JPS6027937B2 - force detector - Google Patents

Description

[Detailed description of the invention] The present invention relates to a force detector for detecting stress.

More specifically, the present invention relates to a force detector that detects stress and converts it into an electrical signal. Devices that detect force include vibration meters, vortex flow meters, pressure gauges, differential pressure gauges, and load cells (scales).

The present invention relates to a force detector suitable for use in these sensors. An example in which the force detector of the present invention is used as a sensor of a vortex flow meter will be described below. FIG. 1 is an explanatory diagram of the configuration of an embodiment of the present invention.

In the figure, 1 is a cylindrical tube body, 2 is a columnar force receiving body inserted perpendicularly into the tube body 1, and is made of stainless steel, and is composed of a vortex generating body 21 and a container 22. The vortex generator 21 has a columnar shape, and one end is fixed to the tube body 1 and the other end is connected to the container 22. The other end of the container 22 is fixed to the other end of the inner cylinder 11, which has one end fixed to the tube body 1. 23 is a recess provided on the side of the container 22 connected to the inner cylinder 11.

Reference numeral 3 denotes a disk-shaped stress detection section provided in the recess 22, and its center axis is on the center axis of the force-receiving body 2.

In this case, the stress detection section 3 consists of a disk-shaped element body 31 and electrodes 32, 33, and 34, as shown in FIG. electrode 32
has a thin disk shape and is provided on one side of the element body 31. On the other hand, the electrodes 33 and 34 are substantially arcuate and are provided symmetrically on the other surface of the element body 31 with the center of the element body 31 in between. In this case, a voltage element made of lithium niobate (LINO03) is used as the element body 31. 4 is made of an insulating material, and the stress detection part 3 is connected to the recess 23.
It is a sealed body that is insulated and sealed inside the container 22, and in this case, a glass material is used.

Reference numeral 5 denotes a converter portion attached to the other end side of the outer tube 12 whose one end side is fixed to the tube body 1.

In the above configuration, when the measurement fluid flows into the tube body 1, an alternating force as indicated by the arrow x shown in FIG. 1 acts on the vortex generator 21 due to the Karman vortex.

This alternating force is applied to the stress detection section 3 through the container 22 and the sealing body 4.
is transmitted to. In this case, as shown in FIG. 1, a stress change occurs in the force receiving body 2 in the opposite direction across the center koji of the force receiving body 2. Therefore, the electrode 32-electrode 33 of the stress detection section 3,
An electrical signal (for example, a voltage change) corresponding to this stress change is generated between the electrode 32 and the electrode 34. By detecting the number of times this change occurs, the vortex generation frequency can be detected. Thus, by differentially processing the electrical output between the electrodes 32 and 33 and between the electrodes 32 and 34, twice the electrical output can be obtained. On the other hand, the entire pipe vibrates due to the influence of vibration noise transmitted through the pipe, such as vibration noise caused by the opening and closing of pumps, compressors, dampers, etc.

Due to this vibration, an alternating bending moment MQ based on the mass distribution of the force receiving body 2 acts on the force receiving body 2 in the direction in which the aforementioned alternating force x acts. The stress generated in the force receiving body 2 by this alternating bending moment MQ is detected as noise by the stress detection section 3. FIG. 3 shows this bending moment MQ, where Mv is the alternating bending moment caused by vortex generation. In the present invention, the bending moment M
The stress detection section 3 is arranged at a position Y where Q becomes zero, and in this case, it is arranged at a position of 0.21 to 0.3 of the distance 1 between the fixed ends of the force receiving body 2. Therefore, the stress detection unit 3 disposed at position Y does not detect the stress due to the bending moment MQ, that is, the noise due to pipe vibration is not detected. The position Y at which the bending moment MQ becomes zero is determined to be a fixed position depending on the structure and positional relationship of the entire device. Depending on the type and magnitude of vibration noise, the only difference is whether the curves forming the moment diagram have a large curvature or a small curvature. Therefore, the vibration noise is added to the entire device, and the bending moment Mv based on the vortex generation is a bending moment based on the vortex that acts only on the portion of the vortex generator 21 in the pipe.

That is, the acting forces and acting ranges are different, and therefore the bending moments MQ and Mv always have different bending moment diagrams. The position Y at which the bending moment MQ becomes zero can also be determined by calculation, but first, the position Y is determined by a rough calculation, and the stress detection unit 3 is placed at various positions near the position determined by the rough calculation. It can be easily determined experimentally by

In this case, find the zero position by vibrating the device using a vibration tester or the like.

