Lubricating oil for electric drive axle of commercial vehicle and preparation method of lubricating oil

Abstract

The invention relates to lubricating oil for an electric drive axle of a commercial vehicle and a preparation method thereof, and belongs to the technical field of lubricating oil. The lubricating oil for the electric drive bridge comprises the following components in parts by weight: 85-95 parts of base oil, 2-10 parts of a composite additive, 2-8 parts of a viscosity index improver and 0.1-0.5 part of an electric drive oil reinforcing agent, the base oil is a combination of coal-to-liquid and poly-alpha-olefin; the total amount of the components is 100 parts. The invention also provides a preparation method of the lubricating oil for driving the axle. By optimizing a lubricating formula, the problems of high rotating speed, high load, large torque and multi-working-condition operation of an electric drive axle are solved in a targeted manner, and compared with traditional GL-5 gear oil, transmission efficiency can be remarkably improved, the service life of parts can be prolonged, electrical safety can be guaranteed, and the lubricating oil is a key guarantee for reliable operation of an electric drive axle system.

Description

Technical Field

[0001] This invention relates to the technical field of lubricating oil, specifically to a lubricating oil for electric drive axles of commercial vehicles and its preparation method. Background Technology

[0002] The electric drive axle is an integrated power transmission device for electric vehicles, combining a traction motor, reducer, differential, and power electronic components. Its core function is to convert electrical energy into driving force for the wheels. As a core component of new energy vehicles or electric drive systems, the electric drive axle integrates functional modules such as a drive motor, reducer, and differential. Its operating environment is characterized by high speed, high load, high torque, wide temperature range, and frequent load changes (e.g., motor speeds can reach 12,000 rpm, and gears are subjected to high contact stress). Currently, electric drive axles are widely used in new energy passenger vehicles and commercial vehicles, and are one of the core components of electric chassis.

[0003] With the rapid development of the new energy commercial vehicle industry, electric drive axles have gradually become a core component of commercial vehicle power systems due to their advantages such as high integration, superior transmission efficiency, and small space occupation. However, commercial vehicle electric drive axles operate under harsh conditions of high load, high torque, and frequent start-stop cycles, making them prone to problems such as gear wear and oil oxidation failure. Furthermore, electric drive axles employ an integrated design of the motor and transmission gears, requiring their working medium to be compatible with various materials such as coils, insulators, and rubber components, and to possess reliable electrical insulation performance. Compared to traditional axles, electric drive axles operate at significantly higher speeds, placing higher demands on the anti-foaming properties of the oil. Insufficient anti-foaming properties can easily lead to hardware cavitation and accelerated oil aging. In addition, the special oil for electric drive axles must have a suitable viscosity to balance the dual needs of hardware lubrication protection and improved transmission efficiency. Currently, the industry often uses traditional GL-5 gear oil as the working medium for electric drive axles. Although this type of gear oil can achieve good lubrication and protection of shafts and teeth, it has many defects such as poor oxidation resistance, insufficient anti-foaming performance, poor compatibility with motor-related materials, lack of electrical insulation, and low transmission efficiency. It can no longer meet the actual application needs of commercial vehicle electric drive axles, and there is an urgent need to develop a more adaptable special oil for electric drive axles. Summary of the Invention

[0004] In view of the technical problems existing when using GL-5 gear oil as the working medium of electric drive axles, such as easy oxidation of the oil and poor electrical insulation performance, the present invention provides a lubricating oil for commercial vehicle electric drive axles and its preparation method to solve the above problems.

[0005] The technical solution of this invention is as follows: In a first aspect, the present invention provides a lubricating oil for electric drive axles of commercial vehicles, comprising the following components in parts by weight: 85-95 parts base oil, 2-10 parts composite additives, 2-8 parts viscosity index improver, and 0.1-0.5 parts electric drive oil reinforcing agent. The base oil is a combination of CTL (coal-to-oil) and polyalphaolefin (PAO), which possesses excellent viscosity-temperature characteristics and thermal oxidation stability, thereby improving the service life of the electric drive axle-specific oil and contributing to efficiency improvement. The total amount of the above components is 100 parts.

