrasonic transducer 2 is lowered.

  In order to prevent mechanical and electrical crosstalk between adjacent ultrasonic transducers 2, it is desirable to use a material with large ultrasonic attenuation as the filler 10, and rubber or the like mixed with filler is preferably used. be able to.

  In order to improve the frequency characteristics of the ultrasonic transducer 1, improve the strength of the ultrasonic transducer 1, or facilitate handling, a back load material 11 is provided on the back surface of the ultrasonic transducer 2. It may be provided.

  The purpose of improving the frequency characteristics of the ultrasonic transducer 2 is to reduce the Q value of the ultrasonic transducer 2 and to provide wideband characteristics. In the case where a piezoelectric body is used as the ultrasonic transducer 2 of the first embodiment, since the conversion efficiency of ultrasonic vibration into an electric signal is enhanced by utilizing a resonance phenomenon, the Q value is high.

  Attenuating the ultrasonic wave propagating to the back side of the ultrasonic transducer 2 and reducing the Q value are effective in improving the frequency characteristics. The material of the back load material 11 is preferably a material having an acoustic impedance close to that of the ultrasonic transducer 2 in order to prevent reflection at the interface between the ultrasonic transducer 2 and the back load material 11, and sufficiently applies ultrasonic waves. In order to attenuate, a material with large ultrasonic attenuation is preferable. As such a material, ferrite rubber (rubber in which iron powder is dispersed) or the like is preferably used.

In addition, an acoustic matching layer 12 may be provided between the ultrasonic transducer 2 and the propagation medium unit 3 for the purpose of improving ultrasonic transmission / reception sensitivity and frequency characteristics. The acoustic impedance of the piezoelectric ceramic used as an example of the ultrasonic vibrator 2 is about 30 × 10 ⁶ kg / m ² / s, and the dry gel used as the propagation medium portion 3 is 0.036 × 10 ⁶ kg / m ² / s. When the one acoustic matching layer 12 is provided, a material having an acoustic impedance intermediate between a piezoelectric ceramic that is an example of the ultrasonic transducer 2 and a dry gel that is an example of the propagation medium unit 3 is desirable.

In particular, the acoustic matching layer 12 has an acoustic impedance of about 1.0 × 10 ⁶ kg / m ² / s, which is the geometric average of the products of the acoustic impedance of the piezoelectric body that is an example of the ultrasonic transducer 2 and the propagation medium unit 3. material is preferred to have, as a material for realizing the acoustic impedance, density of about ^{0.60 × 10 3 kg / m 3} , the use of a porous ceramic made of silica acoustic velocity is about 1600 m / s I can do it. The acoustic matching layer 12 may not be a single layer but may be a plurality of layers. When the acoustic matching layer 12 is formed in multiple layers, the sensitivity and the bandwidth can be further increased.

  In addition, the dry gel used as an example of the propagation medium unit 3 in the first embodiment has a low density and a low sound speed, and therefore has a low strength. In order to prevent the propagation medium unit 3 from being damaged and improve the handleability of the ultrasonic transducer 1, a protective unit 13 may be provided on the outer periphery of the ultrasonic transducer 1. The protection unit 13 may cover not only the propagation medium unit 3 but also the part of the ultrasonic transducer 2 and the like. There is no limitation on the performance of the ultrasonic transmitter / receiver 1 in terms of shape as long as the path through which the ultrasonic wave propagates is not disturbed.

  FIG. 4B shows a perspective view of the ultrasonic transducer 1 for easier understanding of the form of the protection unit 13. In FIG. 4B, as shown in FIG. 4B, the protection unit 13 may cover the entire periphery of the propagation medium unit 3 other than the sound wave emission surface. When the propagation medium unit 3 has a certain level of strength, a shape that covers only one direction as shown in FIG. 4C (for example, covers the front surface, the rear surface, and the lower surface excluding the upper surface and both side surfaces of the ultrasonic transducer 1). Thus, the cross section may be generally L-shaped), and can be designed in consideration of ease of manufacture, cost, and the like. When the intensity of the propagation medium part 3 is low, the shape of FIG. 4B is preferable because of high handling and reliability.

  When the porous ceramic used as the acoustic matching layer 12 is used for the protective portion 13, it is preferable to bond with the dry gel due to the anchor effect, and further integrated with the acoustic matching layer 12 to simplify the manufacturing process. Therefore, the manufacturing cost of the ultrasonic transducer 1 can be reduced.

  Moreover, if the protection unit 13 is equipped with a thermometer 8 for measuring the temperature of the environmental fluid 4, the ultrasonic transducer 1 that is integrated with the thermometer 8 and that is easy to use can be configured without any acoustic interference. . It is important to configure the protection unit 13 so as not to interfere with the propagation path of the ultrasonic waves in order to transmit and receive highly sensitive waves. The thermometer 8 may be provided in a part of the protection unit 13 on the side where the sound wave is not transmitted and received as shown in FIG. 4B, or may be provided over the entire surface on the side where the sound wave is not emitted as shown in FIG. 4D. Alternatively, although not shown, it may be provided on the upper surface of the protection portion 13 on the orthogonal side. That is, it can be installed according to the performance of the thermometer 8 to be used, the required temperature accuracy, or the necessity of the spatial distribution of temperature.

