JPS6256820A - Throttle device for flow rate measurement - Google Patents

Abstract

PURPOSE:To simplify structure, to widen a measurement range, and to measure a flow rate with high precision by providing a partition wall which cuts off the liquid flow passage of a tube body forming the flow passage and fixing the base end of a spring plate which closes the downstream-side opening part of an orifice formed in the partition wall with its tip part to the partition wall. CONSTITUTION:When liquid flows in the tube body 1 to generate a pressure difference between the upstream side and downstream of the orifice 3 formed in the partition wall 2, the spring plate 4 is curved as shown by a dotted line and the tip part is displaced to allow the liquid to passed through the orifice 3. The curvature of the spring plate 4 is larger and larger as the pressure difference is larger and larger and the volumetric flow rate also increases, but the reaction of the spring plate 4 increases, so the degree of the increase in volumetric flow meter decreases and the flow rate is measured with high precision over a wide range.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a throttle device for measuring the flow rate of a fluid, and more specifically, the present invention relates to a restricting device for measuring the flow rate of a fluid. This invention relates to a diaphragm device that makes it possible to measure flow rates.

[Conventional technology]

A measurement method that applies a restriction device is widely used to measure the flow rate of fluid.This method uses a restriction device (generally an orifice or nozzle, etc. It is configured)
By utilizing the fact that the pressure difference that occurs before and after is in a proportional relationship with the flow rate at that time, this pressure difference is measured and the flow rate is determined by calculation based on the proportional relationship.

A flow rate measuring device using this throttle device has a simple structure, is easy to manufacture, and is inexpensive, so it is widely used for research and T-industry purposes.

The pressure difference measuring method in this flow rate measurement method using a throttle device is a liquid column type (using mercury or water).
Although pressure gauges are often used, electric pressure gauges using various pressure sensors have been developed in recent years.

The basic configuration of a conventional throttle device used for this flow rate measurement is shown in FIG.

In this FIG. 7, reference numeral 1 is a tube that forms a fluid flow path, and a partition wall 2 is integrally provided on this tube body 1 in a form that blocks the flow path. An orifice 3 having a diameter of 1.5 mm is formed.

A side pipe 6 is provided on each of the upstream and downstream sides of the flow path partitioned by the partition wall 2, and the tips of the both side pipes 6 are connected to one differential pressure gauge 7.

In the pipe line shown in FIG. 7, one fluid flows through the pipe body 1.
Flow (j, 1 (left side in Figure 7) to orifice 3
When the fluid flows downstream through the office 3, a pressure difference Δp (static pressure) is generated between the upstream side and the downstream side of the office 3 because the flow of the fluid is obstructed by the orifice 3.

This pressure difference Δp represents the pressure on the upstream side of the orifice 3 as pl
Let the pressure on the downstream side be p2.

pi-p2=Δp... (1)
It is detected by the differential pressure gauge 7 from the relationship.

Between this pressure difference Δp and the volumetric flow 1fq, which is the amount of fluid passing through the orifice 3.

q-α・ε・π/4・d2・E stone f ... (2) There is a relationship.

Note that α is a flow rate coefficient, and ε is a fluid expansion correction coefficient.

As is clear from the second equation, the pressure difference Δp is proportional to the square of the volumetric flow rate q, and the relationship is graphed as shown in FIG. 8.

In this Fig. 8, each curve N and L
This represents the difference in characteristics due to the difference in the diameter d of the orifice 3.The smaller the diameter d of the orifice 3, the sharper the rise of the characteristic curve becomes. represents.

[Problem that the invention seeks to solve]

In this way, a fluid flow rate measuring device that uses a throttle device is
Although it is widely used as described above, the flow rate measuring device using this throttle device has the following drawbacks in principle, as is clear from FIG. 8, which shows its characteristics.

