JPH0749982B2 - Mass flow meter - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mass flow meter, and more particularly to a mass flow meter configured to pass a measured flow rate through a linear sensor tube.

2. Description of the Related Art The flow rate of a fluid to be measured is preferably represented by a mass that is not affected by the type of fluid, physical properties (density, viscosity, etc.), and process conditions (temperature, pressure).

Therefore, various mass flow meters for measuring the mass flow rate of the fluid to be measured are being developed, and one of them is the mass flow rate utilizing the Coriolis force generated when the fluid is flown into the vibrating sensor tube. There is a flow meter that directly measures.

As an example of a conventional mass flowmeter of this type, Japanese Patent Application Laid-Open No. 63-3
There is a flowmeter disclosed by the 0721 publication. The mass flowmeter of this publication detects the displacement of the sensor tube due to the Coriolis force proportional to the flow rate by vibrating the linearly extending sensor tube in the radial direction in order to reduce the pressure loss when the fluid to be measured passes. Is configured to. Further, the sensor tube is provided with a bellows-like bellows near the flange having the inflow port and the outflow port, which allows the sensor tube to expand in the axial direction when measuring the flow rate of the high temperature fluid. A sufficiently heavy tightening ring is fixed in between to prevent external vibration from being transmitted to the vibrating portion of the sensor tube.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In the above mass flowmeter, the sensor tube is forcibly vibrated by the electromagnetic force of the exciting coil of the exciter (comprising a magnet and an exciting coil), and the mechanical Q that is the highest in the vibrating direction
The sensor tube is oscillated in a resonance state at a frequency at which (the reciprocal of the damping factor) is obtained. As described above, the Q of the sensor tube needs to be increased in order to prevent disturbance and stabilize the output signal, but it is difficult to increase the Q in the straight tube type sensor tube. Therefore, conventionally, the bellows or the like is used. The axial displacement due to the vibration of the sensor tube was absorbed. However, the conventional mass flowmeter has a problem that the bellows portion not only absorbs the displacement of the sensor tube in the axial direction but also causes bending, and the vibrating portion of the sensor tube easily shifts in the radial direction other than the axial direction. . Especially in the case of the above publication, since the heavy load of the tightening ring acts on the bellows, the bellows part may be deformed over time, which may cause the vibration characteristics of the sensor tube to flap or the output of the pickup to become unstable, resulting in accurate flow rate measurement. There is a problem that it becomes impossible to do.

Then, this invention aims at providing the mass flowmeter which solved the said subject.

Means for Solving the Problems The present invention provides a conduit having a straight pipe portion that linearly extends between an inflow port into which a fluid to be measured flows and an outflow port from which the fluid to be measured flows out; A vibrator that vibrates the pipe portion in a radial direction, a pickup that detects a radial displacement of the straight pipe portion due to the vibration of the straight pipe portion, and a pipe line that absorbs the axial displacement of the straight pipe portion. And a holding mechanism that restricts radial displacement of the straight pipe portion but holds the conduit so as to allow axial displacement of the straight pipe portion.

Action The axial displacement of the linearly extending sensor tube is absorbed by the expansion / contraction part, and the holding mechanism holds the end of the sensor tube so that it does not shift in the radial direction other than the axial direction. Can be stably obtained.

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

In each figure, the mass flowmeter 1 is a closed box-shaped casing 2
A pipe line 3 through which the fluid to be measured passes and a holding mechanism 4 that holds the pipe line 3 axially displaceably are provided. The pipe line 3 includes an inflow pipe 5 having an inflow port 5a, a pair of sensor tubes 6,
7 and an outflow pipe 8 having an outflow port 8a.

The inflow pipe 5 has a flange 5b connected to an upstream pipe (not shown) at an inflow end, and the other end of the inflow pipe 5 is formed inside the casing 2 by penetrating a side wall 2a of the casing 2. Room
It extends to 2b.

