PM2.5 sensor

Abstract

The utility model relates to a PM2.5 sensor which comprises a shell with an inner cavity, a circuit board with a photodiode is arranged in the inner cavity, a sheath flow channel and a sampling flow channel for airflow entering the shell to pass through are arranged in the inner cavity, the sheath flow channel comprises a front section flow channel and a rear section flow channel which are communicated with each other, and a filtering structure is arranged between the front section flow channel and the rear section flow channel. The front-section flow channel is not in contact with the photodiode, the extending path of the rear-section flow channel covers the area where the photodiode is located, the front-section flow channel is communicated with the sampling flow channel, and the sampling flow channel is located on the side, away from the circuit board, of the rear-section flow channel. According to the utility model, since the rear-section flow channel and the sampling flow channel are laminar flow, the rear-section flow channel does not influence the sampling accuracy caused by external airflow passing through the sampling flow channel, and the rear-section flow channel of the sheath flow channel blows clean airflow filtered by the filtering structure towards the photodiode, so that the photodiode is not easy to be polluted by dust; therefore, the use precision and the service life of the photodiode are not affected.

Description

Technical Field

[0001] The utility model relates to the technical field of sensors, in particular to a PM2.5 sensor. Background Art

[0002] When it comes to air quality, PM2.5 levels are a key indicator. PM2.5 refers to particles with an aerodynamic equivalent diameter of 2.5 microns or less in ambient air. They remain suspended in the air for extended periods, and higher concentrations indicate more severe air pollution. Compared to coarser atmospheric particulate matter, PM2.5 particles are smaller, larger, and more reactive, easily carrying toxic and harmful substances. They also reside in the atmosphere for longer periods and travel greater distances, resulting in a greater impact on human health and atmospheric environmental quality. With rising public awareness of health, air quality monitoring and air purification products have garnered widespread attention. With the high level of exposure to cars in daily life, in-vehicle PM2.5 particle detection equipment has become a focus of attention, following in the footsteps of household PM2.5 detectors.

[0003] As people's requirements for air quality gradually increase, monitoring the specific content of PM2.5 has become an important technical issue. Due to the small particle size of PM2.5, general physical monitoring methods are not applicable. Laser monitoring is currently an important monitoring method. By utilizing the scattering properties of PM2.5 particles in the air and using laser combined with photoelectric signal acquisition, the PM2.5 content can be effectively monitored.

[0004] However, for traditional monitoring instruments, since the PM2.5 sensor is in working condition for a long time, it is easy to cause the sedimentation and accumulation of dust particles in the air. The photodiodes in existing laser PM2.5 sensors are easily contaminated by dust. The sedimentation of dust particles will greatly affect the accuracy of the photodiode and even affect its service life.

[0005] In addition, due to the popularity of electric vehicles in the automotive industry, the ambient noise inside the car is decreasing. However, on-board PM2.5 sensors are generally installed close to the passenger compartment, and their vibration and noise are easily complained by passengers. How to reduce the noise generated by the operation of PM2.5 sensors has become an urgent problem to be solved. Utility Model Content

[0006] The purpose of the present invention is to provide a PM2.5 sensor that can at least solve some of the defects in the prior art.

[0007] To achieve the above-mentioned purpose, an embodiment of the present utility model provides the following technical solution: a PM2.5 sensor, comprising a shell having an inner cavity, a circuit board having a photodiode provided in the inner cavity, a sheath air flow channel and a sampling flow channel for the air flow entering the shell to pass through the inner cavity, the sheath air flow channel comprising a connected front section flow channel and a rear section flow channel, a filtering structure being provided between the front section flow channel and the rear section flow channel, the front section flow channel not contacting the photodiode, the path extending from the rear section flow channel covering the area where the photodiode is located, the front section flow channel being connected to the sampling flow channel, and the sampling flow channel being located on the side of the rear section flow channel away from the circuit board.

[0008] Furthermore, an inertial flow channel is provided in the inner cavity, and the shell has an air inlet for external air flow to enter the shell and an air outlet for air flow to discharge from the shell, the air inlet and the air outlet are respectively located at the head end and the tail end of the inertial flow channel, and the inertial flow channel is connected to the sampling flow channel.

[0009] Furthermore, a baffle is provided in the inner cavity, the baffle is arranged opposite to the air inlet, and the baffle is located at the connection point between the inertial flow channel and the sampling flow channel.

[0010] Furthermore, a boss is provided in the inner cavity, and the path along which the sampling flow channel extends passes through the area where the boss is located, and the area where the boss is located is the sampling area.

