JPH0652231B2 - Sedimentation type particle size distribution measuring device - Google Patents

Description

Detailed Description of the Invention a. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to sedimentation type particle size distribution measurement, and more particularly to a technique for removing the dependency of particle shape.

B. Prior Art In an apparatus for measuring the particle size and particle size distribution of powder and granular materials based on the sedimentation velocity, However, V: sedimentation velocity for particles having a particle diameter d, l ₁ : particle density l ₂ : medium liquid density n: medium liquid viscosity K: gravity acceleration in the natural sedimentation method, and centrifugal sedimentation method Is the centrifugal force, and the difference in the sedimentation velocity for each particle size, which is determined based on the Stokes equation, is detected as the change in absorbance over time. This is based on the assumption that the particles are spherical.

However, the powder particles used in recent fine ceramics have a very large variation in the projected area depending on the posture of the particles as shown in FIG. There is a problem that accuracy and reproducibility are extremely lowered (Fig. 6).

C. OBJECT The present invention has been made in view of the above problems, and an object thereof is to provide a sedimentation type particle size distribution measuring apparatus capable of measuring the particle size distribution of irregularly shaped particles with high accuracy and reproducibility. To do.

D. SUMMARY OF THE INVENTION That is, the feature of the present invention is that the optical paths for detecting absorbance are provided in a plurality of directions.

E. Examples Therefore, details of the present invention will be described below based on illustrated examples.

1 and 2 show one embodiment of the present invention,
In the figure, reference numeral 1 is a rotary disk driven by a rotary shaft 2 connected to a motor (not shown). A measuring cell 3 is attached in a radial direction to a portion where a transmission window 1a is formed, and the rotary disk 1 surface Plane mirrors 4 and 5 which are parallel to the optical path L and are inclined at an angle of approximately 45 ° with respect to the optical path L passing through the measuring cell 3.

On one side of the portion facing the window 1a, a light emitting element 6 that is movable in a direction transverse to the sinking direction is provided.
On the other side, a chevron-shaped mirror 7 composed of two plane mirrors 7a and 7b having a reflecting surface directed to about 45 ° on the surface of the rotating disc 1 is provided, and a plane mirror on the rotating disc 1 is provided via a plane mirror 8. 4, an optical system is configured to connect the optical paths to the measurement cell 3, the plane mirror 5, and the light receiving element 9 described later. Reference numeral 9 is a light receiving element, and the plane mirror 5 of the rotary disc 1 is moved in accordance with the movement of the light emitting element 6.
And the reflected light from one flat mirror 7a of the chevron-shaped mirror 7 are received via the flat mirror 10. A measuring circuit 13 receives a signal from the light receiving element 9 via the gate 12 that opens when the measuring cell 3 on the rotating disk 1 reaches the detection region.

In this example, when the measuring cell 3 containing a sample in which spherical particles are dispersed in a liquid medium is set on the rotary disc 1 and the apparatus is operated, the particles in the measuring cell 3 are subjected to centrifugal force. Then, the sedimentation is started at a rate proportional to the particle size.

At this time, if the light emitting element 6 and the light receiving element 9 are arranged in the first region, that is, the position shown by the dotted line in the figure, the light from the light emitting element 6 passes through the measuring cell 3 and is reflected by the chevron mirror 7 and the plane mirror 10. Then, the light passes through the optical path to the light receiving element 9. When the measurement cell 3 faces the detection range in such a state, the gate 12 opens and the absorbance due to the light incident at right angles to the surface of the rotating disk 1 is detected.

Next, when the light emitting element 6 and the light receiving element 9 are moved to the second region shown by the solid line in the figure, the light from the light emitting element 6 is incident on the measurement cell 3 once at a right angle to the surface of the rotating disk 1. , The plane mirror 7b of the chevron-shaped mirror 7, the plane mirror 8, the rotating disk 1
The light is reflected by the upper plane mirror 4, enters the measuring cell 3 again in parallel to the surface of the rotating disk 1, and is absorbed by the particles. The light emitted from the measuring cell 3 is reflected by the plane mirror 5 and received by the light receiving element 9
And the absorbance is measured in the measurement circuit 13.
Needless to say, since the shape of the powder and granules is spherical,
Between the measurement result of 1 and the second measurement result, there is only a change based on the optical path length, and there is no change based on the directionality.

