A low-friction, low-torque composite seal with internal contaminant protection and thermal balance function

Abstract

The embodiment of the present application provides a low-friction low-torque composite seal with internal contaminant protection and heat balance function, and relates to the technical field of seal technology.The method comprises the following steps: a rubber elastomer;the rubber elastomer comprises a main sealing lip and a secondary sealing lip which is integrally formed with the main sealing lip, the main sealing lip extends radially in a first direction to contact a rotating shaft; the secondary sealing lip extends radially in a second direction, and the included angle between the first direction and the second direction is greater than 90 DEG. Through the present application, the problem that the main sealing lip is easily damaged due to the fact that internal contaminants cannot be blocked is solved, and the service life of the seal is improved.

Description

Technical Field

[0001] This invention relates to the field of sealing technology, and more specifically, to a low-friction, low-torque composite seal with internal contaminant protection and thermal balance functions. Background Technology

[0002] Rotary shaft oil seals, as key components in mechanical equipment to prevent fluid (such as lubricating oil) leakage and the intrusion of external impurities, directly affect the operational reliability and lifespan of the equipment. Traditional single-lip oil seals, such as the TC type, are designed to achieve dynamic sealing by forming a stable oil film between the main sealing lip and the rotating shaft surface under spring force. However, in increasingly demanding operating conditions, such as in construction machinery, heavy vehicle gearboxes, or wheel hubs, the sealing system must not only block external contaminants like dust and mud, but also cope with internal contaminants such as metal powder generated by gear wear and carbides formed after high-temperature aging of lubricating oil. These internal contaminants can cause even more severe wear and damage to the main sealing lip than external contaminants. To address this issue, the industry typically employs a double-seal solution with two independent oil seals installed back-to-back. However, this directly leads to a significant increase in frictional power consumption, temperature rise, and shaft wear. Summary of the Invention

[0003] This invention provides a low-friction, low-torque composite seal with internal contaminant protection and thermal balance functions, thereby at least solving the problem that internal contaminants cannot be effectively blocked in related technologies.

[0004] According to one embodiment of the present invention, a low-friction, low-torque composite seal with internal contaminant protection and thermal balance functions is provided, comprising:

[0005] Rubber elastomers;

[0006] The rubber elastomer includes a main sealing lip and a secondary sealing lip integrally formed with the main sealing lip. The main sealing lip extends radially in a first direction to contact the rotating shaft. The secondary sealing lip extends radially in a second direction, and the angle between the first direction and the second direction is greater than 90°.

[0007] In one exemplary embodiment, a spring is provided on the side of the main sealing lip opposite to the rotation axis.

[0008] In one exemplary embodiment, a skeleton is also included, to which the rubber elastomer is fixed.

[0009] In one exemplary embodiment, the rubber elastomer further includes an inner protective lip located above the main sealing lip.

[0010] In one exemplary embodiment, the inner protective lip is a sine wave lip.

[0011] In an exemplary embodiment, the contact surface of the main sealing lip is provided with an oil return groove, the oil return groove is distributed circumferentially along the contact surface of the main sealing lip, and the oil return groove is sinusoidal.

[0012] In one exemplary embodiment, the angle between the lip surface of the secondary sealing lip and the axis of the rotation shaft is less than 60°.

[0013] In one exemplary embodiment, the rubber elastomer further includes a waist portion connecting the main sealing lip and the secondary sealing lip, the main sealing lip and the secondary sealing lip being integrally formed through the waist portion.

[0014] In one exemplary embodiment, the outer diameter surface of the metal skeleton is covered by a rubber layer formed by the rubber elastomer.

[0015] This invention adds a springless inner protective lip to the oil side of the main sealing lip. As the first line of defense, the inner protective lip effectively blocks and discharges wear particles and oil aging products originating from inside the system with low friction cost. This prevents these hard particles from causing wear or damage to the core main sealing lip, effectively protecting the integrity and sealing performance of the main sealing lip. Therefore, it can solve the problem of internal contaminants not being blocked, thereby improving the service life of the main seal and enhancing sealing performance. Attached Figure Description

[0016] Figure 1 This is a cross-sectional view of a low-friction, low-torque composite seal with internal contaminant protection and thermal balance functions according to an embodiment of the present invention.

