Friction modifier and preparation method therefor, and lubricating oil

Abstract

A friction modifier and a preparation method therefor, and lubricating oil. The friction modifier has a structure as shown in formula I, wherein Ra comprises one or more of alkane, olefin and derivatives thereof, Rb comprises one or more of alkane, olefin and a formula -O-CH2CH2-COR', and-COR' is derived from C2-C20 fatty acids. In the friction modifier, a phosphorus ester group and an imide structure form a polar clustering group, enhancing adsorption strength with friction materials and solving the problem of clutch dynamic judder.

Description

Friction modifier and preparation method thereof, and lubricating oil

[0001] This application claims priority to the Chinese patent application filed with the Patent Office of China on February 6, 2024, with application number 202410170833.6 and invention name “A friction modifier, its preparation method, and lubricating oil”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present application belongs to the technical field of lubricating oil additives, and in particular relates to a friction modifier, a preparation method thereof, and lubricating oil. Background Art

[0003] Automotive lubricants are commonly found in engines and transmissions, used to reduce friction, save energy, dissipate heat, and maintain cleanliness. However, electromechanical coupling transmission fluids for new energy vehicles must, in addition to the performance of traditional transmission fluids, possess suitable electrical properties, excellent corrosion protection, appropriate thermal management, compatibility with new materials, and friction properties that mitigate noise, vibration, and harshness (NVH) issues. If the clutch friction plates vibrate during starting and shifting, the driver will experience jerking or trembling as speed increases, which can negatively impact the overall vehicle's sensory quality and diminish the vehicle's brand image. Good friction properties are key to ensuring smooth operation of transmission gear components, reducing noise and extending lifespan.

[0004] During the use of existing lubricants, under sliding film conditions, that is, when the friction plate of a continuously sliding torque-converting clutch continuously changes in the clamping force, the torque does not show a linear correlation, but rather fluctuates at high frequencies, that is, the friction coefficient vibrates. Furthermore, there are the following problems: 1) On an SAE No. 2 friction tester, the static friction coefficient decreases significantly over the entire life cycle, that is, the torque capacity changes significantly, which is not conducive to the distribution of hydraulic system control pressure; (2) On a low-speed SAE No. 2 friction tester, NVH vibration problems are obvious; (3) On a ZF clutch performance tester, the dynamic pressure-torque exhibits severe vibration at 40°C.

[0005] Summary of the Invention

[0006] The technical problem to be solved by the present application is: to provide a friction modifier, a preparation method thereof, and lubricating oil in response to the problem that the existing clutch using lubricating oil has dynamic jitter under speed difference.

[0007] In order to solve the above technical problems, on the one hand, the present application provides a friction modifier, the structure of which is shown in Formula I:

[0008] Among them, Ra Including one or more of alkanes, alkenes and their derivatives, R b It includes one or more alkanes, alkenes, and the formula -O-CH2CH2-COR', where -COR' is derived from a C2-C20 fatty acid.

[0009] Optionally, the R a One selected from C1-C10 alkanes, C1-C10 alkenes and derivatives thereof.

[0010] Optionally, the R b One or more selected from C5-C30 alkanes, C5-C30 alkenes and the formula -O-CH2CH2-COR', wherein -COR' is derived from a C2-20 fatty acid.

[0011] Optionally, the number average molecular weight Mn of the friction modifier is 400-1500, and the molecular weight dispersion Mw / Mn of the friction modifier is 1.0-1.2.

[0012] Optionally, the number average molecular weight Mn of the friction modifier is 800-1200, and the molecular weight dispersion Mw / Mn of the friction modifier is 1.0-1.08.

[0013] On the other hand, the present application also provides a method for preparing the friction modifier as described above, comprising the following steps: mixing an imide compound, a metal cyanide, a halogenated phosphate compound, an auxiliary agent, and a solvent, reacting to obtain a crude product of the friction modifier, and purifying the crude product to obtain a friction modifier as shown in Formula I; the halogenated phosphate compound is shown in Formula II, and the imide compound is shown in Formula III.

[0014] Among them, R a Including one or more of alkanes, alkenes and their derivatives, R b It includes one or more alkanes, alkenes, and the formula -O-CH2CH2-COR', wherein -COR' is derived from a C2-C20 fatty acid, and X is selected from one or more of F, Cl, Br, and I.

