Low viscosity lubricating oil composition with improved durability and NVH performance

Abstract

The present invention provides a low viscosity lubricating oil composition having improved durability and NVH (noise, vibration, and vibration roughness) performance. The durability and NVH performance of the low-viscosity lubricating oil can be improved by appropriately combining the mineral oil and / or the synthetic oil with the viscosity index improver.

Description

Technical Field

[0001] This invention relates to a low-viscosity lubricating oil composition with improved durability and NVH (noise, vibration, and harshness) performance, wherein the durability and NVH performance can be improved by appropriately combining mineral oils and / or synthetic oils with viscosity index improvers. Background Technology

[0002] As extreme weather events related to climate change become more frequent worldwide, countries and alliances are working to curb climate change by announcing plans to reduce carbon emissions and achieve carbon neutrality. As part of this plan, the proportion of electric vehicles in new car sales is increasing to reduce carbon emissions in the transportation sector, and electric vehicle sales have recently seen rapid growth.

[0003] The design of electric vehicle drive systems is gradually shifting from the conventional separate motor and gearbox design to integrated motor and gearbox designs. Therefore, the performance requirements for lubricating oils, which must be compatible with all components in integrated systems, are higher than those for conventional separate systems. Since the lubricating oil used in conventional separate gearboxes is only applied to the reduction gears, extreme pressure performance and wear resistance are crucial for effective gear protection. However, in integrated systems, in addition to these properties, additional performance requirements are needed, such as motor cooling performance, material compatibility with electrical components, and reduced drag losses.

[0004] Reducing the viscosity of lubricating oil used in integrated motor gearbox components is a way to improve energy efficiency because it reduces the internal resistance of the motor, thereby reducing energy consumption due to friction, and the heat generated during motor operation is dissipated more effectively, thus improving drive efficiency. However, there are limitations: when adjusting to reduce viscosity, the lubricating oil film thickness, which is proportional to viscosity, becomes lower, which reduces durability and NVH performance.

[0005] Furthermore, additives added to liquid lubricating oils along with base oils to improve various properties (such as extreme pressure performance and durability, prevention of oil oxidation, prevention of impurity buildup, prevention of deposit formation, and reduction of friction) typically have high viscosity. Therefore, it is difficult to improve durability and NVH performance by adding large amounts of additives to low-viscosity oils. Consequently, it is necessary to develop a lubricating oil composition that can overcome these limitations and achieve improved energy efficiency even at low viscosity.

[0006] The descriptions in this background section are only provided as background information related to the present invention and do not constitute prior art. Summary of the Invention

[0007] This invention aims to address the problems encountered in the prior art. The object of this invention is to provide a lubricating oil composition that improves, in a balanced manner, the extreme pressure properties, wear resistance, cooling performance, and compatibility with electrical components required by conventional lubricating oil compositions.

[0008] Another object of the present invention is to provide a lubricating oil composition for use in integrated motor reducer components, thereby improving energy efficiency and preventing degradation of durability and NVH performance compared to conventional technologies.

[0009] The objectives of this invention are not limited to the foregoing. The objectives of this invention should be more clearly understood from the following description and achieved by the means and combinations thereof described in the claims.

[0010] One aspect of the present invention is to provide a lubricating oil composition comprising: a lubricating oil base oil including mineral oil, a viscosity index improver, and additives. Furthermore, the lubricating oil base oil may include mineral oil and synthetic oil.

[0011] In one embodiment, the lubricating oil composition may include 50 to 80 wt% mineral oil, 1 to 10 wt% viscosity index improver, and 10 to 20 wt% additives based on its total weight.

[0012] In addition, when the lubricating oil base oil of the lubricating oil composition includes mineral oil and synthetic oil, the lubricating oil composition may include 50 to 80 wt% mineral oil, 10 to 40 wt% synthetic oil, 1 to 10 wt% viscosity index improver and 8 to 20 wt% additives based on its total weight.

[0013] In one embodiment, the lubricating oil composition may have a kinematic viscosity in the range of 2.8 to 4.0 cSt at 100°C.

