JPH1165671A - Mass flow controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain mass flow controller which is compact in structure and capable of increasing flow rate by providing plural pipe-shaped seat bodies at the opening of a seat. SOLUTION: In a valve seat 4, an inside face 42 is extended as a taper from a seat port 41, and a seat opening 43 at the upper part is extended to almost the outermost peripheral area of the flat part of a metallic diaphragm. Then, a disc-shaped retainer member 45 made of stainless materials is mounted in the seat opening 43, and total 8 piece of pipe-shaped seat bodies 40a-40h (which are about 0.2 mm thick) are inserted into a hole formed at the retainer member 45, and fixed by a press-fitting means. The seat bodies 40a-40d have large diameters, and seat bodies 40e-40h with small diameters are provided among their clearances. As many seat bodies as possible are provided, so that a large flow rate can be achieved, and it is necessary to consider the diameter and array. Thus, plural partition walls are formed by a simple means at low cost so that the large flow quantity can be flowed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mass flow controller capable of precisely controlling a mass flow rate of a fluid such as a gas, and more particularly to an increase in the flow rate of a flow control valve.

[0002]

2. Description of the Related Art In order to manufacture a semiconductor product by performing a film forming process, an etching process and the like with high precision, it is necessary to flow a small amount of process gas while controlling it with high precision. At this time, a mass flow controller is generally used as a flow control device.

A conventional mass flow controller M is shown in FIG.
As shown in FIG. 2, a sensor unit 2 for detecting a mass flow rate of a trace fluid (hereinafter, described as an example of a gas), a flow control valve 8 provided with an actuator unit 80, and a control circuit unit 3 for controlling these (details will be described below). (Not shown). In the mass flow controller M, first, gas flowing from an inflow port (inflow side joint) 71 is supplied to an inflow channel 72.
In the middle of a, the sensor pipe 20 and the same pipe as this pipe are packed into a predetermined number and branched into a bypass pipe 75 set at a predetermined flow ratio, and they flow again. It flows to the inflow channel 72c.

Here, the sensor pipe 20 is, for example, a stainless pipe having an inner diameter of about 0.5 mm formed in a substantially U-shape, and both ends are open to the inflow channel 72. The upstream and downstream sides of the sensor pipe 20 are heat-sensitive coils 2 respectively.
1 and 22 are wound, and a bridge circuit is formed by combining with other resistors. The sensor circuit 2 is formed by these. The heat sensitive coils 21 and 22 of this sensor
Is heated to a constant temperature higher than the gas temperature,
The upstream heat-sensitive coil 21 is deprived of heat by the flow of gas, and its temperature is lowered. The temperature of the other downstream coil 22 is raised because the gas warmed on the upstream side flows. Occurs. Such heat transfer is detected as an unbalanced voltage in the bridge circuit, and this potential difference is proportional to the mass flow rate, and thus functions as a mass flow sensor. The types of such mass flow sensors include a constant current sensor (Japanese Patent Publication No. 56-23094), a constant temperature sensor (Japanese Patent Publication No. 4-49893), and a constant temperature difference sensor (Japanese Patent Laid-Open No. 1-150817).
No.), etc., and these sensors can be appropriately used.

Next, the flow signal from the mass flow sensor 2 is amplified by an amplifier circuit and then input to a comparison control circuit. Here, a drive signal (valve drive voltage) that is compared with a preset set flow rate signal and eliminates the difference is input to the actuator unit, and as a result,
The gas flow rate can be controlled by adjusting the opening of the flow control valve 8. These controls are performed by the control circuit unit 3 (not shown). Further, in order to precisely control the valve opening, it is necessary to control the stroke within a stroke range of about several tens of μm. Therefore, as the actuator section 80, a laminate that can generate a large thrust with a small stroke. A piezoelectric element is generally used.

