JP2000046613A - Coriolis mass flowmeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flowmeter with improved stability, precision and vibration resistance by preventing the vibration of a vibrating tube in the mass flow meter from leaking to the outside, and allowing the mass flow meter to be hardly affected by the vibration noise and stress from the outside. SOLUTION: A vibrating tube 11 exists as a completely straight pipe on a reference axis 14 at the position A in the initial state when it is not excited. At an initial state, the vibrating tube 11 exist at a position A. When an exciter 3 is operated, a tensile bias component is applied, and the vibrating tube 11 is moved to a position at the radius R from the position on the reference axis 14. The vibrating tube 11 is moved in position to B→C→D→C→B→C→D (repeated) during vibration. The vibrating tube 11 and a compensating body 15 generate opposite rotational vibrations with respect to the reference axis 14. The vibrating tube 11 and the compensating body 15 give forces acting in opposite directions and negating each other at connection sections 16, 17 where they are connected together to form the node of vibrations. The rotational component around the reference axis 14 can be suppressed, and vibration insulation performance can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for preventing the vibration of a vibration tube from leaking out of a Coriolis mass flowmeter and reducing the influence of external vibration noise and stress. The present invention relates to a Coriolis mass flowmeter with improved stability, accuracy, and vibration resistance.

[0002]

2. Description of the Related Art FIG. 43 is an explanatory view of the structure of a conventional example generally used in the prior art.
No. 12 shows a conventional example. In the figure, both ends of a vibration tube 1 are attached to a flange 2. The flange 2 is for attaching the vibration tube 1 to the conduit A.

[0003] The exciter 3 is provided at the center of the vibration tube 1. The vibration detection sensors 4 and 5 are the vibration tube 1
Are provided on both sides. In the housing 6, both ends of the vibration tube 1 are fixed.

In the above configuration, the measurement fluid is flowed 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, a symbol surrounded by “” represents a vector amount),

The mass flow rate can be measured by measuring the amplitude of the vibration proportional to the Coriolis force in which the Coriolis force of Fc = −2 m “ω” × “V” acts.

FIG. 44 is an explanatory view of the structure of another conventional example generally used in the prior art. In this conventional example, the vibration tube 1 is a two-tube type.

[0007]

In a general single straight pipe type Coriolis mass flow meter as shown in FIG.
Is fixed at both ends, but the end point cannot be completely fixed with a flowmeter of a limited size, and the end point slightly vibrates.

The following causes can be considered as the reason why the vibration occurs. When the vibrating tube 1 in which a fluid flows is deformed as shown in FIG. 45 (approximately in a first-order mode resonance state), the length of the tube becomes longer due to the deformation, and a tensile stress is generated in the axial direction of the vibrating tube. I do.

For example, φ9.6 × 0.91 of stainless steel
When the center portion of the 400 L vibrating tube 1 is deformed by 1 mm, a tensile force of 7.5 kgf is generated in the axial direction as shown in FIG.

When the vibrating tube 1 is excited in the primary resonance mode, the tensile force is maximized when the plus and minus deformations are maximum, and the tensile force is minimum and zero when the basic shape has no deformation. .

In one cycle of the excitation vibration, the tensile force repeats maximum and minimum twice. That is, the axial pulling force of the vibration tube 1 is generated at twice the frequency of the excitation frequency.

As a result, it is difficult to completely insulate vibration by setting the end points in a completely fixed state. In this case, there are roughly two problems.

One is that 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 Coriolis mass flow meter cannot completely receive the influence, and external vibration or stress is applied to the internal vibration tube 1. Is added, the vibration state of the vibrating tube 1 changes, and this appears as an error such as output swing or a change in zero point.

Another is that the vibration of the internal vibration tube 1 leaks to the external piping. If the vibration leaks out and the vibration isolation becomes insufficient, the following problems occur.

If the vibration insulation is insufficient, (1) the Q value becomes low, so that the internal vibration becomes unstable, and the vibration is easily affected by extra vibration noise other than the excitation vibration. (2) Large energy is required for excitation, and power consumption increases.

(3) The degree of vibration leakage greatly changes, the vibration state of the vibrating tube 1 changes, and the zero point and the span easily change due to the installation method, environmental changes such as piping stress and temperature, and external factors. . In other words, Coriolis flowmeters that are unstable with respect to these environmental changes and external factors and have poor vibration resistance and accuracy tend to be poor.

On the other hand, in the conventional example shown in FIG. 44, the two vibrating tubes 1 vibrate in directions opposite to each other, so that the forces cancel each other out at the branch portion, and as shown in FIGS. It has a structure that is hard to leak outside. However, the structure of one vibration tube without a branch point cannot be obtained.

The present invention solves this problem. An object of the present invention is to prevent the vibration of the vibrating tube from leaking out inside the Coriolis mass flow meter,
An object of the present invention is to provide a Coriolis mass flowmeter having improved stability, accuracy, and vibration resistance by making it less susceptible to external vibration noise and stress.

[0019]

