Selectable Vehicle Creep Using Engine Disconnect at Low Speed
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Solution Overview
Problem
Vehicles without torque converters do not exhibit natural creep, requiring drivers to adapt their driving style to the powertrain configuration, and there is a need for a system to control low-speed maneuvers effectively.
Innovation Solution
A control system that enables or inhibits vehicle creep by disconnecting the engine from the wheels based on driver input, using a combination of engine and electric machine torque management across various powertrain modes, including parallel and series hybrid electric vehicle modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If vehicle creep is enabled in vehicles without torque converters, then low-speed maneuverability is improved, but driver control complexity increases
Solution Approach 1:
The patent introduces a control system as an intermediary that manages the interaction between the engine, electric machine, and transmission to enable selectable creep functionality. This mediator coordinates torque delivery from multiple sources to achieve creep behavior in powertrains that would naturally lack it, while maintaining driver control through systematic management of the complex interactions.
Solution Approach 2:
The control system is designed to provide multiple functions: it enables creep when selected, provides conventional driver control when creep is disabled, and adapts to different powertrain configurations (hybrid and non-hybrid). This multi-functionality allows a single system to address various operating modes and vehicle types, managing complexity through versatile design rather than separate systems.
2Loss of energy
If engine is disconnected to inhibit vehicle creep, then energy efficiency is improved, but torque availability for acceleration decreases
Solution Approach 1:
The patent combines the torque capabilities of the engine and electric machine to provide seamless power delivery. When the engine is disconnected to improve efficiency, the electric machine compensates for torque availability, and vice versa. This merging of torque sources ensures that energy efficiency gains from engine disconnection do not result in torque deficits, as the electric machine fills the gap.
Solution Approach 2:
The control system dynamically changes operating parameters (torque requests, connection states) based on driver demand and vehicle conditions. When creep inhibition is selected, the system changes the engine connection parameter to disconnected state, and simultaneously adjusts electric machine torque parameters to maintain overall torque availability when needed, thus managing the trade-off between efficiency and power.
3Adaptability or versatility
If selectable creep control is implemented, then adaptability to different driving styles is improved, but system complexity increases
Solution Approach 1:
The system implements dynamic adaptability by allowing drivers to select between creep-enabled and creep-disabled modes, with the control system continuously adjusting torque delivery and component engagement based on the selected mode and current driving conditions. This dynamic behavior provides adaptability to different driving styles while managing complexity through a unified control architecture that handles both modes.
Data Source
AI summary
A control system (208) for enabling deactivation of vehicle creep in a vehicle (10) with an engine (202), the control system (208) comprising one or more controllers (300), wherein the control system (208) is configured to: enable vehicle creep (402) so that wheel drive torque can reach a first value greater than zero without a driver load request and without a brake request, wherein enabling vehicle creep comprises the engine (202) being active while connected to a vehicle wheel (FL, FR); monitor for a vehicle creep deactivation signal (404); and in response to the vehicle creep deactivation signal (404), inhibit vehicle creep (412) so that wheel drive torque cannot reach the first value without a driver load request, and wherein inhibiting vehicle creep comprises causing disconnection (414) of the engine (202), at least in part, from the vehicle wheel (FL, FR).