Manufacturing method of bonded products

Abstract

We manufacture joined products that suppress the occurrence of unjoined parts and increase joint strength. [Solution] A first chamfered portion 13 is formed over the entire entrance portion of the hole portion 11 of the first member 10, and the corner at the tip of the press-fit portion 21 of the second member 20 is left at 90 degrees or a second chamfered portion of 0.35 mm or less is formed, and an overlapping portion R is formed where the inner surface of the hole portion 11 of the first member 10 and the outer surface of the press-fit portion 21 of the second member 20 overlap in the radial direction from the center of the hole portion, and a pressure force is applied to fit the press-fit portion 21 into the hole portion 11, and by passing electricity between the first member and the second member, the press-fit portion 21 is pressed into the hole portion 11 to obtain the joined product.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a joint product of a plate member having a hole and a press-fit member having a press-fit portion. [Background technology]

[0002] Known methods for joining and connecting metallic members to each other include fusion welding such as welding, brazing and soldering such as brazing and soldering, as well as solid state welding and solid state bonding. This solid-state bonding method includes pressure welding as well as diffusion bonding. Solid-state bonding is a technology that uses heat and pressure to promote the movement of atoms at the bonding interface, joining the materials together. By joining the materials in a solid state without melting them, it has the advantage of achieving a bond strength comparable to that of the base materials and with minimal deformation.

[0003] The present applicant has proposed a form of solid-state bonding method using diffusion bonding in Patent Document 1 and the like, and has confirmed the advantages of the solid-state bonding method by utilizing it in the manufacture of various bonded products.

[0004] In Patent Document 1, when joining a plate member having a hole formed therein to a shaft having a press-fit portion that is pressed into the hole, a tapered surface is formed on the outer periphery of the tip of the press-fit portion, and when the press-fit portion is inserted into the hole, the tapered surface of the press-fit portion comes into contact with the entrance (corner) of the hole, and then the press-fit portion is guided into the hole so that the center of the press-fit portion coincides with the center of the hole. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3270758 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-17048 Summary of the Invention [Problem to be solved by the invention]

[0006] However, subsequent research has revealed that although forming a tapered surface on the outer periphery of the tip of the press-fit portion is suitable for guiding the press-fit portion into the hole, it is difficult to reliably join the entire outer surface of the press-fit portion and the entire inner surface of the hole, as will be explained later. If unbonded portions remain, the advantage of the high bonding strength inherent to the solid-state bonding method is lost. For example, in the case of a joined product in which a shaft is press-fitted into a hole in a plate member and torque from the shaft is transmitted to the plate member, insufficient joint strength poses a major problem.

[0007] The invention described in Patent Document 2 relates to mash seam welding (lap seam welding), in which plate materials are overlapped and a roller electrode is moved along the overlap while applying pressure and current, and is a resistance welding method, which differs from the joining method of the present invention, in which press-fit portions are pressed into holes by aligning their respective cores. Also, the joining of steel and aluminum is common, and joining of steel materials together is not envisioned.

[0008] Furthermore, Patent Document 2 also describes forming a tapered surface on the outer periphery of the fitting portion of one of the plates to be fitted, and guiding the fitting portion into the hole portion, similar to Patent Document 1. However, Patent Document 2 mentions the possibility that an unjoined portion may remain between the hole portion and the fitting portion, suggesting that press-fitting is sufficient. As these prior art techniques show, it has been extremely difficult to prevent the occurrence of unbonded portions as much as possible.

[0009] Therefore, a main object of the present invention is to provide a method for manufacturing a bonded product in which the occurrence of unbonded portions is suppressed and the bonding strength is increased. [Means for solving the problem]

[0010] A first aspect of the means for solving the above problems is as follows. A method for manufacturing a joined product in which a first member having a hole portion formed therein and a second member having a press-fit portion to be press-fitted into the hole portion are joined, the method comprising: a first chamfered portion is formed over the entire inlet portion of the hole of the first member; The corner of the tip of the tubular or solid press-fit portion of the second member is left at 90 degrees or a second chamfer having a length of 0.35 mm or less is formed, an overlapping portion is formed between the inner surface of the hole portion of the first member and the outer surface of the press-fit portion of the second member in a radial direction from the center of the hole portion, The lap width is 0.55 mm or less, the first member is connected to a first electrode, the second member is connected to a second electrode, and the press-fit portion of the second member is aligned with the hole portion of the first member, a pressure force is applied to fit the press-fit portion into the hole portion, and an electric current is passed between the first member and the second member to press the press-fit portion into the hole portion, thereby obtaining the joined product. [Effects of the Invention]

