JPH0124616Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to the improvement of a light scattering particulate measuring device that optically measures the size and number of particulates and dust floating in the air, with the aim of improving measurement accuracy and expanding the range of measurement targets. do.

Light scattering particulate measuring equipment is used to measure the size and number of particulates floating in rooms where cleanliness is specially controlled, such as clean rooms. Sample air is sucked into an optical sensor inside the equipment using a pump, etc. The scattered light generated by irradiating fine particles in the air with a light source is received by a photoelectric converter such as a photomultiplier, and converted into an electric pulse signal to measure the optical size and number of the fine particles. That is, since the intensity of the scattered light already corresponds to the actual size of the particles, the size and number of particles in the sample air can be determined by measuring the peak value and number of the electric pulse signal.

This type of light scattering particle measuring device is easy to handle, so it is often used to measure the cleanliness of clean rooms, etc. However, because the amount of sample air sampled per unit time is very small, it is difficult to accurately measure the cleanliness inside the clean room. It was difficult and time consuming to measure. The sample air suction rate of a normal light scattering particulate measurement device is about 300c.c./min. , the amount of suction is too small. The small amount of sample air sucked is also a factor that causes the problem that the collection efficiency varies depending on the particle size due to aerodynamic causes when sample air is sucked. In other words, when the particles are small, they move in almost the same way as air molecules, so they are easily sucked into the light scattering particle measurement device along with the sample air, but as the particles get larger, they move differently from the air flow. . This is more noticeable the smaller the air flow and the slower it is. Therefore, in order to introduce large particles into the light scattering particle measurement device, it is necessary to suck a large amount of sample air, which necessitates increasing the amount of suction per hour.

However, conventional particulate measuring devices are based on the premise that it is necessary to measure the total number of particulates in sample air. It was believed that it was necessary to enlarge the light source image focused on a point, so a narrow nozzle was inevitably used, and the diameter of the nozzle was about 1 mm. The velocity of sample air passing through this nozzle increases as the suction volume increases, and when passing through the nozzle, particles are broken or aggregated by the hydrodynamic movement of air molecules or particles. Unlike the state before being sucked into the measuring device, there was a possibility that the particle size distribution pattern would change significantly. Changes in the particle shape and distribution pattern are proportional to the sample air velocity when passing through the nozzle, so the nozzle passing velocity cannot be increased too much. Therefore, the amount of sample air that can be aspirated by a narrow nozzle determined by optical conditions is limited by considerations of passage speed. In addition, the narrow nozzle has problems such as being unable to pass large particles or viscous particles and getting stuck inside the nozzle.

Therefore, the present invention focuses illumination light from a light source on a sample air containing fine particles, generates scattered light on the fine particles, and detects this scattered light. A cylindrical sample air introduction tube is provided, and a detection section in which the illumination light from the light source is focused on the sample air and scattered light is generated on the particles is provided, and the detection section has a diameter sufficiently larger than the detection section area. It is set approximately in the center of the sample air introduction tube.

Therefore, according to the present invention, the small diameter nozzle through which the sample air passes is eliminated, and particles are detected in a small central part (detection area) of the sample air introduction tube that has a large cross-sectional area. The amount of suction can be easily increased without excessively increasing the sample air passing speed. Therefore, the sampling efficiency can be improved without causing a large change in the particle size distribution pattern. In addition, the diameter of the sample air introduction tube is large, so it is possible to measure relatively large particles without blocking their passage, and it is also effective in measuring highly viscous aerosol particles such as paint. be.

An embodiment of the present invention will be described below with reference to the drawings. In FIGS. 1 and 2, 1 is a light source that irradiates illumination light, and 2 is an illumination lens that is attached to a cylindrical housing and condenses the illumination light emitted from the light source 1.
Reference numeral 3 denotes a detection section which is formed by the illumination light focused by the illumination lens 2, and the particles flowing through the detection section 3 are irradiated with the illumination light to generate scattered light. Reference numeral 4 denotes an illumination light trap that absorbs the light after the illumination light is collected by the detection unit 3 and improves the signal-to-noise ratio. Reference numeral 5 denotes a cylindrical sample air introduction tube through which the sample air A flows, and a light source 1 and an illumination lens 2 are disposed so that the detection section 3 is disposed approximately on the center line of the tube. The size (volume) of the detection section 3 is determined by the illumination light and the optical conditions of the light receiving section, and is selected to be about 3 mm, for example.
On the other hand, the diameter of the sample air introduction tube 5 is made sufficiently large, for example, about 30 mm, by several times or more. Reference numeral 6 denotes a window for an optical passage made of a transparent plate such as glass, and the center line of the window 6 substantially coincides with the center line of each of the windows 6 and is mutually connected to the sample air introduction tube 5 in order to pass illumination light and scattered light. It is located perpendicular to the That is, the detection section is set approximately at the center of the sample air introduction tube. The sample air introduction tube 5 may be entirely made of a transparent material such as a glass tube. 7 is a fan for sucking and introducing sample air. Reference numeral 9 denotes a light-receiving lens, which is attached to the cylindrical housing, and whose long axis is orthogonal to the long axis of the illumination lens 2, and which focuses the scattered light generated by the detection section 3. Reference numeral 10 denotes a slit having a small hole in the center thereof, and is attached to the storage body with the small hole aligned with the point where the scattered light is focused. Reference numeral 8 denotes a light receiving element which receives the scattered light generated by the detecting section 3 through the slit 10 and converts it into an electric pulse signal. In this case, the slit 10 is for restricting the optical system of illumination light and scattered light for detecting only the flow of sample air A into the detection section 3 flowing through the sample air introduction tube 5, The scattering optical system other than the flow 3 is blocked by the slit 10 and does not reach the light receiving element 8. 11 is a scattered light trap for absorbing scattered light generated on the side opposite to the light receiving element 8.

In the above configuration, the sample air A is suctioned into the sample air introduction tube 5 by the fan 7. Next, the illumination light generated from the light source 1 passes through the illumination lens 2 and is condensed by the detection section 3, and irradiates the particles in the sample air passing through the detection section 3. The irradiated particles generate scattered light. The generated scattered light is received by the light receiving element 8 via the light receiving lens 9 and the slit 10, and is converted into an electric pulse signal. The optical size and number of microparticles in a unit volume are measured using this electric pulse signal.

[Brief explanation of drawings]

FIG. 1 is a plan sectional view of this invention, and FIG. 2 is a cross-sectional view taken from FIG. 1. 1: Light source, 2: Illumination lens, 3: Detection unit, 4:
Lighting trap, 5: sample air introduction tube, 6: window,
7: Fan, 8: Light receiving element, 9: Light receiving lens, 1
0: slit, 11: scattered light trap.

Claims (1)

[Claims for Utility Model Registration] (1) In a device that focuses illumination light from a light source 1 on sample air A containing fine particles to generate scattered light on the fine particles, and detects this scattered light. , a cylindrical sample air introduction pipe 5 is provided as a passage through which the sample air A flows, and a detection unit 3 in which the illumination light from the light source 1 is focused on the sample air A and scattering light is generated on the particles is connected to the detector 3. A light scattering particulate measuring device that is set approximately at the center of the sample air introduction tube 5 having a diameter sufficiently larger than the detection section 3 area. (2) The light scattering particle measuring device according to claim 1, wherein the sample air introduction tube 5 is made of a transparent material such as glass.