JP7260555B2 - Composition for cooling and lubricating vehicle drive systems - Google Patents

Description

The present invention relates to the field of compositions for lubricating and cooling drive systems of electric or hybrid vehicles. In particular, the present invention aims to present a composition endowed with both lubricating and cooling properties for the drive system of electric or hybrid vehicles, in particular for cooling and lubricating electric motors. do.

Changes to international standards for reducing CO ₂ emissions and also for reducing energy consumption are forcing vehicle manufacturers to offer alternative solutions to combustion engines.

One of the solutions identified by automakers consists of replacing the combustion engine with an electric motor. Research towards reducing _CO2 emissions has thus led to the development of electric vehicles by a number of automobile companies.

In the context of the present invention, the term "electric vehicle" means a vehicle with an electric motor as the sole means of propulsion, as opposed to a hybrid vehicle with a combustion engine and an electric motor as the combined means of propulsion.

The term "drive system" in the context of the present invention means a system comprising the mechanical parts necessary for propulsion of an electric vehicle. The drive system thus includes, among other things, an electric motor, a battery and possibly a transmission.

Generally, in electric or hybrid vehicles it is necessary to use compositions that satisfy the dual constraints of cooling or lubricating various parts of the drive system. These needs are usually met by using two separate means, a lubricating composition on the one hand and a cooling fluid on the other hand.

As such, lubricating compositions, also known as "lubricants," are conventionally used in engines for the primary purpose of reducing frictional forces between various metal parts moving in the engine. It is also effective in preventing premature wear or even damage to these parts, especially their surfaces.

To this end, lubricating compositions conventionally consist of one or more base oils, generally together with a number of additives intended to enhance the lubricating performance of the base oils, friction modifiers are examples of such additives.

Electric motors, on the other hand, generate heat during their operation. When the amount of heat generated is greater than the amount of heat dissipated into the environment, it is necessary to ensure cooling of the engine. In general, cooling is provided for one or more parts of the engine that generate heat and/or parts of the engine that are heat sensitive in order to avoid reaching dangerous temperatures.

Traditionally, cooling of electric motors with air is known, generally by forced convection. This cooling method has the advantage of not requiring the preparation of a specific cooling fluid. However, with the development of ever increasing power and ever smaller engines, this cooling method is no longer sufficient, especially due to the limited efficiency of air for cooling.

A method of cooling an engine using water is also presented. Although the heat capacity of water is high, it is not possible to envisage direct cooling by contacting the water with an electric motor due to the electrical conductivity of water. As a result, the cooling system requires the use of an outer jacket, adding considerably to the volume of the engine.

Alternative methods have also been considered for cooling electric motors using oil injection.

Liu et al. (EVS28, "Comparison of Thermal Performance between Direct Coil Cooling and Water Jacket Cooling for Electric Traction Motor based on Lumped parameter Thermal Network and Experimentation", International Electric Vehicle Symposium and Exhibition) therefore used analytical and experimental methods We compared the thermal performance of a conventional cooling system using water through an external cooling jacket with that of direct flow of oil for an electric traction motor.

Bennion et al. ("Convective Heat Transfer Coefficients of Automatic Transmission Fluid Jets with Implications for Electric Machine Thermal Management", National Renewable Energy Laboratory) reported that by injecting automatic transmission fluid (ATF) onto surfaces representative of electric motor winding coils, The parameters influencing the heat transfer coefficient by convection during the cooling performed are investigated in more detail.

WO2011/113851 discloses a lubricating composition comprising a base oil, preferably polyalphaolefin (PAO) or GTL, for cooling electric motors of hybrid vehicles or vehicles equipped with a kinetic energy recovery system (KERS) describes the use of However, as the compositions described are optimized for hybrid vehicles, or engines for KERS systems, they may be insufficiently cooling for deployment in fully electric drive systems. In fact, the engines of electric vehicles are subjected to much higher loads than the electric motors of hybrid vehicles due to their much higher frequency of use, implying the use of oil with increased cooling.

EP 2 520 637 describes lubricating compositions containing at least one ester or ether for cooling electric motors and lubricating gears. However, esters are known to be oxidatively unstable. Furthermore, esters cause compatibility problems with and cause deterioration of the varnishes and seals routinely used in electric motors. In particular, the windings of electric motors are commonly coated with varnish. Since the lubricating composition is in direct contact with the windings, it is essential that the latter be inert with respect to this varnish.

Reference may be made to JP 2012/184360, which describes a lubricating composition comprising a synthetic base oil and a fluorinated compound for cooling electric motors. However, the hydrochlorofluorocarbons present in the composition are organic gases that have a large negative impact on the ozone layer and are potent greenhouse gases. Fluorinated gases are also subject to numerous regulations aimed at severely limiting their use.