[0017] In the diagram, 1. Main sealing lip; 2. Secondary sealing lip; 3. Inner protective lip; 4. Oil return groove; 5. Waist; 6. Ring spring; 7. Metal frame. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0019] In the following description, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0020] Furthermore, in this application, directional terms such as "upper," "lower," "left," and "right" may be defined relative to the orientation of the components shown in the accompanying drawings. It should be understood that these directional terms can be relative concepts, used for relative description and clarification, and may change accordingly depending on the orientation of the components in the accompanying drawings.

[0021] In this application, unless otherwise expressly specified and limited, the term "connection" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral part; it can be a direct connection or an indirect connection through an intermediate medium. Furthermore, the term "coupled" can refer to an electrical connection that enables signal transmission.

[0022] As used herein, “about,” “approximately,” or “approximately” includes the stated value and the average value within an acceptable range of deviation from the given value, wherein the acceptable range of deviation is determined by a person skilled in the art taking into account the measurement under discussion and the error associated with the measurement of the given quantity (i.e., the limitations of the measurement system).

[0023] The composite seal provided in this application combines the inner protective lip 3 with the main sealing lip 1 on the oil side to construct a multi-level protection system with functional hierarchy. This system can resist internal and external contaminants at the same time and maintain low friction operation. This solves the technical problem caused by the sharp increase in friction power consumption and temperature rise when using a double oil seal structure to protect against internal contamination in the prior art. Thus, while ensuring sealing performance, it achieves efficient, stable and long-life operation.

[0024] The following is combined Figure 1 A specific embodiment provided in this application will be described in detail.

[0025] Figure 1 The protective composite seal shown includes a metal skeleton 7 as a rigid support matrix and a rubber elastomer for achieving multiple sealing functions. During the high-temperature vulcanization process, the rubber elastomer undergoes a chemical reaction with the adhesive on a predetermined surface of the metal skeleton 7, thereby fixing the rubber elastomer to the metal skeleton 7.

[0026] The metal skeleton 7 provides geometric positioning and structural support for the rubber elastomer, ensuring that the seal maintains its preset geometric shape and spatial position after being pressed into the equipment cavity through an interference fit, and resists harmful structural deformation under working pressure gradients. The metal skeleton 7 is made of a metal material with preset stamping formability and mechanical strength, and can be made of SPCC cold-rolled carbon steel sheet conforming to JIS G3141 standards. To enhance the interfacial bonding strength between the metal skeleton 7 and the rubber elastomer and to inhibit environmental corrosion, the surface of the metal skeleton 7 is chemically converted before being laminated with the rubber. Specifically, this process can be zinc phosphating, which generates a 2-5 μm thick microporous phosphate conversion film on the metal substrate surface. The microstructure of this phosphate conversion film increases the effective surface area of ​​the metal skeleton 7, allowing the subsequently applied hot-curing adhesive to penetrate into the pores of the film and form a mechanical lock. During vulcanization, the adhesive undergoes a chemical cross-linking reaction with the rubber elastomer molecular chains under high temperature and high pressure conditions, bonding and fixing the metal skeleton and the rubber elastomer together. like Figure 1 As shown, the metal skeleton 7 in this embodiment has an L-shaped cross-sectional profile, which is composed of a cylindrical portion parallel to the axis of the seal and a radial flange portion perpendicular to the axis of the seal; the L-shaped structure can provide compressive and torsional stiffness to ensure the dimensional stability of the seal during installation and operation.

[0027] The rubber elastomer is wrapped around the predetermined area of ​​the metal skeleton 7 and integrally formed into multiple lip structures; the material of the rubber elastomer can be selected according to different application environments.

[0028] In a first preferred embodiment, for operating conditions with a temperature range of -20°C to 200°C and in highly corrosive media or requiring high wear resistance (e.g., engine crankshaft rear oil seal), the elastomer material can be fluororubber (FKM) because FKM has heat resistance, oil resistance, and chemical resistance. During the vulcanization molding process, the premixed FKM compound is injected under high pressure into a closed mold cavity containing the metal skeleton 7 via a screw injection machine. At a mold temperature of 175°C and a mold closing pressure of 15 MPa, the compound is held for 300 seconds to allow the rubber molecular chains to crosslink, transforming from a linear plastic state to a three-dimensional network elastic state, and chemically bonding with the adhesive-coated metal skeleton 7 interface.

