After-bending oil seal and preparation method thereof

Abstract

The invention discloses a bent oil seal and a preparation method thereof, and relates to the technical field of oil seals. A bent oil seal comprises a rigid framework and a sealing function layer, the sealing function layer comprises a connecting rubber layer and a sealing piece, the sealing piece is fixedly connected with the rigid framework through the connecting rubber layer, specifically, the connecting rubber layer is made of modified acrylate rubber, and the sealing piece is a modified polytetrafluoroethylene sealing piece. The modified polytetrafluoroethylene sealing element is formed by graft polymerization of acrylate monomers on the surface of the polytetrafluoroethylene sealing element. By means of the technical scheme, on the premise that an existing rigid framework surface treatment technology does not need to be changed and a conventional oil seal preparation technology continues to be used, the connection stability between the sealing function layer and the rigid framework is effectively improved, and the service life of the bent oil seal under the extreme working condition of an engine is prolonged.

Description

Technical Field

[0001] This invention relates to the technical field of oil seals, and in particular to a curved oil seal and its preparation method. Background Technology

[0002] The rear crankcase oil seal, a key static and dynamic seal in the engine sealing system, is primarily installed at the junction of the crankshaft's power output end and the transmission. Its core function is to prevent oil leakage from the crankcase and to block external dust and impurities from entering, thereby ensuring the engine's long-term, reliable, and clean operation. A typical rear crankcase oil seal usually consists of a sealing layer that directly contacts the shaft and possesses wear-resistant, oil-resistant, and high-temperature-resistant properties, as well as a rigid frame that provides installation rigidity and structural support for the entire seal. To ensure continuous contact at the sealing interface, some designs also incorporate elastic clamping elements to compensate for wear and maintain the long-term clamping force of the sealing layer on the shaft surface.

[0003] In existing technologies, polytetrafluoroethylene (PTFE) has become the preferred material for high-performance curved back seal sealing layers due to its extremely low coefficient of friction, excellent chemical resistance, and wide heat resistance range. Meanwhile, metal skeletons such as low-carbon steel and aluminum alloys are also widely used as rigid skeleton materials for oil seals due to their good mechanical strength, mature processing technology, and significant cost advantages. However, reliably and persistently bonding the PTFE sealing layer to the metal skeleton remains a significant technical challenge. This is mainly due to the inherent characteristics of PTFE material—extremely low surface energy and strong chemical inertness—resulting in very weak inherent bonding force between it and the metal interface. Currently, conventional adhesive bonding or simple mechanical embedding processes commonly used in the industry are insufficient to form a long-lasting and stable connection structure at this heterogeneous material interface.

[0004] Specifically, under actual engine operating conditions, the rear crankcase oil seal is subjected to a harsh environment of high temperature, immersion in hot oil, shaft vibration, and cyclic thermal cycling for extended periods. Combined with the inherent properties of PTFE, existing bonding solutions face multiple failure risks: First, the adhesive is prone to thermal aging at high temperatures, leading to a decrease in its bonding effect with PTFE. Second, there is a significant difference in the coefficients of thermal expansion between PTFE and the metal skeleton. During repeated thermal cycles, cumulative shear stress is generated at the interface, gradually weakening the interfacial bond strength. Third, the hot oil medium causes swelling, penetration, and erosion at the bonding interface, further accelerating the failure process of the adhesive on PTFE. The combined effect of these factors leads to premature degradation of the bonding interface between the PTFE sealing layer and the metal skeleton, resulting in problems such as seal peeling, loosening, or displacement, thereby causing oil leakage, loss of sealing function, and seriously threatening the engine's operational reliability and service life.

[0005] Therefore, there is an urgent need to develop an innovative rear-curved oil seal structure or connection method that can ensure a durable, stable, and robust bond between the sealing functional layer and the rigid skeleton under extreme engine operating conditions, thereby achieving a dual optimization of sealing performance and cost-effectiveness. Summary of the Invention

[0006] In order to improve the connection stability between the sealing functional layer and the rigid skeleton while ensuring the sealing effect of the rear crankcase oil seal, and to extend the service life of the rear crankcase oil seal under extreme engine operating conditions, this application provides a rear crankcase oil seal and its preparation method.

