Worm Gear Reducer With Nonlinear Clamping Springs for Smooth Urging
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Solution Overview
Problem
The existing worm gear reducer in electric power steering devices faces challenges in smoothly performing the urging operation of the worm tip end portion while effectively suppressing the momentum of collisions between members in the third direction, due to conflicting requirements for the spring constant of the clamping plate springs.
Innovation Solution
The worm gear reducer incorporates a housing, a worm wheel, a worm, a support bearing, an elastic urging portion, and an elastic clamping portion with clamping plate springs that exhibit a non-linear spring characteristic, where the spring constant increases with deflection amount, including a third-direction component, to address the conflicting requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the spring constant of the clamping plate springs is made small to smooth the urging operation of the worm tip end portion, then the urging operation becomes smooth, but the momentum of collision between members in the third direction cannot be effectively suppressed
Solution Approach 1:
The clamping plate springs are designed with non-linear spring characteristics where the spring constant dynamically changes based on deflection amount. This allows the system to adapt its stiffness: softer during normal urging operation for smoothness, and stiffer during collision events for momentum suppression
Solution Approach 2:
The spring constant parameter of the clamping plate springs is designed to vary with deflection amount. By changing the physical parameter (spring constant) based on the operating condition (deflection magnitude), the system achieves both smooth operation and collision suppression without requiring separate mechanisms
2Reliability
If the spring constant of the clamping plate springs is made large to suppress the momentum of collision in the third direction, then the collision momentum is effectively suppressed, but the urging operation of the worm tip end portion becomes rough
Solution Approach 1:
The system transitions from a static spring constant to a dynamic one where the clamping plate springs become stiffer only when subjected to large deflections during collision events, while maintaining softness during normal operation for smooth urging
Solution Approach 2:
The physical parameter (spring constant) of the clamping plate springs is designed to change based on operating conditions. The non-linear spring characteristic ensures appropriate parameter values are automatically selected: low spring constant for smooth operation, high spring constant for collision suppression
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
This configuration allows for smooth urging operation of the worm tip end portion and efficient suppression of collision momentum in the third direction, thereby reducing abnormal noise and improving the overall performance of the worm gear reducer.
Implementation Method 1
the elastic clamping portion has a pair of clamping plate springs that are disposed on both sides of the radially inner side member in a third direction... each of the clamping plate springs exhibits a non-linear spring characteristic in which a spring constant increases as a deflection amount in a direction including a third-direction component increases
Implementation Method 2
an urging spring (elastic urging portion) that is provided between the outer fitting member and the worm accommodating portion. The urging spring is elastically deformed, and urges the outer fitting member toward a worm wheel side by an elastic restoring force of the urging spring
Data Source
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AI summary
This invention comprises an elastic propelling means (6) and an elastic grasping means (7). The elastic propelling means (6) propels an inner diameter-side member (5) toward a worm wheel (3) side. The elastic grasping means (7) has, in a section between the outer circumferential surface of the inner diameter-side member (5) and the inner circumferential surface of an outer diameter-side member (9), a pair of grasping flat springs (41) disposed on either side of the inner diameter-side member (5) in a third direction. Each of the grasping flat springs (41) exhibits a non-linear spring characteristic such as the spring constant increasing with an increase in the amount of deflection in a direction that includes a third direction component.