Auxiliary frame structure for automobile and reinforcing component thereof

Abstract

The invention provides a subframe structure for an automobile, which can improve the rigidity of a subframe and restrain the increase of the weight of a vehicle body to the minimum. A subframe structure for an automobile is provided with: a pair of left and right side members comprising hollow members extending in the front-rear direction of the body of the automobile, the pair of left and right side members having a connection part of a suspension arm; and two or more cross members composed of hollow members extending in the left-right direction of the vehicle body and coupled to the pair of left and right side members in a direction intersecting the pair of left and right side members, the cross members being provided with reinforcing members inside the cross members in the vicinity of the coupling portions of each of the cross members and each of the side members. The reinforcing member has: a cross-section reinforcing section that blocks all or part of the cross-section of the cross-member; and a plate surface reinforcing part having a shape along the inner surface of the upper plate or the lower plate of the cross beam and the inner surface of at least one of the left and right wall plates.

Description

Technical Field

[0001] The present invention relates to a structure of a subframe provided at a lower part of an automobile body for connecting a suspension arm to the body and a reinforcing member used herein. Background Art

[0002] Some automobile bodies are provided at their lower parts with a subframe for connecting a suspension arm supporting a wheel to the body. The subframe generally has a cross shape in which two cross members extending in the left - right direction of the body are combined with two longitudinal members extending in the front - rear direction of the body, or an H - shaped structure without a front cross member. The longitudinal members and the cross members do not necessarily need to be formed separately and combined with each other, and sometimes they are also integral parts.

[0003] The subframe is deformed due to the load input from the suspension arm accompanying the movement of the suspension, and thus high rigidity is required. Increasing the rigidity of the subframe improves ride comfort and the value of the automobile. On the other hand, from the viewpoint of the energy efficiency of the automobile, the subframe is also required to be lightweight. In the case of forming with a sheet material, reducing the plate thickness is effective for lightweighting, but if the plate thickness is reduced, the rigidity generally decreases, so high rigidity and lightweighting are in a trade - off relationship.

[0004] In addition, as the performance that decreases when the plate thickness is reduced, there are collision performance, static strength, fatigue strength, etc., but these can be solved by applying high - strength materials. However, in general metal materials, even if the strength is increased, the elastic modulus hardly changes, so high rigidity brought about by high - strength materials cannot be expected. Therefore, since it is difficult to ensure rigidity, lightweighting sometimes cannot be achieved. Therefore, in Patent Documents 1 and 2, a method of improving the rigidity of the subframe by arranging a reinforcing member at the optimal position obtained by shape optimization analysis (topology optimization) of a reinforcing member model has been proposed.

[0005] In Patent Document 1, a technique is disclosed in which, in a subframe structure of an automobile in which a longitudinal member and a cross member each formed of a hollow member form a cross shape, a cylindrical member connecting the upper side and the lower side is provided inside the longitudinal member and the cross member at the joint portion of the longitudinal member and the cross member as a reinforcing member. In addition, in Patent Document 2, a technique is disclosed in which a resin reinforcing member having a columnar portion connecting the upper side and the lower side is filled or provided inside the longitudinal member and the cross member at the joint portion of the longitudinal member and the cross member each formed of a hollow member.

[0006] In addition, in Patent Document 3, a reinforcing structure for improving torsional rigidity is disclosed in a subframe at the front part or the rear part of an automobile body. The reinforcing structure is configured as a plate having shear strength, and a charging module is buried in an opening formed by cutting off the material of the reinforcing structure.

[0007] In addition, in Patent Document 4, a technique is disclosed in which a pair of longitudinal beams and a cross beam, which are each formed in a cylindrical shape, are connected by a connecting member, and in a battery frame in which the height of the longitudinal beam is higher than that of the cross beam, a reinforcing member that connects the upper wall and the lower wall is provided at a vulnerable portion at the end of the cross beam having low bending resistance with respect to a side collision. Further, as the reinforcing member, a connecting rod that penetrates the upper wall and the lower wall, or a block formed of a cylindrical steel plate member having a substantially rectangular cross-sectional shape and welded along the inner circumferential surfaces of the upper wall and the lower wall is provided.