[0007] Firstly, the technical solution for a crankcase oil seal provided in this application is as follows: A rear-curved oil seal includes a rigid skeleton and a sealing functional layer. The rigid skeleton has a circular ring structure, and the sealing functional layer includes a connecting adhesive layer and a sealing element. The sealing lip is fixedly connected to the rigid skeleton through the connecting adhesive layer. The connecting adhesive layer is formed of modified acrylate rubber, and the sealing element is a modified polytetrafluoroethylene (PTFE) sealing element, which is formed by grafting and polymerizing acrylate monomers onto the surface of the PTFE sealing element.

[0008] By adopting the above technical solution, a connecting layer formed of modified acrylate rubber, combined with a modified PTFE seal grafted with acrylate monomers, serves as the sealing functional layer of the rear crankcase oil seal. This effectively improves the connection stability between the sealing functional layer and the rigid skeleton without modifying the existing rigid skeleton surface treatment technology and using the conventional oil seal manufacturing process. This helps extend the service life of the rear crankcase oil seal under extreme engine operating conditions. Secondly, by grafting acrylate monomers onto the surface of the modified PTFE seal, it not only retains the original low-friction and chemical resistance properties of PTFE, ensuring the dynamic sealing effect of the seal itself, but also allows the seal to chemically react with the modified acrylate rubber serving as the connecting layer. This further enhances the interfacial bonding force between the seal and the connecting layer, thus helping to prevent oil seal failure caused by detachment or displacement between the seal and the connecting layer. This ensures that the rear crankcase oil seal maintains stable and good sealing performance even under long-term extreme operating conditions.

[0009] Optionally, the surface grafting treatment method for the modified polytetrafluoroethylene seal includes the following steps: Prepare polytetrafluoroethylene (PTFE) seals in advance. After cleaning and drying, completely immerse the seals in a modified emulsion containing the acrylate monomers. Remove them and let them air dry naturally. Then place them in an electron beam irradiation device and irradiate them uniformly in an inert atmosphere. After the irradiation is completed, clean and vacuum dry them to obtain the modified PTFE seals.

[0010] By adopting the above technical solution, a stable grafted polymer layer with excellent compatibility with modified polyacrylate rubber can be formed on the surface of polytetrafluoroethylene, which is beneficial to improving the connection stability between the seal and the adhesive layer. Secondly, the surface grafting modification is carried out by electron beam irradiation, which is not only suitable for industrial-scale modification, but also green, efficient and without chemical residues.

[0011] Optionally, the modified emulsion comprises 15 wt% acrylate monomers, 0.2 wt% hydroquinone and 0.5 wt% fatty alcohol polyoxyethylene ether, with the balance being deionized water. The acrylate monomer is any two of the following: hydroxyacrylate, glycidyl acrylate, and phosphate methacrylate.

[0012] By adopting the above technical solution, hydroquinone can effectively inhibit the self-polymerization reaction of acrylate monomers in the modified emulsion, ensuring that most acrylate monomers can be used in the surface grafting of PTFE seals. Meanwhile, fatty alcohol polyoxyethylene ethers can act as surfactants to improve the surface wettability of PTFE seals, increase the coverage of the modified emulsion on the PTFE surface, and make the grafting reaction more uniform and complete, thus improving the grafting rate. Secondly, the acrylate monomers used all contain multiple active functional groups and can maintain a certain level of reactivity after grafting polymerization. This allows the modified PTFE seals to co-cure and cross-link with the modified acrylate rubber during compression molding and vulcanization, forming chemical bonds, which is beneficial for improving the connection stability between the seals and the adhesive layer.

[0013] Optionally, in the modified emulsion, the acrylate monomer is specifically a composition of glycidyl acrylate and phosphate methacrylate, and the mass ratio of glycidyl acrylate to phosphate methacrylate is 1:(0.2-0.5).

[0014] By adopting the above technical solution, the epoxy groups in glycidyl acrylate and the phosphate groups in methacrylate phosphate can react together during the vulcanization process of modified acrylate rubber, forming a multi-layer chemical bond network between the seal and the connecting adhesive layer. This can further improve the peel strength between the seal and the connecting adhesive layer, while also improving the heat resistance and oil resistance of the composite interface. In addition, within this range, it can also reduce the adverse effects of acidic phosphate groups, which is conducive to ensuring a stable connection between the seal and the connecting adhesive layer and preventing problems such as peeling and delamination of the seal and the connecting adhesive layer after long-term use under extreme working conditions.

