Fastening structure for metallic members and manufacturing method thereof

Abstract

To provide a fastening structure for metal members and a manufacturing method that can improve joint strength while suppressing an increase in manufacturing steps and costs when joining metallic members made of different materials.SOLUTION: A fastening structure 1 for metal members includes a first metallic member 3 made of a metallic material having a predetermined quality and a second metallic member 2 made of a metallic material different from the predetermined quality, the first metallic member 3 being joined to the outer surface of the second metallic member 2. The first metallic member 3 is integrated with the second metallic member 2 by internally insert-casting the second metallic member 2, and the first metallic member 3 and the second metallic member 2 are fastened together by a fastening member 4 that extends through the first metallic member 3 from the outer peripheral surface toward the inner peripheral surface to be engaged with the second metallic member 2.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a structure for fastening together a plurality of metal members made of different materials, and a manufacturing method thereof. [Background technology]

[0002] Patent Document 1 discloses an integrated structure of metal parts made of different material compositions, in which a hollow steering hanger beam made of steel and a steering column mounting part made of light metal are welded together, and a manufacturing method for the same. In the manufacturing method described in Patent Document 1, the steering hanger beam is manufactured by dividing it into three parts along the axial direction. The steering column mounting part is a component for attaching the steering column to the steering hanger beam and is formed by casting a specific central part of the three parts in light metal. After the light metal cools, the specific part is removed, and the cast-in part is joined to other parts by arc welding to produce an integrated structure of the steering hanger beam and steering column mounting part. Patent Document 1 also discloses a configuration in which a ring-shaped anchor member extending radially is attached to the outer periphery of the specific part and then cast-in together with the anchor member to prevent relative rotation between the specific part and the steering column mounting part. The anchor member is positioned so as to be cast-in into the reinforcing part of the steering column mounting part. Patent Document 1 states that with this configuration, metal parts made of different material compositions can be joined easily while maintaining high joint strength, compared to joining metal parts made of different material compositions by welding or the like. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-260479 Summary of the Invention [Problem to be solved by the invention]

[0004] When inspecting the bonding condition at a joint where metal parts are joined together, as described in Patent Document 1, it is known to inspect the bonding condition by so-called non-destructive testing such as X-ray inspection. However, because the degree of penetration of X-rays, gamma rays, etc. varies depending on the metal part, noise also known as metal artifacts may occur. As a result, it is not possible to accurately inspect the degree and strength of bonding between metal parts made of different materials, and it may not be possible to ensure the fastening strength between the metal parts.

[0005] Patent Document 1 also discloses a configuration for improving the fastening strength between a steering hanger beam and a steering column mounting portion by casting a predetermined component in a light metal while positioning a reinforcing portion of the steering column mounting portion and an anchor member attached to the outer peripheral surface of the predetermined component. However, this requires positioning the predetermined component in a mold so that the anchor member fits into the reinforcing portion of the steering column mounting portion, and then precisely welding the anchor member to the predetermined component in a previous step, which may result in inconveniences such as a complicated overall manufacturing process. In other words, the structure of Patent Document 1 does not necessarily ensure the joining strength between metal components, and it is difficult to confirm whether the joining strength is ensured. Therefore, there is still room for improvement in structures that ensure the joining strength when joining metal components made of different materials.

[0006] This invention has been made with an eye on the above-mentioned technical problems, and aims to provide a fastening structure for metal members and a manufacturing method thereof that can improve the strength of the joint while suppressing increases in manufacturing processes and costs when joining metal parts made of different materials. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the present invention provides a fastening structure for metal members, comprising a first metal member made of a predetermined metal material and a second metal member made of a metal material different from the predetermined material, wherein the first metal member is joined to the outer surface of the second metal member, wherein the first metal member is integrated with the second metal member by casting the second metal member into the second metal member, and the first metal member and the second metal member are fastened together by a fastening member that penetrates from the outer peripheral surface of the first metal member toward the inner peripheral surface and engages the first metal member with the second metal member.

[0008] In this invention, the first metal member may be a steering hanger beam for transmitting steering operations to wheels in a vehicle, and the second metal member may be a steering column mounting portion for transmitting the steering operations to the steering hanger beam in the vehicle.

