JP5278105B2 - Subframe support structure for automobile - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To dramatically enhance accuracy when a sub-frame is removed from a side frame by predetermined load. <P>SOLUTION: The sub-frame support structure includes the side frame extending in a longitudinal direction of the vehicle; the sub-frame provided below the side frame and supporting a suspension; and a connection means for connecting the sub-frame relative to a part to be mounted of the side frame. The connection means includes a first connection member provided so as to surround an opening formed on the part to be mounted; and a second connection member engaged with the first connection member via the opening and connecting the sub-frame to the side frame. On the part to be mounted, a notch is formed on an edge of the opening, and the first connection member is partially fixed relative to the part to be mounted. A relative position relationship in a circumferential direction of a fixed position of the first connection member and a formation position of an apex part of the notch is specified such that a circumferential center of the fixed position and the apex part are not overlapped in a circumferential direction. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a subframe support structure for an automobile in which a subframe that supports a suspension is supported below a side frame that extends in the front-rear direction of the vehicle.

  Conventionally, a sub-frame that supports an engine, a transmission, a suspension mechanism, and the like is fixed to a front side frame that is disposed on both front sides of the vehicle and extends in the front-rear direction of the vehicle.

  The sub-frame fixed to the front side frame is configured to be separated from the front side frame in the event of a frontal collision of the vehicle, thereby preventing interference between the sub-frame and the power train disposed in front of the sub-frame. The influence is prevented from reaching the cabin space.

  Patent Document 1 discloses a suspension cross member mounting structure. In this, it is explained that a fragile part is provided in the peripheral part of the bolt hole for fastening the suspension cross member to the front frame with a bolt to ensure the release of the fastening between the suspension cross member and the front frame at the time of collision. Has been.

  Patent Document 2 discloses a vehicle body front structure in which a rear end portion of a subframe is fixed to a rear end member. Among them, by forming reinforcing ribs and notches on the rear end member, the rear end member is destroyed and the subframe is detached from the rear end member at the time of a frontal collision while securing the rigidity of the fixed part at normal times. It is explained that.

JP 2004-148960 A JP 2008-195332 A

  However, with the techniques such as Patent Document 1 and Patent Document 2, when a predetermined load is applied, the accuracy when the subframe is detached from the side frame is gradually improved, but there are still points to be improved. It was left.

  The present invention has been made in view of the above-described conventional problems, and provides an automobile subframe support structure capable of dramatically improving accuracy when the subframe is detached from the side frame with a predetermined load. The purpose is that.

  The sub-frame support structure of the present invention includes a side frame extending in the front-rear direction of the vehicle, a sub-frame provided below the side frame and supporting a suspension, and the sub-frame with respect to a mounting portion of the side frame. A sub-frame support structure having a coupling means for coupling, wherein the coupling means includes a first coupling member provided so as to surround an opening formed in the attached portion, and the first coupling member through the opening. And a second connecting member that connects the sub-frame to the side frame, and the attachment portion has a notch formed at an edge of the opening, and the first connecting member includes: It is partially fixed to the attached portion, and the relative positional relationship in the circumferential direction between the fixing position of the first connecting member and the formation position of the top of the notch is It is characterized in that the circumferential center of the serial fixed position and said top portion is specified so as not to overlap in the circumferential direction.

  According to this invention, the relative positional relationship in the circumferential direction between the fixing position of the first connecting member with respect to the attached portion and the formation position of the top of the notch is such that the circumferential center and the top of the fixing position overlap in the circumferential direction. It is specified not to be. At the time of a vehicle collision, the subframe is intentionally dropped from the side frame. Thus, the positional relationship between the fixing position of the first connecting member and the formation position of the top of the notch is a predetermined position. If the relationship is specified, the dropout of the subframe from the side frame is more appropriately realized. Specifically, in order to disengage the connecting means from the attached portion of the side frame, a crack is generated in the attached portion. This crack overlaps the position where the first connecting member is fixed and the top of the notch. If it is too far or too far away, the progress is not promoted. Therefore, the crack progress can be promoted by arranging the top of the notch serving as the starting point of the crack so as to have a predetermined positional relationship with the fixing position of the first connecting member. And it becomes possible to expand smoothly the opening formed in the to-be-attached part with progress of a crack. Thus, when a predetermined load is applied to the subframe, the opening of the attached portion is smoothly enlarged, so that the connecting means is reliably dropped from the attached portion and the subframe is detached from the side frame. The accuracy can be dramatically improved.

