A differential-pressure flowmeter that can reduce (eliminate) a difference between the ambient temperature of one pressure sensor and the ambient temperature of another pressure sensor so as to allow for accurate and stable pressure measurement is provided, and a flow-rate controller equipped with such a differential-pressure flowmeter is provided. Provided are a body having a main fluid channel through which a fluid, whose pressure is to be measured, flows, and two pressure sensors held by the body and arranged in series relative to the main fluid channel, and a temperature balancer composed of a material with high thermal conductivity is accommodated in a recess that is formed in the body located below the two pressure sensors.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to differential-pressure flowmeters and flow-rate controllers used in fluid transport pipes in various industrial fields, such as chemical factories, semiconductor manufacturing, food manufacturing, and biotechnology.

This application is based on Japanese Patent Application No. 2009-024714, the content of which is incorporated herein by reference.

2. Description of Related Art

Japanese Unexamined Patent Application, Publication No. 2009-2901 discloses a known example of a differential-pressure flowmeter and a flow-rate controller used in fluid transport pipes in various industrial fields, such as chemical factories, semiconductor manufacturing, food manufacturing, and biotechnology.

Two pressure sensors constituting the differential-pressure flowmeter and the flow-rate controller disclosed in Japanese Unexamined Patent Application, Publication No. 2009-2901 each have a characteristic such that an indication value changes as the ambient temperature (surrounding temperature) changes; that is, the indication value increases as the ambient temperature becomes higher.

Therefore, when a temperature difference occurs between the ambient temperature of one of the pressure sensors and the ambient temperature of the other pressure sensor as a result of a change in the ambient temperature of only the one pressure sensor, the pressure measurement by the pressure sensors becomes unstable, possibly causing a malfunction.

BRIEF SUMMARY OF THE INVENTION

The present invention has been made in view of these circumstances, and an object thereof is to provide a differential-pressure flowmeter that can reduce (eliminate) the difference between the ambient temperature of one pressure sensor and the ambient temperature of another pressure sensor so as to allow for accurate and stable pressure measurement, and to provide a flow-rate controller equipped with such a differential-pressure flowmeter.

In order to achieve the aforementioned object, the present invention provides the following solutions.

A differential-pressure flowmeter according to a first aspect of the present invention includes a body having a main fluid channel through which a fluid, whose pressure is to be measured, flows, and two pressure sensors held by the body and arranged in series relative to the main fluid channel, and a temperature balancer composed of a material with high thermal conductivity is accommodated in a recess that is formed in the body located below the two pressure sensors.

With the differential-pressure flowmeter according to the first aspect of the present invention, since the temperature balancer composed of a material with high thermal conductivity (e.g., aluminum alloy A5052) is embedded (fitted) in the body located below the two pressure sensors, a difference between the ambient temperature of one of the pressure sensors and the ambient temperature of the other pressure sensor can be reduced (eliminated), thereby allowing for accurate and stable pressure measurement.

A flow-rate controller according to a second aspect of the present invention includes a differential-pressure flowmeter that can reduce (eliminate) a difference between the ambient temperature of one pressure sensor and the ambient temperature of another pressure sensor so as to allow for accurate and stable pressure measurement.

With the flow-rate controller according to the second aspect of the present invention, the accuracy and stability of a measured flow-rate value (measured flow rate) are enhanced, whereby the accuracy in fluid flow-rate control of the measured flow rate of the fluid flowing through the main fluid channel can be enhanced.

In a flow-rate controller according to a third aspect of the present invention, a body located below a motor that vertically moves a valve plug of a flow-rate control valve and a control board that controls the degree of opening of the flow-rate control valve is connected to a body located below two pressure sensors via a constricted section formed so as to have a width smaller than that of the body located below the two pressure sensors and a height smaller than that of the body located below the two pressure sensors.

With the flow-rate controller according to the third aspect of the present invention, since the body located below the two pressure sensors and the body located below the control board and the motor serving as a heat source are connected to each other via the constricted section, heat transmission from the body located below the control board and the motor serving as a heat source to the body located below the two pressure sensors can be minimized, whereby a difference between the ambient temperature of one of the pressure sensors and the ambient temperature of the other pressure sensor can be reduced (eliminated), and the accuracy in fluid flow-rate control of the measured flow rate of the fluid flowing through the main fluid channel can be further enhanced.

