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Marginal Column

The functionality
at a glance

  • Enables self-actuating diesel engine switch-off during stand-still phases
  • Self-actuating restart of the diesel engine with previously stored hydraulic energy when a drive or operating function is called up
  • Required torque is available in an instant
  • Straightforward implementation as part of the Hydraulic Fly Wheel
  • Also possible as a “stand alone” solution

Hybrid drive relieves the combustion engine

Off-highway machines do not only drive, but they mainly execute hard working tasks. They must have enough power to effectively dig, lift, or carry. Only if no energy is required for the machine’s driving and working functions can the internal combustion engine be turned off – providing there is a sufficient power reserve for a hydraulic start.

For example, wheel loaders in the performance class of up to six tons spend 30 percent of their service life at idle. Drivers frequently leave the cab for short periods to perform other additional duties, often leaving the engine running. Over the course of a year, this easily adds up to 250 to 300 operating hours at idle. The Rexroth Hydraulic Start-Stop switches the combustion engine off during such phases. If for instance, a wheel loader comes to a standstill and no longer performs any work, the engine is automatically switched off after just a few seconds. The engine is restarted as soon as the driver moves the steering unit, the joystick or the accelerator pedal.

What is innovative about the system is that the A10VO working hydraulics pump, which moves the hitch gear and empties the machine's bucket, also charges an accumulator at the same time. This accumulator feeds back the energy needed to restart the diesel engine. In addition, a Rexroth BODAS control unit, a valve block and an accumulator are needed, forming a neat package that only needs limited space in a compact wheel loader. The core component, a swivel-mounted A10VO, charges the accumulator with pressure during operation. When the diesel engine is to be restarted from stop mode, the accumulator is discharged by the swiveled pump acting as a motor to generate the necessary torque to start the engine. The start process is much shorter than one with an electric starter motor, making the machine ready for work immediately.

Just a few additions give the start-stop function other possibilities for saving fuel and extended functions, for example engine braking in deceleration mode and a boost function for power bottlenecks during operation.

Hydraulic Fly Wheel HFW