A connecting rod and engine having a special profile

Abstract

The application discloses a connecting rod with special lines and an engine and relates to the field of engine structure design.The connecting rod comprises a crankshaft and a connecting rod body, the outer surface of the crankshaft is provided with a journal, the end of the connecting rod body is provided with a connecting rod big head, the connecting rod big head is arranged on the outer periphery of the journal, an oil film establishing assembly is arranged between the connecting rod big head and the journal, the middle part of the crankshaft is provided with an oil supply assembly, the oil film establishing assembly comprises a big head hole, the big head hole is arranged in the middle part of the connecting rod big head, and the inner wall of the connecting rod big head is provided with an inner concave line.The big head hole is directly sleeved on the outer surface of the journal, the structure of the bearing bush arranged between the big head hole and the journal is eliminated, the inner wall surface of the big head hole directly contacts the lubricating oil film of the journal surface, the above-mentioned directly matched structure reduces the number of parts in the connecting rod assembly, and the overall development cost of the engine is reduced.

Description

Technical Field

[0001] This application relates to the field of engine structure design, and in particular to a connecting rod and engine with a special profile. Background Technology

[0002] In a reciprocating piston internal combustion engine, the crankshaft and connecting rod mechanism converts the reciprocating motion of the piston into the rotational motion of the crankshaft. Currently, connecting rods are mostly made of metal steel, and the high density of this material results in a heavy overall weight. This heavy weight increases the dissipation work generated by the connecting rod rotating with the crankshaft, hindering improvements in engine thermal efficiency.

[0003] In traditional crankshaft connecting rod mechanisms, the connecting rod big end bore and the crankshaft journal have a plane-to-plane fit, and a bearing bush is required between them to adjust the assembly clearance. This plane-to-plane fit makes it difficult for lubricating oil to accumulate between the mating surfaces, resulting in slow lubricant film formation. Slow lubricant film formation increases the frictional work between the connecting rod big end bore and the crankshaft journal, making bearing failure more likely.

[0004] The clearance between the traditional connecting rod big end bore and the crankshaft journal is typically controlled between 15µm and 20µm. This fit clearance requires strict grouping and selection of the crankshaft journal and connecting rod big end bore dimensions. The additional selection steps and the need for additional bearing structures increase the overall engine development and production management costs. Summary of the Invention

[0005] The purpose of this invention is to provide a connecting rod and engine with a special profile, which at least solves one of the technical problems of existing connecting rods using steel structures, resulting in heavy connecting rod mass and thus high rotational power dissipation; slow establishment of lubricating oil film at the mating surface between the connecting rod big end bore and the crankshaft journal, resulting in high frictional power and easy bearing failure; and high engine development and management costs due to the need to set bearings and strictly control the mating clearance.

[0006] This invention provides the following solution:

[0007] According to a first aspect of the present invention, a connecting rod with a special profile is provided, comprising a crankshaft and a connecting rod body, wherein a journal is provided on the outer surface of the crankshaft, a connecting rod big end is provided at the end of the connecting rod body, the connecting rod big end is disposed on the outer periphery of the journal, an oil film building assembly is provided between the connecting rod big end and the journal, and an oil supply assembly is provided in the middle of the crankshaft;

[0008] The oil film building assembly includes a large end hole, which is located in the middle of the connecting rod large end. The inner wall of the connecting rod large end is provided with a concave profile, and an oil storage space is formed between the concave profile and the mating surface of the journal, with the central radial clearance being greater than the radial clearance on both sides.

[0009] Furthermore, the oil supply assembly includes an oil passage disposed inside the crankshaft, with an inlet and an outlet respectively provided at both ends of the oil passage.

[0010] Furthermore, the concave profile of the inner wall of the large end hole and the outer surface of the journal are both arc-shaped structures, and the arc diameter of the concave profile is larger than the arc diameter of the journal.

[0011] Furthermore, the axis of the large end hole coincides with the axis of the journal.

[0012] Furthermore, both the connecting rod body and the connecting rod big end are made of aluminum, and a groove is provided on the outer side of the connecting rod body.

[0013] Furthermore, the liquid inlet and the liquid outlet are located on the surfaces of the crankshaft and the journal, respectively, and the liquid outlet is connected to the oil storage space.

[0014] Furthermore, no bearing is provided between the large end hole and the journal.

[0015] Furthermore, the fitting clearance between the large end hole and the journal is 55–65 µm.

