JP2623898B2 - Particle measurement device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a microwave induced plasma (Microwave Indus
The present invention relates to a fine particle measuring device (particle meter) for performing elemental analysis using ced Plasma (hereinafter referred to as “MIP”), and more specifically, a fine particle (particle) as an object to be measured collected on a filter from the air atmosphere. The present invention relates to a fine particle measuring apparatus related to a fine particle inhaling means (disperser) that can collect and extract a fine particle using an aspirator as a collecting means.

<Prior Art> Conventionally, an aspirator having a configuration in which a large amount of air is used as a carrier gas, and the carrier gas is flown to suck fine particles and guide the particles to a measuring device such as a dust counter is well known.

 This conventional technique will be described with reference to the drawings.

FIG. 5 and FIG. 6 are diagrams for explanation of a conventional technique.

In FIGS. 5 and 6, air A is introduced as a carrier gas from a carrier gas inlet 1a of the aspirator 1, and the carrier gas causes a horizontal direction (hereinafter referred to as "aspirator inlet") 1b from an aspirator inlet (hereinafter referred to as "aspirator inlet"). After suctioning the fine particles on the filter FL ₁ as shown in FIG. 6 which moves to the arrow X) (“T” in FIG. 6 is a trace of the collected fine particles on the surface of the filter FL), measurement of a dust counter or the like is performed. Vessel 2
To analyze the suction fine particles. At this time, the flow rate of the supplied carrier gas is controlled to a constant flow rate by the meter 3 or the like.

<Problems to be Solved invention> In this technique, since the suction flow rate is large because the distance D between the filter FL ₁ and aspirator inlet 1b can be taken relatively large, be dependent on irregularities of the filter surface There is no.

By the way, for example, carrier flow rate 200 ml / min, suction 100 ml / min
In the case of applying to a fine particle measuring device that performs elemental analysis using MIP using a low-density gas such as helium (He) at a small flow rate such as min, the distance D between the filter / aspirator suction port is set to, for example, The distance (gap) must be as small as 50 μm. However, at this distance (gap), the unevenness of the filter surface cannot be ignored, so that the structure shown in FIG. 5 cannot be used as it is. is there.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems of the prior art, and has as its object to reduce the distance between the upper surface of the filter and the aspirator suction port, and furthermore, to minimize the minute distance with a simple configuration. By controlling so as to keep it constant, there is no need to be affected by the unevenness of the filter surface. It is an object of the present invention to provide a fine particle measuring apparatus provided.

<Means for Solving the Problems> In order to achieve such an object, the present invention suctions fine particles on a filter by an aspirator,
A particle measuring device for guiding a suctioned particle to a spectrometer for analysis, wherein the filter and the aspirator are housed therein, a purge container replaced by a purge gas, and a first mass flow controller for supplying a carrier gas to the aspirator A second mass flow controller for supplying a purge gas to the purge container; and measuring a total flow rate of a flow rate of the carrier gas supplied from the first mass flow controller to the aspirator and a flow rate of the purge gas sucked by the aspirator. And a gap control unit that moves at least one of the filter and the aspirator based on the total flow rate measured by the flow measurement unit and maintains a constant interval between the filter and the aspirator. It is characterized by having .

<Effect> For the fine particle suction means to operate efficiently with a small flow rate, the distance between the filter upper surface and the aspirator suction port must be as small as possible, for example, 0.1 mm or less. Since the irregularities on the filter surface cannot be ignored, the present invention is designed to control the distance so as to be constant regardless of the irregularities on the filter surface.

<Examples> Hereinafter, the present invention will be described with reference to the drawings with reference to specific examples.

In the following drawings, the same parts as those in FIGS. 5 and 6 are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 1 is a block diagram showing a specific embodiment of the present invention.

