JP5753527B2 - Coriolis flow meter and method of operating the same - Google Patents

Description

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

  An oscillating flow tube sensor, such as a Coriolis mass flow meter, typically operates by detecting the motion of a single or multiple oscillating flow tubes that contain material. Properties related to the material in the flow tube, such as mass flow and density, are determined by processing signals from motion transducers attached to the flow tube. The vibration mode of a vibrating, material-filled system is generally affected by the combined mass, stiffness and damping characteristics of the material flow tube and the material contained therein.

  A typical Coriolis mass flow meter includes two flow tubes that are connected in-line with a pipeline or other transport system to carry materials such as fluids, slurries, etc. within the system. Each flow tube can be considered to have a set of natural vibration modes, including, for example, simple bending, twisting, radial and coupled modes. In a typical Coriolis mass flow measurement device, two U-shaped flow tubes arranged in parallel to each other are vibrated so as to vibrate in a first different phase bending mode around an end node. The end node at the end of each tube defines the bending axis of each tube. The plane of symmetry is in the middle of the flow tube. In most common vibration modes, the flow tube motion is a periodic bend that moves toward and away from each other about a plane of symmetry. Excitation is usually performed by an actuator, for example an electromechanical device such as a voice coil type driver, that periodically pushes the flow tube in antiphase with the resonant frequency of the tube.

  As material flows through an oscillating flow tube, the flow tube motion is measured at points spaced along the flow tube by a motion transducer (commonly referred to as a pick-off transducer). Mass flow rate is determined by measuring the time delay or phase difference between movements at each pickoff transducer location. The amount of time delay measured is very small and is often measured in nanoseconds. Therefore, the output of the pickoff transducer must be very accurate.

  The accuracy of a Coriolis mass flow meter is compromised by non-linearities and asymmetries that result from the instrument structure or undesirable movements resulting from external forces. For example, a Coriolis mass flow meter with unbalanced components can cause external vibration of its case and attached pipeline at the instrument's drive frequency. When coupling occurs between the desired flow tube vibration and the unwanted external vibration of the entire instrument, the attenuation of the external vibration of the instrument attenuates the vibration of the flow tube, and the hard instrument mounting increases the frequency of the flow tube, and the soft instrument Installation will reduce the frequency of the flow tube. The change in flow tube frequency due to mounting stiffness has been experimentally observed with instruments having high external vibration amplitude. This is a problem because the frequency of the flow tube is used to determine the density of the fluid. The frequency also indicates the stiffness of the flow tube. Changes in flow tube stiffness due to mounting stiffness will change the calibration factor of the instrument. Direct coupling between the drive vibration and the local environment (due to external vibration) also results in an unstable zero signal (flow signal in the absence of flow).

  Undesirable external vibrations perturb the instrument output signal by an amount determined by the stiffness and damping of the installation. The characteristics of the installation are generally unknown and can vary with time and temperature, so the effects of unbalanced components cannot be compensated for and can significantly affect instrument performance. The effects of these unbalanced vibrations and mounting changes are reduced by using a balanced flow meter design.

  The equilibrium vibration described above is usually accompanied by only a single or Z-direction vibration. The Z direction is the direction in which the flow tube is displaced when the flow tube vibrates in antiphase. This is often referred to as the drive direction. Other directions include the X direction along the pipeline, and the Y direction perpendicular to the Z and X directions. This reference coordinate system is important and will be described repeatedly.

  In addition, there are secondary sources of undesirable vibrations in the Y direction that occur due to tube geometry. The tube geometry is usually designed so that the movement of the center of mass of the tube moves towards and away from each other around a plane of symmetry. Therefore, the momentum of vibration of the mass of the tube (and fluid) is largely canceled out. In order to avoid movement in the Y direction of the center of mass of the tube, each center of mass must lie on each plane parallel to the plane of symmetry, including the respective bending axis. These planes are called equilibrium planes. When the plane of symmetry is vertical, the center of mass must be directly above the bending axis to guarantee cancellation of this Y-direction vibration.

  There are also secondary vibration forces in the Y direction resulting from drivers, pick-off transducers and other masses attached to the vibrating portion of the flow tube. These additional vibrating components are referred to as vibrating components for simplicity. When the center of mass of the vibrating component attached to each flow tube is deviated from the equilibrium surface of the tube, a vibration force in the Y direction is generated. This is because the bending motion of the tube has a rotational component. When the driver mass deviates from the equilibrium plane in the Z direction, the rotational component of the tube motion causes a motion component in the Y direction in the driver mass. The cause of the movement in the Y direction can be understood by shifting the mass extremely. If the mass is offset from the equilibrium plane by an angle of 45 degrees (from the bending axis), the rotational component of motion will move the mass equally in the Y and Z directions as the mass vibrates. If the two vibrating tubes have masses that are shifted by the same amount, the force in the Z direction can be balanced, but the force in the Y direction cannot be balanced.

European Patent Publication No. 1 248 084 A1 provides a problem of vibration in the Y direction by attaching a counterbalance mass to the opposite side of the driver mass of the flow tube and bringing the center of the combined mass to the equilibrium surface of the flow tube. A solution to this is disclosed.

