JP2993294B2 - Coriolis mass flowmeter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a measuring pipe having a simple structure with a small fluid resistance, which does not transmit vibration of the measuring pipe to a pipe line, and which is used to adjust the fixed end conditions at the upstream and downstream of the measuring pipe. The present invention relates to a Coriolis mass flowmeter in which balance does not affect zero point fluctuation.

[0002]

2. Description of the Related Art FIG. 5 is a diagram for explaining the structure of a conventional example generally used in the prior art.
No. 2, the title of the invention "Coriolis Mass Flow Meter". In the figure, reference numeral 1 denotes a measuring tube having both ends attached to a flange 2. The flange 2 is for attaching the measuring pipe 1 to the pipe A. Reference numeral 3 denotes a vibrator provided at the center of the measuring tube 1. Reference numerals 4 and 5 denote vibration detection sensors provided on both sides of the measuring tube 1, respectively.

In the above configuration, a measurement fluid is caused to flow through the measurement tube 1, and the vibrator 3 is driven. Assuming that the angular velocity in the vibration direction of the vibrator 3 is “ω” and the flow velocity of the measurement fluid is “V” (hereinafter, the symbol surrounded by “” indicates a vector quantity), Fc = −2 m “ω” × “V” The mass flow rate can be measured by measuring the amplitude of the vibration in which the Coriolis force acts and which is proportional to the Coriolis force.

FIG. 6 is an explanatory view of the structure of another conventional example which has been generally used. In this conventional example, in order to further reduce the noise and increase the signal, the measurement tube 1 is of a two-tube type so as to cancel the noise.

[0005]

However, in such an apparatus, in the conventional example shown in FIG. 5, the measuring tube 1 vibrates approximately under the condition that both ends are fixed. However, the fixed portion does not necessarily have a completely fixed end. , Will vibrate slightly. In this case, the vibration is transmitted to the pipe A, and the symmetry is broken due to a slight difference in the fixing conditions of the upstream and downstream ends, for example, welding strength and the like.
The zero point easily shifts. On the other hand, in the conventional example shown in FIG. 6, the two measuring tubes vibrate in opposite directions, so that the forces cancel each other out at the branch portion, and as shown in FIGS. It has a structure. However, the structure of one measuring tube having no branch point cannot be taken.

The present invention solves this problem. An object of the present invention is to provide a single measuring tube having a simple structure with low fluid resistance, but not transmitting the vibration of the measuring tube to the case, and the unbalance of the fixed end conditions at the upstream and downstream of the measuring tube to zero point fluctuation. The present invention provides a Coriolis mass flow meter that does not significantly affect the flow rate.

[0007]

In order to achieve this object, the present invention provides a method of flowing a measuring fluid into a vibrating measuring tube, and deforming the measuring tube by a Coriolis force generated by the flow and the angular vibration of the measuring tube. In the Coriolis mass flowmeter to be measured, a measurement pipe through which the measurement fluid flows, two vibration auxiliary rods provided in parallel with the measurement pipe interposed therebetween, and one end of the measurement pipe and one end of the vibration auxiliary rod are fixed. (1) a vibrator support, a second vibrator support to which the other end of the measuring tube and the vibration auxiliary rod are fixed, a first vibrator support and a node of vibration of the second vibrator support; A supporting portion provided at a predetermined location, one end of which is connected to a pipe, and a vibrator which is connected to a central portion of the measuring tube and the vibration auxiliary rod via a vibrator and is vibrated in an axial direction by the vibrator. A rod, and a mounting position of the vibrating rod of the measurement tube and the vibrating body supporting portion. Is obtained by constituting the Coriolis mass flowmeter, characterized by comprising a vibration detecting sensor provided between the.

[0008]

In the above arrangement, when the measuring fluid is flowed through the measuring tube and the vibrator is driven, the Coriolis force acts. By measuring the amplitude of the vibration proportional to the Coriolis force, the mass flow rate can be measured. Thus, since the first vibrator support portion and the second vibrator support portion are provided at portions that serve as nodes of vibration and have one end connected to the pipeline, energy leaking to the outside can be reduced. Can be reduced. Hereinafter, a detailed description will be given based on embodiments.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory diagram of a main portion of an embodiment of the present invention. Reference numeral 11 denotes a straight measurement tube through which a measurement fluid flows.

