JPH0718734B2 - Flowmeter for measuring mass flow rate in a flow of matter - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to mass flow and density measuring devices, and more particularly to one or more such mass flow passages. The present invention relates to an improved device for measuring the mass flow rate of a flowing mass by using the effects of Coriolis force and centrifugal force acting on a portion which is moved or deflected by the vibration of a conduit loop.

Description of the Prior Art There has been a constant need for more accurate, more efficient devices for determining the mass flow rate and density of fluids and flowing solids passed through pipelines and other types of conduits. . In the past, the conventional flowmeter was a gyroscope type mass flowmeter or a Coriolis type mass flowmeter.

One such device that utilizes the Coriolis force to measure mass flow was given to James E. Smith on August 29, 1978, "Mass Flow Measurement Method and Device." (Method and Apparatus for Mass
US Patent No. 4, entitled "Flow Rate Measurement")
No. 109,524. In that patent, 1
By a beam whose ends are mechanically connected to the first and second parts of the two straight conduits, parallel to the first and second parts and to the adjacent ends of the two conduit parts , A device to which mechanical reciprocating force is applied is disclosed. Adjacent ends of the first and second conduit sections are connected together by a short conduit section and a flexible joint, with the outer ends of each conduit section being separately supported in cantilever fashion relative to the base structure. The reciprocating force applied to the conduit is a separate Coriolis force generated in the first and second conduit portions and acting in opposite directions, causing a moment of force about the center of the beam. It is resisted by its separate Coriolis forces, which are things. The force moment is measured by the torque sensor. By measuring the moment of force caused in the conduit (and transferred to the beam) by the Coriolis reaction force, a measurement of the mass flow rate through the conduit can be made. But for that measurement,
The measurement is complicated by the need to avoid erroneously measuring forces due to earthquakes or other seismic forces transmitted through the support structure. Other similar devices include US Pat. No. 3,080,750 to Wiley et al. And US Pat. No. 3,218,851 to Sipin.
U.S. Pat. No. 3,3 granted to Souriau
96,579, and U.S. Pat. No. 3,329,019 to Sipin.

In the mass flow measurement, both ends are pivoted,
U-tubes or similar shapes are generally used, rather than using a straight section of conduit that is reciprocated at adjacent ends. In that case, the inlet end and the outlet end of the leg of the U-tube are fixed to the base and the curved end of the U-tube is reciprocated. Then, the differential displacement caused by Coriolis action in the corresponding part of the lateral leg of the U-tube is measured as a representation of the mass flow rate. Such a technique and apparatus is suggested in the Smith patent and was granted to James E. Smith on February 12, 1980, and is now Reissue Patent No. 31,450. Method and Structure for Flow Measurement "
Shown in U.S. Pat. No. 4,187,721.
As shown in the referenced patent, the U-shaped conduit is cantilevered at its leg ends, and the vibrator is attached to a spring arm having a natural frequency approximately equal to the natural frequency of the U-shaped conduit. It is installed. The vibrating device is used to move up and down the center of the curved end of the U-shaped conduit. A measurement sensor (flag and photodetector) is provided. The measurement sensors detect the leading and trailing portions of the legs of the U-shaped conduit as it passes through the plane defined by the U-shaped conduit at approximately the midpoint of its vibration. The difference in time the legs pass through the mid-plane is measured as an indication of mass flow.
In essence, the same structure is used in later Smith patent 4,422,338. However, in that Smith patent, a pair of velocity sensors are used in place of the photodetector and adjustment electronics are provided to generate a signal corresponding to the passage of the lateral leg through the midplane.

Bruce M. Cox and others 1978 1
"Coriolis mass flow measurement device (Cor
U.S. Pat. No. 4,127,028 entitled "Iolis Mass Flow Rate Metering Means)" describes a pair of oscillating generally U-shaped tubes such that the curved ends of each of the U-shaped tubes are free to move relative to each other. Shaped tubes are fixed at their inlet and outlet ends in parallel, cantilevered fashion. An oscillating drive mechanism is coupled between the curved ends of each tube and actuated to reciprocate the curved ends so that the U-shaped member acts as the free end of the tuning fork. Exercise. The frequency of vibration of the tube is adjusted until the tube vibrates with a constant displacement when a known substance flows between them. The power required to vibrate the tube by a known displacement at a constant frequency determines the density of the unknown flowing material flowing in the U-tube. Mass flow is detected by a photodetector positioned to operate in the same manner as taught by Smith because it is a single tube embodiment. Cox also suggests that a strain gauge or velocity sensor should be substituted for the photodetector, and it is known in the prior art that there is a phase difference between the outputs of the two sensors that is proportional to the Coriolis force couple. I admit it was.

The main teaching of this reference is that each U-shaped tube is adjacent to the supporting end of the U-shaped tube to improve the torsional freedom that can be applied to each U-shaped tube by Coriolis reaction forces. It is to reduce the distance between the legs. This reference also shows the shape of the looped tube in its FIG. 5 but does not teach or suggest how to use that shape to improve flow measurement.
Therefore, it is not believed that the present invention can be inferred therefrom.

Other prior art known to the inventor of the present application is US Pat. No. 2,752,173 issued to Barnaby et al.,
US Pat. Nos. 2,865,201 and 3,049,919 granted to Roth, US Pat. No. 3,355,944 granted to Sipin, US Pat. No. 3,485,098 granted to Sipin, Catherall U.S. Pat. No. 3,955,401 to Shiota, U.S. Pat. No. 4,381,680 to Shiota, Smith EPO Publication, NO.EP O 083 144 A1. That EP
The O publication corresponds to US Pat. No. 4,422,338.
A list of prior art using the Coriolis principle can be found in the aforementioned Sipin patent RE 31,450.

