JP2014041152A - Method and apparatus for force balancing of coriolis flowmeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coriolis flowmeter which prevents vibrations caused by an unbalanced center of mass of a drive mechanism.SOLUTION: The coriolis flowmeter comprises: at least one flow conduit 103; a drive mechanism coupled to the at least one flow conduit; and a balance mechanism 501 coupled to the at least one flow conduit. The balance mechanism 501 is sized and located such that the momentum of the balance mechanism 501 perpendicular to a drive motion and the momentum of the drive mechanism have equal magnitude and opposite directions.

Description

  The present invention relates to balancing the force of a Coriolis flow meter.

  A sensor that vibrates a flow tube, such as a Coriolis mass flow meter, generally passes a substance into the vibrating flow tube and detects the movement of the flow tube as a sensor. It functions. By processing the signal sent from the motion transducer attached to the flow tube, it is possible to measure various properties, such as mass flow rate and density, of the material flowing in the flow tube. The vibration system consisting of a flow tube and the substance flowing through it can generally measure the mass and rigidity of the entire vibration system consisting of the flow tube and the substance. This is because it is affected by the attenuation characteristic.

  The Coriolis mass flow meter includes one or more flow tubes. Its typical use is to incorporate a Coriolis mass flow meter flow tube into a pipeline or other transport system, and for example, a substance such as a fluid or slurry transported by the transport system is connected to the Coriolis mass flow meter flow tube. It is to make it flow through. Each flow tube of the Coriolis mass flowmeter has a plurality of vibration modes as its natural vibration modes. These vibration modes include vibration modes such as simple bending vibration, simple twist vibration, and simple torsion vibration. There is also a composite vibration mode in which these vibration modes are combined. A typical measurement method in the case of performing measurement using a Coriolis mass flowmeter is to excite a flow tube in a state where a substance is flowing to vibrate in one or a plurality of vibration modes, and then the flow tube at that time. Is measured at a plurality of measurement points spaced in the longitudinal direction of the flow tube. As a means for exciting the flow tube, an actuator composed of an electromechanical device or the like is generally used, and as a specific example, a voice coil type driving mechanism or the like is used. This excitation causes periodic perturbations in the flow tube, and measures the time delay or phase difference that exists during the flow tube motion detected at each of the transducer mounting points. The flow rate can be obtained.

  This time delay is very small, and it is not uncommon for the time delay to be measured in nanoseconds. Therefore, the output of the transducer is required to be very accurate. The accuracy of the transducer is lost when the structure of the Coriolis mass flowmeter has non-linearity or asymmetry, and is also lost by movement caused by an external force. For example, if there is an unbalanced component among the components of a Coriolis mass flow meter, this causes vibration at the drive vibration frequency of the Coriolis mass flow meter in the case or flange of the Coriolis mass flow meter. And the Coriolis mass flow meter may vibrate the pipeline at its drive vibration frequency. When such vibration occurs, perturbation occurs in the signal representing the time delay, and the magnitude of the generated perturbation depends on the rigidity of the mounting structure. However, the rigidity of the mounting structure cannot be accurately grasped in most cases, is affected by aging, and may change depending on the temperature. It is not possible to wipe out the effects of the components, and the presence of unbalanced components can have a significant adverse effect on the performance of the Coriolis mass flow meter. The adverse effects of vibrations due to unbalance and the adverse effects of changes in the rigidity of the mounting structure are inconvenient using signal processing technology after the Coriolis flowmeter structure itself is balanced. It can be reduced by compensating for the influence of various motion components.

In the above description, it can be said that only one direction of vibration, that is, vibration in the Z direction can be said to be balanced. Here, the Z direction is a direction in which the flow tube is vibrated and displaced. In other directions, that is, the X direction, which is the pipeline extending direction, and the Y direction, which is a direction perpendicular to both the Z direction and the X direction, vibrations are not balanced. The reason why this reference coordinate system is important is that, in the Coriolis flowmeter, a secondary force that changes in a sine wave shape acting in the Y direction is generated. Because of this secondary force in the Y direction, the Coriolis flowmeter generates unbalanced Y-direction vibrations that cause errors in the Coriolis flowmeters.

