Two-layer disk, commutator provided with same, and method for manufacturing commutator

Abstract

The purpose of the present invention is to achieve a two-layer disk in which solder bonding can be performed on a riser piece without a plating layer, the strength of a metal layer is excellent, and the resistivity of the metal layer is small. The two-layer disk (10) has a carbon layer (1) and a metal layer (2). The metal layer (2) can be soldered to a riser piece (20) without having a plating layer on a surface (2a). The metal layer (2) contains copper powder, and the content of the copper powder is at least 10 mass% when the metal component in the metal layer (2) is 100 mass%.

Description

Dual-layer disc, commutator including same, and method for manufacturing commutator

[0001] The present invention relates to a dual-layer disk, a commutator including the same, and a method for manufacturing the commutator.

[0002] Conventionally, commutators in which riser pieces are joined to disks have been known. When manufacturing such commutators, it is necessary to join the disks and riser pieces. Conventional methods for joining the disks and riser pieces include the techniques disclosed in Patent Documents 1 to 4, for example.

[0003] In the technique disclosed in Patent Document 1, a plated layer is formed on the disk, and the disk and riser piece are soldered together via the plated layer.

[0004] In the technology disclosed in Patent Document 2, a protrusion is provided on a two-layer disk having a metal layer and a carbon layer, and a hole is provided in a riser piece, and the two-layer disk and the riser piece are joined by press-fitting the protrusion of the two-layer disk into the hole of the riser piece.

[0005] In the technology disclosed in Patent Document 3, a protrusion is provided on a single-layer disk having a carbon layer, and a hole is provided in a riser piece. Furthermore, a plating layer is applied to both the single-layer disk and the riser piece. The protrusion of the dual-layer disk is lightly press-fitted into the hole in the riser piece, and is solder-joined to the single-layer disk and the riser piece.

[0006] The technology disclosed in Patent Document 4 is a method for joining a riser piece to the metal layer side of a two-layer disk having a metal layer and a carbon layer. In this technology, the metal layer is solder-joined to the riser piece without a plating layer on the surface of the metal layer. To achieve this solder-joining to the riser piece without a plating layer, the metal layer in the two-layer disk contains brass, tin, and 0 mass% to less than 5 mass% carbon, but does not contain copper powder.

[0007] Japanese Patent Publication No. 2003-502809 Japanese Patent Publication No. 2002-64958 Japanese Patent Publication No. 10-4653 International Publication No. 2019 / 188168

[0008] However, the above-mentioned conventional techniques have the following problems.

[0009] The technology disclosed in Patent Document 1 requires a plating process for plating the disk before joining the disk and the riser piece, which makes joining the disk and the riser piece complicated and difficult to perform.

[0010] The techniques disclosed in Patent Documents 2 and 3 have the problem that the shapes of the disk and riser piece become complicated because a protrusion and a hole must be fitted together to press-fit the disk and riser piece.

[0011] The technique disclosed in Patent Document 4 is simple because it does not require a plating process for plating the disk, but the resistivity and strength of the metal layer of the dual-layer disk are insufficient.

[0012] One aspect of the present invention aims to provide a two-layer disk that can be soldered to a riser piece without a plating layer, has a metal layer with excellent strength and low resistivity, a commutator including the same, and a method for manufacturing the commutator.

[0013] In order to solve the above problems, one aspect of the present invention includes the following.

[0014] A two-layer disk having a carbon layer and a metal layer, wherein the metal layer can be soldered to a riser piece without a surface plating layer, and the metal layer contains copper powder, and when the metal component in the metal layer is 100% by mass, the content of the copper powder is 10% by mass or more.

[0015] A two-layer disk having a carbon layer and a metal layer, wherein the metal layer can be soldered to a riser piece without a surface plating layer, and the metal layer contains copper powder, and the two-layer disk satisfies a / b≧0.34, where a is the content (mass%) of copper powder when the metal component in the metal layer is 100 mass%, and b is the average particle diameter (μm) of the copper powder.

[0016] A method for manufacturing a commutator, comprising: a coating step of coating solder on a surface of a metal layer of a two-layer disk having a carbon layer and a metal layer without forming a plating layer on the surface of the metal layer; and a joining step of overlapping the metal layer coated with solder with a riser piece base and then heating the overlapping parts to join the metal layer and the riser piece base, wherein the metal layer contains copper powder, and the copper powder content is 10 mass % or more when the metal component in the metal layer of the two-layer disk is 100 mass %.

[0017] A method for manufacturing a commutator, comprising: a coating step of coating solder on a surface of a metal layer in a two-layer disk having a carbon layer and a metal layer without forming a plating layer on the surface of the metal layer; and a joining step of overlapping the metal layer coated with solder and a riser piece base body, and then heating the overlapped metal layer and the riser piece base body to join the metal layer and the riser piece base body, wherein the metal layer contains copper powder, and when the metal component in the metal layer is 100 mass%, the copper powder content (mass %) is a and the average particle diameter (μm) of the copper powder is b, the following relationship is satisfied: a / b≧0.34.

[0018] According to one aspect of the present invention, it is possible to realize a two-layer disk that can be soldered to a riser piece without a plating layer, has a metal layer that is strong and has low resistivity, a commutator that includes the same, and a method for manufacturing the commutator.

