Hybrid Vehicle Driveline Torque Control During Regenerative Braking Shifts
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Solution Overview
Problem
Hybrid vehicles with driveline disconnect clutches experience driveline torque disturbances during regenerative braking, leading to abrupt changes in transmission output torque, which can result in noticeable 'torque holes' and reduced vehicle drivability.
Innovation Solution
Adjusting the torque output of the electric machine during the torque transfer and inertia phases of transmission shifting from a higher gear to a lower gear, by reducing the negative torque applied during regenerative braking, allowing for a smoother transition of transmission output torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the electric machine maintains constant negative torque during regenerative braking, then regenerative braking efficiency is improved, but driveline torque disturbances increase during transmission shifting
Solution Approach 1:
The electric machine torque is made dynamic rather than constant. The control system adjusts the negative torque output in real-time based on the transmission shift phase, reducing torque during the torque transfer phase and inertia phase to minimize driveline disturbances while maintaining regenerative braking functionality during other phases
Solution Approach 2:
The torque parameter of the electric machine is changed during operation. By modifying the torque output level based on transmission shift conditions, the system resolves the contradiction between maintaining efficient regenerative braking and preventing driveline torque disturbances during shifting
2Speed
If transmission clutches are applied and released simultaneously during shifting, then shifting speed is improved, but transmission output torque decreases abruptly causing torque holes
Solution Approach 1:
The electric machine torque is reduced in advance during the torque transfer phase before the clutch completion, counteracting the impending torque hole that would result from simultaneous clutch application and release. This preliminary adjustment prevents the abrupt torque decrease that causes drivability issues
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 approach reduces driveline torque disturbances and torque holes, enhancing vehicle drivability by gradually transitioning the transmission output torque, rather than abruptly decreasing it, thereby improving the shifting process during regenerative braking.
Implementation Method 1
the vehicle's kinetic energy may be converted into electrical energy that is stored in an electric energy storage device
Implementation Method 2
The electric machine may also provide vehicle braking when the vehicle's kinetic energy is regenerated into electric energy via producing and applying a negative torque to the hybrid vehicle's driveline
Data Source
AI summary
Systems and methods for improving transmission shifting of a hybrid vehicle are presented. In one example, output torque of an electric machine is adjusted in response to a downshift of a fixed step ratio transmission during regenerative braking. The output torque of the electric machine may be adjusted in response to a phase of the transmission shift.