A thermal conductivity type gas detection device

Abstract

The application provides a thermal conductivity type gas detection device which can improve detection accuracy and comprises a shell, a first detection part, the shell comprises a first shell, the first detection part comprises a first detection element, the first shell comprises a first shell inner cavity and a first through hole, the first shell comprises a circumferential wall corresponding to the first shell inner cavity and a base, the circumferential wall comprises an inner circumferential wall, and the second end of the first through hole is close to the first detection element; a first plane is defined, the first plane is perpendicular to the second direction, the first plane passes through the second end, the flow area of the first shell inner cavity in the first plane is S1, a corresponding inner circumferential wall between two end portions of the first detection element along a first direction is defined as a first inner circumferential wall portion, a plane perpendicular to the first direction is defined as a projection plane, the maximum area surrounded by the orthogonal projection of the first inner circumferential wall portion in the projection plane is S2, and S2 is less than S1.

Description

Technical Field

[0001] This application relates to the field of gas detection technology, and in particular to a thermal conductivity gas detection device applicable to refrigerant leak detection. Background Technology

[0002] Thermal conductivity gas detection devices primarily utilize the differences in thermal conductivity between different gases or gas concentrations to detect leaks. Existing thermal conductivity gas detection devices include a detection element and a housing. The housing has a through-hole and a chamber. When the gas to be detected enters the chamber through the through-hole, the temperature of the chamber changes with the gas type and concentration. This change is fed back to the detection element and characterized as a change in a specific parameter of the detection element. Based on the change in this parameter, whether the gas is leaking and the amount of leakage can be detected. The inventors discovered that thermal conductivity gas sensors rely on the thermal conductivity of different gases to detect refrigerant leaks. However, gas convection is one mode of heat transfer. Therefore, existing thermal conductivity gas detection devices exhibit strong gas convection, leading to errors in the internal temperature changes of the chamber, thus causing deviations in the detection results. Summary of the Invention

[0003] Therefore, it is necessary to provide a thermal conductivity gas detection device that can improve the accuracy of detection results to address the above problems.

[0004] This application provides a thermal conductivity gas detection device, including a housing, the housing comprising a first housing, the thermal conductivity gas detection device comprising a first detection part, the first detection part comprising a first detection element, the first housing comprising a first housing cavity and a first through hole, the first housing cavity and the first through hole communicating, the first detection element being located in the first housing cavity; the first housing comprising a peripheral wall and a base corresponding to the first housing cavity, the first detection element being connected to the base, the peripheral wall comprising an inner peripheral wall, the first through hole comprising a first end and a second end along a second direction, the second end being closer to the first detection element than the first end; a first plane is defined, the first plane being perpendicular to the second direction and passing through the second end, the flow area of ​​the first housing cavity in the first plane being S1.

[0005] Defined as follows: the inner peripheral wall between the two ends of the first detection element along the first direction is called the first inner peripheral wall portion; the plane perpendicular to the first direction is called the projection plane; the maximum area enclosed by the orthographic projection of the first inner peripheral wall portion onto the projection plane is S2, where S2 is less than S1.

[0006] Wherein, the first direction is the thickness direction of the first detection element, and the second direction is the extension direction of the first through hole.

[0007] In this application, the flow area of ​​the first housing cavity on the first plane is S1, and the maximum area of ​​the region enclosed by the orthographic projection of the first inner peripheral wall portion on the projection plane is S2. S2 is less than S1, which can increase the range of the stagnation area formed by the first inner peripheral wall portion. This weakens the gas convection at the first detection element relative to the first housing cavity on the first plane, thereby enabling the first detection element to focus the detection object on the temperature change caused by gas thermal conduction, and improving the accuracy of the detection results of the thermal conductivity gas detection device. Attached Figure Description

[0008] Figure 1 A three-dimensional structural schematic diagram of the thermal conductivity gas detection device according to the first embodiment of this application;

[0009] Figure 2 for Figure 1 A schematic diagram of the three-dimensional structure cut along the AA direction;

[0010] Figure 3 for Figure 2 A schematic diagram showing the area ranges of S1 and S2.

