JP2020159489A - Stacked-joint structure and automobile frame component - Google Patents

Abstract

To provide a stacked-joint structure capable of suppressing breakage of a plate member starting from a first hole formed in a non-fused joint when a stacked portion formed by stacking a plurality of plate members together is joined by non-fused joining means.SOLUTION: A stacked-joint structure according to one aspect of the present invention includes: a plurality of stacked plate members; and a plurality of joints arranged in a stacked portion of the plurality of stacked members, the joints being formed by mechanical joining means or friction-agitation point joining means. The plurality of joints have first holes through which the mechanical joining means is inserted or first holes formed by the friction-agitation point joining. One or more of the plurality of plate members have second holes between the plurality of joins in the stacked portion.SELECTED DRAWING: Figure 1

Description

The present invention relates to a lap joint structure and an automobile frame component.

In order to achieve both improved collision safety and improved fuel efficiency, the application of high-strength steel sheets to structural members (hereinafter referred to as "structural members for automobiles") that form the skeleton of the monocoque body that constitutes the automobile body has expanded. There is. Currently, high-tensile steel sheets having a tensile strength of 980 MPa class are used for structural members for automobiles, and recently, application of high-tensile steel sheets having a tensile strength of 1180 MPa class or more is also being considered. Further, by using a hot stamping method in which quenching is performed at the same time as press molding, a high-strength structural member for automobiles having a tensile strength of 1500 MPa or more is being manufactured. According to the hot stamping method, since the steel sheet is press-formed at a high temperature and soft, there are few problems related to dimensional accuracy after forming, and the press forming can be performed at a high temperature and high ductility. It has the great advantage of being excellent in sex.

However, in a spot welded joint containing a steel plate having a tensile strength of 780 MPa or more, the toughness of the nugget decreases, and the stress in the peeling direction concentrates the stress on the nugget end, so that the tensile strength of the steel plate increases. However, there is a problem that the cross tensile strength (CTS) does not increase or decreases.

As one of the techniques for solving this problem, there is a technique for mechanically joining a plurality of metal plates by using a mechanical joining means such as a rivet or a screw without melting the base metal. By using this technology, there is a possibility that automobile parts with higher strength and reliability than before can be manufactured.

Further, in an automobile body or the like, a combination of different materials such as a steel plate and an aluminum plate or a steel plate and a carbon fiber reinforced plastic (CFRP) plate may be joined for the purpose of weight reduction or the like. As described above, when the materials to be combined are materials having different physical properties such as melting point and coefficient of linear expansion, they are fastened and joined by mechanical joining means as described in Patent Documents 1 and 2, for example. .. Further, in an aluminum plate having a low electric resistance, friction stir welding may be used instead of resistance spot welding. Hereinafter, the mechanical joining means and the friction stir welding point joining means may be collectively referred to as a non-melt joining means.

In order to provide this non-melt bonding means in the lap bonding structure, it is inevitably necessary to provide holes in the plate member. For example, when the overlapped portions of a plurality of stacked plate members are joined by a mechanical joining means such as a blind rivet at the joint portion, a hole through which the rivet is inserted is formed in the joint portion of the plate members. Further, when the overlapped portions are point-bonded by the friction joining means, a hole due to a press-fitting mark of the probe at the tip of the rotating tool remains at the joint portion of the plate member on the rotating tool side.

In the study of the present inventor, in the lap joining structure in which the lap portions are joined by mechanical joining means or friction joining means, when the whole is subjected to tensile deformation, strain is concentrated in the holes formed in the joint. There was a problem that the plate member was broken due to a small deformation starting from the hole. In the prior arts such as Patent Documents 1 and 2, no study has been made on this problem.

Japanese Unexamined Patent Publication No. 2000-272541 Japanese Unexamined Patent Publication No. 2005-119757

In the present invention, when the overlapped portion formed by superimposing a plurality of plate members is joined by the non-melt joining means, the plate member starts from the hole (first hole) formed in the non-melt joint portion. It is an object of the present invention to provide a lap joint structure capable of increasing the amount of elongation (strain) leading to fracture by suppressing fracture, and an automobile frame component.

The gist of the present invention is as follows.
(1) The lap joining structure according to one aspect of the present invention is composed of a plurality of lapped plate members and a mechanical joining means or a friction stir welding point joining means provided in the lap portion of the plurality of plate members. The plurality of joints include a plurality of joints formed therein, the plurality of joints having a first hole through which the mechanical joining means is inserted, or a first hole formed by friction stir welding. One or more of the plurality of plate members has a second hole between the plurality of joints in the overlapped portion.
(2) In the lap joint structure described in (1) above, the width W of the second hole, the length L of the second hole, and the diameter K of the first hole are the following equations 1 and Equation 2 may be satisfied.
L> 2 × K (Equation 1)
W> K (Equation 2)
(3) In the lap joint structure according to (1) or (2), the shortest distance D between the end of the first hole and the end of the second hole, and the diameter of the first hole. K may satisfy the following equation 3.
D ≧ K (Equation 3)
(4) In the lap joint structure according to any one of (1) to (3) above, the first hole may penetrate one or more of the plurality of plate members.
(5) In the lap joint structure according to any one of (1) to (4) above, the second hole may be provided in the plate member having the first hole.
(6) In the lap joint structure according to any one of (1) to (5) above, the second hole may be provided in the main plate member having the largest product of the plate thickness and the tensile strength. ..
(7) In the lap joint structure according to any one of (1) to (6) above, the plate member has a soft portion that surrounds the joint portion and is separated from the second hole. You may.
(8) In the lap joint structure according to any one of (1) to (7) above, the plate member having the second hole may be a steel plate having a tensile strength of 1200 MPa or more.
(9) The automobile skeleton component according to another aspect of the present invention has the lap joint structure according to any one of (1) to (8) above.
(10) The automobile frame component according to (9) above may be an A-pillar, a B-pillar, a side sill, a bumper, a floor member, a front side member, a rear side member, or a roof rail.