[0019] Fig. 1 is a plan view showing a schematic configuration of a commutator according to embodiments 1 and 2 of the present invention. Fig. 2 is a cross-sectional view taken along line II-II of the commutator in Fig. 1. Fig. 3 is an enlarged cross-sectional view showing the joint between the dual-layer disk and the riser piece in Fig. 2. Fig. 4 is a cross-sectional view showing a schematic configuration of a dual-layer disk according to an embodiment of the present invention. Fig. 5 is a graph showing the relationship between the copper powder content / average particle diameter of copper powder and solder wettability for Examples 1 to 7 and Comparative Examples 2 and 5.

[0020] [Embodiment 1] Hereinafter, an embodiment of the present invention will be described in detail. However, the present invention is not limited to this, and various modifications are possible within the described scope. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments and examples are also included in the technical scope of the present invention. In this specification, unless otherwise specified, "A to B" representing a numerical range means "A or more (including A and greater than A)" or "B or less (including B and less than B)."

[0021] (Commutator Configuration) Fig. 1 is a plan view showing a schematic configuration of a commutator 100 according to this embodiment. Fig. 2 is a cross-sectional view of the commutator 100 taken along line II-II in Fig. 1. Fig. 3 is an enlarged cross-sectional view showing the joint between the dual-layer disc 10 and the riser piece 20 in Fig. 2.

[0022] As shown in Figures 1 and 2, the commutator 100 according to this embodiment has a generally disc-shaped exterior shape, and is provided with through-holes 31 that penetrate the generally disc-shaped exterior shape in the direction of axis X. Here, in this application, the direction of axis X of the commutator 100 is the HD direction (height direction), and "HDa" refers to the upper side, which is one side of the HD direction, and "HDb" refers to the lower side, which is the other side of the HD direction. Furthermore, the "circumferential direction" refers to the circumferential direction of the generally disc-shaped exterior shape of the commutator 100 in the plan view of Figure 1. Furthermore, the "radial direction" refers to the radial direction of the generally disc-shaped exterior shape of the commutator 100.

[0023] The commutator 100 includes a dual-layer disk 10, a solder layer 3, a riser piece 20, and a resin base 30. As shown in Fig. 2, the dual-layer disk 10, the solder layer 3, the riser piece 20, and the resin base 30 (lower portion 30a) are arranged in this order in the commutator 100 from the HDa side to the HDb side.

[0024] The resin base 30 is made of a thermosetting resin and has a thick, generally disk-shaped lower portion 30a and two side portions 30b. The two side portions 30b are erected on the HDa side of the lower portion 30a and extend circumferentially. In the external shape of the commutator 100, the two side portions 30b of the resin base 30 each define the outer peripheral surface of the generally disk-shaped portion and the through-hole 31. A plurality of segments 40 are formed on the HDa-side surface of the lower portion 30a of the resin base 30. As shown in FIG. 1 , each segment 40 is formed in a generally fan-like shape in a plan view. The plurality of segments 40 are radially arranged from the through-hole 31 on the HDa-side surface of the lower portion 30a at equal intervals in the circumferential direction. The two side portions 30b cover the circumferential surfaces of the segments 40 in the radial direction.

[0025] The riser pieces 20 are conductive members electrically connected to each segment 40. Each of the riser pieces 20 is supported on the HDa-side surface of the lower portion 30a of the resin base 30, and has a piece body 21 and a hook 22. The piece body 21 and the hook 22 are connected to each other. The piece body 21 is a portion joined to the segment 40 by a solder layer 3. The hook 22 protrudes from the outer peripheral side portion 30b of the resin base 30. The hook 22 is provided for electrical connection to an external circuit, and a wire (not shown) is wound around the hook 22.

[0026] The segment 40 is made of a dual-layer disk 10. The riser piece 20 (piece body 21) is joined on the metal layer 2 side of the dual-layer disk 10. The metal layer 2 is solder-joined to the riser piece 20 without a plated layer on its surface. That is, the metal layer 2 is joined to the riser piece 20 (piece body 21) on the HDb side by a solder layer 3. No plated layer is interposed between the metal layer 2 and the solder layer 3.

[0027] The component of the solder layer 3 is not particularly limited as long as it is a material that is used for conventionally known solder joints, but the component of the solder layer 3 is preferably tin solder containing tin as the main component.

[0028] The commutator 100 also has slits 32 that electrically insulate adjacent segments 40. The slits 32 extend in the HD direction from at least the carbon layer 1 to the piece body 21. The slits 32 separate the segments 40 from one another and also separate the riser pieces 20 from one another.

[0029] (Configuration of Dual-Layer Disk) As described above, a conventional technique has been proposed in which, when joining a riser piece to the metal layer side of a dual-layer disk having a metal layer and a carbon layer, the metal layer is solder-joined to the riser piece without forming a plating layer on the surface of the metal layer, as in Patent Document 4. In order to solder-join the riser piece without forming a plating layer, the metal layer in the dual-layer disk contains brass, tin, and 0 mass% or more but less than 5 mass% carbon, but does not contain copper powder (hereinafter, this may be simply referred to as the conventional configuration).

[0030] However, the present inventors independently discovered that even when a commutator is fabricated using a two-layer disk with a metal layer having a conventional configuration as in Patent Document 4, there is still a problem in that the strength, solder wettability, and resistivity of the metal layer are still insufficient. Therefore, the present inventors have worked diligently to develop a two-layer disk that can be soldered to a riser piece without a plated layer when used in a commutator, and that has a metal layer with excellent strength and low resistivity.