[0015] Optionally, the metal cyanide comprises sodium cyanide.

[0016] Optionally, the imide compound is added dropwise to a solvent containing the metal cyanide at 0-4° C. to obtain a mixed solution after the addition of the imide compound is completed, and the mixed solution is reacted at 40-60° C. for 6-7 hours;

[0017] The halogenated phosphate compound and the auxiliary agent are added dropwise to the mixed solution at 0-4° C., and after the addition is complete, the mixture is reacted at 40-60° C. for 7-8 hours.

[0018] Optionally, the molar ratio of the imide compound, the metal cyanide, the halogenated phosphate compound and the auxiliary agent is (2-2.1):(2-2.1):1:(0.05-0.1).

[0019] Optionally, the auxiliary agent includes a phenolic polymerization inhibitor, and the phenolic polymerization inhibitor includes hydroquinone.

[0020] Optionally, the solvent includes one or more of tetrahydrofuran, diethyl ether and dioxane.

[0021] On the other hand, the present application also provides a lubricating oil comprising the friction modifier as described in any one of the above items or the friction modifier prepared by the method for preparing the friction modifier as described in any one of the above items.

[0022] Optionally, the static friction coefficient change rate of the friction characteristics test of the lubricating oil is less than 7%.

[0023] Optionally, the torque variation characteristic parameter of the lubricating oil in the NVH test is less than 10 N·m. Optionally, in the dynamic pressure-torque test, the torque variation characteristic parameter of the lubricating oil in the process of linear pressure variation from 0 to 12 bar is less than 2 N·m.

[0024] In this application, the phospholipid group of the friction modifier forms a polar clustering group with the imide structure, which improves the adsorption strength with the friction material. In addition, the chain structure on the phospholipid and the chain structure on the imide form a polymer film layer between the shaft teeth, which improves the friction buffering effect and long-term stability of the lubricant. In addition, the friction modifier has the properties of reducing wear, inhibiting copper corrosion, preventing rust, and emulsification stability. It is integrated with the additive system of existing lubricants, has little effect on other properties, and has good compatibility. It is used in new energy DHT electromechanical coupling transmission lubricants, has good low-temperature activity, can effectively solve the problem of dynamic jitter, and improve the problem of rapid decrease in static friction coefficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG1 is a graph showing the coefficient of kinetic friction of the lubricating oil of Comparative Example 1 on an SAE No. 2 friction tester;

[0026] FIG2 is a graph showing the static friction coefficient of the lubricating oil of Comparative Example 1 on an SAE No. 2 friction tester;

[0027] Figure 3 is the μ0 / μ of the lubricating oil of Example 1 on the SAE No.2 friction tester d performance diagram;

[0028] FIG4 is a graph showing the coefficient of kinetic friction of the lubricating oil of Example 1 on an SAE No. 2 friction tester;

[0029] FIG5 is a graph showing the static friction coefficient of the lubricating oil of Example 1 on an SAE No. 2 friction tester;

[0030] Figure 6 is the μ0 / μ of the lubricating oil of Example 1 on the SAE No.2 friction tester d performance diagram;

[0031] FIG7 is a diagram showing the jitter effect of the lubricating oil of Comparative Example 1 on a low-speed SAE No. 2 friction tester (rotation speed 20 r / min);

[0032] FIG8 is a diagram showing the vibration effect of the lubricating oil of Comparative Example 1 on a low-speed SAE No. 2 friction tester (rotation speed 100 r / min);

[0033] FIG9 is a diagram showing the vibration effect of the lubricating oil of Example 1 on a low-speed SAE No. 2 friction tester (rotation speed 20 r / min);

[0034] FIG10 is a diagram showing the vibration effect of the lubricating oil of Example 1 on a low-speed SAE No. 2 friction tester (rotation speed 100 r / min);

[0035] FIG11 is a diagram showing the torque jitter of the lubricating oil of Comparative Example 1 on a ZF dual-motor friction tester;

[0036] FIG12 is a diagram showing the torque jitter of the lubricating oil of Example 1 on a ZF dual-motor friction tester. DETAILED DESCRIPTION

[0037] In order to make the technical problems, technical solutions and beneficial effects solved by this application more clearly understood, this application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0038] The friction modifier provided in the embodiments of the present application has a structure as shown in Formula I:

[0039] Among them, R a Including one or more of alkanes, alkenes and their derivatives, R b It includes one or more alkanes, alkenes, and the formula -O-CH2CH2-COR', where -COR' is derived from a C2-C20 fatty acid.

