Patent ID: 7117858

Claim:
An oil separator provided in combination with a cylinder head cover of an internal combustion engine to separate oil mist from blow-by gas to be discharged out through the cylinder head cover, the oil separator comprising: a separator cover fixed to an inner surface of the cylinder head cover defining a space extending in a first direction perpendicular to axis of a camshaft in plan, between the separator cover and the cylinder head cover, the separator cover including a first end section having an opening through which the space is opened to a valve operating chamber; a partition wall defining in the space an inlet-side separator chamber and an outlet-side separator chamber which are located on opposite sides of the partition wall, the inlet-side separator chamber being located adjacent the opening, the outlet-side separator chamber being defined by a second end section of the separator cover, the second end section being opposite to the first end section in the first direction, the partition wall extending in a second direction parallel with the axis of the camshaft and being formed with a plurality of fine passages which pass through the partition wall; a plurality of projection walls projecting from a part of the inner surface of the cylinder head cover which faces the valve operating chamber through the opening, the projection walls projecting toward the valve operating chamber and extending in the second direction, the projection walls being located separate from each other, and a partition wall projecting from the inner surface of the cylinder head cover toward the separator cover, the partition wall having a lower end separate from the separator cover to form a slit-like gas inlet.