WO2025032374A1

WO2025032374A1 - A monoblock gear for transmission and method of manufacturing thereof

Info

Publication number: WO2025032374A1
Application number: PCT/IB2024/050320
Authority: WO
Inventors: Vishal MAKWANA
Original assignee: Texspin Bearings Limited
Priority date: 2023-08-04
Filing date: 2024-01-12
Publication date: 2025-02-13

Abstract

A method for manufacturing monoblock gears (200) having dog teeth (208) involves pre-machining a forged blank to get an outer profile, the outer profile including a first profile pertaining to a set of splines and a second profile pertaining to a set of gear teeth (206) of the monoblock gear (200). The method involves forming the set of straight splines on the first profile by any of a cold forging or a machining operation, and performing a cold forging operation to provide roof angles and back tapers to the dog teeth. During the cold forging operation, force is applied in a radial direction to shape the splines with a specific roof angle.

Description

A MONOBLOCK GEAR FOR TRANSMISSION AND METHOD OF MANUFACTURING THEREOF TECHNICAL FIELD [0001] The present invention relates to the field of transmission gears. More particularly, the present disclosure relates to method for manufacturing monoblock gears for transmission. BACKGROUND [0002] Transmission gears are integral components in various mechanical systems, such as transmission assemblies used in different applications, and other industrial machinery. They are responsible for maintaining the required speed ratios, ensuring smooth power transfer, and controlling the speed of the driven components. Monoblock gears, as a vital part of transmission assemblies, facilitates engagement and interaction of gear teeth, which directly impacts the efficiency, reliability, and overall performance of the transmission system. [0003] The formation of teeth on monoblock gear is a pivotal manufacturing process that significantly influences the performance of transmission gears. The accuracy and precision of the gear teeth directly impacts the efficiency, reliability, and smooth operation of various mechanical systems, including automotive transmissions, industrial machinery. Properly formed teeth ensure seamless engagement, reduce noise and vibration, and optimize power transmission, contributing to the overall performance and durability of the transmission gears. As the teeth play a crucial role in transmitting power and torque between components, achieving high-quality tooth geometry is imperative to ensure optimal gear functionality and the smooth operation of the mechanical systems they are integrated into. [0004] The process of forming teeth on a monoblock gear involves multiple steps. Initially, after the first hot forging process of blanking, the second hot forging process creates straight spline shapes and a rough roof angle on the dog teeth. Subsequently, the finished roof angle of the teeth is achieved through cold forging. Another cold forging step is used to produce the tooth back taper. Finally, the gear teeth are formed during the gear cutting process. However, in existing methods, creating the roof angle and back taper involves separate processes demanding considerable effort and time, rendering it inefficient in terms of cost. Further, Teeth Roof angle in all the existing art is formed by axial force of the tool. [0005] There is, therefore, a need for a manufacturing process that provide forging operation which is both efficient in terms of time and cost. OBJECTS OF THE PRESENT DISCLOSURE [0006] Some of the objects of the present disclosure, which at least one embodiment herein satisfy, are listed below. [0007] An object of the present disclosure is to provide improved manufacturing process of monoblock gears for transmission. [0008] An object of the present disclosure is to provide a monoblock gears for transmission in which decarburizing is removed as a result of the CNC machining procedure. [0009] An object of the present disclosure is to provide a high-strength monoblock gears for transmission. SUMMARY [0010] Aspects of the present disclosure relate to an enhanced monoblock gears for transmission and its manufacturing method. [0011] In an aspect, a method for manufacturing a monoblock gear for transmission involves pre-machining a forged blank to get an outer profile, the outer profile including a first profile pertaining to a set of splines of the monoblock gear and a second profile pertaining to a set of gear teeth of the monoblock gear. The method involve forming the set of splines on the first profile and performing a cold forging operation to provide a roof angle and a back taper to the splines to form the dog teeth. The method involving cold forging operation, a cold forging force is applied in a radial direction. [0012] In an embodiment, the step of performing the cold forging process involves using a die set that is configured to enable simultaneous cold forming of the roof angle and the back taper of the dog teeth in a single operation. [0013] In an alternate embodiment, the step of performing the cold forging process may use one or more tools, but less than number of splines in the set of splines, and indexing the blank by rotation to align each of the splines with the one or more tools before moving the one or more tools radially inwards to form the roof angles and the back tapers on the corresponding splines. [0014] The method as described in the present invention eliminates the need for separate operations, reducing production time and enhancing manufacturing productivity. As a result, the method improves the accuracy of formation of the teeth and also increases the overall efficiency of the gear manufacturing process. [0015] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components. BRIEF DESCRIPTION OF DRAWINGS [0016] The accompanying drawings are included to provide a