[0011] According to the present invention, it is possible to manufacture a bonded product in which the occurrence of unbonded portions is suppressed and the bonding strength is increased. [Brief explanation of the drawings]

[0012] [Figure 1] 1A to 1C are cross-sectional views illustrating a method for manufacturing a press-fit bonded product according to an embodiment of the present invention. [Figure 2] FIG. 10 is a cross-sectional view of an example of a press-fitted bonded product. [Figure 3] FIG. 10 is a cross-sectional view of another example of a press-fitted bonded product. [Figure 4] FIG. 10 is a cross-sectional view of another example of a press-fitted bonded product. [Figure 5] 1A to 1C are cross-sectional views illustrating a manufacturing method of the present invention. [Figure 6] 1A to 1C are cross-sectional views illustrating a manufacturing method according to a different embodiment of the present invention. [Figure 7A] FIG. 10 is a cross-sectional view illustrating a current flow pattern. [Figure 7B] Cross-sectional view of the final stage of junction. [Figure 8] FIG. 10 is a cross-sectional view of a conventional example. [Figure 9] 1 is an enlarged photograph (50x) of a longitudinal section of a bonded product obtained by a conventional method. [Figure 10] 1 is an enlarged photograph of a longitudinal section of a bonded article obtained in accordance with the first embodiment. [Figure 11] 10 is an enlarged photograph of a longitudinal section of a bonded article obtained in accordance with the second embodiment. [Figure 12] 1 is an enlarged photograph of a longitudinal section of a bonded article obtained in Comparative Example 1. [Figure 13] 10 is an enlarged photograph of another vertical cross section of the bonded article obtained in Comparative Example 1. [Figure 14] 10 is an enlarged photograph of a longitudinal section of a bonded article obtained in Comparative Example 2. [Figure 15] FIG. 1 is a diagram illustrating an outline of a test example. [Figure 16] FIG. 10 is a cross-sectional view of an example of a second member having a rod-shaped press-fit portion. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. The contents of the present invention should be interpreted based on the claims and should not be interpreted as being limited to the embodiments.

[0014] As shown in FIG. 1, the present invention relates to a method for manufacturing a joined product X, which is formed by joining a first member 10 having a hole 11 formed therein and a second member 20 having, for example, a tubular press-fit portion 21 that is press-fitted into the hole 11.

[0015] Here, the first member 10 is typically a plate-shaped member, but is not limited to any particular outer shape other than one having a step portion 12 on its outer shape as shown in FIG.

[0016] Similarly, as long as the press-fit portion 21 serving as the joint is tubular or solid rod-shaped, the second member 20 is not limited to any particular outer shape other than one having a step 22 on the outside as shown in Fig. 3. Furthermore, the shape of the inner space 24 that forms the joint by press-fitting with the first member 10 is not limited to any particular shape, and may have, for example, a step 24a. An example of the second member 20 having a solid rod-shaped press-fit portion 21A is shown in FIG.

[0017] 2, a first member 10 having a hole 11 formed therein and a second member 20 having a press-fit portion 21 that is press-fitted into the hole 11 are joined together to produce a joined product X. This joined product X is subjected to torque, for example, around the axis of the second member 20, and the torque is transmitted to the first member 10.

[0018] In this embodiment, when joining the first member 10 and the second member 20, a first chamfered portion 13 is formed in advance over the entire entrance portion of the hole 11 in the first member 10, as shown in, for example, Figures 5 and 6.

[0019] On the other hand, as shown in FIG. 5, corner 25A at the tip of press-fit portion 21 of second member 20 is left at 90 degrees, or as shown in FIG. 6, second chamfered portion 25B of 0.35 mm or less is formed. The length of this second chamfered portion 25B means that the length wL in the horizontal direction W is 0.35 mm or less, and the length hL in the vertical direction H is 0.35 mm or less. Generally, the chamfered portion 25B has a chamfer angle of 45 degrees and is an inclined surface. is.

