Gear reducer for new energy automobile electric drive system

Abstract

The invention discloses a gear reducer for an electric drive system of a new energy automobile, which belongs to the technical field of electric drive parts of the new energy automobile and comprises a shell, an input shaft, an output shaft and at least two stages of reduction gear sets arranged between the input shaft and the output shaft. The core innovation points of the gear are as follows: high-alloy carburizing steel or high-strength powder metallurgy alloy is adopted as a gear base material, and carburizing fine grinding and surface strengthening processes such as PVD (Physical Vapor Deposition) coating and laser cladding ceramic layer are combined, so that the hardness, the wear resistance and the antifriction performance of the gear are greatly improved, and the pain points of easy wear and fatigue failure of a tooth surface are solved; meanwhile, the tooth shape of the gear is optimized, the tooth profile with the high contact ratio and the low meshing force angle is adopted, low-viscosity synthetic lubricating oil is matched, an oil way is optimized, and friction and energy loss are reduced; a cooling cavity is integrated in the shell, so that the optimal working temperature of components is guaranteed; the high-performance wear-resistant gear has excellent wear resistance, high transmission efficiency and stability, can reduce the energy consumption of an electric drive system, improves the endurance of a vehicle and the reliability of a power system, and meets the high-performance requirement of a new energy vehicle.

Description

Technical Field

[0001] This invention belongs to the technical field of electric drive systems for new energy vehicles, specifically a gear reducer for electric drive systems of new energy vehicles. Background Technology

[0002] With the rapid development of the global new energy vehicle industry, countries are placing increasingly higher demands on the driving range, power performance, service life, and energy consumption of new energy vehicles. As the core power component of new energy vehicles, the electric drive system is equivalent to the engine and transmission of traditional vehicles, and its performance directly determines the vehicle's power response, driving range, and operating costs. As a key core component of the electric drive system, the gear reducer plays an important role in converting the high speed and low torque of the electric motor into the low speed and high torque required for vehicle operation, while ensuring the stability and efficiency of power transmission.

[0003] However, existing gear reducers in electric drive systems for new energy vehicles face numerous technical challenges in actual operation, making it difficult to meet the high-performance requirements of these systems. On the one hand, the electric motors in electric drive systems for new energy vehicles generally operate at high speeds (typically exceeding 10,000 r / min), and the vehicles experience frequent starts, stops, accelerations, and decelerations during operation. This forces the gear reducers to withstand high speeds, high torques, and alternating loads for extended periods, making them prone to wear, scratches, pitting, fatigue spalling, and other failures. This not only reduces transmission efficiency and increases operating noise but also significantly shortens the reducer's lifespan, increases vehicle maintenance costs, and may even lead to electric drive system malfunctions, affecting vehicle safety. On the other hand, the gear tooth profile design of existing reducers is not optimized, resulting in significant frictional losses and energy losses during meshing. Furthermore, the lubrication system design is flawed, with high oil viscosity resistance, preventing the formation of a stable and efficient lubricating film, further exacerbating energy loss and increasing the energy consumption of the electric drive system, indirectly reducing the driving range of new energy vehicles.

[0004] Furthermore, existing gear reducers suffer from insufficient heat dissipation. Under prolonged high-load operation, the temperature of gears and transmission components rises, easily leading to deterioration of lubricating oil performance and degradation of gear material properties. This further exacerbates tooth surface wear and reduces transmission efficiency, creating a vicious cycle. Therefore, addressing the shortcomings of existing technologies, developing a novel gear reducer for new energy vehicle electric drive systems with excellent wear resistance, high transmission efficiency, good heat dissipation performance, and long service life is of significant practical importance and industrial value for improving the performance of new energy vehicle electric drive systems, extending vehicle lifespan, reducing energy consumption, and increasing driving range. It is also a current research focus and development direction in the field of new energy vehicle electric drive components. Summary of the Invention