[0029] For example, DuPont's Viton® series type A fluororubber (FKM) was selected as the elastomer material. Before vulcanization, the premixed FKM compound was plasticized on an open mill, and vulcanizing agents, accelerators, reinforcing agents (such as N550 carbon black), and processing aids were incorporated to prepare a compound for injection molding. During vulcanization, the mold temperature was precisely maintained at 175±2°C by a PID controller, the clamping pressure was 15 MPa, and the vulcanization time was 300 seconds. The resulting rubber elastomer exhibited precisely controlled physical properties, such as hardness (Shore A hardness 75±5), tensile strength (greater than 12 MPa), and compression set (less than 20% after compression for 22 hours at 150°C).

[0030] In a second preferred embodiment, for operating conditions requiring high wear resistance and dynamic performance in the temperature range of -40°C to 150°C (e.g., heavy-duty truck wheel hub units), hydrogenated nitrile butadiene rubber (HNBR) can be selected as the elastomer. HNBR is obtained by catalytic hydrogenation of nitrile butadiene rubber (NBR), and its saturated molecular backbone gives it superior heat and ozone resistance compared to NBR, while maintaining oil resistance and mechanical strength.

[0031] For example, Zetpol® series HNBR from ZEON Corporation of Japan was selected. Its rubber compound formulation uses a peroxide vulcanization system. The vulcanization process parameters are: vulcanization temperature 180±2℃, mold closing pressure 16MPa, and vulcanization time 420 seconds; the hardness of the molded HNBR elastomer is controlled at Shore A hardness 80±5, exhibiting high tear resistance.

[0032] In a third preferred embodiment, for operating conditions that require long-term operation in high-temperature engine oil at 150°C-170°C (e.g., input / output shafts of automatic transmissions), acrylic rubber (ACM) can be selected as the elastomer. ACM is resistant to high-temperature lubricating oils containing sulfur and phosphorus additives.

[0033] For example, NOK's AR series acrylate rubber is selected, and its vulcanization system uses amine or soap-based vulcanizing agents. Typical vulcanization process parameters are: vulcanization temperature 170±2℃, mold closing pressure 14MPa, vulcanization time 360 ​​seconds, supplemented by a two-stage vulcanization process (maintaining at 150℃ in an oven for 4 hours). The final product has a Shore A hardness of 70±5.

[0034] The rubber elastomer includes a main sealing unit, which consists of a main sealing lip 1 extending radially toward the rotating shaft and an annular spring 6 fitted within a spring groove on the outer periphery of the main sealing lip 1. A sealing contact strip protrudes from the side of the main sealing lip 1 closest to the rotating shaft, forming line contact with the cylindrical surface of the rotating shaft. To establish the contact pressure required for sealing, the inner diameter of the main sealing lip 1 in its free state is smaller than the outer diameter of the rotating shaft; this dimensional difference is defined as the interference fit. When the seal is installed on the shaft, the main sealing lip 1 expands radially due to elastic deformation, generating a radial preload pointing toward the shaft center, causing the sealing contact strip to fit tightly against the shaft surface. To compensate for the decrease in elastic force of the rubber material due to temperature changes, wear, or creep aging, the annular spring 6 is fixed within a spring groove on the back of the main sealing lip. This spring provides a persistent and stable radial force, ensuring that the main sealing lip 1 maintains a constant contact pressure on the shaft surface. The presence of this contact pressure causes the lubricating oil inside the seal to form a dynamically stable lubricating oil film at the contact interface between the main sealing lip 1 and the shaft under the coupling effect of centrifugal force and capillary effect. This oil film, as a hydrodynamic lubrication layer, not only prevents macroscopic leakage of oil, but also lubricates the sealing contact area to reduce friction and wear.