[0011] Furthermore, a fan and a partition are provided in the inner cavity, the circuit board, the partition and the fan are stacked in sequence, and the sampling flow channel is provided on a side of the fan away from the partition.

[0012] Furthermore, the partition is provided with a through hole and an opening, the rear section flow channel is located on the side of the partition away from the fan, and the front section flow channel is located on the side of the partition close to the fan. The front section flow channel and the rear section flow channel are connected through the through hole, and the rear section flow channel passes through the opening and flows back to the side of the partition close to the fan.

[0013] Furthermore, the opening is a sloped opening, and the lowest end of the sloped opening is located higher than a position where the photodiode protrudes from the surface of the circuit board.

[0014] Furthermore, a cushion is provided in the inner cavity, and the fan is sandwiched between the partition and the cushion.

[0015] Furthermore, the housing includes an upper cover and a lower cover, and the sampling flow channel is formed in the lower cover.

[0016] Furthermore, it also includes a light emitter that emits light toward the space facing the photodiode.

[0017] Compared with the prior art, the beneficial effects of the present invention are: a PM2.5 sensor, since the rear section flow channel and the sampling flow channel are laminar flow, the rear section flow channel will not affect the external airflow passing through the sampling flow channel and affect the sampling accuracy. The rear section flow channel of the sheath air flow channel blows the clean airflow filtered by the filtering structure toward the photodiode, and can also reduce the probability of particulate matter adhering to the photodiode, so that the photodiode is not easily contaminated by dust, thereby not affecting the use accuracy and service life of the photodiode. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 An explosion diagram of a PM2.5 sensor provided in an embodiment of the present utility model;

[0019] Figure 2 A schematic diagram showing a PM2.5 sensor provided by an embodiment of the present invention, wherein the fan is mounted on the lower cover, as viewed from above;

[0020] Figure 3 for Figure 2 A schematic diagram of the inertial flow channel is shown (the arrow direction is a schematic diagram of the flow direction of the airflow in the inertial flow channel, and the black dots are schematic diagrams of large particles);

[0021] Figure 4 for Figure 2 A schematic diagram of the sampling flow channel is shown (the arrow direction is a schematic diagram of the flow direction of the airflow in the sampling flow channel, and the black box is a schematic diagram of the sampling area);

[0022] Figure 5 A schematic vertical cross-sectional view of the lower cover of a PM2.5 sensor provided in an embodiment of the present invention (illustrating the boss);

[0023] Figure 6 A schematic diagram of the partial structure of the lower cover of a PM2.5 sensor provided by an embodiment of the present utility model (showing the front section of the sheath gas flow channel);

[0024] Figure 7 A schematic diagram of the partial structure of a partition of a PM2.5 sensor provided by an embodiment of the present utility model (showing the rear section of the sheath gas flow channel, the circular hole, and the opening);

[0025] Figure 8 A partial cross-sectional schematic diagram of a PM2.5 sensor provided by an embodiment of the present invention (the arrow direction indicates the flow direction of the airflow in the front section of the sheath airflow channel);

[0026] Figure 9 A partial cross-sectional schematic diagram of a PM2.5 sensor provided by an embodiment of the present invention (the arrow indicates the direction of airflow in the rear section of the sheath airflow channel);

[0027] In the accompanying drawings: 1-upper cover; 2-circuit board; 3-partition; 4-fan; 5-filter structure; 6-laser emitter; 7-cushion; 8-lower cover; 9-air inlet; 10-air outlet; 11-inertial flow channel; 12-sampling flow channel; 13-front section flow channel; 14-baffle; 15-sampling area; 16-boss; 17-support column; 18-rear section flow channel; 19-through hole; 20-opening; 21-photodiode; 22-inlet of sheath flow channel. DETAILED DESCRIPTION

