HYdraulic HYbrid for Extended Electrical Range

Electromobility is continually advancing into new areas of vehicle construction. After e-bikes, Scooters, cars and city buses, it is now commercial vehicles that are increasingly shifting into the focus of research. This vehicle class is especially well-suited for approaches from the field of electromobility that could help to generate a number of essential new vehicle functions for the benefit of operators and citizens alike. At the moment, fully electric commercial vehicles are not feasible because the storage technologies available today cannot match their high energy demand. With the help of hybrid approaches, however, the switch to fully electric vehicles can be initiated.

The term HY²PE²R stands for HYdraulic HYbrid for Extended Electrical Range and describes an enhanced serial hybrid drive for the operation of hydraulic implements consisting of

• electric motor for traction (electric machine 2),
• battery,
• combustion engine coupled with a generator (electric machine 1),
• hydraulic power extraction.

The system’s structure allows a multitude of new operating modes that provide great benefits.

Fully Electric Driving

The energy stored in HY²PE²R’s battery enables fully electric, emission-free operation. This operating mode is very quiet, which is especially desirable for applications such as snow ploughing in the early morning or late at night. Because the traction motor (electric machine 2) also works as a generator, braking energy can be restored to the battery, which reduces brake wear and increases the vehicles’ electric range.

Hydraulic Operation

By opening the clutch that connects the combustion engine and the transmission, electric machine 1 is able to drive the hydraulic pump at very low speed and in a needs-based way. This operating mode saves up to 80 % of energy when used together with a hydraulic lift on the vehicle, and it is especially silent.

Electric Implements

Hydraulic implements are the technological state of the art for commercial vehicles. Until very recently, hydraulic systems were unrivaled in terms of installation space and performance, but they are increasingly being challenged by fully electric approaches. Especially regarding efficiency, electric systems are far superior to hydraulic ones: they can be connected to the 400 V DC intermediate circuit, do not need hydraulic pipes and can be controlled highly dynamically. Because of these advantages, electric systems are the future of implement drives for commercial vehicles.

Conventional Hydraulic Systems

Until the realization of fully electric implements, it is necessary to execute a large number of processes with conventional hydraulic support. For these cases, the drive train can be operated conventionally. The clutch that connects the combustion engine and the transmission is closed and the hydraulic pump is driven directly by the combustion engine.

Combustion engines in conventional commercial vehicles are usually dimensioned for work demanding the engine’s maximum performance. These maximum operating points, however, occur very rarely in day-to-day operation. With the hybrid approach, the combustion engine can be kept at smaller dimensions because additional power is provided be the electric segment of the drive train. This helps save weight and installation space, and it also reduces the combustion engine’s dynamic load, which in turn lowers emissions significantly.

• Concepts for hybrid-driven commercial vehicles with hydraulic implements
• System structure with a multitude of operating modes, e.g., fully electric driving for noise reduction, hydraulic operation for energy savings, and operation of electric implements for highly dynamic control
• Transition concepts for conventional drive trains with the aim of realizing fully electric implements