Integrated rear lower and body frame

Abstract

To provide a vehicle body frame using a component integration type rear lower.SOLUTION: In a side connection member (10) applied to a vehicle body frame (1) of the present invention, a connection section between a side sill (3) and a rear side member (40) is formed of a body frame (21) having a predetermined length, and a rear lower (20) in which front-rear connection members (21-1, 21-2) for fixing a side sill (30) and the rear side member (40), bush mounting members (21-1, 23) for fastening a bush (100), and CTBA mounting members (25, 27, 29) for mounting a rear wheel suspension device are integrated with a body frame (21) is included. Accordingly, not only the rigidity of the CTBA (200) can be secured, but also the design of PBV (purpose Built Vehicle) can be easily modified according to intention.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a parts-integrated rear lower and body frame, and in particular to a parts-integrated rear lower and body frame that are applied to a rear-linked structure and are manufactured using die-casting in a parts-integrated structure, thereby greatly simplifying the number of parts while allowing for easy modification in accordance with the design intent of the PBV (Purpose Built Vehicle). [Background technology]

[0002] Generally, the rear lower (or rear lower member) of a vehicle forms a rear connecting structure of the body frame to absorb impact in a rear collision and protect the vehicle safely. To this end, the rear lower increases rigidity by using a plurality of reinforcing members formed by bending one side protruding forward / backward, and by using rear side members, spring seat / subframe brackets, rear side panels, etc., related parts including brackets are integrated with each other through a joining process. In particular, the rear lower section has a fastening structure for the rear wheel suspension and a support member welding structure using multiple reinforcing members on one side of the spring seat and the side of the rear lower section. However, because the rear lower section is a joint structure of multiple parts using the rear lower panel and multiple reinforcing members, the structure becomes complex and heavy, which can lead to poor welding. As an example, the rear lower section is made up of approximately 10 parts, eight of which are used as reinforcing members for rigidity. However, such a large number of reinforcing members not only increases weight and material costs, but also requires a joining structure between panels using welding, which reduces the rigid support capacity of the rear lower section. In particular, when the rear wheel suspension is installed, there is an offset amount relative to the suspension mounting structure and the side sill and / or rear side member components, which are major components of the body frame, and this offset amount further weakens the rigidity of the rear lower area. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-90270 Summary of the Invention [Problem to be solved by the invention]

[0004] In view of the above, the present invention aims to provide a body frame that uses an integrated-parts lower member, which has an integrated-parts structure made by die-casting and does not use a large number of reinforcing materials, thereby forming a front-rear connecting structure between the side sill and rear side member, thereby achieving weight reduction through structural simplification and reducing material costs, and in particular, ensuring CTBA rigidity through a CTBA (Coupled Torsion Beam Axle) mounting structure using the rear lower, and which can be easily deformed in accordance with the design intent of the PBV (Purpose Built Vehicle) due to the formability of the die-cast rear lower to fit the size. [Means for solving the problem]

[0005] The component-integrated rear lower according to the present invention is a body frame having one side end and an opposite end and a predetermined length, and is characterized by including a body frame that integrates a front / rear connecting member to which a side sill is connected at one side end and a rear side member is connected at the opposite end, a bush mounting member to which a bush is connected at the one side end, and a CTBA mounting member to which one or more of a CTBA, a chassis spring, and a shock absorber are fastened at the opposite end.

[0006] The body frame is made of aluminum and formed by die casting, and is characterized in that the front and rear connecting members, the bush mounting members, and the CTBA mounting members are integrated.

[0007] The body frame has a height difference between the one side end and the opposite side end, thereby forming a rear lower ground clearance.

[0008] The body frame is characterized by having an "H" cross-sectional structure.

[0009] The front and rear connecting members each include a center connector extending from one end of the vehicle in an open upper space on which the side sill is placed, and a rear connector extending from the opposite end of the vehicle as an open space on which the rear side member is inserted.

[0010] The rear connector has an inner wall formed in a side direction relative to an upper surface into which the rear side member is inserted so that the end surface of the rear side member comes into close contact with the inner wall.

[0011] The bush mounting member may include a bush mounting hole drilled in a center connector extending from one side end to form an open upper space so that the side sill can be placed thereon.

[0012] The CTBA mounting member includes a trailing arm connector that protrudes from one end and forms a side open space so that a portion of the CTBA can be inserted into the side; a spring seat that protrudes from the underside of the opposite end and forms a bottom open space so that an upper portion of the chassis spring can be inserted into the top; and a shock absorber connector that forms a side open space on a side of the opposite end so that an upper portion of the shock absorber can be inserted into the side.