[0035] For example, for a rotating shaft with an outer diameter of 50 mm, the free-state inner diameter of the main sealing lip 1 is 48.5 mm, resulting in a radial interference of 1.5 mm. The lip angle (the angle between the sealing surface and the air-side lip) of the main sealing lip 1 is 25 degrees. The annular spring 6 is wound with 0.6 mm diameter SUS304 stainless steel wire, and its free-state coil diameter is 51 mm. After being stretched and installed in the working position, the spring provides a total radial force of approximately 8 N, which is evenly distributed across the entire contact circumference through the main sealing lip; this force value is designed to ensure the formation of a stable oil film with a thickness of approximately 1-3 μm in the contact area at a rotational speed of 3000 rpm.

[0036] To optimize performance, the contact surface of the main sealing lip 1 features a low-friction profile. This low-friction design replaces the traditional sharp edge by introducing an arc with a radius of curvature of 0.1 mm at the tip of the lip. This arc structure alters the pressure distribution in the contact area, transforming it from a traditional triangular distribution to a more parabolic one, thus reducing peak pressure. Furthermore, this pressure distribution helps the lubricating oil form a hydrodynamic wedge at the inlet of the contact area, thereby slightly separating the shaft from the lip and forming a more robust hydrodynamic oil film.

[0037] To accommodate bidirectional rotation, a sinusoidal oil return groove 4 with 120 cycles is provided on the contact surface of the main sealing lip 1. The amplitude of this sinusoidal wave is 0.02 mm, and the wavelength is approximately 1.27 mm. When the 50 mm diameter shaft rotates at 3000 rpm, these micro-waveform structures interact with the oil film, generating a small pumping effect on oil droplets attempting to cross the sealing edge, pumping them back to the oil side. This pumping capability can resist potential leakage tendencies caused by micro-defects on the shaft surface or pressure fluctuations within the cavity.

[0038] Additionally, an integrally formed secondary sealing lip 2 is provided on the axial air side of the main sealing unit. This secondary sealing lip 2 is used to prevent dust, mud, water, and other contaminants from the external environment from entering the working area of ​​the main sealing lip. To achieve dustproof function while reducing the additional frictional torque it brings, the angle between the lip surface of the secondary sealing lip 2 and the axis of the rotating shaft is between 35 degrees and 55 degrees.

[0039] For example, the secondary sealing lip 2 forms a 45-degree lip angle with the axial centerline of the seal, and its free-state inner diameter is designed to be 49.8 mm, resulting in an interference fit of 0.2 mm relative to a 50 mm shaft diameter. Upon installation, this small interference fit combined with the large lip angle results in a very light contact force of approximately 0.5 N between the secondary sealing lip 2 and the shaft surface. This force is sufficient to scrape away dust adhering to the shaft surface, but the resulting frictional torque is negligible. When external mud splashes, the 45-degree angled secondary sealing lip 2 deflects and blocks it outwards. The gap between the main sealing lip 1 and the secondary sealing lip 2 is thus kept relatively clean, and this space is filled with polyurea-based grease to further enhance dustproofing and lubricate the main sealing lip 1.

[0040] In addition, the rubber elastomer also includes a radially inwardly extending inner protective lip 3 on the axial oil side of the main sealing unit. The inner protective lip 3 is usually located above the main sealing lip 1. The inner protective lip 3 can prevent suspended hard particles in the lubricating oil (e.g., metal particles generated by gear wear, carbides formed by high-temperature aging of lubricating oil) from migrating to the main sealing lip area.

[0041] The inner protective lip 3 is a springless structure that relies solely on the elastic interference of the rubber itself to contact the shaft surface. Based on this springless configuration, the inner protective lip 3 achieves its protective function while keeping the generated friction and heat to extremely low levels. When contaminated lubricating oil flows towards the sealing area, it first encounters the inner protective lip, where most larger hard particles are blocked and scraped away. Due to the very low contact pressure of the inner protective lip 3, even when it comes into contact with hard particles, its own wear and wear on the shaft are extremely minor. After this interception, the lubricating oil reaching the main sealing lip 1 area has been initially purified, thereby reducing the risk of wear on the main sealing lip 1.

[0042] For example, the free-state inner diameter of the inner protective lip 3 is designed to be 49.0 mm, with a radial interference of 1.0 mm relative to a shaft diameter of 50 mm. Due to its compliant structure and lack of spring loading, the radial contact force applied to the shaft is precisely controlled at approximately 2 N, far lower than the 8 N of the main sealing lip 1; at a rotational speed of 3000 rpm, the frictional torque generated by the inner protective lip 3 is less than 20% of that of the main sealing lip 1.