  One cause of the generation of this secondary force is the position of the center of mass of the assembly that is a component of the drive mechanism of the Coriolis flowmeter. A typical drive mechanism includes a magnet assembly attached to one flow tube and a coil assembly attached to the other flow tube. The mass center of the magnet assembly of the drive mechanism is not located on the XY plane including the center line of the flow tube to which the magnet assembly is attached, and the mass of the coil assembly of the drive mechanism is also determined. Because the center is not located on the XY plane that includes the centerline of the flow tube to which the coil assembly is attached, vibration in the Y direction occurs. In order to avoid collision between the flow tubes, a certain amount of space is secured between the XY plane including the center line of one flow tube and the XY plane including the center line of the other flow tube. It is necessary to keep. In addition, the mass center of the magnet assembly and / or coil assembly must be offset from the XY plane that includes the centerline of the flow tube to which they are attached, which is necessary. This is because the position of the coil must be concentric with the tip of the magnet, that is, the optimum position in the magnetic field.

  When a flow tube is driven to vibrate, the flow tube does not move exactly in parallel movement, but undergoes bending deformation at the fixed part of the flow tube, thereby causing periodic bending vibration. . This bending motion can be approximated by rotational vibration with the fixed portion of the flow tube as the center of rotation. When approximated as such, the vibration of the flow tube can be regarded as a rotational vibration having a rotation center CR and periodically moving in a small angle range. The angular amplitude of the rotational vibration is determined by the target value of the vibration amplitude in the Z direction and the distance d from the rotational center of the rotational vibration to the center of the flow tube at the mounting position of the drive mechanism. Therefore, the angular amplitude Δθ of this rotational vibration is given by the following equation (1).

  Since the center of mass of the drive mechanism component (magnet assembly or coil assembly) is offset with respect to the center line of the flow tube, the vibration at the center of mass of the drive mechanism component has a vibration component in the Y direction. include. The center of mass of the drive mechanism component is usually offset from the centerline of the flowtube in the Z direction by a distance corresponding at least to the radius of the flowtube. The offset angle φ representing the offset from the center line of the flow tube as an angle has a size that cannot be ignored. The center of mass of the drive mechanism component vibrates with the offset position as a neutral point and the same angular amplitude Δθ as the flow tube. If the motion of the center of mass of the drive mechanism component accompanying this vibration is approximated by a motion perpendicular to the straight line connecting the center of mass and the rotation center CR, the motion of the mass center of the drive mechanism component in the Y direction The component ΔYm is given by the following equation (2).

  Thus, since the movement of the center of mass of the drive mechanism component includes the Y-direction motion component, the entire Coriolis flowmeter vibrates in the Y direction. Here, assuming that the Coriolis flowmeter is supported in a freely movable state, from the law of conservation of momentum, the amplitude of the vibration in the Y direction of the entire Coriolis flowmeter is the vibration of the drive mechanism in the Y direction. The amplitude is multiplied by the mass ratio which is the quotient obtained by dividing the mass of the drive mechanism by the mass of the Coriolis flowmeter. Therefore, the entire Coriolis flowmeter vibrates in the Y direction, which means that the flow tube is vibrated in the Z direction and the mass center of the drive mechanism component is offset in the angular direction. It is a result that will inevitably result from. Thus, since the vibration of the flow tube and the unfavorable Y-direction vibration of the entire Coriolis flow meter are related to each other, when attempting to attenuate the Y-direction vibration of the Coriolis flow meter, Z of the flow tube Even vibrations in the direction are attenuated. Further, if the rigidity of the Coriolis flow meter mounting structure is increased, the vibration frequency of the flow tube is increased, and if the rigidity is decreased, the vibration frequency of the flow tube is decreased. The fact that the vibration frequency of the flow tube fluctuates by changing the rigidity of the mounting structure has been actually observed in an experiment conducted on a Coriolis flowmeter that vibrates with a large amplitude in the Y direction. This is a problem because the vibration frequency of the flow tube is used as basic data for determining the density of the fluid, and the vibration frequency also indicates the rigidity of the flow tube. It is. If the stiffness of the mounting structure is changed, it will change the stiffness of the flow tube and, as a result, the Coriolis flow meter calibration factor. Furthermore, since the vibration generated by the drive mechanism is closely related to the surrounding environment of the Coriolis flow meter, the zero point of the Coriolis flow meter (flow signal value when there is no flow) becomes unstable. .

