Electric wiring member and method for manufacturing same

Abstract

The present invention provides an electric wiring member which is capable of stably securing high insulation properties. The present invention provides an electric wiring member which comprises: a conductor that is composed of an Al base material; and an insulating film that covers at least a part of the conductor. The insulating film has a first layer that is provided on the surface side and a second layer that is provided further toward the Al base material side than the first layer. The first layer has a main hole that extends from the Al base material side to the surface side, and a sub-hole that opens in a part of the side wall of the main hole. The second layer is thicker than the first layer. For example, the thickness of the first layer is 0.1-20 μm, and the thickness of the second layer is 20-200 μm. For example, the first layer is an anodized layer that is obtained by electrolysis in a phosphoric acid solution, and the second layer is an anodized layer that is obtained by electrolysis in a solution of oxalic acid or sulfuric acid.

Description

Electrical wiring member and manufacturing method thereof

[0001] The present invention relates to an electric wiring member or the like made of an insulating coated Al-based conductor.

[0002] A typical example of an electromagnetic device that has an armature and a field is an electric motor (including a generator). There are various types of electric motors that have a rotor and a stator, such as rotating armature types and rotating field types. There are also inner rotor types in which the rotor rotates on the inner periphery of the stator, and outer rotor types in which the rotor rotates on the outer periphery of the stator. All electric motors have in common the fact that they have at least one coil (one application example of an electrical wiring member) built into a core.

[0003] The coils of electric motors mounted on moving bodies such as vehicles are subjected to high voltages and high currents, while also being required to be lightweight and highly efficient (low loss). To achieve these, for example, coils in which an aluminum-based conductor is insulated with an anodized film have been studied. Related disclosures are found in, for example, the following patent documents:

[0004] JP 2000-349320 JP 2014-98200 JP 2017-122271 JP 2021-75763

[0005] In Patent Document 1, an Al alloy is insulated with an anodized film having pores and a plurality of voids extending in a direction substantially perpendicular to the pores. Patent Document 1 merely uses an anodized film (insulating layer) as an insulating layer for a thin-film solar cell substrate (A3004 or A6061), and does not at all consider coils or the like in which the substrate itself is a conductor. Incidentally, in Patent Document 1, the anodized film that achieves the highest withstand voltage is Sample 1, which has an insulating layer thickness of 50 μm and is formed using an A3004 substrate, an oxalic acid aqueous solution as the electrolyte, and an applied voltage of 80 V (Table 1 in Patent Document 1).

[0006] In Patent Document 2, an aluminum conductor is insulated with an anodized coating having an inner layer with a large specific surface area and an outer layer with a small specific surface area. The outer layer is provided to ensure high wear resistance. Incidentally, the outer and inner layers are formed by applying a high first voltage (V1: 16 to 40 V) to an aluminum substrate immersed in an aqueous sulfuric acid solution, followed by a low second voltage (V2: 3 to 14 V) (see paragraph

[0042] of Patent Document 2). Although the inner and outer layers have different pore sizes, they are considered to be composed of porous layers with essentially the same morphology.

[0007] Patent Document 3 proposes an anodized oxide coating having a first coating formed in an electrolyte containing chromic acid and a second coating formed thereafter in an electrolyte containing sulfuric acid. This anodized oxide coating is not an insulating film but a heat insulating film provided on the piston top (substrate). For this reason, in Patent Document 3, after the anodized oxide coating is formed, the pores in the second coating (substrate side / underlying side) are enlarged with an acidic solution, and then the pores in the first coating (surface side) are sealed.

[0008] Patent Document 4 proposes an anodic oxide film having a first oxide film formed in an electrolyte containing phosphoric acid and a second oxide film formed thereafter in an electrolyte containing sulfuric acid. This anodic oxide film is not an insulating film, but merely a base formed on the surface of an aluminum alloy molded product (A5052) to ensure bonding strength (anchor effect) with a resin (sheet). For this reason, the first oxide film is a very thin film (0.6 μm thick) formed by applying 15 V in a phosphoric acid aqueous solution, and the second oxide film is also a thin film (7.1 μm thick) formed by applying 12.5 V in a sulfuric acid aqueous solution (Example 1 of Patent Document 4).

