Parking Pawl Actuation with Parallel-Axis Gears and Cam Locking
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Solution Overview
Problem
Existing non-back drivable actuation systems for vehicle parking mechanisms, such as those using worm gears, suffer from low efficiency and increased power consumption, leading to significant energy loss and higher operational costs.
Innovation Solution
A non-back drivable actuation system utilizing a parallel axis gear train with a drive pin eccentric to a final gear and a locking pin, which locks a lever arm in one of two distinct positions, allowing the pawl to be effectively engaged or disengaged with a parking gear using a small motor movement, thereby maintaining the desired position without back drivability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If worm gears are used to achieve non-back drivability, then the parking mechanism can maintain position reliably, but the system efficiency drops below 50% with significant energy loss
Solution Approach 1:
The patent replaces the traditional worm gear mechanical system with an electronic actuation system comprising an electric motor, parallel axis gear train, and cam mechanism. This substitution eliminates the inherent inefficiency of worm gears (below 50% efficiency) while maintaining the non-back drivable characteristic through the cam's geometric design that prevents reverse motion without requiring high friction engagement.
Solution Approach 2:
The invention changes the mechanical parameters of the transmission system by using a parallel axis gear train with specific gear ratios and a cam profile designed to provide non-back drivability. The cam mechanism transforms rotational motion into linear motion with controlled displacement, achieving reliable position holding with much higher efficiency than worm gears by utilizing precise geometric constraints rather than friction-based locking.
2Measurement precision
If worm gears are used for non-back drivable actuation, then positioning accuracy is maintained, but power consumption increases significantly
Solution Approach 1:
The electric motor coupled with the parallel axis gear train and cam mechanism replaces the worm gear system, reducing power consumption while maintaining positioning accuracy. The cam mechanism provides precise positional control through its geometric profile, ensuring the lever arm reaches exact engagement and disengagement positions without requiring excessive motor power.
Solution Approach 2:
The system uses periodic actuation where the motor rotates the cam through controlled angular displacements to achieve engagement and disengagement. The cam mechanism converts this periodic rotational motion into the required linear motion of the lever arm, maintaining precise positioning while minimizing energy consumption by acting only when state changes are needed rather than continuous power application.
3Ease of operation
If a motor is used to actuate the parking mechanism, then precise control is achieved, but the system complexity increases
Solution Approach 1:
The patent introduces an electric motor with electronic control to replace manual or mechanical actuation systems. This provides precise control of the parking mechanism engagement and disengagement through electrical signals, enabling accurate positioning and reliable operation. The parallel axis gear train and cam mechanism translate this electrical control into precise mechanical motion with minimal complexity addition.
4Loss of energy
If a small motor movement is used to transition the parking mechanism, then energy efficiency improves, but the force multiplication requirement increases
Solution Approach 1:
The cam mechanism dynamically transforms the small rotational movement of the motor into the required linear displacement of the lever arm. The cam profile is designed to provide mechanical advantage during the actuation stroke, multiplying the force from the small motor movement while maintaining energy efficiency. The parallel axis gear train further amplifies this force multiplication effect.
Solution Approach 2:
The cam mechanism utilizes curved surfaces and geometric profiles to transform rotational motion into linear motion with force multiplication. The cam's curved profile creates varying mechanical advantage during rotation, allowing small motor movements to generate the necessary force to engage and disengage the parking pawl while maintaining high energy efficiency.
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 ensures the vehicle remains stationary in park mode and prevents unintentional engagement when shifting out of park, while being cost-effective and efficient, as it requires less energy to transition between engaged and disengaged states.
Implementation Method 1
The drive pin may be coupled to a final gear of the gear train to drive the lever arm, the drive pin being eccentric to the final gear to generate a cam effect
Data Source
AI summary
Methods and systems are provided for an actuation system for a parking mechanism in a transmission system of a vehicle. In one example, a system may include an actuator coupled to a lever arm via one or more parallel axis gears, and a shaft connecting the lever arm to a pawl of the parking mechanism, the lever arm non-back drivable at each of a first state and a second state of the actuation system.