JPH09257540A - Coriolis flowmeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize the alternating vibration of a Coriolis flowmeter, which has an annular loop-shaped measuring tube, so as to improve the mass flow accuracy. SOLUTION: A measuring tube 2, which has an annular loop 2b at one lap or more and less than two laps, is inserted for fixation into a flow-in port 1c and a flow-out pot 1d of an outer cylinder 1 provided with connecting flanges 1a, 1b having the flow-in port 1c and the flow-out port 1d on an axis X-X. The annular loop 2b is integrally supported by first support plates 6, 7, which are arranged at an angle θ (<=30), and driven as a part of the annular loop 2b for resonance around the first support plate 6 and the first support plate 7 by a driving unit 8. With this vibration, although the annular loop 2b within the angle θ is vibrated, the first support plates 6, 7 work as a joint part, bad influence is not applied to the vibration of the curved annular loop 2b, which is driven for resonance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Coriolis flowmeter, and more particularly to a mass flowmeter in which a measuring tube forms an annular loop about a fluid flow direction.

[0002]

2. Description of the Related Art As is well known, in a Coriolis flowmeter, when a measuring tube in which a fluid flows at a mass flow rate M is supported at two points and is alternately driven around a support position at a frequency ω, the mass flow rate M and the drive frequency ω It is a mass flow meter that finds the mass flow rate by detecting the Coriolis force by utilizing the generation of Coriolis force in the direction proportional to the vector product of. Therefore, it is no exaggeration to say that the measuring tube is a main part that generates the Coriolis force, and the shape of the measuring tube determines the characteristics of the mass flowmeter.

As the shape of the measuring tube, there are a straight tube which has a small detection sensitivity of Coriolis force but the simplest shape, and a curved tube which has a high sensitivity but a complicated shape. Since the shape of the curved tube affects the detection sensitivity of the Coriolis force, many types of measuring tubes have been proposed so far, but when roughly classified, they are asymmetrical with respect to the flow direction axis of the fluid to be measured. There are various shapes and symmetrical shapes. The measurement tubes of any curved shape are designed so that the amount of deformation due to the constant Coriolis force generated around the support position is larger than that of the straight tube, but the inside of the tube depends on the size of the flowmeter and the mounting posture. The shape of the measuring pipe is determined in consideration of the contamination that occurs in the pipe and the influence of external vibration from the pipe. Among them, there is a measuring tube having a spiral annular loop with the axis in the flow direction as an axis, which has a high sensitivity even if the shape is small and has a low contamination, and as a Coriolis flowmeter using this measuring tube, Hei 4-54894, Japanese Examination 6-748989
And Japanese Patent Publication No. 7-509070 are disclosed.

The mass flowmeter described in Japanese Examined Patent Publication No. 4-54894 is proposed by the present applicant, and a blocking plate for stopping the fluid flow is provided in the flow tube, and the flow tube is sandwiched between the blocking plates.
A coil-shaped conduit having an inflow port and an outflow port on the downstream side and coaxial with the flow tube is used as a measurement tube, and a support member provided in parallel with the flow tube axis of the coil-shaped conduit is provided at a plurality of positions of the conduit. It is fixed and the conduit is alternately driven at a position axisymmetric to the support member in a direction perpendicular to the conduit surface.

In the Coriolis mass flow sensor having a spiral measuring tube described in Japanese Patent Publication No. 7-509070, the inflow side and outflow side flanges which are coaxially separated from each other are provided in a circular tubular support tube in the vicinity of each flange. Connected and supported, a single spiral measuring tube is connected between the inlet and outlet flanges. The measuring tube is supported in the radial direction by means of a plate-shaped coupling element on a rod-shaped support provided coaxially in the support tube.

As shown in FIG. 4, the mass flowmeter disclosed in Japanese Patent Publication No. 6-74899 has a cylindrical support structure 22 for coaxially supporting a fluid inlet 21a and a fluid outlet 21b.
The flow path pipe 20 is provided around the axis of the cylindrical support structure 22. The flow path pipe 20 has isolation loops 20a, 20d each having one end connected to the inlet 21a and an outlet 21b, and measuring loops 20b, 2 connected between the isolation loops 20a, 20d.
In the double loop structure consisting of 0c, a rigid body bar 23 parallel to the inflow / outflow axis that insulates external force is connected to the measurement loops 20b and 20c of this flow pipe at three points 23a, 23b and 23c. ing.

