Getting a boost from hydraulics

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Under-vehicle view of Ford’s Hydraulic Power Assist system.

Ford, in partnership with Eaton Corp. and the Environmental Protection Agency, is developing a hydraulic technology that harnesses energy normally lost as heat during braking, and uses it to help propel a truck during acceleration.

The new system, Hydraulic Power Assist (HPA), consists of a hydraulic pump/motor, mounted axially in the driveline, and two accumulator/storage tanks; one for high-pressure fluid, and one for low.

When an HPA-equipped vehicle is braked, the pump/ motor becomes a driveshaft-powered pump, forcing low-pressure fluid into the high-pressure accumulator. Because this process absorbs energy, it slows the vehicle.

When it’s time to hit the go-pedal, a valve directs high-pressure fluid to the pump/motor, which goes into motor-mode, and adds energy to the driveshaft. This helps the vehicle accelerate more quickly, while increasing fuel economy by 30 to 35 percent in stop-go driving, and reducing exhaust emissions by at least 20 percent, says Ford.

In fact, an HPA-equipped F350 pickup truck reportedly made it up to a 30-percent grade at Ford’s Dearborn Proving Ground in 6.6 seconds, as opposed to 12.6 seconds for the same vehicle without HPA.

An added benefit of HPA, says Ford, is greatly reduced brake wear. Preliminary testing indicates that pad and lining wear should be reduced by more than 70 percent.

If you attended the North American International Auto Show last January, you might have seen Ford’s Mighty F350 Tonka concept truck, which was equipped with HPA. Next, Ford plans to test the technology on a pilot fleet of urban delivery vehicles with GVWs over 8,500 pounds – the duty cycle and weight range where Ford has determined that HPA will be the most energy- and cost-efficient means of regenerative braking.