JPH0424514A - Mass flowmeter - Google Patents

Abstract

PURPOSE:To remove the effects of external vibration noises and to improve measuring accuracy and response by fixing only magnetic bodies to a sensor tube, fixing an exciting means which attracts the magnetic bodies to a non- vibrating part which is not associated with the vibrations of the sensor tube, vibrating the tubes, and detecting the displacement. CONSTITUTION:A pair of sensor tubes 2 and 3 are shaker with the phase difference of 180 deg., respectively. Coriolis force is generated at straight tube parts 2a and 2b of the upper tube and straight tube parts 3a and 3b of the lower tube 3. The displacements -delta and +delta of the straight tube parts are detected as the signals of the time difference with pickups 9 and 10 based on the Coriolis force, and the signal is made proportional to a flow rate. At this time, compact, light-weight magnetic bodies 12 are fixed to the tubes 2 and 3 in shakers 13 and 14. The tubes 2 and 3 can be vibrated only by fixing an exciting element 11 to an outflow tube 6. An unnecessary weight is not added to the tubes 2 and 3. Therefore, the flowmeter becomes hard to be affected by the external vibration noises, and high accuracy and high response are obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a mass flow meter, and more particularly to a mass flow meter that measures the mass flow rate of a fluid by vibrating a sensor tube.

Conventional technology The flow rate of the fluid to be measured depends on the type of fluid and its physical properties (density, viscosity, etc.)
, it is desirable that it be expressed as a mass that is not affected by process conditions (temperature, pressure).

For this reason, various mass flowmeters are being developed to measure the mass flow rate of the fluid to be measured, and one of them measures mass flow rate using Coriolis generated when fluid flows through a vibrating sensor tube. There is a flow meter.

In this type of mass flowmeter, fluid is caused to flow through a pair of sensor tubes, and the pair of sensor tubes are vibrated toward and away from each other by the driving force of an exciter (excitation coil). Since the Coriolis force acts in the direction of vibration of the sensor tube and is in opposite directions on the inlet and outlet sides, the sensor tube is twisted, and this twist angle is proportional to the mass flow rate. Therefore, a pickup (vibration sensor) for detecting vibration is installed at the twisting position on the inlet side and outlet side of a pair of sensor tubes, and the time difference between the output detection signals of both sensors is measured. Measuring flow rate.

Problems to be Solved by the Invention However, in conventional mass flowmeters, the exciter is connected to the coil section,
The coil part is fixed to one side of the sensor tube, the magnet part is fixed to the part of the sensor tube opposite to the coil part, and the magnet part and the coil part are connected to each other by energizing the coil part. Since the sensor tube was vibrated by suction, the weight of the coil and magnet that make up the vibrator was directly applied to the sensor tube.In particular, when the sensor tube was downsized to reduce the capacity and measure minute flow rates, the vibrator The weight of the sensor tube becomes larger than the weight of the sensor tube, making it susceptible to external vibration noise, resulting in problems such as deterioration of measurement accuracy and responsiveness.

The present invention has been made in view of the above points, and an object of the present invention is to provide a mass flowmeter with good accuracy and responsiveness.

Means for Solving the Problems The present invention vibrates the sensor tube through which the fluid to be measured passes using an excitation means, and detects the displacement of the sensor tube by the Coriolis force generated in accordance with the flow rate of the fluid to be measured, thereby measuring the flow rate. In the mass flowmeter, the vibration excitation means is constituted by a magnetic body fixed to the sensor tube, and an excitation means fixed to a non-vibration part that does not participate in the vibration of the sensor tube and attracts the magnetic body.

It is only necessary to fix the magnetic material to the working sensor tube, and the excitation means for attracting the magnetic material is fixed to the non-vibrating part 12 that does not take part in the vibration of the sensor tube, and the magnetic material is attracted and released by the excitation means. This allows the sensor tube to vibrate.

Embodiment FIGS. 1 to 4 show an embodiment of a mass flowmeter according to the present invention.

