Engine Chain Tensioner with Dynamic Backlash Control
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Solution Overview
Problem
Conventional tensioners face issues with knocking noises at engine start-up and excessive chain tension during operation, requiring precise machining and increased production costs, and often result in severe friction and noise due to reliance on frictional forces for backlash control.
Innovation Solution
A tensioner design featuring a plunger with an open rear side, a housing with an oil pressure chamber, a resilient ring engaging with an outer circumferential groove, and a ring control mechanism that adjusts backlash through a front-side and rear-side restriction mechanism, allowing for reduced backlash at start-up and increased backlash during engine operation, eliminating the need for high biasing forces and precise machining.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the amount of backlash of the ratchet mechanism is set small, then the knocking noises at start-up are reduced, but the plunger may seize or the chain may run with excessive tension during engine operation
Solution Approach 1:
The patent applies a biasing unit that dynamically adjusts the backlash amount of the ratchet mechanism. During engine start-up, the biasing unit maintains small backlash to reduce knocking noises. During engine operation, when oil pressure increases, the biasing unit allows the plunger to move, increasing backlash to prevent plunger seizure and excessive chain tension. This dynamic adjustment resolves the contradiction between reducing noise and preventing seizure.
Solution Approach 2:
The patent changes the backlash parameter of the ratchet mechanism based on operating conditions. The biasing unit modifies the engagement between the resilient ring and engaging grooves by applying force to the plunger, thereby changing the backlash amount from small (at start-up) to large (during operation). This parameter change allows the system to avoid both knocking noises and plunger seizure under different conditions.
2Adaptability or versatility
If the amount of backlash is set large, then the plunger can accommodate chain tension changes, but the knocking noises at start-up increase
Solution Approach 1:
The biasing unit dynamically controls the backlash amount based on oil pressure conditions. At start-up when oil pressure is low, the biasing unit maintains small backlash to reduce knocking noises. During operation when oil pressure increases, the biasing unit allows plunger movement that increases backlash, enabling the system to accommodate chain tension changes from temperature variations and load changes.
Solution Approach 2:
The system changes the backlash parameter from small to large based on operating conditions. The biasing unit applies force to the plunger to modify the engagement state of the ratchet mechanism, thereby adjusting the backlash amount to be small at start-up (reducing noise) and large during operation (improving adaptability to chain tension changes).
3Manufacturing precision
If precise machining is used to control backlash amount, then the backlash control is accurate, but the production cost increases
Solution Approach 1:
The patent replaces the conventional approach of controlling backlash through precise machining of the ratchet mechanism with a mechanical substitution using a biasing unit. Instead of relying on tight tolerances and precise manufacturing, the biasing unit actively controls the backlash amount through applied force. This substitution allows for larger tolerances in manufacturing while achieving accurate backlash control, thereby reducing production costs.
Solution Approach 2:
The patent changes the method of backlash control from geometric parameters (machined dimensions) to force parameters (biasing unit force). By using the biasing unit to apply controlled force to the plunger, the system achieves precise backlash control through force management rather than dimensional precision, simplifying manufacturing requirements and reducing production costs.
4Reliability
If a high biasing force is applied to the plunger, then the backlash is controlled effectively, but severe friction occurs between the chain and tensioner lever
Solution Approach 1:
The biasing unit applies a dynamic force to the plunger that is sufficient to control backlash but not excessive to cause severe friction. The force is optimized to maintain reliable engagement of the resilient ring with the engaging grooves during normal operation while avoiding excessive friction between the chain and tensioner lever. This dynamic force application resolves the contradiction between effective backlash control and friction reduction.
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 reduces knocking noises at start-up, prevents excessive chain tension, and lowers production costs by simplifying the structure and eliminating the need for precise machining, while ensuring stable operation and reduced friction and vibration during engine running.
Implementation Method 1
a main biasing unit that biases the plunger toward the front side
Implementation Method 2
a hydraulic damping effect achieved by supplying oil into an oil pressure chamber formed between the plunger and a housing hole
Implementation Method 3
a resilient ring having a ring-like part that is disposed on an outer circumference of the plunger and engages with an engaging groove formed on an outer circumferential surface of the plunger
Data Source
AI summary
To provide a simple-structured tensioner that generates less knocking noise at the start-up of the engine and that prevents an excessive chain tension, severe friction, noise or vibration during the running of the engine, while also reducing production costs. The tensioner includes a ring control mechanism that controls the position of a resilient ring. The ring control mechanism includes a front-side restricting part having a front-side restricting surface and capable of restricting forward movement of the resilient ring, and a rear-side restriction member having a rear-side restricting surface and capable of restricting rearward movement of the resilient ring. The front-side restricting part is fixed to or formed integrally with the housing. The rear-side restriction member is disposed movable in a front to back direction relative to the housing and the plunger.