JPS6257925B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a particle size measuring device, and more specifically, for measuring the particle size of relatively fine particles such as spray particles, atmospheric dust, and other solution or solute particles. This invention relates to a particle size measuring device.

For example, in the injection nozzle of an engine fuel injection device, measurements are performed to determine the size of the spray droplets and the distribution of the spray droplets in order to completely burn the fuel. There is a need. In such cases, the conventional method has been to freeze the spray droplets with low-temperature nitrogen gas, photograph the spray droplets in this frozen state, and measure the particle size of the spray droplets photographed. However, such conventional methods are disadvantageous in that they are too time-consuming and cannot be expected to provide accurate measurements. In addition, other particle size measurement methods include measuring the particle size of solute particles such as dust and cigarette smoke floating in the atmosphere. There is a method for measuring the particle size by counting the particles, but this method also has the drawback of not being able to accurately measure the particle size.

As a conventional particle diameter measuring device, there is, for example, Japanese Unexamined Patent Application Publication No. 50-84285. The device disclosed in this publication uses a laser beam to measure the particle diameter, but it is necessary to measure the diameter of each particle one by one. must be set to a size that allows the particles with the largest particle diameter to be taken in one by one among the particles to be measured. However, the device disclosed in this publication uses the laser beam as it is, and the measurement volume field is set so as to receive the reflected light of particles falling within a certain length range of the laser beam. If the measurement volume field of view becomes too large, there is a high probability that reflected light from a plurality of particles will be received, or if the measurement field of view becomes too small, there is a high probability that particles will protrude from the measurement field of view, making it difficult to accurately measure particle diameters.

Moreover, since the intensity of laser light has a Gaussian distribution, if the laser beam is used as is, even if each particle passes through the measurement volume field of view, particles with the same particle size will fall in the center of the field of view. When I passed by,
The disadvantage is that there is a difference in the intensity of the reflected light when it passes through the edge, making it difficult to accurately measure the particle size.

The purpose of the present invention is to form a measurement volume field that allows one set maximum particle to be taken in with probability, regardless of whether the particle is a solute or a solution, and to create a measurement volume field that is coherent with particles passing through this measurement volume field. It is an object of the present invention to provide a particle size measuring device that can obtain the amount of scattered light related to the diameter of the particle by applying a beam, and can accurately measure the particle size from this amount of light.

In the present invention, the luminous flux of the laser beam is expanded to a predetermined thickness so as to form a measurement field of view having a cross-sectional area of the luminous flux that can probabilistically capture the largest diameter particles one by one among the particles to be measured. a uniform illuminance incident optical system that narrows down the light beam having uniform intensity in the central part of the expanded light beam to the light beam cross-sectional area;
and a light receiving system that detects scattered light when the particles to be measured pass through the measurement field of view, and the particle diameter of each particle to be measured can be measured based on the scattered detection light. A particle size measuring device is provided.

The present invention will be explained in detail below with reference to the illustrated embodiments.

FIG. 1 shows a block diagram of a particle size measuring device 1 according to the invention. The particle size measuring device 1 includes an optical system 2 for irradiating a coherent beam onto each particle whose particle size is to be measured and obtaining scattered light from the particle. In the illustrated example, in order to measure the particle size of the atomized particles of fuel injected in the form of a mist from the injection nozzle 4 of the fuel injection pump 3, the collector 5 is arranged opposite to the injection nozzle 4, and the
and the collector 5 in a particle stream 6 of atomized particles.

FIG. 2 shows this optical system 2 in detail, and the optical system 2 includes a laser tube 7 for extracting a laser beam, such as a helium neon gas laser device, as a coherent beam light source. The laser beam 8 is formed by a projection lens system 14 consisting of lenses 9, 10, 11, 12 and a mask 13 into a parallel beam of uniform intensity on the optical axis of the projection lens system 14. A light-receiving field of view is provided at a predetermined location of the parallel light beam by a light-receiving lens system 17 comprising a lens 15 and a mask 16. By focusing the laser beam 8 by the light projecting lens system 14 and setting the light receiving field by the light receiving lens system 17, a three-dimensional measurement volume field 18 is established, as shown in FIG. This measurement volume field of view 18 is formed to have a size that allows the predetermined largest particle among each particle 19 in the particle flow 6 to pass through it one by one. That is, as shown in FIG. 2, the laser beam from the laser tube 7 is once thickened to a diameter of 4 to 5 times by the lens 9, made into a parallel beam by the lens 10, and then the central part of the laser beam is divided by the mask 13. A field of view for measuring the cross-sectional area of the light flux is formed so that only components having uniform intensity are allowed to pass through, and furthermore, the set largest particles can pass through lenses 11 and 12 one by one. In this sense, the light projection lens system 14 functions as a uniform illuminance incident optical system that provides incident light with uniform illuminance. Therefore, since the particles 19 pass through this measurement volume field of view one by one, each time a particle 19 moving in the direction of arrow X passes through this measurement volume field of view 18, the laser beam 8 from the direction of arrow Y is emitted. Scattered from the particles 19 in the direction indicated by the arrow Z and passed through the light receiving lens system 17,
and enters the photomultiplier tube 20. Since the amount of this scattered light is related to the diameter of the particle 19, this amount of light has a predetermined functional relationship with the particle size of the particle.

