JPH0642663A - Control valve for mass flow controller - Google Patents

Abstract

PURPOSE:To provide a revolutionary normally closed mass flow controller which is cheap and has a simple structure even though it is normally closed, and which has no factor causing occurrence of particles and a dead volume. CONSTITUTION:An opening 18a of a fluid passage 18 formed in a body 17 is opened and closed by a plug 15 that is urged by a spring in a direction in which the plug 15 is separated from the opening 18a. Further, a contractible laminated piezoelastic element 1 which expands overcoming the force of the spring 11 so as to press the plug 15 against the opening 18a when no voltage is applied, but which contracts so as to allow the spring force to separate the plug 15 from the opening 18a when a voltage is applied.

Description

Detailed Description of the Invention

[0001]

[Industrial application] Explosive monosilane, phosphine, arsine and corrosive gases such as HCl, Cl ₂ and dichlorosilane (SiH ₂ C) in semiconductor and VLSI manufacturing processes.
Since a wide variety of gases and liquids such as l ₂ ) are used,
The present invention relates to an improvement of a control valve of a mass flow controller used for controlling the flow rate of such gas or liquid, for example, though not only the accuracy of the flow rate control but also high safety is required.

[0002]

2. Description of the Related Art In the gas and liquid mass flow controllers used in the manufacturing process of semiconductors and VLSIs, the valve structure is always closed in order to prevent gas and liquid leakage during power failure from the viewpoint of safety. Normally closed type.

This mass flow controller includes a sensor section for accurately measuring the mass flow rate of a small amount of fluid, a bypass section for passing a large amount of fluid in proportion to the flow rate of the sensor section, the sensor section and the bypass section. And a flow rate control unit for accurately controlling the flow rate of the fluid flowing out from the device and supplying the fluid to the apparatus in the next step. The control valve used in this flow rate control unit includes a thermal expansion shaft type, an electromagnetic solenoid type, a laminated piezoelectric element type and the like. Recently, the laminated piezoelectric element method shown in (3) has begun to spread. The reason is that (a) the response speed is much faster than other methods, so it is possible to control the mass flow rate of the gas being supplied at high speed, (b) the generated pressure of the laminated piezoelectric element is different from other methods. Compared to the above, the valve is much higher, the valve can be completely closed, precise valve operation is possible, and the flow rate of a minute flow rate can be controlled. (C) The power consumption as a driving element is extremely low and low. Cost can be realized,
(d) Since there is almost no heat generation, the heat effect on the mass flow rate sensor can be almost ignored, and highly accurate flow rate control that is not affected by heat is possible. (e) Low hysteresis, fast and stable mass This is because the flow rate can be controlled.

In order to have various characteristics as described above,
It is expected that a mass flow controller incorporating this laminated piezoelectric element will become the mainstream in the manufacture of VLSIs and next-generation VLSIs, including semiconductors that require high speed, high accuracy, and minute flow rate control.

A conventional normally closed mass flow controller (B)
The valve structure of Fig. 3 is forced to have a very complicated structure as shown in Fig. 3. The structure will be briefly described below. An orifice block (33) having an opening (31a) is provided in the fluid flow path (31) on the downstream side of the bypass section (not shown). It consists of a valve head (34) and a plunger part (35),
The plug (36) for adjusting the opening of the opening (31a) is the valve head.
It is installed with the (34) close to the opening (31a).

The plug (36) is connected to the metal diaphragm (38) provided in the lower space of the valve block (37) provided at the upper portion of the main body (29), and the plunger portion is connected. A compression spring (40) arranged between the plug nut (39) screwed to (35) and the diaphragm (38) is constantly biased in a direction away from the orifice block (33). , Expansion type laminated piezoelectric element on the upper side through the sphere (41)
It is in contact with (30). The expansion type laminated piezoelectric element (30) is a type of piezoelectric element that expands when a voltage is applied.

The main body (29) has the diaphragm (3
8), a recess is formed, a guide block (42) is fitted to the bottom of the recess, and an orifice block (33) is fitted to the top of the recess.The main body (29) is located at the center of the guide block (42). ), The nozzle block housing hole (42a) communicating with the inlet side fluid flow path (31) is formed, and the orifice block
A valve seat hole (33a) into which the valve head (34) of the plug (36) is fitted is formed in the center of the (33).

