Vehicle underbody structure

Abstract

The aerodynamic performance of the area below the rear suspension must be satisfied, while also satisfying the impact resistance and snow-shedding capabilities of the front and rear arm undercovers attached to the front and rear lower arms of the rear suspension. [Solution] The rear suspension 10 is equipped with a front arm under cover 43 and a rear arm under cover 42, respectively, positioned below the front and rear lower arms 15 and 14, and a floor under cover 41 positioned below the front floor panel 1. The bottom surface 143 of the front arm under cover 43 is set higher than the imaginary straight line La connecting the bottom surface 141 of the floor under cover 41 and the bottom surface 142 of the rear arm under cover 42. The rear arm under cover 42 is provided with a bottom surface 147 that rises from the bottom surface 143 of the front arm under cover 43 in a curved shape towards the front, starting from a position lower than the bottom surface 143 of the front arm under cover 43.

Description

Technical Field

[0001] The present invention relates to a lower body structure of a vehicle in which air covers are respectively provided downward for each of two lower arms arranged along the vehicle width direction on each of the front and rear sides of the lower part of a rear suspension that suspends a rear wheel.

Background Art

[0002] As a lower body structure of a vehicle, as exemplified in Patent Document 1, under the vehicle floor, not only a floor under cover but also various arms provided in a rear suspension region (also referred to as a "rear sus region") located behind it, and an air cover is provided below a subframe that supports the rear suspension so that the underfloor running air flowing rearward along the vehicle floor during vehicle travel is not disturbed in the rear sus region. Such a structure is becoming widespread.

[0003] In Patent Document 1, regarding a lower body structure of a vehicle equipped with a five-link multi-link type rear suspension having five arms (links), the rear suspension has lower arms along the vehicle width direction provided at the lower parts on each of the front and rear sides with respect to the axle.

[0004] Since the vertical movement trajectories of these front and rear lower arms are different from each other, a sus under cover as an air cover is individually set under each lower arm. And these sus under covers need to prevent the underfloor running air from being disturbed even when the front and rear lower arms move vertically, while avoiding interference with each other and due to a vertical step occurring on the bottom surface of the rear sus region.

[0005] In contrast, Patent Document 1 discloses a structure in which, for sus under covers provided in a plurality in the rear sus region, while minimizing the gaps between them, the bottom surface height does not become discontinuous from the rear end of the floor under cover.

[0006] As shown in Patent Document 1, in a configuration in which multiple suspension undercovers are arranged so as to minimize the gaps between them and so as to minimize discontinuities in the bottom surface height, this is advantageous in terms of aerodynamic performance, but it is not necessarily advantageous in terms of other performance aspects.

[0007] For example, if the suspension undercovers, which are positioned beneath the front and rear lower arms that move up and down, are made to minimize the gaps between them or to have the same bottom height as described above, the degree of freedom in their shape will be reduced, and there is a risk of them interfering with each other, which may impair their impact resistance (tolerance for deformation).

[0008] Furthermore, if the gaps between multiple suspension undercovers are made as small as possible, snow and mud will be more likely to accumulate on these undercovers once they get on them, which could actually impair snow and mud removal capabilities.

[0009] In other words, the suspension undercover needs to be designed so as not only that aerodynamic performance deteriorates, but also that other performance aspects such as impact resistance and snow removal when the wheels move up and down are not compromised. However, Patent Document 1 does not mention these issues or any measures to satisfy them, leaving room for improvement. As a result of various experiments, the inventors have found a configuration that satisfies aerodynamic performance while ensuring overall performance, even without filling the gaps in the rear suspension area with multiple aerodynamic covers as much as possible, as shown in Patent Document 1 below. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 2023-37116 [Overview of the project] [Problems that the invention aims to solve]

[0011] Therefore, the present invention aims to provide a vehicle underbody structure that satisfies aerodynamic performance below the rear suspension region while also satisfying various performance aspects such as impact resistance and snow removal capabilities of the front and rear arm undercovers attached to the front and rear lower arms of the rear suspension. [Means for solving the problem]

[0012] This invention relates to a rear suspension that connects a wheel support member supporting the rear wheel to the vehicle body via a front lower arm and a rear lower arm that extend along the vehicle width direction and are positioned front and rear with respect to the axle; a rear arm under cover positioned below the rear lower arm; a front arm under cover positioned directly in front of the rear arm under cover and below the front lower arm, the bottom surface of which is higher than the bottom surface of the rear lower arm; and a front arm under cover positioned directly in front of the front arm under cover and below the vehicle body floor. A lower body structure of a vehicle comprising a floor under cover positioned on the front side, wherein the bottom surface of the front arm under cover is set at a position higher than a virtual straight line connecting the bottom surface of the floor under cover and the bottom surface of the rear arm under cover in the front-to-rear direction, and the bottom surface of the rear arm under cover is provided with a front rising bottom surface that rises from the bottom surface of the front arm under cover in a curved shape towards the front, starting from a position lower than the bottom surface of the front arm under cover.

[0013] According to the above configuration, while satisfying the aerodynamic performance below the rear suspension region, it is also possible to satisfy various performance aspects such as impact resistance and snow removal capabilities of the front and rear arm undercovers attached to the front and rear lower arms of the rear suspension.

[0014] The front arm under cover may be positioned in a downward inclined position along the extending direction of the front lower arm, which is located lower towards the outside in the vehicle width direction. According to the above configuration, the front arm under cover can be positioned along the extending direction of the front lower arm, thereby minimizing the vertical separation between the main surface of the arm under cover and the front lower arm, preventing damage and other problems, and further ensuring snow removal performance.

[0015] Furthermore, in an embodiment of this invention, the lowest point of the bottom surface of the front arm under cover, which moves up and down in conjunction with the up and down movement of the front lower arm, may be set higher in each corresponding part in the vehicle width direction than the lowest point of the bottom surface of the rear arm under cover, which moves up and down in conjunction with the up and down movement of the rear lower arm.

[0016] According to the above configuration, even if the front arm under cover moves up and down in conjunction with the up and down movement of the front lower arm, and the rear arm under cover moves up and down in conjunction with the up and down movement of the rear lower arm, the lowest point of the bottom surface of the rear arm under cover can always be set higher than the lowest point of the bottom surface of the front arm under cover. Therefore, the rearward flow passing below the front arm under cover can always be reattached to the front rising bottom surface of the rear arm under cover immediately afterward, thereby straightening the flow.

