Method for dehumidifying a vehicle's interior

Abstract

Method for dehumidifying a vehicle interior. The present invention relates to a dehumidification method using a refrigerant circuit (1) for a vehicle, characterized in that the dehumidification method incorporates: - at least a first step in which, at a temperature of the interior airflow (28) exiting a third heat exchanger (7) higher than a first temperature, a sealing means (5) is placed in an open position, - at least a second step in which, at a temperature of the interior airflow (28) exiting the third heat exchanger (7) lower than a second temperature, the sealing means (5) is placed in a closed position, the second temperature being lower than the first temperature. (Figure 1)

Description

Title of the invention: Method for dehumidifying the passenger compartment of a vehicle

[0001] The field of the present invention is that of refrigerant circuits for vehicles, particularly hybrid or electric motor vehicles. The present invention relates particularly to dehumidification processes using such refrigerant circuits.

[0002] Motor vehicles are commonly equipped with a refrigerant circuit used to heat or cool different areas or components of the vehicle. It is particularly known to use these refrigerant circuits to cool an electrical storage device such as a battery in a vehicle equipped with such a circuit.

[0003] It is also known to use this refrigerant circuit to thermally treat an airflow sent to the vehicle's passenger compartment. Such thermal treatment makes it possible to send hot or cold air, as desired by the user, to respectively increase or decrease the temperature of the vehicle's passenger compartment.

[0004] In another application of the refrigerant circuit, the airflow is intended to dehumidify the vehicle's passenger compartment. "Dehumidifying" refers to the refrigerant circuit's ability to limit the presence of water in the air inside the vehicle's passenger compartment. When humid air from the passenger compartment comes into contact with a cold surface, the water in the air condenses, and a film of water droplets forms on the cold surfaces of the vehicle's passenger compartment, particularly on the windows. This film of water fogs up, especially on the inside surfaces of the windshield and side windows, obstructing the driver's visibility of the road or their mirrors. This loss of visibility poses a significant risk to the safety of the vehicle's occupants, particularly in the event of a collision with another vehicle.

[0005] It is known to use the refrigerant circuit to dehumidify the airflow sent into the vehicle's passenger compartment. Thus, conventionally, a heating, ventilation, and air conditioning system, which will be referred to hereafter as the "system," includes a radiator and an evaporator that contribute to the thermal treatment of this airflow. The radiator's hot source is, in this particular case, a condenser that is part of the refrigerant circuit. The radiator is therefore a hot point in the refrigerant circuit that helps to increase the temperature of the airflow intended to be sent into the passenger compartment. vehicle. The evaporator is a cold point in the refrigerant circuit; this evaporator helps cool the airflow and, consequently, condense the moisture present in that airflow. This prevents fogging while providing the thermal comfort required by the vehicle's occupants.

[0006] It is also known that at low outside temperatures outside the vehicle's passenger compartment, the evaporator's operating efficiency is affected. For example, at outside temperatures close to 5°C, the evaporator is at risk of clogging because the water vapor in the air freezes upon contact with the evaporator, which has a surface temperature close to 0°C. This risk of evaporator clogging limits its use.

[0007] Furthermore, when the temperature of the airflow entering the evaporator is low, particularly when this temperature is below 12°C, the evaporator lowers the pressure within a low-pressure section of the refrigerant circuit. This low pressure is a limiting factor in the thermodynamic cycle, preventing sufficient heat production at the condenser, thus requiring the use of an additional heat source to reach the temperature desired by the occupants of the passenger compartment.

[0008] The present invention proposes to resolve these various constraints by means of a method for dehumidifying a vehicle passenger compartment through which a refrigerant flows and which comprises at least one primary circuit and one secondary circuit, the primary circuit comprising at least one refrigerant compression device, a first heat exchanger configured to perform heat exchange between the refrigerant and a fluid, an expansion element and a second heat exchanger configured to perform heat exchange between the refrigerant and an external airflow to the vehicle passenger compartment, the secondary circuit being connected to the primary circuit in parallel with the second heat exchanger and the expansion element and comprising an expansion member and a third heat exchanger configured to perform heat exchange between the refrigerant and an internal airflow sent into the vehicle passenger compartment,the secondary circuit comprising at least one closing means capable of assuming a closed position in which the circulation of the refrigerant is prevented within the secondary circuit and an open position allowing the circulation of the refrigerant within the secondary circuit, the primary circuit and the secondary circuit are traversed simultaneously by the refrigerant, a dehumidification process for a vehicle passenger compartment in which the expansion element and the expansion device perform an expansion and where the second heat exchanger and the third heat exchanger ensure the evaporation of the refrigerant characterized in that, at an outside air temperature below a first threshold, the dehumidification process implements: ,

[0009] - at least a first step in which, at a temperature of the internal airflow At the outlet of the third heat exchanger, where the temperature exceeds a first temperature, the sealing device is placed in its open position.