[0015] Optionally, the modified acrylic rubber comprises the following raw materials in parts by weight: Acrylic rubber: 85-90 parts; Fluororubber: 10-15 parts; Composite carbon black: 60-75 parts; Modified filler: 20-25 parts; Curing crosslinking agent: 4-5.5 parts; Plasticizer: 4-6 parts; Release agent: 2-3.5 parts; Flow aid: 4-6 parts; Anti-aging agent: 2-3.2 parts; The modified filler is a composition of silica and boron nanoparticles modified with a silane coupling agent, wherein the mass ratio of silica to boron nanoparticles is (3-4):1.

[0016] By adopting the above technical solution, a small amount of fluororubber and acrylate rubber are blended and compounded to form the main rubber material, which can effectively improve the heat and oil resistance of the modified acrylate rubber. At the same time, the synergistic reinforcing effect of the modified filler and composite carbon black enables the modified acrylate rubber to have both excellent mechanical properties and wear resistance, and is not easily damaged. This ensures that the bonding layer can still stably connect the rigid skeleton and the seal under extreme working conditions, which is beneficial to improving the service life of the back-curved oil seal under extreme working conditions.

[0017] Optionally, the composite carbon black is a composition of N330 carbon black and N660 carbon black, wherein the mass ratio of N330 carbon black to N660 carbon black is 1:(1-1.5).

[0018] By adopting the above technical solution, it is beneficial to balance the reinforcement and toughening effects, so that the bonding adhesive layer can achieve a perfect combination of high wear resistance, high flexibility and high mechanical strength, thus adapting to the extreme working conditions of the engine.

[0019] Optionally, the curing crosslinking agent is specifically a composition of N,N'-di(cinnamyl-1,6-hexanediamine) and sodium stearate, wherein the mass ratio of the composition of N,N'-di(cinnamyl-1,6-hexanediamine) and sodium stearate is (3-4.5):1.

[0020] By adopting the above technical solution, a CC crosslinking network with high bond energy can be formed between the modified acrylic rubber, or between the modified acrylic rubber and the seal, which is beneficial to improving the heat and oil resistance of the connecting layer or between the connecting layer and the seal, and ensuring the performance of the sealing function layer of the back-curved oil seal under extreme working conditions.

[0021] Optionally, the connecting adhesive layer covers the outer periphery of the rigid skeleton, the inner side of the connecting adhesive layer near the rigid skeleton is a thickened part, one end of the seal is connected to the thickened part, the other end of the seal extends toward the inner side of the rigid skeleton and forms a main sealing lip, and a secondary sealing lip is provided at the end of the connecting adhesive layer away from the seal.

[0022] By adopting the above technical solution, the thickened portion of the connecting adhesive layer increases the contact area with the seal, which helps to further improve the peel strength between the connecting adhesive layer and the seal, thereby improving the connection stability between the layers and preventing oil seal failure caused by detachment or displacement between the seal and the connecting adhesive layer. Secondly, the main sealing lip and the secondary sealing lip form a double protection, which helps to improve the dynamic sealing effect of the rear-bend oil seal, thus improving its sealing performance.

[0023] Optionally, the rigid frame includes a support portion and a bending portion, wherein the bending portion bends toward the inner side of the ring of the rigid frame and forms a 90° angle with the support portion.

[0024] By adopting the above technical solution, the bending section not only further increases the contact area between the rigid skeleton and the connecting adhesive layer, but also forms a mechanically interlocking structure with the vulcanized and cross-linked connecting adhesive layer. Combined with conventional chemical bonding processes, this further improves the connection stability between the rigid skeleton and the connecting adhesive layer. In addition, since the rigid skeleton has an overall annular structure, the bending section can enhance the radial support force of the rigid skeleton, which helps to reduce the deformation of the support part of the rigid skeleton under high-pressure conditions and ensures the structural stability of the rear-bend oil seal.

[0025] Secondly, the method for preparing a post-bend oil seal provided in this application adopts the following technical solution: A method for preparing a post-bend oil seal includes the following steps: S1. The rigid skeleton is pretreated to obtain a pre-requisite skeleton; the modified acrylate rubber is cut into strips according to the dimensions to obtain pre-requisite rubber strips; S2. Cover the surface of the prepared rubber strip with the prepared skeleton, and then place them together in the vulcanization mold. Stack the modified polytetrafluoroethylene seal on top of the prepared rubber strip, close the mold and perform hot-press vulcanization through a secondary vulcanization process. After vulcanization, trim the edges, demold and discharge the material, and coat the surface with anti-rust oil to obtain the curved oil seal.