Reference numeral 9 denotes an inflow side manifold, which has an upstream side connection port 9a to which the inflow pipe 5 is connected and fixed and downstream side connection ports 9b and 9c to which the upstream end portions of the sensor tubes 6 and 7 are connected and fixed. The upstream side connection port 9a and the downstream side connection ports 9b and 9c are communicated with each other via the branch channels 9d and 9e.

The outflow side manifold 10 has a pair of connection ports 10a and 10b to which the downstream ends of the sensor tubes 6 and 7 are connected and fixed, and a connection port 10c to which the upstream end of the outflow pipe 8 is connected.
In addition, a pair of connection ports 10a, 10b are provided in the outflow side manifold 10.
Flow paths 10d and 10e are provided to connect the connection port 10c with the connection port 10c.

The pair of sensor tubes 6 and 7 are in the fluid flow direction (direction A)
It is composed of a straight pipe extending in a straight line, and is provided in parallel between the inflow side manifold 9 and the outflow side manifold 10. The sensor tubes 6 and 7 made of straight pipes are easy to manufacture because they have little pressure loss when the fluid to be measured passes and need not be processed into a complicated shape.

The upstream end of the outflow pipe 8 is a connection port of the outflow manifold 10.
10c is connected and fixed, and the downstream end is the side wall 2 of the casing 2.
It penetrates c and projects to the downstream side (direction A). An outlet 8a is opened at the downstream end of the outflow pipe 8, and a flange 8b connected to a downstream pipe (not shown) is provided on the outer periphery of the outlet 8a.

Reference numeral 11 denotes a bellows (expandable portion) formed in a bellows shape, which is provided in the outflow pipe 8. Therefore, the displacement of the sensor tubes 6 and 7 in the axial direction (direction A) due to thermal expansion when the high-temperature fluid passes through the conduit 3 is absorbed by the bellows 11.

The holding mechanism 4 is composed of a diaphragm 12 fixed to the outer circumference of the outflow pipe 8 and a cylindrical column 13 that supports the diaphragm 12. The diaphragm 12 is made of a metal having rigidity, for example, and restricts the outflow pipe 8 from being displaced in the radial direction, but is provided so as to allow the outflow pipe 8 to be displaced in the axial direction. The diaphragm 12 is fixed to the entire circumference of the end of a cylindrical support 13, and the support 13 is fixed to the side wall 2c of the casing 2.

Since the casing 2 has sufficient rigidity, the inflow pipe 5 and the outflow pipe 8 are held so that external vibration is not transmitted to the pipe line 3. Further, since the diaphragm 12 is firmly held by the support columns 13 fixed to the casing 2, the outflow pipe 8 is allowed to be displaced in the axial direction and the outflow pipe 8 is prevented from being displaced in the radial direction. .

Between the pair of sensor tubes 6 and 7 mounted between the inflow side manifold 9 and the outflow side manifold 10, a vibration exciter for vibrating the central part of the pair of sensor tubes 6 and 7 in the radial direction (X direction). 14 and pickups 15 and 16 for detecting displacement due to vibration of the sensor tubes 6 and 7 provided on the downstream side of the vibrator 14 are provided. The vibrator 14 has substantially the same structure as an electromagnetic solenoid, and includes a coil portion 14a provided on the sensor tube 6 side and a magnet portion 14b provided on the sensor tube 7 side, and the coil portion 14a is energized. Then, the sensor tubes 6 and 7 are driven in the X direction to approach or separate from each other.

The pickups 15 and 16 have coil portions 15a and 1
It is composed of 6a and magnet parts 15b and 16b, and obtains an output signal according to the relative displacement of the sensor tubes 6 and 7 accompanying the vibration of the sensor tubes 6 and 7.

