| 摘要 |
PURPOSE:To enable circulation of blow-by gas in accordance with running of an engine while the pressure within a crankcase is held substantially to the atmospheric pressure by changing over a passage along which blow-by gas is circulated by an air pump in accordance with the pressure of a suction passage downstream of a throttle valve and so on. CONSTITUTION:The first blow-by gas passage 13 is provided which communicates a crankcase 6 to a suction passage 12 downstream of a throttle valve 11, and the first control valve 14 is provided intermediate the first blow-by gas passage 13 which is opened or closed in accordance with the supercharging pressure downstream of the throttle valve 11. A second blow-by gas passage 15 is also provided which is branched from the first blow- by gas passage 13 upstream of the control valve 14 and which communicates with the section passage 12 downstream of the throttle valve 11. An air pump 16 is interposed intermediate the second passage 15 which is driven by the engine and a second control valve 17 is provided in the second passage 15 downstream of the air pump 16 which is closed when suction negative pressure is below a predetermined level. Besides, a third blow- by pas passage 18 is provided which is branched from the second passage 15 upstream of the second control valve 17 and which communicates with the crankcase 6. A relief valve 18A is interposed in the third passage 18, and a third control valve 21 is provided in a bypass passage 1 which bypasses the relief valve 18A. |
