Vehicle undercarriage

Abstract

This lower structure for a vehicle comprises: side sills which extend in a front-rear direction of the vehicle and which are provided on both sides in a width direction of the vehicle; side sill reinforcements which extend along the side sills and which are joined to the side sills; and a front-side cross member and a rear-side cross member which extend in the width direction of the vehicle and which have end portions joined to the side sill reinforcements. The side sill reinforcements are lower structures of the vehicle, and extend from in front of the front-side cross member to behind the rear-side cross member. Fragile portions are provided in parts of the side sill reinforcements spaced apart toward the rear of the vehicle from joining parts of the side sill reinforcements and the rear-side cross member.

Description

[Technical Field]

[0001] The present invention relates to a vehicle undercarriage. [Background technology]

[0002] A technology has been proposed in which a reaction force adjustment section is provided on the side sill in order to reduce the collision reaction force generated at the point where the side sills located on both sides of the vehicle's width and the lower end of the B-pillar join in the event of a side collision, compared to the collision reaction force generated at the center of the floor body in the fore-and-aft direction of the vehicle (see Patent Document 1). According to the above-described conventional technology, the collision load acting on the B-pillar is reduced by reducing the collision reaction force during a side collision. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2001-71949 Summary of the Invention [Problem to be solved by the invention]

[0004] However, while the above-mentioned conventional technology is designed to suppress deformation of the vehicle body in a side collision, no particular consideration is given to suppressing deformation of the vehicle body in a frontal collision. The present invention has been devised in view of the above circumstances, and an object of the present invention is to provide a vehicle underbody structure that is advantageous in suppressing deformation of the vehicle body in both a frontal collision and a side collision. [Means for solving the problem]

[0005] In order to achieve the above-mentioned object, one embodiment of the present invention comprises a side sill extending in the fore-and-aft direction of the vehicle and provided on both sides in the vehicle width direction, a side sill reinforcement extending along the side sill and joined to the side sill, and a front cross member and a rear cross member extending in the vehicle width direction at a distance in the fore-and-aft direction of the vehicle and having their ends joined to the side sill reinforcement, wherein the side sill reinforcement is an undercarriage structure of the vehicle extending from in front of the front cross member to behind the rear cross member, and is characterized in that a weak portion is provided in the side sill reinforcement at a location spaced rearward of the vehicle from the joining point between the side sill reinforcement and the rear cross member. [Effects of the Invention]

[0006] According to one embodiment of the present invention, by extending the side sill reinforcement from in front of the front cross member to behind the rear cross member, the strength and rigidity of the side sill can be ensured against loads input from the front of the vehicle in the event of a frontal collision. Furthermore, by providing a weak section at the side sill reinforcement located at a distance to the rear of the vehicle from the joint between the side sill reinforcement and the rear cross member, the bending point of the side sill in the event of a side collision is displaced further rearward of the vehicle than the joint, which is advantageous in ensuring that the cross member can reliably absorb the load input during a side collision. This is therefore advantageous in suppressing deformation of the vehicle body in both frontal and side collisions. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a plan view showing a vehicle undercarriage structure according to an embodiment of the present invention; [Figure 2] FIG. 2 is a perspective view of the side sill, B-pillar, front cross member, and rear cross member to which the side sill reinforcement is joined, as viewed from the inside in the vehicle width direction. [Figure 3] FIG. 2 is an enlarged perspective view of a joint portion between a side sill, a rear cross member, and a B-pillar. [Figure 4]FIG. 4 is a cross-sectional view of a portion where a side sill and a side sill reinforcement are joined together. [Figure 5] FIG. 2 is an explanatory diagram illustrating the relationship between a load F1 input during a side collision and a reaction force F2 of a rear cross member. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following drawings, the symbol UP indicates the upper side of the vehicle, the symbol FR indicates the front side of the vehicle, the symbol IN indicates the inner side in the vehicle width direction, and the symbol OUT indicates the outer side in the vehicle width direction. In this embodiment, a case will be described in which the vehicle is an electric vehicle using an electric motor as a drive source that is driven by power supplied from a battery, but the present invention is of course applicable to vehicles other than electric vehicles.

[0009] As shown in FIG. 1, a vehicle body 10 of a vehicle to which this embodiment is applied is a monocoque body in which a body and a chassis are integrated into one body. The lower part of the vehicle body 10 is composed of a floor panel 12, a center tunnel 14, a pair of side sills 16, an A-pillar 18, a B-pillar 20, a C-pillar 22, a front cross member 24, a rear cross member 26, and a side sill reinforcement 28. The center tunnel 14, the pair of side sills 16, the A-pillar 18, the B-pillar 20, the C-pillar 22, the front cross member 24, the rear cross member 26, and the side sill reinforcement 28 function as vehicle frame members.

