硕士学位毕业论文

硕士研究生：朱小汀

指导教师：沈斌 教授 

答辩时间：2015.03

摘要

轮式装载机是工程机械行业中使用频率和适用范围最高的工程机械之一，其液压系统的驱动通过变速箱的辅助动力输出结构（Power Take Off，简称PTO）实现。目前，世界上普遍使用的轮式装载机变速箱为单辅助动力输出结构；而中国市场现在提出了双辅助动力输出结构的要求。

因此，本文的重点是对一款轮式装载机变速箱进行改型设计，将该变速箱的单辅助动力输出结构改为双辅助动力输出结构。

论文的主要研究工作和成果有：

1.   针对客户要求，基于现有变速箱结构，提出了四个可行的解决方案。在进行初步设计时，重点考虑了以下两点：（1）避免PTO箱体与后箱体中部安装的液压控制模块发生碰撞；（2）双辅助动力输出所驱动的两个液压泵具备足够的轴距。

2.   在完成四个方案的设计之后，依据生产成本、客户要求等，通过使用“两两比对法”和“互补判断矩阵法”定义了评价体系；并对各方案进行量化考核，选出了最优解决方案。

3.   对遴选出的最优方案进行了详细的机械设计，其中包括：后箱体局部的改型设计，驱动轴的改型设计，箱盖的设计；在考虑机械结构合理性的同时，兼顾了PTO结构的润滑/冷却和密封。完成零部件的设计之后，对双辅助动力输出的装配过程进行了分析。此外，还验证了该PTO结构与另一款变速箱进行匹配的可能性。

4. 根据已知的载荷谱，对双辅助动力输出结构中的零部件进行了强度校核。校核结果如下：① 在将齿轮齿厚增加至25mm后，齿轮达到了8000h的疲劳寿命要求；② 轴承疲劳寿命远大于8000h；③轴满足许用安全值要求，且其弯曲刚度亦满足要求；④螺栓连接系统能够承担PTO结构的最大外载荷；⑤对箱盖进行有限元分析，模拟了箱盖在受极限载荷时的应力分布情况，其应力峰值远小于箱盖的许用应力。

关键词：变速箱，辅助动力输出，机械设计，强度校核，轮式装载机

 ABSTRACT

A wheelloader is one of the most widely and frequently used construction machine in the construction machinery industry. And its hydraulic system is driven by the Power-Take-Off-Structure. Normally, the transmission of a wheelloader is with one Power Take Off (PTO) worldwide. However, there is an increased demand for two PTOs in current Chinese market.

Thus the main focus of this thesis ist the redesign of a wheelloder transmission, in which a second Power Take Off is integrated into the transmission.

The main contents are summarized as follows:

Four possible solutions are put forward according to the requirements of the customers, which are all based on one already produced wheelloader transmission. The limited given design space due to the hydraulic controlling module on the housing and the distance between two pumps are taken into consideration.

All design concepts will be assessed with the utility analysis. In regard of the demands proposed by the customers and the production costs, a criteria system will be came up by using a pair-wise comparision. After the assessment, the best solution is the variation with the highest score.

Afterwards is the detailed construction of variation 3, which includes the redesign of the rear housing, the drive shaft, and the construction of the cover. The lubrication/cooling and the sealing of the PTO-structure are also considered during the design. Then the assembly process is roughly introduced. Furthermore, the possibility of the adaptation of the 2 PTOs onto a smaller transmission is also discussed in this thesis.

Based on a load spectrum from a wheelloader, the strenth of the designed components (gears, bearings and bolted connections) are calculated and approved. To widen is the thickness of the gears to reach the required fatigue life. The load capacity of the cover is proven with a FEM analysis.

Key Words: transmission, Power Take Off, construction, strength calculation, wheelloader