Particulate matter detection devices and electronic equipment

Abstract

The present invention provides a particulate sensor and electronic device that can suppress noise from affecting the characteristics of the calculated particulate matter. [Solution] The particulate detection device comprises a housing through which a flow path is formed having an upstream position, an irradiated position and a downstream position through which a plurality of particulates pass sequentially; a light-emitting unit provided inside the housing that irradiates the particulates as it passes through the irradiated position with emitted light; a first light-receiving unit provided inside the housing and positioned at the upstream position that receives first scattered light from the passing particulates and outputs a first signal corresponding to the first scattered light; a second light-receiving unit provided inside the housing and positioned at the downstream position that receives second scattered light from the passing particulates and outputs a second signal corresponding to the second scattered light; and a signal processing unit provided inside the housing that calculates the characteristics of the particulates using the first signal and the second signal.

Description

Technical Field

[0001] The present disclosure discloses a particulate detector and an electronic device.

Background Art

[0002] Patent Document 1 discloses a particulate detection sensor. In the particulate detection sensor, a light-emitting element projects light onto the particulate. The light-emitting element repeats lighting and extinguishing. The SPAD array receives scattered light from the particulate and outputs a pulse signal. The pulse counter counts the output pulse signal. The signal processing unit detects the particulate concentration using a third pulse count value obtained by subtracting a second pulse count value during the extinguishing period from a first pulse count value during the lighting period. Thereby, the particulate concentration can be detected using the third pulse count value that is not affected by fluctuations in the noise component (paragraphs 0046, 0048, 0049, 0059, 0067, 0069, and 0070).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the particulate detection sensor disclosed in Patent Document 1, when the frequency of the noise component output during the lighting period is different from the frequency of the noise component output during the extinguishing period, the third pulse count value is affected by fluctuations in the noise component. Therefore, the particulate concentration detected using the third pulse count value is also affected by fluctuations in the noise component. A situation where the frequency of the noise component output during the lighting period is different from the frequency of the noise component output during the extinguishing period occurs, for example, when the noise component is periodically generated at a time interval longer than the length of the lighting period or the extinguishing period.

[0005] One aspect of this disclosure has been made in view of this problem. One aspect of this disclosure aims to provide, for example, a particulate sensor and electronic equipment that can suppress the influence of noise on the characteristics of the calculated particulate matter. [Means for solving the problem]

[0006] A particulate detection device according to one aspect of this disclosure is: A housing is formed in which a flow path is created having an upstream position, an irradiated position and a downstream position through which multiple fine particles pass sequentially, A light-emitting unit is provided within the housing and irradiates the fine particles passing through the irradiated position with emitted light, A first light receiving unit is provided within the housing and positioned at the upstream location, which receives first scattered light from the passing fine particles and outputs a first signal corresponding to the first scattered light. A second light receiving unit is provided within the housing and positioned downstream, which receives second scattered light from passing particles and outputs a second signal corresponding to the second scattered light. A signal processing unit is provided within the housing and calculates the characteristics of the fine particles using the first signal and the second signal, It is equipped with.

[0007] An electronic device of another aspect of the present disclosure comprises a particulate detection device of one aspect of the present disclosure. [Brief explanation of the drawing]

[0008] [Figure 1] This is an exploded perspective view schematically illustrating the particulate matter detection device 1 of the first embodiment. [Figure 2] This is a block diagram of the first embodiment of the particulate matter detection device 1. [Figure 3] This is a schematic top view illustrating the first cover 21, substrate 12, and detection unit 14 provided in the particulate matter detection device of the first embodiment. [Figure 4] This is a schematic cross-sectional view illustrating the cross-section of the substrate 12 and detection unit 14 provided in the first embodiment of the particulate matter detection device 1 at the position of the cutting line IV-IV shown in Figure 3. [Figure 5] This graph illustrates the first waveform WSa and the second waveform WSb, which show the time evolution of the first signal Sa and the second signal Sb, output by the first light receiving unit 32a and the second light receiving unit 32b provided in the first embodiment of the particulate matter detection device 1. [Figure 6] This graph illustrates the waveform WISb, which shows the time evolution of the inverted signal ISb obtained by inverting the sign of the signal value of the first signal Sa output by the first light receiving unit 32a provided in the first embodiment of the particulate matter detection device 1. [Figure 7] This graph illustrates the difference waveform WDF, which shows the time change of the difference DF between the first signal Sa and the second signal Sb output by the first light receiving unit 32a and the second light receiving unit 32b provided in the particulate matter detection device 1 of the first embodiment. [Figure 8] This is a schematic cross-sectional view illustrating the emitted light EL from the light-emitting unit 31 provided in the first embodiment of the particulate matter detection device 1, and the particulate matter FP passing through the emitted light EL. [Figure 9] This flowchart shows the detection process performed by the particulate matter detection device 1 of the first embodiment. [Figure 10] This is a schematic cross-sectional view illustrating the light-emitting unit 31, the first light-receiving unit 32a, and the second light-receiving unit 32b provided in the first modified particulate detection device 1 of the first embodiment. [Figure 11] This is a schematic cross-sectional view illustrating the light-emitting unit 31, the first light-receiving unit 32a, and the second light-receiving unit 32b provided in the particulate detection device 1 of the second modified example of the first embodiment. [Figure 12] This is a schematic cross-sectional view illustrating the light-emitting unit 31, the first light-receiving unit 32a, the second light-receiving unit 32b, and the third light-receiving unit 32c provided in the particulate matter detection device 1 of the third modified example of the first embodiment. [Modes for carrying out the invention]

[0009] The embodiments of this disclosure will be described below with reference to the drawings. In the drawings, the same or equivalent elements are denoted by the same reference numerals, and redundant descriptions are omitted.

[0010] 1 First Embodiment 1.1 Outline of the Fine Particle Detection Device FIG. 1 is an exploded perspective view schematically showing a fine particle detection device 1 according to the first embodiment. In FIG. 1, arrow lines representing a first direction D1, a second direction D2, and a third direction D3 are also drawn.

[0011] The fine particle detection device 1 is provided in an electronic device. The fine particle detection device 1 passes air containing fine particles and obtains the characteristics of the fine particles contained in the passed air. The obtained characteristics of the fine particles include at least one of the particle concentration C of the air and the particle size D of the fine particles.

[0012] The first direction D1, the second direction D2, and the third direction D3 intersect each other, and preferably, are perpendicular to each other. The fine particle detection device 1 has a rectangular parallelepiped outer shape. For this reason, the fine particle detection device 1 has a width direction, a depth direction, and a height direction. The width direction and the depth direction are the longitudinal direction and the lateral direction, respectively. The first direction D1 is, for example, parallel to the longitudinal direction of the fine particle detection device 1. The second direction D2 is, for example, parallel to the short side direction of the fine particle detection device 1. The third direction D3 is, for example, parallel to the height direction of the fine particle detection device 1.

[0013] As shown in FIG. 1, the fine particle detection device 1 includes a housing 11, a substrate 12, a fixture 13, a detection unit 14, and a blower 15.