[0014] In one embodiment, the mineral oil may include highly refined mineral oil with an aromatic component content of 0.1 wt% or less.

[0015] In one embodiment, the mineral oil may have a kinematic viscosity in the range of 2.0 to 4.0 cSt at 100°C.

[0016] In one embodiment, the mineral oil has a viscosity index (VI) equal to or greater than 100.

[0017] In one embodiment, the synthetic oil may include polyalphaolefin (PAO) synthetic oil.

[0018] In one embodiment, the synthetic oil may have a kinematic viscosity in the range of 2.0 to 3.0 cSt at 100°C.

[0019] In one embodiment, the viscosity index improver may include poly(alkyl methacrylate).

[0020] In one embodiment, the weight-average molecular weight (Mw) of the viscosity index improver can be in the range of 10,000 to 50,000.

[0021] In one embodiment, the additive may include at least one of detergents, antioxidants, anti-wear agents, dispersants, friction modifiers, corrosion inhibitors, or combinations thereof.

[0022] Therefore, detergents may include at least one of sulfonate detergents, phenolic detergents, salicylate detergents, or combinations thereof.

[0023] In addition, antioxidants may include at least one of hindered phenols, aromatic amines, or combinations thereof.

[0024] In one embodiment, the lubricating oil composition may further include at least one of a pour point depressant, an antifoaming agent, or a combination thereof. Attached Figure Description

[0025] Figure 1 The diagram shows the analytical results of the lubricating oil compositions of Example 3 and Comparative Examples 6 to 8 using a miniature tractor unit (MTM). Detailed Implementation

[0026] The above and other objects, features, and advantages of the present invention will become clearer from the following embodiments, taken in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed herein and may be modified in different forms. These embodiments are provided to fully explain the invention and to fully convey the spirit of the invention to those skilled in the art.

[0027] Throughout the accompanying drawings, the same reference numerals refer to the same or similar elements. For clarity of the invention, the dimensions of the structures are depicted as larger than their actual dimensions. It should be understood that although terms such as "first," "second," etc., may be used herein to describe various elements, these elements are not limited by these terms. These terms are used only to distinguish one element from another. For example, a "first" element discussed below may be referred to as a "second" element without departing from the scope of the invention. Similarly, a "second" element may also be referred to as a "first" element. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form as well.

[0028] It should also be understood that when the terms "comprising," "including," "having," etc., are used in this specification, they specify the presence of the stated feature, integer, step, operation, element, component, or combination thereof, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof. Furthermore, it should be understood that when an element, such as a layer, film, region, or sheet, is referred to as being "on" another element, it can be directly located on the other element, or an intermediate element may exist therein. Similarly, when an element, such as a layer, film, region, or sheet, is referred to as being "below" another element, it can be directly located below the other element, or an intermediate element may exist therein.

[0029] Unless otherwise stated, all figures, values, and / or expressions used herein to represent the amounts of components, reaction conditions, polymer compositions, and mixtures should be considered approximate, including the uncertainties in measurement due to various influences inherent in obtaining these values, and should therefore be understood to be modified by the term "about" in all cases. Furthermore, when this specification discloses numerical ranges, the ranges are continuous and include all values ​​from the minimum to the maximum of the range, unless otherwise stated. Additionally, when such ranges involve integer values, all integers from the minimum to the maximum are included, unless otherwise stated.

[0030] In this specification, when describing the range of a variable, it should be understood that the variable includes all values, including the endpoints described within the range. For example, the range “5” to “10” should be understood to include any subranges, such as 6 to 10, 7 to 10, 6 to 9, 7 to 9, etc., as well as the individual values ​​of 5, 6, 7, 8, 9, and 10, and should also be understood to include any values ​​between valid integers within the range, such as 5.5, 6.5, 7.5, 5.5 to 8.5, 6.5 to 9, etc. Similarly, the range “10% to 30%” should be understood to include subranges, such as 10% to 15%, 12% to 18%, 20% to 30%, etc., as well as all integers, including 10%, 11%, 12%, 13%, etc., up to 30%, and should also be understood to include any values ​​between valid integers within the range, such as 10.5%, 15.5%, 25.5%, etc.

