FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
AND
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See Section 10; rule 13)
TITLE OF THE INVENTION CHASSIS FRAME STRUCTURE FOR A VEHICLE
APPLICANT(S)
TATA MOTORS LIMITED
an Indian Company
Bombay House, 24 Homi Mody Street,
Hutatma Chowk, Mumbai 400 001,
Maharashtra, India.
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed.

CHASSIS FRAME STRUCTURE FOR A VEHICLE
FIELD OF THE INVENTION
[0001] The present disclosure relates in general to the field of automobiles. Particularly, but not exclusively, the present disclosure relates to a chassis frame structure of an electric bus, which is designed with a flat floor construction. This invention is not limited to electric buses, but it is particularly useful in this context.
BACKGROUND OF THE INVENTION
[0002] Buses are the favored mode of public transportation, and their design must prioritize the convenience of passengers boarding and disembarking, as well as accommodating standees and their frequent movement during travel. This necessitates a structure with a low floor height and flat gangway. The current invention presents a distinctive frame structure that fulfills both of these requirements for electric buses.
[0003] The current bus design employs a vertically cranked frame with a sloped gangway or an entirely elevated floor to accommodate the rear axle's travel during articulation. This design necessitates a vertically cranked frame above the rear axle to ensure sufficient clearance with the floor, making a flat floor unfeasible. Consequently, standing passengers experience discomfort, and passenger movement within the bus is impeded. Therefore, it is imperative to address this issue to enhance passenger comfort and make it a more viable transportation solution for the public.
[0004] The present disclosure is directed to overcome one or more limitations stated above or any other limitations associated with the conventional systems.

OBJECTS OF THE INVENTION
[0005] The principal object of the embodiments herein is to provide a chassis frame structure for a vehicle.
[0006] Another object of the embodiments herein is to provide arrangement of motor and flat rear axle at a center to allow flat floor construction inside the inner space in the vehicle.
[0007] Yet another object of the embodiments herein is to provide a chassis frame design to provide uniform flat floor inside the vehicle. This chassis frame structure comprises a two-piece frame with straight front and rear assemblies featuring a joggle. The motor assembly with porter axle is positioned below the cross member in the rear assembly. The joggle frame allows for the motors to be placed sideways, ensuring the achievement of a uniformly flat floor.
SUMMARY OF THE INVENTION
[0008] In an aspect the objects are achieved by providing a chassis frame structure for a vehicle. The chassis frame structure includes a front assembly having a left-hand front member and a right-hand front member joined together by a plurality of front cross members. The front assembly is a straight assembly. The chassis frame structure includes a rear assembly with joggle on a horizontal plane. The rear assembly comprises a left-hand rear member and a right-hand rear member joined together by a plurality of rear cross members. The chassis frame structure includes a joint assembly joining the front assembly with rear assembly in the horizontal plane. Further, the chassis frame structure includes a portal axle placed in the rear assembly just below at least one rear cross member of the plurality of rear cross members.

[0009] In an embodiment, each front cross member of the plurality of front cross members are located at a defined distance as per the overall strength requirement of the front assembly.
[0010] In an embodiment, each of the front cross members are located at the defined distance is in a range of 300 mm -600 mm of the front assembly.
[0011] In an embodiment, each rear cross member of the plurality of rear cross members are located at a defined distance as per the overall strength requirement of the rear assembly.
[0012] In an embodiment, each of the rear cross members are located at the defined distance is in a range of 300 mm -600 mm of the front assembly.
[0013] In an embodiment, the joggle is provided towards a centre plane of the vehicle by an amount so as to maintain a minimum clearance of 30 mm with axle parts in a static condition of the vehicle.
[0014] In an embodiment, the rear assembly with joggle enables a flat floor construction in the vehicle.
[0015] In an embodiment, the portal axle comprises a left-hand motor assembly and a right-hand motor assembly.
[0016] In an embodiment, the joggle in the rear assembly provides sufficient clearance with the left-hand motor assembly and the right-hand motor assembly.
[0017] In an embodiment, the joggle in the rear assembly provides clearance for the portal axle which drives wheels of the vehicle.