Reference numeral 12 denotes two vibration auxiliary rods provided in parallel with the measuring tube 11 interposed therebetween. Reference numeral 13 denotes a first vibrating body support to which one ends of the measuring tube 11 and the vibration auxiliary rod 12 are fixed. Reference numeral 14 denotes a second vibrating body support to which the other ends of the measuring tube 11 and the vibration auxiliary rod 12 are fixed.

Reference numeral 15 denotes a rotary bearing provided at a location that serves as a node of vibration between the first vibrating body support 13 and the second vibrating body support 14. Reference numeral 16 is orthogonal to a plane composed of the vibration assisting rod 12, the first vibrating body supporting portion 13, and the second vibrating body supporting portion 14, and is inserted into the bearing 15 and at least one end thereof is connected to the conduit A. It is a support shaft. Thus, the rotary bearing 15 and the support
The shaft 16 forms a support part 160. 17 is
The central portion between the measuring tube 11 and the vibration assisting rod 12 is
And a vibrating rod that is vibrated in the axial direction by the vibrator 18. Reference numeral 19 denotes a vibration detection sensor provided between the vibrating rod 17 of the measuring tube 11 and the mounting positions of the vibrating body supports 13 and 14. Reference numeral 21 denotes a flange to which the other end of the support shaft 16 is connected and which is connected to a pipe (not shown) A. Reference numeral 22 denotes a tube that connects the measurement tube 11 and the flange 21. The tube 22 is made of a soft material that does not transmit the influence of thermal expansion and vibration to the measurement tube 11 and the flange 21.

In the above configuration, when a measuring fluid is caused to flow through the measuring tube 11 and the vibrator 18 is driven, a Coriolis force acts. By measuring the amplitude of the vibration of the measuring tube 11 in proportion to the Coriolis force, Mass flow rate can be measured. Thus, the first
A rotating bearing 15 provided at a location B which serves as a node of vibration between the vibrating body support portion 13 and the second vibrating body support portion 14;
A support shaft 16 which is inserted into the bearing 15 and has at least one end connected to the pipe A is provided orthogonal to a plane formed by the second, first vibrator support portions 13 and second vibrator support portions 14. Energy can be reduced.

That is, as shown in FIG. 1, when the X, Y, and Z axis directions are determined, the measuring tube 11 is vibrated in the Y direction by the vibrator 18 via the vibrating rod 17. Since the vibrator 18 is connected to the auxiliary vibration rod 12, when a force is applied to the measuring tube 11, a reaction force is applied to the auxiliary vibration rod 12. As a result,
As shown by a solid line in FIG. 2, when the measuring tube 11 is deformed to the maximum in the Y-axis direction, the vibration assisting rods 12 on both sides are deformed to the maximum in the negative Y-axis direction.

That is, assuming that the amplitude of the measuring tube 11 is A ₁ and the amplitude of the vibration assisting rod 12 is A ₂ (A ₁ , A ₂ > 0), the vibration in the Y direction of both can be expressed as follows. Measuring tube 11: Y ₁₁ = A ₁ Sin (ωT) Vibration auxiliary rod 12: Y ₁₂ = A ₂ Sin (ωT + π)

Next, the movements of the vibrating body supporting portions 13 and 14 are as follows.
With the movement of the measuring tube 11 and the vibration auxiliary rod 12, vibration is performed as shown in FIG. At the location where the rotary bearing 15 is mounted, the translational motion component is close to zero, but a rotary component around the Z axis is generated. Since the rotation component is absorbed by the rotation bearing 16, it is possible to prevent the transmission of vibration to the outside.

In short, the vibrator 18 is caused to vibrate in the Y-axis direction by the force of the vibrator 18 so that the vibrating system portion has a Y-axis translational motion component and Z
An axial rotation component occurs. Since the measuring tube 11 and the vibration assisting rod 12 vibrate in directions opposite to each other in the Y-axis direction, the translational components in the Y-axis direction cancel each other out at the vibrating body supports 13 and 14 and disappear. The Z-axis rotation components are
Are present in the central portion, but are absorbed by the rotary bearing 15.

As a result, it is possible to prevent the vibration of the measuring tube 11 from being transmitted to the outside (flange 19). By eliminating the dissipation of the vibration energy from both ends of the vibration system, it is not necessary to apply an extra excitation force, and the amount of external energy supply can be suppressed. Further, since there is no imbalance in the amount of vibration energy dissipated upstream and downstream of the measurement tube 11, there is an effect that a zero point and a span that are stable even when the temperature or the flow rate changes can be maintained.