In order to achieve the above object, the present invention provides: (1) a measuring fluid flowing in a vibrating tube, and a flow of the measuring fluid and a Coriolis force generated by angular vibration of the vibrating tube; In a Coriolis mass flowmeter that deforms and vibrates the vibrating tube, a vibrating tube that vibrates with a straight line connecting an upstream fixed end and a downstream fixed end as a reference axis, and both ends provided in parallel with the reference axis and having the vibration A compensator fixedly supported on both ends of the tube; and a vibrating tube that excites the torsion around the reference axis in the vicinity of the fixed end so that the torsion around the reference axis becomes the main body, and the vibration of the compensator is the reference The vibrating tube and the compensator are torsional vibrations rotating about the same axis as the axis or an axis parallel to the reference axis, and having a phase opposite to that of the vibrating tube. A vibrator having an exciting means for vibrating in opposite phases at the connecting portion to excite the torsional vibrations around the reference axis so as to reduce the generated vibrations. (2) The Coriolis mass flowmeter according to (1), wherein an exciter having one end connected to the vibration tube and the other end connected to the compensator is provided as the excitation means. (3) The method according to (1) or (2), wherein the exciting unit includes a first exciter for exciting the vibrating tube and a second exciter for exciting the compensator. Coriolis mass flow meter. (4) The compensator includes a compensator having sufficiently high rigidity so that the shape of the compensator and the vibrating tube does not change when external pipe stress or vibration noise is applied. The Coriolis mass flowmeter according to any one of (1) to (3). (5) As the vibrating tube, the vibrating tube has at least one gently curved portion which is line-symmetric with respect to a middle line equidistant from the upstream fixed end and the downstream fixed end, and has the upstream fixed end and the downstream. (1) to (1) to (1) to (1) to are provided with one vibrating tube which makes a simple vibration on or around a circumferential line at a predetermined distance from each point of the reference axis with a straight line connecting to the side fixed end as a reference axis. The Coriolis mass flowmeter according to any of (4). (6) At least two ends perpendicular to the reference axis or the vibrating tube, one end of which is fixed to the vibrating tube, and the other end are arranged on the opposite side of the vibrating tube with respect to the reference axis and are symmetrical with respect to the center line. Comprising a plurality of plate-shaped vibrators, the mass distribution and shape and rigidity of the vibrating tube, and adjusting the mass distribution, shape, rigidity and spacing of the vibrating tube to adjust the vibration distribution of the vibrating tube in a steady excitation state. (1) to (1) to (1) to (4), wherein a force generated at the both ends connecting portion is only a torsional component around the reference axis so that a component orthogonal to the reference axis due to an exciting force by the exciter is not generated. The Coriolis mass flowmeter according to any one of (5). (7) a plate-shaped vibrating body orthogonal to the reference axis or the vibrating tube, one end of which is fixed to the vibrating tube and the other end of which is disposed on the opposite side of the vibrating tube with respect to the reference axis; And a vibration detection sensor provided at the other end of the Coriolis mass flowmeter according to any one of (1) to (6). (8) The Coriolis mass flowmeter according to any one of (1) to (7), further including an exciter that excites the vibrating tube in a second-order mode or higher-order vibration mode. (9) a flexible structure portion provided on the vibration tube between the upstream fixed end, the downstream fixed end, and the compensator for absorbing expansion and contraction in the direction of the reference axis and rotational vibration around the reference axis; The Coriolis mass flowmeter according to any one of (1) to (8), further comprising: It is what constituted.

[0020]

In the above construction, when the measuring fluid is flowed through the vibrating tube and the exciter is driven, Coriolis force acts.
By measuring the amplitude of the vibration proportional to the Coriolis force, the mass flow rate can be measured.

In the initial state at the time of non-excitation, the vibrating tube exists on the reference axis as a completely straight tube.

When the exciter is operated, a bias component of tension is applied, and the exciter is moved from the position of the reference axis to a position of a predetermined radius. The vibrating tube being excited performs a simple vibration.

As a result, the vibration tube and the compensator are
With respect to the reference axis, vibrations of opposite rotation are generated. The vibrating tube and the compensator are connected at the connected portion where forces act in opposite directions and cancel each other to form a node of vibration.

Since the rotation component around the reference axis can be suppressed, the vibration insulation can be improved. Hereinafter, a detailed description will be given based on embodiments.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory diagram of a main part of an embodiment of the present invention, which is one embodiment of the present invention.
2 is a sectional view taken along line AA of FIG. 1, FIG. 3 is a sectional view taken along line BB of FIG. 1, and FIGS. 4 and 5 are operation explanatory diagrams of FIG. 43, the same symbols as those in FIG. 43 indicate the same functions. Hereinafter, only differences from FIG. 43 will be described.

The vibrating tube 11 vibrates with a straight line connecting the upstream fixed end 12 and the downstream fixed end 13 as a reference axis 14. The compensator 15 is provided in parallel with the reference axis 14,
Both ends are connected to both ends of the vibrating tube 11 respectively.
6 and 17 are connected and fixed.

In this case, the exciter 3 has one end connected to the vibration tube 11 and the other end connected to the compensator 15. Due to the action reaction, the vibration tube 11 and the compensator 15
Are configured to receive forces in opposite directions to each other.

In this embodiment, two sets of exciters 3 are arranged so as to be able to simultaneously vibrate in two directions in the Y direction and the Z direction in FIG. The exciter 3 excites the vibrating tube 11, and excites in the vicinity of the coupling portions 16 and 17 such that the torsion around the reference axis 14 becomes main.

In addition, the exciter 3 controls the vibration of the compensator 15
The compensator 15 is excited so that the torsional vibration rotates about the same axis as the reference axis 14 or an axis parallel to the reference axis 14.

The vibration of the compensator 15 is in the opposite phase to the vibration of the vibrating tube 11, and the connecting portions 16 and 17 of the vibrating tube 11 and the compensator 15 vibrate in the opposite phase, thereby torsion around the reference axis 14. The vibrations cancel each other and the generated vibrations are greatly reduced.

The vibration detection sensors 4 and 5 are connected to the vibration tube 1
1 is detected. In the present embodiment, the Y direction in FIG.
Two sets of vibration detection sensors 4 and 5 are provided so that vibrations in two directions in the Z direction can be detected simultaneously.

In the above configuration, in the initial state at the time of non-excitation, the vibration tube 11 exists on the reference shaft 14 as a complete straight tube. In the initial state, as shown in FIGS. 4 and 5, the vibration tube 11 exists at the position A.

When the exciter 3 operates, a bias component of tension is applied, and the radius R
Move to the position. The vibrating tube 11 being excited has a B →
Change the position like C → D → C → B → C → D (repeated).

As a result, the vibration tube 11 and the compensator 1
5, vibrations of opposite rotations with respect to the reference shaft 14 are generated. The vibrating tube 11 and the compensator 15 are connected to each other at the connecting portions 16 and 17 so that forces act in opposite directions and cancel each other to form a node of vibration.