  Moreover, it is preferable that the top part of the said notch is located inside the external shape of the said 1st connection member fixed to the said to-be-attached part.

  According to the present invention, since the position of the top of the notch is specified, the size of the notch is adjusted so as not to become excessively large, so that the occurrence and progress of cracks due to fatigue can be suppressed. .

  Further, an angle formed by a fixing straight line passing through one end of the fixing position and the center of the opening and a top straight line passing through the top of the notch and the center of the opening is −15 with respect to the top straight line. It is preferable that it is (degree) -60 degree.

  According to the present invention, since the angle formed by the fixing straight line and the top straight line is specified, the progress of the crack can be promoted, and the progress of the crack from the top of the notch can be guided in a predetermined direction. The opening of the attachment portion can be expanded more smoothly.

  In addition, the first connecting member is fixed to the attached portion by welding, and a welding location as the fixing position is extended along an outer peripheral surface of the first connecting member, and the notch The end point is preferably provided on the side away from the top.

  According to the present invention, the welded portion extends along the outer peripheral surface of the first connecting member, and the end point is provided on the side away from the top of the notch, and the first connecting member is attached to the attached portion. On the other hand, since it is welded and fixed, the starting point of the welding location is closer to the top of the notch. Thereby, it is easy to realize an appropriate positional relationship between one end of the weld fixing position and the top of the notch.

  Further, the notches are formed in a pair on a straight line passing through the center of the opening, and the first connecting member has two places facing the attached portion across the center of the opening. It is preferably fixed.

  According to this invention, a pair of notches are formed and two fixing positions are provided. By specifying the number of notches as two, the subframe can be smoothly detached from the side frame at the time of collision while ensuring the difficulty of the subframe being detached from the side frame at the normal time. In addition, since the number of fixing positions is specified as two, the first connecting member can be stably fixed to the attached portion while minimizing the fixing work.

  The sub frame is preferably disposed substantially below the power train on the front side of the vehicle body, and is connected to the front side frame at the lower rear of the power train.

  According to the present invention, if the subframe is detached from the front side frame at the time of a forward collision, a space is secured behind the lower part of the powertrain, and interference between the subframe and the powertrain can be avoided. Therefore, the amount of powertrain retreat can be increased.

  ADVANTAGE OF THE INVENTION According to this invention, the precision at the time of making a sub-frame detach | leave from a side frame with a predetermined load can be improved greatly.

It is a perspective view for demonstrating a sub-frame and a side frame. It is a side view for demonstrating notionally the internal structure ahead of vehicles. It is a side view for demonstrating the behavior of an internal structure when a vehicle collides ahead. FIG. 2 is an enlarged view of a portion A in FIG. 1, showing a state in which the rear end portion of the subframe is connected to the front side frame by the connecting means. It is the IV-IV sectional view taken on the line of FIG. 4, and is a figure for demonstrating the relationship between a welding position and a notch position. FIG. 4 is an enlarged view of a portion A in FIG. 3 for explaining a state in which a mounting portion of the front side frame is cracked, a bolt hole is enlarged, and a sub frame is dropped together with a connecting means. It is a figure for demonstrating the relationship between a welding position and a notch position, and shows the notch and welding position of another form. It is a figure for demonstrating in more detail about the relationship between a welding position and a notch position. It is a figure for demonstrating the relationship between the welding position of an Example, and a notch position. It is a figure for demonstrating the relationship between the welding position of a comparative example, and a notch position.

  Hereinafter, the subframe support structure of the present embodiment will be described in detail with reference to the drawings.

  The figure is a perspective view for explaining the subframe 3 and the front side frame 2. FIG. 2 is a side view for conceptually explaining the frame structure in front of the vehicle. FIG. 3 is a side view for explaining the behavior of the frame structure when the vehicle collides forward. FIG. 4 is an enlarged view of part A in FIG. 2 and shows a state in which the rear end portion of the subframe 3 is connected to the front side frame 2 by the connecting means 4. FIG. 5 is a cross-sectional view taken along the line IV-IV in FIG. 4 and is a diagram for explaining the relationship between the welding position and the notch position. 4 is a cross-sectional view taken along line VV in FIG. FIG. 6 is an enlarged view of a portion A in FIG. 3, and illustrates a state where a crack occurs in the attached portion of the front side frame 2, the bolt hole 21 a expands, and the sub frame 3 falls together with the connecting means. FIG.