The drawback of Smith and Kocks type flow measuring devices, as well as other prior art flow measuring devices, is that they are very sensitive to external seismic forces that expose the measuring pipe to torsion forces other than the torsion forces transmitted by the Coriolis reaction force. Being sensitive, these forces prevent accurate measurement of mass flow rate.

Smith Reissue Patent No. 31,450 and Smith 4,422,338
Another drawback of the preferred embodiment in the patent is that the proposed time difference measurement method in the mid-plane of the U-tube introduces flow measurement errors when the fluid density changes.

Yet another disadvantage of conventional Coriolis type devices is the inability to provide accurate flow data for a wide range of flow rates due to the limited sensitivity of the flow structures used.

Yet another disadvantage of conventional devices is that they are not provided with dynamic damping devices that reduce their sensitivity to external vibrations.

SUMMARY OF THE INVENTION Accordingly, the primary object of the present invention is to provide a new and improved Coriolis type device for measuring the mass flow rate of fluids or flowing solids, or mixtures thereof, through a conduit. is there.

Another object of the invention is to obtain a new and improved apparatus for measuring the density of mass flowing in a conduit.

Another object of the present invention is to provide an apparatus for measuring the mass flow rate and density of a mass flowing in a conduit without the inclusion of turbulence causing objects or features in the fluid flow path.

In summary, the preferred embodiment of the present invention includes at least one spiral loop conduit and a portion of the loop that is perpendicular to the direction of flow through the conduit portion and is located at the central axis of the loop. Including means for oscillating in a generally parallel direction, and means for detecting the Coriolis force applied to the mass as it flows through other parts of the loop and as a result of its oscillatory movement. . A strain gauge and associated processing electronics are also used in combination with the mass flow information to determine the flow density measuring device.

An important advantage of the present invention is that it allows the true mass flow to be measured independently of changes in the properties of the material flowing in the measuring device.

These and other advantages of the invention will no doubt become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiment, which is illustrated in several figures of the drawings. Will.

In the drawings, FIG. 1 is a schematic diagram used to show the theoretical operation of the present invention, FIG. 2 is a schematic diagram showing a simplified embodiment of one aspect of the present invention, and FIG. 3 is a first example of the present invention. Fig. 4 is a schematic diagram showing another embodiment of Fig. 4, and Fig. 4 is a schematic diagram showing a multiple loop embodiment of the present invention.
5 and 6 show an embodiment of the parallel flow multiple loop of the present invention, FIG. 7 outlines one method of imparting vibrational energy to the loop according to the present invention, and FIG. 8 shows the present invention. A schematic diagram outlining the damping technique used according to
FIG. 9 is a schematic diagram showing a method for detecting the action of Coriolis according to the present invention, and FIG. 10 is a set of waveforms showing the operation of the present invention.
FIG. 11 is a schematic view showing another embodiment of the present invention modified to enable higher measurement sensitivity, and FIG. 12 is a book modified to increase measurement sensitivity and lower external vibration sensitivity. FIG. 13 shows another embodiment of the invention, FIG. 13 shows another method for detecting Coriolis force according to the present invention, and FIG. 14 shows an embodiment including a strain gauge and an electronic processing device according to the present invention. FIG. 15 is a block diagram showing the calculation algorithm used in accordance with the present invention.

GENERAL THEORY OF OPERATION The present invention shows that masses flowing in loop tubes and other conduits that have velocity gradients across the flow path are conduits with forces directly related to transverse velocity gradients and mass flow rates. It is based on the principle of interacting with the walls of. The reaction when a velocity gradient is created by transverse movement of the loop or rotation of the loop about an axis other than the central axis of the loop is known as Coriolis force. The magnitude and direction of the reaction force depends on the magnitude and direction of the transverse velocity change and the magnitude and direction of the mass flow. Two parts of the loop have the same transverse velocity gradient, but opposite flow directions result in a couple of equal and oppositely directed forces. According to the invention, this couple is measured as a means of determining the mass flow rate through the conduit.

Reference is now made to FIG. 1 for illustration. This figure shows the conduit
An example of 10 generalized spiral loops is shown. The crossed ends of the conduit 10 are attached to the base structures 12,14. The general theory of the invention described below applies to spiral structures of any shape and tubes of any cross-sectional shape.

Loop 10 has approximately X- because of the simplified mathematical analysis.
It is considered to be located in the Y plane. Z direction (perpendicular to the XY plane) required to allow crossing
The displacement of the pipe at is ignored.

Therefore, for a flow tube that is approximately symmetrical about the X axis in the XY plane, the flow and total Coriolis forces acting on each half 16 and 18 are given by .

P _{1 / 2loop} = F _mass v _D (1) where v _D is the velocity in the Z direction (perpendicular to the XY plane) at the driving point of the loop, such as point 20 in FIG. _mass is the mass flow rate of the fluid.

This equation can be used in another equation below to describe the dynamics of the loop with the approximation below. (1) It is assumed that Coriolis forces are concentrated at one "center of action point" for each half loop, instead of being distributed with varying magnitude along the tube. (2) Assume that the mass of the fluid and the material of the tube are concentrated at one mass point for each left loop instead of being distributed over the half loops. (3) There are two different movements at various points on the loop.
It is represented by the movement of each of the two mass points.

At the "center of action" of the Coriolis force, each half-loop has a certain "participating mass". The center of action is that the resultant force of the forces distributed over the half-loop is applied and can be calculated from the shape of the tubes involved and the overall Coriolis force equation for the individual mass elements. is there. The “participating mass” is approximately the same as the weight of tubing and fluid in each half-loop, but ignore the portion between the X-axis and the support point. This concept takes into account the non-uniform motion for various points on the half-loop. The participating mass can be determined experimentally by measuring the natural frequency of the bending vibration mode about the X axis and comparing it with the theoretical natural frequency of the differential equation to be presented. The participating masses are determined so that the two natural frequencies match.