[0007]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the mass flowmeter described in Japanese Patent No. 894, the inflow and outflow end portions of a conduit, which is a measuring pipe, are directly connected to the flow pipe, and when the flow pipe vibrates due to vibration of the pipe, the pipe also vibrates and the pipe vibrates. Affected to reduce SN ratio. Further, the conduit is fixed by the supporting means on a line parallel to the flow tube axis, and the spiral conduit is driven around the supporting position in a direction perpendicular to the conduit surface.
Since the conduit is supported by the supporting means at a plurality of points at one point in the direction parallel to the flow tube axis, when the conduit is driven, the vibration of the conduit extends to the flow tube supported by the supporting means, and the SN ratio is increased. As a result, there is a decrease.

Since the measuring tube of the mass flow sensor disclosed in Japanese Patent Publication No. 7-509070 is supported by a supporting element coaxial with the supporting tube in the radial direction by a plate-like connecting element, the measuring tube is supported by the supporting tube. Relative vibration occurs due to the difference between the vibration modes of the support element and the support element, and this vibration also affects the measurement position of the measuring tube and causes a measurement error.

The flow path tube 20 of the mass flow meter disclosed in Japanese Patent Publication No. 6-74899 has an isolation loop 20.
In a section of the measurement loops 20b and 20c excluding a and 20d, one rigid body bar 23 supports at three points 23a, 23b, and 23c, but only one rigid body bar 23 has an isolation loop 20a, 20d and measurement loop 20
It is impossible to effectively perform vibration isolation between b and 20c, and when the measurement loops 20b and 20c are driven in opposite phases, vibration leakage occurs in both and the SN ratio is reduced. In this sense, the rigid bar 30 is not an effective vibration isolator.
Further, in order to give the effect of removing the external vibration, it is necessary to increase the number of pitches of the isolation loops 20a and 20d, so that the entire length of the flow path pipe 20 is increased, and the fluid resistance is increased accordingly and the pressure loss is increased. Will increase.

The present invention has been made in view of the above problems, and supports an annular loop-shaped measuring pipe connected between a coaxial inlet and an outlet, at two points sandwiching a predetermined angle of the annular loop. To provide a Coriolis flowmeter that is fixed with a member and completely isolates the vibration of the measurement tube from the outside to eliminate the need for an isolation tube, has an excellent SN ratio, and has a short flow tube length and a small pressure loss. With the goal.

[0011]

According to a first aspect of the present invention, there is provided an inflow-side conduit and an outflow-side conduit which are fixed coaxially to the fluid inflow direction with a space therebetween, and the inflow-side conduit and the outflow-side conduit. A measuring tube having an annular loop with each axis connected to the pipe line with a continuous curve and having one or more rounds and less than two rounds, and the annular loops facing each other at two points sandwiching a predetermined center angle of the annular loop. A support member that is integrally fixed, a driving unit that applies vibration to the measurement tube around the support member, and a detection unit that detects the Coriolis force that the fluid flowing in the measurement tube receives due to the vibration are provided, and are proportional to the Coriolis force. The mass flow rate of the fluid is calculated.

According to a second aspect of the present invention, in the Coriolis flowmeter according to the first aspect, the second support plate that supports the measuring tube supported by the support member at equal intervals from the support position on the drive means side. Is provided.

According to a third aspect of the present invention, in the Coriolis flowmeter according to the first or second aspect, the connecting portion to which the measuring pipe having an annular loop is connected to the inflow side pipe line and the outflow side pipe line is connected to the Coriolis flowmeter. The pipe length of the measuring pipe between the supporting member and the support member is within 30 ° when viewed from the axial direction of the annular loop.

[0014]

1 is a diagram for explaining an example of an embodiment of a Coriolis flowmeter according to the present invention.
1A is a partial cross-sectional view in the flow direction, and FIG. 1B is FIG.
FIG. 6 is a cross-sectional view taken along the line BB of (A), in which 1 is an outer cylinder,
2 is a measuring tube, 3 is a supporting member, 4 and 5 are side plates of the supporting member,
6, 7 are first support plates of the support member, 8 is a drive unit, 9, 10
Is a detector, and 11 and 12 are second support plates. FIG.
In the following figures, the same reference numerals as those in FIG. 1 will be attached to the parts having the same operations as in FIG.

In FIG. 1, an outer cylinder 1 is a cylindrical body having a closed structure, and connecting flanges 1a and 1b are integrally attached to the center of the end face. The connection flange 1a is provided with an inflow port 1c, the connection flange 1b is provided with an outflow port 1d, and the inflow port 1c and the outflow port 1d are arranged on the same axis (XX axis). Between the inlet 1c and the outlet 1d, there is connected a mass flow rate measuring pipe 2 having an annular loop of 1 or more and less than 2 rounds. The measuring pipe 2 is composed of a connecting portion 2a at both ends which is inserted and fixed in the inlet 1c and the outlet 1d at both ends, and an annular loop portion 2b between which the connecting portion 2a and the pipe axis are continuously curved. ing. The annular loop portion 2b is composed of equal-shaped annular loops having one or more turns and less than two turns at equal pitches, and FIG. 1 shows an example in which the annular loops are circular.

Since the annular loop portions 2b have the same shape and the same pitch, the same phase portions are parallel to each other at the center angle viewed from the axis XX. In the present invention, the central angle θ (≦
(30 °), the two parts of the same phase forming the annular loop portion 2
b is supported by the support member 3. The support member 3 includes first support plates 6 and 7 of the support member 3 that fix the annular loop portion 2b at a central angle θ when viewed from the axial direction, and a surface perpendicular to the axis XX of the first support plates 6 and 7. And side plates 4 and 5 for fixing and supporting the both ends. In FIG. 1, the annular loop portion 2b and the first support plate 6 are fixed at two points 6a and 6b, and the first support plate 7 is fixed at two points 7a and 7b.
Are fixed by fan-shaped side plates 4 and 5 having a central angle θ. Therefore, it is fixed by the support member 3 of the annular loop portion 2b (2
Two parallel curved tubes are formed in the range of π−θ).

In the plane perpendicular to the axis XX of the annular loop portion 2b, the central angle (1 /
2) The drive unit 8 is located on the line Y-Y passing through the middle of the support member 3 connecting θ and the detection units 9 and 7 are arranged at positions equidistant from the drive unit 8.
10 are provided. The driving unit 8 includes, for example, a driving coil and a core, and the driving coil or the core is attached to one of the annular loop portions 2b that face each other in parallel, and each bending unit is supported by the driving signal applied to the driving coil. Resonance driving is performed around the position of the member 3 in a sound-like manner with a constant amplitude.
The detection units 9 and 10 are composed of, for example, a detection coil and a permanent magnet, and the detection coil and the permanent magnet are attached to the annular loops 2b facing each other, and are generated in opposite phases at symmetrical positions of the detection units 9 and 10. The Coriolis force is detected as a velocity signal. The velocity signal proportional to the Coriolis force is converted into a position signal by integration, and the mass flow rate is obtained from the phase difference signal.

The annular loop portion 2b shown in FIG. 1 has an axis X-
Since it is supported by the support member 3 at an angle within the central angle θ = 30 ° when viewed from X, it is difficult for external vibration to enter the annular loop portion 2b, and therefore it is necessary for the conventional Coriolis flowmeter. The isolation loop as a cushioning material is unnecessary. Therefore, the inlet 1c and the outlet 1d
The pipe length of the connecting portion 2a between the ring-shaped loop portion 2b and the annular loop portion 2b may be the smallest physically possible structure. In the embodiment of the present invention, the loop length is within an angle range of 30 ° when viewed from the axis XX direction. All you have to do is

Therefore, the entire length of the measuring pipe 2 can be made extremely short, and the pressure loss of the Coriolis flowmeter can be greatly reduced. As described above, since the connecting portion 2a does not need the buffering function, the pressure loss of the measuring pipe 2 can be further reduced by selecting a large diameter of the connecting portion 2a.

