Differential pressure gauge, differential pressure flow meter, and flow rate control device

Abstract

To provide a differential pressure gauge with a new structure in which a reference pressure is acted on facing surfaces of two facing diaphragms and two measured differential pressures are acted on non-facing surfaces of the two diaphragms, and to provide a differential pressure flow meter and flow rate control device using the same.SOLUTION: Differential pressure gauges 10A to 10E include: two diaphragms 11 and 12 arranged facing each other; a first sealed structure 13 supporting the two diaphragms and sealing an interior space along with the two diaphragms; and at least one vibrator 20, 20A / 20B in which ends are fixed to the two diaphragms. The interior of the first sealed structure 13 is set to reference vacuum Pr, and a differential pressure (P1-P2) between the two pressures P1 and P2 acting on the two diaphragms from outside the first sealed structure is detected in accordance with the displacement of the two diaphragms.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a differential pressure gauge, a differential pressure flow meter, a flow control device, etc. using two diaphragms.

Background Art

[0002] A differential pressure gauge generally measures the difference in pressure acting on both sides of one diaphragm (Patent Documents 1 and 2). There is also an example in which each pressure acting on two diaphragms is obtained by a strain gauge or a change in capacitance, and the differential pressure between the pressures is obtained (Patent Document 3).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a conventional differential pressure gauge that measures the difference in pressure acting on both sides of one diaphragm, since the diaphragm is displaced by the differential pressure, especially when the differential pressure is extremely small, the displacement amount is also small and the sensitivity is poor. Moreover, each pressure acting on both sides of the diaphragm cannot be accurately measured.

[0005] A conventional differential pressure gauge that obtains the differential pressure between each pressure acting on two diaphragms has two pressure detection units each having a diaphragm, and the accuracy of the differential pressure depends on the pressure detection accuracy by a strain gauge or a change in capacitance in the two pressure detection units.

[0006] The present invention aims to provide a differential pressure gauge with a novel structure, a differential pressure flow meter, and a flow control device that actuate a reference pressure on the opposing surfaces of two opposing diaphragms and apply two measured pressures for which a differential pressure is sought to the non-opposing surfaces of the two diaphragms.

Means for Solving the Problems

[0007] (1) One aspect of the present invention is two diaphragms arranged opposite to each other, a first sealing structure that supports the two diaphragms and seals the interior together with the two diaphragms, at least one vibrator whose ends are fixed to the two diaphragms, including, wherein the interior of the first sealing structure is set to a reference vacuum, and the differential pressure of each pressure acting on the two diaphragms from outside the first sealing structure is detected based on the displacement of the two diaphragms, relating to a differential pressure gauge.

[0008] According to one aspect of the present invention, when pressures act on each non-opposing surface of two diaphragms on which a reference vacuum acts on the opposing surfaces from the outside, each displacement of the two diaphragms is detected as a frequency change of at least one vibrator. When there is one vibrator, the frequency change of one vibrator corresponding to each displacement of the two diaphragms becomes a signal proportional to the differential pressure regardless of the fluid type. Since the displacements of these two diaphragms have equal absolute values and are opposite to each other, even if the individual displacements are as small as, for example, 7 μm to 10 μm, the sensitivity is doubled.

[0009] (2) In one aspect (1) of the present invention, the at least one vibrator can include two vibrators each having one end fixed to the two diaphragms and the other end fixed to the first sealing structure. When there are two vibrators, output signals proportional to the differential pressure between the reference frequency and the external pressure can be obtained from each of the two vibrators, and the pressure between atmospheric pressure and the reference vacuum can be measured. Furthermore, the differential pressure of each pressure acting on each non-opposing surface of the two diaphragms can also be obtained.

[0010] (3) In one aspect (2) of the present invention, a second sealed structure surrounding the first sealed structure, and two pressure introduction pipes arranged from the outside to the inside of the second sealed structure to act the respective pressures on the two diaphragms, can be further included, and the inside of the second sealed structure can be set as the reference vacuum. In this way, the first sealed structure that instructs the two vibrators is surrounded by the reference vacuum by the second sealed structure, so it is thermally insulated from the external atmosphere and the measurement accuracy can be improved.