[0014] The substrate 12, the fixture 13, the detection unit 14, and the blower 15 are provided in the housing 11.

[0015] The housing 11 is formed with a flow path inlet 11a and a flow path outlet 11b. Air passing through the particulate matter detection device 1 flows into the flow path inlet 11a. Air that has passed through the particulate matter detection device 1 flows out from the flow path outlet 11b. The housing 11 is formed with a flow path FC extending from the flow path inlet 11a to the flow path outlet 11b. Air that flows into the flow path inlet 11a and flows out from the flow path outlet 11b flows through the flow path FC. The air flowing through the flow path FC contains a plurality of particulate matters. The plurality of particulate matters include dust, pollen, PM2.5, etc.

[0016] As shown in FIG. 1, the housing 11 includes a first cover 21, a second cover 22, and a third cover 23.

[0017] The first cover 21, the second cover 22, and the third cover 23 are stacked in the third direction D3. The second cover 22 is provided above the first cover 21 and serves as an upper cover. The third cover 23 is disposed below the first cover 21 and serves as a lower cover. Therefore, the first cover 21 is sandwiched between the second cover 22 and the third cover 23 and serves as an inner cover.

[0018] The first cover 21 is formed with a flow path inlet 21a and a flow path outlet 21b. The second cover 22 is formed with a flow path inlet 22a and a flow path outlet 22b. The flow path inlet 21a and the flow path inlet 22a overlap each other and communicate with each other, constituting the flow path inlet 11a of the housing 11. The flow path outlet 21b and the flow path outlet 22b overlap each other and communicate with each other, constituting the flow path outlet 11b of the housing 11. Therefore, air passing through the particulate matter detection device 1 enters the particulate matter detection device 1 from the flow path inlet 21a and the flow path inlet 22a, and exits the particulate matter detection device 1 from the flow path outlet 21b and the flow path outlet 22b. Therefore, the flow path FC of the housing 11 is formed below the first cover 21.

[0019] The substrate 12 has an upper main surface 12a. A detection unit 14 and a blower 15 are disposed on the upper main surface 12a. Therefore, the substrate 12 constitutes a support for supporting the detection unit 14 and the blower 15.

[0020] The substrate 12 is positioned below the first cover 21 and above the third cover 23. Therefore, the substrate 12 is positioned between the first cover 21 and the third cover 23. As a result, the flow path 11c of the housing 11 is formed between the substrate 12 and the first cover 21. This allows the detection unit 14 and the blower 15, which are positioned on the upper main surface 12a of the substrate 12, to be placed in the flow path FC.

[0021] The fastener 13 secures the circuit board 12 to the second cover 22 and the third cover 23.

[0022] The blower 15 blows air. The blower 15 is positioned near the flow outlet 11b of the housing 11. As a result, the blower 15 blows air outside the housing 11. This causes air to flow from the flow inlet 11a of the housing 11, through the flow FC of the housing 11, to the flow outlet 11b of the housing 11. The air that has flowed to the flow outlet 11b of the housing 11 is then discharged outside the housing 11 by the blower 15.

[0023] Figure 2 is a block diagram of the particulate matter detection device 1 of the first embodiment.

[0024] As shown in Figure 2, the particulate matter detection device 1 comprises a detection unit 14 and a microcontroller unit (MCU) 16. The detection unit 14 comprises a light-emitting unit 31, a first light-receiving unit 32a, and a second light-receiving unit 32b. The MCU 16 comprises a control unit 41, a drive unit 42, and a signal processing unit 43.

[0025] As described above, the detection unit 14 is located inside the housing 11 and is positioned on the upper main surface 12a of the substrate 12. Therefore, the light-emitting unit 31, the first light-receiving unit 32a, and the second light-receiving unit 32b provided in the detection unit 14 are located inside the housing 11 and are positioned on the upper main surface 12a of the substrate 12. The MCU 16 is located inside the housing 11 and is positioned on the lower main surface of the substrate 12, on the side opposite to the upper main surface 12a of the substrate 12. Therefore, the control unit 41, the drive unit 42, and the signal processing unit 43 provided in the MCU 16 are located inside the housing 11 and are positioned on the lower main surface of the substrate 12. By positioning the MCU 16 on the lower main surface of the substrate 12, it is possible to suppress the accumulation of particulate matter FP contained in the air flowing through the flow path FC of the housing 11 formed on the upper main surface 12a on the MCU 16. The MCU 16 may be placed on the upper main surface 12a, or on a location other than the upper main surface 12a or the lower main surface of the substrate 12, or it may be placed outside the housing 11. The substrate 12 includes terminals and patterns (not shown) for electrically connecting the detection unit 14 to the MCU 16.

[0026] The control unit 41 controls the drive unit 42 to drive the light-emitting unit 31.

[0027] The drive unit 42 drives the light-emitting unit 31 to emit light EL from the light-emitting unit 31.

[0028] The light-emitting unit 31 emits light EL and directs the emitted light EL from the light-emitting unit 31 toward the detection area DR. The emitted light EL is a light beam.

[0029] Multiple fine particles FP pass through the detection region DR. As a result, the light-emitting unit 31 irradiates the fine particles FP passing through the detection region DR with the emitted light EL. The fine particles FP irradiated with the emitted light EL scatter the irradiating emitted light EL and generate scattered light SL. The generated scattered light SL includes a first scattered light SLa and a second scattered light SLb directed toward the first light-receiving unit 32a and the second light-receiving unit 32b, respectively.

[0030] The first light-receiving unit 32a and the second light-receiving unit 32b receive the first scattered light SLa and the second scattered light SLb from the fine particles FP passing through the detection region DR, respectively, and output the first signal Sa and the second signal Sb, respectively, corresponding to the received first scattered light SLa and the second scattered light SLb. The output first signal Sa and the second signal Sb each have signal values ​​corresponding to the intensity of the first scattered light SLa and the second scattered light SLb. The signal values ​​are voltage values, current values, etc. The signal values ​​of the first signal Sa and the second signal Sb increase as the intensity of the first scattered light SLa and the second scattered light SLb increases, respectively.

[0031] The signal processing unit 43 processes the output first signal Sa and second signal Sb. The signal processing unit 43 uses the first signal Sa and second signal Sb to calculate the characteristics of the particulate FP. The calculated characteristics of the particulate FP include at least one of the air particle concentration C and the particle size D of the particulate FP.

[0032] The MCU16 comprises a processor, memory, and circuitry for peripheral functions. The processor executes a program stored in memory to operate the MCU16 as a control unit 41, a drive unit 42, and a signal processing unit 43. Some or all of the control unit 41, drive unit 42, and signal processing unit 43 may be configured by dedicated circuits.

[0033] 1.2 Flow Channel Figure 3 is a schematic top view illustrating the first cover 21, substrate 12, and detection unit 14 provided in the particulate matter detection device of the first embodiment. Figure 3 also shows arrow lines indicating the first direction D1 and the second direction D2, as well as dashed arrow lines indicating the airflow path.

