JP6249934B2 - Differential pressure flow meter - Google Patents

Description

  The present invention relates to a differential pressure flow meter, and more particularly to a differential pressure flow meter capable of measuring from a minute flow rate to a large flow rate with a single type.

  There are various types of differential pressure flowmeters such as those using capillaries (capillaries), orifices, oval nozzles or conical venturi tubes. As a prior example, a differential pressure flow meter using an orifice and a capillary (capillary) will be described as an example.

  As fluid passes through the orifice, the orifice causes a pressure drop. Here, when the conditions defined in JIS (Japanese Industrial Standards) are satisfied, the pressure difference (P1 -P2) before and after the orifice is measured using the measured values P1 and P2 of the pressure sensors installed on both sides of the orifice. The flow rate of the fluid F to be measured can be obtained (Patent Document 1).

  The differential pressure flow meter disclosed in Patent Document 1 is effective for a flow having a certain amount of flow, but is not suitable for a differential pressure flow meter used in a semiconductor manufacturing process in which measurement of a minute flow rate is central. It is.

  This is because the differential pressure flowmeter using the orifice (or nozzle) as described above is difficult to obtain a sufficient pressure difference in the throttle portion in the measurement of a minute flow rate. Must have a very small diameter. This not only requires fine processing that requires high technology, but also inevitably increases the manufacturing cost of the drawn portion. In addition, when the diameter of the throttle portion becomes small, it may be blocked by the very small impurities (particles) contained in the liquid passing through the throttle portion, and various obstacles due to vacuum boiling occur on the downstream side of the throttle portion. In some cases, cavitation (foaming phenomenon) occurred.

  Therefore, the invention shown in Patent Document 2 has been proposed. The invention shown in Patent Document 2 uses a capillary (capillary tube), and in order to increase the inner diameter of the capillary serving as the flow path and to store it in the main body in a compact manner, the curved portion is frequently used to reduce its overall length. This was used as a differential pressure generator. And the pressure difference (P1-P2) which generate | occur | produces before and after this differential pressure generation part was measured with the pressure sensor, and the flow volume of the liquid was calculated | required by the arithmetic processing part from the measured value of the said pressure difference. In addition, the temperature of the liquid flowing through the differential pressure generating unit is adjusted to a constant temperature by the temperature adjusting unit. By storing the viscosity of the fluid at a constant temperature, the flow rate of the fluid can be accurately obtained.

JP 2001-125649 A Japanese Patent No. 5119208

  However, as described above, the method of Patent Document 2 is configured with a curve in order to accommodate a thick and long differential pressure generating portion (capillary) in a compact manner. As a result, complicated processing is required and processing costs increase. In addition, the supply amount of the raw material liquid to the film deposition system may vary depending on the operating environment. However, this method cannot be handled unless the entire capillary assembly is replaced because the differential pressure generation unit (capillary) is fixed. is there.

  The present invention has been made in view of such problems of the prior art. First, it can easily cope with a large change in flow rate from a very small flow rate to a large flow rate of a raw material liquid or gas. Secondly, an object is to provide a differential pressure flow meter that is simple in design with low manufacturing cost despite high measurement accuracy.

The differential pressure flow meter A according to claim 1 is:
A flow meter body 1 through which the fluid F to be measured flows;
A differential pressure generator 10 that is built into the flow meter body 1 and provides resistance to the flow of the fluid F to be measured;
The inlet side space 12 provided on both sides of the differential pressure generating unit 10 and into which the fluid F to be measured flowing toward the differential pressure generating unit 10 flows, and the fluid F to be measured from the differential pressure generating unit 10 toward the outside. An outlet side space 14 that flows out;
An inlet side pressure sensor PG1 for detecting the pressure P1 of the inlet side space 12, and an outlet side pressure sensor PG2 for detecting the pressure P2 of the outlet side space 14,
And an arithmetic processing unit 5 for obtaining a flow rate of the fluid F to be measured from a pressure difference (P1-P2) which is a difference between measured values of both sensors PG1, PG2.
The differential pressure generator 10
The cylindrical space 16 connecting the inlet side space 12 and the outlet side space 14 can be inserted into and removed from the core material mounting hole 2 communicating with the inlet side of the cylindrical space 16 from the front surface at the upper part of the inlet side of the flowmeter body 1. Is inserted into the cylindrical space 16, and the core portion 18 b at the tip thereof is inserted into the cylindrical space 16, so that the fluid F to be measured flows through the annular flow gap X between the cylindrical space 16 and the cylindrical space 16. It is characterized by comprising the member 18.

