JP2003156381A - Remaining quantity detecting ultrasonic transducer and supporting method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a remaining quantity detecting ultrasonic transducer (ultrasonic transmitter or ultrasonic receiver/ultrasonic transmitter-receiver) which is small-sized at a low cost, has a simple structure, transmits or receives an ultrasonic wave efficiently, and can be used over a wide range of fields without being influenced by the kind of storage tank, and the difference in kind of substance to be measured, which is stored in the storage tank. SOLUTION: An ultrasonic conversion element 4 is fitted to the bottom part 3 inside a cylindrical case 2, whose bottom part 3 is closed. An annular protrusion 5 is formed on the peripheral surface of the case 2, at a position where the vibration displacement of the side part of the case 2 becomes minimum, when an ultrasonic wave is transmitted or received by the conversion element 4. This annular protrusion 5 serves as a supporting portion, when the case 2 is supported by the body of a remaining quantity detector.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention transmits or receives ultrasonic waves when detecting the remaining amount in a storage tank storing high-pressure gas such as petroleum liquefied gas using ultrasonic waves.
The present invention also relates to an ultrasonic transducer (ultrasonic transmitter or ultrasonic receiver, or ultrasonic transmitter / receiver) for remaining amount detection that transmits / receives, and a supporting method for supporting the ultrasonic transducer with a main body of the remaining amount detection device.

[0002]

2. Description of the Related Art Conventionally, as the remaining amount detecting means for detecting the remaining amount in a storage tank storing an object to be measured using ultrasonic waves, the following two methods are roughly provided.

The first method is, for example, Japanese Patent Laid-Open No. 9-166.
As disclosed in Japanese Patent No. 478, a residual amount detecting device is attached to the upper surface inside a storage tank that stores an object to be measured, and an ultrasonic transmitter of the residual amount detecting device or an ultrasonic wave transmitted from the ultrasonic transmitter / receiver is transmitted. The sound wave passes through the gas layer inside the storage tank, is reflected by the liquid surface of the object to be measured, and from the time taken until it is received by the ultrasonic receiver or ultrasonic transmitter / receiver of the remaining amount detection device,
This is a method of detecting the remaining amount of the measured object.

Another method is, for example, Japanese Patent Application Laid-Open No. 8-21.
As disclosed in Japanese Patent No. 9854, a remaining amount detecting device is attached to an outer bottom surface of a storage tank that stores an object to be measured,
The ultrasonic wave transmitted from the ultrasonic transmitter or ultrasonic transmitter / receiver of the remaining amount detection device passes from the outer bottom surface of the storage tank through the liquid layer of the measured object stored inside the storage tank to the liquid of the measured object. This is a method in which the remaining amount of the object to be measured is detected from the time required for the ultrasonic wave to be reflected on the surface and to be received by the ultrasonic receiver or ultrasonic transmitter / receiver of the remaining amount detecting device.

[0005]

However, in the method of detecting the remaining amount of the object to be measured by mounting the remaining amount detecting device on the upper surface of the inside of the storage tank, since the remaining amount detecting device is installed inside the storage tank, the remaining amount is left in the storage tank. The existing storage tank cannot be used as it is, because modification for mounting the quantity detecting device or a jig for mounting the remaining amount detecting device is required.

When the object to be measured in the storage tank is a high-pressure gas such as liquefied petroleum gas, a transducer for transmitting and receiving ultrasonic waves is mounted inside the storage tank while being exposed.
Enclose the transducer in a housing that can withstand high pressure because the transducer of the remaining amount detector breaks without being able to withstand high pressure, the transducer corrodes, there is a risk of fire due to the voltage applied to the transducer, etc. There is a need.

Transducers for transmitting and receiving ultrasonic waves are
It is desirable to put the transducer outside the storage tank because it is connected to the power supply unit outside the storage tank, the arithmetic control circuit, the remaining amount display meter, etc. by electric lines. However, if the method of attaching the remaining amount detection device to the outer upper surface of the storage tank is used, the ultrasonic waves transmitted from the transducer will change due to a sudden difference in acoustic impedance during the process of entering the gas layer inside the storage tank from the outer upper surface of the storage tank. Ultrasonic waves are rapidly attenuated.

