Hydraulic Tensioner Bar Inside Coil Spring
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Solution Overview
Problem
Conventional hydraulic tensioners experience a delay in initiating damping action after engine start-up due to slow oil replenishment in the high pressure oil chamber, which can be mitigated by reducing the chamber volume, but this typically compromises the spring's load capacity and damping performance.
Innovation Solution
Incorporating a bar within the coil spring to reduce the volume of the high pressure oil chamber without altering the spring's length, thickness, or load capacity, and using a check valve to ensure rapid oil replenishment and prevent the bar from dropping out during assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the high pressure oil chamber volume is reduced to enable rapid oil replenishment, then the delay in damping action is reduced, but the spring's load capacity and damping performance are impaired
Solution Approach 1:
A bar is placed inside the coil spring, utilizing the internal space of the spring to reduce the high pressure oil chamber volume without affecting the spring's external dimensions or performance characteristics
Solution Approach 2:
The bar extends in the axial direction within the spring, utilizing the third dimension (length) to reduce chamber volume while maintaining the spring's radial and thickness dimensions that determine its load capacity
2Loss of time
If the high pressure oil chamber volume is reduced by shortening the spring or plunger stroke, then oil replenishment is faster, but the tensioner's load capacity and damping performance are reduced
Solution Approach 1:
The bar is nested within the coil spring, reducing chamber volume without altering the spring's length, thickness, or load capacity characteristics
Solution Approach 2:
The high pressure oil chamber is segmented into two parts: one portion filled by the spring and bar assembly, and another portion that maintains the necessary volume for proper tensioner operation and damping performance
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 allows for immediate initiation of damping action upon engine start-up with maintained performance equivalent to conventional tensioners, while simplifying assembly and ensuring the bar does not interfere with oil flow or spring extension/contraction.
Implementation Method 1
A coil spring is disposed within the high pressure oil chamber, and wound around the axis of the plunger-accommodating hole. The coil spring is in compression, and biases the plunger in its protruding direction.
Implementation Method 2
A check valve incorporated into the housing allows oil to flow into the high pressure oil chamber and blocks flow of oil out of the high pressure oil chamber.
Implementation Method 3
A bar, at least a part of which is located within said coil spring, reduces the volume of the high pressure oil chamber.
Implementation Method 4
oil in the high pressure oil chamber leaks through a slight clearance between the outer circumferential surface of the plunger 520 and the inner circumferential surface of the plunger-accommodating hole 511, and is discharged to the outside of the housing 510. Because of the viscosity of the oil, there is a resistance to flow through the clearance between the plunger and the plunger-accommodating hole. The resistance to flow enables the tensioner to exert a damping action
Data Source
AI summary
In a hydraulic tensioner having a coiled plunger-biasing spring, the volume of the high pressure oil chamber is reduced by incorporating a bar inside the spring. One of both ends of the spring are formed to block passage of the bar, so that the bar and spring can be installed as a pre-assembled unit, and dropping of the bar out of the spring can be avoided.