Electrically conductive rubber oil seal for wheel bearing

Abstract

The application discloses a kind of electrically-conductive rubber oil seals for wheel hub bearings, including electrically-conductive framework, electrically-conductive rubber and metal retainer, electrically-conductive rubber is fixed in electrically-conductive framework to form sealing lip, metal retainer is sleeved with bearing inner ring, combined structure is arranged in retainer and is filled with lubricating grease.Electrically-conductive rubber composition and weight ratio are as follows:high acrylonitrile butadiene rubber 100 parts, high-conductivity carbon black 30-40 parts, graphene composite powder 20-30 parts, graphene modifier 10-15 parts, and appropriate amount of plasticizer, adhesive, antioxidant and other auxiliaries.The application optimizes component ratio and structure design, improves electrical conductivity and sealing performance, prevents static electricity accumulation, prolongs bearing life, enhances lubricating grease retention and structural stability.

Description

Technical Field

[0001] This invention relates to the field of bearing sealing technology, and more specifically to a conductive rubber oil seal for wheel hub bearings. Background Technology

[0002] Bearing electro-corrosion has long been a pain point and challenge in the industry. Many solutions exist, primarily focusing on two aspects: firstly, insulating the bearing to prevent current from flowing through the bearing raceways and rolling elements; and secondly, diverting the current from the bearing raceways and rolling elements through other means, such as using conductive rubber seals to allow current to flow through the seals and prevent electro-corrosion. While there are many solutions and methods for addressing bearing electro-corrosion, such as plastic-coated insulation of the bearing outer ring and using carbon brushes for conductive contact, these solutions require additional components and manufacturing processes, significantly increasing production difficulty and cost. For example, the utility model patent CN223165009U, entitled "A Conductive Combined Seal," discloses a method that uses a metal conductive oil seal to increase conductivity. While the metal conductive oil seal achieves conductivity, its sealing performance and wear resistance are far inferior to rubber materials. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide a conductive rubber oil seal for wheel hub bearings. By combining conductive rubber with a metal retaining ring, the seal achieves current conduction while ensuring sealing performance and wear resistance, reducing production difficulty and cost without the need for additional accessories.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a conductive skeleton, conductive rubber, and a metal retaining ring are included. The conductive rubber is fixed on the conductive skeleton to form a sealing lip structure. The metal retaining ring is fitted onto the inner ring of the outer bearing. The conductive skeleton and conductive rubber combined structure is located on the metal retaining ring, and grease is filled between them. The components and weight ratios of the conductive rubber are as follows: 100 parts of high acrylonitrile-content nitrile rubber, 30-40 parts of high-conductivity carbon black, 20-30 parts of graphene composite powder, 10-15 parts of graphene modifier, 1-2 parts of fatty oil-based plasticizer, 1-3 parts of adhesive, 2-3 parts of antioxidant, 1-2 parts of internal release agent, 5-10 parts of coupling agent, 0.5-1 part of anti-scorching agent, 1-2 parts of sodium stearate, 7-8 parts of multiple accelerators, and 1-2 parts of vulcanizing agent.

[0005] As a further improvement of the present invention, the graphene composite powder of the conductive rubber is a combination of sheet graphene and carbon nanotubes, wherein the sheet graphene has a diameter of 1-2 μm and a thickness of 1-6 nm; and the carbon nanotubes have a diameter of 6-15 nm and a length of 5-15 μm.

[0006] As a further improvement of the present invention, the preparation process of graphene composite powder is as follows: dissolve the dispersant in anhydrous ethanol and stir mechanically to obtain a dispersant ethanol solution; take a certain amount of graphene composite powder and add it to the ethanol solution containing the modifier and stir mechanically for 0.5 h; transfer it to an oven at 100°C to dry, and the modified graphene composite powder is obtained.

[0007] As a further improvement of the present invention, the graphene composite powder modified grafting agent is an alkaline amine anchoring dispersant. The anchoring group of the alkaline amine anchoring dispersant tightly adsorbs the dispersant onto the graphene surface through ionic bonds, covalent bonds, hydrogen bonds and van der Waals forces.