[0010] - at least a second stage in which, at a temperature of the airflow inside at the outlet of the third heat exchanger lower than a second temperature, the sealing means is placed in its closed position, the second temperature being lower than the first temperature.

[0011] The vehicle refrigerant circuit comprises two circuit sections called the primary circuit and the secondary circuit. The primary circuit includes a compressor, a first heat exchanger, an expansion element, a second heat exchanger, and a refrigerant accumulation device. The secondary circuit includes an expansion element, a shut-off device, and a third heat exchanger. The refrigerant circuit is configured so that this secondary circuit can be isolated from the rest of the circuit. This isolation of the secondary circuit is achieved by the shut-off device, which can be in two positions: an open position and a closed position. In its open position, the shut-off device allows the refrigerant to circulate in the secondary circuit, and more specifically, to reach the third heat exchanger.In the closed position of the shut-off device, the refrigerant does not circulate in the secondary circuit, which is isolated from the rest of the refrigerant circuit. The open or closed position of the shut-off device depends on the temperature of the indoor airflow exiting the third heat exchanger. This temperature data for the indoor airflow exiting the third heat exchanger is provided, for example, by a sensor located at the indoor airflow exiting the third heat exchanger. For example, when the outdoor air temperature is, for instance, below 12°C, advantageously below 7°C, or advantageously between 5°C and 7°C, the process implements both the first and second stages.During the implementation of these steps, when the temperature of the indoor airflow exiting the third heat exchanger is greater than or equal to, for example, 7°C, the shutter is in its open position, while when the temperature of the indoor airflow exiting this third heat exchanger is less than or equal to, for example, 3°C, the shutter is in its closed position. The temperature of the indoor airflow exiting the third heat exchanger oscillates between 3°C and 7°C, tending, in this example, towards an average temperature of 5°C. The position of the shutter creates a cycle of opening and closing. It should be noted, on the one hand, that the temperature towards which the indoor airflow exiting the third heat exchanger tends depends on the temperature range within which the indoor airflow oscillates exiting the third heat exchanger. Furthermore, the sealing device remains in its open or closed position until it reaches the first or second temperature, depending on its position. For example, when the outside air temperature is 5°C, the sealing device will be in its closed position at 3°C ​​and in its open position at 3.8°C.

[0012] According to one feature of the invention, the first heat exchanger raises the temperature of the interior airflow. It is understood that the first heat exchanger acts on the temperature of the airflow by transferring heat to the interior airflow. This heat exchange can occur directly between the first heat exchanger and the interior airflow sent to the vehicle's passenger compartment. This heat exchange can also occur indirectly; in this case, auxiliary equipment, such as a radiator, exchanges heat with the first heat exchanger by means of a fluid circulating through the radiator and the first heat exchanger, and then transfers the heat from the first heat exchanger to the interior airflow sent to the vehicle's passenger compartment.

[0013] According to an advantageous feature, the means for shutting off the secondary circuit is an on / off type valve. The refrigerant circuit is divided into two circuits that separate at a point of divergence and rejoin at a point of convergence, forming two parallel circuit segments. The primary circuit forms a loop extending from the compressor to the second heat exchanger, and the secondary circuit forms a loop extending from the point of divergence to the point of convergence. The secondary circuit includes a valve, adjustable to two positions, open and closed, located between the point of divergence and the third heat exchanger. This valve is an example of an embodiment of the shut-off means for isolating the secondary circuit from the rest of the refrigerant circuit.Indeed, in its open position, the valve allows the refrigerant to circulate in the secondary circuit and supply the third heat exchanger, while in its closed position, this valve isolates the secondary circuit from the rest of the refrigerant circuit. Thus, in the closed position of the valve, the refrigerant circulates only in the primary circuit, while in the open position of the valve, the refrigerant circulates in both the primary and secondary circuits.

[0014] According to an advantageous feature, the expansion valve also serves as the shut-off device. The expansion valve can allow the refrigerant to circulate in the third heat exchanger or prevent the refrigerant from circulating within the third heat exchanger of the refrigerant circuit. The expansion valve can advantageously communicate with equipment to modulate the refrigerant's access to the third heat exchanger according to the temperature temperature of the internal airflow. When the expansion device is also the means of closure, the latter ensures the functions of expansion of the refrigerant and control of the passage of the refrigerant to the third heat exchanger.

[0015] According to one feature of the invention, the compression device regulates the temperature of the interior airflow by adjusting its rotational speed. It is understood that the rotational speed of the compression device can be adjusted, in response to a command given by the vehicle user, to modify the temperature of the interior airflow sent to the vehicle's passenger compartment.

[0016] According to an advantageous feature, when the temperature of the internal airflow at the outlet of the third heat exchanger changes from the first temperature to the second temperature, the sealing means is placed in its open position.

