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Parker Hannifin Introduces Heavy-Duty Hydraulic Hybrid System

Components of the RunWise hydraulic hybrid system.

Parker Hannifin Corp. has introduced a new hydraulic hybrid drive system targeted at heavy-duty vehicles that do a lot of stop-and-go driving such as public buses, delivery and waste trucks.

The company unveiled the RunWise hydraulic system on Thursday at the Waste Expo in Las Vegas in cooperation with refuse-hauling truck maker Autocar LLC.

The system consists of:

  • Two high-pressure hydraulic pump/motors. As pumps they use mechanical energy to deliver high-pressure oil. As motors they accept high-pressure oil and deliver mechanical energy to drive the vehicle.

  • Accumulators. These are the energy-storage devices for the high-pressure oil.

  • Oil cooler to maintain the proper operating temperature.

  • Power Drive Unit to multiply and transfer torque from the engine input and output shafts and the hydrostatic pump/motors.

  • Electronic controller to manage all Power Drive Unit functions. It controls the hydrostatic units, determines when to switch between hydrostatic to direct, maintains oil temperatures and monitors PDU function.

The combustion engine powers the hydraulic power drive unit, with power going to the primary pump and the oil cooler and lubrication pumps. The primary pump supplies the pressure to drive two hydrostatic motors.

These motors drive the output shaft through a simple two-speed gear reduction (Lo and Hi). The vehicle always starts in Lo, then shifts to Hi up to a speed of around 40 mph. At this speed, the Power Drive Unit switches to direct mechanical drive powered by the engine completely bypassing the hydrostatic system.

The Power Drive Unit recovers braking energy when in hydrostatic mode, with the motors becoming pumps that pump high-pressure oil into the accumulators. This stored energy is used the next time the vehicle starts rather than use power from the diesel engine.

Parker Hannifin competitor Eaton is also developing hydraulic hybrid drive systems for waste truck applications. (Earlier post.)

Autocar is showing the RunWise hybrid drive in a prototype E3 refuse truck, and will offer its first vehicle featuring the Parker system in North America in Fall 2007.


Bud Johns

It's about time people start harnessing energy from braking, instead of venting heat to the atmosphere.

roger Conner Jr

It is interesting that there is still very little discussion of applying this technology to passenger cars. A friend of mine and I who own Mercedes Diesel sedans that get 30 plus mile per gallon figure that with anywhere near the improvements claimed on trucks and buses, we would be getting 40 to 45 miles per gallon on a midsize comfy Mercedes Diesel sedan.....that caught our attention! :-) Bring it on!
(Taxi cabs would do even better with all around town driving!)

Rafael Seidl

The real question is, how much smaller can the prime mover be if you apply this hydraulic hybrid technology? How much fuel can you save?

Below 40 mph, this will operate as a series hybrid with intermediate storage. That's good fer emissions incl. noise but less so for fuel economy. Only at high speed does the system switch to parallel mode, but how often does a garbage truck run that fast?


there are many heavy duty work trucks that travel around going those high speeds for hours while moving from a work location back home. what about larger system for 18 wheelers? might seem weird, and possibly be of no gain, just wondering though, any ideas as to how much of an improvement this could/would(with a larger system) make for large 18wheelers? also midrange trucks, moving trucks, uhual, ryder, delivery trucks in rual areas, fedex, ect.


Try This On For Size, I Was One Of Manny People That Help Build This E3 Truck. When The First Truck Was Built It Had So Much Torq At The Rear Wheels , That We Had To Add 5 Tons Of Concrete Blocks On The Back Just To Keep The Frame From Twisting In Half. The Enginers Were Playing With The Truck In Back And Did A Burn Out With Diff-Lock On. Can You Emagine Having 8 Truck Tires Smoking Up A Lot With 5 Tons Of Concrete On The Back End Of It? Doing All That With The Engine At Idle, And Better Fuel Enonomy Then A Duramax In Your Home Pickup. This Truck ROCKS.


This is not new. I know of at least two successful projects that did this almost identical tast back in the 1970's. One got over 75mpg and the other doubled the mpg of the donor vehicle. Neither of the teams could get recognition for it back then, one team got dismissed outright without even looking at it. Hmmmm.


several years ago those "new" approaches were discovered analysed and because it was a "low cost fuel time" not accorded the value they have under the argument it was too expensive. I am glad to see that an evolution is comming. The economies are significative dpending on the degree of system optimization

ahmed elkordi

this is a very good idea.
i am a student in mechanical engineering and i want to apply this idea in my graduation project,so can i get a further informations about its hydraulic circuit and the assemble of this system?
thank you

T S McCrary

Driver behavior will effect fuel economy.I would have went in a differnt direction with a pure hydrostatic system. A pure hydraulic connection from engine to wheels.This is a proven concept used in costruction equipment from the early 1970's. By using variable displacement pump and motor setup. One could have an no shift overdrive transmission with maxumum low speed torque and high speed economy. Heat management is the only major drawback.usefull Links



John v

There was a time that "mud bog" races were running the tour with or the same as monster trucks. These buggys had big$$ big block blown engines. A guy showed up with one that had a hyd motor at each wheel and a stock 1600 cc VW engine to power the unit. He blew away the field then after that a rule was written that the wheels had to be mechaincly linked to the engine.

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