Vehicle-body structure of vehicle and manufacturing method of the same

In a vehicle-body structure of a vehicle, where suspension forming members are attached to a vehicle body, there are provided a first face portion, through which the suspension forming member extends, a second face portion provided to face to the first face portion, and a support member provided between the first face portion and the second face portion and supporting the suspension forming members, and the support member is joined to said second face portion via a reinforcing member which is formed integrally with the support member or formed separately from the support member. Accordingly, vibrations of the support member can be properly restrained.

BACKGROUND OF THE INVENTION

The present invention relates to a vehicle-body structure of a vehicle, and in particular to a vehicle-body structure of a vehicle, in which a suspension forming member is supported by a support member provided between a first face portion the suspension forming member penetrates and a second face portion provided to face to the first face portion, and a manufacturing method of the same.

As a structure to support various members forming part of a suspension device, such as a bolt and nut or a trailing arm, (hereinafter, referred to as “suspension forming member”), a specified structure, in which the suspension forming member is provided to vertically penetrate a plate-shaped member which is arranged substantially horizontally and forms various frames or brackets, and this suspension forming member is supported by a support member which is fixed to the plate-shaped member such that the suspension forming member is positioned above the plate-shaped member with a space, is applied to vehicles, such as automotive vehicles, in some cases.

Japanese Patent Laid-Open publication No. 2001-048050, for example, discloses the structure, referring to FIG. 3, in which the bolt for fixing the rear end portion of the sub frame is provided to penetrate the bottom face portion of the outrigger which is arranged below the boarder portion of the floor panel and the dash panel and fixed to the lower faces of these panels, and this bolt is supported at the upper-and-lower two points of the support member and the penetration portion of the outrigger. Herein, the support member is fixed to the outrigger such that it is provided above the bottom face portion of the outrigger and below the dash panel. According to the technology of the above-described publication, by utilizing the space between the outrigger and the dash panel, the bolt for fixing the sub frame can be positioned at an appropriate level for the suspension device and also supported stably at the above-described upper-and-lower two points.

Further, Japanese Patent Laid-Open publication No. 2006-306135 discloses the structure, referring to FIG. 5, in which the bolt for attaching the suspension cross member is provided to penetrate the bottom face portion of the side frame which is fixed to the lower faces of the floor panel, and this bolt is supported at the upper-and-lower two points of the support member and the penetration portion of the side framer. Herein, the support member is fixed to the side frame such that it is provided above the bottom face portion of the side frame and below the floor panel. According to the technology of the above-described publication, by utilizing the space between the side frame and the floor panel, the bolt for attaching the suspension cross member can be positioned at an appropriate level for the suspension device and also supported stably at the above-described upper-and-lower two points.

However, in a case in which the support member to support the suspension forming member is provided between the first plate-shaped member penetrating the suspension forming member and the second plate-shaped member facing to the first plate-shaped member like the technologies of the above-described publications, there is problem in that the support member joined to the suspension forming member may be easily made vibrate due to the vibration transmission from the suspension device.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a vehicle-body structure of a vehicle or a manufacturing method of the same which can properly restrain vibrations of the support member in the case in which the suspension forming member is supported by the support member provided between the first plate-shaped member penetrating the suspension forming member and the second plate-shaped member facing to the first plate-shaped member.

According to the present invention, there is provided a vehicle-body structure of a vehicle, where a suspension forming member is attached to a vehicle body, comprising a first face portion, which the suspension forming member penetrates, a second face portion provided to face to the first face portion, and a support member provided between the first face portion and the second face portion and supporting the suspension forming member, wherein the support member is joined to the second face portion via a reinforcing member which is formed integrally with the support member or formed separately from the support member.

According to the present invention, since the support member is joined to the second face portion via the reinforcing member in the case in which the suspension forming member is supported by the support member provided between the first plate-shaped member penetrating the suspension forming member and the second plate-shaped member facing to the first plate-shaped member, move of the support member is restricted by the second face portion, so that vibrations of the support member can be properly restrained.

According to an embodiment of the present invention, the support member is joined to the first face portion. Thereby, vibrations of the support member can be effectively restrained.

According to another embodiment of the present invention, the vehicle-body structure of a vehicle further comprises at least one third face portion forming a closed section together with the first and second face portions by connecting the first face portion and the second face portion, wherein at least one of the support member and the reinforcing member is joined the third face portion. Thereby, the move of the support member is restricted by the third face portion as well, so that the vibrations of the support member can be further effectively restrained.