  As shown in FIGS. 1 and 2, the subframe support structure of the present embodiment is provided on both front sides of the vehicle and extends in the front-rear direction of the vehicle, and in a plan view. It includes a subframe 3 that surrounds the engine ENG, the transmission TM, and the like and supports the suspension mechanism, and a connecting means 4 that connects the rear end side of the subframe 3 to the front side frame 2. In addition, a front cross member 6 that also serves as a bumper reinforcement that connects the front end portion of the front side frame 2 via a crash can 7 is provided at the front end of the front side frame 2. In addition, a sub-front cross member 8 is provided at the front end of the sub-frame 3 via a crash can 9 as in the case of the front side frame 2.

  The front side frame 2 has a predetermined strength, rigidity, and durability, and is a member for dispersing the collision energy to other frames while absorbing the collision energy at the time of a frontal collision of an automobile, for example. The front side frame 2 has a kick-up shape that is bent so as to be raised one step toward the front of the vehicle in a side view. The sub frame 3 is disposed below the kick-up portion of the front side frame 2. Further, the front side frame 2 is provided with an attached portion 21 for attaching the sub frame 3 at a kick-up position that is one step higher toward the front of the vehicle.

  The attached portion 21 is a portion in which a part of the front side frame 2 is formed substantially horizontally. As shown in FIG. 5, the attached portion 21 is formed with a circular bolt hole (opening) 21 a in a plan view. A pair of notches 21b is formed at the edge of the bolt hole 21a. The notch 21 is formed to be recessed outward from the center O on a straight line passing through the center of the bolt hole 21a, that is, at a position facing the center O of the bolt hole 21a. The top portion 21T of the notch 21 is processed into a substantially arc shape in plan view. Since the shape of the top portion 21T of the notch 21b has a substantially arc shape in plan view, extreme stress concentration around the top portion 21T can be avoided, and the occurrence and progress of cracks due to fatigue can be prevented. Moreover, the productivity of the to-be-attached part 21 by pressing a steel plate can be improved because the curvature radius of the top part 21T shall be 3 mm or more. Further, the depth of the notch 21, that is, the position of the top 21T of the notch is formed so shallow that it does not exceed the outer diameter of a nut 42 described later. As a result, the depth of the notch 21b is adjusted so as not to become excessively large. Therefore, the peripheral edge of the notch 21 is securely held by the nut 42, so that the input load applied to the peripheral edge of the notch 21b. While being able to suppress deformation, it is possible to suppress a decrease in the strength of the peripheral portion of the bolt hole 21a, thereby suppressing the occurrence and progress of cracks due to fatigue in the peripheral portion of the top portion 21T. In addition, since the number of the notches 21b is specified as two, the bolt holes 21a are less likely to be expanded than in the case of three or more, and the detachment of the subframe 3 from the side frame 2 in the normal state is prevented. Thus, a stable mounting state can be ensured.

  The sub frame 3 is installed below the front side frame 2 so as to extend in the vehicle width direction at a rear portion of the side member 30 and a pair of side members 30 arranged to extend in the front-rear direction of the vehicle. Thus, the first cross member main body 31 that connects the pair of left and right side members 30 and the side member 30 is extended substantially vertically upward from the side member 30, and the upper end portion is fastened to the front side frame 2. A first cross member body that connects the pair of left and right side members 30 by being installed so as to extend in the vehicle width direction at the front portion of the side member 30 and the first vertical member 32 that supports the auxiliary member. 33 and a second vertical member 34 that extends substantially vertically upward from the front end portion of the side member 30 and supports the side member 30 by fastening the upper end portion to the front end portion of the front side frame 3. No. Among these, the first cross member main body 31 functions as a so-called suspension cross member.

  Further, a bolt hole (not shown) is formed in the rear end portion 3 </ b> B of the side member 30, and the subframe 3 is disposed so that the bolt hole communicates with the bolt hole 21 a of the attached portion 21. . The rear end 3B is formed in a closed cross-sectional structure.

  Thus, if the subframe 3 is detached from the front side frame 2 at the time of a forward collision, a space is secured at the lower rear of the power train including the engine ENG and the transmission TM, and the first cross of the subframe 3 is also secured. Interference between the member main body 31 and the power train can be avoided. Therefore, the amount of powertrain retreat can be increased.

