BIELA EM ALUMÍNIO PARA MOTOR A COMBUSTÃO E PROCESSO DE FABRICAÇÃO

Description

1 / 11 Aluminum connecting rod for internal combustion engine and manufacturing process. FIELD OF INVENTION

[01] The present invention relates to the field of mechanical engineering applied to Internal Combustion Alternative Engines (Otto Cycle or Diesel Cycle), more specifically to the construction of connecting rods. The invention concerns a connecting rod manufactured from aluminum alloy, this connecting rod being specially developed to dispense with the use of bearings or bushings in the crankpin (connecting rod foot), promoting a new connection solution between the connecting rod and the crankshaft journal, with application in both single-cylinder and multi-cylinder engines.

[02] The developed connecting rod has specific geometric, metallurgical and surface finish characteristics, which allow it to operate with a pressurized oil film, ensuring wear resistance, low friction and reliable and safe operation even under high mechanical stress such as extreme torque and rotation conditions, without the need for intermediate components traditionally used for bearing between the connecting rod and the crankshaft. BACKGROUND OF THE INVENTION

[03] Connecting rods are fundamental mechanical components in internal combustion engines that perform the function of transmitting the movement generated by the combustion of the piston to the crankshaft, converting the linear movement of the pistons into rotary movement in the crankshaft. Traditionally, these elements are produced in forged steel or nodular cast iron, materials that guarantee high mechanical resistance. However, this structural robustness results in heavy parts, which can compromise energy efficiency and the Petition 870250094139, dated 10 / 15 / 2025, page 5 / 26 2 / 11 overall engine performance, especially in applications requiring weight reduction, such as racing vehicles, portable equipment, and motorcycles.

[04] To enable rotary motion around the crankshaft journal, conventional connecting rods employ bushings or bearings made of antifriction materials, which function as bearing elements. These components depend on a continuous supply of pressurized oil to ensure efficient lubrication, exhibiting gradual wear over time. Consequently, they require periodic maintenance and scheduled replacements. Failures in the lubrication system, in turn, can lead to seizures, stalling, and severe engine damage. There is also a version of connecting rods that uses cage and roller bearings in the bearing system, which are also subject to the same conditions.

[05] Several alternatives have been proposed to eliminate or minimize the use of bushings, including the use of self-lubricating materials or coating the contact surfaces with antifriction compounds. However, these solutions often involve more complex production processes, increase manufacturing costs, or do not perform satisfactorily under conditions of intense cyclic load and high speeds, which limits their widespread adoption by the industry.

[06] The connecting rod is therefore a critical component in reciprocating engines, and its configuration can vary widely depending on the application. It can be classified according to structure (split or integral), rod geometry (I-profile, H-profile or integral), manufacturing method (machined or forged), material (special steels, alloys of Petition 870250094139, dated 10 / 15 / 2025, page 6 / 26 3 / 11 aluminum, titanium or inconel) and bearing system (roller bearing or bushings / sleeves).

[07] In the state of the art, the use of aluminum connecting rods is still limited to high-performance niches, such as in automotive competitions (in Internal Combustion Alternative Engines) or compressors (an application subject to less severe mechanical stresses), always requiring the use of bearing housings. This is due to the low surface hardness of aluminum, which, even after heat treatments, makes it unsuitable for use with roller bearings. Thus, the need remains for innovative constructive solutions that enable the use of aluminum without the limitations imposed by conventional bearing systems.

[08] Thus, the demand persists for a constructive solution that allows the elimination of the use of bushings without compromising the efficiency, durability, reliability and safety of the system. Such a solution must consider alternative materials, optimized geometry and surface treatments that ensure performance comparable to or superior to conventional connecting rods, with lower weight, lower friction and less need for maintenance.

[09] In research conducted on the state of the art, we identified several solutions applied to connecting rods for engines, where we can highlight the following documents:

[010] Document US6502480 (Walker Bruce, 1998) describes a connecting rod made of 7055-T77511 aluminum alloy, extruded and forged under controlled temperatures, which exhibits excellent compressive and tensile strength. This configuration allows its application in racing engines, reducing structural deformations and increasing Petition 870250094139, dated 10 / 15 / 2025, page 7 / 26 4 / 11 significantly extends the connecting rod's lifespan. Despite offering good strength and low cost, this solution requires high control in the forging process and has limitations in its applicability to air-cooled or smaller engines.

