Automatic Transmission Parking Lock Travel Stop for Emergency Release
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Solution Overview
Problem
Existing parking lock devices for automatic transmissions face issues with excessive actuation forces during emergency release, which can exceed the load capacity of components, leading to reduced service life and potential damage.
Innovation Solution
A structurally simple and economical parking lock device with a hydraulically or pneumatically controllable actuator featuring an actuation-travel-limiting unit that prevents undesirably high loads by limiting the piston's travel during emergency actuation, ensuring the actuator housing and connected components are not subjected to excessive stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the emergency release device is used to manually disengage the parking lock, then the parking lock can be released in case of hydraulic failure, but excessive actuation forces can exceed the load capacity of components, leading to reduced service life and potential damage
Solution Approach 1:
The actuation-travel-limiting unit is pre-configured in the actuator housing to define a maximum travel distance for the piston before it contacts the stop surface. This preliminary structural arrangement prevents excessive force application by design, ensuring that even during emergency manual operation, the piston cannot travel beyond the safe limit that would damage components.
Solution Approach 2:
The actuation-travel-limiting unit with its stop surface acts as a protective cushioning element that absorbs and limits the maximum actuation force during emergency release. By providing this predetermined mechanical stop, the system protects load-carrying components from exceeding their load capacity while still allowing effective emergency disengagement of the parking lock.
2Reliability
If the piston is allowed to travel freely during emergency actuation, then complete disengagement of the parking lock can be achieved, but the actuator housing and connected components are subjected to undesirably high loads
Solution Approach 1:
The actuation-travel-limiting unit serves as an intermediary element between the piston and the actuator housing. It mediates the force transmission by providing a defined stop surface that limits piston travel, thereby ensuring reliable parking lock disengagement while simultaneously protecting the actuator housing and connected components from excessive stress.
3Ease of manufacture
If the actuator is designed without travel limitation, then manufacturing is simpler and more economical, but the service life of the parking lock device is reduced due to excessive loads
Solution Approach 1:
The actuation-travel-limiting unit is integrated directly into the actuator housing structure, merging the travel limitation function with the existing housing. This integration approach maintains manufacturing simplicity and economy while adding the critical service life protection feature, as the stop surface can be formed as part of the housing casting or machining process without requiring separate complex components.
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 solution extends the service life of the parking lock device by preventing excessive loads and maintaining the function of the parking lock, while also simplifying manufacturing and reducing the risk of damage to load-carrying actuator parts.
Implementation Method 1
pressure is supplied to the pressure chamber of the actuator, the pressure chamber being formed by the lateral surface of the housing bore together with the hydraulic piston. As a result, the hydraulic piston is axially displaced against the spring force of the engagement spring
Implementation Method 2
the hydraulic piston is axially displaced against the spring force of the engagement spring into its disengaged piston position
Implementation Method 3
The parking lock is engaged by the preloaded engagement spring
Data Source
AI summary
A parking lock device for an automatic transmission includes an actuator having a piston axially movable within an actuator housing between a first piston position and a second piston position. A guide section of the piston axially extends through an opening defined in the actuator housing, where a length of the piston extending outside of the actuator housing is longer when the piston is in the second piston position than when in the first piston position. An emergency actuation device is outside of the actuator housing and is operatively connectable with the piston such that the piston is movable by the emergency actuation device from the first piston position into the second piston position. An actuation-travel-limiting unit is contacted by the emergency actuation device to limit further axial displacement of the piston by the emergency actuation device beyond the second piston position.