JP2003279466A - Measuring cell for particle size sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cost-reducible and miniaturizable measuring cell for a particle size sensor capable of preventing efficiently a powder sample or the like from adhering to optical windows. <P>SOLUTION: This measuring cell for the particle size sensor for measuring the particle size of the sample by irradiating a scattering field 40 inside the measuring cell 4 with measuring light from a light source has a jet nozzle 41 arranged on the position not interfering with the measuring light irradiated from the light source and scattered light diffracted or scattered on the scattering field, for introducing the powder sample into the scattering field, the optical windows 43, 44 for allowing the measuring light to enter the scattering field and emitting the measuring light from the scattering field to the outside of the measuring cell, exhaust nozzles 472, 482 arranged dispersedly on the outer peripheral parts of the inner faces of the optical windows, for jetting pressurized fluid to the inner faces of the optical windows, fluid passages 473, 483 for flowing the pressurized fluid jetted from the exhaust nozzles from the optical windows toward the scattering field, and a discharge nozzle 42 for discharging the powder sample measured in the scattering field. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a measuring cell used for a laser diffraction / scattering type particle size distribution measuring sensor for measuring the particle size distribution of various powder samples in the field of powder industry and the like. The present invention relates to a measuring cell for a particle size sensor capable of preventing a powder sample or the like from adhering to a window.

[0002]

2. Description of the Related Art In the field of powder industry, a particle size distribution measuring device (particle size analyzer) is used as a means for confirming the properties and quality of a powder product during development and manufacturing. The method of measuring etc. is widely used.
As such a particle size distribution measuring device, the ease of measurement,
From the viewpoint of speed and reproducibility of measurement data, the laser diffraction / scattering type particle size distribution measuring apparatus is most widely used.

The measurement of the particle size distribution by the laser diffraction / scattering method is performed by irradiating a particle group (powder sample) to be measured with a laser beam in the particle size sensor section, and the intensity of the scattered light generated by the particle diffraction or scattering with respect to the scattering angle. This is done by detecting the distribution. The scattered light is collected by the optical lens and detected by the detection light receiving element arranged on the focal plane of the lens. From the intensity distribution for the scattering angle of scattered light,
The particle size distribution of sample particles can be obtained by an arithmetic expression based on Fraunhofer's diffraction theory or Mie's scattering theory.

In a particle size sensor used for particle size distribution measurement, a powder sample is introduced into a scattering field set in a measuring cell and the powder sample in the scattering field is irradiated with measuring light. The measurement light is emitted from a light source outside the measurement cell through the optical window.
Further, the scattered light diffracted and scattered by the powder sample reaches the photodetector outside the measurement cell through another optical window.
These optical windows also have a function of shielding the internal space of the measurement cell from the outside, and the powder sample introduced into the measurement cell does not leak to the outside.

In such a measuring cell, it is necessary to prevent the powder sample from adhering to the optical window for passing the measuring light and the scattered light. When the optical window is contaminated due to the powder sample adhering to the optical window or the like, the scattered light due to the contamination of the optical window adversely affects the measurement result and causes a problem such as deterioration of measurement accuracy.

As a means for preventing the powder sample from adhering to such an optical window, there is one described in Japanese Patent No. 3183853. Japanese Patent No. 3183853 discloses an in-line particle size distribution measuring device in which air is caused to flow from the inner surface of a shielding transparent glass provided in a measuring head toward a passage of powder particles. This in-line particle size distribution measuring device uses the above-mentioned air flow to
It is intended to prevent the powder particles from adhering to the shielding transparent glass.

[0007]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The in-line particle size distribution measuring device described in Japanese Patent No. 853 is effective in preventing powder particles from adhering to the shielding transparent glass, but it still has the following problems. . Since the part that ejects air to the shielding transparent glass is a circular slit along the outer periphery of the shielding transparent glass, the ejection speed of the air decreases, and the ejection speed sufficient to prevent the particles from adhering is reduced. You may not get it. Further, in order to sufficiently increase the ejection speed of air, the amount of air to be supplied also becomes large, and it becomes necessary to use a large air pressurizing device. Therefore, there is a problem in that the cost of the entire apparatus increases.

In addition, the air flow to the shielding transparent glass may not be uniform due to the positional relationship with the air inflow hole to the hollow portion. Due to such non-uniformity of the air flow, it may not be possible to effectively prevent the adhesion of the powder or granular material. If a large number of air inlet holes to the hollow portion are uniformly arranged on the entire circumference, such nonuniformity of the air flow is reduced, but it is inevitable that the entire measuring head becomes large. With a small measuring head, it is difficult to arrange a large number of air inflow holes, and there is a problem in that the adhesion of powder particles cannot be effectively prevented due to non-uniform air flow.

