FR2957851A1 - Heating, ventilating and/or air-conditioning device for motor vehicle, has switching unit in position in which refrigerant is flown from compressor toward internal exchanger, accumulator, evaporator, external exchanger and compressor - Google Patents

Abstract

The device (10) has an accumulator (20) whose gas outlet (58) is connected to an internal heat exchanger (16). A switching unit (24) is selectively brought back to a position in which refrigerant is flown from a compressor (12) toward an external heat exchanger (14), the accumulator, the internal heat exchanger, an evaporator (22), and the compressor, and another position in which the refrigerant is flown from the compressor toward the internal heat exchanger, the accumulator, the evaporator, the external heat exchanger and the compressor.

Description

The invention relates to heating, ventilation and / or air conditioning devices for motor vehicles.

It relates more particularly to a heating device, ventilation and / or reversible air conditioning for a motor vehicle, comprising an air conditioning loop 10 to be traversed by a phase change refrigerant fluid and having a compressor, an external heat exchanger, likely to operate as a condenser or evaporator, an indoor heat exchanger, an expansion system, a gas / liquid separator tank or bottle and an evaporator. In the heating, ventilation and / or air conditioning device according to the invention, the evaporator and the indoor heat exchanger are adapted to be traversed in succession by a flow of air to be sent into the passenger compartment of the motor vehicle.

It is already known, in particular from US Pat. No. 5,669,231, a device of this type which is part of a heating, ventilation and / or air-conditioning installation of a motor vehicle.

In such a heating, ventilation and / or air conditioning device, the evaporator and the indoor heat exchanger, both of which are traversed by the coolant, are adapted to be traversed by a flow of air to be cooled and / or warm up to be sent into the passenger compartment of the motor vehicle.

On the other hand, the external heat exchanger, which can function as a condenser or an evaporator as the case may be, exchanges heat with an outside air flow, to respectively transfer or withdraw heat. Such an arrangement is accordingly qualified as a heating, ventilation and / or reversible air conditioning device.

The advantage of such a device is to use the same fluid, especially in the vapor state, in this case the refrigerant, to pass through both the evaporator and the indoor heat exchanger, in a "cooling" mode without disturbing the operation of the device.

As a result, the indoor heat exchanger thus advantageously replaces the traditional heating radiator, traditionally constituted by a heater heated by a heat transfer fluid, in particular a vehicle engine cooling fluid, and optionally supplemented by an additional radiator. electric.

The main problem with this type of device is that the evaporator and the indoor heat exchanger are designed to respectively absorb heat and provide heat continuously.

In the "heating" mode, this is not a disadvantage because the flow of air to be sent into the passenger compartment is first cooled and dehumidified through the evaporator and then reheated through the heat exchanger. inside.

On the other hand, in the "cooling" mode, the flow of air to be sent into the passenger compartment is cooled by passing through the evaporator and should therefore be heated by passing through the indoor heat exchanger, which is not desired.

To solve this problem, it is known a first solution consisting in providing flaps in the vicinity of the indoor heat exchanger to prevent the flow of air through this indoor heat exchanger and be warmed. It is also known a second solution of providing a valve on the heat transfer fluid circuit to prevent it from passing through the indoor heat exchanger.

The first solution is not optimal because, despite the presence of flaps, the indoor heat exchanger is supplied with refrigerant fluid, which contributes to the heating of the air flow, even if this indoor heat exchanger is protected by shutters.

The second solution is also not optimal because it can cause problems of refrigerant accumulation and oil. In addition, it can also lead to a large refrigerant charge and a large difference in the amount of refrigerant circulating between the "cooling" mode and the "heating" mode.

It is also known from document EP 2,090,852, a heating device, ventilation and / or air conditioning, of different configuration, which proposes to bypass the evaporator by a bypass in parallel.

The object of the invention is in particular to overcome the aforementioned drawbacks.

It is more particularly intended to provide a heating, ventilation and / or air conditioning device of the type defined in the introduction, in which the indoor heat exchanger can be rendered inoperative in the "cooling" mode, without it being necessary to provide shutters near the indoor heat exchanger.

The invention proposes for this purpose a heating, ventilation and / or air conditioning device for a motor vehicle, comprising a clean air conditioning loop to be traversed by a refrigerant and comprising a compressor, an outdoor heat exchanger, a heat exchanger inside, a first detent, an accumulator and an evaporator.

