Compression Release Mechanism Reducing Weight via Camshaft Force Transmission
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Solution Overview
Problem
Existing compression release mechanisms for internal combustion engines are bulky and heavy due to the need for a support pin with high rigidity to transmit the urging force of a valve spring, which increases the size and weight of the mechanism.
Innovation Solution
A compression release mechanism with a camshaft, lever, support shaft, and spring, where the urging force of the valve spring is applied to the inner peripheral surface of the camshaft, reducing the force on the support shaft and allowing for a thinner, lighter design by using a centrifugal weight and abutment portion to change the lever's position and transmit force rectilinearly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the support pin is designed with high rigidity to transmit the urging force of the valve spring, then the reliability of force transmission is improved, but the size and weight of the compression release mechanism increase
Solution Approach 1:
The patent introduces a force transmission channel formed by the camshaft body and lever that acts as an intermediary structure. Instead of relying solely on the support pin to transmit the valve spring's urging force, the force is transmitted through the camshaft body via the force transmission channel, which has higher rigidity and can bear larger loads without increasing the support pin's dimensions.
Solution Approach 2:
The patent transitions from a point-contact force transmission system (through the support pin) to a distributed force transmission system (through the camshaft body's force transmission channel). The abutment surface distributed over the camshaft body's inner peripheral surface allows force to be transmitted across a larger area and through multiple structural pathways, effectively utilizing the camshaft body's overall rigidity rather than concentrating the load on a single pin.
2Strength
If the support pin thickness is increased to enhance strength for transmitting valve spring force, then the strength is improved, but the size of the compression release mechanism increases
Solution Approach 1:
The camshaft body serves as an intermediary structure that assumes the primary load-bearing function. The force transmission channel within the camshaft body provides a rigid pathway for force transmission, eliminating the need to increase the support pin's thickness to achieve sufficient strength.
Solution Approach 2:
The patent merges the force transmission function into the camshaft body structure itself. The camshaft body and lever together form an integrated force transmission system where the camshaft body's structural strength is utilized to transmit the valve spring's urging force, rather than relying on a separate, thickened support pin.
3Ease of operation
If the lever is positioned to transmit urging force through the support pin, then the force transmission path is established, but the support pin must be made thicker increasing overall mechanism weight
Solution Approach 1:
The camshaft body acts as an intermediary with higher rigidity than the support pin. The force transmission channel in the camshaft body provides a more efficient pathway for transmitting the valve spring's urging force to the lever, eliminating the weight penalty associated with a thickened support pin.
Solution Approach 2:
The patent changes the force transmission from a one-dimensional path through the support pin to a two-dimensional distributed transmission through the camshaft body's inner peripheral surface. This allows force to be transmitted more efficiently across a broader structural basis, improving transmission efficiency without increasing component weights.
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 mechanism is reduced in size and weight, allowing for more efficient engine starting and reduced vibrations, while maintaining the necessary strength and functionality without increasing the size or weight of the support shaft and camshaft.
Implementation Method 1
a centrifugal weight 22 on which centrifugal force that moves the lever 20 toward the second position is exerted in accordance with rotation of the camshaft 10
Data Source
AI summary
A compression release mechanism including a camshaft, a cam provided on the camshaft and protruding outward in a radial direction of the camshaft, a lever, of which a portion is disposed in the camshaft, a support shaft supporting the lever such that the lever is swingable between a first position and a second position relative to the camshaft, and a spring attached to the camshaft, to urge the lever toward the first position. The lever includes a cam portion configured to protrude out from the camshaft with the lever at the first position, a centrifugal weight for moving the lever toward the second position in accordance with rotation of the camshaft, and an abutment portion configured to be in abutment with an inner peripheral surface of the camshaft with the lever at the first position, and be located away from the inner peripheral surface with the lever at the second position.