JPS5854674Y2 - Gravimetric flow rate metering device - Google Patents

Description

[Detailed description of the invention] This invention uses a gravimetric flow metering device, especially a servo mechanism that uses a fluid that has a bellows filled with a reference gas to correct changes in the density of the fluid to be measured. The present invention relates to a gravimetric flow metering device that maintains the pressure difference across a throttle valve at a predetermined value and measures the gravimetric flow rate from the opening area of the throttle valve.

As shown in Fig. 1, one of the flow metering devices is formed between the pressure P1 on the upstream side of the flow rate detection valve 1 in the flow path and between the flow rate detection valve 1 and the flow rate control valve 2, such as a throttle valve. The pressure difference P1-P2 with respect to the pressure P2 in the intermediate chamber 3 is maintained at a predetermined value, and the flow rate is measured from the opening area of the flow rate detection valve 1.

4 is a servo valve that detects the deviation of the pressure difference P□-P2 before and after the flow rate detection valve 1 and amplifies the detected amount using a fluid mechanism; This is a valve opening device that controls the opening and closing of the valve.

The servo valve 4 has a chamber a and a chamber B partitioned by a differential pressure setting diaphragm 6, a chamber e having the same pressure as the chamber B, a valve 7 that operates in conjunction with the differential pressure setting diaphragm 6, and a variable opening area that changes depending on the valve 7. It consists of a chamber d communicating with a chamber e through an orifice 8.

Pressure P2 acts on chamber a, and pressure P1 acts on chambers b and e.

A bellows 9 for specific gravity correction is installed in the C chamber to make the opening area of the flow rate detection valve proportional to the weight flow rate.

In this case, a reference gas at a reference temperature is sealed inside the bellows (effective area of bellows) x (pressure of reference gas).
= (effective area of differential pressure setting diaphragm of servo valve)
The effective area of the bellows is determined so that x (differential pressure at reference temperature and pressure).

The d chamber communicates with the valve opening device 5 and also with the intermediate chamber 3 via the throttle 10, and the pressure Pn in the d chamber is equal to Pl and P2.
It fluctuates between.

The valve opening device 5 has a chamber e partitioned by a bellows 11 communicating with a chamber d.

In the area type flowmeter A having the above configuration, when the set pressure differences P and -P2 deviate from predetermined values due to the operation of the flow rate control valve 2, the differential pressure setting diaphragm 6 is slightly displaced in accordance with the deviation, and the valve 7 is moved. , the pressure Pn in chamber d fluctuates.

Along with this, the pressure Pn inside the C chamber also fluctuates, causing the bellows 11 to change.
Displace.

Therefore, it opens and closes in a direction that corrects the deviation in the pressure difference P1P2 of the flow rate detection valve 1 which is linked to the displacement of the bellows 11.

The specific gravity correction bellows 9 is displaced due to changes in the temperature and pressure of the fluid to be measured, and corrects the set value of the differential pressure setting diaphragm 6.

By the way, a predetermined differential pressure is set by the compression spring force of this specific gravity correction bellows 9 and the spring force of the differential pressure setting spring 12 inserted in parallel with this bellows 9.

The spring force of this differential pressure setting spring 12 is sufficiently stronger than that of the bellows 9, so if both ends of the bellows 9 are fixed to the presser plate 13 and the spring pressure adjustment board 14 connected to the valve 7, it is necessary to The bellows 9 may undergo plastic deformation in the tensile direction due to the spring force of the differential pressure setting spring 12, and there is a problem in that the bellows 9 must be handled with great care during assembly.

This invention is an improvement on the above-mentioned problem, and the structure of this invention will be explained below based on the embodiment shown in the drawings.

Drawing 2B. In the opening and FIG. 3, 20 is a specific gravity correction bellows, 21 is a differential pressure setting spring, 22 is a spring pressure adjustment board, and 23 is a holding plate connected to the valve 24.

First, referring to FIG. 2A, the bellows 20 is fixed to the spring pressure adjustment board 22 by means of soldering or the like, but is not fixed to the presser plate 23 and is kept movable toward and away from the spring pressure adjustment board 22.

The joint end and the free end may be fixed to the presser plate 23 as shown in FIG. 2, and may be free from the adjustment plate 22.

With such a configuration, the bellows 20 and the differential pressure setting spring 21 can each have their own free lengths during assembly, so that plastic deformation of the bellows can be prevented.

FIG. 3 shows another embodiment, in which the bellows 20 and the presser plate 23
A steel ball 25 is inserted between the two to provide an alignment effect.

As explained above, the pressure difference is set to maintain the pressure difference P, -P2 between the pressure P1 upstream from the flow rate detection valve and the pressure P2 in the intermediate chamber formed between the flow rate detection valve and the flow rate control valve at a predetermined value. A servo mechanism using a fluid having a diaphragm, a bellows that compensates for changes in the density of the fluid to be measured that works in conjunction with the differential pressure setting diaphragm, and a valve whose opening area changes depending on the displacement of the differential pressure setting diaphragm and bellows. In a gravimetric flow metering device in which the opening area of the flow rate detection valve is proportional to the gravimetric flow rate, one end of the bellows is fixed to a presser plate or a spring pressure adjustment board that connects the valve, and the other end is Since the bellows can be freely moved toward and away from the bellows, and the differential pressure setting spring is compressed and interposed between the holding plate and the spring pressure adjustment board concentrically with the bellows, plastic deformation of the bellows can be prevented and assembly can be simplified.

Furthermore, this does not impair the function of setting or adjusting the differential pressure mostly by the elasticity of the differential pressure setting spring and partially by the elasticity of the bellows.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a gravimetric flow metering device according to the present invention, and FIGS. 2 and 3 are explanatory diagrams of main parts of the present invention. 1...Flow rate detection valve, 2...Flow rate control valve, 3...Intermediate chamber, 6...Differential pressure setting diaphragm, 7...・Valve, 9...Bellows, 20...Differential pressure setting spring, 22...
・Spring pressure adjustment board, 23...pressing plate.

Claims (1)

[Scope of utility model registration request] A pressure difference P between the pressure P1 upstream of the flow rate detection valve and the pressure P2 in the intermediate chamber formed between the flow rate detection valve and the flow rate control valve.
A differential pressure setting diaphragm that maintains I-P2 at a predetermined value, a bellows that compensates for changes in the density of the fluid to be measured in conjunction with the differential pressure setting diaphragm, and an opening area that changes due to displacement of the differential pressure setting diaphragm and bellows. In a gravimetric flow metering device in which the opening area of a flow rate detection valve is made proportional to the gravimetric flow rate by a servo mechanism using a fluid having a valve, a presser plate or a spring connects one end of the bellows with the valve. The spring is fixed to the pressure adjustment board, and the other end is movable toward and away from the pressure adjustment board, and a differential pressure setting spring is compressed and interposed concentrically with the bellows between the presser plate and the spring pressure adjustment board. Gravimetric flow rate metering device.