WO2020090503A1

WO2020090503A1 - Pm sensor

Info

Publication number: WO2020090503A1
Application number: PCT/JP2019/040929
Authority: WO
Inventors: 俊輔石黒; 熊田　辰己; 尚敬石山; 河合　孝昌
Original assignee: 株式会社デンソー
Priority date: 2018-10-31
Filing date: 2019-10-17
Publication date: 2020-05-07
Also published as: JP7206814B2; CN112930472A; DE112019005395T5; JP2020071140A

Abstract

This PM sensor comprises: an optical element (221-223) for detecting particulate matter; an inner case (213, 214) that accommodates the optical element and forms a first air flow path (231); and an outer case (211, 212) that forms, between the outer case and inner case, a second air flow path (232) through which air flows so as to bypass the first air flow path. The outer case has, formed therein, an outside inflow opening (211a) for allowing air to flow into the second air flow path and an outside outflow opening (211b) for allowing the air of the second air flow path to flow outside of the outer case. The inner case has, formed therein, an inside outflow opening (214b) for allowing air to flow out from the first air flow path. After some air that has flowed in from the outside inflow opening flows into the first air flow path and the rest flows into the second air flow path, air that has flowed out from the inside outflow opening and air flowing through the second air flow path merge and are discharged to the outside from the outside outflow opening. Pressure reduction in the pressure reduction area formed at the section where air that has flowed out from the inside outflow opening and air flowing through the second air flow path merge is suppressed.

Description

PM sensor

Cross-reference to related application

This application is based on Japanese Patent Application No. 2018-205656 filed on October 31, 2018, the description of which is incorporated herein by reference.

The present disclosure relates to a PM sensor that detects particulate matter contained in air.

Conventionally, there is one disclosed in Patent Document 1 as a ventilation device having a dust sensor. This ventilation device includes a dust sensor having a light emitting unit and a light receiving unit, and the light receiving unit receives scattered light when the light emitted from the light emitting unit hits the floating particles, thereby floating particles in the air. Is being detected.

JP, 2008-24032, A

The present inventors are studying to provide a vehicle air conditioner with a function of detecting the concentration of particles floating in the air like the dust sensor described in Patent Document 1. FIG. 9 is a configuration diagram of the PM sensor 90 under consideration by the present inventors. The PM sensor 90 includes a light emitting element 221, a light receiving element 222, a mirror 223, a sensor substrate 220, and a case 21 that houses them.

The case 21 has a first outer case 211, a second outer case 212, a first inner case 213, and a second inner case 214. The first outer case 211 and the second outer case 212 form an outer case, and the first inner case 213 and the second inner case 214 form an inner case.

A detection flow path 231 through which particles to be detected flow is formed inside the

inner cases

213 and 214. A space is provided between the

outer cases

211, 212 and the

inner cases

213, 214 in order to reduce the impact from the outside on the

inner cases

213, 214 that house optical components such as the light emitting element 221, the light receiving element 222, and the mirror 223. Has been formed. This space is called the non-detection flow path 232. Air also flows through this non-detection flow path 232. The detection flow channel 231 corresponds to the first air flow channel, the non-detection flow channel 232 corresponds to the second air flow channel, and the light emitting element 221, the light receiving element 222, the mirror 223, and the like correspond to optical elements.

The

outer cases

211 and 212 are formed with an outer inflow port 211a that allows air to flow into the non-detection flow channel 232 and an outer outflow port 211b that allows air in the non-detection flow channel 232 to flow out of the

outer cases

211 and 212. .. The outer outlet 211b corresponds to the first outer outlet. Further, the

inner case

213, 214 is formed with an inner outlet port 214b for letting air out from the detection flow path 231.

Then, a part of the air that has flowed into the

outer cases

211 and 212 from the outer inlet 211a flows into the detection flow channel 231, and the rest of the air that has flowed into the

outer cases

211 and 212 flows into the non-detection flow channel 232. After flowing in, the air flowing out from the inner outlet 214b of the detection flow channel 231 and the air flowing in the non-detection flow channel 232 join together and are discharged from the outer flow outlet 211b to the outside of the

outer cases

211, 212. There is.

The PM sensor 90 detects particles in the air by receiving light scattered by the light receiving element 222 when light emitted from the light emitting element 221 hits particles in the air flowing through the detection channel 231.

