Subframe structure of front suspension

A subframe structure of a front suspension that leads a subframe and a vehicle driving apparatus to the lower side after separation of a rear portion of the subframe due to a frontal collision without increasing weight and parts. A subframe structure of the front suspension provides a subframe that supports a vehicle driving apparatus in a mounting manner, and a rear portion of the subframe is mounted on a lower portion of a vehicle body via a fastening member. Fastening between the subframe and the fastening member is configured such that the rear portion of the subframe is separated when a collision load to a vehicle rear side is applied to the subframe. A leading guide portion that abuts against the fastening member and leads the subframe to a lower side after separation from the fastening member is integrally formed on the rear portion of the subframe.

BACKGROUND

Technical Field

The present disclosure relates to a subframe structure of a front suspension in which a subframe that supports a vehicle driving apparatus such as an engine in a mounting manner is provided and a rear portion of the subframe is mounted on a lower portion of a vehicle body via a fastening member.

Background Art

Hitherto, in order to suppress excessive load transmission to a dash panel at the time of a vehicle frontal collision, it has been preferred to employ a structure as follows. Put plainly, a structure in which a part of a vehicle driving apparatus such as an engine is supported by a subframe below the vehicle driving apparatus in a mounting manner, and a rear portion of the subframe is separated from a body such as a front side frame at the time of a frontal collision has been employed. By this structure, the engine can move toward the lower side together with the subframe when the rear portion of the subframe is separated from the body, and hence excessive load transmission of the engine to the dash panel can be suppressed.

The movement of the rear portion of the subframe to the lower side after being separated from the body described above can be attained with use of an inclined portion (see a kick-up portion of the front side frame) of a body frame disposed from a lower portion of the dash panel to the front portion of a floor panel. However, the inclined portion cannot be used when a portion for fastening the rear portion of the subframe to the vehicle body is positioned to be closer to the rear side than the inclined portion due to the layout, for example.

Thus, a way of separately forming the inclined portion with use of a dedicated member on the rear side of the portion for fastening the rear portion of the subframe to the vehicle body is conceived. In this case, the dedicated member is separately needed, the weight increases and the number of parts increases, and the productivity decreases. Therefore, there has been room for improvement.

Incidentally, Japanese Patent Laid-Open No. 2016-188054 discloses a configuration in which a tube nut integrally formed with a lower wall horizontal portion of an inclined portion of a front side frame is provided, and a rear portion of a subframe is mounted with use of a bolt to be fastened with the tube nut. The configuration is a vehicle front portion structure in which the tube nut is broken and the subframe is separated from the front side frame at the time of a vehicle frontal collision.

However, in the configuration disclosed in Japanese Patent Laid-Open No. 2016-188054, the movement of the rear portion of a front subframe to the lower side after the separation from the body (see the front side frame) uses the inclined portion of the front side frame disposed from the lower portion of the dash panel to the front portion of the floor panel, and hence there are problems similar to those described above.

SUMMARY

Thus, the present disclosure provides a subframe structure of a front suspension capable of leading a vehicle driving apparatus to the lower side together with a subframe after the separation of a rear portion of the subframe due to a frontal collision without increasing the weight and the number of parts.

In a subframe structure of a front suspension according to the present disclosure, a subframe that supports a vehicle driving apparatus in a mounting manner is provided, a rear portion of the subframe is mounted on a lower portion of a vehicle body via a fastening member, fastening between the subframe and the fastening member is configured such that the rear portion of the subframe is separated when a collision load to a vehicle rear side is applied to the subframe, and a leading guide portion that abuts against the fastening member and leads the subframe to a lower side after separation from the fastening member is integrally formed on the rear portion of the subframe.

The vehicle driving apparatus described above may be an engine or may be a motor unit of an electrically driven vehicle. According to the configuration above, when the collision load to the vehicle rear side is applied to the subframe, the rear portion of the subframe is separated from the fastening member. After the separation of the rear portion, the leading guide portion abuts against the fastening member and leads the subframe to the lower side, and hence the vehicle driving apparatus falls to the lower side together with the subframe.

