JPH03244882A - Flow quantity control valve - Google Patents

Abstract

PURPOSE:To improve the stability and the reliability by providing a thin plate diaphragm over a communicating part, and making a thin plate composing a lamination type displacement element of the electric mechanism converting material of which piezoelectric distorsion constant in a range of the specified temperature shows a constant value approximately. CONSTITUTION:A thin plate 24 composing a lamination type displacement element 21 is made of a lamination type displacement element (electric mechanism displacement material) of which piezoelectric distorsion constant d33 in a range from an ordinary temperature to a high temperature area more than 100 deg.C shows a constant value approximately. When a direct voltage is applied to the element 21, the element 21 is extended in the laminated direction to push down the central part of a diaphragm 17 downward through a valve rod 22, against the reaction force of a compression coil spring 27, and a space between the diaphragm 17 and a valve seat 15 is reduced, namely, the open degree of a valve port 16 is reduced to reduce a gas flow quantity. When the applying voltage to the element 21 is cancelled, the diaphragm 17 is returned to its original position. In this case, since a sliding part does not exist between the diaphragm 17 and the valve seat 15, the metal powder is never mixed with the gas.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a flow rate control valve that is often used for precisely controlling gas flow rate in the semiconductor industry, in particular, for driving a laminated displacement element. The present invention relates to a flow rate control valve used as a source.

[Prior Art] As a conventional flow control valve using a laminated displacement element as a driving source, there is one having a structure as disclosed in, for example, Japanese Patent Application Laid-open No. 127983/1983.

FIG. 7 is a longitudinal cross-sectional view of the essential parts of the 2itt*+ valve, which is so-called a normally open type valve. In FIG. 7, reference numeral 11 denotes a main body, which is formed into a block shape from a structural material such as stainless steel, and includes a communicating portion 12 that opens upward, and an inflow passage 13 and an outflow passage 14 that open to this communication portion 12. will be established. 15
is the valve seat.

A valve port 16 is provided in the lower part of the communication part 12 and communicates with the outflow passage 14.Next, 17 is a diaphragm, which is formed in a thin plate shape from a metal material and is provided to seal the upper part of the communication part 12. .

A valve body 18 is integrally fixed to the lower surface thereof so as to face the valve port 16. Next, 19 is a housing.

It is formed into a hollow cylindrical shape from the same material as the main body 11, and is fixed above the main body 11 via a presser metal 20 so as to seal the communication portion 12. Reference numeral 21 denotes a laminated displacement element, which has a valve rod 22 fixed to its lower end and is inserted into the housing 19 so that the valve body 22 contacts the diaphragm 17. Reference numeral 23 denotes an opening adjustment screw, which is screwed onto the upper end of the housing 19 so that its lower end comes into contact with the laminated displacement element 21. The laminated displacement element 21 is made of a piezoelectric ceramic material, for example, and has a diameter of 10 to 20 mm and a thickness of 0.5 mm.
300 to 400 'fs plates 24 of 1-0.2 mm and internal electrodes 25 made of a conductive metal material are laminated alternately. Then, every other internal electrode 25 is connected to one external electrode (not shown), and every other internal electrode 25 is connected to the other external electrode (not shown), and these external electrodes is connected to a DC voltage source (not shown) via a lead wire.

With the above configuration, a predetermined gap is ensured between the valve seat 15 and the valve body 18, so that from the inflow channel 13 to the communication section 12.
and gas flows into the outflow channel 14 through the valve port 16.
Next, when a DC current of 150 cm, for example, is applied to the laminated displacement element 21, it expands by 30 to 40 μm in the lamination direction. Therefore, the valve stem 22 is pushed downward, and the valve body 18 is further displaced downward. As a result, the gap between the valve body 18 and the valve seat 15, that is, the opening degree of the valve port 16 becomes small.On the other hand, the laminated displacement element 2
When the DC voltage applied to 1 is removed, the laminated displacement element 2
1 contracts by the amount of expansion caused by the voltage application. Therefore, the valve body 18 returns to its original position due to the restoring force of the diaphragm 17, and the opening degree of the valve port 16 also returns to its original state.

As described above, the opening degree of the valve port 16 can be adjusted by the DC voltage applied to the laminated displacement element 21, and as a result, the flow rate of gas from the outflow channel 14 can be controlled.