[0005] This invention aims to overcome the technical defects of existing gear reducers for electric drive systems in new energy vehicles, and provides a gear reducer for electric drive systems in new energy vehicles, specifically solving the following technical problems: 1. Existing reducer gears have insufficient wear resistance and fatigue resistance, and are prone to tooth surface wear and fatigue failure under high speed, high torque and frequent start-stop conditions, resulting in short service life; 2. An unreasonable gear tooth design results in high frictional loss and energy loss during meshing, leading to low transmission efficiency and affecting the driving range of new energy vehicles; 3. Poor compatibility of the lubrication system, unable to form a stable and efficient lubricating oil film, resulting in high oil viscosity resistance, which further aggravates energy loss and tooth surface wear; 4. Insufficient heat dissipation performance leads to increased component temperature under long-term high-load operation, resulting in deterioration of lubricating oil performance and reduction of gear material performance, affecting transmission stability and service life.

[0006] The core objective of this invention is to achieve the dual advantages of "wear resistance" and "energy saving" in speed reducers through the synergistic optimization of materials, structure, and process, thereby improving the transmission efficiency, wear resistance, and stability of speed reducers, extending their service life, reducing the energy consumption of electric drive systems, and ultimately improving the driving range and power system reliability of new energy vehicles.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a gear reducer for an electric drive system of a new energy vehicle, the core of which includes a housing, an input shaft, an output shaft, and at least two stages of reduction gear sets disposed between the input shaft and the output shaft. Through material optimization, surface treatment strengthening, tooth profile design improvement, lubrication system upgrade and heat dissipation structure addition, a dual improvement in wear resistance and energy saving is achieved. The specific technical solution is as follows: 1. Housing Structure Design: The housing is made of one-piece die-cast aluminum alloy. Aluminum alloy has the advantages of being lightweight and having good thermal conductivity, which can reduce the overall weight of the reducer, achieving lightweight and energy-saving in new energy vehicles, and also improve the heat dissipation capacity of the housing. The top of the housing is equipped with an oil filling hole for injecting lubricating oil, and the bottom is equipped with an oil drain hole for periodic oil replacement to ensure lubrication effect. Both ends of the housing are equipped with seals adapted to the input shaft and output shaft respectively to prevent lubricating oil leakage and to prevent external dust and impurities from entering the housing and damaging the gears and transmission components.

[0008] 2. Gear Materials and Surface Treatment: High-performance high-alloy carburized steel is used as the gear base material, preferably 18CrNiMo7-6 steel or 20CrMnTi steel. These materials have high strength, high toughness, good hardenability and carburizing properties, providing a solid matrix strength for the gears. After gear machining, the gears undergo carburizing, quenching, tempering, and precision grinding in sequence. Carburizing forms a high-carbon layer on the gear surface, improving surface hardness and wear resistance. Quenching further strengthens the gear's hardness and strength. Tempering eliminates internal stress, improves the gear's toughness, and prevents brittle fracture. Precision grinding ensures gear tooth profile accuracy and surface finish, reducing frictional losses during meshing. Based on this, the gear tooth surface is then coated with a PVD (Physical Vapor Deposition) coating, preferably TiN (titanium nitride) or DLC (diamond-like carbon) coating. This coating has a low coefficient of friction, high hardness, good wear resistance and adhesion, further improving the wear resistance, fatigue resistance, and friction reduction properties of the gear tooth surface, reducing meshing frictional losses.

[0009] 3. Gear Tooth Profile Optimization: Based on the principles of meshing mechanics, an optimized tooth profile with a high contact ratio, low meshing force angle, and small helix angle is designed. The contact ratio is >2.0, the meshing force angle is 12-18°, and the helix angle is 5-15°. A high contact ratio can increase the contact area of ​​gear meshing, disperse meshing stress, reduce local stress concentration on the tooth surface, and reduce the risk of tooth surface wear and fatigue failure. A low meshing force angle can reduce the force during meshing and reduce energy loss. A small helix angle can reduce the axial force during gear meshing, improve transmission stability, and at the same time reduce meshing friction loss and improve transmission efficiency.

