Suspension member

Abstract

A suspension member (1) has mounted therein a drive unit (5) for vehicle travel and the suspension member is attached to a front part of a vehicle body or a rear part of the vehicle body. The suspension member (1) comprises: a pair of first arms (7) laterally extending, respectively, from base ends at left and right parts on the vehicle cabin side of the suspension member (1); and a pair of second arms (8) respectively extending from left and right parts on the vehicle body end side of the suspension member (1). Each first arm (7) has a first attachment part (7a) for attachment to the vehicle body, and each second arm (8) has a second attachment part (8b) for attachment to the vehicle body. Each first arm (7) has a fragile part (7b) formed on the base end side of the first arm from the first attachment part (7a).

Description

Suspension members

[0001] The present invention relates to a suspension member that is mounted on the front or rear of a vehicle body and that has a drive unit for running the vehicle.

[0002] A drive unit for vehicle travel is mounted on the suspension member. In the case of hybrid electric vehicles (HEVs) including plug-in hybrid electric vehicles (PHEVs), a hybrid unit integrating an internal combustion engine and an electric motor is mounted on the suspension member as the drive unit. In the case of internal combustion engine (ICE) vehicles, the internal combustion engine is mounted on the suspension member as the drive unit, and in the case of battery electric vehicles (BEVs), the electric motor is mounted on the suspension member as the drive unit. For this reason, the suspension member is also called an engine cradle or a motor cradle. Suspension members include front suspension members attached to the front of the vehicle body and rear suspension members attached to the rear of the vehicle body. Since suspension members are attached to the vehicle body structure, they are also called subframes. Patent Document 1 discloses related technology.

[0003] Japanese Patent Application Laid-Open No. 2008-213736

[0004] In order to protect the drive unit mounted on the suspension member during a vehicle collision (a frontal collision in the case of a front suspension member, and a rearward collision in the case of a rear suspension member), the rigidity of the suspension member may be increased. However, increasing the rigidity of the suspension member reduces the amount of energy absorbed by the deformation of the suspension member and the vehicle body, making it easier for the collision load to be transmitted to the passenger compartment.

[0005] An object of the present invention is to provide a suspension member that can protect a mounted drive unit during a vehicle collision while suppressing the transmission of a collision load to the vehicle interior.

[0006] A suspension member according to one aspect of the present invention is mounted on a front or rear vehicle body and includes a drive unit for vehicle travel. The suspension member includes a pair of first arms extending laterally from base ends on the left and right sides of the suspension member facing the passenger compartment, and a pair of second arms extending laterally from the left and right sides of the suspension member facing the vehicle body end. Each first arm has a first attachment portion to the vehicle body, and each second arm has a second attachment portion to the vehicle body. Each first arm has a weakened portion formed on the base end side of the first attachment portion.

[0007] The suspension member according to the present invention can protect the mounted drive unit during a vehicle collision and suppress the transmission of the collision load to the vehicle interior.

[0008] FIG. 1 is a perspective view showing a suspension member according to an embodiment. FIG. 2 is a plan view of the suspension member of FIG. 1. FIG. 3 is a bottom view of the suspension member of FIG. 1. FIG. 4 is a left side view of the suspension member of FIG. 1. FIG. 5 is a left side view showing the suspension member of FIG. 1 attached to a vehicle body. FIG. 6 is a bottom view showing the suspension link attached to the suspension member of FIG. 1. FIG. 7A is a cross-sectional view of a weak portion of a first arm taken along line VIIA-VIIA of FIG. 2. FIG. 7B is a cross-sectional view of a weakest portion of an upper beam taken along line VIIBC-VIIBC of FIG. 2. FIG. 7C is a cross-sectional view of a weakest portion of a lower beam taken along line VIIBC-VIIBC of FIG. 2. FIG. 7D is a cross-sectional view of a weakest portion of a second arm taken along line VIID-VIID of FIG. 2. FIG. 8 is a bottom view showing deformation behavior of the suspension member of FIG. 1 during a vehicle rear-end collision.

[0009] A suspension member 1 according to an embodiment will be described below with reference to the drawings. The suspension member 1 is a rear suspension member that is attached to the rear of a vehicle body for rear suspension. The vehicle compartment is located in front of the rear suspension member, and the end of the vehicle body, i.e., the rear end of the vehicle, is located behind it. Therefore, the front side of the suspension member 1 corresponds to the vehicle compartment side, and the rear side corresponds to the vehicle body end side.