  As shown in FIG. 4, the connecting means 4 includes a bolt (second connecting member) 41 and a nut (first connecting member) 42. The code | symbol 51 and 52 in FIG. 4, FIG. 6 shows a welding part. In the present embodiment, the nut 42 is disposed so as to surround the bolt hole 21 a of the attached portion 21 of the front side frame 2 and is welded at two locations along the peripheral surface of the nut 42. The nut 42 is partially welded and fixed to the upper surface of the attached portion 21 (see FIG. 5). By specifying the number of fixing positions to two, the nut 42 can be stably fixed to the attached portion 21 while minimizing welding work. Further, the welding operation is performed along the outer peripheral surface of the nut 42 and in a direction away from the top portion 21T of the notch 21b (see the arrow in FIG. 5). Generally, the end point EP of the welding operation is more difficult to control than the start point SP, and it is difficult to set the end on the end point EP side to a desired position. Therefore, in the present embodiment, by specifying the direction of the welding operation, an appropriate positional relationship between one end portion of the welding fixing position that is the starting point SP of the welding operation and the top portion 21T of the notch 21b is realized. ing.

  The bolt 41 is inserted into a bolt hole formed in the rear end portion 3B of the subframe 3 with the shaft portion 41a of the bolt 41 facing upward and the head portion 41b of the bolt 41 facing downward. Further, the shaft portion 41 a of the bolt 41 is inserted into the bolt hole 21 a formed in the attached portion 21 and screwed into the nut 42. Thus, the rear end 3B of the subframe 3 is fastened to the front side frame 2 by the connecting means 4.

  Here, the weld fixing position of the nut 42 will be described in detail. As shown in FIG. 5, the weld fixing position of the nut 42 is specified in advance according to the position of the top portion 21T of the notch 21b. Specifically, the fixing straight line L1 connecting the center O of the bolt hole 21a and the starting point of the welded portion (shaded portion in FIG. 5) and the top connecting the center O of the bolt hole 21a and the top 21T of the notch 21b. By keeping the angle θ (hereinafter referred to as a deviation angle) θ formed with the straight line L2 within a predetermined range, the relative positional relationship between the weld fixing position of the nut 42 and the top portion 21T of the notch 21b is more strictly specified. .

  Here, whether the deviation angle θ is positive or negative is based on whether or not the starting point SP of the welded portion exceeds the top straight line L2 with reference to the top straight line L2 connecting the top 21T of the notch 21b and the center O of the bolt hole 21a. It has been decided. For example, as shown in FIG. 5, in the state where the starting point SP of the welding location does not exceed the top straight line L2, the deviation angle θ is a positive value. Further, in a state where the starting point SP of the welding location exceeds the top straight line L2, that is, in a state where the top portion 21T of the notch 21b overlaps the welding location, the deviation angle θ becomes a negative value.

  In the present embodiment, the shift angle θ is preferably −15 ° or more, and more preferably −10 ° or more. Further, the deviation angle θ is preferably 60 ° or less, and more preferably 45 ° or less. If the deviation angle θ is less than −15 °, the progress of the crack C is not promoted, and there is a tendency that the sub frame 3 cannot be detached from the front side frame 2 even when a predetermined load is applied. Similarly, when the deviation angle θ exceeds 60 °, the progress of the crack C is not promoted, and there is a tendency that the sub frame 3 cannot be detached from the front side frame 2 even when a predetermined load is applied. In particular, when the deviation angle θ is in the range of −10 ° to 45 °, the traveling direction of the crack C can be specified more strictly. Furthermore, the range where the shift angle θ is 0 ° to 20 ° is more preferable. Thus, when the range of the deviation angle θ is specified, the progress direction of the crack C from the top portion 21T of the notch 21b can be guided in a predetermined direction, and the size of the opening of the attached portion 21 can be made smoother. Can be expanded.

  Even if the shift angle θ is −15 ° or more, the closer the center in the circumferential direction of the welds 51 and 52 is to the top 21T of the notch 21b, for example, the starting point of the welds 51 and 52, for example. When the angle is closer than the angle between the SP and the top portion 21T, the progress direction of the crack C is difficult to be specified, and the direction of the crack C faces the welded portions 51 and 52, and the progress may be suppressed.

  The behavior of this subframe support structure will be described in detail below.

  When the front of the vehicle collides forward with the wall body W or the like, as shown in FIG. 3, the crash cans 7 and 9 are crushed and the front side of the front side frame 2 and the front side of the side member 30 are greatly bent. In FIG. 3, it is assumed that the front cross members 6 and 8 and the crash cans 7 and 9 are completely crushed, and these are omitted.