[Second Embodiment]
With reference to FIG. 5A, the configuration and operation of an ultrasonic transducer according to the second embodiment of the present invention will be described. The ultrasonic transmitter / receiver 1A in the second embodiment does not have the thermometer shown in the first embodiment, and controls the timing of driving a plurality of ultrasonic transducers 2 or adding received signals. The feature is that the (displacement time ΔT) is obtained from the received signal of the ultrasonic transducer 2 itself or the ultrasonic transducer for detection 14, and the other configurations and operations are the same as in the first embodiment. . In the ultrasonic transmitter / receiver 1A according to the second embodiment, reflected ultrasonic reception is performed in order to acquire information (deviation time ΔT) for controlling the timing of driving of the plurality of ultrasonic transducers 2 or addition of reception signals. As an example of the reflected ultrasonic wave receiving device, the ultrasonic wave detecting device 14 is configured by the ultrasonic vibrator 2 itself or provided separately from the ultrasonic vibrator 2. Can be configured. Then, the control circuit 9 functioning as an example of the directivity control unit reflects the reflected ultrasonic wave reflected by the interface between the propagation medium unit 3 and the environmental fluid 4 and received by the reflected ultrasonic wave receiving device. Is configured to control the phase of the wavefront of the ultrasonic wave.

Ultrasonic 5 which is transmitting from the ultrasonic transducer 2 at a certain temperature, propagates through the propagation medium portion 3, and reaches the second surface region 32, if the angle theta ₁ is set to the optimum angle Since almost all the ultrasonic waves 5 pass through the second surface region 32 and propagate into the environmental fluid, the reflected wave of the transmitted ultrasonic waves 5 is observed by the ultrasonic transducer 2. No.

However, when the temperature of the environmental fluid 4 changes and the optimum angle θ ₁ in the second surface region 32 changes, the ultrasonic wave 5 cannot be transmitted to the environmental fluid 4 in the second surface region 32 and reflected. As indicated by a solid line arrow 5G in FIG. 5A, the ultrasonic wave 5G reflected by the second surface region 32 propagates again inside the propagation medium portion 3.

The ultrasonic wave 5G reflected and propagated through the propagation medium unit 3 returns to the ultrasonic transducer 2 and is observed as an ultrasonic signal due to the geometric shape of the reflection surface. By adjusting the drive timing of the ultrasonic transducer 2 based on the received information of the reflected ultrasonic wave 5G, the incident angle θ ₁ of the ultrasonic wave 5 is set so that the reflection at the second surface region 32 is always low. It can be set, and stable and highly sensitive ultrasonic wave transmission can be performed.

  The reflected signal for determining the ultrasonic wave transmission direction will be described more specifically with reference to FIGS. 5B and 5C. 5B and 5C schematically show waveforms at the time of transmission of the ultrasonic transducer 2, where the horizontal axis indicates time and the vertical axis indicates the signal magnitude. FIG. 5B shows a case where the ultrasonic wave 5 is hardly reflected at the second surface region 32 and ultrasonic waves can be transmitted with high sensitivity. The first waveform in FIG. 5B is the signal of the ultrasonic wave 5 that is transmitted, and no reflection occurs inside the propagation medium unit 3, so that the ultrasonic wave 5G is not observed subsequently.

  On the other hand, when the temperature of the environmental fluid 4 changes and the ultrasonic wave 5G is reflected by the second surface region 32, the ultrasonic wave 5G reflected further after the signal of the ultrasonic wave 5 transmitted as shown in FIG. 5C. Signal is observed. It is necessary to adjust the angle of the ultrasonic wave so that the level of the reflected signal is reduced.

  FIG. 5D shows a specific procedure for adjusting the angle of the ultrasonic wave so that the level of the reflected signal is reduced.

  FIG. 5D is a flowchart showing a procedure for changing the direction of the ultrasonic waves, and a highly sensitive ultrasonic wave can be transmitted and received by changing the drive timing until no reflected signal is observed in the procedure shown in FIG. 5D.

  As described above, the ultrasonic wave propagation direction is changed by controlling the timing of driving the plurality of ultrasonic transducers 2. By controlling the direction of the ultrasonic wave so as to reduce the reflected signal level of the ultrasonic transducer 2 in this way, it is possible to stably transmit ultrasonic waves with high sensitivity.

  A specific procedure will be described in more detail with reference to FIG. 5D. FIG. 5D illustrates a case where the ultrasonic transducer for detection 14 connected to the control circuit 9 is provided.

  First, the ultrasonic wave 5 is transmitted from the ultrasonic transducer 1A (step S21). At this time, a time difference is not provided in the drive signals of the plurality of ultrasonic transducers 2, and a wavefront parallel to the surface of the ultrasonic transducers 2 is transmitted. When the ultrasonic wave 5 thus transmitted is reflected by the second surface region 32 as indicated by 5G in FIG. 5A, it is received by the ultrasonic transducer for detection 14 (YES in step S22). When the ultrasonic wave is not reflected, the ultrasonic wave is not received by the detection ultrasonic transducer 14 (NO in step S22). In this case, a time difference of the drive signal is provided under the control of the control circuit 9. Without returning to step S21, the ultrasonic wave 5 is transmitted again.

  When a reflected signal is observed (step S22), the control circuit 9 adds a time difference to the signal for driving the ultrasonic transducer 2 and changes the propagation direction of the ultrasonic wave 5 (step S23). The control circuit 9 drives the right side of the plurality of ultrasonic transducers 2 shown in FIG. 5A first, and sequentially drives the left ultrasonic transducer 2 (step S23). This case is defined as shifting the timing of the drive signal to the plus side. In this case, the ultrasonic wave 5 is transmitted by the control circuit 9 in the direction inclined to the right from the direction perpendicular to the vibration surface of the ultrasonic transducer 2 in FIG. 5A. .