Further, in this method, the material, shape, and
Since it is affected by the difference in plate thickness, it is necessary to adjust or change the specifications of the remaining amount detecting device for each type of storage tank to which the remaining amount detecting device is attached. Furthermore, with this method,
Since ultrasonic waves pass through the gas layer of the object to be measured, the temperature change in the process of ultrasonic waves is greater than when ultrasonic waves pass through the liquid layer. The temperature error of is also large.

On the other hand, the method of detecting the remaining amount of the object to be measured by mounting the remaining amount detecting device on the outer bottom surface of the storage tank is a method in which the remaining amount detecting device is provided on the outer bottom surface of the storage tank by a magnet or the like. Since it is attached, the modification for attaching the remaining amount detecting device to the storage tank or the jig for attaching the remaining amount detecting device is unnecessary, and the existing storage tank can be used as it is. Also, in this method, the remaining amount detection device is attached to the outside of the storage tank, so the influence of the high pressure inside the storage tank is eliminated, and the signal line of the remaining amount detection device is also outside the storage tank, so there is a risk of fire and explosion. Has the advantage of being less.

However, since the ultrasonic wave is transmitted from the outside of the storage tank into the liquid layer of the object to be measured, it is affected by the difference in material, shape and plate thickness of the storage tank. It is necessary to adjust the remaining amount detection device or change the specifications for each type of storage tank to be attached. Further, in this method, since ultrasonic waves pass through the liquid layer of the measured object, it is affected by the speed of sound depending on the type of the measured object stored inside the storage tank. Therefore, in this method, it is necessary to adjust the specifications of the remaining amount detecting device or change the specifications in consideration of the sound velocity of the object to be measured stored in the storage tank.

Therefore, in view of the above-mentioned conventional problems, the first object of the present invention is due to the difference in the type of storage tank and the type of the object to be measured stored in the storage tank with a small and simple structure. It can be used in a wide range of fields without being affected, and provides an ultrasonic transducer (ultrasonic transmitter or ultrasonic receiver or ultrasonic transmitter / receiver) for remaining amount detection that can efficiently transmit / receive ultrasonic waves at low cost. To be able to do it.

A second object is that the ultrasonic transducer can be easily supported on the main body of the remaining amount detecting device, and the existing storage tank can be used as it is without modifying the storage tank or requiring a mounting jig. An object of the present invention is to provide a method of supporting an ultrasonic transducer for remaining amount detection that can be used.

[0013]

In the ultrasonic transducer for detecting the remaining amount of the present invention, an ultrasonic transducer is attached to one end of a cylindrical case whose one end is closed, and It is characterized in that the annular convex portion is provided on the outer peripheral surface at a position where the vibration displacement of the side portion of the case is minimized when the ultrasonic wave is transmitted or received by the ultrasonic transducer.

The following forms are preferable. The annular convex portion serves as a support portion for supporting the main body of the remaining amount detection device. A male screw that is screwed into a female screw on the main body side of the remaining amount detecting device is formed on the annular convex portion. The axial length of the case is ± 10% of [(λ / 2) × N (a positive integer)], where λ is the wavelength of the ultrasonic wave transmitted to the case when transmitting or receiving ultrasonic waves. And The case material is brass.

The method of supporting the ultrasonic transducer is such that the ultrasonic transducer as described above is fitted to the mounting hole of the main body of the remaining amount detecting device, and the remaining amount detecting device of the remaining amount detecting device is formed by the annular convex portion. Support the body.

It is preferable that the main body of the remaining amount detecting device also serves as a flange for closing the opening of the storage tank.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view of an ultrasonic transducer for detecting the remaining amount according to an embodiment of the present invention, which is an ultrasonic transceiver. This ultrasonic transmitter / receiver 1 has a cylindrical case 2 as a bottom and closes one end, that is, a bottom part 3, and an ultrasonic conversion element 4 for transmitting and receiving ultrasonic waves is mounted on the bottom part 3 in the case 2. . An annular convex portion 5 is integrally provided on the outer peripheral surface of the case 2.

The size and setting position of the annular convex portion 5 are
The vibration amplitude of the side portion 6 of the case 2 is set to be minimum when a vibration simulation or the like is performed and ultrasonic waves are transmitted and received by the ultrasonic conversion element 4.

2 and 3 are cross-sectional views of the case 2 when vibration simulation is performed on the ultrasonic transceiver 1 shown in FIG. These figures show the state of vibration at each coupling resonance frequency determined by the material, shape, and supporting method of the case 2 when ultrasonic waves are transmitted and received by the ultrasonic conversion element 4.

