Transmission Parking Lock Position Control Using Motor Current Feedback
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Solution Overview
Problem
Existing methods for determining the position of a movable element in a vehicle transmission parking lock device are inaccurate due to assembly tolerances and do not account for the inertia of the rolling element, leading to unacceptable positioning errors.
Innovation Solution
A method that includes angularly displacing the control plate, measuring the angular position and current of the torque output element, and reducing the motor speed when approaching the desired position to ensure precise alignment, using threshold values to stop the motor at the correct position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the angular position sensor connected to the torque output element is used to determine the position of the movable element, then the device complexity is reduced (no additional sensors needed), but the measurement precision deteriorates due to assembly tolerances and inertia effects
Solution Approach 1:
The patent applies feedback by continuously monitoring the current consumed by the electric motor and using it to determine when the rolling element has reached the bottom of the concave portion. The control unit receives feedback from the current sensor and adjusts the motor operation accordingly, stopping the motor when the predetermined current value is reached, thereby achieving precise positioning without additional sensors.
Solution Approach 2:
The patent replaces the mechanical sensing approach (angular position sensor on the torque output element) with an electrical sensing approach (current sensor monitoring motor current). By substituting the mechanical position detection system with an electrical current-based detection system, the patent achieves more precise positioning while maintaining device simplicity.
2Productivity
If the electric motor runs at full speed to quickly position the movable element, then the productivity is improved (faster positioning), but the manufacturing precision deteriorates due to inertia causing the rolling element to overshoot the desired position
Solution Approach 1:
The patent applies preliminary action by first moving the control plate rapidly to bring the rolling element close to the bottom of the concave portion, then detecting the approaching position through current monitoring, and finally applying a braking action by cutting off power when the predetermined current value is reached. This preliminary rapid movement followed by precise braking achieves both high productivity and high precision.
Solution Approach 2:
The patent applies the skipping principle by allowing the motor to run at full speed through the majority of the positioning travel, rushing the rolling element through the intermediate positions, and then applying precise control only at the critical final moment when the predetermined current value indicates proximity to the target position. This minimizes the time spent in precision-critical zones while maintaining overall speed.
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
Achieves an accuracy of ±1.5° without additional components, adapting to temperature changes, and ensuring accurate positioning without the need for real-time training on assembly lines.
Implementation Method 1
an electromechanical actuator makes it possible to modify the position of the blocking finger... This actuator generally comprises an electric motor
Implementation Method 2
it does not take into account the inertia of the rolling element when it travels along the cam path of the control plate, in particular in the descent phases
Data Source
AI summary
A method for controlling the position of a movable element in a device of a vehicle transmission. The method includes (i) angularly displacing a control plate, (ii) measuring the angular position of a torque output element of an actuator and comparing the measured value with a limiting threshold value (m), and (iii) reducing the rotating speed of the electric motor of the actuator. The method further includes (iv) applying a limited current (Ilim) to the electric motor of the actuator, and (v) stopping the driving of the electric motor when, cumulatively, the value of the limited current (Ilim) is substantially reached, the measured value of the angular position of the torque output element of the actuator corresponds substantially to the desired position, and the angular speed of the torque output element is substantially zero.