Lubricating oil compositions for automatic transmissions

Abstract

A lubricating oil composition for automatic transmissions wherein the mass ratio of phosphorus:calcium:boron:sulfur determined by elemental analysis is 1:(0.1 to 2):(0.06 to 2):(0.2 to 20), the concentration of phosphorus is from 0.01 to 0.06 percent by mass, the concentration of the sulfur derived from a base oil is from 0 to 0.1 percent by mass, and the concentration of the sulfur derived from sulfur-based additives is from 0.01 to 0.15 percent by mass, based on the total amount of the composition. The lubricating oil composition can prevent the occurrence of scratch phenomenon even over a long period of time when used in a metal belt type continuously variable automatic transmission.

1 . A method for maintaining g-V characteristics in belt type continuously variable transmissions in a positive gradient, the method comprising lubricating a continuously variable transmission with a lubricating oil composition, wherein the composition comprises a base oil, phosphorus-based additives, calcium-based additives, boron-containing additives and sulfur-based additives, wherein a mass ratio of phosphorus:calcium:boron:sulfur determined by elemental analysis is 1:(0.1 to 2):(0.06 to 2):(0.2 to 20), a concentration of phosphorus is 0.01 to 0.06 percent by mass, a concentration of sulfur derived from a base oil is 0 to 0.1 percent by mass, and a concentration of sulfur derived from sulfur-based additives is 0.01 to 0.15 percent by mass, based on a total amount of the composition. 
   
   
       2 . The method according to  claim 1 , wherein the mass ratio of phosphorus:calcium:boron:sulfur determined by elemental analysis is 1:(0.1 to 1):(0.1 to 0.8):(0.4 to 5), the concentration of phosphorus is 0.02 to 0.05 percent by mass, the concentration of sulfur derived from a base oil is 0 to 0.1 percent by mass, and the concentration of sulfur derived from sulfur-based additives is 0.01 to 0.15 percent by mass, based on the total amount of the composition. 
   
   
       3 . The method according to  claim 1 , wherein the sulfur-based additive is at least one compound selected from the group consisting of (A) thiadiazoles and/or benzothiazoles, (B) dithiocarbamates, (C) dithiophosphates, (D) trithiophosphites, (E) polysulfides, and derivatives of (A) though (E). 
   
   
       4 . The method according to  claim 2 , wherein the sulfur-based additive is at least one compound selected from the group consisting of (A) thiadiazoles and/or benzothiazoles, (B) dithiocarbamates, (C) dithiophosphates, (D) trithiophosphites, (E) polysulfides, and derivatives of (A) though (E). 
   
   
       5 . A method for preventing the occurrence of a scratch phenomenon caused by a belt and elements in belt type continuously variable transmissions, the method comprising lubricating a continuously variable transmission with a lubricating oil composition, wherein the composition comprises a base oil, phosphorus-based additives, calcium-based additives, boron-containing additives and sulfur-based additives, wherein a mass ratio of phosphorus:calcium:boron:sulfur determined by elemental analysis is 1:(0.1 to 2):(0.06 to 2):(0.2 to 20), a concentration of phosphorus is 0.01 to 0.06 percent by mass, a concentration of sulfur derived from a base oil is 0 to 0.1 percent by mass, and a concentration of sulfur derived from sulfur-based additives is 0.01 to 0.15 percent by mass, based on a total amount of the composition. 
   
   
       6 . The method according to  claim 5 , wherein the mass ratio of phosphorus:calcium:boron:sulfur determined by elemental analysis is 1:(0.1 to 1):(0.1 to 0.8):(0.4 to 5), the concentration of phosphorus is 0.02 to 0.05 percent by mass, the concentration of sulfur derived from a base oil is from 0 to 0.1 percent by mass, and the concentration of sulfur derived from sulfur-based additives is from 0.01 to 0.15 percent by mass, based on the total amount of the composition. 
   
   
       7 . The method according to  claim 5 , wherein the sulfur-based additive is at least one compound selected from the group consisting of (A) thiadiazoles and/or benzothiazoles, (B) dithiocarbamates, (C) dithiophosphates, (D) trithiophosphites, (E) polysulfides, and derivatives of (A) though (E). 
   
   
       8 . The method according to  claim 6 , wherein the sulfur-based additive is at least one compound selected from the group consisting of (A) thiadiazoles and/or benzothiazoles, (B) dithiocarbamates, (C) dithiophosphates, (D) trithiophosphites, (E) polysulfides, and derivatives of (A) though (E).