[0013] The trailing arm connecting portion is characterized in that a rear lower hole is drilled for screw fastening with a bolt fastened to a portion of the CTBA.

[0014] The side sill is characterized by having an extruded material structure.

[0015] The body frame according to the present invention comprises side sills, which form the framework of the middle section of the vehicle and extend into the battery space where the battery is installed; rear side members, which form the framework of the rear section of the vehicle; and a body frame of a predetermined length with a height difference so as to form a rear lower ground clearance, wherein the connecting section between the side sills and the rear side members is formed by front and rear connecting members, the fastening portion between the side sills and the bushes is formed by a bush mounting member, and the fastening portion of the rear wheel suspension is formed by a CTBA mounting member.

[0016] The rear lower is made of aluminum and formed by die casting, and the front and rear connecting members, the bush mounting member, and the CTBA mounting member are integrated with the body frame.

[0017] The front and rear connecting members are characterized in that they fix the side sills and the rear side members together with fastening members.

[0018] The fastening members are fixed to the side sills and the fastening members are fixed to the rear side members by the FDS method.

[0019] The front and rear connecting members each include a center connector on which a portion of the side sill is placed in an upper open space formed by extending the body frame in the connecting section of the side sill, and a rear connector on which a portion of the rear side member is inserted into an upper surface of the open space formed by extending the body frame in the connecting section of the rear side member.

[0020] The end of the rear side member is in close contact with the inner wall of the rear connector.

[0021] The side sill has a space divided by a partition rib, and the rear side member has an open rectangular cross-section structure or a closed rectangular cross-section structure.

[0022] The partition rib is fixed to the center connector of the rear lower using a flow drill screw (FDS) method, and the center connector extends from one end of the side sill and is formed as an open space on the top so that the side sill can be placed on top.

[0023] The bush mounting member has a bush mounting hole into which the bush is inserted and fixed by a bush shaft, and in the connecting section of the side sill, the bush mounting hole is formed by drilling into a center connector extending from the body frame as an open upper space on which a portion of the side sill is placed.

[0024] The rear wheel suspension includes a CTBA, a chassis spring, and a shock absorber, and the CTBA mounting structure fastens one or more of the CTBA, the chassis spring, and the shock absorber.

[0025] The CTBA mounting member comprises a trailing arm connection portion protruding from a side surface of the body frame to form a side open space into which the trailing arm of the CTBA is inserted at a connection section of the side sill, a spring seat protruding from a bottom surface of the body frame to form a bottom open space into which an upper portion of the chassis spring located at a spring mounting portion of the CTBA is inserted at an upper portion, and a shock absorber connector recessed in one side surface of the body frame to form a side open space into which an upper portion of the shock absorber is inserted at a connection section of the rear side member.

[0026] The trailing arm connection portion may have a rear lower hole formed therein for screwing in a bolt that is fixed to the trailing arm.

[0027] The spring seat has a cup-shaped structure surrounding the outer diameter of a spring cup provided at the upper end of the chassis spring.

[0028] The side sills may include a left side sill and a right side sill, and a vehicle width including the battery space is determined by a distance between the left side sill and the right side sill.

[0029] The left and right side sills are connected by a center extrusion that crosses the vehicle width. [Effects of the Invention]

[0030] The vehicle body frame to which the component-integrated rear lower of the present invention is applied achieves the following functions and effects. First, the rear lower is manufactured as an integrated part structure by die-casting and is applied to the side sill and rear side member of the body frame, which simplifies the rear connecting structure and achieves weight reduction. Secondly, the integrated CTBA mounting structure using the integrated rear lower section directly fastens the rear wheel suspension CTBA to the chassis spring, ensuring the robustness of the chassis mounting strength, which is the main path of driving noise caused by vibrations being transmitted to the vehicle body, and improving driving noise reduction performance. Thirdly, the integrated CTBA mounting structure using the integrated rear lower allows the rear wheel suspension shock absorber to be positioned inside the rear lower member, thereby ensuring a larger interior space by the amount that the shock absorber's position is moved. Fourth, the integrated CTBA mounting structure using the integrated rear lower part allows the bushing to be fastened to the side sill, eliminating the bushing space that previously existed between the side sills. This expands the high-voltage battery space compared to conventional models, ensuring even greater battery capacity. Fifth, the rear lower is manufactured using a die-cast molding process to form an integrated part structure, and is applied to the rear connecting structure of the body frame, eliminating the need for the many reinforcing materials that were previously used. This reduces material costs and mold costs associated with producing individual items, as well as investment costs such as jig costs associated with assembling individual items, and enables weight reduction. Sixth, because the part-integrated rear lower is manufactured by die-cast molding, the specifications of the rear lower (i.e., size and length) can be easily adjusted, making it suitable for the design characteristics of PBVs (Purpose Built Vehicles), which require length changes depending on the purpose of the vehicle. [Brief explanation of the drawings]

