JP2004352022A - Manufacturing method for floor cross member and floor cross member structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize both of weight reduction and improvement of fatigue strength. <P>SOLUTION: A front floor cross member 10 is constituted of a front floor cross member lower 12 and a front floor cross member upper 14. The front floor cross member lower 12 includes a nut 24 with a washer previously fixed by projection welding. A protective layer 54 is formed on each of a welded surface 58 and an opposite surface 60 of the front floor cross member lower 12. Even if the opposite surface 60 is affected by the projection welding, fretting due to fatigue can be restrained. By ensuring the fatigue strength, the thickness of the front floor cross member 10 can be decreased for weight reduction. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method of manufacturing a floor cross member for supporting a seat rail of a vehicle seat and a floor cross member structure.
[0002]
[Prior art]
The front end and the rear end of the seat rail of the vehicle seat are bolted to a pair of front and rear floor cross members arranged with the vehicle width direction as a longitudinal direction. As a result, the vehicle seat can be slid in the vehicle front-rear direction along the seat rail (see Patent Documents 1 and 2 below).
[0003]
Conventionally, the floor cross member has been manufactured as follows. First, a pair of upper and lower cross members are manufactured by press-forming a steel plate such as a cold-rolled steel plate. Note that, as an example, the lower plate is a channel material having a substantially hat shape in cross section, and the upper plate is a bracket-like short plate material which is later fixed to the longitudinal end of the seat rail by riveting. Next, a nut with a washer is joined by projection welding to three or four places around the bolt insertion hole of the lower plate, and then the bolt insertion hole of the lower plate and the bolt insertion hole of the upper plate are overlapped. Screw the bolt to the nut with washer from the side.
[0004]
[Patent Document 1]
JP-A-7-144662
[Patent Document 2]
JP-A-6-171410
[0005]
[Problems to be solved by the invention]
By the way, in recent years, from the viewpoint of prevention of global warming, importance has been placed on a technology for improving the fuel efficiency of a vehicle by reducing the weight of parts (in this case, a floor cross member) constituting the vehicle. In order to reduce the weight of the floor cross member, the simplest method is to reduce the thickness of the floor cross member. However, it is not preferable because the fatigue strength of the floor cross member decreases.
[0006]
That is, since a bending load in a double swing state is applied to the floor cross member while the vehicle is traveling, stress concentration occurs near the end of the projection welded portion (weld toe). For this reason, it is not preferable to simply reduce the thickness of the floor cross member because fatigue fracture may occur from the site. Further, since the life of the floor cross member is shortened, a simple reduction in plate thickness is not preferable in terms of durability.
[0007]
Then, it is conceivable to manufacture the floor cross member using a material with high strength of about 1 to 2 ranks while keeping the plate thickness as it is, but as a result of verification, if the material is changed, the fatigue strength is slightly improved. , Less than the target. That is, neither the technique of simply reducing the thickness of the sheet nor the technique of replacing the material with a material having a high strength can achieve both reduction in weight and improvement in fatigue strength.
[0008]
An object of the present invention is to provide a method of manufacturing a floor cross member and a floor cross member structure that can achieve both reduction in weight and improvement in fatigue strength in consideration of the above facts.
[0009]
[Means for Solving the Problems]
The method for manufacturing a floor cross member according to the present invention according to claim 1 includes a first step of forming a pair of upper and lower floor cross members that support a seat rail of a vehicle seat by pressing a steel plate. One of the fasteners is welded to the periphery of the fastener insertion hole formed in the lower member fixed to the floor or to the periphery of the fastener insertion hole formed in the upper member to which the seat rail is fixed. A second step of pre-joining, and overlapping the upper member with the lower member so that the fastener insertion hole of the lower member and the fastener insertion hole of the upper member overlap each other; A third step of fastening the lower member and the upper member by tightening the other of the two members into one of the fasteners, the method comprising the steps of: Before performing the third step A protective layer having a predetermined thickness to avoid metal-to-metal contact in the contact surface between the lower member and the upper member, and characterized in that.
[0010]
According to a second aspect of the present invention, there is provided a floor cross member manufacturing method according to the first aspect, wherein a peripheral portion of a fastener insertion hole of an upper member or a lower member to which the other of the fasteners is mounted. , A washer is interposed therebetween, and the protective layer is provided on a contact surface with the washer or on the washer itself.
