CN111373021A

CN111373021A - Composition for cooling and lubricating vehicle drive system

Info

Publication number: CN111373021A
Application number: CN201880075627.XA
Authority: CN
Inventors: J·古林
Original assignee: Total Marketing Services SA
Current assignee: TotalEnergies Marketing Services SA
Priority date: 2017-10-20
Filing date: 2018-10-19
Publication date: 2020-07-03
Also published as: WO2019077105A1; JP7260555B2; ES2968536T3; EP3697876B1; EP3697876A1; FR3072685B1; US20200248095A1; JP2021500463A; FR3072685A1; KR20200073240A

Abstract

The invention relates to the use of a composition for cooling and lubricating the drive system of an electric or hybrid vehicle, said composition having a kinematic viscosity, measured at 100 ℃ according to the standard ASTM D445, of from 3 to 10mm²S and comprises at least: -70% -90% by weight of a base oil or a mixture of base oils having a kinematic viscosity, measured according to standard ASTM D445 at 100 ℃, of from 1.5 to 8.0mm²And is selected from the group consisting of poly α -olefins, and at least one thickening polymer.

Description

Composition for cooling and lubricating vehicle drive system

Technical Field

The present invention relates to the field of compositions for lubricating and cooling the drive system of an electric or hybrid vehicle. The invention aims in particular to propose a composition having both lubricating and cooling properties for use in the drive system of an electric or hybrid vehicle, in particular for cooling and lubricating an electric motor.

Background

For reduction of CO₂The evolution of international standards for emissions and also for reducing energy consumption has forced automobile manufacturers to propose alternative solutions for internal combustion engines.

One of the solutions identified by automotive manufacturers is to replace the internal combustion engine with an electric motor. For reduction of CO₂Emissions research has therefore led a certain number of automotive companies to develop electric vehicles.

The term "electric vehicle" in the meaning of the present invention refers to a vehicle comprising an electric motor as sole propulsion means, in contrast to a hybrid vehicle comprising an internal combustion engine and an electric motor as combined propulsion means.

The term "drive system" in the meaning of the present invention refers to a system comprising the mechanical components necessary for propelling an electric vehicle. The drive system therefore more particularly comprises an electric motor, a battery and optionally a transmission.

In general, there is a need in electric or hybrid vehicles to use compositions that satisfy the dual constraints of cooling and lubricating the components of the drive system. These requirements are typically met by applying two different measures, a lubricating composition on the one hand and a cooling fluid on the other hand.

As such, lubricating compositions, also known as "lubricants," are commonly used in engines, the primary purpose of which is to reduce the friction between the various metal components moving in the engine. Furthermore, they are also effective in preventing premature wear and even damage to these components (especially to their surfaces).

To this end, lubricating compositions are typically composed of one or more base oils to which are generally combined various additives that are specific to stimulating the lubricating properties of the base oil (e.g., friction modifying additives).

On the other hand, the motor generates heat during operation. If the heat generated is greater than that normally dissipated to the environment, cooling of the engine must be ensured. Typically, cooling is performed on one or more portions of the engine that generate heat and/or portions of the engine that are sensitive to heat to avoid reaching dangerous temperatures.

Conventionally, it is known to use air (typically by means of forced convection) to cool the motor. This cooling method has the advantage of avoiding having to prepare a specific cooling fluid. However, with the advent of increasingly smaller and more powerful engines, this cooling method is no longer sufficient, in particular because of the limited efficiency of the air used for cooling.

Methods of using water to cool an engine are also presented. Despite the high heat capacity of water, it is not possible to envisage direct cooling by bringing the water into contact with the motor, due to the electrical conductivity of the water. Therefore, the cooling system requires the installation of an external jacket, which greatly increases the volume of the engine.

Alternative methods of cooling the motor using oil jets have also been investigated.

Liu et al (EVS28, comprehensive of Thermal Performance between Direct Cooling and Water Jack Cooling for Electric Traction Motor based on a simplified parameter Thermal Network and evaluation, International Electric vehicle heating and evaluation) thus analytically and experimentally compared the Thermal Performance of a conventional Cooling system for Electric Traction motors that uses Water via an external Cooling Jacket to the Thermal Performance of a Direct oil flow.

Bennion et al (conductive Heat Transfer fluids with improvements for Electric Machine thermal management, National Renewable Energy Laboratory) more specifically studied the parameters that affect the Convective Heat Transfer coefficient used to perform the cooling by spraying the Automatic Transmission Fluid (ATF) onto the surface of the wound coils representing the Electric motor.

