JOINING JOINT TO BE JOINED TO RESIN, METHOD FOR MANUFACTURING JOINING JOINT, AND JOINING STRUCTURE BETWEEN METAL AND RESIN

Abstract

Provided is a joining structure between metal and resin which has improved junction strength. A joining joint has a hand-drum shape having a constricted portion constricted between both of the bottom surfaces by forming a groove-shaped recess in a circumferential direction of a substantially cylindrical side surface made of metal. Upper and lower end portions of the side surface and the recess form a rough concavo-convex shape, and the side surface including the recess becomes a junction surface. On the junction surface, a fine concavo-convex shape with arithmetic average roughness Ra of 10 to 300 m is formed. By forming the rough concavo-convex shape and the fine concavo-convex shape on the junction surface, the joining joint makes strong joining to resin.

Claims

1. A joining joint made of metal, having a junction surface to be joined to resin on a surface, and having a fine concavo-convex shape formed on the junction surface, where arithmetic average roughness Ra of the fine concavo-convex shape is 10 to 300 m.

2. The joining joint according to claim 1, wherein a groove-shaped recess is formed on the junction surface.

3. The joining joint according to claim 2, wherein the junction surface has a substantially cylindrical shape serving as a side surface, and the recess is formed in a circumferential direction of the side surface.

4. The joining joint according to claim 3, wherein a cross section in a radial direction of a constricted portion formed of the recess in the circumferential direction is substantially polygonal.

5. A method for manufacturing the joining joint according to claim 1, wherein a fine concavo-convex shape is formed on a surface of a casting mold for casting the joining joint by forming the casting mold of coarse aggregate, and a fine concavo-convex shape is formed on a surface of the joining joint casted from the casting mold.

6. The method for manufacturing the joining joint according to claim 5, wherein an average grain size (median diameter d50) of the aggregate is 200 to 2000 m.

7. A joining structure between metal and resin, comprising: the joining joint according to claim 1; and a resin bracket that covers the junction surface of the joining joint, and is formed of resin for fixing the joining joint as a matrix.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0026] FIG. 1 is a perspective view of a joining joint according to an embodiment.

[0027] FIG. 2 is a front view of the same joining joint.

[0028] FIG. 3 is a sectional view taken along line III-III in FIG. 2.

[0029] FIG. 4 is a sectional view of a casting mold for casting the same joining joint.

[0030] FIG. 5 is a perspective view of a joining structure using the same joining joint.

[0031] FIG. 6 is a front view of a bearing device using the same joining joint.

[0032] FIG. 7 is a plan view of the same bearing device.

DESCRIPTION OF EMBODIMENTS

[0033] Hereinafter, joining joints to be joined to resin according to embodiments described in the present description will be described based on the drawings. However, the technique described in this description is not limited to these embodiments. A joining joint 1 according to an embodiment is used as an insert member (insert collar, insert nut), and as illustrated in FIG. 1, the joining joint is formed into a hand-drum shape having a groove-shaped recess 13 formed in a circumferential direction of a substantially cylindrical side surface 11 of metal, and a constricted portion 14 constricted between both bottom surfaces 12. A rough concavo-convex shape 101 is formed of upper and lower end portions 15 of the side surface 11 and the recess 13, and the side surface 11 including the recess 13 becomes a junction surface 10 to be joined to resin. On the junction surface 10, a fine concavo-convex shape 100 with arithmetic average roughness Ra of 10 to 300 m is formed. Due to the formation of the rough concavo-convex shape 101 and the fine concavo-convex shape 100 on the junction surface 10, the joining joint 1 can be strongly joined to resin. In addition, as illustrated in FIGS. 6 and 7, the joining joint 1 of the embodiment can be used as a bolt hole forming portion of a bearing device in which a shaft bearing portion 201 and a bolt hole forming portion (joining joint 1) are formed of metal, and a bracket (resin bracket 2) connecting the shaft bearing portion 201 and the bolt hole forming portion is formed of resin as described in Patent Literature 2 (Japanese Published Unexamined Patent Application No. 2020-012502) described above. Accordingly, the bearing device as a joining structure between metal and resin can be made light in weight. In this description, concerning orientation of the joining joint 1, as illustrated in FIG. 1, a direction of an axis connecting the centers of both of the bottom surfaces 12 is set as the up-down direction, and in the illustration, U represents up, and D represents down. In addition, a radial direction and a circumferential direction may be expressed with respect to the axis connecting the centers of each of the bottom surfaces 12.

