Steel sheet member combination structure, automotive structural member, center pillar, bumper, and door beam

A steel sheet member combination structure includes: a first steel sheet member having a main wall portion, a standing wall portion that stands from an end edge of the main wall portion, and a flange portion that extends parallel to the main wall portion from an end edge of the standing wall portion; and a second steel sheet member having a horizontal wall portion that is joined to at least one of an inner surface or an outer surface of the first steel sheet member and that abuts the main wall portion and a side wall portion that abuts the standing wall portion, and the first steel sheet member and the second steel sheet member satisfy predetermined relational expressions.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a steel sheet member combination structure, an automotive structural member, a center pillar, a bumper, and a door beam.

The present application claims priority on the basis of Japanese Patent Application No. 2015-163063 filed on Aug. 20, 2015, the content of which is incorporated herein by reference.

RELATED ART

Structural members constituting automotive bodies play a role of limiting the effect, on the inside of cabins, of impact in cases in which an automobile collides with an oncoming vehicle or an obstacle, an automobile is hit from a side of a vehicle body, or the like. For example, as shown inFIG. 17AandFIG. 17B, when an impactor5collides with a lower portion of a center pillar1which is one of structural members constituting an automotive body from a side of a vehicle body, and thus the center pillar receives a load, the lower portion of the center pillar1deforms so as to collapse toward the inside of the vehicle body in the width direction. Then, due to this deformation, the center pillar1absorbs collision energy from the impactor5and suppresses an upper portion of the center pillar1coming inside a cabin, thereby securing the safety of a passenger P.

However, in a case in which the center pillar1is broken before the load from the impactor5is sufficiently sustained, the collision energy from the impactor5cannot be sufficiently absorbed, and consequently, the upper portion of the center pillar1comes inside the cabin as shown inFIG. 17A. In order to prevent the breakage or the like of the center pillar1so as to increase the energy absorption amount, an increase in the sheet thickness of the center pillar1can be considered, but an increase in the sheet thickness leads to an increase in the vehicle weight. Therefore, it becomes important to improve the energy absorption efficiency (energy absorption amount per unit weight) when there is collision.

Patent Document 1 discloses a technique in which a foamed material is provided in a center pillar, thereby increasing the initial reactive force to collision from a side of a vehicle body, suppressing the deformation of the center pillar coming inside a cabin due to collision, and improving the safety of passengers in the cabin.

In addition, Patent Document 2 and Patent Document 3 disclose techniques in which a vulnerable portion such as a hole or a recess bead is formed in a lower portion of a center pillar, thereby inducing deformation due to collision mainly in a lower side portion of a vehicle body, suppressing the deformation coming inside a cabin, and improving the safety of passengers in the cabin.

CITATION LIST

Patent Documents

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

However, in Patent Document 1, raw materials and manufacturing steps become complex, and thus manufacturing costs increase, and the energy absorption amount by the foamed material cannot be said to be sufficient. As a result, in order to improve the energy absorption efficiency in Patent Document 1, a large amount of a foamed material becomes necessary, and the manufacturing costs significantly increase.

In addition, in Patent Document 2 and Patent Document 3, there is a possibility that the vulnerable portion such as a hole may break during collision, and there is a possibility that deformation may concentrate in the vulnerable portion and thus cause local deformation. Therefore, in Patent Document 2 and Patent Document 3, the amount of absorbable energy becomes small, and consequently, it is difficult to improve the energy absorption efficiency.

The present invention has been made in consideration of the above-described circumstances, and an object of the present invention is to provide a steel sheet member combination structure, an automotive structural member, a center pillar, a bumper, and a door beam which are capable of improving the collision energy absorption efficiency at low costs.

Means for Solving the Problem

In order to achieve the above-described object, the present invention employs the followings.

(1) A steel sheet member combination structure according to a first aspect of the present invention includes a first steel sheet member having a main wall portion, a standing wall portion that stands from an end edge of the main wall portion, and a flange portion that extends parallel to the main wall portion from an end edge of the standing wall portion; and a second steel sheet member that is joined to at least one of an inner surface or an outer surface of the first steel sheet member and has a horizontal wall portion that abuts the main wall portion and a side wall portion that abuts the standing wall portion, in which, when larger one of a distance between an outer surface of the flange portion and an outer surface of the main wall portion and a distance between the outer surface of the flange portion and an outer surface of the horizontal wall portion is defined as H (mm), a sum of a sheet thickness of the standing wall portion and a sheet thickness of the side wall portion is defined as t (mm), and larger one of a distance between a tip end surface of the side wall portion and the outer surface of the main wall portion and a distance between the tip end surface of the side wall portion and the outer surface of the horizontal wall portion is defined as H1(mm), the first steel sheet member and the second steel sheet member satisfy Expression (a) and Expression (b).
(H/t)≤20.0  Expression (a)
0.6≤(H1/H)≤1.0  Expression (b)

(2) In the aspect according to (1), the steel sheet member combination structure may further include a first joint portion that joins the standing wall portion of the first steel sheet member and the side wall portion of the second steel sheet member.

