Valve element and fluid control valve

The present invention is directed a valve element which is intended to improve a sealing property at a time of closing a fluid control valve and to improve stability while maintaining durability for a long time period, wherein the valve element constitutes one of a valve seat surface or a seating surface and the valve element includes a concave portion formed in an opposing surface facing the valve seat surface and a resin coating film which is formed in the concave portion and contacts the valve seat surface.

TECHNICAL FIELD

The present invention relates to a fluid control valve for use in, for example, a mass flow controller and the like for controlling a flow rate of gas, and in particular relates to a valve body or valve seat for use in the fluid control valve.

BACKGROUND ART

As a mass flow controller for controlling a flow rate of gas for use in, for example, a semiconductor process, there has been known a configuration as shown in Patent Literature 1.

A fluid control valve built in this mass flow controller includes: a valve seat having a valve port formed to communicate with an upstream side flow passage; a diaphragm valve body seated on the valve seat to close the valve port; and an actuator for driving the diaphragm valve body. In this configuration, in order to improve a sealing property while preventing an internal leakage of the fluid, a resin coating is applied over an entire lower surface facing the valve seat in the diaphragm valve body.

Herein, since the sealing property cannot be ensured if there is unevenness on a surface of a thin film formed by the resin coating, the surface of the thin film is required to have flatness with high precision. Therefore, it is necessary to polish the surface of the thin film by a process such as plane-lapping and the like.

However, since the thin film formed by the resin coating is thin in film thickness and low in hardness, a lapped surface formed by the plane-lapping tends to incline, and this results in a problem that the thin film may peel off and the film thickness may not be uniform due to side cutting. Therefore, even though the polishing process such as plane-lapping is performed, the sealing property is not sufficiently ensured, and also it becomes difficult to maintain durability for a long time period.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Field

Therefore, the present invention has been made to solve the problems described above, and an object thereof is to improve flatness of a surface of a resin coating to thereby allow for a uniform film thickness of the resin coating, to improve a sealing property at a time of closing a fluid control valve, and to improve stability of the sealing property by maintaining durability for a long time period.

Solution to Problem

That is, a valve element according to the present invention constitutes one of a valve seat surface or a seating surface seated on the valve seat surface, wherein the valve element includes:

a concave portion formed in an opposing surface facing the other of the valve seat surface or the seating surface; and

a resin coating film which is formed in the concave portion and contacts the other of the valve seat surface or the seating surface.

With this valve element, since the concave portion is formed in the opposing surface of the valve element and the resin coating film is formed in the concave portion, the resin coating film contacts the other of the valve seat surface or the seating surface, whereby the sealing property can be improved at the time of closing the fluid control valve.

Further, since the resin coating film is formed in the concave portion, when a surface of the resin coating film is polished, an opposing surface portion other than the concave portion acts as a guide for polishing the surface to thereby allow for a uniform the film thickness of the resin coating film while improving the flatness of the resin coating film.

Moreover, since the film thickness of the resin coating film is sufficiently small with respect to a main body of the valve element having the opposing surface, a thermal expansion amount of the resin coating film can be made small with respect to a thermal expansion amount of the main body of the valve element, whereby a temperature effect due to formation of the resin coating film can be reduced.

In addition, since the sealing property is ensured by the resin coating film, when the other of the valve seat surface or the seating surface contacts the resin coating film, an elastic deformation amount of the resin coating film can be reduced, thereby making it hard to form a contact impression or unevenness on the resin coating film and the sealing property can be ensured for a long time period.

Thus, the sealing property can be improved at the time of closing the fluid control valve and the stability can be improved while maintaining the durability for a long time period.

Preferably, a peripheral portion of the concave portion in the opposing surface is a polish limiting guide portion in the case of polishing the surface of the resin coating film.

With this polish limiting guide portion, a polishing member is pressedly abutted to the polish limiting guide portion to thereby prevent the polishing member from inclining, whereby the film thickness of the resin coating film can be made uniform. Here, the polish limiting guide portion is preferably configured in an outer peripheral portion of the concave portion. With this configuration, even though a part of the polishing member is floated to be inclined with respect to the polish limiting guide portion, the resin coating film located inside the polish limiting guide portion is protected by the polish limiting guide portion. In the case where the resin coating is applied to the outside of the polish limiting guide, the resin coating film outside the polish limiting guide is to be additionally cut away. However, since the outside resin coating portion does not contribute to the valve seal, there is no problem.