[0009] The present invention also provides a method for manufacturing a fastening structure for metal members in which a first metal member made of a predetermined metal material is joined to the outer surface of a second metal member made of a metal material different from the predetermined material, characterized in that the first metal member is cast-in to the second metal member, thereby integrating the first metal member with the second metal member, and fastening the first metal member to the second metal member by penetrating a fastening member from the outer peripheral surface of the first metal member toward the inner peripheral surface at a position set based on the change in shape of the second metal member that occurs when the first metal member is cast-in to the second metal member, thereby engaging the first metal member with the second metal member.

[0010] In this invention, the first metal member and the second metal member may be fastened together by FDS joining, in which the first metal member and the second metal member are softened by frictional heat generated by rotating the fastening member while pressed against the outer surface of the first metal member, and then joined together by passing the fastening member through the first metal member.

[0011] In the present invention, when the second metal member is cast-in with the first metal member, a cast-out hole may be formed at a location where the FDS joining is to be performed. [Effects of the Invention]

[0012] In the fastening structure for metal members and the manufacturing method thereof of the present invention, a first metal member made of a predetermined material is integrated with the outer surface of a second metal member made of a different material by insert molding. This allows for a higher joining strength compared to joining metal members made of different materials by welding or other methods. Furthermore, in this fastening structure, a fastening member is fastened so as to penetrate the integrated second metal member and first metal member. The fastening member is fastened from the outside of the first metal member integrated with the outer peripheral surface of the second metal member. This further improves the fastening strength between the first metal member and the second metal member. For example, even if a load that would cause relative movement between the first metal member and the second metal member occurs, the fastening member can withstand such a load.

[0013] Furthermore, the position where the fastening member is fastened is determined based on the change in shape of the second metal member that occurs when the second metal member is cast-in with a predetermined material. Therefore, the fastening member can be fastened at a position that can further increase the joint strength while suppressing a decrease in the strength of the second metal member due to fastening the first and second metal members with the fastening member. Furthermore, the fastening member is joined to the first and second metal members by FDS. Therefore, processes for fastening the fastening member, such as forming through holes and attaching nuts, can be omitted. Furthermore, a cast-out hole is formed at the position where the fastening member will be fastened by FDS. Therefore, when fastening the fastening member by FDS, the load on the robot or machine tool that rotates the fastening member can be reduced. [Brief explanation of the drawings]

[0014] [Figure 1]1 is a partial perspective view showing a part of a steering hanger beam and a steering column mounting portion to which a fastening structure for a metal member according to an embodiment of the present invention is applied. [Figure 2] 2 is a partially enlarged view schematically illustrating a portion where the steering hanger beam and the steering column mounting portion shown in FIG. 1 are fastened together. FIG. [Figure 3] FIG. 2 is a cross-sectional view showing a cross section taken along line AA shown in FIG. [Figure 4] FIG. 4 is a cross-sectional view corresponding to FIG. 3, showing a state before the fastening member is fastened, and is a cross-sectional view for explaining a cast hole formed in the steering column mounting portion. [Figure 5] FIG. 10 is a diagram illustrating the change in shape that occurs in the steering hanger beam due to the cast-in process, and is an explanatory diagram for illustrating the positions where fastening members are fastened. DETAILED DESCRIPTION OF THE INVENTION

[0015] The present invention will be described below based on the embodiments shown in the drawings. Note that the embodiments described below are merely examples of specific embodiments of the present invention, and are not intended to limit the present invention.

[0016] FIG. 1 shows an example of a metal structure 1 to which a fastening structure for metal members according to an embodiment of the present invention is applied. The metal structure 1 shown in FIG. 1 is a structure disposed at the front of a vehicle (not shown), and fastened to a steering hanger beam 2 for transmitting the operation of a steering wheel (not shown) in the vehicle to wheels, and a steering column mounting portion 3 for mounting a steering column (not shown) to the steering hanger beam 2. As shown in FIGS. 2 and 3, a fastening member 4 is screwed into the metal structure 1, penetrating the steering hanger beam 2 and the steering column mounting portion 3. Note that the metal structure 1 is not limited to a structure fastening the steering hanger beam 2 and the steering column mounting portion 3, but may be any structure fastening a metal member made of a predetermined metal material with another metal member made of a metal material different from the predetermined material.