(3) In the aspect according to (1) or (2), the steel sheet member combination structure may further include a second joint portion that joins the main wall portion of the first steel sheet member and the horizontal wall portion of the second steel sheet member.

(4) In the aspect according to any one of (1) to (3), the second steel sheet member may be a steel sheet having a tensile strength of 980 MPa or higher.

(5) In the aspect according to (4), the first steel sheet member may be a steel sheet having a tensile strength of 980 MPa or higher.

(6) An automotive structural member according to a second aspect of the present invention includes the steel sheet member combination structure according to any one of (1) to (5).

(7) A center pillar according to a third aspect of the present invention is a center pillar having the steel sheet member combination structure according to any one of (1) to (5), the center pillar including a center pillar inner; a center pillar outer that is constituted of the first steel sheet member of the steel sheet member combination structure and that is joined to the center pillar inner; and a patch member that is constituted of the second steel sheet member of the steel sheet member combination structure and that is joined to at least one of an inner surface or an outer surface of the center pillar outer.

(8) A bumper according to a fourth aspect of the present invention is a bumper having the steel sheet member combination structure according to any one of (1) to (5), the bumper including a baseplate; a bumper main body that is constituted of the first steel sheet member of the steel sheet member combination structure and that is joined to the baseplate; and a patch member that is constituted of the second steel sheet member of the steel sheet member combination structure and that is joined to at least one of an inner surface or an outer surface of the bumper main body.

(9) A door beam according to a fifth aspect of the present invention is a door beam having the steel sheet member combination structure according to any one of (1) to (5), the door beam including a door beam main body constituted of the first steel sheet member of the steel sheet member combination structure; and a patch member that is constituted of the second steel sheet member of the steel sheet member combination structure and that is joined to at least one of an inner surface or an outer surface of the door beam main body.

Effects of the Invention

According to the respective aspects of the present invention, it is possible to improve the collision energy absorption efficiency at low costs.

EMBODIMENTS OF THE INVENTION

Hereinafter, individual embodiments of the present invention will be described in detail with reference to drawings. In the present specification and the drawings, constituent elements having substantially the same functional constitution will be given the same reference symbol and the description thereof will not be repeated.

FIG. 1Ais a schematic perspective view showing a center pillar100(automotive structural member) according to a first embodiment of the present invention. In addition,FIG. 1Bis an exploded perspective view of the center pillar100, (a) is a view showing a center pillar inner110, (b) is a view showing a state in which a center pillar outer120is joined to the center pillar inner110, and (c) is a view showing a patch member130that is joined to the center pillar outer120. In addition,FIG. 2is a cross-sectional view in a direction of the A-A line inFIG. 1A.

As shown inFIG. 1AandFIG. 1B, the center pillar100is long in one direction and includes the center pillar inner110, the center pillar outer120(first steel sheet member) joined to the center pillar inner110, and the patch member130(second steel sheet member) joined to the center pillar outer120. In addition, the center pillar100is disposed on a side of an automotive body in the vertical direction.

In addition, as shown inFIG. 2, a cross-section of the center pillar100which is perpendicular to the longitudinal direction is a hollow cross-section, and, when an impact F is exerted from a side of a vehicle body, the center pillar receives a load from the impact F, bending-deforms, and absorbs collision energy.

As shown inFIG. 2, the center pillar inner110of the center pillar100has a flat sheet shape. In addition, the center pillar inner110is a steel sheet having, for example, a sheet thickness of 0.6 to 1.6 mm and a tensile strength of 980 MPa or higher.

Meanwhile, as the center pillar inner110, a steel sheet having a tensile strength of 1,180 MPa or higher is more preferably used.

The center pillar outer120of the center pillar100is a steel sheet having a sheet thickness of 0.8 to 2.0 mm and a tensile strength of 980 MPa or higher. In addition, as shown inFIG. 2, the center pillar outer120has a hat-like cross-section which is perpendicular to the longitudinal direction and includes a main wall portion121facing the center pillar inner110, a pair of standing wall portions122that vertically stands from both ends121a(both end edges) of the main wall portion121, and a pair of flange portions123that is parallel to the main wall portion121and extends from one end122a(end edge) of each of the standing wall portions122so as to separate from the main wall portion121.

Meanwhile, as the center pillar outer120, a steel sheet having a tensile strength of 1,180 MPa or higher is more preferably used.

In addition, as shown inFIG. 2, the center pillar outer120is joined to an outer surface110a(a surface toward the outside of the vehicle body) of the center pillar inner110by spot-welding the flange portions123. In other words, spot-welding portions150are provided between the outer surface110aof the center pillar inner110and inner surfaces123aof the flange portions123of the center pillar outer120. Meanwhile, the center pillar inner110and the flange portions123of the center pillar outer120may be joined together by means of, for example, laser welding, brazing, or the like instead of spot welding.