In Figure 1, alpha is fine suction means for deriving the particulate on the filter FL ₂ to the means β for performing elemental analysis by using the MIP. Here, particulate inhalation means α is the purge vessel P being opened to the atmosphere, for example in the upper portion relative to the filter FL ₂ the particles taken from the atmosphere are placed so as to be sucked even carrier gas CG of small flow rate Aspirator 10 to be placed and inlet in the aspirator
A first flow controller (hereinafter referred to as "# 1 mass flow controller") 21 for accurately supplying the carrier gas CG having a small flow rate (constant flow rate) from 10a, and a constant flow rate in the purge vessel (from the flow rate supplied to the aspirator). A second flow controller (hereinafter referred to as “# 2 mass flow controller”) 22 for supplying the carrier gas CG of
A gap for controlling the gap between the upper surface of the filter and the aspirator suction port 10b at a very small interval (δ) as small as 0.1 mm or less, for example, irrespective of the unevenness on the upper surface of the filter so as to work efficiently with a small flow rate. Control means
30 consists of configuration of the slide mechanism 40 that can move the filter FL ₂ in the horizontal direction (X) at a constant low speed.
The gap control means 30 includes, for example, a flow rate measuring means 31 (hereinafter, referred to as a mass flow meter 31) having almost no pressure loss connected to the outlet side of the aspirator / analyzer β, Of the elevator mechanism 35, which can move the gap δ in minute units by mounting the filter FL ₂ and moving it up and down with the filter FL ₂ And a controller 32 for controlling 34 (for example, 33 comprises a motor and 34 comprises a gear mechanism). The slide mechanism 40 is a drive unit such as a motor here.
41 and a moving table 42 provided with an elevator mechanism 35 to a driving device 33/34.

 These relationships are as follows.

A carrier gas CG made of, for example, helium is accurately supplied to the aspirator 10 by a # 1 mass flow controller 21 at a constant flow rate of, for example, 200 ml / min. Aspirator 1
From 0 through the analyzer β, the mass flow meter 31 sends the carrier gas CG from the # 1 mass flow controller 21.
The total flow rate of the supply amount and the suction amount in which the carrier gas CG in the purge container supplied through the # 2 mass flow controller 22 is sucked together with the fine particles on the filter surface is measured. Filter FL ₂ is placed on the elevator mechanism 35 to move up and down in small steps precisely e.g. 10 [mu] m, it is facing with a aspirator inlet 10b and minute interval [delta].
The elevator mechanism 35 is mounted on a slide mechanism 40 that moves in the horizontal direction X at a constant low speed. Mass flow meter 31
Is converted into, for example, an electric signal and guided to the controller 32. The controller 32 calculates the amount of suction from the aspirator suction port 10b of the aspirator 10 from the received signal, and adjusts the amount of suction of the elevator mechanism 35 so that the amount of suction matches a preset value (for example, set inside the controller). It controls the driving devices 33/34. here,
At least the filter FL ₂ and aspirator inlet 10b is surrounded by a purge vessel (provided that further aspirator, although the purge vessel for housing the elevator mechanism at the same time this design matters in the figure). The inside of the purge container is purged by the # 2 mass flow controller 22 with a carrier gas CG of an appropriate pressure (higher than the pressure supplied by the # 1 mass flow controller). still,
The purge vessel P is provided with an atmosphere open port, and discharges excess purge gas to the atmosphere to maintain the internal pressure at atmospheric pressure. The supply amount of the carrier gas CG supplied by the # 2 mass flow controller 22 is the maximum value of the suction flow rate of the aspirator 10 (for example, 100 ml / min).
More, for example 500 ml / min, the rest of which will be open to the atmosphere.

In the present embodiment, in order to keep the distance between the filter FL ₂ and the aspirator 10 constant, the filter FL _{2 is connected} to the controller 3.
It has been described for the case of drive control by 2, regardless of this example, may be a slide mechanism for moving at least one of the filter FL ₂ or aspirator 10 at a constant low speed.

FIG. 2 is a diagram provided for the description of FIG. 1, and is a characteristic curve diagram when the horizontal axis indicates the gap δ and the vertical axis indicates the suction amount (suction flow rate) of the aspirator.

FIG. 3 is a diagram provided for explaining FIGS. 1 and 2;
Points γ _{1 to} γ _{3 in the} figure represent the state points of the filter vertical movement surface with respect to the aspirator suction port 10b when the filter FL ₂ is in the movement direction X. That is, rather than the movement of the position of the point gamma ₁ times the film surface, the case where the position of the point gamma ₂ times the film surface where the gap epsilon ₁ direction as shown by a chain line is moved so that [delta], point gamma ₃
Sometimes the position of the film surface shows a case where the gap epsilon ₂ direction as indicated by broken line moves so that [delta].

The operation of FIG. 1 will be described below with reference to FIGS.

For example, the control when the supply amount of the carrier gas to the aspirator 10 is set to 200 ml, the gap δ is set to 50 μm, in other words, the suction amount of the aspirator is set to 50 ml / min is as follows.

(B) when the filter FL ₂ is in the position of the point gamma _1,
The controller 32 sets the measured flow rate (aspirator outlet flow rate) of the mass flow meter 31 to be exactly 250 (200 + 50) ml / min.

