Hydrostatic Travel Drive Pressure Relief Valve
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Solution Overview
Problem
Hydrostatic travel drives in vehicles, particularly agricultural utility vehicles, face challenges with pressure build-up between hydraulic motors during stationary steering, which counters the steering movement and requires operator intervention.
Innovation Solution
A hydrostatic travel drive with a valve device that connects the pressure medium flow path with higher pressure to a low-pressure region for pressure relief, preventing undesirable pressure build-up and allowing smooth steering movements without operator intervention, using a valve device with change-over valves and check valves to manage pressure medium flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If hydraulic motors are connected in series in a hydrostatic travel drive, then synchronous running of the motors is guaranteed, but pressure build-up occurs during stationary steering that counters the steering movement
Solution Approach 1:
A pressure equalization line with a check valve is introduced as an intermediary element between the two series-connected hydraulic motors. This mediator allows pressure to be equalized during stationary steering by enabling reverse flow when pressure difference exceeds a threshold, while maintaining the series connection for synchronous operation during normal driving.
Solution Approach 2:
The system changes the flow direction parameter of the pressure medium based on operating conditions. During stationary steering, the check valve allows reverse flow to equalize pressure; during normal operation, the check valve blocks reverse flow to maintain series connection and synchronous running. This dynamic parameter change resolves the contradiction between the two operating modes.
2Adaptability or versatility
If a switch valve is used to switch between two-wheel drive and four-wheel drive modes, then drive mode switching is possible, but the switching requires operator intervention and experience
Solution Approach 1:
The system uses itself to automatically switch between drive modes based on wheel slip detection. When wheel slip is detected, the control unit automatically activates the appropriate drive mode without requiring operator intervention. The system monitors its own operating conditions and self-adjusts the drive mode accordingly.
Solution Approach 2:
The system incorporates feedback from wheel slip detection to automatically control the switch valve. The control unit receives feedback about wheel rotation speeds and automatically switches between two-wheel and four-wheel drive modes based on this feedback, eliminating the need for operator judgment and intervention.
3Ease of operation
If hydraulic motors are connected in parallel, then flow quantities are balanced during cornering, but cavitations can occur due to different rotation speeds
Solution Approach 1:
The system dynamically switches between parallel and series connections based on operating conditions. During cornering, parallel connection is used for balanced flow distribution. During straight-line driving, series connection is used for synchronous operation. This dynamic reconfiguration prevents cavitation while maintaining cornering performance.
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
The solution enables effortless steering of mobile working devices with articulated steering, even when stationary, by reducing pressure build-up between hydraulic motors, enhancing driving safety and comfort by eliminating the need for operator intervention during mode switching.
Implementation Method 1
a valve device, via which the pressure medium flow path with the higher pressure can be connected for pressure relief to one of the working lines or a low pressure region
Implementation Method 2
a hydraulic pump which is in pressure medium connection via working lines with four hydraulic machines, in particular hydraulic motors
Data Source
AI summary
A hydrostatic travel drive includes a hydraulic pump that is arranged in a hydraulic circuit with two pairs of hydraulic motors. To prevent a pressure build-up between the hydraulic motors of a hydraulic motor pair on steering while stationary, a valve device is configured to set a pressure relief to a working line or to low pressure. A mobile device includes the hydrostatic travel drive.