JP7555834B2 - Gas Detectors - Google Patents

Description

This invention relates to a gas detector.

Conventionally, gas detectors that have a function for protecting the gas detector from high-concentration gases are known (see, for example, Patent Document 1).

The above-mentioned Patent Document 1 discloses a gas detection device in which a main gas detection element, a front gas detection element arranged at a position upstream of the main gas detection element, and a protection mechanism arranged between the front gas detection element and the main gas detection element are provided in the gas transport path. When the main gas detection element is exposed to a high concentration gas in a detection state in which power is supplied, the element deteriorates (detection accuracy decreases). Therefore, in the above-mentioned Patent Document 1, an element that is more resistant to high concentration gas than the main gas detection element is provided in the front gas detection element, and when a high concentration gas is detected by the front gas detection element, the main gas detection element is configured not to detect the high concentration gas. Then, in order to secure the time from when the front gas detection element detects a high concentration gas to when the high concentration gas reaches the main gas detection element, a structure that delays the arrival of gas, such as a long section and a large diameter buffer section, is provided as a protection mechanism.

JP 2001-281194 A

In this way, in the above-mentioned Patent Document 1, a long section or a large-diameter buffer section is provided between the upstream front-end gas detection element and the downstream main gas detection element to delay the arrival of high-concentration gas at the downstream main gas detection element, thereby ensuring a delay time for control to protect the downstream main gas detection element. However, in order to ensure a sufficient delay time, it is necessary to increase the length of the long section or the volume of the buffer section, which creates the problem of an increased size of the device.

This invention was made to solve the above problems, and one of the objects of this invention is to provide a gas detector that can be made smaller while maintaining the protective function of the gas detector against high-concentration gases.

A gas detector according to one aspect of the present invention is a gas detector that detects the concentration of a detectable gas that has flowed in from a gas inlet, and includes a gas flow path that connects the gas inlet and an exhaust port, a first gas detector that detects the detectable gas introduced into the gas flow path, a second gas detector that detects the detectable gas downstream of the first gas detector in the gas flow path, a control means that controls to protect the second gas detector in accordance with the detection result of the first gas detector, and a delay mechanism that is provided between the first gas detector and the second gas detector in the gas flow path and causes a flow delay of the gas, and the delay mechanism includes a delay section and a flow rate restriction section that restricts the gas flow path. Note that "restricting the gas flow path" means that the flow rate cross-sectional area at the flow rate restriction section is made smaller than the flow rate cross-sectional area immediately before the flow rate restriction section.

In the gas detector according to one aspect of the present invention, as described above, a delay mechanism that is provided between the first gas detection unit and the second gas detection unit in the gas flow path and causes a gas flow delay is provided with a delay unit and a flow restriction unit that narrows the gas flow path. This reduces the flow rate of gas passing through the flow restriction unit, so that the delay time from when the detected gas reaches the first gas detection unit until it passes through the flow restriction unit can be extended, and the length or volume of the delay unit can be reduced accordingly. And since the flow restriction unit only needs to narrow the gas flow path, the volume occupied by the flow restriction unit can be reduced. As a result, compared to when only a delay unit such as a long section or a buffer unit is provided, the same delay time can be achieved with a smaller total volume (total volume of the delay unit and the flow restriction unit), so that the device can be made smaller while maintaining the protective function of the gas detection unit against high concentration gases.

In the gas detector according to the above aspect, the flow restriction section preferably has a gas inlet opening, a gas outlet opening, and a space section provided between the gas inlet opening and the gas outlet opening and wider than both the gas inlet opening and the gas outlet opening. With this configuration, the gas flow path can be narrowed at two locations, the gas inlet opening and the gas outlet opening. That is, the gas whose flow rate is restricted at the upstream gas inlet opening can be diffused (reduced in pressure) in the space section, and then the flow rate can be restricted again at the gas outlet opening. As a result, the delay effect in the flow restriction section can be improved.

In this case, the flow rate restricting portion preferably includes a first restricting member that is installed inside the gas flow path and has a gas inlet opening formed therein, and a second restricting member that is installed inside the gas flow path and has a gas outlet opening formed therein, and the space portion is formed by the gap between the first restricting member and the second restricting member in the gas flow path. With this configuration, the space portion can be formed without providing an expanded diameter portion in the gas flow path that expands the inner diameter. Therefore, even if a space portion is provided, it is possible to suppress an increase in the volume occupied by the flow rate restricting portion. Furthermore, since the volume of the space portion can be easily optimized by the size of the gap between the first restricting member and the second restricting member, it becomes easy to minimize the volume occupied by the flow rate restricting portion.

In the gas detector according to the above aspect, the delay section is preferably configured with a long section. Here, the "long section" refers to a section in which the path length of the gas flow path is increased. With this configuration, the delay time can be increased while suppressing the increase in size of the device, compared to forming a large volume space such as a chamber section. In other words, compared to a chamber section that requires a large dedicated space, there is a high degree of freedom in the path design of the gas flow path, so it is easy to effectively utilize dead space within the device, for example. Therefore, the increase in size of the device can be suppressed.

In the gas detector according to the above aspect, preferably, the first gas detector and the second gas detector have different sensitivity characteristics to the components to be detected, and the gas species contained in the gas to be detected are detected based on the outputs of both the first gas detector and the second gas detector. With this configuration, a highly functional gas detector can be provided that can not only detect gas concentrations but also identify gas species. Even in this case, by utilizing the difference in sensitivity characteristics to the components to be detected, a detector element with a relatively high resistance to high-concentration gases can be provided in the first gas detector and a detector element with a relatively low resistance to high-concentration gases can be provided in the second gas detector, thereby protecting the second gas detector from high-concentration gases.

In the gas detector according to the above aspect, preferably, the gas detector further includes a high-concentration gas detector that detects a detectable gas having a higher concentration than the first gas detector and the second gas detector. The gas flow path branches to include a low-concentration detection flow path provided with the first gas detector, the second gas detector, and a delay mechanism, and a high-concentration detection flow path provided with the high-concentration gas detector. The high-concentration detection flow path functions as a pressure relief portion that releases pressure increased by the flow restriction portion of the delay mechanism to the low-concentration detection flow path. With this configuration, the high-concentration gas detector can detect a high-concentration detectable gas that would deteriorate the second gas detector if detected by the second gas detector, so that a gas detector capable of detecting a wide range of detectable gases can be provided. Furthermore, by making the high-concentration detection flow path branched off from the low-concentration detection flow path function as a pressure relief portion, it is not necessary to provide a separate relief structure for pressure relief in the low-concentration detection flow path, and therefore the device configuration can be simplified and the device can be made smaller.

In the gas detector according to the above aspect, the control means is preferably configured to protect the second gas detector by switching the second gas detector between an activated state and an inactivated state. With this configuration, the second gas detector can be protected from high-concentration gas by simply inactivating the second gas detector when high-concentration gas is detected in the first gas detector. Therefore, there is no need to provide a flow path switching structure that switches to a bypass flow path to prevent high-concentration gas from reaching the second gas detector, and this prevents the device from becoming too large.