The heating, ventilation and / or air conditioning device is such that the evaporator and the indoor heat exchanger are adapted to be traversed in succession by a flow of air capable of being sent into a passenger compartment of the motor vehicle.

In addition, the accumulator comprises a liquid outlet, for the refrigerant fluid in the liquid phase, connected to the evaporator and a gas outlet, for the refrigerant fluid in the gas phase, connected to the indoor heat exchanger.

In addition, switching means are provided which can be brought selectively: either in a first position, in which the refrigerant flows from the compressor to the external heat exchanger, then to the accumulator, the exchanger heat and evaporator, then to the compressor, or in a second position, in which the refrigerant flows from the compressor to the indoor heat exchanger, and then to the accumulator, evaporator and outside heat exchanger, then to the compressor.

Thus, in the first position, the evaporator and the indoor heat exchanger operate in parallel being fed respectively by the liquid phase refrigerant and the gas phase refrigerant from the accumulator to provide a "Cooling" where the airflow is cooled through the evaporator, without subsequently changing the temperature through the indoor heat exchanger.

In other words, the indoor heat exchanger then operates as a bypass of the evaporator, and the gas phase refrigerant flowing through the indoor heat exchanger exerts no cooling effect and does not lead to the condensation of the ambient humidity on the outer surface of the indoor heat exchanger, which could pose safety problems once the "heating" mode is started.

The indoor heat exchanger therefore exerts no change in the temperature of the air stream which has been previously cooled by the evaporator. It therefore acts as a neutral component from a thermal point of view.

On the other hand, in the second position, the evaporator is supplied with the refrigerant fluid in the liquid phase from the accumulator, while the internal heat exchanger is supplied with the refrigerant fluid in the gas phase from the compressor, in order to provide a "heating" mode where the airflow is cooled and dehumidified through the evaporator and reheated through the indoor heat exchanger.

Other operating modes are possible, both in the first position and in the second position of the switching means, in particular by providing for the possibility of prohibiting or allowing the passage of the cooling fluid in the liquid phase, coming from the accumulator, to the through the evaporator. In particular, the heating, ventilation and / or air conditioning device is such that the indoor heat exchanger comprises a first orifice connected to a gas inlet / outlet of the accumulator via an inlet / outlet pipe and a second orifice connected to the switching means via a fourth pipe.

Thus, in the first position, the coolant flows from the gas inlet / outlet of the accumulator to the indoor heat exchanger via the first pipe and then from the indoor heat exchanger to the switching means via the fourth line and that, in the second position, the refrigerant flows from the switching means to the indoor heat exchanger via the fourth pipe and the indoor heat exchanger to the gas inlet / outlet of the accumulator via the input / output line.

In particular, the switching means are interposed between a first pipe connected to the outlet of the compressor, a second pipe connected to the inlet of the external heat exchanger, a third pipe connected in parallel to a connecting pipe connecting the evaporator at an inlet of the compressor, and the fourth pipe connected to the indoor heat exchanger.

Thus, in the first position, the switching means put in communication the first pipe with the second pipe as well as the third pipe with the fourth pipe and that, in the second position, the switching means put in communication the first pipe with the fourth pipe as well as the second pipe with the third pipe.

In this configuration, the external heat exchanger is connected to the switching means by the second pipe and to the accumulator via the outlet pipe.

In addition, a first thermostatic expansion valve is interposed in parallel between the second pipe and the outlet pipe.

In addition or alternatively, a second thermostatic expansion valve is interposed in parallel between an inlet line connecting the accumulator to the evaporator and the connecting line connecting the evaporator to the compressor.

In particular, the first expansion member is a single-channel expansion valve mounted on a bypass of the outlet pipe and allowing the circulation of the refrigerant in the bypass, only from the external heat exchanger to the accumulator.

According to a preferred variant, the second thermostatic expansion valve is controlled and can be brought selectively either in an open position or in a closed position, whatever the position of the switching means.

Consequently, in the first position of the switching means, selectively: • a "cooling" mode is provided when the second thermostatic expansion valve is in the open position and allows the cooling fluid to pass through the evaporator in the liquid phase, Or • a "defrost" mode when the second thermostatic expansion valve is in the closed position and prohibits the passage of coolant in the liquid phase through the evaporator.

Furthermore, in the second position of the switching means, one selectively provides: • either a "heating with dehumidification" mode when the second thermostatic expansion valve is in the open position and allows the passage of the cooling fluid in the liquid phase through the evaporator, • either a "heating without dehumidification" mode when the second thermostatic expansion valve is in the closed position and prohibits the passage of refrigerant in the liquid phase through the evaporator. According to a preferred embodiment of the present invention, the switching means are a four-way valve.

