JPS61283827A - Mass flowmeter - Google Patents

Abstract

PURPOSE:To increase measuring accuracy by a simple construction by giving a curved conduit a torsional oscillation that is stable against an external oscillation and controlling the amplitude of the curved conduit to an always constant value regardless of a flow rate. CONSTITUTION:A curved conduit 1 comprising a tubular body which has inlet outlet openings 2 and 3, respectively, both for a fluid to be measured and is symmetric with respect to a first axis XX' is fixedly connected to a support member 4 and constructed so as to be rotatable about a second axis YY'. Magnets 51 and 61 are provided in positions C and D, respectively, and, opposing to these magnets, electromagnetic coils 5 and 6 excited by AC currents with phases different from each other by 180 deg. are provided. When AC current flows through the coils 5 and 6, these coils 5 and 6 are alternately attracted and repulsed by the magnets 51 and 61, respectively, and the curved conduit 1 torsionally oscillates about the first axis XX' with a natural frequency omegato produce a Coriolis force in a Z direction, vertically oscillating with another natural frequency. The amplitudes of these oscillations are detected by amplitude detectors 7-1 and 7-2 and controlled to constant values through a phase-shifting circuit 102, a rectifier 104 and the like. The quantity of the control is indicated by an indicator 105 as the Coriolis force, that is, a mass flow rate.

Description

DETAILED DESCRIPTION OF THE INVENTION 1) Industrial Application Field The present invention relates to a mass flowmeter that utilizes the Coriolis force.

2) Conventional technology When vibration is applied to the fluid flow flowing through the flow tube.

It is known that a Coriolis force is generated in a direction perpendicular to the direction of the fluid flow and the vibration axis of the flow tube, and that this Coriolis force is proportional to the vibration frequency and the mass flow rate of the fluid.
It is disclosed in Japanese Patent Application Laid-Open No. 54-52570. This conventional example has a main body shape in which a curved conduit having an inlet and an outlet is fixed to a support member, and fluid flows from the inlet through the curved pipe and flows out from the outlet. When a curved conduit is vibrated in a direction perpendicular to the conduit surface (the surface on which the conduit is made) about the supporting part fixing line (the line connecting the supporting part where the inlet and outlet are supported) as an axis, the curved conduit becomes curved. A Coriolis force acts on the fluid flowing through it, producing torsional vibrations proportional to the Coriolis force about an axis perpendicular to the anchor line. This Coriolis force is determined from the time difference between each bowl portion of the curved conduit passing through the reference surface. How to excite a curved conduit.

The curved conduit and the reciprocating member having the same natural frequency are made to vibrate in opposite phases about the fixed line as an axis.

3) Problems to be Solved by the Invention In the conventional example described above, the Coriolis force is detected as the amount of twist of the curved conduit, and as a result, vertical vibrations are applied to the conduit surface of the curved conduit.

In order to reduce the excitation energy, it is necessary to increase the arm length between the excitation part of the curved conduit and the support member.

Therefore, it is easily affected by external vibrations.

Additionally, adding a reciprocating member has problems such as the fact that the natural frequency of the reciprocating member is a fixed value, even though the actual natural frequency changes due to density differences due to differences in the fluid to be measured. was there.

4) Means for solving the problem In order to solve the above-mentioned problems, the present invention selects the excitation axis as an axis of symmetry perpendicular to the fixed line of the curved conduit, and achieves stable torsion against external vibrations. By applying vibration and controlling the amplitude of the curved conduit caused by this torsional vibration to be constant regardless of the flow rate, it can be confirmed that this controlled amount is proportional to the magnitude of the Coriolis force, that is, the mass flow rate. Take advantage of it.

The present invention provides a simple and stable mass flow meter.

5) Embodiment FIG. 1 is an explanatory diagram of the present invention. The curved conduit 1 is a symmetrical curved tube with respect to the first axis XX', and has an inlet 2 and an outlet 3 for the measurement fluid.

It is penetrated and fixed to the support member 4 near the opening.

The support member 4 supports the curved conduit 1 and has fixed parts A and B.
The curved conduit 1 is rotatable around a second axis indicated by a line YY' connecting the curved conduit 1. Fixed part A of the curved conduit,
Magnets 51 and 61 are fixed at positions C9D at equal intervals from B, respectively. Opposing the magnets 51 and 61, electromagnetic coils 5 (coil 2) and 6 (coil 2) are fixed to a stationary surface (not shown), respectively. The electromagnetic coil 5.6
is excited by an alternating current having a frequency equal to the natural frequency around the first axis XX' of the curved conduit l, which will be described later, and whose phase differs by 1800, and repeats attraction and repulsion against the magnets 51 and 61. Since the alternating currents differ by 180 degrees, magnet 5
1 is attracted, the magnet 61 is repelled, so that the curved conduit 1 torsionally vibrates around the first axis XX' at a natural frequency ω.