[0010] As shown in Figures 1 to 4, the suspension member 1 has a rectangular frame structure in a plan view, which is composed of a left side beam 2L, a right side beam 2R, a first cross beam 3, and a second cross beam 4. The left side beam 2L and the right side beam 2R each extend in the longitudinal direction of the vehicle and are, for example, closed-section members. The first cross beam 3 connects the ends of the left side beam 2L and the right side beam 2R facing the passenger compartment. The second cross beam 4 connects the ends of the left side beam 2L and the right side beam 2R facing the vehicle body end. The first cross beam 3 and the second cross beam 4 are, for example, closed-section members having a vertically elongated hollow cross section at their centers.

[0011] A drive unit 5 for propelling the vehicle is mounted inside the rectangular frame structure. The vehicle according to this embodiment is a BEV, and the drive unit 5 is an electric motor for driving the vehicle, which is a high-voltage component. The electric motor may be integrated with an inverter, a reduction gear for reducing motor output, a rear differential gear, and the like. The drive unit 5 is attached to and supported by the first cross beam 3 and the second cross beam 4 via, for example, four rubber mounts. A drive shaft for driving the rear wheels 6 extends from the drive unit 5 (see FIG. 6 ).

[0012] The suspension member 1 has a pair of first arms 7 extending laterally from the front left and right portions thereof. Each of the first arms 7 extends horizontally and slightly forward from the front left and right corners of the rectangular frame structure.

[0013] The suspension member 1 also has a pair of second arms 8 extending laterally from the left and right rear portions thereof. Each second arm 8 extends obliquely rearward from the left and right rear corners of the rectangular frame structure, bends, and extends laterally from the bent portion substantially horizontally. A rear end edge 8a of each second arm 8 extends in the vehicle width direction from the base end of the second arm 8 to the second mounting portion.

[0014] In other words, in the suspension member 1, the first cross beam 3 is suspended between the base ends of the first arms 7, and the second cross beam 4 is suspended between the base ends of the second arms 8. Similarly, the left side beam 2L is suspended between the left end of the first cross beam 3 and the left end of the second cross beam 4, and the right side beam 2R is suspended between the right end of the first cross beam 3 and the right end of the second cross beam 4.

[0015] A first mounting portion 7a for mounting to the vehicle body is formed at the tip of each first arm 7, and a second mounting portion 8b for mounting to the vehicle body is formed at the tip of each second arm 8. The first mounting portion 7a and the second mounting portion 8b are, for example, vertical shaft rubber mounts, and each has a bolt insertion hole B extending in the vertical direction in the center. The first mounting portion 7a and the second mounting portion 8b are fastened and fixed to the rear side member 9 by bolts (not shown) that are inserted into the bolt insertion holes B (see FIG. 5).

[0016] A weak portion 7b is formed on each first arm 7 closer to the base end than the first mounting portion 7a. The weak portion 7b is configured to have relatively low strength and rigidity so that it is deformed earlier than other portions due to a load input to the suspension member 1 during a vehicle collision.

[0017] In one embodiment, the weakened portion is formed by forming a notch in the first arm 7 having a closed cross section to locally open the cross section. In another embodiment, the weakened portion is formed by forming a recessed bead in the first arm 7 having a closed cross section to locally reduce the closed cross section dimension. In this embodiment, the weakened portion 7b is formed by making the width of the first arm 7 at its smallest in a plan view at the weakened portion 7b. That is, as shown in FIG. 2 , the portion of the first arm 7 whose width is smallest in a plan view is the weakened portion 7b. The minimum width of each first arm 7, i.e., the width of the weakened portion 7b, is smaller than any of the minimum widths of the second arms 8 in a plan view. The strength of the weakened portion 7b of the first arm 7 against a load input from the vehicle longitudinal direction is set smaller than the strength of the second arm 8 against a load input from the vehicle longitudinal direction.

[0018] 4 and 5, the left side beam 2L and the right side beam 2R each include an upper beam 2a and a lower beam 2b. A drive shaft may be disposed between the upper beam 2a and the lower beam 2b.

