Automobile hub bearing with gradient buffer energy-absorbing structure

Abstract

The application discloses a car hub bearing with gradient buffer energy-absorbing structure, which comprises a bearing outer ring, a bearing inner ring, rolling bodies and a retainer, the rolling bodies are rollably arranged between the bearing outer ring and the bearing inner ring through the retainer, the bearing outer ring and the bearing inner ring are both provided with a raceway for rolling of the rolling bodies, and the bearing outer ring and the bearing inner ring are both base bodies, and the inner circumferential wall of the raceway is sequentially provided with a nano-strengthened surface layer, a gradient elastic buffer layer and a high-strength base body layer in the direction of the respective base body interiors. The application solves the problems that in the prior art, the hardness and toughness are unbalanced due to overall material optimization of the car hub bearing, the "hard-soft" abrupt interface is prone to peeling off due to surface strengthening, and the raceway impact indentation problem cannot be fundamentally improved by both of them, thereby causing the early failure of the bearing.

Description

Technical Field

[0001] This invention relates to the field of bearing technology, specifically to an automotive wheel hub bearing with a gradient buffer energy absorption structure. Background Technology

[0002] As a core component for load transmission and power transmission in vehicles, the reliability of wheel bearings directly determines the overall vehicle's driving safety, comfort, and service life. During actual vehicle operation, the raceway surface of the wheel bearing continuously withstands high-frequency, high-stress impact loads from the road surface (such as when traversing bumpy roads or driving over potholes and obstacles), easily forming impact indentations (i.e., Brinell indentations) on the raceway surface. These indentations are not only a major source of abnormal noise and vibration during bearing operation but also become significant stress concentration points, accelerating the initiation and propagation of fatigue cracks, ultimately leading to premature bearing failure and seriously affecting driving safety.

[0003] To improve the impact resistance of wheel hub bearings, existing technologies mainly employ two types of solutions: one is overall material optimization, which attempts to simultaneously improve the overall hardness and toughness of the material by increasing the purity of the bearing steel and optimizing the heat treatment process. However, this solution has an inherent contradiction: the improvement of overall hardness inevitably comes at the cost of material toughness, which may lead to cracking of the bearing under extreme impact loads. The other is surface strengthening treatment, which forms a high-hardness surface strengthening layer by nitriding, carburizing, and other processes on the raceway surface. However, this solution creates a "hard-soft" abrupt interface structure, which is prone to peeling off the strengthening layer due to insufficient interfacial bonding or uncoordinated plastic deformation under huge impact loads, and cannot fundamentally solve the problem of impact indentation. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides an automotive wheel hub bearing with a gradient buffer energy absorption structure. This addresses the problem that existing automotive wheel hub bearings suffer from imbalances in hardness and toughness due to overall material optimization, and the tendency to peel off due to a sudden "hard-soft" interface caused by surface strengthening. Neither of these methods can fundamentally improve the raceway impact indentation problem, leading to premature bearing failure.

[0005] To achieve the above objectives, the present invention provides an automotive wheel hub bearing with a gradient buffer energy absorption structure, comprising an outer bearing ring, an inner bearing ring, rolling elements, and a cage. The rolling elements are rotatably disposed between the outer and inner bearing rings via the cage. Both the outer and inner bearing rings have raceways for the rolling elements to roll. Both the outer and inner bearing rings are substrates. The inner peripheral walls of the raceways are sequentially provided with a nano-reinforced surface layer, a gradient elastic buffer layer, and a high-strength substrate layer in their respective directions into the substrate.

[0006] The advantages of adopting the above technical solution are as follows: The technology provides high hardness and wear resistance by setting a nano-reinforced surface layer on the raceways of the outer and inner rings of the bearing to resist initial impact. A gradient elastic buffer layer efficiently absorbs and disperses impact energy. A high-strength matrix layer ensures the rigid support of the overall raceway structure. These three elements form a synergistically optimized "hard-tough-strong" structure, effectively solving the problem of hardness and toughness imbalance caused by overall material optimization in existing technologies. It avoids the risk of "hard-soft" interface peeling caused by surface strengthening, fundamentally improving the raceway impact indentation phenomenon, enhancing bearing rotation accuracy, reducing operating vibration and noise, making the wear of rolling elements and raceways more uniform, increasing bearing life and reliability, and ensuring the safety and comfort of the entire vehicle.

