This invention relates to engine balancing and, more particularly, to a combination oil pump and balance shaft module for attachment to an engine frame or crankcase.
It is known in the art relating to reciprocating piston engines to provide one or more balance shafts with balance weights to offset various types of engine unbalance created by the arrangement of the rotating and reciprocating components of the engine. Such balance shafts may be mounted at various locations in or on the engine, depending on the particular type of unbalance forces involved and the space available within or around the engine envelope. In some cases, it is convenient to provide one or more balance shafts located within a module which may be separately assembled and then attached to the frame or crankcase of an engine, sometimes for operation within the engine oil pan.
The present invention provides such a balance shaft module for mounting below the engine frame or crankcase. The module includes a housing supporting a balance shaft geared to the engine crankshaft and having balance weights at opposite ends which are rotated to offset unbalance forces developed by the engine components. Covers are provided around the balance weights to limit contact of the weights with oil in the crankcase. The covers are open at the top, and pumping vanes are provided in conjunction with the balance weights to pump out any oil entering into the enclosed space. One of the balance weights is preferably mounted on a driven gear of the balance shaft which engages a mating gear on the crankshaft for driving the balance weights.
The module of the invention further includes a pair of oil pumps mounted on opposite ends of the housing and having rotors driven by the balance shaft. The housing includes an oil pickup inlet through which oil is drawn into the separate inlets of the oil pumps and oil is discharged through pump outlets to separate oil systems of the engine. In a preferred embodiment, a first one of the oil pumps delivers pressurized oil to the main lubrication system of the engine at a suitable pressure. A second one of the oil pumps has its inlet connected with the outlet of the first oil pump and delivers oil at a higher pressure to a separate engine system provided for actuating various devices within the engine structure.
These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings.