Gas detection device

Abstract

To provide a gas detection device capable of stably performing highly reliable gas detection.SOLUTION: A gas type identification part 140 and a gas detection part 130 are arranged in order from an upstream side in a gas flow direction in a main gas passage 111 into which a gas to be detected is introduced by a gas introduction means 118, and a bypass passage 116 for gas discharge is connected to a position between the gas type identification part 140 and the gas detection part 130 via a passage switching means 113. The gas type identifier 140 is configured to be able to identify the gas type based on the pattern of the measured signal, and the flow path is switched by the gas detection unit controller 125 so that the test gas flows into the gas discharge bypass flow path 116 based on the type of the gas component detected by the gas type identifier 140.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a gas detection device having a protective structure for a gas detection unit. [Background technology]

[0002] A controlled potential electrolysis gas sensor is known as a gas sensor for detecting CO gas. In general, controlled potential electrolysis gas sensors must be protected from contact with gases that can cause undesirable effects such as malfunction. In particular, controlled potential electrolysis CO gas sensors are known to be susceptible to interference from alcohol gas, and if they are exposed to high concentrations of alcohol gas for a long period of time, they will become unusable for a day or more even after the gas is removed.

[0003] On the other hand, gas detectors having a function for protecting a gas sensor are known. For example, Patent Document 1 discloses a gas detector having a function for protecting a gas detection section from high-concentration gases. The gas detector described in Patent Document 1 is provided with a first gas detection unit equipped with a gas detection element durable to high-concentration gases on the upstream side in the gas flow direction, and a second gas detection unit equipped with a gas detection element with different sensitivity characteristics to the detection target components from the first gas detection unit is provided downstream of the first gas detection unit, so that when a high-concentration gas is detected, the high-concentration gas is not supplied to the second gas detection unit. Furthermore, a delay mechanism is provided between the first gas detection unit and the second gas detection unit to ensure time between when the high-concentration gas is detected by the first gas detection unit and when it reaches the second gas detection unit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-110353 Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, the protective function described in Patent Document 1 above is a function to protect the second gas detection unit, which detects the same target gas as the first gas detection unit, by switching the flow path or diluting the gas concentration depending on the gas concentration detected by the first gas detection unit. However, when a gas detection element for detecting a different type of target component from that for the first gas detection unit is used as the second gas detection unit, even if the target component for the second gas detection unit is contained, if the detection result of the first gas detection unit determines that the test gas is a high-concentration gas, the test gas will not be properly introduced into the second gas detection unit. Conversely, if the detection result of the first gas detection unit determines that the test gas is not a high-concentration gas, the test gas will be introduced into the second gas detection unit even if the test gas contains a component that has an undesirable effect on the second gas detection unit. This may result in malfunction or false detection by the second gas detection unit. In addition, in Patent Document 1, the delay mechanism is configured with a delay section and a flow rate restricting section, and the flow rate restricting section is provided in the main gas flow path. Therefore, although it is possible to prevent the test gas from reaching the second gas detection section before the detection result of the first gas detection section is obtained, the flow rate of the test gas introduced into the second gas detection section is restricted, which may reduce the reliability of gas detection by the second gas detection section.

[0006] Such problems also arise when a multi-component gas detection device is configured that is capable of detecting multiple gas components by including multiple types of gas sensors including a potentiostatic electrolysis-type CO gas sensor. In reality, therefore, a sensor protection function is required to avoid false detection by the potentiostatic electrolysis-type CO gas sensor or false alarms based on the detection output of the potentiostatic electrolysis-type CO gas sensor.

[0007] The present invention was completed in view of the above circumstances, and an object of the present invention is to provide a gas detection device that is capable of stably performing highly reliable gas detection. [Means for solving the problem]

[0008] a gas exhaust bypass flow path connected between the gas detection unit and the gas type identifying unit via flow path switching means, which enables the test gas discharged from the gas type identifying unit to be discharged from the gas exhaust path without being introduced into the gas detection unit; and a gas detection unit controller having the function of controlling the operation of the flow path switching means based on the type of gas component detected by the gas type identifying unit, wherein the gas type identifying unit is configured to be able to identify gas types based on measured signal patterns, and the gas detection unit controller is configured to switch the flow path based on the type of gas component detected by the gas type identifying unit so that the test gas flows into the gas exhaust bypass flow path, thereby solving the above-mentioned problems. [Effects of the Invention]

[0009] According to the invention of claim 1, even if the test gas contains gas components other than the target gas components to be measured, the gas components will not come into contact with the gas detection unit, and malfunctions such as breakdowns can be reliably prevented, making it possible to perform stable, highly reliable gas detection.