According to the present invention, when the overlapped portion formed by superimposing a plurality of plate members is joined by a non-melt joining means, the plate starts from a hole (first hole) formed in the non-melt joint portion. It is possible to provide a lap joint structure capable of suppressing the member from breaking.

It is a perspective view of the lap joint structure which concerns on this embodiment. It is sectional drawing of the joint part. It is a conceptual diagram of the mechanical joining means formed by the resistance element welding. It is a conceptual diagram of the mechanical joining means formed by the resistance element welding. It is a conceptual diagram of the friction stir point welding means formed by friction stir welding. It is a figure which schematically explains the example of the shape and arrangement of the 2nd hole. It is a schematic diagram which shows the length L of the 2nd hole, the width W of the 2nd hole, and the diameter K of the 1st hole. It is a perspective view of the lap joint structure having a soft part. It is a perspective view which illustrates the variation of the shape and arrangement of the second hole. It is a perspective view which illustrates the variation of the shape and arrangement of the second hole. It is a perspective view which illustrates the variation of the shape and arrangement of the second hole. It is a perspective view which illustrates the variation of the shape and arrangement of the second hole. It is a perspective view which illustrates the variation of the shape and arrangement of the second hole. It is a perspective view which illustrates the variation of the shape and arrangement of the second hole. It is a perspective view of the B pillar which is an automobile skeleton component which concerns on this embodiment. It is XX sectional view of the B pillar of FIG. It is a perspective view of the A pillar and the roof rail which are an example of the automobile frame parts which concerns on this embodiment. It is a XII-XII sectional view of the roof rail of FIG. It is a perspective view of the hinge reinforcement of the B pillar which is an example of the automobile frame component which concerns on this embodiment. It is a top view and a side view of a test piece simulating a conventional lap joint structure. It is a top view and a side view of the test piece which simulated the lap joint structure of this invention. It is a photograph of the test piece of FIG. 14 after the tensile test.

The present inventors have defined a hole (hereinafter referred to as "first hole") formed in the non-melt joint portion when the overlap portion formed by superimposing a plurality of plate members is joined by the non-melt joint means. ) As a starting point, a method for providing a lap joint structure capable of suppressing the breakage of the plate member was repeatedly studied. As a result, it was conceived that it would be better to provide a means for dispersing the strain so that the strain does not concentrate on the end of the first hole formed in the joint. Then, in the overlapping portion of the plate members, by forming a second hole between the adjacent joint portions, the strain due to the tensile load is dispersed, and the overlapping joint structure starting from the first hole is destroyed. It was found that it is suppressed and the amount of elongation (strain) leading to fracture can be increased.

Hereinafter, the lap joint structure 1 and the automobile skeleton component 2 according to the present embodiment will be described with reference to the drawings as appropriate. As an example of the lap joint structure 1, the plate member 11 having the flange 12 is shown in the figure, but the lap joint structure 1 according to the present embodiment does not have to include the flange 12. Further, although the lap joint structure according to the present embodiment will be described with reference to the configuration in which the number of plate members 11 is 2 or 3 in the drawing, the number of plate members 11 may be 4 or more.

As shown in FIG. 1, the lap-join structure 1 according to one aspect of the present invention obtained from the above findings is provided on a plurality of stacked plate members 11 and a stack portion of the plurality of plate members 11. A plurality of joining portions 13 (not shown in FIG. 1) configured by the mechanical joining means 132 or the friction stir welding point joining means 133, and the plurality of joining portions 13 are inserted with the mechanical joining means. It has a hole 131 of 1 or a first hole 131 formed by friction stir welding, and one or more of the plurality of plate members 11 is a second hole between the plurality of joints 13 in the overlapping portion. Has 14. Further, although the overlapping portion is the flange portion 12 in FIG. 1, the flange portion 12 is not essential as described above.

(1) Plate member 11
The material of the plate member 11 is not particularly limited. The plate member 11 is, for example, a resin plate, a CFRP (Carbon Fiber Reinforced Plastic) plate, or a metal plate such as an aluminum plate, an aluminum alloy plate, a stainless plate, a titanium plate, or a steel plate. The plate member 11 may include a coating film and a surface treatment layer such as plating. The lap joint structure according to the present embodiment is formed by stacking a plurality of plate members 11, but the materials of the plurality of plate members 11 may be the same or different. The plate thickness and mechanical strength (tensile strength, hardness, etc.) of the plate member 11 are also not particularly limited. For example, when the plate member 11 is a steel plate, the thickness of the plate member 11 may be, for example, 0.5 to 2.6 mm. When the plate member 11 is a CFRP plate, the thickness of the plate member 11 may be, for example, 0.3 to 4.0 mm. The plate thickness and mechanical strength of the plurality of plate members 11 may be the same or different.

