Member joining structure

A first member has through holes. A linking member has a first holding portion and a second holding portion that hold an inner circumferential face and outer circumferential face of the first member; and engaging protrusions are formed on the first holding portion and second holding portion. The engaging protrusions are inserted into the through holes, and joined by joining portions formed thereupon. An attaching portion continues to the base edges of the first holding portion and second holding portion via a first supporting portion and a second supporting portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority from Japanese Patent Application No. 2014-068387 filed on Mar. 28, 2014, the entire contents of which are hereby incorporated by reference.

BACKGROUND

1. Technical Field

The present invention relates to a member joining structure, and more particularly relates to a member joining structure where members are joined by a linking material.

2. Related Art

Spot-welding dissimilar materials of different nature, such as an iron-based metal plate and an aluminum alloy plate or resin material or the like, often does not yield a satisfactory bond, due to difference in the electric conductivity, thermal conductivity, melting point, and so forth, of the different materials.

Japanese Unexamined Patent Application Publication No. 2003-236673 attempts to address this issue by a dissimilar material welding method, where an aluminum alloy plate is interposed between two iron-based metal sheets, more specifically two steel sheets, to form a layered article of three layers, and the layered portion is held between a pair of electrodes of a spot welder and welded. This spot welding is performed by applying a strong electric current between upper and lower electrodes holding the layered portion by a predetermined pressure, thereby rapidly melting the aluminum alloy sheet that is the middle layer, and eliminating the molten portion of the aluminum alloy sheet from the spot welding region, thus, directly welding the steel sheets. Thus, the two steel sheets are directly spot-welded, so the bonding strength therebetween is sufficient, and further, the aluminum alloy sheet is strongly bonded to the two steel sheets.

On the other hand, in a case of attaching a member that requires deformation, such as a shock absorbing member that absorbs a shock load through deformation for example, to an automobile body member, the linkage of the shock absorbing member to the automobile body member needs to be maintained in a sure manner while allowing deformation of the shock absorbing member. There are many other structures used in joining other automobile body members as well, where linkage needs to be maintained in a sure manner while allowing deformation of the member when a load is placed thereupon.

There are cases where strongly bonding a member that has to deform restricts the deformation of the member at the bonding portion so that deformation over the entire member is inhibited, and functions according to the deformation of the member are not sufficiently manifested. For example, a shock absorbing member may have its deformability restricted at the bonding portion, such that the shock absorbing functions due to the deformation of the entire shock absorbing member may not be manifested. Moreover, strongly bonding such members may result in load stress being concentrated at the bond portion and surrounding portions when shock is applied, which may even result in rupture and other such damage.

SUMMARY OF THE INVENTION

The present invention has been made in light of the above-described problem, and accordingly it is an object thereof to provide a member joining structure capable of maintaining a joined state in a reliable manner while allowing deforming of members.

An aspect of the present invention provides a member joining structure that joins a first member and a second member by a linking member interposed therebetween. The first member has at least one through hole. The linking member includes: a first holding portion and a second holding portion, which are plate shaped having a side edge and continuing from a base edge to a tip edge, and face one another and hold the first member; an engaging protrusion that is provided on at least either one of the first holding portion and the second holding portion at a position away from the side edges, and is inserted into the at least one through hole and joined to the other holding portion; an attaching portion that is attachable to the second member; a first supporting portion that links the base edge of the first holding portion to the attaching portion; and a second supporting portion that links the base edge of the second holding portion to the attaching portion.

The linking member may includes: the first holding portion and second holding portion, which face each other and upon at least either one of which the engaging protrusion has been formed; the first supporting portion extending to the base edge of the first holding portion; the attaching portion extended to the first supporting portion via a fold portion; and the second supporting portion extending from the base edge of the second holding portion, and linked to the attaching portion via a fold portion.

The linking member may include: the first holding portion and second holding portion, which face each other and upon at least either one of which the engaging protrusion has been formed; the first supporting portion extending to the base edge of the first holding portion; the attaching portion, extending from the first supporting portion in a direction away from the second holding portion, via a fold portion; a pair of side extensions extending from a fold-back portion continuously formed from the attaching portion, that extend following both sides of the attaching portion; and a pair of the second supporting members each extending from the side extensions via fold portions, continuing to the base edge of the second holding portion.

