CN217586904U

CN217586904U - Optical gas sensor

Info

Publication number: CN217586904U
Application number: CN202220581346.5U
Authority: CN
Inventors: 张加俊; 万霞; 黄隆重; 金骑宏
Original assignee: Hangzhou Sanhua Research Institute Co Ltd
Current assignee: Hangzhou Sanhua Research Institute Co Ltd
Priority date: 2022-03-17
Filing date: 2022-03-17
Publication date: 2022-10-14
Anticipated expiration: 2032-03-17

Abstract

The present application provides an optical gas sensor having a main chamber; the housing of the optical gas sensor comprises a first housing and a second housing; the main chamber is located between the first housing and the second housing; the second shell is also provided with a first containing cavity and a second containing cavity; one of the first housing and the second housing has a first mounting portion and a protruding portion, and the other housing is provided with a through hole; the protruding portion comprises a first sub-portion and a second sub-portion, the first sub-portion extends from the first mounting portion to be close to the other shell, the second sub-portion is far away from the first mounting portion than the first sub-portion, at least part of the first sub-portion is located in the perforation, the second sub-portion is located outside the perforation, and the second sub-portion abuts against the shell located at the periphery of the perforation; the light source is at least partially positioned in the first cavity and faces the at least one reflecting surface; the detector is at least partially located in the second cavity and faces the at least one reflective surface. This application is favorable to reducing optical gas sensor's equipment part quantity, convenient assembly.

Description

Optical gas sensor

Technical Field

The application relates to the technical field of measurement, in particular to an optical gas sensor.

Background

Optical gas sensors, such as infrared gas sensors, are commonly used, and the concentration of a gas can be determined by using the relationship between the gas concentration and the absorption intensity based on the selective absorption characteristics of different gas molecules to infrared light.

An optical gas sensor in the related art has a circuit board, a first housing, a second housing, a light source, and a detector. The first shell is matched and fixed with the circuit board, a channel for accommodating the light source and the detector is arranged on the first shell, the first shell and the second shell are assembled together through screws to form an optical transmission channel, and therefore light emitted by the light source can finally reach the detector through the optical transmission channel.

However, in the optical gas sensor of the related art, when the two housings are fixed, the housings are assembled by screws or the like, the number of assembling parts is large, the assembling process is complicated, and the efficiency is low, so that there is a need for improvement.

SUMMERY OF THE UTILITY MODEL

This application is favorable to reducing optical gas sensor's equipment part quantity, convenient assembly.

Embodiments of the present application provide an optical gas sensor having a main chamber; the optical gas sensor further includes:

a housing comprising a first housing and a second housing; the main chamber is located between the first housing and the second housing; the second shell is also provided with a first containing cavity and a second containing cavity which are arranged at intervals; the second shell is provided with a first wall surface forming the first cavity and a second wall surface forming the second cavity, the shell is provided with a third wall surface forming the main cavity, and the first wall surface and the second wall surface are both connected with the third wall surface; the third wall comprises a plurality of reflecting surfaces for transmitting light;

one of the first shell and the second shell is provided with a first mounting part and a protruding part, and the other shell is provided with a through hole; the protruding portion includes a first sub-portion and a second sub-portion extending from the first mounting portion toward the other housing, the second sub-portion being farther from the first mounting portion than the first sub-portion, at least a portion of the first sub-portion being located at the through hole, the second sub-portion being located outside the through hole, and the second sub-portion abutting against the housing located at a periphery of the through hole;

the light source is at least partially positioned in the first cavity and faces at least one reflecting surface;

a detector at least partially located in the second cavity and facing the at least one reflective surface.

In this application, because the at least part of first sub-portion is located the perforation, the second sub-portion is located outside the perforation, and the second sub-portion with be located perforation outlying casing looks butt to be favorable to first casing and second casing can utilize protruding portion and perforation cooperation to realize spacingly, thereby be favorable to reducing optical gas sensor's equipment part quantity, convenient assembly.