[0019] The upper beam 2a has, for example, a closed cross section and may be curved to be slightly convex upward. The front end and rear end of the upper beam 2a are smoothly connected to the base ends of the first arm 7 and the second arm 8, respectively.

[0020] The lower beam 2b has, for example, a U-shaped cross section (see FIG. 1), and its front end may be joined to the first cross beam 3 and also to the lower surface of the upper beam 2a, as in the illustrated example. Also, its rear end may be connected to the third cross beam 10 and also to the second cross beam 4 via a rear plate 11, as in the illustrated example. Both ends of the third cross beam 10 are joined to the upper beam 2a via brackets 12. The central portion of the third cross beam 10 has a closed cross section, and the rear plate 11 is joined to this closed cross section portion.

[0021] 6, the hub carrier 13 of each rear wheel 6 is attached to the suspension member 1 by five link members, which together with the five link members form a multi-link suspension. The five link members are a front upper link 14, a front lower link 15, a rear upper link 16, a rear lower link 17, and a support link 18 disposed between the rear upper link 16 and the rear lower link 17. Five link attachment portions are formed on each of the right and left sides of the suspension member 1, and the inner ends of the five link members are attached to the five link attachment portions, respectively.

[0022] For example, the front upper bracket 14a serving as the link mounting portion of the front upper link 14 may be fixed from the upper surface to the side of the upper beam 2a near the first arm 7. The front lower bracket 15a serving as the link mounting portion of the front lower link 15 may be fixed to the lower surface of the first arm 7, closer to the base end than the first mounting portion 7a. The rear upper bracket 16a (see FIGS. 2 and 3) serving as the link mounting portion of the rear upper link 16 may be fixed to the upper surface of the base end of the second arm 8. The rear lower bracket 17a serving as the link mounting portion of the rear lower link 17 may be formed at the end of the third cross beam 10. The support link bracket 18a serving as the link mounting portion of the support link 18 may be fixed to the lower surface of the upper beam 2a near the second arm 8.

[0023] As shown in Figure 6, a stabilizer 20 is attached to the underside of each second arm 8 via a mount bracket 19. The stabilizer 20 is also called an anti-roll bar. Both ends of the stabilizer 20 are connected to the left and right rear upper links 16 via stabilizer links 21. The center of the stabilizer 20 is attached to the pair of mount brackets 19 with a rubber mount, so that torsion of the stabilizer 20 can be transmitted to the left and right rear upper links 16.

[0024] The second moment of area (hereinafter also referred to as the horizontal second moment of area) about a neutral axis extending in the up-down direction in the cross section of the weak portion 7b of the first arm 7 shown in Fig. 7A is smaller than the horizontal second moment of area in the cross section of the upper beam 2a shown in Fig. 7B. In other words, the portion of the first arm 7 where the weak portion 7b is formed is more likely to bend in the horizontal plane due to a load input during a vehicle collision than the upper beam 2a.

[0025] Furthermore, the horizontal moment of inertia at the cross section of the weak portion 7b of the first arm 7 is smaller than the horizontal moment of inertia at the cross section of the lower beam 2b shown in Fig. 7C. In other words, the portion of the first arm 7 where the weak portion is formed is more likely to bend in the horizontal plane due to the load input during a vehicle collision than the lower beam 2b.

[0026] The horizontal moment of inertia of the weak portion 7b of the first arm 7 is smaller than the horizontal moment of inertia of the cross section of the second arm 8 shown in Fig. 7D. Although not shown, the horizontal moment of inertia of the weak portion 7b may be smaller than the horizontal moment of inertia of any of the first cross beam 3, the second cross beam 4, and the third cross beam 10. In this case, the horizontal moment of inertia of the weak portion 7b is smaller than the horizontal moment of inertia of all the arms and beams of the suspension member 1, and therefore the weak portion 7b is most likely to bend due to the load input to the suspension member 1 during a vehicle collision.

[0027] During a vehicle collision, a collision load is typically input to the rear side member via a bumper reinforcement attached to the rear end of the vehicle. The rear side member collapses together with the rear of the vehicle body to absorb the collision energy. At this time, a load X is input to the suspension member 1 from the second mounting portion 8b of the second arm 8, and a reaction force Y is input to the suspension member 1 from the first mounting portion 7a of the first arm 7. For simplicity, it is assumed that the directions of the load X and reaction force Y are parallel to the fore-and-aft direction of the vehicle.