[0031] As a result, we have succeeded in developing a dual-layer disc in which the strength, solderability, and resistivity of the metal layer are all improved by adjusting the copper powder content in the metal layer to a specific amount or more. Specifically, the inventors discovered that the above-mentioned problems can be solved by adjusting the copper powder content to 10% by mass or more when the metal component in the metal layer is 100% by mass, and this led to the dual-layer disc 10 according to this embodiment.

[0032] In conventional technologies such as Patent Document 4, copper powder is not required in the metal layer of a dual-layer disc. Therefore, the dual-layer disc 10 according to the present embodiment, which is based on the above-mentioned new findings, could not have been predicted from conventional findings, but was independently completed by the inventors of the present application.

[0033] In addition, in order to solve the above problems, the inventors of the present invention conducted further intensive research and discovered that by setting the average particle size of the copper powder to 30 μm or less, all of the properties of the metal layer, including strength, solder wettability, and resistivity, can be further improved.

[0034] The dual-layer disc 10 according to this embodiment will be described in further detail below. FIG. 4 is a cross-sectional view showing a schematic configuration of the dual-layer disc 10 according to this embodiment. As shown in FIG. 4, the dual-layer disc 10 according to this embodiment has a carbon layer 1 and a metal layer 2. The dual-layer disc 10 is configured such that the carbon layer 1 is stacked on the HDa side of the metal layer 2. The metal layer 2 can be solder-bonded to the riser piece 20 without a plated layer on its surface 2a. In other words, the metal layer 2 has an area on its surface 2a where the solder layer 3 is formed, but does not have an area where a plated layer is formed.

[0035] (Carbon Layer 1) In the dual-layer disc 10 according to this embodiment, any carbon layer used in a conventional commutator can be adopted as the carbon layer 1. Preferably, the carbon layer 1 contains a carbon material and a thermoplastic resin.

[0036] The carbon material is the main component of the carbon layer 1, and examples thereof include natural graphite, artificial graphite, and amorphous carbon. Of these, natural graphite is preferred as the carbon material. The content of the carbon material may be any content that allows the carbon layer 1 to function in the commutator 100. The content of the carbon material is preferably 80 mass % or more, and more preferably 85 mass % or more, relative to the carbon layer 1. The average particle size of the carbon material is preferably 5 μm to 70 μm, and more preferably 15 μm to 40 μm.

[0037] The thermoplastic resin has the function of supporting the strength of the carbon layer 1 and the bonding between the carbon layer 1 and the metal layer 2. The thermoplastic resin is not particularly limited as long as it is a resin that can perform this function, but examples include polyphenylene sulfide (PPS), polyether ether ketone (PEEK), etc., and among these, polyphenylene sulfide (PPS) is preferred. The thermoplastic resin preferably has a melting point of 230°C or higher.

[0038] The content of the thermoplastic resin can be appropriately set so as to exhibit the above-mentioned functions. The content of the thermoplastic resin is preferably 3% by mass to 15% by mass, and more preferably 5% by mass to 15% by mass, relative to the carbon layer 1.

[0039] (Metal Layer 2) In the dual-layer disc 10 according to this embodiment, the metal layer 2 can be soldered to the riser piece without a surface plating layer. The metal layer 2 contains copper powder. When the metal components in the metal layer 2 are taken as 100% by mass, the copper powder content is 10% by mass or more, preferably 12% by mass or more, more preferably 13% by mass or more, and most preferably 13.5% by mass or more.

[0040] By ensuring that the copper powder content is within the above range, when used in a commutator, soldering to the riser piece 20 is possible without a plating layer, and a dual-layer disk 10 with excellent strength and low resistivity can be realized. That is, the metal layer 2 of the dual-layer disk 10 has the following effects: (a) improved solder wettability, (b) reduced resistivity of the metal layer 2, and (c) improved strength of the metal layer 2.

[0041] In this specification, the content of copper powder does not mean the content of copper components relative to all metal components in the metal layer 2, and does not include the content of copper components contained in brass. In other words, the content of copper powder can be said to be the content of copper components derived from copper powder relative to all metal components in the metal layer 2. Furthermore, the metal components of the metal layer 2 refer to the components of the metal layer 2 excluding non-metallic components.

[0042] Furthermore, the higher the copper powder content, the more the effects (a) to (c) above tend to improve. Therefore, there is no particular upper limit to the copper powder content. However, when the dual-layer disc 10 according to this embodiment is used in a fuel pump commutator for an automobile or the like, and is used in an application where it comes into contact with fuel containing sulfur as an impurity, in order to suppress corrosion of the dual-layer disc 10 by sulfur, the copper powder content is preferably 90% by mass or less, more preferably 70% by mass or less, and particularly preferably 60% by mass or less.

[0043] The effects of (a) to (c) can also be improved by adjusting the average particle size of the copper powder. In the dual-layer disc 10 according to this embodiment, the average particle size of the copper powder is not particularly limited as long as the effects of (a) to (c) are achieved, but it is preferably 30 μm or less, and more preferably 25 μm or less. By setting the average particle size of the copper powder within the above numerical range, the effects of (a) to (c) are further improved. Furthermore, the smaller the particle size of the copper powder, the more the effects of (a) to (c) tend to be improved.

[0044] On the other hand, the average particle size of the copper powder is preferably 15 μm or more. Therefore, in the dual-layer disc 10 according to this embodiment, the average particle size of the copper powder is preferably 15 μm to 30 μm, and more preferably 15 μm to 25 μm.

[0045] Furthermore, in the dual-layer disc 10 according to this embodiment, the metal layer 2 preferably contains brass powder. The brass powder is made of an alloy of copper and zinc. The brass powder provides the metal layer 2 with excellent filling properties and corrosion resistance. However, compared with copper powder, the brass powder deteriorates the solder wettability and strength of the metal layer 2. Therefore, in order to enable solder bonding to the riser piece 20 without a plating layer and to ensure the strength of the metal layer 2, it is preferable that the metal layer 2 contain brass powder in an amount of 80% by mass or less, assuming that the metal components of the metal layer 2 are 100% by mass. Furthermore, there is no particular lower limit on the brass content.

[0046] The content of the zinc component in the brass powder is preferably 20% by mass to 40% by mass, and more preferably 20% by mass to 30% by mass, when the metal components in the brass powder are taken as 100% by mass. By having the content of the zinc component in the above numerical range, the effect of corrosion resistance is exhibited.

[0047] In the dual-layer disc 10 according to this embodiment, the metal layer 2 preferably contains brass powder, copper powder, and tin. Tin melts at a relatively low temperature. Therefore, the inclusion of tin in the metal layer 2 allows the metal layer 2 to be sintered at a low temperature and improves the solder wettability of the metal layer 2.

[0048] A tin content of 5% by mass or more is a preferable condition for achieving solder bonding to the riser piece 20 without a plating layer. Furthermore, the higher the tin content, the more likely it is that solder wettability will improve. On the other hand, if the tin content exceeds 15% by mass, the dual-layer disc 10 may deform during sintering. Therefore, in the dual-layer disc 10 according to this embodiment, the tin content of the metal layer 2 is preferably 5% to 15% by mass, and more preferably 5% to 10% by mass, when the metal components of the metal layer 2 are taken as 100% by mass.

[0049] The content of each of the copper powder, brass powder, and tin contained in the metal layer 2, when the metal component is taken as 100 mass %, can be calculated by a conventionally known measurement method. The content of each of the copper powder, brass powder, and tin can be calculated, for example, by X-ray measurement, measurement by XRF (X-ray fluorescence analysis), measurement by 3D-SEM-EDX analysis, etc.

[0050] Furthermore, carbon materials such as natural graphite, artificial graphite, and amorphous carbon deteriorate solder wettability. Therefore, in the dual-layer disc 10 according to this embodiment, it is preferable that the metal layer 2 does not contain carbon. Here, "carbon-free" means that the metal layer 2 does not contain more than 0.1% by mass of carbon.

[0051] Furthermore, the metal layer 2 may contain a thermoplastic resin as another component. The thermoplastic resin improves the rigidity of the metal layer 2. Considering the rigidity of the metal layer 2, the content of the thermoplastic resin is 2% by mass or less. On the other hand, thermoplastic resins tend to deteriorate the solder wettability of the metal layer 2. Therefore, considering the solder wettability, it is preferable that the metal layer 2 does not contain a thermoplastic resin. Therefore, taking these factors into consideration, when the entire metal layer 2 is taken as 100% by mass, the content of the thermoplastic resin in the metal layer 2 is preferably 2% by mass or less, preferably 0% to 1% by mass, and more preferably 0% by mass, i.e., it does not contain a thermoplastic resin. Examples of thermoplastic resins used in the metal layer 2 include polyphenylene sulfide (PPS) and polyether ether ketone (PEEK), among which polyphenylene sulfide (PPS) is preferred.

[0052] The dual-layer disc 10 according to this embodiment is manufactured by the following method. First, the metal material (e.g., copper powder, brass powder, etc.) constituting the metal component of the metal layer 2 and the metal layer material, optionally including a non-metallic component such as a thermoplastic resin, are uniformly mixed in a mixer and poured into a mold. Next, a carbon layer material composed of a carbon material and a thermoplastic resin is uniformly mixed in the mixer and poured into the mold and laminated on the metal layer material. The metal layer material and the carbon layer material in the mold are then press-molded and sintered at 320°C in a reducing gas atmosphere, for example, to produce the dual-layer disc 10. When manufacturing the dual-layer disc 10 provided in the commutator 100 shown in FIGS. 1 and 2 , the dual-layer disc 10 serves as a ring-shaped segment base.

[0053] In the dual-layer disc 10 according to this embodiment, in order to achieve the effects (a) to (c) above, it is preferable that the metal layer 2 have all of the following properties (a') to (c').

[0054] The characteristic (a') is that the solder wettability of the metal layer 2 is preferably 1.9 mm or less, more preferably 1.8 mm or less, and even more preferably 1.6 mm or less. The solder wettability can be measured by the following method. 0.09 g of cream solder is applied to a test piece of the metal layer 2 to a height of 3 mm. The test piece to which the cream solder has been applied is then heated on a hot plate at an actual temperature of 300°C for 2 minutes, and the height of the cream solder after melting is measured, and this measured value is taken as the solder wettability. In this measurement method, a smaller height of the cream solder after melting indicates good solder wettability.

[0055] The characteristic (b') is that the resistivity of the metal layer 2 is preferably 2.1 μΩ m or less, more preferably 1.9 μΩ m or less, and even more preferably 1.5 μΩ m or less. The resistivity can be measured by a voltage drop method in accordance with JIS C 2820.

[0056] The characteristic (c') is that the bending strength of the metal layer 2 is preferably 8 MPa or more, and more preferably 10 MPa or more. The bending strength can be measured in accordance with JIS C 2820.