As described above, the present invention provides a gas detector that can be made smaller while maintaining the protective function of the gas detection section against high-concentration gases.

FIG. 1 is a schematic diagram showing a configuration of a gas detector. FIG. 2 is a block diagram showing a configuration related to control of the gas detector. 11 is a diagram for explaining a process for protecting the second gas detection unit. FIG. 5A to 5C are schematic cross-sectional views of a gas flow passage illustrating an example of the configuration of a flow rate restricting portion. 11A and 11B are diagrams for explaining the operation of a flow rate restricting portion. FIG. 4 is a flow chart for explaining the flow of operational control of the gas detector. 5A is a graph showing a schematic representation of sensitivity characteristics of first and third gas detectors, and FIG. 5B is a graph showing a schematic representation of sensitivity characteristics of second and fourth gas detectors. 11A to 11C are schematic diagrams showing modified examples of the delay section. 11A to 11C are schematic diagrams showing modified examples of the delay mechanism. FIG. 13 is a schematic diagram showing a first modified example of the control means. FIG. 13 is a schematic diagram showing a second modified example of the control means.

The following describes an embodiment of the present invention with reference to the drawings.

The configuration of a gas detector 100 according to one embodiment will be described with reference to Figures 1 to 5.

(Overall configuration of gas detector)
1, gas detector 100 is a gas detector that detects detectable gas 1 flowing in from gas inlet 11. Gas detector 100 acquires detectable gas 1 present at an inspection point from gas inlet 11 and detects the concentration of the acquired detectable gas 1. The detectable gas is a gas that gas detector 100 is to detect.

The gas detector 100 comprises at least a gas flow path 10, a first gas detector 21, a second gas detector 22, a controller 30, and a delay mechanism 40. The gas detector 100 of this embodiment is configured to perform an operation to protect the second gas detector 22 from high concentrations of the detectable gas 1 according to the concentration of the detectable gas 1. The controller 30 is an example of the "control means" in the claims.

In the example shown in FIG. 1, the gas detector 100 further includes a first pump 51, a second pump 52, a high-concentration gas detector 60, and a dilution unit 70. The components shown in FIG. 1 (first gas detector 21, second gas detector 22, controller 30, delay mechanism 40, first pump 51, second pump 52, high-concentration gas detector 60, and dilution unit 70) are housed in a housing 5 of the gas detector 100. The housing 5 is the exterior of the gas detector 100, which has a box-like shape.

The gas flow path 10 connects the gas inlet 11 and the exhaust port 12. The gas flow path 10 is composed of a combination of pipe members (such as gas tubes) for circulating gas. One end (upstream end) of the gas flow path 10 is connected to the gas inlet 11, and the other end (downstream end) is connected to the exhaust port 12. The gas inlet 11 is an intake port provided to open from the housing 5 to the outside. The gas inlet 11 constitutes a connector to which a gas inlet tube (not shown) can be connected. By connecting the gas inlet tube to the gas inlet 11, gas (detectable gas 1) at an inspection point away from the gas detector 100 can be introduced into the gas flow path 10. The exhaust port 12 is provided to open from the housing 5 to the outside. The first pump 51 sucks the external detectable gas 1 from the gas inlet 11 and sends it to the exhaust port 12 through the gas flow path 10.

In this embodiment, the gas flow path 10 branches to include a low concentration detection flow path 10a and a high concentration detection flow path 10b. The gas flow path 10 branches into two flow paths, a low concentration detection flow path 10a and a high concentration detection flow path 10b, at a branching section 15 located between the gas detection section and the gas introduction section 11 provided in each detection flow path. For this reason, the gas flow path 10 is connected to the gas introduction section 11 at the upstream end, and is connected to separate exhaust ports 12 and exhaust ports 13 (total of two) at the downstream ends of the low concentration detection flow path 10a and the high concentration detection flow path 10b. The low concentration detection flow path 10a is a flow path for detecting a relatively low concentration of the detection target gas 1. The high concentration detection flow path 10b is a flow path for detecting a relatively high concentration of the detection target gas 1. The gas detector 100 branches into a low concentration detection flow path 10a and a high concentration detection flow path 10b, and performs gas detection in each flow path, making it possible to detect the target gas 1 over a wider concentration range in a shorter detection time (the time from when the gas is introduced to when the detection result is output) than would be possible with a flow path without a branch.

A first pump 51 is disposed between the gas inlet 11 and the branch 15. The first pump 51 draws the detectable gas 1 from the gas inlet 11 into the gas flow path 10 and sends it out to the downstream low concentration detection flow path 10a and high concentration detection flow path 10b. In the low concentration detection flow path 10a, the detectable gas 1 sent out from the first pump 51 passes through the first gas detection unit 21, the delay mechanism 40, and the second gas detection unit 22, and is sent out to the exhaust port 12.

The low concentration detection flow path 10a connects the branching portion 15 and the exhaust port 12. The low concentration detection flow path 10a is provided with a first gas detection unit 21, a second gas detection unit 22, and a delay mechanism 40. The exhaust port 12 of the low concentration detection flow path 10a is provided with a check valve to prevent gas from flowing in.

The high concentration detection flow path 10b is provided in parallel with the low concentration detection flow path 10a, and connects the branching section 15 and the exhaust port 13. The high concentration detection flow path 10b is provided with a high concentration gas detection section 60. In this embodiment, the high concentration detection flow path 10b is also provided with a dilution section 70 and a second pump 52.

<Low concentration detection flow path>
The first gas detection unit 21 is configured to detect the detectable gas 1 introduced into the gas flow path 10. The second gas detection unit 22 is configured to detect the detectable gas 1 downstream of the first gas detection unit 21 in the gas flow path 10.

The first gas detector 21 and the second gas detector 22 are both composed of a gas detector element. The gas detector element outputs a signal corresponding to the concentration of the detectable gas 1 upon contact with the detectable gas 1. The gas detector element is not particularly limited, but in this embodiment, it is a catalytic combustion type gas detector element. The catalytic combustion type gas detector element has a structure in which a sensitive layer made of a metal oxide carrying a combustion catalyst is provided on a precious metal wire coil constituting a heater electrode. When the sensitive layer of the catalytic combustion type gas detector element is heated to an operating temperature by electrical heat generation and comes into contact with the detectable gas 1, catalytic combustion of the detectable gas 1 occurs due to catalytic action, and the electrical resistance value of the element changes due to the temperature change associated with the catalytic combustion. This change in electrical resistance value is acquired by the control unit 30 as an output signal corresponding to the gas concentration via a detection circuit not shown.

The first gas detection section 21 and the second gas detection section 22 are sensitive to a plurality of detection target components, and have different sensitivity characteristics to the detection target components. In this embodiment, the gas species contained in the detectable gas 1 is detected (identified) based on the output of both the first gas detection section 21 and the second gas detection section 22. Then, the concentration of the identified gas species is detected based on the output of the first gas detection section 21. In this manner, the gas detector 100 of this embodiment is configured to be able to distinguish between a plurality of types of detectable gas 1 (gas species) and detect the concentration of the detectable gas 1. The detection method of the gas species and concentration will be described later. The second gas detection section 22 is configured with a gas detection element that has a lower high-concentration gas resistance than the first gas detection section 21. Note that high-concentration gas resistance refers to the resistance to deterioration due to high-concentration gas.