[0034] As shown in Figure 3, the first cover 21 has a first inner surface 21c, a second inner surface 21d, a third inner surface 21e, and a fourth inner surface 21f.

[0035] The first inner surface 21c and the third inner surface 21e of the first cover 21 are perpendicular to the first direction D1. The first inner surface 21c and the third inner surface 21e are separated from each other in the first direction D1. The second inner surface 21d and the fourth inner surface 21f of the first cover 21 are perpendicular to the second direction D2. The second inner surface 21d and the fourth inner surface 21f are separated from each other in the second direction D2.

[0036] As shown in Figure 3, the detection unit 14 has a first side surface 14c, a second side surface 14d, a third side surface 14e, and a fourth side surface 14f. The first side surface 14c, the second side surface 14d, the third side surface 14e, and the fourth side surface 14f are the outer surfaces of the wall 63 of the detection unit 14.

[0037] The first side surface 14c and the third side surface 14e of the detection unit 14 are perpendicular to the first direction D1. The first side surface 14c and the third side surface 14e are separated from each other in the first direction D1. The second side surface 14d and the fourth side surface 14f of the detection unit 14 are perpendicular to the second direction D2. The second side surface 14d and the fourth side surface 14f are separated from each other in the second direction D2.

[0038] The first inner surface 21c of the first cover 21 and the first side surface 14c of the detection unit 14 face each other with a first gap 51c in between. The second inner surface 21d of the first cover 21 and the second side surface 14d of the detection unit 14 face each other with a second gap 51d in between. The third inner surface 21e of the first cover 21 and the third side surface 14e of the detection unit 14 face each other with a third gap 51e in between. The fourth inner surface 21f of the first cover 21 and the fourth side surface 14f of the detection unit 14 are in contact with each other. A flow path inlet 11a of the housing 11 is formed above the first gap 51c. A flow path outlet 11b of the housing 11 is formed above the third gap 51e. The first side surface 14c and the second side surface 14d are adjacent to each other. The second side surface 14d and the third side surface 14e are adjacent to each other. Therefore, the air and particulate FP passing through the particulate detection device 1 flow into the flow path inlet 11a of the housing 11, as shown by the dashed arrow lines in Figure 3, then flow along the first side surface 14c in the second direction D2, then flow along the second side surface 14d in the first direction D1, then flow along the third side surface 14e in the direction opposite to the second direction D2, and then flow out from the flow path outlet 11b of the housing 11.

[0039] The detection area DR is provided in the second gap 51d and along the second side surface 14d of the detection unit 14. Therefore, the detection area DR is included in the flow path FC of the housing 11. As a result, the air and particulate matter FP passing through the particulate matter detection device 1 pass through the detection area DR and the emitted light EL that irradiates the detection area DR. When the air and particulate matter FP pass through the detection area DR, they flow in the first direction D1.

[0040] 1.3 Arrangement of light-emitting and light-receiving units Figure 4 is a schematic cross-sectional view illustrating the cross-section of the substrate 12 and detection unit 14 provided in the first embodiment of the particulate matter detection device 1 at the position of the cutting line IV-IV shown in Figure 3. Arrow lines indicating the first direction D1 and the third direction D3 are also drawn in Figure 4.

[0041] As shown in Figure 4, the detection unit 14 includes a light-emitting unit 31 and a light-receiving unit 32. The light-receiving unit 32 includes a first light-receiving unit 32a and a second light-receiving unit 32b.

[0042] As shown in Figure 3, the light-emitting unit 31 is positioned on the side opposite to the second direction D2 with respect to the detection region DR. As shown in Figure 4, the light-receiving unit 32 is positioned on the side opposite to the third direction D3 with respect to the detection region DR. The emitted light EL travels in the second direction D2 and reaches the detection region DR from the light-emitting unit 31. The first scattered light SLa and the second scattered light SLb travel in the side opposite to the third direction D3 and reach the first light-receiving unit 32a and the second light-receiving unit 32b, respectively, from the detection region DR.

[0043] The flow path FC has an upstream position Pa, an irradiated position P, and a downstream position Pb. The upstream position Pa, the irradiated position P, and the downstream position Pb are at different positions in the first direction D1. The upstream position Pa is on the opposite side of the first direction D1 from the irradiated position P. The downstream position Pb is on the side of the first direction D1 from the irradiated position P. Therefore, the air and particulate matter FP flowing in the first direction D1 pass through the upstream position Pa, the irradiated position P, and the downstream position Pb in sequence. For this reason, the blower 15 generates air that passes through the upstream position Pa, the irradiated position P, and the downstream position Pb in sequence by sending air outside the housing 11.

[0044] The light-emitting unit 31 emits light EL toward the irradiated position P. This causes the light-emitting unit 31 to irradiate the fine particles FP passing through the irradiated position P with the emitted light EL. The first light-receiving unit 32a and the second light-receiving unit 32b are positioned at the upstream position Pa and the downstream position Pb, respectively. This ensures that the time when the intensity of the first scattered light SLa increases arrives first, followed by the time when the intensity of the second scattered light SLb increases later. The fine particle detection device 1 calculates the characteristics of the fine particles FP using the time difference between the earlier and later arrival times.

[0045] 1.4 Structure of the light-emitting and light-receiving sections As shown in Figures 3 and 4, the light-emitting unit 31 comprises a light-emitting element 61, a light-projecting lens 62, and a wall 63.

[0046] The light-emitting element 61 is driven by the drive unit 42 to emit light EL. The light-emitting element 61 is a light-emitting diode, a semiconductor laser, etc.

[0047] The projection lens 62 transmits the emitted light EL, giving directionality to the transmitted light EL. As a result, the light EL that passes through the projection lens 62 becomes a light beam.

[0048] The wall 63 surrounds the space 31a. A recess 63a and an opening 63b are formed in the wall 63. The recess 63a is formed on the side opposite to the second direction D2 from the space 31a and on the side opposite to the side where the detection area DR is located. The opening 63b is formed on the side of the space 31a in the second direction D2, on the side where the detection area DR is located, and faces the detection area DR. As shown in Figure 3, the wall 63 is provided with a convex holding portion 63p. The convex holding portion 63p is positioned between the position where the recess 63a is formed and the position where the opening 63b is formed, with respect to the second direction D2. As a result, the light-emitting element 61 is attached to the wall 63. The attached light-emitting element 61 emits light EL on the side of the second direction D2. The convex holding portion 63p holds the light-emitting lens 62. The held light-emitting lens 62 is positioned in space 31a, and in the second direction D2, it is positioned between the position where the recess 63a is formed and the position where the aperture 63b is formed. As a result, the emitted light EL from the light-emitting element 61 passes sequentially through space 31a and the aperture 63b and reaches the detection area DR. The emitted light EL passes through the light-emitting lens 62 on its way through space 31a.

[0049] As the emitted light EL is directed more by the projection lens 62 and passes through the opening 63b of the wall 63, the emitted light EL does not illuminate the entire detection area DR, but only the area in front of the opening 63b, which occupies a portion of the detection area DR.

