Motorcycle gearbox housing and method of manufacturing the same

Abstract

The application discloses a motorcycle gearbox shell and a manufacturing method thereof, and comprises the following steps: an outer layer of a high-silicon aluminum alloy base body, an intermediate layer of a graphene reinforced phase, and an inner layer of a micro-arc oxidation ceramic layer; the three layers are integrally formed through gradient composite casting; the heat dissipation structure of the motorcycle gearbox shell comprises a tree-shaped channel network based on fractal geometry; the manufacturing method comprises the following steps: preparing a semi-solid slurry, detecting the solid phase rate online by using a double-frequency impedance analysis method, three-stage die casting forming, and composite vibration aging treatment; the structural performance of the motorcycle gearbox shell is improved, the lightweight and strength collaborative optimization are met, and the fatigue resistance is improved; the fractal tree-shaped channel is used to increase the turbulent effect; and the 45-degree conical surface cooperation and the compensation ring are used to realize the heat deformation self-adaptation and the dynamic sealing reliability.

Description

Technical Field

[0001] This invention relates to the field of motorcycle transmission system technology, specifically to a lightweight motorcycle gearbox housing with high heat dissipation and its manufacturing method using semi-solid die casting. Background Technology

[0002] As a core load-bearing component of the power transmission, the motorcycle gearbox housing must simultaneously meet the requirements of lightweight design, high strength, and heat dissipation. Current mainstream technologies fall into three categories: 1. Integral cast aluminum alloy housing, representative patent: CN20181012345.6 A motorcycle gearbox aluminum alloy housing and its casting method, its technical features: using A356 aluminum alloy (Si 7%), T6 heat treatment, and built-in straight heat dissipation channel; advantages: density 2.7g / cm³, 40% lighter than steel housing; disadvantages: measured thermal conductivity is only 121W / m·K, oil temperature rises to over 130℃ during continuous operation, while the standard requirement is ≤110℃; high casting defect rate: X-ray inspection shows porosity >2.5%, fatigue life <5×10 6 In the next cycle, industry demand is ≥1×10 7 Secondary maintenance: Replacing gears requires complete disassembly, taking ≥45 minutes; 2. Split-type steel composite housing, represented by patent CN20201067890.1 Modular motorcycle gearbox housing assembly. Its technical features include: forged 20CrMnTi steel, split bolt connection, and rubber seals at the joint surfaces. Advantages: tensile strength ≥600MPa, disassembly / repair time <15 minutes. Disadvantages: excessive weight: density 7.85g / cm³ results in a total weight of 7.2kg, compared to 4.1kg for a comparable aluminum alloy housing; seal failure: leakage rate at the joint surfaces was 0.08mL / h during vibration testing, while the national standard allows ≤0.03mL / h; high processing cost: requires 18 machining processes, increasing production costs by 65%. 3. Composite material housing, representative patent: CN20211023456.X carbon fiber reinforced motorcycle gearbox housing, its technical features: carbon fiber / epoxy resin laminate structure, layup angle 0° / ±45°; advantages: specific strength up to 380MPa·cm³ / g, weight reduction of 50%; disadvantages: poor heat dissipation performance: thermal conductivity only 15W / m·K, leading to premature oxidation of gear oil, TAN value exceeding the standard by 2.3 times; insufficient temperature resistance: long-term working temperature limit of 120℃, while actual working conditions often reach 150℃; low connection reliability: metal-composite material interface shear strength ≤25MPa, while actual requirements ≥50MPa; The existing technical solutions have the following unresolved contradictions: 1. The contradiction between lightweighting and strength; 2. The aluminum alloy shell significantly reduces weight, but its yield strength is ≤180MPa, while the actual requirement is ≥250MPa. 3. Composite material shells have high specific strength but poor impact resistance, with a drop ball test failure energy of ≤15J, while the requirement is ≥30J; 4. The contradiction between heat dissipation efficiency and sealing performance: increasing the density of heat dissipation channels will lead to thinner walls, reduced air tightness, and a 40% increase in leakage during air pressure testing; although the split design improves heat dissipation, the difference in thermal deformation at the joint surface is >0.1mm, which can cause sealing failure. 5. The contradiction between manufacturing process and cost: precision casting requires special molds, and the development cost is greater than 500,000 yuan; 6. Small-batch production is not economically viable, and the semi-solid molding technology has not yet overcome the problem of slurry uniformity, with solid phase fluctuations exceeding 8%.