The nozzle block accommodating hole (42a) is formed such that a portion in contact with the orifice block (33) has a large diameter, and a lower side thereof is formed as a thin through hole.
It communicates with (31). The nozzle block (43) is formed in a T-shape in cross section in accordance with the nozzle block storage hole (42a), and the head portion (43a) thereof is the nozzle block storage hole (42a).
It is fitted in the large diameter hole (42b) of the nozzle block (43).
The head portion of the nozzle block (43) is constantly urged by the coil spring (44) fitted in the leg portion (43b) so that the head portion of the nozzle block (43) is in pressure contact with the lower surface seat of the orifice block (33). Reference numeral (32) is an outlet side flow passage communicating from the space of the diaphragm (38) to the fluid outlet (45) of the mass flow controller (B).

Since this mass flow controller (B) is of the normally closed type, the head of the nozzle block (43) is always closed by the coil spring (44).
(43a) is pressed and urged so as to come into pressure contact with the lower surface seat of the orifice block (33), while the plug (36) is compressed by the compression spring (40) so that its valve head (34) is located at the nozzle block (43). ) Is held so as to be separated from the head (43a). Therefore, the head portion (43a) of the nozzle block (43) is pressed against the lower surface of the orifice block (33) and the inlet side fluid flow channel (31) and the valve seat hole are formed.
Communication with (33a) is closed.

Here, when the expansion type laminated piezoelectric element (30) is applied and expanded, the plug (39) is pushed down against the compression spring (40) to move the head (43a) of the nozzle block (43) to its valve. The head (44) presses and compresses the coil spring (44). As a result, the head portion (43a) of the nozzle block (43) is separated from the lower surface of the orifice block (33) so that the inlet fluid passage (31) and the valve seat hole (33a) communicate with each other, and the fluid communicates with this. Only a specified amount will flow through the passage.

The fluid has various properties such as corrosive and explosive as described above, and metal particles and the like should not be mixed in the fluid supplied to the next step. There are other strict requirements including the requirement that the coil spring (44) that expands and contracts frequently is installed in the flow path as shown in the figure, so when corrosive gas is used, the coil spring ( Nozzle block (43) during long-term use due to corrosion of 44) and loss of elasticity.
However, there is a problem in that the normally closing function is impaired due to the gradual decrease in the closing force due to.

Further, since the nozzle block (43) and the metal coil spring (44) that frequently move or expand and contract in the fluid passage (31) are housed, the nozzle block (43) and the coil spring are
Particles due to (44) may be generated, which is problematic in maintaining cleanliness of the fluid.

Furthermore, when the type of fluid is changed due to the coil spring (44) and the nozzle block (43) in the flow path (31), dead volume that cannot be purged is generated and residual gas in the previous stroke is generated. There is also a problem that a chemical reaction occurs with the newly supplied gas, which causes the generation of internal products in the channel (31) and the clogging of the channel due to this.

As described above, when the expansion type is used for the piezoelectric element (30) in order to keep the mass flow controller (B) normally closed, the metal coil spring (24), which is easily corroded by corrosive gas, is used as a fluid flow. Road
There are structural problems such as having to be installed in (31) and installing a nozzle block (43) that becomes a dead volume in the fluid flow path (31), and the cost is complicated because of a complicated structure. There is also an economic demerit that it becomes higher.

[0015]

SUMMARY OF THE INVENTION The present invention has a simple structure and a low cost in spite of the normally closed type, and there is no factor that causes particles or dead volume in the fluid passage. It is an object of the invention to provide an epoch-making normally closed mass flow controller.

[0016]

The mass flow controller of the present invention.
The control valve of (A) is, as shown in claim 1, "main body
The fluid channel (18) formed in (17), the plug (15) for opening and closing the opening (18a) of the fluid channel (18), and the plug (15) separated from the opening (18a) A spring (11) that urges in the direction and expands against the spring (11) when no voltage is applied, closes the plug (15) by pressing it against the opening (18a), and contracts when voltage is applied. Then, by the elastic force of the spring (11), the plug (1
5) is composed of a reduction-type laminated piezoelectric element (1) which is separated from the opening (18a) ”.

As a result, in spite of the normally closed type, the structure is simple and the cost is low, and there is no factor that causes generation of particles or dead volume in the fluid flow path. We were able to provide a mass flow controller.

