JP2013203242A - Front sub-frame structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable establishment of effective compatibility between the effect of preventing a side member from causing surface vibrations complying with a lateral force and the like of a suspension arm and the effect of preventing plastic deformation of its cross-sectional shape, by a simple configuration.SOLUTION: A front sub-frame structure includes a pair of right and left side members 7 which are provided with an arm supporting part 18, and a cross member 11 which is elongated in a vehicle-width direction to connect the right and left side members 7. A front part 13 of the side member, which is positioned on the front side of a vehicle with respect to the arm supporting part 18, is formed in a pipe-like cross-sectional shape which has ridgelines elongated in the longitudinal direction of the vehicle and a flat plate part arranged between the ridgelines adjacent to each other. A rear part 14 of the side member provided with the arm supporting part 18 is formed in a pipe-like cross-sectional shape which has a curved surface larger in curvature than the flat plate part of the front part 13 of the side member. Both right and left ends of the cross member 11 are connected to the rear part 14 of the side member.

Description

  The present invention relates to a front sub-frame structure disposed in an arrangement space of a power plant composed of a vehicle engine or the like.

  Conventionally, as shown in Patent Document 1 below, one pipe member having a U-shape in plan view, a connecting member (cross member) that connects left and right side portions of the U-shaped pipe member, and the U In a vehicle suspension system provided with a front subframe provided with a transmission means composed of two pipe members arranged in a U-shape with respect to a U-shaped pipe material, the suspension arm is input to the front subframe. The external force is transmitted to the mounting portion provided on the vehicle body side strength member via the transmission means, thereby increasing the mounting rigidity of the suspension arm and improving its torsional rigidity. Yes.

  Further, as shown in Patent Document 2 below, in the assembly structure of the vehicle subframe supported by the vehicle body frame, the subframe includes a front and rear cross pipe extending in the vehicle width direction and a left and right extension extending in the vehicle front and rear direction. A side pipe is welded and joined at a first joint part, and a mount member support pipe is welded and joined to the front and rear cross pipes or left and right side pipes at a second joint part. A cylindrical mount member attached to the vehicle is welded and joined at a third joint portion whose axis extends in the vertical direction, and the mount in at least one of the vehicle width direction, the vehicle front-rear direction, and the vertical direction A tolerance absorbing structure that enables adjustment of the position of the member is employed in the first to third joint portions.

JP 2009-61879 A JP 2001-39333 A

  As disclosed in Patent Documents 1 and 2, side members of a front subframe consisting of a single pipe member or left and right side pipes having a U-shape in plan view are disposed on the left and right of the front part of the vehicle body, In order to effectively absorb the collision load input at the time of the vehicle collision by the side member, the cross-sectional shape of the side member is disposed between the ridge line extending in the longitudinal direction of the vehicle and the ridge line adjacent to each other. It is preferable to form in the shape of a square pipe having a flat plate portion. However, when the side member is formed in the shape of a square pipe, the flat plate portion constituting the side member is likely to undergo surface vibration in accordance with the lateral force or the like input from the suspension arm to the front subframe when the vehicle is running. There is a problem that the cross-sectional shape of the side member is easily plastically deformed from, for example, a square to a parallelogram.

  The present invention has been made in view of the above-mentioned problems, and the flat plate portion constituting the side member vibrates in accordance with the lateral force or the like input from the suspension arm to the front sub-frame when the vehicle is traveling. It is an object of the present invention to provide a front subframe structure that can effectively achieve both the effect of preventing the above and the effect of preventing the cross-sectional shape of the side member from being plastically deformed with a simple configuration.

  The invention according to claim 1 includes a pair of left and right side members provided with arm support portions for supporting the suspension arm, and a cross member extending in the vehicle width direction so as to connect the left and right side members. A front sub-frame structure, wherein a front side member located on the front side of the vehicle with respect to the arm support portion includes a ridge line extending in the vehicle front-rear direction and a flat plate portion disposed between adjacent ridge lines. A pipe-like cross-sectional shape is formed, and the rear side member provided with the arm support portion is formed in a pipe-like cross-sectional shape having a curved surface with a larger curvature than the flat plate portion of the front side member. The left and right ends of the cross member are connected to the rear of the side member.

  According to a second aspect of the present invention, in the front sub-frame structure according to the first aspect, the front side portion of the side member is inclined outward in the vehicle width direction from the vicinity of the front end of the rear portion of the side member in plan view. It was extended.

  According to a third aspect of the present invention, in the front subframe structure according to the first or second aspect, the rear portion of the side member is provided with a mounting bracket for a vehicle body frame or a mounting portion for a vehicle auxiliary machine. .

  The invention according to claim 4 is the front subframe structure according to any one of claims 1 to 3, wherein the side member front portion and the side member rear portion are integrally formed by a single pipe member. Is.

  According to a fifth aspect of the present invention, in the front subframe structure according to any one of the first to fourth aspects, the vehicle is rearwardly tilted from the center in the vehicle width direction of the cross member to the left and right outer sides. A pipe-like member that is connected to the vehicle body side strength portion installed on the left and right sides of the floor tunnel, and has a pipe-like member connected to the vehicle body side strength portion. The rear end portion of the side member is connected to the front side portion of the portion located on the inner side in the vehicle width direction.

  According to a sixth aspect of the present invention, in the front subframe structure according to the fifth aspect, the rear arm support portion that supports the rear portion of the suspension arm includes the left and right end portions of the pipe-like member and the rear end of the side member. It is constructed so as to straddle the part.

  The invention according to claim 7 is the front sub-frame structure according to any one of claims 1 to 3, wherein the side member front portion and the side member rear portion are formed separately and the arm support is provided. The portion is connected to the cross member.

  In the invention which concerns on Claim 1, the side member front part located in the front side of a vehicle rather than the said arm support part is made into the ridgeline extended in the front-back direction of a vehicle, and the flat plate part arrange | positioned between adjacent ridgelines. Since the pipe has a pipe-like cross-sectional shape, it is possible to sufficiently secure the rigidity of the side member front portion against a vehicle collision load while reducing the weight of the side member front portion. In addition, since the rear part of the side member provided with the arm support part is formed in a pipe-like cross-sectional shape having a curved surface with a larger curvature than the flat part of the front part of the side member, the arm support part is separated from the arm support part when the vehicle is running. It is possible to effectively prevent the wall surface portion of the rear portion of the side member from surface vibration or plastic deformation of the cross-sectional shape according to the input lateral force.

  Therefore, the side member front portion and the like constituting the front subframe are not enlarged, and are provided at the rear side of the side member and behind the side member while sufficiently supporting the collision load input to the front side member. When the collision load can be effectively transmitted to and supported by the vehicle body-side strength member and the collision load input to the front side of the side member exceeds a predetermined value, the front side member is The impact load can be effectively prevented from reaching the rear side of the side member, the passenger compartment, etc. by sufficiently absorbing the impact load by plastic deformation or the like, and from the suspension arm when the vehicle is running It is possible to effectively improve the proof strength against the lateral force while suppressing the vibration of the front sub-frame according to the lateral force input to the rear side member. It is possible to achieve both the effect of that.

  In the invention according to claim 2, since the front side of the side member extends from the vicinity of the front end of the rear side of the side member in the plan view to the front side of the vehicle while being inclined outward in the vehicle width direction, the length of the front side of the side member is increased. Is secured at the front portion of the rear portion of the side member disposed on the inner side in the vehicle width direction on the rear side of the front portion of the side member. By providing the arm support part on the outer surface in the vehicle width direction and positioning the arm support part on the inner side in the vehicle width direction, the arm length of the suspension arm is sufficiently secured, and the suspension geometry is effectively There is an advantage that it can be improved. Further, as described above, the front portion of the rear portion of the side member is positioned on the inner side in the vehicle width direction, and the arm support portion is disposed at a position exposed to the outer side of the side member, whereby the arm support portion is The suspension arm can be easily attached, and the rear part of the side member can be effectively reinforced by the arm support part to improve its rigidity. Sometimes, by concentrating the collision load on the front part of the side member, there is an advantage that the front part of the side member can efficiently function as a collision load absorbing part.