[0008] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2020-083018

[0009] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2020-075656

[0010] Patent Document 3: Japanese Patent No. 5822896

[0011] Patent Document 4: Japanese Unexamined Patent Application Publication No. 2013-035410

[0012] In the methods described in Patent Documents 1 and 2, since a large number of new components are additionally provided, there is a problem of an increase in manufacturing cost. Further, in the reinforcing structure of Patent Document 3, since it is composed of a plate having an opening portion and having shear strength, the torsional rigidity of the subframe is increased, but there is a problem of an increase in vehicle body weight. Moreover, in the method described in Patent Document 4, although bending of the cross beam with respect to a side collision can be suppressed, there are problems that the torsional rigidity of the battery frame in the vehicle up-and-down direction and the bending rigidity of the vehicle body in the left-and-right direction cannot be sufficiently increased. Summary of the Invention

[0013] Therefore, an object of the present invention is to provide a subframe structure for an automobile, which increases the rigidity of a strengthened portion while suppressing an increase in the number of components to a minimum by limiting the strengthened portion to only a part of the cross beam, and increases the rigidity of the subframe while suppressing an increase in vehicle body weight to a minimum. Another object of the present invention is to provide a reinforcing member for the subframe structure.

[0014] The present inventors have intensively studied a strengthened portion effective for increasing the rigidity of a subframe having a closed cross-sectional structure, and as a result, have found that it is important to strengthen the inside of the cross beam near the joint portion of the cross beam that is joined to the longitudinal beams in a direction crossing them. Further, it has been found that suppressing cross-sectional deformation near the joint portion of the cross beam formed of a hollow member is effective for increasing the rigidity of the subframe.

[0015] Based on the above insights of the present inventors, the subframe structure for an automobile of the present invention for solving the existing problems includes:

[0016] A pair of left and right longitudinal beams, which are formed by hollow members extending in the front-rear direction of the vehicle body and have connecting portions for suspension arms; and

[0017] Two or more cross beams, which are formed by hollow members extending in the left-right direction of the vehicle body and are joined to the pair of left and right longitudinal beams in a direction intersecting them,

[0018] The subframe structure for a vehicle is characterized in that

[0019] Reinforcing members are provided inside each of the cross beams near the joint portions of each of the cross beams and each of the longitudinal beams,

[0020] The reinforcing members have: a cross-sectional reinforcing portion that blocks all or part of the cross section of the cross beam; and a plate surface reinforcing portion having a shape along at least one of the inner surfaces of the upper plate or the lower plate of the cross beam and the inner surfaces of the left and right side wall plates.

[0021] In addition, in the subframe structure for a vehicle of the present invention, if each of the longitudinal beams and any one or more of the cross beams are formed of a high-strength steel plate with a tensile strength of 590 MPa or more, the subframe structure can be lightened by thinning the steel plate, so it is preferable. Further, in the subframe structure for a vehicle of the present invention, if the reinforcing members are formed of a steel plate with a tensile strength of 270 MPa or more and 440 MPa or less, the reinforcing members can be manufactured inexpensively and easily, so it is preferable.

[0022] Moreover, the reinforcing members of the subframe structure for a vehicle of the present invention that solve the existing problems based on the above-mentioned insights of the present inventors are for the subframe structure for a vehicle,

[0023] The subframe structure for a vehicle includes:

[0024] A pair of left and right longitudinal beams, which are formed by hollow members extending in the front-rear direction of the vehicle body and have connecting portions for suspension arms; and

[0025] Two or more cross beams, which are formed by hollow members extending in the left-right direction of the vehicle body and are joined to the pair of left and right longitudinal beams in a direction intersecting them,

[0026] The reinforcing members are characterized in that

[0027] The reinforcing members are provided inside each of the cross beams near the joint portions of each of the cross beams and each of the longitudinal beams,

[0028] The reinforcing members have: a cross-sectional reinforcing portion that blocks all or part of the cross section of the cross beam; and a plate surface reinforcing portion having a shape along at least one of the inner surfaces of the upper plate or the lower plate of the cross beam and the inner surfaces of the left and right side wall plates.

