Shift Range Control via Motor Speed Monitoring
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Solution Overview
Problem
The existing shift range control systems for automatic transmissions face challenges in accurately switching shift ranges due to the detection accuracy of the output shaft sensor, which can result in the engagement member not being positioned correctly at the bottom of the recesses, leading to incomplete shift range switching.
Innovation Solution
A shift range control apparatus that includes a rotation speed detection section and a movement determination section to determine when the engagement member has moved to the bottom of the recesses by monitoring the output shaft and motor rotation speeds, allowing for accurate shift range switching regardless of the sensor's detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the output shaft sensor is used to detect shift range, then the shift range can be detected, but the detection accuracy is insufficient causing the engagement member to be mispositioned
Solution Approach 1:
The patent introduces an intermediary detection mechanism that monitors the rotation speeds of both the output shaft and motor. By detecting the speed difference between these two components, the system can indirectly determine the engagement member's position without relying solely on the inaccurate output shaft sensor. This intermediary speed difference detection serves as a mediator to achieve accurate position determination despite sensor limitations.
Solution Approach 2:
The system implements feedback control by continuously monitoring the speed difference between the output shaft and motor. When the speed difference falls within a predetermined range, the system feedback-determines that the engagement member has reached the bottom of the recess, confirming accurate positioning. This feedback mechanism allows the system to verify and correct positioning based on real-time speed measurements.
2Manufacturing precision
If the engagement member positioning relies on sensor detection, then positioning can be achieved, but positioning accuracy is insufficient leading to incomplete shift range switching
Solution Approach 1:
The patent replaces the mechanical positioning detection method (relying on the output shaft sensor to directly detect engagement member position) with a rotational dynamics-based detection method. By substituting the mechanical detection approach with a method that analyzes the relationship between output shaft rotation and motor rotation, the system achieves more accurate positioning determination without being constrained by sensor accuracy limitations.
Solution Approach 2:
The system changes the detection parameter from direct position measurement (which is inaccurate due to sensor limitations) to speed difference measurement. By monitoring how the rotation speeds of the output shaft and motor differ during the positioning process, the system can accurately determine when the engagement member reaches the bottom of the recess, thereby achieving complete and accurate shift range switching.
Data Source
AI summary
A shift range control apparatus is applied to a shift range switching mechanism that includes a rotation member including multiple recesses, and an engagement member that positions the rotation member by engaging to the recesses. The shift range control apparatus controls a motor of a shift actuator connected to the rotation member to switch a shift range. The shift range control apparatus includes a rotation speed detection section that detects an output shaft rotation speed corresponding to a rotation speed of an output shaft of the shift actuator, and a movement determination section that determines that an engagement portion of the engagement member has relatively moved to a bottom of one of the recesses of the rotation member when the output shaft rotation speed is equal to or lower than a predetermined value during switching of the shift range.