According to another embodiment of the present invention, a joint portion of the reinforcing member and another member than the reinforcing member includes a rigid joint portion where the reinforcing member and another member are joined with a direct contact thereof and a flexible joint portion where the reinforcing member and another member are joined via a damping member provided therebetween. Thereby, the reinforcing member and the other member can be joined firmly with the rigid joint portion, thereby ensuring the rigidity-improvement effect can be ensured, and also the vibrations of the reinforcing member and the support member can be reduced with the flexible joint portion. Accordingly, the desired rigidity of the vehicle-body structure is ensured and the vibration transmission is restrained, so that the comfortable ride of a vehicle can be improved and the noises can be reduced. Herein, it may not be required to provide any additional member to restrain the vibration transmission, so that the above-described effects can be advantageously provided, avoiding any improper weight increase of the vehicle body or the like.

According to another embodiment of the present invention, the flexible joint portion is provided at a joint portion of the reinforcing member and the second face portion. Thereby, the strain energy converging at the reinforcing member can be effectively reduced, so that the vibrations of the support member and the reinforcing member can be effectively reduced.

According to another embodiment of the present invention, the damping member is a viscoelastic member having physical properties which fall within a range enclosed by six coordinate points: (1, 0.4), (1, 0.2), (2, 0.1), (1000, 0.1), (10000, 0.2) and (10000, 0.4) in an X-Y coordinate system with X axis of the storage modulus and Y axis of the loss factor, or a range exceeding the loss factor of 0.4. Thereby, since the viscoelastic member is used as the damping member and the storage modulus and the loss factor as its physical properties are specified as any values falling within the specified range which has been confirmed as an effective range capable of providing the vibration-damping effect, the above-described damping effect of vibrations of the reinforcing member and the support member can be surely provided.

According to anther aspect of the present invention, there is provided a manufacturing method of a vehicle-body structure of a vehicle, where a suspension forming member is attached to a vehicle body, the vehicle-body structure comprising a first face portion, through which the suspension forming member extends, a second face portion provided to face to the first face portion, and a support member provided between the first face portion and the second face portion and supporting the suspension forming member, wherein the support member is joined to the second face portion via a reinforcing member which is formed integrally with the support member or formed separately from the support member. A vehicle-body structure of a vehicle manufactured by this method can provide the same effects described above for the present invention.

DETAILED DESCRIPTION OF THE INVENTION

At first, results of simulation conducted to the structures specified in claims of the present invention will be described prior to descriptions of specific applicable structures to a vehicle body.

FIG. 1is a diagram showing a rigid joint model A used for this simulation, andFIG. 2is a diagram showing a rigid-flexible combined joint model B used for this simulation. In each model, a first member1which has a U-shaped section and a second member2which has a plate shape are used as a vehicle-body forming member, which form a hollow frame4having a closed-section portion3with a rectangular section by joining both-side flanges of the first member1to both-side end portion of the second member2. The closed-section portion3of the hollow frame4is formed by a first face portion which is comprised of the second member2, a second face portion which is comprised of an upper face portion11of the first member1and provided to face to the first face portion, and a pair of third face portions which is comprised of side face portions12,13of the first member1and connects the first face portion and the second face portion.

Further, in each of the models A, B, a support member10to support a suspension forming member, not illustrated, is provided between the first face portion2and the second face portion11, and this support member10is joined to the second face portion11via a reinforcing member8. The support member10comprises an upper face portion5which has a rectangular-plate shape and is provided above and facing to the first face portion2, and a pair of leg portions6,7which has a rectangular-plate shape and is provided to extend downward from both ends, in a longitudinal length of the hollow frame4, of the upper face portion5. The leg portions6,7have flanges6a,7aat respective sides of their peripheries. The upper flanges6a,7aare joined to the upper face portion5, the lower flanges6a,7aare joined to the first face portion2, and the side flanges6a,7aare joined to the third face portions12,13, respectively. The reinforcing member8is a member which has a rectangular plate shape and is provided perpendicularly to the upper face portion5of the support member10, and this reinforcing member8has flanges8aat respective sides of its periphery. The upper flange8ais joined to the second face portion11, the lower flange8ais joined to the upper face portion5of the support member10, and the side flange8ais joined to the third face portions12,13, respectively.

In the rigid joint model A shown inFIG. 1, the reinforcing member8is joined to the upper face portion5of the support member10, the third face portions12,13, and the second face portion11by spot welding. Meanwhile, in the rigid-flexible combined joint model B shown inFIG. 2, the reinforcing member8is joined to the upper face portion5of the support member10and the third face portions12,13only by spot welding, but the reinforcing member8is joined to the second face portion11by combination of rigid and flexible joining. Specifically, the upper flange8aof the reinforcing member8is joined to the second face portion11at its central portion by spot welding and also at its both sides via damping members9. Herein, the above-described joint portion with the spot welding constitutes a rigid joint portion X and the above-described joint portion via the damping member9constitutes a flexible joint portion Y.

