Control device for internal combustion engine

Abstract

A switching mechanism switches the pressure stage of oil, which is fed from an oil pan to the individual parts of an internal combustion engine, between two stages, which are a low-pressure stage and a high-pressure stage. An electronic control device controls the action of the switching mechanism. The electronic control device determines that the liquid level of the oil is abnormal on the basis of the fact that the liquid level of the oil, which is detected by a liquid level sensor, in the oil pan becomes lower than a predetermined value. If the pressure stage of the oil is set at the low-pressure stage through the switching mechanism, the predetermined value is set at a higher value than that when the pressure stage is set at the high-pressure stage.

1 . A control device for an internal combustion engine, the engine including a switching mechanism for switching a pressure stage of oil, which is fed from a storage portion to individual parts of the engine, between a plurality of stages, the control device comprising:
 a control portion for controlling action of the switching mechanism;   a liquid level sensor for detecting the liquid level of oil in the storage portion;   a determination portion for determining that the liquid level of the oil is abnormal based on the fact that the oil liquid level detected by the liquid level sensor falls below a predetermined value; and   a setting portion for setting the predetermined value to a larger value if the pressure stage of the oil is set to a low-pressure stage through the switching mechanism, as compared to a case where the pressure stage of the oil is set to a high-pressure stage.   
     
     
         2 . The control device for an internal combustion engine according to  claim 1 , wherein
 the determination portion prohibits determination until a predetermined period has passed after the control portion switches the pressure stage of the oil.   
     
     
         3 . The control device for an internal combustion engine according to  claim 1 , wherein
 the determination portion determines that the oil liquid level is abnormal based on the fact that the oil liquid level detected by the liquid level sensor remains below the predetermined value for a predetermined period.   
     
     
         4 . The control device for an internal combustion engine according to  claim 1 , wherein
 the switching mechanism comprises a relief valve for releasing some of oil ejected from an oil pump driven by the internal combustion engine to an upstream side of the oil pump and a change portion for changing a valve opening pressure of the relief valve.   
     
     
         5 . The control device for an internal combustion engine according to  claim 1 , wherein
 the switching mechanism switches the pressure stage of the oil between two stages, which are a low-pressure stage and a high-pressure stage.