  On the other hand, the control circuit 9 drives the left side of the plurality of ultrasonic transducers 2 first, and sequentially drives the right ultrasonic transducer 2 (step S23). This case is defined as shifting the timing of the drive signal to the minus side. In this case, the control circuit 9 transmits the ultrasonic wave 5 in the direction inclined to the left from the direction perpendicular to the vibration surface of the ultrasonic transducer 2 in FIG. 5A.

  The time difference between the signals for driving the respective ultrasonic transducers 2 is determined by the discretized time measurement accuracy of the transmission circuit 7 and is set by multiplying the minimum time difference by an integer number by the control circuit 9. It is. Here, the minimum driving time difference is defined as Ta.

  The minimum driving time difference Ta is set to the plus side and the minus side, and an ultrasonic wave is transmitted by the control circuit 9 (step S23), and the reflected wave in each case is measured. At this time, the level of the reflected wave is compared by the control circuit 9 (step S24), and if one of the reflected signals is not observed, the control circuit 9 again transmits the ultrasonic wave with a propagation time difference where the reflected signal is not observed. The measurement is continued to continue (step S25).

  If a reflected signal is observed in both cases in step S24, the level of the reflected signal is compared by the control circuit 9, and the reflected signal level is controlled to the lower side, and the drive time difference is controlled to the plus side or the minus side. The ultrasonic wave increased by the circuit 9, that is, a more angled ultrasonic wave is transmitted by the control circuit 9 (step S26). The propagation time difference is increased by the control circuit 9 in order of an integral multiple of the minimum driving time difference Ta, that is, 2 * Ta, 3 * Ta.

  Furthermore, the received signal in this case is observed (step S27), and when the reflected signal is no longer observed, the control circuit 9 transmits ultrasonic waves again at this drive time difference and continues measurement (step S27). S28).

  If the reflected signal level has decreased in step S27, the control circuit 9 further increases the drive time difference and transmits the ultrasonic wave in the control circuit 9 (step S29). The control circuit 9 compares the reflected signal level in this case with the control circuit 9 (step S27), and transmits the ultrasonic wave with the same procedure until the reflected signal is not observed.

  On the other hand, when the reflected signal level increases during this procedure, the reflected signal can be set to 0 only by control below an angle that can be set with the minimum driving time difference Ta, and therefore the reflected signal is minimized. The ultrasonic wave is transmitted by the control circuit 9 according to the driving time difference (step S30), and measurement is performed in a state where the maximum SN is obtained.

The case of receiving waves will be described. The ultrasonic wave received by the ultrasonic transducer 2 is incident on the propagation medium unit 3 through the same path (same angle θ ₁ ) as that of the ultrasonic wave that is basically transmitted. For this reason, in the ultrasonic transducer 1 </ b> A of the second embodiment of the type that performs measurement by alternately repeating transmission and reception (pulse echo method), the drive timing of this transmission is controlled by the control circuit 9. Based on the information to be transmitted, the control circuit 9 controls the timing at which the received ultrasonic signals are added, whereby highly sensitive ultrasonic waves can be transmitted and received.

  Further, as shown in FIG. 5A, in addition to the ultrasonic transducer 2, a detection ultrasonic transducer 14 for detecting reflected ultrasonic waves may be used.

  In the case where the tail of the transmission signal is long and the reflection signal is buried in the transmission signal, the use of the ultrasonic transducer for detection 14 is effective in detecting the reflection signal. In addition, since the reflected ultrasonic wave can be detected earlier in time than the ultrasonic transducer 2 that transmits and receives waves, the ultrasonic measurement can be repeated more quickly and more real-time measurement is possible.

  The ultrasonic transducer for detection 14 uses the piezoelectric effect to change the ultrasonic vibration into an electric signal in the same manner as the ultrasonic transducer 2, and this is dedicated to reception, and thus shows high reception sensitivity. It is preferable to use a material having a large d constant as an index. For example, a polymer piezoelectric material can be suitably used. More specifically, for example, polyvinylidene fluoride (PVDF) or the like is used in selecting the material. preferable.

  The ultrasonic transducer for detection 14 is attached to the side surfaces of the propagation medium portion 3 (the first surface region 31 and the side surfaces of the second surface region 32). By arranging in this way, it is possible to shorten the time until the ultrasonic wave reflected by the second surface region 32 is observed, so that it is possible to transmit ultrasonic waves that are repeated quickly, and in a shorter time. Measurements can be made.

[Third Embodiment]
With reference to FIG. 6A, the ultrasonic transducer 1B of 3rd Embodiment of this invention is demonstrated. The ultrasonic transducer 1B of the third embodiment is characterized in that it has a temperature adjusting unit 15 that is connected to the control circuit 9 and adjusts the temperature of the propagation medium unit 3.

  Further, the ultrasonic transducer 2 in the third embodiment has only one set of electrodes and does not have a function of electronically redirecting ultrasonic waves to be transmitted and received. Therefore, it is impossible to change the ultrasonic wave transmission / reception direction according to the temperature change of the environmental fluid and perform stable ultrasonic wave transmission / reception.

In the ultrasonic transducer 1 </ b> B of the third embodiment, the temperature θ of the propagation medium unit 3, that is, the speed of sound is changed according to the temperature change of the environmental fluid 4 to keep the angle θ ₁ in the second surface region 32 constant. It is characterized by being composed. That is, in the ultrasonic transducer 1B of the third embodiment, in order to keep the angle theta ₁ in the second surface region 32 at a constant, which comprises a sonic speed control unit for changing the sound velocity of the propagation medium portion 3 The temperature adjusting unit 15 and the control circuit 9 function as an example of a sound speed control unit.

