Dust sensors that reduce stray light

Abstract

This utility model relates to a dust sensor that reduces stray light. The dust sensor includes a housing, a light-emitting element, a light-receiving element, and a circuit board. The housing has a partition wall dividing it into a circuit board area and a detection area. A dust passage is located within the detection area. The circuit board is mounted in the circuit board area. The partition wall has light-emitting holes and light-receiving holes corresponding to the light-emitting element and the light-receiving element, respectively. A gap is maintained between the light-emitting element and the light-emitting hole. The circuit board area also has a light-shielding plate extending vertically downward from the housing, corresponding to the light-emitting element. The light-receiving element is embedded in the light-receiving hole. Within the detection area, vertically penetrating light-shielding walls are provided on both sides of the light-receiving element, connecting to the partition wall. The ends of the light-shielding walls extend towards the dust passage. The gap prevents stray light inclined to the optical axis of the light-emitting element from entering the detection area. The light-shielding walls also protect the light-receiving element. This utility model can reduce stray light without the need for a lens, thus reducing assembly costs and difficulty, and improving assembly efficiency.

Description

Technical Field

[0001] This utility model relates to the technical field of dust sensors, and in particular to a dust sensor that reduces stray light. Background Technology

[0002] A dust sensor is used to detect the concentration of dust particles. Patent application number 202010071929.9 provides a relatively systematic summary of existing optical dust sensors. Generally, optical dust sensors include a light-emitting element and a light-receiving element. The light-emitting element emits projected light; this projected light is scattered by dust particles in the detection area, forming scattered light. A portion of the scattered light is received by the light-receiving element. The light-receiving element detects this portion of scattered light and calculates the dust concentration based on the light intensity attenuation. This patent also defines stray light as unwanted light that, unlike scattered light, enters the light-receiving element after being reflected from the projected light, and classifies stray light into two categories: the first category is stray light that enters the light-receiving element after reflection; the second category is stray light that enters the light-receiving element directly after being projected light. The patent explicitly proposes measures to reduce stray light interference by correcting or suppressing measurement errors caused by the pulse technical value of the stray light component. In addition, existing technologies for reducing stray light include placing lenses in the optical path of the light-emitting element and the optical path of the light-receiving element. This requires assembling multiple parts during the dust sensor assembly process, increasing assembly costs and difficulty, and reducing assembly efficiency. Utility Model Content

[0003] The purpose of this invention is to solve the above-mentioned problems and provide a dust sensor that reduces stray light.

[0004] The technical solution of this utility model is as follows: a dust sensor for reducing stray light, comprising a housing, a light-emitting element, a light-receiving element, and a circuit board; the housing has a vertically penetrating partition wall inside; the partition wall divides the interior of the housing into a circuit board area and a detection area; both the top and bottom surfaces of the housing have vertically penetrating dust passage holes; a dust passage channel is formed between the two dust passage holes for dust to pass through; the dust passage channel is located within the detection area; the surfaces of the light-emitting element and the light-receiving element are mounted on the circuit board, and their optical axes both pass through the dust passage channel; the circuit board is mounted in the circuit board area; the partition wall has light-emitting holes and light-receiving holes corresponding to the light-emitting element and the light-receiving element, respectively; the feature is that a gap is maintained between the light-emitting element and the light-emitting hole; the circuit board area also has a light-shielding plate extending vertically downward from the housing corresponding to the light-emitting element; using this gap, some emitted light inclined to the optical axis of the light-emitting element will directly hit the partition wall and then reflect back to the light-shielding plate; at the light-shielding plate, the emitted light is further reflected. The light emitted by these tilted, light-emitting elements is confined within the circuit board area and attenuated after multiple reflections. In addition, the light shield also protects the circuit board and the components on it. The light-receiving element is embedded in the light-receiving hole. In the detection area, vertical light shielding walls that connect to the partition wall are provided on both sides of the light-receiving element to block stray light entering the detection area. The ends of the light shielding walls extend towards the dust vent to ensure that the light-receiving element is adequately protected.

[0005] Preferably, the lower end of the light-shielding plate is provided with a mounting groove corresponding to the light-emitting element; the light-emitting element is embedded in the mounting groove; the mounting groove limits the horizontal position of the light-emitting element to ensure the stability of the installation position of the light-emitting element.