[011] Document CN107740004A (Zhejiang, 2017) discloses a method for producing aluminum connecting rods reinforced with steel fibers. The proposal involves inserting stainless steel fibers into alumina, which is subsequently mixed with aluminum billets, melted, and heat-treated under a nitrogen atmosphere. The aim is to provide mechanical reinforcement to the connecting rod structure. Although the method adds strength to the component, its manufacturing process is complex, involving multiple thermal steps and materials that are difficult to handle industrially, which may compromise economic viability for large-scale applications or in sectors that demand simplicity of production and maintenance.

[012] Document CN218408132U (Chongqing, 2022) describes an aluminum connecting rod developed specifically for air-cooled diesel engines. The connecting rod consists of a main body and a cap, both obtained by aluminum casting, and features a semicircular connection structure that facilitates assembly and the formation of connection holes. This construction allows for greater simplicity in processing and manufacturing, presenting good applicability for medium-sized engines. However, although the design provides ease of manufacturing and assembly, there are still challenges related to the mechanical strength of the assembly, especially in applications involving high loads or intense thermal cycles, such as in engines subjected to continuous use or in adverse environments. Petition 870250094139, dated 10 / 15 / 2025, page 8 / 26 5 / 11

[013] In view of the foregoing, it is observed that the prior art documents present different approaches to the construction of aluminum connecting rods, whether by forging, adding reinforcements or casting. However, gaps remain regarding the ideal balance between mechanical strength, structural lightness, ease of manufacture and feasibility of application in engines of different configurations and operating regimes, and none of them clearly presents the elimination of intermediate elements between the connecting rod and the journal. The present constructive arrangement seeks to overcome these limitations by proposing an aluminum connecting rod with optimized geometries and a modular design that improve heat dissipation, increase fatigue resistance and simplify the production process. SUMMARY OF THE INVENTION

[014] These characteristics give the present invention superior structural performance, with high mechanical strength and lightness, resulting in better efficiency and durability in engine operation, especially in high-performance applications or those subjected to severe loads.

[015] A characteristic of the present invention is the development of an aluminum connecting rod for direct application to the crankshaft journal (or crankshaft pin) without intermediate elements for its operation, whether they are bushings / bearings or roller bearings.

[016] A characteristic of the present invention is an aluminum connecting rod that can be manufactured in different arrangements according to its classification: according to the structure (split or integral), rod geometry (I, H or integral profile) or manufacturing method (machined or forged). Petition 870250094139, dated 10 / 15 / 2025, page 9 / 26 6 / 11

[017] A feature of the present invention is a connecting rod made of high-strength aluminum alloy, preferably SAE 7075 T651, which provides a significant reduction in the weight of the moving assembly of the engine, contributing to lower inertia and better performance of the combustion engine.

[018] A characteristic of the present invention is the elimination of the need for a bushing or bearing in the connecting rod-crankshaft assembly, made possible by dimensional conditions and an internal finishing surface on the connecting rod journal, which operates directly with the crankshaft journal.

[019] A characteristic of the present invention is the surface finish applied to the internal surfaces of the journal and the eye, designed to maintain a stable layer of lubricating oil under pressure, ensuring reliable operation even under extreme torque and rotation conditions.

[020] The present invention features a manufacturing process that includes machining steps, heat treatment to stabilize mechanical properties, and high-precision final finishing, ensuring tight tolerances and high structural durability.

[021] A characteristic of the present invention is the possibility of constructing the connecting rod in different forms, including models with a split journal and with a groove for forming a beam-type profile (I or H), adapting to different applications and engineering requirements.

[022] A characteristic of the present invention is the simplification of the engine system, reducing the number of components subject to wear and periodic replacement, which results in lower maintenance costs and greater operational reliability throughout the engine's service life. Petition 870250094139, dated 10 / 15 / 2025, page 10 / 26 7 / 11

[023] The present invention features the versatile application of the connecting rod, being suitable for both high-performance and conventional engines, offering gains in lightness, efficiency and sustainability.

[024] A characteristic of the present invention is its contribution to sustainability in the automotive sector, through the reduction of the total engine mass, constructive simplification and the elimination of additional materials such as bronze or similar materials. DESCRIPTION OF THE DRAWINGS

[025] Figure 1 shows the perspective and cross-sectional view of the connecting rod, detailing in its first constructive form the point of application of the finishing surface.

