JP5033755B2 - Coriolis flowmeter with vibration direction regulating means - Google Patents

Description

  The present invention is configured to obtain a mass flow rate and / or density of a fluid to be measured flowing in a flow tube by detecting a phase difference and / or vibration frequency proportional to the Coriolis force acting on the curved tubular flow tube. More particularly, the present invention relates to a Coriolis flow meter suitable for measuring a minute flow rate.

  The Coriolis flowmeter supports one or both ends of the flow tube through which the fluid to be measured flows, and when the vibration is applied in the direction perpendicular to the flow direction of the flow tube around the support point, It is a mass flow meter that utilizes the fact that force is proportional to mass flow rate. Coriolis flowmeters are well known, and the shape of the flow tube in the Coriolis flowmeter is roughly divided into a straight tube type and a curved tube type.

  The straight pipe type Coriolis flowmeter is a straight pipe that is supported by the Coriolis force between the straight pipe support section and the center section when vibration is applied in the direction perpendicular to the straight pipe axis of the straight pipe center supported at both ends. A displacement difference of the tube, that is, a phase difference signal is obtained, and the mass flow rate is detected based on the phase difference signal. Such a straight tube type Coriolis flowmeter has a simple, compact and robust structure. However, it also has a problem that high detection sensitivity cannot be obtained.

On the other hand, the curved tube type Coriolis flow meter is superior to the straight tube type Coriolis flow meter in that it can select the shape to effectively extract the Coriolis force. Can be detected. In addition, as a curved tube type Coriolis flowmeter, one provided with one flow tube (see, for example, Patent Document 1), one provided with two flow tubes in parallel (see, for example, Patent Document 2), or one There are known ones provided in a state in which a flow tube is looped (see, for example, Patent Document 3).
Japanese Examined Patent Publication No. 4-55250 Japanese Patent No. 2939242 Japanese Patent Publication No. 5-69453

  The present inventor considers that a highly sensitive tube structure is necessary to measure a very small flow rate in a curved tube type Coriolis flow meter. To ensure vibration resistance, the flow tube is not normally driven with vibrations of 50-60 Hz or less, so in order to ensure the phase difference under such constraints, the mode that receives Coriolis force is used. Therefore, a tube structure with low rigidity is required to achieve high sensitivity. As a tube structure with low rigidity, it is possible to curve the flow tube into a triangle shape or an oval shape, but in order to further increase the sensitivity, it has a sufficient length in the lateral direction as shown in FIG. The inventor of the present application thinks that it is preferable to curve the flow tube into an oval shape.

  However, in the case of such a shape of FIG. 8, the vibration in the Z-axis direction (in-phase, opposite phase) in the figure coincides with or becomes lower than the driving frequency of the flow tube. Axial vibrations can be excited. When vibration in the Z-axis direction is excited, vibration in a direction that should not be driven is generated, so that the instrumental error is worsened or vibration leakage becomes large and the zero point is not stable. Have.

  This invention is made | formed in view of the situation mentioned above, and makes it a subject to provide the highly sensitive Coriolis flowmeter suitable for measuring a very small flow volume.