[0006] Furthermore, the base oil comprises the following components in parts by weight: 64.9 to 80.9 parts coal-derived oil and 10 to 25 parts polyalphaolefin.

[0007] Furthermore, it includes the following components in parts by weight: 89.9 to 90.9 parts base oil, 6 to 8 parts composite additives, 2 to 3 parts viscosity index improver, and 0.1 parts electric drive oil reinforcing agent.

[0008] Furthermore, the composite additive is a special oil additive developed for electric drive axles of commercial vehicles. It is composed of at least two of the following: borate esters, sulfates, molybdenum dithiocarbamate, polyetheramine, zinc dialkyl dithiophosphate, phenolic antioxidants, or polyisobutylene succinimide. It can improve the anti-wear, anti-oxidation, anti-corrosion, and detergency and dispersancy of the special oil for electric drive axles.

[0009] Furthermore, the borate ester is trimethyl borate, tri-n-butyl borate, or diphenyl methyl borate.

[0010] Furthermore, the sulfate is calcium sulfate, zinc sulfate, or barium sulfate.

[0011] Furthermore, the phenolic antioxidant is 2,6-di-tert-butyl-p-cresol, 2,6-di-tert-pentyl-4-methylphenol, or phenyl-α-naphthol.

[0012] Furthermore, the viscosity index improver is one of polystyrene-methyl methacrylate copolymer and radial polyisoprene, which can improve the viscosity-temperature performance of the electric drive bridge oil and effectively improve efficiency.

[0013] Furthermore, the electric drive oil reinforcing agent is at least two of the following: electric drive oil reinforcing agent Z001, electric drive oil reinforcing agent Z002, and electric drive oil reinforcing agent Z003. The electric drive oil reinforcing agent Z001 is composed of propylene glycol block polyether L61 and fluorinated graphene (FG) in a mass ratio of 1:1. The electric drive oil reinforcing agent Z002 is a compound of Dow Corning DC-57 and hexagonal boron nitride (h-BN) in a mass ratio of 1:1. The electric drive oil reinforcing agent Z003 is a compound of trioleic acid glyceride and fluorinated graphene (FG) in a mass ratio of 1:1.

[0014] The electric drive oil reinforcing agent used can effectively control the generation and dissipation of foam during the operation of the electric drive bridge special oil, reduce the risks of hardware cavitation and accelerated oil aging, and at the same time, give full play to the synergistic effect of each component to significantly improve the defoaming properties, thermal oxidation stability and electrical insulation of the oil.

[0015] Secondly, the present invention provides a method for preparing the above-mentioned lubricating oil for electric drive axles of commercial vehicles, comprising the following steps: (1) Raw material pretreatment Base oil preheating: Heat the base oil to 60℃~70℃ to ensure good fluidity and reduce viscosity; Dispersion of viscosity index improver: Add the viscosity index improver separately to a small amount of base oil (about 5% of the total base oil volume), stir at 50℃~60℃ for 15~20min at a speed of 300~500 rpm to initially disperse it.

[0016] (2) Add the preheated base oil from step (1) to the mixing tank, then add the viscosity index improver dispersed in step (1), increase the rotation speed to 800~1000 rpm, keep the temperature at 65℃~70℃, stir for 30 minutes, so that the viscosity index improver is evenly dispersed in the base oil; (3) While stirring, gradually add the composite additive at a temperature of 70-80℃; first add easily soluble components such as borate esters, zinc dialkyl dithiophosphate, phenolic antioxidants, and polyetheramines, and then add poorly soluble components such as molybdenum dithiocarbamate, polyisobutylene succinimide, and sulfates to avoid local oversaturation. (4) Increase the rotation speed to 1000~1200 rpm and stir for 40~60 min to ensure that the composite additive is completely dissolved and evenly dispersed.