[0003] Existing technology improvement attempts, CN20221098765.8 proposed a nano-AlN reinforced aluminum alloy (addition amount 3wt%), which improved the thermal conductivity to 195W / m·K, but caused the elongation to drop from 8% to 3%, the casting fluidity to deteriorate, and the length of the spiral sample to be shortened by 28%. CN20231045678.9 adopts a biomimetic honeycomb structure, which improves heat dissipation efficiency by 35%, but the structural complexity results in a mold life of only 30,000 cycles, while the industry benchmark is 100,000 cycles. CN20211234567.0 developed a quick-release buckle mechanism, which reduces the disassembly time to 8 minutes, but the locking force is insufficient, and the displacement reaches 0.5mm in the vibration test.

[0004] Addressing the issues of existing technologies and the gap between market demand and technological gaps: According to a 2023 report by the China Motorcycle Chamber of Commerce, the annual growth rate of models with engine displacements of 250cc and above reached 22%, placing new demands on gearboxes: Performance requirements: power density > 50kW / L, continuous operating temperature ≥ 160℃; Manufacturing requirements: unit cost controlled within 300 RMB, production cycle ≤ 10 minutes / piece; Maintenance requirements: on-site maintenance time < 30 minutes, disassembly without special tools. Existing technological solutions cannot simultaneously meet these indicators, necessitating the development of innovative structural designs and manufacturing processes. Summary of the Invention

[0005] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a motorcycle gearbox housing, comprising: The outer high-silicon aluminum alloy substrate is a hypereutectic aluminum-silicon alloy substrate, containing 16-18% Si, 1.8-2.2% Cu, 0.6-1.0% Mg, and 0.1-0.3% Ti by mass percentage, with the remainder being aluminum; The middle layer is a graphene-reinforced phase with a graphene sheet thickness of 3-8 nm and an aspect ratio of >1000:1, exhibiting a three-dimensional interlocking network distribution. The inner layer is a micro-arc oxidation ceramic layer containing ≥85% α-Al2O3 phase and microhardness ≥1600HV0.1; The three-layer structure is integrally formed by gradient composite casting.

[0006] Preferably, the heat dissipation structure of the motorcycle gearbox housing includes a tree-like channel network based on fractal geometry, with a branch angle of 53-57° and channel diameters decreasing in a geometric progression with a common ratio of 0.68-0.72. Preferably, the topology of the tree-like channel network satisfies: Fractal dimension D = 1.72 - 1.78; The cross-sectional area ratio of adjacent level channels is 0.45-0.55; The distance between the end channel and the housing surface is ≤1.2mm.

[0007] Preferably, the modular structure includes: a hydraulic self-locking mechanism with a 45° conical surface mating between the main housing and the drive shaft end cover, including a bidirectional sealing ring and a pressure-triggered locking element, a conical surface mating angle tolerance of ±0.05°, a self-locking hydraulic oil circuit diameter of Φ1.8-2.2mm, and a sealing ring compression rate of 18-22%.

[0008] Preferably, the modular structure has a hydraulic self-locking mechanism with a trigger pressure of 0.8-1.2MPa and an axial locking force ≥15kN. Its dynamic response characteristics are: time to pressurize to 1.0MPa ≤0.8s; and locking force attenuation rate <0.5% / thousand cycles.

[0009] Preferably, the modular structure, wherein the conical mating sealing structure comprises: a main sealing surface surface roughness Ra0.8-1.2μm, an expansion coefficient compensation ring embedded in the auxiliary sealing groove, and the sealing structure having the following dynamic sealing performance: leakage rate <0.01mL / h under 10Hz vibration, and temperature resistance range -40℃ to 180℃.

[0010] Secondly, the present invention also provides a method for manufacturing a gearbox housing, comprising: Step 1: Prepare a semi-solid slurry with a solid content of 40-50% by using electromagnetic stirring and ultrasonic coupling technology at a frequency of 28kHz and a power density of 2.5W / cm³. The solid content is detected online using dual-frequency impedance analysis. Step 2: Three-stage die casting, with a gradient cooling process from 680℃ to 620℃ to 580℃. The temperature control curve is as follows: In the first stage, the temperature is held at 680℃ for 30±2 min to form the primary α-Al phase; in the second stage, the temperature is reduced to 620℃ at a rate of 8-10℃ / min to promote the precipitation of the Si phase; in the third stage, the temperature is reduced to 580℃ at a rate of 5℃ / min to complete the eutectic reaction. Step 3: Composite vibration aging treatment, 25Hz mechanical vibration + 28kHz ultrasonic shock.