[0011]
According to a third aspect of the present invention, in the method of manufacturing a floor cross member according to the first or second aspect, the welding is projection welding.
[0012]
In the floor cross member structure according to the present invention, a seat rail of a vehicle seat is fixed to a floor cross member lower fixed to a vehicle body floor and having a fastener insertion hole formed therein, and the fastener is provided. In a state in which the floor cross member upper having the fastener insertion hole formed coaxially with the insertion hole is overlapped, the periphery of the fastener insertion hole of the floor cross member lower or the fastener insertion hole of the floor cross member upper is overlapped. A floor cross member structure configured by fastening one of the fasteners to one of fasteners welded to a peripheral portion in advance, wherein a metal surface is formed on a contact surface between the floor cross member lower and the floor cross member upper. A protective layer for avoiding contact with the protective layer.
[0013]
According to the first aspect of the present invention, in a first step, a steel plate is press-formed to form a pair of upper and lower floor cross members that support a seat rail of a vehicle seat. Next, in the second step, the periphery of the fastener insertion hole formed in the lower member fixed to the vehicle body floor or the periphery of the fastener insertion hole formed in the upper member to which the seat rail is fixed. Then, one of the fasteners is previously joined by welding. Next, in a third step, the upper member is overlapped with the lower member such that the fastener insertion hole of the lower member and the fastener insertion hole of the upper member mutually overlap. Then, the lower member and the upper member are fastened by tightening the other fastener to one of the fasteners. Thereby, a floor cross member is manufactured.
[0014]
Here, when the floor cross member is manufactured by the above-described manufacturing method, one of the fasteners is welded to the periphery of the fastener insertion hole of the lower member or the periphery of the fastener insertion hole of the upper member in the second step. In this case, depending on the welding method including the welding temperature, the influence of welding (for example, a fine convex portion is formed on the plate surface opposite to the welded surface of the member to which one of the fasteners is welded is formed. Etc.) may appear. In this state, when the process proceeds to the third step and the upper member is overlaid on the lower member and the two members are fastened to each other, the periphery of the fastener insertion hole of the lower member and the fastener of the upper member The surrounding portion of the insertion hole comes into metal contact with a fine projection, and if used for a long time with the vehicle seat fixed, fretting may occur due to fatigue. The study turned out.
[0015]
Based on such knowledge, in the present invention, after performing the second step and before performing the third step, protection of a predetermined thickness for avoiding metal-to-metal contact on the contact surface between the lower member and the upper member is performed. Since the layer is provided, even if one of the fasteners is welded to form a fine protrusion on the surface opposite to the welded surface, the protrusion and the upper member or the lower member are metal-to-metal. To avoid direct contact. Therefore, occurrence of fretting due to fatigue can be suppressed, and the fatigue strength of the lower member or the upper member, and thus the floor cross member, can be increased.
[0016]
Furthermore, in the present invention, as described above, the cause of the inability to easily increase the fatigue strength is that fretting due to fatigue is caused. More fundamentally, fine projections are generated on the surface opposite to the welding surface by welding. Since the protective layer is provided based on the result of elucidating the point, even if the plate thickness of the lower member and the upper member is reduced, the effect of providing the protective layer is sufficient. can get. Therefore, according to the present invention, the weight of the floor cross member can be reduced.
[0017]
According to the second aspect of the present invention, the washer is interposed around the fastener insertion hole of the upper member or the lower member to which the other fastener is mounted.
[0018]
Here, in the present invention, since the same protective layer is provided on the contact surface with the washer or on the washer itself, the operation of the invention according to claim 1 can be obtained even in a configuration using the washer.
[0019]
According to the present invention, one of the fasteners is previously welded to the lower member or the upper member by projection welding.
[0020]
Here, in the case of employing projection welding, small projections are previously formed at predetermined intervals in the circumferential direction on one of the fasteners, and welding is performed at a high temperature while pressing the small projections on a member to be welded. Therefore, fine projections corresponding to the small projections are also generated on the surface opposite to the welding surface of the member to be welded. Therefore, it is most suitable for applying the present invention.