[0057] (Method of Manufacturing Commutator 100) A method of manufacturing the commutator 100 according to this embodiment will now be described with reference to FIGS. 1 to 3. The method of manufacturing the commutator 100 according to this embodiment includes a coating step and a joining step. In the coating step, solder is applied to the surface of the metal layer 2 of the dual-layer disk 10, which has a carbon layer 1 and a metal layer 2, without forming a plating layer. This coating step forms a solder layer 3 on the surface of the metal layer 2. In the joining step, the metal layer 2 to which the solder has been applied and the base of the riser piece 20 are superimposed, and then heated to join the metal layer 2 and the base of the riser piece 20 together.

[0058] In the manufacturing method of the commutator 100 according to this embodiment, the metal layer 2 contains copper powder. When the metal component of the metal layer 2 of the dual-layer disk 10 is taken as 100 mass %, the copper powder content is 10 mass % or more. This allows solder bonding to the riser piece without a plating layer, and makes it possible to manufacture a commutator 100 including a dual-layer disk 10 that has excellent strength and low resistivity.

[0059] The dual-layer disc 10 used in the coating process is in the form of a ring-shaped segment matrix formed by connecting a plurality of segments 40 together, as shown in Figures 1 and 2. Such a segment matrix can be manufactured by appropriately setting the shape of the mold used to manufacture the dual-layer disc 10.

[0060] The base body of the riser piece 20 used in the joining process is formed by connecting a plurality of riser pieces 20 together, as shown in Figures 1 and 2. Such a base body of the riser piece 20 can be manufactured by a conventionally known method.

[0061] The method for manufacturing the commutator 100 according to this embodiment preferably includes, after the joining step, a base forming step and a separation step.

[0062] In the base forming step, a resin base 30 is provided to support the base of the riser piece 20 in the solder joint between the segment base (dual-layer disc 10) and the base of the riser piece 20 after the joining step. Specifically, the resin base 30 having a lower portion 30a and two side portions 30b is molded around the solder joint between the segment base and the base of the riser piece 20.

[0063] In the separation process, the segment base body and the base body of the riser piece 20 are cut to separate them into individual riser pieces 20 and individual segments 40. The separation process forms slits 32. The separation process is performed after the base formation process.

[0064] The manufacturing method of the commutator 100 according to this embodiment may further include a riser piece plating step. In the riser piece plating step, the riser pieces 20 exposed from the resin base 30, i.e., the hooks 22, are plated with tin.

[0065] In the manufacturing method of the commutator 100 according to this embodiment, the coating process, the joining process, the base forming process, the separation process, and the riser piece plating process can each be performed by a known method that is known in conventional manufacturing methods of commutators.

[0066] [Embodiment 2] Another embodiment of the present invention will be described below with reference to Figures 1 to 3. A dual-layer disc 10 according to this embodiment is characterized by the ratio of the copper powder content (mass %) to the average particle diameter (µm) of the copper powder, where the metal components in the metal layer 2 are taken as 100 mass %. Other than the above features, the dual-layer disc 10 according to this embodiment has the same configuration as the dual-layer disc according to embodiment 1.

[0067] In addition to the features related to the copper powder content in embodiment 1, the inventors of the present application have been working hard to develop a two-layer disk that can be soldered to a riser piece without a plating layer when used in a commutator, and that has a metal layer with excellent strength and low resistivity.

[0068] The present inventors first considered the effect (a) to be related to the solder wettability of the metal layer 2 and the "total surface area of ​​the copper powder contained in 100 g of the metal component of the metal layer." Specifically, they speculated that the higher the "total surface area of ​​the copper powder contained in 100 g of the metal component of the metal layer," the better the solder wettability, i.e., the above-mentioned characteristic (a') is achieved. The "total surface area of ​​the copper powder contained in 100 g of the metal component of the metal layer" is correlated with the ratio of the copper powder content (mass %) to the average particle diameter (μm) of the copper powder, when the metal component of the metal layer is taken as 100 mass %. Based on this speculation, the present inventors focused on the ratio of the copper powder content (mass %) to the average particle diameter (μm) of the copper powder, when the metal component of the metal layer is taken as 100 mass %, and conducted extensive research into the correlation between this ratio and the above-mentioned characteristic (a'). As a result, the inventors have succeeded in developing a dual-layer disc that achieves the above-mentioned effect (a) by setting the ratio of the copper powder content (mass%) to the average particle diameter (μm) of the copper powder, where the metal component in the metal layer is taken as 100 mass%, to a specific value or more. Furthermore, the inventors have found that the dual-layer disc achieves the above-mentioned effects (b) and (c) in addition to the above-mentioned effect (a).

[0069] The dual-layer disk 10 according to this embodiment has a carbon layer 1 and a metal layer 2. The metal layer 2 can be soldered to a riser piece without a surface plating layer. The metal layer 2 contains copper powder, and when the metal components in the metal layer 2 are 100% by mass, the copper powder content (mass %) is a and the average particle diameter (μm) of the copper powder is b, the following relationship is satisfied: a / b≧0.34.

[0070] The dual-layer disc 10 of this embodiment has the above-mentioned effects (a) to (c), making it possible to solder the riser piece without a plating layer, and realizing a dual-layer disc with excellent metal layer strength and low resistivity.

[0071] From the viewpoint of improving the effects (a) to (c) above, a / b is preferably 0.45 or more, and more preferably 0.67 or more.

[0072] Furthermore, in the dual-layer disc 10 according to this embodiment, the copper powder content is preferably 10% by mass or more, more preferably 12% by mass or more, even more preferably 13% by mass or more, and most preferably 13.5% by mass or more, when the metal components in the metal layer 2 are taken as 100% by mass.

