Battery case side frame

Abstract

The present invention relates to a side frame of a battery case that can sufficiently protect battery cells from external impact while simultaneously achieving weight reduction and cost reduction. In one embodiment, the side frame of the battery case includes a first frame portion formed to have an open cross section, and a second frame portion disposed within the first frame portion so as to close the open cross section of the first frame portion and coupled to the first frame portion, and the first frame portion and the second frame portion may be formed of different materials.

Description

[Technical field]

[0001] The present invention relates to a side frame of a battery case made of different materials to sufficiently protect a battery cell from external impact while simultaneously achieving weight reduction and cost reduction compared to a single material. [Background technology]

[0002] For example, battery systems used in electric vehicles use a variety of load-bearing members to protect the internal battery cells.

[0003] A typical example is a side frame of a battery case, which surrounds the battery cells while forming side walls that partition the space in which the battery cells are mounted in the battery case, and protects the battery cells from external impacts.

[0004] In addition, the side frames allow a mounting frame, which is required for fixing the battery case to the vehicle body, to be attached to the sides.

[0005] Usually, the side frames and battery cases are mainly manufactured using aluminum or aluminum alloys, because aluminum has advantages such as the light weight of the material itself and the molding flexibility that allows side frames with complex cross sections to be easily manufactured using an extrusion process.

[0006] However, despite the aforementioned advantages, aluminum or aluminum alloys are much more expensive than steel and the extrusion process has very low production yields, increasing costs.

[0007] Related prior art includes the invention disclosed in Korean Patent Publication No. 2019-0131415A. Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a side frame for a battery case that can adequately protect a battery cell from external impact while simultaneously achieving weight reduction and cost reduction. [Means for solving the problem]

[0009] A side frame of a battery case according to one embodiment of the present invention includes a first frame portion formed to have an open cross-section, and a second frame portion disposed within the first frame portion to close the open cross-section of the first frame portion and coupled to the first frame portion, and the first frame portion and the second frame portion may be formed of different materials.

[0010] A side frame of a battery case according to another embodiment of the present invention includes a first frame portion formed to have a closed cross-section, and a second frame portion inserted into the first frame portion and coupled to the first frame portion, and the first frame portion and the second frame portion may be formed of different materials. Effect of the Invention

[0011] According to the present invention, by forming the side frame from different materials, it is possible to uniformly utilize the advantages of the extrusion material and the rigid material, thereby not only providing sufficient structural rigidity but also achieving weight reduction and cost reduction. [Brief description of the drawings]

[0012] [Figure 1] 1 is a perspective view showing a battery case to which a side frame according to the present invention is applied; [Diagram 2] 1 is a cross-sectional view showing a side frame according to a first embodiment of the present invention. [Diagram 3] FIG. 4 is a cross-sectional view showing a side frame according to a second embodiment of the present invention. [Figure 4] FIG. 11 is a cross-sectional view showing a side frame according to a third embodiment of the present invention. [Diagram 5]4 is a graph comparing the performance of a conventional side frame made of aluminum material and a side frame having different materials according to the present invention in a side collision. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present invention will now be described in detail with reference to the exemplary drawings. It should be noted that when referring to the components in each drawing, the same components are designated by the same reference numerals as far as possible even if they are shown in different drawings.

[0014] FIG. 1 is a perspective view showing a battery case to which a side frame according to the present invention is applied.

[0015] The battery case may include a first case 1 and a second case 2.

[0016] The first case 1 may include a base plate 20 and a side frame 10 surrounding the base plate. The base plate of the first case may act as a floor material supporting the battery cells, and the side frame may constitute a side wall of the first case.

[0017] The base plate 20 and the side frame 10 can be joined together by welding or the like to form an integrated unit. This allows the first case 1 to have a space within the side frame that forms a closed cross section around the base plate.

[0018] For example, at least four side frames 10 are provided to surround the base plate 20. Both ends of each side frame may be joined to corresponding ends of the other corresponding side frames by welding or the like.

[0019] The second case 2 may be made of a simple flat plate or may include a body 3 having a hollow portion and a flange 4 formed at an end of the body. When the body has a hollow portion, the second case may be manufactured by forming a material having a suitable strength into a predetermined shape using a press.

[0020] The first and second cases are joined together such that the main body 3 of the second case 2 covers the space of the first case 1, thereby forming an accommodation space therein for accommodating battery cells.

[0021] The first and second cases 1, 2 can be joined together, for example, by using a bolting process, i.e., by fastening bolts (not shown) after the flanges 4 formed at the ends of the main body 3 and the side frames 10 overlap each other.

[0022] Meanwhile, evaluation of side impact is important in evaluating the performance of a battery case. Evaluation of side impact is performed by applying impact to the side of a side frame, which has a roughly rectangular cross section, of the battery case with a rigid cylinder to ensure that the battery case can withstand a certain level of collision load. If there is no contact between the side frame and the battery cell before the certain level of collision load is reached, the battery case is evaluated as satisfying the collision performance.

[0023] In evaluating a side collision, the deformation mode of the side frame can be roughly divided into a buckling mode in the early stage of the collision and a bending mode in the later stage of the collision.

[0024] At the initial stage of a collision, which is the first impact point within a few milliseconds (msec), concentrated deformation occurs at the side frame where it comes into contact with the rigid body. At the initial stage of a collision, concentrated forces are applied to the cross members in the width direction (Y direction) of the cross-sectional structure of the side frame, and when buckling occurs in the cross members, the buckling point becomes a plastic hinge, and the cross members lose their function as structural members.