Drawings

FIG. 1 is a schematic diagram of a gas sensing device including an optical gas sensor in accordance with one embodiment of the present application;

FIG. 2 is a schematic view of an exploded view of the gas detection apparatus of FIG. 1;

FIG. 3 is a schematic diagram of an optical gas sensor provided in one embodiment of the present application;

FIG. 4 is a schematic diagram of an exploded view of the optical gas sensor of FIG. 3;

FIG. 5 is an exploded view of the optical gas sensor of FIG. 3 from another perspective;

FIG. 6 is a cross-sectional schematic view of an optical gas sensor according to an embodiment of the present application;

FIG. 7 is a cross-sectional view of another perspective of an optical gas sensor according to an embodiment of the present application;

FIG. 8 is a cross-sectional view of a gas detecting device with a light source according to an embodiment of the present disclosure;

FIG. 9 is a cross-sectional view of a gas detecting device with a probe according to an embodiment of the present disclosure;

fig. 10 is a schematic structural diagram of a top view corresponding to a partial structure of an optical gas sensor according to an embodiment of the present application.

Detailed Description

In order to make those skilled in the art better understand the technical solution of the present invention, the present invention will be further described in detail with reference to the accompanying drawings and specific embodiments.

With the advance of replacing the traditional refrigerant with the environment-friendly refrigerant, the industry finds that some environment-friendly refrigerants have flammability relative to the traditional refrigerant, thereby bringing safety hazards to air-conditioning systems. Therefore, whether the refrigerant leaks or not needs to be detected through the gas concentration detection device, so that the air conditioner control system can timely make a closing and alarm, and potential safety hazards caused by the environment-friendly refrigerant are reduced.

As shown in fig. 1 and 2, a gas detection apparatus 1 according to an embodiment of the present application includes: an optical gas sensor 10 and an outer envelope 20. The outer envelope 20 has an inner cavity so that at least part of the optical gas sensor 10 can be accommodated in the inner cavity. The outer envelope 20 is further provided with an air inlet passage 21 communicating with the inner cavity, the outer envelope 20 may include an upper envelope 22 and a lower envelope 23, the upper envelope 22 and the lower envelope 23 are assembled and fixed together in the direction H of fig. 1, and the upper envelope 22 and the lower envelope 23 may be snap-coupled. In assembly, the optical gas sensor 10 may be secured to the lower enclosure 23, such as by screws or snaps, and then the upper enclosure 22 may be secured to the lower enclosure 23.

In some embodiments, the gas detection device 1 may be used in an air conditioning system or a heat pump system to detect the concentration of a gaseous refrigerant, when a refrigerant leakage occurs in the air conditioning system or the heat pump system, the gaseous refrigerant enters the inner cavity of the outer casing 20 through the air inlet channel 21, and the optical gas sensor 10 can detect the concentration parameter of the gaseous refrigerant in time and feed the parameter back to a control system of the air conditioner, so as to reduce the potential safety hazard caused by the refrigerant leakage.

As shown in fig. 3 to 5, an optical gas sensor 10 according to an embodiment of the present disclosure includes a housing 3, and the housing 3 includes a first housing 11 and a second housing 12 that are separately disposed for easy assembly. The optical gas sensor 10 has a main chamber 100 that transmits light. The main chamber 100 is located between the first housing 11 and the second housing 12. In fig. 3, the first housing 11 and the second housing 12 are assembled together in the up-down direction. The upper housing is a first housing 11, and the lower housing is a second housing 12.

The optical gas sensor 10 also has a circuit board 13, a light source 14, and a detector 15, and the light source 14 and the detector 15 are mounted to the same side in the thickness direction of the circuit board 13 and are electrically connected to the circuit board 13. The light source 14 may be an infrared light source, an ultraviolet light source, a laser light source, or the like. In some embodiments, the light source 14 may be a MEMS type blackbody light source, with the peak of the light emitted by the light source 14 ranging from 1 μm to 16 μm. The detector 15 is a pyroelectric type or thermopile type detection probe, and in some embodiments, the detector 15 may be a dual-channel detection probe, that is, the detector 15 includes a detection channel and a reference channel which are independent of each other, and thus, both the detection channel and the reference channel are affected by temperature, humidity, cross interference between different gases, and the like. When the concentration calculation is realized, the ratio or the difference of the voltage output signals of the two can be used for improving the accuracy of detecting the gas concentration by the detection channel. Of course, in some application scenarios with less requirement on detection accuracy, the detector 15 may only have a detection channel, but not a reference channel, which is beneficial to saving cost. For example, in order to detect the concentration of the refrigerant R32 gas, and the main infrared absorption peak of the gas of R32 is 9 μm, the reference channel may use an optical filter that does not absorb the wavelength of the target gas, so that the infrared light intensities received by the reference channel and the detection channel are inconsistent, weak electrical signals generated by the reference channel and the detection channel are also different, and the calculation unit of the circuit board 13 may calculate the concentration of the refrigerant R32 gas through the processing of the circuit board 13. The light source 14 and detector 15 may both be T039 packages.

