JP4000514B2 - Coriolis mass flow meter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a Coriolis mass flow meter with improved stability, accuracy, and vibration resistance.
[0002]
[Prior art]
FIG. 5 is an explanatory diagram of a configuration of a conventional example that is generally used conventionally, and is disclosed in, for example, Japanese Patent Laid-Open No. 6-109512.
[0003]
In the figure, reference numeral 1 denotes a vibration tube having both ends attached to a flange 2.
The flange 2 is for attaching the vibration tube 1 to the pipe line.
Reference numeral 3 denotes an exciter provided at the center of the vibration tube 1.
[0004]
Reference numerals 4 and 5 denote vibration detection sensors respectively provided on both sides of the vibration tube 1.
Reference numeral 6 denotes a housing to which both ends of the vibration tube 1 are fixed.
[0005]
In the above configuration, the measurement fluid is caused to flow through the vibration tube 1 and the exciter 3 is driven.
Assuming that the angular velocity “ω” in the vibration direction of the exciter 3 and the flow velocity “V” of the measurement fluid (hereinafter, the symbol surrounded by “” represents a vector quantity)
[0006]
Fc = -2m “ω” × “V”
The Coriolis force works. If the vibration proportional to the Coriolis force is measured, the mass flow rate can be obtained.
[0007]
FIG. 6 is a diagram for explaining the configuration of a conventional example that is generally used conventionally, and is disclosed in, for example, Japanese Patent Laid-Open No. 11-108723.
[0008]
11 is a vibration tube that makes a single vibration or a circular motion on a circumferential line of a predetermined distance from each point of the reference axis 14 with a straight line connecting the upstream fixed end 12 and the downstream fixed end 13 as a reference axis 14. It is.
[0009]
Reference numeral 15 denotes an exciter provided at the center of the vibration tube 11.
Reference numerals 16 and 17 denote vibration detection sensors provided on both sides of the vibration tube 11, respectively.
[0010]
In the above configuration, FIG. 7, b-b sectional view of the vibration tube 11 in FIG. 6, FIG. 8 a-a, c-c sectional view of the vibration tube 11 in FIG. 6, the vibration of FIG. 9 is vibration tube 11 It is a perspective view which shows the mode.
7 and 8 , the vibration tube 11 is in the vicinity of the position A in the non-excited state.
[0011]
When in the excited state, the center of the vibration tube 11 moves on a circumference away from the reference axis 14 by a radius R (x).
At the position of the cross section bb, on the circumference away from the reference axis 14 by the radius R (b), at the position of the cross section aa or cc, the radius R (a) or R (c) from the reference axis 14 is obtained. It vibrates on a separated circle in the order of A → B → A → C → A → B → (repeated thereafter).
[0012]
In Figure 9, A, B, C are 7, matching the respective positions of the vibration tube 11 in FIG. 8.
Reference numerals 12 and 13 denote fixed ends, and reference numeral 14 denotes a reference axis.
[0013]
Since the vibration tube 11 vibrates only within a circumferential surface that is equidistant from the reference axis 14, the length of the vibration tube 11 does not change regardless of the position of the vibration tube 11.
[0014]
FIG. 10 is an explanatory diagram of the main part of an embodiment of an application related to the prior application of the present applicant, and is shown in Japanese Patent Application No. 2001383340.
Figure 11 is a side view of FIG. 10, FIG. 12 d-d sectional view of FIG. 11, FIG. 13 e-e sectional view of FIG. 11, FIGS. 14 to 17 are timing charts for explaining the operation of FIG. 10.
[0015]
In the figure, 20 is a vibration tube through which a measurement fluid flows, 2 is a flange for connecting to an external pipe, 6 is a housing forming a flow meter, 12 and 13 are fixed ends at both ends of the vibration tube, and 14 are both fixed. This is a reference axis connecting the parts.
[0016]
21 and 22 are exciters for exciting the vibration tube 20 and have a structure in which a force can be applied to the vibration tube 20 in the Y direction in the figure.