  Even when the masses are equal and arranged on the equilibrium surface of the flow tube, a secondary unbalanced vibration force is generated in the Z direction. These forces, the subject of the present invention, have a moment of inertia where the mass attached to the flow tube is not equal around the line connecting the end nodes of each tube (hereinafter referred to as the bending axis). Occurs when.

European Patent Publication No. 1 248 084 A1

  The present invention improves the balance of the Coriolis flow meter structure by designing the vibrating components such that the moment of inertia of each component is equal to the moment of inertia of the other drive components. The formula for the moment of inertia of the object is

と表され、ここに、
Ｉ＝慣性モーメント
ｍ＝質量
ｒ＝構成要素の回転軸から質量の増分δｍまでの距離
Ｍ＝構成要素の総質量
Ｒ＝構成要素の回転半径
である。

Where,
I = moment of inertia m = mass r = distance from the rotational axis of the component to the mass increment δm M = total mass of the component R = rotation radius of the component.

  The moment of inertia is greatly affected by the distance term r) which is a square term. In the Coriolis flowmeter driver, the tube does not rotate but bends, so the axis of rotation is unknown. Conveniently, the selection of the axis of rotation is not a problem as long as the geometry of the instrument is symmetrical (equal mass at equal positions). According to the parallel axis theorem, the moment of inertia about an axis is the moment of inertia about a parallel axis through the center of the mass multiplied by the square of the distance between the two axes. It is equal to the one added. If the moments of inertia about any symmetrical axis of the two drive components are set equal, the distance from each arbitrary axis to the center of mass of each drive component is equal, and if the masses are equal, the terms of the parallel axes Is offset. This means that all that is required to equalize the moments of inertia of the drive components is to place the centers of mass symmetrically and equalize the moments of inertia around the center of mass. doing.

  The driver and coil components, including the mounting element, are fabricated in a distributed fashion such that the mass of the magnet and its mounting element is equal to the mass of the coil and its mounting element. Further, the magnet and its elements and the coil and its elements are made and mounted such that the center of mass of these elements is in the balance plane of the tube when combined with the center of mass of the respective tube. The moments of inertia around their centers of mass are also made equal. Placing the two (coil and magnet) elements with equal mass and placing the center of the combined mass on the balance plane contributes to reducing unwanted vibrations in the flow meter. Equalizing the moments of inertia of the two components contributes to further reduction of unwanted vibrations.

  However, it may be difficult to set the moment of inertia of each component around the center of mass equally. In that case, an alternative method can be used. Both the mass and the moment of inertia have a strong effect on the balance of the instrument in the Z direction, so if a tube has a small moment of inertia, it can be balanced by increasing the mass of the same tube. This technique essentially uses the parallel axis theorem to balance the moment of inertia around the axis of rotation (in a virtual position).

  In summary, it can be seen that a driver embodying the present invention includes a magnet component and a coil component. Furthermore, the component embodying the magnet component and the device embodying the coil component have a mass of the driver component equal to the mass of the coil component in each flow tube, and the coil and magnet The components have their center of mass combined with their balance surfaces (with the flow tube), and the magnet and coil components are manufactured so that their moments of inertia around their centers of mass are equal. It can be seen that it is attached. When such a drive coil component is attached to the bottom of the first flow tube and a magnet component is attached to the bottom of the second flow tube, the mechanics causes the flow tube to vibrate in anti-phase and inhibits the generation of undesirable internal vibrations. Parallel structures can be provided.

  Further, according to the present invention, the pick-off transducer is designed, fabricated and attached to the flow tube in the same manner as described for the driver. That is, each pick-off transducer has a magnet component attached to the first flow tube, a coil component attached to the second flow tube, and a mechanical that does not contribute significantly to the generation of undesirable vibration forces in the flow meter. And distributed components that provide balanced elements.

Aspects of the invention include a Coriolis mass flow meter, the flow meter comprising:
A first flow tube and a second flow tube adapted to vibrate in anti-phase around a plane of symmetry;
A drive system adapted to oscillate each flow tube about a bending axis connecting nodes at both ends of each flow tube;
A first vibration component including a first vibration drive system component attached to the first flow tube;
A second vibration component including a second vibration drive system component attached to the second flow tube,
The first and second vibration drive system components include the first flow tube and the first vibration drive system component, and the moment of inertia of the first flow tube and the second vibration drive system component They have equivalent dimensions and positions so as to be substantially equal to the added moment of inertia.

  Desirably, the first and second vibration drive system components are dimensioned to have substantially equal mass.

The bending axis of the first flow tube and the combined mass center of the first flow tube plus the first vibration drive system component is on a first balance plane parallel to the symmetry plane;
The center of the combined mass of the second flow tube bend axis and the second flow tube plus the second vibration drive system component is on a second balance plane parallel to the plane of symmetry. Is desirable.

The first vibration drive system component includes a driver coil component attached to the first flow tube;
Preferably, the second vibration drive system component includes a magnet component of the driver attached to the second flow tube and coaxially aligned with the coil component.