further understanding of the present disclosure and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, explain the principles of the present disclosure. The diagrams are for illustration only, which thus is not a limitation of the present disclosure. [0017] Similar components and/or features may have the same reference label in the figures. Further, various components of the same type may be distinguished by following the reference label with a second label that distinguishes among the similar components. Suppose only the first reference label is used in the specification. In that case, the description applies to any similar components with the same first reference label, irrespective of the second reference label. [0018] FIG.1 illustrates an exemplary flowchart of a method for manufacturing a monoblock gear for transmission, in accordance with an embodiment of the present disclosure. [0019] FIG. 2A- 2I illustrates a schematic representation of stepwise expansion of a monoblock gears for transmission, in accordance with an embodiment of the present disclosure. [0020] FIG. 3A-3C illustrates a schematic representation of the cold forging operation, in accordance with an embodiment of the present disclosure. [0021] FIG.4A illustrates a schematic representation of overall tool arrangement to generate the desired tooth profile, in accordance with an embodiment of the present disclosure. [0022] FIG. 4B illustrates a schematic representation of the individual profile of the tool utilized for cold forming of roof angels and back tapers on a single spline, in accordance with an embodiment of the present disclosure. [0023] FIG. 4C illustrates a schematic representation of overall profile of the dog teeth generated, in accordance with an embodiment of the present disclosure. [0024] FIG. 5A-5C illustrates a schematic representation of alternative tooling arrangement to generate the desired tooth profile, in accordance with an embodiment of the present disclosure. DETAILED DESCRIPTION [0025] In the following description, for the purposes of explanation, various specific details are set forth in order to provide a thorough understanding of embodiments of the present disclosure. It will be apparent, however, that embodiments of the present disclosure may be practiced without these specific details. Several features described hereafter can each be used independently of one another or with any combination of other features. An individual feature may not address all of the problems discussed above or might address only some of the problems discussed above. Some of the problems discussed above might not be fully addressed by any of the features described herein. [0026] The word “exemplary” and/or “demonstrative” is used herein to mean serving as an example, instance, or illustration. For the avoidance of doubt, the subject matter disclosed herein is not limited by such examples. In addition, any aspect or design described herein as “exemplary” and/or “demonstrative” is not necessarily to be construed as preferred or advantageous over other aspects or designs, nor is it meant to preclude equivalent exemplary structures and techniques known to those of ordinary skill in the art. Furthermore, to the extent that the terms “includes,” “has,” “contains,” and other similar words are used in either the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term “comprising” as an open transition word without precluding any additional or other elements. [0027] Reference throughout this specification to “one embodiment” or “an embodiment” or “an instance” or “one instance” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this 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. [0028] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. _[0029] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such details as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosures as defined by the appended claims. [0030] FIG. 1 illustrates an exemplary flowchart of a method 100 for manufacturing a monoblock gear for transmission, in accordance with an embodiment of the present disclosure. FIG. 2A- 2I illustrates a schematic representation of stepwise expansion of a monoblock gears for transmission. Referring to FIG. 1 and FIG. 2A-2G, the method 100 involves a series of operations, each serving a specific purpose in transforming the raw material into the final product. [0031] As illustrated, at step 102, the method 100 may involve, pre-machining a forged blank to get an outer profile, the outer profile including a first profile pertaining to a set of splines and a second profile pertaining to a set of gear teeth 206 (as shown in FIG.2I). The method at step 104 may involve, forming a set of splines on the first profile by any of a suitable process known in the art, such as by cold forging or machining operation. as shown in FIG. 2E. The method at step 106 may involve, performing a cold forging operation to provide a roof angle to the splines to form the dog teeth (as shown in FIG. 2F). Further, in the cold forging operation, a cold forging force may be applied in a radial direction. In an example, in the step of the cold forging operation the method may involve forming a back taper to the splines as well as the roof angle (as shown in FIG. 2F) using a specially designed tool that moves radially inwards and applies force on the respective surfaces in the radial direction to form the back taper and the roof angle of the dog teeth 208. [0032] In an example, pre-machining a forged blank to get an outer profile may involve forming a cylindrical member W1 as shown in FIG.2A, having a predetermined axial length and predetermined diameter based on a profile of the transmission. In an example, this operation prepares the basic workpiece for subsequent processing. In a non-limiting example, the suitable cylindrical material for the transmission