[0017] In another aspect of this invention, the front rising bottom portion may be configured to rise from a position lower than the bottom portion of the floor under cover. According to the above configuration, the rear arm under cover rises from a position lower than the bottom surface of the floor under cover, which is lower than the bottom surface of the front arm under cover, to a position higher than the bottom surface of the arm under cover. Therefore, the underfloor airflow that has passed below the bottom surface of the front arm under cover, separated from the rear end of the floor under cover, can be reliably reattached by the front rising portion of the rear arm under cover.

[0018] In another aspect of this invention, the front of the bottom surface of the front arm under cover may be provided with a front rising bottom surface that rises higher towards the front. According to the above structure, even if the underfloor running air separated from the floor under cover diffuses upwards before flowing under the front arm under cover, it can be attached to the front rising bottom surface portion, and can be rectified rearward along the bottom surface portion of the front arm under cover.

[0019] Therefore, even if the gap in the front-rear direction between the floor under cover and the front arm under cover is not set to be extremely small, the underfloor running air separated from the floor under cover can flow rearward below the front arm under cover.

Effect of the Invention

[0020] According to this invention, it is possible to provide a lower body structure of a vehicle that can satisfy the overall performance such as impact resistance and snow removal performance of the front and rear arm under covers attached to the front and rear lower arms provided in the rear suspension while satisfying the aerodynamic performance below the rear suspension area.

Brief Description of the Drawings

[0021] [Figure 1] An external view of the left side of the rear part of the vehicle body equipped with the lower body structure of the present embodiment, viewed from the right, below, and rear. [Figure 2] A bottom view showing the main part of the lower body structure of the present embodiment. [Figure 3] An external view of the left side of the rear part of the vehicle body in FIG. 1, viewed from the left, above, and rear. [Figure 4] A plan view showing the main part of the left side of the rear part of the vehicle body in FIG. 1. [Figure 5] A front view showing the main part of the left side of the rear part of the vehicle body in FIG. 1. [Figure 6] A left side view showing the main part of the left side of the rear part of the vehicle body in FIG. 1. [Figure 7] A rear view showing the main part of the left side of the rear part of the vehicle body in FIG. 1. [Figure 8] A cross-sectional view showing the main part of the lower body structure corresponding to the A-A line in FIG. 4. [Figure 9] A cross-sectional view showing the main part of the lower body structure corresponding to the B-B line in FIG. 4. [Figure 10] Cross-sectional view of the main section along line CC in Figure 4, viewed from the front. [Figure 11] Cross-sectional view of the main section along line DD in Figure 4, viewed from the front. [Figure 12] Perspective view of the rear under cover, seen from the front, left, and below. [Figure 13] A perspective view of the rear under cover, seen from the rear, left, and above. [Figure 14] Diagram illustrating the operation of the lower body structure of this embodiment when underfloor airflow flows along the underside of the vehicle body. [Modes for carrying out the invention]

[0022] One embodiment of the present invention will be described below with reference to the drawings. In the diagram, arrow F indicates the front of the vehicle, arrow U indicates the top of the vehicle, arrow W indicates the width of the vehicle, arrow Rh indicates the right of the vehicle, and arrow Lh indicates the left of the vehicle. The left-right direction of the vehicle is based on the occupant seated in the driver's seat. Furthermore, since the lower part of the vehicle in this embodiment is substantially symmetrical, the following explanation will mainly focus on the left side of the lower part of the vehicle.

[0023] As shown in Figure 1, the lower part of the vehicle of this embodiment to which the lower body structure of the present invention is applied includes a front floor panel 1 that forms the floor surface of the passenger compartment, and a rear floor panel 3 that is connected to the rear end of the front floor panel 1 via a kick-up portion (not shown) and extends to the rear of the vehicle. The rear floor panel 3 forms the floor surface of the rear of the passenger compartment and the cargo compartment, and a rear seat pan 3a is integrally formed with it.

[0024] As shown in Figures 1 to 4, rear side frames 4, which have a closed cross-sectional space extending in the longitudinal direction of the vehicle as part of the vehicle body frame, are provided on both sides of the rear floor panel 3. Further outward in the vehicle width direction from the pair of left and right rear side frames 4 are the rear wheels 5. Hubs 5a (see Figure 2, etc.) are fixed to the wheels of the rear wheels 5.

[0025] As shown in Figures 3 and 4, the rear suspension 10 that suspends the rear wheels 5 is attached to the rear side frame 4 (see Figure 1) via a suspension cross member 30 (hereinafter referred to as "subframe 30"). Note that, in drawings other than Figures 1 and 4, the vehicle body other than the subframe 30 is omitted.

[0026] As shown in Figures 3 to 7, the rear suspension 10 employs a so-called E-type multi-link suspension system. It comprises a wheel support member 11 (knuckle) that rotatably supports the hub 5a fixed to the rear wheel 5, a trailing arm 12 as a longitudinal arm extending forward from the wheel support member 11 with its front end attached to the vehicle body, three width-direction arms 13, 14, and 15 extending inward from the wheel support member 11 with their inner ends attached to the subframe 30, a coil spring 16 and a damper 17 as shock-absorbing members with their upper ends attached to the vehicle body, and a stabilizer link 18 (see Figures 3 and 4) for stabilizing the vehicle body.

[0027] As shown in Figure 3, the three width-direction arms 13, 14, and 15 are: an upper arm 13 positioned forward of the axle W5 of the rear wheel 5 so as to be able to support the upper part of the wheel support member 11 from the subframe 30; a rear lower arm 14 positioned behind the axle W5 so as to be able to support the rear lower part of the wheel support member 11; and a front lower arm 15 positioned forward of the axle so as to be able to support the lower part of the wheel support member 11.

[0028] Of the three width-direction arms 13, 14, and 15, the front lower arm 15 includes, as shown in Figure 3, an inner lower arm shaft 15wa in the width-direction that is supported by the front lower arm support portion 35 at the front lower part of the subframe 30, and, as shown in Figure 6, an outer lower arm shaft 15wb in the width-direction that is connected to the arm connecting portion 11f at the front lower part of the wheel support member 11.