[0040] In this embodiment, the phospholipid groups of the friction modifier form polar clustering groups with the imide structure, enhancing adsorption strength with the friction material. Furthermore, the chain structures of the phospholipids and the imide form a polymer film between the shaft teeth, enhancing the friction cushioning effect and long-term stability of the lubricant. This friction modifier also exhibits properties such as wear reduction, copper corrosion inhibition, rust prevention, and emulsion stability. It integrates well with existing lubricant additive systems, has minimal impact on other properties, and exhibits excellent compatibility. Used in new energy DHT electromechanical coupling transmission lubricants, it exhibits excellent low-temperature activity, effectively addressing dynamic vibration issues and improving the rapid decrease in the static friction coefficient.

[0041] In some embodiments, the friction modifier R a One selected from C1-C10 alkanes, C1-C10 alkenes and derivatives thereof, wherein R b is selected from one or more of C5-C30 alkanes, C5-C30 alkenes and -O-CH2CH2-COR', wherein -COR' is derived from a C2-20 fatty acid. a Selected from C2-C6 alkanes, said R b Selected from C20-C25 olefins.

[0042] In some embodiments, the friction modifier has a number average molecular weight (Mn) of 400-1500, and a molecular weight dispersion (Mw / Mn) of 1.0-1.2. Friction modifiers within this number average molecular weight and molecular weight dispersion range exhibit high friction cushioning and anti-shake effects. Specifically, Mw and Mn can be measured by any known method, typically by gel permeation chromatography (GPC).

[0043] In a preferred embodiment, the friction modifier has a number average molecular weight Mn of 800-1200 and a molecular weight dispersion Mw / Mn of 1.0-1.08. Within this molecular weight range, the phospholipid group and the imide structure form a polar clustering group, satisfying the structure shown in Formula I.

[0044] An embodiment of the present application further provides a method for preparing the friction modifier as described in the above embodiment, comprising the following steps:

[0045] Step 1: Mix an imide compound, a metal cyanide, a halogenated phosphate compound, an auxiliary agent, and a solvent to react to obtain a crude friction modifier. The halogenated phosphate compound is shown in Formula II, and the imide compound is shown in Formula III.

[0046] Among them, R a Including one or more of alkanes, alkenes and their derivatives, Rb It includes one or more alkanes, alkenes, and the formula -O-CH2CH2-COR', wherein -COR' is derived from a C2-C20 fatty acid, and X is selected from one or more of F, Cl, Br, and I.

[0047] In some embodiments, the halogenated phosphate compound is selected from dichlorophosphate compounds. Specifically, the dichlorophosphate compounds include but are not limited to one or more of methyl dichlorophosphate, ethyl dichlorophosphate, and butyl dichlorophosphate, and the imide compounds include but are not limited to one or more of 2-pentane-succinimide, 2-hexene-succinimide, 2-(ethoxypropionate) succinimide, and 2-pentacosyl-succinimide.

[0048] In some embodiments, mixing the imide compound, the metal cyanide, the halogenated phosphate compound, the auxiliary agent, and the solvent specifically comprises the following steps:

[0049] At 0-4° C., the imide compound is added dropwise to a solvent containing a metal cyanide to obtain a mixed solution, and the mixed solution is reacted at 40-60° C. for 6-7 hours;

[0050] The halogenated phosphate compound and the auxiliary agent are added dropwise to the mixed solution at 0-4° C., and after the addition is complete, the mixture is reacted at 40-60° C. for 7-8 hours.

[0051] In a preferred embodiment, the imide compound is added dropwise to a solvent containing a metal cyanide at 0° C. to obtain a mixed solution after the addition of the imide compound is completed, and the mixed solution is reacted at 50° C. for 6 hours;

[0052] The halogenated phosphate compound and the auxiliary agent were added dropwise to the mixed solution at 0° C., and after the addition was completed, the mixture was reacted at 50° C. for 8 hours.