[0021]
According to the present invention, the seat rail of the vehicle seat is fixed to the floor cross member lower fixed to the vehicle body floor and formed with the fastener insertion hole, and is coaxial with the fastener insertion hole. In a state in which the floor cross member upper having the fastener insertion hole formed thereon is overlapped, the floor cross member upper is welded in advance to the periphery of the fastener insertion hole of the lower floor cross member lower or the periphery of the fastener insertion hole of the floor cross member upper. By fastening the other fastener to one of the fasteners, a floor cross member is formed.
[0022]
Here, in the present invention, since a protective layer for avoiding metal-to-metal contact is interposed on the contact surface between the floor cross member lower and the floor cross member upper, it is assumed that one of the fasteners is temporarily welded to be opposite to the weld surface. Even if a fine convex portion is generated on the side surface, it is possible to avoid direct contact between the metal and the metal member between the convex portion and the upper member or the lower member. That is, the protective layer functions as a cushioning material. Therefore, occurrence of fretting due to fatigue can be suppressed, and the fatigue strength of the lower member or the upper member, and thus the floor cross member, can be increased.
[0023]
Furthermore, in the present invention, as described above, the cause of the inability to easily increase the fatigue strength is that fretting due to fatigue is caused. More fundamentally, fine projections are generated on the surface opposite to the welding surface by welding. Since the protective layer is provided based on the result of elucidating the point, even if the plate thickness of the lower member and the upper member is reduced, the effect of providing the protective layer is sufficient. can get. Therefore, according to the present invention, the weight of the floor cross member can be reduced.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a method of manufacturing a floor cross member and a floor cross member structure according to the present invention will be described with reference to FIGS.
[0025]
FIG. 1 shows a vertical cross-sectional structure of the front floor cross member 10. As shown in the figure, the front floor cross member 10 is formed in a flat plate shape with a channel-shaped front floor cross member lower 12 as a “lower member” arranged with the vehicle width direction as a longitudinal direction. The front floor cross member upper 14 as the “upper member” is constituted.
[0026]
The front floor cross member lower 12 is formed in a substantially hat shape in cross section, and its terminal portion is fixed to a vehicle floor (not shown) by spot welding or the like. Further, a bolt insertion hole 16 as a “fastener insertion hole” having a predetermined diameter is formed in the top wall portion 12A of the front floor cross member lower 12.
[0027]
On the other hand, the front floor cross member upper 14 is capable of sliding a vehicle seat (not shown) bent at a predetermined angle with respect to the front portion 14A which is overlapped on the top wall portion 12A of the front floor cross member lower 12 and the front portion 14A. And a rear portion 14B to which a long seat rail 18 is fixed by rivets 20. Further, a bolt insertion hole 22 as a burring-shaped “fastener insertion hole” is formed coaxially with the bolt insertion hole 16 at a predetermined position of the front portion 14A.
[0028]
A washer portion 24A of a nut 24 with a washer as "one of the fasteners" is previously joined to the back side of the bolt insertion hole 16 of the above-described front floor cross member lower 12 by projection welding. Then, with the washer 28 of a predetermined thickness interposed on the outer peripheral portion of the burring portion 26 of the front floor cross member upper 14, the bolt 30 as the "other fastener" is screwed to the nut portion 24B of the nut 24 with washer. , The front floor cross member upper 14 is fastened to the front floor cross member lower 12.
[0029]
On the other hand, FIG. 2 shows a vertical cross-sectional structure of the rear floor cross member 40. As shown in this figure, the rear floor cross member 40 is basically configured similarly to the front floor cross member 10 described above. That is, the rear floor cross member 40 has a rear floor cross member lower 42 as a “lower member” having a substantially hat-shaped cross section fixed to the vehicle body floor, and a step fixed to the rear end of the seat rail 18 with rivets 43. And the rear floor cross member upper 44 as the “upper member”.
[0030]
A bolt insertion hole 46 as a “fastener insertion hole” is formed in the top wall portion 42A of the rear floor cross member lower 42, and the bolt insertion hole 46 is also formed in the rear portion 44A of the rear floor cross member upper 44 correspondingly. A bolt insertion hole 48 as a “fastener insertion hole” is formed coaxially by punching. Further, around the bolt insertion hole 46 on the back surface side of the top wall portion 42A of the rear floor cross member lower 42, a washer portion 50A of a nut 50 with a washer as "one of fasteners" is previously joined by projection welding. . Then, with the rear portion 14B of the rear floor cross member upper 44 superimposed on the top wall portion 42A of the rear floor cross member lower 42, the bolt 52 as the "other fastener" is screwed into the nut portion 50B of the nut 50 with a washer. By doing so, the rear floor cross member upper 44 is fastened to the rear floor cross member lower 42.