[0028] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] See also Figure 1 、 Figure 4 、 Figures 6 to 9An embodiment of the utility model provides a PM2.5 sensor, comprising a shell having an inner cavity, a circuit board 2 having a photodiode 21 being provided in the inner cavity, a sheath flow channel and a sampling flow channel 12 for the airflow entering the shell to pass through being provided in the inner cavity, the sheath flow channel comprising a front section flow channel 13 and a rear section flow channel 18 being connected, a filtering structure 5 being provided between the front section flow channel 13 and the rear section flow channel 18, the front section flow channel 13 not contacting the photodiode 21, the path along which the rear section flow channel 18 extends covering the area where the photodiode 21 is located, the front section flow channel 13 being connected to the sampling flow channel 12, and the sampling flow channel 12 being located on the side of the rear section flow channel 18 away from the circuit board 2. In this embodiment, since the rear section flow channel 18 and the sampling flow channel 12 are laminar flows, the rear section flow channel 18 will not affect the external airflow passing through the sampling flow channel 12 and affect the sampling accuracy. The rear section flow channel 18 of the sheath flow channel blows the clean airflow filtered by the filter structure 5 toward the photodiode 21, and can also reduce the probability of particulate matter adhering to the photodiode 21, making the photodiode 21 less susceptible to dust contamination, thereby not affecting the accuracy and service life of the sensor. A sheath flow channel and a sampling flow channel 12 are designed in the inner cavity, wherein the function of the sampling flow channel 12 is to sample the air entering the cavity. During the sampling process, the photodiode 21 may be contaminated by particulate matter, resulting in low measurement accuracy. The function of the designed sheath flow channel is to reduce the probability of particulate matter adhering to the photodiode 21. Specifically, the sheath flow channel can be divided into a front section flow channel 13 and a rear section flow channel 18, wherein the front section flow channel 13 is connected to the sampling flow channel 12, and the airflow in the sampling flow channel 12 can enter the sheath flow channel and enter the front section. The airflow in the first section flow channel 13 will enter the rear section flow channel 18. The airflow entering the front section flow channel 13 from the sampling flow channel 12 contains particulate matter. After filtering through the filtering structure 5, a clean airflow can be obtained. Since the path extending from the rear section flow channel 18 covers the area where the photodiode 21 is located, or in other words, the flow channel flows through the area where the photodiode 21 is located, when the clean airflow blows through the photodiode 21, the particulate matter in the airflow of the sampling flow channel 12 can be prevented from contaminating the photodiode 21, thereby realizing the self-cleaning of the PM2.5 sensor. Since the sampling channel 12 is located on the side of the rear section channel 18 away from the circuit board 2, it is equivalent to that the sampling channel 12 and the rear section channel 18 form a laminar flow. For example, when the circuit board 2 is placed horizontally, the photodiode 21 is arranged on the lower surface of the circuit board 2 and protrudes downward. At this time, the clean airflow in the rear section channel 18 flows close to the photodiode 21, and the sampling airflow in the sampling channel 12 flows below the clean airflow. The clean airflow can block the sampling airflow to form a blocking barrier. In this way, compared with the sensor without the design of the rear section channel 18, the cleanliness of the photodiode 21 can be greatly improved, thereby ensuring the detection accuracy of the photodiode 21.Since the sampling channel 12 is located below the rear channel 18, a laminar flow is formed, and the sampling channel 12 and the rear channel 18 do not interfere with or affect each other. Figure 4 In the diagram, the arrow points to the sampling channel 12. The sampling airflow passes through the sampling channel 12 in the direction of the arrow and is finally sampled at the sampling area 15 in the black box, where the photodiode 21 is located. The sampling channel 12 can be separated by a plate structure in the inner cavity to limit the airflow to flow only along this channel, such as in Figure 4 In the figure, it can be seen that the sampling airflow is walking around a frame structure, which is constructed by the plate body. Preferably, a fan 4 can be set to attract the airflow, such as Figure 4 As shown, a fan 4 is designed on the left side of the inner cavity, and the fan 4 guides the sampled airflow to the left side and then discharges the inner cavity from the air outlet 10. The following embodiment will further explain in detail how the sheath airflow channel is formed.

[0030] As an optimization solution of the embodiment of the utility model, please refer to Figures 1 to 3 , an inertial flow channel 11 is provided in the inner cavity, and the shell has an air inlet 9 for external air flow to enter the shell and an air outlet 10 for air flow to discharge from the shell. The air inlet 9 and the air outlet 10 are respectively located at the head end and the tail end of the inertial flow channel 11, and the inertial flow channel 11 is connected with the sampling flow channel 12. In this embodiment, the inertial flow channel 11 is designed based on the principle that there is no obstruction when the air flow outside the shell enters the inner cavity and it is closest to the air outlet 10, so the air flow rate is the largest. Since the air flow rate here is large and there is no obstruction, large particles of dust with large inertia that do not need to be detected and are likely to cause pollution to the photodiode 21 can directly enter the inertial flow channel 11 and be discharged from the air outlet 10. This part of large particles of dust does not belong to PM2.5 and does not need to be detected. Figure 3 As shown, the black dots represent large particles, which are directly discharged from the cavity through the inertial flow channel 11 indicated by the arrow. In particular, when combined with the airflow driven by the rotation of fan 4, large particles can be extracted to the greatest extent possible. The combined effect of these three flow channels significantly reduces dust accumulation during long-term operation of the PM2.5 sensor, effectively ensuring the accuracy and service life of the PM2.5 sensor.