  Preferably, the first vibration component further includes a first pick-off component, and the second vibration component includes a second pick-off component.

  Preferably, the first pick-off component is attached to the first flow tube, and the second pick-off component is attached to the second flow tube.

  Desirably, the first and second vibration drive system components are dimensioned to have substantially equal mass.

The bending axis of the first flow tube and the combined mass center of the first flow tube plus the first vibration drive system component is on a first balance plane parallel to the symmetry plane;
The center of the combined mass of the second flow tube bend axis and the second flow tube plus the second vibration drive system component is on a second balance plane parallel to the plane of symmetry. Is desirable.

Another aspect of the present invention provides:
A first flow tube and a second flow tube adapted to vibrate in anti-phase around a plane of symmetry;
A method of operating a Coriolis flow meter comprising a drive system adapted to oscillate each flow tube about a bending axis connecting nodes at each end of each flow tube, the method comprising:
Attaching a first vibration component, including a first vibration drive system component, to the first flow tube;
Attaching a second vibration component including a second vibration drive system component to the second flow tube;
The moment of inertia of the first and second vibration drive system components plus the first flow tube and the first vibration drive system component is the second flow tube and the second vibration drive system component. And an equivalent dimension so as not to be substantially equal to the moment of inertia of the sum of the above and a position at an equivalent position.

  The method preferably further includes the further step of making the first and second vibration drive system components to dimensions having substantially equal mass.

The method further comprises:
The bending axis of the first flow tube and the combined mass center of the first flow tube plus the first vibration drive system components are disposed on a first balance plane parallel to the symmetry plane. Stages,
The bending axis of the second flow tube and the combined mass center of the second flow tube plus the second vibration drive system components are placed on a second balance plane parallel to the symmetry plane. Preferably includes a stage.

The method further comprises:
Attaching the first vibration drive system component, including a driver coil component, to the first flow tube;
Preferably, the second vibration drive system component including the driver magnet component is attached to the second flow tube in alignment with the coil component.

The method includes the first vibration drive system component further including a first pickoff component, the second vibration drive system component further including a second pickoff component, and the method further comprises:
Attaching a first pickoff component to the first flow tube;
Attaching a second pick-off component to the second flow tube.

  Preferably, the method further includes the step of making the first and second pickoff components to dimensions having substantially equal mass.

The method further includes a bending axis of the first flow tube, and a combined mass center of the first flow tube and the first vibration drive system component, the first parallel to the plane of symmetry. Placing on the equilibrium surface;
The bending axis of the second flow tube and the combined mass center of the second flow tube plus the second vibration drive system components are placed on a second balance plane parallel to the symmetry plane. Preferably includes a stage.

1 shows a prior art prior art Coriolis flow meter. 2 shows a representative driver for a prior art Coriolis flow meter. 1 shows a perspective view of a Coriolis flow meter embodying the present invention. Figure 4 shows the Coriolis flow meter of Figure 3 with a portion of the outer shell removed. Figure 4 shows the flow tube and brace bar of the Coriolis flow meter of Figure 3; The perspective view of driver D of the Coriolis flowmeter of Drawing 3 is shown. Fig. 5 shows a vertical cross-sectional view of the flow tube of Fig. 4 attached to a driver element embodying the present invention. The details of the driver D attached to the first and second flow tubes are shown. The details of the pick-off transducer and how to attach the pick-off transducer to the flow tube are shown.

  These and other advantages and aspects of the present invention will be better understood when the following detailed description is read in conjunction with the drawings.

  1-9 and the following description are specific examples to teach those skilled in the art how to make and use the best mode of the present invention. In order to teach the principles of the invention, some conventional aspects have been simplified or omitted. Those skilled in the art will appreciate that derivations from these examples are also within the scope of the present invention. As will be appreciated by those skilled in the art, the features described below can be combined in various ways to form numerous derivatives of the present invention. In other words, the present invention is not limited to the specific examples described below, but is limited only by the scope of the claims and their equivalents.

Description of FIG. 1 FIG. 1 shows a Coriolis flow meter 5 comprising a flow meter assembly 10 and a flow meter electronics 120 . Flow meter electronics 120 is connected to flow meter assembly 10 via lead 100 and provides density, mass flow, volume flow, total mass flow, temperature, and other information through path 126. As will be apparent to those skilled in the art, the present invention can be used with any type of Coriolis flow meter regardless of driver, pick-off sensor, number of flow tubes, or mode of operation of vibration.

The flow meter assembly 10 includes a pair of flanges 101, 101 ′, manifolds 102, 102 ′, a driver D , pick-off sensors LPO, RPO , and flow tubes 103A, 103B. The driver D and the pickoff sensors LPO and RPO are connected to the flow tubes 103A and 103B.