[0031]
As shown in FIG. 1, a protective layer (surface modified portion) 54 is formed around the bolt insertion hole 16 on the upper surface of the top wall portion 12A of the front floor cross member lower 12 described above. Thus, the lower end surface of the burring portion 26 of the front floor cross member upper 14 and the lower surface of the washer 28 are configured to be maintained in a fastened state without being in contact with the upper surface of the front floor cross member lower 12.
[0032]
As shown in FIG. 2, a similar protective layer (surface modified portion) 56 is formed around the bolt insertion hole 46 on the upper surface of the top wall portion 42A of the rear floor cross member lower 42 described above. I have. Thus, the lower surface of the rear portion 44A of the rear floor cross member upper 44 is maintained in a fastened state without being in contact with the upper surface of the top wall portion 42A of the rear floor cross member lower 42.
[0033]
Supplementary information about the protective layer 54 is that the protective layers 54 and 56 are, for example, formed of a coating layer having a thickness of about 30 μm, and a lacquer paint or the like is uniformly sprayed and applied using a small simple spray gun to form a coating film. MoS to the method and washer 28 ₂ Alternatively, a method of baking and fixing the like may be adopted.
[0034]
Next, the operation and effect of the present embodiment will be described.
[0035]
First, a method of manufacturing a floor cross member will be described. Taking the front floor cross member 10 as an example, first, in a first step, a steel plate is press-formed, and a pair of upper and lower front floor cross member lowers 12 and a front floor cross member upper supporting a seat rail 18 of a vehicle seat are provided. 14 are formed. At the time of press molding, a bolt insertion hole 16 is formed in the front floor cross member lower 12, and a bolt insertion hole 22 and a burring portion 26 are formed in the front floor cross member upper 14. The burring portion 26 may be formed by performing secondary processing after the formation of the bolt insertion hole 22.
[0036]
Next, in a second step, a washer portion 24A of a nut 24 with a washer is joined by projection welding to a portion around a bolt insertion hole 16 formed in the front floor cross member lower 12 fixed to the vehicle body floor.
[0037]
Next, in a third step, the front floor cross member upper 14 is moved so that the bolt insertion holes 16 of the front floor cross member lower 12 and the bolt insertion holes 22 of the front floor cross member upper 14 overlap with each other. It is superimposed on the lower 12. At that time, a washer 28 is interposed on the outer peripheral portion of the burring portion 26. Then, the front floor cross member lower 12 and the front floor cross member upper 14 are fastened by tightening the bolt 30 into the nut portion 24B of the washer nut 24. Thereby, the front floor cross member 10 is manufactured.
[0038]
Here, when the front floor cross member 10 is manufactured by the above manufacturing method, when the washer portion 24A of the nut 24 with a washer is projection-welded to the periphery of the bolt insertion hole 16 of the front floor cross member lower 12 in the second step. A fine projection is formed on the plate surface opposite to the surface on which the welding is performed. In this state, when the process proceeds to the third step and the front floor cross member upper 14 is directly overlapped with the front floor cross member lower 12 and the two are fastened, the peripheral portion of the bolt insertion hole 16 of the front floor cross member lower 12 is formed. And the peripheral portion of the bolt insertion hole 22 of the front floor cross member upper 14 comes into metal contact with a fine projection being generated. If the vehicle seat is used for a long time in a fixed state, fretting due to fatigue will occur. Can occur.
[0039]
Hereinafter, this will be described in detail with reference to FIG. FIG. 3 is a partial sectional view showing a welded section of the nut 24 with washer. A portion attached to this figure is a welded portion when the washer portion 24A of the nut 24 with a washer is projection-welded to the lower surface side of the top wall portion 12A of the front floor cross member lower 12, and a B portion is a weld toe portion. is there. When the projection welding is performed, a minute convex portion is generated at the C portion of the surface 60 opposite to the welding surface 58 of the front floor cross member lower 12 to be welded. The reason why the projections are generated is that the welding temperature of the projection welding is high, and under such a high temperature condition, pressure is applied to perform welding to the lower surface of the front floor cross member lower 12 having a relatively thin plate thickness. It is considered that the influence of the welding is exerted on the surface 60, which appears in the form of a protrusion.
