Depac Mechanical Seal,Depac Seal,Vulcan Mechanical Seals,Ksb Mechanical Seal Shanghai Enactus Industrial Co., Ltd. , https://www.enactuseal.com
When designing a valve spring, minimizing vibration is crucial, and the natural frequency of the spring plays a key role in this process. The transition from positive to negative inertial forces creates the most significant fluctuation, which can lead to system detachment if not properly managed. To prevent this, the spring force must be greater than the inertial force caused by the system's vibration, with an additional safety margin. This ensures that the valve remains in contact with the cam throughout all operating conditions.
The point where the spring’s load curve intersects the inertial force curve is critical. At this point, the spring’s length corresponds to the vertical line on the inertial force diagram. The spring’s load characteristic curve must be steep enough so that even under vibration, the load generated by the spring remains higher than the inertial load. This is especially important at maximum engine speed, where the valve system must not detach. Additionally, the spring must have sufficient force to close the valve without causing valve rebound. It is generally recommended that the elastic force of the spring should be at least 30% greater than the inertial force.
To address these challenges, many automotive and motorcycle engines use variable pitch valve springs. These springs are designed to optimize performance across different operating conditions. There are two main types: one-end variable pitch springs, where the pitch increases from one end to a certain point before becoming constant, and symmetrical variable pitch springs, where the pitch increases from both ends toward the center.
As vehicle performance improves, the materials used for valve springs must meet higher standards. They need high tensile strength, good heat resistance, and strong anti-relaxation properties. Oil-quenched alloy spring steel wire, often made from low-silicon, chromium-containing carbon steel, is cold-drawn and then continuously quenched and tempered. Surface imperfections such as dents, scratches, decarburization, or non-metallic inclusions can significantly reduce the spring’s lifespan. Japan has set strict standards for surface quality. Modern oil-hardened steel wires have slightly modified compositions, such as adding small amounts of nickel, to slow crack propagation and improve durability. Common materials include 50CrVA, 60SiZCIA, 60SiZCrVA, and 55Crsi.
In addition to material improvements, profiled valve spring wires have been developed to enhance fatigue resistance. These include oval sections with straight lines, circular sections, multi-arc ovals, and elliptical shapes. Japanese manufacturers now widely use special-shaped cross-sections (such as elliptical or egg-shaped) in valve spring production. During manufacturing, special tools like adjustable guide plates and coil pins are used to ensure precision. Surface hardness after soft nitriding should exceed 90Hv, and if internal hardness is insufficient, shot peening and heat setting techniques are applied to improve durability.