Patent Application
20250122441
This application claims priority to and the benefit of Korean Patent Application No. 2023-0136851, filed on Oct. 13, 2023, the disclosure of which is incorporated herein by reference in its entirety.
The present invention relates to an oil composition for automotive parts, and more specifically, to an oil composition with improved load-carrying capacity and wear resistance, which can be applied inside power steering gearboxes.
Since noise and vibrations from automobiles have a negative impact on the performance of automotive parts and cause fatigue to passengers, research is being continuously conducted to reduce noise and vibrations. In general, grease or lubricating oil is used to reduce noise caused by friction between automobile parts.
Recently, electric power steering systems are being widely applied as a vehicle steering device to change a steering force depending on the driving speed. The electric power steering system supplements steering power with the rotational force of the motor and includes an MDPS column part where the driver provides steering inputs, a motor that generates power for steering, an ECU that receives vehicle speed inputs and controls the operation of the motor, and a worm wheel part that is mounted on the output shaft of the motor and transmits a steering force to a steering gearbox, and the steering gearbox connected to the output shaft of the worm wheel part with a universal joint.
The steering gearbox includes a steering gear part and a support yoke part, but there is a problem that when the steering wheel is steered, stick-slip noise is generated due to excessive friction between the rack bar of the steering gearbox and the support yoke of the steering gear yoke part. In other words, due to the excessive support load of the support yoke on the rack bar, noise and vibrations are generated by excessive friction between the rack bar and the support yoke during steering.
To solve the above problem, there is a need to develop an oil composition with high (i.e., excellent) wear resistance and load-carrying capacity, which can be applied to the support yoke part of power steering gearbox and maintain lubricating performance in various temperature and humidity environments, and extreme pressure conditions.
The present invention is directed to providing an oil composition for automotive parts with improved load-carrying capacity, wear resistance, and corrosion properties.
The present invention is also directed to providing an oil composition which can effectively prevent vibrations and noise caused by friction at the support yoke of power steering gearbox in the automotive steering system.
This Summary is provided to introduce a selection of concepts in simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
In a general aspect of the disclosure, An oil composition for power steering, includes: a) 75 to 85 weight percent (wt %) of a paraffinic base oil; b) 5 to 15 wt % of a dioctyl adipate plasticizer; c) 1 to 5 wt % of a polymethacrylate viscosity modifier; d) 0.01 to 1 wt % of an overbased calcium sulfonate detergent/dispersant; and e) 1 to 5 wt % of a load-carrying and wear resistant additive package.
The load-carrying and wear resistant additive package may include at least one additive selected from the group consisting of e1) thiophene, tetrahydro 1,1-dioxide, and 3-(C9-11-isoalkyloxy) derivatives, e2) 1-(tert-dodecylthio)propan-2-ol, and e3) 1,3,4-thiadiazolidine-2,5-dithione.
The paraffinic base oil may include a hydrotreated heavy paraffinic distillate.
The paraffinic base oil may include a mixture of a first base oil and a second base oil in a mixing ratio of 6:4 to 8:2, wherein the first base oil may have: a specific gravity of 0.83 to 0.84; a kinematic viscosity of 4 cSt to 5 cSt, at a temperature of 100° C.;
The plasticizer may have: a specific gravity of 0.92 to 0.93; a kinematic viscosity of 7.5 cSt to 8.5 cSt, at a temperature of 40° C.; and a saponification value of 299 to 305.
The viscosity modifier may have: a specific gravity of 0.875 to 0.905; and a kinematic viscosity of 650 cSt to 750 cSt, at a temperature of 100° C.
The overbased calcium sulfonate detergent/dispersant may have: a kinematic viscosity of 50 cSt to 100 cSt at a temperature of 100° C.; and a total base number (TBN) of 290 or more.
The oil composition may have a load-carrying capacity of 200 kgf or more, corresponding to a measurement of the load-carrying capacity in accordance with an ASTM D 2783 Standard test method.
The ASTM D 2783 Standard test method may include a four-ball load carrying capacity test.
The oil composition may have a wear resistance of 0.4 mm or less, corresponding to a measurement of the wear resistance in accordance with an ASTM D 2783 Standard test.
The oil composition may have a corrosion resistance rating of Grade 1a, corresponding to a measurement of corrosion resistance in accordance with an ASTM D 130 Standard test.