Therefore, the present invention solves the above problems and can efficiently prevent the powder sample and the like from adhering to the optical window, and further, can reduce the cost and the size. It is intended to provide a measuring cell for a particle size sensor.

[0010]

In order to achieve the above object, a measuring cell for a particle size sensor of the present invention is a particle size for measuring a particle size of a sample by irradiating a scattered field inside the measuring cell with a measuring light from a light source. A sensor measurement cell, which is arranged at a position that does not interfere with the measurement light emitted from the light source and the scattered light diffracted or scattered in the scattering field, and a jet nozzle for introducing a powder sample into the scattering field, While the measurement light is incident on the scattered field, an optical window for emitting scattered light from the scattered field to the outside of the measurement cell, and the optical window is arranged discretely on the outer peripheral portion of the inner surface of the optical window, and the inner surface of the optical window. An outlet for ejecting a pressurized fluid onto the inner surface, a fluid passage for allowing the pressurized fluid ejected from the outlet to flow from the optical window toward the scattering field, and a powder sample measured in the scattering field is discharged. Discharge noz And it has a door.

Further, in the above-mentioned measurement cell for particle size sensor, it is preferable that the ejection port is arranged so that the pressurized fluid is ejected onto the inner surface of the optical window substantially uniformly.

Further, in the above-mentioned particle size sensor measuring cell, there is a pressurized fluid supply passage, and the ejection ports are arranged such that the distribution density on the supply passage side is higher than the distribution density on the opposite side. Preferably.

Further, in the above measuring cell for particle size sensor, with respect to the optical axis of the measuring light incident from the light source,
It is preferable to perform measurement by arranging the measurement cell so that the normal line of the surface of the optical window is inclined.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing the configuration of a particle size distribution measuring device 1 using a measuring cell 4 of the present invention.
In the particle size distribution measuring device 1, a particle size sensor including a laser light source 2, a measuring cell 4, a condenser lens 5 and a photodetector 6 is provided. The laser light generated by the laser light source 2 passes through the collimator 3 and is converted into parallel light, which is applied to the scattered field 40 in the measurement cell 4. Scattering field 4 of measuring cell 4
At 0, a powder sample for measuring the particle size distribution is introduced. Diffraction / scattering of the measurement light (parallel laser light) is caused by the sample particles, and the particle size distribution of the sample is measured by measuring the intensity distribution of the scattered light.

The specific structure of the measuring cell 4 of the present invention will be described later in detail. The condenser lens 5 has a scattered field 40.
It is for collecting the scattered light scattered by the sample particles. The photodetector 6 is for detecting the intensity distribution of scattered light, and is composed of a plurality of detection elements as described later.

With respect to the intensity distribution of the scattered light detected by the plurality of detection elements of the photodetector 6, the multiplexer 7 multiplexes the detection data of each detection element with respect to the time axis.
The intensity distribution data is further amplified by the amplification amplifier 8 and converted by the A / D converter 9 into digital data for each detection data of each detection element. The output of the A / D converter 9 is sent to the arithmetic control means 10. Arithmetic control means 10
Then, the particle size distribution is obtained from the detection data of each detection element by a predetermined arithmetic expression based on the Fraunhofer diffraction theory or Mie scattering theory.

Then, the arithmetic control means 10 outputs the calculated particle size distribution of the sample to the output means 11 for display. The output means 11 includes a display device such as a CRT or a liquid crystal panel for displaying characters and figures, a printer for printing characters and figures, and the like. Further, the arithmetic and control unit 10 is provided with an input device (keyboard, mouse, etc.) for the operator to input data.

FIG. 2 is a diagram showing the overall structure of the photodetector 6. The overall shape of the photodetector 6 is substantially fan-shaped with a central angle α. The central angle α is set to 20 degrees, for example. The photodetector 6 includes E1 to E1 for detecting scattered light.
Included are 17 (17 channels) detector elements of E17. Since the detection elements E1 to E17 are configured so that their dimensions sequentially expand exponentially, the detection elements E1 to E9 on the center side are not shown in FIG.
Further, the detection element for detecting scattered light is not limited to 17 channels, and any number of channels can be provided.

