JPS58123429A - Mass flowmeter - Google Patents

Abstract

PURPOSE:To form the vibration type mass flowmeter, which is hard to be subjected to vibration noises, has stable operating property, and can obtain high resolution. CONSTITUTION:Magnets 7 and 8 form a magnetic field generating means and are provided in the inside of a pipe 1 constituted by a conductor so that the different poles face the pipe. When the U shaped pipe 1 is excited by a driving means, the pipe is vibrated in a driving mode (symmetrical deflecting vibration). The legs of the pipe 1 are interlinked with the magnetic fields generated by the magnets 7 and 8. Therefore electromotive forces are generated in the legs of the pipe 1 due to the vibration described above. When the U shaped pipe is vibrated in the driving mode, currents i1 and i2 induced in the legs of the U shaped pipe 1 become opposite to each other and are offset. Therefore the vibration of the pipe 1 is not affected. On the contrary, when the U shaped pipe 1 is vibrated in a Coriolis vibration mode (asymmetrical deflecting vibration), the vibrating directions of the legs of the U shaped pipe 1 are opposite to each other, and the current i3 and i4 induced in the legs flow in the same direction. As a result, the asymmetrical deflecting energy is converted into Joule loss in a short circuit formed by a base 3 and the U shaped pipe and attenuated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an improved mass flow meter using the Coriolis force.
This is related to lLK.

FIG. 1 is a configuration explanatory diagram for explaining the operating principle of a Coriolis flowmeter. Reference numeral 1 denotes a U-shaped tube through which a measuring fluid flows, a permanent magnet 2 is fixed at the center of the tip thereof, and both ends of the U-shaped tube 10 are fixed to a base 5. 4 is an electromagnetic drive/detection coil installed opposite to the U-shaped tube 1; 5 is a support beam that supports this electromagnetic drive/detection coil at its tip; the other end is fixed to the base 5. The U-shaped tube 1 and the support beam 5 mutually form a tuning fork structure. That is, the U-shaped tube 1 and the beam 5 vibrate opposite each other, just like the teeth of a tuning fork vibrate, and like a tuning fork, the base 30 is a nodal point of vibration, so that less vibrational energy is lost. It becomes. 61 and 62 are displacement detectors for detecting the displacement of both legs of the U-shaped tube 1.

When the 8-shaped tube 1 is excited at its natural frequency by the electromagnetic force acting between the drive coil 4 and the permanent magnet 2 fixed to the opposing U-shaped tube 1 (longitudinal vibration (symmetrical flexural vibration): rattan 2 (Ml, M2 and M3 in the figure indicate putter 7 at each moment),
Coriolis force is generated in the fluid flowing inside the U-shaped tube 1. The size of this Coriolis is proportional to the mass of the fluid flowing in the U-shaped tube 1, and the direction of the force corresponds to the direction of the kutor product of the moving direction of the fluid and the angular velocity that excites the U-shaped tube 1. Also, since the direction of the fluid is opposite on the input side and output side of the 8-shaped tube 1,
Coriolis on both leg sides generates a torque of screw 9 (asymmetrical deflection) in the figure-8 tube 1. This torque varies with the same frequency as the excitation frequency, and its amplitude value is proportional to the mass flow rate of the fluid. Figure 2 ■) shows the vibration mode (Coriolis vibration mode) caused by this torsional torque.
M4. M5. Me indicates the vibration pattern at each moment.

Therefore, by detecting the amplitude of this torsional vibration (asymmetrical flexural vibration) torque using the displacement detectors 61, 62, for example, with a pulse width of 4, the mass flow rate can be determined.

Mass flowmeters using the above-mentioned principle have been conventionally known (for example, Japanese Patent Application Laid-Open No. F@54-52570), but there are the following problems in this case. In other words, the Q of a conduit is generally designed to be high in order to give the conduit rotational vibration with less energy loss and to increase the stability of the vibration frequency. This results in a drawback that the output amplitude becomes unstable because external vibration noise is easily picked up, and the resolution of the mass flowmeter is reduced.

The present invention has been made to solve the above-mentioned drawbacks.
The purpose of the present invention is to realize a vibrating mass flowmeter that is not affected by vibration noise, has stable operation, and can obtain high resolution.

The present invention will be explained below with reference to the drawings.