[0053] In some embodiments, the metal cyanide includes but is not limited to sodium cyanide.

[0054] In some embodiments, the molar ratio of the imide compound, the metal cyanide, the halogenated phosphate compound, and the auxiliary agent is (2-2.1):(2-2.1):1:(0.05-0.1).

[0055] In some embodiments, the auxiliary agent includes a phenolic polymerization inhibitor, and the phenolic polymerization inhibitor includes hydroquinone, which prevents the halogenated phosphate compound from self-polymerizing.

[0056] In some embodiments, the solvent includes one or more of tetrahydrofuran, diethyl ether, and dioxane.

[0057] Step 2: purifying the crude product to obtain a friction modifier as shown in Formula I.

[0058] In some embodiments, the purification method uses column chromatography for separation and purification.

[0059] One embodiment of the present application further provides a lubricating oil, comprising the friction modifier as described in any one of the above items or the friction modifier prepared by the method for preparing the friction modifier as described in any one of the above items.

[0060] In some embodiments, based on 100% by mass of the lubricating oil, the content of the friction modifier is 0.2-0.4%.

[0061] In some embodiments, the static friction coefficient change rate of the lubricating oil friction characteristics test is less than 8%. The lubricating oil friction characteristics test is conducted in accordance with JASO M348 standard "Road Vehicle Automatic Transmission Fluid Friction Characteristics Test Method" for at least 10,000 cycles.

[0062] In some embodiments, the torque variation characteristic parameter of the lubricant during NVH testing is less than 10 N·m. The torque variation characteristic parameter refers to the torque variation of a friction plate coated with the lubricant at a predetermined speed difference during the NVH testing of the lubricant. Specifically, during the NVH testing of the lubricant, the torque variation of the friction plate coated with the lubricant at a speed difference of 20 rpm is less than 5 N·m, and the torque variation at a speed difference of 100 rpm is less than 10 N·m.

[0063] Specifically, the NVH test of the lubricating oil was performed on a low-speed SAE No. 2 friction tester.

[0064] In the dynamic pressure-torque test, the lubricant exhibited a torque variation characteristic parameter of less than 2 N·m during a linear pressure change from 0 to 12 bar. The dynamic pressure-torque test operates within a pressure range of 0-12 bar, with the friction plate speed differential varying from Δ20 r / min to Δ100 r / min. During the test, a speed differential, such as Δ20 r / min, is determined. The pressure is then controlled to increase from 0 bar to 12 bar and then decrease from 12 bar to 0 bar, thereby determining the lubricant's torque variation characteristic parameter under varying pressure and speed differential conditions.

[0065] Specifically, the dynamic pressure-torque test was performed on a ZF dual-motor tribometer.

[0066] The present application will be further described in detail below in conjunction with preferred embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application.

[0067] Preparation Example 1

[0068] The preparation method of the friction modifier is as follows: at 0°C, an imide compound is added dropwise to a tetrahydrofuran solvent containing sodium cyanide to obtain a mixed solution after the addition of the imide compound is completed, and the mixed solution is reacted at 50°C for 6 hours; at 0°C, the halogenated phosphate compound and an auxiliary agent are added dropwise to the mixed solution, and after the addition is completed, the mixture is reacted at 50°C for 8 hours; the solvent and the auxiliary agent are removed by rotary evaporation, and then 200 mL of ether is added and mixed and stirred to wash the unreacted monomer components in the product, and the process is repeated three times; after washing, the ether is removed by rotary evaporation, and then ethyl acetate is used as an eluent, and the product is purified by alumina column chromatography to obtain the friction modifier.

[0069] The molar ratio of the imide compound, the sodium cyanide, the halogenated phosphate compound and the auxiliary agent is 2:2:1:0.05. The halogenated phosphate compound is ethyl dichlorophosphate, and the imide compound is 2-(5-eicosenyl)-succinimide.

[0070] Preparation Example 2

[0071] The difference from Preparation Example 1 is that the imide compound is 2-pentacosyl-succinimide.

[0072] Preparation Example 3

[0073] The difference from Preparation Example 1 is that the imide compound is 2-(ethoxyeicosanoate)-succinimide.