[0018]

The present invention will be described in detail below with reference to the illustrated embodiments. FIG. 1 is a sectional view of a flow rate control unit (Aa) of a mass flow rate controller (A) according to the present invention. (17) is a main body body, and an inlet side fluid flow path (18) communicating with the upper surface of the main body body (17),
An outlet side fluid flow path (2) formed so as to communicate with an outlet (19) from a discharge groove (21) recessed around the inlet side flow path (18).
2) and are formed. The inlet side fluid flow path (18) includes a sensor unit (not shown) that accurately measures the mass flow rate of a small amount of fluid (20), and a bypass unit (a part that allows a large amount of fluid to pass in proportion to the flow rate of the sensor unit). (Not shown). Around the opening (18a) of the inlet side fluid flow path (18), a valve seat surface (16) is formed by gold plating, for example, and
(15) is designed to abut.

On the upper surface of the main body (17), a lower housing (13) having a hollow central portion is installed and fixed. The lower housing (13) has a discharge groove (21) on the bottom surface.
A ring-shaped claw (13b) is provided so as to surround the upper end of the main body (17) so as to completely seal the periphery of the discharge groove (21).

An upper housing (12) is installed and fixed on the lower housing (13), and a concave step portion (13a) formed on the upper surface of the lower housing (13) is attached to the lower surface of the upper housing (12). The formed convex step portion (12a) is fitted, and the outer peripheral portion of the diaphragm (14) is sandwiched and fixed in an airtight manner between the concave step portion (13a) and the convex step portion (12a). Upper housing (1
At the center of 2), a guide hole (12b) is bored in accordance with the opening (18a) of the inlet side fluid flow path (18), and the plug (15) slides.

The plug (15) has an inverted T-shaped cross section with a large diameter at the bottom.
The large-diameter valve body (15b) has a ring-shaped projection (15a) protruding from the lower surface of the main body (17) that contacts and separates from the valve seat surface (16). , Valve seat surface (16)
When the ring-shaped projection (15a) contacts the plug chamber (P) surrounding the valve body portion (15b) of the plug (15) and the inlet side fluid flow path (1
It is possible to completely block the opening (18a) of 8). Further, the diaphragm (14) is provided on the upper surface of the valve body (15b).
The inner peripheral edge of the plug is fixed and covers the hollow portion of the lower housing (13) to form a plug chamber (P). The upper end of the plug (15) protrudes upward from the guide hole (12a), the O-ring (9) is fitted into this protruding end, and the leaf spring (11) is arranged via the washer (10). Therefore, the plug (15) is constantly pushed upward and biased so as to be separated from the valve seat surface (16). It goes without saying that the leaf spring (11) can be replaced with a compression coil spring. In this case, as can be seen from the figure, there is no such thing as dead volume in the inlet side fluid flow channel (18), the plug chamber (P) and the outlet side fluid flow channel (22).

(7) is a valve case, and the upper housing (1
It is fixed to 2) with a bolt (8), and the stroke adjustment screw (5) is screwed into the upper end.After adjusting the lifting stroke of the plug (15), adjust the stroke with the fixing nut (6). The screw (5) is fixed. (1) is a reduction type laminated piezoelectric element,
The lower surface protrusion (4a) of the plunger (4) provided at the lower end is the plug.
It is in contact with the upper surface of the (15), and the upper surface of the reduction-type laminated piezoelectric element (1) is in contact with the lower surface of the stroke adjusting screw (5) through the sphere (3).

The reduction-type laminated piezoelectric element (1) is of a type that contracts when a voltage is applied, and as shown in FIG. 2, plate-like ceramics (1b) are laminated in a horizontal direction via internal electrodes (1a). The external electrode (1c) is installed on the upper end. As a result, when no voltage is applied to the reduction-type laminated piezoelectric element (1), the element (1) is extended and pushes down the plug (15) against the leaf spring (11), and the valve seat surface (16 ) Plug (1
The ring-shaped projection (15a) on the lower surface of 5) is pressed in an airtight manner. As a result, it is a normally closed type. An example of the conventional expansion type laminated piezoelectric element (30) is shown in FIG. According to this, the ceramic plates (30b) are vertically laminated via the internal electrodes (30a), and the external electrodes (30c) are installed from both sides, and the entire length is extended by applying a voltage.