Since the rotation component around the reference shaft 14 can be suppressed, the vibration insulation can be improved. As described above, the following advantages are exhibited by increasing the vibration isolation.

(1) The internal vibration system can realize a high Q value, and even if external noise is applied, the influence thereof is relatively small and the vibration is stable, so that a Coriolis mass flowmeter resistant to external vibration noise can be obtained.

(2) Since stable excitation can be realized with a small amount of energy, a Coriolis mass flowmeter with low current consumption can be obtained.

(3) If the amount of vibration energy dissipated to the outside changes, or if the balance of the amount dissipated upstream and downstream is disturbed, the internal vibration system is affected, and the zero point and span fluctuate. In the present invention, since the vibration is always confined inside, there is no need to worry about this, and a highly accurate Coriolis mass flowmeter can be realized.

(4) By installing the exciter 3 between the vibrating tube 11 and the compensator 15, it is possible to vibrate both the vibrating tube 11 and the compensator 15 in opposite phases. Will be possible. Since the exciters 3 for the vibrating tube 11 and the compensator 15 can be combined into one, the configuration is simplified, and a low-cost Coriolis mass flowmeter can be obtained.

FIG. 6 is an explanatory view of the structure of the main part of another embodiment of the present invention. FIG. 7 is an operation explanatory diagram of FIG. In this embodiment, the vibration tube 21
In the vicinity of the fixed ends 12 and 13 at both ends of the vibration tube, the vibration tube exists on the reference axis 14.

As the exciting means, a first exciter 31 for exciting the vibration tube 21 and a second exciter 32 for exciting the compensator 15 are used. In this case, the first exciter 31 and the second exciter 32 are supported by the housing 6.

FIG. 7 is an operation explanatory view showing a state of vibration of the vibration tube 21 in the above configuration. Along with the excitation vibration, the vibration tube 11 and the compensation vibration body 15 vibrate as shown by dotted lines E and F and arrows G and H.

The vibrating tube 11 and the compensator 15 have torsional vibrations around the reference axis 14 near the connecting portions 16 and 17 on both sides thereof, but are opposite to each other.
In 6 and 17, the vibration is canceled.

As a result, (1) the vibration of the vibration tube 11 and the vibration of the compensator 15 are separately vibrated by using the first and second exciters 31 and 32. Finer vibration control becomes possible.

(2) Even if the resonance frequency of the vibrating tube 11 is different from that of the compensator 15, vibrations with different phases are individually performed, so that the nodes of vibration can be easily formed without complicated resonance frequency design. And an inexpensive Coriolis mass flowmeter can be obtained.

FIG. 8 is an explanatory view of a main part of another embodiment of the present invention. FIG. 9 is a side view of FIG. In this embodiment, the flange 2 for connection to the external piping is omitted.

In this embodiment, as the compensator 41,
A compensator having sufficiently high rigidity is used so that the shape of the compensator 41 and the vibration tube 21 does not change when external pipe stress or vibration noise is applied.

As a result, since the compensator 41 having sufficiently large rigidity is provided, even if stress or vibration noise is applied from the outside, the influence is not transmitted to the vibration tube 21 inside the compensator 41, Stable excitation can be continued.
That is, it is possible to obtain a stable and accurate Coriolis mass flow meter which is hardly affected by external stress or vibration.

In this embodiment, as the exciting means 3 and the detecting means 4 and 5, the electromagnetic coils 301 and 40 provided on one of the vibrating tube 21 or the compensator 41 are used.
1, 501, and magnets 302, 402, and 502 provided on the other side of the vibration tube 21 or the compensator 41 are used.

In this case, the excitation coil 301 and the sensor coils 401 and 501 are installed in the vibration tube 21.
An excitation magnet 302 and sensor magnets 402 and 502 are provided on the compensation vibrator 15.

In the above configuration, the coil 3 of the exciter 3
When the magnet 01 and the magnet 302 rebound, as shown in FIG. 9, the vibration tube 21 twists clockwise about the reference axis 14 as shown by the arrow I, and
As for arrow 5, a counterclockwise twist occurs around the reference axis 14 as indicated by an arrow J.

Since the rotations are opposite to each other, the forces cancel each other out at the connecting portions 16 and 17 which are the connecting portions.
Vibration does not occur like a node of vibration.

As a result, the exciter 3 is connected to the vibration tube 21
And the compensator 15, both the vibration tube 21 and the compensator 15 can be vibrated in opposite phases.

FIG. 10 is an explanatory view of a main part of another embodiment of the present invention. 11, 12,
FIG. 13 is an operation explanatory diagram of FIG.

In this embodiment, the vibration tube 51
Has at least one gently curved portion 53 that is line-symmetric with respect to a midline 52 equidistant from the upstream fixed end 12 and the downstream fixed end 13.

The vibrating tube 51 uses the straight line connecting the upstream fixed end 12 and the downstream fixed end 13 as a reference axis 14 to generate a simple vibration on a circumferential line at a predetermined distance from each point of the reference axis 14. Consists of a single tube.

In this case, if the distance between the upstream fixed end 12 and the downstream fixed end 13 is L and the distance between the reference shaft 14 and the vibrating tube 51 is h, then approximately h ≦ 0.2.
It is desirable that the shape satisfy L.

FIG. 11 is a sectional view taken along line bb of the vibration tube 51 of FIG. 10, FIG. 12 is a sectional view taken along lines aa and cc of the vibration tube 51 of FIG. 10, and FIG. It is a perspective view which shows the mode of the vibration of 51. FIG.
In FIG. 12, the vibration tube 5 is in the non-excited state.
1 is near the position of A.

In the excited state, the center of the vibration tube 51 moves on a circumference separated from the reference axis 14 by a radius R (x). At the position of the cross section bb, the radius R (b)
At the position of the section a-a or cc on the distant circle, the circle at a radius R (a) or R (c) away from the reference axis 14 is A →
Vibrates as B → A → C → A → B → A (repeated).

