LUBRICATION AND COOLING SYSTEM

Abstract

The invention relates to a method for lubricating and cooling the powertrain of an electric vehicle, said method comprising: a) Providing at least one powertrain component at least partially coated with one or more layers of electrically insulating polymer, b) Contacting said powertrain component of step a) with an aqueous lubricating composition comprising at least one thickening polymer, c) Operating said powertrain component, said at least one partially coated powertrain component being selected from one or more components including an electric motor, a battery, or power electronics. Abstract: Figure 1.

Description

Title of the invention: LUBRICATION AND COOLING SYSTEM TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to the field of lubrication and cooling systems for the electric vehicle powertrain. STATE OF THE ART

[0002] The evolution of international standards for the reduction of CO2 emissions, but also for the reduction of energy consumption, is pushing car manufacturers to offer alternative solutions to combustion engines.

[0003] One of the solutions identified by car manufacturers is to replace combustion engines with electric motors. Research into reducing CO2 emissions has therefore led to the development of electric or hybrid vehicles by a number of automotive companies.

[0004] In general, it is necessary to implement, in electric or hybrid vehicles, compositions to meet the dual constraint of lubrication and cooling of the various elements of the propulsion system mentioned above.

[0005] On the one hand, lubricating compositions, also called "lubricants," are commonly used in engines to reduce friction between the various moving metal parts within the engines, thereby protecting the parts against wear. In addition to wear, friction can impede the relative movement of the contacting parts and induce energy losses that are detrimental to the optimal operation of the propulsion system.

[0006] To achieve this, a lubricating composition is classically composed of one or more base oils, to which are generally associated several additives dedicated to stimulating the lubricating performance of the base oils, such as friction modifier additives.

[0007] On the other hand, electric propulsion systems generate heat during operation via the electric motor, power electronics, and batteries. Since the amount of heat generated is greater than the amount of heat normally dissipated to the environment, it is necessary to ensure cooling of the motor, power electronics, and batteries. Generally, cooling is carried out on several parts of the propulsion system that generate heat and / or on heat-sensitive parts of the system, in order to prevent dangerous temperatures from reaching the required levels, and in particular on the power electronics and the batteries. This cooling is typically provided by a coolant, separate from the hydrocarbon lubricant, such as air, an aqueous fluid, such as water, or a mixture of water and glycol.

[0008] The present invention aims to provide a method and a system for both lubricating and cooling the elements of the electric vehicle powertrain, by means of a high-performance and simple-to-implement solution. Summary of the invention

[0009] According to a first aspect, the invention relates to a method for lubricating and cooling the powertrain of an electric vehicle, said method comprising:

[0010] a) Provision of at least one element of the powertrain at least partially coated with one or more layers of electrically insulating polymer,

[0011] b) Bringing said element of the powertrain of step a) into contact with an aqueous lubricating composition comprising at least one thickening polymer,

[0012] c) Operation of said powertrain element,

[0013] said at least one element of the powertrain at least partially coated being chosen from one or more elements including an electric motor, a battery or power electronics.

[0014] According to one embodiment, the lubrication and cooling process according to the invention comprises one or more of the following features: - said at least one element of the powertrain, at least partially coated with one or more layers of electrically insulating polymer, is the stator and / or the wound rotor of the electric motor, and / or - the stator, battery and power electronics are at least partially coated with one or more layers of electrically insulating polymer and if the rotor is a wound rotor then said wound rotor is also at least partially coated with one or more layers of electrically insulating polymer, preferably the reduction gear of the powertrain is not coated with one or more layers of electrically insulating polymer, and / or - the contacting step b) includes a step of vaporizing the aqueous lubricating composition comprising at least one thickening polymer onto said powertrain component of step a) or a step of total or partial immersion of said powertrain component of step a) in the aqueous lubricating composition comprising at least one thickening polymer, and / or - the surfaces of the electric motor and power electronics in contact with the aqueous lubricating composition are completely coated with one or more layers of electrically insulating polymer, and / or - the electrical insulating polymer is a polymer obtained by polymerization of an aromatic compound, possibly substituted, preferably by polymerization of para-xylylene, and / or - the layer(s) of electrically insulating polymer coating represent a total thickness ranging from 0.1 µm to 1 mm and / or - all powertrain components are in contact with the aqueous lubricant composition, in particular the stator, rotor, power electronics, gearbox and battery of the electric vehicle are in contact with the aqueous lubricant composition, and / or - The aqueous lubricating composition includes: • at least 20% water by mass, preferably 35% to 90% water by mass, more preferably 40% to 75% water by mass, • at least 5.0% by mass of thickening polymer(s), preferably from 5.0% to 50% by mass of thickening polymer(s), more preferably from 10% to 40% by mass of thickening polymer(s), • possibly from 0.001 to 55% by mass of additives other than water and thickening polymers, preferably from 0.01 to 50% by mass of additives other than water and thickening polymers, more preferably from 0.05 to 45% by mass of additives other than water and thickening polymers,

[0015] relative to the total mass of the aqueous lubricating composition, and / or - the thickening polymer is chosen from poly(alkylene glycol), vinylpyrrolidone polymers, biopolymers for example of cellulosic type, and their mixtures.

[0016] According to a second aspect, the invention relates to a powertrain of an electric vehicle comprising at least one element at least partially coated with one or more layers of electrical insulating polymer, said element being selected from an electric motor, a battery or power electronics, said coated element being at least partially in contact in an aqueous lubricating composition comprising at least one thickening polymer.

[0017] According to one embodiment, the powertrain according to the invention comprises one or more of the following features: - said at least one element of the powertrain at least partially coated with one or more layers of electrically insulating polymer is the stator and / or the wound rotor of the electric motor, preferably in which the stator, the battery and the power electronics are at least partially coated with one or more layers of electrically insulating polymer and if the rotor is a wound rotor then said wound rotor is also at least partially coated with one or more layers of electrically insulating polymer, and / or - the powertrain of an electric vehicle according to the invention further comprises at least one gearbox, the gearbox being free of layer(s) of electrically insulating polymer coating, and / or - the aqueous lubricating composition is in contact, preferably following vaporization or immersion, with all the elements of the electric vehicle's powertrain, in particular with the stator, the wound rotor, the power electronics, the gearbox and the battery of the electric vehicle, and / or - the electrical insulating polymer is a polymer obtained by polymerization of an aromatic compound, possibly substituted, preferably by polymerization of para-xylylene and / or in which the thickening polymer is chosen from poly(alkylene glycol), biopolymers for example of the cellulosic type, and their mixtures, and / or - The aqueous lubricating composition includes: • at least 20% water by mass, preferably 35% to 90% water by mass, more preferably 40% to 75% water by mass, • at least 5.0% by mass of thickening polymer(s), preferably from 5.0% to 50% by mass of thickening polymer(s), more preferably from 10% to 40% by mass of thickening polymer(s), • possibly from 0.001 to 30% by mass of additives other than water and thickening polymers, preferably from 0.01 to 20% by mass of additives other than water and thickening polymers, more preferably from 0.05 to 20% by mass of additives other than water and thickening polymers,

[0018] relative to the total mass of the aqueous lubricating composition.

