JPH067324Y2 - Mass flow meter - Google Patents

Description

TECHNICAL FIELD The present invention relates to a mass flow meter, and more particularly to a mass flow meter configured to directly measure the mass flow rate of a fluid to be measured.

Conventional technology It is desirable that the flow rate of the fluid to be measured be expressed as a mass that is not affected by the type of fluid, physical properties (density, viscosity, etc.) and process conditions (temperature, pressure). Conventionally, as a mass flow meter for measuring the mass flow rate of a fluid to be measured, for example, a so-called indirect mass flow meter that measures the volumetric flow rate of the fluid to be measured and converts this measurement value into mass, and an indirect mass flow meter There is a so-called direct type mass flow meter that has a small error and directly measures the mass flow rate of the fluid to be measured. In this type of mass flowmeter, various types of flowmeters based on different principles are being proposed as direct mass flowmeters that can measure the flow rate with higher accuracy. Further, as one of them, there is a flow meter that directly measures the mass flow rate by utilizing the Coriolis force generated when a fluid is flowed in an oscillating sensor tube.

For example, a conventional mass flowmeter utilizing Coriolis force has a flowmeter main body having an inflow passage and an outflow passage extending in the pipe direction, a U-shaped one end of which communicates with the inflow passage. It has a pair of sensor tubes fixed to the opening of the flowmeter main body in a direction orthogonal to the piping direction so that the end communicates with the outflow passage. In this mass flowmeter, the tip ends of a pair of sensor tubes are vibrated in a direction in which they approach or separate from each other (direction orthogonal to the axis of the flowmeter body) to generate a Coriolis force proportional to the flow rate of the flowing fluid. The displacement of the sensor tube at this time is detected by a pickup to measure the mass flow rate.

Problems to be Solved by the Invention In the mass flowmeter which measures the flow rate by using the Coriolis force, both ends of the U-shaped sensor tube are fixed to the opening of the flowmeter body in a cantilever shape. Therefore, when vibrating the sensor tube, stress concentration may occur at the end of the sensor tube, which may cause fatigue failure.

Further, in the above mass flowmeter, it is desirable to vibrate the sensor tube with a smaller exciting force, and the stress acting on the sensor tube due to the vibration is further reduced, so that the mechanical life is required to be long.

Therefore, an object of the present invention is to solve the above problems and to provide a mass flowmeter that meets the above demands.

Means and Action for Solving Problems The present invention provides the above mass flowmeter, wherein the opening is provided so as to match the flow direction of the fluid in the inflow / outflow pipe line, and the U-shaped sensor pipe has a U-shaped end portion. It is provided by bending so that it is located outside the letter shape, and the bent end is connected to the opening,
When the pipe is vibrated, an excessive stress is prevented from acting on the pipe to improve the measurement life.

Embodiment An embodiment of the mass flowmeter according to the present invention is shown in FIGS. 1 and 2 (A) and (B). In each drawing, the mass flowmeter 1 is provided in the middle of the pipe through which the fluid to be received flows. On the base 2 of the mass flowmeter 1, an upstream side support part 5 for supporting the sensor tubes 3 and 4 and a downstream side support part 6 are fixed.
The support portion 5 has a flow dividing chamber 5a having a predetermined capacity therein, and an inflow pipe line 7 communicates with the flow dividing chamber 5a. Further, the support portion 6 on the downstream side has a merging chamber 6a having a predetermined capacity therein, and an effluent conduit 8 communicates with the merging chamber 6a.

The sensor tubes 3 and 4 are formed in the same shape and face each other at positions displaced in the upper and lower directions, and the one-dot chain line
It extends parallel to the horizontal direction (in FIG. 1). The upper sensor tube 3 is curved in a U shape and extends in a horizontal direction orthogonal to the extending direction of the inflow conduit 7 and the outflow conduit 8, and one end of the conduit 3a is an upstream side support portion. 5, and a second curved portion 3c that connects the other end of the conduit 3a to the downstream support portion 6 is formed. The lower sensor tube 4, like the sensor tube 3, includes a U-shaped conduit 4a and curved portions 4b and 4c.