Presently, in view of the above-discussed limitations with respect to cooling compositions, electric vehicle drive systems presented by manufacturers currently primarily use compositions containing air, water, or water and glycol. Cooled.

For obvious reasons of economy and ease of use, a composition is utilized which can be used to simultaneously meet the requirements for lubrication and cooling of drive systems (motors, batteries, etc.) of electric or hybrid vehicles. It would be advantageous to allow

Unfortunately, these two properties of lubrication and cooling are seemingly contradictory constraints. In fact, in order to cool the electric motor as well as possible, it is known to use substances such as water that are as fluid as possible. In fact, this type of fluid cannot be used to ensure a good level of lubrication. In contrast, highly viscous compositions, which can ensure a good level of lubrication and protection of parts in wear-resistant contact, suffer from unsatisfactory cooling capacity.

WO 2011/113851 EP 2 520 637 JP 2012/184360 WO9418288 EP 2 363 454 EP 2 164 885 EP 0 699 694 WO 2007/003238 WO 2007/025837 WO2015/116496

EVS28, "Comparison of Thermal Performance between Direct Coil Cooling and Water Jacket Cooling for Electric Traction Motor based on Lumped parameter Thermal Network and Experimentation", International Electric Vehicle Symposium and Exhibition "Convective Heat Transfer Coefficients of Automatic Transmission Fluid Jets with Implications for Electric Machine Thermal Management", National Renewable Energy Laboratory

Rather, the present invention aims at presenting a novel composition capable of simultaneously fulfilling both these functions, lubrication and cooling, while overcoming the disadvantages of the prior art.

More precisely, the inventors found that the lubricating compositions formed by one or more oils selected from polyalphaolefins and by one or more specific polymers were much more fluid than known lubricating compositions. We have found that it is possible to provide the dual functions of lubrication and cooling by using a mixture of thickened bases.

Accordingly, the present invention provides a kinematic viscosity in the range of 3-10 mm ² /sec (cSt) measured at 100° C. according to standard ASTM D445 for cooling and lubricating drive systems of electric or hybrid vehicles. Use of a composition comprising at least
- base oils or mixtures of base oils having a kinematic viscosity of 1.5 to 8.0 mm ² /s measured at 100°C according to standard ASTM D445, and
- Ester polymers; linear or star, hydrogenated or non-hydrogenated homopolymers or copolymers of styrene, butadiene and isoprene; polyacrylates; linear or comb polymethacrylates, and olefin copolymers, especially ethylene/ at least one thickening polymer selected from propylene copolymers
Described is the use of a composition comprising

In particular, in a first aspect, the present invention provides a cooling and lubricating drive system for electric or hybrid vehicles of 3-10 mm ² /sec (cSt) measured at 100° C. according to standard ASTM D445. Use of a composition having a kinematic viscosity in the range of
- 70% to 90% by weight base oil or mixture of base oils selected from polyalphaolefins having a kinematic viscosity of 1.5 to 8.0 mm ² /s measured at 100°C according to standard ASTM D445 ,and
- Ester polymers; linear or star, hydrogenated or non-hydrogenated homopolymers or copolymers of styrene, butadiene and isoprene; polyacrylates; linear or comb polymethacrylates; It relates to the use of compositions comprising at least one thickening polymer selected from propylene copolymers.

Advantageously, the compositions according to the invention used in drive systems of electric or hybrid vehicles are used to reach good properties both in terms of cooling and lubrication of the parts of the drive system. be able to.

In particular, the composition according to the invention can be used for cooling and lubricating electric motors of electric or hybrid vehicles. It is particularly effective for cooling power electronics and/or rotors and/or stators of electric motors. It can also lubricate bearings located between the rotor and stator of electric motors in electric or hybrid vehicles.

Advantageously, the composition according to the invention may be used to ensure lubrication of the transmission of electric or hybrid vehicles, especially reduction gears, if present.

Furthermore, the compositions according to the invention may advantageously be used to efficiently cool batteries present in electric or hybrid vehicles.

Advantageously, therefore, by using a single composition according to the invention it is possible to ensure both the cooling of the battery and the lubrication of the transmission, in particular the reduction gear, of e.g. electric or hybrid vehicles.

Advantageously, the composition is injected under fairly high pressure into the zone to be cooled, and the resulting shear at the level of the injector advantageously reduces the dynamic viscosity at the level of the injection zone compared to the kinematic viscosity at rest. is used to reduce the viscosity of the fluid, thereby further enhancing the cooling capacity of the composition.

