The invention relates to devices for controlling the level of gear lubricant in a gear housing as a function of the speed of the gear.
Drive axles and transmissions typically have several gear sets that are splash lubricated from an oil sump, or reservoir. As the gears turn in the oil, the gears and bearings are coated with the circulating oil. At high speeds, the gears are essentially pumping the oil creating a force corresponding to energy, or shear, losses in the fluid. Energy losses result in lower fuel economy for the vehicle. Lowering the volume of fluid in the gear housing would minimize losses. However, a lower level would be insufficient at lower speeds to properly lubricate and cool the components.
Devices have been proposed for lubricating a power transmission system and adjusting for speed. One such device uses an active mechanical pump driven by the power transmission system and which has an oil reservoir for storing oil. As the speed of the transmission system increases, oil stored at the bottom of the transmission casing is splashed into the oil reservoir thereby decreasing the amount of oil in the casing. When the speed of the transmission decreases, the mechanical pump pumps the oil from the oil reservoir into the casing to insure proper lubrication of the power transmission. This device, however, is an active mechanical device adding cost and reliability concerns to the manufacture of the automotive vehicle.
Thus, there exists a need for an inexpensive, yet reliable device for minimizing shear losses in the lubricating oil in a gear housing without jeopardizing the components at low speed.