In FIG. 13, A, B, and C correspond to the respective positions of the vibration tube 51 in FIGS.

As for the vibration detection and signal processing, the same processing as that of a normal Coriolis mass flow meter may be performed. For example, the vibration detection sensors 4 and 5 can detect the Y component of the vibration, determine the phase difference between the two sensor outputs, and apply frequency correction, temperature correction, and the like to determine the mass flow rate flowing inside the tube.

Since the vibration tube 51 vibrates only in a circumferential surface equidistant from the reference shaft 14, the vibration tube 5
No matter where the position 1 is, the length of the vibration tube 51 does not change.

Therefore, the pulling force in the axial direction is always constant. That is, due to the change in the axial force,
Vibration leakage can be eliminated.

FIG. 14 is an operation explanatory view showing a state of vibration of the conventional single-tube straight tube type vibration tube 1, FIG. 15 is an operation explanatory view seen from the side of FIG. 14, and FIG. FIG. 1 is an operation explanatory view showing a state of vibration of the vibration tube 51 of FIG.
FIG. 7 is an operation explanatory diagram viewed from the side of FIG.

In FIG. 14, in order to satisfy the same conditions as in FIG. 16, both ends of the vibrating tube 1 are connected to the connecting portions 16, 1.
In the case where the compensator 15 fixed by 7 is provided, as shown in FIG. 15, a case where ordinary vibration is applied to the vibration tube 1.

The vibrating tube 1 is fixed at the connecting portions 16 and 17. However, in a Coriolis mass flowmeter whose size and weight are practically limited, it cannot be a completely fixed end. The portions of the vibrating tube 1 of the outer portions 54 and 55 of 16 and 17 also vibrate as shown in FIG.
That is, it means that the vibration isolation is insufficient.

On the other hand, in the case of FIG.
Since the directional force is small, the outer portions 5 of the connecting portions 16 and 17
No change in shape was observed in 6,57, and the leakage of vibration was small.
Further, the torsional vibration around the reference axis 14 can be canceled by the compensator 15, so that the vibration does not leak outside the connecting portions 16 and 17.

In this embodiment, the vibration inside the Coriolis mass flowmeter is stabilized by increasing the vibration isolation, and a highly accurate and stable Coriolis mass flowmeter can be realized.

More specifically, since the Q value of the internal vibration is increased, it is hardly affected by vibration noise, low power consumption is realized, and a zero point or a span change due to a change in the amount of vibration leakage can be reduced. A mass flow meter is obtained. By increasing the vibration isolation in this way, the following advantages are exhibited.

As a result, (1) the internal vibration system can realize a high Q value, the influence of external noise is relatively small even when external noise is applied, and the vibration is stable, so that a Coriolis mass flowmeter resistant to external vibration noise can be obtained. Can be

(2) Since stable excitation can be realized with small energy, a Coriolis mass flowmeter with low current consumption can be obtained.

(3) If the amount of vibration energy dissipated to the outside changes, or if the balance of the amount of dissipated energy is disrupted upstream and downstream, the internal vibration system is affected, and the zero point and span fluctuate. In the present invention, since the vibration is always confined inside, there is no need to worry about this, and a highly accurate Coriolis mass flowmeter can be obtained.

(4) The measurement fluid flow path is provided at the inlet (inlet) of the flow meter.
There is no branch or gap from the outlet to the outlet
Because of the single penetrating structure, a Coriolis mass flowmeter with low flow velocity loss, less clogging, and easy cleaning can be obtained.

(5) Not a straight tube but a vibrating tube 5
1 is curved in a predetermined shape beforehand in a non-excited state, so that it is easy to absorb a change in ambient temperature at the curved portion 53, and a Coriolis mass flowmeter having good temperature characteristics can be obtained.

A Coriolis mass flowmeter which is not a general curved tube nor a perfect straight tube, but has an appropriate curve, and which can simultaneously realize the advantages of a curved tube and a straight tube can be obtained.

FIG. 18 is an explanatory view of a main part of another embodiment of the present invention. FIG. 19 is a side view of FIG.

In this embodiment, the vibrators 61 and 62 are
The reference shaft 14 or the vibration tube 21 is orthogonal to the reference shaft 14, one end is fixed to the vibration tube 21, and the other end is
Are arranged on the opposite side to the vibration tube 21 and at least two are arranged at positions symmetrical with respect to the center line 52 to form a plate shape.

By adjusting the mass distribution, shape, and rigidity of the vibrating tube 21 and the mass distribution, shape, rigidity, and spacing of the vibrating body 61.62, the both ends connecting portion 16.17 of the vibrating tube 21 in the steady excitation state. Is generated only by the torsional component around the reference axis 14 so that a component orthogonal to the reference axis 14 due to the excitation force by the exciter 3 is not generated.

FIG. 20, FIG. 21, FIG. 22, and FIG.
8 is a diagram illustrating the operation of FIG. 8 and shows a modal analysis result of the finite element method using a beam element. 20, 21, 22, and 2
In FIG. 3, the housing 6 forming the Coriolis mass flowmeter, the flange 2 for connection to external piping and the compensator 15 are omitted.

FIG. 20 is a perspective view, FIG. 21 is a projection view from the X direction in FIG. 20, FIG. 22 is a projection view from the Y direction in FIG.
FIG. 23 is a projection view from the Z direction in FIG. 20, showing both the shape D in the initial state and the shape E in the maximum deformation.

In the present embodiment, the rigidity of the vibrating tube 21, the interval between the two vibrating bodies 61.62, the vibrating body 61.6
By adjusting the shape and mass distribution of No. 2, only the restoring force due to the spring stiffness is considered in the static deformation state (static deformation), but it is actually necessary to consider the influence of the inertial force in the dynamic state. ) The torsional component around the reference axis (ROT in the figure)
X) occurs, but translational components (FY, FZ in the figure) due to the excitation vibration are not generated.

However, since the torsion component around the reference axis 14 is canceled by the action of the compensator 15, the structure is substantially free from vibrations leaking out.

