Cooling structure, battery unit, and method for manufacturing cooling structure

Abstract

This cooling structure is provided with a press forming member which comprises groove parts and bank parts provided around the groove parts, a flow path upper lid which is a flat plate placed in a position covering the groove parts of the press forming member and which configures a flat cooling surface, and a laser welded parts which bond mutually facing surfaces of the flow path upper lid and the bank parts and which form flows path for flow of the cooling liquid. The press forming member and the flow path upper lid are plated steel plates comprising a base steel plate and Al-base plating, the flow paths comprise a parallel flow path area where multiple sub flow paths extending in a first direction are arranged in a second direction perpendicular to the first direction, and in the parallel flow path area, the interval between the mutually adjacent sub flow paths is less than or equal to 20 mm.

Description

[Technical Field]

[0001] The present invention relates to a cooling structure, a battery unit, and a method for manufacturing a cooling structure. This application claims priority based on Japanese Patent Application No. 2021-085188, filed on May 20, 2021, the contents of which are incorporated herein by reference. [Background technology]

[0002] In order to reduce carbon dioxide emissions, automobiles are increasingly being converted to electric vehicles (EVs). The battery boxes of EVs need to be equipped with a cooling structure to prevent battery deterioration due to temperature rise. Until now, air-cooled cooling structures have been the mainstream, but in recent years, as batteries have become larger in capacity, water-cooled structures with high cooling capacity have increasingly been adopted (see, for example, Patent Documents 1, 2, and 3). In water-cooled battery packs, a water coolant flow path through which a coolant flows is formed on the outside of the battery pack. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-107443 [Patent Document 2] Japanese Patent No. 6125624 [Patent Document 3] Japanese Patent Application Publication No. 2012-17954 Summary of the Invention [Problem to be solved by the invention]

[0004] The outer wall and cooling structure of a water-cooled battery pack are often made of aluminum, which has high corrosion resistance against the coolant. However, aluminum has cost issues. Furthermore, because aluminum is soft, it is difficult to reduce the weight of a cooling structure made of aluminum plate by thinning the outer wall while maintaining its strength. Using steel plate for these components would enable water-cooled battery packs to be offered at low cost and their weight to be reduced.

[0005] Here, an LLC (long life coolant) solution containing organic components flows through the water coolant flow path as the coolant. Therefore, the components that make up the water coolant flow path are required to have high corrosion resistance against the coolant. Furthermore, because the battery pack and cooling structure are located on the bottom of the vehicle, they are exposed to the external environment. Therefore, the components that make up the battery pack and cooling structure are required to have corrosion resistance comparable to that of the vehicle's suspension parts. Hereinafter, corrosion resistance against the coolant will be referred to as coolant corrosion resistance or internal corrosion resistance, and corrosion resistance against the external environment will be referred to as external corrosion resistance. Furthermore, when simply referred to as "corrosion resistance," it refers to both coolant corrosion resistance and external corrosion resistance.

[0006] One way to improve the corrosion resistance of steel sheets is by plating. For example, by forming an Al-based plating on the surface of a steel sheet, both the corrosion resistance to coolants and the corrosion resistance of the outer surface can be improved.

[0007] Naturally, cooling structures require high cooling efficiency. Additionally, liquid-tightness of the flow passages is also necessary to maintain cooling efficiency and prevent LLC leakage. However, there have been few examples of cooling structures with flow passages formed using galvanized steel sheets, and therefore, no studies have been conducted on methods for joining galvanized steel sheets. Spot welding is typically used to firmly join galvanized steel sheets, but because spot welding is a point-to-point joining method, it is difficult to ensure liquid-tightness of the flow passages. While it is possible to ensure liquid-tightness of spot welds using a sealer, there is a risk that the sealer will be degraded by LLC. Therefore, when manufacturing cooling structures, a joining method that can ensure liquid-tightness of the flow passages while maintaining corrosion resistance is also required. In the technology of Patent Document 3, a cooler is manufactured by brazing aluminum-based plated steel sheets. However, the technology of Patent Document 3 is intended to be applied exclusively to small devices, and it is difficult to adapt it to coolers of various sizes. Furthermore, the issue with Patent Document 3 is preventing deformation of the exterior members, and it is difficult to change the means for joining the exterior members.

[0008] In view of the above circumstances, the present invention aims to provide a cooling structure, a battery unit, and a method for manufacturing a cooling structure that have high cooling efficiency, excellent liquid-tightness of the flow paths, and high coolant corrosion resistance and outer surface corrosion resistance. [Means for solving the problem]

[0009] The gist of the present invention is as follows.

[0010] (1) A cooling structure according to one aspect of the present invention comprises a press-formed member having a groove and a bank portion arranged around the groove; a flow path lid which is a flat plate superimposed on the press-formed member in a position covering the groove and which forms a flat cooling surface; and a laser welded portion which joins the opposing surfaces of the flow path lid and the bank portion to form a flow path through which a coolant can flow, wherein the press-formed member and the flow path lid are plated steel plates having a base steel plate and an Al-based plating, and the flow path has a parallel flow path portion in which a plurality of partial flow paths extending along a first direction are arranged in a second direction perpendicular to the first direction, and in some or all of the parallel flow path portion, the spacing between adjacent partial flow paths is 20 mm or less. (2) In the cooling structure described in (1) above, in the parallel flow path section, the interval between adjacent partial flow paths may be 0.8 to 15 mm. (3) In the cooling structure described in (1) or (2) above, the partial flow path may have a width of 6 to 60 mm. (4) In the cooling structure described in (1) or (2) above, the partial flow path may have a width of 6 to 20 mm. (5) In the cooling structure according to any one of (1) to (4) above, the Al-based plating may contain Si. (6) In the cooling structure described in (5) above, the Al-based plating may have a Si content of 2.0 to 15 mass %. (7) In the cooling structure described in any one of (1) to (6) above, the plated steel sheet may have, on its surface, a chemical conversion coating containing a Zr-based component, a Ti-based component, or a Si-based component in a proportion of 50% by mass or more. (8) In the cooling structure described in any one of (1) to (7) above, the cross-sectional shape of the bank portion may be an approximately arc, and the radius of curvature of the bank portion at the contact portion between the flow path upper cover and the bank portion may be 15 mm or less. (9) In the cooling structure described in any one of (1) to (8) above, the thickness of the Al-based plating may be 10.0 μm or more, the distance between the press-formed member and the flow path upper cover near the laser weld may be 0.3 mm or less, and the larger of the bead width on the surface of the laser weld on the flow path upper cover and the bead width on the surface of the laser weld on the press-formed member may be 0.8 to 1.5 mm. (10) In the cooling structure according to any one of (1) to (9) above, the plated steel sheets constituting the press-formed member and the flow path upper cover may have a thickness of 0.3 to 1.2 mm. (11) In the cooling structure described in any one of (1) to (10) above, the laser weld may have a flow path outer edge weld that surrounds all of the flow paths, and the start and end of the laser weld may be excluded from the flow path outer edge weld. (12) In the cooling structure according to any one of (1) to (11) above, the starting and ending portions of the laser welded portion may be excluded from the cooling structure. (13) In the cooling structure described in any one of (1) to (12) above, a part or all of the surface of the laser welded portion between the press-formed member and the flow path upper cover may be covered with the Al-based plating. (14) In the cooling structure described in any one of (1) to (13) above, 30% or more of the surface of the laser weld between the press-formed member and the flow path upper cover may be covered with the Al-based plating. (15) In the cooling structure according to any one of (1) to (14) above, the bead height of the laser welded portion on the flow path upper cover may be 0.3 mm or less.

[0011] (16) A battery unit according to another aspect of the present invention comprises a battery cell, a battery pack in which the battery cell is housed, and a cooling structure described in any one of (1) to (15) above, wherein the flow path upper cover of the cooling structure is joined to the battery pack. (17) A battery unit according to another aspect of the present invention comprises a battery cell, a battery pack in which the battery cell is housed, and a cooling structure described in any one of (1) to (15) above, wherein the flow path upper cover of the cooling structure is the battery pack.

