A method of controlling a system for modulating a flow of cooling air of a vehicle in low-speed conditions of the vehicle

Abstract

Method (50) of controlling a system for modulating a flow of cooling air of a vehicle in low-speed conditions of the vehicle, wherein a current speed (Vehicle_Speed) of the vehicle is sensed and compared to at least one threshold value (Vehicle_Speed[_0, Vehicle_SpeedH i), it is checked whether the conditioning system of the vehicle demands activation (Cab_Cool_Req) of a cabin evaporator for conditioning the cabin of the vehicle, in response to (504) the current speed (Vehicle_Speed) of the vehicle being lower than the threshold value and the conditioning system demanding activation (Cab_Cool_Req) of the cabin evaporator, a signal of complete opening (AGSopeninig-AntiAging) of the system for modulating a flow of cooling air is asserted (502, Ctr_2, S2), in response to (506) the current speed (Vehicle_Speed) of the vehicle being above the threshold value and / or the conditioning system not demanding activation (Cab_Cool_Req) of the cabin evaporator, the signal of complete opening (AGSopeninig-AntiAging) of the system for modulating a flow of cooling air is de-asserted (502, Ctr_2, S2), in response to the signal of complete opening (AGSopeninig-AntiAging) being asserted, the system for modulating a flow of cooling air is brought to a condition of complete opening, and in response to the signal of complete opening (AGSopeninig-AntiAging) being de-asserted, the system for modulating a flow of cooling air is brought to a condition of partial or full closure.

Description

[0001] “A method of controlling a system for modulating a flow of cooling air of a vehicle in low-speed conditions of the vehicle”

[0002] ****

[0003] TEXT OF THE DESCRIPTION

[0004] Field of the invention

[0005] The present invention relates to vehicles provided with systems for modulating a flow of cooling air entering the vehicle, for example of the type conventionally called “Active Grill Shutter”, AGS.

[0006] Solutions as described herein can be applied to vehicles with (even partially) electric propulsion, for example BEV (Battery Electric Vehicle) or HEV (Hybrid Electric Vehicle) type vehicles, provided with such a system for modulating a flow of cooling air.

[0007] Prior art

[0008] Figure 1 schematically illustrates the operation of a system for modulating a flow of cooling air entering a vehicle V, of which the anterior or front portion is represented in a top view.

[0009] As is known, when the vehicle is in motion, an airflow can be let enter the vehicle V (and in particular, the engine compartment) through an air intake located in the front part of the vehicle V (not illustrated in Figure 1 for simplicity), and directed to a vehicle cooling system that comprises a group of heat exchangers located inside the vehicle. Such heat exchangers may comprise, for example, a condenser 102 and / or a radiator 104. The cooling system may further comprise a compressor (not illustrated in Figure 1 for simplicity), driven by a respective electric motor, which is operated using the rotational speed of the compressor itself as a control variable. Although useful for cooling some components of the vehicle V, the entering of an air flow to the vehicle exchangers 102, 104 may negatively affect the aerodynamic properties of the vehicle and, consequently, its performance. In some vehicles, a system 100 for modulating an air flow is therefore provided at the air intake, for example a system of the type conventionally known as “Active Grill Shutter” (AGS) 100, configured to modulate the flow rate of air entering the vehicle V and passing through the group of heat exchangers 102, 104. As illustrated in Figures 2A, 2B and 2C, an AGS system 100 comprises baffle plates 201 (or deflectors) whose orientation with respect to the direction of the air flow can be varied (e.g., by means of one or more electric actuators), so as to vary the surface area of the baffle plates 201 that counteracts the passage of the air flow to the exchangers 102, 104 or, in other words, to vary the area of the actual section of the air intake. In this regard, Figures 2A, 2B and 2C illustrate such an AGS system 100 in different configurations. Specifically, Figure 2A illustrates an AGS system 100 in a “closed” configuration, where the surface of each baffle plate 201 is oriented perpendicular to the direction of the incoming air flow FIN SO as to counteract (possibly completely blocking) the passage of the incoming air flow to the vehicle V. Figure 2B illustrates the AGS system 100 in a partially closed configuration, where the surface of each baffle plate 201 is oriented in an oblique direction with respect to the direction of the incoming air flow FIN SO as to only partially counteract the passage of the incoming air flow to the vehicle V and allow an exit flow Four of lower flow rate than the incoming flow FIN. Figure 2C illustrates the AGS system 100 in an “open” configuration, where the surface of each baffle plate 201 is oriented parallel to the direction of the air flow so as to minimize the surface area of the baffle plates 201 that opposes the incoming air flow FIN and to oppose as little as possible the passage of the air flow entering the vehicle V (or, in other words, to maximize the outlet air flow Four, which takes a flow rate almost equal to that of the incoming flow FIN). Obviously, it will be understood that intermediate configurations between those represented as an example in Figures 2A, 2B and 2C are also possible and that, in general, the orientation of the baffle plates 201 can be varied continuously between the “fully closed” configuration and the “fully open” configuration depending on the cooling needs.

