JP7595309B2 - Vibration transmitting member, transducer using same, and fluid type discriminating device - Google Patents

Description

The present invention relates to a vibration transmission member that is connected to a vibrating body and operates by transmitting ultrasonic waves of multiple frequencies from one member. It also relates to a transducer and a fluid type discrimination device that use the same.

Conventionally, devices that measure gas values (calorific value, etc.) by transmitting multiple frequencies are known (see, for example, Patent Document 1).

Figure 9 is a schematic diagram of a gas value measurement device using a conventional transducer. In Figure 9, the gas value measurement device 101 has a gas inlet 102 and an outlet 103. Transducers 105 and 106 are arranged so that measurement is performed by the measurement unit 104. The transducers 105 and 106 transmit and receive at a first frequency f1. Also, an ultrasonic transducer 108 and a reflector 109 arranged to transmit and receive ultrasonic waves from the ultrasonic transducer 108 are arranged opposite each other so that measurement is performed by the measurement unit 107. The ultrasonic transducer 108 transmits and receives at a second frequency f2. In this way, the transducers 105 and 106 constitute a measurement system 110. Also, the ultrasonic transducer 108 and the reflector 109 constitute a measurement system 111.

In this configuration, the gas to be measured flows in from the inlet 102, passes through the measuring section 104, and flows out from the outlet 103. During this time, the gas also fills the measuring section 107. In the measuring section 104, the amount of gas attenuation is measured by ultrasonic waves of frequency f1 transmitted and received between the transducers 105 and 106. In addition, the amount of gas attenuation is measured by ultrasonic waves of frequency f2 transmitted and received between the ultrasonic transducer 108 and the reflector 109. Using these attenuation amounts at frequencies f1 and f2, the gas value of the measured gas is derived based on the relationship between the frequency stored in advance and the gas value (heat value, etc.) associated with the attenuation amount.

Special Publication No. 11-511260

However, in the conventional gas value measurement device, in order to use two different frequencies to identify the gas type, three transducers and two measurement systems composed of them are required, and because the number of parts is large, the configuration becomes complex and the size becomes large, resulting in problems such as increased costs. In addition, because the gas value is estimated from two types of physical quantities, the types of gas to be identified are limited, and the accuracy is also limited.

The present invention addresses the above-mentioned problems, and is a vibration transmission member that operates by being joined to one surface of a vibrating body, and is formed of a top plate, a bottom plate, side walls, and a partition wall arranged approximately perpendicular to the top plate and bottom plate. It uses vibrations generated in multiple membrane structures formed by the top plate and the partition wall, and by setting the spacing between the partition walls to different values, the multiple membrane structures generate different resonance frequencies, thereby enabling a single member to transmit and receive multiple frequencies, and by using this, it is possible to distinguish the type of fluid with a single system.

In order to solve the above-mentioned problems, the vibration propagation member of the present invention is a vibration propagation member that operates by being joined to one surface of a vibrating body, and is formed of a top plate, a bottom plate, a side wall, and a partition wall arranged approximately perpendicular to the top plate and bottom plate. It uses vibrations generated by multiple membrane structures formed by the top plate and the partition wall, and by setting the spacing between the partition walls to different values, the multiple membrane structures are made to generate different resonance frequencies. This makes it possible to configure a configuration that transmits and receives multiple frequencies using only one vibration propagation member, and by using a transmitter/receiver that uses this, it is possible to accurately determine the type of fluid with a single system.

The vibration transmission member of the present invention is formed from a top plate, a bottom plate, side walls, and a partition wall arranged approximately perpendicular to the top plate and bottom plate, and multiple membrane structures are made to generate different resonance frequencies, making it possible to configure a single vibration transmission member to transmit and receive multiple frequencies, and by using a transducer incorporating this, a single system can accurately determine the type of fluid.