[0012] (18) A manufacturing method of a cooling structure according to another aspect of the present invention includes the steps of press-forming a steel plate to obtain a press-formed member having a groove portion and a bank portion provided around the groove portion, and overlapping a flat flow path lid in a position that covers the groove portion of the press-formed member, and laser-welding the flow path lid and the bank portion of the press-formed member to obtain a laser welded portion that forms a flow path through which a coolant can flow, wherein the press-formed member and the flow path lid are plated steel plates having a base steel plate and an Al-based plating, and the flow path has a parallel flow path portion in which a plurality of partial flow paths extending along a first direction are aligned in a second direction perpendicular to the first direction, and in the parallel flow path portion, the distance between adjacent partial flow paths is 20 mm or less. (19) In the manufacturing method of the cooling structure described in (18) above, the Al-based plating may have a film thickness of 10.0 μm or more, the laser welding may have a beam diameter of 0.2 to 0.8 mm, a heat input per unit weld length of 30 to 120 kJ / m, and a gap between the press-formed member and the flow path upper cover in the vicinity of the laser weld may be 0.3 mm or less. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a cooling structure, a battery unit, and a method for manufacturing a cooling structure that have high cooling efficiency, excellent liquid-tightness of the flow paths, and high coolant corrosion resistance and outer surface corrosion resistance. [Brief explanation of the drawings]

[0014] [Figure 1] 10 is a cross-sectional view of a cooling structure in which the cross-sectional shape of the press-formed member is rectangular, taken along a plane perpendicular to the extension direction of the partial flow passages. FIG. [Figure 2A] FIG. 10 is a plan view of a cooling structure in which a flow path communication portion and a partial flow path intersect at right angles, as viewed from the press-formed member side. [Figure 2B] 1 is a plan view of a cooling structure in which a flow path communication section has a branch structure, as viewed from the press-formed member side. FIG. [Figure 3] 10 is a cross-sectional view of a cooling structure in which the cross-sectional shape of the press-formed member is corrugated, taken along a plane perpendicular to the extension direction of the partial flow passages. FIG. [Figure 4] FIG. 10 is an enlarged cross-sectional view of the cooling structure for explaining the interval D between the partial flow paths. [Figure 5A] 1 is a perspective view of a cooling structure in which an intermediate portion of a laser weld is disposed between a flow path and a start end and an end of the laser weld; [Figure 5B] FIG. 10 is a perspective view of the cooling structure with the beginning and end portions of the laser welds removed. [Figure 6A] FIG. 10 is a schematic diagram of a cooling structure in which the start and end portions of the laser weld are removed from the outer edge weld of the flow channel. [Figure 6B] FIG. 10 is a schematic diagram of a cooling structure in which the start and end portions of the laser weld are removed from the outer edge weld of the flow channel. [Figure 7] 1 is a schematic diagram of a method for measuring the surface coverage of a laser weld between a press-formed part and a flow channel top cover. FIG. [Figure 8A] FIG. 2 is a perspective view of the battery unit. [Figure 8B] FIG. 10 is a cross-sectional view of a battery unit using a battery pack as a lid on a flow path. [Figure 8C] FIG. 10 is a cross-sectional view of a battery unit in which a battery pack and a flow path upper cover are joined together. [Figure 9] FIG. 1 is a perspective view of a cooling structure according to a first embodiment. [Figure 10A] 10 is a graph showing the relationship between bead width and coverage in the cooling structure of Example 2 manufactured from a steel plate with a plating film thickness of 10 μm. [Figure 10B] 10 is a graph showing the relationship between bead width and coverage in the cooling structure of Example 2 manufactured from a steel plate with a plating film thickness of 60 μm. [Figure 11A] FIG. 11 is a perspective view of a press-formed member of the cooling structure of Example 3 before laser welding. [Figure 11B]FIG. 11 is a perspective view of a flow path upper cover before laser welding in the cooling structure of Example 3. [Figure 11C] FIG. 10 is a perspective view of a cooling structure according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0016] (1. Cooling structure) First, a cooling structure according to a first embodiment of the present invention will be described. As shown in Fig. 1 and Fig. 2A, the cooling structure 1 according to this embodiment includes a press-formed member 11, a flow path upper cover 12, and a laser weld 13 that joins them together. The laser weld is a joint formed of a linear bead (i.e., weld metal). Fig. 1 is a cross-sectional view of the cooling structure 1, and Fig. 2A is a plan view of the cooling structure 1 from the press-formed member 11 side.

[0017] (1.1 Overview of cooling structure) The press-formed member 11 is a member obtained by press-forming a plated steel sheet, and has a groove portion 111 and a bank portion 112 provided around the groove portion 111. In FIG. 1 , the bottom of the press-formed member 11 and its periphery form the groove portion 111, and the top of the press-formed member 11 and its periphery form the bank portion 112. The flow path upper cover 12 is a member that forms a flat cooling surface, has a flat plate shape, and is superimposed in a position that covers the groove portion 111 of the press-formed member 11.

[0018] (1.2 Shape of press-formed parts) The press-formed member 11 and the channel lid 12 are joined by a laser weld 13. Specifically, the laser weld 13 joins the opposing surfaces of the channel lid 12 and the bank portion 112 of the press-formed member 11. As a result, the channel lid 12 and the groove 111 form a channel 14 through which a coolant can flow. As shown by the dashed line in FIG. 2A , any coolant, such as LLC, introduced from a coolant inlet 143 can flow through the channel 14 to a coolant outlet 144. This allows the channel lid 12, which is the cooling surface, and any object in contact with the channel lid 12 to be cooled. The channel shown in FIG. 2A includes a parallel channel portion 141 in which multiple partial channels 1411 extending along a first direction are aligned in a second direction perpendicular to the first direction, and a channel communication portion 142 that connects these partial channels 1411. The first direction is, for example, the longitudinal direction or the lateral direction of the cooling structure 1. The specific configuration of the flow path 14 will be described later.

[0019] The shapes of the bank portions 112 and the groove portions 111 are not particularly limited. In the press-formed member 11 illustrated in Fig. 1, the cross sections of the bank portions 112 and the groove portions 111 are generally rectangular (trapezoidal). However, the cross sections of one or both of the bank portions 112 and the groove portions 111 of the press-formed member 11 may be partially circular or generally arc-shaped. As shown in Fig. 3, a press-formed member 11 in which the cross sections of both the bank portions 112 and the groove portions 111 are partially circular or generally arc-shaped is called a corrugated sheet.

[0020] When the cross-sectional shape of the bank portion 112 is a substantially circular arc, the radius of curvature of the bank portion 112 at the contact portion between the flow path upper cover 12 and the bank portion 112, i.e., the laser welded portion 13, may be 15 mm or less, 13 mm or less, or 10 mm or less. The smaller the radius of curvature of the bank portion 112 at the laser welded portion 13, the wider the width W of the partial flow path 1411 can be, and the more the cooling efficiency of the cooling structure 1 is improved.

[0021] The radius of curvature of the bank portion 112 at the contact portion between the flow path upper cover 12 and the bank portion 112 is measured in a cross section of the partial flow path 1411 that is parallel to a second direction that is orthogonal to the first direction that is the extension direction of the partial flow path 1411 and is perpendicular to the surface of the flow path upper cover 12. As shown in Figure 3, in this cross section, the radius of a circle R that includes a total of three points: the center of the weld metal at the center in the plate thickness direction of the bank portion 112, and two points 1 mm away from the center of the weld metal along the second direction is the radius of curvature of the bank portion 112 at the contact portion between the flow path upper cover 12 and the bank portion 112.

[0022] (1.3 Composition of plated steel sheets) The press-formed member 11 and the flow path upper cover 12 are plated steel sheets having a base steel sheet and an Al plating formed on the surface of the base steel sheet. The configuration of the Al-plated steel sheet is not particularly limited, but examples of suitable configurations are as follows.

[0023] The plated steel sheets constituting the press-formed member 11 and the flow path upper covers 12 may have a thickness of 0.3 mm or more. By setting the thickness to 0.3 mm or more, press formability and the rigidity of the cooling structure 1 can be further improved. The plated steel sheets constituting the press-formed member 11 and the flow path upper covers 12 may have a thickness of 0.4 mm or more, 0.6 mm or more, or 0.8 mm or more. On the other hand, the plated steel sheets constituting the press-formed member 11 and the flow path upper covers 12 may have a thickness of 1.2 mm or less. By setting the thickness of the press-formed member 11 to 1.2 mm or less, it becomes easier to adhere the press-formed member 11 to the flow path upper covers 12, further improving the liquid-tightness of the flow paths. Furthermore, by setting the thickness of the flow path upper covers 12 to 1.2 mm or less, the cooling efficiency of the cooling structure 1 can be further improved. The plated steel sheets constituting the press-formed member 11 and the flow path upper covers 12 may have a thickness of 1.1 mm or less, 1.0 mm or less, or 0.8 mm or less. The press-formed member 11 and the flow path lid 12 may have different thicknesses. The thinner the plate thickness, the higher the cooling efficiency, so the thinner the flow path lid 12 is.

[0024] (1.4 Composition of base steel sheet of plated steel sheet) The base steel sheet of the plated steel sheet constituting the press-formed member 11 and the flow path upper cover 12 is not particularly limited. For example, to further increase the rigidity of the cooling structure 1, the base steel sheet of the flow path upper cover 12 may be a high-strength steel sheet having a tensile strength of 980 MPa or more. On the other hand, to further increase press formability, the base steel sheet of the press-formed member 11 may be a mild steel sheet having a tensile strength of approximately 270 MPa, such as SPCC. Various forms can be applied to the base steel sheet constituting the press-formed member 11 and the flow path upper cover 12 depending on the shape and application of the cooling structure 1. Examples of base steel sheets include IF steel containing Ti, Nb, B, etc., Al-k steel, Cr-added steel, stainless steel, high-tensile steel, low-carbon steel, medium-carbon steel, high-carbon steel, and alloy steel.