Of the plurality of plate members 11 constituting the lap joint structure, the plate member having the largest product of the plate thickness and the tensile strength has the greatest effect on the mechanical strength of the lap joint structure. In the lap joint structure according to the present embodiment, the plate member 11 having the largest product of the plate thickness and the tensile strength is referred to as a main plate member, and the other plate members 11 are referred to as sub plate members. When the lap joint structure has two or more plate members 11 having the same product of plate thickness and tensile strength, and the product of these plate thickness and tensile strength is the maximum among the plurality of plate members 11. Both of these can be regarded as main plate members.

The most preferable example of the plate member 11 is a high-strength steel plate, specifically, a steel plate having a tensile strength of 1200 MPa or more. By applying the lap joint structure according to the present embodiment to such a steel sheet, a remarkable effect can be obtained. On the other hand, it is not hindered that the steel plate having a tensile strength of 1200 MPa or less is used as the plate member 11. For example, a high-strength steel plate having a tensile strength of 1200 MPa or more and a steel plate having a tensile strength of 270 MPa to 980 MPa may be combined. ..

When the plate member 11 is a steel plate, the steel plate may be a non-plated steel plate whose surface is not plated, and may be alloyed hot-dip galvanizing (GA plating), hot-dip galvanizing (GI plating), or electrozinc plating (EG). ), Zn-Al plating, Zn-Al-Mg plating, Zn-Mg plating or other zinc-based plating may be used as a steel sheet, or a steel sheet coated with chromate, resin or the like may be used, and aluminum may be used. It may be a plated steel sheet. When the plate member 11 is a hot stamping material, the plate member 11 is made of a non-plated steel plate, aluminum plating, an intermetallic compound of iron and aluminum, or a composite layer composed of an iron-zinc solid solution layer and a zinc oxide layer. It may be a coated steel plate or a steel plate coated with a composite layer composed of a solid solution layer of zinc iron-zinc nickel and a zinc oxide layer.

According to the mechanical joining means described later, it is possible to join the plate member 11 which is not suitable for welding. For example, the mechanical joining means can be applied to a lap joining structure 1 in which a plurality of aluminum materials are combined, a lap joining structure 1 in which an aluminum material and a steel material are combined, and the like. Further, the mechanical joining means can be applied to the lap joining structure 1 in which a CFRP material is used instead of the metal plate. The friction stir welding point joining means 133, which will be described later, can also be used to join materials that are not suitable for welding. For example, the friction stir welding point joining means 133 can be applied to a lap joining structure 1 in which a plurality of aluminum materials are combined, a lap joining structure 1 in which an aluminum material and a steel material are combined, and the like. For the above reasons, the material of the plate member 11 is not particularly limited.

(2) Joint portion 13 and first hole 131
A part or all of the plurality of plate members 11 are overlapped with each other, and are joined to each other at the overlapped portion. The joining portion 13 is a non-melt joining means, that is, a mechanical joining means 132, a friction stir point joining means 133, and the like.

The mechanical joining means 132 includes, for example, blind rivets, self-piercing rivets (self-perforated rivets, SPR), hollow rivets, flat rivets, drill screws, bolts, EJOWELD (registered trademark), FDS (registered trademark) and the like. According to these, the plate members 11 are joined by plastic working cold or hot. The plate member 11 may be joined by a combination of these mechanical joining means and energization heating and pressurization. The mechanical joining means 132 includes one that penetrates all the stacked metal plate members 11 such as a blind rivet and one that does not penetrate a part of the stacked metal plate members 11 such as a self-piercing rivet. However, all of them can be used in the superposition structure 1 according to the present embodiment. In the example of the joint portion 13 shown in FIG. 2, the mechanical joining means 132 is composed of rivets.

As the mechanical joining means 132, Resistance Element Welding (REW) may be used. As shown in FIGS. 3A and 3B, the REW includes a plate member 11 (for example, an aluminum alloy plate) in which a first hole 131 penetrating in the plate thickness direction is formed, and another plate member 11 (for example, a boron). (Steel plate such as steel) is overlapped, a mechanical joining means 132 which is a rivet with a steel flange is inserted into the first hole 131, and two plate members 11 are sandwiched by the electrode X. While (see FIG. 3A), by energizing the two plate members 11 at a predetermined current value, the contact portion between the tip portion of the mechanical joining means 132 and the plate member 11 is melted to form the nugget 132'. It is a joining means to be formed (see FIG. 3B). As described above, although REW partially uses the melt joining means, it is essentially a joining means using a mechanical element called a flanged rivet, so such a joining means is also a mechanical joining means. As 132, it can be suitably used in the present invention.

When the plate member 11 is joined by the mechanical joining means 132, it is necessary to provide the plate member 11 with a first hole 131 for inserting the mechanical joining means 132. That is, the joint portion 13 formed by the mechanical joining means 132 has a first hole 131 through which the mechanical joining means 132 is inserted. The first hole 131 through which the mechanical joining means 132 is inserted may or may not penetrate the plate member 11.