[0008] As a further improvement of the present invention, the conductive rubber and the conductive skeleton are bonded, vulcanized and molded to form an outer lip and an inner lip. The outer wall of the outer lip has an arched portion that abuts against the outer ring of the bearing. The inner wall of the inner lip has an abutting edge near the end, which abuts against the metal retaining ring. The abutting edge and the arched portion cooperate to make the conductive rubber and the inner and outer rings of the bearing have an interference fit.

[0009] As a further improvement of the present invention, a plurality of grease-locking grooves are provided on the inner wall of the inner lip, and a gap is left between the plurality of grease-locking grooves and the metal retaining ring, and the grease is filled in the gap.

[0010] The beneficial effect of this invention is that bearings using conductive rubber seals do not require additional production processes. The purpose of conducting current can be achieved simply by using conductive rubber and an oil seal with a conductive structure. The conductive oil seal of this invention utilizes the conductive properties of its rubber. The conductivity of the filler in the rubber is achieved through the contact between conductive filler particles, which overlap to form a chain-like and mesh-like three-dimensional conductive structure, creating a conductive channel capable of transmitting electrons. The conductive process after the conductive channel is formed is a process of charge carrier migration. When the concentration of added conductive filler particles reaches the percolation critical value, a large number of conductive filler particles come into contact with each other, causing electrons to move directionally under the carrying capacity of charge carriers, forming a current. The oil seal lip directly contacts the inner and outer rings of the bearing, forming a good conductive path, thereby preventing bearing electro-corrosion. Attached Figure Description

[0011] Figure 1 This is a schematic cross-sectional view of the conductive rubber oil seal used in this wheel hub bearing.

[0012] Figure 2 This is a schematic diagram of the process for modifying graphene composite powder.

[0013] Figure 3 A schematic diagram illustrating the improvement of the surface morphology of the rubber fracture surface;

[0014] Figure 4 To improve the surface morphology of the rubber fracture surface;

[0015] Figure 5 This is a schematic diagram showing the appearance of the steel balls in a non-conductive oil-sealed bearing after testing.

[0016] Figure 6 This is a schematic diagram showing the appearance of the steel balls in the conductive oil seal bearing after testing. Detailed Implementation

[0017] The present invention will now be described in further detail with reference to the embodiments shown in the accompanying drawings.

[0018] Reference Figure 1 As shown, the conductive rubber oil seal for the wheel hub bearing in this embodiment includes a conductive skeleton 1, conductive rubber 2, and a metal retaining ring 3. The conductive rubber 2 is fixed on the conductive skeleton 1 to form a sealing lip structure. The metal retaining ring 3 is fitted onto the inner ring of the outer bearing. The combined structure of the conductive skeleton 1 and conductive rubber 2 is located on the metal retaining ring 3, and grease is filled between them. The oil seal in this embodiment is formed by bonding, vulcanizing, and molding the conductive rubber 2 and conductive skeleton 1. The oil seal structure has a lip seal, and grease is applied to the lip to reduce rotational torque. The lip seal and the metal retaining ring 3 combine to form an oil seal, further improving the sealing performance of the wheel hub bearing. At the same time, the oil seal and the inner and outer rings of the bearing form a conductive path, allowing the current generated during bearing operation to pass directly through the conductive oil seal, avoiding corrosion of the bearing raceway and steel ball surface, which could lead to premature bearing failure. The rubber material is conductive rubber 2. Through a special design of the rubber formulation, the rubber has good conductivity and high wear resistance. The contact part between the conductive rubber 2 and the metal retaining ring 3 is coated with grease to reduce rotational torque. The single lip of the oil seal contacts the metal retaining ring 3 to ensure that the current flows smoothly from the inner ring to the outer ring, thereby reducing the occurrence of electro-corrosion during bearing operation. Furthermore, the oil seal is made of conductive rubber 2 bonded to a conductive skeleton 1, and has a lip-shaped contact structure designed near the inner ring of the bearing to make interference contact with the metal retaining ring 3. The conductive rubber 2 near the outer ring of the bearing is designed as a boss to ensure interference contact with the outer ring of the bearing. In this way, when current passes through the bearing, the inner and outer rings of the bearing can be connected to the conductive oil seal to form a complete conductive path, preventing the current from passing through the bearing chamber, breaking through the grease film, and corroding the rolling elements and raceways. The rubber prepared using the above rubber formulation has high conductivity and good wear resistance. The above formulation relies on the combination of highly conductive carbon black and graphene composite powder to achieve good conductivity. Because of its high structural density, highly conductive carbon black easily combines with rubber to form encapsulated rubber, resulting in good dispersion properties within the rubber. However, it significantly increases the hardness of the rubber. Therefore, to ensure that the rubber maintains good conductivity while also possessing suitable hardness, graphene composite powder is used to enhance the conductivity of the rubber.

