Pressure detector

The present invention relates to a pressure detector. In a body that constitutes part of the pressure detector, a through hole is formed, which is directed upwardly from a substantially central portion of a flow passage through which a pressure fluid flows. The through hole communicates with a sensor chamber in which a pressure sensor is disposed, and a rod-shaped member is disposed displaceably in the through hole. In addition, an end of the rod-shaped member, which is exposed to the flow passage, is pressed by the pressure fluid and displaced upwardly thereby, and pressure is detected as a result of the pressure sensor being pressed by a head of the rod-shaped member.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2012-025755 filed on Feb. 9, 2012, the contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a pressure detector for detecting the pressure of a fluid that flows through the interior of a flow passage.

2. Description of the Related Art

Heretofore, for example, in a manufacturing process for semiconductor manufacturing or the like, liquids consisting of chemicals and pure water or the like are used, and a pressure detector is connected with respect to tubes through which such liquids are made to flow, whereby measurement of the pressure of the liquid that flows through the interior of the tubes is carried out by the pressure detector.

As one type of such a pressure detector, for example, as disclosed in Japanese Laid-Open Patent Publication No. 11-512827 (PCT) (Patent Document 1), a disk membrane is provided between an internally disposed pressure sensor, which is connected with respect to a fluid flow circuit through which a corrosive liquid flows, and a hole portion that the corrosive liquid flows into, whereby the pressure sensor is separated from and is prevented from coming into direct contact with the corrosive liquid. In this case, a fluid pressure, which is transmitted through the disk membrane, is detected by the pressure sensor.

Further, in Japanese Laid-Open Patent Publication No. 09-166512 (Patent Document 2), a fluid pressure sensor is disclosed in which the pressure sensor is built into the interior of a tube fitting, and the pressure sensor is separated from the fluid by a diaphragm, which is disposed between the pressure sensor and a flow passage through which the pressure fluid flows.

Furthermore, in the pressure sensor disclosed in Japanese Laid-Open Patent Publication No. 2005-207946 (Patent Document 3), a recessed upper surface is provided, which is located at an intermediate portion of a flow passage connected between an upstream side connection port and a downstream side connection port, and fluid pressure measurement is carried out by arranging the pressure receiving surface of a sensor main body so as to face an opening of the flow passage, which opens at a top part of the recessed upper surface.

SUMMARY OF THE INVENTION

However, with the conventional technique disclosed in Patent Document 1, since the disk membrane is arranged in an upwardly offset position with respect to the hole portion through which the corrosive liquid flows, a dead space is created between the hole portion and the disk membrane. Further, similarly, in the conventional technique disclosed in Patent Document 2, a dead space is created between the diaphragm and the fluid passage. Due to such dead spaces, smooth flowing of the fluid is hindered, and there is a concern that pooling of liquid or retention of debris or the like may occur within the dead space. For this reason, if such a pressure detector is used for measuring the pressure of a fluid such as ultrapure water or the like used in a semiconductor manufacturing apparatus, bacteria or the like may develop within the dead space. Further, it is easy for air bubbles (air) to become attached inside the dead space, so that collection of air due to such air bubbles tends to occur, and high precision measurement of pressure cannot be performed.

On the other hand, with the conventional technique disclosed in Patent Document 3, for avoiding the problems of the dead space discussed above, a mountain-shaped curved portion is provided in the center of the flow passage. However, since flow passage resistance occurs in the fluid that flows through the curved portion, pressure loss tends to increase, and further, a sufficient flow rate cannot be assured.

Furthermore, with the pressure detectors disclosed in Patent Documents 1 through 3, the distance between the flow passage through which the fluid flows and the pressure sensor itself is extremely short, while in addition, since the pressure sensor is arranged and separated from the fluid merely by a disk membrane or a diaphragm or the like, for example, in the event there is a change in the temperature of the fluid, a concern exists that such a change may adversely influence the pressure measurement made by the pressure sensor.

A general object of the present invention is to provide a pressure detector that avoids a dead space therein that impedes the smooth flow of fluid, and which by preventing the influence of temperature changes of the fluid, enables pressure measurements of the fluid to be carried out with high accuracy.

The present invention is a pressure detector including a body having a flow passage therein through which a fluid flows, a sensor chamber provided in the body and in which a pressure sensor is arranged, and a through hole that extends from the flow passage to the sensor chamber. A pressure transmitting body is disposed in the through hole and is displaceable along an axial direction in the through hole, such that the pressure transmitting body is capable of transmitting a pressure of the fluid to the pressure sensor. One end of the pressure transmitting body extends in the through hole to an end on the side of the flow passage, such that the one end is constantly exposed to the fluid.

According to the present invention, in the pressure detector, the pressure transmitting body is disposed displaceably in the through hole that communicates between the flow passage through which the fluid flows and the sensor chamber in which the pressure sensor is disposed. Further, one end of the pressure transmitting body extends in the through hole to an end on the side of the flow passage, and the one end is constantly exposed to the fluid. Thus, creation of a dead space in the through hole is prevented, pooling of liquid or generation of air bubbles due to such a dead space can reliably be prevented, and detection of pressure can be carried out with high precision. Further, since the pressure sensor can be disposed at a location distanced from the fluid, degradation of the detection accuracy of the pressure sensor due to the temperature of the fluid can be prevented, and detection of pressure with high accuracy can be performed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown inFIGS. 1 through 4, the pressure detector10includes a body16having first and second ports12,14through which a pressure fluid is supplied and discharged, a pressure sensor18disposed on an upper part of the body16, and a lid member20that closes and blocks the upper part of the body16. For the aforementioned pressure fluid, for example, there may be used a chemical liquid or pure water, which is used in a semiconductor manufacturing apparatus.

The body16is formed from a resin material, for example. The first port12opens on one side of the body16, and the second port14opens on another side of the body16. The first and second ports12,14open horizontally, and on the outer circumferential surfaces thereof, screw threads24are engraved to which fastening members22a,22bare screw-engaged.

In addition, after tubes26have been inserted respectively over the outer circumferential sides of the first and second ports12,14, the tubes26are fastened and connected respectively to the first and second ports12,14by screw-engagement of the cylindrical fastening members22a,22b, through which the aforementioned tubes26have been inserted, with respect to the screw threads24.

A non-illustrated pressure fluid supply source is connected to the first port12via the tube26, for example, whereas a separate apparatus, which has a need for the pressure fluid, is connected to the second port14via the tube26.

Between the first port12and the second port14, a flow passage28is formed in a straight line so as to connect the two ports, and so that the first port12and the second port14are placed in communication through the flow passage28.

Further, in the body16, a through hole30is formed that extends in an upward direction perpendicularly with respect to the flow passage28, and which is formed in a roughly central portion of the flow passage28. A rod-shaped member (pressure transmitting body)32is inserted displaceably in the through hole30. The through hole30is formed with a substantially constant diameter along the axial direction, and by extending from the flow passage28to a sensor chamber34, which is formed on the upper part of the body16, communication is established mutually between the flow passage28and the sensor chamber34.

The rod-shaped member32is constituted from a shaft-like body formed with a substantially constant diameter from an elastic resin material, which is inserted displaceably in the through hole30. The rod-shaped member32comprises a shaft-like main body portion36, and a head38that is formed on an upper part of the main body portion36. The main body portion36has an outer diameter which is substantially the same as the inner diameter of the through hole30, whereas the head38is formed in a disk-like shape and is expanded in diameter in a radial outward direction with respect to the main body portion36.

The axial length of the main body portion36is formed to be slightly longer than the axial length of the through hole30, such that the lower end of the main body portion36is disposed at a boundary region between the through hole30and the flow passage28. Consequently, in the interior of the through hole30, a dead space is not created into which the pressure fluid can flow. Further, the upper portion of the head38of the rod-shaped member32is formed with a curved shape, which protrudes convexly in an upward direction.

Furthermore, for the material of the rod-shaped member32, there may be used a material having water resistance or chemical resistance, corresponding to the type of pressure fluid that flows through the flow passage28.

The sensor chamber34is formed in a bottomed shape and opens in an upward direction. On the bottom thereof, a seal mounting portion40is formed, which is recessed toward the side of the flow passage28. A seal member42formed, for example, from an elastic material is mounted on the seal mounting portion40.

The seal member42is made from an elastic material such as rubber or the like, and includes an annular base section44, an outer edge section46formed on an outer circumferential side of the base section44and which projects perpendicularly with respect to the base section44, and a thin film shaped skirt section48that extends radially inward with respect to the base section44. The seal member42may be formed from an elastic material such as Teflon (registered trademark) or the like.

The base section44, for example, is formed as a flat plate having a predetermined thickness. The base section44abuts against a bottom surface of the seal mounting portion40, whereas the pressure sensor18abuts against the upper surface of the base section44. More specifically, the base section44is gripped between the pressure sensor18and the seal mounting portion40.

Further, as shown inFIG. 3, a first projection (annular projection)50, which is semicircular in cross section, projects downwardly on the lower surface of the base section44and abuts against the bottom surface of the seal mounting portion40. Owing thereto, leakage of pressure fluid from between the body16and the base section44of the seal member42is prevented by the first projection50.

The outer edge section46is inserted into an annular groove51formed in the seal mounting portion40, and on the outer circumferential surface thereof, a pair of second projections (annular projections)52a,52bare formed, and abuts against the wall surface of the annular groove51. The second projections52a,52b, for example, are semicircular in cross section and project in a radial outward direction with respect to the outer circumferential surface of the outer edge section46, and are separated mutually from each other. In addition, by abutment of the second projections52a,52bagainst the annular groove51, passage of pressure fluid toward the side of the sensor chamber34from between the annular groove51and the outer edge section46of the seal member42is prevented.

A hole53(seeFIG. 4) is formed in the center of the skirt section48, and the rod-shaped member32is inserted through the hole53. In addition, in a state in which the seal member42is mounted on the seal mounting portion40, the outer edge section46is fixed with respect to the body16through a later-described holder54, and the skirt section48is retained as a result of being gripped between the head38of the rod-shaped member32and the body16.

Further, as shown inFIG. 4, in the vicinity of the hole53in the skirt section48, an annular third projection (annular projection)56is formed, which projects downwardly from the lower surface, and an annular fourth projection (annular projection)58is formed, which projects upwardly from the upper surface of the skirt section48. In addition, the third projection56abuts against the seal mounting portion40of the body16, so that leakage of pressure fluid from between the seal mounting portion40and the skirt section48is prevented. On the other hand, by abutment of the fourth projection58against the head38of the rod-shaped member32, leakage of pressure fluid from between the skirt section48and the head38is prevented.

The pressure sensor18, for example, is capable of converting a pressing force from the exterior into an electric signal and outputting the electric signal. The pressure sensor18is equipped with a sensor element60, which is disposed in the sensor chamber34on upper portions of the seal member42and the rod-shaped member32, and terminals62, which are connected to the sensor element60. The terminals62also are connected electrically to a circuit board64. A lead wire74is connected to the circuit board64for outputting, to the exterior, pressure values detected by the pressure sensor18.

The sensor element60is disposed such that the head38of the rod-shaped member32abuts against a central portion of the lower surface thereof, which functions as a pressure receiving surface for receiving a pressing force, whereas the base section44of the seal member42abuts against a peripheral portion thereof. In addition, the sensor element60is fixed in the interior of the sensor chamber34by a holder54to which the circuit board64is fastened by bolts66.

The lid member20is connected to an upper part of the body16so as to cover the sensor chamber34, and is formed with an extraction hole68in a central portion thereof through which the lead wire74is inserted. By insertion of the lead wire74through the extraction hole68, and by fastening of a nut72thereon together with a pressing member70, the lead wire74is fixed with respect to the lid member20.

The pressure detector10according to the first embodiment of the present invention basically is constructed as described above. Next, operations and advantages of the pressure detector10shall be explained.

First, in an initial state in which pressure fluid is not flowing through the flow passage28of the body16, since a pressing force from the pressure fluid is not imposed on the lower end of the rod-shaped member32, the rod-shaped member32is not pressed and displaced toward the side of the pressure sensor18, and the pressure sensor18is in a condition of not being pressed by the head38. Thus, no pressure is detected by the pressure sensor18.

Next, when a pressure fluid is supplied to the first port12on the upstream side, and the pressure fluid passes through the flow passage28and flows to the second port14, as a result of the pressure of the pressure fluid inside the flow passage28, the lower end of the rod-shaped member32is pressed upwardly, and the rod-shaped member32is compressed in an axial direction along the through hole30. As a result, the sensor element60of the pressure sensor18is pressed by the head38of the rod-shaped member32, and based on the pressing force (pressure amount) an electric signal is output by the sensor element60to the circuit board64from the terminals62. Thus, the pressure of the pressure fluid is detected in the pressure sensor18, and is output externally through the lead wire74.

On the other hand, from the above condition, in the case of a decrease in the pressure of the pressure fluid, the pressing force against the rod-shaped member32by the fluid is decreased. Accompanying such a decrease, the upwardly compressed state of the rod-shaped member32is released, and the pressing force (pressure amount) on the pressure sensor18is reduced. Therefore, the electric signal based on the pressing force is output from the pressure sensor18, whereby it can be confirmed that the pressure of the pressure fluid has been lowered.

More specifically, the rod-shaped member32is disposed for displacement along the through hole30at a displacement amount which corresponds to the pressure of the pressure fluid flowing in the flow passage28.

Further, in this case, although the pressure fluid flows from the flow passage28into a space between the outer circumferential surface of the rod-shaped member32and the through hole30, since the seal member42, which is made from an elastic material, is disposed between the rod-shaped member32and the sensor element60of the pressure sensor18, the pressure fluid is prevented from flowing to the side of the pressure sensor18(into the sensor chamber34).

In greater detail, on the seal member42, since the first projection50is provided on the base section44that abuts against the body16, leakage of the pressure fluid to the side of the annular groove51of the seal mounting portion40is prevented. Further, since the pair of second projections52a,52bis provided on the outer edge section46, leakage of the pressure fluid to the side of the sensor chamber34from the annular groove51is prevented. Still further, since the third and fourth projections56,58are provided respectively on the lower surface and the upper surface of the skirt section48, leakage of pressure fluid to the side of the sensor chamber34from between the seal member42and the rod-shaped member32is prevented.

In the foregoing manner, according to the first embodiment, in the pressure detector10, the rod-shaped member32is disposed displaceably in the through hole30that communicates between the sensor chamber34in which the pressure sensor18is arranged and the flow passage28through which the pressure fluid flows. In addition, the lower end of the rod-shaped member32is arranged so as to extend to the end of the through hole30. Consequently, since the pressure of the pressure fluid is transmitted to the pressure sensor18via the rod-shaped member32, by disposing the rod-shaped member32in the interior of the through hole30, creation of a dead space in the through hole30can be avoided. As a result, pooling of liquid or the occurrence of bacteria or generation of bubbles, which tend to be problematic in the case that a dead space is created, can reliably be prevented, and the pressure of the pressure fluid can be detected with high accuracy.

Further, since the sensor element60of the pressure sensor18can be arranged at a predetermined distance from the flow passage28through which the pressure fluid flows, lowering of the detection accuracy of the pressure sensor18due to the temperature of the pressure fluid can be prevented, and detection of pressure with high accuracy can be performed.

Furthermore, since the rod-shaped member32is configured to receive the pressure of the pressure fluid, the seal member42does not directly receive the pressure, and a reduction in durability, which would be of concern if the seal member42were deformed excessively, can be avoided.

Still further, the flow passage28is formed in a straight line along the axial direction, and since a curved part and a projection, as in the pressure detector according to the conventional technique, are not required to be provided in the flow passage28, the pressure fluid can be made to flow smoothly, and thus the pressure of the pressure fluid can be detected more reliably.

Still further, by separately constructing the rod-shaped member32, which is in direct contact with the pressure fluid, and the seal member42, which is not in direct contact with the pressure fluid, it is possible for the rod-shaped member32and the seal member42to be formed from different materials. Thus, for example, in the case that the pressure fluid is a chemical liquid or the like, advantageously, only the rod-shaped member32needs to be formed from a material that is chemically resistant, whereas the seal member42can be formed from a material possessing elasticity such as Teflon (registered trademark) or the like.

Further, since the head38of the rod-shaped member32is formed with an upwardly projecting curved shape, the sensor element60of the pressure sensor18can reliably be pressed by a center portion of the head38.

Next, a pressure detector100according to a second embodiment is shown inFIG. 5. Constituent elements thereof, which are the same as those of the pressure detector10according to the first embodiment, are designated by the same reference characters, and detailed descriptions of such features are omitted.

The pressure detector100according to the second embodiment differs from the pressure detector10according to the first embodiment, in that a pressure transmitting body102is provided, in which the rod-shaped member32and the seal member42according to the first embodiment are formed together integrally.

As shown inFIG. 5, the pressure detector100is equipped with a pressure transmitting body102. The pressure transmitting body102has a rod-shaped member104that receives the pressure of the pressure fluid, and a seal member106that retains a liquid-tight condition between the through hole30of the body16and the sensor chamber34. The seal member106is formed integrally with an upper portion of the rod-shaped member104. In addition, the rod-shaped member104is inserted displaceably in the through hole30of the body16, whereas the seal member106is mounted on the seal mounting portion40formed in the sensor chamber34.

The rod-shaped member104includes a shaft-like main body portion36, and when inserted in the through hole30, the lower end thereof is arranged so as to face toward the flow passage28. Conversely, on an upper part of the main body portion36, the skirt section48constituting the seal member106is joined thereto. Concerning the structure of the rod-shaped member104, which is the same as the rod-shaped member32of the pressure detector10according to the first embodiment, detailed explanations of such features are omitted.

The skirt section48is formed in a thin film shape substantially in the center of the seal member106, and the center portion thereof is joined integrally to the upper part of the rod-shaped member104. Concerning the structure of the seal member106, which is the same as the seal member42of the pressure detector10according to the first embodiment, detailed explanations of such features are omitted.

The pressure transmitting body102, which is constituted from the rod-shaped member104and the seal member106, is formed from an elastic resin material, for example, polypropylene or Teflon (registered trademark) or the like. The upper end of the rod-shaped member104is placed in abutment against the sensor element60of the pressure sensor18.

Additionally, by causing a pressure fluid to flow through the flow passage28of the body16, the lower end of the rod-shaped member104on the pressure transmitting body102is pressed upwardly by the pressure of the pressure fluid, and the rod-shaped member104is displaced slightly along the through hole30. As a result, the sensor element60of the pressure sensor18is pressed by the rod-shaped member104of the pressure transmitting body102, and based on the pressing force (pressure amount) an electric signal is output by the sensor element60to the circuit board64from the terminals62. Thus, the pressure of the pressure fluid is detected in the pressure sensor18, and is output externally through the lead wire74.

At this time, in the pressure transmitting body102, the skirt section48of the seal member106is displaced together with the rod-shaped member104, whereupon the skirt section48is deformed by flexing about an adjoined region thereof with the rod-shaped member104.

In the foregoing manner, with the pressure detector100according to the second embodiment, the rod-shaped member104of the pressure transmitting body102is pressed by the pressure of the pressure fluid that flows through the flow passage28of the body16, whereby the sensor element60of the pressure sensor18is pressed by the upper end part of the rod-shaped member104, and the pressure of the pressure fluid is detected. Owing thereto, by inserting the rod-shaped member104of the pressure transmitting body102in the through hole30of the body16, creation of a dead space in the through hole30can be avoided. As a result, pooling of liquid or the occurrence of bacteria or generation of bubbles, which would tend to be problematic if such a dead space were created, can reliably be prevented, and the pressure of the pressure fluid can be detected with high accuracy.