In addition, in order to eliminate the additional resin coating portion which does not contribute to the valve seal and stably perform the polishing guided by the polish limiting guide portion, the polish limiting guide portion is preferably formed on the outermost peripheral edge portion of the opposing surface.

The opposing surface preferably includes a driving force acting surface that contacts a drive mechanism for driving the valve element, wherein no resin coating film is formed on the driving force acting surface.

With this configuration, since a stroke amount by the drive mechanism can be transmitted to the valve element without a loss, the sealing property can be ensured for a long time period and the flow rate control can be accurately performed.

In addition, in the case where the resin coating film is formed on the driving force acting surface, when the drive mechanism applies the driving force onto the driving force acting surface, the resin coating film is elastically deformed and a stroke amount by the drive mechanism is partly absorbed. Therefore, it is difficult to ensure the sealing property for a long time period and it is difficult to accurately perform the flow rate control.

Advantageous Effects of Invention

According to the present invention configured as described above, since the concave portion is formed in the opposing surface and the resin coating film is formed in the concave portion, the film thickness of the resin coating film can be made uniform while improving the flatness of the resin coating surface. Thus, the sealing property can be improved at the time of closing the fluid control valve and the stability can be improved while maintaining the durability for a long time period.

DESCRIPTION OF EMBODIMENTS

First Embodiment

The following describes one embodiment of a mass flow controller100incorporating a fluid control valve including a valve element according to the present invention referring to the accompanying drawings.

The mass flow controller100of the present embodiment is intended to be used in a semiconductor manufacturing apparatus, and as shown inFIG. 1, the mass flow controller100is equipped with: a body5; a flow rate detecting mechanism2; a fluid control valve3; and a control unit (not shown). In this body5, formed is a flow passage51through which fluid such as gas flows, wherein the gas is a measurement target to be used, for example, in a semiconductor process. The flow rate detecting mechanism2is adapted to sense a flow rate of the fluid flowing through the flow passage51in this body5. The fluid control valve3is adapted to control the flow rate of the fluid flowing through the flow passage51. The control unit (not shown) is adapted to control a valve opening degree of the fluid control valve3for closely approximating a measurement flow rate outputted from the flow rate detecting mechanism2to a predetermined set flow rate. Each of the parts is described in detail as follows.

The body5is formed to have a block-like shape through which the flow passage51penetrates, wherein an upstream end of the flow passage51serving as an upstream side port5A is connected to an external inlet pipe (not shown) and a downstream end thereof serving as a downstream side port5B is connected to an external outlet pipe (not shown).

As the flow rate detecting mechanism2, there may be conceivable various types such as a thermal type, Coriolis type, ultrasonic type and the like, and in this case, there is adopted a so-called thermal flow rate detecting mechanism. This thermal flow rate detecting mechanism2is equipped with: a capillary21which is connected in parallel with the flow passage51so that partial fluid of a predetermined ratio of the entire fluid flowing through the flow passage51is to be guided; a heater24provided on the capillary21; and a pair of temperature sensors22and23provided in the front and rear of the heater24. Thus, in the case where the fluid flows through the capillary21, there occurs a temperature difference corresponding to a mass flow rate thereof between these two temperature sensors22and23, whereby it is configured that the flow rate is measured based on this temperature difference.

In this embodiment, it is configured that, while providing an elongated housing25for accommodating the capillary21, heater24, temperature sensors22and23and a peripheral electrical circuit thereof, there are provided a pair of branch flow passages2aand2bbranched from the flow passage51of the body5and the housing25is attached to the body5, whereby an introduction port of the capillary21is connected to the branch flow passage2ain the upstream side and a derivation port of the capillary21is connected to the branch flow passage2bin the downstream side. It is noted that the flow rate sensor is not limited to this type.

The fluid control valve3is a normally closed typed one provided on the flow passage51and this fluid control valve3is provided with: a pair of valve elements, i.e., a valve seat member4and a valve body member6accommodated in the body5; and an actuator7for driving the valve body member6to set a valve opening degree, i.e., to set a space distance between the valve seat member4and the valve body member6.