[0006] The actuator portion of the flow control valve 8 in FIG. 4 also uses a laminated piezoelectric element body 80 (hereinafter, referred to as a piezoelectric actuator), and directly moves a metal diaphragm (hereinafter, referred to as a metal diaphragm) up and down to flow the gas. It is a flow control valve to be controlled. This flow control valve is provided with an inflow passage 72c.
And a metal valve seat 81 provided at an end of the metal plate, and a peripheral edge thereof is sandwiched by a diaphragm holder 83 so as to face the valve seat 81, and has a flat portion at the center and a semi-circular elastic deformation portion formed outside the flat portion. Metal diaphragm 82, a valve rod 84 that accommodates the laminated piezoelectric element body 80 therein and presses the metal diaphragm 82, and the valve rod 84 is always in the valve seat 8
1 and a spring member 88 for bringing the valve into a closed state. Here, the upper end of the laminated piezoelectric element body 80 is locked by an adjusting member 89, and one lower end is connected to the valve rod 8.
4 and is supported by a bridge member 85 placed on the block-shaped main body 7.

[0007] Therefore, when the laminated piezoelectric element body 80 is expanded by applying a voltage, the direction of the thrust is reversed by the bridge member 85 and acts in the direction of pushing up the valve stem 84 against the spring member 88. As a result, the metal diaphragm 82 is separated from the valve seat 81 by its own restoring force and the flow rate is adjusted. Although this example shows a normally closed type flow control valve, a normally open type flow control valve in which the structure of a bridge member or a spring member is changed has been conventionally used.

Now, mass flow controllers are
It is used from 10 SCCM (10 cc per minute) for small flow to 50 SLM (50 liters per minute) or more for large flow. However, these are uniformly called for downsizing and cost reduction, and have the same size. A mass flow controller that can flow up to a large flow rate even in the dimension between planes is desired. However, as a means for obtaining a mass flow controller with a large flow rate, it is conceivable to increase the so-called stroke of the flow control valve. However, the effective stroke of the laminated piezoelectric element can be obtained only about 40 to 50 μm, and the stroke is reduced. Has limitations. It is also conceivable to increase the diameters of the valve seat and the valve body. However, for example, it is necessary to consolidate a piping system including a mass flow controller and collect them in a cylinder cabinet. Therefore, there is a problem that the valve seat and the valve element cannot be enlarged.

For this reason, as disclosed in Japanese Patent No. 2567959, by providing a partition which draws a continuous closed curve in the seal portion of the valve seat while encroaching from the peripheral portion of the valve body to the central portion. It has been proposed to increase the seal length and increase the flow rate.

[0010]

The flow rate can be increased by increasing the length of the partition wall which draws a closed curve as in this example. However, such a partition wall that draws a continuous closed curve while being intricate is generally difficult and difficult to form, but is expensive and time-consuming.

Accordingly, the present invention is to provide a mass flow controller which can form a large number of partitions by inexpensive and easy means so that a large flow rate can be flowed.

[0012]

SUMMARY OF THE INVENTION The present invention relates to a mass flow controller having a flow sensor for detecting a flow rate of a fluid flowing in a sensor flow path, a flow control valve for controlling a flow rate of the fluid, and a control circuit. The flow control valve includes an inflow-side flow path, an outflow-side flow path, a valve seat provided at an end of the inflow-side flow path, a valve body that comes into contact with and separates from the valve seat, and a valve located above the valve body. The mass flow controller includes an actuator that generates a pressing force on a valve seat side, and a plurality of pipe-shaped valve seats are installed in an upper opening of the valve seat.

In the above, it is desirable that the valve element is a metal diaphragm having a flat portion that separates the inflow-side flow path and the outflow-side flow path and that directly contacts and separates from the valve seat. Further, it is desirable that the sealing surface of each valve seat is formed substantially flush with the upper surface of the mass flow controller body.

By providing a large number of valve seats in this manner, the fluid flows out of each of these valve seats, and eventually the seal length of the valve seat seal portion, which affects the flow rate, is increased to allow a large flow rate to flow. Can be done. The valve seat can be simply assembled at a low cost by caulking a pipe-shaped tubular body such as a ready-made stainless pipe to the upper opening of the valve seat, and thus can be constructed very simply and at low cost.