In the figure, (A) shows the case where the amplitude of the vibration becomes maximum in one cycle of the vibration of the case 2 at the coupling resonance frequency, while (B) shows (A). In contrast, when the phase of the vibration cycle is shifted by 180 °, the amplitude of the vibration of Case 2 is maximized. At the coupled resonance frequency shown in FIG. 2, only the bottom portion 3 of the case 2 bends and vibrates. On the other hand, at the coupled resonance frequency shown in FIG.
The entire case 2 including the bottom portion 3, the side portion 6 and the convex portion 5 of FIG.

In the case of the vibration mode shown in FIGS. 2 and 3, when ultrasonic waves are transmitted in the direction of the bottom shown by the arrow c in the figure, in the case of the vibration mode shown in FIG. Therefore, the ultrasonic waves are not only directed in the c direction but also on the side part 6.
The directivity is slow because it is transmitted in the direction of. Further, when the energy of the ultrasonic wave that can be generated by the ultrasonic conversion element 4 is the same in the vibration modes of FIG. 2 and FIG. 3, in the vibration mode of FIG. The energy of the ultrasonic waves dispersed and transmitted in the c direction becomes small.
On the other hand, in the case of the vibration mode shown in FIG. 2, since only the bottom portion 3 of the case 2 bends and vibrates, ultrasonic waves are transmitted only in the c direction, so that the directivity is sharp. In the vibration mode of FIG. 2, the energy of the ultrasonic waves is concentrated only on the bottom portion 3, and the energy of the ultrasonic waves transmitted in the c direction becomes large.

Therefore, when transmitting ultrasonic waves in the c direction,
In the case of the vibration mode shown in FIG. 2, the directivity in the c direction is sharper and the sound pressure level is higher than in the case of the vibration mode shown in FIG. 3, and the ultrasonic waves are efficiently transmitted in the c direction. can do.

The length of the case 2 in the axial direction is [(λ / 2) × N (a positive integer)], where λ is the wavelength transmitted in the side portion 6 when transmitting and receiving ultrasonic waves. When set to ± 10%, the ultrasonic waves propagated in the side portion 6 form an antinode of vibration at the position of the bottom portion 3 and are radiated, so that ultrasonic waves can be transmitted and received efficiently.

In FIG. 1, the ultrasonic transducer according to the present invention is an ultrasonic transmitter / receiver, but the same applies to the case where it is an ultrasonic transmitter or an ultrasonic receiver.

FIG. 4 shows an ultrasonic transducer and an ultrasonic receiver 1 according to the present invention used as the ultrasonic transmitter 11.
2 is a sectional view of the remaining amount detecting device 10 of the first embodiment in which the ultrasonic transducer according to the present invention used as No. 2 is installed in parallel.

The main body 13 of the remaining amount detecting device 10 also serves as, for example, a disc-shaped flange that closes the opening of the storage tank as will be described later, and the ultrasonic transmitter 11 and the ultrasonic receiver 12 are provided. Are fitted and attached to the respective mounting holes 13a and 13b provided in the main body 13.

Ultrasonic transmitter 11 and ultrasonic receiver 12
A packing 14 having a U-shaped cross section is attached to each of the casings so as to cover the convex portion 5 of each case 2.

The ultrasonic transmitter 11 and the ultrasonic receiver 12 are fitted into the respective mounting holes 13a and 13b provided in the main body 13 via packing 14, and the lower plate 15 holds them down. It is pressed from the side and attached to the main body 13, and a part of each protrudes from the lower surface of the main body 13.

The packing 14 serves as a cushioning material for preventing the vibration and reverberation of the ultrasonic transmitter 11 and the ultrasonic receiver 12 from being transmitted to the main body 13, and the pressure in the storage tank storing the object to be measured. Plays the role of a sealing material that seals the The shape does not have to be U-shaped as long as it can fulfill these roles.

The pressing plate 15 has mounting holes 13a and 13b for the ultrasonic transmitter 11 and the ultrasonic receiver 12.
And the role of preventing it from falling out of the storage tank,
In order to maintain the sealing property of the packing 14, it plays a role of applying pressure to the packing 14, and is attached to the lower surface of the main body 13 by a bolt 16 or the like through a hole 15a provided in the pressing plate 15.