In addition, the patch member130of the center pillar100is a steel sheet having a sheet thickness of 0.8 to 3.0 mm and a tensile strength of 980 MPa or higher. In addition, as shown inFIG. 2, the patch member130has a channel-like cross-sectional shape and includes a horizontal wall portion131and a pair of side wall portions132that vertically stands from both ends131a(both end edges) of the horizontal wall portion131.

In addition, the patch member130is joined to an outer surface of the center pillar outer120by spot-welding the side wall portions132and the standing wall portions122of the center pillar outer120and spot-welding the horizontal wall portion131and the main wall portion121of the center pillar outer120. In other words, spot-welding portions160(first joint portions) are formed between outer surfaces122bof the standing wall portions122of the center pillar outer120and inner surfaces132aof the side wall portions132of the patch member130, and spot-welding portions170(second joint portions) are formed between an outer surface121bof the main wall portion121of the center pillar outer120and an inner surface131bof the horizontal wall portion131of the patch member130. Meanwhile, the center pillar outer120and the patch member130may be joined together by means of, for example, laser welding, brazing, or the like instead of spot welding.

As the patch member130, a variety of steel sheets such as a hot-stamped material can be used. In addition, as the patch member130, a steel sheet having a tensile strength of 1,180 MPa or higher is more preferably used, and a steel sheet having a tensile strength of 1,500 MPa or higher is still more preferably used.

The horizontal wall portion131of the patch member130has a shape that follows the shape of the main wall portion121of the center pillar outer120. In addition, the side wall portion132of the patch member130has a shape that follows the shape of the standing wall portion122of the center pillar outer120. That is, in the center pillar100, the horizontal wall portion131of the patch member130abuts the main wall portion121of the center pillar outer120, and the side wall portions132of the patch member130abut the standing wall portions122of the center pillar outer120.

As described above, in the center pillar100, the patch member130is joined to the center pillar outer120, and thus it is possible to reinforce the center pillar outer120. In addition, the patch member130is joined to the center pillar outer120, and thus it is possible to reinforce only necessary portions. Therefore, compared with a case in which the sheet thickness of the entire center pillar outer120is increased, it is possible to reduce an increase in weight.

As shown inFIG. 2, at least a portion of the spot-welding portion160is preferably formed in a range of L1(mm) from a side end surface132b(tip end surface) of the side wall portion132of the patch member130. Here, L1represents 40% of the height (the distance from the side end surface132bof the side wall portion132to an outer surface131cof the horizontal wall portion131) of the side wall portion132of the patch member130. That is, for example, in a case in which the height of the side wall portion132of the patch member130is 60 mm, at least a portion of the spot-welding portion160is preferably formed in a range of L1=24 mm from the side end surface132bof the side wall portion132of the patch member130.

At least a portion of the spot-welding portion170is preferably formed in a range of L2(mm) from the inner surface132aof the side wall portion132. Here, similar to L1, L2represents 40% of the height (the distance from the side end surface132bof the side wall portion132to the outer surface131cof the horizontal wall portion131) of the side wall portion132of the patch member130. Meanwhile, in a case in which an R portion is provided between the main wall portion121and the standing wall portion122, at least a portion of the spot-welding portion170is preferably formed in a range of L2from an R stop.

Next, individual parameters of the center pillar100will be described. In the center pillar100, the center pillar outer120and the patch member130satisfy both Expressions (1) and (2) below.
(H/t)≤20.0  Expression (1)
0.6≤(H1/H)≤1.0  Expression (2)

Here, as shown inFIG. 2, H (mm) represents larger one of the distance between an outer surface123bof the flange portion123and the outer surface121bof the main wall portion121and the distance between the outer surface123bof the flange portion123and the outer surface131cof the horizontal wall portion131. That is, in the center pillar100, since the patch member130is joined to the outer surface of the center pillar outer120, the H represents the distance (height) from the outer surface123bof the flange portion123of the center pillar outer120to the outer surface131cof the horizontal wall portion131of the patch member130.

In addition, t (mm) represents the sum of the sheet thickness of the standing wall portion122of the center pillar outer120and the sheet thickness of the side wall portion132of the patch member130.

In addition, H1(mm) represents a larger distance (height) of the distance between the side end surface132bof the side wall portion132and the outer surface121bof the main wall portion121and the distance between the side end surface132bof the side wall portion132and the outer surface131cof the horizontal wall portion131. That is, in the center pillar100, since the patch member130is joined to the outer surface of the center pillar outer120, the H1represents the distance (height) from the side end surface132bof the side wall portion132to the outer surface131cof the horizontal wall portion131.

In the center pillar100, as described below, the patch member130is joined to the center pillar outer120, and thus the center pillar outer120is reinforced, and both Expression (1) and Expression (2) are satisfied. Therefore, it is possible to improve the energy absorption efficiency when the impact F is exerted. Here, the reason for establishing Expression (1) and Expression (2) is as described below.