Furthermore, the compositions according to the invention have the advantage of being simple to formulate. In addition to its combined cooling and lubricating properties, it has good stability, especially with respect to oxidation, and good degassing properties. Therefore, the composition advantageously maintains its good cooling properties over time.

Advantageously, it also has good corrosion resistance and can be used to limit the risk of deterioration of seals or varnishes present in drive systems.

Finally, it meets environmental and health standards.

The invention also relates to a method for cooling and lubrication of a drive system of an electric or hybrid vehicle, comprising at least one step of contacting at least one mechanical part of said system with a composition according to the invention as described above. Regarding the method of containing.

Other properties, variants and advantages of using the composition according to the invention will become more apparent from the following description, examples and figures, given by the non-limiting description of the invention.

1 shows a drive system for an electric or hybrid vehicle; FIG. Figure 2 is a graph showing the thermal properties of compositions CL1 and CL2 according to the invention (● and +, respectively) and CC1 not according to the invention (▴), tested according to Examples 1 and 2 below.

In the rest of the text, the expressions "within", "from" and "varying from" are equivalent and expressly include that boundary unless otherwise indicated. intended to

Unless otherwise indicated, the phrase "including one (one)" should be interpreted to mean "including at least one (one)."

Compositions As indicated above, compositions used in accordance with the present invention comprise at least
- 70% to 90% by weight base oil or mixture of base oils selected from polyalphaolefins having a kinematic viscosity of 1.5 to 8.0 ^mm2 /s measured at 100°C according to standard ASTM D445, and
- ester polymers; linear or star, hydrogenated or non-hydrogenated homopolymers or copolymers of styrene, butadiene and isoprene; polyacrylates; linear or comb polymethacrylates (PMA), and olefin copolymers; It comprises one or more thickening polymers selected especially from ethylene/propylene copolymers.

In the remainder of the text, the term "fluid base" is used to refer to an oil or mixture of base oils having a kinematic viscosity of 1.5 to 8 ^mm2 /s measured at 100°C according to standard ASTM D445. be.

As discussed above, the flowable base/thickening polymer combination according to the present invention can be further enhanced by the effect of shear applied at the injection level, while obtaining good lubricity. can be used to obtain compositions with good cooling properties, which are also consistent with the rheological behavior, especially in terms of viscosity.

In particular, the compositions according to the invention have kinematic viscosities in the range from 3 to 10 mm ² /s, preferably in the range from 3 to 9 mm ² /s, measured at 100° C. according to standard ASTM D445.

In particular, the composition used is a non-Newtonian fluid.

In this description, the term "Newtonian fluid" refers to a fluid in which a linear relationship exists between the applied mechanical load (the force exerted on the fluid per unit surface area) and the fluid's shear (i.e., the fluid's velocity gradient). means. Thus, a "non-Newtonian fluid" is a fluid that is not Newtonian.

Base Oil The composition according to the invention is formed by one or more base oils selected from polyalphaolefins and has a base oil of 1.5 to 8 mm ² /s, measured at 100° C. according to standard ASTM D445, in particular A flowable base is used having a kinematic viscosity of 1.5 to 6.1 mm ² /s, especially 1.5 to 4.1 mm ² /s, more especially 1.5 to 2.1 mm ² /s.

Generally, in the field of lubricants, base oils belong to groups IV of the type defined in the API classification (or their equivalents according to the ATIEL classification) and are of mineral or synthetic origin as indicated in Table A below. oils, or mixtures thereof.

Mineral base oils are obtained by atmospheric and vacuum distillation of crude oils, followed by refining operations such as solvent extraction, deasphalting, solvent dewaxing, hydrotreating, hydrocracking, hydroisomerization and hydrofinishing. All types of base oils are included.

Mixtures of synthetic and mineral oils may also be used.

Lubricating bases used to prepare compositions according to the present invention must also meet the viscosity criteria cited above and have properties, in particular viscosity index, sulfur content, or oxidation resistance. and these properties are adapted for use in electric or hybrid vehicle drive systems.

Base oils may also be selected from synthetic oils, such as certain esters of carboxylic acids and alcohols, and polyalphaolefins (PAOs).

The oil or base oil of the composition used according to the invention is selected from polyalphaolefins (PAO). PAOs used as base oils are derived, for example, from monomers having 4 to 32 carbon atoms, such as octene or decene.

The mass-average molecular weight of PAOs can take on a relatively wide range of values. Preferably, the PAO has a weight average molecular weight of less than 600 Da. The weight average molecular weight of the PAO may also be 100-600 Da, 150-600 Da, or even 200-600 Da.

