CN114292683A - Lubricating oil composition - Google Patents
Lubricating oil composition Download PDFInfo
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- CN114292683A CN114292683A CN202110993899.1A CN202110993899A CN114292683A CN 114292683 A CN114292683 A CN 114292683A CN 202110993899 A CN202110993899 A CN 202110993899A CN 114292683 A CN114292683 A CN 114292683A
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Abstract
A lubricating oil composition which contains 0.1 to 3.0 mass% of an ethylene-propylene copolymer having a weight average molecular weight of 5000 to 20000 and is used for a helical gear mechanism.
Description
Technical Field
The present invention relates to a lubricating oil composition, and more particularly to a lubricating oil composition for a helical gear mechanism.
Background
Conventionally, in a gear mechanism used for a power transmission mechanism or the like, a gear (gear) mechanism is usedFrom the viewpoint of improving the power transmission efficiency, various lubricating oil compositions have been studied for use. For example, International publication No. 2013/136582 (patent document 1) discloses a thermoplastic elastomer composition containing a kinematic viscosity at 100 ℃ of 5mm2A mineral base oil having a weight average molecular weight of 15000 or less, and a polymer having a weight average molecular weight of 15000 or less, wherein the polymer having a weight average molecular weight of 15000 or less is a copolymer of an α -olefin and an α, β -ethylenically unsaturated dicarboxylic acid diester.
Documents of the prior art
Patent document
Patent document 1: international publication No. 2013/147162
Disclosure of Invention
Problems to be solved by the invention
The purpose of the present invention is to provide a lubricating oil composition which, when used in a helical gear mechanism, can sufficiently improve power transmission efficiency even under severe conditions such as high temperature and high load.
Means for solving the problems
The present inventors have conducted extensive studies and, as a result, have found that: the conventional lubricating oil composition described in patent document 1 can improve the power transmission efficiency when used in a spur gear mechanism, but when used directly in a helical gear (helical gear: helical gear) mechanism, the power transmission efficiency cannot necessarily be sufficiently improved under severe conditions of high temperature of about 100 to 140 ℃ (preferably around 120 ℃), and high load (for example, load conditions such as high load (preferably around 30Nm to 70 Nm) and relatively high rotational speed (about 2000 to 4000 rpm)). Further, even if reference is made to a known technique such as patent document 1, it is not easy for a person skilled in the art to think: the effect of improving the power transmission efficiency tends to be different between the case of using the spur gear mechanism and the case of using the helical gear mechanism.
Based on the above-mentioned findings, the inventors of the present invention have further made intensive studies and, as a result, have found that: the present inventors have found that when a lubricating oil composition is used for a helical gear mechanism, the power transmission efficiency can be sufficiently improved even under severe conditions of high temperature and high load, by adding 0.1 to 3.0 mass% of an ethylene-propylene copolymer having a weight average molecular weight of 5000 to 20000 to the lubricating oil composition, and have completed the present invention.
Namely, the lubricating oil composition of the present invention is as follows.
[ 1 ] A lubricating oil composition which contains 0.1 to 3.0 mass% of an ethylene-propylene copolymer having a weight average molecular weight of 5000 to 20000 and is used for a helical gear mechanism.
[ 2 ] A lubricating oil composition according to the above [ 1 ], wherein the kinematic viscosity at 80 ℃ of a lubricating base oil contained in the lubricating oil composition is 2.0 to 7.0mm2In seconds.
[ 3 ] A lubricating oil composition according to the above [ 1 ] or [ 2 ], wherein the lubricating base oil contained in the lubricating oil composition contains 60% by mass or more, based on the total amount of the lubricating base oil, of a mineral base oil satisfying the condition that the API is classified into group II or group III.
Effects of the invention
According to the present invention, it is possible to provide a lubricating oil composition which can sufficiently improve power transmission efficiency when used in a helical gear mechanism, particularly even under severe conditions such as high temperature and high load.
Drawings
FIG. 1 is a sectional view schematically showing a test apparatus for a helical gear mechanism used for evaluating the properties of the lubricating oil compositions obtained in examples and the like.
Description of the symbols
A 10 Input engine (Input Motor), an 11 rotating shaft (Input side), a 12 torque meter (Input side), a 20 Output engine (Output Motor), a 21 rotating shaft (Output side), a 22 torque meter (Output side), G1 and G2 helical gears, a tank 40 for storing lubricating oil composition, a 41 oil supply pipe, a1 schematically show arrows of the moving direction of lubricating oil composition inside the oil supply pipe.
Detailed Description
The present invention will be described in detail below based on preferred embodiments of the invention. In the present specification, unless otherwise specified, the expression "X to Y" for the numerical values X and Y means "X or more and Y or less". In this expression, when a unit is added to only the value Y, the unit is also applied to the value X.
The lubricating oil composition of the present invention contains 0.1 to 3.0 mass% of an ethylene-propylene copolymer having a weight average molecular weight of 5000 to 20000, and is a lubricating oil composition for a helical gear mechanism.
