WO2024038412A1

WO2024038412A1 - An axle and a method of manufacturing thereof

Info

Publication number: WO2024038412A1
Application number: PCT/IB2023/058279
Authority: WO
Inventors: Babasaheb Neelkanth Kalyani; Basavraj Prabhakar KALYANI; Madan Umakant TAKALE; Sangameshwar PAWAR; Narsing BHOSALE; Manas NAG; Kedar PARANJAPE
Original assignee: Bharat Forge Limited
Priority date: 2022-08-18
Filing date: 2023-08-18
Publication date: 2024-02-22

Abstract

The present disclosure relates to an axle (100) and a method (500) of manufacturing the axle (100). The axle (100) includes spindles (102), pads (104) and central areas (106). Further, the axle includes a first bias (401) and a second bias (402). The first bias (401) is symmetrically downwards at pads (104) of the axle (100) and the second bias (402) is symmetrically sidewards at spindles (102) of the axle (100). The method (500) for manufacturing an axle (100) of a vehicle includes steps of, heating (501), a billet in a furnace (202). Further, reduce rolling (502) the billet to form a Reduced Rolled (RR) preform (300). Furthermore, bending (503) the RR preform (300), to form a bender preform (400). Also, the bender preform (400) is bent in more than one planes in a multi-plane bender assembly (201).

Description

TITLE OF INVENTION:

AN AXLE AND A METHOD OF MANUFACTURING THEREOF

CROSS-REFERENCE TO RELATED APPLICATIONS AND PRIORITY

The present application claims priority from the Indian patent application, having application number 202221046899, filled on 18^th August 2022, incorporated herein by a reference.

TECHNICAL FIELD

The present invention relates to an axle beam used in a vehicle. More specifically, the present invention relates to manufacturing of a rear axle beam using a closed die hot forging process.

BACKGROUND

The subject matter discussed in the background section should not be assumed to be prior art merely as a result of its mention in the background section. Similarly, a problem mentioned in the background section or associated with the subject matter of the background section should not be assumed to have been previously recognized in the prior art. The subject matter in the background section merely represents different approaches, which in and of themselves may also correspond to implementations of the claimed technology.

Rear Axle Beam is one of the critical components of a vehicle. In the case of electric vehicles, drive and electrical components (EV) are assembled/mounted on rear axle beam. The rear axle beam has to be designed such that it should be able to withstand fatigue loads. Various factors play a key role in enhancing the fatigue properties of the rear axle beam, the predominant one is the manufacturing process used for producing it. One of the most common methods to produce a rear axle beam is hot forging. The microstructure and grain flow obtained during the hot forging process gives optimum fatigue strength to the rear axle beam. These properties are not achievable through other manufacturing processes, for example, casting method.

The typical rear axle beam is made up of plurality pad areas, a central area, and a plurality of spindles with or without stems and portions connecting to these areas. The rear axle beam is symmetric from the central axis which divides equally it at its central area. Each spindle is connected to each pad by a portion and each pad is connected to the central area by another portion. The spindles (with or without stem), pad areas and central areas lie in three different planes. The longitudinal axis is nothing but an axis of spindles. The planes of pads, spindles and central areas are at an offset distance from each other in two different plane areas. i This kind of complex and intricate configuration of the rear axle beam has a significant effect on the hot forging process used to produce it. As its various sections lie in different planes and these planes are also at different offset distances from each other, this adds complexity in manufacturing the rear axle beam. These sections which lie in different planes need different stages of forging, each stage involving the forging of different sections. Thus, there is a need for different configuration of preforms for producing the rear axle beam using closed die hot forging process.

The typical hot forging process for components like rear axle beam starts from a “rolled” round or rounded corner section (RCS) hot billet which is then subjected to various forging operations. Typically, rear axle beam forging process consists of Reduce Rolling (RR) - Blocker Forging (BLK) - Finisher Forging (FIN). The hot forging process is explained briefly with the help of Figure 2, involving the following steps:

1. Providing, raw material as billet.

2. Reduce Rolling - Hot billet first undergoes a reduce rolling (RR) operation. The RR operation reduces the cross-sectional dimension (diameter or RCS) of the billet at the locations where the material requirement is less while keeping these dimensions unchanged where the material requirement is more.

