FR3013270A1 - METHOD FOR CONTROLLING A THERMAL CONDITIONING DEVICE FOR A MOTOR VEHICLE, AND CORRESPONDING CONDITIONING DEVICE - Google Patents

Abstract

The invention relates to a method for controlling a thermal conditioning device (100) for a motor vehicle, with a view to slowing down the icing of said thermal conditioning device (100), the thermal conditioning device (100) comprising an evaporator outside (3) traversed by an external air flow (9) for a heat exchange between the outside air flow (9) and a heat transfer fluid, an internal condenser (7) for a heat exchange between an air flow interior (13) and the coolant, and an airflow distribution member (15) between an air duct (11b) in which the inner condenser (7) is disposed and an air duct (11a). bypassing said inner condenser, characterized in that said method comprises the following steps: - a minimum operating pressure (Pext_min) of the external evaporator (3) is determined to limit the formation of ice, - an optimum pressure of fon operation (Pext_opt) of the external evaporator (3) is determined to obtain a target heating power (Pchauff) at the internal condenser (7), - if the optimum operating pressure (Pext_opt) is below the minimum pressure operating pressure (Pext_min), the pressure in the external evaporator (3) is set to the minimum operating pressure (Pext_min) and the airflow distribution element (15) is actuated to increase the amount of air bypassing said inner condenser (7).