  The present invention intends to solve the above problems caused by unbalanced vibration forces using a balance mechanism whose size and mounting position are selected so as to cancel the influence of the drive mechanism. .

  Among the specific configuration examples of the balance mechanism, there is one in which the balance mechanism is composed of a Y-direction balance mass attached to the flow tube, and this Y-direction balance mass is the configuration of the flow tube drive mechanism. Installed on the side opposite the part. And the size and mounting position of this Y-direction balance mass so that the combined mass center of the mass of the drive mechanism component and this Y-direction balance mass is located on the XY plane including the center line of the flow tube Is selected.

  In addition, among specific configuration examples of the balancing mechanism, there is a configuration in which a balancing mechanism called a dynamic Y-direction balancing mechanism can be configured on the flow tube. This dynamic Y-direction balance mechanism is configured by connecting a balance mass to one end of a leaf spring and connecting the other end of the leaf spring to a location close to the drive mechanism of the flow tube. This dynamic Y-direction balancing mechanism is based on the position of the center of mass of the magnet, the position of the center of mass of the coil, and the structure of the Coriolis flow meter (single tube or double tube). Or may be configured on two flow tubes.

  The dynamic Y-direction balancing mechanism functions by vibrating the dynamic Y-direction balancing mass in the Y direction using the Z-direction motion of the flow tube. In designing, the momentum in the Y direction of the dynamic Y-direction balancing mass and the momentum in the Y direction of the drive mechanism components cancel each other, so that the case of the Coriolis flowmeter and the Coriolis flow rate are set. It can prevent that the member of the surrounding environment of a meter vibrates. Further, based on the same principle as this, it is possible to prevent the vibration of the member in the surrounding environment and the vibration damping action by the member in the surrounding environment from affecting the Coriolis flowmeter.

As one aspect of the present invention, there is a Coriolis flow meter.
At least one flow tube;
A drive mechanism attached to the at least one flow tube;
A balancing mechanism attached to the at least one flow tube,
The size and mounting position of the balance mechanism are selected so that the momentum in the direction orthogonal to the drive motion of the balance mechanism and the momentum of the drive mechanism are equal in size and opposite to each other. Yes,
This is a Coriolis flowmeter characterized by the above.

  It is preferable that the balance mechanism is composed of a balance mass.

  The combined mass center of the drive mechanism and the balance mechanism is located in the vicinity of the plane including the center line of the at least one flow tube, and the plane including the center line is orthogonal to the drive motion. It is preferable to select the size and mounting position of the balance mechanism.

  The balancing mechanism preferably comprises a balancing mass attached to the at least one flow tube via a leaf spring.

  It is preferable to select the rigidity of the leaf spring and the size of the balance mass so that the natural vibration frequency of the balance mechanism is lower than the drive vibration frequency of the Coriolis flowmeter.

  It is preferable that the balance mechanism vibrate with a phase different from that of the at least one flow tube.

  The balancing mechanism is attached to a side surface of the at least one flow tube opposite to the drive mechanism, and is about 45 ° with respect to a plane including a center line of the at least one flow tube. It is preferable to extend at an angle.

  It is preferable that the balance mechanism is attached to a side surface of the at least one flow tube opposite to the drive mechanism.

Another aspect of the present invention is a method of balancing the force of a Coriolis flow meter with at least one flow tube,
Attaching a drive mechanism to the at least one flow tube;
Attaching a balancing mechanism to the at least one flow tube;
Selecting the mounting position and size of the balancing mechanism such that the momentum of the balancing mechanism and the momentum of the driving mechanism are equal in magnitude and opposite to each other;
It is the method characterized by including.

  Preferably, the method includes the step of configuring the balancing mechanism with a balancing mass.

  In the method, the combined mass center of the driving mechanism and the balancing mechanism is located in the vicinity of the plane including the center line of the at least one flow tube, and the plane including the center line is orthogonal to the driving motion. Thus, it is preferable to include a step of selecting the mounting position and size of the balancing mechanism.

  Preferably, the step of attaching the balancing mechanism to the at least one flow tube comprises the step of attaching a balancing mass to the at least one flow tube via a leaf spring.

Preferably, the method includes a step of selecting a rigidity of the leaf spring and a size of the balance mass so that a natural vibration frequency of the balance mechanism is lower than a drive vibration frequency of the Coriolis flowmeter. .

