Viscous shear drives and methods using nanoparticles in the viscous medium

Abstract

A device such as a cooling fan drive for a motor vehicle engine has first and second members that are relatively moveable at a differential velocity. A liquid fills space separating relatively moving confronting surfaces of the respective members. The viscosity of the liquid enables the liquid to serve as a motion transmitting medium from one member to the other. Heat is generated within the liquid by shearing stress created by the relative movement of the members at a differential velocity with at least some of the generated heat being dissipated by conduction from at least one of the members through its surface. The viscous liquid comprises a nanoparticle-free base liquid to which have been added nanoparticles in an amount sufficient to measurably increase the thermal conductivity of the liquid filling the space over that of the base liquid.

1 . A device comprising a first member and a second member that are relatively moveable at differential velocity, and a viscous liquid which fills space separating relatively moving confronting surfaces of the respective members and internally of which heat is generated by shearing stress created in the liquid by the relative movement of the members at differential velocity with at least some of the generated heat being dissipated into at least one of the members through its confronting surface, wherein the viscous liquid comprises a nanoparticle-free base liquid to which have been added nanoparticles in an amount sufficient to measurably increase the thermal conductivity of the liquid filling the space over that of the base liquid. 
   
   
       2 . A device as set forth in  claim 1  in which the viscosity of the base liquid is greater than about 1000 cp. 
   
   
       3 . A device as set forth in  claim 2  in which the base liquid comprises liquid silicone. 
   
   
       4 . A device as set forth in  claim 1  in which the base liquid comprises a magnetorheological (MR) liquid. 
   
   
       5 . A device as set forth in  claim 1  in which at least a majority of the nanoparticles are each asymmetric and have a molecular size less than 100 nm (nanometers) in one of their dimensions. 
   
   
       6 . A device as set forth in  claim 1  in which the volume fraction of nanoparticles is no less than 1% of the space. 
   
   
       7 . A device as set forth in  claim 1  in which one of the members comprises a driving member and the other member comprises a driven member that is driven by the driving member via the liquid in the space. 
   
   
       8 . A device as set forth in  claim 7  including a control for controlling the degree to which the liquid is effective to transmit motion of the driving member to the driven member. 
   
   
       9 . A device as set forth in  claim 8  in which the base liquid comprises a magnetorheological (MR) liquid and the control comprises a magnetic field that is selectively effective on the magnetorheological (MR) liquid. 
   
   
       10 . A device as set forth in  claim 8  in which the base liquid comprises a liquid silicone and the control comprises a liquid flow path including a control valve for controlling flow of liquid through the space between the confronting surfaces. 
   
   
       11 . A device as set forth in  claim 1  in which the nanoparticles are selected from a group consisting of metals, metal compounds, and combinations thereof. 
   
   
       12 . A method for removing heat generated internally of viscous liquid within space separating relatively movable confronting surfaces of respective members that are movable relative to each other at a velocity differential and that generate the heat by shearing the liquid when relatively moving, the method comprising making the liquid by mixing a nanoparticle-free base liquid and nanoparticles in an amount sufficient to measurably increase the thermal conductivity of the resulting mixture in comparison to that of the base liquid, and filling the space with the mixture. 
   
   
       13 . A method as set forth in  claim 12  including selecting the nanoparticles from a group consisting of metals, metal compounds, and combinations thereof. 
   
   
       14 . A method as set forth in  claim 12  in which the mixing step comprises mixing a sufficient amount of nanoparticles to create a volume fraction of nanoparticles no less than about 1% of the mixture. 
   
   
       15 . A method as set forth in  claim 12  in which the mixing step comprises mixing the nanoparticles with a base liquid having viscosity greater than about 1000 cp. 
   
   
       16 . A method as set forth in  claim 12  in which the mixing step comprises mixing the nanoparticles with a base liquid comprising liquid silicone. 
   
   
       17 . A method as set forth in  claim 12  in which the mixing step comprises mixing the nanoparticles with a base liquid comprising magnetorheological (MR) liquid.