Method, structure and device for improving contact reliability of electric brush and reverser of direct current speed measuring power generator

Abstract

The invention discloses a method, a structure and a device for improving contact reliability of an electric brush and a reverser of a direct current speed measuring power generator. The method comprises the steps of arranging the direct current speed measuring power generator for applying voltage to the electric brush by a volute spring, mounting the volute spring on a brush box, mounting and fixing the brush box on a brush frame ring of an end cover of a direct current motor by using a binding post, controlling a matching gap between a mounting hole in the brush box and the binding post within 0.015 to 0.08mm, meanwhile, manufacturing the width of the electric brush to be equal to or larger than a reversing segment pitch of the direct current speed measuring power generator, wherein a reversing segment of the direct current speed measuring power generator is made of silver, copper and nickel alloy, and the electric brush adopts a silver graphite electric brush with the brand number being J385. The method, the structure and the device have the advantages of simple structure, easiness in manufacturing, high work efficiency, good quality, stable and reliable product work performance and stable output voltage, and large-scale burr are not easily generated for output voltage waveforms.

Description

technical field [0001] The invention relates to a method, structure and device for improving the contact reliability between brushes and commutators of DC tachogenerators, and belongs to the technical field of brushed DC motor production. Background technique [0002] Since the brushed DC tachogenerator has the characteristics of simple structure, little influence by temperature changes, and easy processing of electrical signals, it has been widely used in various control systems. When the DC tachogenerator is working, the back electromotive force generated by the armature winding is commutated and rectified by the commutator, and then the DC voltage is output to the control system through the brushes in contact with the commutator. The brush and the commutator are in sliding contact, and whether they can be in reliable contact has a crucial impact on the quality of the output voltage waveform of the DC tachogenerator. At present, the frame size of most DC tachogenerators ...

AI Technical Summary

Problems solved by technology

At present, the frame size of most DC tachogenerators is below 30mm. Due to the limitation of their internal space, most of these tachogenerators use compact scroll springs and rotary brush boxes. The brush boxes are sleeved on the terminal posts. The existing The reliability of the contact between the brush and the commutator of this structure is not very ideal, and it is easy to cause large burrs in the output voltage waveform of the tachogenerator, and even produce a piece of burrs to zero (that is, no output voltage instantaneously), which is easy cause system jitter; in addition, since the ratio of the brush width of the DC tachogenerator to the commutator pitch of the commutator in the prior art is designed to be small, the ratio of the brush width to the commutator pitch is generally controlled Between 0.6 and 0.8, since the commutator has lower grooves, this will further reduce the contact area between the brush and the commutator. When the tachometer works at the highest speed, the brush will be on the commutator A sudden jump occurs on the surface, resulting in a burr in the output voltage waveform; in addition, due to the contact of the brush of the DC tachometer in the prior art with the commutator, the brush will wear and produce carbon powder after working for a period of time. The graphite or carbon grains in the carbon powder interact with the moisture in the air to form a graphite film; in addition, the commutator piece made of cadmium copper is affected by the air temperature and humidity to produce a metal oxide film, namely cuprous oxide or copper oxide.

Graphite film and metal oxide film are semiconducting, which will increase the contact resistance between the brush and the commutator, which will also cause burrs in the output voltage waveform.

Therefore, the structure or manufacturing method of the existing brushed DC tachogenerator is not ideal enough to meet the needs of use.

Images