21 and 22 are equal in magnitude and direction, and apply antiphase forces.
[0017]
In this case, as shown in FIG. 12 , the exciters 21 and 22 are composed of magnets 211 and 221 and coils 212 and 222, and the magnets 211 and 221 are fixed to the vibration tube 20, and the coil 212 is disposed at an opposing position. , 222 are fixed to a non-vibrating non-vibrating place such as the housing 6.
[0018]
In practice, the magnets 211 and 221 are disposed inside the cylindrical coils 212 and 222. However, the magnets 211 and 221 and the coils 212 and 222 are shown separately.
[0019]
Reference numerals 23 and 24 denote vibration detection sensors for detecting vibration, which measure the vibration speed or deformation in the Y direction in the figure.
[0020]
In this case, as shown in FIG. 13 , the vibration detection sensors 23 and 24 are composed of magnets 231 and 241 and coils 232 and 242, and the magnets 231 and 241 are fixed to the vibration tube 20, and the coils are disposed at opposing positions. 232 and 242 are fixed to a non-vibrating non-vibrating place such as the housing 6.
[0021]
In practice, magnets 231 and 241 are arranged inside cylindrical coils 232 and 242, but the magnets 231 and 241 and the coils 232 and 242 are shown separately to clearly show them.
[0022]
As shown in FIG. 10 , the vibration tube 20 is point-symmetric about the midpoint 25 of the upstream end 12 and the downstream end 13 and has an S-shaped curved shape having three inflection points. 20 exists on the reference axis 14 in the vicinity of both ends.
[0023]
In the above configuration, FIG. 14 f-f sectional view in FIG. 10, FIG. 15 g-g sectional view of FIG. 10, FIG. 16 is a h-h cross-sectional view of FIG. 10.
[0024]
For the sake of clarity, the housing 6 and the exciters 21 and 22 are omitted, and only the vibration tube 20 is shown.
The position of the vibrating tube applied with the force in the opposite direction in the Y direction by the exciters 21 and 22 is changed in the order of D → E → D → F → D → E → D → F (repeating this).
[0025]
At the midpoint 25 that is equidistant from the fixed ends at both ends, the vibration tube does not change its position and only performs rotational vibration around the reference axis 14.
As can be seen from FIG. 17 , the vibration tube 20 is always located on the circumference of a predetermined distance from the reference axis 14 or in the vicinity thereof.
[0026]
A single vibration is performed on the circumference at a distance R (f) from the reference axis in the ff cross section and on the circumference at a distance R (h) from the reference axis in the hh cross section.
At the middle point 25, which is the center point of both the fixed ends 12, 13, R (g) = 0, and only rotational vibration is performed without changing the position.
[0027]
Here, for the sake of easy understanding, the amplitude of the simple vibration is illustrated to be large, but in a general Coriolis mass flowmeter, the vibration amplitude is very small.
When the amplitude is small, the vibration on the circumference can be approximated to the vibration of only the Y direction component in the figure.
[0028]
Both the exciters 21 and 22 and the vibration detectors 23 and 24 originally need to correspond not only to the Y direction but also to the Z direction component or the rotation component. You can use equipment that only supports
[0029]
FIG. 17 schematically shows the state of the vibration. The vibration tube changes its position in the order of A → B → A → C → A → B → A and continues the single vibration.
The vibration amplitude is the largest in the vicinity of 1 / 4L and 3 / 4L of the tube length L, and the rotational vibration (RotX) around the reference axis 14 is in the vicinity of both fixed ends 12 and 13 and 1 / 2L near the middle point 25. Even in such a case, there is almost no change in position (UX, UY, UZ) of the component in the reference axis direction and the direction orthogonal to the reference axis.
[0030]
In short, the vibration tube 20 has a predetermined distance from each point of the reference axis 14 using a straight line connecting the upstream fixed end 12 and the downstream fixed end 13 as a reference axis 14 while maintaining a point-symmetric curved shape. Makes a simple vibration on the circumference.