[Problem to be solved by the invention]

In the conventional flow control valve described above, a valve body 18 is present in the communication portion 12 through which gas flows, and this valve body 18 controls the flow rate by entering and exiting the valve port 16 provided in the valve seat 15. The structure is as follows. The valve body 18 is used when the gas flow is interrupted.

There is a problem in that metal powder that comes into contact with the end of the valve port 16 and is generated by abrasion while sliding on the end of the valve port 16 and the inner circumferential surface during flow rate control gets mixed into the gas.

Although not shown in the drawings, in a normally closed type flow control valve, the frequency of contact and sliding between the valve body 18 and the valve port 16 is much higher than in a normally open type, so it may be caused by wear. The amount of metal powder generated is also large,
The above problems become even more serious.

In order to solve the above problems, the present applicant has already filed an application for a flow control valve in which the valve body 18 is omitted and the diaphragm 17 is formed directly in contact with and detachable from the valve seat 15 (for example, a patent application No. 194492).

FIG. 1 is a longitudinal cross-sectional view of a main part of the flow control valve, and the same parts are designated by the same reference numerals as in FIG. 7. In FIG. 1, a diaphragm retainer 26 is formed in the shape of a hollow bowl and is sandwiched between the housing 19 and the main body 11 to fix the diaphragm 17. A compression coil spring 27 is interposed between the valve stem 22 and the diaphragm retainer 26 so as to press the valve stem 22 upward.

With the above configuration, a predetermined distance is secured between the valve seat 15 and the diaphragm 17, so that gas flows from the inflow channel 13 to the outflow channel 14 via the valve port 16 and the communication portion 12. And directly to the laminated displacement element 21! When a voltage is applied, it expands in the stacking direction, pushes down the center of the diaphragm 17 via the valve rod 22 against the repulsive force of the compression coil spring 27, and reduces the distance between the diaphragm 17 and the valve seat 15. In other words, since the opening degree of the valve port 16 is reduced,
The gas flow rate can be reduced. Laminated displacement element 2
1, the valve stem 22 and diaphragm 17 return to their original positions. Therefore, the gas flow rate can be controlled in the same way as in FIG. 7.

In the device shown in FIG. 1 above, the diaphragm 17 only comes into contact with and separates from the valve seat 15, and there is no sliding movement between the two, so metal powder due to wear as shown in FIG. 7 is generated. Did not occur.

Therefore, metal powder is not mixed into the gas. However, in the flow rate control valve as shown in FIG. needs to be large. Note that the piezoelectric strain constant d1. is calculated by the following formula.

dl,=mu77E M '373' K33However,
ε. : Vacuum dielectric constant ε, lT + 'relative permittivity S 7z ' Elastic compliance Ko: Electromechanical coupling coefficient 1 Elastic compliance S33 in the above equation is approximately 15X10-''rd/N in piezoelectric ceramics,
ift mechanical coupling coefficient K. Since the limit is about 0.6 to 0.7, the piezoelectric strain constant d is usually increased by lowering the Curie temperature Tc of piezoelectric ceramics and increasing the relative permittivity ε and T3 near room temperature. Measures are being taken. Therefore, the Curie temperature Tc of piezoelectric ceramics used in conventional laminated displacement elements is 150.
C., and there is a problem in that it cannot be used in applications that require a substantially constant displacement in the range from near room temperature to about 130.degree. C., such as control valves for high-temperature, high-speed response mass flow controllers. That is, when the temperature of the laminated displacement element exceeds 100° C., the piezoelectric strain constant d13 decreases rapidly, the amount of displacement decreases drastically, and it becomes impossible to secure a predetermined amount of displacement.

The present invention solves the problems existing in the above-mentioned prior art, and provides a flow control valve that has a substantially constant displacement and is highly stable and reliable in the range from normal temperature to a high temperature range of 100°C or higher. The purpose is to provide.

[Means to solve the problem] In order to achieve the above object, one aspect of the present invention is as follows.