[0031] In this invention, each phrase such as “A or B”, “at least one of A and B”, “at least one of A or B”, “A, B or C”, “at least one of A, B and C”, “at least one of A, B or C”, and “at least one of A, B or C, or a combination thereof” may include any one or all possible combinations of items listed together in the corresponding phrase.

[0032] According to one aspect of the invention, the lubricating oil composition may include a lubricating oil base oil (including mineral oil and / or synthetic oil), a viscosity index improver, and additives. More specifically, the lubricating oil composition may include 50 to 80 wt% mineral oil, 1 to 10 wt% viscosity index improver, and 10 to 20 wt% additives based on its total weight. Furthermore, when the lubricating oil base oil of the lubricating oil composition includes both mineral oil and synthetic oil, the lubricating oil composition may include 50 to 80 wt% mineral oil, 10 to 40 wt% synthetic oil, 1 to 10 wt% viscosity index improver, and 8 to 20 wt% additives based on its total weight.

[0033] By combining the above components in appropriate amounts, the lubricating oil composition according to embodiments of the present invention can improve the NVH performance of vehicles when applied to vehicle components, particularly integrated motor reducer components installed in electric vehicles.

[0034] Furthermore, the kinematic viscosity of the electric vehicle lubricant composition can be related to the energy efficiency of the electric vehicle. Kinematic viscosity is a measure of the resistance of a fluid to flow over time under temperature conditions, particularly at temperatures equal to or above room temperature. Therefore, the lower the kinematic viscosity, the less friction in the lubricant composition, which can improve energy efficiency. For reference, when the lubricant composition according to embodiments of the present invention is applied to existing internal combustion engine components, the term "energy efficiency" mentioned above and as used below can be understood as "fuel efficiency".

[0035] In one embodiment, the lubricating oil composition may have a kinematic viscosity of 2.8 to 4.0 cSt at 100°C. Since the lubricating oil composition according to embodiments of the present invention has a kinematic viscosity of 2.8 to 4.0 cSt at 100°C, when applied to integrated motor reducer components, its internal resistance can be reduced, thereby reducing energy consumption and heat generated due to friction.

[0036] If the kinematic viscosity at 100°C is less than 2.8 cSt, when the lubricating oil composition is applied to components such as integrated motor gearboxes, the oil film may become too thin due to the low viscosity, resulting in poor extreme pressure performance. On the other hand, if the kinematic viscosity at 100°C exceeds 4.0 cSt, the effect on improving energy efficiency may be negligible compared to conventional lubricating oil compositions used in electric vehicles.

[0037] The components included in the lubricating oil composition are described in more detail below.

[0038] mineral oil

[0039] Mineral oil is a general term for oils obtained from mineral raw materials such as petroleum, coal, tar, and shale oil, and is commonly used as a lubricant to reduce friction between machine parts. The mineral oil according to embodiments of the present invention is not particularly limited, as long as it is generally used in lubricant compositions. However, including highly refined mineral oils is advantageous. Highly refined mineral oils can be defined as mineral oils refined to have an aromatic component content of 0.1 wt% or less.

[0040] Aromatic components in mineral oils are easily oxidized at high temperatures. Therefore, when using highly refined mineral oils with low aromatic component content as described in this invention, the lubricating oil composition can exhibit excellent oxidative stability. Furthermore, since impurities are typically removed during the manufacturing process of highly refined mineral oils, their performance can be improved and their service life extended.

[0041] Furthermore, mineral oils with a viscosity index (VI) of 100 or higher can be used. The lubricating oil composition according to embodiments of the present invention can exhibit excellent thermal stability because it comprises a mineral oil with a viscosity index of 100 or higher.