[0019] Furthermore, the graphene composite powder of conductive rubber 2 is a combination of sheet graphene (sheet diameter 1-2 μm, thickness 1-6 nm) and carbon nanotubes (tube diameter 6-15 nm, tube length 5-15 μm). Through the synergistic effect of the two nanomaterials, it achieves excellent conductivity without significantly increasing the hardness of the rubber. The tubular fiber nanotubes can be embedded in the pores of spherical and sheet-like contacts, ensuring the integrity of the conductive material contact. This allows the rubber material to achieve suitable hardness and conductivity. Carbon nanotubes are wound around the graphene surface, and the connection between conductive particles is a combination of line and surface contact. Large-diameter graphene sheets overlap to form a conductive network framework, and carbon nanotubes fill most of the gaps, making the conductive network more complete and greatly increasing the effective contact area between conductive particles. This reduces the resistance encountered by electrons during migration, improving conductivity. Graphene also has high rigidity, enabling it to withstand large loads during friction, reducing the depth of surface wear and maintaining wear stability. This also increases the wear resistance of the oil seal.

[0020] Reference Figure 2 As shown, the further preparation process of graphene composite powder is as follows: The dispersant is dissolved in anhydrous ethanol and mechanically stirred to obtain an ethanol solution of the dispersant; a certain amount of graphene composite powder is added to the ethanol solution containing the modifier and mechanically stirred for 0.5 hours; then it is dried in an oven at 100°C. Since 90% of the graphene composite powder is exfoliated sheet graphene, it is difficult to disperse in rubber, and filler agglomeration is likely to occur, leading to pores and bubbles on the surface of the prepared rubber due to uneven filler dispersion. Simultaneously, the prepared rubber sample exhibits a layered distribution, and it easily delaminates after being broken. To improve this phenomenon, the graphene surface needs to be modified and grafted to increase the bonding degree between graphene and rubber, avoiding agglomeration between the sheet graphene layers.

[0021] Furthermore, the graphene composite powder modification grafting agent is an alkaline amine-anchored dispersant. Through ionic bonds, covalent bonds, hydrogen bonds, and van der Waals forces, the dispersant is tightly adsorbed onto the graphene surface. Simultaneously, to prevent dispersant desorption, the alkaline anchoring groups have a stronger adsorption capacity for graphene. The other end of the amine-anchored dispersant is an organic group, exhibiting good compatibility with rubber. This allows for stable dispersion in the rubber system, maintaining the stability of the rubber dispersion system. The degree of internal dispersion of the rubber material before and after modification is shown in the figure. Figure 3 and Figure 4 .

[0022] Reference Figure 1As shown, the conductive rubber 2 and the conductive skeleton 1 are bonded, vulcanized, and molded to form an outer lip and an inner lip. The arched part of the outer lip abuts against the outer ring of the bearing, and the abutting edge of the inner lip abuts against the metal retaining ring 3. The interference fit design ensures that the sealing lip maintains contact pressure during bearing operation, solving the gap leakage problem that easily occurs in dynamic sealing. At the same time, the double-lip structure forms a double sealing barrier.

