JP3321482B2 - Laser diffraction type particle size distribution measuring apparatus and method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser diffraction type particle size distribution measuring apparatus and method.

[0002]

2. Description of the Related Art As a method for examining the particle size distribution of powders and granules, there is a laser diffraction type particle size distribution measuring method. This particle size distribution measuring method uses an intensity pattern of scattered light generated when a sample powder dispersed in the air is irradiated with laser light, for example, using a CPU.
Is used to calculate the particle size distribution in a powder sample, and is used in a wide range of fields such as medicines, foods, ceramics, cosmetics, paints, and pigments.

FIG. 2 schematically shows the structure of an apparatus used in the above-mentioned laser diffraction type particle size distribution measuring method. In this figure, reference numeral 1 denotes a hopper, in which a sample powder S is stored.
Reference numeral 2 denotes a flow cell provided below the hopper 1, the upper end of which is connected to the hopper 1 via an inlet pipe 3, and the lower end of which is connected to a dust collector 5 via a discharge pipe 4. 6 is a dust collector 5
Is a vacuum pump connected to.

[0004] Reference numeral 7 denotes a light source provided on one side of the flow cell 2 and made of, for example, a He-Ne laser. . Reference numeral 10 denotes a photodetector that detects scattered light from the flow cell 2 side. Reference numeral 11 denotes a condenser lens provided on the other side of the flow cell 2. Reference numeral 12 denotes a ring-shaped photodetector provided behind the condenser lens 11, which detects scattered light and transmitted light from the flow cell 2 side. Reference numeral 13 denotes a signal switching circuit for appropriately switching the output signals of the photodetectors 10 and 12 and transmitting the output signals to the AD converter 14.

Reference numeral 15 denotes a CPU which performs various controls for each part of the apparatus, and which controls the signal switching circuit 13 and the AD converter.
It processes the output signals of the photodetectors 10 and 12 input via the converter 14 and performs a particle size distribution calculation. 16
Is a display operation unit having various function keys 18 around a display screen 17 such as a CRT, which is configured to be able to display an output obtained by the particle size distribution calculation on the display screen 17 as a particle size distribution graph 19. . Also, 2
Numeral 0 denotes a printer for printing out the result of the particle size distribution calculation.

Conventionally, the measurement is performed by the procedure as shown in FIG. 3 using the laser diffraction type particle size distribution measuring apparatus having the above configuration. That is, the supply of the sample powder S to the flow cell 2 is started (step S11), and the operator instructs the CPU to start measurement (step S1).
2). The scattered light generated from the sample powder S is detected by the photodetectors 10, 1
2 and the scattered light measurement is started (step S1).
3). When the measurement of the scattered light is completed, the particle size distribution is calculated by the CPU 15 from the scattered light intensity pattern (step S14). After the completion of the predetermined calculation, the supply of the sample powder S is stopped (step S15), and preparations are made for the next measurement.

[0007]

Incidentally, in the above measurement, the sample powder S supplied to the flow cell 2 and irradiated with the laser beam is collected by the dust collector 5 and is not reused. The supply of the sample powder S is performed only at the time of measuring the scattered light. However, in the above-described conventional measuring method, the supply of the sample powder S is performed from the operation of supplying the sample powder S (step S11) to the operation of starting the measurement (step S12) and after the end of the scattered light measurement (step S14). Until the stop (step S15), the sample powder S
Is supplied to the flow cell 2, the sample powder S supplied between them is wasted and the sample powder S is consumed more than necessary.

The present invention has been made in consideration of the above-mentioned problems, and has as its object to reduce the consumption of a sample powder to a minimum and to perform a desired measurement at a low cost by a laser diffraction type particle size distribution. It is to provide a measuring device and a method.

[0009]

In order to achieve the above object, according to the first aspect of the present invention, a sample powder dispersed in the air is supplied to a flow cell, and the flow cell is irradiated with a laser beam. and, in the laser diffraction particle size distribution measuring apparatus for measuring a particle size distribution in the sample powder based on the scattered light intensity pattern obtained at that time, the sample powder
The degree of increase or decrease in the scattered light intensity or transmittance caused by the
That the sample powder is supplied based on the degree of
Automatically when the sample powder is no longer supplied
It is characterized in that it is configured to judge . Soshi
The invention according to claim 2 provides a sample powder dispersed in air.
To the flow cell and
Photodetector obtained by irradiating a laser beam to it
Calculate the scattered light intensity and transmittance based on the output of
Particle size of sample powder based on the scattered light intensity pattern
Laser diffraction particle size distribution measuring apparatus odor for measuring the distribution
After supplying the sample powder, the scattered light
Prescribed degree of increase in intensity or degree of decrease in transmittance
Of scattered light data when it is determined that the
It is characterized in that the product is started automatically. In addition,
The invention as set forth in claim 3 is a method in which the sample powder dispersed in the air is flowed.
To the flow cell and to the flow cell
Irradiation of laser light, the output of the photodetector obtained at that time
Calculate the scattered light intensity and transmittance based on the
Particle size distribution in sample powder based on light intensity pattern
In the laser diffraction type particle size distribution measuring device,
After the supply of the powder is stopped, the intensity of the scattered light
Degree of decrease or increase of transmittance
Accumulation of scattered light data when it is determined that the set value has been exceeded
Is automatically terminated. In addition,
The invention as set forth in claim 4 is a method in which the sample powder dispersed in the air is flown.
To the flow cell and to the flow cell
Irradiation of laser light, the output of the photodetector obtained at that time
Calculate the scattered light intensity and transmittance based on the
Particle size distribution in sample powder based on light intensity pattern
In the laser diffraction type particle size distribution measuring device,
After supplying the powder, increase the scattered light intensity in the above calculation.
The degree of addition or the degree of decrease in transmittance is a predetermined set value.
Automatically accumulates scattered light data when it is determined that
Start, and after stopping the supply of sample powder,
In the above calculation, the degree of decrease or transmission of the scattered light intensity
It has been determined that the rate of increase has exceeded the specified value
Automatically terminates the accumulation of scattered light data.
It is a sign. And the invention according to claim 5 is a
When the sample powder dispersed in
First, the flow cell is irradiated with laser light,
Scattered light intensity based on the output of the photodetector
Calculate the transmittance and test based on the scattered light intensity pattern.
Laser diffraction particle size measurement of particle size distribution in powdered materials
In the cloth measurement method, irradiate the flow cell with laser light.
Irradiation step and the flow cell to which the laser light is being irradiated.
Supplying the sample powder to the
The degree of increase in scattered light intensity or decrease in transmittance
Scattering when the degree is judged to exceed the set value
Automatically starting the storage of optical data;
Supply sample powder to the flow cell where light is irradiated
Stopping the scattered light intensity in the calculation.
Predetermined degree of decrease or increase of transmittance
If it is determined that the value has exceeded the
And dynamically terminating steps.
You.

[0010]

In the above-mentioned laser diffraction type particle size distribution measuring apparatus and measuring method, the CPU sets the sample powder S in the following manner.
Can be determined whether or not is supplied to the flow cell 2. That is, even when the sample powder S is not supplied to the flow cell 2, the laser light is applied to the flow cell 2. At this time, the CPU 15 calculates the scattered light intensity and the transmittance based on the output signals of the photodetectors 10 and 12. When the sample powder S is supplied to the flow cell 2, scattered light is generated, and the scattered light intensity increases.
At this time, the transmission of a part of the laser light is hindered by the sample powder S, so that the intensity of the transmitted light decreases and the transmittance decreases. When the supply of the sample powder S to the flow cell 2 is stopped, the intensity of the scattered light decreases, and
The transmittance increases.