Description

The invention relates to a conditioning device for ventilation, heating and / or air conditioning of a motor vehicle. . The invention particularly relates to a control method of an air conditioning device for slowing down its icing in winter conditions, and the associated system. A motor vehicle is commonly equipped with a ventilation, heating and / or air conditioning system to modify the aerothermal parameters of the air inside the passenger compartment of the vehicle by conditioning a flow of air to the cockpit. Such a packaging system can generally be used in summer for a need for cooling of the passenger compartment, but also in winter for a need for heating the passenger compartment. The conditioning system generally comprises a heat exchanger working in condenser mode or in evaporator mode, respectively to cool or heat the flow of air to the passenger compartment. According to a known solution, such a heat exchanger is for example arranged at the front face of the vehicle for a heat exchange between the coolant and a flow of air outside the vehicle obtained either by active ventilation or by circulation of the vehicle in an immobile atmosphere. The disadvantage of such a solution when it is used to heat the cabin is the risk of icing of the external heat exchanger working in evaporator mode because of the condensation of water vapor in the cabin. air and its cooling in contact with the walls when the conditioning system is operating in heat pump mode. In particular, fins inside the heat exchanger may be covered with ice. This has the effect of significantly reducing heat exchange within this heat exchanger, and therefore the power and efficiency of the conditioning system. It is known from the prior art, a solution that consists in temporarily using the heat exchanger in condenser mode. To do this, the conditioning system is commonly used in air conditioning mode. Thus, the heat exchanger in condenser mode is traversed by hot gases which allows defrosting. However, this solution causes thermal discomfort. Cooling can therefore be felt in the passenger compartment of the vehicle. To this end, the subject of the invention is a method for controlling a thermal conditioning device for a motor vehicle, with a view to slowing down the icing of said thermal conditioning device, the thermal conditioning device comprising an external evaporator traversed by a external air flow for a heat exchange between the outside air flow and a heat transfer fluid, an internal condenser for a heat exchange between an indoor air flow and the coolant, and a flow distribution element of air between an air duct in which is disposed the internal condenser and an air duct bypassing said inner condenser, characterized in that said method comprises the following steps: a minimum operating pressure of the external evaporator is determined to limit the formation of frost or ice, an optimal operating pressure of the external evaporator is If the optimum operating pressure is lower than the minimum operating pressure, the pressure of the outdoor evaporator is set to the minimum operating pressure and the element is determined to obtain a nominal heating power at the indoor condenser. air flow distribution is operated to increase the amount of air bypassing said inner condenser. The method makes it possible, by heating more importantly, initially to reduce the difference between the nominal heating value and the power delivered by deliberately degrading the performance of the device in order to limit the icing of the device. evaporator, which remains at a higher temperature. The method may further include one or more of the following features. The minimum operating pressure is determined taking into account the properties of the outside air flow. The optimum operating pressure is determined from the target heating power by optimizing the performance coefficient of the device. It comprises an additional step in which the speed of the compressor is increased, and in particular regulated until the total heating power of the device is approximately equal to the nominal heating power. The conditioning device comprises an additional heating device, and the method comprises an additional step located between the step of actuating the airflow control element and the step of increasing the speed of the compressor. wherein the difference between the set heating power and the power supplied to the indoor air by the indoor condenser at the minimum operating pressure is compared with the maximum power of the additional heating device, and that if said difference and less than the maximum power of the resistor, the resistor is supplied so as to supply the flow of internal air with a power corresponding to said difference, the subsequent steps of the process then being canceled. The invention also relates to a thermal conditioning system for an associated motor vehicle, comprising an external evaporator traversed by an external air flow for a heat exchange between the outside air flow and a heat transfer fluid, an internal condenser for a heat exchange. between an inner air flow and the coolant, characterized in that it comprises: an inner condenser disposed in an inner pipe, said inner pipe having two air channels, one containing the inner condenser, and bypassing said inner condenser, - an internal air flow distribution element, configured to distribute in its state the incoming air flow between the two air channels, a control unit connected to Sensors configured to determine properties of the outside air flow, and configured to: - determine a minimum operating pressure of the external evaporator to limit frost formation, - derive from a set heating capacity an optimum operating pressure value of the outdoor evaporator, and compare the optimum operating pressure to the minimum operating pressure of the evaporator outside, - and, if the optimum operating pressure is lower than the minimum operating pressure, regulate the pressure in the outdoor evaporator (3) to the minimum operating pressure and actuate the air flow control element to increasing the amount of air bypassing said inner condenser. The airflow control element may in particular comprise a flap, whose angular position with respect to an axis of rotation determines the distribution of the airflow inside the airways. It may furthermore comprise an additional heating device and the control unit is then configured to compare the maximum power of the additional heating device with the difference between the nominal heating power and an estimated value of the heating power supplied. at the minimum operating pressure, and if the maximum power of the electrical resistance is greater, the control unit supplies the electrical resistance so as to provide a power corresponding to said difference. The additional heating device may be placed in one of the air paths of the inner pipe, so as to heat the air passing through said air path. The additional heating device may be placed in the two air channels of the inner pipe, so as to heat all the air passing through said inner pipe. Other features and advantages of the invention will emerge more clearly on reading the following description, given by way of illustrative and nonlimiting example, and the appended drawings in which: FIG. 1 is a schematic view of the conditioning system according to the invention implemented in a heat pump mode, Figure 2 schematically shows the different stages of the process in a simplified flowchart. In these figures, the substantially identical elements bear the same references.