WO2011/113851 describes the use of a lubricating composition comprising a base oil, preferably a poly α -olefin (PAO) or GTL, for cooling the electric motor of a vehicle or hybrid vehicle equipped with a Kinetic Energy Recovery System (kens), however, as the described composition is optimized for the engines of the KERS System or hybrid vehicle, they have insufficient cooling performance for use in a fully electric drive System because the engines of electric vehicles are subjected to much higher loads than the electric motors of hybrid vehicles, which is due to the much higher frequency of use, which means that an oil with enhanced cooling performance is used.

With reference to document EP 2520637, it describes a lubricating composition comprising at least one ester or ether for cooling electric motors and lubricating gear transmissions (engreages). However, esters are known to have oxidative instability. In addition, esters cause compatibility problems with varnishes and joints conventionally used in electric motors, which can lead to their deterioration. In particular, the windings of the motor are usually coated with varnish. Since the lubricating composition is in direct contact with the windings, it is essential that the windings are inert to the varnish.

Document JP 2012/184360 may also be cited, which describes a lubricating composition for cooling electric motors comprising a synthetic base oil and a fluorinated compound. However, the fluorochlorohydrocarbons present in these compositions are organic gases which have a large negative impact on the ozone layer and are potent greenhouse gases. Fluorinated gases are also the subject of many regulations that aim to strictly limit their use.

At present, in view of the above mentioned limitations regarding cooling compositions, the drive systems of electric vehicles proposed by manufacturers are currently cooled essentially using air, water or a composition comprising water and glycol.

For obvious reasons of economy and ease of use, it would be advantageous to provide a composition that can be used to simultaneously meet the lubrication and cooling requirements of the drive system (engine, battery, etc.) of an electric or hybrid vehicle.

Unfortunately, these two properties of lubrication and cooling present opposite constraints at a glance. In practice, in order to cool the motor as best as possible, it is known to use a product that is as fluid as possible, for example water. Such fluids do not ensure a good level of lubrication. In contrast, high viscosity compositions capable of ensuring good levels of lubrication and protecting the contacting components from wear have unsatisfactory cooling potential.

Disclosure of Invention

Specifically, the present invention aims to propose a new composition capable of fulfilling both the lubricating and cooling functions simultaneously, while overcoming the drawbacks of the prior art.

More precisely, the inventors have found that the dual function of lubrication and cooling can be ensured by using a base mixture formed by one or more oils chosen from poly α -olefins, having a much greater fluidity than known lubricating compositions, thickened by one or more specific polymers.

The invention therefore describes the use of a composition for cooling and lubricating the drive system of an electric or hybrid vehicle, said composition having a kinematic viscosity, measured at 100 ℃ according to the standard ASTM D445, of from 3 to 10mm²(cSt) and comprises at least:

-a base oil or a mixture of base oils having a kinematic viscosity, measured at 100 ℃ according to the standard ASTM D445, of from 1.5 to 8.0mm²S; and

-at least one thickening polymer selected from ester polymers; linear or star, hydrogenated or non-hydrogenated homopolymers or copolymers of styrene, butadiene and isoprene; a polyacrylate; linear or comb-like polymethacrylates; and olefin copolymers, especially ethylene/propylene copolymers.

In particular, the invention relates, according to a first aspect thereof, to the use of a composition for cooling and lubricating the drive system of an electric or hybrid vehicle, said composition having a kinematic viscosity, measured at 100 ℃ according to the standard ASTM D445, of from 3 to 10mm²(cSt) and comprises at least:

-70% -90% by weight of a base oil or a mixture of base oils having a kinematic viscosity, measured according to standard ASTM D445 at 100 ℃, of from 1.5 to 8.0mm²Is/s and is selected fromPoly α -olefin, and

Advantageously, the composition according to the invention used in the drive system of an electric or hybrid vehicle makes it possible to jointly achieve good performance in terms of cooling and lubrication of the components of the drive system.

More particularly, the composition according to the invention enables cooling and lubrication of the electric motor of an electric or hybrid vehicle. It has proven to be particularly effective in cooling the power electronics of the electric motor and/or the rotor and/or the stator. It also ensures the lubrication of the bearings located between the rotor and the stator of the electric motor of an electric or hybrid vehicle.

Advantageously, the composition according to the invention makes it possible to ensure the lubrication of the transmission, in particular of the retarder (reducer), of an electric or hybrid vehicle when present.

In addition, the composition according to the invention enables advantageously effective cooling of the batteries present in electric or hybrid vehicles.