[0010] An electronic control unit (not illustrated in the figures for simplicity) can be installed on board the vehicle and configured to control the system 100 for modulating a flow of cooling air according to management modes that allow the cooling air flow Four to be modulated (by varying the configuration of the modulation system 100 between the configurations exemplified in Figures 2A, 2B and 2C or other intermediate configurations) as a function of the quantity of cooling air that one wishes to send to the group of exchangers 102 and 104 (for example, as a function of the desired conditioning power). This electronic control unit can be, for example, a control unit of the conditioning and refrigeration system (or HVAC, “Heating, Ventilation and Air Conditioning”, system) or a vehicle control unit. It is known in the art that the greater the degree of closure of the AGS system 100, the better the aerodynamic properties of the vehicle, since the reduction of the air flow passing through the AGS system 100 determines a reduction in the aerodynamic drag of the vehicle. On the other hand, a greater closure of the AGS system 100 determines a lower cooling capacity of the vehicle components. Therefore, the electronic control unit can be configured to manage the AGS system 100 in such a way as to obtain a good balance between aerodynamic and cooling performance.

[0011] An AGS system 100 as just described is otherwise known in the art, which makes it superfluous to provide a more detailed description here. Furthermore, the particular system described is purely exemplary since solutions according to embodiments of the present description can be applied to systems for modulating air flows entering the vehicle other than the one described above.

[0012] It is known that conventional AGS systems suffer from aging and are characterized by a certain operational life (e.g., a certain number of opening / closing cycles after which the probability of failures or breakdowns increases considerably).

[0013] Therefore, there is a need in the art to develop an algorithm to control the system for modulating a flow of cooling air of a vehicle (or AGS system) that allows to reduce the number of actuations of the system (i.e., the number of opening / closing cycles) in certain conditions of use, in order to increase the operational life of the AGS system and reduce the incidence of failures and breakdowns, without excessively affecting the efficiency of the vehicle.

[0014] Object of the invention

[0015] The object of the invention is to solve the above-mentioned technical problem. In particular, the object of the invention is to provide a method of controlling an AGS system that allows to reduce, compared to known methods, the number of actuations of the system (i.e., the number of opening / closing cycles) in certain conditions of use to increase the operating life of the AGS system, without excessively affecting the efficiency of the vehicle.

[0016] Summary of the invention

[0017] The object of the invention is achieved by a method having the features forming the subject of the following claims, which form an integral part of the technical teaching provided here in relation to the invention.

[0018] The method can be implemented by one or more electronic control units of a vehicle, for example a control unit of the HVAC system and / or a unit for the thermal control of the vehicle.

[0019] Brief description of the figures

[0020] The invention will now be described with reference to the attached figures, provided purely by way of non-limiting example, in which:

[0021] - Figure 1 and Figures 2A to 2C, already described previously, schematically illustrate the operation of a system for modulating the flow of cooling air entering the vehicle, such as an “Active Grill Shutter” (AGS) system;

[0022] - Figure 3 illustrates a diagram of a conditioning and refrigeration system of a vehicle (electric or hybrid);

[0023] - Figures 4 and 5 are block diagrams illustrating some steps of the method of controlling the AGS system, according to one or more embodiments of the present description; and

[0024] - Figure 6 is a time diagram illustrating the behavior of an opening signal of the AGS system as a function of the speed of the vehicle, according to one or more embodiments of the present description.