[0026] In summary, the technical solution of this application has at least one of the following beneficial effects: 1. By using a connecting layer formed of modified acrylic rubber, combined with a modified polytetrafluoroethylene seal grafted with acrylic monomers on its surface, as the sealing functional layer of the rear crankcase oil seal, the connection stability between the sealing functional layer and the rigid skeleton can be effectively improved without changing the existing rigid skeleton surface treatment technology and without using the conventional oil seal manufacturing process. This is beneficial to extending the service life of the rear crankcase oil seal under extreme engine operating conditions.

[0027] 2. By using a small amount of fluororubber and acrylic rubber to form the main rubber material, and with the synergistic effect of other fillers and additives, the modified acrylic rubber used as the connecting layer can have excellent heat and oil resistance, mechanical properties and wear resistance, and is not easily damaged. This ensures that the connecting layer can still stably connect the rigid skeleton and the seal under extreme working conditions, which is beneficial to improving the service life of the back-curved oil seal under extreme working conditions.

[0028] 3. By grafting acrylate monomers onto the surface of PTFE seals, not only are the original low-friction and chemical-resistant properties of PTFE retained, ensuring the dynamic sealing effect of the seals themselves, but the seals also undergo a chemical reaction with the modified acrylate rubber used as the connecting layer, further enhancing the interfacial bonding between the seals and the connecting layer. This helps prevent oil seal failure caused by detachment or displacement between the seals and the connecting layer, ensuring that the oil seals maintain stable and good sealing performance even under long-term extreme working conditions. Attached Figure Description

[0029] Figure 1 This is a top view of a rear-bend oil seal according to Embodiment 1 of this application.

[0030] Figure 2 yes Figure 1 Sectional view of AA.

[0031] Explanation of reference numerals in the attached figures: 1. Rigid frame; 11. Support part; 12. Bending part; 2. Connecting adhesive layer; 21. Thickened part; 22. Secondary sealing lip; 3. Sealing element; 31. Main sealing lip. Detailed Implementation

[0032] The present application will be further described in detail below with reference to the accompanying drawings, preparation examples, embodiments and comparative examples.

[0033] The acrylate rubber was specifically purchased from Anhui Huajing New Materials, with the grade RK-101.

[0034] The fluororubber was specifically purchased from Zhonghao Chenguang, with the brand name FKM 2604. Preparation Example

[0035]

Preparation Example 1

[0036] The adhesive used is Solef 5130 PVDF adhesive from the United States.

[0037]

Preparation Example 2-1

[0038] In this preparation example, the composite carbon black is a composition of N330 type carbon black and N660 type carbon black, and the mass ratio of N330 type carbon black to N660 type carbon black is 1:1.5, that is, it includes 3 kg of N330 type carbon black and 4.5 kg of N660 type carbon black.

[0039] In this preparation example, the modified filler is a composition of silica and boron nitride nanoparticles modified with a silane coupling agent, and the mass ratio of silica to boron nitride nanoparticles is 3:1, i.e., it includes 1.5 kg of silica and 0.5 kg of boron nitride nanoparticles. The modification method for the modified filler includes the following steps: First, take 100g of silane coupling agent KH-550 and add it to deionized water at 5wt%, stir evenly to obtain a filler modification solution. Then, weigh 1.5kg of silica and 0.5kg of nano boron nitride, mix them thoroughly and add them to the filler modification solution. Heat to 60℃ and stir continuously for 1 hour. Separate by high-speed centrifugation and collect the precipitate. Dry under vacuum to obtain the modified filler.

[0040] In this preparation example, the curing crosslinking agent is a composition of N,N'-di(cinnamyl-1,6-hexanediamine) and sodium stearate, comprising 0.3 kg of N,N'-di(cinnamyl-1,6-hexanediamine) and 0.1 kg of sodium stearate. The plasticizer is a polyadipate-based polyester plasticizer, specifically PARAPLEX A-8200 from HallStar Company, USA. The flow aid is vinyl bis-stearamide. The mold release agent is VAM, a rubber release agent. The antioxidant is a composition of antioxidant RD and antioxidant 4010NA, comprising 0.1 kg of antioxidant RD and 0.1 kg of antioxidant 4010NA.