[0050] As shown in Figures 3 and 4, the light-receiving unit 32 comprises a first light-receiving unit 32a, a light-receiving unit 32b, and a light-receiving cover (sensor cover) 100. Each of the first light-receiving unit 32a and 32b comprises a light-receiving lens 81 and a light-receiving element 82. The light-receiving cover 100 comprises a light-receiving window (not shown), an outer wall 101, a light-shielding wall 102, and a convex holding portion 103p for holding the light-receiving lens 81. The light-shielding wall 102 is provided between the first light-receiving unit 32a and 32b.

[0051] The light-receiving windows provided in the first light-receiving section 32a and the second light-receiving section 32b transmit the first scattered light SLa and the second scattered light SLb. The light-receiving windows may also be optical filters that selectively transmit wavelength components having wavelengths close to the wavelength of the emitted light EL.

[0052] The condensing lenses 81 provided in the first light-receiving section 32a and the second light-receiving section 32b respectively allow the first scattered light SLa and the second scattered light SLb that have passed through the light-receiving window to pass through, and then concentrate the first scattered light SLa and the second scattered light SLb onto the light-receiving elements 82 provided in the first light-receiving section 32a and the second light-receiving section 32b, respectively, for light reception.

[0053] The light-receiving elements 82 provided in the first light-receiving section 32a and the second light-receiving section 32b respectively receive the first scattered light SLa and the second scattered light SLb that have passed through the focusing lens 81 provided in the first light-receiving section 32a and the second light-receiving section 32b, respectively, and convert the received first scattered light SLa and the second scattered light SLb into electrical signals using photoelectric conversion to obtain the first signal Sa and the second signal Sb, respectively, and output the obtained first signal Sa and the second signal Sb, respectively. The light-receiving elements 82 are elements that detect light. Elements that detect light include photodetectors, single-photon avalanche diodes (SPADs), etc. The light-receiving elements 82 are mounted on the upper main surface 12a of the substrate 12. As a result, the light-receiving elements 82 are positioned below the flow path FC of the housing 11. The light-receiving elements 82 have a light-receiving surface 82a. The light-receiving surfaces 82a of the light-receiving elements 82 provided in the first light-receiving section 32a and the second light-receiving section 32b receive the first scattered light SLa and the second scattered light SLb, respectively. The light-receiving surfaces 82a are parallel to the upper main surface 12a of the substrate 12.

[0054] The sensor covers 100 provided on the first light-receiving section 32a and the second light-receiving section 32b each hold and house the condensing lenses 81 provided on the first light-receiving section 32a and the second light-receiving section 32b, and each house the light-receiving elements 82 provided on the first light-receiving section 32a and the second light-receiving section 32b. As shown in Figure 4, the sensor cover 100 includes a convex holding portion 103p. The convex holding portions 103p provided on the first light-receiving section 32a and the second light-receiving section 32b each hold the condensing lenses 81 provided on the first light-receiving section 32a and the second light-receiving section 32b. The sensor cover 100 is positioned on the upper main surface 12a of the substrate 12. As a result, the sensor cover 100 and the condensing lenses 81 held by the sensor cover 100 are positioned below the flow path FC.

[0055] The light-shielding wall 102 is positioned between the condensing lens 81 and light-receiving element 82 provided in the first light-receiving unit 32a and the condensing lens 81 and light-receiving element 82 provided in the second light-receiving unit 32b. The light-shielding wall 102 blocks scattered light caused by diffuse reflection of light that has entered the light-receiving unit. Therefore, light incident on the first light-receiving unit 32a is received by the light-receiving element 82 of the first light-receiving unit 32a, and light incident on the second light-receiving unit 32b is received by the light-receiving element 82 of the second light-receiving unit 32b.

[0056] The light-receiving cover 100 houses and covers the condensing lens 81 and light-receiving element 82 provided in the first light-receiving section 32a, the condensing lens 81 and light-receiving element 82 provided in the second light-receiving section 32b, and the light-shielding wall 102. The light-receiving cover 100 may be replaced by a set of a first light-receiving cover that covers the condensing lens 81 and light-receiving element 82 provided in the first light-receiving section 32a, and a second light-receiving cover that covers the condensing lens 81 and light-receiving element 82 provided in the second light-receiving section 32b. In other words, the first light-receiving section 32a and the second light-receiving section 32b do not necessarily have to be covered by a single light-receiving cover.

[0057] The wall 63 provided on the light-emitting unit 31 and the light-receiving cover 100 provided on the light-receiving unit 32 may be integrally molded to form a single molded product, and this integral molded product may be placed on the upper main surface 12a of the substrate 12. When the wall 63 and the light-receiving cover 100 are integrally molded, the number of parts provided in the particulate detection device 1 can be reduced, making it easier to attach the light-emitting unit 31 and the light-receiving unit 32 to the substrate 12, and efficiently suppressing crosstalk that causes noise in the particulate detection device 1.

[0058] 1.5 Support of the light-receiving section by the substrate The first light-receiving unit 32a and the second light-receiving unit 32b are arranged on the substrate 12. Therefore, the substrate 12 serves as a support for the first light-receiving unit 32a and the second light-receiving unit 32b.

[0059] The first light-receiving unit 32a and the second light-receiving unit 32b are arranged on the upper main surface 12a of the substrate 12. Therefore, the upper main surface 12a serves as a support surface for each of the light-receiving units of the first light-receiving unit 32a and the second light-receiving unit 32b. The upper main surface 12a is located below the flow channel FC. Therefore, each of the light-receiving units of the first light-receiving unit 32a and the second light-receiving unit 32b, which are arranged on the upper main surface 12a, is located below the flow channel FC. The MCU 16 is arranged on the lower main surface 12b of the substrate 12.

[0060] 1.6 Relationship between the arrangement of the light-receiving unit and measurement Figure 5 is a graph illustrating the time evolution of the first waveform WSa and the second waveform WSb, which are output by the first light receiving unit 32a and the second light receiving unit 32b provided in the first embodiment of the particulate matter detection device 1. Figure 6 is a graph illustrating the time evolution of the inverted signal ISb, which is obtained by inverting the sign of the signal value of the second signal Sb, which is output by the second light receiving unit 32b provided in the first embodiment of the particulate matter detection device 1. Figure 7 is a graph illustrating the time evolution of the difference waveform WDF, which is the difference between the first signal Sa and the second signal Sb, which are output by the first light receiving unit 32a and the second light receiving unit 32b provided in the first embodiment of the particulate matter detection device 1.

[0061] In the graph of Figure 5, time is plotted on the horizontal axis and the signal value on the vertical axis. In the graph of Figure 5, the solid line illustrates the first waveform WSa, and the dashed line illustrates the second waveform WSb. In the graph of Figure 6, time is plotted on the horizontal axis and the signal value on the vertical axis. In the graph of Figure 7, time is plotted on the horizontal axis and the voltage value on the vertical axis.