By way of example, PAOs used in connection with the present invention having kinematic viscosities of 1.5-8 mm ² /s measured at 100° C. according to standard ASTM D445 have the trade names Durasyn® 162, Durasyn ® 164, Durasyn® 166, and Durasyn® 168 from Ineos.

According to a particular embodiment, the composition used according to the invention comprises a polyalkylene glycol (PAG) obtained by polymerization or copolymerization of alkylene oxides having 2 to 8 carbon atoms, especially 2 to 4 carbon atoms. do not have.

According to a particular embodiment, the fluid base of the composition used according to the invention is strictly an ester- and ether-type base oil with a content of less than 30% by weight, in particular an ester- and ether-type base oil with a content of less than 25% by weight. Ester- and ether-type base oils, especially containing less than 10% by weight of ester- and ether-type base oils.

In particular, the fluid base of the composition used according to the invention does not contain ester-type oils.

Preferably, the compositions used according to the present invention are formed by one or more base oils having a kinematic viscosity in the range of 1.5 to 8 mm ² /s measured at 100° C. according to standard ASTM D445. Contains a fluid base.

In other words, the composition according to the invention may for example be free of base oils or mixtures of base oils which do not meet the criteria for kinematic viscosity measured at 100° C. according to standard ASTM D445, in particular 9 mm ² /sec. It may contain no oils or mixtures of base oils with viscosities greater than

It is within the competence of the person skilled in the art to adjust the flowable base content for use in the composition according to the invention in order to obtain the desired viscosity for the composition.

As indicated above, the fluid base provides the cooling capacity of the compositions used in accordance with the present invention. Especially when the composition is used for drive systems of electric or hybrid vehicles, the flow properties of the base ensure good cooling.

The cooling properties of the composition used are more advantageously enhanced by the shear applied to the composition at the level of injection, which causes the fluid to have a lower level of viscosity than at rest. Thereby, advantageously, the effect of using the thickening polymer according to the invention on the cooling capacity of the composition is controlled.

The lubricating composition comprises a base oil or a mixture of base oils having a kinematic viscosity of 1.5 to 8 mm ² /sec measured at 100° C. according to standard ASTM D445, from 60% by weight to the total weight of the composition. It may contain 90% by mass.

In particular, the composition used according to the invention comprises a base oil or a mixture of base oils having a kinematic viscosity of 1.5 to 8 mm ² /s measured at 100° C. according to standard ASTM D445, the total weight of the composition being 70% to 90% by mass, preferably 80% to 90% by mass.

thickening polymer
The compositions used according to the invention further comprise one or more polymers known as thickening polymers.

The polymer(s) is selected for its ability to thicken the flowable base according to the present invention to provide the desired lubricating properties to the composition.

The thickening polymer according to the invention may in particular be selected from polymers known as "viscosity index improvers" (VI).

Viscosity-improving polymers of this type are described, for example, in the documents WO 9418288, EP 2 363 454, EP 2 164 885, EP 0 699 694, WO 2007/003238 and in WO 2007/025837.

It should be understood that the thickening polymer(s) is different than the oil or the base oil mentioned above.

In particular they are ester polymers; linear or star, hydrogenated or non-hydrogenated homopolymers or copolymers of styrene, butadiene, and isoprene; polyacrylates; linear or comb polymethacrylates; It may also be a polymer selected from copolymers, especially ethylene/propylene copolymers.

Preferably, the thickening polymer may be selected from inter alia linear or comb polymethacrylates, linear or hydrogenated star copolymers of styrene, butadiene and isoprene, and mixtures thereof.

Advantageously, the thickening polymer may be selected, inter alia, from comb polymethacrylates, hydrogenated star copolymers of styrene, butadiene and isoprene, and mixtures thereof.

By way of example, polymethacrylate comb polymers within the meaning of the invention are described in EP 2 164 885, EP 0 699 694, WO 2007/003238 and WO 2007/025837. and the structures and definitions of these polymers described in those documents are hereby incorporated into the description of the present application.

An example of a polymethacrylate comb polymer within the meaning of the invention is commercially available from Evonik under the trade name Viscoplex® 3-200.

As another example, hydrogenated star copolymers of styrene, butadiene and isoprene within the meaning of the present invention are described in EP 2 363 454 and those described in EP 2 363 454. The structures and definitions of polymers are hereby incorporated into the description of the present application.

An example of a hydrogenated star copolymer of styrene, butadiene and isoprene within the meaning of the invention is sold by the company Infineum under the trade name SV®261.