The side extensions may be curved in an extending direction thereof.

The linking member may include: the first holding portion and second holding portion, which face each other and upon at least either one of which the engaging protrusion has been formed; a pair of the first supporting portions, each extending in a stepped form to both edges of the base edge of the first holding portion; a pair of side extensions formed extending in a direction away from the second holding portion, via the first supporting portion and fold portion; the attaching portion, extending from a fold-back portion formed continuously from both side extensions, following both side extensions; and the second supporting portion extended in a stepped form via the attaching portion and fold portion, and continuing to the base edge of the second holding portion.

The linking member may include: the first holding portion and second holding portion, which face each other and upon at least either one of which the engaging protrusion has been formed; a pair of the first supporting portions divided by side slits formed following each side edge of the first holding portion, the pair of the first supporting portions extending following each side edge and protruding beyond the base edge; a pair of side extensions formed extending in a direction away from the second holding portion, via the first supporting portion and fold portion; the attaching portion, extending from a fold-back portion formed continuously from both side extensions, following both side extensions; and the second supporting portion extended from the attaching portion and continuing to the base edge of the second holding portion.

The first holding portion may have a slit formed extending on at least either one of the base edge and the tip edge.

DETAILED DESCRIPTION

An implementation of a member joining structure according to the present invention will be described. The member joining structure according to the present invention can be applied to a member joining portion of a vehicle, for example.FIG. 1is a schematic perspective view of a vehicle, as an example of applicable portions of an implementation of the member joining structure according to the present invention.

A bumper1is disposed extending in the lateral direction of a vehicle at the front thereof. Side sills2extend in the longitudinal direction of the vehicle at the lower part of a passenger compartment, and A pillars3, B pillars4, and C pillars5extend upwards from the front, middle, and rear parts of the side sill2. The upper ends of the A pillars3, B pillars4, and C pillars5tie into left and right side rails6, across which a roof panel7is laid, as illustrated inFIG. 1.

End portions of a roof brace8extending laterally underneath the roof panel7are joined to the left and right side rails6. The joining structure of the roof brace8and the side rails6will be described later.

The bumper1that extends in the lateral direction at the front of the vehicle is configured including a steel bumper beam that is an iron-based metal member extending in the lateral direction of the vehicle, a shock absorbing material such as foamed resin or the like disposed on the front face of the bumper beam, a bumper face1athat covers the shock absorbing material, and so forth. Portions of the bumper beam near to the ends thereof are joined to the front ends of left and right side members, which are body structural members, via shock absorbing members10that is a first member, and the like.

FIG. 2is a schematic disassembled perspective view of a joining portion that joins the bumper1using the shock absorbing member10and a side member9. The shock absorbing member10has a cylindrical shape including an inner circumferential face11and an outer circumferential face12. The shock absorbing member10extends longitudinally, and is formed from carbon fiber reinforced plastic (CFRP) that is both light and strong, for example. Multiple, four in the implementation, through holes13are formed equidistantly following a front edge10athat is one end of the shock absorbing member10. In the same way, four through holes13are formed equidistantly following a rear edge10b. These through holes13have cross-sectional circular shapes, and continue from the inner circumferential face11side to the outer circumferential face12side. For sake of convenience, the region between the through holes13and the front edge10awill be referred to as an end portion14, and a nearby range of the through holes13will be referred to as a through hole perimeter portion15.

An attachment plate17formed of an iron based metal that can be welded, that is, steel. The attachment plate17is joined to the front edge portion of the shock absorbing member10using four linking members20. The rear edge portion of the shock absorbing member10is also joined to an attachment plate17by four linking member20.

The attachment plate17at the front side is fastened by bolts, for example, to the bumper beam of the bumper1, and the attachment plate17at the rear side is fastened by bolts to an attachment flange9aformed at the front end of the side member9. The bumper1is thus attached to and supported by the front end of the side member9via the shock absorbing member10.

The linking members20that link the shock absorbing member10to the attachment plates17will be described with reference toFIGS. 3A through 6B.FIG. 3Ais a perspective view of the linking member20, andFIG. 3Bis an unfolded perspective view of the linking member20.