[0029] In addition, in the subframe structure for an automobile and its reinforcing member according to the present invention, if the plate surface reinforcing portion of the reinforcing member reinforces the inner ridge line portion that is bent in an L shape at the joint portion where the longitudinal beam and the cross beam are joined, deformation of the joint portion where the longitudinal beam and the cross beam are joined and where stress concentration is likely to occur can be suppressed, and the rigidity of the entire subframe structure can be improved. Therefore, this is preferable.

[0030] According to the subframe structure for an automobile and its reinforcing member of the present invention, the rigidity of the subframe can be improved. At the same time, by suppressing deformation, improvement in collision performance, static strength, and fatigue strength can also be expected. In addition, by suppressing an increase in the number of components with respect to the existing subframe structure to the minimum, an increase in vehicle body weight can be suppressed to the minimum. Moreover, compared with the case of adding multiple components and new components as in the existing strengthening methods, fewer joining parts of the reinforcing member to the subframe are required, so an improvement in productivity can be expected. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a top view schematically showing a subframe structure for an automobile according to an embodiment of the present invention.

[0032] Figure 2 (a) of is a perspective view showing a reinforcing member according to an embodiment of the present invention in a state of being observed from two directions, Figure 2 (b) of is an enlarged perspective view showing a state where the reinforcing member of this embodiment is provided in Figure 1 the subframe structure of the embodiment shown.

[0033] Figure 3 (a) of is an explanatory diagram showing the constraint position, load application position, and direction during torsional analysis using a finite element method analysis model of the subframe structure of the above embodiment, Figure 3 (b) of is an explanatory diagram showing the constraint position, load application position, and direction during bending analysis using a finite element method analysis model of the subframe structure of the above embodiment.

[0034] Figure 4 is a perspective view showing a part of the cross beam of the subframe structure, the joint portion, and the upper portion in the vehicle body up and down direction of the longitudinal beam, and is an explanatory diagram showing the reinforcing members of Example (inventive example) and Comparative Examples 2 to 5.

[0035] Figure 5 (a) of is an explanatory diagram showing the torsional stiffness improvement rate and bending stiffness improvement rate of Example and Comparative Examples 2 to 5 based on Comparative Example 1, Figure 5Fig. (b) is an explanatory diagram showing the torsional stiffness improvement rate and the flexural stiffness improvement rate of Comparative Examples 2 to 5 based on the embodiments. Detailed Description

[0036] Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings. Figure 1 Fig. is a plan view schematically showing a subframe structure for an automobile according to an embodiment of the present invention. The subframe structure of the embodiment indicated by reference numeral 1 in the figure is formed by a pair of left and right longitudinal beams 3 and a pair of front and rear cross beams 5, and has a cross shape.

[0037] The longitudinal beam 3 is composed of a hollow member extending in the longitudinal direction of the vehicle body, and has a connecting portion 9 for a suspension arm. The cross beam 5 is composed of a hollow member extending in the lateral direction of the vehicle body, and is joined to the pair of left and right longitudinal beams 3 in a direction intersecting them through a joining portion 7 (a portion bent in an L shape) that is bent inward in the lateral direction of the vehicle body toward these longitudinal beams 3. The joining portion 7 has a bent ridge line portion 7a that connects the ridge line portion 3a on the inner side in the lateral direction of the vehicle body of the longitudinal beam 3 and the ridge line portion 5a on the rear side in the longitudinal direction of the vehicle body of the front cross beam 5. In addition, the subframe structure of the present invention may also be an H-shaped structure (ladder frame) without the front cross beam 5. Further, the subframe structure 1 of the above-described embodiment is a member in which the longitudinal beam 3 and the cross beam 5 are integrated, but it does not necessarily have to be an integrated member, and the longitudinal beam 3 and the cross beam 5 may be formed separately and joined to each other.

[0038] Figure 2 Fig. (a) is a perspective view showing, as a representative example, a reinforcing member according to an embodiment of the present invention in a state of being observed from two different directions and disposed inside the right side of the front cross beam 5 of the subframe structure 1 of the above-described embodiment. Figure 2 Fig. (b) is a perspective view showing an enlarged view of the state in which the reinforcing member of the above-described embodiment indicated by reference numeral 11 in the figure is disposed inside the right side of the front cross beam 5 of the subframe structure 1 of the above-described embodiment. The reinforcing member 11 is formed by stamping a steel plate into a groove shape, and has a plate surface reinforcing portion 11a and a cross-sectional reinforcing portion 11b.