[0040]
If the process proceeds to the third step in a state where the above-mentioned convex portion is generated, and the front floor cross member upper 14 is superimposed on the front floor cross member lower 12 and the two are fastened to each other, the front floor cross member lower 12 The upper surface of the peripheral portion of the bolt insertion hole 16 and the lower surface of the peripheral portion of the bolt insertion hole 22 of the front floor cross member upper 14 come into metallic contact with the fine projections being generated. When used for a period, fatigue cracks occur from the D portion near the weld toe B portion and the E portion of the surface 60 on the opposite side, and the crack progresses across the thickness of the front floor cross member lower 12. Go.
[0041]
Based on such knowledge, in the present embodiment, after the second step and before performing the third step, the front floor cross member lower serving as a contact surface between the front floor cross member lower 12 and the front floor cross member upper 14 is provided. Since a protective layer 54 (a protective layer 56 in the case of the rear floor cross member lower 42) having a predetermined thickness is provided on the upper surface of the top wall portion 12A of the base 12, the temporarily-welded nut 24 is temporarily welded to the side opposite to the welding surface 58. Even if a minute convex portion is formed on the surface 60, it is possible to prevent the metal from directly contacting the convex portion and the front floor cross member upper 14 with each other. Therefore, occurrence of fretting due to fatigue can be suppressed, and the fatigue strength of the front floor cross member lower 12 can be increased.
[0042]
Furthermore, in the present embodiment, as described above, the cause of the fact that the fatigue strength cannot be easily increased is due to fretting due to fatigue. More fundamentally, fine projections are formed on the opposite side of the welding surface 58 by projection welding. Since the protective layers 54 and 56 are provided based on the result of elucidating the fact that the point is generated on the surface 60, the front floor cross member lower 12, the front floor cross member upper 14, the rear floor cross member lower 42 and the rear floor Even when the thickness of the cross member upper 44 is reduced, the effect of providing the protective layers 54 and 56 can be sufficiently obtained. Therefore, according to the present embodiment, the weight of the front floor cross member 10 and the rear floor cross member 40 can be reduced.
[0043]
Generally speaking, according to the method for manufacturing a floor cross member and the floor cross member structure according to the present embodiment, it is possible to achieve both reduction in weight of the floor cross member and improvement in fatigue strength.
[0044]
FIG. 4 shows an outline of the results of an accelerated endurance test performed by simulating a practical traveling mode of a floor cross member and using an on-machine endurance test machine. (1) is the case where the plate thickness t = 1.4 mm, and (2) is the case where the plate thickness t is 1.2 mm and a high-strength material is used instead of the protective layers 54 and 56. 3) The case where the plate thickness t = 1.2 mm and the protective layers 54 and 56 by coating were provided, and 4) The case where the plate thickness t = 1.2 mm and the protective layers 54 and 56 by coating were provided, and further high strength was obtained. In this case, a material is used.
[0045]
As can be seen from this figure, it was possible to reduce the thickness originally set at the plate thickness t = 1.4 mm (that is, in the case of (1)) to the plate thickness t = 1.2 mm ( That is, (3). Incidentally, when the plate thickness is reduced from 1.4 mm to 1.2 mm, the weight is reduced by about 14%. This is a value that sufficiently contributes to improving the fuel efficiency of the automobile.
[0046]
Hereinafter, other effects (effects corresponding to the dependent claims) of the present embodiment will be described.
[0047]
First, as shown in FIG. 1, in the front floor cross member 10, the washer 28 is interposed on the outer peripheral portion of the burring portion 26. Since the protective layer 54 is provided, the operation and effect of the present embodiment described above can be obtained even in the configuration using the washer 28 as described above.