[0031] [Figure 1] 1 is a diagram illustrating the configuration of a body frame to which a component-integrated rear lower section according to the present invention is applied. [Figure 2] 1 is a perspective view of a part-integrated rear lower section that is manufactured by aluminum die-casting according to the present invention and that constitutes a side connecting member. FIG. [Figure 3] 1 shows a state in which the body frame according to the present invention is being assembled with a rear wheel suspension using a component-integrated rear lower section. [Figure 4] 1 is a cross-sectional view of a rear connection structure formed by a body frame according to the present invention via a rear lower section; [Figure 5] This is an example showing that the vehicle body frame according to the present invention has a bush mounting structure via the rear lower section, thereby expanding the battery mounting space. [Figure 6] This is an example showing that the vehicle body frame according to the present invention forms a CTBA mounting structure via the rear lower section, thereby expanding the interior space of the vehicle. [Figure 7]1 is a cross-sectional perspective view of an assembly in which a chassis spring for rear wheel suspension according to the present invention is supported by a rear lower spring seat. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0032] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0033] 1, a vehicle body frame 1 is configured with side sills 30 and rear side members 40 as side connecting members 10. In this case, a front side member (not shown) is connected to the vehicle body frame 1 in front of the side sills 30. Specifically, the side connecting member 10 connects the side sill 30 and the rear side member 40 via the rear lower 20, and the left and right side sills 30A, 30B are fixed by the center extrusion member 50.

[0034] As an example, the rear lower section 20 forms a front-rear connecting member (or a front-rear connecting structure) that connects the side sill 30 and the rear side member 40 together. Therefore, the rear lower 20 is composed of a left rear lower and a right rear lower, and the left rear lower connects the left side sill 30A of the side sill 30 and the left rear side member 40A of the rear side member 40, and the right rear lower connects the right side sill 30B of the side sill 30 and the right rear side member 40B of the rear side member 40. In particular, the rear lower section 20 is characterized by being an integrated rear lower section 20 consisting of a single part to which no separate reinforcing member is applied, since the left rear lower section and the right rear lower section are each manufactured by a die-casting method using aluminum as the material.

[0035] For example, the side sill 30 is composed of a left side sill 30A and a right side sill 30B, which are connected by a center extrusion 50. In this case, the left side sill 30A and the right side sill 30B form the left and right lower side surfaces in the middle section of the vehicle and are spaced apart to form a battery space Lb. The center extrusion 50 is composed of two or more pieces spaced apart from each other, connecting the left and right side sills 30A and 30B across the battery space Lb. In particular, the left side sill 30A and the right side sill 30B each have an extruded material structure similar to the center extrusion 50, and can have enhanced rigidity and durability. In this case, the extruded material is made of aluminum.

[0036] Therefore, the side sill 30 has an integral structure of extruded material and forms a center frame of the vehicle body frame 1. Therefore, one side end of the left side sill 30A of the side sills 30 is assembled to the left rear lower section of the rear lower section 20 together with a fastening member 60 (see Figure 4), and one side end of the right side sill 30B of the side sills 30 is assembled to the right rear lower section of the rear lower section 20 together with a fastening member 60 (see Figure 4). For example, the rear side member 40 is composed of a left rear side member 40A and a right rear side member 40B, which form the left and right lower side surfaces in the rear section of the vehicle. At this time, one side end of the left and right rear side members 40A and 40B is connected to a rear bumper back beam 6, which is a component of the rear bumper (not shown).