When a voltage is applied to the reduction type laminated piezoelectric element (1) during operation, the element (1) contracts in proportion to the voltage. The leaf spring (11), which had been flexed according to this contraction, expanded and the plug
(15) and the element (11) are pushed up, and the ring-shaped protrusion (15a) on the lower surface of the plug (15) separates from the valve seat surface (16).
This separation amount corresponds to the contraction amount of the element (1). As a result, the valve opening can be accurately controlled by the voltage applied to the element (1).

When the valve body portion (15b) is opened, the fluid (20) flows from the opening (18a) of the inlet side fluid flow path (18) to the ring-shaped protrusion (15a) of the plug (15) and the valve seat surface (16). ) Enters the plug chamber (P) through a controlled gap, and further, from the discharge groove (21) through the outlet side fluid flow path (22) to the outlet (19), to the device of the next stroke. The mass flow rate of the fluid (20) is accurately metered and delivered. On the contrary, when the voltage applied to the element (1) becomes 0, the element (1) expands again and resists the leaf spring (11).
Push down (15) and close the opening (18a).

[0026]

Since the control valve of the mass flow controller of the present invention has the structure as set forth in claim 1, the piezoelectric element directly presses the plug to open the opening portion although the control valve is always closed. It has an extremely simple structure that opens and closes, and the cost is low,
In addition, unlike the conventional example, there is no factor that causes particles or dead volume in the fluid channel, the risk of causing clogging is extremely small, and the fluid in the channel is corroded by the fluid. Since there is no metal spring, it has the effect of being extremely safe.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of a flow rate control unit of a mass flow rate controller according to the present invention.

FIG. 2 is a schematic perspective view of a reduction-type laminated piezoelectric element used in the present invention.

FIG. 3 is a sectional view of a flow rate control unit of a conventional mass flow rate controller.

FIG. 4 is a schematic perspective view of a reduction-type laminated piezoelectric element used in a conventional example.

[Explanation of symbols]

(A)… Mass flow controller (1)… Reduced type laminated piezoelectric element (11)… Spring (15)… Plug (17)… Body body (18)… Fluid flow path (18a)… Opening

[Procedure amendment]

[Submission date] July 22, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 1

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be amended] Detailed explanation of the invention

[Correction method] Change

[Correction content]

Detailed Description of the Invention

[0001]

[Industrial application] In the manufacturing process of semiconductors and VLSIs, various gases and liquids such as explosive monosilane, phosphine, arsine and corrosive gases such as HCl, Cl ₂ and dichlorosilane (SiH ₂ Cl ₂ ) are used. Therefore, not only the accuracy of the flow rate control but also the high safety are required. However, the present invention controls the mass flow rate controller used for controlling the flow rate of such gas or liquid, for example. Regarding the improvement of the valve.

[0002]

2. Description of the Related Art A gas or liquid mass flow controller used in the above-mentioned semiconductor or VLSI manufacturing process has a valve structure that is always closed in order to prevent gas or liquid leakage during a power failure from a safety point of view. Normally closed type.

This mass flow controller includes a sensor section for accurately measuring the mass flow rate of a small amount of fluid, a bypass section for passing a large amount of fluid in proportion to the flow rate of the sensor section, the sensor section and the bypass section. And a flow rate control unit for accurately controlling the flow rate of the fluid flowing out from the device and supplying the fluid to the apparatus in the next step. The control valve used in this flow rate control unit includes a thermal expansion shaft type, an electromagnetic solenoid type, a laminated piezoelectric element type and the like. Recently, the laminated piezoelectric element method shown in 1 has begun to spread. The reason is that (a) the response speed is much faster than that of other methods, so that the mass flow rate of the supplied gas can be controlled at high speed. (B) The generated pressure of the laminated piezoelectric element is different from that of other methods. Compared to the above, the valve is remarkably high, the valve can be completely closed, the valve can be operated precisely, and the flow rate of a minute flow rate can be controlled. (C) The power consumption as a driving element is extremely low and low. Cost can be realized, (d) Since there is almost no heat generation, the heat influence on the mass flow rate sensor can be almost ignored, and highly accurate flow rate control not affected by heat is possible. (E) Little hysteresis This is because of the feature that high-speed and stable mass flow rate control is possible.