The present invention will be better understood, other characteristics and advantages will become apparent upon reading the following detailed description comprising exemplary embodiments given by way of illustration with reference to the appended figures, given by way of non-limiting examples, which may be used to complete the understanding of the present invention and the presentation of its implementation and, where appropriate, contribute to its definition, in which: - Figure 1 shows the diagram of a heating, ventilation and / or air conditioning according to the invention in "cooling" mode comprising switching means in a first position, FIG. 2 is a pressure / enthalpy diagram corresponding to the "cooling" mode of FIG. 1, FIG. 3 is a view similar to FIG. in a "heating" mode with a dehumidification function, in which the switching means are in a second position, - the FIG. 4 is a diagram similar to that of FIG. 1 in an alternative embodiment corresponding to a "defrosting" mode, and FIG. 5 is a pressure / enthalpy diagram corresponding to the "defrosting" mode of FIG. 4.

FIG. 1 shows a heating, ventilation and / or air conditioning device 10 comprising an air conditioning loop capable of being traversed by a refrigerant fluid, in particular a phase-change refrigerant fluid, in particular a fluoro fluid such as the fluid known under the designation R134A or the like. The refrigerant may be in the liquid phase and / or gas phase or vapor.

The heating, ventilation and / or air conditioning device 10 comprises a compressor 12 capable of compressing the refrigerant in the gas phase, an indoor heat exchanger 16, a first expansion device 18, an accumulator 20, or a suitable reserve cylinder 20. forming a gas / liquid separator, and an evaporator 22.

In addition, the heating, ventilation and / or air conditioning device 10 comprises an external heat exchanger 14 able, as the case may be, to function as a condenser or an evaporator, while being traversed by the same refrigerant fluid.

Moreover, the heating, ventilation and / or air conditioning device 10 comprises switching means 24, for example made in the form of a four-way valve, a first thermostatic expansion valve 26 and a second thermostatic expansion valve 28, capable of being able to be controlled by a control device 30.

Such an arrangement thus forms a heating, ventilation and / or air conditioning device functioning as a reversible heat pump.

The evaporator 22 and the indoor heat exchanger 16 are adapted to be traversed successively by a flow of air F, intended to be sent into a passenger compartment H of a motor vehicle. On the other hand, the external heat exchanger 14 can be traversed by an outside air flow. It is advantageously placed in the front-end module of the vehicle. The outdoor heat exchanger 14 can operate either as a condenser to return heat energy from the passenger compartment to the outside air stream in a "cooling" mode, or as an evaporator to recover from the heat energy to the outside air flow and return it to the passenger compartment, via the indoor heat exchanger 16, in a "heating" or "dehumidification" mode.

The switching means 24 are interposed between four pipes comprising: • a first pipe 32 connected to an outlet 34 of the compressor 12, • a second pipe 36 connected to an inlet 38 of the external heat exchanger 14, • a third pipe 40 connected in shunt to a connecting pipe 42 connecting the evaporator 22 to an inlet 44 of the compressor 12, and • a fourth pipe 46 connected to the indoor heat exchanger 16.

The switching means 24 are capable of taking up several positions in order to modify the circulation of the cooling fluid in the air-conditioning loop of the heating, ventilation and / or air-conditioning device 10.

In the first position of the switching means 24, as shown in Figure 1, on the one hand, the first pipe 32 and the second pipe 36 are placed in communication, and, on the other hand, the third pipe 40 and the fourth channel 46 are placed in communication.

The inlet 38 of the external heat exchanger 14 is connected to the switching means 24 by the second pipe 36. In addition, the external heat exchanger 14 has an outlet 48 connected by an outlet pipe 50 to an inlet / outlet. output 52 of the accumulator 20.

The second duct 36 and the inlet / outlet duct 50 are adapted to be traversed in one direction or the other depending on the position of the switching means 24, as described below.

The first expansion member 18 is, preferably, a single-channel expander. The first expansion member 18 is mounted on a branch 54 of the inlet / outlet line 50, between the outlet 48 of the external heat exchanger 14 and the inlet / outlet 52 of the accumulator 20. The first member 18 allows the flow of refrigerant in the bypass 54 of the inlet / outlet pipe 50, only from the outer heat exchanger 14 to the accumulator 20. The first expansion member 18 thus has the dual function of Expansion valve and check valve.

