Multi-Pawl Park Lock Torque Distribution
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Solution Overview
Problem
Existing park lock mechanisms are upstream of the final drive ratio, resulting in reduced torque, which can be insufficient for electric axles with park lock mechanisms on output shafts.
Innovation Solution
A multi-pawl park lock design featuring a gear wheel with a castellated outer diameter, two rotatable pawls, and strut rods connected to an actuation ring, allowing the pawls to engage and disengage with the gear wheel's teeth to prevent or permit rotation, utilizing strut springs for enhanced torque handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-pawl park lock mechanism is used upstream of the final drive ratio, then the device complexity is reduced, but the torque handling capability deteriorates
Solution Approach 1:
The park lock mechanism is divided into multiple independent pawls (first pawl and second pawl) that operate in parallel. Each pawl engages with separate castellations on the gear wheel, distributing the torque load across multiple engagement points. This segmentation allows the mechanism to handle higher torque loads while maintaining a relatively simple overall structure.
Solution Approach 2:
Multiple pawls are combined within a single actuation system that operates upstream of the final drive ratio. The actuation ring simultaneously controls both the first and second pawls through interconnected strut rods, merging the function of multiple locking elements into one coordinated mechanism. This combining approach increases torque capacity without proportionally increasing actuation complexity.
2Ease of operation
If the park lock mechanism is placed upstream of the final drive ratio, then the ease of operation is improved, but the torque on the park lock deteriorates
Solution Approach 1:
The torque load is segmented across multiple pawl-tooth engagements rather than concentrated on a single pawl. This distribution allows the mechanism to operate with simpler actuation forces while collectively bearing higher total torque loads that would be excessive for a single-pawl design.
3Force
If multiple pawls are used to increase torque handling, then the torque handling capability is improved, but the device complexity increases
Solution Approach 1:
Multiple pawls are merged into a single actuated system where the actuation ring and interconnected strut rods coordinate the movement of both pawls simultaneously. This merging reduces the need for separate actuation mechanisms for each pawl, thereby limiting the increase in overall system complexity despite the addition of multiple locking elements.
Solution Approach 2:
The actuation ring serves multiple functions: it actuates both the first and second pawls, provides the locking action for both engagement points, and maintains the relative positioning of the strut rods. This multi-functionality reduces the need for additional components that would otherwise be required to control multiple independent pawls.
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 multi-pawl park lock effectively manages torque by engaging and disengaging with the gear wheel's teeth, ensuring reliable operation even in high-torque applications, such as electric axles.
Implementation Method 1
the first strut rod includes a first strut spring, and the second strut rod includes a second strut spring. The first strut spring is compressed when the actuation ring is rotated in the first rotational direction and the first tooth is aligned with one of the protrusions
Implementation Method 2
the first strut spring is arranged to further rotate the first pawl after a rotation of the gear wheel that aligns the first tooth with a one of the pockets
Data Source
AI summary
A multi-pawl park lock includes a gear wheel, an actuation ring, a first pawl, a second pawl, and first and second strut rods. The first pawl includes a first tooth and the second pawl includes a second tooth. The strut rods connect the actuation ring to respective pawls. The actuation ring is arranged to rotate in a first rotational direction to rotate the first pawl about a first pawl axis and engage the first tooth with the gear wheel, and rotate the second pawl about a second pawl axis and engage the second tooth with the gear wheel, preventing rotation of the gear wheel. The actuation ring is also arranged to rotate in a second rotational direction, opposite the first rotational direction, to rotate the first pawl and disengage the first tooth, and rotate the second pawl and disengage the second tooth, permitting rotation of the gear wheel.