Valf prujinasi ishlayotganda buralish ta'siriga duchor bo'lganligi sababli, uning aylana qismida kuchlanish taqsimoti notekis bo'ladi. Markazga yaqin joylashgan boshlang'ichdan chekkadagi har bir nuqtaga qadar kuchlanish asta-sekin o'sib boradi va sirtdagi kuchlanish kattaroqdir. Sirt nuqtalari nuqtai nazaridan, ijobiy ichki sirt ko'proq stressga duchor bo'ladi va tekislik kuchlanishiga duchor bo'ladi. Shu sababli, valf kamon yuzasi nuqsonli bo'lgandan so'ng, nuqsonda ko'proq kuchlanish kontsentratsiyasini hosil qilish mumkin, bu esa bahorning erta sinishiga olib keladi.
Vana kamonlarining sinishi sabablari, ishlab chiqarish nuqsonlari bilan bir qatorda, noto'g'ri foydalanish tufayli ularning erta shikastlanishiga olib kelishi mumkin. Eng keng tarqalgan sabablar quyidagilardir:
①There are pits and corrosion pits on the surface of the spring. Due to improper storage, corrosion pits will be formed on the surface of the spring. When the spring is subjected to a large torsion force, it is easy to cause stress concentration at the corrosion pit, which will eventually lead to fatigue fracture of the spring.
Yangi valf kamonining sifatini tekshirish usuli: kamonni skameykada kichik uzunlikka siqib qo'ying, shunda halqalar orasidagi bo'shliq imkon qadar ko'proq bo'lmaydi va uni 48 soat davomida ushlab turing. Agar bahor yuzasida nuqsonlar mavjud bo'lsa, bu siqilishdan keyin ishlov berishdan keyin buziladi. Buning sababi shundaki, buloqning ichki kuchlanishi nuqson yaqinida yuqori darajada to'plangan bo'lib, buloqning buzilishiga olib keladi.
Valf kamonining elastikligining kuchini taqqoslash usuli bilan aniqlash mumkin. Muayyan usul: birinchi navbatda, tekshirilishi kerak bo'lgan eski valf kamonini ketma-ket yangi valf kamoniga ulang va ularni po'lat yuvish vositasi bilan ajrating. Keyin valf kamoniga ma'lum miqdorda bosim qo'shing va eski va yangi buloqlarning siqilish darajasini kuzating. Qadimgi buloqning elastikligi etarli bo'lmasa, avval uni bosish kerak.
②The center line of the spring is skewed. If the two end faces of the valve spring are not perpendicular to the center line of the spring, the spring will work at high speed for a long time, and the metal material will be easily broken due to fatigue. The inspection method for the verticality of the valve spring is: first place the spring vertically on the flat plate, use a square to lean on the bottom of the spring, and then rotate the spring for a circle, and measure the greater value of the distance between the upper circle of the spring and the square. . Usually, the inclined distance of the valve spring to the vertical line is 1.0-1.5mm. If it exceeds this value, it is better to replace it with a new one.
③The valve guide is moving or the camshaft bearing is loose. If the valve guide moves during use, it may cause the valve spring to break due to the bending stress when it is compressed. Loose camshaft bearings can cause valve springs to resonate and cause them to break.
④ Improper operation or installation. During the operation of the diesel engine, if the rotational speed frequently changes suddenly, the frequency of the valve spring being compressed and stretched will suddenly increase sharply, resulting in its fatigue fracture.
⑤ The valve spring is not assembled as required. When assembling valve springs, some models have special requirements. For example, the Isuzu 6BBl diesel engine requires that the blue-coated side of the spring face the upper plane of the cylinder head. Otherwise, the spring is easy to break.