[0017] According to another advantageous feature, when the temperature of the indoor airflow exiting the third heat exchanger changes from the second temperature to the first temperature, the shutter means is placed in its closed position. A temperature sensor, located in the airflow exiting the third heat exchanger, controls, at least indirectly, the shutter means such that as soon as the temperature of the indoor airflow exiting the third heat exchanger reaches the second temperature, for example, 3°C or less, the shutter means is configured to move to its closed position. The shutter means then remains in this closed position as long as the temperature of the indoor airflow exiting the third heat exchanger is, for example, below 7°C.This same temperature sensor controls, at least indirectly, the shuttering mechanism so that as soon as the temperature of the indoor airflow exiting the third heat exchanger reaches the first temperature, for example, greater than or equal to 7°C, the shuttering mechanism is configured to switch to its open position. The shuttering mechanism then remains in this open position as long as the temperature of the indoor airflow exiting the third heat exchanger is, for example, greater than 3°C.

[0018] According to one feature of the invention, the secondary circuit closure means is alternately in an open or closed position according to a periodic phenomenon forming a cycle of openings and closings of the closure means. The open or closed position of the closure means is a function of the temperature of the internal airflow at the outlet of the third heat exchanger. The closure means transitions from its closed position to its open position when the temperature of the internal airflow at the outlet of the third heat exchanger is, for example, at least 7°C. Similarly, the closure means transitions from its open position to its closed position when the temperature of the internal airflow at the outlet of the third heat exchanger is, for example, at less than or equal to 3°C. The temperature drop from 7°C to 3°C and the temperature rise from 3°C to 7°C of the indoor airflow exiting the third heat exchanger occur over a substantially equal time interval. This fluctuation in the temperature of the indoor airflow exiting the third heat exchanger is a periodic phenomenon in which the number of times per unit of time that the shutter transitions from its open to its closed position is substantially the same.

[0019] According to another feature of the invention, the opening and closing cycle of the shutter means operates at a frequency of less than three cycles per minute. This frequency represents the number of times the shutter means performs an opening and closing cycle in a given unit of time. A cycle is defined as the movement of the shutter means from an initial position to an intermediate position and then back to its initial position.

[0020] According to one feature of the invention, the temperature of the interior airflow exiting the third heat exchanger is measured by at least one sensor installed at the level of the interior airflow exiting the third heat exchanger. The vehicle cabin dehumidification process allows the temperature of the interior airflow exiting the third heat exchanger to be controlled so that this temperature oscillates between the first and second temperatures. Thus, this sensor communicates directly or indirectly with the shut-off means that controls the refrigerant supply to the third heat exchanger such that the temperature of the refrigerant exiting the third heat exchanger varies between the first and second temperatures.

[0021] According to another feature of the invention, the first threshold is a temperature between 5°C and 12°C. When the outside air temperature in the vehicle's passenger compartment is below 12°C, there is a risk that, during prolonged operation, the third heat exchanger will freeze. The dehumidification process mitigates this risk.

[0022] According to an advantageous feature, the refrigerant circuit includes a refrigerant accumulation device.

[0023] According to another feature of the invention, the second heat exchanger thermodynamically contributes to increasing the temperature of the indoor airflow by utilizing the heat captured from the outdoor airflow. The second heat exchanger behaves like an evaporator and acts as a cold point in the refrigerant circuit, recovering heat from the outdoor airflow. This heat, according to the principles of thermodynamics, contributes to increasing the temperature of the hot point in the refrigerant circuit; this hot point is the first heat exchanger. The increase in the temperature of the first heat exchanger facilitates the rise in temperature. of the temperature of the indoor airflow. Thus, the second heat exchanger contributes to indirectly increasing the temperature of the indoor airflow.

[0024] The present invention also relates to a refrigerant circuit comprising at least one primary circuit and at least one secondary circuit, the primary circuit comprising at least one compression device, a first heat exchanger,

[0025] an expansion element and a second heat exchanger, the secondary circuit being connected to the primary circuit in parallel with the second heat exchanger and the expansion element and comprising an expansion member and a third heat exchanger as well as at least one shut-off means capable of assuming a closed position in which the circulation of the refrigerant is prevented within the secondary circuit and an open position allowing the circulation of the refrigerant within the secondary circuit, the primary circuit and the secondary circuit are traversed simultaneously by the refrigerant, the shut-off means being in its open position,characterized in that the refrigerant circuit implements the dehumidification process, the sealing means being configured to be actuated cyclically.

[0026] Other features and advantages of the invention will become apparent from the following description on the one hand, and from several illustrative and non-limiting examples of embodiments given by reference to the accompanying schematic drawings on the other hand, in which:

[0027] [Fig. 1] is a schematic representation of a refrigerant fluid circuit implementing the dehumidification process according to the invention.

[0028] [Fig.2] is a schematic representation of a variant of the fluid circuit refrigerant implementing the dehumidification process according to the invention, in which the first heat exchanger is directly integrated into the installation.

[0029] [Fig.3] is a schematic representation of the refrigerant circuit in a operating mode ensuring cooling of the vehicle's passenger compartment.