Referring to fig. 4, 8 and 9, the second housing 12 is provided with a first receiving cavity 30 and a second receiving cavity 40 arranged at a distance. Light source 14 is at least partially disposed in first volume 30 and detector 15 is at least partially disposed in second volume 40. Second housing 12 has a first wall 301 defining first volume 30 and a second wall 401 defining second volume 40, the housing having a third wall 101 defining main chamber 100, first wall 301 and second wall 401 each being connected to third wall 101. Thus, the first and

second cavities

30 and 40 and the main chamber 100 are in a communication state. The first housing 11 is provided with a plurality of vent holes 51, and the vent holes 51 communicate with the main chamber 100. Thus, the gas entering the inner cavity of the outer envelope 20 can enter the main chamber 100 via the vent hole 51 on the first housing 11.

The third wall 101 comprises several reflecting surfaces 52 for transmitting light. The light source 14 faces at least one reflective surface 52. The detector 15 faces at least one reflective surface 52. The reflective surfaces 52 facing the light source 14 and the detector 15 may be the same reflective surface 52 or different reflective surfaces 52. When the number of the reflecting surfaces 52 is plural, the light emitted from the light source 14 can be transmitted to the detector 15 after being reflected by the reflecting surfaces 52 for plural times. The light path structure formed by multiple reflections of the light path greatly improves the path length of light transmission, thereby being beneficial to enhancing the absorption effect of gas on light.

The detection principle of the optical gas sensor 10 is explained as follows, different gases have different absorption spectra due to differences in their molecular structures, concentrations and energy distributions. When detecting a target gas, the absorption of light of a characteristic wavelength by the target gas follows Lambert-Beer's law. When the light source 14 emits a light beam and transmits the light beam to the detector 15, the target gas absorbs light of a specific wavelength. The detector 15 can calculate information such as the concentration of the refrigerant gas by detecting the change in the light intensity.

Of course, in addition to the light source 14 and the detector 15, the circuit board 13 is mounted with a plurality of electronic components (not shown), and the surface of the circuit board 13 has a plurality of conductive paths (not shown) electrically connecting the electronic components and the light source 14, and the conductive paths electrically connecting the electronic components and the detector 15. The electronic components may include capacitors, resistors, inductors, and processing chips, among others. The processing chip can detect the signal of the concentration of the gaseous refrigerant and transmit the signal to an external control board or perform signal processing by the processing chip.

Further, the optical gas sensor 10 has a third cavity 50, the third cavity 50 is located between the second housing 12 and the circuit board 13, the optical gas sensor 10 further has a plurality of electronic components mounted on the circuit board 13, and at least a portion of the electronic components are accommodated in the third cavity 50. This makes it possible to make full use of the board surface space of the circuit board 13, and is advantageous for downsizing the optical gas sensor 10. The circuit board 13 and the second housing 12 may be fastened by screws 70. Specifically, the second housing 12 may be provided with screw holes 71, and the screw holes 71 are recessed from the side of the second housing 12 close to the circuit board 13 in a direction away from the circuit board 13, so that the screws 70 pass through the openings of the circuit board 13 and are finally fastened in the screw holes 71. There are, of course, many ways of securing the circuit board 13 to the second housing 12, and the present application is not intended to be limited thereto.