[0037] In particular, a cross section consisting of a hollow interior space is formed by welding two panels to each of the left rear side member 40A and the right rear side member 40B. In this case, each of the left and right rear side members 40A and 40B is made of aluminum. The rear side members 40 have an open rectangular "U" cross section or a closed rectangular "□" cross section (see FIG. 4), and are made up of a left rear side member and a right rear side member. In particular, the left rear side member of the rear side members 40 has one side end assembled to the left rear lower section of the rear lower section 20 together with a fastening member 60 (see Figure 4), and the right rear side member has one side end assembled to the right rear lower section of the rear lower section 20 together with a fastening member 60 (see Figure 4).

[0038] On the other hand, referring to FIG. 2, the rear lower 20 is made up of a gently curved body frame 21, and the front and rear connecting members, bush mounting members (or bush mounting structures), and CTBA mounting members (or CTBA mounting structures) are integrally formed in the body frame 21, making it a parts-integrated rear lower 20.

[0039] For example, the body frame 21 is composed of a horizontal transverse body 21A and a left vertical body 21B and a right vertical body 21C perpendicular thereto, forming an "H" cross-sectional structure, and one side and the other side have a height difference to form a rear lower ground clearance H, which facilitates the installation of a chassis spring 300 and a shock absorber 400 of the rear wheel suspension. In this case, the position of the left vertical body 21B can be defined as a position facing the inner space of the vehicle, and the position of the right vertical body 21C can be defined as a position facing the outer space of the vehicle. In particular, the body frame 21 is formed so that the horizontal body 21A is such that the lower position B of the left / right vertical bodies 21B, 21C is located higher than the upper position b, and the lower width A of the left / right vertical bodies 21B, 21C is wider than the upper width a, so that the "H" cross-sectional structure is trapezoidal.

[0040] As an example, the front and rear connecting members consist of a center connector 21-1 formed integrally with one end of the body frame 21 and extending horizontally, and a rear connector 21-2 formed integrally with the opposite end and extending horizontally. For example, the bush mounting member is formed of a bush mounting hole 23 drilled in the center connector 21-1. At this time, the bush mounting hole 23 is formed in a circular shape.

[0041] Specifically, the CTBA mounting member comprises a trailing arm connecting portion 25 formed on one side of the body frame 21, protruding horizontally from the side surface at a distance from the center connector 21-1; a spring seat 27 formed on the opposite side of the body frame 21, protruding vertically from the underside at a distance from the rear connector 21-2; and a shock absorber connector 29 formed on one side of the body frame 21, at a distance from the rear connector 21-2, leaving a space between them. As an example, the trailing arm connection portion 25 consists of left and right flanges that protrude horizontally from the left and right vertical bodies 21B and 21C of the body frame 21, respectively, and surrounds the trailing arm 200A (see Figure 6) of the CTBA 200 portion, and the left and right flanges are drilled with rear lower holes 25A that form female threads for screwing in with bolts 200B (see Figure 6).

[0042] As an example, the spring seat 27 is formed by extending the left and right flanges protruding vertically from the left and right vertical bodies 21B and 21C of the body frame 21 into a cup shape (see Figure 7), and the cup-shaped flanges surround and place the end of the chassis spring 300 connected to the spring cup 300A. As an example, the shock absorber connector 29 is formed in a structure in which the left vertical body 21B of the body frame 21 is pushed toward the horizontal body 21A at the location where the spring seat 27 is formed, thereby forming an open side structure, and the upper end portion of the shock absorber 400 (see Figure 6) is located in the open side structure.

[0043] On the other hand, FIGS. 3 to 7 show an example in which a rear wheel suspension is mounted to the body frame 1 by a side connecting member 10 using a part-integrated rear lower 20. Referring to FIG. 3, the vehicle body frame 1 is connected by a side connecting member 10 that connects the side sills 30 and the rear side members 40 via a rear lower 20. Specifically, in the side connecting member 10, the side sill 30 and the rear side member 40 are fixed by the front and rear connecting members of the rear lower 20, the bush 100 and the side sill 30 are fixed via the bush shaft 100A by the bush mounting member, and the CTBA 200, chassis spring 300, and shock absorber 400, which are components of the rear wheel suspension device, are fixed by the CTBA mounting member.

[0044] In particular, since the rear lower 20 is manufactured by injection molding aluminum using a die-casting method (i.e., low-pressure die-casting method), the specifications of the rear lower (i.e., size and length) can be easily adjusted, and this ease of changing the specifications of the rear lower satisfies the design characteristics of a PBV (Purpose Built Vehicle), which requires the length to be changed depending on the purpose of the vehicle. 4 and 2, the front and rear connecting members are realized using a center connector 21-1 and a rear connector 21-2 formed on the body frame 21 of the rear lower section 20.