  A differential pressure flow meter A according to a second aspect is characterized in that the columnar member 18 is concentrically disposed in the cylindrical space 16 in the first aspect.

  According to this, since the columnar member 18 is detachably disposed in the cylindrical space 16, the diameter of the core portion 18b of the columnar member 18 is increased when the fluid F to be measured has a very small flow rate. The flow gap X is narrowed, and conversely, when the fluid F to be measured has a large flow rate, the diameter of the cylindrical member 18 is narrowed to widen the flow gap X so that the flow rate can be changed from a small flow rate to a large flow rate. I can do it. That is, the flow rate can be changed only by replacing the cylindrical member 18.

  If the columnar member 18 is concentrically disposed in the cylindrical space 16, the “relational expression of the differential pressure of the fluid flowing through the concentric circular pipe and the flow rate” is well applied and measurement can be performed with high accuracy.

It is sectional drawing of one Example of this invention. It is sectional drawing of the direction orthogonal to FIG.

  Hereinafter, the present invention will be described in detail according to illustrated embodiments. The flow meter main body 1 of the differential pressure flow meter A of the present invention is a rectangular parallelepiped metal member, in which a flow path for the fluid F to be measured is formed. The flow path includes an inlet 11, an inlet-side space 12, a cylindrical space 16 that forms part of the differential pressure generating unit 10, an outlet-side space 14, and an outlet 15. The figure schematically shows a differential pressure flow meter A of the present invention.

  The cylindrical space 16 is a space formed in a straight cave shape with a circular cross section as shown in FIG. An inlet 11 and an outlet 15 are formed at the front end and the rear end of the flow meter main body 1. An inlet-side space 12 is recessed at the bottom front end of the flow meter main body 1 and an outlet-side space 14 is recessed at the bottom rear end, and the inlet-side pressure sensor PG1 and the outlet-side pressure sensor PG2 are fitted in each. The diaphragms D1 and D2 are disposed so as to face the inlet side space 12 and the outlet side space 14, respectively.

  An inlet 11 and an outlet 15 are connected to the inlet side space 12 and the outlet side space 14, and the inlet side space 12 is further connected to the inlet side of the cylindrical space 16 by an inlet side communication passage 17 that is a part of the inlet side space 12. The outlet side space 14 is connected to the outlet side of the cylindrical space 16 by an outlet side communication passage 19 which is a part of the outlet side space 14 and constitutes a single flow path.

  Further, a core material mounting hole 2 communicating from the front surface to the inlet side of the cylindrical space 16 is formed in the upper part on the inlet side of the flow meter main body 1, and in order to ensure airtightness or liquid tightness at the hole edge. An O-ring 8 is fitted. In the present embodiment, the core material mounting hole 2 and the cylindrical space 16 are provided concentrically (that is, the central axes coincide with each other, in other words, are coaxial). In the present embodiment, the diameter of the core material mounting hole 2 is smaller than the diameter of the cylindrical space 16.

  The columnar member 18 is provided with a flange 18c having a large diameter at the base of the fitting portion 18a, and the main body portion is formed in the core material mounting hole 2 so that the main body portion can be inserted and removed. A fitting portion 18 a that is removably fitted into the core material mounting hole 2 is formed with the same diameter as the core material mounting hole 2, and the O-ring 8 keeps the inside airtight. The diameter of the core portion 18b of the columnar member 18 inserted into the cylindrical space 16 is appropriately set according to the flow rate of the fluid F to be measured flowing through the annular flow gap X described later. In the case of the figure, the entire cylindrical member 18 including the core part 18b is cylindrical, but as the flow rate increases, the diameter of the core part 18b inserted into the cylindrical space 16 is indicated by the phantom line. In this case, a stepped cylinder is formed. Therefore, many types of cylindrical members 18 are prepared depending on the flow rate range. This makes it possible to measure a wide range from minute flow rates to large flow rates.

