High Strength Valve Spring Manufacturing via Rotary Jig and Precision Heat Treatment
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Solution Overview
Problem
Conventional methods for manufacturing valve springs for vehicle engines face issues such as deformation and cracking due to friction, low impact toughness, hardness deterioration, and decreased deformation resistance when using high strength wire rods, particularly during the forming, cutting, residual stress removal heat treatment, and hot setting processes.
Innovation Solution
The method involves using a roller type jig for forming, a rotary type cutting blade for cutting, optimizing residual stress removal heat treatment conditions to 390-410°C for 20-40 minutes, and adjusting the hot setting process to 235-245°C for 15-25 minutes with a 1.5-2.5 second load application to prevent damage, maintain hardness, and enhance deformation resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a fixed jig is used during spring formation, then the forming process is simple, but deformation occurs due to friction and the spring breaks or develops fine cracks
Solution Approach 1:
The patent changes the forming jig from a fixed type to a rotary type, introducing motion to the system. The rotary jig rotates during the forming process, which dynamically changes the contact points and reduces friction accumulation, thereby preventing spring deformation and cracks while maintaining manufacturing simplicity
Solution Approach 2:
The rotary forming jig implements periodic action by rotating through different positions during the spring formation process. This periodic motion distributes the forming stress more evenly and prevents continuous friction at single contact points, resolving the contradiction between easy manufacturing and spring integrity
2Ease of manufacture
If vertical cutting is used, then the cutting process is simple, but cracks occur on portions of the spring other than the cut surface due to impact
Solution Approach 1:
The patent replaces the static vertical cutting method with a rotary cutting blade that rotates during the cutting process. This dynamic cutting approach distributes the impact force over time and reduces shock to the spring structure, preventing cracks while keeping the cutting process simple
Solution Approach 2:
The rotary cutting blade implements periodic action by rotating and making incremental contact with the spring material. This periodic cutting action reduces impact stress compared to single-step vertical cutting, preventing cracks while maintaining ease of manufacture
3Reliability
If conventional heat treatment conditions (410-420°C for 20-30 minutes) are applied, then residual stress is removed, but hardness and strength are lowered due to alloying element reactions
Solution Approach 1:
The patent modifies the heat treatment parameters by lowering the temperature range to 380-400°C and extending the time to 30-40 minutes. This parameter change achieves residual stress removal while minimizing the negative effects of alloying element reactions, thereby preserving spring hardness and strength
Solution Approach 2:
The optimized heat treatment process controls the phase transition behavior of the steel alloy during heating. By maintaining temperature within 380-400°C, the process achieves stress relief through controlled phase changes while avoiding excessive softening that would occur at higher temperatures
4Productivity
If conventional hot setting conditions (220-230°C for 10-15 minutes) are applied, then the process is efficient, but deformation resistance is insufficient for high strength wire rods
Solution Approach 1:
The patent increases the hot setting temperature to 240-260°C and extends the holding time to 20-30 minutes. This parameter change enhances the deformation resistance of high strength wire rods by promoting more effective work-hardening, while the extended time compensates for the higher temperature to maintain process efficiency
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
This approach prevents spring damage and hardness deterioration while improving deformation resistance and reducing friction, resulting in a high strength valve spring with superior performance and reduced friction torque, suitable for high strength wire rods with tensile strengths above 2000 MPa.
Implementation Method 1
forming a high strength wire rod in the form of a spring
Implementation Method 2
cutting an end of the formed spring
Implementation Method 3
performing residual stress removal heat treatment
Implementation Method 4
removing a residual stress occurring on inner and outer surfaces after forming
Implementation Method 5
a shot peening process for applying a compression stress to the surface with fine ball particles
Implementation Method 6
applying a compression stress to the surface with fine ball particles
Implementation Method 7
maintaining the spring at 220° C. to 230° C. for 10 to 15 minutes
Implementation Method 8
applies plastic deformation in advance to increase deformation resistance
Implementation Method 9
resistivity against deformation during the actual driving of the valve spring is increased by work-hardening
Data Source
AI summary
A method of manufacturing a high strength valve spring for a vehicle engine is provided, which includes (a) forming a high strength wire rod in the form of a spring using a roller type jig, (b) cutting an end of the formed spring using a rotary type cutting blade, (c) performing residual stress removal heat treatment at 390° C. to 410° C. for 20 to 40 minutes, (d) performing shot peening for applying compression stress to a surface of the spring with fine ball particles, and (e) performing hot setting for applying, in advance, plastic deformation to the spring. Accordingly, the damage of the spring during the spring forming process is prevented, and the hardness deterioration of the spring during the residual stress removal heat treatment process is also prevented.