[0010] 4. High-efficiency lubrication system: Utilizes low-viscosity, high-performance PAO (polyalphaolefin)-based fully synthetic lubricating oil with a viscosity grade of ISO VG 22-32. This type of lubricating oil exhibits excellent low-temperature fluidity, high-temperature stability, anti-wear properties, and oxidation resistance. Its low viscosity reduces viscous resistance and energy loss, while simultaneously forming a stable and efficient lubricating film on the gear surface, isolating tooth surface contact and reducing frictional losses. The housing features an optimized internal oil passage structure, including inclined oil ridges and oil channels. During gear rotation, the inclined oil ridges carry the oil to the meshing area and bearings, while the oil channels assist in oil circulation, ensuring uniform and sufficient lubrication. The input and output shaft bearings employ a labyrinth seal combined with an oil seal structure to further prevent lubricating oil leakage, ensuring the stability and long-term effectiveness of the lubrication system.

[0011] 5. Heat dissipation structure design: The housing integrates a cooling chamber that surrounds the outside of the reduction gear set. The cooling chamber has a flow guiding structure inside, which can improve heat dissipation efficiency and keep the temperature of the gears and transmission components within the optimal operating range of 80-120℃ during operation. This avoids the deterioration of lubricating oil performance and the degradation of gear material performance due to excessive temperature, further ensuring transmission stability and wear resistance, while reducing additional energy loss caused by excessive temperature.

[0012] In addition, this invention also provides two derivative technical solutions to adapt to electric drive systems for new energy vehicles with different power requirements: Derivative Solution: A gear reducer for an electric drive system of new energy vehicles includes a housing, an input shaft, an output shaft, and a second-stage reduction gear set located between the input and output shafts. It is suitable for low-power or medium-power electric drive systems. The gears of the second-stage reduction gear set are made of 20CrMnTi carburized steel. The tooth surfaces undergo carburizing, quenching, tempering, and grinding treatment, followed by a low-friction coefficient graphene-based coating. The graphene-based coating has excellent wear resistance and friction reduction properties, which can further improve the wear resistance of the gears. The housing integrates a cooling cavity and a grease lubrication system, using a low-viscosity (VG22) grease formulated based on PAO, which is suitable for the long-term lubrication requirements of low-power operating conditions, while reducing oil resistance and energy consumption.

[0013] Compared with the prior art, the beneficial effects of the present invention are: (1) Significantly improved wear resistance and extended service life: High alloy carburized steel is used as the gear base material, combined with a composite surface treatment process of carburizing, quenching, tempering, fine grinding and PVD coating (or graphene-based coating, laser cladding ceramic layer), which greatly improves the surface hardness, wear resistance, fatigue resistance and friction reduction performance of the gear, effectively solving the technical pain points of easy wear, pitting and fatigue spalling of the gear tooth surface in the existing reducer; the gear tooth surface hardness can reach HV800-2500, and the service life can be extended by more than 50% depending on the coating type, which can adapt to the complex working conditions of high speed, high torque and frequent start and stop of the electric drive system of new energy vehicles, reduce maintenance costs and improve the reliability of the power system; (2) High transmission efficiency and significant energy saving effect: The optimized gear tooth profile design (high contact ratio, low meshing force angle, small helix angle) reduces friction loss and energy loss during meshing, and reduces meshing impact and operating noise; the low viscosity PAO-based fully synthetic lubricating oil and the optimized internal oil circuit structure can quickly form a stable and efficient lubricating oil film, reduce oil viscosity resistance and tooth surface friction loss, and the low friction coefficient of the PVD coating (or other composite coating) further reduces meshing friction; the overall transmission efficiency is increased to 96%-98%, which is 2-3% higher than that of traditional reducers, which can effectively reduce the energy loss of the electric drive system of new energy vehicles, directly improve the vehicle range, and meet the energy saving requirements of new energy vehicles; (3) Good transmission stability and strong adaptability: The integrated die-cast aluminum alloy shell has good thermal conductivity and structural strength. Combined with the integrated cooling cavity inside the shell, it can effectively control the working temperature of gears and transmission components, avoid the deterioration of lubricating oil performance and the deterioration of gear material performance due to excessive temperature, and ensure transmission stability; multiple technical solutions are adapted to new energy vehicle electric drive systems with different power and torque requirements, and have a wide range of applications; the sealing structure of labyrinth seal and oil seal effectively prevents lubricating oil leakage and avoids the entry of external impurities, further improving transmission stability and service life; (4) Lightweight design to further improve energy saving effect: Compared with the traditional cast iron shell, the aluminum alloy shell is significantly lighter, realizing the lightweight design of the reducer, thereby reducing the overall weight of the new energy vehicle, reducing energy consumption during driving, and indirectly improving the vehicle's range, which is in line with the development trend of lightweight and energy saving of new energy vehicles. Attached Figure Description

