The HLA system functions in much the same way as the hydraulic hybrid system we saw on an experimental UPS delivery truck earlier this year. A hydraulic pump/motor is connected to the drive shaft along with a high pressure accumulator. During braking the pump/motor is driven to pressurize the accumulator and recapture kinetic energy. During acceleration the pressure is used to drive the motor and provide a boost so the engine doesn't have to work as hard. Essentially it acts as a mild hybrid system without the automatic start-stop functionality. At this point it's not known if start/stop will also be included. The press release on the original concept is after the jump.
[Source: All Cars, All the Time]
FORD'S INNOVATIVE USE OF HYDRAULICS ADDRESSES LARGE TRUCK FUEL ECONOMY
DETROIT, Jan. 6, 2002 – Ford Motor Company today introduces a clever adaptation of existing hydraulic technology designed to improve fuel economy in large trucks in city driving by an estimated 25 to 35 percent.
The new Hydraulic Launch Assist (HLA) system is showcased on the Ford Mighty F-350 TONKA concept truck debuting at the 2002 North American International Auto Show.
"HLA is just one of the numerous technologies Ford is researching that is aimed at improving fuel economy and reducing emissions," says Richard Parry-Jones, group vice president, Global Product Development, and Chief Technical Officer, Ford Motor Company. "We believe this technology holds promise for making large trucks more fuel efficient and environmentally sound."
The Hydraulic Launch Assist system recovers energy normally lost during deceleration, stores it as hydraulic pressure, and then reuses it during acceleration.
Ford's HLA system is mounted downstream of the conventional powertrain on the Mighty F-350 TONKA.
It consists of two major components: a reversible hydraulic motor/pump coupled to the drive shaft through a clutch system and an energy storage module containing two large accumulators filled with hydraulic fluid and nitrogen gas.
During deceleration – when the driver is applying the brakes – the pump/motor, powered by the vehicle's kinetic energy, forces hydraulic fluid out of the low-pressure accumulator and into the high-pressure accumulator, compressing the nitrogen gas and storing energy. The pressure is significant – up to 5,000 psi.
During acceleration, the flow of hydraulic fluid is reversed, forced by the pressure in the accumulator. The HLA system is switched from pump mode to motor mode, and torque is applied to the driveshaft through the clutch. For approximately 10 to 15 seconds, normal acceleration is handled by the HLA system, allowing the vehicle's primary engine to idle.
Up to 80 percent of the initial kinetic energy is returned to the vehicle as hydraulic fluid flows from the high- to the low-pressure accumulator.
If quicker acceleration is required, HLA works in tandem with the primary engine, which is the Power Stroke® Super-600 concept diesel engine in the Mighty F-350 TONKA. The system is most effective during initial acceleration, when the engine works the hardest. In addition to significantly increasing city-driving fuel economy, HLA virtually eliminates turbo lag during launch in vehicles equipped with turbo-diesel engines.
Early research indicates that application of HLA could be ideal for larger vehicles such as commercial trucks, delivery vans, buses and work trucks. Heavier vehicles employ more energy in stop-and-go traffic, creating greater opportunities to capture and reuse energy.
Using hydraulic pressure to drive a vehicle is a key aspect of the innovative hydraulic hybrid research project being conducted jointly by Ford Motor Company, Eaton Corporation and the Environmental Protection Agency (EPA). In future, optimized hydraulic hybrid applications, highly efficient internal combustion engines would produce hydraulic pressure to drive the vehicle. The system also would capture this energy during vehicle deceleration.