Design and manufacturing method for self-lubricating surface microstructure on the inner surface of a sealing ring for a rolling bearing.

Abstract

The base oil separated from the lubricating grease in the gap between the inner ring and the seal ring of the rolling bearing is self-transported to the outer ring side of the rolling bearing, improving oil leakage between the seal ring and the inner ring and enhancing the sealing performance of the bearing. [Solution] By providing an ultra-oleophobic surface on the inner surface of the seal ring, the problem of lubricating grease adhering to the inner surface of the seal ring is eliminated. Furthermore, based on the characteristics of the base oil, and the contact angle within the wedge-shaped surface microstructure of the oil droplet, the contact angle outside the wedge-shaped surface microstructure, and the receding contact angle, the solid-liquid contact boundary length between the base oil droplet and one side edge of the wedge-shaped surface microstructure is designed to satisfy the self-transportation conditions of the base oil, thereby ensuring that the length of the wedge-shaped surface microstructure is greater than the solid-liquid contact boundary length. In addition, multiple groups of surface microstructures are provided on the inner surface of the seal ring at equal intervals in the radial direction, and each group of surface microstructures is composed of multiple wedge-shaped surface microstructures provided at equal intervals in the circumferential direction, with the tip of each wedge-shaped surface microstructure facing the inner wall side of the seal ring.

Description

[Technical Field]

[0001] This invention belongs to the field of rolling bearing seal technology, and more specifically, to a method for designing and manufacturing a self-lubricating surface microstructure on the inner surface of a sealing ring for a rolling bearing. [Background technology]

[0002] Bearings are essential core rotating components in critical construction equipment such as aerospace, nuclear power, transportation, and tunnel excavation. They have a large number of applications and a wide range of uses, and their stability directly affects the operating performance and lifespan of mechanical components.

[0003] Lubricants are one of the core elements for ensuring stable bearing operation, reducing friction, and improving bearing life. Grease is the most commonly used lubricant in current industrial fields due to its excellent structure, economy, and sealing performance. It mainly consists of a base oil, a thickener, and additives, and the leakage of the base oil can be reduced by adsorbing the base oil onto the thickener, which has a soap fiber structure. During the operation of the bearing, centrifugal force and pressure from the rolling elements cause the grease to scatter or be pushed out from the contact area, the amount of grease in the track gradually decreases, and some of the scattered grease adheres to the inner surface of the seal ring. The most common mounting method for seal rings is to fix the outer edge to the outer ring by transient press-fitting or a locking groove, maintaining a stationary state relative to the bearing outer ring, while the inner ring rotates with the shaft. After being subjected to pressure, the base oil easily leaks out from the gap between the inner ring and the seal ring. Therefore, by improving the adhesion of grease to the inner surface of the seal ring and enabling self-transport of the oil from the inner ring to the outer ring, the sealing performance of the bearing can be effectively improved, and friction between the rolling elements, cage and seal ring can be reduced, thereby improving the lubrication effect of the rolling bearing. [Overview of the Initiative]

[0004] In view of the problems of lubricating grease adhesion to the inner surface of the seal ring and leakage in the gap between the seal ring and the inner ring of the bearing during long-term operation of rolling bearings, the present invention proposes a method for designing and manufacturing a self-lubricating surface microstructure on the inner surface of a seal ring for rolling bearings.

[0005] The present invention relates to a method for designing a self-lubricating surface microstructure on the inner surface of a sealing ring for a rolling bearing, wherein a superoleophobic surface is provided on the inner surface of the sealing ring, and a plurality of groups of surface microstructures are provided on the inner surface of the sealing ring at equal intervals in the radial direction, and each group of surface microstructures is composed of a plurality of wedge-shaped surface microstructures provided at equal intervals in the circumferential direction, and the tip of each wedge-shaped surface microstructure faces the inner wall side of the sealing ring, and the length of the wedge-shaped surface microstructures to realize self-transport of the base oil is designed based on the wedge angle of the wedge-shaped surface microstructure, and the conditions for realizing self-transport of the base oil are,

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[0006] Preferably, the wedge angle β = 15° is half of the wedge angle of the wedge-shaped surface microstructure, and the depth of the wedge-shaped surface microstructure is 0.3 mm.