[0030] [Fig.4] is a schematic representation of the refrigerant circuit in a operating mode ensuring heating of the vehicle's passenger compartment.

[0031] [Fig.5] is a schematic representation of the refrigerant circuit in a operating mode ensuring dehumidification of the vehicle's passenger compartment.

[0032] [Fig.6] is a graphical representation of the evolution of the temperature of the interior airflow at the outlet of the third heat exchanger as a function of time when the refrigerant circuit is used in an operating mode ensuring the dehumidification of the vehicle's passenger compartment.

[0033] [Fig.7] is a graphical representation of the evolution of the airflow temperature interior at the radiator outlet depending on the time when the refrigerant circuit is in use an operating mode ensuring dehumidification of the vehicle's passenger compartment.

[0034] The terms upstream and downstream used in the following description refer to the direction of flow of the fluid in question, i.e., the refrigerant or the indoor airflow. The refrigerant is symbolized by an arrow illustrating its direction of flow in the pipe in question. In Figures 3 to 5, solid lines illustrate a portion of the circuit where the refrigerant flows, and dashed lines illustrate a portion of the refrigerant circuit where the refrigerant does not flow. In Figures 3 to 5, the open position of the valves is illustrated by a solid white fill, and the closed position by a solid black fill. Furthermore, when a valve is in its open position at one time and in its closed position at another during the operation of the refrigerant circuit, this valve is represented by a mixed black and white fill.

[0035] Figure 1 illustrates a refrigerant circuit 1 comprising a primary circuit 25, a secondary circuit 24, and a bypass branch 26, within which a refrigerant circulates. The secondary circuit 24, the primary circuit 25, and the bypass branch 26 are arranged such that the refrigerant circuit 1 is a closed circuit in which a thermodynamic cycle takes place.

[0036] The primary circuit 25 and the secondary circuit 24 separate at a point of divergence 14 and rejoin at a point of convergence 15 such that between the point of divergence 14 and the point of convergence 15, the secondary circuit 24 and the primary circuit 25 are mounted in parallel with respect to each other.

[0037] The primary circuit 25 will be described according to the direction of refrigerant flow in this primary circuit 25 from an outlet 92 of a compression device 9 to an inlet 91 of the compression device 9. The compression device 9 is, in the embodiment shown, a fixed-displacement, variable-speed electric compressor. This compression device 9 is designed to compress the low-pressure refrigerant entering through the inlet 91. This compression of the refrigerant releases a high-pressure refrigerant through the outlet 92 of the compression device. Due to the thermodynamic principles implemented in the refrigerant circuit 1, the change of the refrigerant from a gaseous state at the outlet of the compression device 9 to a liquid state at the outlet of a first heat exchanger 2 generates heat.The volume of high-pressure refrigerant at the outlet of the compression device 9 depends on the compression speed of this compression device 9. The higher the rotational speed of the compression device 9, the more heat the refrigerant circuit 1 will produce. Thus, it is possible to control the thermal output of the refrigerant circuit 1 by adjusting the rotational speed of this compression device 9.

[0038] The high-pressure refrigerant exiting the compression device 9 flows through the first heat exchanger 2, which in the embodiment shown is a condenser, i.e., a heat exchanger in which the refrigerant condenses. The first heat exchanger 2 performs a heat exchange with a fluid which, in the embodiment shown in [Fig. 1], is a heat transfer fluid circulating in a heat transfer fluid loop 200. The heat from the high-pressure refrigerant generated during the refrigerant's phase change is transferred, at the level of this first heat exchanger 2, to the heat transfer fluid of the heat transfer fluid loop 200.

[0039] Thus, this heat transfer fluid transports the heat from the first heat exchanger 2 to a radiator 8 located in the installation 20. The heat transfer fluid loop 200 comprises a first branch 21, through which the heat transfer fluid flows from the first heat exchanger 2 to the radiator 8, and a second branch 29 through which the heat transfer fluid flows from the radiator 8 to the first heat exchanger 2. This heat transfer fluid loop 200 forms a closed loop in which a pump 22 ensures the circulation of the heat transfer fluid in this heat transfer fluid loop 200.

[0040] In an alternative embodiment, this first heat exchanger 2 can be directly installed in the installation 20. It is then not necessary to install the heat transfer fluid loop 200.

[0041] The refrigerant, which has changed from a gaseous to a liquid state by condensation within the first heat exchanger 2, passes through an accumulation device 4 which, in the embodiment shown, is a desiccant bottle designed to remove moisture and fine particles present in the refrigerant. It should be noted that this desiccant bottle can advantageously be integrated into the first heat exchanger 2.