Furthermore, the first thermostatic expansion valve 26 is interposed on the inlet pipe 36 and the inlet / outlet pipe 50.

Advantageously, on the inlet / outlet pipe 50, the first thermostatic expansion valve 26 is arranged in parallel with the first expansion element 18.

The first thermostatic expansion valve 26 has the function of controlling the circulation of the refrigerant at the inlet 38 and the outlet 48 of the outdoor heat exchanger 14 under controlled conditions. In particular, the controlled conditions are dependent on the desuperheating between the discharge of the compressor 12 and the condensation temperature. In some cases, the controlled conditions may allow the first thermostatic expansion valve 26 to be completely closed.

The accumulator 20, also called reserve bottle 20, forms a refrigerant reserve in the liquid phase and in the gas phase. The accumulator 20 also allows the separation of the liquid and gas phases.

In addition to the input / output 52, the accumulator 20 comprises a liquid outlet 56 for the coolant in the liquid phase and a gas inlet / outlet 58 for the refrigerant fluid in the gas phase.

Preferably, the liquid outlet 56 is at the bottom of the accumulator 20 while the gas inlet / outlet 58 is at the top of the accumulator 20.

The evaporator 22 is connected to the liquid outlet 56 of the accumulator 20 via an intake pipe 60. Furthermore, the evaporator 22 is connected to the inlet 44 of the compressor 12 via the connecting pipe 42.

The second thermostatic expansion valve 28 is interposed on the intake pipe 60 and the connecting pipe 42. The second thermostatic expansion valve 28 serves to control the circulation of the refrigerant at the inlet and outlet of the evaporator 22 in controlled conditions. In particular, the controlled conditions are dependent on the desuperheating between the discharge of the compressor 12 and the condensation temperature. In some cases, the controlled conditions may allow the second thermostatic expansion valve 28 to be completely closed.

Furthermore, the second thermostatic expansion valve 28 is controlled by the control device 30, which is not the case of the first thermostatic expansion valve 26. The control device 30 makes it possible selectively to bring the second thermostatic expansion valve 28, either in a open position, causing it to function as an overheating controller, either in a closed position, regardless of the position of the switching means 24.

The gas inlet / outlet 58 of the accumulator 20 is connected to the indoor heat exchanger 16 via an inlet / outlet line 62. Advantageously, the inlet / outlet line 62 contains a second expansion member 64, preferably made in the form of a calibrated orifice, forming an expander.

Further, the indoor heat exchanger 16 is connected to the switching means 24 via the fourth pipe 46. The inlet / outlet pipe 62 and the fourth pipe 46 are respectively connected to a first port 66 and a second port 68. of the indoor heat exchanger 16 which, depending on the position of the switching means 24, may constitute an inlet or an outlet for the refrigerant fluid in the gas phase.

We will now describe the operation of the device in the case of Figure 1, corresponding to the mode "cooling". In the "cooling" mode, the switching means 24 put into communication: • the first pipe 32 and the second pipe 36, on the one hand, and • the third pipe 40 on the pipe 46, on the other hand. Fourth, the refrigerating fluid, in the gas phase, is sent by the compressor 12, at a pressure and discharge temperature, to the external heat exchanger 14, then functioning as a condenser. At outlet 48 of the outdoor heat exchanger 14, the condensed coolant is in the liquid phase. Under the effect of the discharge temperature of the compressor 12, the first thermostatic expansion valve 26, at the inlet / outlet line 50, is closed. As a result, the coolant is expanded by the first expansion member 18 to an intermediate pressure and reaches the accumulator 20 via the inlet / outlet 52.

The expanded refrigerant is both in the liquid phase and in the gas phase.

According to the embodiment shown, the liquid phase of the coolant accumulates towards the bottom of the accumulator 20 and the gaseous phase towards the upper part of the accumulator 20. The accumulator 20 functions as a gas / liquid separator .

The liquid phase leaves the accumulator 20 via the liquid outlet 56, while the gaseous phase leaves the accumulator 20 via the gas inlet / outlet 58.

The liquid phase joins the evaporator 22 via the second thermostatic expansion valve 28, which is in the open position by means of the control device 30. In parallel, the gas phase is sent through the inlet / outlet of gas 58 successively through the second expansion member 64 and then to the indoor heat exchanger 16.

The saturation pressure in the accumulator 20 is defined by the mass flow ratio R (steam / liquid) respectively for the gas flow to the indoor heat exchanger 16 and the liquid flow to the evaporator 22.

