Gear transmission is a transmission form widely used in mechanical transmission. Its transmission is relatively accurate, high in efficiency, compact in structure, reliable in operation and long in life.

Gear classification

1. According to the relative position of the two shafts and the direction of the gear teeth, it can be divided into the following types:

Spur gear drive

Helical Cylindrical Gear Transmission

Herringbone gear transmission

Bevel gear transmission

Cross-axis helical gear transmission

2. According to the working conditions of the gear, it can be divided into:

Open gear transmission type gear transmission, the gears are exposed and cannot guarantee good lubrication

Semi-open gear transmission, the gears are immersed in the oil pool, with guards, but not closed

Closed gear transmission, the gears, shafts and bearings are all installed in the closed box, the lubrication conditions are good, the dust is not easy to enter, the installation is accurate, the gear transmission has good working conditions, and it is the most widely used gear transmission.

How to deal with gear transmission failure

【Faults caused by manufacturing errors】

Several typical errors, such as eccentricity, pitch error, base pitch error and tooth profile error, usually occur in the manufacture of gears. There are many reasons for these errors, including errors from machine tool movement, cutting tool errors, improper installation and debugging of tools, workpieces, and machine tool systems, fixture errors, and gear deformation caused by heat treatment internal stress, etc. When these errors of the gears are large, it will cause the micro-inertia of the gear transmission to interfere with the rotation, which will cause shock and vibration when the gear pairs are meshing, causing large noise.

[Faults caused by assembly errors]

Due to the assembly technology and assembly method, the assembly error of "one end is in contact and one end is suspended" is usually caused when assembling the gear; the linearity deviation of the gear shaft (coaxiality, neutrality error) and the unbalance of the gear, etc. One-end contact or linearity deviation of the gear shaft will cause the gears to bear uneven loads, resulting in excessive loads on individual gear teeth, causing local early wear, and even causing gear teeth to break in severe cases. Unbalanced gears will cause impact vibration and noise.

【Faults generated during operation】

1. Fracture of gear teeth

During gear transmission, the active force of the driving gear and the reaction force of the driven gear act on the opposing gear teeth respectively through the contact points. The most dangerous situation is that the contact point is located at the top of the gear teeth at a certain moment; at this time, the gear teeth Like a cantilever beam, the bending stress generated at the tooth root of the loaded rear wheel is the largest. If it is overloaded suddenly or impacted, it is easy to cause overload fracture at the tooth root.

2. Tooth surface wear or scratches

There is relative sliding of the gear teeth during the meshing transmission process, coupled with poor lubrication, dirty lubricating oil, deterioration of lubricating oil, low speed and heavy load, or poor heat treatment quality, etc., can cause adhesive wear, abrasive wear, and corrosion of the tooth surface of the gear teeth. Scuffs and scratches etc.

3. Tooth surface fatigue

The so-called tooth surface fatigue mainly includes tooth surface pitting and spalling. The cause of pitting is mainly due to the microscopic fatigue cracks caused by the pulsating contact stress on the working surface of the gear teeth. When the lubricating oil enters the surface crack area, the entrance is first closed and then squeezed during the meshing process. The lubricating oil in the microscopic fatigue crack area expands the crack area on the tooth surface under high pressure, causing the surface metal particles to fall off the tooth surface, leaving small pits to form tooth surface pitting. When the fatigue cracks on the surface of the gear tooth continue to expand to a deeper and farther distance, it will cause a large area or a large piece of peeling off, which forms the tooth surface spalling.

4. Plastic deformation of tooth surface

When the gear material is soft and the transmission load is large, plastic deformation of the tooth surface is easy to occur. Under the action of excessive friction between the tooth surfaces, the contact stress of the tooth surfaces will exceed the material’s anti-extrusion yield limit, and the tooth surface materials will enter a plastic state, resulting in plastic flow of the tooth surface metal. As a result, concave grooves are formed on the tooth surface of the driving gear near the pitch line, while convex ribs are formed on the tooth surface of the driven gear near the pitch line, thereby destroying the tooth shape.