  Thus, when a load is applied to the front side of the vehicle, first, the first vertical member 32 is broken, and the front side frame 2 and the side member 30 are greatly deformed. The side member 30 has such a force that the front side of the side member 30 moves downward (in FIG. 3, the side member 30 rotates counterclockwise around the rear end portion 3B). Works. When such a force is applied to the side member 30, the rear end portion 3 </ b> B of the side member 30 pulls the bolt 41 in the direction in which the bolt 41 falls out of the attached portion 21. At this time, since the nut 42 is integrated with the bolt 41, the upper surface of the attached portion 21 is pressed downward together with the bolt 41.

  And when this pressing force becomes large, while the to-be-attached part 21 begins to deform | transform downward, the crack C will generate | occur | produce from the top part 21T of the notch 21b. The crack C proceeds so as to wrap around the boundary of the welding fixing position arranged in a predetermined positional relationship with the top portion 21T of the notch 21b (see the one-dot chain line in FIG. 5). As described above, the crack C is formed along the boundary of the weld fixing position due to the stress concentration, that is, in a portion where the difference in rigidity is remarkably exhibited at the welding fixed position and the surrounding heat affected part and other parts. Along the way. Thus, by specifying the location and direction of the crack C, the size of the bolt hole 21a can be expanded more reliably. Then, when the size of the bolt hole 21a increases, the bolt 41 and the nut 42 come together and fall down below the mounted portion 21 as shown in FIGS. 3 and 6, and the rear end of the side member 30. It falls with the part 3B.

  According to the above embodiment, the relative positional relationship in the circumferential direction between the weld fixing position of the nut 42 to the mounted portion 21 and the formation position of the top portion 21T of the notch 21b is the state direction center of the fixing position and the top portion 21T. Are specified so as not to overlap in the circumferential direction. At the time of a vehicle collision, the subframe 3 is intentionally dropped from the front side frame 2. In this way, the positional relationship between the weld fixing position of the nut 42 and the formation position of the top portion 21T of the notch 21b. Is specified in the predetermined positional relationship, the dropout of the subframe 3 from the front side frame 2 is more appropriately realized. More specifically, in order to detach the bolt 41 from the attached portion 21 of the front side frame 2, a crack C is generated in the attached portion 21. This crack C is caused by the weld fixing position of the nut 42 and the notch 21b. If the position of the top portion 21T overlaps too much or is too far, the progress is not promoted.

  Specifically, as shown in FIG. 8, the distance between the top 21T and one end (welding start point SP) of the weld 51 is such that the boundary point BP between the notch 21b and the bolt hole 21a and one end of the weld 51. It is considered that the effect of prompting the progress of the crack C to go around the welds 51 and 52 decreases as the distance from the welding start point SP increases. In order to urge the progress of the crack C to go around the welded portions 51 and 52, a straight line connecting one end portion (welding start point SP) of the welded portion 51 (or welded portion 52) and the top portion 21T, and the welded portion 51 (or It is presumed that the angle formed by one end (welding start point SP) of the welded portion 52) and a straight line connecting the notch 21b and the boundary point BP of the bolt hole 21a is preferably 60 ° or less.

  Therefore, by arranging the top portion 21T of the notch 21b serving as a starting point of the crack C so as to have a predetermined positional relationship with respect to the welding fixing position of the nut 42, the progress of the crack C can be promoted. As the crack C progresses, the edge portion of the bolt hole 21a is smoothly deformed, and the bolt hole 21a formed in the attached portion 21 can be smoothly enlarged. In this way, when a predetermined load is applied to the subframe 3, the bolt hole 21a of the attached portion 21 is smoothly enlarged, so that the bolt 41 is reliably dropped from the attached portion 21 and the subframe 3 is moved to the side. The accuracy at the time of detachment from the frame 2 can be greatly improved.

  In the above embodiment, a description has been given of a form in which the notches 21b are formed in a pair on a straight line passing from the edge of the bolt hole 21a through the center O of the bolt hole 21a, but the present invention is not limited to this. Absent. FIG. 7 is a diagram for explaining the relationship between the welding position and the notch position, and shows another form of the notch and the welding position. As shown in FIG. 7, three or more notches 21b may be formed from the edge of the bolt hole 21a, and the planar shape thereof may have a substantially rectangular shape. In this case, two corners on the outer side in the radial direction of the notch 21b can also be crack starting points, and can be substantially regarded as the top, so that the relative position with respect to the welding location 51 may be determined based on these corners. Further, the top portion 21T of the notch 21b does not necessarily have a substantially arc shape in plan view, and the top portion 21T of the notch 21b may have a pointed shape in plan view.

