JPH067325Y2 - 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.

Further, as a mass flow meter utilizing the above Coriolis force,
For example, there is one in which both ends of a U-shaped sensor tube are fixed to the flowmeter body, and each end of the sensor tube is connected to the inflow port and the outflow port.

Problems to be Solved by the Invention In a mass flowmeter which measures the flow rate by utilizing the Coriolis force, both ends of a U-shaped sensor tube are fixed to 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, and the measurement 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 TO SOLVE THE PROBLEM AND ACTION The present invention has an inflow conduit communicating with an inflow port, an outflow conduit arranged in parallel with the inflow conduit and communicating with an outflow conduit, an inflow conduit and an outflow conduit. A crossing sensor conduit, a first connecting conduit connecting the inflow conduit to one end of the sensor conduit, a second connecting conduit connecting to the other end of the sensor conduit of the outflow conduit, and a first And a vibrator for vibrating the sensor conduit so as to bend the second connecting conduit, and a pickup for detecting displacement of the sensor conduit due to vibration of the sensor conduit, when vibrating the sensor conduit This is intended to improve the measurement life by preventing stress concentration in the pipeline.

Embodiment FIG. 1 and FIG. 2 show an embodiment of the mass flowmeter according to the present invention. In each figure, the mass flowmeter 1 is the inflow side manifold 2
And a pair of sensor tubes 4 and 5 whose ends are fixed to the outflow side manifold 3.

The inflow side manifold 2 is connected to the upstream side pipe 6 and has a branch passage 2a (indicated by a broken line in FIG. 1) as an inflow port divided into two inside. The inflow conduits 4a and 5a of the sensor tubes 4 and 5 formed of, for example, a metal pipe made of stainless steel or the like are connected and fixed to the divided flow passage 2a. Further, the outflow side manifold 3 is connected to the downstream side pipe 7 and is internally provided with a confluent channel 3a (in FIG. 2,
(Indicated by a broken line). The outflow conduits 4b and 5b of the sensor tubes 4 and 5 are connected and fixed to the combined flow path 3a.

The sensor tube 4 is located above and the sensor tube 5 is located below, and the sensor tubes 4 and 5 are arranged so as to face each other in the upward and downward directions.

Moreover, the sensor tubes 4 and 5 are symmetrically shaped in the upper and lower portions, respectively. Therefore, one of the following sensor tubes 4
Will be described and the description of the other sensor tube 5 will be omitted.

The sensor tube 4 includes the inflow conduit 4a and the outflow conduit 4b.
, And the sensor conduit 4c and the substantially circular connecting conduits 4d and 4e. The inflow pipe line 4a and the outflow pipe line 4b linearly extend horizontally from the manifolds 2 and 3 and are arranged in parallel. The sensor channel 4c is an inflow conduit 4a and an outflow conduit 4
It extends below b in a direction orthogonal to the extending direction of the inflow conduit 4a and the outflow conduit 4b.

One of the connecting conduits 4d is formed in an arc shape of about 3/4 circle so that the tip of the inflow conduit 4a is connected to one end of the sensor conduit 4c. Since the sensor conduit 4c is located below the inflow conduit 4a, the connecting conduit 4d is spirally bent with a relatively large radius.

The other connecting conduit 4e is formed in a substantially circular shape so as to connect the tip of the outflow conduit 4b and the other end of the sensor conduit 4c, like the connecting conduit 4e. The connecting conduit 4d is also formed in a spiral arc shape having a relatively large radius.

Since the connecting portions 4d and 4e are bent with a large radius corresponding to the length dimension of the sensor conduit 4c, the sensor conduit 4c can be set longer. This means that a larger Coriolis force can be obtained in the sensor conduit 4c than during flow rate measurement, as will be described later.
Further, when the sensor pipe 4c is vibrated in the direction of the arrow X (shown in FIG. 2), the connecting pipes 4d and 4e on both sides are elastically deformed like coil springs, and bending stress is generated in the inflow pipe 4a and the outflow pipe 4b. Prevents concentration at the base end.

Reference numeral 8 denotes an exciter, which is interposed between an intermediate position of the upper sensor conduit 4c and an intermediate position of the lower sensor conduit 5c. As shown in FIG. 3, the vibration exciter 8 has substantially the same structure as an electromagnetic solenoid, and includes a coil portion 8a, a magnet 8b inserted into the coil portion 8a from above, and a lower portion inside the coil portion 8a. The magnet 8c is inserted more.