[0042] Upon exiting the accumulation device 4, the refrigerant reaches the divergence point 14. At this divergence point 14, the refrigerant can enter the secondary circuit 24 and / or reach an expansion element 12. This expansion element 12 is located upstream of a second heat exchanger 13. This expansion element 12 can advantageously be electrically controlled and operated electrically or electronically. Thus, the expansion element 12 is capable of allowing, in an open position, or preventing, in a closed position, the passage of the refrigerant to the second heat exchanger 13. This expansion element 12 is also capable of assuming any intermediate positions to generate an expansion of the refrigerant, that is to say, to decrease the pressure of the refrigerant.It should be noted that this expansion element 12 can be thermodynamically neutral, that is to say that the expansion element 12 can be an element of the fluid circuit re. refrigerant 1 not involved in the thermodynamic cycle, especially when it is at maximum opening and does not generate a pressure loss.

[0043] The refrigerant exiting the expansion element 12 enters the second heat exchanger 13, which, in the illustrated embodiment, is an evaporator-condenser located at the front of the vehicle. When the refrigerant exiting the expansion element 12 is at low pressure, i.e., when the expansion element 12 has generated a high-pressure expansion of the refrigerant, the second heat exchanger 13 behaves as an evaporator. When the refrigerant exiting the expansion element 12 is at high pressure, i.e., when the expansion element 12 is thermodynamically neutral, the second heat exchanger 13 behaves as a condenser. It should be noted that the second heat exchanger 13 is traversed by a flow of air from outside the passenger compartment 27, directed towards the outside of the passenger compartment. This flow of outside air to the passenger compartment 27 is intended to perform a heat exchange with the refrigerant.

[0044] The refrigerant fluid at the outlet of the second heat exchanger 13 reaches a first connection point 40, located downstream of the second heat exchanger 13, at which point the bypass branch 26 is connected to the primary circuit 25.

[0045] This branch 26 extends from the first connection point 40 to a second connection point 41 located on the secondary circuit 24. Thus, the branch 26 allows the refrigerant to pass from the primary circuit 25 to the secondary circuit 24. It should be noted that the branch 26 includes a non-return valve 10 which, when the refrigerant passes through the branch 26, prevents the passage of the refrigerant from the secondary circuit 24 to the primary circuit 25, in particular when the refrigerant circuit 1 performs the cooling function.

[0046] On the primary circuit 25, downstream of the first connection point 40, there is a first valve 11. This first valve 11 has two positions: an open position and a closed position. In its open position, the first valve 11 allows the refrigerant to flow through the primary circuit 25. In this open position, the refrigerant does not flow through the bypass branch 26 due to the pressure differential between the secondary circuit 24 and the primary circuit 25. In its closed position, the first valve 11 prevents the refrigerant from flowing through the primary circuit 25 beyond the connection point 40. The refrigerant then flows through the bypass branch 26 to rejoin the secondary circuit 24.Advantageously, when the expansion element 12 generates an expansion of the refrigerant, the first valve 11 is in its open position allowing the low-pressure refrigerant to reach the compression device 9 via the primary circuit 25. When the expansion element 12 is thermodynamically neutral, the refrigerant at the outlet of the second heat exchanger 13 is at high. At pressure, the first valve 11 is then in its closed position and the refrigerant flows through the bypass branch 26. It should be noted that this first valve 11 is advantageously electrically controlled and of the "on / off" type. Thus, when the expansion element 12 is thermodynamically neutral, the first valve 11 is in the closed position, while when the expansion element 12 generates an expansion of the refrigerant, the first valve 11 is in its open position.

[0047] The low-pressure refrigerant downstream of the first valve 11 reaches the convergence point 15, where the secondary circuit 24 and the primary circuit 25 join. The refrigerant circuit includes a heat exchanger 16 that allows heat exchange between the low-pressure and high-pressure refrigerants. This heat transfer improves the performance of the thermodynamic cycle implemented in the refrigerant circuit 1. The primary circuit 25, downstream of the convergence point 15, joins the compression device 9 and its inlet port 91.

[0048] The secondary circuit 24 extends from the divergence point 14 to the convergence point 15 and includes an expansion valve 6, a third heat exchanger 7, and a shut-off means 5, which, in the illustrated embodiment, is a second valve 5a. The second valve 5a is located between the divergence point 14 and the second connection point 41 and is advantageously electrically controlled and of the on / off type. The second valve 5a has two positions: an open position in which the second valve 5a allows the high-pressure refrigerant to flow through the secondary circuit 24, and a closed position in which the second valve 5a prevents the high-pressure refrigerant from flowing through the secondary circuit 24.

[0049] The expansion valve 6, located downstream of the second valve 5a, between the second connection point 41 and the third heat exchanger 7, is a component of the secondary circuit 24 capable of generating an expansion of the refrigerant, i.e., reducing the pressure of the refrigerant. This expansion of the high-pressure refrigerant contributes to the evaporation of the refrigerant within the second heat exchanger 7. Due to the thermodynamic principles implemented in the refrigerant circuit 1, the change of the refrigerant from a liquid state, at the outlet of the first heat exchanger 2, to a gaseous state at the outlet of the third heat exchanger 7 generates cooling.