Referring to fig. 5 to 6, the first housing 11 has a first mounting portion 110 and a protrusion 111, and the second housing 12 is provided with a through hole 120. The protrusion 111 includes a first sub-portion 61 and a second sub-portion 62 extending from the first mounting portion 110 to be close to the second housing 12, the second sub-portion 62 is farther from the first mounting portion 110 than the first sub-portion 61, at least a portion of the first sub-portion 61 is located in the through hole 120, the second sub-portion 62 is located outside the through hole 120, and the second sub-portion 62 abuts against the housing structure of the second housing 12 located at the periphery of the through hole 120. The circuit board 13 is located at one side of the through hole 120 in the axial direction, and the first mounting portion 110 is located at the other side of the through hole 120 in the axial direction. The second housing 12 is limited between the second sub portion 62 and the first mounting portion 110. Thus, the first housing 11 and the second housing 12 can be limited and fixed by clamping. Of course, the first mounting portion 110 and the protruding portion 111 may also be located on the second housing 12, and the through hole 120 is located on the first housing 11, as long as the two housings can be limited and fixed by the above structure, which is not limited in this application.

In one embodiment of the present application, the number of the through holes 120 is two, and the number of the protrusions 111 is also two, and each protrusion 111 is correspondingly matched with one through hole 120. The first housing 11 further has a positioning column 112, the positioning column 112 extends from the first mounting portion 110 to a direction close to the second housing 12, the length of the positioning column 112 is smaller than the length of the protruding portion 111, and the positioning column 112 is located between the two protruding portions 111. The second housing 12 further has a positioning hole 121, and at least a portion of the positioning post 112 is received in the positioning hole 121. The positioning posts 112 and the positioning holes 121 can further realize the stable fixation of the first housing 11 and the second housing 12. The first housing 11 and the second housing 12 are not easily displaced and moved when subjected to an external force.

Referring to fig. 6 and 7, the first sub-portion 61 includes a root portion 611 and an intermediate portion 612, and the root portion 611 is connected between the intermediate portion 612 and the first mounting portion 110. The number of the intermediate portions 612 is two, and the two intermediate portions 612 are spaced apart from each other and are disposed to face each other. The outer peripheral surface of the intermediate portion 612 abuts at least a partial region of the inner surface of the second mounting portion 125 forming the through-hole 120.

The second sub-portion 62 includes two terminal portions 620, one of the two terminal portions 620 being connected to one of the intermediate portions 612 and the other terminal portion 620 being connected to the other of the intermediate portions 612. The distal end portion 620 protrudes relative to the intermediate portion 612 in a direction away from the axis of the bore 120. The distance between the outermost side in the protruding direction of one distal end portion 620 and the outermost side in the protruding direction of the other distal end portion 620 is greater than the inner diameter of the through hole 120. With this arrangement, when the first housing 11 and the second housing 12 are assembled, the two distal end portions 620 can be brought close to each other by an external force to pass through the through hole 120, and after the two distal end portions 620 are extended outward away from each other so that the outer peripheral surface of the middle portion 612 abuts against the inner surface of the second mounting portion 125 where the through hole 120 is formed, the two distal end portions 620 abut against the housing structure of the second housing 12 at the outer periphery of the through hole 120, so that the two distal end portions 620 are not easily removed from the through hole 120, and thus, the first housing 11 and the second housing 12 can be fixed without using a screw or the like, but can be fastened by matching the housing structures thereof.

To facilitate the transmission of light, referring to fig. 6, the first housing 11 further includes a recess 113, and the recess 113 is recessed from the first mounting portion 110 in a direction away from the second housing 12. The second housing 12 includes a lateral wall portion 122 and a longitudinal wall portion 123. The transverse wall portion 122 includes a second mounting portion 125 and a mating portion 126, the first mounting portion 110 and the second mounting portion 125 face each other at least in part, the recess 113 and the mating portion 126 face each other at least in part, and the main chamber 100 is located between the recess 113 and the mating portion 126. The second mounting portion 125 and the engaging portion 126 may be spaced apart by a partition 72, the partition 72 may extend from the transverse wall portion 122 toward the first housing 11, and correspondingly, the first housing 11 may be provided with a groove for engaging the partition 72, so that the first housing 11 and the second housing 12 may be positioned in a certain manner. The partition 72 also reduces the leakage of light from within the main chamber 100.