By the way, the PM sensor 90 has a low-pass filter for removing noise included in the signal output from the light receiving element 222. The low pass filter removes noise contained in the signal output from the light receiving element 222, and it is possible to accurately detect the presence or absence and the concentration of particles in the air.

However, when the air volume of the air flowing through the air conditioning unit in the vehicle air conditioner increases and the velocity of the particles of the air flowing through the detection flow path 231 increases, the effect of the low-pass filter decreases the particle detection capability of the PM sensor 90. I will end up. Therefore, there is a problem in that it becomes impossible to accurately detect the presence and concentration of particles in the air.

The present disclosure is intended to improve the detection accuracy of particulate matter contained in air.

According to one aspect of the present disclosure, a PM sensor that detects particulate matter contained in air includes an optical element for detecting the particulate matter, and a first air flow path that accommodates the optical element and allows air to flow. And an outer case that forms a second air flow path between the inner case and the inner case in which air bypasses the first air flow path. The outer case is formed with an outer inlet for letting air into the second air passage and an outer outlet for letting air out of the second air passage out of the outer case. An inner outlet that allows air to flow out from the passage is formed, and a portion of the air that has flowed into the outer case from the outer inlet flows into the first air flow path and the rest of the air that has flowed into the outer case is the first. After flowing into the second air passage, the air flowing out from the inner outlet of the first air passage and the air flowing in the second air passage merge and are discharged from the outer outlet to the outside of the outer case. ing. Further, it has a structure in which the pressure drop in the pressure drop region that occurs at the confluence of the air flowing out from the inner outlet and the air flowing in the second air passage is suppressed.

According to the above configuration, the present PM sensor has a structure that suppresses the pressure drop in the pressure drop region that occurs at the confluence of the air flowing out from the inner outlet and the air flowing through the second air passage. Therefore, the velocity of the air flowing through the first air flow path is suppressed, and the detection accuracy of particles in the air can be improved.

Note that the reference numerals in parentheses attached to the respective constituent elements and the like indicate an example of a correspondence relationship between the constituent elements and the like and specific constituent elements and the like described in the embodiments described later.

It is the whole air-conditioner lineblock diagram for vehicles provided with a PM sensor of a 1st embodiment. It is a schematic sectional drawing of the PM sensor of 1st Embodiment. It is a block diagram of a light receiving circuit. It is the figure which showed the frequency characteristic of the detection capability of a PM sensor. FIG. 10 is a partially enlarged view of FIG. 9. FIG. 3 is a partially enlarged view of FIG. 2. It is a schematic sectional drawing of the PM sensor which concerns on 2nd Embodiment. It is a schematic sectional drawing of the PM sensor which concerns on 3rd Embodiment. FIG. 3 is a schematic cross-sectional view of a PM sensor under study by the inventors.

Hereinafter, an embodiment of the present disclosure will be described based on the drawings. In the following respective embodiments, the same or equivalent portions are designated by the same reference numerals in the drawings.

(First embodiment)
The PM sensor according to the first embodiment will be described with reference to FIGS. 1 to 6. The PM sensor 20 according to the present embodiment is installed in a vehicle and is arranged in a vehicle air conditioner 10 that air-conditions a vehicle interior. As shown in FIG. 1, the vehicle air conditioner 10 includes an air conditioning unit 100 and a PM sensor 20.

First, the configuration of the air conditioning unit 100 will be described. The air conditioning unit 100 is a part of the vehicle air conditioner 10, and performs air conditioning of the air taken in from the outside and supplies the conditioned air into the vehicle interior. The air conditioning unit 100 includes a blower storage section 101, a blower 130, a connecting section 140, and an air conditioning section 150.

The blower storage part 101 is a part of the vehicle air conditioner 10 that takes in air from the outside. A blower 130 is housed inside the blower housing 101. An inner air inlet 111 and an outer air inlet 112 are formed in the blower storage portion 101. The inside air inlet 111 is an opening formed as an inlet for air introduced from the passenger compartment. The outside air inlet 112 is an opening formed as an inlet for air introduced from outside the vehicle. The space outside the vehicle and the outside air inlet 112 are also connected by a duct (not shown).

An inside / outside air switching door (not shown) is provided between the inside air inlet 111 and the outside air inlet 112 in the blower storage unit 101. By the operation of the inside / outside air switching door, the ratio between the air flowing in from the inside air inlet 111 and the air flowing in from the outside air inlet 112 is adjusted. Since a publicly known one can be adopted as the structure of such an inside / outside air switching door, a concrete illustration and description thereof will be omitted.