The friction stir point joining means 133 is a joint portion 13 formed by friction stir point joining. Here, Friction Stir Spot Welding (FSSW) is, as shown in FIG. 4, press-fitting into the plate member 11 while rotating the rotation tool Y, which is relatively harder than the plate member 11. It is a kind of solid-state bonding in which 11 is bonded without melting. In friction stir welding, the deformation resistance of the plate member 11 is reduced by the frictional heat generated by the rotation of the rotary tool Y, and the plate member 11 around the rotary tool Y is plastically flowed and stirred by the movement of the rotary tool Y. Integrate (see FIG. 4B). The rotary tool Y used in these series of steps usually has a probe with a threaded tip. When the rotary tool is press-fitted into the plate member 11, friction stir welding is performed, and then the rotary tool Y is pulled out from the plate member 11, the plate member 11 into which the rotary tool Y is press-fitted inevitably has a press-fitting mark of the probe. (See FIG. 4 (C)). That is, the joint portion 13 configured by the friction stir welding point joining means 133 has a first hole 131 which is a press-fitting mark of the probe. The lap bonding structure 1 according to the present embodiment is preferably applied when a first hole having a depth of 80% or more of the plate thickness is formed by press-fitting the probe.

It should be noted that the combination of these non-melt bonding means and other bonding means (for example, resin or the like) is not hindered. For example, an adhesive (for example, an epoxy resin-based adhesive) may be interposed on the overlapping surfaces, and the adhesive bonding may be used in combination with the non-melt bonding means. A sealing resin (sealer, electrodeposition coating, etc.) may be interposed on the overlapping surfaces to waterproof or insulate the seams. It is a preferable form of the superposition structure 1 according to the present embodiment that a structural adhesive, an impact-resistant adhesive or the like is interposed on the superposition surface and the bonding by the adhesive is used in combination with the non-melt bonding means. is there. In particular, in the case of a structural member in which an aluminum material and a steel material are combined, it is preferable to use a resin and an adhesive having a sealing function capable of electrically insulating and a non-melt bonding means in combination.

The position of the joint portion 13 is not particularly limited, but by separating the position of the first hole 131 formed in the joint portion 13 from the end portion of the plate member 11, there is a possibility of breaking from the first hole 131 as a starting point. Can be further suppressed. For example, it is preferable that the shortest distance L between the end of the first hole 131 and the end of the plate member 11 and the diameter K of the first hole 131 satisfy the following equations.
L ≧ 0.8K

The pitch of the joints 13 (distance between adjacent joints 13) is also not particularly limited. The pitch may be appropriately set according to the structure to which the lap joint structure 1 is applied and the application site. When the lap joint structure 1 is applied to an automobile part, for example, the pitch of the joint portion 13 may be about 20 mm to 100 mm.

In the lap joint structure 1 according to the present embodiment, the first hole 131 is not limited to a hole (through hole) that penetrates the plate member 11, but is a hole (blind hole) that does not penetrate the plate member 11 and an inner surface. It may be a hole with a step (stepped hole), a hole having a conical inner surface (tapered hole), a hole with a thread on the inner surface (female screw hole), or the like. Further, the first hole 131 may be provided in either the main plate member or the sub plate member.

(3) Second hole 14
As described above, in the lap joining structure 1 in which the lap portion is joined by the mechanical joining means 132 or the friction stir welding point joining means 133, the lap joining structure 1 is formed in the joining portion 13 when the entire lap joining structure 1 is subjected to tensile deformation. When the strain is concentrated in the first hole 131, the plate member 11 starting from the first hole 131 may be broken. Therefore, the present inventors have studied a means for dispersing the strain so that the strain does not concentrate on the end of the first hole 131 formed in the joint portion 13. As a result, in the overlapping portion of the plate member 11, the second hole 14 is formed between the adjacent joint portions 13, so that the strain due to the tensile load is dispersed, and the overlapping portion starts from the first hole 131. It was found that the destruction of the joint structure 1 is suppressed.

Based on the above findings, the lap joint structure 1 according to the present embodiment has a second hole 14 between a plurality of joint portions 13 in the lap portion. The shape of the second hole 14 is not particularly limited, and for example, as shown in FIG. 5, a circle (FIG. 5A), an ellipse (FIG. 5B), a square (FIG. 5C), a rectangle (FIG. 5D), and a rounded rectangle (FIG. 5D). It can be two parallel lines of equal length, and a shape consisting of two semicircles provided at both ends of these parallel lines) (FIG. 5E). In FIGS. 5A to 5E, the center of the second hole 14 and the center of the first hole 131 on both sides thereof are aligned in a straight line, but the center of the second hole 14 is the first on both sides thereof. It may deviate from the line connecting the centers of the holes 131 (FIG. 5F). That is, the region indicated by the term "between the plurality of joints 13 (first holes 131) in the overlapped portion" is the first hole 131 of the overlapped joint structure 1 by arranging the second holes 14. It refers to the entire region where it is possible to alleviate strain concentration and improve elongation.