[0062] As shown in Figure 5, the first signal Sa includes the first signal component Sas and the first noise component San. The second signal Sb includes the second signal component Sbs and the second noise component Sbn. The first noise component San and the second noise component Sbn are superimposed on the first signal component Sas and the second signal component Sbs, respectively. The first noise component San and the second noise component Sbn are components such as noise caused by crosstalk occurring in the particulate matter detection device 1, electromagnetic noise, noise generated when external light is incident on the particulate matter detection device 1, and noise generated when vibration is applied to the particulate matter detection device 1.

[0063] The first light-receiving unit 32a and the second light-receiving unit 32b are positioned at the upstream position Pa and the downstream position Pb, respectively. Therefore, the first light-receiving unit 32a and the second light-receiving unit 32b are positioned at different locations with respect to the first direction D1 through which air and particulate matter FP flow. Consequently, the time at which the first light-receiving unit 32a receives the first scattered light SLa and the time at which the second light-receiving unit 32b receives the second scattered light SLb are approximately the same, but the time at which the intensity of the first scattered light SLa is maximum and the time at which the intensity of the second scattered light SLb is maximum are different. Consequently, the time at which the signal value of the first signal component Sas is maximum and the time at which the signal value of the second signal component Sbs is maximum are different.

[0064] Air and particulate matter FP flow through the flow channel FC from the upstream side to the downstream side. Therefore, the air and particulate matter FP pass sequentially through the upstream position Pa, the irradiated position P, and the downstream position Pb. The particulate matter FP passes through the region in front of the opening 63b of the wall 63, and as it passes through the region in front of the opening 63b, it is irradiated by the emitted light EL, scattering the emitted light EL and generating scattered light SL. The generated scattered light SL spreads into the detection region DR. As a result, the first light receiving unit 32a and the second light receiving unit 32b receive the first scattered light SLa and the second scattered light SLb, respectively, which are contained in the scattered light SL.

[0065] If the fine particle FP is located upstream of the flow channel FC, the intensity of the first scattered light SLa received by the first light-receiving unit 32a located upstream of the flow channel FC from the fine particle FP will be stronger than the intensity of the second scattered light SLb received by the second light-receiving unit 32b located downstream of the flow channel FC from the fine particle FP. If the fine particle FP is located downstream of the flow channel FC, the intensity of the second scattered light SLb received by the second light-receiving unit 32b located downstream of the flow channel FC from the fine particle FP will be stronger than the intensity of the first scattered light SLa received by the first light-receiving unit 32a located upstream of the flow channel FC from the fine particle FP. Therefore, the time at which the intensity of the first scattered light SLa is maximum and the time at which the intensity of the second scattered light SLb is maximum are different. Consequently, at the same time, the intensities of the first scattered light SLa and the second scattered light SLb are different. The signal value of the first signal component Sas output by the first light receiving unit 32a and the signal value of the second signal component Sbs output by the second light receiving unit 32b increase as the intensity of the first scattered light SLa and the intensity of the second scattered light SLb increase, respectively. Therefore, the time at which the signal value of the first signal component Sas is maximum and the time at which the signal value of the second signal component Sbs is maximum are different from each other. Also, at the same time, the signal values ​​of the first signal component Sas and the second signal component Sbs are different from each other.

[0066] The signal value of the first noise component San output by the first light receiving unit 32a and the signal value of the second noise component Sbn output by the second light receiving unit 32b are almost the same magnitude. Furthermore, there is almost no time difference between the signal value of the first noise component San and the signal value of the second signal component Sbs.

[0067] As shown in Figures 5 to 7, when the difference is obtained from the first waveform WSa and the inverted waveform IWSb (the second waveform WSb), the first noise component San and the second noise component Sbn are almost completely eliminated. The difference between the first signal component Sas and the second signal component Sbs contains components resulting from the temporal difference between the times when the signal value of the first signal component Sas is maximized and the times when the signal value of the second signal component Sbs is maximized. Therefore, the difference waveform WDF contains components originating from the first signal component Sas and the second signal component Sbs. The time Δt during which this difference remains reflects the time required for the fine particle FP to pass through the emitted light EL. The time required for the fine particle FP to pass through the emitted light EL reflects the particle size D of the fine particle FP. Thus, the time Δt during which this difference remains reflects the particle size D of the fine particle FP. In this way, the particle size D of the fine particle FP can be obtained from this difference.

[0068] The signal processing unit 43 takes the difference between the first signal Sa and the second signal Sb, and calculates the particle size D of the fine particles FP from the difference. The difference obtained contains almost no components caused by the first noise component San included in the first signal Sa and the second noise component Sbn included in the second signal Sb. This suppresses the influence of noise on the particle size D of the fine particles FP calculated from the difference.

[0069] When the signal processing unit 43 takes the difference between the first signal Sa and the second signal Sb, it inverts the sign of the signal value of the second signal Sb to obtain an inverted signal ISb, as illustrated in Figure 6, and then combines the first signal Sa and the inverted signal ISb to obtain the difference DF, as illustrated in Figure 7. Alternatively, the signal processing unit 43 may invert the sign of the signal value of the first signal Sa to obtain an inverted signal, and then combine the obtained inverted signal and the second signal Sb to obtain the difference DF.

[0070] 1.7 Relationship between the position of the light-receiving part and the position of the detection area As shown in Figure 4, the first light-receiving unit 32a and the second light-receiving unit 32b are positioned upstream and downstream of the irradiated position P, respectively, with respect to the first direction D1, and are located at the upstream position Pa and the downstream position Pb, respectively, flanking the irradiated position P. When the first light-receiving unit 32a and the second light-receiving unit 32b are positioned in this manner, as illustrated in Figure 7, the difference waveform WDF, which shows the time change of the difference DF between the first signal Sa and the second signal Sb, takes a maximum value MAX, which is the highest point of the peak, and a minimum value MIN, which is the lowest point of the trough. The time difference Δt between the first time when the difference waveform WDF takes its maximum value MAX and the second time when the difference waveform WDF takes its minimum value MIN, reflects the time required for the fine particle FP to pass through the emitted light EL. For this reason, the signal processing unit 43 calculates the particle size D of the fine particle FP from the first time when the difference waveform WDF takes its maximum value MAX and the second time when the difference waveform WDF takes its minimum value MIN. Therefore, the signal processing unit 43 generates a first waveform WSa and a second waveform WSb that show the time evolution of the first signal Sa and the second signal Sb, respectively, and generates a difference waveform WDF that shows the difference DF between the generated first waveform WSa and the second waveform WSb. The signal processing unit 43 calculates the particle size D of the fine particles FP from the first time when the difference waveform WDF takes its maximum value MAX and the second time when the difference waveform WDF takes its minimum value MIN. The signal processing unit 43 calculates the particle size D of the fine particles FP from the time difference Δt between the first time and the second time.

[0071] The distance from the upstream position Pa where the first light-receiving unit 32a is located to the irradiated position P and the distance from the downstream position Pb where the second light-receiving unit 32b is located to the irradiated position P are preferably the same. That is, the distance from the upstream position Pa to the center of the emitted light EL and the distance from the downstream position Pb to the center of the emitted light EL are preferably the same. When these distances are equal, the absolute values ​​of the maximum value MAX and the minimum value MIN become the same, and the time difference Δt can be easily derived.

