1. Asosiy tushunchalar
1. Rulman hayoti: rulman tarkibidagi har qanday tarkibiy qismdan oldin inqiloblarning umumiy soni yoki ma'lum bir tezlikdagi ish soatlari charchoqning tarqalishi va kengayish belgilarini ko'rsatadi.
Tarkiblarni ommaviy ishlab chiqarish, notekis material tufayli, rulman hayoti katta tarqalishga ega, eng uzoq va eng qisqa umr o'nlab martagacha, biz engish uchun statistik usullardan foydalanishimiz kerak.
2. Asosiy xizmat muddati: L10 (r) yoki L10h (h) belgisi bilan ifodalangan 90% ishonchlilik, tez-tez ishlatiladigan materiallar va ishlov berish sifati va normal ish sharoitida.
3. Asosiy nominal dinamik yuk (C): asosiy nominal hayot bir million aylanish (106) bo'lganida, u ko'tarishi mumkin bo'lgan doimiy yuk. Ya'ni, asosiy nominal dinamik yuk ta'sirida, rulman 106 ishlay oladi, uning ishlashida nosozliklar yuz bermaydi, uning ishonchliligi 90% ni tashkil qiladi. Asosiy nominal dinamik yuk katta, va rulmanning charchoqqa qarshi chidamliligi nisbatan kuchli.
4. Asosiy nominal statik yuk (radial C0r, eksenel C0a): bu xayoliy radial yuk yoki markaziy eksenel statik yukni eng yuqori ko'taruvchi yuk ko'taruvchi tanasi va rakeway o'rtasidagi aloqa markazidan kelib chiqadigan quyidagi aloqa stressiga tenglashtiradi.
Dizaynda rulmanli rulmanning uchta asosiy parametrlari tez-tez ishlatiladi: charchoqning ma'lum bir talablariga javob beradigan asosiy nominal dinamik yuk Cr (radial) yoki Ca (eksenel), asosiy nominal statik quvvat C0r (radial) yoki C0a (eksenel). ma'lum bir statik quvvat talablari va rulman aşınmasını boshqaruvchi chegara tezligi N0. C, C0, N0 rulman ishlash ko'rsatkichlarining barcha turlari tegishli qo'llanmani tekshirishi mumkin.
2. Hayotni tekshirishning hisoblash formulasi
Rulmanning ishlash muddati yuk ortishi bilan kamayadi. Hayot va yuk o'rtasidagi munosabatlar egri chizig'i FIGda ko'rsatilgan. 17-6 va egri tenglama
P epsilon L10 = doimiy
Bu erda, P - ekvivalent dinamik yuk, N; L10 - odatda 106r birliklarida hisoblangan asosiy hayot (L10 = 1 million million aylanish bo'lsa); - hayot ko'rsatkichi, rulman = 3, rulman = 10/3.
Qo'l bilan olingan asosiy nominal dinamik yuk C L10 = 1 ga asoslangan va ishonchlilik 90% ga teng. Shunday qilib, aylanish tezligining birligidagi L10 asosiy umrini rulmanning teng dinamik yuki P ga teng bo'lganida olish mumkin
C epsilon * 1 = P epsilon * L10
L10 = (C / P) epsilon 106 r (17.6)
Agar podshipnikning ish tezligi nr / min bo'lsa, soatlab hisoblangan asosiy hayotni olish mumkin
H (17.7)
L10 l boshidan katta yoki unga teng bo'lishi kerak. Lh '- bu rulmanning kutilayotgan xizmat muddati. Mashinaning kutilgan xizmat muddati odatda mukammal ta'mirlash davri deb nomlanadi.
Agar ekvivalent dinamik yuk P va rulmanning kutilayotgan xizmat muddati Lh 'ma'lum bo'lsa, tegishli hisoblangan nominal dinamik yuk C' quyidagi tenglamaga muvofiq olinishi mumkin, bu C ning qiymati bilan quyidagi tenglamaning talablariga javob berishi kerak. tanlangan rulman modeli
N (17.8)
3 teng dinamik yuk
Haqiqiy ish holatida, rulman ko'pincha bir vaqtning o'zida estrodiol radial va eksenel yuklarga duchor bo'ladi. Xuddi shu sharoitda asosiy nominal dinamik yukni haqiqiy yuk bilan taqqoslash uchun haqiqiy ish yukini ekvivalent dinamik yukga aylantirish kerak. Ekvivalent dinamik yuk ta'sirida, rulmanning umri haqiqiy qo'shma yuk ostida bo'lgani kabi bir xil bo'ladi. Ekvivalent dinamik yukni hisoblash formulasi P dir
P = XFr + YFa
Qaerda, fr-radial yuk, N; Faksial yuk, N; X, Y - radial dinamik yuk koeffitsienti va 17-7 jadvalda ko'rsatilgan eksenel dinamik yuk koeffitsienti.
Burchakli kontaktli rulmani yuklarni hisoblash
"3" va "7" podshipniklari uchun, o'zlarining tuzilish xususiyatlariga ko'ra, radial kuch hosil bo'lgan S hosil bo'lganda hisobga olinishi kerak.
