Lubricant composition

Abstract

Provided by the present invention is a lubricating oil composition showing, though containing ZnDTP as an abrasion resistant agent, a low friction coefficient when used as a lubricating oil for a low friction sliding material, that is, a specific lubricating oil composition which is prepared by blending a lubricant base oil with (A) a specific alkali earth metal-containing cleaning agent, (B) a specific boron-non-containing succinimide base ashless dispersant, (C) a zinc dialkyldithiophosphate and (D) a specific sulfur base compound and which is used for a low friction sliding material.

1 . A lubricating oil composition used for a low friction sliding material, which is prepared by blending a lubricant base oil with (A) an alkali earth metal salicylate base and/or alkali earth metal sulfonate base cleaning agents, (B) a boron-non-containing succinimide base ashless dispersant having an alkenyl group or an alkyl group having a number average molecular weight of 500 to 4000, (C) a zinc dialkyldithiophosphate and (D) a sulfur base compound selected from polysulfide compounds, sulfurized oil & fats, olefin sulfides, thiophosphoric esters, thiophosphorous esters and amine salts of the esters, wherein blending amounts thereof based on a whole amount of the composition are 0.05 to 0.25% by mass of the component (A) in terms of alkali earth metal concentration, 0.03 to 0.50% by mass of the component (B) in terms of nitrogen concentration, 0.01 to 0.12% by mass of the component (C) in terms of phosphorus concentration, 0.02 to 2.0% by mass of the component (D) in terms of sulfur concentration, 0.10% by mass or less of an alkali earth metal phenate base cleaning agent in terms of alkali earth metal concentration and 0.04% by mass or less of boron-containing succinimide in terms of nitrogen concentration. 
     
     
         2 . The lubricating oil composition according to  claim 1 , wherein the blending amount of a zinc dialkyldithiophosphate is 0.03 to 0.10% by mass in terms of phosphorus concentration. 
     
     
         3 . The lubricating oil composition according to  claim 1 , wherein the blending amount of the boron-non-containing succinimide base ashless dispersant having an alkenyl group or an alkyl group having a number average molecular weight of 500 to 4000 is 0.05 to 0.30% by mass in terms of nitrogen concentration. 
     
     
         4 . The lubricating oil composition according to  claim 1 , wherein the sulfur base compound is a compound represented by a general formula (I):
   R 1 —S n —R 2    (I)
   
       (wherein “n” is an integer selected from 1 to 4; R 1  and R 2  each represent independently an alkyl group or an aralkyl group). 
     
     
         5 . The lubricating oil composition according to  claim 4 , wherein “n” in the general formula (I) is 2 or 3. 
     
     
         6 . The lubricating oil composition according to  claim 1 , wherein the low friction sliding material is a material having a diamond-like carbon (DLC) film.