[0072] If the distance from the upstream position Pa where the first light-receiving unit 32a is located to the irradiated position P and the distance from the upstream position Pa where the second light-receiving unit 32b is located to the irradiated position P are different, and one of the first light-receiving unit 32a and the second light-receiving unit 32b is far from the irradiated position P, then only one of the maximum value MAX and the minimum value MIN will appear in the difference waveform WDF. If only the maximum value MAX appears in the difference waveform WDF, the signal processing unit 43 uses the time required for the value of the difference waveform WDF to decrease from the maximum value MAX to 0 as an approximation of the time difference Δt, and calculates the approximate particle size D of the fine particles FP from the time difference Δt. If only the minimum value MIN appears in the difference waveform WDF, the signal processing unit 43 uses the time required for the value of the difference waveform WDF to decrease from 0 to the minimum value MIN as an approximation of the time difference Δt, and calculates the approximate particle size D of the fine particles FP from the time difference Δt.

[0073] 1.8 Calculation of particle size Figure 8 is a schematic cross-sectional view illustrating the emitted light EL from the light-emitting unit 31 provided in the first embodiment of the particulate detection device 1, and the particulate matter FP passing through the emitted light EL.

[0074] When a fine particle FP passes through the center of the optical path of the emitted light EL, the radius R of the emitted light EL, the particle size D of the fine particle FP, the flow velocity v of the fine particle FP, and the time Δt during which the entire fine particle FP is in the emitted light EL satisfy the relationship expressed by equation (1).

[0075]

number

[0076] The radius R of the emitted light EL is half the beam diameter of the emitted light EL, which is a beam of light. Therefore, the radius R of the emitted light EL has a value unique to the light-emitting unit 31 that emits the emitted light EL. As the value of the radius R of the emitted light EL, a value calculated by various calculation methods can be used.

[0077] The flow velocity v of the particulate FP is the speed at which the air flows through the flow path FC. Therefore, the flow velocity v of the particulate FP can be set based on, for example, the strength of the wind supplied by the blower 15, the pressure difference within the particulate detection device 1, etc.

[0078] The particle size D of a fine particle (FP) is a one-dimensional numerical value, or length, that represents the size, or particle size, of the FP. Particle size is also called particle diameter. Generally, the diameter of the FP is used as the particle size D for fine particle FP. If the FP has a complex and irregular shape, the particle size D can be determined by various measurement methods.

[0079] Equation (2) can be derived from equation (1).

[0080]

number

[0081] If the light intensity distribution is uniform in the cross-section of the emitted light EL, the intensity of the first scattered light SLa received by the first light receiving unit 32a is strongest at the time when the entire particle FP enters the emitted light EL, and the signal value of the first signal Sa output by the first light receiving unit 32a is largest. Also, the intensity of the second scattered light SLb received by the second light receiving unit 32b is strongest at the time when the entire particle FP enters the emitted light EL, and the signal value of the second signal Sb output by the second light receiving unit 32b is largest. Therefore, the time Δt during which the entire particle FP enters the emitted light EL is approximately the same as the time difference Δt between the first time when the difference waveform WDF, which shows the time change of the difference DF between the first signal Sa and the second signal Sb, takes its maximum value MAX, and the second time when the difference waveform WDF takes its minimum value MIN. Therefore, the signal processing unit 43 can calculate the particle size D of the fine particles FP according to equation (2) from the radius R of the emitted light EL, the flow velocity v of the fine particles FP, and the time difference Δt between the first time when the differential waveform WDF takes its maximum value MAX and the second time when the differential waveform WDF takes its minimum value MIN.

[0082] 1.9 Calculation of particle concentration The cross-sectional area S of the flow path FC, the flow velocity v of the particulate matter FP, and the volume V of air that has passed through the irradiated position P during time s satisfy the relationship expressed by equation (3).

[0083]

number

[0084] From equation (3) and the number of particles N that passed the irradiated position P during time s, equation (4) can be derived.

[0085]

number

[0086] Therefore, the cross-sectional area S of the flow path FC, the flow velocity v of the fine particles FP, the number N of fine particles that passed through the irradiated position P during time s, and the particle concentration C of the air that passed through the irradiated position P during time s satisfy the relationship expressed by equation (5).

[0087]

number

[0088] Therefore, the signal processing unit 43 can calculate the particle concentration C of the air that has passed through the irradiated position P during time s, according to equation (5), from the cross-sectional area S of the flow path FC, the time s required for the multiple fine particles FP to pass through the irradiated position P, and the number N of the multiple fine particles FP.

[0089] 1.10 Detection Flow Figure 9 is a flowchart showing the detection process performed by the particulate matter detection device 1 of the first embodiment.

[0090] The particulate matter detection device performs steps S101 to S108 shown in Figure 9.

[0091] In step S101, the light-emitting element 61 starts emitting emitted light EL.

[0092] In step S102, the signal processing unit 43 receives the first signal Sa and the second signal Sb, which are output by the first light receiving unit 32a and the second light receiving unit 32b, respectively, when the fine particle FP scatters the emitted light EL.

[0093] In the subsequent step S103, the signal processing unit 43 takes the difference DF between the input first signal Sa and the second signal Sb. The difference waveform WDF, which shows the time change of the taken difference DF, includes a portion that indicates that the fine particle FP has passed through the emitted light EL. Noise components have been removed from the difference waveform WDF.

[0094] In the following step S104, the signal processing unit 43 calculates the time difference Δt between the first time when the difference waveform WDF takes its maximum value MAX and the second time when the difference waveform WDF takes its minimum value MIN.

[0095] In the following step S105, the signal processing unit 43 calculates the particle size D of the fine FP from the time difference Δt obtained according to equation (2).

[0096] In the subsequent step S106, the signal processing unit 43 classifies the particulate FPs according to the calculated particle size D of the particulate FPs. Multiple classes are used when classifying the particulate FPs. Each of the multiple classes has a set range of particle sizes that are different from each other. The signal processing unit 43 selects a particle size range that includes the calculated particle size D, classifies the particulate FPs into the class set for the selected particle size range, and counts the number of particulate FPs classified into each class.

[0097] In this way, when the particle size D of a microparticle FP is calculated from the time difference Δt between the first time when the differential waveform WDF takes its maximum value MAX and the second time when the differential waveform WDF takes its minimum value MIN, the particle size D of the microparticle FP can be calculated appropriately even when there are many microparticle FPs and other microparticle FPs pass through the emitted light EL before the signal indicating that one microparticle FP has passed through the emitted light EL has attenuated, compared to when the particle size D of a microparticle FP is calculated from the width of the base of the peak that appears in the waveform showing the time change of a single signal.

[0098] In the following step S107, the signal processing unit 43 determines whether or not it has calculated the particle size D of the particulate FP and classified it over the set time. If the signal processing unit 43 determines that it has calculated the particle size D of the particulate FP and classified it over the set time, it executes step S108. If the signal processing unit 43 determines that it has not calculated the particle size D of the particulate FP and classified it over the set time, it executes step S102.

