Hydraulic Tensioner Spring Segmentation for Retainer Wear
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Solution Overview
Problem
Conventional hydraulic tensioners for timing chains suffer from wear and breakage of the check valve unit due to radial and axial expansion of the plunger-biasing spring, which restricts the spring's fit and increases production costs, especially under high load conditions.
Innovation Solution
A hydraulic tensioner design featuring a plunger-biasing spring with a close-wound portion that fits over the retainer without expansion or contraction, allowing reliable fitting and operation, and a portion with spaced windings that supports axial movement, enabling the use of larger wire diameters without modifying the retainer or ball seat, and allowing adaptation to higher loads through spring replacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the plunger-biasing spring is made to fit over the retainer with clearance, then the spring can be installed, but the spring cannot fit snugly and wear and breakage of the retainer occurs
Solution Approach 1:
The spring is divided into two distinct portions: a close-wound portion that fits over the retainer and a spaced-winding portion that provides biasing force. This segmentation allows each portion to serve its specific function optimally, with the close-wound portion providing a secure fit without clearance issues.
Solution Approach 2:
Different portions of the spring have different structural properties. The close-wound portion has tightly spaced windings for stable fitting over the retainer, while the spaced-winding portion has larger gaps to accommodate radial and axial expansion during operation.
2Ease of manufacture
If the retainer size is reduced to allow spring fit, then the spring can be installed, but the retainer becomes vulnerable to wear and breakage under high load
Solution Approach 1:
The spring structure is segmented so that the close-wound portion handles the fitting function over the retainer, while the spaced-winding portion handles the load-bearing function. This allows the retainer to be optimized for strength without being constrained by spring installation requirements.
Solution Approach 2:
The spring has localized different winding densities: tight windings where structural stability is needed (over the retainer) and spaced windings where flexibility and expansion room are needed (in the high-pressure chamber).
3Volume of moving object
If the spring inner diameter is made smaller to reduce size, then the spring is more compact, but it cannot fit over the retainer without clearance
Solution Approach 1:
The spring is segmented into a close-wound portion with smaller effective diameter for fitting over the retainer, and a spaced-winding portion that provides the necessary volume for compression and expansion during operation.
4Strength
If the spring is allowed to expand and contract radially and axially, then the spring can sustain high load, but the retainer experiences wear and breakage
Solution Approach 1:
The spring is divided into portions with different freedom of movement: the close-wound portion is constrained by the retainer to prevent excessive radial movement, while the spaced-winding portion is free to expand and contract axially to sustain load.
Solution Approach 2:
Different portions of the spring have different structural qualities: the close-wound portion provides structural stability and snug fitting, while the spaced-winding portion provides flexibility for expansion and contraction under load.
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
Prevents wear and breakage of the check valve unit, ensures reliable plunger biasing without retainer restraint, and allows adaptation to higher loads without increasing production costs, maintaining tension effectively in timing chains.
Implementation Method 1
A plunger-biasing spring, accommodated in the high pressure oil chamber, urges the plunger in a protruding direction
Implementation Method 2
Oil can flow through the check valve into the high pressure chamber R, but the check valve blocks reverse flow of oil
Data Source
AI summary
A hydraulic tensioner comprises a hollow plunger slidable in a plunger-accommodating hole in a housing, the plunger and housing forming a high pressure oil chamber. A check valve unit, which includes a check ball and a check ball retainer, allows oil to flow into the oil chamber, but prevents reverse flow. A plunger-biasing spring, disposed inside the high-pressure chamber includes a close-wound portion fitting over the retainer of the check valve unit, and a portion having spaced windings, which extends and compresses axially with protruding and retracting movement of the plunger. The outer diameter of the close-wound portion is greater than the outer diameter of the portion having spaced windings.