Engine cooling apparatus
An engine cooling apparatus includes a mechanical water pump having a suction hole and N discharge holes (N is an integer not less than two), N water jackets that are arranged in an engine and correspond to the N discharge holes, N joint passages, each of which joins one of the N discharge holes to the associated water jacket, a return passage that returns coolant to the suction hole after the coolant has passed through the N water jackets and has merged in a merging portion, a coolant stopping mechanism that blocks return flow of coolant through the return passage, and N communication passages each of which allows the corresponding one of the N joint passages to communicate with the suction hole while bypassing the N water jackets and the coolant stopping mechanism.
1. An engine cooling apparatus comprising:
a mechanical water pump configured to be driven by rotation of an output shaft of an engine, the water pump having a suction hole through which coolant is drawn and N discharge holes through which the coolant is discharged;
N water jackets arranged in the engine to extend around a combustion chamber of the engine, the water jackets each corresponding to one of the N discharge holes;
N joint passages each of which joins one of the N discharge holes to the associated water jacket;
a merging portion in which the coolant merges after passing through the N water jackets;
a return passage that returns the coolant that has merged in the merging portion to the suction hole;
a coolant stopping mechanism configured to block return flow of the coolant through the return passage; and
N communication passages each of which allows one of the N joint passages to directly communicate with the suction hole while bypassing the N water jackets and the coolant stopping mechanism,
wherein N is an integer not less than two.
2. The engine cooling apparatus according to claim 1 , wherein
the N communication passages are merged in a suction-side passage connected to the suction hole,
the suction-side passage has N draw-in holes to each of which one of N communication passages is connected, and
each of the N draw-in holes is arranged to be offset from the other draw-in holes.
3. The engine cooling apparatus according to claim 1 , wherein the N communication passages are configured such that pressure losses of the coolant are the same in all of the N communication passages when the coolant returns from the joint passages to the suction hole through the communication passages.
4. The engine cooling apparatus according to claim 1 , wherein tubes configuring the N communication passages have equal lengths and equal inner diameters.
5. The engine cooling apparatus according to claim 1 , wherein the N communication passages are configured such that the pressure loss of the coolant when the coolant returns from the joint passages to the suction hole through the communication passages is greater than the pressure loss of the coolant when the coolant returns from the joint passages to the suction hole through the water jackets and the return passage.
6. The engine cooling apparatus according to claim 1 , wherein
the water pump, the N joint passages, and an in-cover passage connected to the suction hole are arranged in a chain cover, and
the N communication passages are each configured by a hose that connects one of the N joint passages to the in-cover passage.
7. The engine cooling apparatus according to claim 1 , wherein
the engine cooling apparatus is employed in a V engine having two banks, and
the N water jackets are two water jackets each arranged in one of the two banks.