Explosion-proof gas sensor filter and method for manufacturing the same

Abstract

To provide an explosion prevention gas sensor filter that improves strength and eliminates the need for a routine test.SOLUTION: An explosion prevention gas sensor filter is used for an explosion prevention gas sensor 1 to which a detection object gas for an object area is introduced from a gas introduction hole 13c of a gas introduction flange 13 mounted to a container 2 storing a detection element 8, and which detects the introduced detection object gas with the detection element 8, and includes a holder 18 having a stepped through hole 19 including a small-diameter hole 19a having a diameter approximately equal to the diameter of the gas introduction hole 13c and a large-diameter hole 19b having a diameter larger than the diameter of the small-diameter hole 19a, and removably mounted to the gas introduction flange 13, and a sintered filter 20 integrally formed with the small-diameter hole 19a and the large-diameter hole 19b of the stepped through hole 19 by filling stainless powder in the small-diameter hole 19a and the large-diameter hole 19b of the stepped through hole 19 and performing discharge plasma sintering.SELECTED DRAWING: Figure 1

Description

Technical Field

[0006] ,

[0001] The present invention relates to an explosion-proof gas sensor filter used for an explosion-proof gas sensor that detects a detection target gas introduced into a container with an explosion-proof structure, and a method for manufacturing the same.

Background Art

[0002] Conventionally, as an explosion-proof gas sensor that detects a detection target gas introduced into a container with an explosion-proof structure for use in gas detection at a location where a flammable gas is generated, for example, a pressure-resistant explosion-proof gas detector disclosed in Patent Document 1 below is known. The pressure-resistant explosion-proof gas detector disclosed in Patent Document 1 includes a fire escape prevention member made of a metal sintered body such as a sintered body of stainless steel powder or a sintered body of a copper alloy powder in order to obtain sufficient gas permeability and reliably prevent fire escape, and is provided at the opening of the holder member.

[0003] More specifically, the fire escape prevention member used in the pressure-resistant explosion-proof gas detector of Patent Document 1 is housed in a recess partitioned by the small-diameter cylindrical portion and the protruding edge portion of the holder member having a small-diameter cylindrical portion and a large-diameter cylindrical portion, and is held and fixed to the holder member so as to close the front-side opening of the holder member.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the fire escape prevention member disclosed in Patent Document 1 described above has a holding structure in which it is housed and sandwiched in the small-diameter cylindrical portion of the holder member, so the strength of the holding portion of the fire escape prevention member is not sufficient, and there has been a demand for a structure that does not require a routine test while further improving the strength.

[0006] Therefore, the present invention has been made in view of the above problems, and aims to provide an explosion-proof gas sensor filter and a method for manufacturing the same that improves strength and eliminates the need for routine testing. [Means for solving the problem]

[0007] To achieve the above objective, the explosion-proof gas sensor filter described in claim 1 of the present invention is an explosion-proof gas sensor filter used in an explosion-proof gas sensor in which a target gas to be detected in a target area is introduced from a gas introduction hole of a gas introduction flange attached to a container housing a gas detection unit, and the introduced target gas to be detected is detected by the gas detection unit, A stepped through-hole is formed, consisting of a small-diameter hole approximately the same diameter as the gas inlet hole and a large-diameter hole larger in diameter than the small-diameter hole, and a holder that is detachably attached to the gas inlet flange, Stainless steel powder is filled into the small diameter and large diameter holes of the stepped through hole and integrally formed into the small diameter and large diameter holes of the stepped through hole by discharge plasma sintering. Ta Sintered filter and, It is characterized by having the following features.

[0008] A method for manufacturing an explosion-proof gas sensor filter according to claim 2 of the present invention is a method for manufacturing an explosion-proof gas sensor filter used in an explosion-proof gas sensor in which a target gas to be detected in a target area is introduced from a gas introduction hole of a gas introduction flange attached to a container housing a gas detection unit, and the introduced target gas to be detected is detected by the gas detection unit, The step of setting a holder, which is detachable from the gas introduction flange and has stepped through holes formed therein, consisting of a small diameter hole approximately the same diameter as the gas introduction hole and a large diameter hole larger in diameter than the small diameter hole, on top of the punch, The steps include filling the small-diameter and large-diameter holes of the stepped through-hole with the measured amount of stainless steel powder, and then inserting the holder into the die from below. The holder, which is set above the punch, is inserted from below the die. Punch Insert the die from above.The steps include forming a gas sampling filter in the holder by discharge plasma sintering, in which sintered filters are integrated into the small-diameter and large-diameter holes of the stepped through-hole, while holding down the stainless steel powder, The steps include: ultrasonically cleaning the gas sampling filter, which has reached a temperature below a predetermined level; The steps include: testing the aforementioned gas sampling filter using the bubble point method; It is characterized by including. [Effects of the Invention]

