Axial vibration and noise of the end cap

The axial vibration of the end cap is one of the sources of mechanical noise, which is mainly excited by the vibration of the bearing and is important in small motors. The smaller the axial dynamic stiffness of the end cap, the easier it is to excite larger vibration speeds and noise.

Vibration and noise of the brush device

The vibration and noise of the brush device are caused by poor condition of the surface of the commutator, large gap between the brush and the brush holder, small pressure of the brush or improper pressure application, and the brush is skewed, as well as the brush holder, the brush holder and the brush rod. Structural and process reasons such as insufficient stiffness are produced.

The sliding contact condition of the brush and the commutator during the operation of the DC motor and the cuprous oxide film formed on the surface of the commutator and the layer of graphite film and dust particles covered thereon not only affect the commutation performance of the motor, but also affect To vibration and noise.

Practice has proved that the film is not easy to form due to the low temperature of the sliding contact surface at no load, and the dry friction between the brush and the commutator increases the noise. For example, when the rolling steel DC motor accounts for more than 50% of the total time of the no-load operation cycle, the noise under no-load conditions is 6~10 dB higher than that at the load. This vibration differs from the vibration caused by mechanical causes on the surface of the commutator, which can be checked at low speeds of the motor (light touch on the brush with vibration). The spectrum of brush vibration noise generated by sliding contact is generally in the range of 1000~-8000Hz, and it does not change much when the motor speed changes, which is one of the characteristics that distinguish it from mechanical reasons.