Zeroshift, which launched the second generation of its automated manual transmission at the SAE World Congress in 2007 (earlier post), is introducing two new actuator systems and a new control system at the 2008 SAE World Congress. The Zeroshift AMT can deliver a 2% improvement in fuel economy compared to a manual transmission, and 7% compared to a six-speed planetary automatic, according to the company.
The Zeroshift system replaces the synchromesh in a conventional manual transmission with paired interlocking rings that allows ratios to be changed without torque interruption. Shifts are made via an automated actuation system.
Until now, Zeroshift used pneumatic actuators. For lighter-duty vehicles, Zeroshift is developing both an electric actuation system and an hydraulic system.
The electrical actuation system comprises a number of low-inertia, brushed motors to actuate the forks. The hydraulic alternative provides an option for automakers that are already using some kind of automated manual transmission.
Most AMTs so far have relies on electro-hydraulic actuation systems. These actuators have hydraulic pistons controlled by hydraulic solenoid valves which provide proportional control of the pistons using pulse width modulation (PWM). It’s a system that will already be very familiar to most of the automotive industry and one which most car manufacturers are very comfortable with.—Steve Hands, senior electronics engineer
Work on the hydraulic system started at the end of 2007 and bench testing is nearly complete. The next phase will be to test the system in a rig before fitting transmissions equipped with it into vehicles.
The use of the hydraulic system will enable the transmission to change ratios at much higher engine speeds than before, according to Hands. Smaller hydraulic pistons will deliver and even faster action.