Abstract: An internal combustion engine includes a first blow-by gas passage defined in a second wall. The internal combustion engine includes a second blow-by gas passage defined in a third wall. The internal combustion engine includes a third blow-by gas passage defined in a fourth wall. The first blow-by gas passage to the third blow-by gas passage connect an oil chamber and an oil separator to each other. The second wall includes a first connecting path. The fourth wall includes a second connecting path. The first connecting path connects the first crank chamber and the second crank chamber. The second connecting path connects the third crank chamber and the fourth crank chamber to each other. The third wall does not have a passage connecting the second crank chamber and the third crank chamber to each other.

Abstract: An internal combustion engine includes a first blow-by gas passage defined in a second wall. The internal combustion engine includes a second blow-by gas passage defined in a third wall. The internal combustion engine includes a third blow-by gas passage defined in a fourth wall. The first blow-by gas passage to the third blow-by gas passage connect an oil chamber and an oil separator to each other. The second wall includes a first connecting path. The fourth wall includes a second connecting path. The first connecting path connects the first crank chamber and the second crank chamber. The second connecting path connects the third crank chamber and the fourth crank chamber to each other. The third wall does not have a passage connecting the second crank chamber and the third crank chamber to each other.

Abstract: An internal combustion engine includes a bottomed box-shaped oil pan in which oil is stored. In addition, the internal combustion engine includes an oil pump configured to suck the oil in the oil pan and pressure-feed the oil to each part of the internal combustion engine. A suction pipe extends toward a bottom surface of the oil pan from the oil pump. A strainer is attached to a tip end of the suction pipe. A projection portion protrudes from a bottom surface which is one of inner wall surfaces defining an oil storing space inside the oil pan. The resonance frequency of the projection portion falls in the range of frequency of vibration that is generated at an engine rotational speed at which the internal combustion engine continues to operate independently.

Abstract: An internal combustion engine includes a bottomed box-shaped oil pan in which oil is stored. In addition, the internal combustion engine includes an oil pump configured to suck the oil in the oil pan and pressure-feed the oil to each part of the internal combustion engine. A suction pipe extends toward a bottom surface of the oil pan from the oil pump. A strainer is attached to a tip end of the suction pipe. A projection portion protrudes from a bottom surface which is one of inner wall surfaces defining an oil storing space inside the oil pan. The resonance frequency of the projection portion falls in the range of frequency of vibration that is generated at an engine rotational speed at which the internal combustion engine continues to operate independently.

Abstract: An internal combustion engine includes a bottomed box-shaped oil pan in which oil is stored. In addition, the internal combustion engine includes an oil pump configured to suck the oil in the oil pan and pressure-feed the oil to each part of the internal combustion engine. A suction pipe extends toward a bottom surface of the oil pan from the oil pump. A strainer is attached to a tip end of the suction pipe. A projection portion protrudes from a bottom surface which is one of inner wall surfaces defining an oil storing space inside the oil pan. The resonance frequency of the projection portion falls in the range of frequency of vibration that is generated at an engine rotational speed at which the internal combustion engine continues to operate independently.

Abstract: A cooling apparatus for an engine includes a main circuit, a warm-up circuit, a coolant passage, a coolant pump, a pre-branching passage, a coolant temperature sensor and an agitator. The warm-up circuit allows a coolant to bypass the main circuit. The coolant passage is provided inside an engine body. The coolant pump is configured to cause the coolant to flow through the coolant passage. The pre-branching passage is communicated with an outlet side of the coolant passage, and communicated with the main circuit and the warm-up circuit. The coolant temperature sensor is configured to detect a coolant temperature inside the pre-branching passage. The agitator is disposed downstream of the coolant temperature sensor in a direction of coolant flow when the coolant pump is operating. The agitator is disposed at a boundary between the pre-branching passage and the main circuit or in a vicinity of the boundary.

Abstract: A cooling apparatus for an engine includes a main circuit, a warm-up circuit, a coolant passage, a coolant pump, a pre-branching passage, a coolant temperature sensor and an agitator. The warm-up circuit allows a coolant to bypass the main circuit. The coolant passage is provided inside an engine body. The coolant pump is configured to cause the coolant to flow through the coolant passage. The pre-branching passage is communicated with an outlet side of the coolant passage, and communicated with the main circuit and the warm-up circuit. The coolant temperature sensor is configured to detect a coolant temperature inside the pre-branching passage. The agitator is disposed downstream of the coolant temperature sensor in a direction of coolant flow when the coolant pump is operating. The agitator is disposed at a boundary between the pre-branching passage and the main circuit or in a vicinity of the boundary.