FIG. 2 is an exploded perspective view of a vibration propagation member according to the first embodiment of the present invention; 1 is a cross-sectional view of a vibration propagation member according to a first embodiment of the present invention; 1 is a diagram showing a method for forming a vibration propagation member in accordance with the first embodiment of the present invention; FIG. 11 is a cross-sectional view of a transducer according to a second embodiment of the present invention. A characteristic graph of a transducer according to the second embodiment of the present invention. FIG. 11 is a cross-sectional view of a fluid type determination device according to a third embodiment of the present invention. FIG. 11 is a configuration diagram of a calculation unit according to a third embodiment of the present invention. Gas frequency characteristic diagram in the third embodiment of the present invention Schematic diagram of a gas value measuring device using a conventional transducer

The first invention is a vibration propagation member that operates by being joined to one surface of a vibrating body, and is formed of a top plate, a bottom plate, a side wall, and a partition wall arranged approximately perpendicular to the top plate and bottom plate. It uses vibrations generated in multiple membrane structures formed by the top plate and the partition wall, and by setting the spacing between the partition walls to different values, the multiple membrane structures generate different resonance frequencies, making it possible to transmit multiple frequencies using only one vibration propagation member.

The second invention is a transducer that includes a vibrating body and the vibration transmission member of the first invention that is bonded to one surface of the vibrating body, and a transducer that can transmit and receive multiple frequencies can be constructed using only one vibrating body and one vibration transmission member attached to it.

The third invention comprises a pair of ultrasonic transmitters and receivers of the second invention arranged between the fluid to be measured, a control unit configured to transmit from one of the pair of ultrasonic transmitters and receive from the other, and a calculation unit that processes the received signals of the pair of ultrasonic transmitters and receivers, the transmitters and receivers being configured to be capable of transmitting and receiving at multiple resonant frequencies, the calculation unit being a fluid type discrimination device that discriminates the type of the fluid to be measured based on the signal characteristics of the received signals at the multiple resonant frequencies, and by using a pair of ultrasonic transmitters and receivers capable of transmitting and receiving at multiple frequencies, the type of fluid can be discriminated with high accuracy.

Below, the embodiments will be described in detail with reference to the drawings. However, more detailed explanation than necessary may be omitted. For example, detailed explanation of already well-known matters or duplicate explanation of substantially the same configuration may be omitted. This is to avoid the following explanation becoming unnecessarily redundant and to make it easier for those skilled in the art to understand.

The accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

(Embodiment 1)
The first embodiment will be described with reference to FIGS. 1 and 2. FIG.

Figure 1 is an exploded perspective view of a vibration propagation member in embodiment 1 of the present invention. As shown in Figure 1, the vibration propagation member 1 is composed of a top plate 2, a bottom plate 3, and a number of partitions 6, 7, 8, and 9 arranged approximately perpendicular to the top plate 2 and bottom plate 3 in a space surrounded by side walls 4 and 5. In Figure 1, in order to make it easier to understand the internal structure of the vibration propagation member, the bottom plate 3 and side walls 5 are shown removed. With this configuration, the top plate 2 is divided into a membrane surface 10 partitioned by partitions 6 and 7, a membrane surface 11 partitioned by partitions 7 and 8, and a membrane surface 12 partitioned by partitions 8 and 9.

Figure 2 shows a cross section of the vibration propagation member 1 in Figure 1. Figure 2(a) is the horizontal cross section AA' of Figure 1, and Figure 2(b) is the vertical cross section BB' of Figure 1. As shown in Figure 2(a), the widths (W) of membrane surfaces 10, 11, and 12 are equal, but their respective lengths (Ma, Mb, Mc) are configured to have the following relationship. This membrane length can also be said to be the distance between the partition walls.

Ma < Mb < Mc
On the other hand, as shown in FIG. 2B, the heights H of the partition walls 6, 7, 8, and 9 are equal, and the thicknesses La of the partition walls 6, Lb of the partition walls 7, Lc of the partition walls 8, and Ld of the partition walls 9 are substantially equal.