[0011] (4) Another aspect of the present invention is the differential pressure gauge described in one aspect (2) of the present invention, a fluid pipeline, a flow passage with a constant conductance provided in the middle of the pipeline, a first branch pipe branched from the pipeline so as to guide the fluid upstream of the constant-conductance flow passage to one of the two diaphragms of the differential pressure gauge, a second branch pipe branched from the pipeline so as to guide the fluid downstream of the constant-conductance flow passage to the other of the two diaphragms of the differential pressure gauge, and relates to a differential pressure flow meter having the above.

[0012] According to the differential pressure flow meter of another aspect (4) of the present invention, for example, in the molecular flow region, according to Bernoulli's theorem, from the differential pressure (P1 - P2) between the upstream and downstream of the constant-conductance flow passage and the constant-conductance value C, the flow rate Q = C(P1 - P2) of the fluid flowing through the pipeline can be obtained.

[0013] (5) Still another aspect of the present invention is the differential pressure gauge described in one aspect (3) of the present invention, a fluid pipeline, a flow passage with a constant conductance provided in the middle of the pipeline, a first branch pipe branched from the pipeline upstream of the constant-conductance flow passage, a second branch pipe branched from the pipeline downstream of the constant-conductance flow passage, and has The first branch pipe is connected to one of the two pressure introduction pipes, The second branch pipe is connected to the other of the two pressure introduction pipes, relating to a differential pressure flowmeter.

[0014] Even in the differential pressure flowmeter according to still another aspect (5) of the present invention, in the molecular flow region, according to Bernoulli's theorem, from the differential pressure (P1 - P2) between the upstream and downstream of the flow path with a constant conductance and the constant conductance value C, the flow rate Q of the fluid flowing through the pipeline can be obtained as Q = C(P1 - P2).

[0015] (6) In still another aspect (4) or (5) of the present invention, the fluid is a gas, and the flow path with a constant conductance can be a particulate sintered body. The particulate sintered body can make the holes corresponding to the orifice diameter a very small. Therefore, the condition of λ / a ≧ 1 for achieving molecular flow is also satisfied in a region close to atmospheric pressure. Thus, the gas passing through the particulate sintered body becomes in the molecular flow region even in a region close to atmospheric pressure. Moreover, since the particulate sintered body has a large number of holes, the constant conductance value C of the flow path can also be increased to ensure the flow rate Q.

[0016] (7) Still another aspect of the present invention is the differential pressure flowmeter according to still another aspect (6) of the present invention, a variable valve provided upstream of the first branch pipe of the differential pressure flowmeter and controlling the flow rate based on the measured value of the differential pressure flowmeter, relating to a flow rate control device having.

[0017] According to the flow rate control device of still another aspect (7) of the present invention, the flow rate Q can be variably controlled by adjusting the opening degree of the variable valve based on the differential pressure (P1 - P2) in Q = C(P1 - P2).

Brief Description of the Drawings

[0018]

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Embodiments for Carrying Out the Invention

[0019] Hereinafter, a differential pressure gauge according to an embodiment of the present invention, a differential pressure flowmeter and a flow control device using the same will be described with reference to the drawings. However, the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the gist of the present invention.

[0020] 1. Differential Pressure Gauge FIG. 1 and FIG. 2 are cross-sectional views of a differential pressure gauge 10A having two diaphragms 11, 12 and two vibrators 20A, 20B. The first and second diaphragms 11, 12 are supported opposite to each other in a first sealing structure 13 that seals the interior together with the first and second diaphragms 11, 12. The two vibrators 20A, 20B have one end fixed to the two diaphragms 11, 12 respectively and the other end fixed to a protrusion 13A of the first sealing structure 13. The interior of the first sealing structure 13 is set to a reference vacuum Pr of, for example, 10 -5 Pa. That is, the reference vacuum Pr acts on the opposing surfaces of the two diaphragms 11, 12 respectively. Pressure P1 acts on the non-opposing surface of the first diaphragm 11, and pressure P2 acts on the non-opposing surface of the second diaphragm 12. For this purpose, two pressure introduction pipes 30A, 30B for applying the respective pressures P1, P2 to the non-opposing surfaces of the two diaphragms 11, 12 can be provided.