That is, as −, the pressure difference Δ is reduced using a throttling device.
In order to generate p, the fluid flow rate will be uniform. (For fluid to flow efficiently, the smaller the pressure difference Δp, the better.) Secondly, the pressure difference Δp generated by the throttle device increases in proportion to the square of the volumetric flow rate q, so the measurement range It is difficult to increase the

Thirdly, in order to increase the measurement range, it is necessary to widen the measurement range of the differential pressure gauge 7.
Increasing the measurement range reduces measurement accuracy. (Normally, measurement accuracy is determined in relation to the full scale, which is the upper limit of the measurement range.) Fourth, when an abnormal flow rate exceeding the measurement range flows, the pressure difference Δp increases rapidly and the differential pressure meter 7 may be damaged.

Fifth, in the case of the electrical differential pressure gauge 7, it is necessary to linearize the relationship between the pressure difference Δp and the volumetric flow rate q, and an electric circuit is needed to convert the obtained quadratic function change into a linear function change. This increases complexity and increases the cost of the entire device.

There were other problems and drawbacks.

The present invention was devised to solve the problems and drawbacks of the conventional examples described above, and utilizes the characteristic of a thin spring plate that the resistance characteristic against the fluid passing through the orifice 3 is inversely proportional to the pressure difference Δp of the fluid. , the relationship between the volumetric flow rate q and the pressure difference Δp in the fluid passing through the orifice 3 described above can be compensated, and the resulting volumetric flow iq
The purpose of this invention is to make the relationship between the pressure difference Δp and the pressure difference Δp linear, so that flow rate measurement can be carried out with a simple structure, a wide measurement range, and a highly accurate measurement.

[Failure to solve the problem]

Hereinafter, nine aspects of the present invention will be explained with reference to FIGS. 1 to 6 showing three embodiments of the present invention.

Components that are the same as those shown in FIG. 7 described above are designated by the same reference numerals, and their explanations will be omitted.

The diaphragm device for flow rate measurement according to the present invention includes a pipe body 1 that forms a fluid flow path, and a partition wall 2 that blocks this flow path.
An orifice 3 with a set diameter d is formed in this partition wall 2, and a thin spring plate 4 that closes the downstream opening of this orifice 3 at its tip end is assembled to the downstream wall surface portion of the partition wall 2 at its base end. is configured in a fixed manner.

The shape of the spring plate 4 is not specified, and the spring plate 4 can be positioned at its tip facing the orifice 3 in a posture that closes this orifice 3 from the downstream side, and can act through the orifice 3 on the upstream side. Any material may be used as long as it can be easily elastically deformed in the direction of opening the orifice 3 under pressure from the above.

Therefore, it is acceptable to make only the tip part into a flat plate shape and the remaining part into a thin rod shape or a coil shape.

[Effect]

Since the throttle device t of the present invention has the above-described configuration, when fluid flows in the pipe body 1 and a pressure difference Δp exists between the upstream side and the downstream side of the orifice 3, this pressure difference Δp
As a result, the spring plate 4 is deformed into a curve as shown by the dotted line in FIG. 1, and its tip is displaced downstream to allow the fluid to pass through the orifice 3.

The degree of bending deformation of the spring plate 4 toward the downstream side is determined by the pressure difference Δp
9 The larger the amount of dirt, the more the volumetric flow rate q increases. However, the larger the degree of bending deformation of the spring plate 4, the more it becomes a reaction force, and the larger the elasticity of the spring plate, the slower the increase in the volumetric flow rate q becomes. .

The relationship between the pressure difference Δp due to the action of the spring plate 4 and the volume flow rate q is as shown by the curve in FIG. 3, and the pressure difference Δp at the orifice 3 and the volume flow rate q! It is designed to emit a characteristic of 1 m that is opposite to that of a curved mouth, which is a characteristic related to q.

Therefore, by appropriately setting the elasticity of the spring plate 4, can the characteristic curve be shaped like the characteristic curve shown in FIG. When set to a value that can compensate for 11i, the relational characteristic between the pressure difference Δp of the fluid passing through the orifice 3 and the volumetric flow rate q becomes a composite characteristic of this curve opening and the curve C.

The characteristic curve becomes linear as shown in A.

Further, the pressure difference Δp can be reduced by selecting and setting the diameter d of the orifice 30 and the spring constant of the spring plate 4.

〔Example〕

A specific example of the spring plate 4 used in the present invention is shown in FIG.