Therefore, the subframe and the vehicle driving apparatus can be led to the lower side after the separation of the rear portion of the subframe due to a frontal collision, and the excessive load transmission to the dash panel at the time of a frontal collision can be suppressed without increasing the weight and the number of parts even when the rear portion of the subframe is not mounted on the inclined portion of the body.

According to one embodiment of the present disclosure, the fastening member is fastened to a vehicle body side in an inseparable manner and is fastened to a subframe side in a separable manner via a slit portion provided on a front side of the fastening member, and the leading guide portion that abuts against the fastening member and is inclined to a lower rear side is integrally formed on a front side of the fastening member on the subframe side.

According to the configuration above, the fastening state of the fastening member to the vehicle body side is maintained at the time of a vehicle frontal collision. When the rear portion of the subframe moves to the rear side, the fastening member relatively moves to a front side via the slit portion and is separated from the rear portion of the subframe. As a result, the rear portion of the subframe comes off from the fastening member.

After the separation between the rear portion of the subframe and the fastening member, the subframe is led to the lower side by the abutment of the leading guide portion inclined to the lower rear side against the fastening member. As described above, the facilitation of the separation of the rear portion of the subframe from the fastening member by the slit portion, and the facilitation of the abutment of the fastening member against the leading guide portion can be compatible.

According to one embodiment of the present disclosure, the leading guide portion is formed such that an opening is placed between the leading guide portion and the fastening member on the subframe side. According to the configuration above, by the formation of the opening, the necessary space needed when the fastening member is separated from the rear portion of the subframe via the slit portion can be secured. Therefore, the relative front side movement of the fastening member can be secured, and the weight of the front subframe can be saved by the formation of the opening.

According to one embodiment of the present disclosure, a lower arm from which a front wheel is suspended is provided, the lower arm has a rear portion supported by a suspension arm mounting bracket in which a bush is fitted, a vehicle-width-direction inner side of the suspension arm mounting bracket is mounted to the subframe, and the suspension arm mounting bracket has a rear portion on which a portion in which the fastening member for the rear portion of the subframe with respect to the vehicle body is disposed and the leading guide portion are integrally formed.

According to the configuration above, the portion in which the fastening member is disposed and the leading guide portion are integrally formed on the rear portion of the suspension arm mounting bracket. Therefore, the portion in which the fastening member is disposed and the leading guide portion can be formed without causing the subframe itself to become complicated.

According to the present disclosure, such an effect that the vehicle driving apparatus can be led to the lower side together with the subframe after the separation of the rear portion of the subframe due to a frontal collision without increasing the weight and the number of parts even when the rear portion of the subframe is not mounted on the inclined portion of the body is provided.

DETAILED DESCRIPTION

Leading a vehicle driving apparatus to the lower side together with a subframe after the separation of a rear portion of the subframe due to a frontal collision without increasing the weight and the number of parts, even when the rear portion of the subframe is not mounted on an inclined portion of a body, is attained by a configuration in which a subframe that supports a vehicle driving apparatus in a mounting manner is provided, a rear portion of the subframe is mounted on a lower portion of a vehicle body via a fastening member, fastening between the subframe and the fastening member is configured such that the rear portion of the subframe is separated when a collision load to a vehicle rear side is applied to the subframe, and a leading guide portion that abuts against the fastening member and leads the subframe to a lower side after separation from the fastening member is integrally formed on the rear portion of the subframe.

One embodiment of the present disclosure is described in detail with reference to the following drawings below. The drawings illustrate a subframe structure of a front suspension.FIG. 1is a bottom view of a front vehicle body structure including the subframe structure,FIG. 2is an arrow cross-sectional view of a main part taken along line A-A inFIG. 1, andFIG. 3is a main-part-enlarged cross-sectional view ofFIG. 2.FIG. 4Ais a bottom view of a subframe,FIG. 4Bis a side view of the subframe, andFIG. 5is a plan view of a main part illustrating the subframe structure of the front suspension.

