Description:TECHNICAL FIELD
[0001] The present disclosure generally relates to sub-frame assemblies of vehicles and more particularly, the present disclosure relates to a rear sub-frame assembly for integrating a five-link suspension system and mounting a rear motor of an electric vehicle.
BACKGROUND
[0002] Conventionally in a vehicle, a rear multi-link suspension system, which is assembled on a rear sub-frame of the vehicle, is achieved typically with a four-link suspension with a control blade design. However, the higher the number of links in the suspension system, the better the kinematic performance of the suspension system. This is because the higher number of links increases the degree of freedom and therefore provides higher flexibility to tune the stiffness of insulator bush stiffness and position hard-points and suspension of the links mounted on the rear sub-frame.
[0003] Although the conventional rear frame assemblies of the prior arts include a five-link suspension system, the integration of the five-link suspension is complex, especially in vehicles with rear wheel drive and all-wheel drive. The complexity of integrating the five-link suspension system with the rear sub-frame of the vehicle increases in electric vehicles, specifically in electric sport utility vehicles wherein an additional motor is required to be mounted onto the rear sub-frame within the available packaging space. Therefore, the rear sub-frame in such vehicles needs to be designed to accommodate the rear motor as well as include multiple hard-points for mounting links of the suspension system on the sub-frame.
[0004] While a complicated design of the rear sub-frame facilitates accommodating multiple hard-points and mounting space for the rear motor, the ease of manufacturing is compromised. This also results in an increase in initial and production costs of manufacturing the rear-sub frame. Therefore, it becomes difficult to achieve a cost-effective rear sub-frame without compromising on the stiffness, weight and ride quality of the vehicle.
[0005] The prior arts employ an aluminium rear sub-frame in order to offer design flexibility and better packaging of the 5-link suspension system. Alternatively, the rear sub-frame can also be made up of cast iron to attain the same design flexibility and higher stiffness, although with a higher weight. The aluminium sub-frame is integrated with all the brackets and mounts for mounting the links, therefore, providing a robust alternative with better stiffness and lower weight. Further, the sub-frame is machined at critical points such as joineries, making the assembly of the links of the suspension system easier while ensuring accuracy of dimensional control. Therefore, aluminium sub-frames are preferred over cast-iron sub-frames.
[0006] However, there are major drawbacks of the aluminium rear sub-frame. Firstly, the initial investment for setting up the dies for pressure casting of the aluminium sub-frame is high. Secondly, the manufacturing cost is higher proportional to the weight of the aluminium material used for rear sub-frame pressure casting. Hence it is challenging to achieve design flexibility, stiffness and lower weight of the sub-frame with a lower manufacturing cost.
[0007] Therefore, there is a requirement for a rear sub-frame assembly which can integrate a multi-link suspension system as well as accommodate a motor, has lower manufacturing cost, and provides flexibility in design by allowing versatility in placing of hard-points for mounting of links of the suspension system on the sub-frame.
OBJECTS
[0008] The principal object of an embodiment of this invention is to provide a rear frame sub-assembly for integrating a multi-link suspension system and mounting a rear motor in an electric vehicle.
[0009] Another object of an embodiment of this invention is to provide the rear sub-frame assembly which provides flexibility and versatility in positioning of hard points for mounting of links of the multi-link suspension system.
[0010] Yet another object of an embodiment of this invention is to provide the rear sub-frame assembly that defines a skewed profile whereby a front cross member and a rear cross member of the sub-frame are positioned at a differential height along a Z-axis.
[0011] Still another object of an embodiment of this invention is to provide the rear sub-frame assembly which includes a front cross member having a skewed profile.
[0012] Yet another object of an embodiment of this invention is to provide the rear-sub-frame assembly which is made of sheet metal.
[0013] Another object of an embodiment of this invention is to provide the rear sub-frame assembly which provides flexibility in positioning of hard-points on a sub-frame structure without affecting the strength of the rear sub-frame structure.
[0014] Still another object of an embodiment of this invention is to provide the rear sub-frame assembly in which the differential height of the front and rear cross members along Z-axis and the skewed profile of the front cross member facilitates in accommodating interfacing parts of the vehicle for better packaging.
[0015] Yet another object of an embodiment of this invention is to provide the rear sub-frame assembly which provides flexibility in placing hard-points on the sub-frame structure, thereby enhancing the kinematic and dynamic performance of the vehicle.
