JP7795952B2 - Explosion-proof gas sensor - Google Patents

Description

The present invention relates to an explosion-proof gas sensor that detects explosive flammable gases, such as hydrogen, in a target area.

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 an airflow, the airflow takes 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 cause it to ignite, and depending on the 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 an airflow blocking effect and an explosion-proof design.

By the way, this type of thermal conduction type explosion-proof gas sensor is equipped with an environmental sensor separate from the hydrogen sensor element within the device to cancel out the effects of environmental changes, which will be described later.

Patent No. 5888747

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 environmental sensor are located in the same space, resulting in a large spatial volume.

The present invention was made in consideration of the above problems, and aims to provide an explosion-proof gas sensor that can improve gas response performance.

In order to achieve the above object, the present invention provides an explosion-proof gas sensor, which detects a target gas in a target area, and in which an element unit is attached to the sensor body to prevent a fire in the sensor body from leaking to the outside, and
The element unit includes:
a sensor holder to which a heat equalizing base having two accommodating 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;
The environmental 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.

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.

According to the present invention, the sensor element and environmental sensor are housed in separate storage compartments, creating an independent structure, and gas introduction members made of sintered metal are arranged corresponding to the sensor element and environmental sensor, respectively. This prevents the measured values of the environmental sensor from being affected by heat from the sensor element, and improves gas response performance.

FIG. 10 is a side cross-sectional view of an improved element unit of the explosion-proof gas sensor according to the present invention. 1 is a perspective view showing the overall configuration of an explosion-proof gas sensor according to the present invention; FIG. 2 is an external view of a hydrogen sensor element provided in the element unit. 1 is a side cross-sectional view of an element unit of an explosion-proof gas sensor according to the present invention before improvement. 5 is a graph showing a comparison of gas response rates between the element unit before improvement shown in FIG. 4 and the element unit after improvement shown in FIG. 1. FIG.

The following describes in detail the embodiments of the present invention, with reference to the accompanying drawings.

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 embodiment, an explosion-proof hydrogen sensor (hereinafter abbreviated as "hydrogen sensor") that detects hydrogen gas as the target gas will be used as an example.

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 warning lamps; 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.

The element unit 3 includes a hydrogen sensor element 5, the element body 5a of which is made of a metal can container, as shown in Figure 3.

The hydrogen sensor element 5 and 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 porous dust/waterproof filter (present only above the hydrogen sensor element 5) are provided between the external air (atmosphere) and the space between the element unit 3.

In the applicant's conventional structure for the element unit 3 containing the hydrogen sensor element 5, a fully sintered metal structure was used between the element unit 3 and the atmosphere. However, the hydrogen sensor of the present invention is designed 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.

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.

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.

The analog board 22 is installed in the stepped through-hole 21a of the sensor holder 21 and is electrically connected to the circuit board (not shown) of the sensor main body 2 via wiring.

The heat-soaking base 23 is made of, for example, stainless steel, is heated to maintain a constant temperature, and is installed below the analog board 22 within the stepped through-hole 21a of the sensor holder 21.

The hydrogen sensor element 5 is attached to the heat-soaking base 23 and is wired to the analog board 22, detecting hydrogen gas introduced from the target area.

The porous filter 24 is installed directly below the hydrogen sensor element 5 as a dustproof/waterproof filter.

The environmental sensor 11 is mounted alongside the hydrogen sensor element 5 on the heat-soaking base 23 and is connected via wiring to the analog board 22, measuring the environment (e.g., temperature and humidity) near the element unit 3A.

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 environmental sensor 11.

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. A sintered filter 26b made of stainless steel is integrally formed at the lower end of the gas introduction hole 26a.

The sintered filter 26b blocks fire inside the sensor body 2 to prevent it from leaking to the outside, blocks foreign matter, and allows hydrogen gas introduced from the target area to pass through to the hydrogen sensor element 5.

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

However, in the element unit 3A shown in Figure 4 above, the hydrogen sensor element 5 and 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. Additionally, the spatial volume of the hydrogen sensor element 5 and porous filter 24 within the element cover 25 is large. This means that 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.