[0045] As an example, the center connector 21-1 of the rear lower section 20 places the side sill 30 on top of an open space extending from one end of the rear lower section 20. In contrast, the rear connector 21-2 of the rear lower section 20 extends from the opposite end of the rear lower section 20 as a U-shaped open space, and the rear side member 40 is inserted into the upper surface of the open space to be placed and fixed.

[0046] Furthermore, the center connector 21-1 and the side sill 30, and the rear connector 21-2 and the rear side member 40 are fixed together using fastening members 60. In this case, screws (or bolts) are used as the fastening members 60, and the screws (or bolts) are fixed to the side sill 30 and the rear side member 40 using a flow drill screw (FDS) method, which allows for convenient directional joining of dissimilar materials. As an example, the fastening member 60 uses a flow drill screw (FDS) method to insert a plurality of screws (or bolts) from the center connector 21-1 side, as shown in cross sections AA and BB, through the surface contact portion where the wall surface of the center connector 21-1 and the wall surface of the side sill 30 abut, thereby fixing the center connector 21-1 and the side sill 30. In this case, the side sill 30 can have greater rigidity and durability because the space is divided by the multiple partition ribs 31.

[0047] As an example, the fastening member 60 fixes the rear connector 21-2 and the rear side member 40 by using an FDS (Flow Drill Screw) method, as shown in cross section CC, with multiple screws (or bolts) penetrating the surface contact area where the wall surface of the rear connector 21-2 and the wall surface of the rear side member 40 abut. In particular, the open top structure of the center connector 21-1 is in close contact with the side wall of the center connector 21-1 as shown in cross section AA when the side sill 30 is placed on top, maximizing the support rigidity against external forces applied in the length direction (i.e., lateral direction) of the rear lower 20. In this case, close contact means that a weld is formed in a surface contact state.

[0048] In addition, the "C"-shaped open top space structure of the rear connector 21-2 allows the rear side member 40 to be inserted into the top surface of the open space, and in this inserted state, the end of the rear side member 40 comes into close contact (Z) with the inner wall of the rear connector 21-2 in the inner space of the rear connector 21-2, as shown in cross section DD, thereby maximizing the support rigidity against external forces applied in the longitudinal direction (i.e., lateral direction) of the rear lower 20. Referring to FIG. 5, the bush mounting member is realized by assembling a bush 100 using a center connector 21-1 and a bush mounting hole 23 formed in a body frame 21 of the rear lower section 20.

[0049] As an example, the bush 100 is inserted into the bush mounting hole 23, and the bush shaft 100A passes through the shaft hole of the bush 100, passes through the partition rib 31 of the side sill 30, and is fixed to a bush cap (or bush cap nut) connected to the shaft end. Therefore, as shown in cross section EE, the bush width Lc of the bush 100 is absorbed into the side sill width (S / SILL Width) La of the side sill 30, and this overlapping structure of the bush 100 and the side sill 30 makes it possible to remove the bush width Lc from the vehicle width L formed by the left / right side sills 30A, 30B.

[0050] As a result, as shown in the cross section FF, in the vehicle width L formed by the left and right side sills 30A, 30B, the body frame 1 excludes only the left and right side sill width La in utilizing the battery space width Lb, unlike the conventional case in which the bush width Lc and the left and right side sill width La were excluded, thereby expanding the battery space width Lb. As a result, the high-voltage battery 500 mounted on the body frame 1 has a larger battery space width Lb than conventional batteries, and the battery capacity can be increased compared to conventional batteries under the same conditions.

[0051] Referring to Figure 6, the CTBA mounting member is realized by assembling the CTBA 200 of the rear wheel suspension, the chassis spring 300, and the shock absorber 400 using the trailing arm connection portion 25, the spring seat 27, and the shock absorber connector 29 formed on the body frame 21 of the rear lower 20. As an example, the CTBA 200 forms an approximately "U" shape with the spring mounting portions 200C on the left and right side surfaces relative to the linear axle body, and the trailing arm 200A formed at the bent portion of the spring mounting portion 200C is inserted into the open side space formed in the trailing arm connection portion 25 of the rear lower 20. Then, as shown in cross section GG, bolt 200B is screwed into pinhole 200A of trailing arm 200A through rear lower hole 25A of trailing arm connecting portion 25, thereby assembling and integrating CTBA200 with rear lower 20.