[0039] The plate surface reinforcing portion 11a has a top plate 11c and an inclined surface 11e shaped like at least a part of the inner surface of the upper plate or the lower plate of the cross beam 5 near the joint portion 7, which is the upper plate in the illustrated example, and longitudinal walls 11d shaped like at least a part of the inner surfaces of the left and right side wall plates of the cross beam 5. Here, the longitudinal walls 11d and the inclined surface 11e have the shape of the inner surface along the joint portion 7 from the inner bent portion of the L-shaped bend to the vicinity of the boundary with the longitudinal beam 3. Thus, the plate surface reinforcing portion 11a reinforces the bent ridge line portion 7a on the inner side of the L-shaped bend in the joint portion 7 that joins the longitudinal beam 3 and the front cross beam 5. In addition, the plate surface reinforcing portion 11a extends to approximately 15% - 20% of the vehicle width direction length of the cross beam 5. Moreover, the plate surface reinforcing portion 11a is adhered to the upper plate of the cross beam 5, the left and right side walls, and the inner surface of the inner portion of the L-shaped bend of the joint portion 7 by welding or an adhesive (resin), etc. The plate surface reinforcing portion 11a can increase the stiffness of the subframe structure 1 by increasing the apparent plate thickness of the portion of the cross beam 5 to be reinforced. In addition, by using an adhesive (resin) in the adhesion, a resin with a specified thickness is sandwiched between the upper plate of the cross beam 5, the left and right side walls, and the plate surface reinforcing portion 11a of the reinforcing member 11, thereby further increasing the apparent plate thickness of the portion to be reinforced. When the apparent plate thickness of the portion to be reinforced is increased, the bending stiffness of this portion becomes higher, so it is possible to expect a stiffness greater than the sum of the plate thicknesses of the original component and the plate surface reinforcing portion 11a. In addition, the plate surface reinforcing portion 11a reinforces the bent ridge line portion 7a in the joint portion 7 from the longitudinal beam 3 to the front cross beam 5. Thus, it is possible to suppress the deformation of the joint portion 7 that connects the longitudinal beam 3 and the cross beam 5 and is prone to stress concentration, and improve the stiffness of the entire subframe structure 1. In addition, examples of the type of adhesive (resin) include thermoplastic resin, thermosetting resin, or elastic system resin, etc.

[0040] The cross-section reinforcing portion 11b blocks all or a part of the hollow cross-section of the cross beam 5 near the joint portion 7 that joins the longitudinal beam 3 and the front cross beam 5. When an external force (load) that induces bending deformation and torsional deformation of the subframe structure 1 is applied, it suppresses the cross-section deformation of the cross beam 5 whose strength is lower than that of the longitudinal beam 3 designed to withstand a collision from the front of the vehicle, thereby enabling the stiffness of the entire subframe structure 1 to be increased.

[0041] The reason for arranging the reinforcing member 11 inside the portion of the cross beam 5 near each joint portion 7 that joins the cross beam 5 and the longitudinal beam 3 is as follows. As in the joint portion 7, in a portion where the overall shape changes, such as the middle portion of the longitudinal beam 3 and the cross beam 5 (hereinafter referred to as the "shape change portion"), stress concentration occurs, and it is more likely to deform compared to the portions of the longitudinal beam 3 and the cross beam 5 before and after the shape change portion. Therefore, this becomes a cause of the reduction in the stiffness of the subframe structure 1. Thus, it is important to reinforce the portion near the joint portion 7.