In a case in which Expression (1) is not satisfied ((H/t)>20.0): The standing wall portions122of the center pillar outer120easily buckling-deform, and there is a concern that the standing wall portions122may break before sufficiently sustaining the load from the impact. In this case, the load after breakage is received by the center pillar inner110, the main wall portion121of the center pillar outer120, and the horizontal wall portion131of the patch member130. In such a case, when the center pillar100is seen in the longitudinal direction, there is a concern that the center pillar100may deform in a wide range including locations away from an impact point and may come inside the cabin.

In a case in which the lower limit value of Expression (2) is not satisfied (0.6>(H1/H)): The standing wall portions122of the center pillar outer120are incapable of sufficiently obtaining the reinforcement effect of the side wall portions132of the patch member130, and thus the standing wall portions122easily buckling-deform, and there is a concern that the standing wall portions122may break before sufficiently sustaining the load from the impact. In this case, the load after breakage is received by the center pillar inner110, the main wall portion121of the center pillar outer120, and the horizontal wall portion131of the patch member130. In such a case, when the center pillar100is seen in the longitudinal direction, there is a concern that the center pillar100may deform in a wide range including locations away from an impact point and may come inside the cabin.

In a case in which the upper limit value of Expression (2) is not satisfied ((H1/H)>1.0): This case cannot occur in a dimensional sense, and thus it is not possible to join the patch member130to the center pillar outer120. Therefore, it is not possible to sufficiently obtain the reinforcement effect of the patch member130, and thus the standing wall portions122easily buckling-deform, and there is a concern that the standing wall portions122may break before sufficiently sustaining the load from the impact.

In a case in which both Expression (1) and Expression (2) are satisfied: This case is within the scope of the present invention, and it is possible to prevent the standing wall portions122of the center pillar outer120from breaking due to impact. In addition, collision energy can be reliably absorbed by the deformation operation of the standing wall portions122of the center pillar outer120and the side wall portions132of the patch member130.

Meanwhile, regarding Expression (1), from the viewpoint of a breakage-preventing effect, the value of H/t is preferably smaller. For example, H/t is preferably 17.5 or less, more preferably 15.0 or less, and still more preferably 12.5 or less. On the other hand, the lower limit of H/t is not particularly limited, but H/t is, for example, 5.0 or more.

In addition, regarding Expression (2), from the viewpoint of the breakage-preventing effect, H1/H is preferably 0.7 or more, and more preferably 0.8 or more.

An example of deformation occurring in a case in which the impact F is exerted on the center pillar100satisfying both Expressions (1) and (2) is shown inFIG. 3. InFIG. 3, since the center pillar100satisfies both Expressions (1) and (2), the standing wall portions122of the center pillar outer120are sufficiently reinforced by the patch member130, and it is possible to prevent the standing wall portions122from easily buckling-deforming.

On the other hand, an example of deformation occurring in a case in which the impact F is exerted on a center pillar50not satisfying Expression (1) is shown inFIG. 4A. InFIG. 4A, since the center pillar50does not satisfy Expression (1), it is not possible to sufficiently reinforce the standing wall portions122of the center pillar outer120using the patch member130, and the standing wall portions122easily buckling-deform.

In addition, an example of deformation occurring in a case in which the impact F is exerted on a center pillar60not satisfying Expression (2) is shown inFIG. 4B. InFIG. 4B, since the center pillar60does not satisfy Expression (2), it is not possible to sufficiently obtain the reinforcement effect of the patch member130, and the standing wall portions122easily buckling-deform.

As described above, according to the center pillar100of the present embodiment, since the patch member130is joined to the center pillar outer120, it is possible to reinforce only necessary portions without increasing the sheet thickness of the entire center pillar outer120. Therefore, it is possible to reinforce the center pillar outer120while suppressing an increase in the weight of the center pillar100. In addition, since the center pillar outer120and the patch member130satisfy both Expression (1) and Expression (2), in a case in which an impact is exerted from a side of a vehicle body, it is possible to prevent the breakage of the standing wall portions122of the center pillar outer120. Therefore, it is possible to improve the collision energy absorption efficiency at low costs.

Meanwhile, in the center pillar100, a predetermined distance D (mm) is preferably provided between the side end surface132bof the side wall portion132of the patch member130and the outer surface123bof the flange portion123of the center pillar outer120as shown inFIG. 2(D>0). In other words, regarding Expression (2), H1/H is preferably less than 1.0 ((H1/H)<1.0). In this case, since a gap is generated between the side end surface132bof the side wall portion132of the patch member130and the outer surface123bof the flange portion123of the center pillar outer120, it is possible to prevent the side end surface132bof the patch member130from being confined in the flange portion123of the center pillar outer120when the patch member130is deformed by the impact F. Therefore, it is possible to cause the side wall portions132of the patch member130to reliably follow the deformation of the standing wall portions122of the center pillar outer120, and consequently, it is possible to prevent the peeling of the spot-welding portions160.

Meanwhile, the distance D is more preferably set to, for example, 10% or more of H. That is, regarding Expression (2), H1/H is more preferably 0.9 or less.

