The object of the “smart” axle project would be a microprocessor controlled truck axle having three continuously variable and reversible hydrostatic motors to implement a complete transmission system within each driven truck axle. The axle would provide a torque response as a nonlinear function of the engine speed similar to that of an automatic transmission with torque converter and would reverse the torque for engine compression braking in response to service air brake pressure. It might also add hydraulic breaking in response to service air brake pressure.
The microprocessor control would implement a limited slip differential function to maintain drive capability if the wheels become unweighted on one side of the axle. With the addition of an accelerometer, the microprocessor control could further implement skid control functions possibly avoiding tractor jackknife incidents. The microprocessor could further collect engine performance data and report if the engine needs service.
The project would need to start with a survey of ongoing development efforts of truck transmission and axle manufacturers including Eaton Fuller and Dana followed by a survey of available and recently patented hydrostatic motor designs including the one disclosed in this proposal. The project would then performance test and evaluate the possible adaptation of motors for this application. Because the engine speed is higher than the axle speed on a big truck, the optimal design could be different for the engine and axle motors. Access to a dynamometer would be useful for this phase. Phase one would also follow through on securing patent protection for the motor disclosed in this proposal.
If no motor is found to meet the requirements of the “Smart Axle” then it may be possible to modify the project objectives and still solve some truck operability problems if not the dramatic reduction in cost and weight that would result from the integrated axle solution.
Ten speed transmissions generally combine a five speed transmission with an air pressure operated two speed transmission mounted to the back of the five speed. The two speed generally provides a high and low speed range selecting speeds 1 thru 5 or 6 thru 10, but some manufacturers use the two speed to select even and odd speeds. Since many of the aforementioned operability problems occur in the lower speed range, operability could be improved if the lower speed range were replaced by a continuously variable hydrostatic transmission. Thus, the five transmission would connect speed 1 and reverse to the hydrostatic transmission output rather than directly to the countershaft and the driver would have a separate shift lever for the variable transmission.
The hybrid solution would maintain the high efficiency of the fully mechanical transmission in speeds 2 thru 5. In highway driving, drivers rarely need to downshift to the lower speed range. This only occurs on very steep hills or in slow moving traffic. With a variable first gear, driver fatigue would be significantly reduced as shifting gears is eliminated at slower speeds. This capability would also reduce vehicle maintenance by eliminating the very high torques created from driver abuse in the lower speeds. The hydrostatic transmission would not need to be a very high torque by utilizing the gear reduction from the mechanical drive system.
A second phase of the “Smart Axle” project would be to build prototype motors, performance test them and again evaluate the feasibility of continuing the project. At this point the progression of the project would become straightforward although not necessarily easy. An axle manufacture, e.g., Dana, could contract to build the “Smart” axles while a software development project would be started to implement the automatic transmission, engine braking, limited slip differential and skid control functions.
Because axles are more standardized both in size and mounting for trucks than for other vehicles, the “Smart” axles could be introduced as an aftermarket product for drivers who have broken a transmission or other transmission component. If the solution proves to be effective in increasing commercial vehicle safety as expected by reducing driver fatigue and providing more reliable braking, then the project would likely draw support from trucking companies and the Department Of Transportation (DOT).