Machining method for wear-resistant gear in new energy electric bicycle hub

Abstract

The invention discloses a method for machining a wear-resistant gear in a hub of a new energy electric bicycle, which comprises the following steps of: forging and pre-treating a gear blank, roughly machining and pre-forming the gear, strengthening and toughening a gear base body, precisely machining a gear tooth profile, precisely finishing and stabilizing, cleaning and detecting. Composite surface wear-resistant strengthening treatment is adopted between the gear tooth profile precision machining and the precision finishing and stabilizing treatment; the composite surface wear-resistant strengthening treatment comprises the following specific steps: 1) deep carburizing treatment; 2) carrying out laser cladding on a wear-resistant alloy layer; and 3) low-temperature ion implantation. In this way, according to the machining method for the wear-resistant gear in the new energy electric bicycle hub, the carburized layer, the wear-resistant alloy layer and the surface modification layer are adopted for the gear manufactured through the method to form a composite wear-resistant structure, the wear resistance, pitting corrosion resistance and fatigue resistance of the gear can be improved, and therefore the durability of a hub transmission system is improved.

Description

Technical Field

[0001] This invention belongs to the field of electric bicycle transmission component manufacturing technology, specifically relating to a method for processing wear-resistant gears in the hub of a new energy electric bicycle. Background Technology

[0002] With the increasing popularity of new energy electric bicycles, the performance and reliability of their core drive component, the hub motor, are receiving more and more attention.

[0003] Hub motors typically contain a set of planetary gears or reduction gears, which convert the motor's high speed and low torque into the low speed and high torque required by the wheel. These gears are subjected to frequent starts and stops, high load impacts, and continuous cyclic stresses in a confined space. Their durability directly determines the overall service life of the hub motor and the user experience.

[0004] Currently, most electric bicycle hub gears on the market are made of engineering plastics (such as nylon with glass fiber) or conventional alloy steel (such as 20CrMnTi). While engineering plastic gears have the advantages of being lightweight and low-noise, their wear resistance, creep resistance, and load-bearing capacity are limited. Under long-term high load or high temperature environments, they are prone to wear, deformation, and even tooth breakage, making it difficult to meet the needs of high-performance, long-range electric bicycles. On the other hand, conventional alloy steel gears, although having higher strength, rely heavily on traditional heat treatment processes (such as integral quenching) or simple surface carburizing to improve their surface hardness and wear resistance. These methods have the following drawbacks: 1. Overall quenching may result in the gear core being too hard and lacking toughness, making it prone to brittle fracture under impact loads; 2. The conventional carburized layer depth and hardness gradient are not precisely controlled, the surface wear-resistant layer is thin, and the bonding force with the substrate is limited, making it prone to fatigue spalling under long-term cyclic stress. 3. Insufficient machining precision of gear teeth leads to uneven stress distribution during meshing, which exacerbates local pitting and wear. Summary of the Invention

[0005] The main technical problem solved by this invention is to provide a processing method for wear-resistant gears in hubs of new energy electric bicycles, which can improve the wear resistance, pitting resistance and fatigue resistance of the gears, thereby improving the durability of the hub transmission system.

[0006] To solve the above-mentioned technical problems, one technical solution adopted by the present invention is: to provide a processing method for wear-resistant gears in hubs of new energy electric bicycles, including: forging and pretreatment of gear blanks, rough machining and initial forming of gears, strengthening and toughening heat treatment of gear matrix, precision machining of gear teeth, precision finishing and stabilization treatment, and cleaning and inspection, wherein a composite surface wear-resistant strengthening treatment is adopted between the precision machining of gear teeth and the precision finishing and stabilization treatment; The specific steps of the composite surface wear-resistant strengthening treatment include: 1) Deep carburizing treatment: The gear with the precision-machined gear tooth profile is placed in a controlled atmosphere carburizing furnace for deep gas carburizing to form a carburized layer; 2) Laser cladding wear-resistant alloy layer: Using a coaxial powder feeding laser cladding equipment, composite powder is selected to selectively laser clad the working area of ​​the gear tooth surface and the transition area of ​​the tooth root fillet after the deep carburizing treatment in step 1) to form a wear-resistant alloy layer. 3) Low-temperature ion implantation: The gear that has undergone laser cladding in step 2) is placed in an ion implantation device, and nitrogen ions and titanium ions are implanted to form a surface modification layer on the surface of the wear-resistant alloy layer and the carburized layer that is not covered by the wear-resistant alloy layer.

