Explosion-proof gas sensor

Abstract

To improve gas responsiveness performance.SOLUTION: An element unit 3B includes: a sensor holder 31 to which a soaking pedestal 33 provided with two storage parts 33a, 33b in parallel is fixed, and which is mounted to a sensor main body; a hydrogen sensor element 5 stored in one of the two storage parts 33a, 33b; a first gas introduction member 36A in which a gas introduction hole 36b for introducing an inflammable gas in an object area to the hydrogen sensor element 5 is formed and a sinter filter 36c is integrally formed in the gas introduction hole 36b; an environment sensor 11 stored in the other of the two storage parts 33a, 33b; and a second gas introduction member 36B provided in parallel with the first gas introduction member 36A, and in which the gas introduction hole 36b for introducing an inflammable gas in the object area to the environment sensor 11 is formed and the sinter filter 36c is integrally formed in the gas introduction hole 36b.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an explosion-proof gas sensor that detects an explosive flammable gas, such as hydrogen, as a detection target gas in a target area. [Background technology]

[0002] Conventionally, a specific gas concentration sensor disclosed in Patent Document 1 below is known as an example of an explosion-proof gas sensor for detecting explosive, flammable gases such as hydrogen. This specific gas concentration sensor is a thermal conduction type sensor, and when there is airflow, the airflow absorbs heat from the heater, making it impossible to accurately measure the specific gas concentration. Furthermore, if the specific gas is a flammable gas such as hydrogen, heating by the heater can ignite the gas, and depending on the gas concentration, there is a risk of explosion. Therefore, the specific gas concentration sensor disclosed in Patent Document 1 employs a configuration in which the sensor element and heater are covered with a cap having a mesh structure. This achieves both airflow blocking and explosion protection.

[0003] Incidentally, this type of thermal conduction type explosion-proof gas sensor is provided with an environment sensor in the device that is independent of the hydrogen sensor element in order to cancel the influence of environmental changes, which will be described later. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5888747 Summary of the Invention [Problem to be solved by the invention]

[0005] However, conventional thermal conduction type explosion-proof gas sensors, including the specific gas concentration sensor of Patent Document 1 mentioned above, have been unable to achieve sufficient gas response performance because the hydrogen sensor element and the environmental sensor are placed in the same space, resulting in a large spatial volume.

[0006] SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide an explosion-proof gas sensor which is capable of improving gas response performance. [Means for solving the problem]

[0007] In order to achieve the above object, the explosion-proof gas sensor according to claim 1 of the present invention is an explosion-proof gas sensor that detects a target gas in a target area, and in which an element unit is attached to the sensor body to prevent a fire inside the sensor body from leaking to the outside, The element unit includes: a sensor holder to which a heat equalizing base having two storage sections arranged side by side is fixed and which is attached to the sensor body; a sensor element accommodated in one of the two accommodation portions; a first gas introduction member having a gas introduction hole formed therein for introducing the detection target gas from the target area into the sensor element, and a sintered filter integrally formed with the gas introduction hole; an environmental sensor housed in the other of the two housing parts; The sensor is characterized by comprising a second gas introduction member arranged in parallel with the first gas introduction member, having a gas introduction hole formed therein for introducing the target gas of the target area into the environmental sensor, and having a sintered filter integrally formed in the gas introduction hole.

[0008] The explosion-proof gas sensor according to claim 2 of the present invention is the explosion-proof gas sensor according to claim 1, A porous filter is provided between the sensor element and the first gas introducing member. [Effects of the Invention]

[0009] According to the present invention, the sensor element and the environmental sensor are housed in separate storage compartments, and are configured as independent structures. Gas introduction members made of sintered metal are arranged corresponding to the sensor element and the environmental sensor, respectively. This prevents the measurement values ​​of the environmental sensor from being affected by heat from the sensor element, and improves gas response performance. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 10 is a side cross-sectional view of an improved element unit of the explosion-proof gas sensor according to the present invention. [Figure 2] 1 is a perspective view showing the overall configuration of an explosion-proof gas sensor according to the present invention; [Figure 3] FIG. 2 is an external view of a hydrogen sensor element provided in the element unit. [Figure 4] 1 is a side cross-sectional view of an element unit of an explosion-proof gas sensor according to the present invention before improvement. [Figure 5] FIG. 5 is a comparison diagram of gas response rates between the element unit before improvement in FIG. 4 and the element unit after improvement in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0012] The present invention relates to an explosion-proof gas sensor that detects a target gas in a target area introduced into an explosion-proof container. In the following, the present embodiment will be described taking as an example an explosion-proof hydrogen sensor (hereinafter abbreviated as hydrogen sensor) that detects hydrogen gas as the target gas.