  The flanges 101 and 101 'are attached to the manifolds 102 and 102'. Manifolds 102, 102 ′ are attached to the opposite ends of spacer 106. The spacer 106 maintains a spacing between the manifolds 102 and 102 'to prevent unwanted vibrations in the flow tubes 103A, 103B. When the flow meter assembly 10 is inserted into a pipeline system (not shown) carrying the material to be measured, the material enters the flow meter assembly 10 through the flange 101 and passes through the inlet manifold 102 where the material. Is directed to enter flow tubes 103A and 103B, flows through flow tubes 103A and 103B, returns to outlet manifold 102 ', where it exits flow meter assembly 10 through flange 101'.

  The flow tubes 103A and 103B are selected to have substantially the same mass distribution, moment of inertia, and elastic modulus with respect to the bending axes W--W and W '-W', respectively, and the inlet manifold 102 and the outlet manifold 102 ' Is attached properly. These axes include the tube end node (rest point) of each flow tube. Both flow tubes extend outwardly from the manifold in a basically parallel fashion.

  The flow tubes 103A-B are driven by the driver D in anti-phase with respect to the respective bending axes W and W ', in a mode other than the so-called first bending of the flow meter. Driver D comprises one of many known devices, such as a magnet attached to flow tube 103A and an opposing coil attached to flow tube 103B. Alternating current is passed through the opposing coils, causing both flow tubes to vibrate in opposite phase. An appropriate drive signal is applied to driver D via lead 110 by flow meter electronics 120. The description of FIG. 1 is provided only as an example of the operation of a Coriolis flow meter and is not intended to limit the teaching of the present invention.

The flow meter electronic circuit 120 sends a sensor signal to each of the leads 111, 111 ′. Flow meter electronics 120 generates a drive signal on lead 110 and causes driver D to vibrate flow tubes 103A and 103B in opposite phases. The flow meter electronics 120 processes the left and right velocity signals from the pickoff transducers LPO, RPO and calculates the mass flow rate. Path 126 provides input and output means for flow meter electronics 120 to contact the operator.

Description of FIG. 2 FIG. 2 shows a drive system D for a preferred embodiment of the Coriolis flow meter 5. In one preferred exemplary embodiment, driver D is a coil and magnet assembly. As those skilled in the art are aware, other types of drive systems such as piezoelectric devices may be used.

The driver D has a magnet assembly 210 and a coil assembly 220. Each bracket 211 extends outward from the magnet assembly 210 and the coil assembly 220 in opposite directions. The bracket 211 is a wing extending outward from a flat base, and has a substantially curved edge 290 formed along the flow tube 103A or 103B on the bottom side. . The curved edge 290 of the bracket 211 is welded or otherwise attached to the flow tubes 103A and 103B to attach the driver D to the Coriolis flow meter 5.

  The magnet assembly 210 has a magnet holding part 202 as a base part. The bracket 211 extends from the first side of the magnet holding part 202. The walls 213 and 214 extend outward from the outer edge portion on the second side of the magnet holding portion 202. Walls 213 and 214 control the direction of the magnetic field of magnet 203 perpendicular to the winding of coil 204.

  Magnet 203 is a substantially cylindrical magnet having first and second ends. The magnet 203 is fitted in a magnet sleeve (not shown). The magnet sleeve and the magnet 203 are attached to the second surface of the magnet holding part 202 in order to fix the magnet 203 in the magnet assembly 210. Magnet 203 typically has a pole (not shown) attached to its second side. A magnetic pole (not shown) is a cap and is attached to the second end of the magnet 203 to direct the magnetic field toward 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 has a spool protruding from the first surface around which the coil 204 is wound. The coil 204 is mounted on a coil bobbin 205 that faces the magnet 203. The coil 204 is connected to a lead wire 110 that applies alternating current to the coil 204. The alternating current causes the coil 204 and the magnet 203 to attract and repel each other, causing the flow tubes 103A and 103B to vibrate in opposite directions.

Description of FIG. 3 FIG. 3 discloses a Coriolis flow meter 300 embodying the present invention. The flow meter 300 includes a spacer 303 that surrounds the lower part of the flow tubes 301 and 302, and the flow tube is connected to the flange 304 through the neck 308 at the left end and the neck 320 at the right end. To the flange 305 and the manifold 307. FIG. 3 also shows the outlet 306 of the flange 305, the left pickoff LPO, the right pickoff RPO, and the driver D. The right pickoff RPO is shown in some detail and includes a magnet structure 315 and a coil structure 316. Element 314 at the bottom of manifold spacer 303 is an opening for receiving wire 100 extending from flow meter electronics 120 to driver D and pickoffs LPO and RPO. When used, the flow meter 300 is connected to a pipeline or the like via flanges 304 and 305.

FIG . 4 is a cutaway view of the flow meter 300. This figure has removed the front portion of the manifold spacer 303 to show the portion inside the manifold spacer. 4 but not shown in FIG. 3, the outer end brace bars 401, 404, the inner brace bars 402, 403, the right end flow tube outlet openings 405, 412 and , Flow tubes 301, 302 and curved flow tube sections 414, 415, 416, 417. In use, flow tubes 301 and 302 vibrate about bending axes W and W ′, respectively. The outer end brace bars 401, 404 and the inner brace bars 402, 403 help determine the positions of the bending axes W and W ′. Element 406 is a wire fixture attached to driver D and pickoffs LPO and RPO and is not shown in FIG. 4 to avoid complications. Surface 411 is the flow meter inlet and surface 306 is the flow meter outlet.