3. Blocker forging - The RR preform is further subjected to a blocker forging operation to produce a blocker preform. The blocker dies have cavities in both top and bottom die which have rough external shape of the rear axle beam. Maximum material deformation and hence, material flow is produced in the blocker forging.

4. Finisher forging - The blocker preform is next subjected to a finisher forging operation to produce final forged rear axle beam. In this operation, finisher dies are used which have cavities in both top and bottom dies which have shape exactly same as the external shape of the rear axle beam with machining allowances. Finisher operation produces the final shape of the forged rear axle beam.

Due to the complex shape of the rear axle bream, the conventional forging process sequence i.e., Reduce Rolling (RR) -> Blocker Forging ->Finisher Forging, has certain disadvantages which are listed below:

1. Forging Defects - In a conventional forging process, the material distribution produced in the RR operation is not optimum and hence, die fill-up is not good in both blocker and finisher operation. This leads to defects in the final rear axle beam like underfill, cold shuts, cracks etc. 2. Poor Yield of forging - Yield of forging process is defined as the ratio of weight of input material (or billet) to the weight of the final forged rear axle beam. In the conventional forging process explained above, excess material has to be provided in the billet in order to achieve final shape of the rear axle beam and avoid the aforementioned forging defects. This reduces the yield of the process to 70 to 75%. This means up to 25 to 30% of the material is wasted in the form of flash formation.

3. Lower die life - Higher input material means more material flow which leads to early wear of the dies. Further, due to underfill issues, higher pressures have to be produced in the forging die cavities for fill-up and this leads to die cracking.

4. Higher cost of production - Due to higher defect rates, lower yield, and lower die life, the cost of production is also unnecessarily high.

Thus, there exists room for advancement over the existing technology for forging an axle in more than one plane, to achieve better material distribution and, consequently, lower defects, higher yields, better die life and lower cost of production.

SUMMARY

This summary is provided to introduce concepts related to an axle which is used in an electric vehicle or any vehicle. More specifically, the present invention relates to manufacturing of the rear axle beam using closed die hot forging process.

Before the present system and its components are described, it is to be understood that this disclosure is not limited to the particular system and its arrangement as described, as there can be multiple possible embodiments which are not expressly illustrated in the present disclosure. It is also to be understood that the terminology used in the description is for the purpose of describing the versions or embodiments only and is not intended to limit the scope of the present application. This summary is not intended to identify essential features of the claimed subject matter nor is it intended for use in detecting or limiting the scope of the claimed subject matter.

In one implementation, the present disclosure describes an axle of a vehicle. The axle may include of spindles, pads and central areas of the axle. Further, the axle may include a first bias and a second bias. The first bias may be symmetrically downwards at pads of the axle and the second bias may be symmetrically sidewards at spindles of the axle.

In another implementation, the present disclosure describes a method for manufacturing an axle of a vehicle. The method may include steps of heating a billet, in a furnace. Further, reduce rolling the billet to form a Reduced Rolled (RR) preform. Furthermore, bending the RR preform, to form a bender preform. The bender preform is bent in more than one plane in a multi-plane bender assembly.

In yet another non-limiting embodiment of the present disclosure, the bending step is further described. The bending may include steps of pressing the multi-plane bender assembly downwards to form a first bias. The first bias may be symmetrically downwards at pad areas of the axle. Further, die of the multi-plane bender assembly slides sidewards to form a second bias. The second bias may be symmetrically sidewards at spindle areas of the axle. Furthermore, the first and the second bias are forged in a single forging stroke.

BRIEF DESCRIPTION OF DRAWINGS

The detailed description is described with reference to the accompanying figures. The same numbers are used throughout the drawings to refer like features and components.