As a result, the vibration propagation member 1 has vibrating parts made up of three membrane structures (each shown by a dashed dotted line): membrane structure 13 made up of partitions 6, 7 and membrane surface 10, membrane structure 14 made up of partitions 7, 8 and membrane surface 11, and membrane structure 15 made up of partitions 8, 9 and membrane surface 12.

In FIG. 1, the vibration propagation member 1 is configured as separate members, with the top plate 2, bottom plate 3, side walls 4 and 5, and partitions 6, 7, 8 and 9, but as shown in FIG. 3, the partitions and side walls can be formed by stacking multiple intermediate plates 54, which are made by etching thin metal (e.g., SUS) plates into a predetermined shape, and then stacking top plates 52 and bottom plates 53 above and below them to form the vibration propagation member 51.

The operation of this vibration transmission member will be explained in the next section, "Operational Description 2."

(Embodiment 2)
The second embodiment will be described with reference to FIGS.

Figure 4 shows a cross-sectional view of the transducer 16. The transducer 16 is configured by attaching a vibrating body 17 to the bottom plate 3 of the vibration propagation member 1 described in the first embodiment. The vibrating body 17 is, for example, a piezoelectric body. The vibration propagation member 1 is the same as in the first embodiment, so the same numbers are used for the same parts as in Figures 1 and 2.

Next, the operation of the transducer 16 will be explained using FIG. 4, but first, the basic characteristics of the vibration propagation member 1 having such a configuration will be explained.

In Figure 4, the lengths of the membrane surfaces 10, 11, and 12 are different, but the relationship between the length and the resonant frequency of the membrane surface is shown in Figure 5. The horizontal axis of Figure 5 shows the length of the membrane surface (= the spacing between the partition walls), and the vertical axis shows the resonant frequency of the membrane structure.

As shown in Figure 5, as the membrane surface length of the membrane structure increases, the resonant frequency decreases. This means that a membrane structure with a large membrane surface length resonates at a low frequency, and a membrane structure with a small membrane surface length resonates at a high frequency. Therefore, by forming membrane structures with various membrane surface lengths, it is possible to generate resonances at multiple frequencies.

The operation of the vibration transmission member 1 based on the basic characteristics of the vibration transmission member 1 is explained with reference to Figure 4.

Now, when the vibrating body 17 is excited by a drive signal containing the resonant frequency component of the vibrating membrane, and the generated vibration is supplied through the bottom plate 3, the vibration is transmitted to the top plate 2 through the partitions 6, 7, 8, and 9, respectively. At this time, since the lengths of the membrane surfaces 10, 11, and 12 are different as described above, the membrane surfaces 10, 11, and 12 vibrate at different resonant frequencies. In other words, ultrasonic waves of different frequencies are emitted from the membrane surfaces 10, 11, and 12, and the resonant frequency of the membrane surface 10, which has a smaller membrane surface length, is higher, and the resonant frequency of the membrane surface 12, which has a larger membrane surface length, is lower.

The above is for the case where the transducer 16 is used to transmit ultrasonic waves, but even if it is used for receiving waves, the relationship between the membrane length and the resonant frequency does not change, so this relationship should be taken into consideration. In other words, in Figure 4, when ultrasonic waves reach the membrane, the resonant frequency values of membranes 10, 11, and 12 correspond in this order from largest to smallest.

Therefore, when two transducers 16 are used facing each other, as shown in Figure 4, they can be arranged so that the transducers with the same membrane length face each other directly opposite each other, allowing the ultrasonic waves transmitted from the transducer to be received by the transducer.

As explained above, by changing the membrane length, the resonant frequency can be controlled, and as a result, ultrasonic waves of multiple resonant frequencies can be emitted from the top plate. In other words, with a simple configuration of one vibrating body and one vibration transmitting body, ultrasonic waves of multiple resonant frequencies can be emitted simultaneously.

(Embodiment 3)
The third embodiment will be described with reference to FIGS.

