Engine balance shaft housing and method of assembling same

An engine assembly, comprising:

• an engine block;
• an oil pan mounted to the engine block;
• a balance shaft housing mounted to the engine block and disposed within the oil pan;
• wherein the balance shaft housing includes a first housing portion and a second housing portion each partially defining balance shaft chambers for containing a respective balance shaft, with the first housing portion being between the balance shaft chambers and the engine block and the second housing portion being between the balance shaft chambers and the oil pan;
• and
• a plate member secured to the second housing portion between the second housing portion and the oil pan to partially define therewith an air flow path extending from an inlet formed by the first housing portion and passing between the balance shaft chambers to first and second inlet ports defined by the second housing portion, thereby establishing fluid communication with the first and the second balance shaft chambers, respectively, and the inlet.

A method of assembling a balance shaft housing, comprising:

• casting a first housing portion;
• casting a second housing portion;
• wherein the cast first and second housing portions define first and second balance shaft chambers therebetween when placed together, with an air inlet passage extending through the housing portions between the balance shaft chambers;
• and
• securing a cover member to the second housing portion to enclose a cavity defined between the second housing portion and the sheet member open to the air inlet passage.