When a metal diaphragm is used as a valve body, the structure becomes simple and the control of a minute flow rate becomes easy. Then, by forming the sealing surface of each valve seat body substantially on the same plane as the upper surface of the mass flow controller main body, after the valve seat is assembled to the main body of the mass flow controller, the upper surface of the main body and the sealing surface of each valve seat body are simultaneously formed. Lapping is possible. Therefore, precision control can be performed by absorbing dimensional errors of components and variations during assembly.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view showing one embodiment of the mass flow controller of the present invention. FIG. 2 is an enlarged cross-sectional view around the valve seat, and is an AOB cross section of FIG. 3 regarding the valve seat, the retainer member, and the valve seat body. FIG. 3 is a plan view in which a valve seat is inserted into a retainer member.

First, the overall configuration of the mass flow controller shown in FIG. 1 will be described. The mass flow controller main body 1 is composed of a main body 1a made of stainless steel (SUS316L) or the like and having an outflow-side joint and a main body 1b having an inflow-side joint. The main body 1a is an integral block including a joint portion, and its flow paths are an inflow flow path 12a, a bypass flow path 15, an inflow flow path 12b connected to the inflow port 11, and stainless steel (SUS316L) at an end of the flow path 12b. ) A metal valve seat 4 made of a material or the like is mounted by caulking means. A metal diaphragm 5 is arranged so as to face the valve seat 4.
And the outflow side flow path 13 are partitioned. The outflow channel 1 is provided around the valve seat 4 partitioned by the metal diaphragm 5.
3a is directly expanded and the inner wall 13w of the outflow channel 13a
Is a mounting portion of the valve seat. And the outflow channel 13
a is bent by 90 degrees and connected to the outflow channel 13 b and the outflow port 14. In addition, the outflow channel 13b may be a channel facing obliquely downward.

The mass flow controller main body 1a may have a separate outflow-side joint as in the prior art.
As in the present embodiment, the integral arrangement is more efficient in concentrically processing the inflow-side flow paths 12a and 12b, the outflow-side flow path 13b, and the upper opening flow path 13a. In order to attach the valve seat 4 to the main body 1a, screwing means may be used. However the dimensions of the mounting portion prior almost the same city, the diameter d ₀ of the valve seat inlet 41 is preferably made large as possible on the wall thickness strength.

The valve seat 4 has a tapered inner surface 42 that extends outward from the middle of the inflow port 41 and forms a valve seat opening 43 that extends as far outward as possible. The pipe-shaped valve seat body 40 shown in FIG.
Eight from 40h are mounted. Each of these valve seats 4
As for the arrangement of 0 (40a to 40h), large and small valve seats may be provided in combination as shown in FIG. 2, and it is desirable to mount as many as possible to increase the seal length. The height of the sealing surface 44 at the upper end of each valve seat body and the upper surface 16 of the main body 1a are formed on the same plane, and after the valve seat is attached, the sealing surface 44 of each valve seat body and the upper surface 16 of the main body are simultaneously wrapped. Finishing is possible. In this lapping, the entire upper surface 16 of the main body is finished to a mirror surface of about 0.2 S, so that the sealing surface of the metal O-ring of the sensor portion is good, and is extremely efficient in processing and assembly. The outflow channel 13a extends so as to gouge around the valve seat opening 43 of the valve seat 4, and the valve seat opening protrudes with respect to the distance from the center of the valve seat to the inner wall 13w. Conversely speaking, the passage structure is located inside the valve seat opening, so that this structure improves the ease of flow and helps increase the flow rate.