[0017] (5) Add the electric drive oil reinforcing agent slowly at 70℃~75℃. This component should be protected from high-temperature decomposition or reaction. After addition, use a high-shear emulsifier and control the speed ≥8000 rpm. Process for 5~10 minutes to ensure that the reinforcing agent is uniformly dispersed at the nanoscale.

[0018] (6) Transfer the mixture to a high-pressure homogenizer and circulate it 2 to 3 times under a pressure of 80 to 100 MPa to eliminate micro bubbles and refine the particle distribution; then degas it for 15 to 20 minutes at 60 to 70°C and a vacuum of -0.08 MPa to remove bubbles and moisture introduced during the mixing process.

[0019] (7) Filtration: The mixed oil is filtered through a 5~10 μm filter to remove impurities and obtain lubricating oil for electric drive axles of commercial vehicles.

[0020] The beneficial effects of this invention are as follows: The lubricating oil for commercial vehicle electric drive axles provided by this invention has the following advantages compared to traditional GL-5 gear oil: (1) Precisely matching lubrication requirements to reduce wear on key components. Components such as gears (helical gears) and bearings (ball bearings, cylindrical roller bearings) in the electric drive axle need to operate stably under high speed and heavy load. The lubricating oil for the electric drive axle provided by this invention achieves oil film stability at high speeds by optimizing viscosity and additive formulation. Low viscosity high shear stability (HVLS) base oils (such as coal-derived oil and polyalphaolefins) are used to form a tough oil film during high-speed rolling or sliding friction, avoiding wear caused by direct metal contact (such as pitting and galling). In addition, the lubricating oil for the electric drive axle provided by this invention also provides heavy-load protection for the gearbox. For high torque output scenarios of the reducer (such as climbing and rapid acceleration), the borate esters in the composite additives can form a chemical reaction film on the metal surface, reducing contact stress and extending gear life (the special oil can increase gear fatigue life by more than 30%).

[0021] (2) High-efficiency thermal management to inhibit oil aging. Electric drive axles generate a large amount of heat due to motor losses, gear oil churning, and energy conversion during braking energy recovery (local temperatures can reach 120~150℃, and exceed 180℃ under extreme conditions). The lubricating oil for electric drive axles provided by this invention achieves high thermal conductivity and oxidation resistance by selecting appropriate viscosity and base oil type, and adding amines, phenolic compounds, and zinc dialkyl dithiophosphate in the formula, thus enhancing heat dissipation efficiency. Compared with traditional GL-5 gear oil, the lubricating oil for electric drive axles provided by this invention has a lower viscosity and optimizes the thermal conductivity of the base oil (e.g., synthetic oil is 20%~30% higher than mineral oil). Combined with the oil cooling system (some electric drive axles integrate an oil pump for forced circulation), heat is quickly transferred to the radiator, avoiding component damage or oil film rupture caused by local overheating. Secondly, it also has the effect of delaying oxidation degradation. The electric drive axle lubricating oil provided by this invention contains amines, phenolic compounds, and zinc dialkyl dithiophosphate, which inhibit the oxidation reaction of the base oil at high temperatures and extend the oil change cycle (200,000 to 300,000 kilometers for light trucks and 100,000 to 150,000 kilometers for heavy trucks).

[0022] (3) Material compatibility to avoid seal and coating failure. Seals (such as fluororubber and nitrile rubber) and coatings (such as epoxy resin) of the electric drive bridge need to be in long-term contact with lubricating oil; otherwise, swelling, shrinkage, or peeling may occur. This invention avoids swelling of fluororubber (FKM) (volume change rate ≤5%) by controlling the hydrocarbon composition of the base oil (e.g., reducing aromatic hydrocarbon content); and controls the swelling rate of nitrile rubber (NBR) to within 10% (meeting IP67 sealing requirements). This invention avoids the use of strong solvent-based additives, ensuring adhesion to electrophoretic paint and powder coatings (peeling rate ≤5% in cross-cut test), and preventing coating blistering or peeling.