The higher the mass ratio R, the higher the pressure in the accumulator 20 is close to the evaporation pressure. When the mass flow of the refrigerant in the indoor heat exchanger 16 is zero, the pressure is defined as the saturation pressure at the inlet of the expander 18. On the other hand, when this mass flow is at a maximum and when the The mass flow in the evaporator 22 is a pure liquid, the pressure in the accumulator 20 is slightly higher than the evaporation pressure.

In the "cooling" mode configuration, the refrigerant, in the gaseous state, bypasses the evaporator 22 by the indoor heat exchanger 16. As a result, the evaporator 22 and the indoor heat exchanger 16 operate in parallel with a liquid phase at the inlet of the evaporator 22 and a gaseous phase at the inlet of the indoor heat exchanger 16. The indoor heat exchanger 16 does not produce heat and is not This means that the air flow F passes through the evaporator 22, in which it is cooled, and then the indoor heat exchanger 16 without any major change in temperature because of the temperature of the air flow F. the low thermal potential of the vapor phase refrigerant in the indoor heat exchanger 16.

The vapor or gas phase content of the refrigerant at the inlet of the evaporator 22 is very low, in particular less than 5% with reference to FIG. 2, compared to the conventional "heating" mode where this value is of the order of 30% or more. The present invention thus makes it possible to improve the performance with respect to the situation envisaged in the known devices.

In addition, the bypass of the evaporator 22 by the refrigerant in the vapor phase is effected by the indoor heat exchanger 16 while the known devices provide a bypass in parallel with the evaporator. As a result, it is not necessary to provide flaps to protect the indoor heat exchanger 16 in the "cooling" mode. The structure of the air conditioning loop is therefore simpler to achieve.

The diagram of FIG. 2 represents the cycle of operation of the air conditioning loop in the Pressure (P) / Enthalpy (E) diagram of the air-conditioning loop in the "cooling" mode configuration according to FIG. 1. The different points of the cycle are identified by the symbols {1} to {9}. The superheated refrigerant is sucked by the compressor 12 to the enthalpy and the suction pressure {1} and then discharged to a higher enthalpy and discharge pressure {2}. The refrigerant fluid thus discharged in the gaseous state and at high temperature passes through the external heat exchanger 14, functioning as a condenser, to cool and then condense and pass to a liquid enthalpy at the condensation pressure Pc { 3}. The condensation pressure Pc is substantially equal to the discharge pressure, neglecting the pressure drops in the external heat exchanger 14 and the pipes.

By passing through the first expansion member 18, the refrigerant undergoes an isenthalpic pressure drop from the condensing pressure Pc to the pressure Pa {4} of the accumulator 20 forming a reserve bottle 20.

In the accumulator 20, the liquid and gaseous phases are separated, and the liquid part of the expanded fluid {5} is sent to the second thermostatic expansion valve 28, while the vapor part {6} is sent to the second expansion device 64 , forming a fixed expander made, for example, as a calibrated orifice.

The liquid refrigerant is expanded from the pressure Pa {5} to the evaporation pressure Pe {7} while the gas-phase refrigerant {6} is expanded through the second expansion member 64 to the same evaporation pressure Pe and exits the indoor heat exchanger 16 {8}.

On leaving the second thermostatic expansion valve 28, the refrigerant passes through the evaporator 22 and changes phase to exit to an enthalpy of superheated steam at the evaporation pressure Pe {9}. At the outlet of the indoor heat exchanger 16 and the evaporator 22, the vapor state fluid {8} and the superheated vapor state {9} mix to complete the enthalpy and the suction pressure of the compressor {1}.

Referring now to Figure 3 which corresponds to another mode of operation, said mode "heating and dehumidification", wherein the switching means 24 are in a second position.

Thus arranged in the second position, the switching means 24 put in communication • the first pipe 32 and the fourth pipe 46, on the one hand, and • the second pipe 36 and the third pipe 40, on the other hand. The gas phase refrigerant from the compressor 12 is sent to the indoor heat exchanger 16 where it is condensed to form a liquid phase. The refrigerant thus condensed then leaves the internal heat exchanger 16 to reach the accumulator 20 via the inlet / outlet line 62 via the second expansion member 64, which serves in particular as a pressure reducer as a calibrated orifice.

The coolant in the liquid phase leaves the accumulator 20 through the inlet / outlet 52 and the liquid outlet 56.