[0025] Detailed description

[0026] As mentioned, the invention is applicable to conditioning and / or refrigeration systems comprising one or more heat exchangers which, when the vehicle is in motion, are hit by a flow of cooling air whose flow rate is adjustable by means of an AGS system, in which the conditioning and / or refrigeration system comprises at least one electric compressor driven by its own electric motor, and in which the electric motor driving the compressor is driven in order to reach a certain target rotational speed of the compressor depending on the cooling requirements.

[0027] In this regard, Figure 3 illustrates a diagram of a conditioning and refrigeration system 1 (or HVAC system) of an electric or hybrid vehicle in which a coolant flows, for example R1234YF. In the diagram of Figure 1 , the dotted lines indicate the portions of the system in which the coolant is at high pressure, and the thick continuous lines indicate the portions of the system in which the coolant is at low pressure. System 1 comprises an electric compressor C, driven by a dedicated electric motor, which compresses the coolant, increasing its pressure. The coolant thus compressed passes through a condenser CNDS which, when the vehicle is in motion, is touched by a flow of ambient air with which it exchanges heat, thus facilitating a phase change (from gaseous to liquid) of the coolant. The condenser CNDS may correspond, for example, to the condenser 102 shown in Figure 1. At the outlet of the condenser CNDS, a temperature sensor TS1 and a pressure sensor PS1 are arranged, which measure the temperature and pressure of the coolant, respectively. The coolant at high pressure can be directed through a cabin evaporator EVAP, which, when active, is touched by a flow of cabin air with which it exchanges heat, thus supporting a phase change (from liquid to gaseous) of the coolant to cool the cabin air, and / or through at least one chiller CHL, which, when active, is touched by a flow of cooling liquid with which it exchanges heat, thus supporting a phase change (from liquid to gaseous) of the coolant, for the refrigeration of a corresponding group of batteries of the vehicle (and / or other components of the vehicle). In the example described here, two chillers CHL1 and CHL2 are arranged in parallel, which can be activated independently. In general, the invention is applicable to systems that have a single chiller or even more than two chillers. At the inlet of each evaporation element (be it the cabin evaporator EVAP or any of the chillers CHL1 and CHL2) the coolant passes through respective shut-off valves and thermal expansion valves TXV: see the shut-off valve SOV1 and the thermal expansion valve TXV1 at the inlet of the evaporator EVAP, and the valves V1 and V2 at the inlet of the respective chillers CHL1 and CHL2 (these valves acting both as shut-off valves and as thermal expansion valves). System 1 also includes a temperature sensor TS2 that measures the temperature of the cabin air that touches the evaporator EVAP. The coolant exiting the evaporation elements EVAP, CHL1 and CHL2 flows towards the compressor C to close the circuit of system 1 .

[0028] Compressor C is characterized by a minimum rotational speed below which it is not able to operate correctly. For this reason, the control algorithm of the conditioning and / or refrigeration system 1 cannot require compressor C to operate at a speed between zero and this minimum rotational speed. Under certain operating conditions, for example when little cooling power is requested for the cabin evaporator EVAP, this minimum rotational speed of compressor C may still be too high (i.e., disproportionate to the cooling power requested by the system), which may lead to an overcooling condition of the cabin evaporator EVAP, resulting in ice forming on the surface of the evaporator due to humidity in the air.