The differential equations describing the inertial force, damping force, and spring action force are as follows.

Where A is the tamping characteristic of the material and the damping coefficient including the damping coil described below, and B is the restoring force from the spring action because the end of the pipe 10 is fixed and attached. The spring coefficient to describe, M _P is the participating mass for half of the loop, t is the time, Z _D is the motion of the action point center due to the driving motion only, and Z is the Coriolis at the action point center. It is a movement caused by the force and driving movement.

The natural frequency expressed in radians / unit time of the above equation (1) is expressed by the following equation.

The natural vibration mode related to the equations (2) and (3) is called “Coriolis mode”.

The spring coefficient B is determined by statically applying a couple in the Z direction (acting in the opposite directions around the points 24 and 26 on the two sides of the loop 10) about the point of action and measuring the deviation of the point of action. it can.

Assuming that the loop 10 is excited at a point 20 by a vibrational force in the Z direction that changes sinusoidally at an angular frequency of w,
Coriolis force P _1/2 (It is a sine wave signal having the same frequency at a constant flow rate. The above equation (1) almost determines the magnitude of the Coriolis force. Here, v _D is a sine wave. Make a wavy time change.

The phase transition between P _1/2 and (Z−Z _D ) according to equation (2) is well understood as published in the literature. For example, Grabbe, Ramo, Woodridge, “Automation Computer, and Control Handbook (Handbook o
f Automation Computation and Control) "Volume 1, 20
See page 59. The damping coefficient Z is defined as Z = (1 / 2W _th ) (A / M _p ) (4). Then, for example, the driving frequency W is selected to be 0.5 times the natural frequency W _th , and the damping coefficient Z is set to
If it is selected as 0.01 times, it is found that the phase shift amount is about −0.8 degrees using the above equations (2) and (3).

In this example, the ratio of damping coefficient A and mass M _p is Can be determined from equation (4).

The amount of damping in this example results from applying a certain amount of damping force to the loop. This will be described in detail later. Even if the Coriolis mode has the same natural frequency, different amounts of phase shifting are performed by selecting different damping amounts or different driving frequencies w.

When the density of the fluid changes, the natural frequency of the Coriolis mode changes, and the amount of phase shift at the drive frequency also changes somewhat. For normal changes in fluid density, changes in density can be neglected in order to calculate the approximate transfer rate for a given fluid, and to provide approximate compensation for phase shifts by the specific circuitry described below.

To determine the approximate compensation of the phase shift between the Coriolis force couple and the structural position, velocity or acceleration of the loop,
Differential measurements of gap widths or points can be used. In that case, the structural bias is g. This g is proportional to the magnitude of the Coriolis force couple having a predetermined coefficient by weighting. A linear combination of the time derivative of g with the integral of the same variable g (e.g., done by analog integration as described below) can be represented by the symbol G.

G = K ₁ + K ₂ ∫dt = K ₁ + K ₂ g (6) where is a symbol defined by the following equation.

= Dg / dt (7) After the Laplace transform, G can be expressed by the following equation.

G (s) = K ₁ s g (s) + K ₂ g (s) (8) By selecting this K ₁ / K ₂ , any positive phase shift amount between 0 degree and 90 degree is included. And a new function G can be associated with the measured value of. This ratio is the differential equation (2)
Is selected to produce a positive amount of phase shift equal to a negative amount of phase shift resulting from inertia of motion as described more approximately by. By properly selecting K ₁ / K ₂ , there is a large phase difference between the calculated variable G and the driving point speed v _D in Eq. (1) as long as the driving speed is approximately a sine function. do not do. But one sine wave (not including harmonics)
Some deviation from the waveform of is acceptable. For example, it is the displacement that is caused by the turbulent mechanical vibration. In fact, it is a great advantage of the present invention that it does not feel this kind of disturbance.

When performing signal analysis, the variable G and the drive point velocity v _D are sampled periodically. The sampling period is typically 20 times each full cycle of driving force applied. However, in the presence of very high frequency high frequency disturbances, higher frequencies are more appropriate. The lower sampling rate speeds up the analysis of the signal, and it may be desirable if the flow meter is to be used for fast operating flow control.

The samples for G and v _D are called G _i and v _i , respectively. i
= 1,2,3 ... N, where N is the number of sample pairs used for each measurement. Static couple and static structure measurements acts as a Coriolis force couple static relationship "g stat" is _{g stat = K 3 P 1 /} 2loop-static (9).

For the dynamic Coriolis force, the function G describing the dynamic gap change can be expressed by the following equation using the equation (6).

G = K ₁ ′ K ₃ ′ + K ₂ ′ K ₃ g (10) Here, in the equation (6), K ₁ ′ K ₃ = K ₁ and K ₂ ′ K ₃ =
It is K ₂ .

For simplicity, choose K ₂ equal to 1 / K ₃ and assume G = g + (K ₁ ′ / K ₂ ′) (11).

This equation indicates that G is approximately a differential position, velocity or acceleration measurement value modified by a differential term to correct the phase lag defined by equation (2) above.

_{Depending on the} compensation defined by equation (11), the variables P _{1 / 2loop} and G
Are approximately in-phase, the following equation can be used for dynamic devices.

P _{1 / 2loop} = (1 / K ₂ ) G (12) Similar to the equation (9), when the equation (12) is substituted into the equation (1) and G is solved, G = 2K ₃ F _mass v _D ( 13) is obtained. Here, G and v _D are almost in phase. In a digital device, the variables G and v _D are sampled and the sampled pair _i is called G _i , v _i .

Define the following.

α = 2K ₃ F _mass (14) Then, G = αv _D (14a) is obtained from Eq. (13). Then, α can be determined by linear regression analysis of the sample numbers of G _i and v _i . The solution of this equation is for one of the two regression lines associated with equation (14a).

Also, another regression line defined by the following equation can be used.