The use of a thickening polymer ensures that the composition thickens sufficiently to ensure a satisfactory level of protection, i.e., anti-wear lubrication, when used in electric or hybrid vehicle drive systems. , in no way affects the cooling capacity of the composition.

In particular, the content of the thickening polymer(s) in the composition according to the invention is between 0.5% and 10% by weight, preferably between 1% and 8% by weight, more preferably 1.5% by weight, relative to the total weight of the composition. % to 5% by mass.

This amount refers to the amount of active substance in the polymer. In fact, the polymers used in connection with the present invention may be in the form of dispersions in one or more mineral or synthetic oils.

Also in particular, the compositions used according to the invention are diluted in one or more base oils to give 1% to 25% by weight, preferably 2% to 20% by weight, relative to the total weight of the composition. %, more preferably 4% to 20% by weight of thickening polymer(s).

It is within the competence of the person skilled in the art to adjust the proportions of the various constituents of the composition, in particular the flowable base (liquid base) and the thickening polymer, in order to obtain the viscosity required according to the invention. be.

According to a particular embodiment, the composition used according to the invention comprises at least one base oil selected from PAO and hydrogenated star copolymers of comb polymethacrylate, styrene, butadiene and isoprene and their It contains at least one polymer selected from the mixture.

In particular, when the base oil is selected from PAO in the composition used according to the invention, it is combined with at least one polymer selected from comb polymethacrylates.

In particular, if again in the composition used according to the invention the base oil is selected from PAO, it is combined with at least one polymer selected from hydrogenated star copolymers of styrene, butadiene and isoprene.

According to one embodiment variant, the composition used according to the invention comprises
- a base oil or mixture of base oils having a kinematic viscosity of 1.5 to 8 mm ² /s measured at 100°C according to standard ASTM D445, and
- is formed from, or consists of, a mixture of one or more thickening polymers as defined above.

Preferably, the composition used according to the invention comprises
- one or more base oils having a kinematic viscosity of 1.5 to 8 ^mm2 /s measured at 100°C according to standard ASTM D445, and
- formed from one or more thickening polymers as defined above.

Alternatively, the composition used may further comprise one or more additives more precisely defined in the description below.

Additives Additives that may be incorporated in compositions according to the present invention include friction modifiers, detergents, antiwear additives, extreme pressure additives, dispersants, antioxidants, pour point improvers, antifoam agents, and mixtures thereof.

It should be understood that the nature and amount of additives used are selected so as not to affect the combined lubricating and cooling power properties of the compositions of the present invention.

These additives are commercially available for vehicle engines with performance levels defined individually and/or by the ACEA (Association des Constructeurs Europeens d'Automobiles) [European Automobile Manufacturers Association] and/or API (American Petroleum Institute). It may be introduced in a mixture that reflects additives already marketed for lubricating formulations, and these additives are well known to those skilled in the art.

Antiwear and extreme pressure additives protect friction surfaces by forming a protective film adsorbed on those surfaces.

A wide variety of antiwear additives exist. Preferably, for lubricating compositions according to the present invention, the antiwear additive is selected from phosphorus sulfur additives such as metal alkylthiophosphates, especially zinc alkylthiophosphates, especially zinc dialkyldithiophosphates or ZnDTP. Preferred compounds have the formula Zn((SP(S)(OR ² )(OR ³ )) ₂ [wherein R ² and R ³ may be the same or different and are independently alkyl groups, preferably represents an alkyl group having 1 to 18 carbon atoms].

Amine phosphates are also antiwear additives that can be used in compositions according to the invention. However, since these additives generate ash, the phosphorus provided by these additives can act as a poison for automotive catalyst systems. These effects can be minimized by partially replacing the amine phosphates with non-phosphorous donating additives such as polysulfides, especially sulfur-containing olefins.

The composition used according to the invention contains from 0.01% to 6%, preferably from 0.05% to 4%, more preferably from 0.1% to 2% by weight of an antiwear additive, relative to the total weight of the composition. and extreme pressure additives.

According to a particular embodiment, the composition used according to the invention is free of antiwear and extreme pressure additives. In particular, the compositions used according to the invention are advantageously free of phosphorus-containing additives.

Compositions used in accordance with the present invention may include at least one friction modifying additive. Friction modifying additives may be selected from compounds that provide metallic elements and ash-free compounds. Examples of compounds supplying metal elements that may be mentioned are complexes of transition metals such as Mo, Sb, Sn, Fe, Cu, Zn, etc., whose ligands are oxygen, nitrogen, sulfur or phosphorus atoms. It may be a hydrocarbon compound containing. Ash-free antiwear additives are generally of organic origin and include monoesters of fatty acids and polyhydric alcohols, alkoxylated amines, alkoxylated aliphatic amines, aliphatic epoxy compounds, aliphatic epoxy compounds of boric acid, It may be selected from fatty amines or fatty acid glycerol esters. According to the invention, an aliphatic compound contains at least one hydrocarbon group containing 10 to 24 carbon atoms.

