JPH08313321A - Coriolis mass flow meter - Google Patents

Abstract

PURPOSE: To provide a Coriolis mass flow meter which is excellent in vibration noise resistance, in vibration proof, and is highly stable by exciting measuring tubes having same shapes both ends of which are fixed and which are arranged in parallel mutually when fluid to be measured flows in the measuring tube in mutually reverse directions, and measuring vibration amplitude in the central portion of the tube. CONSTITUTION: Measuring tubes 11, 12 having same shapes are fixed 2 at both end 13 to 16 thereof, are arranged mutually in parallel, one end thereof are connected by a communicating tube 17. Fluid to be measured (f) caused to flow in from one end of the measuring tube 11 flows in the measuring tubes 11, 12 mutually in reverse directions. When the fluid flow in the measuring tube 11, 12, if the measuring tubes 11, 12 'are excited at the vibration mode of the lowest resonance frequency by vibration exciters 18, 19 connected to the central portions 21, 22 of the measuring tubes 11, 12, the measuring tubes 11, 12 vibrate in a same phase in a vertical direction, and Coriolis force acts as the fluid (f) flows so that a vibration mode in which a fexural vibration becomes symmetrical in a upstream portion and in a downstream portion against the central portions 21, 22 is generated. When the amplitude of this vibration is measured by vibration detection sensors 23 to 26, the a mass flow rate can be measured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly stable Coriolis mass flowmeter which is resistant to external vibration noise and has excellent vibration resistance.

[0002]

2. Description of the Related Art FIG. 8 is a structural explanatory view of a conventional parallel double U-tube type Coriolis mass flowmeter which is generally used in the past. For example, US Pat. No. 4,491,025, title of the invention. "PARALLEL PATH CORIOLIS MASS FLOW RATE METE
R ", filed Nov. 3, 1982, patented Jan. 1, 1985. 9 and 10 are operation explanatory diagrams of FIG. 8.

In the figure, reference numeral 1 is a U-shaped measuring tube having both ends attached to a fixed body 2, which branches into two at the inlet of the flowmeter and joins again at the outlet. Therefore, the measurement fluid f flows in from the flow meter inlet and flows out from the flow meter outlet.

Reference numeral 2 is a fixed body for mounting the measuring pipe 1 on the pipe line A. Reference numeral 3 denotes an exciter provided in the central portion of the U-shaped measuring tube 1, which vibrates the measuring tube 1 in a direction perpendicular to the plane in which the U-shaped measuring tube 1 is present. Reference numerals 4 and 5 are vibration detection sensors respectively provided between the fixed end and the central portion of the measuring tube 1.

In the above construction, when the vibration is applied from the vibrator 3 installed in the central portion while the measuring fluid is flowing in the measuring pipe 1, as shown in FIG. 9, the central portions are indicated by M1 and M3. The measurement tube 1 vibrates in a first-order mode shape in which is an antinode of vibration.

Considering these vibrations on the upstream side and the downstream side of the measuring pipe 1, it can be considered that they are rotating around the fixed end, respectively. Therefore, the angular velocity of the vibration exciter 3 in the vibration direction " Letting “ω” be the flow velocity of the measured fluid be “V” (the symbol surrounded by “” represents a vector quantity), the Coriolis force of Fc = −2 m “ω” × “V” works.

Due to this Coriolis force, as shown in FIG. 10, vibration modes M4 and M6 in which the flexural vibrations are symmetrical in the upstream portion and the downstream portion with respect to the center point of the measuring tube 1 are generated. In addition, actually, the pipe 1 vibrates in a form in which these two types of vibration patterns are superimposed. The mass flow rate Q can be known by measuring this deformation with the vibration detecting means (usually a displacement sensor) 4, 5.

Usually, the vibration amplitude in the vibration detecting means 4 and 5 and the phase difference in the vibration detecting means 4 and 5 are obtained, correction is made by the vibration frequency and temperature, and the mass flow rate is obtained.

