How to prevent gear damage?
1 Broken teeth
Element analysis: gear fracture includes fatigue fracture and overload fracture. During the operation of gear transmission, the gear teeth are subjected to alternating load for many times, which acts on the bending fatigue stress on the risk profile of the tooth root, and fatigue cracks occur at the tooth root. Under the action of alternating bending fatigue stress, fatigue cracks gradually widen, which, after all, causes the gear teeth to bend, fatigue and break; During the operation of gear transmission, the gear is subject to short-term overload, or impact load, or the gear teeth are seriously worn and thinned, which will lead to overload fracture
Treatment method: increase the fillet radius of the tooth root transition and reduce the roughness value of the machined surface as much as possible, which can reduce the impact of stress convergence, increase the stiffness of the shaft and support, and ease the load on the tooth surface; So that the tooth center of the gear has sufficient toughness; Proper strengthening treatment at the tooth root can advance the anti fracture ability of gear teeth.
2 Gear pitting and falling
Element analysis: the main element of pitting and falling on the gear surface is the lack of contact fatigue strength of the gear. The difference between pitting, dropping and wear is that the metal is not worn out by particles, but dropped in chunks, forming pits on the tooth surface, seriously damaging the correctness of the tooth profile. The damage process is as follows: first, a small crack occurs on the tooth surface, and the lubricating oil enters the fatigue crack. Then, through repeated meshing, the crack is continuously widened and extended, and the lubricating oil continues to fill the crack depth with the widening and extension of the crack until a small piece of metal falls off the tooth surface. This phenomenon damages the normal meshing function of the gear. The primary elements of pitting corrosion on the tooth surface are:
A. Materials, hardness and defects. The material of the gear does not meet the requirements; The primary factor affecting the contact fatigue strength of gears is the low hardness after heat treatment, which cannot guarantee the due contact fatigue strength of gears. In addition, defects on the surface or inside of the teeth are also one of the indispensable factors for contact fatigue strength.
b. Gear accuracy is poor. Gear processing and equipment accuracy do not meet the requirements, such as poor meshing accuracy and motion accuracy. Also, the housing base distance of circular arc gear is too large.
c. The lubricating oil does not meet the request. The brand of the lubricating oil used is incorrect, the viscosity of the oil is low, and the lubricating function is poor.
d. The oil level is too high. The oil level is too high and the oil temperature rises too high, which reduces the viscosity of the lubricating oil, damages the lubrication function and reduces the working thickness of the oil film.
Treatment method: advance the hardness of the gear surface, reduce the roughness value of the gear surface, select a large modification coefficient as far as possible, increase the viscosity of the lubricating oil and reduce the dynamic load, which can help prevent fatigue pitting on the gear surface.