  In the invention according to claim 3, since the mounting portion of the mounting bracket for the vehicle body frame or the auxiliary device for the vehicle is provided at the rear portion of the side member, the mounting is performed without providing a separate reinforcing member for reinforcing the rear portion of the side member. The rear portion of the side member can be effectively reinforced with a simple configuration using a bracket or the like. Therefore, the rigidity of the front sub-frame with respect to the collision load of the vehicle input to the rear portion of the side member and the cross member and the lateral force at the time of traveling, etc. can be secured easily and sufficiently, and the rear portion of the side member falls inward according to the collision load. And the like, and it is possible to effectively improve the running stability of the vehicle by suppressing the deformation of the front subframe due to the lateral force input from the suspension arm during the running of the vehicle. is there.

  In the invention according to claim 4, since the side member front part and the side member rear part are integrally formed of a single pipe material, it is possible to easily manufacture a side member that is lightweight and has high rigidity against a collision load. In addition, it is possible to more effectively prevent the wall surface portion of the rear portion of the side member from surface vibration or plastic deformation of the cross-sectional shape according to the lateral force input from the arm support portion when the vehicle is running. There is an advantage that you can.

  In the invention according to claim 5, the cross member extends from the center in the vehicle width direction of the cross member to the left and right outer sides while extending to the rear side of the vehicle, and the left and right sides thereof are installed on the left and right of the floor tunnel. A pipe-like member joined to the vehicle body-side strength portion, and the rear end of the side member on the front side portion of the portion located on the inner side in the vehicle width direction from the joint portion of the pipe-like member to the vehicle body-side strength portion Since the portions are connected, the collision load input to the side member at the time of a vehicle collision can be received by the left and right side portions of the cross member. Therefore, the collision load can be transmitted to the vehicle body side strength member and effectively supported while effectively preventing the rear end portion of the side member from bending and deforming.

  In the invention according to claim 6, the rear arm support portion for supporting the suspension arm is constructed so as to straddle the joint portion provided at the side end portion of the pipe-like member and the rear end portion of the rear side portion of the side member. The rear portion of the rear side of the side member can be effectively reinforced with a simple structure without using a separate reinforcing member for reinforcing the rear end of the rear side of the side member. it can. Therefore, it is possible to easily and sufficiently ensure the rigidity against the collision load of the vehicle input to the rear part of the side member and the pipe-like member and the lateral force at the time of traveling, etc. There is an advantage that the front subframe can be prevented from being deformed by a lateral force or the like input from the suspension arm when the vehicle is traveling, and the traveling stability of the vehicle can be effectively improved.

  In the invention according to claim 7, the side member front part and the side member rear part are formed separately and the arm support part is connected to the cross member. By transmitting the lateral force or the like input to the cross member, there is an advantage that the lateral force or the like can be more efficiently dispersed and effectively supported throughout the vehicle body.

It is side surface sectional drawing which shows 1st Embodiment of the front sub-frame structure which concerns on this invention. It is a perspective view which shows the state which looked at the said front sub-frame structure from diagonally lower back. It is a top view which shows the specific structure of the said front sub-frame structure. It is a bottom view which shows the specific structure of the said front sub-frame structure. It is a disassembled perspective view which shows the specific structure of the said front sub-frame structure. It is front sectional drawing which shows the specific structure of a side member front part. It is front sectional drawing which shows the specific structure of a side member rear part and a 2nd mounting bracket. It is front sectional drawing which shows the structure of the junction part of a front sub-frame and a vehicle body. It is a top view which shows the specific structure of a lower arm. It is side surface sectional drawing which shows the modification of the said front sub-frame structure. It is a top view which shows 2nd Embodiment of the front sub-frame structure which concerns on this invention. It is a perspective view which shows the state which looked at the said front sub-frame structure from diagonally upper front. It is a perspective view which shows the state which looked at the said front sub-frame structure from diagonally lower front. It is front sectional drawing which shows the specific structure of a closed cross-section structure. It is a plane sectional view showing the concrete composition of a closed section structure.

  FIGS. 1-5 has shown the vehicle provided with the front sub-frame structure which concerns on 1st Embodiment of this invention. A power plant 1 including a driving engine or a driving motor is disposed at the front of the vehicle, and a vehicle compartment and an installation space (engine room) for the power plant 1 are partitioned behind the power plant 1. A dash panel 2 is provided. A pair of left and right side frames 3 are installed so as to extend from the lower end of the dash panel 2 to the front side of the vehicle, and a front subframe 5 that supports a lower arm 4 for front suspension and the like below the side frame 3. Is installed.

  The side frame 3 has a front part 3a extending substantially horizontally along the front-rear direction of the vehicle in a side view, and a rear side of the dash panel 2 from the rear end part toward the lower end part of the dash panel 2 while being inclined rearward. And a rear frame 3b, which will be described later, is connected to the rear end of the rear portion 3b. In addition, a crash can 6 made of a metal cylindrical body or the like is projected from the front end of the side frame 3 toward the front side of the vehicle, and a bumper extending in the vehicle width direction is provided at the front end. A side end portion of the reinforcement 49 is attached.

  The front sub-frame 5 is disposed below the side frame 3 and extends in the front-rear direction of the vehicle, and a pair of left and right side members 7 and the lower side of the side frame 3 on the rear side of the space where the power plant 1 is disposed. And a first cross member 8 made of a pipe-like member described later. The floor panel 9 constituting the bottom of the passenger compartment is provided with a floor tunnel 35 bulging upward in the center in the vehicle width direction so as to extend in the longitudinal direction of the vehicle.

  The front upper wall of the floor tunnel 35 is provided with an inclined portion 35a (see FIG. 1) inclined rearward and lower, more specifically on the front side of the rear end of the inclined portion 35a. A second cross member (rear cross member) 10 that couples the left and right end portions of the first cross member 8 extends in the vehicle width direction. Further, a third cross member 11 (center cross member) that connects the front and rear intermediate portions of the left and right side members 7 extends substantially linearly along the vehicle width direction, and the front portions of the left and right side members 7 are A fourth cross member (front cross member) 12 to be phase-coupled extends in the vehicle width direction.

  As shown in FIGS. 3 to 5, the side member 7 is positioned on the front side of the vehicle with respect to a front arm support portion 18 to be described later, and is installed in an inclined state in which the side member 7 is lifted forward in side view (see FIG. 1). The side member front portion 13 and the side member rear portion 14 that are connected to the rear end portion of the side member front portion 13 and that are disposed substantially horizontally in a side view. Further, a crash can 15 made of a metal cylindrical body or the like protruding toward the front of the vehicle is attached to the front end portion of the side member front portion 13.

  The side member front portion 13 is arranged between four ridge lines 13a extending in the front-rear direction of the vehicle and adjacent ridge lines 13a by hydroforming a pipe member having a predetermined diameter, as shown in FIG. It is formed in a substantially square pipe-like cross-sectional shape having four flat plate portions 13b provided. Also, as shown in FIG. 3, the side member front portion 13 is installed so as to extend to the front side of the vehicle while inclining outward from the front end of the side member rear portion 14 in the vehicle width direction in a plan view. Yes. A first mount bracket 16 is installed on the upper surface of the front end portion of the side member front portion 13 so that the upper end portion thereof is fastened to the lower surface of the front portion of the side frame 3 with a fastening bolt. The side end portion of the fourth cross member 12 is integrally joined to the portion by welding or the like.

  As shown in FIG. 7, the side member rear portion 14 is configured in a cross-sectional shape (a round pipe shape in this embodiment) having a curved surface having a larger curvature than the flat plate portion 13 b of the side member front portion 13. . As shown in FIG. 3 in plan view, the front portion of the side member rear portion 14 is installed so as to extend substantially straight from the rear end portion of the side member front portion 13 toward the rear side of the vehicle. The rear part of the member rear part 14 is installed so as to extend toward the rear side of the vehicle while inclining inward in the vehicle width direction.