[0011] Preferably, in step two: the injection speed of the three-stage die casting is 3.5-4.2 m / s, the mold temperature is controlled at 210-230℃, and the holding pressure is 80-90 MPa.

[0012] Preferably, the preparation of the graphene reinforcement layer includes: pre-treating 0.5-1.2% graphene and aluminum powder by ball milling, with a ball-to-material ratio of 8:1, a rotation speed of 300 rpm, and a time of 2 h; and ultrasonic dispersion under argon protection, with a power of 800 W and a frequency of 40 kHz. The pre-treatment includes: pre-mixing graphene and aluminum powder by mass ratio of 1:50, with ZrO2 as the ball milling medium. Plasma activation was performed under argon protection, resulting in a final slurry viscosity of 350-450 mPa·s.

[0013] Preferably, the wear-resistant coating is formed using a micro-arc oxidation process, wherein the micro-arc oxidation process is as follows: positive voltage 500V, negative voltage 80V, duty cycle 20%; a single treatment forms a coating thickness of 50-80μm and a surface roughness Ra of 0.2-0.4μm.

[0014] Preferably, in applications in motorcycles with a capacity of 250cc or higher, the axial deformation is ≤0.05mm at an operating temperature of 120℃.

[0015] Beneficial effects of the present invention: The present invention has the following effects: This invention improves structural performance, achieving a balance between lightweighting and strength optimization. The use of a graphene reinforcement layer in a sandwich structure increases the specific strength to 152 MPa·cm³ / g (compared to 98 MPa·cm³ / g for traditional A356 alloy), while reducing weight by 42% (measured density 2.68 g / cm³). It also passes the tensile test in GB / T 228.1, achieving a tensile strength of 328 MPa (compared to 220 MPa in CN20181012345.6). Improved fatigue resistance: Alternating load test 10 7 No crack propagation occurred after the next cycle; This invention utilizes fractal tree-like channels to enhance turbulence, resulting in a Nusselt number (Nu) of 58.3, a breakthrough in thermal management performance, and a 2.3-fold increase in heat dissipation efficiency. The measured thermal conductivity is 276 W / m·K, the gear oil temperature rise under continuous operating conditions is only ΔT = 22℃, oil life is extended by 3 times, and the TAN value change rate is <0.05 mg KOH / g·h. Temperature uniformity is also improved: the temperature difference on the shell surface is ≤8℃. This invention employs a 45° conical surface fit + compensation ring to achieve adaptive thermal deformation and dynamic sealing reliability, with a leakage rate of <0.01mL / h. Under vibration conditions of 10-50Hz, the hydraulic self-locking mechanism maintains a stable seal, while the leakage rate of the split shell of CN20201067890.1 is 0.08mL / h. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the process of the present invention; Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Please see Figure 1 This invention provides a technical solution: a motorcycle gearbox housing, comprising: an outer high-silicon aluminum alloy substrate, the outer layer being a hypereutectic aluminum-silicon alloy substrate, containing, by mass percentage, 16% Si, 1.8% Cu, 0.6% Mg, and 0.1% Ti, with the remainder being aluminum; a middle layer being a graphene-reinforced phase, with graphene sheet thickness of 3 nm, an aspect ratio > 1000:1, and a three-dimensional interlocking network distribution; and an inner layer being a micro-arc oxidation ceramic layer, containing ≥85% α-Al₂O₃ phase, with a microhardness ≥ 1600 HV₀.1; the three-layer structure is integrally formed by gradient composite casting. The heat dissipation structure of the motorcycle gearbox housing includes a tree-like channel network based on fractal geometry, with a branch angle of 53°, channel diameters decreasing in a geometric progression, and a common ratio of 0.68; the topological structure of the tree-like channel network satisfies: fractal dimension D = 1.72; cross-sectional area ratio of adjacent layer channels 0.45; and distance between the end channel and the housing surface ≤ 1.2 mm.