< ethylene-propylene copolymer >
The ethylene-propylene copolymer used in the present invention has a weight average molecular weight (Mw) of 5000 to 20000. When the weight average molecular weight is not more than the upper limit, the shear stability of the resulting lubricating oil composition can be made more excellent than when the weight average molecular weight exceeds the upper limit, and the performance of maintaining an oil film for a long period of time (oil film retention) can be further improved. From the same viewpoint, the weight average molecular weight of the ethylene-propylene copolymer is more preferably 5000 to 15000, still more preferably 6000 to 13000, and particularly preferably 6500 to 12000.
The number average molecular weight (Mn) of the ethylene-propylene copolymer is preferably 2000 to 10000 (more preferably 3500 to 7000). When the number average molecular weight is not more than the upper limit, the obtained lubricating oil composition can be made more excellent in shear stability and can be further improved in oil film retention property than when the number average molecular weight exceeds the upper limit, while when the number average molecular weight is not less than the lower limit, the viscosity of the obtained lubricating oil composition can be further improved than when the number average molecular weight is less than the lower limit, and the lubricating state of the contact interface between gears can be maintained in a more favorable state during use, and power transmission efficiency can be further improved.
Further, the molecular weight distribution (Mw/Mn) of the ethylene-propylene copolymer is preferably 3.0 or less (more preferably 2.5 or less). When the molecular weight distribution is not more than the upper limit, the shear viscosity stability of the obtained lubricating oil composition can be further improved as compared with the case where the molecular weight distribution exceeds the upper limit, and the lubrication state of the contact interface between the gears can be maintained in a more favorable state during use, and the power transmission efficiency can be further improved.
In the present specification, the Mw, Mn and Mw/Mn of the ethylene-propylene copolymer are values (molecular weight in terms of polystyrene) determined by Gel Permeation Chromatography (GPC). The measurement conditions for obtaining Mw, Mn and Mw/Mn by GPC are as follows.
[ GPC measurement conditions ]
The device comprises the following steps: ACQUITY (registered trademark) APC UV RI system manufactured by Waters Corporation
A chromatographic column: 2 ACQUITY (registered trademark) APC XT900A (gel particle diameter 2.5 μm, column size (inner diameter. times.length) 4.6 mm. times.150 mm) manufactured by Waters Corporation and 1 ACQUITY (registered trademark) APC XT200A (gel particle diameter 2.5 μm, column size (inner diameter. times.length) 4.6 mm. times.150 mm) manufactured by Waters Corporation were connected in series in this order from the upstream side
Temperature of the column: 40 deg.C
Sample solution: tetrahydrofuran solution with sample concentration of 1.0 mass%
Solution injection amount: 20.0 μ L
The detection device comprises: differential refractive index detector
Reference substance: standard polystyrene (Agilent EasiCal (registered trademark) PS-1, product of Agilent Technologies) 8 dots (molecular weight: 2698000, 597500, 290300, 133500, 70500, 30230, 9590, 2970)
GPC measurement was performed under the above conditions, and when the weight average molecular weight was 10000 or more, the measurement was terminated as it is. On the other hand, when the weight average molecular weight is less than 10000, the re-measurement is performed under the same conditions as described above except that the column and the reference substance are changed as follows.
A chromatographic column: 1 piece of ACQUITY (registered trademark) APC XT125A (gel particle diameter 2.5 μm, column size (inner diameter. times.length) 4.6 mm. times.150 mm) manufactured by Waters Corporation and 2 piece of ACQUITY (registered trademark) APC XT45A (gel particle diameter 1.7 μm, column size (inner diameter. times.length) 4.6 mm. times.150 mm) manufactured by Waters Corporation were connected in series in this order from the upstream side
Reference substance: standard polystyrene (Agilent EasiCal (registered trademark) PS-1, manufactured by Agilent Technologies) 10 dots (molecular weight: 30230, 9590, 2970, 890, 786, 682, 578, 474, 370, 266).
In the ethylene-propylene copolymer, the content of the structural unit derived from ethylene (ethylene content) is preferably 30 to 80 mol% (more preferably 40 to 60 mol%). When the ethylene content is not more than the upper limit, a lubricating oil composition having more excellent low-temperature viscosity characteristics can be obtained than when the ethylene content exceeds the upper limit, while when the ethylene content is not less than the lower limit, the temperature dependence of viscosity can be further reduced than when the ethylene content is less than the lower limit. In the present application, the term "ethylene content" means that the measurement is carried out under the following measurement conditions13C-NMR measurement was carried out, and values calculated from the following formulas (I) to (III) were calculated using the measurement results.
(13C-NMR measurement conditions)
The using device comprises the following steps: AVANCE400 type NMR, Bruker
Solvent: CDCl3
Sample tube: diameter of 10mm
The determination method comprises the following steps: 1H-inverse gated decoupling (1H-inverted gated decoupling)
Cumulative number of times: 3000 times (twice)
Waiting time: 10 seconds
Measuring temperature: at room temperature
Chemical shift standard: CDCl3(77.1ppm)
(calculation of ethylene content formulas (I) to (III))
AP＝3×AM (I)
AE＝100-AP (II)
X＝100×(0.5×AE)/{(0.5×AE)+(1/3×AP)} (III)
[ in formulae (I) to (III), AMTo represent13Integral value of 19 to 21ppm region in C-NMR, APTo represent13Integral value of carbon derived from propylene in C-NMR, AETo represent13The integral value of ethylene-derived carbon in C-NMR, X, is the ethylene content (%). In addition, will use13The integral value of all peaks (except the solvent) detected by C-NMR was set to 100.]。
The ethylene-propylene copolymer may be a block copolymer or a random copolymer. Further, the method for producing the ethylene-propylene copolymer is not particularly limited, and a known method can be suitably employed. Further, commercially available products can be used as the ethylene-propylene copolymer.
