COMMUTATOR, MOTOR USING SAME AND METHOD OF MANUFACTURING THE COMMUTATOR

Abstract

The invention relates to a commutator, comprising an insulating base and a plurality of commutator segments arranged on the insulating base, wherein each commutator segment comprises a metal layer, a transition layer and a graphite layer arranged on the base in sequence. The transition layer contains a material identical to that of the graphite layer and a material identical to that of the metal layer. The invention further relates to a motor comprising the commutator and a method for manufacturing the commutator. As the transition layer contains the material identical to that of the graphite layer and the metal layer, the problem that the graphite layer and the metal layer are cracked during high temperature sintering is resolved. The service life of the commutator is prolonged. The method for manufacturing the commutator reduces chemical contamination and production cost caused by electroplating and brazing used in a traditional technology.

Claims

1. A commutator, comprising an insulating base and a plurality of commutator segments arranged on the insulating base, wherein each of the commutator segment comprises a metal layer, a transition layer and a graphite layer all arranged in sequence, the transition layer containing a material identical to that of the graphite layer and a material identical to that of the metal layer.

2. The commutator of claim 1, wherein the commutator further comprises a plurality of conductive terminals, each of the conductive terminals being connected to the metal layer of corresponding one of the commutator segments.

3. The commutator of claim 1, wherein the material of the graphite layer is graphite powder, which is at least one selected from a group consisting of natural graphite, artificial graphite and meso-carbon microbeads.

4. The commutator of claim 1, wherein the material of the transition layer is a mixture of graphite powder and metal powder.

5. The commutator of claim 4, wherein the mass ratio of the graphite powder in the transition layer is 10% to 30%, and the mass ratio of the metal powder is 70% to 90%.

6. The commutator of claim 4, wherein the graphite powder is at least one selected from a group consisting of natural graphite, artificial graphite, coke and meso-carbon microbeads, and the metal powder is at least one selected from a group consisting of Al, Cu, Ag, Ni, Bi, Sb or an alloy at least containing one of the metals.

7. The commutator of claim 1, wherein the material of the metal layer is metal powder, and the metal powder is at least one selected from a group consisting of Al, Cu, Ag, Ni, Bi, Sb.

8. The commutator of claim 1, wherein the transition layer thickness is 100-500 μm, the metal layer thickness is 100-500 μm, and the graphite layer thickness is 1600-2400 μm.

9. A motor, comprising a housing, and a rotor and an electric brush installed in the housing, further comprising the commutator for being in sliding contact with the electric brush, wherein the commutator comprises: an insulating base, and; a plurality of commutator segments arranged on the insulating base, each of the commutator segment comprising a metal layer, a transition layer and a graphite layer all arranged in sequence, the transition layer containing a material identical to that of the graphite layer and a material identical to that of the metal layer.

10. A method of manufacturing a commutator, comprising the following steps of: forming a metal layer, a graphite layer and a transition layer which is sandwiched between the metal layer and the graphite layer in a die, wherein the transition layer containing a material identical to that of the graphite layer and a material identical to that of the metal layer; forming a green body by pressing the graphite layer, the transition layer and the metal layer; and forming a sintered mature body by sintering the green body.

11. The method of claim 10, wherein: the graphite layer is formed by: filling graphite powder in a die, and pressing the graphite powder; the transition layer is formed on the graphite layer by: filling graphite powder and metal powder in the die on the graphite layer, and pressing the graphite powder and the metal powder; the metal layer is formed on the transition layer by: filing metal powder in the die on the transition layer, and pressing the metal powder.

12. The method of claim 10, wherein: the metal layer is formed by: filling metal powder in a die, and pressing the metal powder; the transition layer is formed on the metal layer by: filling graphite powder and metal powder in the die on the metal layer, and pressing the graphite powder and the metal powder; the graphite layer is formed on the transition layer by: filing graphite powder in the die on the transition layer, and pressing the graphite powder.

13. The method of claim 10, wherein the graphite powder of the graphite layer is at least one selected from a group consisting of natural graphite, artificial graphite and meso-carbon microbeads.

14. The method of claim 10, wherein the mass ratio of the graphite powder in the transition layer is 10% to 30%, and the mass ratio of the metal powder is 70% to 90%.

15. The method of claim 10, wherein the graphite powder is at least one selected from a group consisting of natural graphite, artificial graphite, coke and meso-carbon microbeads, and the metal powder is at least one selected from a group consisting of Al, Cu, Ag, Ni, Bi, Sb or an alloy at least containing one of the metals.

16. The method of claim 10, wherein a thickness range of the transition layer is 100-500 μm, a thickness range of the metal layer is 100-500 μm, and a thickness range of the graphite layer is 1600-2400 μm.

17. The method of claim 10, wherein the method further comprising: forming a plurality of commutator segments by slotting the sintered mature body, two adjacent ones of the commutator segments being spaced by an insulating slot.