A communication part that opens upward in the main body, an inflow passage and an outflow passage that open to this communication part are provided, and a valve seat is provided at the opening of the inflow passage or the outflow passage, and a valve seat is provided above the communication part in a sealed manner. A thin plate-like diaphragm made of a metal material is provided, and a laminated displacement element is provided in a housing provided above the main body so as to drive the diaphragm so as to be able to come into contact with and detach from the valve seat, and The piezoelectric strain constant d of the thin plate constituting this laminated displacement element in the range from room temperature to a high temperature region of 100° C. or higher. It is formed from an electromechanical transducer material that exhibits a substantially constant value. A technical method was adopted.

1 in the present invention! The Curie temperature of the mechanical conversion material can be 150''C or higher.

[For production]

With the above configuration, the diaphragm can be moved into and out of contact with the valve seat, and the flow rate can be controlled.
This allows the predetermined function to be fully performed.

[Example] FIGS. 2(a) to 2C are perspective views showing examples of laminated bodies constituting laminated displacement elements in examples of the present invention. First, in FIG. 2(a), a thin plate 1 is formed in the following manner. First, the raw materials are mixed in the following weight ratio. Namely.

3b and 03 (wt%) are blended in the ratio shown in the table.

Conventional example After mixing the above raw materials in a ball mill for 24 hours.

Calcinate at 800℃ for 1 hour. After pulverizing the calcined powder, polyvinyl butyral is added to the calcined powder and dispersed in trichlene to form a slurry, and this mixed material is processed into sorted IFiI with a thickness of 100 μm using a doctor blade method.
to form. Next, the inside 1iii is applied to the entire surface of this thin plate 1.
Screen print the platinum conductive paste or silver-palladium paste forming 2a, 2b. For example, 100 thin plates l having the internal electrodes 2a and 2b formed as described above are alternately laminated and crimped, then cut into a predetermined size and shape to form a laminate, and after removing the binder at 500 ° C. Sintering in oxygen at 1050-1200°C for 1-5 hours,
A laminate 5 is formed by cutting into a predetermined size.

The dimensions of this laminate 5 are, for example, 5x5xlOj! (Kaku). Next, coatings 7a and 7b made of an insulating material are provided on adjacent side surfaces of this laminate 5 so as to cross the internal electrodes 2a and 2b. In FIG. 2(C), 8a and 8b are grooves, which are carved using a dicer or the like at positions corresponding to the internal electrodes 2a and 2b of the coatings 7a and 7b.In FIG. , 7b so as to cross the grooves 8a, 8b, the external electrodes 3a,
3b and the internal electrodes 2a, 2b can be connected correspondingly to the primary external 11Hii3a, 3b.
and voltage supply lead wires are connected via solder (none of which is shown), but the solder has a 1 weight ratio of 5.
It consists of n25%, Pb74.5%, Sb0.5%, and has a liquidus temperature of 260°C. The laminate 5 formed as described above was subjected to polarization of 1.5 to 1/W and its characteristics were measured. The results are also shown in the table.

As is clear from the table, the piezoelectric strain constant d31 can be increased by increasing the amount of 5bzOt added, but on the other hand, the Curie temperature Tc is decreased. This composition system has an electromechanical coupling coefficient of 3. is extremely large at 0.75, which indicates that the piezoelectric strain constant d31 is extremely large even when the Curie temperature is 150° C. or higher. In case 4, the amounts of Sb and O are too large to form a complete solid solution in one crystal, and a decrease in the piezoelectric strain constant d33 is observed. In numbers 1 to 3, the Curie temperature Tc is 150°C or higher, and the piezoelectric strain constant d
33 is also large. Therefore, it can be seen that a large displacement can be generated even in a high temperature region.

FIG. 3 is a diagram showing the relationship between temperature and generated displacement, and the holes in the diagram correspond to the floors in the table above. Note that the generated displacement in FIG. 3 is for an applied voltage of 150V. Third
As is clear from the comparison example, that is, the conventional example Nα
In No. 4, the displacement generated by 1 gradually decreases as the temperature rises, and becomes a significantly low value in the high temperature region of 100° C. or higher. On the other hand, in Cases 1 to 3 corresponding to the present example, the values of generated displacement at room temperature are all large, and they maintain a substantially constant value of 10 μm or more up to a high temperature region of 100° C. or higher. . However, the laminate with the above structure should be heated to 120°C.
When we conducted a driving test for 1,000 hours under the conditions of 150V and 10 seconds in a high-temperature atmosphere, the displacement occurred in each of 100 test pieces. It was confirmed that there was no functional deterioration or conduction failure of the air-mechanical conversion material.