[0020] Furthermore, an overlapping area R is formed between the inner surface of the hole 11 of the first member 10 and the outer surface of the press-fit portion 21 of the second member 20 in the radial direction, with the center of the hole as the radial center, and this overlapping area R is set to 0.55 mm or less. The overlapping area R shown in FIG. 5 has an overlapping area of ​​2R in the entire horizontal direction (entire diameter direction).

[0021] Prior to the start of the press-fitting, as shown in FIG. 7A, the first member 10 is connected to the first electrode 40, and the second member 20 is connected to the second electrode 50. With the press-fit portion 21 of the second member 20 aligned with the hole 11 of the first member 10, a pressure is applied to fit the press-fit portion 21 into the hole 11, and electricity is passed through the first electrode 40 and the second electrode 50 to establish electrical continuity between the first member 10 and the second member 20. As shown in FIG. 7B, the press-fit portion 21 is press-fit into the hole 11, thereby obtaining a joined product X, for example, as shown in FIG. 2.

[0022] Next, various test examples that led to the completion of the present invention will be described. <Conventional example> A test example of a conventional example is shown in Figure 8. The inner surface of hole 11 in plate-like first member 10 is straight, including the entrance portion. Therefore, the portion that intersects with the top surface of first member 10 is a corner 11a of hole 11 after machining. A second member 20 having an annular press-fit portion 21 is press-fitted into hole 11 of this first member 10.

[0023] The plate thickness of the first member 10 is 4 mm. The material of the first member 10 is a workable rolled high-tensile steel plate (SPF590) for automobiles. The second member 20 has a cylindrical shape with an outer diameter of 33.2 mm, an inner diameter of 25.5 mm, and a length of 36.5 mm, and is made of carbon steel for mechanical structures (JIS G 4051 "S35C", ISO C 35) that has been heat-treated (Rockwell hardness HRC25).

[0024] The "lap allowance R" indicated by the symbol "R" in Figure 6 or Figure 8, which indicates the position of the outer peripheral surface of the second member 20 when pressed into the hole portion 11 of the first member 10, is the length of overlap in the radial direction with the center of the hole portion 11 as the radial center, and therefore, when the diameter of the second member 20 is used as a reference, it is defined as [diameter of the outer peripheral surface of the second member 20 - diameter of the inner peripheral surface of the hole portion 11] / 2.

[0025] As shown in Fig. 8, in the conventional example, the press-fit was performed with an overlap R of 0.15 mm (0.30 mm / 2). In addition, a second chamfered portion 25Z of C = 0.50 mm was formed at a 45-degree angle on the corner of the tip of the press-fit portion 21 of the second member 20. That is, with reference to the dimension symbols shown in Fig. 6, the second chamfered portion 25Z is an inclined surface with wL 0.50 mm in the horizontal direction (left-right direction in the drawing) and 0.50 mm in the vertical direction (up-down direction in the drawing). Furthermore, a chamfered portion 40Z was formed at the corner of the inlet of the lower electrode 40 at an angle of 45 degrees, with a horizontal chamfer of 0.50 mm and a vertical chamfer of 0.50 mm.

[0026] 7A, the press-fit portion 21q of the second member 20 was press-fitted into the hole 11 of the first member 10 on the lower electrode 40 to bond them together. At this time, electricity was passed between the lower electrode 40 and the upper electrode 30 on the second member 20. The pressing force (pressure) was 24 KN, the current value was 54 KA, and the current application time was 40 cycles.

[0027] The bonded product was cut longitudinally in the front-to-back (0-360 degrees) and left-to-right (90-270 degrees) positions in a plan view, and an enlarged photograph (50x magnification, same below) of the cross section shown in Figure 9 was taken. Focusing on the bottom S1 in this enlarged photograph, it was found that an unjoined portion with a length of about 0.8 mm had been generated. This unjoined portion had a length in the thickness direction that could not be overlooked in comparison with the first member 10 having a plate thickness of 4 mm. Furthermore, when attention is paid to the inlet portion S2, since the second member 20 is hard and difficult to deform compared to the soft first member 10, the excess material portion of the second member 20 is deformed into a "V-shape."

