Check Valve Retainer Fatigue Failure Prevention
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Solution Overview
Problem
Conventional chain tensioners for automotive engines experience fatigue failure in the retainer due to high-frequency pressure fluctuations, leading to stress concentration and potential cracks at the punched section of the check valve retainer.
Innovation Solution
The retainer opening is formed by punching from inside to outside, with a ruptured surface located radially outwardly, and subjected to surface treatments like soft nitriding, carburizing/quenching, and shot peening to increase durability and fatigue strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the opening is formed by punching from outside to inside, then the manufacturing process is simple, but the ruptured surface is located radially inwardly causing stress concentration and fatigue failure
Solution Approach 1:
The patent inverts the conventional punching direction from outside-to-inside to inside-to-outside. This reversal changes the location of the ruptured surface from the radially inner portion to the radially outer portion, where stress is lower, thereby preventing fatigue failure while maintaining manufacturing simplicity
2Reliability
If the retainer is subjected to high-frequency pressure fluctuations, then the check valve functions to control oil flow, but stress concentrates at the radially inner portion causing fatigue failure
Solution Approach 1:
By inverting the punching direction, the ruptured surface is relocated from the high-stress radially inner portion to the low-stress radially outer portion, eliminating stress concentration at the critical border area while maintaining the check valve's pressure control function
Solution Approach 2:
The patent applies different surface treatments to different regions: the radially outer portion receives shot peening to induce compressive stress and prevent crack initiation, while the overall design ensures the ruptured surface is positioned in a low-stress region, creating local quality improvements where needed
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 modified retainer design minimizes stress concentration and enhances durability, with fatigue tests showing increased resistance to failure by up to 3.3 times compared to conventional designs, and further improvements with shot peening increasing fatigue strength by up to 10%.
Implementation Method 1
subjected to soft nitriding
Implementation Method 2
carburizing/quenching
Implementation Method 3
shot peening increasing fatigue strength by up to 10%
Implementation Method 4
the check ball of the check valve repeatedly collide against the bottom of the retainer, thus producing stress
Data Source
AI summary
A chain tensioner includes a plunger axially slidable in a cylinder to define a pressure chamber, filled with hydraulic oil, whose volume is variable upon axial plunger movement. A restricted passage defined between the plunger and the cylinder communicates the chamber with outside. A spring biases the plunger to increase the pressure chamber volume. An oil supply passage supplies oil to the pressure chamber and a check valve allows only oil flow into the pressure chamber, and includes an annular valve seat, a check ball movable into and out of contact with the valve seat, and a check ball retainer formed by drawing. The retainer includes a tubular portion with a bottom at one end. The tubular portion has an opening, formed by punching outwardly, through which oil can flow in and out. The opening extends to a border between the tubular portion and the bottom of the retainer.