In the lubricating oil composition of the present invention, the content of the ethylene-propylene copolymer is required to be 0.1 to 3.0 mass%. When the content of the ethylene-propylene copolymer is not less than the lower limit, the viscosity of the lubricating oil composition can be adjusted more easily with the ethylene-propylene copolymer than with the ethylene-propylene copolymer, and the power transmission efficiency of the helical gear mechanism can be sufficiently improved under severe conditions such as high temperature and high load. On the other hand, when the content of the ethylene-propylene copolymer is not more than the upper limit, the viscosity index can be increased while suppressing an increase in viscosity of the obtained lubricating oil composition, as compared with the case where the content exceeds the upper limit, and the power transmission efficiency can be sufficiently increased under high temperature conditions. The reason why the content of the ethylene-propylene copolymer is more preferably 0.15 to 2.5% by mass (more preferably 0.20 to 2.0% by mass) is that the power transmission efficiency of the helical gear mechanism can be further improved under severe conditions such as high temperature and high load.
The lubricating oil composition of the present invention may contain 0.1 to 3.0 mass% of an ethylene-propylene copolymer having a weight average molecular weight of 5000 to 20000, and the types of other components contained in the lubricating oil composition are not particularly limited, and known lubricating base oils and known other components (additives) which can be used in gear mechanisms can be suitably used. Hereinafter, a lubricant base oil and other components that can be used in the lubricating oil composition of the present invention will be described.
< lubricating base oil >
The lubricant base oil contained in the lubricant composition of the present invention is not particularly limited, and a known lubricant base oil (for example, the lubricant base oils described in japanese patent laid-open nos. 2003-155492, 2017/073748, 2020-76004, and the like) may be suitably used, and may be a mineral oil-based lubricant base oil or a synthetic oil-based lubricant base oil. Hereinafter, as such a lubricant base oil, a lubricant base oil which can be preferably used will be described.
The lubricant base oil preferably has a kinematic viscosity at 80 ℃ of 2.0 to 7.0mm2Second (more preferably 3.0 to 6.0 mm)2In seconds). When the kinematic viscosity at 80 ℃ is not more than the upper limit, the power transmission efficiency can be further improved in a high temperature range (about 100 to 140 ℃) as compared with the case where the kinematic viscosity at 80 ℃ is more than the lower limit, and on the other hand, when the kinematic viscosity at 80 ℃ is not less than the lower limit, the oil film forming property and the oil film retaining property of the lubricating oil composition at the lubricated part can be further improved in a high temperature range (about 100 to 140 ℃) as compared with the case where the kinematic viscosity is less than the lower limit, and a more favorable lubricated state can be maintained. In the present specification, the "kinematic viscosity at 80 ℃" refers to the kinematic viscosity at 80 ℃ measured according to JIS K2283-.
The lubricant base oil preferably contains a mineral base oil that satisfies the condition that the base oil classification (referred to as "API classification" in the present specification) by API (American mineral oil Institute) is group II or group III (hereinafter, sometimes simply referred to as "condition (a)"). Further, the base oil classified as group II by API is a mineral base oil having a sulfur content of 0.03 mass% or less, a saturated content (saturated hydrocarbon) of 90 volume% or more, and a viscosity index of 80 or more but less than 120. The base oil classified by API into group III is a mineral base oil having a sulfur content of 0.03 mass% or less, a saturated content (saturated hydrocarbon) of 90 vol% or more, and a viscosity index of 120 or more. The content of the mineral base oil satisfying the condition (a) as the lubricant base oil is more preferably 60 mass% or more (further preferably 80 mass% or more) based on the total amount of the lubricant base oil.
Further, the lubricant base oil preferably satisfies the condition that the concentration of the sulfur component is 200 mass ppm or less (more preferably 100 mass ppm or less, and still more preferably 1 mass ppm or less). When the concentration of the sulfur component is not more than the upper limit, a composition having more excellent thermal and oxidation stability can be obtained. In the present specification, the "concentration of sulfur component" refers to a value measured according to JIS K2541-6-2003 (ultraviolet fluorescence method).
The lubricant base oil preferably satisfies the condition that the nitrogen component concentration is 300 mass ppm or less (more preferably 100 mass ppm or less, and still more preferably 1 mass ppm or less). When the concentration of the nitrogen component is not more than the upper limit, a composition having more excellent thermal and oxidation stability can be obtained. In the present specification, the "concentration of nitrogen component" refers to a value measured according to JIS K2609-1998 (chemiluminescence method).