Thus, advantageously, by using a single composition according to the invention, it is possible, for example, to ensure both the cooling of the battery and the lubrication of the transmission, in particular of the retarder, in an electric or hybrid vehicle.

Advantageously, the composition is injected into the area to be cooled under a rather high pressure, the shear forces generated at the injector making it possible to advantageously reduce the viscosity of the fluid at the injection area with respect to the kinematic viscosity at rest and thus further increase the cooling potential of the composition.

In addition, the composition according to the invention has the advantage of being easy to formulate. In addition to the combination of cooling and lubricating properties, it also has good stability, especially in terms of oxidation, and good degassing properties. Thus, the composition advantageously retains its good cooling properties over time.

Advantageously, it also has good corrosion protection properties and makes it possible to limit the risk of deterioration of joints (joints) or varnishes present in the drive system.

Finally, it meets environmental and health standards.

The invention also relates to a method for cooling and lubricating the drive system of an electric or hybrid vehicle, comprising at least one step of bringing at least one mechanical component of said system into contact with a composition according to the invention as described above.

Drawings

Further characteristics, variations and advantages of the use of the composition according to the invention will become more apparent from reading the description, examples and figures given by way of illustration and not of limitation of the invention.

FIG. 1 is a schematic diagram of a drive system for an electric or hybrid vehicle.

Figure 2 is a graph showing the thermal properties of compositions CL1 and CL2 (respectively · and +) according to the invention and of composition CC1(▲) not according to the invention, tested according to examples 1 and 2 below.

Detailed Description

In the following, the expressions "between", "from.

Unless otherwise indicated, the expression "component un (e) (comprising …)" is to be understood as "component audions un (e) (comprising at least one (or one) …)".

Composition comprising a metal oxide and a metal oxide

As indicated above, the composition used according to the invention comprises at least:

-70% -90% by weight of a base oil or a mixture of base oils having a kinematic viscosity, measured according to standard ASTM D445 at 100 ℃, of from 1.5 to 8.0mm²And is selected from the group consisting of poly α -olefins, and

-one or more thickening polymers selected from ester polymers; linear or star, hydrogenated or non-hydrogenated homopolymers or copolymers of styrene, butadiene and isoprene; a polyacrylate; linear or comb Polymethacrylates (PMA); and olefin copolymers, especially ethylene/propylene copolymers.

Hereinafter, the term "base fluid" is used to indicate a fluid having a kinematic viscosity, measured at 100 ℃ according to the standard ASTM D445, of from 1.5 to 8mm²A base oil or a mixture of base oils.

As mentioned above, the combination of fluid base/thickening polymer according to the invention makes it possible to obtain compositions having good cooling properties which are further enhanced by the shearing action exerted at the injection site; at the same time, the lubricating oil conforms to rheological behavior, particularly in the aspect of viscosity, and can obtain good lubricating performance.

More particularly, the compositions according to the invention have a thickness, measured at 100 ℃ according to the standard ASTM D445, of between 3 and 10mm²A/s of between 3 and 9mm, preferably²Kinematic viscosity between/s.

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

In this specification, the term "newtonian fluid" refers to a fluid: for this fluid, there is a linear relationship between the mechanical stress applied (force applied to the fluid per unit surface area) and the shear of the fluid (i.e., the velocity gradient of the fluid). "non-Newtonian fluid" thus refers to a fluid that is not a Newtonian fluid.

Base oil

The composition according to the invention uses a fluid base formed of one or more base oils selected from the group consisting of poly α -olefins and having a viscosity measured at 100 ℃ according to standard ASTM D445 of from 1.5 to 8mm²S, in particular from 1.5 to 6.1mm²S, more particularly from 1.5 to 4.1mm²S, even more particularly from 1.5 to 2.1mm²Kinematic viscosity in/s.

Generally, in the field of lubricants, the base oil may be chosen from oils of mineral or synthetic origin (or their equivalents classified according to ATIEL) belonging to groups I to V according to the categories defined in the API classification (shown in table a below) or mixtures thereof.

TABLE A

Mineral base oils include all types of base oils obtained by: crude oil is distilled at atmospheric pressure and vacuum, and then subjected to refining operations such as solvent extraction, desalting (lysophatage), solvent deparaffinization, hydrotreating, hydrocracking, hydroisomerization, and hydrofinishing.

Mixtures of synthetic and mineral oils may also be used.