[0009] According to the present invention, an integrated structure in which the holder and stainless steel powder are simultaneously sintered can be used to improve strength and realize an explosion-proof structure, making it possible to manufacture an explosion-proof gas sensor filter that does not require routine testing. [Brief explanation of the drawing]

[0010] [Figure 1] This figure shows a partial cross-section of a sensor section, including a filter for an explosion-proof gas sensor according to the present invention. [Figure 2] This is an explanatory diagram relating to a method for manufacturing an explosion-proof gas sensor filter according to the present invention. [Figure 3] This is an explanatory diagram relating to the testing of a filter for an explosion-proof gas sensor according to the present invention. [Modes for carrying out the invention]

[0011] The embodiments for carrying out the present invention will be described in detail below with reference to the attached drawings.

[0012] The explosion-proof gas sensor of this embodiment consists of a natural diffusion type heat conduction sensor equipped with a detection element and a reference element. Briefly explaining its detection principle, when a detection target gas introduced by natural diffusion as a sampling method touches a detection element heated to a predetermined temperature, the state of heat dissipation changes due to the gas-specific thermal conductivity, the temperature of the detection element changes, and along with this temperature change, the resistance value of the platinum resistor constituting the element also changes. The gas concentration is calculated by taking out the amount of change in the resistance value as a voltage by a bridge circuit (a circuit composed of a detection element, a reference element, and two fixed resistors).

[0013] As shown in FIG. 1, the container 2 with an explosion-proof structure forming the detection part of the explosion-proof gas sensor 1 is made of, for example, aluminum, has an opening 2a, and a through screw hole 2c with threads cut on the inner circumference and communicating with the opening 2a is formed at the central part of the tapered tip 2b.

[0014] In addition, in FIG. 1, only the container 2 of the detection part including the filter, which is the main part of the present invention, is shown, but the container 2 is connected to a main body not shown via a cable, and the gas concentration is calculated, the result is displayed, and a signal is output, etc. at the main body not shown.

[0015] A container lid 3 made of, for example, aluminum is detachably attached to the base end part 2d of the container 2 so as to cover the opening 2a. A flat heat dissipation block fixing holder 4 is fixed to the opening 2a of the container 2 by screwing, and a part of the opening 2a forms a housing part 2e.

[0016] A heat dissipation block 5 is fixed to the heat dissipation block fixing holder 4 via a spacer 6 in the housing part 2e. An insulating material 7 made of, for example, Aeroflex is attached to the outer circumference of the heat dissipation block 5 in order to improve the temperature controllability of the heat dissipation block 5.

[0017] In the soaking block 5, a sensing element 8 as a gas detection unit is provided along the central axis L of the tip 2b of the container 2. The sensing element 8 has a platinum resistor provided in a glass tube so as to contact the gas to be detected, and a conducting wire drawn from the platinum resistor is connected to the element substrate 9. The tip portion of the sensing element 8 is fixed to the soaking block 5 via an O-ring 10.

[0018] Also, a reference element 11 is provided in parallel with the sensing element 8 in the soaking block 5. The reference element 11 has a platinum resistor housed in a sealed manner so as not to contact the gas to be detected, and a conducting wire drawn from the platinum resistor is connected to the element substrate 9. Further, a thermistor 12 for controlling the temperature of the soaking block 5 is provided in the soaking block 5.

[0019] A gas introduction flange 13 for introducing the gas to be detected is detachably attached to the through-hole 2c of the tip 2b of the container 2. The gas introduction flange 13 has an opening 13a at one end located on the opposite side of the tip 2b of the container 2, and a protruding portion 13b with a thread cut on its outer periphery is formed at the other end, and the protruding portion 13b is attached to the through-hole 2c of the tip 2b of the container 2. The protruding portion 13b of the gas introduction flange 13 is formed so that a part thereof faces inside the opening 13a, and a gas introduction hole 13c for guiding the gas to be detected to the sensing element 8 is formed along the central axis L of the tip 2b of the container 2.

[0020] A soaking block heat insulation plate 14 made of, for example, PEEK resin for preventing heat leakage of the soaking block 5 is provided between the soaking block 5 and the protruding portion 13b of the gas introduction flange 13 via an O-ring 15.

[0021] The protruding portion 13b facing inside the opening 13a of the gas introduction flange 13 has a thread cut on its outer periphery, and a gas sampling filter 17 is detachably attached via a fluororubber sheet 16. The fluororubber sheet 16 is provided to seal between the gas introduction flange 13 and the gas sampling filter 17 to maintain airtightness.

