Shift Range Switching System Cogging Torque Control
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Solution Overview
Problem
Conventional shift range switching systems face issues with intermediate range stop abnormalities when motor-off failures occur during range switching, leading to potential failures in automatic transmissions due to imbalanced torque conditions.
Innovation Solution
A shift range switching system incorporating a motor with cogging torque, a shift range switching mechanism with troughs and crests, and a control unit that includes an allowance for the engagement member to drop into troughs, ensuring continued motor operation and preventing intermediate range stop abnormalities by balancing cogging torque and urging member torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a motor with cogging torque is used to drive the shift range switching mechanism, then the motor can generate sufficient torque for switching, but intermediate range stop abnormalities occur when motor-off failures happen during range switching
Solution Approach 1:
The control unit performs preliminary detection of motor-off failures before they cause intermediate range stop abnormalities. By monitoring motor current and detecting abnormality in advance, the system can take preventive actions to ensure the engagement member reaches the correct trough position, avoiding the harmful effect of intermediate stopping.
Solution Approach 2:
The system converts the potentially harmful motor-off failure condition into a manageable situation by using the cogging torque characteristics. The control unit utilizes the cogging torque peaks and valleys to guide the engagement member to stable trough positions even when motor power is lost, transforming a failure mode into a controlled transition.
2Productivity
If the engagement member moves from one trough toward one crest during range switching, then shift range transition is achieved, but torque imbalance between cogging torque and urging member torque causes intermediate range stop abnormalities
Solution Approach 1:
The control unit continuously monitors the position of the engagement member and the motor operating state during the transition from trough to crest. By providing feedback on the actual position and detecting torque imbalance conditions, the system can adjust motor control signals to maintain proper torque balance, ensuring complete transition without intermediate stopping.
Solution Approach 2:
The control unit dynamically adjusts motor control parameters during the switching process. By changing current, voltage, or switching frequency parameters in response to detected conditions, the system maintains optimal torque balance between cogging torque and urging member torque throughout the transition, preventing intermediate range stops.
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
The system effectively avoids intermediate range stop abnormalities and prevents automatic transmission failures by ensuring continuous motor operation even during abnormal conditions, maintaining appropriate hydraulic pressure.
Implementation Method 1
a motor that includes motor windings and generates a cogging torque by a permanent magnet
Data Source
AI summary
A shift range switching system includes: a motor that includes motor windings and generates a cogging torque by a permanent magnet; drive circuits; an output shaft; a shift range switching mechanism that includes a trough providing member with troughs and crests and integrally rotates with the output shaft, an engagement member that fits in one trough corresponding to a shift range, and an urging member that urges the engagement member toward one trough; and a control unit with one calculation unit. The engagement member drops into one trough with an allowance. When an abnormality occurs in motor drive systems in an ascending action in which the engagement member moves from one trough toward one crest, the shift range switching systems avoids an occurrence of an intermediate range stop abnormality.