An optical axis adjusting detection element is provided in the vicinity of the central position of the sector formed by the photodetector 6.
In the state where the sample does not exist in the scattered field 40, the laser light is output from the laser light source 2 to adjust the optical axis. Then, background measurement is performed in the state where the sample does not exist in the scattering field 40. The laser light is output from the laser light source 2, and the detection element E
The detection intensity at 1 to E17 is measured.

This is a measurement for detecting the background scattered light intensity in the absence of a sample.
The scattered light in the background is caused by particles suspended in the air and scattered by an optical system and an optical window. Next, the sample is introduced into the scattering field 40, and the main measurement of the particle size distribution is performed. That is, the intensity distribution of scattered light is detected by the detection elements E1 to E17, and the arithmetic control means 10 performs data processing for measuring the particle size distribution of the sample.

FIG. 3 is a sectional view showing the structure of the measuring cell 4 of the present invention. A scattering field 40 is provided as a space for causing the measurement light to be diffracted / scattered by the sample particles at approximately the center of the measurement cell 4. The powder sample is continuously introduced into the scattering field 40 from the jet nozzle 41, the particle size distribution and the like are measured by diffraction and scattering of the measurement light, and then the powder sample is discharged from the discharge nozzle 42 along with the air flow. The jet nozzle 41 and the discharge nozzle 42 are arranged at positions that do not interfere with the measurement light emitted from the laser light source 2 and the scattered light diffracted or scattered by the scattering field 40.

Further, the measuring cell 4 has optical windows 43 and 44.
Is provided. The measurement light is incident on the scattering field 40 through the optical window 43, and the scattered light diffracted / scattered by the scattering field 40 is emitted from the optical window 44. These optical windows 4
The scattered field 40 is physically shielded from the outside by 3,44. The optical windows 43 and 44 are made of optically polished disc-shaped optical glass or the like and fixed to the measurement cell 4 in a sealed state. Further, the surfaces of the optical windows 43 and 44 are subjected to a treatment for reducing light reflection such as antireflection coating.

Inside the optical windows 43 and 44, passage members 47 and 48 having a substantially pincushion shape are arranged. A donut-shaped air chamber 471 is provided on the outer peripheral side of the passage member 47. A compressed air supply passage 45 communicates with the air chamber 471, and compressed air from an external compressed air source is supplied to the air chamber 471. The passage member 47 communicates with the air chamber 471 and has a plurality of ejection ports 472.
Are discretely formed along the outer peripheral portion of. Further, a central passage 473 is formed in the central portion of the passage member 47 so as to penetrate the optical window 43 side and the scattering field 40 side. The central passage 473 is formed in a tapered shape having a small diameter on the side of the scattered field 40.

The structure of the passage member 48 is similar to that of the passage member 47, and the passage member 48 is formed with an air chamber 481, a plurality of ejection ports 482 and a central passage 483. The measurement light from the laser light source 2 passes through the optical window 43 and the central passage 473 to reach the scattering field 40 as indicated by the thick arrow, and the scattered light from the scattering field 40 is indicated by the dotted arrow. Measuring cell 4 passing through 483 and optical window 44
Is emitted outside and reaches the photodetector 6.

In the actual measurement, the optical window 4
The measurement cells are not arranged so that the surfaces of the optical fibers 3, 44 are orthogonal to the optical axis of the measuring light, and the normal lines of the surfaces of the optical windows 43, 44 are inclined at a slight angle with respect to the optical axis of the measuring light. 4 is arranged and measurement is performed. The inclination angle is, for example, 1 to 2 degrees.
By arranging the measurement cell in this way, the optical window 4
It is possible to prevent the light reflected by the surfaces of 3, 44 from reaching the photodetector 6 after being repeatedly reflected in the cell, and improve the measurement accuracy by eliminating the deterioration of the measurement accuracy due to such stray light. Can be made.

The compressed air supplied into the air chamber 471 is
As indicated by the thin line arrows, the air is ejected from the plurality of ejection ports 472 toward the outer peripheral portion of the inner surface of the optical window 43, is folded back at the inner surface of the optical window 43, and travels in the central passage 473 as an air flow toward the scattering field 40. . Similarly, the compressed air supplied into the air chamber 481 is also ejected from the plurality of ejection ports 482 toward the outer peripheral portion of the inner surface of the optical window 44, is folded back at the inner surface of the optical window 44, and is scattered in the central passage 483 to the scattering field 40. It becomes a heading air flow. These air streams are discharged from the measurement cell 4 through the discharge nozzle 42 together with the powder sample.