FIG. 2 is a diagram for explaining a partial view for explaining an embodiment of the connecting portion of the Coriolis flowmeter according to the present invention, in which 13 is a connecting pipe. The connecting pipe 13 shown in FIG. 2 is on the inlet side, and the outlet side also has the same structure as the inlet side, and illustration of the outlet side is omitted. Since the annular loop portion 2b of the measuring tube 2 has a precise loop shape, the bending cost increases. The connecting pipe 13 is formed separately from the annular loop portion 2b, and the connecting pipe 13 has a tube diameter larger than that of the annular loop portion 2b.
And the connecting pipe 13 are integrally configured as a rigid body. Therefore, the connection pipe 13 is welded to the annular loop portion 2b, which is the measurement pipe, at the end portion 13b of the first support plate 6,
The outer cylinder 1 is welded to the outer cylinder 1 at a portion 13c penetrating the outer cylinder 1. In addition, in FIG. 1, the inflow port 1 a, the outflow port 1 b and the measuring pipe 2 are connected by the outer cylinder 1, but the inflow port 1 a, the outflow port 1
It may be supported on the axis coaxial with b through a coupling member that is integrally coupled with the annular loop portion 2b inside the annular loop portion 2b.

FIG. 3 is a diagram for explaining the vibration of the annular loop portion of the Coriolis flowmeter shown in FIG. 1, in which D ₁ ,
D ₂ indicates the mounting position of the drive unit. In FIG. 3, the annular loop portion 2b is joined to the first support plate 6 by 6a and 6b,
The first support plate 7 7a, joined at 7b, the spacing between junctions 6a and 6b and between 7a and 7b are equal, therefore, the annular portion 6a-D ₁ -7a and 6b-D ₂ -7b isomorphic, etc. It is a long parallel annular portion, and the joint portions 6a, 6 of the first support plates 6, 7 are attached at the attachment positions D ₁ , D ₂ of the central drive portion 8.
It is driven in the opposite direction shown by the arrow in the shape of a tuning fork around the support positions of b and 7a, 7b.

[0022] from being joined by the respective side plates 4 and 5 and the first supporting plate 6 and 7, the annular portion 6a-D ₁ -7a and 6b-D ₂ -7b each 6a-7a and 6b-7b
It vibrates like a tuning fork with the line connecting them as the axis. Since this and the support interval between the first support plates 6 and 7 are small angles within 30 ° in the central angle, the annular loop portion 2 in the support member 3 is formed.
Since b is seen as substantially rigid, annular portion 6a-D ₁ -7
resonance of a and 6b-D ₂ -7b is not subject to a vibration effect of the annular portion 6a-7a and 6b-7b in the support 3, not subject to vibration effects of connecting portions 2a, stable resonance vibrations Is obtained.

As described above, in the Coriolis flowmeter shown in FIG. 1, the annular loop 2b is supported in the range of the central angle θ and is resonantly driven as curved parallel tubes having the same shape. The vibration of the annular loop 2b portion within the range of the central angle θ (≦ 30 °) becomes the vibration with the first support plates 6 and 7 as the nodes, and the influence of this vibration is the curved tubular annular loop 2b of the resonance driving portion. Stable resonance vibration is obtained because it does not extend to any part, and as a result high mass flow rate with high accuracy is required. Further, since the measuring pipe has a continuous annular loop, contamination does not occur especially when the measuring pipe is mounted in a vertical pipe posture.

In addition, in the curved tubular loop 2b driven by resonance, a second support plate 11 for supporting the measuring tube portion parallel to the first support plate 6 is provided, and similarly, the first support plate 6 is provided. The second support plate 12 is provided at a position that is equally distant from the measurement pipe 7, so that the measuring tube 2 is attached to the second support plate 1
Therefore, the portion of the annular loop portion 2b which is not resonantly driven is resonantly driven between the first and second support plates 11 and 12.
Besides, since it is supported by the support member 3, more stable resonant drive of the measuring tube 2 can be obtained.