[0014] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0015] In the attached diagram: Figure 1 This is a front view structural diagram of the speed reducer according to Embodiment 1 of the present invention; Figure 2 This is a rear view structural diagram of the speed reducer according to Embodiment 1 of the present invention; Figure 3 For the present invention Figure 1 A schematic diagram of the cross-sectional structure; Figure 4 For the present invention Figure 3 A schematic diagram of the cross-sectional structure; Figure 5 For the present invention Figure 4 A schematic diagram of the cross-sectional structure; Figure 6 This is a front view schematic diagram of the speed reducer according to Embodiment 2 of the present invention; Figure 7 This is a rear view schematic diagram of the speed reducer in Embodiment 2 of the present invention; Figure 8 For the present invention Figure 6 A schematic diagram of the cross-sectional structure; In the diagram: 1. Housing; 2. Input shaft; 3. Output shaft; 4. Two-stage reduction gear set; 41. First stage gear; 42. Second stage gear; 43. Helical gear; 44. Driven helical gear; 5. Seal; 6. Input shaft seal; 7. Oil filling hole; 8. Oil drain hole; 9. Cooling chamber. Detailed Implementation

[0016] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0017] Example 1: A two-stage reduction gear reducer using high-alloy carburized steel and TiN coating. As shown in the attached figure. Figures 1 to 5 As shown, this embodiment provides a two-stage reduction gear reducer using high-alloy carburized steel and TiN coating. It is mainly suitable for medium- to high-power electric drive systems of new energy vehicles, such as pure electric cars and SUVs. The specific structure and technical parameters are as follows: a) Overall Structure: The reducer includes an integrally die-cast aluminum alloy housing 1. The aluminum alloy material used is 6061 aluminum alloy, which has excellent thermal conductivity, strength, and formability. The housing thickness is 8-12mm, ensuring structural strength while achieving lightweight design and efficient heat dissipation. The housing 1 houses the input shaft 2, output shaft 3, and a two-stage reduction gear set 4. Both the input shaft 2 and output shaft 3 are made of 20CrMnTi steel, with surface tempering and fine grinding to improve strength and surface finish. The input shaft 2 is rigidly connected to the motor output end via a spline to receive the power transmitted by the motor and drive the first-stage gear 41 to rotate. The first-stage gear 41 meshes with the second-stage gear 42 to achieve the first reduction and torque increase. The second-stage gear 42 is splined to the half-shaft of the output shaft 3, transmitting the reduced and increased torque power to the output shaft 3, and then through the output shaft 3 to the vehicle drive. The housing 1 has a moving bridge; one end of the housing 1 is equipped with a seal 5 for sealing the output shaft 3. The seal 5 is made of fluororubber oil seal, which has excellent high temperature resistance, oil resistance and sealing performance; the other end of the housing 1 is the opening of the input shaft 2, and an input shaft seal 6 is installed. The input shaft seal 6 adopts a structure combining a labyrinth seal and a fluororubber oil seal, providing double sealing protection and effectively preventing lubricating oil leakage; the top of the housing 1 is equipped with an M12-sized oil filling hole 7 for injecting lubricating oil, and the bottom is equipped with an M10-sized oil drain hole 8 for periodically changing the lubricating oil. The oil drain hole 8 is located on the lower part of the side wall of the housing to facilitate the complete discharge of waste oil; the housing 1 integrates a cooling chamber 9, which surrounds the outside of the two-stage reduction gear set 4. The cooling chamber 9 has a spiral flow guiding structure inside to improve heat dissipation efficiency. The cooling chamber 9 has inlet and outlet water ports at both ends, which can be connected to the cooling circuit of the electric drive system to achieve circulating heat dissipation.