Figure 1 A illustrates an axle (100) having spindles with steam, in accordance with an embodiment of the present subject matter;

Figure IB illustrates an axle (120) having spindles without steam, in accordance with an embodiment of the present subject matter;

Figure 2 illustrates a system (200) for manufacturing an axle (100) of a vehicle, in accordance with an embodiment of the present subject matter;

Figure 2A illustrates isometric view of a top bender die (211), in accordance with an embodiment of the present subject matter;

Figure 2B illustrates a bottom bender die (221), in accordance with an embodiment of the present subject matter;

Figure 2C illustrates top view of a top bender die (221), in accordance with an embodiment of the present subject matter;

Figure 2D illustrates a top bender die assembly (210), in accordance with an embodiment of the present subject matter;

Figure 2E illustrates a bottom bender die assembly (220), in accordance with an embodiment of the present subject matter; Figure 3 illustrates a Reduce Rolled (RR) preform (300), in accordance with an embodiment of the present subject matter;

Figure 4 illustrates a bender preform (400), in accordance with an embodiment of the present subject matter;

Figure 4 A illustrates a blocker preform (410), in accordance with an embodiment of the present subject matter;

Figure 5 illustrates a method (500) for manufacturing an axle (100) of a vehicle, in accordance with an embodiment of the present subject matter.

DETAILED DESCRIPTION

Reference throughout the specification to “various embodiments,” “some embodiments,” “one embodiment,” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases “in various embodiments,” “in some embodiments,” “in one embodiment,” or “in an embodiment” in places throughout the specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

The terms “comprise(s)”, “comprising”, “include(s)”, “including”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a setup, system or method 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 system or method. In other words, one or more elements in a system or apparatus proceeded by “comprises... a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or apparatus.

In the following detailed description of the embodiments of the disclosure, reference is made to the accompanying drawings that form a part hereof, and which are shown by way of illustration specific embodiments in which the disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present disclosure. The following description is, therefore, not to be taken in a limiting sense. The present disclosure relates to an axle which is used in an electric vehicle or any vehicle. More specifically, the present invention relates to manufacturing of the rear axle beam using a closed die hot forging process.

Referring to Figure 1 A and IB, according to an embodiment of the present disclosure, Rear Axle Beams are shown. The rear axle beams (100, 120) shown in the figures 1A & IB are used in electrical vehicles. The Figure 1 A shows a rear axle beam (100) having spindles with steam. Figure IB shows the rear axle beam (120) having spindles without stem. These rear axle beams have a central axis (110, 130) as well as a longitudinal axis (108, 128). The spindles (102, 122), a plurality of pads (104, 124)) and central area (106, 126) lie in three different planes respectively Plane A, D & G, Plane B, E & H and Plane C, F & I. Plane A, B and C are having Y & Z as a coordinate axis. Planes C, D and F are having X & Y as a coordinate axis. Planes G, H and I are having X & Z as a coordinate axis. Planes A, B and C are parallel to each other but are offset from each other by some specific distances. Planes C, D and E are also parallel to each other but are offset from each other by some specific distances. Similarly, planes G, H and I are also parallel to each other but are offset from each other by some specific distances. These offset distances are different for different rear axle beams depending upon their capacity. Planes A, D & G are perpendicular to each other, planes B, E & H are also perpendicular to each other and planes C, F & I are perpendicular to each other.

Figure 2 illustrates a system (200) to manufacture the axle (100), in accordance with an embodiment of the present disclosure. It should be understood that the system (200) may be used to manufacture both axle (100) and axle (120), with a slight change in the dimensions of the dies.

In one non-limiting embodiment of the present disclosure, the system (200) may include a furnace (202), a reduce rolling equipment (203), a multi-plane bender assembly (201), blocker dies (204), finisher dies (205), one or more forging equipment (206), and one or more post-forging equipment (207).

The furnace (202) is configured to heat billet used as raw material. The furnace (202) can be of different types such as oil-fired, gas-fired, electric, or induction heating. Additionally, the billet processed in the furnace (202) can have various forms such as forged, extruded, or rolled billets, enabling the furnace to cater to different manufacturing processes.

Moreover, the billet may have a cylindrical shape or a rounded cross section (RCS), depending on the desired product. In one embodiment, the billet is composed of a steel alloy, providing strength and durability for applications that require high-performance materials. Alternatively, in another embodiment, the billet can be made of cast iron or any other suitable metal alloy, depending on the specific application and desired material properties.