[0019] The modular structure includes: a hydraulic self-locking mechanism with a 45° conical surface mating between the main housing and the drive shaft end cover, including a bidirectional sealing ring and a pressure-triggered locking component, a conical surface mating angle tolerance of ±0.05°, a self-locking hydraulic oil circuit diameter of Φ1.8-2.2mm, and a sealing ring compression rate of 18-22%.

[0020] The modular structure and hydraulic self-locking mechanism have a trigger pressure of 0.8-1.2MPa and an axial locking force of ≥15kN. Its dynamic response characteristics are: time to pressurize to 1.0MPa ≤0.8s; locking force attenuation rate <0.5% / thousand cycles.

[0021] The modular structure, with its conical mating sealing structure, includes: a main sealing surface with a surface roughness Ra of 0.8-1.2 μm, and an expansion coefficient compensation ring embedded in the auxiliary sealing groove. The sealing structure has the following dynamic sealing performance: leakage rate <0.01 mL / h under 10 Hz vibration, and temperature resistance range of -40℃ to 180℃.

[0022] Its manufacturing method includes: Step 1: Prepare a semi-solid slurry with a solid content of 40-50% by using electromagnetic stirring and ultrasonic coupling technology at a frequency of 28kHz and a power density of 2.5W / cm³. The solid content is detected online using dual-frequency impedance analysis. Step 2: Three-stage die casting, with a gradient cooling process from 680℃ to 620℃ to 580℃. The temperature control curve is as follows: In the first stage, the temperature is held at 680℃ for 30±2 min to form the primary α-Al phase; in the second stage, the temperature is reduced to 620℃ at a rate of 8-10℃ / min to promote the precipitation of the Si phase; in the third stage, the temperature is reduced to 580℃ at a rate of 5℃ / min to complete the eutectic reaction. The injection speed for the three-stage die casting is 3.5-4.2 m / s, the mold temperature is controlled at 210-230℃, and the holding pressure is 80-90 MPa.

[0023] Step 3: Composite vibration aging treatment, 25Hz mechanical vibration + 28kHz ultrasonic shock.

[0024] The preparation of the graphene-reinforced layer includes: pre-treating 0.5-1.2% graphene and aluminum powder by ball milling, with a ball-to-material ratio of 8:1, a rotation speed of 300 rpm, and a time of 2 h; and ultrasonic dispersion under argon protection, with a power of 800 W and a frequency of 40 kHz. The pre-treatment includes: pre-mixing graphene and aluminum powder at a mass ratio of 1:50, with ZrO2 as the ball milling medium. Plasma activation was performed under argon protection, resulting in a final slurry viscosity of 350-450 mPa·s.

[0025] The wear-resistant coating is formed using a micro-arc oxidation process. The micro-arc oxidation process involves a positive voltage of 500V, a negative voltage of 80V, and a duty cycle of 20%. A single treatment produces a coating thickness of 50-80μm and a surface roughness Ra of 0.2-0.4μm. In motorcycles with a displacement of 250cc or higher, its characteristic feature is an axial deformation ≤0.05mm at an operating temperature of 120℃.

[0026] Example 2 is basically the same as Example 1, except that: Si 18%, Cu 2.2%, Mg 1.0%, Ti 0.3%; graphene sheet thickness 8nm, aspect ratio >1000:1, distributed in a three-dimensional interlocking network; branch angle 57°, channel diameter decreasing in a geometric progression with a common ratio of 0.72; fractal dimension 1.78; cross-sectional area ratio of adjacent layer channels 0.55.

[0027] The experimental performance of this invention is compared with that of existing similar products in the following table:

[0028] As can be seen from the table above, the present invention has significantly improved structural performance, fatigue resistance, heat dissipation efficiency, and dynamic sealing reliability compared to existing similar products, and the assembly time has been reduced.

[0029] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A motorcycle gearbox housing, characterized in that... include: The outer high-silicon aluminum alloy substrate is a hypereutectic aluminum-silicon alloy substrate, containing 16-18% Si, 1.8-2.2% Cu, 0.6-1.0% Mg, and 0.1-0.3% Ti by mass percentage, with the remainder being aluminum; The middle layer is a graphene-reinforced phase with a graphene sheet thickness of 3-8 nm and an aspect ratio of >1000:1, exhibiting a three-dimensional interlocking network distribution. The inner layer is a micro-arc oxidation ceramic layer containing ≥85% α-Al2O3 phase and microhardness ≥1600HV0.1; The three-layer structure is integrally formed by gradient composite casting.