[0022] The gas sampling filter 17 is formed by filling the stepped through-hole 19 of the holder 18, which serves as the filter base, with stainless steel powder (for example, SUS304 powder) and then integrating the sintered filter 20 into the stepped through-hole 19 of the holder 18 by discharge plasma sintering.

[0023] Furthermore, the holder 18, which serves as the filter base for the gas sampling filter 17, has threads cut into its inner circumference and an opening 18a formed therein that is attached to the projection 13b of the gas introduction flange 13. In addition, the holder 18 has a projection 18b integrally formed on the opposite side of the opening 18a, and a stepped through hole 19 is formed communicating with the opening 18a. The stepped through hole 19 consists of a small-diameter hole 19a, which is approximately the same diameter as the gas introduction hole 13c of the gas introduction flange 13, and a large-diameter hole 19b, which is larger in diameter than the small-diameter hole 19a and continuous with the small-diameter hole 19a.

[0024] Next, the manufacturing method of the gas sampling filter 17 used in the explosion-proof gas sensor 1 described above will be explained with reference to Figures 2 and 3.

[0025] Figure 2 is an explanatory diagram regarding the manufacturing method of the gas sampling filter 17, and Figure 3 is an explanatory diagram regarding the testing of the gas sampling filter 17.

[0026] The gas sampling filter 17 is manufactured according to the following procedure (1) to (12). (1) Quantify the amount of stainless steel powder (SUS304) 21 with a predetermined particle size (e.g., 150-300 μm). (2) As shown in Figure 2, the holder 18 which will serve as the filter base for the gas sampling filter 17 is set on the bottom of the punch 22. (3) The stainless steel powder 21 is filled into the small diameter hole 19a and the large diameter hole 19b of the stepped through hole 19 of the holder 18. (4) Insert the product created in (3) into die 23 in Figure 2 from below. (5) The stainless steel powder 21 is pressed down from above (4) by the upper part of the punch 24 in Figure 2. (6)(5) is placed in a discharge plasma sintering apparatus (hereinafter referred to as the SPS apparatus). (7) Set the load to a predetermined value (for example, 0.4 to 0.5 kN). (8) Control the temperature of the SPS device. For example, 0°C → 880~920°C (held for 15~25 minutes) → 0°C. The temperature is raised at a gradient of, for example, 25~35°C / min. During this heating process, the sintered body of stainless steel powder 21 expands due to heat, and the stainless steel powder 21 begins to bond to the small diameter hole 19a and the large diameter hole 19b of the stepped through hole 19 of the holder 18. (9) After the sintered body of stainless steel powder 21 switches from expansion to contraction, the current is stopped while it is still contracting by a predetermined amount (e.g., 0.3 mm). (10) When the temperature drops below 100℃, the holder 18 and the gas sampling filter 17, which consists of a sintered body of stainless steel powder 21, are removed from the SPS device. (11) The gas sampling filter 17 removed from the SPS device is subjected to ultrasonic cleaning with pure water and alcohol for a predetermined time (e.g., 5 min) each. (12) Test the gas sampling filter 17 using the bubble point method. The valve 25 in Figure 3 is opened gradually and air is supplied by the air pump 26. The porosity is calculated from the critical pressure at which air begins to escape from the sintered filter 20 of the gas sampling filter 17 in the IPA (isopropyl alcohol) 27. The correspondence between pore size and critical pressure is, for example, 1.6 kPa for a pore size of 50 μm, 1.4 kPa for a pore size of 60 μm, and 1.2 kPa for a pore size of 70 μm.

[0027] Here, with the aim of confirming compliance with the International Harmonized Technical Guidelines (Ex Guidelines 2015), Part 2, Explosion-Proof Structures, 15.1.3.1 Overpressure Test - Method 1 (Static Overpressure Test), an overpressure test was conducted using a hydrostatic testing machine: T-100K (Kyowa Corporation) as the measuring instrument. The test was performed by applying a static pressure equal to four times the reference pressure obtained from the explosion test results to container 2, under the conditions of pressurized pressure: 3.20 MPa (0.74 MPa: reference pressure × 4 = 2.96 MPa or higher), and pressurized time: test time: 30 seconds (10 seconds or more).

[0028] The above tests showed no deformation or damage affecting explosion-proof performance, withstood four times the standard pressure, and because the breather section is fixed by co-sintering rather than welding, routine testing is not required.

[0029] Routine testing is conducted to ensure that the container can withstand pressure and that there are no holes or cracks that lead to the outside, and includes the matters described in TIIS Technical Document Ex2015, Volume 1, Part 2, Pressure-Resistant Explosion-Proof Structures "d", 16 Routine Tests, 2-46 to 2-47.

