JPS6148722A - Mass flow meter - Google Patents

Abstract

PURPOSE:To obtain high sensitivity and a large S/N and measure a large flow rate by flowing a current in the tangential direction of a disk or cylindrical resonator which oscillates symmetrically about an axis, and driving the resonator by a driving means so that the sum of squares of signals from detecting means is constant. CONSTITUTION:A conduit 6 is formed of flange parts 4 and 5 on both flanks of an external cylinder 2 and driving means D1 and D2 such as an electromagnet are provided inside the resonator 3 at an angle of 45 deg. to the center axis at a distance lambda/4 of the wavelength of oscillation. Detecting means P1 and P2 are provided at the opposite sides of the means D1 and D2 and a partition wall 7 form a fluid intake E and a fluid outlet F with leg parts 8 and 9. Grains of fluid from the intake E move while oscillating in the tangential direction of the resonator 3 and a progressive wave is generated at the resonator 3 to control the means D1 and D2 so that the sum of squares of signals of the means P1 and P2 is constant. Opposite-phase outputs are obtained by the means P1 and P2 and a comparison output is inverted every time the progressive wave travels by a half wavelength. Consequently, pulses proportional to mass are generated.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an improvement in a mass flow meter that utilizes the Coriolis force.

<Conventional Example> FIG. 8 is a configuration explanatory diagram for explaining the operating principle of a Coriolis flowmeter. Reference numeral 1 denotes a U-shaped tube through which a measuring fluid flows, a permanent magnet 2 is fixed at the center of the tip thereof, and both ends of the U-shaped tube 10 are fixed to a base 3. 4 is the electromagnetic 1 stationary/detection coil installed opposite the U-shaped tube 1, 5 is a support beam that supports this electromagnetic drive/detection coil at its tip, and the oil leak is fixed to the base 3. . The U-shaped tube 1 and the support beam 5 mutually form a tuning fork groove structure. That is, U
The tube 1 and the beam 5 vibrate opposite each other, just like the teeth of a tuning fork vibrate, and like a tuning fork, the base 3 serves as a nodal point of vibration, so that less vibrational energy is lost. . 61 and 62 are displacement detectors for detecting the displacement of both legs of the U-shaped tube 1.

When the U-shaped tube 1 is excited at its natural frequency by the electromagnetic force acting between the drive coil 4 and the permanent magnet 2 fixed to the opposing U-shaped tube 1 (longitudinal imaging (symmetrical flexural vibration): Figure 9 (
, ) Ml, M2. M5 indicates a pattern at each moment), a Coriolis force is generated in the fluid flowing inside the U-shaped tube 1. The size of this Coriolis is proportional to the mass of the fluid flowing inside the U-shaped tube 1 and its velocity (((), and the direction of the force corresponds to the direction of the movement of the fluid and the direction of the angular velocity vector that excites the U-shaped tube 1. Furthermore, since the direction of the fluid is reversed on the input side and output side of the U-shaped tube 1, torsional torque (asymmetrical deflection) is generated in the U-shaped tube 1 due to the Coriolis on both leg sides.

This torque changes with the same frequency as the excitation frequency, and its amplitude value is proportional to the fluid mass flow ff1K. Figure 9 (b
) indicates the vibration mode (Coriolis vibration mode) caused by this torsional torque, and M4. M5° and M6 indicate the vibration pattern at each moment. Therefore, the amplitude of this torsional vibration (asymmetrical flexural vibration) and torque can be measured using a displacement detector (
(not shown), the mass flow rate can be determined by detecting the pulse width, for example.

A mass flow meter using the above-mentioned principle has been known for some time (for example, Japanese Patent Application Laid-Open No. 54-52570), but this method has the following problems. That is, Coriolis flowmeters generally have low sensitivity, have problems in terms of S/N ratio, ease of signal processing, etc., and have drawbacks such as difficulty in measuring large flow rates.

<Object of the invention> The present invention has been made in view of the drawbacks of the above-mentioned prior art.
The purpose of the present invention is to provide a vibrating mass flowmeter that has a high sensitivity of 9 degrees, a large SA ratio, easy signal processing, and can measure large flow rates.