At the time of measuring the flow rate, the pair of sensor tubes 6 and 7 are vibrated by the vibrating device 14 while the fluid is flowing inside. The fluid that has flowed into the conduit 3 through the inflow port 5a is the inflow side manifold 9
Is divided into two by the branch flow passages 9d and 9e, and flows at the same flow rate in the sensor tubes 6 and 7.
They merge at d and 10e and flow out from the outflow pipe 8 to the downstream side pipe.
As described above, when the fluid flows through the vibrating sensor tubes 6 and 7, Coriolis force corresponding to the flow rate is generated. Therefore, an operation delay occurs between the inflow side and the outflow side of the straight sensor tubes 6 and 7, which causes a phase difference in the output signals of the pickups 15 and 16. Since this phase difference is proportional to the flow rate, the flow rate can be obtained based on the phase difference between the output signals from the pickups 15 and 16.

The displacement due to the Coriolis force generated according to the flow rate passing through the vibrating sensor tubes 15 and 16 is picked up.
Since the principle of the flow rate measurement detected in 6 is the same as that of the mass flow meter filed previously, detailed description of the flow rate measurement operation will be omitted here.

Also, the bellows 11 absorbs displacement due to thermal expansion of the sensor tubes 6 and 7 and is therefore easily elastically deformed. However, since the outflow pipe 8 is held by the holding mechanism 4 having the diaphragm 12, the bellows 11 is not in the axial direction. The force of does not act, and it is a structure that is difficult to deform.

A second embodiment of the present invention is shown in FIGS.

In both figures, a mass flowmeter 21 is formed by arranging a pair of sensor tubes (pipe lines) 23, 24 in parallel in a cylindrical casing 22. An inflow side manifold 25 and an outflow side manifold 26 are fitted and fixed to the openings at both ends of the casing 22. The inflow side manifold 25 is provided with a pair of flow paths 25a and 25b in which the inflow side end portions of the sensor tubes 23 and 24 are inserted and fixed. Further, the outflow side manifold 26 is provided with a pair of flow paths 26a and 26b into which the outflow side end portions of the sensor tubes 23 and 24 are inserted and fixed. The pair of sensor tubes 23 and 24 are straight tubes extending in the direction A, and both ends thereof are connected and fixed to the inflow side manifold 25 and the outflow side manifold 26. Support plates 27 and 28 that are fixed to are horizontally mounted. Then, between the support plates 27 and 28, an exciter 2 for exciting the intermediate position of the sensor tubes 23, 24 in the X direction.
9 and the sensor tube 2 that vibrates on the downstream side of the exciter 29
Pickups 30 and 31 for detecting displacements of 3 and 24 are provided. The vibrator 29 and the pickups 30 and 31 have substantially the same structure as the vibrator 14 and the pickups 15 and 16 of the first embodiment, and the description thereof will be omitted.

Bellows-shaped bellows 32, 33 are provided near the outflow side ends of the sensor tubes 23, 24. Therefore, when the high temperature fluid passes through the sensor tubes 23 and 24, the sensor tube 2
The axial displacement due to the thermal expansion of 3,24 is absorbed by the expansion and contraction operation of the bellows 32,33.

Reference numeral 34 denotes a holding mechanism, and as shown in FIG. 6, a pair of support columns 35, 36 protruding from the end surface of the outflow side manifold 26, and a support column 35, 36.
The cross-shaped support plate 37 is supported by 36. Support plate 37
Are the support portions 37a and 37b fixed to the columns 35 and 36, and the support portions 37a and 37a.
The holding portions 37c and 37d project in the X direction orthogonal to 37b. The sensor tube 2 is attached to the ends of the holding portions 37c and 37d.
3,24 penetrates and is fixed.

Since the holding portions 37c, 37d of the support plate 37 hold the sensor tubes 23, 24 in a cantilevered state, when the sensor tubes 23, 24 are displaced in the axial direction, the holding portions 37c, 37d bend in the axial direction. Directional displacement is allowed. However, since the support plate 37 has rigidity in directions other than the axial direction, it supports the bellows 32 and 33 so as not to bend in the radial direction.

In addition, an inlet 38a and an outlet 39a are provided at the ends of the manifolds 25 and 26.
The reducers 38 and 39 having the are fixed. Flange 38b, 39b connected to a downstream pipe (not shown) is fixed on the outer periphery of the ends of the reducers 38, 39.