[0041] A method for preparing modified acrylic rubber, comprising the following steps: First, the acrylic rubber and fluororubber are heated to 80°C for intensive mixing and plasticization to obtain a compound. Plasticizer and antioxidant are added and mixed evenly. Then, composite carbon black is added in batches, with 25% of the mass of composite carbon black added in 4 batches. Each batch is added only after the compound carbon black has been mixed evenly. After the composite carbon black and the compound are fully mixed, modified filler, release agent and flow aid are added. After mixing evenly, the mixture is discharged and transferred to a two-roll mill for two-roll milling. Curing crosslinking agent is added and rapid tumbling is carried out at the same time. The overall two-roll milling temperature is controlled not to exceed 60°C. After mixing evenly, the mixture is passed through a thin pass at least 3 times and discharged to obtain modified acrylic rubber.

[0042]

Preparation Example 2-2

[0043] In this preparation example, the composite carbon black is a composition of N330 type carbon black and N660 type carbon black, and the mass ratio of N330 type carbon black to N660 type carbon black is 1:1, that is, it includes 3 kg of N330 type carbon black and 3 kg of N660 type carbon black.

[0044] In this preparation example, the modified filler is a composition of silica and boron nitride nanoparticles modified with a silane coupling agent, and the mass ratio of silica to boron nitride nanoparticles is 4:1, i.e., it includes 2 kg of silica and 0.5 kg of boron nitride nanoparticles. The modification method for the modified filler includes the following steps: First, 125g of silane coupling agent KH-550 was added to deionized water at 5wt% and stirred evenly to obtain a filler modification solution. Then, 2kg of silica and 0.5kg of nano boron nitride were weighed, mixed thoroughly, and added to the filler modification solution. The mixture was heated to 60℃ and stirred continuously for 1 hour. The precipitate was separated by high-speed centrifugation and collected. The precipitate was then dried under vacuum to obtain the modified filler.

[0045] In this preparation example, the curing crosslinking agent is a composition of N,N'-di(cinnamyl-1,6-hexanediamine) and sodium stearate, comprising 0.45 kg of N,N'-di(cinnamyl-1,6-hexanediamine) and 0.1 kg of sodium stearate. The plasticizer is a polyadipate-based polyester plasticizer, specifically PARAPLEX A-8200 from HallStar Company, USA. The flow aid is vinyl bis-stearamide. The mold release agent is VAM, a rubber release agent. The antioxidant is a composition of antioxidant RD and antioxidant 4010N, comprising 0.2 kg of antioxidant RD and 0.12 kg of antioxidant 4010NA.

[0046]

Preparation Example 3-1

[0047] In this preparation example, based on 10 kg of modified emulsion, the following raw materials are included: 1.5 kg acrylate monomers, 0.02 kg hydroquinone and 0.05 kg fatty alcohol polyoxyethylene ether, with the remainder being deionized water.

[0048] The acrylate monomers are a composition of hydroxyethyl acrylate and glycidyl acrylate, specifically comprising 1 kg of hydroxyethyl acrylate and 0.5 kg of glycidyl acrylate. The fatty alcohol polyoxyethylene ether is specifically AEO-9.

[0049]

Preparation Example 3-2

[0050] In this preparation example, the acrylate monomer is a composition of hydroxyethyl acrylate and phosphate methacrylate, specifically including 1 kg of hydroxyethyl acrylate and 0.5 kg of phosphate methacrylate.

[0051]

Preparation Example 3-3

[0052] In this preparation example, the acrylate monomer is a composition of glycidyl acrylate and phosphate methacrylate, specifically comprising 1 kg of glycidyl acrylate and 0.5 kg of phosphate methacrylate.

[0053]

Preparation Examples 3-4

[0054] In this preparation example, the acrylate monomer is a composition of glycidyl acrylate and phosphate methacrylate, specifically including 1.25 kg of hydroxyethyl acrylate and 0.25 kg of phosphate methacrylate. Example

[0055]

Example 1

[0056] Specifically, the rigid frame 1 includes a support portion 11 and a bending portion 12. The bending portion 12 bends towards the inner side of the ring of the rigid frame 1 and forms a 90° angle with the support portion 11. The connecting adhesive layer 2 covers the outer periphery of the rigid frame 1. The inner side of the connecting adhesive layer 2 near the ring of the rigid frame 1 is a thickened portion 21. One end of the sealing member 3 is fixedly connected to the thickened portion 21, and the other end of the sealing member 3 extends towards the inner side of the ring of the rigid frame 1 to form a main sealing lip 31. A secondary sealing lip 22 is provided at the end of the connecting adhesive layer 2 away from the sealing member 3.