The spring plates 4 shown in FIG. 6 are basically the same, but the one in FIG. 6(a) has a simple rectangular shape, and the spring plate 4 in FIG. 6(b) has a simple rectangular shape. The elasticity of the spring plate 4 is reduced and adjusted by forming notches 4a on both sides of the middle portion of the spring plate 4 shown in (a).

The spring plate 4 shown in FIG. 6(a) is made of phosphor bronze.

The width is 6.5 mm, the thickness is 0.2 mm, and the height h from the part fixed by the set screw 5 to the center of the orifice 3 is set to 12 fins.

Using the spring plate 4 shown in FIG. 6(a), the pressure difference Δ
p and volumetric flow! When we measured the relationship characteristics with q, as shown in Fig. 4, when the diameter d of orifice 3 is 2φ, curve 2 is obtained, when the diameter d of orifice 3 is 3φ, curve E is obtained, and when the diameter d of orifice 3 is 2φ, curve 2 is obtained. When it was 4φ, it became a curve.

Further, the spring plate 4 shown in FIG. 6(b) is similar to that shown in FIG. 6(a).
It is exactly the same as the spring plate 4 shown in , except for the notch 4a.
The width of the plate at the part where this is formed is 1.5 mm, as shown in Figure 6 (a).
It is easier to elastically deform than the spring plate 4 shown in FIG.

Using the spring plate 4 shown in FIG. 6(b), the pressure difference Δ
p and volumetric flow! When the relationship characteristics with q were similarly measured,
As shown in Fig. 5, the diameter d of the orifice 3 is 1.5.
When φ, the curve becomes 1~, and the diameter d of the orifice 3 is 2.
When the diameter d of the orifice 3 was 3φ, the curve was curved.

Note that the above measurements were performed using dry air as the fluid.

As is clear from the characteristic diagrams in FIGS. 4 and 5, the larger the diameter d of the orifice 3, the smaller the pressure difference Δp, and the smaller the spring constant of the spring plate 4, the more the above-mentioned tendency It can be seen that it becomes stronger.

〔Effect of the invention〕

As is clear from the above explanation, the flow rate measurement throttle device according to the present invention can linearize the relationship between pressure difference and volumetric flow rate, so if it is applied to an electric differential pressure gauge, the configuration of the differential pressure gauge will be extremely simple. In addition to being able to
High measurement accuracy can be obtained, the pressure difference can be made small, so the restriction of fluid flow rate can be reduced, and the relationship between pressure difference and volumetric flow rate is linear, so high measurement accuracy can be obtained. The measurement range can be widened while maintaining accuracy, and even if the fluid flow rate increases rapidly, the pressure difference will not increase rapidly, so there is less risk of damaging the differential pressure gauge. It is something that can be demonstrated.

[Brief explanation of drawings]

FIG. 1 is a vertical sectional view showing the basic configuration of the present invention. FIG. 2 is a front view of the embodiment shown in FIG. 1, viewed from the downstream side. FIG. 3 is a characteristic diagram of pressure difference and volumetric flow rate for explaining the operating characteristics of the apparatus of the present invention. FIGS. 4 and 5 show characteristic diagrams of pressure difference and volumetric flow rate corresponding to different embodiments of the spring plate used in the apparatus of the present invention. FIGS. 6(a) and 6(b) are front views showing different embodiments of the spring plate used in the device of the present invention. FIG. 7 is a longitudinal sectional view showing a conventional example. FIG. 8 is a characteristic diagram of pressure difference and volumetric flow rate in the conventional example shown in FIG. Explanation of symbols 1; Pipe body, 2; Partition wall, 3 Niorifice, 4; Spring plate, 5
; set screw, Δp; pressure difference, q; volumetric flow rate. Applicant Shin Meguro Keiki Co., Ltd.-h;AtP
qωa/m舊〜 ψso7t → Michibishi q (cc/win) bu9otsu77

Claims (1)

[Claims] A partition wall (2) is provided in a pipe body (1) forming a fluid flow path in a form that blocks the flow path, an orifice (3) having a set diameter is formed in the partition wall (2), and the orifice (3
) A spring plate (4) that closes the downstream opening of the valve (4) at its distal end is assembled and fixed to the partition wall (2) at its proximal end.