[0010] According to the invention of claim 2, it is possible to adjust the flow rate of gas flowing into the delay piping section, which makes it possible to shorten the flow path length of the delay piping section and reduce its size. As a result, it is possible to supply a sufficient gas flow rate required for gas detection by the gas detection section to the gas detection section, while easing restrictions on the placement of the delay piping section, and making it possible to reduce the size of the gas detection device. According to the inventions of claims 3 and 4, the gas pipe constituting the flow rate adjustment bypass flow path itself becomes a load, or the flow rate adjustment bypass flow path is provided with a piping load section, making it possible to appropriately adjust the gas flow rate flowing into the delay piping section, and making it possible to more reliably reduce the size of the delay piping section. According to the invention of claim 5, even if the detected gas contains gas components that interfere with the gas detection unit, it is possible to reliably prevent erroneous concentration indications and false alarms due to the influence of the interfering gas components, thereby further improving the reliability of gas detection. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a block diagram schematically showing the overall configuration of a gas detection device according to one embodiment of the present invention. [Figure 2] FIG. 2 is a perspective view, seen from the front side, showing the configuration of the gas detection unit. [Figure 3] FIG. 2 is a perspective view showing the configuration of the gas detection unit, as viewed from the rear side. [Figure 4] FIG. 2 is a cross-sectional view schematically showing the configuration of a non-dispersive infrared absorption gas sensor that constitutes a gas type identifying unit. [Figure 5] FIG. 10 is a diagram showing an example of a discrimination sensitivity pattern for various gas components. DETAILED DESCRIPTION OF THE INVENTION

[0012] 1, gas detection device 100 according to the present invention is composed of gas detection unit 120 having gas inlet 121 and output control unit 150 having gas outlet 151, and is provided with main gas flow path 111 extending from gas inlet 121 to gas outlet 151, and gas introduction means 118 connected to main gas flow path 111 and allowing a gas to be detected to flow through main gas flow path 111. In this embodiment, gas introduction means 118 is composed of, for example, a suction pump.

[0013] As also shown in Figures 2 and 3, gas detection unit 120 comprises gas detection section 130 arranged upstream of gas introduction means 118 in the gas flow direction of main gas flow path 111, gas type identification section 140 arranged upstream of gas detection section 130, and gas detection unit control section 125.

[0014] The gas detection unit 130 includes at least one type of gas sensor. In this embodiment, the gas detection unit 130 includes two gas sensors for detecting different types of target gases. One gas sensor 131, located upstream in the gas flow direction of the main gas flow passage 111, is a constant-potential electrolysis gas sensor that detects, for example, CO gas, and the other gas sensor 132, located downstream of the one gas sensor 131, is a catalytic combustion gas sensor that detects, for example, H gas. The gas detection unit 130 may be configured to include one gas sensor, or may be configured to include three or more gas sensors. Furthermore, when multiple gas sensors are included, the combination and arrangement of the gas sensors are not particularly limited.

[0015] The gas type identifying section 140 is configured to be able to identify and detect a plurality of types of gas components, including interference gas components to which the gas detection section 130 is sensitive and gas components that should not be introduced and that have undesirable effects on the gas detection section 130 .

[0016] In this embodiment, the gas type identifying unit 140 is configured by, for example, a non-dispersive infrared absorption (NDIR) gas sensor. Specifically, as shown in Fig. 4, it includes a cylindrical measurement cell 141 that forms a space into which a test gas is introduced. A light source unit 143 and a light receiving unit 145 are disposed at one end of the measurement cell 141, and a reflecting member 148 that reflects light from the light source unit 143 toward the light receiving unit 145 is disposed at the other end of the measurement cell 141. The measurement cell 141 is provided with a gas discharge path 142b at one end and a gas introduction path 142a at the other end. Reference numeral 149 denotes a light-transmitting window that airtightly partitions the space in which the light source unit 143 and the light receiving unit 145 are disposed.

