Electrohydraulic Axle Drive for Independent Torque Distribution
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Solution Overview
Problem
Commercial vehicles require space and weight-saving drive solutions that enable flexible drive torque control and are not dependent on internal combustion engines, as existing electric motor designs are cumbersome and inefficient for steerable axles.
Innovation Solution
An electro-hydraulic drive device with a purely electrically drivable axle and an electro-hydraulically drivable axle, featuring an integrated electro-hydraulic drive unit where electric and hydraulic machines are fluidically coupled, allowing independent and variable drive torque distribution without direct mechanical connection to the axles, powered solely by electrical energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a powerful electric motor is installed on each wheel hub to enable flexible drive control, then drive torque distribution flexibility is improved, but vehicle weight and space requirements worsen
Solution Approach 1:
The drive system is segmented into multiple independent drive units, each comprising an electric machine and a hydraulic machine. This segmentation allows flexible torque distribution to different axles and wheels while sharing hydraulic infrastructure, reducing overall system weight compared to fully independent electric motors at each wheel.
Solution Approach 2:
The hydraulic machines serve multiple functions: they can operate as hydraulic motors to drive wheels, as hydraulic pumps to generate hydraulic fluid flow, and as energy storage devices by storing potential energy in pressurized hydraulic fluid. This multi-functionality eliminates the need for separate components, reducing vehicle weight and space requirements.
2Productivity
If electric machines are directly connected to axles for drive transmission, then mechanical efficiency is improved, but adaptability to different driving situations worsens
Solution Approach 1:
Hydraulic fluid serves as an intermediary medium between the electric machines and the wheels. The electric machines drive hydraulic pumps that pressurize the fluid, which then acts as an energy carrier to hydraulic motors at the wheels. This intermediary allows flexible torque distribution and adaptive control while maintaining high overall efficiency through the hydrostatic transmission system.
Solution Approach 2:
The system dynamically adjusts torque distribution by controlling the operation mode of hydraulic machines (pump or motor) and regulating hydraulic fluid flow. This dynamic control enables rapid response to different driving situations such as wheel slippage, varying terrain, and steering requirements, while maintaining mechanical efficiency through optimized power transmission paths.
3Power
If internal combustion engines are used for propulsion, then power availability is improved, but environmental compatibility and energy efficiency worsen
Solution Approach 1:
The internal combustion engine is replaced with an electric-hydraulic drive system. Electric machines convert electrical energy to mechanical energy with high efficiency, and hydraulic transmission provides flexible power distribution. This substitution eliminates combustion losses, reduces energy waste, and improves overall energy efficiency while maintaining power availability through electric motors and hydraulic amplification.
Solution Approach 2:
The system changes the energy conversion parameters from chemical energy (combustion) to electrical energy conversion. Electric machines offer higher conversion efficiency and controllable operating points, allowing the system to operate in optimal efficiency ranges across varying load conditions, thereby reducing energy losses while maintaining required power levels.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution provides a compact, flexible, and powerful drive system that improves driving stability and responsiveness to different driving situations by enabling independent torque control on multiple axles, reducing the need for internal combustion engines and simplifying installation and maintenance.
Implementation Method 1
The first hydraulic machine is also in fluid communication with at least one hydraulic machine arranged on the electro-hydraulically driven axle for power transmission. This can be achieved, for example, by means of fluids (e.g., mineral oil) conveyed in hydraulic lines and/or other liquid pressure media known to those skilled in the art for hydrostatic power transmission
Data Source
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AI summary
The invention relates to an electro-hydraulic drive device (10) for a motor vehicle (20), preferably a commercial vehicle, comprising a purely electrically driven axle (A1) on which at least one electric machine (1a) is arranged, and an electro-hydraulically driven axle (A2) on which at least one hydraulic machine (2a) is arranged. Furthermore, the electro-hydraulic drive device (10) has a first electro-hydraulic drive unit (31) comprising a first electric machine (3e1) and a first hydraulic machine (3h1). The first hydraulic machine (3h1) is in drive communication with the first electric machine (3e1) for power transmission and in fluid communication with at least one hydraulic machine arranged on the electro-hydraulically driven axle (A2) for power transmission.This advantageously enables independent and variable provision of drive torques to the two axles (A1, A2), allowing for flexible responses to different driving situations. Furthermore, the invention also relates to a motor vehicle (20), preferably a commercial vehicle, with such an electro-hydraulic drive device (10).