The lubricating base stock used to obtain the lubricating composition according to the invention should have properties suitable for use in the driveline of an electric or hybrid vehicle, in particular viscosity index, sulphur content or oxidation resistance, in addition to meeting the above viscosity criteria.

The base oil may also be selected from synthetic oils such as certain esters of carboxylic acids and alcohols, and from poly α -olefins (PAO).

The base oil or base oils of the composition used according to the invention are selected from the group consisting of poly α -olefins (PAO) the PAO used as base oil is obtained, for example, from monomers comprising from 4 to 32 carbon atoms, for example, from octene or decene.

The weight average molecular weight of the PAO can vary considerably. Preferably, the PAO has a weight average molecular weight of less than 600 Da. The PAO may also have a weight average molecular weight of from 100 to 600Da, from 150 to 600Da, or even from 200 to 600 Da.

For example, those used within the scope of the present invention have a kinematic viscosity, measured at 100 ℃ according to the standard ASTM D445, of from 1.5 to 8mm²PAO/s is sold under the trade name Ineos

162、

164、

166 and

168, and sold.

According to a particular embodiment, the composition used according to the invention is free of polyalkylene glycols (PAGs) obtained by polymerization or copolymerization of alkylene oxides containing from 2 to 8 carbon atoms, in particular from 2 to 4 carbon atoms.

According to a particular embodiment, the fluid base of the composition used according to the invention comprises a content of strictly less than 30% by mass of base oils of the ester and ether type, in particular less than 25% by mass, in particular 10% by mass of base oils of the ester and ether type.

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

Preferably, the composition used according to the invention comprises a fluid base formed from one or more base oils having a viscosity measured at 100 ℃ according to the standard ASTM D445 of 1.5 and 8mm²Kinematic viscosity between/s.

In other words, the composition of the invention may be free of base oil or of a mixture of base oils not meeting the kinematic viscosity standard measured at 100 ℃ according to the standard ASTM D445, in particular free of base oils having a viscosity greater than 9mm²A base oil or a mixture of base oils of viscosity/s.

It is within the ability of the person skilled in the art to adjust the content of the fluid base to be used in the composition according to the invention to achieve the desired viscosity of the composition.

As indicated above, the fluid base provides the cooling potential of the composition used according to the invention. In particular, when the composition is used in the drive system of an electric or hybrid vehicle, the fluidity of the base ensures good cooling performance.

The cooling properties of the composition employed are advantageously further enhanced by the shear forces applied to the composition at the point of injection, which bring the fluid to a viscosity level below that at rest. Thus, advantageously, the effect of the use of the thickening polymer according to the invention on the cooling capacity of the composition is controlled.

The lubricating composition may comprise from 60% to 90% by mass, relative to the total weight of the composition, of a lubricating oil having a kinematic viscosity, measured according to the standard ASTM D445 at 100 ℃, of from 1.5 to 8mm²A base oil or a mixture of base oils.

The composition used according to the invention more particularly comprises from 70% to 90% by mass, preferably from 80% to 90% by mass, relative to the total weight of the composition, of a compound having a kinematic viscosity, measured according to the standard ASTM D445 at 100 ℃, of from 1.5 to 8mm²Base oil or base oil mixture

Thickening polymer

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

The polymer or polymers are selected to have the ability to thicken the fluid base according to the invention, to ensure the desired lubricating properties of the composition.

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

Such viscosity index improving polymers are described, for example, in the following documents: WO 9418288, EP 2363454, EP 2164885, EP 0699694, WO 2007/003238 and WO 2007/025837.

It is to be understood that the thickening polymer or polymers are different from the base oil or mixture of base oils as described above.

In particular, this may relate to a polymer selected from: an ester polymer; linear or star, hydrogenated or non-hydrogenated homopolymers or copolymers of styrene, butadiene and isoprene; a polyacrylate; linear or comb-like polymethacrylates; and olefin copolymers, especially ethylene/propylene copolymers.

Preferably, the thickening polymer may be more particularly chosen from linear or comb-like polymethacrylates; linear or star-shaped hydrogenated copolymers of styrene, butadiene and isoprene; and mixtures thereof.

Advantageously, the thickening polymer may be more particularly chosen from comb polymethacrylates; star-shaped hydrogenated copolymers of styrene, butadiene and isoprene; and mixtures thereof.

Comb-like polymethacrylate polymers within the meaning of the present invention are described, for example, in patent applications EP 2164885, EP 0699694, WO 2007/003238 and WO 2007/025837; and the structures and definitions of these polymers as described in these documents are incorporated in the specification of the present application.