[0025] (1.5 Coating composition of plated steel sheets) The Al-based plating of the plated steel sheet constituting the press-formed member 11 and the flow path upper cover 12 is, for example, a two-component or multi-component plating having an Al content of 70% by mass or more. Preferably, the Al-based plating is a two-component or multi-component plating having an Al content of 70 to 98% by mass and a Si content of 2.0 to 15% by mass. The Si content of the Al-based plating may be 3.0% by mass or more, 4.0% by mass or more, or 5.0% by mass or more. The Si content of the Al-based plating may be 14% by mass or less, 12% by mass or less, or 10% by mass or less. By keeping the Si content within the above range, the workability and corrosion resistance of the Al-based plated steel sheet can be further improved. Trace amounts of Fe, Ni, Co, etc. may be present as impurity elements in the plating layer. Furthermore, the Al-based plating may contain Mg, Sn, misch metal, Sb, Zn, Cr, W, V, Mo, etc., as needed.

[0026] There are no particular limitations on the method for producing the Al-based plated steel sheet. For example, the Al-based plating can be provided by hot-dip plating using the Sendzimir method or the all-radiant method, hot-dip flux plating, electroplating, or vapor deposition plating.

[0027] The thickness of the Al-based plating is not particularly limited. For example, the thickness of the Al-based plating may be 10 μm or more, 12 μm or more, 15 μm or more, or 20 μm or more. The thickness of the Al-based plating may be 60 μm or less, 50 μm or less, or 40 μm or less. The larger the thickness of the Al-based plating, the higher the internal corrosion resistance of the cooling structure 1. Furthermore, as described below, by setting the thickness of the Al-based plating, the laser welding conditions, and the gap between the press-formed member and the flow path upper cover within predetermined ranges, it is possible to arrange Al on the surface of the weld metal of the laser welded portion 13.

[0028] (1.6 Composition of chemical conversion coating on plated steel sheets) In order to further improve the exterior corrosion resistance and coolant corrosion resistance of Al-plated steel sheets and the like, it is preferable to apply a chemical conversion treatment to the surface of the Al-plated steel sheets and the like. While a commonly known chemical conversion treatment may be used for the chemical conversion treatment, it is preferable to form a chemical conversion coating containing one or more components selected from the group consisting of Zr-based components, Ti-based components, and Si-based components as the main component (e.g., 50% by mass or more). When the chemical conversion coating contains two or more of the Zr-based components, Ti-based components, and Si-based components, the total content of these components should be 50% by mass or more. Furthermore, the chemical conversion coating may contain an organic component. Hereinafter, the "main component" of the chemical conversion coating refers to a component that accounts for 50% by mass or more of the chemical conversion coating.

[0029] Examples of chemical conversion treatment films are listed in, for example, JP 2008-115442 A, JP 2013-7108 A, JP 2004-232040 A, Japanese Patent No. 3302676 A, Japanese Patent No. 4776458 A, and Japanese Patent No. 5336002 A. Therefore, the chemical conversion treatment films listed in these publications can be suitably used as the chemical conversion treatment film of this embodiment. Here, an overview of the chemical conversion treatment film will be described.

[0030] The first example of the chemical conversion coating is an example of a coating containing a Zr-based component as the main component, consisting only of Zr, F, P, C, O, N, and H, and containing no organic substances with a number average molecular weight of 200 or more. The components of the chemical conversion coating are adjusted so that the mass ratio of Zr to F, Zr / F, is 1.0 to 10.0, the mass ratio of Zr to P, Zr / P, is 8.5 to 18.0, and the Zr content in the chemical conversion coating is 23.0 mass% to 48.0 mass%. The sources of each component of the chemical conversion coating are one or more inorganic acids and / or their ammonium salts selected from the group consisting of carbonic acid, phosphoric acid, and hydrofluoric acid, and zirconium-containing complex compounds excluding zirconium hydrofluoric acid.

[0031] The second example of the chemical conversion coating is an example of a coating containing a Zr-based component as the main component, and contains (A) at least one of titanium compounds and zirconium compounds, (B) at least one of 2-6 bond phosphate esters of myo-inositol and their alkali metal salts, alkaline earth metal salts, and ammonium salts, and (C) silica. In this chemical conversion coating, the mass ratio of the metal equivalent amounts of (A) (Zr+Ti):(B):(C) is 1:0.2-1.7:0.2-5.

[0032] Examples of titanium compounds include potassium titanium oxalate, titanyl sulfate, titanium chloride, titanium lactate, titanium isopropoxide, isopropyl titanate, titanium ethoxide, titanium 2-ethyl-1-hexanolate, tetraisopropyl titanate, tetra-n-butyl titanate, and titania sol.

[0033] Examples of the zirconium compound include zirconyl nitrate, zirconyl acetate, zirconyl sulfate, ammonium zirconyl carbonate, potassium zirconium carbonate, sodium zirconium carbonate, and zirconium acetate.

[0034] Examples of 2- to 6-linked phosphate esters of myo-inositol include myo-inositol diphosphate ester, myo-inositol triphosphate ester, myo-inositol tetraphosphate ester, myo-inositol pentanephosphate ester, and myo-inositol hexanephosphate ester.

[0035] Examples of silica include water-dispersible silica compounds. Water-dispersible silica compounds include liquid-phase colloidal silica and gas-phase silica. Liquid-phase colloidal silica is not particularly limited, but examples include Snowtex C, Snowtex O, Snowtex N, Snowtex S, Snowtex UP, Snowtex PS-M, Snowtex PS-L, Snowtex 20, Snowtex 30, and Snowtex 40 (registered trademark) (all manufactured by Nissan Chemical Industries, Ltd.), Adelite AT-20N, Adelite AT-20A, and Adelite AT-20Q (all manufactured by Asahi Denka Kogyo Co., Ltd.).

[0036] The vapor phase silica is not particularly limited, but examples thereof include Aerosil 50, Aerosil 130, Aerosil 200, Aerosil 300, Aerosil 380, Aerosil TT600, Aerosil MOX80, and Aerosil MOX170 (all manufactured by Nippon Aerosil).

[0037] The third example of the chemical conversion coating is a coating containing a Zr-based component as the main component, and is a composite coating made of a zirconium compound, a vanadium compound, a silica compound, a phosphate compound, and an organic compound having at least one functional group selected from the group consisting of a hydroxyl group, a carbonyl group, and a carboxyl group. This chemical conversion coating contains 2 to 1200 mg / m of zirconium per side of the Al-based plated steel sheet. 2 , vanadium 0.1 to 300 mg / m 2 , phosphate compounds PO4 3- Equivalent to 0.3 to 450 mg / m 2 Furthermore, the content of chromium or chromium compounds in the chemical conversion coating is 0.1 mg / m 2 The following substances contain fluorine or fluorine compounds with a fluorine content of 0.1 mg / m2 The details are as follows.

[0038] Examples of the zirconium compound include zirconyl nitrate, zirconyl acetate, zirconyl sulfate, ammonium zirconyl carbonate, potassium zirconium carbonate, sodium zirconium carbonate, and zirconium acetate.

[0039] Examples of vanadium compounds include vanadium pentoxide, metavanadic acid, ammonium metavanadate, sodium metavanadate, vanadium oxytrichloride, vanadium trioxide, vanadium dioxide, vanadium oxysulfate, vanadium oxyacetylacetonate, vanadium acetylacetonate, vanadium trichloride, phosphovanadomolybdic acid, vanadium sulfate, vanadium dichloride, and vanadium oxide.

[0040] Examples of silica compounds include water-dispersible silica compounds. Examples of water-dispersible silica compounds include colloidal silica and gas-phase silica. Examples of colloidal silica include, but are not limited to, Snowtex C, Snowtex O, Snowtex N, Snowtex S, Snowtex UP, Snowtex PS-M, Snowtex PS-L, Snowtex 20, Snowtex 30, Snowtex 40 (all manufactured by Nissan Chemical Industries), Adelite AT-20N, Adelite AT-20A, Adelite AT-20Q (all manufactured by Asahi Denka Kogyo).

[0041] The vapor phase silica is not particularly limited, but examples thereof include Aerosil 50, Aerosil 130, Aerosil 200, Aerosil 300, Aerosil 380, Aerosil TT600, Aerosil MOX80, and Aerosil MOX170 (all manufactured by Nippon Aerosil).

[0042] The phosphate compound may contain phosphate ions, and examples of the phosphate compound include orthophosphoric acid (phosphoric acid), metaphosphoric acid, pyrophosphoric acid, and salts of these substances in which some or all of the hydrogen ions have been replaced, such as ammonium salts, sodium salts, calcium salts, and potassium salts, which can be used alone or in combination.

[0043] Examples of organic compounds having at least one functional group selected from the group consisting of a hydroxyl group, a carbonyl group, and a carboxyl group include alcohols such as methanol, ethanol, isopropanol, and ethylene glycol; carbonyl compounds such as formaldehyde, acetaldehyde, furfural, acetylacetone, ethyl acetoacetate, dipivaloylmethane, and 3-methylpentanedione; organic acids such as formic acid, acetic acid, propionic acid, tartaric acid, ascorbic acid, gluconic acid, citric acid, and malic acid; monosaccharides such as glucose, mannose, and galactose; oligosaccharides such as maltose and sucrose; natural polysaccharides such as starch and cellulose; aromatic compounds such as tannic acid, humic acid, lignosulfonic acid, and polyphenols; and synthetic polymers such as polyvinyl alcohol, polyethylene glycol, polyacrylic acid, polyacrylamide, polyethyleneimine, and water-soluble nylon.