The line that separates the angle between the two regression lines is given by:

α (avg) = tan [1/2 (arcTanα ⁽¹⁾ + arcTanα ⁽²⁾ )]
(17) Then, the calculation of the mass flow rate from this line is obtained from the equation (14) as follows.

F _mass = (1 / 2K ₃ ) α ^(avg) (18) Of course, one of the regression lines can be used instead of the middle line. The F _mass calculated using _Eqs. (14) and (15) will be described later, but is also shown in FIG.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference is first made to FIG. 2, in which a simplified embodiment of the invention is shown. A circular loop 30 of conduit is attached to the base 32 by two supports 34,36. Note that loop 30 is bent up from axis 37 of the pipeline at position 38 and down from axis 37 at position 40 to create a gap at intersection 41. Alternatively, the pipeline-compatible deformation can be performed outside the supports 34 and 36.

On the opposite side of the intersection 41, a loop actuation mechanism 42 is attached to the base 32, and the armature or the like exerting the force of the mechanism is electromagnetically coupled to the position 44 of the loop 30. The loop actuating mechanism 42 is of any suitable type as long as it can reciprocate the engaged loop portion along the Z axis as defined by the equation (2). Can be

Appropriate sensors 46, 48 are located on each side of the loop 30. These sensors are loop points 50,5 relative to the base 32.
The two movements are detected at the same time, and the measured values are given to an appropriate calculation circuit and indicator 54. This calculation circuit and indicator 54
Gives a measure of the Coriolis moment and hence the mass flow rate through the loop 30. Alternatively, indicator 54 can be connected to a suitable means 56 coupled to the intersection of loop 30 at intersection 41, indicator 54 operative to provide a signal indicative of loop spacing, relative velocity or relative acceleration. The signal also causes the indicator 54 to indicate the mass flow rate through the conduit loop 30.

The invention shown in the embodiment of FIG. 2 is a significant improvement over the conventional device, but the vibration in the pipeline is
The disadvantage of requiring a sturdy base 32 to support the supports 34, 36 as well as the actuation mechanism 42 so as to prevent them from being transmitted to the device in a way that affects the measurements taken by the device. Have. In this example, because the base is sturdy, it is
It will be appreciated that the seismic motion transmitted to 32 is similarly transmitted to drive mechanism 42 and loop position detectors 46,48. Therefore, turbulence due to vibration does not usually affect the measurement accuracy. However, it will also be appreciated that seismic disturbances may cause the supported loops to move relative to the base, thus affecting measurement accuracy.
However, if the loop detection source is the detector 56, the seismic motion due to the earthquake in the Z direction is equally transmitted to the upper loop portion and the lower loop portion, and the two portions are biased in the same direction with equal strength. , Will be largely protected against the disturbance caused by the earthquake.

FIG. 3 shows a modification of the embodiment shown in FIG. In the embodiment shown in FIG. 3, instead of attaching the drive mechanism directly to the base, the drive means 60 is attached to the counterbalance structure 62 which is fixed to the supports 64,66. In this embodiment, the balance arm 62 is constructed such that its natural frequency about its support axis is the same as the natural frequency of the loop 68, and is expected to flow through the loop 68. An adjustable sliding weight 70 is additionally provided to allow adjustment to accommodate different densities of the. Thus, while this embodiment requires a robust end mount, it is not necessary to make the base seismic resistant because the drive mechanism 60 is not directly attached to the base. Using this alternative embodiment, the vibrations generated by the flow meter driver 60 effectively affect the installed pipelines that may reflect energy back to the device of the present invention. Since it is blocked, another risk of measurement error is eliminated.

A feature of the invention to be noted from the embodiment shown in FIGS. 2 and 3 is that the drive means 42 (60) is caused to the tube at the point of attachment of the tube to the supports 34 (64) and 36 (66). ) The stress caused by the operation, that is, the driving mode stress is not the bending stress but the torsional stress. On the other hand, the stress caused at those points by the Coriolis force, that is, the Coriolis mode stress, is mainly a bending stress by its nature.

To improve the sensitivity of the present invention to Coriolis forces, a series combination of crossed loops can be utilized, as shown in FIGS. 4-6. In the series double crossover loop of FIG. 4, driving force may be applied to 74 between the two loops 70 and 72, which biases the two loops in opposite directions. By means provided in 76 and 78, the separation between the loops, ie changes in relative position and changes in velocity or acceleration, can be detected. The dynamic difference in separation is used as an indicator of mass flow rate. Alternatively, the detected result of the loop separation at 80 and 82, or the difference between them, can be used as an indication of mass flow rate. Similarly, detection of separation between loops at 84 can be utilized as well.

The relative position of the corresponding parts of the individual loops above the base or other criteria can also be detected as shown in FIG.
The difference between them is used to determine the mass flow rate. The series double crossover loop has high flow sensitivity and is especially suitable for small flow measurements. However, this structure is somewhat sensitive to external vibrations, which necessitates the use of damping means, as will be described later.

In the parallel loop embodiment shown in FIG. 5, both loops are spirally wound in the same direction, whereas in the embodiment of FIG. 6, the upper loop is spirally wound in the upward direction. However, the lower loop is spirally wound in the downward direction. When an actuating force is applied during the loop at 86 in FIG. 5 and at 88 in FIG. 6, the loop separation difference measurement (position, velocity, acceleration or other time derivative) described for the embodiment shown in FIG. Or time integration)
The upper gap 100 (114 in FIG. 6) or the lower gap 102 (11
6) can be measured. That is, the difference between the upper gap 100 (114) and the lower gap 102 (116) can be measured. Similarly, 108
The differential loop feature of the separation at (118), 110 (120), 112 (122) can be taken as representative of the mass flow rate, 11
The difference between 0 and 112 (120 and 120) can be taken as an indication of mass flow as well. Measuring the position difference, or velocity of relative motion, or the acceleration between the upper and lower loops on either side of the loop, and then calculating their distance (or velocity or acceleration) is This measurement mode is believed to have the highest sensitivity.