[0028] Considering the factors that led to this result, it was inferred that the lap allowance R was small at 0.15 mm at the position where contact begins when the second member 20 is pressed into the hole 11 of the first member 10, and that the central portion of the second chamfered portion 25Z is larger than the corner 11a of the hole 11 of the first member, making this central portion less susceptible to plastic deformation even when pressed into place. That is, during press-fit joining, the vicinity of the inner peripheral surface of the hole portion 11 of the soft first member 10 is deformed by a horizontal component force associated with the press-fit of the outer peripheral portion of the press-fit portion 21 of the hard second member 20, and the outer peripheral portion of the press-fit portion 21 of the second member is joined to the inner peripheral surface of the hole portion 11 of the first member in a manner that it bites into (crushes) it, so to speak. At the start of the press-fitting, the second chamfered portion 25Z first comes into contact with the entrance corner 11a of the hole portion 11, and the portion of the second chamfered portion 25Z closer to the center than the corner 11a of the hole portion 11 of the first member tends to be less likely to deform even with subsequent press-fitting. As a result, it is presumed that the excess material portion of the second member 20 was deformed into a "V" shape. It is also assumed that the unbonded portion occurred because the outer periphery of the press-fit portion 21 of the second member did not exert enough force to bite (crush) into the inner periphery of the hole portion 11 of the first member.

[0029] [Embodiment 1] In the example of the first embodiment, the first member 10 and the second member 20 are the same as those in the conventional example (the same applies to the following examples). That is, the plate thickness of the first member 10 is 4 mm, and the material of the first member 10 is a workable rolled high-tensile steel plate (SPF590) for automobiles. The second member 20 has a cylindrical shape with an outer diameter of 33.2 mm, an inner diameter of 25.5 mm, and a length of 36.5 mm, and is made of carbon steel for mechanical structures (JIS G 4051 "S35C", ISO C 35) that has been heat-treated (Rockwell hardness HRC25). On the other hand, as shown in Fig. 6, a second chamfered portion 25B is formed with a light chamfering (C = 0.10 mm). That is, the length wL of the second chamfered portion 25B in the horizontal direction W is 0.10 mm, and the length hL in the vertical direction H is 0.10 mm. The lap width R was set to 0.15 mm (the lap width in the entire horizontal direction (entire diameter direction) was 2R=0.30 mm).

[0030] Furthermore, a first chamfered portion 13 is formed over the entire inlet portion of the hole 11 of the first member 10 (that is, the entire circumferential direction of the inlet portion, continuing from the hole 11). As shown in FIG. 5, it is preferable that the inclination angle θ of the first chamfered portion 13 relative to the surface of the first member 10 is 10 to 70 degrees, and the surface length (length in the horizontal direction W) wL is 0.25 mm or more and 0.75 mm or less. In the first embodiment, however, C=0.50 mm, i.e., the inclination angle θ is 45 degrees, the length wL in the horizontal direction W is 0.50 mm, and the length hL in the up-down direction H is 0.50 mm. In the explanation, the "inclination angle with respect to the surface of the first member" is defined, but please note that this "inclination angle with respect to the surface of the first member" is the same as the inclination angle θ with respect to the horizontal direction W (see Figure 7A) plane parallel to the "surface of the first member" that passes through the intersection of the first chamfered portion 13 and the hole portion 11 shown in Figure 5.

[0031] Under these conditions, the press-fit was carried out under the same conditions as in the conventional example. An enlarged photograph of the joined product is shown in Figure 10. Looking at other enlarged photographs of vertical sections taken in the front-to-back (0-360 degrees) and left-to-right (90-270 degrees) positions, it was also possible to confirm that the first and second parts were completely joined. Furthermore, each of the longitudinally joined pieces was immersed in acid and inspected for crack-like corrosion due to tensile residual stress, but no corrosion was observed in any of them.

[0032] [Embodiment 2] The second embodiment is the same as the first embodiment except that the inclination angle θ is set to 30 degrees and the length hL in the up-down direction H is set to 0.50 mm.

[0033] Under these conditions, press-fitting was performed under the same conditions as in the conventional example and the first embodiment. An enlarged photograph of the joined product is shown in Figure 11. Looking at other enlarged photographs of vertical sections taken in the front-to-back (0-360 degrees) and left-to-right (90-270 degrees) positions, it was also possible to confirm that the first and second members were completely joined. Furthermore, each of the longitudinally joined pieces was immersed in acid and inspected for crack-like corrosion due to tensile residual stress, but no corrosion was observed in any of them.

[0034] [Comparative Example 1] In Comparative Example 1, the lap allowance R is 0.15 mm, as in the conventional example, and the corner at the tip of the press-fit portion 21 of the second member 20 has an inclination angle of 45 degrees, C = 0.15 mm, and a second chamfered portion 25Z is formed with wL 0.15 mm in the horizontal direction (left and right direction in the drawing) and 0.15 mm in the vertical direction (up and down direction in the drawing).

[0035] Under these conditions, the press-fitting was carried out under the same conditions as in the conventional example, embodiment 1, and embodiment 2. An enlarged photograph of the joined product in the "front" position is shown in Fig. 12. Looking at other enlarged photographs of vertical sections cut vertically at positions to the left and right (90 degrees - 270 degrees), it was also possible to confirm that the first member and the second member were completely joined. In contrast, an enlarged photograph of the "rear" position is shown in Figure 13. An unbonded area was observed at the tip of the second component. This result was inferred to be due to the fact that in Comparative Example 1, although the second member 20 could be guided and pressed into the hole 11 of the first member 10, the lap distance R was small at 0.15 mm and the second chamfered portion 25Z was C=0.15 mm, so the central portion was extremely large compared to the corner 11a of the hole 11 of the first member, and this central portion was difficult to plastically deform even with the press-in force. The unbonded portion was generated in the "rear" position, which can be considered to be the result of the second component not being properly guided into the hole of the first component, causing the first component to shift "rear" when pressed in.

[0036] <Comparative Example 2> The conditions for the conventional example, where the lapping allowance R was 0.15 mm, were the same as those for the conventional example, except that the lapping allowance R was changed to 0.25 mm. An enlarged photograph of the welded part in the "front" position is shown in Figure 14. An unwelded area was observed at the tip of the second component. Additionally, enlarged photographs (not shown) in the "front," "left," and "right" positions all showed inclusions at the tip of the second component. Considering this in relation to conventional examples, it was found that if the second chamfered portion of the second member is large, changing the contact position with the first member at the start of press-fitting will not result in complete joining.

[0037] The outline of the above test format is summarized in Figure 15. Based on these test results, it was found that the following conditions are desirable. A first chamfered portion 13 is formed over the entire entrance portion of the hole 11 of the first member 10. By forming a chamfered portion 13 on the first member 10, plastic deformation of the first member 10 and the second member 20 can be promoted from the initial stage when the second member 20 begins to press-fit, thereby preventing or suppressing the occurrence of unjoined portions and obtaining a joined product with increased joint strength.

[0038] In this case, it is desirable that the inclination angle θ of the first chamfered portion 13 relative to the surface of the first member 10 is 10 to 70 degrees, and particularly 20 to 55 degrees. If the inclination angle θ is too small, it is difficult to accurately guide the second member into the hole of the first member and align them coaxially, which may result in an unbonded portion occurring in part of the circumferential direction.If the inclination angle θ is too large, the position at which the press-fitting of the second member 20 begins tends to move from the surface of the first member 10 in the depth direction of the hole, making it difficult to promote plastic deformation of the first member 10 and the second member 20 over the entire area from the surface to the back side of the first member 10, and making it difficult to prevent or suppress the occurrence of an unbonded portion.

[0039] The surface length of the first chamfered portion 13, that is, the horizontal length wL parallel to the surface of the first member 10, is preferably 0.25 mm to 0.75 mm, and more preferably 0.35 mm to 0.60 mm. The length wL of the surface of the first chamfered portion 13 is also related to the lap allowance R, and if the length wL is excessively short, the amount of plastic deformation of the first member 10 and the second member 20 will be reduced, making it difficult to prevent or suppress the occurrence of unjoined portions. If the length wL is excessively long, it is necessary to increase the plastic deformation of the first member 10 and the second member 20, which imposes an excessive burden, and from this point of view, there is a possibility that an unjoined portion will occur.

[0040] On the other hand, it is preferable to leave the corner of the tip of the press-fit portion 21 of the second member 20 at 90 degrees, that is, to leave the second member 20 as is after cutting, or to form a second chamfered portion 25B of 0.35 mm or less. The second chamfered portion 25B may be a so-called "light-chamfered" surface with an inclined surface at an angle of 45 degrees. The dimensions of wL and hL shown in FIG. 6 are preferably 0.35 mm or less, and particularly preferably 0.25 mm or less. The reason why the corner at the tip of the press-fit portion 21 of the second member 20 is left at 90 degrees or is made into the second chamfered portion 25B of 0.35 mm or less is to allow the second member 20 to undergo plastic deformation from the initial stage of press-fitting. In contrast, in the conventional example shown in Figure 8, due to the second chamfered portion 25Z, plastic deformation at the entrance portion of the hole 11 of the first member 10 becomes dominant in the early stages of press-fitting, which may result in insufficient plastic deformation of the second member, leading to the occurrence of unjoined portions.

[0041] An overlapping area R is formed where the inner surface of the hole portion 11 of the first member 10 and the outer surface of the press-fit portion 21 of the second member 20 overlap in the radial direction with the center of the hole portion 11 as the radial center, and this overlapping area R is 0.55 mm or less. The lower limit of the lap allowance R is preferably 0.09 mm. Therefore, the lapping allowance R is preferably 0.09 to 0.55 mm, more preferably 0.13 mm to 0.50 mm, and particularly preferably 0.15 mm to 0.45 mm. If the overlap distance R is too short, the amount of plastic deformation of the first member 10 and the second member 20 will be small, making it difficult to prevent or suppress the occurrence of unjoined areas; if it is too long, the plastic deformation of the first member 10 and the second member 20 will need to be increased, which will impose an excessive burden and may lead to the occurrence of unjoined areas from this perspective.

[0042] The materials for the first and second members according to the present invention can be selected from appropriate metal materials, such as aluminum or aluminum alloy, copper, gold, silver, nickel (Ni), carbon steel, alloy steel, and stainless steel. The above-mentioned conventional example, embodiment example, and comparative example are examples of joined products of steel materials. Therefore, even if other metal materials that can be easily plastically deformed are used, it is clear that a joined product can be obtained with stable suppression of unjoined portions and increased joining strength. In addition, joined products made of carbon steel (S35C, etc.), steel (HRC18-50, etc.), and high-strength steel (SPF590, SPF980, etc.) are particularly valuable in industry. Regarding hardness, the second member may have a higher hardness than the first member.

[0043] As the first member 10, driving parts such as gear materials, levers, sprocket materials, plate-shaped materials, and disk-shaped materials, metallic element parts, and the like can be applied. The thickness of the first member (at least the plate thickness around the hole) is preferably 1.5 mm to 13 mm, and particularly 2.5 mm to 5.5 mm. Furthermore, to ensure sufficient joint strength, the thickness is preferably 3.7 mm to 5.5 mm. If the plate thickness is small, it is difficult to obtain sufficient joint strength.

[0044] The hole 11 of the first member 10 has a circular shape in a plan view, and the diameter of the hole 11 is constant. The shape of the hole 11 in a plan view may be a perfect circle, or may be other shapes such as an ellipse or a polygon (such as a rectangle), but if the hole 11 is polygonal, stress will be generated at the corners of the hole 11 during joining, and the stress will not be distributed uniformly, so a circular shape is preferable.

[0045] The thickness of the press-fit portion 21 of the second member 20 is preferably 2.0 mm to 12.0 mm, and more preferably 4.0 mm to 8.0 mm. This is a desirable range for ensuring the necessary thickness and achieving plastic deformation. From the viewpoint that a joined product with high joining strength can be obtained according to the present invention, it is desirable that the second member be configured as a part that constitutes a drive system that particularly requires torque. For example, as shown in Figure 3, the second member 20 can have a stepped portion 22 on its outer surface, the outer surface of which is a sprocket, and the sprocket can receive torque from the drive system and apply a rotational force to the first member 10.

[0046] A known press-fit bonding device can be used for bonding. This press-fit bonding device has a control mechanism (not shown) and, for example, as shown in Figures 7A and 7B, has an upper electrode 50 and an upper platen (not shown) that holds it, and a lower electrode 40 and a lower platen (not shown) that holds it, and is also provided with a moving mechanism that positions and moves the upper platen to a predetermined position, a press mechanism that applies pressure to the upper platen, and the like (all mechanisms are also not shown).

[0047] The upper electrode 50 and the lower electrode 40 can be made of chromium copper or beryllium copper as the material of the electrode (electrode body). The upper electrode 50 can be a collet chuck-type electrode that is divided into multiple electrode pieces and each electrode piece grips the second member 20. The lower electrode 40 has a plate shape that ensures a sufficient contact area in consideration of large currents, and current loss between the contact surfaces of the first member 10 and the lower electrode 40 can be reduced. The upper electrode 10 and the lower electrode 12 can be energized via an upper platen and a lower platen, respectively, using a DC inverter type power supply with high heat generation efficiency.

[0048] As described above, prior to the start of the press-fitting, the first member 10 is connected to the first electrode 40, and the second member 20 is connected to the second electrode 50 as shown in FIG. 7A. The press-fit portion 21 of the second member 20 is aligned with the hole portion 11 of the first member 10, and a pressure force is applied to fit the press-fit portion 21 into the hole portion 11. Electricity is then passed through the first electrode 40 and the second electrode 50 to establish electrical continuity between the first member 10 and the second member 20. As shown in FIG. 7B, the press-fit portion 21 is pressed into the hole portion 11, and a joined product such as that shown in FIG. 2 can be obtained.

[0049] Then, when power is supplied in response to an instruction from the control mechanism and primary current flow begins between the upper electrode 50 and the lower electrode 40, a large amount of current flows between the second member 20 and the hole 11 of the first member 10 (joint), generating electrical resistance heat and softening the joint, starting the press-fitting of the second member 20, and the press-fit portion 21 of the second member 20 moves downward into the hole 11 of the first member 10. During this press-fitting, the portion of the first member 10 adjacent to the hole 11 and the portion in contact with the press-fit portion 21 of the second member 20 are ironed and plastically deformed by the downward pressing force of the press-fit portion 21 of the second member 20, forming a joint interface between the press-fit portion 21 of the second member 20 and the first member 10, achieving solid-state diffusion bonding.

[0050] In the manufacturing method using press-fit joining, the press-fit joining is performed by applying pressure and electricity as described above, the joint generates heat in a short time, and the second member 20 is press-fit into the hole 11 in a short time, completing the joining. After heating and press-fitting by the primary current, the current is stopped. The primary current is used for press-fit joining, but internal stress may occur in the joint of this joined product. If necessary, annealing by tempering current is effective in improving the structure of the joint and removing internal stress.

[0051] Furthermore, the joined product produced by the manufacturing method of the present invention can be obtained as element parts and drive system parts for automobiles, motorcycles, industrial machines, etc., and is suitable for the manufacture and production of parts and the like in a form in which members are joined together, such as control lever components of a transmission, gears, sprockets, or engine parts. Furthermore, since only the outer periphery of the press-fit portion of the second member is plastically deformed, it may be rod-shaped as well as tubular. [Explanation of symbols]

[0052] 10 First member 11 Hole 11a Corner 13 First chamfer 20 Second member 21, 21A press-fit part 25A Corner 25B Second chamfer 25Z Second chamfer 40 Lower electrode 50 Upper electrode R Radial overlap

Claims

1. A method for manufacturing a joined product in which a first member having a hole portion formed therein and a second member having a press-fit portion press-fitted into the hole portion are joined together, the method comprising: a first chamfered portion is formed over the entire inlet portion of the hole of the first member; The corner of the tip of the tubular or solid press-fit portion of the second member is left at 90 degrees or a second chamfer of 0.35 mm or less is formed, an inner surface of the hole portion of the first member and an outer surface of the press-fit portion of the second member overlap each other in a radial direction from a center of the hole portion, The lap length is 0.55 mm or less, the first member is connected to a first electrode, the second member is connected to a second electrode, and a press-fit portion of the second member is aligned with a hole portion of the first member, A method for manufacturing a bonded product, characterized in that a pressure force is applied to fit the press-fit portion into the hole portion, and electricity is passed between the first member and the second member to press the press-fit portion into the hole portion, thereby obtaining the bonded product.

2. 2. The method for manufacturing a bonded article according to claim 1, wherein the first chamfered portion has an inclination angle of 10 to 70 degrees with respect to the surface of the first member, and the length of the surface is 0.25 mm or more and 0.75 mm or less.

3. 3. The method for manufacturing a bonded article according to claim 1, wherein the thickness of the first member is 1.5 mm to 13 mm.

4. 3. The method for manufacturing a bonded article according to claim 1, wherein the press-fit portion is tubular and has a wall thickness of 2.0 mm to 12.0 mm.

5. 3. The method for manufacturing a bonded article according to claim 1, wherein the hardness of the second member is greater than the hardness of the first member.

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