JPH09222345A - Fluid vibration detection sensor and flow rate detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the flow rate of a fluid more accurately by improving noise elimination capacity without being affected by the difference in the length of a plurality of pressure-guiding paths and the difference in the volume of a plurality of pressure-guiding paths or pressure rooms. SOLUTION: With a pressure fluctuation transferred to a second pressure room 8 and a fourth pressure room 13, the attenuation of a frequency component that is equal to or more than a specific frequency by setting the effective inner diameter of a pressure-introducing pipe to a specific inner diameter that is thinner than the original inner diameter by a first acoustic filter 14 or a second acoustic filter 15 and a low-frequency component that is less than a specific frequency can be attenuated, thus increasing sensor output at a higher frequency side than a specific frequency, making clear a waveform, and positively reading a fluid vibration period. Therefore, by detecting flow rate based on the sensor output, flow rate can be measured accurately with less error.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluid vibration detecting sensor and a flow rate detecting device, and more particularly to a fluid vibration detecting sensor for detecting fluidic vibration in a flowmeter using a fluidic element and the detected fluidic vibration. The present invention relates to a flow rate detection device that detects a flow rate based on.

[0002]

2. Description of the Related Art First Conventional Example FIG. 14 is a partial sectional perspective view of a conventional fluidic flow sensor when the conventional fluidic flow sensor is configured as a flow rate detecting device.

The fluidic flow rate sensor 80 has a set ring space 83 for rectifying a fluid flow into a two-dimensional flow on a flow path connecting an inflow port 81 into which a fluid to be measured flows and an exhaust pipe 82. , A flow path reducing portion 84 for rectifying the flow of the fluid and reducing the flow path diameter of the fluid, a jet nozzle 85 for rectifying the flow of the fluid and converting it into a predetermined jet flow, and the flow path diameter of the fluid is enlarged again. And a flow path expanding portion 86 for performing the operation.

In the flow passage expanding portion 86, a pendulum 87 for inducing vibration of the fluid, a side block 88 for forming a flow passage for changing the flow direction of the jet flow, and a side block 88 are provided in cooperation with each other. End block 89 that works and changes the flow of the jet flow by the collision of the jet flow
And a discharge space 90 arranged on a surface side of the end block 89 different from the jet flow collision surface.

The end block 89 is the side block 8
A wall 89a extending toward the upstream side of the flow path along 8
A wall 89b, a first pressure detection hole (pressure guide port) 91a, and a second pressure detection hole (pressure guide port) 91b are provided.
Further, the pressure guiding pipe 92a and the pressure guiding pipe 9 are provided in the first pressure detecting hole (pressure guiding port) 91a and the second pressure detecting hole (pressure guiding port) 91b.
A flow rate detection unit 93 incorporating a fluid vibration detection sensor, which will be described later, is connected via 2b.

FIG. 15 shows a schematic block diagram of a fluid vibration detection sensor of the first conventional example. The fluid vibration detection sensor 101 is separated from a first pressure chamber 104 that communicates with the first pressure guide port 103 via the first pressure introducing pipe 102, and a first pressure chamber 104 and a first piezoelectric film 105, A second pressure chamber 109 communicating with the second pressure introducing port 108 via a third pressure introducing pipe 107 that joins in the middle of the second pressure introducing pipe 106, and a second pressure introducing via the second pressure introducing pipe 106. The third pressure chamber 110 communicating with the port 108 is separated from the third pressure chamber 110 via the second piezoelectric film 111, and the fourth pressure introducing pipe 112 is joined in the middle of the first pressure introducing pipe 102. And a fourth pressure chamber 113 communicating with the first pressure guide port 103.

First pressure chamber 1 of fluid vibration detection sensor 101
04 and the fourth pressure chamber 113 are communicated with the first pressure detection hole 91a in the fluidic element of the fluidic flow rate sensor 80 shown in FIG. 14 via the pressure guiding pipe 92a and the first pressure guiding port 103, and Pressure chamber 109 and third pressure chamber 11
Zero is communicated with the second pressure detection hole 91b in the fluidic element of the fluidic flow sensor via the pressure guiding tube 92b and the second pressure guiding port 108.

FIG. 16 shows a schematic structure of a detection circuit corresponding to the fluid vibration detection sensor of FIG. The detection circuit 120 is
A first amplification amplifier 121 that detects and amplifies the output voltage of the first piezoelectric film 105, a second amplification amplifier 122 that detects and amplifies the output voltage of the second piezoelectric film 111, and a first amplification amplifier 12
A differential amplifier 1 for differentially amplifying the output signal of 1 and the output signal of the second amplification amplifier 122 and outputting an output detection signal
23, and is comprised.

Now, the operation of the detection circuit will be described. The first piezoelectric film 105 will bend due to the difference between the fluid pressure in the first pressure chamber 104 and the fluid pressure in the second pressure chamber 109. As a result, an output voltage corresponding to the bending state is generated in the first piezoelectric film 105, and the first amplification amplifier 12
1 detects and amplifies the output voltage of the first piezoelectric film 105, and outputs it to the differential amplifier 123.