[0023] Reference Figure 1 As shown, furthermore, the grease-locking groove on the inner wall of the inner lip is filled with grease between it and the metal retaining ring 3. This structure can store excess grease, and during bearing operation, centrifugal force evenly distributes the grease to the contact surface, reducing friction and wear between the sealing lip and the retaining ring, thus extending the service life of the oil seal.

[0024] In summary, the oil seal of this embodiment, through a special formulation design of conductive rubber and adjusting the addition ratio of highly conductive carbon black and graphene composite powder to 2:1, ultimately yields an oil seal product with suitable hardness and high conductivity. The resistivity of the rubber material can reach 10 Ω·cm, and the performance of the rubber material still meets relevant technical standards. When this conductive rubber is assembled into a bearing as an oil seal, and the bearing resistance is 2 Ω, under a 0.5 A current condition, after 200 hours of bearing operation, the rolling elements of a bearing with a conventional rubber oil seal show electro-corrosion pits, while the rolling elements of the bearing with the conductive rubber oil seal do not exhibit electro-corrosion. See [link / reference]. Figure 5 and Figure 6 Therefore, conductive rubber materials play a role in charge conduction to a certain extent, thereby reducing the occurrence of electro-corrosion.

[0025] The test table is as follows:

[0026]

[0027] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A conductive rubber oil seal for a wheel hub bearing, characterized in that: The structure includes a conductive skeleton (1), conductive rubber (2), and a metal retainer (3). The conductive rubber (2) is fixed on the conductive skeleton (1) to form a sealing lip structure. The metal retainer (3) is fitted onto the inner ring of the outer bearing. The combined structure of the conductive skeleton (1) and the conductive rubber (2) is located on the metal retainer (3), and grease is filled between them. The components and weight ratios of the conductive rubber (2) are as follows: 100 parts of high acrylonitrile content nitrile rubber, 30-40 parts of high conductivity carbon black, 20-30 parts of graphene composite powder, 10-15 parts of graphene modifier, 1-2 parts of fatty oil plasticizer, 1-3 parts of adhesive, 2-3 parts of antioxidant, 1-2 parts of internal release agent, 5-10 parts of coupling agent, 0.5-1 part of anti-scorching agent, 1-2 parts of sodium stearate, and various accelerators. Use 7-8 parts of vulcanizing agent and 1-2 parts of the conductive rubber (2). The graphene composite powder of the conductive rubber (2) is a combination of sheet graphene and carbon nanotubes. The sheet graphene has a diameter of 1-2 μm and a thickness of 1-6 nm. The carbon nanotubes have a diameter of 6-15 nm and a length of 5-15 μm. The preparation process of the graphene composite powder is as follows: Dissolve the dispersant in anhydrous ethanol and stir mechanically to obtain a dispersant ethanol solution. Take a certain amount of graphene composite powder and add it to the ethanol solution containing the modifier and stir mechanically for 0.5 h. Transfer it to a 100°C oven to dry, and the modified graphene composite powder is obtained. The graphene composite powder modification grafting agent is an alkaline amine anchoring dispersant. The anchoring group of the alkaline amine anchoring dispersant tightly adsorbs the dispersant onto the graphene surface through ionic bonds, covalent bonds, hydrogen bonds and van der Waals forces.

2. The conductive rubber oil seal for wheel hub bearings according to claim 1, characterized in that: The conductive rubber (2) and the conductive skeleton (1) are bonded, vulcanized and molded to form an outer lip and an inner lip. The outer wall of the outer lip has an arched portion that abuts against the outer ring of the bearing. The inner wall of the inner lip has an abutting edge near the end, which abuts against the metal retaining ring (3). The abutting edge and the arched portion make the conductive rubber (2) and the inner and outer rings of the bearing an interference fit.

3. The conductive rubber oil seal for wheel hub bearings according to claim 2, characterized in that: The inner wall of the inner lip has several grease-locking grooves, and there is a gap between the several grease-locking grooves and the metal retaining ring (3), and the grease is filled in the gap.

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