[0021] The first diaphragm 11 has the reference vacuum Pr acting on the surface facing the second diaphragm 12 and pressure P1 acting on the non-opposing surface. The second diaphragm 12 has the reference vacuum Pr acting on the surface facing the first diaphragm 11 and pressure P2 acting on the non-opposing surface. The first diaphragm 11 displaces according to the differential pressure (P1 - Pr). The frequency change of the vibrator 20A corresponding to the displacement of the first diaphragm 11 becomes a signal proportional to the differential pressure (P1 - Pr) regardless of the gas species. Similarly, the frequency change of the vibrator 20B becomes a signal proportional to the differential pressure (P2 - Pr) regardless of the gas species. Therefore, the desired differential pressure (P1 - P2) can be obtained by eliminating the differential pressure (P1 - Pr) from the first vibrator 20A, the differential pressure (P1 - Pr) from the second vibrator 20B, and the reference vacuum Pr. If the reference vacuum Pr is known, the pressures P1, P2 can also be measured from the frequency changes of the vibrators 20A, 20B. Thereby, the pressures P1, P2 between atmospheric pressure and the reference vacuum can be measured.

[0022] FIG. 3 shows a cross-sectional view of a modified example of the differential pressure gauge of FIG. 1. In FIG. 1, the two vibrators 20A and 20B are arranged in a row, but as shown in FIG. 3, the two vibrators 20A and 20B may be arranged in two rows. For this purpose, one end of the first vibrator 20A is fixed to the first diaphragm 11, and the other end is fixed to the first protrusion 13B of the first sealed structure. One end of the second vibrator 20B is fixed to the second diaphragm 12, and the other end is fixed to the second protrusion 13C of the first sealed structure.

[0023] FIG. 4 shows a cross-sectional view of still another modified example of the differential pressure gauge of FIG. 1. This differential pressure gauge 10C further has a second sealed structure 40 surrounding the first sealed structure 13. The inside of the second sealed structure 40 is also set to the reference vacuum Pr. In FIG. 4, the two vibrators 20A and 20B are arranged in a row, but as shown in FIG. 5, the two vibrators 20A and 20B may be arranged in two rows in the same manner as in FIG. 3.

[0024] According to FIGS. 4 and 5, the two vibrators 20A and 20B are arranged in the reference vacuum Pr, and the first sealed structure 13 indicating the vibrators 20A and 20B is also surrounded by the reference vacuum (Pr), so the two vibrators 20A and 20B are insulated from the outside. Therefore, the measurement accuracy can be further improved.

[0025] 2. Differential pressure flowmeter FIG. 6 is a cross-sectional view of a differential pressure flowmeter 50A using the differential pressure gauge 10A shown in FIG. 1, for example. This differential pressure flowmeter 50A includes, for example, the differential pressure gauge 10A shown in FIG. 1, a fluid pipeline 51A, a constant-conductance flow passage 60A provided in the middle of the pipeline 51, a first branch pipe 52 branched from the pipeline on the upstream side of the constant-conductance flow passage 60A, and a second branch pipe 53 branched from the pipeline 51A on the downstream side of the constant-conductance flow passage 60A. The first branch pipe 52 is connected to the first pressure introduction pipe 30A in order to guide the fluid upstream of the constant-conductance flow passage 60A to the non-opposing surface of the first diaphragm 11 of the differential pressure gauge 10A. The second branch pipe 53 is connected to the second pressure introduction pipe 30B in order to guide the fluid upstream of the constant-conductance flow passage 60A to the non-opposing surface of the second diaphragm 12 of the differential pressure gauge 10A. Note that the first pressure introduction pipe 30A and the first branch pipe 52 can be integrated and referred to as the first branch pipe, and the second pressure introduction pipe 30B and the second branch pipe 53 can be integrated and referred to as the second branch pipe.

[0026] Here, in the present embodiment, the constant-conductance flow passage 60A is formed of a fine particle sintered body. The fine particle sintered body can make the holes corresponding to the diameter a of the orifice minute. Thus, the condition of λ / a≥1 for molecular flow is satisfied even in a region close to atmospheric pressure. Therefore, the gas passing through the fine particle sintered body becomes a molecular flow region even in a region close to atmospheric pressure. Moreover, since the fine particle sintered body has a large number of holes, the constant-conductance value C of the flow passage can be increased to ensure the flow rate Q. Further, as shown in FIG. 6, the present invention is not limited to providing the fine particle sintered body 60A across the pipeline 51A, and as shown in FIG. 7, a bypass may be provided in the middle of the pipeline 51B, and a cylindrical fine particle sintered body 60B may be provided in the bypass. In this way, since the surface area of the fine particle sintered body 60B is increased, the constant-conductance value C can be further increased. Note that the fine particle sintered bodies 60A and 60B can be obtained, for example, by sintering SUS particles having substantially the same diameter in the range of 0.5 to 2.0 μm.