[0052] As an example, shock absorber 400 has its lower end fastened to the side of CTBA 200, and its upper end placed in the open space on the side formed in shock absorber connector 29 of rear lower section 20. Then, as shown in cross section HH, the upper end of shock absorber 400 is positioned in the space of shock absorber connector 29 and fixed with a mounting pin or the like, thereby assembling and integrating chassis shock absorber 400 with rear lower section 20.

[0053] As an example, the chassis spring 300 has its lower end portion placed on the spring mounting portion 200C of the CTBA 200, and its upper end portion to which the spring cup 300A is coupled is placed in the space formed in the spring seat 27 of the rear lower 20. As a result, as shown in cross section II, the upper end portion of the chassis spring 300 is placed together with the spring cup 300A and surrounded by the cup-shaped structure of the spring seat 27, whereby the chassis spring 300 is assembled and integrated with the rear lower 20.

[0054] Referring to Figure 7, when the chassis spring 300 is positioned between the spring mounting portion 200C of the CTBA 200 and the spring seat 27 of the rear lower 20, the spring seat 27 swages the cup-shaped structure and engages with the outer diameter of the spring cup 300A. As described above, the side connecting member 10 applied to the body frame 1 according to this embodiment forms a connecting section connecting the side sill 30, which forms the framework of the middle section of the vehicle, and the rear side member 40, which forms the framework of the rear section of the vehicle, by using the body frame 21 of a predetermined length with a height difference so as to form the rear lower ground clearance H, and includes the rear lower 20 in which front and rear connecting members 21-1, 21-2 that secure the side sill 30 and rear side member 40, which form the battery space Lb, bush mounting members 21-1, 23 that fasten the bush 100, and CTBA mounting members 25, 27, 29 that mount the rear wheel suspension device are integrated with the body frame 21.

[0055] Therefore, the side connecting member 10 has a part-integrated rear lower structure using die casting, which simplifies the structure, making it possible to reduce weight, reduce material costs, and ensure the rigidity of the CTBA (Coupled Torsion Beam Axle) 200.In particular, the moldability of the die-cast to suit the size of the rear lower 20 makes it easy to change according to the design intent of the PBV (Purpose Built Vehicle). [Explanation of symbols]

[0056] 1 Body frame 6 Rear bumper back beam 10 Side connecting member 20 Rear lower 21 Body Frame 21A horizontal body 21B, 21C left / right vertical body 21-1 Center connector 21-2 Rear connector 23 Bush mounting holes 25 Trailing arm connection part 25A rear lower hole 27 Spring seat 29 Shock absorber connector 30 Side sill 30A, 30B Left / Right Side Sill 31 Compartment Rib 40 Rear side member 40A, 40B Left / right rear side members 50 Center extrusion 60 Fastening members 100 Bush 100A bushing shaft 200 CTBA(Coupled Torsion Beam Axle) 200A trailing arm 200B bolts 200C spring rest 300 Chassis spring 300A Spring Cup 400 shock absorber 500 batteries

Claims

1. It comprises a body frame of a predetermined length having one end and an opposite end, The body frame includes a front / rear connecting member that connects a side sill at one end and connects a rear side member at the other end; a bush mounting member having a bush attached to one end thereof; The opposite end of the bearing is integrally formed with a CTBA (Coupled Torsion Beam Axle) mounting member to which one or more of a CTBA, a chassis spring, and a shock absorber are fastened, The CTBA mounting member is a trailing arm connector protruding from the one side end to form a side open space so that a portion of the CTBA can be inserted into the side; a spring seat protruding from a lower surface of the opposite end portion to form an open lower space so that an upper portion of the chassis spring can be inserted therein; a shock absorber connector that forms a side open space on the side of the opposite end so that an upper portion of the shock absorber can be inserted into the side.

2. The body frame is made of aluminum, 2. The integrated-parts type rear lower section according to claim 1, wherein the front and rear connecting members, the bush mounting member, and the CTBA mounting member are integrally formed by die casting.

3. The integrated rear lower section according to claim 1 , wherein the body frame has a height difference between the one side end and the opposite side end, thereby forming a rear lower ground clearance.

4. 2. The integrated rear lower section according to claim 1, wherein the body frame has an "H" cross-sectional structure.

5. The front and rear connecting members are a center connector on which the side sill is placed in an upper open space extending from the one side end; 2. The integrated-parts type rear lower section according to claim 1, further comprising: a rear connector extending from the opposite end as an open space, the rear side member being inserted into an upper surface of the open space.

