Sliding member, rotary device, and method for manufacturing sliding member

Abstract

A slide-contact portion of a motor has a slide-contact face that contacts a rotating rotor. The slide-contact portion is composed of a material containing an intermetallic compound phase produced by chemical reaction between a first metal which is Sn or an alloy including Sn and a second metal which is a CuNi alloy, a CuMn alloy, an AgPd alloy, a CuAl alloy, or a CuCr alloy.

Claims

1. A sliding member for a rotary device, the sliding member comprising: a slide-contact portion having a slide-contact face that contacts a rotating object, wherein the slide-contact face that contacts the rotating object contains an intermetallic compound that is an alloy containing one of (1) at least two selected from a first group consisting of Sn, Cu and Ni, and (2) at least two selected from a second group consisting of Sn, Cu, and Mn.

2. The sliding member according to claim 1, wherein the intermetallic compound is the result of a reaction between a first metal which is Sn or an alloy including Sn and a second metal which is a CuNi alloy, a CuMn alloy, an AgPd alloy, a CuAl alloy, or a CuCr alloy.

3. The sliding member according to claim 2, further comprising an arm section composed of a third metal bonded to the slide-contact portion with an alloy layer composed of the first metal and the third metal interposed therebetween.

4. The sliding member according to claim 1, wherein the intermetallic compound is a CuNiSn alloy.

5. The sliding member according to claim 1, wherein the intermetallic compound is one of Cu.sub.6Sn.sub.5, Ni.sub.3Sn.sub.4 and Cu.sub.2NiSn.

6. The sliding member according to claim 1, wherein the slide-contact portion is a portion of a commutator or a brush.

7. The sliding member according to claim 1, wherein the slide-contact portion further contains carbon.

8. The sliding member according to claim 1, wherein the slide-contact portion is a porous material.

9. The sliding member according to claim 8, wherein the slide-contact portion has a porosity of 0.1 to 60%.

10. The sliding member according to claim 1, further comprising an arm section bonded to the slide-contact portion with a conductive bonding material.

11. A rotary device comprising: the slide-contact portion according to claim 1; and a rotor contacting the slide-contact portion.

Description

BRIEF EXPLANATION OF THE DRAWINGS

(1) FIG. 1 is an external perspective view of a motor 100 including a brush 7 according to a first embodiment of the present invention.

(2) FIG. 2 is a sectional view of the brush 7 illustrated in FIG. 1.

(3) FIG. 3 is an enlarged sectional view of a distal portion of the brush 7 illustrated in FIG. 1.

(4) FIG. 4 is a flow chart illustrating a method for manufacturing the brush 7 illustrated in FIG. 1.

(5) FIG. 5 is a sectional view illustrating a loading step in FIG. 4.

(6) FIG. 6 is a sectional view illustrating an inserting step in FIG. 4.

(7) FIG. 7 is a sectional view illustrating a pressure-heating step in FIG. 4.

(8) FIG. 8 is a sectional view of a brush 207 according to a second embodiment of the present invention.

(9) FIG. 9 is an enlarged sectional view of a distal portion of the brush 207 illustrated in FIG. 8.

(10) FIG. 10 is a flow chart illustrating a method for manufacturing the brush 207 illustrated in FIG. 8.

(11) FIG. 11 is a sectional view illustrating a loading step in FIG. 10.

(12) FIG. 12 is a sectional view illustrating a pressure-heating step in FIG. 10.

(13) FIG. 13 is a sectional view illustrating a bonding step in FIG. 10.

(14) FIG. 14 is a sectional view of a brush 307 according to a third embodiment of the present invention.

(15) FIG. 15 is a sectional view of a brush 407 according to a fourth embodiment of the present invention.

(16) FIG. 16 is a sectional view of a brush 507 according to a fifth embodiment of the present invention.

(17) FIG. 17 is a sectional view of a brush 607 according to a sixth embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

(18) A brush according to a first embodiment of the present invention will now be described.

(19) FIG. 1 is an external perspective view of a motor 100 including a brush 7 according to the first embodiment of the present invention. FIG. 2 is a sectional view of the brush 7 illustrated in FIG. 1. FIG. 3 is an enlarged sectional view of a distal portion of the brush 7 illustrated in FIG. 1.

(20) The motor 100 includes a casing 9, a permanent magnet 2, a rotor 3, and a brush 7. The motor 100 converts electric energy into rotational energy (torque) by rotation of the rotor 3.

(21) The casing 9 houses the permanent magnet 2, the rotor 3, and the brush 7. The casing 9 is composed of a case body 91 and a cap 92. The cap 92 is detachably attached to the case body 91. The permanent magnet 2 is fixed to the inner circumference of the case body 91. A fixing section 60 of the brush 7, which will be described later, is fixed to the inner circumference of the cap 92.

(22) The rotor 3 includes a rotor shaft 4 rotatably supported inside the casing 9, and an armature 5 and commutators 6 electrically connected to a coil (not shown) of the armature 5 are provided on the rotor shaft 4. The armature 5 is composed of an iron core and a coil (illustration is omitted). Three commutators 6 are each a curved sheet of metal taking a form of a segment of a cylinder and are provided on a cylindrical insulating body by integral molding or by bonding with adhesive.

(23) As illustrated in FIGS. 2 and 3, the brush 7 includes the fixing section 60, an arm section 51, and a slide-contact portion 20. The end of the arm section 51 opposite the slide-contact portion 20 is bonded to the fixing section 60 with a conductive bonding material such as solder interposed therebetween. The fixing section 60 is fixed to the inner face of the casing 9. The arm section 51 is composed of third metal.

(24) A flexible conductive metal such as phosphor bronze or nickel silver that can be formed into a spring may be used as the material of the arm section 51. Regarding conductivity, the material of the arm section 51 is preferably composed of a metal containing copper. A relatively hard material such as stainless steel may be used as the material of the fixing section 60.

(25) The slide-contact portion 20 has a slide-contact face 71 that contacts the rotating rotor 3. The commutator 6 also has a slide-contact face that contacts the rotating rotor 3. The slide-contact portion 20 of the brush 7 is always in slide contact with the commutators 6 to make a current flow into the coil of the armature 5. The brush 7 and the commutators 6 reach high temperature by resistance loss and slide contact (friction). Thus, the temperature in the internal space of the casing 9 also becomes high.

(26) As illustrated in FIG. 3, the slide-contact portion 20 is composed of an intermetallic compound phase 12 produced by chemical reaction between first metal 11 (see FIG. 5) and second metal 21, which will be described later. The slide-contact portion 20 contains carbon 27, pores 26, and the second metal 21 in the intermetallic compound phase 12. The first metal 11, the second metal 21, and the carbon 27 take a form of powder particles.

(27) The first metal 11 is a pure metal of Sn. The second metal 21 is an alloy of CuNi. The intermetallic compound phase 12 is composed of a CuNiSn alloy. The alloy layer 25 will be described later.

(28) The slide-contact portion 20 has as a main phase the intermetallic compound phase 12 produced by reaction between Sn and a CuNi alloy. The CuNiSn alloy composing the intermetallic compound phase 12 has a reaction temperature of about 200 C. and a melting point of 300 C. or above.

(29) Thus, the slide-contact portion 20 does not require such a high sintering temperature as the non-resin-based brushes and can be formed at a low temperature. That is, the brush 7 can be manufactured easier and with higher accuracy than the non-resin-based brushes.

(30) The intermetallic compound phase 12 has a hardness (indentation hardness) of about 300 to 500 mg/m.sup.2. Thus, there is a little chance of the metal powder coming out of the intermetallic compound phase 12. That is, the brush 7 has higher durability than the resin-based brushes.

(31) Therefore, the brush 7 according to the embodiment has high durability and can be manufactured easily and with high accuracy.

(32) The CuNiSn alloy has approximately the same conductivity as a carbon containing copper powder that is used for a slide-contact portion of a conventional brush. The brush 7 according to the embodiment has high conductivity.

(33) The slide-contact portion 20 preferably contains the carbon 27 in the intermetallic compound phase 12. With the carbon 27 contained, the abrasion resistance of the slide-contact portion 20 can further be improved.

(34) As illustrated in FIG. 3, the slide-contact portion 20 is preferably composed of a porous material including pores 26.

(35) The brush 7 and the commutator 6 are heated by resistance loss, and frictional heat caused by slide contact is generated at the slide-contact faces of the brush 7 and the commutator 6. Here, the slide-contact portion 20 composed of a porous material offers a large specific surface area. A large area contacting the air stream produced by the rotation of the rotor 3 increases heat dissipation of the slide-contact portion 20.

(36) A porosity of the slide-contact portion 20 below 0.1% can hardly provide an air cooling effect, whereas a porosity of the slide-contact portion 20 above 60% cannot provide sufficient strength. Thus, the porosity of the slide-contact portion 20 is preferably within a range from 0.1 to 60%.

(37) The motor 100 including the brush 7 according to the embodiment also provides a similar effect as the brush 7.

(38) A method for manufacturing the brush 7 will now be described below.

(39) FIG. 4 is a flow chart illustrating a method for manufacturing the brush 7 illustrated in FIG. 1. FIG. 5 is a sectional view illustrating a loading step in FIG. 4. FIG. 6 is a sectional view illustrating an inserting step in FIG. 4. FIG. 7 is a sectional view illustrating a pressure-heating step in FIG. 4.

(40) The pressure-heating step in FIG. 4 corresponds to a forming step of the present invention.

(41) First, an arm section 51 and a fixing section 60 bonded together with a bonding material and a die-cast container D are prepared.

(42) As illustrated in FIG. 5, the first metal 11, the second metal 21, and the carbon 27 are loaded in the container D (S1 in FIG. 4). In the embodiment, Sn powder of an average particle size of 20 m, CuNi alloy powder of an average particle size of 5 m, and carbon powder of an average particle size of 1 m are loaded in the container D. The compounding ratio of Sn powder, CuNi alloy powder, and carbon powder is 10:10:1 by weight.

(43) After loading the powder, the first metal 11, the second metal 21, and the carbon 27 are mixed using a pestle or the like to prepare a uniformly mixed powder mixture 10. The powder mixture 10 corresponds to the mixture of the present invention.

(44) The compounding ratio of Sn powder and CuNi alloy powder is preferably within a range from 5:95 to 50:50 by weight. Excessive Sn powder results in remaining Sn component which may melt at high temperature or adhere by sliding. When CuNi alloy powder is excessively mixed, the excessive CuNi alloy component may adhere by sliding.

(45) The Sn powder preferably has an average particle size (D50) within a range from 5 to 50 m. The CuNi alloy powder preferably has an average particle size (D50) within a range from 0.1 to 80 m.

(46) The Sn powder having an average particle size below 5 m may not melt. The Sn powder having an average particle size above 50 m may cause variation in composition of the material resulting from the reaction.

(47) The CuNi alloy powder having an average particle size below 0.1 m may result in poor wettability which may cause the CuNi alloy powder and the Sn powder to separate from each other. The CuNi alloy powder having an average particle size above 80 m results in remaining CuNi alloy powder which may adhere by sliding.

(48) The contained amount of the carbon powder is preferably within a range from 0.1 to 20% by weight of the total amount of the Sn powder and the CuNi alloy powder. The carbon powder preferably has an average particle size (D50) within a range from 0.01 to 50 m.

(49) The compounding amount of carbon powder below 0.1% by weight may cause adhesion of metal composition by sliding. The compounding amount of the carbon powder above 20% by weight may increase contact resistance.

(50) The carbon powder having an average particle size below 0.01 m may come out of the resulting material, which causes a loss in a lubricating effect. The average particle size above 50 m may increase contact resistance.

(51) As illustrated in FIG. 6, the distal end of the arm section 51 is inserted in the powder mixture 10 (S2 in FIG. 4).

(52) With the distal end of the arm section 51 inserted in the powder mixture 10, as illustrated in FIG. 7, the powder mixture 10 is heated at a predetermined temperature (200 C. in the embodiment) under a predetermined pressure (20 MPa in the embodiment) (S3 in FIG. 4).

(53) By heating the powder mixture 10 illustrated in FIG. 6, the slide-contact portion 20 illustrated in FIG. 7 is formed. The slide-contact portion 20 is composed of the intermetallic compound phase 12, the second metal 21 contained in the intermetallic compound phase 12, the carbon 27, the pores 26, and the CuSn alloy layer 25.

