Leakage detection device

A leakage detection system that detects leakage in a Positive Crankcase Ventilation (PCV) passage of an engine, the leakage detection system comprising:

• a valve control unit;
• a pressure measurement unit that measures a pressure in the PCV passage;
• a first valve that opens/closes a fresh air line of the PCV passage;
• a second valve capable of electronic control by the valve control unit of a flow rate of a blow-by gas to be delivered from a crank chamber of the engine to a scavenging line of the PCV passage;
• and
• a leakage determination unit that determines a presence or absence of leakage in the PCV passage on a basis of the pressure in the PCV passage at a time when the first valve closes compared to the pressure in the PCV passage after a predetermined lapse of time,
• wherein the scavenging line communicates between the crank chamber of the engine and a portion of an intake passage of the engine that is on a downstream side of a throttle valve, and the fresh air line communicates between the crank chamber and a portion of the intake passage that is on an upstream side of the throttle valve,
• wherein the PCV passage comprises a balance line that communicates between the crank chamber of the engine and an oil catch tank so as to retain a pressure in the oil catch tank to be equal to the pressure in the crank chamber and prevents an excess negative pressure in the oil catch tank caused by a suction of oil by a scavenging pump, and
• wherein the valve control unit closes the first valve to block a flow of fresh air into the crank chamber when the engine is under a low load and controls an opening of the second valve so as to maintain a flow rate of blow-by gas from the crank chamber to the scavenging line to be constant when the first valve is closed, in a manner that concurrently ensures that a negative pressure in the crank chamber remains less than an amount predetermined as excessive.

A method of detecting a leakage in a Positive Crankcase Ventilation (PCV) passage that at least includes a scavenging line that communicates between a crank chamber of an engine and a portion of an intake passage of the engine that is on a downstream side of a throttle valve, the leakage detection method comprising:

• closing a first valve in a fresh air line of the PCV passage to block a flow of fresh air into the crank chamber, the fresh air line communicating between the crank chamber and a portion of the intake passage that is on an upstream side of the throttle valve;
• opening an electronically-controlled Positive Crankcase Valve (PCV) valve formed between the scavenging line and the crank chamber;
• measuring an air pressure in the PCV passage while concurrently adjusting an opening setting of the PCV valve to control a negative pressure in the crank chamber to be less than an amount predetermined as excessive;
• and
• determining a presence or absence of leakage in the PCV passage on a basis of the pressure in the PCV passage at a time when the first valve is closed and the PCV valve is open.