On the other hand, the second piezoelectric film 111 has the third pressure chamber 1
The bending occurs due to the difference between the fluid pressure inside 10 and the fluid pressure inside the fourth pressure chamber 113. Thereby, the second piezoelectric film 1
An output voltage corresponding to the bending state is generated at 11
The amplification amplifier 122 detects and amplifies the output voltage of the second piezoelectric film 111, and outputs it to the differential amplifier 123.

As a result, the differential amplifier 123 has the first
Output signal of amplification amplifier 121 and second amplification amplifier 122
The output detection signal is output by differentially amplifying the output signal of (1), and the flow rate detection unit detects the flow rate of the fluid based on this output detection signal.

FIG. 17 shows a fluid vibration frequency of about 300 [H
z] shows the output detection signal waveform of the differential amplifier 123. FIG. 17A is an output detection signal waveform when the time scale on the horizontal axis is 4 [msec] per scale.

As can be seen from FIG. 17A, the signal waveform is not clear and the period cannot be detected clearly. In FIG. 17B, the measurement period is made longer than in the case of FIG. 17A, and the time scale on the horizontal axis is 40 [mse per scale].
It is an output detection signal waveform in the case of [c].

As can be seen from FIG. 17 (b), the low frequency component is superimposed on the signal waveform of the input waveform of about 300 [Hz], and undulation occurs in the waveform. Second Conventional Example FIG. 18 shows a schematic configuration diagram of a fluid vibration detection sensor of a second conventional example.

The fluid vibration detection sensor 131 is connected to the first pressure introducing port 133 via the first pressure introducing pipe 132.
Pressure chamber 134, first pressure chamber 134 and first piezoelectric film 135
The second pressure chamber 139 and the second pressure introducing pipe 136, which are separated via the second pressure introducing pipe 137 and communicate with the second pressure introducing port 138 via the third pressure introducing pipe 137 that joins in the middle of the second pressure introducing pipe 136.
The third pressure chamber 14 communicated with the second pressure guide port 138 via the
0 is separated from the third pressure chamber 140 via the second piezoelectric film 141, and is communicated with the first pressure introducing port 133 via the fourth pressure introducing pipe 142 that joins in the middle of the first pressure introducing pipe 132. And a fourth pressure chamber 143.

Further, the second pressure chamber 139 is separated into a first sub pressure chamber 139A and a second sub pressure chamber 139B by a first pressure damper 150 for absorbing a minute fluctuation in pressure.
The fourth pressure chamber 143 is separated into a third sub pressure chamber 143A and a fourth sub pressure chamber 143B by a second pressure damper 151 for absorbing a minute fluctuation in pressure.

First pressure chamber 1 of fluid vibration detection sensor 101
34 and the fourth pressure chamber 143 communicate with the first pressure detection hole 91a in the fluidic element of the fluidic flow sensor 80 shown in FIG. 14 via the pressure guiding pipe 92a and the first pressure guiding port 133, and the second pressure detecting hole 91a Pressure chamber 139 and third pressure chamber 14
0 is communicated with the second pressure detection hole 91b in the fluidic element of the fluidic flow sensor via the pressure guiding pipe 92b and the second pressure guiding port 138.

As a result, according to the second conventional example, FIG.
By using the detection circuit 120 of FIG. 3, compared to the operation of the first conventional example, it is possible to absorb a minute fluctuation in pressure and obtain an output detection signal waveform with lower noise.

[0019]

In the fluid vibration detecting sensor of the first conventional example, when the path from the pressure guide port of the fluidic element to each piezoelectric film is a pressure guide path, each pressure guide path is provided. If the paths can be made equal in length and have the same volume, the influence of external vibration detected as an in-phase component can be reduced by subtracting the detection output corresponding to the amount of deformation of each piezoelectric film. It should be possible to cancel each other out and improve the noise removal capability.

However, as a practical problem, it is difficult to manufacture the pressure guiding passages in the same length and the same volume in terms of structure. Therefore, there is a problem that it is practically difficult to improve the noise removal capability.

Further, the signal waveform is not clear, the period cannot be clearly detected, and unnecessary low-frequency components are superimposed on the signal waveform, so that an accurate flow rate cannot be calculated. there were. Further, in the fluid vibration detecting sensor of the second conventional example, a pressure damper having elasticity for absorbing a minute fluctuation of pressure is provided, so that the volume inside the pressure chamber is the same in actual operation. However, there is a problem that it is difficult to improve the noise removal capability by the subtraction process as in the first conventional example.

Therefore, it is an object of the present invention to improve the noise removing capability without being affected by the difference in the length of the plurality of pressure guiding paths and the difference in the volume of the plurality of pressure guiding paths or the pressure chambers. Another object of the present invention is to provide a simple fluid vibration detection sensor and a flow rate detection device capable of detecting a more accurate flow rate of a fluid.