[0048]
Further, in the present embodiment, projection welding is employed among various types of welding, so that it is most effective. That is, as described above, when projection welding is adopted, small projections are formed in the nut portion 24B of the nut 24 with a washer in advance at predetermined intervals in the circumferential direction (for example, three locations at 120-degree intervals). Since this is to be welded at a high temperature while being pressed against the top wall portion 12A of the front floor cross member lower 12, which is the welding partner, the small surface is also provided on the surface 60 opposite to the welding surface 58 of the member to be welded. Fine projections are generated corresponding to the projections. Therefore, when projection welding is used, it can be said that problems such as a decrease in fatigue strength and a decrease in durability are likely to occur. Conversely, the present invention works most effectively.
[0049]
In the above-described embodiment, the projection welding is used. However, the present invention is not limited to this, and the welding temperature, welding time, plate thickness and material of the member to be welded, etc. The present invention can be applied to various kinds of welding if the frictional resistance is increased.
[0050]
Further, in the above-described embodiment, the floor cross member is applied to the present invention. However, the present invention can be applied to members other than the above as long as the same situation occurs. is there. In this case, if the member is not a floor cross member but is a member that can be attached to the vehicle body floor, the name of the present invention may be appropriate to be "method of manufacturing vehicle body floor member and vehicle body floor member structure" as an example. In the case where the present invention is applied to members other than the vehicle body floor, the name of the present invention may suitably be, for example, "the manufacturing method of the vehicle body member and the vehicle body member structure".
[0051]
An example of a claim in the case of "the manufacturing method of the vehicle body floor member and the vehicle body floor member structure" will be described below.
(1) a first step of forming a pair of upper and lower vehicle body floor members by press-forming a steel sheet;
A second step of pre-joining one of the fasteners to the periphery of the fastener insertion hole formed in the lower member or the periphery of the fastener insertion hole formed in the upper member by welding,
The upper member is overlapped with the lower member so that the fastener insertion hole of the lower member and the fastener insertion hole of the upper member overlap each other, and the other of the fasteners is connected to one of the fasteners. A third step of fastening the lower member and the upper member by tightening
A method of manufacturing a vehicle body floor member having
After performing the second step and before performing the third step, a protective layer having a predetermined thickness is provided on a contact surface between the lower member and the upper member to avoid contact between metals,
A method of manufacturing a vehicle body floor member.
(2) In a state where a vehicle body floor member upper having a fastener insertion hole formed coaxially with the fastener insertion hole is superimposed on a vehicle body floor member lower having a fastener insertion hole formed on a lower side, A vehicle body formed by fastening the other of the fasteners to one of the fasteners welded in advance to the periphery of the fastener insertion hole of the vehicle body floor member lower or to the periphery of the fastener insertion hole of the vehicle body floor member upper. A floor member structure,
A protective layer that avoids contact between metals is interposed on a contact surface between the vehicle body floor member lower and the vehicle body floor member upper,
A vehicle body floor member structure.
[0052]
Further, in the above-described embodiment, the nuts 24 and 50 with washers are configured to be projection-welded to the front floor cross member lower 12 and the rear floor cross member lower 42, but various configurations may be adopted depending on an application site, working conditions, and the like. It is possible. For example, a configuration in which a bolt with a washer is projection-welded to a lower member and a nut is tightened on the upper member, a configuration in which a nut with a washer is projection-welded to the upper member, and a bolt is tightened on the lower member, Various embodiments are conceivable.
[0053]
Further, as another embodiment, it is possible to adopt a configuration in which a protective layer is provided on the washer 28 itself.
[0054]
【The invention's effect】
As described above, according to the method for manufacturing a floor cross member according to the present invention, the peripheral portion of the fastener insertion hole or the seat rail formed in the lower member fixed to the vehicle body floor is fixed. After a second step of welding one of the fasteners to the periphery of the fastener insertion hole formed in the upper member by welding in advance, the fastener insertion hole of the lower member and the fastener of the upper member The third member for fastening the lower member and the upper member by superimposing the upper member on the lower member so that the insertion holes overlap with each other, and tightening the other of the fasteners into one of the fasteners. Before performing the process, since a protective layer having a predetermined thickness is provided on the contact surface between the lower member and the upper member to avoid contact between metals, occurrence of fretting due to fatigue can be suppressed as much as possible. As a result, both weight reduction and improvement in fatigue strength have been achieved. It has an excellent effect that it is Rukoto.