[0010] The floor panel 12 is made up of panel members extending in the longitudinal direction and width direction of the vehicle, and a cutout 1202 is provided in the front portion of the floor panel 12 for arranging a drive source such as an electric motor or an engine. The center tunnel 14 protrudes upward from the center of the front part of the floor panel 12 in the vehicle width direction, extends in the vehicle front-rear direction, and has its rear end connected to a rear cross member 26. The pair of side sills 16 are provided on both sides of the floor panel 12 in the vehicle width direction, extending in the vehicle longitudinal direction from the front to the rear of the floor panel 12.

[0011] The front cross member 24 and the rear cross member 26, which are cross members, extend in the vehicle width direction at the front of the floor panel 12 and are spaced apart in the vehicle front-rear direction. The front cross member 24 is a location where the front legs of the front seats (not shown) are attached, and the rear cross member 26 is a location where the rear legs of the front seats are attached. The lower portions of the front cross member 24 and the rear cross member 26 are joined to the upper surface of the floor panel 12, and the inner ends of the front cross member 24 and the rear cross member 26 in the vehicle width direction are joined to the center tunnel 14, and the outer ends in the vehicle width direction are joined to the side sill 16. In addition, a battery (not shown) is located below the floor panel 12 between the front cross member 24 and the rear cross member 26 in the center of the floor panel 12 in the vehicle width direction, and a covering portion 30 that covers the upper part of this battery is provided on the floor panel 12 and protrudes above the other parts of the floor panel 12.

[0012] The A pillar 18, the B pillar 20, and the C pillar 22 are provided to stand upward from the pair of side sills 16 at positions spaced apart in the vehicle longitudinal direction. As shown in Figure 2, the side sill 16 has a closed cross-sectional structure including a side sill inner wall 1602 facing inward in the vehicle width direction, a side sill outer wall 1604 facing outward in the vehicle width direction, a side sill lower wall 1606 facing downward and joined to the floor panel 12, and a side sill upper wall 1608 facing upward. As shown in FIG. 3, the B-pillar 20 is attached to the side sill 16 by joining the flange 2002 at its lower end to the side sill inner wall 1602, the side sill outer wall 1604, and the side sill upper wall 1608, and this attachment structure also attaches the A-pillar 18 and the C-pillar 22 to the side sill 16. An opening 2004 for arranging a seat belt retractor (not shown) is provided at the lower end of the inner surface of the B-pillar 20 facing inward in the vehicle width direction.

[0013] As shown in FIGS. 2 and 3, the side sill reinforcement 28 extends along the side sill 16 and is joined to the inside of the side sill 16. The side sill reinforcement 28 extends from the front of the vehicle at the front cross member 24 to the rear of the vehicle at the rear cross member 26. As shown in Figure 4, the side sill reinforcement 28 is U-shaped and has a reinforcement inner surface 2802 joined to the inner surface of the side sill inner wall 1602, a reinforcement upper surface 2804 joined to the inner surface of the side sill upper wall 1608, and a reinforcement lower surface 2805 joined to the inner surface of the side sill lower wall 1606.

[0014] As shown in Figures 2 and 3, both ends of the rear cross member 26 in the vehicle width direction are joined to the inner surface 2802 of the reinforcement via flanges 2602, and therefore both ends of the rear cross member 26 in the vehicle width direction are connected to the inner surface 2802 of the reinforcement via the inner side wall 1602 of the side sill 16. The rear end 2810 of the side sill reinforcement 28 is located rearward of the joining point X between the side sill 16 and the B-pillar 20, and more specifically, is located rearward of the flange 2002 of the B-pillar 20 that is joined to the side sill 16. A weak portion 32 having a lower strength than other portions is provided at a portion of the side sill reinforcement 28 spaced rearward of the vehicle from a joining portion X between the side sill 16 and the rear cross member 26. In this embodiment, the weakened portion 32 is configured by a bent portion 34 that extends in the vertical direction toward the outside in the vehicle width direction on the inner surface 2802 of the reinforcement. In this embodiment, the fragile portion 32 is configured as a bent portion 34 that is convex on the outside in the vehicle width direction, but various structures that have previously been known as fragile portions 32 can be used, such as a bent portion that is convex on the inside in the vehicle width direction, a thin portion in which part of the reinforcement inner surface 2802 is thinner than other parts, or a portion with an opening or a cut-out in the thickness. The weakened portion 32 is provided within the range of the width of the opening 2004 along the vehicle front-rear direction when viewed in the vehicle width direction.