The Coriolis flowmeter of the present invention according to claim 1, that is, a Coriolis flowmeter having a vibration direction restricting means according to the present invention, which has been made to solve the above problems, includes a housing, a flow tube accommodated in the housing, and the flow. Drive means for driving the tube and phase difference detection means for detecting a phase difference proportional to the Coriolis force, driving at least one flow tube, and proportional to the Coriolis force acting on the flow tube In a Coriolis flowmeter configured to obtain a mass flow rate and / or density of a fluid to be measured flowing in the flow tube by detecting a phase difference and / or a vibration frequency,
When the vibration direction of the flow tube is defined as the X axis, the tube axis direction at the antinode position of the flow tube vibration is defined as the Y axis, and the direction perpendicular to the X axis and the Y axis is defined as the Z axis,
The housing is
It has a structure that is strong against bending and twisting, and is sized to accommodate the flow tube fixed to the flow tube fixing member, protecting the flow meter body from the outside, and an inert gas inside And configured to prevent condensation on the flow tube ,
The flow tube is
A thin tube and a straight tube portion on the drive side where the tube axis extends straight along the Y-axis direction, and a fixed tube formed in parallel with the straight tube portion on the drive side and separated at the approximate center in the tube axis direction. possess a straight pipe portion of the side, and a straight portion and inlet-side curved pipe portion and the outlet-side curved pipe portion of the semicircular connecting straight portion of the fixed side of the drive side, the Y-axis direction length The ratio of the length (width) to the length (height) in the Z-axis direction is formed into a substantially oval shape long in the Y-axis direction of 8.5: 1, and two are arranged side by side at a predetermined interval. Housed and configured in the housing ,
The flow tube fixing member is
And a manifold inlet side manifold and the outlet side of the fluid to be measured flows, and fixed to each of the fixed end of the two flow tubes, which are separated by the tube axis direction approximate center of said flow tube, said 2 to function as each of the fixed end is fixed, the vibration direction regulating means which does not vibrate in the Y-axis and Z-axis directions of the two flow tubes, which are separated in each tube axis direction approximate center of the flowtube Is composed of
The driving means includes
Be of to oppose vibrations straight pipe portion of the drive side of the flow tube, constituted by a coil and a magnet, wherein the flow tube fixing member of the central straight part of the driving side of the two flow tubes Is placed between the two flow tubes so as to be sandwiched between the straight tube portions on the drive side, and attached to a position not offset with respect to the vibration direction (drive direction) of the flow tubes. When the action occurs, the magnet is inserted into the coil and the straight tube portions on the driving side of the flow tube come close to each other. The straight tube portions are separated from each other, and the flow tube is driven alternately in the rotation direction around the flow tube fixing member. And it will be,
The phase difference detecting means includes
It detects the vibration of the flow tube, a sensor for detecting a phase difference proportional to a Coriolis force acting on the flow tube, constituted by a coil and a magnet, each of the inflow of the two flow tubes Provided at a position where the phase difference proportional to the Coriolis force can be detected at a position within the range sandwiched between the side curved tube portions and between the respective outflow side curved tube portions of the two flow tubes, detects the vibrations of the two flow tubes, will be configured to detect a phase difference proportional to a Coriolis force acting on the two flow tubes,
A plate spring or two strips formed by disposing two strip-shaped stainless steel plates disposed at both ends of the flow tube fixing member at intervals in a direction perpendicular to the longitudinal direction of the flow tube. A plate spring formed by forming a single X plate by crossing the plate-shaped stainless steel plate material on an axis connecting the fixed end portions of the two flow tubes of the flow tube fixing member One end is fixed, and the other end is fixed to the mounting position of the driving means at the center of the straight pipe portion on the driving side of each of the two flow tubes, just below the flow tube fixing member, and the flow tube is fixed. The member and the straight pipe portion on the driving side of each of the two flow tubes are connected and fixed, and formed so that the rigidity in the X-axis direction is lower than the rigidity in the Y-axis and Z-axis directions . Above A vibration direction restricting means for restricting vibration of the two flow tubes is provided so as not to vibrate each of the two flow tubes in the Y-axis direction and the Z-axis direction.

  According to the first aspect of the present invention having such characteristics, the elastic body fixed to the rigid body is connected to the flow tube. The flow tube is supported at a position other than the tube fixing end by the presence of the elastic body. When the flow tube is driven by the driving unit, the flow tube vibrates while vibrations other than the driving direction are restricted by the rigidity characteristics of the elastic body. In the present invention, the rigid body and the elastic body fixed to the rigid body correspond to the vibration direction regulating means. A highly sensitive Coriolis flowmeter suitable for measuring an extremely small flow rate is provided by having a vibration tube having a vibration direction regulating means and a tube structure with low rigidity.

  According to the present invention, it is possible to prevent the occurrence of vibration in a direction that should not be driven originally, prevent deterioration of instrumental error, and stabilize the zero point. Therefore, there is an effect that it is possible to provide a highly sensitive Coriolis flowmeter suitable for measuring an extremely small flow rate.

