Cooling system of engine

Abstract

A cooling system of an engine may include an engine that has a cylinder block where a cylinder is formed therein and a cylinder head that covers the cylinder block, a radiator that is disposed outside the engine, a first thermostat that is disposed on a coolant line connecting the engine with the radiator in such a way that the coolant passes the radiator or does not pass the radiator, and a second thermostat that is configured to make the coolant selectively pass the coolant line that is formed in the cylinder block.

What is claimed is: 
     
         1 . A cooling system of an engine, comprising:
 an engine including a cylinder block having at least one piston cylinder and a cylinder head mounted to the cylinder block covering at least one piston cylinder;   a radiator disposed outside the engine;   a first thermostat disposed on a coolant line connecting the engine with the radiator, wherein the first thermostat selectively limits the amount of coolant passing from the radiator to the engine; and   a second thermostat disposed on the engine, wherein the second thermostat selectively limits the flow of coolant through the cylinder block.   
     
     
         2 . The cooling system of an engine of  claim 1 , wherein the first thermostat or the second thermostat is an electrical thermostat that opens a valve by heating wax. 
     
     
         3 . The cooling system of an engine of  claim 1 , wherein a first operating temperature of coolant in which the second thermostat allows the coolant to flow through a coolant line of the cylinder block is higher than a second operating temperature of coolant in which the first thermostat allows unlimited flow of coolant passing from the radiator to the engine. 
     
     
         4 . The cooling system of an engine of  claim 1 , wherein the first thermostat is disposed adjacent an outlet where coolant is exhausted from the engine and the second thermostat is disposed at a point where coolant is exhausted from the cylinder block. 
     
     
         5 . The cooling system of an engine of  claim 4 , wherein the second thermostat is disposed at a boundary portion connected from the cylinder block to the cylinder head. 
     
     
         6 . The cooling system of an engine of  claim 4 , wherein the power supplied to the first thermostat is Pulse Width Modulation (PWM) controlled and the second thermostat is ON/OFF controlled. 
     
     
         7 . The cooling system of an engine of  claim 4 , wherein the second thermostat is operably connected to a battery and a relay is disposed the second thermostat and the battery to turn the second thermostat ON/OFF. 
     
     
         8 . The cooling system of an engine of  claim 4 , wherein a control portion supplies power with the second thermostat with a predetermined current for a predetermined time and then supplies power with the second thermostat again after a predetermined time elapses from a point that the power is halted when the temperature of coolant is higher than the first operating temperature. 
     
     
         9 . The cooling system of an engine of  claim 1 , wherein the second thermostat opens/closes the coolant line allowing the coolant temperature of the cylinder block to become higher than the coolant temperature of the cylinder head.