[0018] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
[0019] The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present subject matter in any way.
[0020] FIG. 1 is a perspective view of a chassis frame structure of a vehicle, according to embodiments as disclosed herein.
DETAILED DESCRIPTION OF THE INVENTION
[0021] Reference will now be made in detail to various embodiments of the present subject matter, examples of which are illustrated in the accompanying drawings and described below. While the present subject matter will be described in conjunction with exemplary embodiments, it will be understood that present description is not intended to limit the present subject matter to those exemplary embodiments. On the contrary, the present subject matter is intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents, and other embodiments, which may be included within the scope of the invention.
[0022] Embodiments herein provide a chassis frame structure for a vehicle. The chassis frame structure includes a front assembly having a left-hand front member and a right-hand front member joined together by a plurality of front cross members. The front assembly is a straight assembly. The chassis frame structure includes a rear assembly with joggle on a horizontal plane. The rear assembly comprises a left-hand rear member and a right-hand rear member joined together by a plurality of rear cross members. The chassis frame structure includes a joint

assembly joining the front assembly with rear assembly in the horizontal plane. Further, the chassis frame structure includes a portal axle placed in the rear assembly just below at least one rear cross member of the plurality of rear cross members.
[0023] The present invention pertains to a Porter E axle packaging with a joggled frame, which achieves a uniform flat floor throughout the inside of the bus. As outlined in the background section, existing buses utilize a rear axle with a crown and pinion arrangement at the center, resulting in a vertical hump on the long member to clear axle movement in articulation. This causes a slope in the floor above the rear axle, making a flat floor unattainable and elevating the floor instead. This inconvenience standee passengers and hinders passenger movement inside the bus.
[0024] The present invention addresses these concerns of passenger comfort inside the bus by providing a more suitable mobility solution for public transport. It describes a unique frame structure to meet the requirements for EV buses. In EV bus porter axles, which comprise two separate motors at both axle ends, the conventional straight frame cannot be used due to the side-wise positioning of the motors. Therefore, a joggle frame is designed to package these porter axles, offering a flat gangway construction.
[0025] The terms “comprises”, “comprising”, or any other variations thereof used in the specification, are intended to cover a non-exclusive inclusion, such that an assembly that comprises a list of components or steps does not include only those components or steps but may include other components or steps not expressly listed or inherent to such setup or method. In other words, one or more elements in an assembly proceeded by “comprises… a” does not, without more constraints, preclude the existence of other elements or additional elements in the assembly.

[0026] The flat floor construction of the chassis frame structure offers several advantages, such as ease of access for passengers, greater comfort, and increased safety. This disclosure presents a detailed description of the electric bus chassis frame structure with a flat floor construction, along with its various features and benefits. The invention is expected to have a significant impact on the automobile industry, particularly in the area of public transportation.
[0027] Henceforth, the present disclosure is explained with the help of one or more figures of exemplary embodiments. However, such exemplary embodiments should not be construed as limitation of the present disclosure. In the figures neither the vehicle nor the complete chassis frame structure of an electric vehicle is depicted for the purpose of simplicity. The chassis frame structure of any vehicle including but not limiting to passenger vehicles, commercial vehicles, electric vehicle and the like.
[0028] FIG. 1 is a perspective view of a chassis frame structure of a vehicle, according to embodiments as disclosed herein. The chassis frame structure includes a front assembly (17), a rear assembly (18), a joint assembly (21) joining the front assembly (17) with rear assembly (18) in a horizontal plane, and a portal axle (16) placed in the rear assembly (18) just below a rear cross members.
[0029] The front assembly (17) includes a left-hand front member (1) and a right-hand front member (2) joined together by front cross members (3-8). The front assembly (17) is a straight assembly. Each of the front cross members (3-8) are located at a defined distance as per the overall strength requirement of the front assembly (17). In an embodiment, each of the front cross members (3-8) are located at the defined distance is in a range of 300-600 mm based on the overall strength requirement such as a tortional rigidity , a von mises stress distribution, a bending rigidity, etc. This distance range is determined based on various strength requirements, such as, but is not limited to, torsional rigidity, von Mises stress distribution, and bending rigidity. These strength requirements are important for