In the steady excitation state, the vibration tube 21
Since no force of the translational component other than the torsional component around the reference axis 14 is generated at the connecting portions 16 and 17 at both ends of the above, vibration does not leak out.

In claim 5, the axial expansion and contraction force is reduced to zero or greatly reduced. According to claim 6, the Coriolis mass flowmeter further reduces the translational component such as the vibration direction to zero or greatly reduced. can get.

The following advantages are exhibited by increasing the vibration isolation. (1) Since the internal vibration system can realize a high Q value, the influence of external noise is relatively small even if external noise is applied, and the vibration is stable, a Coriolis mass flowmeter resistant to external vibration noise can be obtained.

(2) Since stable excitation can be realized with a small amount of energy, a Coriolis mass flowmeter with low current consumption can be obtained.

(3) If the amount of vibration energy dissipated to the outside changes, or if the balance of the amount dissipated upstream and downstream is disturbed, the internal vibration system is affected and the zero point and span fluctuate. In the present invention, since the vibration is always trapped inside, there is no need to worry about the vibration, and a highly accurate Coriolis mass flowmeter can be obtained.

FIG. 24 is an explanatory view of a main part of another embodiment of the present invention. FIG. 25 is a side view of FIG.

In this embodiment, the vibration detecting sensors 4 and
5 is provided at the other end of the vibrating bodies 61 and 62.

The vibration detecting sensors 4, 5 are connected to the vibrating body 61,
By installing near the tip of 62, vibration can be detected at an optimum position.

By being located at the tips of the vibrators 61 and 62, vibration can be measured at the place where the amplitude is the largest in the vibration system. Also, the phase difference generated by the Coriolis force becomes very large.

Actually, as a result of comparing the embodiment of FIG. 18 with the embodiment of FIG. 24 (corresponding to claim 7) by experiment, as an example,
It was as follows. The ratio of the sensor amplitude / drive amplitude is 0.8 in the embodiment of FIG. 18 and 3.5 in the embodiment of FIG. The generated phase difference <m rad> is 8.8 in the embodiment of FIG. 18 and 37.5 in the embodiment of FIG. Becomes

As described above, in both the amplitude ratio and the generated phase difference, values that are slightly more than four times larger than those in the embodiment of FIG. 18 were observed.

As a result, (1) If the measured amplitude is large, the S / N is improved. Conversely, if the measurement amplitude is the same as the conventional one, the excitation force can be reduced, and a Coriolis mass flowmeter with low power consumption can be obtained. If the maximum amplitude is small, vibration energy is small, leakage to the outside is small, vibration isolation is easy, and a stable and accurate Coriolis mass flowmeter can be obtained.

(2) If the generated phase difference is large, the signal processing in the signal conversion portion becomes easy. That is, a Coriolis mass flowmeter capable of realizing stable and highly accurate performance even with a simple and inexpensive signal processing circuit can be obtained.

Conversely, if the signal processing performance is equivalent to the conventional one, stable measurement can be performed up to a low flow rate region where the generated phase difference is small. A possible Coriolis mass flow meter is obtained.

As a result, since both the amplitude and the phase difference are larger than 4 times, it is very advantageous and a dramatic improvement effect can be obtained.

FIGS. 26, 27, 28 and 29 are views for explaining the operation of the main part of another embodiment of the present invention. FIG. Excitation is performed in a higher-order vibration mode than the second-order mode. FIG. 24 shows the result of performing modal analysis on the embodiment in FIG. 24 by the finite element method using shell elements.

FIG. 26 is a perspective view, FIG. 27 is a projection view from the X direction in FIG. 26, FIG. 28 is a projection view from the Y direction in FIG.
FIG. 29 is a projection view from the Z direction in FIG. 26, and shows both the shape D in the initial state and the shape E in the maximum deformation.

In the third mode resonance state of the embodiment in FIG. 24, the resonance frequency is 267 Hz. Normally, when self-excited, the lowest vibration mode is easily excited, but in this embodiment,
The exciter 3 is adjusted so that the third-order mode is excited, and self-excited.

The first mode resonance frequency in the embodiment of FIG. 24 is 153 Hz, and has the vibration mode shapes as shown in FIGS. 30, 31, 32, and 33.

FIG. 30 is a perspective view, FIG. 31 is a projection view from the X direction in FIG. 30, FIG. 32 is a projection view from the Y direction in FIG.
FIG. 33 is a projection view from the Z direction in FIG. 30, and shows both the shape D in the initial state and the shape E in the maximum deformation.

Referring to FIGS. 30, 31, 32, and 33,
The entire vibration system is deformed in the + Z direction. Since it is not a circumferential vibration, the excitation force is directly applied to the ends 16 and 17,
A large force is applied to the ends 16 and 17 in the X direction and the Z direction.

In the embodiment shown in FIG. 24, the secondary mode resonance frequency is 250 Hz, and the vibration mode shape is as shown in FIGS. 34, 35, 36 and 37.

FIG. 34 is a perspective view, FIG. 35 is a projection view from the X direction in FIG. 34, FIG. 36 is a projection view from the Y direction in FIG.
FIG. 37 is a projection view from the Z direction in FIG. 34, and shows both the shape D in the initial state and the shape E at the time of maximum deformation.

In FIGS. 34, 35, 36, and 37,
The deformation in the Z direction of the vibrating tube 21 is reversed in the plus and minus directions near the center thereof. Since the amount of deformation of the vibration tube 21 itself is small, the generation of Coriolis force is also small,
Not a very practical vibration mode.

In the embodiment of FIG. 24, the fourth-order mode resonance frequency is 397 Hz, and the vibration mode shapes are as shown in FIGS. 38, 39, 40 and 41.

FIG. 38 is a perspective view, FIG. 39 is a projection view from the X direction in FIG. 38, FIG. 40 is a projection view from the Y direction in FIG.
FIG. 41 is a projection view from the Z direction in FIG. 38, and shows both the shape D in the initial state and the shape E in the maximum deformation.