[026] Figure 2 shows a perspective view of the connecting rod applied to the assembly, detailing the construction.

[027] Figure 3 shows the perspective and cross-sectional view of the connecting rod, detailing in its second constructive form the point of application of the finishing surface.

[028] Figure 4 shows the perspective and cross-sectional view of the connecting rod, detailing in its third constructive form the point of application of the finishing surface.

[029] Figure 5 shows the perspective and cross-sectional view of the connecting rod, detailing in its fourth constructive form the point of application of the finishing surface. DETAILED DESCRIPTION OF THE INVENTION

[030] The aluminum connecting rod for combustion engine, object of the present invention, comprises a connecting rod (10) made of alloyed aluminum for application in internal combustion engines, being Petition 870250094139, dated 10 / 15 / 2025, page 11 / 26 8 / 11 applicable to both high-performance engines and conventional engines.

[031] The connecting rod (10) made of aluminum is formed by the rod (11) equipped with an eyelet (12) and journal (13) which allows the application of a surface finish on its inner face (13A), eliminating the need for the use of a bushing or sleeve, as detailed in Figure 1.

[032] Figure 2 shows the connecting rod (10) equipped with the rod (11), eyelet (12) and journal (13) positioned next to the journal (M) of the crankshaft (V) and the piston (P) through the pin (P1). The journal (13) of the connecting rod (10) is equipped with an internal finishing surface (13A) that eliminates the use of other components.

[033] The constructive difference of the model now proposed lies in the elimination of the need to use a bushing or bearing in the assembly formed between the connecting rod (10) and the crankshaft journal (M), resulting in a lighter, more efficient and lower cost system. This innovative solution contributes significantly to the reduction of the mass of the moving assembly, decreasing inertia and allowing for better engine performance.

[034] The connecting rod (10) is preferably manufactured from SAE 7075 aluminum alloy, in the T651 heat treated condition, giving the component an ideal combination of high mechanical strength, good ductility and lightness.

[035] The manufacturing process of the aluminum connecting rod (10) has the following steps: a) Initially, the part is machined into its intermediate shape from rolled or forged material, according to the engine model to which it will be applied. Petition 870250094139, dated 10 / 15 / 2025, page 12 / 26 9 / 11 b) Subsequently, it undergoes additional heat treatment to stabilize the mechanical properties of the aluminum, ensuring the structural strength necessary to withstand the cyclic stresses typical of combustion engine operation. The heat treatment developed to increase the structural strength of the proposed model involves processes (with specifically developed parameters) of solution treatment with temperatures ranging from 470 to 490 °C, artificial aging with temperatures ranging from 165 to 175 °C and times that may vary according to the chemical composition of the aluminum, in order to achieve hardness ranges between 160 and 170 HB. c) After heat treatment, finishing machining is performed on the crankshaft journal (13) and connecting rod eye (12) housings, with the aim of ensuring strict dimensional tolerances so that a specific radial clearance is achieved between the crankshaft journal and the connecting rod journal at the time of assembly and adequate surface roughness standards. The journal (13) is the housing where the crankshaft journal (M) (V) is coupled, while the eye (12) is the part of the connecting rod responsible for receiving the piston pin (P1). Both diameters are machined with specific tools, allowing for the obtaining of surfaces with excellent finish. d) The finish applied to the inner surface of the journal (13) and the eyelet (12) is designed to maintain a stable layer of lubricating oil under pressure from the radial clearance calculated and executed in the machining, preventing direct contact between metals even under extreme torque and rotation conditions. This Petition 870250094139, dated 10 / 15 / 2025, p. 13 / 26 The 10 / 11 lubrication system, provided by the engine's lubrication system oil pump, forms a protective film that ensures reliable and durable operation of the assembly. The surface finish is performed directly on the base metal (aluminum) without the need to add a second material or part to these connecting rod sections, whether by mechanical or metallurgical process, by installation or deposition. The manufacturing process developed and applied to achieve such surface finish, tolerances, and shape conditions includes the use of machining inserts and cutting parameters for high-speed operation.Preferably, but not exclusively, micrometric adjustment boring bars are used for this type of machining with CBN inserts (machining elements made from Cubic Boron Nitride). The machining parameters are adjusted according to the diameter to be machined and the final cutting speed (Vc) to achieve a machined surface that meets the surface roughness characteristics for this application. Alternatively, but not exclusively, other necessary or desirable machining elements that can lead to similar results may be used.

