METHOD FOR CONTROLLING A COEFFICIENT OF FRICTION

• US 20110287986A1
• Filed: 05/20/2010
• Published: 11/24/2011
• Est. Priority Date: 05/20/2010
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company), Regents of the University of California (University of California)
• Original Assignee: GM Global Technology Operations Incorporated (Motors Liquidation Co. GUC Trust), Regents of the University of California (University of California)
• Inventors: Israelachvili, Jacob N., Mordukhovich, Gregory
• Granted Patent: US 8,551,576 B2
• Time in Patent Office: Days
• US Class Current: 508/100
• CPC Class Codes: F16C 2202/02 Mechanical properties
• CPC Class Codes: F16C 2202/40 Magnetic magnetic material in general H01F1/00
• CPC Class Codes: F16C 2202/50 Lubricating properties
• CPC Class Codes: F16C 2240/48 Particle sizes
• CPC Class Codes: F16C 2240/64 in the nanometer range
• CPC Class Codes: F16C 33/04 Brasses; Bushes; Linings

Abstract

A method for controlling a coefficient of friction involves applying a magnetic force, an electro-magnetic force, and/or an electrostatic force to nanoparticles disposed on a surface. The method further involves controlling a rolling-to-sliding ratio of the nanoparticles on the surface by i) adjusting a value of the force applied to the nanoparticles, and/or ii) adjusting an orientation of the nanoparticles by adjusting a direction of the force applied to the nanoparticles.

Claims

1. A method for controlling a coefficient of friction, comprising:

providing a plurality of nanoparticles on a surface;

applying a force to the plurality of nanoparticles, the force being selected from a magnetic force, an electro-magnetic force, an electrostatic force, and combinations thereof; and

controlling a rolling-to-sliding ratio of the plurality of nanoparticles on the surface by at least one of i) adjusting a value of the force applied to the plurality of nanoparticles, or ii) adjusting an orientation of the nanoparticles by adjusting a direction of the force applied to the plurality of nanoparticles.

2. The method as defined in claim 1 wherein the magnetic force is applied to the plurality of nanoparticles, and wherein each of the plurality of nanoparticles have a nanoparticle core including a ferromagnetic material that is responsive to the applied magnetic force.

3. The method as defined in claim 1 wherein each of the plurality of nanoparticles include a nanoparticle shell formed from a material exhibiting an adhesiveness ranging from about 3 kT energy per inter-particle interaction to about 20 kT energy per inter-particle interaction.

4. The method as defined in claim 3 wherein the material exhibiting the low adhesiveness is selected from silanes, non-conductive phosphorus-based materials, non-conductive carbon-based surfactants, polymeric materials, hydrocarbons, fluorocarbons, or combinations thereof.

5. The method as defined in claim 1 wherein the adjusting of the direction of the applied force affects an angle of the plurality of nanoparticles on the surface, the angle corresponding to an angle between a pure rolling state of the nanoparticles and a pure sliding state of the nanoparticles.

6. The method as defined in claim 5, further comprising maintaining the value of the force applied to the plurality of nanoparticles during the adjusting of the direction of the applied force.

7. The method as defined in claim 1 wherein an anisotropic force is applied to the plurality of nanoparticles, and wherein when the anisotropic force is applied to the plurality of nanoparticles on the surface, the anisotropic field concentrating the plurality of nanoparticles at one or more pre-selected areas of the surface.

8. The method as defined in claim 1 wherein the adjusting of i) the value of the force, or ii) the direction of the force is based on at least one of a roughness or a topography of the surface.

9. The method as defined in claim 1, further comprising adjusting the rolling-to-sliding ratio to achieve a controlled shift or slip in a limited slip differential transmission, a torque converter transmission, or a dual clutch transmission.

10. The method as defined in claim 1 wherein controlling includes adjusting both direction and intensity of the applied field.

11. The method as defined in claim 1 wherein the adjusting of the value of the force is accomplished relative to a value of tangential forces applied to achieve relative motion of the surface, or wherein adjusting of the direction of the force is accomplished relative to a direction of tangential forces applied to achieve relative motion of the surface.

12. A lubrication system, comprising:

a plurality of nanoparticles disposed on a surface; and

a force applied to the plurality of nanoparticles, the force being at least one of a magnetic force, an electrostatic force, an electro-magnetic force, or an anisotropic force, the force including a value or a direction that is adjustable for controlling a rolling-to-sliding ratio of the plurality of nanoparticles on the surface.

13. The lubrication system as defined in claim 12 wherein each of the nanoparticles include:

a nanoparticle core; and

a shell formed on the nanoparticle core formed from a material having an adhesiveness ranging from about 3 kT energy per inter-particle interaction to about 20 kT energy per inter-particle interaction.

14. The lubrication system as defined in claim 13 wherein the nanoparticle core is a ferromagnetic material.

15. The lubrication system as defined in claim 12 wherein the surface is selected from transmission clutch plates, gears of a gearbox, drive shafts, rotating shafts, and sliding contacts.