  Further, a second mount bracket 17 whose upper end is connected to the lower surface of the side frame 3 via a fastening bolt 53 as described later is installed on the front outer surface of the side member rear portion 14. On the lower outer surface of the second mount bracket 17, a front arm support portion 18 that supports a below-described front side connection portion 43 provided at the base end portion of the lower arm 4 is provided.

  On the side member rear portion 14, three round pipe members 19, which are attachment parts for vehicle auxiliary equipment including a stabilizer or a steering rack (not shown), are located near the rear portion of the second mount bracket 17 and on the rear side thereof. (See FIG. 5). As shown in FIG. 4 and the like, the rear end portion of the side member rear portion 14 is more inward in the vehicle width direction than the joint portion 20 to the floor frame 37 provided at the left and right end portions of the first cross member 8. Welded to a portion located on the side, specifically, a front side portion of a portion facing a fixing portion 34 for a tunnel lower frame 38 (described later) provided on both left and right sides of the first second cross member 10. Are connected together.

  As shown in FIGS. 1 and 5, the third cross member 11 includes an upper panel 22 and a lower panel 23 made of a steel plate or the like that form a substantially rectangular closed cross section extending in the vehicle width direction. Then, the left and right end portions of the upper panel 22 and the lower panel 23 are respectively welded to the upper and lower sides of the inner side surface in the vehicle width direction of the side member rear portion 14 at a position corresponding to the installation portion of the second mount bracket 17. The vehicle front-rear direction intermediate portions of the left and right side members 7 are connected to each other via the third cross member 11.

  Further, an opening 25 serving as an introduction portion of a rear mount 24 of the power plant 1 (see FIG. 3) including a vehicle engine or the like, and the rear mount 24 are provided in the vehicle width direction central portion of the third cross member 11. A power plant support portion 26 is provided for support, and a support bracket 27 for supporting the vehicle width direction center portion 28 of the first cross member 8 made of a pipe-like member is provided at the rear portion thereof.

  The first cross member 8 is made of a pipe-like member formed by bending a circular steel pipe or the like, and has a vehicle width direction central portion 28 installed so as to extend in the vehicle width direction, and the vehicle width in plan view. It has a pair of left and right inclined portions 29 that are installed so as to extend from the left and right end portions of the direction center portion 28 toward the rear side of the vehicle in a C shape. Then, the first cross member 8 and the third cross member 11 are connected to each other in the vehicle width direction by, for example, welding the center portion 28 in the vehicle width direction of the first cross member 8 to the support bracket 27 of the third cross member 11. They are connected together at the center.

  The rear end portion of the inclined portion 29 is bent so as to extend outward in the vehicle width direction, and the end portion thereof is crushed into a flat shape, thereby forming a joint portion 20 to be joined to the floor frame 37 described below. Has been. Further, the side member 7 and the first cross member 8 are integrally connected by welding the rear end portion of the side member 7 to the front surface of the rear portion of the inclined portion 29. Further, the left and right end portions of the second cross member 10 are welded to the rear rear side of the inclined portion 29, so that the left and right end portions of the first cross member 8 are interposed via the second cross member 10. Are connected to each other.

  The left and right ends of the first cross member 8 are vertically connected so as to straddle the joint 20 to the floor frame 37 provided at the rear end of the inclined portion 29 and the rear end of the side member rear portion 14. A rear arm support portion 31 made of a pair of plate members is installed (see FIG. 5). As will be described later, a rear connection portion 44 provided at the base end portion of the suspension arm including the lower arm 4 is supported by the rear arm support portion 31.

  The second cross member 10 is composed of an upper panel 32 and a lower panel 33 made of a steel plate or the like constituting a substantially rectangular closed cross section extending in the vehicle width direction, and side portions of the upper panel 32 and the lower panel 33 are arranged. Welded and phase joined. The left and right ends of the second cross member 10 are provided with fixing portions 34 that are wider than the center in the vehicle width direction. The fixing portions 34 are provided at the front end of the tunnel lower frame 38. It is fixed to the vehicle body by bolting.

  As shown in FIG. 1, the vertical dimension of the second cross member 10 is set smaller than the vertical dimension of the first cross member 8, and the longitudinal dimension of the second cross member 10 is the same as that of the first cross member 8. It is set to the same extent as the front and rear dimensions. As a result, the area of the closed cross section formed by the second cross member 10 in the vehicle width direction central portion is larger than the area of the closed cross section in the vehicle width direction central portion 28 of the first cross member 8 made of the pipe-shaped member. It is set to a small value.

  A floor tunnel 35 that bulges toward the vehicle interior side (upper side) and extends in the front-rear direction of the vehicle is provided at the center in the vehicle width direction of the floor panel 9 that constitutes the vehicle compartment bottom. On the lower surface of the floor panel 9, as shown in FIG. 2 and the like, a floor frame 37 extending to the rear side of the vehicle continuously to the rear end portion of the side frame 3 is placed at a predetermined distance from the floor tunnel 35. A pair of left and right tunnel lower frames 38 are installed along the lower side of the floor tunnel 35 so as to extend in the front-rear direction of the vehicle.

  Then, the joint portion 20 provided at the rear end portion of the first cross member 8 is fastened to the front end portion of the floor frame 37 via a fastening bolt, and at the side end portion of the second cross member 10. The provided fixing portion 34 is fastened to the lower surface of the front end portion of the tunnel lower frame 38 via a fastening bolt, so that the rear portions of the side members 7 are fixed to the vehicle body side strength member at the left and right positions respectively. Yes. As shown in FIG. 8, the floor frame 37 and the tunnel lower frame 38, and the joint portion 20 of the first cross member 8 and the fixing portion 34 of the second cross member 10 that connect the floor frame 37 and the tunnel lower frame 38 are U-shaped in a front view. A continuous structure is formed, and an opening 40 corresponding to the vertical dimension of the fixed portion 34 and the joint portion 20 is formed between the structure and the floor panel 9.

  In addition, side sills 36 are installed on the left and right sides of the floor panel 9 so as to extend in the front-rear direction of the vehicle, and a torque box 39 that connects the front part of the side sill 36 and the front part of the floor frame 37 is connected. Is installed (see FIGS. 2 and 4). The torque box 39 has a front plate extending in the vehicle width direction along the lower portion of the dash panel 2 disposed in the front portion of the passenger compartment, and a bottom plate extending from the lower end portion to the rear side of the vehicle. The front plate and a ridge line provided at the lower end thereof extend from the position adjacent to the portion where the joint 20 is disposed toward the outer side in the vehicle width direction.

  As shown in FIGS. 3 and 9, the lower arm 4 supported by the front subframe 5 has a tip end portion 42 connected to a wheel support member (axle housing) (not shown) via a ball joint or the like. It consists of a so-called A-type arm in which a pair of front and rear front connection parts 43 and a rear connection part 44 are provided on the inner side (base end) in the vehicle width direction. The front connecting portion 43 and the rear connecting portion 44 of the lower arm 4 are swingable and elastic to the front arm supporting portion 18 and the rear arm supporting portion 31 provided on the side member rear portion 14 of the front sub-frame 5, respectively. It is configured to be supported so as to be displaceable.

  In other words, the front connecting portion 43 of the lower arm 4 is provided with a support shaft 45 extending in the front-rear direction of the vehicle and a rubber bush 46 that holds the support shaft 45. And the fastening part provided in the front-and-rear both ends of the said support shaft 45 is fastened by the front side arm support part 18 provided in the base end part of the said 2nd mount bracket 17 via a fastening bolt, The said lower arm 4 is connected to the support shaft 45 as a fulcrum, and is supported so as to be elastically displaceable according to the elasticity of the rubber bush 46.

  As shown in FIG. 7, the second mount bracket 17 installed on the front outer surface of the side member rear portion 14 is obliquely upward and vehicle width from the upper portion of the outer surface of the round pipe-shaped member constituting the side member rear portion 14. The upper panel 51 projecting outward in the direction, the lower panel 52 projecting obliquely upward and outward from the lower outer surface of the side member rear portion 14, and the fastening bolt 53. And a cylindrical mounting portion 54 fastened to the lower surface of the side frame 3.