[0009]

However, in such an apparatus, the vibration mode as shown in FIGS. 9 and 10 was used. However, in such a parallel double tube structure, the measuring tube fixing portion is not provided. As shown in FIG. 11, it is not a complete fixed end but a vibration node of the tuning fork structure. Therefore, as shown in FIG.
There is a vibration mode with the lowest resonance frequency.

In the Coriolis mass flowmeter for detecting the vibration of the measuring tube 1, when external vibration noise having the same vibration frequency component as the natural frequency of the measuring tube 1 is applied, the output is affected and an error occurs. (It is hardly affected by vibration noise other than natural frequency).

Further, in the environment of use in a plant or the like, 10
While there are many low-frequency noises of 0 Hz or less, there are few high-frequency noises, and the size is also small.
In addition to the vibration modes essential for flow rate measurement as shown in FIGS. 9 and 10, unnecessary vibration modes as shown in FIG.
Existence at a low resonance frequency is a major drawback in terms of vibration resistance.

The present invention solves this problem. An object of the present invention is to provide a highly stable Coriolis mass flowmeter that is resistant to external vibration noise and has excellent vibration resistance.

[0013]

In order to achieve this object, the present invention provides: (1) Flowing a measuring fluid in the vibrating measuring tubes of the measuring tubes arranged in parallel with each other, and the flow of the measuring fluid and the measuring tube. The Coriolis mass flowmeter that deforms the measuring pipe by the Coriolis force generated by the angular vibration of the, and measures the vibration change with the vibration detection sensor to obtain the mass flow rate and density has the same shape and both ends are fixed and parallel to each other. Two measuring pipes arranged so that the measuring fluids flowing in the pipes flow in mutually opposite directions, one end of which is connected to the central portion of each of the measuring pipes and the other end of which is connected to the main body of the Coriolis mass flowmeter. In the above measuring tube, the two fixed measuring tubes are excited in the vibration mode in which the resonance frequency of the measuring tube is the lowest, and the fixed ends at both ends become nodes of vibration and the vicinity of the central part is the only antinode of vibration. Phase of A Coriolis mass flowmeter, comprising a vibrating device that excites in a vibration mode that vibrates in the same phase in the same direction perpendicular to the plane in which the respective measuring tubes are present in mutual relation.

(2) A measuring fluid is caused to flow in the vibrating measuring tubes arranged in parallel with each other, and the measuring tube is deformed and vibrated by the Coriolis force generated by the flow of the measuring fluid and the angular vibration of the measuring tube to cause the vibration. In a Coriolis mass flowmeter that measures changes with a vibration detection sensor to determine mass flow rate and density, both ends of the Coriolis mass flowmeter are fixed and arranged parallel to each other, and the measurement fluids flowing in the pipe are configured to flow in opposite directions. Each of the two measuring tubes has one end connected between the fixed end and the central part of one of the measuring tubes and the other end connected between the fixed end and the central part of the other measuring tube. So that the fixed ends at both ends and the vicinity of the central part become nodes of vibration, and the upstream and downstream sides vibrate in opposite directions with the node at the central part as a boundary in a direction perpendicular to the plane in which the measuring tube exists. Excited in various vibration modes The mutual relationship between the two measuring pipes is such that the two vibration measuring pipes are excited in a vibration mode such that the two measuring pipes vibrate in symmetrical directions about a plane equidistant from the two planes in which the respective measuring pipes are present. A Coriolis mass flowmeter comprising a shaker.

[0015]

In the above structure, when the measuring fluid is flown into the measuring tube and the vibrator is driven, the Coriolis force acts. By measuring the amplitude of vibration proportional to this Coriolis force, the mass flow rate can be measured. . Hereinafter, detailed description will be given based on examples.

[0016]

【Example】

FIG. 1 is an explanatory view of the essential structure of an embodiment of the present invention, and FIGS. 3 and 4 are operation explanatory views of FIG. In the figure, the same symbols as those in FIG. 8 indicate the same functions. Less than,
Only parts different from FIG. 8 will be described. Reference numerals 11 and 12 denote two measuring tubes which have the same shape and whose both ends 13, 14, 15, 16 are fixed to the fixed body 2 and which are arranged in parallel with each other. In this case, it has a U shape.