The valve seat member4is intended to be a valve seat, and as shown inFIG. 2, this valve seat member4is formed to have a generally rotary body shape with its lower surface including a valve seat surface4aprojecting to a side of the valve body member6, and an internal flow passage41is formed inside the valve seat member4. In the present embodiment, the internal flow passage41includes a first internal flow passage411and a second internal flow passage412, wherein one end of the first internal flow passage411is opened to the valve seat surface4aand the other end thereof is opened to an upper surface of the valve seat member4and wherein one end of the second internal flow passage412is opened to the upper surface of the valve seat member4and the other end thereof is opened to a side peripheral surface of the valve seat member4. Further, a drive shaft (i.e., an abutment shaft portion722) of the actuator7to be described later is inserted to the first internal flow passage411. Here, one end opening of the first internal flow passage411is opened to a central portion of the valve seat surface4aand the valve seat surface4ais thereby formed to have a generally annular shape in plan view. Further, the first internal flow passage411and the second internal flow passage412communicate with each other via a space which is formed of a concave portion formed on the upper surface of the valve seat member4and a diaphragm member721for closing the concave portion. It is noted that the internal flow passage41is not limited to the configuration that includes the first and second internal flow passages411and412, and the internal flow passage41may be configured such that the first and second internal flow passages411and412communicate within the valve seat member4.

This valve seat member4is accommodated in a column-shaped accommodating concave portion52provided in the body5. This accommodating concave portion52is arranged so as to divide a flow passage51of the body5into an upstream side flow passage51(A) and a downstream side flow passage51(B). The upstream side flow passage51(A) of the flow passage51divided by this accommodating concave portion52is configured to be opened to, for example, a central portion of a bottom surface of the accommodating concave portion52and the downstream side flow passage52(B) of the flow passage51divided by this accommodating concave portion52is configured to be opened to, for example, a peripheral edge portion of the bottom surface or a side surface of the accommodating concave portion52.

Thus, in a state of accommodating the valve seat member4in the accommodating concave portion52, a gap is formed between an outer peripheral surface of the valve seat member4and an inner peripheral surface of the accommodating concave portion52, resulting in that the downstream side flow passage51(B) of the body5is communicated to the internal flow passage41via the side peripheral surface of the accommodating concave portion52.

The valve body member6is intended to be a valve body which is formed to have a generally rotary body shape having a seating surface6aon its upper surface, and this valve body member6is arranged so as to oppose to the valve seat member4in the accommodating concave portion52of the body5and arranged via a predetermined space from the inner peripheral surface of the accommodating concave portion52without contacting this inner peripheral surface.

Thus, the valve body member6is forcibly urged by receiving a driving force generated by the actuator7serving as a drive mechanism and moved from a close state in which the valve body member6is in contact with the valve seat member4to block the upstream side flow passage51(A) and downstream side flow passage51(B) to an open state in which the valve body member6is spaced away from the valve seat member4to communicate the upstream side flow passage51(A) with the downstream side flow passage51(B). In this way, a direction toward the open state from the close state, that is, an acting direction of the driving force by the actuator7to the valve body member6corresponds to a valve opening direction. Meanwhile, a direction toward the close state from the open state, that is, an opposite direction to the acting direction of the driving force by the actuator7to the valve body member6corresponds to a valve closing direction.

The actuator7is provided with, for example, a piezoelectric stack71which is formed by laminating a plurality of piezoelectric elements and an actuating body72which is displaced by extending the piezoelectric stack. This piezoelectric stack71is accommodated in the casing member73and its distal end is connected to the actuating body72via an intermediate connection member74. The actuating body72of the present embodiment includes a diaphragm member721and an abutment shaft portion722which is provided at a center of the diaphragm member721and penetrates a center of the valve seat member4(first internal flow passage411) to abut to an upper surface of the valve body member6. Thus, the piezoelectric stack71is extended by applying a predetermined voltage, whereby the actuating body72forcibly urges the valve body member6in the valve opening direction and the valve seat surface4ais spaced away from the seating surface6ato be in the open state. Moreover, upon applying a voltage below the predetermined voltage, the valve seat surface4ais spaced away from the seating surface6aby a distance corresponding to the voltage value. Then, the upstream side flow passage51(A) and downstream side flow passage51(B) communicate through this gap.