In each figure, a mass flowmeter 1 is assembled to a pair of sensor tubes 2.3 or a manifold 4. The manifold 4 is provided between an inflow pipe 5 and an outflow pipe 6, and has an inflow path 4a connected to the inflow pipe 5 and an outflow path 4b connected to the outflow pipe 6.
and has. In addition, the inflow path 4a has a connection port 4 that branches left and right.
It communicates with a+ and 4az.

Note that the outflow path 4b also communicates with the branched connection ports 4bz and 4b similarly to the inflow path 4a.

The sensor tube 2 has its base end connected to the connection port 4 of the inflow path 4a.
a+, and extends in the piping direction; and the straight pipe part 2a, whose base end is connected to the connection port 4b of the outflow path 4b.
A straight pipe section 2b extending parallel to the straight pipe section 2b, curved sections 2c and 2d bent back at the tips of the straight pipe sections 2a and 2b, and a U-shaped adhesive section connecting the curved sections 2c and 2d. (pipeline) 2
Consists of e.

The sensor tube 3 is formed in the same shape as the sensor tube 2, and is connected to the sensor tube 2 and above so that the straight pipe parts 3a and 3b are parallel to the outflow pipe 6 and the straight pipe parts 2a and 2b.
They are arranged symmetrically below.

Note that the connecting portions 2e and 3e of the sensor tubes 2 and 3 are connected and held by a holding member 8.

The holding member 8 has a connecting portion 8b that is connected and fixed to the outer periphery of a ring portion 8a through which the outflow pipe 6 passes, at an intermediate position between the connecting portions 2e3e of the sensor tubes 2 and 3.

8c. That is, the holding member 8 mutually holds the opposing connecting parts 2e and 3e with the outflow pipe 6 interposed therebetween.

Note that the inner diameter D1 of the ring portion 8a is larger than the outer diameter of the outflow pipe 6, and a gap exists between the outer circumference of the outflow amount 6 and the inner circumference of the ring portion 8a. Therefore, the connecting portion 2e of the pair of sensor tubes 2 and 3.

3e is held at a predetermined position without contacting the outflow pipe 6, and the piping vibration from the outflow pipe 6 is transmitted to the sensor tubes 2 and 3.
is not directly transmitted to.

In addition, the sensor tubes 2 and 3 are fixedly connected and fixed by the holding member 8, so that the connecting portions 2e3e are positioned at predetermined positions without any variation with respect to the outflow pipe 6. In this way, the holding member 8 holds the connecting parts 2e and 3e at the tips of the sensor tubes 2 and 3 at the designed predetermined positions even though they are separated, and the connecting parts 2e and 3e are connected to each other. The straight pipe parts 2a, 2b and 3a, 3b are positioned at predetermined positions, and each straight pipe part 2a.

The parallelism of 2b, 3a, and 3b is maintained. Therefore, when manufacturing the sensor tube 2.3, each straight tube section 2a.

Even if the extending positions or parallelism of the connecting portions 2b, 3a, 3b are slightly deviated, the holding member 8 connects and holds the connecting portions 2e, 3a, thereby maintaining the straight pipe portions 2a, 2b+.
The assembly positions of the straight pipe portions 2a, 2b, 3a, and 3b can be corrected so as to eliminate the assembly processing errors of 3a and 3b.

Therefore, the holding member 8 holds the connection parts 2e and 3e when the sensor tubes 2 and 3 are assembled, and also holds each straight pipe part 2.
a, 2b, 3a, 3b (7) It can also function as an assembly gauge for positioning the extension position and parallelism.

That is, since the sensor tube 2.3 is assembled in the correct position, the pickup 9. which will be described later. It becomes possible to accurately regulate the positional relationship between the coil part and the magnet part of IO. Therefore, it is not necessary to adjust the relative positions of the coil section and the magnet section of the pickup 9, 10 after assembly is completed.

A straight pipe portion 2a of a pair of sensor tubes 2 and 3.

2 b + 3 a, 3 b pass through the support plate 7 and are fixed to the support plate 7 by welding, and their ends are connected to each connection port 4 al r 4 bl + 4 at of the manifold 4
It is fixedly connected to +4b2.

Therefore, the sensor tube 2 is provided extending in the piping direction on one side of the outflow pipe 6, and the sensor tube 3 is also provided extending in the piping direction on the other side of the outflow pipe 6. Although the mass flowmeter 1 includes a pair of sensor tubes 2 and 3, it requires only a small installation space and has a compact configuration.

