JPS6251405B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a throttle flowmeter that integrates an annular throttle mechanism and a differential pressure converter. As is well known, a throttle flow meter calculates the flow rate by measuring the differential pressure before and after the throttle mechanism, and this differential pressure is guided to a differential pressure converter and converted directly to mechanical displacement, pneumatic pressure, or electricity. Ru. Among the many types of conventional aperture mechanisms, concentric orifice,
Flow nozzles and ventilate tubes are most commonly used, and the throttling mechanism TH and differential pressure converter TR are constructed separately as shown in Figures 1 and 2, with a pressure impulse tube between them. connected by c. However, in the case of such conventional throttle flowmeters, all holes in the center or eccentric positions are used as the throttle openings, so they are easily affected by direct dynamic pressure and eddy currents, and mechanism
Since the TH and the differential pressure converter TR are constructed separately, connecting them requires a sealing device such as a pressure impulse pipe c or a seal diaphragm SD as shown in Figure 2, which makes the structure, assembly, and Due to complicated installation conditions,
The drawbacks were that manufacturing costs were high and measurement and handling were complicated. This invention was made by focusing on the above-mentioned drawbacks, and employs an annular throttle section that uses a circular disk as the throttle mechanism, and a rectifying plate is provided on the inflow side in front of the disk to reduce the dynamic pressure. The present invention attempts to eliminate the above-mentioned drawbacks by reducing the influence of eddy currents and eddy currents, and by integrally configuring the throttle mechanism and the differential pressure converter. Hereinafter, this invention will be explained based on the drawings. Third
4 and 4 are diagrams illustrating the principle and one embodiment of the present invention. First, the configuration will be explained. In Fig. 3, T is a hollow cylinder, a disk Dk fixed to the axis R passing through the axis of the cylinder is provided in the center of the cylinder, and an annular constriction part Th is formed between the circumference of the disk and the inner wall of the cylinder. It has been formed. Both ends of the shaft R are slidably supported in the axial direction by bearings B provided at the center of end walls that close both ends of the cylinder. l and O are the inlet and outlet of the measurement fluid, respectively. Fa is a disc-shaped current plate installed on the front inflow side of the disc Dk to eliminate the influence of dynamic pressure and vortex flow of the inflow fluid.The outer periphery is fixed to the inner wall of the hollow cylinder T, and the disc A plurality of communication openings are provided near the outer periphery of the section and are arranged at equal intervals circumferentially, and a through hole is provided at the center to allow free movement of the shaft R in the axial direction. The differential pressure (p ₁ − p ₂ ) generated by the restriction is expressed by the disk Dk
, and if the pressure-receiving area of the disk Dk is A, a thrust force F=(p ₁ −p ₂ )A is generated. By measuring this force F, the relational expression

