Cooling circuit for internal combustion engines
A cooling circuit for internal combustion engines includes an internal combustion engine, a pressure-feeding unit for feeding coolant, which cools the internal combustion engine under pressure, a valve unit having a plurality of heat exchangers connected in parallel thereto, an exhaust heat recovery system for recovering heat from exhaust air of the internal combustion engine by the coolant, a first circulation circuit including the pressure-feeding unit, the valve unit and the exhaust heat recovery system, and a second circulation circuit including the pressure-feeding unit and the exhaust heat recovery system.
1. A cooling circuit for an internal combustion engine, comprising:
an internal combustion engine;
a pressure-feeding pump configured to feed coolant under pressure, the coolant cooling the internal combustion engine;
a valve unit having a plurality of heat exchangers connected in parallel thereto and configured to change a coolant flowing state in the plurality of heat exchangers;
an exhaust heat recovery system configured to recover heat from exhaust air of the internal combustion engine by the coolant;
a first circulation circuit including the pressure-feeding pump, the valve unit and the exhaust heat recovery system; and
a second circulation circuit not including the valve unit and including the pressure-feeding pump and the exhaust heat recovery system,
wherein a flow rate of the coolant flowing through the exhaust heat recovery system via the second circulation circuit is made smaller than that of the coolant flowing through the exhaust heat recovery system via the first circulation circuit by an orifice arranged in the second circulation circuit or by a passage of the second circulation circuit, and the pressure-feeding pump is a mechanical pump driven by power of the internal combustion engine.
2. The cooling circuit according to claim 1 , wherein:
the valve unit is arranged upstream of the exhaust heat recovery system in the first circulation circuit; and
the second circulation circuit is branched off from the first circulation circuit at a position upstream of the valve unit and joins the first circulation circuit between the valve unit and the exhaust heat recovery system.
3. The cooling circuit according to claim 2 , wherein:
the valve unit has a valve opening pattern configured to shut off all circulation circuits passing through the valve unit including the first circulation circuit.
4. The cooling circuit according to claim 3 , wherein:
the plurality of heat exchangers includes
a heater to heat an inside of a cabin of a vehicle mounted with the internal combustion engine through heat radiation from the coolant;
a cooler to cool lubricating oil of a transmission configured to change a speed of output rotation of the internal combustion engine through heat radiation to the coolant; and
a radiator configured to radiate heat of the coolant; and
the valve unit includes
a valve opening pattern configured to cause the coolant to flow through the heater out of the plurality of heat exchangers;
a valve opening pattern configured to cause the coolant to flow through the heater and the cooler out of the plurality of heat exchangers; and
a valve opening pattern configured to cause the coolant to flow through the heater, the cooler and the radiator out of the plurality of heat exchangers.
5. The cooling circuit according to claim 4 , wherein:
the valve unit includes a valve opening pattern configured to cause the coolant to flow only through the radiator out of the plurality of heat exchangers.
6. The cooling circuit according to claim 1 , wherein:
the valve unit is arranged downstream of the exhaust heat recovery system in the first circulation circuit; and
the second circulation circuit is branched off from the first circulation circuit between the exhaust heat recovery system and the valve unit and joins the first circulation circuit at a position downstream of the valve unit.
7. The cooling circuit according to claim 6 , wherein:
the valve unit has a valve opening pattern configured to shut off all circulation circuits passing through the valve unit including the first circulation circuit.
8. The cooling circuit according to claim 1 , wherein:
the plurality of heat exchangers includes a heater configured to heat an inside of a cabin of a vehicle mounted with the internal combustion engine through heat radiation from the coolant; and
the first circulation circuit further includes the heater.
9. The cooling circuit according to claim 1 , wherein:
the plurality of heat exchangers includes a cooler configured to cool lubricating oil of a transmission configured to change a speed of output rotation of the internal combustion engine through heat radiation to the coolant; and
the first and second circulation circuits further include the cooler, and the exhaust heat recovery system is arranged upstream of the cooler.
10. The cooling circuit according to claim 1 , wherein:
the exhaust heat recovery system includes a heat exchanger configured to perform heat exchange between the exhaust air and the coolant;
the exhaust heat recovery system is configured as a bypass-less exhaust heat recovery system configured to cause flowing-in exhaust air to flow via the heat exchanger.
11. The cooling circuit according to claim 1 , wherein:
the second circulation circuit circulates the coolant in a state where the pressure-feeding pump is feeding the coolant under pressure.