[0011] Figure 4 This is a three-dimensional structural schematic diagram of the thermal conductivity gas detection device according to the second embodiment of this application;

[0012] Figure 5 A cross-sectional schematic diagram of the front view of the thermal conductivity gas detection device of the third embodiment provided in this application;

[0013] Figure 6 A cross-sectional schematic diagram of the front view of the thermal conductivity gas detection device of the fourth embodiment provided in this application;

[0014] Figure 7 A schematic diagram of the structure of the thermal conductivity gas detection device according to the fifth embodiment of this application;

[0015] Figure 8 for Figure 7 A sectional view taken along the BB direction;

[0016] Figure 9 A three-dimensional structural schematic diagram of the thermal conductivity gas detection device according to the sixth embodiment of this application;

[0017] Figure 10 A three-dimensional structural schematic diagram of the thermal conductivity gas detection device according to the seventh embodiment of this application;

[0018] Figure 11 for Figure 10 A cross-sectional view showing the first flange section cut along the CC direction;

[0019] Figure 12 for Figure 11 Exploded view;

[0020] Figure 13 A three-dimensional cross-sectional view of the thermal conductivity gas detection device according to the eighth embodiment of this application.

[0021] Figure label:

[0022] 1- Thermal conductivity gas detection device; 11- Seventh end; 12- Eighth end; 2- Housing; 20- First detection section; 21- Second detection section;

[0023] 201-First detection element; 2011-Fifth terminal; 2012-Sixth terminal; 201a-First thermistor; 211-Second detection element; 211a-Second thermistor; 23-Terminal; 203-First terminal; 231a / 231b-First lead; 232a / 232b-First conductive terminal;

[0024] 30 - First housing; 301 - First through hole; 301-1 - Hole wall corresponding to the first through hole; 301-11 - First end; 301-12 - Second end; 302 - Peripheral wall; 302a - Inner peripheral wall; 3021a - First inner peripheral wall portion; 3021b - Third end; 3021c - Fourth end; 3022a - Second inner peripheral wall portion; 3023a - Third inner peripheral wall portion; 304 - First flange portion; 305 - Inner cavity of the first housing;

[0025] 31-Second housing; 315-Second housing cavity;

[0026] 40- Waterproof and breathable membrane;

[0027] 50 - Base; 51 - First end face; 52 - First boss; 521 - Third through hole; 522 - Fourth through hole;

[0028] 60 - Sealing ring;

[0029] 70 - Mounting bracket. Detailed Implementation

[0030] To better understand the technical solution of this application, the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0031] The first direction is the thickness direction of the first detection element 201, and the second direction is the extension direction of the first through hole 301.

[0032] Figure 1 A three-dimensional structural schematic diagram of the thermal conductivity gas detection device according to the first embodiment of this application; Figure 2 for Figure 1 A schematic diagram of the three-dimensional structure after being cut along AA; Figure 3 for Figure 2 A schematic diagram showing the area ranges of S1 and S2. Figure 4 This is a schematic diagram of the structure of the thermal conductivity gas detection device according to the second embodiment of this application.

[0033] refer to Figure 1 , Figure 2 The thermal conductivity gas detection device 1 includes a housing 3 and a first detection part 20. The housing 3 includes a first housing 30, and the first detection part 20 includes a first detection element 201. The first housing 30 includes a first housing cavity 305 and a first through hole 301. The first through hole 301 connects to the first housing cavity 305 and the outside of the thermal conductivity gas detection device 1. The first detection element 201 is located in the first housing cavity. The thickness direction of the first detection element 201 is defined as the first direction, and the second direction is defined as the second direction. The first housing 30 includes a peripheral wall 302 corresponding to the first housing cavity 305 and a base 50. The first detection element 201 is connected to the base 50. The peripheral wall 302 includes an inner peripheral wall 302a. The hole wall 301-1 corresponding to the first through hole 301 includes a first end 301-11 and a second end 301-12 distributed relatively along the second direction. Compared with the first end 301-11, the second end 301-12 is closer to the first detection element 201. The first detection element 201 is the element that mainly performs the function of gas detection.

[0034] In this embodiment, the base 50 and the first through hole 301 are respectively disposed at both ends of the first housing 30 along the first direction, and the second direction is parallel to the first direction. It can be understood that in other embodiments, when the first housing 30 can be bent or the first through hole 301 passes through the base 50 or is disposed on the opposite side of the base 50, the second direction can intersect or be parallel to the first direction.