[0007] The present invention further comprises: the nano-reinforced surface layer is made by at least one of mechanical grinding, plasma nitriding, or laser nano-sizing processes; the nano-reinforced surface layer has a nanocrystalline or ultrafine crystalline structure; the thickness of the nano-reinforced surface layer ranges from 10 to 50 μm; and the microhardness of the nano-reinforced surface layer is 1.5 to 2.5 times that of the material used to prepare the substrate.

[0008] The advantages of adopting the above technical solution are: the preparation process of the nano-reinforced surface layer in the above technology is flexible and selective, which can be adapted to different production needs and scenarios. Its nanocrystalline or ultrafine crystalline structure endows the surface layer with excellent hardness and wear resistance; it can effectively resist micro-cutting and plastic deformation under impact load, providing the first impact barrier for the raceway, forming a synergistic protection with the gradient elastic buffer layer and high-strength matrix layer, avoiding the performance limitations brought about by a single process, ensuring the surface reinforcement effect without affecting the overall mechanical properties of the bearing, adapting to the cost control requirements of mass production or the high performance requirements of high-end products, strengthening the raceway's resistance to initial impact, laying the foundation for subsequent impact energy dispersion and absorption, and improving the overall failure resistance of the bearing.

[0009] The present invention further comprises: the gradient elastic buffer layer being located between the nano-reinforced surface layer and the high-strength substrate layer; the gradient elastic buffer layer being a composite layer formed by at least one of the following processing techniques: multilayer physical vapor deposition, gradient thermal treatment, or laser cladding; the material composition of the gradient elastic buffer layer comprising an iron-based alloy and dispersed silicon nitride or tungsten carbide particles; the thickness of the gradient elastic buffer layer being 0.1-0.5 mm; and the elastic modulus of the gradient elastic buffer layer decreasing continuously or in a stepwise manner from the junction of the gradient elastic buffer layer and the nano-reinforced surface layer to the junction of the gradient elastic buffer layer and the high-strength substrate layer.

[0010] The advantages of adopting the above technical solution are: the preparation process of the gradient elastic buffer layer in the above technology has strong compatibility and can be flexibly combined and selected according to actual needs; the composite material of its iron-based alloy and dispersed particles enhances the structural stability and load-bearing capacity; and the gradient decreasing characteristic of the elastic modulus realizes the gradient absorption and transmission of impact energy, effectively dispersing concentrated impact stress and avoiding structural damage caused by stress concentration; by connecting the nano-reinforced surface layer and the high-strength matrix layer, the performance abrupt change between different layers is eliminated, ensuring tight interlayer bonding, preventing surface peeling under impact load, improving the reliability and durability of the buffer structure, providing continuous and stable buffer protection for the raceway, and enhancing the bearing's impact resistance and fatigue resistance.

[0011] The present invention further specifies that the elastic modulus of the gradient elastic buffer layer is 200-250 GPa on the side near the nano-reinforced surface layer, and the elastic modulus of the gradient elastic buffer layer is 100-150 GPa on the side near the high-strength matrix layer.

[0012] The advantages of adopting the above technical solution are: the elastic modulus on both sides of the gradient elastic buffer layer forms a reasonable gradient difference, which causes the buffer layer to undergo controllable plastic deformation under impact load, efficiently absorbs impact energy, and thus significantly attenuates the stress peak transmitted to the high-strength matrix layer, avoids plastic deformation indentation of the raceway due to stress overload, enhances the coordination of mechanical properties between layers, improves the bonding reliability of the buffer layer with the nano-reinforced surface layer and the high-strength matrix layer, prevents structural damage caused by deformation incoordination between layers, strengthens the stability of the bearing under high-frequency impact scenarios, extends the service life of the bearing, and ensures the smoothness and safety of the vehicle during driving.

[0013] The present invention further comprises: the surface of the nano-reinforced surface layer is coated with a diamond-like film with a thickness of 1-3 μm.