6. 6. The integrated rear lower section according to claim 5, wherein the rear connector has an inner wall formed in a side direction relative to an upper surface into which the rear side member is inserted so that the end surface of the rear side member comes into close contact with the rear connector.

7. 2. The integrated rear lower section according to claim 1, wherein the bush mounting member comprises a bush mounting hole drilled in a center connector extending from the one side end to form an open upper space so that the side sill can be placed thereon.

8. The integrated rear lower assembly according to claim 1 , wherein the trailing arm connecting portion has a rear lower hole for screwing with a bolt fastened to a portion of the CTBA.

9. 2. The integrated rear lower section according to claim 1, wherein the side sill has an extruded material structure.

10. a side sill that forms the framework of the middle section of the vehicle and extends into a battery space where a battery is installed; A rear side member that forms the framework of the rear section of the vehicle; and a rear lower section comprising a body frame of a predetermined length having a height difference so as to form a rear lower ground clearance, wherein a connecting section between the side sill and the rear side member is formed by a front and rear connecting member, a fastening portion between the side sill and a bush is formed by a bush mounting member, and a fastening portion of a rear wheel suspension is formed by a CTBA (Coupled Torsion Beam Axle) mounting member, The rear wheel suspension device includes a CTBA (Coupled Torsion Beam Axle), a chassis spring, and a shock absorber, the CTBA mounting member is fastened to one or more of the CTBA, the chassis spring, and the shock absorber; The CTBA mounting member is a trailing arm connection portion protruding from a side of the body frame to form a side open space into which the trailing arm of the CTBA is inserted at a connection section of the side sill; a spring seat protruding from a lower surface of the body frame to form a lower open space into which an upper portion of the chassis spring located in a spring mounting portion of the CTBA is inserted in a connecting section of the rear side member; a shock absorber connector recessed into one side of the body frame to form a side open space in the connecting section of the rear side member into which an upper portion of the shock absorber is inserted.

11. the rear lower is made of aluminum, 11. The vehicle body frame according to claim 10, wherein the front and rear connecting members, the bush mounting members, and the CTBA mounting members are integrated with the body frame by die casting.

12. 11. The vehicle body frame according to claim 10, wherein the front and rear connecting members fix the side sills and the rear side members together with fastening members.

13. 13. The vehicle body frame according to claim 12, wherein the fastening members are fixed to the side sills and the fastening members are fixed to the rear side members by an FDS (Flow Drill Screw) method.

14. The front and rear connecting members are a center connector on which a portion of the side sill is placed in an upper open space formed by extending the body frame in a connecting section of the side sill; 13. The vehicle body frame according to claim 12, further comprising: a rear connector that extends the body frame as an open space in a connecting section of the rear side member, and into which a portion of the rear side member is inserted onto an upper surface of the open space.

15. 15. The vehicle body frame according to claim 14, wherein the end of the rear side member is in close contact with an inner wall of the rear connector.

16. The side sill has a space divided by a partition rib, 13. The vehicle body frame according to claim 12, wherein the rear side members form an open rectangular cross-section structure or a closed rectangular cross-section structure.

17. The partition rib is fixed to the center connector of the rear lower section by a flow drill screw (FDS) method, 17. The vehicle body frame according to claim 16, wherein the center connector extends from one end of the side sill and is formed as an open space on its top so that the side sill can be placed thereon.

18. The bush mounting member has a bush mounting hole into which the bush is inserted and fixed by a bush shaft, 11. The vehicle body frame according to claim 10, wherein the bush mounting hole in the connecting section of the side sill is formed by drilling a center connector extending from the body frame as an open upper space on which a portion of the side sill is placed.

19. The vehicle body frame according to claim 10, wherein the trailing arm connecting portion has a rear lower hole into which a bolt for fixing the trailing arm is screwed.

20. 11. The vehicle body frame according to claim 10, wherein the spring seat has a cup-shaped structure surrounding an outer diameter of a spring cup provided at an upper end of the chassis spring.

21. The side sills include a left side sill and a right side sill, The vehicle body frame according to claim 10, wherein a distance between the left side sill and the right side sill defines a vehicle width including the battery space.

22. 22. The vehicle frame of claim 21, wherein the left side sill and the right side sill are connected by a center extrusion that extends across the width of the vehicle.

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