[0055]
According to a second aspect of the present invention, there is provided a floor cross member manufacturing method according to the first aspect of the present invention, wherein the upper member or the lower member to which the other of the fasteners is attached is provided around the fastener insertion hole. Since the washer is interposed and the protective layer is also provided on the contact surface with the washer or on the washer itself, even in a configuration using the washer, the operation of the invention according to claim 1 can be obtained, and as a result, Even in a simple configuration, there is an excellent effect that both reduction in weight and improvement in fatigue strength can be achieved.
[0056]
In the method for manufacturing a floor cross member according to the third aspect of the present invention, since the welding is performed by projection welding in the first or second aspect of the present invention, the effects brought by the present invention, that is, the reduction in weight and fatigue strength. It has an excellent effect that the improvement can be achieved most effectively.
[0057]
In the floor cross member structure according to the present invention, the seat rail of the vehicle seat is fixed and the fastener is inserted into the floor cross member lower fixed to the vehicle body floor and having the fastener insertion hole formed therein. In a state in which the floor cross member upper having the fastener insertion hole formed coaxially with the hole is overlapped, the floor cross member lower is formed around the fastener insertion hole or the floor cross member upper around the fastener insertion hole. In a floor cross member structure constituted by fastening one of the fasteners to one of the previously welded fasteners, a protective layer for avoiding metal-to-metal contact on the contact surface between the floor cross member lower and the floor cross member upper Intervening minimizes the occurrence of fretting due to fatigue, resulting in both reduced weight and improved fatigue strength. It has an excellent effect that can be achieved.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a front floor cross member according to the present embodiment.
FIG. 2 is a longitudinal sectional view of a rear floor cross member according to the embodiment.
FIG. 3 is a weld sectional view of a nut with a washer.
FIG. 4 is a graph showing a durable life of a floor cross member member.
[Explanation of symbols]
10 Front floor cross member
12 Front floor cross member lower (lower member)
14 Front floor cross member upper (upper member)
16 Bolt insertion hole (fastener insertion hole)
18 seat rail
22 Bolt insertion hole (fastener insertion hole)
24 Nuts with washers (one of fasteners)
28 Washer
30 bolts (the other of the fasteners)
40 Rear floor cross member
42 Rear floor cross member lower (lower member)
44 Rear floor cross member upper (upper member)
46 Bolt insertion hole (fastener insertion hole)
48 Bolt insertion hole (fastener insertion hole)
50 Nut with washer (one of fasteners)
52 bolts (the other of the fasteners)
54 protective layer
56 protective layer

Claims (4)

A first step of forming a pair of upper and lower floor cross members supporting a seat rail of a vehicle seat by press forming a steel plate;
One of the fasteners is welded to a periphery of a fastener insertion hole formed in a lower member fixed to the vehicle body floor or a periphery of a fastener insertion hole formed in an upper member to which the seat rail is fixed. A second step of pre-joining by
The upper member is overlapped with the lower member so that the fastener insertion hole of the lower member and the fastener insertion hole of the upper member overlap each other, and the other of the fasteners is connected to one of the fasteners. A third step of fastening the lower member and the upper member by tightening
A method of manufacturing a floor cross member having
After performing the second step and before performing the third step, a protective layer having a predetermined thickness is provided on a contact surface between the lower member and the upper member to avoid contact between metals,
A method for manufacturing a floor cross member. A washer is interposed around the fastener insertion hole of the upper member or the lower member to which the other of the fasteners is attached,
Providing the protective layer on the contact surface with the washer or on the washer itself;
The method for manufacturing a floor cross member according to claim 1, wherein: The welding is projection welding;
The method for manufacturing a floor cross member according to claim 1 or 2, wherein: A floor in which a seat rail of a vehicle seat is fixed to a floor cross member lower fixed to a vehicle body floor and formed with a fastener insertion hole, and a fastener insertion hole is formed coaxially with the fastener insertion hole. In a state where the cross member upper is overlapped, the fastener is attached to one of the fasteners which are welded in advance around the fastener insertion hole of the floor cross member lower or the fastener insertion hole of the floor cross member upper. A floor cross member structure constituted by fastening the other,
A protective layer that avoids contact between metals is interposed on the contact surface between the floor cross member lower and the floor cross member upper,
A floor cross member structure characterized by the following.

Images