[0031] To further optimize the above solution, please refer to Figures 1 to 3 , a baffle 14 is provided in the inner cavity, the baffle 14 is arranged opposite to the air inlet 9, and the baffle 14 is located at the connection point between the inertial flow channel 11 and the sampling flow channel 12. In this embodiment, Figure 3As shown, the baffle 14 is designed to be arranged opposite the air outlet 10, which can guide most of the airflow to the inertial flow channel 11. Large particles enter the inertial flow channel 11 along with the large airflow, reducing the probability of large dust particles entering the sampling flow channel 12. Preferably, the size of the baffle 14 is larger than that of the air inlet 9.

[0032] As an optimization solution of the embodiment of the utility model, please refer to Figure 4 and Figure 5 A boss 16 is provided in the inner cavity, and the sampling channel 12 extends through the area where the boss 16 is located. The boss 16 is the sampling area 15. In this embodiment, the design of the boss 16 can maximize the speed of the sampling airflow passing through the sampling area 15, greatly reducing the probability of dust settling and accumulating in the sampling area 15.

[0033] As an optimization solution of the embodiment of the utility model, please refer to Figure 1 and Figure 2 , a fan 4 and a partition 3 are provided in the inner cavity, the circuit board 2, the partition 3 and the fan 4 are stacked in sequence, and the sampling flow channel 12 is provided on the side of the fan 4 away from the partition 3. In this embodiment, the function of the fan 4 is to drain the flow, and the partition 3 is designed to separate the circuit board 2 and the fan 4. Figure 1 In the orientation shown, the sampling flow channel 12 and the above-mentioned inertial flow channel 11 are both located at the lowermost layer, and are arranged in the lower cover 8.

[0034] To further optimize the above solution, please refer to Figure 6 、 Figure 7 、 Figure 8 and Figure 9 , the partition 3 is provided with a through hole 19 and an opening 20, the rear section flow channel 18 is located on the side of the partition 3 away from the fan 4, the front section flow channel 13 is located on the side of the partition 3 close to the fan 4, the front section flow channel 13 and the rear section flow channel 18 are connected through the through hole 19, and the rear section flow channel 18 flows back to the side of the partition 3 close to the fan 4 through the opening 20. In this embodiment, the rear section flow channel 18 and the front section flow channel 13 of the above-mentioned sheath flow channel can be distinguished from the through hole 19, or can be distinguished by the above-mentioned filtering structure 5. In fact, the definition of the front section flow channel 13 and the rear section flow channel 18 is for the convenience of describing the inlet 22 of the sheath flow channel and the sheath flow channel extending to pass through the photodiode 21. There is no particularly clear distinction between the two. Under the action of the fan 4, the airflow in the sheath flow channel can be guided from the bottom layer to the upper layer, such as Figure 8As shown, after the airflow is guided to the top of the partition 3, it flows back from the opening 20 to the bottom of the partition 3 and returns to the sampling area 15 of the sampling channel 12. Of course, in addition to the above-mentioned method of guiding the flow channel vertically and then returning it, the sheath flow channel can also be constructed using other methods using a plate body. For example, it is feasible to form a sheath flow channel by making a circle in a plane, as long as laminar flow can be formed. This embodiment does not limit this.

[0035] To further optimize the above solution, please refer to Figure 6 、 Figure 7 、 Figure 8 and Figure 9 The opening 20 is a sloped opening, and the lowest end of the sloped opening is positioned higher than the position where the photodiode 21 protrudes from the surface of the circuit board 2. In this embodiment, the opening 20 is designed as a sloped opening, and the height of the sloped opening is designed to be slightly higher than the height of the photodiode 21 on the circuit board 2. This allows the clean airflow to flow out closely to the surface of the photodiode due to viscosity, forming a sheath gas protective layer of clean air on its surface.

[0036] As an optimization solution of the embodiment of the utility model, please refer to Figure 6 A support column 17 is provided in the front section flow channel 13 of the sheath flow channel, and the above-mentioned filter structure 5 is provided on this support column 17. The filter structure 5 is preferably a dust-proof filter paper. There are multiple support columns 17 for supporting and placing the dust-proof filter paper.