<Configuration of the Invention> The configuration of the present invention that achieves this object includes a disc or cylindrical resonator that vibrates axially symmetrically, a conduit through which a fluid flows in the tangential direction of the resonator, and a vibration of the resonator. 1/ for the wavelength of
At least two sets of drive and detection means provided at a distance of 4λ, and an excitation circuit that drives the drive means so that the sum of squares of signals from the detection means is constant. 0 <Example> Figure 1 (a), (b), and (c) show an example of the present invention, and Figure 1 (,) shows an example of the present invention. FIG. 1(b) is a sectional view taken along line A in FIG. 1(a), and FIG. 1(C) is a sectional view taken along line BB in FIG. 1(b). In Figures 1 (Todoroki) and (b) + (c), 2 is an outer cylinder, 3 is a cylindrical resonator, and 7 flange parts 4.5 on both sides of the outer cylinder 2 form a conduit 6. are doing. Dl and D2 are drive means (two in this embodiment) such as electromagnets that drive the resonator 3.
(In this example, in order to generate the strongest secondary mode wave on the vibrator s, the position at the 45° angle is the position of the vibration wave. Reference numeral 7 denotes a partition wall, and leg portions 8.9 form a fluid population E and a fluid outlet F. Note that the drive means D1, D2, the detection means p, , p2, and the partition wall 7 are slightly separated from the resonator 6. Particularly, the partition wall 7 is provided in a non-contact state.
is a gap within an error range even if the fluid flowing in from the inlet E bypasses and flows between the partition wall and the resonator.

FIG. 2 shows an excitation circuit that drives the detectors p, . . . p2 so that the sum of squares of the signals is constant. In FIG. 2, one driving means D1. 10°+Oa so that D2 oscillates with positive feedback.
Amplifier gain and filter 11. Set the phase of Ha. Drive means D1. The output of D2 is rectifier 12°12
rectified by squarer 13.a. 13a, its output is compared with the voltage of the reference voltage 14, the difference is amplified by the amplifier 15, and the multiplier 16. 16a detecting means P1. It is multiplied by the output of P2 and provides negative feedback.

17 is the detector P1. This is a phase comparator that outputs outputs with different phases from P2 as pulse outputs. This excitation circuit provides a driving means.1. The sum of squares of the amplitude of D2 is controlled to be constant, and the standing wave generated on the cylinder can stand at any position on the cylinder.

Now, when fluid is caused to flow from the inlet E of the mass flowmeter 1 shown in FIG. 1(c), the particles of the fluid move in the tangential direction of the resonator 3 while vibrating. At this time, driving means D1. Coriolis is generated by the flow of fluid particles in the resonator 5 vibrating in the secondary mode due to D2, and a traveling wave is generated. Figure 3 (,) shows the motion of the joint due to Coriolika.
Shown in (b). Figure 3 (&) shows that the resonator 3 is θ in the vertical axis direction.
FIG. 3(b) shows the state of vibration on the circumference of the resonator 3 using a sine wave. Node θ2. In this case, the resonator 3 and surrounding fluid particles are in oral motion at an angular velocity Ω. This angular velocity Ω is expressed by the following equation.

Ω=upper ωeos QIt Here, a = amplitude of the resonator t = turning radius ω = cylinder angular frequency It is.

On the other hand, the fluid particle passes through the node θ1 with a momentum of mv. At this time, the following Coriolis force is generated.

Fc=20 mv This Coriolis force causes the node θ1 to be displaced inside the resonator 5. On the other hand, at the node θ, the same phenomenon as the node θ occurs, but since the direction of Ω is different, the node θ2 is displaced to the outside of the resonator 2. Therefore, the node θ1. θ2 is no longer a node, and a new node θ', 02' is generated. As this motion continues, a traveling wave is generated on the resonator 3. Therefore, the detection means provided at an angle of 45° detects an output whose phase is reversed, and the output of the phase comparator 17 in FIG. A proportional pulse output can be obtained.

Figures 4 to 7 all show other embodiments.
Figures (a) and (b) show the above-mentioned cylindrical resonator 3 provided in a conduit 201C. FIG. 4(a) is a partial sectional view taken along the vertical axis of the conduit 20, and FIG. 4(+) is a sectional view taken along line HH in FIG. 4(a). Figure 4(a),
In (b), 21 is an outer cylinder provided at the bottom of the conduit 20, and the 7 flange parts 22.23 allow the υ resonator 3 to be placed perpendicular to the conduit 20 and below the axis of the conduit 20. The resonator 3 is held so that its outer periphery is positioned. D4. D2. P
, , P2 are driving and detecting means similar to those in FIG.

In the above configuration, the fluid flows in the pipe line 20 in the direction of the arrow.
When passing the outer circumference of the resonator 3 with a momentum of v, the third
Coriolis force corresponding to the momentum of mv is generated in the same way as explained in FIGS. (a) and (b), and a traveling wave is generated on the oscillator s. According to the above configuration, an ljt flow meter with a large flow rate can be realized compared to the configuration shown in FIG.