As a result, the refrigerant passes through, on the one hand, the evaporator 22 and, on the other hand, the external heat exchanger 14, operating as an evaporator.

Furthermore, the control device 30 controls the opening of the second thermostatic expansion valve 28. Thus, the evaporation of the refrigerant is done through the evaporator 22 and the external heat exchanger 14 fed in parallel via the two thermostatic expansion valves 26 and 28.

According to an alternative embodiment, it is conceivable that a single thermostatic expansion valve 26 or 28 is in the open position.

In particular, the control device 30 can control the closing of the second thermostatic expansion valve 28. In this particular configuration, a "heating without dehumidification" mode is provided. By keeping the second thermostatic expansion valve 28 in the closed position, it is possible to neutralize the evaporator 22. It then acts as a neutral component which does not modify the temperature of the air flow F which passes therethrough.

Under these conditions, the air flow F is only heated through the indoor heat exchanger 16 without having been previously cooled and dehumidified. Thus, the mode "heating without dehumidification" is obtained.

Similarly, depending on the discharge temperature of the compressor 12, the first thermostatic expansion valve 26 at the inlet / outlet line 50 is closed. According to this configuration, only the evaporator 22 ensures the evaporation of the refrigerant. This ensures a mode "heating and dehumidification".

Then, the refrigerant leaving the evaporator 22 via the connecting pipe 42 joins the refrigerant leaving the external heat exchanger 14, the second pipe 36, the switching means 24 and the third pipe 40, upstream of the compressor 12. Then, the coolant reaches the inlet 44 of the compressor 12.

This ensures controlled superheating by both the first thermostatic expansion valve 26 at the outlet of the external heat exchanger 14 and the second thermostatic expansion valve 28 at the outlet of the evaporator 22.

The external heat exchanger 14, acting as an evaporator, and the evaporator 22, both operating in parallel, are connected to the inlet 44 of the compressor 12, while the indoor heat exchanger 16 is connected to the outlet of the compressor 12, via the switching means 24.

A heat pump is thus made comprising two evaporators consisting of the evaporator 22 and the external heat exchanger 14, and the two thermostatic expansion valves 26 and 28, which supply the two evaporators in parallel, in the "heating and cooling" mode. dehumidification ".

In this configuration enabling the "heating and dehumidification" mode and the "heating without dehumidification" mode, if the second expansion element 64 is not used, the operation of a conventional air conditioning loop with an accumulator at the output is obtained. condenser without additional subcooling pass.

As a result, the air flow F is successively cooled and dehumidified through the evaporator 22 and then reheated through the indoor heat exchanger 16. Thus, a "heating with dehumidification" mode is obtained.

Referring now to Figure 4 which corresponds to a "defrost" mode for which the switching means 24 are in the same position as in the case of Figure 1.

The configuration of FIG. 4 differs from the configuration of FIG. 1 in that the control device 30 controls the closing of the second thermostatic expansion valve 28.

The "defrost" mode is of interest in certain special cases. Indeed, after a certain period of use of the "heating and dehumidification" mode or of the "heating without dehumidification" mode, which corresponds to the heat pump arrangement of FIG. 3, the external heat exchanger 14, operating as an evaporator, can become blocked because of a strong accumulation of frost on its faces.

Frost buildup tends to reduce or eliminate the passage of the outside air flow through the outdoor heat exchanger 14. As a result, the performance of the air conditioning loop is degraded. Such a situation can occur especially in case of low outdoor temperature and / or high hygrometry.

In this case, it is necessary to switch to the "defrost" mode of the outdoor heat exchanger 14 to improve the performance of the air conditioning loop.

The "defrosting" mode is selected, first, from the switching means 24 which are in the first position, that is to say identical to that of the mode 30 shown in FIG.

This makes it possible to send the gaseous refrigerant fluid from the compressor 12 to the external heat exchanger 14, which then functions as a condenser, and makes it possible to melt the frost which has just formed on the surface of the exchanger external heat 14, while operating as an evaporator.

In this particular mode, the second thermostatic expansion valve 28 is in the closed position to prevent the refrigerant from passing through the evaporator 22 and to cool, undesirably, the passenger compartment.