The composition used according to the invention contains from 0.01% to 2% or from 0.01% to 5% by weight, preferably from 0.1% to 1.5% or from 0.1% to 2% by weight relative to the total weight of the composition. % by weight of anti-wear additives may be included.

Advantageously, the composition according to the invention does not contain antiwear additives.

The composition used according to the invention may contain at least one antioxidant additive.

Antioxidant additives generally retard the decomposition of the composition during use. This degradation can be manifested, inter alia, by the formation of deposits, the presence of sludge, or an increase in composition viscosity.

In particular, antioxidant additives act as radical inhibitors or hydroperoxide destroyers. Examples of antioxidant additives in common use that may be mentioned are phenol-type antioxidant additives, amine-type antioxidant additives, and phosphorus-sulfur antioxidant additives. Certain of these antioxidant additives, such as the phosphorous sulfur antioxidant additive, can generate ash. Phenolic antioxidant additives may be ashless or indeed in the form of salts of neutral or basic metals. Antioxidant additives include, among others, sterically hindered phenols, sterically hindered phenol esters, and sterically hindered phenols, including thioether bridges, diphenylamines, diphenylamines substituted with at least one C ₁ -C ₁₂ alkyl group, N, It may be selected from N'-dialkylaryldiamines, as well as mixtures thereof.

Preferably, according to the present invention, the sterically hindered phenol is a C ₁ -C ₁₀ alkyl group, preferably a C ₁ -C ₆ alkyl group, with at least one adjacent carbon to the carbon bearing the alcohol function. are selected from compounds containing a phenol group substituted with a group, preferably a _C4 alkyl group, preferably a tert-butyl group.

Amine compounds are another type of antioxidant additive that may optionally be used in combination with the phenolic antioxidant additive. Examples of amine compounds are aromatic amines such as those of the formula NR ⁴ R ⁵ R ⁶ [wherein R ⁴ represents an optionally substituted aliphatic or aromatic group and R ⁵ is optionally substituted ^R6 represents a hydrogen atom, an alkyl group, an aryl group or a group of the formula ^R7S (O) _zR8 [wherein ^R7 represents an alkylene group or an alkenylene group, ^R8 represents an alkyl ^group , represents an alkenyl group or an aryl group, and z represents 0, 1 or 2].

Sulfur-containing alkylphenols or their alkali and alkaline earth metal salts may also be used as antioxidant additives.

Another group of antioxidant additives are copper-containing compounds such as copper thiophosphates or dithiophosphates, copper with salts of carboxylic acids, dithiocarbamates, sulfonates, phenates, copper acetylacetonate. Copper I and II salts, and succinic acid or anhydride salts may also be used.

The compositions used in accordance with the present invention may contain any type of antioxidant additive known to those skilled in the art.

Advantageously, the composition used according to the invention comprises at least one ash-free antioxidant additive.

The composition used according to the invention may comprise from 0.5% to 2% by weight of at least one antioxidant additive relative to the total weight of the composition.

The compositions used according to the invention may also contain at least one cleaning additive.

Cleaning additives generally can be used to reduce deposit formation on the surface of metal parts by dissolving secondary oxidation and secondary combustion products.

Cleaning additives that may be used in compositions used in accordance with the present invention are generally known to those skilled in the art. Detergent additives may be anionic compounds containing a lipophilic long chain hydrocarbon and a hydrophilic head group. The accompanying cations may be metal cations of alkali or alkaline earth metals.

The cleaning additives are preferably selected from alkali metal or alkaline earth metal salts of carboxylic acids, sulfonic acids, salicylic acids, naphthenic acids and salts of phenates. Alkali and alkaline earth metals are preferably calcium, magnesium, sodium or barium.

These metal salts are generally contained in stoichiometric amounts or indeed in excess, ie greater than stoichiometric amounts. As such, they are overbased cleaning additives, and the excess metals that provide the overbasing properties of cleaning additives are then generally oil-insoluble metal salts such as carbonates, hydroxides, oxalates, It is in the form of salts, acetates or glutamates, preferably carbonates.

The compositions used according to the invention may contain, for example, 2% to 4% by weight of cleaning additives relative to the total weight of the composition.

The composition used according to the invention may also comprise at least one additive that lowers the pour point.

Additives which lower the pour point by slowing the formation of paraffin crystals generally improve the low temperature behavior of the composition.