[0016] A second aspect of the present invention provides an engine including a connecting rod having a special profile as described in any of the first aspects of the present invention.

[0017] Furthermore, the engine is a naturally aspirated engine, and the engine contains four connecting rod bodies, which together with a crankshaft constitute a connecting rod assembly.

[0018] The above solution achieves the following beneficial technical effects:

[0019] This invention creates an oil reservoir by forming a concave profile on the inner wall of the connecting rod big end bore, with the arc diameter of the concave profile being larger than that of the journal. This creates a central radial clearance larger than the radial clearances at the two side edges between the concave profile and the journal. This oil reservoir allows lubricating oil to remain and flow within the central radial clearance. The flowing lubricating oil prevents heat generated by friction from accumulating in the center of the journal, reducing the frictional work generated during high-speed relative rotation between the connecting rod big end and the journal. Simultaneously, the clearance between the big end bore and the journal is increased to 60µm, eliminating the need for dimensional grouping and selection of the big end bore and journal.

[0020] This invention reduces the weight of the connecting rod body and big end to one-third of that of a steel connecting rod by using aluminum. This weight reduction decreases the dissipation work generated as the connecting rod rotates with the crankshaft, improving engine thermal efficiency and reducing fuel consumption.

[0021] This invention eliminates the need for a bearing bush between the large end bore and the journal by directly fitting the large end bore onto the outer surface of the journal. The inner wall surface of the large end bore directly contacts the lubricating oil film on the journal surface. This direct-fit structure reduces the number of internal components in the connecting rod assembly, thereby lowering the overall engine development cost. Attached Figure Description

[0022] Figure 1 This is a perspective view of an embodiment of the present invention.

[0023] Figure 2 This is a schematic diagram of the crankshaft structure according to an embodiment of the present invention.

[0024] Figure 3 This is a schematic diagram of the linkage structure according to an embodiment of the present invention.

[0025] Figure 4 This is a schematic diagram of the oil film building component structure according to an embodiment of the present invention.

[0026] Figure 5 This is a schematic diagram of the cross-sectional structure of the connecting rod according to an embodiment of the present invention.

[0027] Figure 6 for Figure 4 Enlarged view of point A in the middle.

[0028] Among them, 1. crankshaft; 2. journal; 3. liquid inlet; 4. liquid outlet; 5. connecting rod body; 6. groove; 7. big end bore; 8. oil passage; 9. concave profile; 10. connecting rod big end. Detailed Implementation

[0029] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] See appendix Figure 1 Appendix Figure 4 and attached Figure 6The present invention provides a connecting rod with a special profile, including a crankshaft 1 and a connecting rod body 5. A journal 2 is provided on the outer surface of the crankshaft 1, and a connecting rod big end 10 is provided at the end of the connecting rod body 5. The connecting rod big end 10 is provided on the outer periphery of the journal 2. An oil film building assembly is provided between the connecting rod big end 10 and the journal 2, and an oil supply assembly is provided in the middle of the crankshaft 1.

[0031] In one specific embodiment, the connecting rod big end 10 is fitted onto the outside of the journal 2, eliminating the need for the bearing structure that must be assembled in traditional connecting rod mechanisms. The connecting rod body 5 moves along with the crankshaft 1. The crankshaft 1, the four connecting rod bodies 5, and the four connecting rod big ends 10 together constitute the connecting rod assembly. When the engine is running, the piston is pushed by the explosive pressure of the combustion gases to make linear reciprocating motion, and the connecting rod assembly converts the up-and-down reciprocating motion of the connecting rod body 5 into the high-speed rotational motion of the crankshaft 1. In this high-speed, heavy-load relative motion, the crankshaft 1 usually rotates at several thousand revolutions per minute, and the connecting rod big end 10 bears huge alternating inertial forces and pulse pressures from the work done by gas expansion. To avoid direct contact between metal parts under such harsh conditions, which could lead to wear or even seizure, an oil film building assembly is used to quickly and stably form a lubricating oil film between the connecting rod big end 10 and the journal 2.

[0032] This lubricating oil film isolates the metal surfaces of the connecting rod big end 10 and the journal 2, significantly reducing the frictional resistance generated when the connecting rod big end 10 and the journal 2 rotate relative to each other, thus converting boundary friction into fluid friction. Simultaneously, the oil supply assembly continuously and directionally delivers lubricating oil to the oil film building assembly, ensuring the continuous establishment and dynamic renewal of the lubricating oil film. Because during continuous operation, old oil is squeezed out to both sides under pressure and lost, a continuous supply of fresh oil is necessary to maintain the balance of hydrodynamic pressure.

