Cylinder head cover

A cylinder head cover for a hydrogen-fueled internal combustion engine, comprising:

• a head cover body that defines a main passage for blow-by gas that has leaked from a combustion chamber to a crankcase;
• and
• an outlet passage that is connected to a downstream end of the main passage and configured to conduct the blow-by gas to an intake passage, wherein
• the main passage includes a restriction in a middle of the main passage,
• a section of the main passage on an upstream side of the restriction is referred to as an upstream passage,
• a section of the main passage on a downstream side of the restriction is referred to as a downstream passage,
• a cross-sectional flow area of the restriction is smaller than a cross-sectional flow area of the upstream passage and smaller than a cross-sectional flow area of the downstream passage, and
• the cylinder head cover further comprises an auxiliary passage that is connected to the upstream passage and configured to conduct the blow-by gas to the outlet passage or to the intake passage, wherein
• the head cover body includes a plurality of ribs that protrudes from a wall surface that defines the main passage,
• a dimension in a direction orthogonal to the wall surface is defined as a height dimension, and
• the height dimension of a rib in the downstream passage is smaller than the height dimension of a rib in the upstream passage.