[0023]

According to the first aspect of the present invention,
A fluid vibration detection sensor for detecting fluidic vibration of a fluid based on a first fluid pressure at a first pressure introducing port and a second fluid pressure at a second pressure introducing port, wherein the first pressure introducing pipe is used for the fluid vibration detecting sensor. A first pressure chamber communicating with the pressure guide port,
A second pressure chamber, which is separated from the first pressure chamber via the first piezoelectric film and communicates with the second pressure introducing port via a third pressure introducing pipe, and the second pressure chamber via the second pressure introducing pipe. A third pressure chamber communicating with the second pressure guide port, a third pressure chamber separated from the third pressure chamber via a second piezoelectric film, and a fourth pressure chamber communicating with the first pressure guide port via a fourth pressure introducing pipe. A pressure chamber; and a first acoustic filter provided on the second pressure chamber side of the third pressure introducing pipe and having an effective inner diameter of the third pressure introducing pipe as a predetermined inner diameter smaller than the original inner diameter, A second acoustic filter which is provided on the fourth pressure chamber side of the fourth pressure introducing pipe and has an effective inner diameter of the fourth pressure introducing pipe which is a predetermined inner diameter smaller than the original inner diameter. To do.

According to the first aspect of the present invention, the first fluid pressure, which is the pressure of the fluid at the first pressure guide port, is transmitted to the first pressure chamber via the first pressure introducing pipe, and the fourth pressure introducing port is introduced. It is transmitted to the fourth pressure chamber via the pipe and the second acoustic filter.
At the same time, the second fluid pressure, which is the pressure of the fluid at the second pressure guide port, is transmitted in the second pressure chamber via the third pressure introducing pipe and the first acoustic filter, and then passes through the second pressure introducing pipe. Is transmitted to the third pressure chamber.

As a result, the first piezoelectric film bends in accordance with the difference between the pressure inside the first pressure chamber and the pressure inside the second pressure chamber, and a predetermined potential is generated. According to the difference between the pressure in the first pressure chamber and the pressure in the fourth pressure chamber, the bending causes a predetermined potential to be generated.

At this time, the pressure fluctuation transmitted to the second pressure chamber is equal to or higher than a predetermined frequency by setting the effective inner diameter of the third pressure introducing pipe to a predetermined inner diameter smaller than the original inner diameter by the first acoustic filter. The attenuation of the frequency component of is suppressed, and the low frequency component below the predetermined frequency is attenuated. Similarly, the pressure fluctuation transmitted to the fourth pressure chamber is attenuated by the second acoustic filter by making the effective inner diameter of the fourth pressure introducing pipe smaller by a predetermined inner diameter than the original inner diameter. Is suppressed, and low frequency components below a predetermined frequency are attenuated.

According to a second aspect of the present invention, in the first aspect of the present invention, the second pressure chamber is provided with a first pressure damper for absorbing a minute fluctuation in pressure, and the second auxiliary pressure chamber and the second pressure chamber.
The fourth pressure chamber is divided into a sub-pressure chamber, and the fourth pressure chamber is divided into a third sub-pressure chamber and a fourth sub-pressure chamber by a second pressure damper for absorbing a minute fluctuation in pressure.

According to the second aspect of the invention, in addition to the operation of the first aspect of the invention, the first pressure damper absorbs minute fluctuations in the pressure in the second pressure chamber, and the second pressure damper Absorbs minute fluctuations in pressure in the fourth pressure chamber. According to a third aspect of the present invention, in the first or second aspect of the invention, the inner diameters of the first acoustic filter and the second acoustic filter are configured to be φ0.5 [mm] or less.

According to the invention of claim 3, in the invention of claim 1 or 2, since the inner diameters of the first acoustic filter and the second acoustic filter are φ0.5 [mm] or less, 250 Attenuation of frequency components above [Hz] is suppressed, and low frequency components below 250 [Hz] are attenuated.

According to a fourth aspect of the invention, in the invention according to any one of the first to third aspects, the inner diameters of the first acoustic filter and the second acoustic filter are φ0.5.
[Mm], and the original inner diameters of the third pressure introducing pipe and the fourth pressure introducing pipe are φ2 [mm].

According to a fourth aspect of the invention, in the invention according to any one of the first to third aspects, the inner diameters of the first acoustic filter and the second acoustic filter are φ0.5 [m
m], and the original inner diameters of the second pressure introduction pipe and the fourth pressure introduction pipe are φ2 [mm], so that the sensor output is high in the effective detection frequency range required for the fluid vibration detection sensor. Output and improve stability.

A fifth aspect of the present invention includes the fluid vibration detection sensor according to any one of the first to fourth aspects, and detects the flow rate of the fluid based on the fluid vibration in the fluidic element. An apparatus for detecting the pressure of one of a first pressure detection hole and a second pressure detection hole provided at a predetermined symmetrical position in the fluidic element with respect to the flow direction of the fluid in the fluidic element. The first pressure chamber and the fourth pressure chamber are communicated with the hole, the second pressure chamber and the third pressure chamber are communicated with the other pressure detection hole, and depending on the bending state of the first piezoelectric film. A first detection means for outputting a first detection signal, a second detection means for outputting a second detection signal according to a bending state of the second piezoelectric film, and a first detection signal and a second detection signal. Calculate the flow rate of the fluid based on Configuring comprises a quantity calculating means.

According to the fifth aspect of the present invention, the first pressure detecting hole and the second pressure detecting hole provided at symmetrical predetermined positions in the fluidic element with respect to the flow direction of the fluid in the fluidic element. The first one of the fluid vibration detection sensors according to any one of claims 1 to 4 in one of the pressure detection holes.
The pressure chamber and the fourth pressure chamber communicate with each other, and the second pressure chamber and the third pressure chamber of the fluid vibration detection sensor communicate with the other pressure detection hole.