[0013] As shown in Figure 2, the hydrogen sensor 1 of this embodiment is generally composed of a sensor main body 2 equipped with a display unit 2a that displays various display contents such as the detected gas concentration and a warning lamp, an element unit 3 that is attached to the sensor main body 2 to prevent a fire inside the sensor main body 2 from leaking to the outside and detects hydrogen gas present in the target area, and a cable lead-out unit 4 for leading various cables such as a sensor cable that outputs a detection signal detected by the element unit 3 and a power cable from the sensor main body 2 to the outside.

[0014] The element unit 3 includes a hydrogen sensor element 5 having an element body 5a formed of a metal can container as shown in FIG.

[0015] The hydrogen sensor element 5 and the environmental sensor 11 are housed inside the element unit 3 and detect gas within this space. Although not shown, a sintered metal with air resistance and a dustproof / waterproof porous filter (present only above the hydrogen sensor element 5) are provided between the space between the external air (atmosphere) and the element unit 3.

[0016] In the conventional structure of the present applicant for the element unit 3 including the hydrogen sensor element 5, a fully sintered metal structure was used between the element unit 3 and the atmosphere. However, the hydrogen sensor according to the present invention is intended to obtain pressure-resistant explosion-proof certification, and the fully sintered metal structure does not provide explosion-proof performance. For this reason, the element unit 3A was modified to have the structure shown in Figure 4.

[0017] The element unit 3A in Figure 4 is roughly composed of the hydrogen sensor element 5 and environmental sensor 11 described above, as well as a sensor holder 21, an analog board 22, a heat-soaking base 23, a porous filter 24, an element cover 25, a gas introduction member 26, and a sensor cover 27.

[0018] The sensor holder 21 is made of, for example, stainless steel, has a stepped through-hole 21a formed therein, and is attached to the sensor body 2.

[0019] The analog board 22 is provided in a stepped through-hole 21a of the sensor holder 21, and is electrically connected to a circuit board (not shown) of the sensor main body 2 by wiring.

[0020] The heat-equalizing base 23 is made of, for example, stainless steel, is heated to maintain a constant temperature, and is provided below the analog board 22 in the stepped through-hole 21 a of the sensor holder 21 .

[0021] The hydrogen sensor element 5 is attached to the heat-soaking base 23 and is connected by wiring to the analog board 22, and detects hydrogen gas introduced from the target area.

[0022] The porous filter 24 is provided directly below the hydrogen sensor element 5 as a dustproof / waterproof filter.

[0023] The environment sensor 11 is attached to the heat-equalizing base 23 in parallel with the hydrogen sensor element 5, and is connected by wiring to the analog board 22, and measures the environment (for example, temperature and humidity) in the vicinity of the element unit 3A.

[0024] The element cover 25 is made of, for example, stainless steel, and is attached to the tip of the sensor holder 21 so as to cover the hydrogen sensor element 5 and the environment sensor 11 .

[0025] The gas introduction members 26 are arranged in the center of the element cover 25 in the depth direction of the paper in Figure 4, and have gas introduction holes 26a formed therein for introducing hydrogen gas from the target area, and a sintered filter 26b made of stainless steel is integrally formed at the lower end portion of the gas introduction hole 26a.

[0026] The sintered filter 26b blocks fire so that a fire inside the sensor main body 2 does not leak to the outside, blocks foreign matter, and allows hydrogen gas introduced from the target area to pass through to the hydrogen sensor element 5 side.

[0027] The sensor cover 27 is made of, for example, an aluminum alloy casting, and has multiple opening holes 27a formed therein for introducing hydrogen gas from the target area.The sensor cover 27 is removably attached to the sensor body 2 so as to cover the element cover 25 and the gas introduction member 26.

[0028] However, in the element unit 3A of Figure 4 described above, the hydrogen sensor element 5 and the environmental sensor 11 are arranged in the same space within the element cover 25, and the area between the atmosphere and the gas introduction member 26 within the element unit 3A is narrowed. In addition, the spatial volume of the hydrogen sensor element 5 and the porous filter 24 within the element cover 25 is large. As a result, it takes time for hydrogen gas to be introduced from the gas introduction member 26 to the hydrogen sensor element 5, resulting in a decrease in gas response performance.

