Double-material split type oil discharge port screw

Abstract

This application discloses a dual-material, split-type drain port screw, comprising: a screw body and a plug structure, wherein the screw body is threadedly connected to the drain port of a caliper; the screw body has a through central channel along the axial direction; the plug structure includes a conical part and a sealing part, wherein the outer conical surface of the conical part is used to fit and seal against the inner conical surface of the drain port of the caliper; the sealing part is located on the side of the conical part away from the drain port of the caliper and is disposed within the central channel on the side near the drain port of the caliper; the screw body is made of a first metal material, and the plug structure is made of a second metal material, wherein the hardness of the first metal material is greater than that of the second metal material, and the ductility of the second metal material is better than that of the first metal material. This application can ensure both the overall torsional strength and structural rigidity of the screw, and can also ensure a tight seal against the inner conical surface of the drain port of the caliper, solving the problems of poor sealing performance and easy leakage under extreme working conditions of traditional one-piece steel screws.

Description

Technical Field

[0001] This application relates to the field of caliper technology, and in particular to a dual-material split-type oil drain screw. Background Technology

[0002] The brake caliper bleed screw is a core component of the automotive braking system, mainly used for bleeding and changing the brake fluid. Its sealing performance and structural reliability directly determine the working stability and driving safety of the braking system. Especially in extreme conditions such as track racing and high-performance modifications, the performance requirements for the bleed screw are extremely high.

[0003] In existing technologies, traditional brake caliper drain plugs generally use a one-piece steel structure. Steel has high hardness and excellent torsional strength, which can meet the high torque tightening requirements of repeated disassembly and assembly of the screw. However, its core defect is very prominent: the hardness of steel is much different from that of aluminum alloy. At the interface between steel and aluminum alloy, the steel part can hardly deform. The seal relies solely on the hard bonding of the machined metal conical surface, which cannot adaptively compensate for machining errors and wear. The sealing performance is insufficient, and during repeated wear, the steel will cause the aluminum alloy to wear, resulting in seal failure.

[0004] In extreme high-temperature and high-pressure environments such as racetracks, the brake fluid temperature rises rapidly and is prone to vaporization. The high-pressure oil vapor will leak from the joints of the steel cone surface, causing internal pressure loss in the brake caliper. The reduced internal pressure will further lower the boiling point of the brake fluid, creating a vicious cycle that ultimately leads to a serious decrease in braking performance or even a fatal safety accident caused by complete brake failure. Summary of the Invention

[0005] This application aims to at least partially solve one of the technical problems in the aforementioned technologies.

[0006] To achieve the above objectives, the first aspect of this application proposes a dual-material split-type drain port screw, comprising: a screw body and a plug structure, wherein the screw body is threadedly connected to the drain port of a caliper; the screw body has a through central channel along the axial direction; the plug structure includes a conical part and a sealing part, wherein the outer conical surface of the conical part is used to fit and seal against the inner conical surface of the drain port of the caliper; the sealing part is located on the side of the conical part away from the drain port of the caliper and is disposed within the central channel on the side near the drain port of the caliper; the screw body is made of a first metal material, and the plug structure is made of a second metal material, wherein the hardness of the first metal material is greater than that of the second metal material, and the ductility of the second metal material is better than that of the first metal material, so as to form a dual-material combination structure in which the screw body bears the tightening torque and the conical part achieves a fitting seal.

[0007] In addition, the dual-material split-type oil drain screw proposed in this application may also have the following additional technical features:

[0008] As a further description of the above technical solution: the coefficient of thermal expansion of the second metal material is between the coefficient of thermal expansion of the first metal material and the coefficient of thermal expansion of the caliper body material.

[0009] As a further description of the above technical solution: the sealing part and the central channel are fixed by interference fit or hot pressing.

[0010] As a further description of the above technical solution: the Rockwell hardness of the screw body is HRC≥20.

[0011] As a further description of the above technical solution: the Brinell hardness HB of the plug structure is 20-100.

[0012] As a further description of the above technical solution: the cone angle of the outer cone surface of the cone-shaped part is consistent with the cone angle of the inner cone surface of the caliper drain port.

[0013] As a further description of the above technical solution: the screw body includes a screw section with external threads in the middle section, and an operating part integrally formed with the screw section is provided at the end of the screw section away from the plug structure; wherein, the external threads are threadedly connected to the internal threads of the caliper drain port.

[0014] As a further description of the above technical solution: the operating part is a polygonal nut structure.

[0015] The dual-material split-type drain plug screw of this application adopts a split design with a screw body and a plug structure. The screw body, made of a first metal material, ensures the overall torsional strength and structural rigidity of the screw, and can withstand high torque tightening and repeated disassembly and assembly operations without problems such as stripping or plastic deformation. The plug structure, made of a second metal material, makes full use of ductility, plasticity, high temperature resistance and chemical stability. The conical part fits and seals with the inner conical surface of the caliper drain port, which fundamentally solves the problem of poor sealing and easy leakage under extreme high temperature and high pressure conditions of traditional one-piece steel screws. It eliminates the safety risks of brake pressure loss, reduced boiling point, performance degradation or even complete failure caused by brake fluid vaporization and leakage.