At this time, the first detection means outputs the first detection signal corresponding to the bending state of the first piezoelectric film to the flow rate calculation means. Further, the second detection means outputs a second detection signal according to the bending state of the second piezoelectric film to the flow rate calculation means. As a result, the flow rate calculation means calculates the flow rate of the fluid based on the first detection signal and the second detection signal.

According to a sixth aspect of the present invention, in the fifth aspect of the invention, the flow rate calculation means includes differential means for outputting a difference signal corresponding to the difference between the first detection signal and the second detection signal. And a flow rate detecting means for calculating the flow rate of the fluid based on the difference signal.

According to the invention of claim 6, in addition to the operation of the invention of claim 5, the differential means of the flow rate calculating means is:
A difference signal corresponding to the difference between the first detection signal and the second detection signal is output to the flow rate detecting means. The flow rate detecting means calculates the flow rate of the fluid based on the difference signal.

[0037]

Preferred embodiments of the present invention will now be described with reference to the drawings. FIG. 1 shows a schematic configuration diagram of a fluid vibration detection sensor as a fluid vibration detection sensor. The fluid vibration detection sensor 1 is separated from the first pressure chamber 4 communicating with the first pressure guide port 3 via the first pressure introducing pipe 2, the first pressure chamber 4 and the first piezoelectric film 5, A second pressure chamber 8 communicating with the second pressure guide port 7 via a third pressure introduction pipe 9 that joins in the middle of the second pressure introduction pipe 6, and a second pressure introduction via the second pressure introduction pipe 6. A third pressure chamber 10 communicating with the port 7, and a third pressure chamber 10
And the second piezoelectric film 11 to separate the fourth pressure introduction pipe 1
A fourth pressure chamber 13 that communicates with the first pressure guide port 3 via 2
Is provided on the second pressure chamber 8 side of the second pressure introducing pipe 6, and the effective inner diameter of the second pressure introducing pipe 6 is smaller than the original inner diameter (= φ2 [mm]) of the third pressure introducing pipe 9. Thin predetermined inner diameter (= φ
0.5 [mm]) the first acoustic filter 14 and the fourth acoustic filter 14.
A predetermined inner diameter which is provided on the fourth pressure chamber 13 side of the pressure introducing pipe 12 and whose effective inner diameter is smaller than the original inner diameter (= φ2 [mm]) of the fourth pressure introducing pipe 12. (= Φ
The second acoustic filter 15 having a thickness of 0.5 [mm]) is provided.

Furthermore, the second pressure chamber 8 is separated into a first sub pressure chamber 8A and a second sub pressure chamber 8B by a first pressure damper 20 for absorbing a minute fluctuation in pressure, and the fourth pressure chamber 13 is separated.
Is a second pressure damper 2 for absorbing minute fluctuations in pressure.
1 separates the third auxiliary pressure chamber 13A and the fourth auxiliary pressure chamber 13B.

FIG. 2 shows the fluid vibration detection sensor of FIG.
2 is a schematic configuration diagram when connected to the fluidic element of FIG. The first pressure guide port 3 is communicated with the first pressure detection hole 91a of the fluidic flow sensor 80 through the first communication passage 39, and the second pressure guide port 7 is communicated with the fluidic flow sensor through the second communication passage 40. The second pressure detection hole 91b of 80 is communicated.

FIG. 3 shows a schematic block diagram of a flow rate detection display device as a flow rate detection device. Flow rate detection display device 5
Reference numeral 0 denotes a first amplifier 51 that amplifies the first electric detection signal SD1 that is the output signal of the fluid vibration detection sensor 1 and outputs it as a first amplified detection signal ASD1; A second amplifier 52 for amplifying the electrical detection signal SD2 and outputting it as a second amplified detection signal ASD2;
A differential amplifier 53 that differentially amplifies the amplified detection signal ASD1 and the second amplified detection signal ASD2 and outputs the difference signal SDEL, and a predetermined frequency band component is removed to remove a noise component of the difference signal SDEL. Output filter circuit 54
And a Schmitt trigger circuit 55 that performs waveform shaping based on the output signal of the filter circuit 54 and outputs a rectangular wave output signal, and an operation is performed based on the rectangular wave output signal of the Schmitt trigger circuit 55 to determine the flow rate of the fluid. A processor 56 that outputs a display control signal SCD for obtaining and displaying the calculation result on a monitor, which will be described later, and a monitor 57 such as a liquid crystal monitor that performs various displays are configured. Principle of Operation Here, the principle of operation will be described prior to specific description of the operation.

When the acoustic circuit is made to correspond to the electric circuit, FIG.
As shown in Fig. 4, the acoustic mass (inertance) can be represented as an inductance (see Fig. 4 (a)), the acoustic capacitance can be represented as a capacitance (see Fig. 4 (b)), and the pressure damper as a transformer. Can be represented (Fig. 4 (c)
reference).