[0034] The joining joint 1 is formed of metal, and as the metal, specifically, a nodular graphite cast iron product FCD500 (JIS G 5502:2007) is used. The nodular graphite cast iron product has excellent tensile strength and heat resistance, and excellent durability as the joining joint 1. As another embodiment, aluminum alloy diecasting ADC12 (JIS H 5302:2006) is used. ADC12 is excellent in mechanical properties, machinability, and castability. The joining joint 1 is manufactured by die-casting using a casting mold which realizes low-cost manufacturing and is suitable for mass production although details thereof will be described later.

[0035] As illustrated in FIGS. 1 to 3, the joining joint 1 of the embodiment has a hand-drum shape including one groove-shaped recess 13 formed across the whole circumference of the substantially cylindrical side surface 11 in the circumferential direction, thick upper and lower end portions 15 and 15, and the constricted portion 14 at the center in the up-down direction. The joining joint 1 has a rough concavo-convex shape 101 formed of the upper and lower end portions 15 and 15 and the constricted portion 14 formed at the center in the up-down direction. Due to the rough concavo-convex shape 101, as illustrated in FIG. 5, when the joining joint 1 is fixed to the resin bracket 2, resin intrudes into the recess, and the effect of preventing the joining joint 1 from coming off is improved.

[0036] As illustrated in FIG. 2, at external corner portions in the circumferential direction which define the recess 13, chamfered portions 13a chamfered to be round inward are formed, and at internal corner portions in the circumferential direction, chamfered portions 13b chamfered to be round outward are formed. Due to the chamfered portions 13a and the chamfered portions 13b, a stress to be applied to resin when the joining joint 1 is fixed to the resin bracket 2 can be distributed.

[0037] As illustrated in FIG. 3, the constricted portion 14 has a substantially quadrangular cross section in a radial direction. Since the constricted portion 14 has a substantially quadrangular cross section, when the joining joint 1 is fixed to the resin bracket 2, the constricted portion 14 formed of the recess 13 and the resin that has intruded into the recess 13 fit in a quadrangular shape, so that the junction strength between metal and the resin with respect to rotation of the joining joint in the circumferential direction can be improved. At external corner portions in the up-down direction which form the substantially quadrangular shape of the constricted portion 14, chamfered portions 14a chamfered to be round inward are formed. Due to the chamfered portions 14a, a stress to be applied to resin when the joining joint 1 is fixed to the resin bracket 2 can be distributed.

[0038] Each of upper and lower bottom surfaces 12 of the joining joint 1 has a circular shape, and has a screw hole 16 opened through a central axis in the up-down direction. Due to the screw hole 16, the joining joint 1 can be joined to another member by a screw or the like. The screw hole 16 may be changed to a threadless circular or odd-shaped hole such as a polygonal hole.

[0039] The side surface 11 including the recess 13 of the joining joint 1 of the embodiment serves as a junction surface 10 to be joined to resin of the resin bracket 2. On the junction surface 10, a fine concavo-convex shape 100 with arithmetic average roughness Ra of approximately 90 m is formed. Due to the formation of the fine concavo-convex shape 100 with arithmetic average roughness Ra of approximately 90 m on the junction surface 10, when the joining joint 1 is joined to resin of the resin bracket 2, the resin intrudes into the fine concavo-convex shape 100 and exerts an effect as an anchor, so that coupling between the joining joint 1 and the resin can be made strong.

[0040] Although details of the fine concavo-convex shape 100 with arithmetic average roughness Ra of approximately 90 m will be described later, a casting mold 3 for casting the joining joint 1 is formed of coarse aggregate 32 (FIG. 4), and accordingly, the fine concavo-convex shape 100 is formed on a surface of the casting mold 3, and is formed by transferring the fine concavo-convex shape 100 onto the side surface 11 of the joining joint 1 casted from the casting mold 3.