Furthermore, in the mass flowmeter 1, the sensor tube 2゜3 is provided near the outflow pipe 6 so as to extend in the piping direction, making it less susceptible to piping vibrations and measuring the flow rate more accurately. Can be measured.

Note that a hole 7a is bored in the center of the support plate 7, and the outflow pipe 6 passes through this hole 7a.

A pickup 9°lO is provided between the straight pipe sections 2a and 3a on the inflow side and between the straight pipe sections 2b and 3b on the outflow side.

Note that since the pickups 9 and 10 have the same configuration, only one pickup 9 will be described.

In FIG. 8, the pickup 9 has a coil portion 9a held by a bracket 15 that protrudes upward from the middle of the straight pipe portion 3a of the sensor tube 3, and has a U-shape so as to face the coil portion 9a upwardly and downwardly. It consists of magnets 9b and 9c provided on the bracket 16. Note that the bracket 16 extends upward and is connected to the straight pipe portion 2a of the sensor tube 2.

Therefore, when the sensor tubes 2 and 3 vibrate, the straight tube section 3
The coil portion 9a provided in the magnet 9a is relatively displaced in the direction of the arrow X between the magnets 9b and 90.

Therefore, an electromotive force corresponding to the relative displacement of the straight pipe parts 2a and 3a is generated in the coil part 9a, and the pickup 9 detects the displacement of the straight pipe part 3a from the voltage of the coil part 9a. In addition, pickup 9. No support member is required to support IO. Also, pickup 9. The lO is not limited to an electromagnetic type, but may be an optical type using an optical sensor or the like.

13.14 is an exciter, between the tips of the straight pipe parts 2a and 2b,
It is provided between the tips of the straight pipe portions 3a and 3b.

The vibrator 13 consists of a magnetic body 12 and an excitation element 11, as shown in FIG. The magnetic bodies 12 are fixed to the straight pipe portion 2a of the sensor tube 2 so as to face each other. Further, the excitation element 11 is formed by winding a drive coil 11a around a yoke member 11b, and fixing the drive coil lla and the yoke member 11b inside a coil cover 11c. Coil cover 11
c is fixed to the outflow pipe 6, and the excitation element is connected to the sensor tube 2.
It is arranged between the magnetic bodies 12 of the straight pipe portion 2a. Vibrator 13
By energizing the drive coil lla, a magnetic circuit passing through the yoke member 11b and the magnetic body 12 is formed, and the sensor tube 2 can be deflected by attracting the magnetic body 12 to the yoke member 11b.

Incidentally, since the vibrator 14 has the same configuration as the vibrator 13 described above, a description thereof will be omitted. The drive coil of the vibrator 13 is energized at the timing shown in FIG. 6(A),
The drive coil lla of the vibrator 14 is energized at the timing shown in FIG. 6(B), and the sensor tubes 2.3 are vibrated with a phase difference of 180° as shown in FIG.

Next, the measurement operation of the mass flowmeter having the above configuration will be explained.

When measuring the flow rate, the pair of sensor tubes 2 and 3 are vibrated with a 180° phase difference by the operation of the vibrator 13, 3 while fluid is flowing inside. The fluid to be measured that flows into the inflow path 4a of the manifold 4 from the inflow pipe 5 is divided and flows into the straight pipe portions 2a and 3a of the sensor tube 2.3.
Curved sections 2c and 3c.

The straight pipe part 2 passes through the connecting parts 2e and 3e and the curved parts 2d and 3d.
b, 3b, merge at the outflow path 4b of the manifold 4, and flow out from the outflow pipe 6. Also, since the sensor tubes 2 and 3 are vibrated by the vibrator 13.14, they vibrate in the direction of the arrow X at a natural frequency determined by the spring constant of the sensor tube 2.3 and the flow rate flowing inside the sensor tube 2.3. Vibrate.

First, the operation of the upper sensor tube 2 of the pair of sensor tubes 2.3 will be explained.