[0015] Next, the effects of this embodiment will be described. According to this embodiment, the side sill reinforcement 28 extends from in front of the front cross member 24 to the rear of the rear cross member 26, so that the length of the side sill reinforcement 28 can be sufficiently ensured, which is advantageous in ensuring the strength and rigidity of the side sill 16 against loads input from the front of the vehicle during a frontal collision. Here, the breaking point is the point where the side sill 16 breaks due to the load input from the side of the vehicle when a pole collides with the middle part between the front cross member 24 and the rear cross member 26 from the side of the vehicle, a so-called pole side collision. As described above, even if the length of the side sill reinforcement 28 is sufficiently ensured, if the strength of the side sill 16 reinforced by the side sill reinforcement 28 is constant along its extension direction, the load input in a side collision will be concentrated at the joint X between the side sill reinforcement 28 and the rear cross member 26, and the bending point will be near the joint X. Therefore, even though the length of the side sill reinforcement 28 is sufficiently secured, the rear cross member 26 may not be able to fully absorb the collision load, which may result in a large amount of deformation of the side sill 16, which may be disadvantageous in suppressing the amount of intrusion of the pole.

[0016] Therefore, in this embodiment, a weak portion 32 having lower strength than other portions is provided in a portion of the side sill reinforcement 28 that is spaced rearward of the vehicle from the joint point X between the side sill reinforcement 28 and the rear cross member 26, thereby displacing the bending point of the side sill 16 rearward of the vehicle from the joint point X in the event of a side collision with a pole. This improves the effect of the rear cross member 26 in absorbing the load input in the event of a side collision with a pole, as will be explained next.

[0017] The following description will be made with reference to FIG. F1 is the input load of the pole that is input to the side sill 16 in the event of a side collision of the pole. F2 is a reaction force applied to the side sill 16 from the rear cross member 26 during a side collision with a pole. L1 is the distance from the pole to the joint point X where the side sill reinforcement 28 and the rear cross member are joined in the vehicle longitudinal direction, and this distance L1 is constant. L2 is the distance from the joint X between the side sill reinforcement 28 and the rear cross member to the bending point P. Here, the balance of moments around the break point P can be expressed mathematically as follows: F1(L1+L2)-F2×L2=0……(1) Calculating F2 from the above formula (1), F2=F1(L1+L2) / L2……(2). Transforming this equation (2) gives: F2=(F1×L1) / L2+F1……(3). Here, by providing a weak portion 32 having lower strength than other portions at a portion of the side sill reinforcement 28 spaced rearward of the vehicle from the joining point X between the side sill reinforcement 28 and the rear cross member 26, the bending point P of the side sill 16 is displaced rearward of the vehicle from the joining point X in the event of a side collision with a pole. That is, since the value of L2 (the distance from the joint location X to the bending point P) in the denominator of the first term on the right side of equation (3) increases, the reaction force F2 of the rear cross member 26 decreases. Therefore, the load input in the event of a side collision with a pole is reliably received by the rear cross member 26, suppressing deformation of the side sill 16 inward in the vehicle width direction, which is advantageous in preventing the pole from entering. Therefore, this is advantageous in suppressing vehicle body deformation in both frontal collisions and side collisions with poles, without increasing the thickness of the side sill reinforcement 28 or the rear cross member 26, i.e., without increasing weight or worsening fuel efficiency.

[0018] In addition, in this embodiment, the lower end of the B-pillar 20 is joined to the side sill 16, and the rear end 2810 of the side sill reinforcement 28 is located rearward of the joining point X between the side sill 16 and the B-pillar 20. This is advantageous in ensuring the strength and rigidity of the side sill reinforcement 28 against a frontal collision, and is advantageous in suppressing deformation of the side sill 16, i.e., deformation of the vehicle body, due to a frontal collision.

