Damperli Bir Vites Değiştirme Mekanizmasının Mekanik Modellemesi ve Dinamik Yönden İncelenmesi

Öz

Kara taşıtlarında motordan vites kutusuna aktarılan dönme hareketinin hızı ya da torku yol şartlarına göre farklı oranlarda değiştirilerek diferansiyele iletilmektedir. Dönme hareketinin hızını ya da torkunu değiştirmek gerektiğinde farklı dişli çarkların birbirine kenetlenmesi gerekmektedir. İki dişli çarkın birbirine kenetlenebilmesi için önce çevresel hızlarının eşitlenmesi gerekmektedir. Bu işlem senkronizasyon olarak adlandırılmakta olup senkronizasyon işini yapan mekanizmalara senkromeç denilmektedir. Sekromeçler kinetik enerjiyi sürtünme yolu ile ısıya dönüştürerek sürtünen parçalar arasındaki açısal hız farkını yok eden mekanik sistemlerdir. Bu çalışmada öncelikle dört ileri ve bir geri hız değişimi sağlayan bir vites kutusu mekanizmasının tasarımı yapılmıştır. Mekanizmada yarıçapı 35 mm olan tek halkalı bir senkronizasyon mekanizmasının kullanılması kararlaştırılmıştır. Böyle bir sürtünme halkasına tepe değeri 300 N’dan daha fazla olan bir harmonik kuvvet fonksiyonunun uygulanması gerektiği belirlenmiştir. Bu kadar büyük bir kuvvet ancak damperli bir senkronizasyon mekanizması ile sağlanabilmektedir. Çalışmanın devamında damperli bir senkronizasyon mekanizmasının matematik modeli kurularak, gerçekçi verilere göre boyutlandırılması yapılmıştır. Boyutlandırma yapılırken grup dişlinin hızının 2400 rpm’den 1263 rpm’e düşürüldüğü, yavaşlayan elemanlarının toplam kütle atalet momentinin 0.00508 m2 kg olduğu ve birinci vitesten ikinci vitese geçiş yapıldığı kabul edilmiştir. Tasarlanan senkronizasyon mekanizmasında damper sabiti 14000 Ns/m olarak kabul edilir, toplam sürtünme periyodu 0.25-0.35 s aralığında değiştirilirse 4-4.5 Nm civarında bir sürtünme torku yaratarak vites değiştirme işini sorunsuz gerçekleştirebilmektedir. Tasarlanan mekanizmanın mevcut vites mekanizmalarında kullanılmakta olan birden çok sürtünme halkasına sahip senkronizasyon tertibatlarına ve bloklama halkası olarak adlandırılan tertibatlara olan gereksinimi yok edebileceği görülmektedir.

Anahtar Kelimeler

• Vites kutusu
• Damperli senkromeç
• Bilyeli tetikleme düzeneği
• Sürtünmeli kavrama
• Bloklama halkası

Mechanical Modeling And Dynamic Investigation of A Gear Shift Mechanism With Damper

Öz

In road vehicles, the speed or torque of the rotational motion transferred from the engine to the gearbox is changed at different rates according to road conditions and transmitted to the differential. When it is necessary to change the speed or torque of the rotational motion, different gears must be interlocked. In order to interlock two gears, their peripheral speeds must first be equalized. This process is called synchronization and the mechanisms that perform the synchronization are called synchromeshes. Synchromeshes are mechanical systems that eliminate the angular speed difference between the frictioning components by converting kinetic energy into heat through friction. In this study, first of all, the design of a gearbox mechanism providing four forward and one reverse speed changes was performed. It was decided to use a single-ring synchronization mechanism with a radius of 35 mm in the mechanism. It was determined that a harmonic force function with a peak value of more than 300 N should be applied to such a friction ring. Such a large force can only be provided by a synchronization mechanism with a damper. After that a mathematical model of a damperical synchronization mechanism was established and dimensions of synchronization mechanism were determined. During dimensioning, it was assumed that the speed of the counter shaft gear was reduced from 2400 rpm to 1263 rpm, the total mass moment of inertia of the decelerating elements was 0.00508 m2 kg and the shift was made from the first to second gear. When the damping constant is taken to be 14000 Ns/m the designed synchronization mechanism can perform the gear shifting within 0.25-0.35 s by creating a friction torque of around 4 Nm. It is seen that the designed mechanism can eliminate the need for multi-ring synchronization mechanisms and blocking ring mechanisms used in existing gear mechanisms.

Anahtar Kelimeler

• Gearbox
• Damperical synchronizers
• Ball type trigger mechanism
• Frictional clutch
• Blocking ring

Kaynakça

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