The linking member20has a first holding portion21and a second holding portion31that can be laid on the outer circumferential face12and inner circumferential face11of the shock absorbing member10in a layered manner, with a gap therebetween corresponding to a thickness t of the shock absorbing member10. The first holding portion21is formed in a rectangular plate shape having a base edge21aand a tip edge21b, and side edges21cand21dextended from both ends of the base edge21ato both ends of the tip edge21b. The second holding portion31similarly is formed in a rectangular plate shape having side edges31cand31dextended from both ends of a base edge31ato both ends of a tip edge31b.

A first supporting portion22, a fold portion23, and an attaching portion24, are formed continuously. The first supporting portion22is formed as a plate having a smaller width Wa that the width W of the first holding portion21, and extending continuously from the width-wise middle portion of the base edge21aof the first holding portion21. The fold portion23has the same width as that of the first supporting portion22, and is bent away from the second holding portion31. The attaching portion24is continuously formed from the first supporting portion22via the fold portion23.

A fold-back portion25is formed continuously from the tip of the attaching portion24. An extension26, which has the same width as the width W of the first holding portion21and the second holding portion31, extends from the attaching portion24via the fold-back portion25.

The extension26has a rectangular opening26athat is somewhat wider than the width Wa of the attaching portion24into which the attaching portion24can be inserted, and side extensions27aand27bare formed on the sides of the opening26a. Fold portions28aand28bare formed at the tips of the side extensions27aand27b. Second support portions29aand29bare formed as flat plate forms continuing to both ends of a base edge31aof the second holding portion31. The first holding portion21, second holding portion31, first supporting portion22, attaching portion24, fold-back portion25, side extensions27aand27b, and second support portions29aand29b, are formed integrally and continuously. The side extensions27aand27band the fold portions23,28a, and28bmaintain their respective shapes under normal conditions, but in a case where a load of a predetermined value or greater is input, the side extensions27aand27bflex, and the fold portion23is deformed by crushing so that the first supporting portion22moves away from the second holding portion31. Also, the fold portions28aand28bare deformed by crushing so that the second support portions29aand29bmove away from the first holding portion21.

A first engaging protrusion30that is cylindrical in shape and has a base face, is formed at the middle portion of the first holding portion21, at a position away from the base edge21a, tip edge21b, and side edges21cand21d. A second engaging protrusion32is formed in the same way at the middle portion of the second holding portion31, at a position away from the base edge31a, tip edge31b, and side edges31cand31d.

The first engaging protrusion30has an outer circumferential face30athat can be fit into a through hole13formed in the shock absorbing member10, and a joining portion30bat the apex thereof. In the same way, the second engaging protrusion32has an outer circumferential face32athat can be fit into a through hole13formed in the shock absorbing member10, and a joining portion32bcapable of contact with the joining portion30b. The tip edge21band tip edge31bof the first holding portion21and second holding portion31are each formed so as to tilt away from each other due to fold portions21eand31e.

The linking member20thus configured can easily be manufactured by folding the flat plate member such as illustrated in its unfolded state inFIG. 3B, by pressing. That is to say, The linking member20can easily be formed by folding the flat plate member where the first holding portion21in which the first engaging protrusion30has been formed, the first supporting portion22, the attaching portion24, the extension26in which the opening26ahas been formed, and the second holding portion31where the second engaging protrusion32has been formed, are continuously formed, on the fold portions28a,28b,21e,31e, and folding back at the fold-back portion25.

Next, procedures to join the shock absorbing member10and the attachment plate17using the linking members20will be described with reference toFIGS. 4A through 5C.

First, in a linking member mounting procedure, the tip edges21band31bof the first holding portion21and second holding portion31of the linking member20are positioned at the front edge10aof the shock absorbing member10so as to face each other, as illustrated inFIGS. 4A and 5A. Once positioned, the shock absorbing member10is inserted from the front edge10aside into between the first holding portion21and second holding portion31, the first engaging protrusion30formed on the first holding portion21is inserted into the through hole13from the outer circumferential face12side so that the first holding portion21is overlaid on the outer circumferential face12, and the second engaging protrusion32formed on the second holding portion31is inserted into the through hole13from the inner circumferential face11side, so that the second holding portion31is overlaid on the inner circumferential face11. Thus, the linking member20is attached to the front edge10ain a sure manner, by the first holding portion21and the second holding portion31holding the shock absorbing member10from the outer circumferential face12side and the inner circumferential face11side.