[0029] As shown in Figure 5, the front lower arm 15 is positioned in an inclined position, with the outer side in the vehicle width direction being lower, and is configured to swing vertically with the lower arm shaft 15wa, located at the inner end in the vehicle width direction, as the pivot point.

[0030] As shown in Figure 7, the rear lower arm 14 includes a lower arm shaft 14wa that is on the inside in the vehicle width direction and is supported by the rear lower arm support portion 34 at the lower rear of the subframe 30, and a lower arm shaft 14wb that is on the outside in the vehicle width direction and is connected to the arm connecting portion 11r at the lower rear of the wheel support member 11.

[0031] As shown in Figure 7, the rear lower arm 14 is positioned in an inclined position, with the outer side in the vehicle width direction being lower, and is configured to swing vertically with the lower arm shaft 14wa, located at the inner end in the vehicle width direction, as the pivot point.

[0032] As shown in Figures 2 and 3, the rear lower arm 14 is larger than the front lower arm 15, with longer lengths in the vehicle width direction, vertical direction, and longitudinal direction. As a result, the lowest point of the bottom surface portion 14b (see Figure 7) of the rear lower arm 14, which moves up and down around the lower arm shaft 14wa as a pivot point, is located lower in the corresponding parts in the vehicle width direction than the lowest point of the bottom surface portion 151 (see Figure 5) of the front lower arm 15, which moves up and down around the lower arm shaft 15wa as a pivot point.

[0033] As shown in Figures 2 and 3, the rear lower arm 14 gradually increases in front-to-back width from the inner and outer ends (14wa, 14wb) in the vehicle width direction (longitudinal direction) toward the center, and a large-diameter section 14a is provided in the center in the vehicle width direction (longitudinal direction).

[0034] As shown in Figures 8 to 11, the rear lower arm 14 has a bottom surface portion 14b, a front wall portion 14c that rises vertically from the front end of the bottom surface portion 14b, a front edge flange portion 14d that protrudes forward from the upper end of the front wall portion 14c, a rear wall portion 14e that rises vertically from the rear end of the bottom surface portion 14b, and a rear edge flange portion 14f that protrudes rearward from the upper end of the rear wall portion 14e, and the cross-sectional shape perpendicular to the vehicle width direction is formed in an upwardly open hat shape.

[0035] As shown in Figure 10, a spring seat 26 that supports the lower end of the coil spring 16 is integrally formed on the bottom surface 14b of the large diameter portion 14a of the rear lower arm 14. As shown in Figures 4 to 7, a spring seat 27 is also provided above the spring seat 26 (see Figure 10) of the rear lower arm 14 on the rear side frame 4 (see Figure 1), which serves as the vehicle body frame. This spring seat 27 faces downwards and supports the upper end of the coil spring 16. The coil spring 16 is interposed between the spring seat 27 on the vehicle body and the spring seat 26 on the rear lower arm 14.

[0036] As shown in Figures 3, 4, 8, 10, and 11, reinforcements 18a and 18b are attached and fixed to the inner and outer sides in the vehicle width direction of the rear lower arm 14, avoiding the large diameter portion 14a. Both of these reinforcements 18a and 18b are provided to connect the front wall portion 14c and the rear wall portion 14e so as to close the upper opening of the rear lower arm 14, which has an open-top hat-shaped cross-section.

[0037] As shown in Figures 3, 4, and 6-9, the rear lower arm 14 is provided with locking pieces 19 on both sides of the large-diameter portion 14a in the vehicle width direction of the rear wall portion 14e, for locking and fixing the rear arm under cover 42, which will be described later and is located below the rear lower arm 14. Both the left and right locking pieces 19 extend rearward from the rear wall portion 14e, and their base ends are integrally attached to the rear wall portion 14e by welding. At the tip, there is a grommet insertion hole 19a (see Figure 3) for locking to the rear arm under cover 42 via a grommet G, which is a resin locking member, and a bolt insertion hole 19b (see Figure 3) for fastening to the rear arm under cover 42 via a bolt B and nut N, which are fastening members, both located along the vehicle width direction.

[0038] As shown in Figures 1 to 5 and Figure 7, the subframe 30 is located inward in the vehicle width direction from the left and right rear suspensions 10, and mainly comprises front and rear cross members 31 that are spaced apart from each other in the vehicle's longitudinal direction and run along the vehicle's width direction, and left and right side members 32 that are spaced apart from each other on each side and run along the longitudinal direction. These multiple members 31 and 32 are assembled in a grid-like pattern in plan view to form a single unit.

[0039] The subframe 30 supports the widthwise inner ends of the vehicle width direction arms 13, 14, and 15. Regarding the support of the front lower arm 15 and the rear lower arm 14 among the vehicle width direction arms 13, 14, and 15, as shown in Figures 3 to 5, a front lower arm support portion 35 is provided at the lower outer end of the front cross member 31 of the subframe 30, supporting the lower arm shaft 15wa of the front lower arm 15. Similarly, a rear lower arm support portion 34 is provided at the lower outer end of the rear cross member 31, supporting the lower arm shaft 14wa of the rear lower arm 14, as shown in Figures 2 and 7.

[0040] As shown in Figures 2 to 7, the front and rear ends of the left and right side members 32 of the subframe 30 are each provided with vehicle body mounting parts 36 that are attached to the mounting points on the front and rear sides of the left and right rear side frames 4 on the vehicle body side. Furthermore, the rear suspension 10 and subframe 30 described above are configured to be approximately symmetrical with respect to a center line that extends in the front-rear direction along the middle of the vehicle body in the width direction (see Figure 2).

[0041] Furthermore, as shown in Figures 1 to 4, the vehicle of this embodiment is equipped with a floor under cover 41 located below the front floor panel 1 under the vehicle body floor, and suspension under covers 42, 43, and 44 located below the rear suspension 10. Both the floor under cover 41 and the suspension under covers 42, 43, and 44 function as aerodynamic covers, forming a rectifying surface for the underbody airflow.