  The ultrasonic transducer 1B according to the third embodiment will be described. The materials of the ultrasonic transducer 2 and the propagation medium unit 3 in the third embodiment are the same as those in the first embodiment and the second embodiment. The temperature adjusting unit 15 is provided so as to be in contact with the side surface of the propagation medium unit 3 so as not to hinder the propagation of ultrasonic waves, and can change the temperature of the propagation medium unit 3 by heating or cooling. It has become.

  The temperature adjusting unit 15 can appropriately select a device having a function corresponding to the range and level of temperature change performed on the propagation medium unit 3 such as a resistance heating element such as a heater or a Peltier element. It is preferable that the temperature adjusting unit 15 can uniformly set the entire propagation medium unit 3 to a set temperature under the control of the control circuit 9 as short as possible. For example, as shown in FIG. It may be formed so as to surround. FIG. 6B is a cross-sectional view, but shows a form in which the front and back side surfaces of the propagation medium unit 3 are also surrounded by the temperature control unit 15.

  In addition, for the propagation medium part 3 which is a porous body, it is also effective for temperature control to send a cooled or heated fluid, and a pump for sending or sucking the heated or cooled fluid also has a temperature. It can be used as the adjustment unit 15. In this case, attention should be paid because not only the temperature change but also the sound speed change due to filling with different fluids may occur.

  The ultrasonic transducer 1B according to the third embodiment has a large number of ultrasonic transducers 2 and electronically controls them to change the ultrasonic wave 1A. This is advantageous in that it can be provided at a low cost.

A method of performing stable ultrasonic transmission / reception while keeping the angle θ ₁ constant will be described. As described above, the reflectance R of the ultrasonic wave at the interface (second surface region 32) between the propagation medium portion 3 and the environmental fluid 4 is expressed by (Equation 1).

Further, the condition for setting the reflectance R to 0 is determined by (Equation 2), and the angle θ ₁ for setting the reflectance to 0 is the density and sound velocity of the propagation medium portion 3 and the environmental fluid 4, ρ ₁ , ρ ₂ , It is shown by (Formula 8) using C ₁ and C ₂ .

The density ρ ₂ and the sound velocity C ₂ of the environmental fluid 4 can be expressed as a function of temperature as in (Equation 4) and (Equation 5), and the change in the angle θ ₁ when the density ρ ₂ and the sound velocity C ₂ change. In order to minimize the above, it is necessary to change the density ρ ₁ and the sound speed C ₁ of the propagation medium unit 3 in accordance with the changes in the density ρ ₂ and the sound speed C ₂ of the environmental fluid 4.

Here, with respect to the silica dry gel which is an example of the material of the propagation medium portion 3, there is a relationship such as (Equation 9) and (Equation 10) between the temperature t, the density ρ ₁ , and the sound velocity C ₁ . Also for solids, as with gases, the density generally decreases with temperature, and the speed of sound increases.

ここで、実験的に密度ρ_１は殆ど変化しない事が分かっているため、常数α＝０として密度ρ_１は一定値として取り扱う。一方で、音速Ｃ_１は温度によってわずかに変化する。

Here, since it is known experimentally that the density ρ ₁ hardly changes, the density ρ ₁ is treated as a constant value with the constant α = 0. On the other hand, the sound velocity C ₁ slightly varies with temperature.

FIG. 7 shows the relationship between the temperature of the environmental fluid 4 and the propagation medium part 3 and the angle θ ₁ in the second surface region 32. In FIG. 7, in (Equation 8), the change of the angle θ ₁ when the sound speed C ₁ of the propagation medium section 3 is changed based on (Equation 10) is calculated.

When the temperature of the propagation medium portion 3 is changed at the same temperature as the environmental fluid 4, the graph shown in FIG. 7, it is found that the change in the angle theta ₁ at constant beta = 0.3 vicinity becomes extremely small.

  Therefore, a dry gel material having such characteristics is selected for the propagation medium portion 3 as an example. In order to obtain such a material for a normal dry gel, it is effective to insert a molecule that disturbs the structure of the regular silica skeleton so that the speed of sound easily changes depending on the temperature.

Alternatively, when it is difficult to change the material, the angle θ ₁ is kept constant by giving a temperature change according to the value of the constant β, and stable and highly sensitive ultrasonic wave transmission / reception is performed. I can do it. The method of giving the temperature change according to the value of the constant β is that the temperature of the environmental fluid 4 is 10 times as high as the temperature of the environmental fluid 4 if the propagation medium portion 3 is made of a material having a constant β = 0.03. by providing a change in propagation medium portion 3, the acoustic velocity of the propagation medium portion 3 may be the speed of sound for the angle theta ₁ is constant.

  Here, more specifically, a procedure of how to change the temperature of the propagation medium unit 3 will be described with reference to FIG. 6C. In this case, the propagation medium part 3 is a material having a sound velocity that changes according to (Equation 10) with respect to the temperature. Here, a description will be given using a material set as β = 0.1. The environmental fluid 4 is air, and the speed of sound changes according to (Equation 4).

  Here, in the ultrasonic transducer 1B of the third embodiment, the first surface region 31 and the second surface region 32 are approximately 31 degrees so that ultrasonic waves can be efficiently transmitted and received at a temperature of 30 degrees. It is formed with an angle (step S41).