The delay mechanism 40 is provided at a position between the first gas detector 21 and the second gas detector 22 in the gas flow path 10 (low concentration detection flow path 10a). The delay mechanism 40 is configured to cause a gas flow delay.

The delay mechanism 40 of this embodiment uses multiple types of structures with different principles to cause a gas flow delay. That is, the delay mechanism 40 includes a delay section 41 and a flow restriction section 42 that narrows the gas flow path 10. The delay section 41 and the flow restriction section 42 are both flow path portions that constitute part of the gas flow path 10 (low concentration detection flow path 10a). In this embodiment, the delay mechanism 40 includes one delay section 41 and one flow restriction section 42. The delay section 41 is disposed on the upstream side (first gas detection section 21 side), and the flow restriction section 42 is disposed on the downstream side (second gas detection section 22 side).

The delay section 41 is composed of a long section. The long section is a section in which the path length between the first gas detector 21 and the second gas detector 22 is made longer (than the length that is originally required). The long section can be composed of a detour section, a U-turn section, a loop-shaped (coil-shaped) section, etc., of the gas flow path 10 (low concentration detection flow path 10a) formed between the first gas detector 21 and the second gas detector 22. In this embodiment, the delay section 41 is composed of a long section made of a coil-shaped gas tube (coil tube). The coil tube can have a longer path length as the number of turns of the coil is increased and the radius of curvature of the coil is increased. The longer the path length, the longer the gas travel distance, and therefore the longer the delay time.

The flow rate restriction section 42 is configured to reduce the flow rate cross-sectional area of the gas flow rate 10 (low concentration detection flow rate 10a). The flow rate restriction section 42 is configured as a so-called orifice. The flow rate restriction section 42 is configured to delay the timing of gas reaching the second gas detection section 22 by reducing the flow rate of gas passing through. The low concentration detection flow rate 10a has the smallest flow rate cross-sectional area at the flow rate restriction section 42. The flow rate restriction section 42 will be described in detail later.

In this way, in the low concentration detection flow path 10a, the branch section 15, the first gas detection section 21, the delay mechanism 40, the second gas detection section 22, and the exhaust port 12 are arranged in this order from upstream to downstream.

<High concentration detection flow path>
In the high concentration detection flow path 10b, the dilution unit 70, the high concentration gas detection unit 60, the second pump 52, and the exhaust port 13 are arranged in this order from the upstream side to the downstream side. As described above, the flow rate limiting unit 42 is provided in the low concentration detection flow path 10a, and therefore the flow rate resistance (pressure) is high on the low concentration detection flow path 10a side. In order to balance the pressures in the branching unit 15, the high concentration detection flow path 10b functions as a pressure relief unit that releases the pressure increased by the flow rate limiting unit 42 of the delay mechanism 40 to the low concentration detection flow path 10a.

The dilution unit 70 is configured to dilute the detectable gas 1 flowing into the high concentration detection flow path 10b by mixing it with external air. The dilution unit 70 includes an air introduction unit 71 and a throttle valve 72. The air introduction unit 71 is a suction port that opens from the housing 5 to the outside. The throttle valve 72 is provided between the air introduction unit 71 and the branch unit 15 and is configured to be adjustable in opening. By adjusting the opening of the throttle valve 72, the mixing ratio of the detectable gas 1 from the branch unit 15 and the external air from the air introduction unit 71 (i.e., the dilution ratio of the detectable gas) can be adjusted. For example, the dilution unit 70 dilutes the detectable gas 1 flowing into the high concentration detection flow path 10b by 25 times with external air.

The high concentration gas detection unit 60 is configured to detect a higher concentration of the detectable gas 1 than the first gas detection unit 21 and the second gas detection unit 22. In this embodiment, the high concentration gas detection unit 60 is composed of two gas detection units, a third gas detection unit 61 and a fourth gas detection unit 62.

The third gas detector 61 and the fourth gas detector 62 are each composed of a gas detector element. In this embodiment, the third gas detector 61 is composed of the same gas detector element as the first gas detector 21. The fourth gas detector 62 is composed of the same gas detector element as the second gas detector 22. Therefore, the third gas detector 61 and the fourth gas detector 62 have different sensitivity characteristics to the detection target components. Then, based on the outputs of both the third gas detector 61 and the fourth gas detector 62, the gas species contained in the detection target gas 1 is detected (identified). Then, based on the output of the third gas detector 61, the concentration of the identified gas species is detected. The fourth gas detector 62 has a lower resistance to high concentration gases than the third gas detector 61.

In the gas detector 100 of this embodiment, no control is performed to protect the fourth gas detector 62 from high-concentration gas. In other words, in the high-concentration detection flow path 10b, the detectable gas 1 diluted by the dilution section 70 to a predetermined ratio (25 times) is introduced, so that the concentration of the detectable gas 1 to which the fourth gas detector 62 may actually be exposed is lower than the concentration of the detectable gas 1 to which the second gas detector 22 may be exposed in the low-concentration detection flow path 10a. Therefore, no protective control is required for the fourth gas detector 62, and the delay mechanism 40 is not provided in the high-concentration detection flow path 10b. In FIG. 1, the fourth gas detector 62 is arranged upstream of the third gas detector 61, but the fourth gas detector 62 may be arranged downstream of the third gas detector 61.

The third gas detector 61 and the fourth gas detector 62 output a signal for the detectable gas 1 diluted to a predetermined ratio (25 times). Based on the output of the third gas detector 61 and the fourth gas detector 62, the control unit 30 acquires the actual (before dilution) concentration value of the detectable gas 1 taking into account the dilution ratio. This makes it possible for the high concentration gas detector 60 to detect the detectable gas 1 in a concentration range with an upper limit concentration value that is higher than the measurement concentration range by the first gas detector 21 and the second gas detector 22.

As an example, in this embodiment, the detectable gas 1 is a fuel gas. The gas detector 100 can detect three types of fuel gases and their concentrations: city gas, LP gas, and methane gas. In the first gas detector 21 and the second gas detector 22 of the low concentration detection flow path 10a, LEL concentration values from 0% LEL to 100% LEL are detected as the measurement concentration range. In the high concentration gas detector 60 of the high concentration detection flow path 10b, VOL concentration values from 0% VOL to 100% VOL are detected as the measurement concentration range. LEL is an abbreviation for Lower Explosive Limit, and 100% LEL is the lower explosive limit concentration value for that gas type. The VOL concentration value is a value that indicates the ratio (volume ratio) of the detectable gas 1 per unit volume as a percentage. Depending on the gas type, 100% LEL is about a few percent VOL.

The second pump 52 is disposed between the high concentration gas detection section 60 and the exhaust port 13 of the high concentration detection flow path 10b. The second pump 52 draws external air into the high concentration detection flow path 10b from the air introduction section 71 in the dilution section 70, and draws the detectable gas 1 into the high concentration detection flow path 10b from the throttle valve 72, diluting the detectable gas 1. The second pump 52 sends the diluted detectable gas 1 to the exhaust port 13.