A particle filter 120 is arranged at a position on the upstream side (upper side in FIG. 1) of the blower 130 along the air flow direction in the blower housing 101. The particle filter 120 is a filter for removing particles from the air flowing in from the inside air inlet 111 or the outside air inlet 112. As the air passes through the particle filter 120, clean air with a reduced particle concentration is blown into the vehicle interior.

The blower 130 is a blower that blows out air so that it is blown into the passenger compartment. When the blower 130 is driven, air is drawn into the blower housing portion 101 from the inside air inlet 111 and the outside air inlet 112. The air is blown into the vehicle compartment through the connection unit 140 and the air conditioning unit 150 described below.

The connection part 140 is a part provided as a flow path connecting the blower storage part 101 and the air conditioning part 150. In this embodiment, the blower storage part 101 and the connection part 140 are integrally formed.

The air conditioner 150 is a part that adjusts the temperature of the air. Inside the air conditioning unit 150, an evaporator for dehumidifying and cooling the air, a heater core for heating the air, an air mix door for adjusting the amount of air flowing through each of the evaporator and the heater core, and the like are arranged.

A defroster blowing unit 151, a face blowing unit 152, and a foot blowing unit 153 are provided at the downstream side of the air conditioning unit 150 along the air flow direction. The defroster blowout part 151 is a part which blows out conditioned air toward the window of the vehicle. The face blowing section 152 is a section that blows out the conditioned air toward the face of the vehicle occupant. The foot blowout portion 153 is a portion that blows out conditioned air toward the feet of an occupant of the vehicle.

A door (not shown) is provided in each of the defroster blowing unit 151, the face blowing unit 152, and the foot blowing unit 153, and the flow rate of the air blown from each blowing unit is adjusted by the opening of the door. Since a known structure can be adopted as the structure of the air conditioning unit 150 as described above, a concrete illustration and description thereof will be omitted.

As shown in FIG. 1, an air introducing chamber 160 is formed at a position in the blower housing 101 near the end of the particle filter 120. The air introduction chamber 160 is formed as a space in which the air introduced into the air conditioning unit 100 flows from the outside of the air conditioning unit 100.

The opening 161 serving as an air inlet of the air introduction chamber 160 is formed at a position above the particle filter 120 and the PM sensor 20 described later. The opening 161 communicates the space around the air conditioning unit 100 with the air introduction chamber 160. The opening 162, which serves as an air outlet, in the air introduction chamber 160 is formed at a position slightly below the particle filter 120.

The opening 162 communicates between the air introduction chamber 160 and the space of the blower housing 101 below the particle filter 120.

When the blower 130 is driven, the suction force of the blower 130 causes the air in the air introduction chamber 160 to be discharged to the blower 130 side through the opening 162. To compensate for this, outside air flows into the air introduction chamber 160 through the opening 161. Therefore, inside the air introduction chamber 160 in the present embodiment, air flows downward from the opening 161 located above the opening 162.

The blower storage unit 101 is arranged inside the instrument panel of the vehicle. The space inside the instrument panel, that is, the space outside the air introducing chamber 160, is connected to the vehicle interior. Therefore, the air flowing into the air introduction chamber 160 from the opening 161 is the air in the vehicle compartment.

As shown in FIG. 1, the part of the air conditioning unit 100 where the air introduction chamber 160 is formed is the part to which the PM sensor 20 is attached. The PM sensor 20 is attached to the blower housing portion 101 from the outside so as to partition a side portion of the air introduction chamber 160. The position of the upper end of the PM sensor 20 is lower than the opening 161.

The positions of the opening 161, the opening 162, the PM sensor 20 and the like as described above are merely examples. The opening 161, the opening 162, the PM sensor 20 and the like may be formed at positions different from the above.

The PM sensor 20 is a sensor unit for measuring the presence and concentration of particles in the air. As shown in FIG. 2, the PM sensor 20 includes a light emitting element 221, a light receiving element 222, a mirror 223, a sensor substrate 220, and a case 21 for housing them.

The light emitting element 221 emits light. The light emitted from the light emitting element 221 is reflected by the mirror 223. Then, the reflected light reflected by the mirror 223 is received by the light receiving element 222 through a through hole formed in the first inner case 213 described later.

By arranging the

outer cases

211 and 212 outside the

inner cases

213 and 214 housing the light receiving elements 222, the light receiving elements 222 are prevented from being affected by light from the outside of the

outer cases

211 and 212.

inner cases

213 and 214.

A space is provided between the

outer cases

211, 212 and the

inner cases

213, 214 in order to reduce the impact from the outside on the

inner cases

213, 214 containing the optical components such as the light emitting element 221, the light receiving element 222, and the mirror 223. The non-detection flow path 232 is provided.

The

outer cases

211 and 212. .. Further, the

inner cases

213 and 214 each have an inner inlet port 214a through which air flows from the non-detection flow channel 232 to the detection flow channel 231, and an inner outlet port 214b through which air flows from the detection flow channel 231 to the non-detection flow channel 232. And are formed.

Then, a part of the air that has flowed into the

outer cases

211 and 212 flows into the non-detection flow channel 232. Inflow. Then, the air flowing out from the inner outlet 214b of the detection flow channel 231 and the air flowing in the non-detection flow channel 232 join together and are discharged from the outer flow outlet 211b to the outside of the

outer cases

211, 212.

The PM sensor 20 detects presence / absence and concentration of particles in the air by receiving scattered light when the light emitted from the light emitting element 221 hits particles in the air flowing through the detection channel 231 with the light receiving element 222. To do. The PM sensor 20 detects the presence or absence and the concentration of particles in the air based on the amount of light received by the light receiving element 222.

As shown in FIG. 3, a light receiving circuit 30 is connected to the light receiving element 222. The light receiving circuit 30 includes a current amplification unit 31 that amplifies the current flowing through the light receiving element 222, and an amplifier 32 that converts the current amplified by the current amplification unit 31 into a voltage and amplifies it. The light receiving circuit 30 further includes a low-pass filter 33 that removes noise included in the output signal of the amplifier 32, and a voltage output unit 34 that outputs the signal that has passed through the low-pass filter 33.

Fig. 3 shows the frequency characteristics of the detection capability of the PM sensor 20. As shown in the figure, the detection capability of the PM sensor 20 is high in the low frequency region. However, the detection capability of the PM sensor 20 decreases as the frequency increases. This is considered to be due to the influence of the low pass filter 33.

When the blower is rotating at a low speed and the speed of the air flowing in the air conditioning unit is low, the PM sensor 20 has a high detection capability and can detect the presence or absence and concentration of particles with high accuracy. However, when the blower rotates at high speed and the speed of the air flowing through the air conditioning unit becomes high, the detection capability of the PM sensor 20 decreases. For this reason, there is a problem in that the presence / absence of particles and the detection accuracy of the concentration decrease.

Therefore, the present inventors examined the flow of air flowing through the detection channel 231 and the non-detection channel 232.

In the configuration of the PM sensor 90 under study shown in FIG. 9, the center line of the inner outlet 214b coincides with the center line of the outer outlet 211b, as shown in FIG. Therefore, an aspiration effect occurs at the outer outlet 211b. With such a configuration, the flow velocity of air at the confluence of the air flowing out from the inner outlet 214b and the air flowing through the non-detection flow path 232 is increased. In addition, according to Bernoulli's theorem, the pressure decreases as the flow velocity of air increases. That is, as shown in FIG. 5, a pressure drop region that becomes a negative pressure is generated at the confluence of the air flowing out from the inner outlet 214 b and the air flowing through the non-detection flow path 232.

In this way, when the pressure at the confluence of the air flowing out from the inner outlet 214b and the air flowing through the non-detection flow channel 232 becomes negative, the air in the detection flow channel 231 is drawn into the confluence, so that the detection flow channel is further detected. The flow velocity of the air inside 231 becomes high. As described above, it has been found that when the flow velocity of the air inside the detection flow path 231 is increased, the detection capability of the PM sensor 20 is reduced and the detection accuracy of particles is reduced.

Therefore, in the PM sensor 20 of the present embodiment, as shown in FIG. 6, the pressure drop in the pressure drop region that occurs at the confluence of the air flowing out from the inner outlet 214b and the air flowing through the non-detection flow path 232 is suppressed. The center line of the inner outlet 214b and the center line of the outer outlet 211b are eccentric.

Due to such eccentricity, the pressure drop at the confluence of the air flowing out from the inner outlet 214b and the air flowing through the non-detection flow passage 232 is suppressed, and the increase in the flow velocity of the air inside the detection flow passage 231 is suppressed. It Therefore, the presence or absence of particles and the decrease in the detection accuracy of the concentration are suppressed.

If the eccentricity between the center line of the inner outlet 214b and the center line of the outer outlet 211b is too large, the pressure loss at the inner inlet 214a increases, so that it becomes difficult to introduce air into the detection flow passage 231. I will end up.

Therefore, in the PM sensor 20 of the present embodiment, the center line of the inner outlet 214b and the center line of the outer outlet 211b are eccentric. When the

outer cases

211 and 212 are projected onto the

outer cases

211 and 212 from the direction normal to the surface of the

outer cases

211 and 212 on which the outer outlets 211b are formed, a part of the outer outlets 211b is an inner outlet. It is formed so as to be included inside 214b.

As described above, the PM sensor of this embodiment detects the particulate matter contained in the air. The PM sensor of the present embodiment includes optical elements 221 to 223 for detecting particulate matter, and

inner cases

213 and 214 that house the optical elements 221 to 223 and form a first air flow path 231 through which air flows. , Are provided. Further, it is provided with

outer cases

211 and 212 that form second air channels 232 between the

inner cases

213 and 214 and the air bypasses the first air channels 231 and flow.

In addition, the

outer cases

211 and 212 include an outer inlet 211a that allows air to flow into the second air flow path 232 and an outer outlet 211b that allows air in the second air flow path 232 to flow out of the

outer cases

211 and 212. Has been formed.

Further, the

inner case

213, 214 is formed with an inner outlet 214 b for letting air out from the first air flow path 231. Then, a part of the air that has flowed into the

outer cases

211 and 212 from the outer inlet 211a flows into the first air flow path 231, and the rest of the air that has flowed into the

outer cases

211 and 212 is the second air flow. It flows into the path 232. After that, the air flowing out from the inner air outlet 214b of the first air flow passage 231 and the air flowing in the second air flow passage 232 join together and are discharged from the outer air outlet 211b to the outside of the

outer cases

211, 212. ing.

The structure has a structure in which the pressure drop in the pressure drop region that occurs at the confluence of the air flowing out from the inner outlet 214b and the air flowing in the second air flow path 232 is suppressed.

According to the above configuration, the present PM sensor has a structure in which the pressure drop in the pressure drop region that occurs at the confluence of the air flowing out from the inner outlet 214b and the air flowing through the second air flow path 232 is suppressed. There is. Therefore, the velocity of the air flowing through the first air flow path 231 is suppressed, and the detection accuracy of particles in the air can be improved.

Further, the center line of the inner outlet 214b is located at the center of the outer outlet 211b so as to suppress the pressure drop in the pressure lowering region that occurs at the confluence of the air flowing out from the inner outlet 214b and the air flowing through the second air passage 232. It is eccentric with the line.

As described above, the center line of the inner outlet port 214b is eccentric with the center line of the outer outlet port 211b, so that the pressure drop generated at the confluence of the air flowing out from the inner outlet port 214b and the air flowing in the second air passage 232. It is possible to suppress the pressure drop in the region.

In addition, the center line of the inner outlet 214b and the center line of the outer outlet 211b are controlled so as to suppress the pressure drop in the pressure drop region that occurs at the confluence of the air flowing out from the inner outlet 214b and the air flowing through the non-detection flow path 232. And are eccentric.

In this way, by eccentricizing the center line of the inner outlet 214b and the center line of the outer outlet 211b, it is possible to reduce the pressure at the confluence of the air flowing out of the inner outlet 214b and the air flowing in the non-detection flow path 232. Can be suppressed. Furthermore, it is possible to prevent the flow velocity of the air inside the detection flow path 231 from increasing, and it is possible to improve the detection accuracy of particles in the air.

Further, in the PM sensor 20 of the present embodiment, the center line of the inner outlet 214b and the center line of the outer outlet 211b are eccentric. When the

outer cases

211 and 212 are projected onto the

outer cases

211 and 212 from the direction normal to the surface of the

outer cases

Therefore, the pressure loss at the inner inlet 214a does not become too large, and the air can be easily introduced into the detection flow path 231. Further, it is possible to suppress light from entering the inside of the

outer cases

211, 212 from the outside of the

outer cases

211, 212. By suppressing the entry of light into the

outer cases

211, 212, the ratio of the light entering from the outside of the

outer cases

211, 212 to the scattered light obtained by the light emitted from the optical element can be reduced. The detection accuracy of particulate matter can be improved.