The lubricant base oil preferably has a density of 0.800 to 0.850g/cm at 15 DEG C2(more preferably 0.805 to 0.845 g/cm)2). When the density is not more than the upper limit, a composition having more excellent thermal and oxidation stability can be obtained than when the density exceeds the upper limit, and when the density is not less than the lower limit, the composition has more excellent heat transfer characteristics than when the density is less than the lower limit, and excessive temperature rise of the sliding surface can be further suppressed. In the present specification, the "density at 15 ℃" refers to the density at 15 ℃ measured according to JIS K2249-1-1995.
The viscosity index of the lubricant base oil is preferably 80 or more, and more preferably 95 to 160. When the viscosity index is not more than the upper limit, the content of normal paraffins in the base oil is less than when the viscosity index exceeds the upper limit, and therefore, a sharp increase in viscosity at low temperatures is further suppressed, whereas when the viscosity index is not less than the lower limit, the temperature dependence of the viscosity of the obtained lubricating oil composition can be further reduced as compared with when the viscosity index is less than the lower limit, and the power transmission efficiency can be further improved under high temperature conditions. In the present specification, the term "viscosity index" refers to a viscosity index measured in accordance with JIS K2283-1993.
The lubricant base oil may be composed of a single base oil component or may be composed of a plurality of base oil components as a whole.
In the lubricating oil composition of the present invention, the content of the lubricating base oil is preferably 50 to 99 mass% (more preferably 70 to 97 mass%) based on the total amount of the lubricating oil composition. When the content of the lubricant base oil is not more than the upper limit, it is easier to improve the properties such as the formability of the lubricant film by the additive than when the content exceeds the upper limit, and when the content of the lubricant base oil is not less than the lower limit, the temperature dependence of the viscosity can be further reduced than when the content is less than the lower limit.
< other additives >
In the lubricating oil composition of the present invention, other components (other additives) generally used may be suitably used in the lubricating oil composition in order to further improve the performance thereof, depending on the purpose. The other components are not particularly limited, and known components used in the field of lubricating oil compositions (for example, components described in Japanese patent laid-open Nos. 2003-155492, 2017/073748, 2013/147162, 2020-76004, etc.) can be suitably used. The other components are not particularly limited, but additives such as an anti-wear agent, an ashless dispersant, a pour point depressant, a friction modifier, a metal-based detergent, an antioxidant, a metal deactivator, a rubber swelling agent, an antifoaming agent, and a diluent can be preferably used. Hereinafter, components that can be preferably used as the other components will be described.
The anti-wear agent is not particularly limited, and a known compound used as an anti-wear agent in the field of lubricating oil compositions can be suitably used (see, for example, Japanese patent laid-open Nos. 2003-155492, 2020-76004, and 2013/147162). As the anti-wear agent, for example, a sulfur-based, phosphorus-based, or sulfur-phosphorus-based anti-wear agent can be used. Among the above-mentioned anti-wear agents, from the viewpoint of excellent wear resistance, phosphorus-based or sulfur-phosphorus-based anti-wear agents are more preferable, and phosphite esters and thiophosphate esters are further more preferable. Further, the anti-wear agent may be used alone in 1 kind, or may be used in combination in 2 or more kinds. When the anti-wear agent is used, the content thereof is not particularly limited, and is preferably 0.02 to 2.0 mass% (more preferably 0.05 to 1.0 mass%) based on the total amount of the above-mentioned lubricating oil composition. When the content of the anti-wear agent is not more than the upper limit, the thermal and oxidation stability can be further improved as compared with the case where the content exceeds the upper limit, while when the content is not less than the lower limit, the wear resistance of the lubricating oil composition can be further improved as compared with the case where the content is less than the lower limit, and the power transmission efficiency can be further improved even under high load conditions.
Further, as the ashless dispersant, a known compound used as an ashless dispersant in the field of lubricating oil compositions can be suitably used (for example, see Japanese patent laid-open Nos. 2003-155492, 2020-76004, and 2013/147162). As ashless dispersants, non-borated succinimides, and mixtures thereof may be preferably used. Further, the ashless dispersant may be used alone in 1 kind, or may be used in combination in 2 or more kinds. When an ashless dispersant is used, the content thereof is not particularly limited, and is preferably 0.2 to 6.0 mass% (more preferably 0.5 to 5.0 mass%) based on the total amount of the above-described lubricating oil composition.
Examples of the pour point depressant include poly (meth) acrylates and ethylene-vinyl acetate copolymers, and among them, polymethacrylates are preferred. The polymethacrylate preferably has a weight average molecular weight (Mw) of 20000 to 100000. The pour point depressant may be used alone in 1 kind, or may be used in combination in 2 or more kinds. When a pour point depressant is used, the content thereof is preferably 0.01 to 1.0 mass% (more preferably 0.03 to 0.6 mass%) based on the total amount of the lubricating oil composition.
The friction modifier is not particularly limited, and examples thereof include amine-based, amide-based, imide-based, fatty acid ester-based, fatty acid-based, aliphatic alcohol-based, and aliphatic ether-based friction modifiers, and among them, amine-based friction modifiers are more preferable from the viewpoint of obtaining a higher friction reduction effect. In addition, as the amine-based friction modifier, alkylamine and alkenylamine are preferable. The friction modifier may be used alone in 1 kind, or may be used in combination in 2 or more kinds. When a friction modifier is used, the content thereof is preferably 0.005 to 3.0% by mass (more preferably 0.01 to 2.5% by mass) based on the total amount of the lubricating oil composition.