<Control System>
As shown in FIG. 2, the gas detector 100 includes, in addition to the control unit 30 described above, a storage unit 31, a power supply unit 32, a speaker 33, and a display operation unit .

The control unit 30 includes a processor such as a CPU. The storage unit 31 is composed of a semiconductor storage element and the like. The control unit 30 (processor) functions as a control unit that controls the entire gas detector 100 by executing the operation program stored in the storage unit 31. The control unit 30 controls the operation of the first pump 51 and the second pump 52. The control unit 30 controls the detection operation of the first gas detector 21, the second gas detector 22, and the high-concentration gas detector 60 (the third gas detector 61, the fourth gas detector 62). That is, the control unit 30 controls the activation of the gas detector by energizing each of the first gas detector 21, the second gas detector 22, and the high-concentration gas detector 60 at the gas detection timing. Then, the control unit 30 acquires the electrical resistance value of the gas detector in the activated state as the output (gas detection result) of the gas detector. In addition, the control unit 30 performs control to deactivate the gas detection units by not energizing the first gas detection unit 21, the second gas detection unit 22, and the high concentration gas detection unit 60 except at the timing of gas detection. Activating the gas detection unit means heating the temperature of the gas detection unit to a predetermined operating temperature by heat generation through energization. Deactivating the gas detection unit means setting the temperature of the gas detection unit to a temperature lower than the operating temperature without energizing it.

The power supply unit 32 supplies power to each part of the gas detector 100 (the control unit 30, the memory unit 31, the speaker 33, the display operation unit 34, the first pump 51, the second pump 52, and each gas detector). The gas detector 100 of this embodiment is battery-powered, and the power supply unit 32 is composed of a battery and a power supply circuit. The power supply unit 32 may be connectable to an external commercial power source.

The speaker 33 is configured to output various sounds under the control of the control unit 30. The display operation unit 34 is configured to include a display device such as a liquid crystal monitor, and an input device such as a mechanical button or a touch panel. The control unit 30 causes the display operation unit 34 to display various information such as the detection result and the state of the gas detector 100 (remaining battery power and the presence or absence of an error). The control unit 30 accepts input operations such as an instruction to start a detection operation via the display operation unit 34. The detection result includes information indicating the gas type of the detected gas 1 and concentration information of the detected gas type. For example, if the detected gas concentration value can be displayed within the LEL range (0% LEL to 100% LEL), the control unit 30 causes the concentration information to be displayed as an LEL concentration value, and if the concentration value is a high concentration value that exceeds the LEL range, the control unit 30 causes the concentration information to be displayed as a VOL concentration value.

<Protection control of the second gas detection unit>
In this embodiment, the control unit 30 is configured to perform control to protect the second gas detection unit 22 according to the detection result of the first gas detection unit 21. Specifically, the control unit 30 is configured to protect the second gas detection unit 22 by switching the second gas detection unit 22 to either an activated state or an inactivated state. That is, as shown in FIG. 1, the control unit 30 activates the first gas detection unit 21 and the second gas detection unit 22 while the first pump 51 is causing the detectable gas 1 to flow toward the exhaust port 12 of the low concentration detection flow path 10a. As a result, the control unit 30 acquires the output of the first gas detection unit 21, which the detectable gas 1 reaches first. When the acquired output of the first gas detection unit 21 exceeds a preset threshold value, the control unit 30 stops the supply of electricity to the second gas detection unit 22 and switches the second gas detection unit 22 to an inactivated state. As a result, at the time when the second gas detection unit 22 is exposed to the detectable gas 1 that has passed through the first gas detection unit 21 and the delay mechanism 40, the second gas detection unit 22 is in an inactivated state, and the second gas detection unit 22 is protected from deterioration due to high concentration gas.

The flow of the protection control over time will be described with reference to FIG. 3. After the introduction of the detectable gas 1 starts, the detectable gas 1 reaches the first gas detector 21 at time t1. Then, at time t2, the control unit 30 acquires the detection result of the first gas detector 21. Then, after the detectable gas 1 passes through the delay mechanism 40, the detectable gas 1 reaches the second gas detector 22 at time t3. When the control unit 30 detects a high concentration gas based on the detection result at time t2, it switches the second gas detector 22 to an inactivated state by time t3. The delay mechanism 40 increases the length of time required from time t1 to time t3 (delays time t3) so that the second gas detector 22 can be switched to an inactivated state prior to time t3.

<Flow Restriction Unit Details>
Next, a detailed configuration of the flow rate limiting unit 42 will be described. As shown in Fig. 4, the flow rate limiting unit 42 is provided inside the gas flow path 10 (low concentration detection flow path 10a). The flow rate limiting unit 42 has a gas inflow opening 42a, a gas outflow opening 42b, and a space 42c.

The gas inlet opening 42a is the inlet of the flow rate restricting section 42 and is an opening on the upstream side (the first gas detector 21 side). The gas outlet opening 42b is the outlet of the flow rate restricting section 42 and is an opening on the downstream side (the second gas detector 22 side). The opening area of the gas inlet opening 42a and the opening area of the gas outlet opening 42b are both smaller than the flow path cross-sectional area of the gas flow path 10 (low concentration detection flow path 10a). In the example of FIG. 4, the gas inlet opening 42a and the gas outlet opening 42b both have a circular shape (are circular holes), and the inner diameter d1 of the gas inlet opening 42a and the inner diameter d2 of the gas outlet opening 42b are equal. The gas flow path 10 (low concentration detection flow path 10a) has a circular cross-sectional shape and an inner diameter d0. The inner diameters d1 and d2 are smaller than the inner diameter d0. Therefore, the gas flow path 10 is narrowed at each of the gas inlet opening 42a and the gas outlet opening 42b.

The inner diameter d1 (inner diameter d2) is, for example, 3/4 or less of the inner diameter d0. The inner diameter d1 (inner diameter d2) can be 1/2 or less of the inner diameter d0. The inner diameter d1 (inner diameter d2) can be 1/4 or less of the inner diameter d0.

The space 42c is provided between the gas inlet opening 42a and the gas outlet opening 42b. The space 42c is formed to be a space wider than both the gas inlet opening 42a and the gas outlet opening 42b. In the example of FIG. 4, the space 42c is a cylindrical space with a circular cross section, and has an inner diameter d3 and a length L. The inner diameter d3 of the space 42c is larger than the inner diameter d1 of the gas inlet opening 42a and the inner diameter d2 of the gas outlet opening 42b. In FIG. 4, the inner diameter d3 is smaller than the inner diameter d0 of the gas flow path 10 (low concentration detection flow path 10a).

More specifically, the flow rate restricting section 42 includes a first restricting member 43 that is installed inside the gas flow path 10 and has a gas inlet opening 42a formed therein, and a second restricting member 44 that is installed inside the gas flow path 10 (low concentration detection flow path 10a) and has a gas outlet opening 42b formed therein. The space 42c is formed by the gap between the first restricting member 43 and the second restricting member 44 in the gas flow path 10.