[0035] Furthermore, the first detection element 201 includes a first thermistor 201a, which is located in the inner cavity 305 of the first housing. During detection, the first thermistor 201a is energized, monitoring the temperature in the inner cavity 305 of the first housing in real time and feeding back the change in its resistance. Utilizing the principle that gases of different compositions and concentrations have different thermal conductivity, when different types and concentrations of gas enter the inner cavity 305 of the first housing, the temperature of the inner cavity 305 will change, which is reflected in the change in the resistance of the first thermistor 201a. When the change in the resistance of the first thermistor 201a reaches a certain level, the thermal conductivity gas detection device alarms. The thermal conductivity gas detection device can be used to detect gaseous fluids such as refrigerants, for example, in systems such as air conditioners or refrigerators, to detect whether refrigerant leaks and to promptly issue an alarm. Of course, the thermal conductivity gas detection device can also be used to detect leaks of other gases. Different gases have different thermal conductivity, and those skilled in the art can obtain the amount of gas leakage by observing the temperature change value of the inner cavity 305 of the first housing based on the inherent thermal conductivity of different gases.

[0036] In this embodiment, reference Figure 2 , Figure 3 , Figure 4 Let a first plane be defined, perpendicular to the second direction and passing through the second end 301-12. The flow area of ​​the inner cavity 305 of the first housing in the first plane is S1. Let the inner peripheral wall 302a corresponding to the two ends of the first detection element 201 along the first direction be the first inner peripheral wall portion 3021a. Let the plane perpendicular to the first direction be the projection plane. The maximum area enclosed by the orthographic projection of the first inner peripheral wall portion 3021a onto the projection plane is S2, where S2 is less than S1. When the first housing 30 is a frustum, and the flow surface of the inner cavity 305 of the first housing in the first plane is a circle with radius R1, then S1 equals πR1. 2 If the largest region enclosed by the orthographic projection of the first inner peripheral wall portion 3021a onto a plane perpendicular to the first direction is a circle with radius R2, then S2 equals πR2. 2 S2 is less than S1, and radius R1 is greater than the maximum radius R2 of the first inner peripheral wall 3021a.

[0037] As gas moves, it encounters resistance and flow instability, causing changes in its flow direction and velocity. This disturbance prolongs the gas's residence time. Therefore, when the first shell follows... Figure 1 , 2 When the device is arranged in this manner, the maximum area S2 of the region enclosed by the orthographic projection of the first inner peripheral wall portion 3021a on the projection plane is smaller than the flow area S1 of the first housing cavity 305 on the first plane. This results in the maximum amount of gas that the first inner peripheral wall portion 3021a can accommodate being smaller than the amount of gas that the upper end of the first housing cavity 305 (i.e., the first housing cavity at the first plane) can accommodate. The downward flow of gas is hindered by the first inner peripheral wall portion 3021a, thereby increasing the momentum loss of the gas. This increases the range of the stagnation area formed at the first inner peripheral wall portion, weakening the gas convection at the first detection element relative to the first housing cavity at the first plane. Consequently, the first detection element 201 can focus the detection object on the temperature change caused by gas thermal conduction, improving the accuracy of the detection results of the thermal conductivity gas detection device.

[0038] Figure 5 A cross-sectional schematic diagram of the front view of the thermal conductivity gas detection device of the second embodiment provided in this application.

[0039] refer to Figure 5In this embodiment, the second direction intersects the first direction. The first detection element 201 includes a fifth end 2011 and a sixth end 2012 along the first direction. The sixth end 2012 is closer to the base 50 than the fifth end 2011. The minimum distance from the sixth end 2012 to the hole wall 301-1 corresponding to the first through hole is H1. The minimum distance between the two ends of the inner peripheral wall 302a of the first housing 30 along the first direction is H, and H1 is less than or equal to two-thirds of H. Alternatively, in a specific embodiment, a plane parallel to the first direction is defined as the second projection plane. Along the direction perpendicular to the first direction, the orthographic projection of the first through hole 301 on the second projection plane is at least partially offset from the orthographic projection of the first detection element 201 on the second projection plane. This arrangement further allows the first detection element 201 to be located in the middle of the inner cavity 305 of the first housing, enabling the air in the inner cavity 305 of the first housing to provide better heat insulation and reduce the adverse effects of external temperature on the first detection element.