As an alternative embodiment to the difference measurement, the sensor 4 in FIG.
The difference in the measured phase angle θ at a given signal level can be used for the position, velocity or acceleration signals generated by the 6,48. Assuming that the speed sensor is used, F _mass from the following equation by computing electronic device for
Is calculated.

Where Δθ is the phase angle difference between the outputs of the two speed sensors, W _C is the actual natural frequency of the mode excited by the Coriolis force (Coriolis mode), which corresponds to the theoretical value W _th in equation (3), and z _C is the actual damping coefficient for the Coriolis mode ((4 ) Corresponding to the theoretical value z in the equation).

The difference Δθ in the phase angle, the driving frequency w _D, 46 in Figure 2
And 48, and 76 and 78 in FIG. 4, multiplied by the difference in the waveforms produced by the detectors operating in the left and right positions. See Frederick E. Turman, "Electronic and Radio Engineering," McGraw-Hill, 1955.

Equation (19) differs from the equations proposed and put into practice in the prior art and is more accurate than those equations.

When using the differential phase angle and the drive frequency, it is desirable to drive the device at its natural frequency because the waveform generated by the detector in response to the Coriolis force does not contain harmonics. Similar equations can easily be obtained using position or acceleration sensors.

A well-known conventional device that can detect the difference in phase angle is Dranetz Engineering Laboratori, New Jersey South Plainfied's Dranetz Engineering Laboratories.
es, Inc.) "Precision phase measurement application bandbook (App
lications Handbook of Precision Phase Measuremen
t) ”(1975), and“ Precision Time Interval using an electronic counter (Precision Time Interval)
Measurement Using an Electronic Counter) "Hewlett-Packard Application Note 200-3 (19
74).

Reference is now made to FIG. 7, which details one possible embodiment of a drive of the type shown at 42 in FIG. A permanent magnet 132 is attached to one tube 130 by a separation insulator 131. As indicated by the tube section 134,
A dual coil mechanism 133 is mounted just above the loop.
The dual coil arrangement includes an upper winding 136 and a lower winding 138, which are mechanically attached to each other by a member 140 but electrically isolated from each other. The assembly 133 is installed with respect to the magnet 132 such that an actuating force is applied to the magnet when the winding 136 is energized so that the magnet drives the loop portion 130 relative to the loop portion 132. Movement of the magnet 132 within the lower coil 138 induces a signal in the coil that is proportional to the speed of the magnet relative to the speed at which the coil moves along the axis of the assembly 133. The signal, shown as current i ₁ , is proportional to the speed difference between tubes 130 and 134.
voltage generated in the resistor R ₁ by i ₁ is input to the differential amplifier A _1. This amplifier produces a voltage signal V ₁ which is also proportional to the speed difference.

Its voltage V ₁ is sent through amplifier A ₃ . The output V of that amplifier is subtracted by the analog calculator 142 from the input voltage V ₀ generated by the oscillator 144. The oscillator produces a suitable periodic voltage signal V ₀ having a sinusoidal waveform. The difference V ₀ −V = V ₂ is applied to the amplifier A ₂ . This amplifier produces a drive current i ₂ . The current is the drive coil
A magnetic field is generated when flowing through 136. The magnetic field produces a magnetizing force that acts on the permanent magnet 132 to cause it to oscillate up and down in the winding 136, thereby bringing the loop 130 and the loop 134 together and pulling them apart. To drive.

The purpose of the velocity feedback loop, which includes winding 138 and amplifier A ₁ , is to control the amplitude of the tube vibration to the desired magnitude even when the oscillator is operated at or near the tube natural frequency. Is. Without this velocity feedback or some other means of applying a damping force to the tube, when the oscillation frequency was set to the tube's natural frequency, the tube would be driven to its elastic limit, probably The tube is destroyed.

The behavior of the closed feedback loop shown in FIG. 7 can be approximately described by the following transfer function.

Where K = gain of velocity feedback loop (V / V ₁ ) X = spacing of tubes at points 161 and 165 of FIG. 9, K ₁ is gain coefficient (V ₁ / I _i ), K ₂ is gain coefficient (V I ₂ / V ₂ ), K ₃ is the drive coil 136 and magnet 1 of FIG. 7 per unit current I ₂ .
The force between 32, K ₄ is the magnitude of the current I ₁ per unit speed difference between the drive coil 136 and the permanent magnet 132, s is the sign of the Laplace operator, m is the tube 130, 134 and only the circular part of the loop The mass with the fluid contained in the inside of those tubes containing a, a is the damping constant of the structure for driving motion, and b is the spring constant of the structure for driving motion.

The expression a + K K ₁ K ₂ K ₃ K ₄ indicates that the normally small damping constant “a” was increased in the absence of the velocity feedback loop. By choosing the appropriate gain factor, the damping can be chosen to cause the drive amplitude and velocity signal V ₁ to follow the oscillator signal V ₀ in the desired manner.

Every flow tube shows its own seismic mode with low damping. Of course, artificial damping and control of the drive can be performed as shown in FIG. However, a similar device, such as that shown in FIG. 8, can be used to provide damping without controlling velocity and amplitude. Although such a device is a costly addition to any type of Coriolis flow sensor, it represents a significant improvement over the device shown in the Smith patent.

