Hydrostatic Drive Pressure Control for Efficiency
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Solution Overview
Problem
Hydrostatic propulsion drives experience reduced efficiency in part-load operations due to low operating pressure leading to increased friction and leakage, which affects transmission ratios and driver comfort.
Innovation Solution
The swept volumes of the hydraulic pump and motor are adjusted using a correction factor based on rotational speed and drive torque, increasing operating pressure to minimize friction and leakage, while maintaining driver-set diesel engine speed, using electronic control units and characteristic diagrams to optimize pivot angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the operating pressure is increased to reduce friction and leakage, then the degree of efficiency improves, but the flow-induced pressure drops increase
Solution Approach 1:
The patent changes the operating pressure parameter dynamically based on load conditions. In part-load operation, the control unit increases the operating pressure above the normally prevailing pressure to compensate for increased friction losses, while in full-load operation, the normal pressure is maintained. This parameter change resolves the contradiction by adapting pressure to operational conditions.
2Loss of energy
If the swept volumes of hydraulic pump and motor are adjusted to optimize efficiency, then the degree of efficiency improves, but the transmission ratio control complexity increases
Solution Approach 1:
The control unit continuously monitors the load condition of the hydraulic motor and uses this feedback to automatically adjust the swept volumes of the hydraulic pump and motor. The control unit receives signals about the actual load and dynamically modifies the pivot angles accordingly, implementing a closed-loop feedback system that optimizes efficiency without requiring complex manual intervention.
Solution Approach 2:
The control unit is pre-programmed with characteristic diagrams that define the optimal swept volume adjustments for various load conditions. These preliminary settings allow the system to automatically apply the correct correction factors without real-time optimization calculations, reducing control complexity while maintaining efficiency optimization.
3Loss of energy
If the pivot angles are manipulated in part load operation to increase pressure, then the degree of efficiency increases, but the transmission ratio precision may be affected
Solution Approach 1:
The patent applies different control strategies to different operating conditions. In part-load operation, the operating pressure is increased to improve efficiency, while in full-load operation, the normal pressure and standard transmission ratio control are maintained. This local differentiation ensures that transmission ratio precision is preserved under full-load conditions while efficiency is optimized under part-load conditions.
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 approach enhances efficiency in part-load operations by reducing friction and leakage, maintaining driver comfort, and optimizing transmission ratios without the need for real-time optimization during operation.
Implementation Method 1
a hydraulic pump (11) with an adjustable swept volume and a hydraulic motor (13) which likewise has an adjustable swept volume and is arranged with the hydraulic pump (11) in a preferably closed hydraulic circuit
Implementation Method 2
the operating pressure which prevails at the hydraulic motor (13) being increased if the correction factor is used
Data Source
AI summary
A hydrostatic propulsion drive for a vehicle is disclosed including an electronic control unit and a hydrostatic transmission having a hydraulic pump with an adjustable swept volume and a hydraulic motor with an adjustable swept volume, the hydraulic pump being arranged in a closed hydraulic circuit. The swept volumes of the hydraulic pump and the hydraulic motor are changeable in accordance with a correction factor which is stored in a characteristic diagram and is dependent on the rotational speed and the drive torque of the hydraulic motor, the operating pressure at the hydraulic motor being increased if the correction factor is used. Due to the increased operating pressure, flow-induced pressure drops are reduced by way of volumetric flows, and leakage flows via gaps between moving parts of the hydraulic pump and the hydraulic motor are kept large enough to avoid excessive friction and loss of efficiency.