In addition, when the straight pipe parts 2a, 2b and 3a, 3b vibrate,
After being elastically deformed in the direction of separating from each other, the straight pipe portions 2a, 2
b, 3a, and 3b are deformed in the direction of approaching each other by their own elastic restoring force.

As shown in FIG. 10, since the straight pipe portions 2a and 2b are fixed by the support plate 7, they vibrate more strongly in the direction of the arrow X toward the tip using the penetrating portion of the support plate 7 as a fulcrum. Therefore, deformation of the angular velocity ω occurs in the straight pipe portions 2a and 2b due to the above-mentioned vibration. In addition, since the curved portions 2c and 2d connecting portion 2e are bent into a U shape, even if the vibration exciter 13 performs vibration operation in the direction of arrow X, the curved portions 2c and 2d will bend in the vibration direction, causing the straight Part 2a.

Displacement of the distal end side of 2b is allowed.

As described above, when fluid flows into the vibrating sensor tube 2, the amplitude increases toward the tip of the straight pipe portion 2a on the inflow side, so that the fluid is given acceleration in the vibration direction. Furthermore, in the straight pipe portion 2b on the outflow side, the velocity in the direction of arrow X gradually decreases as it returns to the manifold 4 side, so that the fluid is accelerated. In this way, when the fluid is accelerated due to the vibration of the sensor tube 2,
Coriolis (F c) occurs in the direction opposite to the direction of acceleration.

As shown in FIGS. 9(A) and 9(B), the straight pipe section 2a on the inflow side
Suppose that the straight pipe portion 2b on the outflow side is displaced in the direction of arrow X2 at an angular velocity of −ω and the straight pipe portion 2b on the outflow side is displaced in the direction of arrow X2 at an angular velocity of −ω. In this way, the straight pipe portion 2a.

10(A) and (B), the straight pipe portion 2a
, 2b, Coriolis Fc occurs in the direction of arrow X2. Therefore, the straight pipe portions 2a and 2b are shifted by −δ and 10δ from the original displacement positions shown by two-dot chain lines to the positions shown by solid lines, respectively.

Next, as shown in FIGS. 9(C) and (D), the straight pipe section 2a on the inflow side is displaced in the direction of arrow X2 with an angular velocity ω, and the straight pipe part 2b on the inflow side is displaced in the direction of arrow X with an angular velocity ω. Suppose that it is displaced to .

In this way, the straight pipe portion 2a.

10(C) and (D), the straight pipe portions 2a,
2b, Coriolis Fc is generated in the direction of arrow X1. Therefore, the straight pipe portions 2a and 2b are moved by 1 δ from the two-dot chain line (original displacement position) to the position shown by the solid line.

deviates by 10δ.

The pair of sensor tubes 2.3 are each excited with a phase difference of 180 degrees. For example, when the straight pipe portions 2a and 2b of the upper sensor tube 2 are separated, the lower sensor tube 3 is vibrated. The direct portions 3a3b are close to each other.

That is, the sensor tube 2 is shown in FIG. 9(A).

When the sensor tube 3 is displaced as shown in FIG. 9(B), the sensor tube 3 is displaced as shown in FIGS. 9(C) and 9(D). Therefore,
In the straight pipe portions 2a and 2b of the upper sensor tube 2, the first O
Coriolis occurs as shown in Figures (A) and (B), and in the straight pipe portions 3a and 3b of the lower sensor tube 3, as shown in Figure 10 (C).

Coriolis as shown in (D) is produced.

The above-mentioned Coriolis Fc is determined by detecting the magnitude of the displacement -δ and +δ of the straight pipe portions 2a and 2b or the phase angle difference between the straight pipe portions 2a and 2b using the pickups 9 and 10. Moreover, Coriolika Fc is expressed as Fc=2ωmv,
The mass flow rate (mv) is obtained by determining the angular velocity ω and Coriolis Fc.

The pickups 9 and 10 are configured to detect the displacement -δ of the straight pipe portions 2a and 2b,
10 δ is detected as a time difference signal.

Therefore, the time required for the voltage obtained at the coil portion of the pickup 9 or 10 to change from a certain reference voltage to a different voltage is measured, and this time is proportional to the flow rate.