[0033] See appendix Figure 3 -Appendix Figure 6 The oil film building assembly includes a large end bore 7, which is located in the middle of the connecting rod large end 10. The inner wall of the connecting rod large end 10 is provided with a concave profile 9. The concave profile 9 and the mating surface of the journal 2 form an oil storage space with a central radial clearance greater than the radial clearances on both sides. The concave profile 9 on the inner wall of the large end bore 7 and the outer surface of the journal 2 are both arc-shaped structures, and the arc diameter of the concave profile 9 is greater than the arc diameter of the journal 2.

[0034] In one specific embodiment, the inner wall surface of the connecting rod big end 10 is machined with a concave profile 9 of an arc-shaped structure. In actual machining processes, this concave profile 9 can be machined using a high-precision CNC boring machine or a dedicated forming reamer to ensure that the surface roughness of the arc surface meets the requirements of hydrodynamics. The concave profile 9 of the arc-shaped structure mates with the journal 2 of the arc-shaped structure, and the arc diameter of the concave profile 9 is larger than the arc diameter of the journal 2, thus forming a hydrodynamic oil storage space between the mating surfaces of the concave profile 9 and the journal 2. This oil storage space exhibits a shape with a large radial clearance in the middle and a small radial clearance on both sides in the axial direction.

[0035] Those skilled in the art will understand that, according to the theory of hydrodynamic lubrication (i.e., the Reynolds equation principle), when a wedge-shaped gap exists between two relatively moving surfaces, and the fluid has a certain viscosity, the fluid is drawn into the converging wedge-shaped gap, generating a hydrodynamic effect and forming a hydrodynamic oil film with load-bearing capacity. In traditional planar-to-planar fits, the axial clearance is evenly distributed. Due to the lack of axial geometric constraints, under alternating heavy loads, this leads to poor oil accumulation and a high rate of end-leakage, meaning a high proportion of lubricating oil leaks from the edges of the journal 2. This results in slow oil film formation and easy rupture. In this application, the aforementioned oil storage space allows the lubricating oil to remain within the wider radial gap in the middle and maintain good fluidity. The smaller radial gaps on both sides act as physical throttle valves, reducing the end-leakage rate of the oil and forcing the oil to build up a higher internal fluid pressure within the larger central oil storage space, forming a wedge-shaped and stepped composite hydrodynamic oil film with strong load-bearing stiffness. This composite oil film remains unbroken even in harsh boundary lubrication zones such as low engine speeds and high loads.

[0036] Furthermore, since the radius of curvature of the concave profile 9 is set to be greater than that of the journal 2, when the journal 2 rotates eccentrically within the hole, the wedge-shaped gap formed between them not only converges circumferentially but also forms a three-dimensional space that gradually converges from the center to both ends axially. This causes the fluid dynamic pressure field generated by the internal oil under shearing action to exhibit an extremely full three-dimensional parabolic shape. Compared to the localized pressure peaks that easily occur in traditional cylindrical surface fits, this method can evenly distribute the supporting force over a wider bearing area, reducing the ultimate pressure per unit area.

[0037] Furthermore, this oil reservoir plays a crucial protective role during engine cold starts. It is well known that over 70% of engine wear occurs during a cold start, when the oil pump has not yet established sufficient system oil pressure, and traditional flat bearings are often in a state of dry friction. However, the oil reservoir in this invention, due to its surface tension and its grooved structure, can accommodate a large amount of residual oil after shutdown. During the first few working cycles of the next cold start, this residual oil is immediately dragged into the wedge-shaped gap by rotation, forming an emergency oil film. This perfectly fills the vacuum period before system oil pressure is established, thereby extending the physical life of the mechanical mating surfaces.