[Modification Example of First Embodiment]

In the present embodiment, a case in which the channel-like patch member130is joined to the center pillar outer120has been described. However, a pair of patch members140having an L-like cross-sectional shape may be joined to the center pillar outer120as shown inFIG. 5. In this case, the volume of the horizontal wall portions131of the patch members140which abut the main wall portion121of the center pillar outer120becomes small, and thus it is possible to reduce the weight of the center pillar100.

Next, a center pillar200according to a second embodiment of the present invention will be described.

FIG. 6is a horizontal cross-sectional view showing the center pillar200according to the present embodiment. In the center pillar100according to the first embodiment, a case in which the patch member130is joined to the outer surface of the center pillar outer120has been described. In contrast, in the center pillar200according to the present embodiment, the patch member130is joined to an inner surface of the center pillar outer120as shown inFIG. 6.

In the center pillar200, as shown inFIG. 6, the horizontal wall portion131of the patch member130is joined to an inner surface121cof the main wall portion121of the center pillar outer120using the spot-welding portions170, and the side wall portions132of the patch member130are joined to inner surfaces122cof the standing wall portions122of the center pillar outer120using the spot-welding portions160.

That is, the center pillar200according to the present embodiment is, similar to the center pillar100according to the first embodiment, capable of reinforcing the center pillar outer120. In addition, the center pillar200is, similar to the center pillar100according to the first embodiment, capable of improving the collision energy absorption efficiency by satisfying Expression (1) and Expression (2).

Meanwhile, regarding Expression (1) and Expression (2), in the center pillar200, since the patch member130is joined to the inner surface of the center pillar outer120, H (mm) becomes the distance (height) from the outer surface123bof the flange portion123of the center pillar outer120to the outer surface121bof the main wall portion121of the center pillar outer120. In addition, H1(mm) becomes the distance (height) from the side end surface132bof the side wall portion132of the patch member130to the outer surface121bof the main wall portion121of the center pillar outer120.

[Modification Example of Second Embodiment]

In the present embodiment, a case in which the channel-like patch member130is joined to the inner surface of the center pillar outer120has been described. However, the pair of patch members140having an L-like cross-sectional shape may be joined to the inner surface of the center pillar outer120as shown inFIG. 7. In this case, the volume of the horizontal wall portions131of the patch members140which abut the main wall portion121of the center pillar outer120becomes small, and thus it is possible to reduce the weight of the center pillar200.

Next, a bumper300according to a third embodiment of the present invention will be described.

FIG. 8is a schematic perspective view showing the bumper300(automotive structural member) according to a third embodiment of the present invention. In addition,FIG. 9is a cross-sectional view in a direction of the B-B line inFIG. 8. In the first embodiment and the second embodiment, cases in which the center pillar100or the center pillar200includes the patch member130have been described. In contrast, in the present embodiment, the bumper300includes a pair of patch members330.

As shown inFIG. 8andFIG. 9, the bumper300is long in one direction and includes a baseplate310, a bumper main body320(first steel sheet member) joined to the baseplate310, and the pair of patch members330(second steel sheet members) joined to the bumper main body320. In addition, the bumper300is disposed on the front side or rear side of an automotive body.

In addition, as shown inFIG. 9, a cross-section of the bumper300which is perpendicular to the longitudinal direction is a hollow cross-section, and, when the impact F is exerted from the front side or rear side of a vehicle body, the bumper receives a load from the impact F, bending-deforms, and absorbs collision energy.

The baseplate310of the bumper300has a flat sheet shape. In addition, the baseplate310of the bumper300is a steel sheet having, for example, a sheet thickness of 1.4 mm and a tensile strength of 980 MPa or higher.

Meanwhile, as the baseplate310, a steel sheet of 1,180 MPa or higher is more preferably used.

As shown inFIG. 9, the bumper main body320of the bumper300has a hat-like cross-section which is perpendicular to the longitudinal direction and is a steel sheet having a sheet thickness of 0.8 to 2.0 mm and a tensile strength of 980 MPa or higher. In addition, the bumper main body320includes a main wall portion321facing the baseplate310, a pair of standing wall portions322that vertically stands from both ends321aof the main wall portion321, and a pair of flange portions323that is parallel to the main wall portion321and extends from one end322aof each of the standing wall portions322so as to separate from the main wall portion321.

Meanwhile, as the bumper main body320, a steel sheet of 1,180 MPa or higher is more preferably used.

The main wall portion321of the bumper main body320has a protrusion portion324that protrudes toward the baseplate310in a widthwise central portion. In addition, the protrusion portion324has a pair of center-reinforcing wall portions324athat stands toward the baseplate310from the main wall portion321and a flat surface portion324bthat connects the pair of center-reinforcing wall portions324a.

In addition, the bumper main body320is joined to an outer surface310a(a surface toward the outside of the vehicle body) of the baseplate310by spot-welding the flange portions323. In other words, the spot-welding portions150are provided between the outer surface310aof the baseplate310and inner surfaces323aof the flange portions323of the bumper main body320.

