METHOD AND SYSTEM FOR EXHAUST PARTICULATE MATTER SENSING

• US 20160223432A1
• Filed: 02/03/2015
• Published: 08/04/2016
• Est. Priority Date: 02/03/2015
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Kubinski, David John
• Granted Patent: US 9,803,524 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: F01N 3/027 using electric or magnetic heating means
• CPC Class Codes: G01N 15/0656 using electric, e.g. electrostatic methods or magnetic methods by investigating individual particles G01N15/1031, G01N15/12
• CPC Class Codes: G01N 2015/0046 in gas, e.g. smoke

Abstract

Methods are described for increasing the sensitivity of particulate matter detection in an exhaust system of a vehicle. An example particulate matter sensor assembly comprises a pair of planar interdigitated electrode structures held at a voltage bias with respect to each other. An alternate embodiment may comprise a planar interdigitated electrode pair, and a conducting plate assembly again held at a voltage bias with respect to the planar interdigitated electrode pair. The bias may overlay an additional electric field drive, which improves the capture of soot particles on the sensor assembly surface thereby increasing sensitivity of particulate matter sensors.

Claims

1. A method for an exhaust particulate matter (PM) sensor, comprising:

generating a first electric field via a planar interdigitated electrode pair; and

generating a second electric field via the planar interdigitated electrode pair and a second planar element parallel with the planar interdigitated electrode pair.

2. The method of claim 1, wherein the second electric field is normal to both the second planar element and the planar interdigitated electrode pair.

3. The method of claim 1, wherein the planar interdigitated electrode pair is a first planar interdigitated electrode pair and the second planar element is a second planar interdigitated electrode pair.

4. The method of claim 1, wherein the second planar element is a conducting plate.

5. The method of claim 4, wherein a first electrode of the planar interdigitated electrode pair is coupled to a positive terminal of a first voltage source and held at a positive voltage, and wherein a second electrode of the pair is coupled to a negative terminal of the first voltage source and held at a negative voltage.

6. The method of claim 5, wherein the second planar element is coupled to a second voltage source, and wherein the second planar element is held at a voltage that is more positive than the positive voltage of the first electrode or more negative than the negative voltage of the second electrode.

7. The method of claim 3, wherein a first electrode of the first planar interdigitated electrode pair is coupled to a positive terminal of a first voltage source and held at a first positive voltage, a second electrode of the first pair is coupled to a negative terminal of the first voltage source and held at a first negative voltage, a first electrode of the second planar interdigitated electrode pair is coupled to a positive terminal of a second voltage source and held at a second positive voltage, and a second electrode of the second pair is coupled to a negative terminal of the second voltage source and held at a second negative voltage, wherein the first positive voltage is more positive than the second positive voltage or the first negative voltage is more negative than the second negative voltage.

8. The method of claim 7, wherein a difference between the first positive voltage and the second positive voltage or a difference between the first negative voltage and the second negative voltage is based on a gap between the first and second planar interdigitated electrode pair, the difference increased as the gap increases.

9. The method of claim 1, further comprising, flowing exhaust gas from an engine between the second planar element and the planar interdigitated electrode pair.

10. The method of claim 9, further comprising, determining a soot level in the exhaust gas based on an electrical resistance between electrodes of the planar interdigitated electrode pair.

11. The method of claim 1, wherein the first electric field includes a plurality of electrical dipoles generated along a length of the electrode pair.

12. A method for an engine, comprising:

regenerating an exhaust particulate filter responsive to a voltage difference between electrodes of a first planar interdigitated electrode pair, the first electrode pair positioned parallel to a second planar element, the second planar element held at a voltage that is biased with relation to a voltage of at least one of the electrodes of the first pair, wherein a first major surface of the first planar pair and a second major surface of the second planar element face one another such that a center of the first major surface is aligned with a center of the second major surface.

13. The method of claim 12, wherein the regenerating includes initiating regeneration of the exhaust particulate filter when the voltage difference is less than a lower threshold, and terminating regeneration of the exhaust particulate filter when the voltage difference is higher than an upper threshold.

14. The method of claim 12, wherein the regenerating includes repeatedly regenerating the first electrode pair to indicate soot level responsive to the voltage difference.

15. The method of claim 14, wherein the indication of soot level is based on one or more of a frequency of repeatedly regenerating the first electrode pair and a duration between regenerations of the electrode pair.

16. The method of claim 12, wherein the second planar element includes one of a second planar interdigitated electrode pair and a conducting plate, and holding the second planar element at a voltage that is biased includes applying a current to hold the second planar element at a voltage that is more positive than a positive voltage of a first electrode of the first pair or more negative than a negative voltage of a second electrode of the second pair.

17. A particulate matter sensor system, comprising:

a first voltage source producing a first voltage;

a first planar interdigitated electrode pair having a first electrode and a second electrode, the first electrode electrically coupled to a positive terminal of the first voltage source, the second electrode electrically coupled to a negative terminal of the first voltage source;

a second voltage source producing a second voltage higher than the first voltage;

a second planar element positioned parallel to the first planar interdigitated electrode pair and electrically coupled to the second voltage source.

18. The system of claim 17, wherein the second planar element is a second planar interdigitated electrode pair having a first electrode and a second electrode, the first electrode electrically coupled to a positive terminal of the second voltage source, the second electrode electrically coupled to a negative terminal of the second voltage source such that a positive voltage of the first electrode of the second planar element is more positive than a positive voltage of the first electrode of the first planar element and/or a negative voltage of the second electrode of the second planar element is more negative than a negative voltage of the second electrode of the first planar element.

19. The system of claim 18, further comprising, a controller with computer readable instructions stored on non-transitory memory for:

adjusting the second voltage output by the second voltage source based on a gap between the first pair and the second planar element and further based on a voltage difference between the first and second electrode of the first pair.

20. The system of claim 19, wherein the sensor system is positioned downstream of a particulate filter in an engine exhaust passage, and wherein the controller includes further instructions for:

regenerating the first pair in response to the voltage difference between the first and second electrode of the first pair being smaller than a threshold;