[0040] Figure 6 A cross-sectional schematic diagram of the front view of the thermal conductivity gas detection device of the third embodiment provided in this application;

[0041] Figure 7 A schematic diagram of the structure of the thermal conductivity gas detection device according to the fourth embodiment provided in this application;

[0042] Figure 8 for Figure 7 A sectional view taken along the BB direction.

[0043] refer to Figure 6 The first inner peripheral wall portion 3021a includes a third end 3021b and a fourth end 3021c that are relatively distributed along the first direction; compared to the fourth end 3021c, the third end 3021b is closer to the first through hole 301; the inner peripheral wall 302a corresponding to the two ends of the first detection element 201 along the first direction is defined as the first inner peripheral wall portion 3021a, and the plane perpendicular to the first direction is defined as the projection plane, and the maximum area of ​​the region enclosed by the orthographic projection of the first inner peripheral wall portion 3021a onto the projection plane is defined as S2; along the first direction, from the fourth end 3021c to the base 50, the maximum flow area of ​​the inner peripheral wall 302a is less than or equal to S2. Further, in a specific embodiment, from the fourth end 3021c to the base 50, the inner peripheral wall 302a is at least partially inclined toward the first detection portion 20; or, in a specific embodiment, along the first direction, from the first through hole 301 to the third end 3021b, the flow area of ​​at least part of the inner peripheral wall 302a is less than or equal to S1. Furthermore, in one specific embodiment, the cross-section of the first inner peripheral wall portion 3021a in the first direction is circular, and the ratio of the maximum diameter to the minimum diameter of the first inner peripheral wall portion 3021a along the first direction is less than or equal to 2, for example, 1.5.

[0044] This configuration controls the range of gas flow through the inner peripheral wall 302a, increasing the likelihood of more stagnation zones forming in the first inner peripheral wall portion 3021a. This weakens gas convection in the chamber of the first inner peripheral wall portion 3021a compared to the inner cavity of the first housing at the first plane, thereby enabling the first detection element 201 to focus the detection object on the temperature change caused by gas thermal conduction, thus improving the accuracy of the detection results of the thermal conductivity gas detection device.

[0045] refer to Figure 6 In this embodiment, the first through hole 301 and the base 50 are located at the two ends of the first housing 30 along the first direction, and the second direction is parallel to the first direction. The first housing 30 is a frustum, the cross-section of the first inner peripheral wall 3021a perpendicular to the first direction is circular, the flow surface of the third end 3021b of the first inner peripheral wall 3021a is a circle with diameter AA', the flow surface of the fourth end 3021c is a circle with diameter BB', the flow area of ​​the third end 3021b of the first inner peripheral wall 3021a is greater than or equal to the flow area of ​​the fourth end 3021c, and the length of the diameter AA' of the third end 3021b is greater than or equal to the length of the diameter BB' of the fourth end 3021c. Similarly, when the first housing 30 is cubic, the flow surfaces of the third end 3021b and the fourth end 3021c of the first inner peripheral wall 3021a are both rectangular, and the flow area of ​​the third end 3021b is greater than the flow area of ​​the fourth end 3021c. With this configuration, the flow area of ​​the end of the first inner peripheral wall portion 3021a away from the first through hole 301 is less than or equal to the flow area of ​​the end near the first through hole 301, which can reduce the gas flow at the first detection element 201.

[0046] In one specific embodiment, the diameter of the first inner peripheral wall portion 3021a remains unchanged along the first direction from the third end 3021b to the fourth end 3021c; or in one specific embodiment, the first inner peripheral wall portion 3021a is at least partially inclined along the first direction from the third end 3021b to the fourth end 3021c, or further, referring to Figure 6 From the third end 3021b to the fourth end 3021c, the diameter of the first inner peripheral wall portion 3021a gradually decreases. This arrangement ensures that the diameter of the first inner peripheral wall portion 3021a remains constant or at least decreases relatively uniformly in part, which helps stabilize the gas flow velocity at the first detection element 201. It further increases the likelihood of a stagnation zone forming at the first detection element 201, thereby further improving the detection accuracy of the thermal conductivity gas detection device. The shape and size of the peripheral wall 302 determine the volume of the inner cavity 305 of the first housing. The wall thickness and outer shape of the peripheral wall 302 can be adaptively designed according to specific circumstances and are not limited here.