[0007] In a preferred embodiment of the present invention, in step 1), the carburizing temperature is controlled at 920~950℃, the carburizing time is controlled at 4~10 hours, and the carbon potential is controlled at 1.0%~1.2%.

[0008] In a preferred embodiment of the present invention, in step 2), the laser power is controlled to be 1000~2000W, the scanning speed is 400~800mm / min, and the spot diameter is 1~2mm.

[0009] In a preferred embodiment of the present invention, in step 2), the composite powder is a mixture of Ni60A alloy powder and 30% to 40% by mass of tungsten carbide powder.

[0010] In a preferred embodiment of the present invention, in step 3), the implanted ion energy is 50~100keV and the implantation dose is 1×10¹. 7 ~5×10¹ 7 ions / cm².

[0011] In a preferred embodiment of the present invention, the base of the gear is a chromium-molybdenum alloy steel with a tempered sorbitic structure, and the teeth adopt a composite wear-resistant structure, wherein the composite wear-resistant structure consists of, from the inside to the outside, the carburized layer, the wear-resistant alloy layer and the surface modification layer.

[0012] The beneficial effects of this invention are: This invention provides a processing method for wear-resistant gears in hubs of new energy electric bicycles. The gears manufactured by this method adopt a composite wear-resistant structure composed of a carburized layer, a wear-resistant alloy layer, and a surface modification layer, which can improve the wear resistance, pitting resistance, and fatigue resistance of the gears, thereby improving the durability of the hub transmission system. Detailed Implementation

[0013] The preferred embodiments of the present invention will now be described in detail so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0014] A method for processing wear-resistant gears in hubs of new energy electric bicycles includes: forging and pretreatment of gear blanks, rough machining and initial forming of gears, heat treatment to strengthen and toughen the gear matrix, precision machining of gear teeth, precision finishing and stabilization treatment, and cleaning and inspection. The precision machining of gear teeth and the precision finishing and stabilization treatment adopt a composite surface wear-resistant strengthening treatment. The gears manufactured by this method adopt a composite wear-resistant structure composed of a carburized layer, a wear-resistant alloy layer and a surface modification layer, which can improve the wear resistance, pitting resistance and fatigue resistance of the gears, thereby improving the durability of the hub transmission system.

[0015] The specific steps of the composite surface wear-resistant strengthening treatment include: 1) Deep carburizing treatment: The gear with the precision-machined gear tooth profile is placed in a controlled atmosphere carburizing furnace for deep gas carburizing. The carburizing temperature is controlled at 920~950℃, the carburizing time is 4~10 hours, and the carbon potential is controlled at 1.0%~1.2% to form a carburized layer. The thickness of the carburized layer is controlled at 0.6~1.0mm to ensure precise control of the carbon potential and to form a high carbon concentration gradient in the tooth surface and tooth root area.

[0016] 2) Laser cladding of wear-resistant alloy layer: Using a coaxial powder feeding laser cladding equipment, a mixture of Ni60A alloy powder and 30%~40% by mass of tungsten carbide powder is selected for selective laser cladding on the working area of ​​the gear tooth surface and the transition area of ​​the tooth root fillet after the deep carburizing treatment in step 1). The laser power is controlled at 1000~2000W, the scanning speed is 400~800mm / min, and the spot diameter is 1~2mm to form a wear-resistant alloy layer. The thickness of the wear-resistant alloy layer is 0.2~0.4mm, the microstructure of the wear-resistant alloy layer is uniform, and the hardness is ≥62HRC.