[0050] It should be noted that in an alternative embodiment of the invention, the expansion member 6 can be the closing means 5. In this case the closing means 5 ensures the expansion of the refrigerant and modulates the passage of the refrigerant to the third heat exchanger 7.

[0051] The installation 20 includes the radiator 8 and the third heat exchanger 7 which, In the embodiment shown, the radiator 8 and the third heat exchanger 7 are traversed by an interior airflow 28, originating from outside or inside the vehicle's passenger compartment and flowing towards the vehicle's passenger compartment. Thus, within this system 20, heat exchange occurs between the interior airflow 28 and, on the one hand, the third heat exchanger 7, and on the other hand, the radiator 8. A temperature sensor 17 installed in the interior airflow 28 at the outlet of the third heat exchanger 7 measures the temperature of the interior airflow 28. This data relating to the temperature of the interior airflow 28 is transmitted to a control device, such as a computer, to modulate the position of the second valve 5a.It should be noted that in an alternative embodiment, the computer can also communicate this data relating to the temperature of the internal airflow 28 by means of a shutter 5. The low-pressure refrigerant fluid, at the outlet of the third heat exchanger 7, joins the primary circuit 25, at the point of convergence 15, upstream of the compression device 9.

[0052] Thus, the valves 11 and 5a modulate the refrigerant circuit to allow the refrigerant to circulate between the primary circuit 25, the secondary circuit 24 and the bypass branch 26. This modulating circulation of the refrigerant allows the refrigerant circuit to perform different functions, including heating, cooling and dehumidification of the vehicle's passenger compartment.

[0053] Fig. 2 illustrates a variant of the refrigerant fluid circuit 1, in this variant the first heat exchanger 2 is installed in the installation 20 and operates a heat exchange with a fluid which, in the embodiment shown, is the indoor airflow 28. This variant of the refrigerant fluid circuit 1 allows it to do without the heat transfer fluid loop 200.

[0054] Figure 3 illustrates the refrigerant circuit 1 providing passenger compartment cooling. In this configuration of the refrigerant circuit 1, each of the first valve 11 and the second valve 5a are in their closed position. In this configuration of the refrigerant circuit 1, the refrigerant flows in the direction of refrigerant flow 30 in the primary circuit 25, the bypass branch 26, and the secondary circuit 24. In this configuration of the refrigerant circuit 1 shown in Figure 3, the expansion element 12 is thermodynamically neutral, and the second heat exchanger 13 is used as a condenser. The refrigerant undergoes a single expansion at the expansion element 6.The interior airflow 28 performs a heat exchange with the third heat exchanger 7 such that the interior airflow 28 exiting the system 20 lowers the temperature of the vehicle's interior relative to the temperature outside the vehicle's interior.

[0055] Figure 4 illustrates the refrigerant fluid circuit 1 providing the heating function of the vehicle's passenger compartment. In this configuration of the refrigerant circuit 1, the first valve 11 is in its open position, while the second valve 5a is in its closed position. The refrigerant circulates in the primary circuit 25 and does not circulate in the secondary circuit 24 or the bypass branch 26. This refrigerant circulates in the refrigerant circuit 1 in a refrigerant flow direction 30 from the compressor unit 9 to the second heat exchanger 13, which acts as an evaporator, and from this second heat exchanger 13 back to the compressor unit 9. In this configuration of the second valve 5a, the refrigerant does not reach the third heat exchanger 7, which, not being supplied with refrigerant, is thermally neutral.Within the installation 20, a heat exchange occurs between the interior airflow 28 and the radiator 8 such that the interior airflow 28 is able to increase the temperature of the passenger compartment relative to the outside temperature. It should be noted that in the embodiment shown in [Fig. 4], the first heat exchanger 2 indirectly exchanges heat with the airflow 28 by means of the heat transfer fluid loop 200.

[0056] Figure 5 illustrates the refrigerant circuit 1 which ensures the dehumidification of the vehicle's passenger compartment by compensating for the icing constraints of the third heat exchanger 7 and by providing heating for the interior airflow 28. In the configuration shown in Figure 5, the refrigerant circulates in parallel in the primary circuit 25 and in the secondary circuit 24. The first valve 11 of the primary circuit 25 is in its open position and the expansion element 12 generates an expansion of the high-pressure refrigerant from the first heat exchanger 2; the third heat exchanger 13 then behaves as an evaporator.

[0057] According to the method of the invention, the second valve 5a is alternately in its open position, in which the third heat exchanger 7 is supplied with refrigerant, and in its closed position, in which the second valve 5a prevents the refrigerant from reaching the third heat exchanger 7.