The aforementioned flow-rate controller preferably includes base components disposed between the bodies and an installation surface and fixed to the bodies with fastening members, and a base component positioned between a base component located below the two pressure sensors and a base component located below the motor and the control board is preferably provided with at least one slit that extends therethrough in a thickness direction thereof.

With such a flow-rate controller, since at least one (e.g., seven) slit is formed in the base component positioned between the base component located below the two pressure sensors and the base component located below the control board and the motor serving as a heat source, heat transmission from the base component located below the control board and the motor serving as a heat source to the base component located below the two pressure sensors can be minimized, whereby a difference between the ambient temperature of one of the pressure sensors and the ambient temperature of the other pressure sensor can be reduced (eliminated), and the accuracy in fluid flow-rate control of the measured flow rate of the fluid flowing through the main fluid channel can be further enhanced.

In the aforementioned flow-rate controller, it is more preferable that at least one cooling groove that allows a front surface and a rear surface to communicate with each other be formed in an upper surface of the base component located below the motor and the control board.

With such a flow-rate controller, since at least one (e.g., two) cooling groove is formed in the upper surface of the base component located below the control board and the motor serving as a heat source and the heat in the body and the base component located below the control board and the motor serving as a heat source is carried away by the air passing through the cooling groove, heat transmission from the body and the base component located below the control board and the motor serving as a heat source to the body and the base component located below the two pressure sensors can be minimized, whereby a difference between the ambient temperature of one of the pressure sensors and the ambient temperature of the other pressure sensor can be reduced (eliminated), and the accuracy in fluid flow-rate control of the measured flow rate of the fluid flowing through the main fluid channel can be further enhanced.

In the aforementioned flow-rate controller, it is more preferable that at least one groove that allows a front surface and a rear surface to communicate with each other be formed in a lower surface of the base component located below the motor and the control board.

With such a flow-rate controller, since at least one (e.g., one) groove is formed in the lower surface of the base component located below the control board and the motor serving as a heat source, the heat from an installation surface can be prevented from entering the base components, whereby a difference between the ambient temperature of one of the pressure sensors and the ambient temperature of the other pressure sensor can be reduced (eliminated), and the accuracy in fluid flow-rate control of the measured flow rate of the fluid flowing through the main fluid channel can be further enhanced.

In the aforementioned flow-rate controller, it is more preferable that at least one groove that allows a front surface and a rear surface to communicate with each other be formed in a lower surface of the base component located below the two pressure sensors.

According to such a flow-rate controller, since at least one (e.g., one) groove is formed in the lower surface of the base component located below the two pressure sensors, the heat from the installation surface can be prevented from entering the base components, whereby a difference between the ambient temperature of one of the pressure sensors and the ambient temperature of the other pressure sensor can be reduced (eliminated), and the accuracy in fluid flow-rate control of the measured flow rate of the fluid flowing through the main fluid channel can be further enhanced.

With the differential-pressure flowmeter according to the present invention, a difference between the ambient temperature of one of the pressure sensors and the ambient temperature of the other pressure sensor can be reduced (eliminated), thereby advantageously allowing for accurate and stable pressure measurement.

With the flow-rate controller that controls the degree of opening of the flow-rate control valve by using a measured value of the differential-pressure flowmeter according to the present invention, the accuracy and stability of a measured flow-rate value (measured flow rate) are enhanced, whereby the accuracy in fluid flow-rate control of the measured flow rate of the fluid flowing through the main fluid channel can advantageously be enhanced.

DETAILED DESCRIPTION OF THE INVENTION

A differential-pressure flowmeter and a flow-rate controller according to an embodiment of the present invention will be described below with reference toFIGS. 1 to 5C.

FIG. 1is a front view of the flow-rate controller according to this embodiment.FIG. 2is a plan view ofFIG. 1.FIG. 3is a sectional view taken along line A-A inFIG. 2.FIG. 4is a sectional view taken along line B-B inFIG. 2.FIG. 5Ais a plan view illustrating a temperature balancer incorporated in the differential-pressure flowmeter according to this embodiment.FIG. 5Bis a front view of the temperature balancer.FIG. 5Cis a side view of the temperature balancer.

A flow-rate controller10is a flow-rate controlling device that is incorporated in a pipe11communicating with a main fluid channel12, to be described later, and keeps the fluid flow rate of a liquid (such as a chemical solution) flowing through the main fluid channel12constant. The flow-rate controller10mainly includes a differential-pressure flowmeter20for measuring an actual fluid flow rate and a flow-rate control valve60capable of controlling the degree of opening of a valve plug.