[0044] The chemical conversion coating may contain, as an additional component, a lubricity-imparting component made of at least one of polyolefin wax and paraffin wax.

[0045] A fourth example of a chemical conversion coating is a coating containing a Ti-based component as the main component, in which an oxide or hydroxide of a valve metal and a fluoride coexist. Examples of valve metals include Ti and V. Among these, tetravalent compounds of Ti are preferred because they are stable compounds and can form coatings with excellent properties. Examples of coatings containing a Ti-based component as the main component include coatings in which oxides [TiO2] and hydroxides [Ti(OH)4] are combined. When a fluoride of Ti, for example, X, is added to this coating, nFluorides such as TiF6 (X: alkali metal, alkaline earth metal or NH4, n=1 or 2) and TiF4 coexist.

[0046] A fifth example of a chemical conversion coating is a coating primarily containing a silicon-based component, specifically an organosilicon compound (silane coupling agent). The organosilicon compound is obtained by blending a silane coupling agent (A) containing one amino group in the molecule with a silane coupling agent (B) containing one glycidyl group in the molecule in a solids mass ratio [(A) / (B)] of 0.5 to 1.7. The organosilicon compound contains two or more functional groups (a) represented by the formula -SiR1R2R3 (wherein R1, R2, and R3 each independently represent an alkoxy group or a hydroxyl group, with at least one representing an alkoxy group), and one or more hydrophilic functional groups (b) selected from the group consisting of a hydroxyl group (different from those that may be contained in functional group (a)) and an amino group, and has an average molecular weight of 1,000 to 10,000.

[0047] A sixth example of a chemical conversion coating is an example of a coating containing a silicon-based component as a main component, that is, a chemical conversion coating containing an organosilicon compound (silane coupling agent) as a main component. The organosilicon compound has a cyclic siloxane structure within its structure. Here, "cyclic siloxane bond" refers to a cyclic structure having a structure in which Si-O-Si bonds are continuous, and which is composed only of Si and O bonds, with 3 to 8 Si-O repeating units.

[0048] The organosilicon compound is obtained by blending a silane coupling agent (A) containing at least one amino group in the molecule with a silane coupling agent (B) containing at least one glycidyl group in the molecule in a solids mass ratio [(A) / (B)] of 0.5 to 1.7. The organosilicon compound (W) thus obtained preferably contains two or more functional groups (a) represented by the formula -SiR1R2R3 (wherein R1, R2, and R3 each independently represent an alkoxy group or a hydroxyl group, and at least one of R1, R2, and R3 represents an alkoxy group) and one or more hydrophilic functional groups (b) selected from the group consisting of a hydroxyl group (if the functional group (a) contains a hydroxyl group, the functional group (a) is separate from the hydroxyl group) and an amino group, and has an average molecular weight of 1,000 to 10,000.

[0049] Examples of the chemical conversion coating of this embodiment are not limited to those described above.

[0050] The method for forming the above-mentioned chemical conversion coating is not particularly limited, and a chemical conversion solution (coating solution) corresponding to each of the above compositions may be applied to an Al-based plated steel sheet by a known method, followed by baking and drying.

[0051] (1.7 Flow path configuration) Next, the configuration of the flow path 14 of the cooling structure 1 according to this embodiment will be described. In order to improve the cooling efficiency of the cooling structure 1, it is preferable to increase the contact area between the coolant and the flow path lid 12, that is, to increase the area of ​​the region of the flow path lid 12 facing the flow path 14. For this reason, the flow path 14 has a parallel flow path section 141 in which multiple partial flow paths 1411 extending along a first direction are aligned in a second direction perpendicular to the first direction. The first direction is, for example, the longitudinal direction or lateral direction of the cooling structure 1. By providing the parallel flow path section 141 in which multiple partial flow paths 1411 are arranged in parallel, it is possible to increase the contact area between the coolant and the flow path lid 12. However, in order to ensure even better cooling efficiency, the present inventors conducted further studies.

[0052] Increasing the width W of the partial flow path 1411 has been considered as a means for further increasing the contact area between the coolant and the flow path upper cover 12. However, the wider the width W of the partial flow path 1411, the greater the stress applied to the laser welded portion 13, which may shorten the life of the cooling structure 1. Furthermore, if the width W of the partial flow path 1411 is too wide, the coolant will not flow stably along the extension direction of the partial flow path 1411, i.e., the first direction, which may result in uneven cooling.

[0053] Another method for further increasing the contact area between the coolant and the flow path upper cover 12 is to narrow the spacing D between the partial flow paths 1411. This method can improve cooling efficiency while preventing an increase in stress applied to the laser welded portion 13 and the occurrence of uneven cooling. For the above reasons, in the cooling structure 1 according to this embodiment, the spacing D between adjacent partial flow paths 1411 is set to 20 mm or less in part or all of the parallel flow path section 141. The spacing D between the partial flow paths 1411 may also be set to 18 mm or less, 16 mm or less, or 15 mm or less. Although the lower limit of the spacing D between the partial flow paths 1411 is not particularly limited, from the viewpoint of preventing poor joining, the spacing D may be set to 0.8 mm or more, 1 mm or more, 3 mm or more, 5 mm or more, or 8 mm or more.

[0054] The interval D between the partial channels 1411 is preferably within the above-mentioned range throughout the entire parallel channel section 141. However, for example, by arranging another component such as a screw hole between the partial channels 1411, the interval D between the partial channels 1411 may be greater than 20 mm in part of the parallel channel section 141. In other words, the interval D between the partial channels 1411 may be within the above-mentioned range in part of the parallel channel section 141.

[0055] As long as the spacing D between the partial channels 1411 is within the above-described range, the width W of the partial channels 1411 is not particularly limited. From the viewpoint of further increasing the contact area between the channel formation portion and the channel lid 12, the width W of the partial channels 1411 may be set to 6 mm or more, 8 mm or more, or 10 mm or more. On the other hand, from the viewpoint of further increasing the bonding strength between the press-formed member 11 and the channel lid 12 and further improving the cooling uniformity, the width W of the partial channels 1411 may be set to 60 mm or less, 30 mm or less, 25 mm or less, or 20 mm or less. The height of the partial channels 1411 is also not particularly limited, but may be, for example, 1 mm or more to further improve the cooling efficiency. On the other hand, to reduce the weight of the cooling structure 1, the height of the partial channels 1411 may be set to 10 mm or less. The above-described shape of the partial channels 1411 may be applied to the partial channels constituting the channel communication portion 142.

[0056] In the cooling structure 1 according to this embodiment, the flow path 14 and the partial flow path 1411 included therein refer to spaces through which the coolant can easily flow and provide a substantial cooling effect. Therefore, as shown in FIG. 4 , the flow path 14 and the partial flow path 1411 are defined as spaces between the flow path lid 12 and the press-formed member 11, with a thickness of 0.5 mm or more along a direction perpendicular to the flow path lid 12. The spacing D of the partial flow path 1411 refers to the spacing between the spaces defined above. That is, the spacing D of the partial flow path 1411 refers to the sum of the widths of the regions where the laser welded portion 13, the flow path lid 12, and the press-formed member 11 are in contact, and the width of the region where the gap between the flow path lid 12 and the press-formed member 11 is less than 0.5 mm. Although not shown in FIG. 4 , the width W of the partial flow path 1411 refers to the width of the space defined above. That is, the width W of the partial flow path 1411 is the width of a space having a thickness of 0.5 mm or more along a direction perpendicular to the flow path upper cover 12. The interval D of the partial flow paths 1411 and the width W of the partial flow paths are values ​​measured along a second direction perpendicular to the first direction, which is the extension direction of the partial flow paths 1141.

[0057] (1.8 Structure of laser welded parts) In order to set the spacing D of the partial flow channels 1411 within the above-mentioned range, in the cooling structure 1 according to this embodiment, the joining portions for forming the flow channels 14 are laser welded portions 13. Laser welding can reduce the bead width. Therefore, it is an effective joining method for narrowing the spacing D of the partial flow channels 1411. Furthermore, because laser welding forms a linear bead, it can improve the liquid-tightness of the flow channels 14 compared to point joining methods such as spot welding.

[0058] The configuration of the laser welded portion 13 is not particularly limited, and various configurations can be adopted depending on the shape of the flow path 14. Preferred embodiments of the laser welded portion 13 will be described below.

[0059] For example, the bead width on the laser irradiation side, i.e., the wider of the bead width on the surface of the laser welded portion 13 on the flow path upper cover 12 and the bead width on the surface of the laser welded portion 13 on the press-formed member 11, may be set to 0.8 to 1.5 mm. By setting the bead width to 0.8 mm or more, the liquid-tightness of the flow path 14 can be further improved. On the other hand, by setting the bead width to 1.5 mm or less, evaporation of the plating near the bead can be prevented, and the corrosion resistance of the cooling structure 1 can be further improved.

