Breather device for internal combustion engine

A breather device for an internal combustion engine for guiding blow-by gas generated in a crank chamber to an intake system, the breather device comprising:

• a breather chamber formed adjacent to the crank chamber such that the breather chamber communicates with the crank chamber, wherein the breather chamber is separated from the crank chamber by a first wall and communicates with the crank chamber via a gas inlet formed in the first wall separating the breather chamber from the crank chamber, the breather chamber being configured to separate oil from the blow-by gas that flows in the breather chamber from the crank chamber;
• a filter chamber formed adjacent to the crank chamber such that the filter chamber communicates with the breather chamber, the filter chamber accommodating a filter for separating oil from the blow-by gas that flows in the filter chamber from the breather chamber;
• and
• a breather passage that communicates the filter chamber and the intake system with each other,
• wherein a second wall defining a part of the breather chamber and a filter housing defining the filter chamber are both formed integrally with a crankcase defining the crank chamber,
• wherein the breather chamber and the filter chamber are connected to each other by a communication passage separated from the crank chamber by a third wall constituting a part of the crankcase, and
• wherein the gas inlet formed in the first wall separating the breather chamber from the crank chamber is closed by a one-way valve that allows the blow-by gas to flow from the crank chamber to the breather chamber.