ensuring that the overall structure of the vehicle is strong and able to withstand various forces and stresses.
[0030] The front assembly (17) is designed to provide stability and support for the vehicle or machinery, particularly in the front section where impacts or other stresses may occur. The use of the straight assembly and carefully positioned cross members suggests that this design may be optimized for strength and durability, which could be important in applications where the vehicle or machinery is subjected to heavy use or harsh conditions.
[0031] The front assembly (17) is made up of two front members - the left-hand front member (1) and the right-hand front member (2). These two members are joined together by the front cross members (3-8), which are positioned at specific distances from each other to ensure that the overall strength requirements of the front assembly (17) are met. The front cross members (3-8) are connected to the left-hand front member (1) and the right-hand front member (2) using mechanical joints.
[0032] The rear assembly (18) with joggle on the horizontal plane, The rear assembly (18) includes a left-hand rear member (14) and a right-hand rear member (15) joined together by the rear cross members (9-13). Each of the rear cross members (9-13) are located at a defined distance as per the overall strength requirement of the rear assembly (18). In an embodiment, each of the rear cross members (9-13) are located at the defined distance is in a range of 300-600 mm based on the overall strength requirement. This distance is determined based on the overall strength requirements of the structure, including factors such as, but is not limited to, torsional rigidity, von Mises stress distribution, and bending rigidity. These factors are important considerations in designing a strong and stable structure of the vehicle that can withstand various stresses and forces.

[0033] The rear assembly (18) is made up of two rear members - a left-hand rear member (14) and a right-hand rear member (15). These two members are joined together by rear cross members (9-13), which are positioned at specific distances from each other to ensure that the overall strength requirements of the rear assembly (18) are met. The joggle on the horizontal plane refers to a type of joint or connection between the left-hand and right-hand rear members that helps to provide additional stability and strength to the entire rear assembly. The rear cross members (9-13) are connected to the left-hand rear member (14) and the right-hand rear member (15) using the mechanical joints.
[0034] The joggle is provided towards a centre plane of the vehicle by an amount so as to maintain a minimum clearance of 30 mm with axle parts in a static condition of the vehicle. The rear assembly (18) with joggle enables a flat floor construction in the vehicle. The floor is flat and does not have any bumps or raised areas. For example, the flat floor measures 2400 X 900 mm in size. Without this feature, a ramp would need to be provided in order to compensate for any unevenness in the floor.
[0035] The joggle refer is a type of bend in the straight front assembly (17). This bend is unique in that it does not require any joints or connections to be made in the rear assembly. Additionally, the joggle is positioned towards the center plane of the vehicle, which has implications for the overall design and functionality of the vehicle. The purpose of this positioning is to maintain a minimum clearance of 30 mm or 50 mm with the axle parts of the vehicle, even when the vehicle is in a static (non-moving) condition. This clearance is important to prevent any unwanted contact or interference between the joggle and the axle parts.
[0036] The rear assembly (15) of the vehicle includes this joggle which allows for a flat floor construction in the vehicle. This means that the floor of the vehicle will be level and free from any obstructions or protrusions, which can be beneficial for passengers or cargo. The joggle is a key component in achieving this flat floor

design, as it allows for the sufficient clearance with the axle parts while still maintaining a strong and secure connection between the vehicle components.
[0037] The portal axle (16) includes a left-hand motor assembly (19) and a right-hand motor assembly (20). The joggle in the rear assembly (18) provides the sufficient clearance with the left-hand motor assembly (19) and the right-hand motor assembly (20). The joggle in the rear assembly (18) provides clearance for the portal axle (16) which drives wheels of the vehicle. A minimum clearance of 50 mm is needed between the chassis frame of the vehicle and any dynamic moving parts of the vehicle. To achieve this clearance, a local unique joggle is provided on the rear assembly, which moves them 50 mm towards the vehicle's central plan. This design feature ensures that there is enough space between the frame and any moving parts, such as the engine or suspension of the vehicle, to prevent them from colliding and causing damage or safety hazards.
[0038] The portal axle (16) is used to drive the wheels of the vehicle. The portal axle includes two motor assemblies, one on the left-hand side (19) and one on the right-hand side (20). The rear assembly (18) has a joggle that provides enough clearance for the portal axle (16) to function properly without interfering with the left-hand and right-hand motor assemblies. In other words, the joggle in the rear assembly ensures that there is enough space for the portal axle (16) to rotate and drive the wheels of the vehicle without colliding with the motor assemblies. This design feature is important for the efficient operation of the vehicle and helps to prevent damage to the motor assemblies and the portal axle (16).
[0039] The proposed invention provides a new design for the vehicle frame that offers several advantages over traditional designs. One of the key benefits is the joggled frame design, which allows for a flat floor construction. This means that the interior of the vehicle is more spacious and comfortable for passengers or cargo. Additionally, the new design integrates Rear Pneumatic Suspension with the joggled frame and the porter axle (16). This integration results in a significant