  In measuring the fluid F to be measured, the most appropriate columnar member 18 is selected in consideration of the flow rate of the fluid F to be measured, and is inserted and fixed in the core material mounting hole 2. Thereby, the central axis of the core portion 18 b of the columnar member 18 is inserted in a state (concentric state) that coincides with the central axis of the cylindrical space 16. And the core part 18b is inserted in the cylindrical space 16, and an annular | circular shaped clearance gap is formed at equal intervals between both. This annular gap is the flow gap X and serves as the differential pressure generator 10 that provides flow resistance to the fluid F to be measured. The passage L of the differential pressure generating unit 10 has a length from the inlet to the outlet of the flow gap X. The core portion 18b and the cylindrical space 16 are preferably coaxial, but a slight deviation is substantially coaxial as long as the measurement does not affect the measurement. A relational expression between the differential pressure ΔP of the fluid flowing through the concentric circular pipe (flow gap X) and the flow rate Q is shown below.

Q = ΔPπ [a ⁴ −b ⁴ − {(a ² −b ² ) ² / In (a / b)}] / 8 μL
Q = flow rate ΔP = differential pressure a = radius of cylindrical space 16 b = radius of columnar member 18 μ = fluid viscosity L = flow path length In the arithmetic processing unit 5, the inlet side pressure sensor PG1 and the outlet side pressure sensor PG2 The pressure data is input, the differential pressure ΔP is calculated, and the flow rate Q is calculated. In order to measure the accurate flow rate of various fluids, a method of measuring and calibrating the flow rate using an electronic balance or the like is used.

  The present invention can also be applied to a high-temperature fluid. In this case, a pressure sensor that can withstand high temperatures is used, and the entire flowmeter (excluding the arithmetic processing unit) is heated to a high temperature to adjust the temperature.

  A: Differential pressure flow meter, D1, D2: Diaphragm, F: Fluid to be measured, P1: Inlet side pressure, P2: Outlet side pressure, PG1: Inlet side pressure sensor, PG2: Outlet side pressure sensor, X: Flow gap 1: flow meter main body, 2: core material mounting hole, 5: arithmetic processing unit, 8: O-ring, 10: differential pressure generating unit, 11: inlet, 12: inlet side space, 14: outlet side space, 15: Outlet, 16: cylindrical space, 17: inlet side communication passage, 18: columnar member, 18a: fitting portion, 18b: core material portion, 18c: flange, 19: outlet side communication passage.

Claims (2)

A flow meter body through which the fluid to be measured flows;
A differential pressure generator that is built in the flow meter body and provides resistance to the flow of the fluid to be measured;
An inlet side space provided on both sides of the differential pressure generating unit, and into which the fluid to be measured flowing toward the differential pressure generating unit flows; and an outlet side space from which the fluid to be measured from the differential pressure generating unit flows out to the outside. ,
An outlet-side pressure sensor for detecting the pressure of the inlet-side pressure sensor and the outlet-side space for detecting the pressure of the inlet-side space,
An arithmetic processing unit that obtains the flow rate of the fluid to be measured from the pressure difference that is the difference between the measured values of both sensors,
The differential pressure generating portion, a cylindrical space connecting said outlet space and the inlet side space, the core communicating with the inlet side of the cylindrical space from the front at an inlet side upper portion of the meter body mounted A fluid to be measured is caused to flow through an annular flow gap between the cylindrical space by being inserted into the hole so as to be removably inserted and a core material portion at the tip thereof is inserted into the cylindrical space. A differential pressure flow meter comprising a cylindrical member. Differential pressure flow meter according to claim 1, wherein said cylindrical member is disposed in the cylindrical space at concentric.

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