As shown in FIGS. 3 and 4, one end of each of the curved portions 3b and 4b is fitted and fixed to the opening 5c of the outer peripheral surface 5b of the supporting portion 5, and the other end is bent in a 90 ° arc shape to be horizontal. It extends in the direction. Similarly to the curved portions 3b and 4b, one end of each of the curved portions 3c and 4c is fitted and fixed in the opening 6c of the outer peripheral surface 6b of the support portion 6, and the other end is bent in a 90-degree arc shape to be horizontally oriented. Extend. The openings 5c and 6c are provided so as to match the flow directions of the fluid in the inflow conduit 7 and the outflow conduit 8, respectively. That is, the ends of the sensor tubes 3 and 4 are U-shaped.
It is provided so as to be bent so as to be located outward of the character shape, and the bent end portion is connected to the openings 5c and 6c.

Therefore, when the sensor tubes 3 and 4 are vibrated as will be described later, torsional stress acts on the curved portions 3b, 3c, 4b and 4c. That is, the sensor tubes 3 and 4 are not supported in a cantilever shape as in the conventional case, and the curved portion 3
Since it is supported via b, 3c, 4b and 4c, the strength against vibration is further improved.

The fluid to be measured flows into the flow dividing chamber 5a through the inflow pipe 7,
The flow is divided into two at a flow dividing ratio equal to that of the sensor tubes 3 and 4 decelerated in the flow dividing chamber 5a. Further, the split measured fluid passes through the curved portions 3b and 4b, the pipes 3a and 4a, and the curved portions 3b and 4b to reach the merging chamber 6a, and flows out from the outflow pipe 8. In this way, since the fluid to be measured is temporarily decelerated in the flow dividing chamber 5a and the flow merging chamber 6a, the flow during the flow dividing and the flow joining is more stable. Therefore, the flow in the sensor tubes 3 and 4 is also stable.

Reference numeral 9 denotes a vibrator, which is a U-shaped curved portion 3 of the pipe lines 3a and 4a.
a _1, intermediate position 4a ₁ (in FIG. 1, the position of the one-dot chain line 0,0 ') is provided between. This vibration exciter 9 has substantially the same structure as an electromagnetic solenoid, and includes a coil portion 9a attached to the conduit 3a and a magnet 9b having one end fitted into the coil portion 9a and the other end attached to the conduit 4a. Become. Therefore, when the coil portion 9a is energized, the coil portion 9a
A magnetic field is further generated, and the electromagnetic force drives the magnet 9b.

That is, the pair of sensor tubes 3 and 4 are separated from each other by the vibration exciter 9 and are vibrated in the downward direction. It vibrates at the frequency.

Numerals 10 and 10 'are pickups, which are provided on both sides of the curved portions 3a ₁ and 4a ₁ of the conduits 3a and 4a, and detect relative displacements of the vibrating sensor tubes 3 and 4.

As shown in FIG. 5, the pickup 10 includes a coil portion 1 held by a lower sensor tube 4 via a holding member 11.
0a and a magnet 10 provided on a U-shaped bracket 12 so as to face the coil portion 10a above and below.
b and 10c. The bracket 12 is fixed to the upper sensor tube 3.

When the sensor tubes 3 and 4 vibrate, the coil portion 10a
Is displaced upward and downward between the magnets 10b and 10c, so that an electromotive force corresponding to the displacement of the sensor tubes 3 and 4 is generated in the coil portion 10a. That is, the pickup 10 detects the displacement of the sensor tubes 3 and 4 based on the voltage obtained by the coil portion 10a.

The pickup 10 'has the same structure as the pickup 10.

Here, the flow rate measuring operation of the mass flow meter having the above-mentioned configuration will be described with reference to FIGS. 6 to 8.

As shown in FIG. 6, the sensor tubes 3 and 4 are vibrated by the vibration exciter 9 and vibrate so that the curved portions 3a ₁ and 4a ₁ of the conduits 3a and 4a are separated from or close to each other. In this way, when the sensor tubes 3 and 4 vibrate, the sensor tubes 3 and 4 are displaced about the curved portions 3b, 4b and 3c, 4c connected and fixed to the outer peripheral surfaces 5b, 6b of the support portions 5, 6, respectively. To do. Therefore, not the bending stress but the torsion stress acts on each of the curved portions 3b, 4b and 3c, 4c.