Comb polymethacrylate polymers within the meaning of the invention are for example under the trade name Evonik

3-200.

Also for example, star-shaped hydrogenated copolymers of styrene, butadiene and isoprene within the meaning of the present invention are described in patent application EP 2363454, and the structure and definition of these polymers as described in EP 2363454 are incorporated in the description of the present application.

Star-shaped hydrogenated copolymers of styrene, butadiene and isoprene within the meaning of the present invention are, for example, those sold under the trade name Infineum

261, and selling.

The use of the one or more thickening polymers ensures that the composition is sufficiently thickened to ensure a satisfactory level of antiwear protection (i.e., lubricity) when used in a drive system for an electric or hybrid vehicle, without affecting the cooling potential 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 mass, preferably between 1% and 8% by mass, more preferably between 1.5% and 5% by mass, relative to the total mass of the composition.

This amount is understood to mean the amount of active substance of the polymer. This is because the polymers used within the scope of the invention can be in the form of dispersions in one or more mineral or synthetic oils.

Also in particular, the composition used according to the invention may comprise from 1% to 25% by mass, preferably from 2% to 20% by mass, more preferably from 4% to 20% by mass, relative to the total weight of the composition, of one or more thickening polymers diluted in one or more base oils.

It is within the ability of the person skilled in the art to adjust the proportions of the various ingredients of the composition, in particular the proportions of fluid base and thickening polymer, to achieve the desired viscosity according to the invention.

According to a particular embodiment, the composition used according to the invention comprises at least one base oil chosen from PAOs and at least one polymer chosen from comb polymethacrylates; star-shaped hydrogenated copolymers of styrene, butadiene and isoprene; and mixtures thereof.

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

Also in particular, when the base oil is chosen from PAOs, it is combined in the composition used according to the invention with at least one star-shaped hydrogenated copolymer chosen from styrene, butadiene and isoprene.

According to a variant embodiment, the composition used according to the invention is formed, in other words consists, of a mixture of:

-has a kinematic viscosity, measured according to standard ASTM D445 at 100 ℃, of from 1.5 to 8mm²A base oil or a mixture of base oils; and

-one or more thickening polymers as defined above.

Preferably, the composition used according to the invention is formed from:

-has a kinematic viscosity, measured according to standard ASTM D445 at 100 ℃, of from 1.5 to 8mm²One or more base oils per second; and

-one or more thickening polymers as defined above.

Alternatively, the composition used may also comprise one or more additives as defined more precisely below.

Additive agent

Additives which may be incorporated in the composition according to the invention may be selected from friction modifiers, detergents, antiwear additives, extreme pressure additives, dispersants, antioxidants, pour point improvers, antifoams and mixtures thereof.

It will be appreciated that the nature and amount of the additives used are selected in a manner that does not affect the combined performance of the lubricating and cooling capabilities of the compositions of the present invention.

These additives may be introduced individually and/or in the form of mixtures, similar to those already provided on the market for commercial vehicle engine lubricant formulations, with performance levels as defined by ACEA (Association structures Europ elemental tens' Automobiles) and/or API (American Petroleum institute), as is well known to those skilled in the art.

Antiwear and extreme pressure additives are used to protect friction surfaces by forming a protective film that adsorbs onto these surfaces.

A wide variety of anti-wear additives exist. Preferably for the lubricating composition of the present invention, the antiwear additive is selected from phosphorus-sulfur additives, such as metal alkyl thiophosphates, especially zinc alkyl thiophosphates, and more specifically zinc dialkyl dithiophosphate or ZnDTP. Preferred compounds have the formula Zn ((SP (S)) (OR)²)(OR³))₂Wherein R is²And R³Identical or different, independently represent an alkyl group, preferably an alkyl group comprising from 1 to 18 carbon atoms.

Amine salts of phosphoric acid esters are also antiwear additives, which may be used in the lubricating composition according to the present invention. However, the phosphorus provided by these additives may act as a poison to automotive catalytic systems because these additives are ash generators. These effects can be minimized by partial replacement of the amine phosphate salt with additives that do not provide phosphorus, such as polysulfides, especially sulfur-containing olefins.

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

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.

The composition used according to the invention may comprise at least one friction modifying additive. The friction modifying additive may be selected from the group consisting of metal element providing compounds and ash-free compounds. Among the compounds providing the metallic element, complexes of transition metals such as Mo, Sb, Sn, Fe, Cu, Zn, whose ligands may be hydrocarbon compounds containing oxygen, nitrogen, sulfur or phosphorus atoms, may be mentioned. The ash-free friction modifying additive is typically of organic origin and may be selected from monoesters of fatty acids and polyols, alkoxylated amines, alkoxylated fatty amines, fatty epoxides, borated fatty epoxides, fatty amines or fatty acid glycerides. According to the invention, the fatty compound comprises at least one hydrocarbon group comprising from 10 to 24 carbon atoms.