[0073] The manufacturing method of the commutator 100 according to this embodiment also includes a coating step and a joining step. In the coating step, solder is applied to the surface of the metal layer 2 of the dual-layer disk 10 having the carbon layer 1 and the metal layer 2 without forming a plating layer. This coating step forms a solder layer 3 on the surface of the metal layer 2. In the joining step, the metal layer 2 to which the solder has been applied and the base of the riser piece 20 are overlapped, and then heated to join the metal layer 2 and the base of the riser piece 20 together.

[0074] Furthermore, in the manufacturing method of the commutator 100 according to this embodiment, the metal layer 2 contains copper powder. When the metal component of the metal layer 2 is 100 mass %, the content (mass %) of the copper powder is defined as a, and the average particle diameter (μm) of the copper powder is defined as b, the following relationship is satisfied: a / b≧0.34. This allows solder bonding to the riser piece without a plating layer, and makes it possible to manufacture a commutator 100 including a two-layer disk 10 that has excellent strength and low resistivity.

[0075] Based on the inequality "a / b" mentioned above, the smaller the average particle size of the copper powder, the smaller the minimum amount of copper powder content (mass %) required to realize a dual-layer disc with improved metal layer strength, solderability, and resistivity. Therefore, from the viewpoint of reducing the amount of copper powder content (mass %) used, a smaller average particle size of the copper powder is preferable.

[0076] An embodiment of the present invention may have the following configuration.

[0077] <1> A two-layer disk having a carbon layer and a metal layer, wherein the metal layer can be soldered to a riser piece without a surface plating layer, and the metal layer contains copper powder, and when the metal component in the metal layer is 100% by mass, the content of the copper powder is 10% by mass or more.

[0078] <2> A two-layer disk having a carbon layer and a metal layer, wherein the metal layer can be soldered to a riser piece without a surface plating layer, and the metal layer contains copper powder, and the two-layer disk satisfies a / b≧0.34, where a is the content (mass%) of copper powder when the metal component in the metal layer is 100 mass%, and b is the average particle diameter (μm) of the copper powder.

[0079] <3> The dual-layer disc according to <1> or <2>, wherein the copper powder has an average particle size of 30 μm or less.

[0080] <4> The dual-layer disc according to any one of <1> to <3>, wherein the metal layer contains brass powder.

[0081] <5> The dual-layer disc according to any one of <1> to <4>, wherein the metal layer contains brass powder, copper powder, and tin.

[0082] <6> The dual-layer disk according to <4> or <5>, wherein the metal layer contains brass powder in an amount of 80% by mass or less when the metal component in the metal layer is taken as 100% by mass.

[0083] <7> The dual-layer disc according to <5>, wherein the metal layer has a tin content of 5 to 15% by mass when the metal component of the metal layer is taken as 100% by mass.

[0084] <8> The dual-layer disc according to any one of <1> to <7>, wherein the copper powder has an average particle size of 15 μm or more.

[0085] <9> The dual-layer disc according to any one of <1> to <8>, wherein the metal layer does not contain carbon.

[0086] <10> A commutator comprising a dual-layer disk according to any one of <1> to <9> and a riser piece joined to the metal layer side of the dual-layer disk, wherein the metal layer is solder-joined to the riser piece without a plating layer on its surface.

[0087] <11> A method for manufacturing a commutator, comprising: a coating step of coating solder on a surface of a metal layer in a two-layer disk having a carbon layer and a metal layer without forming a plating layer on the surface of the metal layer; and a joining step of overlapping the metal layer coated with solder with a riser piece base and then heating the overlapping parts to join the metal layer and the riser piece base, wherein the metal layer contains copper powder, and the copper powder content is 10 mass% or more when the metal components in the metal layer of the two-layer disk are 100 mass%.

[0088] <12> A method for manufacturing a commutator, comprising: a coating step of coating solder on a surface of a metal layer in a two-layer disk having a carbon layer and a metal layer without forming a plating layer on the surface of the metal layer; and a joining step of overlapping the metal layer coated with solder with a riser piece base and then heating to join the metal layer and the riser piece base, wherein the metal layer contains copper powder, and where a is the content (mass %) of copper powder when the metal components in the metal layer are 100 mass %, and b is the average particle diameter (μm) of the copper powder, the relationship a / b≧0.34 is satisfied.

[0089] <13> The method for producing a commutator according to <11> or <12>, wherein the copper powder has an average particle size of 30 μm or less.

[0090] <14> The method for manufacturing a commutator according to any one of <11> to <13>, wherein the metal layer contains brass powder.

[0091] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0092] The measurement methods used in the following examples and comparative examples are as follows.

[0093] <Measurement methods> [Resistivity, flexural strength, solder wettability] The materials for the metal layers of the examples and comparative examples were uniformly mixed, press-molded, and heat-treated in a reducing gas atmosphere at 320° C. to prepare test pieces for the metal layers. The obtained test pieces were long in the direction of press molding.

[0094] Resistivity: A current was passed through the test piece in the longitudinal direction, and the resistivity was measured by the voltage drop method in accordance with JIS C 2820.

[0095] Flexural strength: In accordance with JIS C 2820, the load at break of the test piece was measured using a material testing machine (trade name: Universal Material Testing Machine, Model No. 5966, manufactured by Instron Corporation).