Figure 6 shows a cross section of a fluid type discrimination device 20 in embodiment 3 of the present invention. As shown in Figure 6, a pair of ultrasonic transmitters and receivers 22 and 23 are arranged to face each other in a flow path 21 through which the fluid to be measured flows. The ultrasonic transmitters and receivers 22 and 23 are the same as those described in embodiment 2. That is, the membrane length is formed as shown in Figure 4. Arrow 24 indicates the flow direction of the fluid to be measured. The pair of ultrasonic transmitters and receivers 22 and 23 are arranged to face each other across the fluid to be measured. In this case, the ultrasonic transmitters and receivers 22 and 23 are arranged so that the ones with the same membrane length face each other directly, as described in embodiment 2. The control unit 25 controls the transmission unit 26, the reception unit 27, the switching unit 28, and the calculation unit 29.

Figure 7 is a configuration diagram of the calculation unit 29 in embodiment 3 of the present invention.

As shown in FIG. 7, the calculation unit 29 includes an A/D converter 30 for an input signal, a filter A 31, a filter B 32, and a filter C 33, which correspond to predetermined frequencies f1, f2, and f3, respectively.
It is composed of processing units A34, B35, and C36 for signals that have passed through filter A31, filter B32, and filter C33, and an integrated processing unit 37 for signals processed by processing units A34, B35, and C36.

Figure 8 is an example of a simulated frequency characteristic diagram of a gas, which is the fluid to be measured. In Figure 8, the horizontal axis is frequency f, and the vertical axis is the reception strength S at a specified distance when a specified signal is transmitted in the target gas. Gas Ga and gas Gb have different frequency characteristics (signal characteristics of the received signal); gas Ga decreases monotonically with changes in frequencies f1, f2, and f3, but gas Ga has a minimum value. Therefore, if the reception strength at a specific frequency (e.g., f1, f2, f3) is known, it is possible to distinguish between gas Ga and gas Gb from the trend and value.

The reason why the received intensity changes in this way is simply because the ultrasonic waves propagating through the fluid interact with the molecules or atoms of the fluid and are absorbed or scattered.

The factors that cause the frequency dependence of ultrasonic reception strength depending on the gas type are detailed below. For example, the weight and size of atoms vary greatly in the case of monoatomic gases helium (He: 4), neon (Ne: 20), and argon (Ar: 40). Note that the parentheses indicate the element symbol and atomic weight. Gases made of light elements are thought to interact with ultrasonic waves up to high frequencies, while gases made of heavy elements are thought to interact with ultrasonic waves only in the low frequency range.

As such, it is believed that the interaction with ultrasound is frequency dependent, and therefore the transmittance of ultrasound is thought to change depending on the gas type. Furthermore, in the case of diatomic gases, such as hydrogen (H2:2), nitrogen (N2:28), and oxygen (O2:32), the weights of the gas molecules differ greatly, and the bonding strength between atoms also differs greatly, which results in differences in the vibrations or contraction/expansion movements between atoms. Furthermore, it is believed that there are also large differences in the torsional vibrations between atoms. These are thought to show frequency dependency in the interaction with ultrasound.

Furthermore, in the case of polyatomic gases, such as water vapor (H2O: 18), carbon dioxide (CO2: 44), nitrogen dioxide (N2O: 44), methane (CH4: 16), and ethane (C2H6: 30), the weights of the gas molecules vary greatly, and there are also large differences in their three-dimensional structures. For this reason, it is thought that frequency dependence occurs in the interaction with ultrasound.

The operation of the fluid type discrimination device configured based on the frequency characteristics of gas as described above will now be explained.

First, the control unit 25 controls the transmission unit 26 and the switching unit 28 to transmit a drive signal to the ultrasonic transmitter/receiver 22, and transmits ultrasonic waves into the fluid to be measured. The ultrasonic waves transmitted into the fluid to be measured propagate toward the ultrasonic transmitter/receiver 23 and are received by the ultrasonic transmitter/receiver 23.

