Hydrostatic Traction Drive Automatic Slip Switching
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Solution Overview
Problem
Existing hydrostatic travel drives for vehicles, particularly agricultural tractors, face challenges in seamlessly switching between two-wheel and four-wheel drive modes, relying on driver experience and potentially leading to operational safety issues due to arbitrary interventions.
Innovation Solution
A hydrostatic travel drive system with a variable displacement pump supplying hydraulic motors connected in series, featuring a valve device that limits pressure medium flow to the low-pressure side, allowing automatic switching based on permitted slip, ensuring the downstream hydraulic motor is only activated when necessary, thereby enhancing operational safety and minimizing pressure medium losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a switching valve is used to manually switch between two-wheel and four-wheel drive, then the drive mode can be changed, but the switching becomes arbitrary and depends on driver experience, reducing operational safety
Solution Approach 1:
The system automatically detects wheel slip and switches between two-wheel and four-wheel drive modes without driver intervention. The control unit monitors the hydraulic motors and activates the downstream motor when slip is detected, making the system self-regulating and eliminating arbitrary manual switching.
Solution Approach 2:
The system uses feedback from wheel slip detection to automatically control the switching between drive modes. The control unit receives information about motor performance and wheel slip, then automatically activates the bypass line or downstream motor based on the detected conditions, creating a closed-loop control system that improves reliability.
2Productivity
If the downstream hydraulic motor is kept idle in two-wheel drive mode, then pressure medium can flow freely, but this may lead to unnecessary pressure medium losses
Solution Approach 1:
The system dynamically adjusts the flow path based on operating conditions. In two-wheel drive mode, the bypass line is closed to prevent pressure medium losses. When wheel slip is detected, the system automatically opens the bypass line to engage the downstream motor, creating a dynamic adaptation to actual traction needs.
3Extent of automation
If the valve device limits pressure medium flow to a predetermined amount, then automatic switching can be achieved, but the system complexity increases
Solution Approach 1:
The system uses hydraulic pressure itself to control the switching mechanism. The quantity-limiting valve and bypass valve work together with the hydraulic pressure medium to automatically engage or disengage the downstream motor based on pressure buildup from wheel slip, using the existing hydraulic system to achieve automation without adding complex external control mechanisms.
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 system enables safe and automatic switching between two-wheel and four-wheel drive modes without driver error, ensuring the downstream hydraulic motor is only engaged when required, improving operational safety and reducing pressure medium losses.
Implementation Method 1
the valve device is designed in such a way that it limits the flow of pressure medium to the low-pressure side to a predetermined amount. This amount corresponds to a permitted slip on the upstream hydraulic motor. If this permitted slip is exceeded, pressure builds up in the pressure medium flow path between the two hydraulic motors
Data Source
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AI summary
The drive (1) has a variable flow pump (26) connected with two downstream hydraulic motors (10, 12, 14, 16) in series manner, where pressure is supplied through the flow pump. A valve device (56) is provided in a pressure flow path (62) between the hydraulic motors, where the pressure flow is guided by bypassing the hydraulic motors to a low pressure side or to a tank (T) through the valve device. The valve device limits a flow rate of the pressure to a maximum value corresponding to allowed slippage of the hydraulic motors.