[0006] Furthermore, the circuit board area is provided with a support plate that extends vertically upward from the outer shell, corresponding to the light-emitting element; the support plate supports the circuit board where the light-emitting element is located, improves the installation stability of the light-emitting element, and ensures the stability of the light path of the emitted light.

[0007] Furthermore, the circuit board area is also provided with an upper clamping plate extending vertically downward from the outer shell and a lower clamping plate extending vertically upward from the outer shell; the upper clamping plate and the lower clamping plate clamp the circuit board at the location of the light receiving element, improve the installation stability of the light receiving element, and ensure that the light receiving element stably receives scattered light.

[0008] Furthermore, there are two light-receiving elements, symmetrically arranged on the top and bottom of the circuit board, to improve the signal-to-noise ratio (S / N). Generally, the higher the S / N ratio, the higher the detection accuracy of the dust sensor.

[0009] Furthermore, both the upper and lower clamping plates are provided with mounting slots B at their ends corresponding to the light-receiving element; the light-receiving element is embedded in the mounting slots B and is horizontally limited to stably receive the scattered light.

[0010] Furthermore, the outer shell includes a cover and a box that are interlocked vertically; the partition includes an upper wall integral with the cover and a lower wall integral with the box; the partition has a clamping groove that matches the edge of the circuit board; the upper edge of the clamping groove is located on the upper wall; the lower edge of the clamping groove is located on the lower wall; the clamping groove clamps the edge of the circuit board, increasing the installation stability of the circuit board.

[0011] Furthermore, the upper clamping plate is integrated with the upper wall; the lower clamping plate is integrated with the lower wall; this improves the structural stability of the upper and lower clamping plates.

[0012] Preferably, the edge of the detection area is provided with a sharp corner extending toward the dust passage, which can reduce the reflection of stray light; a light trap is formed between adjacent sharp corners, which can cause stray light to be repeatedly reflected and attenuated in the light trap; the included angle between adjacent sharp corners is ≤30°, which ensures that the light trap attenuates stray light and reduces stray light directed toward the light receiving element.

[0013] Preferably, the light-emitting hole is a speaker structure facing the circuit board area, which can reduce the probability of stray light passing through the light-emitting hole.

[0014] Furthermore, the dust sensor that reduces stray light also includes connecting screws; the cover has an upper connecting post; the housing has a lower connecting post; the upper connecting post has a countersunk hole; the lower connecting post has a threaded hole; the connecting screws pass through the countersunk hole, the circuit board, and the threaded hole to achieve a fixed connection between the cover and the housing; both the cover and the housing are made of conductive resin; the area of ​​the circuit board through which the connecting screws pass is the grounding part of the circuit board; the cover and the housing form a complete shield that is connected to the grounding part of the circuit board, which can reduce the use of metal shielding components, reduce the cost of the dust sensor, and improve the quality of the dust sensor.

[0015] The beneficial effects of this invention are as follows: The dust sensor of this invention, which reduces stray light, has the following advantages:

[0016] (1) This utility model utilizes the gap between the light-emitting element and the light-emitting hole to prevent stray light inclined to the optical axis of the light-emitting element from entering the detection area. Instead, it is attenuated by the repeated reflection process of the light shield and the partition wall. The light shield protects the light-receiving element, so that stray light in the detection area is as little as possible directed to the light-receiving element. This utility model can reduce stray light without the need for a lens, which can reduce assembly costs and assembly difficulty and improve assembly efficiency.

[0017] (2) The light-emitting element and the light-receiving element of this utility model are provided with light trapping portions on opposite sides; the light trapping portions opposite to the light-emitting element can specifically reduce most of the stray light; the light trapping portions opposite to the light-receiving element can prevent stray light from being reflected to the light-receiving element. Attached Figure Description

[0018] Figure 1This is a top view of the dust sensor for reducing stray light according to this utility model;

[0019] Figure 2 yes Figure 1 AA rotated section view;

[0020] Figure 3 yes Figure 2 BB section view;

[0021] Figure 4 yes Figure 3 CC section view;

[0022] Figure 5 yes Figure 3 DD sectional view;

[0023] Figure 6 yes Figure 5 EE sectional view;

[0024] Figure 7 This is a perspective view of the dust sensor for reducing stray light according to this utility model;

[0025] Figure 8 It is a three-dimensional diagram of the cover;

[0026] Figure 9 It is a 3D view of the box;

[0027] Figure 2-3 In the diagram, solid arrows indicate the directions of emitted and scattered light; dashed arrows indicate the direction of stray light within the circuit board area.