[0042] As shown in Figures 1 to 5, the suspension undercovers 42, 43, and 44 include a rear arm undercover 42 positioned below the rear lower arm 14 of the rear suspension 10, a front arm undercover 43 positioned directly in front of the rear arm undercover 42 and below the front lower arm 15, the front arm undercover 43 having a bottom surface 151 higher than the bottom surface 14b of the rear lower arm 14, and a subframe undercover 44 positioned directly below the subframe 30.

[0043] As shown in Figure 5, the subframe under cover 44 and the front arm under cover 43 are positioned in front of the rear suspension region, directly in front of the rear arm under cover 42, and are separated from each other by a gap wt in the vehicle width direction on the inner and outer sides in the vehicle width direction (see the enlarged area of ​​region Z in Figure 5 in particular).

[0044] As described above, the subframe under cover 44 has its bottom surface 144 positioned approximately horizontally along the vehicle width direction, whereas the front arm under cover 43 is set so that its inner end is the highest in the vehicle width direction, and is positioned in a downward-sloping posture, with the outer side in the vehicle width direction being lower.

[0045] As shown in the enlarged area of ​​region Z in Figure 5, the inner end 43t in the vehicle width direction of the front arm under cover 43 and the outer end 44t in the vehicle width direction of the subframe under cover 44 face each other in the vehicle width direction separated by the gap wt. However, the bottom surfaces 143t and 144t of these inner and outer ends 43t and 44t in the vehicle width direction are positioned at different heights. In this example, the bottom surface 143t of the inner end 43t of the front arm under cover 43 is positioned higher than the bottom surface 144t of the outer end 44t of the subframe under cover 44.

[0046] Furthermore, as shown in Figure 8, the front arm under cover 43 is attached to the front lower arm 15 via a bracket 60, and is formed as a flat plate with plate thickness in the vertical direction for almost its entire length except for the front part, and is positioned directly behind the rear end of the floor under cover 41 with a gap in the front-rear direction.

[0047] The front portion of the front arm under cover 43 is formed in a curved shape that curves upward towards the front. As a result, while the bottom surface 143 of the front arm under cover 43 is formed to be substantially flat in the front-to-back direction except for the front portion, the front portion is provided with a curved, rising bottom surface 143a that rises towards the front.

[0048] As shown in Figures 5 and 8, the front arm under cover 43 is positioned in a downward inclined position along the extending direction of the front lower arm 15, which is located lower towards the outer side in the vehicle width direction. Accordingly, the bottom surface portion 143, which serves as a rectifying surface, is positioned inclined linearly so that it is located lower towards the outer side in the vehicle width direction.

[0049] For example, as shown in Figure 8, the bottom surface 143 of the front arm under cover 43 is set at a position higher than the imaginary straight line La that connects the bottom surface 141 of the floor under cover 41 and the bottom surface 142 of the rear arm under cover 42 (more specifically, the bottom surface 146 of the flat plate portion 46) in the front-to-back direction, across the entire width of the vehicle.

[0050] As shown in Figure 5, the front arm under cover 43, which is fixed to the front lower arm 15, has its bottom surface 143 positioned above the bottom surface 142 of the rear arm under cover 42, which is fixed to the larger rear lower arm 14, throughout its entire width direction, even when the vehicle is loaded or in motion.

[0051] For example, when the vehicle is in motion, the front arm under cover 43, which is fixed to the front lower arm 15, swings up and down as the front lower arm 15 swings up and down. On the other hand, the rear arm under cover 42, which is fixed to the rear lower arm 14, swings up and down as the rear lower arm 14 swings up and down. Even in such cases, the lowest point of the bottom surface 143 of the vertically moving front arm under cover 43 is set higher in the corresponding parts in the vehicle width direction than the lowest point of the bottom surface 142 of the vertically moving rear arm under cover 42.

[0052] As shown in Figures 3, 4, and 8, the bracket 60 of the front arm under cover 43 is integrally formed in a plate shape with a roughly rectangular shape in plan view, consisting of an arm holding portion 61 which is curved upward in a projection shape when viewed from the side of the vehicle so as to embrace the front lower arm 15 from above, a front edge portion 62 which is aligned in the vehicle width direction at the front end of the arm holding portion 61, and a rear edge portion 63 which is aligned in the vehicle width direction at the rear end of the arm holding portion 61.

[0053] The bracket 60 is attached to the upper surface of the front arm under cover 43 at mounting points located at the four corners in a plan view, using mounting members, with the front edge 62 and rear edge 63 of the bracket 60 embracing the front lower arm 15 from above by the arm holding portion 61.

[0054] In this embodiment, as shown in Figure 8, of the mounting locations at each of the four corners of the rectangular bracket 60 in plan view, the two mounting locations located at both ends of one diagonal are formed with mounting holes 64a that can be fastened with bolts B and nuts N as mounting members, while the two mounting locations located at both ends of the other diagonal are formed with mounting holes 64b that can be locked with resin locking members, i.e., grommets G, as mounting members.

[0055] On the other hand, as shown in Figure 8, mounting holes 38a and 38b are formed vertically through the upper surface of the front arm under cover 43 at locations corresponding to the four mounting holes 64a and 64b of the bracket 60 in a plan view.

[0056] As shown in Figures 5 and 9, the subframe under cover 44 is attached to the subframe 30 via a bracket 70, and is formed in a substantially flat shape with a plate thickness in the vertical direction for almost its entire length, and is positioned substantially horizontally immediately behind the rear end of the floor under cover 41 with a gap in the front-rear direction.

[0057] As shown in Figure 5, the subframe under cover 44 has a length in the vehicle width direction that allows it to be positioned directly below the area extending from the outer side in the vehicle width direction of the front cross member 31 of the subframe 30 to the inner side of the vehicle width of the front lower arm 15.

[0058] As shown in Figures 5 and 9, the bracket 70 of the subframe under cover 44 comprises a bottom portion 71 attached to the upper surface of the subframe under cover 44 using bolts B, and left and right vertical wall portions 72 rising upward from both sides of the bottom portion 71, forming a gate-like shape that opens upward when viewed from the front. The upper ends of the left and right vertical wall portions 72 of the bracket 70 are integrally attached to the lower surface of the outer end in the vehicle width direction of the front cross member 31 by welding or the like.