The ultrasonic conversion element 4 of the ultrasonic transmitter 11 and the ultrasonic conversion element 4 of the ultrasonic receiver 12 are respectively connected to a calculation / control / power supply section 18 mounted on the main body 13 via lead wires 17. It is connected and exchanges electrical signals. The lead wire 17 in the ultrasonic transmitter 11 has a mounting hole 13
a through the cushioning member 19 fitted in the upper opening of a,
The lead wire 17 in the ultrasonic receiver 12 penetrates the cushioning member 19 fitted in the upper opening of the mounting hole 13b.

As the cushioning member 19, a cushioning material such as resin or rubber is used. Each buffer member 19
Prevents the ultrasonic waves transmitted and received from the ultrasonic conversion element 4 from being radiated in the upper opening direction of the mounting hole 13a and the upper opening direction of the mounting hole 13b, and serves to attenuate the ultrasonic waves. Instead of the cushioning material, liquid rubber or the like may be poured into the upper opening of the mounting hole 13a and the upper opening of the mounting hole 13b as long as it can play such a role.

In this example, the calculation / control / power supply unit 18 is attached to the upper surface of the main body 13, but it may be installed at a remote place via a signal line or the like.

On the outer periphery of the main body 13, the main body 13 is provided with a storage tank 2.
A plurality of fixing holes 13c for fixing on the ceiling portion of 0 are provided.

On the other hand, as shown in FIG. 8, an opening 20a is formed in the ceiling of the storage tank 20, and a ring-shaped flange mounting portion 21 is provided around the opening 20a.
In the remaining amount detecting device 10, the main body 13 is fixed on the flange mounting portion 21 with a fixing screw 23 via packings 22 such as an O-ring, and the main body 13 opens the opening 20 a of the storage tank 20.
To block.

FIG. 5 shows the remaining amount detecting device 10a of the second embodiment.
FIG. In this remaining amount detecting device 10a, the ultrasonic transmitter / receiver 1 shown in FIG. 1 is used, and this ultrasonic transmitter / receiver 1 is attached to the main body 13 in the same manner as the ultrasonic transmitter 11 in FIG. The other configuration is the same as that of FIG. By doing so, the number of parts can be reduced, and the size and cost can be reduced as compared with the remaining amount detecting device 10 in FIG.

FIG. 6 shows the remaining amount detecting device 10b of the third embodiment.
FIG. In the remaining amount detecting device 10b, an ultrasonic transceiver 1a in which a male screw 5a is formed on the outer circumference of the convex portion 5 of the case 2 is used in the ultrasonic transceiver 1 shown in FIG.
The male screw 5a is screwed into the female screw 13d formed on the inner circumference of the mounting hole 13a of the main body 13 to form the ultrasonic transceiver 1a.
Is attached to the main body 13. In this case, the convex portion 5
Instead of the packing 14 covering the above, a packing 14a to be interposed between the step portion of the mounting hole 13a and the end surface of the convex portion 5 is used. In addition, the reference numerals used for corresponding portions in FIGS. 4 and 5 are used as they are.

In all of the above-mentioned examples, the bottom 3 side of the cylindrical case 2 of the ultrasonic transmitter / receiver 11 is closed, but for example, the bottom of the cylindrical case 2 having the annular convex portion 5 as shown in FIG. Open the side and conversely close the top 7 side,
The ultrasonic transducer 4 may be mounted on the top 7. With this configuration, when ultrasonic waves are transmitted and received by the ultrasonic conversion element 4, it is possible to increase the energy of ultrasonic waves that reverberate in the case 2 and are transmitted in the c direction.

Next, using the remaining amount detecting device 10 of FIG. 4 as an example, a usage example in the case of attaching the device to be measured to a storage tank will be described in more detail. In FIG. 8, generally, the opening 20a of the storage tank 20 is provided with some attachments in advance, such as an attachment for a float type fuel gauge. Among such mounting parts, an unused ring-shaped mounting part such as a mounting part for a float type fuel gauge is used as the flange mounting part 21, and The main body 13 is fixed onto the flange mounting portion 21 with the fixing bolt 23 via the packing 22. In FIG. 8, reference numeral 24 indicates the liquid layer of the measured object stored in the storage tank 20, reference numeral 25 indicates the gas layer of the measured object, and reference numeral 26 indicates the liquid surface of the measured object.

