Hybrid Engine Reverse Rotation Control via Torque Prediction
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Solution Overview
Problem
In hybrid vehicles with a planetary gear mechanism, when a slip occurs at the drive wheel during motor running, the internal combustion engine's rotation shaft may rotate in the opposite direction due to inertial forces, leading to unintended engine rotation when the brake is actuated to reduce drive wheel rotation speed.
Innovation Solution
The vehicle is controlled to actuate the internal combustion engine or bring the clutch into a motive power interruption state when the change in rotation speed of the drive wheel exceeds a threshold, using a rotating electric machine with the engine stopped, to prevent reverse rotation of the engine shaft.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the brake is actuated to reduce the rotation speed of the drive wheel in order to immediately suppress the slip, then the slip at the drive wheel is suppressed, but the rotation shaft of the internal combustion engine may rotate in the direction opposite to the direction at the time of actuation due to inertial forces
Solution Approach 1:
The control device predicts the rotation speed of the drive wheel at a future time point based on current rotation speed and deceleration characteristics. When this predicted rotation speed approaches a predetermined threshold, the control device preemptively increases engine output torque before the actual deceleration occurs. This preliminary action prevents the engine shaft from rotating in reverse by preparing the engine to absorb inertial forces before they manifest.
Solution Approach 2:
The control device continuously monitors the actual rotation speed of the drive wheel and compares it with the predicted rotation speed. Based on this feedback, the control device adjusts the engine output torque in real-time. When the actual rotation speed deviates from the predicted trajectory, the control device modifies engine torque to maintain the predicted rotation speed, thereby preventing reverse rotation of the engine shaft while ensuring slip suppression.
2Reliability
If the torque from the motor is restricted to suppress the slip, then the slip is suppressed, but the vehicle loses driving force and acceleration performance
Solution Approach 1:
Instead of simply restricting motor torque, the control device dynamically adjusts the engine output torque parameter based on predicted rotation speed. By changing the engine torque parameter preemptively when predicted rotation speed approaches the threshold, the system suppresses slip while maintaining overall driving force through increased engine contribution, rather than merely reducing motor torque.
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 solution effectively suppresses the rotation of the internal combustion engine's shaft in the opposite direction, enhancing engine durability and preventing unnecessary startups by setting appropriate threshold values based on antilock brake system usability and transmission speed ratios.
Implementation Method 1
a planetary gear mechanism having a sun gear, a ring gear and a carrier; an internal combustion engine coupled to the carrier; a drive wheel coupled to one rotation element which is one of the sun gear and the ring gear
Implementation Method 2
a rotation shaft of the internal combustion engine that was in the stop state may rotate in a direction opposite to a direction at the time of actuation due to the inertial force and the like acting on the other rotation elements
Data Source
AI summary
An HV-ECU executes a control process including the step of executing reverse rotation prevention control for an engine when EV running is in execution in a vehicle (YES in S100), an ABS is usable (YES in S102) and a magnitude of an amount of change in rotation speed of a ring gear of a differential unit is larger than a threshold value A (YES in S104), or when the ABS is unusable (NO in S102) and a magnitude of an amount of reduction in rotation speed of the ring gear of the differential unit is larger than a threshold value B (YES in S106).