[0059] As shown in Figures 1 to 4 and Figures 6 to 13, the rear arm under cover 42 is formed by resin molding so as to be generally symmetrical with respect to the cover center line in the vehicle's longitudinal direction, which passes through the midpoint of the rear arm under cover 42 in the vehicle's width direction.

[0060] As shown in Figures 6 and 8 to 12, the rear arm under cover 42 comprises a flat plate portion 46 positioned substantially horizontally below the rear lower arm 14 and a front curved portion 47 that forms an upward-sloping curved shape at the front of the rear arm under cover 42. That is, as shown in Figures 8 to 11, the rear arm under cover 42 extends continuously in the vertical and front-rear directions from the front upper side of the rear lower arm 14, through below the bottom portion 14b, to the rear lower side.

[0061] The flat plate portion 46 covers the bottom surface portion 14b of the rear lower arm 14 from below and protrudes rearward from the rear wall portion 14e of the rear lower arm 14. The flat plate portion 46 is formed in a substantially flat shape with a length in the vehicle width direction that covers the portion of the rear lower arm 14 from directly below over the entire length in the vehicle width direction, excluding the lower arm shafts 14wa and 14wb on both the inner and outer sides in the vehicle width direction. Furthermore, as shown in Figures 2, 6 to 8, 11, and 13, the flat plate portion 46 is formed to be attachable to locking pieces 19 provided on both the left and right sides of the rear of the rear lower arm 14 via grommets G, bolts B, and nuts N.

[0062] More specifically, as shown in Figures 12 and 13, the flat plate portion 46 has a grommet insertion hole 48a (see Figures 3 and 6) that communicates vertically with the grommet insertion hole 19a (see Figures 3, 6, 8, 9, and 11) in the locking piece portion 19, and a bolt insertion hole 48b that communicates vertically with the bolt insertion hole 19b in the locking piece portion 19. The flat plate portion 46 and the locking piece portion 19 are locked together by grommets G inserted into the grommet insertion holes 19a and 48a of both, and fastened together by bolts B and nuts N inserted into the bolt insertion holes 19b and 48b of both.

[0063] As shown in Figure 12, the front curved portion 47 has a front rising bottom portion 147 that extends smoothly forward from the bottom portion 146 of the flat plate portion 46 in the vehicle width direction and gradually rises upward towards the front.

[0064] As shown in Figure 8, the front rising bottom portion 147 rises from a position lower than the bottom portion 143 of the front arm under cover 43 and the bottom portion 141 of the floor under cover 41, and rises in a curved shape towards the front, reaching a position higher than the bottom portion 143 of the front arm under cover 43.

[0065] Furthermore, as shown in Figure 5, the front rising bottom portion 147 rises from a position lower than the lower end wtd of the gap wt, with a curved shape as it moves forward, and is positioned in the area immediately behind at least the entire area of ​​the gap wt in the vehicle width direction.

[0066] Here, as shown in the enlarged area of ​​region Z in Figure 5, the height of the lower end wtd of the gap wt corresponds to the height of the bottom surface 144t of the opposing end 44t on the lower side. On the other hand, the height of the upper end wtu of the gap wt corresponds to the height of the actual bottom surface 143t of the opposing end 43t on the higher side.

[0067] More specifically, as shown in Figure 5, the front rising bottom portion 147 rises along the vehicle width direction, including the area immediately behind each of the opposing ends 43t and 44t in the vehicle width direction, from a position lower than the bottom portion 144t of the lower opposing end 44t to a position higher than the bottom portion 143t of the higher opposing end 43t.

[0068] In this example, as shown in Figures 2 and 5, the front rising bottom portion 147 is positioned over the entire area in the vehicle width direction of the area immediately behind the subframe under cover 44, excluding the inner portion in the vehicle width direction, and the front arm under cover 43, including the gap wt between them.

[0069] Furthermore, as shown in Figures 12 and 13, the front curved surface portion 47 has a front edge 47f formed in a straight line along the vehicle width direction along its entire length in the vehicle width direction, and comprises a front curved central portion 47a located in the center in the vehicle width direction, and front curved outer portions 47b located on both the left and right sides thereof. The upper part 47U of the front curved central portion 47a is formed to protrude above the front edge 47f located at the front upper edge of the front curved outer portions 47b on both the left and right sides.

[0070] As shown in Figures 8, 10, and 11, the upper part 47U of the central part 47a of the front curved surface is provided with a hook portion 49 that protrudes backward and hooks onto the front edge flange portion 14d of the rear lower arm 14 from the front and above, and works in cooperation with the locking piece portion 19 to fix it to the rear lower arm 14.

[0071] As shown in Figures 10 to 13, the hook portion 49 is formed such that the entire upper edge portion 49a of the upper part 47U of the central part 47a of the front curved surface, which is aligned in the vehicle width direction, and the entire left and right side edges 49b, which are aligned in the vertical direction, both protrude to the rear. On both the left and right sides of the upper edge 49a of the upper part 47U of the central part 47a of the front curved surface, forward-projecting pieces 49c are formed that protrude further forward than other parts at the upper end (see Figures 11 and 13). The left and right side edges 49b of the front curved surface 47 are formed in a forward-concave shape so that the front edge flange portion 14d of the rear lower arm 14 can be fitted into them, as shown in Figures 8, 10, and 11.

[0072] As shown in Figures 3 and 4, the hook portion 49 is provided at a location that coincides with the vehicle width direction of the large-diameter portion 14a of the rear lower arm 14, which has a spring seat 26 for receiving the spring. Therefore, the hook portion 49 is hooked onto the leading edge flange portion 14d of the large-diameter portion 14a. As shown in Figure 8, the locking pieces 19 provided on both sides of the rear wall portion 14e of the rear lower arm 14 are provided on both the left and right sides relative to the hook portion 49 in the vehicle width direction.

[0073] Furthermore, as shown in Figures 11 to 13, hollow sections 50 are provided on both the left and right sides of the rear arm under cover 42. The left and right hollow sections 50 each consist of the front curved outer section 47b which forms the front wall, the front vertical wall section 51 which forms the rear wall, and the upper wall section 52 which forms the upper wall, and have a hollow section 50s (closed cross-sectional space) inside that is aligned with the vehicle width direction.

[0074] The front vertical wall portion 51 rises upward from the rear (base) of the front curved outer portion 47b, which has a forward-sloping curved shape, in the direction upward of the vehicle. The upper wall portion 52 is formed in a horizontal plane. As a result, the hollow portion 50s inside the front vertical wall portion 51 has a roughly triangular cross-section perpendicular to the vehicle width direction. Furthermore, as shown in Figure 13, on both the left and right sides, the hollow forming portions 50 are provided spaced apart outward in the vehicle width direction from the front curved central portion 47a, while the upper wall portion 52 extends in the vehicle width direction to the lower end of the side edge portion 49b of the upper part 47U of the front curved central portion 47a, and are integrally formed with each other.

[0075] As shown in Figures 8 and 11, the rear end portion 52r of the upper wall portion 52 that extends horizontally in the front-rear direction on the front curved outer portion 47b of the rear arm under cover 42 is positioned near the front of the upper end of the front wall portion 14c of the rear lower arm 14, with the lower surface of the front edge flange portion 14d abutting against its upper surface from above. This vertical and front-rear alignment between the front curved outer portion 47b and the rear arm under cover 42 is formed along the vehicle width direction of the upper wall portion 52 (in this example, over approximately the entire length of the left and right front curved outer portions 47b in the vehicle width direction).

[0076] As a result, the rear arm under cover 42 is configured such that the front curved surface 47 is firmly supported from the rear side against impacts from the front by the front wall portion 14c, which minimizes the gap between the front and rear ends of the upper wall portion 52 and the rear end ends 52r of the front curved outer portion 47b, with the front edge flange portion 14d pressing down from above.

[0077] Furthermore, as shown in Figure 13, multiple reinforcing ribs 551 and 552 are provided on the surface of the rear arm under cover 42 facing the rear lower arm 14, i.e., the upper surface. The ribs 551 and 552 consist of longitudinal ribs 551 that run along the longitudinal direction and widthwise ribs 552 that run along the vehicle width direction.

[0078] The longitudinal ribs 551 are arranged at intervals from each other in the vehicle width direction, and further, extending outward from the center of the rear arm under cover 42 in the vehicle width direction, there are longitudinal inner ribs 551a, longitudinal intermediate ribs 551b, and longitudinal outer ribs 551c.

[0079] The longitudinal inner ribs 551a are formed in pairs on the left and right sides at the central part 47a of the front curved surface. The longitudinal intermediate ribs 551b are arranged in parallel with a gap in the vehicle width direction between the hollow forming part 50 and the central part 47a of the front curved surface, and their upper ends are joined to the upper wall part 52. The longitudinal outer ribs 551c are formed at the front part up to the front longitudinal wall part 51. Furthermore, the longitudinal outer ribs 551c are formed at the rear part from the front curved surface part 47 to the rear end of the rear arm under cover 42, and both sides are connected in the vehicle width direction by the vehicle width direction ribs 552.

[0080] Next, we will explain, using Figure 8, the function of the underbody airflow w, which is rectified along the bottom surface 141 of the floor under cover 41 during vehicle operation and then separated from the rear end of the floor under cover 41, as it passes under the rear suspension 10.

[0081] A gap in the front-to-back direction is maintained between the rear end of the bottom surface 141 of the floor under cover 41 and the front end of the bottom surface 143 of the front arm under cover 43. As a result, the underfloor airflow w that separates from the rear end of the floor under cover 41 is gradually diffused vertically as it passes through this gap (see arrow w1 in Figure 8). Note that Figure 8 only shows the upward turbulent portions w1 to w3 of the turbulent portions that have been diffused from the main stream of underfloor airflow w.

[0082] Furthermore, in this embodiment, as shown in Figure 8, the bottom surface 143 of the front arm under cover 43 is set at a position higher than the imaginary straight line La that connects the bottom surface 141 of the floor under cover 41 and the bottom surface 142 of the rear arm under cover 42 (specifically, the bottom surface 146 of the flat plate portion 46) in the front-to-back direction, over the entire width of the vehicle.

[0083] Thus, the bottom surface 143 of the front arm under cover 43 is arranged in a stepped manner relative to the bottom surface 141 of the floor under cover 41 and the bottom surface 142 of the rear arm under cover 42, and therefore there is a vertical gap between it and the virtual straight line La. In this example, the virtual straight line La is defined as the straight line connecting the rear end of the bottom surface 141 of the floor under cover 41 and the front end of the bottom surface 146 of the flat plate portion 46.

[0084] Furthermore, as shown in Figure 5, the front arm under cover 43 is inclined to correspond to the front lower arm 15, such that the height of the bottom surface 14b is higher towards the inside than towards the outside in the vehicle width direction. Therefore, the vertical gap between the bottom surface 143 of the front arm under cover 43 and the virtual straight line La is larger towards the inside than towards the outside in the vehicle width direction. In other words, although the vertical gap between the bottom surface 143 of the front arm under cover 43 and the virtual straight line La is small at the cross-sectional position shown in Figure 8, it becomes larger towards the inside in the vehicle width direction.

[0085] Therefore, the underfloor airflow w passing directly beneath the front arm under cover 43 does not receive sufficient rectification from the front arm under cover 43, and as shown in the turbulent portion w2 in Figure 8, it diffuses upward towards the rear. Furthermore, when the underfloor airflow w passes under the gap in the front-rear direction between the rear end of the bottom surface portion 143 of the front arm under cover 43 and the front end of the bottom surface portion 142 of the rear arm under cover 42, no rectification effect is obtained, and as shown in the turbulent portion w3 in Figure 8, it diffuses further upward towards the rear.

[0086] Thus, even if the underfloor airflow w is disturbed due to discontinuities in the front-to-rear direction or steps in the vertical direction between the floor under cover 41 and the rear arm under cover 42, as shown in Figure 8, the underfloor airflow w, including the disturbed portions w1, w2, and w3 that are turbulent relative to the main stream, can be smoothly directed from the front to the front rising bottom surface 147 of the rear arm under cover 42 and released towards the rear.