Conditioning device As represented in FIG. 1, a conditioning device 100 comprises a coolant circuit 1. The heat transfer fluid circuit 1 is here partially represented. It comprises in particular: an external evaporator 3, a compressor 5 and an internal condenser 7. The evaporator 3 is in contact with an outside air flow 9, characterized by its flow F't, its temperature T't and its humidity H't. In heat pump mode, the evaporator 3 operates at a relatively low pressure P't, at which the coolant evaporates in contact with the outside air 9. In particular, when the outside air 20 9 is at temperature relatively close to 0 ° C and its moisture H't is important, a risk of frost or ice formation occurs. By evaporating, the coolant absorbs heat from the outside air 9, and is circulated in the circuit 1 by the compressor 5, operating at a rotation speed Vcomp. The coolant is conveyed in the circuit 1 by the compressor 5 to the internal condenser 7, working at a pressure Ps', where it condenses by restoring the heat. The internal condenser 7 is disposed at an inner air duct 11, in which circulates an interior air flow 13, heated by the internal condenser 7, and directed towards the interior of the passenger compartment for the purpose of heating in the heat pump mode. In this heat pump mode, the pressure of the coolant is low at the level of the external evaporator 3 and high at the level of the internal condenser 7. The evaporator 3 and the condenser 7 may in particular be heat exchangers can be used both as a condenser and as an evaporator, the packaging device can then be used to cool the passenger compartment in summer by reversing the respective roles of the evaporator 3 and the condenser 7, a principle known as reversible air conditioning. The heat transfer fluid circuit 1 potentially comprises other elements, such as in particular an expander and expansion vessels, not shown. The inner pipe 11 is divided into two air channels 11a, 11b. In one of the two airways 1 lb is disposed the inner condenser 7, the other channel 11a forming a bypass ("bypass") of said inner condenser 7. A flap 15, with an adjustable position, is disposed at upstream end of the airway separation 11a, 11b. Depending on the position of said flap 15, a greater or lesser portion of the inner air 13 passes through the inner condenser 7 or bypasses it. Other forms of air distribution device may be used, for example diaphragms whose relative opening makes it possible to adjust the air flows in the pipes 11a, 11b. A variable V ranging from a minimum value to a maximum value between 0 and 100% is associated with the state of the air distribution device, here the position of the flap 15, and 20 represents the quantity of air passing through the air distribution device. 7. For example if V is 100%, all the air passes through the condenser 7, and no air flow is present in the air path 11 bypassing the condenser 7. For intermediate values of V , air passing through the internal condenser 7 and the air around it are mixed, in proportions corresponding to V, and the air mixture is directed to the passenger compartment. An additional heating device, such as a positive temperature coefficient resistance 17, of adjustable power, is placed in the inner air duct 11, here within the two air ducts 11a, 11b. Alternative embodiments can be obtained by not taking resistance 17 or by arranging it in a single air path 11a or 11b. Air channels 11a, 11b open into a common space (not shown) where the air they convey is mixed before dispensing into the passenger compartment. A control unit 19 controls, in particular, the speed of the compressor Vcomp, the position of the shutter 1 and the power of the resistor 17. The control unit 19 is in particular connected to a first set of sensors 21, arranged on the path of the flow. outside air 9 upstream of the evaporator 3 relative to the outside air flow 9 and configured to measure the properties of the outside air flow 9: its flow F't, its temperature T't and its rate of humidity H't. The control unit 19 is also connected to a second set of sensors 23a, 23b located on the path of the internal air flow 13, a portion 23a of said sensors is located upstream of the condenser 7 with respect to the air flow. 13 and is configured to measure the properties of the internal flow 13, and the other part of the sensors 23b, comprising at least one temperature sensor is disposed at the outlet of the condenser 7, in particular to estimate the heat provided by said condenser 7.

A method of controlling an air conditioner Figure 2 is a flowchart showing in a simplified manner the method 200 of controlling an air conditioner applied to the aforementioned device.

The first step 201 of the method is the evaluation of the parameters of the outside air flow 9: flow F't, temperature T't and humidity rate H't. In particular by means of the sensors 21 through which the outside air 9 passes. From the parameters of the outside air flow 9 is determined by the control unit 19 a minimum operating pressure P't min for the evaporator 3 for limit frost or ice formation when the heat transfer fluid circuit is in heat pump mode. This pressure can for example be determined from charts determined for a range of values comprising at least the usual values of the region in which the vehicle is used. Depending on the heating power P huff (depending on the temperature and the hot air flow) required, and the temperature T t and the flow rate F t of the outside air, an optimum pressure Pext opt in the external evaporator 3 is determined by the control unit 19 in the second step 203 for example by maximizing the coefficient of performance of the device including taking into account the parameters of the outside air flow 9, the flow of 13 and the power of the internal condenser 7. This optimum pressure Pext opt is compared in the third step 205 to the minimum operating pressure P - ext If the optimum operating pressure Pext opt is greater than the minimum pressure, the control unit 19 adapts in step 207 the speed Vcomp compressor 5 so that the pressure in the evaporator 3 is close to or equal to the optimum pressure 10 Pext opt, and the method 200 is stopped (the power of record e being reached). If the optimum operating pressure Pext opt is lower than the minimum operating pressure P ext the control unit 19, regulates in step 209 the speed of the compressor 5 so that the pressure in the evaporator 3 is equal to the pressure minimum P - ext min and estimates the heat Qair supplied by the internal condenser 7 to the inside air 13 passing through the pipe 11a in which there is said inner condenser 7. The heat supplied Qair depends in particular on the condenser temperature inside 7 (and therefore the energy supplied to it), the internal air flow 13 in the pipe 1 lb containing said inner condenser 7 and the upstream temperature of the inner air 13.

