Hybrid Vehicle Over Rotation Limitation Control for Planetary Gear Protection
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Solution Overview
Problem
In hybrid vehicles, when an abnormality occurs, switching to limp-home travel mode can cause the pinion gear rotation speed to exceed its allowable limit, leading to secondary failures of the planetary gear set, resulting in increased repair costs due to the need to replace multiple components.
Innovation Solution
A control apparatus with a limp-home travel control section and an over rotation limitation control section that limits the pinion gear rotation speed by controlling the engine rotation speed or vehicle travel speed, preventing it from exceeding predetermined limits during mode changes to limp-home travel mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the engine operation is stopped immediately when changing to limp-home travel mode, then the abnormality response time is reduced, but the pinion gear rotation speed exceeds the allowable limit causing secondary failure
Solution Approach 1:
The control apparatus performs preliminary action by detecting abnormalities in the first MG system before they cause catastrophic failure, and proactively prepares the engine and pinion gear for the upcoming limp-home travel mode transition. This prevents the pinion gear from exceeding rotation speed limits during mode switching.
Solution Approach 2:
The control apparatus continuously monitors the rotation speed of the pinion gear and provides feedback to the control unit. When the pinion gear rotation speed approaches the allowable limit during limp-home travel mode, the control unit adjusts the engine operation accordingly to prevent over-rotation damage.
2Productivity
If the pinion gear rotation speed is not limited during mode change, then the vehicle can quickly transition to limp-home travel mode, but the planetary gear set fails causing increased repair costs
Solution Approach 1:
The control apparatus introduces an intermediary control mechanism that manages the transition between normal operation and limp-home travel mode. By controlling the engine operation as an intermediary element, the system prevents direct damage to the pinion gear during mode transition, avoiding the need for expensive planetary gear set replacement.
3Reliability
If the engine rotation speed is controlled to limit pinion gear rotation speed, then secondary failure is prevented, but the vehicle speed may be restricted during limp-home travel mode
Solution Approach 1:
The control apparatus dynamically adjusts the engine rotation speed based on real-time conditions during limp-home travel mode. The control unit monitors pinion gear rotation speed and dynamically modifies engine operation to maintain it within safe limits while maximizing vehicle speed within those constraints, rather than using a fixed speed limitation.
Data Source
AI summary
Over rotation limitation control is performed to control an engine rotation speed so that a rotation speed of a pinion gear of a planetary gear set will not exceed a limit value, when a travel mode is changed to a limp-home travel mode in response to an abnormality in an inverter for a first motor generator. With this over rotation limitation control, a difference between rotation speeds of a ring gear coupled to a wheel side and a carrier coupled to an engine side. Thus, when the limp-home travel mode is performed due to the abnormality in the inverter for the first motor generator, a secondary failure, in which the pinion gear burns out and the planetary gear set fails, is prevented.