The fluid to be measured from the upstream side pipe is branched into the flow paths 25a and 25b of the inflow side manifold 25 from the inflow port 39a and passes through the pair of sensor tubes 23 and 24. The sensor tubes 23 and 24 vibrate in the X direction with the support plates 27 and 28 as fulcrums, and a Coriolis force proportional to the flow rate is generated. Further, the fluids pass through the flow paths 26a and 26b of the outflow-side manifold 26, merge, and flow out from the outflow port 39a. Since the sensor tubes 23 and 24 vibrate between the support plates 27 and 28, the frequency of the vibration excited by the vibrator 29 can be separated from the vibration frequencies of other modes. Therefore, the pickups 30 and 31 can obtain a more stable output signal.

A third embodiment of the present invention is shown in FIGS.

In both figures, the mass flowmeter 41 has a pipe 43 in a cylindrical casing 42.
Are arranged in the A direction. The conduit 43 has an inlet 44a at one end.
And an inflow pipe 44 having a bellows 44b at the other end, a pair of sensor tubes 45 and 46 formed by arranging straight pipes in parallel, and an outflow pipe having an outflow port 47a at one end and a bellows 47b at the other end. 47
And consists of.

An inflow side manifold 48 has a connection port 48a to which the inflow pipe 44 is connected, and a pair of connection ports 48b and 48c to which the upstream ends of the sensor tubes 45 and 46 are connected. Further, in the inflow side manifold 48, flow paths 48d and 48e are provided which connect the connection port 48a and the connection ports 48b and 48c.

49 is an outflow side manifold, and the above inflow side manifold 48
The connection port 49a has the same configuration as that of the connection port 49a to which the outflow pipe 47 is connected.
And a pair of connection ports 49b, 49c to which the downstream ends of the sensor tubes 45, 46 are connected. Further, in the outflow side manifold 49, flow paths 49d and 49e which connect the connection ports 49a to 49b and 49c are provided.

Further, the inflow pipe 44 has a flange 44c on the inflow port 44a side, the bellows 44b side penetrates the side wall 42a of the casing 42, and is fixed to the inflow side manifold 48. Outflow pipe 47 is also outlet 47a
Side has a flange 47c, and the bellows 47b side has a casing 42
It penetrates the side wall 42b and is fixed to the outflow side manifold 49.

Between the pair of sensor tubes 45,46 is the sensor tube 45,46.
A vibration exciter 50 that vibrates the intermediate position in the X direction in the X direction, and pickups 51 and 52 that detect the displacement of the sensor tubes 45 and 46 that vibrate on the downstream side are disposed above the vibration exciter 50. Support plates 53 and 54, which hold the pair of sensor tubes 45 and 46 at predetermined intervals, are fixed on the upstream side of the pickups 51 and 52. Therefore, the pair of sensor tubes 45 and 46 vibrate in the X direction with the support plates 53 and 54 as fulcrums, and are held by the casing 2 and the support plates 53 and 54 having sufficient strength, so that they are affected by external vibration. It is a difficult structure.

Reference numeral 55 denotes an inflow side holding mechanism, which is positioned between the columns 55a and 55b protruding from the side wall 42a of the casing 42 into the casing 42 and the sensor tubes 45 and 46 supported by the columns 55a and 55b, and fixed to the inflow side manifold 48. Fixed plate 55c. Reference numeral 56 denotes an outflow side holding mechanism, which is located between the columns 56a and 5b protruding from the side wall 42b of the casing 42 into the casing 42 and the sensor tubes 45 and 46 supported by the columns 56a and 56b, and fixed to the outflow side manifold 49. Fixed plate 56c.