  Hereinafter, description will be given with reference to the drawings. FIG. 1 is a perspective view showing an embodiment of a Coriolis flowmeter having vibration direction regulating means of the present invention. FIG. 2 is an enlarged view of the main part of FIG.

  In FIG. 1, a Coriolis flow meter 11 (hereinafter simply abbreviated as Coriolis flow meter 11) having a vibration direction regulating means of the present invention includes a housing 12 and flow tubes 13 and 13 accommodated in the housing 12. And a driving means 14 for driving the flow tubes 13, 13; phase difference detecting means 15, 15 for detecting a phase difference proportional to the Coriolis force; a temperature sensor (not shown); A signal calculation processing unit (not shown) to perform and an excitation circuit unit (not shown) for exciting the driving means 14 are configured.

  Further, the Coriolis flow meter 11 of the present invention functions as leaf springs 16 and 16 (corresponding to elastic bodies described in the claims) functioning as vibration direction restricting means, and also functions as vibration direction restricting means and the flow tube 13. , 13 and a flow tube fixing member 17 (corresponding to a rigid body described in claims) as a fixing member.

  Hereinafter, each component will be described with reference to FIGS. 1 and 2 (in the description, the driving direction of the driving means 14 (corresponding to the vibration direction of the flow tubes 13 and 13) is the X axis, and the flow tubes 13 and 13). The tube axis direction at the anti-vibration position (in the figure, which corresponds to the driven position) is defined as the Y axis, and the X axis and the direction perpendicular to the Y axis are defined as the Z axis (each direction is as shown in the figure).

  The housing 12 has a structure that is strong against bending and twisting. The housing 12 is formed in a size that can accommodate the flow tubes 13 and 13 fixed to the flow tube fixing member 17. Furthermore, the housing | casing 12 is formed so that the flowmeter main body which consists of the flow tubes 13, 13 grade | etc., Can be protected from the outside. The inside of the housing 12 is filled with an inert gas such as argon gas. Condensation on the flow tubes 13, 13 and the like is prevented by filling with the inert gas.

  The said flow tubes 13 and 13 are formed using materials usual in this technical field, such as stainless steel, hastelloy, a titanium alloy, and metallic glass. The flow tubes 13 and 13 are thin and thin tubes in this embodiment, and are formed in a substantially oval shape that is long in the Y-axis direction (the width in the Y-axis direction is sufficiently larger than the height in the Z-axis direction). Although not particularly limited, the ratio of the length (width) in the Y-axis direction to the length (height) in the Z-axis direction is 8.5 in this embodiment. : 1). The flow tubes 13 and 13 are arranged so as to be arranged at a predetermined interval. The fixed ends of the flow tubes 13 and 13 are fixed to the flow tube fixing member 17.

  Here, each part of the flow tubes 13 and 13 of this form is demonstrated. The flow tubes 13, 13 are parallel to the straight tube portions 18, 18 on the drive side whose tube axis extends straight along the Y-axis direction, and to the flow tube fixing member 17 parallel to the straight tube portions 18, 18 on the drive side. Fixed-side straight pipe portions 19, 19 to be fixed, driving-side straight pipe portions 18, 18 and semi-circular inflow-side curved pipe portions 20, 20 connecting the fixed-side straight pipe portions 19, 19 and outflow It has side curved tube portions 21, 21. The fixed ends of the flow tubes 13, 13 communicate with the inflow side manifold 22 and the outflow side manifold 23 inside the flow tube fixing member 17. The arrows in the figure indicate the flow direction of the fluid to be measured (not shown).

  The shape of the flow tubes 13 and 13 is an example (for example, the shape disclosed in Japanese Patent Application Laid-Open No. 2005-221251 in which one tube is curved is possible). It is not limited. Further, the flow tube facing the inside of the flow tube fixing member 17 is an upstream measurement tube portion and a downstream measurement tube portion, and a flow channel connecting the terminal end and the start end of each tube is included, and one flow tube It may be a so-called dual loop type form equivalent to a state in which is looped.