The differential-pressure flowmeter20is disposed on the upstream side of the flow-rate control valve60, as viewed in the direction of flow of the fluid flowing through the main fluid channel12.

The differential-pressure flowmeter20is configured such that a pair of pressure sensors21A and21B are arranged in series with an orifice unit40therebetween. Specifically, in the differential-pressure flowmeter20, pressure values of the fluid creating a pressure difference as a result of passing through the orifice unit40are individually detected by the two pressure sensors21A and21B, and these two pressure values are converted to electrical signals which are then input to a control unit (not shown). The control unit receiving the input signals of the pressure values can measure the flow rate of the fluid flowing through the main fluid channel12by converting a differential pressure obtained from the two pressure values to a flow rate. In the description below, the pressure sensor21A disposed on the upstream side relative to the orifice unit40will be referred to as “first sensor” and the pressure sensor21B disposed on the downstream side will be referred to as “second sensor” so as to distinguish the two pressure sensors from each other.

Since the first sensor21A and the second sensor21B basically have the same configuration, the following description will be directed to the first sensor21A disposed on the upstream side.

As shown inFIG. 3, the first sensor21A includes, for example, a sensor body (pressure detecting section)23disposed in a pressure introduction channel22that branches off upward in a T-shape from the main fluid channel12through which the fluid, whose pressure is to be measured, flows. In this embodiment, the pressure introduction channel22that communicates with a sensor accommodation space25located thereabove is provided substantially orthogonal to the main fluid channel12extending through a body24. The pressure introduction channel22has an inclined surface26at a wall surface thereof on the downstream side as viewed in the direction of flow of the fluid. The inclined surface26is inclined in a direction that widens the opening area at the fluid entrance side. This inclined surface26provides a slope on a sidewall surface of the pressure introduction channel22by forming a downstream half thereof in a substantially truncated cone shape, and the pressure introduction channel22is configured such that the channel sectional area at the lower side, which is the fluid entrance side communicating with the main fluid channel12, is larger than that at the fluid exit side communicating with the sensor accommodation space25.

The sensor body23is not limited in particular so long as it can detect the fluid pressure, but is preferably, for example, a piezoelectric-type pressure sensor, a capacitance-type pressure sensor, or a strain-gauge-type pressure sensor. In this embodiment, a strain-gauge-type pressure sensor is used as the sensor body23.

The body24is integrally formed by using, for example, polytetrafluoroethylene (PTFE). A recess28(seeFIG. 4) that accommodates a temperature balancer27shown inFIG. 5is formed in a lower surface of the body24located below the first sensor21A and the second sensor21B.

As shown inFIGS. 5A to 5C, the temperature balancer27is a thin-plate-like component with a rectangular shape in plan view and an angular U-shape in side view, and is integrally formed by using, for example, aluminum alloy A5052. A through-hole27athat is rectangular in plan view is formed in the middle of the temperature balancer27.

The body24located below the first sensor21A and the second sensor21B and a body24located below a motor61and a control board66, to be described later, are connected to each other via a connecting section (constricted section)24A formed so as to have a width (i.e., length in the vertical direction inFIG. 2) smaller than that of the body24located below the first sensor21A and the second sensor21B and a height (i.e., length in the vertical direction inFIGS. 1 and 3) smaller than that of the body24located below the first sensor21A and the second sensor21B. The main fluid channel12is formed within this connecting section24A.

A cover29is attached to an upper section of the body24so as to cover associated components of the sensor body23. The body24is firmly supported above a base component14with fastening members, such as screws13, and the body24is joined (connected) to the pipe11, which communicates with the main fluid channel12, by using cap nuts15having a joint structure.

The base component14is integrally formed by using, for example, polypropylene (PP). As shown inFIG. 2, the base component14positioned between the base component14located below the first sensor21A and the second sensor21B and the base component14located below the motor61and the control board66, to be described later, is provided with one or more (seven in this embodiment) slits14aarrayed in the width direction (i.e., the vertical direction inFIG. 2). The slits14aare through-holes extending through the aforementioned base component14in the thickness direction thereof and are formed in the shape of an elongate hole in the longitudinal direction (i.e., the horizontal direction inFIG. 2).

As shown inFIG. 1, one or more (two in this embodiment) cooling grooves (first grooves)14barranged in the longitudinal direction (i.e., the horizontal direction inFIG. 1) are formed in an upper surface of the base component14located below the motor61and the control board66, to be described later. The cooling grooves14bare rectangular in front view and allow the front and rear surfaces to communicate with each other, and are formed along the width direction (i.e., a direction orthogonal to the plane of the drawing inFIG. 1).