The patch member330is a steel sheet having a sheet thickness of 0.8 to 3.0 mm and a tensile strength of 980 MPa or higher. In addition, the patch member330has a channel-like cross-sectional shape that is perpendicular to the longitudinal direction and includes a horizontal wall portion331, a side wall portion332that vertically stands from one end331aof the horizontal wall portion331, and a holding wall portion333that stands from the other end331dof the horizontal wall portion331.

Meanwhile, as the patch member330, a variety of steel sheets such as a hot-stamped material can be used. In addition, as the patch member330, a steel sheet having a tensile strength of 1,180 MPa or higher is more preferably used, and a steel sheet having a tensile strength of 1,500 MPa or higher is still more preferably used.

The patch member330is joined to the outer surface of the bumper main body320by spot-welding the side wall portion332and the standing wall portion322of the bumper main body320, spot-welding the horizontal wall portion331and the main wall portion321of the bumper main body320, and spot-welding the holding wall portion333and the center-reinforcing wall portion324aof the bumper main body320. In other words, the spot-welding portion160is formed between an outer surface322bof the standing wall portion322of the bumper main body320and an inner surface332aof the side wall portion332of the patch member330, the spot-welding portions170are formed between an outer surface321bof the main wall portion321of the bumper main body320and an inner surface331bof the horizontal wall portion331of the patch member330, and a spot-welding portion380is formed between an outer surface324a1of the center-reinforcing wall portion324aof the bumper main body320and an inner surface333aof the holding wall portion333of the patch member330.

The horizontal wall portion331of the patch member330has a shape that follows the shape of the main wall portion321of the bumper main body320. In addition, the side wall portion332of the patch member330has a shape that follows the shape of the standing wall portion322of the bumper main body320. In addition, the holding wall portion333of the patch member330has a shape that follows the shape of the center-reinforcing wall portion324aof the bumper main body320. That is, in the bumper300, the horizontal wall portion331of the patch member330abuts the main wall portion321of the bumper main body320, the side wall portion332of the patch member330abuts the standing wall portion322of the bumper main body320, and the holding wall portion333of the patch member330abuts the center-reinforcing wall portion324aof the bumper main body320.

As described above, in the bumper300, the patch members330are joined to the bumper main body320, and thus it is possible to reinforce the bumper main body320. Therefore, in a case in which the impact F is exerted on the bumper300, it is possible to prevent the breakage or the like of the standing wall portions322of the bumper main body320. In addition, the bumper main body320is reinforced by the patch members330, and thus it is possible to reinforce only necessary portions. Therefore, compared with a case in which the sheet thickness of the entire bumper main body320is increased, it is possible to reduce an increase in weight.

Next, individual parameters of the bumper300will be described. In the bumper300, the bumper main body320and the patch member330satisfy both Expressions (1) and (2) which have been described in the first embodiment.
(H/t)≤20.0  Expression (1)
0.6≤(H1/H)≤1.0  Expression (2)

Here, similar to the case of the first embodiment, H (mm) represents the distance (height) from the outer surface323bof the flange portion323of the bumper main body320to the outer surface331cof the horizontal wall portion331of the patch member330. In addition, t (mm) represents the sum of the sheet thickness of the standing wall portion322of the bumper main body320and the sheet thickness of the side wall portion332of the patch member330. In addition, H1(mm) represents the distance (height) from a side end surface332b(tip end surface) of the side wall portion332of the patch member330to the outer surface331cof the horizontal wall portion331.

In the bumper300, similar to the case of the first embodiment, the patch members330are joined to the bumper main body320, and thus the bumper main body320is reinforced, and both Expression (1) and Expression (2) are satisfied. Therefore, it is possible to improve the energy absorption efficiency when the impact F is exerted.

[Modification Example of Third Embodiment]

In the present embodiment, a case in which the channel-like patch members330are joined to the bumper main body320has been described. However, a pair of patch members340and a pair of patch members345which have an L-like cross-sectional shape may be joined to the bumper main body320as shown inFIG. 10. In this case, the volume of the horizontal wall portions331of the patch members330which abut the main wall portion321of the bumper main body320becomes small, and thus it is possible to further reduce the weight of the bumper300.

Next, a bumper400according to a fourth embodiment of the present invention will be described.

FIG. 11is a horizontal cross-sectional view showing a bumper400according to the present embodiment. In the bumper300of the third embodiment, a case in which the patch members330are joined to the outer surface of the bumper main body320has been described. In contrast, in the bumper400according to the present embodiment, the patch members330are joined to an inner surface of the bumper main body320as shown inFIG. 11.

As shown inFIG. 11, in the bumper400, the horizontal wall portion331of the patch member330is joined to an inner surface of the main wall portion321of the bumper main body320using the spot-welding portions170, and the side wall portion332of the patch member330is joined to an inner surface of the standing wall portion322of the bumper main body320using the spot-welding portion160.

