Electric Transmission Park Actuation for Hydraulic-Free Braking
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Solution Overview
Problem
Existing park systems in transmissions often rely on external or hydraulic mechanisms, which can be cumbersome and prone to failures, particularly in electrical failures or when transitioning to a park mode.
Innovation Solution
A transmission park system that includes an electric actuator and an actuation linkage, allowing for the selective braking of the output shaft through a park actuation assembly. This system operates in engaged, disengaged, and staged states, facilitating a transition to the engaged state in case of electrical failure or operator input.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hydraulic mechanisms are used to drive the park system, then the park system can be operated, but the system becomes more complex and prone to failures
Solution Approach 1:
The patent removes the hydraulic system from the park mechanism, extracting the problematic fluid-powered components and replacing them with a purely mechanical actuation system. This eliminates hydraulic leaks, fluid management complexity, and associated failure modes while maintaining park functionality through mechanical advantage in the linkage system.
Solution Approach 2:
The patent replaces the hydraulic actuation system with a mechanical actuator and linkage system. The electric actuator converts electrical energy to mechanical motion, which is then transmitted through the linkage to engage or disengage the park brake, eliminating the need for hydraulic fluid and pressure systems entirely.
2Ease of operation
If external mechanisms are used to drive the park system, then the park system can be operated, but the overall system complexity increases
Solution Approach 1:
The patent integrates the actuator and linkage system directly into the park mechanism housing, merging what were previously separate external components into a unified integrated assembly. This reduces the number of external connections, simplifies installation, and decreases overall system complexity while maintaining ease of operation through the control system.
3Reliability
If a staged state is added to facilitate transition, then reliability during electrical failure is improved, but device complexity increases
Solution Approach 1:
The staged state serves as a preliminary intermediate position that the park mechanism passes through during engagement and disengagement transitions. This intermediate state ensures proper sequencing of mechanical components before reaching the final engaged or disengaged position, providing a safety buffer that prevents improper engagement even if electrical control fails.
Solution Approach 2:
The staged state acts as a protective intermediate condition that cushions against potential failure modes. By requiring the system to pass through this intermediate state, the design provides a mechanical checkpoint that prevents direct transition between extremes, thereby protecting against catastrophic failure from improper engagement during electrical anomalies.
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 provides reliable and efficient operation by eliminating the need for hydraulic components and enabling smooth transitions between states, ensuring safe and controlled braking of the output shaft.
Implementation Method 1
The actuation linkage may include a screw directly coupled to the actuator to be driven by the actuator and a nut or axial cam coupled to the screw for translation along a first longitudinal axis in response to movement of the screw
Implementation Method 2
The actuation linkage may include a preloaded spring supported by the rod that extends along the second longitudinal axis between the sleeve and a plurality of rollers of the park actuation assembly
Implementation Method 3
In the engaged state, rotation of the park gear may be constrained to resist rotation of the output shaft
Data Source
AI summary
Transmissions, park systems, and methods of operating transmissions are disclosed. A transmission includes an input shaft to receive torque from a drive unit, an output shaft to transmit torque to a load, and a park system to selectively brake the output shaft. The park system includes a park actuation assembly having a park gear in direct contact with the output shaft, an actuator to supply rotational power, and an actuation linkage coupled between the actuator and the park actuation assembly.