(B) filter FL ₂ is moved in the X direction, and the surface is adapted to point gamma _2. At this time, the position of the fill surface with respect to the aspirator suction port 10b comes downward, and the gap becomes larger than δ, so that the suction amount of the aspirator increases. As a result, the flow rate measured by the mass flow meter 31 increases, so that the controller
In the direction to raise. The rise of the elevator mechanism 35 is caused by the fact that the flow rate measured by the mass flow
Stop when it reaches 0ml / min.

(C) It is assumed that the filter FL ₂ is further moved in the X direction, and its surface is as shown by a point γ ₃ . At this time, since the position of the filter surface with respect to the aspirator suction port 10b is located upward, the gap becomes smaller than δ, and the suction amount of the aspirator decreases. As a result, the flow rate measured by the mass flow meter 31 also decreases, so that the controller
Move in the direction of lowering. When the elevator mechanism 35 descends, the measured flow rate of the mass flow meter 31 in the item (a) is just 25.
Stop when it reaches 0ml / min.

The above operation is repeated until the horizontal movement of the filter is completed. This makes it possible to efficiently absorb fine particles collected on the filter from the air atmosphere by suction at a small flow rate and at a small flow rate without being affected by the unevenness of the filter surface. Can be the measured amount of fine particles at a constant gap δ.

By the way, the present invention is not limited to the contents described above, and may be modified as follows.

(I) In the above description, the carrier gas and the suction amount have been described as low flow rates. However, it goes without saying that a flow rate as needed, for example, a large flow rate may be used.

(II) In the above configuration, the case where the filter is moved in the horizontal / vertical direction has been described. However, since the gap may be made relatively constant, the aspirator 10 is moved in the horizontal / vertical direction opposite to the filter. Needless to say, it may be configured to be moved, or both may be operated at the same time or one of them may be individually operated according to the movement state. Here, when the aspirator 10 is configured to be moved, if the aspirator suction port 10b is made slightly longer, as described above, the purge container can be formed so as to cover the filter and a part of the aspirator suction port. The shape can be made easy. In any case, it is a design modification.

(III) FIG. 4 is a view for explaining another embodiment of FIG. 1. The trajectory T of the particulate collection due to the relative movement of the filter with respect to the aspirator suction port is shown in FIG.
(Ii) may be a fan shape as shown in FIG. (Ii), or may be wavy over the front surface (not shown). This is a design matter on the moving mechanism.

(IV) In the gap control means 30, the gap δ is controlled by using the mass flow meters 31... Based on the suction amount of the aspirator. However, the present invention is not limited to this. For example, a position sensor such as an ultrasonic wave or light may be used. Needless to say, the configuration may be such that control is performed by the

<Effects of the Invention> Since the present invention is configured as described above,
The following effects are obtained.

: Since the gap itself can be reduced by controlling the gap to be constant (for example, about 50 μm), even if the carrier gas has a low flow rate and a low density, the fine particles on the filter can be efficiently sucked and introduced into the analyzer. Can be.

: Since the gas flow rate at the outlet of the aspirator can be kept constant, the plasma in the analyzer is stabilized, so that accurate analysis can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a specific embodiment of the present invention, FIG. 2 is a diagram for explaining FIG. 1, FIG. 3 is a diagram for explaining FIGS. 1 and 2, FIG. FIG. 1 is a diagram for explaining another embodiment of FIG. 1, and FIGS. 5 and 6 are diagrams for explaining a conventional technique. 1,10 aspirator, 1a, 10a carrier gas inlet, α fine particle suction means, β MIP element analyzer, C
G ...... carrier gas, FL _1, FL ₂ ...... filter, 10 ...... aspirator, 21 ...... first flow controller (# 1 mass flow controller), 22 ...... second flow controller (# 2 mass flow controller), 30: gap control means, 40: slide mechanism.

Claims (1)

(57) [Claims] 1. A fine particle measuring device for suctioning fine particles on a filter by an aspirator and guiding the sucked fine particles to an analyzer for analysis, wherein the filter and the aspirator are housed,
A purge container replaced by a purge gas; a first mass flow controller for supplying a carrier gas to the aspirator; a second mass flow controller for supplying a purge gas to the purge container; and a supply from the first mass flow controller to the aspirator Flow rate measuring means for measuring the total flow rate of the carrier gas flow rate and the flow rate of the purge gas sucked by the aspirator; and at least one of the filter or the aspirator based on the total flow rate measured by the flow rate measuring means. A fine particle measuring device, comprising: a gap control means for moving one of the gaps to keep a constant distance between the filter and the aspirator.