As illustrated inFIG. 1andFIG. 2, a dash lower panel3that separates an engine room1(however, a motor room for a case of an electrically driven vehicle) and a vehicle interior2from each other in the front-rear direction is provided. A dash cross member4extending in the vehicle width direction is joined and fixed to a front surface portion of the dash lower panel3. A closed cross-section portion5extending in the vehicle width direction is formed between the dash cross member4and the dash lower panel3described above.

As illustrated inFIG. 2, a floor panel6forming a floor surface of the vehicle interior2is provided on a lower portion of the dash lower panel3described above in a continuous manner. As illustrated inFIG. 1, a tunnel portion7protruding into the vehicle interior2is provided on a central portion of the dash lower panel3and the floor panel6described above in the vehicle width direction.

As illustrated inFIG. 1, floor frames8serving as vehicle body rigidity members extending in the vehicle front-rear direction are joined and fixed to a lower portion of the floor panel6. As illustrated inFIG. 1andFIG. 2, front side frames9extending to the vehicle front side from the dash lower panel3and the dash cross member4described above are provided. The front side frames9are vehicle body strengthening members extending in the vehicle front-rear direction on both of left and right sides of the engine room1.

As illustrated inFIG. 2, each of the front side frames9is formed so as to be separated into a front frame portion9aand a rear frame portion9b. A rear portion of the front frame portion9aand a front portion of the rear frame portion9bare connected to each other by a connecting frame10. As illustrated inFIG. 2, each of the front side frames9described above includes a closed cross-section portion11extending in the vehicle front-rear direction. In the closed cross-section portion11, a place between an intermediate portion of the front frame portion9ain the front-rear direction and a front portion of the connecting frame10is reinforced by a reinforcement12.

As illustrated inFIG. 2, a reinforcement13is provided on a surface of the rear frame portion9bof the front side frame9on the closed cross-section portion11side thereof so as to correspond to a fastening position of a rear portion (in detail, a rear portion of a suspension arm mounting bracket62) of a subframe30described below.

As illustrated inFIG. 2, a reinforcement14is also provided on a surface of a front end of the front frame portion9aof the front side frame9on the closed cross-section portion11side thereof so as to correspond to a fastening position of a front portion of the front subframe30described below.

As illustrated inFIG. 2, a main crash can17is mounted on a front end of the front side frame9via a set plate15and a mounting plate16. As illustrated inFIG. 1, a main bumper beam18extending in the vehicle width direction is mounted between the pair of left and right main crash cans17and17.

As illustrated inFIG. 1, the subframe30(in detail, the front subframe) is disposed on lower portions of the pair of left and right front side frames9and9. As illustrated inFIG. 2, the subframe30is fastened to and supported by lower surface portions of the front side frames9with use of a plurality of fastening members described below. The subframe30supports an engine20that is a vehicle driving apparatus via a mounting bracket19in a mounting manner. As illustrated inFIG. 5, the mounting bracket19is mounted on the subframe30with use of a plurality of mounting portions19a,19b, and19c. In this embodiment, the engine20described above is disposed in a vertically installed manner so that a cylinder array is placed along the vehicle front-rear direction.

As the subframe30is illustrated inFIGS. 4A and 4B, the subframe30includes a pair of left and right front-rear frames31and31extending in the vehicle front-rear direction, a transverse member32, and a center member33. The transverse member32connects front ends of the pair of left and right front-rear frames31and31to each other in the vehicle width direction. The center member33connects intermediate portions of the pair of left and right front-rear frames31and31in the longitudinal direction to each other in the vehicle width direction.

The transverse member32described above has a closed cross-section portion extending in the vehicle width direction by a combination of an upper member and a lower member.

The center member33described above also has a closed cross-section portion extending in the vehicle width direction by a combination of an upper member and a lower member.

As illustrated inFIG. 4B, each of the front-rear frames31described above includes a main body36having a closed cross-section portion extending in the vehicle front-rear direction by a combination of an upper member34and a lower member35, and an extending portion39having a closed cross-section portion extending in the vehicle front-rear direction by a combination of an upper member37and a lower member38.

As illustrated inFIGS. 4A and 4B, the extending portion39described above extends from a front end of the main body36to the vehicle front side. The extending portion39includes a rear horizontal portion39aformed to be substantially horizontal, an inclined portion39bextending from a front end thereof toward the upper front side, and a front horizontal portion39chorizontally extending from a front end thereof to the vehicle front side.

As illustrated inFIG. 2, a rear end of the front horizontal portion39cis disposed so as to be positioned to be closer to the vehicle front side than a front end of the engine20disposed in a vertically installed manner. As a result, at the time of a vehicle frontal collision, a front portion of the subframe30that is closer to the front side than the engine20is bent into a Z-shape in a vehicle side view, to thereby absorb collision energy (seeFIGS. 7A-7D).

The magnitude relationship of the strengths between the upper members34and37and the lower members35and38illustrated inFIG. 4Bis set as follows. Put plainly, the strength of the lower member38of the extending portion39is relatively the lowest, and the strength of the upper member37of the extending portion39is set to be higher than the strength of the lower member38. The strengths of the upper member34and the lower member35of the main body36are set to be even higher than the strength of the upper member37. Note that the strengths of the upper member34and the lower member35of the main body36are set to be equal. The magnitude relationship of the strengths as above can be set as described above in accordance with the selection of the material forming the members and the plate thickness thereof. By the magnitude relationship of the strengths described above, the Z-shaped bending of the front portion of the subframe30in a vehicle side view at the time of a vehicle frontal collision is achieved in an even more secure manner.

As illustrated inFIG. 2, a pair of front and rear mounting members40and41are joined and fixed to a front end of the extending portion39forming the front-rear frame31of the subframe30. The mounting members40and41extend from the front end of the extending portion39to the upper side, and an L-shaped bracket42is joined and fixed to a front surface portion of the mounting member40on the rear side.

A cylindrical shaft-like spacer43is vertically fixed to an upper surface portion of the bracket42described above, upper ends of the mounting members40and41described above are caused to abut against the outer periphery of the spacer43, and the outer periphery of the spacer43and the upper ends of the mounting members40and41described above are fixed to each other by welding.

As illustrated inFIG. 2, a weld nut44is vertically fixed to the upper surface of the reinforcement14of the front side frame9facing the spacer43described above in the up-down direction. The front portion of the subframe30is mounted on the front side frame9with use of a bolt45serving as a fastening member screwed into the weld nut44described above via the spacer43from the lower side of the bracket42.

As illustrated inFIG. 1andFIG. 2, sub crash cans47are mounted on the front portion of the mounting member41on the front side via mounting plates46, and a sub bumper beam48extending in the vehicle width direction is mounted between the pair of left and right sub crash cans47and47.

As illustrated inFIG. 2, on the mounting bracket19described above, a cylindrical shaft-like spacer49extending from an outer portion thereof in the vehicle width direction to the upper side is formed. A weld nut50is vertically fixed to the upper surface of the reinforcement12of the front side frame9facing the spacer49in the up-down direction.

An intermediate portion of the subframe30in the front-rear direction is mounted on the front side frame9via the mounting bracket19with use of a bolt51serving as a fastening member screwed into the weld nut50described above via the spacer49from the lower side of the spacer49described above.

Incidentally, as illustrated inFIG. 1, lower arms52serving as suspension arms from which front wheels are suspended are provided. The subframe30described above supports the engine20in a mounting manner, and axially supports the lower arms52. Each of the lower arms52described above is an A-type arm obtained by integrally forming a front arm portion53made by aluminum die casting and a rear arm portion54made by aluminum die casting.

As illustrated inFIG. 2, a suspension arm mounting bracket59formed by a lower bracket55, a front bracket56, a rear bracket57, and an upper bracket58is joined and fixed to the main body36of the front-rear frame31in the subframe30described above. A base end of the front arm portion53is axially supported by the suspension arm mounting bracket59(hereinafter referred to as a front arm mounting bracket59) serving as an axially supporting portion.