1. Yig'ish shakli juft shaklda o'rnatilishi kerak: rasmiy (yoki "yuzma-yuz") - ikkala tulkaning orasidagi masofa qisqa; 17-7 a rasmda ko'rsatilganidek. Teskari o'rnatish (yoki "orqaga") - uzatish podshipniklarini o'rnatish uchun mos keladigan ikkita nuqta orasidagi uzoq masofa (17-7b-rasmga qarang).
2. Milga yuk ko'taruvchi kuchning harakatlanish nuqtasi
Eksa ustidagi burilish nuqtasi FIG da ko'rsatilganidek, normal chiziq va eksa, aylanma korpus va o'tish yo'li o'rtasidagi aloqa joyida joylashgan. 17-8. Rasmda tashqi chetidan masofa a ga teng bo'lib, uni qo'llanmada topish mumkin.
3. Eksenel kuchni hisoblash
Burchakli kontaktli rulmanning eksenel yukini tahlil qilishda bir vaqtning o'zida radial kuch va boshqa ishchi eksenel kuch tufayli kelib chiqqan qo'shimcha eksenel kuch hisobga olinishi kerak.
FR va FA millarga ishlaydigan radial va eksenel yuklardir, ikkita rulmanning radial reaktsiya kuchlari Fr1 va Fr2, mos ravishda hosil bo'lgan qo'shimcha eksenel kuchlar Fs1 va Fs2. Eksa bo'ylab harakat qiluvchi eksenel kuchlar FIGda ko'rsatilgan. 17-10.
Milya rulmanining muvozanat munosabatlariga ko'ra the, ikkita vaziyat bo'yicha, eksenel kuch bo'yicha tahlil:
- agar FS1 + FA & gt; Fs2 (17-11-rasm), mil o'ngga siljish moyilligini Ⅱ "bosimni", milning ko'tarilishida a muvozanatli reaksiya Fs2 yordamida amalga oshiradi, bunda rulmanning eksenel kuchi Ⅱ uchun
Fa2 = Fs2 + Fs2 '= Fs1 + FA
Additional faqat qo'shimcha eksenel kuchga, sababga ko'ra
Fa1 = FS1
- agar FS1 + FA22 (17-12-rasm), mil chapga siljish moyilligini namoyon qilsa, rulmani pressure "bosim" qiladi, bu safar milning chap uchi rulman a balansi reaktsiyasi bilan bo'ladi, bu esa mos ravishda rulman ustidagi eksenel kuchni ham hisoblashi mumkin
Fa1 = Fs1 + Fs1 '= Fs2 - FA
Fa2 = Fs2
The method to calculate the axial force of angular contact bearing can be summarized as follows: 1) determine the direction of the resultant force of all the axial forces on the shaft (including external load and additional axial force of the bearing), and determine the bearing at the "compression" end;2) the axial force of the bearing at the "compaction" end is equal to the algebraic sum of all the axial forces except the additional axial forces of the bearing itself;3) the axial force of the other bearing is equal to the additional axial force of the bearing itself.
Formula for calculating static load and limit speed
1.Static load calculation
Static load refers to the load applied on the bearing when the relative speed of the bearing ring is zero.In order to limit excessive contact stress and permanent deformation of rolling bearing under static load, static load calculation is needed.The bearing is selected according to the rated static load, and the basic formula is
C0 acuity C0 '= S0P0
Where, C0- basic rated static load, N;C0 '- calculation of rated static load, N;P0- equivalent static load, N;S0- safety factor.
For stationary bearings, slow oscillating bearings or bearings with very low speed, the safety coefficient can be selected according to table 17-9.
If the bearing speed is low and the requirements for running accuracy and friction torque are not high, it is allowed to have a large contact stress.1.Thrust centering roller bearing, whether rotating or not, should be S0≥4.
2.Limit speed
If the speed of rolling bearing is too high, high temperature will be generated between the friction surfaces, which will affect the performance of lubricant and damage the oil film, which will result in the failure of rolling body tempering or component bonding.
The ultimate speed N0 of rolling bearing refers to the speed value when the bearing reaches the maximum thermal equilibrium temperature under certain working conditions.The working speed of the bearing shall be lower than its limit speed.
Rolling bearing performance given in the table limit speed values are established in the grease lubrication and oil lubrication conditions, and applies only to a level 0 tolerance, lubrication cooling normal, cooperate with rigid bearing and shaft, bearing load P 0.1 C or less (C for bearing the basic dynamic load rating, centripetal bearing only by radial load, thrust bearing only by axial load) of the bearing.
Rulmanli yuklarni ko'tarishda P & gt; 0,1 s da kontaktli stress kuchayadi; Rulman qo'shma yukni ko'targanda, yuk ko'taruvchi rulman tanasi ko'payadi, bu esa rulmanning aloqa yuzasi orasidagi ishqalanishni kuchaytiradi va soqol holatini yomonlashtiradi. Bu vaqtda chegara tezligining qiymati qayta ko'rib chiqilishi kerak, haqiqiy ruxsat etilgan tezlik qiymati quyidagi formula bo'yicha hisoblanishi mumkin
N = f1f2N0
Bu erda, N - ruxsat etilgan haqiqiy tezlik, r / min; N0 - rulmanning eng yuqori tezligi, r / min; F1 - yuk koeffitsienti (17-13-rasm); F2 - yukni taqsimlash koeffitsienti.