[0009] The present invention has been made in view of the above circumstances, and has an object to provide a new electrical wiring member or the like made of an Al-based conductor.

[0010] As a result of intensive research aimed at solving the above-mentioned problems, the inventors have discovered a new, distinctive anodic oxide film with excellent insulating properties as an example of an insulating film to be provided on an electrical wiring member. By expanding on this finding, the inventors have completed the present invention, which will be described below.

[0011] <<Electrical Wiring Member>> The electrical wiring member of the present invention is an electrical wiring member including a conductor made of an aluminum base material (referred to as "Al base material") and an insulating film covering at least a portion of the conductor, wherein the insulating film has the first layer on the surface side and the second layer on the Al base side of the first layer, the first layer has a main hole extending toward the surface side of the insulating film and a sub-hole opening in a portion of a side wall of the main hole, and the second layer is an electrical wiring member formed to be thicker than the first layer.

[0012] The insulating film according to the present invention can exhibit stable insulating properties even under high-load environments (high voltage, high temperature, etc.) due to the synergistic effect of the thick second layer and the flexible first layer having main holes and sub-holes.

[0013] <<Method of Manufacturing Electrical Wiring Member, etc.>> The present invention can also be understood as a method of manufacturing an electrical wiring member. For example, when the first layer and the second layer are anodized layers (i.e., when the insulating film has a first anodized layer and a second anodized layer), the present invention may be a method of manufacturing an electrical wiring member, including a first electrolysis step of forming the first layer using a phosphoric acid solution, and a second electrolysis step of forming the second layer using an oxalic acid solution or a sulfuric acid solution after the first electrolysis step.

[0014] <Electromagnetic Devices, etc.> One application example of an electrical wiring member is a coil member. The present invention can also be understood as a coil (assembly of coil members) manufactured using the coil member, an electromagnetic device (e.g., an electric motor) equipped with the coil, or a component thereof (e.g., an armature). A specific example of such an armature is an armature in which the above-mentioned coil member (e.g., a segment conductor) is inserted into a slot in a core.

[0015] The armature referred to in this specification is not limited to that used in electric motors (including generators). If the armature is used in an electric motor, it may be a stator, a rotor, or both. The electric motor may be a DC motor or an AC motor. The electric motor may also be a synchronous machine or an asynchronous machine (such as an induction machine). For example, the electrical wiring member (coil member) of the present invention may be used in the rotor of an induction machine. The induction machine may be either a squirrel-cage type or a wound type.

[0016] <<Others>> In this specification, "x to y" includes a lower limit x and an upper limit y, unless otherwise specified. Any numerical value included in the various numerical values ​​or numerical ranges described in this specification may be used as a new lower limit or upper limit to establish a new range such as "a to b." Furthermore, in this specification, "α to β μm" means α μm to β μm, unless otherwise specified. The same applies to other unit systems (nm, etc.).

[0017] 1 is an SEM image of the surface (top surface) of an insulating film (anodic oxide film); FIG. 2 is an SEM image of the longitudinal cross section (surface region) of an insulating film; FIG. 3 is an SEM image of the longitudinal cross section near the boundary between a first anodized layer and a second anodized layer; and FIG. 4 is an SEM image of the longitudinal cross section (whole) of an insulating film. FIG. 5 is a schematic diagram showing the cross-sectional structure of a coil member and an insulating film.

[0018] The contents described in this specification may apply not only to the product of the present invention but also to the method, as appropriate. One or more components arbitrarily selected from this specification may be added to the components of the present invention. Which embodiment is best depends on the target, required performance, etc.

[0019] The conductor is made of an Al base material having excellent electrical conductivity. Such an Al base material is, for example, pure Al (JIS A1000 series, etc.) containing 98 mass % or more, 98.5 mass % or more, 99 mass % or more, or even 99.6 mass % or more of Al. When the first layer or the second layer is made of an anodized oxide film, the Al base material should preferably contain as few components (such as Si) that inhibit the desired film morphology as possible.

