CN1113981C

CN1113981C - Technology and material for plating electric brush of commutator of special miniature motor with palladium

Info

Publication number: CN1113981C
Application number: CN99116933A
Authority: CN
Inventors: 蔡珣; 杨瑞鹏; 陈秋龙
Original assignee: Shanghai Jiaotong University
Current assignee: Shanghai Jiaotong University
Priority date: 1999-09-30
Filing date: 1999-09-30
Publication date: 2003-07-09
Anticipated expiration: 2019-09-30
Also published as: CN1249364A

Abstract

The present invention discloses a process and material for plating palladium on a commutator of a special miniature motor by utilizing electric brush plating. According to the process, the commutator is pretreated first, and then, the commutator is connected with an electric brush plating device for brush plating, wherein a plating solution is prepared from a PdCl2 solution, a NaNO2 solution and an NH4NO3 solution of certain concentration. An electrode 1 and an electrode 2 of the device, which are connected with a power supply, are in a shape of a crescent which is similar with the shape of external electrodes; internal circle diameters of the electrodes are equal to an external circle diameter of a rotor 4. The present invention has the advantages of simple device, favorable quality of film plating, no environmental pollution and no adverse influence on the electric insulation performance of a device after plating.

Description

The brush Pd-electroplating process that is used for commutator of special miniature motor with

The present invention relates to a kind of application of brushes electroplating method plates palladium on commutator of special miniature motor with technology and material.Belong to the process for modifying surface field.

The reverser of direct current small and special electric machine has not only required good conduction and wear-resisting, anti-electric ablation property, but also requires the contact resistance between it and the brush little and stable, and weather-resistance is good.Therefore the reverser of small and special electric machine often adopts the Ag-Ni-Cu alloy.But silver alloys easily produces the sulfide staining phenomenon, has a strong impact on its reliability.Need be on reverser the plating layer protecting film, prevent the sulfuration of silver, to improve its weather-resistance.This layer plated film be good except chemical stability, be difficult for reacting with sulphur, require also that it conducts electricity very well, contact resistance is stablized, and had certain wear resistance, electric erosion resistance.In addition, when this layer of plating protective membrane, can not destroy electric property, the mechanical property of original workpiece, workpiece must keep high surface smoothness and dimensional precision.So industrial selection palladium is as the cash equivalent coating of electrical contact device.Chemical palladium-plating novel process (" electroplating and environmental protection " 1997 17 2 phases of volume) as the development of department of chemistry of Xiamen University.But plate technologies such as general plating of adopting of palladium and electroless plating at present and have following problem: 1) process time long, coating is thinner, internal stress is big, and is easy to crack.The ionization potential of water very near the deposition potential of palladium, the sedimentary while of palladium coating, often produces the hydrogen by product.And palladium is inhaled the very capable of hydrogen, and therefore, hydrogen infiltrates coating and unsettled β-the hydrogenation palladium mutually on the thermodynamics in conjunction with easily forming with palladium.2) owing to adopt multiple additives (as brightening agent, stress depressant etc.), its comprehensive action may make palladium reach the reduction scope of hydrogen in higher potential reduction, more promotes the generation of hydrogen.3) electroless plating has intensive corrodibility to matrix metal, and plating rear surface state is also relatively poor, is difficult to meet comparatively accurate processing requirement, and the plating bath of electroless plating has intensive toxicity, and human body and environment are had intensive harm.

The purpose of this invention is to provide a kind of Pd-electroplating process and material that is used for the brush plating of commutator of special miniature motor with." brush plating " is a new technology that grows up on the basis electroplating, and moves back and forth on workpiece to be plated with plating like the brush exactly and the plating carried out.Make a return journey dehydrogenation in the nucleation site of coating surface by anode in the to-and-fro movement on the surface of negative electrode on the one hand, impel hydrogen to break away from, thereby can reduce the content of hydrogen in the coating, reduce the internal stress of coating, improve the safe thickness of coating from coating surface; On the other hand, the to-and-fro movement of anode on the surface of negative electrode reduces concentration polarization, improved the limit current density of plating bath, makes its sedimentation rate than the fast 5-10 of general deposition method doubly.Because the sedimentation rate height, the densification of brush coated coating, crystal grain are tiny, thereby the low and hardness height of coating internal stress.