[0025] In order to minimize the buckling and plastic hinge phenomena, the thickness of the material that constitutes the side frame needs to be increased. For example, aluminum material is lighter than steel material and can be designed to be thicker, but steel material can only be made thinner to reduce weight, and side frames made of steel material are very vulnerable to the buckling mode at the beginning of a collision.

[0026] For this reason, side frames made of steel are heavier and have inferior performance than side frames made of aluminum or aluminum alloy materials.

[0027] When the above-mentioned initial buckling mode of the collision ends, the cross-sectional structure of the side frame suddenly collapses, and the concentrated deformation changes to bending deformation of the entire side frame. In other words, the deformation of the side frame switches to a bending mode similar to three-point bending, and at this time, the role of the vertical members in the height direction (Z direction) of the cross-sectional structure of the side frame becomes much larger than that of the horizontal members.

[0028] In the bending mode, the vertical members are subjected to maximum compression or tension, so the strength of the vertical members becomes an important factor. For example, a side frame made of high-strength steel can increase bending resistance and is advantageous in withstanding the compressive or tensile stresses that occur in the bending mode.

[0029] Due to the deformation characteristics of the side frame, the thickness of the horizontal members is important in the early stage of the collision, while the strength of the vertical members is an important factor in the later stage of the collision. However, no single material satisfies both of the above two conditions.

[0030] Furthermore, a conventional battery case is provided with a mount frame that is coupled to one side of the side frame in order to secure the battery case to the vehicle body.

[0031] Here, the member that first comes into contact with the rigid body in the early stage of a collision is the mount frame, and if the side frame is designed to be sufficiently sturdy, the buckling mode in the early stage of a collision will occur in the mount frame rather than the side frame.

[0032] Conversely, if the mounting frame is stronger than the side frame, the buckling mode will likely occur in the side frame.

[0033] As a result, the mount frame also requires mechanical considerations such as the buckling mode at the beginning of a collision. However, the mount frame and side frames are usually manufactured separately and then joined by welding or the like, which results in an imbalance in the mechanical balance between the mount frame and side frames, and the battery case inevitably has structural weaknesses.

[0034] Therefore, in the side frame of the battery case according to the present invention, different materials are used for the horizontal and vertical members, and the mounting frame is integrated into the side frame to satisfy the mechanical properties required of the side frame and maximize the efficiency of the structure.

[0035] FIG. 2 is a cross-sectional view showing a side frame according to a first embodiment of the present invention.

[0036] The side frame 10 according to the first embodiment of the present invention may include a first frame portion 30 and a second frame portion 40.

[0037] The first frame portion 30 can be formed by bending a single plate material having a predetermined width and length multiple times so as to have, for example, an L-shaped cross section. This allows the first frame portion to have a hollow portion with an open cross section inside.

[0038] The first frame portion 30 may include a first vertical member 32 having a first height H1; a first horizontal member 31 having one end connected to the lower end of the first vertical member and extending in the width direction by a first length L1; a second vertical member 34 spaced from the first vertical member by a second length L2 shorter than the first length and having a second height H2 shorter than the first height; a second horizontal member 33 connecting the upper end of the first vertical member and the upper end of the second vertical member; and a third horizontal member 35 having one end connected to the lower end of the second vertical member and extending in the width direction by a third length L3 shorter than the first length.

[0039] The first frame portion 30 may be integrally formed, for example, by machining a single plate material such as a metal.

[0040] For example, the plate material is extended in the width direction (Y direction) by a first length L1 from one end to form the first horizontal member 31, and then folded once in the first direction (clockwise in FIG. 2). Next, it is raised in the height direction (Z direction) by a first height H1 to form the first vertical member 32, and then folded once in the same direction. It is extended in the width direction by about a second length L2 to form the second horizontal member 33, and then folded once more in the same direction. Next, it is lowered in the height direction by a second height H2 to form the second vertical member 34, and then folded once in the second direction (counterclockwise in FIG. 2), which is opposite to the first folding direction. It is then extended in the width direction by a third length L3 to form the third horizontal member 35.

[0041] This process of extending to a desired length and then bending is repeated until an open cross section is formed with the desired number of horizontal members 31, 33, 35 and vertical members 32, 34, and then the plate is terminated at the other end.

[0042] Thus, the first frame portion 30 may include a wall portion 37 having a first height H1, and a protrusion 38 extending from the wall portion to one side in the width direction (Y direction) by a third length L3.

[0043] The wall portion 37 may be defined by approximately the first vertical member 32, a portion of the first horizontal member 31, the second vertical member 34, and the second horizontal member 33. The protrusion 38 may be formed by the third horizontal member 35 and a portion of the first horizontal member 31 corresponding thereto.

[0044] The wall portion 37 corresponds to an existing side frame, while the protrusion portion 38 corresponds to an existing mount frame. As a result, in the side frame 10 according to the first embodiment of the present invention, the mount frame can be integrated into the side frame and formed integrally with the side frame.

[0045] In addition, in the first frame portion 30, the first vertical member 32 and the second vertical member 34 can be spaced apart from each other by a second length L2, and the first horizontal member 31 and the third horizontal member 33 can be spaced apart from each other by the height difference between the first height H1 and the second height H2, and can have an opening 39 between the end of the first horizontal member and the end of the third horizontal member.

[0046] As a result, the protrusion 38 of the first frame portion 30 may include an opening 39, and the protrusion and the opening have a height that corresponds to the height difference between the first height H1 and the second height H2.

[0047] Here, the horizontal members and the vertical members are not necessarily formed completely horizontally or vertically, but may have an inclination, so that the separation distance and height difference may be variable.