Herein, while the model B equipped with both the rigid joint portion X and the flexible joint portion Y has a higher rigidity than the model A equipped with only the rigid joint portion X and therefore there exists a difference in the resonance frequency between the models A, B, in order to compare these models properly by making their resonance frequency uniform, the area of the rigid joint portion X of the model A is set to be slightly larger than that of the rigid joint portion X of the model B. Further, the damping member9provided at the flexible joint portion Y is comprised of a viscoelastic member which has the loss factor of 0.4 and the storage modulus of 200 MPa (20° C., 30 Hz).

FIG. 3shows simulation results, which shows a comparison of the respective inertance at a responsive point y (a magnitude of an acceleration amplitude per an exciting force: m/s2/N), in which in each of the models A, B, a specified corner portion of the closed-section portion3at one end of the frame4is set as an exciting point x and another corner portion of the closed-section face3which is located diagonally to the other end of the frame4is set as the responsive point y.

As apparent from this figure, a peak value of the inertance of the rigid-flexible combined joint model B is lower than that of the rigid joint model A. Accordingly, it is shown that the amount of damping occurring in the process of vibration transmission from the exciting point x to the responsive point y becomes greater by providing the flexible joint portion Y.

FIG. 4shows simulation results of a mode-damping-ratio variation characteristic for the storage modulus and the loss factor when using plural viscoelastic members having different values of the loss factor as the damping member9in the above-described rigid-flexible combined joint model B. Herein, the damping member having the loss factor of 0.05 is a comparative sample, which is an adhesive agent for structure generally used in the vehicle body.

As apparent from this figure, it is shown that the mode-damping-ratio variation in a case of using the viscoelastic member is greater than that in a case of using the general adhesive agent for structure (the loss factor of 0.05) in a whole area of the storage modulus, thereby damping the vibration more easily. In particular, it is shown that the mode-damping-ratio variation becomes greater as the loss factor becomes greater, and that the mode-damping-ratio variation becomes the maximum when the storage modulus is 100 MPa regardless of the value of the loss factor.

FIG. 5shows relationships between the loss factor and the storage modulus which can substantially obtain the damping effect in a case in which the viscoelastic member is used as the damping member9from the simulation results ofFIG. 4. In this figure, it is determined that the effect can be obtained in a case in which the mode-damping-ratio variation is a threshold M or greater which is shown inFIG. 4, while no effect can be obtained in a case in which the mode-damping-ratio variation is less than the threshold M.

Consequently, it has been found out that the damping effect can be obtained in substantially a range enclosed by six coordinate points: (1, 0.4), (1, 0.2), (2, 0.1), (1000, 0.1), (10000, 0.2) and (10000, 0.4) in an X-Y coordinate system with X axis of the storage modulus and Y axis of the loss factor, and a range exceeding the loss factor of 0.4.

Next, preferred embodiments in which the structure of the present invention is applied to the vehicle body will be described. In the descriptions below, terms showing directions, such as “forward,” “rearward,” “longitudinal,” “right,” “left” and “right and left,” will generally indicate respective directions when the vehicle's advance direction is considered as the “forward” direction.

FIG. 6is a perspective view of a structure of a vehicle body to which a first embodiments is applied, when viewed obliquely from the front and below. As shown inFIG. 6, as members forming a framework of a front portion of the vehicle body around an engine room, there are provided a right-and-left front side frames22which extend longitudinally, bumper stays24which extend forward from respective front end portions of the front side frames22, a bumper reinforcement26which is connected to respective front end portions of the bumper stay24at its both end portions and extends in a vehicle width direction, and a front-suspension cross member34which is provided to extend in the vehicle width direction in back of the bumper reinforcement26. Right-and-left lower arms36, part of a suspension device of front wheels, are arranged near right-and-left end portions of the front suspension cross member34.

Further, behind the engine room is provided a dash panel31which partitions the engine room from a vehicle compartment. A floor panel32extends rearward from a lower end of the dash panel31. Side sills44extend longitudinally at right-and-left both side portions of the floor panel32. Meanwhile, at upper portions of right-and-left both side portions of the vehicle body are provided roof rails52to extend longitudinally. Further, front pillars45, hinge pillars46, center pillars48, and rear wheel houses50are provided between the roof rails52and the side sills44.