  The driving means 14 is for causing the straight tubes 18 and 18 on the driving side of the flow tubes 13 and 13 to vibrate oppositely, and includes a coil 24 and a magnet 25. The driving means 14 is arranged at the center of the straight pipe portions 18 on the driving side and sandwiched between them. The drive means 14 is attached at a position where it is not offset as much as possible with respect to the vibration direction (drive direction) of the flow tubes 13 and 13.

  When an attracting action is generated in the driving means 14, the magnet 25 is inserted into the coil 24. As a result, the straight pipe portions 18 and 18 on the driving side of the flow tubes 13 and 13 are brought close to each other. It has become. On the other hand, when a repulsive action occurs, the straight pipe portions 18 on the driving side are separated from each other. Since the flow tubes 13 and 13 are fixed to the flow tube fixing member 17 as described above, the driving means 14 is connected to the flow tube 13 and 13 in the rotational direction around the flow tube fixing member 17. It is comprised so that it may drive.

  The phase difference detection means 15 and 15 are sensors for detecting the vibration of the flow tubes 13 and 13 and detecting the phase difference proportional to the Coriolis force acting on the flow tubes 13 and 13, respectively. 26 and a magnet 27 (not limited to this, means for detecting any one of displacement, speed, acceleration, such as an acceleration sensor, optical means, capacitance type, distortion type (piezo type)) As long as it is.) The phase difference detection means 15, 15 is, for example, a position within a range between the inflow side bending tube portions 20, 20 and the outflow side bending tube portions 21, 21 of the flow tubes 13, 13 and a phase difference proportional to the Coriolis force. It is arranged at a position where it can be detected.

  The temperature sensor (not shown) is for compensating the temperature of the Coriolis flow meter 11, and is fixed in the vicinity of the fixed end of one flow tube 13 by appropriate means. Wiring drawn from a temperature sensor (not shown), the coil 26 of the phase difference detector 15, and the coil 24 of the driving means 14 is connected to a substrate (not shown) housed inside the housing 12. A wire harness (not shown) is connected to the substrate. The wire harness is drawn out of the housing 12.

  The signal calculation processing unit (not shown) receives detection signals related to the deformation of the flow tubes 13 and 13 from the phase difference detectors 15 and 15 and detection signals related to the temperature of the flow tube 13 from the temperature sensor, respectively. Wiring and connection are made as described above. The signal calculation processing unit is configured to calculate mass flow rate and density based on each input detection signal. The signal calculation processing unit is configured to output the mass flow rate and density obtained by the calculation to a display (not shown).

  The leaf springs 16 and 16 are elastic bodies that function as vibration direction regulating means, and are formed in a strip shape as shown in the figure (for example, the reference numerals as shown in FIG. The shape may be 16 'or 16 ". The shape is not particularly limited as long as it can have the rigidity characteristics described below. The leaf springs 16 and 16 have an X greater than the rigidity in the Y-axis and Z-axis directions. It is formed so as to have low axial rigidity.

  The plate springs 16 and 16 are formed of a plate material suitable as a plate spring material such as stainless steel. One ends of the leaf springs 16 and 16 are fixed to the center of the straight pipe portions 18 and 18 on the driving side of the flow tubes 13 and 13 (fixed on the opposite side of the driving means 14. It may be fixed in this vicinity). The other ends of the leaf springs 16 and 16 are fixed to the flow tube fixing member 17. As a method for fixing the leaf springs 16 and 16, for example, brazing is used. A special small bracket may be used, or the end may be processed so as to be easily fixed.

  The leaf springs 16 and 16 support the flow tubes 13 and 13 at positions other than the fixed ends of the flow tubes 13 and 13. The leaf springs 16 and 16 are also configured to regulate vibrations other than the driving direction of the driving means 14 by this rigidity characteristic. The leaf springs 16 and 16 are useful members for preventing the flow tubes 13 and 13 from vibrating in the Y-axis direction and the Z-axis direction.

  In the above configuration, when the fluid to be measured is caused to flow through the flow tubes 13 and 13 and the driving means 14 is driven to vibrate the flow tubes 13 and 13, the Coriolis force at the positions of the phase difference detectors 15 and 15 is generated. A mass flow rate is calculated by the signal calculation processing unit based on the generated phase difference. In this embodiment, the density is also calculated from the vibration frequency. During the driving of the driving means 14, since the vibrations in the direction that should not be driven are prevented by the action of the leaf springs 16 and 16, the calculated mass flow rate and density are output as reliable data. .