Therefore, the stress due to the vibration of the sensor tubes 3 and 4 is received by the entire wall thickness of the curved portions 3b and 4b and 3c and 4c. Therefore, stress concentration does not occur at the ends of the sensor tubes 3 and 4.

Therefore, the mechanical strength at the connection between the pair of sensor tubes 3 and 4 and the support portions 5 and 6 can be increased, so that the measurement life of the mass flowmeter 1 can be further extended and the durability can be improved.

Also, when the sensor tubes 3 and 4 are vibrated, each curved portion 3
Since torsion stress acts on b, 4b and 3c, 4c,
Excitation force is small. Therefore, it becomes possible to use the small vibrator 9.

When the fluid to be measured flows in the vibrating sensor tubes 3 and 4 as described above, twisting due to the Coriolis force is generated in the curved portions 3a ₁ and 4a _{1 of the} conduits 3a and 4a.

Consider one stroke when the sensor tube 3 is swung upward at the angular velocity ω in FIGS. 6 and 7.

In FIG. 6, since the amplitude becomes larger from the base end side of the sensor tube 3 toward the tip end side, the velocity of the fluid flowing in the sensor tube 3 in the vertical direction is also larger toward the tip end side. Accordingly, the acceleration a of the fluid is increased toward the tip side of the sensor tube 3, and the vertical velocity is gradually decreased on the outflow side that has passed through the curved portion 3a ₁ , resulting in a negative acceleration a of the fluid. . Coriolis force F (= ma) acts on the acceleration a in the direction opposite to the acceleration direction.

Therefore, as shown in FIG. 7, the bending portion 3a ₁ has an angular velocity ω
When the sensor tube 3 is displaced by, the force F of the same magnitude acts on the inflow side and the outflow side of the sensor tube 3 in opposite directions, so that the sensor tube 3 is twisted.

Further, in the sensor tube 4 located below the sensor tube 3 which operates as described above, the bending portion 4a ₁ is displaced downward at the angular velocity −ω. Therefore, the sensor tube 4 has a completely symmetrical shape with the sensor tube 3, and the Coriolis force F in the direction opposite to that of the sensor tube 3 acts. Therefore, when the curved portion 4a ₁ is displaced at the angular velocity −ω, the sensor tube 4 is twisted by the Coriolis force. The relative displacement of the sensor tubes 3 and 4 is detected by the pickups 10 and 10 '.
0 and 10 'detect the twist angle 2θ of the sensor tubes 3 and 4 as a time difference signal.

When the pickups 10 and 10 'are electromagnetic pickups, the time until the voltage changes from a certain reference voltage to another different voltage is proportional to the flow rate, and the flow rate can be obtained by measuring this time.

That is, the mass flow rate of the fluid flowing in the sensor tube 3 is proportional to the time difference Δt when the points P ₁ and P ₂ cross the AA axis in FIG. It doesn't matter. Further, as shown in FIG. 8, the voltage induced by the pickups 10 and 10 'is measured as a sine wave. The midline diagram I of FIG. 8 shows the pickup 10 on the inflow side.
2 is a detection signal of the pickup 10 'on the outflow side.
The phase difference of the voltage generated from 0 ', that is, the time difference Δt is represented.

The phase difference signals of both pickups 10 and 10 'are shaped and amplified, and then become a voltage signal proportional to the mass flow rate by time integration. Further, this voltage signal is converted into a frequency signal and output as a voltage pulse signal and an analog signal from an output circuit (not shown).

Further, in the above-described embodiment, by detecting the twist angle 2θ due to the relative displacement of the pair of sensor tubes 3 and 4, a Coriolis force twice as large as that in the case of measuring the flow rate of only one sensor tube is generated, which is larger. There is an advantage that the voltage can be obtained and the measurement accuracy is improved.

In addition, external vibration may act on the mass flowmeter 1 via a pipe or the like. The influence of external vibration such as pipe vibration is canceled by detecting the relative displacement (or relative speed) of the pair of sensor tubes 3 and 4. Therefore, the mass flowmeter 1 also has an advantage that the mass flow rate flowing in the sensor tubes 3 and 4 can be measured without being affected by external vibration.