[0023] (4) Achieving a good balance between extreme pressure protection performance and motor material compatibility. Traditional GL-5 gear oil contains a large amount of active sulfur-containing components, which have outstanding extreme pressure protection performance, but are extremely prone to corroding metal parts in the motor, such as copper wires. Therefore, it is not suitable for use in electric drive axles. At the same time, commercial vehicle electric drive axles inevitably encounter heavy loads, climbing, and other high torque output conditions, which pose a significant challenge to the gear protection of the reducer. In order to balance extreme pressure protection performance and motor material compatibility, the lubricating oil for electric drive axles provided by this invention selects a specific sulfur-phosphorus component designed to achieve good compatibility with motor materials (mainly copper wires) while providing sufficient shaft and gear protection performance (FZG≥10 FLS).

[0024] (5) Good electrical insulation to ensure the safety of the drive motor. The motor windings, sensors (such as resolver sensors) and wiring harnesses of the electric drive bridge need to coexist with the lubricating oil. If the oil's insulation performance is insufficient, it may cause leakage, signal interference, or even short circuit. The lubricating oil for the electric drive bridge provided by this invention has low electrical conductivity. The base oil is selected from low polarity synthetic oils (such as polyalphaolefins and coal-derived oils) to avoid polar substances from conducting electricity. The additives avoid introducing ionic components (such as metal salts in traditional anti-wear agents), so that the lubricating oil for the electric drive bridge provided by this invention has high volume resistivity and breakdown voltage, thereby meeting the insulation requirements of the motor windings.

[0025] (6) Wide temperature range adaptability, ensuring stable operation under all climate conditions. New energy vehicles need to operate in an environment of -40℃ to 60℃, and the electric drive axle oil needs to balance low-temperature fluidity and high-temperature viscosity retention. Compared with traditional GL-5 gear oil, the electric drive axle lubricant provided by this invention achieves superior low-temperature performance through synthetic base oil + viscosity index improver. This invention uses low pour point (≤-40℃) synthetic oil (such as coal-derived oil combined with low viscosity polyα-olefin), which can still maintain fluidity at low temperature (-40℃), avoiding lubrication delay caused by oil viscosity during cold start (reducing the risk of dry friction of gears / bearings by 90%). The viscosity index (VI) of the electric drive axle lubricant provided by this invention is ≥130 (the VI of ordinary gear oil is about 90~110), and the viscosity decrease rate at high temperature (100℃) is small, ensuring stable oil film thickness (such as kinematic viscosity maintained at 8.5~11mm² / s at 100℃, meeting the lubrication requirements of high-speed gears).

[0026] (7) Suppressing foam, self-repairing, and extending system life. During the operation of the electric drive bridge, gear churning and oil pump circulation can cause air to be entrained in the oil, forming foam. The lubricating oil for the electric drive bridge provided by this invention solves the wear generated during hardware operation by adding reinforcing agents. This invention adds organosilicon or polyether compounds to control foam tendency (foam volume ≤ 20%) and defoaming speed (foam disappears within 5 seconds), avoiding lubrication failure or oil overflow caused by foam. This invention uses fluorinated graphene (FG) and hexagonal boron nitride (h-BN) composite nanomaterials to provide rapid repair capabilities through non-covalent interactions such as hydrogen bonding and metal coordination.

[0027] In summary, this invention, through optimized lubrication formula, specifically addresses the challenges of high-speed, high-load, high-torque, and multi-condition operation of electric drive axles. Compared to traditional GL-5 gear oil, it significantly improves transmission efficiency (reducing energy consumption by 2% to 5%), extends component life (gear or bearing life increased by more than 30%), and ensures electrical safety (insulation performance meets standards), making it a key guarantee for the reliable operation of electric drive axle systems. Detailed Implementation

[0028] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0029] In a specific implementation, the material information used is as follows: The coal-to-oil (CTL) product was purchased from Shanghai Daopu Chemical Co., Ltd., product model: ICCSYN®4.

[0030] Polyalphaolefin (PAO) was purchased from Shanghai Daopu Chemical Co., Ltd., product model: PAO2.

[0031] Polyisobutylene succinimide: molecular weight 1050~1250 Da.

[0032] Polystyrene-methyl methacrylate copolymer: molecular weight approximately 150,000 Da.

[0033] All other raw materials are commercially available products.

[0034] Example 1 A lubricating oil for an electric drive axle comprises the following components in parts by weight: 89.9 parts base oil (64.9 parts coal-derived oil, 25 parts polyalphaolefin), 8.0 parts composite additive (the mass percentage of each component in the composite additive is as follows: 19% trimethyl borate, 12% zinc sulfate, 12% molybdenum dithiocarbamate, 20% polyetheramine D-400, 20% zinc dialkyl dithiophosphate, 9% 2,6-di-tert-butyl-p-cresol (BHT) and 19% polyisobutylene succinimide), 2.0 parts polystyrene-methyl methacrylate copolymer, 0.05 parts electric drive oil reinforcing agent Z002, and 0.05 parts electric drive oil reinforcing agent Z003.

[0035] The steps include the following: (1) Base oil preheating: Mix 60.4 parts of coal-derived oil and 25 parts of polyα-olefin and heat to 60°C; take polystyrene-methyl methacrylate copolymer, add 4.5 parts of coal-derived oil, and stir at 300 rpm for 15 min at 50°C; (2) Add the base oil preheated in step (1) to the mixing tank, then add the polystyrene-methyl methacrylate copolymer dispersed in step (1), increase the speed to 800 rpm, keep the temperature at 65℃, and stir for 30 min; (3) While stirring, gradually add the composite additive and control the temperature at 70℃; (4) Increase the rotation speed to 1000 rpm and stir for 40 min; (5) Slowly add electric drive oil reinforcing agent Z002 and electric drive oil reinforcing agent Z003 at 70℃; after the addition is completed, use a high shear emulsifier and control the speed at 8000 rpm; process for 5 min; (6) Transfer the mixture to a high-pressure homogenizer and circulate it twice at 80 MPa; then degas it for 15 min at 60°C and a vacuum of -0.08 MPa. (7) Filtration: The mixed oil is filtered through a 5 μm filter to remove impurities and obtain lubricating oil for electric drive axles of commercial vehicles. It is packaged in a clean environment at a specification of 1L / drum.

[0036] Example 2 A lubricating oil for an electric drive axle comprises the following components in parts by weight: 90.9 parts base oil (75.9 parts coal-derived oil, 15 parts polyalphaolefin), 6.5 parts composite additive (the mass percentages of each component in the composite additive are as follows: 15% tri-n-butyl borate, 15% barium sulfate, 8% molybdenum dithiocarbamate, 15% polyetheramine D-400, 7% zinc dialkyl dithiophosphate, 10% 2,6-di-tert-pentyl-4-methylphenol (AO-80), and 30% polyisobutylene succinimide), 2.5 parts radial polyisoprene, 0.05 parts electric drive oil reinforcing agent Z001, and 0.05 parts electric drive oil reinforcing agent Z003.

[0037] The steps include the following: (1) Base oil preheating: Mix 71.4 parts of coal-derived oil and 15 parts of polyα-olefin and heat to 65°C; take radial polyisoprene, add 4.5 parts of coal-derived oil, and stir for 17 minutes at 55°C and 400 rpm. (2) Add the preheated base oil from step (1) to the mixing tank, then add the radially dispersed polyisoprene from step (1), increase the rotation speed to 900 rpm, keep the temperature at 65℃, and stir for 30 min; (3) While stirring, gradually add the composite additive and control the temperature at 75℃; (4) Increase the rotation speed to 1100 rpm and stir for 50 min; (5) Add electric drive oil reinforcing agent Z001 and electric drive oil reinforcing agent Z003 slowly at 70℃; after the addition is completed, use a high shear emulsifier and control the speed at 8500 rpm; process for 8 min; (6) Transfer the mixture to a high-pressure homogenizer and circulate it twice at a pressure of 90 MPa; then degas it for 15 min at 60°C and a vacuum of -0.08 MPa. (7) Filtration: The mixed oil is filtered through a 5 μm filter to remove impurities and obtain lubricating oil for electric drive axles of commercial vehicles. It is packaged in a clean environment at a specification of 18L / drum.

