US Patent 11181021 Oil mist separator

An oil mist separator includes a case including an inflow port into which blow-by gas flows and an outflow port out of which blow-by gas flows, a separation unit arranged in the case, and an oil discharge unit arranged at a lower part of the case. The oil mist separator is configured to separate oil mist contained in blow-by gas by the separation unit and discharge oil separated by the separation unit to an outside of the case through the oil discharge unit. The oil discharge unit includes a discharge port through which oil is discharged to the outside of the case and a constriction arranged above the discharge port. The constriction is partially decreased in a small cross-sectional flow area.