[0027] In the molecular flow region, according to Bernoulli's theorem, the flow rate Q of the fluid flowing through the pipeline can be obtained from the differential pressure (P1 - P2) between the upstream and downstream of the constant conductance flow path 60A and the constant conductance value C, where Q = C(P1 - P2). The differential pressure (P1 - P2) can be obtained by the differential pressure gauge 10A. The constant conductance value C is C = 36A / √(T / M), where A is the cross-sectional area of the orifice, T is the temperature, and M is the molecular weight of the gas, and it is constant without depending on the pressure.

[0028] Figure 8 shows the measurement accuracy of the differential pressure flowmeter 50A shown in Figure 6, and high accuracy can be maintained over a wide flow rate range. The reason is that the pressure measurement accuracy of the differential pressure gauge 10A used in the differential pressure flowmeter 50A is as shown in Figure 9, and the accuracy of the constant conductance value of the fine particle sintered body 60A (60B) is as shown in Figure 10, and both can maintain high accuracy over a wide pressure range. Here, the differential pressure flowmeter 50A can measure from atmospheric pressure to -2 10 -1 Pa, and the error becomes large due to the influence of the ambient temperature below 10 4 Pa. On the other hand, the decrease in the measurement accuracy on the atmospheric pressure side is because the fine particle sintered body 60A deviates from the molecular flow condition (λ / a ≥ 1) at a pressure of 10

[0029] 3. Flow rate control device Figure 11 shows a flow rate control device 70 using, for example, the differential pressure flowmeter 50B shown in Figure 7. The flow rate control device 70 is provided upstream of the first branch pipe 52 of the differential pressure flowmeter 50B and has a variable valve 80 that controls the flow rate based on the measured value of the differential pressure gauge 10B. Since the differential pressure flowmeter 50B measures the flow rate with high accuracy over a wide pressure range, accurate flow rate control can be implemented over a wide pressure range by controlling the variable valve 80 based on the measured value of the differential pressure flowmeter 50B.

[0030] 4. Vacuum system As described above, the differential pressure flowmeter 50B can measure the flow rate regardless of the gas species. Therefore, as shown in FIG. 12, in order to supply a plurality of types of gases, for example, Ar, O2, and N2, to the process chamber 90 by switching, conventionally, a flow rate control device (MFC) was required for each gas species, but now one flow rate control device 70 can be used for a plurality of types of gases. In this case, according to the gas species used, by inputting the molecular weight M of the gas into the flow rate control device 70, the flow rate of the gas can be controlled.

[0031] FIG. 13 shows a vacuum system 100 in which a gas whose flow rate is controlled by a flow rate control device 70 is supplied to a process chamber 90, and the gas in the process chamber 90 is exhausted by an exhaust pump 91. As shown in FIG. 13, a compound pressure gauge 110 for measuring the pressure in the process chamber 90 and a pressure controller 120 for controlling the flow rate control device 70 based on the output from the compound pressure gauge 110 are provided.

[0032] This compound pressure gauge 110 is a pressure gauge defined in claims 8 to 10 of Patent No. 7096628 proposed by the present inventor, and is a combination of a diaphragm pressure gauge disposed under the pressure to be measured and an ionization vacuum gauge disposed under the pressure to be measured. The diaphragm pressure gauge has a measurement range from, for example, atmospheric pressure (10 +5 Pa) to medium vacuum (10 -2 Pa), and the ionization vacuum gauge has a measurement range from, for example, medium vacuum (1 Pa) to ultra-high vacuum (10 -6 Pa). Thus, the compound pressure gauge 110 can have a measurement range from, for example, atmospheric pressure (10 +5 Pa) to ultra-high vacuum (10 -6 Pa). By controlling the variable valve 80 of the flow rate control device 70 based on the measured pressure by the compound pressure gauge 110, the pressure in the process chamber 90 can be set, for example, from 10 +4 Pa to 10 -2 Pa.

