Convex Chain Guide Reducing Friction in Automotive Engines
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Solution Overview
Problem
In vehicle engine chain driving systems, increased engine speed leads to higher frictional resistance between the chain and the chain guide, resulting in deteriorated fuel consumption due to increased moment of inertia and driving torque, which existing chain guides fail to adequately address by minimizing the frictional force and oil film thickness.
Innovation Solution
A chain guide with a convex curved surface contact portion and increased oil groove thickness at both sides of the contact area, transitioning the friction condition from line contact to surface contact and enhancing oil film thickness, thereby reducing boundary frictional force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the contact surface area between the chain and chain guide is increased, then the oil film thickness can be maintained, but the frictional resistance increases leading to deteriorated fuel consumption
Solution Approach 1:
The chain guide surface is designed with different local properties: a convex curved contact portion with specific curvature radius to maintain oil film thickness, and oil grooves at specific locations to enhance lubrication. This local differentiation allows the surface to provide both adequate lubrication and reduced frictional resistance simultaneously.
Solution Approach 2:
The contact portion of the chain guide is formed as a convex curved surface with a specifically controlled curvature radius. This curvature design distributes the chain load more effectively, maintains adequate oil film thickness in the contact zone, and reduces the actual contact area compared to a flat surface, thereby lowering frictional resistance while ensuring proper lubrication.
2Productivity
If the engine speed is increased to improve productivity, then the power output increases, but the moment of inertia and driving torque increase leading to higher frictional resistance
Solution Approach 1:
Oil grooves are pre-formed on the chain guide surface at strategic locations before operation. These grooves ensure that oil is readily available in the contact zone from the start, maintaining adequate oil film thickness even at high engine speeds where centrifugal forces and increased loading would otherwise deplete the lubrication film and increase friction.
3Loss of energy
If the contact portion is designed to minimize frictional force, then energy loss is reduced, but the oil film thickness becomes insufficient leading to increased boundary friction
Solution Approach 1:
Oil grooves are introduced as intermediary structures that facilitate oil delivery to the contact portion. These grooves act as channels that ensure continuous supply of lubricant to the convex curved contact area, maintaining adequate oil film thickness and preventing boundary friction conditions even when the contact area is minimized for reduced frictional 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 solution effectively minimizes frictional force and energy loss by reducing the contact area and increasing oil film thickness, leading to improved fuel efficiency by reducing frictional resistance between the chain and the chain guide.
Implementation Method 1
reduces frictional force by making the contact portion that contacts the back of the chain in the chain guide have a convex curved surface
Implementation Method 2
increasing the thickness of an oil groove at both sides of the convex curved surface
Data Source
AI summary
A chain guide that contacts a chain connecting a cam sprocket and a crank sprocket, and has a contact portion contacting the back of the chain in a length direction of the chain and a convex curved line in a cross-section of the contact portion.