  The upper panel 51 constituting the second mount bracket 17 includes an upper wall plate 55 whose base end portion (lower end portion) is joined to the front outer surface of the side member rear portion 14, and both front and rear side ends of the upper wall plate 55. And a pair of side wall plates 56 extending downward from the portion. The cylindrical mounting portion 54 is fixed to the tip portions (outer end portions in the vehicle width direction) of the upper wall plate 55 and the side wall plate 56 by welding. Further, the side frame 56 is deformed at the front end portion of the side wall plate 56 by deforming the support portion of the cylindrical mounting portion 54 when a predetermined collision load is input to the front subframe 5 at the time of a vehicle collision. A pair of upper and lower cutouts 57 and 58 are formed as a weakened portion for facilitating the second mount bracket 17 from detaching from 3.

  The lower panel 52 of the second mount bracket 17 is disposed below the upper wall plate 55 of the upper panel 51 at a predetermined interval. The lower end of the cylindrical mounting portion 54 is disposed on the upper surface of the distal end portion of the lower panel 52. The parts are to be welded. The closed section 59 extending in the vehicle width direction is welded to the lower side portion of the side wall plate 56 of the upper panel 51 to the side side portion of the lower panel 52 so that the upper panel 51 and the lower panel of the second mount bracket 17 52.

  In addition, a pair of front and rear nut members constituting the front arm support portion 18 are fixed to the vicinity of the base end portion of the lower panel 52. The fastening portions provided at both front and rear ends of the support shaft 45 are fastened to the front arm support portion (nut member) 18 provided on the second mount bracket 17 via the fastening bolts 47, thereby lower arm. 4 is connected to the lower outer surface of the second mount bracket 17.

  As shown in FIG. 9, a support shaft 62 extending in the vertical direction and a rubber bush 63 for holding the support shaft 62 are provided in the rear connection portion 44 of the lower arm 4. The upper and lower end portions of the support shaft 62 are fixed to the rear arm support portion 31 made of a pair of upper and lower plate members laid across the side member rear portion 14 and the joint portion 20 of the first cross member 8. Thus, the rear connecting portion 44 of the lower arm 4 is supported so as to be rotatable with the support shaft 62 as a fulcrum, and is supported so as to be elastically displaceable according to the elasticity of the rubber bush 63.

  The front sub-frame 5 is carried into the vehicle assembly line in a state where the front suspension device having the lower arm 4 is sub-assembled, and is introduced from the lower side of the side frame 3 to the front of the vehicle body. Then, the upper ends of the first and second mount brackets 16 and 17 provided on the side member 7 of the front subframe 5 are bolted to the lower surface of the side frame 3, so that the front end of the side member 7 and Center portions in the front-rear direction are attached to the side frames 3, respectively.

  Further, the joint portion 20 provided at the rear end portion of the first cross member 8 is bolted to the front end portion of the floor frame 37 installed on the lower surface of the floor panel 9, and the second cross member 10 is The fixing portions 34 provided at both left and right ends are bolted to the front end portion of the tunnel lower frame 38 installed along the lower end portion of the floor tunnel 35, so that both the left and right portions of the front subframe 5 are provided. The rear end portions of the side members 7 are fixed to the vehicle body-side strength member including the floor frame 37 and the tunnel lower frame 38 at two positions on the left and right, respectively.

  A power plant 1 including a vehicle engine or the like is installed between the left and right side frames 3, and the rear mount 24 of the power plant 1 is powered from an opening 25 formed on the front surface of the third cross member 11. The rear part of the power plant 1 is supported by the front sub-frame 5 by being introduced into the plant support part 26 and bolted.

  In the above configuration, when the vehicle travels, for example, as shown by an arrow A in FIGS. 3 and 4, the front arm support provided on the side member 7 from the front connection portion 43 of the lower arm 4 located on one side (right side) of the vehicle body. When a lateral force is input to the portion 18, the lateral force is transmitted to the other (left side) side member 7 via the third cross member 11 as indicated by an arrow B, and the arrow C As shown, a floor frame 37, a tunnel lower frame 38, etc., which are transmitted from the support bracket 27 of the third cross member 8 to the vehicle width direction central portion 28 and the left inclined portion 29 of the first cross member 8 and located on the rear side thereof. It is transmitted to and supported.

  Further, when the vehicle is running, for example, as shown by an arrow D in FIGS. 3 and 4, a rear arm support provided on the side member 7 from the rear connecting portion 44 of the lower arm 4 located on one side (right side) of the vehicle body. As indicated by an arrow E, the lateral force input to the portion 31 is transmitted from the right inclined portion 29 of the first cross member 8 to the vehicle width direction central portion 28 and the third cross member 11. Then, the lateral force transmitted to the third cross member 11 is transmitted to the other (left side) side member 7 as indicated by an arrow B and supports the third cross member 8 as indicated by an arrow C. It is transmitted from the bracket 27 to the vehicle width direction central portion 28 and the left inclined portion 29 of the first cross member 8, and is transmitted to and supported by the floor frame 37, the tunnel lower frame 38, and the like located on the rear side.

  On the other hand, when a collision load is input to the side member front portion 13 located on the left side of the vehicle body, for example, as indicated by an arrow F in FIGS. , H, a floor frame 37 and a tunnel lower on the left side of the vehicle body via a joint portion 20 disposed on the rear portion of the first cross member 8 located on the left side of the vehicle body and a fixing portion 34 of the second cross member 10. Each is transmitted to the frame 38 and dispersed and supported by these. Further, as indicated by arrows I and J, the collision load is applied to the floor frame 37 and the tunnel lower via the joint portion 20 of the first cross member 8 and the fixing portion 34 of the second cross member 10 located on the right side of the vehicle body. It is transmitted to the frame 38 and is also dispersed and supported by these.

  Therefore, when a predetermined collision load that cannot be absorbed according to the deformation of the crash can 15 is input to the side member 7 of the front subframe 5, the side member rear portion 14 may fall inward or the side member 7 While effectively preventing the rear end portion of the rear member from detaching from the vehicle body side strength member, a collision load is applied to the side member front portion 13 in a concentrated manner to deform it into a bellows shape, for example. Thus, it is possible to efficiently absorb the collision load input at the time of the collision of the vehicle.

  Further, when a large collision load acts in a direction in which the power plant 1 supported by the front subframe 5 is moved backward in the event of a vehicle collision, the axle shaft of the power plant 1 abuts on the second mount bracket 17. For example, a load that pushes the cylindrical mounting portion 54 of the second mount bracket 17 fastened to the lower surface of the side frame 3 backward acts. The supporting portion of the cylindrical mounting portion 54 is provided with a weak portion that facilitates the second mount bracket 17 being detached from the side frame 3, that is, the notches 57 and 58 of the side wall plate 56. Therefore, when a predetermined collision load is applied during a vehicle collision, the support portion of the cylindrical mounting portion 54 can be greatly deformed, and the second mount bracket 17 can be detached from the side frame 3.

  Further, as shown in FIG. 1, a collision load K that pushes the side member front part 13 diagonally downward at the time of a vehicle collision is applied to the side member front part 13 that is installed in an upwardly inclined state in a side view. Therefore, the front sub-frame 5 may be swung downward with the two fixed portions including the joint portion 20 and the fixed portion 34 disposed at the rear portion of the first cross member 8 as fulcrums. The power plant 1 allowed and held by the front subframe 5 is guided downward and descends.