The oil composition may lubricate a power steering gearbox of a vehicle.
The oil composition may have an aniline point of 90° C. or higher, corresponding to a measurement of the aniline point in accordance with an ASTM D 61 Standard test method.
Hereinafter, the present invention will be described in more detail with reference to embodiments and drawings. However, the following embodiments are provided as examples to aid understanding of the present invention, and the scope of the present invention is not limited thereto. The present invention may be subject to various changes and may be implemented in various forms, and should be understood to include all changes, equivalents, and substitutes included in the spirit and technical scope of the present invention.
The terms used in this application are only used to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the term “include” or “have” is intended to designate the presence of features, numbers, steps, operations, elements, parts, or combinations thereof described herein, and it should be understood that it does not exclude in advance the possibility of the presence or addition of other features, numbers, steps, operations, elements, parts, or combinations thereof.
Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by those skilled in the art to which the present invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related technology, and unless explicitly defined herein, they are not to be interpreted in an idealistic or overly formal sense.
The oil composition for power steering according to an embodiment includes a base oil, a plasticizer, a viscosity modifier, a detergent/dispersant, and a load-carrying and wear resistant additive package. The oil composition for power steering may further include a dye if necessary.
More specifically, the oil composition for power steering, in weight percent (wt %), may include: a) 75 to 85 wt % of a paraffinic base oil; b) 5 to 15 wt % of a dioctyl adipate plasticizer; c) 1 to 5 wt % of a polymethacrylate viscosity modifier; d) 0.01 to 1 wt % of an overbased calcium sulfonate detergent/dispersant; and e) 1 to 5 wt % of a load-carrying and wear resistant additive package.
The base oil accounts for 75 wt % to 85 wt % of the oil composition for power steering. Distillates (petroleum) hydrotreated heavy paraffinic may be used as the base oil.
According to an embodiment, the paraffinic base oil may be used by mixing two types of base oils with different physical properties. For example, a first base oil may be a paraffinic distillate with a specific gravity of 0.83 to 0.84, a 100° C. kinematic viscosity, in centistokes (cSt), of 4 cSt to 5 cSt, a viscosity index of 120 or higher and a flash point of 210° C. or higher, and a second base oil may be a paraffinic distillate with a specific gravity of 0.84 to 0.85, a 100° C. kinematic viscosity of 8 cSt to 9 cSt, a viscosity index of 130° C. or higher, and a flash point of 230° C. or higher.
The first base oil and the second base oil may be mixed and used at a mixing ratio of 6:4 to 8:2, and the mixing ratio of 7:3 is preferred because appropriate viscosity and lubricity may be maintained.
The oil composition for power steering may include dioctyl adipate as a plasticizer that can improve oiliness. The plasticizer may have a specific gravity of 0.92 to 0.93 and a 40° C. kinematic viscosity of 7.5 cSt to 8.5 cSt. The plasticizer preferably has a saponification value in the range of 299 to 305.
In the oil composition for power steering, polymethacrylate, that is, a methacrylate copolymer, may be used as a viscosity modifier. The viscosity modifier preferably has a specific gravity of 0.875 to 0.905 and a 100° C. kinematic viscosity of 650 cSt to 750 cSt.
In the oil composition for power steering, an overbased calcium sulfonate may be used as a detergent/dispersant. The detergent/dispersant preferably has a 100° C. kinematic viscosity of 50 cSt to 100 cSt and a total base number (TBN) of 290 or more.
The oil composition for power steering may include an additive package to improve corrosion resistance, load-carrying capacity, and wear resistance. The additive package includes one or more additives selected from thiophene, tetrahydro 1,1-dioxide, and 3-(C9-11-isoalkyloxy) derivatives (C10-rich), 1-(tert-dodecylthio)propan-2-ol), and 1,3,4-thiadiazolidine-2,5-dithione (reaction products with hydrogen peroxide and tert-nonanethiol).
In a specific example, based on the total weight of the additive package, e1) 10 to 20 wt % of thiophene, tetrahydro 1,1-dioxide, and 3-(C9-11-isoalkyloxy) derivatives, e2) 1 to 10 wt % of 1-(tert-dodecylthio)propan-2-ol, and e3) 1 to 5 wt % of 1,3,4-thiadiazolidin-2,5-dithione may be included. Within this additive mixing ratio range, the corrosion resistance, load-carrying capacity, and wear resistance of the oil composition may be significantly improved, which may be confirmed through the following experimental examples.