First, when the environmental temperature is measured by the thermometer 8, the sound velocity C ₂ of environmental fluid 4 to the measured temperature t is calculated by the control circuit 9 (step S42). For example, when the temperature changes once from 30 degrees to 31 degrees, the sound speed changes from 349.5 m / s to 350.1 m / s.

At this time, the angle θ _{1 at} which the optimum transmission / reception of ultrasonic waves is possible changes from 183 m / s to 183.1 m / s when the sound speed of the propagation medium unit 3 changes in the same temperature as the environmental fluid 4. (Step S43).

At the temperature of 30 degrees, the angle 31.57 degrees is the optimum angle θ ₁ , while at 31 degrees, the optimum angle θ ₁ changes to 31.53 degrees. In order to maintain the optimum angle θ ₁ = 31.57 degrees, the sound speed of the propagation medium portion 3 is set to 183.3 m / second with respect to air (sound speed 350.1 m / s) as an example of the environmental fluid 4 having a temperature of 31 degrees. For this purpose, the temperature of the propagation medium section 3 needs to be 33 degrees (step S44). Therefore, under the control of the control circuit 9, as 33 degrees the temperature of the propagation medium portion 3 by the temperature adjusting unit 15, to keep it at optimum angle theta ₁ to 31.57 degrees (step S45). Even if the temperature of the environmental fluid 4 changes more greatly, such control is similarly performed so that ultrasonic waves can be transmitted and received efficiently. Thereafter, when continuously transmitting and receiving ultrasonic waves, steps S42 to S45 may be repeated.

  In the third embodiment, an example in which dry gel is used as an example of the propagation medium unit 3 has been described. However, it is only necessary that the propagation medium unit 3 is made of a material that satisfies (Equation 2) in relation to the environmental fluid 4. The material is not limited to dry gel.

[Fourth Embodiment]
With reference to FIG. 8A, the ultrasonic transducer 1C of 4th Embodiment of this invention is demonstrated. The ultrasonic transducer 1C of the fourth embodiment is characterized in that an actuator 16 that compresses or expands the propagation medium section 3 is provided on the side surface of the propagation medium section 3 in connection with the control circuit 9. Other than the above, the configuration and operation are the same as those of the ultrasonic transducer 1B of the third embodiment. The actuator 16 and the control circuit 9 function as another example of the sound speed control unit.

In the third embodiment, the angle θ ₁ in the second surface region 32 is kept constant by adjusting the temperature of the propagation medium portion 3 to change the sound speed, whereas in the fourth embodiment, the propagation medium is changed. compressing section 3, or by varying the speed of sound by stretching maintained by the angle theta ₁ at a constant value, and makes it possible to stably transducing operation.

  A stress in the compression or extension direction is applied to the propagation medium section 3 under the control of the control circuit 9 by the actuator 16 provided on the side surface of the propagation medium section 3 as shown in FIG. 8A. The actuator 16 is configured to bend and deform to apply a force to the propagation medium unit 3. For example, the actuator 16 is a unimorph type actuator in which a material such as a piezoelectric body and a metal plate is bonded, or has an opposite polarization direction. A bimorph actuator in which two piezoelectric bodies are bonded together can be used.

  Alternatively, by bending an actuator 16 formed of a piezoelectric body or the like to the side surface of the protective portion 13 shown in FIG. 4A, the deflection deformation utilizing the difference in size between the deforming actuator and the non-deforming protective portion 13 is used. Can be given to the propagation medium section 3, and the speed of sound can be changed. An example of such a form is shown in FIG. 8B. The ultrasonic transducer 1C having such a configuration applies force to the propagation medium unit 3 by bending the actuator 16 as shown in FIG. 8C, so that the hardness of the propagation medium unit 3, that is, within the propagation medium unit 3. The speed of sound can be changed.

  The actual sound speed control method will be described with reference to FIG. 8D. Note that the first surface region 31 and the second surface region 32 are formed with an optimum angle so that ultrasonic waves can be efficiently transmitted and received at a temperature of 30 degrees (step S51).

First, the temperature t of the environmental fluid 4 is measured by the thermometer 8, the sound velocity C ₂ of the environmental temperature t is calculated by the control circuit 9 (step S52). Based on this information, the sound velocity C ₁ of the propagation medium portion 3 necessary for transmitting and receiving an ultrasonic wave with high efficiency is calculated by the control circuit 9 (step S53).

  Based on the sound velocity value of the propagation medium section 3, the hardness at which the sound speed of the propagation medium section 3 becomes a predetermined value, that is, the elastic modulus K is calculated by the control circuit 9 (step S54). Hereinafter, the compression force F of the actuator 16 having the elastic modulus K, and the applied voltage V that becomes the compression force F are calculated by the control circuit 9 (steps S55 and S56). It is applied to the actuator 16 to deform the actuator 16 and apply a force to the propagation medium section 3 to change the sound speed. Thereafter, when the sound speed control is continuously performed, steps S52 to S56 may be repeated.

  When a silica dry gel or the like is used as an example for the propagation medium portion 3, it is desirable to design so that the sound velocity is always changed by applying pressure in the compression direction. Silica dry gel deforms in the force in the compression direction, and when the force is released, it returns to its original shape, and the force of sound can be changed over and over again, while in the tensile direction. This is because the deformation is destroyed by a relatively weak force, and the sound speed of the propagation medium unit 3 cannot be changed.