Further, the valve body member6is provided with a valve body return spring8for forcibly urging the valve body member6in the valve close direction. By this valve body return spring8, the valve body member6is in the close state in a normal state in which no voltage is applied to the actuator7.

This valve body return spring8is a plate spring which is supported by a spring guide member10accommodated in the accommodating concave portion52of the body5and is provided to be in contact with a downward surface of the valve body member6as shown inFIG. 2. It is noted that an elastic member other than the plate spring may be used as the valve body return spring8so long as the elastic member forcibly urges the valve body member6. The elastic member may forcibly urge the valve body member6directly or indirectly.

The spring guide member10is formed to have a generally rotary body shape with a concave shape in cross-section for supporting the valve body return spring8in the accommodating concave portion52, and in a bottom wall of this spring guide member10, there is formed an opening portion10xcommunicated to the upstream side flow passage51(A) which opens to the bottom surface of the accommodating concave portion52, and an upper end portion of a side peripheral wall of the spring guide member10is in contact with the peripheral edge portion of the valve seat member4. The valve body return spring8is provided on an inner peripheral surface of the spring guide member10. In the present embodiment as described above, it is configured that the valve body member6is accommodated in the space formed by the valve seat member4and the spring guide member10. Further, the valve body member6is disposed with a predetermined distance from the inner peripheral surface of the spring guide member10, and an outer peripheral surface of the valve body member6is spaced from the inner peripheral surface of the spring guide member10facing the outer peripheral surface.

Thus, in the valve body member6which is one of the valve elements of the present embodiment, there is formed a concave portion61in an opposing surface (upper surface) facing the valve seat surface4aof the valve seat member4. In the concave portion61, there is formed a resin coating film62contacting the valve seat surface4aof the valve seat member4. It is noted that the valve body member6is formed of a material having excellent heat resistance and corrosion resistance, and in the present embodiment, the valve body member6is formed of stainless steel. However, the valve body member6may be formed of the other high heat-resistant and corrosion-resistant alloys such as hastelloy.

The concave portion61is formed so as to surround a driving force acting surface6bwhich contacts the abutment shaft portion722of the actuator7to receive a driving force and the concave portion61has a generally annular shape in plan view and a generally U character shape in cross-section. The driving force acting surface6bis formed in the central portion of the upper surface of the valve body member6and is formed to have slightly larger than a contacting area contacting with the abutment shaft portion722. In this way, the driving force acting surface6band concave portion61are concentrically formed in the upper surface of the valve body member6.

This concave portion61has a shape corresponding to the valve seat surface4aand is shaped to have a range including a range of the valve seat surface4ain a state that the valve body member6is seated on the valve seat member4, wherein the depth of the concave portion61is, for example, 50 to 150 μm.

Further, a ridge portion formed on the outer peripheral portion of the concave portion61serves as a polish limiting guide portion63. This polish limiting guide portion63has a generally annular shape in plan view that is formed on the outermost peripheral portion on the opposing surface (upper surface). The upper surface of this polish limiting guide portion63is positioned to be coplanar with the driving force acting surface6b. In this way, the concave portion61and the polish limiting guide portion63are concentrically formed on the upper surface of the valve body member6.

The resin coating film62to be formed in the concave portion61is formed by coating in the concave portion61and its shape in plan view is the same shape as the concave portion61, that is, a generally annular shape in the present embodiment. The entire part of the valve seat surface4acontacts the resin coating film62formed in this concave portion61. The thickness of the resin coating film62is the same as the depth of the concave portion61, that is, for example, 50 to 150 μm. In this way, since the thickness of the resin coating film62is the same as the depth of the concave portion61, it is configured that the upper surface of the outer peripheral portion of the concave portion61is positioned to be coplanar with the upper surface of the resin coating film62. Moreover, the resin coating film62is formed of, for example, a fluorine resin having excellent heat resistance, corrosion resistance, chemical resistance and low friction characteristics, and (PFA) polyfluoroalkoxy is used in the present embodiment.