[0057] In this embodiment, the rigid skeleton 1 is specifically made of carbon steel SPCC; the connecting adhesive layer 2 is formed by secondary vulcanization of the modified acrylic rubber obtained in [Preparation Example 2-1]; and the sealing element 3 is the modified polytetrafluoroethylene sealing element obtained in [Preparation Example 3-1].

[0058] A method for preparing a post-bend oil seal includes the following steps: S1. The rigid skeleton 1 is pretreated according to [Preparation Example 1] to obtain a pre-skeleton; the modified acrylate rubber is cut into strips according to the dimensions to obtain pre-rubber strips; S2. Cover the surface of the prepared rubber strip with the prepared skeleton, and then place them together in the vulcanization mold. Stack the modified polytetrafluoroethylene seal on top of the prepared rubber strip, close the mold and perform hot-press vulcanization through a secondary vulcanization process. After vulcanization, trim the edges, demold and discharge the material, and coat the surface with anti-rust oil to obtain the curved back oil seal.

[0059] In the secondary vulcanization process of S2, the first vulcanization is hot pressing at 175℃ and 1.3MPa for 30 minutes, and the second vulcanization is hot drying at 150℃ in an oven for 4 hours.

[0060]

Example 2

[0061] In this embodiment, the connecting adhesive layer 2 is formed by secondary vulcanization of the modified acrylate rubber obtained in [Preparation Example 2-2]; the sealing element 3 is the modified polytetrafluoroethylene sealing element obtained in [Preparation Example 3-1].

[0062] A method for preparing a post-bend oil seal includes the following steps: S1. The rigid skeleton 1 is pretreated according to [Preparation Example 1] to obtain a pre-skeleton; the modified acrylate rubber is cut into strips according to the dimensions to obtain pre-rubber strips; S2. Cover the surface of the prepared rubber strip with the prepared skeleton, and then place them together in the vulcanization mold. Stack the modified polytetrafluoroethylene seal on top of the prepared rubber strip, close the mold and perform hot-press vulcanization through a secondary vulcanization process. After vulcanization, trim the edges, demold and discharge the material, and coat the surface with anti-rust oil to obtain the curved back oil seal.

[0063] In the secondary vulcanization process of S2, the first vulcanization is hot pressing at 180℃ and 1.3MPa for 30 minutes, and the second vulcanization is hot drying at 155℃ in an oven for 3 hours.

[0064]

Example 3

[0065] In this embodiment, the seal 3 is the modified polytetrafluoroethylene seal obtained in [Preparation Example 3-2].

[0066]

Example 4

[0067] In this embodiment, the seal 3 is the modified polytetrafluoroethylene seal obtained in [Preparation Example 3-3].

[0068]

Example 5

[0069] In this embodiment, the seal 3 is the modified polytetrafluoroethylene seal obtained in [Preparation Examples 3-4]. Comparative Example

[0070] Comparative Example 1 A type of back-curved oil seal differs from [Example 1] in that the sealing functional layer is different; specifically, it does not have a connecting adhesive layer 2.

[0071] In this comparative example, the sealing element 3 is directly heat-pressed and bonded to the surface of the rigid frame 1.

[0072] Comparative Example 2 A type of back-curved oil seal differs from [Example 1] in that the sealing functional layer is different, specifically the sealing element 3 is different.

[0073] In this comparative example, seal 3 is an unmodified polytetrafluoroethylene seal.

[0074] Comparative Example 3 A type of back-curved oil seal differs from [Example 1] in that the sealing functional layer is different, specifically the sealing element 3 is different.