[0047] Furthermore, the first through hole 301 and the base 50 are respectively located at both ends or the same end of the first housing 30 along the first direction. Along the first direction from the first through hole 301 to the base 50, the inner peripheral wall 302a is at least partially inclined. (Reference) Figure 6 In this embodiment, the diameter of the inner peripheral wall 302a gradually decreases along the first direction from the first through hole 301 to the base 50. With this configuration, the inner peripheral wall 302a corresponding to the inner cavity 305 of the first housing and the base 50 form a funnel-like shape. When the first housing 30... Figure 6 When arranged as shown, the inner cavity 305 of the first housing is larger at the top and smaller at the bottom, which further increases the possibility of a stagnation area at the first detection element 201, thereby improving the detection accuracy of the thermal conductivity gas detection device. At the same time, it makes the gas convection in the inner cavity 305 of the first housing near the first through hole 301 stronger, which can quickly exchange gas with the outside gas, so that once the gas to be tested leaks, it can immediately enter the inner cavity 305 of the first housing, improving the response speed of the thermal conductivity gas detection device 1. Furthermore, from the second end 301-12 to the base 50, the diameter of the inner peripheral wall 302a is gradually reduced, and the inner peripheral wall 302a is inclined, which can guide the gas to flow quickly along the inner peripheral wall 302a to the base 50, further improving the response speed. For example, when the gas to be detected in the thermal conductivity gas detection device is a refrigerant, since the refrigerant is denser than air, when the refrigerant is mixed with air, the refrigerant flows downwards; under the guiding effect of the inner peripheral wall 302a, the refrigerant can quickly deposit at the first detection element 2012, thereby improving the response speed of the thermal conductivity gas detection device.

[0048] The first housing 30 includes a seventh end 11 and an eighth end 12 along a first direction. The inner peripheral wall 302a includes a second inner peripheral wall portion 3022a and a third inner peripheral wall portion 3023a. Compared to the second inner peripheral wall portion 3022a, the third inner peripheral wall portion 3023a is closer to the first through hole 301. The second inner peripheral wall portion 3022a includes the first inner peripheral wall portion 3021a. Along the first direction, the flow area of ​​the third inner peripheral wall portion 3023a is larger than the flow area of ​​the second inner peripheral wall portion 3022a. Specifically, refer to... Figure 7 , Figure 8In this embodiment, the first through hole 301 penetrates the base 50. The first through hole 301 and the base 50 are located at the same end of the first housing 30 along the first direction. The base 50 is located at the eighth end 12. The maximum value of the flow area of ​​the second inner peripheral wall portion 3022a perpendicular to the first direction is less than the minimum value of the flow area of ​​the third inner peripheral wall portion 3023a perpendicular to the first direction. Or, in a specific embodiment, the cross-sections of the second inner peripheral wall portion 3022a and the third inner peripheral wall portion 3023a perpendicular to the first direction are circular, and the diameter of the second inner peripheral wall portion 3022a is less than the diameter of the third inner peripheral wall portion 3023a. This configuration aims to ensure that the inner cavity 305 of the first housing changes uniformly as much as possible, and that the flow area of ​​the inner peripheral wall 302a perpendicular to the first direction does not increase dramatically. In particular, it ensures that from the seventh end 11 to the eighth end 12 of the first housing 30, the flow area of ​​the inner peripheral wall 302a perpendicular to the first direction generally shows a decreasing trend, thereby avoiding a sudden increase in gas flow rate at the first detection element 201 and improving the detection accuracy of the thermal conductivity gas detection device 1.

[0049] To further enable the first thermistor 201a to detect gas changes more quickly and make rapid detections, refer to Figure 6 In this embodiment, the first housing 30 is a frustum-like cone, and the diameter of the first through hole 301 is greater than or equal to the maximum diameter of the first inner peripheral wall portion 3021a. This configuration ensures sufficient gas intake while maintaining relatively weak convection in the first inner peripheral wall portion 3021a, allowing leaked gas to quickly enter the chamber, thus improving the detection accuracy of the thermal conductivity gas detection device and accelerating the response speed.