More specifically, the acoustic mass M is the total mass m
And the cross-sectional area of the flow path is S, the volume velocity is U, the volume flow rate is u, and the sound pressure is δP, then M = m / S ²

[0043]

[Equation 1]

Is as follows. Also, the acoustic capacity CA is W
0, and the speed of sound and is c, the density and ρ0, CA = W0 / (ρ0 · c 2)

[0045]

[Equation 2]

It becomes By the way, the fluid vibration detection sensor 1
When the structure of is represented by a single line diagram in which the pressure introducing pipe is represented by a single line,
As shown in FIG. FIG. 6 shows each element shown in FIG. 5 as an equivalent electric circuit according to the expression by the equivalent electric circuit (see FIG. 4).

In this case, the first piezoelectric film 5 has the symbol Z.
1, the second piezoelectric film 11 corresponds to the symbol Z2, and
The acoustic filter 14 corresponds to the inductance L24, and the second
The acoustic filter 15 corresponds to the inductance L14. When the broken line frame in FIG. 6 is divided into a first block B1 and a second block B2 as shown in FIG. 7, the piezoelectric film equivalent portion corresponding to the piezoelectric film portion is shown in FIG. The potential difference between the Z output terminals is the voltage V1 'and the voltage V2.
It becomes the potential difference of '.

Therefore, the voltage V1 'and the voltage V2' will be obtained. First, if the voltage V1 'is s = jω,

[0049]

(Equation 3)

Is as follows. On the other hand, the voltage V2 'is

[0051]

(Equation 4)

Is as follows. From these, the potential difference VZ between both output terminals of the piezoelectric film equivalent portion Z is

[0053]

(Equation 5)

Is as follows. Therefore, as can be seen from the above formula 1, the potential difference VZ can be increased by increasing the inductance L2. In order to increase the inductance L2, the inner diameter of the acoustic filter may be made smaller than the inner diameter of the pressure introducing tube, or the length may be increased while keeping the inner diameter of the acoustic filter constant.

More specifically, if the inner diameter of the acoustic filter 14 is set to φ0.5 [mm], which is smaller than the inner diameter of the pressure introducing tube, the inductance L2 can be increased, so that the first piezoelectric film (FIG. 6). It is possible to increase the potential difference VZ1 between the two output terminals in (corresponding to the symbol Z1). Similarly, if the inner diameter of the acoustic filter 15 is φ0.5 [mm], which is smaller than the inner diameter of the pressure introducing tube, the inductance can be increased, so that the second piezoelectric film (Z2 in FIG. 6).
(Correspondingly), the potential difference VZ2 between both output terminals can be increased.

As a result, as shown by the broken line in FIG. 9, the potential difference VZ between both output terminals of the piezoelectric film can stably maintain a high output even in a region where the output signal frequency f is high (250 [Hz] or more). Therefore, the output waveform becomes stable, the output waveform can be reliably read, and the reading error can be reduced.

Next, the operation of the fluid vibration detection sensor 1 and the flow rate detection display device 50 will be described with reference to FIGS. A) In the case of P1> P2 FIG. 10 is an operation explanatory diagram in the case of P1> P2.

In the case of P1> P2, that is, the fluid pressure is high on the first pressure detecting hole 91a side and the second pressure detecting hole 91b.
When the fluid pressure on the side is low, the fluid pressure on the second pressure chamber 8 side is low and the fluid pressure on the first pressure chamber 4 side is high, as shown in FIG. Second pressure chamber 8
It will bend so as to be convex to the side (drawing, upper side).

As a result, the first electric detection signal SD1 according to the bending state of the first piezoelectric film 5 (see FIGS. 10B and 10I).
Is output to the first amplification amplifier 51. First amplification amplifier 5
1 amplifies the first electric detection signal SD1 and outputs it to the non-inverting input terminal of the differential amplifier 53 as the first amplification detection signal ASD1.

Since the fluid pressure on the side of the fourth pressure chamber 13 is high and the fluid pressure on the side of the third pressure chamber 10 is low, the second piezoelectric film 11 is placed on the side of the third pressure chamber 10 (the lower side in the drawing). It will bend so as to be convex. As a result, the second electric detection signal SD2 (FIG. 10B) corresponding to the bending state of the second piezoelectric film 11 is generated.
(See (ii)) is output to the second amplification amplifier 52.

The second amplification amplifier 52 amplifies the second electric detection signal SD2 and outputs it as the second amplification detection signal ASD2 to the inverting input terminal of the differential amplifier 53. As a result, the differential amplifier 53 differentially amplifies the first amplification detection signal AS D1 and the second amplification detection signal AS D2 to generate the difference signal SDEL (see FIG. 1).
0 (b) (iii)) to the filter circuit 54.

In this way, the first detection signal SD1 (substantially the first amplification detection signal ASD1) and the second electric detection signal SD2
(Substantially, the second amplification detection signal AS D1) is differentially amplified, so that a minute change in the flow rate can be easily detected, and the in-phase noise component included in both signals can be removed. Therefore, the flow rate can be detected with higher accuracy.

Next, the filter circuit 54 removes a predetermined frequency band component in order to remove the noise component of the difference signal SDEL and outputs it to the Schmitt trigger circuit 55. The Schmitt trigger circuit is based on the output signal of the filter circuit 54. Waveform shaping is performed and a rectangular wave output signal is output to the processor 56.