Next, the operation will be described with reference to FIG. The ultrasonic wave 27 is transmitted from the ultrasonic transmitter 11 by the transmission signal transmitted from the calculation / control / power supply unit 18. Ultrasonic wave 2
7 is a liquid surface 26 of the measured object which passes through the gas layer 25 of the measured object.
The ultrasonic wave is reflected by the ultrasonic wave receiver 12 again through the gas layer 25 of the object to be measured, and the received signal is input to the arithmetic / control / power supply unit 18.

The calculation / control / power supply unit 18 calculates the liquid level from the time taken from the transmission of the ultrasonic waves 27 to the reception thereof. The calculation / control / power supply unit 18 performs temperature correction or the like on the calculated liquid level based on the temperature information measured by a temperature sensor or the like as necessary, and displays the corrected remaining amount information of the measured object on the display unit 28. . At the same time, the remaining amount information can be transmitted to a centralized monitoring center located at a remote place via a wireless or wired communication means.

9A, 9B, and 9C, the material of the case 2 of the ultrasonic transducer according to the present invention is brass, stainless steel, and aluminum, and the sound pressure of each material is maximized. The results of the ultrasonic transmission test are shown below. In this case, the test was conducted under the same conditions except for the material of the case 2, such as dimensions, shape, and ultrasonic transducer 4. The horizontal axis of the test data represents time, and the vertical axis represents the sound pressure of ultrasonic waves. From this test result, it was confirmed that when the material of the case 2 was brass, the sound pressure was highest and the ultrasonic waves could be transmitted and received efficiently.

[0044]

According to the first aspect of the present invention, the ultrasonic transducer is mounted on one end of the cylindrical case whose one end is closed. Therefore, the ultrasonic transducer is installed in the storage tank. It can protect from damage and corrosion due to high pressure. In addition, there is no risk of fire due to the voltage applied to the ultrasonic transducer. Further, when transmitting and receiving ultrasonic waves from the ultrasonic conversion element, since the annular convex portion is provided at a position where the vibration displacement of the side portion of the case is minimized, even after attaching the remaining amount detecting device to a storage tank or the like, The ultrasonic waves can always be efficiently transmitted and received without changing the coupling resonance frequency and the vibration mode of the remaining amount detecting device. Furthermore, it is installed in the opening of the ceiling of the storage tank to transmit ultrasonic waves directly into the gas layer of the DUT, and receive the ultrasonic waves reflected by the liquid surface of the DUT at the ultrasonic receiving unit. Therefore, it is possible to provide the remaining amount detecting device which is hardly affected by the type of the object to be measured in the storage tank and the type of the storage tank and which can be used in a wide field.

According to the second aspect of the present invention, since the annular convex portion is a supporting portion supported by the main body of the remaining amount detecting device, it is easy to support it by the main body of the remaining amount detecting device.

According to the third aspect of the present invention, the annular convex portion is formed with the male screw which is screwed into the female screw on the main body side of the remaining amount detecting device. Therefore, the mounting structure is simplified and the mounting property is further improved. It will be easier.

According to the fourth aspect of the present invention, the length of the case in the axial direction is expressed as [(λ /
2) × N (a positive integer)] ± 10%, so the ultrasonic waves that propagate inside the side part of the case become an antinode of the vibration at the position of the closed one side end, and are efficiently radiated. Sound waves can be sent and received.

According to the invention of claim 5, since the case is made of brass, the sound pressure is the highest in terms of material, and ultrasonic waves can be transmitted and received more efficiently.

According to the sixth aspect of the invention, the annular convex portion is supported by the main body of the remaining amount detecting device in a state where the case is fitted in the mounting hole of the main body of the remaining amount detecting device. It can be installed in the opening of the storage tank to transmit ultrasonic waves directly into the gas layer of the object to be measured, and the ultrasonic wave reflected by the liquid surface of the object to be measured can be received by the ultrasonic wave receiving unit. It is possible to provide a remaining amount detecting device which is hardly affected by the type of the object to be measured and the type of the storage tank and which can be used in a wide field.

According to the invention of claim 7, the main body of the remaining amount detecting device also serves as a flange for closing the opening of the ceiling of the storage tank. , Without the need for mounting jigs,
The existing storage tank can be used as it is.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a remaining amount detecting ultrasonic transducer of an embodiment of the present invention as an ultrasonic transceiver.