[0042] In addition, since the longitudinal beams 3 and the cross beams 5 are formed of hollow members having a substantially rectangular cross section, when a bending or torsional load is applied to the subframe structure 1, stress concentration occurs at the ridge portions of the substantially rectangular cross section. Therefore, it is important to strengthen the ridge portions, which are the shape-changing portions, as the strengthening portions within the cross section of the joint portion 7. Here, in Figure 2 In the reinforcing member 11 shown in (a) of, the ridge portions are a collective term for the ridges between the top plate 11c and the longitudinal wall 11d, between the top plate 11c and the inclined surface 11e, and between the longitudinal wall 11d and the inclined surface 11e. The plate surface reinforcing portion 11a has a shape along all or part of the inner peripheral surface of the portion of the cross beam 5 near the joint portion 7, and strengthens the ridge portions of the portion of the cross beam 5 near the joint portion 7 in a manner of covering from the inside.

[0043] In addition, Figure 2 The reinforcing member 11 shown in is joined by welding the peripheral portions of the plate surface reinforcing portion 11a and the cross section reinforcing portion 11b to each other, whereby a higher reinforcing effect than when the plate surface reinforcing portion 11a and the cross section reinforcing portion 11b are only independently strengthened can be obtained. In addition, in the subframe structure 1 of the above-described embodiment, as a representative example, the reinforcing member 11 is provided on the right side inside the front cross beam 5, but the reinforcing member 11 having the same structure is also provided on the left side inside the front cross beam 5, and is also provided on the left and right sides inside the rear cross beam 5.

[0044] <Regarding material strength>

[0045] Since the reinforcing member 11 is used to increase the rigidity of the subframe structure 1, it is not necessary to apply a high-strength material to the reinforcing member 11. As long as the tensile strength is 270 MPa or more and 440 MPa or less, it is preferable from both the viewpoint of material price and the ease of processing. On the other hand, in the present embodiment, since the high rigidity of the subframe structure 1 can be achieved by the reinforcing member 11, the thickness of the steel plate for the subframe structure 1 can be reduced from the viewpoint of rigidity. In order to make it lightweight while maintaining the strength of the subframe structure 1, it is preferable to use a high-strength material having a tensile strength of 590 MPa or more in any one of the components of the subframe structure 1. There is no particular limitation on the component using the high-strength material, but since the plate thickness of the pair of left and right longitudinal beams 3 is often determined from the viewpoint of strength, from the viewpoint of improving the collision strength, using a high-strength material can often achieve thinning.

[0046] (Analysis and investigation example 1)

[0047] In Analysis and Investigation Example 1, the influence of the subframe structure 1 of the above-described embodiment on the rigidity of a general subframe was analyzed and investigated as follows. The example (invention example) was set asFigure 2 The reinforcing member 11 shown in FIGS. (a) and (b) is disposed on the left and right sides inside the front cross member 5 and on the left and right sides inside the rear cross member 5. Figure 1 For the subframe structure 1, Comparative Example 1 is the subframe structure 1 without the reinforcing member 11. Figure 1 In Figure 2 In the coordinate axes shown in FIG. (b), the X-axis represents the left-right direction of the vehicle body (positive indicates the right side of the vehicle body), the Y-axis represents the front-rear direction of the vehicle body (positive indicates the front side of the vehicle body), and the Z-axis represents the up-down direction of the vehicle body (positive indicates the upper side of the vehicle body).

[0048] Here, the pair of left and right longitudinal beams 3 and the front and rear cross members 5 of the subframe structure 1 in the embodiment and Comparative Example 1 are made of steel plates with a plate thickness of 2.0 mm and a tensile strength of 590 MPa. The plate surface reinforcing portion 11a and the cross-sectional reinforcing portion 11b of each reinforcing member 11 in the subframe structure 1 of the embodiment are made of steel plates with a plate thickness of 1.0 mm and a tensile strength of 270 MPa. The length of each reinforcing member 11 is approximately 10% of the length of each cross member 5 in the left-right direction of the vehicle body, and each reinforcing member 11 is bonded to the inside of the vicinity of the joint portion 7 of each cross member 5 with a thermoplastic-based structural adhesive.

[0049] The analysis conditions are Figure 3 the torsion shown in FIG. (a) and Figure 3 the bending shown in FIG. (b). Using the finite element method, the displacement of the load point relative to the unit load is obtained, and the reciprocal of the displacement is used as the stiffness, and the stiffness change rate relative to the existing component is calculated. Figure 3 FIGS. (a) and (b) respectively show the positions where the load is applied and the positions where the subframe structure 1 is constrained.