[0020] The conductivity of the Al base material is preferably 50% IACS (International Annealed Copper Standard) or more, 55% IACS or more, or even 60% IACS or more. "% IACS" refers to the electrical conductivity of annealed standard soft copper (volume resistivity: 1.7241×10 -８ The electrical conductivity is a relative index (ratio) to the electrical conductivity (100% IACS) of Ωm. The Al substrate may be a sintered material in addition to an ingot material (a wrought material or a cast material).

[0021] <<First Layer and Second Layer>> The insulating film has a first layer on the surface side and a second layer on the Al base side. The insulating film is not limited to two layers, but may have three or more layers. For convenience, the present specification will explain the case where the first layer and the second layer are made of an anodic oxide film with a two-layer structure.

[0022] (1) First Layer The first layer is located on the second layer and has main pores extending to the surface and sub-pores opening on the side walls (pore walls). Because the first layer has sub-pores in addition to the main pores, it also has a high porosity. This first layer has excellent flexibility and is less likely to crack even when exposed to high-temperature environments.

[0023] The main pores are tubular (cylindrical) and extend almost straight from the Al substrate side to the surface side. The pore diameter (maximum width in the horizontal direction as seen in the longitudinal cross section) or the opening diameter (maximum length as seen on the surface side) is, for example, 50 to 1000 nm or 150 to 350 nm.

[0024] The sub-holes have openings in the side walls of the main holes and extend in the horizontal direction (a direction substantially perpendicular to the side walls). At least some of the sub-holes may penetrate the side walls of the main holes (connecting adjacent main holes). The distribution of the sub-holes may be uniform or non-uniform along the longitudinal direction of the main holes.

[0025] At least one sub-pore may be observed within a field of view when observing a longitudinal cross section (side surface) of the first layer. For example, one or more, three or more, or even five or more sub-pores may be observed in a surface region (depth 1 μm × width 10 μm). Since the first layer has main pores and sub-pores at least in the surface region, its porosity is, for example, 20 to 75% or 35 to 50%.

[0026] The porosity, pore size, opening size, etc. referred to in this specification are determined by image analysis of a microscopic image of each layer (membrane) using software (e.g., Image J). For example, the porosity is determined as the ratio of the pore area (total value) to the total area within the field of view of the surface (top surface) observation image. The opening size (pore size) is determined as the average arithmetic value of the circle-equivalent diameter of each pore within the same field of view.

[0027] The field of view (evaluation range) of the observation image is not limited, but is, for example, 5 × 4 μm to 12.7 × 8.8 μm (the same applies below). The presence or absence (number) and shape of sub-holes may be determined by visually checking the observation image. It is sufficient that the first layer has main holes and sub-holes at least in the surface layer region (for example, a region 10 μm deep from the outermost surface).

[0028] The thickness of the first layer is, for example, 0.1 to 20 μm, 1 to 16 μm, or 5 to 13 μm. The thickness of the first layer is the distance (height) from its surface to the interface with the second layer. Because it is difficult to precisely identify the interface, the thickness (film thickness) referred to in this specification refers to the average thickness measured with a film thickness meter, unless otherwise specified. If necessary, the thickness may be determined based on an observation image or the like (the same applies hereinafter).

[0029] The first layer is, for example, mainly made of aluminum oxide (Al ２ O ３ The anodized layer (referred to as a first anodized layer) may contain components or compounds (salts) derived from the composition of the electrolyte. For example, if the first anodized layer is formed using a phosphoric acid solution, a phosphate (e.g., Al-P-O-based compound, Al-P-O-H-based compound) coating may be formed on the inner surfaces of the main holes and sub-holes.

[0030] In this specification, for convenience, the surface side of the first layer (the side where the main holes are open) is also referred to as the upper side, and the opposite side (the side facing the Al substrate) is also referred to as the lower side or bottom side. The thickness direction of the layer (film) is also referred to as the vertical direction, and the direction approximately perpendicular to the vertical direction is also referred to as the horizontal direction.

[0031] (2) Second Layer The second layer is formed on the Al base material and is thicker than the first layer. The second layer ensures high insulation.