In another non-limiting embodiment of the present disclosure, the billet may be heated to reach the specific temperature required for further processing. The furnace (202) is employed to facilitate this heating process. In one embodiment, the temperature range considered suitable for achieving the desired results is between 1000 °C to 1300 °C. Alternatively, it is also possible to heat the billet at any temperature exceeding 1150°C to prepare it for subsequent processing in the reduce rolling equipment (203).

In one embodiment of the present disclosure, the processed billet may be transferred to reduce rolling equipment (203). The reduce rolling equipment (203) performs reduce rolling operations. A set of reduce rolling dies may be used for performing this operation. During the reduce rolling operation, the processed billet may be deformed into a stepped Reduced Rolled (RR) preform as shown in Figure 3. The output of this process is an RR preform (300).

In a non-limiting embodiment of the present disclosure, the multi-plane bender assembly (201) may be disclosed. The multi-plane bender assembly (201) may be configured to bend the RR preform (300), the bending may not be restricted to one plane. Further, the multi-plane bender assembly (201) may include a top bender die (211), shown in Figure 2A and a bottom bender die (221), shown in Figure 2B. The top die (211) and bottom die (221) may be configured to form contours for spindles, pads, and central areas of the axle.

In a related embodiment, the top bender die (211) may include one or more pins (215). The one or more pins (215) may be configured to limit motion and maintain alignment of the multi-plane bender assembly (201) in the forging stroke. Similarly, the bottom bender die (221) may include one or more plungers (225). The one or more plungers (225) may be configured to guide motion of the multi-plane bender assembly (201).

In an exemplary embodiment of the present disclosure, the top bender die (211) of the multi-plane bender assembly (201) may be pressed during forging stroke. The one or more pins (215) may be configured to limit the motion and maintain alignment of the top bender die (211) and the bottom bender die (221) of the multi-plane bender assembly (201) in the forging stroke. Such limitation on the motion prohibits unwanted material displacement while forging.

Figure 2C illustrates top view of the top bender die (221), in accordance with an embodiment of the present subject matter. The figure may further illustrate one or more depressions. The one or more depressions may be configured to position the top die cassette (212) and the top die holder (213) on the top bender die (211). Further, the depressions may be rectangular, circular, or in any polygon shape, as per the bender assembly requirement. The depressions may be further configured to limit motion of the top die cassette (212) and the top die holder (213) on the top bender die (211).

Similarly, the bottom bender die (221) may include one or more depressions. The one or more depressions may be further configured to position the bottom bender die (221) on the bottom die cassette (222) and the bottom die holder (223). Further, the depressions may be rectangular, circular, or in any polygon shape, as per the bender assembly requirement. The depressions may be further configured to limit motion of the bottom bender die (221) on the bottom die cassette (222) and the bottom die holder (223).

Now referring to Figure 2D, The top die assembly (210) may further include a top bender die (211), a top cassette (212), and a top die holder (213). Further, referring to figure 2E, the bottom die assembly (220) may include a bottom bender die (221), a bottom cassette (222), and a bottom die holder (223). The top die assembly (210) and bottom die assembly (220) may be coupled with a forging equipment (not shown in figures), to enable forging process. The forging equipment may be selected from any type of forging equipment like a mechanical press, screw press, wedge press, hydraulic press or hammer.

The multi-plane bender assembly (201) may be configured to bend the RR preform (300) into a bender preform (400) as shown in the figure 4. Further, the bending may not be restricted to one plane. The bender preform (400) may include a first bias (401), a second bias (402) and an elongation (403) along the length of the axle (100). The first bias (401) may be symmetrically downwards at pad areas of the axle (100) and the second bias (402) may be symmetrically sidewards at spindle areas of the axle (100). Further, the first bias (401) may be deformation of material at the pad areas of the axle (100) and the second bias (402) may be deformation of material at the spindle areas of the axle (100). The said deformation of material in first bias (401) and second bias (402) may be in the range of 120 mm to 160 mm in length. Furthermore, the multiplane bender assembly (201) executes the bending and elongation in a single forging stroke of the forging equipment.