In Figures 5(a) and (b), the resonator is formed as a disk! It is. 5(,) is a partial sectional view taken along the vertical axis of the conduit 20, and FIG. 5(b) is a sectional view taken along line II in FIG. 5(,). In FIGS. 5(a) and 5(b), 32 is an outer cylinder provided at the bottom of the conduit 20, and the outer cylinder 32 has a circular resonator 30 located at the center of the conduit 20. The outer circumferential portion of the plate is held so as to be located below the axis of the conduit 20, and the inner side thereof is formed to have a width that does not come into contact with the resonator. Drive means D1 in this example. D2 and detection means P1. P2 is embedded in the outer cylinder 52 side and is provided at an angle of 45° with respect to the axis of the resonator 30, for example. FIGS. 6(a), (b), and (C) are diagrams for explaining the state of vibration of this resonator 50. FIG. Fifth
When a fluid flows through the pipe 20 shown in the figure with a momentum of mv,
The disk-shaped resonator 30 shown in FIG. 6(a) is distorted due to Coriolis, for example, with 0 parts and 0 parts distorted toward the front side and 0 parts and 0 parts distorted toward the back side. This state of distortion becomes larger on the outer circumferential side as shown by the dotted line in section 6 (b). FIG. 6(c) shows the state of the surface near the outer periphery of the resonator as a sine wave, and this wave moves in accordance with the momentum mv and generates a traveling wave. The mass flowmeter with the above configuration is compared to the one in Figure 4,
It is possible to achieve something with less pressure loss.

7(a) and 7(b) show a resonator in which a spiral conduit 55 is formed, and FIG. 7(,) is a partial cross-sectional side view showing the overall configuration, and ) is a cross-sectional view showing a state in which the pipe line 55 of the resonator is cut into rings. In Fig. 7(,), the arc is a resonator, and this resonance preset is shown in Fig. 6(b).
A spiral pipe 55 is provided on one side as shown in FIG.
It is formed by sandwiching the partition plate 42 between two plates 41 and 41a in a square shape. Support plates 45 and 44 are provided with a plurality of spacers 47 in between, and inlet nozzles 45 and 44 are provided in the center of each of them. An outlet nozzle 46 is provided and supports a resonant pre-arrangement in the middle part of the support plate 45.44. D1
1D2. Pl and P2 are driving and detecting means comparable to a resonator, and are fixed to the support plate 44 at a position 45'' apart from the axis of the resonator and slightly away from the side surface of the resonator.

In the above configuration, when the fluid flows in from the inlet nozzle 45, the fluid reaches the central part 481C of one of the thinly wound plates 41 forming the resonator, flows in the direction of arrow A (see Fig. 7), and goes around the pipe. After that, the liquid flows to the outermost pipe by the partition wall 49 as shown by the arrow, and reaches the outermost pipe. Reference numeral 50 indicates the position of a through hole provided in the partition plate 42, and fluid flows through this through hole 50 into the spiral 41a, and the fluid flows through the through hole 50 into the spiral 41a.
The flow exits the outlet nozzle 46 inwardly in the same direction as the flow direction. The above-mentioned mass flowmeter of 1"4 can have higher sensitivity than other embodiments. In this embodiment, an electromagnet and a pick-off coil were used as the drive and detection means, but other In addition, the driving and detecting means may be used in other vibration modes instead of the secondary vibration mode.In that case, the driving and detecting means may be placed at a position of 45° with respect to the axis of the resonator. In this embodiment, the driving and detecting means are described as two sets, but the number is not limited to two sets.

<Effects of the Invention> As specifically explained above in conjunction with the embodiments, according to the present invention, fluid is caused to flow in the tangential direction of the resonator, and the sum of squares of the signals from the resonator is constant. Since the drive means is driven in this way and the output is obtained as a frequency signal, the mass flow rate is highly sensitive, has a large S/N ratio, is easy to process signals, and can measure from large flow rates to small flow rates. can be realized.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram illustrating an embodiment of the present invention, Fig. 2 is an explanatory diagram showing a drive and detection circuit, Fig. 3 is an explanatory diagram showing a state in which a traveling wave is generated by Coriolika, and Fig. 4 7 to 7 are explanatory diagrams showing other embodiments, and FIGS. 8 and 9 (, ), (b) are explanatory diagrams showing a conventional example. 1...Mass flow meter, 2...Outer cylinder, 3, 50, 4
0... Resonator, 4, 5... Flange, 6, 20
, 55... Pipe line, D11D2... Drive means, Pl,
P2...Detection means. −? -1 / Figure 1 (a) l (b) Figure 2 Figure 4 ((1"I Figure 5 (α) Figure 7 (a) Figure 8 Figure 9 (b)

Claims (1)

[Scope of Claims] (1) a disc or cylindrical resonator that vibrates axially symmetrically; (2) a conduit through which fluid flows in the tangential direction of the resonator; (3)
) at least two sets of drive and detection means provided near the inner or outer circumference of the resonator at a distance of 1/4λ with respect to the wavelength of vibration; (4) the sum of squares of signals from the detection means; 1. A mass flowmeter comprising: an excitation circuit that drives the driving means so that the current is constant.