Reference numeral 17 connects one end of one measurement pipe 11 of the measurement pipes and one end of the other measurement pipe 12 so that one measurement pipe 1
It is a communication tube that allows a measurement fluid to flow in from the other end of the first measurement tube 1 and to flow out from the other end of the other measurement tube 12.

Reference numerals 18 and 19 denote measuring tubes 11 and 1, respectively.
The vibration exciter has one end connected to the central portions 11 and 12 of 2 and the other end connected to a Coriolis mass flowmeter main body (not shown). In each of the measuring tubes 11 and 12, the vibrators 18 and 19 have fixed ends 13, 14, 15 and 16 at both ends serving as nodes of vibration, and the central portions 21 and 22 serve as antinodes of vibration. Further, the measurement tubes 11 and 12 are excited in the vibration mode having the lowest resonance frequency, and in the mutual relationship between the two parallel measurement tubes 11 and 12, the measurement tubes 11 and 12 are perpendicular to the plane in which they exist. It is excited in a vibration mode that vibrates in the same direction and in the same phase.

Reference numerals 23, 24, 25, and 26 are vibration detection sensors arranged between the fixed ends 13, 14, 15, 16 of the measuring pipe and the centers 21, 22 of the measuring pipe. In this case, a coil sensor is used to measure the absolute positions of the measuring tubes 11 and 12 with the Coriolis mass flowmeter main body as a reference.

FIG. 2 shows a general example of a signal processing system. Sensor unit 31, preamplifier circuit unit 32, time (difference) / phase (difference)
Detection circuit unit 33, flow rate calculation circuit unit 34, vibration circuit unit 35
Consists of

In the above structure, the measuring tubes 11 and 12
Is controlled by the vibrators 18 and 19 to generate M11, M12,
Vibration as shown by M13 is performed. At this time, when the fluid flows in the measuring pipe, Coriolis force is generated, and M14 and M1 in FIG.
5, a vibration mode as shown by M16 is generated.

Actually, the measuring tubes 11 and 12 vibrate in a form in which the two types of vibration patterns shown in FIGS. 3 and 4 are superimposed.
Measuring tube 1 with vibration detection sensors 23, 24, 25, 26
Absolute vibrations of 1 and 12 are required. The vibration amplitude due to the excitation vibration is A, and the vibration amplitude due to the Coriolis vibration is C (C = k
Assuming that Q and Q are mass flow rates (generally A >> C), the output of the sensor coil is as follows.

Coil 23: S ₂₃ = + Asin θ−Ccos θ = A′sin (θ−δ) (1) Coil 24: S ₂₄ = + A sin θ + C cos θ = A′sin (θ + δ) (2) Coil 25: S ₂₅ = + Asinθ + Ccosθ = A'sin (θ + δ) (3) Coil 26: S ₂₆ = + Asinθ-Ccosθ = A'sin (θ-δ) (4) However, A '= (A ² + C ² ) ^{1 / 2} , δ = atan (C / A) ≒
k′Q, k, k ′ are constants The phase difference δ is calculated from the formulas (1) to (4), and the mass flow rate is calculated.

The signal processing circuit of FIG. 2 amplifies the sensor signal in the preamplifier circuit section 32, and in the time (difference) / phase (difference) detection circuit section 33, the time difference or phase (difference) between the two sensor outputs.
Is detected. Further, the mass flow rate is obtained by correcting the vibration frequency, temperature, density, amplitude, etc. in the flow rate calculation circuit section 34. In addition to this, a drive signal for vibrating the measuring tubes 11 and 12 is generated by the vibrating circuit unit 35.

As a result, (1) the measuring tubes 11 and 1 are set to a frequency lower than the resonance frequency of the vibration mode (excitation vibration mode and vibration mode generated by Coriolis force) which is directly related to the operation of the Coriolis flowmeter.
There is no resonant frequency of 2. That is, since the extra vibration mode does not exist in the low resonance frequency region, it is less likely to be affected by the vibration noise from the outside.

Specifically, although the value differs depending on the shape and length of the measuring tube, one of the experimental examples that the applicant experimented with is basically directly related as in the following example. Even if the resonance frequency of the vibration mode does not change (in this case 80H
z), the minimum resonance frequency can be increased by shortening the tube length (in this case, 60 to 80 Hz), and the influence of external vibration noise can be reduced.