The composition used according to the invention may comprise from 0.01% to 2% by mass or from 0.01% to 5% by mass, preferably from 0.1% to 1.5% by mass or from 0.1% to 2% by mass of friction-improving additive, relative to the total mass of the composition.

Advantageously, the composition according to the invention is free of friction-improving additives.

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

The antioxidant additive typically enables the degradation of the composition in use to be delayed. This degradation may be manifested in particular by the formation of deposits, the presence of sludge or an increase in the viscosity of the composition.

The antioxidant additive is particularly useful as a structure-breaking agent or free radical inhibitor for hydroperoxides. Among the usual antioxidant additives, mention may be made of phenolic antioxidant additives, aminic antioxidant additives, phosphorusA sulfur antioxidant additive. Some of these antioxidant additives (e.g., phosphorus sulfur antioxidant additives) may be ash generators. The phenolic antioxidant additives may be ashless, or may be in the form of neutral or basic metal salts. The antioxidant additive may in particular be chosen from sterically hindered phenols, sterically hindered phenol esters and sterically hindered phenols containing thioether bridges, diphenylamines, substituted by at least one C₁-C₁₂Alkyl group substituted diphenylamines, N, N' -dialkyl-aryl diamines, and mixtures thereof.

According to the invention, the sterically hindered phenol is preferably chosen from compounds comprising a phenol group whose carbon bearing an alcohol function is substituted by at least one C at least one carbon ortho to the carbon bearing the alcohol function₁-C₁₀Alkyl radical, preferably C₁-C₆Alkyl radical, preferably C₄Alkyl groups, preferably tert-butyl groups.

Aminated compounds are another class of antioxidant additives that can be used, optionally in combination with phenolic antioxidant additives. Examples of aminating compounds are aromatic amines, e.g. of the formula NR⁴R⁵R⁶Wherein R is⁴Represents an optionally substituted aliphatic or aromatic radical, R⁵Represents an optionally substituted aromatic radical, R⁶Represents a hydrogen atom, an alkyl group, an aryl group or the formula R⁷S(O)_zR⁸Wherein R is⁷Represents an alkylene group or alkenylene group, R⁸Represents an alkyl group, an alkenyl group or an aryl group and z represents 0, 1 or 2.

Sulfurized alkylphenols or their alkali and alkaline earth metal salts can also be used as antioxidant additives.

Another class of antioxidant additives are copper compounds, such as copper thiophosphates or dithiophosphates, salts of copper and carboxylic acids, dithiocarbamates, sulfonates, phenates, copper acetylacetonate. Salts, succinic anhydrides or acid salts of copper I and II may also be used.

The compositions used according to the invention may comprise all types of antioxidant additives known to the person skilled in the art.

Advantageously, the composition used according to the invention comprises at least one antioxidant additive without ash content.

The composition used according to the invention comprises 0.5-2% by mass of at least one antioxidant additive, relative to the total mass of the composition.

The compositions used according to the invention may also comprise at least one detergent additive (additif detergent).

Detergent additives generally enable the formation of deposits on the surface of metal parts to be reduced by dissolving the byproducts of oxidation and combustion.

Detergent additives useful in the compositions used according to the present invention are generally known to those skilled in the art. Detergent additives may be anionic compounds comprising a lipophilic long hydrocarbon chain and a hydrophilic top end. The relevant cation may be a metal cation of an alkali metal or alkaline earth metal.

The detergent additive is preferably selected from the group consisting of alkali or alkaline earth metal salts of carboxylic acids, sulfonates, salicylates, naphthenates and phenates. The alkali and alkaline earth metals are preferably calcium, magnesium, sodium or barium.

These metal salts generally contain a stoichiometric or excess (and thus an amount greater than stoichiometric) of the metal. This thus relates to overbased detergent additives; the excess metal to impart overbased character to the detergent additive is then typically in the form of an oil-insoluble metal salt, such as a carbonate, hydroxide, oxalate, acetate, glutamate, preferably a carbonate.

The compositions used according to the invention may comprise from 2 to 4% by mass of detergent additives, relative to the total mass of the composition.

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

Pour point depressant additives generally improve the cold behavior of the composition by slowing the formation of paraffin crystals.