[036] The main innovation lies in its geometry, surface finish and material characteristics that allow direct operation with the crankshaft journal (M) without the need for a bushing or bearing.

[037] Figure 3 shows the connecting rod (10), in a second constructive embodiment, provided with a groove (14) for forming the beam profile. Petition 870250094139, dated 10 / 15 / 2025, p. 14 / 26 11 / 11

[038] Figure 4 shows the connecting rod (10), in a third constructive embodiment, equipped with an eyelet (12) and a split journal (13.1) equipped with an internal finishing surface (13.1A) that eliminates the use of other components.

[039] Figure 5 shows the connecting rod (10), in a fourth constructive embodiment, equipped with an eyelet (12) and split journal (13.1) equipped with an internal finishing surface (13.1A) that eliminates the use of other components, said connecting rod having a groove (14) for forming the beam profile.

[040] In addition to providing a significant weight reduction in the powertrain assembly, the absence of the bearing simplifies the engine manufacturing and maintenance process. This also reduces the number of components subject to wear and periodic replacement, increasing system reliability and decreasing the total cost of ownership of the engine over its service life. Therefore, the proposed connecting rod (10) becomes highly advantageous for both sporting applications, where performance is critical, and for everyday vehicles, where durability and efficiency are paramount.

[041] Finally, the connecting rod object of this invention presents a technological solution that adds value to the engine system, combining materials engineering, dimensional precision and mechanical efficiency. By eliminating one of the components traditionally considered indispensable in the connecting rod-crankshaft assembly, the present proposal represents a significant advance in the construction of internal combustion engines, aligning with trends in structural optimization and sustainability through mass reduction and system simplification. Petition 870250094139, dated 10 / 15 / 2025, page 15 / 26

Claims

1 / 2 CLAIMS:

1. PROCESS, characterized by comprising the steps of: a) machining the intermediate shape from rolled or forged material; b) solution heat treatment between 470 and 490 °C and artificial aging between 165 and 175 °C, with time adjusted according to the composition of the aluminum, in order to achieve hardness between 160 and 170 HB; and c) finishing machining of the journal housings (13) and the eyelet (12) with rigorous dimensional tolerances and surface roughness suitable for direct operation with the journal (M) of the crankshaft (V) and with the pin (P1) of the piston (P).

2. PROCESS, according to claim 4, characterized in that the finishing machining is performed using micrometric boring bars and CBN (Cubic Boron Nitride) inserts, adjusted according to the diameter and final cutting speed (Vc) to obtain a surface with roughness suitable for the application.

3. ALUMINUM CONNECTING ROD FOR COMBUSTION ENGINE, according to the process of claim 1, comprising a connecting rod (10) formed by a rod (11) provided with an eyelet (12) and journal (13), characterized in that the journal (13) has an internal finishing surface (13A) configured to operate directly with the journal (M) of the crankshaft (V), eliminating the need for the use of a bushing or bearing.

4. ALUMINUM CONNECTING ROD FOR COMBUSTION ENGINE, according to claim 3, characterized in that the internal finish surface (13A) is obtained by high precision machining directly on the base metal, without the addition of any coating, insert or additional component.

5. ALUMINUM CONNECTING ROD FOR COMBUSTION ENGINE, according to claim 3, characterized in that the internal finish (13A) is made in such a way as to maintain a stable layer of lubricating oil under pressure, from the radial clearance calculated during machining.

6. CONNECTING ROD, according to claim 3, characterized in that the rod (11) includes a groove (14) for forming the beam profile, intended to increase structural rigidity and reduce the weight of the part.

7. ALUMINUM CONNECTING ROD FOR COMBUSTION ENGINE, according to claim 3, characterized in that the journal (13.1) is configured in a split form, having an internal finishing surface (13.1A) capable of operating directly with the journal (M) of the crankshaft (V) without the use of a bushing or bearing.

8. ALUMINUM CONNECTING ROD FOR COMBUSTION ENGINE, according to claim 3, characterized by simultaneously including the groove (14) for forming the beam profile and the split journal (13.1). Petition 870250094139, dated 15 / 10 / 2025, p. 17 / 26

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