Vibration mechanism analysis of gearbox

1. Generation of gear vibration

Gear transmission is through a number of teeth at the end of the previous tooth mesh exit, after the tooth into mesh, so repeatedly to achieve the transmission of power and motion. In an ideal state, the process is smooth, but because of tooth backlash, elastic deformation, manufacturing and assembly errors and wear, pitting and peeling off, broken teeth and other factors, the meshing process of teeth will inevitably produce impact vibration phenomenon. Gear vibration is the reflection of dynamic response after dynamic excitation. Different reasons can produce different excitation, which can be divided into normal meshing excitation and fault excitation.

Because of the time-varying characteristics of both stiffness and error excitations, both of them belong to displacement excitations, so they are classified as displacement excitations, and they are combined as static transfer errors, which are used as parameter excitations to study recurrence errors.

2. Transmission path of gear vibration

The vibration of gear system, shafting, bearing and other moving parts is transmitted to the gearbox in all directions with solid and air as the medium. Compared with the transmission of solid, the vibration transmitted by air is much smaller. This paper will not make too much analysis. In practical application, the sensor used to obtain the vibration signal is usually installed on the bearing seat or the case, and the transmission path of the vibration signal of the gear box of a certain level of transmission. Every moving element in the gearbox is a vibration source, an input signal, and the vibration signal at the measuring point is an output signal, so the gearbox belongs to a multi input single output system. The signals acquired by the sensor include normal vibration signals, fault vibration signals and other noise interference signals. In the process of signal transmission from the vibration source to the vibration pickup point, the distance between the two points will cause time delay and local resonance. Each vibration signal will modulate and couple with each other, which will change the frequency composition and phase of the signal. For example, the natural frequency of a certain order of signal will be released To a certain extent, it is more difficult to filter out the real signal features of gear fault.

3. analysis of gear vibration mechanism

The composition of the gear transmission system is relatively complex, and its engineering structure is a continuous system with continuous distribution of mass, stiffness and damping. In order to better analyze the dynamics of the gear transmission system, it needs to be simplified into a discrete system with finite number of degrees of freedom, which is described by ordinary differential equation. When establishing the discrete analysis model of spur gear pair, the gear is usually regarded as a component with large mass and small elasticity, and simplified as an equivalent mass component and equivalent damping component. The meshing stiffness of the gear is simplified as a linear spring acting on the node. At the same time, in order to highlight the key factors affecting the vibration of the gear, the secondary factors in the analysis system need to be ignored to make the analysis model The results are as follows:

1) Considering the influence factors of gear load, the movement perpendicular to the direction of meshing force is ignored;

2) The lateral vibration, torsional stiffness and damping of the gear shaft are ignored;

3) Ignore backlash and face friction.

Scroll to Top