Figure fs3 is a structural perspective view showing the main parts of the device according to the present invention. This device is characterized by attenuating the unnecessary torsional (asymmetrical deflection) vibration component included in the vibration of the zero-shaped tube by converting it into Joule loss based on the interaction between the magnetic field and the short circuit. . In the figure, magnets 7 and 8 form a magnetic field generating means and are installed inside a conduit 1 made of a conductor with different poles facing the tube. The base 3 made of a conductor and the 8-shaped tube 1 form an electrical short circuit. When the figure-8 tube 1 is excited by the driving means, it vibrates in a driving mode (symmetrical flexural vibration). Since each leg of the conduit 1 is interlinked with the magnetic field created by the magnets 7 and 8,
The vibrations described above generate an electromotive force in each leg of the conduit 1.

Due to this electromotive force, a closed circuit current flows in the short circuit. When the figure-8 tube 1 is vibrating in the drive mode (symmetrical flexural vibration), the currents induced in each leg of the figure-8 tube 1 are 1□, 1
□ Since the directions are opposite to each other, they cancel each other out and do not affect the vibration of the tube 1. On the other hand, as shown in Fig. 4 (where V s V2 is the vibration velocity of both legs), if the figure-8 tube 1 is vibrating in the Coriolis vibration mode (asymmetrical flexural vibration), the figure-8 Since the directions of vibration of each leg of the tube 1 are opposite to each other, the currents 13 and 1° induced in each leg flow in the same direction. As a result, asymmetrical deflection vibrational energy is converted into di-route losses within the short circuit. In actual use, the Coriolis vibration mode (asymmetrical flexural vibration) and the drive mode (symmetrical flexural vibration) are superimposed, but only the Coriolis vibration (asymmetrical flexural vibration) component is damped by braking.

The phase of the displacement of the pipe vibration lags behind the driving force of the 8-shaped pipe 1 by 90'' at the resonance point.Since the induced current is proportional to the product of the vibration speed and the magnetic flux density (constant), the vibration displacement Therefore, the phase of the induced current coincides with the phase of the driving force at the resonance point, generating a force that cancels out the driving force.As a result, Coriolis vibration mode (asymmetric nine-deflection vibration) ) will act selectively at the resonance point of the 8-shaped tube 1.

The figure-8 tube 1 is excited in a drive mode (symmetrical flexural vibration) at a driving frequency that is one of the resonance points, and the Coriolis vibration mode (asymmetrical flexural vibration) caused by fluid flowing through the tube 1 is excited. The frequency is equal to the driving frequency. Generally Coriolis vibration mode (asymmetrical flexural vibration)
The resonance point of is different from the driving frequency (generally higher)
becomes the frequency. Therefore, the Coriolis vibration mode (asymmetrical flexural vibration) exhibited by Coriolis vibrates away from its resonance point, and therefore is not subject to the selective damping described above. On the other hand, for asymmetrical flexural vibrations that occur at the resonance point of the U-shaped tube due to external noise, etc., the fbll power is selectively attenuated, resulting in errors and instability of the output amplitude. High-resolution mass flow output can be obtained without the need for

Furthermore, since it is no longer necessary to lower the Q of the symmetrical flexural vibration mode in order to reduce asymmetrical 9-flexural vibrations caused by external noise, etc., the stability of the frequency of the drive vibration (symmetrical flexural vibration) mode can be sufficiently increased.

In FIG. 3, it is assumed that the excitation means and vibration detection means for driving the O-shaped conduit 1 are of known dampness.

Further, although the magnets 7 and 8 are installed inside the conduit in FIG. 3, they may be installed outside the conduit.

Furthermore, in FIG. 5, the magnets 7 and 80 may be replaced with electromagnets or other effective magnets.

FIG. 5 is a perspective view showing a main part configuration of another embodiment of the device according to the present invention. In this embodiment, two tubes 1.2 are configured in the shape of a tuning fork, and have excellent sensitivity and stability.
By appropriately connecting tubes 1 and 2, it can be configured as a sum or difference flow rate needle.

The magnets 7.8 constitute magnetic field generating means and are arranged so that braking torque acts on the two pipes 1 and 2 simultaneously. Other configurations and effects are the same as those in FIG. 3.

FIG. 6 is a plan view showing the main part configuration of another embodiment of the device according to the present invention, and FIG. 7 is a cross-sectional view taken along line XX in FIG.