[0031]
As a result,
(1) By adopting vibration on the circumference, the rotational vibration component around the reference axis 14 is mainly in the vicinity of both fixed ends 12 and 13 of the vibration tube 20, and the reference axis 14 is at both fixed ends 12 and 13. Generation of a force in the direction perpendicular to the direction and the reference axis 14 can be greatly suppressed, and a Coriolis mass flow meter with improved stability, accuracy, and vibration resistance can be obtained.
[0032]
(2) By adopting the shape and vibration mode of the vibration tube 20 that is point-symmetric, the center of gravity of the vibration tube 20 is always positioned at the midpoint 25 of both the fixed ends 12 and 13, and the center of gravity does not move.
[0033]
Since there is no movement of the center of gravity of the vibration system, a Coriolis mass flowmeter capable of preventing vibration from leaking out through both the fixed ends 12 and 13 and further improving the vibration insulation can be obtained.
[0034]
(3) Improved vibration insulation makes it less susceptible to external vibration noise, enables low power consumption, reduces zero point and span fluctuations due to environmental changes and external factors, and provides high accuracy and high accuracy. A stable Coriolis flow meter can be realized.
[0035]
(4) The fluid flow path is a single through structure with no branching or gaps from the inlet to the outlet of the flowmeter, and the vibration tube 20 having a shape close to a straight pipe with a gentle curve is adopted, making it compact and pressure loss. Therefore, a Coriolis mass flowmeter having a characteristic that is resistant to thermal stress due to temperature change of a fluid or the like can be obtained.
[0036]
[Patent Document 1]
JP-A-6-109512 (2nd page, FIG. 5)
[Patent Document 2]
JP-A-11-108723 (page 3-4, FIG. 1-5)
[0037]
[Problems to be solved by the invention]
However, in such an apparatus, as shown in FIGS. 12 and 13 , all the magnets 211, 221, 231, and 241 are arranged on the lower side in the Y direction.
Therefore, the mass distribution of the vibration system including the vibration tube 20 and the magnets 211, 221, 231, and 241 is in an unbalanced state where the Y direction negative side is heavy and the Y direction positive side is light.
[0038]
If there is such a mass imbalance, if the position of the vibration tube 20 changes due to excitation vibration, the position of the center of gravity of the entire vibration system also moves, and a large amount of vibration leaks to the outside of the vibration system, and vibration insulation does not work well.
[0039]
The following problems occur when the vibration insulation is poor.
1) It is susceptible to external influences.
That is, when pipe vibration or pipe stress is applied from the outside of the flow meter, the housing (housing) 6 of the flow meter cannot be completely affected by the influence, and external vibration or stress is applied to the internal vibration tube 20 to cause vibration. The vibration state of the tube 20 changes and appears as an error such as output fluctuation or zero point change.
[0040]
2) The vibration of the internal vibration tube 20 leaks to the external piping.
When vibration leaks out and vibration isolation becomes insufficient, the following problems occur.
(1) Since the Q value becomes low, internal vibration becomes unstable, and it is easy to be affected by extra vibration noise other than excitation vibration.
[0041]
(2) Large energy is required for excitation, and power consumption increases.
(3) Depending on the installation method, environmental changes such as piping stress and temperature, and external factors, the degree of vibration leakage changes greatly, the vibration status of the vibration tube 20 also changes, and the zero point and span are likely to change.
[0042]
An object of the present invention is to solve the above-described problems and to provide a Coriolis mass flow meter with improved stability, accuracy, and vibration resistance.
[0043]
That is, the present invention relates to a single tube type Coriolis mass flow meter having no branching,
Adopting a shape close to a straight pipe with a gentle curve, it is compact, has little pressure loss, and has strong characteristics against thermal stress due to temperature changes such as fluid.
