JPS6143221Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a particle size distribution measuring device for ultrafine particles floating in the air, and more particularly to a particle size distribution measuring device comprising a charging mechanism and a charged particle sedimentation mechanism.

Conventionally, this type of measuring device is the Electrical Aerosol Analyzer (Electrical Aerosol Analyzer).
Known examples include the differential mobility analyzer (abbreviated as "EAA") and Differential Mobility Analyzer (abbreviated as "DMA").

The purpose of the present invention is to provide a new particle size distribution measuring device that can measure the particle size distribution of aerosols, similar to EAA and DMA.
A measuring device is formed from a charging mechanism for charging particles and a sedimentation mechanism for sedimenting charged particles.The charging mechanism is a bidirectional unipolar charging device, and the sedimentation chamber forming the sedimentation mechanism has its upper surface at a negative potential. Alternatively, the bottom surface of the earth is charged to a positive potential to cause the charged particles in the settling chamber to settle, and the amount of sedimentation is measured using a high-sensitivity ammeter to measure the particle size distribution. It has the advantage of being able to perform measurements.

Next, embodiments of the present invention will be described with reference to the drawings.

In FIG. 1, 1 is a charging device;
A bidirectional unipolar charging device, which will be described later, is provided in the charging device 1, and an aerosol inlet pipe 2 and a charged particle outlet pipe 3 are provided in the charging device 1, respectively. Reference numeral 4 denotes a settling chamber, and the settling chamber 4 is formed of a side surface 5, an upper surface 6, and a lower surface 7 made of an insulating material, and is connected to the outlet pipe 3 via a timing valve 8, and also has a timing valve 9. It is connected to the discharge pipe 10 via. Both timing valves 8 and 9 are opened in conjunction with each other according to a certain program during measurement operations.
It operates closed. Further, the upper surface 6 is charged to earth or a negative potential, and the lower surface 7 is charged to a positive potential by operation of the high voltage device 11. 12 is the bottom surface 7
This is a high-sensitivity ammeter installed between the terminal and ground.

FIG. 2 is an explanatory diagram of the principle of a bidirectional unipolar charging device. In FIG. When V is applied, an alternating main electric field E is formed in the charged space C between both electrode assemblies. When the assembly A becomes negative polarity, a high frequency excitation voltage VA is applied between the discharge electrode d and the induction electrode e to cause a high frequency creeping discharge on the surface f, forming a planar plasma rich in positive and negative ions. form. Only negative unipolar ions from this plasma are extracted by the main electric field E,
The charged space C is traversed to reach the electrode assembly B (which is not energized at this time). The polarity of the AC mains voltage V is then reversed, and similarly negative unipolar ions reach the electrode assembly A.

In this way, the negative unipolar ions always fly across the charged space C alternately on the left and right, so the charged object X in this space is bombarded with negative unipolar ions from both the left and right directions. .

As mentioned above, since the bidirectional unipolar charging device uses an alternating current electric field, there is very little adhesion of particles to the peripheral wall, etc., and even if particles do adhere, the accumulated charge of the negative ions flying onto the particles will be absorbed in the next half cycle. The plasma generated during the excitation period completely removes the charge to zero, so the particle layer does not accumulate enough charge to cause dielectric breakdown, and since the charged object receives unipolar ions from both sides, it effectively covers the entire surface. It has advantages such as being electrically charged. In operation, the charging device 1 is activated to charge the aerosol particles introduced through the inlet tube 2 and introduced into the settling chamber 4 through the outlet tube 3. At this time, it is assumed that both the valves 8 and 9 are in an open state and the settling chamber 4 is in an uncharged state. When the introduction of the aerosol is completed, both valves 8 and 9 are closed, and at the same time, the sedimentation chamber 4 is charged (the lower surface is positive and the upper surface is negative or grounded). Then, each particle in the sedimentation chamber receives a force from the electric field according to the amount of charge of each particle, and moves toward the lower surface 7. Since these particles are charged in accordance with the particle size at the charging portion described above, the moving speed of the particles is expressed as a function of the particle size. When such particles are deposited on the lower surface, an electric charge is transferred to the lower surface, and the amount thereof is measured as a current by the high-sensitivity ammeter 12 connected thereto. This current value is determined by the amount of charge on the particles and the number of particles deposited per unit time.

Therefore, if the temporal change in this current value I is recorded, a graph as shown in FIG. 3 can be obtained. If this is analyzed, the particle size will be determined from a certain time _t1 , and the amount corresponding to the particle size will be determined from the current value _I1 at that time. (This is similar to the conventional sedimentation method such as the Andriazenpipette method, in which particles settle due to gravity at a speed that depends on their particle size, so the details are (Explanation will be omitted.) As mentioned above, since the present invention uses a bidirectional unipolar charging device as the charging mechanism, the aerosol introduced into the charging mechanism is reliably charged and does not adhere to the outer wall etc. forming the charging mechanism. Because there's nothing to do,
The sensitivity of the measuring device can be improved. In addition, the settling chamber is equipped with valves on the inlet and discharge sides, and during measurement, both valves are closed, and after measurement, the valves are opened to discharge the measured particles from the settling chamber, and then introduce the particles to be measured into the settling chamber. By doing so, it is possible to carry out continuous measurements.

[Brief explanation of drawings]

Figure 1 is a system diagram of the particle size distribution measuring device of the present invention.
FIG. 2 is a diagram illustrating the principle of a bidirectional unipolar charging device used in the device of the present invention, and FIG. 3 is a graph showing the relationship between current I and time t during operation of the device of the present invention. 1... Charging device, 4... Sedimentation chamber, 5... Side surface,
6...Top surface, 7...Bottom surface, 8, 9...Timing valve, 12...High sensitivity ammeter.

Claims (1)

[Scope of utility model registration request] It consists of a charging mechanism and a charged particle sedimentation mechanism provided downstream thereof, the charging mechanism is composed of a bidirectional unipolar charging device, and the side surface of the charged particle sedimentation mechanism is made of an insulating material and the top surface is connected to a negative potential or ground. This particle size distribution measuring device consists of a sedimentation chamber whose bottom surface is positively charged, a timing valve installed on the inlet and discharge sides of the sedimentation chamber, and a high-sensitivity ammeter installed on the bottom surface of the sedimentation chamber.