JPH0441296Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a Coriolis force flowmeter, and more particularly to magnetic isolation between a detection section of a Coriolis force flowmeter and a pipe body through which fluid flows.

Prior Art When a pipe body with both ends fixed and through which fluid flows is driven in a direction perpendicular to the pipe body at the center of the pipe body, a Coriolis force is generated near the fixed ends, and this Coriolis force causes vibrations. It is known that it is proportional to the frequency and the mass flow rate of the fluid.

FIG. 2 is a diagram for explaining an example of a Coriolis force flowmeter to which the present invention is applied. As disclosed in Japanese Patent Publication No. 60-34683, the Coriolis force flowmeter is Curved tube body 2 made of non-magnetic material
passes through the fixed member 1 at points A and B, and the curved tube 2 has a drive coil 4 driven by a power source (not shown) and a magnet 5 fixed to the curved tube 2 around the first axes X and X'. is driven by its natural vibration frequency. The drive coil 4 is attached to the reciprocating member 3 fixed in parallel to the first axis of the fixed member 1 so as to be substantially equal to the natural frequency of the curved tube body 2 . When fluid flows into the curved tube 2, an alternating Coriolis couple is generated around a second axis Y-Y' that is perpendicular to the first axis and passes through the midpoint between A and B. The magnitude of this alternating couple is proportional to the mass flow rate, and this is due to the detection magnets 71 and 72 fixed to the respective pillars 61 and 62 fixed to the bottom of the fixed member 1 toward the shoulder of the curved tube body 2. , and are detected by detection coils 81 and 82 which are opposed to the magnets 71 and 72, respectively, and which are attached to the curved tube body 2. That is, a voltage value outputted in proportion to a relative speed change caused by the Coriolis alternating couple between these detection coils 81 and 82 is detected as a phase change amount at a position crossing the stationary plane of the curved conduit.

Problems with the prior art In the Coriolis force flowmeter as described above, the detector may be of any type, such as optical or electromagnetic, as long as it can detect displacement or velocity, but the structure is not robust. Generally, an electromagnetic method is adopted because the output is stable even when dust or the like is attached. However, when measuring a fluid with high magnetic permeability such as a magnetic fluid, the relative position with the magnet changes due to alternating positional changes of the magnetic fluid, and the reluctance during this period changes. As a result, in the detection coils 81 and 82, interference occurs in which the output based on the change in reluctance overlaps with the AC signal due to the Coriolis couple, resulting in a problem that detection becomes impossible.

Means for Solving the Problems When the curved tube body is driven, the detection coil and the detection coil are detected so that the change in reluctance caused by the relative displacement with the magnetic fluid flowing inside the curved tube body does not affect the detection coil. This is applied to the detection unit composed of a magnet.

Embodiment FIG. 1 is an enlarged perspective view of a main part for explaining an embodiment of the present invention, that is, an enlarged perspective view of a portion corresponding to the parts and ′ of FIG. 2, detection magnets 71, 72, and detection coils 81, 82 are isolated by a magnetic shielding plate 10, as shown.

Effects As described above, according to the present invention, when a Coriolis force flowmeter is used to measure a fluid with high magnetic permeability such as a magnetic fluid, reluctance fluctuations caused by alternating positional fluctuations of the magnetic fluid can be reduced. Therefore, even if the fluid to be measured is a magnetic material, the mass flow rate of the fluid to be measured can be measured with high accuracy.

[Brief explanation of the drawing]

Fig. 1 is an enlarged perspective view of the main parts (parts and '' in Fig. 2) for explaining one embodiment of the present invention, and Fig. 2 is an example of a Coriolis force type flowmeter to which the present invention is applied. FIG. 2 is an overall perspective view for explaining. DESCRIPTION OF SYMBOLS 1... Fixed member, 2... Curved pipe body, 3... Reciprocating member, 4... Drive coil, 5... Drive magnet, 1
0... Magnetic shielding plate, 71, 72... Detection magnet, 8
1,82...Detection coil.

Claims (1)

[Scope of utility model registration request] A tube body with both ends fixed and through which fluid flows; a drive means that drives the central part of the tube body in a direction perpendicular to the tube body; 1. A Coriolis force type flowmeter comprising a detection unit for detecting the mass flow rate of fluid as a phase change amount, characterized in that a magnetic shield is provided between the detection unit and the pipe body. Total.