In this embodiment, a straight pipe is used instead of a U-shaped pipe, and the straight pipe 1 is installed between the magnets 10 and 110, and a short circuit in the shape of an '.8' is connected between the straight pipe 1 and the magnet. 9 can be installed to form a mass flow needle. Now, conduit, 1 fC
When the excitation current 15 is applied, the tube 1 exerts force in a direction perpendicular to both the current 15 and the static magnetic field due to the interaction with the static magnetic field created by the magnet 10.11, as shown in the near diagram. The receiver is excited. The excitation current 15 flowing through the conduit 1 also acts as a magnetic field generating means. The braking torque described below is generated between the That is, when the conduit 1 is excited in the drive mode, the conduit 1 performs symmetrical flexural vibration (M7 in FIG. 6), so the change in the magnetic field generated by the conduit 1 also changes as shown in "8" in FIG. The left and right sides are symmetrical with respect to the axis of symmetry that passes through the intersection of the 8° V and is perpendicular to the conduit 1 in the same plane as the plane containing the ``°'', and the current induced in each loop in the short circuit 9 is The sum 16+1□ becomes zero. On the other hand, if the pipe line 1 is vibrating in the Cicoriolis vibration mode due to Coriolis acting on the fluid flowing inside the straight pipe, the pipe line 1 will perform asymmetrical flexural vibration (M8 in Figure 6). The change in the magnetic field generated by the magnet 1 is also asymmetrical with respect to the axis of symmetry. As a result, the direction of the current induced in each loop portion is the direction in which they are added together, and the sum of both is
+i, flows through the short circuit 9. As a result, the asymmetric deflection vibration component in the vibration energy is converted into Joule loss in the short circuit 9. Therefore, if the electrical resistance of the short circuit is kept small, sufficient braking force can be obtained. The braking force selectively acts on asymmetrical deflection vibrations generated at the resonance point of the straight pipe due to external noise, etc., and other effects are the same as in the case of the U-shaped pipe shown in FIG.

FIG. 8 is a perspective view showing a main part configuration of another embodiment of the present invention. In this example, two straight tubes 1°2 are mutually configured in the shape of a tuning fork, and it has excellent sensitivity and stability.As in the case of Fig. 5, tubes 1 and 2 can be connected appropriately. By doing so, it can also be configured as a sum or difference flow rate needle. short circuit 9
In addition to 1.92 being used for 6-pipe braking, the configuration,
The effect is the same as in the case of FIG.

The unique features of the straight pipe system shown in FIGS. 6 and 8 include the fact that it is easy to manufacture, has a simple structure, and prevents clogging.

In addition, by using a composite pipe line consisting of a plurality of independent flow paths as the vibrating pipe line in the embodiments shown in FIGS. 3, 5, 6, and 8, the fluid flowing through each wave path can be It is also possible to obtain the sum or difference of each flow rate depending on the direction of the flow rate.

In addition, the method using the combination of the stationary magnetic field generating means used for the U-shaped tube in the embodiments of FIGS. 3 and 5 and the vibrating short circuit part is explained in the embodiments of FIGS. 6 and 8. It can also be applied to straight pipes. On the contrary, used in the embodiment of Fig. 6, f317,
The combination of a fixed short circuit and an oscillating magnetic field generating means can also be applied to the embodiments of FIGS. 3 and 5.

As described above, according to the present invention, it is possible to realize a mass flow needle with a simple configuration that is not affected by vibration noise, has stable operation, and can obtain high resolution.

Furthermore, since there is no need to lower the Q of the drive mode, there is also the advantage that the stability of the drive frequency can be sufficiently increased.

[Brief explanation of the drawing]

Fig. 2: Diagram of the operating principle of Rioli flow rate needle, Fig. 2 (A)
(B) is an explanatory diagram of the operation of FIG. 1, FIG. 3 is a perspective view of the main part of an embodiment of the present invention, and FIG.
The figure is a perspective view of a main part of another embodiment of the present invention, the fs6 figure is a plan view of a main part of another embodiment of the present invention, FIG. 7 is a sectional view taken along line XX in FIG. FIG. 7 is a perspective view of main parts of another embodiment of the invention. 1.2...Pipeline, 5...Base, 7.8...Magnet, 9.91°92...Short circuit. M1 figure erased 2 figure M3 figure M4 figure W! J7 Figure 10 Figure 8

Claims (1)

[Scope of Claims] (1) A mass flow needle configured to cause a fluid to flow through a vibrating pipe and cause the pipe to deform and vibrate due to the Coriolis force generated by the flow and the angular vibration of the pipe, including a magnetic field generating means. ,
A short circuit is provided that interlinks with the magnetic field generated by this, and when the pipe line vibrates, a specific vibration component generated in the front pipe line is suppressed by the braking force acting between the magnetic field generating means and the short circuit. A mass flow rate needle characterized by being attenuated. (2) The mass flow needle according to claim 1, in which a magnet is used as the magnetic field generating means and the pipe line is part of a short circuit. (5) The mass according to claim 1, in which the short circuit is a loop-shaped conductor installed close to the conduit, and by passing a current through the conduit, this conduit is made a part of the magnetic field generating means. flow needle.