[0018] b) Gear Material and Surface Treatment: Both the first-stage gear 41 and the second-stage gear 42 use 18CrNiMo7-6 steel as the base material. This material is a high-performance, high-alloy carburizing steel containing alloying elements such as Cr, Ni, and Mo. It has excellent hardenability, strength, toughness, and carburizing performance, and can withstand high speeds and high torques. The gear processing flow is as follows: forging → normalizing → rough machining → semi-finishing → carburizing → quenching → tempering → precision grinding → PVD coating → finished product inspection. Specific processing parameters are as follows: carburizing temperature is 920-950℃, carburizing time is 8-12h, carburized layer thickness is 0.8-1.2mm, and the carbon content on the gear surface after carburizing reaches 0.8%-1.2%; quenching is done by oil quenching, quenching temperature is 850-880℃, holding time is 2-3h, and the gear hardness reaches HRC60-64 after quenching; tempering temperature is 180-220℃, and tempering... The grinding process takes 4-6 hours to eliminate internal stress in the gears, adjusting the core hardness to HRC58-62 and the surface layer hardness to HV800-900, thereby improving the gear's toughness and overall mechanical properties. The fine grinding process uses a high-precision gear grinding machine, achieving a grinding accuracy of Grade 6 in GB / T10095.1-2008, with a gear tooth surface roughness Ra≤0.8μm, ensuring tooth profile accuracy and surface finish, and reducing meshing friction. Finally, a physical vapor deposition (PVD) treatment is performed on the gear tooth surface, specifically a titanium nitride (TiN) coating. The coating is prepared using an arc ion plating process, with a thickness of 2-5μm and a hardness exceeding HV2000. The coefficient of friction is 0.15-0.25. The TiN coating exhibits strong adhesion to the gear tooth surface, is not easily detached, and significantly improves the wear resistance, fatigue resistance, and friction reduction performance of the gear tooth surface, effectively preventing tooth surface wear, pitting, and fatigue spalling.

[0019] c) Tooth Profile Design: The two-stage reduction gears adopt an optimized full-circular arc tooth profile, combined with a high contact ratio, low meshing force angle, and a suitable helix angle. The specific parameters are: contact ratio of 2.2, meshing force angle of 14°, and helix angle of 10°. The full-circular arc tooth profile optimizes the transition between the gear tooth tip and tooth root, reduces stress concentration, and lowers the risk of tooth root fracture. The high contact ratio increases the contact area of ​​gear meshing, distributing meshing stress to a larger tooth surface area and reducing tooth surface wear caused by excessive local stress. The low meshing force angle reduces the force during meshing, reducing energy loss and meshing impact. The suitable small helix angle reduces the axial force during gear meshing, avoiding excessive axial force that leads to accelerated bearing wear, while improving transmission stability and reducing meshing noise and friction loss.

[0020] d) Lubrication System: The reducer is filled with PAO (polyalphaolefin) based fully synthetic low-viscosity lubricating oil with a viscosity grade of ISO VG 32. This lubricating oil has excellent low-temperature fluidity (pour point ≤ -40℃), high-temperature stability (operating temperature range -40℃ to 150℃), anti-wear properties, and oxidation resistance. It can quickly start lubrication in low-temperature environments and maintain stable lubrication performance under high-temperature conditions, and is not prone to aging and deterioration. At the same time, the low viscosity characteristic can reduce the viscous resistance of the oil, reduce energy loss, and improve transmission efficiency. The housing 1 is equipped with inclined oil ridges and oil grooves. The inclined oil ridges are set on the housing wall outside the gear and are adapted to the gear rotation direction. When the gear rotates, the inclined oil ridges can carry the lubricating oil at the bottom of the housing to the gear meshing area and the input shaft. The output shaft bearing section has oil grooves located in the bearing housing and gear mounting area to guide the circulation of lubricating oil, ensuring uniform and sufficient lubrication, forming a stable and efficient lubricating oil film, isolating tooth surface contact, and reducing friction loss. The bearings of input shaft 2 and output shaft 3 are deep groove ball bearings. The outer ring of the bearing fits with the housing, and the inner ring fits with the shaft. The bearing section adopts a sealing structure combining labyrinth seal and oil seal. The labyrinth seal can form multi-stage sealing gaps to prevent lubricating oil leakage, and the oil seal further enhances the sealing effect, effectively preventing lubricating oil leakage, while preventing external dust and impurities from entering the bearing, thus extending the bearing service life.