As a result, the processor 56 performs an operation based on the rectangular wave output signal of the Schmitt trigger circuit to obtain the flow rate of the fluid and outputs the display control signal SCD for displaying the operation result to the monitor. ,
The flow rate as the calculation result is displayed on the monitor. B) In the case of P1 <P2 FIG. 11 shows an operation explanatory diagram in the case of P1 <P2.

When P1 <P2, that is, the first pressure detecting hole 91a side has a low fluid pressure and the second pressure detecting hole 91b
When the fluid pressure on the side is high, the fluid pressure on the second pressure chamber 8 side is high and the fluid pressure on the first pressure chamber 4 side is low, as shown in FIG. First pressure chamber 4
It will bend so as to be convex toward the side (drawing, lower side).

As a result, the first electric detection signal SD1 (see FIGS. 11B and 11I) corresponding to the bending state of the first piezoelectric film 5 is output to the first amplification amplifier 51. First amplification amplifier 51
Outputs the first electric detection signal SD1 to the non-inverting input terminal of the differential amplifier 53 as the first amplification detection signal ASD1.

Further, since the fluid pressure on the side of the fourth pressure chamber 13 is low and the fluid pressure on the side of the third pressure chamber 10 is high, the second piezoelectric film 11 is convex toward the side of the fourth pressure chamber 13 (upper side in the drawing). Will be bent to become. As a result, the second electric detection signal SD2 (FIG. 11B) corresponding to the bending state of the second piezoelectric film 11 is generated.
(See (ii)) is output to the second amplification amplifier 52.

The second amplification amplifier 52 amplifies the second electric detection signal SD2 and outputs it as the second amplification detection signal ASD2 to the inverting input terminal of the differential amplifier 53. As a result, the differential amplifier 53 differentially amplifies the first amplification detection signal AS D1 and the second amplification detection signal AS D2 to generate the difference signal SDEL (see FIG. 1).
1 (b) (iii)) to the filter circuit 54.

As described above, the first detection signal SD1 (substantially the first amplification detection signal ASD1) and the second electric detection signal SD2
(Substantially, the second amplification detection signal AS D1) is differentially amplified, so that a minute change in the flow rate can be easily detected, and the in-phase noise component included in both signals can be removed. Therefore, the flow rate can be detected with higher accuracy.

Next, the filter circuit 54 removes a predetermined frequency band component in order to remove the noise component of the difference signal SDEL and outputs it to the Schmitt trigger circuit 55. The Schmitt trigger circuit is based on the output signal of the filter circuit 54. Waveform shaping is performed and a rectangular wave output signal is output to the processor 56.

As a result, the processor 56 calculates based on the rectangular wave output signal of the Schmitt trigger circuit, obtains the flow rate of the fluid, and outputs the display control signal SCD for displaying the calculation result to the monitor. ,
The flow rate as the calculation result is displayed on the monitor. C) When noise such as external vibration occurs FIG. 12 shows an operation explanatory diagram when noise such as external vibration occurs.

When noise such as external vibration is generated (typically, it is easy to understand assuming that P1 = P2), that is, the fluid pressure on the first pressure detecting hole 91a side and the second pressure detecting hole 91b side. Regardless of the fluid pressure, the first piezoelectric film 5 and the second piezoelectric film 11 are bent in the same direction due to external vibration or the like.

As a result, the first electric detection signal SD1 (see FIGS. 12B and 12I) corresponding to the bending state of the first piezoelectric film 5 is output to the first amplification amplifier 51 and the first amplification amplifier 51.
Outputs the first electric detection signal SD1 to the non-inverting input terminal of the differential amplifier 53 as the first amplification detection signal ASD1.

Similarly, the second electric detection signal SD2 (see FIG. 12 (b) (ii)) corresponding to the bending state of the second piezoelectric film 11 is output to the second amplification amplifier 52, and the second amplification amplifier 52 is output.
Outputs the second electrical detection signal SD2 to the inverting input terminal of the differential amplifier 53 as the second amplification detection signal ASD2.

As a result, the differential amplifier 53 differentially amplifies the first amplified detection signal AS D1 and the second amplified detection signal AS D2 to obtain a difference signal SDEL (see FIG. 12B (iii)). To 54. FIG. 12 (b)
As shown in (iii), the first detection signal SD1 (substantially the first amplified detection signal ASD1) and the second electrical detection signal SD2
(Substantially, the second amplified detection signal AS D1) is canceled by the differential amplification, and the deflection due to noise is detected.

Therefore, it is understood that the flow rate can be detected with high accuracy without being affected by such disturbance.
FIG. 13 shows an output detection signal waveform of the differential amplifier 123 when the fluid vibration frequency is about 300 [Hz].

In FIG. 13A, the time scale on the horizontal axis is 1
It is an output detection signal waveform when 4 [msec] per graduation. As can be seen from FIG. 13 (a), FIG. 17 (a)
The signal waveform is clear (close to the sin waveform) as compared with the case (3), and the fluid vibration period can be clearly detected.

FIG. 13B shows an output detection signal waveform when the measurement period is longer than that in FIG. 13A and the time scale on the horizontal axis is 40 [msec] per scale. As can be seen from FIG. 13B, as compared with the case of FIG. 17B, the amount of low frequency components superimposed on the signal waveform of the input waveform of about 300 [Hz] is small, and the waviness of the waveform is reduced. ing.