In the example of FIG. 4, the flow rate restricting section 42 further includes an inner cylinder 45 that is fitted to the inner surface of the gas flow path 10 (low concentration detection flow path 10a). The inner cylinder 45 has a cylindrical shape that matches the gas flow path 10 (low concentration detection flow path 10a). The outer diameter of the inner cylinder 45 is formed to be approximately the same as or slightly larger than the inner diameter d0 of the gas flow path 10 (low concentration detection flow path 10a), and the outer circumferential surface of the inner cylinder 45 is in close contact with the inner surface of the gas flow path 10. The first restricting member 43 and the second restricting member 44 are each fitted to the inner circumference of this inner cylinder 45.

The first and second limiting members 43 and 44 each have a circular shape that matches the inner diameter of the inner tube 45. The outer diameters of the first and second limiting members 43 and 44 are formed to be approximately the same as or slightly larger than the inner diameter of the inner tube 45, and the outer peripheries of the first and second limiting members 43 and 44 are in close contact with the inner circumferential surface of the inner tube 45.

The first and second restricting members 43 and 44 are orifice plates with an opening formed in the center. That is, the gas inflow opening 42a penetrates the center of the first restricting member 43 in the thickness direction. The gas outflow opening 42b penetrates the center of the second restricting member 44 in the thickness direction. The first restricting member 43 is fitted into the end opening on the upstream side (first gas detector 21 side) of the inner cylinder 45, and the second restricting member 44 is fitted into the end opening on the downstream side (second gas detector 22 side) of the inner cylinder 45. As a result, the opening of the first restricting member 43 functions as the gas inflow opening 42a, and the opening of the second restricting member 44 functions as the gas outflow opening 42b. In the example of FIG. 4, the first restricting member 43 and the second restricting member 44 have the same shape.

The space 42c is an internal space of the inner tube 45 formed between the first and second restricting members 43 and 44. Therefore, in the example of FIG. 4, the inner diameter d3 of the space 42c is equal to the inner diameter of the inner tube 45. The length L of the space 42c corresponds to the length of the inner tube 45 minus the thicknesses of the first and second restricting members 43 and 44. In this configuration, the space 42c having a constant length L can be reproducibly formed by simply fitting and fixing the surfaces of the first and second restricting members 43 and 44 into the inner tube 45 so that they are aligned with the positions of the upstream and downstream opening end faces of the inner tube 45.

The gas flow path 10 (low concentration detection flow path 10a) and the inner cylinder 45 are made of a resin material. The first restriction member 43 and the second restriction member 44 are made of a metal material such as brass.

Next, the delay effect of the flow restriction section 42 will be described with reference to FIG. 5. The left column of FIG. 5 shows the configuration of this embodiment in which the flow restriction section 42 is provided, and the right column of FIG. 5 shows a comparative example in which the flow restriction section 42 is not provided. FIG. 5 shows the movement of the detected gas 1 over time from the top to the bottom of each column in a frame-by-frame format. In FIG. 5, the flow restriction section 42 is shown diagrammatically as a single orifice plate.

In the comparative example, since no restriction is provided in the low concentration detection flow path 10a, the gas moves at a generally constant gas flow rate Q2. On the other hand, in the present embodiment, since the flow rate restriction section 42 is provided in the gas flow path 10 (low concentration detection flow path 10a), the gas flow rate Q1 in the flow rate restriction section 42 is smaller than the gas flow rate Q2 in the comparative example. Therefore, in the present embodiment, the movement speed of the gas at least upstream of the flow rate restriction section 42 is restricted by the gas flow rate Q1 in the flow rate restriction section 42. That is, when the detection target gas 1 is sent into the low concentration detection flow path 10a by the operation of the first pump 51, the air 2 that was present up to that point is pushed out, but since the flow rate of this air 2 is restricted by the gas flow rate Q1, the movement speed of the detection target gas 1 is also restricted by the gas flow rate Q1. As a result, in the present embodiment, the time required for the detection target gas 1 to reach the flow rate restriction section 42 increases compared to the comparative example (the arrival of the detection target gas 1 is delayed). Therefore, for example, when achieving a delay time equivalent to that of the comparative example, the path length in the delay unit 41 can be shortened by the delay time obtained by the flow rate restriction unit 42.

Simply put, it is believed that the smaller the opening (inner diameters d1, d2) of the flow restriction section 42 and the smaller the flow rate Q2, the greater the delay effect of the flow restriction section 42. However, upstream of the flow restriction section 42, the pressure in the flow path increases due to the flow restriction, and the capacity required of the first pump 51 increases. If the opening of the flow restriction section 42 is made too small and the first pump 51 becomes large, its contribution to the miniaturization of the entire device will be reduced. Therefore, the size of the opening of the flow restriction section 42 can be determined to be an optimal value for miniaturization of the entire device, taking into account the path length of the delay section 41 shortened by the flow restriction section 42 and the size and capacity margin of the first pump 51.

(Gas detector operation)
Next, the operational control of the gas detector 100 of this embodiment will be described with reference to Figures 6 and 7. The following control is executed by the control unit 30. In the following description, Figures 1 and 2 will be referred to for the configuration of each part of the gas detector 100.

In step S1, the control unit 30 starts driving the first pump 51 and the second pump 52. The control unit 30 executes the drive start process, for example, by receiving an operation input to start a detection operation on the display operation unit 34.

In step S2, the control unit 30 controls each gas detection unit (first gas detection unit 21, second gas detection unit 22, third gas detection unit 61, and fourth gas detection unit 62) to energize them and activate them.

In step S3, the control unit 30 determines whether or not a high concentration gas has been detected by the first gas detection unit 21. That is, the control unit 30 determines whether or not the output of the first gas detection unit 21 has exceeded the threshold value.

If it is determined in step S3 that the output of the first gas detection unit 21 exceeds the threshold value, the control unit 30 performs control to deactivate the second gas detection unit 22 in step S4. In other words, the control unit 30 stops the supply of electricity to the second gas detection unit 22. This protects the second gas detection unit 22 from high concentration gas.

On the other hand, if it is determined in step S3 that the output of the first gas detection unit 21 does not exceed the threshold value, the control unit 30 performs control in step S5 to continue activating (energizing) the second gas detection unit 22.

In step S6, the control unit 30 processes the detection result data based on the output from each gas detection unit (first gas detection unit 21, second gas detection unit 22, third gas detection unit 61, and fourth gas detection unit 62).

In this embodiment, for example, the first gas detection unit 21 (third gas detection unit 61) has the sensitivity characteristic shown in FIG. 7(A), and the second gas detection unit 22 (fourth gas detection unit 62) has the sensitivity characteristic shown in FIG. 7(B). In the graph of the sensitivity characteristics, the horizontal axis indicates the gas concentration, and the vertical axis indicates the output of the gas detection unit.

In Figure 7, the gas types to which the gas detection unit is sensitive are shown as the first gas type to the third gas type. In this embodiment where the detected gas 1 is a fuel gas, the first gas type is methane, the second gas type is a combustible gas component other than methane in city gas, and the third gas type is propane, which is the main component of LP gas.