[0014] The advantages of adopting the above technical solution are: the diamond-like carbon film on the surface of the nano-reinforced layer further improves the surface hardness and wear resistance, while enhancing the friction reduction performance and reducing frictional loss between the rolling elements and the raceway; it slows down the surface wear rate, extends the service life of the nano-reinforced surface, strengthens its resistance to initial impact and micro-cutting, and through the synergistic effect with the core performance of the nano-reinforced surface, reduces vibration and abnormal noise during bearing operation, improves rotational smoothness, avoids premature failure of the surface layer leading to a decline in bearing performance, and further enhances the overall reliability and durability of the bearing, making it suitable for long-term use under complex vehicle driving conditions.

[0015] The present invention further comprises: the high-strength substrate layer is made of high-quality carbon structural steel.

[0016] The advantages of adopting the above technical solution are: the high-strength matrix layer in the above technology is made of high-quality carbon structural steel, which has excellent rigidity and load-bearing capacity, providing stable support for the overall structure of the raceway. Attached Figure Description

[0017] Figure 1 This is a simplified cross-sectional view of the present invention;

[0018] Figure 2 This is a simplified view of the preparation process of the present invention. Detailed Implementation

[0019] This invention provides an automotive wheel hub bearing with a gradient buffer energy absorption structure, comprising an outer bearing ring, an inner bearing ring, rolling elements, and a cage. The rolling elements are rotatably disposed between the outer and inner bearing rings via the cage. The bearing is characterized by: raceways for the rolling elements being rolled on both the outer and inner bearing rings; both the outer and inner bearing rings being substrates; and a nano-reinforced surface layer, a gradient elastic buffer layer, and a high-strength substrate layer sequentially disposed on the inner peripheral wall of the raceways towards their respective substrate interior directions. The nano-reinforced surface layer is manufactured using at least one of the following processes: mechanical grinding, plasma nitriding, or laser nano-sizing. The nano-reinforced surface layer has a nanocrystalline or ultrafine crystalline structure, a thickness ranging from 10-50 μm, and a microhardness 1.5-2.5 times that of the material used to prepare the substrate. The gradient elastic buffer layer is located between the nano-reinforced surface layer and the high-strength substrate layer. Between the substrate layers, the gradient elastic buffer layer is a composite layer formed by at least one of the following processing techniques: multilayer physical vapor deposition, gradient thermal treatment, or laser cladding. The material composition of the gradient elastic buffer layer includes an iron-based alloy and dispersed silicon nitride or tungsten carbide particles. The thickness of the gradient elastic buffer layer ranges from 0.1 to 0.5 mm. The elastic modulus of the gradient elastic buffer layer decreases continuously or stepwise from the junction of the gradient elastic buffer layer and the nano-reinforced surface layer to the junction of the gradient elastic buffer layer and the high-strength substrate layer. The elastic modulus of the gradient elastic buffer layer near the nano-reinforced surface layer is 200-250 GPa, and the elastic modulus of the gradient elastic buffer layer near the high-strength substrate layer is 100-150 GPa. The surface of the nano-reinforced surface layer is coated with a diamond-like carbon film with a thickness of 1-3 μm. The high-strength substrate layer is made of high-quality carbon structural steel.

[0020] Through the above structural design, when the wheel hub bearing is subjected to impact loads, the contact stress between the rolling elements and the raceway surface first acts on the nano-reinforced surface layer, whose high hardness resists direct plastic deformation of the surface layer. Subsequently, the impact energy is transferred to the gradient elastic buffer layer through the nano-reinforced surface layer. The gradient elastic buffer layer absorbs a large amount of impact energy through its own gradient elastic deformation, effectively attenuating and dispersing the stress finally transmitted to the high-strength matrix layer. This significantly reduces the maximum contact stress on the raceway surface and avoids plastic deformation indentation caused by stress exceeding the material's yield limit. Because the generation of raceway indentations is effectively avoided or mitigated, the rotational accuracy of the wheel hub bearing is guaranteed during long-term use, vibration and noise are significantly reduced, and the wear between the rolling elements and the raceway is more uniform. This greatly improves the service life of the wheel hub bearing and the safety and comfort of the entire vehicle.