[0032] The second layer is, for example, an anodized layer (referred to as a second anodized layer) having a dense and thin barrier layer (active layer) and a porous layer (growth layer) grown thereon. The porous layer has a regular arrangement of approximately straight tubular micropores. The pores are usually cylindrical with a bottom, with the barrier layer at the bottom, and do not have fine pores (sub-pores) in the pore walls. The pore diameter (maximum width in the horizontal direction as seen in the vertical cross section) is, for example, about 10 to 100 nm, or about 30 to 85 nm.

[0033] The thickness of the second layer (including the thickness of the barrier layer in the case of an anodized layer) is, for example, 20 to 200 μm, 25 to 150 μm, or 30 to 120 μm. The thickness of the second layer is the distance (height) from the interface with the Al base (barrier layer) to the interface with the first layer, and can be measured using a film thickness meter or the like, as described above. The thickness of the barrier layer is usually about 10 to 100 nm.

[0034] (3) Interface Near the interface between the first and second layers, at least some of the main pores of the first layer may be connected to the pores of the second layer (columnar pores extending in a substantially straight tube shape from the Al substrate side). Furthermore, at least some of the pores of the second layer may extend continuously from the main pores of the first layer. An insulating film consisting of such a first and second layer is less susceptible to cracking or other problems at the interface. Furthermore, if the first and second layers are anodized layers, sealing of the second layer can be easily performed from the first layer side.

[0035] At least one interconnected or continuously elongated main pore (vertical pore of the first layer) may be present in the observation image near the interface. The proportion of such main pores relative to the total number of main pores observed may be 50% or more, 75% or more, or even 90% or more. The total number may be within a range that can be arbitrarily extracted in the observation image, but may be, for example, 100 or more.

[0036] (4) Sealing Treatment The second layer may be sealed. This can improve the corrosion resistance and insulating properties of the insulating film. The sealing treatment may be performed depending on the type and form of the second layer (and the first layer). The second anodized layer may be sealed using a metal salt (nickel acetate, cobalt acetate, etc.), or, taking into account costs, the environment, etc., it may be sealed using heated water (or boiling water), pressurized steam, etc. When sealing is performed using boiling water, etc., the second anodized layer (pores) will contain hydrates due to a hydration reaction.

[0037] <<Third Layer>> The insulating film may further include a third layer. The third layer may be the same as or different from the first or second layer. When the first and second layers are anodized layers, the third layer is, for example, a resin layer formed on the first layer. The resin layer covering the first layer contributes to improving and stabilizing the insulating properties. For convenience, the present specification will be described by exemplifying a case in which the third layer is a resin layer.

[0038] The resin constituting the third layer may be a thermoplastic resin or a thermosetting resin, such as polyimide, polyamideimide, polyesterimide, epoxy, polyvinylformal, polyurethane, or polyester.

[0039] The resin layer may be thinner than the first layer (and even the second layer). Its specific thickness is not critical, but may be, for example, 1 to 35 μm, 5 to 30 μm, or 10 to 20 μm. The resin may penetrate deep into the first layer, but sufficient adhesion (anchor effect) can be obtained even if it only engages with the main pores and sub-pores in the surface layer region. The resin layer (resin coating) is formed after the second layer is formed or after the sealing treatment (sealing treatment) is performed.

[0040] The resin layer is formed, for example, by applying an electrically insulating paint (varnish) to the first layer by coating, spraying, dipping, electrodeposition, etc. Depending on the type of resin, the resin may be appropriately dried by heating or cured by heating.

[0041] <<Anodizing Treatment>> When the first layer and the second layer are anodized layers (films), the anodizing treatment of the Al base material is preferably performed in at least two separate steps. Hereinafter, an example will be described in which the first layer (first anodized layer) is formed in a first electrolysis step (first anodizing treatment) and the second layer (second anodized layer) is formed in a second electrolysis step (first anodizing treatment).

[0042] (1) First Electrolysis Step The electrolytic solution is, for example, a phosphoric acid solution. The solution is, for example, an aqueous solution (the same applies to the second electrolysis step). The phosphoric acid concentration is, for example, 1 to 30%, 2 to 15%, or 3 to 10%. The concentration of the electrolytic solution referred to in this specification is a mass percentage relative to the total unless otherwise specified. The temperature of the electrolytic solution (bath temperature) is, for example, 10 to 50°C, 20 to 40°C, or 25 to 35°C. If the concentration or bath temperature is too low, the film formation rate will be insufficient. If the concentration or bath temperature is too high, the anodized layer itself will dissolve, making film formation difficult (the same applies to the second electrolysis step).