For the mirror-finished main body upper surface 16,
Metal O-ring and spacer 69, valve seat spacer (80μ
m), the peripheral edge of the metal diaphragm 5 is clamped by the diaphragm retainer 62, and the housing 63 and the bridge 64 are placed thereon.
Are fastened to the main body 1a using bolts. On the other hand, a disk-shaped diaphragm spacer 61 is placed on the upper surface of the metal diaphragm 5, and a hard ball 65 having a centering action and a valve stem 64 are pressed by a pressing force of the piezoelectric actuator 60 via a spring 67 or a bridge 66. It is placed so as to transmit. That is, the inside of the valve stem 64 is
6 are fixed to the main body through the piezoelectric actuator 60 at the upper part of the bridge 66 and the spring 67 and the spring receiver 6 at the lower part.
7b is provided.

The piezoelectric actuator 60 has a laminated piezoelectric element sealed in a case made of a metal such as stainless steel, preferably a metal material having an extremely small coefficient of thermal expansion.
The screw is screwed into the housing 63 in a state where the axis is aligned with the housing 63 by b. Therefore, in this mass flow controller, the valve rod 64 is normally pushed down by the spring 67, and the metal diaphragm 5 is pressed against the valve seat in a closed state. When the piezoelectric actuator 60 is energized, the tension is inverted by the bridge 66 and converted into a force that pushes up the valve stem 64 against the spring force. Therefore, the metal diaphragm 5 is lifted up by its own elastic restoring force and fluid pressure to be in the valve open state. Thereafter, it is a normally closed mass flow controller which controls the flow rate by adjusting the moving amount of the metal diaphragm 5. This can be configured as a normally open type mass flow controller.

Each of the above members is basically made of stainless steel (SUS316L or the like). However, for the metal diaphragm 5, a Co-based alloy or a Ni—Co alloy, for example, Ni 13-18%,
Cr 18-23%, Mo 5-9%, Co 38-44%,
It is made of a highly elastic metal material composed of a balance of Fe and impurities, has high corrosion resistance and durability, and has a self-restoring force. It is a circular thin plate having a thickness of about 0.15 mm, in which a flat portion of φD is formed at the center, an elastically deformable portion having a semicircular cross section is formed outside the flat portion, and a peripheral edge portion is further formed outside the flat portion. This metal diaphragm is formed by laminating a plurality of thin plates with a mold, but in order to further increase rigidity, a circular thin plate of the same material is integrally attached to a flat part with spot welding or adhesive etc. It is effective to use.

Next, the features of the mass flow controller 1 will be described with reference to FIGS. The inner surface 42 of the valve seat 4 extends from the valve seat opening 41 in a tapered shape, and the upper valve seat opening 43 extends substantially to the outermost peripheral region of the flat portion of the metal diaphragm. A disk-shaped retainer member 45 made of stainless steel (SUS316L) is mounted in the valve seat opening 43, and a pipe-shaped (about 0.2 mm thick) valve seat body is inserted into a hole formed in the retainer member 45. 40a ~
A total of eight for 40 hours are inserted and fixed by press-fitting means. Among them, the valve seats 40a to 40d have a large diameter, and small gaps of the valve seats 40e to 40h are provided in these gaps. Since the flow rate can be increased by providing as many valve seats as possible, it is necessary to consider the diameter and arrangement.
Further, the upper end of each valve seat is a sealing surface 44, which is set to be flush with the upper surface of the mass flow controller body as described above. Also,
The order of assembling the valve seats is not limited. For example, as shown in FIG. 3, first, valve seats 40a to 40h are first press-fitted into the through holes of the retainer member 45 and attached. 4 can be press-fitted into the opening and fixed.