[0016] Another object of an embodiment of the invention is to provide the rear sub-frame assembly which allows mounting of a lower control arm at an overhanging position from the rear cross member, therefore enhancing drive and handling performance by providing design flexibility in spring and damper of the suspension system.
[0017] Still another object of an embodiment of this invention is to provide the rear sub-frame assembly which is a low-cost solution for integrating five-link suspension system with a rear motor on the sub-frame.
[0018] These and other objects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.
BRIEF DESCRIPTION OF DRAWINGS
[0019] The embodiments herein are illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various Figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:
[0020] Fig. 1 is a perspective view of a conventional rear sub-frame assembly with a four-link suspension system having a control blade design;
[0021] Fig. 2 is an isometric view of a rear sub-frame assembly for integrating a five-link suspension system and mounting a motor, according to an embodiment of the invention as disclosed herein;
[0022] Fig. 3 is a perspective view of the rear sub-frame assembly from a rear side, according to an embodiment of the invention as disclosed herein;
[0023] Fig. 4 is another perspective view of the rear sub-frame assembly from the rear side, according to an embodiment of the invention as disclosed herein;
[0024] Fig. 5 depicts a top view of the rear sub-frame assembly, according to an embodiment of the invention as disclosed herein;
[0025] Fig. 6 is a side view of the rear sub-frame assembly depicting a height difference H1 along a Z-axis between a front sub-frame mounting sleeve and a rear sub-frame mounting sleeve, according to an embodiment of the invention as disclosed herein;
[0026] Fig. 7 is a front view of the rear sub-frame assembly depicting a skewed profile S1 of a front cross member of the rear sub-frame assembly, according to an embodiment of the invention as disclosed herein;
[0027] Fig. 8 is a rear view of the rear sub-frame assembly depicting an overhang H2 of a lower arm mounting, according to an embodiment of the invention as disclosed herein; and
[0028] Fig. 9 is a perspective view of the rear sub-frame assembly depicting a plurality of hard-points on the rear sub-frame structure corresponding to the links of the suspension system, according to an embodiment of the invention as disclosed herein.
DETAILED DESCRIPTION
[0029] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
[0030] The embodiments herein achieve a rear sub-frame assembly for integrating a multi-link suspension system and mounting a rear motor of an electric vehicle. Further, the embodiments herein achieve the rear sub-frame assembly which provides flexibility and versatility in positioning of hard-points for mounting links of the multi-link suspension system, therefore enhancing kinematic and dynamic performance of the vehicle. Furthermore, the embodiments herein provide the rear sub-frame assembly in which cross members of the sub-frame are positioned at a differential height along Z -axis resulting in a skewed sub-frame structure. The embodiments herein achieve the rear sub-frame assembly in which the front cross member has a skewed profile. Further, the embodiments herein achieve the rear sub-frame assembly which enables accommodating interfacing parts of the vehicle for better packaging due to the differential height of the front and rear cross members and the skewed profile of the front cross member. Furthermore, the embodiments herein achieve the rear sub-frame assembly which enables overhanging of a lower control arm hard-point from the rear cross member, therefore, enhancing drive performance of the vehicle. Additionally, the embodiments herein achieve the rear sub-frame assembly which is made of sheet metal, thus reducing the manufacturing cost of the rear sub-frame assembly. Referring now to the drawings, and more particularly to FIGS. 1 through 9, where similar reference characters denote corresponding features consistently throughout the Figures, there are shown embodiments.
[0031] Fig. 1 depicts a conventional rear sub-frame assembly (100) with a four-link suspension system (102) having a control blade design integrated with a sub-frame structure (101). In the conventional rear sub-frame assembly (100), the sub-frame structure (101) may or may not include a mounting space for mounting a rear motor depending on the type of vehicle. An electric vehicle with a rear wheel or all-wheel drive requires an additional motor to be mounted on the rear sub-frame of the vehicle. In such vehicles, the sub-frame structure (101) is required to be designed to include a mounting space for the rear motor. Further, the conventional rear sub-frame assembly (100) includes two cross members and two longitudinal members attached between the two cross members. The cross members and the longitudinal members have a straight and flat profile to achieve higher strength and sturdiness of the sub-frame. Due to the straight profile of the members in the conventional rear sub-frame assembly (100), there is a limitation on positioning of hard points on the sub-frame structure (101) for mounting of links of the suspension system (102). Therefore, such sub-frames lack versatility and flexibility in design by limiting the hard point locations.
