Transmission Park Release Torque Control
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Solution Overview
Problem
Automatic transmissions experience abrupt energy release and driveline oscillation when shifting out of Park range, leading to unintended vehicle rolling and harsh energy release.
Innovation Solution
Engaging a park brake to hold vehicle wheels and epicyclic gear components against rotation, then gradually releasing the braking torque to prevent rolling and smooth energy release by selecting a transmission drive range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the park brake is released abruptly when shifting out of Park range, then the transmission can quickly engage the drive range, but the stored energy in the driveline is suddenly released causing a harsh boom and driveline oscillation
Solution Approach 1:
The system applies a brake control element to hold the epicyclic gear unit against rotation before the Park range is disengaged. This preliminary braking action prepares the driveline for controlled energy release when the park brake is released, preventing the harsh boom and oscillation that would otherwise occur during abrupt energy release.
Solution Approach 2:
The brake control element dynamically adjusts the braking torque on the epicyclic gear unit during the transition from Park to drive range. By modulating the brake application and release timing, the system controls the rate of energy release, transforming the abrupt static release into a controlled dynamic process that eliminates driveline oscillation.
2Reliability
If the park brake is used to hold vehicle wheels against rotation, then the vehicle is prevented from rolling on a grade, but the stored energy in the driveline causes unintended rolling when the brake is released
Solution Approach 1:
The brake control element acts as an intermediary between the park brake and the driveline. It absorbs and controls the stored energy in the driveline by applying controlled braking torque to the epicyclic gear unit, preventing this energy from converting into unintended vehicle rolling when the park brake is released.
Solution Approach 2:
The system extracts the harmful stored energy from the driveline by applying the brake control element to the epicyclic gear unit. This separates the energy dissipation function from the park brake itself, allowing the park brake to reliably hold the vehicle on grade while the brake control element manages the energy release to prevent unintended rolling.
3Stability of the object's composition
If friction control elements are engaged in both first gear and reverse gear when Park range is engaged, then the transmission is secured against rotation, but the abrupt release of stored energy causes driveline oscillation
Solution Approach 1:
The brake control element is activated in advance during the Park range disengagement sequence to hold the epicyclic gear unit. This preliminary action ensures that when the friction control elements are released, the driveline energy is already being controlled, preventing the harsh boom and oscillation that would result from abrupt energy release.
Solution Approach 2:
The system changes the braking torque parameter applied to the epicyclic gear unit during the transition from Park to drive range. By gradually reducing the brake torque rather than releasing it abruptly, the system controls the energy release rate, eliminating driveline oscillation while maintaining stable transmission engagement.
Data Source
AI summary
A method for controlling a vehicle transmission during a park release event includes engaging a park brake to hold vehicle wheels against rotation, holding against rotation a first component and a second component of an epicyclic gear unit connected to the wheels, releasing the park brake, selecting a transmission drive range, releasing said first component, and operating the transmission in the selected drive range.