In one embodiment of the present disclosure, blocker dies (204) may be disclosed. The bender preform (400) may be transferred to the blocker dies (204). The blocker dies (204) are configured to perform blocker forging operations. The blocker forging operation may produce a rough shape of the rear axle beam with maximum material flow, with some access material thrown out as a flash. The output of this stage is the blocker preform (410). The output of this operation is a blocker preform ( 10).

In one embodiment of the present disclosure, finisher dies (205) may be disclosed. The blocker preform (410) may be transferred to the finisher dies (205). The finisher dies (205) performs the finisher forging operation. In this operation, the final shape of the rear axle beam is formed with a small amount of material thrown in the form of flash. It is to be noted that the finisher operation produces the final as forged axle. Thus, the shape of the output the finisher forging step is exactly same as that of final axle.

Further, the finisher operation may be followed by post-forging operations which include but may not be limited to trimming, padding, shot blasting, heat treatment, machining etc. Such postforging operations may be executed on one or more post-forging equipment (207). The postforging operations produce the final axle.

Referring to Fig. 5, according to an embodiment of the present disclosure, a method (500) for manufacturing an axle (100) may be disclosed. The method may include various steps as described below.

At step (501), the billet as raw material is heated, in the furnace (202). The billet may be heated to the required temperature. The required temperature may be 1000 °C to 1300 °C. Further, the billet may be a forged, extruded or rolled billet. The billet can be cylindrical or rounded cross section (RCS) billet. The billet material may be steel alloys or any other suitable metal alloy.

At step (502), reduce rolling operation may be performed on the processed/heated billet to form the Reduced Rolled (RR) preform (300). The reduce rolling equipment (203) may be used for performing this operation. During the reduce rolling operation, the processed billet may be deformed into a stepped Reduced Rolled (RR) preform (300) as shown in Figure 3.

At step (503), bending operation may be performed on the RR preform (300), by the multi-plane bender assembly (201), to form the bender preform (400). Further, the bender preform (400) is bent in more than one plane in the multi -plane bender assembly (201).

At step (504), blocker forging operation may be performed on the bender preform (400), to form a blocker preform (410). The blocker forging operation may produce a rough shape of the rear axle beam with maximum material flow, with some access material thrown out as flash.

At step (505), finisher forging operation may be performed on the blocker preform (410), to form the final shape of the axle (100). The final shape of the rear axle beam is formed with small amount of material thrown in the form of flash. It is to be noted that the finisher operation produces the final as forged axle. Thus, the shape of the output of the finisher forging step is exactly the same as that of final axle.

At step (506), post-forging operations may be performed to manufacture the final axle (100). Postforging operations which include but are not limited to trimming, padding, shot blasting, heat treatment, machining etc. Such post-forging operations may be executed on one or more postforging equipment (207).

In a non-limiting embodiment of the present disclosure, the step (503) of bending the RR preform (300) may further include various steps as described below (not shown in figures).

At step (531), the multi-plane bender assembly (201) may be pressed downwards to form the first bias (401). The first bias (401) may be symmetrically downwards at pad areas of the axle (100).

At step (532), die of the multi-plane bender assembly (201) may be further pressed downwards to form the second bias (402) and an elongation (403), along the length of the axle (100). The second bias (402) may be symmetrically sidewards at spindle areas of the axle (100). The preform material may slide sidewards to form the second bias (402).

Further, the first bias (401), the second bias (402) and the elongation (403) formed due to the multiplane bender assembly (201), are forged in a single forging stroke.

Technical Advance & Economic Significance

The presently disclosed method for manufacturing an axle may have the following advantageous functionalities on the conventional art:

- The invented forging process leads to better material distribution in the bender preform which leads to better die fill-up. This eliminates defects like underfill, cold shuts, die cracks etc.

- Better material distribution in the bender preform ensures that no material is wasted. Thus, with the invented design, the same rear axle beam fills up with lesser input material. Yield improvement of 10 to 20% can be achieved using the invented design thus reducing the material wastage.