In FIG. 38, FIG. 39, FIG. 40, and FIG. 41, the shapes are complicated, but since the resonance frequency is high,
It does not have much adverse effect.

As a result, the following advantages can be obtained by exciting in the second, third, or higher order mode.

(1) It is easy to set a higher excitation frequency.
Vibration at low frequency is susceptible to vibration noise in the field, whereas high frequency excitation provides a Coriolis mass flowmeter that is less susceptible to vibration noise.

(2) The resonance frequencies of the excitation mode and the vibration mode generated by the Coriolis force can be made close to each other. According to the experimental results corresponding to FIG.
z, Coriolis approximation mode is close to 246Hz,

From the following equation, since P = 1.057 and Q = 1000, the dynamic magnification G = 8.5 is large and the generated phase difference is large. Here, dynamic magnification G = (1−P ² ) / ((1−P ² ) ² + (P / Q)) P = (drive frequency) / (resonance frequency of Coriolis approximation mode)

(3) If the generated phase difference is large, signal processing in the signal conversion unit becomes easy. That is, a Coriolis mass flowmeter capable of realizing stable and highly accurate performance even with a simple and inexpensive signal processing circuit can be obtained.

On the other hand, if the signal processing performance is equivalent to the conventional one, it is possible to measure stably even in a low flow rate region where the generated phase difference is small, or to measure the mass flow rate of a gas originally generated with a small phase difference. A possible Coriolis mass flow meter is obtained.

FIG. 42 is an explanatory view of a main part of another embodiment of the present invention. In the present embodiment, the flexible structure 71 that absorbs the expansion and contraction in the direction of the reference shaft 14 and the rotational vibration around the reference shaft 14 includes the upstream and downstream fixed ends 1.
The vibration tube 51 is provided between the compensator 15 and 2 and 13.

As a result, since the flexible structure 71 is provided in the vibration tube 51 between the upstream and downstream fixed ends 12 and 13 and the compensator 15, (1) thermal expansion can be absorbed. Thus, a Coriolis mass flowmeter capable of performing stable and accurate measurement over a wide temperature range can be obtained.

(2) Even when pipe stress is applied, it can be absorbed by the flexible structure 71 and does not affect the inside, so that a stable and accurate Coriolis mass flow meter can be obtained.

[0119]

As described above, according to the first aspect of the present invention,
According to this, the vibration tube and the compensator generate vibrations that rotate in opposite directions with respect to the reference axis. The vibrating tube and the compensator are connected at the connected portion where forces act in opposite directions and cancel each other to form a node of vibration.

Since the rotation component about the reference axis can be suppressed, the vibration insulation can be improved. As described above, the following advantages are exhibited by increasing the vibration isolation.

(1) The internal vibration system can realize a high Q value, and even if external noise is applied, the influence thereof is relatively small and the vibration is stable, so that a Coriolis mass flowmeter resistant to external vibration noise can be obtained.

(2) Since stable excitation can be realized with a small amount of energy, a Coriolis mass flowmeter with low current consumption can be obtained.

(3) If the amount of vibration energy dissipated to the outside changes, or if the balance of the amount dissipated upstream and downstream is disturbed, the internal vibration system is affected, and the zero point and span fluctuate. In the present invention, since the vibration is always confined inside, there is no need to worry about this, and a highly accurate Coriolis mass flowmeter can be realized.

According to the second aspect of the present invention, by disposing the exciter between the vibrating tube and the compensator, it is possible to vibrate both the vibrating tube and the compensator in opposite phases. Will be possible. Since the exciters for the vibrating tube and the compensator can be combined into one, the configuration is simplified and a low-cost Coriolis mass flowmeter can be obtained.

According to the third aspect of the present invention, (1) the vibration of the vibration tube 11 and the vibration of the compensator 15 are separately excited using the first and second exciters 31 and 32. Since the vibration is performed, finer vibration control becomes possible.

(2) Even if the resonance frequency of the vibration tube 11 is different from the resonance frequency of the compensator 15, individual vibrations with different phases can be easily performed without complicated resonance frequency design. And an inexpensive Coriolis mass flowmeter can be obtained.

According to the fourth aspect of the present invention, since the compensator having sufficiently large rigidity is provided, even if stress or vibration noise is applied from the outside, the influence is exerted on the vibration tube inside the compensator. , And stable excitation can be continued. That is, a stable and high-accuracy Coriolis mass flowmeter which is hardly affected by stress or vibration from the outside can be obtained.

According to the fifth aspect of the present invention, since the vibration tube vibrates only in the circumferential plane equidistant from the reference axis, the length of the vibration tube can be increased regardless of the position of the vibration tube. It will not change.

Therefore, the pulling force in the axial direction is always constant. That is, due to the change in the axial force,
Vibration leakage can be eliminated.

As a result, (1) the internal vibration system can realize a high Q value, the influence of external noise is relatively small even if external noise is applied, and the vibration is stable, so that a Coriolis mass flowmeter resistant to external vibration noise can be obtained. Can be

(2) Since stable excitation can be realized with a small amount of energy, a Coriolis mass flowmeter with low current consumption can be obtained.

(3) If the amount of vibration energy dissipated to the outside changes, or if the balance of the amount dissipated upstream and downstream is disturbed, the internal vibration system is affected and the zero point and span fluctuate. In the present invention, since the vibration is always confined inside, there is no need to worry about this, and a highly accurate Coriolis mass flowmeter can be obtained.

(4) The measurement fluid flow path is provided at the inlet (inlet) of the flow meter.
There is no branch or gap from the outlet to the outlet
Because of the single penetrating structure, a Coriolis mass flowmeter with low flow velocity loss, less clogging, and easy cleaning can be obtained.

(5) Since the vibrating tube is not a complete straight tube but is curved in a predetermined shape in a non-excited state, it can easily absorb changes in ambient temperature at the curved portion, and the temperature characteristics , A good Coriolis mass flowmeter can be obtained.