[0007] Preferably, in the specific process of setting the conditions for realizing the self - transportation of the base oil, when it is assumed that the seal ring is horizontally arranged, the Laplace pressure T at the single contact point at the position of the wedge - shaped surface microstructure of the oil droplet L and the driving force T of the internal and external surface tension difference q are calculated by

Equation

Equation

Equation

Equation

Equation

Equation

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[0008] Preferably, for the movement resistance f1 received by the oil droplet on the length microelement of the arc-shaped solid-liquid contact boundary DE inside the wedge-shaped surface microstructure when the oil droplet advances, and the movement resistance f2 received by the oil droplet on the length microelements of the solid-liquid contact boundaries CD and CE at the two side edge positions of the wedge-shaped surface microstructure, in the dynamic movement process of the oil droplet, when the leading edge is affected by resistance when advancing inside the wedge-shaped surface microstructure, Young's equation is

Equation

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[0009] In another view, the present invention provides a method for manufacturing a self-lubricating surface microstructure on the inner surface of a sealing ring for a rolling bearing. This manufacturing method includes a length determination step of determining the length H of the wedge-shaped surface microstructure based on the design method described above, an oleophobic surface formation step of forming an oleophobic surface on the inner surface of the sealing ring, and a microstructure group formation step of subsequently forming a plurality of surface microstructure groups on the inner surface of the sealing ring, each of which consists of a plurality of wedge-shaped surface microstructures arranged to be equally spaced radially, with each surface microstructure group being arranged to be equally spaced circumferentially, wherein in the microstructure group formation step, the length H of the wedge-shaped surface microstructure is the length determined in the length determination step.

[0010] In the superoleophobic surface forming step, preferably, nanoparticles with hydroxyl group modification on their surface are added to deionized water, the nanoparticles and deionized water are mixed using an ultrasonic particle disperser, and then stirred with a magnetic stirrer to obtain a mixed solution, where the mass of the nanoparticles accounts for 1% of the mass of the mixed solution. Next, an activator is added to the mixed solution and stirred at room temperature to obtain an aqueous suspension, where the mass of the activator accounts for 10% of the mass of the mixed solution. After cleaning the inner surface of the seal ring using an ultrasonic cleaner, the obtained aqueous suspension is uniformly sprayed onto the inner surface of the seal ring, and finally, the seal ring after spraying the aqueous suspension is dried in a vacuum dryer.

[0011] More preferably, as nanoparticles whose surface has been modified with hydroxyl groups, nanoparticles having hydroxyl groups on the surface of SiO2 or Fe3O4 are used.

[0012] More preferably, a fluorine-based surfactant is used as the activator.

[0013] In the microstructure formation step, preferably, a group of surface microstructures is formed on the inner surface of the seal ring at equal radial intervals using femtosecond laser ablation technology, and then the inner surface of the seal ring is cleaned using an ultrasonic cleaner.

[0014] In the microstructure formation step, more preferably, a fine mesh-like groove pattern is provided on the bottom surface of the wedge-shaped surface microstructure, and the fine mesh-like groove pattern is formed on the bottom surface of the wedge-shaped surface microstructure using femtosecond laser ablation technology as the processing method, wherein the fine mesh-like groove pattern is formed by the intersection of a plurality of first grooves distributed at equal intervals and a plurality of second grooves distributed at equal intervals or at equal angles, wherein the first grooves and the second grooves are parallel to the two side edges of the wedge-shaped surface microstructure, or the first grooves are parallel to the bottom edge of the wedge-shaped surface microstructure, and each of the second grooves is distributed at equal angles with respect to a vertex opposite the bottom edge of the wedge-shaped surface microstructure, or the first grooves are parallel to the bottom edge of the wedge-shaped surface microstructure.

[0015] Compared to the prior art, the present invention has the following beneficial effects. In this invention, the wettability of the inner surface of the seal ring is adjusted using a surface coating technology with modified nanoparticles, thereby making the inner surface of the seal ring ultraoleophobic and solving the problem of lubricating grease adhesion to the inner surface of the seal ring. Furthermore, this property is used as a major control factor for realizing autonomous transport of the base oil of the lubricating grease. Based on the properties of the base oil and observations of the contact angle within the wedge-shaped surface microstructure of the base oil droplet on the seal ring, the contact angle outside the wedge-shaped surface microstructure, and the receding contact angle, the length of the solid-liquid contact boundary between the base oil droplet that satisfies the conditions for self-transportation of the base oil and the lateral edge position of the wedge-shaped surface microstructure is designed, thereby designing the wedge-shaped surface microstructure so that its length is greater than the length of the solid-liquid contact boundary. Furthermore, the multiple groups of surface microstructures arranged at equal radial intervals on the inner surface of the seal ring can be formed by femtosecond laser ablation. Each group of surface microstructures consists of multiple wedge-shaped surface microstructures arranged at equal circumferential intervals, with the tips of each wedge-shaped surface microstructure facing the inner wall of the seal ring. As a result, the wedge-shaped surface microstructures can self-transport the base oil separated from the lubricating grease in the gap between the inner ring of the rolling bearing and the seal ring to the outer ring of the rolling bearing, thereby improving oil leakage between the seal ring and the inner ring of the rolling bearing and enhancing the sealing performance of the rolling bearing. [Brief explanation of the drawing]