In addition, the optical elements 221 to 223 receive the scattered light when the light emitted from the light emitting element 221 hits the particulate matter contained in the air flowing through the first air flow path 231 by the light receiving element 222 to receive the scattered light. It can be configured to detect particles therein.

(Second embodiment)
The PM sensor according to the second embodiment will be described with reference to FIG. 7. The PM sensor of the present embodiment is different from the PM sensor of the first embodiment in the width a of the non-detection flow path 232.

The width a of the non-detection flow path 232 corresponds to the length of the outer outlet 211b in the center line direction. The width a of the non-detection flow path 232 of the PM sensor 20 of the present embodiment is longer than the width of the non-detection flow path 232 of the PM sensor 20 of the first embodiment. As a result, the pressure drop in the pressure drop region that occurs at the confluence of the air flowing out from the inner outlet 214b and the air flowing through the non-detection flow path 232 is suppressed.

In the present embodiment, the same effect as that obtained from the configuration common to the first embodiment can be obtained similarly to the first embodiment.

Further, the width a of the non-detection flow path 232 of the PM sensor 20 of the present embodiment is longer than the width of the non-detection flow path 232 of the PM sensor 20 of the first embodiment. Therefore, it is possible to suppress the pressure drop in the pressure drop region that occurs at the confluence of the air flowing out from the inner outlet 214b and the air flowing through the non-detection flow path 232, and it is possible to improve the detection accuracy of particles in the air. ..

(Third Embodiment)
The PM sensor according to the third embodiment will be described with reference to FIG. Compared with the PM sensor of the first embodiment, the PM sensor of the present embodiment further allows air in the non-detection flow path 232 to flow in the

outer case

211, 212 at a position different from the outer outlet 211b. A second outer outlet 211c is formed to flow out.

In this way, the second outer outlet 211c that allows the air in the non-detection flow path 232 to flow out of the outer case can be provided at a position different from the outer outlet 211b.

(Other embodiments)
(1) In each of the above-described embodiments, the example in which the PM sensor 20 is mounted on the vehicle air conditioner 10 that air-conditions the vehicle interior has been described. Can also be installed.

(2) In each of the above-described embodiments, an example in which the air in the vehicle compartment flows into the air introduction chamber 160 from the opening 161, and the presence or absence and concentration of particles in the air that has flowed into the air introduction chamber 160 is detected by the PM sensor 20. It was However, the detection target of the PM sensor 20 is not limited to the air inside the vehicle interior, and for example, the presence or absence and concentration of particles in the air outside the vehicle interior can also be detected.

(3) In each of the above embodiments, the particle filter 120 is arranged on the upstream side of the blower 130 in the air flow. However, for example, the particle filter 120 may be arranged on the downstream side of the blower 130 in the air flow.

It should be noted that the present disclosure is not limited to the above-described embodiments, and can be modified as appropriate. Further, the above embodiments are not unrelated to each other, and can be appropriately combined unless a combination is obviously impossible. Further, in each of the above-described embodiments, it goes without saying that the elements constituting the embodiment are not necessarily essential unless explicitly stated as being essential or in principle considered to be essential. Yes. Further, in each of the above-described embodiments, when numerical values such as the number of components of the embodiment, numerical values, amounts, ranges, etc. are referred to, it is clearly limited to a particular number and in principle limited to a specific number. The number is not limited to the specific number, except in the case of being performed. Further, in each of the above-mentioned embodiments, when referring to the material, shape, positional relationship, etc. of the constituent elements, etc., unless specifically stated or in principle limited to a specific material, shape, positional relationship, etc. However, the material, shape, positional relationship, etc. are not limited.