Therefore, an accurate flow rate can be calculated.

[0080]

According to the invention of claim 1, the first fluid pressure, which is the pressure of the fluid at the first pressure guide port, is transmitted to the first pressure chamber via the first pressure introducing pipe, It is transmitted to the fourth pressure chamber via the pressure introducing pipe and the second acoustic filter. At the same time, the second fluid pressure, which is the pressure of the fluid at the second pressure guide port, is transmitted in the second pressure chamber via the third pressure introducing pipe and the first acoustic filter, and then passes through the second pressure introducing pipe. Is transmitted to the third pressure chamber. As a result, the first piezoelectric film bends in accordance with the difference between the pressure in the first pressure chamber and the pressure in the second pressure chamber, and a predetermined potential is generated, and the second piezoelectric film becomes equal to the pressure in the third pressure chamber. Depending on the difference between the pressure in the fourth pressure chamber and the pressure in the fourth pressure chamber, a predetermined potential is generated by bending. At this time, the pressure fluctuation transmitted to the second pressure chamber is caused by the first acoustic filter to make the effective inner diameter of the third pressure introducing pipe a predetermined inner diameter smaller than the original inner diameter, thereby causing a frequency component of a predetermined frequency or more. Is suppressed, and low frequency components below a predetermined frequency are attenuated. Similarly, the pressure fluctuation transmitted to the fourth pressure chamber is attenuated by the second acoustic filter by making the effective inner diameter of the fourth pressure introducing pipe smaller by a predetermined inner diameter than the original inner diameter. Is suppressed and low-frequency components below the predetermined frequency are attenuated, the sensor output can be increased on the higher frequency side than the predetermined frequency, the waveform becomes clear, and the fluid vibration cycle can be read reliably. I can do it.

According to the second aspect of the invention, in addition to the operation of the first aspect of the invention, the first pressure damper absorbs minute fluctuations in the pressure in the second pressure chamber, and the second pressure damper is Since minute fluctuations in the pressure in the fourth pressure chamber are absorbed, noise components higher than the measurement target fluid vibration frequency can be easily removed, and stable flow rate measurement can be performed.

According to the invention of claim 3, in the invention of claim 1 or 2, since the inner diameters of the first acoustic filter and the second acoustic filter are φ0.5 [mm] or less, 250 Since attenuation of frequency components above [Hz] is suppressed and low frequency components below 250 [Hz] are attenuated, the sensor output is increased in a practical fluid vibration frequency band to read the fluid vibration cycle. It can be performed more reliably.

According to the invention of claim 4, in the invention of any one of claims 1 to 3, the inner diameters of the first acoustic filter and the second acoustic filter are φ0.5 [m
m], and the original inner diameters of the third pressure introduction pipe and the fourth pressure introduction pipe are φ2 [mm], so that the sensor output is high in the effective detection frequency range required for the fluid vibration detection sensor. The output is improved and the stability is improved, and more accurate measurement can be performed.

According to the fifth aspect of the present invention, the first pressure detection hole and the second pressure detection hole provided at predetermined symmetrical positions in the fluidic element with respect to the flow direction of the fluid in the fluidic element. The first one of the fluid vibration detection sensors according to any one of claims 1 to 4 in one of the pressure detection holes.
The pressure chamber and the fourth pressure chamber are communicated with each other, the other pressure detection hole is communicated with the second pressure chamber and the third pressure chamber of the fluid vibration detection sensor, and the first detection means is in the flexed state of the first piezoelectric film. And outputs a first detection signal corresponding to the flow rate calculation means to the flow rate calculation means. The second detection means outputs a second detection signal corresponding to the bending state of the second piezoelectric film to the flow rate calculation means. Since the flow rate of the fluid is calculated based on the signal and the second detection signal,
Since the flow rate is calculated using a large sensor output, accurate flow rate measurement with less error can be performed.

According to the invention of claim 6, in addition to the operation of the invention of claim 5, the differential means of the flow rate calculating means is:
Since the difference signal corresponding to the difference between the first detection signal and the second detection signal is output to the flow rate detection means, and the flow rate detection means calculates the flow rate of the fluid based on the difference signal, the common-mode noise component caused by vibration or the like is generated. Can be easily removed to perform more accurate flow rate measurement.

[Brief description of drawings]

FIG. 1 is a sectional view of a fluid vibration detection sensor.

FIG. 2 is a schematic configuration diagram when a fluid vibration detection sensor is connected to a fluidic element.

FIG. 3 is a schematic block diagram of a flow rate detection display device.

FIG. 4 is an explanatory diagram of an equivalent electric circuit corresponding to the acoustic circuit.

FIG. 5 is a single line diagram showing the structure of the fluid vibration detection sensor by expressing the pressure introducing pipe as a single line.

FIG. 6 is a diagram showing each element shown in FIG. 5 by an equivalent electric circuit.

FIG. 7 is a diagram illustrating the inside of a broken line frame of FIG. 6 by blocking.

FIG. 8 is a diagram illustrating a potential difference between both output terminals of the piezoelectric film equivalent portion Z.

FIG. 9 is a diagram illustrating a relationship between a potential difference between both output terminals of the piezoelectric film and an output signal frequency.

FIG. 10 is an explanatory diagram of an operation when P1> P2.