[0017] The steering hanger beam 2 is a frame for supporting the steering column. The steering hanger beam 2 is a long metal member arranged at the front of the vehicle with its long dimension aligned with the width direction of the vehicle. As shown in FIG. 2, the steering hanger beam 2 is a hollow cylindrical member made of steel. The steering hanger beam 2 is connected to the wheels via a steering shaft, a drive shaft, and the like, neither of which are shown. The steering hanger beam 2 corresponds to the second metal member in this embodiment of the present invention.

[0018] The steering column mounting portion 3 is a metal member joined to the outer peripheral surface of the steering hanger beam 2 by cast-in processing. The steering column mounting portion 3 is provided for mounting the steering column to the steering hanger beam 2, with the mounting position set according to the position of the steering wheel. The steering column mounting portion 3 is made of a light metal (light alloy) such as aluminum, magnesium alloy, or aluminum alloy. Furthermore, the light alloy is a non-heat-treatable alloy whose strength can be increased by cold working. The steering column mounting portion 3 corresponds to the first metal member in this embodiment of the present invention.

[0019] Furthermore, a cast hole 5 is formed in the steering column mounting portion 3, as shown in FIG. 4. The cast hole 5 is formed at a position in the steering column mounting portion 3 where the fastening member 4 is to be fastened. The cast hole 5 does not penetrate the steering column mounting portion 3, but is formed to a predetermined thickness (length) in the plate thickness direction from the outer peripheral surface of the steering column mounting portion 3, as shown in FIG. 4. The cast hole 5 is formed during a cast-in insert process using a cast pin or the like, as is conventionally known. The inner diameter and length of the cast hole 5 are formed to dimensions that allow easy processing when fastening the fastening member 4. Note that, although only one cast hole 5 is formed in the metal structure in the embodiment of the present invention, the number of cast holes may correspond to the number of fastening members 4 to be fastened to the metal structure 1.

[0020] Furthermore, the positions at which the fastening members 4 are fastened are set according to the deformations that occur in the steering hanger beam 2. Figure 5 shows an example of a fastening location P1 where the fastening members 4 are fastened. When the steering column mounting portion 3 is cast using the cast-in-place method, deformations can occur in the steering hanger beam 2 due to the shape and temperature of the steering column mounting portion 3 and the temperature of the steering hanger beam 2. This deformation is not uniform, and as shown in Figure 5, deformations that cause the inner diameter of the steering hanger beam 2 to vary slightly in the circumferential direction can occur. The positions at which such deformations are likely to occur in the circumferential direction of the steering hanger beam 2 are set based on experiments, simulations, or the specific shape changes that occur when performing the cast-in-place process.

[0021] For example, in the cast-in process, molten metal is poured into a mold through a mold gate. In this case, the temperature of the steering hanger beam 2 near the gate tends to be higher or remain higher than that of other parts. This makes the shape of the steering hanger beam 2 more likely to change. As a result, as shown in FIG. 5 , for example, deformation may occur in the area P2 near the gate, causing the inner diameter of the steering hanger beam 2 to become slightly smaller than that of other parts. The fastening area P1 shown in FIG. 5 is set based on the previously determined position so as not to reduce the strength of the steering hanger beam 2, which is deformed as described above. The cast-in hole 5 in the steering column mounting portion 3 is set so that the fastening member 4 can be fastened to the corresponding position. This configuration allows the fastening member 4 to be fastened while preventing a reduction in the strength of the steering hanger beam 2.

[0022] The fastening member 4 penetrates the steering column mounting portion 3 from the outside and also penetrates the steering hanger beam 2. The fastening member 4 is composed of a screw or a bolt. The fastening member 4 is fastened using a so-called FDS (Flow Drill Screw), which is achieved by rotating the fastening member 4 at high speed using a machine tool or the like to penetrate the steering column mounting portion 3 and the steering hanger beam 2. That is, by rotating the fastening member 4 at high speed, frictional heat is generated between the fastening member 4 and the steering hanger beam 2 and the steering column mounting portion 3. The steering hanger beam 2 and the steering column mounting portion 3 are softened by the frictional heat, and the fastening member 4 penetrates them while forming a female thread. Note that, although only one fastening member 4 is fastened to the metal structure in the embodiment of the present invention, multiple fastening members may be fastened depending on the joining strength between the steering hanger beam 2 and the steering column mounting portion 3, etc.