The metal-based detergent is not particularly limited, and examples thereof include alkaline earth metal sulfonates, alkaline earth metal phenates, and alkaline earth metal salicylates. The metal-based detergent may be used alone in 1 kind, or may be used in combination in 2 or more kinds. When a metal-based detergent is used, the content thereof is preferably 0.01 to 1.0 mass% (more preferably 0.05 to 0.6 mass%) based on the total amount of the lubricating oil composition.
The antioxidant is not particularly limited, and examples thereof include a phenol-based antioxidant and an amine-based antioxidant. The antioxidant may be used alone in 1 kind, or may be used in combination in 2 or more kinds. When an antioxidant is used, the content thereof is preferably 0.1 to 2.0 mass% (more preferably 0.2 to 1.0 mass%) based on the total amount of the lubricating oil composition.
The metal deactivator is not particularly limited, and examples thereof include imidazoline, pyrimidine derivatives, alkylthiadiazoles, mercaptobenzothiazole, benzotriazole or derivatives thereof, tolyltriazole or derivatives thereof, 1, 3, 4-thiadiazole polysulfide, 1, 3, 4-thiadiazole-2, 5-dialkyldithiocarbamate, 2- (alkyldithio) benzimidazole, and β - (ortho-carboxybenzylthio) propionitrile. The metal deactivators may be used alone in 1 kind, or may be used in combination in 2 or more kinds. When a metal deactivator is used, the content thereof is preferably 0.01 to 0.5 mass% (more preferably 0.02 to 0.3 mass%) based on the total amount of the lubricating oil composition.
The rubber swelling agent is not particularly limited, and known compounds that can be used as a seal swelling agent for lubricating oil can be suitably used, and examples thereof include ester-based, sulfur-based, and aromatic-based seal swelling agents (e.g., sulfolane compounds). The rubber swelling agent may be used alone in 1 kind, or may be used in combination in 2 or more kinds. When a rubber swelling agent is used, the content thereof is not particularly limited, and is preferably 0.01 to 1.0 mass% (more preferably 0.05 to 0.8 mass%) based on the total amount of the above-mentioned lubricating oil composition.
The defoaming agent may have a kinematic viscosity at 25 ℃ of 1000 to 100000mm2Silicone oil, alkenyl succinic acid derivatives, esters of polyhydroxyaliphatic alcohols with long-chain fatty acids, methyl salicylate, o-hydroxybenzyl alcohol, etc. per second. The defoaming agent may be used alone in 1 kind, or may be used in combination in 2 or more kinds. When the defoaming agent is used, the content is not particularly limited, and is preferably 0.0001 to 0.005 mass% (more preferably 0.0003 to 0.003 mass%) based on the total amount of the lubricating oil composition.
< characteristics of lubricating oil composition, etc. >
Preferred conditions for the composition of the lubricating oil composition of the present invention are described above, and preferred conditions for the properties of the lubricating oil composition of the present invention are described below.
The lubricating oil composition of the present invention preferably has a kinematic viscosity at 120 ℃ of 1.5 to 4.0mm2Second, more preferably 1.8 to 3.5mm2In seconds. When the kinematic viscosity at 120 ℃ is not more than the upper limit, the power transmission efficiency can be further improved in a high temperature range of about 100 to 140 ℃ when the gear is used in a helical gear mechanism, as compared with when the kinematic viscosity exceeds the upper limit. On the other hand, when the kinematic viscosity at 120 ℃ is not less than the lower limit, the oil film forming property and the oil film retaining property of the lubricating oil composition at the lubricated part can be further improved, and a more satisfactory lubricated state can be maintained even under high temperature conditions, as compared with the case where the kinematic viscosity is less than the lower limit, particularly in a high temperature region of about 100 to 140 ℃. In the present specification, the "kinematic viscosity at 120 ℃" refers to the kinematic viscosity at 120 ℃ measured according to JIS K2283-.
In addition, the kinematic viscosity at 80 ℃ of the lubricating oil composition of the present invention is preferably 3.0 to 9.0mm2Second, more preferably 3.5 to 7.0mm2In seconds. When the kinematic viscosity at 80 ℃ is not more than the upper limit, the power transmission efficiency can be further improved under severe conditions such as high temperature and high load, as compared with the case where the kinematic viscosity exceeds the upper limit. In addition, when the kinematic viscosity at 80 ℃ is not less than the lower limit, the oil film forming property and the oil film retaining property of the lubricating oil composition at the lubrication site can be further improved in use, and a more favorable lubrication state can be maintained even under high temperature conditions, as compared with the case where the kinematic viscosity is less than the lower limit.