From the viewpoint of avoiding strain concentration in the first hole 131, it is preferable that the shape of the second hole 14 is a shape composed of only curved lines (for example, a circle, an ellipse, a rounded rectangle, or the like). Further, considering the efficiency of the process of forming the second hole 14, it is preferable that the shape of the second hole 14 is either a circle or a rectangle with rounded corners. Circular holes can be easily formed using a drill, and rounded rectangular holes can be easily formed by moving the end mill linearly. In addition, it can be easily punched by punching with a die or by a laser cutting device. Further, from the viewpoint of further improving the elongation of the lap joint structure 1 when the tensile stress along the flange end is applied to the lap joint structure 1, the shape of the second hole 14 is the shape of the adjacent first. It is preferable to use an elongated hole (for example, a rectangle, an ellipse, or a rounded rectangle) extending along a line connecting the centers of the holes 131. However, even if the stretching direction of the second hole 14 is slightly deviated from the line connecting the centers of the adjacent first holes 131, the above effect can be obtained (FIG. 5F). Hereinafter, in explaining the lap joint structure 1 according to the present embodiment, the second hole 14 is a long hole having a rounded rectangle extending along a line connecting the centers of the adjacent first holes 131. However, the second hole 14 is not limited to this shape.

The second hole 14 needs to be provided in one or more of the plurality of plate members 11 constituting the lap joint structure 1, but which plate member 11 to be arranged can be appropriately selected. .. Preferably, the second hole 14 is provided in the main plate member. As described above, since the main plate member is a member that most affects the mechanical properties of the lap joint structure 1, by providing the second hole 14 in the main plate member, the strain concentration relaxation effect in the first hole 131 can be obtained. It can be maximized. Further, preferably, the second hole 14 is provided in the plate member 11 in which the first hole 131 is present. Hereinafter, the lap joint structure 1 according to the present embodiment will be described with a configuration in which the second hole 14 is provided in the main plate member having the first hole 131. However, the second hole 14 may be provided in the sub-plate member, or may be provided in the plate member 11 that does not have the first hole 131.

The size of the second hole 14 is not particularly limited, and for example, the length L of the second hole 14, the width W of the second hole 14, and the diameter K of the first hole 131 are the following equations 1. And it is preferable to determine the size and shape of the second hole 14 so as to satisfy the formula 2.
L> 2 × K (Equation 1)
W> K (Equation 2)

As shown in FIG. 6, the length L of the second hole 14 is a projection of the second hole 14 on a line connecting the centers of the first holes 131 adjacent to each other with the second hole 14 in between. It is the length of the normal projection of the second hole 14 at the time of. The width W of the second hole 14 is the second hole 14 when the second hole 14 is projected onto a line perpendicular to the line connecting the centers of the first holes 131 adjacent to each other with the second hole 14 in between. This is the length of the normal projection of the hole 14. However, when the second hole 14 has a shape including a region that does not contribute to the improvement of the elongation of the lap joint structure 1, the region is ignored when measuring L and W. For example, in the second hole 14 having a shape like a combination of a rounded rectangle and a slit, if the width of the slit portion is narrow enough not to substantially contribute to the improvement of the elongation of the lap joint structure 1, the first hole 14 When measuring the length L and the width W of the hole 14 of 2, the slit portion thereof is ignored.

The diameter K of the first hole 131 is the diameter of the first hole 131 when the plate member 11 is viewed in a plan view when the first hole 131 is cylindrical. When the first hole 131 has a non-cylindrical shape such as a cone, the diameter of a cylinder having the same volume and depth as the actual volume of the first hole 131 and the actual depth of the first hole 131. Is regarded as the diameter K of the first hole 131. When the diameters of the first holes 131 on both sides of the second hole 14 are different, the larger of the diameters of the first holes 131 on both sides of the second hole 14 is the diameter K of the first hole 131. I reckon. For example, as shown in FIG. 6, whether or not the second hole 14 between the first hole having a diameter K and the first hole 131 having a diameter K'smaller than K satisfies Equation 2. In evaluating, the value of K is substituted into the equation. When the shape of the first hole 131 in a plan view is not a circle, the diameter corresponding to the circle is regarded as the diameter K of the first hole 131. In the case of a female screw hole, the wide portion of the uneven pitch is regarded as the diameter K.

As is clear from the above definition, the evaluation of whether or not each of the plurality of second holes 14 that can be provided in the lap joint structure 1 satisfies the equations 1 and 2 is evaluated by the second hole 14 and its neighbors. This is done based on the relationship with the first hole 131. When the second hole 14 and the first hole 131 are provided in different plate members 11, the second hole 14 is the second when the plate member 11 is viewed in a plan view with the plurality of plate members 11 joined. The above value may be specified based on the positional relationship between the hole 14 and the first hole 131.

Since the second hole 14 satisfying the equation 1 is sufficiently long with respect to the diameter K of the first hole 131, when stress is applied to the lap joint structure 1, the lap joint structure 1 until it breaks. The amount of elongation can be increased. In order to obtain this effect, the longer the length L of the second hole 14, is preferable. For example, the length L of the second hole 14 is three times or more (that is, L ≧ 3 × K), four times or more (that is, L ≧ 4 × K), or five times or more the diameter K of the first hole 131. (That is, L ≧ 5 × K) may be specified. However, if the length L of the second hole 14 is too large, the shortest distance D between the end of the first hole 131 and the end of the second hole 14, which will be described later, will be narrowed. When the length L of the second hole 14 is determined while considering the shortest distance D between the end of the first hole 131 and the end of the second hole 14, the distance between the first holes 131, and the like. Good.