[0019] The invention proposes a simple cooling and lubrication system to to implement enabling excellent performance in both lubrication and cooling, with a reduced or even eliminated risk of short circuit and using a lubricant with a reduced environmental impact.

[0020] Other features and advantages of the invention will become apparent from reading the following detailed description. BRIEF DESCRIPTION OF THE FIGURES

[0021] [Fig.1] represents a schematic view of the powertrain of an electric vehicle. DETAILED DESCRIPTION OF THE INVENTION

[0022] The invention thus proposes a method for lubricating and cooling the powertrain of an electric vehicle, said method comprising:

[0023] a) Provision of at least one element of the powertrain at least partially coated with one or more layers of electrically insulating polymer,

[0024] b) Bringing said element of the powertrain of step a) into contact with an aqueous lubricating composition comprising at least one thickening polymer,

[0025] c) Operation of said powertrain element,

[0026] said at least one element of the powertrain being selected from one or more elements including an electric motor, a battery or power electronics.

[0027] The invention also relates to a powertrain of an electric vehicle implemented in the lubrication and cooling process of the invention. Thus, the powertrain according to the invention comprises at least one element at least partially coated with one or more layers of electrically insulating polymer, said element being selected from an electric motor, a battery or power electronics, said element being at least partially in contact with an aqueous lubricating composition comprising at least one thickening polymer.

[0028] For the purposes of the present invention, "electric vehicle" means a vehicle comprising an electric motor as the sole means of propulsion, as opposed to a "hybrid vehicle," which means a vehicle comprising a combustion engine and an electric motor as combined means of propulsion.

[0029] The term "propulsion system" or "powertrain" in the context of the present invention refers to a system comprising the mechanical parts necessary for the propulsion of an electric vehicle. The propulsion system thus includes, more specifically, an electric motor, the rotor-stator assembly, power electronics (dedicated to speed regulation), a gearbox, and a battery.

[0030] Typically, the powertrain components are at least partially located in one or more housings.

[0031] By "housing", it is understood, within the framework of the present invention, to mean a container capable of receiving a lubricating composition and at least one element of the powertrain. The housing may be watertight on its own or, if not, the arrangement of the powertrain components and the housing may be such that this arrangement is watertight.

[0032] The elements of the powertrain advantageously include at least the electric motor, the power electronics, the reducer and the battery of the electric vehicle.

[0033] In the context of the invention, at least one element selected from an electric motor, a battery, or power electronics is coated wholly or partially with one or more layers of electrically insulating polymer. Preferably, at least the electric motor is coated with one or more layers of electrically insulating polymer; in particular, the stator and rotor, if wound, of the electric motor are coated with one or more layers of electrically insulating polymer.

[0034] Advantageously, the electric motor, in particular the stator and the rotor if wound, and the power electronics are both coated with one or more layers of electrically insulating polymer.

[0035] According to one embodiment, the battery, the electric motor, in particular the stator and the rotor if wound, and the power electronics are both coated with one or more layers of electrically insulating polymer.

[0036] The coating may be total or partial on said element.

[0037] Typically, the powertrain reducer is not coated with layer(s) of electrically insulating polymer as defined in the invention.

[0038] Typically, all parts of the battery, electric motor and / or power electronics that come into contact with the aqueous lubricating composition are totally coated with one or more layers of electrically insulating polymer.

[0039] According to one embodiment, the electrical insulating polymer is a polymer obtained by polymerization of an aromatic compound, possibly substituted, preferably by polymerization of para-xylylene.

[0040] The electrically insulating polymer can be deposited on the electric motor and / or the power electronics by a coating process known to those skilled in the art, for example by chemical vapor deposition (CVD) or atomic layer deposition (ALD). The coating can be applied in one or more layers with the same electrically insulating polymer or a different electrically insulating polymer, advantageously in one or more layers of the same electrically insulating polymer. The layers can have the same thickness or different thicknesses.

[0041] According to one embodiment, the layer(s) of electrically insulating polymer coating have a total thickness ranging from 0.1 µm to 1 mm. Advantageously, Each layer has a thickness ranging from 0.1 to 10 pm, or even from 0.1 to 5 pm or from 0.1 to 3 pm.

[0042] The lubrication and cooling process according to the invention may include a step of coating at least one element selected from an electric motor and power electronics with one or more layers of electrically insulating polymer.

[0043] The step of bringing said element of the powertrain of step a) into contact with an aqueous lubricating composition comprising at least one thickening polymer can be carried out for example by vaporization or by immersion, preferably by immersion, said immersion may be total or partial.

[0044] In the context of the invention, the contact is a direct contact.

[0045] In the case of vaporization, the aqueous lubricating composition is vaporized on said powertrain component at least partially coated. Thus, advantageously, all parts of the electric motor and power electronics that are in contact with the aqueous lubricating composition will be completely coated with one or more layers of electrically insulating polymer.

[0046] In the case of immersion, said powertrain element, at least partially coated, is immersed at least partially in the aqueous lubricating composition. Thus, advantageously, all parts of the electric motor and power electronics that are immersed in the aqueous lubricating composition will be completely coated with one or more layers of electrically insulating polymer.

[0047] The inventors observed that the combination of the coating and the aqueous lubricating composition made it possible to obtain both very good lubrication properties and very good cooling properties, while minimizing or even eliminating short circuits.

[0048] According to an advantageous embodiment, all the elements of the powertrain are in contact with the aqueous lubricating composition, in particular the electric motor, the power electronics, the reducer and the battery of the electric vehicle are in contact with the (same) aqueous lubricating composition.

[0049] Indeed, the inventors discovered that said aqueous lubricating composition could be implemented throughout the powertrain to lubricate and cool all the elements of said powertrain, in particular the electric motor, the power electronics, the reducer and the battery.

[0050] The aqueous lubricating composition implemented within the framework of the invention comprises at least one thickening polymer.