Therefore, the silica dry gel material that is the propagation medium portion 3 is designed to be at a temperature of 0 ° C., which is the slowest speed of sound in the assumed operating temperature range, and is highly sensitive without applying force in this temperature range. There is a method of adjusting the speed of sound so that the angle θ ₁ does not change by applying a force in the compression direction to the propagation medium unit 3 when the temperature of the environmental fluid 4 is increased. desirable.

  In the fourth embodiment, an example in which dry gel is used as an example of the propagation medium unit 3 has been described. However, if the propagation medium unit 3 is made of a material that satisfies (Equation 2) in relation to the environmental fluid 4. Well, the material is not limited to dry gel.

  Further, in FIG. 8A, the actuator 16 is provided only on a pair of opposing surfaces of the propagation medium portion, but the actuator 16 may be provided on a surface orthogonal thereto. In this case, a larger pressure can be applied to the propagation medium unit 3 than in the case of the single actuator 16, so that desired control can be performed at a low voltage, and cost can be reduced. Alternatively, even if the same actuator 16 is used, the ultrasonic transducer 1C that can be adapted in a wider temperature range can be configured.

[Fifth Embodiment]
With reference to FIG. 9A-FIG. 9D, ultrasonic transducer 1D of 5th Embodiment of this invention is demonstrated. In the ultrasonic transducer 1D of the fifth embodiment, the transmission / reception surface of the ultrasonic transducer 2 has one convex curved surface as shown in FIG. 9A, or one concave curved surface as shown in FIG. 9B. There is a feature. Other than this, the configuration and operation are the same as those of the first to fourth embodiments, and the configuration of the control circuit 9 and the like is not shown.

The ultrasonic transducer 2 in the fifth embodiment can transmit and receive the ultrasonic wave 5 in a plurality of directions by the single ultrasonic transducer 2 due to its shape effect. For this reason, even if the temperature θ of the environmental fluid 4 changes and the angle θ ₁ at which the transmission / reception sensitivity increases, the ultrasonic waves 5 transmitted from the ultrasonic transducer 2 are at least partially ultrasonic waves 5. The ultrasonic wave transmitter / receiver 1 </ b> D capable of stably transmitting / receiving the ultrasonic wave 5 with respect to the temperature change of the environmental fluid 4 is obtained because the optimum angle θ ₁ is always transmitted.

Also in the fifth embodiment, one convex surface type or one concave surface shape of the ultrasonic transducer 2 is formed so as to be compatible with use under the conditions described in the first to fourth embodiments so far. The case will be described. Angle theta ₁ changes according to the temperature changes in the environmental fluid 4 as described above, i.e., to accommodate the range of about 4 °, the shape of the piezoelectric body is defined.

  More specifically, the radiation surface of the ultrasonic wave 5, that is, the shape of the interface between the ultrasonic transducer 2 and the propagation medium part 3 that becomes the first surface region 31 in FIGS. 9A and 9B becomes a part of a circle. It is formed as follows.

  For example, when the lengths of the propagation medium part 3 and the ultrasonic transducer 2 in the X direction in FIGS. 9A and 9B are 20 mm, the diameter of the circle forming the ultrasonic transducer 2 can be calculated geometrically, It can be calculated that the shape of the ultrasonic transducer 2 corresponding to an angle of 4 ° is formed to be a part of a circle having a radius of about 286 mm.

  At this time, in the case of FIG. 9A, the center of the circle is located 286 mm below the ultrasonic transducer 2 below the ultrasonic transducer 2 from the center in the X direction of the ultrasonic transducer 2, and in the case of FIG. 9B, Similarly, the ultrasonic transducer 2 is positioned 286 mm above the center in the X direction.

  The ultrasonic transducer 1 according to the fifth embodiment is not limited to the size described above, but is designed and formed in a necessary size at the appropriate time.

  The propagation medium part 3 of the ultrasonic transducer 1 shown in FIGS. 9A and 9B may be further covered with a protective part 13 as in the previous embodiment, as shown in FIGS. 9C and 9D. . In this case, similarly to the previous embodiment, a low-intensity propagation medium section 3 can be used, and the design range of the ultrasonic transducer 1 can be widened. Reliability for external impacts can be improved.

[Sixth Embodiment]
With reference to FIG. 10A and FIG. 10B, the ultrasonic transducer 1E of 6th Embodiment of this invention is demonstrated. In the ultrasonic transducer 1E of the sixth embodiment, the second surface region 32 that is the interface between the propagation medium section 3 and the environmental fluid 4 has one convex curved surface as shown in FIG. 10A, or as shown in FIG. 10B. 1 is characterized by having a propagation medium part 3 having a concave curved surface. Other than this, the configuration and operation are the same as those of the first to fourth embodiments, and the configuration of the control circuit 9 and the like is not shown.

Like the fifth embodiment, the temperature of the environmental fluid 4 is changed, even larger angle theta ₁ of transducing sensitivity is changed, satisfying a large angle theta ₁ of the ultrasonic 5 always transmittance of at least a portion Therefore, the ultrasonic transducer 1E can transmit and receive the ultrasonic wave 5 that is stable against environmental changes.

One convex or concave curved surface shape of the ultrasonic transducer 2 can correspond to a change of the angle θ ₁ corresponding to a temperature change of the environmental fluid 4, that is, a range of about 4 °, as in the fifth embodiment. Is shaped.

  The specific curved surface shape of the second surface region 32 is the same as that in the fifth embodiment, that is, when the length of the ultrasonic transducer 2 in the X direction in FIGS. 10A and 10B is 20 mm. become that way.