In the conventional example of two parallel U-shapes, if the extra mode is 45 Hz, the excitation mode is 60 Hz, and the Coriolis mode is 170 Hz, the tube length is shortened in order to reduce the influence of external vibration noise. If the resonance frequency of the extra mode is increased by doing so, the extra mode: 60Hz, the excitation mode: 80Hz, the Coriolis mode: 200Hz, and the resonance frequency of the excitation mode and the resonance frequency of the Coriolis mode also increase all at once.

In the example of this proposal, if the extra mode is 80 Hz, the excitation mode is 60 Hz, and the Coriolis mode is 200 Hz, the tube length is shortened in order to reduce the influence of external vibration noise. If you increase the resonance frequency of this mode, the extra mode is 100Hz, the excitation mode is 80Hz, the Coriolis mode is 230Hz, and even if the lowest resonance frequency on the excitation mode and Coriolis mode side is 80Hz, which is the same as the conventional example, it becomes extra. The resonance frequency of various modes can be set to 100 Hz, and the influence of external vibration noise can be reduced.

(2) Further, since the measuring pipes 11 and 12 are communicated with each other by the communication pipe 17, there is no branching or merging in the fluid flow path, so that fluid is clogged at the branching or merging portion, or pressure loss occurs. There is no worry of increasing. Stable and low-pressure loss can be measured even with high-viscosity fluids and foods and other fluids that easily perish and clog.

FIG. 5 is an explanatory view of a main part configuration of another embodiment of the present invention, and FIGS. 6 and 7 are operation explanatory views of FIG. 41,
Reference numeral 42 denotes two measuring tubes that have the same shape and both ends 43, 44, 45, 46 are fixed to the fixed body 2 and are arranged in parallel with each other. In this case, it has a U shape.

Reference numeral 47 connects one end of one measurement pipe 41 of the measurement pipes and one end of the other measurement pipe 42 to connect one measurement pipe 4
It is a communication tube that allows the measurement fluid to flow in from the other end of the one and to flow out from the other end of the other measurement tube 42.

Reference numerals 48 and 49 denote fixed ends 43 and 45 of one of the measuring tubes 41 and 42 arranged in parallel with each other.
And the central portion 51, one end of which is connected to the other measuring tube 42
The other end is connected between the fixed ends 44, 46 and the central portion 52 of the vibrator.

The vibrators 48, 49 are connected to the individual measuring tubes 41,
In 42, the fixed ends 43, 44, 45, 46 at both ends and the central portions 51, 52 are nodes of vibration, and the central portion is in a direction perpendicular to the plane in which the measuring tubes 41, 42 exist. Excited so that the upstream side and the downstream side oscillate in opposite directions with the node 51, 52 as a boundary, and two parallel measuring tubes 41, 42
In the mutual relationship, the two vibration measuring tubes are excited in a vibration mode such that the two vibration measuring tubes vibrate in symmetrical directions about a plane equidistant from the two planes where the respective measuring tubes 41 and 42 exist.

53, 54, 55 and 56 are fixed ends 43, 44, 45 and 46 of the measuring pipe and central portions 51 and 52 of the measuring pipe.
It is a vibration detection sensor arranged between. in this case,
A coil sensor is used to measure the absolute position of the measuring tubes 41, 42 relative to the Coriolis mass flowmeter body (not shown).

In the above structure, the measuring tubes 41, 42
Is controlled by the vibrators 48, 49 to generate M21, M22,
Vibration as shown in M23 is performed. At this time, when the fluid flows in the measuring tube, Coriolis force is generated, and M24 and M2 in FIG.
5, a vibration mode such as M26 is generated.