Further, in the present embodiment, in order to improve adhesion between the inner surface of the concave portion61and the resin coating film62, a primer resin having an adhesive component is interposed between the inner surface of the concave portion61and the resin coating film62. The primer resin of the present embodiment is obtained by mixing an adhesive component and a fluorine resin, for example, PTFE (polytetrafluoroethylene) or the like. In addition, it is conceivable to improve the adhesion by a roughening process such as a blasting process of the bottom surface of the concave portion61.

Next, a manufacturing method of the valve body member6of the present embodiment is described below referring toFIG. 4.

First, the concave portion61is formed on the upper surface of the valve body member6. As this method of forming the concave portion61, a machining process such as a cutting process is used. At this time, the bottom surface of the concave portion61is made to be a fine uneven shape by a roughening process, whereby the adhesion between the inner surface of the concave portion61and the resin coating film62can be improved.

Subsequently, the entire upper surface of the valve body member6including the concave portion61is coated with PTFE which is a primer resin to thereby form a primer layer. Then, the upper surface of the primer layer is coated with, for example, a fluorine resin such as PFA several times by a thin film coating or the like to form a top coat layer to be used as the resin coating film62. At this time, the total film thickness of the primer layer and the top coat layer is adjusted to be equal to or larger than the depth of the concave portion61(for example, 120 μm).

Thereafter, the primer layer and top coat layer formed on the upper surface are polished by a polishing process such as a plane lapping. At this time, the polishing amount is, for example, on the order of 50 μm. That is, not only the primer layer and top coat layer formed on the upper surface of the valve body member6but also the inner peripheral portion (i.e., a portion corresponding to the driving force acting surface6b) and the outer peripheral portion (i.e., polish limiting guide portion63) of the concave portion61formed on the upper surface of the valve body member6are polished as well. By this polishing, it is configured that the resin remains only in the concave portion61and the resin remaining in the concave portion61serves as the resin coating film62. By polishing the inner peripheral portion and outer peripheral portion of the concave portion61in this way, the resin in the concave portion61is prevented from being excessively polished and the resin in the concave portion61can be polished to have a uniform film thickness. In addition, since the polish limiting guide member63is formed throughout in the circumferential direction and this polish limiting guide member63is also polished as well, there is no fear that side-cutting of the resin in the concave portion61is performed.

According to the mass flow controller100of the present embodiment configured as described above, since the concave portion61is formed in the opposing surface of the valve body member6and the resin coating film62is formed in the concave portion61, the resin coating film62contacts the valve seat surface4aof the valve seat member4, thereby enabling improvement in the sealing property at the time of closing and reducing an internal leakage amount.

Further, since the resin coating film62is formed in the concave portion61, when the surface of the resin coating film62is polished, the opposing surface portion (particularly, polish limiting guide portion63) other than the concave portion61serves as the guide for polishing the surface, whereby the film thickness of the resin coating film62can be made uniform while ensuring the flatness of the surface of the resin coating film62to thereby obtain a flatness of the seating surface6awith high precision.

Moreover, since the film thickness of the resin coating film62is small (for example, 50 to 150 μm) relative to the entire valve body member6, a thermal expansion amount of the resin coating film62can be reduced relative to a thermal expansion amount of the valve body member6, whereby it is possible to reduce a temperature effect due to formation of the resin coating film62.

In addition, since the sealing property is ensured by forming the resin coating film62to be a thin film of, for example, 50 to 150 μm, when the valve seat surface4aof the valve seat member4is in contact with the resin coating film62, an elastic deformation amount of the resin coating film62can be reduced and it is hard to form a contact impression or unevenness on the resin coating film62, whereby the sealing property can be ensured for a long time period.

Thus, it is possible to improve the sealing property in the closing state of the fluid control valve3and the stability can be improved while keeping the durability for a long time period. Therefore, in the case where the fluid control valve3is incorporated in the mass flow controller, it is possible to perform the flow rate control stably and with high precision for a long time period.