In this embodiment, permanent magnets 150 are attached to the central roof portion 152 of a dual series loop device driven by actuation assembly 154, as previously described at 133 in FIG. The magnet 150 is arranged for vertical movement within a damping coil 156 that is secured to the base 158 of the device.
A variable load resistor R is connected between the terminals of the coil 156. The current flowing in the resistor R is generated by the current induced in the coil by the movement of the magnet 150 inside the coil 156.
The current is proportional to the speed of movement of the magnet relative to coil 156. The power generated by the movement of the magnet in coil 156 is absorbed by the power consumed in resistor R. Therefore, by selecting the dimensions of the coil, the number of turns, the strength of the permanent magnet, and the value of resistance R, the degree of damping provided by the device can be selected to suit a particular application.

As another embodiment shown in FIG. 9, damping coils 160 and 162 are provided.
Can be physically connected to the speed sensing coils 164, 166 in a dual loop series or parallel device configuration. In this particular embodiment, the velocity sensing coils 164 and 166 are wound in opposite directions and the total induced when both gaps close at the same rate.
The coils are connected in series with each other so that the EMF is zero. The output current generated by the coils 164, 166 in this embodiment is passed through the resistor R to generate a voltage. The voltage is provided to the differential amplifier 168 and the tube section 161.
And 165, 163 and 167 produce an output signal S ₁ proportional to the speed difference of the relative movements. Amplifiers 170 and 172 and potentiometer
P ₁ and P ₂ have a phase shift function to compensate for the phase transition between Coriolis and the associated motion of the flow tube, as mathematically expressed in Eqs. (2) to (8). To do. This compensation is
This is an alternative design feature that is particularly useful for digital signal analysis methods as described by equations (9)-(18). The signal S ₁ is sent through a variable potentiometer P ₁ to generate a proportional voltage. This proportional voltage is
0 is given to one side. At the same time, S ₁ is integrator 1
It is also sent through 70 to generate the corresponding position signal S ₀ .
This signal is sent through a _second potentiometer P ₂ to generate a proportional voltage. This proportional voltage is provided to the other side of amplifier 170. The resulting output signal S ₂
Is described by equation (8). In equation (8), the coefficient K ₁ and
K ₂ corresponds to the settings of potentiometers P ₁ and P ₂ , respectively.

In this embodiment, position information can be obtained by integrating the velocity (and, if an acceleration sensor is used, by integrating the acceleration twice), and as shown in FIG. It can be calculated by integration of the speed difference (or twice integration of the acceleration difference). For measurement, velocity data is equivalent to position information. Since the amplitude analysis is performed during many cycles of the periodic excitation of the loop for each measurement point of the mass flow rate, the effect of the initial conditions associated with the integration disappears rapidly.

In the illustrated embodiment, as previously mentioned, the tube section 16
The parallel movement of 5 to 167 produces a reverse current through resistor R, resulting in a net voltage drop across resistor R of zero. Under the influence of the flow in the pipe, parts 165 and 167
The Coriolis force generated therein moves the tube sections relatively in reverse, causing a net current generated from the sum of the induced voltages in the sensing coils 164,166 to flow through resistor R. As mentioned above, the voltage generated across the terminals of the resistor R is applied to the differential amplifier 168, the output of which is integrated by 172 for relative movement between tubes 161 and 165 and between tubes 163 and 167. The signal S ₁ representing the speed difference of is converted into the separation difference signal S ₀ .

FIG. 10 shows the relationship of steady-state signals with sinusoidal velocities. More specifically, in part (a) of FIG. 10, the drive position of the tube portion 130 is shown by the solid line 174 and the corresponding velocity curve is shown by the broken line 175. You will see that the velocity is a derivative of the driving motion, so it is 90 degrees out of phase with it. Assuming that there is no flow in the illustrated tubes, the locations of tube sections 165 and 167 are
It will be seen that it is in phase with the 130 position. Their positions are the drive component curves 176 in the part (c) of FIG.
In the portion (b), the drive component curve 177 is shown. Similarly, it will be appreciated that the Coriolis-induced bias is approximately in phase with the velocity component of the drive motion, and is positive for tube section 167 and negative for tube section 165. Therefore, by adding the Coriolis component and the drive component, a Coriolis-induced positional displacement of the tube portions 176 and 165 can be obtained. Those displacements are indicated by the waveforms 178 and 179 shown in portions (b) and (c), respectively.

In part (d), the position difference between curves 165 and 167 is shown as 180, but there is no visible phase delay between drive speed and Coriolis force. In practice, depending on the drive, the "Coriolis mode", the natural frequency ratio, and the damping,
It will be seen that there is a small phase delay of 1 degree. Curve 181 shows this exaggeratedly. Also note that the size of the Coriolis component 178 or 179 is very small compared to the drive components 171,176, and that FIG. 10 shows exaggerated dimensions of the Coriolis component for ease of illustration.

For effective signal analysis using digital sampling of drive speed and Coriolis force response, it is desirable to synchronize the signals. By appropriately selecting the settings of the potentiometers P ₁ and P _{2 in} the circuit of FIG. 9, the signal S ₂ is made to be substantially in phase with the drive speed signal.
Appropriate compensation can be provided.

To increase the sensitivity of the device described above, 1
One possible modification is to stretch the part of the loop that receives the Coriolis force. Such extension is shown in FIGS. 11 and 12 with the sides 182 and 183 of the loop lengthened. However, this can result in two potential problems: "wobble" and "roll." FIG. 11 shows that when the loop is actuated, the lengthened portion of the tube bends vertically as indicated by the dashed line 184, causing vertical swaying. One solution to strengthening the sides 182 to eliminate the problem of rocking up and down is to add a stiffener 185 to each side 182 so that the sides no longer bend freely.
It is to be attached to.

The second problem that occurs with such a modification, the roll problem, is illustrated by the dashed line 186 in FIG. In this situation, in the plane of the loop 182 the loop is bent to the left or to the right (parallel to the XY plane), ie it is actually “rolled”. In order to eliminate this tendency,
A roll restraint arm as shown at 187 and 188 can be utilized. The restraining arms can consist of rigid or semi-rigid rods or bars that are welded directly to either end of the tube. However, since the property of restraint applied is tension, the members can also consist of flexible cables. It will also be appreciated that a combination of the two solutions shown in FIGS. 11 and 12 can be used to avoid deformation due to vertical and lateral wobbling.