[0038] Meanwhile, from a thermodynamic perspective, the bearing failure phenomenon in connecting rods of internal combustion engines is essentially a result of heat imbalance. Since the viscosity of engine oil is greatly affected by temperature, the higher the temperature, the thinner the oil becomes, which is less conducive to lubrication. When a traditional flat-to-flat structure experiences minor friction, a sudden increase in local temperature causes the engine oil to thin instantly and leak out, creating a vicious cycle. Ultimately, dry friction and welding occur on the metal surfaces (i.e., bearing failure). In this design, the wider oil reservoir in the middle accommodates a larger volume of engine oil, increasing the fluid heat capacity of this area. The flowing lubricating oil can promptly carry away the heat generated by the high-speed friction between the connecting rod big end 10 and the journal 2, preventing excessive heat accumulation in the middle of the journal 2 and resulting in localized high temperatures. This not only prevents the engine oil from thinning and losing its lubricating ability due to high temperatures but also prevents bearing seizure caused by localized overheating. Sufficient oil flow is equivalent to providing a built-in liquid-cooled micro-circulation system for the journal 2, making the temperature field distribution at the friction interface more uniform, thereby preventing the induction of bearing failure.

[0039] Furthermore, high-speed alternating load environments often lead to momentary negative pressure in localized areas within the lubricating oil film, causing the precipitation of dissolved gases in the oil and the collapse of bubbles, resulting in cavitation. The anti-friction alloy layer on the surface of traditional bearings is relatively soft and easily peeled off by the micro-jet flow generated by cavitation collapse, forming pitting corrosion and ultimately leading to bearing fatigue failure. In this design, the wider central oil reservoir provides excellent buffer volume for pressure fluctuations within the oil. Even when the burst pressure reaches its peak, causing a momentary change in clearance, the abundant surrounding oil can quickly fill and compensate, effectively suppressing the formation of a negative pressure zone and eliminating the physical conditions for cavitation. During the early break-in phase of the engine, the microscopic protrusions on the inner wall surface of the aluminum large-end bore 7 will have extremely slight contact with the surface of the journal 2. Thanks to the excellent microscopic compliance and embedding properties of the aluminum alloy material, the tiny metal debris generated during break-in can be quickly carried away by the abundant oil flow in the oil reservoir and intercepted by the oil filter, preventing severe abrasive wear on the contact surface. As the break-in period ends, a highly dense oxide film will form on the surface of the large end bore 7, which is completely conformable to the journal 2. Combined with a stable thick oil film, it can achieve a near-zero wear operation state throughout the entire life cycle of the engine.

[0040] Furthermore, thanks to the strong oil storage and self-lubricating capabilities of the aforementioned oil storage space, the clearance between the large end bore 7 and the journal 2 can be widened to 55–65 µm, preferably controlled at 60 µm. In conventional connecting rod designs, to ensure oil film establishment and prevent seizing, the clearance is typically limited to 15–20 µm. This is because traditional flat surfaces suffer from severe end leakage, requiring extremely small clearances to maintain oil pressure. However, the 15–20 µm tolerance requirement is difficult to achieve in actual mass production, necessitating high-precision coordinate measuring of the shaft and bore dimensions, the establishment of multiple tolerance grades for manual or automatic grouping, and rigorous pairing selection. Even a slight error in pairing can lead to premature wear failure. In this case, a tolerance clearance of 55–65 µm is used, which is not only about three times larger than the traditional clearance, but more importantly, this clearance range can be directly controlled through conventional simple machining processes, such as ordinary honing or precision boring. Any connecting rod big end 10 on the production line can be directly installed onto any crankshaft journal 2, achieving interchangeable assembly. This avoids the tedious steps of precision dimensional grouping and selection of big end bore 7 and journal 2, eliminates the matching station, reduces the scrap rate, and significantly reduces production management and manufacturing costs.

[0041] See appendix Figure 1 Appendix Figure 2 and attached Figure 6 The oil supply assembly includes an oil passage 8, which is located inside the crankshaft 1. The oil passage 8 has an inlet 3 and an outlet 4 at both ends. The inlet 3 and the outlet 4 are located on the surfaces of the crankshaft 1 and the journal 2, respectively, and the outlet 4 is connected to the oil storage space.

[0042] In one specific embodiment, external lubricating oil with a certain pressure is pumped by the engine via the oil pump and flows into the oil passage 8 from the inlet 3. The lubricating oil then travels along the oil passage 8 inside the crankshaft 1 to the outlet 4. When the crankshaft 1 rotates at high speed, the lubricating oil inside the oil passage 8 is also subjected to centrifugal force, which provides an additional pumping and pressurizing effect. The lubricating oil then flows out from the outlet 4 and is directly pumped into the oil storage space, where the radial clearance in the middle is larger than the radial clearance on both sides. The lubricating oil in the oil storage space rapidly spreads between the large end bore 7 and the journal 2 to form an oil film with considerable thickness and load-bearing capacity. Under the throttling effect of the smaller clearance on both sides, the lubricating oil is prevented from flowing out too quickly, thereby maintaining the oil film pressure. When the engine completes its power stroke and the connecting rod body 5 is subjected to a large downward impact force, the oil film in the oil storage space will generate a squeezing effect similar to a hydraulic buffer pad, further absorbing and dissipating the impact energy and mitigating the fatigue damage of alternating loads to the metal matrix.