  Preferably, the method includes oscillating the balancing mechanism in a phase different from that of the at least one flow tube.

The step of attaching a balancing mechanism to the at least one flow tube;
Attaching the balancing mechanism to a side of the at least one flow tube opposite to the drive mechanism;
Extending the balancing mechanism at an angle of about 45 ° relative to a plane including a centerline of the at least one flow tube;
It is preferable to consist of.

  Preferably, the method includes the step of attaching the balancing mechanism to a side surface of the at least one flow tube opposite to the drive mechanism.

It is the figure which showed the Coriolis flowmeter. It is the figure which showed the drive mechanism of the Coriolis flowmeter. It is the figure which showed the X-axis cross section of the flow tube of a Coriolis flowmeter. It is the figure which showed the balance mechanism in 1st Example of this invention. It is the figure which showed the balance mechanism in 2nd Example of this invention.

  1-5 and the following description illustrate specific embodiments of the invention to teach those skilled in the art how to make and use the best mode for carrying out the invention. It is for the purpose. Therefore, since the present invention is intended to teach the principle of the present invention, among the specific configurations of the present invention, the existing configurations may be simply shown or not shown at all. May be omitted. However, it is natural for those skilled in the art to come up with various modifications of the embodiments shown below that can be included in the scope of the present invention. Those skilled in the art should also understand that many variations of the present invention can be constructed by various combinations of the many features described below. Therefore, the present invention is not limited to the specific embodiments described below, but is limited to those described in the claims and equivalents thereof. It is.

  FIG. 1 is a view showing a Coriolis flow meter 5, and the Coriolis flow meter 5 includes a flow meter assembly 10 and a flow meter electronic circuit unit 20. The flow meter electronics 20 is connected to the flow meter assembly 10 via a lead 100, and includes a density, mass flow, volume flow, cumulative mass flow, temperature, etc. via a signal path 26. It is configured to send various information. As will be readily understood by those skilled in the art, the present invention can be applied to various types of Coriolis flowmeters, in particular, the number of drive mechanisms provided in the Coriolis flowmeters, There are no restrictions on the number, the number of flow tubes, etc., and there is no restriction on the vibration mode when the Coriolis flowmeter functions.

  The flow meter assembly 10 includes a pair of flanges 101 and 101 ', manifolds 102 and 102', drive mechanism 104, pick-off sensors 105 and 105 ', and flow tubes 103A and 103B. Drive mechanism 104 and pickoff sensors 105 and 105 'are attached to flow tubes 103A and 103B.

The flanges 101 and 101 ′ are fixed to the manifolds 102 and 102 ′, respectively. Manifolds 102 and 102 ′ are mounted at both ends of spacer 106, respectively. The spacer 106 functions to maintain an interval between the manifold 102 and the manifold 102 'and to prevent undesired vibrations in the flow tubes 103A and 103B. When the flow meter assembly 10 is incorporated into a pipeline system (not shown) in which the substance to be measured flows, the material flowing through the pipeline system passes through the flange 101 and flows into the flow meter assembly 10. Flows in. The entire amount of the inflowing substance passes through the inflow side manifold 102, and from the inflow side manifold 102, into the flow pipe 103A and the flow pipe 10
It flows separately into 3B. Both the material that has passed through the flow tube 103A and the material that has passed through the flow tube 103B flow into the outflow manifold 102 ′ and out through the flange 101 ′ from the outflow manifold 102 ′. Exit from the flow meter assembly 10.

  The flow tubes 103A and 103B have the mass distribution, moment of inertia, and elastic modulus of the flow tube 103A when the flow tube 103A is bent and deformed about the bending axis WW, and the flow tube 103B is bent about the bending axis W ′. The mass distribution, the moment of inertia, and the elastic modulus of the flow tube 103B at the time of bending deformation about −W ′ are appropriately designed so as to be substantially equal to each other, and the inflow side manifold 102 and the outflow side manifold 102 are 'Properly installed. Also, the flow tubes 103A and 103B extend from the manifolds 102 and 102 'so as to extend substantially parallel to each other.