As shown in FIG. 7A, the first gas detector 21 (third gas detector 61) has a linear sensitivity characteristic for each of the first to third gas species in the detection concentration range, but the output of the third gas species is less than half that of the first and second gas species. On the other hand, as shown in FIG. 7B, the second gas detector 22 (fourth gas detector 62) has a linear sensitivity characteristic for each gas species in the detection concentration range, but the slope increases in the order of the first gas species, the second gas species, and the third gas species. For this reason, the control unit 30 compares the output of the first gas detector 21 (third gas detector 61) with the output of the second gas detector 22 (fourth gas detector 62) to identify whether the introduced detectable gas 1 contains the first gas species, the second gas species, or the third gas species. For example, the control unit 30 identifies the gas species contained in the detectable gas 1 based on the ratio between the output of the first gas detector 21 and the output of the second gas detector 22. The control unit 30 then obtains the gas concentration of the identified gas species based on the output of the first gas detector 21 (third gas detector 61). In the example of FIG. 7A, the output of the first gas detector 21 for the third gas species is lower than the first and second gas species, so when the third gas species is identified, the control unit 30 corrects the output of the first gas detector 21 to calculate the gas concentration. However, even when the third gas species is identified, the output of the third gas detector 61 on the high concentration side is not corrected.

In step S6, data processing is performed on the detection results from the low concentration detection flow path 10a and the high concentration detection flow path 10b. That is, the control unit 30 acquires the gas type identification result based on the output of both the first gas detection unit 21 and the second gas detection unit 22, and the detection result of the LEL concentration value based on the output of the first gas detection unit 21. The control unit 30 also acquires the gas type identification result based on the output of both the third gas detection unit 61 and the fourth gas detection unit 62, and the detection result of the VOL concentration value based on the third gas detection unit 61 and the dilution ratio. Note that if the control unit 30 performs control to protect the second gas detection unit 22 in step S4 (i.e., if a high concentration gas is detected), the detection result based on the output of the second gas detection unit 22 is not acquired.

In step S7, the control unit 30 controls the display operation unit 34 to output (display) the acquired detection results (gas type and concentration value). This completes the detection operation of the gas detector 100.

(Effects of this embodiment)
In this embodiment, the following effects can be obtained.

In this embodiment, as described above, the delay mechanism 40, which is provided between the first gas detection unit 21 and the second gas detection unit 22 of the gas flow path 10 and causes a gas flow delay, is provided with a delay unit 41 and a flow restriction unit 42 that narrows the gas flow path 10. This reduces the flow rate of the gas passing through the flow restriction unit 42, so that the delay time from when the detected gas 1 reaches the first gas detection unit 21 until it passes through the flow restriction unit 42 can be extended, and the length or volume of the delay unit 41 can be reduced accordingly. And since the flow restriction unit 42 only needs to narrow the gas flow path 10, the volume occupied by the flow restriction unit 42 can be reduced. As a result, compared to the case where only the delay unit 41 such as a long section or a buffer section is provided, the same delay time can be achieved with a smaller total volume (the total volume of the delay unit 41 and the flow restriction unit 42), so that the device can be made smaller while maintaining the protective function of the gas detection unit against high concentration gases.

In addition, in the device configuration used in the demonstration test by the inventors of the present application, the path length of the delay section 41 could be shortened by about 70% compared to when only the delay section 41 was provided. The flow rate restriction section 42 was provided inside the gas flow path 10, and since there was no substantial increase in the volume occupied by the flow rate restriction section 42, the effect of miniaturizing the device was confirmed.

In addition, in this embodiment, as described above, the flow rate restricting section 42 has the gas inlet opening 42a and the gas outlet opening 42b, and the space portion 42c that is provided between the gas inlet opening 42a and the gas outlet opening 42b and is wider than both the gas inlet opening 42a and the gas outlet opening 42b. This allows the gas flow path 10 to be narrowed at two locations, the gas inlet opening 42a and the gas outlet opening 42b. That is, the gas whose flow rate is restricted at the upstream gas inlet opening 42a can be diffused (reduced in pressure) in the space portion 42c, and then the flow rate can be restricted again at the gas outlet opening 42b. As a result, the delay effect in the flow rate restricting section 42 can be improved.

In addition, in this embodiment, as described above, the flow rate restricting section 42 includes a first restricting member 43 installed inside the gas flow path 10 and having a gas inlet opening 42a formed therein, and a second restricting member 44 installed inside the gas flow path 10 and having a gas outlet opening 42b formed therein, and the space portion 42c is formed by the gap portion between the first restricting member 43 and the second restricting member 44 in the gas flow path 10. This allows the space portion 42c to be formed without providing an expanded diameter portion in the gas flow path 10 that expands the inner diameter. Therefore, even when the space portion 42c is provided, the volume occupied by the flow rate restricting section 42 can be prevented from increasing. Furthermore, since the volume of the space portion 42c can be easily optimized by the size of the gap between the first restricting member 43 and the second restricting member 44, it becomes easy to minimize the volume occupied by the flow rate restricting section 42.

In addition, in this embodiment, as described above, the delay section 41 is configured with a long section. This makes it possible to increase the delay time while suppressing the increase in size of the device, compared to forming a large volume space such as a chamber section. In other words, compared to a chamber section that requires a large dedicated space, the path design of the gas flow path 10 has a high degree of freedom, making it easy to effectively utilize dead space within the device, for example. This makes it possible to suppress the increase in size of the device.

In addition, in this embodiment, as described above, the first gas detection unit 21 and the second gas detection unit 22 have different sensitivity characteristics to the components to be detected, and the gas species contained in the detectable gas 1 is detected based on the outputs of both the first gas detection unit 21 and the second gas detection unit 22. This makes it possible to provide a highly functional gas detector 100 that can not only detect gas concentrations but also identify gas species. Even in this case, by taking advantage of the different sensitivity characteristics to the components to be detected, a detection element with a relatively high resistance to high-concentration gases is provided in the first gas detection unit 21, and a detection element with a relatively low resistance to high-concentration gases is provided in the second gas detection unit 22, thereby protecting the second gas detection unit 22 from high-concentration gases.

In addition, in this embodiment, as described above, the high concentration gas detection unit 60 is further provided to detect a detectable gas 1 having a higher concentration than the first gas detection unit 21 and the second gas detection unit 22, and the gas flow path 10 is branched to include a low concentration detection flow path 10a in which the first gas detection unit 21, the second gas detection unit 22, and the delay mechanism 40 are provided, and a high concentration detection flow path 10b in which the high concentration gas detection unit 60 is provided, and the high concentration detection flow path 10b functions as a pressure relief unit that relieves the pressure increased by the flow rate restriction unit 42 of the delay mechanism 40 with respect to the low concentration detection flow path 10a. As a result, the high concentration gas detection unit 60 can detect a high concentration of the detectable gas 1 that would deteriorate the second gas detection unit 22 if detected by the second gas detection unit 22, so that a gas detector 100 capable of detecting a wide concentration range of the detectable gas 1 can be provided. Furthermore, by having the high concentration detection flow path 10b, which branches off from the low concentration detection flow path 10a, function as a pressure relief section, it is not necessary to provide a separate relief structure for pressure relief in the low concentration detection flow path 10a, which simplifies the device configuration and makes the device more compact.

