1. Technical Field
The present invention generally relates to drive line power transfer mechanisms and more particularly to drive line power transfer mechanisms that include a cooling system.
2. Discussion
Modern vehicles typically include an axle assembly having a housing and a differential assembly. The housing includes a cavity into which the differential assembly is positioned. The differential assembly is rotatably supported by the housing within the cavity. The differential assembly is mechanically coupled to the vehicle engine by a drive shaft. The differential assembly is also coupled to the vehicle drive wheels via a pair of axle shafts. The differential assembly regulates drive torque between the axle shafts, thereby permitting the shafts to rotate at different velocities as when the vehicle is operated in a cornering maneuver.
During the operation of the vehicle, friction between the various components of the axle assembly can cause the components to heat up and decrease the useful life of the components of the axle assembly. One solution that has been proposed is the circulation of a lubricating fluid through a heat exchanger located remotely from the axle assembly. One drawback associated with this approach is that due to the viscosity of the axle assembly lubricating fluid, this fluid is difficult to pump to a remote location, particularly when the ambient temperature is relatively cold.
Another solution that has been proposed is the use of a separate heat exchanger within the cavity of the axle housing. The heat exchanger is mounted to the interior of the axle housing such that it is suspended within a pool of lubricating fluid. One drawback associated with this approach is that any fluid that leaks from the heat exchanger will contaminate the lubricating fluid. In severe cases, the lubricating characteristics of the lubricating fluid can be destroyed if a sufficient quantity of fluid leaks from the heat exchanger.
Accordingly, the remains in need art for an axle assembly having an improved cooling system that provides adequate cooling of the axle lubricant while minimizing the risk of contamination of the axle lubricant in the event of a coolant leak.
In one preferred form, the present invention provides a drive line power transfer mechanism having a housing, a power transfer mechanism, a first fluid, at least one cooling conduit and a fluid source. The housing has a wall member that defines a cavity. The power transfer mechanism is positioned within the cavity. The first fluid is at least partially contained within a cavity. The first fluid lubricates and extracts heat from the power transfer mechanism during the operation of the drive line power transfer mechanism. The cooling conduit is formed within the wall member. The fluid source is in fluid communication with the fluid conduit and passes a second fluid through the cooling conduit to draw heat out of the housing that is generated by the operation of the drive line power transfer mechanism. A method for cooling an axle assembly is also provided.