[0038] Example 3 A lubricating oil for an electric drive axle comprises the following components in parts by weight: 90.9 parts base oil (80.9 parts coal-derived oil, 10 parts polyα-olefin), 6.0 parts composite additive (the mass percentages of each component in the composite additive are as follows: 11% diphenyl borate, 7% calcium sulfate, 19% molybdenum dithiocarbamate, 12% polyetheramine D-400, 14% zinc dialkyl dithiophosphate, 9% phenyl-α-naphthylphenol, and 28% polyisobutylene succinimide), 3.0 parts radial polyisoprene, 0.05 parts electric drive oil reinforcing agent Z001, and 0.05 parts electric drive oil reinforcing agent Z002.

[0039] The steps include the following: (1) Base oil preheating: Mix 76.4 parts of coal-derived oil and 10 parts of polyα-olefin and heat to 70°C; take radial polyisoprene, add 4.5 parts of coal-derived oil, and stir for 20 minutes at 60°C and 500 rpm. (2) Add the base oil preheated in step (1) to the mixing tank, then add the radially dispersed polyisoprene in step (1), increase the speed to 1000 rpm, keep the temperature at 70℃, and stir for 30 min; (3) While stirring, gradually add the composite additive and control the temperature at 80℃; (4) Increase the rotation speed to 1200 rpm and stir for 60 min; (5) Add electric drive oil reinforcing agent Z001 and electric drive oil reinforcing agent Z002 slowly at 70℃; after the addition is completed, use a high shear emulsifier and control the speed at 8500 rpm; process for 10 min; (6) Transfer the mixture to a high-pressure homogenizer and circulate it 3 times at a pressure of 90 MPa; then degas it for 20 min at 70°C and a vacuum of -0.08 MPa. (7) Filtration: The mixed oil is filtered through a 10 μm filter to remove impurities and obtain lubricating oil for electric drive axles of commercial vehicles. It is packaged in a clean environment at a specification of 1L / drum.

[0040] Test case The physicochemical properties of the lubricating oils used in the electric drive axles of Examples 1-3 were tested according to the standard methods for lubricating oil testing. The test results are shown in Tables 1-3 below.

[0041] Table 1 - Physicochemical Test Results of Lubricating Oil for Electric Drive Axles

[0042] Table 2 - Performance Test Results of Lubricating Oil for Electric Drive Axles

[0043] Table 3 - Test Results of Electrical Performance of Lubricating Oil for Electric Drive Axles

[0044] As shown in Tables 1-3, compared with traditional GL-5 gear oil, the electric drive axle-specific oil has lower kinematic viscosity at 40℃ and 100℃, lower pour point, and lower apparent viscosity at -40℃, indicating that the electric drive axle-specific oil has superior viscosity-temperature performance and better low-temperature fluidity, which is beneficial to improving hardware efficiency. The lower foaming value indicates better anti-foaming properties. The copper strip corrosion test (150℃, 168h) is a more stringent copper strip corrosion test, and the results show that the electric drive axle-specific oil has good copper coil compatibility. The volume resistivity, breakdown voltage, conductivity, and thermal conductivity at 80℃ indicate that the electric drive axle-specific oil has excellent electrical insulation and good heat dissipation capabilities.

[0045] Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should also be covered within the protection scope of the present invention.

Claims

1. A lubricating oil for electric drive axles of commercial vehicles, characterized in that, It comprises the following components in parts by weight: 85-95 parts base oil, 2-10 parts composite additives, 2-8 parts viscosity index improver, and 0.1-0.5 parts electric drive oil reinforcing agent; the base oil is a combination of coal-derived oil and polyalphaolefin; the total amount of the above components is 100 parts.