The lubricating oil composition of the present invention preferably has a kinematic viscosity at 40 ℃ of 8.0 to 30.0mm2Second, more preferably 9.0 to 20.0mm2In seconds. When the kinematic viscosity at 40 ℃ is not more than the upper limit, the power transmission efficiency can be further improved under severe conditions such as high temperature and high load, as compared with the case where the kinematic viscosity exceeds the upper limit. When the kinematic viscosity at 40 ℃ is not lower than the lower limit, the viscosity at the time of use is higher than that when the kinematic viscosity is lower than the lower limitThe lubricating oil composition can further improve the oil film forming property and the oil film retaining property at the lubricated part, and can maintain a more favorable lubricating state even under high temperature conditions. In the present specification, the "kinematic viscosity at 40 ℃" refers to the kinematic viscosity at 40 ℃ measured according to JIS K2283-.
The viscosity index of the lubricating oil composition of the present invention is preferably 90 or more, and more preferably 100 or more. When the viscosity index is not less than the lower limit, the temperature dependence of the viscosity of the lubricating oil composition can be further reduced and the power transmission efficiency can be further improved, as compared with the case where the viscosity index is less than the lower limit.
The pour point of the lubricating oil composition of the present invention is preferably-30 ℃ or lower (more preferably-40 ℃ or lower). When the pour point is not more than the upper limit, a lubricating oil composition having excellent low-temperature viscosity characteristics can be obtained as compared with a case where the pour point exceeds the upper limit. In the present specification, "pour point" refers to a pour point measured in accordance with JIS K2269-.
The method for producing the lubricating oil composition of the present invention is not particularly limited as long as the ethylene-propylene copolymer having a weight average molecular weight of 5000 to 20000 can be contained in the lubricating oil composition in such a content, and can be produced by adding the ethylene-propylene copolymer and other components to a lubricating base oil, which is selected as appropriate depending on the intended use and design, and the other components (e.g., the viscosity modifier, the ashless dispersant, etc.) as described above.
In the case where such other components are added to the lubricating oil composition of the present invention, the other components may be separately prepared for each component and then added, or a mixture of the other components may be prepared and then added. As the mixture of the other components, commercially available packages (for example, additive packages containing ashless dispersants, metal-based detergents, antioxidants, friction modifiers, anti-wear agents, rubber swelling agents, metal deactivators, diluent components (diluent oils), and the like) may be suitably used
Examples
Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to the following examples.
[ Components used in examples, etc. ]
The lubricant base oil, the low-molecular-weight polymer component and other additives used in each example and the like are shown below. The density of the lubricant base oil shown below was 15 ℃. In the following low molecular weight polymer components, the weight average molecular weight is a value analyzed by Gel Permeation Chromatography (GPC) under the above-mentioned GPC measurement conditions.
(1) Lubricating oil base oil
[ mineral oil (I)]Kinematic viscosity at 80 ℃: 3.61mm2Second, sulfur content: less than 1 mass ppm, nitrogen component: less than 1 mass ppm, API classification: group II (mineral oil), density: 0.837g/cm3
(2) Polymer component having molecular weight of 20000 or less
[ Polymer (A) ] an ethylene-propylene copolymer (weight-average molecular weight: 11500, ethylene content: 60%)
[ Polymer (B) ] an ethylene-propylene copolymer (weight-average molecular weight: 7080, ethylene content: 58%)
[ Polymer (C) ] A copolymer of an alpha-olefin and an alpha, beta-ethylenically unsaturated dicarboxylic acid diester (weight-average molecular weight: 4730)
[ Polymer (D) ] copolymer of alpha-olefin and alpha, beta-ethylenically unsaturated dicarboxylic acid diester (weight-average molecular weight: 6000)
[ Polymer (E) ] non-dispersible polymethacrylate (weight-average molecular weight: 7950)
[ Polymer (F) ] non-dispersible polymethacrylate (weight-average molecular weight: 20000)
(3) Other additives
Additive package an additive package containing the following ingredients: ashless dispersants (mixtures of non-boron succinimides and boron succinimides); a metal-based detergent (calcium sulfonate, total base number: 300(TBN 300)); antioxidants (mixtures of amine-based antioxidants and phenol-based antioxidants); friction modifiers (amine-based); anti-wear agents (phosphites); a rubber swelling agent (sulfolane compound); metal deactivators (thiadiazoles); and diluent oil
[ pour Point depressant ] polymethacrylate (non-dispersed, weight average molecular weight: 50000).
Examples 1 to 4 and comparative examples 1 to 5
Lubricating oil compositions were prepared using the components so as to have the compositions shown in table 1 below. In addition, "-" in Table 1 indicates that the component was not used. In table 1, "mass% in units of the content of the lubricant base oil" indicates the content (mass%) of the mineral oil (I) with respect to the total amount of the lubricant base oil contained in the composition, and "mass% in units of the content of the polymer component and other additives" indicates the content (mass%) of each component with respect to the total amount of the lubricant composition. Table 1 also shows values of kinematic viscosity at 40 ℃, 80 ℃ and 120 ℃ (measured according to JIS K2283-.
[ Properties of lubricating oil compositions obtained in examples 1 to 4 and comparative examples 1 to 5 ]
The lubricating oil compositions obtained in examples 1 to 4 and comparative examples 1 to 5 were used, and the properties were evaluated as follows.