[0016] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0017] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0018] Figure 1 This is a schematic diagram of the structure of a dual-material split-type oil drain screw according to an embodiment of this application;

[0019] Figure 2 This is a schematic diagram of the split structure of the screw body and the plug structure of a dual-material split drain screw according to an embodiment of this application;

[0020] Figure 3 This is a schematic diagram of the screw body according to an embodiment of this application;

[0021] Figure 4 This is a schematic diagram of a plug structure according to an embodiment of this application;

[0022] Figure 5 This is a schematic diagram of the internal structure of a dual-material split-type oil drain screw according to an embodiment of this application;

[0023] Figure 6 This is a comparative illustration of a dual-material split-type oil drain screw according to an embodiment of this application and an existing screw.

[0024] As shown in the figure:

[0025] 100. Screw body; 101. Central channel; 102. Oil port; 110. Screw part; 111. External thread; 120. Operating part; 200. Plug structure; 210. Conical part; 220. Sealing part. Detailed Implementation

[0026] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0027] The following describes the dual-material split-type oil drain screw according to an embodiment of this application, with reference to the accompanying drawings.

[0028] like Figures 1 to 5 As shown in the embodiment of this application, the dual-material split oil drain screw consists of a screw body 100 and a plug structure 200.

[0029] The screw body 100 is threadedly connected to the caliper drain port, and the screw body 100 has a through central channel 101 along the axial direction.

[0030] The plug structure 200 includes a conical section 210 and a sealing section 220.

[0031] The outer conical surface of the conical part 210 is used to fit and match the inner conical surface of the caliper drain port for sealing; the sealing part 220 is located on the side of the conical part 210 away from the caliper drain port, and is disposed in the center channel 101 on the side near the caliper drain port.

[0032] It should be noted that relevant personnel can classify and design the conical surface 210 of this application according to different models and specifications of caliper drain ports, so that the cone angle of the outer conical surface of the conical surface 210 of the plug structure 200 is consistent with the cone angle of the inner conical surface of the matching caliper drain port, ensuring that after tightening the screw, the outer conical surface of the conical surface 210 can form a full-circumference, gapless fit and seal with the inner conical surface of the caliper drain port.

[0033] The screw body 100 is made of a first metal material, and the plug structure 200 is made of a second metal material. The hardness of the first metal material is greater than that of the second metal material, and the ductility of the second metal material is better than that of the first metal material, so as to form a dual-material combination structure in which the screw body 100 bears the tightening torque and the conical part 210 achieves a close seal.

[0034] It should be noted that the high hardness of the first metal material ensures that the screw body can maintain extremely high structural rigidity when subjected to high frequency of disassembly and assembly and high torque tightening; while the excellent ductility of the second metal material allows the conical surface to undergo microscopic plastic yielding deformation when subjected to compressive preload to adaptively fill the processing gap.

[0035] To ensure the normal use of the screw body 100, the Rockwell hardness of the screw body 100 is HRC≥20. This hardness range ensures that the screw body 100 meets the requirements of structural rigidity while having appropriate impact toughness, avoiding brittle fracture caused by excessive hardness, and fully adapting to the high frequency of disassembly and assembly and high load use requirements under extreme working conditions such as racetracks.

[0036] To ensure the proper use of the plug structure 200, the Brinell hardness HB of the plug structure 200 is 20-100. This hardness range will not cause excessive plastic deformation or crushing failure when tightening due to excessively low hardness, nor will it cause insufficient ductility or inability to self-adapt to the sealing due to excessively high hardness. It perfectly matches the core requirements of the brake caliper cone surface seal.

[0037] Meanwhile, the plug structure 200, through its ductility, allows the conical surface 210 to adaptively compensate for machining errors and slight wear on the inner conical surface of the caliper. It achieves excellent sealing performance without relying on extremely high machining precision, fundamentally solving the problem of inherently insufficient sealing performance of traditional one-piece steel screws with hard-fit sealing.

[0038] Understandably, this application is specially designed for the extreme working conditions of the racetrack environment, completely solving the problem of sealing failure of traditional structures under high temperature and pressure. The core characteristics of extreme racetrack conditions are: when a vehicle brakes continuously and heavily, the working temperature of the brake fluid can reach 180℃-260℃, far exceeding the working temperature of normal road driving. At this temperature, the brake fluid vaporizes in large quantities, forming high-pressure oil-gas with a much stronger permeability than liquid brake fluid. At the same time, the traditional one-piece steel screw has high cone surface hardness and extremely poor ductility. After tightening, it can only form line contact or local discontinuous surface contact with the cone surface inside the caliper. It cannot adapt to the micro-tool marks and small roundness errors of the cone surface produced by machining, leaving a large number of micron-level leakage gaps. However, the brake fluid vapor that vaporizes under racetrack conditions has a molecular diameter much smaller than that of liquid brake fluid, which can easily penetrate these micro-gaps that the steel cone surface cannot seal, causing leakage and pressure relief.