FIG. 9 shows a modification of the present invention. In FIG. 9, the same parts as those in the above embodiment are designated by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 9, the pair of sensor tubes 22 and 23 of the mass flowmeter 21 have the same C as the sensor tubes 3 and 4.
The V-shaped conduits 22 a and 23 a extend in parallel to the horizontal direction orthogonal to the extending direction of the inflow conduit 27 and the outflow conduit 8. In addition, the conduits 22a and 23a have U-shaped curved portions 22b and 2a.
It is supported by the support portions 5 and 6 fixed to the base 2 via 2c, 23b and 23c. Each curved portion 22b, 22
c, 23b and 23c are outer peripheral surfaces 5b and 6b of the supporting portions 5 and 6, respectively.
It is fixed to the openings 5c and 6c of and is bent 180 degrees in the horizontal direction.

Therefore, when vibrating the sensor tubes 22 and 23,
Torsional stress acts on the curved portions 22b, 23b and 22c, 23c instead of excessive bending stress. Therefore, music part 2
2b, 23b and 22c, 23c are the sensor tubes 2
By supporting the displacements of 2 and 23 with the entire wall thickness of the entire circumference of the pipe, the strength against vibration is improved.

Further, in this modified example, the arrows X and Y of the pipelines 22a and 23a are used.
By increasing the ratio L ₁ / L ₂ of the length in the direction,
It is possible to increase the twist angle θ due to the Coriolis force in the conduits 22a and 23a.

In the above description, an electromagnetic pickup is used, but the present invention is not limited to this, and it goes without saying that an optical sensor or the like may be used. In this case, the time from when one optical sensor detects the operation of the inflow conduit to when the other optical sensor detects the operation of the outflow conduit is proportional to the flow rate.

Effect of the Invention As described above, the mass flowmeter according to the present invention, the stress generated by the vibration of the sensor pipeline during flow rate measurement acts as a torsional stress on the bent portion, so that an excessive bending stress is applied to the end of the pipeline. It can be prevented from acting and the torsional stress is applied to the entire wall thickness of the bent end portion around the entire circumference of the pipe, so that the mechanical strength can be improved and the measurement life can be extended. Further, the force required for vibrating the sensor conduit is small, and it becomes possible to use a small-sized vibration exciter. Further, external vibration can be canceled by detecting the relative displacement of the pair of pipe lines, and the mass flow rate can be measured with high accuracy without being affected by pipe vibration or the like. Further, the fluid pressure acts in a direction orthogonal to the direction of separating the sensor conduit from the opening, so that the strength against the fluid pressure is increased, and the end portion of the U-shaped portion tends to expand outward. Since the bent end portion can be fitted into the opening by utilizing the spring property, it has features such as easy assembly.

[Brief description of drawings]

FIG. 1 is a perspective view of an embodiment of a mass flowmeter according to the present invention,
2 (A) and 2 (B) are side views seen from the extending direction of the sensor tube and vice versa, FIG. 3 is a plan view of the essential portion of the present invention, and FIG. 4 is an arrow Z in FIG. FIG. 5 is a side view of the pickup, FIG. 6 and FIG. 7 are perspective views for explaining the operation at the time of measuring the flow rate, a side view, and FIG. A waveform diagram and FIG. 9 are modifications of the present invention. 1 ... Mass flowmeter, 3, 4 ... Sensor tube, 3a,
4a ... pipe, 3b, 4b ... first curved portion, 3c, 4c
...... Second curved part, 5 ... Supporting part, 6 ... Supporting part, 9 ...
Shaker, 10, 10 '... Pickup.

Claims (1)

[Scope of utility model registration request] 1. An inflow conduit into which a fluid to be measured flows, an outflow conduit extending along a fluid inflow direction of the inflow conduit, an opening provided in each of the outflow and outflow conduits, and an opening connected to the opening. Flowmeter comprising a U-shaped sensor pipe line provided in such a manner that the vibrator vibrates the sensor pipe line, and a pickup that detects displacement of the sensor pipe line due to vibration of the sensor pipe line In the above, the opening is provided so as to match the flow direction of the fluid in the inflow / outflow conduit, and the U-shaped sensor conduit is bent so that its end portion is located outside the U-shape. A mass flowmeter provided with the bent end connected to the opening.