  As described above, the pair of left and right side members 7 provided with the arm support portion including the front arm support portion 18 that supports the front connection portion 43 of the lower arm 4 and the left and right side members 7 are connected in the vehicle width direction. In the front sub-frame structure having a center cross member formed of a third cross member 11 extending in the front side, the side member front portion 13 positioned on the front side of the vehicle with respect to the front arm support portion 18 is arranged in the vehicle front-rear direction. Arm support comprising a square pipe-like cross-sectional shape having a plurality of ridge lines 13a extending in parallel to each other and a flat plate portion 13b disposed between adjacent ridge lines 13a (see FIG. 6), and comprising the front arm support portion 18 and the like. The side member rear portion 14 provided with the portion is a round pipe-like cross-sectional shape having a curved surface having a larger curvature than the flat plate portion 13b of the side member front portion 13. 7 (see FIG. 7), and the left and right ends of the third cross member 11 are joined to the side member rear portion 14, so that the vehicle can be input to the front subframe 5 via the lower arm 4 when the vehicle is traveling with a simple and compact configuration. There is an advantage that it is possible to appropriately and effectively support both the lateral force generated and the collision load input to the front sub-frame 5 at the time of a vehicle collision.

  That is, in the said embodiment, the side member front part 13 located in the front side rather than the front arm support part 18 which supports the front side connection part 43 of the lower arm 4 was installed between the four ridge lines 13a and each ridge line 13a. Since it has a substantially square pipe-like cross-sectional shape including four flat plate portions 13b, the side member front portion 13 is reduced in weight, and the side member front portion 13 has sufficient rigidity against a vehicle collision load. Can do. Therefore, the side member rear portion 14 and the rear side thereof are supported while sufficiently supporting the collision load input to the side member front portion 13 without increasing the size of the side member front portion 13 and the like constituting the front subframe 5. The impact load can be effectively transmitted to and supported by the vehicle body side strength member provided on the vehicle body. When the collision load input to the side member front portion 13 becomes a certain value or more, the collision load can be sufficiently absorbed by plastically deforming the side member front portion 13 in a bellows shape or the like. Therefore, there is an advantage that the collision load can be effectively prevented from reaching the side member rear portion 14 and the passenger compartment.

  In addition, although it is conceivable that the rear part of the side member located on the rear side of the front arm support part 18 has a substantially square pipe-like cross-sectional shape as in the case of the side member front part 13, The flat plate portion constituting the rear portion of the side member is susceptible to surface vibration in response to a lateral force or the like input from the lower arm 4 to the rear portion of the side member through the front arm support portion 18 when the vehicle is running. There is a problem that the cross-sectional shape is easily plastically deformed from a substantially square shape to a parallelogram shape.

  On the other hand, as shown in the above embodiment, when the cross-sectional shape of the side member rear portion 14 provided with the arm support portion including the front arm support portion 18 and the rear arm support portion 31 is formed in a round pipe shape. Further, it is possible to effectively prevent the wall surface portion of the side member rear portion 14 from surface vibrations or plastic deformation of the cross-sectional shape thereof according to the lateral force. Therefore, as described above, the side member front portion 13 has a substantially square pipe-like cross-sectional shape, and the side member rear portion 14 has a round pipe-like cross-sectional shape. The front subframe according to the effect of improving the proof stress against the collision load input to 13 and effectively absorbing the collision load and the lateral force input from the lower arm 4 to the side member rear portion 14 during traveling of the vehicle It is possible to achieve both the effect of effectively improving the proof strength against the lateral force while suppressing the vibration of 5.

  The side member front portion 13 has a pipe-like cross-sectional shape other than a substantially square shape, for example, a square pipe-like cross-sectional shape provided with a plurality of ridgelines made of rectangles or hexagons and flat plate portions disposed between the ridgelines. Further, the side member rear portion 14 has a pipe-like cross-sectional shape other than the above round pipe shape, for example, an elliptical or heart-shaped cross-sectional shape having a curved surface having a larger curvature than the flat plate portion of the side member front portion 13. Also good. Even in such a configuration, it is possible to effectively absorb the collision load by improving the resistance against the collision load input to the side member front portion 13 at the time of the collision of the vehicle, and the traveling of the vehicle. There is an effect that the load resistance against the lateral force can be effectively improved while effectively preventing the front sub-frame 5 from vibrating in response to the lateral force or the like input to the side member rear portion 14 sometimes. There is an advantage that it can be obtained at the same time.

  In the above embodiment, the side member front part 13 is installed so as to extend from the vicinity of the front end of the side member rear part 14 to the front side in the vehicle width direction in a plan view so as to extend to the front side of the vehicle. The length of 13 can be secured sufficiently and the whole can function as a collision load absorbing portion. Further, since the front arm support portion 18 is provided on the outer side surface in the vehicle width direction located at the front side portion of the side member rear portion 14 disposed on the inner side in the vehicle width direction on the rear side of the side member front portion 13, the front side The arm support portion 18 can be positioned on the inner side in the vehicle width direction, so that the arm length (dimension in the vehicle width direction) of the suspension arm composed of the lower arm 4 is sufficiently ensured, and the suspension geometry is effectively achieved. There is an advantage that it can be improved.

  Further, as described above, the front side portion of the side member rear portion 14 is positioned on the inner side in the vehicle width direction, and the front arm support portion 18 is disposed at a position exposed to the outer side of the side member 7, thereby The operation of attaching the suspension arm composed of the lower arm 4 to the arm support portion 18 can be easily performed, and the side arm rear portion 14 can be effectively reinforced by the front arm support portion 18 to improve its rigidity. Therefore, by concentrating the collision load on the side member front part 13 at the time of a vehicle collision, the side member front part 13 can be efficiently functioned as a collision load absorbing part with a simple and lightweight configuration. There are advantages.

  Further, in the above embodiment, the side member rear portion 14 is provided with the second mount bracket 17 attached to the vehicle body frame made up of the side frame 3 and the three attachment portions for the vehicle auxiliary equipment made up of a stabilizer or a steering rack not shown. Since the round pipe member 19 is provided, the side member rear portion 14 is attached to the side member rear portion 14 by using a mounting bracket made of the second mount bracket 17 without providing a separate reinforcing member for reinforcing the side member rear portion 14. Effective reinforcement can be achieved with a simple configuration. Therefore, the rigidity of the front subframe 5 with respect to the collision load of the vehicle input to the side member rear portion 14 and the first cross member 8 and the lateral force at the time of traveling, etc. is easily and sufficiently secured, and the side according to the collision load. It is possible to effectively prevent the rear part 14 of the member from falling inward and to suppress the deformation of the front sub-frame 5 due to a lateral force or the like input from the lower arm 4 when the vehicle is running, thereby improving the running stability of the vehicle. There is an advantage that it can be improved.

  Instead of the embodiment in which the side member front portion 13 and the side member rear portion 14 are integrally formed by hydroforming a single pipe-shaped member, the side member front portion 13 formed separately is provided. The side member 7 can be configured by welding the side member rear portion 14 or the like. However, as shown in the above embodiment, the side member front portion 13 and the side member rear portion 14 of the front subframe 5 are provided as a single piece. When the pipe member is integrally formed, the side member 7 having a light weight and high rigidity with respect to a collision load can be easily manufactured, and in accordance with a lateral force input from the arm support portion when the vehicle travels. There is an advantage that it is possible to more effectively prevent the wall surface portion of the rear portion of the side member from surface vibration or plastic deformation of its cross-sectional shape.

  Further, as shown in the above embodiment, a rear arm support portion 31 for supporting the rear connection portion 44 of the suspension arm made of the lower arm 4 is provided at the side end portion of the first cross member 8 made of the pipe-like member. In the case of laying over the joined portion 20 and the rear end portion of the side member rear portion 14, a reinforcing member for reinforcing the rear end portion of the side member rear portion 14 is not provided separately. The rear portion of the side member rear portion 14 can be effectively reinforced with a simple configuration using the rear arm support portion 31. Therefore, the vehicle can easily and sufficiently secure rigidity against the collision load of the vehicle input to the side member rear portion 14 and the first cross member 8 and the lateral force at the time of traveling. It is possible to effectively prevent the vehicle from falling down and to effectively improve the running stability of the vehicle by suppressing the front subframe 5 from being deformed by a lateral force or the like input from the lower arm 4 when the vehicle is running. There are advantages.