[0021] The specific steps of manufacturing an automotive wheel hub bearing with a gradient buffer energy absorption structure are as follows:

[0022] 1. Matrix blank preparation steps: Provide matrix blanks for the outer and inner rings of the bearing. The matrix blanks are made of 55# steel and are forged and annealed to remove internal stress, ensuring the compactness of the blank structure and providing a basic carrier for the subsequent formation of a high-strength matrix layer.

[0023] 2. High-strength matrix layer forming steps: The preset raceway area of ​​the matrix blank is turned and ground to control the machining accuracy so that the dimensional tolerance of the raceway prototype meets the design requirements, forming the preliminary shape of the high-strength matrix layer and ensuring that the high-strength matrix layer has stable rigid support capability.

[0024] 3. Gradient elastic buffer layer preparation steps: On the surface of the raceway prototype, a gradient elastic buffer layer is prepared by at least one surface engineering technique among multilayer physical vapor deposition, gradient thermal treatment, or laser cladding. During the preparation process, the composition ratio of the composite layer material is controlled so that the iron-based alloy is used as the substrate and silicon nitride or tungsten carbide particles are dispersed. At the same time, the process parameters are adjusted so that the elastic modulus decreases continuously or stepwise from the side near the subsequent nano-reinforced surface layer to the side near the high-strength substrate layer, ensuring that the thickness of the layer meets the design requirements.

[0025] 4. Nano-reinforced surface layer preparation steps: On the surface of the gradient elastic buffer layer, a nano-reinforced surface layer is prepared by at least one of the following processes: surface mechanical polishing, plasma nitriding, or laser nano-sizing, so that the surface layer forms a nanocrystalline or ultrafine crystalline structure, ensuring that it has the preset hardness and wear resistance, and can resist micro-cutting and plastic deformation under initial impact.

[0026] 5. Diamond-like carbon film coating step: A layer of diamond-like carbon film is coated on the surface of the nano-reinforced surface using a physical vapor deposition process to further improve the surface hardness, wear resistance and friction reduction performance. After coating, ensure that the film is uniformly covered and free from cracks and peeling.

[0027] 6. Finishing process: The outer and inner rings of the prepared gradient buffer energy absorption structure are finely ground and polished to control the surface roughness of the raceway to meet the assembly requirements, and to remove impurities such as burrs and oxide scale generated during the processing to ensure the flatness and dimensional accuracy of the raceway surface.

[0028] 7. Assembly steps: Assemble the finished outer and inner rings with the pre-selected rolling elements and cage. During the assembly process, ensure that the rolling elements can roll smoothly between the inner and outer ring raceways under the constraint of the cage, thus completing the overall manufacturing of the automotive wheel hub bearing with a gradient buffer energy absorption structure.

[0029] The nano-reinforced surface layer described above is manufactured through at least one of the following processes: surface mechanical polishing, plasma nitriding, or laser nano-sizing. The specific process can be selected based on requirements, including surface mechanical polishing, plasma nitriding, laser nano-sizing, surface mechanical polishing combined with plasma nitriding, surface mechanical polishing combined with laser nano-sizing, plasma nitriding combined with laser nano-sizing, or surface mechanical polishing combined with plasma nitriding and laser nano-sizing.

[0030] Advantages of using a single process:

[0031] 1. Surface mechanical grinding is a conventional surface grain refinement process in the mechanical manufacturing field. It uses the mechanical impact of the grinding head to cause plastic deformation of the metal surface, thereby refining the grain to the nano / ultrafine level. It has been widely used in the surface pretreatment of bearings, gears and other parts, and the technology is highly mature.

[0032] 2. Ion nitriding is a classic chemical heat treatment technology. It uses low-temperature plasma to diffuse nitrogen atoms into the metal surface to form a high-hardness nitrided layer, which can refine the grains and improve corrosion resistance. It is currently one of the mainstream processes for surface strengthening of automotive bearings and engineering machinery parts, and the equipment and parameter system have been standardized.