[0023] The metal structure configured as described above is manufactured as follows. First, similar to conventionally known pipe manufacturing methods, the steering hanger beam 2 is formed by processing a steel material, such as by rolling, extruding, casting, or welding. Note that the steering hanger beam 2 may be formed by dividing it into multiple members, as in the structure described in Patent Document 1 cited above.

[0024] The steering column mounting part 3 is joined to the outer peripheral surface of the steering hanger beam 2 formed in this way by a cast-in insert method. The position where the cast-in insert method is performed is the casting position set according to the position of the steering wheel, as described above. That is, with the steering hanger beam 2 fixed, a predetermined mold (not shown) is placed so that the steering column mounting part 3 can be joined to the casting position. That is, the mold has a cavity or depression shaped according to the outer shape of the steering column mounting part 3. Also, a core (not shown) is placed in the mold to form a cast-out hole 5 at a position corresponding to the position where the fastening member 4 will be fastened. A molten, liquid light metal is poured or pressed into the mold through a sprue (not shown). Thereafter, the hardened light metal is integrated with the outer peripheral surface of the steering hanger beam 2 by cooling, thereby forming the steering column mounting part 3.

[0025] The core described above forms a cored hole 5 on the outer peripheral surface of the steering column mounting portion 3 integrated with the steering hanger beam 2. A fastening member 4 is fastened to the cored hole 5 by FDS. That is, the fastening member 4 is aligned with the cored hole 5 and then rotated at high speed by a robot or machine tool while being pressed into the cored hole 5. This generates frictional heat between the fastening member 4 and the steering column mounting portion 3, softening the steering column mounting portion 3 and the steering hanger beam 2. This allows the fastening member 4 to penetrate the steering column mounting portion 3. The cored hole 5 also makes it easier for the fastening member 4 to penetrate the steering column mounting portion 3 and the steering hanger beam 2. The cored hole 5 also reduces the load on the robot or machine tool that corresponds to the pressing load of the fastening member 4 when fastening the fastening member 4.

[0026] The fastening member 4 that has penetrated the steering column mounting portion 3 in this way also penetrates the steering hanger beam 2. That is, the fastening member 4 is pushed into the steering hanger beam 2 from the outer circumferential surface by a robot or machine tool, penetrating the steering hanger beam 2. At this time, female threads are formed in the steering column mounting portion 3 and the steering hanger beam 2 by the fastening member 4, and fastening is completed by tightening the fastening member 4 into the female threads. Note that if the steering hanger beam 2 is formed in sections, the steering column mounting portion 3 is fastened, and then the divided sections are welded together to form the steering hanger beam 2.

[0027] As described above, in the metal structure 1 according to the embodiment of the present invention, the steering column mounting portion 3 made of light metal is integrated with the outer peripheral surface of the steering hanger beam 2 made of steel by a cast-in-place method. Therefore, compared to joining the steering column mounting portion 3 to the steering hanger beam 2 by welding or the like, the integration can be achieved with high joint strength while reducing manufacturing man-hours. Furthermore, in the metal structure, the fastening member 4 is fastened from the outside of the steering column mounting portion 3 integrated with the outer peripheral surface of the steering hanger beam 2, penetrating the steering hanger beam 2 and the steering column mounting portion 3. Therefore, the fastening strength between the steering hanger beam 2 and the steering column mounting portion 3 can be further improved. For example, a load that causes relative movement between the steering column mounting portion 3 and the steering hanger beam 2 may be generated between them. Specifically, a load that causes relative rotation between the steering column mounting portion 3 and the steering hanger beam 2 or a load that causes relative axial movement between the steering column mounting portion 3 and the steering hanger beam 2 may be input. Even in such a case, the fastening member 4 can withstand such a load, and therefore the joining strength between the steering hanger beam 2 and the steering column mounting portion 3 can be further increased.

[0028] Furthermore, the fastening member 4 is fastened by penetrating the steering hanger beam 2 from the outside of the steering column mounting portion 3. For example, if an anchor member is integrally molded with the steering hanger beam 2 and the anchor member is positioned at a predetermined position in a mold to perform a cast-in-place method, the positioning becomes complicated. That is, because the welding accuracy of a typical pipe is lower than the accuracy of a casting mold, the position of the anchor member may be misaligned in the axial direction. In such a case, the anchor member may not be properly attached to the steering column mounting portion 3. Furthermore, since the degree of adhesion and bonding between the steering column mounting portion 3 and the anchor member cannot be confirmed by nondestructive testing, the bonding strength between them may not be guaranteed. In contrast, with the metal structure 1 according to the embodiment of the present invention, high bonding strength can be achieved simply by fastening the fastening member 4 from the outside of the steering column mounting portion 3 after the steering hanger beam 2 and the steering column mounting portion 3 are cast. That is, high bonding strength can be achieved while suppressing increases in the number of processes and costs throughout the entire process of manufacturing the metal structure.

[0029] Although the embodiments of the present invention have been described above, the present invention is not limited to the above examples and may be modified as appropriate within the scope of achieving the object of the present invention. For example, the metal structure 1 in the embodiments of the present invention is not limited to the configuration described above, and may be formed using metal members made of other materials or other fastening members 4. That is, it may be formed by joining metal members made of different materials using a cast-in process and then fastening the fastening members 4 from the outside. Furthermore, it is sufficient that the fastening members 4 are fastened by penetrating the steering column mounting portion 3 and the steering hanger beam 2. Therefore, instead of being limited to joining using FDS, it may be configured so that holes penetrating the steering column mounting portion 3 and the steering hanger beam 2 are formed and the fastening members 4 are fastened to the holes. [Explanation of symbols]

[0030] 1 Metal structure 2 Steering hanger beam 3 Steering column mounting part 4 Fastening members 5 Cast-out holes P1 Fastening part P2 site

Claims

1. A fastening structure for metal members, comprising: a first metal member made of a predetermined metal material; and a second metal member made of a metal material different from the predetermined material, wherein the first metal member is joined to an outer surface of the second metal member, the first metal member is integrated with the second metal member by insert casting the second metal member; The first metal member and the second metal member are fastened together by a fastening member that penetrates from the outer peripheral surface of the first metal member toward the inner peripheral surface and engages the first metal member with the second metal member. A fastening structure for metal members characterized by the above.

2. The fastening structure for metal members according to claim 1, The first metal member is a steering hanger beam for transmitting a steering operation to a wheel in a vehicle, and the second metal member is a steering column mounting portion for transmitting the steering operation to the steering hanger beam in the vehicle. A fastening structure for metal members characterized by the above.

3. A method for manufacturing a fastening structure for metal members, in which a first metal member made of a predetermined metal material is joined to an outer surface of a second metal member made of a metal material different from the predetermined material, The first metal member and the second metal member are integrated by inserting the first metal member into the second metal member, A fastening member is passed through the first metal member from its outer peripheral surface toward its inner peripheral surface at a position set based on a change in the shape of the second metal member that occurs when the first metal member is cast-in to the second metal member, thereby engaging the first metal member with the second metal member, thereby fastening the first metal member and the second metal member. A method for manufacturing a fastening structure for metal members, comprising:

4. A method for manufacturing the fastening structure of metal members according to claim 3, The first metal member and the second metal member are fastened together by FDS joining, in which the first metal member and the second metal member are softened by frictional heat generated by rotating the fastening member while it is pressed against the outer surface of the first metal member, and the fastening member penetrates the first metal member and the second metal member to join them. A method for manufacturing a fastening structure for metal members, comprising:

5. A method for manufacturing a fastening structure for metal members according to claim 4, When the second metal member is cast-in with the first metal member, a cast-out hole is formed at the location where the FDS joining is to be performed. A method for manufacturing a fastening structure for metal members, comprising:

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