[0075] In this comparative example, the seal 3 is a polytetrafluoroethylene seal, and the surface of the seal 3 that is composite with the connecting adhesive layer 2 is coated with a 5% concentration of KH550 silane coupling agent at a rate of 2 ml / cm2, and is thoroughly dried after coating. Performance test data

[0076] 1. Interface Composite Strength: Modified acrylic rubber and modified polytetrafluoroethylene (PTFE) seals were prepared according to the connecting adhesive layer 2 and seal 3 in each embodiment and comparative example, respectively. These were then made into rubber strips 100 mm long, 25 mm wide, and 2 mm thick. The strips were then composited using the molding and vulcanization process described in each embodiment and comparative example, simulating the actual molding process of the curved oil seal. Test samples were prepared corresponding to the composite of modified acrylic rubber and modified PTFE seals. The peel strength (N / mm) of the test samples was tested according to GB / T 2791-1995 Adhesives R Peel Strength Test Method Flexible Materials to Flexible Materials. The peel strength of the test samples was tested at room temperature and under hot oil aging conditions. The hot oil aging conditions were immersion in IRM901 oil at 150°C for 70 hours.

[0077] 2. Long-term performance of oil seals: The corresponding rear crankcase oil seals were prepared as test samples according to the various embodiments and comparative examples. They were then installed in the test engine and subjected to long-term tests under conditions A and B respectively. Condition A was continuous operation for 500 hours at 0.5 MPa and 2500 rpm, and Condition B was continuous operation for 200 hours at 0.5 MPa and 3700 rpm. The medium used was engine oil at 150℃. The leakage of the rear crankcase oil seals was observed and recorded.

[0078] Table 1. Partial performance test data of the rear crankcase oil seal.

[0079] Based on Examples 1 and Comparative Examples 1-3, and the data in Table 1, it can be seen that by using modified acrylate rubber as the connecting adhesive layer 2, combined with modified polytetrafluoroethylene (PTFE) seals grafted with acrylate monomers, as the sealing functional layer of the back-bend oil seal, the connection stability between the sealing functional layer and the rigid skeleton 1 can be effectively improved without modifying the existing surface treatment technology of the rigid skeleton 1 and by using the conventional oil seal manufacturing process. This significantly improves the long-term sealing performance of the back-bend oil seal under extreme operating conditions. Specifically, by introducing modified acrylate rubber as the connecting adhesive layer 2, the existing surface treatment technology of the rigid skeleton 1 can be used. Under the same adhesive treatment, the bonding stability between the rigid skeleton 1 and the modified acrylate rubber is significantly better than that between the rigid skeleton 1 and PTFE. This effectively reduces the problem of sealing failure caused by peeling, loosening, or displacement of the rigid skeleton 1 and the sealing functional layer in the oil seal. On the other hand, modified acrylic rubber also has excellent heat resistance and oil resistance. Even when used for a long time in a hot oil medium environment with high temperature and high pressure, it can maintain stable physical properties, which helps to ensure that the sealing effect of the oil seal after the bend is not greatly affected.

[0080] Meanwhile, with the introduction of modified acrylate rubber as the connecting adhesive layer 2, the use of surface-grafted modified PTFE seals made of acrylate monomers allows the grafted polymer layer to participate in the vulcanization and crosslinking reaction of the modified acrylate rubber during hot-press vulcanization molding, forming a stronger chemical bond. Compared to unmodified PTFE seals or PTFE seals simply surface-modified with silane coupling agents, surface-grafted modified PTFE seals can further achieve a stable connection between the seal 3 and the connecting adhesive layer 2, greatly enhancing the interfacial bonding force between the seal 3 and the connecting adhesive layer 2. This helps prevent oil seal failure caused by detachment or displacement between the seal 3 and the connecting adhesive layer 2.

[0081] Combining Examples 1 and 3-5 with the data in Table 1, it can be seen that by adjusting the acrylate monomers in the polymer layer on the surface of the modified PTFE seal, the peel strength and connection stability of the seal 3 and the connecting adhesive layer 2 can be further improved. Specifically, when the polymer monomers grafted onto the surface of the seal 3 are glycidyl acrylate and phosphate methacrylate, the peel strength between the seal 3 and the connecting adhesive layer 2 is higher at room temperature, and the attenuation of peel strength under long-term aging in hot oil media is less, which is beneficial for the long-term use of the crankcase oil seal under extreme conditions. Furthermore, as the content of phosphate methacrylate grafted onto the surface of the seal 3 gradually decreases, although the change in peel strength between the seal 3 and the connecting adhesive layer 2 is not significant, the attenuation rate of peel strength under long-term aging in hot oil media is reduced, meaning that higher peel strength can be maintained under long-term hot oil media conditions, resulting in better connection stability.