Therefore, when the degree of increase in the amount of scattered light or the degree of decrease in the transmittance exceeds a predetermined value, the CP
U15 determines that the sample powder S is being supplied to the flow cell 2, automatically starts scattered light intensity measurement for particle size distribution measurement, and starts accumulation of scattered light intensity data. Also,
When the degree of decrease in the amount of scattered light or the degree of increase in transmittance exceeds a predetermined set value, the sample powder S is removed from the flow cell 2.
Then, the accumulation of the scattered light intensity data is terminated, and the particle size distribution is obtained based on the scattered light intensity data accumulated so far.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a flow chart showing an example of the laser diffraction type particle size distribution measuring method according to the present invention. An apparatus for carrying out the present measuring method has essentially no difference from the apparatus shown in FIG.

First, an operator turns on a power switch of the apparatus. As a result, a laser beam is emitted from the light source 7, and the laser beam is applied to the flow cell 2 via the mirror 8 and the beam expander 9. In this state, the function key “vacuum pump on” of the display operation unit 16 is operated. Thereby, the vacuum pump 6 discharges the air in the flow cell 2 through the dust collector 5 and sucks the air from the upper part of the cell, thereby forming a downward airflow indicated by an arrow in FIG. 2 (step S1).

At the stage when the vacuum pump 6 is started, the sample powder S is not supplied to the flow cell 2 and the
In U15, the scattered light intensity and the transmittance are calculated based on the output signals of the photodetectors 10 and 12 (step S15).
2).

By turning on the function key "Start sample supply", the sample powder S in the hopper 1 is drawn into the flow cell 2 by the air flow as the lower part of the hopper 1 is opened (step). S3). The sample powder S that has passed while flying in the flow cell 2 is collected by the dust collector 5.

As described above, when the sample powder S passes through the flow cell 2, the laser light irradiating the flow cell 2 is partially scattered or absorbed by the sample powder S and partially To Penetrate. The light scattered by the sample powder S is received by the photodetectors 10 and 12, and the particle size distribution is calculated by the CPU 15 from the scattered light intensity pattern. The intensity of the transmitted light is measured by the photodetector 10, and the transmittance is obtained by comparing the transmitted light intensity with the transmitted light intensity of the example in which the sample powder S is not supplied.

When the sample powder S is supplied to the flow cell 2 as described above, the amount of scattered light increases, but the transmission of a part of the light is stopped. Decrease.

Therefore, when the degree of the increase in the amount of scattered light or the degree of the decrease in the transmittance exceeds a predetermined value, the CP
U15 determines that the sample powder S is supplied to the flow cell 2, automatically starts scattered light intensity measurement for particle size distribution measurement, and starts accumulation of scattered light intensity data (step S4).

Thereafter, when the operator turns on the function key "stop sample supply", the lower portion of the hopper 1 is closed, and the supply of the sample powder S to the flow cell 2 is stopped (step S5). reduction in the degree or extent of the increase in transmittance exceeds a predetermined set value Tei Runode, whereby, CPU 15 samples the powder S
Is determined to be no longer supplied to the flow cell 2, accumulation of the scattered light intensity data is terminated (step S6), and a particle size distribution is obtained based on the scattered light intensity data accumulated up to that time (step S7).

The result of the particle size distribution calculation is stocked in the memory of the CPU 15 and displayed as a particle size distribution graph on the display screen 17 of the display / operation unit 16 or printed out by the printer 20 in some cases. You.

As will be understood from the above description, the sample powder S is not supplied to the flow cell 2 when the particle size distribution is not measured, so that the sample powder S is consumed more than necessary. There is no.

Note that the measurement of the scattered light may be terminated after a predetermined measurement time elapses or by an operator's termination operation, other than when the supply end of the sample powder S is detected.
In this case, the supply of the sample powder S may be stopped after the measurement of the scattered light is completed, so that the unnecessary supply of the sample powder S during non-measurement may be eliminated.

In the above-described embodiment, the degree of increase and decrease of the scattered light intensity and the degree of increase and decrease of the transmittance are detected at the same time, thereby supplying or stopping the sample powder S. The invention is not limited to this, and it is also possible to supply or stop the sample powder S based on only one of the degree of increase and decrease of the scattered light intensity and the degree of increase and decrease of the transmittance. Not even.