[0087] In other words, the underfloor airflow w that flows smoothly backward to adhere along the bottom surface 141 of the floor under cover 41 can be detached from the rear end of the floor under cover 41, reattached to the front rising bottom surface 147 of the rear arm under cover 42, and then flow smoothly backward along the substantially horizontal bottom surface 146 of the rear flat plate portion 46.

[0088] Furthermore, as shown in Figure 14, of the underfloor airflow w that separates from the rear end of the floor under cover 41 and flows backward, the underfloor airflow wi (hereinafter referred to as "inside underfloor airflow wi") that flows on the inside of the vehicle body in the vehicle width direction, i.e., directly below the subframe under cover 44, has a faster flow velocity in the main stream flowing backward than the underfloor airflow wo (hereinafter referred to as "outside underfloor airflow wo") that flows on the outside of the vehicle body in the vehicle width direction, i.e., directly below the front arm under cover 43, and is therefore less prone to turbulence.

[0089] Furthermore, since the subframe under cover 44 is positioned lower in height than the inner portion of the front arm under cover 43 in the vehicle width direction, the vertical step difference between it and the adjacent under covers 41 and 42 at the front and rear is small. Therefore, as shown in Figure 14, the turbulent portion wit of the underfloor airflow wi on the inner side of the vehicle width is smaller and less pronounced compared to the turbulent portion wot of the underfloor airflow wo on the outer side of the vehicle width. In other words, the underfloor airflow wi on the inner side of the vehicle width can flow more smoothly with less turbulence compared to the underfloor airflow wo on the outer side of the vehicle width that flows directly beneath the front arm under cover 43.

[0090] Furthermore, as shown in Figure 14, in the underfloor airflow wm (hereinafter referred to as "underfloor airflow wm in the middle of the vehicle width") that passes directly beneath the gap wt between the front arm under cover 43 and the subframe under cover 44 in the vehicle width direction, a turbulent vortex portion wmt is likely to occur due to being pulled upward through the gap wt. In contrast, in this embodiment, the front rising bottom surface portion 147 of the rear arm under cover 42 is positioned to face forward immediately after the gap wt. As described above, the underfloor airflow wm that has passed directly beneath the gap wt can be straightened by adhering to the front rising bottom surface portion 147 of the rear arm under cover 42 from the front, including the turbulent portion wmt relative to its main flow.

[0091] In short, the underfloor airflow wi on the inside of the vehicle width, the underfloor airflow wm in the middle of the vehicle width, and the underfloor airflow wo on the outside of the vehicle width, even if turbulence occurs as they pass under the floor in front of the rear suspension area, can be straightened by adhering to the front rising bottom surface 147 of the rear arm under cover 42 located immediately afterward, and then flowing smoothly to the rear.

[0092] As shown in Figures 1 to 7, the lower body structure of the vehicle in this embodiment described above includes a rear suspension 10 that connects a wheel support member 11 supporting the rear wheel 5 to the vehicle body via a front lower arm 15 and a rear lower arm 14 that extend along the vehicle width direction and are positioned front and rear with respect to the axle W5; a rear arm under cover 42 positioned below the rear lower arm 14; a front arm under cover 43 positioned directly in front of the rear arm under cover 42 and below the front lower arm 15, the front arm under cover 43 having a bottom surface 151 higher than the bottom surface 14b of the rear lower arm 14; and a floor under cover 41 positioned directly in front of the front arm under cover 43 and below the front floor panel 1 which serves as the vehicle body floor.

[0093] Furthermore, as shown in Figure 8, the bottom surface 143 of the front arm under cover 43 is set higher than the imaginary straight line La that connects the bottom surface 141 of the floor under cover 41 and the bottom surface 142 of the rear arm under cover 42 in the front-to-back direction.

[0094] As shown in Figure 8, the bottom surface 142 of the rear arm under cover 42 is provided with a front rising bottom surface 147 that rises from a position lower than the bottom surface 143 of the front arm under cover 43, and rises to a position higher than the bottom surface 143 of the front arm under cover 43, with a curved shape towards the front.

[0095] According to the above configuration, while satisfying the aerodynamic performance of the underbody airflow that flows towards the rear of the vehicle below the rear suspension 10, it is also possible to satisfy various performance aspects such as impact resistance and snow removal capabilities of the front and rear arm undercovers 42 and 43 attached to the front and rear lower arms 14 and 15 of the rear suspension 10.

[0096] More specifically, as shown in Figure 8, the bottom surface 143 of the front arm under cover 43 is positioned higher than the imaginary straight line La connecting the bottom surface 141 of the floor under cover 41 and the bottom surface 142 of the rear arm under cover 42, thereby positioning it above the bottom surface 141 of the floor under cover 41 and the bottom surface 142 of the rear arm under cover 42. As a result, a step portion that is recessed upward is formed directly below the bottom surface 143 of the front arm under cover 43.

[0097] Furthermore, even if the underfloor airflow that flows along the floor under cover 41 towards the rear of the vehicle and separates from the floor under cover 41 is disturbed due to passing over the stepped portion directly below the bottom surface 143 of the front arm under cover 43, it can be reattached to the front rising bottom surface 147 of the rear arm under cover 42. In addition, the reattached underfloor airflow can be straightened along the curved front rising bottom surface 147 towards the rear of the vehicle.

[0098] Furthermore, the bottom surface 143 of the front arm under cover 43 can be positioned shifted upward without aligning its height with the bottom surface 141 of the floor under cover 41 and the bottom surface 142 of the rear arm under cover 42. As a result, the front arm under cover 43 can have greater freedom in shape, and the risk of interference with the under covers 41 and 42 on the front and rear sides can be reduced, thus ensuring impact resistance (tolerance for deformation). In addition, since the front arm under cover 43 can be positioned as close as possible to the front lower arm 15 from below, impact resistance against chipping and other impacts can also be improved.

[0099] Furthermore, in response to the front lower arm 15, whose bottom surface 151 is higher than the bottom surface 14b of the rear lower arm 14, the front arm under cover 43 can be positioned at a height close to the front lower arm 15 from below by shifting it upward relative to the front and rear under covers 41 and 42 as described above. This minimizes the vertical space between the front arm under cover 43 and the front lower arm 15, making it less likely for snow and mud to remain in that space, thus ensuring snow and mud removal capabilities.