In addition, in this embodiment, as described above, the control unit 30 is configured to protect the second gas detection unit 22 by switching the second gas detection unit 22 between an activated state and an inactivated state. This makes it possible to protect the second gas detection unit 22 from high-concentration gas by simply inactivating the second gas detection unit 22 when a high-concentration gas is detected by the first gas detection unit 21. Therefore, for example, there is no need to provide a flow path switching structure that switches to a bypass flow path to prevent high-concentration gas from reaching the second gas detection unit 22, which prevents the device from becoming too large.

[Modification]
It should be noted that the embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims, not by the description of the embodiments above, and further includes all modifications (variations) within the meaning and scope of the claims.

For example, in the above embodiment, the flow rate restricting section 42 has the gas inlet opening 42a, the gas outlet opening 42b, and the space 42c, but the present invention is not limited to this. In the present invention, the flow rate restricting section 42 does not need to have the space 42c.

In the above embodiment, the flow rate restricting section 42 includes the first restricting member 43 and the second restricting member 44, but the present invention is not limited to this. In the present invention, the flow rate restricting section 42 may be composed of a single restricting member (such as an orifice plate).

In the above embodiment, the first and second restricting members 43 and 44 are provided inside the inner cylinder 45, but the present invention is not limited to this. The restricting members may be provided directly on the inner surface of the gas flow path 10 without going through the inner cylinder 45. In other words, the flow rate restricting section 42 may not have an inner cylinder 45. In addition, instead of constructing the first and second restricting members 43 and 44 and the inner cylinder 45 as separate parts, the first and second restricting members 43 and 44 and the inner cylinder 45 may be formed as a single molded product.

In addition, in the above embodiment, an example was shown in which the inner diameter d1 of the first restricting member 43 and the inner diameter d2 of the second restricting member 44 are equal, but the present invention is not limited to this. The inner diameter d1 of the first restricting member 43 and the inner diameter d2 of the second restricting member 44 may be different.

In the above embodiment, the inner diameter d3 of the space 42c between the gas inlet opening 42a and the gas outlet opening 42b is smaller than the inner diameter d0 of the gas flow path 10, but the present invention is not limited to this. In the present invention, the inner diameter d3 of the space 42c may be the same as the inner diameter d0 of the gas flow path 10 or may be larger than the inner diameter d0 of the gas flow path 10.

In the above embodiment, an example was shown in which the delay section 41 in the delay mechanism 40 is configured with a long section made of a coiled gas tube (coil tube), but the present invention is not limited to this. The delay section 41 may have the configuration shown in Figures 8(A) to (C), for example.

The delay section 41a shown in FIG. 8(A) is composed of a long section that is folded back to make multiple U-turns. The delay section 41b shown in FIG. 8(B) is composed of a long section that makes a detour to the connection destination. The delay section 41b is composed of a long section that makes a detour around the downstream flow restriction section 42 and then connects to the flow restriction section 42. The delay section 41c shown in FIG. 8(C) is composed of a buffer section that is wider than the gas flow path 10, rather than a long section. The buffer section is a gas chamber that has an internal volume corresponding to a predetermined delay time.

In the above embodiment, an example was shown in which the delay mechanism 40 includes one delay section 41 arranged on the upstream side (the first gas detection section 21 side) and one flow restriction section 42 arranged on the downstream side (the second gas detection section 22 side), but the present invention is not limited to this. The delay mechanism 40 may include multiple delay sections 41, or multiple flow restriction sections 42. The delay mechanism 40 may have the configuration shown in Figures 9 (A) to (C), for example.

In FIG. 9(A), the delay mechanism 40a includes one flow restriction section 42 arranged on the upstream side (first gas detection section 21 side) and one delay section 41 arranged on the downstream side (second gas detection section 22 side). That is, the number of delay sections 41 and flow restriction sections 42 is the same as in the above embodiment, but the positional relationship between the delay section 41 and the flow restriction section 42 is reversed from the above embodiment. In FIG. 9(B), the delay mechanism 40b includes one delay section 41 and multiple (two) flow restriction sections 42. One flow restriction section 42 is arranged on the upstream side (first gas detection section 21 side) and downstream side (second gas detection section 22 side) of the delay section 41. In FIG. 9(C), the delay mechanism 40c includes multiple (two) delay sections 41 and one flow restriction section 42. Small (short path length) delay sections 41 are arranged on the upstream side (first gas detection section 21 side) and downstream side (second gas detection section 22 side) of the flow restriction section 42. Alternatively, the delay mechanism 40 may include multiple delay sections 41 and multiple flow restriction sections 42, but from the viewpoint of simplifying the device configuration and miniaturizing the device, it is preferable to have a small number of delay sections 41 and flow restriction sections 42.

In addition, in the above embodiment, an example has been shown in which the control unit 30 protects the second gas detection unit 22 by switching the second gas detection unit 22 between an activated state and an inactivated state, but the present invention is not limited to this. In the present invention, the second gas detection unit 22 may be protected by a method different from that of the above embodiment.

For example, in the modified example shown in FIG. 10, a flow path switching valve 111 is provided to switch between a path 110a through which the detectable gas 1 that has passed through the first gas detector 21 passes through the second gas detector 22 and a path 110b through which the detectable gas 1 is sent to the exhaust port 12 without passing through the second gas detector 22. In this modified example, the high-concentration gas detector 60 is disposed in the path 110b, but the high-concentration gas detector 60 may not be provided. The control unit 30 performs control to protect the second gas detector 22 by switching the flow path switching valve 111 according to the detection result of the first gas detector 21. When the first gas detector 21 does not detect a high-concentration gas, the control unit 30 switches the flow path switching valve 111 so that the detectable gas 1 is sent to the path 110a, and when the first gas detector 21 detects a high-concentration gas, the control unit 30 switches the flow path switching valve 111 so that the detectable gas 1 is sent to the path 110b. As a result, the second gas detector 22 is protected from high-concentration gas. In this modification, the controller 30 and the flow path switching valve 111 are an example of the "control means" in the claims.

In the modified example shown in FIG. 11, a dilution section 121 for introducing dilution gas (external air) is provided at the connection point 122 between the first gas detection section 21 and the second gas detection section 22. The dilution section 121 includes an air introduction section 121a including an air intake, and a switching valve 121b for switching between introduction and stop of introduction of dilution gas from the air introduction section 121a to the gas flow path 10. The control section 30 performs control to protect the second gas detection section 22 by switching the switching valve 121b according to the detection result of the first gas detection section 21. When the first gas detection section 21 does not detect a high concentration gas, the control section 30 closes the switching valve 121b so that the dilution gas is not introduced, and when the first gas detection section 21 detects a high concentration gas, the control section 30 opens the switching valve 121b so that the dilution gas is introduced to the connection point 122. As a result, the high concentration gas is diluted to a concentration that can suppress deterioration of the second gas detection section 22, so that the second gas detection section 22 is protected from the high concentration gas. In this modified example, the control unit 30 and the switching valve 121b are an example of the "control means" in the claims.

