Particle count measurement device

Patent metadata

Field	Value
Publication number	US-9606038-B2
Application number	US-201214402611-A
Country	US
Kind code	B2
Filing date	May 21, 2012
Priority date	May 21, 2012
Publication date	Mar 28, 2017
Grant date	Mar 28, 2017

Abstract

A particle count measurement device includes a preprocessing section configured to place an aerosol introduced into a measurement region in an electrical state of any of a neutralized state, a positively charged state or a negatively charged state, a unipolar charging section configured to place the aerosol which has been introduced in an electrical state different from at a time of introduction, an ion trap arranged on a downstream of the unipolar charging section in terms of a flow of the aerosol for generating an electric field that draws only gas ions in the aerosol, an exhaust mechanism configured to discharge the aerosol from the measurement region at a constant flow rate, and an ammeter for detecting, as a measurement value corresponding to a particle count concentration, a difference between current supplied by the unipolar charging section and current flowing into the ion trap.

First claim

The invention claimed is:

1. A particle count measurement device for measuring a particle count concentration of an aerosol flowing through a measurement region, the particle count measurement device comprising:
a preprocessing section configured to introduce the aerosol into the measurement region in an electrical state of a positively charged state or a negatively charged state;
a unipolar charging section inside the measurement region, the unipolar charging section being configured to place the introduced aerosol in a positively charged state or a negatively charged state that is an electrical state different from at a time of introduction into the measurement region;
an ion trap arranged inside the measurement region, on a downstream of the unipolar charging section in terms of a flow of the aerosol, the ion trap including an ion trap electrode for generating an electric field that draws only gas ions in the aerosol;
an exhaust mechanism outside the measurement region, the exhaust mechanism being configured to discharge the aerosol from the measurement region at a constant flow rate; and
an ammeter for detecting, wherein the ammeter measures a difference between a current value of charged particles entering the unipolar charging section and a current value of charged particles flowing through the unipolar charging section and the ion trap and leaving the ion trap, and wherein the measured values correspond to the particle count concentration.

2. The particle count measurement device according to claim 1 ,
wherein the preprocessing section is a discharge neutralizer for placing the aerosol in a neutralized state by AC corona discharge, and
wherein the unipolar charging section is a discharge charger based on unipolar corona discharge, the discharge charger including a DC high-voltage power supply and an electrode.

3. The particle count measurement device according to claim 1 ,
wherein the preprocessing section is a discharge charger for placing the aerosol in an electrical state of a positively charged state or a negatively charged state by DC corona discharge, and
wherein the unipolar charging section is a discharge charger based on unipolar corona discharge, the discharge charger including a DC high-voltage power supply and an electrode.

4. The particle count measurement device according to claim 1 , further comprising:
a diffusion filter arranged between the ion trap and an outlet of the measurement region and formed from a conductive mesh for removing charged particles of particle diameters smaller than a predetermined particle diameter,
wherein the ammeter is configured to measure a difference between current supplied by the unipolar charging section and current flowing into the ion trap and the diffusion filter to measure a particle count concentration of particles having particle diameters equal to or greater than the predetermined particle diameter.

5. The particle count measurement device according to claim 1 , further comprising:
a pair of counter electrodes arranged between the ion trap and an outlet of the measurement region, the pair of counter electrodes being arranged in parallel with the flow of the aerosol; and
a classification power supply for generating, at the counter electrodes, an electric field for drawing charged particles having particle diameters smaller than a predetermined particle diameter,
wherein the ammeter is configured to measure a difference between current supplied by the unipolar charging section and current flowing into the ion trap and the counter electrodes to measure a particle count concentration of particles having particle diameters equal to or greater than the predetermined particle diameter.

6. The particle count measurement device according claim 1 , wherein the exhaust mechanism includes a flow rate adjustment section for making an exhaust flow rate constant.

7. The particle count measurement device according to claim 6 , wherein the flow rate adjustment section is a critical orifice.

8. The particle count measurement device according claim 1 , further comprising:
a pair of counter electrodes arranged between the ion trap and an outlet of the measurement region, the pair of counter electrodes being arranged in parallel with the flow of the aerosol;
a classification power supply for generating, at the counter electrodes, an electric field for drawing charged particles having particle diameters smaller than a predetermined particle diameter; and
a classification ammeter for measuring current flowing into the counter electrodes,
wherein the particle count measurement device also measures a particle count concentration of particles having particle diameters smaller than the predetermined particle diameter based on a measurement value of the classification ammeter.

9. The particle count measurement device according to claim 8 ,
wherein voltage is applied to the ion trap electrode of the ion trap so as to generate an electric field that draws not only the gas ions in the aerosol, but also charged particles of particle diameters smaller than the predetermined particle diameter, and
wherein the particle count measurement device also measures a particle count concentration of particles having particle diameters greater than particle diameters to be captured by the ion trap and smaller than the predetermined particle diameter based on a measurement value of the classification ammeter.

Assignees

• Okuda Daiji
• Shimadzu Corp

Inventors

• Okuda Daiji

Classifications

• B03C3/38

  Particle charging or ionising stations, e.g. using electric discharge, radioactive radiation or flames · CPC title

• B03C3/08

  characterised by presence of stationary flat electrodes arranged with their flat surfaces parallel to the gas stream · CPC title

• G01N27/62

  by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode · CPC title

• B03C2201/06

  Ionising electrode being a needle · CPC title

• G01N2015/0038

  Investigating nanoparticles · CPC title