A method for the derating of performance of a compressor of a refrigerant cycle cooling circuit in a vehicle with an electric powertrain

Abstract

There is described a method for the derating of performance of a compressor of a refrigeration cycle cooling circuit of a combined cooling system (CS) in a vehicle (V) with an electric powertrain comprising one or more traction units, wherein each traction unit comprises an electric traction motor (M1, M2, M3, M4 ), an inverter operatively connected to the traction motor, and a transmission which connects the electric traction motor to one or more drive wheels and comprises a transmission lubricant. Thanks to the method according to the invention it is possible to increase the availability of cooling power to the traction units in conditions of full use thereof, by limiting the electrical power absorbed by the compressor, while at the same time safeguarding the need of cooling a battery configured for supplying each electric traction motor (M1, M2, M3, M4).

Description

[0001] "A method for the derating of performance of a compressor of a refrigerant cycle cooling circuit in a vehicle with an electric powertrain"

[0002] ★★★★

[0003] TEXT OF THE DESCRIPTION

[0004] Field of the Invention

[0005] The present invention refers to vehicles with an electric powertrain, specifically BEVs. The invention has been developed with particular reference to the performance derating of a compressor of a refrigeration cycle cooling circuit in conditions of full use of the thermal cooling power available for the traction components (one or more electric traction motors, the respective inverters and the respective transmissions to one or more corresponding drive wheels) in order to avoid damages due to overtemperature.

[0006] Prior Art

[0007] In the vehicles with an electric powertrain, especially in BEVs, the traction units of the powertrain may develop heat as a natural consequence of dissipation phenomena taking place therein, and they may develop - or, better, reject - a thermal power which needs to be disposed of by a cooling system. Therefore, the need is felt of strategies for containing the thermal power rejected by the traction components, so as to limit the temperature of the components and to prevent damages due to overtemperature. In this regard, the Applicant has developed a strategy for derating the performances of one or more traction units of an electric powertrain of a vehicle, in the Patent Application n. 102024000019417, precisely for said purpose.

[0008] However, the intervention of derating the performances of the traction units, in itself, may not be sufficient to limit the evolution of the temperatures towards values which are dangerous for the integrity of the traction components; thus, the only remaining possibility consists in increasing the cooling power which is available to the traction components.

[0009] However, the prior art does not offer any effective solution to such issue. Specifically, no intervention is taught regarding the increase of the cooling power available to the traction components, or regarding the protection of every component of the vehicle (either traction components or non-traction components, such as e.g. the high-voltage battery) against damages due to overtemperature .

[0010] Object of the Invention

[0011] The invention aims at solving the technical problem outlined in the foregoing. Specifically, the object of the invention consists in increasing the availability of cooling power for the traction components of one or more traction units of a powertrain of a vehicle, while at the same time protecting the vehicle components, specifically a battery configured for the supply of each electric traction motor, against damages due to overtemperature .

[0012] Summary of the Invention

[0013] The object of the invention is achieved by means of a method having the features set forth in the annexed claims, which form an integral part of the technical disclosure provided herein in relation to the invention.

[0014] Brief Description of the Figures

[0015] The invention will now be described with reference to the annexed Figures, which are provided by way of non-limiting example only and wherein:

[0016] - Figure 1, already described in the foregoing, shows a partial circuit diagram of a cooling system equipping a vehicle with an electric powertrain, whereon it is possible to implement the method according to the invention, - Figure 2 shows an aspect of the method according to the invention,

[0017] Figures 3 to 10 schematically show some configurations of an electric powertrain whereon it is possible to implement the method according to the invention,

[0018] - Figure 11 is a block diagram representative of the method according to the invention,

[0019] - Figures 12 to 17 comprise diagrams representative of steps of the method according to the invention.

[0020] Detailed Description

[0021] As a preliminary discussion, Figure 1 schematically shows a combined cooling system CS equipping a vehicle with an electric powertrain, whereon it is possible to implement the method according to the invention. The system CS generally comprises a pair of radiating elements (i.e., heat exchange elements) in such a position as to intercept a refrigeration air flow rate while the vehicle is travelling.

[0022] Such radiating elements comprise a condenser CNDS and a radiator RAD, the former being arranged in front of the latter in the travelling direction of the vehicle, so that an air flow rate riiAir intercepted during the travel impinges upon the condenser CNDS first, then upon the radiator RAD (after having traversed the condenser CNDS).