[0017] The light source unit 143 is composed of an infrared light source that emits light in a wavelength range of, for example, 2 μm to 15 μm, and a reflecting member. The light receiving unit 145 is composed of a light receiving sensor including a plurality of light receiving elements 146 and band pass filters 147 arranged corresponding to each of the light receiving elements 146. Each band pass filter 147 has a different center wavelength and half width, and has light transmission characteristics according to the absorbance of various interference gas components. The number of light receiving elements 146 is not particularly limited, and in this embodiment, there may be at least three light receiving elements including those having properties that allow identification of the gas to be identified, such as the target gas component, interference gas component, and introduction avoidance gas component, and a reference light receiving element may also be included.

[0018] Specific examples of gases to be identified by the gas type identifying section 140 include PFCs (perfluorocarbons) such as CH3F and CH2F2, and ethanol (C2H5OH). Here, the gases to be identified by the gas type identifying unit 140 are basically interference gas components to which at least one of the CO gas sensor and the H2 gas sensor constituting the gas detection unit 130 is sensitive. Among these, ethanol (C2H5OH), for example, is a gas component that should not be introduced into the gas detection unit 130 because it has undesirable effects on either or both of the CO gas sensor and the H2 gas sensor, such as causing deterioration or failure due to poisoning.

[0019] A delay piping section 112 is disposed between the gas type identification section 140 and the flow path switching means 113 to delay the flow of the test gas into the gas detection section 130. The delay piping section 112 is configured, for example, by winding a gas pipe in a spiral shape, and has a flow path length that allows the time required for gas identification by the gas type identification section 140 to be ensured.

[0020] The gas detection unit control section 125 controls the operation of the gas type identification section 140 and the gas detection section 130, and has a gas type identification function that identifies the type of gas component contained in the detected gas based on the gas detection output of the gas type identification section 140, and a concentration calculation function that calculates the gas concentration based on the gas detection output of the gas detection section 130.

[0021] The gas components contained in the test gas are identified by using the sensitivity of each of the multiple detection light receiving elements 146 for the test gas as a parameter, obtaining a sensitivity pattern consisting of a set of multiple parameters (Pa, Pb, Pc, ...), and comparing it with identification sensitivity patterns previously obtained for each of the various interfering gas components for the gas detection unit 130. An example of the discrimination sensitivity pattern is shown in Fig. 5. Fig. 5 shows the discrimination sensitivity pattern for various gases when three detection light-receiving elements are used, and the vertical axis shows the normalized value of the sensitivity of each light-receiving element 146, with the maximum sensitivity of the light-receiving element 146 set to 1.0. As shown in Figure 5, the target gas components CH3F and CH2F2 to be measured and the interference gas ethanol have different combinations of gas sensitivity for the parameters Pa, Pb, and Pc. Specifically, CH3F is most sensitive to parameter Pb, with only slight sensitivity to parameters Pa and Pc. CH2F2 is most sensitive to parameter Pa, next to parameter Pb, and has no sensitivity to parameter Pc. Like CH3F, ethanol has the highest sensitivity to parameter Pb, but is characterized by a higher sensitivity to parameter Pa than CH3F and no sensitivity to parameter Pc. In this way, target gas components are distinguished from non-target gases. Gas components not illustrated here can also be distinguished if they have unique sensitivity patterns distinct from other gas components. In this embodiment, a configuration has been described in which the sensitivity pattern is used for gas type identification, but gas type identification may also be performed based on an output pattern based on the output of each light receiving element 146.

[0022] The output control unit 150 includes a display unit 152, an alarm unit 153, an external output unit 154, and an output control unit 155. The output control unit 155 has a function of outputting a gas detection signal related to a concentration indication value based on the gas detection output of the gas detection unit 130 to the display unit 152, and outputting an alarm signal to the alarm unit 153 when the gas detection output of the gas detection unit 130 exceeds an alarm point. The output control unit 155 may be configured to output a gas detection signal related to a concentration indication value of the gas component detected by the gas type identification unit 140 to the display unit.

[0023] In this embodiment, when the gas type identification unit 140 detects that the detected gas contains an interference gas component detected by the gas detection unit 130, the output control unit 155 is configured not to output a gas detection signal or an alarm signal to the display unit 152 or the alarm unit 153. This reliably prevents erroneous concentration indications or false alarms caused by the influence of interference gas components, thereby further improving the reliability of gas detection.

