Park Lock Mechanism Cam Control for Driveline Immobilization
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Solution Overview
Problem
Existing park lock mechanisms for vehicle driveline components are susceptible to improvement as they can be inefficient in immobilizing the vehicle when parked, due to limitations in the engagement and disengagement of the dog ring and pawl mechanism.
Innovation Solution
A park lock mechanism incorporating a housing, dog ring, pawl, pawl spring, cam follower, cam, first actuator assembly, and second actuator assembly, which allows for precise control of the pawl's pivot position through a cam system, enabling effective engagement and disengagement of the dog ring's teeth to prevent or allow rotation, utilizing a lost motion coupling and loader mechanism for efficient operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a traditional dog ring and pawl mechanism is used for park lock, then the structure is simple, but the engagement and disengagement efficiency is poor
Solution Approach 1:
The patent applies dynamics by replacing the traditional direct engagement mechanism with a cam-based dynamic control system. The cam mechanism converts rotational motion into controlled linear displacement, enabling the pawl to dynamically engage and disengage from the dog ring teeth in a controlled manner, significantly improving engagement efficiency while maintaining manageable complexity through standardized cam profiles.
Solution Approach 2:
The cam mechanism serves as an intermediary between the actuator and the pawl engagement system. Instead of direct actuator-pawl connection, the cam translates actuator rotation into precise pawl displacement, mediating the force and motion transmission to achieve smoother and more reliable engagement while distributing mechanical stresses more effectively.
2Reliability
If the pawl is always engaged with the dog ring teeth, then the vehicle is securely immobilized, but the mechanism cannot allow rotation when needed
Solution Approach 1:
The cam mechanism enables dynamic control of pawl engagement state. By rotating the cam, the system can dynamically transition the pawl between engaged and disengaged positions, providing reliable immobilization when needed while allowing free rotation when the cam is positioned to disengage the pawl from the dog ring teeth.
Solution Approach 2:
The mechanism incorporates inherent feedback through the cam profile design, which automatically positions the pawl based on the cam's rotational state. The geometric relationship between cam rotation angle and pawl displacement provides automatic feedback control, ensuring the pawl is engaged when the vehicle should be immobilized and disengaged when rotation is permitted.
3Measurement precision
If a single actuator is used to control the cam, then the device complexity is reduced, but the control precision and reliability are insufficient
Solution Approach 1:
The control system is segmented into two independent actuator assemblies, each responsible for specific cam position control tasks. This segmentation allows each actuator to be optimized for its specific function, improving control precision while maintaining manageable complexity through modular design and independent operation of each actuator assembly.
Solution Approach 2:
The cam mechanism acts as an intermediary that translates actuator motion into precise pawl positioning. The cam profile geometry provides mechanical advantage and motion transformation, enabling high positioning precision even with relatively simple actuators, while the dual-actuator configuration with lost motion coupling provides redundant control capability for enhanced reliability.
4Manufacturing precision
If the cam mechanism is added to control pawl position, then the engagement precision is improved, but the device complexity increases
Solution Approach 1:
The cam mechanism provides dynamic control of pawl engagement position through its rotational profile. The cam geometry is designed to provide precise engagement positioning at specific rotation angles, enabling accurate control of when and how the pawl engages with the dog ring teeth, thereby improving manufacturing and engagement precision while the modular cam design keeps complexity manageable.
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 mechanism ensures reliable immobilization of the vehicle by precisely controlling the pawl's engagement with the dog ring's teeth, enhancing the efficiency and reliability of the park lock function.
Implementation Method 1
The cam follower is coupled to the pawl for movement therewith about the pivot axis. The cam is rotatable about a movement axis that is transverse to the pivot axis between a first cam position and a second cam position. The cam contacts the follower and includes a first cam portion and a second cam portion.
Implementation Method 2
The pawl spring biases the pawl toward the second pivot position.
Implementation Method 3
The lost motion coupling is configured to decouple the first output member from the coupling output within a predetermined range of motion of the coupling output relative to the first output member.
Data Source
AI summary
A park lock mechanism having first and second actuator assemblies for selectively moving a cam against a cam follower to engage a pawl to a dog ring. The first actuator assembly can be selectively operated to coordinate movement of the cam between first and second cam positions. The second actuator assembly can be selectively operated to drive the cam from the first cam position to the second cam position.