Power transmission fluids with enhanced lifetime characteristics

Abstract

A power transmission fluid having improved characteristics, a method of lubricating a transmission, and a vehicle containing the transmission fluid is disclosed. The transmission fluid includes an amount of silicon-containing antifoam agent having a kinematic viscosity of greater than about 20,000 centistokes at 25° C. that is effective to provide gear shifting times of no more than about 0.75 seconds over a useful lifetime of the transmission fluid.

1 . A power transmission fluid comprising an amount of silicon-containing antifoam agent having a kinematic viscosity of greater than about 20,000 centistokes at 25° C. that is effective to provide gear shifting times of no more than about 0.75 seconds over a useful lifetime of the transmission fluid.  
     
     
         2 . The fluid of  claim 1 , wherein the silicon-containing antifoam agent is selected from the group consisting of fluorosilicones, polydimethylsiloxane, phenyl-methyl polysiloxane, linear siloxanes, cyclic siloxanes, branched siloxanes, silicone polymers and copolymers, organo-silicone copolymers, and mixtures thereof.  
     
     
         3 . The fluid of  claim 2 , wherein the silicon-containing antifoam agent comprises a mixture of polydimethylsiloxane and fluorosilicone compounds.  
     
     
         4 . The fluid of  claim 1 , further comprising an acrylate polymer antifoam agent.  
     
     
         5 . The fluid of  claim 4 , wherein the acrylate polymer antifoamant is selected from the group consisting of a polymethacrylate, a polyacrylate, a dispersant polymethacrylate, a dispersant polyacrylate, and a mixture thereof.  
     
     
         6 . The fluid of  claim 1 , wherein the silicon-containing antifoam agent has a kinematic viscosity ranging from about 40,000 to about 80,000 centistokes at 25° C.  
     
     
         7 . An automotive transmission fluid comprising from about 0.08 to about 0.30 weight percent N-aliphatic alkyl-substituted diethanolamine; from about 2.5 to about 5.0 weight percent phosphorylated and boronated ashless dispersant; from about 0.6 to about 1.2 weight percent sulfurized fatty oil friction modifier; from about 0.02 to about 0.10 weight percent copper corrosion inhibitor; from about 0.02 to about 0.10 percent silicon-containing antifoam agent having a kinematic viscosity at 25° C. of greater than about 20,000 centistokes; from about 0.15 to about 0.45 weight percent nonylated diphenyl amine; from about 0.02 to about 0.10 weight percent Ca(OH) 2  salt of sulfurized alkyl phenate (TBN 150); from about 0.02 to about 0.10 weight percent octanoic acid; from about 0.02 to about 0.10 weight percent 3-decyloxypropylamine; from about 0.005 to about 0.10 weight percent ethylene oxide-propylene oxide block copolymer; from about 0.02 to about 0.10 weight percent alkyl polyoxyalkylene ether; from about 0.015 to about 0.060 acrylate polymer; and greater than about 0.10 weight percent diluent oil.  
     
     
         8 . An automatic transmission fluid, comprising: 
 a) an oil of lubricating viscosity having a kinematic viscosity at 100° C. of 2-10 centistokes;    b) sufficient weight percent of 2,5-dimercapto-1,3,4-thiadiazole (DMTD) and/or derivatives or precursors thereof to provide the fluid with antiwear properties;    c) a silicon-containing antifoam agent having a kinematic viscosity at 25° C. of greater than about 20,000 centistokes; and    d) an acrylate, methacrylate, polyacrylate, polymethacrylate, or copolymer or terpolymer thereof.    
     
     
         9 . The fluid of  claim 8 , wherein the silicon-containing antifoam agent is selected from the group consisting of fluorosilicones, polydimethylsiloxane, phenyl-methyl polysiloxane, linear siloxanes, cyclic siloxanes, branched siloxanes, silicone polymers and copolymers, organo-silicone copolymers, and mixtures thereof.  
     
     
         10 . The fluid of  claim 9 , wherein the silicon-containing antifoam agent comprises a mixture of polydimethylsiloxane and fluorosilicone compounds.  
     
     
         11 . An automatic transmission lubricated with a lubricating oil comprising the fluid of  claim 1 .  
     
     
         12 . The automatic transmission of  claim 11 , wherein the transmission is a continuously variable transmission.  
     
     
         13 . An automatic transmission lubricated with a lubricating oil comprising the automatic transmission fluid of  claim 7 .  
     
     
         14 . A method of treating an automatic transmission having space between moving parts, comprising directly injecting into said space in said transmission a fluid composition comprising at least one silicon-containing antifoam agent having a kinematic viscosity at 25° C. of greater than about 20,000 centistokes.  
     
     
         15 . The method of  claim 14 , wherein the composition further comprises a carrier oil.  
     
     
         16 . A method of maintaining a lower increase in gear shifting time in an automatic transmission containing an aged transmission fluid, comprising lubricating the transmission with a fluid comprising an oil having kinematic viscosity at 100° C. of 2-10 centistokes and an effective amount of a silicon-containing antifoam agent having a kinematic viscosity at 25° C. of greater than about 20,000 centistokes, wherein the gear shifting time for the aged fluid is reduced relative to the gear shifting time for an aged fluid in a transmission containing an antifoam agent having a kinematic viscosity at 25° C. of less than about 20,000 centistokes.  
     
     
         17 . The method of  claim 16 , wherein the silicon-containing antifoam agent has a kinematic viscosity at 25° C. ranging from about 40,000 to about 80,000 centistokes.  
     
     
         18 . A method for maintaining an increased surface tension in an automotive transmission fluid over a life of the fluid in an automotive transmission so as to reduce an amount of air solubilized and/or dispersed in the automatic transmission fluid, said method comprising lubricating the transmission with a transmission fluid comprising at least one silicon-containing antifoam agents having a kinematic viscosity at 25° C. of greater than about 20,000 centistokes.  
     
     
         19 . A method for reducing foaming of a hydrocarbon oil used as a transmission lubricating and power transmitting fluid in a vehicle, said method comprising injecting directly into said oil in a transmission a composition comprising a silicon-containing antifoam agent and an inert carrier oil, wherein the antifoam agent has a kinematic viscosity at 25° C. of greater than about 20,000 centistokes.  
     
     
         20 . The method of  claim 19 , wherein the silicon-containing antifoam agent is selected from the group consisting of fluorosilicones, polydimethylsiloxane, phenyl-methyl polysiloxane, linear siloxanes, cyclic siloxanes, branched siloxanes, silicone polymers and copolymers, and organo-silicone copolymers.  
     
     
         21 . The method of  claim 20 , wherein the injecting occurs into the transmission case, a sump, a fluid pump, a fill tube, a dipstick, a service port, a torque converter, a valve body, an accumulator, or a hydraulic line.  
     
     
         22 . A vehicle comprising a transmission lubricated with a lubricant comprising the fluid of  claim 1 .  
     
     
         23 . A vehicle lubricated by the method of  claim 14 .  
     
     
         24 . A vehicle lubricated by the method of  claim 16 .  
     
     
         25 . A vehicle lubricated by the method of  claim 18 .  
     
     
         26 . A vehicle lubricated by the method of  claim 19.