  Moreover, in the said embodiment, although the form which shifted the welding location from the top part of the notch 21b was demonstrated, this invention is not limited to this, At the design stage of the to-be-attached part 21, the notch 21b The form which shifts a formation position from a welding location and may design may be sufficient. In this case, there is an advantage that the ease of welding work can be ensured. In addition, when providing two or more welding locations 51 in the circumferential direction, it is more preferable that the top part 21T has shifted | deviated to the welding location 51 of one side rather than the center between the two adjacent welding locations 51. FIG. This is because when the nut 42b deforms and pulls out the edge of the bolt hole 21a, the deformation of the edge of the notch 21b on the side close to the welded part 51 in the circumferential direction with respect to the notch 21b is far from the welded part 51. This is because it is presumed that the deformation of the edge of the notch 21b is suppressed and the shearing force is easily generated at the edge of the top portion 21T.

  Moreover, in the said embodiment, although the connection means 4 demonstrated the form body comprised by the nut 42 and the volt | bolt 41, this invention is not limited to this, As a connection means, screwing is required. There may be no fasteners or rivets.

  Moreover, although the said embodiment demonstrated the form which fixed the nut (1st connection member) 42 with respect to the to-be-attached part 21 by welding, this invention is not limited to this, The 1st connection member May be fixed to the attached portion 21 with an adhesive or the like. Even in this case, since the rigidity of the attached portion is different between the fixing position by the adhesive and the non-fixing position, the crack C is likely to advance along this boundary.

  In the above embodiment, the front side frame has been described as the side frame, but the present invention is not limited to this. For example, examples of the side frame include a rear side frame, a floor frame, and the like, and a form in which the subframe is fixed to these may be used.

  Hereinafter, the present invention will be described in detail based on examples. However, the following examples are not intended to limit the present invention, and all modifications made without departing from the spirit of the preceding and following descriptions are included in the technical scope of the present invention.

  As shown in FIGS. 9 and 10 and Table 1, simulation test pieces 1 to 8 are prepared on the assumption that a mounting portion for mounting a suspension cross member (subframe) is attached to the rear portion of the front side frame of the vehicle. did. In addition, the shaded part in FIGS. 9 and 10 represents a welded part.

(Specimen common specifications)
Material of the mounting part simulation test piece; Cold rolled steel sheet Thickness of the mounting part simulation test piece; 1.6 mm
Planar shape of the attached portion simulated test piece; approximately square attached portion simulated test piece and others; the attached portion simulated test piece is fixed to the fixed member by arc welding over the entire circumference, A bolt hole having a shape as shown in FIGS. 8 and 9 is formed.
Diameter of nut fixed to the test piece for mounting part; 36mm
Fixed state of nut: The nut was fixed to the mounted portion simulation test piece by arc welding. There are two welding locations at positions facing each other across the center O of the bolt hole along the circumferential surface of the nut.
Others: The shape of the bolt hole and the shape of the notch formed in the simulated test pieces 1 to 4 and the welded state correspond to FIGS. 9 (a) to 9 (d), respectively. The shape of the formed bolt hole, the shape of the notch, and the welded state correspond to FIGS. 10 (a) to 10 (d), respectively.

(Test method)
In the test, a pulling load was applied to the nut fixed to the to-be-attached part simulation test piece with the fixing member fixed. The pull-out load was applied in a direction perpendicular to the surface of the to-be-attached part simulated test piece, and the load was applied until the reference load range was exceeded.

(Evaluation item)
The evaluation focused on the following items a to c.
a. In order to obtain an accurate nut removal load, the nut can be removed without damage to the weld.
b. The nut removal load is within the standard load range.
c. A crack has occurred from the top.

  Table 1 shows the analysis results.

  The test piece 1 in Table 1 is an example of the embodiment of the present invention, and has the form shown in FIG. 9A, and has a weld length of 10 mm (distance 5 mm from the reference line x to the welding start point). Are provided at two locations facing each other across the bolt hole center O, and a notch with a sharp top is formed. The protruding length of the notch from the bolt hole is 5 mm. The angle formed between the reference line x and the top straight line L2 is 20 °.

