Engine Torque Control for Smooth Freewheel Exit
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Solution Overview
Problem
Current methods for restarting engine speed to exit freewheel operating mode in motor vehicles result in high fuel consumption, pollution, and unpleasant acoustic signals due to abrupt torque changes, which counteract the fuel-saving and emission-reducing benefits of this mode.
Innovation Solution
A control unit that regulates engine torque by comparing calculated torque levels with predefined thresholds associated with accelerator and brake pedal positions, controlling the torque to the minimum value between the calculated and threshold levels until the target engine speed is reached, allowing for a smoother transition and reducing initial torque gradient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the engine torque is increased abruptly to restart engine speed and exit freewheel mode, then the engine speed can be restored quickly, but fuel consumption increases and pollution is generated due to high initial torque gradient
Solution Approach 1:
The patent applies dynamics by making the engine torque variable rather than fixed. The torque is adjusted dynamically based on the current engine speed and the difference between current and target speeds. The torque evolution follows a progressive pattern where it starts at zero and increases gradually as the engine speed approaches the target speed, optimizing the balance between speed restoration and fuel consumption
Solution Approach 2:
The patent changes the parameter of engine torque from a constant or abrupt value to a variable that evolves over time. The torque is calculated as a function of engine speed difference and is updated continuously during the restart process. This parameter change allows the system to adapt the torque level to the current operating conditions, reducing fuel consumption while achieving speed restoration
2Speed
If the engine torque is increased abruptly to restart engine speed, then the target speed can be reached faster, but unpleasant acoustic signals are generated due to sudden torque changes
Solution Approach 1:
The patent makes the engine torque dynamic and progressive rather than abrupt. The torque starts at zero and increases gradually as the engine speed approaches the target speed. This dynamic adjustment smooths the torque changes, reducing mechanical vibrations and unpleasant acoustic signals while still achieving speed restoration within an acceptable time frame
Solution Approach 2:
The patent applies beforehand cushioning by preparing the engine torque in advance to avoid sudden jumps. The torque is calculated to evolve progressively from zero, cushioning the transition from idle to operating speed. This gradual torque buildup prevents sudden mechanical shocks and reduces acoustic emissions during the engine restart process
3Loss of time
If the engine torque is kept high to ensure rapid exit from freewheel mode, then the response time is reduced, but the fuel-saving benefits of freewheel mode are counteracted
Solution Approach 1:
The patent applies dynamics by making the torque profile adaptive rather than fixed. The torque is calculated based on the current engine speed and the remaining speed difference. As the engine speed approaches the target speed, the required torque naturally decreases. This dynamic torque adjustment allows for a balanced exit from freewheel mode that minimizes both time loss and energy consumption
Solution Approach 2:
The patent applies partial action by providing just enough torque to achieve the speed restoration goal rather than applying maximum torque throughout. The torque is modulated to match the actual needs of the engine restart process, avoiding excessive torque application that would waste fuel. The torque is sufficient to exit freewheel mode efficiently without being overly aggressive
Data Source
Figure 1~3
AI summary
Control unit for controlling an engine torque (CM) making it possible to exit a freewheeling mode of operation of a motor vehicle provided with an acceleration member and with a braking member, the control unit being provided with an engine speed regulator configured to calculate an engine torque to be commanded in order to reach the target engine speed, this control unit being configured, as long as the target engine speed is not reached, to – compare the calculated engine torque against a predefined threshold level of engine torque associated with the degree to which the acceleration member is depressed and with the instantaneous engine speed of the vehicle; – command the engine torque level given by the minimum value between the threshold engine torque level and the calculated engine torque level.