Hybrid CVT Virtual Gear Shift Control
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Solution Overview
Problem
In hybrid vehicles with electronic continuously variable transmissions, manual shift modes lack proportional engine speed changes with vehicle speed when the engine is OFF, leading to inconsistent virtual gear shifts due to engine noise and speed changes being tied to driver-demanded torque and battery state of charge.
Innovation Solution
A powertrain system with a controller that starts the engine regardless of driver-demand torque and operates the electric machine to shift the transmission to a predetermined virtual discrete speed ratio, ensuring consistent virtual gear shifts by using vehicle speed to select the initial gear and engine speed when the engine is OFF.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the engine is started only when driver-demanded torque is high or battery state of charge is low, then energy consumption is reduced, but virtual gear shifts become inconsistent and lack sensory feedback
Solution Approach 1:
The patent segments the gear shifting process into two independent parts: (1) engine starting decision based on gear shift request alone, and (2) torque management separated into driver-demand torque and counter-torque components. This allows the engine to start consistently for sensory feedback while using counter-torque management to control actual vehicle acceleration.
Solution Approach 2:
The patent changes the control parameter for engine starting from a composite decision (torque + battery state) to a simple gear shift request trigger. Additionally, it introduces counter-torque as a separate controllable parameter to manage vehicle acceleration independently, allowing consistent engine engagement for sensory feedback while maintaining energy efficiency.
2Loss of energy
If the engine speed changes are tied to driver-demanded torque, then energy efficiency is improved, but the driver experiences inconsistent sensory feedback during virtual gear shifts
Solution Approach 1:
The patent segments torque into two independent components: driver-demand torque (from accelerator pedal) and counter-torque (applied by the electric machine). This segmentation allows the engine speed to change consistently during virtual gear shifts while using counter-torque to prevent excessive vehicle acceleration, maintaining both energy efficiency and sensory feedback consistency.
Solution Approach 2:
The electric machine acts as an intermediary that applies counter-torque to offset the torque from engine deceleration during virtual upshifts. This mediator allows the engine speed to change proportionally with vehicle speed (providing consistent sensory feedback) while preventing the vehicle from accelerating too quickly, thus maintaining energy efficiency.
3Use of energy by moving object
If the engine is kept OFF during electric vehicle operation, then energy consumption is reduced, but manual shift mode lacks proportional engine speed changes with vehicle speed
Solution Approach 1:
The patent implements preliminary action by starting the engine in advance when a manual gear shift request is detected, before any torque demand occurs. This ensures the engine is ready to provide proportional speed changes for sensory feedback while the vehicle operates in electric mode, and the engine is stopped again after the shift sequence completes.
Solution Approach 2:
The patent implements periodic action by temporarily engaging the engine only during the brief period of manual gear shift transitions, rather than keeping it running continuously. The engine starts for the shift, provides proportional speed changes for sensory feedback, then stops again, allowing energy-efficient electric operation between shifts.
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 solution provides consistent and lively virtual shifts by ensuring engine speed changes are proportional to vehicle speed, enhancing the driver's sensory experience and improving manual shift mode operation in hybrid vehicles.
Implementation Method 1
an electric machine configured to actuate the gearing arrangement to change a speed ratio between the input and output shafts
Implementation Method 2
command starting of the engine regardless of a driver-demand torque
Data Source
AI summary
A vehicle includes an engine, a continuously variable transmission including an input shaft coupled to the engine, an output shaft, an electric machine, and a gearing arrangement. The electric machine is configured to actuate the gearing arrangement to change a speed ratio between the input and output shafts. A controller is programmed to, responsive to a request to manually shift the transmission to one of a predetermined number of virtual discrete speed ratios and the engine being OFF, command starting of the engine regardless of a driver-demand torque and operate the electric machine to shift the transmission to the one of the speed ratios.