A Coriolis mass flowmeter which is not a general curved tube nor a perfect straight tube but has an appropriate curve and can realize the advantages of a curved tube and a straight tube at the same time is obtained.

According to the sixth aspect of the present invention, in the steady excitation state, no force in the translational direction component other than the torsional component around the reference axis is generated at the connecting portions at both ends of the vibrating tube. Not leak.

In claim 5, the axial expansion and contraction force is reduced to zero or greatly reduced. According to claim 6, the Coriolis mass flowmeter further reduces the translational component such as the vibration direction to zero or greatly reduced. can get.

By increasing the vibration isolation as described above, the following advantages are exhibited. (1) Since the internal vibration system can realize a high Q value, the influence of external noise is relatively small even if external noise is applied, and the vibration is stable, a Coriolis mass flowmeter resistant to external vibration noise can be obtained.

(2) Since stable excitation can be realized with small energy, a Coriolis mass flowmeter with low current consumption can be obtained.

(3) If the amount of vibration energy dissipated to the outside changes, or if the balance of the amount dissipated upstream and downstream is disturbed, the internal vibration system is affected and the zero point and span fluctuate. In the present invention, since the vibration is always confined inside, there is no concern about the vibration, and a highly accurate Coriolis mass flowmeter can be obtained.

According to the seventh aspect of the present invention, the vibration detecting sensor is disposed in a direction opposite to the vibration tube with respect to the reference axis.
By installing the vibrator near the tip, vibration can be detected at an optimum position.

By being located at the tip of the vibrating body, vibration can be measured at the place where the amplitude is the largest in the vibration system.
Also, the phase difference generated by the Coriolis force becomes very large.

Actually, as a result of comparing the embodiment of FIG. 18 with the embodiment of FIG. 24 (corresponding to claim 7) by experiment, as an example,
It was as follows. The ratio of the sensor amplitude / drive amplitude is 0.8 in the embodiment of FIG. 18 and 3.5 in the embodiment of FIG. The generated phase difference <m rad> is 8.8 in the embodiment of FIG. 18 and 37.5 in the embodiment of FIG. Becomes

As described above, in both the amplitude ratio and the generated phase difference, values that are slightly more than four times larger than those in the embodiment of FIG. 18 were observed.

As a result, (1) S / N is improved if the measured amplitude is large. Conversely, if the measurement amplitude is the same as the conventional one, the excitation force can be reduced, and a Coriolis mass flowmeter with low power consumption can be obtained. If the maximum amplitude is small, vibration energy is small, leakage to the outside is small, vibration isolation is easy, and a stable and accurate Coriolis mass flowmeter can be obtained.

(2) If the generated phase difference is large, the signal processing of the signal conversion part becomes easy. That is, a Coriolis mass flowmeter capable of realizing stable and highly accurate performance even with a simple and inexpensive signal processing circuit can be obtained.

Conversely, if the signal processing performance is equivalent to the conventional one, stable measurement can be performed up to a low flow rate region where the generated phase difference is small. A possible Coriolis mass flow meter is obtained.

As a result, since both the amplitude and the phase difference are larger than 4 times, it is very advantageous and a dramatic improvement effect can be obtained.

According to the eighth aspect of the present invention, the following advantages are obtained by exciting in the second, third, or higher order mode.

(1) It is easy to set the excitation frequency higher.
Vibration at low frequency is susceptible to vibration noise in the field, whereas high frequency excitation provides a Coriolis mass flowmeter that is less susceptible to vibration noise.

(2) The resonance frequencies of the excitation mode and the vibration mode generated by the Coriolis force can be made close to each other. Further, the generated phase difference is large.

(3) If the generated phase difference is large, the signal processing of the signal conversion unit becomes easy. That is, a Coriolis mass flowmeter capable of realizing stable and highly accurate performance even with a simple and inexpensive signal processing circuit can be obtained.

Conversely, if the signal processing performance is equivalent to the conventional one, stable measurement can be performed up to the low flow rate region where the generated phase difference is small, and the mass flow rate measurement of the gas originally generated with the small phase difference can be performed. A possible Coriolis mass flow meter is obtained.

According to claim 9 of the present invention, the flexible structure portion is
Since it is provided in the vibrating tube between the upstream and downstream fixed ends and the compensator, (1) it is possible to absorb thermal expansion, and it is possible to measure stably with high accuracy over a wide temperature range A Coriolis mass flow meter is obtained.

(2) Even when pipe stress is applied, the flexible structure can absorb the stress and does not affect the inside, so that a stable and accurate Coriolis mass flowmeter can be obtained.

Therefore, according to the present invention, a Coriolis mass flowmeter with improved stability, accuracy and vibration resistance can be realized by improving the insulation of internal vibration.

[Brief description of the drawings]

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

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a sectional view taken along line BB of FIG. 1;

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

FIG. 5 is an operation explanatory diagram of FIG. 1;

FIG. 6 is an explanatory diagram of a main part configuration of another embodiment of the present invention.

FIG. 7 is an operation explanatory diagram of FIG. 6;

FIG. 8 is an explanatory diagram of a main part configuration of another embodiment of the present invention.

FIG. 9 is a side view of FIG.

FIG. 10 is an explanatory diagram of a main part configuration of another embodiment of the present invention.

FIG. 11 is an operation explanatory diagram of FIG. 10;

FIG. 12 is an operation explanatory diagram of FIG. 10;

FIG. 13 is an operation explanatory diagram of FIG. 10;

FIG. 14 is an operation explanatory diagram of FIG. 10;

FIG. 15 is an operation explanatory diagram of FIG. 14;

FIG. 16 is an operation explanatory diagram of FIG. 10;

FIG. 17 is an operation explanatory diagram of FIG. 16;

FIG. 18 is an explanatory diagram of a main part configuration of another embodiment of the present invention.

FIG. 19 is a side view of FIG. 18;

20 is an operation perspective view of FIG.

21 is a projection view from the X direction in FIG.