The vertical wall 123 extends from the second mounting portion 125 in a direction away from the first housing 11. The through hole 120 penetrates the second mounting portion 125 and the vertical wall portion 123. The thickness of the second housing 12 can be reduced to some extent by the transverse wall portion 122 and the longitudinal wall portion 123 which are engaged with each other, and the transverse wall portion 122 and the longitudinal wall portion 123 are also beneficial to extending the length of the through hole 120 in the axial direction, so as to improve the stability of the engagement between the first housing 11 and the second housing 12.

Referring to fig. 10, in some embodiments of the present application, second housing 12 is generally rectangular with rounded corners in cross-section, and second housing 12 includes a peripheral sidewall 124 extending from an edge of transverse wall portion 122 away from first housing 11, peripheral sidewall 124 circumferentially surrounding third cavity 50. The peripheral sidewall 124 includes a first sidewall 1241, a second sidewall 1242, a third sidewall 1243 and a fourth sidewall 1244 connected in sequence. The first and third sidewalls 1241 and 1243 are located at different sides in the length direction of the second case 12, respectively, and the second and

fourth sidewalls

1242 and 1244 are located at different sides in the width direction of the second case 12, respectively. The first and third sidewalls 1241 and 1243 are a set of parallel sidewalls, and the second and

fourth sidewalls

1242 and 1244 are a set of parallel sidewalls.

Of the four intersections formed by the plurality of side walls, the first volume 30 is closer to the intersection of the first and second side walls 1241, 1242 and the second volume 40 is closer to the intersection of the first and fourth side walls 1241, 1244. So that the light source 14 and the detector 15 are located at two corner positions of the second housing 12, respectively.

In some embodiments of the present application, the perforations 120 are further from the second side wall 1242 than the first volume 30, and the perforations 120 are further from the fourth side wall 1244 than the second volume 40. The perforation 120 is closer to the third sidewall 1243 than the first volume 30. Thus, the perforation 120 is located approximately at the center of the second housing 12. The clamping strength of the two shells is improved. The mating portion 126 forms a wall of the main chamber 100, a portion of which is located between the through-hole 120 and the second side wall 1242, a portion of which is located between the through-hole 120 and the third side wall 1243, and a portion of which is located between the through-hole 120 and the fourth side wall 1244. Thus, the space can be fully utilized and the optical path can be prolonged. After the light is emitted from the light source 14, it needs to be reflected and bent several times before it reaches the detector 15. This is advantageous for extending the optical path.

In an alternative embodiment to the reflected light path of the present application, the axial directions of the first cavity 30 and the second cavity 40 are parallel. Several reflecting surfaces 52 are provided on the surface of the recess 113 exposed to the main chamber 100. Light emitted by the light source 14 can be transmitted to the detector 15 after multiple reflections by the reflecting surface 52. The plurality of reflective surfaces 52 includes a first reflective surface 521 and a second reflective surface 522, the light source 14 facing the first reflective surface 521, and the detector 15 facing the second reflective surface 522. The first and second reflection surfaces 521 and 522 are inclined in a direction away from the second housing 12 with respect to the surface of the first mounting portion 110 close to the second housing 12, and the first reflection surface 521 is inclined at a larger angle than the second reflection surface 522. Referring to the illustrations of fig. 8 and 9, an angle at which the first reflecting surface 521 is inclined in a direction away from the second housing 12 with respect to the surface of the first mounting portion 110 close to the second housing 12 is denoted as β 1, an angle at which the second reflecting surface 522 is inclined in a direction away from the second housing 12 with respect to the surface of the first mounting portion 110 close to the second housing 12 is denoted as β 2, and β 1 is larger than β 2. This has the advantage that for the detector 15 receiving light, the more light enters the detector 15, the more light can be detected to a certain extent, and β 2 is relatively small, the larger the emitting area of light at the second reflecting surface 522, i.e. the more light can be reflected by the second reflecting surface 522 to the detector 15. For the light source 14 emitting light, the light emitted by the light source 14 is reflected at the first reflecting surface 521 with a larger inclination angle, and the incident area of the light at the first reflecting surface 521 is smaller, so that the first reflecting surface 521 can increase the convergence of the light source 14. In some embodiments of the present application, β 1 is at an angle of 45 ° and β 2 is at an angle of 30 °.