  Elements 405 and 412 are the inner surfaces of the left ends of flow tubes 301 and 302. Bending axes W and W ′ extend over the length of flow meter 300.

Description of FIG. 5 FIG. 5 is an end view of the flow tubes 301 and 302 illustrated as being displaced outwardly from each other under the influence of a driver D (not shown in FIG. 5). Inner brace bars 402 and 403, outer brace bars 401 and 404, and outlet openings 405 and 412 are also shown in FIG. The depiction of the outward displacement of the flow tubes 301, 302 is exaggerated to facilitate understanding of the operation. In use, the displacement of the flow tube by the driver D is so small that it cannot be detected with the naked eye. The bending axes W and W ′ of the flow tubes 301 and 302 are also shown.

Description of FIG. 6 FIG. 6 discloses a driver D having a coil section C and a magnet section M. Coil section C is shown having an end 601 of a bolt (not shown) that extends through the entire coil section C in the axial direction. Surface 604 is the axially outer end of coil section C. Element 602 is a coil spacer that surrounds coil section C. The surface 603 is a spacer. Element 604 supports a wire (not shown) connected to the end of the coil winding of coil section C. Element 605 is the outer surface of the coil bobbin. Element 606 is the surface around which the wire of coil section C is wound. Element 608 is the wire making up coil section C.

  The right magnet section includes a holding portion 609, a cylindrical magnet bracket 610 surrounding the inner magnet, a transition surface 612, a counterweight and magnet bracket 613, and a left end surface 611 of the magnet bracket 613.

  In use, a voltage is applied to the coil 608 by a sine wave signal coming from the flow meter electronics 120 via the conductor 110. The magnetic field created by the pressurized coil 608 interacts with the magnetic field at the end of the magnet and is affected by the pressurization signal from the flow meter electronics 120 to reverse the coil element C and magnet element M in the axial direction. Move to phase. Accordingly, the right end portion of the coil element C in FIG. 6 including the coil 608 and the surface 607 enters and exits the magnet holding portion 609 in the axial direction. As shown in FIG. 8, the upper surface of the coil spacer 602 is fixed to the lower surface of the flow tube 301. Similarly, the upper surface of the magnet bracket 610 is fixed to the lower surface of the flow tube 302. The oscillatory motion of the coil and magnet components of driver D causes a similar oscillatory motion in flow tubes 301 and 302, causing them to vibrate in anti-phase under the influence of the drive signal on path 110.

Description of FIG. 7 FIG. 7 is a cross-sectional view of the flow tubes 301 and 302 at the center in the longitudinal direction, and a cross-sectional view of the coil component C and the magnet component M of the driver D. The upper surface of the coil 602 is fixed to the lower surface of the flow tube 301. The upper surface of the magnet spacer 610 is fixed to the lower surface of the flow tube 302. Elements 602 and 610 may be attached to the flow tube by brazing and / or spot welding. A bolt 701 having an end 601 enters the coil spacer 602, extends inward through the spacer 303, and terminates at an element 606. Element 606 is attached to element 704 having a surface around which coil 608 of FIG. 6 is wound.

  The magnet M component of driver D includes an element 702 at the outer right end. The left end of the magnet M is an element 703, and the central portion of the magnet M is an element 710. The right part 702 is in the counterweight 613. When a voltage is applied to the component coil C of the driver D, the right portion of the coil component C and the left portion of the magnet component M vibrate axially inward and outward relative to each other, resulting in a flow The tubes 301 and 302 cause similar inward and outward vibrations.

  When driver D vibrates flow tubes 301 and 302, flow tube 301 vibrates about bending axis W 'and flow tube 302 vibrates about bending axis W. This is shown more clearly in FIGS. The vertical line 716 is in the equilibrium plane of the flow tube 301. The balancing surface 716 includes a bending axis W ′ and is parallel to the symmetry plane 708. The vertical line 717 is in the equilibrium plane of the flow tube 302. The balance surface 717 includes a bending axis W, which is also parallel to the plane of symmetry 708 that is intermediate between the surfaces 716 and 717.

  The flow tubes 301 and 302 vibrate like a tuning fork around their respective bending axes W 'and W. However, the two flow tubes by themselves are not fully mechanically balanced structures, and are therefore considered to generate low levels of undesirable vibrations in the Coriolis flow meter of which they are a part.

  FIG. 7 shows the bending axes W ′ and W located slightly inward from the centerlines 706 and 707 of the flow tubes 301 and 302. These bending axes W 'and W are often located on the centerlines 706 and 707 of the flow tube. However, in the present invention, as shown in FIG. 7, the bending axes W ′ and W are separated from the flow tube centerlines 706 and 707 due to the mass of the flow tube and the rigidity of the structure to which the flow tube is attached. It's off. Flow tube mass centers 712 and 715 (ignoring attached components) are above the tube centerlines 706 and 707. As the tube bends inward, its mass centers 715 and 712 move along a circumferential path about bending axes W 'and W. Thus, the center of mass moves slightly upward as it approaches the respective balance surfaces 716 and 717. Similarly, flow tube mass centers 715 and 712 move downward as they move away from their respective balancing surfaces 716 and 717. If not balanced, the vertical movement of the flow tube mass centers 715 and 712 will cause the instrument to rock in the Y direction.