FIG. 13 shows another detector that can utilize an optical fiber sensor instead of using electromagnetic detection means to detect relative movement between adjacent tube sections or between the tube section and the base. ing. In this case, the optical fiber bundle 190 is attached to the upper tube 192, and the reflector 195 is attached to the lower tube 194 (or base). The optical fiber sensor device 196 then causes the light beam to pass through a portion of the light flux 190. The light beam is reflected by surface 195 and returned to sensor 196 through another portion of bundle 190 for position sensing. It will be appreciated that any other suitable device may be used in accordance with the present invention to detect relative position information, relative velocity information or relative acceleration information.

The inclusion of density measurements as part of the present invention
As shown in the figure. For simplicity, the Coriolis measuring device is not shown in this figure. This density measuring device is a tube
This is due to the fact that the centrifugal force acting on each element of the fluid flowing through the looped section 202 of 200 is perpendicular to the tube section containing the element from the center of curvature of that element. Because the loops are relatively flat, centrifugal forces on the elements do not depart significantly from the paper surface on which they are drawn. Therefore, its centrifugal force is inversely proportional to the radius of curvature of the element, proportional to the mass in the element, and proportional to the square of the fluid velocity. Further, the centrifugal force acting on the exit half 204 of the loop causes a pull to the left at point 205, and the force applied to the entrance half 206 causes a pull to the right at point 205. Therefore, the opposite force at 205 causes a strain in the material associated with the collection of centrifugal forces applied to the entire test section. Since the Coriolis force does not cause any strain at point 205, the strain at that point 204 can be measured using a simple strain gauge 208. Strain gage measurements taken anywhere along the loop will provide information that allows density measurements to be made along with Coriolis mass flow measurements, although the calibration relationship is more complex.

In the configuration shown, the ratio of the total centrifugal force on the semicircle 204 acting horizontally at point 205 to the total Coriolis force acting on the same semicircle is directly proportional to the velocity of the substance in the fluid and It is independent of all characteristics.

The density of the material in the conduit is directly proportional to the square of the measured mass flow rate divided by the centrifugal force acting on the half loop. A circuit which makes it possible to obtain such information is shown in FIG. This circuit consists of drive signal V ₁ (from FIG. 7) and signal S ₂ (from FIG. 9) and strain gauge signal C.
Means 210 for sampling (from FIG. 14), means 212 for calculating the mass flow rate F _mass from the sampled signals V ₁ and S _1, and means 214 for calculating the centrifugal force P _centr from the strain gauge signal C And means 216 for calculating the density from the mass flow rate and the centrifugal force.

Although the present invention has been described with reference to the several embodiments illustrated in the drawings, it is understood that the embodiments are presented only for the purpose of illustration and not to limit the present invention. Should be. It is intended that the appended claims cover all embodiments, changes and modifications that fall within the true scope of the invention.

Claims (20)