In order to have various characteristics as described above,
It is expected that a mass flow controller incorporating this laminated piezoelectric element will become the mainstream in the manufacture of VLSIs and next-generation VLSIs, including semiconductors that require high speed, high accuracy, and minute flow rate control.

Now, as shown in FIG. 3, the valve structure of the conventional normally closed mass flow controller (B) is forced to have a very complicated structure. The structure will be briefly described below. An orifice block (33) having an opening (31a) is provided in the fluid flow path (31) on the downstream side of the bypass section (not shown). A plug (36) including a valve head (34) and a plunger portion (35) for adjusting the opening of the opening (31a) brings the valve head (34) close to the opening (31a). It is installed in the state.

This plug (36) has a body (2
9) is connected to a metal diaphragm (38) provided in the lower space of a valve block (37) provided at the upper part of 9) and has a plug nut (39) screwed to the plunger part (35). A compression spring (40) provided between the diaphragm (38) and the diaphragm (38) constantly presses and biases the expansion block (33) in a direction away from the orifice block (33). It abuts the element (30). The expansion type laminated piezoelectric element (30) is a type of piezoelectric element that expands when a voltage is applied.

A recess is formed in the main body (29) so as to correspond to the diaphragm (38). A guide block (42) is fitted to the bottom of the body and an orifice block (33) is fitted to the top of the guide block. , Guide block (4
A nozzle block housing hole (42a) communicating with the inlet side fluid flow path (31) of the main body (29) is bored in the center of 2), and the plug (36) is placed in the center of the orifice block (33). Is formed with a valve seat hole (33a) into which the valve head (34) is fitted.

The nozzle block accommodating hole (42a) is
The portion in contact with the orifice block (33) is formed to have a large diameter, and the lower side thereof is formed into a thin through hole, which communicates with the inlet side fluid flow channel (31). Nozzle block (4
3) is formed in a T-shaped cross-section in accordance with the nozzle block housing hole (42a), and the head (43a) thereof is fitted into the large diameter hole (42b) of the nozzle block housing hole (42a). , The leg of the nozzle block (43) (43
The head of the nozzle block (43) is constantly urged by the coil spring (44) fitted in b) so that the head of the nozzle block (43) is in pressure contact with the lower surface seat of the orifice block (33). (32)
Is an outlet-side outflow passage communicating from the space of the diaphragm (38) to the fluid outlet (45) of the mass flow controller (B).

Since this mass flow rate controller (B) is a normally closed type, the nozzle block (4
The head (43a) of 3) is pressed and urged so as to come into pressure contact with the lower surface seat of the orifice block (33), while the plug (36) is compressed by the compression spring (40) to its valve head (34). Are held so as to be separated from the head portion (43a) of the nozzle block (43). Therefore, the head portion (43a) of the nozzle block (43) is pressed against the lower surface of the orifice block (33) to close the communication between the inlet side fluid flow channel (31) and the valve seat hole (33a).

Here, when the expansion type laminated piezoelectric element (30) is applied and expanded, the plug (39) is pushed down against the compression spring (40) and the head portion (43a) of the nozzle block (43) is pushed by the valve. The head (44) presses and compresses the coil spring (44). As a result, the head portion (43a) of the nozzle block (43) is moved to the orifice block (3
The inlet side fluid flow path (31) and the valve seat hole (33a) communicate with each other while being separated from the lower surface of 3), and the fluid flows through a specified amount through the communication path.

The fluid has various properties such as corrosive and explosive as described above, and metal particles and the like should not be mixed in the fluid supplied to the next step. There are other strict requirements including the requirement that the coil spring (44) that expands and contracts frequently is installed in the flow path as shown in the figure. Therefore, when corrosive gas is used, the coil spring ( 44) is corroded and the elastic force is gradually impaired, and there is a problem that the closing force by the nozzle block (43) is gradually reduced during long-term use and the normally closed function is impaired.

In addition, the nozzle block (43) and the metal coil spring (4) that frequently move or expand and contract in the fluid flow path (31).
Since 4) and the like are stored, particles may be generated due to the nozzle block (43) and the coil spring (44), and there is a problem in maintaining cleanliness of the fluid.