[0039] The plug structure of this application has a hardness controlled between HB20 and 100, which has better ductility than the screw body. Under the pre-tightening force of the standard screw tightening torque, the conical surface of the plug structure will undergo a small amount of plastic deformation, which can completely fill the machining marks, micro-unevenness and small dimensional tolerances of the conical surface inside the caliper, forming a full-circumference continuous surface contact sealing band. From the assembly source, it completely eliminates the micro-leakage channels that can be penetrated by high temperature and high pressure oil and gas, and the sealing redundancy is far greater than that of traditional steel hard bonding structures.

[0040] This application utilizes the principle that after the screw is tightened to the correct position, the full tightening preload of the screw body 100 is transmitted to the conical surface 210 through the rigidly fixed sealing part 220. This causes the conical surface 210 to undergo slight plastic deformation under the preload, adaptively conforming to all the microscopic unevenness of the conical surface inside the caliper, forming a seamless surface contact sealing strip around the entire circumference. This completely eliminates the microscopic gaps caused by the hard contact of traditional steel screws, thus preventing highly permeable high-temperature and high-pressure oil and gas from passing through the gapless surface sealing strip.

[0041] Example 1

[0042] The first metal material can be the steel material commonly used in brake system fasteners in this field, such as 45# carbon structural steel, 40Cr alloy structural steel, etc. Such materials typically have a Rockwell hardness of HRC above 50, possessing excellent torsional strength, structural rigidity and deformation resistance. They can withstand the large torque tightening force during repeated disassembly and assembly of the brake system drain port screw without problems such as stripping, plastic deformation, or breakage. This ensures that the screw body can withstand the tightening torque of repeated disassembly and assembly, possessing sufficient structural strength and deformation resistance, thereby meeting the requirement that the screw body can bear 100% of the tightening torque.

[0043] The second metal material can be copper, such as pure copper (industrial copper), which has a Brinell hardness of about 50.

[0044] The following are the spectral analysis and mechanical property test results of No. 45 carbon structural steel as the first metal material and copper as the second metal material.

[0045] Serial Number Inspection items Technical indicators Actual test result 1 Measured results 2 3 Test Results Current judgment 1 Carbon (C) 0.42%–0.50% 0.48% 0.45% 0.43% qualified 2 Silicon (Si) 0.17%–0.37% 0.21% 0.29% 0.34% qualified 3 Manganese (Mn) 0.50%–0.80% 0.76% 0.72% 0.66% qualified 4 Chromium (Cr) ≤0.25% 0.20% 0.18% 0.21% qualified 5 Nickel (Ni) ≤0.30% 0.27% 0.24% 0.23% qualified 6 Copper (Cu) ≤0.25% 0.20% 0.24% 0.23% qualified 7 Phosphorus (P) ≤0.035% 0.02% 0.02% 0.02% qualified 8 Sulfur (S) ≤0.035% 0.02% 0.02% 0.02% qualified 9 Iron (Fe) margin margin margin margin qualified

[0046] Table 1 shows the spectral analysis results of No. 45 carbon structural steel.

[0047] Serial Number Inspection items Technical indicators Actual test result 1 Measured results 2 3 Test Results Current judgment 1 Tensile strength (Rm) ≥600MPa 680 757 708 qualified 2 Yield strength (Rp0.2) ≥355MPa 407 386 421 qualified 3 Elongation after fracture (A) ≥16% 20% 32% 25% qualified 4 Impact energy (KV2) ≥39J 41 48 52 qualified 5 Rockwell hardness HRC ≥20 58 82 65 qualified

[0048] Table 2 shows the test results of the mechanical properties of No. 45 carbon structural steel.

[0049] As can be seen from Tables 1 and 2, the primary metal material used as the screw body, No. 45 carbon structural steel, has a standard metallographic structure. Its high tensile and yield strength proves that the screw body can withstand the large torque tightening force of repeated disassembly and assembly of the braking system without stripping or breaking.

[0050] Serial Number Inspection items Technical indicators Actual test result 1 Measured results 2 3 Test Results Current judgment 1 Copper + Silver (Cu + Ag) ≥99.00% 99.900% 99.810% 99.500% qualified 2 Phosphorus (P) ≤0.015% 0.010% 0.013% 0.012% qualified 3 Total of other impurities ≤0.10% 0.006% 0.008% 0.007% qualified

[0051] Table 3 shows the spectral analysis results of copper.

[0052] Serial Number Inspection items Technical indicators Actual test result 1 Measured results 2 3 Test Results Current judgment 1 Tensile strength (Rm) 200-250 238 226 234 qualified 2 Yield strength (Rp0.2) ~70 48 50 43 qualified 3 Elongation after fracture (A) ≥45% 58% 62% 70% qualified 4 conductivity ≥98% 98% 99% 98% qualified 5 Brinell hardness HB 20－100 58 68 45 qualified

[0053] Table 4 shows the test results of the mechanical properties of copper.

[0054] As can be seen from Tables 3 and 4, the purity of copper as the second metal material in the plug structure proves that there are no hard impurities inside the plug structure. This is crucial for sealing, because if the material is impure, the hard particles inside will scratch the inner conical surface of the aluminum caliper when subjected to strong pre-tightening force. This proves that the second metal material can safely contact the inner conical surface of the caliper.

[0055] In addition, its low yield strength and high elongation after fracture demonstrate that the surface of the plug structure can undergo slight deformation under standard tightening torque, filling the machining marks and gaps on the inner conical surface of the caliper.