[0048] The first frame portion 30 formed in this manner can constitute the exterior of the side frame 10.

[0049] The first frame portion 30 is formed long to have a predetermined length, and one side surface, such as a bottom surface, of the first cross member 31 may be joined to the base plate 20 by joining, such as welding.

[0050] The second frame portion 40 may be formed long to have a predetermined length and may be formed of a tube member having a substantially rectangular cross section with a constant height and width, so that the second frame portion may have a hollow portion with a closed cross section inside.

[0051] The second frame portion may include a first horizontal member 41 and a second horizontal member 43 spaced apart from each other in the height direction (Z direction), and a first vertical member 42 and a second vertical member 44 spaced apart from each other in the width direction (Y direction) and connecting the first horizontal member and the second horizontal member.

[0052] Here, the thickness of the first horizontal member 41 and the second horizontal member 43 may be formed to be thicker than the thickness of the first vertical member 42 and the second vertical member 44. For example, the horizontal members may have a thickness three or more times that of the vertical members.

[0053] Also, at least the lateral members 41 , 43 of the second frame portion 40 may have a greater thickness than the first frame portion 30 .

[0054] The height of the second frame portion 40 may correspond to the height of the open portion 39 of the first frame portion 30, and the width of the second frame portion may correspond to the first length L1 of the first cross member 31 of the first frame portion. In other words, the first cross member 41 and the second cross member 43 may have the same length as the first length L1.

[0055] The second frame portion 40 can be positioned within the first frame portion 30 in alignment with at least the protrusion 38, and the open cross-section of the first frame portion, i.e., the open portion 39, can be closed to form the entire side frame 10 with a closed cross-section.

[0056] The second frame portion 40 thus formed and arranged can constitute the interior of the side frame 10.

[0057] In the side frame 10 according to the first embodiment of the present invention, the first frame portion 30 and the second frame portion 40 may be made of different materials.

[0058] For example, the first frame portion 30 may be made of a heavy metal material such as steel having a specific gravity of 4 or more. The second frame portion 40 may be made of a material having a specific gravity lower than that of the first frame portion.

[0059] Alternatively, the second frame portion 40 can be made of a material having a higher specific strength than the first frame portion 30 .

[0060] More specifically, the first frame portion 30 may be made of a plate material such as 1470MART (Martensitic) steel having a thickness of about 0.5 mm to 1.5 mm, which is manufactured by the present applicant. Here, 1470MART steel is a type of steel that has improved collision safety by having a tensile strength of 1,470 MPa or more and a yield strength of 1,050 MPa or more.

[0061] In this case, the first frame part 30 may be formed by bending, roll forming, press forming, or the like.

[0062] The second frame portion 40 can be made of a material that can be molded by extrusion, for example, a light metal such as aluminum or an alloy thereof, a plastic, a composite material, or the like.

[0063] As such, since the first frame portion 30 and the second frame portion 40 are formed from different materials, the first frame portion and the second frame portion can be joined to each other by mechanical bonding using fasteners such as rivets 51, and chemical bonding using an adhesive 52 such as a structural adhesive.

[0064] When assembling the side frame 10 according to the first embodiment of the present invention, first, the first frame portion 30 and the second frame portion 40, which are formed separately, are moved relative to each other in the longitudinal direction (X direction), and the second frame portion can be fitted into the protrusion 38 in the first frame portion.

[0065] Next, the first vertical member 32 of the first frame part 30 can be connected to the first vertical member 42 of the second frame part 40 by a rivet 51. The first horizontal member 31 of the first frame part and the first horizontal member 41 of the second frame part, and the third horizontal member 35 of the first frame part and the second horizontal member 43 of the second frame part can be bonded to each other with an adhesive 52 interposed therebetween.

[0066] Such adhesive 52 not only bonds the first frame portion 30 and the second frame portion 40, but also has the effect of preventing corrosion caused by direct contact between dissimilar materials, for example, when the first frame portion is made of steel and the second frame portion is made of aluminum.

[0067] Of course, the assembly method is not necessarily limited to the above example, and a combination of fasteners such as rivets 51 and an adhesive 52 such as a structural adhesive can be used to join the first frame portion 30 and the second frame portion 40.

[0068] This allows the second frame portion 40 made of a lightweight material to provide an additional cross member (i.e., the second cross member 43) within the first frame portion 30 made of a high strength material, or to add at least additional thickness to the first and third cross members 31, 35.

[0069] The side frame 10 according to the first embodiment of the present invention comprises a first frame portion 30 and a second frame portion 40 made of different materials, with lightweight materials used in areas requiring thick horizontal members and high-strength materials used in vertical members which require strength. The side frame is integrated with a mounting frame, thereby offering the advantage of achieving a highly efficient structure with high performance and low cost.

[0070] As a result, in the early stage of the collision, the thick horizontal members can prevent buckling and plastic hinge phenomena, and in the later stage of the collision, the high-strength vertical members can accommodate bending deformation.

[0071] In addition, taking into consideration the role of the mount frame to receive the initial impact, the cross member is extended to the position of the existing mount frame and the outside is surrounded by high-strength material, allowing the side frame alone to satisfy the mechanical properties and maximize the efficiency of the structure.

[0072] FIG. 3 is a cross-sectional view showing a side frame according to a second embodiment of the present invention.

[0073] The side frame 10 according to the second embodiment of the present invention may include a first frame portion 30 and a second frame portion 40.

[0074] The first frame portion 30 can be formed by bending a single plate material having a predetermined width and length multiple times so as to have, for example, an L-shaped cross section. This allows the first frame portion to have a hollow portion with an open cross section inside.

[0075] The first frame portion 30 may include a first vertical member 32 having a first height H1; a first horizontal member 31 having one end connected to the lower end of the first vertical member and extending in the width direction by a first length L1; a second vertical member 34 spaced from the first vertical member by a second length L2 shorter than the first length and having a second height H2 shorter than the first height; a second horizontal member 33 connecting the upper end of the first vertical member and the upper end of the second vertical member; a third vertical member 36 having a lower end connected to the other end of the first horizontal member and having a third height H3 shorter than the first height; and a third horizontal member 35 having one end connected to the upper end of the third vertical member and extending in the width direction toward the first vertical member by a third length L3 shorter than the first length.

[0076] The first frame portion 30 can be integrally formed, for example, by machining a single plate material such as a metal.

[0077] For example, the plate material is extended in the width direction (Y direction) by the third length L3 from one end to form the third horizontal member 35, and then folded once in the first direction (clockwise in FIG. 3). Next, it is lowered in the height direction (Z direction) by the third height H3 to form the third vertical member 36, and then folded once in the same direction. Next, it is extended in the width direction by the first length L1 to form the first horizontal member 31, and then folded once in the same direction. Next, it is raised in the height direction by the first height H1 to form the first vertical member 32, and then folded once in the same direction. It is extended in the width direction by the second length L2 to form the second horizontal member 33, and then folded once more in the same direction. Then, it is lowered in the height direction by the second height H2 to form the second vertical member 34.

[0078] This process of extending to a desired length and then bending is repeated until an open cross section is formed with the desired number of horizontal members 31, 33, 35 and vertical members 32, 34, 36, and then the plate is terminated at the other end.

[0079] As a result, the first frame portion 30 can include a wall portion 37 having a first height H1 and a protrusion portion 38 extending from the wall portion to one side in the width direction (Y direction) by a third length L3 or slightly longer than the third length.

[0080] The wall portion 37 can be defined approximately by the first vertical member 32, a portion of the first horizontal member 31, the second vertical member 34, and the second horizontal member 33. The protrusion 38 can be defined by the third horizontal member 35, a portion of the first horizontal member 31 corresponding thereto, and the third vertical member 36.

[0081] In the side frame 10 according to the second embodiment of the present invention, the mount frame can be integrated into the side frame and formed integrally therewith.

[0082] Furthermore, in the first frame portion 30, the first vertical member 32 and the second vertical member 34 can be spaced apart from each other by a second length L2, and the first vertical member 32 and the third vertical member 36 can be spaced apart from each other by a first length L1.

[0083] Additionally, the first frame portion 30 may have an opening 39 between an end of the second vertical member 34 and an end of the third horizontal member 35 .

[0084] As a result, the first frame portion 30 can include an opening 39 between the wall portion 37 and the protrusion portion 38, and the opening has a height corresponding to the remainder obtained by subtracting the sum of the second height H2 and the third height H3 from the first height H1.

[0085] Here, the horizontal members and the vertical members are not necessarily formed completely horizontally or vertically, but may have an inclination, so that the distance between them may be variable.

[0086] The first frame portion 30 formed in this manner can constitute the exterior of the side frame 10.

[0087] The first frame portion 30 is formed long to have a predetermined length, and one side surface, such as a bottom surface, of the first cross member 31 may be joined to the base plate 20 by joining, such as welding.

[0088] The second frame portion 40 may be formed long to have a predetermined length and may be formed of a tube member having a substantially rectangular cross section with a constant height and width, so that the second frame portion may have a hollow portion with a closed cross section inside.

[0089] The second frame portion 40 may include a first horizontal member 41 and a second horizontal member 42 spaced apart from each other in the height direction (Z direction), and a first vertical member 42 and a second vertical member 44 spaced apart from each other in the width direction (Y direction) and connecting the first horizontal member and the second horizontal member.

[0090] The second frame portion 40 may further include a third transverse member 45 extending from the second vertical member 44 to or parallel to the first transverse member 41, and a third vertical member 46 extending from the first transverse member 41 to or parallel to the first vertical member 42.

[0091] Here, the thickness of each of the first horizontal member 41, the second horizontal member 43, and the third horizontal member 45 may be formed to be thicker than the thickness of each of the first vertical member 42, the second vertical member 44, and the third vertical member 46. For example, the horizontal members may have a thickness three or more times that of the vertical members.

[0092] Also, at least the lateral members 41 , 43 , 45 of the second frame portion 40 may have a greater thickness than the first frame portion 30 .

[0093] In the second frame portion 40, the first lateral member 41 and the second lateral member 43 may have the same length as the second length L2.

[0094] The second frame portion 40 can be positioned within the first frame portion 30 in alignment with at least the wall portion 37, and the open cross-section of the first frame portion, i.e., the open portion 39, can be closed to form the entire side frame 10 with a closed cross-section.

[0095] The third longitudinal member 46 of the second frame portion 40 may be supported by the first longitudinal member 32 of the first frame portion 30 .

[0096] The third cross member 45 of the second frame part 40 may be disposed on the third cross member 35 of the first frame part 30 .

[0097] However, the arrangement of the third horizontal member 45 of the second frame portion 40 is not necessarily limited to this. For example, the third horizontal member of the second frame portion may be arranged between the third horizontal member 35 and the first horizontal member 31 of the first frame portion 30, and then an end of the third horizontal member may be supported by abutting against the third vertical member 36 of the first frame portion.

[0098] The second frame portion 40 thus formed and arranged can constitute the interior of the side frame 10.