On the other hand, when a non-spherical powder is used as a sample for measurement,
Each particle of the powder and granular material starts to settle in the liquid medium with its surface facing in all directions.

In this state, if the absorbance in the first region is detected,
This light is absorbed according to the number of particles with the particle surface oriented at right angles to the optical path, and is thus greatly affected by the particle posture due to Brownian motion, etc., and the result will vary from measurement to measurement (6th Figure).

Next, when the light emitting element 6 and the light receiving element 9 are moved to the second region, the light from the light emitting element 6 is incident on the measurement cell 3 from the direction perpendicular to the rotating disk 1 and the particles P _{1 to} P on this light beam. ₄ is irradiated once, receives the light absorption corresponding to the particle area projected on the rotating disk 1, and goes out of the measurement cell 3 (FIG. 4I). This light is reflected by the chevron mirrors 7 and the plane mirrors 8 and 4 and is incident on the measurement cell 3 again from the direction parallel to the surface of the rotating disk 1 and the other surface side of the particles P _{1 to} P ₄ involved in the previous absorption. That is, after receiving the light absorption that matches the area projected on the plane perpendicular to the rotating plate (II), it is incident on the light receiving element 9. As a result, the measurement circuit 13 receives the absorbance signal corresponding to the size of the same particles P _{1 to} P ₄ viewed from both sides, and outputs the particle size distribution value based on the value obtained by geometrically averaging the major axis and the minor axis of the granular material. Will be
Even if the same sample is measured many times, the same particle size distribution value is always output (Fig. 5).

In this embodiment, the measurement optical system for the first region which is incident on the measurement cell 3 from one direction is provided.
It is clear that the particle size distribution can be measured by using only the region regardless of whether it is spherical or non-spherical.

Further, in this embodiment, the light emitting element 6 and the light receiving element 9 are moved and shared, but the same effect can be obtained even if the light emitting element and the light receiving element are separately arranged in each region.

FIG. 3 shows a second embodiment of the present invention,
Reference numerals 20 and 21 in the figure denote light emitting elements arranged on an optical path that intersects in the measurement cell 3 region on a plane that crosses the sedimentation direction.
23 is provided and the outputs from the two light receiving elements 22 and 23 are input to the adder circuit 24 to obtain the geometric average particle size of the granular material. According to this embodiment, In addition to not requiring a system and simplifying the apparatus, it is possible to grasp the absorbance in each direction independently and to know the shape of the granular material more accurately.

Although the absorbance is measured in two directions in the above-described embodiment, it goes without saying that the measurement accuracy improves as the number of directions in which the absorbance is measured increases.

Further, in the above-described embodiment, the example in which the centrifugal force is applied has been described, but it is obvious that the present invention can be applied to the natural sedimentation type that utilizes the action of gravity.

F. Effects As described above, according to the present invention, since the absorbance is detected from a plurality of directions of the measurement measurement cell, it is possible to detect the absorbance corresponding to the practical shape of the granular material. Even in the case of spherical powder particles, the influence of the posture difference can be minimized to accurately measure the particle size distribution based on the geometric mean in a short time.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 and FIG. 2 are a perspective view and a structural view of an apparatus showing an embodiment of the present invention, respectively. FIG. 3 is a structural view showing another embodiment of the present invention, and FIG. Is an explanatory view for showing the operation of the above device,
FIG. 5 is a particle size distribution chart showing an example of the measurement result by the same apparatus, FIG. 6 is a particle size distribution chart showing the measurement result by the conventional apparatus, and FIGS. It is explanatory drawing which shows the projected area by the attitude | position difference of a particle, and the spherical size equivalent to this. 1 ... Rotating disk, 3 ... Measuring cell 6 ... Light emitting element, 9 ... Light receiving element 20, 21 ... Light emitting element 22, 23 ... Light receiving element

Claims (1)

[Claims] 1. A cell containing a sample in which a granular material is dispersed in a liquid medium and a plurality of optical paths passing through the cell from a plurality of directions on the same plane crossing the sedimentation direction are set, and the measurement is performed on the optical path. A sedimentation-type particle size distribution measuring apparatus comprising: an absorbance measuring means, which is provided with a light emitting means and a light receiving means so as to sandwich a cell, and a means for adding the absorbance detection signals from the absorbance measuring means in each direction.