The work of mounting the linking member20to the shock absorbing member10is easy, since the first holding portion21is connected to the relatively narrow attaching portion24and first supporting portion22extending from the fold-back portion25, and the second holding portion31that faces the first holding portion21is connected to the relatively narrow side extensions27aand27band second support portions29aand29bextending from the fold-back portion25, so the first holding portion21and second holding portion31can be readily distanced from each other. In other words, the linking member20can be unclasped and easily mounted to the shock absorbing member10.

Next, in a linking member fixing procedure, the joining portion30bof the first engaging protrusion30and joining portion32bof the second engaging protrusion32that have been fit into the through hole13of the shock absorbing member10and are into contact with each other, are held under a predetermined pressure by a pair of electrodes101and102of a welder, and welded by electroconduction, as illustrated inFIGS. 4B and 5B.

The joining here is sure in this spot welding, since two steel sheets are directly welded by spot welding. The shock absorbing member10is strongly held from the outer circumferential face12side and the inner circumferential face11side by the first holding portion21and second holding portion31, on which are formed the first engaging protrusion30and second engaging protrusion32that have been inserted into the through hole13and joined. Thus, the linking member20and the shock absorbing member10are strongly joined.

In a subsequent attaching procedure, the shock absorbing member10to which linking members20have been attached corresponding to the through holes13is attached to the attachment plate17. This is performed by the attaching portions24of the linking members20attached to the shock absorbing member10being placed on the attachment plate17, and the attachment plate17and attaching portions24are held under a predetermined pressure by the pair of electrodes101and102of the welder, and welded by electroconduction, as illustrated inFIGS. 4C and 5C.

The joining here is sure in this spot welding, since the steel attachment plate17and the steel linking members20are directly welded by spot welding. Thus, the shock absorbing member10is strongly joined to the attachment plate17by way of the linking members20.

The linking member20configured this way is strongly linked to the shock absorbing member10by the first engaging protrusion30and second engaging protrusion32inserted into the through hole13being strongly joined. On the other hand, the base edges21aand31a, tip edges21band21b, and side edges21cand31c, and21dand31d, which are on the perimeter edges and face one another are not linked with each other, but rather easily deformed so as to be distanced from each other under a relatively small load. Deformation without constraint by the through hole perimeter portion15of the shock absorbing member10is permitted.

Thus, the shock absorbing member10to which attachment plates17have been attached on either end with linking members20interposed therebetween is fastened by bolting, for example, to the bumper beam of the bumper1as illustrated inFIG. 2. The attachment plates17at the rear side are fastened by bolting to attachment flanges9aof the side members, and thus are disposed between the bumper1and the front end of the side members9.

When the bumper1is subjected to a shock load P of a predetermined lever or greater, due to a collision or the like for example, the shock absorbing member10disposed thus exhibits crushing or compression deformation and absorbs the input load input from the attachment plates17via the linking members20die to relative backward movement of the bumper1, and reactive load from the linking members20supported by the attachment plates17disposed at the front ends of the side members9.

The operations of the linking members20configured in this way will be described with reference to the schematic illustrations inFIGS. 6A and 6B. The first engaging protrusion30of the first holding portion21and the second engaging protrusion32of the second holding portion31extending from the attaching portion24welded to the attachment plate17are inserted into a through hole13of the shock absorbing member10and the joining portions30band32bthereof are welded, as illustrated inFIG. 6A. Also, the inner circumferential face11and outer circumferential face12of the shock absorbing member10are firmly held by first holding portion21and second holding portion31, so that the shock absorbing member10is strongly attached to and supported by the attachment plate17.

On the other hand, when a shock load P exceeding the predetermined value is input to the attachment plate17at the bumper1side, the end portion14between the through hole13and the front edge10ais crushed, between the attachment plate17, or more particularly the side extensions27aand27b, and the first engaging protrusion30and second engaging protrusion32inserted into the through hole13, as illustrated inFIG. 6B. At this time, the fold portion23provided between the attaching portion24attached to the attachment plate17, and the fold portions28aand28bprovided between the attaching portion24and the first holding portion21and second holding portion31, exhibit crushing deformation such that they separated from each other as if being unclasped. Thus, the first supporting portion22and the second support portions29aand29bfall away such that the base edge21aof the first holding portion21and the base edge31aof the second holding portion31separate from each other. Accordingly, the end portion14can freely be crushed and deformed without constraint.

Also, the nearby range of the through hole13pressed by the first engaging protrusion30and second engaging protrusion32, i.e., the through hole perimeter portion15, is crushed. The first holding portion21and second holding portion31are opened over the range of the side edges21cand31c, and21dand31d, to the tip edges21band31b, so the tip edges21band31band side edges21cand31c, and21dand31d, of the first holding portion21and second holding portion31, readily deform in the direction of being distanced from each other, so the through hole perimeter portion15is sufficiently deformed by crushing without constraint. In this state as well, the joined state of the first engaging protrusion30and second engaging protrusion32joined within the through hole13of the shock absorbing member10is maintained, so the joining of the shock absorbing member10, linking member20, and attachment plate17is maintained in a sure manner.

Permitting this deformation of the shock absorbing member10avoids destruction and the like of the shock absorbing member10, since stress is not locally concentrated at the through hole perimeter portion15of the through hole13where the first engaging protrusion30and second engaging protrusion32are inserted, and the attachment range held between the first holding portion21and second holding portion31, when shock load P acts thereupon.

Accordingly, the shock absorbing member10is held by the linking members20and so forth in a stable manner under normal conditions, and on the other hand, in a case where shock load or the like is input, the shock absorbing member10can exhibit sufficient shock absorbing functions due to deformation of the entirety thereof, without deformation of the shock absorbing member10being locally constrained by the linking member20. The side extensions27aand27bcan also be spot welded to the attachment plate17so as to bond the linking members20to the attachment plate17even more firmly.

Now, modifications of the linking member20according to the present invention will be described with reference toFIGS. 7 through 10. Note that the same reference numerals will be used as in the above-describedFIGS. 1 through 6B, even though illustration of some parts may be omitted for sake of convenience.

The linking member40illustrated inFIG. 7differs from the linking member20illustrated inFIG. 3Awith regard to the configuration of the side extensions27aand27b, and other configurations are the same. This linking member40has side extensions27aand27b, which bridge between the fold-back portion25and the fold portions28aand28bfrom which continue the second support portions29aand29b, formed so as to curve such that the middle portion in the length direction thereof gradually rises. The side extensions27aand27bthus formed maintain their form under normal conditions, but once a load of a certain value or greater is input, deform by curving or starching, thus functioning as a weak portion that stretches and shrinks between the fold-back portion25and the fold portions28aand28b.

The linking member40thus configured has, under normal conditions, the first engaging protrusion30of the first holding portion21and the second engaging protrusion32of the second holding portion31inserted into the through hole13of the shock absorbing member10and the joining portions30band32bthereof joined by welding. Also, the shock absorbing member10is held from the inner circumferential face11and outer circumferential face12side by the first holding portion21and second holding portion31, so that the shock absorbing member10is strongly attached to and supported by the attachment plate17.

On the other hand, in a case where a shock load is input, the end portion14is crushed between the attachment plate17, side extensions27aand27b, and first engaging protrusion30and second engaging protrusion32inserted into the through hole13. At this time, the fold portion23between the attaching portion24, and the fold portions28aand28bbetween the side extensions27aand27band the second support portions29aand29bseparate from each other, and also the side extensions27aand27bthat have been formed curved deform by stretching, so that the base edge21aof the first holding portion21and the base edge31aof the second holding portion31separate from each other. Accordingly, sufficient deformation of the end portion14is secured without being constrained.

Also, the through hole perimeter portion15of the through hole13, at the tip edges21band31bpressed by the first engaging protrusion30and second engaging protrusion32, is crushed. The first holding portion21and second holding portion31are opened over the range of the side edges21cand31c, and21dand31d, to the tip edges21band31b, so these readily separate from each other, and deformation of the through hole perimeter portion15is permitted. That is to say, sufficient shock absorbing functions of the shock absorbing member10can be secured, due to deformation of the entirety thereof, without deformation of the shock absorbing member10being locally constrained by the linking member20.