[0042] The term "viscosity index" indicates the relationship between the viscosity of an oil (such as mineral oil, synthetic oil, etc.) and temperature. A higher value indicates less viscosity change due to temperature fluctuations. Generally, a higher viscosity index indicates greater thermal stability of the oil, which can increase its lifespan and usability. The viscosity index can be obtained using formulas known in the art or procedures that reflect such formulas.

[0043] In one embodiment, the lubricating oil composition may include a mineral oil with a kinematic viscosity of 2.0 to 4.0 cSt at 100°C. According to embodiments of the present invention, when the lubricating oil composition includes 50 to 80 wt% of a mineral oil with a kinematic viscosity of 2.0 to 4.0 cSt at 100°C, a kinematic viscosity of 2.8 to 4.0 cSt at 100°C can be achieved.

[0044] Synthetic oil

[0045] Synthetic oils are oils composed of artificially modified or synthesized compounds, which can be made from crude oil and chemically modified petroleum components or other raw materials.

[0046] The synthetic oils described in this invention can be used without particular limitation, as long as they are commonly used in lubricating oil compositions. For example, synthetic hydrocarbon oils, ester oils, phenyl ethers, polyethylene glycol, etc., can be used. For example, polyalphaolefin (PAO) synthetic oils can be used.

[0047] Polyalphaolefin synthetic oils are a type of synthetic oil made from the oligomerization of linear alpha olefins produced during the polymerization of ethylene, and are widely used in automotive and industrial lubricants.

[0048] The polyalphaolefin synthetic oil according to embodiments of the present invention consists only of isoparaffins, and therefore has a higher viscosity index than mineral oil, excellent low-temperature fluidity, narrow molecular weight distribution, low evaporation loss, and excellent thermal oxidation stability and friction properties.

[0049] The lubricating oil composition according to embodiments of the present invention, due to the use of a lubricating oil base oil including highly refined mineral oil and polyalphaolefin synthetic oil, can exhibit excellent frictional properties, thereby achieving the effect of improving the energy efficiency and NVH performance of vehicles using the lubricating oil composition.

[0050] In one embodiment, the lubricating oil composition may include a synthetic oil with a kinematic viscosity of 2.0 to 3.0 cSt at 100°C. According to embodiments of the present invention, the lubricating oil composition, when comprising 10 to 40 wt% of a synthetic oil with a kinematic viscosity of 2.0 to 3.0 cSt at 100°C, can achieve a kinematic viscosity of 2.8 to 4.0 cSt at 100°C.

[0051] Viscosity index improver

[0052] Adding viscosity index improvers improves the viscosity index of the lubricating oil composition, thereby increasing the viscosity index of the lubricating oil composition, reducing low-temperature viscosity, and improving energy efficiency.

[0053] When viscosity index improvers are added to lubricating oil compositions, the degree of improvement in viscosity index may be proportional to the polarity of the polymer used as the viscosity index improver. However, since the solubility of the polymer in the lubricating oil composition decreases with increasing polymer polarity, it is important to optimize both viscosity index and solubility by increasing the polarity of the polymer within the solubility range of the viscosity index improver.

[0054] Furthermore, the viscosity index increases proportionally to the molecular weight of the viscosity index improver, but extreme pressure performance is often inversely proportional to its molecular weight. Therefore, optimizing the molecular weight can improve the viscosity index and extreme pressure performance of the lubricating oil composition.

[0055] In one embodiment, the viscosity index improver according to embodiments of the present invention includes olefin copolymers, hydrogenated styrene-diene compounds, and poly(alkyl methacrylate). For example, the viscosity index improver includes poly(alkyl methacrylate).

[0056] Viscosity index improvers, including those made of poly(alkyl methacrylate), exhibit excellent low-temperature performance and shear stability. Specifically, due to the advantage of a high viscosity index, a certain oil film can be formed to prevent wear of integrated motor gearbox components at high temperatures, and the energy efficiency of vehicles can be improved by reducing the viscosity of the lubricating oil composition at low temperatures. Furthermore, due to excellent shear stability, the viscosity index improver can be prevented from cracking during prolonged use under harsh conditions, thereby improving durability and lifespan.

