JPH0346334Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a mass flow meter, and more particularly to a conduit structure for a mass flow meter that measures the Coriolis force acting on a fluid flowing through the conduit to determine the mass flow rate.

Prior Art When vibration is applied to a fluid flow flowing through a 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. In Publication No. 54-52570,
A mass flow meter utilizing the Coriolis force as described above is disclosed. This flowmeter is shown in Figure 3 A and B.
As shown in FIG. 1, a U-shaped conduit 1 is fixedly supported by a support member 2 symmetrically about the axis XX', and one end of a reciprocating member 3 extending in the direction of the axis XX' is fixed to the support member 2. An electromagnetic coil 4 is disposed at the other end of the reciprocating member 3 and vibrates at a frequency substantially equal to the natural frequency of the conduit 1 around an axis YY' connecting the fixed points of the conduit 1. A magnet 5 is attached to the conduit 1 via a holding plate 6 on the axis of the electromagnetic coil 4.
The conduit 1 is attracted and repelled in the ZZ' direction by a drive source (not shown), and as a result, the conduit 1 is driven around the axis YY'. As a result, a Coriolis force acts on the fluid flowing in the Q direction, and a rotational force is generated around the XX' axis. From the change in the light intensity at the photodetector 7, which is blocked by the shielding plate 8 fixed symmetrically to both arms of the conduit 1, the time difference between the two arms of the conduit 1 passing through the neutral plane is calculated, and from this Coriolis seeking the power of

Problems with the conventional technology The Coriolis mass flowmeter described above determines the Coriolis force as a moment around the axis XX', but high sensitivity detection can also be achieved by lengthening the moment arm. However, in order to improve detection sensitivity with the same shape, it is necessary to reduce the wall thickness of the conduit and reduce its rigidity. As a result,
A problem arises in that the pressure resistance of the conduit is reduced and high pressure fluid cannot be measured. In addition, although the case where the conduit is a U-shaped tube has been described above, in the case of a straight tube, the Coriolis force is detected as a phase change that occurs near the support point on the conduit, so the U
Since the rigidity is much higher than in the case of a shaped tube, and the detection sensitivity is correspondingly lower, a thin-walled conduit is more strongly required, and the pressure resistance is even worse.

Means for solving the problem By fixing a plurality of plate-shaped pressure-resistant fins at equal intervals on the outer peripheral wall of the conduit so as to be perpendicular to the conduit axis,
The pressure resistance is improved without changing the torsional rigidity around the XX' axis and the bending rigidity around the YY' axis of the fluid conduit from the conventional ones.

Embodiment FIG. 1 is a diagram showing an embodiment of a mass flowmeter according to the present invention, but elements having the same functions as the mass flowmeter explained in the conventional example shown in FIG. 3 are omitted. be. That is, the U-shaped conduit 1 is fixedly supported on the support member 2 symmetrically with respect to the axis XX', and furthermore, the support member 2 has a natural vibration around the YY' axis connecting the fixed points of the support member 2 of the conduit 1. A reciprocating member 3 having a natural frequency substantially equal to the number of vibrations is fixed and vibrates in a tuning fork shape around the YY′ axis, and this vibration is attracted and repelled by the electromagnetic coil 4 that is the driving source. As a result, a moment due to the Coriolis force is generated around the XX' axis which is proportional to the mass flow rate of the fluid, and the detection means 7 and 8 cause the conduit at the detection position to align with the reference plane which is the stationary surface of the conduit. Although it has a function of detecting a passing time difference, elements having such a function are omitted in FIG. Therefore, in the present invention, plate-shaped pressure-resistant fins 11 are fixed to the pipe wall by welding or the like at equal intervals so as to be orthogonal to the pipe axis, and FIG. 1A shows such pressure-resistant fins. It is a plan view with the fins fixedly installed, and Figure B is a sectional view taken along arrow BB' in Figure A. Although the pressure resistance is improved by such pressure fins, the torsional rigidity around the XX' axis and the bending rigidity around the YY' axis do not change significantly from the conventional ones. FIG. 2 shows another embodiment, in which the fluid conduit 10 is a straight pipe, and is fixed at two points, support members 21 and 22, between which a pressure fin 11 is inserted. They are fixed to the straight pipe wall at equal intervals.

In addition, in the case of straight pipes, the center of the support members 21 and 22
By vibrating up and down on the MM' axis, the fluid is given opposite motion in the supporting members 21 and 22, so Coriolis forces of opposite phase are generated near each supporting member, which causes the upward and downward movements. It appears in the direction of vibration in addition to the excited conduit displacement in the direction. Therefore, even in the case of a straight pipe, the pressure resistance is improved, but the rigidity against deformation due to the Coriolis force generated in the same direction as the vibration direction does not change significantly from the conventional pipe.

Effects As described above, according to the present invention, by fixing a simple pressure-resistant fin to the conduit wall, pressure-resistant characteristics can be improved at low cost and without significantly reducing sensitivity.

[Brief explanation of drawings]

FIG. 1 is a block diagram of main parts for explaining one embodiment of the mass flowmeter according to the present invention, FIG. 2 is a block diagram of main parts for explaining another embodiment, and FIG. FIG. 1 is a configuration diagram for explaining an example of a mass flowmeter, in which A is a plan view and B is a front view. DESCRIPTION OF SYMBOLS 1... Conduit, 2... Supporting member, 3... Reciprocating member, 4... Electromagnetic coil, 5... Magnet, 7... Photodetector, 8... Shielding plate.

Claims (1)

[Scope of utility model registration request] It has support points at two points on the conduit through which the fluid flows,
The Coriolis force generated when the fluid flow moves around the support points by applying a simple harmonic motion to the section between these support points is measured, and the mass flow proportional to this Coriolis force is measured. 1. A mass flowmeter characterized in that a plurality of plate-like pressure-resistant fins are fixed at equal intervals on the outer peripheral wall of the conduit so as to be perpendicular to the axis of the conduit.