gear is selected from a group comprising any or a combination of steel, alloy steel, and carbon steel. _[0033] In an example, pre-machining a forged blank may further involve performing hot forging on the formed cylindrical member to obtain a blank suitable W2 as shown in FIG 2B. In a non-limiting example, the cylindrical material W1 may be subjected to hot forging, where it is heated to a high temperature (e.g., 1200 degrees Celsius) and then molded into a desirable blank W2 appropriate for a transmission gear. Temperature parameter of 1200 degrees Celsius is illustrative in essence and is by no means confined or restricted in any manner. Any temperature values that are well-known and within the purview of an individual possessing ordinary skill in the pertinent art can be suitably adjusted and employed for the purpose of performing the hot forging process. [0034] In an embodiment, the hot forging may be performed without developing teeth profile. In an example, developing a shape for the teeth, so it does not necessitate a specialized precision hot forging facility. This eliminates the repetitive costs associated with tool replacement, thereby eliminating the need for a substantial investment in tooling. Additionally, all essential teeth shapes are attainable through cold forging, resulting in superior teeth accuracy and sharpness of the roof angle. [0035] In an example, pre-machining a forged blank may further involve, annealing the forged blank using a heat treatment to transform the forged blank into a stress-relieved material. In an example, annealing the forged blank may involve a heat treatment and transforming it into a stress-relieved material W3 as shown in FIG.2C. In an embodiment, the material obtained after rough hot forging (W2) undergoes annealing. Annealing is a heat treatment process used to enhance the properties of a material, particularly metals and alloys. In an example, annealing involves heating the material to a specific temperature and holding it at that temperature for a certain period, followed by controlled cooling. Performing annealing may relive stress and provide improvement in material properties. After this process, the material is converted into W3. [0036] In the example, W3 is the raw material or beginning point for the CNC turning operation. This material, however, has a surface scale. Due to exposure to high temperatures in an oxidizing atmosphere, the surface layer of a material (typically steel or other carbon- containing alloys) loses some of its carbon content during decarburization. During thermal treatment or high-temperature processing of carbon-containing materials, this issue frequently arises. _[0037] As illustrated, pre-machining may involve, machining the stress-relieved material by a CNC turning machine to remove decarburizing layer from a surface of the corresponding material. In an embodiment, machining the material W3 by CNC turning is to remove decarburizing (surface scale) and achieve the desired overall packaging dimensions. The result of this operation is material W4 as shown in FIG.2D. The CNC turning process involves removing the surface scale (decarburized layer) from material W3. CNC turning process may be essential because the surface scale is often brittle and undesirable for most engineering applications. By removing this layer, the machined surface will have improved mechanical properties and surface finish. In an example, the decarburizing layer removal during the CNC operation may be achieved by precision machining tools. Apart from removing the decarburized layer, the CNC turning operation also shapes the material W3 to attain the required overall packaging dimensions. This involves cutting, shaping, and refining the workpiece to meet the precise specifications and tolerances. [0038] As illustrated, at step 104, the method 100 may involve, forming a set of splines on the first profile (as shown in FIG. 2E) by a cold forging operation, though machining the splines is well within the scope of the present disclosure. In an example, the material W4 after the CNC turning is subjected to a cold forging process to form the splines, which after forming the roof angle and the back angle get transformed to dog teeth 208. In an example, cold forging is a metal forming process that occurs at room temperature or slightly elevated temperatures, typically below the recrystallization temperature of the material. During this step, the material W4, is subjected to compressive forces within specialized dies and molds. The pressure applied causes the material to flow and take the shape of the dies, resulting in the formation of straight dog tooth as shown in FIG.2E. [0039] In an embodiment, as depicted in FIG.3A-3C illustrates a schematic representation of cold forging operation. When the straight splines are formed by cold forging process, a vertical axial force (referred to as Fa) may be applied from the top onto the blank W4 to facilitate the creation of the desired straight splines configuration, as shown in FIG. 3B and FIG. 3C. In an example, cold forging may be employed to shape the initial blank into the desired spline profile. The dies used in the process may have the negative impression of the splines geometry. When the raw material is inserted between the dies and subjected to pressure, it undergoes deformation, which changes its shape without altering its composition. [0040] In an embodiment, the method at step 106 may involve, performing a cold forging operation to provide a roof angle to the straight dog teeth. In an example, the material W5, undergoes cold forging process after the straight splines have been formed. _[0041] In an example, at this step, a single operation creates a pair of roof angles, such as left roof angle 202-1 and right roof angle 202-2 (collectively and individually refereed as roof angles/roof angle 