Resilient Ring Chain Tensioner for Engine Noise Reduction
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Solution Overview
Problem
Existing chain tensioner mechanisms experience excessive plunger retraction during engine start-up, leading to rattling and noise, and are complicated and costly due to the need for ratchet mechanisms that restrict movement to prevent excessive tension, which also restricts necessary retraction when chain tension increases.
Innovation Solution
A simplified chain tensioner design using a resilient ring with angled surfaces within a cylindrical plunger-accommodating hole, allowing controlled protruding and retracting movements by adjusting the angles of the surfaces, enabling the plunger to maintain adequate chain tension without excessive retraction at start-up and accommodating varying tension levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a ratchet mechanism is used to restrict plunger retraction during engine start-up, then rattling and noise are reduced, but the plunger cannot retract sufficiently when chain tension increases, leading to excessive chain tension and potential damage
Solution Approach 1:
The resilient ring provides dynamic, force-dependent engagement with the plunger grooves. At low forces (start-up), the ring engages the grooves to prevent excessive retraction and rattling. At high forces (excessive chain tension), the ring disengages from the grooves, allowing the plunger to retract and relieve chain tension. This dynamic behavior resolves the contradiction between preventing rattling and allowing necessary retraction.
Solution Approach 2:
The engagement force between the resilient ring and plunger grooves changes based on the applied load. The ring transitions from an engaged state (preventing retraction) to a disengaged state (allowing retraction) as the chain tension increases. This parameter change enables the mechanism to adapt its behavior to different operating conditions, resolving the contradiction between restricting and allowing plunger movement.
2Adaptability or versatility
If the ratchet mechanism is designed with a cam to allow plunger retraction under excessive tension, then chain tension is reduced, but the tensioner structure becomes complicated and assembly/maintenance becomes difficult
Solution Approach 1:
The cam mechanism is extracted and replaced with a simpler resilient ring that interacts directly with grooves on the plunger. The resilient ring's elastic deformation and engagement/disengagement behavior provide the necessary adaptability without requiring an external cam structure, thereby simplifying the overall tensioner design and reducing assembly complexity.
Solution Approach 2:
The functions of the cam and the ratchet mechanism are merged into a single resilient ring component. The ring simultaneously provides the ratcheting action (one-way engagement) and the cam-like function (allowing retraction under excessive load) through its elastic deformation and interaction with the plunger grooves, eliminating the need for separate cam and ratchet components.
3Adaptability or versatility
If the ratchet mechanism allows greater backlash to accommodate chain tension changes, then chain tension is reduced, but rattling increases during engine start-up
Solution Approach 1:
The resilient ring provides dynamic engagement that adapts to the magnitude of the applied force. During start-up when forces are low, the ring maintains firm engagement with the plunger grooves, minimizing backlash and preventing rattling. When chain tension increases significantly, the ring allows greater movement by disengaging from the grooves, thereby accommodating tension changes without causing rattling.
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 reduces production costs, minimizes backlash and rattling, and facilitates assembly and maintenance by allowing independent control of ratchet forces, ensuring the plunger maintains adequate chain tension while preventing excessive retraction and noise, thus optimizing the tensioner's performance and reducing operational noise.
Implementation Method 1
A plunger-biasing spring urges the plunger in a protruding direction
Implementation Method 2
a resilient ring within the tensioner housing for engaging surfaces of the grooves... ring is expandable into the annular groove
Implementation Method 3
The oil flows out of the high pressure oil chamber through a restricted space between the plunger and the wall of the plunger-accommodating hole... retraction of the plunger is controlled by hydraulic damping
Data Source
AI summary
In a chain tensioner, an expansible ring is disposed in an internal groove formed in the inner wall of a plunger-accommodating hole near an open end thereof. The ring cooperates with grooves formed on the plunger to exert a ratchet action. The relationship between the angles of the surfaces of the internal groove and the grooves on the plunger allows the plunger to protrude, restricts retraction of the plunger on start-up of a chain transmission, but allows retraction when chain tension becomes excessive. In one embodiment, in which the ring is a C-ring, the tensioner housing can be formed with external threads for mounting in a threaded hole on a timing chain cover or other engine part. In other embodiments, the ring can have externally protruding levers for manipulation of the ring.