[0056] In this combination, the screw body provides excellent torsional strength and anti-slip properties of the threads; while the plug structure can achieve good plastic deformation on its surface when compressed, thereby filling the gaps. This combination is suitable for braking systems that require extremely high performance, such as racing cars. Moreover, this split structure can significantly reduce contact scratches on the aluminum inner cone surface of the caliper during disassembly, thereby ensuring subsequent sealing performance.

[0057] Example 2

[0058] The first metallic material is titanium alloy (such as TC4 titanium alloy). TC4 titanium alloy has extremely high specific strength (i.e., the ratio of strength to weight) and excellent corrosion resistance. Although its Rockwell hardness HRC is usually above 20 at room temperature, the Rockwell hardness of titanium alloy materials treated with boronizing or diamond-like coating processes can reach HRC 70-75, thus meeting the requirement of the screw body bearing 100% tightening torque.

[0059] The second metallic material can be a pure aluminum alloy (such as 1060 pure aluminum). 1060 pure aluminum is extremely soft and has high ductility. Its Brinell hardness HB is between 20 and 30.

[0060] In this material combination, the properties of titanium alloy enable it to meet the stringent requirements of high-end racing calipers for reducing the weight under the suspension system. In addition, because pure aluminum has excellent ductility and titanium and aluminum are not prone to severe electrochemical corrosion, this material combination can effectively solve the problem of rusting of caliper drain ports caused by long-term exposure to high salt spray environment while withstanding extremely high torque.

[0061] Example 3

[0062] The first metal material uses surface-strengthened stainless steel (such as 17-4PH precipitation-hardening stainless steel or 440C martensitic stainless steel as the base material, whose surface is treated with plasma nitriding or deposited with chromium nitride hard coating). The material itself has excellent structural strength and natural rust resistance, so it can effectively prevent corrosion in harsh environments such as mud. In addition, through plasma nitriding or CrN physical vapor deposition process, a dense, corrosion-resistant, ultra-hard protective layer can be formed on the threaded parts and end faces of the stainless steel, thereby further improving its protective performance. The Rockwell hardness of the surface contact parts can stably reach HRC70 or above.

[0063] The second metallic material is annealed brass, such as H62 brass. H62 brass has excellent machinability and moderate ductility, and its Brinell hardness is 55-65.

[0064] In this composite structure, the ultra-hardened stainless steel surface not only meets the rust prevention requirements in extreme environments but also avoids surface damage caused by repeated disassembly. Meanwhile, the brass with moderate hardness can achieve effective micro-plastic deformation under appropriate tightening force, thereby ensuring a good sealing effect. This composite structure is suitable for braking systems that require frequent wading, long-term exposure to muddy and watery environments, and have extremely high requirements for corrosion resistance and wear resistance, such as the braking systems used in off-road vehicles.

[0065] Example 4

[0066] The first metal material uses high-strength carbon structural steel or alloy structural steel (such as No. 45 steel or 40Cr) as the base material, and its surface is treated with boronizing or deposited with TiN (titanium nitride) superhard coating, which can form an extremely hard compound layer on the surface of the screw body, giving it excellent overall structural rigidity and torsional resistance, thereby ensuring that it will never strip or wear during high-frequency disassembly and assembly.

[0067] The second metal material is a soft pure aluminum alloy (such as 1060 pure aluminum). 1060 pure aluminum is characterized by its extremely soft texture and high plasticity, and its Brinell hardness HB is between 20 and 25.

[0068] In this composite structure, the ultra-hardened steel material supports the loading of extremely high torque, while the pure aluminum material is able to undergo microscopic plastic rheology to achieve a tight seal.

[0069] More importantly, since the second metal material (pure aluminum) and the caliper body material (usually aluminum alloy) to which the caliper drain port belongs are of the same metal family, electrochemical corrosion is extremely difficult to occur when the two are tightly bonded together. This solves the problem of corrosion and seizing inside the drain port when the vehicle is driving on coastal salt spray or winter de-icing agent roads, and ensures that the parts will not slip or wear during frequent disassembly and installation.

[0070] Example 5

[0071] The first metal material uses steel (such as 42CrMo or 35CrMo) as the base material. Its surface is treated with composite salt bath or deposited with DLC coating, which can stably reach HRC70 or above. This allows the screw body to withstand extremely high oil pressure impact in the braking system, exhibiting extreme wear resistance and crush resistance.

[0072] The second metal material is tin bronze (e.g., QSn6.5-0.1). Tin bronze has extremely high wear resistance and impact resistance. Through the control of the annealing process, its Brinell hardness HB reaches between 90 and 100.

[0073] In this composite structure, tin bronze is more robust than copper or pure aluminum. When facing ultra-high pressure brake fluid (such as in some special racing cars), softer pure aluminum or copper is at risk of being "squeezed out" or "torn" outward from the microscopic gaps by the high-pressure oil and gas. However, tin bronze, with a hardness of HB 90-100, can still achieve the required surface plastic micro-filling under the strong extrusion of the steel screw body with high preload. Moreover, due to its high structural strength, it can resist the scouring and extrusion effects of ultra-high pressure fluid after filling, thus making it suitable for ultra-high pressure hydraulic circuit systems with extremely high pressure resistance requirements for the sealing components.

