This invention is the idea of a mechanic with forty years in the field. The purpose of the invention is to increase the efficiency of the final drive unit in a vehicle by increasing performance and thereby using less energy. Vehicles, such as cars, pickup trucks, load hauling semi tractors, and the like, typically have an engine that generates power, a transmission that provides speed-torque conversion for that power, and a drive that provides the converted power to the axle and wheels. The combination of the transmission, drive, and axle is known as the drive train.
In rear wheel drive vehicles, power passes from the engine to the transmission, through the transmission to a drive shaft, and through the drive shaft to a single ratio drive. The transmission changes the rotation rate between the engine and the drive shaft. The single ratio drive includes a pinion gear in contact with a ring gear, which changes the plane of rotation from the drive shaft to the axles. A differential attached to the ring gear allows the axles to turn independently of each other and to turn the drive wheels.
In front wheel drive vehicles and rear engine, rear drive vehicles, the engine is mounted transversely (side to side) in the vehicle and the engine crankshaft turns in the same plane as the drive wheels. A transaxle houses the transmission and the drive assembly in a single transaxle case. Larger front wheel drive vehicles use a drive planetary gear set, which has a single ratio sun gear driven by the transmission output shaft, and a drive assembly that has the planet assembly and differential assembly built together as one assembly. The single ratio sun gear drives several single ratio planet gears in contact with a single ratio ring gear lugged to the transaxle case that the drive assembly walks around. Because the ring gear is lugged to the transaxle case and does not turn, the differential assembly attached to the drive assembly turns, turning the axles and the wheels. smaller front wheel drive vehicles use an idler gear driven by the transmission output shaft to drive a pinion gear, which drives a ring gear positively attached to the differential assembly
Unfortunately, changes in the gear ratio between the engine and the wheels in the drive train of both rear wheel and front wheel drive vehicles are limited to the transmission: the drive is limited to a single gear ratio. A high gear ratio, such as four-to-one, is desirable for quick starts with high torque to get the vehicle moving, but is undesirable for high speed operation. A low gear ratio, such as one-to-one, is desirable for high speed operation, but is undesirable or unable to start vehicle motion. Typically, a compromise gear ratio of three-to-one is selected, but this is only efficient at mid range speeds. The compromise gear ratio wastes energy because the gear ratio is not matched to the operating speed. In addition, the gear ratio limits the ability to attain maximum acceleration. Although the gear ratio can be changed by disassembling the drive and changing out the gears, the gear ratio cannot be changed in operation.
It would be desirable to have a multi ratio drive that would overcome the above disadvantages.