Actually, the exciting vibration (M21, M2
2, M23) and vibration due to Coriolis force (M24, M2
5, M26), the measuring tubes 41 and 42 vibrate in a form in which two kinds of vibration patterns are superposed. When the vibration amplitude due to the excitation vibration is A and the vibration amplitude due to the Coriolis vibration is C (C = kQ, Q is a mass flow rate) (generally A >> C), the outputs of the sensor coils 53, 54, 55, 56 are It looks like this:

Coil 53: S ₅₃ = + Asinθ-Ccosθ = A'sin (θ-δ) (5) Coil 54: S ₅₄ = -Asinθ-Ccosθ = -A'sin (θ + δ) (6) Coil 55 _{: S 55 = -Asinθ-Ccosθ =} -A'sin (θ + δ) ... (7) coil _{56: S 56 = + Asinθ-} Ccosθ = A'sin (θ-δ) ...... (8) where, A '= (A ² + C ² ) ^1/2 , δ = atan (C / A) ≈
k'Q and k, k 'are constants. The phase difference δ is obtained from the equations (5) to (8), and the mass flow rate is obtained. Normally, the outputs of the coils 54 and 55 are inverted to facilitate the determination of the phase difference δ.

As a result, (1) the measuring tubes 41, 4 are set to frequencies lower than the resonance frequency of the vibration mode (excitation vibration mode and vibration mode generated by Coriolis force) which is directly related to the operation of the Coriolis flowmeter.
There is no resonant frequency of 2. That is, since the extra vibration mode does not exist in the low resonance frequency region, it is less likely to be affected by the vibration noise from the outside.

Specifically, although the value varies depending on the shape and length of the measuring tube, one of the experimental examples that the applicant experimented with is basically directly related as in the following example. Even if the resonance frequency of the vibration mode does not change (in this case 80H
z), the minimum resonance frequency can be increased by shortening the tube length (in this case, 60 to 80 Hz), and the influence of external vibration noise can be reduced.

In an example of the conventional two parallel U-shapes, if the extra mode is 45 Hz, the excitation mode is 60 Hz, and the Coriolis mode is 170 Hz, the tube length is shortened in order to reduce the influence of external vibration noise. If the resonance frequency of the extra mode is increased by doing so, the extra mode: 60Hz, the excitation mode: 80Hz, the Coriolis mode: 200Hz, and the resonance frequency of the excitation mode and the resonance frequency of the Coriolis mode also increase all at once.

In the example of this proposal, if the extra mode is 80 Hz, the excitation mode is 200 Hz, and the Coriolis mode is 60 Hz, in order to reduce the influence of the external vibration noise, the tube length is shortened to make it unnecessary. If you increase the resonance frequency of this mode, the extra mode becomes 100Hz, the excitation mode: 230Hz, the Coriolis mode: 80Hz, and even if the lowest resonance frequency of the excitation mode and the Coriolis mode side is 80Hz, which is the same as the conventional example, it becomes extra. The resonance frequency of various modes can be set to 100 Hz, and the influence of external vibration noise can be reduced.

(2) Excited vibration is measured by the measuring tube 4 as shown in FIG.
Since the first and second 42 and 42 have symmetrical movements, moments in opposite directions are applied to the fixed ends 43 and 44 and 45 and 46 of FIG. 5, so that vibrations cancel each other out, and vibration isolation can be easily configured.

For this reason, the Q value of the vibration system becomes high and the vibration noise from the outside becomes strong, and a small energy is applied to the vibration exciter 4.
It becomes possible to excite just by adding it to 8,49. In addition, changes in the zero point and span that occur when the vibration of itself leaks to the outside can be reduced.

The vibration due to the generated Coriolis force is
The movement is not symmetrical as in FIG. But in general,
Since the vibration amplitude due to the Coriolis force is as small as several tens to several hundreds even at the full-scale flow rate as compared with the excitation vibration amplitude, the above advantages can be sufficiently exhibited if the symmetry of the excitation vibration is maintained.

(3) In addition, since the measuring pipes 41 and 42 are communicated with each other by the communication pipe 47, there is no branching or merging in the fluid flow path, so that the fluid is clogged at the branching or merging portion. There is no concern that pressure loss will increase. Stable and low-pressure loss can be measured even with high-viscosity fluids and foods and other fluids that easily perish and clog.