As a result, all the coolant discharged by the compressor 12 is sent to the accumulator 20 in the form of steam which is then expanded through second expansion member 64, in particular in the form of a calibrated orifice, in the form of a of steam. This steam then passes into the indoor heat exchanger 16 without having an impact on the temperature of the air flow F sent into the passenger compartment H of the vehicle. FIG. 5 shows the operating cycle of the air conditioning loop in "defrost" mode according to FIG. 4. The different points of the cycle are identified by the symbols {1} to {4}. This cycle is done in a triangle because there is no heat transfer in the evaporator 22. The frost is just melted with the gases at the discharge of the external heat exchanger 14, acting as a condenser. The gas sucked by the compressor 12 {1} is discharged at a higher pressure and temperature {2}. As a result, the coolant passes into the outdoor heat exchanger 14, operating as a condenser, to melt the frost while cooling {3}, but still remains in the gaseous state. The coolant subsequently passes through the first expansion member 18 to lower the pressure from the discharge pressure, substantially also to the condensing pressure PO, to the pressure of the accumulator Pa keeping the same enthalpy (4). }. This first relaxation is represented by the arrow segment P1. By keeping the second thermostatic expansion valve 28 in the closed position, all the gas passes through the second expansion member 64 to undergo a second isenthalpic expansion, represented by the arrow segment AP2.

It will be understood that the device of the invention has a certain number of advantages as indicated below. The indoor heat exchanger 16 is at a low temperature close to the temperature of the air discharged from the evaporator 22, which does not create heating disturbances. There are fewer parameters to control, which allows easier control of the operation of the air conditioning loop. On the other hand, the device is of a simpler design since it has no protective flaps for the indoor heat exchanger 16.

In addition, higher performance is achieved in the "cooling" mode, as well as lower imbalance. On the other hand, a lower pressure drop in the evaporator 22 and less noise associated with the injection of the coolant into the evaporator 22 is obtained, unlike most of the previously proposed devices including a heat exchanger. indoor heat located in the heating, ventilation and / or air conditioning, which operates even in "cooling" mode transmitting the sound pulses of the compressor discharge.

There are other configurations that suggest a bypass on the indoor heat exchanger.

These two strategies are not the best for cooling mode. Indeed, if the indoor heat exchanger is supplied with hot gas, it contributes to the heating of the air flow to be sent into the passenger compartment, even if the indoor heat exchanger is protected by flaps.

The second solution may cause problems with refrigerant and oil build-up and may also lead to a large difference in the amount of refrigerant circulating between the "cooling" and "heating" modes.

The invention makes it possible to overcome these drawbacks because all the heat exchangers present contribute to improving the performances, both in the "heating" and "cooling" modes. In particular, the indoor heat exchanger 16 operates as a bypass of the gaseous coolant that is sent to the inlet of the evaporator 22 which has no interest and no cooling potential. The vapor phase that enters the indoor heat exchanger 16 has no cooling effect and does not lead to the condensation of ambient humidity on the outer surface of this component, which can cause problems. once in the "heating" mode, the gas in the indoor heat exchanger 16 is at the same temperature as the air discharged from the evaporator 22. the role of the indoor heat exchanger 16, in this case, is to reduce the pressure drop in the evaporator 22 and improve its performance. In addition, this configuration protects the cabin against noise that may come from the compressor discharge pulsations.

Furthermore, it is conceivable to integrate an internal heat exchanger to the heating, ventilation and / or air conditioning. In particular, it is capable of being interposed between the second inlet / outlet duct connecting the external heat exchanger to the accumulator and the intake duct connecting the evaporator to the inlet of the compressor. The presence of this internal heat exchanger improves the performance of the air conditioning loop, especially in "cooling" mode.

Finally, it should be noted that various implementations can be made according to the principles of the invention. It should be understood, however, that these examples of operation are given by way of illustration of the subject of the invention. Of course, the invention is not limited to these embodiments described above and provided solely by way of example. It encompasses various modifications, alternative forms and other variants that may be considered by those skilled in the art within the scope of the present invention and in particular any combination of the various embodiments described above. In addition, the various modes of operation described above can be taken separately or in combination in order to achieve alternative embodiments and various configurations of a heating, ventilation and / or air conditioning device as defined according to the present invention.