[0060] Alternatively, the laser welded portion 13 may be formed so as to satisfy all of the following three requirements. (1) The width of the thicker bead of the laser welded portion 13 is set to 0.8 to 1.5 mm as described above. (2) The thickness of the Al-based plating on the plated steel sheets constituting the press-formed member 11 and the flow path upper cover 12 is set to 10.0 μm or more as described above. (3) The distance between the press-formed member 11 and the flow path upper cover 12 in the vicinity of the laser welded portion 13 is set to 0.3 mm or less. When the laser welded portion 13 is formed so as to satisfy all of the above requirements (1) to (3), a part or all of the surface of the laser welded portion 13 between the press-formed member 11 and the flow path upper cover 12 is covered with an Al-based plating, thereby further improving the coolant corrosion resistance of the cooling structure 1.

[0061] Normally, the base steel sheet and the Al-based coating melt and solidify during laser welding, so no Al-based coating is present on the surface of the weld metal that constitutes the laser weld. However, the present inventors welded Al-based coated steel sheets under various conditions and investigated the weld metals obtained thereby. They found that the weld metal obtained by laser welding that satisfied all of the above requirements (1) to (3) had its surface covered with Al-based coating between the press-formed member 11 and the flow path upper cover 12. The reason for this is unclear, but it is presumed that the heat from the laser welding melts the Al-based coating around the laser weld and transfers it to the surface of the weld metal at the laser weld 13.

[0062] The specific mechanism is presumed to be as follows. First, the bead width of the above requirement (1) is strongly correlated with the amount of heat input during laser welding. If the bead width is too large, the heat input during laser welding is too large, causing the Al-based coating to disappear over a wide area around the weld metal, and preventing the hot-dip Al-based coating from migrating to the surface of the weld metal. On the other hand, if the bead width is too small, there is a risk that the flow path upper cover 12 and the press-formed member 11 will not be sufficiently joined.

[0063] If the coating thickness of the above requirement (2) is too small, the hot-dip Al-based coating will be insufficient and will not migrate to the surface of the weld metal. Also, if the spacing between the coated steel sheets of the above requirement (3) is too large, the weld metal will become too large and will not be covered by the hot-dip Al-based coating.

[0064] Here, the sheet spacing of the plated steel sheet in the above requirement (3) refers to the spacing between the press-formed member and the flow path upper cover, measured in the vicinity of the laser weld 13. The vicinity of the laser weld 13 refers to the region within 0.1 mm from the weld metal contained in the laser weld 13. In the region within 0.1 mm from the molten metal, the spacing between the press-formed member and the flow path upper cover is substantially constant, so the spacing can be measured at any location within this region. Furthermore, even in the case of a substantially arc-shaped plated steel sheet, if it is within this range, the change in the sheet spacing of the plated steel sheet is small, and the value measured within this range can be used as the sheet spacing of the plated steel sheet.

[0065] The distance between the press-formed member 11 and the flow path upper cover 12 in the vicinity of the laser welded portion 13 is preferably 0.2 mm or less, 0.1 mm or less, or 0.05 mm or less.

[0066] 5A, the laser welded portion 13 is composed of a starting portion 131, a terminal portion 132, and an intermediate portion 133 therebetween. The starting portion 131 of the laser welded portion 13 is a portion corresponding to the location where the laser welding starts, and the terminal portion 132 of the laser welded portion 13 is a portion corresponding to the location where the laser welding ends. In this embodiment, it is not necessary to distinguish between the starting portion 131 and the terminal portion 132. The starting portion 131 and the terminal portion 132 are clearly different from the intermediate portion 133 in terms of width, etc., and therefore the starting portion 131 and the terminal portion 132 can be clearly distinguished from the intermediate portion 133.

[0067] The intermediate portion 133 tends to have fewer weld defects than the starting portion 131 and the terminal portion 132, and therefore has better corrosion resistance and liquid-tightness. Therefore, it is preferable that the flow path 14 is formed using the intermediate portion 133 of the laser welded portion 13 and is spaced apart from the starting portion 131 and the terminal portion 132. In other words, as illustrated in Fig. 5A, it is preferable that the laser welding is performed so that the intermediate portion 133 of the laser welded portion 13 is located between the starting portion 131 and the terminal portion 132 of the laser welded portion 13 and the flow path 14. This makes it possible to prevent the starting portion 131 and the terminal portion 132 from being exposed to the coolant. 5B, it is more preferable that the starting end 131 and the terminal end 132 of the laser welded portion 13 are removed from the cooling structure 1. For example, a tab plate T is provided on the flow path upper cover 12 or the press-formed member 11 before laser welding, and laser welding is performed so that the starting end 131 and the terminal end 132 are formed on the tab plate T, and then the tab plate T is cut and removed, thereby obtaining a cooling structure 1 that does not include the starting end 131 and the terminal end 132 of the laser welded portion 13.

[0068] A configuration in which the start end 131 and the end end 132 are removed only in areas of the cooling structure 1 where liquid leakage is a concern may be applied. For example, in the cooling structure 1 shown in FIGS. 6A and 6B , if the flow path lid 12 peels off from the press-formed member 11 at a portion of the laser weld 13 provided along the outer edges of the press-formed member 11 and the flow path lid 12 (the dark portion designated by reference numeral 13A), the coolant will leak out of the cooling structure 1. On the other hand, in the cooling structure 1 shown in FIGS. 6A and 6B , even if the flow path lid 12 peels off from the press-formed member 11 at a laser weld 13 provided in an area surrounded by the flow paths 14, the coolant will not leak out of the cooling structure 1. Therefore, if the portion of the laser weld 13 that surrounds all of the flow paths 14 (the dark portion designated by reference numeral 13A) is defined as the flow path outer edge weld 13A, it is preferable that the start end 131 and the end end 132 be removed from the flow path outer edge weld 13A. In this case, even if the laser welded portion 13 excluding the flow path outer edge welded portion 13A includes a starting end 131 and an ending end 132, it is possible to sufficiently prevent the cooling water from leaking outside the cooling structure 1. 5A, the cooling structure 1 illustrated in FIG. 6A is obtained by manufacturing a flow path outer edge weld 13A using only the middle portion 133 of the laser weld 13. In this case, the starting end and the ending end are excluded from the flow path outer edge weld 13A but remain in the cooling structure 1. On the other hand, the cooling structure 1 illustrated in FIG. 6B is obtained by providing a tab plate T to the flow path upper cover 12 or the press-formed member 11 before laser welding, performing laser welding so that a starting end 131 and an ending end 132 are formed on the tab plate T, and then cutting and removing the tab plate T, as in FIG. 5B. In this case, the starting end and the ending end created when forming the flow path outer edge weld 13A do not remain in the cooling structure 1. In addition, by starting laser irradiation from a point that does not hit the flow path upper cover 12 and the press-formed member 11, then performing laser welding, and irradiating the laser so that it runs through to a point that does not hit the flow path upper cover 12 and the press-formed member 11, and then stopping the laser irradiation, the starting and ending ends of the formation of the flow path outer edge weld 13A do not remain in the cooling structure 1.

[0069] The bead height of the laser welded portion 13 on the flow path upper cover 12 may be 0.3 mm or less. By setting the bead height of the laser welded portion 13 to 0.3 mm or less, the gap between the flow path upper cover 12 and the object to be cooled (e.g., a battery pack or battery cell) can be reduced, thereby further improving cooling efficiency. The bead height of the laser welded portion 13 may be reduced, for example, by controlling the laser welding conditions. The bead height may also be reduced by grinding the bead after laser welding is completed.

[0070] (1.9 Other Configurations) As shown in FIG. 2A , the flow path 14 may further be provided with a flow path communication portion 142 that communicates the plurality of partial flow paths 1411. The flow path 14 may further be provided with a coolant inlet 143 and a coolant outlet 144 for introducing a coolant into the flow path. When the flow path 14 has the flow path communication portion 142, the flow path 14 forms a single space. In this case, the cooling structure 1 may be provided with one coolant inlet 143 and one coolant outlet 144. On the other hand, the cooling structure 1 may not be provided with the flow path communication portion 142. In this case, the plurality of partial flow paths 1411 may each be provided with a coolant inlet 143 and a coolant outlet 144. Only some of the plurality of partial flow paths 1411 may be connected by the flow path communication portion 142, and the flow path 14 may form two or more spaces. 2A and other figures, each of the two flow path communication sections 142 is a straight flow path, and the flow path communication section 142 is connected to all of the partial flow paths 1411 so as to be perpendicular to the flow path. However, the shape of the flow path communication section 142 and the arrangement of the flow path communication section 142 and the partial flow paths 1411 are not limited to this. For example, the angle between the flow path communication section 142 and the partial flow paths 1411 is not limited to 90° and can be appropriately selected depending on the application of the cooling structure 1. Furthermore, the flow path communication section 142 may have a branched structure. As shown in FIG. 2B, each of the two flow path communication sections 142 may branch in a fan shape starting from the coolant inlet 143 or the coolant outlet 144, and may communicate with each of the partial flow paths 1411 at various angles at the branched ends. Note that the laser welded section 13 is omitted from FIG. 2B.

