Perpendicular Motor Webbing Take-up Device for Compact Seatbelt Retractor
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Solution Overview
Problem
Conventional motor retractors for seat-belt webbing take-up devices are bulky and unbalanced, making them inefficient in terms of space and weight distribution, and require complex arrangements for gear ratios and mechanisms.
Innovation Solution
A compact webbing take-up device design where the motor is positioned between leg plates with a perpendicular rotation shaft, a clutch is integrated between the motor and take-up shaft, and a worm gear system allows for efficient transmission of rotational force while preventing reverse rotation, enabling easy adjustment of gear ratios and improving weight balance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the motor is disposed at the outer side of the frame and at the upper side or lower side, then the clutch can be positioned opposite the take-up shaft end portion, but the entire body of the motor retractor becomes large and the weight balance becomes bad
Solution Approach 1:
The motor is repositioned from the conventional outer side/upper-lower side arrangement to an intermediate position between the pair of leg plates. The rotation shaft of the motor is arranged perpendicular to the take-up shaft, utilizing the three-dimensional space within the frame structure. This dimensional reconfiguration allows the motor to be compactly integrated without increasing the overall device volume while maintaining proper clutch engagement with the take-up shaft.
2Ease of operation
If the motor is disposed at the outer side of the frame, then the clutch can be disposed at the outer side of the leg plate, but the weight balance of the motor retractor becomes bad
Solution Approach 1:
The motor is positioned asymmetrically within the frame structure, specifically between the pair of leg plates rather than at the outer side. This asymmetric placement optimizes the weight distribution and moment of inertia of the rotating assembly, improving the weight balance and dynamic characteristics of the motor retractor while still allowing the clutch to function properly at the appropriate location.
3Ease of manufacture
If a conventional motor retractor structure is used, then the clutch and motor can be disposed, but it is difficult to change and set gear ratio and rotational speed
Solution Approach 1:
The motor positioning between the leg plates with perpendicular shaft arrangement creates a flexible mechanical architecture. This configuration allows for easier modification of the gear train and transmission components, enabling adjustment of gear ratios and rotational speeds to optimize webbing take-up characteristics for different applications. The intermediate motor position provides better access for maintenance and modification compared to the conventional outer-side mounting.
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 results in a more compact, balanced, and efficient webbing take-up device that can easily adjust webbing take-up characteristics, reducing the overall size and weight while maintaining effective operation.
Implementation Method 1
a worm gear which is disposed with its own shaft being disposed parallel to the rotation shaft of the motor and which is removably connected to a final spur gear of the motor gear portion; and a worm wheel which is disposed coaxially with the take-up shaft, which meshes with the worm gear to transmit rotation force of the worm gear to the clutch
Data Source
AI summary
A webbing take-up device (10, 100) is disclosed, wherein a motor (44) is provided directly below a take-up shaft (20) between a pair of leg plates (16, 18) with a rotary shaft (50) of the motor (44) disposed perpendicularly to the take-up shaft (20), and a clutch (26) is provided at one side of one leg plate (16). Further, a gear (76) of a motor gear portion (46) is removably connected to a worm gear (34) in a clutch gear portion (28), and a mounting stay (84) is detachably attached to a case (30) with screws (86), so that the motor (44) and the motor gear portion (46) can be detached independently of the case (30) while still being assembled together. Still further, a pretensioner mechanism (156) and a sensor mechanism (182) are provided at one end side of a spool (118), and an urging mechanism (136) is disposed at the other end side thereof.