[0074] Examples 1-3

[0075] Lubricating oils were prepared according to the ingredients and ratios shown in Table 1. The friction modifiers used in Examples 1-3 were the friction modifiers prepared in Preparation Examples 1-3, respectively.

[0076] Comparative Example 1

[0077] The difference from Example 1-3 is that the friction modifier is omitted, and the other ingredients and proportions are as shown in Table 1.

[0078] Table 1

[0079] In Table 1, the components except the friction modifier are described as follows:

[0080] Base oil: Choose the three types of base oil commonly used on the market, Yubase produced by South Korea's SK, GTL produced by the Netherlands Shell, or CTL produced by Sinopec, which are universal.

[0081] Viscosity Index Improvers: Finished oils may contain one or more viscosity index improvers, including but not limited to polymethacrylates, vinyl aromatic monomers, polyalphaolefins, polyisobutylene, hydrogenated styrene-butadiene copolymers, ethylene-propylene copolymers, and esterified copolymers of unsaturated carboxylic acids, anhydrides, or their derivatives. Example 1 and Comparative Example 1 utilize transmission viscosity improver ○RR5008.

[0082] Additives include dispersants, detergents, extreme pressure agents (typically containing boron and / or sulfur and / or phosphorus), antiwear agents, antioxidants (such as hindered phenols, amine antioxidants, or molybdenum compounds), corrosion inhibitors, friction modifiers, rubber swelling agents, and mixtures thereof. Example 1 and Comparative Example 1 employed the widely available commercial additive package HiTec® R3491.

[0083] Antifoaming agent and pour point depressant: The antifoaming agent is a copolymer of ethyl acrylate, 2-ethylhexyl acrylate and optionally vinyl acetate, or polydimethylsiloxane. The pour point depressant is polymethacrylate, polyacrylate or polyacrylamide.

[0084] The lubricating oils prepared in Comparative Example 1 and Examples 1-3 were subjected to performance testing, NVH testing, and dynamic pressure-torque testing, respectively.

[0085] (1) Friction property test: The lubricating oils of Comparative Example 1 and Examples 1-3 were tested on an SAE No. 2 friction tester according to the JASO M348 standard. The friction plate material was NW461E and the steel plate material was T903. 10,000 cycles were performed for an extended period of time. The dynamic friction coefficient μ d It refers to the friction coefficient when two contacting surfaces have a relative motion speed, representing the shift speed. μ0 refers to the friction coefficient measured at the end of the shift or the final friction coefficient when the friction plate surface speed is relatively low, that is, when the friction plate engagement is completed. It is the maximum dynamic friction coefficient when the speed is less than 200r / min, μ0 / μ d The ratio affects the shift quality. Static friction coefficient μ s Calculated based on the maximum torque value immediately after the start of dragging, it is the measured value at the moment when two stationary contact surfaces begin to slide relative to each other under load, representing the torque capacity. The test results are reported in Table 2. The test diagrams for Example 1 and Comparative Example 1 are shown in Figures 1 to 6.

[0086] Table 2

[0087] (2) Lubricant NVH Testing: The lubricants from Comparative Example 1 and Example 1 were tested for NVH on a low-speed SAE No. 2 friction tester. The friction plate material was BW4329, the steel plate material was SPCC-1B, the speed was constant at 20 or 100 r / min, and the oil temperature was 40°C. The results are shown in Figures 7-10, and the difference in vibration performance is clearly visible.

[0088] (3) Dynamic pressure-torque test: The lubricating oils of Comparative Example 1 and Example 1 were subjected to dynamic pressure-torque test of friction plates on a ZF dual-motor friction tester. The friction plate material was BW4329, the steel plate material was SPCC-1B, and the oil temperature was 40°C. The speed of one side of the dual motor was 1000 r / min, and the speed of the other side was 900 r / min in the first test, 950 r / min in the second test, and 980 r / min in the third test. The process of the pressure rising uniformly from 0 bar to 12 bar and then falling back to 0 bar formed three torque peaks with speed differences of Δ100 r / min, Δ50 r / min, and Δ20 r / min, respectively. The results are shown in Figures 11 and 12. The difference in the jitter can be clearly seen, which is consistent with the test results of low-speed SAE No. 2.

[0089] The test results of Example 2 are similar to those of Example 1, and the test chart and data thereof are not attached herewith.