[0096] Solder wettability: 0.09 g of cream solder was applied to the test piece to a height of 3 mm. The test piece with the applied cream solder was then heated on a hot plate at a temperature of 300°C for 2 minutes, and the height of the melted cream solder was measured, and this measurement value was taken as the solder wettability. The solder cream used in this method was the same as the solder actually used in manufacturing commutators.

[0097] [Average Particle Diameter of Copper Powder Contained in the Metal Layer of a Dual-Layer Disc] The dual-layer disc was embedded in resin. The embedded disc was then polished from the metal layer side until the metal layer was exposed, and from the sides until the metal layer was exposed. A microscope image (photograph) of the exposed metal layer of the polished embedded disc was then obtained. Copper powder was identified from the microscope image, and the particle diameters of 50 particles of copper powder were measured. The average of the particle diameter measurements of the obtained copper powder was taken as the average particle diameter of the copper powder.

[0098] (Examples 1 to 7, Comparative Examples 1 to 5) Metal layers and dual-layer discs were produced using the following materials: Brass powder: average particle size of 34 μm and zinc content of 30% by mass Tin powder: average particle size of 43 μm Silver powder: average particle size of 18 μm Copper powder: electrolytic copper powder with an average particle size of 20 μm, electrolytic copper powder with an average particle size of 25 μm, electrolytic copper powder with an average particle size of 30 μm, and electrolytic copper powder with an average particle size of 35 μm.

[0099] The metal layer materials of Examples 1 to 7 and Comparative Examples 1 to 5 were blended in the composition ratios shown in Table 1 and uniformly mixed using a mixer to prepare a metal layer material mixture. The metal layer material mixture was press-molded to prepare long test pieces. The resistivity, flexural strength, and solder wettability of the prepared test pieces were then measured. Note that a resistivity of 2.1 μΩ·m or less was considered to have a resistivity-reducing effect, a flexural strength of 8 MPa or more was considered to have a strength-improving effect, and a solder wettability of 1.9 mm or less was considered to have a solder wettability-improving effect. The measurement results are shown in Table 1. Note that in Table 1, the content of the metal component of each metal layer is expressed in mass %, and represents the percentage when the metal component in the metal layer is 100 mass %.

[0100] The metal layer material mixture and carbon powder were placed in a mold, pressed, and then sintered at 320°C in a reducing gas atmosphere to produce a dual-layer disk. The average particle size of the copper powder contained in the metal layer of the dual-layer disk was measured. The results are shown in Table 2.

[0101] A comparison of Examples 1 to 5 and Comparative Examples 1 and 2 in Table 1 shows that when the copper powder content is 10 mass% or more, there is an effect of reducing resistivity, an effect of improving strength, and an effect of improving solder wettability. Furthermore, it was found that in Examples 1 to 5, as the copper powder content increases, there is a tendency for the effect of reducing resistivity, the effect of improving strength, and the effect of improving solder wettability to improve.

[0102] From Examples 2, 6, and 7 in Table 1, it was found that when the average particle size of the copper powder is 30 μm or less, there is an effect of reducing resistivity, an effect of improving strength, and an effect of improving solder wettability. Furthermore, it was found that the effect of reducing resistivity, an effect of improving strength, and an effect of improving solder wettability tend to improve as the average particle size of the copper powder becomes smaller.

[0103] Comparative Examples 1, 3 to 5 have roughly the same composition of the metal layer as the example and comparative examples in Patent Document 4. From a comparison between Example 2 and Comparative Examples 1, 3 to 5, it was found that Example 1 has a greater effect of reducing resistivity, improving strength, and improving solder wettability than Comparative Examples 1, 3 to 5.

[0104] In Table 2, a dual-layer disc having the metal layer composition of Example 2 was produced, and the average particle size of the copper powder contained in the metal layer of the dual-layer disc was measured. As a result, it was found that the average particle size of the copper powder used to produce the metal layer was equivalent to the average particle size of the copper powder contained in the metal layer of the finished dual-layer disc. In other words, it was found that the average particle size of the copper powder used to produce the metal layer was maintained even in the finished dual-layer disc.

[0105] (Relationship between the copper powder content (mass%) and the average particle diameter (μm) of the copper powder) It is believed that there is a correlation between the solder wettability and the "total surface area of ​​the copper powder contained in 100 g of the metal component of the metal layer." Specifically, it was thought that the higher the total surface area of ​​the copper powder, the better the solder wettability of the metal layer (i.e., the lower the "solder wettability" value). Therefore, the correlation between the "total surface area of ​​the copper powder contained in 100 g of the metal component of the metal layer" and the solder wettability was confirmed.

[0106] Here, the "total surface area of ​​copper powder contained in 100 g of the metal component of the metal layer" can be calculated using the following formula: "Total surface area of ​​copper powder contained in 100 g of the metal component of the metal layer" = "Surface area of ​​one copper powder particle" × "Number of copper powder particles contained in 100 g of the metal component of the metal layer" = "Surface area of ​​one copper powder particle" × "Total volume of copper powder particles contained in 100 g of the metal component of the metal layer" ÷ "Volume of one copper powder particle".

[0107] And the density of copper (g / cm ３ ): A, mass (g) of copper powder contained in 100 g of the metal component of the metal layer: a, average particle diameter (μm) of copper powder: b, then "total surface area of ​​copper powder contained in 100 g of the metal component of the metal layer" = (4π(b / 2×10 －４ ) ２ ×(a / A)÷(4 / 3×π×(b / 2×10 －４ ) ３ ) = (6 / A × 10４ ) x a / b.