[0099] In the side frame 10 according to the second embodiment of the present invention, the first frame portion 30 and the second frame portion 40 may be made of different materials, similar to the first embodiment.

[0100] For example, the first frame portion 30 may be made of a heavy metal material such as steel, and the second frame portion 40 may be made of a material having a lower specific gravity than the first frame portion.

[0101] Alternatively, the second frame portion 40 can be made of a material having a higher specific strength than the first frame portion 30 .

[0102] More specifically, the first frame portion 30 can be made of a plate material such as 1470MART steel having a thickness of about 0.5 mm to 1.5 mm, which is produced by the present applicant.

[0103] In this case, the first frame portion 30 can be formed by bending, roll forming, press forming, or the like.

[0104] Also, the second frame portion 40 can be made of a material that can be formed by extrusion, for example, a light metal such as aluminum or an alloy thereof, a plastic, or a composite material.

[0105] As such, since the first frame portion 30 and the second frame portion 40 are formed of different materials, the first frame portion and the second frame portion can be joined to each other by mechanical bonding using fasteners such as rivets 51 and chemical bonding using an adhesive 52 such as a structural adhesive.

[0106] When assembling the side frame 10 according to the second embodiment of the present invention, first, the first frame portion 30 and the second frame portion 40, which are formed separately, are moved relative to each other in the longitudinal direction (X direction), and the second frame portion can be fitted into the wall portion 37 inside the first frame portion.

[0107] Then, the first vertical member 32 of the first frame portion 30 can be connected to the first vertical member 42 and the third vertical member 46 of the second frame portion 40 by rivets 51. The second vertical member 34 of the first frame portion can be connected to the second vertical member 44 of the second frame portion by rivets 51. The third horizontal member 35 of the first frame portion 30 and the third horizontal member 45 of the second frame portion 40 can be joined to each other with an adhesive 52 interposed therebetween.

[0108] Such adhesive 52 not only bonds the first frame portion 30 and the second frame portion 40, but also has the effect of preventing corrosion caused by direct contact between dissimilar materials, for example, when the first frame portion is made of steel and the second frame portion is made of aluminum.

[0109] Of course, the assembly method is not necessarily limited to the above example, and a combination of fasteners such as rivets 51 and an adhesive 52 such as a structural adhesive can be used to join the first frame portion 30 and the second frame portion 40.

[0110] This allows the second frame portion 40 made of a lightweight material to provide additional cross members (i.e., the first cross member 41 and the second cross member 43) within the first frame portion 30 made of a high strength material, while also adding thickness to the third cross member 35.

[0111] The side frame 10 according to the second embodiment of the present invention includes a first frame portion 30 and a second frame portion 40 made of different materials, with lightweight materials used in areas requiring thick horizontal members and high-strength materials used in vertical members requiring strength. The side frame is integrated with a mounting frame, thereby achieving an extremely efficient structure with high performance and low cost.

[0112] As a result, in the early stage of the collision, the thick horizontal members can prevent buckling and plastic hinge phenomena, and in the later stage of the collision, the high-strength vertical members can accommodate bending deformation.

[0113] In addition, taking into consideration the role of the mount frame to receive the initial impact, the cross member is extended to the position of the existing mount frame and the outside is surrounded by high-strength material, allowing the side frame alone to satisfy the mechanical properties and maximize the efficiency of the structure.

[0114] FIG. 4 is a cross-sectional view showing a side frame according to a third embodiment of the present invention.

[0115] The side frame 10 according to the third embodiment of the present invention may include a first frame portion 30 and a second frame portion 40.

[0116] The first frame portion 30 can be formed by bending a single plate material having a predetermined width and length multiple times to have an L-shaped cross section, and then welding the adjacent ends. This allows the first frame portion to have a hollow portion with a closed cross section inside.

[0117] The first frame portion 30 may include a first vertical member 32 having a first height H1; a first horizontal member 31 having one end connected to the lower end of the first vertical member and extending in the width direction by a first length L1; a second vertical member 34 spaced from the first vertical member by a second length L2 shorter than the first length and having a second height H2 shorter than the first height; a second horizontal member 33 connecting an upper end of the first vertical member and an upper end of the second vertical member; a third vertical member 36 having a lower end connected to the other end of the first horizontal member and having a third height H3 shorter than the first height; and a third horizontal member 35 connecting a lower end of the second vertical member and an upper end of the third vertical member and having a third length L3 shorter than the first length.

[0118] The first frame portion 30 can be integrally formed, for example, by machining a single plate material such as a metal.

[0119] For example, the plate material is lowered in the height direction (Z direction) by the second height H2 from one end to form the second vertical member 34, and then folded once in the second direction (counterclockwise in FIG. 4). Next, it is extended in the width direction (Y direction) by the third length L3 to form the third horizontal member 35, and then folded once in the first direction (clockwise in FIG. 4) that is opposite to the initial folding direction. Next, it is lowered in the height direction by the third height H3 to form the third vertical member 36, and then folded once in the same first direction. Next, it is extended in the width direction by the first length L1 to form the first horizontal member 31, and then folded once in the same direction. Next, it is raised in the height direction by the first height H1 to form the first vertical member 32, and then folded once in the same direction. Next, it is extended in the width direction by the second length L2 to form the second horizontal member 33, and then folded once more in the same direction. Then, the other end of the plate material is welded to the one end to form the welded part 53.

[0120] After extending the plate to a desired length, the plate is folded and folded repeatedly until a closed section is formed with a desired number of horizontal members 31, 33, 35 and vertical members 32, 34, 36, and then both ends of the plate are connected by welding.