[0090] As shown in Figures 1-6 and Table 2, the dynamic and static friction coefficients of the lubricating oil containing the friction modifier are lower than those of the lubricating oil without the friction modifier, and the rate of change of the static friction coefficient of Example 1 is significantly lower than that of Comparative Example 1. The torque changes in Figures 7-10 clearly show that the jitter of Example 1 is significantly improved compared to Comparative Example 1. The test charts in Figures 11 and 12 further verify the experimental results of Figures 7-10, confirming that the addition of the friction modifier of the present embodiment to the lubricating oil can effectively solve the problem of dynamic jitter.

[0091] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A friction modifier, characterized in that The structure of the friction modifier is shown in Formula I, Among them, R a Including one or more of alkanes, alkenes and their derivatives, R b It includes one or more alkanes, alkenes, and the formula -O-CH2CH2-COR', where -COR' is derived from a C2-C20 fatty acid.

2. The friction modifier according to claim 1, characterized in that The R a One selected from C1-C10 alkanes, C1-C10 alkenes and derivatives thereof.

3. The friction modifier according to claim 1, characterized in that The R b One or more selected from C5-C30 alkanes, C5-C30 alkenes and the formula -O-CH2CH2-COR', wherein -COR' is derived from a C2-20 fatty acid.

4. The friction modifier according to claim 1, characterized in that The number average molecular weight Mn of the friction modifier is 400-1500, and the molecular weight dispersion Mw / Mn of the friction modifier is 1.0-1.

2.

5. The friction modifier according to claim 4, characterized in that The number average molecular weight Mn of the friction modifier is 800-1200, and the molecular weight dispersion Mw / Mn of the friction modifier is 1.0-1.

08.

6. The method for preparing the friction modifier according to claims 1 to 5, characterized in that: The following steps are involved: An imide compound, an alkali metal cyanide, a halogenated phosphate compound, an auxiliary agent and a solvent are mixed and reacted to obtain a crude friction modifier product, and the crude product is purified to obtain a friction modifier as shown in Formula I; the halogenated phosphate compound is shown in Formula II, and the imide compound is shown in Formula III. Among them, R a Including one or more of alkanes, alkenes and their derivatives, R b It includes one or more alkanes, alkenes, and the formula -O-CH2CH2-COR', wherein -COR' is derived from C2-20 fatty acid, and X is selected from one or more of F, Cl, Br, and I.

7. The method for preparing a friction modifier according to claim 6, wherein: At 0-4° C., the imide compound is added dropwise to the solvent containing the metal cyanide to obtain a mixed solution, and the mixed solution is reacted at 40-60° C. for 6-7 hours; The halogenated phosphate compound is added dropwise to the mixed solution at 0-4° C. After the halogenated phosphate compound is added dropwise, the mixture is reacted at 40-60° C. for 7-8 hours.

8. The method for preparing a friction modifier according to claim 6, wherein: The metal cyanide includes sodium cyanide.

9. The method for preparing a friction modifier according to claim 6, wherein: The molar ratio of the imide compound, the metal cyanide, the halogenated phosphate compound and the auxiliary agent is (2-2.1):(2-2.1):1:(0.05-0.1).

10. The method for preparing a friction modifier according to claim 6, wherein: The auxiliary agent includes a phenolic polymerization inhibitor, and the phenolic polymerization inhibitor includes hydroquinone.

11. The method for preparing a friction modifier according to claim 6, wherein: The solvent includes one or more of tetrahydrofuran, diethyl ether and dioxane.

12. A lubricating oil, characterized in that: The friction modifier comprises the friction modifier according to any one of claims 1 to 5 or the friction modifier prepared by the preparation method of the friction modifier according to any one of claims 6 to 11.

13. The lubricating oil according to claim 12, characterized in that The static friction coefficient change rate of the lubricating oil in the friction characteristic test is less than 7%.

14. The lubricating oil according to claim 12, characterized in that The torque variation characteristic parameter of the NVH test of the lubricating oil is less than 10 N·m.

15. The lubricating oil according to claim 12, characterized in that In a dynamic pressure-torque test, the torque variation characteristic parameter of the lubricating oil during a linear pressure change of 0-12 bar is less than 2 N·m.

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