[0043] During the energization, the current (density) or applied voltage may be constant or may vary (fluctuate). The energization may be direct current, alternating current, or superimposed AC current, which is a combination of an AC component and a DC component. The waveform of the alternating current may be, for example, a sine wave, a rectangular wave, a pulse wave, or the like. A platinum electrode, a graphite electrode, or the like is usually used as the counter electrode. This also applies to the second electrolysis step.

[0044] When the electrolysis step is performed using direct current, it is advisable to apply to the Al base material at least temporarily (in the initial or middle stage) a high voltage of about 50 to 250 V, 75 to 200 V, or even 100 to 175 V. If the applied voltage is too low throughout the entire step, it becomes difficult to form main holes and sub-holes and ensure the film formation rate, whereas if the applied voltage is too high, burning may occur or a non-uniform anodic oxide layer may be formed (the same applies to the second electrolysis step).

[0045] (2) Second Electrolysis Step The electrolytic solution is, for example, an oxalic acid solution or a sulfuric acid solution. Using an oxalic acid solution suppresses dissolution of the already formed first layer. In the case of an oxalic acid solution, the oxalic acid concentration is, for example, 1 to 30%, 2 to 15%, or 3 to 10%. The bath temperature is, for example, 0 to 50°C, 10 to 40°C, or 15 to 35°C. The applied voltage during direct current is, for example, about 10 to 100V, 30 to 85V, or 45 to 75V.

[0046] (3) Voltage Drop Treatment When transitioning from the first electrolysis step, in which a high voltage is applied to the Al substrate, to the second electrolysis step, in which a low voltage is applied, the applied voltage may be dropped to terminate the first electrolysis step. This voltage drop treatment (also referred to as "VD treatment") allows the barrier layer, which increases in thickness depending on the applied voltage, to be thinned before transitioning to the second electrolysis step. This allows the initial voltage of the second electrolysis step to fall within an appropriate range, resulting in the formation of a uniform or homogeneous second layer.

[0047] When the applied voltage is reduced, the current flow is temporarily or instantaneously cut off and resumes once the barrier layer becomes thinner. This phenomenon is known as the current recovery phenomenon. A sudden voltage drop increases the time required for the current flow to be restored. Therefore, when the voltage drop is large, it is recommended to reduce the applied voltage stepwise or continuously.

[0048] When the applied voltage is decreased stepwise, the voltage step width and holding time may be uniform or non-uniform. The voltage drop width per step is, for example, about 1 to 20 V or 3 to 10 V. The voltage holding time per step is, for example, about 10 to 120 seconds or 20 to 60 seconds.

[0049] The pore size (cell size) corresponds (approximately proportional) to the applied voltage during the electrolysis step. １ｆ ) and the starting voltage of the second electrolysis step (V ２ｓ ) is approximately the same (V １ｆ ≒V ２ｓ ) allows the pore diameters of the first and second layers to be approximately equal, which means that the pores of the second layer can be made to extend continuously from the main pores of the first layer.

[0050] For example, the voltage (V １ｆ ) is applied to the Al base material at the beginning of the second electrolysis step (V ２ｓ ) to 0.8 to 1.5 times (0.8≦V １ｆ / V ２ｓ ≦1.5), 0.9 to 1.3 times, or 1 to 1.1 times, the first and second layers can be smoothly connected near the boundary.

[0051] The electrical wiring member of the present invention can be of any specific form (shape or size) or purpose. An example of the electrical wiring member is a coil member shown in Fig. 3. In this specification, the coil member will be described by way of example where appropriate.

[0052] The electrical wiring member may be a continuous conductor or a segmented conductor. The use of segmented conductors improves the freedom of shape and space factor of the electrical wiring member. One example of a segmented conductor is a segment conductor (coil member) inserted into a slot in a core (e.g., a stator core or a rotor core). A segment conductor is connected to another segment conductor at its adjacent ends to form a coil. The ends of such a segment conductor may not have an insulating coating. Ends without an insulating film are joined (connected) by, for example, welding, deposition, or the like. The cross-sectional shape of the segment conductor may be (elliptical) circular, but a rectangular shape (particularly a substantially rectangular shape) improves the space factor.

