Start-Stop Device Wheel Torque Strategy
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Solution Overview
Problem
Current start-stop systems for motor vehicles lack a suitable strategy for automatic switch-off and switch-on operations while moving, particularly at low speeds, leading to inconsistent and inefficient energy transitions.
Innovation Solution
A start-stop device that utilizes wheel torque-based operating strategies to determine when to automatically switch off or on the drive machine, considering current and predicted torques such as crawl torque, vehicle tractive torque, downhill torque, and braking torque to ensure comfortable and energy-efficient transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If automatic switch-off is implemented when vehicle is at standstill, then fuel consumption is reduced, but driver comfort and operational reliability deteriorate due to inconsistent switching behavior
Solution Approach 1:
The patent introduces multiple parameter thresholds (speed threshold of 3 km/h, brake pedal position thresholds, accelerator pedal position thresholds) to dynamically determine switch-off and switch-on conditions. This multi-parameter approach resolves the contradiction by ensuring reliable operation across diverse driving scenarios while maintaining fuel efficiency through accurate identification of appropriate switch-off moments.
Solution Approach 2:
The system continuously monitors vehicle speed, brake pedal position, accelerator pedal position, and transmission state to dynamically adjust switching decisions. This feedback mechanism ensures that the engine is switched off only when appropriate conditions are met, preventing premature or inappropriate restarts while maintaining fuel efficiency benefits.
2Use of energy by moving object
If engine is automatically switched off during travel at low speeds, then energy efficiency improves, but vehicle responsiveness and driver comfort worsen
Solution Approach 1:
The patent uses a speed threshold of 3 km/h as a critical parameter to distinguish between stop-and-go traffic conditions (where switch-off is appropriate) and conditions requiring immediate responsiveness. Additionally, the system monitors brake and accelerator pedal positions to ensure the vehicle can respond promptly to driver inputs, resolving the contradiction between energy efficiency and responsiveness.
Solution Approach 2:
The system performs preliminary assessment of multiple conditions (speed, brake pedal position, accelerator pedal position, transmission state) before initiating engine switch-off during travel. This preliminary action ensures that switch-off only occurs when it will not compromise vehicle responsiveness or driver comfort, while still capturing energy efficiency opportunities.
3Device complexity
If simple switch-off criteria are used, then system complexity is reduced, but switching accuracy and energy savings worsen due to premature or missed switch-off events
Solution Approach 1:
The patent uses a single control unit that performs multiple functions: monitoring vehicle speed, brake pedal position, accelerator pedal position, and transmission state, then integrating this information to make switch-off/switch-on decisions. This multi-functional approach achieves high switching accuracy without proportionally increasing system complexity, as one unit handles all monitoring and decision-making.
Solution Approach 2:
The system monitors multiple parameters simultaneously (speed, brake pedal position, accelerator pedal position, transmission state) rather than relying on a single simple criterion. This multi-parameter monitoring approach significantly improves switching accuracy by capturing the complete driving context, while the use of standardized thresholds keeps the implementation relatively simple.
Data Source
AI summary
A start-stop device and a corresponding method brings about an automatic switch-off and/or switch-on operation of an automatically switched-off drive machine of a motor vehicle, in particular of a motor vehicle having an automatic transmission. The start-stop device has a switch-off logic, by way of which an automatic switch-off of the drive machine can be brought about in the case of a moving vehicle in accordance with a predefined switch-off operating strategy, and a switch-on logic, by way of which an automatic switch-on of the automatically switched-off drive machine can be brought about in accordance with a predefined switch-on operating strategy. The switch-off operating strategy and/or the switch-on operating strategy are/is configured in a manner which is based on wheel torque.