After all, by adopting the structure of three tuning forks, the above-mentioned effects can be obtained without using two parallel pipes or curved pipes for the measurement pipe and keeping one straight pipe type. it can. FIG. 3 is an explanatory diagram of a main part configuration of another embodiment of the present invention, and FIG. 4 is a conceptual diagram of operation. In this embodiment, the center part of the vibration assisting rod 12 is divided. In such an apparatus, an apparatus in which stress is hardly generated due to a difference in thermal expansion between the measurement pipe 11 and the vibration assisting rod 12 based on a temperature change or the like due to a measurement fluid in the measurement pipe 11 can be obtained.

[0019]

As described above, the present invention relates to a Coriolis mass flowmeter which deforms and vibrates a measuring tube by flowing a measuring fluid into a vibrating measuring tube and causing Coriolis force generated by the flow and the angular vibration of the measuring tube. A measurement pipe through which the measurement fluid flows, two vibration auxiliary rods provided in parallel with the measurement pipe interposed therebetween, and a first vibrating body support portion to which one end of the measurement pipe and the vibration auxiliary rod is fixed. A second vibrating body supporting portion to which the other end of the measuring tube and the vibration auxiliary rod are fixed;
The vibrator support part and the support part, which is provided at a location that becomes a node of vibration of the second vibrator support part and one end of which is connected to a pipe, and the central part of the measuring tube and the vibration auxiliary rod are connected to a vibrator. A vibrating rod connected through the vibrator and vibrated in the axial direction by the vibrator; and a vibration detection sensor provided between the vibrating rod of the measurement tube and a mounting position of the vibrating body support. Thus, a Coriolis mass flowmeter was constructed.

As a result, since the first vibrating body support portion and the second vibrating body support portion are provided at the portions that serve as nodes of vibration and have one end connected to the conduit, the vibration of the measuring tube is provided. Can be prevented from being transmitted to the outside (flange). By eliminating the dissipation of the vibration energy from both ends of the vibration system, it is not necessary to apply an extra excitation force, and the amount of external energy supply can be suppressed. Furthermore, by eliminating the imbalance in the amount of vibration energy dissipated upstream and downstream of the measurement tube,
There is an effect that a stable zero point and span can be maintained even when the temperature or the flow rate changes.

Therefore, according to the present invention, the Coriolis mass flowmeter which does not transmit the vibration of the measuring tube to the pipeline, and the imbalance of the fixed end conditions upstream and downstream of the measuring tube hardly affects the zero point fluctuation. 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.

FIG. 2 is an operation explanatory diagram of FIG. 1;

FIG. 3 is an explanatory diagram of a main part configuration of another embodiment of the present invention.

FIG. 4 is an operation explanatory diagram of FIG. 3;

FIG. 5 is an explanatory diagram of a configuration of a conventional example generally used in the related art.

FIG. 6 is an explanatory view of the configuration of another conventional example generally used in the prior art.

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

FIG. 8 is an operation explanatory diagram of FIG. 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Measuring pipe 12 ... Vibration auxiliary rod 13 ... 1st vibrating body support part 14 ... 2nd vibrating body support part 15 ... Rotating bearing 16 ... Support shaft 17 ... Exciting rod 18 ... Vibrator 19 ... Vibration detection sensor 21 ... Flange 22 ... Tube

Claims (1)

(57) [Claims] 1. A measuring fluid is passed through a vibrating measuring tube, and
Due to Coriolis force generated by flow and angular vibration of the measuring tube
And a Coriolis mass flow meter that deforms and vibrates the measurement tube
A measuring pipe through which the measuring fluid flows, and two vibration assisting rods provided in parallel with the measuring pipe interposed therebetween.
A first vibration in which one end of the measuring tube and one end of the vibration assisting rod are fixed.
A body support, and a second vibration to which the other ends of the measurement tube and the vibration auxiliary rod are fixed.
A moving body supporting portion; a node of vibration of the first vibrating body supporting portion and the second vibrating body supporting portion
Support where one end is connected to a conduitDepartment
And a central portion between the measuring tube and the vibration assist rod via a vibrator.
And a vibrating rod that is vibrated in the axial direction by the vibrator
Mounting position of the vibrating rod of the measuring tube and the vibrating body support portion
And a vibration detection sensor provided between the
A Coriolis mass flowmeter characterized by the following.