That is, in the sixth embodiment, the interface of the propagation medium unit 3 with the environmental fluid 4, that is, the second surface region 32 is a curved surface, from the center in the X direction of the ultrasonic transducer 2 in FIGS. 10A and 10B. for ultrasonic 5 is formed at an angle theta ₁ is 31 ° in the second surface region 32, in the normal direction of the plane forming an angle of 31 °, the propagation medium portion in the case of FIG. 10A As shown in FIG. 10B, it is formed as a part of a circular arc centered on the environmental fluid 4 side as a part of a circular arc centered at a position about 286 mm away on the 3 side.

  The ultrasonic transducer 1E according to the sixth embodiment is not limited to the size described above, but is designed and formed in a necessary size at the appropriate time.

  Similarly to the fifth embodiment, the propagation medium portion 3 of the ultrasonic transducer 1E may be covered with a protection portion 13 as shown in FIGS. 10C and 10D. In this case, similarly, the low-intensity propagation medium section 3 can be used, and the design range of the ultrasonic transducer 1E can be expanded, and handling, long-term reliability, external impact, etc. The reliability with respect to can be improved.

  It is to be noted that, by appropriately combining arbitrary embodiments of the various embodiments described above, the effects possessed by them can be produced.

  According to the ultrasonic wave transmitter / receiver of the present invention, it is possible to stably transmit and receive waves over a wide frequency with high sensitivity to environmental changes (for example, −20 ° C. to 60 ° C.). This enables stable and accurate ultrasonic measurement. The ultrasonic transmitter / receiver of the present invention can be used for specific applications such as high-accuracy back sonar for automobiles, control of robots that work outdoors (such as obstacle detection), and outdoor installation type city gas with a large temperature difference. Or a gas flow meter for propane gas, a business gas flow meter with a large pipe diameter installed outdoors (high sensitivity is required because the attenuation of ultrasonic waves is large when the pipe diameter is large), semiconductor processes, etc. For example, a flow meter for controlling the flow rate with high accuracy (higher sensitivity allows higher resolution because of higher resolution).

The perspective view of the ultrasonic transmitter-receiver in 1st Embodiment of this invention. Sectional drawing of the ultrasonic transducer in 1st Embodiment of this invention The schematic diagram explaining the transmission / reception method of the ultrasonic wave to the diagonal direction in 1st Embodiment of this invention The flowchart explaining the ultrasonic wave transmission / reception method in 1st Embodiment of this invention. Sectional drawing of the ultrasonic transducer of another form in 1st Embodiment of this invention The perspective view of the ultrasonic transducer of another form in 1st Embodiment of this invention The perspective view of the ultrasonic transducer of another form in 1st Embodiment of this invention The perspective view of the ultrasonic transducer of another form in 1st Embodiment of this invention Sectional drawing of the ultrasonic transducer in 2nd Embodiment of this invention The figure which shows the reflected ultrasound in 2nd Embodiment of this invention. The figure which shows the reflected ultrasound in 2nd Embodiment of this invention. Flowchart for explaining an ultrasonic wave transmitting / receiving method according to the second embodiment of the present invention. Sectional drawing of the ultrasonic transducer in 3rd Embodiment of this invention. Sectional drawing of the ultrasonic transducer in 3rd Embodiment of this invention. Flowchart for explaining an ultrasonic wave transmitting / receiving method according to the third embodiment of the present invention. The graph which shows the relationship between temperature and angle (theta) ₁ in 3rd Embodiment of this invention. Sectional drawing of the ultrasonic transducer in 4th Embodiment of this invention Sectional drawing of another form of the ultrasonic transducer in 4th Embodiment of this invention Sectional drawing at the time of deformation | transformation of the ultrasonic transducer in 4th Embodiment of this invention The flowchart explaining the transmission / reception method of ultrasonic transmission in 4th Embodiment of this invention. Sectional drawing of the ultrasonic transducer in 5th Embodiment of this invention. Sectional drawing of the ultrasonic transducer in 5th Embodiment of this invention. FIG. 9A is a cross-sectional view of another form of the ultrasonic transducer according to the fifth embodiment of the present invention. Sectional drawing of another form of the ultrasonic transducer in 5th Embodiment of this invention of FIG. 9B. Sectional drawing of the ultrasonic transducer in 6th Embodiment of this invention Sectional drawing of the ultrasonic transducer in 6th Embodiment of this invention Sectional drawing of another form of the ultrasonic transducer in 6th Embodiment of this invention of FIG. 10A. Sectional drawing of another form of the ultrasonic transducer in 6th Embodiment of this invention of FIG. 10B. Cross-sectional view of a conventional ultrasonic transducer in Patent Document 1 The graph which shows the ultrasonic reflectivity with respect to the angle (theta) ₁ of an ultrasonic wave and environmental fluid temperature in the ultrasonic transducer of patent document 1 The graph which shows the ultrasonic reflectivity with respect to the angle (theta) ₂ of an ultrasonic wave, and environmental fluid temperature in the ultrasonic transducer of patent document 1

Explanation of symbols

1, 1A, 1B, 1C, 1D, 1E Ultrasonic transducer 2 Ultrasonic transducer 3 Propagation medium section 31 First surface area 32 Second surface area 4 Environmental fluid 5 Ultrasonic wave 6 Signal line 7 Transceiver circuit 8 Temperature Detection unit 9 Control circuit 10 Filling material 11 Back load material 12 Acoustic matching layer 13 Protection unit 14 Detection vibrator 15 Temperature adjustment unit 16 Actuator