The additive package may further include alcohols such as dicocoalkylamine, substituted or unsubstituted alkanediols having 1 to 4 carbon atoms, and substituted or unsubstituted alkanols having 2 to 5 carbon atoms, and it may be a mixture of a mineral oil and a paraffinic base oil.
The additive package preferably includes, based on the total weight of the additive package, 0.1 to 1 wt % of dicocoalkylamine, 1 to 5 wt % of substituted or unsubstituted alkanediol having 1 to 4 carbon atoms, and 0.1 to 1 wt % of substituted or unsubstituted alkanol having 2 to 5 carbon atoms, and it may further include 10 to 20 wt % of mineral oil and 10 to 20 wt % of paraffinic base oil (distillates (petroleum), hydrotreated light paraffinic).
The oil composition for power steering according to an embodiment has a four-ball load-carrying capacity evaluation result of 200 kilogram-force (kgf) or more according to the ASTM D 2783 standard, and from this result, it can be confirmed that the oil composition has a very high (i.e., excellent) load-carrying capacity, that is, extreme pressure resistance.
The oil composition for power steering according to an embodiment has a four-ball wear resistance evaluation result of 0.4 mm or less according to the ASTM D 4172 standard, and from this result, it can be confirmed that the oil composition has very high (i.e., excellent) wear resistance.
In addition, the oil composition for power steering according to an embodiment has a corrosion resistance evaluation result of Grade 1a according to the ASTM D 130 standard, and it can be confirmed that the effect of preventing corrosion is also superior (i.e., excellent).
Base oils and additives were mixed according to the compositions in Table 1 and Table 2 below.
Distillates (petroleum), hydrotreated heavy paraffinic, was used as the base oil for the oil composition for power steering, and first and second base oils with the physical properties shown in Table 1 below were mixed at a weight ratio of 7:3.
An additive package was prepared to prevent oxidation and improve the wear resistance and extreme pressure properties of the oil composition for power steering.
Specifically, the additive package includes e1) thiophene, tetrahydro 1,1-dioxide, and 3-(C9-11-isoalkyloxy) derivatives, e2) 1-(tert-dodecylthio)propan-2-ol, e3) 1,3,4-thiadiazolidine-2,5-dithione, e4) a Cr to 04 alkanediol, e5) a 02 to 05 alkanol, e6) dicocoalkylamine, e7) 1H-imidazole-1-ethanol and 2-(8-heptadecenyl)-4,5-dihydro, e8) a mineral oil, and e9) a paraffinic base oil, and the content is as shown in Table 2 below.
After preparing the base oil and the additive, an oil composition for power steering was prepared by heating and mixing components as shown in Table 3 below.
The physical properties and performance of the conventionally used oil composition and the oil composition according to the present invention were compared. The specific composition of the oil composition according to Comparative Example is shown in Table 4 below.
The physical properties of oil compositions for power steering prepared according to the above example and comparative example were measured using the following test methods.
Red dye was used to prevent mixing with other oils, and the oil used in Comparative Example was light yellow.
Specific gravity (=oil density/water density) was measured according to the ASTM D 1298 standard in order to check whether it is a specified lubricant or whether foreign substances are mixed, and it is possible to predict the type of base oil and the molecular composition of hydrocarbons and calculate the amount of heat.
Kinematic viscosity was measured using a Stabinger Viscometer (Anton Paar/SVM3000) according to the ASTM D 7042 standard. Kinematic viscosity is the time it takes for the oil to fall by gravity over a certain distance, and it needs to have sufficient viscosity at high temperatures to prevent gear wear.
The viscosity index was measured using a Stabinger Viscometer (Anton Paar/SVM3000) according to ASTM D 7042 standard. The higher the viscosity index (VI), the lower the viscosity change due to temperature changes. The test method calculates the viscosity index using the kinematic viscosity measured at a certain temperature (40° C., 100° C.) and the correlation known in the ASTM D 2270 standard.
The flash point was measured using a Flash Point Tester (Duck woo scientific) according to the ASTM D 92 standard. The flash point refers to the lowest temperature at which oil vapor generated by continuous heating can be ignited. It is an indicator of the risk of ignition during handling and use, and it is possible to determine whether impurities are added. After filling the specified cup with an oil to the specified level, a test flame is passed over the cup. The temperature at which the test flame ignites the vapor above the oil is called the flash point.