  Next, another example of a rigid body and an elastic body functioning as vibration direction regulating means will be described with reference to FIG. FIG. 4 is a perspective view showing another example of a rigid body and an elastic body. Note that the same reference numerals are given to the same components as those in the above-described embodiment, and the description thereof will be omitted.

  In FIG. 4, a pedestal 28 is integrally provided on the flow tube fixing member 17 that functions as a vibration direction regulating means and is a member for fixing to the flow tubes 13 and 13. Also, leaf springs 16 and 16 that function as vibration direction regulating means are fixed between the flow tube fixing member 17 and the antinodes (driven positions) of the flow tubes 13 and 13. The pedestal 28 is a rigid body that functions as vibration direction regulating means, and is formed in a U-shape here. Specifically, it extends in the Z-axis direction between the flow tubes 13 and 13, and one end is continuous with the flow tube fixing member 17, and the leg portions 29 and 29 are continuous with the other ends of the leg portions 29 and 29. And a connecting portion 30 in the Y-axis direction.

  The leg portions 29 and 29 are formed to have a length approximately twice that of the leaf springs 16 and 16. The connecting portion 30 has a pair of convex portions whose side intermediate portions protrude in the X-axis direction. Leaf springs 31 and 31 are fixed between the pair of convex portions and the antinodes (driven positions) of the flow tubes 13 and 13. The leaf springs 31 and 31 are elastic bodies that function as vibration direction regulating means, and are formed and fixed in the same manner as the leaf springs 16 and 16.

  In the above configuration, when the flow tubes 13 and 13 are driven by the driving means 14, the flow tubes 13 and 13 are driven in directions other than the driving direction (X-axis direction) depending on the rigidity characteristics of the leaf springs 16 and 16 and the leaf springs 31 and 31. Vibrates while the vibration is regulated. Therefore, the generation of vibrations in the direction that should not be driven is prevented.

  5 to 7 show other examples of a rigid body and an elastic body that function as vibration direction regulating means. In the figure, reference numeral 41 indicates a flow tube. Reference numeral 42 indicates a rigid body. Further, reference numeral 43 indicates an elastic body. In addition, the broken line in a figure has shown that the rigid body and the elastic body may exist in this part. By applying the vibration direction regulating means shown in FIGS. 5 to 7, the same effects as described above are obtained.

  In addition, it goes without saying that the present invention can be variously modified without departing from the spirit of the present invention.

It is a perspective view which shows one Embodiment of the Coriolis flowmeter which has a vibration direction control means of this invention. It is a principal part enlarged view of FIG. It is a perspective view which shows the other example of a leaf | plate spring. It is a perspective view which shows the other example of the rigid body and elastic body which function as a vibration direction control means. It is a schematic diagram which shows the other example of the rigid body and elastic body which function as a vibration direction control means. It is a schematic diagram which shows the other example of the rigid body and elastic body which function as a vibration direction control means. It is a schematic diagram which shows the other example of the rigid body and elastic body which function as a vibration direction control means. It is a perspective view which shows the elliptical flow tube of a prior art example.

Explanation of symbols

11. Coriolis flowmeter with vibration direction regulating means (Coriolis flowmeter)
12 ......... Case 13 ......... Flow tube 14 ......... Drive means 15 ......... Phase difference detection means 16 ............... Plate spring (elastic body)
17 ……………… Flow tube fixing member (rigid body)
18 ............ Straight pipe portion 19 on the drive side ............ Straight pipe portion 20 on the fixed side ............ Inflow side curved tube portion 21 ............ Outflow side curved tube portion 22 ............ ... Inlet side manifold 23 ......... Outlet side manifolds 24 and 26 ... Coils 25 and 27 ... Magnet 28 ......... Pedestal (rigid body)
29 .......... Leg 30 .......... Connecting part 31 ........... Plain spring (elastic body)
41 ……………… Flow tube 42 ……………… Rigid body 43 ……………… Elastic body