When the high temperature fluid passes through the pipe 43 during flow rate measurement, the sensor tubes 45 and 46 are displaced in the axial direction (direction A) by thermal expansion. In that case, the displacement of the sensor tubes 45 and 46 is absorbed by the expansion and contraction operations of the bellows 44b of the inflow pipe 44 and the bellows 47b of the outflow pipe 47. Although the bellows 44b and 47b are easily displaced in directions other than the axial direction, the fixing plate 55 of the holding mechanisms 55 and 56 is
c, 56c bends together with bellows 44, 49 bellows 44b, 47
Allow only axial displacement as the displacement direction of b. That is, even if a radial force acts on the bellows 44b, 47b, the manifolds 55, 56 are held by the holding mechanisms 55, 56, so that the radial displacement is prevented. Therefore, the pair of sensor tubes 45, 46 perform a stable vibration operation even when measuring the flow rate of the high temperature fluid, and the output signal according to the flow rate is stably obtained from the pickup.

In the above embodiment, the fixing plates 55c and 56c are located between the pair of sensor tubes 45 and 46, but it is not limited to this. For example, in FIG. 7, a pair of fixing plates 55c ', 55c' are positioned above and below the sensor tubes 45, 46 and fixed to the outflow side manifold 48 as shown by the one-dot chain line, and a pair of fixing plates 56c ' Alternatively, 56c 'may be located above and below the sensor tubes 45, 46 and fixed to the outflow side manifold 49. Further, the fixed plate 55c and the pair of fixed plates 55c ', 5
5c 'is fixed to the inlet side manifold 48, and the fixing plate 56c
And a pair of fixing plates 56c ', 56c' to the outflow side manifold 49
It may be fixed to.

Although the bellows absorbs the thermal expansion of the sensor tube in each of the above-described embodiments, it is of course possible to absorb the axial displacement of the sensor tube with other configurations.

EFFECTS OF THE INVENTION As described above, the mass flowmeter according to the present invention can absorb and displace axial displacement due to thermal expansion of the sensor tube by the expansion and contraction operation of the expansion and contraction portion even when measuring the flow rate of a high temperature fluid. It is possible to restrict the straight pipe portion so that it can be displaced only in the axial direction by the holding mechanism so that a force other than the axial direction does not act on the portion. Therefore, the vibration operation of the sensor tube is stable, the output signal of the flow rate measurement can be prevented from fluttering, and more accurate flow rate measurement can be performed.

[Brief description of drawings]

1 is a transverse sectional view of a first embodiment of the mass flow meter according to the present invention, FIG. 2 is a longitudinal sectional view of the mass flow meter shown in FIG. 1, and FIG.
The figure is a longitudinal sectional view taken along the line III-III in FIG. 2, and FIG.
FIG. 5 is a longitudinal sectional view taken along line IV-IV in FIG. 5, FIG. 5 is a lateral sectional view of a second embodiment of the present invention, and FIG. 7 is a perspective view for explaining a holding mechanism. [FIG. 3] is a horizontal sectional view and a vertical sectional view, respectively, of a third embodiment of the present invention. 1,21,41 ... Mass flowmeter, 2 ... Casing, 3,43 ... Pipeline,
4,34,55,56… Holding mechanism, 6,7,23,24,45,46… Sensor tube, 9,25,48… Inflow side manifold, 10,26,49… Outflow side manifold, 11,32, 33, 44b, 47b ... Bellows, 12 ... Diaphragm, 27, 28, 53, 54 ... Support plate, 13, 35, 36 ... Struts, 37 ... Support plate, 44 ... Inflow pipe, 47 ... Outflow pipe.

Claims (1)

[Claims] 1. A pipe line having a straight pipe portion linearly extending between an inflow port into which the fluid to be measured flows and an outflow port from which the fluid to be measured flows out, and the straight pipe portion is vibrated in a radial direction. A vibration exciter, a pickup that detects a radial displacement of the straight pipe portion due to the vibration of the straight pipe portion, and an expandable portion provided in the pipeline so as to absorb the axial displacement of the straight pipe portion. And a holding mechanism that holds the pipe passage so as to restrict the displacement of the straight pipe portion in the radial direction but allow the displacement of the straight pipe portion in the axial direction. .