[0043] See appendix Figure 4 The axis of the large end hole 7 coincides with the axis of the journal 2.

[0044] In one specific embodiment, the arrangement of the axis of the large end bore 7 coinciding with the axis of the journal 2 ensures that when the connecting rod large end 10 rotates relative to the crankshaft 1, a stable radial clearance dimension can be maintained throughout the entire circumference, avoiding uneven wear and ensuring the uniformity of the oil film thickness. If there is a deviation in the axis, the two ends of the large end bore 7 will make edge contact, destroying the sealing and throttling effect of the smaller radial clearance on both sides, resulting in a sudden drop in local oil film pressure. Therefore, the structural layout of the coincident axis is the basic geometric condition for maintaining the fluid sealing of the oil storage space of the present invention.

[0045] See appendix Figure 3 -Appendix Figure 5 Both the connecting rod body 5 and the connecting rod big end 10 are made of aluminum, and the outer side of the connecting rod body 5 is provided with a groove 6.

[0046] In one specific embodiment, considering that conventional engine connecting rods on the market are made of high-rigidity but heavy steel materials, such as 45 steel or 40Cr forged alloy steel, to withstand high explosion pressure, the connecting rod body 5 and connecting rod big end 10 in this solution are specifically made of aluminum, for example, using high-silicon aluminum alloy die castings or forged aluminum alloys of specific grades, to adapt to naturally aspirated engines with low explosion pressure. After the connecting rod body 5 and connecting rod big end 10 are made of aluminum, their overall weight can be reduced to about one-third of the weight of traditional steel materials. This reduction in weight of the connecting rod body 5 and connecting rod big end 10 has extremely important implications for dynamics.

[0047] On the one hand, it reduces the reciprocating inertial force generated by the reciprocating motion of the piston and connecting rod assembly;

[0048] On the other hand, it also reduces the rotational inertial force generated when the connecting rod big end 10 rotates with the crankshaft 1.

[0049] By significantly reducing inertial forces, the moment of inertia of the connecting rod assembly is directly reduced, thereby decreasing the mechanical dissipation work generated when the connecting rod rotates with the crankshaft 1. This reduction in dissipation work directly improves the engine's mechanical and thermal efficiency and reduces fuel consumption. Furthermore, the lighter weight of the moving parts reduces the amplitude of second-order vibrations during engine operation, optimizing engine noise, vibration, and acoustic roughness. Simultaneously, the groove 6, located on the side wall of the connecting rod body 5, forms an I-shaped cross-sectional feature while ensuring sufficient bending and compressive strength, further reducing the bulk volume and excess weight of the connecting rod body 5 and optimizing the utilization of the material's cross-sectional moment of inertia.

[0050] By using aluminum for the connecting rod body 5 and connecting rod big end 10 to reduce weight, not only are their mechanical properties optimized, but a positive cascading effect is also generated on the overall dynamic balance of the engine. In the crankshaft and connecting rod mechanism, to balance the centrifugal inertial force generated by the rotation of the connecting rod big end 10 and the crank pin, a large counterweight is usually placed in the opposite direction of the crankshaft 1. When the mass of the connecting rod big end 10 is reduced to one-third of that of traditional steel, according to the dynamic balance equation, the mass of the balancing weight required on the crankshaft 1 is also reduced accordingly. The forging material, machining allowance, and overall rotational inertia of the crankshaft 1 itself are all reduced a second time. This lightweighting makes the engine run more smoothly at idle and the speed increase response becomes extremely rapid during rapid acceleration, giving the vehicle more sensitive throttle response and a more sporty power output performance.

[0051] No bearing is installed between the large end hole 7 and the journal 2.