[0021] e) Technical Effects: The reducer in this embodiment, through a composite surface treatment process of 18CrNiMo7-6 steel substrate and carburizing + TiN coating, significantly improves the wear resistance and fatigue resistance of the gears. Compared with traditional reducers, its service life is extended by more than 50%, effectively withstanding the high speed and high torque conditions of medium to high power electric drive systems, avoiding problems such as tooth surface wear and fatigue failure. The optimized tooth profile design and low viscosity PAO-based fully synthetic lubricating oil, combined with the low friction coefficient characteristics of the TiN coating, increase the transmission efficiency to 97%-98%, which is 2-3% higher than traditional reducers, effectively reducing energy loss. Based on a pure electric vehicle range of 500km, it can increase the range by 10-15km, with significant energy-saving effects. The design of the aluminum alloy shell and cooling cavity keeps the gear operating temperature in the optimal range of 80-120℃, ensuring transmission stability and lubricating oil performance. At the same time, the lightweight design further reduces vehicle energy consumption. The overall structure is compact and stable, adapting to the needs of medium to high power new energy vehicle electric drive systems, and has good practicality and promotional value.

[0022] Example 2: Single-stage helical gear reducer with DLC coating As shown in the attached figure. Figures 6 to 8As shown, this embodiment provides a single-stage helical gear reducer with DLC coating, suitable for some low-power or medium-power new energy vehicle electric drive systems, such as small pure electric cars, electric mobility scooters, and auxiliary electric drive systems of hybrid vehicles. This reducer features a compact structure, lightweight design, high efficiency and energy saving, and excellent wear resistance. Specific structure and technical parameters are as follows: a) Overall Structure: A compact housing design is adopted. The housing 1 is still a one-piece die-cast 6061 aluminum alloy housing. The housing volume is reduced by 20%-30% compared to Embodiment 1, which is more suitable for the installation space requirements of low-power electric drive systems. The housing 1 internally houses the input shaft 2, the output shaft 3, and the single-stage helical gear reduction structure 4. The input shaft 2 is connected to the output end of the motor through a spline. The helical gear 43 is fixedly installed on the input shaft 2 and meshes with the driven helical gear 44 on the output shaft 3 to achieve single-stage reduction and torque increase. The housing 1 has seals at both ends that are adapted to the input and output shafts. Silicone rubber oil seals are selected to meet the sealing requirements of low-power conditions. The top of the housing 1 has an oil filling hole and the bottom has an oil drain hole for easy lubrication. The housing 1 internally integrates a cooling chamber with a ring structure that surrounds the outside of the helical gear. The cooling chamber does not need to be connected to the cooling circuit of the electric drive system. It relies on the thermal conductivity of the aluminum alloy housing and the wind effect of the gear rotation to achieve a combination of natural heat dissipation and forced heat dissipation to meet the heat dissipation requirements under low-power conditions.