A linking member41illustrated inFIG. 8differs from the linking member20illustrated inFIG. 3Awith regard to the point that a slit extending in the width direction is formed in the first holding portion21and second holding portion31, and other configurations are the same. The linking member41has a base side slit42aopened extending generally parallel to the base edge21ain the width direction, between the first engaging protrusion30of the first holding portion21and the base edge21a, and a tip side slit42bopened extending generally parallel to the tip edge21bin the width direction, between the first engaging protrusion30and the tip edge21b. In the same way, the linking member41has an unillustrated base side slit43aopened in the width direction, between the second engaging protrusion32of the second holding portion31and the base edge31a, and an unillustrated tip side slit43bopened in the width direction, between the second engaging protrusion32and the tip edge31b.

The first holding portion21and second holding portion31maintain their forms under normal conditions, but in a case where a load of a predetermined value or greater is input from between the first holding portion21and the second holding portion31, that is to say from the inner side, the first holding portion21and second holding portion31that have been divided by the base side slits42aand43acan be deformed such that the base edges21aand31amove away from each other, and in the same way the tip edges21band31bof the first holding portion21and second holding portion31divided by the tip side slits42band43bcan be deformed such that the tip edges21band31bmove away from each other.

The linking member41thus configured has, under normal conditions, the first engaging protrusion30of the first holding portion21and the second engaging protrusion32of the second holding portion31inserted into the through hole13of the shock absorbing member10and the joining portions30band32bthereof joined by welding. Also, the shock absorbing member10is held from the inner circumferential face11and outer circumferential face12side by the first holding portion21and second holding portion31, so that the shock absorbing member10is strongly attached to and supported by the attachment plate17.

On the other hand, in a case where a shock load is input, the end portion14is crushed between the attachment plate17, side extensions27aand27b, and first engaging protrusion30and second engaging protrusion32inserted into the through hole13. At the time of the through hole perimeter portion15of the through hole13being crushed, the fold portion23between the attaching portion24and first supporting portion22, and the fold portions28aand28bbetween the side extensions27aand27band the second support portions29aand29bseparate from each other by crushing deformation, and also the so the base edge21aand31asides and tip edge21band31bsides of the first holding portion21and second holding portion31that have been formed in a slender shape due to the base side slits42aand43aand the tip side slits42band43bare readily opened, and deformation of the through hole perimeter portion15is permitted. That is to say, the shock absorbing member10can exhibit sufficient shock absorbing functions due to deformation of the entirety thereof, without deformation of the shock absorbing member10being locally constrained by the linking member41. Note that part of the base side slits42aand43aand the tip side slits42band43bmay be omitted as appropriate.

A linking member45illustrated inFIG. 9has the first holding portion21where the first engaging protrusion30has been formed, and the second holding portion31where the second engaging protrusion32has been formed, in the same way as the linking member20illustrated inFIG. 3A. First supporting portions46aand46bare provided in a stepped form on both edges of the base edge21aof the first holding portion21, with the first supporting portions46aand46bcontinuing to the fold-back portion25via fold portions23aand23band the rectangular side extensions27aand27b. The second holding portion31has a second supporting portion47formed by folding the middle portion of the base edge31ain a stepped shape, continuing to the middle portion of the fold-back portion25via the rectangular attaching portion24.

The first supporting portions46aand46band the second supporting portion47maintain their shapes under normal conditions, but in a case where a load of a predetermined value or greater is input, the base edges21aand31asides of the first holding portion21and second holding portion31deform in a direction separating from each other. Also, movement in the buckling direction of the first supporting portions46aand46band the second supporting portion47formed in stepped shapes, which is in-plane movement of the first holding portion21and second holding portion31, is facilitated.

The through hole perimeter portion15at the side of the tip edges21band31b, pressed by the first engaging protrusion30and second engaging protrusion32, is crushed. The side edges21cand31c, and21dand31d, of the first holding portion21and second holding portion31are open up to the tip edges21band31b.

The linking member45thus configured has, under normal conditions, the first engaging protrusion30of the first holding portion21and the second engaging protrusion32of the second holding portion31inserted into the through hole13of the shock absorbing member10and the joining portions30band32bthereof joined by welding. Also, the shock absorbing member10is held from the inner circumferential face11and outer circumferential face12side by the first holding portion21and second holding portion31, so that the shock absorbing member10is strongly attached to and supported by the attachment plate17.