Next, a laminate made of the material Nα1 (5X5X10ff
i(m)) are laminated via a polyimide adhesive to form a laminated displacement element with a length of 40 m, - the first
The temperature dependence of flow rate was measured by incorporating it into the flow rate control valve shown in the figure. In this case, N2 gas is used as the fluid, and the outer diameter of the contact part of the valve seat 15 with the diaphragm 17 is set to 2.2
M, the inner diameter of the valve port 16 was closed to 2.0 mm. That is, first, a direct current of 150 cm was applied to the laminated displacement element 21, and the opening adjustment screw 2 was adjusted while Nz gas was flowing (differential pressure 3 kg/c-d).
3 downward and connect the diaphragm 1 through the valve stem 22.
7 in contact with the valve seat 15, and press N! Adjust the gas flow rate to 0. Next, when the application of the DC voltage to the laminated displacement element 21 is released, the compression coil spring 27 pushes up the valve stem 22 due to its repulsive force.

The diaphragm 17 separates upward from the valve seat 15 and opens into the valve port 16.
Open. The N2 gas flow rate at this time shows the maximum value.

FIG. 4 is a diagram showing the relationship between temperature and maximum flow rate. Fourth
As is clear from the figure, even if the temperature rises, the maximum flow rate remains at 1.
It remains approximately constant up to a high temperature region around 80°C. That is, the stroke of the diaphragm 17 shown in FIG. 1 is approximately constant in the range from room temperature to a high temperature region of 100° C. or more. This is due to the large displacement of the laminated displacement element 21 and the fact that the piezoelectric strain constant d ii is approximately constant from room temperature to high temperature range.

Such characteristics cannot be obtained by using conventional piezoelectric materials.
It is effective for valves for controlling the flow rate of organometallic gases such as G () (limethyl gallium). In other words, since organometallic gases have high boiling points (e.g. dimethylzinc 44℃, tetramethyltin 78℃, triethylgallium 142.6℃, etc.), it is necessary to heat and keep the supply piping system warm, which inevitably requires flow rate control. valves are also used in high temperature conditions. Therefore, in some conventional devices where the displacement tends to decrease as the temperature rises, for example, the stroke of the diaphragm 17 in FIG. 1 decreases, making it impossible to obtain a sufficient gas flow rate.

FIG. 5 is a main part configuration diagram showing another embodiment of the present invention,
This is an example of the mass flow controller for controlling the organometallic gas. In FIG. 5, reference numeral 30 denotes a flow rate control valve 1, which has the structure shown in FIG. 1, for example, and the laminated displacement element 21 for driving is made of the material shown in Ntll in the table above. 31 and 32 are an inflow channel and an outflow channel, respectively, through which fluid flows in the direction of the arrow. Reference numeral 33 denotes a flow rate sensor, which is connected to the inflow channel 31 in a U-shape, for example, and is formed so that, for example, 10% of the fluid flow rate of the inflow channel 31 flows therethrough. 34 is a measuring element, which is wound around the flow rate sensor 33 and electrically connected to the bridge circuit 35. Next, reference numerals 36, 37, 38, and 39 denote an amplifier circuit, a phase compensation circuit, a comparator circuit, and a drive circuit, respectively, which are connected in series to the bridge circuit 35 so as to be able to sequentially transmit the output signals of the bridge circuit 35. 40 is a setting signal output section, which is connected to the comparison circuit 38. Note that drive circuit 3
The output voltage No. 9 is formed so as to be input to the laminated displacement element 30a constituting the flow rate control valve 30.

With the above configuration, the setting signal output unit 40 outputs, for example, O to
When a 5V signal is input to the comparator circuit 38, a DC voltage corresponding to this signal is applied to the laminated displacement element 30a via the drive circuit 39, so that the valve port 16 opens as shown in FIG. The fluid can be made to flow as shown by the arrows in FIG. Note that the flow rate of the fluid can be measured by outputting an output signal of a bridge circuit 35 connected to a measuring element 34 wound around a flow rate sensor 33 to an output section 40a via an amplifier circuit 36 and a phase compensation circuit 37, and using this signal. I can do it.

