Hybrid Starter-Generator Pinion Engagement for Belt Slip Reduction
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Solution Overview
Problem
Hybrid vehicle powertrains with belt-driven integrated starter/generators face issues with belt slip and degradation, leading to reduced energy transfer and increased noise and vibration during engine starting, especially in cold conditions.
Innovation Solution
Engaging a pinion gear coupled to the integrated starter/generator with the engine flywheel during engine starting to enhance rigidity and reduce belt slip, and disengaging it during lower energy transfer conditions to minimize noise and vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a belt connection is used between the integrated starter/generator and the engine, then the device complexity is reduced and ease of manufacture is improved, but belt slip and belt degradation occur leading to reduced reliability and energy transfer efficiency
Solution Approach 1:
The patent applies a dual-path connection system that dynamically switches between belt connection and pinion gear connection based on operating conditions. The controller selectively engages the pinion gear with the flywheel during high energy transfer conditions (cold starts, high load) while using the belt connection during normal operating conditions, thereby maintaining reliability while managing complexity.
Solution Approach 2:
The pinion gear acts as an intermediary mechanism that supplements the belt connection. During conditions requiring high reliability (cold engine starts, high energy transfer), the pinion gear engages the flywheel directly to ensure positive mechanical drive without slip, while the belt serves as the primary connection during normal conditions.
2Reliability
If a pinion gear is engaged with the flywheel during engine starting, then energy transfer reliability and rigidity are improved, but device complexity and noise increase
Solution Approach 1:
The system dynamically engages and disengages the pinion gear based on real-time operating conditions. The controller monitors parameters such as engine temperature, load, and energy transfer requirements to selectively activate the pinion gear only when necessary (e.g., cold starts, high load conditions), thereby maintaining reliability while minimizing the impact of added complexity.
Solution Approach 2:
The pinion gear mechanism is designed to serve multiple functions: providing positive mechanical drive during cold starts, assisting during high energy transfer conditions, and being disengageable during normal operation. This multi-functionality justifies the added complexity by delivering reliability across diverse operating scenarios.
3Reliability
If the pinion gear remains engaged during all operating conditions, then energy transfer reliability is maintained, but noise and vibration increase during low energy transfer conditions
Solution Approach 1:
The pinion gear engagement is dynamically controlled based on operating conditions. During low energy transfer conditions (normal operation, warm engine), the pinion gear is disengaged to eliminate noise and vibration sources. During high energy transfer conditions (cold starts, high load), the pinion gear engages to ensure reliable energy transfer, thus balancing noise reduction with reliability maintenance.
Solution Approach 2:
The pinion gear engagement operates periodically rather than continuously, activating only during specific high-demand intervals (cold starts, high load conditions) and disengaging during normal operation. This periodic engagement pattern reduces cumulative noise and vibration exposure while maintaining reliability when needed.
4Reliability
If the belt tension is increased to prevent belt slip, then energy transfer reliability is improved, but the risk of belt degradation and failure increases
Solution Approach 1:
The pinion gear serves as an intermediary that provides positive mechanical drive during high energy transfer conditions, eliminating the need for excessive belt tension. By engaging the pinion gear with the flywheel during cold starts and high load conditions, the system ensures reliable energy transfer without subjecting the belt to high stress that would cause degradation.
Solution Approach 2:
The patent substitutes the friction-based belt drive with a positive mechanical engagement (pinion gear and flywheel teeth) during conditions requiring high reliability. This replacement eliminates belt slip and the associated need for high tension, thereby preventing belt degradation while maintaining energy transfer reliability.
Data Source
AI summary
Systems and methods for operating a hybrid powertrain or driveline that includes an engine and an integrated starter/generator are described. In one example, the integrated starter/generator may crank the engine via a pinion gear during a first engine start. The integrated starter/generator may crank the engine via a belt during a second engine start.