[0058] This alternation between the open and closed positions of the second valve 5a is a function of the temperature of the indoor airflow 28 at the outlet of the third heat exchanger 7. Thus, the temperature sensor 17 communicates information relating to the temperature of the indoor airflow 28 at the outlet of the third heat exchanger 7 to a control device, such as a computer, which controls the second valve 5a. The second valve 5a is configured to be in its closed position when the temperature of the indoor airflow 28 at the outlet of the third heat exchanger 7 is, in the embodiment shown, less than or equal to 3°C and in its open position when the temperature of the indoor airflow 28 at the outlet of the third heat exchanger 7 is, in the embodiment shown, greater than or equal to 7°C.

[0059] It should be noted that when the second valve 5a moves from its open position to its closed position, i.e., when the temperature of the indoor airflow 28 exiting the third heat exchanger 7 is less than or equal to 3°C, the third heat exchanger 7 is no longer supplied with refrigerant and the temperature of the indoor airflow 28 exiting this third heat exchanger 7 gradually increases. Similarly, when the second valve 5a moves from its closed position to its open position, i.e., when the temperature of the indoor airflow 28 exiting the third heat exchanger 7 is greater than or equal to 7°C, the third heat exchanger 7 is supplied with refrigerant and the temperature of the indoor airflow 28 exiting this third heat exchanger 7 gradually decreases.

[0060] Thus, the alternation between the closed position and the open position of the second valve 5a makes it possible to maintain the temperature of the interior airflow 28 at the outlet of the third heat exchanger 7 between approximately 3°C and 7°C without however negatively impacting the thermodynamic cycle which would lead, without the invention, to a slowing down of the rotation speed of the compression device and consequently the impossibility of producing enough calories in the first heat exchanger 2 to ultimately heat the passenger compartment.

[0061] Furthermore, this alternation between the closed and open positions of the second valve 5a makes it possible to maintain the temperature of the radiator 8 sufficiently high to heat the interior airflow 28 exiting the third heat exchanger 7. Indeed, this alternation between the open and closed positions of the second valve 5a makes it possible to maintain a high pressure level in the low-pressure section of the refrigerant circuit 1. By maintaining the third heat exchanger 7 at a temperature level between 3°C and 7°C, the refrigerant pressure in the low-pressure section of the refrigerant circuit 1 makes it possible to maintain a high rotational speed of the compressor device 9. This rotational speed of the compressor device 9 makes it possible to maintain a high level of condensation in the first heat exchanger 2, capable of heating the interior airflow 28.

[0062] Figure 6 illustrates a first graph 39 representing the initial evolution of a temperature 31 of the indoor airflow 28 at the outlet of the third heat exchanger 7 as a function of time 35. When the refrigerant circuit 1 is switched on, according to its dehumidification function under outdoor temperature conditions below a first threshold of 12°C, the second valve 5a is in its open position and the temperature 31 of the indoor airflow 28 gradually decreases until it reaches a second temperature T2 which, in the rea mode The temperature T1 of the internal airflow T2, as shown, is substantially less than or equal to 3°C. When the temperature T1 of the internal airflow T2 exiting the third heat exchanger T3 reaches this second temperature T2, the second valve T5a moves to its closed position, and the temperature T1 of the internal airflow T2 gradually rises until it reaches a first temperature T1, which, in the embodiment shown, is substantially greater than or equal to 7°C. It should be noted that the temperatures T1 and T2 can be varied according to the desired temperature in the third heat exchanger T1. For example, the temperatures T1 and T2 can be 3.8°C and 3°C respectively, so the temperature in the third heat exchanger T1 oscillates between 3°C and 3.8°C.

[0063] When the temperature 31 of the internal airflow 28 exiting the third heat exchanger 7 reaches this first temperature T1, having previously reached the second temperature T2, the second valve 5a switches to the open position and the temperature 31 of the internal airflow 28 gradually decreases until it again reaches the second temperature T2. Such a cycle repeats itself as time 35 elapses, provided that the preconditions are met.

[0064] Thus, the alternation of passages between the open position and the closed position of the second valve 5a allows the temperature 31 of the internal air flow 28 at the outlet of the third heat exchanger 7 to oscillate around a first target temperature 32 which, in the embodiment shown, is substantially equal to 5°C, according to a periodic phenomenon in which each period represents a similar unit of time.

[0065] Fig. 7 illustrates a second graph 42 representing the evolution of a temperature 36 of the indoor airflow 28 at the outlet of the radiator 8 as a function of time 35. When the refrigerant fluid circuit 1 is switched on, according to its dehumidification function in conditions of outside temperature below a first threshold, between 9°C and 11°C, the temperature 36 of the indoor airflow 28 at the outlet of the radiator 8 increases progressively until it stabilizes around a second target temperature 45 requested by the user.

[0066] Thus, the alternation between the open position and the closed position of the second valve 5a makes it possible to ensure that the compression device 9 has a rotational speed greater than the rotational speed that it would have taken without the cycling method according to the invention.

[0067] Of course, the invention is not limited to the examples just described and many modifications can be made to these examples without departing from the scope of the invention.

