Hydromechanical Transmission Smooth Range Switching
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Solution Overview
Problem
Hydromechanical transmissions experience speed jumps when switching between forward driving ranges, leading to inefficiencies and potential pressure jumps in the fluid line, which can cause damage.
Innovation Solution
A continuously variable hydromechanical transmission with a split transmission including an input connection, an output connection, and two compensation connections, where the clutch arrangement connects the hydrostatic transmission to either the input or output connection and one compensation connection, allowing for smooth ratio changes and independent adjustment of hydrostatic units to manage power flow and pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the hydrostatic transmission is swung out to maximum to increase spread, then the transmission ratio range is improved, but speed adjustment and pressure adjustment are required causing speed jumps when switching ranges
Solution Approach 1:
The control unit pre-adjusts the absorption volumes of the hydrostatic units before switching between driving ranges. By anticipating the range switch and preparing the hydrostatic units in advance, the system avoids sudden speed jumps and ensures smooth transitions while maintaining the expanded transmission ratio range.
Solution Approach 2:
The control unit continuously monitors the operating state of the hydrostatic transmission and dynamically adjusts the absorption volumes based on real-time feedback. This closed-loop control ensures that speed jumps are minimized during range switching while maintaining the full spread of the transmission ratio range.
2Adaptability or versatility
If the hydrostatic transmission is used to achieve continuously variable ratio, then the transmission flexibility is improved, but friction losses increase compared to mechanical transmissions
Solution Approach 1:
The system dynamically switches between hydrostatic and mechanical transmission modes based on operating conditions. The hydrostatic transmission provides continuously variable ratio when flexibility is needed, while the mechanical transmission handles high-load scenarios to minimize friction losses, optimizing the balance between adaptability and energy efficiency.
Solution Approach 2:
The control unit dynamically adjusts the absorption volumes of the hydrostatic units to optimize efficiency across different operating ranges. By changing the operational parameters of the hydrostatic transmission and switching to mechanical transmission when appropriate, the system minimizes friction losses while maintaining transmission flexibility.
3Adaptability or versatility
If multiple clutches are used to enable different driving ranges, then the transmission range spread is improved, but the complexity of switching operations increases
Solution Approach 1:
The control unit automatically manages the switching of multiple clutches based on real-time monitoring of transmission ratio requirements and operating conditions. This automated feedback control simplifies the complexity of multi-clutch switching operations by eliminating manual intervention and optimizing the switching sequence.
Solution Approach 2:
The system performs self-management of clutch switching through the control unit, which automatically determines when and how to engage or disengage clutches based on the desired transmission ratio and current operating state. This self-service approach reduces operational complexity while maintaining the full driving range spread.
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 configuration minimizes speed jumps and pressure jumps, enhancing the transmission's efficiency and reliability by allowing for seamless switching between driving ranges without overloading the fluid line, even at high speeds.
Implementation Method 1
a hydrostatic transmission which comprises a fluid circuit with two hydrostatic units (16, 22)
Implementation Method 2
A disadvantage of hydrostatic transmissions is that they have higher friction losses than mechanical transmissions
Data Source
Figure 1~2
Figure 3~7
Figure 8~11
AI summary
The hydro-mechanical transmission has a mechanical branched transmission (3), which has multiple terminals (1,7,10,14) for injecting or tapping torque. Three forward driving ranges are provided, where a coupling arrangement (17,23) of a hydrostatic transmission (30) connects with pair of the terminal of the branched transmission in each forward driving range. USE : Hydro-mechanical transmission for use in a drive train of an agricultural vehicle such as a tractor. ADVANTAGE : The hydro-mechanical transmission has three forward driving ranges, where a coupling arrangement of a hydrostatic transmission connects with pair of the terminal of the branched transmission in each forward driving range, and hence ensures compact and cost-effective hydro-mechanical transmission. DESCRIPTION OF DRAWINGS : The drawing shows a schematic view of a hydro-mechanical transmission. 1,7,10,14 : Terminals 3 : Mechanical branched transmission 17,23 : Coupling arrangement 30 : Hydrostatic transmission 35,36 : Fixed wheels.