Hybrid Vehicle Torque Control During Engine Start Transition
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Solution Overview
Problem
Existing hybrid electric vehicles face challenges in improving driving force responsiveness due to battery output limitations during engine start transitions, leading to reduced assisting effects and potential engine start delays.
Innovation Solution
A vehicle control device that manages torque output from rotary electric machines and engine engagement to enhance driving force responsiveness by limiting torque increase in one machine during clutch engagement and optimizing power distribution between machines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the torque of the second rotary electric machine is increased during engine start, then the engine start may be delayed depending on the state of the battery, but the responsiveness of the driving force may be lowered
Solution Approach 1:
The patent segments the engine start process into two distinct sections: section 1 for cranking the engine using only the second rotary electric machine, and section 2 for assisting driving force using the first rotary electric machine. This segmentation allows the system to prioritize engine starting in section 1 without compromising driving force responsiveness in section 2, thereby resolving the contradiction between engine start reliability and driving force responsiveness.
Solution Approach 2:
The patent dynamically adjusts the torque output of the first rotary electric machine based on the operating section. In section 1, the torque is limited to ensure sufficient power for engine cranking, while in section 2, the torque is increased to provide driving force assistance. This dynamic adjustment resolves the contradiction by adapting the torque distribution to the specific operational requirements of each section.
2Power
If most of the battery output is consumed by the starter motor for starting the engine, then the output of the first rotary electric machine becomes equal to or less than the steady output of the battery output, but the assisting effect of the response delay of the driving force becomes small
Solution Approach 1:
The patent divides the power distribution into two sections: in section 1, battery power is dedicated to cranking the engine via the second rotary electric machine, while in section 2, battery power is allocated to the first rotary electric machine for driving force assistance. This segmentation ensures that the first rotary electric machine receives sufficient power for effective driving force compensation without compromising engine starting capability.
Solution Approach 2:
The patent performs preliminary engine cranking in section 1 using the second rotary electric machine before transitioning to section 2 where the first rotary electric machine provides driving force assistance. This preliminary action ensures that the engine is successfully started before allocating battery power to the first rotary electric machine, thereby maintaining both engine start reliability and driving force compensation effectiveness.
3Speed
If the torque of the first rotary electric machine is increased during engine start, then the driving force compensation is improved, but the engine start may be delayed
Solution Approach 1:
The patent segments the operational timeline into section 1 (engine cranking phase) and section 2 (driving force assistance phase). During section 1, the torque of the first rotary electric machine is limited to prioritize engine starting, while during section 2, the torque is increased to improve driving force responsiveness. This temporal segmentation resolves the contradiction by addressing both requirements at appropriate times.
Solution Approach 2:
The patent implements periodic action by switching the torque control strategy of the first rotary electric machine based on the operational phase. In section 1, torque is limited; in section 2, torque is increased. This periodic adjustment of torque based on operational timing resolves the contradiction between engine start speed and driving force responsiveness.
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
Improves driving force responsiveness by ensuring equal or higher torque output than battery capacity before clutch engagement, reducing engine start failures, and enhancing overall vehicle performance without increasing battery capacity.
Implementation Method 1
a section 1 and a section 2 are included in a period until a clutch engagement at a time of starting the engine when shifting from the first traveling mode to the second traveling mode. The section 1 is a section for cranking the engine by an output of the second rotary electric machine
Implementation Method 2
the section 2 is a section after the section 1 and a section for assisting a driving force of the engine by an output of the first rotary electric machine
Data Source
AI summary
A vehicle control device mounted on a vehicle includes a first traveling mode being driven by the torque output from a first rotary electric machine, and a second traveling mode being driven by the engine torque output from an engine and the torque output from the first rotary electric machine, wherein a section 1 for cranking the engine by the output of the second rotary electric machine and a section 2 for assisting the driving force of the engine by the output of the first rotary electric machine are provided during a period from the first traveling mode to the engagement of the clutch at the time of starting the engine to the second traveling mode, and the torque increase of the first rotary electric machine is limited in the section 1.