As illustrated inFIG. 1andFIG. 5, a connecting bracket61is mounted on a rear portion of the main body36of each of the front-rear frames31with use of fastening members60such as a bolt and a nut, and the suspension arm mounting bracket62made by aluminum die casting is connected to the connecting bracket61.

A rear portion of the rear arm portion54in the lower arm52described above is axially supported by the suspension arm mounting bracket62(hereinafter referred to as a rear arm mounting bracket62) serving as an axially supporting portion.

As illustrated inFIG. 1, the front arm portions53described above are arm portions linearly extending in the vehicle width direction. Each of the rear arm portions54extends to the vehicle-width-direction outer side so as to curve in an arc shape from a rear portion to a front portion thereof. Knuckle supporting portions63are provided on vehicle-width-direction outer ends of the rear arm portions54. As illustrated inFIG. 1andFIG. 2, the rear arm mounting bracket62described above is formed so as to be positioned directly below the rear frame portion9bof the front side frame9.

As illustrated inFIG. 2, an inner pivot shaft64is mounted between the front bracket56and the rear bracket57in the front arm mounting bracket59. An arm bush68is disposed on the outer periphery of the inner pivot shaft64via a cylinder65, rubber66, and an external cylinder67. The arm bush68is a bush integrally formed on a base end of the front arm portion53described above.

As illustrated inFIG. 2, a pivot shaft69extending in the vehicle front-rear direction is integrally formed on a rear end of the rear arm portion54, and the pivot shaft69is supported by the rear arm mounting bracket62via an arm bush70.

As illustrated inFIG. 2andFIG. 3, the arm bush70described above includes an inner cylinder71, rubber72, and an external cylinder73. In other words, a rear portion of the rear arm portion54of the lower arm52is supported by the rear arm mounting bracket62in which the arm bush70is fitted.

As illustrated inFIG. 1andFIG. 5, the inner side of the rear arm mounting bracket62in the vehicle width direction is mounted on the main body36of the front-rear frame31of the subframe30via the connecting bracket61. An inner portion of the connecting bracket61described above in the vehicle width direction is fastened to the main body36with use of the fastening members60. An outer portion of the connecting bracket61in the vehicle width direction abuts against the external cylinder73described above via a hole portion (not shown) formed in the rear arm mounting bracket62. The outer portion of the connecting bracket61in the vehicle width direction is fixed to the external cylinder73by welding.

As illustrated inFIG. 2andFIG. 3, a rear portion of the subframe30, in detail, a rear portion62aof the rear arm mounting bracket62mounted on the subframe30is mounted on a lower portion of the front side frame9serving as a vehicle body.

In detail, an upper surface of the rear frame portion9bof the front side frame9facing the rear portion62aof the rear arm mounting bracket62described above in the up-down direction is joined and fixed to the reinforcement13described above. A subframe mounting seat74is joined and fixed to a lower surface of the rear frame portion9b(seeFIG. 2andFIG. 3).

As illustrated inFIG. 3, a weld nut75is fixed to a horizontal portion of the subframe mounting seat74described above by welding. The weld nut75is vertically provided toward the upper side from the horizontal portion of the subframe mounting seat74, and the weld nut75is provided so as to protrude to a place above the reinforcement13via the rear frame portion9b.

The rear portion62aof the rear arm mounting bracket62is mounted on the lower portion of the front side frame9with use of a bolt76(fastening member) screwed into the weld nut75via the subframe mounting seat74from a place below the rear portion62aof the rear arm mounting bracket62.

FIG. 6is a perspective view of the rear arm mounting bracket62. As illustrated inFIG. 3,FIG. 5, andFIG. 6, the fastening between the subframe30and the fastening member (the fastening between the rear arm mounting bracket62and the bolt76) is configured such that the rear portion62aof the rear arm mounting bracket62is separated from the bolt76when a collision load to the vehicle rear side is applied to the subframe30.