[0050] To enable the first thermistor 201a to detect gas changes more quickly and make rapid detections, the first thermistor 201a is at least partially aligned with the first through-hole 301. Specifically, as shown... Figure 6 , Figure 7 As shown, in one embodiment, the projection from the hole wall 301-1 corresponding to the first through hole onto the base 50 along the first direction, the projection surface of the hole wall 301-1 corresponding to the first through hole at least partially overlaps with the projection surface of the first detection element 201. Similarly, when the first through hole 301 is opened on the side of the inner peripheral wall 302a, in another specific embodiment, the first through hole 301, the first detection element 201, and the base 50 are coaxially arranged. With this arrangement, the shape of the first housing 30 is more regular, which is convenient for processing, and the gas flow path is shorter than that of an irregular shape, resulting in a faster response speed for the thermal conductivity gas detection device.

[0051] Figure 9 A three-dimensional structural schematic diagram of the thermal conductivity gas detection device according to the fifth embodiment of this application.

[0052] refer to Figure 9While controlling the flow area of ​​the first through hole 301, the first through hole 301 can be set as a mesh. The mesh-shaped through hole makes the air intake more uniform, which greatly improves the detection accuracy of the thermal conductivity gas detection device 1 and shortens the response time of the gas detection device 1.

[0053] Figure 10 A three-dimensional structural schematic diagram of the thermal conductivity gas detection device according to the sixth embodiment of this application;

[0054] Figure 11 for Figure 10 A cross-sectional view showing the first flange section cut along the CC direction;

[0055] Figure 12 for Figure 11 Exploded view.

[0056] refer to Figures 10-12 The housing 2 includes a waterproof and breathable membrane 40, which is connected to the first housing 30. The waterproof and breathable membrane 40 can cover the first through hole 301. Since the humidity of the gas to be tested will affect the test results, the waterproof and breathable membrane can effectively isolate the moisture carried in the gas to be tested and improve the accuracy of the test results.

[0057] The base 50 is sealed to the peripheral wall 302, ensuring that the inner cavity 305 of the first housing can only communicate with the outside through the first through hole 301. (Reference) Figure 13 The thermal conductivity gas detection device includes a sealing element 60, and at least a portion of the base 50 is located in the first cavity 305. The base 50 is tightly fitted with the peripheral wall 302, so that the inner cavity 305 of the first housing can only communicate with the outside through the first through hole 301, thereby controlling the gas convection to remain within a certain range and improving the accuracy of the detection results of the thermal conductivity gas detection device.

[0058] In one embodiment, reference Figure 11-12 The first housing 30 includes a first flange 304, which is close to the base 50 relative to the first through hole 301. Along a first direction, the peripheral wall 302 is at least partially close to the first thermistor 201a relative to the first through hole 301. The base 50 includes a first end face 51, which is connected to a first boss 52, and the first end face 51 is located away from the first detection element 201 relative to the first boss 52. For better sealing, the first flange 304 is sealed to the first end face 51. In some embodiments, the sealing connection includes welding, sealant bonding, or bonding via a sealing ring. The first boss 52 is at least partially located within the inner cavity 305 of the first housing. For ease of installation, the first boss 52 is at least partially connected to the inner peripheral wall 302a, wherein the first boss 52 serves a positioning function.

[0059] In one embodiment, such as Figure 11 , Figure 12 As shown, the thermal conductivity gas detection device includes a base 50, which has a third through hole 521 and a fourth through hole 522. The first detection unit 20 includes a first detection element 201 and a terminal block 23. A first boss 52 protrudes from the base 50 toward the first detection element 201. The first detection element 201 includes a first thermistor 201a, which is connected to the terminal block 23 and connected to a circuit board. The terminal block 23 includes first leads 232a and 232b and first conductive terminals 231a and 231b. The first leads 232a and 232b, the first conductive terminals 231a and 231b, and the first thermistor 201a are located on the same side of the first boss 52. The first thermistor 201a is electrically connected to the first leads 202a and 202b, and the first leads 202a and 202b are electrically connected to the first conductive terminals 201a and 201b.

[0060] Figure 13 A three-dimensional cross-sectional view of the thermal conductivity gas detection device according to the seventh embodiment of this application.

