First and second oil chambers arranged in a cylinder arrangement direction with a partition wall interposed therebetween are formed in a cylinder block. A cylinder head includes first and second communication passages respectively connected to the first and second oil chambers. The communication passages are configured so that a resistance generated when gas is caused to flow from the first oil chamber to a space above the head through the first communication passage is smaller than a resistance generated when gas is caused to flow from the second oil chamber to the space above the head through the second communication passage. The cylinder block includes an oil passage connected to both the oil chambers. The partition wall includes a connection hole for allowing the first and second oil chambers to communicate with each other.

First and second oil chambers arranged in a cylinder arrangement direction with a partition wall interposed therebetween are formed in a cylinder block. A cylinder head includes first and second communication passages respectively connected to the first and second oil chambers. The communication passages are configured so that a resistance generated when gas is caused to flow from the first oil chamber to a space above the head through the first communication passage is smaller than a resistance generated when gas is caused to flow from the second oil chamber to the space above the head through the second communication passage. The cylinder block includes an oil passage connected to both the oil chambers. The partition wall includes a connection hole for allowing the first and second oil chambers to communicate with each other.

A high-performance internal combustion engine includes: a crankshaft chamber; at least two cylinder chambers; a crankshaft linkage mechanism, disposed in the crankshaft chamber; at least two pistons, connected to the crankshaft linkage mechanism and accommodated in the cylinder chambers; an inlet pipe, only communicated with the crankshaft chamber; at least two flow guiding pipes, having one end thereof only communicated with the crankshaft chamber and another end thereof only communicated with the cylinder chamber; and a check valve unit, including a check valve disposed at a connecting location of the inlet pipe and the crankshaft chamber, and two first switch valves disposed at connecting locations of the flow guiding pipes and the cylinder chambers. Accordingly, the working efficiency of the high-performance internal combustion engine can be increased.

A high-performance internal combustion engine includes: a crankshaft chamber; at least two cylinder chambers; a crankshaft linkage mechanism, disposed in the crankshaft chamber; at least two pistons, connected to the crankshaft linkage mechanism and accommodated in the cylinder chambers; an inlet pipe, only communicated with the crankshaft chamber; at least two flow guiding pipes, having one end thereof only communicated with the crankshaft chamber and another end thereof only communicated with the cylinder chamber; and a check valve unit, including a check valve disposed at a connecting location of the inlet pipe and the crankshaft chamber, and two first switch valves disposed at connecting locations of the flow guiding pipes and the cylinder chambers. Accordingly, the working efficiency of the high-performance internal combustion engine can be increased.

The first opening part penetrates the first partition wall that separates the crank chamber and the oil sump chamber. The lubricating device of the engine includes an oil mist generation control part. The oil mist generation control part disperses gas injected from the crank chamber into the oil sump chamber through the first opening part when the crank chamber has a positive pressure or restricts the flow of oil with which the injected gas collides, thereby controlling an amount of oil mist generated in the oil sump chamber.

The first opening part penetrates the first partition wall that separates the crank chamber and the oil sump chamber. The lubricating device of the engine includes an oil mist generation control part. The oil mist generation control part disperses gas injected from the crank chamber into the oil sump chamber through the first opening part when the crank chamber has a positive pressure or restricts the flow of oil with which the injected gas collides, thereby controlling an amount of oil mist generated in the oil sump chamber.

An actuator of a variable compression ratio mechanism for an internal combustion engine includes an arm link 13 configured to change a posture of the variable compression ratio mechanism for the internal combustion engine by swinging, a second control shaft 11 fixed to the arm link 13, and a housing 20 including a first bearing hole 301a supporting the second control shaft 11. The housing 20 includes a lubricant oil supply oil passage 202 opened to a pressure-receiving range over which a contact pressure is received at the first bearing hole 301a from the second control shaft 11 during an expansion stroke of the internal combustion engine.

An internal combustion engine having an internal space including a crankcase chamber includes an oil tank, a first passage communicating a lower part of the internal space with a gas phase part of the oil tank, a first check valve provided in the first passage to permit a flow from the internal space to the oil tank, a second passage communicating the gas phase part with the internal space, a second check valve provided in the second passage to permit a flow from the second passage to the internal space, a third passage communicating a liquid phase part of the oil tank with the second passage, a third check valve provided in the third passage to permit a flow from the oil tank to the second passage, and a flow regulator valve provided in the third passage for regulating a flow of lubricating oil flowing through the third passage.

An internal combustion engine having an internal space including a crankcase chamber includes an oil tank, a first passage communicating a lower part of the internal space with a gas phase part of the oil tank, a first check valve provided in the first passage to permit a flow from the internal space to the oil tank, a second passage communicating the gas phase part with the internal space, a second check valve provided in the second passage to permit a flow from the second passage to the internal space, a third passage communicating a liquid phase part of the oil tank with the second passage, a third check valve provided in the third passage to permit a flow from the oil tank to the second passage, and a flow regulator valve provided in the third passage for regulating a flow of lubricating oil flowing through the third passage.

An oil passageway structure for internal combustion engines includes a cylinder head having an inter-bearing wall fluid communication oil passage for providing fluid communication between a plurality of bearing walls to allow oil to flow therebetween. The cylinder head further includes a bearing wall oil passage branched from the inter-bearing wall fluid communication oil passage to supply oil to a bearing surfaces of at least one of the bearing walls. The inter-bearing wall fluid communication oil passage is defined in one of facing side walls. The bearing wall oil passageway is defined in at least one of the bearing walls. The oil passageway structure is thus made up of a reduced number of parts, can be assembled with a reduced number of man-hours, can lead to productivity growth, and is inexpensive to manufacture.