[0052] In one specific embodiment, the large end hole 7 is directly fitted onto the outer surface of the journal 2, and the inner aluminum surface of the large end hole 7 directly contacts the lubricating oil film on the surface of the journal 2. This eliminates the need for a traditional bearing structure between the large end hole 7 and the journal 2. Traditional connecting rods, to protect the steel connecting rod body 5 from wear, must have a sliding bearing made of a steel back and a friction-reducing alloy layer, such as Babbitt metal or copper-lead alloy, pressed into its inner hole. This not only increases the number of parts but also easily leads to the fatal failure of the bearing rotating outwards during high-speed operation, i.e., the bearing rotating within the connecting rod hole. In this application, the aluminum connecting rod large end 10, being a lightweight metal material, often contains hard particles such as silicon in its metallographic structure, possessing certain self-reducing and wear-resistant properties. Combined with the thick oil film isolation effect provided by the aforementioned special concave profile 9, it makes it possible for the connecting rod to directly mate with the journal 2. It eliminates the cost of developing separate bearing molds and removes the bearing installation process on the assembly line, avoiding potential quality risks such as bearing misalignment and misalignment. It also reduces the number of internal parts in the connecting rod assembly, thereby lowering the overall development and assembly costs of the engine.

[0053] The present invention also provides an engine, including a connecting rod with a special profile as described above.

[0054] In one specific embodiment, the engine is a naturally aspirated engine. Compared to the widely used turbocharged engines of today, naturally aspirated engines operate in a low-detonation-pressure environment, resulting in a relatively mild combustion explosion force within the cylinders. Their peak combustion pressure is often within a controllable safety threshold, thus perfectly suited to the connecting rod body 5 made of aluminum. This avoids the risk of yielding deformation or fracture that may occur in aluminum under high detonation pressure, achieving a precise match between material strength and operating conditions. Furthermore, the engine contains four connecting rod bodies 5, a common inline four-cylinder engine design. The four connecting rod bodies 5, together with a crankshaft 1, constitute the connecting rod assembly.

[0055] This engine product comprehensively utilizes the lightweight advantages of aluminum connecting rods and the excellent self-lubrication and tolerance advantages brought by their special profile. During the four strokes of intake, compression, power, and exhaust, this connecting rod assembly exhibits excellent speed response due to its ultra-low inertia, thereby reducing the overall engine development cost, production management cost, and final fuel consumption, demonstrating strong market mass production prospects and economic benefits.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A connecting rod with a special profile, characterized in that, The crankshaft (1) includes a crankshaft (1) and a connecting rod body (5). The outer surface of the crankshaft (1) is provided with a journal (2). The end of the connecting rod body (5) is provided with a connecting rod big end (10). The connecting rod big end (10) is located on the outer periphery of the journal (2). An oil film building assembly is provided between the connecting rod big end (10) and the journal (2). An oil supply assembly is provided in the middle of the crankshaft (1). The oil film building assembly includes a large end hole (7), which is located in the middle of the connecting rod large end (10). The inner wall of the connecting rod large end (10) is provided with a concave profile (9), and an oil storage space is formed between the concave profile (9) and the mating surface of the journal (2) with a central radial clearance greater than the radial clearance on both sides.

2. A connecting rod with a special profile according to claim 1, characterized in that, The oil supply assembly includes an oil passage (8), which is located inside the crankshaft (1). The two ends of the oil passage (8) are respectively provided with an inlet (3) and an outlet (4).

3. A connecting rod with a special profile according to claim 1, characterized in that, The concave profile (9) on the inner wall of the large hole (7) and the outer surface of the journal (2) are both arc-shaped structures, and the arc diameter of the concave profile (9) is greater than the arc diameter of the journal (2).

4. A connecting rod with a special profile according to claim 1, characterized in that, The axis of the large end hole (7) coincides with the axis of the journal (2).

5. A connecting rod with a special profile according to claim 1, characterized in that, Both the connecting rod body (5) and the connecting rod big end (10) are made of aluminum, and a groove (6) is provided on the outer side of the connecting rod body (5).

6. A connecting rod with a special profile according to claim 2, characterized in that, The inlet (3) and the outlet (4) are located on the surfaces of the crankshaft (1) and the journal (2), respectively, and the outlet (4) is connected to the oil storage space.

7. A connecting rod with a special profile according to claim 1, characterized in that, No bearing is provided between the large end hole (7) and the journal (2).

8. A connecting rod with a special profile according to claim 1, characterized in that, The clearance between the large end hole (7) and the journal (2) is 55-65µm.

9. An engine, characterized in that, Includes a connecting rod with a special profile as described in any one of claims 1-8.

10. An engine according to claim 9, characterized in that, The engine is a naturally aspirated engine, and the engine is equipped with four connecting rod bodies (5), which together with a crankshaft (1) constitute a connecting rod assembly.

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