18. The method of claim 10, wherein the method further comprising: connecting the sintered mature body with a conductive member and assembled on an insulating base; forming a plurality of commutator segments and conductive terminal by slotting the sintered mature body and the conductive member.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG. 1 is a schematic diagram of a cross section of a motor provided by one embodiment of the present invention;

[0030] FIG. 2 is a schematic plan view of the commutator used in the motor of FIG. 1;

[0031] FIG. 3 is a schematic diagram of a cross section of the commutator of FIG. 1, showing a graphite layer, a transition layer and a metal layer of a commutator segment;

[0032] FIG. 4a is a scanning electron microscope of a mixture formed by metal powder and graphite powder in the transition layer of the commutator of FIG. 2;

[0033] FIG. 4b is an enlarged drawing of the V portion in FIG. 4a;

[0034] FIG. 5 illustrates atomic absorption peak of main elements in the metal layer measured by an atomic absorption photometer; and

[0035] FIG. 6 is a flow chart of a method of manufacturing a commutator according to an embodiment of the present invention.

[0036] The present invention is further illustrated by the following specific detailed description of various embodiments with reference to the above drawings.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

[0037] The technical solution and the other advantageous effects of the present invention will be obvious through detailed description of various embodiments of the present invention with reference to the drawings.

[0038] FIG. 1 is a schematic diagram of a cross section of a motor 100 according an embodiment of the present invention. Please referring to FIG. 1, the motor 100 comprises a stator 2 and a rotor 4 rotatably mounted to the stator 2. The stator 2 comprises a housing 3, permanent magnets 5 mounted onto inner wall of the housing 3, a brush holder 7 directly or indirectly mounted to the housing 3, and electric brushes 10 slidably mounted to the brush holder 7. The rotor 4 comprises a shaft 15, a rotor core 6 fixed onto the shaft 15, a commutator 9 fixed onto the shaft 15 and adjacent to the rotor core 6, and rotor windings 8 wound onto the rotor core 6. The rotor core 6 forms a plurality of winding slots for receiving the windings 8. The electric brushes 10 are for in sliding contact with the commutator 9 so as to commutating current of the rotor windings 8. The commutator 9 comprises a contact surface 11a for in sliding contact with the brushes 11a.

[0039] Please referring to FIG. 2 together, the commutator 9 is preferably a flat type graphite commutator, comprising an insulating base 905, a plurality of commutator segments 903 and conductive terminals 904. The commutator segments 903 are circumferentially distributed on the insulating base 905 and mutually spaced at an interval, and are used for being in sliding contact with the electric brushes 10 of the motor 100. Each commutator segment 903 is provided with one conductive terminal 904. The conductive terminals 904 are used for being electrically connected with the windings 8. An insulating groove 907 is arranged between every two adjacent commutator segments 903 for electrical isolation.

[0040] Referring to FIG. 3, the commutator segment 903 is in a three-layer structure, comprising a graphite layer 11, a transition layer 12 and a metal layer 13. The transition layer 12 is connected between the graphite layer 11 and the metal layer 13. The transition layer 12 contains a material identical to that of the graphite layer 11 and a material identical to that of the metal layer 13. The graphite layer 11 comprises a contact surface 11a away from the transition layer 12 for being in sliding contact with the electric brushes 10. The metal layer 13 is arranged on the insulating base 905 (shown in FIG. 2) for fixedly welding with a connecting end of the conductive terminal 904 that extends into the insulating base.

[0041] The material of the graphite layer 11 is graphite powder. The graphite powder is at least one selected from a group consisting of natural graphite, artificial graphite and meso-carbon microbeads.

[0042] The transition layer 12 is sandwiched between the graphite layer and the metal layer 13. The material of the transition layer 12 is graphite powder and metal powder. The transition layer 12 is used for reducing heat expansion of the commutator 9 during motor operation. In this embodiment, the graphite powder is at least one selected from a group consisting of natural graphite, artificial graphite, coke and meso-carbon microbeads. The metal powder is at least one selected from a group consisting of one or combination of copper powder and silver-plated copper powder.

[0043] FIG. 4a and FIG. 4b illustrates solid surface of the transition layer 12 observed through a scanning electron microscopy. It can be seen that the graphite powder and metal powder used in the transition layer 12 are in various morphologies such as flaky, branch-like, spherical or irregular shapes.

[0044] The material of the metal layer 13 is metal powder, preferably the metal is difficult to react with graphite to form carbide. For example, the metal can be at least one selected from a group consisting of Al, Cu, Ag, Ni, Bi, Sb.

[0045] Referring to FIG. 5, the metal powder of the metal layer 13 in this embodiment is mixture power containing copper powder and silver-plated copper powder. As seen in the atomic absorption peak drawing, there are four atomic absorption peaks in total, wherein three of the four atomic absorption peaks are copper-element absorption peaks, and the other one of the four atomic absorption peaks is a silver-element absorption peak. The metal powder used in the implementation manner has low hardness and strong resistance to oxidation.

[0046] The mass ratio of the graphite powder in the transition layer 12 is 10% to 30%. The mass ratio of the metal powder in the metal layer 13 is 70% to 90%. The mass ratio is calculated according raw material.

[0047] The material of the transition layer 12 comprises graphite powder, so that the transition layer 12 has self-lubrication as graphite characteristic. The material of the transition layer 12 also comprises metal powder, so that the layer has excellent thermal conductance and excellent thermal conductivity.