[0028] In the diagram: 111. Light-emitting hole, 112. Light-receiving hole, 113. Upper wall, 114. Lower wall, 115. Clamping groove, 12. Circuit board area, 121. Gap, 122. Light-shielding plate, 1221. Mounting slot A, 123. Support plate, 124. Upper clamping plate, 125. Lower clamping plate, 126. Mounting slot B, 13. Detection area, 131. Dust passage, 1321. Upper sharp corner, 1322. Lower sharp corner, 133. Light trapping area, 134. Shielding... 14. Dust vent, 15. Cover, 151. Upper connecting post, 1511. Recessed hole, 152. Inner retaining ring, 16. Box body, 161. Lower connecting post, 1611. Threaded hole, 162. Outer retaining ring, 163. Positioning post, 1631. Conical head, 164. Limiting post, 171. Inner retaining thread, 172. Outer retaining thread, 2. Light-emitting element, 3. Light-receiving element, 4. Circuit board, 41. Positioning hole, 42. Limiting hole, 5. Connecting screw. Detailed Implementation

[0029] Example 1: See Figure 1-9A dust sensor for reducing stray light includes a housing, a light-emitting element 2, a light-receiving element 3, and a circuit board 4. The housing has a vertically penetrating partition wall inside, dividing the interior into a circuit board area 12 and a detection area 13. Vertically penetrating dust passages 14 are provided on both the top and bottom surfaces of the housing. A dust passage channel 131 is formed between the two dust passages 14, allowing dust to pass through. The dust passage channel 131 is located within the detection area 13. The light-emitting element 2 and the light-receiving element 3 are mounted on the circuit board 4, and their optical axes both pass through the dust passage channel 131. The circuit board 4 is installed in the circuit board area 12; the partition plate is provided with light-emitting holes 111 and light-receiving holes 112 corresponding to the light-emitting element 2 and the light-receiving element 3, respectively; characterized in that a gap 121 is maintained between the light-emitting element 2 and the light-emitting hole 111; the circuit board area 12 is also provided with a light-shielding plate 122 that extends vertically downward from the outer shell corresponding to the light-emitting element 2; using this gap, some emitted light that is inclined to the optical axis of the light-emitting element 2 will directly hit the partition wall and then be reflected back to the light-shielding plate 122; the emitted light is further reflected in the light-shielding plate 122. The light emitted by these tilted light-emitting elements 2 is confined within the circuit board area 12 and attenuated after multiple reflections. In addition, the light shield 122 also shields the circuit board 4 and the components on the circuit board 4. The light-receiving element 3 is embedded in the light-receiving hole 112. In the detection area 13, vertical light shielding walls 134 connected to the partition wall are provided on both sides of the light-receiving element 3 to shield stray light entering the detection area 13. The ends of the light shielding walls 134 extend towards the dust vent 14 to ensure that the light-receiving element 3 is fully shielded.

[0030] Compared with the prior art, this utility model utilizes the gap between the light-emitting element 2 and the light-emitting hole 111 to prevent stray light tilted on the optical axis of the light-emitting element 2 from entering the detection area 13. Instead, the stray light is attenuated by the repeated reflections of the light-shielding plate 122 and the partition wall. The light-shielding wall 134 protects the light-receiving element 3, so that as little stray light in the detection area 13 is directed towards the light-receiving element 3 as possible. This utility model can reduce stray light without the need for a lens, thereby reducing assembly costs and assembly difficulty and improving assembly efficiency.

[0031] The lower end of the light-shielding plate 122 is provided with a mounting groove A 1221 corresponding to the light-emitting element 2; the light-emitting element 2 is embedded in the mounting groove A 1221; the mounting groove A 1221 horizontally limits the light-emitting element 2 to ensure that the installation position of the light-emitting element 2 is stable.

[0032] The circuit board area 12 is provided with a support plate 123 that extends vertically upward from the outer shell corresponding to the light-emitting element 2; the support plate 123 supports the circuit board 4 where the light-emitting element 2 is located, improves the installation stability of the light-emitting element 2, and ensures the stability of the light path of the emitted light.