[0029] For this reason, in this embodiment, the gas response performance is improved by adopting the element unit 3B shown in Fig. 1. In the element unit 3B of Fig. 1, the hydrogen sensor element 5 and the environment sensor 11 are separated into separate spaces, and the hydrogen sensor element 5 is placed directly above the sintered metal space.

[0030] The structure of the element unit 3B will now be described in detail with reference to Fig. 1. The element unit 3B in Fig. 1 is roughly configured to include, in addition to the hydrogen sensor element 5 and environmental sensor 11 described above, a sensor holder 31, an analog board 32, a heat-soaking base 33, a heat-soaking cover 34, a porous filter 35, a gas introduction member 36, and a sensor cover 37.

[0031] The sensor holder 31 is made of, for example, stainless steel, has a stepped through hole 31a formed therein, and is attached to the sensor body 2.

[0032] The analog board 32 is provided in a stepped through-hole 31a of the sensor holder 31, and is electrically connected to a circuit board (not shown) of the sensor main body 2 by wiring.

[0033] The heat-equalizing base 33 is made of, for example, stainless steel, keeps the temperature constant, has accommodating sections 33a and 33b arranged side by side, and is provided below the analog board 32 in the stepped through-hole 31a of the sensor holder 31.

[0034] The heat equalizing cover 34 is made of, for example, stainless steel, and is formed in a cup shape that matches the shape of the storage sections 33a, 33b of the heat equalizing base 33.It consists of a first heat equalizing cover 34A that is attached to one of the storage sections 33a, 33b of the heat equalizing base 33 (for example, 33a), and a second heat equalizing cover 34B that is attached to the other of the storage sections 33a, 33b of the heat equalizing base 33 (for example, 33b).

[0035] The hydrogen sensor element 5 is located on top of the first heat equalization cover 34A attached to one of the storage sections 33a, 33b of the heat equalization base 33, is housed in the storage section 33a of the heat equalization base 33, is wired and connected to the analog board 32, and detects hydrogen gas introduced from the target area.

[0036] The porous filter 35 is provided as a dustproof / waterproof filter directly below the hydrogen sensor element 5 (between the hydrogen sensor element 5 and a first gas introducing member 36A, which will be described later).

[0037] The environment sensor 11 is arranged alongside the hydrogen sensor element 5 and housed in a second heat equalizing cover 34B attached to the other of the housing sections 33a, 33b of the heat equalizing base 33, and is connected by wiring to the analog board 32, and measures the environment near the element unit 3B. Specifically, it may be a sensor that measures the environment such as temperature and humidity.

[0038] The gas introduction member 36 is made of sintered metal and is composed of a first gas introduction member 36A and a second gas introduction member 36B arranged side by side in the left-right direction of the paper surface of FIG.

[0039] The first gas introduction member 36A is provided below the hydrogen sensor element 5. The first gas introduction member 36A has a flange 36a formed on the outer periphery of the lower part, and a gas introduction hole 36b formed therein for introducing hydrogen gas from the target area, and a sintered filter 36c made of stainless steel is integrally formed at the lower end of the gas introduction hole 36b.

[0040] The second gas introduction member 36B is disposed alongside the first gas introduction member 36A below the environmental sensor 11. Like the first gas introduction member 36A, the second gas introduction member 36B has a flange 36a formed on the outer periphery of its lower part, and has a gas introduction hole 36b similar to that of the first gas introduction member 36A formed therein in order to expose the environmental sensor 11 to the same atmosphere as the hydrogen sensor element 5, and a sintered filter 36c made of stainless steel is integrally formed at the lower end of the gas introduction hole 36b.

[0041] The sintered filter 36c of the first gas introducing member 36A blocks the fire so that a fire inside the sensor main body 2 does not leak to the outside, and blocks foreign matter, allowing hydrogen gas introduced from the target area to pass to the hydrogen sensor element 5. The sintered filter 36c of the second gas introducing member 36B blocks the fire so that a fire inside the sensor main body 2 does not leak to the outside, and blocks foreign matter, allowing hydrogen gas introduced from the target area to pass to the environment sensor 11.

[0042] The gas introduction member 36 (36A, 36B) is positioned and fixed by fastening a hexagon socket set screw 38 attached to the center of the sensor cover 37 so that the tip of the hexagon socket set screw 38 abuts against the flange 36a.

