Hydraulic Shift Rod Layout for Stable Gear Positioning
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Solution Overview
Problem
Existing vehicle transmission systems face challenges in achieving reliable and precise gear shifting due to imprecise hydraulic pressure conditions, leading to undesired axial movements and mispositioning of shift rods, which affect shift quality.
Innovation Solution
A shifting device with shared pressure chambers and a common valve unit, incorporating a check valve and air ducts, ensures stable pressure conditions and prevents accidental mispositioning of shift rods by using a common tank line and check valve, and efficiently removes air from hydraulic chambers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate valve units are used for each return line, then each pressure chamber can be controlled independently, but manufacturing tolerances cause different check pressures leading to shift rod mispositioning
Solution Approach 1:
The patent combines two separate valve units into a single common valve unit that serves both return lines. This merging eliminates the problem of manufacturing tolerances between separate valve units causing different check pressures, while still providing independent control of each pressure chamber through the shared valve unit's design
2Reliability
If larger movement play is dimensioned for shift rod, then mispositioning can be compensated, but shift quality and precision deteriorate
Solution Approach 1:
The patent changes the pressure parameters in the hydraulic system by implementing a common tank line with a common valve unit that maintains equal check pressures in both pressure chambers. This parameter change stabilizes the shift rod position without requiring increased movement play, thereby preserving shift quality while improving position stability
3Reliability
If common tank line with common valve unit is used, then pressure conditions are stabilized and mispositioning prevented, but device complexity increases
Solution Approach 1:
The common valve unit performs multiple functions: it controls both return lines, maintains equal check pressures in both pressure chambers, and prevents mispositioning of the shift rod. This multi-functionality achieves pressure stabilization without proportionally increasing device complexity
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 provides stable pressure conditions and prevents mispositioning of shift rods, ensuring high-quality gearshift behavior and comfortable driving by maintaining precise shift rod positions even under pressure fluctuations.
Implementation Method 1
both rod-free ends of the shift rod can be hydraulically acted upon... hydraulic pressure to both rod ends... hydraulic medium (e.g. oil) to enter the pressure chambers in order to be able to apply hydraulic pressure
Implementation Method 2
The valve unit is designed as a check valve, which can prevent an undesired outflow of the hydraulic medium from the pressure chambers
Data Source
Figure 1
Figure 2~3
AI summary
The invention relates to a shifting device (40) for shifting gears of a vehicle transmission (30). The shifting device (40) contains at least one shift rod (42) which is translationally movable along a shifting direction (48), the two rod free ends (44) of which are each mounted in a pressure chamber (46) for hydraulic medium and can be hydraulically actuated. The shifting device (40) has a pressure connection (50) and a hydraulic pressure line (52) connected thereto at each pressure chamber (46). Furthermore, a tank connection (54) and a hydraulic return line (56) connected thereto are arranged at each pressure chamber (46). The two return lines (56) open into a common tank line (58) for connection to a hydraulic tank. The invention further relates to a towing vehicle (10) having such a shifting device (40).