JP3003420B2 - 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” (the symbol enclosed by “” represents 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 vibrating body support, a second vibrating body support to which the other end of the measuring tube and the vibration auxiliary rod are fixed, and a tear vibration of the first vibrating body supporting part and the second vibrating body supporting part. A connection spring having one end connected to each of the nodes, a pipe line to which the other end of the connection spring is connected and both ends of the measuring tube are connected, and a center of the two vibration assisting rods A connecting rod connecting the parts, a central part of the connecting rod and A vibrator provided between the center portion of the fixed tube and vibrating in a direction perpendicular to a plane formed by the measuring tube and the vibration assisting rod; and a vibrator of the measuring tube and the vibrating body supporting portion. A Coriolis mass flow meter comprising a vibration detection sensor provided between the mass flow meter and the mounting position.

[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, a connection spring having one end connected to a portion of the first vibrator support portion and the second vibrator support portion which serves as a node of torsional vibration, the other end of the connection spring being connected and both ends of the measuring tube Are connected to each other, so that energy leaking to the outside can be eliminated. 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 four connection springs each having one end connected to a portion of the l-th vibrating body supporting portion 13 and the second vibrating body supporting portion 14 which serves as a node of torsional vibration. It is needless to say that the number of connection springs 15 is not limited to four. 16
Is a connecting rod connecting the central portions of the two vibration assisting rods 12. 17 is provided between the central part of the connecting rod 16 and the central part of the measuring pipe 11,
Is a vibrator that vibrates in a direction perpendicular to the plane composed of.

Reference numeral 18 denotes a vibration detection sensor provided on the measuring tube 11 on both sides of the vibrator 17. 19 is the connection spring 1
5 is a flange to which the other end is connected and both ends of the measuring tube 11 are connected via a tube 21 described later. The flange 19 is for connecting to a pipe A (not shown). Further, both ends of the measuring tube 11 are substantially connected to the flange 19 via the tube 21. Therefore, the measurement pipe 11 and the connection spring 15 may be directly connected to the pipe A (not shown). Thus, the connection spring 15 plays a role of supporting the entire vibration system while insulating the vibration system portion and the flange 19 and having an elastic structure capable of absorbing thermal expansion. 21
Is a tube that connects the measurement tube 11 and the flange 19. The tube 21 measures the influence of thermal expansion and vibration.
The flange 19 is made of a soft material that does not transmit to each other.

In the above arrangement, when a measuring fluid is flowed through the measuring tube 11 and the vibrator 17 is driven, a Coriolis force acts. The amplitude of the vibration of the measuring tube 11 in proportion to the Coriolis force is measured. Mass flow rate can be measured. Thus, the first
The connection springs 15 each having one end connected to the torsion vibration node of the vibrating body supporting portion 13 and the second vibrating body supporting portion 14 and the other end connected to the flange are provided. 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 moved by the vibrator 17 to the Z direction.
Vibrates in the direction. Since the vibrator 17 is connected to the vibration assisting rod 12 via the connecting rod 16, when a force is applied to the measuring tube 11, a reaction force is applied to the connecting rod 16. As a result, as shown by a solid line in FIG. 2, when the measuring tube 11 is deformed to the maximum in the Z-axis direction, the vibration assisting rods 12 on both sides are deformed to the maximum in the negative Z-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 vibrations of the two in the Z direction can be expressed as follows. Measuring tube 11: Z ₁₁ = A ₁ Sin (ωT) Vibration auxiliary rod 12: Z ₁₂ = A ₂ Sin (ωT + π)

Next, the movements of the vibrating body supporting parts 13 and 14 are as follows.
With the movement of the measuring tube 11 and the vibration assisting rod 12, as shown in FIG. Since the vibration directions of the measuring tube 11 and the vibration assisting rod 12 are opposite, the directions of the screws are opposite on the side where the measuring tube 11 is attached and on the side where the vibration assisting rod 12 is attached. For this reason, the vibrating body support 1
A portion B which is a node of the torsional vibration exists in the middle of 3, 14 where both the translational component and the rotational component are zero and stopped. Since the connection portion (connection spring 15) between the flange 19 and the vibrating body support portions 13 and 14 is provided in the portion B, it is possible to prevent the transmission of vibration to the outside.

In short, the vibrator 17 is caused to vibrate in the Z-axis direction by the force of the vibrator 17 so that the vibrating system portion has a Z-axis translational motion component and Y
An axial rotation component occurs. Since the measuring tube 11 and the vibration assisting rod 12 vibrate in opposite directions in the Z-axis direction, the Z-axis translational motion components cancel each other out at the vibrating body supports 13 and 14 and disappear. The Y-axis rotation components are
However, since the portion B is a node of torsional vibration, the stationary state is maintained.

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 the three tuning forks, the above-mentioned effect can be obtained without changing the measuring pipe to two parallel pipes or curved pipes 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 a device, a device in which torsional stress is less likely to occur due to a difference in thermal expansion between the measurement tube 11 and the vibration assisting rod 12 based on a temperature change or the like due to the measurement fluid in the measurement tube 11 is obtained.

[0020]

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;
A connection spring having one end connected to each of the vibrating body supporting portions and a portion of the second vibrating body supporting portion that serves as a node of tearing vibration, and the other end of the connecting spring being connected and both ends of the measuring tube being respectively connected A connected pipe, a connecting rod connecting a central part of the two vibration-aid rods, and a connecting rod provided between the central part of the connecting rod and a central part of the measuring pipe. A vibrator that vibrates in a direction perpendicular to a plane formed by an auxiliary rod; and a vibration detection sensor provided between the vibrator of the measurement tube and a mounting position of the vibrating body support. A Coriolis mass flowmeter was characterized.

As a result, a connection spring having one end connected to each of the torsional vibration nodes of the first vibrator support and the second vibrator support is connected, and the other end of the connection spring is connected to the measuring tube. Is provided with a pipe line to which both ends are connected, so that the vibration of the measuring pipe can be prevented from being transmitted to the outside (pipe line). 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, since there is no 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 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 pipe line 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 ... Connection spring 16 ... Connection rod 17 ... Vibrator 18 ... Vibration detection sensor 19 ... Flange 21 ... Tube A ... Pipe B ... part

Claims (1)

(57) [Claims] 1. A Coriolis mass flowmeter for causing a measurement fluid to flow in a vibrating measurement tube, and deforming and vibrating the measurement tube by Coriolis force generated by the flow and the angular vibration of the measurement tube. Two vibration-aid bars provided in parallel with the measurement tube interposed therebetween; an l-th vibrator support portion to which one end of the measurement tube and the vibration-aid rod is fixed; the measurement tube and the vibration assist A second vibrator support having the other end of the rod fixed thereto; a connection spring having one end connected to each of the first vibrator support and a portion of the second vibrator support which serves as a node of torsional vibration; The other end of the connection spring is connected and both ends of the measuring tube
Are respectively connected, a connecting rod connecting the central portions of the two vibration assisting rods, and provided between the central portion of the connecting rod and the central portion of the measuring tube. A vibrator that vibrates in a direction perpendicular to a plane formed by the vibration auxiliary rod; and a vibration detection sensor provided between the vibrator of the measurement tube and a mounting position of the vibrating body support. A Coriolis mass flowmeter, characterized in that: