Pressure sensor with fluid passage and pressure receiving surface protruding therein

[0002] The present invention relates to a pressure sensor which detects a fluid pressure. More particularly, it relates a pressure sensor which detects pressure of various types of gas or chemical, such as chemicals used for a semiconductor producing process.

[0003] A conventional pressure sensor will be explained in the following.

[0004] The conventional pressure sensor has a conduit which constitutes a passage for flowing a fluid, such as chemical, from one end to the other end thereof. Small space (dead space) is formed on the part of the passage, and a thin diaphragm for receiving fluid pressure directly is disposed above the dead space.

[0005] A sensor head is disposed on the diaphragm and has a pressure sensitive area responsive to the fluid pressure. The pressure sensitive area contacts the diaphragm. The pressure sensitive area of the sensor head is positioned on the passage via the dead space and the diaphragm. In such a structure, the pressure in the passage is transmitted to the pressure sensitive area of the sensor head via the fluid, which is trapped in the dead space, and then the diaphragm.

[0006] When the pressure sensor is used, both ends of the conduit are first connected to a piping for flowing fluid such as chemicals. And then, when the fluid is flowed through the passage, the fluid is trapped in the dead space. The fluid pressure is transmitted to the diaphragm via the trapped fluid and then the pressure acting on the diaphragm is detected by the pressure sensitive area of the sensor head.

[0007] In the conventional pressure sensor, since the dead space is formed on the part of the passage and the diaphragm is disposed above such the dead space, air or fluid may be remained in the dead space when the fluid is flowed through the passage. Accordingly, the dead space should be eliminated and a pressure sensor without dead space is required.

[0008] In view of the problems, the object of the present invention is to provide a pressure sensor in which dead space is not formed under the diaphragm so that air or fluid is not remained in the sensor.

[0009] In order to solve the problems, the present invention provides a pressure sensor, having a passage for flowing fluid from one end to the other end thereof, comprises a sensor head having a pressure sensitive area responsive to the fluid pressure, and a diaphragm having a pressure receiving surface for receiving the fluid pressure directly, wherein said pressure receiving surface is disposed so as to protrude to the inside of the passage, and said pressure sensitive area is disposed on the opposite surface from the pressure receiving surface of the diaphragm.

[0010] Here, the fluid means both gas and liquid.

[0011] In said pressure sensor, since the pressure receiving surface is disposed so as to protrude into the inside of the passage, dead space will not be formed under the diaphragm. In this structure, air and fluid will not be remained in the sensor.

[0012] And, in said pressure sensor according to the present invention, the sensor head may be covered with the diaphragm.

[0013] And, in said pressure sensor according to the present invention, it is preferred that an air hole for escaping air near the sensor head to the outside is formed at the diaphragm. In this manner, the fluid pressure will be detected accurately.

[0014] And, in said pressure sensor according to the present invention, it is preferred that the fluid pressure in the passage is transmitted to the pressure sensitive area via the pressure receiving surface.

[0015] And, said pressure sensor according to the present invention may further comprise a conduit which constructs the passage.

[0016] And, said pressure sensor according to the present invention may further comprise a body which is integrally formed with the conduit.

[0017] And, in said pressure sensor according to the present invention, it is preferred that the body has a through bore which communicates with the passage, the trough bore being provided with the diaphragm and the sensor head.

[0018] And, in said pressure sensor according to the present invention, it is preferred that the conduit is connected to a piping for flowing a fluid at both ends thereof.

[0019] And, in said pressure sensor according to the present invention, it is preferred that the diaphragm is made of fluororesin.

[0020] FIG. 1 is a sectional drawing showing a pressure sensor according to the present invention.

[0021] FIG. 2 is a side drawing showing the pressure sensor shown in FIG. 1.

[0022] FIG. 3(A) is a plane drawing showing the diaphragm shown in FIG. 1 and FIG. 3(B) is a sectional drawing along a line 12b—12bshown in FIG. 3(A).

[0023] Referring to the drawings, specific examples of the present invention will be explained.

[0024] FIG. 1 is a sectional drawing showing a pressure sensor according to the present invention. FIG. 2 is a side drawing showing the pressure sensor shown in FIG. 1. FIG. 3(A) is a plane drawing showing a diaphragm shown in FIG. 1 and FIG. 3(B) is a sectional drawing along a line 12b—12bshown in FIG. 3(A).

[0025] As shown in FIG. 1 and FIG. 2, the pressure sensor has a conduit 10 which constitutes a passage 10afor flowing fluid (for example, chemicals) from one end to the other end thereof. The conduit 10 is integrally formed with a body 1 (a housing) made by Teflon (fluororesin). That is, the passage 10ais composed of the body 1 and the conduit 10. The inner wall of the passage 10ais made of any material having chemical resistance.

[0026] The body 1 has a concave portion 10bon the middle portion thereof and the concave portion 10bis communicated with the passage 10a. A diaphragm 2 made by Teflon (fluororesin) is disposed in the concave portion 10b. The diaphragm 2 has a chemical resistive property. As shown in FIGS. 3(A) and (B), the diaphragm 2 has a thin wall portion 2ahaving a pressure receiving surface 2cfor receiving the fluid pressure directly and a cover portion 2bfor covering a sensor head 14.

[0027] The diaphragm 2 is shaped like a cup. That is, the thin wall portion 2ais shaped like a thin disk, and the cover portion 2bhas an inclined wall on the surround of the thin wall portion 2a.In such a structure, when the sensor head 14 is mounted on the thin wall portion 2a,it is covered with the cover portion 2b.

[0028] The pressure receiving surface of the thin wall portion 2ais positioned so as to protrude into the inside of the passage 10a,as shown in FIG. 1 and FIG. 2.

[0029] The pressure sensitive area 14aresponsive to the fluid pressure is formed at the sensor head 14 while being disposed so as to contact to the thin wall portion 2a. The pressure sensitive area 14aof the sensor head is positioned in the passage 10avia the thin wall portion 2aand composed such that the fluid pressure in the passage can be transmitted via the thin wall portion 2a.

[0030] A sensor holder 3 is disposed on the sensor head 14 to fix the sensor head 14 to the inside of the body 1. An O-ring 16 is disposed between the body 1 and the cover portion 2bof the diaphragm 2 and isolates the sensor head 14 from being exposed to the fluid that flows through the passage 10a.

[0031] The sensor holder 3 and the body 1 are placed between an upper plate 7 and a lower plate 6. The upper plate 7, the body 1 and the lower plate 6 are fixed together by a screw 18. A base bracket 9 is fixed to the sensor holder 3 by a screw 20. One end of a cable 13 is electrically connected to a base 15. The base 15 is fixed to the base bracket by a screw 21.

[0032] The base 15 is covered with a shield case 4, which is covered with a body cap 5. The shield case 4 is fixed to the sensor holder 3 by a screw 19. The upper portion of the body cap 5 is covered by a cap 12. A cable guard 8 is mounted at the upper portion of the body cap 5 and covers the other end of the cable 13 extending from the body cap 5 to the outside for protection.

[0033] An air hole 11 is formed at the sensor holder 3 and the cover portion 2bso that air near the sensor head 14 can escape to the outside. In this manner, the fluid pressure can be detected accurately.

[0034] When the pressure sensor is used, firstly, both end of the conduit 10 is connected to a piping for flowing fluid, such as chemical, and then the fluid is flowed through the passage. Consequently, the fluid pressure is transmitted to the pressure receiving surface of the thin wall portion 2aof the diaphragm 2, and then the pressure acting on the pressure receiving surface is detected by the pressure sensitive area of the sensor head 14 via the thin wall portion.

[0035] In one aspect of the pressure sensor according to the present invention, the body 1 has the concave portion 10bwhich is formed in the nature of a bore and is communicated with the passage. And, the diaphragm 2 is disposed in the concave portion so that the pressure receiving surface of the thin wall portion 2aof the diaphragm is protruded to the inside of the passage 10a. In this structure, dead space, as shown in a conventional pressure sensor, might not be formed under the thin wall portion 2a. So, air and fluid will not be remained in the sensor. Accordingly, the fluid pressure in the passage will be accurately detected by the pressure receiving surface and then transmitted to the pressure sensitive area of the sensor head 14, thereby improving the accuracy of the pressure sensor.

[0036] This invention is not limited to the embodiment, and it is possible to carry out in various aspects within not deviating from the sprit. For example, the material of the various members can be changed to a suitable one.

[0037] In the aspect, the sensor head 14 is covered with the cover portion 2bof the diaphragm 2. However, as long as the diaphragm 2 has the thin wall portion 2awhich makes a pressure receiving surface, it dose not need to have the cover portion for covering the sensor head 14. Accordingly, a pressure sensor which dose not have a cover portion for covering the sensor head 14 can be also provided.

[0038] As mentioned above, according to the present invention, the pressure receiving surface of the diaphragm is disposed so as to protrude to the inside of the passage. Accordingly, the dead space is not formed under the diaphragm, thereby preventing air and fluid from being remained in the sensor.