[Claims] 1. A tubular conduit means for receiving, passing through and discharging a flow of material, comprising at least one loop, an inlet portion, an outlet portion intersecting the inlet portion at a distance, and a drive. A driven part for receiving the first detected part between the driven part and the inlet part, and a second detected part between the driven part and the outlet part. The portion and the outlet are configured so that the direction of the flow of the substance flowing into the inlet is the same as the direction of the flow of the substance flowing out from the outlet, and the natural frequency W _C in Coriolis mode And different from this W _C , tubular conduit means having a natural frequency W _D in the drive mode, and drive means for vibrating the driven part about its rest position, Coupled to said tubular conduit means, Damping means for selectively adjusting the extinction coefficient; and the inlet portion derived from the Coriolis force generated in the first and second detection portions when the driven portion is vibrated by the driving means. And detection means for detecting a difference in movement between the outlet and the outlet portion, and calculation / instruction means responsive to the detection means for indicating the mass flow rate of the substance flowing through the tubular conduit means. Also, a flow meter that measures the mass flow rate in the flow of matter. 2. A flowmeter according to claim 1, wherein:
The detection means detects a dynamic position of the first detection part with respect to a reference member to generate a first position signal, and a movement of the second detection part with respect to the reference member. Second position signal for detecting a desired position and generating a second position signal
And a sensor means, and the calculation / instruction means includes the first
And a flow meter that utilizes a difference in the second position signal to indicate a mass flow rate of a substance through the tubular conduit means. 3. A flowmeter according to claim 2, wherein:
The first sensor means is magnetically coupled to the first magnetic element attached to the reference member and to the first magnetic element, but is attached to the first detection unit to provide the first sensor element. A magnetic signal generator having a second magnetic element that moves relative to the magnetic element of. 4. A flowmeter according to claim 1, 2 or 3 wherein said tubular conduit means is two equal loops, one outlet of which is the other. Flowmeter, comprising two loops connected to the inlets of the two and connected in series with each other, and said damping means is connected between the connection point of the two loops and the reference member. 5. A flowmeter according to claim 4, wherein:
The damping means is magnetically coupled to the first magnetic component attached to the reference member and to the first magnetic component, and is attached to the coupling point to the first magnetic element. A magnetic signal generator having a second magnetic component moving with respect to the first magnetic component, wherein the damping means is further connected to the first magnetic component and consumes the power induced in the first magnetic component. A flow meter including load resistance means. 6. A flowmeter according to claim 1, wherein:
The tubular conduit means has two loops connected in two loops to form parallel flow paths, each corresponding portion being spaced and parallel.
The driving means is a flowmeter which is coupled between the driven parts of the loops and simultaneously applies a force acting in the opposite direction to the loops at the same time. 7. A flowmeter according to claim 6, wherein:
The detection means includes a first detection unit coupled to the first detection unit of the one loop and a first detection unit of the other loop.
Sensor and second sensor means coupled between the second detector of the one loop and the second detector of the other loop, the first and second sensors thereof A flow meter, the means generating an output signal indicative of movement between corresponding portions of each of the one and the other loops. 8. A flowmeter according to claim 7, wherein:
Each of the first and second sensors includes a pair of coaxially arranged electromagnetic windings and a permanent magnet element electromagnetically coupled to the pair of electromagnetic windings, the pair of electromagnetic windings being fixed to one loop, A magnet element is fixed to the other loop, and one of the pair of electromagnetic windings is arranged so as to consume the electric power induced in one of the pair of electromagnetic windings by the movement of the permanent magnet element with respect to the pair of electromagnetic windings. A flowmeter, wherein connected resistive impedance means is provided, and an electromagnetic winding of the pair of electromagnetic windings that is not connected to the resistive impedance means is connected to the calculation / indication means. 9. A flowmeter according to claim 1, wherein:
A flow meter, wherein said tubular conduit means comprises at least two such loops, the outlet of one loop being connected to the inlet of the other loop to provide a serial flow path for the flow of material. 10. The flowmeter according to claim 7, wherein the first and second sensor means are speed sensors, and the calculation / instruction means calculates Δθ from the first and second values. The phase angle difference of the output signals generated by the sensor means, K is a constant, Where W _D is the natural frequency of the tubular conduit means in the drive mode, W _C is the actual natural frequency of the tubular conduit means in Coriolis mode, and Z _C is the actual damping coefficient for the Coriolis mode. A flow meter that calculates the mass flow rate Fmass according to. 11. The flowmeter according to claim 7, wherein the output generated by the first and second sensor means is supplied to a first differential amplifier included in the calculation / instruction means. The speed difference signal that is input and is generated by the first differential amplifier is input to the second differential amplifier first input terminal and the integrator included in the calculation / instructing means, and is generated by the integrator. The separated differential signal is input to the second input terminal of the second differential amplifier, whereby the second differential amplifier corresponds to the net value of the Coriolis force detected by the detection means. A flow meter that produces an output. 12. A flowmeter according to claim 6 or 9, wherein said drive means is coupled to said one loop and has a pair of coaxially arranged electromagnetic windings, and the pair of electromagnetic windings. A permanent magnet element magnetically coupled to the pair of electromagnetic windings and fixed to the other loop, wherein one of the pair of electromagnetic windings receives a driving current and the permanent magnet element is coupled to the other loop together with the other loop. Electromagnetically driven to the loop, the movement of the permanent magnet element with respect to the other of the pair of electromagnetic windings,
A flow meter in which a velocity feedback current proportional to the velocity of the other loop relative to the one loop is induced in the other of the pair of electromagnetic windings. 13. The flowmeter according to claim 12, wherein the driving means includes a periodic voltage source, a means for generating a feedback voltage in response to the feedback current, the periodic voltage and the feedback. Means for generating a drive voltage in response to the voltage,
Means for generating the drive current in response to the drive voltage. 14. A flowmeter according to claim 1, wherein the tubular conduit means are generally parallel to each other and each of the elongated legs constitutes the first detection part and the second detection part. A flowmeter having a section and each of these legs has a reinforcing means to prevent bending in a direction perpendicular to the plane containing them. 15. The flowmeter according to claim 1, wherein the tubular conduit means comprises elongated legs that respectively constitute the first detection unit and the second detection unit, and these legs. A first roll restraint member that connects one of the two to the inlet,
A flowmeter having a second roll restraining member that connects the other of the legs and the outlet, and prevents the loop from being distorted in the plane formed by the elongated legs. 16. A flowmeter according to claim 1, wherein said tubular conduit means is provided with strain gauge means for producing a strain signal proportional to the centrifugal force generated in the loop by the flow of the substance. The calculation / instruction means is responsive to the distortion signal,
A flow meter that uses the strain signal along with the obtained mass flow rate to indicate the density of material flowing into the tubular conduit means. 17. The flowmeter according to claim 1, wherein the detection means detects a change in a gap between the inlet portion and the outlet portion at a position where the inlet portion and the outlet portion intersect with each other. Total. 18. The flowmeter according to claim 17, wherein the difference in the movement is based on a predetermined reference value of arrival times of velocity signals corresponding to respective movements of the inlet portion and the outlet portion. The difference is the flow meter. 19. A pair of tubular conduit means for receiving, passing through and discharging a flow of material to form parallel flow paths through the loops, each loop having an inlet section and a distance from the inlet section. An exit portion that intersects with the driven portion, a driven portion that receives a drive, a first detection portion between the driven portion and the inlet portion, and a second detection portion between the driven portion and the outlet portion. And the inlet part and the outlet part are configured such that the direction of the flow of the substance flowing into the inlet part and the direction of the flow of the substance flowing out from the outlet part are the same, The driven portion is relatively close to the tubular conduit means having a natural frequency W _C in the Coriolis mode and a natural frequency W _D in the drive mode that is different from this W _C. Drive means for vibrating so that the A difference in motion between the inlet portion and the outlet portion caused by the Coriolis force generated in the first and second detecting portions when the driven portion is vibrated by the means. A flow meter for measuring a mass flow rate in a flow of a substance, comprising: a detection unit that operates in response to the detection unit; 20. The flowmeter according to claim 19, wherein the detection means is a speed sensor, and the calculation / instruction means generates Δθ by the first and second sensor means. Output signal phase angle difference, K is a constant, Where W _D is the natural frequency of the tubular conduit means in the drive mode, W _C is the actual natural frequency of the tubular conduit means in Coriolis mode, and Z _C is the actual damping coefficient for the Coriolis mode. A flow meter that calculates the mass flow rate Fmass according to.