[0048] The graphite layer 11, the transition layer 12 and the metal layer 13 all have a certain thickness. The thickness of the transition layer 12 is preferred within 100-500 μm. The thickness of the metal layer 13 is preferred within 100-500 μm. The thickness of the graphite layer is preferred within 1600-2400 μm. The metal material used in the transition layer 12 is not limited within Cu and Ag. For example, the metal material can be at least one selected from a group consisting of Al, Ni, Bi, Sb and other metals.

[0049] In the present invention, “the thickness of the graphite layer 11”, “the thickness of the metal layer 13” and “the thickness of the transition layer 12” refer to a thickness observed and measured through an optical microscope.

[0050] Referring to FIG. 6, the method of manufacturing the commutator comprises the following processes.

[0051] In step S101, graphite powder is filled in a die, and then a graphite layer 11 is formed by pressing the graphite powder. The graphite powder is at least one selected from a group consisting of natural graphite, artificial graphite and meso-carbon microbeads.

[0052] In step S102, graphite powder and metal powder are filled on the graphite layer 11, and then a transition layer 12 is formed on the graphite layer 11 by pressing. In this step, the graphite powder is at least one selected from a group consisting of natural graphite, artificial graphite, coke and meso-carbon microbeads. The metal powder is at least one selected from a group consisting of copper powder and silver-plated copper powder. Preferably, the graphite powder used to form the transition layer 12 is identical to the graphite powder used to form the graphite layer

[0053] In step S103, the metal powder is filled on the transition layer 12, and then a metal layer 13 is formed on the transition layer by pressing. The metal powder is at least one selected from a group consisting of copper powder and silver-plated copper powder. Preferably, the metal powder used to form the metal layer 13 is identical to the metal powder used to form the transition layer 12.

[0054] In step S104, a green body is formed by pressing the graphite layer 11, the transition layer 12 and the metal layer 13. In the embodiment, and the green body can be pressed by a Cold-Isostatic Pressing (CIP molding) molding machine.

[0055] In step S105, the green body is sintered. Curing and sintering temperature, time and atmosphere of the green body are properly set according to the material, shape and size of the metal powder and graphite powder. For example, the curing and sintering temperature of the green body can be set as a softening-melting temperature of the metal powder forming the metal layer 13. In this embodiment, the curing temperature of the green body is preferably set as 200-450° C., and the sintering temperature of the green body is preferably set as 550-850° C.

[0056] When green body is sintered, the sintered mature body is connected with the conductive terminal 904 (FIG. 2) and assembled on the insulating base. The sintered mature body is then slotted to form commutator segments 903 (FIG. 2) arranged mutually spaced by corresponding slots 907 (FIG. 2). The conductive terminal 904 (FIG. 2) can be connected to the sintered mature body by welding. The heating temperature and a heating pressure during welding are appropriately set according to the type, size and combining area of the graphite powder and metal powder.

[0057] In alternative embodiments, the steps of manufacturing the commutator can be regulated. For example, firstly filling the metal powder in a die to form the metal layer 13 by pressing; and then filling a mixture of the metal powder and the graphite powder on the metal layer 13 to form the transition layer 12 on the metal layer 13 by pressing; and filling the graphite powder on the transition layer 12 to form the graphite layer 11 on the transition layer 12 by pressing.

[0058] It's contemplated that the sintered mature body is manufactured by the steps: forming a metal layer, a graphite layer and a transition layer which is sandwiched between the metal layer and the graphite layer; forming a green body by pressing the graphite layer, the transition layer and the metal layer; and sintering the green body.

[0059] It's contemplated that the graphite layer could be formed in advance and then the transition layer is formed on the graphite layer, and the metal layer is formed on the transition layer.

[0060] It's contemplated that the metal layer is formed in advance and then the transition layer is formed on the metal layer, and the graphite layer is formed on the transition layer.

[0061] The manufacturing method for the commutator further can be optimized by regulating the proportion between the metal powder and the graphite powder in the transition layer 12, so that the performance of the commutator can be improved to a certain extent.

[0062] Compared with the prior art, as the transition layer contains the material identical to that of the graphite layer and the metal layer, the commutator provided by the invention solves a problem that the graphite layer and the metal layer are cracked during high temperature sintering. The service life of the commutator is prolonged. The method of manufacturing the commutator provided by the present invention reduces the chemical contamination and the production cost caused by the electroplating and brazing used in the traditional technology. The binding force between the graphite and a metal surface is improved by die pressing and sintering technology. The curing and sintering temperature used by the manufacturing method is lower, which can meet the operation in an environment at a higher application temperature. The commutator provided by the embodiment of the present invention is particularly suitable for the motor of such fluid transportation devices as an oil pump and the like.

[0063] Although the invention is described with reference to one or more preferred embodiments, it should be appreciated by those skilled in the art that various modifications are possible. Therefore, the scope of the invention is to be determined by reference to the claims that follow.

[0064] In the description and claims of the present application, each of the verbs “comprise”, “include”, “contain” and “have”, and variations thereof, are used in an inclusive sense, to specify the presence of the stated item but not to exclude the presence of additional items.