[0024] In gas detection device 100 of this embodiment, gas exhaust bypass flow path 115, which can exhaust the test gas exhausted from delay piping section 112 through gas outlet 151 without introducing the test gas into gas detection section 130, is connected between delay piping section 112 and gas detection section 130 via flow path switching means 113, which may be, for example, an electromagnetic valve, and gas detection unit control section 125 has the function of controlling the operation of flow path switching means 113 based on the type of gas component in the test gas detected by gas type identification section 140. When performing gas detection operation, the gas detection unit control section 125 controls the flow path switching means 113 to an open state so that the test gas flows into the gas detection section 130, and when the gas type identification section 140 detects that the test gas contains an interference gas component with the gas detection section 130, the gas detection unit control section 125 controls the flow path switching means 113 to a closed state and switches the flow path so that the test gas flows into the gas exhaust bypass flow path 115.

[0025] Furthermore, this embodiment is provided with a gas flow rate adjustment bypass flow path 116 that bypasses an upstream position of delay piping section 112 and a downstream position of gas detection section 130 in the gas flow direction of main gas flow path 111. This makes it possible to adjust the flow rate of gas flowing into delay piping section 112, thereby shortening the flow path length of delay piping section 112 and making delay piping section 112 more compact. This relaxes restrictions on the placement of delay piping section 112 while still allowing gas detection section 130 to be supplied with a sufficient gas flow rate necessary for gas detection by gas detection section 130, making it possible to make gas detection device 100 more compact.

[0026] The flow rate adjustment bypass flow path 116 is configured by a gas pipe having a flow path diameter smaller than that of the gas pipe configuring the main gas flow path 111. This makes it possible for the gas pipe configuring the flow rate adjustment bypass flow path 116 itself to act as a load and adjust the gas flow rate flowing into the delay piping section. Furthermore, the flow rate adjustment bypass flow path 116 is provided with a piping load section 117 that limits the flow rate of the test gas flowing into the delay piping section 112. This makes it possible to appropriately adjust the load on the entire flow rate adjustment bypass flow path 116, and to reliably adjust the flow rate of the gas flowing into the delay piping section 112. Note that, although the present embodiment is configured to include the piping load section 117, the configuration may not include the piping load section 117.

[0027] In gas detection device 100 of this embodiment, when the test gas is sucked in by gas introduction means 118 and introduced into main gas flow path 111, first, the gas components contained in the test gas are identified based on the detection output of gas type identification unit 140. A portion of the test gas discharged from gas type identification section 140 flows into gas flow rate adjustment bypass flow path 116, thereby regulating the flow rate of the test gas flowing into delay piping section 112. By allowing the test gas to flow into delay piping section 112 with the flow rate regulated, the time required to identify the gas type is ensured, and the test gas is prevented from flowing into gas detection section 130 before the types of gas components contained in the test gas have been identified.

[0028] When it is determined that the test gas contains a gas component that must be avoided from being introduced into gas detection section 130, gas detection unit control section 125 switches flow path switching means 113 to the closed state, causing the test gas to flow into gas exhaust bypass flow path 115. This allows the test gas to be directly exhausted from gas exhaust section 151 without flowing into gas detection section 130.

[0029] On the other hand, in this embodiment, the target gas component to be measured by the gas detection unit 130 cannot be detected by the gas type identification unit 140, so when it is identified that the gas to be detected does not contain any gas components to be avoided from being introduced into the gas detection unit 130, the flow path switching means 113 is maintained in an open state, and the detected gas flows into the gas detection unit 130.

[0030] At this time, if it is determined that the detected gas contains an interference gas component for the gas detection unit 130, the detection output of the gas detection unit 130 contains fluctuations due to the interference gas component, and therefore the output control unit 155 does not output a gas detection signal to the display unit 152, and does not display the gas detection result, or outputs a command signal to display something else. Also, even if the detection output of the gas detection unit 130 exceeds at least one of the alarm points set for CO gas and H2 gas, no alarm signal is output to the alarm unit 153.

[0031] In gas detection device 100 of this embodiment, when it is determined that the gas being detected does not contain any gas components to be avoided from being introduced into gas detection unit 130 or any interference gas components, the gas detection result by gas detection unit 130 is displayed on display unit 152, and an alarm is issued by alarm unit 153 when it is detected that the detection output by gas detection unit 130 exceeds the alarm point.