Examples of pour point-lowering additives that may be mentioned are alkylpolymethacrylates, polyacrylates, polyarylamides, polyalkylphenols, polyalkylnaphthalenes, and alkylpolystyrenes.

Furthermore, the composition used according to the invention may comprise at least one dispersing agent.

Dispersants may be selected from Mannich bases, succinimides and their derivatives.

The composition used according to the invention may contain, for example, from 0.2% to 10% by weight of dispersant relative to the total weight of the composition.

As indicated above , due to their combined properties in terms of cooling and lubrication, the compositions described above can be used both as lubricants and as cooling fluids for drive systems of electric or hybrid vehicles.

In particular, the invention relates to the use of a composition as defined above for cooling and lubricating electric motors of electric or hybrid vehicles and various parts thereof, in particular moving parts. The invention is also applicable to batteries for electric or hybrid vehicles.

As shown diagrammatically in FIG. 1, the drive system of an electric or hybrid vehicle includes, inter alia, an electric motor portion (1). It typically includes power electronics (11) connected to a stator (13) and a rotor (14).

The stator includes coils, in particular copper coils, which are supplied with alternating current. This can generate a rotating magnetic field. The rotor itself contains coils, permanent magnets, or other magnetic material, and is induced to rotate by a rotating magnetic field.

The power electronics (11), the stator (13) and rotor (14) of the electric motor (1) are components with complex structures and generate a large amount of heat during operation of the motor. Therefore, providing cooling for electric motors, especially power electronics, is extremely important.

Furthermore, the bearings 12, which are generally installed between the stator 13 and rotor 14, are subject to high mechanical loads and create problems with wear due to fatigue. Therefore, it is necessary to lubricate the bearings to prolong their service life.

The compositions used in accordance with the present invention as described above are used to provide both the function of lubrication and the function of protection against wear of contacting members, and the function of cooling, inside electric or hybrid vehicles. can do.

Therefore, in particular, the present invention relates to the use of a composition as defined above for cooling and lubricating electric motors of electric or hybrid vehicles.

In particular, it can be used for cooling power electronics and/or rotors and/or stators of electric motors. It can also lubricate bearings located between the rotor and stator of electric motors in electric or hybrid vehicles.

The drive system of an electric or hybrid vehicle also includes a speed reduction gear (3) which can be used to reduce the speed of rotation at the exit of the transmission, in particular the electric motor, to adapt the speed transmitted to the wheels. may be included, thereby simultaneously allowing control of the speed of the vehicle.

This reduction gear is subjected to high friction loads and therefore must be lubricated in a suitable manner to prevent it from being damaged too quickly.

The invention therefore also relates to the use of a composition as defined above for the lubrication of transmissions, in particular reduction gears, in electric or hybrid vehicles.

Advantageously, the compositions according to the invention may therefore be used to lubricate and cool both electric motors and transmissions, in particular reduction gears, in electric or hybrid vehicles.

As mentioned above, the electric motor is generally powered by a battery (2). Lithium-ion batteries are the most widespread in the field of electric vehicles. The development of ever more powerful batteries in ever smaller sizes implies that there will be problems associated with cooling these batteries. In fact, as soon as the battery exceeds a temperature of the order of 50°C to 60°C, there is a high risk of ignition or even explosion of the battery. It is also necessary to maintain the battery above a temperature of approximately 20-25°C so that the battery does not discharge too quickly and to extend its service life.

As such, the compositions of the present invention may be used to cool the batteries of electric or hybrid vehicles.

It is understood that the above uses may be combined and the above compositions may be used both as lubricants and as cooling fluids for engines, batteries and transmissions of electric or hybrid vehicles. should.

The present invention thus has the advantage of allowing a single composition that combines lubricating and cooling properties to be used as a lubricant and as a cooling fluid in electric or hybrid vehicles.

The present invention also relates to a method of cooling and lubricating the drive system of an electric or hybrid vehicle, wherein at least one mechanical component of the electric motor and/or battery and/or transmission is brought into contact with the composition defined above. It relates to a method comprising at least one step of causing

The properties and preferences described for the composition used according to the invention and the set of uses thereof also apply to this method.

Cooling with compositions used in accordance with the present invention may be performed using any method known to those skilled in the art.

Examples of direct uses that may be mentioned are jet cooling, spray cooling, i.e., in practice, the mist from the composition according to the invention under pressure and gravity, in particular the rotor and/or This is due to formation on the windings of the stator.