(Summary)
According to the first aspect described in part or all of each of the above embodiments, the PM sensor is a PM sensor that detects particulate matter contained in air, and is an optical sensor for detecting particulate matter. An inner case that includes an element and that houses an optical element and that forms a first air flow path through which air flows, and second air that flows around the first air flow path between the inner case and the inner case. And an outer case that forms a flow path. Further, the outer case is formed with an outer inflow port for letting air into the second air passage and an outer outflow port for letting air in the second air passage out of the outer case. In addition, the inner case is formed with an inner outlet that allows air to flow out from the first air flow path. In addition, a part of the air that has flowed into the outer case from the outer flow inlet flows into the first air flow path, and the rest of the air that has flowed into the outer case flows into the second air flow path. The air flowing out from the inner outlet of the air flow channel and the air flowing in the second air flow channel join together and are discharged from the outer flow outlet to the outside of the outer case. Further, it has a structure in which the pressure drop in the pressure drop region that occurs at the confluence of the air flowing out from the inner outlet and the air flowing in the second air passage is suppressed.

Further, according to the second aspect, the center line of the inner outlet is located outside so that the pressure drop in the pressure drop region that occurs at the confluence of the air flowing out from the inner outlet and the air flowing through the second air passage is suppressed. It is eccentric with the center line of the outlet.

In this way, by eccentricizing the center line of the inner outlet with the center line of the outer outlet, the pressure drop in the pressure drop region that occurs at the confluence of the air flowing out from the inner outlet and the air flowing through the second air passage Can be suppressed.

Further, according to a third aspect, when the outer case is projected onto the outer case from a direction normal to a surface of the outer case where the outer outlet is formed, a part of the outer outlet is inside the inner outlet. Is formed to be included.

Therefore, the pressure loss at the inner inflow port does not become too large, and air can be easily introduced into the detection flow path. Further, it is possible to prevent light from entering the inside of the outer case from the outside of the outer case. By suppressing the penetration of light into the outer case, the ratio of the light entering from the outside of the outer case to the scattered light obtained by the light emitted from the optical element can be reduced, so the detection accuracy of particulate matter can be reduced. Can be improved.

Further, according to a fourth aspect, the outer outlet is the first outer outlet, and the air in the second air flow path is disposed in the outer case at a position different from that of the first outer outlet. A second outer outlet is formed to allow the water to flow out to.

In this way, it is possible to provide a second outer outlet at a position different from that of the first outer outlet so that the air in the non-detection flow passage flows out of the outer case.

Further, according to the fifth aspect, the optical element receives the scattered light when the light emitted from the light emitting element hits the particulate matter contained in the air flowing through the first air flow path, by the light receiving element.

In this way, the optical element can be configured so that the light receiving element receives scattered light when the light emitted from the light emitting element hits the particulate matter contained in the air flowing through the first air flow path.

Claims

A PM sensor for detecting particulate matter contained in air,
An optical element (221 to 223) for detecting the particulate matter,
An inner case (213, 214) that houses the optical element and forms a first air flow path (231) through which the air flows;
An outer case (211, 212) forming a second air flow path (232) between the inner case and the air, the air bypassing the first air flow path;
The outer case has an outer inlet (211a) for allowing the air to flow into the second air passage and an outer outlet (211b) for allowing the air in the second air passage to flow out of the outer case. Formed,
An inner outlet (214b) for letting out the air from the first air passage is formed in the inner case,
Part of the air that has flowed into the outer case from the outer inlet flows into the first air flow path, and the rest of the air that has flowed into the outer case flows into the second air flow path. After that, the air flowing out of the inner outlet of the first air passage and the air flowing in the second air passage are combined and discharged from the outer outlet to the outside of the outer case. Has become
A PM sensor having a structure that suppresses a pressure drop in a pressure drop region that occurs in a confluence portion of the air flowing out from the inner outlet and the air flowing in the second air flow path.
The center line of the inner outlet is the center of the outer outlet so as to suppress the pressure drop in the pressure drop region that occurs at the confluence of the air flowing out from the inner outlet and the air flowing through the second air flow path. The PM sensor according to claim 1, which is eccentric to the line.
The outer case is formed such that a part of the outer outlet is included in the inner outlet when projected onto the outer case from a direction normal to a surface of the outer case on which the outer outlet is formed. The PM sensor according to claim 2, which is provided.
The outer outlet is a first outer outlet,
A second outer outlet is formed in the outer case at a position different from that of the first outer outlet so as to allow the air in the second air passage to flow out of the outer case. The PM sensor according to any one of 1.
The optical element receives light scattered by the light receiving element (222) when the light emitted from the light emitting element (221) hits the particulate matter contained in the air flowing through the first air flow path. The PM sensor according to any one of claims 1 to 4, which detects particles in the air by means of: