Hybrid Vehicle Torque Limiting via DC-DC Converter
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Solution Overview
Problem
Existing hybrid vehicle systems lack an effective method to control and limit the torque drawn by the front electric machine while maintaining comfort acceleration, especially when the thermal engine reaches its maximum torque, leading to inadequate response to driver demands in automatic speed regulation.
Innovation Solution
A method that estimates resistive forces and calculates maximum possible acceleration, then adjusts torque by offloading energy from the low-voltage battery to the thermal engine, allowing for comfort acceleration without changing transmission ratios, and engages the rear electric machine if necessary to ensure torque requirements are met.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the thermal engine operates at maximum torque to meet driver acceleration demands, then the acceleration performance is improved, but the energy storage device cannot be recharged effectively and the low-voltage battery cannot supply sufficient current
Solution Approach 1:
The patent implements dynamic torque management by continuously adjusting the torque demand on the thermal engine based on real-time operating conditions. The control system dynamically switches between different torque strategies: when the vehicle is stationary or at low speed, maximum torque is demanded to enable fast recharging of the energy storage device; when the vehicle is moving and acceleration is needed, torque demand is increased to meet driver demands while maintaining adequate charging current through coordinated control of the low-voltage battery and DC-DC converter.
Solution Approach 2:
The patent introduces a DC-DC converter as an intermediary power conversion device between the thermal engine and the low-voltage battery. This intermediary enables flexible power flow management by converting electrical energy from the thermal engine to charge the low-voltage battery, which then supplies current during high-torque demand periods. This mediation resolves the contradiction by creating an additional energy pathway that allows both recharging and high-power delivery to coexist.
2Speed
If the low-voltage battery supplies high current to the thermal engine at maximum torque, then the acceleration response is improved, but the battery discharge rate increases excessively causing voltage drop and reduced reliability
Solution Approach 1:
The DC-DC converter serves as an intermediary power source that supplements the low-voltage battery during high-torque demand. When the battery discharge rate becomes excessive and voltage drops below the threshold, the DC-DC converter automatically activates to provide additional current to the thermal engine, thereby reducing the battery's discharge burden and maintaining voltage stability. This intermediary support ensures both rapid acceleration response and battery reliability.
Solution Approach 2:
The patent implements a feedback control mechanism that continuously monitors the low-voltage battery's discharge rate and terminal voltage. When the discharge rate exceeds a predetermined threshold or voltage drops below the threshold, the control system receives feedback signals and automatically adjusts the torque distribution and activates the DC-DC converter. This closed-loop feedback ensures that the battery operates within safe parameters while maintaining acceleration performance.
3Use of energy by moving object
If the front electric machine draws excessive torque during thermal engine operation, then the generator charging function is improved, but the available torque for vehicle acceleration is reduced
Solution Approach 1:
The patent implements dynamic torque management by continuously adjusting the torque demand on the thermal engine based on real-time operating conditions. The control system dynamically switches between different torque strategies: when the vehicle is stationary or at low speed, maximum torque is demanded to enable fast recharging of the energy storage device; when the vehicle is moving and acceleration is needed, torque demand is increased to meet driver demands while maintaining adequate charging current through coordinated control of the low-voltage battery and DC-DC converter.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method preserves torque for vehicle acceleration, maintains comfort, and optimizes fuel consumption by avoiding unnecessary gear changes and electrical energy expenditure, ensuring the vehicle meets speed control demands while minimizing fuel consumption.
Implementation Method 1
a first electric machine (12) coupled to a thermal traction engine (2) which drives this vehicle (1) by a transmission (4) comprising different ratios, this first machine (12) being provided for supplying current to a low voltage battery (10)
Implementation Method 2
an energy storage device (16) which delivers this energy to a second electric traction machine (20), the vehicle comprising an automatic system for controlling its speed to regulate or limit it
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A method for a hybrid vehicle for limiting the torque drawn by a first electric machine (12) linked to a combustion engine (2) linked to a transmission (4), said first machine being designed to supply current to a battery (10) of the onboard network of the vehicle, and an energy storage device (16) which delivers said energy to a second traction electric machine (20), the vehicle comprising an automatic system for controlling the speed of same, characterised in that, in case the combustion engine (2) is not able, on a given ratio of the transmission (4), in response to a request from the automatic speed control system, to deliver the preferred acceleration, it sheds the load of the energy storage device (16) or of the battery (10) of the onboard network before using the second electric machine, or changing the ratio, if this load shedding alone is not sufficient to provide the preferred acceleration.