Neutral State Detection via Motor Torque Comparison
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Solution Overview
Problem
When the selection lever is in a neutral state between the N-range and D-range positions, the inhibitor switch signal may incorrectly indicate the D-range position, leading to issues with vehicle control as no control hydraulic pressure is supplied to the clutch hydraulic pressure chamber, causing problems when the driver accelerates, as the system assumes control hydraulic pressure is available.
Innovation Solution
The system determines the neutral state by controlling the motor's rotational speed and comparing it to the estimated motor torque based on the target transmission clutch torque capacity, accurately identifying the neutral state when the motor torque is smaller than the estimated torque, indicating no torque is transmitted to the rear wheels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the inhibitor switch signal is used to determine the selection lever position, then the system can respond quickly to gear changes, but the determination accuracy deteriorates when the lever stops between positions
Solution Approach 1:
The patent introduces an intermediary determination process that uses motor torque characteristics as a mediator to verify the actual transmission state. When the inhibitor switch indicates D-range but the motor torque is below the threshold, the system recognizes the neutral state, thus resolving the contradiction between quick response and accurate determination.
Solution Approach 2:
The system implements feedback by continuously monitoring motor torque and comparing it against the threshold value. This feedback mechanism allows the system to correct the position determination based on actual transmission engagement status, ensuring accuracy even when the inhibitor switch signal is ambiguous.
2Productivity
If the system assumes control hydraulic pressure is available based on inhibitor switch signal, then vehicle control can be executed without delay, but harmful effects occur when the assumption is wrong and no pressure is actually supplied
Solution Approach 1:
The patent applies preliminary anti-action by proactively checking motor torque before executing vehicle control. When the motor torque is below the threshold, the system preemptively identifies the neutral state and prevents erroneous control execution, thus avoiding the harmful effects of incorrect assumptions about hydraulic pressure availability.
Solution Approach 2:
The continuous monitoring of motor torque provides feedback that verifies whether control hydraulic pressure is actually available. This feedback mechanism prevents the system from executing vehicle control when the assumption of pressure availability is wrong, eliminating control errors and shock.
3Device complexity
If the selection lever position is determined solely by inhibitor switch signal, then the device complexity is low, but the reliability of neutral state determination deteriorates
Solution Approach 1:
The patent applies self-service by using the motor's own torque characteristics as the determination criterion. The motor controller utilizes existing motor torque data to identify neutral state, avoiding the need for additional sensors or complex determination systems while significantly improving reliability.
Solution Approach 2:
The system changes the determination parameter from positional information (inhibitor switch signal) to operational parameter (motor torque). This parameter change enables reliable neutral state determination using existing motor control data without increasing device complexity.
Data Source
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AI summary
When an inhibitor switch signal indicates that a vehicle operates in a "D" range, a motor generator MG is controlled in terms of rotational speed, and when a motor torque during the rotational speed control is less than an estimated motor torque based on a target transmission torque capacity of a second clutch CL2 that is interposed between the motor generator MG and a rear wheel RR/RL and connects and disconnects the motor generator MG and the rear wheel RR/RL to and from each other, a determination is made that an automatic transmission AT is in a neutral state.