  The flow tubes 103A and 103B are driven in opposite directions by the drive mechanism 104, whereby the flow tube 103A vibrates so as to bend and deform around the bending axis W-W, and the flow tube 103B has the bending axis W. It vibrates so as to bend and deform around “−W”. This vibration mode is referred to as a primary bending vibration mode of the Coriolis flow meter. Various drive mechanisms are known, and the drive mechanism 104 may be selected from the known drive mechanisms. As a specific example, for example, the drive mechanism 104 may be configured by a magnet attached to the flow tube 103A and a coil attached to the flow tube 103B so as to face the magnet. According to this structure, both flow tubes can be vibrated by supplying an alternating current to the coil opposed to the magnet. Further, an appropriate drive signal for this purpose may be supplied from the flowmeter electronic circuit unit 20 to the drive mechanism 104 via the lead wire 110. The above explanation regarding FIG. 1 is an explanation for showing a specific example of the operation of the Coriolis flowmeter, and the teaching of the present invention is not limited to the above explanation.

  The flow meter electronic circuit unit 20 is configured to transmit the sensor signal via the lead wires 111 and 111 ′. Further, the flowmeter electronic circuit unit 20 is configured such that a drive signal for vibrating the flow tubes 103A and 103B is supplied to the drive mechanism 104 via the lead wire 110. Further, the flowmeter electronic circuit unit 20 performs signal processing on the left speed signal sent from the pickoff sensor 105 and the right speed signal sent from the pickoff sensor 105 ′ so as to calculate the mass flow rate. It is configured. The signal path 26 functions as an input / output means for an interface between the flowmeter electronic circuit unit 20 and the operator.

  FIG. 2 is a diagram showing a drive mechanism 104 used in the Coriolis flow meter 5 according to the preferred embodiment. In this preferred embodiment, the drive mechanism 104 comprises a coil assembly and a magnet assembly. However, as will be readily understood by those skilled in the art, it is possible to use a drive mechanism having a configuration different from that shown in the figure.

  The drive mechanism 104 includes a magnet assembly 210 and a coil assembly 220. The pair of bracket portions 211 of the magnet assembly 210 and the pair of bracket portions 211 of the coil assembly 220 extend toward opposite sides, that is, outward. Each pair of bracket portions 211 is a pair of protruding pieces extending outward from the flat base member, and these protruding pieces are curved edges 290 into which the outer peripheral surfaces of the flow tubes 103A to 103B are fitted. Is formed on the lower side. The drive mechanism 104 is attached to the Coriolis flow meter 5 by joining the bent edge portions 290 of the bracket portions 211 to the outer peripheral surfaces of the flow tubes 103A to 103B using an appropriate joining means such as welding.

  The magnet assembly 210 includes a yoke 202 that guides magnetic flux as a base member. The pair of bracket portions 211 described above extends from the first side surface of the yoke 202. In addition, a pair of wall portions 213 and 214 extend outward from both side ends of the second side surface of the yoke 202. The wall portions 213 and 214 regulate the direction of the magnetic field of the magnet 203 so that the direction of the magnetic field is perpendicular to the extending direction of the winding of the coil 204.

  The magnet 203 is a substantially cylindrical permanent magnet having a first end and a second end. The magnet 203 is fitted in a magnet sleeve (not shown). Further, the magnet sleeve fitted with the magnet 203 is fixed to the second side surface of the yoke 202, whereby the magnet 203 is fixed to the magnet assembly 210. A magnetic pole piece (not shown) is usually attached to the second end of the magnet 203, and this magnetic pole piece (not shown) is a cap-shaped member that is fitted to the second end of the magnet 203, The direction of the magnetic field is guided into the coil 204.

  The coil assembly 220 includes a coil 204 and a coil bobbin 205. The coil bobbin 205 is attached to the bracket 211. The coil bobbin 205 includes a spool protruding from the first surface, and the coil 204 is wound around the spool. The coil 204 is attached to the coil bobbin 205 so as to face the magnet 203. A lead wire 110 is connected to the coil 204, and an alternating current is supplied to the coil 204 via the lead wire 110. Then, when an alternating current is supplied, the coil 204 and the magnet 203 are attracted to each other and rejected, so that the flow tube 103A and the flow tube 103B vibrate in opposite directions.