As already explained, the ultrasonic transmitter/receivers 22 and 23 use the transmitter/receiver described in embodiment 2, so when transmitting from the ultrasonic transmitter/receiver 22, ultrasonic waves of multiple frequencies are transmitted. In addition, in the ultrasonic transmitter/receiver 23, ultrasonic waves of multiple frequencies are received by the corresponding membrane surface of the ultrasonic transmitter/receiver 22. The received signal is received by the receiver 27 via the switching unit 28, and reaches the calculation unit 29 via the control unit 25.

Next, the processing contents of the calculation unit 29 are explained with reference to FIG.

The signal input to the calculation unit 29 is converted into a digital signal by the A/D converter 30. Thereafter, the signal is filtered by a filter A 31 of frequency f1, a filter B 32 of frequency f2, and a filter C 33 of frequency f3, and the reception strength at each frequency is obtained by processing units A 34, B 35, and C 36, respectively.

These reception intensity data are compared in the integrated processing unit 37 with the reception intensity at frequencies f1, f2, and f3 in FIG. 8 that are stored in advance to determine the type of gas that is the measured fluid.

As explained above, the fluid type determination device of the present invention uses an ultrasonic transmitter/receiver capable of transmitting and receiving signals at multiple frequencies, allowing for highly accurate determination of the type of fluid being measured with a simple configuration.

In this embodiment, three types of frequencies have been described, but three or more types are possible by increasing the number of partitions in the vibration propagation member and setting different values for the membrane surface length. The more the number, the more types of gas that can be distinguished can be increased, and the accuracy of the distinction can be improved, making it possible to distinguish even if the frequency characteristic curves are close to each other.

As an example of the configuration of the discrimination device, a pair of ultrasonic transmitters and receivers are arranged opposite each other, but it is also possible to use a single ultrasonic transmitter and receiver with a reflector at the opposing part, and have the ultrasonic transmitter and receiver receive the transmitted signal.

In addition, the characteristics of the reception strength when the frequency changes are used as a criterion for distinguishing the gas type, but reception signal characteristics other than reception strength, such as attenuation rate, can also be used. In addition, although a rectangular shape is shown as the shape of the membrane surface, it is not limited to this and can be a circle, an ellipse, a polygon, etc. In addition, although a one-dimensional membrane structure arrangement is shown, a two-dimensional arrangement is also possible.

As described above, the vibration transmission member of the present invention can transmit and receive signals at multiple frequencies with a small number of parts, and can be used to determine the type of fluid as an ultrasonic transmitter/receiver by attaching a piezoelectric body to the vibration transmission member, allowing for accurate determination of a wide variety of fluids. Therefore, it can be widely used in applications requiring the determination of the type of fluid, such as various ultrasonic flowmeters and gas meters, which are applied products of the same.

Reference Signs List 1, 51 vibration transmission member 2, 52 top plate 3, 53 bottom plate 4, 5 side wall 6, 7, 8, 9 partition wall 13, 14, 15 membrane structure 16 transducer 17 vibrator 20 fluid type determination device 22, 23 ultrasonic transducer (transmitter/receiver)
25 Control unit 29 Calculation unit 54 Intermediate plate (side wall, partition wall)

Claims (3)

A vibration transmission member that operates by being joined to one surface of a vibrating body,
The container is formed of a top plate, a bottom plate, a side wall, and a plurality of partition walls arranged substantially perpendicular to the top plate and the bottom plate,
Using vibrations generated in a plurality of membrane structures formed by the top plate and the partition walls,
A vibration propagation member in which the distance between one of the plurality of partitions and the other partition adjacent to the one partition is set to a different value, so that the plurality of membrane structures generate different resonant frequencies. A transducer comprising a vibrating body and a vibration transmission member according to claim 1 bonded to one surface of the vibrating body. A pair of transducers according to claim 2 arranged with a fluid to be measured therebetween;
A control unit that is configured to transmit from one of the pair of transducers and receive from the other;
A calculation unit that processes the reception signals of the pair of transducers,
The transducer is configured to transmit and receive signals at a plurality of resonant frequencies;
The calculation unit is a fluid type determination device that determines the type of the fluid to be measured based on signal characteristics of received signals of a plurality of resonant frequencies.