[0051] According to one embodiment, the aqueous lubricating composition comprises: - at least 20% water by mass, preferably 35% to 90% water by mass, more preferably 40% to 75% water by mass, - at least 5.0% by mass of thickening polymer(s), preferably from 5.0% to 50% by mass of thickening polymer(s), more preferably from 10% to 40% by mass of thickening polymer(s), - possibly from 0.001 to 55% by mass of additives other than water and thickening polymers, preferably from 0.01 to 50% by mass of additives other than water and thickening polymers, more preferably from 0.05 to 45% by mass of additives other than water and thickening polymers,

[0052] relative to the total mass of the aqueous lubricating composition.

[0053] According to a particular embodiment, the water used in an aqueous lubricating composition required according to the invention is demineralized or osmosis water, in particular deionized water.

[0054] Preferably, the thickening polymer is chosen from poly(alkylene glycol), vinylpyrrolidone polymers, biopolymers for example of cellulosic type, and their mixtures.

[0055] Poly(alkylene glycol) (denoted "PAG") are selected from water-soluble polyalkylene glycols.

[0056] By "water soluble" is meant a polyalkylene glycol having a solubility in water of at least 10 g / L, preferably of at least 500 g / L, in water at room temperature (about 25 °C).

[0057] Polyalkylene glycols can more particularly be formed of alkylene oxide units comprising 1 to 4 carbon atoms, preferably 1 to 3 carbon atoms, more particularly 2 to 3 carbon atoms.

[0058] Advantageously, a polyalkylene glycol used in an aqueous lubricating composition required according to the invention comprises at least 50% by mass, in particular at least 80% by mass, more preferably at least 90% by mass of propylene oxide and / or ethylene oxide units. It may be a copolymer, possibly random, of ethylene oxide / propylene oxide.

[0059] Preferably, a polyalkylene glycol used in an aqueous lubricating composition according to the invention has a weight average molecular mass (Mw) between 100 and 50,000 g / mol, preferably between 5,000 and 25,000 g / mol.

[0060] The average molecular mass by weight can be measured by gel permeation chromatography (GPC).

[0061] Preferably, a polyalkylene glycol used in an aqueous lubricating composition according to the invention has a kinematic viscosity measured at 100 °C (KV100), according to ASTM D445, between 100 and 25,000 mm² / s, in particular between 150 and 10,000 mm² / s. Preferably, a polyalkylene glycol used in an aqueous lubricant composition according to the invention has a kinematic viscosity measured at 40 °C (KV40), according to ASTM D445, between 500 and 100,000 mm² / s, more particularly between 1,000 and 95,000 mm² / s.

[0062] The flash point of a polyalkylene glycol used in an aqueous lubricating composition according to the invention is preferably greater than or equal to 160°C, in particular greater than or equal to 220°C. The flash point can be measured according to ISO 2592 or ASTM D92.

[0063] Preferably, a polyalkylene glycol used in an aqueous lubricating composition according to the invention has a viscosity index measured according to ASTM D2270, between 100 and 800, preferably between 250 and 550.

[0064] In particular, the polyalkylene glycol compound(s) may be used in an aqueous lubricant composition required according to the invention in a content of at least 5.0% by mass, preferably between 5.0% and 50% by mass, more preferably between 10% and 40% by mass, in particular between 10% and 20% by mass, relative to the total mass of the composition.

[0065] Preferably, an aqueous lubricating composition implemented according to the invention comprises less than 17% of polyalkylene glycol compound(s), more preferably between 10% and 15% by mass of polyalkylene glycol compound(s).

[0066] It is understood that an aqueous lubricating composition implemented according to the invention may comprise a single polyalkylene glycol or a mixture of several different polyalkylene glycols.

[0067] In particular, an aqueous lubricating composition according to the invention may comprise a mixture of at least two distinct polyalkylene glycols, more particularly of at least one polyalkylene glycol of low average molecular weight and at least one polyalkylene glycol of high average molecular weight.

[0068] It is within the general competence of a person skilled in the art to adjust the type and content of low and high weight-average molecular weight polyalkylene glycols in the polyalkylene glycol mixture, particularly with regard to the desired viscosity of the final lubricating composition. The combination of at least one low weight-average molecular weight polyalkylene glycol and at least one high weight-average molecular weight polyalkylene glycol is particularly advantageous for achieving good solubilization of the various compounds introduced into the aqueous lubricating composition.

[0069] The term “vinylpyrrolidone polymer” means, in a broad sense, to refer to both vinylpyrrolidone homopolymers and copolymers formed from vinylpyrrolidone and one or more other monomers.

[0070] Thus, more generally, an aqueous lubricating composition implemented according to the invention may comprise one or more vinylpyrrolidone polymer(s), in particular chosen from polyvinylpyrrolidones (denoted PVPs).

[0071] Polyvinylpyrrolidones correspond more particularly to the following formula:

[0072] [Chem.l] 'HAS /

[0073] in which n represents the average number of constituent units of the polymer.

[0074] Such compounds can be synthesized by any method known to those skilled in the art, in particular by polymerization of N-vinylpyrrolidone, and may also be commercially available.

[0075] Polyvinylpyrrolidones more particularly suitable for the invention have a weight average molecular mass (Mw) between 20,000 and 50,000 g / mol, preferably between 25,000 and 45,000 g / mol.

[0076] In particular, the vinylpyrrolidone polymer(s), in particular selected from polyvinylpyrrolidones, may be present in an aqueous lubricating composition according to the invention in a content of at least 5.0% by mass, preferably between 5.0% and 50% by mass, more preferably between 10% and 40% by mass, in particular between 10% and 20% by mass, relative to the total mass of the composition.

[0077] The aqueous lubricating composition implemented according to the invention may include one or more additives (other than water and thickening polymers), preferably in a proportion ranging from 0.001 to 30% by mass, more preferably from 0.01 to 20% by mass, more preferably from 0.05 to 20% by mass.

[0078] It is understood that the said additive(s) are compatible with their use in an aqueous medium. Advantageously, the additives are used in a form that is soluble or emulsifiable in water, for example in the form of salts or ionic liquids.

[0079] The said additive(s) are of course chosen with regard to the intended application for the aqueous lubricant.

[0080] Such additives may be more particularly selected from antifreeze compounds, antifoaming agents, biocides, pH regulators, inhibitors corrosion, anti-wear and / or extreme-pressure additives, sequestering agents, metal passivating agents, colorants, dispersants, emulsifying agents, and mixtures thereof.