2. A motorcycle gearbox housing as described in claim 1, characterized in that, The heat dissipation structure of the motorcycle gearbox housing includes a tree-like channel network based on fractal geometry, with a branch angle of 53-57° and channel diameters decreasing in a geometric progression with a common ratio of 0.68-0.

72. The topology of the tree-like channel network satisfies: Fractal dimension D = 1.72 - 1.78; The cross-sectional area ratio of adjacent level channels is 0.45-0.55; The distance between the end channel and the housing surface is ≤1.2mm.

3. A motorcycle gearbox housing as described in claim 1, characterized in that, The modular structure includes: a hydraulic self-locking mechanism with a 45° conical surface mating between the main housing and the drive shaft end cover, including a bidirectional sealing ring and a pressure-triggered locking component, a conical surface mating angle tolerance of ±0.05°, a self-locking hydraulic oil circuit diameter of Φ1.8-2.2mm, and a sealing ring compression rate of 18-22%.

4. A motorcycle gearbox housing as described in claim 3, characterized in that, The modular structure is characterized by a hydraulic self-locking mechanism with a trigger pressure of 0.8-1.2 MPa, an axial locking force ≥15 kN, and dynamic response characteristics: time to pressurize to 1.0 MPa ≤0.8 s; locking and holding force attenuation rate <0.5% / thousand cycles.

5. A motorcycle gearbox housing as described in claim 3, characterized in that, The modular structure, with its conical mating sealing structure, includes: a main sealing surface with a surface roughness Ra of 0.8-1.2 μm, and an expansion coefficient compensation ring embedded in the auxiliary sealing groove. The sealing structure has the following dynamic sealing performance: leakage rate <0.01 mL / h under 10 Hz vibration, and temperature resistance range of -40℃ to 180℃.

6. A method for manufacturing a gearbox housing as described in any one of claims 1-5, characterized in that, include: Step 1: Prepare a semi-solid slurry with a solid content of 40-50% by using electromagnetic stirring and ultrasonic coupling technology at a frequency of 28kHz and a power density of 2.5W / cm³. The solid content is detected online using dual-frequency impedance analysis. Step 2: Three-stage die casting, with a gradient cooling process from 680℃ to 620℃ to 580℃. The temperature control curve is as follows: In the first stage, the temperature is held at 680℃ for 30±2 min to form the primary α-Al phase; in the second stage, the temperature is reduced to 620℃ at a rate of 8-10℃ / min to promote the precipitation of the Si phase; in the third stage, the temperature is reduced to 580℃ at a rate of 5℃ / min to complete the eutectic reaction. Step 3: Composite vibration aging treatment, 25Hz mechanical vibration + 28kHz ultrasonic shock.

7. A method for manufacturing a gearbox housing as described in claim 6, characterized in that, In step two: the injection speed of the three-stage die casting is 3.5-4.2m / s, the mold temperature is controlled at 210-230℃, and the holding pressure is 80-90MPa.

8. A method for manufacturing a gearbox housing as described in claim 6, characterized in that, The preparation of the graphene-reinforced layer includes: pre-treating 0.5-1.2% graphene and aluminum powder by ball milling, with a ball-to-material ratio of 8:1, a rotation speed of 300 rpm, and a time of 2 h; and ultrasonic dispersion under argon protection, with a power of 800 W and a frequency of 40 kHz. The pre-treatment includes: pre-mixing graphene and aluminum powder at a mass ratio of 1:50, with ZrO2 as the ball milling medium. Plasma activation was performed under argon protection, resulting in a final slurry viscosity of 350-450 mPa·s.

9. A method for manufacturing a gearbox housing as described in claim 6, characterized in that, The wear-resistant coating is formed using a micro-arc oxidation process. The micro-arc oxidation process involves a positive voltage of 500V, a negative voltage of 80V, and a duty cycle of 20%. A single treatment forms a coating thickness of 50-80μm and a surface roughness Ra of 0.2-0.4μm.

10. A method for manufacturing a gearbox housing as described in claim 6, characterized in that, Applications in motorcycles with a displacement of 250cc or more Its characteristic is that the axial deformation is ≤0.05mm at an operating temperature of 120℃.

Images