[0025]

【The invention's effect】

Effect corresponding to claim 1: An inflow side conduit and an outflow side conduit which are coaxial and fixed at a distance in the inflow direction of the fluid, and respective axes are continuous to the inflow side conduit and the outflow side conduit. A measuring tube having a circular loop that is connected with a curved line and that has one or more rounds and less than two rounds, and a first unit that integrally fixes the annular loops that face each other at two locations that sandwich a predetermined center angle of the circular loop.
Since a supporting member having a supporting plate, a driving means for vibrating the measuring tube around the supporting member, and a detecting means for detecting a Coriolis force received by the fluid flowing in the measuring tube due to the vibration are provided, the annular loop is predetermined. The two supporting points supported by the center angle of the are the vibration nodes, and do not affect the resonance vibration that drives the annular loop outside this range, so a stable high SN ratio vibration is obtained, resulting in high accuracy. The mass flow rate of is determined. The measuring tube is a vibration of a single-length annular loop, which gives a stable vibration, unlike the case of two single-loop vibrations. Since the annular loop surface of the measuring pipe is substantially perpendicular to the easy vibration direction of the main pipe (pipe), it is not affected by the pipe vibration. The couple due to the Coriolis force can increase the arm length from the supporting position, so that the detection sensitivity can be increased. Since the annular loop portion surrounds the main pipe axis, a small Coriolis flowmeter can be obtained, and the mounting space can be reduced. Since the support plate is floated, vibration can be blocked. Since the measuring tube is a single tube without a protruding joint portion, the inside can be easily cleaned.

An effect corresponding to claim 2: In the Coriolis flowmeter according to claim 1, the Coriolis flowmeter is supported at a position having an equal distance from the measuring pipe supporting position on the side of the driving means supported by the supporting member. Since the two support plates are provided, more stable vibration can be obtained and the mass flow rate measurement accuracy can be improved.

Effect corresponding to claim 3: Claim 1 or 2
The Coriolis flowmeter according to claim 1, wherein the pipe length of the measurement pipe between the connection member and the support member to which the measurement pipe having an annular loop is connected to the inflow-side pipe and the outflow-side pipe is Since the angle is within 30 ° when viewed from the axial direction of the annular loop, the total length of the measuring tube can be shortened. Further, since the pipe diameter of the connecting portion can be increased, the pressure loss can be reduced. Further, since the connecting portion of the measuring tube can be formed separately from the annular loop portion as a rigid body and integrally formed with the connecting flange portion, it can be manufactured at low cost.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an embodiment of a Coriolis flowmeter according to the present invention.

FIG. 2 is a diagram for explaining a partial view for explaining an example of an embodiment of a connection portion of a Coriolis flowmeter according to the present invention.

FIG. 3 is a perspective view for explaining vibration of an annular loop portion of the Coriolis flowmeter shown in FIG.

FIG. 4 is a perspective view for explaining the operation of a conventional mass flowmeter having a measurement loop.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Outer cylinder, 2 ... Measuring tube, 3 ... Support member, 4, 5 ... Side plate of support member, 6, 7 ... 1st support plate of support member 3, 8 ... Drive part, 9, 10 ... Detection part, 11 , 12 ... Second support plate, 13
… Connection tube.

Claims (3)

[Claims] 1. An inflow-side conduit and an outflow-side conduit fixed coaxially to a fluid inflow direction with a space therebetween, and respective axes connected to the inflow-side conduit and the outflow-side conduit with continuous curves. Is
A support member having a measuring tube having an annular loop with one or more turns and less than two turns, and first support plates for integrally fixing the annular loops facing each other at two locations sandwiching a predetermined center angle of the annular loop. A driving means for vibrating the measuring tube around the supporting member, and a detecting means for detecting a Coriolis force received by the fluid flowing in the measuring tube due to the vibration, and a mass flow rate of the fluid proportional to the Coriolis force is obtained. A Coriolis flowmeter characterized in that. 2. A second supporting plate for supporting the measuring tube supported by the first supporting plate of the supporting member at positions equidistant from a supporting position on the driving means side. The Coriolis flowmeter according to 1. 3. A pipe line of the measuring pipe between a connection part to which the measuring pipe having an annular loop is connected to the inflow side pipe line and the outflow side pipe line and the first support plate of the supporting member. Is within 30 ° when viewed from the axial direction of the annular loop, The Coriolis flowmeter according to claim 1 or 2, wherein.