A tunnel reinforcement33which extends rearward from the dash panel31is arranged at a central portion, in the vehicle width direction, of the floor panel32. Between the front-and-left side sills44and the tunnel reinforcement33are respectively provided front floor frames42which extend rearward from rear end portions of the front side frames22. Respective lower-arm brackets38are attached to a lower face of the floor panel32, extending between the tunnel reinforcement33and the right-and-left front floor frames42. Rear end portions of the lower arms36are fixed to the lower-arm brackets38.

FIG. 7is a sectional view of the lower-arm bracket38and its surrounding structure taken along line a-a ofFIG. 6, andFIG. 8is a perspective view of the structure shown inFIG. 7, when viewed obliquely from the rear and above. Herein, whileFIGS. 7 and 8show the right lower-arm bracket38and its surrounding structure, the left lower-arm bracket38and its surrounding structure have the same constitution. InFIG. 8, a mark x shows a spot-welding portion, which is the same in other figures as well.

As shown inFIGS. 7 and 8, the lower-arm bracket38comprises a bottom face portion61which is provided below the dash panel31with a specified distance, a front face portion62which rises toward the dash panel31from a front end of the bottom face portion61, a rear face portion63which rises toward the dash panel31from a rear end of the bottom face portion61, and a side wall portion64which rises toward the dash panel31from an inside end portion, in the vehicle width direction, of the bottom face portion61. Further, the lower-arm bracket38includes a flange65which extends along respective upper edge portions of the front face portion62, the side wall portion64and the rear face portion63. This flange65is joined to a lower face of the dash panel31.

Further, as shown inFIG. 8, the lower-arm bracket38has an open shape which opens outward in the vehicle width direction. An open face of the lower-arm bracket38is covered with a side face of the front floor frame42, and a closed section is formed by the side face of the front floor frame42, the dash panel31, and the side wall portion64and the bottom face portion61of the lower-arm bracket38. Herein, the lower-arm bracket38further includes a flange66which extends from an outside end portion, in the vehicle width direction, of the front face portion62to an outside end portion, in the vehicle width direction, of the bottom face portion61. This flange66is joined to the front floor frame42.

As shown inFIG. 7, a rear end portion of the lower arm36includes a side upper member36aand a side lower member36bwhich is provided below and facing to the side upper member36aand joined to the side upper member36a. The side upper member36aand the side lower member36bare fixed to the lower-arm bracket38by a nut90joined to an upper face of the bottom face portion61of the lower-arm bracket38by welding and a bolt92penetrating the side lower member36b, the side upper member36aand the bottom face portion61of the lower-arm bracket38from below.

A support member70to support the above-described bolt92is provided between the bottom face portion61of the lower-arm bracket38as the first face portion which the bolt92penetrates and the dash panel31as the second face portion provided above and facing to the bottom face portion61.

As shown inFIGS. 7 and 8, the support member70comprises a support portion71which is provided above and facing to the bottom face portion61of the lower-arm bracket38and supports the bolt92via the nut90, a slant portion72which extends obliquely rearward and downward from a rear end of the support portion71, a front flange73which rises from a front end of the support portion71, a rear flange74which rises from a rear end of the slant portion72, and a pair of side flanges75,76which rises from both ends, in the vehicle width direction, of the support portion71and the slant portion72. The nut90penetrates the support portion71and is joined to this support portion71by welding. The front flange73is joined to the front face portion62of the lower-arm bracket38, the rear flange74is joined to the rear face portion63of the lower-arm bracket38, the inside side flange76is joined to the side wall portion64of the lower-arm bracket38, and the outside side flange75is joined to a side face of the front floor frame42, respectively, by welding.

The support member70is joined to the lower face of the dash panel31via the reinforcing member80, so that move of the support member70is restricted. Thereby, vibrations of the support member70can be effectively restrained.

The reinforcing member80comprises a base portion82which is joined to an upper face of the support portion71of the support member70, a rising portion81which rises toward the dash panel31from a front end of the base portion82, and a joined portion85which extends forward from an upper end of the rising portion81and is joined to the lower face of the dash panel31. The reinforcing member80further includes a pair of side flanges83,84which extends rearward from both ends, in the vehicle width direction, of the rising portion82. An upper half portion of the inside side flange84is joined to the side wall portion64of the lower-arm bracket38, and a lower half portion of the inside side flange84is joined to the side flange76of the support member70, respectively. An upper half portion of the outside side flange83is joined to a side face of the front floor frame42, and a lower half portion of the outside side flange83is joined to the side flange75of the support member70, respectively.

Herein, plural opening portions86are formed at the rising portion81for lightweight achievement, and a notch87is formed at the base portion82for interference avoidance with the nut90.