  FIG. 3 is a schematic diagram showing an X-axis cross section of the flow tube 103. A driving mechanism 104 is attached to the flow tube 103. The drive mechanism 104 is attached to the flow tube 103 with an offset, and the offset angle is represented by φ. The flow tube 103 vibrates in the Z direction, and the vibration amplitude is represented by ΔZ. When the flow tube 103 moves parallel to the Z direction, the flow tube 103 actually rotates about the fixed portion of the flow tube 103 as a rotation center. The center of rotation is represented by CR, and the angular amplitude when it vibrates in such a rotational motion is represented by Δθ. Along with the rotational vibration of the flow tube 103, the drive mechanism 104, that is, the mass center CM of the drive mechanism 104 also rotationally vibrates, and its angular amplitude is equal to the angular amplitude of the flow tube 103. . However, since the drive mechanism component 104 is mounted with an offset angle φ with respect to the flow tube 103, the vibration of the center of mass CM of the drive mechanism component 104 is along the inclined straight line L. . Therefore, the motion of the center of mass CM of the drive mechanism component 104 includes the vertical motion component ΔYm.

FIG. 4 is a view showing a balancing mechanism 400 in the first embodiment of the present invention. The balance mechanism 400 is composed of balance weights 401 and 402 attached to the flow tubes 103A and 103B. As a method for attaching the counterweights 401 and 402, various methods including a mechanical attachment method, a brazing method, a method using an adhesive, and the like can be used. CM _b1 in the figure is the center of mass of the counterweight 401. For the counterweight 401, the synthetic mass center CC of the center of mass CM _c center of mass CM _b1 and coil assembly of the counterweight 401
M ₁ is to be positioned on an XY plane including the central line of the flow tube 103A, it is selected the size and mounting position of the counterweight 401. Further, CM _b2 in the figure is the center of mass of the counterweight 402. For the counterweight 402, so that the synthetic centroid CCM ₂ the center of mass CM _b2 and center of mass CM _m of the magnet assembly of the counterweight 402 is positioned on an XY plane including the central line of the flow tube 103B In addition, the size and mounting position of the counterweight 402 are selected. The characteristics of these counterweights are that, in each flow tube, the product obtained by multiplying the mass of the counterweight attached to the flow tube by the velocity component in the Y direction of the counterweight is attached to the flow tube. The product obtained by multiplying the mass of the drive mechanism component by the velocity component in the Y direction of the drive mechanism component is equal in size and opposite to each other. (3)

  In other words, in each flow tube, the momentum of the counterweight attached to the flow tube and the momentum of the drive mechanism assembly attached to the flow tube cancel each other. This is expressed by the following equation (4).

  FIG. 5 is a view showing a balancing mechanism 500 in the second embodiment of the present invention. The balance mechanism 500 includes balance weights 501 and 502 attached to the flow tubes 103A and 103B via leaf springs 504 and 505. The leaf spring 504 is attached to the side surface of the flow tube 103A opposite to the coil assembly 220 so as to extend at an angle of about 45 ° with respect to the XY plane. The rigidity of the leaf spring 504 and the mass of the counterweight 501 are such that the primary natural vibration frequency of the dynamic Y-direction counterweight 501 (the natural vibration frequency in a vibration mode that vibrates like a diving plate) is the same as that of the Coriolis flowmeter. It is selected to be lower than the drive vibration frequency. Thus, by making the primary natural vibration frequency of the counterweight 501 lower than the excitation vibration frequency (drive vibration frequency), the counterweight 501 comes to vibrate with a phase different from that of the flow tube 103A. That is, when the flow tube 103A moves to the left (−Z direction), the dynamic Y-direction counterweight 501 moves to the right (+ Z direction) relative to the flow tube 103A. However, since the leaf spring 504 extends at an angle of about 45 ° with respect to the XY plane, the movement direction of the counterweight 501 is restricted by the leaf spring 504 and moves to the right (+ Z direction). Sometimes it is forced to move downward (-Y direction) at the same time. This provides good results because when the flow tube 103A moves to the left, the coil assembly 220 mounted offset to the flow tube 103A is to the left (-Z direction). It is because it moves upward (+ Y direction) at the same time. Therefore, when designing, the momentum in the Y direction (mass × speed) of the dynamic Y-direction counterweight and the momentum in the Y direction of the drive mechanism components that are mounted with an offset are equal in magnitude and opposite to each other. Thus, by selecting the mass and the spring constant, external vibration in the Y direction as the entire Coriolis flow meter can be almost completely eliminated. The same design principle is applied to the flow tube 103B.