[0050] In Figure 3 In the case of "analysis condition torsion" in FIG. (a), the left and right end portions of the rear cross member 5 are constrained, and loads (1 kN) are respectively applied upward and downward in the up-down direction of the vehicle body to the left and right end portions of the front cross member 5, and the displacement amount in the up-down direction of the vehicle body per unit load of the left and right end portions of the cross member 5 is obtained as the torsional stiffness, and the improvement rate of the torsional stiffness of the embodiment based on Comparative Example 1 (torsional stiffness improvement rate) is evaluated.

[0051] In addition, in Figure 3 in the case of "analysis condition bending" in FIG. (b), the left and right end portions of the rear cross member 5 are constrained, and loads (1 kN) are respectively applied toward the right direction of the vehicle body to the left and right end portions of the front cross member 5, and the displacement amount in the left-right direction of the vehicle body per unit load of the left and right end portions of the cross member 5 is obtained as the bending stiffness, and the improvement rate of the bending stiffness of the embodiment based on Comparative Example 1 (bending stiffness improvement rate) is evaluated.

[0052] The results show that, taking the subframe structure 1 without the strengthening member 11 (i.e., Comparative Example 1) as a reference, the torsional stiffness improvement rate is 4.8% in the case of torsion, and the bending stiffness improvement rate is 4.0% in the case of bending. The torsional stiffness and the bending stiffness are improved respectively. Figure 1

[0053] (Analysis and Investigation Example 2)

[0054] In Analysis and Investigation Example 2, the contribution degrees of the plate surface strengthening part 11a, the cross-section strengthening part 11b, and the bending ridge line part 7a of the plate surface strengthening part 11a of the strengthening member 11 constituting the subframe structure 1 of the above-described embodiment to the torsional stiffness improvement rate and the bending stiffness improvement rate were investigated. Figure 4 A part of the cross member 5, the joint part 7, and the upper part in the vehicle body up-and-down direction of the longitudinal member 3 of the subframe structure 1 are set in a perspective state (not shown), showing the strengthening members of the embodiment (invention example) and Comparative Examples 2 to 5 shown below.

[0055] Figure 4 The embodiment (invention example) shown in (a) is the same as the embodiment in the above Analysis and Investigation Example 1. Figure 4 Comparative Example 2 shown in (b) is obtained by deleting the cross-section strengthening part 11b in the strengthening member 11 of the embodiment shown in (a) and only leaving the plate surface strengthening part 11a. Figure 4 Figure 4 Comparative Example 3 shown in (c) is obtained by deleting the part of the bending ridge line part 7a (refer to Figure 4 ) on the inner side where the joint part 7 of the strengthening member 11 of the embodiment shown in (a) is bent into an L shape. Figure 1 Figure 4 Comparative Example 4 shown in (d) is obtained by deleting the parts corresponding to the inclined surface 11e and the longitudinal wall 11d in the plate surface strengthening part 11a in the strengthening member of Comparative Example 3 shown in (c). Figure 4 Figure 4 Comparative Example 5 shown in (e) is obtained by deleting the plate surface strengthening part 11a in the strengthening member 11 of the embodiment shown in (a) and only leaving the cross-section strengthening part 11b. Figure 4

[0056] Figure 5 Figure (a) shows the torsional stiffness improvement rate (%) and the bending stiffness improvement rate (%) of the embodiment and Comparative Examples 2 to 5 based on the above Comparative Example 1. In addition, Figure 5 Figure (b) shows the torsional stiffness improvement rate (%) and the bending stiffness improvement rate (%) of Comparative Examples 2 to 5 based on the embodiment (100%).

[0057] ​​​​​By comparing Comparative Example 2 with Comparative Example 5, it was determined that the torsional stiffness improvement rate of the plate surface strengthening portion 11a of the strengthening member 11 was 4.7 times that of the cross-sectional strengthening portion 11b, and the bending stiffness improvement rate was 1.9 times that of the cross-sectional strengthening portion 11b. The plate surface strengthening portion 11a had a high contribution to the stiffness improvement. In addition, by comparing the embodiments with Comparative Examples 3 to 5, it was determined that by strengthening the bent ridge line portion 7a on the inner side that is bent in an L shape in the joint portion 7, the torsional stiffness can be greatly improved.