Note that the signals from the pickups 9 and 10 are shaped and amplified, and then become voltage signals proportional to the mass flow rate through time integration. Furthermore, this voltage signal is converted into a frequency signal, and outputted as a voltage pulse signal and an analog signal from an output circuit (not shown).

The mass flowmeter 1 detects twice the displacement of the straight pipe portions 2a, 3a, and 2b3b due to Coriolis generated in the sensor tube 2.3, and can measure the flow rate with high accuracy. Also,
When detecting the phase difference of the sensor tube 2.3 due to the occurrence of Coriolis, even if external vibration (vibration noise) is input, it is canceled out and the flow rate can be stably measured without being affected by external vibration.

Furthermore, the connecting portions 2e and 3 of the pair of sensor tubes 2 and 3
Since the outflow pipe 6 is held at a predetermined spaced position by the non-contact holding member 8 during the interval a, vibrations in the outflow pipe 6 are not transmitted to the sensor tubes 2 and 3 via the holding member 8. . Therefore, in the mass flowmeter 1, the vibration is transmitted to the sensor tubes 2 and 3 via the pipe vibration manifold 4, and is attenuated therebetween. Therefore, even if the pickup 9.10 detects vibration noise, it is extremely small and tolerable in terms of flow rate measurement.

In addition, in the exciter 13.14, as shown in FIG. can vibrate the sensor tube 2゜3 by fixing it to the outflow pipe 6.
No unnecessary weight is added to ゜3, therefore, it is less susceptible to external vibration noise, and high performance such as high precision and high reactivity can be achieved.

On the other hand, even if the sensor tubes 2 and 3 are made thinner, it is possible to perform measurements with high accuracy and to measure small volumes and minute flow rates.

In this embodiment, the magnetic body 12 was in the shape of a flat plate.The magnetic body 12 is not limited to the shape of a flat plate, but may be cylindrical, semi-cylindrical, elliptical, or cylindrical, and may have any shape that is easily attracted to the excitation element 11. Bye. Furthermore, the magnetic material 12 can be formed into a sheet and can be easily attached to the sensor tube, thereby improving assembly efficiency.

In this embodiment, a mass flowmeter configured to measure mass flow rate using two sensor tubes has been described, but the present invention is not limited to this, and for example, as shown in FIG. The present invention can also be applied to a mass flowmeter composed of a single tube. In this case, the excitation element 11 is energized at the timing shown in FIG.

Effects of the Invention As described above, according to the present invention, the magnetic material can be fixed to the sensor tube and the sensor tube can be made to vibrate.
It has the advantage of not adding unnecessary weight to the sensor tube, thereby improving measurement accuracy and responsiveness.

[Brief explanation of drawings]

FIG. 1 is a perspective view of an embodiment of a mass flowmeter according to the present invention;
Figure 2 is a partially cutaway bottom view of the mass flowmeter, Figure 3 is a partially cutaway front view of the mass flowmeter, Figure 4 is a sectional view taken along line 1-1 in Figure 1, and Figure 5. is a sectional view of a main part of an embodiment of the present invention,
Fig. 6 is an exciter drive waveform diagram, Fig. 7 is a sectional view to explain the operation of the exciter, Fig. 8 is an enlarged view of the pickup,
Fig. 9 and Fig. 10 are process diagrams for explaining the operation of the sensor tube during flow rate measurement, Fig. 11 is a perspective view of another implementation, and Fig. 12 is a driving diagram of the vibrator of another embodiment. FIG. 1...Mass flow meter, 23...Sensor tube, 1.
...Excitation element, lla...Drive coil, llbl
- Yaw material, LLC...Coil cover 12...Residence, 13.14...Exciter.

Claims (1)

[Scope of Claims] A mass that measures the flow rate by vibrating a sensor tube through which a fluid to be measured passes by an excitation means and detecting the displacement of the sensor tube by the Coriolis force generated in accordance with the flow rate of the fluid to be measured. In the flowmeter, the excitation means includes a magnetic body fixed to the sensor tube, and an excitation means fixed to a non-vibrating part that does not participate in the vibration of the sensor tube and attracts the magnetic body, and the excitation means A mass flowmeter characterized in that the sensor tube is vibrated by attracting and releasing the magnetic body by a means.