According to the present invention, at first reverser is done pre-treatment such as polishing, polishing and cleaning, the commutator brush plating appts is installed then, carry out brush Pd-electroplating.The plating pen (anode) that the brush plating time will be connected on the dc power anode contacts with workpiece (negative electrode) on being connected on dc power cathode, and do relative movement, constituted a miniature electroplanting device, be adsorbed on metal ion in the plating bath on the anode jacket under the effect of DC electric field, spread to workpiece surface, in its surface reduction deposition, form metal plating.Along with the prolongation of brush plating activity duration and the increase of consumes power, the coating progressive additive is till reaching required thickness.

The present invention adopts the brush electroplating method, and equipment is simple, and the plating quality is good, non-environmental-pollution.And the local electroplating of the commutator of special miniature motor with rotor device after can realizing precision sizing finished.Can not have a negative impact to the device electrical insulation capability behind the plating.Palladium coating outward appearance is silvery white in color, and the luminance brightness height need not polish after the plating.Because this effectively dehydrogenation of technology utilization anode quick travel, thereby improve the safe thickness of coating, can reach 6.5 microns.The outside of coating is smooth than matrix one side, illustrates that plating bath has stronger leveling ability.Hardness and wear resistance see Table 1.

Table 1 Pd and Cu, Ag-Ni-Cu performance comparison

Pd Cu Ag-Ni-Cu hardness (HV ₁₀) 160～200 110.4 96 wear resistance (30min, to the mill material is graphite) load 100g (weightlessness, mg) there are not 0.10 0.16 load 5000g (weightlessness, mg) 0.20 0.40 0.62

Fig. 1 is a commutator brush plating appts synoptic diagram of the present invention.

The invention will be further described below in conjunction with drawings and Examples.In the present invention,------------ultrasonic wave water cleans, and----ultrasonic wave acetone cleans oil removing----washing to the polishing of W1 diamond paste to the polishing of W5 diamond paste at first commutator face to be carried out pre-treatment: the fine grinding of W3 abrasive paper for metallograph.Connect the commutator brush plating appts then, carry out brush Pd-electroplating.Because commutator segment and rotor inner wall insulation, junction circuit in a general manner.So design is carried out brush plating with lower device.Among Fig. 1,1 and 2 is crescent profiling electrodes, and circular diameter equates that with reverser rotor 4 outside diameters 2 connect power cathode in it, and 1 connects positive source.During brush plating, 1 and 2 lean against on the reverser of outside surface of rotor 4, constitute the loop after connecting power supply.3 is the plating bath transfer lime, introduces anode 1, the supply plating bath.5 is the anode jacket.Palladium coating outward appearance of the present invention is silvery white in color, and the luminance brightness height need not polish after the plating.Its composition and tissue: coating mainly is organized as palladium sosoloid, and the solid solution material is anode and matrix composition, and palladium content 94%～97% if use insoluble anode, can obtain the higher coating of purity.The prescription and the processing parameter of plating bath see Table 2:

Table 2 Pd brush plating electroplate liquid formulation and processing parameter

PdPdCl ₂G/L 5-10NaNO ₂G/L 10-20NH ₄NO ₃G/L 60-100 voltage (V) 7-14pH 7.9-9.0 power consumption coefficient (Ah/dm ²μ m) 0.105

Claims

1, a kind of brush Pd-electroplating process that is used for commutator of special miniature motor with, at first the reverser outside surface is carried out sanding and polishing and cleans oil removing with sand paper and lapping paste, connect reverser to electric brushing coating installation then and carry out the brush plating, it is characterized in that: plating bath is composed of the following components: PdCl ₂Concentration is 5-10g/L, NaNO ₂Concentration is 10-20g/L, NH ₄NO ₃Concentration is 60-100g/L; Processing parameter: voltage 7-14V, the pH value is 7.9-9.0, the power consumption coefficient is 0.105Ah/dm ²μ m.

2, according to the described brush Pd-electroplating process of claim 1, it is characterized in that: the electrode that connects power positive cathode and reverser is a crescent profiling electrode, and circular diameter equates with the reverser outside diameter in it; During brush plating, electrode (1) and electrode (2) lean against on rotor (4) outside surface.