[0074] To verify the sealing effect of the dual-material split-type drain port screw of this application, the screw body 100 and the plug structure 200 were made of the first metal material and the second metal material in Example 1, respectively, and a color coating method was used for bonding verification, such as... Figure 6 As shown, the left side is the dual-material split drain port screw of this application, and the right side is a conventional one-piece hard steel screw. After the conical surfaces of the two screws are evenly coated with color, they are assembled to the drain port of the caliper with the same torque. After disassembly, the state of paint peeling is observed.

[0075] pass Figure 6 As can be seen on the right, conventional one-piece carbide screws, due to their high material hardness, can hardly deform when they come into contact with the inner conical surface of the caliper. This results in interference only on a narrow circumference, thus only scraping away a narrow annular contact band (i.e., Figure 6 The narrow ring marked by the black line on the right is not only low in sealing redundancy, but is also very prone to local leakage due to high-pressure oil and gas impact.

[0076] like Figure 6 As can be seen on the left, the dual-material split drain plug screw of this application, due to the use of a second metal material with softer hardness and better ductility in the plug structure, undergoes slight deformation of its soft conical surface, adaptively filling and conforming to the shape of the inner conical surface of the caliper. Therefore, the annular contact zone formed in the middle section of its conical surface (i.e., Figure 6 The width of the wide ring marked by the black line on the left is significantly larger than that of the conventional one-piece hard steel screw on the right. Therefore, the dual-material split drain screw of this application has better sealing performance than the conventional one-piece hard steel screw. It can effectively prevent oil and gas leakage when facing extreme high temperature and high pressure conditions, thereby eliminating the safety risks of brake pressure loss, boiling point reduction, performance degradation or even complete failure caused by brake fluid vaporization and leakage.

[0077] In one embodiment of this application, the coefficient of thermal expansion of the second metal material is between that of the first metal material and the coefficient of thermal expansion of the caliper body material.

[0078] It should be noted that in the high-temperature environment of continuous heavy braking on the track, the difference in thermal expansion of materials is an important reason for the failure of traditional structural seals. The thermal expansion coefficient of traditional steel screws is much lower than that of aluminum alloy calipers. After the temperature rises, the inner cone hole diameter of the aluminum caliper expands and becomes larger, while the steel cone cannot compensate synchronously, resulting in an increase in the sealing gap, a sudden drop in sealing pressure, and easy leakage of oil and gas.

[0079] This application utilizes a dual-material design, which allows the thermal expansion of the conical surface 210 to compensate for the expansion of the inner conical surface of the caliper under high-temperature conditions. At the same time, the low thermal expansion characteristics of the screw body 100 ensure that the tightening preload will not decrease significantly due to thermal expansion, maintaining a stable sealing pressure throughout the process. This ensures that the sealing surface remains tightly fitted under high-temperature conditions and will not leak due to thermal expansion and contraction.

[0080] Specifically, taking Example 1 as an example, the coefficients of linear expansion of the core components of the braking system differ. The coefficient of linear expansion of high-performance aluminum alloy calipers (such as commonly used 6061 aluminum alloy / 7075 aluminum alloy) is approximately 23.6 × 10⁻ 6 / ℃, while the coefficient of linear expansion of a copper plug structure 200 (such as commonly used red copper / oxygen-free copper) is approximately 17.5×10⁻ 6 At / ℃, the coefficient of linear expansion of steel screw bodies (such as commonly used 45 steel / 40Cr) is approximately 11.5×10⁻ 6 / ℃, which shows that the coefficient of linear expansion of copper is exactly between that of steel screws and aluminum alloy calipers, thus forming an ideal high-temperature compensation effect.

[0081] Taking the extreme operating temperature of 250℃ on the racetrack as an example, when the nominal diameter of the cone surface is 10mm at room temperature, the radial expansion of the inner cone surface of the aluminum alloy caliper after the temperature rises by 225℃ is approximately 10×23.6×10⁻ 6 ×225≈0.0531mm; The radial expansion of the steel screw is approximately: 10×11.5×10⁻ 6 ×225≈0.0259mm; there is an expansion difference of about 0.027mm between the two, that is, at a high temperature of 250℃, the traditional steel conical surface will have a significant contact gap with the inner conical surface of the aluminum caliper, the sealing pressure drops sharply, and high temperature and high pressure oil and gas can directly leak from the gap.

[0082] The radial expansion of the copper conical surface 210 in this application, under the same working conditions, is approximately 10 × 17.5 × 10⁻ 6 ×225≈0.0394mm. This expansion amount can completely fill the expansion difference between the steel screw and the aluminum caliper (i.e., 0.027mm), and there is even a fitting allowance. This ensures that the fitting and clamping force of the sealing cone surface will not decrease due to thermal expansion at high temperatures. On the contrary, it will further increase with the rise in temperature, thereby solving the pain point of the traditional steel screw having a larger fitting gap and sealing failure at high temperatures.