The following steps 211 to 215 are only present if a resistor 17 is present. In step 211, the control unit 19 compares the maximum power of the resistor Pap m 'with the difference between the heat supplied to the air Qatr and the power required (Pchauff Qau.). If the maximum power Pap max of the resistor 17 is greater than the difference P huff the control unit 19 feeds the resistance 17 in step 213 with a current which causes the power delivered by the resistor to be approximately equal to the difference P huff (In., So that the total power delivered by the device is approximately equal to the required power P huff, and the method 200 is stopped (the target power then being reached).

If the maximum power Pap ma, resistance 17 is insufficient, the control unit 19 adapts in step 215 the current delivered to the resistor 17 so that its power is equal to its maximum value Pap max . In step 217, (which follows step 215 in the presence of resistor 17, step 209 if not), the control unit 19 modifies the position of the flap 15, in the direction increasing the amount of air bypassing the internal condenser 7 (V decreases). In this way, the temperature and the pressure Pd in the internal condenser 7 increase. A smaller amount of air is heated to a higher temperature. A first relatively simple embodiment can stop here, the previous steps being repeated over time to obtain a control loop. The reduction of the heating power of the air-conditioning device is thus limited compared with devices which do not use flaps 15 according to the process previously described. The embodiment shown in Figure 2, however, goes further. In the next step 219, the heat supplied to the air Qair is estimated at the end of the preceding steps, and compared with the setpoint value P huff or P huff Pctp max according to whether a resistor 17 is not or is respectively present. If the total heating power (Qair or Qair + Pap max) differs from the set heating value Pchauff, by a value greater than a limit value e (for example 5% of the setpoint value), the control 19 changes in step 221 the compressor speed Vcomp upwards if the total power is lower than the setpoint power P huff, or downwards if the total power is higher. In this way, the overall coefficient of performance of the device 100 is intentionally lowered, in order to respect the pressure limit imposed by the possible formation of ice, which degrades the performance of the device potentially much more importantly. However, the set heating power P huff is reached. The method 200 is advantageously regularly repeated as part of a regulation over time. In particular, proportional-integral (PI) control can be used in steps 207, 213, 217 and 221 to modify the functional parameters of the device 100.

The device 100 thus designed makes it possible to slow down or even to prevent the formation of ice on the external evaporator 3 by degrading in a controlled manner the performance of the heat pump: the high temperature and the high pressure in the internal condenser 7 are raised by diverting a part of the air flow, and by heating at a higher temperature the portion of the internal air 13 which passes through said internal condenser 7.

Claims (11)