In some embodiments of the present application, the first housing 11 is made of plastic, and the recessed portion 113 is exposed to the inner surface of the main chamber 100 and plated with gold to form the reflecting surface 52. The second housing 12 may also be made of plastic, the first housing 11 made of plastic has low processing cost, and the two middle portions 612 of the protruding portion 111 extending from the first housing 11 have better elastic force, so as to be more convenient for installation and disassembly. In order to increase the light reflection capability of the plastic housing, a gold plating process may be performed on the inner surface of the first housing 11 to reduce the light transmission loss. Of course, the first housing 11 and the second housing 12 may be made of metal, such as stainless steel.

The optical gas sensor provided by the present invention has been described in detail above. The principles and embodiments of the present invention have been explained herein using specific examples, and the above descriptions of the embodiments are only used to help understand the core concepts of the present invention. It should be noted that, for those skilled in the art, without departing from the principle of the present invention, the present invention can be further modified and modified, and such modifications and modifications also fall within the protection scope of the appended claims.

Claims

1. An optical gas sensor, characterized in that it has a main chamber (100); the optical gas sensor further includes:

a housing (3), the housing (3) comprising a first housing (11) and a second housing (12); the main chamber (100) is located between the first casing (11) and the second casing (12); the second shell (12) is also provided with a first accommodating cavity (30) and a second accommodating cavity (40) which are arranged at intervals; -said second shell (12) has a first wall (301) forming said first volume (30) and a second wall (401) forming said second volume (40), -said shell (3) has a third wall (101) forming said main chamber (100), -said first wall (301) and said second wall (401) are both connected to said third wall (101); the third wall (101) comprises a plurality of reflecting surfaces (52) for transmitting light;

one of the first case (11) and the second case (12) has a first mounting portion (110) and a protruding portion (111), and the other case is provided with a through hole (120); said protrusion (111) comprising a first sub-portion (61) and a second sub-portion (62) extending from said first mounting portion (110) closer to the other housing, said second sub-portion (62) being further from said first mounting portion (110) than said first sub-portion (61), at least part of said first sub-portion (61) being located at said perforation (120), said second sub-portion (62) being located outside said perforation (120), and said second sub-portion (62) being in abutment with the housing located at the periphery of said perforation (120);

a light source (14), said light source (14) being at least partially located within said first volume (30) and facing at least one of said reflective surfaces (52);

a detector (15), said detector (15) being at least partially located in said second volume (40) and facing at least one of said reflecting surfaces (52).

2. The optical gas sensor according to claim 1, further comprising a circuit board (13); the circuit board (13) is fixed with the second shell (12), and the light source (14) and the detector (15) are both electrically connected with the circuit board (13);

the first shell (11) comprises the first mounting part (110) and the protruding part (111), and the through hole (120) is arranged on the second shell (12); the circuit board (13) is positioned on one side of the axial direction of the through hole (120), and the first mounting part (110) is positioned on the other side of the axial direction of the through hole (120); the second shell (12) is limited between the second sub-portion (62) and the first mounting portion (110).

3. Optical gas sensor according to claim 2, characterized in that the first subsection (61) comprises a root portion (611) and an intermediate portion (612), the root portion (611) being connected between the intermediate portion (612) and the first mounting portion (110); the number of the middle parts (612) is two, and the two middle parts (612) are arranged at intervals and opposite to each other; the outer peripheral surface of the intermediate part (612) abuts against at least partial region of the inner surface of the second shell (12) forming the perforation (120);

the second sub-portion (62) comprises two end portions (620), one (620) of the two end portions (620) being connected to one of the intermediate portions (612) and the other end portion (620) being connected to the other of the intermediate portions (612); the tip portion (620) protrudes relative to the intermediate portion (612) in a direction away from an axis of the through-hole (120); the distance between the outermost side in the protruding direction of one end portion (620) and the outermost side in the protruding direction of the other end portion (620) is larger than the inner diameter of the through hole (120).