[0083] The dramatic temperature rise under track conditions not only causes the size of the parts to expand, but also causes slight shape and position deviations and local out-of-roundness of the inner conical surface of the aluminum caliper due to thermal stress. At the same time, the temperature rise further enhances the plasticity and ductility of the copper material. The copper conical surface 210 can adapt to the slight deformation of the inner conical surface of the aluminum caliper caused by thermal stress while it is thermally expanding, forming a dynamic thermal compensation seal. In contrast, the traditional steel conical surface maintains high rigidity at high temperatures and cannot adapt to the thermal deformation of the aluminum conical surface. It will only further amplify the fitting gap due to the difference in thermal expansion.

[0084] In addition, in track use scenarios, calipers will repeatedly undergo severe hot and cold cycles between room temperature and room temperature. The thermal expansion coefficients of traditional steel conical surfaces and aluminum calipers are very different. During hot and cold cycles, huge contact thermal stress will be generated on the contact surface, which will directly crush the low hardness inner conical surface of the aluminum caliper, resulting in irreversible plastic deformation. After cooling, a permanent sealing gap will be formed, and even if new screws are replaced, the sealing performance cannot be restored.

[0085] The copper conical surface 210 of this application, with its coefficient of thermal expansion between steel and aluminum, can effectively mitigate the thermal stress difference between the steel screw and the aluminum caliper during thermal cycling, avoiding crushing damage to the inner conical surface of the aluminum due to hard contact, and protecting the reference sealing surface of the caliper's drain port. At the same time, the plastic deformation capacity of copper can adapt to dimensional changes during thermal cycling, and after cooling, it will not produce permanent fitting gaps due to differences in shrinkage. Even after multiple thermal cycles under track conditions, it can still maintain stable sealing performance, fully meeting the high-frequency and high-intensity usage requirements of the track.

[0086] Similarly, in other embodiments of this application, the above-mentioned dynamic thermal compensation mechanism is also applicable and effective. For example, in Embodiment 2 (titanium alloy and pure aluminum) and Embodiment 4 (steel and pure aluminum), the coefficient of thermal expansion of the first metal material is much lower than that of the aluminum alloy caliper, while the pure aluminum, as the second metal material, has a basically consistent coefficient of thermal expansion with the aluminum caliper, which can achieve near-synchronous thermal expansion following. In Embodiment 3 (stainless steel and brass) and Embodiment 5 (steel and tin bronze), the high expansion characteristics of the second metal material can also effectively fill the relative shrinkage gap of the first metal at high temperature. Through the above-mentioned different material combinations, this application can establish a reliable dynamic thermal compensation sealing structure under various working conditions and material combinations.

[0087] In one embodiment of this application, the sealing part 220 and the central channel 101 are coaxially fixed by interference fit or hot pressing.

[0088] Understandably, this fixing method can precisely ensure the coaxiality and rigid connection strength of the plug structure 200 and the screw body 100. After assembly, there is no relative axial displacement or radial runout. It can withstand the high pressure impact under extreme working conditions, and the process is mature and controllable, making it suitable for large-scale mass production needs.

[0089] It should be noted that under track conditions, the high-pressure oil and gas inside the caliper will continuously impact the cone-shaped surface 210. The plug structure 200 is prone to radial wobble and circumferential misalignment, resulting in uneven stress distribution on the sealing cone surface and insufficient local sealing pressure. The highly permeable, high-temperature, and high-pressure oil and gas can easily leak from the weak points in the seal, leading to a vicious cycle of brake pressure loss, a decrease in the boiling point of the brake fluid, and a decline in braking performance.

[0090] In this embodiment, the plug 220 is fixed in the central channel 101, so that the plug structure 200 and the screw body are absolutely coaxial throughout the entire process and there is no relative axial / radial displacement. The entire tightening preload of the screw is evenly transmitted to the entire sealing cone surface. No swaying or misalignment will occur under high pressure impact. Even when the track is continuously braked heavily, it can still be sealed stably without gaps, completely eliminating the safety risk of oil and gas leakage.

[0091] Therefore, the fixed connection between the plug structure 200 and the screw body 100 in this embodiment of the application, for the ultra-high pressure conditions during heavy braking on the track, can make the tightening preload of the screw body 100 offset the opening force generated by the high pressure oil and gas, and will not cause the cone part 210 to be lifted up and the seal to fail. In addition, during operation, the cone part 210 and the screw body 100 move synchronously along the axial direction, and will not cause offset wear to the inner cone surface of the aluminum caliper seal.

[0092] In one embodiment of this application, the screw body 100 includes a screw portion 110 with external threads 111 in the middle section, and an operating portion 120 integrally formed with the screw portion 110 is provided at one end of the screw portion 110 away from the plug structure 200.

[0093] The external thread 111 is threaded to the internal thread of the caliper drain port. The high hardness and structural rigidity of the steel screw body 100 allow the external thread 111 to withstand the large torque of repeated disassembly and assembly, making it less prone to stripping or deformation and reducing wear on the caliper threads during disassembly and assembly.

[0094] As one possible scenario, the operating part 120 is a polygonal nut structure. The operating part 120 is preferably a polygonal nut structure, which is a universal standardized design for brake system fasteners. It can be adapted to conventional tools such as sleeves and open-end wrenches, and can be quickly disassembled and assembled without special accessories, meeting the needs of high-frequency track maintenance.