A spot-welding joining is applied to a joint portion of the reinforcing member80to the support portion71of the support member70at the base portion82, a joint portion of the reinforcing member80to the side wall portion64of the lower-arm bracket38and the side flange76of the support member70at the inside side flange84, and a joint portion of the reinforcing member80to the side face of the front floor frame42and the side flange75of the support member70at the outside side flange83. These welding portions constitute rigid joint portions X having a direct contact.

Meanwhile, a joining via a viscoelastic member100as a vibration damping member is applied to the other joint portion of the reinforcing member80to the dash panel31at the joined portion85. This joint portion constitutes a flexible joint portion Y.

The viscoelastic member100generates (stores) the strain energy and transfers the strain energy to the thermal energy, whereby the strain energy can be dispersed. Thus, the viscoelastic member100can reduce the vibrations. While this viscoelastic member100can be joined to the both joint faces by an adhesive agent or its own viscosity, it may be joined by coating. Further, the viscoelastic member100is preferably placed between the both joint face portions in its compressive state, whereby a high pressing force against the both joint face portions can be obtained. A material of the viscoelastic member100is not limited to a particular one, but a silicon-based material or an acryl-based material, for example, can be used. Herein, the constitution of the viscoelastic member100described in this paragraph is applicable to all other vibration reduction members than the viscoelastic member100described in this specification, and hereinafter the similar descriptions are omitted.

According to the vehicle-body structure of the first embodiment, since the reinforcing member80is provided as described above, any deformation or collapse of the support member70and the lower-arm bracket38, and the like can be restrained with the above-described rigid joint portions X. Further, vibrations transmitted from the bolt92and the nut90as the suspension forming member to the dash panel31via the support member70and the reinforcing member80can be reduced with the flexible joint portions Y, thereby restraining the vibration transmission to passengers in the vehicle compartment.

Moreover, according to the first embodiment, since the flexible joint portion Y with the viscoelastic member100is applied to the joint portion to the dash panel31provided above the reinforcing member80, rusting can be prevented more properly compared with a case in which the flexible joint portion Y is provided below the support member70.

A second embodiment of the present invention will be described referring toFIGS. 9 through 11. Herein, the same members as those of the above-described first embodiment are denoted by the same numeral references inFIGS. 9 through 11, descriptions of which are omitted here.

FIG. 9shows a structure of the vehicle body to which the second embodiment is applied. As shown inFIG. 9, a front portion of the vehicle compartment is formed by the dash panel31, and a bottom portion of that is formed by the floor panel32. In a rear portion of the vehicle compartment, a bottom portion is formed by a center floor pan56which is continuous to the floor panel32, and a trunk floor pan57is provided in back of the center floor pan56to rise stepwise.

Further, between the right-and-left side sills44and the tunnel reinforcement33are provided a No. 2 cross member51and a No. 2.5 cross member52which extend in the vehicle width direction, respectively. Additionally, a No. 3 cross member53is provided at a border of the floor panel32and the center floor panel56, and a No. 4 cross member54is provided at a border of the center floor panel56and trunk floor pan57.

Moreover, rear side frames142are respectively provided to extend rearward from rear end portions of the front floor frames42at both end portions of the rear portion of the vehicle body.

FIG. 10is a sectional view of a bolt192fixing part of a rear suspension device to a rear side frame142and its surrounding structure, taken along line of b-b ofFIG. 9, andFIG. 11is a perspective view showing a support member170to support the bolt192. Herein, whileFIGS. 10 and 11show the structure of the right-side rear side frame142, the left-side rear side frame has the same structure.

InFIG. 10in which only a bottom portion143of the rear side frame142is illustrated, the rear side frame142has a U-shaped section which has a pair of right-and-left flanges at its upper end. A rear frame reinforcement140is provided above and facing to the bottom portion143of the rear side frame142, and the above-described pair of flanges of the rear side frame142are joined to the rear frame reinforcement140, thereby forming a closed section. The rear frame reinforcement140is formed stepwise to rise in front of and near the bolt192. A pair of front-and-rear flanges of a brace bracket138having a U-shaped section is joined to an upper face of the rear frame reinforcement140just behind the above-described rising portion.

As shown inFIG. 10, the bolt192penetrates the bottom portion143of the rear side frame142and the rear frame130joined to a lower face of the bottom portion143from above, and an head portion of the bolt192is joined to the support member170by welding. The support member170is provided between the bottom portion143of the rear side frame142as the first face portion and the rear frame reinforcement140as the second face portion.