[0081] Advantageously, an aqueous lubricating composition according to the invention may comprise one or more additives selected from antifreeze compounds, antifoaming agents, extreme-pressure agents, corrosion inhibitors, pH regulators, metal passivating agents, colorants, and mixtures thereof. Antifreeze compound

[0082] An aqueous lubricating composition implemented according to the invention may comprise at least one antifreeze compound selected from glycols, preferably alkylene glycols, glycerol, diglycerol, triglycerol, and mixtures thereof.

[0083] Thus, according to a preferred embodiment, an aqueous lubricating composition implemented according to the invention comprises at least:

[0084] - water, preferably deionized water;

[0085] - at least one polyalkylene glycol; and

[0086] - at least one antifreeze compound selected from glycols, preferably alkylene glycols, glycerol, diglycerol, triglycerol, and their mixtures.

[0087] These compounds are known for their antifreeze action, in other words for reducing the freezing temperature of the composition.

[0088] Glycols are diols in which the two hydroxyl groups are borne by different carbon atoms, preferably by vicinal carbon atoms.

[0089] Preferably, the glycols are alkylene glycols, in particular having from 2 to 10 carbon atoms, in particular from 2 to 6 carbon atoms. Examples include monoethylene glycol, diethylene glycol and propylene glycol.

[0090] The antifreeze compound can further be chosen from glycerol, diglycerol, triglycerol and mixtures thereof.

[0091] Preferably, the antifreeze compound used according to the invention is selected from monoethylene glycol, diethylene glycol, propylene glycol, glycerol, and mixtures thereof. Preferably, the antifreeze compound is diethylene glycol.

[0092] In particular, the said antifreeze compound(s), in particular as defined above, for example diethylene glycol, can be implemented in an aqueous lubricating composition according to the invention in a content of at least 1.0% by mass, preferably between 5.0% and 50% by mass, more preferably between 10% and 45% by mass, in particular between 20% and 40% by mass, relative to the total mass of the composition.

[0093] Preferably, an aqueous lubricating composition implemented according to the invention comprises an antifreeze compound(s), in particular as defined above, for example diethylene glycol, greater than or equal to 33% in particular between 33.5% and 40% mass, relative to the total mass of said composition.

[0094] According to a particular embodiment, the aqueous lubricating composition comprises at least:

[0095] - water;

[0096] - at least one polyalkylene glycol; and

[0097] - at least one antifreeze compound selected from glycols in a higher content or equal to 33% by mass, relative to the total mass of the composition; said aqueous lubricating composition comprising a content of phosphate ester salt(s), in particular selected from alkali metal salts of phosphate esters, strictly less than 0.1% by mass, relative to the total mass of said composition.

[0098] According to a particular embodiment, the aqueous lubricating composition comprises:

[0099] - at least 45% by mass of water, relative to the total mass of the composition;

[0100] - at least one polyalkylene glycol; and

[0101] - at least one antifreeze compound selected from glycols in a higher or equal to 33% by mass, relative to the total mass of the composition.

[0102] According to a particular embodiment, the aqueous lubricating composition implemented according to the invention comprises at least:

[0103] - at least 35% by mass of water, in particular deionized water, preferably 40 to 60% water by mass; in particular from 45 to 60% water by mass;

[0104] - at least 10% by mass, in particular between 10 and 20% by mass, of at least one polyalkylene glycol, in particular as defined above;

[0105] - at least 5.0% by mass, in particular between 20 and 40% by mass, of at least an antifreeze compound selected from glycols, preferably alkylene glycols; glycerol; diglycerol; triglycerol, and mixtures thereof, said antifreeze compound preferably being diethylene glycol.

[0106] According to a particular embodiment, the assembly consisting of water, said polyalkylene glycol(s), and possibly said antifreeze compound(s) represent more than 90% of the total mass of said aqueous lubricating composition, in particular more than 95%, notably more than 96%, or even more than 97%, of the total mass of said aqueous lubricating composition. pH regulator

[0107] An aqueous lubricating composition according to the invention may include at least one pH-regulating additive, in particular an alkaline buffer. The pH regulator makes it possible to maintain the desired pH of the lubricating composition, in particular to preserve an alkaline pH, advantageously between 8 and 15.

[0108] The said pH regulator(s), by ensuring that the pH of the aqueous lubricating composition is maintained between 8 and 15, makes it possible in particular to prevent corrosion of the metal surfaces, but also to promote the solubilization of the different compounds in the lubricating composition, in particular of the polyalkylene glycol(s), in particular as defined above.

[0109] The pH regulator can be chosen from the family of amines, in particular alkanolamines and amino alcohols.

[0110] This may include a pH regulating additive selected from alkanolamines, such as dimethylethanolamine (DMEA), ethanolamines, such as monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), isopropanolamines, such as mono-isopropanolamine (MIPA), diisopropanolamine (DIPA) and triisopropanolamine (TIPA); diglycolamine (DGA); ethylene amines, such as ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA) and tetraethylenepentamine (TEPA); cyclamines, such as cyclohexylamine; 2-amino-2-ethyl-1,3-propanediol; 2-amino-2-methyl-1-propanol; and mixtures thereof.

[0111] An aqueous lubricating composition implemented according to the invention may in particular comprise from 0.1% to 10% by mass of pH regulating additive(s), preferably from 0.5% to 5% by mass, relative to the total mass of the composition.

[0112] Advantageously, an aqueous lubricating composition implemented according to the invention comprises at least one pH-regulating additive for maintaining the pH of said lubricating composition between 8 and 15, in particular between 8.5 and 14, more particularly between 9 and 13, said pH-regulating additive being selected in particular from alkanolamines, preferably ethanolamines, and more particularly from dimethylethanolamine (DMEA), triethanolamine (TEA) and mixtures thereof

[0113] Thus, in a particular embodiment, an aqueous lubricating composition required according to the invention comprises at least:

[0114] - water, in particular deionized water;

[0115] - at least one polyalkylene glycol, in particular as defined above; and

[0116] - at least one pH regulating additive for maintaining the pH of said Lubricating composition between 8 and 15, specifically chosen from alkanolamines. Corrosion inhibitor

[0117] An aqueous lubricating composition according to the invention may comprise at least one corrosion inhibitor. Corrosion inhibitors advantageously reduce or even prevent the corrosion of metal parts. The nature of said corrosion inhibitor(s) may be chosen with regard to the metal to be protected against corrosion, such as aluminum, steel, galvanized steel, or yellow metals, for example copper or brass. Among the inorganic corrosion inhibitors may Examples include nitrites, sulfites, silicates, borates, sodium, potassium, calcium or magnesium phosphates, alkali metal phosphates, hydroxides, molybdates, zinc, magnesium or nickel sulfates.