  The test piece 2 is an example of the embodiment of the present invention, and has the form shown in FIG. 9B. The weld end point side is extended by 5 mm as a manufacturing tolerance with respect to the designed weld length of 10 mm. Two welds (that is, the weld length of the test piece 2 is 15 mm) are provided, and the tops are rounded (R3) notches are formed at two points across the bolt hole center O. . The angle formed between the reference line x and the top straight line L2 is 20 °.

  Each of the test pieces 3 and 4 is an example of the embodiment of the present invention, and has the form shown in FIGS. 9 (c) and 9 (d). Each of the test pieces 3 and 4 is different from the test number 2 in the deviation angle θ. is there. The test piece 3 has a weld length of 15 mm (distance from the reference line x to the welding start point), and the test piece 4 has a weld length of 15 mm (distance from the reference line x to the welding start point).

  In these embodiments, cracks occurred from the tops of the cutouts within the standard load range, and the nuts were removed. In particular, the test piece 2 had good results.

  Moreover, the test pieces 5-8 are comparative examples.

  The test piece 5 and the test piece 6 are of the form shown in FIG. 10A, and are provided with two welded portions having a weld length of 20 mm at positions facing each other across the bolt hole center O. The test piece 5 and the test piece 6 have different inner diameters of the bolt holes, but neither has a notch formed.

  The test piece 7 is of the form shown in FIG. 10 (c), and has two welded portions with a weld length of 20 mm, and is formed in a cross shape at four locations, approximately the center position of both welded portions and a position orthogonal to the welded portions. A notch (projection length is about 5 mm, the top is rounded with R3) is formed. In this case, although a slight crack occurred in a notch in a direction perpendicular to the welded portion, the fixed portion was damaged while exceeding the reference load range.

  Moreover, the test piece 8 is a thing of the aspect shown in FIG.10 (d), and the welding part of 10 mm in welding length is located in two positions which oppose on both sides of the bolt hole center O (the center part of a welding part is a reference | standard). Provided on the line x), and notches (projection length is about 5 mm, the top is pointed) are formed in two places on the reference line x.

  From the results shown in Table 1, it can be seen that the positional relationship between the weld fixing position of the nut to the attached portion and the formation position of the top of the notch is related to the promotion of crack generation.

2 Front side frame (side frame)
21 Mounted part 21a Bolt hole (opening)
21b Notch 21T Top 3 Subframe 4 Connecting means 41 Bolt (second connecting member)
42 Nut (first connecting member)
51, 52 Welded portion L1 Fixed straight line L2 Top straight line θ Deviation angle

Claims (6)

A side frame extending in the longitudinal direction of the vehicle;
A subframe provided below the side frame and supporting the suspension;
A sub-frame support structure having a connecting means for connecting the sub-frame to the attached portion of the side frame,
The connecting means engages with the first connecting member through the opening and a first connecting member provided so as to surround the opening formed in the attached portion, and connects the sub frame to the side frame. A second connecting member,
In the attached portion, a notch is formed at the edge of the opening, and the first connecting member is partially fixed to the attached portion, and the fixing position of the first connecting member And the relative positional relationship in the circumferential direction of the formation position of the top of the notch is specified so that the circumferential center of the fixing position and the top do not overlap in the circumferential direction. Construction.   The subframe support structure according to claim 1, wherein a top portion of the notch is positioned on an inner side than an outer shape of the first connecting member fixed to the attached portion. An angle formed between a fixing straight line passing through one end of the fixing position and the center of the opening, and a top straight line passing through the top of the notch and the center of the opening,
The subframe support structure according to claim 1, wherein the subframe support structure is −15 ° to 60 ° with respect to the top straight line.   The first connecting member is fixed to the attached portion by welding, and a welding location as the fixing position extends along an outer peripheral surface of the first connecting member, and from the top of the notch. The subframe support structure according to any one of claims 1 to 3, wherein an end point is provided on the side to be separated. A pair of notches are formed on a straight line passing through the center of the opening;
The subframe support structure according to any one of claims 1 to 4, wherein the first connecting member is fixed to the attached portion at two locations facing each other with the center of the opening interposed therebetween.   The subframe support structure according to any one of claims 1 to 5, wherein the subframe is disposed substantially below a power train on a front side of a vehicle body and is connected to a front side frame at a lower rear side of the powertrain.

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