[0121] Thus, the first frame portion 30 may include a wall portion 37 having a first height H1, and a protrusion 38 extending from the wall portion to one side in the width direction (Y direction) by a third length L3.

[0122] The wall portion 37 can be defined approximately by the first vertical member 32, a portion of the first horizontal member 31, the second vertical member 34, and the second horizontal member 33. The protrusion 38 can be defined by the third horizontal member 35, a portion of the first horizontal member 31 corresponding thereto, and the third vertical member 36.

[0123] In the side frame 10 according to the third embodiment of the present invention, the mount frame can be integrated into the side frame and formed integrally therewith.

[0124] Furthermore, in the first frame portion 30, the first vertical member 32 and the second vertical member 34 can be spaced apart from each other by a second length L2, and the first vertical member 32 and the third vertical member 36 can be spaced apart from each other by a first length L1.

[0125] In addition, in the first frame portion 30, the first horizontal member 31 and the third horizontal member 35 can be spaced apart from each other by a third height H3.

[0126] Here, the horizontal members and the vertical members are not necessarily formed completely horizontally or vertically, but may have an inclination, so that the distance between them may be variable.

[0127] The first frame portion 30 formed in this manner can constitute the exterior of the side frame 10.

[0128] The first frame portion 30 is formed long to have a predetermined length, and one side surface, such as a bottom surface, of the first cross member 31 may be joined to the base plate 20 by joining, such as welding.

[0129] The second frame portion 40 may be formed to have a predetermined length and may be formed of a tube member having a substantially rectangular cross section with a constant height and width, so that the second frame portion may have a hollow portion with a closed cross section inside.

[0130] The second frame portion 40 may include a first horizontal member 41 and a second horizontal member 42 spaced apart from each other in the height direction (Z direction), and a first vertical member 42 and a second vertical member 44 spaced apart from each other in the width direction (Y direction) and connecting the first horizontal member 42 and the second horizontal member.

[0131] The second frame portion 40 may further include a third transverse member 45 extending from the second vertical member 44 to or parallel to the first transverse member 41, and a third vertical member 46 extending from the first transverse member 41 to or parallel to the first vertical member 42.

[0132] Here, the thickness of each of the first horizontal member 41, the second horizontal member 43, and the third horizontal member 45 may be formed to be thicker than the thickness of each of the first vertical member 42, the second vertical member 44, and the third vertical member 46. For example, the horizontal members may have a thickness three or more times that of the vertical members.

[0133] Also, at least the lateral members 41 , 43 , 45 of the second frame portion 40 may have a greater thickness than the first frame portion 30 .

[0134] In the second frame portion 40, the first lateral member 41 and the second lateral member 43 can have the same length as the second length L2. The second frame portion can be positioned within the first frame portion in alignment with at least the wall portion 37.

[0135] The third longitudinal member 46 of the second frame portion 40 may be supported by the first longitudinal member 32 of the first frame portion 30 .

[0136] The third transverse member 45 of the second frame part 40 is positioned between the third transverse member 35 and the first transverse member 31 of the first frame part 30, and then the end of the third transverse member can be abutted against and supported by the third vertical member 36 of the first frame part.

[0137] The second frame portion 40 thus formed and arranged can constitute the interior of the side frame 10.

[0138] In the side frame 10 according to the third embodiment of the present invention, the first frame portion 30 and the second frame portion 40 may be made of different materials, similar to the first and second embodiments.

[0139] For example, the first frame portion 30 may be made of a heavy metal material such as steel, and the second frame portion 40 may be made of a material having a lower specific gravity than the first frame portion.

[0140] Alternatively, the second frame portion 40 can be made of a material having a higher specific strength than the first frame portion 30 .

[0141] More specifically, the first frame portion 30 can be made of a plate material such as 1470MART steel having a thickness of about 0.5 mm to 1.5 mm, which is produced by the present applicant.

[0142] In this case, the first frame portion 30 can be formed by roll forming or the like.

[0143] Also, the second frame portion 40 can be made of a material that can be formed by extrusion, for example, a light metal such as aluminum or an alloy thereof, a plastic, or a composite material.

[0144] As such, since the first frame portion 30 and the second frame portion 40 are formed from different materials, the first frame portion and the second frame portion can be joined to each other by mechanical bonding using fasteners such as rivets 51, and chemical bonding using an adhesive 52 (see Figure 2 or Figure 3), such as a structural adhesive.

[0145] When assembling the side frame 10 according to the third embodiment of the present invention, first, the first frame portion 30 and the second frame portion 40, which are formed separately, are moved relative to each other in the longitudinal direction (X direction), and the second frame portion can be fitted into the wall portion 37 inside the first frame portion.

[0146] The first longitudinal member 32 of the first frame part 30 can then be joined to the first longitudinal member 42 and the third longitudinal member 46 of the second frame part 40 by rivets 51. The second longitudinal member 34 of the first frame part can be joined to the second longitudinal member 44 of the second frame part by rivets 51.

[0147] However, the assembly method is not necessarily limited to the above example, and a combination of fasteners such as rivets 51 and an adhesive such as a structural adhesive can be used to join the first frame portion 30 and the second frame portion 40.

[0148] This allows the second frame portion 40 made of a lighter material to provide additional cross members (ie, the first cross member 41 and the second cross member 43) within the first frame portion 30 made of a higher strength material.

[0149] The side frame 10 according to the third embodiment of the present invention includes a first frame portion 30 and a second frame portion 40 made of different materials, with lightweight materials used in areas requiring thick horizontal members and high-strength materials used in vertical members requiring strength. The side frame is integrated with a mounting frame, thereby achieving an extremely efficient structure with high performance and low cost.