[0057] Furthermore, the viscosity index improver according to embodiments of the present invention improves extreme pressure performance by optimizing the polarity and molecular weight of the polymer, and the weight-average molecular weight (Mw) of the viscosity index improver can be in the range of 10,000 to 50,000 g / mol. If the weight-average molecular weight of the viscosity index improver exceeds 50,000 g / mol, the durability of the lubricating oil composition may also decrease due to the decline in extreme pressure performance.

[0058] The lubricating oil composition according to embodiments of the present invention includes 1 to 10 wt% of a viscosity index improver, which comprises poly(alkyl methacrylate). If the amount of the viscosity index improver is less than 1 wt%, the viscosity index may be low, thereby reducing frictional performance, wear performance, and further reducing energy efficiency. On the other hand, if the amount of the viscosity index improver exceeds 10 wt%, the viscosity may become too high due to thickening, which may reduce energy efficiency and may cause the viscosity index improver to break down due to shear.

[0059] additive

[0060] The lubricating oil composition according to embodiments of the present invention includes additives to improve its performance. The use of additives is not particularly limited, as long as they are generally used in the art to improve the performance of the lubricating oil composition, and may include, for example, at least one of detergents, antioxidants, anti-wear agents, dispersants, friction modifiers, corrosion inhibitors, or combinations thereof (e.g., any one selected from detergents, antioxidants, anti-wear agents, dispersants, friction modifiers, corrosion inhibitors, and combinations thereof). For example, the additives are used in packaged form, wherein two or more selected from detergents, antioxidants, anti-wear agents, dispersants, friction modifiers, and corrosion inhibitors are mixed and combined in a predetermined proportion.

[0061] Furthermore, the amount of additive added may correspond to wt% of the remaining amount of lubricating oil base oil and viscosity index improver in the total weight of the lubricating oil composition after the addition. For example, the lubricating oil composition may include 8 wt% to 40 wt%, 10 wt% to 40 wt%, 8 wt% to 20 wt%, or 10 wt% to 20 wt% of additives.

[0062] When deposits are formed due to oxidation of the lubricating oil composition, the detergent is used to inhibit the growth of the deposits and may include at least one of, for example, sulfonate detergents, phenolic detergents, salicylate detergents, or combinations thereof (e.g., selected from any one of sulfonate detergents, phenolic detergents, salicylate detergents, or combinations thereof).

[0063] Specifically, sulfonate detergents may include highly alkaline calcium sulfonate, magnesium sulfonate, barium sulfonate, etc., while phenolate detergents may include calcium phenolate, sodium phenolate, barium phenolate, etc. Furthermore, salicylate detergents may include calcium salicylate, etc.

[0064] Antioxidants are used to prevent lubricating oil compositions from reacting with oxygen in the air to produce corrosive acids or sludge. Antioxidants are broadly classified as chain reaction terminators, peroxide decomposers, and inactivators. Examples of chain reaction terminators can include hindered phenols, such as 2,6-di-tert-butyl-p-cresol, or aromatic amines, such as dioctyldiphenylamine and phenyl-α-naphthylane. For example, 2,6-di-tert-butyl-p-cresol is used.

[0065] Anti-wear agents are additives that prevent wear by adsorbing polar organic compounds onto a metal surface and reacting with it to form a solid lubricating film. Anti-wear agents include, for example, organophosphorus compounds and reactive sulfur compounds. For example, organophosphorus anti-wear agents are used. Reactive sulfur anti-wear agents, when dissolved in a lubricating oil composition, pose a risk of corrosion to non-ferrous metals such as copper, brass, and bronze due to the dissolved sulfur.

[0066] Dispersants can be used to disperse sludge that may appear in lubricating oil compositions and to uniformly disperse soot or other small insoluble particles in the lubricating oil composition, inhibiting the formation of sludge deposits and neutralizing acids. When the dispersants of the present invention are used as a mixture of low molecular weight dispersants and high molecular weight dispersants, the dispersion of by-products can be improved.