  Further, as shown in the above embodiment, the third cross member 11 extends from the center in the vehicle width direction toward the left and right outer sides while extending to the rear side of the vehicle, and both the left and right sides are floor tunnels 35. A first cross member 8 made of a pipe-like member joined to a floor frame (vehicle body side strength portion) 37 installed on the left and right sides of the vehicle is provided, and the vehicle is located more than the joint portion 20 of the first cross member 8 with respect to the vehicle body side strength portion. When the rear end portion of the side member 7 is connected to the front side portion of the portion located on the inner side in the width direction, the collision load input to the side member 7 at the time of a vehicle collision is applied to the first cross member 8. Since the rear end of the side member 7 is effectively prevented from being bent and deformed, the collision load input to the side member 7 can be received by the first cross member 8. Can be effectively supported from disposed a joint 20 to the part is transmitted to the floor frame 37 and the like. When a predetermined collision load is applied to the side member 7 of the front subframe 5, the collision load is concentratedly applied to the side member front portion 13 to deform the side member front portion 13 into a bellows shape. For example, there is an advantage that the collision load can be absorbed efficiently.

  That is, in the above embodiment, the front arm support portion 18 that supports the front connection portion 43 of the suspension arm that is the lower arm 4 and the rear arm support portion 31 that supports the rear connection portion 44 of the lower arm 4 are supported on the front subframe 5. And a third cross extending between the left and right side members 7 and extending in the vehicle width direction so as to connect the installation portion of the front arm support portion 18. In a front sub-frame structure having a member (center cross member) 11, a vehicle width direction center portion 28 supported by a support bracket 27 provided on the third cross member 11, and both left and right end portions thereof outward. A first cross member 8 made of a pipe-like member having a pair of inclined portions 29 extending toward the rear side of the vehicle while inclining is installed, Since the joint portions 20 provided at the left and right end portions of the scmember 8 are joined to the vehicle body side strength member composed of the floor frame 37, the vehicle width direction central portion 28 of the first cross member 8 is positioned below the front portion of the floor tunnel 35. Without causing the lateral force A and D input to the side member 7 from the front connecting portion 43 and the rear connecting portion 44 of the lower arm 4 to travel, the third cross member 8 and the first cross member 8 are used. Thus, it can be stably supported by transmitting to the vehicle body side strength member comprising the floor frame 37 and the tunnel lower frame 38 installed on the floor panel 9.

  Therefore, the main part of the connecting member made of a large-diameter U-shaped pipe material or the rear cross pipe constituting the vehicle subframe is installed below the front part of the floor tunnel 35 as in the conventional example. Thus, the layout of the engine exhaust pipe 1a and the propeller shaft installed in the floor tunnel 35 is obstructed, and the large-diameter U-shaped pipe member is disposed below the floor panel 9. As a result, the ground height of the floor panel 9 is increased, and the lower arm 4 is moved from the lower arm 4 to the front subframe 5 while the vehicle is running without causing adverse effects such as deterioration of the boarding / alighting performance, the safety, and the aerodynamic characteristics. There is an advantage that the input lateral force and the like can be stably supported.

  Further, the rear end portion of the side member 7 installed so as to extend in the front-rear direction of the vehicle along the side portion of the power plant placement space as described above is joined to the vehicle body side strength member such as the floor frame 37. Since the first cross member 8 is connected to the left and right front surfaces of the first cross member 8 located on the inner side in the vehicle width direction with respect to 20, the collision load input to the side member 7 at the time of a vehicle collision is applied to both the left and right sides of the first cross member 8. It can be received by the department. Therefore, it is possible to effectively prevent the rear end portion of the side member 7 from bending and deforming, and to apply the collision load input to the side member 7 to the joint portion 20 disposed at the rear portion of the first cross member 8. Can be effectively supported by being transmitted to the floor frame 37 or the like. When a predetermined collision load is applied to the side member 7 of the front subframe 5, the collision load is concentratedly applied to the side member front portion 13 to deform the side member front portion 13 into a bellows shape. For example, there is an advantage that the collision load can be absorbed efficiently.

  Further, as shown by arrows I and J in FIGS. 3 and 4, the collision load is transmitted obliquely rearward of the vehicle from the support bracket 27 of the third cross member 11 through the inclined portion 29 of the first cross member 8. Then, it is dispersed from the joint portion 20 disposed at the rear end portion of the first cross member 8 and the fixing portion 34 of the second cross member 10 to the floor frame 37 and the tunnel lower frame 38 located on the right side of the vehicle body. Each can be supported. For this reason, the side member rear portion 14 is tilted inward according to the collision load by the first cross member 8 and the collision load is applied to the side member front portion 13 in a concentrated manner. By compressing and deforming, for example, in a bellows shape or the like, it is possible to efficiently absorb a collision load input at the time of a vehicle collision.

  Further, in the event of a vehicle collision, the axle shaft of the power plant 1 is applied to the second mount bracket 17 of the side member 7 in accordance with a collision load that acts in the direction of retreating the power plant 1 supported by the front subframe 5. The second mount bracket 17 is released from the fastened state, for example, by being brought into contact with it, and as shown in FIG. The front subframe 5 is allowed to swing downward with the two fixed portions provided at the rear of the first cross member 8 as fulcrums according to the collision load K acting in the direction. Therefore, when the vehicle collides, the power plant 1 held by the front subframe 5 is guided downward so that the power plant 1 Can be suppressed from interfering with the Sshupaneru 2, it has the advantage of effectively preventing such a power plant 1 from entering the passenger compartment.

  In the above-described embodiment, the second cross member (rear cross member) 10 is provided immediately below the front end of the floor tunnel 35 and extending in the vehicle width direction so as to connect the left and right ends of the first cross member 8. Further, the area of the closed cross section in the vehicle width direction central portion of the second cross member 10 is set to a value smaller than the area of the closed cross section in the vehicle width direction central portion 28 of the first cross member 8 made of the pipe-shaped member. As in the case where a large rear cross member or the like is provided below the front portion of the floor tunnel 35, the layout of each member including the engine exhaust pipe 1a or the propeller shaft installed in the floor tunnel 35 is improved. The vehicle collision load and the lateral force at the time of traveling input from the first cross member 8 to the tunnel lower frame 38 while suppressing obstruction, etc. There is an advantage that the rigidity can be effectively improved for. Therefore, the floor tunnel 35 is expanded and contracted according to the lateral force or the like input from the first cross member 8 of the front sub-frame 5 to the tunnel lower frame 38 when the vehicle is running, with a simple and lightweight configuration. There is an advantage that can be prevented.

  In particular, as shown in the above-described embodiment, in a vehicle in which a rearwardly inclined portion 35a is formed on the front upper wall of the floor tunnel 35, the second cross member 10 is placed in front of the rear end of the inclined portion 35a. When the vertical dimension of the second cross member 10 in the vehicle width direction central portion is set to a value smaller than that of the first cross member 8 made of the pipe-shaped member, the upper surface portion of the floor tunnel 35 is disposed. The floor tunnel 35 is secured by the second cross member 10 while a sufficient space is provided between the (inclined portion 35a) and the second cross member 10 for installing the exhaust pipe 1a or the propeller shaft of the engine. It is possible to effectively reinforce the lower part of the front part and effectively prevent the expansion / contraction deformation.

  A second cross member 10 for connecting the left and right end portions of the first cross member 8 is disposed on the front side of the front end of the downwardly inclined portion 35a formed on the front upper wall of the floor tunnel 35. Even when the vertical dimension of the second cross member 10 in the vehicle width direction central portion is set to a value larger than that of the first cross member 8, the vehicle in the vehicle width direction central portion of the second cross member 10 is also used. By setting the front-rear dimension to a value smaller than that of the first cross member 8 and positioning the second cross member 10 on the front side of the vehicle as much as possible, the upper surface portion (inclined portion 35a) of the floor tunnel 35 and the first cross member There is an advantage that a space for installing the exhaust pipe 1a of the engine or the propeller shaft can be sufficiently secured between the two cross members 10.