REVENDICATIONS1. A method of controlling a thermal conditioning device (100) for a motor vehicle, for the purpose of slowing down the icing of said thermal conditioning device (100), the thermal conditioning device (100) comprising an external evaporator (3) traversed by a external air flow (9) for a heat exchange between the outside air flow (9) and a heat transfer fluid, an internal condenser (7) for a heat exchange between an internal air flow (13) and the fluid coolant, and an airflow distribution member (15) between an air duct (11b) in which the inner condenser (7) is disposed and an air duct (11a) bypassing said inner condenser, characterized in that said process comprises the following steps: - a minimum operating pressure (P, --- ext mm) of the external evaporator (3) is determined to limit the formation of ice, - an optimum operating pressure is determined; (P .- ext opt) of the external evaporator (3) - to obtain a nominal heating power (P huff) at the internal condenser 7, if the optimum operating pressure (P .- ext opt) is less than the minimum operating pressure (P, --- ext mm), the external evaporator pressure (3) is set to the minimum operating pressure (P s-ext mm) and the flow distribution element air (15) is actuated to increase the amount of air bypassing said inner condenser (7). 2. Method according to claim 1, characterized in that the minimum operating pressure (P .-- ext mm) is determined by taking into account properties of the outside air flow (13). 3. Method according to claim 1 or 2, characterized in that the optimum operating pressure (P .- ext opt) is determined from the heating power of -12- setpoint (Pchauff) by optimizing the coefficient of performance of the device (100). 4. Method according to claim 1, 2 or 3, characterized in that it comprises an additional step in which the speed of the compressor (5) is increased. 5. Method according to claim 4, characterized in that the speed of the compressor (5) is regulated until the total heating power of the device is approximately equal to the set heating power (P huff). 6. Method according to claim 4, wherein the conditioning device comprises an additional heating device (17), characterized in that it comprises an additional step located between the step of actuating the flow control element. of air (15) and the step of increasing the speed of the compressor (5), wherein the difference between the nominal heating power (Pchauff) and the power (Qan) supplied to the indoor air (13) by the internal condenser (7) at the minimum operating pressure (P't ',') is compared with the maximum power (Pctp max) of the additional heating device (17), and that if said difference (Pchauff Qa, r) and less than the maximum power of the resistor, the resistor is supplied so as to supply to the inner air flow (13) a power corresponding to said difference (Pchaut Pctp max), the following steps of the method being canceled. 7. Thermal conditioning device for a motor vehicle, comprising an external evaporator (3) traversed by an outside air flow (9) for a heat exchange between the outside air flow (9) and a heat transfer fluid, an internal condenser (7) for a heat exchange between an inner air flow (13) and the heat transfer fluid, characterized in that it comprises: an inner condenser (7) disposed in an inner pipe (11), said inner pipe (11) ) having two air paths (11a, 11b), one containing the inner condenser (7), and one bypassing said inner condenser (7), - an internal airflow distribution element (15), configured to distribute according to its state (V) the interior air flow (13) entering between the two air channels, -13- - a control unit (19) connected to sensors configured to determine properties of the flow of air outside air (13), and configured to: - determine a pressure n minimum operating (P ext mm) of the external evaporator (3) to limit the formation of frost, - deduce from a nominal heating power (Pchauff) an optimum pressure value (P ext opt) of operation in the external evaporator (3), and compare the optimal operating pressure (P ext opt) with the minimum operating pressure (P ext mm) of the external evaporator (3), and, if the optimal operating pressure ( P ext opt) is lower than the minimum operating pressure (P ext mm), regulate the pressure in the external evaporator (3) to the minimum operating pressure (Pext mm) and activate the flow control element. air (15) for increasing the amount of air bypassing said inner condenser (7). 8. Device according to the preceding claim, characterized in that the air flow control element (15) comprises a flap, the angular position relative to an axis of rotation determines the distribution of the indoor air flow ( 13) between the air channels (11a, 11b). 9. Device according to claim 7 or 8, characterized in that it further comprises an additional heating device (17) and in that the control unit (19) is configured to compare the maximum power (P etp max ) of the additional heating device (17) to the difference between the nominal heating power and an estimated value of the heating power supplied to the minimum operating pressure (Pehm Qmr), and if the maximum power (P etp max) the electrical resistance (17) is greater, the control unit (19) supplies the electrical resistance (17) so as to provide a power corresponding to the difference (Qair heater) - 14- 10. Device according to claim 9, characterized in that the additional heating device (17) is placed in one of the air ducts (11a, 11b) of the inner pipe (11), so as to heat the air passing by said air path (11a, 11b). 11. Device according to claim 9, characterized in that the additional heating device (17) is placed in the two air channels (11a, 11b) of the inner pipe (11), so as to heat the whole of the air passing through said inner pipe (11).