Claims (1)

A flow comprising at least one , comprising a housing, a flow tube accommodated in the housing, a driving means for driving the flow tube, and a phase difference detection means for detecting a phase difference proportional to the Coriolis force The mass flow rate and / or density of the fluid to be measured flowing in the flow tube is detected by driving the tube and detecting a phase difference and / or vibration frequency proportional to the Coriolis force acting on the flow tube. In the Coriolis flow meter,
When the vibration direction of the flow tube is defined as the X axis, the tube axis direction at the antinode position of the flow tube vibration is defined as the Y axis, and the direction perpendicular to the X axis and the Y axis is defined as the Z axis,
The housing is
It has a structure that is strong against bending and twisting, and is sized to accommodate the flow tube fixed to the flow tube fixing member, protecting the flow meter body from the outside, and an inert gas inside And configured to prevent condensation on the flow tube ,
The flow tube is
A thin tube and a straight tube portion on the drive side where the tube axis extends straight along the Y-axis direction, and a fixed tube formed in parallel with the straight tube portion on the drive side and separated at the approximate center in the tube axis direction. possess a straight pipe portion of the side, and a straight portion and inlet-side curved pipe portion and the outlet-side curved pipe portion of the semicircular connecting straight portion of the fixed side of the drive side, the Y-axis direction length The ratio of the length (width) to the length (height) in the Z-axis direction is formed into a substantially oval shape long in the Y-axis direction of 8.5: 1, and two are arranged side by side at a predetermined interval. Housed and configured in the housing ,
The flow tube fixing member is
And a manifold inlet side manifold and the outlet side of the fluid to be measured flows, and fixed to each of the fixed end of the two flow tubes, which are separated by the tube axis direction approximate center of said flow tube, said 2 to function as each of the fixed end is fixed, the vibration direction regulating means which does not vibrate in the Y-axis and Z-axis directions of the two flow tubes, which are separated in each tube axis direction approximate center of the flowtube Is composed of
The driving means includes
Be of to oppose vibrations straight pipe portion of the drive side of the flow tube, constituted by a coil and a magnet, wherein the flow tube fixing member of the central straight part of the driving side of the two flow tubes Is placed between the two flow tubes so as to be sandwiched between the straight tube portions on the drive side, and attached to a position not offset with respect to the vibration direction (drive direction) of the flow tubes. When the action occurs, the magnet is inserted into the coil and the straight tube portions on the driving side of the flow tube come close to each other. The straight tube portions are separated from each other, and the flow tube is driven alternately in the rotation direction around the flow tube fixing member. And it will be,
The phase difference detecting means includes
It detects the vibration of the flow tube, a sensor for detecting a phase difference proportional to a Coriolis force acting on the flow tube, constituted by a coil and a magnet, each of the inflow of the two flow tubes Provided at a position where the phase difference proportional to the Coriolis force can be detected at a position within the range sandwiched between the side curved tube portions and between the respective outflow side curved tube portions of the two flow tubes, detects the vibrations of the two flow tubes, will be configured to detect a phase difference proportional to a Coriolis force acting on the two flow tubes,
A plate spring or two strips formed by disposing two strip-shaped stainless steel plates disposed at both ends of the flow tube fixing member at intervals in a direction perpendicular to the longitudinal direction of the flow tube. A plate spring formed by forming a single X plate by crossing the plate-shaped stainless steel plate material on an axis connecting the fixed end portions of the two flow tubes of the flow tube fixing member One end is fixed, and the other end is fixed to the mounting position of the driving means at the center of the straight pipe portion on the driving side of each of the two flow tubes, just below the flow tube fixing member, and the flow tube is fixed. The member and the straight pipe portion on the driving side of each of the two flow tubes are connected and fixed, and formed so that the rigidity in the X-axis direction is lower than the rigidity in the Y-axis and Z-axis directions . Above Coriolis having a vibration direction restricting means provided with a vibration direction restricting means for restricting vibration of the two flow tubes so as not to vibrate each of the two flow tubes in the Y-axis direction and the Z-axis direction. Flowmeter.

Images