[0041] Next, a method for manufacturing the joining joint 1 of the embodiment will be described. The joining joint 1 is manufactured by casting using the casting mold 3, and the method for manufacturing the joining joint 1 of the embodiment will be described by being divided into a method for manufacturing the casting mold 3 for casting the joining joint 1 and a method for manufacturing the joining joint 1 by using the casting mold 3.

[0042] The method for manufacturing the casting mold 3 includes a primary mold manufacturing process for manufacturing a primary mold by replicating a master model from a master model (3D data) of the joining joint 1, and a casting mold manufacturing process for manufacturing a secondary mold (casting mold 3) having the fine concavo-convex shape 100 on a surface from the primary mold by using coarse aggregate 32.

[0043] In the primary mold manufacturing process, by a versatile method, a primary mold made of metal (or resin) is manufactured by replicating a master model from a master model of the joining joint 1.

[0044] In the casting mold manufacturing process, as illustrated in FIG. 4, the casting mold 3 (secondary mold) is molded by pouring a die molding material for forming a gas-hardening sand mold so as to make a cast of the primary mold. The die molding material for forming a gas-hardening sand mold is hardened by using a cold box process as a kind of gas-hardening mold making methods in which the die molding material is hardened by supplying gas thereto, and accordingly, the casting mold 3 is molded.

[0045] The die molding material is prepared by mixing aggregate 32, resin, and a hardening agent, and as the aggregate 32, molding silica sand #3.5 (JIS G 5901:2016) as aggregate which remains most on a screening surface of a sieve with a nominal opening of 1180 m is used, and as the resin and hardening agent, a general-purpose resin and hardening agent to be used for the cold box process are used. The die molding material contains 98.4% aggregate 32, 0.8% resin, and 0.8% hardening agent.

[0046] The die molding material is mostly made of coarse aggregate 32, so that the casting mold 3 made of the die molding material has, as a surface shape, a fine concavo-convex shape 100 formed of the shape (grain size) of the aggregate 32.

[0047] A method for manufacturing the joining joint 1 by using the casting mold 3 consists of a pouring process of pouring molten metal into the casting mold 3, and a demolding process of demolding to take the joining joint 1 out.

[0048] In the pouring process, molten metal is poured into the casting mold 3, and cooled and solidified to mold a joining joint 1. Pouring is performed by a versatile method.

[0049] In the demolding process, the joining joint 1 is demolded from the casting mold 3, unnecessary objects such as burrs are removed, and by machining the bottom surfaces 12, the fine concavo-convex shapes 100 of the bottom surfaces 12 are eliminated, and the joining joint 1 is made usable.

[0050] In the joining joint 1 manufactured in this way, on the junction surface 10 of the side surface 11, the fine concavo-convex shape 100 is formed. In addition, the rough concavo-convex shape 101 is formed of the upper and lower end portions 15 and 15, the groove-shaped recess 13 in the circumferential direction of the side surface 11 of the joining joint 1, and the constricted portion 14 at the center in the up-down direction. In the joining joint 1, just by changing the size of the aggregate 32 forming the casting mold 3, the size of the fine concavo-convex shape 100 can be adjusted.

[0051] Next, a joining structure between metal and resin which uses the joining joint 1 of the embodiment will be described. In the embodiment, concerning a bearing device that supports a shaft of a vehicle turnably, a joining structure using the joining joint 1 at the bolt hole forming portion to be joined to a vehicle body will be described by way of example.

[0052] As illustrated in FIGS. 6 and 7, the bearing device 200 includes an annular shaft bearing portion 201 through which a shaft is inserted via a bearing, joining joints 1 into which bolts for fixing the shaft bearing portion 201 to a fixation portion, and a bracket that connects the shaft bearing portion 201 and the joining joints 1, the shaft bearing portion 201 and the joining joints 1 are formed of metal, and the bracket (resin bracket 2) connecting the shaft bearing portion 201 and the joining joints 1 are formed of resin. Accordingly, the bearing device 200 is made light in weight.