202, herein), on each tooth. Further, the step of the cold forging operation may also include forming a back taper of the dog teeth in addition to the roof angle. [0042] In an alternate embodiment, the method may involve forming the roof angle 202 and the back taper 204 of the dog teeth in separate cold forming operations. However, forming the roof angle 202 and the back taper 204 of the dog teeth is preferred as it results in monoblock gears 200 with highly accurate dog teeth. Further, the cold forging operations for forming roof angle and the back angle, either singly/individually or together, i.e., in combination with the other, may be performed using a die set that moves radially applying cold forging force in a radial direction, as shown in FIG. 4A, to enable development of the roof angle and the back taper of the dog teeth. [0043] FIGs. 4A to 4C illustrate schematic representations of overall tool arrangement to generate the desired dog tooth profile, FIG. 4B illustrates a schematic representation of individual profile of the tool which is use to generate single tooth, and FIG. 4C illustrates a schematic representation of overall profile generated. For an instance, the depicted tool configuration as shown in FIG 4(A), is configured to achieve the intended tooth profile on the material W5. In an example, in the cold forging operation, a cold forging force is applied in a radial direction. In this process, as shown in FIG 4A, a radial force is uniformly applied in a 360˚ manner. The applied radial force is applied by the individual tools for each spline that simultaneously move inward radially, exerting the necessary force on the respective spline to bring about material deformation to generate the required profile having the desired roof angles and the back angles. [0044] In implementation, the die set can include multiple tools for cold forming of the roof angles and the back tapers, one tool for each of the plurality of splines. Each of the tools can simultaneously move radially inward to provide the roof angles and the back tapers to each of the splines in a single operation. In an alternate application, the die set can include one or more tools, but less than the number of splines, and the blank can be indexed by rotation to align each of the splines with the tools and thereafter the tools can be move radially inwards to form the roof angles and the back tapers on the corresponding splines. [0045] Further, FIG. 4B illustrates the specific profile of the individual tool employed for generating a single tooth. Additionally, Figure 4C provides an overview of the overall profile within the tool, representing the cavity responsible for shaping the desired tooth profile. Further, this method enables the simultaneous creation of the desired tooth geometry, encompassing both the roof angle 202 and the back taper 204. [0046] In an embodiment, FIG. 5A- 5C depicts an alternative tooling setup. In this configuration, modifications have been made to the tool profile. Specifically, in this configuration each tool possesses half of the tooth cavity at both ends, as illustrated in FIG 5B and 5C. This modification allows for the concurrent shaping of the tooth geometry, ensuring the desired roof angle and back taper are achieved simultaneously. _[0047] Further in the conventional methods, the roof angle is typically formed by applying axial force using tools. The present disclosure provides technical advantage by employing radial force, ensuring precise and efficient results. By exerting pressure uniformly from all directions, the tool ensure consistency in shaping the teeth roof angle. This leads in uniform tooth profile on the material, elevating the overall quality and functionality of the manufactured components. Furthermore, the use of radial force reduces the risk of irregular or distorted tooth formations often associated with axial force methods. The heightened precision not only meets rigorous quality standards but also enhances the performance and longevity of the end product. [0048] In an example, forming both profiles (roof angle and teeth back taper) eliminates the need for separate forging steps and reduces the chances of errors or deviations that could occur when carrying out the profiles individually. As a result, the precision and accuracy of the teeth, denoted as W6, are significantly improved. Additionally, the combined cold forging process leads to higher productivity as it reduces the overall number of manufacturing steps and simplifies the production flow. This increased efficiency allows for more gear components to be produced in a shorter time frame, resulting in a rise in overall production output. The synergy of enhanced precision and improved productivity makes the manufacturing process more cost-effective and yields high-quality transmission gears with reliable performance characteristics. [0049] It is to be further appreciated that while the exemplary illustrations depict tooling arrangement in such a way that both roof angle and back taper of tooth are generated simultaneously. However, it is also possible to generate both the profiles independently. For an example, in a first operation by applying desired force roof angle is generated and in a subsequent cold forming operation tooth back taper is generated, and all such variations are well within the scope of the present application without any limitations, whatsoever. [0050] In an embodiment, the method 100 of manufacturing monoblock gears 200 may further involve machining the blank i.e., second profile to form a gear tooth 206 as shown in 2I. The desired teeth are formed on the material W6 to form W7. The gear machining process may utilize specialized cutting tools and machinery to remove excess material from the gear, thereby creating the intricate tooth profiles required for efficient power transmission in the transmission