[0017] 3) Low-temperature ion implantation: The gear, after laser cladding in step 2), is placed in an ion implantation device, and nitrogen and titanium ions are implanted. The implantation ion energy is 50~100keV, and the implantation dose is 1×10¹. 7 ~5×10¹ 7 An ions / cm² surface modification layer is formed on the surface of the wear-resistant alloy layer and the carburized layer not covered by the wear-resistant alloy layer, further reducing the surface friction coefficient and improving the anti-adhesive wear capability.

[0018] The base of the gear is a chromium-molybdenum alloy steel with a tempered sorbitic structure, and the teeth adopt a composite wear-resistant structure, which consists of a carburized layer, a wear-resistant alloy layer and a surface modification layer from the inside to the outside.

[0019] The gear blank forging and pretreatment uses chromium-molybdenum alloy steel as raw material. The gear blank is formed by precision die forging process to obtain dense metal flow lines. Then, normalizing treatment is carried out to refine the grains and uniform the structure. The types of chromium-molybdenum alloy steel include 42CrMo and 30CrMnTi.

[0020] The rough machining and initial forming of the gear are carried out by turning and drilling the blank on a CNC machine tool to machine the basic shape and inner hole of the gear, and leave a finishing allowance.

[0021] The gear matrix strengthening heat treatment involves quenching and tempering the rough-machined gear, i.e., quenching followed by high-temperature tempering, to obtain a tempered sorbite structure, thereby possessing excellent comprehensive mechanical properties, i.e., high strength while maintaining sufficient toughness. The hardness of the gear body after the quenching and tempering treatment is 28~35HRC.

[0022] The gear teeth are precision machined using a high-precision CNC gear hobbing machine to ensure that the tooth profile accuracy reaches the national standard level 6 or above, and the tooth surface roughness Ra≤0.8μm.

[0023] The precision finishing and stabilization treatment involves low-temperature aging of the gear after the composite surface wear-resistant strengthening treatment to eliminate stress. Subsequently, the tooth surface is finished by precision grinding or polishing to further reduce surface roughness. The low-temperature aging treatment is carried out at a temperature of 150~200℃ for 2~6 hours. The final roughness of the tooth surface after finishing is Ra≤0.2μm, ensuring that the tooth profile accuracy is not lost.

[0024] The cleaning and testing process involves ultrasonic cleaning of the finished gears to remove oil and impurities, followed by non-destructive testing of tooth profile accuracy, surface hardness, thickness of carburized and wear-resistant alloy layers, and bonding strength.

[0025] Example 1 1) 42CrMo round steel is selected, and the planetary gear blank is precision forged and normalized.

[0026] 2) The gear is machined on a CNC lathe, with the outer diameter, end face and inner hole machined, leaving a 0.5mm finishing allowance.

[0027] 3) The gears after rough machining are subjected to quenching and tempering treatment, oil quenching at 850℃ and tempering at 580℃, with a hardness of 28~32HRC.

[0028] 4) The gear is machined using a high-precision CNC gear hobbing machine. The gear has 11 teeth, a module of 1.5, a precision of grade 6, and a tooth surface Ra=0.6μm.

[0029] 51) The gear is placed in a controlled atmosphere carburizing furnace for deep gas carburizing, the carburizing temperature is controlled at 930°C, the carburizing time is 8 hours, the carbon potential is controlled at 1.1%, and a carburized layer with a thickness of 0.8 mm is formed.

[0030] 52) Using a coaxial powder feeding laser cladding equipment, a mixture of Ni60A alloy powder and 35% by mass of tungsten carbide powder is selected to selectively laser cladize the working area of ​​the gear tooth surface and the transition area of ​​the tooth root fillet. The laser power is controlled at 1500W, the scanning speed at 600mm / min, and the spot diameter at 1mm to form a wear-resistant alloy layer with a thickness of 0.3mm and a hardness of 63HRC.

[0031] 53) The gear is placed in an ion implantation device, and nitrogen ions and titanium ions are implanted. The implantation ion energy is 80 keV, and the implantation dose is 3 × 10¹. 7 ions / cm², forming a surface modification layer on the surface of the wear-resistant alloy layer and the carburized layer not covered by the wear-resistant alloy layer.

[0032] 6) The gear is subjected to low-temperature aging treatment at a temperature of 180°C for 4 hours, and the final surface roughness of the finished gear is Ra μm.

[0033] 7) The finished gears are ultrasonically cleaned to remove oil and impurities. Finally, non-destructive testing is performed, including tooth profile accuracy, surface hardness, thickness and bonding strength of the carburized layer and wear-resistant alloy layer. After the gears have been running continuously for 2000 hours under rated load, the wear on the tooth surface is only 25% of that of traditional 20CrMnTi quenched gears. No pitting or peeling has occurred. The expected service life is more than 4 times that of traditional gears.

[0034] Compared with the prior art, the present invention provides a processing method for wear-resistant gears in hubs of new energy electric bicycles. The gears manufactured by this method adopt a composite wear-resistant structure composed of a carburized layer, a wear-resistant alloy layer and a surface modification layer, which can improve the wear resistance, pitting resistance and fatigue resistance of the gears, thereby improving the durability of the hub transmission system.

[0035] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for processing wear-resistant gears in the hub of a new energy electric bicycle, comprising: The gear blank forging and pretreatment, gear rough machining and initial forming, gear matrix strengthening heat treatment, gear tooth profile precision machining, precision finishing and stabilization treatment and cleaning and inspection are characterized in that a composite surface wear-resistant strengthening treatment is adopted between the gear tooth profile precision machining and the precision finishing and stabilization treatment. The specific steps of the composite surface wear-resistant strengthening treatment include: 1) Deep carburizing treatment: The gear with the precision-machined gear tooth profile is placed in a controlled atmosphere carburizing furnace for deep gas carburizing to form a carburized layer; 2) Laser cladding wear-resistant alloy layer: Using a coaxial powder feeding laser cladding equipment, composite powder is selected to selectively laser clad the working area of ​​the gear tooth surface and the transition area of ​​the tooth root fillet after the deep carburizing treatment in step 1) to form a wear-resistant alloy layer. 3) Low-temperature ion implantation: The gear that has undergone laser cladding in step 2) is placed in an ion implantation device, and nitrogen ions and titanium ions are implanted to form a surface modification layer on the surface of the wear-resistant alloy layer and the carburized layer that is not covered by the wear-resistant alloy layer.

2. The method for processing wear-resistant gears in the hub of a new energy electric bicycle according to claim 1, characterized in that, In step 1), the carburizing temperature is controlled at 920~950℃, the carburizing time is 4~10 hours, and the carbon potential is controlled at 1.0%~1.2%.

3. The method for processing wear-resistant gears in the hub of a new energy electric bicycle according to claim 1, characterized in that, In step 2), the laser power is controlled at 1000~2000W, the scanning speed at 400~800mm / min, and the spot diameter at 1~2mm.

4. The method for processing wear-resistant gears in the hub of a new energy electric bicycle according to claim 1, characterized in that, In step 2), the composite powder is a mixture of Ni60A alloy powder and 30%~40% by mass of tungsten carbide powder.

5. The method for processing wear-resistant gears in the hub of a new energy electric bicycle according to claim 1, characterized in that, In step 3), the implanted ion energy is 50~100keV, and the implantation dose is 1×10¹. 7 ~5×10¹ 7 ions / cm².

6. The method for processing wear-resistant gears in the hub of a new energy electric bicycle according to claim 1, characterized in that, The base of the gear is a chromium-molybdenum alloy steel with a tempered sorbitic structure, and the teeth adopt a composite wear-resistant structure, which consists of a carburized layer, a wear-resistant alloy layer and a surface modification layer from the inside to the outside.