Mention may be made, as examples of pour point depressant additives, of polyalkylmethacrylates, polyacrylates, polyarylamides, polyalkylphenols, polyalkylnaphthalenes and alkylated polystyrenes.

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

The dispersant may be selected from Mannich bases, succinimides and derivatives thereof.

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

Applications of

As mentioned above, the above-mentioned composition can be used both as a lubricant and as a cooling fluid for the drive system of an electric or hybrid vehicle, due to its combination of cooling and lubrication properties.

In particular, the invention relates to the use of a composition as defined above for cooling and lubricating the electric motor of an electric or hybrid vehicle and its various components, in particular in motion. The invention is also applicable to batteries for electric or hybrid vehicles.

As schematically shown in fig. 1, the drive system of an electric or hybrid vehicle comprises, inter alia, an electric motor part (1). This typically includes power electronics (11) connected to the stator (13) and rotor (14).

The stator comprises coils, in particular copper coils, which are supplied with alternating current. This generates a rotating magnetic field. The rotor itself comprises coils, permanent magnets or other magnetic material and is rotated by this rotating magnetic field.

The power electronics (11), the stator (13) and the rotor (14) of the electric motor (1) are components which have a complex structure and generate a large amount of heat during operation of the electric motor. It is therefore of critical importance to ensure cooling of the electric motor, in particular the power electronics.

In addition, the bearings (12), which are normally integrated between the stator (13) and the rotor (14), are subjected to high mechanical stresses and wear problems arise due to fatigue. It is therefore necessary to lubricate the bearings to improve their service life.

The composition used according to the invention as described above makes it possible to ensure both the function of lubricating and protecting the contact elements against wear and the cooling function inside an electric or hybrid vehicle.

The invention therefore relates in particular to the use of a composition as described above for cooling and lubricating the electric motor of an electric or hybrid vehicle.

In particular, it enables cooling of the power electronics and/or the rotor and/or the stator of the electric motor. It also enables the lubrication of the bearings located between the rotor and the stator of the electric motor of an electric or hybrid vehicle.

The drive system of an electric or hybrid vehicle may also comprise a transmission, in particular a reducer (3), which makes it possible to reduce the rotational speed of the motor output and to adapt the speed transmitted to the wheels, so that the speed of the vehicle can be controlled simultaneously.

This reducer is subjected to high friction stresses and must therefore be lubricated in a suitable manner to avoid its excessively rapid deterioration.

The invention therefore also relates to the use of a composition as described above for lubricating a transmission, in particular a retarder, in an electric or hybrid vehicle.

Advantageously, the composition according to the invention can therefore be used for simultaneously lubricating and cooling the electric motor and the transmission, in particular the retarder, in an electric or hybrid vehicle.

As mentioned above, the motor is typically powered by a battery (2). Lithium ion batteries are the most widely used batteries in the field of electric vehicles. The development of batteries that are increasingly powerful and their size is becoming smaller means that cooling problems of such batteries can arise. This is because, once the battery exceeds a temperature of about 50 to 60 ℃, the battery has a high risk of ignition or even explosion. It is also desirable to maintain the battery at a temperature greater than about 20 c to 25 c to avoid discharging the battery too quickly and to extend its useful life.

The composition of the invention can thus be used for cooling the battery of an electric or hybrid vehicle.

It will be appreciated that the above applications may be combined and that the compositions described above may be used as both lubricants and cooling fluids for electric motors, batteries and transmissions of electric or hybrid vehicles.

Accordingly, the present invention is advantageous in that a single composition having both lubricating and cooling properties can be used as a lubricant and a cooling fluid in an electric or hybrid vehicle.

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

All the characteristics and preferences described for the composition used according to the invention and its use also apply to this process.

The cooling of the composition used according to the invention can be carried out using any method known to the person skilled in the art.

As an example of direct use, mention may be made of cooling by spraying, misting or forming a mist of the composition of the invention, in particular on the windings of the rotor and/or stator, under pressure and by gravity.

Advantageously, the composition is injected into the area to be cooled of the drive system by spraying under a rather high pressure, as described for example in the publications of Liu et al and Bennion et al. Advantageously, the shear forces generated by this injection make it possible to reduce the viscosity of the fluid at the injection zone with respect to the kinematic viscosity at rest and thus further increase the cooling potential of the composition.

Furthermore, it is possible to use the oil circulation systems currently used in electric motors, as described for example in document WO 2015/116496.