[0067] Friction modifiers are additives that improve lubrication performance by imparting a low coefficient of friction during sliding between metals. According to embodiments of the present invention, the additive may include alcohol-based friction modifiers to improve friction reduction performance at low temperatures.

[0068] Corrosion inhibitors are additives that inhibit rusting caused by oxygen and water in the air, and can be designed to optimize corrosion protection when used in mixtures of inactive sulfur-based and non-sulfur-based corrosion inhibitors.

[0069] Furthermore, the lubricating oil composition according to embodiments of the present invention may also include at least one of pour point depressants, defoamers, or combinations thereof (e.g., any one selected from pour point depressants, defoamers, or combinations thereof).

[0070] Pour point depressants are additives that lower the pour point. When lubricating oil forms wax at low temperatures, the pour point depressant adsorbs onto the wax to prevent it from solidifying, thereby lowering the pour point of the lubricating oil composition. Any pour point depressant commonly used in the art can be used.

[0071] In addition, defoamers can be used to suppress foaming by altering the surface tension of the lubricating oil composition. Any defoamer commonly used in the art can be used.

[0072] Therefore, the lubricating oil composition according to embodiments of the present invention is a low-viscosity lubricating oil with a kinematic viscosity of 2.8 to 4.0 cSt at 10°C. However, by appropriately combining highly refined mineral oil and polyalphaolefin synthetic oil and adding poly(alkyl methacrylate) with an appropriate molecular weight as a viscosity index improver, it is possible to prevent the reduction of the durability and NVH performance of the low-viscosity lubricating oil.

[0073] Furthermore, the lubricating oil composition according to embodiments of the present invention can not only improve the extreme pressure performance and wear resistance required by conventional lubricating oil compositions in a balanced manner, but also improve the cooling performance, compatibility with electrical components, etc. in a balanced manner.

[0074] A better understanding of the present invention can be obtained through the following embodiments and comparative examples. However, these embodiments should not be construed as limiting the technical spirit of the present invention.

[0075] Examples 1 to 3 and Comparative Examples 1 to 8

[0076] To prepare the low-viscosity lubricating oil composition according to an embodiment of the present invention, individual lubricating oil compositions were obtained by mixing the components shown in the amounts shown in Tables 1 and 2 below. Examples 1 to 3 are shown in Table 1 below, and Comparative Examples 1 to 8 are shown in Table 2 below. The individual components used herein are as follows. For reference, additives were added to the lubricating oil composition to make the total proportion of the components 100 wt%.

[0077] [Components]

[0078] 1) The mineral oil used is a highly refined mineral oil commercially available from Ssangyong Refining Co., Ltd. (S-OIL) in South Korea.

[0079] aramcoULTRA 2: A highly refined mineral oil with a kinematic viscosity of approximately 2 cSt at 100°C.

[0080] aramcoULTRA 3: Highly refined mineral oil with a kinematic viscosity of approximately 3 cSt at 100°C.

[0081] aramcoULTRA 4: Highly refined mineral oil with a kinematic viscosity of approximately 4 cSt at 100°C.

[0082] 2) The synthetic oils used are commercially available polyalphaolefin synthetic oils from ExxonMobil and INEOS.

[0083] PAO 2: Polyalphaolefin synthetic oil with a kinematic viscosity of approximately 2 cSt at 100°C.

[0084] PAO 3.5: Polyalphaolefin synthetic oil with a kinematic viscosity of approximately 3.5 cSt at 100°C.

[0085] PAO 4: Polyalphaolefin synthetic oil with a kinematic viscosity of approximately 4 cSt at 100°C.

[0086] 3) The viscosity index improver used is a commercially available modified poly(alkyl methacrylate) viscosity index improver (VISCOPLEX series) from Evonik.

[0087] Low molecular weight: polymethacrylate with a weight average molecular weight (Mw) of 10,000 to 50,000 g / mol, SSI (shear stability index) 9 (KRL shear stability tester, 20 hours (test standard: CEC L-45-A-99)).