[0028] 2 , if a straight line that passes through the first mounting portion 7a and is parallel to the vehicle longitudinal direction is defined as a first reference line L1, and the distance between the first reference line L1 and the base end of the first arm 7 is defined as a first distance, the first distance corresponds to the length of a moment arm A1 of the reaction force Y in the first arm 7. Furthermore, if a straight line that passes through the second mounting portion 8b and is parallel to the vehicle longitudinal direction is defined as a second reference line L2, and the distance between the second reference line L2 and the base end of the second arm 8 is defined as a second distance, the second distance corresponds to the length of a moment arm A2 of the load X in the second arm 8.

[0029] In the present embodiment, the first distance in each first arm 7 is greater than any of the second distances in each second arm 8. In other words, when viewed in the vehicle front-rear direction, the distance between the base end of each first arm 7 and the first mounting portion 7 a is greater than any of the distances between the base end of each second arm 8 and the second mounting portion 8 b.

[0030] The position of the base end of the right-side first arm 7 is defined as the center in the thickness direction at the point where the center line of the right-side first arm 7 and the center line of the right side beam 2R intersect in a plan view. The position of the base end of the right-side second arm 8 is defined as the center in the thickness direction at the point where the center line of the right-side second arm 8 and the center line of the right side beam 2R intersect in a plan view. The positions of the base ends of the left-side first arm 7 and the second arm 8 are defined similarly. The center line is a line connecting points equidistant from two adjacent contour lines in a plan view. In Figures 2 and 3, the approximate positions of the center lines of the first arm 7, the second arm 8, and the right side beam are indicated by dashed lines, and the approximate positions of the base ends of the first arm 7 and the second arm 8 are indicated by ●.

[0031] The position of the first mounting portion 7a is determined as the center position of the vertical dimension of the bolt insertion hole B on the central axis of the bolt insertion hole B. Similarly, the position of the second mounting portion 8b is determined as the center position of the vertical dimension of the bolt insertion hole B on the central axis of the bolt insertion hole B.

[0032] The effects of the suspension member 1 according to this embodiment will be described.

[0033] (1) The suspension member 1 includes a pair of first arms 7 and a pair of second arms 8. The first arms 7 extend laterally from base ends on the left and right sides of the suspension member 1 facing the vehicle cabin, and each have a first attachment portion 7a to be attached to the vehicle body. The second arms 8 extend from the left and right sides of the suspension member 1 facing the vehicle body end, and each have a second attachment portion 8b to be attached to the vehicle body. Here, a weak portion 7b is formed on each of the first arms 7 closer to the base end than the first attachment portion 7a.

[0034] According to the suspension member 1, because the first arm 7 is formed with the weakened portion 7b, when a collision load is input to the suspension member 1 during a vehicle collision, the first arm 7 can deform before the second arm 8. Therefore, the first arm 7 can be moved toward the vehicle cabin without significantly deforming portions of the suspension member 1 other than the first arm 7. This movement toward the vehicle cabin increases the crash stroke at the end of the vehicle body, thereby increasing the amount of energy absorbed by deformation of the vehicle body. Furthermore, the suspension member 1 can absorb a portion of the collision energy through deformation of the first arm 7. As a result, the suspension member 1 can suppress transmission of the collision load to the vehicle cabin. Furthermore, because the suspension member 1 can move the first arm 7 toward the vehicle cabin without significantly deforming portions other than the first arm 7, the drive unit 5 mounted in that portion can be protected.

[0035] (2) In the suspension member 1, the strength of the weakened portion 7 b of the first arm 7 against a load input in the vehicle longitudinal direction is set to be smaller than the strength of the second arm 8 against a load input in the vehicle longitudinal direction. Therefore, when a collision load is input to the suspension member 1 in the event of a vehicle collision, the first arm 7 can be more reliably deformed before the second arm 8.

[0036] (3) In the suspension member 1, in a plan view, the minimum width of each first arm 7 is smaller than the minimum width of any of the second arms 8. Therefore, the portion of the first arm 7 having the minimum width becomes the weak portion 7b, and in the event of a vehicle collision, the first arm 7 is more reliably deformed before the second arm 8. This makes it possible to more reliably move the portions of the suspension member 1 other than the first arm 7 toward the vehicle interior.