That is, in the bumper400according to the present embodiment, similar to the bumper300according to the third embodiment, it is possible to reinforce the bumper main body320. In addition, the bumper400is, similar to the bumper300according to the third embodiment, capable of improving the collision energy absorption efficiency by satisfying Expression (1) and Expression (2).

Meanwhile, regarding Expression (1) and Expression (2), in the present embodiment, since the patch member330is joined to the inner surface of the bumper main body320, H (mm) becomes the distance (height) from the outer surface323bof the flange portion323of the bumper main body320to the outer surface321bof the main wall portion321of the bumper main body320. In addition, H1(mm) becomes the distance (height) from the side end surface332bof the side wall portion332of the patch member330to the outer surface321bof the main wall portion321of the bumper main body320.

[Modification Example of Fourth Embodiment]

In the present embodiment, a case in which the channel-like patch members330are joined to the inner surface of the bumper main body320has been described. However, the pair of patch members340and the pair of patch members345which have an L-like cross-sectional shape may be joined to the bumper main body320as shown inFIG. 12. In this case, the volume of the horizontal wall portions331of the patch members340and345which abut the main wall portion321of the bumper main body320becomes small, and thus it is possible to further reduce the weight of the bumper400.

Next, a door beam500according to a fifth embodiment of the present invention will be described.

FIG. 13is a schematic perspective view showing the door beam500(automotive structural member) according to the present embodiment. In addition,FIG. 14is a cross-sectional view in a direction of the C-C line inFIG. 13. In the first embodiment, a case in which the center pillar100includes the patch member130has been described. In contrast, in the present embodiment, the door beam500includes patch members530.

As shown inFIG. 13andFIG. 14, the door beam500is long in one direction and includes a door beam main body520(first steel sheet member) and a pair of patch members530(second steel sheet members) joined to the door beam main body520. In addition, the door beam500is disposed in a door of an automobile (not shown) by spot-welding inner surfaces523aof flange portions523of the door beam main body520to the door of the automobile.

The door beam main body520of the door beam500is a steel sheet having a sheet thickness of 0.8 to 2.0 mm and a tensile strength of 980 MPa or higher. In addition, as shown inFIG. 14, the door beam main body520has a hat-like cross-section which is perpendicular to the longitudinal direction and includes a main wall portion521, a pair of standing wall portions522that stands from both ends521aof the main wall portion521, and a pair of the flange portions523that is parallel to the main wall portion521and extends from one end522aof each of the standing wall portions522so as to separate from the main wall portion521.

Meanwhile, as the door beam main body520, a steel sheet having a tensile strength of 1,180 MPa or higher is more preferably used.

The main wall portion521of the door beam main body520has a protrusion portion524which is provided in the widthwise central portion and protrudes toward the flange portion523. In addition, the standing wall portion522of the door beam main body520has a first inclined portion525which is connected to the end521aof the main wall portion521and has a predetermined inclination angle and a second inclined portion526which is connected to the first inclined portion525and has an inclination angle that is different from the above-described inclination angle.

The patch member530of the door beam500is a steel sheet having a sheet thickness of 0.8 to 3.0 mm and a tensile strength of 1,180 MPa or higher. In addition, as shown inFIG. 14, the patch member530has an L-like cross-sectional shape and has a horizontal wall portion531and a side wall portion532that stands from one end531aof the horizontal wall portion531.

In addition, the patch member530is joined to an outer surface of the door beam main body520by spot-welding the horizontal wall portion531and the main wall portion521of the door beam main body520and spot-welding the side wall portions532and the standing wall portions522of the door beam main body520. In other words, the spot-welding portion160is formed between an outer surface522bof the standing wall portion522of the door beam main body520and an inner surface532aof the side wall portion532of the patch member530, and the spot-welding portion170is formed between an outer surface521bof the main wall portion521of the door beam main body520and an inner surface531bof the horizontal wall portion531of the patch member530.

Meanwhile, as the patch member530, a variety of steel sheets such as a hot-stamped material can be used. In addition, as the patch member530, a steel sheet having a tensile strength of 1,180 MPa or higher is more preferably used, and a steel sheet having a tensile strength of 1,500 MPa or higher is still more preferably used.

The horizontal wall portion531of the patch member530has a shape that follows the shape of the main wall portion521of the door beam main body520. In addition, the side wall portion532of the patch member530has a shape that follows the shape of the standing wall portion522of the door beam main body520. That is, in the door beam500, the horizontal wall portion531of the patch member530abuts the main wall portion521of the door beam main body520, and the side wall portion532of the patch member530abuts the standing wall portion522of the door beam main body520.

As described above, in the door beam500, the patch members530are joined to the door beam main body520, and thus it is possible to reinforce the door beam main body520. Therefore, in a case in which the impact is exerted on the door beam500, it is possible to prevent the breakage or the like of the standing wall portions522of the door beam main body520. In addition, the patch members530are joined to the door beam main body520, and thus it is possible to reinforce only necessary portions. Therefore, compared with a case in which the sheet thickness of the entire door beam main body520is increased, it is possible to reduce an increase in weight.