Advantageously, the composition is jetted under fairly high pressure into zones of the drive system to be cooled, for example as described in the publications by Liu et al. and Bennion et al. cited above. is injected. Advantageously, the shear resulting from this injection can be used, at the level of the injection zone, to reduce the viscosity of the fluid compared to the kinematic viscosity at rest, thereby increasing the potential of the composition. further enhance cooling.

Furthermore, oil circulation systems currently used in electric motors may be used, for example as described in document WO2015/116496.

According to the invention, the inherent properties, advantages or preferred aspects of the composition according to the invention can also be used to define special, advantageous or preferred uses according to the invention.

The invention will now be described with the aid of the following examples given, by way of course non-limiting illustration of the invention.

Example 1
Lubricating compositions according to the invention (CL), and comparative compositions (CC), as shown in Table 1 below, depending on the nature and amount of the product (expressed as percent by weight), the various components of the composition were mixed.

The properties of the compositions thus prepared are shown in Table 2.

Example 2
Measurement of Thermal Properties of Compositions According to the Invention One method of measuring the thermal properties of a fluid consists of measuring the heat exchange coefficient (heat transfer per unit surface area and temperature) of the fluid. The higher the heat exchange coefficient, the better the cooling properties of the fluid.

Tests were performed to determine the heat exchange coefficient of each of the compositions listed in Table 1.

The test principle consisted of spraying the oil with the aid of a perpendicular spray nozzle onto a metal plate heated by induction. A thermal camera placed above the plate records the temperature profile during the oil discharge. From the value of the change in temperature on the plate it is then possible to calculate the average heat exchange coefficient of the composition.

It is possible to vary various parameters, in particular the temperature of the plate, the size of the spray nozzles and the pressure with which the oil is discharged. Thermal coefficient measurements are made at various distances (this distance corresponds to the radius) from the point of impact of the jet on the metal plate. The test conditions are listed in Table 3 below.

The results obtained are shown in the graph of FIG.

Various temperatures (in degrees Celsius) sensed on the heated plate are shown on the vertical axis, and radii (in meters) corresponding to various distances from the impingement point of the jet on the metal plate are shown on the horizontal axis.

At a radius greater than 0.01 m, the composition of the invention (CL1, ● and CL2, +) and the comparative composition (CC1, ▲) were each detected on the heated plate fired thereon. It can be seen from Figure 2 that there is a significant difference of at least 5°C between the temperatures.

This therefore means that the composition according to the invention is able to cool the heated plate better and maintain a stable temperature compared to a comparative composition without thickening polymer. .

As a result, the compositions according to the invention can be used not only for lubricating but also for cooling drive systems of electric or hybrid vehicles.

DESCRIPTION OF SYMBOLS 1... Electric motor 2... Battery 3... Reduction gear 11... Power electronics 12... Bearing 13... Stator 14... Rotor

Claims (10)

The use of compositions having kinematic viscosities in the range of 3-10 mm ² /sec (cSt) measured at 100° C. according to standard ASTM D445 for cooling and lubricating drive systems of electric or hybrid vehicles. wherein the composition comprises at least
- 70% to 90% by weight base oil having a kinematic viscosity of 1.5 to 2.1 mm ² /s measured at 100°C according to standard ASTM D445 and selected from polyalphaolefins or a mixture of base oils, and
linear or star-shaped, hydrogenated or non-hydrogenated homopolymers or copolymers of styrene, butadiene and isoprene; polyacrylates; linear or comb polymethacrylates; and olefin copolymers. Use of compositions comprising at least one thickening polymer. Use according to claim 1, wherein the composition has a kinematic viscosity in the range from 3 to 9 mm ² /s measured at 100°C according to standard ASTM D445. 3. Use according to claim 1 or 2, characterized in that the thickening polymer is selected from comb polymethacrylates; hydrogenated star copolymers of styrene, butadiene and isoprene; and mixtures thereof. Use according to any one of the preceding claims, wherein the composition comprises from 0.5% to 10% by weight of thickening polymer relative to the total weight of the composition. wherein the composition comprises at least one selected from friction modifiers, detergents, antiwear additives, extreme pressure additives, dispersants, antioxidants, pour point improvers, defoamers, and mixtures thereof; 5. Use according to any one of claims 1 to 4, further comprising additives. 6. Use according to any one of claims 1 to 5, for cooling and lubricating electric motors of electric or hybrid vehicles. 7. Use according to claim 6, for cooling power electronics and/or rotors and/or stators of electric motors. 8. Use according to claim 6 or 7, for lubricating bearings arranged between the rotor and stator of an electric motor. 9. Use according to any one of claims 1 to 8, for cooling batteries of electric or hybrid vehicles. 10. Use according to any one of claims 1 to 9 for lubricating transmissions of electric or hybrid vehicles.

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