[0088] High molecular weight: Polymethacrylate with a weight-average molecular weight (Mw) greater than 50,000 g / mol, SSI (shear stability index) 26 (KRL shear stability tester, 20 hours (test standard: CEC L-45-A-99)).

[0089] 4) The additives used are additive packages for lubricating oils for integrated motor gearboxes from INFINIUM (including detergents, friction modifiers, anti-wear agents, antioxidants, etc.).

[0090] 5) The pour point depressant used is Evonik's commercially available PAMA (poly(alkyl methacrylate)) type pour point depressant.

[0091] 6) The defoamer used is a commercially available silicone oil-based defoamer from Evonik.

[0092] [Table 1]

[0093]

[0094] [Table 2]

[0095]

[0096]

[0097] Test case

[0098] To evaluate the required extreme pressure performance, wear resistance, cooling performance, and compatibility with electrical components, various performance tests were performed on Examples 1 to 3 and Comparative Examples 1 to 8. The performance test methods are as follows, and the test results are shown in Tables 3 to 7 below. Figure 1 The results are shown in Table 7. For reference, Table 7 presents the results of the comparative examples described in Tables 4 to 6 in one table.

[0099] [Testing Method]

[0100] The kinematic viscosity of the lubricating oil composition at 40°C and at 100°C was determined according to ASTM D445.

[0101] The low-temperature viscosity of the lubricating oil composition at -40°C was determined according to ASTM D2983 (Brookfield Low-Temperature Viscosity).

[0102] The wear resistance of the lubricating oil composition is determined according to ASTM D5182 (Wear Load Test Method, FZG). und Getriebebau) visual method) determination.

[0103] The extreme pressure properties of the lubricating oil composition were determined according to ASTM D2783 (4-ball).

[0104] The frictional properties of the lubricating oil composition were determined using an MTM (micro traction machine) at 40°C and 30% SRR (slip rolling ratio).

[0105] The transfer efficiency of the lubricating oil composition was determined using an electric force gauge.

[0106] [Table 3]

[0107]

[0108]

[0109] [Table 4]

[0110]

[0111] [Table 5]

[0112]

[0113] [Table 6]

[0114]

[0115] [Table 7]

[0116]

[0117] Comparing the results of Example 1 with those of Comparative Examples 1 to 3 shown in Table 4, it can be confirmed that the lower the kinematic viscosity at 100°C, the better the transfer efficiency.

[0118] Furthermore, Comparative Example 2, which contains some PAO, has a slightly better transfer efficiency than Comparative Example 3, which does not contain PAO and has a lower kinematic viscosity, indicating that adding PAO can effectively improve energy efficiency due to its excellent frictional properties.

[0119] The lower the viscosity, the lower the extreme pressure performance as determined by the four-ball BP test. Comparative Example 4, with a kinematic viscosity of 2.781 cSt at 100°C, is expected to improve energy efficiency due to its low kinematic viscosity, but its extreme pressure performance level is lower than that of Comparative Example 1. Therefore, it is confirmed that a viscosity of approximately 2.8 to 4.0 cSt is suitable for improving energy efficiency and maintaining durability.

[0120] When comparing the kinematic viscosity, viscosity index, and abrasion resistance of Example 2 and Comparative Example 5 in Table 5, it was confirmed that the use of poly(alkyl methacrylate) (low molecular weight polymethacrylate) with a molecular weight of 10,000 to 50,000 as a viscosity index improver exhibited excellent durability.

[0121] In addition, refer to Table 6 and Figure 1 The results show the frictional properties of the lubricating oil compositions of Examples 3 and Comparative Examples 6 to 8, which were mixed under the condition of maintaining the same kinematic viscosity at 100°C. Example 3, which used PAO 2 as a polyalphaolefin synthetic oil, had the best frictional properties.

[0122] In Comparative Example 6, which used only highly refined mineral oil, the frictional properties were poor, which was detrimental to NVH performance. Therefore, it was necessary to use a polyalphaolefin synthetic oil with excellent frictional properties. Furthermore, referring to the results of Examples 3 and Comparative Examples 7 and 8, when a product with a kinematic viscosity of 2 cSt at 100°C was used as the polyalphaolefin synthetic oil, the frictional properties were superior compared to products with kinematic viscosities of 3.5 and 4 cSt.

