Crankcase structure for internal combustion engine

Abstract

The invention provides a crankcase structure for an internal combustion engine, the crankcase structure can inhibit change of oil level, inhibit increase of friction of a crankshaft and a speed changer, and prevent cavitation generation of an oil pump. The crankcase structure for an internal combustion engine is provided with an oil bottom housing (2p) at a lower part of the crankcase (2), wherein, lower side separating walls (61L, 61R, 62L, 62R) in an upper and lower separation at a lower part of the oil level (S) of oil stored in the oil bottom housing (2p) in a proper amount when the internal combustion engine stops are formed by extending from case outside circumferential walls (2Ls, 2Rs) to case inner space, at an upper part in specified spacing with the lower side separating walls,upper-lower separated upper side separating walls (65L, 65R, 66L, 66R) of at least one party of the crankshaft or the speed changer are formed by extending from the case outside circumferential walls(2Ls, 2Rs) to the case inner space.

Description

technical field [0001] The present invention relates to a crankcase structure of an internal combustion engine provided with an oil pan below the crankcase. Background technique [0002] An internal combustion engine equipped with an oil pan under the crankcase has a lubrication system that sucks the oil stored in the oil pan and supplies it to parts that require lubrication. The inlet is set close to the bottom of the oil pan and is not affected by the amount of oil stored in the oil pan, while the oil suction port is always completely immersed in the oil to prevent air from being sucked in. [0003] If air is sucked in, the discharge oil pressure of the oil pump fluctuates due to cavitation (Japanese original: エア噛み), and oil cannot be supplied to the lubricated part at a stable oil pressure. [0004] Therefore, in an internal combustion engine with the oil suction port close to the bottom surface of the oil pan, and especially in an internal combustion engine mounted on a...

AI Technical Summary

Problems solved by technology

[0016] However, since the discharge port of the upper bulkhead is located at a relatively high position, and as the crank arm rotates, the oil on the upper bulkhead flows out from the discharge port in a manner that is swung out, so it is easy to dislodge the oil on the lower bulkhead at the front and rear. Air bubbles are generated at the opening between the openings, and the possibility of air bubbles being sucked into the oil suction port below the opening is high, and the discharge oil pressure of the oil pump is likely to be unstable due to cavitation

[0017] In addition, there is a gap between the upper partition wall and the front side wall of the tank outer peripheral wall. Therefore, especially when the internal combustion engine swings back and forth, there is a phenomenon that the oil accumulated on the lower partition wall on the front side runs along the outer peripheral wall of the tank. The inner surface of the front side wall flows upward in the gap, and is supplied to the upper partition wall in a large amount, which increases the friction of the crankshaft.

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