Automotive Latch Single Motor Differential Gear
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Solution Overview
Problem
Current automotive tailgate or boot latches requiring power for both release and closure face inefficiencies due to the need for separate motors, complex geartrains, and lack of reversibility, leading to size, weight, and cost issues, as well as compromised speed and force requirements for rapid release and slow controlled closure.
Innovation Solution
A latch design utilizing a single electric motor with an intermediate gear assembly providing differential transmission ratios for rapid release and slow controlled closure, incorporating a worm gear for reversibility and a kick-start mechanism, allowing the same motor to operate in both directions without complex control systems or dedicated gear mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a single motor is used for both power release and power close, then size, weight and cost are reduced, but the speed of actuation for power release becomes too slow and/or the speed of actuation for power close becomes too fast
Solution Approach 1:
The patent applies dynamics by making the transmission ratio variable through a selectable geartrain mechanism. The system can switch between different gear ratios (e.g., 1:1 for release, 1:5 for close) depending on the operational mode, allowing the single motor to achieve both fast release and controlled slow closing without requiring multiple motors or complex control systems
2Weight of moving object
If a geartrain is used to reduce motor speed and increase torque for power close, then the motor size is reduced, but the mechanism becomes more complex and less reliable
Solution Approach 1:
The patent segments the geartrain into distinct selectable stages (first geartrain for release, second geartrain for close) that can be independently engaged. This segmentation allows each geartrain to be optimized for its specific function while keeping the overall system manageable through selective engagement rather than requiring a single complex multi-stage transmission for both operations
3Ease of operation
If a worm gear and wormwheel are used in the geartrain, then smooth and quiet operation is achieved, but the mechanism cannot be back-driven in case of power failure
Solution Approach 1:
The patent inverts the traditional worm gear configuration by using a wormwheel as the drive element and a worm gear as the driven element, with the worm gear capable of rotating in reverse. This inversion allows the mechanism to be back-driven when power fails, as the worm gear can rotate backward to release the latch, while still providing the smooth and quiet operation characteristic of worm drives during normal powered operation
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
Enables fast and reliable power release with slow, controlled closure using a single motor, reducing size, weight, and cost while ensuring mechanical operability in case of power failure, through a compact and economical design compatible with conventional motor control signals.
Implementation Method 1
a claw (2), which is spring-biased towards an unlatched position
Implementation Method 2
a single electric motor selectively drivingly coupled to the pawl and the claw
Implementation Method 3
an intermediate gear assembly connected to the motor and arranged to act on the pawl when the motor rotates in one direction and on the claw when the motor rotates in the opposite direction
Implementation Method 4
The intermediate gear assembly includes a worm gear in mesh with a worm wheel
Data Source
Figure 1~2
Figure 3
Figure 4a~4b
AI summary
A latch for an automotive closure comprises a claw (2), which is spring- biased towards the semi-latched position, for engaging a striker (15) fixed to the closure, a pawl (4) for latching open the claw (2) and a single electric motor (40) selectively coupled to the pawl to cause it to release the claw to open the latch, in one direction of rotation of the motor, and to claw to move it into the fully latched position, in the opposite direction of the motor.