As described above, since the air flow from the optical windows 43 and 44 to the scattering field 40 is always present, the powder sample introduced into the scattering field 40 diffuses to the optical windows 43 and 44. And the powder sample adheres to the optical window 4
It is possible to effectively prevent the inner surfaces of 3, 44 from being contaminated.

Here, since the jet outlets 472 and 482 are discretely provided on the outer peripheral edges of the optical windows 43 and 44, the velocity of the air flow jetted from the jet outlets 472 and 482 is increased, and even if the optical window 43 is used. , 44, even if the powder adheres to them, it has an effect of efficiently removing them. In addition, since the velocity of the air flow that goes through the central passages 473 and 483 toward the scattering field 40 also increases, the effect of preventing contamination of the optical windows 43 and 44 is further improved.

When the ejection port is formed in a slit shape over the entire outer peripheral edges of the optical windows 43 and 44, the velocity of the air flow ejected from the ejection port decreases, so that the adhered substances on the optical windows 43 and 44 are removed. The action and the anti-pollution effect are also reduced. In this case, it is possible to increase the pressure and supply amount of the compressed air in order to obtain the deposit removing effect and the pollution preventing effect to the same extent as in the present invention, but this requires an external large-capacity compressed air source. Therefore, the cost of the entire system increases. In the present invention, a high-speed air flow can be generated by a small compressed air source, and the cost of the entire system can be reduced.

FIG. 4 is a view showing the arrangement of the ejection ports 472 and 482 in the passage members 47 and 48. FIG. 4 is a view of the passage member 47 viewed from the left side in FIG. Although FIG. 4 shows the passage member 47, the same applies to the passage member 48. In FIG. 4A, the ejection ports 472 of the passage member 47a are arranged so as to be evenly distributed over the entire circumference of the outer peripheral edge. The arrangement of the ejection port 472 is simple and the manufacturing cost is reduced. However, when the compressed air is supplied from only one side of the air chamber 471 as shown in the drawing, the jet port 472 on the compressed air supply side is provided.
There is a problem that the ejection amount from the ejection port 472 on the opposite side is slightly larger than the ejection amount from the.

FIG. 4B shows an arrangement for eliminating such nonuniformity of the ejection amount and further improving the uniformity of the ejection amount. In FIG. 4B, the ejection ports 472 of the passage member 47b are arranged so that the distribution density of the compressed air on the supply side is higher than the distribution density on the opposite side. That is, on the side of the passage member 47b opposite to the compressed air supply (the lower side of the figure), the distribution density of the ejection ports 472 is the same as the arrangement of the passage member 47a of FIG. 4A, but the compressed air supply side ( In the upper part of the drawing), the distribution density of the ejection ports 472 is arranged to be larger than that of the lower half. Thereby, the amount of air jetted from the jet port 472 can be made substantially uniform over the entire circumference of the optical window. The distribution density of the ejection ports 472 is set by experiments or the like so that the air ejection amount becomes uniform.

Even in the arrangement of the jet outlets 472 as shown in FIG. 4A, the compressed air is uniformly supplied from the entire circumference of the air chamber 471 (for example, it is supplied from two vertically symmetrical directions in the drawing).
By doing so, it is possible to reduce the non-uniformity of the air ejection amount. However, the supply passages 45 must be evenly arranged around the air chamber 471, which complicates the structure of the measuring cell and increases the cost, and also makes it difficult to downsize the measuring cell. As shown in FIG. 4B, if the distribution density of the ejection ports 472 is adjusted to make the air ejection amount uniform, the cost hardly increases and the measurement cell can be easily downsized.

The operation control means 10 or another computer or controller controls the amount of compressed air supplied to the supply passages 45 and 46 to control the jet ports 472 and 48.
The air ejection amount from 2 can be controlled to an optimum value.
Further, the air ejection amount can be changed by a manual operation. Furthermore, for example, at the start of measurement, the amount of air ejected from the ejection port can be temporarily increased to remove the deposits on the surface of the optical window, or the deposits can be similarly removed at any time during the measurement. You can also do it.

As described above, according to the measuring cell of the present invention, the jet air flow from the jet outlet can be made high speed and uniform, and the powder sample or the like can be efficiently attached to the optical window. This can be prevented, and the cost and size of the measuring cell can be reduced. Since the effect of preventing contamination of the optical window is improved, continuous or intermittent particle size measurement can be performed for a long time without manually cleaning the optical window. In addition, the measurement result is highly accurate and stable. Furthermore, the work of cleaning the measuring cell is almost unnecessary, and the maintenance work can be reduced.