FIG. 11 is an operation explanatory diagram in the case of P1 <P2.

FIG. 12 is an operation explanatory diagram when noise such as external vibration occurs.

FIG. 13 is an explanatory diagram of an output detection signal waveform of the differential amplifier according to the embodiment when the fluid vibration frequency is set to about 300 [Hz].

FIG. 14 is a partial cross-sectional perspective view of a conventional fluidic flow sensor when the conventional fluidic flow sensor is configured as a flow rate detection device.

FIG. 15 is a schematic configuration diagram of a fluid vibration detection sensor of a first conventional example.

16 is a schematic configuration diagram of a detection circuit corresponding to the fluid vibration detection sensor of FIG.

FIG. 17 is an explanatory diagram of an output detection signal waveform of the conventional differential amplifier when the fluid vibration frequency is about 300 [Hz].

FIG. 18 is a schematic configuration diagram of a fluid vibration detection sensor of a second conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fluid vibration detection sensor 2 1st pressure introduction pipe 3 1st pressure introduction port 4 1st pressure chamber 5 1st piezoelectric film 6 2nd pressure introduction pipe 7 2nd pressure introduction port 8 2nd pressure chamber 8A 1st auxiliary pressure chamber 8B 2nd sub pressure chamber 9 3rd pressure introduction pipe 10 3rd pressure chamber 11 2nd piezoelectric film 12 4th pressure introduction pipe 13 4th pressure chamber 13A 3rd sub pressure chamber 13B 4th sub pressure chamber 14 1st acoustic filter 15 Second Acoustic Filter 20 First Pressure Damper 21 Second Pressure Damper 50 Flow Rate Detection Display Device 51 First Amplifier 52 Second Amplifier 53 Differential Amplifier 54 Filter Circuit 55 Schmitt Trigger Circuit 56 Processor 57 Monitor ASD1 First Amplification Detection Signal ASD2 Second amplification detection signal SCD Display control signal SD1 First electric detection signal SD2 Second electric detection signal SDEL Difference signal

Claims (6)

[Claims] 1. A fluid vibration detection sensor for detecting fluidic vibration of a fluid based on a first fluid pressure at a first pressure guide port and a second fluid pressure at a second pressure guide port, wherein a first pressure introducing pipe is provided. A first pressure chamber communicating with the first pressure guide port via a first pressure chamber and a first pressure chamber separated from the first pressure chamber via a third pressure introducing pipe communicating with the second pressure guide port. A second pressure chamber, a third pressure chamber communicating with the second pressure guide port via a second pressure introducing pipe, a third pressure chamber separated from the third pressure chamber via a second piezoelectric film, and a fourth pressure chamber A fourth pressure chamber communicating with the first pressure introducing port via a pressure introducing pipe, and an effective inner diameter of the third pressure introducing pipe provided on the second pressure chamber side of the third pressure introducing pipe. A first acoustic filter having a predetermined inner diameter smaller than the original inner diameter, and a fourth acoustic chamber provided on the fourth pressure chamber side of the fourth pressure introducing pipe. And a second acoustic filter having an effective inner diameter of the fourth pressure introducing pipe that is a predetermined inner diameter smaller than the original inner diameter, and a fluid vibration detecting sensor. 2. The fluid vibration detection sensor according to claim 1, wherein the second pressure chamber is separated into a first sub pressure chamber and a second sub pressure chamber by a first pressure damper for absorbing a minute fluctuation in pressure. The fourth vibration chamber is separated into a third auxiliary pressure chamber and a fourth auxiliary pressure chamber by a second pressure damper for absorbing a minute change in pressure, and a fluid vibration detecting sensor. 3. The fluid vibration detection sensor according to claim 1 or 2, wherein the inner diameters of the first acoustic filter and the second acoustic filter are set to φ0.5 [mm] or less. Vibration detection sensor. 4. The fluid vibration detection sensor according to claim 1, wherein inner diameters of the first acoustic filter and the second acoustic filter are φ0.5 [mm], and 2. The fluid vibration detecting sensor, wherein the original inner diameters of the second pressure introducing pipe and the fourth pressure introducing pipe are φ2 [mm]. 5. A flow rate detection device comprising the fluid vibration detection sensor according to claim 1, wherein the flow rate detection device detects a flow rate of a fluid based on fluid vibration in a fluidic element, The first pressure is applied to one of pressure detection holes of a first pressure detection hole and a second pressure detection hole provided at a predetermined symmetrical position in the fluidic element with respect to the flow direction of the fluid in the fluidic element. Chamber and the fourth pressure chamber are communicated with each other, the second pressure chamber and the third pressure chamber are communicated with the other pressure detection hole, and a first detection signal corresponding to the bending state of the first piezoelectric film is transmitted. A first detection means for outputting; a second detection means for outputting a second detection signal according to a bending state of the second piezoelectric film; and a flow rate of the fluid based on the first detection signal and the second detection signal. Flow rate calculation means to calculate Flow rate detecting device, characterized in that was e. 6. The flow rate detection device according to claim 5, wherein the flow rate calculation means outputs a difference signal corresponding to a difference between the first detection signal and the second detection signal, and the difference signal. And a flow rate detecting means for calculating the flow rate of the fluid based on the above.