[0023] b) Gear Material and Surface Treatment: Both helical gear 43 and driven helical gear 44 use 20CrMnTi steel as the base material. This material is a commonly used high-performance carburizing steel with good carburizing performance, strength, and toughness. It is moderately priced, suitable for low-power operating conditions, and ensures the service life of the gears. The gear processing flow is as follows: forging → normalizing → rough machining → semi-finishing → carburizing → quenching → tempering → fine grinding → DLC coating → finished product inspection. Specific processing parameters are as follows: carburizing... The carburizing temperature is 900-930℃, the carburizing time is 6-8 hours, the carburized layer thickness is 0.6-1.0 mm, and the carbon content on the gear surface reaches 0.7%-1.1% after carburizing. The quenching treatment uses oil quenching at a temperature of 840-870℃ for 1.5-2.5 hours, resulting in a gear hardness of HRC58-62. The tempering treatment temperature is 170-210℃ for 3-5 hours to eliminate internal stress and improve gear toughness. The tooth surface hardness reaches HRC58-60; the fine grinding process uses a high-precision gear grinding machine, and the grinding accuracy reaches grade 7 of GB / T10095.1-2008, with a gear tooth surface roughness Ra≤0.6μm, ensuring tooth profile accuracy and surface finish, and reducing meshing friction; finally, a diamond-like carbon (DLC) coating is applied to the gear tooth surface, specifically an aC:H (amorphous hydrocarbon) coating, prepared by plasma-enhanced chemical vapor deposition (PECVD) process, with a coating thickness of 1-3μm, a coating hardness of HV1500-2500, and a friction coefficient as low as 0.05-0.1, far lower than TiN coating. The DLC coating has excellent wear resistance, anti-scratch and friction reduction properties, and also has good chemical stability, not easily reacting with lubricating oil, which can effectively improve the wear resistance and friction reduction effect of the gear tooth surface, especially in harsh environments where small particles are present, showing good anti-scratch ability and avoiding scratches and wear on the tooth surface.

[0024] c) Tooth profile design: The helical gear adopts an improved involute tooth profile, combined with optimized tooth tip and root fillet design, and is manufactured using a high-precision hobbing process. The involute tooth profile has the advantages of smooth meshing and constant transmission ratio, which is suitable for the transmission requirements of single-stage reduction. The optimized tooth tip and root fillets can effectively reduce tooth root stress concentration, reduce the risk of tooth root fracture, and reduce tooth tip wear. The high precision of the hobbing process can ensure the consistency of tooth profile and surface finish, further reducing friction loss and noise during meshing. The specific tooth profile parameters are: contact ratio of 2.1, meshing force angle of 15°, and helix angle of 8°, taking into account both transmission stability and energy saving effect.

[0025] d) Lubrication System: Considering the operating characteristics of low-power electric drive systems, this embodiment adopts a grease lubrication system instead of lubricating oil lubrication, simplifying the lubrication structure and achieving long-term lubrication. A low-viscosity (VG22) grease formulated based on PAO is used. This grease has good high-temperature resistance, oil resistance, wear resistance, and adhesion, and can adhere to the gear tooth surface and bearing parts for a long time to form a stable lubricating film and reduce friction loss. The amount of grease added is 1 / 3 to 1 / 2 of the internal volume of the housing to avoid excessive filling, which would increase viscous resistance and affect transmission efficiency. The housing 1 is designed with an oil chamber located below the gear to store grease. During gear rotation, the gear tooth surface will splash the grease onto the meshing area and bearing parts to achieve comprehensive lubrication. At the same time, the housing is provided with a grease guide groove to guide the circulation of grease, ensuring uniform lubrication and avoiding wear caused by insufficient local lubrication.

[0026] e) Technical Effects: The reducer in this embodiment uses 20CrMnTi steel as the base material combined with DLC coating treatment. While ensuring cost control, it provides excellent wear resistance and anti-scratch capability, extending the service life by more than 40% compared to traditional low-power reducers. It can adapt to low-power, light-load operating conditions, avoiding tooth surface wear and failure. The extremely low coefficient of friction of the DLC coating (0.05-0.1), combined with optimized involute tooth profile and low-viscosity grease, significantly reduces meshing friction and viscous resistance, achieving a transmission efficiency of 96%-97%, which is significantly higher than traditional low-power reducers. The speed reducer improves efficiency by 1.5-2.5%, resulting in significant energy savings and effectively extending the driving range of small new energy vehicles. Its compact aluminum alloy housing design achieves lightweight and miniaturization, adapting to the installation space requirements of low-power electric drive systems. Meanwhile, the cooling chamber design ensures stable gear operating temperatures. The grease lubrication system simplifies the structure, reduces the risk of lubricant leakage, and lowers maintenance costs. The overall structure is simple, reliable, and cost-effective, facilitating mass production and making it suitable for electric drive systems in low-power new energy vehicles such as small pure electric cars and electric mobility scooters.