[0123] As can be seen from the above, the lubricating oil composition according to the embodiments of the present invention is a low-viscosity lubricating oil with a kinematic viscosity of 2.8 to 4.0 cSt at 100°C. However, by appropriately combining highly refined mineral oil and polyalphaolefin synthetic oil and adding poly(alkyl methacrylate) with an appropriate molecular weight as a viscosity index improver, the durability and NVH performance of the low-viscosity lubricating oil can be prevented from decreasing.

[0124] The low-viscosity lubricating oil composition according to embodiments of the present invention can reduce energy consumption caused by friction by reducing the internal resistance of the motor, and improve drive efficiency by more effectively dissipating the heat generated during generator operation, thereby ultimately improving energy efficiency.

[0125] The effects of this invention are not limited to those described above. It should be understood that the effects of this invention include all effects that can be inferred from the description of this invention.

[0126] Since embodiments of the present invention have been described above, those skilled in the art should understand that various modifications and alterations can be made by changing, deleting, or adding components without departing from the scope and spirit of the present invention as described in the claims, and such modifications and alterations should also be considered to be included within the scope of the present invention.

Claims

1. A lubricating oil composition, the lubricating oil composition comprising: a lubricating oil base oil including a mineral oil; a viscosity index improver; and an additive.

2. The lubricating oil composition of claim 1, the lubricating oil composition comprising, based on the total weight of the lubricating oil composition: 50 to 80 wt% of the mineral oil; 1 to 10 wt% of the viscosity index improver; and 10 to 20 wt% of the additive.

3. The lubricating oil composition of claim 1, wherein the lubricating oil base oil includes the mineral oil and a synthetic oil.

4. The lubricating oil composition of claim 3, the lubricating oil composition comprising, based on the total weight of the lubricating oil composition: 50 to 80 wt% of the mineral oil; 10 to 40 wt% of the synthetic oil; 1 to 10 wt% of the viscosity index improver; and 9 to 20 wt% of the additive.

5. The lubricating oil composition of claim 3, wherein the synthetic oil includes a polyalphaolefin (PAO) type synthetic oil.

6. The lubricating oil composition of claim 3, wherein the synthetic oil has a kinematic viscosity in the range of 2.0 to 3.0 cSt at 100 °C.

7. The lubricating oil composition of claim 1, wherein the lubricating oil composition has a kinematic viscosity in the range of 2.8 to 4.0 cSt at 100 °C.

8. The lubricating oil composition of claim 1, wherein the mineral oil includes a highly refined mineral oil having an aromatic component content of 0.1 wt% or less.

9. The lubricating oil composition of claim 1, wherein the mineral oil has a kinematic viscosity in the range of 2.0 to 4.0 cSt at 100 °C.

10. The lubricating oil composition of claim 1, wherein the mineral oil has a viscosity index (VI) equal to or greater than 100.

11. The lubricating oil composition of claim 1, wherein the viscosity index improver includes a poly(alkyl methacrylate).

12. The lubricating oil composition of claim 1, wherein the viscosity index improver has a weight average molecular weight (Mw) in the range of 10,000 to 50,000 g / mol.

13. The lubricating oil composition of claim 1, wherein the additive includes at least one of a detergent, an antioxidant, an anti-wear agent, a dispersant, a friction modifier, a corrosion inhibitor, or a combination thereof.

14. The lubricating oil composition of claim 13, wherein the detergent includes at least one of a sulfonate detergent, a phenate detergent, a salicylate detergent, or a combination thereof.

15. The lubricating oil composition of claim 13, wherein the antioxidant includes at least one of a hindered phenol, an aromatic amine, or a combination thereof.

16. The lubricating oil composition of claim 1, wherein the lubricating oil composition further includes at least one of a pour point depressant, an anti-foam agent, or a combination thereof.

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