  The second embodiment further has other advantages. Since the counterweights 501 and 502 are attached to the flow tubes 103A and 103B via the leaf springs 504 and 505, they vibrate at a phase different from that of the flow tubes 103A and 103B. Therefore, only a very small mass of the total mass of the counterweight is required to be connected to the flow tubes 103A and 103B.

The operational effects of the embodiment described above are not limited to compensating for the influence of the offset of the center of mass of the drive mechanism component. For example, when the member constituting the manifold is elastically deformed by a force acting from the flow tube, the flange of the Coriolis flow meter may vibrate in the Y direction. Therefore, if the vibration of the flange and the vibration generated due to the offset of the center of mass of the drive mechanism component are in phase, increasing the mass of the counterweight causes the manifold to It is also possible to cancel the vibration generated due to the elastic deformation. On the contrary, if the flange vibration caused by the elastic deformation of the manifold is out of phase with the vibration caused by the offset of the center of mass of the drive mechanism component, What is necessary is just to reduce the mass of the weight.

Claims (16)

At least one flow tube;
A drive mechanism attached to the at least one flow tube;
A balancing mechanism attached to the at least one flow tube,
The size and mounting position of the balance mechanism are selected so that the momentum in the direction orthogonal to the drive motion of the balance mechanism and the momentum of the drive mechanism are equal in size and opposite to each other. Yes,
Coriolis flowmeter characterized by that.   2. The Coriolis flowmeter according to claim 1, wherein the balance mechanism comprises a balance mass.   The composite mass center of the drive mechanism and the balance mechanism is positioned in the vicinity of the plane including the center line of the at least one flow tube, and the plane including the center line is orthogonal to the drive motion. 2. The Coriolis flowmeter according to claim 1, wherein a size and a mounting position of the balance mechanism are selected.   2. A Coriolis flow meter according to claim 1, wherein the balance mechanism comprises a balance mass attached to the at least one flow tube via a leaf spring.   The rigidity of the leaf spring and the size of the balance mass are selected so that the natural vibration frequency of the balance mechanism is lower than the drive vibration frequency of the Coriolis flowmeter. Coriolis flow meter.   2. The Coriolis flow meter according to claim 1, wherein the balance mechanism vibrates at a phase different from that of the at least one flow tube.   The balancing mechanism is attached to a side surface of the at least one flow tube opposite to the drive mechanism, and is about 45 ° with respect to a plane including the center line of the at least one flow tube. The Coriolis flowmeter according to claim 1, wherein the Coriolis flowmeter extends at an angle of.   The Coriolis flowmeter according to claim 1, wherein the balance mechanism is attached to a side surface of the at least one flow tube opposite to the drive mechanism. In a method of balancing the force of a Coriolis flow meter with at least one flow tube,
Attaching a drive mechanism to the at least one flow tube;
Attaching a balancing mechanism to the at least one flow tube;
Selecting the mounting position and size of the balancing mechanism such that the momentum in the direction orthogonal to the driving motion of the balancing mechanism and the momentum of the driving mechanism are equal to each other and opposite to each other. When,
A method comprising the steps of:   The method of claim 9 including the step of configuring the balancing mechanism with a balancing mass.   The composite mass center of the drive mechanism and the balance mechanism is positioned in the vicinity of the plane including the center line of the at least one flow tube, and the plane including the center line is orthogonal to the drive motion. The method according to claim 9, further comprising the step of selecting a mounting position and a size of the balance mechanism.   10. The method of claim 9, wherein the step of attaching a balancing mechanism to the at least one flow tube comprises attaching a balancing mass to the at least one flow tube via a leaf spring.   The step of selecting the rigidity of the leaf spring and the size of the balance mass so that the natural vibration frequency of the balance mechanism is lower than the drive vibration frequency of the Coriolis flowmeter. The method described.   The method of claim 9, comprising oscillating the balancing mechanism in a phase different from that of the at least one flow tube. The step of attaching a balancing mechanism to the at least one flow tube;
Attaching the balancing mechanism to a side of the at least one flow tube opposite to the drive mechanism;
Extending the balancing mechanism at an angle of about 45 ° relative to a plane including the centerline of the at least one flow tube;
10. The method of claim 9, comprising:   The method of claim 9, comprising attaching the balancing mechanism to a side of the at least one flow tube opposite the drive mechanism.