[0095] In one embodiment of this application, the screw body 100 has an oil passage 102 connected to the central channel 101 along the outer wall of the end near the plug structure 200, and the plug 220 does not block the oil passage 102, so as to ensure that when performing oil and gas discharge operations, the oil and gas can be discharged normally from the oil discharge port to the central channel 101 without being blocked by the plug 220, and will not affect the discharge of oil and gas.

[0096] Specifically, when installing the dual-material split drain plug screw of this application embodiment, the pre-assembled drain plug screw is aligned with the drain plug screw hole of the brake caliper, and slowly screwed into the screw body 100. The screw is tightened to the correct position according to the standard tightening torque of the brake system fastener. At this time, under the action of the tightening force, the conical surface 210 self-adaptively compresses and fits the inner conical surface of the caliper through its own extensibility, forming a stable and leak-free surface sealing structure, thus completing the installation and fixing.

[0097] After the screws are tightened, the braking system enters normal working condition. When the brake pedal is pressed during vehicle operation, the master cylinder pushes brake fluid into the caliper, builds braking pressure in the caliper, and pushes the piston to clamp the brake disc to achieve braking.

[0098] Under extreme conditions on the track, continuous heavy braking causes high-temperature and high-pressure oil and gas to be generated inside the caliper. At this time, the cone surface 210 maintains a tight seal throughout the entire process, blocking the leakage channels of high-temperature and high-pressure oil and gas, and preventing oil and gas leakage and brake pressure relief.

[0099] When the brake system needs to be changed or bled, it is not necessary to completely remove the screws. Simply loosen the drain plug by 1 / 2 to 1 turn according to the standard brake system maintenance procedure. At this time, the screw body 100 drives the plug structure 200 to move outward, and a connecting gap is formed between the inner conical surface of the caliper drain port and the outer conical surface of the conical part 210. The oil flows through the connecting gap, through the oil port 102, to the central channel 101, and is discharged from the end of the screw body 100, completing the oil draining and bleed operation.

[0100] In one embodiment of this application, two oil passages 102 are provided, and the two oil passages 102 are symmetrically distributed along the screw body 100.

[0101] It should be noted that, compared to the single oil inlet 102 design, the two oil inlets 102 are symmetrically arranged around the screw body 100, forming a double-sided symmetrical flow inlet at the end of the screw body 100 near the plug structure 200. On the one hand, this can significantly increase the overall flow area, allowing the oil and air inside the caliper and the brake fluid to enter the central channel 101 from both sides simultaneously, effectively accelerating the speed of oil and air venting. This is suitable for the high-frequency and high-efficiency maintenance needs of pre-race venting and post-race oil changes in track scenarios, avoiding problems such as slow oil venting and untimely air bubble removal caused by insufficient flow area of ​​a single hole.

[0102] On the other hand, the symmetrically distributed structure can ensure the uniformity of the force when the oil and gas enter the central channel 101, and will not cause the oil and gas flow direction to deflect due to the impact force generated by the unilateral inflow. This avoids the accumulation of air and eddies in the central channel 101, and ensures that the air bubbles can be smoothly discharged with the oil, completely eliminating problems such as soft foot feel and reduced braking performance caused by residual air bubbles in the braking system.

[0103] Meanwhile, the symmetrical opening method allows the wall thickness of the screw body 100 to be evenly stressed, avoiding local stress concentration caused by single-hole opening, ensuring the structural rigidity of the screw body 100 under high pressure conditions, preventing failure problems such as cracks and deformation at the opening, and adapting to the high-load use requirements of extreme track conditions.

[0104] Furthermore, the cross-sectional diameter of the oil outlet 102 is one-third to two-thirds of the cross-sectional diameter of the central channel 101.

[0105] It should be noted that if the cross-sectional diameter of the oil passage 102 is less than one-third of the cross-sectional diameter of the central channel 101, a significant throttling effect will occur. When the oil and air in the caliper and the brake fluid pass through the oil passage 102, the flow rate will drop sharply and the flow area will be insufficient. Not only will the oil and air discharge speed be greatly reduced, but air bubbles will also easily form and stagnate at the junction of the oil passage 102 and the central channel 101. This will prevent the air in the braking system from being completely discharged, resulting in a soft braking feel and reduced efficiency under track conditions, which violates the original design intention of this application for efficient oil discharge.

[0106] If the diameter of the oil outlet 102 is greater than two-thirds of the diameter of the central channel 101, although it can improve the flow efficiency, it will excessively weaken the structural rigidity of the screw body 100 and the screw rod 110. Due to the large diameter opening, the screw rod 110 will experience significant strength reduction. Under repeated high-torque tightening during disassembly and assembly and the continuous impact of high-pressure pulses on the racetrack, it is very easy to cause problems such as thread stripping and screw breakage, which cannot guarantee the load-bearing performance and safety of the screw body 100.

[0107] Preferably, the cross-sectional diameter of the two oil passages 102 is half the cross-sectional diameter of the central channel 101.