In addition, the measured volume field of view from the injection nozzle is expressed as a numerical value.
Placed at 3600mm, dimensions are width W 450μ, height H 250
μ and depth D are formed to be 800 μm, but they can be determined as appropriate depending on the set maximum diameter of the particles to be measured.

Returning to FIG. 1, the photomultiplier tube 20 amplifies the scattered light from the particles within the measurement volume field and converts it into an electrical signal with a magnitude according to the amount of scattered light, and this output signal S ₁ is Further, it is amplified by an amplifier 21.

As can be seen from the above explanation, the peak value of the amplified output signal _S2 from the amplifier 21 is determined by the particle 19 within the measurement volume field of view.
Each time the particles pass through, the size changes according to the particle size of the particles. In FIG. 4a, the signal group S ₂ is shown as voltage on the vertical axis and time t on the horizontal axis. This amplified output signal _S2 is input to the hold circuit 22, which accurately holds each peak value of the voltage in the signal _S2 , and is converted into a pulse waveform with a constant width for waveform shaping, as shown in FIG. 4b. Pulse train signal S ₃ as shown
is output as In this process, distortions in the waveform of the signal _S2 caused by noise due to the surface shape of the particles, sphericity, and small non-uniformities in the illuminance of the field of view are processed independently.

In order to statistically process the measurement results of the particle size of the particles in the particle stream 6, the pulse train signal _S3 is input to the latch counter 23, the number of pulses is counted, and only a predetermined number of pulses are passed. I'm starting to forgive myself. Among the pulses having various peak values included in the pulse train signal _S3 , the latch counter 23
The pulses allowed to pass are sent to the peak value analyzer 2.
4 is input. The peak value analyzer 24 is for analyzing how many pulses of what peak value are input, and calculates the peak value of each pulse according to the predetermined number of clock pulses corresponding to the pulse peak value. Replace with the number of clock pulses. This clock pulse is a reference pulse for analog-to-digital conversion and has a temporally stable period. After the peak value is converted into the number of clock pulses in this way, this number of clock pulses is confirmed and an operation is performed to add "1" to the contents of a predetermined address determined by the number of clock pulses in the memory in the peak value analyzer. . A similar operation is performed for the pulses input one after another from the latch counter, and as a result, the number of particles of which size are included in the memory is stored as measurement data. This memory content is output by the tape puncher 25 in the form of tape data. Incidentally, instead of the punching machine 25 serving as the output device, the information may be displayed as a graph on, for example, a cathode ray tube display device, or this information may be directly processed on a minicomputer.

According to such a configuration, the particle to be measured moves within the measurement volume field of view set by the optical system 2.
At this time, the laser beam is scattered with an amount of light proportional to the diameter of the particle, and this scattered light is amplified by the photomultiplier tube 20 and photoelectrically converted into an electric signal. In this case, since a laser beam is used, it requires very little heat to obtain the same amount of light as monochromatic light, so it does not increase the temperature of the particles sprayed from the fuel injection device. This can prevent evaporation due to heating in the case of liquid particles. This electrical signal is waveform-shaped by the hold circuit 22 as described above and statistically processed by the peak value analyzer 24, so that not only the particle size of each particle but also the particle size distribution can be determined.

In the above embodiment, the constancy of the particle size distribution can be achieved by setting the latch counter 23 to 50,000. Of course, the number of pulses may be limited by allowing input pulses to pass for a predetermined time, and in this way, the number of particles can be measured, for example, the amount of fuel injected within a predetermined rotation speed of a fuel injection pump can be measured. It is possible to do so.

Furthermore, since the amplifier 21 obtains a signal with a waveform as shown in FIG. and the transit time, from which the particle velocity can also be determined.

In the above embodiment, a case was described in which the particle size of atomized particles from a fuel injection device was measured, but the measurement target is not limited to atomized particles, but may also be solute particles such as dust in the atmosphere, or other solution particles. Of course, it is possible.

As described above, according to the present invention, by configuring as above, the size of the measurement volume field of view can be
By using a laser beam with uniform intensity at the center, it is possible to set the size to match the largest particle diameter among the particles to be measured, allowing probabilistic measurement of particles one by one. This allows the particles to be captured within a volumetric field of view, making it possible to accurately measure particle diameters. Further, according to the present invention,
Statistical processing allows accurate understanding of spray distribution trends.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a detailed diagram of the optical system shown in FIG. 1, FIG. 3 is an explanatory diagram of the measurement volume field of view, and FIGS. 1
It is a waveform chart of each part of a figure. 1... Particle size measuring device, 2... Optical system, 7...
Laser tube, 8... Laser beam, 14... Light projecting lens system, 17... Light receiving lens system, 18... Measurement volume field of view, 19... Particle, 20... Photomultiplier tube, 22...
hold circuit.

Claims (1)

[Claims] 1 Among the particles to be measured, the one with the largest diameter is probability 1
The light beam of the laser beam is expanded to a predetermined thickness so as to form a measurement field of view having a cross-sectional area of the light beam that can be taken in individually. It has a uniform illuminance incident optical system that focuses on a cross-sectional area, and a light receiving system that detects scattered light when the particle to be measured passes through the measurement field of view. A particle size measuring device characterized by being capable of measuring particle size.