Compound Transmission Shift Control for Smooth Tractive Force
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Solution Overview
Problem
Dual clutch transmissions experience interruptions in tractive force during gear shifting, leading to discomfort and increased friction losses, which shorten the lifespan and cause noise, while existing solutions require complex calibration and result in slow gear changes.
Innovation Solution
A method for shifting a composite transmission that controls the output torque of the hydraulic motor and the maximum transferable torque of the clutches to maintain a consistent tractive force, using a control algorithm that adjusts the slip between the hydraulic motor and the primary part of the dual clutch transmission to avoid fluctuations in tractive force during gear changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional dual clutch transmission shifting is used, then gear changes can be implemented, but interruptions in tractive force occur causing discomfort and friction losses
Solution Approach 1:
The control algorithm prepares the clutches for engagement before the actual gear shift occurs by pre-positioning them in the optimal state. This preliminary preparation ensures that when the gear change happens, there is minimal interruption in tractive force transmission, thereby reducing friction losses and improving driving comfort without requiring highly dynamic actuators
2Productivity
If existing gear change control methods are used, then gear shifting can be performed, but complex calibration is required and gear changes are slow
Solution Approach 1:
The control algorithm autonomously determines the optimal gear shift timing and clutch engagement parameters based on real-time operating conditions without requiring complex external calibration. The system self-adjusts to achieve quick gear changes by calculating the precise moment when clutch engagement should occur, eliminating the need for complicated calibration procedures while maintaining fast shifting performance
3Productivity
If clutch engagement is accelerated to reduce gear change time, then productivity improves, but friction losses and wear increase
Solution Approach 1:
The control algorithm maintains continuous tractive force transmission during the gear shift process by carefully coordinating clutch disengagement and engagement timing. This continuous action approach allows for faster gear changes without creating abrupt torque interruptions that would increase friction and wear, thereby improving gear change time while preserving clutch lifespan and reliability
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 method achieves smooth and quick gear changes with minimal tractive force fluctuations, reducing the first torque drop to zero and significantly reducing the second torque drop, resulting in improved driving comfort and reduced friction losses, without requiring highly dynamic actuators.
Implementation Method 1
a hydrostatic transmission comprising a hydraulic pump with adjustable displacement and a hydraulic motor arranged with the hydraulic pump in a closed hydraulic circuit
Implementation Method 2
the primary side and secondary side of the other clutch are frictionally coupled to one another
Data Source
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AI summary
The invention relates to a method for shifting a combined transmission that enables a vehicle to be driven in multiple driving ranges. This method combines a mechanical powershift transmission with two clutches and two gear stages with a hydrostatic transmission comprising a hydraulic pump with variable displacement and a hydraulic motor. The motor is arranged in a closed hydraulic circuit with the hydraulic pump and its drive shaft is connected to the primary side of the clutches. When switching from one driving range to another, the primary and secondary sides of one clutch are disengaged, and the primary and secondary sides of the other clutch are positively engaged. The combined transmission is controlled according to a control algorithm stored in an electronic control unit.In order to improve the driving behavior during gear changes with such a drive system, the output torque of the hydraulic motor and the maximum torque that can be transmitted by the clutches are controlled by the control algorithm in such a way that fluctuations in traction force are largely avoided when switching from one driving range to another.