Alternatively, it can be determined by flowing a known constant flow rate through the device and observing the vibration waveform using a cathode ray tube oscillograph or the like. In this case, the signal frequency based on vortex generation is a low frequency, and the vibration noise is generally in a high frequency range. Therefore, when observing the waveform, the location where the high-frequency waveform overlaps the low-frequency waveform is not the location where the moment MQ is zero, but the location where only a clean low-frequency waveform is detected is the location where the bending moment MQ is zero. It is. As described above, the point where the bending moment MQ becomes zero can be easily found.

Therefore, according to the device of the present invention, it is possible to obtain a device with good vibration resistance without detecting noise caused by pipe vibration.

It is particularly effective when used to measure fluids to be measured, such as air, whose vortex force is generally small. In addition, in the case of a double-supported structure like this example, the position where the bending moment MQ becomes zero is 2.
There are places.

That is, it goes without saying that the stress detection section 3 may be arranged at the position Z in FIG. 3. Further, when the force receiving body is supported at one end and fixed at the other end, there is one position where the bending moment MQ becomes zero as shown in FIG. Further, the position where the bending moment MQ becomes zero can be freely moved by changing the mass distribution of the force receiving body 2, and can be placed at a position where the bending moment Mv due to vortex generation is large.

In this embodiment, the force receiving body 2 and the transducer portion 5 are separately fixed to the tube body 1 by the inner tube 11 and the outer tube 12, respectively, and the influence of vibration due to the relatively large mass of the transducer portion 5 is eliminated. The structure is such that the force does not reach the force receiving body 2 as much as possible.

FIG. 5 is an explanatory diagram of the configuration of another embodiment of the present invention, where A is an overall view and B is an explanatory diagram of the main part configuration.

In this embodiment, one end of the force receiving body 2 is fixed to the tube body 1 with a bolt 13, the other end is fixed to the tube body 1 via a support part 14, and the support part 14 is fixed to the tube body 1 with a reinforcing plate 15. By reinforcing and fixing it, you can get even more sturdiness.

FIG. 6 is an explanatory diagram of the main part configuration of another embodiment of the present invention.

In this embodiment, a recess 21 is provided at one end of the vortex generator 21.
1 is provided, and a spherical portion 131 provided at the tip of the bolt 13 is inserted into the recess 211 to support one end of the vortex generator 21, and the threaded portion 132 is a Booper screw. Note that the threaded portion 132 of the bolt 13 may be connected to the tubular body 1 or may have a loose structure, and the joint portion with the tubular body 1 may be welded.

In this way, a structure with even better sealing performance can be achieved. In this embodiment, the force-receiving body 2 can be easily attached and detached, and the elongation of the force-receiving body 2 in the axial direction when measuring a high-temperature fluid to be measured can be absorbed.

FIG. 7 is an explanatory diagram of the diamond portion configuration of another embodiment of the present invention.

In this embodiment, a cylindrical lid 14 with a flexible portion 142 provided on a flange 141 is attached and fixed to the tube body 1, and a convex portion 143 is inserted into a concave portion 211 of a vortex generator 21 to generate a vortex. It is designed to support one end of the body 2, and the same effect as shown in FIG. 6 can be expected. In addition, in the above-mentioned example,
We have explained the case where it can be implemented in a vortex flowmeter, but for example,
Of course, it is also effective when applied to force detectors such as pressure gauges in engine rooms of vehicles or ships where external vibrations are severe.

As explained above, in the present invention, the force detector is disposed at a position of the force receiving body where the stress generated in the force receiving body due to the disturbance force becomes zero. As a result, it is possible to realize a force detector that does not pick up noise due to disturbance force, has excellent vibration resistance, and is robust. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram of the configuration of an embodiment of the present invention, FIG. 2 is an explanatory diagram of the main part configuration of FIG. 1, FIG. 3 is a bending moment diagram of FIG. 1, and FIG. is an explanatory diagram of an example of a bending moment diagram when one end of the force-receiving body is supported at one end and fixed at the other; FIG. 6 and 7 are explanatory views of the main parts of another embodiment of the present invention.

1... Tube body, 2... Force receiving body, 21... Vortex generating body, 2
2... Container, 23... Concavity, 3...
... Stress detection section, 31 ... Element body, 32, 33
,34... ...electrode, 4...sealing body, 5.
...Converter part.

Tsutomu Z box vertical J Kaede Tsutomu box Figure 7 Tsutomu'12 Chrysanthemum diagram Figure 5

Claims (1)

[Claims] 1. A force-receiving body configured such that one end is fixed and the other end is fixed or supported so that stress generated inside the body differs depending on a disturbance force and a force to be measured; A force detector comprising: a stress detecting section disposed at a position of the force receiving body such that the stress generated is approximately zero.