(54) In detail, heating of the powder mixture 10 causes chemical reaction between the first metal and the second metal to produce the intermetallic compound (for example, Cu.sub.6Sn.sub.5, Ni.sub.3Sn.sub.4, Cu.sub.2NiSn). The reaction is generated by, for example, transient liquid phase diffusion bonding (TLP bonding). The produced intermetallic compound is an alloy containing at least two selected from a group of Cu, Ni, and Sn. The melting point of the intermetallic compound is 300 C. or above, or in some cases, 400 C. or above.

(55) The intermetallic compound phase 12 is composed of the intermetallic compound. That is, the slide-contact portion 20 has a CuNiSn alloy phase as a main phase in which the second metal particles, the carbon particles, and the pores are dispersed.

(56) Heating of the powder mixture 10 also causes chemical reaction between the first metal 11 and the third metal composing the arm section 51 to form the CuSn alloy layer 25. The intermetallic compound phase 12 and the arm section 51 are thereby firmly bonded together.

(57) CuNi alloy powder may remain in the intermetallic compound phase 12. Preferably, no remaining Sn particle substantially exists. Cu-10Ni alloy powder, for example, may be used as CuNi alloy powder.

(58) Preferably, the heating temperature in S3 is about 50 to 300 C. and the pressure is about 0.1 to 50 MPa. A heating step in S3 can be performed at a low heating temperature by treating under a high pressure. The heating time in S3 is preferably about 1 to 10 minutes.

(59) Treating below a heating-pressurizing condition of 50 C. and 0.1 Pa results in a remaining metal component that may adhere by sliding. Treating above a heating-pressurizing condition of 300 C. and 50 Pa excessively promotes the reaction, causing the resulting material to be fragile.

(60) With a heating time shorter than one minute, a metal component may remain and adhere by sliding. With a heating time longer than ten minutes, the resulting material becomes fragile and may crack or chip.

(61) After naturally cooled, the distal end of the arm section 51 is pulled out from the container D (S4 in FIG. 4). With this step, manufacturing of the brush 7 (see FIGS. 2 and 3) having the slide-contact portion 20 on the distal end of the arm section 51 is completed.

(62) As described above, the brush 7 having high durability can be manufactured under a low temperature by the manufacturing method according to the embodiment. The brush 7 can be manufactured easily and thus keeps a high dimensional accuracy.

(63) A brush according to a second embodiment of the present invention will now be described.

(64) FIG. 8 is a sectional view of a brush 207 according to the second embodiment of the present invention. FIG. 9 is an enlarged sectional view of a distal portion of the brush 207 illustrated in FIG. 8. FIG. 9 is an enlarged view of the section encircled by a dashed line in FIG. 8.

(65) The brush 207 according to the second embodiment is different from the brush 7 according to the first embodiment in that a slide-contact portion 220 is bonded to an arm section 51 with a conductive bonding material 225 interposed therebetween. The conductive bonding material 225 is, for example, a Sn-based solder (SnAgCu solder in the embodiment). The slide-contact portion 220 has a slide-contact face 271 as well. Other part of the structure is the same as the brush 7.

(66) The slide-contact portion 220 uses the same material as the slide-contact portion 20. As illustrated in FIG. 9, the slide-contact portion 220 is composed of an intermetallic compound phase 12 produced by chemical reaction between the first metal 11 (see FIG. 11) and the second metal 21, which will be described later. The slide-contact portion 220 contains the carbon 27, the pores 26, and the second metal 21 in the intermetallic compound phase 12.

(67) The first metal 11 is a pure metal of Sn. The second metal 21 is an alloy of CuNi. The intermetallic compound phase 12 is composed of a CuNiSn alloy.

(68) The slide-contact portion 220 has as a main phase the intermetallic compound phase 12 produced by reaction between Sn and a CuNi alloy. The CuNiSn alloy composing the intermetallic compound phase 12 has a reaction temperature of about 200 C. and a melting point within a range from 300 C. to 600 C.

(69) Thus, the slide-contact portion 220 does not require such a high sintering temperature as the non-resin-based brushes and can be formed at a low temperature. That is, the brush 207 can be manufactured easier and with higher accuracy than the non-resin-based brushes.

(70) The intermetallic compound phase 12 has a hardness (indentation hardness) of about 300 to 500 mg/m.sup.2. Thus, there is a little chance of the metal powder coming out of the intermetallic compound phase 12. That is, the brush 207 has higher durability than the resin-based brushes.

(71) Therefore, the brush 207 according to the embodiment has high durability and can be manufactured easily and with high accuracy like the brush 7 according to the first embodiment.

(72) The slide-contact portion 220 preferably contains the carbon 27 in the intermetallic compound phase 12. With the carbon 27 contained, the abrasion resistance of the slide-contact portion 220 can further be improved.

(73) As illustrated in FIG. 9, the slide-contact portion 220 is preferably composed of a porous material including pores 26. This gives a large area that contacts the air stream produced by the rotation of the rotor 3, which increases heat dissipation of the slide-contact portion 220.

(74) The motor 100 can include the brush 207 in place of the brush 7. In such a configuration, the brush 207 is fixed to the casing 9 in place of the brush 7.

(75) A method for manufacturing the brush 207 will now be described below.

(76) FIG. 10 is a flow chart illustrating a method for manufacturing the brush 207 illustrated in FIG. 8. FIG. 11 is a sectional view illustrating a loading step in FIG. 10. FIG. 12 is a sectional view illustrating a pressure-heating step in FIG. 10. FIG. 13 is a sectional view illustrating a loading step in FIG. 10.

(77) The method for manufacturing the brush 207 illustrated in FIG. 10 is different from the method for manufacturing the brush 7 illustrated in FIG. 4 in a pressure-heating step S22 and a bonding step in S23. A loading step S1 in FIG. 10 is the same as the loading step S1 in FIG. 4, and thus a detailed description thereof is omitted.

(78) The pressure-heating step S22 and the bonding step S23 correspond to the forming step of the present invention.

(79) First, an arm section 51 and a fixing section 60 bonded together with a bonding material and a die-cast container D are prepared.

(80) As illustrated in FIG. 11, first metal 11, second metal 21, and carbon 27 are loaded in the container D (S1 in FIG. 10). After loading the powder, the first metal 11, the second metal 21, and the carbon 27 are mixed using a pestle or the like to prepare a uniformly mixed powder mixture 10.

(81) Then as illustrated in FIG. 12, the powder mixture 10 is heated at a predetermined temperature (200 C. in the embodiment) under a predetermined pressure (20 MPa in the embodiment) (S22 in FIG. 10).

(82) By heating the powder mixture 10 illustrated in FIG. 11, a slide-contact portion 220 illustrated in FIG. 12 is formed. The slide-contact portion 220 is composed of an intermetallic compound phase 12, the second metal 21 contained in the intermetallic compound phase 12, the carbon 27, and pores 26.

(83) In detail, heating of the powder mixture 10 causes chemical reaction between the first metal and the second metal to produce the intermetallic compound (for example, Cu.sub.6Sn.sub.5, Ni.sub.3Sn.sub.4, Cu.sub.2NiSn). The intermetallic compound phase 12 is composed of the intermetallic compound. That is, the slide-contact portion 220 has a CuNiSn alloy phase as the main phase in which the second metal particles, carbon particles, and the pores are dispersed.

(84) CuNi alloy powder may remain in the intermetallic compound phase 12. Preferably, no remaining Sn particle substantially exists. Cu-10Ni alloy powder, for example, may be used as CuNi alloy powder.

(85) Preferably, the heating temperature in S22 is about 50 to 300 C. and the pressure is about 0.1 to 50 MPa. The heating time in S22 is preferably about 1 to 10 minutes.

(86) Treating below a heating-pressurizing condition of 50 C. and 0.1 Pa results in a remaining metal component that may adhere by sliding. Treating above a heating-pressurizing condition of 300 C. and 50 Pa excessively promotes the reaction, causing the resulting material to be fragile.

(87) With a heating time shorter than one minute, a metal component may remain and adhere by sliding. With a heating time longer than ten minutes, the resulting material becomes fragile and may crack or chip.