When tensile stress (tensile stress along the line connecting the centers of adjacent first holes 131) is applied to the lap joint structure 1 provided with the second hole 14 satisfying the formula 2, the first hole 131 The second hole 14 is preferentially deformed over the periphery of the. Therefore, the second hole 14 satisfying the equation 2 has a strain concentration relaxation effect on the first hole.

The distance between the second hole 14 and the first hole 131 is not particularly limited, but a larger one is preferable. For example, it is preferable that the shortest distance D between the end of the first hole 131 and the end of the second hole 14 and the diameter K of the first hole 131 satisfy the following equation 3.
D ≧ K (Equation 3)

According to the lap joint structure 1 satisfying the formula 3, the fracture strain (the amount of strain of the lap joint structure 1 until the lap joint structure 1 is broken) can be further improved. This is because when the lap joint structure 1 in which the distance between the second hole 14 and the first hole 131 is secured so as to satisfy the equation 3 is deformed, the first hole 131 is changed to the second hole 14. This is because the growth of cracks toward them is effectively prevented. In order to obtain this effect, the longer the distance between the second hole 14 and the first hole 131, the more preferable. For example, the shortest distance D between the end of the first hole 131 and the end of the second hole 14 is twice or more the diameter K of the first hole 131 (that is, D ≧ 2 × K), and the first It may be three times or more the diameter K of the hole 131 (that is, D ≧ 3 × K), or four times or more the diameter K of the first hole 131 (that is, D ≧ 4 × K). However, if the shortest distance D between the end of the first hole 131 and the end of the second hole 14 is too large, the length L of the second hole 14 described above becomes short. When the shortest distance D between the end of the first hole 131 and the end of the second hole 14 is determined while considering the length L of the second hole 14 and the distance between the first holes 131. Good.

As shown in FIG. 7, even if the plate member 11 of the lap joint structure 1 has a soft portion 15 that surrounds the joint portion 13 (not shown in FIG. 7) and is separated from the second hole 14. Good. By providing the plate member 11 with the soft portion 15 before joining the plurality of plate members 11, the joint portion 13 can be easily formed. For example, when the hot stamp material having a tensile strength of more than 1500 MPa is the plate member 11, the plate member 11 may be too hard to drive the mechanical joining means 132 such as a self-piercing rivet. By providing the soft portion 15 on the plate member 11 in advance, it is possible to facilitate the joining of the plurality of plate members 11. Here, in order to effectively prevent the growth of cracks from the first hole 131 toward the second hole 14, the second hole 14 and the soft portion 15 are separated from each other.

The method for manufacturing the lap joint structure 1 according to the present embodiment, particularly the method for forming the second hole 14 (and the soft portion 15 if necessary) is not particularly limited. The step of forming the second hole 14 and the soft portion 15 may be performed before or after the step of joining the plate members 11. As described above, when the step of forming the soft portion 15 is performed before the step of joining the plate members 11, it is preferable because the joining portion 13 can be easily formed.

A specific example of the lap joint structure 1 according to the present embodiment described above will be described below with reference to FIGS. 8A to 8F. In FIGS. 8A to 8F, the plate member 11 has a bent portion and a flange portion 12, and the plate members 11 are overlapped with each other at the flange portion 12 and joined by a joint portion 13 (not shown in FIGS. A to 8F). These are various lap joint structures 1. In each of the examples, the second hole 14 is provided between the joints 13, but the shape of the second hole 14 can be various.

In FIG. 8A, the second hole 14 has a rectangular shape along a line connecting the centers of the first holes 131 located at both ends thereof, and the centers of the second holes 14 are at both ends thereof. This is an example on a line connecting the centers of the first holes 131 located.

8B and 8F show that the second hole 14 has a rounded rectangular shape along a line connecting the centers of the first holes 131 located at both ends thereof, and the center of the second hole 14 is This is an example on a line connecting the centers of the first holes 131 located at both ends of the hole 131.

In FIG. 8C, the second hole 14 has a rounded rectangular shape along a line connecting the centers of the first holes 131 located at both ends thereof, and the center of the second hole 14 is the center of the second hole 14. This is an example in which the flange ends are closer to the line connecting the centers of the first holes 131 located at both ends. In FIG. 8D, the second hole 14 has a rounded rectangular shape along a line connecting the centers of the first holes 131 located at both ends thereof, and the center of the second hole 14 is the center of the second hole 14. This is an example in which the flange is inside the line connecting the centers of the first holes 131 located at both ends. As in FIGS. 8C and 8D, the second hole 14 goes to the first hole 131 even if the center of the second hole 14 is not on the line connecting the centers of the first holes 131 located at both ends of the second hole 14. It is possible to achieve the effect of alleviating strain concentration and the effect of improving the elongation of the lap joint structure 1.

FIG. 8E is an example in which two second holes 14 are provided between the first holes 131. As described above, a plurality of second holes 14 may be provided between the first holes 131. When a plurality of second holes 14 are provided between the first holes 131 and are arranged along the direction in which the first holes 131 are arranged as shown in FIG. 8E, the length of the second hole 14 is long. The L is defined as the sum of the lengths L of the plurality of second holes 14, and the width W of the second holes 14 is defined as the maximum value among the widths W of the plurality of second holes 14. ..