On the other hand, in a case where a shock load is input, the end portion14at the through hole13and front edge10ais crushed between the attachment plate17, side extensions27aand27b, and first engaging protrusion30and second engaging protrusion32inserted into the through hole13, and the through hole perimeter portion15pressed by the first engaging protrusion30and second engaging protrusion32is crushed. The first holding portion21and second holding portion31are open at the side edges21cand31c, and21dand31d, up to the tip edges21band31b, and accordingly readily separate and deformation of the through hole perimeter portion15is permitted.

A linking member50illustrated inFIG. 10has the first holding portion21where the first engaging protrusion30has been formed, and the second holding portion31where the second engaging protrusion32has been formed, in the same way as the linking member20illustrated inFIG. 3A. Side slits51aand51bare opened on both sides of the first holding portion21across the first engaging protrusion30, formed from nearby the first engaging protrusion30, extending following the side edges21cand21d, and reaching the base edge21a. A slender first supporting portion52ais formed interposed between the side edge21cand the side slit51aand protruding beyond the base edge21a, and a slender first supporting portion52bis formed interposed between the side edge21dand the side slit51band protruding beyond the base edge21a. The first supporting portions52aand52bcontinue to the fold-back portion25via the fold portions23aand23band the side extensions27aand27b.

On the other hand, a second supporting portion53is formed at the middle of the base edge31aof the second holding portion31, bulging in a cross-sectional arc shape away from the second holding portion31. The second supporting portion53continues to the middle portion of the fold-back portion25via the rectangular attaching portion24.

The first supporting portions52aand52b, and second supporting portion53maintain their shapes under normal conditions, but in a case where a load of a predetermined value or greater is input, the second supporting portion53and the fold portions23aand23bare deformed by crushing so as to move away from each other, and the first supporting portions52aand52b, and second supporting portion53can be deformed by flexure in the axial direction thereof. Also, a middle range21A defined by the first engaging protrusion30isolated by the side slits51aand51and the base edge21ais readily deformed by curving so as to move away from the second holding portion31side.

The linking member50thus configured has, under normal conditions, the first engaging protrusion30of the first holding portion21and the second engaging protrusion32of the second holding portion31inserted into the through hole13of the shock absorbing member10and the joining portions30band32bthat are the tops thereof joined by welding. Also, the shock absorbing member10is held from the inner circumferential face11and outer circumferential face12side by the first holding portion21and second holding portion31, so that the shock absorbing member10is strongly attached to and supported by the attachment plate17.

On the other hand, in a case where a shock load is input, the end portion14at the through hole13and front edge10ais crushed between the attaching portion24and the first engaging protrusion30and second engaging protrusion32inserted into the through hole13, and the through hole perimeter portion15at the base edge21aand31aside pressed by the first engaging protrusion30and second engaging protrusion32is crushed. The second supporting portion53and fold portions23aand23bare deformed by crushing so as to move away from each other, and the first supporting portions52aand52bare deformed by crushing so as to move away from the second holding portion31side. The side edges21cand31c, and21dand31d, of the first holding portion21and second holding portion31are opened up to the tip edges21band31b, and the middle range21A deforms by curving away from the second holding portion31, thus permitting deformation of the through hole perimeter portion15.

Next, an example of joining a CFRP roof brace8, serving as the first member, to the side rail6, serving as a second member, will be described with reference toFIGS. 11A through 11C. A linking member that is essentially the same as the above-described linking members may be used as the linking members here. A linking member equivalent to the above-described linking member20will be described as an example.

The linking member in this implementation is essentially of the same configuration as the linking member20described above, except for a bolt hole24abored in the attaching portion24for attachment to the side rail, so detailed description will be omitted. Also, a pair of through holes13are bored at a side edge8aof the roof brace8, into which the first engaging protrusions30and second engaging protrusions32of the linking members20are inserted.