FIG. 2 is a cross-sectional view of a case when vibration simulation is performed on the ultrasonic transceiver shown in FIG.

FIG. 3 is a sectional view of a vibration mode different from that in FIG.

FIG. 4 is a cross-sectional view of a remaining amount detecting device in which an ultrasonic transducer according to the present invention used as an ultrasonic transmitter and an ultrasonic transducer according to the present invention used as an ultrasonic receiver are juxtaposed.

5 is a cross-sectional view of the remaining amount detecting device using the ultrasonic transmitter / receiver shown in FIG. 1 and attached to the main body in the same manner as the ultrasonic transmitter / receiver in FIG.

FIG. 6 is a cross-sectional view of a remaining amount detecting device in which an ultrasonic transceiver is attached to a main body by screwing a convex portion of a case.

FIG. 7 is a cross-sectional view of a remaining amount detecting ultrasonic transducer of another embodiment of the present invention which is an ultrasonic transceiver.

FIG. 8 is a cross-sectional view showing an example of use when the remaining amount detecting device of FIG. 4 is attached to a storage tank storing an object to be measured.

[Fig. 9] The materials for the case are brass, stainless steel, and aluminum. When the sound pressure of each material is maximized,
It is a graph which shows an ultrasonic transmission test result.

[Explanation of symbols]

1 Ultrasonic transceiver 1a Ultrasonic transceiver 2 cases 4 Ultrasonic transducer 5 convex 5a male screw 10 Remaining amount detector 10a Remaining amount detection device 10b Remaining amount detection device 11 Ultrasonic transmitter 12 Ultrasonic receiver 13 body 13a Mounting hole 13b mounting hole 13d female screw 14 packing 14a packing 15 Holding plate 17 Lead wire 18 Arithmetic / control / power supply 19 Buffer member 20 storage tanks 20a opening 21 Flange mount 22 Packings 23 fixing screw 24 liquid layers 25 air layer 26 Liquid level 27 ultrasonic waves

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ identification code FI theme code (reference) F17C 13/02 301 G01S 7/52 A 5J083 (72) Inventor Hatano Ho Kugenumamatsugaoka, Fujisawa-shi, Kanagawa 5-11- 16 F-term (reference) 2F014 AB01 AB02 AC02 FB01 2F068 AA22 BB27 CC09 DD02 FF03 FF12 GG01 HH01 LL11 LL29 LL30 3E070 AA02 AB32 CA03 CB06 DA01 3E072 AA03 GA30 3E083 AA20 AJ10 5J083 CA01 BA05 ADA01

Claims (7)

[Claims] 1. A remaining amount detecting ultrasonic transducer for detecting the remaining amount of an object to be measured according to the time taken from the transmission of the ultrasonic wave to the time when the ultrasonic wave is reflected by the surface of the object to be measured in the storage tank and received. The ultrasonic transducer is attached to one end of a cylindrical case whose one end is closed, and the outer peripheral surface of the case is used when transmitting or receiving ultrasonic waves with the ultrasonic transducer. An ultrasonic transducer for remaining amount detection, characterized in that an annular convex portion is provided at a position where the vibration displacement of the side portion of the case is minimized. 2. The annular convex portion is a support portion for supporting the main body of the remaining amount detecting device,
The ultrasonic transducer for detecting the remaining amount according to claim 1. 3. The ultrasonic transducer for remaining amount detection according to claim 2, wherein the annular convex portion is formed with a male screw that is screwed into a female screw on the main body side of the remaining amount detecting device. 4. The length of the case in the axial direction is [(λ / 2) × N (a positive integer), where λ is the wavelength of the ultrasonic wave transmitted to the case when transmitting or receiving ultrasonic waves. )] ± 10% of the ultrasonic transducer for residual quantity detection according to any one of claims 1 to 3. 5. The ultrasonic transducer for residual quantity detection according to claim 1, wherein the case is made of brass. 6. An ultrasonic transducer according to claim 1, wherein the case is fitted into a mounting hole of a main body of the remaining amount detecting device, and the annular convex portion is attached to the remaining amount detecting device. A method for supporting an ultrasonic transducer, characterized in that the ultrasonic transducer is supported by the body of the. 7. The method for supporting an ultrasonic transducer according to claim 6, wherein the ultrasonic transducer is supported by the main body of the remaining amount detecting device that closes the opening of the storage tank.