Oil cooling system for supercharged engine

Abstract

In an oil cooling system for a supercharged engine, coolant is introduced from a third coolant supply passage that branches from a first coolant supply passage into a coolant circulation passage of an oil cooler. The coolant has not cooled an engine and a turbocharger. By efficiently cooling lubricating oil (lubricating oil after lubricating supercharger) having lubricated the respective cooled portions of the turbocharger, oil-deterioration-suppressing effect can be improved even with the coolant of a small amount.

What is claimed is: 
     
         1 . An oil cooling system for a supercharged engine in which a supercharger is mounted on an internal combustion engine, comprising:
 an oil supply passage that supplies lubricating oil to the supercharger;   an oil discharge passage that returns the lubricating oil which has lubricated the supercharger to the inside of the internal combustion engine;   an oil cooling device that is installed in the oil discharge passage and cools the lubricating oil which has lubricated the supercharger by utilizing coolant;   a first coolant passage that supplies coolant at least to the supercharger; and   a second coolant passage that branches from the first coolant passage on the upstream side of the supercharger in the flow direction of the coolant, and supplies the coolant to the oil cooling device.   
     
     
         2 . The oil cooling system for a supercharged engine according to  claim 1 , wherein
 the oil discharge passage comprises a first oil discharge passage that leads lubricating oil which has lubricated the supercharger to the oil cooling device, and a second oil discharge passage that leads the lubricating oil having been cooled in the inside of the oil cooling device to the inside of an oil pan formed in a crankcase of the internal combustion engine.   
     
     
         3 . The oil cooling system for a supercharged engine according to  claim 1 , further comprising:
 a first intake passage that supplies intake air having passed through an air cleaner of the internal combustion engine to the supercharger;   a second intake passage that supplies the intake air having been compressed by the supercharger to a throttle valve of the internal combustion engine;   a third intake passage that supplies the intake air of which flow rate has been adjusted by the throttle valve to cylinders of the internal combustion engine;   a fresh air introduction passage that branches from the first intake passage and connects the air cleaner and a valve gear chamber of the internal combustion engine to each other;   a first blow-by gas reduction passage that connects the crankcase and the third intake passage;   a check valve that is arranged in the blow-by gas reduction passage and prevents back flow of blow-by gas that flows from the third intake passage to the crankcase;   a second blow-by gas reduction passage that connects is connected from any position communicating with the inside of the crankcase to the first intake passage on the downstream side of a branch position of the fresh air introduction passage; and   a negative pressure generating device that is installed in the second blow-by gas reduction passage and generates negative pressure in the second blow-by gas reduction passage.   
     
     
         4 . The oil cooling system for a supercharged engine according to  claim 3 , wherein,
 the negative pressure generating device comprises:   an intake reduction passage that branches from the second intake passage is connected to the first intake passage for returning the intake air from the downstream side to the upstream side of the supercharger;   a flow rate control device that adjusts the flow rate of intake air circulating through the intake reduction passage; and   an ejector that generates negative pressure in the second blow-by gas reduction passage.   
     
     
         5 . The oil cooling system for a supercharged engine according to  claim 1 , wherein
 the first coolant passage has a first coolant supply passage that supplies coolant to the internal combustion engine and a second coolant supply passage that branches from the first coolant supply passage and supplies the coolant to the supercharger; and   the second coolant passage has a third coolant supply passage that branches from the first coolant supply passage.   
     
     
         6 . The oil cooling system for a supercharged engine according to  claim 1 , wherein
 the oil cooling device has an oil cooling passage which is connected to the oil discharge passage and through which lubricating oil cooled by utilizing coolant introduced from the third coolant passage circulates, and an oil mist separator that captures oil mist in the oil cooling passage.   
     
     
         7 . The oil cooling system for a supercharged engine according to  claim 6 , wherein
 the oil mist separator has collision plates that project to the inside of the oil cooling passage so as to be thermally in contact with lubricating oil which has lubricated the supercharger.   
     
     
         8 . The oil cooling system for a supercharged engine according to  claim 6 , wherein
 the oil mist separator has a coolant circulation passage through which the coolant cooling the lubricating oil circulating through the oil cooling passage circulates, and collision plates that project to the inside of the coolant circulation passage so as to be thermally in contact with the coolant circulating through the coolant circulation passage.   
     
     
         9 . The oil cooling system for a supercharged engine according to  claim 6 , wherein
 the oil cooling device has an oil cooling passage which is connected to the oil discharge passage and through which lubricating oil cooled by utilizing coolant introduced from the third coolant passage circulates;   the oil discharge passage has a first oil discharge passage that leads lubricating oil having which has lubricated the supercharger into the oil cooling device, and a second oil discharge passage that leads the lubricating oil which has been cooled in the oil cooling device into an oil pan formed in a crankcase of the internal combustion engine; and   the engine has a liquid seal section that is arranged in at least one passage out of the oil cooling passage, the first oil discharge passage, and the second oil discharge passage and shuts off the communicating state between the supercharger and the inside of the crankcase by lubricating oil staying in the middle of the at least one passage.   
     
     
         10 . The oil cooling system for a supercharged engine according to  claim 9 , wherein
 the liquid seal section is arranged with at least one passage out of the oil cooling passage, the first oil discharge passage, and the second oil discharge passage being U-shaped.   
     
     
         11 . The oil cooling system for a supercharged engine according to  claim 10 , wherein
 the liquid seal section is arranged with the downstream end of the second oil discharge passage being connected to a position below the liquid surface of lubricating oil stored inside the oil pan.   
     
     
         12 . The oil cooling system for a supercharged engine according to  claim 1 , wherein
 the oil discharge passage has a first oil discharge passage that leads lubricating oil having lubricated the supercharger into the oil cooling device, a second oil discharge passage that leads the lubricating oil having been cooled in the inside of the oil cooling device into an oil pan formed in a crankcase of the internal combustion engine, and an oil mist separator that is installed in the second oil discharge passage and captures oil mist in the second oil discharge passage.   
     
     
         13 . The oil cooling system for a supercharged engine according to  claim 12 , wherein
 the oil cooling device has an oil cooling passage which is connected to the oil discharge passage and through which lubricating oil cooled by utilizing coolant introduced from the third coolant passage circulates, and an oil mist separator that captures oil mist in the oil cooling passage; and   the oil mist separator is configured so that the oil cooling passage or the second oil discharge passage communicates with a chain case of the internal combustion engine.   
     
     
         14 . The oil cooling system for a supercharged engine according to  claim 13 , wherein
 the internal combustion engine has a first partition wall that partitions the internal space of the internal combustion engine into the chain case and the valve gear chamber, and a second partition wall that partitions the internal space of the internal combustion engine into the crankcase and the chain case;   the second partition wall has a lower end at a position below the liquid surface of lubricating oil in the oil pan; and   the internal combustion engine has a liquid seal section that shuts off the communicating state between the crankcase and the chain case by lubricating oil in the oil pan.