< test for measuring power transmission efficiency in spur gear mechanism: FZG spur gear test >
The FZG spur gear test was carried out under the following test conditions in the same manner as described in the documents "FVA Information Sheet No.345, March 2002 (hereinafter, this document may be abbreviated as" reference 1 ")" except that the conditions were different from those described belowThe power transmission efficiency when the device is operated is tested. That is, a power circulation type FZG spur gear test apparatus was used as a test apparatus, a gear box provided with a test gear C-pt (C) (gear material: 16MnCr5) was set to a level of being impregnated with a lubricating oil composition into the center of a shaft, and on a load bed: 7(ST7[ surface pressure: about 1300N/mm)2]) The test apparatus was operated under test conditions of a test temperature (temperature of the lubricating oil composition at the time of the test) of 90 ℃ and an engine speed of 1440rpm, and an input torque [ unit: nm]And loss torque [ [ unit: nm]]The power transmission efficiency (gear efficiency) is obtained by calculating the following equation (1). In addition, in this measurement, a product name "Super oil M100" manufactured by kindergarten corporation is used instead of the reference oil "minor oil FVA 3A" described in reference 1, and the procedure described in the column of "Vc) Steady-state-temperature" in the procedure described in chapter 7.4 of reference 1 is omitted, and the measured value under the above test condition is directly used as the value of the loss torque instead of the value obtained by subtracting the value of "no load torque loss" (no load torque) as described in chapter 8.2 of reference 1, and although conditions different from those of reference 1 are used at these points, the same method as that described in reference 1 is used except for this. The results obtained by the FZG spur gear test described above are shown in table 3. Table 3 also shows the increase in power transmission efficiency (increase from the reference value: difference in power transmission efficiency from comparative example 1: increase in efficiency) for each example and the like, with the power transmission efficiency of comparative example 1 as the reference value.
[ Power Transmission efficiency (%)]＝{(Tin-Tout)/Tin}×100 (1)
(in the formula (1), TinIndicating input torque, ToutRepresenting the lost torque. )
< test for measuring power transmission efficiency in helical gear mechanism: helical gear test >
Using a test apparatus for a helical gear mechanism schematically shown in fig. 1, a lubricating oil composition was supplied to a pair of helical gears, and the power transmission efficiency (gear efficiency) was determined as follows. Hereinafter, the test apparatus and the test conditions will be described.
(relevant test device)
First, the test apparatus will be explained. In fig. 1, the test apparatus is a test apparatus using a gear case 30 including a pair of helical gears including a helical gear G1 and a helical gear G2. More specifically, the test apparatus shown in fig. 1 includes: an Input Motor (Input Motor) 10 for inputting a driving force, a rotary shaft 11 for inputting the engine 10, a helical gear G1 provided on an Input side (driving side) of a tip end of the rotary shaft 11, a torque meter 12 connected to the rotary shaft 11 for measuring an Input torque (driving torque), an Output Motor (Output Motor) 20, a rotary shaft 21 for the Output Motor 20, a helical gear G2 attached to the output side (absorption side) of the front end of the rotating shaft 21, a torque meter 22 connected to the rotating shaft 21 for measuring the output torque (absorption torque), a gear case 30 in which a pair of helical gears G1 and G2 are arranged, a tank 40 for storing a lubricating oil composition to be supplied to the gears, and an oil supply pipe 41 for supplying the lubricating oil composition from the tank 40 to the contact portion (gear meshing portion) of the pair of helical gears G1 and G2. An oil introduction pipe (not shown) for introducing the lubricating oil composition into the tank is connected to the tank 40 shown in fig. 1, and is designed to introduce a necessary amount of the lubricating oil composition into the tank. Further, an arrow a1 in fig. 1 schematically shows the moving direction of the lubricating oil composition when it moves in the supply pipe 41. The specifications of the gears used in such a test apparatus are shown in table 2.
TABLE 2
(conditions of the test)
Next, test conditions and the like will be described. That is, the test apparatus of the helical gear mechanism shown in fig. 1 was operated under the following conditions, and the input torque [ unit: nm ] and output torque [ unit: nm ], the power transmission efficiency (gear efficiency) is obtained by calculating the following equation (1') from the measured values and the values of the rotation speeds of the respective rotating shafts on the input side (drive side) and the output side (absorption side).
[ Power Transmission efficiency (%)]＝{(T2×n2)/(T1×n1)}×100 (1’)
[ in formula (1'), T1Indicating input torque (drive torque), n1The rotation speed (driving rotation speed) T of the helical gear G1 on the input side is shown2Indicating output torque (absorption torque), n2The rotation speed (absorption rotation speed) of the helical gear G2 on the output side is shown. Angle (c)
The measurement of the power transmission efficiency described above was performed 2 times (for convenience, the 2 measurement tests are hereinafter referred to as test (a) and test (B), respectively) after changing the test conditions (the operating conditions of the test apparatus) relating to the test temperature (the temperature at the time of supplying the lubricating oil composition: the supplied oil temperature), the rotational speed (the rotational speed of the rotary shaft 11 (input side: drive side)), and the load (the load applied to the tooth surface of the helical gear G2 (output side)). In each test, the supply rate of the lubricating oil composition to the contact portion (meshing portion of gears) between the pair of helical gears G1 and G2 in the test apparatus was set to 1.0L/min (same). The following are the test conditions used in each test.