[0025]

As described above, according to the present invention,
The sample powder is not supplied unnecessarily from the sample powder supply operation to the measurement start operation and before the sample powder supply stop operation is performed after the scattered light measurement. As a result, the sample powder is not supplied, and only the sample powder truly required for the measurement is consumed, so that the desired measurement can be performed at low cost.

[Brief description of the drawings]

FIG. 1 is a flowchart showing an example of a procedure of a laser diffraction type particle size distribution measuring method according to the present invention.

FIG. 2 is a diagram schematically showing a configuration of an apparatus for performing the measurement method.

FIG. 3 is a flowchart showing a procedure of a conventional method.

[Explanation of symbols]

 2 ... Flow cell, 15 ... CPU, S ... Sample powder.

Claims (5)

(57) [Claims] 1. A method for supplying a sample powder dispersed in the air to a flow cell, irradiating the flow cell with laser light, and obtaining a particle size distribution in the sample powder based on a scattered light intensity pattern obtained at that time. Caused by the sample powder in a laser diffraction type particle size distribution measuring device
The degree of change in scattered light intensity or the degree of change in transmittance
That the sample powder is supplied based on
Automatically determine when your body is no longer supplied
Laser diffraction particle size distribution measurement instrumentation, characterized in that configuration the
Place . (2) Sample powder dispersed in air is placed in a flow cell
Laser beam to the flow cell
And based on the output of the photodetector obtained at that time
To calculate the scattered light intensity and the transmittance.
Measuring particle size distribution in sample powder based on turn
In the laser diffraction particle size distribution analyzer, supply the sample powder.
After the supply, the degree of increase in the scattered light intensity
Or the degree of decrease in transmittance exceeds the specified value
Automatically starts storing scattered light data when it is determined
A laser diffraction type particle size distribution measuring device. (3) Sample powder dispersed in air is placed in a flow cell
Laser beam to the flow cell
And based on the output of the photodetector obtained at that time
To calculate the scattered light intensity and the transmittance.
Measuring particle size distribution in sample powder based on turn
In the laser diffraction type particle size distribution analyzer,
After the supply is stopped, the scattered light intensity decreases in the above calculation.
The degree of increase or the degree of increase in transmittance
Automatically accumulates scattered light data when it is determined to exceed
Laser diffraction particle size distribution measurement
apparatus. (4) Sample powder dispersed in air is placed in a flow cell
Laser beam to the flow cell
And based on the output of the photodetector obtained at that time
To calculate the scattered light intensity and the transmittance.
Measuring particle size distribution in sample powder based on turn
Laser diffraction particle size distribution analyzer The sample powder.
After the supply, the degree of increase in the scattered light intensity
Or the degree of decrease in transmittance exceeds the specified value
Automatically starts accumulating scattered light data when it is determined that
After the supply of the sample powder is stopped,
The degree of decrease in scattered light intensity or increase in transmittance
If it is determined that the degree of
Automatically terminates storage of scattered light data
Laser diffraction particle size distribution analyzer. (5) Sample powder dispersed in air is placed in a flow cell
Laser beam to the flow cell
And based on the output of the photodetector obtained at that time
To calculate the scattered light intensity and the transmittance.
Measuring particle size distribution in sample powder based on turn
In the laser diffraction particle size distribution measurement method, the flow cell
Irradiating the laser light to the
For supplying sample powder to the flow cell
And the degree of increase in the scattered light intensity in the above calculation.
Or that the degree of decrease in transmittance exceeds a specified value.
Automatically start scattered light data accumulation when interrupted
Step and the flow cell irradiated with the laser light
Stopping the supply of the sample powder by performing
The degree of decrease in scattered light intensity or increase in transmittance
Scattering when the degree is judged to exceed the set value
Automatically terminating the accumulation of optical data
A laser diffraction type particle size distribution measuring method, characterized in that: