Spiral bevel gear is one of the main parts of machine parts, which is used for motion and power transmission. The development process of spiral bevel gear can be roughly divided into two categories. One is that the gear industry has determined the development direction of arc gear system. During this period, the machining machine bed of arc gear system mainly comes from import, while a large number of extended epicycloid gear machine tools are introduced. The other is that with the improvement of production efficiency of spiral bevel gear, the product quality has been greatly improved.
Gear transmission, as a traditional and efficient transmission form, has appeared a long time ago. With the progress of science and technology, a series of gear transmission forms have emerged, and corresponding gear meshing theory, design and processing methods have been formed. All these work enrich and develop the theoretical system of gear transmission.
As a kind of gear, spiral bevel gear is widely used in all kinds of machinery. In the drive axle of automobile, spiral bevel gear is indispensable for the automobile with longitudinal engine. Spiral bevel gear is used for the transmission between intersecting shafts. The single-stage transmission ratio can be up to 6, and the maximum transmission efficiency can be up to 8 or above. The transmission efficiency is generally 0.94-0.98. Because the design, manufacture and installation of spur and helical bevel gears are simple, but the noise is large, they are used for low-speed transmission (< 5m / s), the transmission power of spiral bevel gear can reach 370kW, and the peripheral speed is 5m / s. The bevel gear drives smoothly and has high load-carrying capacity. Therefore, according to the characteristics of spiral bevel gears, they are generally used in high-speed and heavy load situations. It is divided into straight bevel gear and spiral bevel gear. The manufacturing technology of spiral bevel gear plays an important role in automobile manufacturing industry.
The main functions of spiral bevel gear in automobile are as follows:
- The power output by the engine is transmitted to the driving wheel through the gearbox and the main transmission;
- Change the direction of rotation output by the longitudinally configured engine, so that the driving wheel can obtain a rotation movement consistent with the driving direction of the vehicle;
- Reduce the rotation speed of the engine output, increase the torque of the engine output, and make the driving wheel obtain enough traction.
The automobile industry usually calls the spiral bevel gear as the reduction gear, and the assembly composed of it is called the reducer assembly. CA1092 automobile adopts double pole main transmission, one pair of spiral bevel gears realizes the first level deceleration, one pair of spiral cylindrical gears realizes the second level deceleration.
There are four speed ratios of spiral bevel gears: 11:25, 12:25, 13:25, 9:25
There are two speed ratios for helical gears: 14:47 and 15:46
The drive axle consists of four speed ratios:
25/1147/14=7.63，25/1246/15=6.39，25/1346/15=5.897，25/947/14=9.33。
The driving condition of the car changes rapidly with the external conditions, so the working condition of the spiral bevel gear is extremely complex. The linear speed of spiral bevel gear of medium-sized truck can be up to 17m / s, which requires the tooth surface to have wear resistance, impact resistance and bending resistance. It is usually required that the tooth surface has high hardness and the center has good willfulness.
Based on the analysis of the driving wheel of spiral bevel gear in CA1092 automobile drive axle, the machining process specification of automobile spiral bevel gear and the design of special machine fixture are carried out. In this paper, the conventional design method is used, the general machine tool and the general fixture are used, and only the fixture for gear milling is designed. There is no innovation in this paper, but through this design to sort out the knowledge learned, combine theory with practice.