Starter Device Damper Spring with Asymmetric Cross Section
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Solution Overview
Problem
Starter devices for internal combustion engines with circular cross-sectional damper springs are insensitive to dirt but have a small section modulus against bending, requiring a larger outer diameter for the same spring constant, while rectangular cross-sectional springs are more robust but prone to dirt accumulation.
Innovation Solution
A starter device with a damper spring where at least a portion of the spring wire's cross section on the outer side runs straight, increasing the section modulus and allowing a smaller outer diameter, and the inner side is rounded to prevent dirt accumulation and promote elasticity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a circular cross-section spring wire is used, then the starter device is insensitive to dirt, but the section modulus against bending is small requiring a larger outer diameter
Solution Approach 1:
The spring wire cross-section is designed with non-uniform properties: the inner side (facing the stud) has a rounded cross-section to prevent dirt accumulation and allow self-cleaning, while the outer side has a straight cross-section to maximize the section modulus against bending. This local differentiation resolves the contradiction by optimizing each surface for its specific functional requirement.
2Strength
If a rectangular cross-section spring wire is used, then the section modulus against bending is increased, but dirt accumulation occurs on the inner side
Solution Approach 1:
Instead of using a uniform rectangular cross-section, the invention applies local quality by rounding only the inner side of the spring wire cross-section while keeping the outer side straight. This selective modification maintains the high section modulus benefit of rectangular sections while eliminating the dirt accumulation problem on the inner side through the rounded geometry that prevents particle trapping.
3Strength
If a larger outer diameter is used, then the section modulus against bending is increased, but the weight of the starter device increases
Solution Approach 1:
The invention changes the geometric parameters of the spring wire cross-section from a conventional circular or uniform rectangular shape to an asymmetric shape with a rounded inner side and straight outer side. This parameter modification optimizes the distribution of material to maximize the section modulus for a given outer diameter, thereby achieving the required bending strength without increasing the overall diameter and weight of the starter device.
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 provides a robust and lightweight starter device with improved dirt resistance and elasticity, maintaining damping characteristics while reducing weight and avoiding damage from inner edges.
Implementation Method 1
the cross section of the spring wire on the inner side of the spring wire is rounded... the attachment and compaction of dirt deposits on the inner side of the spring wire, and on the outer side of the at least one stud on which the damper spring is mounted, is avoided
Implementation Method 2
at least a portion of the cross section of the spring wire on the outer side of the spring wire runs straight... the section modulus of the spring wire against bending is increased
Implementation Method 3
a damper spring is arranged in operative connection between the entrainer and the actuating device... promoting a slight deformation of the stud, whereby a higher elasticity of the arrangement is achieved
Implementation Method 4
a damper spring is arranged in operative connection between the entrainer and the actuating device
Data Source
AI summary
A starter device for an internal combustion engine has an entrainer for coupling to the engine. The entrainer and an actuator of the starter device are mounted rotatably about a rotational axis. A damper spring is arranged between and operatively connects the entrainer and the actuator to each other. The starter device has at least one stud, on whose outer periphery the damper spring is mounted. The damper spring is a hinge spring wound from a spring wire. The cross section of the spring wire is rounded on the inner side of the spring wire. At least a portion of the cross section runs linearly on the outer side of the spring wire.