[0019] In addition, in this embodiment, an opening 2004 for positioning a seat belt retractor is formed in the lower part of the B-pillar 20, and a weak portion 32 is provided within the width range of the opening 2004 along the fore-and-aft direction of the vehicle when viewed from the vehicle width direction. Therefore, the area within the width of the opening 2004 is where stress concentrates during a side collision, and by providing the weakened portion 32 at this stress concentration, which is spaced rearward from the joint X, the bending point P at which the side sill 16 bends can be positioned closer to the weakened portion 32. In other words, this is advantageous in displacing the bending point P rearward of the vehicle relative to the joint X between the side sill 16 and the B-pillar 20, which is advantageous in suppressing deformation of the vehicle body due to a side collision with a pole. Conversely, compared to the above case, stress concentrates less at locations of side sill reinforcement 28 that are further rearward from opening 2004 during a side collision. Although weak portions 32 may be provided at such locations, providing weak portions 32 within the width of opening 2004 along the vehicle front-to-rear direction, as in the present embodiment, is more advantageous in terms of exerting the effect of displacing bending point P further rearward from joining point X between side sill 16 and B-pillar 20, and is more advantageous in terms of suppressing vehicle body deformation due to a pole side collision.

[0020] In this embodiment, the weakened portion 32 is configured as a bent portion 34 that is convex in the vehicle width direction and extends in the up-down direction on the inner surface of the side sill reinforcement 28 in the vehicle width direction. Therefore, compared to when the fragile portion 32 is configured as a thin portion or a notch portion, the configuration of the fragile portion 32 can be simplified, which is advantageous in terms of reducing costs.

[0021] In addition, in this embodiment, when viewed in a plane, the battery is positioned between the front cross member 24 and the rear cross member 26, which is advantageous in protecting the battery because it suppresses deformation of the side sill 16, i.e., deformation of the vehicle body 10, in the event of a side collision with a pole and suppresses intrusion of the pole.

[0022] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present invention is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present invention. Furthermore, the components of the above-described embodiments may be combined in any manner without departing from the spirit of the invention.

[0023] This application is based on a Japanese patent application (Patent Application No. 2022-051470) filed on March 28, 2022, the contents of which are incorporated herein by reference. [Explanation of symbols]

[0024] 10. Body 12 Floor Panel 1202 Notch 14 Center tunnel 16 Side sill 1602 Side sill inner wall 1604 Side sill outer wall 1606 Side sill lower wall 1608 Side sill upper wall 18 A-pillar 20 B-pillar 2002 flange 2004 Opening 22 C-pillar 24 Cross member (front cross member) 26 Cross member (rear cross member) 2602 flange 28 Side sill reinforcement 2802 Reinforcement inner surface 2804 Reinforcement top surface 2810 Rear end 30 Covering part 32 Weak part 34 Bend X Binding point (bonding point) P break point

Claims

1. a side sill having a closed cross-sectional structure extending in the vehicle longitudinal direction and provided on both sides in the vehicle width direction, the side sill having an inner side wall facing inward in the vehicle width direction, an outer side sill wall facing outward in the vehicle width direction, a lower side sill wall facing downward, and an upper side sill wall facing upward; a side sill reinforcement extending along the side sill inner wall and joined to the side sill; a front cross member and a rear cross member extending in the vehicle width direction at a distance from each other in the vehicle longitudinal direction, the ends of which are connected to the side sill reinforcement; The side sill reinforcement is a vehicle understructure extending from in front of the front cross member to behind the rear cross member, a weakened portion is provided at a location of the side sill reinforcement spaced rearward of the vehicle from a joining point between the side sill reinforcement and the rear cross member, The weakened portion is configured by a bent portion extending in the vertical direction toward the outside in the vehicle width direction on the inner surface of the side sill reinforcement in the vehicle width direction. A vehicle undercarriage characterized by:

2. A lower end of a B-pillar is connected to the side sill, The rear end of the side sill reinforcement is located rearward of the vehicle relative to a joining point between the side sill and the B-pillar.

2. The vehicle undercarriage structure according to claim 1.

3. An opening for arranging a seat belt retractor is formed in the lower part of the B-pillar, When viewed from the vehicle width direction, the fragile portion is provided within a range of the width of the opening along the vehicle front-rear direction.

3. The vehicle undercarriage structure according to claim 2.

4. The weakened portion is configured as a bent portion that is convex in the vehicle width direction and extends in the up-down direction on the inner surface of the side sill reinforcement in the vehicle width direction.

2. The vehicle undercarriage according to claim 1.

5. In a plan view, a battery is disposed between the front cross member and the rear cross member.

5. The vehicle underbody structure according to claim 1, wherein the vehicle underbody structure is a vehicle body.

6. The side sill reinforcement is joined to the side sill inner wall.

2. The vehicle undercarriage according to claim 1.

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