[0100] Therefore, while satisfying the aerodynamic performance of the underbody airflow that flows towards the rear of the vehicle below the rear suspension 10, it is also possible to satisfy the impact resistance and snow-shedding performance of the front and rear arm undercovers 42 and 43 attached to the front and rear lower arms 14 and 15 of the rear suspension 10.

[0101] In one aspect of this invention, as shown in Figure 5, the front arm under cover 43 is positioned in a downward inclined position along the extending direction of the front lower arm 15, which is located lower towards the outer side in the vehicle width direction.

[0102] According to the above configuration, the front arm under cover 43 can be positioned along the extending direction of the front lower arm 15. This minimizes the vertical separation between the main surface of the front arm under cover 43 and the front lower arm 15 in the vehicle width direction (extending direction), thereby improving the protective performance of the front arm under cover 43 against chipping and the like, and also ensures better snow removal.

[0103] In one aspect of this invention, as shown in Figure 5, the lowest point of the bottom surface portion 143 of the front arm under cover 43, which moves up and down in conjunction with the up and down movement of the front lower arm 15, is set higher in the corresponding parts in the vehicle width direction than the lowest point of the bottom surface portion 142 of the rear arm under cover 42, which moves up and down in conjunction with the up and down movement of the rear lower arm 14.

[0104] According to the above configuration, the front arm under cover 43 moves up and down in conjunction with the up and down movement of the front lower arm 15, and the rear arm under cover 42 moves up and down in conjunction with the up and down movement of the rear lower arm 14. However, the lowest point of the bottom surface portion 142 of the rear arm under cover 42 can be set higher than the lowest point of the bottom surface portion 143 of the front arm under cover 43 at corresponding points in the vehicle width direction. As a result, the underbody airflow passing below the front arm under cover 43 can be reliably reattached to the front rising bottom surface portion 147 of the rear arm under cover 42 immediately behind it, thereby rectifying the airflow.

[0105] As shown in Figure 8, in this embodiment of the invention, the front rising bottom portion 147 is configured to rise from a position lower than the bottom portion 141 of the floor under cover 41. According to the above configuration, the front rising bottom portion 147 rises from a position lower than the bottom portion 141 of the floor under cover 41, which is lower than the bottom portion 143 of the front arm under cover 43, to a position higher than the bottom portion 143 of the front arm under cover 43. As a result, the underfloor airflow that has moved away from the rear end of the floor under cover 41 and passed below the bottom portion 143 of the front arm under cover 43 can be reliably reattached by the front rising bottom portion 147 of the rear arm under cover 42.

[0106] As shown in Figure 8, in this embodiment of the invention, a front rising bottom portion 143a is provided at the front of the bottom portion 143 of the front arm under cover 43, which rises higher towards the front.

[0107] According to the above configuration, even if the underfloor airflow that has separated from the floor under cover 41 rises before flowing below the front arm under cover 43, it can adhere to the front rising bottom surface 143a, and the airflow can be straightened to the rear along the bottom surface 143 of the front arm under cover 43.

[0108] Therefore, even without setting the gap between the floor under cover 41 and the front arm under cover 43 to be as small as possible, the underbody airflow separated from the floor under cover 41 can be directed towards the rear below the front arm under cover 43.

[0109] In the correspondence between the configuration of this invention and the embodiments described above, the vehicle body floor corresponds to the front floor panel 1. However, this invention is not limited to the configuration of the embodiments described above, and many embodiments can be obtained.

[0110] For example, in this embodiment, the front arm under cover 43 and the subframe under cover 44 are provided as separate components in the vehicle width direction below the front region of the rear suspension. However, in the present invention, the subframe under cover 44 does not need to be provided as long as at least the front arm under cover 43 is provided below the front region of the rear suspension. Alternatively, the front arm under cover 43 and the subframe under cover 44 may be formed as a single component integrally along the vehicle width direction. [Explanation of symbols]

[0111] 1…Front floor panel (vehicle floor) 5…Rear wheel 11...Wheel support member 10…Rear suspension 14…Rear lower arm 15…Front lower arm 14b...Bottom surface of the rear lower arm 41... Floor undercover 42...Rear arm under cover 43... Front arm under cover 141... Bottom surface of the floor under cover 142...Bottom surface of the rear arm under cover 143...Bottom surface of the front arm under cover 143a... Front arm under cover, front rising bottom section 147... Front rising bottom part of the rear arm under cover 151...Bottom surface of the front lower arm W5...Axle La... virtual line

Claims

1. A rear suspension system that connects a wheel support member that supports the rear wheel to the vehicle body via a front lower arm and a rear lower arm that extend along the width direction of the vehicle and are positioned front to rear of the axle, A rear arm under cover is positioned below the aforementioned rear lower arm, A lower body structure of a vehicle comprising a front arm under cover positioned directly in front of the rear arm under cover, below the front lower arm, having a bottom surface higher than the bottom surface of the rear lower arm, and a floor under cover positioned directly in front of the front arm under cover, below the vehicle body floor, The bottom surface of the front arm under cover is set to a position higher than the imaginary straight line connecting the bottom surface of the floor under cover and the bottom surface of the rear arm under cover in the front-to-back direction. The bottom surface of the rear arm under cover is provided with a front rising bottom surface that rises from a lower position than the bottom surface of the front arm under cover, and has a curved shape that rises further forward. The lower body structure of the vehicle.

2. The aforementioned front arm under cover is positioned in a downward inclined position along the extending direction of the front lower arm, which is located lower towards the outside in the vehicle width direction. The lower body structure of the vehicle according to claim 1.

3. The lowest point of the bottom surface of the front arm under cover, which moves up and down in conjunction with the up and down movement of the front lower arm, is set higher in the vehicle width direction at corresponding points than the lowest point of the bottom surface of the rear arm under cover, which moves up and down in conjunction with the up and down movement of the rear lower arm. The lower body structure of the vehicle according to claim 1.

4. The aforementioned front rising bottom portion is configured to rise from a position lower than the bottom portion of the floor under cover. The lower body structure of the vehicle according to claim 1.

5. The front of the bottom surface of the front arm under cover is provided with a front rising bottom surface that rises higher towards the front. The lower body structure of the vehicle according to claim 1.

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