[0043] The sensor cover 37 is made of, for example, an aluminum alloy casting, and has multiple opening holes 37a formed therein for introducing hydrogen gas from the target area. The sensor cover 37 is removably attached to the sensor body 2 so as to cover the gas introduction member 36 and the tip of the sensor holder 31.

[0044] Incidentally, it is desirable that the environment sensor 11 be located in the same space as the hydrogen sensor element 5 for accurate correction.

[0045] Here, in order to evaluate the gas responsiveness of the element unit 3A before improvement in FIG. 4 and the element unit 3B after improvement in FIG. 1, an evaluation chamber was attached to the outside of the element units 3A and 3B with the temperature stabilized, and a gas responsiveness test was performed.

[0046] In this gas response test, base gas was flowed into the IN side of the joint of the evaluation chamber (the other side is the OUT side), and the stable output was taken as the base output. 1% hydrogen gas was also flowed, and the stable output was used as the hydrogen sensitivity (amount of change) to calculate the response rate. When introducing hydrogen gas, the gas was allowed to flow right up to the evaluation chamber before inserting it into the joint, eliminating errors due to gas replacement time.

[0047] FIG. 5 shows the results of a comparison of the gas response rates of the element units 3A and 3B before and after the improvement in the gas response test described above.

[0048] As is clear from Figure 5, the 50% response time of the unimproved element unit 3A was approximately 24 seconds, whereas the 50% response time of the improved element unit 3B was approximately 12 seconds, which satisfied the 50% response time of 20 seconds or less specified in JIS T 8206.

[0049] As described above, according to the embodiment, the hydrogen sensor element and the environmental sensor are housed in separate storage compartments in an independent structure, and an element unit is adopted in which gas introduction members made of sintered metal are arranged corresponding to the hydrogen sensor element and the environmental sensor, respectively.This means that the measurement values ​​of the environmental sensor are not affected by heat from the hydrogen sensor element, and gas response performance can be improved.

[0050] In the above embodiment, the configuration of the present invention is described as being applied to a hydrogen sensor, but the present invention is not limited to this. The present invention can also be applied to an explosion-proof sensor that detects gases other than hydrogen gas, such as flammable gases.

[0051] While the best mode for carrying out the explosion-proof gas sensor according to the present invention has been described above, the present invention is not limited to the description and drawings of this mode. In other words, all other modes, embodiments, and operational techniques that can be achieved by those skilled in the art based on this mode are naturally included in the scope of the present invention. [Explanation of symbols]

[0052] 1. Hydrogen sensor (explosion-proof hydrogen sensor) 2 Sensor body 2a Display section 3, 3A, 3B element unit 4 Cable outlet 5 Hydrogen sensor element 11 Environmental Sensors 21 Sensor holder 21a Stepped through hole 22 Analog board 23 Heating pedestal 24 Porous filter 25 Element cover 26 Gas introduction member 26a Gas inlet hole 26b Sintered filter 27 Sensor cover 27a Opening hole 31 Sensor holder 31a Stepped through hole 32 Analog board 33 Heating pedestal 33a, 33b Receptacle 34(34A, 34B) Heat-equalizing cover 35 Porous Filter 36 (36A, 36B) Gas introduction member 36a flange 36b Gas inlet hole 36c sintered filter 37 Sensor cover 37a opening hole 38 Hexagon socket set screw

Claims

1. In an explosion-proof gas sensor that detects a target gas in a target area, an element unit is attached to the sensor body to prevent a fire inside the sensor body from leaking to the outside, The element unit includes: a sensor holder to which a heat equalizing base having two storage sections arranged side by side is fixed and which is attached to the sensor body; a sensor element accommodated in one of the two accommodation portions; a first gas introduction member having a gas introduction hole formed therein for introducing the target gas from the target area into the sensor element, and a sintered filter integrally formed with the gas introduction hole; an environmental sensor housed in the other of the two housing parts; an explosion-proof gas sensor comprising: a second gas introduction member arranged in parallel with the first gas introduction member, having a gas introduction hole formed therein for introducing the target gas in the target area into the environmental sensor, and having a sintered filter integrally formed in the gas introduction hole.

2. 2. The explosion-proof gas sensor according to claim 1, further comprising a porous filter disposed between said sensor element and said first gas introducing member.

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