KISSsoft를 이용한 정유압 기계식 변속기 주축 베어링의 최적 설계에 관한 연구

Abstract

Hydro-mechanical transmission has the advantage of maximizing the efficiency of power transfer by utilizing hydraulic power favorable to high torque in the low speed area to increase mobility at low speed and by using a lot of machine power in the high speed area. Hydro-mechanical transmission continuously combines the flow of mechanical and hydraulic power, resulting in the synthesized power flowing out to the output shaft. In this process, the main shaft is subjected to different directions and force loads depending on the hydrostatic transmission operation, which affects the life of the bearing supporting the load. Currently, hydro-mechanical transmission is designed by applying the load on each bearing at the maximum theoretical value per bearing, resulting in a somewhat excessive bearing selection. Therefore, in this study, we will interpret the safety factor, rating life, shaft bending of the currently manufactured hydro-mechanical transmission main shaft bearings as KISSsoft, and then proceed with the optimal design. Summarizing the results of the existing Hydro-mechanical transmission simulation conducted in this study, in all sections with Hydro-static unit exclusion volumes of +50cc/rev to -50cc/rev, each bearing safety factor is 5.22 to 316.37, exceeding the target safety factor of 1.25 so it is considered that the bearing of the Hydro-mechanical transmission is designed safely. The rating life of the bearing also exceeded the Hydro-mechanical transmission target rating life of 5,000 hours, and it is judged that the rating life of the bearing also satisfies the target. However, the existing safety factor and rating life expectancy are conservative and judged to be somewhat excessively designed. Through KISSsoft simulation analysis, 11 of the 12 bearings were changed to bearings with a smaller size than before, and the safety factor and rating life were also reduced, but it was interpreted that the design reference safety factor was 1.25 or more and the rating life was 5,000 hours or more. In addition, bending support bearings were applied to the maximum shaft bending point to alleviate the shaft bending of the existing Hydro-mechanical transmission, reducing the maximum shaft bending value by about 80% from 0.0891mm to 0.0171mm based on +50cc/rev – 2 stage through KISSsoft simulation analysis. In this study, the main shaft bearing of the Hydro-mechanical transmission for tractors was improved using KISSsoft. Using the Hydro-mechanical transmission optimal design results derived in this study, it will be applied to actual Hydro-mechanical transmission products.