[0053] The resin bracket 2 integrally connects the shaft bearing portion 201 and the joining joints 1, and is made of a resin mixture, and molded by a forming mold. As resin to be used in the resin mixture, two types of resins are used separately. One of the resins is polyamide resin as thermoplastic resin, and another resin is phenol resin as thermosetting resin. By using polyamide resin or phenol resin as a resin to be used in the resin mixture, the resin bracket 2 can be made excellent in heat resistance and mechanical strength.

[0054] Glass fiber is mixed as fiber into the resin mixture to be used for the resin bracket 2, and accordingly made as a fiber-mixed resin. By mixing fiber into the resin mixture, hardening shrinkage of the resin can be reduced, and the physical strength can be improved. A mixture fraction of fiber in the fiber-mixed resin is set to 40 mass % to efficiently improve the physical strength.

[0055] The joining joint 1 used in the bearing device 200 has the fine concavo-convex shape 100 formed on the junction surface 10 of the side surface 11 including the recess 13, so that joining to the resin of the resin bracket 2 can be made strong. As illustrated in FIG. 5, the joining joint 1 has the rough concavo-convex shape 101 formed of the upper and lower end portions 15 and 15 and the recess 13 at the center in the up-down direction, so that the effect of preventing coming-off from the resin bracket 2 is improved, and since the cross section of the constricted portion 14 in a radial direction is substantially quadrangular, the rotation prevention effect is improved.

[0056] The joining joint 1 and the connection structure between metal and resin of the embodiment can also be realized when their configurations are changed to the following forms.

[0057] Although the nodular graphite cast iron product FCD500 is used as an iron alloy (cast iron) used for molding the joining joint 1 in the joining joint 1 of the embodiment, nodular graphite cast iron products (FCD350, FCD400, FCD450, FCD600, FCD700, FCD800) prescribed in JIS G 5502:2001 may be used. This is because these are excellent in mechanical strength.

[0058] Although ADC12 is used as aluminum alloy diecasting for molding the joining joint 1 in the joining joint 1 of the embodiment, aluminum alloy diecastings (ADC1,ADC3, ADC5, ADC6, ADC10, ADC10Z, ADC12Z, ADC14) prescribed in JIS H 5302:2006 may be used.

[0059] In the joining joint 1 of the embodiment, although the cross section of the constricted portion 14 in a radial direction is set to be substantially quadrangular, the cross-sectional shape of the constricted portion 14 in a radial direction may be set to be substantially triangular to substantially hexagonal. This improves the coming-off prevention effect and the rotation prevention effect with respect to the resin bracket 2. The cross section of the constricted portion 14 in a radial direction may be set to be circular.

[0060] In the joining joint 1 of the embodiment, one groove-shaped recess 13 is provided across the whole circumference of the side surface 11 in the circumferential direction, however, one to three groove-shaped recesses 13 may be provided in the up-down direction. This improves the coming-off prevention effect with respect to the resin bracket 2. When groove-shaped recesses 13 more than three in number are provided, the structure of the joining joint 1 may become complicated. As another embodiment, one or two groove-shaped recesses 13 may be provided in the up-down direction.

[0061] The joining joint 1 of the embodiment is a substantially cylindrical insert member (insert collar, insert nut), however, without limitation to the insert member, joining joints to be used for joining metal and resin may be used. The shape is not limited to the substantially cylindrical shape, and may be, for example, a conical shape, a prismatic shape, a pyramidal shape, etc.

[0062] In the method for manufacturing the joining joint 1 of the embodiment, the casting mold 3 is molded by a gas-hardening sand mold, however, as the casting mold 3, a green sand mold, a self-hardening sand mold, a thermosetting sand mold, etc., may also be used for molding.

[0063] In the method for manufacturing the joining joint 1 of the embodiment, as the aggregate 32 to be mixed into the die molding material for forming the gas-hardening sand mold serving as the casting mold 3, molding silica sand 190 3 (average grain size (median diameter d50): 1500 m) as aggregate which remains most on a screening surface of a sieve with a nominal opening of 1180 m is used, however, as the aggregate 32, aggregate may be used as long as its average grain size is 200 to 2000 m. This enables formation of the fine concavo-convex shape 100 that makes strong joining to resin. When the average grain size of the aggregate is less than 200 m, the fine concave-convex shape 100 becomes finer, and joining to resin may not be made strong. On the other hand, when the average grain size is more than 2000 m, the strength of the casting mold 3 may deteriorate. As another embodiment, the average grain size of the aggregate 32 may be 600 to 1700 m.