system. [0051] In an embodiment, the method 100 may involve, heat treating the machined gear teeth to achieve a predefined hardness. In an example, the material W7 undergoes heat treatment to achieve the desired hardness and improve its mechanical properties and form W8 as shown in FIG. 2H. Heat treatment is a controlled heating and cooling process that is applied to the material to achieve specific mechanical properties and improve its overall performance. _[0052] In an example, during heat treatment, the monoblock gears 200 is subjected to carefully controlled temperatures for a predetermined period. This process allows for the transformation of the material's microstructure, which affects its hardness, strength, toughness, and other mechanical properties. The heat treatment aims to achieve the desired balance of these properties, making the monoblock gears 200 for transmission. [0053] In an example, heat treatment may include but not limited to annealing, quenching, and tempering. The method 100 may involve annealing that involves heating the material to a specific temperature and then slowly cooling it, to reduce internal stresses and increase ductility. In an example, the method 100 may involve quenching where the material is rapidly cooled to achieve a higher hardness, making it more wear-resistant. In an example, the method 100 may involve tempering. After quenching, the material is reheated to a lower temperature to reduce brittleness and increase toughness. [0054] Further, the method 100 may also involve, performing a final hard finishing on the heat-treated gear, wherein the hard finishing includes grinding of the gear teeth and honing a through bore, to obtain the monoblock gear 200. In an example, the method 100 of manufacturing monoblock gear 200 may involve, hard finishing of the material W8 to obtain W9 as shown in FIG.2I _[0055] In an example, during the grinding process, the external gear teeth 206 is carefully machined to achieve the exact desired tooth profiles, size, and surface finish. Grinding ensures the teeth have precise dimensions and eliminates any irregularities or imperfections that might have resulted from earlier manufacturing steps. This process attain a high level of accuracy in the gear teeth, allowing for smooth and efficient meshing with other gears in the transmission system. [0056] In an example, the hard finishing may involve honing the through bore of the gear. Honing is a process that refines the internal surface of the bore to achieve superior dimensional accuracy, surface finish, and straightness. This step ensures that the bore meets tight tolerances and is ready to accommodate a shaft or other components that fit within the gear's interior. [0057] Consequently, the above-described method 100 of manufacturing monoblock gear involves a cold forging operation, which simultaneously develops roof angle and back taper geometries. By integrating these operations, the process achieves precise tooth profiles and enhances overall productivity. This innovative approach eliminates the need for separate manufacturing steps, leading to higher accuracy in tooth formation and a more efficient production process. Further, by exerting radial force uniformly from all directions, the tool guarantees consistency in shaping the teeth roof angle. As a result, the monoblock gears for transmission produced through this method exhibits improved teeth accuracy and presents a highly productive manufacturing solution. ADVANTAGES OF THE INVENTION [0058] The proposed invention provides enhanced manufacturing process of monoblock gears for transmission. [0059] The proposed invention provides a monoblock gears for transmission in which decarburizing is removed as a result of the CNC machining procedure. [0060] The proposed invention provides a high-strength monoblock gears for transmission. [0061] The proposed invention provides a method that is reliable and productive. [0062] The proposed invention provides a solution for manufacturing monoblock gears for transmission that is cost effective. [0063] The proposed invention provides a solution for manufacturing monoblock gears for transmission that extends the tool life. [0064] The proposed invention provides a solution for manufacturing monoblock gears for transmission in which teeth accuracy and sharpness of roof angle is high.

Claims

We Claim: 1. A method (100) for manufacturing a monoblock gear (200) with a set of dog teeth (208), the method (100) comprising the steps of: pre-machining a forged blank to get an outer profile, the outer profile comprising a first profile pertaining to a set of splines of the monoblock gear (200) and a second profile pertaining to a set of gear teeth (208) of the monoblock gear (200); forming the set of splines on the first profile; and performing a cold forging operation to provide roof angles (202) and back tapers (204) to the splines (208) to form the dog teeth (208); wherein, in the cold forging operation, a cold forging force is applied in a radial direction. 2. The method (100) as claimed in claim 1, wherein the step of forming the set of splines is carried out by any of a machining operation and a cold forging operation. 3. The method (100) as claimed in claim 1, wherein the step of performing the cold forging process involves using a die set that is configured to enable simultaneous cold forming of the roof angle (202) and the back taper (204) of all the dog teeth (208) in a single operation. 4. The method (100) as claimed in claim 1, wherein the step of performing the cold forging process involves using one or more tools, but less than number of splines in the set of splines, and indexing the blank by rotation to align each of the splines with the one or more tools before moving the one or more tools radially inwards to form the roof angles and the back tapers on the corresponding splines.