Webbing Retractor Clutch Mechanism for Spring Load Alleviation
Solution Overview
Problem
Existing webbing retractors with reducing balance springs face increased cost and weight issues due to the need to prevent buckling at the inner end of the spring, which affects the urging force and overall functionality.
Innovation Solution
A webbing retractor design that includes a spool, a retracting spring, a first rotating body, a clutch member, a second rotating body, a reducing balance spring, and a regulating member, where the clutch member's pressure contact with the first rotating body is loosened by the reducing balance spring's urging force, offsetting the retracting spring's urging force and alleviating the load on the reducing balance spring without increasing cost or weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a reducing balance spring is used to reduce the urging force of the retracting spring, then the pressure on the occupant is reduced, but the inner end of the reducing balance spring buckles outward requiring additional cost and weight for prevention
Solution Approach 1:
A clutch member is introduced as an intermediary between the reducing balance spring and the first rotating body. The clutch member selectively transmits or blocks the urging force based on operational conditions, allowing the reducing balance spring to function without directly causing buckling issues while maintaining force reduction benefits
Solution Approach 2:
The clutch member dynamically adjusts the transmission of urging force from the reducing balance spring to the first rotating body. During webbing payout, the clutch member engages to transmit force; during retraction, it disengages to prevent buckling and unnecessary load, making the system adaptive rather than static
2Strength
If the reducing balance spring is designed to prevent buckling, then structural integrity is maintained, but cost and weight increase
Solution Approach 1:
The clutch member serves as a mediator that protects the reducing balance spring from conditions that would cause buckling. By controlling when the spring's force is transmitted to the rotating body, the clutch member prevents structural integrity issues without requiring the spring itself to be over-engineered for buckling resistance
Solution Approach 2:
The problematic function of preventing buckling is extracted from the reducing balance spring and assigned to the clutch member instead. This allows the spring to be designed for its primary function (force reduction) while the clutch member handles the secondary function of preventing structural failure, reducing overall weight
3Reliability
If the clutch member maintains constant pressure contact with the first rotating body, then reliable force transmission is achieved, but the reducing balance spring cannot effectively offset the retracting spring's urging force
Solution Approach 1:
The clutch member transitions from a static constant-pressure design to a dynamic variable-pressure design. It automatically adjusts its pressure contact with the first rotating body based on the operational state: maintaining contact during webbing payout for reliable force transmission, and releasing contact during retraction to allow the reducing balance spring to effectively offset the retracting spring's urging force
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 effectively reduces the feeling of pressure on the occupant by offsetting the retracting spring's urging force with the reducing balance spring's force, maintaining the balance without exceeding a predetermined magnitude, thus alleviating the burden on the reducing balance spring and preventing excessive weight and cost increments.
Implementation Method 1
a reducing balance spring that has one end engaged with the second rotating body, urging force of the reducing balance spring increasing by the one end rotating in an orientation corresponding to rotation of the spool in the retraction direction with respect to another end of the reducing balance spring
Implementation Method 2
a clutch member that is provided at the first rotating body in a state in which the clutch member is elastically in pressure contact with the first rotating body, and that rotates together with the first rotating body
Data Source
AI summary
A webbing retractor that can alleviate the load on a reducing balance spring without increasing cost and weight is obtained. When a ring inertially rotates in a retraction direction together with a ratchet gear, a ring-side pressing portion of a load receiving portion accommodating portion formed in the ring presses a spring-side load receiving portion of a clutch spring in the retraction direction. Due to this, the clutch spring is loosened, whereby the ring can easily inertially rotate in the retraction direction together with the ratchet gear, and the load acting on a reducing balance spring can be alleviated.