[0016] [Figure 1] Figure 1 is a schematic diagram of the structure of a rolling bearing. [Figure 2] Figure 2 is a schematic diagram of the structure of the seal ring in the present invention. [Figure 3] Figure 3 is a schematic diagram showing the angle between the axis of symmetry of the wedge-shaped surface microstructure according to the present invention and the vertical plane. [Figure 4] Figure 4 is a schematic diagram showing the spreading state and force-receiving state of oil droplets at the wedge-shaped surface microstructure location according to the present invention. [Figure 5] Figure 5 is a schematic diagram showing the contact angles of oil droplets inside and outside the wedge-shaped surface microstructure according to the present invention. [Figure 6]Figure 6 is a schematic diagram showing the contact angle of an oil droplet advancing at the wedge-shaped surface microstructure location according to the present invention. [Figure 7] Figure 7 is a schematic diagram showing a fine mesh-like groove pattern formed on the bottom surface of the wedge-shaped surface microstructure according to the present invention. [Modes for carrying out the invention]

[0017] The present invention will be further described below with reference to the drawings.

[0018] As shown in Figure 1, the rolling bearing includes a seal ring 1, an inner ring 2, a cage, rolling elements 3, and an outer ring 4. Here, the rolling elements 3 form a rolling friction pair between the running paths of the inner ring 2 and the outer ring 4. The seal ring 1 is fixed to the bearing outer ring 4 by a locking portion or transient press-fit, and is not fixed to the inner ring 2 during the rotation process, thus forming a dynamic seal.

[0019] The design method for the self-lubricating surface microstructure on the inner surface of a sealing ring for a rolling bearing according to the present invention is specifically as follows. That is, an ultra-oleophobic surface is provided on the inner surface 6 of the sealing ring (the surface facing the rolling element 3), and a plurality of surface microstructure (texture) groups are provided at equal intervals in the radial direction. As shown in Figure 2, each surface microstructure group consists of a plurality of wedge-shaped surface microstructures provided at equal intervals in the circumferential direction, with the tip of each wedge-shaped surface microstructure facing the inner wall 5 of the sealing ring and the flat end facing the outer wall 7 of the sealing ring. The present invention can not only improve wettability and solve the problem of lubricating grease adhesion to the inner surface of the sealing ring, but can also self-transport the base oil separated from the lubricating grease in the gap between the inner ring of the rolling bearing and the sealing ring to the outer ring side of the rolling bearing, thereby improving the sealing performance of the rolling bearing.

[0020] Here, assuming the wedge angle of the wedge-shaped surface microstructure, the length of the wedge-shaped surface microstructure required to achieve self-transport of the base oil is designed as follows.

[0021] In an equilibrium state with a uniform surface and no external force acting between the solid and the oil droplet, Young's equation is as follows:

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[0022] When an oil droplet is between two solid surfaces with different contact angles, the unbalanced surface tension causes the oil droplet to move towards the solid surface with higher surface free energy. (Unbalanced surface tension T) Y This is calculated using Young's unequilibrium force equation.

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[0023] The tensile force generated by the solid-liquid contact boundary at contact points A and B is then expressed by the following equation.

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[0024] In this invention, the exterior of the wedge-shaped surface microstructure is a superoleophobic surface, and oil droplets have a relatively large contact angle αout, while the interior of the wedge-shaped surface microstructure is superoleophilic (by using femtosecond laser ablation technology), and therefore oil droplets have a relatively small contact angle αIn. αout and αIn can be measured using images captured by a high-speed camera, as shown in Figure 5. Assuming the seal ring is positioned horizontally, the tensile force T is equal to the Laplace pressure T. L and the driving force T due to the difference in inner and outer surface tension. q Includes only.

[0025]

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[0026] As shown in Figure 4, the Laplace pressure and surface tension difference driving force of the entire oil droplet at the wedge-shaped surface microstructure location are calculated by the following equation.