[ test conditions used in test (A) ]
Test temperature (supply oil temperature): 120 ℃, rotational speed (input side): 3000rpm, load (output side): 30Nm, feed rate of lubricating oil composition: 1.0L/min
[ test conditions used in test (B) ]
Test temperature (supply oil temperature): 120 ℃, rotational speed (input side): 2000rpm, load (output side): 50Nm, feed rate of lubricating oil composition: 1.0L/min.
The results (power transmission efficiency of each example and the like) obtained by the above-described helical gear test are shown in table 3. The kind and content of the low molecular weight polymer component to be used are shown together. In Table 3, the increase in power transmission efficiency (increase from the reference value: difference from the power transmission efficiency of comparative example 1: increase in efficiency) of each example and the like with the power transmission efficiency of comparative example 1 as the reference value and the average value thereof are shown together.
It is clear from the results of FZG spur gear tests shown in table 3 that the lubricating oil compositions obtained in examples 1 to 4 were not different from the lubricating oil compositions obtained in comparative examples 1, 4 to 5 in terms of the power transmission efficiency of spur gears, and the power transmission efficiency was the same value. It is thus understood that the lubricating oil compositions obtained in examples 1 to 4 have the same effects as the lubricating oil composition obtained in comparative example 1, which is the standard, from the viewpoint of the power transmission efficiency of the spur gear.
In contrast, as is clear from the results of the helical gear tests shown in table 3, the lubricating oil compositions obtained in examples 1 to 4 had an increase in power transmission efficiency (efficiency increase) of 0.1 or more relative to the lubricating oil composition obtained in comparative example 1 as a reference, regardless of the test conditions of the test (a) and the test (B). It is also understood from the results of the helical gear tests shown in table 3 that the lubricating oil compositions obtained in examples 1 to 4 were all 0.2, while the lubricating oil compositions obtained in comparative examples 1 to 5 were 0.1 at maximum, with respect to the average of the increase amounts (increase in efficiency) of the power transmission efficiency in both test (a) and test (B). Further, it is also understood that since the power transmission efficiency of the lubricating oil composition obtained in comparative example 1 is at a high level of 99.4% in both test (a) and test (B), by setting the increase in power transmission efficiency compared with this power transmission efficiency to 0.1 or more, that is, by increasing the power transmission efficiency by 0.1% or more as compared with comparative example 1, the degree of reduction of loss torque in the gear mechanism becomes sufficiently large, and if the increase in power transmission efficiency in each test with reference to comparative example 1 reaches 0.1 or more, it can be determined that the power transmission efficiency of the helical gear mechanism can be sufficiently increased. From the above-described viewpoints, it was confirmed that the lubricating oil compositions (examples 1 to 4) of the present invention exhibited sufficiently high power transmission efficiency of the helical gear mechanism under severe operating conditions such as conditions of 120 ℃ temperature, 30Nm load, 3000rpm (test (a)) and 120 ℃ temperature, 50Nm load, and 2000rpm (test (B)) because the increase in power transmission efficiency (efficiency increase) in both test (a) and test (B) was 0.1 or more relative to the lubricating oil composition obtained in comparative example 1 as a reference, and the average value of the increase in power transmission efficiency (efficiency increase) in both test (a) and test (B) was a value (0.2) exceeding 0.1.
Further, as is clear from the results shown in table 3, particularly in the test (B) under the high load condition of 50Nm load (output side), the increase in power transmission efficiency (efficiency increase) of the lubricating oil compositions obtained in examples 1 to 4 was 0.2 or more, while the increase in power transmission efficiency (efficiency increase) of the lubricating oil compositions obtained in comparative examples 1 to 5 was 0, and therefore, when the lubricating oil compositions of the present invention (examples 1 to 4) were used in the helical gear mechanism, the power transmission efficiency of the helical gear mechanism could be improved to a higher level under the high temperature and high load condition, particularly under the condition that the load on the gear on the output side became higher.
Industrial applicability
As described above, according to the present invention, it is possible to provide a lubricating oil composition which can sufficiently improve power transmission efficiency even when used in a helical gear mechanism, particularly under severe conditions of high temperature and high load. Therefore, the lubricating oil composition of the present invention can be suitably used in various devices utilizing a helical gear mechanism, and is particularly useful for transmissions (automatic transmissions, manual transmissions, and the like) and speed reducers for various automobiles including electric automobiles, hybrid automobiles, and the like.
Claims (3)
1. A lubricating oil composition which contains 0.1 to 3.0 mass% of an ethylene-propylene copolymer having a weight average molecular weight of 5000 to 20000 and is used for a helical gear mechanism.
2. The lubricating oil composition according to claim 1, wherein the kinematic viscosity at 80 ℃ of the lubricating base oil contained in the lubricating oil composition is 2.0 to 7.0mm2In seconds.
3. The lubricating oil composition according to claim 1 or 2, wherein the lubricating base oil contained in the lubricating oil composition contains 60% by mass or more, based on the total amount of the lubricating base oil, of a mineral base oil that satisfies the condition that the API is classified as group II or group III.
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| JP2020170073A JP7492427B2 (en) | 2020-10-07 | Lubricating Oil Composition | |
| JP2020-170073 | 2020-10-07 |
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