[0032] Fig. 2 is a perspective view of a rear sub-frame assembly (200) for integrating a multi-link suspension system and mounting a motor of an electric vehicle. The suspension system includes multiple links, wherein an inboard hard-point (not shown) for mounting a link is provided on the sub-frame structure (200A) and an outboard hard point (not shown) for connecting the link to a rear wheel (not shown) is provided on a knuckle (not shown) of the rear wheel of the vehicle. In an embodiment, the rear sub-frame assembly (200) is adapted to integrate a five-link suspension system comprising a front upper link, a front lower link, a rear upper link, a lower control arm, and a toe link. As shown in Fig.9, a hard-point is designed/located on the sub-frame structure (200A) for mounting each link on the sub-frame structure (200A) and the inboard point of the link is attached onto the sub-frame structure (200A) via a corresponding mounting bracket or mounting slot at the designated hard-point. The number of hard points available for mounting links of the suspension system on the sub-frame structure (200A) has a direct effect on the performance of the vehicle. The higher the number of hard points provided on the sub-frame structure (200A), the higher is the flexibility in positioning of the links. Higher flexibility results in better performance of the links and collectively of the suspension system, thereby providing better comfort to a passenger and enhancing the kinematic performance of the vehicle.
[0033] According to an embodiment of the invention, as shown in Figs.2 and 4, the rear sub-frame assembly (200) comprises a sub-frame structure (200A), a plurality of mountings (204, 205, 206, 207, 208) provided on corresponding hard points for mounting a plurality of links of the multi-link suspension system, at least four mounting sleeves (209) integrated with the sub-frame structure (200A) at four ends of the sub-frame structure (200A) for enabling mounting of the rear sub-frame assembly (200) onto a body of the vehicle, and a plurality of motor mounting brackets (201A, 202A) for mounting of the motor on the sub-frame structure (200A). The sub-frame structure (200A) comprises a front cross member (201), a rear cross member (202) disposed parallelly from the front cross member (201) towards a rear side of the vehicle, a left side longitudinal member (203L) and a right-side longitudinal member (203R), each of the longitudinal members (203L,203R) is connected transversely to the front and rear cross members (201, 202), such that a mounting space (M) is created at the center of the sub-frame structure (200A) for mounting the motor.
[0034] In an embodiment, the front cross member (201) and the rear cross member (202) are positioned/ disposed at a differential height H1 along a Z-axis wherein each of the longitudinal members (203L, 203R) is adapted to connect the front cross member (201) and the rear cross member (202) at the differential height H1. In an embodiment, the front cross member (201) is positioned at a height lower than the rear cross member (202), wherein the longitudinal members (203L, 203R) include a sloping portion positioned towards a front end of the longitudinal members (203L,203R). However, it is within the scope of this invention to provide the sub-frame structure (200A) wherein the rear cross member (202) is positioned at a lower height than the front cross member (201), wherein the sloping portion of the longitudinal members (203) is positioned towards a rear end of the longitudinal members (203). Fig. 6 depicts the longitudinal member (203), wherein the longitudinal member (203) has the sloping portion such that a front mounting sleeve (209F) of the rear sub-frame assembly (200) is positioned at the differential height H1 along the Z axis from the rear mounting sleeve (209R). In an embodiment the differential height H1 is 80mm. The placement of the front cross member (201) and the rear cross member (202) at differential height H1 provides greater flexibility in positioning the link hard-points on the sub-frame structure (200A).
[0035] In an embodiment of the invention, as shown in Fig. 7, the front cross member (201) has a skewed profile S1, wherein a mid-section of the front cross member (201) is positioned lower than end sections of the front cross member (201). In an embodiment of the invention a skew of the middle section of the front cross member (201) with respect to the end sections of the cross members (201, 202) is 80mm. The skewed profile S1 of the front cross member (201) provides better packaging space by accommodating interfacing parts placed at a rear side of the vehicle. In an embodiment, the skewed profile S1 of the front cross member (201) is adapted to provide packaging space for a wiring harness and coolant hose passage of the vehicle. In another embodiment, the skewed profile S1 of the front cross member (201) is adapted to create a space between terminals of a battery connector of the electric vehicle. In an embodiment, the front cross member (201) includes a plurality of reinforcing supports (not shown) inserted within an interior portion of the front cross member (201) to increase the strength of the front cross member (201).