Further, by using the pressure transmitting body102in which the rod-shaped member104and the seal member106are formed together integrally, the number of parts can be reduced and the structure thereof can be simplified, accompanied by a reduction in the number of assembly steps.

Furthermore, since the sensor element60of the pressure sensor18can be arranged at a predetermined distance from the flow passage28through which the pressure fluid flows, degradation in the detection accuracy of the pressure sensor18due to the temperature of the fluid can be prevented, and detection of pressure with high accuracy can be performed.

Still further, since the rod-shaped member104of the pressure transmitting body102is configured to receive the pressure of the pressure fluid, the seal member106does not directly receive the pressure, and a reduction in durability, which would be of concern if the seal member106were deformed excessively, can be avoided.

Next, a pressure detector120according to a third embodiment is shown inFIG. 6. Constituent elements thereof, which are the same as those of the pressure detector10according to the first embodiment, are designated by the same reference characters, and detailed descriptions of such features are omitted.

The pressure detector120according to the third embodiment differs from the pressure detectors10,100according to the first and second embodiments, in that a seal member122is provided which does not include a hole in the center thereof, and the head38of the rod-shaped member32is arranged so as to abut against the center of the seal member122from below.

As shown inFIG. 6, the pressure detector120is equipped with the rod-shaped member32, which is inserted in the through hole30of the body16and receives a pressure from the pressure fluid, and a seal member122, which is provided so as to cover the upper portion of the rod-shaped member32. The seal member122is formed, for example, from an elastic material such as rubber or the like, and is made up from a base section44formed in an annular shape, an outer edge section46formed on the outer periphery of the base section44and which projects perpendicularly with respect to the base section44, and a thin film shaped skirt section124that extends in a radial inward direction with respect to the base section44. Concerning the rod-shaped member32, since it has the same structure as the aforementioned rod-shaped member32of the pressure detector10according to the first embodiment, detailed descriptions thereof are omitted.

In addition, the seal member122is mounted on the seal mounting portion40of the body16, such that the head38of the rod-shaped member32, which is inserted in the through hole30, abuts against the lower surface of the skirt section124of the seal member122.

In the pressure detector120constructed in the foregoing manner, when a pressure fluid is made to flow through the flow passage28of the body16, the lower end of the rod-shaped member32is pressed upwardly by the pressure of the pressure fluid, whereupon the rod-shaped member32is displaced slightly along the through hole30. As a result, the skirt section124of the seal member122is pressed upwardly and is flexed by the upper end of the rod-shaped member32, whereby the sensor element60of the pressure sensor18is pressed thereby. Based on the pressing force (pressure amount) applied from the rod-shaped member32and the seal member122, an electric signal is output from the sensor element60to the circuit board64through the terminals62. Thus, the pressure of the pressure fluid is detected in the pressure sensor18, and is output externally through the lead wire74.

In the foregoing manner, with the pressure detector120according to the third embodiment, the rod-shaped member32is pressed by the pressure of the pressure fluid that flows through the flow passage28of the body16, whereby the sensor element60of the pressure sensor18is pressed via the skirt section124of the seal member122, which is abutted by the upper end of the rod-shaped member32, and then the pressure of the pressure fluid is detected. Owing thereto, by insertion of the rod-shaped member32in the through hole30of the body16, creation of a dead space in the through hole30can be avoided. As a result, pooling of liquid or the occurrence of bacteria or generation of bubbles, which would tend to be problematic if a dead space were created, can reliably be prevented, and the pressure of the pressure fluid can be detected with high accuracy.

Further, since the rod-shaped member32and the seal member122can be formed separately from different materials, ease of assembly of the pressure detector120can be enhanced, and the rod-shaped member32, for example, can be formed from a suitable material corresponding to the type of pressure fluid that flows through the flow passage28.

The pressure detector according to the present invention is not limited to the aforementioned embodiments, and it is a matter of course that various additional or modified structures may be adopted therein without deviating from the essential gist of the present invention.