2. The lubricating oil for electric drive axles of commercial vehicles as described in claim 1, characterized in that, The base oil comprises the following components in parts by weight: 64.9 to 80.9 parts coal-derived oil and 10 to 25 parts polyalphaolefin.

3. The lubricating oil for electric drive axles of commercial vehicles as described in claim 1, characterized in that, The following components are included in parts by weight: 89.9-90.9 parts base oil, 6-8 parts composite additives, 2-3 parts viscosity index improver, and 0.1 parts electric drive oil reinforcing agent.

4. The lubricating oil for electric drive axles of commercial vehicles as described in claim 1, characterized in that, The composite additive is a special oil additive developed for electric drive axles of commercial vehicles. It is composed of at least two of the following: borate esters, sulfates, molybdenum dithiocarbamate, polyetheramine, zinc dialkyl dithiophosphate, phenolic antioxidants, or polyisobutylene succinimide. It can improve the anti-wear, anti-oxidation, anti-corrosion, and detergency and dispersancy of the special oil for electric drive axles.

5. The lubricating oil for electric drive axles of commercial vehicles as described in claim 1, characterized in that, The borate ester is trimethyl borate, tri-n-butyl borate, or diphenyl methyl borate.

6. The lubricating oil for electric drive axles of commercial vehicles as described in claim 1, characterized in that, The sulfate is calcium sulfate, zinc sulfate, or barium sulfate.

7. The lubricating oil for electric drive axles of commercial vehicles as described in claim 1, characterized in that, The phenolic antioxidant is 2,6-di-tert-butyl-p-cresol, 2,6-di-tert-pentyl-4-methylphenol, or phenyl-α-naphthylphenol.

8. The lubricating oil for electric drive axles of commercial vehicles as described in claim 1, characterized in that, The viscosity index improver is one of polystyrene ester and radial polyisoprene.

9. The lubricating oil for an electric drive axle of a commercial vehicle as described in claim 1, characterized in that, The electric drive oil reinforcing agent is at least two of the following: electric drive oil reinforcing agent Z001, electric drive oil reinforcing agent Z002, and electric drive oil reinforcing agent Z003; The electric drive oil reinforcing agent Z001 is composed of propylene glycol block polyether L61 and fluorinated graphene in a mass ratio of 1:

1. The electric drive oil reinforcing agent Z002 is a compound of Dow Corning DC-57 and hexagonal boron nitride in a mass ratio of 1:

1. The electric drive oil reinforcing agent Z003 is composed of trioleic acid glyceride and fluorinated graphene in a mass ratio of 1:

1.

10. A method for preparing the lubricating oil for an electric drive axle of a commercial vehicle as described in claim 1, characterized in that, Includes the following steps: (1) Raw material pretreatment Base oil preheating: Heat the base oil to 60℃~70℃; Viscosity index improver dispersion: Add viscosity index improver to base oil II and stir at 50℃~60℃ for 15~20min at a speed of 300~500 rpm; the total amount of base oil I and base oil II is 85~95 parts. (2) Add the preheated base oil from step (1) to the mixing tank, then add the viscosity index improver dispersed in step (1), increase the rotation speed to 800~1000 rpm, keep the temperature at 65℃~70℃, and stir for 30 minutes; (3) While stirring, gradually add the composite additive at a temperature of 70~80℃; (4) Increase the rotation speed to 1000~1200 rpm and stir for 40~60 min; (5) Slowly add the electric drive oil reinforcing agent at 70℃~75℃ and control the rotation speed ≥8000 rpm; treat for 5~10 min to ensure that the reinforcing agent is uniformly dispersed at the nanoscale; (6) Transfer the mixture to a high-pressure homogenizer and circulate it 2 to 3 times under a pressure of 80 to 100 MPa; then degas it for 15 to 20 minutes at 60 to 70°C and a vacuum of -0.08 MPa. (7) Filtration: The mixed oil is filtered through a 5~10 μm filter to remove impurities and obtain lubricating oil for electric drive axles of commercial vehicles.

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