As shown inFIGS. 10 and 11, the support member170comprises a support portion171which is provided above and facing to the rear side frame142and supports the bolt192, a slant portion172which extends obliquely forward and downward from a front end of the support portion171, and a lower joined portion173which extends forward from a front end of the slant portion172and is joined to an upper face of the rear side frame142by welding. A bolt hole168for the bolt192is formed at a central portion of the support portion171. Flanges174,175,176,177,178and179are respectively formed at both ends of the support portion171, the slant portion172and the lower joined portion173. These flanges174-179are joined to a side face portion of the rear side frame142by welding.

In the present embodiment, the support member170includes a reinforcing-member portion180integrally formed therewith. This reinforcing-member portion180comprises a rising portion181which rises toward the rear frame reinforcement140from a rear end of the support portion171and an upper joined portion182which extends rearward from an upper end of the rising portion181and is joined to a lower face of the rear frame reinforcement140.

The rising portion181slants obliquely rearward and upward. Further, the rising portion181has flanges183,184at its both ends in the vehicle width direction. These flanges183,184are joined to a side face portion of the rear side frame142by spot welding, respectively. These spot-welding portions constitute the rigid joint portions X having a direct contact.

Meanwhile, the upper joined portion182is joined to the lower face of the rear frame reinforcement140below a joint portion of the rear flange of the brace bracket138to the rear frame reinforcement140. A joining via a viscoelastic member200as a vibration damping member is applied to this joint portion of the upper joined portion182to the rear frame reinforcement140. This joint portion constitutes a flexible joint portion Y.

According to the vehicle-body structure of the second embodiment, since the support member170is joined to the lower face of the rear frame reinforcement140via the reinforcing-member portion180, move of the support member170is restricted by the rear frame reinforcement140, so that vibrations of the support member170can be effectively restrained.

Further, according to the second embodiment, since the support member170is joined not only to the rear frame reinforcement140as the second face portion but also to the bottom portion143of the rear side frame142as the first face portion, the vibrations of the support member170can be more effectively restrained.

Moreover, according to the second embodiment, any deformation or collapse of the support member170and the rear side frame142, and the like can be restrained with the above-described rigid joint portions X. Further, vibrations transmitted from the bolt192as the suspension forming member to the rear frame reinforcement140and the rear side frame142via the support member170can be reduced with the flexible joint portion Y, thereby restraining the vibration transmission to passengers in the vehicle compartment.

A third embodiment of the present invention will be described referring toFIGS. 12 through 15. Herein, the same members as those of the above-described first and second embodiments are denoted by the same numeral references inFIGS. 12 through 15, descriptions of which are omitted here.

FIG. 12shows a structure of the vehicle body to which the third embodiment is applied,FIG. 13shows a sectional view taken along line c-c ofFIG. 12,FIG. 14is a sectional view taken along line d-d ofFIG. 13, andFIG. 15shows an exploded perspective view of a support member270according to the third embodiment.

In the third embodiment, as shown inFIGS. 13 and 14, a structure of an attachment portion of a trailing bracket210, part of a suspension device of rear wheels, to the rear side frame142will be described. Herein, whileFIGS. 13 and 14show the right rear side frame142, the left rear side frame142has the similar structure.

In a portion shown inFIGS. 13 and 14, the rear side frame142has a U-shaped section opening downward, and comprises an upper face portion242and a pair of side face portions243,244which extends downward from both ends, in the vehicle width direction, of the upper face portion242. A rear frame reinforcement240is provided below and facing to the upper face portion242of the rear side frame142, and lower ends of both-side face portions243,244of the rear side frame142are joined to an upper face of the rear frame reinforcement240. Thereby, a closed section is formed.

As shown inFIG. 13, an opening portion245for avoiding with the trailing bracket210is formed at the rear frame reinforcement240. A front end portion of the trailing bracket210is inserted into the opening portion245, whereby the trailing bracket210is arranged to penetrate the rear frame reinforcement240. As shown inFIGS. 13 and 14, a front end portion of the trailing bracket210is pivotally supported at an axis212which extends in the vehicle width direction above the rear frame reinforcement240and below the upper face portion242of the rear side frame142. The axis212is provided to extend between a pair of fixing members214,215which is arranged inside the rear side frame142with a gap in the vehicle width direction, and the fixing members214,215are fixed to the support member270.

The support member270is provided between the rear frame reinforcement240as the first face portion and the upper face portion242of the rear side frame142as the second face portion. As shown inFIG. 15, the support member270comprises a support-member body171and first and second connecting members280,290which are connected to the support-member body271.