[0027] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0028] 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 gear reducer for an electric drive system of a new energy vehicle, comprising a housing, an input shaft, an output shaft, and at least two stages of reduction gear sets disposed between the input shaft and the output shaft, characterized in that: The reduction gear set uses high-alloy carburized steel as the gear base material, and the gear tooth surface is successively treated by carburizing, quenching, tempering and fine grinding, and then subjected to low friction coefficient PVD (physical vapor deposition) coating treatment; the housing integrates a cooling cavity and a high-efficiency lubrication system. The cooling cavity is used to help the gear maintain the optimal working temperature, and the high-efficiency lubrication system is used to reduce transmission loss.

2. The gear reducer for an electric drive system of a new energy vehicle according to claim 1, characterized in that: The high-alloy carburizing steel is 18CrNiMo7-6 steel or 20CrMnTi steel. After carburizing treatment, the core hardness of the gear substrate reaches HRC58-62 and the surface layer hardness reaches HV800-1000.

3. The gear reducer for a new energy vehicle electric drive system according to claim 1, characterized in that: The PVD coating is a titanium nitride (TiN) coating or a diamond-like carbon (DLC) coating; the TiN coating has a thickness of 2-5 μm and a hardness ≥ HV2000; the DLC coating is an aC:H amorphous hydrocarbon coating with a thickness of 1-3 μm, a hardness of HV1500-2500, and a friction coefficient as low as 0.05-0.

1.

4. The gear reducer for an electric drive system of a new energy vehicle according to claim 1, characterized in that: The gear set has an optimized tooth profile with high contact ratio, low meshing force angle, and small helix angle, wherein the contact ratio is >2.0, the meshing force angle is 12-18°, and the helix angle is 5-15°.

5. A gear reducer for an electric drive system of a new energy vehicle according to claim 1, characterized in that: The high-efficiency lubrication system includes a low-viscosity synthetic lubricating oil and an optimized internal oil passage structure. The low-viscosity synthetic lubricating oil is a PAO (polyalphaolefin) based fully synthetic lubricating oil with a viscosity grade of ISO VG 22-32. The internal oil passage structure includes inclined oil ridges and oil channel grooves, which are used to efficiently deliver the lubricating oil to the gear meshing area and bearing parts to form a stable oil film.

6. A gear reducer for an electric drive system of a new energy vehicle according to claim 1, characterized in that: The bearings of the input and output shafts adopt a sealing structure combining labyrinth seals and oil seals to prevent lubricating oil leakage and ensure the stability of the lubrication system.

7. A gear reducer for an electric drive system of a new energy vehicle according to claim 1, characterized in that: The housing is an integral die-cast aluminum alloy housing. The top of the housing is provided with an oil filling hole, the bottom is provided with an oil drain hole, and the two ends of the housing are respectively provided with seals adapted to the input shaft and the output shaft.

8. A gear reducer for an electric drive system of a new energy vehicle, characterized in that: It includes a housing, an input shaft, an output shaft, and a second-stage reduction gear set located between the input shaft and the output shaft; the gears of the second-stage reduction gear set are made of 20CrMnTi carburized steel, and the tooth surface is treated with carburizing, quenching, tempering, and grinding, and then coated with a low-friction coefficient graphene-based coating; the housing integrates a cooling cavity and a grease lubrication system.

9. A gear reducer for an electric drive system of a new energy vehicle according to any one of claims 1 or 8, characterized in that: The cooling chamber surrounds the outside of the reduction gear set, and the interior of the cooling chamber is equipped with a flow guiding structure to improve heat dissipation efficiency and keep the gear working temperature in the optimal range of 80-120℃.

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