[0150] As a result, the thick horizontal members can prevent buckling and plastic hinge phenomena in the early stages of a collision, and the high-strength vertical members can accommodate bending deformation in the later stages of the collision.

[0151] In addition, taking into consideration the role of the mount frame to receive the initial impact, the cross member is extended to the position of the existing mount frame and the outside is surrounded by high-strength material, allowing the side frame alone to satisfy the mechanical properties and maximize the efficiency of the structure.

[0152] FIG. 5 is a graph comparing the performance of a conventional side frame made of aluminum material and a side frame made of different materials according to the present invention during a side collision.

[0153] The applicant conducted a performance analysis by simulation on the side frame according to the second embodiment of the present invention.

[0154] In relation to the ability to withstand a certain level of collision load when a rigid cylinder impacts the side of the side frame, the degree of deformation of a conventional side frame made only of a hypothetical aluminum extrusion material (FIG. 5a) was compared with that of the side frame according to the second embodiment of the present invention (FIG. 5b).

[0155] In the side frame according to the second embodiment of the present invention, the first frame portion is formed by roll forming using 1470 MART steel, and the second frame portion is formed by extruding 6000 series aluminum.

[0156] The results of the performance analysis are shown in Table 1 below.

[0157] [Table 1]

[0158] In the side frame made of different materials of the present invention, the deformation (displacement) was the same as that of the conventional side frame using aluminum extrusion material, and there was no contact with the battery cell. Furthermore, it was confirmed that the side frame of the present invention has a very efficient structure because it can reduce the weight by about 86% and the cost to the level of 44% while satisfying the same performance as the conventional side frame.

[0159] As described above, according to the present invention, by forming the side frame from different materials, it is possible to uniformly utilize the advantages of the extrusion material and the rigid material, thereby not only providing sufficient structural rigidity but also achieving weight reduction and cost reduction.

[0160] The above description is merely an illustrative example of the technical concept of the present invention, and various modifications and variations can be made by a person having ordinary knowledge in the technical field to which the present invention pertains without departing from the essential characteristics of the present invention.

[0161] In this specification and drawings, only examples in which the second frame portion has an approximately rectangular cross-section are described and illustrated, but the cross-sectional shape of the second frame portion is not limited to this and may have, for example, an elliptical or any other polygonal cross-section, or an open cross-section in an arc shape or an inverted U shape.

[0162] It should be made clear that the terms "horizontal member of the first frame section and horizontal member of the second frame section," as well as "vertical member of the first frame section and vertical member of the second frame section," are used merely for the purpose of distinguishing between terms, and do not have any other technical meaning.

[0163] Meanwhile, the embodiments described and illustrated above in the present invention can be combined with each other, and each embodiment can selectively adopt some components of other embodiments as necessary.

[0164] Therefore, the embodiments disclosed in the specification and drawings are for the purpose of illustrating, not for the purpose of limiting, the technical idea of ​​the present invention, and the scope of the technical idea of ​​the present invention is not limited by such embodiments. The scope of protection of the present invention should be interpreted according to the following claims, and all technical ideas within the scope equivalent thereto should be interpreted as being included in the scope of the present invention. [Industrial Applicability]

[0165] INDUSTRIAL APPLICABILITY As described above, the present invention is useful for, for example, an electric vehicle equipped with a battery system.

Claims

1. A first frame portion formed to have an open cross section including an empty space; a second frame portion disposed in the empty space of the first frame portion so as to close the open cross section of the first frame portion and coupled to the first frame portion; Including, The first frame portion and the second frame portion are formed of different materials, The first frame portion includes a first vertical member having a first height and a second vertical member having a second height, the open space being connected to an open cross section; The second frame portion is a side frame of a battery case having a hollow portion with a closed cross section therein.

2. The first frame portion is a first horizontal member having one end connected to a lower end of the first vertical member and extending in a width direction by a first length; a second horizontal member connecting an upper end of the first vertical member and an upper end of the second vertical member; a third horizontal member having one end connected to the lower end of the second vertical member and extending in the width direction by a third length shorter than the first length; Including, the second longitudinal member is spaced from the first longitudinal member by a second length that is less than the first length; The second height is less than the first height, The side frame of the battery case according to claim 1 , wherein an opening is formed between the other end of the first horizontal member and the other end of the third horizontal member.

3. The first frame portion is a wall having the first height; a protrusion extending from the wall to one side in a width direction by the third length; Including, The side frame of a battery case according to claim 2 , wherein the opening is formed on one side of the protrusion.

4. The side frame of the battery case according to claim 3 , wherein the second frame portion is disposed at least on a protruding portion within the first frame portion and closes the opening.

5. The second frame portion is a first lateral member and a second lateral member spaced apart vertically from one another; a first longitudinal member and a second longitudinal member spaced apart from each other in a width direction and connecting the first lateral member and the second lateral member; The side frame of the battery case according to claim 2 , comprising:

6. The side frame of the battery case according to claim 5 , wherein the thickness of each of the first horizontal member and the second horizontal member is greater than the thickness of each of the first vertical member and the second vertical member.

7. The side frame of a battery case according to claim 5 , wherein the first lateral member and the second lateral member have a thickness greater than that of the first frame portion.

8. the first transverse member and the second transverse member have a length equal to the first length; the first longitudinal member is connected to the first longitudinal member by a mechanical joint; The side frame of the battery case according to claim 5 , wherein the first horizontal member and the first horizontal member, and the third horizontal member and the second horizontal member are bonded by chemical bonding.