[0061] refer to Figure 13 To improve the accuracy of the thermal conductivity gas detection device 1, in one embodiment, the housing 2 further includes a second housing 31 and a second detection unit 21. The second housing 31 has a second housing cavity 315, which is a closed cavity. The second detection unit 21 includes a second detection element 211, which includes a second thermistor 211a. The second thermistor 211a is located in the second housing cavity 315 and serves as a reference resistor in the second housing cavity 315. Different gases have different thermal conductivity. Those skilled in the art can accurately determine the gas leakage amount by measuring the temperature difference between the inner cavity 305 and the inner cavity 315 of the first housing based on the inherent thermal conductivity of different gases. For example, when a gas leak occurs, the leaking gas enters the inner cavity 305 of the first housing. At this time, the thermal conductivity of the gas in the inner cavity 305 is different from that in the inner cavity 315 of the second housing. Consequently, the temperature values ​​detected by the first thermistor 201a and the second thermistor 211a are different, causing a corresponding change in the resistance values ​​of the first thermistor 201a and the second thermistor 211a. Therefore, the voltages across the first thermistor 201a and the second thermistor 211a are different. The amount of gas leakage can be obtained by measuring the change in the ratio of these two voltages. By setting up this system and using the controlled variable method, a control experimental group with the second housing 31 is included. This ensures that the difference between the second housing 31 and the first housing 30 is only the type or concentration of gas in the inner cavity, thus eliminating errors caused by parameters not related to the target gas and improving the accuracy of the thermal conductivity gas detection device.

[0062] Furthermore, in one embodiment, the first thermistor 201a and the second thermistor 211a are both NTC thermistor chips, thereby facilitating component selection.

[0063] Furthermore, in one embodiment, the housing 2 includes a mounting frame 70, and the first housing 30 and the second housing 31 are respectively connected to the mounting frame 70. The mounting frame 70 can be used to support the first housing 30 and the second housing 31.

[0064] Furthermore, in one embodiment, along the first direction, from the second end 301-12 to the fourth end 3021c, the inner peripheral wall 302a is provided with a protrusion. The protrusion protrudes from the inner peripheral wall 302a in a direction intersecting with the first direction, further intercepting the airflow from the second end 301-12 to the fourth end 3021c, reducing gas convection at the first detection element, and improving the accuracy of the detection results of the thermal conductivity gas detection device.

[0065] It should be noted that the above embodiments are only used to illustrate this application and are not intended to limit this application. Although this specification has described this application in detail with reference to the above embodiments, those skilled in the art should understand that they can still make modifications or equivalent substitutions. All improvements and substitutions that do not depart from the spirit and scope of this application should be covered within the scope of this application.

Claims

1. A thermal conductivity type gas detection device, characterized in that, The device includes a housing (2), which includes a first housing (30). The thermally conductive gas detection device includes a first detection unit (20), which includes a first detection element (201). The first housing (30) includes a first housing cavity (305) and a first through hole (301), which are connected. The first detection element (201) is located in the first housing cavity (305). The first housing (30) includes a peripheral wall (302) and a base (50) corresponding to the first housing cavity (305). The component (201) is connected to the base (50). The peripheral wall (302) includes an inner peripheral wall (302a). The hole wall (301-1) corresponding to the first through hole (301) includes a first end (301-11) and a second end (301-12) distributed opposite to each other along the second direction. Compared to the first end (301-11), the second end (301-12) is closer to the first detection element (201). A first plane is defined, which is perpendicular to the second direction and passes through the second end (301-12). The flow area of ​​the inner cavity (305) of the first housing in the first plane is S1. Defined as follows: the inner peripheral wall (302a) between the two ends of the first detection element (201) along the first direction is defined as the first inner peripheral wall portion (3021a). Let the plane perpendicular to the first direction be the projection plane. The maximum area enclosed by the orthographic projection of the first inner peripheral wall portion (3021a) onto the projection plane is S2, where S2 is less than S1. The first direction is the thickness direction of the first detection element (201), and the second direction is the extension direction of the first through hole (301).

2. The thermal conductivity gas detection device according to claim 1, characterized in that, The first inner peripheral wall portion (3021a) includes a third end (3021b) and a fourth end (3021c) that are distributed opposite to each other along the first direction; compared to the fourth end (3021c), the third end (3021b) is closer to the first through hole (301), and along the first direction, from the fourth end (3021c) to the base (50), the maximum flow area of ​​the inner peripheral wall (302a) is less than or equal to S2.