[0118] Among the organic corrosion inhibitors that can be cited are alkanolamines such as triethanolamine, monocarboxylic aliphatic acids, in particular those having 4 to 15 carbon atoms, for example octanoic acid, dicarboxylic aliphatic acids having 4 to 15 carbon atoms, for example decanedioic acid, undecanedioic acid, dodecanedioic acid or mixtures thereof, polycarboxylic acids possibly neutralized by triethanolamine, such as 1,3,5-triazine-2,4,6-tri-(6-aminocaproic acid), alkanoylamidocarboxylic acids, in particular isononanoylamidocaproic acid, and mixtures thereof. Borated amides, products of the reaction of amines or amino alcohols with boric acid, can also be used.

[0119] Preferably, the corrosion inhibitor(s) are separate from the pH regulating additive(s), in particular allowing the pH of the lubricating composition to be maintained between 8 and 15, and defined previously.

[0120] An aqueous lubricating composition according to the invention may in particular comprise from 0.1% to 5% by mass of corrosion inhibitor(s), in particular as defined above, preferably from 0.5% to 4% by mass, more preferably from 1% to 2.5% by mass, relative to the total mass of the composition.

[0121] In a particular embodiment, an aqueous lubricating composition required according to the invention comprises:

[0122] - water, in particular deionized water;

[0123] - at least one polyalkylene glycol, in particular as defined above; and

[0124] - at least one corrosion inhibitor, in particular selected from the inhibitors of organic corrosion, particularly among monocarboxylic aliphatic acids. Anti-wear / extreme-pressure additive

[0125] An aqueous lubricating composition according to the invention may include at least one anti-wear and / or extreme-pressure additive. Their function is to reduce wear and the coefficient of friction, or to prevent metal-to-metal contact by forming a protective film adsorbed onto these surfaces.

[0126] There is a wide variety of anti-wear additives, among which can be cited those chosen from among the phosphosulfur additives such as metallic alkylthiophosphates or their salts.

[0127] Additives that do not provide phosphorus are preferred, such as, for example, polysulfides, in particular sulfur olefins.

[0128] According to a particular embodiment, an aqueous lubricating composition implemented according to the invention may include at least one extreme-pressure additive selected from sulfur fatty acids and dimercaptothiadiazoles, preferably implemented in their neutralized form, in particular by inorganic alkalizing agents or alkanolamines, emulsifiable or soluble in water.

[0129] Advantageously, an aqueous lubricating composition implemented according to the invention comprises less than 0.1% by mass of an extreme-pressure additive of the sulfur fatty acid type, in particular in a neutralized form, preferably less than 0.01% by mass, more particularly less than 0.001% by mass, relative to the total mass of the composition, or is even totally free of extreme-pressure additive of the sulfur fatty acid type.

[0130] Sulfur fatty acids may comprise from 8 to 22 carbon atoms, in particular from 12 to 18 carbon atoms. The amount of sulfur, according to ASTM D2622, provided by said sulfur fatty acid(s) may be between 5% and 30% by mass, in particular between 10% and 20% by mass, relative to the total mass of the composition.

[0131] Preferably, the amount of active sulfur at 150°C according to ASTM D 1662 provided by said sulfur fatty acid(s) in the aqueous lubricating composition according to the invention is less than or equal to 2% by mass, in particular less than or equal to 1% by mass, more particularly less than 0.1% by mass, relative to the total mass of the lubricating composition.

[0132] For the purposes of this invention, "active sulfur" means the sulfur that a chemical compound is capable of donating or releasing when that compound is placed under the conditions of ASTM D-1662. ASTM D-1662 defines the active sulfur content of a compound at a given temperature as the difference, expressed as a percentage by weight, in sulfur content before and after reacting a sample of that sulfur compound with a given amount of copper for a fixed time.

[0133] As mentioned previously, the said sulfur fatty acid(s) are generally used in an aqueous lubricating composition in their form neutralized by an alkalizing agent, such as sodium hydroxide, potassium hydroxide, or an alkanolamine, such as monoethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine and triisopropanolamine.

[0134] A water-based lubricating composition required according to the invention may comprise between 0.01% and 10% by mass of anti-wear and / or extreme-pressure additive(s), preferably between 0.2% and 5% by mass, relative to the total mass of the composition. Anti-foaming agent

[0135] An aqueous lubricating composition according to the invention may include at least one antifoaming additive. Antifoams prevent foaming of the lubricating fluid.

[0136] This could be, for example, an antifoaming agent based on polysiloxanes or acrylate polymers. Preferably, the antifoaming agent is chosen from among three-dimensional siloxanes.

[0137] Also, the antifoaming agents can be polar polymers such as polymethylsiloxanes or polyacrylates. In particular, an aqueous lubricating composition according to the invention can comprise from 0.001% to 3.0% by mass of antifoaming additive(s), preferably from 0.005% to 1.5% by mass, more preferably from 0.01% to 1.0% by mass, relative to the total mass of the lubricating composition.

[0138] In a particular embodiment, an aqueous lubricating composition required according to the invention comprises:

[0139] - water, in particular deionized water;

[0140] - at least one polyalkylene glycol, in particular as defined above; and

[0141] - at least one anti-foaming additive, in particular selected from siloxanes three-dimensional. Metal passivating agents

[0142] An aqueous lubricating composition according to the invention may include at least one metal passivating agent. Metal passivating agents protect metal parts by promoting the formation of metal oxide on their surface.