4. The optical gas sensor according to claim 2, wherein the first housing (11) further comprises a recess (113), the recess (113) being recessed from the first mounting portion (110) in a direction away from the second housing (12);

the second housing (12) includes a transverse wall portion (122) and a longitudinal wall portion (123); the transverse wall portion (122) comprises a second mounting portion (125) and a mating portion (126), the first mounting portion (110) and the second mounting portion (125) face each other at least in part, the recess (113) and the mating portion (126) face each other at least in part, and the main chamber (100) is located between the recess (113) and the mating portion (126);

the longitudinal wall portion (123) extends from the second mounting portion (125) in a direction away from the first housing (11); the through hole (120) penetrates the second mounting portion (125) and the longitudinal wall portion (123).

5. The optical gas sensor according to claim 4, wherein the second housing (12) further comprises a peripheral sidewall (124) extending from an edge of the transverse wall portion (122) away from the first housing (11), the peripheral sidewall (124) comprising a first sidewall (1241), a second sidewall (1242), a third sidewall (1243) and a fourth sidewall (1244) connected in sequence; the first side wall (1241) and the third side wall (1243) are respectively located on different sides in the length direction of the second case (12), and the second side wall (1242) and the fourth side wall (1244) are respectively located on different sides in the width direction of the second case (12);

of the four intersections formed by the side walls, the first plenum (30) is closer to the intersection of the first side wall (1241) and the second side wall (1242), and the second plenum (40) is closer to the intersection of the first side wall (1241) and the fourth side wall (1244);

said perforations (120) being further from said second side wall (1242) than said first volume (30), said perforations (120) being further from said fourth side wall (1244) than said second volume (40); said perforations (120) being closer to said third side wall (1243) than said first volume (30);

the mating portion (126) forms a wall of the main chamber (100) that is located partially between the bore (120) and the second sidewall (1242), partially between the bore (120) and the third sidewall (1243), and partially between the bore (120) and the fourth sidewall (1244).

6. Optical gas sensor according to claim 2, characterized in that the number of said perforations (120) is two and the number of said protrusions (111) is also two, each protrusion (111) cooperating with a respective one of said perforations (120);

the first shell (11) is further provided with a positioning column (112), the positioning column (112) extends from the first mounting part (110) to a direction close to the second shell (12), the length of the positioning column (112) is smaller than that of the protruding part (111), and the positioning column (112) is located between the two protruding parts (111);

the second shell (12) is further provided with a positioning hole (121), and at least part of the positioning column (112) is contained in the positioning hole (121).

7. The optical gas sensor according to claim 4, characterized in that the axial directions of the first volume (30) and the second volume (40) are parallel; the reflecting surfaces (52) are arranged on the surface of the concave part (113) exposed to the main chamber (100); the light emitted by the light source (14) can be transmitted to the detector (15) after being reflected for multiple times by the reflecting surface (52).

8. The optical gas sensor according to claim 7, wherein the number of reflecting surfaces (52) comprises a first reflecting surface (521) and a second reflecting surface (522), the light source (14) facing the first reflecting surface (521), the detector (15) facing the second reflecting surface (522);

the first reflecting surface (521) and the second reflecting surface (522) are both inclined in a direction away from the second housing (12) with respect to the surface of the first mounting portion (110) close to the second housing (12), and the angle at which the first reflecting surface (521) is inclined is greater than the angle at which the second reflecting surface (522) is inclined.

9. Optical gas sensor according to claim 2, characterized in that the circuit board (13) and the second housing (12) are fastened by screws.

10. The optical gas sensor according to claim 5, characterized in that it has a third volume (50), said third volume (50) being located between said second housing (12) and said circuit board (13), said peripheral side wall (124) circumferentially surrounding said third volume (50);

the optical gas sensor is also provided with a plurality of electronic components arranged on the circuit board (13), and at least part of the electronic components are accommodated in the third accommodating cavity (50);

the first shell (11) is provided with a plurality of vent holes (51), and the vent holes (51) are communicated with the main cavity (100);

the first shell (11) is made of plastic, and the concave part (113) is exposed to the inner surface of the main cavity (100) and plated with gold to form the reflecting surface (52).