Incidentally, the dimensions of each part in this embodiment are as follows: the outer diameter of the mounting portion of the valve seat is the same as the conventional _one, φd ₁ = 8 mm, the inlet diameter φd ₀ = 5 mm of the valve seat, and the diameter φd _{2 of the} valve seat opening 43. = 1
3.8 mm, diameter φd ₃ of valve seats 40 a to 40 d = 4.
1 mm, diameter φd ₄ of valve seats 40 e to 40 h = 1.0 m
m. The overall seal length has therefore been extended to 65.3 mm. On the other hand, since the valve seat diameter of the conventional valve seat 41 was uniformly φd ′ = 13 mm, the product of the present invention was about 1.6 times as large as the seal length. Next, an experiment on the flow characteristics with this mass flow controller showed that the maximum flow rate was about twice as large as that of the conventional one. That is, with this configuration, the length of the sealing surface of the valve seat is expanded, and the fluid flows out from the entire periphery of each sub-valve seat, and a large flow rate can be achieved. Further, since the auxiliary valve seat itself can be selected from existing pipe materials and the assembling is simple, the valve seat can be manufactured at a cost of about 1/3 as compared with the above-mentioned conventional example.

As described above, each of the sub-valve seats 40a to 40h
And the upper surface 16 of the main body 1a are assembled so that they are flush with each other, and then lapping is performed.
Thereby, the sealing surface 44 of the valve seat and the metal diaphragm 5
The flatness of the diaphragm and the surface on which the diaphragm retainer 62 and the like are stacked coincide with each other, and the axis of the actuator coincides with the axis of the valve seat and the metal diaphragm. Therefore, the displacement of the piezoelectric actuator is accurately transmitted, and the entire stroke can be effectively used without waste. In addition, since the sealing surface of the valve seat and the flat portion of the metal diaphragm always move while keeping the plane, more precise flow control can be performed. On the other hand, structurally, the valve seat 4
Since the entire positions of the metal diaphragm 5 and the diaphragm retainer 62 and the like move upward, the portion S called the conventional valve chamber shown in FIG. 3 is eliminated. This makes it possible to reduce the dimension between surfaces. In the present example, the valve seat 4 was formed to have an enlarged valve seat opening, and the inter-surface dimension L could be 106 mm. This is because the conventional device had L = 156 mm, so that the size between the surfaces could be reduced by about 32%.

[0026]

As described above, according to the present invention, there is provided a mass flow controller which is compact and can flow a large flow rate by a simple means of providing a large number of pipe-shaped valve seats in the opening of the valve seat. We were able to.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a mass flow controller showing one embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a valve seat portion. A- of the plan view
It is an OB cross section.

FIG. 3 is a plan view of a retainer member.

FIG. 4 is a longitudinal sectional view showing an example of a conventional mass flow controller.

[Explanation of symbols]

1: Mass flow controller
2: Sensor part 3: Control circuit part 4,
9: Valve seat 5: Metal diaphragm
6: Flow control valve 11: Inlet 12 (a,
b): Inflow channel 13 (a, b): Outflow channel 1
4: Outflow port 15: Bypass channel 2
0: Sensor pipe 21: Upstream coil 2
2: Downstream coil 40 (a to h): Valve seat 4
1: Inlet of valve seat 42: Inner surface of taper 4
3: Valve seat opening 44: Seal surface of valve seat 4
5: retainer member 60: piezoelectric actuator 6
1: Diaphragm spacer 62: Diaphragm holder 6
3: Housing 64: Valve stem 6
5: Hard ball 66: Bridge 6
7: Spring 67a: Spring receiver 68
a: Housing cap 68b: Nut 6
9: Outer diameter spacer

Claims (3)

[Claims] 1. A mass flow controller having a flow rate sensor unit for detecting a flow rate of a fluid flowing in a sensor flow path, a flow rate control valve for controlling a flow rate of a fluid, and a control circuit unit, wherein the flow rate control valve has an inflow A side flow path, an outflow side flow path, a valve seat provided at the end of the inflow side flow path, a valve body which comes into contact with and separates from the valve seat, and a pressing force on the valve seat side located above the valve body. A mass flow controller, comprising: a plurality of pipe-shaped valve seats provided at an upper opening of the valve seat. 2. The mass flow controller according to claim 1, wherein the valve body is a metal diaphragm having a flat portion that comes into contact with and separates from the valve seat. 3. The mass flow controller according to claim 1, wherein a sealing surface of each of said valve seats is formed substantially flush with an upper surface of said mass flow controller body.