In the above embodiment, the measuring tube 1
Although it has been described that the communication pipes 1 and 12 are communicated with each other by the communication pipe 17, the communication pipes 17 and 12 may be communicated with each other substantially outside, for example. In short, it suffices that the measuring fluids in the measuring pipes 11 and 12 flow in mutually opposite directions.

In the above-described embodiment, the vibration detection sensors 23, 24, 25 and 26 are electromagnetic coils (speed sensors). However, the present invention is not limited to this. Alternatively, a stress sensor or a strain sensor may be used. In short, what is necessary is just to be able to detect the vibration of the measuring pipes 11, 12, 41, 42.

In the above-described embodiment, the method of detecting the time (difference) or the phase (difference) is shown in the signal processing explanatory diagram of FIG. 2, but the method is not limited to this.
For example, a method of separating the excitation component and the Coriolis component by synchronous rectification and integration and obtaining the mass flow rate from the ratio may be used.
In short, any method capable of signal processing may be used.

[0050]

As described above, according to the present invention, (1) a measuring fluid is caused to flow in an oscillating measuring tube of measuring tubes arranged in parallel with each other, and Coriolis caused by the flow of the measuring fluid and angular vibration of the measuring tube. A Coriolis mass flowmeter that uses a force to deform and vibrate the measurement pipe and measure the change in vibration with a vibration detection sensor to determine the mass flow rate and density. Two measuring tubes configured so that fluids flow in mutually opposite directions, one end of which is connected to the central portion of each measuring tube and the other end of which is connected to the Coriolis mass flowmeter main body The fixed end serves as a node of vibration, and the vicinity of the central portion serves as the only antinode of vibration, and the two parallel measurement tubes are excited by the vibration mode in which the resonance frequency of the measurement tube is the lowest. A Coriolis mass flowmeter, comprising: a vibration exciter that is excited in a vibration mode that vibrates in the same phase in the same direction perpendicular to the plane in which the measurement tube exists.

(2) A measuring fluid is caused to flow in the vibrating measuring tubes arranged in parallel with each other, and the measuring tube is deformed and vibrated by the Coriolis force generated by the flow of the measuring fluid and the angular vibration of the measuring tube to cause the vibration. In a Coriolis mass flowmeter that measures changes with a vibration detection sensor to determine mass flow rate and density, both ends of the Coriolis mass flowmeter are fixed and arranged parallel to each other, and the measurement fluids flowing in the pipe are configured to flow in opposite directions. Each of the two measuring tubes has one end connected between the fixed end and the central part of one of the measuring tubes and the other end connected between the fixed end and the central part of the other measuring tube. So that the fixed ends at both ends and the vicinity of the central part become nodes of vibration, and the upstream and downstream sides vibrate in opposite directions with the node at the central part as a boundary in a direction perpendicular to the plane in which the measuring tube exists. Excited in various vibration modes The mutual relationship between the two measuring pipes is such that the two vibration measuring pipes are excited in a vibration mode such that the two measuring pipes vibrate in symmetrical directions about a plane equidistant from the two planes in which the respective measuring pipes are present. A Coriolis mass flowmeter, comprising a shaker. Was configured.

As a result, according to the first aspect, the resonance frequency of the measuring tube becomes lower than the resonance frequency of the vibration mode (excitation vibration mode and vibration mode generated by Coriolis force) which is directly related to the operation of the Coriolis flowmeter. Does not exist. Since the extra vibration mode does not exist in the low resonance frequency region, it is less likely to be affected by vibration noise from the outside.

Further, according to the second aspect, since the excited vibrations are symmetrically moved by the two measuring tubes, moments in opposite directions are applied to the fixed ends. Therefore, the vibrations cancel each other out, and the vibration isolation is achieved. You can easily.

For this reason, the Q value of the vibration system becomes high and the vibration noise becomes strong against the external vibration noise, and the vibration can be excited only by applying a small energy to the vibration exciter. Furthermore, changes in the zero point and span that occur when the vibration of the user leaks to the outside can be reduced.

The vibration due to the generated Coriolis force is
Not a symmetrical movement. However, in general, the vibration amplitude due to Coriolis force is smaller than the excitation vibration amplitude by several tens to several hundreds even at full scale flow rate, so if the symmetry of the excitation vibration is maintained, the above advantages are sufficient. Can be demonstrated.