[0037] (4) The suspension member 1 is attached to the rear of the vehicle body as a rear suspension, and therefore can suppress the transmission of collision load to the vehicle interior in the event of a rear-end collision.

[0038] (5) In the suspension member 1, link attachment portions to which link members of the rear suspension are attached are provided on or near each first arm 7. For example, the front upper link 14 serving as a link member is attached to the front upper bracket 14a serving as a link attachment portion provided near the first arm 7. The front lower link 15 serving as a link member is attached to the front lower bracket 15a serving as a link attachment portion provided on the first arm 7. Therefore, during a vehicle rear collision, a collision load input to the rear wheel 6 can be input to the first arm 7 or its vicinity via the link member. More specifically, a force having a component directed toward the vehicle cabin and a component directed inward in the vehicle width direction can be input to a portion of the first arm 7 that is inward in the vehicle width direction. This can promote deformation of the weakened portion 7b of the first arm 7. Note that "near" refers to a position where a load having a component directed toward the vehicle cabin and a component directed inward in the vehicle width direction, input from the link member, can be transmitted to the base end of the first arm 7.

[0039] (6) The suspension member 1 includes a first cross beam 3, a second cross beam 4, a left side beam 2L, and a right side beam 2R. The first cross beam 3 spans between the base ends of the first arms 7, and the second cross beam 4 spans between the base ends of the second arms 8. The left side beam 2L spans between the left ends of the first cross beam 3 and the second cross beam 4, and the right side beam 2R spans between the right ends of the first cross beam 3 and the second cross beam 4. The left side beam 2L and the right side beam 2R each include an upper beam 2a and a lower beam 2b. Therefore, with the suspension member 1, the drive unit 5 can be mounted inside the rectangular frame structure formed by the first cross beam 3, the second cross beam 4, and the left side beam 2L and the right side beam 2R, thereby more reliably protecting the drive unit 5. Furthermore, since the left and right side beams each include an upper beam 2a and a lower beam 2b, they have high strength against a load X and a reaction force Y in the fore-and-aft direction of the vehicle. As a result, the suspension member 1 can suppress deformation of the rectangular frame structure and more reliably protect the drive unit 5 .

[0040] (7) In the suspension member 1, the second moment of area about the neutral axis extending in the vertical direction of the weak portion 7b is smaller than the second moment of area about the neutral axis extending in the vertical direction of the upper beam 2a. Furthermore, the second moment of area about the neutral axis extending in the vertical direction of the weak portion 7b is smaller than the second moment of area about the neutral axis extending in the vertical direction of the lower beam 2b. In other words, the weak portion 7b is more likely to bend due to a load input during a vehicle collision than the upper beam 2a and the lower beam 2b. Therefore, the suspension member 1 can promote deformation of the first arm 7 while suppressing deformation of the rectangular frame structure, thereby more reliably protecting the drive unit 5.

[0041] (8) In the suspension member 1, the stabilizer 20 is attached to the second arm 8. This increases the rigidity of the second arm 8 and suppresses deformation thereof, so that in the event of a vehicle collision, the first arm 7 is more reliably deformed before the second arm 8. This makes it possible to more reliably move the portions of the suspension member 1 other than the first arm 7 toward the vehicle interior.

[0042] (9) In the suspension member 1, when viewed in the vehicle longitudinal direction, the distance between the first mounting portion 7a and the base end of each first arm 7 is greater than the distance between the second mounting portion 8b and the base end of each second arm 8. Therefore, the length of the moment arm of the first arm 7 is greater than the length of the moment arm of the second arm 8, making the first arm 7 more likely to deform at the weak portion 7b during a vehicle collision. As a result, the portions of the suspension member 1 other than the first arm 7 can be more reliably moved toward the vehicle compartment.

[0043] (10) During a vehicle collision, for example, as shown in FIG. 8 , part of the collision load may be directly input from a collision obstacle Z to the second arm 8. In the suspension member 1, the end edge 8a of each second arm 8 on the vehicle body end side extends in the vehicle width direction from its base end to the second mounting portion 8b. Therefore, the load X is more likely to be input to the portion of the second arm 8 closer to the base end. As a result, the moment arm or second distance of the second arm 8 is substantially shorter, and the second arm 8 is less likely to bend or deform. This more reliably causes the first arm 7 to deform before the second arm 8, and makes it possible to more reliably move the portion of the suspension member 1 other than the first arm 7 toward the vehicle cabin.