  On the other hand, as shown in FIG. 10, the front upper wall 35 b of the floor tunnel 35 is formed substantially horizontally, and the left and right end portions of the first cross member 8 are located behind the front end of the floor tunnel 35. In the vehicle in which the second cross member 10A is connected, the vertical dimension of the second cross member 10A is the vertical dimension of the first cross member 8 regardless of the longitudinal dimension at the center in the vehicle width direction. By setting the second cross member 10A to a lower side of the vehicle as much as possible by setting it to a smaller value, the engine is placed between the front upper wall 35b of the floor tunnel 35 and the second cross member 10A. A sufficient space can be secured for installing the exhaust pipe 1a or the propeller shaft.

  Further, in the above-described embodiment, the fixing portions 34 provided on the left and right side portions of the second cross member 10 are arranged at the lower side portion of the floor tunnel 35 at a position spaced apart from the vehicle body-side strength member composed of the floor frame 37. It is fixed to another vehicle body side strength member consisting of a tunnel lower frame 38 arranged along the road. Then, as shown in FIG. 8, the vehicle body side strength member including the floor frame 37 and the tunnel lower frame 38, the joint portion 20 of the first cross member 8, and the fixing portion 34 of the second cross member 10, Since the U-shaped continuous structure was formed, the rigidity of the vehicle body at the support portions of the first cross member 8 and the second cross member 10 was sufficiently ensured and input to the first cross member 8. Lateral force and the like during traveling can be transmitted from the joint portion 20 and the fixed portion 34 to the floor frame 37 and the tunnel lower frame 38 to be effectively supported. Moreover, a harness or the like routed between the floor frame 37 and the tunnel lower frame 38 is connected to the engine room from the joint 20 and the opening 40 formed between the fixing part 34 and the floor panel 9. There is an advantage that it can be easily derived.

  Further, as shown in the above embodiment, the third cross member (center cross member) 11 including the support bracket 27 for supporting the vehicle width direction central portion 28 of the first cross member 8 made of a pipe-shaped member is provided in the vehicle width direction. In the vehicle installed so as to extend to the left, the lower arm 4 is formed at a position located on the front side of the vehicle width direction central portion 28 of the first cross member 8 at both left and right side portions of the third cross member 11. When the front arm support portion 18 that supports the front connection portion 43 of the suspension arm is disposed, a lateral force or the like input from the front connection portion 43 of the lower arm 4 to the side portion of the third cross member 11 is By transmitting from the third cross member 11 to the rear side of the first cross member 8 through the vehicle width direction central portion 28 and the left and right inclined portions 29, the floor panel 9 Has the advantage of effectively supported at the vehicle body side strength member such as a floor frame 37 which is location.

  11 to 15 show a front subframe structure according to the second embodiment of the present invention. In the front subframe structure, the same members as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. In the front subframe structure according to the second embodiment, the side member 7 of the front subframe 5 includes a side member front portion 71 having a substantially square pipe-like cross-sectional shape and a side member having a round pipe-like cross-sectional shape. It is divided into a rear part 72.

  The left and right side members 7 support a third cross member (center cross member) 11 extending in the vehicle width direction so as to connect the intermediate portions in the front-rear direction, and the front connection portion 43 of the suspension arm including the lower arm 4. The front arm support portion 18 is connected to each other via a closed section structure 74 that forms a closed section extending in the vehicle width direction.

  The closed cross-section structure 74 includes an upper panel 75 projecting obliquely upward and laterally from a side end of the third cross member 11, and a lower panel 76 disposed below the upper panel 75. The second mounting bracket includes a cylindrical mounting portion 54 that is fastened to the lower surface of the side frame 3 via a fastening bolt 53.

  The upper panel 75 of the closed cross-section structure 74 includes an upper wall plate 77 extending obliquely upward from the upper surface of the side end portion of the third cross member 11, and a pair of lower walls extending from the front and rear side end portions of the upper wall plate 77. A side wall plate 78 and an inner wall plate 79 extending downward from the inner end in the vehicle width direction of the upper wall plate 77 are provided. The outer peripheral portion of the lower panel 76 is joined to the lower ends of the side wall plate 78 and the inner wall plate 79. As a result, a closed cross section 80 extending in the vehicle width direction is formed (see FIG. 14).

  As shown in FIG. 15, the upper panel 75 and the lower panel 76 constituting the closed cross-section structure 74 are formed thicker than the plate thickness of the pipe member constituting the side member front part 71 and the side member rear part 72. In addition, the third cross member 11 is formed of a steel plate material thicker than the steel plate materials constituting the upper panel 22 and the lower panel 23 of the third cross member 11. The rear end portion of the side member front portion 71 is welded to the front surface of the base end portion of the closed cross-section structure 74, and the front end portion of the side member rear portion 72 is the base end of the closed cross-section structure 74. The side member front part 71 and the side member rear part 72 are connected to each other via the closed cross-section structure 74 by being welded to the rear surface of the part.

  A side end portion of the third cross member 11 constituting a substantially rectangular closed section extending in the vehicle width direction by the upper panel 22 and the lower panel 23 is an inner wall of the upper panel 75 constituting the closed section structure 74. While being joined to the plate 79, a pair of front and rear nut members constituting the front arm support portion 18 are fixed to the base end portion (lower portion) of the lower panel 76. The front arm support 18 provided at the base end portion of the lower panel 76 and the third cross member 11 joined to the inner wall plate 79 of the upper panel 75 are connected via the closed cross-section structure 74. They are linked together.

  The rear end portion of the third cross member 11 is disposed on the rear side of the rear end portion of the closed cross-section structure 74, and the rear outer surface of the third cross member 11 is the side member rear portion 14. It is joined to the inner surface of the front part. Further, a support bracket 27 to which a vehicle width direction center portion 28 of the first cross member 8 made of a pipe-like member is joined to a vehicle width direction center portion of the third cross member 11 as in the first embodiment. Is provided. The left and right inclined portions 29 of the first cross member are installed so as to extend in a C shape from the left and right end portions of the vehicle width direction center portion 28 toward the rear side of the vehicle in a plan view. A joining portion 20 is provided at the rear end portion of the inclined portion 29 to be joined to the vehicle body side strength member formed of the floor frame 37.

  As described above, the front arm support portion 18 that supports the suspension arm composed of the lower arm 4, the pair of left and right side members 7, and the third cross extending in the vehicle width direction so as to connect the left and right side members 7. In a front sub-frame structure having a center cross member made up of members 11, the side member 7 is closed with a side member front portion 71 having a closed cross section located on the front side of the front arm support portion 18, and the front arm support. A closed cross-section that is divided into a side member rear portion 72 having a closed cross-sectional shape located on the rear side of the portion 18 and that forms a closed cross-section extending in the vehicle width direction between the front arm support portion 18 and the third cross member 11. When configured to be phase-coupled via the structure 74, the front arm 4 can be moved from the lower arm 4 when the vehicle is running with a simple and compact configuration. The lateral force or the like to be input to the sub-frame 5 has the advantage that it is possible to stably support.

  That is, since the side member 7 is constituted by the side member front part 71 and the side member rear part 72 made of a pipe-like body having a closed cross-sectional shape, the side member 7 can be formed with light weight and high rigidity. When the vehicle travels, for example, a lateral force or the like input from the lower arm 4 positioned on one side of the vehicle body to the front arm support portion 18 is transferred from the closed cross-section structure 74 and the third cross member 11 to the other side of the vehicle body. Therefore, the lateral force and the like can be stably supported while suppressing the side member front portion 71 and the side member rear portion 72 from vibrating according to the lateral force and the like.

  In the above embodiment, since the rear end portion of the side member front portion 71 and the front end portion of the side member rear portion 72 are joined to the closed cross-section structure 74, respectively, A function as a connecting member between the front portion 71 and the side member rear portion 14 can be provided. Accordingly, with a simple and compact configuration, the collision load input to the side member front part 71 at the time of a vehicle collision is transmitted to the side member rear part 72 and the third cross member 11 via the closed cross-section structure 74. Thus, there is an advantage that it can be dispersed efficiently throughout the vehicle body and supported efficiently.