[0044]
Furthermore, stability, accuracy, vibration resistance, and zero point fluctuation are also small by preventing the vibration of the vibration tube inside the flow meter from leaking out and making it less susceptible to external vibration noise and stress. The goal is to realize a highly accurate and stable Coriolis flow meter.
[0045]
[Means for Solving the Problems]
In order to achieve such an object, in the present invention, in the Coriolis mass flow meter of claim 1,
A vibration tube through which a measurement fluid flows, an exciter that excites the vibration tube, and a vibration detection sensor that detects deformation vibration of the vibration tube due to Coriolis force generated by the flow of the measurement fluid and angular vibration of the vibration tube. In the Coriolis mass flowmeter provided, the upstream side while maintaining the point-symmetric curve shape with a point-symmetrical curve shape having three inflection points around the midpoint of the upstream fixed end and the downstream fixed end Using a straight line connecting the fixed end and the downstream fixed end as a reference axis, a vibration tube that makes simple vibrations on a circumference of a predetermined distance from each point of the reference axis, and a midpoint between the upstream fixed end and the downstream fixed end Each of the reference axes is defined by a straight line connecting the upstream fixed end and the downstream fixed end while maintaining the point symmetrical curve shape with a point-symmetrical curve shape having three inflection points. From the point A vibrating tube simple harmonic motion at a respectively predetermined distance in the circumferential line, and a vibration detection sensor and exciter with the magnet attached to the vibration tube and a coil provided to face the magnet, respectively, the A balancer that is attached to a vibration tube and prevents an imbalance caused by vibration of the magnet, and is arranged so that the placement location and mass are in a point-symmetric relationship with respect to the midpoint, and the position of the center of gravity is the midpoint A Coriolis mass flowmeter comprising the magnet and the balancer arranged above .
[0046]
In the Coriolis mass flow meter according to claim 2 of the present invention,
The Coriolis according to claim 1, wherein the distance W of the maximum bending portion from the reference axis with respect to the total length L includes a vibrating tube having a relationship of approximately ± 0.01 ≦ W / L ≦ ± 0.1. Mass flow meter.
[0047]
DETAILED DESCRIPTION OF THE INVENTION
Figure 1 is a fragmentary diagram illustrating the configuration of an embodiment of the present invention, FIG 2 is a side view of FIG. 1, FIG. 3 is k-k sectional view of FIG. 1, FIG. 4 is a l-l cross-sectional view of FIG. 1 .
In this embodiment, 41 and 42 are exciters, and 43 and 44 are vibration detection sensors.
[0048]
In this case, as shown in FIG. 3 , the exciters 41 and 42 are composed of magnets 411 and 421 and coils 412 and 422, and the magnets 411 and 421 are fixed to the vibration tube 20, and the coil 412 is disposed at an opposing position. , 422 are fixed to a non-vibrating non-vibrating place such as the housing 6.
[0049]
In this case, as shown in FIG. 4 , the vibration detection sensors 43 and 44 are composed of magnets 431 and 441 and coils 432 and 442. The magnets 431 and 441 are fixed to the vibration tube 20, and the coils are disposed at opposing positions. 432 and 442 are fixed to a non-vibrating non-vibrating place such as the housing 6.
[0050]
In practice, magnets 411, 421, 431, 441 are arranged inside cylindrical coils 412, 422, 432, 442, but magnets 411, 421, 431, 441 and coils 412, 422, 432, 442 are connected. Shown separately for clarity.
[0051]
Reference numerals 45, 46, 47 and 48 are balancers having the same mass and shape as the magnets 411, 421, 431 and 441 installed in the vibration tube 20.
The balancers 45, 46, 47, and 48 are installed at positions symmetrical to the magnets 411, 421, 431, and 441 with respect to the XZ plane.
[0052]
Balancers 45 and 46 are installed for the magnets 411 and 421 of the exciters 41 and 42, and balancers 47 and 48 are installed for the magnets 431 and 441 of the vibration detection sensors 43 and 44.