Embodied Example

Next, the following shows results of a performance comparison experiment between the flow rate control valve of the present invention and a conventional flow rate control valve. The flow rate control valve of the present invention refers to that of the present embodiment described above. Meanwhile, in the conventional flow rate control valve, the valve seat member and the valve body member are respectively composed of a valve seat surface made of SUS and a seating surface made of SUS without applying a resin coating to any of the valve seat member and the valve body member.

FIG. 5shows an outflow rate (internal leakage amount) (Pa·cm3/sec(He)) in the conventional flow rate control valve.FIG. 6shows an outflow rate (internal leakage amount) (Pa·cm3/sec(He)) in the flow rate control valve of the present invention. As apparent fromFIG. 5, it is understood that, with use of the flow rate control valve, the outflow rate gradually increases. Meanwhile, as apparent fromFIG. 6, it is understood that, in the flow rate control valve of the present invention, the outflow rate remains nearly constant even in the case of using the flow rate control valve. Thus, by applying the resin coating in the concave portion, the outflow rate can be kept substantially constant and the flow rate control valve can be stably used for a long time period. Further, comparing the results shown inFIGS. 5 and 6, it is understood that the outflow rate per se can be reduced by applying the resin coating in the concave portion.

Next,FIG. 7shows valve temperature rise characteristics of the flow rate control valve of the present invention and the conventional flow rate control valve. The flow rate control valve of the present invention refers to that of the present embodiment described above. Meanwhile, in the conventional flow rate control valve, the valve seat member and the valve body member are respectively composed of a valve seat surface made of SUS and a seating surface made of SUS without applying a resin coating to any of the valve seat member and the valve body member.

The valve temperature rise characteristics shown inFIG. 7show a flow rate of change relative to an initial reference value when an ambient temperature is changed. Here, the initial reference value is a flow rate of fluid in the case where a voltage of 100V is applied to the actuator under the condition of the ambient temperature being 25° C. As shown inFIG. 7, the flow rate control valve of the present invention shows a temperature rise characteristic substantially similar to that of the conventional flow rate control valve and it is understood that, by forming a resin coating film, the temperature rise characteristic is not deteriorated relative to that of the conventional flow rate control valve.

It is noted that the present invention is not limited to the first embodiment. For example, although the valve body member6has a solid shape in the first embodiment, it may be also configured that one or more internal flow passages601each having one end opening to the lower surface and the other end opening to the upper surface are formed inside the valve body member6as shown inFIGS. 8 and 9, in the case of forming one internal flow passage601, the opening in the upper surface of the internal flow passage601is intended not to be overlapped with the opening in the valve seat surface4aof the internal flow passage41. Further, in the case of forming a plurality of internal flow passages601, the openings of the plurality of internal flow passages601in the upper surface (seating surface6a) are formed in a circular shape (seeFIG. 9) and disposed concentrically with the openings in the valve seat surface4aof the plurality of internal flow passages41but not to be overlapped with each other.

In this case, as a configuration of disposing each component on the upper surface of the valve body member6, the driving force acting surface6bis formed in the central portion, the concave portion61having the resin coating film62formed so as to surround the driving force acting surface6bis formed, an opening forming region6cof the internal flow passages601is formed so as to surround the concave portion61, the concave portion61having the resin coating film62formed so as to surround the opening forming region6cis formed, and the polish limiting guide portion63is formed so as to surround the concave portion61. InFIG. 9, since the openings of the internal flow passages41are concentrically formed inside and outside in the lower surface of the valve seat member4, the concave portions61having the resin coating films62concentrically formed inside and outside in the upper surface of the valve body member6are formed so as to receive the concentrically formed openings of the internal flow passages41. It is noted that the disposition of the concave portion61formed with the resin coating film62may be variously modified in accordance with the disposition of the openings of the internal flow passages41of the valve seat member4.

Second Embodiment

A fluid control valve3according to the second embodiment is normally open type (NO type) one which is different from the first embodiment in a point that the positions of the valve seat member4and the valve body member6are reversed. Note that the same reference numerals are assigned to members corresponding to the first embodiment.

That is, as shown inFIG. 10, a diaphragm member721of an actuator7corresponds to the valve body member6of the first embodiment and the valve seat member4is provided in a side of a body5rather than the diaphragm member721. The valve seat member4is fitted into an accommodating concave portion52provided in the body5. Similarly to the first embodiment, the accommodating concave portion52is arranged so as to divide a flow passage51of the body5.