[0033] 3. Laser nano-sizing technology relies on mature high-power laser equipment and uses the thermal cycle effect of "high-temperature rapid heating - rapid cooling" to refine the surface grains of metal into nanocrystals in a non-equilibrium state. It has been applied to the surface treatment of high-requirement parts in aerospace, precision machinery and other fields. Process parameters (such as laser power and scanning speed) can be precisely controlled.

[0034] Advantages of using a combination of two processes:

[0035] 1. Surface mechanical grinding followed by plasma nitriding: Mechanical grinding removes the oxide scale from the surface of the parts and reduces the roughness, providing a uniform "clean substrate" for subsequent plasma nitriding and avoiding impurities from affecting the nitrogen atom penetration efficiency.

[0036] 2. Surface mechanical grinding plus laser nano-sizing: Pretreatment through mechanical grinding optimizes surface flatness and ensures that laser energy is applied uniformly to the surface layer, avoiding uneven local grain refinement.

[0037] 3. Plasma nitriding combined with laser nano-sizing: Plasma nitriding first forms a preliminary strengthening layer, and then laser nano-sizing further refines the grains of the nitrided layer and improves the uniformity of nitride distribution. The combination simultaneously enhances hardness and toughness.

[0038] The advantages of using a combination of three processes are as follows: mechanical grinding provides the foundation for nitriding by removing impurities and roughening the surface; nitriding provides a surface layer containing a strengthening phase for laser nano-sizing by introducing elements and initially strengthening the surface; and laser nano-sizing achieves the final nanocrystalline structure by refining the surface. The entire process does not involve any new breakthroughs in principles; it only requires controlling the connection parameters of each process (such as the surface cleanliness after nitriding and the temperature of laser treatment to avoid the brittle range of the nitrided layer). Similar multi-process superposition has been used in high-end parts such as aero-engine bearings, and the technical feasibility has been verified.

[0039] The gradient elastic buffer layer in the above technology is prepared by at least one surface engineering technique selected from multilayer physical vapor deposition, gradient thermal treatment, or laser cladding. The surface engineering technique can be selected according to actual needs and application requirements, i.e., a single process (multilayer physical vapor deposition / gradient thermal treatment / laser cladding), a combination of two processes (multilayer physical vapor deposition plus gradient thermal treatment / multilayer physical vapor deposition plus laser cladding / gradient thermal treatment plus laser cladding), or a combination of three processes (multilayer physical vapor deposition plus gradient thermal treatment plus laser cladding). Each process has its advantages.

[0040] Advantages of using a single process:

[0041] 1. Multilayer physical vapor deposition: Through multiple rounds of deposition, a composite layer containing iron-based alloys and dispersed particles is formed. The uniformity of layer thickness can be precisely controlled, and the elastic modulus can be reduced in a stepwise manner by adjusting the deposition parameters of each layer (such as target composition and deposition power). The process is clean, and the coating is tightly bonded to the substrate, making it suitable for scenarios with high requirements for surface flatness.

[0042] 2. Gradient heat treatment: By gradually adjusting the heat treatment temperature / time, the particle distribution in the pre-made iron-based alloy layer is made more uniform, and the elastic modulus is induced to decrease continuously along the thickness direction. There is no need to prepare an additional coating. The performance can be directly controlled by heat treatment, resulting in low process cost.

[0043] 3. Laser cladding: Using a laser, iron-based alloy powder and silicon nitride / tungsten carbide particles are clad onto the surface of the raceway to form a metallurgically bonded composite layer. This layer has the highest density and the strongest bond with the substrate. Furthermore, the elastic modulus gradient can be achieved by adjusting the cladding path, thus enabling the preparation of thick layers in one go, with excellent particle distribution uniformity.

[0044] Advantages of using a combination of two processes:

[0045] 1. Multilayer physical vapor deposition with gradient heat treatment: A composite layer containing particles is first deposited through multilayer physical vapor deposition, and then the particle dispersion state is further optimized and the elastic modulus gradient is controlled through gradient heat treatment. At the same time, the interfacial bonding force between the coating and the substrate is improved. In the end, the elastic modulus continuity and structural stability of the composite layer are better than those of the single process, which is suitable for scenarios with high requirements for gradient smoothness.