  Further, the side member front portion 71 is formed of a plurality of ridge lines extending in the vehicle front-rear direction and a flat plate portion disposed between adjacent ridge lines, similarly to the side member front portion 13 according to the first embodiment. In the case of a cross-sectional shape such as a square pipe with a front side frame, the side member front part 71 constituting the front subframe 5 is input to the side member front part 71 at the time of a vehicle collision without increasing the size. The collision load can be effectively transmitted to the side member rear portion 72 and the vehicle body side strength member provided behind the side member while sufficiently supporting the collision load. When the collision load input to the side member front portion 71 becomes a certain value or more, the collision load can be effectively absorbed by plastically deforming the side member front portion 71 in a bellows shape or the like. Therefore, there is an advantage that the collision load can be effectively prevented from reaching the side member rear portion 72 and the vehicle interior.

  In addition, the side member rear portion 72 has a round pipe-like cross section having a curved surface having a larger curvature than the flat plate portion of the side member front portion 71, like the side member rear portion 14 according to the first embodiment. In the case of the shape, the wall surface portion of the side member rear portion 72 undergoes surface vibration or a section thereof according to the lateral force input to the side member rear portion 72 from the rear side connection portion 44 or the like of the lower arm 4 when the vehicle is traveling. It is possible to effectively prevent the shape from being plastically deformed. Therefore, as described above, the side member front part 71 has a cross-sectional shape such as a square pipe, and the side member rear part 72 has a cross-sectional shape such as a round pipe. While suppressing the vibration of the front sub-frame 5 according to the lateral force input during traveling of the vehicle and the effect of improving the proof strength against the collision load input to the vehicle and effectively absorbing the collision load, The effect that the yield strength against the lateral force can be effectively improved can be achieved.

  Moreover, in the said embodiment, the closed cross-section structure body 74 which mutually connects the front side arm support part 18 which supports the front side connection part 43 of the lower arm 4, and the 3rd cross member 11 installed between the left and right side members 7 is provided. Since the second mount bracket is attached to the center portion in the front-rear direction of the vehicle body frame including the side frame 3, the lateral force input from the lower arm 4 to the front arm support portion 18 during the traveling of the vehicle is closed. By transmitting from the body 74 to the vehicle body frame composed of the side frame 3, there is an advantage that the lateral force and the like can be more efficiently dispersed and effectively supported throughout the vehicle body.

  As shown in the above embodiment, when the plate thickness of the steel plate material or the like constituting the closed cross-section structure 74 is formed thicker than the plate thickness of the pipe material constituting the side member front portion 71 and the side member rear portion 72 The side member 7 constituting the main part of the front sub-frame 5 is effectively reduced in weight, and the lateral force input from the lower arm 4 to the closed cross-section structure 74 when the vehicle is running, There is an advantage that it can be effectively supported by being dispersed throughout the vehicle body via the third cross member 11 and the side member 7.

  Further, when the plate thickness of the steel plate material or the like constituting the closed cross-section structure 74 is formed thicker than the upper panel 22 and the lower panel 23 constituting the third cross member 11, the front subframe The center cross member formed by the third cross member 11 constituting the main portion of 5 is effectively reduced in weight, and the collision load input to the closed cross-section structure 74 from the sub-frame front portion 13 at the time of vehicle collision is reduced. There is an advantage that it can be stably supported by transmitting to the side member rear part 14.

  Further, as shown in the above embodiment, the third cross member 11 is constituted by an upper panel 22 and a lower panel 23 that form a closed cross section extending in the vehicle width direction, and a rear end portion of the third cross member 11 is formed. When the third cross member 11 and the closed cross-section structure 74 are arranged offset in the front-rear direction of the vehicle so as to be positioned rearward of the rear end portion of the closed cross-section structure 74, the first cross section 3 The side end of the cross member 11 is installed so as to straddle the closed cross-section structure 74 and the front portion of the side member rear portion 14, thereby connecting the connecting portion between the closed cross-section structure 74 and the side member rear portion 14. Since the three cross members 11 can reinforce, the rigidity of the front sub-frame 5 can be effectively improved.

  In addition, a first cross comprising a pipe-like member having a pair of left and right inclined portions 29 extending toward the rear side of the vehicle while inclining from the vehicle width direction center portion 28 of the third cross member 11 to the left and right outer sides thereof. When the member 8 is provided and both the left and right side portions of the first cross member 8 are connected to the vehicle body side strength portion including the floor frames 37 installed on the left and right sides of the floor tunnel 35, the front side of the lower arm 4 is provided. A lateral force or the like input from the connecting portion 43 to the front portion of the third cross member 11 is transferred to the floor from the third cross member 11 via the vehicle width direction center portion 28 and the left and right inclined portions 29 of the first cross member 8. There is an advantage that it can be effectively supported by transmitting to a vehicle body side strength member such as a floor frame 37 installed on the panel 9.

  In addition, at the time of a vehicle collision, the collision load input to the side member front portion 71 is disposed behind the third cross member 11 in the vehicle width direction center portion and the left and right inclined portions 29 of the first cross member 8. Can be transmitted to the floor frame 37 and the like, and can be dispersed and supported by them, so that the first cross member 8 can effectively prevent the side member rear portion 72 from falling in response to the collision load. On the other hand, there is an advantage that the collision load input at the time of the collision of the vehicle can be efficiently absorbed by concentrating the collision load on the side member front portion 71 and compressing and deforming the collision load into, for example, a bellows shape. .

3 Side frame (body frame)
4 Lower arm (suspension arm)
5 Front sub-frame 7 Side member 8 First cross member (pipe-shaped member)
11 Third cross member 13, 71 Side member front part 13a Ridge line 13b Flat plate part 14, 72 Side member rear part 17 Second mount bracket (mounting bracket)
18 Front arm support part 19 Round pipe material (Vehicle auxiliary machine attachment part)
20 Joint portion 31 Rear arm support portion 35 Floor tunnel 37 Floor frame (vehicle body side strength member)

Claims (7)

  A front subframe structure having a pair of left and right side members provided with arm support portions for supporting a suspension arm, and a cross member extending in the vehicle width direction so as to connect the left and right side members, The side member front portion located on the front side of the vehicle with respect to the arm support portion is formed in a pipe-like cross-sectional shape having a ridge line extending in the vehicle front-rear direction and a flat plate portion disposed between adjacent ridge lines. In addition, the side member rear portion provided with the arm support portion is formed in a pipe-like cross-sectional shape having a curved surface with a larger curvature than the flat plate portion of the side member front portion, and the cross member is disposed on the side member rear portion. A front sub-frame structure characterized in that both left and right ends of the are connected.   2. The front subframe structure according to claim 1, wherein the front side of the side member extends from the vicinity of the front end of the rear portion of the side member in a plan view to the front side of the vehicle while being inclined outward in the vehicle width direction.   The front sub-frame structure according to claim 1 or 2, wherein a mounting bracket for a vehicle body frame or a mounting portion for an auxiliary machine for a vehicle is provided at a rear portion of the side member.   The front subframe structure according to any one of claims 1 to 3, wherein the side member front portion and the side member rear portion are integrally formed of a single pipe material.   The cross member extends from the center of the cross member in the vehicle width direction to the left and right outer sides and extends to the rear side of the vehicle, and both the left and right sides are joined to the vehicle body side strength portions installed on the left and right of the floor tunnel. The rear end portion of the side member is connected to the front side portion of the portion located on the inner side in the vehicle width direction from the joint portion of the pipe-shaped member to the vehicle body-side strength portion. The front sub-frame structure according to any one of claims 1 to 4, wherein the front sub-frame structure is characterized by the following.   6. The front according to claim 5, wherein a rear arm support portion that supports the rear portion of the suspension arm is constructed so as to straddle the left and right end portions of the pipe-like member and the rear end portion of the side member. Subframe structure.   The front side according to any one of claims 1 to 3, wherein the side member front part and the side member rear part are formed separately and the arm support part is connected to the cross member. Subframe structure.

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