[0071] Between the press-formed member 11 and the flow path upper cover 12, 30% or more of the surface of the laser welded portion 13 may be covered with Al-based plating. This improves the corrosion resistance of the laser welded portion 13 to the coolant, and ultimately further enhances the corrosion resistance of the cooling structure 1 to the coolant.

[0072] The coverage of the laser welded portion 13 with Al-based plating is measured by the following procedure. First, any one of the plurality of partial flow paths 1411 included in the cooling structure 1 is cut perpendicular to its extension direction, i.e., the first direction. The cutting points are a total of three points: the midpoint between both ends of the partial flow path 1411, and two midpoints between this midpoint and each end of the partial flow path 1411. When the above-mentioned flow path communication part 142 is included in the cooling structure 1, the both ends of the partial flow path 1411 are the points where the partial flow path 1411 and the flow path communication part 142 intersect, and when the flow path communication part 142 is not included in the cooling structure 1, the both ends of the partial flow path 1411 are the points where the coolant inlet 143 and the coolant outlet 144 are provided. Next, micrographs of the laser welded portion 13 at the cut surfaces at the three locations mentioned above are taken. 7, the coverage rate at each cross section is measured using the length a of the surface of the weld metal constituting the laser welded portion 13 in the cross section as the denominator and the sum of the lengths b of the Al-based plating adhered to the surface of this welded metal along the welded metal surface as the numerator. Furthermore, the average value of the coverage rates at the three cross sections is calculated, and this is regarded as the coverage rate of the laser welded portion 13 by the Al-based plating. Laser welding is a joining method that forms a homogeneous weld metal along the welding direction, so the coverage rate across the entire cooling structure 1 can be estimated based on the values ​​obtained by the above-mentioned means. In FIG. 7, the symbol 15 represents the base steel sheet, and the symbol 16 represents the Al-based plating.

[0073] The planar shapes of the press-formed member 11 and the flow path lids 12 that constitute the cooling surfaces of the cooling structure 1 are not particularly limited. For example, when the cooling structure 1 is used to cool an EV battery, the flow path lids 12 desirably have a rectangular shape in plan view. In this case, the size of the flow path lids 12 in plan view is preferably 1000 mm to 2300 mm in the longitudinal direction and 200 mm to 1500 mm in the lateral direction. Similarly, the size of the press-formed member 11 in plan view is preferably 1000 mm to 2300 mm in the longitudinal direction and 200 mm to 1500 mm in the lateral direction. When manufacturing a cooling structure 1 in which the press-formed member 11 and / or the flow path lids 12 have a large area and the flow path interval D is narrow, poor bonding between the bank portions 112 and the flow path lids 12 is likely to be a problem. However, poor bonding can be easily avoided by, for example, using the manufacturing method described below. The longitudinal size of the flow path lid 12 in a plan view may be 1200 mm or more, 1400 mm or more, or 1600 mm or more. The longitudinal size of the flow path lid 12 in a plan view may be 2200 mm or less, 2000 mm or less, or 1800 mm or less. The lateral size of the flow path lid 12 in a plan view may be 250 mm or more, 500 mm or more, or 700 mm or more. The lateral size of the flow path lid 12 in a plan view may be 1400 mm or less, 1300 mm or less, or 1200 mm or less. The longitudinal size of the press-formed member 11 in a plan view may be 1200 mm or more, 1400 mm or more, or 1600 mm or more. The longitudinal size of the press-formed member 11 in a plan view may be 2200 mm or less, 2000 mm or less, or 1800 mm or less. The lateral size of the press-formed member 11 in a plan view may be 250 mm or more, 500 mm or more, or 700 mm or more. The lateral size of the press-formed member 11 in a plan view may be 1400 mm or less, 1300 mm or less, or 1200 mm or less.

[0074] As described above, in order to increase the cooling efficiency of the cooling structure 1, it is preferable to increase the contact area between the coolant and the flow path upper cover 12.

[0075] As described above, in the cooling structure according to the first embodiment, the press-formed member 11 and the flow path upper cover 12 are made of Al-based plated steel sheets, thereby improving the corrosion resistance of the outer surface and the coolant. This makes it possible to suppress water path corrosion and the occurrence of contamination that can cause a decrease in thermal conductivity and clogging. Furthermore, in the cooling structure according to the first embodiment, by laser welding the press-formed member 11 and the flow path lid 12, the distance D between the partial flow paths 1411 in the parallel flow path section 141 can be set to 20 mm or less, thereby increasing the area of ​​contact between the coolant and the flow path lid 12 and improving the cooling efficiency. Additionally, in the cooling structure according to the first embodiment, the press-formed member 11 and the flow path upper cover 12 are laser-welded, thereby making it possible to improve the liquid-tightness of the flow path 14.

[0076] (2. Battery unit) Next, a battery unit according to a second embodiment of the present invention will be described. As shown in Figures 8A to 8C, the battery unit 2 according to this embodiment includes battery cells 21, a battery pack 22 in which the battery cells 21 are housed, and the cooling structure 1 according to the first embodiment.

[0077] When incorporating the cooling structure 1 into the battery unit 2, as shown in Fig. 8B, the battery pack 22 can be used as the flow path upper cover 12 of the cooling structure 1. In other words, the bank portion 112 of the press-formed member 11 and the battery pack 22 can be laser welded together. By integrating the battery pack 22 with the cooling structure 1, the battery unit 2 can cool the battery cells 21 extremely efficiently.

[0078] Alternatively, a structure in which the battery pack 22 and the cooling structure 1 are separated may be employed. For example, the battery unit 2 may be manufactured by joining the flow path lid 12 and the battery pack 22. In this case, as shown in FIG. 8C , a gap filler 23 may be disposed between the flow path lid 12 and the battery pack 22. It may be difficult to join the battery pack 22 and the flow path lid 12 of the cooling structure 1 without gaps due to some reasons (such as errors in dimensional accuracy or the battery pack 22 having a complex uneven shape). In such cases, the gap filler 23 can be used. The gap filler 23 is generally a resin containing a pigment with high thermal conductivity. Inserting the gap filler 23 between different materials can improve heat exchange efficiency. In this embodiment, the thermal conductivity of the gap filler 23 is preferably 3.5 W / m or more. An example of the gap filler 23 is "SDP-3540-A" manufactured by Shin-Etsu Silicones Co., Ltd. The thickness of the gap filler is preferably 0.1 mm to 8.0 mm, and more preferably 0.5 mm to 3.0 mm.

[0079] The configuration of the battery pack 22 is not particularly limited. For example, the battery pack 22 may be substantially rectangular, with the cooling structure 1 disposed on its bottom surface, or the bottom surface may serve as the flow path lid 12 of the cooling structure 1. From the viewpoint of improving corrosion resistance, the steel plate constituting the battery pack 22 is preferably an Al-based plated steel plate or a Zn-based plated steel plate. However, when a structure in which the battery pack 22 and the cooling structure 1 are separated is adopted as shown in FIG. 8C , it is not essential that the portion of the battery pack 22 where the cooling structure 1 is attached, for example, the bottom surface, be resistant to coolant corrosion.

[0080] The thickness of the Al-plated steel sheet that forms the bottom surface of the battery pack 22 is not particularly limited, but is preferably 0.2 to 1.2 mm or 0.3 to 1.2 mm, and more preferably 0.4 to 0.6 mm, for example. In this case, the bottom surface of the battery pack 22 can be made thin while maintaining its strength. Therefore, the distance between the coolant and the internal structure of the battery pack 22 can be reduced, which not only improves the cooling efficiency of the battery pack 22 but also improves the cooling responsiveness of the battery pack 22.

[0081] (3. Manufacturing method of cooling structure) Next, a manufacturing method of a cooling structure according to a third embodiment of the present invention will be described. The manufacturing method of a cooling structure according to the third embodiment includes a step S1 of press-forming a plated steel sheet to obtain a press-formed member 11, and a step S2 of laser-welding the press-formed member and the flow path upper cover. Details of these steps will be described below. This manufacturing method can suitably manufacture the cooling structure according to the first embodiment. However, the following description does not limit the manufacturing method of the cooling structure according to the first embodiment.

[0082] (S1 Press molding) In the manufacturing method of the cooling structure according to this embodiment, first, a plated steel sheet is press-formed. This results in a press-formed member 11 having grooves 111 and bank portions 112 provided around the grooves 111. The plated steel sheet used in the press forming has an Al-based coating. A suitable form of the plated steel sheet is as described above. Furthermore, in the cooling structure 1 finally obtained, the flow path 14 has parallel flow path portions 141 in which multiple partial flow paths 1411 extending along a first direction are aligned in a second direction perpendicular to the first direction, and in the parallel flow path portions 141, the distance D between adjacent partial flow paths 1411 is 20 mm or less. The grooves 111 need to be formed in the press forming so that this shape of the flow path 14 is achieved.

[0083] (S2 laser welding) Next, a flat flow path lid 12 is placed over the press-formed member 11 in a position that covers the groove 111, and the flow path lid 12 is laser-welded to the bank 112 of the press-formed member 11. This results in a laser welded portion 13 that forms a flow path 14 through which a coolant can flow.