The support-member body271comprises a support portion272which is provided above and facing to the rear frame reinforcement240and supports the trailing bracket210, a front face portion276which extends downward from a front end of the support portion272, and a rear face portion275which extends downward from a rear end of the support portion272. At a central portion of the support portion272is provided a protrusion portion273which protrudes upward to avoid interference with the front end portion of the trailing bracket210. Further, a semicircular projection portion274which projects rearward is provided at a rear end portion of the support portion272, and the rear face portion275is of a semicircular shape corresponding to an outer peripheral shape of the projection portion274in a plan view below the projection portion274. As shown inFIG. 14, the above-described fixing member214,215are fixed to a lower face of the support portion272by bolts216,217, for example, on the both sides, in the vehicle width direction, of the protrusion portion273. Thereby, the support member270supports the trailing bracket210via the axis fixing members214,215and the axis212.

Further, a pair of flanges277,278is provided at both-side end portions of the support-member body271, and the respective flanges277,278are provided to extend upward from the both ends of the support portion272and forward from the both ends of the front face portion276, respectively, and joined to the side face portions243,244of the rear side frame142by welding.

The first connecting member280comprises a lower joined portion282which is joined to the upper face of the rear frame reinforcement240, a rising portion281which rises from a rear end of the lower joined portion282, and an upper joined portion283which extends rearward from an upper end of the rising portion281.

The upper joined portion283is joined to the lower face of the upper face portion242of the rear side frame142, so that the first connecting member280functions as the reinforcing member. A joint portion of the upper joined portion283to the rear side frame142is the one via a viscoelastic member299as the vibration damping member, which constitutes a flexible joint portion Y.

Further, a pair of flanges284,285which extends forward is provided at both-side end portions of the rising portion281of the first connecting member280, and the respective flanges284,285are joined to the side face portions243,244of the rear side frame142and front end portions of the flanges277,278of the support-member body271, by spot welding. Moreover, a rear face of the rising portion281is joined to the front face portion276of the support-member body271by spot welding. Thereby, the first connecting member280is connected to the support-member body271. These welding portions constitute rigid joint portions X having a direct contact.

The second connecting member290comprises a lower joined portion296which is joined to the upper face of the rear frame reinforcement240, a rising portion291which rises from a front end of the lower joined portion296, and an upper joined portion293which extends forward from an upper end of the rising portion291.

The upper joined portion293is joined to the lower face of the upper face portion242of the rear side frame142, so that the second connecting member290functions as the reinforcing member. A joint portion of the upper joined portion283to the rear side frame142is the one via a viscoelastic member300as the vibration damping member, which constitutes a flexible joint portion Y.

Further, a pair of flanges294,295which extends forward is provided at both-side end portions of the rising portion291of the second connecting member290, and the respective flanges294,295are joined to the side face portions243,244of the rear side frame142by spot welding. Moreover, a semicircular recess portion292which is recessed rearward is formed at a lower portion of the rising portion291, which corresponds to the shape of the projection portion274of the support-member body271. This second connecting member290is joined to the support-member body271by joining a rear face of the rear face portion271to a front face of the rising portion291by spot wielding in a state in which the projection portion274of the support-member body271engages with the recess portion292.

According to the vehicle-body structure of the third embodiment, since the support member270is joined to the upper face portion242of the rear side frame142via the first and second connecting members280,290, move of the support member270is restricted by the rear side frame142, so that vibrations of the support member270can be effectively restrained.

Further, according to the third embodiment, since the support member270is joined not only to the upper face portion242of the rear side frame142as the second face portion but also to the frame reinforcement240as the first face portion, the vibrations of the support member270can be more effectively restrained.

Moreover, according to the third embodiment, any deformation or collapse of the support member270and the rear side frame142, and the like can be restrained with the above-described rigid joint portions X. Further, vibrations transmitted from the trailing bracket210as the suspension forming member to the rear side frame142via the support member270can be reduced with the flexible joint portions Y, thereby restraining the vibration transmission to passengers in the vehicle compartment.

A fourth embodiment of the present invention will be described referring toFIGS. 16 through 19. Herein, the same members as those of the above-described first, second and third embodiments are denoted by the same numeral references inFIGS. 16 through 19, descriptions of which are omitted here.

FIG. 16shows a structure of the vehicle body to which the fourth embodiment is applied. As shown inFIG. 16, a No. 4.5 cross member58is provided in back of the No. 4 cross member54to extend in the vehicle width direction between the right and left rear side frames142at a rear portion of the vehicle body.

FIG. 17shows a sectional view taken along line e-e ofFIG. 16,FIG. 18shows a sectional view taken along line f-f ofFIG. 17, andFIG. 19shows a perspective view of a support member380and a reinforcing member390according to the fourth embodiment.