[0058] As described above, the description has been made based on the illustrated examples, but the present invention is not limited to the above illustrated examples and can be appropriately changed within the scope described in the claims. For example, in the above-described embodiment, the strengthening member 11 is provided along the upper plate of the cross member 5, but the subframe structure of the present invention may also provide the strengthening member 11 along the lower plate of the cross member 5.

[0059] In addition, the subframe structure of the above-described embodiment is applied to the subframe at the rear of the vehicle body to increase its stiffness, but the subframe structure of the present invention may also be applied to the subframe at the front of the vehicle body to increase its stiffness.

[0060] Industrial Applicability

[0061] According to the subframe structure and the strengthening member for an automobile of the present invention, the stiffness of the subframe can be increased. At the same time, by suppressing deformation, an improvement in collision performance, static strength, and fatigue strength can also be expected. In addition, by suppressing the increase in the number of components with respect to the existing subframe structure to the minimum, the increase in the vehicle body weight can be suppressed to the minimum. Moreover, compared with the case of adding multiple components and new components as in the existing strengthening method, fewer joints of the strengthening member to the subframe are required, so an improvement in productivity can be expected.

[0062] Description of Reference Numerals

[0063] 1... Subframe structure; 3... Longitudinal beam; 3a... Ridge line portion on the inner side in the left-right direction of the vehicle body; 5... Cross member; 5a... Ridge line portion on the rear side in the front-rear direction of the vehicle body; 7... Joint portion; 7a... Bent ridge line portion; 9... Connecting portion of the suspension arm; 11... Strengthening member; 11a... Plate surface strengthening portion; 11b... Cross-sectional strengthening portion; 11c... Top plate; 11d... Longitudinal wall; 11e... Inclined surface.

Claims

1. An automotive subframe structure, comprising: A pair of left and right longitudinal beams, which are hollow members extending in the longitudinal direction of the vehicle body and have connection parts for suspension arms; and Two or more cross beams, which are hollow members extending in the lateral direction of the vehicle body and are joined to the pair of left and right longitudinal beams in a direction intersecting them, Characterized in that, Reinforcing members are provided inside each of the cross beams near the joint parts of each of the cross beams and each of the longitudinal beams, The reinforcing members have: a cross-sectional reinforcing part that blocks all or part of the cross section of the cross beam; and a plate surface reinforcing part that has a shape along at least one of the inner surfaces of the upper plate or the lower plate and the left and right side plates of the cross beam.

2. The automotive subframe structure according to claim 1, characterized in that, The plate surface reinforcing part of the reinforcing member reinforces the inner ridge line part that is bent in an L shape at the joint part that joins the longitudinal beam and the cross beam.

3. The automotive subframe structure according to claim 1 or 2, characterized in that, Each of the longitudinal beams and any one or more of the cross beams are formed of high-strength steel plates with a tensile strength of 590 MPa or more.

4. The automotive subframe structure according to claim 1 or 2, characterized in that, The reinforcing member is formed of a steel plate with a tensile strength of 270 MPa or more and 440 MPa or less.

5. A reinforcing member for an automotive subframe structure, which is a reinforcing member for an automotive subframe structure, The automotive subframe structure comprises: A pair of left and right longitudinal beams, which are hollow members extending in the longitudinal direction of the vehicle body and have connection parts for suspension arms; and Two or more cross beams, which are hollow members extending in the lateral direction of the vehicle body and are joined to the pair of left and right longitudinal beams in a direction intersecting them, Characterized in that, The reinforcing member is provided inside each of the cross beams near the joint parts of each of the cross beams and each of the longitudinal beams, The reinforcing member has: a cross-sectional reinforcing part that blocks all or part of the cross section of the cross beam; and a plate surface reinforcing part that has a shape along at least one of the inner surfaces of the upper plate or the lower plate and the left and right side plates of the cross beam.

6. The reinforcing member for an automotive subframe structure according to claim 5, characterized in that, The plate surface reinforcing part of the reinforcing member reinforces the inner ridge line part that is bent in an L shape at the joint part that joins the longitudinal beam and the cross beam.

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