Engine lubrication system

1. An engine lubrication system for a multi-cylinder engine, comprising:

a plurality of crank chambers that are partitioned by crankshaft bearing portions of the engine;

a number of pumps that take out oil from a lower portion of the engine, the number of the pumps being at least one and less than a number of the crank chambers;

an oil storage section that temporarily stores the oil taken out from the lower portion of the engine;

a lubrication part that supplies the oil in the oil storage section to a portion to be lubricated of the engine; and

a pressure variation suppression section including oil collection passages that are respectively provided for the crank chambers, a designated number of the oil collection passages being merged and connected to at least one of suction ports of the pumps, the pressure variation suppression section being provided between the suction ports of the pumps and the designated number of the crank chambers to be merged, and the pressure variation suppression section suppressing pressure variations in the crank chambers by only the crank chambers between which pressure difference is minimum being permanently merged via an always opened oil flow path through the merged oil collection passages or by only the crank chambers in which pressure variations are in a same phase being permanently merged via the always opened oil flow path through the merged oil collection passages.

2. The engine lubrication system according to claim 1 , wherein

the crank chambers between which pressure difference is minimum are the designated number of the crank chambers to be merged, and

the pressure variation suppression section includes the oil collection passages that are connected to the respective crank chambers such that the oil collection passages have a designated length and a designated inner diameter that are required to suppress pressure variations in the respective crank chambers.

3. The engine lubrication system according to claim 1 , wherein

the oil collection passages have the same length from a point at which each oil collection passage is connected to a corresponding crank chamber to a point at which the oil collection passages are merged.

4. The engine lubrication system according to claim 1 , wherein

the crank chambers between which pressure difference is minimum are the designated number of the crank chambers to be merged,

the pressure variation suppression section includes chambers to which downstream sides of the oil collection passages to be merged are respectively connected, the chambers having a specific volume that is required to suppress pressure variations in the crank chambers corresponding to the oil collection passages, and

the chambers are connected to the suction ports of the pumps though a single common passage.

5. The engine lubrication system according to claim 1 , wherein

the oil collection passages are formed integrally in a plate-like member attached to a lower side of the crank chambers.

6. The engine lubrication system according to claim 5 , wherein

the plate-like member in which the oil collection passages are formed is an oil pan or a lower plate.

7. The engine lubrication system according to claim 1 , wherein

in the case where an even number of the crank chambers are provided, every two crank chambers between which pressure difference is minimum are paired, and the number of the pumps is the same as the number of pairs of the crank chambers.

8. The engine lubrication system according to claim 1 , wherein

in the case where an odd number of the crank chambers are provided, one pump is connected to one crank chamber positioned centrally in a direction in which cylinders are arranged, and every two other crank chambers between which pressure difference is minimum are each connected to one pump using an oil collection passage with a 2-in-1 construction.

9. The engine lubrication system according to claim 1 , wherein the pumps are each a mechanical oil pump.

10. The engine lubrication system according to claim 1 , wherein the pumps are each an electric oil pump.

11. An engine lubrication system for a multi-cylinder engine, comprising:

a plurality of crank chambers that are partitioned by crankshaft bearing portions of the engine;

means for pumping that take out oil from a lower portion of the engine, a number of the pumping means being at least one and less than a number of the crank chambers;

means for temporarily storing the oil taken out from the lower portion of the engine;

means for lubricating that supplies the oil in the temporary storage means to a portion to be lubricated of the engine; and

means for suppressing pressure variation including means for collecting oil that are respectively provided for the crank chambers, a designated number of the oil collecting means being merged and connected to at least one of suction ports of the pumping means, the means for suppressing pressure variation being provided between the suction ports of the pumping means and the designated number of the crank chambers to be merged, and the pressure variation suppression means suppressing pressure variations in the crank chambers by only the crank chambers between which pressure difference is minimum being permanently merged via an always opened oil flow path through the merged oil collecting means or by only the crank chambers in which pressure variations are in a same phase being permanently merged via the always opened oil flow path through the merged oil collecting means.