[0053]
In practice, it is used by placing a magnet 411,421,431,441 inside the cylindrical coil 412,422,432,442, 3, 4, a magnet 411, 421, 431, 441 and coils 412, 422, 432, 442 are shown separately for the sake of clarity.
[0054]
With the structure of the present invention, not only the vibration tube 20 but also the entire mass distribution of the vibration system including the exciters 31 and 32 and the vibration detection sensors 33 and 34 can be arranged in a balanced manner.
[0055]
The center of gravity of the entire vibration system can be arranged at the midpoint 25 of the upstream fixed point and the downstream fixed point, and a point-symmetric mass distribution can be realized with the midpoint 25 as the center. .
[0056]
By having such a structure, the center of gravity position of the entire vibration system is fixed more completely than the conventional example, and a symmetric mass balance is realized. As a result, vibration insulation to the outside world can be increased. Become.
[0057]
By improving the vibration insulation, there are the following advantages.
1) Even if pipe vibration or pipe stress is applied from the outside of the flow meter, it is affected by the flow meter housing 6 (casing) and does not affect the internal vibration. Thus, a Coriolis mass flowmeter that can reduce such errors is obtained.
[0058]
2) By preventing the vibration of the internal vibration tube 20 from leaking to the outside,
(1) A Coriolis mass flowmeter can be obtained in which the Q value can be increased, the internal vibration becomes stable, and is less susceptible to extra vibration noise.
(2) A Coriolis mass flowmeter that can be excited with small energy and can reduce power consumption can be obtained.
[0059]
(3) Since the Q value is high and the amount of leakage is small in the first place, even if there is an environmental change such as the installation method, piping stress, temperature, etc., the amount of vibration leakage does not change much.
Therefore, a Coriolis mass flowmeter having a stable zero point and span against these external factors can be obtained.
[0060]
In addition,
3) Since the magnet can be installed on the vibration tube 20, a Coriolis mass flow meter can be obtained that does not require worrying about the installation location of the lead wire as in the case where the coil is installed on the vibration tube 20.
[0061]
4) When the lead wire is arranged in the vibrating tube 20 that vibrates, there are various problems such as mass problems such as the lead wire and the adhesive that fixes the lead wire, an increase in damping resistance due to deformation of the lead wire, and the location of the lead wire. Although there is a disadvantage, there is no worry about it, and a Coriolis mass flow meter with increased design freedom can be obtained.
[0062]
5) Since the exciters 31 and 32 and the vibration detection sensors 33 and 34 can be installed at the same XZ coordinate position as the tube axis 14, a Coriolis mass flow meter capable of saving a small space can be obtained.
[0063]
Specifically, in this case, the vibration tube 20 is made of stainless steel, the outer shape is 14 mm, the thickness is 1 mm, the total length L is 500 mm, the distance W of the maximum bending portion from the reference shaft 14 is 15 mm, the exciter The mass of 41 and 42 (including the balancer) M = 21 g, and the mass of the detectors 43 and 44 (including the balancer) M = 11 g.
[0064]
In this case, the circumferential vibration mode resonance frequency is 570 Hz (experimental value), the low-order mode resonance frequency is 220 Hz, and the high-order mode resonance frequency is 1200 Hz.
[0065]
Therefore, in the present embodiment, the distance of the maximum bending portion from the reference axis 14 with respect to the total length L is W / L = 15/500 = 0.03.
± about 0.01 ≦ W / L ≦ ± about 0.1 is excellent in total balance, although it varies depending on the physical properties of the vibrating tube 20, the bent shape, the mass of the accessory, and the like.
[0066]
The ratio of the distance W of the maximum bending portion from the reference axis 14 to the total length L of the vibration tube 20: If W / L is too small, the resonance frequency of the torsion mode becomes high and the resonance mode of circumferential vibration does not exist. Sometimes.
[0067]
On the other hand, if it is too large, the entire vibration tube 20 and the entire flow meter become large, resulting in a cost increase.