The valve seat member4of the present embodiment is formed to have a generally rotary body shape with its upper surface including a valve seat surface4a, and an upstream side internal flow passage413and a downstream side internal flow passage414are formed inside the valve seat member4. In the present embodiment, the upstream side internal flow passage413has one end opened to the valve seat surface4aand the other end opened to a lower surface of the valve seat member4. And the other end of this upstream side internal flow passage413is communicated to an upstream side flow passage51(A) which is opened to a bottom surface of the accommodating concave portion52. Further, the downstream side flow passage414has one end thereof opened to a portion of the valve seat member4, except the valve seat surface4a, and the other end thereof opened to a lower surface of the valve seat member4. And the other end of this downstream side internal flow passage414is communicated to a downstream side flow passage51(B) which is opened to the bottom surface of the accommodating concave portion52.

In a normal state in which no voltage is applied to the actuator7, the valve body member6is in an open state in which the seating surface6aof the diaphragm member721is spaced from the valve seat surface4aof the valve seat member4. When a voltage is applied to the actuator7to extend this actuator7, the diaphragm721is moved to a valve closing direction, whereby the seating surface6aof the diaphragm721is in close contact with the valve seat surface4aof the valve seat member4to be in a close state.

Particularly, in the diaphragm721, a concave portion61is formed in a lower surface which is an opposing surface opposing to the valve seat member4as shown inFIG. 11. In this concave portion61, there is formed a resin coating film62having the seating surface6awhich contacts the valve seat surface4aof the valve seat member4.

In the present embodiment, the valve seat surface4ahas an annular shape formed in a central portion of the valve seat member4, wherein the concave portion61formed in the diaphragm member721is sized to include the valve seat surface4a. In addition, the depth of the concave portion61, configuration of the resin coating film62and manufacturing method are similar to those of the first embodiment.

Further, a polish limiting guide portion63in this case is formed by an outer peripheral portion of the concave portion61, and in the present embodiment, the outer peripheral portion which is a portion except the central portion where the concave portion61is formed in the diaphragm member721serves as the polish limiting guide portion63. Furthermore, a peripheral edge portion of the diaphragm member721serves as a seal member contacting surface with which a seal member9is in contact at a time of mounting the body5.

Also, in the fluid control valve3of the present embodiment configured as described above, the same effects as in the first embodiment can be obtained.

It is noted that the present invention is not limited to the second embodiment. For example, although the diaphragm721of the actuator serves as the valve body member in the second embodiment, a valve body member driven by the diaphragm721may be provided between the diaphragm721and the valve seat member4. Also, in this case, there is provided a concave portion having a resin coating film formed on an opposing surface (lower surface) opposing to the valve seat member4in the valve body member.

Further, in each of the embodiments, although there is exemplified a configuration that the concave portion61having the resin coating film62formed therein is provided in the valve body member, it may be also possible that a concave portion is provided in the opposing surface to the valve body member in the valve seat member and the resin coating film contacting the seating surface may be formed in the concave portion.

Moreover, in addition to the valve element constituting the entire valve body member or entire valve seat member, the valve element constituting a part thereof may be used. That is, in the case where the valve body member is composed of a plurality of members, the valve element may be composed of a member having a seating surface. Alternatively, in the case where the valve seat member is composed of a plurality of members, the valve element may be composed of a member having a valve seat surface.

Although the present invention is applied to the flow rate control valve in each of the embodiments, the present invention may be also applied to an ON/OFF switching valve. Further, the actuator is not limited to a piezoelectric type but an electromagnetic coil and the like may be used. Moreover, it is not limited to a mass flow controller incorporating the fluid control valve, but the fluid control valve may be configured as a single unit. In addition, a pressure control valve for controlling a pressure of fluid may be used as the fluid control valve.

In addition, it is needless to say that, the above embodiments and modified embodiment may be partly or entirely combined appropriately and the present invention is not limited to the above embodiments and various changes and modifications can be made within the scope of the present invention unless departing from the spirit thereof.

EXPLANATION OF REFERENCE NUMERALS