[0027]

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[0028] During the process of dynamic movement, as an oil droplet advances through the wedge-shaped surface microstructure, its leading edge is affected by resistance, and in this case, Young's equation is expressed as follows:

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[0029] When an oil droplet recedes at the solid-liquid contact boundaries CD and CE at the two lateral edge positions of the wedge-shaped surface microstructure, it is affected by resistance, and in this case, Young's equation is expressed as follows:

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[0030] Therefore, the resistance force that the entire oil droplet experiences on the arc-shaped solid-liquid contact boundary DE inside the wedge-shaped surface microstructure as it advances is expressed by the following equation.

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[0031]

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[0032] The method for manufacturing the self-lubricating surface microstructure on the inner surface of a sealing ring for a rolling bearing according to the present invention is as follows. Specifically, first, the length H of the wedge-shaped surface microstructure is determined based on the design method described above, and an ultra-oleophobic surface is formed on the inner surface of the sealing ring. Then, a plurality of surface microstructure groups are formed on the inner surface of the sealing ring, each of which consists of a plurality of wedge-shaped surface microstructures arranged at equal intervals in the radial direction, with each surface microstructure group being arranged at equal intervals in the circumferential direction. At this time, the wedge-shaped surface microstructures are made to have the length H determined as described above.

[0033] In one preferred embodiment, a surface coating technique using modified nanoparticles is used to form an ultraoleophobic surface on the inner surface 6 of the seal ring. The specific details are as follows.

[0034] Nanoparticles with a particle size of less than 50 nm and a hydroxyl group modification on their surface are added to deionized water. The nanoparticles and deionized water are mixed using an ultrasonic particle disperser, and then stirred with a magnetic stirrer for 15 minutes to obtain a mixed solution. Here, the mass of the nanoparticles accounts for 1% of the mass of the mixed solution. Next, an activator is added to the mixed solution and stirred at room temperature for 60 minutes to obtain an aqueous suspension. Here, the mass of the activator accounts for 10% of the mass of the mixed solution. A seal ring with a deformation of less than 20% is selected, and the inner surface of the seal ring is cleaned using an ultrasonic cleaner, after which the obtained aqueous suspension is uniformly sprayed onto the inner surface of the seal ring. Finally, the seal ring after spraying with the aqueous suspension is dried in a vacuum dryer at 100°C.

[0035] More preferably, as nanoparticles with hydroxyl groups modified on their surface, nanoparticles having hydroxyl groups on the surface of SiO2 or Fe3O4 are used. In SiO2, silicon atoms undergo hydrolysis to produce silanol groups Si-OH, and in Fe3O4, iron ions react with water to produce iron hydroxyl groups Fe-OH.

[0036] More preferably, a fluorine-based surfactant is used as the activator.

[0037] As a preferred embodiment, the specific process for forming a plurality of surface microstructure groups arranged radially at equal intervals on the inner surface of the seal ring is as follows.

[0038] Using femtosecond laser ablation technology, multiple groups of surface microstructures are formed on the inner surface of the seal ring at equal radial intervals. Subsequently, the inner surface of the seal ring is cleaned using an ultrasonic cleaner to remove unstable modified nanoparticles and impurities from the surface.

[0039] More preferably, the processing method for forming a fine mesh groove pattern on the bottom surface of a wedge-shaped surface microstructure is as follows: A fine mesh groove pattern is formed on the bottom surface of the wedge-shaped surface microstructure using femtosecond laser ablation technology. As shown in Figure 7, the fine mesh groove pattern is a mesh-like pattern formed by the intersection of a plurality of equally spaced first grooves and a plurality of equally spaced or equally angled second grooves. The first grooves and second grooves may be parallel to the two side edges of the wedge-shaped surface microstructure, or the first grooves may be parallel to the bottom edge of the wedge-shaped surface microstructure and each second groove may be distributed at an equal angle with respect to a vertex opposite the bottom edge of the wedge-shaped surface microstructure, or the first grooves may be parallel to the bottom edge of the wedge-shaped surface microstructure and the second grooves may be parallel to the axis of symmetry X of the wedge-shaped surface microstructure.

[0040] More preferably, when cleaning the inner surface of the seal ring using an ultrasonic cleaner, petroleum ether is used as the cleaning solution.

[0041] More preferably, the wedge angle of the wedge-shaped surface microstructure is designed to be 15°, and the depth is designed to be 0.3 mm.

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