[0099] As a result, steps S102 to S107 are repeatedly executed until the set time has elapsed, and step S108 is executed in synchronization with the elapsed time.

[0100] In step S108, the signal processing unit 43 calculates the air particle concentration C from the number N of particulate matter FPs that have been classified into classes with a range of α to β, according to equation (5). For example, if 100 particulate matter FPs have passed through the flow path FC, and 30 of these FPs have been classified into a class, the signal processing unit 43 calculates the air particle concentration C from this number of 30.

[0101] In steps S102 to S108, the signal processing unit 43 calculates the air particle concentration C from the number N of particulate matter FPs that are classified into classes within a set range of α to β within a set time.

[0102] The signal processing unit 43 may not calculate the particle size D of the particulate FP in step S105, and may calculate the air particle concentration C without considering the particle size D of the particulate FP. This allows the signal processing unit 43 to calculate the air particle concentration C from the number of particulate FP that have passed through the particulate detection device 1 without considering the particle size D of the particulate FP. Therefore, it is possible to calculate the air particle concentration C that reflects the number of particulate FP present in the air, regardless of the size of the particulate FP. For example, if the number of particulate FP that have passed through the flow path FC is 100, the signal processing unit 43 will calculate the air particle concentration C from this number.

[0103] 1.11 Variations Figure 10 is a schematic cross-sectional view illustrating the light-emitting unit 31, the first light-receiving unit 32a, and the second light-receiving unit 32b provided in the first modified particulate detection device 1 of the first embodiment.

[0104] In the first modified example of the first embodiment, as shown in Figure 10, the light-emitting unit 31, the first light-receiving unit 32a, and the second light-receiving unit 32b are arranged along the flow path FC. The light-emitting unit 31, the first light-receiving unit 32a, and the second light-receiving unit 32b are arranged on the side of the second direction D2 with respect to the detection area DR and are aligned in the first direction D1. Therefore, the first light-receiving unit 32a and the second light-receiving unit 32b are not positioned in the direction of emission of the light EL emitted from the light-emitting unit 31. The light-emitting unit 31 is positioned between the first light-receiving unit 32a and the second light-receiving unit 32b. The light-receiving surfaces 82a of the light-receiving elements 82 of the first light-receiving unit 32a and the second light-receiving unit 32b are perpendicular to the upper main surface 12a of the substrate 12. Even when the light-emitting unit 31, the first light-receiving unit 32a, and the second light-receiving unit 32b are arranged in this manner, the first light-receiving unit 32a and the second light-receiving unit 32b are positioned at different locations relative to each other in the first direction D1, from upstream to downstream of the flow path FC.

[0105] The light-emitting element 61 and the light-emitting lens 62 are held by a wall (not shown). The light-collecting lens 81 and the light-receiving element 82 are held by a light-receiving cover (not shown). The wall and the light-receiving cover may be integrally molded. If the wall and the light-receiving cover 100 are integrally molded, the number of parts provided in the particulate detection device 1 can be reduced, making it easier to attach the light-emitting unit 31 and the light-receiving unit 32 to the substrate 12, and efficiently suppressing crosstalk that causes noise in the particulate detection device 1.

[0106] Figure 11 is a schematic cross-sectional view illustrating the light-emitting unit 31, the first light-receiving unit 32a, and the second light-receiving unit 32b provided in the particulate detection device 1 of the second modified example of the first embodiment.

[0107] In the second modified example of the first embodiment, as shown in Figure 11, the light-emitting unit 31, the first light-receiving unit 32a, and the second light-receiving unit 32b are arranged along the flow path FC. The light-emitting unit 31 is positioned on the side of the second direction D2 with respect to the detection region DR. The first light-receiving unit 32a and the second light-receiving unit 32b are positioned on the side opposite to the second direction D2 with respect to the detection region DR. Therefore, the light-emitting unit 31 and the light-receiving unit 32 are arranged in the second direction D2, sandwiching the detection region DR. The light-receiving surfaces 82a of the light-receiving elements 82 of the first light-receiving unit 32a and the second light-receiving unit 32b are perpendicular to the upper main surface 12a of the substrate 12. Even when the light-emitting unit 31, the first light-receiving unit 32a, and the second light-receiving unit 32b are arranged in this manner, the first light-receiving unit 32a and the second light-receiving unit 32b are positioned at different locations relative to each other in the first direction D1, from upstream to downstream of the flow path FC.

[0108] The light-emitting element 61 and the light-emitting lens 62 are held by a wall (not shown). The light-collecting lens 81 and the light-receiving element 82 are held by a light-receiving cover (not shown). By holding the light-receiving cover with the light-collecting lens 81 and the light-receiving element 82, the side walls of the light-receiving cover function as light-shielding walls. This effectively suppresses crosstalk, which causes noise, in the particulate matter detection device 1.

[0109] The first light-receiving unit 32a and the second light-receiving unit 32b may be integrated or they may be separate. If the first light-receiving unit 32a and the second light-receiving unit 32b are integrated, the number of components provided in the particulate matter detection device 1 can be reduced, and it becomes easier to attach the first light-receiving unit 32a and the second light-emitting unit 32b to the substrate 12.

[0110] Figure 12 is a schematic cross-sectional view illustrating the light-emitting unit 31, the first light-receiving unit 32a, the second light-receiving unit 32b, and the third light-receiving unit 32c provided in the third modified particulate matter detection device 1 of the first embodiment.

[0111] In the third modified example of the first embodiment, as shown in Figure 12, the light-emitting unit 31, the first light-receiving unit 32a, the second light-receiving unit 32b, and the third light-receiving unit 32c are arranged along the flow path FC. The light-emitting unit 31 is positioned on the side of the second direction D2 with respect to the detection area DR. The first light-receiving unit 32a, the second light-receiving unit 32b, and the third light-receiving unit 32c are positioned on the side opposite to the second direction D2 with respect to the detection area DR. Therefore, the light-emitting unit 31 and the light-receiving units 32 are arranged in the second direction D2, sandwiching the detection area DR. The light-receiving surfaces 82a of the light-receiving elements 82 of the first light-receiving unit 32a, the second light-receiving unit 32b, and the third light-receiving unit 32c are perpendicular to the upper main surface 12a of the substrate 12. Even when three light-receiving units are provided, consisting of a first light-receiving unit 32a, a second light-receiving unit 32b, and a third light-receiving unit 32c, the light-emitting unit 31, the first light-receiving unit 32a, the second light-receiving unit 32b, and the third light-receiving unit 32c are arranged in this manner, the first light-receiving unit 32a, the second light-receiving unit 32b, and the third light-receiving unit 32c are positioned at different locations relative to each other in the first direction D1, from upstream to downstream of the flow path FC.

[0112] The first light-receiving unit 32a, the second light-receiving unit 32b, and the third light-receiving unit 32c preferably each have a first optical axis OAa, a second optical axis OAb, and a third optical axis OAc that pass through the same point within the irradiated position P. This also applies when two light-receiving units or four or more light-receiving units are provided.

