Hybrid Vehicle Double-Step Gear Shift Torque Hole Elimination
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Solution Overview
Problem
Hybrid electric vehicles with powershift transmissions experience brief, sharp power reductions known as 'torque holes' during double-step gear shifts, which are perceived as harsh shifting by vehicle occupants.
Innovation Solution
The control method utilizes the ERAD motor to provide torque during double-step shifts, allowing the shift to be completed with a single clutch, thereby eliminating torque holes and enhancing the gear shift process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a powershift transmission performs double-step gear shifts between gears on the same layshaft, then gear ratio changes are achieved, but brief sharp reductions in power (torque holes) occur at the transmission input
Solution Approach 1:
The ERAD motor acts as an intermediary device to fill the torque hole during double-step gear shifts. When a gear shift is detected, the control system commands the ERAD motor to provide compensating torque to the transmission input, offsetting the power reduction that occurs during the shift event. This mediator approach eliminates the perceived harshness while maintaining the speed benefit of direct shifts.
Solution Approach 2:
The system dynamically changes the torque output parameter of the ERAD motor in response to gear shift events. The control module monitors transmission gear position and ERAD torque, adjusting the ERAD motor's torque contribution to compensate for the transient power loss during shifts. This parameter adjustment ensures continuous power delivery despite the mechanical shift process.
2Productivity
If conventional clutch-to-clutch shifting is used in double-step shifts, then gear changes are achieved, but the shifting process is perceived as harsh by vehicle occupants
Solution Approach 1:
The ERAD motor serves as a mediator that smooths the torque delivery during clutch-to-clutch shifts. By providing additional torque during the shift event, the ERAD motor compensates for the temporary disconnection of power flow, eliminating the harsh perception while maintaining the efficiency of direct clutch-to-clutch shifting without requiring intermediate gears.
3Productivity
If input clutches and synchronizers are used frequently in heavy driver demand conditions, then gear shifts are achieved, but their durability is reduced
Solution Approach 1:
The ERAD motor acts as a torque intermediary that reduces the workload on input clutches and synchronizers during heavy demand conditions. By providing torque support during shift events, the ERAD motor allows these components to operate under less stress, extending their service life while maintaining rapid shift responsiveness when needed.
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 significantly reduces torque holes, improves shift responsiveness, and increases clutch and synchronizer durability by reducing their usage during heavy driver demand conditions, enabling faster change-of-mind shifts and maintaining positive torque throughout the process.
Implementation Method 1
The ERAD motor to provide torque during a double step shift
Data Source
AI summary
In a powertrain for a vehicle that includes an engine, a transmission having an input, a current gear, an input clutch, a target gear and an output for driving a load, and an electric machine for driving the load, a method for performing a gearshift from the current gear to the target gear comprising the steps of opening the input clutch, releasing a drive connection between the current gear and the output, producing a drive connection between the target gear and the output, using the electric machine to produce torque at the load, closing the input clutch; and reducing the torque produced by the electric machine.