[0084] The laser welding conditions are not particularly limited, and suitable conditions can be appropriately selected depending on the thickness of the plated steel sheet, etc. One example of particularly suitable laser welding conditions is when the thickness of the Al-based coating is 10.0 μm or more and the distance between the press-formed member 11 and the flow path upper cover 12 near the laser weld is 0.3 mm or less. The beam diameter is preferably 0.2 to 0.8 mm and the heat input per unit weld length is preferably 30 to 120 kJ / m. This melts the Al-based coating around the weld and transfers it to the surface of the laser weld 13, thereby covering part or all of the surface of the laser weld 13 between the press-formed member 11 and the flow path upper cover 12 with the Al-based coating. A more preferred beam diameter is 0.4 to 0.6 mm and the heat input per unit weld length is 30 to 60 kJ / m. [Example]

[0085] The effects of one embodiment of the present invention will be explained in more detail using examples. However, the conditions in the examples are merely examples adopted to confirm the feasibility and effects of the present invention. The present invention is not limited to these examples. Various conditions may be adopted in the present invention as long as they do not deviate from the gist of the present invention and achieve the object of the present invention.

[0086] Example 1: Relationship between flow path spacing, assembly feasibility, and cooling structure performance A press-formed member was created by press-forming an Al-based plated steel sheet. This press-formed member was laser-welded to a channel top cover made of a flat sheet of Al-based plated steel sheet to produce a cooling structure. The channel widths and channel spacing of the multiple partial channels extending in parallel are shown in Table 1. Note that the manufacturing conditions not included in Table 1 were as follows. No channel connecting portions connecting the partial channels were created. Type of plated steel sheet: 0.5mm thick aluminum plated mild steel sheet (Al-9%Si plated steel sheet used) Laser welding machine: Fiber laser welding machine Laser welding heat input: 45,000 J / m The shape of the cooling structure of the embodiment: shown in Figure 9 Partial flow path length: 200mm Partial channel height: 10mm

[0087] Figure 9 is a schematic diagram of a portion of the manufactured cooling structure. For convenience, only two partial flow paths are shown in Figure 9, but in reality, the cooling structure was provided with enough partial flow paths to cover a battery with a width of 120 mm. In all of the examples shown in the table, the cooling structure was able to be assembled by laser welding.

[0088] The evaluation results of the cooling structures created as described above are also shown in Table 1. The evaluation criteria were as follows: Regarding the flow path width W of the partial flow paths, those of 20 mm or less were ranked "S," those between 20 mm and 30 mm were ranked "A," and those over 30 mm were ranked "B." This is because the smaller the flow path width W, the more stable the flow of the coolant can be, further improving the cooling efficiency. "D / 2" is the value obtained by dividing the distance D between multiple partial channels by 2. This value is the maximum distance along the channel width direction at points where partial channels are not in direct contact with each other, and the smaller the value, the better. If D / 2 is too large, the points not in contact with the channel will not be sufficiently cooled, and there is a risk that the cooling structure will not function sufficiently. D / 2 of 7.5 mm or less was ranked "A," that of more than 7.5 mm and less than 10 mm was ranked "B," and that of more than 10 mm was ranked "C." Samples rated as rank A or rank B were judged to have sufficiently narrow channel spacing.

[0089] [Table 1]

[0090] All of the examples shown in Table 1 could be manufactured by laser welding. Therefore, it is clear that laser welding can manufacture partial flow channels that can demonstrate high cooling capacity, even in the case of the narrowest partial flow channel width of 10 mm among the manufactured partial flow channels.

[0091] (Example 2: Relationship between bead width and coverage rate) Various cooling structures were manufactured by changing the heat input conditions within the range of 30 to 120 kJ / m so that the width of the larger of the laser weld beads on the flow path lid and the press-formed member (hereinafter simply referred to as "bead width") was within the range of 1.2 mm to 2.2 mm. The gap between the flow path lid and the press-formed member near the laser weld was within the range of 0 to 0.2 mm. The plating thickness was 10 μm or 60 μm. Furthermore, for laser welding, plated steel sheets of the same thickness were combined.

[0092] Next, the cross section of the laser weld was observed to confirm whether the surface of the laser weld between the press-formed member and the front-passage top cover was covered with Al-based plating. The ratio of the area of ​​the Al-based plating covering the laser weld to the surface area of ​​the laser weld (hereinafter referred to as "coverage") was measured. The method for measuring the coverage was as described above with reference to FIG. 7.

[0093] Figure 10A shows the relationship between bead width and coverage for a cooling structure manufactured from a steel sheet with a plating thickness of 10 μm. Figure 10B shows the relationship between bead width and coverage for a cooling structure manufactured from a steel sheet with a plating thickness of 60 μm. In all examples where the bead width was 1.5 mm or less, the entire surface of the laser weld was covered with Al-based plating. These examples are considered to have high internal corrosion resistance. Furthermore, when the bead width was greater than 1.5 mm, there was a tendency for the coverage to decrease as the bead width increased.

[0094] (Example 3: Evaluation of Corrosion Resistance) Various cooling structures were manufactured using the welding method, partial channel spacing, distance between steel sheets, plating thickness, and laser welding heat input shown in Table 2. The distance between steel sheets refers to the distance between the channel top cover and the press-formed member at the location where laser welding is performed. This distance was adjusted by inserting a spacer of the same thickness as the desired distance between the steel sheets in a location that does not obstruct welding. However, in manufacturing cooling structure No. 1, spot welding was used with a general welding electrode with an electrode diameter of φ16 mm instead of laser welding. Heat input data for cooling structure No. 1 manufactured by spot welding is omitted. In all examples except No. 21, the shapes of the press-formed member and channel top cover before welding were as shown in Figures 11A and 11B, and the shape of the channel was as shown in Figure 11C. In Example No. 21, the cross-sectional shape of the partial channel was made to be the wave shape shown in Figure 3, but the other shapes were similar to those of the other examples. In all examples, the channel shape in plan view was U-shaped, with two vertically extending channels representing the partial channel. The flow path width was 20 mm in all cooling structures. The bead width of the manufactured cooling structures was measured and listed in Table 3. The bead width listed in Table 3 is the wider width of the bead of the laser weld on the flow path upper cover and the bead of the laser weld on the press-formed member.

[0095] A pump was also connected to the cooling structure, and long-life coolant (LLC) was circulated. A filter was connected between the pump and the cooling structure to prevent any corrosion products from entering the pump. The LLC was circulated for 100 hours under conditions where the pressure in the flow path was 1.5 atmospheres and the LLC temperature was 50°C. After that, the inner surface plating condition, bead width, and inner surface corrosion resistance were evaluated using the following methods, and the results are listed in Table 3. The condition of the inner surface plating was evaluated by fabricating a flow path under the same conditions, then dismantling the flow path and observing the cross section of the weld. The weld cross section was observed at three points: the midpoint between both ends of the partial flow path, and two midpoints between this midpoint and the ends of the partial flow path. If the entire surface of the laser weld between the press-formed part and the upper flow path cover was covered with Al-based plating, it was rated as rank "A." If only part of the surface was covered with Al-based plating, it was rated as rank "B." If it was not covered at all, it was rated as rank "C." Samples rated as rank A or rank B were judged to have a good condition of the inner surface plating. For internal corrosion resistance, if the filter became clogged during LLC circulation and circulation could no longer continue, it was rated as rank "C." The flow paths in which LLC was able to circulate for 100 hours were disassembled and the state of corrosion on the internal surface was visually inspected. If LLC circulation for 100 hours was possible but red rust had formed on the internal surface of the flow path, it was rated as rank "B," and if no rust had formed, it was rated as rank "A." Samples rated as rank A or rank B were judged to have good internal corrosion resistance.

[0096] [Table 2]

[0097] [Table 3]

[0098] In Example 1, spot welding could not be performed. This was because the φ16 mm electrode could not contact the intended welding point when the flow path interval was 5 mm.

[0099] On the other hand, in all examples manufactured using laser welding, joining was possible despite the small flow path spacing. Furthermore, in none of the examples, red rust was observed in the LLC after the above-mentioned LLC circulation test. Therefore, all examples had excellent internal corrosion resistance. Furthermore, in none of the examples, LLC leakage was observed. Therefore, all examples had excellent liquid-tightness. In addition, since the flow path spacing was narrow in all examples, high cooling efficiency can be achieved when these are used to cool battery cells, etc. Although external corrosion resistance was not evaluated, it is expected that external corrosion resistance will be high, just like internal corrosion resistance. [Explanation of symbols]

[0100] 1 Cooling structure 11 Press-formed parts 111 Groove 112 Embankment 12 Flow channel cover 13 Laser welded section 13A Flow channel outer edge weld 131 Starting end 132 Termination 133 Middle section 14 Flow path 141 Parallel flow path section 1411 Partial channel 142 Flow path connecting part 143 Coolant inlet 144 Coolant outlet 15 Base steel plate 16 Al-based plating 2 Battery Unit 21 Battery Cells 22 Battery pack 23 Gap Filler R: Circle showing the radius of curvature of the bank T-tab plate L Laser D Channel spacing W: width of the flow path

Claims

1. a press-formed member having a groove portion and a bank portion provided around the groove portion; a flow path upper cover that is a flat plate superimposed on the press-formed member in a position that covers the groove portion and forms a flat cooling surface; a laser welded portion that joins opposing surfaces of the flow path cover and the bank portion to form a flow path through which a coolant can flow; Equipped with the press-formed member and the flow path upper cover are plated steel sheets having a base steel sheet and an Al-based plating, the flow path has a parallel flow path portion in which a plurality of partial flow paths extending along a first direction are aligned in a second direction perpendicular to the first direction, In some or all of the parallel flow path portions, the interval between adjacent partial flow paths is 20 mm or less, The Al-based plating contains Si Cooling structure.