(88) After naturally cooled, the slide-contact portion 220 is bonded to the arm section 51 with a conductive bonding material 225 interposed therebetween (S23 in FIG. 10). With this step, manufacturing of the brush 207 (see FIGS. 8 and 9) having the slide-contact portion 220 on the distal end of the arm section 51 is completed.

(89) As described above, the brush 207 having high durability can be manufactured under a low temperature by the manufacturing method according to the embodiment. The brush 207 can be manufactured easily and thus keeps a high dimensional accuracy.

Other Embodiments

(90) In the embodiments described above, the invention is applied to a motor that converts electric energy into rotational energy (torque). The invention is applicable not only to a motor. For example, the invention may be applied to a dynamo that converts rotational energy (torque) into electric energy.

(91) The first metal is pure Sn metal in the embodiment but not limited to such metal. The first metal of the embodiment may be an alloy containing Sn.

(92) The second metal is a CuNi alloy in the embodiment but not limited to such alloy. The second metal of the embodiment may be a CuMn alloy, an AgPd alloy, a CuAl alloy, or a CuCr alloy. For example, in a case where the second metal is a CuMn alloy, melted Sn (first metal) and the CuMn alloy (second metal) react with each other to produce an intermetallic compound containing at least two selected from a group of Cu, Mn, and Sn.

(93) In the embodiment, the first metal 11, the second metal 21, and the carbon 27 are loaded in the container D in the loading step in S1 in FIGS. 4 and 10. The material loaded in S1 is not limited to such materials. For example, powder of a thermoplastic resin may be loaded. In this case, the melted thermoplastic resin intrudes into the pores 26 during the pressure-heating step. On completion of this step, the thermoplastic resin serves as a lubricant.

(94) In the embodiment, the brush 7 has the slide-contact portion 20 and the brush 207 has the slide-contact portion 220. The invention is not limited to such configurations. For example, the embodiments may include a plate brush 307 illustrated in FIG. 14, a precious metal brush 407 illustrated in FIG. 15, and carbon brushes 507 and 607 illustrated in FIGS. 16 and 17 respectively having slide-contact portions 320, 420, 520, and 620 on distal ends of arm sections 351, 451, 551, and 651.

(95) The precious metal brush 407 is used mainly in a motor that operates under low current and voltage to generate small power. The slide-contact portion of a conventional precious metal brush is composed of precious metal (for example, AgPd or Pd), whereas the slide-contact portion 420 of the precious metal brush 407 is composed of an intermetallic compound. The carbon brushes 507 and 607 are used mainly in a motor that operates under high current and voltage to generate large power.

(96) The plate brush 307, the precious metal brush 407, and the carbon brushes 507 and 607 respectively include fixing sections 360, 460, 560, and 660 each bonded to an end opposite the slide-contact portion 320, 420, 520, or 620 of the arm section 351, 451, 551, or 651.

(97) In the embodiments, the whole slide-contact portion is composed of an intermetallic compound. The slide-contact portion however is not necessarily composed in such a manner. Only the surface of the slide-contact portion may be composed of an intermetallic compound in the embodiment.

(98) In the embodiment, the brush has the slide-contact portion. The slide-contact portion needs not always be provided on a brush. A commutator may be provided with a slide-contact portion in the embodiment.

(99) The embodiments described above are all described by way of illustration, not by way of limiting the scope of the present invention. The scope of the present invention is determined by the claims, not by the embodiments. Alterations equivalent to the claims all fall within the scope of the present invention.

DESCRIPTION OF REFERENCE SYMBOLS

(100) D: container 2: permanent magnet 3: rotor 4: rotor shaft 5: armature 6: commutator 7: brush 9: casing 10: powder mixture 11: first metal 12: intermetallic compound phase 20: slide-contact portion 21: second metal 25: alloy layer 26: pore 27: carbon 51: arm section 60: fixing section 71: slide-contact face 91: case body 92: cap 100: motor 207: brush 220: slide-contact portion 225: conductive bonding material 271: slide-contact face 307: plate brush 320: slide-contact portion 351: arm section 360: fixing section 407: precious metal brush 420: slide-contact portion 460: fixing section 507: carbon brush 520: slide-contact portion 560: fixing section 607: carbon brush 620: slide-contact portion 660: fixing section