Both ends of the coil portion 8a are at the walls 2 of the manifolds 2 and 3.
It is attached to a U-shaped support member 9 fixed to b and 3b, and is held at a position between the sensor conduits 4c and 5c. The upper magnet 8b projects from the lower side of the sensor conduit 4c, and the lower magnet 8c projects from the upper side of the sensor conduit 5c.

Therefore, when a current is applied to the coil portion 8a, a magnetic field is generated in the coil portion 8a, and the magnets 8b, 8
c repels and separates the sensor conduits 4c and 5c from each other and drives them downward. The sensor conduits 4c and 5c are returned to their original positions by the elastic restoring force of the connection conduits 4d, 4e, 5d and 5e which are substantially circular.

That is, at the time of flow rate measurement, the pair of sensor tubes 4 and 5 are vibrated in the sensor conduits 4c and 5c by the vibrating force of the vibrating device 9, and the spring constants of the sensor tubes 4 and 5 themselves and the sensor tubes 4 and 5 are measured. It vibrates at a natural frequency determined by the flow rate flowing inside.

When the sensor tubes 4c and 5c of the sensor tubes 4 and 5 are vibrated, the stress generated in the sensor tubes 4 and 5 due to the vibration is caused by the connecting tubes 4d, 5d and 4 having a large radius.
It becomes a torsional stress that bends e and 5e. Therefore, the sensor tubes 4 and 5 have a flexible structure in which bending stress caused by the vibration of the sensor conduits 4c and 5c does not occur in the inflow conduits 4a and 5a and the outflow conduits 4b and 5b. Therefore, when measuring the flow rate, stress concentration does not occur in the sensor tubes 4 and 5, and the sensor tubes 4 and 5 are formed in a shape that prolongs the mechanical life.

When the sensor conduits 4c and 5c are vibrated, the spiral connecting conduits 4d, 5d and 4e and 5e having a large radius receive torsional stress in the entire conduits, so that the sensor conduit 4c can be applied with a relatively small force. , 5c can be excited. In this way, the sensor tubes 4 and 5 have a flexible structure that can be easily vibrated with a small exciting force, so that the small exciter 8 can be used accordingly.

Pickups 10 and 11 are provided between the sensor conduits 4c and 5c, and are located on both sides of the vibrator 8. That is, the pickups 10 and 11 are located at both ends of the sensor conduits 4c and 5c, respectively, and detect the relative displacement between the sensor conduits 4c and 5c when they vibrate. Also, the pickups 10 and 11
As the coil portions 10a and 11a and the magnet 10
An electromagnetic pickup consisting of b and 11b is conceivable.

In the case of this embodiment, the coil portions 10a and 11a are provided in the lower sensor conduit 5c, and the magnets 10b and 11b are provided in the upper sensor conduit 4c. Therefore, when the sensor conduits 4c and 5c vibrate, the coil portions 10a and 11a and the magnets 10b and 11b are displaced along with the relative displacement of the sensor conduits 4c and 5c. Therefore, the coil portion 10
Electromotive force corresponding to the displacement positions of the sensor conduits 4c and 5c is generated in a and 11a.

Here, the flow rate measuring operation of the mass flow meter having the above-mentioned configuration will be described with reference to FIGS. 4 to 6.

When measuring the flow rate, the fluid fed through the upstream pipe 6 is divided into two in the inflow-side manifold 2 and flows into the inflow pipes 4a and 5a. Then, after reaching the sensor conduits 4c, 5c via the connecting conduits 4d, 5d and passing through the sensor conduits 4c, 5c, the outflow conduits 4b, 5b via the connecting conduits 4e, 5d.
More outflow.

In this way, the sensor tubes 4, 5 in which the fluid flows in the tubes
Is excited by the vibrator 8 in directions opposite to each other in the sensor conduits 4c and 5c. Therefore, as shown in FIG. 4, the sensor conduits 4c and 5c vibrate so as to be spaced apart from or close to each other.

As described above, when the fluid to be measured flows into the vibrated sensor tubes 4 and 5, twisting due to Coriolis force occurs in the vibrating sensor conduits 4c and 5c.

Consider one stroke when the sensor conduit 4c is swung upward at the angular velocity ω in FIGS. 4 and 5. Sensor line 4
When c is excited in the upward direction by the exciting force of the exciter 8, it is displaced at the angular velocity ω from the position indicated by the alternate long and short dash line in FIG. 4 to the position indicated by the solid line. When the sensor conduit 4c is displaced upward, its amplitude is set so that the sensor conduit 4c does not contact the inflow conduit 4a and the outflow conduit 4b.