[0029] In order to avoid ice formation on the evaporator EVAP, compressor C can be controlled in a discontinuous or “on / off” mode (i.e., alternating times of operation at the minimum allowed speed and times of inactivity), which does not cause problems for the compressor itself. In this regard, Figure 4 is a block diagram illustrating the steps of a control algorithm 40 to determine the rotational speed ncompjwn of compressor C, as a function of the requested cooling power. Essentially, a selector S1 receives a null value (zero) at a first input, the value of the minimum allowed rotational speed ncomp_Min_Fix of compressor C at a second input, and a control signal Ctr_1, so that if the control signal Ctr_1 is asserted (equal to one) the rotational speed ncomP_Min is set equal to zero, while if the control signal Ctr_1 is deasserted (equal to zero) the rotational speed ncompjwn is set equal to the minimum allowed rotational speed ncomP_Min_Fix. The minimum allowed rotational speed ncomP_Min_Fix may be stored in a vehicle control unit, and thus represents an input constant for the control algorithm 40. The control signal Ctr_1 of the selector S1 is produced at the output of a set-reset (SR) flip-flop 402. Essentially, the flip-flop 402 is set (by asserting the signal at the set input S of the flip-flop, produced by a comparator 404) when the temperature TAircabEvapOut of the air at the outlet of the cabin evaporator EVAP (e.g., measured by the temperature sensor TS2) is lower than or equal to a certain lower threshold TAircabEvapOutwnLo, and is reset (by asserting the signal at the reset input R of the flip-flop, produced by a comparator 406) when the temperature TAircabEvapout is higher than or equal to a certain upper threshold TAircabEvapoutMinHi. So, essentially, comparators 404 and 406 together with set-reset flip-flop 402 behave overall as a comparator with hysteresis, which asserts the control signal Ctr_1 when the temperature TAircabEvapout drops below the lower threshold TAircabEvapoutMinLo and deasserts the control signal Ctr_1 when the temperature TAircabEvapout rises above the upper threshold TAircabEvapoutMinHi. The upper threshold TAircabEvapoutMinHi and the lower threshold TAircabEvapoutMinLo can be stored in a vehicle control unit, and therefore represent two input constants for the control algorithm 40.

[0030] Therefore, the set of operations illustrated in Figure 4 essentially has the effect of setting the rotational speed ncompjwn of compressor C to a null value when the measured temperature TAircabEvapout of the air at the outlet of the cabin evaporator drops below the lower threshold TAircabEvapoutMinLo (which means that compressor C can be deactivated, switched off) and setting the rotational speed ncompjwn of compressor C to the minimum allowed value ncomp_Min_Fix when the temperature TAircabEvapout rises above the upper threshold TAircabEvapoutMinHi (which means that compressor C can be activated at the minimum speed that allows its regular operation). It will be noted that the use of two distinct temperature thresholds TAircabEvapoutMinLo and TAircabEvapoutMinHi is useful for the stability of the control algorithm 40 (since it allows to obtain a behavior with hysteresis) but, in principle, not necessary.

[0031] Such discontinuous operation (on / off) of compressor C consequently requires that also the air flow that touches the condenser CNDS (or 102 in Figure 1 ) be regulated in a discontinuous manner. As for compressor C, also for the cooling fan the discontinuous operation (on / off) mode does not cause problems. On the other hand, the discontinuous operation could lead to a premature aging of the AGS system 100, due to the numerous opening / closing cycles of the baffle plates 201 that would be requested. Therefore, it is appropriate to determine a control algorithm for the AGS system 100 (in particular, an algorithm that produces the opening / closing signal for the baffle plates 201 ) which, even in the presence of discontinuous operation of the compressor C, limits the number of actuations of the AGS system to prevent its premature aging. In this regard, Figure 5 is a block diagram illustrating the steps of a control algorithm 50 for determining the signal AGSoPening_AntiAging that controls the opening (if asserted) and the closing (if de-asserted) of the AGS system 100. Essentially, a selector S2 receives at a first input an asserted value (one, T, indicating the complete opening of the AGS system), at a second input a de-asserted value (zero, ‘O’, indicating the complete or partial closing of the AGS system), and a control signal Ctr_2, such that if the control signal Ctr_2 is asserted (equal to one) the signal AGSoPening_AntiAging is also asserted to demand the complete opening of the AGS system, while if the control signal Ctr_2 is de-asserted (equal to zero) the signal AGSoPening_AntiAging is also de-asserted to allow the complete or partial closing of the AGS system. The control signal Ctr_2 of selector S2 is produced at the output of a set-reset (SR) flip-flop 502. Essentially, flip-flop 502 is set (by asserting the signal at the set input S of the flip-flop, produced by a logic gate AND 504) when the current speed of the vehicle Vehicle_Speed (e.g., measured by a speed sensor of the vehicle V) is lower than or equal to a given lower threshold Vehicle_SpeedLo and at the same time the conditioning system of the vehicle V demands activation of cabin cooling (as signaled by a signal Cab_Cool_Req which takes on a logic value of “TRUE”). Flip-flop 502 is reset (by asserting the signal to the reset input R of the flip-flop, produced by a logic gate OR 506) when the current speed of the vehicle Vehicle_Speed is higher than or equal to a certain upper threshold Vehicle_SpeedHi and / or at the same time the conditioning system of the vehicle V does not require cabin cooling to be activated (as signaled by the signal Cab_Cool_Req which takes on a logic value of “FALSE”). The upper threshold Vehicle_SpeedHi and the lower threshold Vehicle_SpeedLo can be stored in a vehicle control unit, and therefore represent two input constants for the control algorithm 50.

[0032] Therefore, essentially, when the vehicle speed is lower than a certain threshold and at the same time there is a demand for cabin cooling, the AGS system is completely opened (signal AGSoPening_AntiAging in asserted condition). Conversely, when one of the two previous conditions is not satisfied (i.e., when the vehicle speed is higher than the threshold and / or there is no demand for cabin cooling), the AGS system is completely or partially closed (signal AGSoPening_AntiAging in de-asserted condition). In particular, when the signal AGSoPening_AntiAging is in de-asserted condition, the closure percentage of the AGS system is determined based on a conventional algorithm as a function of the demanded cooling power and / or as a function of other operating parameters of the conditioning system, in a way known per se that will not be further explored here. It will be noted that the use of two distinct speed thresholds Vehicle_SpeedLo and Vehicle_SpeedHi is useful for the stability of the control algorithm (as it allows to obtain a behavior with hysteresis) but, in principle, not necessary.

[0033] Qualitatively, the speed threshold or thresholds ( Vehicle_SpeedLo and Vehicle_SpeedHi) are defined to obtain a good balance between the reduction of the AGS system aging (i.e., a reduction of the discontinuous operation of the AGS system) and the overall efficiency of the vehicle (in fact, for low values of vehicle speed, a condition of complete opening of the AGS system does not appear to be particularly impactful in terms of increase in aerodynamic drag).

[0034] Figure 6 is a time diagram qualitatively illustrating an example of the behavior of the signal AGSoPening_AntiAging as a function of the vehicle speed Vehicle_Speed, when the cabin cooling demand is active (i.e., when the signal Cab_Cool_Req is asserted and the cabin evaporator EVAP is active). At time to the vehicle speed Vehicle_Speed drops below the lower threshold Vehicle_SpeedLo, and consequently the signal AGSoPening_AntiAging is asserted, such that the conventional AGS system control algorithm (which would impose a certain percentage of AGS system opening to adjust the air flow to a certain level) is completely overridden (or bypassed) and the AGS system is brought to a condition of complete opening. At time ti the vehicle speed Vehicle_Speed rises above the upper threshold Vehicle_SpeedHi, and consequently the signal AGSoPening_AntiAging is asserted, such that a conventional AGS system control algorithm is implemented again, which imposes a certain percentage of AGS system closure to adjust the air flow to the desired level.

[0035] With the present invention, it is possible to control the AGS system in such a way as to bring it into a condition of complete opening when the control unit of the conditioning and refrigeration system (or HVAC, “Heating, Ventilation and Air Conditioning”, system) of the vehicle demands cooling of the cabin evaporator EVAP, even if the compressor activation is not requested, while the vehicle is below a certain threshold speed. In this way, by keeping the AGS system completely open, the actuations (opening / closing cycles) are reduced and the operating life of the AGS system is increased (i.e. , its wear is reduced) without appreciably negatively affecting the efficiency of the vehicle, since the increase in aerodynamic drag at low speeds has little impact.

[0036] Of course, the details of construction and the embodiments may be widely varied with respect to what is described and illustrated without departing from the scope of the invention as defined by the attached claims.