[0053] Such segment conductors are used, for example, in armatures (particularly stators) of high-power motors for electric vehicles (including hybrid vehicles) and the like.

[0054] Assuming that segment conductors (SC) to be incorporated into the stators of motors are an example of electrical wiring members, various samples were fabricated in which an insulating film was formed on the surface of a flat plate of an Al base material (conductive material), and their insulating properties were evaluated. The present invention will be described in more detail with reference to such specific examples.

[0055] <<Preparation of Samples>> (1) Test Pieces For samples 1 to 5 and C3 shown in Table 1, flat plates (100 mm × 50 mm × 2 mm thick) made of pure aluminum (JIS A1070) were used as test pieces (Al-based conductors), and for samples C1 and C2, flat plates (50 mm square × 2 mm thick) made of pure aluminum (JIS A1050) were used as test pieces.

[0056] Each test piece was subjected to the treatments shown in Table 1. Test pieces 1 to 5 were subjected to the first anodizing treatment (first electrolysis step) and the second anodizing treatment (second electrolysis step). Test pieces C1 and C2 were not subjected to the first anodizing treatment, but were subjected to only the second anodizing treatment. Test piece C3 was not subjected to either anodizing treatment, but was only resin coated.

[0057] Samples 2 to 4 and C2 were also subjected to a sealing treatment after the anodizing treatment. Furthermore, samples 3 and 4 were also subjected to a resin coating treatment (resin layer formation step) after the sealing treatment. The specific details of each treatment are as follows:

[0058] (2) Anodizing Treatment The test piece was immersed entirely in an electrolytic solution tank, and a stainless steel piece (JIS SUS304) was used as the anode and the cathode, respectively, and direct current was applied to the test piece while stirring the electrolytic solution. The treatment conditions are summarized in Table 1.

[0059] The concentration of the electrolyte solution is the mass ratio (mass %) of phosphoric acid or oxalic acid to the entire aqueous solution. The current density was measured by measuring the applied current to the treated area (15 cm²) of the masked test piece. ２ ) is the value obtained by dividing the applied current value (constant) by the

[0060] The anodizing treatment was basically carried out by constant current (density) electrolysis. Samples 1 to 4 were also subjected to voltage drop (VD) treatment at the end of the first anodizing treatment. That is, after the current application time (12 minutes) shown in Table 1 had elapsed, the voltage was dropped from about 130 V to 60 V at a rate of 5 V / 30 seconds, and then held at 60 V for 1 minute. Including the VD treatment (about 8 minutes = 7 minutes + 1 minute), the total time for the first anodizing treatment was about 20 minutes. For reference, the applied voltage (final voltage V １ｆ ) and the applied voltage immediately after the start of the second anodizing treatment (start voltage V ２ｓ ) are also shown in Table 1.

[0061] After the anodizing treatment, the test piece was washed with tap water and thoroughly dried in the air before being subjected to the next step.

[0062] (3) Post-treatment Sealing treatment was performed by immersing the anodized test piece for 30 minutes in ultrapure water heated to 90° C. Specifically, a beaker filled with ultrapure water was heated in a water bath with a built-in stirrer, and the test piece was placed in the beaker for sealing treatment.

[0063] The resin coating (formation of the resin layer) was performed by spraying a photosensitive polyimide varnish (Photoneece manufactured by Toray Industries, Inc.) onto the anodized film or the surface of the substrate, and then thermally curing the varnish by heating in an oven (200°C x 1 hour).

[0064] In this way, test pieces of Samples 1 to 5 and Samples C1 to C3 shown in Table 1 were obtained. Each test piece was subjected to the following measurements, observations and tests.

[0065] <<Film Thickness Measurement>> The thickness of the first anodized layer, the second anodized layer, and the resin layer of each sample was measured using an eddy current film thickness meter (SWT-9200, manufactured by Sanko Electronics Laboratory Co., Ltd.). Measurements were taken for each treatment, and the difference was taken as the thickness of each layer. The results are also shown in Table 1.

