Vehicle Door Latch Eccentric Pawl Torque Control
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Solution Overview
Problem
Existing vehicle door latches require high energy to release the striker from the ratchet, resulting in excessive user effort and increased motor energy consumption, and generate an unpleasant 'pop noise due to rapid transition from closing to opening positions.
Innovation Solution
A latch design featuring a ratchet and two pawls, where the second pawl eccentrically rotates to gradually increase the opening torque, allowing for a smooth transition from the closing to the opening position, reducing the energy required and minimizing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single pawl is used to hold the ratchet in the closing position, then the structure is simple, but the energy required to release the striker is high and the operation is difficult
Solution Approach 1:
The single pawl is divided into two separate pawls: a first pawl that holds the ratchet in the closing position and a second pawl that assists in the release process. This segmentation allows each pawl to perform a specific function, reducing the overall effort needed while maintaining structural simplicity.
Solution Approach 2:
The second pawl acts as an intermediary element between the release lever and the ratchet. It receives the force from the release lever and transmits it to the ratchet in a controlled manner, facilitating the transition from closing to opening position with reduced effort.
2Speed
If the ratchet transitions quickly from closing to opening position, then the release is fast, but unpleasant pop noise is generated
Solution Approach 1:
The release process is divided into two distinct phases: first, the second pawl moves to disengage from the ratchet, and second, the ratchet transitions to the opening position. This periodic action allows the system to control the transition speed and reduce noise by avoiding a single rapid movement.
Solution Approach 2:
The second pawl performs a preliminary action by disengaging from the ratchet before the ratchet itself transitions to the opening position. This preliminary disengagement prepares the system for a quieter, more controlled transition, reducing the pop noise that would otherwise occur.
3Reliability
If friction is present during pawl-ratchet sliding movement, then the connection is stable, but the energy required for release is considerably high
Solution Approach 1:
The sliding friction between the pawl and ratchet is replaced with a rolling contact mechanism. The second pawl rotates about a second axis distinct from the first axis, converting sliding friction into rolling friction, which significantly reduces the energy required for release while maintaining connection stability.
Solution Approach 2:
The contact between the second pawl and the ratchet is designed with curved surfaces that enable rolling motion. This curvature allows the pawl to rotate smoothly about the second axis, reducing friction and energy consumption during the release process.
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 design reduces the energy needed to release the striker, lowers the noise associated with the release, and makes the latch more user-friendly and cost-effective by minimizing motor requirements.
Implementation Method 1
a second pawl which cooperates with the first pawl, cooperates with the ratchet at least in a contact point (P) at least when the ratchet is in the closing position, and which is rotatable about a second axis (D) distinct from the first axis (B) so that the second pawl may eccentrically rotate with respect to the first axis (B)
Implementation Method 2
The line (L) being arranged relative to the first axis (B) in such a position that the force (F) generates an opening torque (T2) on the first pawl directed in the first rotation direction when the second pawl is in the intermediate position
Implementation Method 3
The line (L) being characterized in that the distance of the line (L) from the first axis (B) increases, along an end portion of the first stroke, so that the force (F) generates onto the first pawl an increasing opening torque (T2) directed in the first rotation direction
Data Source
AI summary
A latch for a door of motor vehicle having a closing assembly adapted to cooperate with a latch striker comprising: a ratchet which can assume an opening position, in which ratchet enables engagement and disengagement between latch striker and a seat of ratchet, and a closing position, in which ratchet holds latch striker within seat; a first pawl rotatable about a first axis (B) and in a first rotation direction from a coupled position, in which it keeps, at least indirectly, ratchet in closing position and prevents disengagement of striker from seat, and a decoupled position, in which it permits the movement of ratchet from closing position to opening position; and a second pawl which cooperates with first pawl, cooperates with ratchet at least in a contact point (P) at least when ratchet is in closing position, and which is rotatable about a second axis (D) distinct from first axis (B).