[0033] 5. Differential pressure gauge having one vibrator Figure 14 shows a differential pressure gauge 10E having one oscillator 20. Different from Figure 1 etc., both ends of the oscillator 20 are fixed to the opposing surfaces of two diaphragms 11 and 12. When pressures act from the outside on the non-opposing surfaces of the two diaphragms 11 and 12 on which the reference vacuum Pr acts on the opposing surfaces, the displacements of the two diaphragms 11 and 12 are detected as a frequency change of one oscillator 20. In this case, since the two diaphragms 11 and 12 are connected to one oscillator 20, they displace according to the differential pressure (P1 - P2). Therefore, the frequency change of one oscillator 20 becomes a signal proportional to the differential pressure (P1 - P2) regardless of the gas species. Moreover, since the displacements of the two diaphragms 11 and 12 are equal in absolute value and opposite to each other, even if the individual displacements are as small as, for example, 7 μm to 10 μm, the sensitivity is doubled. The frequency change of the oscillator 20 corresponding to the displacements of the two diaphragms 11 and 12 becomes a signal proportional to the differential pressure (P1 - P2) to be obtained, and the differential pressure (P1 - P2) can be obtained.

[0034] Moreover, since the displacements of these two diaphragms 11 and 12 are equal in absolute value and opposite to each other, even if the individual displacements are as small as, for example, 7 μm to 10 μm, the sensitivity is doubled. In this regard, the differential pressure gauge 10E in Figure 14 is superior to the differential pressure gauge 10A etc. in Figure 1. However, the differential pressure gauge 10E in Figure 14 is inferior to the differential pressure gauge 10A etc. in Figure 1 in that it cannot accurately measure each pressure P1 and P2, but it can function only as a differential pressure gauge. The differential pressure gauge 10E shown in Figure 14 can also be used as the differential pressure gauge of the differential pressure flow meters 50A and 50B shown in Figures 6 and 7 and the flow control device 70 shown in Figures 11 and 13.

Explanation of Symbols

[0035] 10A~10E…Differential pressure gauge, 11…First diaphragm, 12…Second diaphragm, 13…First sealed structure, 13A~13C…Fixed part, 20, 20A, 20B…Vibrator, 30A…First pressure introduction pipe, 30B…Second pressure introduction pipe, 40…Second sealed structure, 50A, 50B…Differential pressure flowmeter, 51A, 51B…Flow path, 52…First branch pipe, 53…Second branch pipe, 60A, 60B…Fine particle sintered body (constant conductance flow path), 70…Flow rate control device, 80…Variable valve, 90…Process chamber, 91…Exhaust pump, 100…Vacuum system, 110…Compound pressure gauge, 120…Pressure controller

Claims

1. Two diaphragms arranged opposite to each other, A first sealing structure that supports the two diaphragms and seals the interior together with the two diaphragms, At least one vibrator whose ends are fixed to the two diaphragms, Including, The interior of the first sealing structure is set to a reference vacuum, and the differential pressure of each pressure acting on the two diaphragms from the outside of the first sealing structure is detected based on the displacement of the two diaphragms. A differential pressure gauge.

2. In Claim 1, The at least one vibrator includes two vibrators each having one end fixed to the two diaphragms and the other end fixed to the first sealing structure. A differential pressure gauge.

3. In Claim 2, A second sealing structure surrounding the first sealing structure, Two pressure introduction pipes arranged from the outside to the inside of the second sealing structure to apply the respective pressures to the two diaphragms, Further having, The interior of the second sealing structure is set to the reference vacuum. A differential pressure gauge.

4. The differential pressure gauge according to Claim 2, A fluid pipeline, A flow passage with a fixed conductance provided in the middle of the pipeline, A first branch pipe branched from the pipeline so as to guide the fluid upstream of the fixed-conductance flow passage to one of the two diaphragms of the differential pressure gauge, A second branch pipe branched from the pipeline so as to guide the fluid downstream of the fixed-conductance flow passage to the other of the two diaphragms of the differential pressure gauge, Having a differential pressure flow meter.

5. The differential pressure gauge according to Claim 3, A fluid pipeline, A flow passage with a fixed conductance provided in the middle of the pipeline, A first branch pipe branched from the pipeline upstream of the fixed-conductance flow passage, A second branch pipe branched from the pipeline downstream of the fixed-conductance flow passage, Having, The first branch pipe is connected to one of the two pressure introduction pipes, The second branch pipe is connected to the other of the two pressure introduction pipes. A differential pressure flow meter.

6. In Claim 4 or 5, The fluid is a gas, The flow passage with a fixed conductance is a microporous sintered body. A differential pressure flow meter.

7. The differential pressure flow meter according to Claim 6, A variable valve provided upstream of the first branch pipe of the differential pressure flow meter and controlling the flow rate based on the measured value of the differential pressure flow meter, Having a flow rate control device.

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