  The typical flowmeter driver also has a mass that is not mechanically balanced when attached to a typical Coriolis flowmeter flow tube. Such a driver is shown in FIG. 2, and it can be seen that it comprises a first structure 220 attached to the first flow tube and a second structure 210 attached to the second flow tube. Such a driver adds significant mass to the vibrating structure of the flow tube. The driver also adds mass in such a way that most of the mass is placed in the space between the two flow tubes. This mass includes the elements 204, 203, 205, 213, 214 of the driver of FIG.

When the structure of the driver of FIG. 2 is added to the flow tubes 301, 302 instead of the driver D of the present invention, the center of mass of the driver component of FIG. 2 is between the radial centers 706 and 707 of the flow tubes 301 and 302. The flow meter will remain unbalanced. The centers of these masses are on the far side of the balance surfaces 716 and 717. Because of this position, the center of mass of the drive component moves down when the flow tubes move toward each other and moves up when the flow tubes move away from each other. This counteracts the Y- direction imbalance from the bare flow tube, but unfortunately, in prior art drivers, the effect of the offset of the drive component is from the equilibrium surface at the center of the mass of the flow tube. The effect of offset will be overwhelming. This dynamically unbalanced condition results in the creation of a significant amount of undesirable vibration in such a flow meter.

The driver D of the present invention includes a coil component C and a magnet component M that are attached to the bottom of each of the flow tubes 301 and 302 in such a way that the flow tube can operate with minimal undesirable vibrations. This is because, according to the present invention, by designing, fabricating and configuring the coil component C and the magnet component M so that each has a mechanically balanced structure with equal and consistent inertial properties, Realized. Both elements are individually attached to the bottom of flow tubes 301 and 302. They axial center of the coil and the magnet has a common central axis, the two components, so that it can vibrate in antiphase along a common axis, axially aligned with each other Be placed. When a drive element C having a center of mass 718 is attached to a flow tube 301 having a center of mass 715, the combined center of mass 727 is on the balance surface 716. Similarly, when a drive element M having a center of mass 713 is attached to a flow tube 302 having a center of mass 712, the combined center of mass 714 is above the balance surface 717. By placing the combined mass center on the balance surfaces 716 and 717, it can be ensured that the components brought together do not interfere with the vibrational balance of the instrument and are therefore undesirable in the Y direction. No vibration is created.

  The coil C component and the magnet M component of the driver D are designed, manufactured and configured to have the vibration characteristics described below. First, the mass of the coil C component is equal to the mass of the magnet M component of the driver D. The center of mass 718 of the coil and the center of mass 713 of the magnet are equal in distance from the bending axes W ′ and W. Next, the moment of inertia is configured such that the moments of inertia of the coil C component and the magnet M component are basically equal. The moment of inertia of each of these elements is

と表され、ここに、
Ｉ＝構成要素の慣性モーメント
ｍ＝各増分要素の質量
ｒ＝各増分要素から構成要素の質量の中心までの距離
である。最後に、各駆動構成要素の質量の中心は、各駆動構成要素とそれぞれの流管の組み合わせられた質量の中心が、平衡面７１６と７１７の上に位置するように配置される。ドライバをこれらの規則に則って設計すると、力学的に平衡な構造が保証され、望ましくない信号の生成を回避しながら、流管を逆位相に振動させることができる。

Where,
I = moment of inertia of component m = mass of each incremental element r = distance from each incremental element to the center of mass of the component. Finally, the center of mass of each drive component is positioned such that the combined mass center of each drive component and the respective flow tube is located above the balance surfaces 716 and 717. Designing the driver according to these rules ensures a mechanically balanced structure and allows the flow tube to oscillate in anti-phase while avoiding unwanted signal generation.

Description of FIG. 8 FIG. 8 discloses details when the driver D of FIGS. 6 and 7 is attached to the bottom of the flow tubes 301 and 302. FIG. 8 shows a bolt end 601 extending through the coil C. FIG. Figure 8 is a further coil section and the end face 614 of the coil spacer cover, coil plane 603, illustrates the wire terminal 60 4. FIG. 8 further shows elements 609, 610, 612, 613 of the magnet component M. FIG. 8 shows conductors 806 and 807 extending from the bracket 802 to the coil end 604. Conductors 806 and 807 are connected by conductor 110 (not shown) to apply pressurization signal 110 from flow meter electronics 120 to coil section C. Brackets 801, 802, 803, 804 and 805 are mounting brackets for supporting the conductors 806 and 807. Bracket 610 is attached to the bottom of flow tube 301 in the same manner that coil spacer element 602 is attached to the bottom of flow tube 301.