[0066] <<Surface Observation>> The surfaces of Sample 1 and Sample C1 were observed with a scanning electron microscope (SEM / S-5500 manufactured by Hitachi High-Technologies Corporation). The SEM images are shown together in FIG.

[0067] The SEM images were analyzed using ImageJ (free software) to determine the size (opening diameter) of the pores on the surface of the anodized layer. First, the maximum diameter (maximum length) of 10 randomly selected pores was measured, and the arithmetic mean value was calculated. Next, this operation was performed on five fields of view, and the average value for the five fields of view was taken as the opening diameter. The opening diameter was 160 nm for Sample 1 and 26 nm for Sample C1.

[0068] <<Cross-Section Observation>> (1) Presence or Absence of Sub-holes> The cross sections (depth 1 μm × width 10 μm) of the surface layer regions of Sample 1 and Sample C1 were observed using an SEM. The SEM images (partially) are shown together in FIG. 2A. As is clear from FIG. 2A, Sample 1 had a thick main hole extending in a substantially straight tube shape from the Al substrate side, and a thin sub-hole that penetrated into the side wall of the main hole and opened (even penetrated) it. On the other hand, no such sub-holes were observed in Sample C1.

[0069] (2) Interface of the Anodized Oxide Layer The cross sections of Sample 1 and Sample 5 were observed by SEM. SEM images of the vicinity of the boundary (interface) between the first anodized layer and the second anodized layer are shown together in Figure 2B. As is clear from Figure 2B, in both Sample 1 and Sample 5, the vertical pores (main pores) in the first anodized layer were connected to the vertical pores (pores) in the second anodized layer.

[0070] In particular, sample 1 (V １ｆ / V ２ｓ In the case of ≈1), each pore in the first anodized layer was connected to each pore in the second anodized layer, i.e., each pore in the second anodized layer was connected to and extended from each pore in the first anodized layer.

[0071] On the other hand, sample 5 (V １ｆ / V ２ｓ In the case of ≒2), one pore in the first anodized layer was connected to two pores in the second anodized layer. These results indicate that the VD treatment almost completely eliminates the difference in applied voltage between the anodized treatments, allowing for a smooth transition from the first anodized treatment to the second anodized treatment while the barrier layer is thin.

[0072] (3) Resin layer and hydrate The cross section of Sample 3 was observed by SEM. SEM images of the surface and bottom layers (on the substrate side) are shown together in Figure 2C. As is clear from Figure 2C, the resin layer formed on the first anodized layer penetrated and became entangled not only in the main pores of the first anodized layer but also in the sub-pores, and was in close contact with and held by the first anodized layer.

[0073] Furthermore, many hydrates were observed in the pores of the second anodized layer. On the other hand, no hydrates were observed in the first anodized layer. This is thought to be because the surface of the first anodized layer is covered with an insoluble phosphorus-based film, which inhibits the hydration reaction.

[0074] Since the main pores and the like of the first anodized layer were not sealed even after the sealing treatment, it was possible to form a highly adhesive resin layer on the first anodized layer after the sealing treatment.

[0075] <<Crack Resistance>> Visual inspection of the surfaces after the sealing treatment revealed no cracks in Sample 2, but cracks were found in Sample C2. Thick anodic oxide films are inherently prone to cracking due to heating during the sealing treatment. However, it is believed that the flexible first anodic oxide layer with main and sub-holes prevented cracks from occurring even when the anodic oxide film was thickened.

[0076] <<Insulation Properties>> (1) Breakdown Voltage A breakdown test was conducted to measure the breakdown voltage of each sample. An ultra-high voltage withstand voltage tester (7473 manufactured by Keisoku Giken Co., Ltd.) was used for the measurement. The measurement environment was a temperature of 25°C and a relative humidity of 50% RH. The test conditions were an applied voltage of sinusoidal AC (50 Hz), a voltage rise rate of 50 V / s, and a breaking current of 10 mA. A 6 mm diameter hemispherical electrode was used as the high-voltage electrode. The breakdown test was conducted five times, and the arithmetic mean value of the voltages (n = 5) that exceeded the breaking current was taken as the breakdown voltage and is also shown in Table 1. Note that when a voltage of 4.0 kV or higher was applied, creeping discharge occurred, and the breakdown voltage of such samples was expressed as "≧4.0 (kV)."