Since this signal is also output to the comparison circuit 38, the opening degree of the flow rate control valve 30 is controlled via the drive circuit 39 by comparison with the setting signal.

FIG. 6 is a diagram showing the relationship between set voltage and control flow rate,
This is a case where the flow rate of triethyl gallium gas (TEG) is controlled by a mass flow controller as shown in FIG. In this case, the mass flow controller was heated to 160° C. The differential pressure of the gas was set as the vapor pressure of TEG. As is clear from FIG. 6, the set voltage and the controlled flow rate are in a completely proportional relationship. Furthermore, since the stroke of the diaphragm (numeral 17 in Figure 1) of the flow control valve that constitutes the mass flow controller can be increased, clogging and dirt adhesion can be prevented, and the stroke is sufficiently large even at low differential pressures. It is possible to obtain a flow rate of

In this embodiment, a normally open type case has been described, but the operation is the same even if a normally closed type is used. Note that the target fluid may be not only a gas but also a liquid, and it is also applicable to low-temperature fluids and normal-temperature fluids in addition to high-temperature fluids. Next, the laminated displacement element includes not only the full-surface electric bridge type element shown in Figure 2, but also a so-called alternating electrode type element, and an element in which internal electrodes are provided on both sides of a thin plate, and these are stacked or glued. Naturally, it can also be applied to

In addition, the planar projection shape of the thin plate and internal electrodes is not only rectangular but also
It can be a square, a circle, an oval or other geometric shapes. Alternatively, in order to obtain a larger displacement, it is also possible to use a plurality of the elements bonded together with a heat-resistant adhesive. Furthermore, it is also applicable to a type in which lead wires are omitted and lead members are fixed to the upper and lower end surfaces of the laminate. In the above embodiment, an example was described in which screen printing was used as a means of forming the internal electrodes and external electrodes, but the method is not limited to this, and the same effect can be achieved by other methods such as plating vapor deposition or coating. be.

〔Effect of the invention〕

Since the present invention has the structure and operation as described above, 2
For example, even if the target is an organometallic gas with a boiling point of 50 to 150°C, the piezoelectric strain constant dff3 of the material constituting the laminated displacement element maintains a sufficiently large value, so the stroke of the diaphragm is large and sufficient flow rate can be obtained. In addition, the valve seat and diaphragm are not clogged or contaminated by fluid (reliability can be greatly improved).The piezoelectric strain constant d33 of the material constituting the laminated displacement element is stable from room temperature to high temperature range of 100℃ or more. Since it is substantially constant, it can be applied even when the temperature of the target fluid changes over a wide range, and has the effect of expanding the range of applications.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of the main part showing an embodiment of the present invention.
) or C) are respectively perspective views showing examples of laminated bodies constituting laminated displacement elements in embodiments of the present invention, FIG. 3 is a diagram showing the relationship between temperature and generated displacement, and FIG. 4 is a diagram showing the relationship between temperature and maximum displacement. FIG. 5 is a diagram showing the main part configuration of another embodiment of the present invention, FIG. 6 is a diagram showing the relationship between set voltage and control n flow rate, and FIG. 7 is a conventional flow rate diagram. FIG. 3 is a vertical cross-sectional view of a main part showing a control valve. 1: I plate, 5: Laminated body, 1: Main body, 15: Valve seat 17: Diaphragm, 21: Laminated displacement element.

Claims (2)

[Claims] (1) A communicating part opening upwardly in the main body, an inflow passage and an outflow passage opening to this communication part are provided, and a valve seat is provided at the opening of the inflow passage or the outflow passage, and a valve seat is provided at the opening of the inflow passage or the outflow passage. A laminated displacement element is provided with a thin plate-shaped diaphragm made of a metal material so as to be sealed upwardly, and is formed in a housing provided above the main body so as to drive the diaphragm so as to be able to come into contact with and detach from the valve seat. A flow rate characterized in that the thin plate constituting the laminated displacement element is formed of an electromechanical transducer material whose piezoelectric strain constant d_3_3 exhibits a substantially constant value in the range from room temperature to a high temperature region of 100° C. or more. Control valve. (2) The flow rate control valve according to claim (1), wherein the Curie temperature of the electromechanical conversion material is 150° C. or higher.