[0082] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this specific embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A type of rear-curved oil seal, characterized in that: It includes a rigid frame (1) and a sealing functional layer. The rigid frame (1) has a ring-shaped structure. The sealing functional layer includes a connecting adhesive layer (2) and a sealing element (3). The sealing element (3) is fixedly connected to the rigid frame (1) through the connecting adhesive layer (2). The connecting adhesive layer (2) is formed of modified acrylate rubber, and the sealing element (3) is a modified polytetrafluoroethylene sealing element, which is formed by grafting and polymerizing acrylate monomers on the surface of the polytetrafluoroethylene sealing element.

2. The crankcase oil seal according to claim 1, characterized in that: The surface grafting treatment method for the modified polytetrafluoroethylene seal includes the following steps: Prepare polytetrafluoroethylene (PTFE) seals in advance. After cleaning and drying, immerse the seals (3) completely in the modified emulsion containing the acrylate monomers. After taking them out, let them air dry naturally. Then place them in an electron beam irradiation device and irradiate them uniformly in an inert atmosphere. After the irradiation is completed, clean and vacuum dry them to obtain the modified PTFE seals.

3. A crankcase oil seal according to claim 2, characterized in that: Based on the modified emulsion, it comprises 15 wt% acrylate monomers, 0.2 wt% hydroquinone and 0.5 wt% fatty alcohol polyoxyethylene ether, with the balance being deionized water; The acrylate monomer is any two of the following: hydroxyacrylate, glycidyl acrylate, and phosphate methacrylate.

4. A crankcase oil seal according to claim 3, characterized in that: In the modified emulsion, the acrylate monomer is specifically a composition of glycidyl acrylate and phosphate methacrylate, and the mass ratio of glycidyl acrylate to phosphate methacrylate is 1:(0.2-0.5).

5. A crankcase oil seal according to claim 1, characterized in that: The modified acrylic rubber comprises the following raw materials in parts by weight: Acrylic rubber: 85-90 parts; Fluororubber: 10-15 parts; Composite carbon black: 60-75 parts; Modified filler: 20-25 parts; Curing crosslinking agent: 4-5.5 parts; Plasticizer: 4-6 parts; Release agent: 2-3.5 parts; Flow aid: 4-6 parts; Anti-aging agent: 2-3.2 parts; The modified filler is a combination of silica and boron nitride nanoparticles modified with a silane coupling agent, wherein the mass ratio of silica to boron nitride nanoparticles is (3-4):

1.

6. A crankcase oil seal according to claim 5, characterized in that: The composite carbon black is a composition of N330 carbon black and N660 carbon black, and the mass ratio of N330 carbon black to N660 carbon black is 1:(1-1.5).

7. A crankcase oil seal according to claim 5, characterized in that: The curing crosslinking agent is specifically a composition of N,N'-di(cinnamyl-1,6-hexanediamine) and sodium stearate, wherein the mass ratio of the N,N'-di(cinnamyl-1,6-hexanediamine) and the sodium stearate is (3-4.5):

1.

8. A crankcase oil seal according to any one of claims 1-7, characterized in that: The connecting adhesive layer (2) covers the outer periphery of the rigid skeleton (1). The connecting adhesive layer (2) is thickened (21) near the inner side of the ring of the rigid skeleton (1). One end of the sealing member (3) is connected to the thickened part (21). The other end of the sealing member (3) extends toward the inner side of the ring of the rigid skeleton (1) and forms a main sealing lip (31). A secondary sealing lip (22) is provided at the end of the connecting adhesive layer (2) away from the sealing member (3).

9. A crankcase oil seal according to claim 8, characterized in that: The rigid frame (1) includes a support portion (11) and a bending portion (12), the bending portion (12) bends toward the inner side of the ring of the rigid frame (1) and forms a 90° angle with the support portion (11).

10. A method for preparing a post-bend oil seal, used to prepare the post-bend oil seal as described in any one of claims 8-9, characterized in that, Includes the following steps: S1. The rigid skeleton (1) is pre-treated to obtain a pre-requisite skeleton; the modified acrylate rubber is cut into strips according to the dimensions to obtain pre-requisite rubber strips; S2. Cover the surface of the prepared rubber strip with the prepared skeleton, and then place them together in the vulcanization mold. Stack the modified polytetrafluoroethylene seal on top of the prepared rubber strip, close the mold and perform hot-press vulcanization through a secondary vulcanization process. After vulcanization, trim the edges, demold and discharge the material, and coat the surface with anti-rust oil to obtain the curved oil seal.

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