Further, a coil spring (4) is provided in the flow path (31).
4) and the nozzle block (43), when changing the type of fluid, dead volume that cannot be purged is generated, causing a chemical reaction between the residual gas in the previous stroke and the newly supplied gas, There is also a problem that internal products are generated in the passage (31) and the flow passage is clogged due to this.

As described above, when the expansion type is used for the piezoelectric element (30) in order to keep the mass flow controller (B) always closed, the metal coil spring (24) is easily corroded by corrosive gas.
Need to be installed in the fluid flow path (31), or the nozzle block (43) that becomes a dead volume must be installed in the fluid flow path (31), and there is a structural problem. Because of this, there is also an economic disadvantage that the cost becomes high.

[0015]

SUMMARY OF THE INVENTION The present invention has a simple structure and a low cost in spite of the normally closed type, and there is no factor that causes particles or dead volume in the fluid passage. It is an object of the invention to provide an epoch-making normally closed mass flow controller.

[0016]

A control valve of a mass flow controller (A) according to the present invention has a fluid flow passage (18) formed in a "main body (17)" as described in claim 1. Plug (15) for opening and closing the opening (18a) of the fluid channel (18)
A spring (11) for urging the plug (15) away from the opening (18a), and a spring (11) that extends when the voltage is not applied, against the spring (11),
Is pressed against the opening (18a) to close it, contracts when a voltage is applied, and the plug (15) is separated from the opening (18a) by the elastic force of the spring (11). ) And is characterized by being composed of '.

As a result, in spite of the normally closed type, the structure is simple and the cost is low, and there is no factor that causes generation of particles or dead volume in the fluid flow path. We were able to provide a mass flow controller.

[0018]

The present invention will be described in detail below with reference to the illustrated embodiments. FIG. 1 is a sectional view of a flow rate control unit (Aa) of a mass flow rate controller (A) according to the present invention. Reference numeral (17) denotes a main body body, which includes an inlet side fluid flow channel (18) communicating with the upper surface of the main body body (17) and a discharge groove (21) recessed around the inlet side fluid flow channel (18). An outlet side fluid channel (22) formed so as to communicate with the outlet (19) is formed. The inlet fluid flow path (18) contains a small amount of fluid (20).
Sensor unit (not shown) for accurately measuring the mass flow rate of
And a bypass section (not shown) that allows a large amount of fluid to pass in proportion to the flow rate of the sensor section. A valve seat surface (16) made of, for example, gold plating is formed around the opening (18a) of the inlet side fluid flow path (18) so that the plug (15) abuts.

On the upper surface of the main body (17), a lower housing (13) having a hollow central portion is installed and fixed. A ring-shaped claw (13) is formed on the lower surface of the lower housing (13) so as to surround the discharge groove (21).
b) is projectingly provided so as to bite into the upper surface of the main body (17) to completely seal the periphery of the discharge groove (21).

An upper housing (12) is installed and fixed on the lower housing (13), and a concave step (13a) formed on the upper surface of the lower housing (13) is attached to the lower surface of the upper housing (12). Formed convex step (12a)
Is inserted, and the concave step portion (13a) and the convex step portion (1
The outer peripheral portion of the diaphragm (14) is sandwiched and fixed in an airtight manner between the outer peripheral portion of the diaphragm (2) and (2a). A guide hole (12b) is formed in the center of the upper housing (12) so as to match the opening (18a) of the inlet side fluid flow path (18), and the plug (15) slides. There is.

The plug (15) has an inverted T-shaped cross section with a large diameter at the bottom, and the valve seat surface (the upper surface of the main body (17) ( 1
A ring-shaped protrusion (15a) that comes in contact with and separates from the ring-shaped protrusion (6) is provided on the valve seat surface (16).
When a) contacts, the valve body part (15b) of the plug (15)
The plug chamber (P) that surrounds the inlet and the opening (18a) of the inlet side fluid flow path (18) can be completely blocked. Further, the inner peripheral edge of the diaphragm (14) is fixed to the upper surface of the valve body portion (15b), and the lower housing (1
The hollow chamber of 3) is covered to form a plug chamber (P).
The upper end of the plug (15) protrudes upward from the guide hole (12a), the O-ring (9) is fitted into this protruding end, and the leaf spring (11) is arranged via the washer (10). The plug (15) onto the valve seat surface (16)
It always pushes upward and urges it away from. It goes without saying that the leaf spring (11) can be replaced with a compression coil spring. In this case, as can be seen from the figure, there is nothing in the inlet side fluid passage (18), the plug chamber (P) and the outlet side fluid passage (22) that cause dead volume.