[0023] The condenser CNDS is traversed by a refrigerant fluid (flow rate riiRfr) the change of phase whereof (from gas to liquid) is favoured. The refrigerant fluid circulates in a first refrigeration cycle cooling circuit, which moreover comprises an electrically operated compressor and at least one evaporation element for the refrigerant fluid, which element is not shown but generally comprises at least one battery evaporator, which is part of a chiller and therefore is in a heat exchange relationship with a heat transfer liquid of a cooling circuit of the high-voltage battery, and preferably a cabin evaporator for cooling an air flow rate of the passenger compartment. The high-voltage battery, as is commonly known, is configured for supplying the electric traction motors of the electric powertrain of the vehicle, as well as for supplying the electrically operated compressor (and it supplies said users as the vehicle is travelling, and not, specifically - in this last case - the compressor).

[0024] The radiator RAD is traversed by a heat transfer liquid (flow rate mcint) which does not undergo phase changes during the circulation, and which circulates in a second, largely branched cooling circuit which comprises, i.a., a cabin heater which is part of the conditioning system mentioned in the foregoing, a cooling circuit of each electric motor, and the cooling circuit BT of the high-voltage battery, the latter - as mentioned above - being in a heat exchange relationship with the one or more battery evaporators of the corresponding chillers CHL. Generally speaking, the second cooling circuit is configured for cooling the traction components of each traction unit, and optionally (under given conditions) of the battery configured for supplying each electric traction motor. Each traction unit - as will be described in detail in the following - comprises an electric traction motor (of the electric powertrain) , an inverter, operatively connected to the traction motor, and a transmission which connects the electric traction motor to one or more drive wheels, and which comprises a transmission lubricant.

[0025] Upstream of the set of heat exchange devices described in the foregoing (condenser CNDS and radiator RAD) there is preferably arranged a device for actively modulating the air flow rate mAir, denoted by the reference AGS in Figure 1. The reference corresponds to the acronym which is normally used to refer to this kind of devices, i.e. Active Grille Shutter. The device AGS comprises, as is commonly known, a plurality of shutters LV which are pivotably rotatable around the respective rotation axes orthogonal to the plane of the drawing, in such a way as to define a passage section which enables the transit of an air flow rate which may vary from a maximum value, wherein all the shutters LV are rotated so as to be substantially aligned with the direction of the air flow rate riiAir, to a minimum value wherein all the shutters LV are united, thus defining a blind wall which is substantially impermeable to the air flow rate lilAir.

[0026] Downstream of the set of heat exchange devices described in the foregoing (condenser and radiator), i.e. downstream of said device AGS, there is moreover preferably arranged a cooling fan F, configured for generating an air flow rate through the set of heat exchange devices for the cooling needs thereof (phase change - condensation - in the condenser CNDS, and reduction of the temperature of the coolant in the radiator RAD). The flow rate generated by the cooling fan F is in particular generated as a further flow rate in addition to the flow rate which transits through the device AGS, so as to increase the flow rate riiAir to values which cannot be reached only with the travelling of the vehicle and with the device AGS in configuration of maximum passage section.

[0027] The configuration in Figure 1 clearly shows that the air flow rate impinging upon the radiator RAD has a temperature value which is higher than the air flow rate impinging upon the condenser CNDS, since it is influenced by the effect of thermal power rejection by the condenser CNDS, which is necessary to promote the phase change from gas to liquid of the refrigerant fluid which traverses the condenser CNDS. This means that, if the possibility of increasing the thermal cooling power available to the traction components - which is only demanded to the radiator RAD - were depleted, the only remaining degree of freedom in the system CS would be the thermal power rejected by the condenser CNDS. In other words, the action on such degree of freedom requires the reduction of the performances of the compressor by limiting the electric power absorbed thereby, the management whereof takes place according to the method of the invention. The following description generally applies to cooling systems with a condenser CNDS upstream of a radiator RAD, wherein the radiator RAD is dedicated, i.a., to the cooling of the traction components (one or more electric traction motors and corresponding inverters and transmissions). Referring to Figure 2, the method according to the invention implements, according to the fashion which will be described in the following, a thermal management of the vehicle V which is schematically shown by three temperature ranges of the traction components Tc, respectively denoted as A, B, C in Figure 2.

[0028] Reference A denotes a reference temperature range wherein, thanks to the radiator RAD, there is an availability of thermal cooling power for the traction units of the powertrain, whereas the references B, C identify a first and a second temperature range corresponding to respective operating modes which occur concurrently with the impossibility of further increasing the thermal cooling power output by the radiator RAD. The temperature range A ends at the lower end of the range B, and such boundary denotes the impossibility of further increasing the thermal cooling power output by the radiator RAD for cooling the traction components .

[0029] The temperature range B corresponds to conditions wherein the cooling power available for the traction components can no longer be increased, and performance derating strategies are implemented for the traction components, specifically for the electric traction motor (s), for example as disclosed in the Patent Application n. 102024000019417 in the name of the same Applicant .

