Double Ratchet Vehicular Latch with Soft Reset
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Solution Overview
Problem
Double ratchet, double pawl vehicular latches are noisy during reset due to the hard stop encountered by the electromechanical actuator, especially when the vehicle door is open, as the noise of the gear train is not masked by the door opening.
Innovation Solution
A vehicle latch design that includes a ratchet, primary pawl, auxiliary ratchet, and secondary pawl, with a drive mechanism using a motor-driven cam and gear set to softly reset the latch by decelerating with an elastic member, eliminating the hard stop and noise, and incorporating a sensor to switch off the motor before full travel, allowing the gear chain to softly stop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If an electromechanical actuator is used to reset the secondary pawl and auxiliary ratchet, then the latch can be reset automatically, but a hard stop is encountered during reset operation causing noise
Solution Approach 1:
The patent introduces a cushioning element (spring or elastomeric material) positioned at the reset position of the auxiliary ratchet. This cushioning element absorbs the impact when the cam resets the auxiliary ratchet, preventing the hard stop that generates noise. The cushioning is built into the latch structure beforehand, specifically at the point where the cam interacts with the auxiliary ratchet during reset operation.
Solution Approach 2:
The patent introduces a cushioning element as an intermediary between the cam and the auxiliary ratchet. This intermediary absorbs the shock and impact during the reset operation, mediating the interaction between the moving cam and the stationary auxiliary ratchet, thereby eliminating the direct hard stop contact that produces noise.
2Object-generated harmful factors
If the cam continues to travel after actuating the auxiliary ratchet to enable the primary pawl, then the gear train can be softly decelerated, but the motor must be precisely controlled to switch off at the right moment
Solution Approach 1:
The patent incorporates a sensor that detects the position of the cam or auxiliary ratchet to provide feedback to the control system. This feedback mechanism allows the controller to know when the auxiliary ratchet has been actuated and when to switch off the motor, enabling precise control without complex synchronization mechanisms. The sensor provides real-time information about the state of the latch components.
3Object-generated harmful factors
If the hard stop is eliminated by allowing the cam to over-travel, then noise is reduced, but the motor travel distance increases
Solution Approach 1:
The patent allows the cam to perform a partial over-travel beyond the point where it first actuates the auxiliary ratchet. This excessive action is controlled and limited by the cushioning element, which absorbs the impact after a predetermined distance. The motor travels slightly farther than the minimum required, but this partial excessive action is acceptable because it eliminates noise and the cushioning element prevents damage.
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 reduces noise during the latch reset operation by decelerating the gear chain with a cushioning spring, eliminating impact noise and allowing for quiet operation without synchronization issues during door closure.
Implementation Method 1
the cam continues to travel in the second direction to load an elastic member, which decelerates the cam
Data Source
AI summary
A low release effort eccentric double ratchet, double pawl vehicle latch includes a ratchet, a primary pawl, an auxiliary ratchet and a secondary pawl. A drive mechanism including a gear cam wheel sequences movement of the secondary pawl to open and reset the latch. Upon reset, the drive mechanism actuates the auxiliary ratchet back to a closed state in a soft manner without using a hard stop; instead the latch has a cushioning spring that is used to softly stop the gear train during the reset absorbing motor energy and thus eliminating impact noise.