In the lap joint structure 1 according to the present embodiment, it is not necessary to provide the second hole 14 between all the first holes 131. This is because in the lap joint structure 1, the susceptibility to deformation is not always uniform. For example, the second hole 14 may be provided only in a place where deformation is particularly likely to occur and strain concentration in the first hole 131 is feared, and the second hole 14 may not be provided in other places. That is, the lap joint structure 1 in which the second hole 14 is provided only between a part of the first holes 131 also corresponds to the lap joint structure 1 according to the present embodiment.

The use of the lap joint structure 1 according to the present embodiment is not particularly limited. One of the preferred uses of the lap-bonded structure 1 is an automobile part composed of a plurality of joined steel plates, particularly an automobile skeleton part. Since the automobile skeleton part is composed of a high-strength steel plate containing martensite, the lap joint structure 1 according to the present embodiment can be easily applied, and in this case, it is remarkable that the collision safety of the automobile is enhanced. The effect is obtained. On the other hand, it is possible to apply the lap joining structure 1 according to the present embodiment to any plate member 11 joined by the mechanical joining means 132 and / or the friction stir point joining means 133. For example, even for bridge members joined by rivets or high-strength bolts, aluminum railroad vehicle structures joined by friction stir welding, etc., breakage can be suppressed by applying the lap joint structure 1 according to the present embodiment. Is considered possible. It is also conceivable to apply the lap joint structure 1 according to the present embodiment to home appliances such as fittings, beams, link members, simple warehouses, furniture, refrigerators, televisions, copiers, cooler outdoor units, and fixtures for construction.

Next, an automobile frame component according to another aspect of the present invention will be described. The automobile skeleton part according to the present embodiment is an automobile skeleton part having the lap joint structure 1 according to the present embodiment. The automobile frame parts are, for example, A pillars, B pillars, side sills, bumpers, floor members, front side members, rear side members or roof rails. Hereinafter, an example of the automobile frame parts according to the present embodiment will be described.

FIG. 9 is a perspective view of the B-pillar 2, which is an example of the automobile frame component according to the present embodiment. In this figure, the side panel outer is omitted. The B-pillar 2 of FIG. 9 is provided between the mechanical joint portion 13 having the first hole 131 (not shown) and the adjacent mechanical joint portion 13 (that is, between the first hole 131). It also has a second hole 14. However, the second hole 14 is not provided between some of the mechanical joints 13 (the region surrounded by the dotted line in FIG. 9). This is because the occurrence of distortion at the time of a side collision of the vehicle body differs depending on the part of the B pillar, and it is not always necessary to provide a second hole at the part where the amount of distortion is small, where breakage from the hole is unlikely to occur at the time of collision. For the reason.

FIG. 10 is a cross-sectional view taken along the line XX of the B pillar 2 of FIG. The B-pillar 2 is composed of a B-pillar inner 22 which is a normal steel plate, a B-pillar reinforcement 21 which is a high-strength steel plate, and a side panel outer 23 which is aluminum or mild steel. These correspond to the plate member 11, and in particular, the B-pillar reinforcement 21 corresponds to the main plate member. The B-pillar reinforcement 21, the B-pillar inner 22, and the side panel outer 23 are joined at both ends thereof, and the B-pillar reinforcement 21 corresponding to the main plate member is provided with a second hole 14.

FIG. 11 is a perspective view of the A pillar 3 and the roof rail 4 which are examples of the automobile frame parts according to the present embodiment. Even in the component shown in FIG. 11, the second hole 14 is provided only between some of the first holes.

FIG. 12 is a sectional view taken along line XII-XII of the roof rail 4 shown in FIG. This automobile frame component is composed of a roof rail inner 42 which is a high-strength steel plate, a roof rail outer reinforcement 41 which is a high-strength steel plate, and a side panel outer 43 which is aluminum or mild steel. These correspond to the plate member 11, and in particular, the roof rail outer ring force 41 corresponds to the main plate member. The roof rail inner 42, the roof rail outer line force 41, and the side panel outer 43 are joined at both ends thereof, and the roof rail outer line force 41 corresponding to the main plate member is provided with a second hole 14.

FIG. 13 is a perspective view of the hinge reinforcement 5 of the B-pillar, which is an example of the automobile frame component according to the present embodiment. In this automobile frame component, the hat-shaped member 52 and the high-strength steel plate 51 arranged along the inside of the hat-shaped member are joined by a joining portion 13 (not shown) which is a mechanical joining means. A second hole 14 is provided between the joint portions 13 of the high-strength steel plate (that is, between the first holes 131). The configuration shown in FIG. 13 can also be used for the floor members.

In the description of the lap joint structure 1 according to the present embodiment, a lap joint structure in which a joint portion is formed in a lap portion obtained by superimposing two or three plate members 11 is exemplified, but four or more plate members 11 May be overlapped. Further, in the description of the lap joint structure 1 according to the present embodiment, when a second hole is formed in one plate member 11 or two plate members 11 out of two or three plate members 11. However, for example, a joint portion may be formed in an overlapped portion in which four or more (plurality) plate members 11 are overlapped to form a lap joint structure. In such a case, a second hole is formed. The number of plate members 11 formed can be arbitrarily set. Further, it is not necessary to use the overlapped portion formed by superimposing the plate members 11 as the flange portion. Needless to say, the lap joining structure according to the present embodiment also includes a lap joining structure in which plate members 11 having no flange are overlapped and joined for the purpose of partial reinforcement or the like.

Sample No. 14 in which the plate member A and the plate member B not provided with the second hole are joined as shown in FIG. 1 and No. Sample No. 8 and the plate member A having a second hole and the plate member B not having a second hole, as shown in FIG. 15, are joined. 2-No. 7 and No. 9 to No. 11 was created. The second hole was machined by laser cutting. Here, FIGS. 14 (A) and 15 (A) are plan views of the sample (rivet-bonded), and FIGS. 14 (B) and 15 (B) are side views of the sample (rivet-bonded). Is. In addition, in FIGS. 14 and 15, the plate member A is a plate having a length of 200 mm (scoring interval 50 mm) having a parallel portion having a width of 20 mm and holding portions (shoulders) having a width of 35 mm provided at both ends of the parallel portion. Is. In FIGS. 14 and 15, the plate member B is a plate having a width of 20 mm and a length of 60 mm, which is overlapped with parallel portions of the plate member A. The type, plate thickness, and hardness of the plate member A were the same for all the samples, and the contents were as shown in Table 1. The type, plate thickness, and hardness of the plate member B were two types, B1 and B2 shown in Table 1. The metal structure of the plate member A was almost all martensite.

The joining means of the plate member A and the plate member B was any one of rivets, SRP (self-piercing rivets), and friction stir welding. Among the samples in which the joining means was SRP, No. In No. 6, a soft portion was formed in the SRP portion of the plate member A. The width W3 of the soft portion was 10 mm, and the hardness of the soft portion was HV270. The diameter K of the first hole of the plate members A and B and the shape of the second hole are as shown in Table 2.

Then, the sample No. of Table 2 Tensile tests were performed on 1 to 11 and the breaking strain was measured. The measurement results are shown in Table 2.

As shown in Table 2, the sample No. of the lap joint structure composed of a plate member having no second hole. 1 and No. Compared with No. 8, the sample No. of the lap joint structure including the plate member A having the second hole. 2-No. 7 and No. 9 to No. No. 11 had excellent breaking strain.

When each sample after the tensile test was confirmed in detail, the test piece having no second hole was broken starting from the first hole as shown as a broken portion Z in FIG. For reference, No. 1 provided with a mechanical joint but not a second hole. The photograph after the test of No. 1 is shown in FIG. On the other hand, the test piece provided with the second hole was broken at the second hole as shown in FIG. 15 as the fractured portion Z.

According to the present invention, when the overlapped portion formed by superimposing a plurality of plate members is joined by a non-melt joining means, the plate starts from a hole (first hole) formed in the non-melt joint portion. It is possible to provide a lap joint structure capable of suppressing the member from breaking. For example, when the present invention is applied to an automobile, the occupant protection performance at the time of a collision can be dramatically improved. Therefore, the present invention has high industrial applicability.

1 Lap joint structure 11 Plate member 12 Flange part 13 Joint part 131 First hole 132 Mechanical joining means 132'Nugget 133 Friction stirring point joining means 14 Second hole 15 Soft part 2 B pillar 21 B pillar Reinforce 22 B Pillar Inner 23 Side Panel Outer 3 A Pillar 4 Roof Rail 41 Roof Rail Outer Linforce 42 Roof Rail Inner 43 Side Panel Outer 5 Hinge Reinforce 51 High Strength Steel Plate 52 Hat-shaped Member X Electrode Y Rotating Tool Z Breaking Part

Claims (10)

With multiple superposed plate members,
A plurality of joints formed by mechanical joining means or friction stir welding point joining means provided in the overlapping portions of the plurality of plate members, and
With
The plurality of joints have a first hole through which the mechanical joining means is inserted, or a first hole formed by friction stir welding.
A lap joint structure, characterized in that one or more of the plurality of plate members has a second hole between the plurality of joint portions in the lap portion. The first aspect of claim 1, wherein the width W of the second hole, the length L of the second hole, and the diameter K of the first hole satisfy the following formulas 1 and 2. Laminated joint structure.
L> 2 × K (Equation 1)
W> K (Equation 2) Claim 1 or 2 characterized in that the shortest distance D between the end of the first hole and the end of the second hole and the diameter K of the first hole satisfy the following equation 3. The lap joint structure described in.
D ≧ K (Equation 3) The lap joint structure according to any one of claims 1 to 3, wherein the first hole penetrates one or more of the plurality of plate members. The lap joint structure according to any one of claims 1 to 4, wherein the second hole is provided in the plate member having the first hole. The lap joint structure according to any one of claims 1 to 5, wherein the second hole is provided in a main plate member having the largest product of plate thickness and tensile strength. The lap joint structure according to any one of claims 1 to 6, wherein the plate member has a soft portion that surrounds the joint portion and is separated from the second hole. The lap joint structure according to any one of claims 1 to 7, wherein the plate member having the second hole is a steel plate having a tensile strength of 1200 MPa or more. An automobile skeleton component having the lap joint structure according to any one of claims 1 to 8. The automobile frame component according to claim 9, wherein the A-pillar, the B-pillar, the side sill, the bumper, the floor member, the front side member, the rear side member, or the roof rail.