According to the present invention, the particular features, advantages or preferences of the composition according to the invention may be used to define the uses according to the invention, which also have the particular features, advantages or preferences.

The invention will now be described by way of the examples given below, which are of course given by way of illustration and not of limitation of the invention.

Examples

Example 1

Preparation of lubricating Composition (CL) according to the invention and Comparative Composition (CC)

The components of the composition were mixed according to the nature and amount (expressed in mass percentage) of the product shown in table 1 below.

(1) By Evonik under the trade name

Comb polymethacrylate polymers sold at 3-200;

(2) by Infineum under the trade name

261, and a star hydrogenated copolymer of styrene, butadiene, and isoprene.

TABLE 1

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

	CL1	CL2	CC1
				KV100-ISO 3104(mm².s^-1)^*	6.10	5.95	5.90

Kinematic viscosity measured at 100 ℃ according to standard ISO3104

TABLE 2

Example 2

Measurement of thermal Properties of compositions according to the invention

One way to measure the thermal properties of a fluid is to measure the heat exchange coefficient (heat transfer per unit surface area and temperature) of the fluid. Fluids with higher heat exchange coefficients have better cooling performance.

Tests were conducted to measure the heat exchange coefficient for each of the compositions described in table 1.

The principle of this test consists in spraying a jet of oil by means of a nozzle perpendicular to the inductively heated metal plate. A thermal imaging camera placed above the plate recorded the temperature profile during oil spray. The average heat exchange coefficient of the composition can be calculated from the temperature change value on the plate.

Different parameters can be varied, in particular the temperature of the plate, the size of the nozzles and the pressure of the oil sprayed. The measurement of the thermal coefficient is performed at different distances from the point of impact of the jet on the metal plate, this distance corresponding to the radius. The test conditions are described in table 3 below.

Characteristics of	Unit of	Numerical value
			Temperature of	℃	80-140
Pressure of	Bar	10
			Radius of	mm	0-0.016

TABLE 3

The results obtained are shown in fig. 2.

The various temperatures (in degrees celsius) detected on the heating plate are displayed along the ordinate; the radii (in meters) corresponding to different distances on the metal sheet from the jet impact point are shown along the abscissa.

It can be seen from fig. 2 that, starting from a radius of 0.01m, there is a significant difference of at least 5 ℃ between the temperatures detected on the heating plates on which the compositions of the invention (CL1,. and CL2, +) and the comparative compositions (CC1, ▲), respectively, were sprayed.

This thus means that the composition according to the invention can cool the heating plate better and maintain a stable temperature compared to a comparative composition not comprising a thickening polymer.

As a result, the composition according to the present invention can not only lubricate but also cool the drive system of an electric or hybrid vehicle.

Claims

1. Use of a composition having a kinematic viscosity measured at 100 ℃ according to the standard ASTM D445 of from 3 to 10mm for cooling and lubricating the drive system of an electric or hybrid vehicle²And/s, and comprises at least:

-70% -90% by weight of a base oil or a mixture of base oils having a kinematic viscosity, measured according to standard ASTM D445 at 100 ℃, of from 1.5 to 8mm²And is selected from the group consisting of poly α -olefins, and

2. Use according to claim 1, the composition having a viscosity measured at 100 ℃ according to the standard ASTM D445 of 3 and 9mm²Kinematic viscosity between/s.

3. Use according to any one of the preceding claims, characterized in that the thickening polymer(s) are chosen from comb polymethacrylates; star-shaped hydrogenated copolymers of styrene, butadiene and isoprene; and mixtures thereof.

4. Use according to any one of the preceding claims, the composition comprising from 0.5% to 10% by mass, preferably from 1% to 8% by mass, more preferably from 1.5% to 5% by mass of the thickening polymer(s), relative to the total mass of the composition.

5. Use according to any one of the preceding claims, the composition further comprising at least one additive selected from friction modifiers, detergents, antiwear additives, extreme pressure additives, dispersants, antioxidants, pour point improvers, antifoaming agents and mixtures thereof.

6. Use according to any one of the preceding claims for cooling and lubricating an electric motor of an electric or hybrid vehicle.

7. Use according to the preceding claim for cooling the power electronics and/or the rotor and/or the stator of an electric motor.

8. Use according to claim 6 or 7 for lubricating a bearing located between a rotor and a stator of an electric motor.

9. Use according to any one of the preceding claims for cooling a battery of an electric or hybrid vehicle.

10. Use according to any one of the preceding claims, for lubricating a transmission, in particular a retarder, of an electric or hybrid vehicle.