[0032] Thus, with gas detection device 100 having the above configuration, even if the test gas contains gas components other than the target gas component to be measured, the gas components will not come into contact with gas detection unit 130, reliably preventing malfunctions and other problems. Moreover, even if the test gas contains gas components that interfere with gas detection unit 130, it is possible to reliably prevent erroneous concentration indications and false alarms due to the influence of the interfering gas components, thereby enabling stable, highly reliable gas detection. Furthermore, because it is possible to adjust the flow rate of gas flowing into delay piping section 112, it is possible to shorten the flow path length of delay piping section 112 and thereby reduce the size of delay piping section 112. As a result, it is possible to supply gas detection section 130 with a sufficient gas flow rate necessary for gas detection by gas detection section 130, while easing restrictions on the placement of delay piping section 112, making it possible to reduce the size of gas detection device 100.

[0033] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and various modifications can be made. For example, in the above embodiment, the gas type identification unit is described as being configured as an NDIR gas sensor, but the NDIR gas sensor is not limited to the above configuration. For example, in the above NDIR gas sensor, a cell and a reflector are used in the light guide path, but these may be omitted or multiple reflectors may be used. Furthermore, the gas type identification unit is not limited to an NDIR gas sensor as long as it is configured to be able to identify and detect gas components contained in the test gas. Furthermore, the gas concentration of the gas component detected by the gas type identification unit may be calculated and displayed on the display unit. Furthermore, the delay piping section is not limited to a configuration in which the gas pipe is wound in a spiral shape, but may be configured to have a flow path length or volume that ensures the time required for the gas type identification process. Furthermore, in the above embodiment, the gas detection device is composed of a gas detection unit and an output control unit, but these may be the same or may have different configurations. The gas detection device does not have to be an independent detector, but may be linked to some other device. [Explanation of symbols]

[0034] 100 Gas detection device 111 Main gas flow path 112 Delay piping section 113 Flow path switching means 115 Gas exhaust bypass passage 116: Bypass flow path for adjusting gas flow rate 117 ··· Piping load section 118 Gas introduction means 120 Gas Detection Unit 121 Gas inlet 125 Gas detection unit control section 130 Gas detection unit 131 One gas sensor 132 Other gas sensor 140 Gas type identification unit 141 Measuring cell 142a Gas inlet 142b Gas exhaust passage 143... Light source section 145... Light receiving section 146 ··· Light receiving element 147 Bandpass Filter 148 Reflective member 149 Light-transmitting window 150 Output Control Unit 151 Gas exhaust section 152... Display section 153... Alarm section 154 External output section 155 Output control section

Claims

1. A gas detection device comprising: a gas detection unit disposed in a main gas flow path extending from a gas inlet to a gas outlet; and gas introducing means connected to the main gas flow path for circulating a test gas through the main gas flow path, a gas type identifying section disposed upstream of the gas detection section in the gas flow direction of the main gas flow passage; a gas exhaust bypass flow passage connected between the gas detection section and the gas type identifying section via a flow passage switching means, which allows the test gas exhausted from the gas type identifying section to be exhausted from the gas exhaust section without being introduced into the gas detection section; and a gas detection unit control section having a function of controlling the operation of the flow passage switching means based on the type of gas component detected by the gas type identifying section, the gas type identification unit is configured to be able to identify a gas type based on a pattern of a measured signal; the gas detection unit control section switches the flow path to allow the test gas to flow into the gas exhaust bypass flow path based on the type of gas component detected by the gas type identification section.

2. a delay piping section is disposed in the main gas flow path between the gas type identifying section and the flow path switching means; 2. The gas detection device according to claim 1, further comprising a gas flow rate adjustment bypass flow path that bypasses an upstream position of the delay piping section and a downstream position of the gas detection section in the gas flow direction of the main gas flow path.

3. 3. The gas detection device according to claim 2, wherein the gas flow rate adjusting bypass passage has a passage diameter smaller than that of the main gas passage.

4. 3. The gas detection device according to claim 2, wherein the gas flow rate adjusting bypass passage includes a piping load section that limits the flow rate of the test gas flowing into the delay piping section.

5. a display unit, an alarm unit, and an output control unit that outputs a gas detection signal related to a concentration indication value based on the gas detection output of the gas detection unit to the display unit and outputs an alarm signal to the alarm unit when the gas detection output of the gas detection unit exceeds an alarm point, the gas type identification unit is configured to be able to identify and detect interference gas components other than the target gas component to be measured, to which the gas detection unit is sensitive; 2. The gas detection device according to claim 1, wherein the output control unit is configured not to output a gas detection signal and an alarm signal related to the gas detection unit to the display unit and the alarm unit when the gas type identification unit detects that the detected gas contains the interference gas component.

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