For this reason, in this embodiment, the element unit 3B shown in Figure 1 is adopted to improve gas response performance. The element unit 3B in Figure 1 has a structure in which the hydrogen sensor element 5 and the environmental sensor 11 are separated into separate spaces, with the hydrogen sensor element 5 located directly above the sintered metal space.

The structure of element unit 3B will now be described in detail with reference to Figure 1. In addition to the hydrogen sensor element 5 and environmental sensor 11 described above, element unit 3B in Figure 1 is generally configured to include 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.

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.

The analog board 32 is installed in the stepped through-hole 31a of the sensor holder 31 and is electrically connected to the circuit board (not shown) of the sensor main body 2 via wiring.

The heat-soaking base 33 is made of, for example, stainless steel, maintains a constant temperature, has side-by-side storage compartments 33a and 33b, and is installed below the analog board 32 within the stepped through-hole 31a of the sensor holder 31.

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 and 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 and 33b (for example, 33a) of the heat equalizing base 33, and a second heat equalizing cover 34B that is attached to the other of the storage sections 33a and 33b (for example, 33b) of the heat equalizing base 33.

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

The porous filter 35 is installed directly below the hydrogen sensor element 5 (between the hydrogen sensor element 5 and the first gas introduction member 36A, described below) as a dustproof/waterproof filter.

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

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 Figure 1.

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

The second gas introduction member 36B is installed alongside the first gas introduction member 36A at the bottom of the environmental sensor 11. Like the first gas introduction member 36A, the second gas introduction member 36B has a flange 36a formed around the outer periphery of its lower part. To expose the environmental sensor 11 to the same atmosphere as the hydrogen sensor element 5, the second gas introduction member 36B has a gas introduction hole 36b formed therein, similar to that of the first gas introduction member 36A. A sintered filter 36c made of stainless steel is integrally formed at the bottom end of the gas introduction hole 36b.

The sintered filter 36c of the first gas introduction member 36A blocks the fire to prevent any fire inside the sensor body 2 from leaking to the outside, blocks foreign matter, and allows hydrogen gas introduced from the target area to pass through to the hydrogen sensor element 5. The sintered filter 36c of the second gas introduction member 36B blocks the fire to prevent any fire inside the sensor body 2 from leaking to the outside, blocks foreign matter, and allows hydrogen gas introduced from the target area to pass through to the environmental sensor 11.

The gas introduction member 36 (36A, 36B) is positioned and fixed by tightening 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.

The sensor cover 37 is made of, for example, an aluminum alloy casting and has multiple openings 37a formed therein for introducing hydrogen gas from the target area. It 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.

By the way, it is desirable that the environmental sensor 11 be located in the same space as the hydrogen sensor element 5 for accurate calibration.

Here, to evaluate the gas responsiveness of the element unit 3A before improvement in Figure 4 and the element unit 3B after improvement in Figure 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.

In this gas response test, base gas was flowed into the IN side of the fitting of the evaluation chamber (the other side was 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 up to just before the evaluation chamber before inserting it into the fitting, eliminating errors due to gas replacement time.

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

As is clear from Figure 5, the 50% response time for the unimproved element unit 3A was approximately 24 seconds, while the 50% response time for the improved element unit 3B was approximately 12 seconds, satisfying the 50% response time of 20 seconds or less specified in JIS T 8206.

As such, according to the above-described embodiment, the hydrogen sensor element and the environmental sensor are housed in separate storage compartments, providing an independent structure, and an element unit is used 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 measured values of the environmental sensor are not affected by heat from the hydrogen sensor element, and gas response performance can be improved.

In the above-described embodiment, the configuration was explained using an example in which the sensor was used as a hydrogen sensor, but the present invention is not limited to this. It can also be used in explosion-proof sensors that detect gases other than hydrogen gas, such as flammable gases.

The above describes the best mode for the explosion-proof gas sensor according to the present invention, but 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 are conceived by those skilled in the art based on this mode are naturally included within the scope of the present invention.

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

Claims (2)

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 accommodating 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. The explosion-proof gas sensor described in claim 1, characterized in that a porous filter is provided between the sensor element and the first gas introduction member.