[0143] Metal passivating agents may, for example, be selected from triazole derivatives, such as tetrahydrobenzotriazole (THBTZ), tolyltryazole (TTZ), benzotriazole (BTZ), amines substituted with a triazole group, such as N,N-bis(2-ethylhexyl)-1,2,4-triazol-1-yl methanamine, N'-bis(2-ethylhexyl)-4-methyl-1H-benzotriazole-1-methylamine, N,N-bis(heptyl)-ar-methyl-1H-benzotriazole-1-methanamine, N,N-bis(nonyl)-ar-methyl-1H-benzotriazole-1-methanamine, N,N-bis(decyl)-ar-methyl-1H-benzotriazole-1-methanamine, N,N-bis(undecyl)-ar-methyl-1H-benzotriazole-1-methanamine, N,N-bis(dodecyl)-ar-methyl-1H-benzotriazole-1-methanamine, N,N-bis(2-ethylhexyl)-ar-methyl-1H-benzotriazole-1-methanamine, 1,2,4-triazoles, benzimidazoles, 2-alkyldithiobenzimidazoles, 2-alkyldithiobenzothiazoles, 2-(N,N-dialkyldithiocarbamoyl)benzothiazoles, 2,5-bis(alkyldithio)-1,3,4-thiadiazoles, such as 2,5-bis(tert-octyldithio)-1,3,4-thiadiazole,2,5-bis(tert-nonyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-decyl dithio)-1,3,4-thiadiazole, 2,5-bis(tert-undecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-dodecyldithio)-1,3,4- thiadiazole, 2,5-bis(tert-tridecyldithio)-l,3,4-thia diazole, 2,5-bis(tert-tetradecyldithio)-l,3,4-thiadiazole, 2,5-bis(tert-pentad cyldithio)-l,3,4-thiadiazole, 2,5-bis(tert- hexadecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-heptadecyldithio)-1,3,4-thiadiazole, 2.5-bis(tert-octadecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-nonadecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-eicosyldithio)-1,3,4-thiadiazole, 2,5-bis(N,N-dialkyldithiocarbamoyl)-1,3,4-thiadiazoles, 2-alkyldithio-5-mercaptothiadiazoles, and mixtures thereof.

[0144] Preferably the metal passivating agents are chosen from tetrahydrobenzotriazole (THBTZ), tolyltriazole (TTZ), benzotriazole (BTZ), and their salts, taken alone or in mixtures.

[0145] An aqueous lubricating composition according to the invention may in particular comprise from 0.01% to 2.0% by mass of metal passivating agent(s), preferably from 0.1% to 1.0% by mass, more preferably from 0.2% to 0.8% by mass, relative to the total mass of the composition.

[0146] In a particular embodiment, an aqueous lubricating composition required according to the invention comprises:

[0147] - water, in particular deionized water;

[0148] - at least one polyalkylene glycol, in particular as defined above; and

[0149] - at least one metal-passivating agent, in particular selected from derivatives of Triazole, more specifically chosen from tetrahydrobenzotriazole (THBTZ), tolyltriazole (TTZ), benzotriazole (BTZ), and their salts, taken alone or in mixtures. Dyes

[0150] An aqueous lubricating composition according to the invention may comprise one or more colorants. The colorants may be natural or synthetic, generally organic. The colorants that can be used in an aqueous lubricating composition may be particularly chosen from natural or synthetic water-soluble colorants, for example, FDC Red 4, DC Red 6, DC Red 22, DC Red 28, DC Red 30, DC Red 33, DC Orange 4, DC Yellow 5, DC Yellow 6, DC Yellow 8, FDC Green 3, DC Green 5, FDC Blue 1, betanin (beetroot), xanthenes, carmine, a chlorophyllin, methylene blue, anthocyanins (enocianin, black carrot and hibiscus), caramel and riboflavin.

[0151] An aqueous lubricating composition according to the invention may comprise between 0.01% and 2.0% by mass of colorant(s), preferably between 0.01% and 1.5% by mass, more preferably between 0.02% and 1.0% by mass, relative to the total mass of the composition.

[0152] In a particular embodiment, an aqueous lubricating composition required according to the invention comprises:

[0153] - water, in particular deionized water;

[0154] - at least one polyalkylene glycol, in particular as defined above; and

[0155] - at least one dye, in particular selected from the xanthenes. Emulsifying agents

[0156] An aqueous lubricating composition according to the invention may comprise one or more emulsifying agents, also called emulsifiers. Their function is to generate stable emulsions in water.

[0157] Emulsifying agents may be, more particularly, non-ionic, such as ethoxylated fatty alcohols, ethoxylated fatty acids, ethoxylated fatty amides; anionic, for example, KOH soaps, NaOH soaps; sulfonates; cationic, such as quaternary ammonium compounds; or water-soluble or water-emulsifiable carboxylic acid esters. In particular, an aqueous lubricating composition according to the invention may comprise from 0.01% to 10% by mass of emulsifying agent(s), preferably from 0.1% to 5.0% by mass, relative to the total mass of the lubricating composition. Seizuring agents

[0158] An aqueous lubricating composition according to the invention may include at least one sequestering agent. Sequestering agents, also called chelating agents, limit the encrustation of metal ions in the composition.

[0159] Examples of sequestering agents include those derived from phosphonic acids and phosphonates, such as diethylenetriaminepentamethylphosphonic acid (DTPMPA), aminotri(methylenephosphonic) acid (ATMP), hydroxyethanediphosphonic acid (HEDP), 1,1-hydroxyethylidene diphosphonate, 2-hydroxyethylaminedi(methylenephosphonic) acid (HEAMBP), diethylenetriaminopenta(methylenephosphonic) acid (DTMP), multifunctional organic acids and hydroxylated acids, such as ethylenediaminetetraacetic acid (EDTA), pteroyl-L-glutamic acid (PGLU), organic polyacids, such as maleic acid and polyaspartic acid, polysaccharides and carbohydrates, such as rinulin, carboxymethylinulin and the carbonky methy Ichito sane.

[0160] An aqueous lubricating composition according to the invention may comprise from 0.001% to 2.0% by mass of sequestering agent(s), preferably from 0.01% to 1.0% by mass, relative to the total mass of the composition. Biocides and fungicides

[0161] An aqueous lubricating composition according to the invention may comprise at least one biocidal and / or fungicidal agent. The biocides and fungicides may be used to improve the biological stability of the composition by limiting the proliferation of bacteria, fungi, and yeasts in the lubricating fluid.

[0162] Such biocides may be selected from parabens, aldehydes, reactive acetylacetone compounds, isothiazolinones, phenolic compounds, acid salts, halogenated compounds, quaternary ammonium compounds, certain alcohols and their mixtures.

[0163] Preferably, the biocides can be selected from among the benzisothiazolinones (BIT), possibly substituted, such as N-butyl-1,2-benzisothiazolin-3-one, the methylisothiazolinones (MIT), mixtures of methylisothiazolinone and chloromethylisothiazolinone (MIT / CMIT), orthophenylphenol (OPP) or its sodium salt, 3-iodo-2-propynylbutylcarbamate (IPBC), chlorocresol and N,N-methylenebismorpholine (MBM); sorbic acid; preferably from among orthophenylphenol (OPP) or its sodium salt, 3-iodo-2-propynylbutylcarbamate, chlorocresol, the benzisothiazolinones and N,N-methyleneisomorpholine.