[0113] Each of the first light-receiving unit 32a, the second light-receiving unit 32b, and the third light-receiving unit 32c may be a light-receiving unit equipped with an inner cover. When each of the first light-receiving unit 32a, the second light-receiving unit 32b, and the third light-receiving unit 32c is a light-receiving unit equipped with an inner cover, the inner cover functions as a light-shielding wall, which effectively suppresses crosstalk that causes noise in the particulate matter detection device 1.

[0114] If the particle sensor 1 is equipped with three or more light-receiving units, each consisting of a first to the N+Mth light-receiving unit where N and M are integers of 1 or more, with N units on the upstream side of the light source and M units on the downstream side of the light source, the signal processing unit 43 obtains NM diameters of particle FP from the difference between the i-th signal output by the i-th light-receiving unit and the j-th signal output by the j-th light-receiving unit for each integer i from 1 to N and j from 1 to M, and then combines the obtained NM diameters to obtain the final diameter of particle FP.

[0115] This disclosure is not limited to the embodiments described above, and may be replaced with configurations that are substantially the same as those shown in the embodiments, configurations that produce the same effects, or configurations that can achieve the same purpose. [Explanation of Symbols]

[0116] 1. Particulate matter detection device 11 cabinets 11a Channel Inlet 11b Flow outlet FC flow path 12 circuit boards 12a Upper main surface 12b Lower main surface 13 Fasteners 14 Detection unit 14c First side 14d Second aspect 14e Third Aspect 14f Fourth side 15 Blower 16. Microcontroller Unit (MCU) 21 First cover 21a Inlet 21b Flow outlet 21c First inner surface 21d Second inner surface 21e Third inner surface 21f Fourth inner surface 22 Second cover 22a Inlet 22b Flow outlet 23 Third Cover 31 Light-emitting part 31a Space 32 Light receiving part 32a First light receiving unit 32b Second light receiving section 32c Third light-receiving section 41 Control Unit 42 Drive unit 43 Signal Processing Unit 51c First gap 51d Second gap 51e Third gap 61 Light-emitting element 62 Floodlight Lens 63 Wall 63a Recess 63b aperture 63p Convex holding part 81 Focusing lens 82 Photodetector 82a Photosensitive surface 102 Light-blocking wall 100 Light-receiving cover (sensor cover) 103p Convex holding part FP fine particles EL output light DR detection area SL Scattered light SLa First scattered light SLb Second scattered light Sat 1st signal SAS first signal component San's first noise component Sb Second signal Sbs (Second Signal Component) Sbn Second noise component ISb inverted signal DF difference WSa first waveform WSb Second waveform WISb waveform WDF difference waveform Maximum MIN (Minimum value) OAa First optical axis OAb Second optical axis OAc Third Optical Axis

Claims

1. A housing is formed in which a flow path is created having an upstream position, an irradiated position and a downstream position through which multiple fine particles pass sequentially, A light-emitting unit is provided within the housing and irradiates the fine particles passing through the irradiated position with emitted light, A first light receiving unit is provided within the housing and positioned at the upstream location, which receives first scattered light from the passing fine particles and outputs a first signal corresponding to the first scattered light. A second light receiving unit is provided within the housing and positioned downstream, which receives second scattered light from passing particles and outputs a second signal corresponding to the second scattered light. A signal processing unit is provided within the housing and calculates the characteristics of the fine particles using the first signal and the second signal, A particulate matter detection device equipped with the following features.

2. The characteristics of the fine particles include at least one of the particle concentration or particle size of the fine particles. The particulate matter detection device according to claim 1.

3. The housing is provided with a support that supports the first light-receiving unit and the second light-receiving unit. The particulate matter detection device according to claim 1.

4. The housing comprises a first cover having a flow channel inlet and a flow channel outlet, A second cover is provided on the upper side of the first cover, and the flow channel inlet and flow channel outlet are formed therein. The device comprises a third cover provided on the lower side of the first cover, The support is positioned between the first cover and the third cover. The flow path is formed between the support and the first cover, and extends from the flow path inlet to the flow path outlet. The particulate matter detection device according to claim 3.

5. The support is a substrate, The first light-receiving unit and the second light-receiving unit are arranged on the substrate. The particulate matter detection device according to claim 3.

6. The enclosure is equipped with a blower that generates airflow that blows air outside the enclosure, causing the fine particles to sequentially pass through the upstream position, the irradiated position, and the downstream position. The particulate matter detection device according to claim 1.

7. The characteristic of the aforementioned fine particles is their particle size. The signal processing unit calculates the particle size from the difference between the first signal and the second signal. The particulate matter detection device according to claim 2.

8. The characteristic of the aforementioned fine particles is their particle size. The signal processing unit generates a first waveform and a second waveform that show the time changes of the first signal and the second signal, respectively, generates a difference waveform that shows the difference between the first waveform and the second waveform, and calculates the particle size from the first time when the difference waveform takes its maximum value and the second time when the difference waveform takes its minimum value. The particulate matter detection device according to claim 2.

9. The signal processing unit calculates the particle size D from the radius R of the emitted light, the flow velocity v of the fine particles, and the time difference Δt between the first time and the second time, according to equation (11). [Math 1] The particulate matter detection device according to claim 8.

10. The signal processing unit calculates the particle concentration C according to formula (12) based on the cross-sectional area S of the flow path, the time s required for the particles to pass through the irradiated position, and the number of particles N. [Math 2] The particulate matter detection device according to claim 2.

11. The signal processing unit classifies the fine particles according to their particle size. The particulate matter detection device according to claim 7.

12. The characteristics of the fine particles are the particle size and the particle concentration. The signal processing unit calculates the particle concentration from the number of fine particles that have been classified into a specific class within a set period. The particulate matter detection device according to claim 11.

13. Each of the first and second light-receiving units comprises a condensing lens that collects and receives scattered light, a light-receiving element that converts the scattered light that has passed through the condensing lens into an electrical signal and outputs it, and a sensor cover that has a holding part for holding the condensing lens. The particulate matter detection device according to claim 1.

14. The support has a support surface that supports each of the light-receiving parts, Each of the light-receiving units is positioned below the flow path. The light-receiving element has a light-receiving surface that is parallel to the support surface and receives the scattered light. The particulate matter detection device according to claim 13.

15. The first light-receiving unit and the second light-receiving unit are positioned along the flow path, The light-emitting unit is positioned along the flow path and between the first light-receiving unit and the second light-receiving unit. The light-receiving element has a light-receiving surface that is perpendicular to the support surface and receives the scattered light. The particulate matter detection device according to claim 13.

16. The light-emitting unit is positioned along the flow path, Each of the light-receiving units is positioned along the flow path and on the opposite side from the position where the light-emitting unit is located. The light-receiving element has a light-receiving surface that is perpendicular to the support surface and receives the scattered light. The particulate matter detection device according to claim 13.

17. The first light-receiving unit and the second light-receiving unit each have a first optical axis and a second optical axis that pass through the same point within the irradiated position. The particulate matter detection device according to claim 1.

18. An electronic device comprising the particulate detection device described in claim 1.

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