First, in the linking member mounting procedure, the tip edges21band31bof the first holding portion21and second holding portion31of the linking member20are positioned facing the side edge8aof the roof brace8as illustrated inFIG. 11A. The side edge8aof the roof brace8is inserted between the first holding portion21and second holding portion31, the first engaging protrusion30formed on the first holding portion21is inserted into the through hole13so that the first holding portion21is overlaid on the lower face of the roof brace8, and the second engaging protrusion32formed on the second holding portion31is inserted into the through hole13so that the second holding portion31is overlaid on the upper face thereof. Thus, the roof brace8is held at both faces by the first holding portion21and the second holding portion31, and the linking member20is securely attached to the roof brace8.

Next, in the linking member fixing procedure, the joining portion30bof the first engaging protrusion30and joining portion32bof the second engaging protrusion32which have been fit into the through hole13of the roof brace8and are into contact with each other, are held under a predetermined pressure by a pair of electrodes101and102of a spot welder, and welded by electroconduction, as illustrated inFIG. 11B.

The joining here is sure in this spot welding, since two steel sheets are directly welded by spot welding. The roof brace8is strongly joined by being held by the first holding portion21and second holding portion31, due to the first engaging protrusion30and second engaging protrusion32having been inserted into the through hole13and joined.

In the subsequent attaching procedure, the roof brace8to which linking members20have been attached corresponding to the through holes13, is attached to the side rail6. Specifically, as illustrated inFIG. 11C, the attaching portions24of the linking members20which have been mounted to the side edge8aof the roof brace8corresponding to the through holes13are overlaid on the side rail6, bolts61are inserted through the bolt holes24aof the attaching portion24, and screwed into nuts provided to the side rail6beforehand, thus attaching the roof brace8to the side rail6.

In a case where a shock load exceeding a predetermined value is input to the roof brace8, according to this configuration, an end portion of the roof brace8at the through hole13and side edge8ais crushed between the side extensions27aand27band the and the first engaging protrusion30and second engaging protrusion32inserted through the through hole13. The first supporting portion22and the fold portions28aand28bare deformed so as to curve away from each other, the first supporting portion22and second support portions29aand29bdeform by bulging away from each other, and the base edge21aof the first holding portion21and the base edge31aof the second holding portion31move away from each other, thereby permitting deformation of the end portion of the roof brace8.

Also, a through hole perimeter portion around the through hole13, at the tip edge21band31bside, which is pressed by the first engaging protrusion30and second engaging protrusion32, is crushed. The side edges of the first holding portion21and second holding portion31are open up to the tip edges21band31b, and thus readily separate and permit deformation of the through hole perimeter portion.

This avoids destruction and the like of the shock roof brace8, since stress is not locally concentrated around the through hole13where the first engaging protrusion30and second engaging protrusion32are inserted, and the attachment range held between the first holding portion21and second holding portion31, when shock load acts thereupon.

Note that the present invention is not restricted to the above-described implementation, and that various modifications may be made without departing from the essence of the invention. For example, while examples have been described above where a shock absorbing member10and a roof brace8formed of CFRP are linked using linking members20and the like formed of an iron-based metal, that is to say steel, the material of the shock absorbing member10and roof brace8is not restricted to CFRP, and may be changed to other materials as appropriate, such as metal materials like steel, aluminum alloy, or the like, synthetic resin material, or the like.

Also, while description has been made in the above implementation that the joining portion30bof the first engaging protrusion30of the first holding portion21and joining portion32bof the second engaging protrusion32of the second holding portion31are joined by spot welding, the he joining portion30bof the first engaging protrusion30and joining portion32bof the second engaging protrusion32may be fastened by bolting instead of spot welding. Also, an arrangement may be made wherein the configuration is simplified by omitting one or the other of the joining portion30bof the first engaging protrusion30of the first holding portion21and the joining portion32bof the second engaging protrusion32of the second holding portion31, and forming, the one of the first holding portion21and second holding portion31from which the omission has been made, as a flat face.

Also, while description has been made in the above implementation that the attachment plate17and attaching portion24are spot-welded, the side extensions27aand27bmay be joined to the attachment plate17by spot welding instead of the attaching portion24. Further, both the attaching portion24and the side extensions27aand27bmay be joined to the attachment plate17by spot welding.

Also, base side slits and tip side slits may be provided to the first holding portion21and second holding portion31of the linking members illustrated inFIGS. 7, 9, 10, and so forth, as well.

It should be noted that the present invention is not restricted to joining the above-described shock absorbing member and roof brace, and may be applied to joining other members as well.