Gear transmission type and fault response

Gear transmission type and fault response

Gear transmission is a transmission form widely used in mechanical transmission. It has the advantages of accurate transmission, high efficiency, compact structure, reliable operation and long service 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 transmission

Helical cylindrical gear transmission

herringbone gear

Bevel gear drive

crossed helical gear

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

Open gear transmission type gear transmission, gear exposed, can not guarantee good lubrication

Semi open gear transmission, gear immersed in oil pool, with shield, but not closed

Closed gear transmission, gear, shaft and bearing are installed in a closed box, with good lubrication conditions, dust and sand are not easy to enter, and the gear transmission has good working conditions. It is a widely used gear transmission.

How to deal with gear transmission failure

[fault caused by manufacturing error]

The manufacturing of gears usually produces several typical errors, such as eccentricity, pitch error, base pitch error and tooth profile error. There are many reasons for these errors, including the error of machine tool movement, the error of cutting tools, the error of improper installation and commissioning of tools, workpieces and machine tool systems, the error of fixtures and the gear deformation caused by internal stress of heat treatment. When these errors of the gear are large, it will cause the micro inertia interference rotation of the gear transmission which is slow and fast, resulting in impact and vibration when the gear pair is meshed, resulting in large noise.

[fault caused by assembly error]

Due to the reasons of assembly technology and assembly method, the assembly error of "one end contact and one end suspension" will be caused when assembling gears; Straightness deviation of gear shaft (coaxiality, alignment error) and imbalance of gear, etc. One end contact or the straightness deviation of the gear shaft will cause uneven load on the gear, resulting in excessive load on individual gear teeth, local early wear and even fracture of gear teeth. The imbalance of gears will cause shock, vibration and noise.

[faults caused by operation]

1. Fracture of gear teeth

When the gear is driven, the force of the driving gear and the reaction force of the driven gear act on each other's teeth respectively through the contact point. The dangerous situation is that the contact point is at the top of the teeth at a certain moment; At this time, the tooth is like a cantilever beam, and the bending stress at the root of the tooth is very large after being loaded. If it is due to sudden overload or impact overload, it is easy to produce overload fracture at the root of the tooth.

2. Worn or scratched tooth surface

The relative sliding of gear teeth in the process of meshing transmission, coupled with poor lubrication, unclean lubricating oil, deterioration of lubricating oil, low-speed heavy load or poor heat treatment quality, can cause adhesion wear, abrasive wear, corrosion wear and scratches on the tooth surface of gear teeth. 3. Tooth surface fatigue

The so-called tooth surface fatigue mainly includes tooth surface pitting and spalling. The cause of pitting corrosion is mainly the micro fatigue crack caused by the fluctuating contact stress on the working surface of gear teeth. When the lubricating oil enters the surface crack area, the inlet is closed first and then squeezed in the meshing process. The lubricating oil in the micro fatigue crack area expands the crack area on the tooth surface under high pressure, causing the surface metal particles to fall off from the tooth surface, leaving small pits to form pitting corrosion on the tooth surface. When the fatigue crack on the tooth surface continues to expand to a deeper and farther distance, it will cause large area or large block falling off, which will form tooth surface spalling.

4. Plastic deformation of tooth surface

When the gear material is soft and the transmitted load is large, it is easy to produce plastic deformation on the tooth surface. Under the action of excessive friction between the tooth surfaces, the contact stress of the tooth surface will exceed the extrusion yield of the material, and the tooth surface material will enter the plastic state, resulting in the plastic flow of the tooth surface metal. As a result, the driving gear forms a concave groove on the tooth surface near the pitch line, while the driven gear forms a convex edge on the tooth surface near the pitch line, resulting in the destruction of the tooth shape.