Description of FIG. 9 FIG. 9 shows details of the pickoffs RPO and LPO of FIG. 3 attached to the top of the flow tubes 301 and 302. Each pickoff has a coil component C and a magnet component M in the same manner as driver D. The coil C component has a spacer 315 attached to the top of the flow tube 301, and the magnet M component has a spacer 316 attached to the top of the flow tube 302. The pickoff RPO has a conductor 907 connected to the conductor paths 111 and 111 ′ of FIG. 1 by means not shown in detail in FIG. These conductors are supported by a bracket 906. The coil C component has elements 902 and 904 to support the coil conductor, and further has an axially inner end face 903. The magnet M component has an inner end 905 corresponding to the element 609 of the magnet component M of FIG.

  Pickoffs RPO and LPO are designed, constructed and fabricated in the same way as described for the driver so that each component has equal mass, the center of mass is on the balance plane and the moment of inertia is equal. ing. This includes a mechanically balanced structure that can be attached to the flow tube as shown so that the pickoff component can operate the flow tube in a manner that does not create undesirable vibrations. Guarantee that.

  According to a first aspect of the present invention, in the Coriolis flow meter, each of a first flow tube (301) and a second flow tube (302) adapted to vibrate in an anti-phase around a symmetry plane (708), A drive system (D) adapted to vibrate the flow tube about a bending axis connecting nodes at both ends of each flow tube, and a first vibration drive system component (C) attached to the first flow tube A first vibration component (D, LPO, RPO) including a second vibration drive system component (M) attached to a second flow tube, and a first vibration component including And the second vibration drive system component is substantially the same as the moment of inertia of the first flow tube and the first vibration drive system component plus the second flow tube and the second vibration drive system component. Equivalent dimensions and It has a location.

  According to a second aspect of the present invention, in the Coriolis flow meter of the first aspect, the first and second vibration drive system components are dimensioned to have substantially equal mass.

  According to a third aspect of the present invention, in the Coriolis flow meter according to the first or second aspect, a bending axis of the first flow tube, a first flow tube, and a first vibration drive system component (C) are added. The combined center of mass (727) is on the first balance plane (716) parallel to the plane of symmetry (708), the bending axis of the second flow tube, the second flow tube and the second vibration drive system configuration. The combined center of mass (714) of element (M) plus is on a second balance surface (717) parallel to the plane of symmetry (708).

  According to a fourth aspect of the present invention, in the Coriolis flow meter according to any one of the first to third aspects, the first vibration drive system component is a coil component (C) of a driver attached to the first flow tube. The second vibration drive system component includes a driver magnet component (M) attached to the second flow tube and coaxially aligned with the coil component.

  According to a fifth aspect of the present invention, in the Coriolis flow meter according to any one of the first to fourth aspects, the first vibration component further includes a first pick-off component (602), and the second vibration The component includes a second pickoff component (610).

  According to a sixth aspect of the present invention, in the Coriolis flow meter of the fifth aspect, the first pick-off component (602) is attached to the first flow tube (301), and the second pick-off component (610) is the second. Attached to the flow tube (302).

  According to a seventh aspect of the present invention, in the Coriolis flow meter of the sixth aspect, the first and second vibration drive system components are dimensioned to have substantially equal mass.

  According to an eighth aspect of the present invention, in the Coriolis flow meter of the fourth aspect, the bending axis of the first flow pipe (301), the first flow pipe and the first vibration drive system component (C) are added. The combined center of mass (727) is on the first balance surface (716) parallel to the symmetry plane (708), the bending axis of the second flow tube (302), the second flow tube and the second vibration. The combined center of mass (714) of the drive system component (M) plus is on a second balance surface (717) parallel to the plane of symmetry.

According to a ninth aspect of the present invention, in a method of operating a Coriolis flow meter, a first flow tube and a second flow tube configured to vibrate in opposite phases around a symmetry plane, and each flow tube, and a and drive system adapted to vibrate around a shaft bend connecting ends nodes of the flow tube, provided with a method, the first vibration component that includes a first vibrating drive system component first Attaching the first vibration tube to the second flow tube and attaching the second vibration component including the second vibration drive system component to the second flow tube, the method further comprising first and second vibration drive system configurations So that the moment of inertia of the element plus the first flow tube and the first vibration drive system component is substantially equal to the moment of inertia of the second flow tube plus the second vibration drive system component; Equivalent dimensions and equivalent It includes the step of placing the position.

  A tenth aspect of the present invention further comprises the step of making the first and second vibration drive system components to dimensions having substantially equal masses in the method of the ninth aspect.

  According to a tenth aspect of the present invention, in the method of the ninth or tenth aspect, the combined mass of the bending axis of the first flow tube, the first flow tube and the first vibration drive system component is added. The center of the combined mass of placing the center on a first balance plane parallel to the symmetry plane, the bending axis of the second flow tube, and the second flow tube and second vibration drive system components On the second balance plane parallel to the plane of symmetry.

  According to a tenth aspect of the present invention, in the method according to any one of the ninth to eleventh aspects, the step of attaching the first vibration drive system component including the driver's coil component to the first flow tube; Attaching a second vibration drive system component, including a magnet component, to the second flow tube in coaxial alignment with the coil component.