Next, individual parameters of the door beam500will be described. In the door beam500, the door beam main body520and the patch member530satisfy both Expressions (1) and (2) which have been described in the first embodiment.
(H/t)≤20.0  Expression (1)
0.6≤(H1/H)≤1.0  Expression (2)

Here, similar to the case of the first embodiment, H (mm) represents the distance (height) from the outer surface523bof the flange portion523of the door beam main body520to the outer surface531cof the horizontal wall portion531of the patch member530. In addition, t (mm) represents the sum of the sheet thickness of the standing wall portion522of the door beam main body520and the sheet thickness of the side wall portion532of the patch member530. In addition, H1(mm) represents the distance (height) from a side end surface532b(tip end surface) of the side wall portion532of the patch member530to the outer surface531cof the horizontal wall portion531.

In the door beam500, similar to the case of the first embodiment, the patch members530are joined to the door beam main body520, and thus the door beam main body520is reinforced, and both Expression (1) and Expression (2) are satisfied. Therefore, it is possible to improve the energy absorption efficiency when the impact is exerted.

Meanwhile, similar to the case of the first embodiment, the patch members530may also be joined to an inner surface of the door beam main body520as shown inFIG. 15.

EXAMPLES

Next, examples carried out in order to confirm the action effects of the present invention will be described.

An FEM analysis of the three-point bending deformation of a hat-like member which simulated the cross-sectional shape (refer toFIG. 2) of the center pillar100according to the first embodiment was carried out, and the energy absorption amount per unit weight was obtained. Specifically, the hat-like member was supported at two points which were located in the longitudinal direction at a predetermined interval, a predetermined load was applied to the central location of the two points, and the energy absorption amount was obtained. In addition, the energy absorption amount was divided by the weight of the hat-like member, thereby obtaining the energy absorption amount per unit weight. At this time, as the hat-like member, a steel sheet having a tensile strength of 980 MPa was used.

In addition, for comparison, the same analysis was also carried out on cases in which Expression (1) and/or Expression (2) were not satisfied. Meanwhile, in Test Nos. 1 to 11 shown in Table 1, the same conditions were set except for H, t, and H1.

In Table 1, Test Nos.1to4indicate cases in which Expression (1) and/or Expression (2) were not satisfied, that is, comparative examples. On the other hand, Test Nos.5to11indicate cases in which Expression (1) and/or Expression (2) were satisfied, that is, invention examples.

In addition, graphs obtained by plotting the results of Table 1 are shown inFIG. 16AandFIG. 16B. Meanwhile, inFIG. 16A, the horizontal axis indicates H/t, and the vertical axis indicates the energy absorption amount per unit weight EA/mass (kJ/kg). In addition, inFIG. 16B, the horizontal axis indicates H1/H, and the vertical axis indicates the energy absorption amount per unit weight EA/mass (kJ/kg).

As shown in Table 1 and shown inFIG. 16AandFIG. 16B, it could be confirmed that, in the cases in which both Expression (1) and/or Expression (2) were satisfied, the energy absorption amount per unit weight increased compared with the cases in which any one of Expression (1) and Expression (2) was not satisfied and the cases in which both Expression (1) and/or Expression (2) were not satisfied.

While the embodiments of the present invention have been described, but the embodiments are simply examples, and the scope of the present invention is not limited only to the above-described embodiments. The embodiments can be carried out in a variety of other forms and can be omitted, substituted, or modified in various manners within the scope of the gist of the invention. The embodiments or modifications thereof are included in the scope of the invention described in the claims and equivalence thereof as is the case of being included in the scope or gist of the invention.

For example, in the embodiments, the cases in which the automotive structural member is the center pillar, the bumper, or the door beam have been described. However, the present invention is not limited to automotive structural members, and the present invention may be applied to, for example, side sills.

In addition, for example, in the first embodiment, the case in which the patch member130is joined to the inner surface of the center pillar outer120of the center pillar100has been described. However, the patch members130may be joined to both the inner surface and the outer surface of the center pillar outer120.

In addition, for example, in the first embodiment, the case in which the main wall portion121of the center pillar outer120has a flat sheet shape has been described; however, similar to the bumper300, a protrusion portion may be provided in the main wall portion121of the center pillar outer120. In addition, in the third embodiment, the case in which the protrusion portion is provided in the main wall portion321of the bumper main body320has been described, but the main wall portion321may have a flat sheet shape. In addition, in the fifth embodiment, the case in which the protrusion portion is provided in the main wall portion521of the door beam main body520has been described, but the main wall portion521may have a flat sheet shape.

INDUSTRIAL APPLICABILITY

According to the present invention, it is possible to provide a steel sheet member combination structure, an automotive structural member, a center pillar, a bumper, and a door beam which are capable of improving the collision energy absorption efficiency at low costs.

BRIEF DESCRIPTION OF THE REFERENCE SYMBOLS

110: center pillar inner

121: main wall portion of center pillar outer

122: standing wall portion of center pillar outer

123: flange portion of center pillar outer