The bolt76described above is fastened to the front side frame9on the vehicle body side in an inseparable manner. The bolt76described above is fastened to the rear arm mounting bracket62on the subframe30side in a separable manner via a slit portion62cprovided on the front side of the bolt76.

In detail, as illustrated inFIG. 3, in the bolt76, a shaft portion76a, a screw portion76bpositioned on an upper portion of the shaft portion76a, and a head portion76cpositioned on a lower portion of the shaft portion76aare integrally formed. As illustrated inFIG. 5andFIG. 6, an opening of a bolt insertion hole62bof which inner diameter is greater than outer diameters of the shaft portion76aand the screw portion76bof the bolt76is formed in the rear portion62aof the rear arm mounting bracket62.

As illustrated inFIG. 5andFIG. 6, the slit portion62cdescribed above is provided on the front side of the shaft portion76aof the bolt76, and a rear end of the slit portion62ccommunicates with the bolt insertion hole62b. The width of the slit portion62cin the vehicle width direction is set to a width with which the shaft portion76aof the bolt76can be relatively moved to a front side while the slit portion62cis plastically deformed when a frontal collision load is input. As a result, when the collision load is input, the rear portion62aof the rear arm mounting bracket62comes off from the shaft portion76aof the bolt76.

As illustrated inFIG. 3, a leading guide portion62dthat abuts against the head portion76cof the bolt76and leads the rear arm mounting bracket62to the lower side as illustrated inFIG. 9after the rear portion62aof the rear arm mounting bracket62is separated from the bolt76is integrally formed on the rear arm mounting bracket62.

As illustrated inFIG. 3, the leading guide portion62dis provided on the front side of the head portion76cof the bolt76. The leading guide portion62dis inclined to the lower rear side so as to abut against the head portion76cof the bolt76and lead the rear arm mounting bracket62to the lower side after the rear portion62acomes off from the bolt76. In this embodiment, the leading guide portion62dis inclined to the lower rear side at 35 degrees with respect to an upper surface of the rear arm mounting bracket62, but the inclination angle of the leading guide portion62dmay be any angle as long as the angle is within the range of from 35 degrees to 45 degrees. In the rear portion62aof the rear arm mounting bracket62described above, a bolt insertion hole62bthat is a portion in which the fastening member (the bolt76) for the rear portion62awith respect to the vehicle body is disposed and the leading guide portion62dare integrally formed.

In a normal state (a state in which the collision load is not input) illustrated inFIG. 3, the height position of a lower end of the head portion76cof the bolt76is positioned above the height position of a lower end of the leading guide portion62d. In other words, a raised wall62eextending to the lower side from the lower end is integrally formed on the lower end of the leading guide portion62d. The height relationship is set because an expected effect cannot be secured if the head portion76cof the bolt76abuts against the raised wall62eafter the rear portion62acomes off from the bolt76.

As illustrated inFIG. 3,FIG. 5, andFIG. 6, the leading guide portion62ddescribed above is formed such that an opening62fis placed between the leading guide portion62dand a portion of the bolt76positioned below a horizontal portion of the subframe mounting seat74. As a result, a separation space for the portion of the bolt76is secured.

InFIG. 1andFIG. 2, reference numeral21denotes a steering rack portion of a steering apparatus, reference numeral22denotes a tie rod, reference numeral23denotes an assist motor for power steering, and reference numeral24denotes a stabilizer serving as a torsion bar spring provided between the left and right lower arms52and52. In the drawings, arrow F indicates the vehicle front side, arrow R indicates the vehicle rear side, arrow IN indicates the inner side in the vehicle width direction, arrow OUT indicates the outer side in the vehicle width direction, and arrow UP indicates the vehicle upper side.