[0077] As can be seen from Table 1, the insulating film having the first anodized layer and the second anodized layer exhibited a large breakdown voltage. Also, the insulating film with a thick second anodized layer and the insulating film that was subjected to sealing treatment or resin coating exhibited a larger breakdown voltage.

[0078] (2) Partial Discharge Inception Voltage A partial discharge test was conducted to measure the partial discharge inception voltage of each sample. A partial discharge measuring device (DAC-PD-7 manufactured by Soken Denki Co., Ltd.) was used for the measurement. The measurement environment was a temperature of 24°C and a relative humidity of 33% RH. The test conditions were an applied voltage of sinusoidal AC (60 Hz), a voltage rise rate of 50 V / s, and a threshold discharge charge of 100 pC. A hemispherical electrode with a diameter of 6 mm was used as the electrode on the high voltage side. The partial discharge test was conducted five times, and the arithmetic mean value of the voltages (n = 5) at which the discharge charge exceeded the threshold was taken as the partial discharge inception voltage. The high and low partial discharge inception voltages are also shown in Table 1, with a threshold of 1.4 kV.

[0079] As can be seen from Table 1, the insulating film having the first anodized layer and the second anodized layer exhibited a large partial discharge inception voltage. In particular, the insulating film having a thick second anodized layer exhibited a larger partial discharge inception voltage.

[0080] From the above, it has been confirmed that the present invention can provide an electrical wiring member that stably ensures high insulation properties.

[0081]

Claims

1. An electrical wiring component comprising a conductor made of an aluminum substrate (referred to as "Al substrate") and an insulating film covering at least a portion of the conductor, wherein the insulating film has the first layer on the surface side and the second layer on the Al substrate side of the first layer, the first layer has a main hole extending to the surface side of the insulating film and a sub-hole opening in part of the side wall of the main hole, and the second layer is formed thicker than the first layer.

2. The electrical wiring member according to claim 1, wherein the thickness of the first layer is 0.1 to 20 μm, and the thickness of the second layer is 20 to 200 μm.

3. The electrical wiring member according to claim 1, wherein at least a portion of said sub-hole penetrates a side wall of said main hole.

4. An electrical wiring member according to claim 1, wherein the second layer has pores extending in a generally straight tube shape from the aluminum base side, and at least a portion of the main holes of the first layer communicate with the pores.

5. The electrical wiring member according to claim 4, wherein at least a portion of said pores extends continuously from said main hole.

6. The electrical wiring member according to claim 1, wherein the insulating film further comprises a third layer.

7. The electrical wiring member according to claim 1, which is a coil member.

8. The electrical wiring member according to claim 7, wherein the coil member is a segment conductor inserted into a slot in the core.

9. The electrical wiring member according to claim 1, wherein the aluminum base is pure aluminum containing 98 mass % or more of aluminum based on the entire aluminum base.

10. The electrical wiring member according to any one of claims 1 to 9, wherein the first layer and the second layer are anodized layers.

11. The electrical wiring member according to claim 10, wherein the second layer contains a hydrate.

12. The electrical wiring member according to claim 6, wherein the third layer is a resin layer.

13. A manufacturing method for obtaining the electrical wiring member according to claim 10, comprising: a first electrolysis step in which the first layer is formed using a phosphoric acid solution; and a second electrolysis step in which the second layer is formed using an oxalic acid solution or a sulfuric acid solution after the first electrolysis step.

14. The method for manufacturing an electrical wiring member according to claim 13, wherein the first electrolysis step includes a voltage drop treatment that ends by dropping the voltage applied to the Al base material.

15. The voltage (V) applied to the Al substrate at the end of the first electrolysis step １ｆ ) is the voltage (V) applied to the Al base material at the beginning of the second electrolysis step. ２ｓ ) or less than 1.5 times (V １ｆ / V ２ｓ 15. The method for producing an electrical wiring member according to claim 14, wherein the tensile strength is 1.5 or less.

16. The method for producing an electrical wiring member according to claim 13, wherein the second layer is sealed and / or the first layer is coated after the second electrolysis step.

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