2. 2. The cooling structure according to claim 1, wherein the Si content of the Al-based plating is 2.0 to 15 mass %.

3. a press-formed member having a groove portion and a bank portion provided around the groove portion; a flow path upper cover that is a flat plate superimposed on the press-formed member in a position that covers the groove portion and forms a flat cooling surface; a laser welded portion that joins opposing surfaces of the flow path cover and the bank portion to form a flow path through which a coolant can flow; Equipped with the press-formed member and the flow path upper cover are plated steel sheets having a base steel sheet and an Al-based plating, the flow path has a parallel flow path portion in which a plurality of partial flow paths extending along a first direction are aligned in a second direction perpendicular to the first direction, In some or all of the parallel flow path portions, the interval between adjacent partial flow paths is 20 mm or less, The plated steel sheet has a chemical conversion coating on the surface thereof, the chemical conversion coating containing a Zr-based component, a Ti-based component, or a Si-based component in a proportion of 50 mass % or more. Cooling structure.

4. a press-formed member having a groove portion and a bank portion provided around the groove portion; a flow path upper cover that is a flat plate superimposed on the press-formed member in a position that covers the groove portion and forms a flat cooling surface; a laser welded portion that joins opposing surfaces of the flow path cover and the bank portion to form a flow path through which a coolant can flow; Equipped with the press-formed member and the flow path upper cover are plated steel sheets having a base steel sheet and an Al-based plating, the flow path has a parallel flow path portion in which a plurality of partial flow paths extending along a first direction are aligned in a second direction perpendicular to the first direction, In some or all of the parallel flow path portions, the interval between adjacent partial flow paths is 20 mm or less, The cross-sectional shape of the bank portion is a substantially circular arc, The radius of curvature of the bank portion at the contact portion between the flow path upper cover and the bank portion is 15 mm or less. Cooling structure.

5. a press-formed member having a groove portion and a bank portion provided around the groove portion; a flow path upper cover that is a flat plate superimposed on the press-formed member in a position that covers the groove portion and forms a flat cooling surface; a laser welded portion that joins opposing surfaces of the flow path cover and the bank portion to form a flow path through which a coolant can flow; Equipped with the press-formed member and the flow path upper cover are plated steel sheets having a base steel sheet and an Al-based plating, the flow path has a parallel flow path portion in which a plurality of partial flow paths extending along a first direction are aligned in a second direction perpendicular to the first direction, In some or all of the parallel flow path portions, the interval between adjacent partial flow paths is 20 mm or less, The thickness of the Al-based plating is 10.0 μm or more, a distance between the press-formed member and the flow path upper cover in the vicinity of the laser weld is 0.3 mm or less; The larger of the bead width on the surface of the laser welded portion of the flow path upper cover and the bead width on the surface of the laser welded portion of the press-formed member is 0.8 to 1.5 mm. Cooling structure.

6. a press-formed member having a groove portion and a bank portion provided around the groove portion; a flow path upper cover that is a flat plate superimposed on the press-formed member in a position that covers the groove portion and forms a flat cooling surface; a laser welded portion that joins opposing surfaces of the flow path cover and the bank portion to form a flow path through which a coolant can flow; Equipped with the press-formed member and the flow path upper cover are plated steel sheets having a base steel sheet and an Al-based plating, the flow path has a parallel flow path portion in which a plurality of partial flow paths extending along a first direction are aligned in a second direction perpendicular to the first direction, In some or all of the parallel flow path portions, the interval between adjacent partial flow paths is 20 mm or less, A part or the whole of the surface of the laser welded portion between the press-formed member and the flow path upper cover is covered with the Al-based plating. Cooling structure.

7. a press-formed member having a groove portion and a bank portion provided around the groove portion; a flow path upper cover that is a flat plate superimposed on the press-formed member in a position that covers the groove portion and forms a flat cooling surface; a laser welded portion that joins opposing surfaces of the flow path cover and the bank portion to form a flow path through which a coolant can flow; Equipped with the press-formed member and the flow path upper cover are plated steel sheets having a base steel sheet and an Al-based plating, the flow path has a parallel flow path portion in which a plurality of partial flow paths extending along a first direction are aligned in a second direction perpendicular to the first direction, In some or all of the parallel flow path portions, the interval between adjacent partial flow paths is 20 mm or less, Between the press-formed member and the flow path upper cover, 30% or more of the surface of the laser welded portion is covered with the Al-based plating. Cooling structure.

8. a press-formed member having a groove portion and a bank portion provided around the groove portion; a flow path upper cover that is a flat plate superimposed on the press-formed member in a position that covers the groove portion and forms a flat cooling surface; a laser welded portion that joins opposing surfaces of the flow path cover and the bank portion to form a flow path through which a coolant can flow; Equipped with the press-formed member and the flow path upper cover are plated steel sheets having a base steel sheet and an Al-based plating, the flow path has a parallel flow path portion in which a plurality of partial flow paths extending along a first direction are aligned in a second direction perpendicular to the first direction, In some or all of the parallel flow path portions, the interval between adjacent partial flow paths is 20 mm or less, The bead height of the laser welded portion of the flow path upper cover is 0.3 mm or less. Cooling structure.

9. 9. The cooling structure according to claim 1, wherein the distance between adjacent partial flow paths in the parallel flow path section is 0.8 to 15 mm.

10. 9. The cooling structure according to claim 1, wherein the width of the partial flow passage is 6 to 60 mm.

11. 9. The cooling structure according to claim 1, wherein the width of the partial flow path is 6 to 20 mm.

12. 9. The cooling structure according to claim 1, wherein the plated steel sheets constituting the press-formed member and the flow path upper cover have a thickness of 0.3 to 1.2 mm.

13. the laser welds include flow channel outer edge welds that surround all of the flow channels; The start and end of the laser weld are excluded from the outer edge weld of the flow channel. The cooling structure according to any one of claims 1 to 8.

14. 9. The cooling structure according to claim 1, wherein a start end and a finish end of the laser weld are excluded from the cooling structure.

15. A battery cell; a battery pack containing the battery cells; Cooling structure and Equipped with The cooling structure includes a press-formed member having a groove and a bank portion provided around the groove, a flow path upper cover which is a flat plate superimposed on the press-formed member in a position covering the groove and which forms a flat cooling surface, and a laser welded portion which joins opposing surfaces of the flow path upper cover and the bank portion to form a flow path through which a coolant can flow, the press-formed member and the flow path upper cover are plated steel sheets having a base steel sheet and an Al-based plating, the flow path has a parallel flow path portion in which a plurality of partial flow paths extending along a first direction are aligned in a second direction perpendicular to the first direction, In some or all of the parallel flow path portions, the interval between adjacent partial flow paths is 20 mm or less, a battery unit in which the flow path upper cover of the cooling structure is joined to the battery pack;

16. A battery cell; a battery pack containing the battery cells; Cooling structure and Equipped with The cooling structure includes a press-formed member having a groove and a bank portion provided around the groove, a flow path upper cover which is a flat plate superimposed on the press-formed member in a position covering the groove and which forms a flat cooling surface, and a laser welded portion which joins opposing surfaces of the flow path upper cover and the bank portion to form a flow path through which a coolant can flow, the press-formed member and the flow path upper cover are plated steel sheets having a base steel sheet and an Al-based plating, the flow path has a parallel flow path portion in which a plurality of partial flow paths extending along a first direction are aligned in a second direction perpendicular to the first direction, In some or all of the parallel flow path portions, the interval between adjacent partial flow paths is 20 mm or less, The battery unit wherein the flow path upper cover of the cooling structure is the battery pack.

17. a step of press-forming a steel plate to obtain a press-formed member having a groove portion and a bank portion provided around the groove portion; a step of overlapping a flat flow path lid at a position covering the groove portion of the press-formed member, and laser welding the flow path lid to the bank portion of the press-formed member to obtain a laser welded portion that forms a flow path through which a coolant can flow; Equipped with the press-formed member and the flow path upper cover are plated steel sheets having a base steel sheet and an Al-based plating, the flow path has a parallel flow path portion in which a plurality of partial flow paths extending along a first direction are aligned in a second direction perpendicular to the first direction, In the parallel flow path section, the interval between adjacent partial flow paths is 20 mm or less, The thickness of the Al-based plating is 10.0 μm or more, In the laser welding, the beam diameter is 0.2 to 0.8 mm, and the heat input per unit weld length is 30 to 120 kJ / m; and The distance between the press-formed member and the flow path upper cover in the vicinity of the laser welded portion is set to 0.3 mm or less. A method for manufacturing a cooling structure.

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