reduction in the overall weight of the vehicle. This reduction in weight can lead to several benefits, such as improved fuel efficiency, better handling, and reduced wear and tear on the vehicle's components. Overall, the present subject matter offers a more efficient and effective design for vehicles, which can result in cost savings for manufacturers and improved performance for consumers.
[0040] The current buses employ a vertically cranked frame, featuring either a sloped gangway or a fully elevated floor to accommodate the rear axle travel during articulation. This design necessitates a vertically cranked frame above the rear axle to provide adequate clearance with the floor, precluding the possibility of a flat floor. In contrast, the proposed invention utilizes a joggled frame that enables the construction of a flat floor. This innovative design incorporates Rear Pneumatic Suspension with the joggled frame and porter axle, effectively reducing the vehicle's overall weight.
[0041] The present invention addresses the challenge of providing a flat floor inside a 900 mm floor bus, which is a common issue in existing buses due to the rear axle with a crown and pinion arrangement at the center. This arrangement requires a vertical hump on the long member to clear the axle movement in articulation, and the floor above the rear axle needs to slope to clear the axle dome at the center. To overcome this challenge in an electric vehicles such as bus, the porter axles with two separate motors at both axle ends are used. However, the conventional straight frame cannot be used as the motors are located side-wise. Therefore, a joggle frame has been designed to offer a flat gangway construction, resolving the challenge of providing convenience to standee passengers and ensuring their comfort inside the bus.
[0042] The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of

the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof.

[0043] List of reference numbers are as follows:

Reference Numeral Description
1 Left-hand front member
2 Right-hand front member
3 Cross member
4 Cross member
5 Cross member
6 Cross member
7 Cross member
8 Cross member
9 Cross member
10 Cross member
11 Cross member
12 Cross member
13 Cross member
14 Left-hand rear member
15 Right-hand rear member
16 Porter axle
17 Front assembly
18 Rear assembly
19 Left-hand motor assembly
20 Right-hand motor assembly
21 Joint assembly

We Claim:
1. A chassis frame structure for a vehicle, comprising:
a front assembly (17) comprising a left-hand front member (1) and a right-hand front member (2) joined together by a plurality of front cross members (3-8), wherein the front assembly (17) is a straight assembly;
a rear assembly (18) with joggle on a horizontal plane, wherein the rear assembly (18) comprises a left-hand rear member (14) and a right-hand rear member (15) joined together by a plurality of rear cross members (9-13);
a joint assembly (21) joining the front assembly (17) with rear assembly (18) in the horizontal plane; and
a portal axle (16) placed in the rear assembly (18) just below at least one rear cross member of the plurality of rear cross members (9-13).
2. The chassis frame structure as claimed in claim 1, wherein each front cross member of the plurality of front cross members (3-8) are located at a defined distance as per an overall strength requirement of the front assembly (17).
3. The chassis frame structure as claimed in claim 2, wherein each front cross member of the plurality of front cross members (3-8) are located at the defined distance is in a range of 300-600 mm of the front assembly (17).
4. The chassis frame structure as claimed in claim 1, wherein each rear cross member of the plurality of rear cross members (9-13) are located at a defined distance as per an overall strength requirement of the rear assembly (18).
5. The chassis frame structure as claimed in claim 4, wherein each rear cross member of the plurality of rear cross members (9-13) are located at the defined distance is in a range of 300-600 mm of the front assembly (17).

6. The chassis frame structure as claimed in claim 1, wherein the joggle is provided towards a centre plane of the vehicle by an amount so as to maintain a minimum clearance of 30 mm with axle parts in a static condition of the vehicle.
7. The chassis frame structure as claimed in claim 1, wherein the rear assembly (18) with the joggle in the horizontal plane enables a flat floor construction in the vehicle.
8. The chassis frame structure as claimed in claim 1, wherein the portal axle (16) comprises a left-hand motor assembly (19) and a right-hand motor assembly (20).
9. The chassis frame structure as claimed in claim 8, wherein the joggle in the rear assembly (18) provides a clearance with the left-hand motor assembly (19) and the right-hand motor assembly (20).
10. The chassis frame structure as claimed in claim 1, wherein the joggle in the rear
assembly (18) provides a clearance for the portal axle (16) which drives wheels
of the vehicle.