Hydrostatic Travel Drive Shifting With Zero-Volume Torque Detection
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Solution Overview
Problem
Conventional transmission arrangements in travel drives face reliability issues during stage shifting due to the risk of residual torque after time-parameterized zero expulsion volume is reached, potentially leading to damage from frictional energy absorption by synchronizing rings.
Innovation Solution
A hydrostatic transmission arrangement with a second hydraulic machine having an adjustable expulsion volume and a detection unit, such as a proximity switch, to ensure zero or near-zero expulsion volume before shifting, preventing torque transmission and ensuring a reliable torque-free state for safe stage changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a time-parameterized procedure is used to reduce expulsion volume to zero before shifting, then the shifting process can be automated, but there is a risk that residual torque remains due to technical defects, potentially damaging the transmission
Solution Approach 1:
The patent implements a feedback mechanism by using a detection unit to monitor the actual expulsion volume of the hydraulic motor before shifting. The control device receives detection signals indicating whether the expulsion volume has reached zero and only permits shifting when the detection unit confirms the torque-free state, creating a closed-loop control system that eliminates the risks of time-parameterized procedures
Solution Approach 2:
The patent replaces the mechanical/time-based assumption of zero expulsion volume with an electronic detection system. Instead of relying on predetermined time delays and mechanical synchronization, the system uses electronic sensors to detect the actual state of the hydraulic motor and electronically controls the shifting permission, substituting mechanical reliability with electronic detection and control
2Strength
If the hydraulic motor maintains zero expulsion volume during synchronization, then the synchronizing ring can absorb frictional energy, but this requires additional time parameterization that risks residual torque
Solution Approach 1:
The detection unit provides real-time feedback on the expulsion volume state, allowing the control device to verify that the hydraulic motor has reached true zero volume before permitting the shift. This eliminates the need for time-parameterized waiting periods and ensures the synchronizing ring operates under confirmed torque-free conditions, protecting it from damage while avoiding residual torque risks
3Reliability
If a detection unit is added to verify zero expulsion volume, then shifting reliability is improved, but device complexity increases
Solution Approach 1:
The detection unit is integrated into the existing control device of the hydrostatic transmission, allowing the control device to perform both its original control functions and the new detection function. This multi-functionality approach avoids adding a completely separate detection system, thereby reducing the increase in device complexity while still achieving reliable verification of the torque-free state
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 enhances process reliability and durability by accurately detecting zero expulsion volume, preventing damage and minimizing interruptions in tractive force, thus reducing the occurrence of critical situations during shifting.
Implementation Method 1
This is the case when the second expulsion volume is zero or has only such a small value that the second hydraulic machine is dragged hydraulically and therefore no drag torque is present between the manual transmission and the second hydraulic machine
Data Source
AI summary
A transmission arrangement for a travel drive, in particular a mobile machine, includes a first hydraulic machine configured to be coupled to a drive machine, and a second hydraulic machine having an adjustable second expulsion volume, the second hydraulic machine configured to be connected fluidically to the first hydraulic machine via a first working line and a second working line of the transmission arrangement. The second hydraulic machine configured to be coupled or is coupled to a manual transmission of the transmission arrangement. The manual transmission has at least two transmission stages, and coupling of the second hydraulic machine to the manual transmission has the result that a torque can be transmitted. The transmission arrangement further includes a control apparatus configured to reduce to zero or to nearly zero the second expulsion volume at least during a changeover from one transmission stage to another transmission stage of the manual transmission.