dust sensor

Abstract

To provide a dust sensor of light scattering type with which dust hardly accumulates in a light projection unit or a light receiving unit, and with which it is possible to reduce the frequency of maintenance.SOLUTION: Provided is a dust sensor that detects dust floating in the air, said sensor comprising: a measurement air intake opening for drawing in a measurement air from the outside, a measurement passage in which the drawn-in measurement air flows; a casing that forms an exhaust opening where the drawn-in measurement air is discharged; a heater that causes a measurement air current heading from the measurement air intake opening to the exhaust opening to occur in the measurement passage; a light projection unit that emits detection light to a prescribed detection area that is set to the measurement passage; a light receiving unit that senses scattering light that is scattered by dust in the detection area; and a protective air current generation mechanism that causes a protective air current flowing toward the detection area to occur between the light projection and light receiving units and the detection area.SELECTED DRAWING: Figure 2

Claims

1. A dust sensor that detects dust floating in the air, A casing that forms a measuring air intake port for taking in measuring air from the outside, a measuring air path through which the taken-in measuring air flows, and an exhaust port for discharging the taken-in measuring air, A heater that generates a measuring airflow in the measuring path from the measuring air intake port toward the exhaust port, A light-emitting unit that emits detection light into a predetermined detection area set on the measurement channel, A light receiving unit that senses scattered light scattered by dust in the aforementioned detection area, Between the light-emitting unit and the light-receiving unit and the detection area, there is a protective airflow generating mechanism that generates a protective airflow that flows toward the detection area. A dust sensor in which the protective airflow generation mechanism generates the protective airflow using heat from a heater located below the detection area.

2. The measurement channel is formed extending from the bottom surface to the top surface of the casing. The dust sensor according to claim 1, wherein the light-emitting unit and the light-receiving unit are arranged diagonally on the bottom side of the detection area so as to face the detection area.

3. It has a detection light passage space that guides the detection light emitted from the light-emitting unit to the detection area, and a scattered light passage space that guides the scattered light from the detection area to the light-receiving unit, The dust sensor according to claim 2, wherein the detection light passage space and the scattered light passage space are tunnel-shaped, with their entire circumference surrounded by the inner wall of the casing when viewed from the optical axis direction of the respective optical axes of the light-emitting unit and the light-receiving unit, and one end along the optical axis direction is open toward the detection area.

4. The protective airflow generation mechanism is, A heater positioned on the bottom side of the detection light passage space and the scattered light passage space, The system includes a protective airflow supply channel that supplies the rising airflow generated by heating the heater as a protective airflow to the detection light passage space and the scattered light passage space, The dust sensor according to claim 3, wherein the protective airflow supply channel opens to the inner wall of the casing that forms the detection light passage space and the scattered light passage space, respectively.

5. The light-emitting unit and the light-receiving unit are arranged to be substantially symmetrical with respect to the measurement channel. The dust sensor according to claim 4, configured such that the protective airflow flowing through the detection light passage space and the protective airflow flowing through the scattered light passage space merge in the detection region and then flow through the measurement channel toward the exhaust port.

6. The dust sensor according to claim 1, wherein the measuring airflow and the protective airflow are configured to be generated using the heat of a common heater.

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