[0033] The circuit board area 12 is also provided with an upper clamping plate 124 extending vertically downward from the outer shell and a lower clamping plate 125 extending vertically upward from the outer shell; the upper clamping plate 124 and the lower clamping plate 125 clamp the circuit board 4 at the location of the light receiving element 3, improve the installation stability of the light receiving element 3, and ensure that the light receiving element 3 stably receives scattered light.

[0034] There are two light-receiving elements 3, symmetrically arranged on the top and bottom of the circuit board 4, to improve the signal-to-noise ratio (S / N). Generally, the higher the S / N ratio, the higher the detection accuracy of the dust sensor.

[0035] Both the upper clamping plate 124 and the lower clamping plate 125 have a mounting groove B 126 at their ends corresponding to the light receiving element 3; the light receiving element 3 is embedded in the mounting groove B 126 and is horizontally limited to stably receive the scattered light.

[0036] The outer casing includes a cover 15 and a box 16 that are snapped together. The partition includes an upper wall 113 integral with the cover 15 and a lower wall 114 integral with the box 16. The partition has a clamping groove 115 that matches the edge of the circuit board 4. The upper edge of the clamping groove 115 is located on the upper wall 113. The lower edge of the clamping groove 115 is located on the lower wall 114. The clamping groove 115 clamps the edge of the circuit board 4, increasing the installation stability of the circuit board 4.

[0037] The upper clamping plate 124 is integral with the upper wall 113; the lower clamping plate 125 is integral with the lower wall 114; this improves the structural stability of the upper clamping plate 124 and the lower clamping plate 125.

[0038] The detection area 13 has sharp corners extending towards the dust passage 14 along its edge, which can reduce the reflection of stray light; a light trap portion 133 is formed between adjacent sharp corners, which allows stray light to be repeatedly reflected and attenuated in the light trap portion 133. The included angle between adjacent sharp corners is ≤30°, which ensures that the light trap portion 133 attenuates stray light and reduces stray light directed towards the light receiving element 3.

[0039] The light-emitting hole 111 is a horn structure facing the circuit board area 12, which can reduce the probability of stray light passing through the light-emitting hole 111.

[0040] The angle between the optical axes of the light-emitting element 2 and the light-receiving element 3 is 70° to 110°. In this embodiment, the angle between the optical axes of the light-emitting element 2 and the light-receiving element 3 is 90°.

[0041] Light trapping portions 133 are provided on opposite sides of the light-emitting element 2 and the light-receiving element 3; the light trapping portion 133 opposite to the light-emitting element 2 can specifically reduce most of the stray light; the light trapping portion 133 opposite to the light-receiving element 3 can prevent stray light from being reflected to the light-receiving element 3.

[0042] The working principle of this embodiment is as follows: by utilizing the gap between the light-emitting element 2 and the light-emitting hole 111, stray light inclined to the optical axis of the light-emitting element 2 does not enter the detection area 13, but is attenuated by the repeated reflection process of the light-shielding plate 122 and the partition wall; the light-shielding wall 134 protects the light-receiving element 3, so that the stray light in the detection area 13 is as little as possible directed to the light-receiving element 3; this utility model can reduce stray light without the need for a lens, which can reduce assembly costs and assembly difficulty, and improve assembly efficiency.

[0043] Example 2: Example 2 is basically the same as Example 1, and the similarities will not be repeated. The difference is that the dust sensor for reducing stray light also includes a connecting screw 5; the cover 15 is provided with an upper connecting post 151; the box 16 is provided with a lower connecting post 161; the upper connecting post 151 is provided with a recessed hole 1511; the lower connecting post 161 is provided with a threaded hole 1611; the connecting screw 5 passes through the recessed hole 1511, the circuit board 4 and the threaded hole 1611 are threaded together to realize the fixed connection between the cover 15 and the box 16; both the cover 15 and the box 16 are made of conductive resin; the circuit board area 12 through which the connecting screw 5 passes is the grounding part of the circuit board 4; the cover 15 and the box 16 form a complete shield connected to the grounding part of the circuit board 4, which can reduce the use of metal shielding components, reduce the cost of the dust sensor and improve the quality of the dust sensor.