[0036] In an embodiment, as shown in Figs. 2, 3 and Fig. 9, the rear sub-frame assembly (200) includes the plurality of mountings (204, 205, 206, 207, 208) for mounting links of the five-link suspension system corresponding to the inboard hard points of the links provided on the sub-frame structure (200A). The plurality of mountings (204, 205, 206, 207, 208) include a front upper link mounting bracket (204) attached to each of the longitudinal members (203L, 203R) at a predetermined position corresponding to the designated hard point (204h) of the front upper link, a front lower link mounting bracket (205) disposed on each of the longitudinal members (203L, 203R) at predetermined positions corresponding to the designated hard points (205h), a rear upper link mounting bracket (206) connected to each of the longitudinal members (203L, 203R) at the designated hard points (206h), a lower control arm mounting slot (208) provided at a rear side of the sub-frame structure (200A) in communication with the rear cross member (202) at the predetermined hard point (207h), and a toe link mounting slot (207) provided at the rear side of the sub-frame structure (200A) at the pre-determined hard point (208h).
[0037] In an embodiment, the front upper link mounting bracket (204) is attached at an upper surface of the longitudinal members (203L, 203R) towards the front end of the longitudinal member (203L, 203R), the front lower link mounting bracket (205) is mounted at a bottom surface of the longitudinal members (203L, 203R) towards a front end of the longitudinal member (203L, 203R). Further, the rear upper link mounting bracket (206) is connected at a middle section of the longitudinal member (203L, 203R). The toe link mounting slot (207) is provided at the rear side of the sub-frame structure (200A), positioned below the rear cross member (202) and on a portion defined between the rear cross member (202) and a lower rear cross member (202B). The lower control arm mounting slot (208) is disposed on a portion defined between the two rear cross members (202, 202B) and below the toe link mounting slot (207). In an embodiment, the hard-point location of the lower control arm is located at an overhang H2 of 160mm from the rear mounting sleeve (209R) of the rear sub-frame assembly (200). The placement of the rear cross member (202) at the differential height H1 from the front cross member (201) provides the flexibility of positioning the hard-points of the links at multiple and varied positions than possible in a conventional rear sub-frame assembly (100). This design flexibility in providing the hard points for the links enhances the kinematic and dynamic performance of the vehicle, thereby enhancing passenger comfort.
[0038] In an embodiment of the invention the rear-sub frame assembly includes two motor mounting brackets (201A) attached to the front cross member (201) towards each of the end of the front cross member (201), and a rear motor mounting slot (202A) provided at the portion defined between the rear cross member (202) and the lower cross member (202B), at a middle section of the rear cross member (202). The two motor mounting brackets (201A) and the rear motor mounting slot (202A) are provided to support the mounting of the rear motor onto the rear sub-frame structure (200A) at the space defined at the center of the rear sub-frame structure (200A).
[0039] The rear sub-frame structure (200A), according to an embodiment, is adapted to be made of sheet metal. Use of sheet metal in fabrication of the rear sub-frame structure (200A) lowers the initial costs incurred in creation of dyes for casting operations, and also enables to lower the subsequent production cost due to the ease of manufacturing process.
[0040] The technical advantages achieved by the embodiments disclosed herein include flexibility and versatility in positioning of hard-points for mounting of links of the multi-link suspension system on the sub-frame, therefore enhancing the kinematic and dynamic performance of the vehicle. The skewed profile of the rear sub-frame structure enables accommodating of interfacing parts and provides better packaging of the parts. Further, the placement of the hard-point for mounting the lower control arm of the suspension system in an overhanging position from the rear cross member enhances ride and handling performance of the vehicle. Furthermore, the rear sub-frame assembly is adapted to be made of sheet metal, therefore lowers the cost of manufacturing of the rear sub-frame assembly.
[0041] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
, Claims:1. A rear sub-frame assembly (200) for integrating a multi-link suspension system and mounting a motor of an electric vehicle, the rear sub-frame assembly (200) comprising:
a sub-frame structure (200A), the sub-frame structure (200A) comprising:
a front cross member (201) and a rear cross member (202) disposed parallel to each other in a spaced relation; and
a left side longitudinal member (203L) and a right-side longitudinal member (203R) connecting the front cross member (201) and the rear cross member (202),
wherein,
the front cross member (201) defines a skew profile S1 such that the front cross member (201) is at a height H1 below the rear cross member along a Z-axis of the sub-frame structure (200A); and
the sub-frame structure (200A) defines a space M at a center of the sub-frame structure (200A) for mounting the motor.