[0164] An aqueous lubricating composition according to the invention may in particular comprise between 0.01% and 10% by mass of biocide(s) and / or fungicide(s), preferably between 0.5% and 5.0% by mass, relative to the total mass of the composition.

[0165] In a particular embodiment, an aqueous lubricating composition required according to the invention comprises:

[0166] - water, in particular deionized water;

[0167] - at least one polyalkylene glycol, in particular as defined above; and

[0168] - one or more additives selected from antifoaming agents, inhibitors of corrosion, pH regulators, metal passivating agents, dyes, in particular as defined above.

[0169] In a particular embodiment, an aqueous lubricating composition required according to the invention comprises:

[0170] - water, in particular deionized water;

[0171] - at least one polyalkylene glycol, in particular as defined above;

[0172] - at least one antifreeze compound selected from glycols, preferably alkylene glycols; glycerol; diglycerol; triglycerol, and mixtures thereof; and

[0173] - one or more additives selected from antifoaming agents, inhibitors of corrosion, pH regulators, metal passivating agents, dyes, in particular as defined above.

[0174] According to a particular embodiment, an aqueous lubricating composition implemented according to the invention comprises:

[0175] - at least 35% water by mass, in particular 40 to 60% by mass, notably at least 50% water by mass, preferably deionized water;

[0176] - from 5.0% to 50% by mass, in particular from 10% to 20% by mass, of at least one polyalkylene glycol, in particular as defined above;

[0177] - possibly from 5.0% to 45%, in particular from 20% to 40% by mass, of at least an antifreeze compound, chosen from glycols, preferably alkylene glycols; the glycerol; diglycerol; triglycerol, and mixtures thereof; preferably diethylene glycol; and

[0178] - possibly from 0.1% to 10% by mass of one or more additives chosen from antifoaming agents, extreme pressure agents, corrosion inhibitors, pH regulators, metal passivating agents, dyes, emulsifying agents, sequestering agents, and mixtures thereof.

[0179] In particular, an aqueous lubricating composition implemented according to the invention may consist of:

[0180] - from 5.0% to 50% by mass, in particular from 10% to 20% by mass, of at least one polyalkylene glycol, in particular as defined above;

[0181] - possibly from 5.0% to 45%, in particular from 20% to 40% by mass, of at least an antifreeze compound, selected from glycols, preferably alkylene glycols, glycerol, diglycerol, triglycerol, and mixtures thereof, preferably diethylene glycol; and

[0182] - possibly from 0.1% to 10% by mass of one or more additives chosen from antifoaming agents, extreme-pressure agents, corrosion inhibitors, pH regulators, metal passivating agents, colorants, emulsifying agents, sequestering agents, and mixtures thereof, the contents being expressed in relation to the total mass of the lubricating composition, the remainder being made up of water, preferably deionized water.

[0183] It is understood that the various particular embodiments described above can be combined, as far as possible, to define other particular embodiments.

[0184] In particular, each of the additives specifically described above can be introduced alone, or in combination with at least one other of the additives specifically described, thus defining different embodiments of an aqueous lubricating composition according to the invention. In other words, particular embodiments of the invention are defined by an aqueous lubricating composition according to the invention, comprising at least water; and one or more polyalkylene glycols, in particular as defined above, preferably in the proportions indicated above, and further comprising one or more of the additives specifically detailed in the text.

[0185] According to a particular embodiment, an aqueous lubricating composition implemented according to the invention comprises:

[0186] - 40 to 55% by mass of water, in particular deionized water, especially more than 45 mass percentage of water;

[0187] - 10 to 15% by mass of one or more polyalkylene glycols;

[0188] - possibly 30 to 40% by mass of an antifreeze compound selected from the glycols, preferably alkylene glycols; glycerol; diglycerol; triglycerol, and mixtures thereof; preferably diethylene glycol;

[0189] - possibly from 0.1% to 10% by mass of one or more selected additives among antifoaming agents, corrosion inhibitors, pH regulators, metal passivating agents, colorants, emulsifying agents, sequestering agents, and mixtures thereof, said composition being free from phosphate ester salts and, more preferably, free from phosphorus compounds, said composition being free from extreme pressure additives of the sulfur fatty acid type.

[0190] According to a particular embodiment, an aqueous lubricating composition implemented according to the invention comprises hypericin in a content strictly less than 0.1% by mass, preferably less than or equal to 0.01% by mass, more preferably less than or equal to 0.01% by mass, relative to the total weight of the composition. In particular, an aqueous lubricating composition implemented according to the invention is completely free of hypericin.

[0191] More generally, an aqueous lubricating composition implemented according to the invention comprises one or more polycyclic dianthraquinone-type compounds in a content strictly less than 0.1% by mass, preferably less than or equal to 0.01% by mass, more preferably less than or equal to 0.01% by mass, relative to the total weight of the composition. In particular, an aqueous lubricating composition implemented according to the invention is completely free of polycyclic dianthraquinone-type compounds.

[0192] Typically, the powertrain of an electric vehicle includes a battery, an electric motor, power electronics and a reduction gear.

[0193] As schematically represented in [Fig.1], the propulsion system of an electric vehicle includes in particular the electric motor part 1, an electric battery 2, power electronics 11 and a transmission, and in particular a speed reducer 3. As suitable batteries for the propulsion systems of an electric or hybrid vehicle, Li-ion batteries or nickel-cadmium batteries may be mentioned in particular.

[0194] The electric motor typically comprises a stator 13 and a rotor 14. The rotor and stator are typically connected to power electronics 11. The stator comprises coils, in particular copper coils, which are alternately energized by an electric current. This generates a rotating magnetic field. The rotor itself comprises coils, permanent magnets, or other magnetic materials, and is set in rotation by the rotating magnetic field. Thus, the rotor can be a magnetized rotor or a wound rotor. Advantageously, within the scope of the invention, if the rotor is wound, then it will be coated with one or more polymer layers. insulator defined in the invention and if the rotor is magnetized then it will typically not be coated with the insulating polymer layer(s) defined in the invention.

[0195] The power electronics 11, the stator 13 and the rotor 14 of a propulsion system 1 are complex components that generate a significant amount of heat during motor operation. Therefore, it is essential to ensure cooling of the electric motor and the power electronics.

[0196] A bearing 12 is generally integrated between the stator 13 and the rotor 14. A transmission, and in particular a speed reducer 3, makes it possible to reduce the rotational speed at the output of the electric motor and to adapt the speed transmitted to the wheels, allowing at the same time to control the speed of the vehicle.