A valve case (7) is fixed to the upper housing (12) by a bolt (8), and a stroke adjusting screw (5) is screwed into the upper end of the plug case (1).
After adjusting the lifting stroke adjustment of 5), the stroke adjusting screw (5) is fixed by the fixing nut (6).
(1) is a reduction type laminated piezoelectric element, the lower surface protrusion (4a) of the plunger portion (4) provided at the lower end is in contact with the upper surface of the plug (15), and the top surface of the reduction type laminated piezoelectric element (1) is a sphere. It is in contact with the lower surface of the stroke adjusting screw (5) via (3).

The reduction-type laminated piezoelectric element (1) is of a type that contracts when a voltage is applied thereto, and as shown in FIG. 2, plate-like ceramics (1b) are laminated laterally via internal electrodes (1a). The external electrode (1c) is installed on the upper end. As a result, when no voltage is applied to the reduction-type laminated piezoelectric element (1), the element (1) is extended and pushes down the plug (15) against the leaf spring (11), and the valve seat surface (16 ), The ring-shaped protrusion (15a) on the lower surface of the plug (15) is pressed in an airtight manner. As a result, it is a normally closed type. An example of the conventional expansion type laminated piezoelectric element (30) is shown in FIG. According to this, the ceramic plates (30b) are vertically laminated via the internal electrodes (30a), and the external electrodes (30c) are installed from both sides, and the entire length is extended by applying a voltage.

In operation, the laminated piezoelectric element (1) having a reduced voltage
When applied to the element (1), the element (1) contracts in proportion to the voltage.
The leaf spring (11) that has been bent in accordance with this contraction expands and pushes up the plug (15) and the element (11), and the ring-shaped projection (15a) on the lower surface of the plug (15) is removed from the valve seat surface (16). Separate. This distance is the element (1)
Is equal to the contraction amount of. As a result, the valve opening can be accurately controlled by the voltage applied to the element (1).

When the valve body (15b) is opened, the fluid (20)
Enters the plug chamber (P) through the controlled gap between the ring-shaped protrusion (15a) of the plug (15) and the valve seat surface (16) from the opening (18a) of the inlet side fluid flow path (18). Further, the discharge side fluid flow path (22) from the discharge groove (21)
Through to the outlet (19), the mass flow rate of the fluid (20) is accurately measured and sent to the apparatus in the next step.
On the contrary, when the voltage applied to the element (1) becomes 0, the element (1) expands again and pushes the plug (15) against the leaf spring (11) to close the opening (18a).

[0026]

Since the control valve of the mass flow controller of the present invention has the structure as set forth in claim 1, the piezoelectric element directly presses the plug to open the opening portion although the control valve is always closed. It has an extremely simple structure that opens and closes, and the cost is low,
In addition, unlike the conventional example, there is no factor that causes particles or dead volume in the fluid channel, the risk of causing clogging is extremely small, and the fluid in the channel is corroded by the fluid. Since there is no metal spring, it has the effect of being extremely safe.

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of a flow rate control unit of a mass flow rate controller according to the present invention.

FIG. 2 is a schematic perspective view of a reduction-type laminated piezoelectric element used in the present invention.

FIG. 3 is a sectional view of a flow rate control unit of a conventional mass flow rate controller.

FIG. 4 is a schematic perspective view of a reduction-type laminated piezoelectric element used in a conventional example.

[Explanation of Codes] (A) ... Mass flow controller (1) ... Reduced type laminated piezoelectric element (11) ... Spring (15) ... Plug (17) ... Main body (18) ... Fluid flow path (18a) ... Opening Department

Claims (1)

[Claims] 1. A fluid channel formed in a main body, a plug that opens and closes an opening of the fluid channel, a spring that biases the plug in a direction away from the opening, and the spring when no voltage is applied. It is composed of a reduction type laminated piezoelectric element that expands against the pressure, presses the plug against the opening to close it, contracts when a voltage is applied, and the plug is separated from the opening by the elastic force of the spring. A control valve for a mass flow controller.