2. The rear sub-frame assembly (200) as claimed in claim 1, wherein the skewed profile S1 includes a middle section of the front cross member (201) positioned lower than each of an end section of the front cross member (201) at a differential height.

3. The rear sub-frame assembly (200) as claimed in claim 1, wherein a plurality of mountings (204,205,206,207,208) is connected to the sub-frame structure (200A) and the plurality of mountings (204, 205, 206, 207, 208) are adapted to facilitate mounting of the plurality of the links on the sub-frame structure (200A) at predetermined positions corresponding to hard-points (204h, 205h, 206h, 207h, 208h) of a plurality of links of the multi-link suspension system.
4. The rear sub-frame assembly (200) as claimed in claim 2, wherein a difference in height of the middle section and the end sections of the front cross member (201) due to the skewed profile S1 of the front cross member (201) ranges between 0 mm to 120 mm.

5. The rear sub-frame assembly (200) as claimed in claim 1, wherein a plurality of reinforcing supports is disposed within an interior portion of the front cross member (201), the plurality of reinforcing supports configured to increase strength and rigidity of the front cross member (201).

6. The rear sub-frame assembly (200) as claimed in claim 1, wherein the rear cross member (202) is disposed at a higher height with respect to the front cross member (201), wherein the differential height H1 is 80mm.

7. The rear sub-frame assembly (200) as claimed in claim 1, wherein the longitudinal members (203R, 203L) are adapted to have a sloping portion positioned towards a front end of the longitudinal members (203).

8. The rear sub-frame assembly (200) as claimed in claim 1, wherein the rear sub-frame assembly (200) comprises four mounting sleeves (209) connected to the sub-frame structure (200A), the mounting sleeves (209) provided for mounting the rear sub-frame assembly (200) on a body of the electric vehicle, wherein:
two front mounting sleeves (209F) are connected to the front cross member (201) at each end of the front cross member (201);
other two rear mounting sleeves (209R) are connected to the rear cross member (202) at each end of the rear cross member (202); and
the front mounting sleeves (209F) are positioned at the height H1 from the rear mounting sleeves (209R), the rear mounting sleeves (209R) positioned higher with respect to the front mounting sleeves (209F).

9. The rear sub-frame assembly (200) as claimed in claim 1, wherein the rear sub-frame assembly (200) is configured to integrate a five-link suspension system comprising a front upper link, a front lower link, a rear upper link, a lower control arm, and a toe link.

10. The rear sub-frame assembly (200) as claimed in claim 9, wherein a plurality of mountings (204, 205, 206, 207) comprises:
a front upper link mounting bracket (204) attached to each of the longitudinal members (203L, 203R) at a position corresponding to a front upper link hard point (204h);
a front lower link mounting bracket (205) attached to each of the longitudinal members (203L, 203R) at a position corresponding to a front lower link hard point (205h);
a rear upper link mounting bracket (206) attached to each of the longitudinal members (203L, 203R) at a position corresponding to a rear upper link mounting hard point (206h);
a toe link mounting slot (207) disposed at a rear side of the sub-frame structure (200A) and connected to the rear cross member (202) at a position corresponding to a lower control arm hard point (207h); and
a lower control arm mounting slot (208) disposed at the rear side of the sub-frame structure (200A) at a position corresponding to a toe link hard point (208h).

11. The rear sub-frame assembly (200) as claimed in claim 10, wherein,
the front upper link mounting bracket (204) is attached at an upper surface of the longitudinal members (203) towards a front end of the longitudinal members (203);
the front lower link mounting bracket (205) is attached at a lower surface of the longitudinal members (203) towards the front end of the longitudinal members (203);
the rear upper link mounting bracket (206) is attached to the upper surface, at middle portion of the longitudinal members (203);
the toe link mounting slot (207) is disposed below the rear cross member (202) on a portion defined between the rear cross member (202) and a lower rear cross member (202B); and
the lower control arm mounting slot (208) is disposed on the portion defined between the rear cross member (202) and the lower rear cross member (202B), positioned below the toe link mounting slot (207).

12. The rear sub-frame assembly (200) as claimed in claim 11, wherein the lower control arm mounting slot (208h) is disposed at an overhanging position H2 from the rear cross member (202), wherein the overhanging position H2 of the lower control arm hard-point (208h) is 160 mm below the rear cross member (202).

13. The rear sub-frame assembly (200) as claimed in claim 1, wherein the sub-frame structure (200A) is adapted to be made of sheet metal.

14. The rear sub-frame assembly (200) as claimed in claim 1, wherein the rear sub-frame assembly (200) comprises a plurality of motor mounting brackets (201A, 202A) connected to the sub frame structure (200A) at predetermined positions, said mounting brackets (201A, 202A) facilitates mounting of the motor on the sub-frame structure (200A).

15. The rear sub-frame assembly (200) as claimed in claim 14, wherein the plurality of motor mounting brackets (201A, 202A) comprise:
two motor mounting brackets (201A) mounted at each end of the front cross member (201); and
a rear motor mounting slot (202A) disposed between the rear cross member (202) and a lower rear cross member (202B).