The pour point was measured in a low-temperature chamber according to the ASTM D 97 standard. The pour point is defined as the temperature at which an oil initially flows at low temperatures. After cooling 45 ml of an oil to −60° C. or lower without stirring in a test tube with a thermometer inserted, the temperature of the sample is raised at 3° C. intervals, and the temperature when the sample moves within 5 seconds is called the pour point.
It is appropriate to have a low pour point in order to easily shift gears in cold weather. When the temperature of the lubricant is continuously lowered, the wax begins to precipitate and solidify, and the pour point refers to the temperature just before this point. The pour point is a value that determines the use, storage, and supply of oil in extremely cold areas.
The viscosity index was measured using a Stabinger Viscometer (Anton Paar/SVM3000) according to the ASTM D 7042 standard. The low-temperature viscosity of the oil composition needs to be sufficiently low to easily shift gears. It is suitable for the low-temperature viscosity to be 2,000 Centipose (cP) or less at −20° C., 5,000 cP or less at −30° C., and 20,000 cP or less at −40° C. The low-temperature viscosity is a physical property of the engine oil related to initial engine startability, and the lower the low-temperature viscosity, the shorter the time it takes for the oil to reach the entire engine.
The aniline point was measured according to the ASTM D 61 standard. This test method is used to find the point where equal volumes of hydrocarbon and aniline are completely dissolved and become transparent, which determines the usability of an oil. In the case of CA, CN, the more double bonds, the lower the aniline point, and in the case of Cp, the fewer double bonds, that is, the higher the oxidation stability, the higher the aniline point. It is suitable for oil compositions for power steering according to the present invention to have an aniline point of 90° C. or higher.
The measurement results of the physical properties of oil compositions according to Example and Comparative Example are shown in Table 5 below. Accordingly, it can be confirmed that the oil composition according to Example satisfies all the physical properties required for oil compositions for power steering.
The durability performance of the oil compositions for power steering prepared according to Example and Comparative Example was measured using the following test methods.
The copper plate corrosion (100° C.×3 hr) grade of the oil compositions was measured according to the ASTM D 130 standard. It is a method to check whether metals are corroded due to organic sulfur and corrosive substances contained in the oil, which is divided into Grades 1a to 4c. For use as oil for power steering, Grade 1 or lower is suitable.
The four-ball load-carrying capacity, that is, breaking limit load, was measured according to the ASTM D 2783 standard. Gears are small, but since they transmit large forces to a small area, the local load is very large. Thus, the oil composition for power steering needs to undergo a performance test for wear prevention from extreme pressure loads, that is, an oil-film risk assessment. When the test result according to ASTM D 2783 is 80 kfg or more, it is suitable for oil compositions for power steering.
The load-carrying capacity of the oil compositions was measured using a four-ball tester (SETA STANHOPE-SETA/Seta-Shell Four Ball Lubricant Tester) according to the ASTM D 4172 standard. It is a standard for determining the wear resistance of oil, and those of 0.4 mm or less are suitable for oil compositions for power steering.
The test method is specifically the shell-type four-ball test, and after operating under certain conditions by making point contact with 3 fixed balls and 1 rotating ball, the average wear surface of the 3 fixed balls in mm is confirmed.
The compatibility of the oil composition with a seal made of rubber was evaluated according to the ASTM D 471 standard. After immersing a sample (rubber) in the oil composition, leakage prevention performance was tested by measuring the volume, tensile strength, elongation, and hardness change rates. An oil composition with a volume change rate of 10% or less, a tensile strength change rate of −30% or less, an elongation change rate of −50% or less, and a hardness change in the range of −10 to 10 Hs is suitable as an oil composition for power steering.
The performance measurement results of the oil compositions according to Example and Comparative Example are shown in Table 6 below. Accordingly, it can be seen that the corrosion resistance, load-carrying capacity, wear resistance, and seal compatibility of the oil composition for power steering according to Example are significantly improved.
An oil composition for power steering according to the present invention has high (i.e., excellent) wear resistance and load-carrying capacity and effectively prevents corrosion, which can significantly reduce noise and vibrations due to friction when applied to the support yoke in the gearbox of a power steering system, thereby greatly improving the performance of automotive power steering system.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2023-0136851 | Oct 2023 | KR | national |