[0197] As detailed within the scope of the invention, the electric motor, in particular the stator and the rotor if wound, is advantageously coated with one or more layers of electrical insulating polymer as defined in the invention and said coated elements of the electric motor are in contact with the aqueous lubricating composition as defined in the invention, advantageously said coated elements are immersed in the aqueous lubricating composition as defined in the invention.

[0198] According to an advantageous embodiment, the transmission is not coated with one or more layers of electrically insulating polymer as defined in the invention but is advantageously immersed in the aqueous lubricating composition as defined in the invention.

[0199] According to one embodiment, the powertrain of the invention comprises a circuit in which the aqueous lubricating composition circulates from one element to another of the powertrain. Advantageously, the circuit comprises the same aqueous lubricating composition as that which is in contact with the element(s) of the powertrain. According to this embodiment, the lubrication and cooling process further comprises circulating the lubricating composition between at least two elements of the powertrain.

[0200] In the context of the invention, a reservoir may be provided to store the aqueous lubricant composition. Advantageously, no reservoir for the lubricant composition is present in the system of the invention. This makes it possible to reduce the weight and therefore the energy consumption of the electric vehicle.

[0201] Of course, various other modifications can be made to the invention within the scope of the annexed claims.

Claims

Demands

1. A method for lubricating and cooling the powertrain of an electric vehicle, said method comprising: a. Making at least one powertrain element at least partially coated with one or more layers of electrically insulating polymer available, b. Contacting said powertrain element of step a) with an aqueous lubricating composition comprising at least one thickening polymer, c. Operating said powertrain element, said at least one partially coated powertrain element being selected from one or more elements including an electric motor, a battery, or power electronics.

2. A lubrication and cooling method according to claim 1, wherein said at least one element of the powertrain at least partially coated with one or more layers of electrically insulating polymer is the stator and / or the wound rotor of the electric motor.

3. A lubrication and cooling method according to claim 1 or 2, wherein the stator, battery and power electronics are at least partially coated with one or more layers of electrically insulating polymer and if the rotor is a wound rotor then said wound rotor is also at least partially coated with one or more layers of electrically insulating polymer, preferably wherein the drive unit reducer is not coated with one or more layers of electrically insulating polymer.

4. Lubrication and cooling method according to any one of claims 1 to 3, wherein the contacting in step b) comprises a step of vaporizing the aqueous lubricating composition comprising at least one thickening polymer on said powertrain element of step a) or a step of total or partial immersion of said powertrain element of step a) in the aqueous lubricating composition comprising at least one thickening polymer.

5. A lubrication and cooling method according to any one of claims 1 to 4, wherein the surfaces of the electric motor and power electronics in contact with the aqueous lubricating composition are totally coated with one or more layers of electrically insulating polymer.

6. A lubrication and cooling method according to any one of claims 1 to 5, wherein the electrical insulating polymer is a polymer obtained by polymerization of an aromatic compound optionally substituted, preferably by polymerization of para-xylylene.

7. A lubrication and cooling method according to any one of claims 1 to 6, wherein the electrical insulating polymer coating layer(s) represent a total thickness from 0.1 pm to 1 mm.

8. A lubrication and cooling method according to any one of claims 1 to 7, wherein all the elements of the powertrain are in contact with the aqueous lubricating composition, in particular the stator, rotor, power electronics, gearbox and battery of the electric vehicle are in contact with the aqueous lubricating composition.

9. A lubrication and cooling method according to any one of claims 1 to 8, wherein the aqueous lubricating composition comprises: - at least 20% by mass of water, preferably from 35% to 90% by mass of water, more preferably from 40% to 75% by mass of water, - at least 5.0% by mass of thickening polymer(s), preferably from 5.0% to 50% by mass of thickening polymer(s), more preferably from 10% to 40% by mass of thickening polymer(s), - optionally from 0.001 to 55% by mass of additives other than water and thickening polymers, preferably from 0.01 to 50% by mass of additives other than water and thickening polymers, more preferably from 0.05 to 45% by mass of additives other than water and thickening polymers, relative to the total mass of the aqueous lubricating composition.

10. A lubrication and cooling method according to any one of claims 1 to 9, wherein the thickening polymer is selected from poly(alkylene glycol), vinylpyrrolidone polymers, biopolymers for example of cellulosic type, and mixtures thereof.

11. Powertrain of an electric vehicle comprising at least one element at least partially coated with one or more layers of electrically insulating polymer, said element being selected from an electric motor, a battery or power electronics, said coated element being at least partially in contact with an aqueous lubricating composition comprising at least one thickening polymer.

12. Powertrain of an electric vehicle according to claim 11, wherein said at least one element of the powertrain at least partially coated with one or more layers of electrical insulating polymer is the stator and / or the wound rotor of the electric motor, preferably wherein the stator, the battery and the power electronics are at least partially coated with one or more layers of electrical insulating polymer and if the rotor is a wound rotor then said wound rotor is also at least partially coated with one or more layers of electrical insulating polymer.

13. Powertrain of an electric vehicle according to claim 11 or 12, comprising at least one reducer, the reducer being free of electrical insulating polymer coating layer(s).

14. Powertrain of an electric vehicle according to any one of claims 11 to 13, wherein the aqueous lubricating composition is in contact, preferably following vaporization or immersion, with all the elements of the powertrain of the electric vehicle, in particular with the stator, wound rotor, power electronics, gearbox and battery of the electric vehicle.

15. Powertrain of an electric vehicle according to any one of claims 11 to 14, wherein the electrically insulating polymer is a polymer obtained by polymerization of an aromatic compound, optionally substituted, preferably by polymerization of para-xylylene, and / or wherein the polymer The thickener is chosen from poly(alkylene glycol), biopolymers (e.g., cellulosic type), and mixtures thereof, and / or in which the aqueous lubricating composition comprises: - at least 20% water by mass, preferably 35% to 90% water by mass, more preferably 40% to 75% water by mass, - at least 5.0% by mass of thickening polymer(s), preferably from 5.0% to 50% by mass of thickening polymer(s), more preferably from 10% to 40% by mass of thickening polymer(s), - possibly from 0.001 to 30% by mass of additives other than water and thickening polymers, preferably from 0.01 to 20% by mass of additives other than water and thickening polymers, more preferably from 0.05 to 20% by mass of additives other than water and thickening polymers, relative to the total mass of the aqueous lubricating composition.

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