[0037] As an optimization solution of the embodiment of the utility model, please refer to Figure 1 A soft pad 7 is provided in the inner cavity, and the fan 4 is sandwiched between the partition 3 and the soft pad 7. In this embodiment, the soft pad 7 is used to support the fan 4 and reduce the vibration transmission of the fan 4. Specifically, the vibration and noise generated by the fan 4 during rotation are greatly reduced by the soft pad 7 covering it. Preferably, the partition 3 is a soft board, which can also cooperate with the soft pad 7 to reduce the vibration of the fan 4. In addition, the partition 3 can also support the circuit board 2 and form a seal with the lower cover 8.

[0038] As an optimization solution of the embodiment of the utility model, please refer to Figure 1 The housing includes an upper cover 1 and a lower cover 8, and the sampling flow channel 12 is formed in the lower cover 8. In this embodiment, the housing is composed of the upper cover 1 and the lower cover 8.

[0039] As an optimization solution of the embodiment of the utility model, please refer to Figure 1, the sensor also includes a light emitter that emits light toward the space directly facing the photodiode 21. In this embodiment, the light emitter can be a laser emitter, or other emitters such as infrared light. For example, when a laser emitter is used, the circuit board 2 is placed horizontally according to the horizontal circuit board 2 mentioned in the above embodiment, and the photodiode 21 is provided on the lower surface of the circuit board 2, protruding downward. The laser emitted by the laser emitter is emitted toward the space below the photodiode 21. Due to the presence of particulate matter in the airflow in the space below the photodiode 21, the particulate matter will scatter the laser to the photodiode 21. After receiving the scattered light, the photodiode 21 converts the optical signal into an electrical signal, which is received and processed by the circuit board 2 and then outputted to obtain the PM2.5 value. This is a prior art, and a more detailed working principle will not be provided here.

[0040] Although the embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A PM2.5 sensor comprising a housing having an inner cavity, wherein a circuit board having a photodiode is disposed in the inner cavity, characterized in that: A sheath flow channel and a sampling flow channel for the air flow entering the shell are provided in the inner cavity. The sheath flow channel includes a front section flow channel and a rear section flow channel that are connected. A filtering structure is provided between the front section flow channel and the rear section flow channel. The front section flow channel does not contact the photodiode. The path along which the rear section flow channel extends covers the area where the photodiode is located. The front section flow channel is connected to the sampling flow channel, and the sampling flow channel is located on the side of the rear section flow channel away from the circuit board.

2. The PM2.5 sensor according to claim 1, wherein: An inertial flow channel is provided in the inner cavity, and the shell has an air inlet for external air flow to enter the shell and an air outlet for air flow to discharge from the shell. The air inlet and the air outlet are respectively located at the head end and the tail end of the inertial flow channel, and the inertial flow channel is connected to the sampling flow channel.

3. The PM2.5 sensor according to claim 2, wherein: A baffle is provided in the inner cavity, the baffle is arranged opposite to the air inlet, and the baffle is located at the connection point between the inertial flow channel and the sampling flow channel.

4. The PM2.5 sensor according to claim 1, wherein: A boss is provided in the inner cavity, and the path along which the sampling flow channel extends passes through the area where the boss is located, and the area where the boss is located is the sampling area.

5. The PM2.5 sensor according to claim 1, wherein: A fan and a partition are provided in the inner cavity. The circuit board, the partition and the fan are stacked in sequence. The sampling flow channel is provided on a side of the fan away from the partition.

6. The PM2.5 sensor according to claim 5, characterized in that: The partition is provided with a through hole and an opening, the rear section flow channel is located on the side of the partition away from the fan, and the front section flow channel is located on the side of the partition close to the fan. The front section flow channel and the rear section flow channel are connected through the through hole, and the rear section flow channel flows back through the opening to the side of the partition close to the fan.

7. The PM2.5 sensor according to claim 6, characterized in that: The opening is a slope-shaped opening, and the lowest end of the slope-shaped opening is located higher than the position where the photodiode protrudes from the surface of the circuit board.

8. The PM2.5 sensor according to claim 5, characterized in that: A soft cushion is provided in the inner cavity, and the fan is sandwiched between the partition plate and the soft cushion.

9. The PM2.5 sensor according to claim 1, wherein: The housing comprises an upper cover and a lower cover, and the sampling flow channel is formed in the lower cover.

10. The PM2.5 sensor according to claim 1, characterized in that: Also included is a light emitter that emits light toward the space facing the photodiode.

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