[0068] The invention, as described above, achieves its objectives and provides a method for dehumidifying the passenger compartment of a vehicle in maintaining the temperature of the interior airflow exiting the installation at a level sufficiently high to ensure the comfort of the vehicle's occupants, without the need for an additional auxiliary heating system. Variations not described here could be implemented without departing from the scope of the invention, provided that, in accordance with the invention, they include a dehumidification process conforming to the invention.

Claims

1. Demands A method for dehumidifying a vehicle passenger compartment employing a refrigerant circuit (1) of the vehicle through which a refrigerant flows and which includes at least one primary circuit (25) and one secondary circuit (24), the primary circuit (25) including at least one refrigerant compression device (9), a first heat exchanger (2) configured to perform heat exchange between the refrigerant and a fluid, an expansion element (12) and a second heat exchanger (13) configured to perform heat exchange between the refrigerant and an external airflow (27) to the vehicle passenger compartment,the secondary circuit (24) being connected to the primary circuit (25) in parallel with the second heat exchanger (13) and the expansion element (12) and comprising an expansion member (6) and a third heat exchanger (7) configured to perform a heat exchange between the refrigerant and an interior airflow (28) sent into the passenger compartment of the vehicle, the secondary circuit (24) comprising at least one shut-off means (5) capable of assuming a closed position in which the circulation of the refrigerant is prevented within the secondary circuit (24) and an open position allowing the circulation of the refrigerant within the secondary circuit (24), the primary circuit (25) and the secondary circuit (24) are traversed simultaneously by the refrigerant,a dehumidification process for a vehicle passenger compartment in which the expansion element (12) and the expansion device (6) perform an expansion and where the second heat exchanger (13) and the third heat exchanger (7) ensure the evaporation of the refrigerant fluid characterized in that, at an outside air temperature to the passenger compartment below a first threshold, the dehumidification process implements: - at least one first step in which, at a temperature of the internal airflow (28) at the outlet of the third heat exchanger (7) greater than a first temperature (Tl), the sealing means (5) is placed in its open position, - at least a second step in which, at a temperature of the internal airflow (28) at the outlet of the third heat exchanger (7) lower than a second temperature (T2), the sealing means (5) is placed in its closed position, the second temperature (T2) being lower than the first temperature (T1).

2. A method for dehumidifying the passenger compartment of a vehicle according to the preceding claim, characterized in that the first heat exchanger (2) raises the temperature of the interior airflow (28).

3. A method for dehumidifying the passenger compartment of a vehicle according to any one of the preceding claims, characterized in that the means for closing (5) the secondary circuit (24) is an "on-or-nothing" type valve (5a).

4. Method for dehumidifying a vehicle passenger compartment according to any one of claims 1 and 2, characterized in that the expansion member (6) is also the sealing means (5).

5. A method for dehumidifying the passenger compartment of a vehicle according to any one of the preceding claims, characterized in that the compression device (9) regulates the temperature of the interior airflow (28) by adapting its rotation speed.

6. A method for dehumidifying a vehicle passenger compartment according to any one of the preceding claims, characterized in that, when a temperature (31) of the interior airflow (28) at the outlet of the third heat exchanger (7) changes from the first temperature (T1) to the second temperature (T2), the sealing means (5) is placed in its open position.

7. A method for dehumidifying a vehicle passenger compartment according to any one of the preceding claims, characterized in that when the temperature (31) of the interior airflow (28) at the outlet of the third heat exchanger (7) changes from the second temperature (T2) to the first temperature (T1), the sealing means (5) is placed in its closed position.

8. A method for dehumidifying the passenger compartment of a vehicle according to any one of the preceding claims, characterized in that the first threshold is a temperature between 5°C and 12°C.

9. A method for dehumidifying the passenger compartment of a vehicle according to any one of the preceding claims, characterized in that the cycle of openings and closings of the sealing means (5) is carried out at a frequency of less than three cycles per minute.

10. Dehumidification method according to any one of the preceding claims, characterized in that the second heat exchanger (13) thermodynamically contributes to increasing the temperature of the indoor airflow (28) by taking advantage of the heat captured in the outdoor airflow (27).

11. Refrigerant circuit (1) comprising at least one primary circuit (25) and at least one secondary circuit (24), the primary circuit (25) comprising at least one compression device (9), a first heat exchanger (2), an expansion element (12) and a second heat exchanger (13), the secondary circuit (24) being connected to the primary circuit (25) in parallel with the second heat exchanger (13) and the expansion element (12) and comprising an expansion member (6) and a third heat exchanger (7) as well as at least one shut-off means (5) capable of assuming a closed position in which the circulation of the refrigerant is prevented within the secondary circuit (24) and an open position permitting the circulation of the refrigerant within the secondary circuit (24), the primary circuit (25) and the secondary circuit (24) are traversed simultaneously by the refrigerant,the sealing means (5) being in its open position, characterized in that the refrigerant fluid circuit (1) implements the dehumidification process according to any one of the preceding claims, the sealing means (5) being configured to be actuated cyclically.

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