[0064] In the method for manufacturing the joining joint 1 of the embodiment, as the aggregate 32 to be mixed into the die molding material for forming the gas-hardening sand mold serving as the casting mold 3, molding silica sand #3 as aggregate which remains most on a screening surface of a sieve with a nominal opening of 1180 m is used, however, as the silica sand, molding silica sand #6 to molding silica sand #3 may be used. As another embodiment, the size of silica sand may be molding silica sand #4 to molding silica sand #3. As the aggregate 32, calcium carbonate powder, cerben (crushed sanitary ware), crushed stone powder, etc., may also be used as long as they have an average grain size equivalent to the size described above.

[0065] In the method for manufacturing the joining joint 1 of the embodiment, as the die molding material for forming the gas-hardening sand mold serving as the casting mold 3, a die molding material containing 98.4% aggregate 32, 0.8% resin, and 0.8% hardening agent is used, however, a die molding material may be used as long as it contains 70 to 99% aggregate 32, 0.5 to 15% resin, and 0.5 to 15% hardening agent. As another embodiment, the die molding material may contain 90 to 99% aggregate 32, 0.5 to 5% resin, and 0.5 to 5% hardening agent.

[0066] As the thermoplastic resin of the resin mixture for forming the resin bracket 2, polyamide resin has been used in the embodiment, however, thermoplastic resin such as polypropylene, polyvinyl chloride, polystyrene, acrylic resin, polycarbonate resin, ABS resin may be used which have excellent heat resistance.

[0067] As the thermosetting resin of the resin mixture for forming the resin bracket 2, phenol resin has been used in the embodiment, however, thermosetting resin such as amino resin and urea resin may be used. This is because these have excellent heat resistance.

[0068] As fiber of the fiber-mixed resin as the resin mixture for forming the resin bracket 2, glass fiber that is inorganic fiber is used in the embodiment, however, inorganic fiber such as carbon fiber, metal fiber, and ceramic fiber, or organic fiber such as cellulose fiber, acrylic fiber, polyamide fiber, and polyester fiber may also be used.

[0069] The mixture fraction of fiber in the fiber-mixed resin is 40 mass % in the embodiment, however, fiber-mixed resin may be used as long as the mixture fraction of fiber is 10 to 70 mass %. A mixture fraction less than 10 mass % may not sufficiently improve the strength. On the other hand, a mixture fraction more than 70 mass % may cause an increase in density of the fiber-mixed resin and may not make the bearing device 200 light in weight. The mixture fraction is more preferably 20 to 60 mass %, and further preferably 30 to 50 mass %.

[0070] The fiber-mixed resin containing polyamide resin or phenol resin as resin and mixed with 40 mass % glass fiber is used in the embodiment, however, fiber-mixed resin available on the market may also be used. Usable glass-fiber-mixed resin available on the market includes A1022GFL15, A1022GFL, A1030GFL, A1030GFL45, A1022GFL60 (A), EX-8406G30, A175S, A190S, A192S, A690S (the foregoing resins are made by UNITIKA, LTD.), CM1011G-15, CM1001G-15, CM1001G-20, CM1011G-30, CM1016G-30, CM1011G-45, CM1012G-45N, CM3001G-15, CM3006G-15, CM3001G-30, CM3006G-30, CM3001G-45, CM3006G-45 (the foregoing resins are made by Toray Industries, Inc.), etc.

REFERENCE SIGNS LIST

[0071] 1 Joining joint [0072] 2 Resin bracket [0073] 3 Casting mold [0074] 3a Side surface portion [0075] 10 Junction surface [0076] 11 Side surface [0077] 12 Bottom surface [0078] 13 Recess [0079] 13a Chamfered portion [0080] 13b Chamfered portion [0081] 14 Constricted portion [0082] 14a Chamfered portion [0083] 15 End portion [0084] 16 Screw hole [0085] 32 Aggregate [0086] 100 Fine concavo-convex shape [0087] 101 Rough concavo-convex shape [0088] 200 Bearing device [0089] 201 Shaft bearing portion