The effect of the subframe structure of the front suspension configured as described above is described below.FIG. 7AtoFIG. 7Dare side views illustrating deformation states of the sub bumper beam48, the sub crash can47, and the subframe30at the time of a full-overlap collision (at the time of a frontal collision). As illustrated inFIG. 7A, when the frontal collision load (the collision load to the vehicle rear side) is input to the sub bumper beam48, the front portion of the sub crash can47is crushed by axial compression.

When the frontal collision further proceeds, the sub crash can47is crushed across the full length thereof in the front-rear direction, and bending starting point portions α and β for Z-shaped bending are formed on a lower front portion and an upper rear portion of the inclined portion39bof the subframe30as illustrated inFIG. 7B.

When the frontal collision further proceeds, bending deformation is performed such that the front side of the inclined portion39brises to the upper side and the rear side with use of the bending starting point portions α and β described above as fulcrums as illustrated inFIG. 7C.

When the frontal collision further proceeds, the extending portion39is bent to a Z-shape in a side view, and absorbs the frontal collision energy as illustrated inFIG. 7D. At this time, the main body36in the front-rear frame31of the subframe30is displaced to the lower front side by from about 5 degrees to about 7 degrees.

FIG. 8is an explanatory view illustrating the separation of the rear arm mounting bracket62from the bolt76at the time of a collision, andFIG. 9is an explanatory view illustrating the leading of the rear arm mounting bracket62to the lower side at the time of a collision. When the collision load (frontal collision load) to the vehicle rear side is applied to the subframe30from the normal state illustrated inFIG. 3, the load is transmitted to the rear arm mounting bracket62connected to a vehicle-width-direction outer side of the rear portion of the subframe30. As a result, the rear arm mounting bracket62moves to the vehicle rear side together with the subframe30.

In this case, the fastening state of the bolt76to the front side frame9side is maintained. When the rear arm mounting bracket62moves to the rear side, the bolt76relatively moves to a front side via the slit portion62c. As a result, the bolt76is separated to the opening62fon the front side of the slit portion62c. As a result, as illustrated inFIG. 8, the rear portion62aof the rear arm mounting bracket62comes off from the bolt76.

After the separation between the rear portion62aof the rear arm mounting bracket62and the bolt76, the rear arm mounting bracket62is led to the lower side by the abutment of the leading guide portion62dinclined to the lower rear side against the head portion76cof the bolt76as illustrated inFIG. 9.

As a result, the rear portion of the subframe30connected to the rear arm mounting bracket62is led to the lower side, the engine20falls to the lower side together with the subframe30, and excessive load transmission to the dash lower panel3is suppressed.

As described above, in the subframe structure of the front suspension of the embodiment described above, the subframe30that supports the vehicle driving apparatus (see the engine20) in a mounting manner is provided, the rear portion (see the rear arm mounting bracket62) of the subframe30is mounted on the lower portion of the vehicle body (the front side frame9) via the fastening member (see the bolt76), the fastening between the subframe30and the fastening member (the bolt76) is configured such that the rear portion (see the rear arm mounting bracket62) of the subframe30is separated when the collision load to the vehicle rear side is applied to the subframe30, and the leading guide portion62dthat abuts against the fastening member (the bolt76) and leads the subframe30to the lower side after the separation from the fastening member (the bolt76) is integrally formed on the rear portion (see the rear arm mounting bracket62) of the subframe30(seeFIG. 2,FIG. 3, andFIG. 9).

According to this configuration, when the collision load to the vehicle rear side is applied to the subframe30, the rear portion (see the rear arm mounting bracket62) of the subframe30is separated from the fastening member (the bolt76). After the separation of the rear portion, the leading guide portion62dabuts against the fastening member (the bolt76) and leads the subframe30to the lower side, and hence the vehicle driving apparatus (see the engine20) falls to the lower side together with the subframe30.

Therefore, the excessive load transmission to the dash panel at the time of a vehicle frontal collision can be suppressed by leading the vehicle driving apparatus to the lower side together with the subframe30after the separation of the rear portion of the subframe30without increasing the weight and the number of parts even when the rear portion of the subframe30is not mounted on the inclined portion of the body.