9. The first frame portion is a first horizontal member having one end connected to a lower end of the first vertical member and extending in a width direction by a first length; a second horizontal member connecting an upper end of the first vertical member and an upper end of the second vertical member; a third vertical member having a lower end connected to the other end of the first horizontal member and having a third height shorter than the first height; a third horizontal member having one end connected to the upper end of the third vertical member and extending widthwise toward the first vertical member by a third length that is shorter than the first length; Including, the second longitudinal member is spaced from the first longitudinal member by a second length that is less than the first length; The second height is less than the first height, The side frame of the battery case according to claim 1 , wherein an opening is formed between a lower end of the second vertical member and the other end of the third horizontal member.

10. The first frame portion is a wall having the first height; a protruding portion extending from the wall to one side in a width direction by the third length or longer than the third length; Including, The side frame of the battery case according to claim 9 , wherein the opening is formed between the wall portion and the protrusion.

11. The side frame of the battery case according to claim 10 , wherein the second frame portion is disposed at least on the wall portion within the first frame portion and closes the opening.

12. The second frame portion is a first lateral member and a second lateral member spaced apart vertically from one another; a first longitudinal member and a second longitudinal member spaced apart from each other in a width direction and connecting the first lateral member and the second lateral member; The side frame of the battery case according to claim 9 , comprising:

13. The second frame portion is a third transverse member extending from the second longitudinal member to or parallel with the first transverse member; a third longitudinal member extending from the first transverse member to or parallel with the first longitudinal member; The side frame of the battery case according to claim 12, further comprising:

14. 14. The side frame of the battery case according to claim 13, wherein the thickness of each of the first horizontal member, the second horizontal member, and the third horizontal member is formed to be thicker than the thickness of each of the first vertical member, the second vertical member, and the third vertical member.

15. The side frame of a battery case according to claim 13 , wherein the first lateral member, the second lateral member and the third lateral member have a thickness greater than that of the first frame portion.

16. the first transverse member and the second transverse member have a length equal to the second length; the third transverse member is disposed on the third transverse member; the first longitudinal member and the third longitudinal member are coupled to the first longitudinal member by a mechanical joint; the second longitudinal member is connected to the second longitudinal member by a mechanical joint; The side frame of the battery case according to claim 13 , wherein the third horizontal member and the third horizontal member are bonded together by chemical bonding.

17. the first transverse member and the second transverse member have a length equal to the second length; The third horizontal member is disposed between the third horizontal member and the first horizontal member, and an end of the third horizontal member abuts the third vertical member; the first longitudinal member and the third longitudinal member are coupled to the first longitudinal member by a mechanical joint; The side frame of the battery case according to claim 13 , wherein the second longitudinal member is coupled to the second longitudinal member by a mechanical joint.

18. A first frame portion having an open space and formed to have a closed cross section; a second frame portion inserted into an empty space of the first frame portion and coupled to the first frame portion; Including, The first frame portion and the second frame portion are formed of different materials, The first frame portion is a first longitudinal member having a first height, a second longitudinal member having a second height, and a third longitudinal member having a third height, the open space being connected to the closed cross section; The second frame portion is a side frame of a battery case having a hollow portion therein.

19. The first frame portion is a first horizontal member having one end connected to a lower end of the first vertical member and extending in a width direction by a first length; a second horizontal member connecting an upper end of the first vertical member and an upper end of the second vertical member; a third horizontal member connecting a lower end of the second vertical member and an upper end of the third vertical member, the third horizontal member having a third length shorter than the first length; Including, the second longitudinal member is spaced from the first longitudinal member by a second length less than the first length, and the second height is less than the first height; The side frame of a battery case according to claim 18 , wherein a lower end of the third vertical member is connected to the other end of the first horizontal member, and the third height is shorter than the first height.

20. The first frame portion is a wall having the first height; a protrusion extending from the wall to one side in a width direction by the third length; The side frame of a battery case according to claim 19, comprising:

21. The side frame of the battery case according to claim 20 , wherein the second frame portion is disposed at least on the wall portion within the first frame portion.

22. The second frame portion is a first lateral member and a second lateral member spaced apart vertically from one another; a first longitudinal member and a second longitudinal member spaced apart from each other in a width direction and connecting the first lateral member and the second lateral member; The side frame of a battery case according to claim 19, comprising:

23. The second frame portion is a third transverse member extending from the second longitudinal member to or parallel with the first transverse member; a third longitudinal member extending from the first transverse member to or parallel with the first longitudinal member; The side frame of the battery case according to claim 22, further comprising:

24. 24. The side frame of the battery case according to claim 23, wherein the thickness of each of the first horizontal member, the second horizontal member, and the third horizontal member is formed to be thicker than the thickness of each of the first vertical member, the second vertical member, and the third vertical member.

25. The side frame of a battery case according to claim 23 , wherein the first lateral member, the second lateral member and the third lateral member have a thickness greater than that of the first frame portion.

26. the first transverse member and the second transverse member have a length equal to the second length; The third horizontal member is disposed between the third horizontal member and the first horizontal member, and an end of the third horizontal member abuts the third vertical member; the first longitudinal member and the third longitudinal member are coupled to the first longitudinal member by a mechanical joint; The side frame of a battery case according to claim 23 , wherein the second longitudinal member is coupled to the second longitudinal member by a mechanical joint.

27. The side frame of the battery case according to claim 1 , wherein the second frame portion is made of a material having a lower specific gravity than the first frame portion.

28. The side frame of a battery case according to claim 1 , wherein the second frame portion is made of a material having a higher specific strength than the first frame portion.

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