In the above embodiment, the compressed fluid is described as an example of the pressurized fluid, but other gas or liquid may be used. Also, as the light source of the measurement light, a light source other than the laser light source can be used.

[0036]

Since the present invention is constructed as described above, it has the following effects.

Since the jet outlets for jetting the pressurized fluid to the inner surface of the optical window are arranged discretely on the outer peripheral portion inside the optical window, the jet air flow from the jet outlet can be made uniform at high speed. Therefore, it is possible to efficiently prevent the powder sample and the like from adhering to the optical window, and further reduce the cost and size of the measurement cell. Since the effect of preventing contamination of the optical window is improved, without manually cleaning the optical window,
Continuous or intermittent particle size measurements can be performed over long periods of time. In addition, the measurement result is highly accurate and stable. Furthermore, the work of cleaning the measuring cell is almost unnecessary, and the maintenance work can be reduced.

Since the ejection port is arranged so that the pressurized fluid is ejected almost uniformly on the inner surface of the optical window, the air flow ejected from the ejection port becomes uniform, and the powder sample or the like is ejected onto the optical window. Can be efficiently prevented from adhering.

Since the jet outlets are arranged so that the distribution density on the supply passage side is higher than the distribution density on the opposite side, the jet air flow from the jet outlets can be made uniform and the optical window It is possible to efficiently prevent the powder sample and the like from adhering to the.

Since the measurement cell is arranged so that the normal line of the surface of the optical window is inclined with respect to the optical axis of the measuring light incident from the light source, the measurement is performed, so that the light is reflected by the surface of the optical window. It is possible to prevent the light from reaching the photodetector after being repeatedly reflected in the cell, and to prevent the deterioration of the measurement accuracy due to such stray light and improve the measurement accuracy.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the configuration of a particle size distribution measuring apparatus using a measuring cell of the present invention.

FIG. 2 is a diagram showing a specific example of a photodetector.

FIG. 3 is a cross-sectional view showing a configuration of a measuring cell.

FIG. 4 is a diagram showing an arrangement of ejection ports in a passage member.

[Explanation of symbols]

1. Particle size distribution measuring device 2 ... Laser light source 3 ... Collimator 4 ... Measuring cell 5 ... Condensing lens 6 ... Photodetector 7 ... Multiplexer 8 ... Amplifying amplifier 9 ... A / D converter 10 ... Arithmetic control means 11 ... Output means 40 ... Scattering field 41 ... Jet nozzle 42 ... Discharge nozzle 43, 44 ... Optical window 45, 46 ... Supply passage 47, 48 ... Passage member 471, 481 ... Air chamber 472, 482 ... Spout 473, 483 ... Central passage

Claims (4)

[Claims] 1. A particle size sensor measuring cell for measuring the particle size of a sample by irradiating the scattered light (40) inside the measuring cell with the measuring light from the light source (2), which is irradiated from the light source (2). An ejection nozzle (41) arranged at a position that does not interfere with the measurement light and the scattered light diffracted or scattered by the scattering field (40) and introducing a powder sample into the scattering field (40); 40), and an optical window (43, 44) that causes the scattered light from the scattered field (40) to be emitted to the outside of the measurement cell (4) while the measuring light is incident on the inner surface of the optical window (43, 44). Of the nozzles (472, 482), which are discretely arranged on the outer peripheral portion of the optical window (43, 44) and eject the pressurized fluid onto the inner surface of the optical window (43, 44), and the pressure applied from the nozzles (472, 482). A fluid from the optical window (43, 44) to the scattering field A measuring cell for a particle size sensor, which has a fluid passage (473, 483) flowing toward (40) and an ejection nozzle (42) for ejecting the powder sample measured in the scattering field (40). 2. The measurement cell for the particle size sensor according to claim 1, wherein the jetted fluid (472, 482) jets the pressurized fluid substantially uniformly onto the inner surface of the optical window (43, 44). A measuring cell for a particle size sensor, which is arranged as follows. 3. The measurement cell for a particle size sensor according to claim 2, further comprising a supply passage (45, 47) for pressurized fluid, wherein the jet outlets (472, 482) are provided in the supply passage (4).
5, 47) A measuring cell for a particle size sensor, which is arranged so that the distribution density on the side is higher than the distribution density on the opposite side. 4. The measurement cell for a particle size sensor according to claim 1, wherein the measurement light incident from the light source (2) is an optical axis.
A measuring cell for a particle size sensor, which is arranged so that the normal line of the surface of the optical window (43, 44) is inclined to perform the measurement.