[0030] The temperature range B ends at the lower end of the range C, and corresponds to conditions wherein the temperatures of the traction components cannot be limited only by means of derating strategies of the performances of the one or more electric motors of the powertrain, but it is necessary to reduce the thermal power rejected by the condenser CNDS.

[0031] As a further preliminary discussion, Figures 3 to 10 schematically show some configurations of an electric powertrain of a vehicle V, whereon it is possible to implement the method according to the invention. Each configuration of electric powertrain comprises one or more traction units, each comprising an electric traction motor, an inverter operatively connected to the electric traction motor, and a transmission connecting the electric traction motor to one or more drive wheels and comprising a transmission lubricant.

[0032] The detailed description of the method will be set forth with reference to the most general configuration possible shown in Figure 1, and it may be applied to all further configurations by simply adapting the inferences to the number of traction units / electric traction motors on board the vehicle V.

[0033] The one or more electric motors are operatively associated with a front axle and / or a rear axle of the vehicle, or with respective single wheels of a same axle, as a function of the number and of the characteristics of the traction units. In this way, there is a power flow exchanged between each motor and (at least) one axle or (at least) one wheel of the vehicle, for the traction of said vehicle.

[0034] The phrase "power flow" denotes both a power flow into the electric motor (from a battery BT), i.e. a flow which originates a driving action of the same motor, and a power flow leaving the electric motor (and entering the battery BT), i.e. a flow originated when the electric motor is subjected to a drag load (braking or slowing down due to the inertia of the vehicle) and operates as an electric generator. The reference Pn in the Figures (with n= 1, 2, 3, 4 in the presently considered embodiments) represents the general power flow associated with the n-th motor.

[0035] For simplicity, the vehicle configurations schematically shown in the Figures envisage the presence of a single battery for supplying each electric motor, but the method may be applied irrespective of the number or the configuration of the batteries, and irrespective of the association thereof with the one or more electric motors of the powertrain.

[0036] Figure 3 shows a first configuration of a powertrain with four motors, comprising four traction units. Specifically, the powertrain of Figure 3 comprises a first electric motor Ml operatively associated with a rear left wheel RL of the vehicle, a second electric motor M2 Operatively associated with a rear right wheel RR of the vehicle, a third electric motor M3 operatively associated with a front left wheel of the vehicle, and a fourth motor M4 operatively associated with a front right wheel of the vehicle V. This means that each electric motor M1-M4 delivers a torque to the wheel operatively associated therewith. Each motor Ml, M2, M3, M4 is associated with a respective inverter, whereas the transmission which connects each motor Ml, M2, M3, M4 to the corresponding (single) drive wheel generally corresponds to a direct drive transmission or, more preferably, to a transmission comprising a reduction gear. Each of the four traction units thus defined comprises one of the motors Ml, M2, M3, M4, the respective inverter and the respective transmission.

[0037] The electric motors Ml, M2, M3, M4 are supplied by a single battery (or battery pack) BT. In the schematic representation of Figure 3, the arrows in solid lines indicate a power flow into the motors Ml, M2, M3, M4 from the battery BT (power absorbed by the motors), whereas the arrows in dashed lines indicate a power flow leaving the motors Ml, M2, M3, M4 towards the battery BT (power output by the motors).

[0038] Figure 4 shows a second configuration of a powertrain with three motors, comprising three traction units. The powertrain specifically comprises a first electric motor Ml operatively associated with a rear left wheel RL of the vehicle, a second electric motor M2 operatively associated with a rear right wheel RR of the vehicle, and a third electric motor M3 operatively associated with the front axle FA, thereby meaning a condition wherein the electric motor M3 delivers a torque to both the right and the left wheels FR, FL of the front axle FA. Each motor Ml, M2, M3 is associated to a respective inverter, whereas the transmission which connects each motor Ml, M2, M3 to the corresponding one or more drive wheels corresponds, for the motors Ml, M2, to a direct drive transmission or, more preferably, to a transmission including a reduction gear, and for the motor M3 it corresponds to a differential, by means of which it is connected to two drive wheels (FL and FR). Each of the three traction units thus defined comprises one of the motors Ml, M2, M3, the respective inverter and the respective transmission.

[0039] The electric motors Ml, M2, M3 are supplied by a single battery (or battery pack) BT. In the schematic representation of Figures 3, 4, the arrows in solid lines indicate a power flow into the motors Ml, M2, M3 from the battery BT, whereas the arrows in dashed lines indicate a power flow leaving the motors Ml, M2, M3 towards the battery BT.

[0040] Figure 5 substantially corresponds to a configuration mirroring the configuration of Figure 4, with a first electric motor Ml operatively associated with a front left wheel FL, a second electric motor M2 operatively associated with a front right wheel FR, and a third electric motor M3 operatively associated with a rear axle RA.

[0041] Figure 6 and Figure 7 show a vehicle V with a powertrain with a single motor, including a single electric motor Ml operatively associated with the rear axle only (Figure 6) or with the front axle only (Figure 7). In both cases, a single traction unit is present which comprises the motor Ml, an inverter associated with the motor Ml, and a transmission which connects the motor Ml to the pair of drive wheels of the axle by means of a differential.

[0042] Referring to the Figures 8, 9, they show a vehicle V with a powertrain with two motors, respectively comprising :

[0043] - a first electric motor Ml operatively associated with a rear left wheel RL of the vehicle, and a second electric motor M2 operatively associated with a rear right wheel RR of the vehicle (Figure 8), or

[0044] - a first electric motor Ml operatively associated with a front left wheel FL of the vehicle, and a second electric motor M2 operatively associated with a front right wheel FR of the vehicle (Figure 9).

[0045] The electric motors Ml, M2 are supplied by a single battery (or battery pack) BT and, as in the schematic representation of the previous Figures, the arrows in solid lines indicate a power flow into the motors Ml, M2 from the battery BT, whereas the arrows in dashed lines indicate a power flow leaving the motors Ml, M2 towards the battery BT.

[0046] Each motor Ml, M2 is associated with a respective inverter, whereas the transmission which connects each motor Ml, M2 to the corresponding (single) drive wheel corresponds to a direct drive transmission or, more preferably, to a transmission comprising a reduction gear. Each of the two traction units thus defined comprises one of the motors Ml, M2, the respective inverter and the respective transmission.

[0047] Figure 10 represents a vehicle V with a powertrain with two motors, comprising a first electric motor Ml operatively associated with the rear axle RA, and a second electric motor M3 associated with the front axle FA. Each motor Ml, M3 is associated with a respective inverter, whereas the transmission which connects each motor Ml, M3 to the corresponding pair of drive wheels of the axle comprises a differential. Each of the two traction units thus defined comprises one of the motors Ml, M3, the respective inverter and the respective transmission .

[0048] As stated in the foregoing, the description which follows is set forth with reference to the powertrain of Figure 3, and therefore the employed references apply to said Figure.

[0049] Referring to Figure 11, according to the invention there is defined a method for the derating of performance of a compressor of a refrigeration cycle cooling circuit of a combined cooling system, such as the system CS, in a vehicle with an electric powertrain comprising one or more traction units, wherein each traction unit comprises an electric traction motor Ml, M2, M3, M4, an inverter operatively connected to the traction motor, and a transmission which connects the electric traction motor to one or more drive wheels and comprises a transmission lubricant. The method includes: determining (block 2, Figure 11) a limit of electric power that can be absorbed PeAc_TrcDer_Lim by the compressor as a function of a temperature TMot_i, TMot_2, TMot_3, TMot_4 of the electric traction motor Ml, M2, M3, M4 of each traction unit, as a function of a temperature Tinv_i, Tinv_2, Tinv_3, Tinv_4of the inverter associated with the electric traction motor Ml, M2, M3, M4 of each traction unit, as a function of a temperature TOII_GBX_I, TOII_GBX_2, TOII_GBX_3, TOII_GBX_4 of the transmission lubricant of the transmission associated with the electric traction motor Ml, M2, M3, M4 of each traction unit, and as a function of a drive mode DrvMode currently selected for the control of the powertrain,

[0050] - determining (block 4, Figure 11) a corrected value PeAc_TrcBatDer_Lim of the limit of electric power that can be absorbed PeAc_TrcDer_Lim by the compressor as a function of a temperature of a battery (specifically a high-voltage battery, preferably a 800V battery) configured for supplying each electric traction motor of the powertrain, controlling the compressor according to the corrected value PeAc_TrcBatDer_Lim of the limit of electrical power PeAc_TrcDer_Lim that can be absorbed.

[0051] Generally, controlling the compressor according to the corrected value PeAc_TrcBatDer_Lim of the limit of electrical power PeAc_TrcDer_Lim that can be absorbed comprises limiting the electrical power absorbed by the compressor to the corrected value PeAc_TrcBatDer_Lim. Referring to Figure 12, which shows a preferred embodiment of the determination as per block 2, said defining the limit of electrical power that can be absorbed PeAc_TrcDer_Lim by the compressor includes determining the lowest (block 6, Figure 12) of:

[0052] - a first limit of electrical power PeAc_invDer_Lim_i, PeAC_InvDer_Lim_2, PeAC_InvDer_Lim_3, PeAC_InvDer_Lim_4 that C8U be absorbed by the compressor to avoid an overtemperature condition of the inverter associated with the corresponding electric motor Ml, M2, M3, M4 of each traction unit,

[0053] - a second limit of electrical power PeAc_MotDer_Lim_i, PeAC_MotDer_Lim_2, PeAC_MotDer_Lim_3, PeAC_MotDer_Lim_4 that Can be absorbed by the compressor to avoid an overtemperature condition of the electric motor Ml, M2, M3, M4 of each traction unit,

[0054] - a third limit of electrical power PeAc_oiiGBXDer_Lim_i, PeAC_0ilGBXDer_Lim_2, PeAC_0ilGBX_Der_Lim_3, PeAC_0ilGBX_Der_Lim_4 that Can be absorbed by the compressor to avoid an overtemperature condition of the transmission associated with the corresponding electric motor Ml, M2, M3, M4 of each traction unit, in particular of the transmission lubricant.

[0055] In other words, the limit of electrical power PeAc_TrcDer_Lim that can be absorbed by the compressor, determined at block 2, represents an upper limitation of the absorption of electrical power to the value resulting from the traction component in the most critical conditions, thus the traction component which requires the maximum reduction of thermal power rejected by the condenser in order for the temperature thereof to be controlled by means of the thermal cooling power that can be output by the radiator RAD (in this case, with the addition of the amount recovered by reducing the rejection of thermal power from the condenser CNDS). The notation used herein refers, as mentioned in the foregoing, to the most general case of the configuration with four motors of the powertrain shown in Figure 3 but, generally speaking, the description may be applied to each i-th traction unit, i.e. to each i-th electric traction motor, as well as to the i-th inverter and to the i-th transmission associated thereto. For this reason, and for brevity of description, the diagrams of the following Figures 13 to 15 show the general notation with the index "i" instead of the extended notation, which uses the whole range of values of the index i within the powertrain of the vehicle.

[0056] In this regard, with reference to Figure 13, diagram 10, the first limit of electrical power PeAc_invDer_Lim_i is determined for each traction unit as a function of the temperture Tinv_i of the inverter associated with the i- th electric traction motor and of the drive mode DrvMode currently selected for the control of the powertrain. In more detail, the limit PeAc_invDer_Lim_i is determined by a map MIO, which provides the value PeAc_invDer_Lim_i by means of curves as a function of the temperature Tinv_i, which are parameterized with respect to the currently selected drive mode DrvMode.

[0057] By way of example, four curves are shown which are parameterized with respect to four corresponding drive modes DrvModel, DrvMode2, DrvMode3, DrvMode4, which are mentioned in a decreasing order of aggressiveness (therefore, DrvModel is the most aggressive and highest- performing drive mode, DrvMode4 is the least aggressive mode, which aims at maximizing the driving range). Qualitatively, the value of the limit of power PeAc_invDer_Lim_i increases as the aggressiveness of the drive mode increases, since with performance-oriented drive modes it is important to maximize the use of the thermal capacity of the traction component and to limit the performance derating of the compressor, whereas in less aggressive drive modes, which aim at maximizing the driving range, it is important to preserve the thermal capacity of the traction component and to limit the performance derating of the traction unit in regeneration. Moreover, the limit of power PeAc_invDer_Lim_i decreases as the temperature of the inverter Tinv_i increases, in order to protect the component against damages due to overtemperature.

[0058] Similarly, Figure 14, diagram 20, the second limit of electrical power PeAc_MotDer_Lim_i is determined for each traction unit as a function of the temperature TMot_i of the i-th electric traction motor and of the drive mode DrvMode currently selected for the control of the powertrain. In more detail, the limit PeAc_MotDer_Lim_i is determined by a map M20, which provides the value PeAc_MotDer_Lim_i by means of curves as a function of the temperature TMot_i, which are parameterized with respect to the currently selected drive mode DrvMode.

[0059] By way of example, also in this case, four curves are shown which are parameterized with respect to the drive modes DrvModel, DrvMode2, DrvModeS, DrvMode4, described and mentioned in a decreasing order of aggressiveness (therefore, DrvModel is the most aggressive and highest-performing drive mode, DrvMode4 is the least aggressive mode, which aims at maximizing the driving range). Qualitatively, the value of the limit of power PeAc_MotDer_Lim_i increases as the aggressiveness of the drive mode increases, for the same reasons as for the limit PeAc_invDer_Lim_i, and it decreases as the temperature of the electric traction motor TMot_i increases, in order to protect the electric traction motor against damages due to overtemperature.

[0060] Again, similarly, Figure 15, diagram 20, the third limit of electrical power PeAc_oiiGBXDer_Lim_i is determined, for each traction unit, as a function of the temperature ToiiGBx_i of the transmission lubricant of the transmission associated with the i-th electric traction motor, and of the drive mode DrvMode currently selected for the control of the powertrain.

[0061] In more detail, the limit PeAc_oiiGBXDer_Lim_i is determined by a map M30, which provides the value PeAc_oiiGBXDer_Lim_i by means of curves as a function of the temperature TOIIGBX_I, which are parameterized with respect with the currently selected drive mode DrvMode.

[0062] By way of example, again, four curves are shown which are parameterized with respect to the drive modes DrvModel, DrvMode2, DrvMode3, DrvMode4, described and mentioned in a decreasing order of aggressiveness (therefore, DrvModel is the most aggressive and highest- performing drive mode, DrvMode4 is the least aggressive mode, which aims at maximizing the driving range). Qualitatively, the value of the power limit PeAc_oiiGBXDer_Lim_i increases as the aggressiveness of the drive mode increases, for the same reasons as for the limit PeAc_invDer_Lim_i, and decreases as the temperature of the electric traction motor TOIIGBX_I increases, in order to protect the transmission against damages due to an overtemperature .

[0063] Due to what has been observed with respect to Figure 2, each of the temperatures Tinv_i, TMot_i and TOII_GBX_I belongs to a temperature range wherein there is no longer a possibility of increasing the thermal cooling power which can be output by the radiator RAD, and a performance derating of at least one electric traction motor of the powertrain is underway. In other embodiments of the method, however, it is possible not to follow the intervention sequence suggested by the diagram of Figure 2.

[0064] The following Figure 16, diagram 40, functionally shows the determination of the corrected value PeAc_TrcBatDer_Lim of the limit of electrical power that can be absorbed PeAc_TrcDer_Lim by the compressor. The correction is necessary since the performance derating of the compressor, in order to limit the rejection of thermal power by the condenser CNDS, cannot go to the detriment of the integrity of the high-voltage battery which supplies each electric traction motor, since said battery is a critical component both for the vehicle operation in general and for the safety of the vehicle, since an uncontrolled thermal drift of the battery rapidly evolves towards phenomena of overtemperature and of so-called venting of the battery, with a consequent risk of fire. For this reason, the corrected value PeAc_TrcBatDer_Lim is the result of a lower limitation of the value of the limit PeAc_TrcDer_Lim to a minimum value of electrical power PeAc_Batcig_Min that can be absorbed by the compressor in order to meet a (current) cooling target for the battery configured for supplying each electric traction motor. In other words, determining the corrected value PeAc_TrcBatDer_Lim of the limit of the electrical power PeAc_TrcDer_Lim that can be absorbed by the compressor comprises determining the higher (block 42, MAX) of the limit of electrical power PeAc_TrcDer_Lim and the minimum value of electrical power PeAc_Batcig_Min.

[0065] The latter value, however, is a function of the request for cooling the battery which the compressor must currently meet. Specifically, with reference to Figure 17, diagram 50, the minimum value of electrical power PeAc_Batcig_Min that can be absorbed by the compressor to meet a cooling target of said battery is determined as:

[0066] - a value of electrical power PeAc_Batcig_MinRaw that is a function of a maximum cell temperature TBat_ceii_Max of the battery, if there is a request for cooling the battery by means of an action of the compressor, or

[0067] - a zero value, if there is no request for cooling the battery by means of an action of the compressor.

[0068] Figure 17 exemplifies said determination by means of a switch SW50, the output whereof is determined by a logic condition BatteryCoolingByCompressor which acquires the logic state "True" ("1") when there is a request for cooling the battery by means of an action of the compressor, and the logic state "False" ("0") when there is no request for cooling the battery by means of an action of the compressor. A block 52, which controls the switch SW50, corresponds to the condition BatteryCoolingByCompressor = True; therefore, when said condition occurs, the value PeAc_Batcig_Min coincides with the value PeAc_Batcig_MinRaw, as shown in the Figure, whereas in the opposite instance BatteryCoolingByCompressor = False, the value PeAc_Batcig_Min coincides with the zero value, represented by a block 54.

[0069] As can be seen in Figure 17, preferably the value of electrical power PeAc_Batcig_MinRaw (which is a raw value, since it has not been yet mediated by the switch SW50) as a function of the maximum cell temperature TBat_ceii_Max is determined by a map M50 and has a piecewise variable evolution; specifically, it is zero for values of the maximum cell temperature TBat_ceii_Max of the battery which are lower than or equal to a threshold value THS, and it increases up to a maximum value of electrical power PeAc_Batcig_Max that can be absorbed by the compressor for cooling the battery for maximum cell temperature values TBat_ceii_Max of the battery greater than the threshold temperature THL. This is due to the fact that, up to the threshold value THL (e.g. 49°C), the temperature of the battery is not so critical, and it is possible to prioritize the need to recover the thermal cooling power in favour of the radiator RAD. Beyond said temperature, the risk of damaging or destroying the battery increases very rapidly, and therefore the priority goes to the need of protecting the battery, to the detriment of the recovery of thermal cooling power by the radiator, if necessary while tolerating overtemperature events of the traction components.

[0070] Thanks to the method according to the invention, therefore, it is possible to increase the availability of cooling power for the traction components of one or more traction units of the powertrain of a vehicle (which is output by the radiator RAD and is increased by reducing the thermal power which is rejected by the condenser CNDS), while at the same time protecting the components of the vehicle, and particularly the battery configured for supplying each electric traction motor, from damages due to overtemperature, and moreover averting catastrophic events of battery or vehicle destruction .

[0071] Of course, the implementation details and the embodiments may amply vary with respect to what has been described and illustrated, without departing from the extent of the present invention, as defined by the annexed claims.

Claims

1. CLAIMS1. A method for performance derating of a compressor of a refrigeration cycle cooling circuit of a combined cooling system (CS) in a vehicle (V) with an electric powertrain comprising one or more traction units, wherein each traction unit comprises an traction electric motor (Ml, M2, M3, M4), an inverter operatively connected to the traction motor, and a transmission that connects the traction electric motor to one or more drive wheels and includes a transmission lubricant, wherein the combined cooling (CS) system comprises:- a first, refrigeration cycle, circuit through which a refrigerant fluid flows, the first circuit including a condenser (CNDS), and further including at least one evaporator and said compressor, the at least one evaporator being in a heat exchange relationship with a heat transfer liquid that flows in a cooling circuit of a battery configured to supply each traction electric motor (Ml, M2, M3, M4) of the powertrain,- a second cooling circuit through which a coolant flows, said second cooling circuit comprising a radiator (RAD) for the coolant, the second cooling circuit being configured for cooling the traction components of each traction unit, wherein the condenser (CNDS) of the first circuit (Cl) is installed on the vehicle in a position in front of the radiator (RAD) in a flow direction of an air flow rate (liiAir) fed through the condenser (CNDS) and radiator (RAD), the method including:- determining (2, 6, 10, 20, 30) a limit of electric power that can be absorbed (PeAc_TrcDer_Lim) by the compressor as a function of a temperature (TMot_i, TMot_2, TMot_3, TMot_4) of the traction electric motor (Ml, M2, M3, M4) of each traction unit, as a function of a temperature(Tinv_i, Tinv_2, Tinv_3, Tinv_4) of the inverter associated with the traction electric motor (Ml, M2, M3, M4) of each traction unit, as a function of a temperature (TOII_GBX_I, TOII_GBX_2, TOII_GBX_3, TOII_GBX_4) of the transmission lubricant of the transmission associated with the traction electric motor (Ml, M2, M3, M4) of each traction unit, and as a function of a drive mode (DrvMode) currently selected for the control of the powertrain, determining (4, 40, 50) a corrected value(PeAc_TrcBatDer_Lim) of the limit of electric power that can be absorbed (PeAc_TrcDer_Lim) by the compressor as a function of a temperature of said battery configured to supply each traction electric motor (Ml, M2, M3, M4) of the powertrain, controlling the compressor according to the corrected value (PeAc_TrcBatDer_Lim) of the limit of electrical power (PeAc_TrcDer_Lim) that can be absorbed by the compressor.

2. The method of claim 1, wherein said determining the limit of electric power that can be absorbed (PeAc_TrcDer_Lim) by the compressor includes determining the lowest (6) of:- a first limit of electric power (PeAc_invDer_Lim_i, PeAC_InvDer_Lim_2, PeAC_InvDer_Lim_3, PeAC_InvDer_Lim_4) that C8U be absorbed by the compressor to avoid an overtemperature condition of the inverter associated with the corresponding electric motor (Ml, M2, M3, M4) of each traction unit,- a second limit of electric power (PeAc_MotDer_Lim_i, PeAC_MotDer_Lim_2, PeAC_MotDer_Lim_3, PeAC_MotDer_Lim_4) that Can be absorbed by the compressor to avoid an overtemperature condition of the electric motor (Ml, M2, M3, M4) of each traction unit,- a third limit of electric power (PeAc_oiiGBXDer_Lim_i, PeAC_OilGBXDer_Lim_2, PeAC_OilGBX_Der_Lim_3, PeAC_OilGBX_Der_Lim_4) thatcan be absorbed by the compressor to avoid an overtemperature condition of the transmission associated with the corresponding electric motor (Ml, M2, M3, M4) of each traction unit, in particular of the transmission lubricant .

3. The method of claim 2, wherein the first limit Of electric power (PeAC_InvDer_Lim_l, PeAC_InvDer_Lim_2, PeAC_InvDer_Lim_3, PeAC_InvDer_Lim_4) is determined for each traction unit as a function of said temperature (Tinv_i, Tinv_2, Tinv_3, Tinv_4) of the inverter associated with the traction electric motor (Ml, M2, M3, M4) and of said drive mode (DrvMode) currently selected for the control of the powertrain.

4. The method of claim 2, wherein the second limit Of electric power (PeAC_MotDer_Lim_l, PeAC_MotDer_Lim_2, PeAc_MotDer_Lim_3, PeAc_MotDer_Lim_4) is determined for each traction unit as a function of said temperature (TMot_i, TMot_2, TMot_3, TMot_4) of the traction electric motor (Ml, M2, M3, M4) and of this drive mode (DrvMode) currently selected for the control of the powertrain.

5. The method of claim 2, wherein the third limit of electric power (PeAC_011GBXDer_Llm_l, PeAC_0ilGBXDer_Lim_2, PeAC_0ilGBX_Der_Lim_3, PeAC_0ilGBX_Der_Lim_4) is determined for each traction unit as a function of said temperature (TOil GBX_1, TOil GBX_2, TOil_GBX_3, TOil GBX_4) of the transmission lubricant associated with the traction electric motor (Ml, M2, M3, M4) and of said drive mode (DrvMode) currently selected for the control of the powertrain .

6. The method of claim 1, wherein said determining the corrected value (PeAc_TrcBatDer_Lim) of the limit of electric power that can be absorbed (PeAc_TrcDer_Lim) by the compressor includes determining the highest (42) of the limit of electric power that can be absorbed (PeAc_TrcDer_Lim) by the compressor and a minimum value ofelectric power (PeAc_Batcig_Min) that can be absorbed by the compressor to meet a cooling target of said battery configured to supply each traction electric motor (Ml, M2, M3, M4).

7. The method of claim 6, wherein the minimum value of electric power (PeAc_Batcig_Min) that can be absorbed by the compressor to meet a cooling target of said battery configured to supply each traction electric motor (Ml, M2, M3, M4) is determined (50, SW50) as:- a value of electric power (PeAc_Batcig_MinRaw) that is a function of a maximum cell temperature (TBat_ceii_Max) of said battery configured to supply each traction electric motor (Ml, M2, M3, M4 ) if there is (52,BatteryCoolingByCompressor = True) a request for cooling the battery by means of a compressor action, or a zero value (54) if there is no (BatteryCoolingByCompressor = False) a request to cool the battery by means of a compressor action.

8. The method of claim 7, wherein said electric power value (PeAc_Batcig_MinRaw) that is a function of a maximum cell temperature (TBat_ceii_Max) of said battery configured to supply each traction electric motor (Ml, M2, M3, M4) is zero for maximum cell temperature values(TBat_ceii_Max) of the battery less than or equal to a threshold value (THL), and increases up to a maximum value of electric power (PeAc_Batcig_Max) that can be absorbed by the compressor to cool the battery for maximum cell temperature (TBat_ceii_Max) values of the battery greater than said threshold value (THL).

9. The method of any of the above claims, wherein the temperature (TMot_i, TMot_2, TMot_3, TMot_4) of the traction electric motor (Ml, M2, M3, M4) of each traction unit, the temperature (Tinv_i, Tinv_2, Tinv_3, Tinv_4) of the inverter associated with the traction electric motor (Ml, M2, M3, M4) of each traction unit, and thetemperature (TOII_GBX_I, TOII_GBX_2, TOII_GBX_3, TOII_GBX_4) of the transmission lubricant associated with the traction electric motor (Ml, M2, M3, M4) of each traction unit belong to a temperature range wherein the availability of cooling thermal power that can be output by the radiator (RAD) cannot be increased and a performance derating of the least one traction electric motor (Ml, M2, M3, M4) of the powertrain is underway.

10. The method of any of the foregoing claims, wherein said controlling the compressor according to the corrected value (PeAc_TrcBatDer_Lim) of the limit of electrical power absorbable (PeAc_TrcDer_Lim) by the compressor includes limiting the electrical power absorbed by the compressor to the corrected value (PeAC_TrcBatDer_Lim)•

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