Electromagnetic Clutch Leaf Spring Low-Strength Portion Design
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Solution Overview
Problem
Existing electromagnetic clutches are prone to the armature falling outside when the leaf spring breaks due to excess load, caused by stress concentration at the rivet hole leading to cracking and detachment from the armature hub.
Innovation Solution
The design includes a leaf spring with a low-strength portion between the base and connecting piece, which deforms under stress, preventing the armature from falling by maintaining the stopper rubber member's contact with the armature, even if the leaf spring breaks, and features a flange with a triangular shape and semicircular notches to distribute stress and prevent rivet hole failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the stopper rubber member is formed in the stopper of the leaf spring to reduce the flange outer diameter, then the electromagnetic clutch becomes lighter and cheaper, but the armature may fall outside the clutch when the leaf spring breaks due to excess load
Solution Approach 1:
The patent applies local quality by creating a low-strength portion at a specific location (boundary between base and connecting piece) of the leaf spring. This localized weak point is designed to deform and break first under excess load, preventing stress concentration at the rivet hole and protecting the overall structural integrity needed to keep the armature contained.
Solution Approach 2:
The patent implements beforehand cushioning by designing the low-strength portion to deform and break in advance under excess load conditions. This preemptive failure mechanism absorbs the excess energy and prevents catastrophic failure at the rivet connection, ensuring the armature remains contained even when the leaf spring can no longer function.
2Strength
If the proximal end portion of the leaf spring is fixed to the armature hub by a rivet, then the leaf spring can be securely attached, but stress concentrates at the rivet hole causing cracking and breakage under excess load
Solution Approach 1:
The patent applies local quality by creating a low-strength portion at a specific location (boundary between base and connecting piece) of the leaf spring. This localized weak point is designed to deform and break first under excess load, preventing stress concentration at the rivet hole and protecting the overall structural integrity needed to keep the armature contained.
Solution Approach 2:
The low-strength portion acts as an intermediary element between the base and connecting piece. It serves as a sacrificial component that deforms and breaks under excess load, protecting the rivet connection and other critical parts from stress concentration and catastrophic failure.
3Weight of moving object
If the flange outer diameter is made smaller than the armature inner diameter to reduce weight, then the electromagnetic clutch becomes lighter, but the armature is not supported by the flange when the leaf spring breaks
Solution Approach 1:
The patent applies local quality by creating a low-strength portion at a specific location (boundary between base and connecting piece) of the leaf spring. This localized weak point is designed to deform and break first under excess load, preventing stress concentration at the rivet hole and protecting the overall structural integrity needed to keep the armature contained.
Solution Approach 2:
The patent implements beforehand cushioning by designing the low-strength portion to deform and break in advance under excess load conditions. This preemptive failure mechanism absorbs the excess energy and prevents catastrophic failure at the rivet connection, ensuring the armature remains contained even when the leaf spring can no longer function.
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 effectively prevents the armature from falling outside the clutch even when the leaf spring is broken, ensuring reliable operation by distributing stress and maintaining the stopper's contact with the armature, thus enhancing the clutch's durability and stability.
Implementation Method 1
an electromagnetic coil configured to generate a magnetic flux, and magnetically attract the armature to the first rotary member against the spring force of the leaf spring
Implementation Method 2
a leaf spring configured to connect the armature to the flange, and bias the armature away from the first rotary member by a spring force
Implementation Method 3
When power supply to the electromagnetic coil is stopped, the armature is separated from the rotor by the spring force of the leaf spring, and abuts against the stopper rubber member and stops
Data Source
AI summary
An electromagnetic clutch includes an armature to be attracted to a rotor, an armature hub formed on one end portion of a rotating shaft, and a leaf spring which connects the armature to the armature hub and biases the armature away from the rotor. The leaf spring includes a base fixed to the armature hub, a stopper connected to the base, and a connecting piece surrounding the stopper by projecting outside from the base, and fixed to the armature. A through hole into which a rivet for fixing the base to the armature hub is inserted is formed in the base. A low-strength portion having strength lower than that in the periphery of the through hole is formed in a boundary portion between the base and a connecting portion.