Service conditions and performance requirements of the driving spiral bevel gear of the loader

1. Service conditions of driving spiral bevel gear parts

Gears play the role of transmitting power and changing speed in the working process of loaders. There are rolling and sliding between meshing tooth surfaces, and the root of teeth is also affected by pulsating or alternating bending. Under the action of all kinds of stress caused by this, the gear will be broken, glued, fatigued and worn. The main stresses causing gear failure are friction, contact stress and bending stress. According to the form and reason of gear failure, the choice of gear material and heat treatment method should be considered from the following aspects: (1) the surface of gear has enough hardness. The tooth surface is actually uneven, so there will be a lot of local pressure, causing metal plastic deformation or embedded in the relative surface, leading to metal direct contact and adhesion. When the meshing tooth surface is relatively sliding, there will be friction. Tooth surface wear is the result of mutual friction. The key to reduce this kind of wear is to improve the plastic resistance of the tooth surface, that is, to improve the hardness of the tooth surface. Improving the hardness of the tooth surface can also improve the contact state of the tooth surface, so as to improve the anti fatigue ability of the tooth surface. (2) The tooth core should have enough strength and toughness to ensure that the tooth has enough impact resistance under the action of variable load or impact load. (3) The big and small gears should have a certain hardness difference to improve their scuffing resistance. (4) Consider material processability and economy.

2. Performance requirements of driving spiral bevel gear

The spiral bevel gear is the main driving part of the loader. The driving spiral bevel gear transmits the power from the automobile transmission to the driven bevel gear, and the driven bevel gear transmits the power to the differential. Therefore, on the part structure, the driving spiral bevel gear is a gear shaft, one end is a spline, which is connected with the power output shaft of the transmission, and the other end is a spiral bevel gear; the driven bevel gear is a disc gear, whose diameter is larger than the driving spiral bevel gear, which plays a deceleration role, and at the same time, some bolt holes are evenly distributed along the circumference, so that the driven bevel gear is fixed on the differential housing by bolts, which will move after deceleration The force is transmitted to the differential. The driving bevel gear not only has high transmission speed, but also transmits large torque, and bears impact load when loading and braking. The main failure modes of these gears are wear, pitting and fracture. Therefore, the driving spiral bevel gear should meet the following performance requirements: ① good mechanical performance; ② good carburizing and quenching performance; ③ good impact resistance; ④ good core hardness; ⑤ good thermal deformation performance.

3. Technical requirements for driving spiral bevel gear

Based on the above service conditions and performance requirements of the driving spiral bevel gear, the following technical requirements are put forward: ① forging shall be free of any forging defects. ② Normalizing hb179-217. ③ The surface carburizing hardness is HRC58-62, the core hardness is hrc32-45, the hardness of the transition layer should change slowly until the matrix is low carbon, the carburizing depth is 1.0-1.4mm, and the carbon content is 0.8% – 1.05%. ④ The metallographic inspection standard shall conform to the metallographic inspection standard for Automobile Carburized Gears (jb1673-75). ⑤ Shot peening shall be conducted for low temperature tempering.

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