[0030] By the way, although a thermal conduction type gas sensor was illustrated and explained as the explosion-proof gas sensor 1 to which the gas sampling filter 17 of the above embodiment is employed, it can also be used with other types of gas sensors, such as catalytic combustion type or semiconductor type. Furthermore, examples of gases to be detected include H2, He, CO2, CH4, NH3, and water vapor.

[0031] As described above, according to the embodiment described, an explosion-proof gas sensor is used as an explosion-proof gas sensor in which a detection element is housed in an explosion-proof container and the detection element detects the target gas in a target area introduced from the gas introduction hole of the gas introduction flange. In this embodiment, a stepped through hole 19 is formed in a holder 18, which has a small diameter hole 19a that is approximately the same diameter as the gas introduction hole 13c of the gas introduction flange 13 and a large diameter hole 19b that is larger in diameter than the small diameter hole 19a. Stainless steel powder 21 is filled into the small diameter hole 19a and the large diameter hole 19b of the stepped through hole 19, and a sintered filter 20 is integrally formed in the small diameter hole 19a and the large diameter hole 19b of the stepped through hole 19 by discharge plasma sintering.

[0032] As a result, an explosion-proof structure with improved strength compared to the holding structure disclosed in Patent Document 1 can be realized by simultaneously sintering the holder 18 and the stainless steel powder 21 into an integrated structure, making it possible to manufacture an explosion-proof gas sensor filter that does not require routine testing.

[0033] Furthermore, since the small-diameter hole 19a of the stepped through-hole 19 of the holder 18 into which the sintered filter 20 is integrally formed and the gas introduction hole 13c of the gas introduction flange 13 are approximately the same diameter, the target gas to be detected in the target area can be efficiently introduced to the detection element 8 through the gas introduction hole 13c via the sintered filter 20.

[0034] The best mode of the explosion-proof gas sensor filter and its manufacturing method according to the present invention has been described above, but the present invention is not limited by this description and drawings. That is, other modes, examples, and operational techniques based on this embodiment, as made by those skilled in the art, are all included in the scope of the present invention. [Explanation of Symbols]

[0035] 1. Explosion-proof gas sensor 2 containers 2a opening 2b Tip 2c through screw hole 2d proximal end 2e Storage Unit 3 Container lid 4. Heat distribution block fixing holder 5. Heat distribution block 6 Spacers 7. Insulation 8 detection elements 9-element substrate 10 O-rings 11 Reference Elements 12 Thermistor 13 Gas introduction flange 13a opening 13b Projection 13c gas inlet 14. Heat-distributing block heat shield 15 O-rings 16 Fluororubber Sheet 17. Gas sampling filter 18 holder 18a opening 18b Projection 19 stepped through holes 19a Small diameter hole 19b Large diameter hole 20 Sintered Filters 21 Stainless steel powder 22 Punch Down 23 Die 24 Punch Up 25 valves 26 Air pump 27 IPA (Isopropyl Alcohol)

Claims

1. An explosion-proof gas sensor filter used in an explosion-proof gas sensor, wherein the target gas to be detected in a target area is introduced through a gas introduction hole of a gas introduction flange attached to a container housing a gas detection unit, and the introduced target gas to be detected is detected by the gas detection unit, A stepped through-hole is formed, consisting of a small-diameter hole approximately the same diameter as the gas inlet hole and a large-diameter hole larger in diameter than the small-diameter hole, and a holder that is detachably attached to the gas inlet flange, A sintered filter is formed integrally in the small-diameter and large-diameter holes of the stepped through-hole by filling the small-diameter and large-diameter holes of the stepped through-hole with stainless steel powder and discharge plasma sintering. A filter for explosion-proof gas sensors, characterized by having the following features.

2. A method for manufacturing a filter for an explosion-proof gas sensor used in an explosion-proof gas sensor, wherein the gas to be detected in a target area is introduced through a gas introduction hole of a gas introduction flange attached to a container housing a gas detection unit, and the introduced gas to be detected is detected by the gas detection unit, The step of setting a holder, which is detachable from the gas introduction flange and has stepped through holes formed therein, consisting of a small diameter hole approximately the same diameter as the gas introduction hole and a large diameter hole larger in diameter than the small diameter hole, on top of the punch, The steps include filling the small-diameter and large-diameter holes of the stepped through-hole with the measured amount of stainless steel powder, and then inserting the holder into the die from below. The holder, which is set above the punch, is inserted from below the die, and the punch is inserted from above the die, and while the stainless steel powder is held down, a gas sampling filter is formed in the holder by discharge plasma sintering, in which the sintered filter is integrated into the small diameter hole and the large diameter hole of the stepped through hole. The steps include: ultrasonically cleaning the gas sampling filter, which has reached a temperature below a predetermined level; The steps include: testing the aforementioned gas sampling filter using the bubble point method; A method for manufacturing an explosion-proof gas sensor filter, characterized by including the following:

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