[0108] It should be noted that the half-diameter ratio allows the flow capacity of the oil passage 102 to be precisely matched with the flow capacity of the central channel 101. After the oil and brake fluid enter the central channel 101 through the oil passage 102, there is no throttling or turbulence, maintaining a smooth flow state. The oil and air venting efficiency is optimized, and high-frequency operations such as pre-race venting and post-race oil change can be quickly completed.

[0109] In one embodiment of this application, the oil passage 102 is a vertical through hole, and the oil passage 102 is perpendicular to the central channel 101.

[0110] It should be noted that the oil passage 102 is a vertical through hole, which has a mature processing technology and excellent mass production and precision controllability. The vertical through hole is a structure that can be achieved by conventional drilling process. There is no need to adjust the processing angle. It can be processed synchronously with the central channel 101 in the machining process of the screw part 110. The processing efficiency is high and the process is simple, which greatly reduces the processing cost of mass production. At the same time, the dimensional accuracy and positional accuracy of vertical drilling are easy to control, which can accurately ensure the connectivity between the oil passage 102 and the central channel 101, avoiding problems such as drilling offset and insufficient flow area. The mass production yield is higher and it is suitable for large-scale promotion and application.

[0111] Furthermore, the vertical through-hole structure is non-directional, adapting to the installation requirements of multiple caliper models. The vertical through-hole runs radially through the screw body 100, without any bias in the oil inlet direction. Regardless of the installation angle of the screw body 100 at the caliper drain port, the oil and brake fluid in the caliper can enter the oil port 102 from any radial direction. Flow can be achieved without precise angle alignment of the screw. It is compatible with the drain port layout of different brands and models of high-performance multi-piston calipers, with extremely strong versatility, while also reducing the difficulty of on-site installation and maintenance.

[0112] In addition, the vertical through-hole structure has no bends or dead angles in the flow channel, making cleaning and maintenance convenient. The vertical through-hole and the central channel 101 form a 90° direct connection flow channel structure. There are no dead angles or steps on the inner wall of the flow channel. When maintaining the braking system, if brake fluid impurities or metal debris block the oil port 102, they can be directly cleared from the outer wall of the central channel 101 or the screw part 110 using conventional tools such as steel wire or high-pressure air gun. The cleaning and maintenance operation is simple and can quickly restore the flow performance, which is suitable for the needs of rapid maintenance in the track scene.

[0113] In summary, the dual-material split-type drain plug screw according to the embodiments of this application adopts a split design of screw body 100 and plug structure 200. The screw body of the first metal material ensures the overall torsional strength and structural rigidity of the screw, and can withstand high torque tightening and repeated disassembly and assembly operations without problems such as stripping or plastic deformation. The plug structure of the second metal material makes full use of ductility, plasticity, high temperature resistance and chemical stability. Through the conical part and the inner conical surface of the caliper drain port, it seals the screw, fundamentally solving the problem of poor sealing and easy leakage under extreme high temperature and high pressure conditions of traditional one-piece steel screws. It eliminates the safety risks of brake pressure loss, boiling point reduction, performance degradation or even complete failure caused by brake fluid vaporization and leakage.

[0114] In the description of this specification, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0115] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0116] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A dual-material, split-type oil drain port screw, characterized in that, include: The screw body (100) and the plug structure (200), wherein, The screw body (100) is threadedly connected to the caliper drain port; The screw body (100) has a through central channel (101) along the axial direction. The plug structure (200) includes a conical section (210) and a sealing section (220), wherein, The outer conical surface of the conical part (210) is used to fit and seal with the inner conical surface of the caliper drain port; The sealing part (220) is located on the side of the conical part (210) away from the caliper drain port, and is disposed in the central channel (101) on the side near the caliper drain port; The screw body (100) is made of a first metal material, and the plug structure (200) is made of a second metal material. The first metal material has a higher hardness than the second metal material, and the second metal material has better ductility than the first metal material, so as to form a dual-material combination structure in which the screw body (100) bears the tightening torque and the conical part (210) achieves a close seal.

2. The dual-material split-type oil drain screw according to claim 1, characterized in that, The coefficient of thermal expansion of the second metal material is between that of the first metal material and the coefficient of thermal expansion of the caliper body material.

3. The dual-material split-type oil drain screw according to claim 1, characterized in that, The sealing part (220) and the central channel (101) are fixed by interference fit or hot pressing.

4. The dual-material split-type oil drain screw according to claim 1, characterized in that, The Rockwell hardness (HRC) of the screw body (100) is ≥20.

5. The dual-material split-type oil drain screw according to claim 1, characterized in that, The Brinell hardness HB of the plug structure (200) is 20-100.

6. The dual-material split-type oil drain port screw according to claim 1, characterized in that, The cone angle of the outer cone surface of the cone-shaped part is consistent with the cone angle of the inner cone surface of the caliper drain port.

7. The dual-material split-type oil drain screw according to claim 1, characterized in that, The screw body (100) includes a screw portion (110) with external threads (111) in the middle section, and an operating part (120) integrally formed with the screw portion (110) is provided at one end of the screw portion (110) away from the plug structure (200). The external thread is threadedly connected to the internal thread of the caliper drain port.

8. A dual-material split-type oil drain screw according to claim 7, characterized in that, The operating part (120) is a polygonal nut structure.

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