If the rotation about the '1st axis xx't is now in the direction of the arrow ω, a Coriolis force proportional to the mass flow rate of the fluid will occur in the Z direction. On the other hand, the Coriolis force in the direction of τ is −Z
occurs in the direction of That is, when the rotational vibration around the first axis is one cycle, the point P on the xx' axis of the curved conduit 1 makes one reciprocation. That is, it vibrates vertically with its natural frequency. The amplitude due to the vertical vibration due to the Coriolis force is added to the amplitude at the 0 point and the D point when the fluid is at rest. This amplitude is detected by extracting the in-phase signal from an amplitude detector 7-1, 7-2, such as a differential transformer. Detection of light, etc. other than a differential transformer may be used, and an electromagnetic speed conversion type detector may be used. The signal of this amplitude detector 7 is transmitted to the phase shift circuit 101 of FIG.
The phase shift circuit 102 shifts the phase of the electromagnetic coil f[6 by 180° via the amplifier 103, and is fed back and controlled so that the electromagnetic coil f[6 is excited. On the other hand, the amplitude signal amplification output is rectified by the rectifier 104 and fed back negatively to the amplifier 103, so that the amplitude is controlled to be constant. This control amount is the indicator 105
will be instructed. This indicated quantity indicates the Coriolis force, ie, the mass flow rate.

FIG. 2 is an explanatory view of another embodiment of the present invention, in which curved conduits 200 having the same shape and size as the above-mentioned curved conduit 1 are arranged parallel to each other on the conduit surface, and each opening is fixed to the flow tube 8. Fixation points A+B+ and Az B of curved conduit 1 +' 200, respectively
t forms a second axis Y, Y,' and Yz Yz';
The curved conduit 1.200 is made rotatable about the axis.

Inside the flow tube 8, a curved conduit 1.200 mm is formed by partition plates 9 and 10.
Similarly to the case shown in FIG.
It is fixed at point t. The electromagnetic coil 5.6 is fixed at the Cz and Dt positions of the curved conduit 200 corresponding to the C1 and Dr points.

The excitation currents of these electromagnetic coils have a phase difference of 180°. When there is a flow in the direction of the arrow in the curved conduit 1, 200, the torsional vibration between the curved conduits 1 and 200 is attracted at C1°Ct point and repelled at D, , D, then the curved conduit 1 is x, x,'
For curved conduit 200, the rotation is about ω about the first axis of . The Coriolis force caused by this vibration causes the curved conduit 1 to be displaced in the Z direction, and the curved conduit 200 to be displaced in the -Z direction, thereby causing the curved conduit 200 to move away from each other. If the vibration is opposite, it will be attracted.

This amount of displacement is twice that of the single conduit shown in Figure 1, and S
/N ratio is improved. This displacement is added to the displacement due to torsional vibration, so this displacement is detected by the amplitude detector 7-1.7-2.
The mass flow rate can be detected by extracting the in-phase signal, and the mass flow rate can be indicated by the control method shown in FIG. 3, as in the case of FIG.

FIG. 4 shows yet another embodiment of the invention.

So to speak, the amplitude detector 7-1 in the embodiment shown in FIG.
7-2 are combined into one and placed at point P shown in FIG. The vibration component at point P shown in FIG. 1 has a form in which there is substantially no component based on the above-mentioned torsional vibration. For this purpose, the in-phase components of the respective detection signals of the amplitude detectors 7-1 and 7-2 were extracted in the case of the embodiment shown in FIG. 1, but signal processing for this purpose is no longer necessary. .

FIG. 5 is a block diagram showing the principle of driving and directing the main body shown in FIG. 4, and has the same functions as shown in FIG. 3. In the case shown in FIG. 5, the optical/resistance conversion element 206
The instruction by the indicator/meter 207 is read while the vibration at the point P is controlled to have a constant amplitude.

6) Effect According to the present invention, the S/N ratio is excellent because the teardrop drive is hardly affected by external vibrations, and the mass flow rate is highly accurate because the measurement is performed using the zero position method. The meter can be provided in the simplest configuration at a low cost.

[Brief explanation of the drawing]

FIG. 1 is an embodiment of the present invention, FIGS. 2 and 4 are other embodiments, and FIG. 3 is a block diagram showing the principle of driving and directing the main body shown in FIGS. 1 and 2, FIG. 5 is a block diagram showing the principle of driving and directing the main body shown in FIG. 4. In the figure, 1.200 is a curved conduit, and 2.202 is an inlet. 3.203 is the outflow 0.5.51.6.61 is the vibration device,
7.7-1.7-2 represents an amplitude detector. Patent applicant Oval Equipment Industry Co., Ltd. Agent Patent attorney Mori 1) Hiroshi (2 others) Fang 3 diagram instruction io5

Claims (2)

[Claims] (1) A flexible curved conduit that is symmetrical about a first axis and has two openings at symmetrical positions, and a flexible curved conduit that is fixed near the opening of the curved conduit and that connects the fixed parts. a support member rotatably supporting the curved conduit around a second axis; a vibrating means for applying torsional alternating vibration to the curved conduit around a first axis; a displacement detector for detecting the amplitude of vibration of the curved conduit around the second axis, a control means for keeping the output of the displacement detector constant, and an instruction section for instructing the control amount of the control means. A mass flowmeter characterized by: (2) The curved conduit is configured by a first curved conduit and a second curved conduit having the same shape and size as the first curved conduit and arranged so that the conduit surfaces are parallel to each other. A mass flowmeter according to claim (1).