Dynamic Torque Allocation in Hybrid Vehicles
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Solution Overview
Problem
Existing methods for dynamic torque allocation in hybrid electric vehicles often compromise between fuel economy and engine performance, as they either limit maximum engine torque too much, leading to inefficient fuel use or sacrifice performance for optimal efficiency, especially under varying conditions like different fuel octane ratings and engine internal conditions.
Innovation Solution
A method that dynamically limits the maximum available engine torque based on the operator's selected performance mode and torque demand, using a spark retard torque ratio to learn and apply a constrained torque limit for improved fuel economy while allowing unconstrained torque during transient conditions for better acceleration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If maximum engine torque is limited to meet vacuum demand, then fuel vapor purging is improved, but fuel economy deteriorates
Solution Approach 1:
The patent applies dynamics by making the maximum engine torque limit variable rather than fixed. The torque limit dynamically adjusts based on operating conditions including vacuum demand, engine speed, load, and temperature. This allows the system to optimize between fuel vapor purging requirements and fuel economy by adapting the torque limitation strategy to current operating conditions, rather than applying a constant restrictive limit.
Solution Approach 2:
The patent changes the parameter of maximum engine torque limit based on multiple operating parameters. By monitoring engine speed, load, temperature, and vacuum demand, the system adjusts the torque limitation parameter in real-time. This enables the engine to operate at higher torque levels when conditions permit (improving fuel economy) while still ensuring adequate vacuum for fuel vapor purging when needed.
2Power
If maximum engine torque is set for best performance, then vehicle acceleration is improved, but fuel economy deteriorates due to operation in borderline spark reduction region
Solution Approach 1:
The system dynamically adjusts the maximum torque limit based on real-time operating conditions. During transient conditions requiring acceleration, the torque limit can be raised to allow borderline spark reduction operation for improved power delivery. During steady-state cruising conditions, the torque limit is reduced to promote operation at MBT spark for optimal fuel economy. This dynamic adaptation resolves the contradiction between acceleration performance and fuel efficiency.
Solution Approach 2:
The system periodically evaluates operating conditions and adjusts torque limits accordingly. By continuously monitoring parameters such as engine speed, load, and temperature, the system determines when to allow high-torque performance mode versus when to enforce fuel-economy-oriented torque limitation. This periodic assessment and adjustment enables the system to optimize the trade-off between acceleration and fuel economy based on current driving demands.
3Use of energy by moving object
If maximum engine torque is reduced to MBT spark under all conditions, then fuel economy is improved, but engine performance deteriorates
Solution Approach 1:
Rather than enforcing a static MBT-only torque limit, the system dynamically allows operation in the borderline spark reduction region when performance is needed. The torque limit adapts based on whether the vehicle requires acceleration (needing higher torque) or is in steady-state cruising (benefiting from MBT efficiency). This dynamic flexibility resolves the contradiction by permitting performance-oriented operation when necessary while maintaining fuel economy optimization when possible.
4Ease of manufacture
If a smaller battery is used, then cost is reduced, but vehicle performance may deteriorate due to limited motor torque availability
Solution Approach 1:
The system allows the engine to serve itself by maximizing its torque output within dynamically determined limits. By optimizing the torque allocation between engine and motor based on real-time conditions, the system enables the engine to compensate for reduced motor torque availability. This self-service approach allows the powertrain to maintain performance with a smaller, less costly battery by relying more on optimized engine torque delivery.
Solution Approach 2:
The system changes the torque allocation parameters dynamically to optimize the contribution of each power source. When battery capacity is limited, the control algorithm adjusts the torque split to maximize engine contribution while using motor torque strategically for transient assistance. This parameter optimization enables equivalent vehicle performance with reduced battery size and cost.
Data Source
AI summary
Methods and systems are provided for dynamically allocating engine torque and motor torque in a hybrid vehicle to meet operator torque demand. The allocation is adjusted by constraining the maximum engine torque allowable under selected conditions to provide a better trade-off between performance and fuel economy. A maximum engine torque that provides best fuel economy is learned during engine operation at different engine speed-load conditions based on a deviation in spark retard torque ratio from a threshold ratio as spark timing is moved to MBT.