Claims

CLAIMS1. A method (50) of controlling a system (100) for modulating a flow of cooling air of a vehicle (V) in low-speed conditions of the vehicle(V), the method comprising: sensing a current speed ( Vehicle_Speed) of the vehicle (V) and comparing said current speed ( Vehicle_Speed) with at least one threshold speed value ( Vehicle_SpeedLo, Vehicle_SpeedHi)', checking whether a conditioning system (1 ) of the vehicle (V) demands the activation (Cab_Cool_Req) of a cabin evaporator (EVAP) for conditioning the cabin of the vehicle; in response to (504) said current speed ( Vehicle_Speed) of the vehicle (V) being lower than said at least one threshold speed value and said conditioning system of the vehicle (V) demanding activation (Cab_Cool_Req) of said cabin evaporator (EVAP), asserting (502, Ctr_2, S2) a full-opening signal (AGSoPening_AntiAging) of the system (100) for modulating the flow of cooling air; in response to (506) said current speed ( Vehicle_Speed) of the vehicle (V) being higher than said at least one threshold speed value and / or said conditioning system of the vehicle (V) not demanding activation (Cab_Cool_Req) of said cabin evaporator (EVAP), de-asserting (502, Ctr_2, S2) said full-opening signal (AGSoPening_AntiAging) of the system (100) for modulating the flow of cooling air; in response to said full-opening signal (AGSoPening_AntiAging) being asserted, setting the system (100) for modulating the flow of cooling air in a condition of complete opening; and in response to said full-opening signal (AGSoPening_AntiAging) being de-asserted, setting the system (100) for modulating the flow of cooling air in a condition of partial or full closure.

2. The method (50) according to claim 1 , wherein: the step of comparing said current speed ( Vehicle_Speed) with at least one threshold speed value ( Vehicle_SpeedLo, Vehicle_SpeedHi) comprises comparing said current speed ( Vehicle_Speed) with a lower threshold speed value ( Vehicle_SpeedLo) and with an upper threshold speed value (Vehicle_SpeedHi)',said full-opening signal (AGSoPening_AntiAging) is asserted (502, Ctr_2, S2) in response to said current speed (Vehicle_Speed) falling below said lower threshold speed value ( Vehicle_SpeedLo) and said conditioning system of the vehicle (V) demanding activation (Cab_Cool_Req) of said cabin evaporator (EVAP); and said full-opening signal (AGSoPening_AntiAging) is de-asserted (502, Ctr_2, S2) in response to said current speed ( Vehicle_Speed) rising above said upper threshold speed value ( Vehicle_SpeedHi) and / or said conditioning system of the vehicle (V) not demanding activation (Cab_Cool_Req) of said cabin evaporator (EVAP).

3. A method (50) according to claim 1 or claim 2, comprising: in response to said full-opening signal (AGSoPening_AntiAging) being de-asserted, adjusting the closure percentage of said system (100) for modulating the flow of cooling air as a function of a current cooling power requested by said conditioning system of the vehicle (V).

4. A method (40; 50) according to any of the previous claims, comprising: sensing (TS2) the temperature (TAircabEvaPout) of an airflow that flows out from said cabin evaporator (EVAP) of said conditioning system (1 ) of the vehicle (V); comparing (404, 406) said temperature ( TAircabEvaPout) with at least one threshold temperature value ( TAircabEvaPoutMinLo, TAircabEvaPoutMinHi)', in response to said temperature (TAircabEvaPout) being lower than said at least one threshold temperature value, deactivating (402, S1 ) a compressor (C) of said conditioning system (1 ) of the vehicle (V); and in response to said temperature ( TAircabEvaPout) being higher than said at least one threshold temperature value, operating (402, S1 ) said compressor (C) of said conditioning system (1 ) of the vehicle (V) at a rotational speed (ncomP_Min) equal to a minimum allowed rotational speed (ncomP_Min_Fix) .

5. A method (40; 50) according to claim 4, wherein: the step of comparing (404, 406) said temperature ( TAircabEvaPout) with at least one threshold temperature value ( TAircabEvaPoutMinLo, TAircabEvaPoutMinHi) comprises comparing said temperature ( TAircabEvaPout) with a lower threshold temperature value (404;TAircabEvapoutMinLo) and with an upper threshold temperature value (406; TAirCabEvapOutMinHi) ; said compressor (C) is deactivated in response to said temperature ( TAircabEvapout) falling below said lower threshold temperature value (404; TAircabEvapoutMinLo)', and said compressor (C) is operated at said minimum allowed rotational speed (ncomp_Min_Fix) in response to said temperature ( TAircabEvapout) rising above said upper threshold temperature value ( TAirCabEvapOutMinHi) .

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