Therefore, according to the present invention, it is possible to realize a highly stable Coriolis mass flowmeter which is resistant to vibration noise from the outside and is excellent in vibration resistance.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a main part configuration of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of signal processing of FIG.

FIG. 3 is an operation explanatory diagram of FIG. 1.

FIG. 4 is an operation explanatory diagram of FIG. 1;

FIG. 5 is an explanatory diagram of a main part configuration of another embodiment of the present invention.

FIG. 6 is an operation explanatory diagram of FIG. 5;

FIG. 7 is an operation explanatory diagram of FIG. 5;

FIG. 8 is an explanatory diagram of a configuration of a conventional example that is generally used in the past.

9 is an operation explanatory diagram of FIG. 8;

10 is an explanatory diagram of the operation of FIG.

11 is an explanatory diagram of the operation of FIG.

12 is an explanatory diagram of the operation of FIG.

13 is an explanatory diagram of the operation of FIG.

[Explanation of symbols]

 11 Measuring tube 12 Measuring tube 13 Fixed end 14 Fixed end 15 Fixed end 16 Fixed end 17 Communication pipe 18 Exciter 19 Exciter 21 Central part 22 Central part 23 Vibration detection sensor 24 Vibration detection sensor 25 Vibration detection sensor 26 Vibration detection Sensor 31 Sensor part 32 Preamplifier circuit part 33 Time (difference) / phase (difference) detection circuit part 34 Flow rate calculation circuit part 35 Excitation circuit part 41 Measuring tube 42 Measuring tube 43 Fixed end 44 Fixed end 45 Fixed end 46 Fixed End 47 Communication pipe 48 Exciter 49 Exciter 51 Central part 52 Central part 53 Vibration detection sensor 54 Vibration detection sensor 55 Vibration detection sensor 56 Vibration detection sensor

Claims (2)

[Claims] 1. A change in vibration is caused by causing a measuring fluid to flow in a vibrating measuring tube arranged in parallel with each other, and causing the measuring tube to deform and vibrate due to Coriolis force generated by the flow of the measuring fluid and angular vibration of the measuring tube. In a Coriolis mass flowmeter for measuring mass flow rate and density by measuring with a vibration sensor, both ends of the Coriolis mass flowmeter are fixed and arranged parallel to each other, and the measurement fluids flowing in the pipe are configured to flow in opposite directions. One measuring tube and one end is connected to the central part of each measuring tube and the other end is connected to the main body of the Coriolis mass flowmeter. In each measuring tube, the fixed ends at both ends are vibration nodes and the vicinity of the central part is unique. Of the two parallel measuring tubes which are excited in the vibration mode having the lowest resonance frequency of the measuring tube and are parallel to each other in the same vertical direction to the plane in which each measuring tube exists. Coriolis mass flowmeter, characterized by comprising a vibrator to excite a vibration mode in which vibrate in the same phase direction. 2. A measuring fluid is caused to flow through the vibrating measuring tubes arranged in parallel with each other, and the measuring tube is deformed and vibrated by the Coriolis force generated by the flow of the measuring fluid and the angular vibration of the measuring tube to change the vibration. In a Coriolis mass flowmeter for measuring mass flow rate and density by measuring with a vibration sensor, both ends of the Coriolis mass flowmeter are fixed and arranged parallel to each other, and the measurement fluids flowing in the pipe are configured to flow in opposite directions. One of the measuring tubes is connected between the fixed end and the central part of one of the measuring tubes, and the other end is connected between the fixed end and the central part of the other measuring tube. The fixed ends of both ends and the vicinity of the central part become nodes of vibration, and the upstream side and the downstream side vibrate in opposite directions across the node of the central part in a direction perpendicular to the plane in which the measuring tube exists. Excited in vibration mode and parallel In the mutual relation of the two measuring tubes, a vibration exciter that excites in a vibration mode such that the two vibrating measuring tubes vibrate in symmetrical directions about a plane equidistant from the two planes in which the respective measuring tubes are present. A Coriolis mass flowmeter characterized by comprising: