Anticipatory Heat Engine Start in Hybrid Powertrains
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In hybrid powertrains, there is a delay in starting the heat engine when transitioning from an electric state to a hybrid or thermal state due to the engine's start-up time, which can exceed reliability limits and delay torque availability, especially when the vehicle's speed is high, leading to suboptimal performance in meeting driver requests.
Innovation Solution
A method is developed to anticipate the start of the heat engine by calculating the force available at the wheel at the foreseeable instant of engine start, considering the start-up time, and comparing it with the target force request, sending an anticipated start request based on vehicle longitudinal acceleration and start time before each kinematic chain state change, ensuring the heat engine starts before it is needed to meet driver demands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the heat engine starts only when needed (reactive start), then fuel consumption is optimized by keeping the engine off during electric-only states, but the torque availability is delayed and reliability limits may be exceeded during state transitions
Solution Approach 1:
The control unit sends an anticipatory start request to the heat engine before the actual state transition occurs. By calculating the predicted state transition time based on current driving conditions and engine characteristics, the system initiates engine start-up in advance, ensuring the engine is ready when the hybrid state is needed without unnecessary prolonged operation that would waste fuel.
2Power
If the heat engine starts immediately when a hybrid state is requested, then torque availability is improved, but the delay between state selection and engine availability is excessive when transitioning from electric-only states
Solution Approach 1:
The control unit calculates the predicted state transition time based on current driving conditions and engine characteristics, then sends an anticipatory start request before the actual transition occurs. This timing optimization ensures the engine becomes available exactly when needed, minimizing both premature starts and delayed responses.
Solution Approach 2:
The control unit continuously monitors actual state transition times and compares them with predicted times, adjusting the anticipatory start timing based on feedback from previous transitions. This closed-loop approach optimizes the balance between torque availability and response time across varying operating conditions.
Data Source
AI summary
A method for the anticipatory starting of a heat engine in a hybrid power train comprising at least a heat engine, a traction electric machine, and an automatic transmission transmitting the drive power to the wheels of the vehicle in at least one initial state of the drive train of same in which the traction machine alone provides the traction of the vehicle and the heat engine is switched off, and at least one other target state in which the heat engine provides tractive power, characterised in that it involves sending, to the heat engine, an anticipatory starting request (Mth_allumé_req) depending on the longitudinal acceleration of the vehicle (A_longi) and the starting time (T_dem_Mth) of same, before each change of state of the drive train between an initial state not requiring a started heat engine, and a target state requiring same to be started.