Hydrostatic Transmission Gear Shifting Under Drag Torque Limits
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Solution Overview
Problem
Existing transmission arrangements with hydrostatic and mechanical manual transmissions face challenges in safely engaging new transmission stages due to high drag torque, which can hinder successful gear engagement, especially when the drag torque exceeds predetermined limits.
Innovation Solution
A method that involves regulating the expulsion volume of the second hydraulic machine to bring the drag torque within a predetermined range by adjusting the electrical actuation current, allowing for sequential steps of requesting a changeover, setting a setpoint value signal to zero, disengaging the first transmission stage, and engaging the second stage through synchronization, ensuring the expulsion volume reaches a value greater than zero to reduce drag torque and enable safe engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the expulsion volume of the hydraulic motor is reduced to zero for transmission stage changing, then the torque between the hydraulic motor and transmission input is lowered to zero, but the drag torque may still exceed predetermined limits and hinder safe gear engagement
Solution Approach 1:
The control method performs preliminary actions by first disengaging the first transmission stage before reducing the expulsion volume to zero and engaging the second transmission stage. This sequence ensures that the drag torque is minimized during the critical engagement phase, preventing engagement failure even when drag torque exceeds predetermined limits during the transition process.
Solution Approach 2:
The system dynamically adjusts the expulsion volume of the hydraulic motor during the transmission stage changing process. By continuously modulating the expulsion volume according to the specific phase of gear changing (disengagement, transition, engagement), the control method optimizes torque characteristics at each stage, ensuring safe engagement while maintaining system responsiveness.
2Reliability
If the expulsion volume is set to zero and held there during gear changing, then the torque is reduced for engagement, but the transmission stage changing process takes longer and productivity decreases
Solution Approach 1:
The control method employs periodic action by cycling the expulsion volume through specific phases: maintaining zero expulsion volume during the critical disengagement and engagement periods, then rapidly increasing it during the transition phase. This periodic modulation of expulsion volume ensures reliable engagement while minimizing the total time the system spends in low-productivity states.
Solution Approach 2:
The system performs preliminary disengagement of the first transmission stage before reducing expulsion volume to zero and engaging the second stage. This preliminary action separates the engagement process into distinct phases, allowing the expulsion volume to be optimized for each phase independently, thereby reducing overall changing time while ensuring successful engagement.
3Productivity
If the expulsion volume is gradually increased after engagement to reach desired amount, then the transmission returns to normal operation, but the drag torque during the transition may cause engagement failure
Solution Approach 1:
The control method performs the critical engagement operation (engaging the second transmission stage) before gradually increasing the expulsion volume from zero to the desired amount. This preliminary completion of engagement ensures that the gear is securely in place before torque is reapplied, preventing engagement failure during the torque increase phase.
Solution Approach 2:
The system dynamically controls the expulsion volume increase rate after engagement. By modulating the rate at which expulsion volume increases from zero to the desired amount, the control method ensures that drag torque remains within safe limits during the transition, preventing engagement failure while efficiently returning to normal operational torque levels.
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 method effectively reduces drag torque during shifting operations, allowing for successful engagement of transmission stages by maintaining the drag torque within allowed ranges, ensuring reliable and safe gear changes.
Implementation Method 1
a second hydraulic machine (14) having an adjustable expulsion volume, wherein the second hydraulic machine is fluidically connected to the first hydraulic machine (8) via a first working line (10) of the transmission arrangement (3) and a second working line (12) of the transmission arrangement (3)
Data Source
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AI summary
The present invention relates a method for changing over transmission stages (46, 48) of a transmission arrangement (3), the transmission arrangement (3) comprising: a first hydraulic machine (8) coupled to a drive machine (2), a second hydraulic machine (14) having an adjustable expulsion volume (VH), wherein the second hydraulic machine (14) is fluidically connected to the first hydraulic machine (8) via a first working line (10) of the transmission arrangement (3) and a second working line (12) of the transmission arrangement (3), wherein the second hydraulic machine (14) is coupled to a manual transmission (6) of the transmission arrangement (3) so that a torque can be transmitted, the manual transmission (6) having at least two transmission stages (46, 48). The method comprises the following sequential steps: requesting a changeover of an engaged transmission stage (46, 48) from a first transmission stage (46, 48) to a second transmission stage (46, 48); setting a setpoint value signal of the expulsion volume (VH) of the second hydraulic machine (14) to zero; disengaging the first transmission stage (46, 48); regulating the second hydraulic machine (14) so that expulsion volume (VH) of the second hydraulic machine (14) reaches a value greater than zero; engaging the second transmission stage (46, 48).