- Better material distribution, improved fill-up and good material flow leads to improvement in die life. Wear and cracks in the dies are reduced drastically improving the productivity of the forging process. Lower defect rates, higher yield and increased die life helps in reducing the cost of production.

Claims

WE CLAIM:

1. An axle (100) of a vehicle, wherein the axle comprises: spindles (102); pads (104); central areas (106) of the axle (100); a first bias (401); and a second bias (402), wherein the first bias (401) is symmetrically downwards at pads of the axle (100) and the second bias (402) is symmetrically sidewards at spindles of the axle (100).

2. The axle as claimed in claim 1, wherein the first bias (401) and the second bias (402) are 120 mm to 160 mm.

3. The axle as claimed in claim 1, wherein a system (200) is configured to manufacture the axle (100), wherein the system (200) comprises: a multi-plane bender assembly (201) configured to bend a reduced rolled preform (300) into a bender preform (400), wherein the multi -plane bender assembly (201) comprises: a top die assembly (210) and a bottom die assembly (220) configured to form contours for spindles, pads, and central areas of the axle.

4. The system (200) as claimed in claim 3, wherein the bender preform (400) comprises: a first bias (401), symmetrically downwards at pad areas of the axle (100); a second bias (402), symmetrically sidewards at spindle areas of the axle (100); and an elongation (403) along length of the axle (100), wherein the first bias (401), the second bias (402) and the elongation (403) are forged in a single forging stroke.

5. The system (200) as claimed in claim 3, wherein the top die assembly (210) comprises a top bender die (211), atop cassette (212), and atop die holder (213), wherein the top bender die (211) comprises one or more pins (215) configured to limit motion and maintain alignment of the multi-plane bender assembly (201) in the forging stroke.

6. The system (200) as claimed in claim 3, wherein the bottom die assembly (220) comprises a bottom bender die (221), a bottom cassette (222), and a bottom die holder (223), wherein the bottom bender die (221) comprises one or more plungers (225) configured to guide motion of the multi-plane bender assembly (201) in the forging stroke.

7. The system (200) as claimed in claim 3, wherein the system further comprises: a furnace (202) configured to heat a steel alloy billet; a reduce rolling equipment (203) configured to form an RR preform (300); a bender equipment configured to form bender preform (give number) blocker dies (204) configured to form blocker preform ( 10); finisher dies (205) configured to form the axle; one or more forging equipment (206) configured to form preforms; and one or more post-forging equipment (207) configured to perform post-forging operations on the axle.

8. The system (200) as claimed in claim 3, wherein one or more forging equipment comprise a mechanical press, screw press, wedge press, and hydraulic press or hammer.

9. A method (500) for manufacturing an axle (100) of a vehicle, wherein the method comprises steps of heating (501) a billet, in a furnace (202); reduce rolling (502) the billet to form a Reduced Rolled (RR) preform (300); bending (503) the RR preform (300), to form a bender preform (400), wherein the bender preform (400) is bent in more than one planes in a multi-plane bender assembly (201).

10. The method as claimed in claim 3, wherein the bending (503) comprises steps of pressing (531), the multi-plane bender assembly (201) downwards to form a first bias (401), wherein the first bias (401) is symmetrically downwards at pad areas of the axle (100); and pressing (532), the multi-plane bender assembly (201) downwards to form a second bias (402) and an elongation (403), wherein the second bias (402) is symmetrically sidewards at spindle areas of the axle (100), wherein the first bias (401), the second bias (402) and the elongation (403) are forged in a single forging stroke.

11. The method as claimed in claim 3 further comprises steps of: blocker forging (504), the bender preform (400), to form a blocker preform (410); finisher forging (505), the blocker preform (410), to form the axle (100); and post-forging operations (506), to manufacture the final axle (100).

12. The method as claimed in claim 3, wherein post-forging operations (506) comprising trimming, padding, shot blasting, heat treatment, and machining.

13. The method as claimed in claim 3, wherein the billet comprises forged billet, extruded billet or rolled billet.

14. The method as claimed in claim 3, wherein the billet is heated in a temperature range of 1000°C to 1300°C.