In the above embodiment, an example was shown in which the low concentration detection flow path 10a and the high concentration detection flow path 10b are provided in the gas flow path 10, but the present invention is not limited to this. In the present invention, as shown in FIG. 11, the high concentration detection flow path 10b does not have to be provided. Therefore, in the present invention, the high concentration gas detection unit 60 does not have to be provided.

In the above embodiment, the high concentration gas detection unit 60 includes the third gas detection unit 61 and the fourth gas detection unit 62, but the present invention is not limited to this. In the present invention, the high concentration gas detection unit 60 may be composed of a single gas detection unit (gas detection element), or the high concentration gas detection unit 60 may include three or more gas detection units.

In addition, in the above embodiment, an example including one first gas detection unit 21 and one second gas detection unit 22 has been shown, but the present invention is not limited to this. Three or more gas detection units may be included, in which case, control may be performed to protect one gas detection unit (second gas detection unit) depending on the detection unit provided, or control may be performed to protect two or more gas detection units (second gas detection units).

In the above embodiment, the high concentration detection flow path 10b functions as a pressure relief section that releases the pressure increased by the flow restriction section 42 of the delay mechanism 40, but the present invention is not limited to this. In the present invention, instead of making the high concentration detection flow path 10b function as a pressure relief section, a pressure relief section such as a relief valve may be provided upstream of the flow restriction section 42. In this case, the high concentration detection flow path 10b and the low concentration detection flow path 10a do not need to be branch flow paths, and the high concentration detection flow path 10b and the low concentration detection flow path 10a may be independent flow paths that are not fluidically connected to each other.

In the above embodiment, an example was shown in which the gas species contained in the detectable gas 1 is detected (identified) based on the outputs of both the first gas detection unit 21 and the second gas detection unit 22, but the present invention is not limited to this. The present invention may be configured not to identify the gas species. In other words, for the same gas species, the first gas detection unit 21 may be configured to detect a relatively high concentration range, and the second gas detection unit 22 may be configured to detect a relatively low concentration range. Even in this case, a delay mechanism 40 similar to the above embodiment may be provided to protect the second gas detection unit 22, which is highly sensitive to gases in the low concentration range, from high concentration gases.

In the above embodiment, the detectable gas 1 is a fuel gas, but the present invention is not limited to this. In the present invention, the type of detectable gas is not particularly limited. The present invention is applicable when the deterioration of the second gas detection section 22 is accelerated due to a high concentration of a component in the detectable gas.

In the above embodiment, an example was shown in which each gas detection unit, including the second gas detection unit 22, is configured with a catalytic combustion type gas detection element, but the present invention is not limited to this. Each gas detection unit may be configured with a type of gas detection element other than a catalytic combustion type gas detection element, such as a semiconductor gas detection element. In addition, the sensitivity characteristics of the gas detection unit shown in Figure 7 are merely an example, and the present invention is not limited to this.

In the above embodiment, an example was shown in which the gas species contained in the detectable gas 1 is detected (identified) based on the outputs of both the first gas detector 21 and the second gas detector 22, and the concentration of the identified gas species is detected based on the output of the first gas detector 21, but the present invention is not limited to this. In the present invention, the gas species contained in the detectable gas 1 may be detected (identified) based on the outputs of both the first gas detector 21 and the second gas detector 22, and the concentration of the identified gas species may be detected based on the outputs of both the first gas detector 21 and the second gas detector 22. In addition, the concentration of the identified gas species may be detected based on the output of the second gas detector 22.

In the above embodiment, an example was shown in which the gas species contained in the detectable gas 1 is detected (identified) based on the outputs of both the third gas detector 61 and the fourth gas detector 62, and the concentration of the identified gas species is detected based on the output of the third gas detector 61, but the present invention is not limited to this. In the present invention, the gas species contained in the detectable gas 1 may be detected (identified) based on the outputs of both the third gas detector 61 and the fourth gas detector 62, and the concentration of the identified gas species may be detected based on the outputs of both the third gas detector 61 and the fourth gas detector 62. In addition, the concentration of the identified gas species may be detected based on the output of the fourth gas detector 62.

In addition, in the above embodiment, the first limiting member 43 and the second limiting member 44 are formed from a metal material, but the present invention is not limited to this, and they may be formed from other materials, such as a resin material.

REFERENCE SIGNS LIST 1 gas to be detected 10 gas flow path 10a low concentration detection flow path 10b high concentration detection flow path 11 gas inlet 12, 13 exhaust port 21 first gas detection part 22 second gas detection part 30 control part (control means)
40, 40a, 40b, 40c Delay mechanism 41, 41a, 41b, 41c Delay section 42 Flow rate restricting section 42a Gas inlet opening 42b Gas outlet opening 42c Space section 43 First restricting member 44 Second restricting member 60 High concentration gas detection section 100 Gas detector 111 Flow path switching valve (control means)
121b Switching valve (control means)

Claims (7)

A gas detector that detects the concentration of a detection target gas flowing in from a gas inlet,
a gas flow path connecting the gas inlet and an exhaust port;
a first gas detection unit that detects the detection target gas introduced into the gas flow path;
a second gas detection unit that is located downstream of the first gas detection unit in the gas flow passage and detects the detection target gas;
a control means for controlling protection of the second gas detection unit in accordance with a detection result of the first gas detection unit;
a delay mechanism provided between the first gas detection unit and the second gas detection unit in the gas flow path to cause a gas flow delay;
The delay mechanism includes a delay section and a flow rate restricting section that narrows the gas flow path. The flow rate restricting unit is
a gas inlet opening and a gas outlet opening;
2. The gas detector according to claim 1, further comprising a space provided between said gas inlet opening and said gas outlet opening, said space being wider than both said gas inlet opening and said gas outlet opening. the flow rate restricting unit includes a first restricting member installed inside the gas flow passage and having the gas inlet opening formed therein, and a second restricting member installed inside the gas flow passage and having the gas outlet opening formed therein,
3. The gas detector according to claim 2, wherein the space is defined by a gap between the first restricting member and the second restricting member in the gas flow passage. The gas detector according to any one of claims 1 to 3, wherein the delay section is composed of a long section. The first gas detection unit and the second gas detection unit have different sensitivity characteristics to a detection target component,
5. The gas detector according to claim 1, wherein a gas species contained in the detectable gas is detected based on outputs from both the first gas detection section and the second gas detection section. a high concentration gas detection unit that detects the detection target gas at a higher concentration than the first gas detection unit and the second gas detection unit;
The gas flow path is
a low concentration detection flow path provided with the first gas detection unit, the second gas detection unit, and the delay mechanism;
a high concentration detection flow path in which the high concentration gas detection unit is provided;
A gas detector as described in any one of claims 1 to 5, wherein the high concentration detection flow path functions as a pressure relief section for releasing pressure increased by the flow restriction section of the delay mechanism to the low concentration detection flow path. The gas detector according to any one of claims 1 to 6, wherein the control means is configured to protect the second gas detector by switching the second gas detector between an activated state and an inactivated state.

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