In addition, when the curvature is large, the pressure loss of the measurement fluid flowing inside the vibration tube 20 also increases.
[0068]
The value W / L = 0.03 in the present example is a straight pipe approximate shape with a gentle curve and a small amount of overhang, and realizes a compact and low pressure loss.
[0069]
Next, when the resonance frequency of the excitation mode is about several tens of Hz, it is not preferable because it is easily affected by piping noise, and the size of the entire vibration system becomes large, which increases the cost of the space.
[0070]
On the other hand, when the frequency is about 1000 Hz or more, the vibration amplitude is small, and the signal processing speed is not in time, which causes a problem.
As in this case, about several hundred Hz is an appropriate value from the viewpoint of vibration resistance noise and the convenience of the signal processing circuit.
[0071]
Next, it is desirable that the vibration tube 20 has no other unnecessary resonance mode in the vicinity of the excitation vibration frequency. As in this example, it is more desirable if it is far from other resonance vibration modes.
[0072]
The above description merely shows a specific preferred embodiment for the purpose of explanation and illustration of the present invention. Therefore, the present invention is not limited to the above-described embodiments, and includes many changes and modifications without departing from the essence thereof.
[0073]
【The invention's effect】
According to claim 1 of the present invention, the following effects.
According to the structure of the present invention, not only the vibration tube but also the entire mass distribution of the vibration system including the exciter and the vibration detection sensor can be arranged with good balance.
[0074]
The center of gravity of the entire vibration system can be arranged at the midpoint position between the upstream fixed point and the downstream fixed point, and further, a point-symmetric mass distribution can be realized with the midpoint as the center.
[0075]
By having such a structure, the center of gravity position of the entire vibration system is fixed more completely than the conventional example, and a symmetric mass balance is realized. As a result, vibration insulation to the outside world can be increased. Become.
[0076]
By improving the vibration insulation, there are the following advantages.
1) Even if pipe vibration or pipe stress is applied from the outside of the flow meter, it is affected by the flow meter housing (case) and does not affect the internal vibration, output fluctuation, zero point change, etc. A Coriolis mass flow meter that can reduce the error is obtained.
[0077]
2) By preventing the vibration of the internal vibration tube from leaking outside,
(1) A Coriolis mass flowmeter can be obtained in which the Q value can be increased, the internal vibration becomes stable, and is less susceptible to extra vibration noise.
(2) A Coriolis mass flowmeter that can be excited with small energy and can reduce power consumption can be obtained.
[0078]
(3) Since the Q value is high and the amount of leakage is small in the first place, even if there is an environmental change such as the installation method, piping stress, temperature, etc., the amount of vibration leakage does not change much.
Therefore, a Coriolis mass flowmeter having a stable zero point and span against these external factors can be obtained.
[0079]
In addition,
3) Since the magnet can be installed on the vibration tube, a Coriolis mass flow meter can be obtained which does not require worrying about the location of the lead wire as in the case where the coil is installed on the vibration tube.
[0080]
4) When the lead wire is placed on a vibrating tube that vibrates, there are various demerits such as the mass of the lead wire and the adhesive that fixes the lead wire, the increase in damping resistance due to deformation of the lead wire, the location of the lead wire, etc. However, there is no need to worry about this, and a Coriolis mass flowmeter with increased design freedom can be obtained.
[0081]
5) Since a detector and a vibration detection sensor can be installed at the same XZ coordinate position as the tube axis, a Coriolis mass flowmeter capable of saving space can be obtained.
[0082]
According to claim 2 of the present invention, there are the following effects.
If the ratio of the distance of the maximum bending portion from the reference axis to the total length of the vibration tube is too small, the resonance frequency of the torsion mode becomes high and the resonance mode of circumferential vibration may not exist.
[0083]
On the other hand, if it is too large, the entire vibration tube and the entire flow meter become large, resulting in an increase in cost.