[0044] The lid 15 has an inner snap ring 152 along its edge; the box 16 has an outer snap ring 162 along its edge. The outer snap ring 162 and the inner snap ring 152 are interlocked. The sharp corners include an upper sharp corner 1321 and a lower sharp corner 1322 that are interlocked. The upper wall 113 and the upper sharp corner 1321 are both provided with inner snap teeth 171; the lower wall 114 and the lower sharp corner 1322 are both provided with outer snap teeth 172. The inner snap teeth 171 and the outer snap teeth 172 are interlocked. The structure of the lid 15 and the box 16 is more stable after they are snapped together.

[0045] The upper connecting column 151 is integrally formed with the cover body 15, which improves the structural stability.

[0046] The circuit board area 12 of the housing 16 is also provided with positioning posts 163 and limiting posts 164; the circuit board 4 is provided with positioning holes 41 that match the positioning posts 163 and limiting holes 42 that match the limiting posts 164; the positioning posts 163 and limiting posts 164 are respectively inserted into the positioning holes 41 and limiting holes 42 to realize the positioning and limiting of the circuit board 4.

[0047] The end of the positioning post 163 is provided with a tapered head 1631 to guide the positioning post 163 into the positioning hole 41.

Claims

1. A dust sensor for reducing stray light, comprising a housing, a light-emitting element, a light-receiving element, and a circuit board; the housing has a vertically penetrating partition wall inside; the partition wall divides the interior of the housing into a circuit board area and a detection area; the top and bottom surfaces of the housing each have vertically penetrating dust passage holes; a dust passage channel is formed between two dust passage holes; the dust passage channel is located within the detection area; the surfaces of the light-emitting element and the light-receiving element are mounted on the circuit board, and their optical axes both pass through the dust passage channel; the circuit board is mounted in the circuit board area; the partition wall has light-emitting holes and light-receiving holes corresponding to the light-emitting element and the light-receiving element, respectively; characterized in that, A gap is maintained between the light-emitting element and the light-emitting hole; the circuit board area is also provided with a light-shielding plate that extends vertically downward from the outer shell corresponding to the light-emitting element; the light-receiving element is embedded in the light-receiving hole; in the detection area, there are vertically penetrating light-shielding walls on both sides of the light-receiving element that are connected to the partition wall; the ends of the light-shielding walls extend towards the dust vent.

2. The dust sensor for reducing stray light according to claim 1, characterized in that: The lower end of the light-shielding plate is provided with a mounting slot corresponding to the light-emitting element; the light-emitting element is embedded in the mounting slot.

3. The dust sensor for reducing stray light according to claim 2, characterized in that: The circuit board area is provided with a support plate that extends vertically upward from the outer shell, corresponding to the light-emitting element; the support plate supports the circuit board where the light-emitting element is located.

4. The dust sensor for reducing stray light according to claim 3, characterized in that: The circuit board area is also equipped with an upper clamping plate extending vertically downward from the outer shell and a lower clamping plate extending vertically upward from the outer shell; the upper clamping plate and the lower clamping plate clamp the circuit board at the location of the light-receiving element.

5. The dust sensor for reducing stray light according to claim 4, characterized in that: There are two light-receiving elements, arranged symmetrically on the top and bottom of the circuit board.

6. The dust sensor for reducing stray light according to claim 1 or 5, characterized in that: The outer shell includes a cover and a box that are snapped together; the partition includes an upper wall integral with the cover and a lower wall integral with the box; the partition has a clamping groove that matches the edge of the circuit board; the upper edge of the clamping groove is located on the upper wall; the lower edge of the clamping groove is located on the lower wall; the clamping groove clamps the edge of the circuit board.

7. The dust sensor for reducing stray light according to claim 6, characterized in that: The upper clamping plate is integrated with the upper wall; the lower clamping plate is integrated with the lower wall.

8. The dust sensor for reducing stray light according to claim 1, characterized in that: The detection area has sharp corners extending towards the dust vent; light traps are formed between adjacent sharp corners; the included angle between adjacent sharp corners is ≤30°.

9. The dust sensor for reducing stray light according to claim 1, characterized in that: The light-emitting hole is a speaker structure facing the circuit board area.

10. The dust sensor for reducing stray light according to claim 6, characterized in that: It also includes connecting screws; the cover has an upper connecting post; the box has a lower connecting post; the upper connecting post has a countersunk hole; the lower connecting post has a threaded hole; the connecting screws pass through the countersunk hole, and the circuit board is threadedly connected to the threaded hole; both the cover and the box are made of conductive resin; the area of ​​the circuit board through which the connecting screws pass is the grounding part of the circuit board.

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