The flow rate Q can be determined from [Formula] (where k is a constant and ρ is the fluid density).
The force F can be measured using a differential pressure transducer such as a strain gauge or spring S placed in contact with the end of the axis R.
By determining the directional displacement, the differential pressure is converted into the required signal. FIG. 4 is a longitudinal sectional view of an example of an actual configuration based on the principle of FIG. 3. 1 is a hollow cylinder with stepped inner diameters, the cylindrical wall of which has an inlet 2 and an outlet 3 for the fluid to be measured in the radial direction near both ends. Reference numerals 4 and 4' denote end walls fixed to close both ends of the hollow cylinder. Inside the hollow cylinder 1, a shaft 7 with one throttle disk 5 in the center and pistons 6, 6' fixed on both sides is disposed passing through the cylinder axis, and both ends of the shaft 7 are Bearings 8, 8' provided at the centers of the end walls 4, 4' support the end walls 4, 4' so as to be slidable a short distance in the axial direction. Each of the pistons 6, 6' has a flexible diaphragm 9, 9' having an annular circumferential fold 9'', which is held by a retainer 10, 10' and tightened with a nut 11, 11', respectively. The outer peripheral edges 12, 12' of each of the diaphragms 9, 9' are sandwiched between the center cylinder 1 and the end walls 4, 4', respectively, and are hermetically fixed. On the front inflow side of the hollow cylinder 1, a disc-shaped baffle plate 13 having a plurality of openings 13' around the periphery and a free passage hole for the shaft 7 at the center is fixed in the stepped inner diameter of the hollow cylinder 1. 7
A strain gauge 14 as a differential pressure transducer TR is provided so as to come into contact with the outflow side end of the transducer, and is held by a cover 15 and fixed to the end wall 4'. (This strain gauge 14 can also be provided at the opposite inflow side end.) 16 is a lead wire for taking out a signal from the strain gauge 14, and 16, 16' are the end wall 4.
This is an air flow opening provided at 4'. Next, the effect will be explained. The fluid to be measured is introduced into the hollow cylinder 1 from the inlet 2, passes through each opening 13' of the rectifier plate 13, passes through the annular constriction part Th formed between the disk 5 and the inner wall of the cylinder, and then passes through the outlet. Reach 3. At this time, the pressures p ₁ and p ₂ generated before and after the throttle disk 5 also act on the diaphragms 9 and 9', respectively. When the pressure-receiving area of the disc 5 is A and the effective pressure-receiving area of the diaphragms 9 and 9' is A _D , a force F = (p ₁ - _{p 2} )(A _D
-A) acts, and when A _D > A, F pushes the shaft 7 in the upstream direction, and when A _D < A, F pushes the shaft 7 in the downstream direction, and this force is measured by the strain gauge 14. The output signal is led to a flow rate indicator (not shown) through a lead wire 16. Instead of the strain gauge 14, other known differential pressure transducers (displacement-force transducers) such as springs, photodiodes, and differential transformers may be used. FIG. 5 shows another embodiment. This example is the annular constriction part between the cylinder walls by the disk 5 in Fig. 4.
Cylinder 5a with a thicker disk instead of Th
This is a flowmeter that utilizes the differential pressure of an annular cylindrical laminar flow constriction section Tha with minute gaps. Except for the above parts and the omission of the rectifying plate, the basic configuration is completely the same as that in Fig. 4, and each of the same configurations is a
They are indicated by the same reference numerals, and redundant explanation will be omitted. As described above, the flowmeter according to the present invention has an inlet and an outlet for measuring fluid near both ends of a cylindrical wall, and a shaft inside a hollow cylinder with both ends closed. An aperture disk is fixed to the center of the shaft to form an annular aperture between the shaft and the inner wall of the hollow cylinder, and both ends of the shaft are connected to the center of the end wall of the hollow cylinder. The shaft is supported slidably in the axial direction by each bearing provided on the shaft, and the shaft is further provided with two flexible shafts having annular circumferential folds spaced apart from each other by an appropriate distance on both sides of the aperture disc. A diaphragm is provided, the center and outer edges of which are fixed to the shaft and the inner wall of the hollow cylinder, respectively, and a differential pressure transducer is provided at one or both ends of the shaft in contact with the shaft end; On the inflow side of the throttle disk, a disk-shaped rectifying plate having a plurality of openings and a shaft through hole is provided at the periphery and the center, respectively, and the outer peripheral edge thereof is fixed to the inner wall of the hollow cylinder. In particular, since the throttle mechanism and differential pressure transducer are integrated, sealing devices such as impulse tubes and seal diaphragms are not required, and the mechanism is extremely simplified, reducing manufacturing costs. This has the effect of making measurement and handling easier. Furthermore, since differential pressure transducers such as strain gauges are installed outside without any contact with the fluid, there is no risk of corrosion or leakage caused by the fluid, and there is no relation to fluid pressure, fluid temperature, etc. Therefore, there is an advantage that only the ambient temperature of the space in which the converter is placed needs to be considered. Furthermore, the parts that come into direct contact with the fluid, e.g.
The structure has been realized using highly corrosion-resistant materials such as 316 stainless steel, Monel metal, titanium, and tantalum, and is easily coated with Teflon, and the diaphragm is made of a wide range of corrosion-resistant materials such as silicone rubber, nitrile rubber, and fluorine rubber. It can be selected from suitable heat-resistant materials, and by clamping and fixing it between the piston and the retainer, extremely high pressure resistance can be obtained, which has the advantage of being applicable to high-pressure fluids of about 100 atmospheres. In addition, since the shaft can move freely in the axial direction, the relative positional relationship between the differential pressure transducer such as a strain gauge and the throttle disk is automatically brought into contact by the differential pressure without the need for any detailed adjustment. Because it moves to the position,
It has the great feature of being extremely easy to assemble and adjust. Furthermore, even when the fluid flows in opposite directions, the above characteristics can be ensured in both directions by disposing differential pressure transducers at both ends of the shaft. The above features can be obtained in exactly the same way when a cylinder is used as the aperture mechanism. As described above, the present invention makes it possible to provide a flowmeter that is excellent overall in terms of manufacturing cost, accuracy, handling, etc.

[Brief explanation of the drawing]

1 and 2 are schematic diagrams of the configuration of a conventional throttle flowmeter, FIGS. 3 and 4 are a principle diagram and a vertical sectional view of an embodiment of the throttle flowmeter according to the present invention, respectively, and FIG. The figure is a longitudinal sectional view showing another embodiment. 1, T...Hollow cylinder, 2, l...Inlet, 3,
O... Outlet, 4, 4'... End wall, 5, Dk... Disc for throttle, 5a... Cylinder for throttle, 6, 6a... Piston, 7, R... Shaft, 8, 8' , B...Bearing,
9,9'...Diaphragm, 9''...Circumferential fold, 1
2, 12'... Outer periphery, 13, Fa... Current plate, 1
4...strain gauge, TH...throttle mechanism, Th...
Annular aperture part, Tha... annular cylindrical aperture part,
TR…Differential pressure converter.

Claims (1)

[Scope of Claims] 1. A hollow cylinder having an inlet and an outlet for measuring fluid near both ends of a cylindrical wall and closed at both ends is provided with a shaft passing through its axis, A throttle disk is fixed to the center of the hollow cylinder to form an annular throttle part between the inner wall of the hollow cylinder, and both ends of the shaft are slid in the axial direction into bearings provided at the centers of both end walls of the hollow cylinder. Further, two flexible diaphragms having annular circumferential folds are disposed on the shaft at an appropriate distance on both sides of the aperture disk, and the central portion of the diaphragm is and the outer peripheral edge thereof are respectively fixed to the shaft and the inner wall of the hollow cylinder, and a differential pressure transducer is provided at one or both ends of the shaft in contact with the shaft end, and further, on the inflow side of the throttle disk. A flow meter comprising: a disc-shaped rectifying plate having a plurality of openings and a shaft through-hole at the periphery and the center thereof, the outer peripheral edge of which is fixed to the inner wall of the hollow cylinder. 2. Claim 1, characterized in that the throttling disk is made into a cylinder with increased thickness, and an annular cylindrical laminar flow throttling portion having a fine gap with the inner wall of the hollow cylinder is formed. Flow meter as described.