PURPOSE: To maintain lubrication in an excellent state by a method wherein during a high oil temperature time at which a lubricating oil temperature is increased to a value exceeding a given value, a fuel feed amount causes promotion of switching to a low speed cam from a high speed cam and until the lubricating oil temperature is decreased to a value exceeding a different given value, a valve is opened and closed by means of the low speed cam.
CONSTITUTION: A switching region between a low speed cam 101 and a high speed cam 102 is set by a means 103 and according to the switch region, the cams 101 and 102 are switched by a means 104. In this case, the lubricating oil temperature of an engine is detected by a means 105. Further, a high oil temperature time at which a detected lubricating oil temperature is increased to a value exceeding a given value T2 is decided by a means 106. Further, at the high oil temperature time, on an operation condition on which a valve is opened and closed by the high speed cam 102, an amount of fuel fed to an engine is decreased by a means 107 until switch to the low speed cam 101 from the high speed cam 102 is effected. Until a detecting lubricating oil temperature is reduced to a value exceeding a given value T1, switching to the high speed cam 102 is prohibited by a means 108.
NAKAMURA MAKOTO
TAKEMURA SHINICHI
