Parking Lock Actuator With Radial Blocking for Reliable State Detection
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Solution Overview
Problem
Existing parking lock systems in automatic transmissions face challenges in accurately determining the engaged or disengaged state due to issues like chip-induced misalignment and friction, leading to unreliable sensor readings, and often lack the necessary installation space for limit switches.
Innovation Solution
A device with a piston guided in a cylinder, actuated by a spring and radially displaceable blocking elements, which are form-lockingly fixed in different positions to represent engaged and disengaged states, allowing for accurate sensor differentiation and adaptation to account for manufacturing tolerances, using an actuation element with specific geometric features to ensure unambiguous locking conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a PNP sensor is used to detect the parking lock piston position, then the sensor can provide a signal, but the sensor reading becomes unreliable due to chip-induced misalignment and friction causing the piston to not reach end positions
Solution Approach 1:
A blocking device with radially displaceable blocking elements is introduced as an intermediary mechanism between the piston and the sensor system. This blocking device form-lockingly fixes the piston in defined positions (engaged and disengaged), ensuring that the piston reaches precise end positions that can be reliably detected by the sensor, thereby eliminating the unreliability caused by chips and friction
Solution Approach 2:
The blocking elements change their radial position (parameter) to either block or release the piston movement. When radially displaced outward, they form-lockingly fix the piston in specific positions, ensuring precise parameter values for piston position that enable reliable sensor detection, overcoming the parameter variability caused by contamination and friction
2Measurement precision
If a limit switch is used to accurately determine parking lock state, then measurement accuracy improves, but installation space requirements increase which is not available in the compact actuator
Solution Approach 1:
The blocking device is merged with the existing piston-cylinder actuator system. The blocking elements are radially displaceable within the compact actuator structure and work in conjunction with the piston, combining the actuation function and the positioning function in a single integrated component without requiring additional installation space for separate limit switches
Solution Approach 2:
The blocking elements utilize radial displacement (a different dimension from the axial piston movement) to achieve the locking function. By moving radially outward, the blocking elements engage with the piston to form-lockingly fix it in position, enabling precise position determination without requiring additional axial or lateral space that would be needed for conventional limit switches
3Measurement precision
If the piston is form-lockingly fixed in defined positions by radially displaceable blocking elements, then position determination accuracy improves, but the device complexity increases
Solution Approach 1:
The blocking device serves multiple functions: it form-lockingly fixes the piston in defined positions for accurate sensor detection, ensures reliable parking lock state determination, and maintains compatibility with the existing sensor system. This multi-functionality justifies the added complexity by delivering multiple benefits from a single integrated component
Solution Approach 2:
The blocking elements are nested within the actuator structure, radially displaceable within the cylinder assembly. The blocking device is integrated into the existing piston-cylinder arrangement, with the blocking elements able to move radially to engage or release the piston, creating a compact nested structure that minimizes space requirements while achieving the positioning function
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
This solution enables precise determination of the parking lock system's state, ensuring accurate engagement and disengagement detection, and provides a structurally simple means to differentiate interlocking conditions, enhancing sensor accuracy and reliability.
Implementation Method 1
The blocking elements are radially displaceable by an actuation element (17)
Implementation Method 2
The piston (3) is hydraulically displaceable counter to the spring force of an actuation spring (4)
Implementation Method 3
counter to the spring force of an actuation spring (4)
Data Source
AI summary
A device (1) for actuating a parking lock device (2) of an automatic transmission includes a piston (3) guided in a cylinder (5) and hydraulically displaceable counter to a spring force of an actuation spring (4). The piston (3) is form-lockingly fixable in a first position and in a second position by radially displaceable blocking elements (26) of a blocking device (15). The blocking elements (26) are radially displaceable by an actuation element (17). The radial displacement path of the blocking elements (26) and an operating condition of the actuation element (17) corresponding thereto in the first position of the piston (3) deviate from the radial displacement path of the blocking elements (26) and the operating condition of the actuation element (17) corresponding thereto in the second position of the piston (3).