[0046] 2. Multilayer physical vapor deposition plus laser cladding technology: A thick substrate is first clad with laser to ensure the overall thickness and bonding strength of the composite layer. Then, a thin layer is deposited through multilayer physical vapor deposition to optimize the elastic modulus of the surface layer, forming a gradient structure of "thick substrate + finely tuned surface". This balances the layer thickness and gradient accuracy, avoiding the single surface roughness problem caused by laser cladding, and eliminating the need for additional fine grinding.

[0047] 3. Gradient heat treatment plus laser cladding technology: The composite layer containing particles is first clad by laser cladding, and then the residual stress of the cladding layer is eliminated by gradient heat treatment, while the elastic modulus gradient is precisely controlled. It retains the high density after laser cladding and solves the brittleness problem that may be caused by laser cladding through gradient heat treatment, which is suitable for the impact resistance requirements in heavy load scenarios.

[0048] The advantages of using a combination of three processes (multilayer physical vapor deposition plus gradient thermal treatment plus laser cladding technology) are as follows: first, the substrate is pretreated (to optimize surface roughness), then the core composite layer is clad (to ensure thickness and bonding strength), and finally gradient thermal treatment is performed (to control the elastic modulus gradient and eliminate residual stress), ultimately forming an optimal buffer layer with "dense structure, smooth gradient, and strong bonding", which perfectly matches the core objective of "absorbing impact energy and decreasing elastic modulus gradient".

[0049] In the above technology, the outer ring of the bearing is identified as 1 in the attached drawings of the specification, the inner ring of the bearing is identified as 2, the rolling element is identified as 3, the raceway is identified as 4, and the cage is identified as 5.

[0050] The foregoing has shown and described the basic principles and main features of the present invention, as well as its advantages. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the present invention. Various changes and modifications can be made to the present invention without departing from its spirit and scope. All such changes and modifications fall within the scope of the present invention as claimed, which is defined by the appended claims and their equivalents.

Claims

1. A wheel hub bearing with a gradient buffer energy absorption structure, comprising an outer ring, an inner ring, rolling elements, and a cage, wherein the rolling elements are rotatably disposed between the outer ring and the inner ring via the cage, characterized in that: Both the outer and inner rings of the bearing have raceways for the rolling elements to roll. Both the outer and inner rings are substrates. The inner circumferential walls of the raceways, moving inwards towards their respective substrate interiors, are sequentially provided with a nano-reinforced surface layer, a gradient elastic buffer layer, and a substrate layer. The nano-reinforced surface layer is fabricated using at least one of the following processes: mechanical polishing, plasma nitriding, or laser nano-sizing. The nano-reinforced surface layer has a nanocrystalline or ultrafine crystalline structure, a thickness ranging from 10 to 50 μm, and a microhardness 1.5 to 2 times that of the material used to prepare the substrate. The gradient elastic buffer layer is located between the nano-reinforced surface layer and the substrate layer. The gradient elastic buffer layer is a composite layer formed by at least one of the following processing techniques: multilayer physical vapor deposition, gradient thermal treatment, or laser cladding. The material composition of the gradient elastic buffer layer includes iron-based alloys and dispersed silicon nitride or tungsten carbide particles. The thickness of the gradient elastic buffer layer ranges from 0.1 to 0.5 mm. The elastic modulus of the gradient elastic buffer layer decreases continuously or stepwise from the junction of the gradient elastic buffer layer and the nano-reinforced surface layer to the junction of the gradient elastic buffer layer and the substrate layer.

2. The automotive wheel hub bearing with a gradient buffer energy absorption structure according to claim 1, characterized in that: The gradient elastic buffer layer has an elastic modulus of 200-250 GPa on the side near the nano-reinforced surface layer and an elastic modulus of 100-150 GPa on the side near the matrix layer.

3. The automotive wheel hub bearing with a gradient buffer energy absorption structure according to claim 1, characterized in that: The surface of the nano-reinforced surface layer is coated with a diamond-like carbon film with a thickness of 1-3 μm.

4. The automotive wheel hub bearing with a gradient buffer energy absorption structure according to claim 1, characterized in that: The substrate layer is made of carbon structural steel.

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