  According to a tenth aspect of the present invention, in the method according to any one of the ninth to twelfth aspects, the first vibration drive system component further includes a first pickoff component, and the second vibration drive system component is A second pick-off component, and further comprising the steps of: attaching the first pick-off component to the first flow tube; and attaching the second pick-off component to the second flow tube. Yes.

  A tenth aspect of the present invention further comprises the step of making the first and second pickoff components to dimensions having substantially equal masses in the method of the thirteenth aspect.

  According to a tenth aspect of the present invention, in the method according to any one of the ninth to fourteenth aspects, the bending axis of the first flow tube, the first flow tube, and the first vibration drive system component are added. Placing the center of mass on the first balance plane parallel to the symmetry plane, the bending axis of the second flow tube, and the addition of the second flow tube and the second vibration drive system component Disposing the center of mass on a second balance plane parallel to the plane of symmetry.

  It is to be expressly understood that the claimed invention is not limited to the description of the preferred embodiments, but includes other modifications and alternatives within the scope and spirit of the inventive concept. I want.

Claims (11)

A Coriolis flow meter,
A first flow tube (301) and a second flow tube (302) adapted to vibrate in anti-phase around a plane of symmetry (708);
A drive system (D) adapted to vibrate each flow tube about a bending axis connecting nodes at both ends of each flow tube;
A first vibration component (D, LPO, RPO) including a first vibration drive system component (C) attached to the first flow tube;
A second vibration component including a second vibration drive system component (M) attached to the second flow tube,
The moment of inertia of the first and second vibration drive system components plus the first flow tube and the first vibration drive system component is the second flow tube and the second vibration drive system component. A Coriolis flowmeter with equivalent dimensions and position so that it is substantially equal to the moment of inertia of the addition,
The bending axis of the first flow tube and the combined mass center (727) of the first flow tube plus the first vibration drive system component (C) is parallel to the symmetry plane (708). On the first equilibrium surface (716)
The bending axis of the second flow tube and the combined mass center (714) of the second flow tube plus the second vibration drive system component (M) is parallel to the symmetry plane (708). On the second equilibrium surface (717)
The center line (706) and the center of mass (715) of the first flow tube are at positions other than the first balance surface (716),
The Coriolis mass flowmeter, wherein a center line (707) and a center of mass (712) of the second flow tube are located at positions other than the second balance surface (717).   The Coriolis flow meter of claim 1, wherein the first and second vibration drive system components are dimensioned to have substantially equal mass. The first vibration drive system component includes a driver coil component (C) attached to the first flow tube;
The second vibration drive system component includes a magnet component (M) of the driver attached to the second flow tube and coaxially aligned with the coil component. Item 2. The Coriolis flow meter according to Item 1. The first vibration component further includes a first pick-off component ( 315 ), and the second vibration component includes a second pick-off component ( 316 ). The Coriolis flow meter according to 1. The first pickoff component ( 315 ) is attached to the first flow tube (301);
The Coriolis flow meter of claim 4, wherein the second pickoff component ( 316 ) is attached to the second flow tube (302). 6. The Coriolis flow meter of claim 5, wherein the first and second pickoff components are dimensioned to have substantially equal mass. A method of operating a Coriolis flow meter,
A first flow tube and a second flow tube adapted to vibrate in anti-phase around a plane of symmetry;
Wherein each flow tube has a, a drive system adapted to vibrate around a bending axis connecting the nodes at both ends of each flow tube, the method comprising:
Attaching a first vibration component, including a first vibration drive system component, to the first flow tube;
Attaching a second vibration component including a second vibration drive system component to the second flow tube;
The moment of inertia of the first and second vibration drive system components added to the first flow tube and the first vibration drive system component is added to the second flow tube and the second vibration drive system component. An equivalent dimension so as to be substantially equal to the moment of inertia of the object, and a position at an equivalent position.
The bending axis of the first flow tube and the combined mass center of the first flow tube plus the first vibration drive system components are disposed on a first balance plane parallel to the symmetry plane. A center line and a center of mass of the first flow tube are located at a position other than the first balance plane; and
The bending axis of the second flow tube and the combined mass center of the second flow tube plus the second vibration drive system components are placed on a second balance plane parallel to the symmetry plane. And further comprising the step of: the center line of the second flow tube and the center of mass being at a location other than the second balance plane. Wherein the first and second vibration drive system components, further comprises the step of making the dimensions have substantially equal mass The method of claim 7. Attaching the first vibration drive system component, including a driver coil component, to the first flow tube;
Attaching the second vibration drive system component, including the driver magnet component, to the second flow tube in coaxial alignment with the coil component. the method of. It said first vibration Do構 formed elements are further includes a first pickoff component, characterized in that the second vibration Do構 formed element further includes a second pickoff component, further,
Attaching a first pickoff component to the first flow tube;
Attaching a second pickoff component to the second flow tube. Wherein the first and second pin Kkuofu component further includes the step of making the dimensions have substantially equal mass The method of claim 10.

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