On the other hand, as shown inFIGS. 1 and 3, at least one (one in this embodiment) groove (second groove)14cis formed along the width direction (i.e., the direction orthogonal to the plane of the drawing inFIGS. 1 and 3) in a lower surface of the base component14located below the motor61and the control board66, to be described later. The groove14cis rectangular in front view and allows the front and rear surfaces to communicate with each other.

Furthermore, as shown inFIGS. 1 and 3, at least one (one in this embodiment) groove (third groove)14dis formed along the width direction (i.e., the direction orthogonal to the plane of the drawing inFIGS. 1 and 3) in a lower surface of the base component14located below the first sensor21A and the second sensor21B. The groove14dis rectangular in front view and allows the front and rear surfaces to communicate with each other.

The orifice unit40includes an orifice body41disposed between the first sensor21A and the second sensor21B. This orifice body41is provided with an orifice channel42having a channel sectional area smaller than that of the main fluid channel12formed in the body24of the first sensor21A and the second sensor21B. In the example shown in the drawings, the channel sectional area decreases in a stepwise manner from the main fluid channel12to the orifice channel42with the minimum diameter.

One end (i.e., the lower end inFIG. 3) of the orifice body41that has the orifice channel42extends into the body24.

In the main fluid channel12at the downstream side of the second sensor21B, the flow-rate control valve60is disposed in the body24used in common with the first sensor21A and the second sensor21B. The flow-rate control valve60is configured to control the degree of opening so that a difference between a measured flow-rate value of the differential-pressure flowmeter20and a preliminarily set flow rate is within a predetermined range.

The flow-rate control valve60has a configuration that opens and closes a needle (valve plug)62by vertically moving the needle62using a driving mechanism equipped with the motor61, such as a stepping motor, so as to set the needle62in a desired opening position relative to a valve seat63. However, regarding the flow-rate control valve60, the driving mechanism and the valve-plug mechanism thereof are not limited in particular so long as the degree of opening of the needle62can be adjusted.

Reference numeral64in the drawings denotes a cover that covers the motor61and the like,65denotes a lid that covers an opening formed at one end (i.e., the upper end inFIG. 3) of the cover64, and66denotes a control board.

Prior to commencing operation, the flow-rate controller10having the above configuration inputs and stores, in the control unit, a desired fluid flow rate (referred to as “set flow rate” hereinafter) Qr to be kept constant. The control unit operates the needle62of the flow-rate control valve60so as to set an initial degree of opening thereof to a degree of valve opening corresponding to the input set flow rate Qr. When a fluid is made to flow through the flow-rate controller10, since the differential-pressure flowmeter20measures a flow rate (referred to as “measured flow rate” hereinafter) Qf of the actually flowing fluid and inputs the measured flow rate Qf to the control unit, the control unit calculates therein a flow-rate difference ΔQ (ΔQ=Qr−Qf) between the measured flow rate Qf and the set flow rate Qr and performs a comparison.

The aforementioned flow-rate difference ΔQ is compared with a preliminarily set allowable range q. When the absolute value of the flow-rate difference ΔQ is smaller than the allowable range q (ΔQ<q), it is determined that the fluid is flowing at the desired set flow rate Qr, and the flow-rate control valve60is maintained at the initial degree of opening.

On the other hand, when the aforementioned flow-rate difference ΔQ is a positive value (Qr>Qf) and the absolute value of the flow-rate difference ΔQ is larger than or equal to the allowable range q (ΔQ≧q), it can be determined that the fluid is in a low flow-rate state where the measured flow rate Qf does not satisfy the desired set flow rate Qr. Therefore, in order to increase the measured flow rate Qf, the needle62of the flow-rate control valve60is moved in a direction for increasing the degree of opening from the initial degree of opening.

When the aforementioned flow-rate difference ΔQ is a negative value (Qr<Qf) and the absolute value of the flow-rate difference ΔQ is larger than or equal to the allowable range q (ΔQ≧q), it can be determined that the fluid is in a high flow-rate state where the measured flow rate Qf does not satisfy the desired set flow rate Qr. Therefore, in order to decrease the measured flow rate Qf, the needle62of the flow-rate control valve60is moved in a direction for reducing the degree of opening from the initial degree of opening.