[0044] The above-described embodiments are merely examples described to facilitate understanding of the invention. The technical scope of the invention is not limited to the specific technical matters disclosed in the above-described embodiments, but also includes various modifications, changes, alternative technologies, etc. that can be easily derived therefrom.

[0045] In the above embodiment, a rear suspension member has been described as an example of the suspension member 1. However, the suspension member may also be a front suspension member for a front suspension that is mounted with a drive unit and attached to the front of the vehicle body. In this case, the rear side of the suspension member corresponds to the passenger compartment side, and the front side corresponds to the end side of the vehicle body, i.e., the vehicle front end side.

[0046] In the above embodiment, the quadrangular frame structure formed by the first cross beam 3, the second cross beam 4, the left side beam 2L, and the right side beam 2R is substantially square in plan view. However, the quadrangular frame structure may be rectangular or isosceles trapezoid in plan view. Furthermore, while the drive unit 5 in the above embodiment is an electric motor for a BEV, it may also be a hybrid unit for an HEV such as a PHEV, or an internal combustion engine for an ICE vehicle. It goes without saying that the suspension member according to the present invention can be applied to general vehicles equipped with electric motors and general vehicles equipped with internal combustion engines.

[0047] REFERENCE SIGNS LIST 1 Suspension member 2L Left side beam 2R Right side beam 2a Upper beam 2b Lower beam 3 First cross beam 4 Second cross beam 5 Drive unit 7 First arm 7a First mounting portion 8 Second arm 8b Second mounting portion 8a End edge (end edge of second arm on vehicle body end side) 14 Front upper link (link member) 14a Front upper bracket (link mounting portion) 15 Front lower link (link member) 15a Front lower bracket (link mounting portion) 20 Stabilizer

Claims

1. A suspension member that is mounted on a front or rear of a vehicle body and has a drive unit for running the vehicle mounted thereon, a pair of first arms extending laterally from base ends at the left and right portions of the suspension member on the vehicle cabin side, and each having a first attachment portion to be attached to a vehicle body; a pair of second arms extending from left and right vehicle body end portions of the suspension member, respectively, and each having a second attachment portion to be attached to the vehicle body; a first cross beam spanning between base ends of the pair of first arms; a second cross beam spanning between base ends of the pair of second arms; a left side beam spanning between a left end of the first cross beam and a left end of the second cross beam; a right side beam spanning between the right end of the first cross beam and the right end of the second cross beam, Each of the left side beam and the right side beam includes an upper beam and a lower beam, a fragile portion is formed on each of the pair of first arms closer to the base end than the first attachment portion, a second moment of area about a neutral axis extending in the vertical direction of the weak portion is smaller than a second moment of area about a neutral axis extending in the vertical direction of the upper beam and is also smaller than a second moment of area about a neutral axis extending in the vertical direction of the lower beam, A suspension member, wherein stabilizers are attached to the pair of second arms.

2. 2. The suspension member according to claim 1, wherein the strength of the weakened portion of the first arm against a load input in the vehicle longitudinal direction is set to be smaller than the strength of the second arm against a load input in the vehicle longitudinal direction.

3. 3. The suspension member according to claim 1, wherein, in a plan view, the minimum width of each of the pair of first arms is smaller than the minimum width of either of the pair of second arms.

4. The suspension member according to any one of claims 1 to 3, wherein the suspension member is attached to the rear of the vehicle body for a rear suspension.

5. 5. The suspension member according to claim 4, wherein a link attachment portion to which a link member of the rear suspension is attached is provided on each of the pair of first arms or in the vicinity of each of the pair of first arms.

6. 6. The suspension member according to claim 1, wherein, when viewed in the vehicle longitudinal direction, a distance between a base end of each of the pair of first arms and the first mounting portion is greater than a distance between a base end of each of the pair of second arms and the second mounting portion.

7. 7. A suspension member according to claim 1, wherein the vehicle body end side edge of each of the pair of second arms extends in the vehicle width direction from the base end of each of the second arms to the second mounting portion.