In one embodiment of the present disclosure, the fastening member (the bolt76) is fastened to the vehicle body (see the front side frame9) side in an inseparable manner and is fastened to the subframe30side via the slit portion62cprovided on the front side of the fastening member (the bolt76) in a separable manner, and the leading guide portion62dthat abuts against the fastening member (the bolt76) and is inclined to the lower rear side is integrally formed on the front side of the fastening member (the portion of the bolt76below the horizontal portion of the subframe mounting seat74) on the subframe30side (seeFIG. 3,FIG. 5, andFIG. 6).

According to this configuration, the fastening state of the fastening member (the bolt76) to the vehicle body (the front side frame9) side is maintained at the time of a vehicle frontal collision. When the rear portion of the subframe30moves to the rear side, the fastening member (the bolt76) relatively moves to a front side via the slit portion62c, and is separated from the rear portion of the subframe30. As a result, the rear portion of the subframe30comes off from the fastening member (the bolt76).

After the separation between the rear portion of the subframe30and the fastening member (the bolt76), the subframe30is led to the lower side by the abutment of the leading guide portion62dinclined to the lower rear side against the fastening member (the bolt76). As described above, the facilitation of the separation of the rear portion of the subframe30from the fastening member (the bolt76) by the slit portion62c, and the facilitation of the abutment of the fastening member (the bolt76) against the leading guide portion62dcan be compatible.

In one embodiment of the present disclosure, the leading guide portion62dis formed such that the opening62fis placed between the leading guide portion62dand the fastening member (the bolt76) on the subframe30side (seeFIG. 3,FIG. 5, andFIG. 6). According to this configuration, by the formation of the opening62f, the necessary space needed when the fastening member (the bolt76) is separated from the rear portion of the subframe30via the slit portion62ccan be secured. Therefore, the relative front side movement of the fastening member (the bolt76) can be secured, and the weight of the subframe30can be saved by the formation of the opening62f.

In one embodiment of the present disclosure, the lower arm52from which the front wheel is suspended is provided, the rear portion of the lower arm52is supported by the suspension arm mounting bracket (see the rear arm mounting bracket62) in which the bush (see the arm bush70) is fitted, the vehicle-width-direction inner side of the suspension arm mounting bracket (the rear arm mounting bracket62) is mounted on the subframe30, and the portion (see the bolt insertion hole62b) in which the fastening member (the bolt76) for the rear portion of the subframe30with respect to the vehicle body (see the front side frame9) is disposed and the leading guide portion62dare integrally formed on the rear portion of the suspension arm mounting bracket (the rear arm mounting bracket62) (seeFIG. 1,FIG. 3,FIG. 5, andFIG. 6).

According to this configuration, the portion (the bolt insertion hole62b) in which the fastening member (the bolt76) is disposed and the leading guide portion62dare integrally formed on the rear portion of the suspension arm mounting bracket (the rear arm mounting bracket62). Therefore, the portion (the bolt insertion hole62b) in which the fastening member (the bolt76) is disposed and the leading guide portion62dcan be formed without causing the subframe30itself to become complicated.

Regarding the correspondence between the configuration of the present disclosure and the embodiment described above, the vehicle driving apparatus of the present disclosure corresponds to the engine20disposed in a vertically installed manner (so-called longitudinal engine) of the embodiment. Similarly, the fastening member corresponds to the bolt76. The vehicle body corresponds to the front side frame9. The bush corresponds to the arm bush70. The suspension arm mounting bracket corresponds to the rear arm mounting bracket62. The portion in which the fastening member is disposed corresponds to the bolt insertion hole62b, but the present disclosure is not limited to the configuration of the embodiment described above.

For example, the vehicle driving apparatus may be a motor unit of an electrically driven vehicle instead of the engine20.

As described above, the present disclosure is useful for a subframe structure of a front suspension in which a front subframe that supports a vehicle driving apparatus such as an engine in a mounting manner is provided, and a rear portion of the front subframe is mounted to a lower portion of a vehicle body via a fastening member.