In addition, when the curvature is large, the pressure loss of the measurement fluid flowing inside the vibration tube also increases.
[0084]
That is, a compact Coriolis mass flow meter that can realize low-pressure loss can be obtained with a straight tube approximate shape with a gentle curve and a small overhang.
[0085]
Therefore, according to the present invention, a Coriolis mass flowmeter with improved stability, accuracy, and vibration resistance can be realized.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a main part configuration of an embodiment of the present invention.
Is a side view of FIG. 1;
3 is a k-k sectional view of FIG.
4 is a cross-sectional view taken along line l-l in FIG. 1 ;
FIG. 5 is an explanatory diagram of a main part configuration of a conventional example generally used conventionally.
FIG. 6 is an explanatory diagram of a main configuration of another conventional example that is generally used conventionally.
7 is a b-b cross section of Fig.
8 is a cross-sectional view taken along the lines aa and cc in FIG. 6 ;
FIG. 9 is an operation explanatory diagram of FIG. 6 ;
FIG. 10 is an explanatory diagram showing the main configuration of an embodiment of an application related to a prior application.
FIG. 11 is a side view of FIG. 10.
It is a d-d cross-sectional view of FIG. 12 FIG. 11.
13 is a e-e sectional view of FIG. 11.
FIG. 14 is an operation explanatory diagram of FIG. 10.
Is an operation explanatory diagram of FIG. 15] FIG. 10.
It is an operation explanatory diagram of Figure 16 Figure 10.
FIG. 17 is an operation explanatory diagram of FIG. 10 ;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Vibration tube 2 Flange 3 Exciter 4 Vibration detection sensor 5 Vibration detection sensor 6 Housing 11 Vibration tube 12 Upstream fixed end 13 Downstream fixed end 14 Reference shaft 15 Exciter 16 Vibration detection sensor 17 Vibration detection sensor 20 Vibration tube 21 Excitation 211 Magnet 212 Coil 22 Exciter 221 Magnet 222 Coil 23 Vibration detection sensor 231 Magnet 232 Coil 24 Vibration detection sensor 241 Magnet 242 Coil 25 Middle point 41 Exciter 411 Magnet 412 Coil 42 Exciter 421 Magnet 422 Coil 43 Vibration sensor Magnet 432 Coil 44 Vibration detection sensor 441 Magnet 442 Coil 45 Balancer 46 Balancer 47 Balancer 48 Balancer

Claims (2)

A vibrating tube in which the measurement fluid flows;
An exciter for exciting the vibrating tube;
A Coriolis mass flowmeter comprising: a vibration detection sensor that detects a deformation vibration of the vibration tube due to a Coriolis force generated by the flow of the measurement fluid and the angular vibration of the vibration tube;
An upstream fixed end and a downstream fixed end with a curved shape having three inflection points that are symmetric with respect to the midpoint of the upstream fixed end and the downstream fixed end, while maintaining the point-symmetric curved shape. A vibration tube that makes a single vibration on a circumferential line at a predetermined distance from each point of the reference axis, with a straight line connecting
An upstream fixed end and a downstream fixed end with a curved shape having three inflection points that are symmetric with respect to the midpoint of the upstream fixed end and the downstream fixed end, while maintaining the point-symmetric curved shape. A vibration tube that makes a single vibration on a circumferential line at a predetermined distance from each point of the reference axis, with a straight line connecting
An exciter and a vibration detection sensor each having a magnet attached to the vibration tube and a coil provided facing the magnet;
A balancer which is attached to the vibration tube and prevents unbalance generated based on vibration of the magnet;
The magnet and the balancer are arranged such that the placement location and the mass are in a point-symmetrical relationship with respect to the midpoint and the center of gravity is located on the midpoint. Coriolis mass flow meter. The distance W of the maximum bending portion from the reference axis with respect to the total length L is approximately ± 0.01 ≦ W / L ≦ ± 0.1.
  The Coriolis mass flowmeter according to claim 1, comprising:

Images