Due to various reasons, the center of mass or inertial principal axis of the coupling does not coincide with the axis of rotation, and the phenomenon of unbalanced centrifugal inertial force, centrifugal inertial couple force and dynamic deflection (vibration shape) will occur during operation, which is called the unbalance of the rotor. Phenomenon, this imbalance phenomenon will inevitably cause the vibration of the shaft system, thereby affecting the normal operation and service life of the machine, so it must be paid attention to. The degree of unbalance (unbalance U) is usually expressed by the product mr of the mass m of the rotor and the distance r from the center of mass to the axis of rotation of the rotor, which is called the product of mass diameter. It is also expressed by the product of mass diameter per unit mass, which is called the eccentricity e (not geometrically eccentric.) The product of mass diameter mr is a relative quantity related to the mass of the rotor, while the eccentricity e is a value that has nothing to do with the mass of the rotor. The absolute amount. The former is relatively intuitive, and is often used for specific balancing operations of a given rotor. The latter is used to measure the pros and cons of the rotor balance or to detect the balance accuracy. The balance grade standard of the coupling is evaluated by e. For a flexible rotor, use the mode eccentricity (the nth mode) en=Un/mn, and Un and mn are the nth mode and the first mode quality respectively.
In order to correct or minimize the unbalance of the coupling, the appropriate balance level should be selected according to the needs, and after the product is manufactured and installed on the machine, on the specified balance (correction) plane of the coupling, pass Methods to increase or decrease the appropriate quality to achieve the balance level requirements. This process is called balance correction, or balance for short.