In this manner, the flow-rate controller10performs feedback control so that the absolute value of the flow-rate difference ΔQ obtained by a comparison with the set flow rate Qr on the basis of the measured flow rate Qf input from the differential-pressure flowmeter20satisfies the predetermined allowable range, whereby the flow rate of the fluid flowing through the main fluid channel12can be kept constant.

With the differential-pressure flowmeter20according to this embodiment, since the temperature balancer27composed of a material with high thermal conductivity (aluminum alloy A5052 in this embodiment) is embedded (fitted) in the body24located below the first sensor21A and the second sensor21B, a difference between the ambient temperature of the first sensor21A and the ambient temperature of the second sensor21B can be reduced (eliminated), thereby allowing for accurate and stable pressure measurement.

Furthermore, with the flow-rate controller10that controls the degree of opening of the flow-rate control valve60by using a measured value of the differential-pressure flowmeter20according to this embodiment, the accuracy and stability of a measured flow-rate value (measured flow rate Qf) are enhanced, whereby the accuracy in fluid flow-rate control of the measured flow rate Qf of the fluid flowing through the main fluid channel12can be enhanced.

With the flow-rate controller10according to this embodiment, since the body24located below the first sensor21A and the second sensor21B and the body24located below the control board66and the motor61serving as a heat source are connected to each other via the connecting section24A, heat transmission from the body24located below the control board66and the motor61serving as a heat source to the body24located below the first sensor21A and the second sensor21B can be minimized, whereby a difference between the ambient temperature of the first sensor21A and the ambient temperature of the second sensor21B can be reduced (eliminated), and the accuracy in fluid flow-rate control of the measured flow rate Qf of the fluid flowing through the main fluid channel12can be further enhanced.

Furthermore, with the flow-rate controller10according to this embodiment, since the base component14positioned between the base component14located below the first sensor21A and the second sensor21B and the base component14located below the control board66and the motor61serving as a heat source is provided with one or more (seven in this embodiment) slits14a, heat transmission from the base component14located below the control board66and the motor61serving as a heat source to the base component14located below the first sensor21A and the second sensor21B can be minimized, whereby a difference between the ambient temperature of the first sensor21A and the ambient temperature of the second sensor21B can be reduced (eliminated), and the accuracy in fluid flow-rate control of the measured flow rate Qf of the fluid flowing through the main fluid channel12can be further enhanced.

Furthermore, with the flow-rate controller10according to this embodiment, since one or more (two in this embodiment) cooling grooves14bare formed in the upper surface of the base component14located below the control board66and the motor61serving as a heat source and the heat in the body24and the base component14located below the control board66and the motor61serving as a heat source is carried away by the air passing through the cooling grooves14b, heat transmission from the body24and the base component14located below the control board66and the motor61serving as a heat source to the body24and the base component14located below the first sensor21A and the second sensor21B can be minimized, whereby a difference between the ambient temperature of the first sensor21A and the ambient temperature of the second sensor21B can be reduced (eliminated), and the accuracy in fluid flow-rate control of the measured flow rate Qf of the fluid flowing through the main fluid channel12can be further enhanced.

Furthermore, with the flow-rate controller10according to this embodiment, since at least one (one in this embodiment) groove14cis formed in the lower surface of the base component14located below the control board66and the motor61serving as a heat source and at least one (one in this embodiment) groove14dis formed in the lower surface of the base component14located below the first sensor21A and the second sensor21B, the heat from an installation surface (not shown) can be prevented from entering the base components14, whereby a difference between the ambient temperature of the first sensor21A and the ambient temperature of the second sensor21B can be reduced (eliminated), and the accuracy in fluid flow-rate control of the measured flow rate Qf of the fluid flowing through the main fluid channel12can be further enhanced.

Furthermore, with the flow-rate controller10according to this embodiment, since at least one (one in this embodiment) groove14cis formed in the lower surface of the base component14located below the control board66and the motor61serving as a heat source and the heat in the base component14located below the control board66and the motor61serving as a heat source is carried away by the air passing through the groove14c, heat transmission from the base component14located below the control board66and the motor61serving as a heat source to the base component14located below the first sensor21A and the second sensor21B can be minimized, whereby a difference between the ambient temperature of the first sensor21A and the ambient temperature of the second sensor21B can be reduced (eliminated), and the accuracy in fluid flow-rate control of the measured flow rate Qf of the fluid flowing through the main fluid channel12can be further enhanced.

The present invention is not limited to the above embodiment, and various changes and modifications are permissible so long as they do not depart from the spirit of the invention.