As described above, as shown in FIGS. 4 and 5, when the sensor conduit 4c is displaced at the angular velocity ω, the downward Coriolis force F is applied to the inflow side and the inflow side connecting conduit 4d of the sensor conduit 4c. Occurs, and an upward Coriolis force F is generated in the outflow side of the sensor conduit 4c and the connection conduit 4e on the outflow side.

As a result, the sensor conduit 4c is twisted as shown by the solid line in FIG. Further, when the sensor conduit 4c is displaced downward, the Coriolis force F in the opposite direction to the above acts, and the sensor conduit 4c is twisted as shown by the one-dot chain line in FIG.

As described above, the above-mentioned twist is generated as the sensor conduit 4c vibrates, and the twist angle at that time is θ. The twist angle θ is proportional to the mass flow rate of the fluid flowing in the sensor tube 4.

Also, in the lower sensor conduit 5c, the sensor conduit 4 is also
A twist symmetrical to c occurs. Therefore, the twist angle due to the relative displacement between the sensor conduits 4c and 5c is 2θ. Therefore,
The twist angle can be easily detected and the detection accuracy is high. The relative displacements of the sensor pipes 4c and 5c are detected by the pickups 10 and 11, and the pickups 10 and 11 detect the twist angle 2θ of the sensor pipes 4c and 5c as a signal of a time difference.

When the pickups 10 and 11 are electromagnetic pickups, the time required for changing 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 tubes 4, 5 is proportional to the time difference Δt when both ends of the sensor conduits 4c, 5c in FIG. 6 cross the AA axis. It has no relation to the vibration frequency. Further, as shown in FIG. 7, the voltage induced by the pickups 10 and 11 is measured as a sine wave. In FIG. 7, a line I is a detection signal of the pickup 10 on the inflow side, a line II is a detection signal of the pickup 11 on the outflow side, and a phase difference between the voltages generated from the two pickups 10 and 11 according to the lines I and II. That is, the time difference Δt is represented.

The phase difference signals of both pickups 10 and 11 are shaped,
After being amplified, it becomes 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).

In addition, in the mass flowmeter 1 of the above embodiment, the vibrator 8
Is fixed to the manifolds 2 and 3 via the support member 9, so that the sensor conduits 4c and 5c can be vibrated more stably. Therefore, the mass flowmeter 1 has an advantage that the flow rate measuring operation is more stable and the flow rate can be measured well.

Further, in the above-described embodiment, it is not necessary to provide a base or the like for supporting the vibration exciter 8, and the configuration of the entire flow meter can be further simplified.

The pick-up is not limited to the electromagnetic pick-up described above, and of course, an optical sensor or a magnetic sensor may be used.

Effect of the Invention As described above, the mass flowmeter according to the present invention can have a flexible structure such that the connecting pipe can relieve the stress when the sensor pipe is vibrated at the time of flow measurement, and the inflow conduit can be relaxed. Also, since fatigue fracture can be prevented from occurring by not applying excessive bending stress to the fixed end of the outflow pipe, durability against vibration can be improved and the measurement life can be improved. Furthermore, since the sensor conduit can be set longer without increasing the size of the entire flow meter, a greater Coriolis force can be obtained, and the flow measurement accuracy can be further improved.

[Brief description of drawings]

FIG. 1 is a plan view of an embodiment of a mass flowmeter according to the present invention,
2 and 3 are a side view and a front view of the mass flowmeter shown in FIG. 1, and FIGS. 4 and 5 are a side view and a front view for explaining the operation at the time of measuring the flow rate, and FIG. Is a diagram showing a twisting operation of the sensor conduit, and FIG. 7 is a waveform diagram of a detection signal of the pickup. 1 ... Mass flowmeter, 4,5 ... Sensor tube, 4a,
5a ... inflow conduit, 4b, 5b ... outflow conduit, 4c, 5
c ... Sensor line, 4d, 5d, 4e, 5e ... Connecting line, 8 ... Vibrator, 10,11 ... Pickup.

Claims (1)

[Scope of utility model registration request] 1. An inflow conduit communicating with the inflow port, an outflow conduit arranged in parallel with the inflow conduit and communicating with the outflow port, and a sensor conduit intersecting with the inflow conduit and the outflow conduit. A first connecting pipeline connecting the inflow pipeline to one end of the sensor pipeline; a second connecting pipeline connecting the outflow pipeline to the other end of the sensor pipeline; 2. A mass flowmeter comprising a vibrator for vibrating the sensor conduit so as to bend the second connecting conduit, and a pickup for detecting displacement of the sensor conduit due to vibration of the sensor conduit.