3. The thermal conductivity gas detection device according to claim 1 or 2, characterized in that, The inner peripheral wall (302a) includes a second inner peripheral wall portion (3022a) and a third inner peripheral wall portion (3023a) distributed along the first direction. The second inner peripheral wall portion (3022a) includes the first inner peripheral wall portion (3021a). Compared with the second inner peripheral wall portion (3022a), the third inner peripheral wall portion (3023a) is closer to the first through hole (301). Along the first direction, the minimum flow area of ​​the third inner peripheral wall portion (3023a) is greater than or equal to the maximum flow area of ​​the second inner peripheral wall portion (3022a).

4. The thermal conductivity gas detection device according to claim 3, characterized in that, The second inner peripheral wall portion (3022a) has a circular cross-section perpendicular to the first direction, and the third inner peripheral wall portion (3023a) has a circular cross-section perpendicular to the first direction; the diameter of the second inner peripheral wall portion (3022a) is smaller than the diameter of the third inner peripheral wall portion (3023a); And / or, the first inner peripheral wall portion (3021a) includes a third end (3021b) and a fourth end (3021c) that are distributed opposite to each other along the first direction; relative to the fourth end (3021c), the third end (3021b) is closer to the first through hole (301), and from the fourth end (3021c) to the base (50), the inner peripheral wall (302a) is inclined toward the first detection portion (20).

5. The thermal conductivity gas detection device according to claim 1, characterized in that, The first through hole (301) and the base (50) are located at both ends or the same end of the first housing (30) along the first direction; the maximum flow area of ​​the first housing (30) perpendicular to the first direction is equal to S1, and / or, along the first direction, from the first through hole (301) to the base (50), the inner peripheral wall (302a) is at least partially inclined.

6. The thermal conductivity gas detection device according to claim 5, characterized in that, The first inner peripheral wall portion (3021a) includes a third end (3021b) and a fourth end (3021c) along the first direction. Compared with the fourth end (3021c), the third end (3021b) is closer to the first through hole (301). The cross section of the first inner peripheral wall portion (3021a) perpendicular to the first direction is circular. The diameter of the third end (3021b) is greater than or equal to the diameter of the fourth end (3021c). And / or, the second inner peripheral wall portion (3022a) is provided with a protrusion.

7. The thermal conductivity gas detection device according to any one of claims 1, 2, 5, or 6, characterized in that, The first shell (30) has a circular cross-section perpendicular to the first direction, and the ratio of the maximum diameter to the minimum diameter of the inner peripheral wall (302a) along the first direction is less than or equal to 2. And / or, the diameter of the first through hole (301) is greater than or equal to the maximum diameter of the first inner peripheral wall portion (3021a).

8. The thermal conductivity gas detection device according to any one of claims 1, 2, 5, or 6, characterized in that, The first detection element (201) includes a fifth end (2011) and a sixth end (2012) along the first direction. Compared to the fifth end (2011), the sixth end (2012) is closer to the base (50). The minimum distance from the sixth end (2012) to the hole wall (301-1) corresponding to the first through hole is H1. The minimum distance between the two ends of the inner peripheral wall (302a) of the first housing (30) along the first direction is H. H1 is less than or equal to two-thirds of H.

9. The thermal conductivity gas detection device according to any one of claims 1, 2, 5, or 6, characterized in that, The plane perpendicular to and parallel to the first direction is defined as the projection plane. Projection is performed along the direction perpendicular to the first direction. The orthographic projection of the hole wall (301) corresponding to the first through hole (301) on the projection plane is at least partially aligned with the orthographic projection of the first detection element (201) on the projection plane.

10. The thermal conductivity gas detection device according to any one of claims 1, 2, 5, or 6, characterized in that, The first through hole (301) is mesh-like; and / or, the housing (2) includes a second housing (31), the thermal conductivity gas detection device includes a second detection part (21), the second housing (31) has a second housing cavity (315), the second housing cavity (315) is a closed cavity; the second detection part (21) includes a second detection element (211), the second detection element (211) includes a second thermistor (211a), the second thermistor (211a) is located in the second housing cavity (315); there is a gap between the first housing (30) and the second housing (31); or, the first housing (30) and the second housing (31) are an integral piece.

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