Claims (12)

An ultrasonic transducer for transmitting or receiving ultrasonic waves to the surrounding space filled with environmental fluid,
At least an ultrasonic transducer,
A propagation medium that is filled between the ultrasonic transducer and the environmental fluid and forms a propagation path of the ultrasonic wave; and
The density ρ _{1 of} the propagation medium part, the sound speed C ₁ in the propagation medium part, the density ρ _{2 of the} environmental fluid filling the surrounding space, and the sound speed C ₂ in the environmental fluid are (ρ ₂ / ρ ₁ ) <(C ₁ / C ₂ ) <1 to form the propagation medium portion from a material satisfying the relationship:
The ultrasonic transducer further includes a directivity control unit that controls directivity of ultrasonic transmission or reception. With a plurality of the ultrasonic transducers,
The directivity control unit shifts the drive timing of adjacent ultrasonic transducers among the plurality of ultrasonic transducers in the case of transmission, and the plurality of ultrasonic transducers in the case of reception. By shifting the addition timing of the reception signals of the adjacent ultrasonic transducers of the two, by controlling the phase of the ultrasonic wave front in the case of transmission and reception, the transmission of the ultrasonic wave or The ultrasonic transducer according to claim 1, wherein the directivity of received waves is controlled. A thermometer for measuring the temperature of the environmental fluid;
The ultrasonic transducer according to claim 2, wherein the directivity control unit controls a phase of a wavefront of the ultrasonic wave based on information on a temperature of the environmental fluid measured by the thermometer. A reflection ultrasonic wave receiving device for receiving an ultrasonic wave reflected at the interface between the propagation medium part and the environmental fluid;
The directivity control unit controls the phase of the wavefront of the ultrasonic wave based on information of the reflected ultrasonic wave reflected at the interface between the propagation medium unit and the environmental fluid and received by the reflected ultrasonic wave receiving device. The ultrasonic transducer according to claim 2. An ultrasonic transducer for transmitting or receiving ultrasonic waves to the surrounding space filled with environmental fluid,
At least an ultrasonic transducer,
A propagation medium that is filled between the ultrasonic transducer and the environmental fluid and forms a propagation path of the ultrasonic wave; and
The density ρ _{1 of} the propagation medium part, the sound speed C ₁ in the propagation medium part, the density ρ _{2 of the} environmental fluid filling the surrounding space, and the sound speed C ₂ in the environmental fluid are (ρ ₂ / ρ ₁ ) <(C ₁ / C ₂ ) <1 to form the propagation medium portion from a material satisfying the relationship:
An ultrasonic transducer further comprising a sound speed controller that changes the sound speed of the propagation medium.   The said sound speed control part is provided with the temperature adjustment part which adjusts the temperature of the said propagation medium part, The temperature of the said propagation medium part is changed by the said temperature adjustment part, The sound speed of the said propagation medium part is changed. Ultrasonic transducer.   The sound speed control unit includes an actuator that compresses or expands the propagation medium part, and changes the sound speed of the propagation medium part by applying a pressure or an extension force to the propagation medium by the actuator. The described ultrasonic transducer.   The ultrasonic transducer according to claim 7, wherein the actuator is disposed in contact with a side surface of the propagation medium portion. A thermometer for measuring the temperature of the environmental fluid;
The ultrasonic transducer according to any one of claims 5 to 8, wherein the sound velocity control unit changes the sound velocity of the propagation medium portion based on information on the temperature of the environmental fluid measured by the thermometer. . A reflection ultrasonic wave receiving device for receiving an ultrasonic wave reflected at the interface between the propagation medium part and the environmental fluid;
The sound velocity control unit changes the sound velocity of the propagation medium portion based on information of the reflected ultrasonic wave reflected at the interface between the propagation medium portion and the environmental fluid and received by the reflected ultrasonic wave receiving device. The ultrasonic transducer according to any one of claims 5 to 8. An ultrasonic transducer for transmitting or receiving ultrasonic waves to the surrounding space filled with environmental fluid,
At least an ultrasonic transducer,
A propagation medium that is filled between the ultrasonic transducer and the environmental fluid and forms a propagation path of the ultrasonic wave; and
The density ρ _{1 of} the propagation medium part, the sound speed C ₁ in the propagation medium part, the density ρ _{2 of the} environmental fluid filling the surrounding space, and the sound speed C ₂ in the environmental fluid are (ρ ₂ / ρ ₁ ) <(C _{1 /} C 2) constitutes the propagation medium portion from materials satisfying _<1 relationship, and the ultrasound transmitting and receiving surface of the ultrasonic vibrator ultrasonic transducer which is a convex type or concave type of surface. An ultrasonic transducer for transmitting or receiving ultrasonic waves to the surrounding space filled with environmental fluid,
At least an ultrasonic transducer,
A propagation medium that is filled between the ultrasonic transducer and the environmental fluid and forms a propagation path of the ultrasonic wave; and
The density ρ _{1 of} the propagation medium part, the sound speed C ₁ in the propagation medium part, the density ρ _{2 of the} environmental fluid filling the surrounding space, and the sound speed C ₂ in the environmental fluid are (ρ ₂ / ρ ₁ ) <(C ₁ / C ₂ ) An ultrasonic transducer in which the propagation medium portion is made of a material satisfying a relationship of 1 and the interface between the propagation medium portion and the environmental fluid is a convex or concave curved surface.

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