[0108] From the above formula, it can be seen that the "total surface area of ​​copper powder contained in 100 g of the metal component of the metal layer" is correlated with a ÷ b, i.e., (mass (g) of copper powder contained in 100 g of the metal component of the metal layer) ÷ (average particle diameter (μm) of the copper powder). Note that the "mass (g) of copper powder contained in 100 g of the metal component of the metal layer" is the "content (% by mass) of copper powder when the metal component in the metal layer is taken as 100% by mass."

[0109] Therefore, referring to Table 1, the correlation between the copper powder content / average particle size of copper powder and properties such as solder wettability for Examples 1 to 7 and Comparative Examples 2 and 5, which used copper powder, is summarized in Table 3 below.

[0110] Fig. 5 is a graph showing the relationship between the copper powder content / average particle size of the copper powder and solder wettability. As is clear from Fig. 5, there is a high correlation between the "copper powder content (mass%) when the metal component in the metal layer is taken as 100 mass% ÷ (average particle size of the copper powder)" and "solder wettability."

[0111] In FIG. 5, when "the copper powder content (mass%) when the metal component in the metal layer is 100 mass% ÷ (average particle diameter of the copper powder)" is defined as x and "solder wettability" is defined as y, the correlation between x and y is approximated by the relational expression "y = -0.89x + 2.2".

[0112] As mentioned above, a solder wettability of 1.9 mm or less is considered to be effective in improving solder wettability. Therefore, from the above relational expression, when the solder wettability is 1.9 mm or less, the "copper powder content (mass%) when the metal component in the metal layer is taken as 100 mass% ÷ (average particle size of the copper powder)" (a / b) is expressed as follows: a / b≧0.34.

[0113] Furthermore, as mentioned above, a resistivity of 2.1 μΩ·m or less is considered to have a resistivity reduction effect, and a bending strength of 8 MPa or more is considered to have a strength improvement effect. In the same manner as above, a graph of the relationship between a / b and resistivity and a graph of the relationship between a / b and bending strength were derived. It was confirmed that when a / b≧0.34, (1) the resistivity is 2.1 μΩ·m or less, and (2) the bending strength is 8 MPa or more. Therefore, it was found that satisfying a / b≧0.34 results in a resistivity reduction effect, an improvement in strength, and an improvement in solder wettability.

[0114] The present invention can be used in a commutator using carbon.

[0115] REFERENCE SIGNS LIST 1 carbon layer 2 metal layer 2a surface 10 two-layer disk 20 riser piece 100 commutator

Claims

1. A two-layer disk having a carbon layer and a metal layer, wherein the metal layer can be soldered to a riser piece without a surface plating layer, and the metal layer contains copper powder, and when the metal component of the metal layer is taken as 100% by mass, the content of the copper powder is 10% by mass or more.

2. A two-layer disk having a carbon layer and a metal layer, wherein the metal layer can be soldered to a riser piece without a surface plating layer, and the metal layer contains copper powder, and where the content (mass%) of copper powder when the metal components in the metal layer are 100 mass%, is a, and the average particle size (μm) of the copper powder is b, the two-layer disk satisfies a / b≧0.

34.

3. The dual-layer disc according to claim 1 or 2, wherein the copper powder has an average particle size of 30 μm or less.

4. The dual-layer disc according to claim 1 or 2, wherein the metal layer contains brass powder.

5. The dual-layer disc according to claim 1 or 2, wherein the metal layer contains brass powder, copper powder, and tin.

6. The dual-layer disc according to claim 4, wherein the metal layer contains 80% by mass or less of the brass powder when the metal component of the metal layer is taken as 100% by mass.

7. The dual-layer disc according to claim 5, wherein the metal layer contains 5 to 15% by mass of tin when the metal component of the metal layer is taken as 100% by mass.

8. The dual-layer disc according to claim 1 or 2, wherein the copper powder has an average particle size of 15 μm or more.

9. The dual-layer disc of claim 1 or 2, wherein the metal layer does not contain carbon.

10. A commutator comprising: a dual-layer disk according to claim 1 or 2; and a riser piece joined to the metal layer side of said dual-layer disk, said metal layer being solder-joined to said riser piece without a plating layer on its surface.

11. A method for manufacturing a commutator, comprising: a coating step of coating solder on the surface of a metal layer of a two-layer disk having a carbon layer and a metal layer without forming a plating layer on the surface of the metal layer; and a joining step of overlapping the metal layer coated with solder with a riser piece base and then heating to join the metal layer and the riser piece base, wherein the metal layer contains copper powder, and when the metal components in the metal layer of the two-layer disk are taken as 100% by mass, the content of the copper powder is 10% by mass or more.

12. A method for manufacturing a commutator, comprising: a coating step of coating solder on the surface of a metal layer in a two-layer disk having a carbon layer and a metal layer without forming a plating layer on the surface of the metal layer; and a joining step of overlapping the solder-coated metal layer and a riser piece base and then heating to join the metal layer and the riser piece base, wherein the metal layer contains copper powder, and where a is the content (mass %) of copper powder when the metal components in the metal layer are 100 mass %, and b is the average particle size (μm) of the copper powder, the relationship a / b≧0.34 is satisfied.

13. A method for manufacturing a commutator according to claim 11 or 12, wherein the copper powder has an average particle size of 30 μm or less.

14. The method for manufacturing a commutator according to claim 11 or 12, wherein the metal layer contains brass powder.

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