[0043] The rubber elastomer also includes a waist 5 connecting the main sealing lip 1 and the secondary sealing lip 2. The flexibility of the waist 5 determines the ability of the main sealing lip 1 to follow radial runout or vibration of the rotating shaft. The thickness of the waist 5 includes a tapered profile that gradually thins from the root near the secondary sealing lip 2 (2.5 mm) to the neck near the main sealing lip 1 (1.5 mm). This gradual thickness design gives the waist 5 non-linear stiffness characteristics in the radial direction. It exhibits flexibility at small displacements to absorb high-frequency small vibrations of the shaft, and increases stiffness at large displacements to prevent excessive deflection of the lip.

[0044] To accommodate the equipment cavity made of a material with a high coefficient of thermal expansion (such as aluminum alloy), a layer of rubber is wrapped around the outer diameter surface of the metal frame 7. The coefficient of thermal expansion of this rubber layer is much greater than that of the metal. When the temperature rises, the expansion of the outer rubber layer can compensate for the thermal expansion of the cavity to maintain sufficient radial clamping force and ensure static sealing of the outer circumference.

[0045] For example, the outer diameter surface of the seal is covered with a 1.0 mm thick layer of FKM material, which has an outer diameter of 70.2 mm at room temperature, with an interference fit of 0.2 mm relative to a 70.0 mm cavity. When the system temperature rises from 20°C to 120°C, the diameter of the 6061 aluminum alloy cavity will expand by approximately At the same time, the coefficient of thermal expansion is approximately The thermal expansion of the FKM rubber layer itself, coupled with the expansion of the internal metal skeleton, causes its outer diameter to increase accordingly. Finite element thermo-structural coupling analysis shows that at a high temperature of 120℃, the outer diameter of the seal and the cavity can still maintain an effective interference of not less than 0.1mm, thus eliminating static leakage caused by thermal expansion mismatch.

[0046] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A low-friction, low-torque composite seal with internal contaminant protection and thermal balance functions, characterized in that, include: Rubber elastomers; The rubber elastomer includes a main sealing lip and a secondary sealing lip integrally formed with the main sealing lip, the main sealing lip extending radially in a first direction to contact the rotating shaft; The secondary sealing lip extends radially in a second direction, and the angle between the first direction and the second direction is greater than 90°.

2. The low-friction, low-torque composite seal with internal contaminant protection and thermal balance functions according to claim 1, characterized in that, A spring is provided on the side of the main sealing lip opposite to the rotating shaft.

3. The low-friction, low-torque composite seal with internal contaminant protection and thermal balance functions according to claim 1, characterized in that, It also includes a skeleton, to which the rubber elastomer is fixed.

4. The low-friction, low-torque composite seal with internal contaminant protection and thermal balance functions according to claim 1, characterized in that, The rubber elastomer also includes an inner protective lip, which is located above the main sealing lip.

5. The low-friction, low-torque composite seal with internal contaminant protection and thermal balance functions according to claim 4, characterized in that, The inner protective lip is a sine wave lip.

6. The low-friction, low-torque composite seal with internal contaminant protection and thermal balance functions according to claim 1, characterized in that, The contact surface of the main sealing lip is provided with an oil return groove, which is distributed circumferentially along the contact surface of the main sealing lip and is sinusoidal.

7. The low-friction, low-torque composite seal with internal contaminant protection and thermal balance functions according to claim 1, characterized in that, The angle between the lip surface of the secondary sealing lip and the axis of the rotating shaft is less than 60°.

8. The low-friction, low-torque composite seal with internal contaminant protection and thermal balance functions according to claim 1, characterized in that, The rubber elastomer also includes a waist portion connecting the main sealing lip and the secondary sealing lip, wherein the main sealing lip and the secondary sealing lip are integrally formed through the waist portion.

9. The low-friction, low-torque composite seal with internal contaminant protection and thermal balance functions according to claim 3, characterized in that, The outer diameter surface of the skeleton is covered by a rubber layer formed by the rubber elastomer.

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