Door Latch Device with Integrated Waterproof Circuit Board
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Solution Overview
Problem
Existing door latch devices face issues with long-term lock mechanism functionality due to grease hardening and rust, require multiple components and complex mounting processes, and lack sufficient waterproofing, leading to durability concerns and restricted component arrangement.
Innovation Solution
A door latch device design that integrates a motor-driven cam wheel for single-motor operation of the lock mechanism, incorporates a waterproof circuit board housing with external and internal seals, and simplifies the component layout to enhance durability and waterproofing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the lock mechanism is maintained in the locked state for long periods without operation, then security is improved, but grease hardens and rust occurs causing the mechanism to fail when needed
Solution Approach 1:
The cam wheel is designed to automatically rotate periodically even when the door is locked, causing the lock mechanism to cycle between locked and unlocked states. This periodic action prevents grease from hardening and prevents rust by keeping moving parts in constant motion, ensuring the mechanism remains reliable after long periods of door inactivity
Solution Approach 2:
The lock mechanism temporarily discards its locked state to transition to an unlocked state during the cam wheel rotation, then recovers the locked state. This temporary state change allows maintenance of the mechanism without requiring the door to be physically opened or closed, preventing deterioration while maintaining security
2Reliability
If the circuit board is housed separately in a waterproof ECU, then waterproofing is improved, but the number of components and mounting steps increases
Solution Approach 1:
The circuit board is integrated directly into the door latch device housing rather than being housed separately in a waterproof ECU. This merging eliminates the need for separate waterproof ECU housing, harness connections, and additional mounting steps, while the integrated design incorporates waterproof seals and structures that provide sufficient waterproofing protection
Solution Approach 2:
The door latch device housing serves multiple functions: it houses the mechanical latch mechanism, provides structural mounting on the vehicle door, and incorporates waterproof sealing structures that also protect the integrated circuit board. This multi-functionality eliminates the need for a separate waterproof ECU housing
3Device complexity
If a single motor is used to operate both the latch release and lock mechanism, then device complexity is reduced, but the mechanism must be designed to perform multiple functions
Solution Approach 1:
The cam wheel is designed as a multi-functional component that performs three distinct functions: releasing the latch mechanism by engaging with release levers, operating the lock mechanism by engaging with lock levers, and providing periodic motion to prevent grease hardening and rust. This universal design allows a single motor to control all functions through one cam wheel, reducing device complexity while maintaining full functionality
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 ensures smooth lock mechanism operation, improves durability by preventing rust and grease issues, and achieves comprehensive waterproofing of the circuit board, reducing component complexity and mounting steps.
Implementation Method 1
The cam wheel is held at a reference position by energizing force of a neutral return spring
Implementation Method 2
an external waterproof seal disposed between the case and the second cover, and configured to waterproof the second housing space against outside; and an internal waterproof seal disposed between the pin holder and the pin hole, and configured to waterproof a space between the first housing space and the second housing space
Data Source
AI summary
A door latch device includes: an electric component including a motor; a machine mechanism; a circuit board; a case; a first cover forming a first housing space in which the motor and the machine mechanism are housed; a second cover forming a second housing space in which the circuit board is housed; a pin hole disposed in the case to establish communication between the first housing space and the second housing space; a pin erected from the circuit board to project to the first housing space through the pin hole; a pin holder configured to support the pin with respect to the circuit board by covering a periphery of a base of the pin; an external waterproof seal configured to waterproof the second housing space against outside; and an internal waterproof seal configured to waterproof a space between the first housing space and the second housing space.