FIG. 22 is a projection view from the Y direction in FIG. 20;

FIG. 23 is a projection view from the Z direction in FIG. 20;

FIG. 24 is an explanatory diagram of a main part configuration of another embodiment of the present invention.

FIG. 25 is a side view of FIG. 21.

FIG. 26 is an explanatory perspective view of an operation of a main part of another embodiment of the present invention.

FIG. 27 is a projection view from the X direction in FIG. 26;

FIG. 28 is a projection view from the Y direction in FIG. 26;

FIG. 29 is a projection view from the Z direction in FIG. 26;

FIG. 30 is an explanatory perspective view of the operation in the primary mode of FIG. 24;

FIG. 31 is a projection view from the X direction in FIG. 30;

FIG. 32 is a projection view from the Y direction in FIG. 30.

FIG. 33 is a projection view from the Z direction in FIG. 30;

FIG. 34 is an explanatory perspective view of the operation in the secondary mode shown in FIG. 24;

FIG. 35 is a projection view from the X direction in FIG. 34;

FIG. 36 is a projection view from the Y direction in FIG. 34;

FIG. 37 is a projection view from the Z direction in FIG. 34.

38 is an explanatory perspective view of the operation of the fourth mode shown in FIG. 24. FIG.

FIG. 39 is a projection view from the X direction in FIG. 38;

40 is a projection view from the Y direction in FIG. 38.

FIG. 41 is a projection view from the Z direction in FIG. 38;

FIG. 42 is an explanatory diagram of a main part configuration of another embodiment of the present invention.

FIG. 43 is an explanatory diagram of a configuration of a conventional example generally used in the related art.

FIG. 44 is an explanatory view of the configuration of another conventional example generally used in the related art.

FIG. 45 is a diagram illustrating the operation of FIG. 43.

FIG. 46 is an operation explanatory diagram of FIG. 44;

FIG. 47 is an operation explanatory diagram of FIG. 44;

[Explanation of symbols]

 2 Flange 3 Exciting means 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 Compensator 16 Connecting part 17 Connecting part 21 Vibrating tube 31 First exciter 32 2nd exciter 41 compensator 51 vibrating tube 52 midline 53 gentle curved part 54 outer part 55 outer part 56 outer part 57 outer part 61 vibrator 62 vibrator 71 flexible structure part 301 coil 302 magnet 401 coil 402 magnet 501 Coil 502 Magnet

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[Procedure amendment]

[Submission date] July 29, 1998 (1998.7.2
9)

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] FIG.

[Correction method] Change

[Correction contents]

FIG. 11

[Procedure amendment 2]

[Document name to be amended] Drawing

[Correction target item name] FIG.

[Correction method] Change

[Correction contents]

FIG. 34

Claims (9)

[Claims] 1. A Coriolis mass flowmeter for deforming and vibrating a vibrating tube by a flow of a measuring fluid flowing in a vibrating tube, and a Coriolis force generated by the flow of the measuring fluid and angular vibration of the vibrating tube. A vibrating tube that vibrates with a straight line connecting the downstream fixed end as a reference axis, a compensator provided in parallel with the reference axis, and both ends of which are fixedly supported at both end sides of the vibrating tube, In the vicinity of the fixed end, the torsion vibration is generated such that the torsion around the reference axis is predominant and the compensator is rotated around the same axis as the reference axis or an axis parallel to the reference axis. And the connecting portion between the vibrating tube and the compensator in the opposite phase to the vibration of the vibrating tube. Coriolis mass flowmeter, wherein the exciting means for exciting such Gillet vibrations reduce the cancellation occurs oscillations with respect to each other, by comprising a. 2. A Coriolis mass flowmeter according to claim 1, wherein said exciting means comprises an exciter having one end connected to said vibrating tube and the other end connected to said compensator. 3. The exciter includes a first exciter that excites the vibrating tube and a second exciter that excites the compensator. The Coriolis mass flowmeter described. 4. A compensator having sufficiently high rigidity so that the shape of the compensator and the vibrating tube does not change when external piping stress or vibration noise is applied. The Coriolis mass flowmeter according to any one of claims 1 to 3, wherein 5. The vibrating tube has at least one gently curved portion which is line-symmetric with respect to a midline equidistant from the upstream fixed end and the downstream fixed end, and has at least one gentle curved portion. A single vibrating tube that makes a single vibration on or near a circumferential line at a predetermined distance from each point of the reference axis with a straight line connecting the downstream fixed end as a reference axis is provided. The Coriolis mass flow meter according to claim 1. 6. The reference axis or the vibrating tube is perpendicular to the vibrating tube, one end is fixed to the vibrating tube, and the other end is disposed on the opposite side of the vibrating tube with respect to the reference axis and is located at a position symmetrical to the center line. At least two plate-shaped vibrators are provided, and the vibration in the steady excitation state is adjusted by adjusting the mass distribution, shape, and rigidity of the vibrating tube, and the mass distribution, shape, rigidity, and interval of the vibrator. The force generated in the connecting portion at both ends of the tube is made only a torsional component around the reference axis so that a component orthogonal to the reference axis due to an exciting force by an exciter is not generated. A Coriolis mass flowmeter according to any one of claims 1 to 5. 7. A plate-shaped vibrating body orthogonal to said reference axis or said vibrating tube, one end of which is fixed to said vibrating tube and the other end of which is disposed on the opposite side of said vibrating tube with respect to said reference axis. 7. The Coriolis mass flowmeter according to claim 1, further comprising a vibration detection sensor provided at the other end of the vibrating body. 8. The Coriolis mass flowmeter according to claim 1, further comprising an exciter for exciting the vibrating tube in a second-order mode or higher order vibration mode. 9. A flexible structure provided on the vibrating tube between the upstream fixed end, the downstream fixed end, and the compensator for absorbing expansion and contraction in the direction of the reference axis and rotational vibration about the reference axis. The Coriolis mass flowmeter according to any one of claims 1 to 8, further comprising a unit.