Shift Range Switching System With Trough Allowance
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Solution Overview
Problem
Existing 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 and inability to generate appropriate hydraulic pressure.
Innovation Solution
A shift range switching system incorporating a motor with cogging torque, a drive circuit, an output shaft, a shift range switching mechanism with a trough providing member and an urging member, and a control unit, which reduces the occurrence probability of intermediate range stop abnormalities by allowing the engagement member to drop into troughs using an allowance, thereby balancing torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the engagement member is designed to fit precisely in the trough without allowance, then the shift range switching precision is improved, but the system becomes vulnerable to intermediate range stop abnormalities when motor-off failures occur
Solution Approach 1:
The patent introduces an allowance (clearance) between the engagement member and the trough bottom as a pre-designed buffer zone. When motor-off failures occur during the ascending action, this allowance prevents the engagement member from stopping at intermediate positions by providing enough space for the member to complete its movement to the crest without encountering resistance, thereby cushioning against the harmful effect of abnormal stopping.
Solution Approach 2:
The patent changes the dimensional parameter by introducing an allowance (clearance) between the engagement member and the trough bottom. This parameter modification transforms the rigid precise-fit design into a flexible design with built-in tolerance, enabling the system to accommodate motor-off failures during the ascending action without causing intermediate range stop abnormalities.
2Device complexity
If the motor drive system operates without considering cogging torque, then the control simplicity is improved, but the torque balance during shift range switching deteriorates
Solution Approach 1:
The patent utilizes the cogging torque generated by the motor's permanent magnet as a self-balancing mechanism. The cogging torque naturally opposes the load torque during the ascending action, and by designing the trough profile and engagement member geometry appropriately, the system achieves torque balance without requiring complex external control interventions, thereby maintaining control simplicity while ensuring force equilibrium.
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 reduces the occurrence probability of intermediate range stop abnormalities, ensuring the automatic transmission operates correctly even during motor drive system abnormalities, by balancing cogging torque and load torque.
Implementation Method 1
a motor that includes a motor winding and generates a cogging torque by a permanent magnet
Data Source
AI summary
A shift range switching system includes: a motor that includes a motor winding and generates a cogging torque by a permanent magnet; a drive circuit; 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 the one trough; and a control unit. The engagement member drops into the one trough with an allowance. When an abnormality occurs in a motor drive system in an ascending action in which the engagement member moves from one trough toward one crest, the shift range switching system reduces an occurrence probability of an intermediate range stop abnormality.