In the fourth embodiment, as shown inFIGS. 17 and 18, a structure of an attachment portion of a member bracket320for attaching part of the rear suspension device to the rear side frame142will be described. Herein, whileFIGS. 17 and 18show a structure of the right-side rear side frame142, the left-side rear side frame142has the same structure.

In a portion shown inFIGS. 17 and 18, the rear side frame142has a U-shaped section opening upward, and comprises a bottom face portion302and a pair of side face portions304,306which rises from both ends, in the vehicle width direction, of the bottom face portion302. Herein, a reinforcing member310is overlapped and joined to an upper face of the bottom face portion302of the rear side frame142.

The rear frame reinforcement140is provided above and facing to the bottom face portion302of the rear side frame142, and upper ends of both-side face portions304,306of the rear side frame142are joined to a lower face of the rear frame reinforcement140. Thereby, a closed section is formed.

The member bracket320is fixed to a lower face of the bottom face portion302of the rear side frame142by a bolt340. This bolt340penetrates the bottom face portion302of the rear side frame142and the member bracket320, and is fastened with an upper nut344which is placed onto an upper face of the reinforcing member310and a lower nut346which is placed onto a lower face of the member bracket320. Further, a head portion of the bolt340is supported by the above-described support member380.

As shown inFIG. 19, the support member380comprises a support portion381which is provided between the bottom face portion302of the rear side frame142as the first face portion and the rear frame reinforcement140as the second face portion, a front face portion382which extends downward from a front end of the support portion381, and a rear face portion383which extends downward from a rear end of the support portion381.

Further, a pair of flanges384,388which extends forward is provided at both-side end portions of the front face portion282, and the respective flanges384,388are joined to the side face portions304,306of the rear side frame142by spot welding. Moreover, a flange386extending forward is formed at a lower end of the front face portion382, and this flange386is joined to an upper face of the above-described reinforcing member310by spot welding.

Meanwhile, a pair of flanges385,389which extends rearward is provided at both-side end portions of the rear face portion283, and the respective flanges385,389are joined to the side face portions304,306of the rear side frame142by spot welding. Also, a flange387(seeFIG. 17) which extends rearward is formed at a lower end of the rear face portion383, and this flange387is joined to an upper face of the above-described reinforcing member310by spot welding.

This support member380is joined to the rear frame reinforcement140as the second face portion via the above-described reinforcing member390. The reinforcing member390comprises a joined portion391which is joined to a lower face of the rear frame reinforcement140, a front face portion392which extends downward from a front end of the joined portion391, and a rear face portion393which extends downward from a rear end of the joined portion391. Thus, this reinforcing member390is formed in a U shape in a side view as a whole. The reinforcing member390is joined to the support member380such that the joined portion391is located above the support portion381of the support member380with a specified distance.

Specifically, the front face portion392of the reinforcing member390is joined to a front face of the front face portion382of the support member380and the rear face portion393of the reinforcing member390is joined to a rear face of the rear face portion383of the support member380, respectively, by spot welding. These joint portions constitute rigid joint portions X.

Meanwhile, the joined portion391of the reinforcing member390and the rear frame reinforcement140are joined together via a viscoelastic member400as the vibration damping member, which constitutes a flexible joint portion Y.

According to the vehicle-body structure of the fourth embodiment, since the support member380is joined to the rear frame reinforcement140via the reinforcing member390, move of the support member380is restricted by the rear frame reinforcement140, so that vibrations of the support member380can be effectively restrained.

Further, according to the fourth embodiment, since the support member380is joined not only to the rear frame reinforcement140as the second face portion but also to the bottom face portion302of the rear aide frame142as the first face portion, the vibrations of the support member380can be more effectively restrained.

Moreover, according to the fourth embodiment, any deformation or collapse of the support member380, the reinforcing member390, and the rear side frame142, and the like can be restrained with the above-described rigid joint portions X. Further, vibrations transmitted from the bolt340as the suspension forming member to the rear frame reinforcement140and the rear side frame142via the support member280and the reinforcing member390can be reduced with the flexible joint portion Y, thereby restraining the vibration transmission to passengers in the vehicle compartment.

The present invention should not be limited to the above-described embodiments.

For example, while the above-described embodiments describe the case in which the rigid joint portion is constituted by the welding, the present invention is not limited to this welding joint, but any other joint manner, such as bolt-nut fastening, may be used.

Further, while the above-described embodiments describe the case in which the flexible joint portion Y is applied only to the joint portion of the reinforcing member to the second face portion, it may be applied to any other joint portions than this.

Moreover, while either the rigid joint portion X or the flexible joint portion Y is applied to respective joint portions of the reinforcing member to the other members, both the rigid joint portion X and the flexible joint portion Y may be applied to a single joint portion.