Claims (14)

Revendications1. Heating, ventilation and / or air conditioning device (10) for a motor vehicle, comprising an air conditioning loop capable of being traversed by a refrigerant fluid and comprising a compressor (12), an external heat exchanger (14), a heat exchanger indoor heat (16), a first expansion device (18), an accumulator (20) and an evaporator (22), a heating, ventilation and / or air conditioning device (10) in which the evaporator (22) and the internal heat exchanger (16) are adapted to be traversed in succession by a flow of air (F) adapted to be sent into a passenger compartment (H) of the motor vehicle, characterized in that the accumulator (20) comprises an output liquid coolant fluid (56) connected to the evaporator (22) and a gas outlet (58) for the gas phase refrigerant fluid connected to the indoor heat exchanger (16) , and in that switching means (24) are can be brought selectively: • in a first position, in which the coolant flows from the compressor (12) to the external heat exchanger (14), then to the accumulator (20), the exchanger heat sink (16) and the evaporator (22), then to the compressor (12), • in a second position, in which the refrigerant flows from the compressor (12) to the indoor heat exchanger (16), then to the accumulator (20), the evaporator (22) and the external heat exchanger (14), then to the compressor (12). Heating, ventilation and / or air conditioning device (10) according to claim 1, characterized in that, in the first position, the evaporator (22) and the internal heat exchanger (16) operate in parallel while being powered. respectively by the liquid phase refrigerant and the gas phase refrigerant from the accumulator (20) to provide a "cooling" mode where the air stream (F) is cooled through the evaporator ( 22) without subsequently changing the temperature through the indoor heat exchanger (16). Heating, ventilation and / or air conditioning device (10) according to one of claims 1 and 2, characterized in that, in the second position, the evaporator (22) is supplied with the cooling fluid in the liquid phase from of the accumulator (20), while the indoor heat exchanger (16) is supplied with the gas phase refrigerant fluid from the compressor (12) to provide a "heating" mode where the air flow ( F) is cooled and dehumidified through the evaporator (22) and reheated through the indoor heat exchanger (16). Heating, ventilation and / or air conditioning device (10) according to one of claims 1 to 3, characterized in that the indoor heat exchanger (16) comprises a first orifice (66) connected to an inlet / outlet of gas (58) of the accumulator (20) via an inlet / outlet line (62) and a second port (68) connected to the switching means (24) via a fourth line (46), so that in the first position, the refrigerant flows from the gas inlet / outlet (58) of the accumulator (20) to the indoor heat exchanger (16) via the first pipe (62) and then from the indoor heat exchanger (16) to the switching means (24) via the fourth pipe (46) and in the second position the refrigerant flows from the switching means (24) to the indoor heat exchanger (16) via the fourth line (46) and then the internal heat exchanger (16) to the gas inlet / outlet (58) of the ccumulator (20) via the input / output line (62). Heating, ventilation and / or air conditioning device (10) according to one of claims 1 to 4, characterized in that the switching means (24) are interposed between a first pipe (32) connected to the outlet (34). ) of the compressor (12), a second pipe (36) connected to the inlet (38) of the external heat exchanger (14), a third pipe (40) connected in shunt to a connecting pipe (42) connecting the evaporator (22) at an inlet (44) of the compressor (12), and the fourth pipe (46) connected to the indoor heat exchanger (16). Heating, ventilation and / or air-conditioning device (10) according to claim 5, characterized in that, in the first position, the switching means (24) put the first pipe (32) into communication with the second pipe ( 36) and the third pipe (40) with the fourth pipe (46) and that, in the second position, the switching means (24) put the first pipe (32) in communication with the fourth pipe (46) as well as the second pipe (36) with the third pipe (40). Heating, ventilation and / or air conditioning device (10) according to Claim 5 or 6, characterized in that the external heat exchanger (14) is connected to the switching means (24) via the second pipe (36). and to the accumulator (20) via an outlet line (50). Heating, ventilation and / or air conditioning device (10) according to claim 7, characterized in that a first thermostatic expansion valve (26) is interposed in parallel between the second pipe (36) and the outlet pipe (50). . Heating, ventilation and / or air conditioning device (10) according to one of claims 5 to 8, characterized in that a second thermostatic expansion valve (28) is interposed in parallel between an inlet pipe (60) connecting the accumulator (20) at the evaporator (22) and the connecting line (42) connecting the evaporator (22) to the compressor (12). Heating, ventilation and / or air conditioning device (10) according to one of Claims 5 to 9, characterized in that the first expansion element (18) is a single-channel expansion valve mounted on a bypass (54) of the outlet pipe (50) and allowing the flow of refrigerant in the bypass (54), only from the outer heat exchanger (14) to the accumulator (20). Heating, ventilation and / or air conditioning device (10) according to claim 9, characterized in that the second thermostatic expansion valve (28) is controlled and can be selectively brought into either an open position or a closed position, whatever the position of the switching means (24). Heating, ventilation and / or air conditioning device (10) according to claim 11, characterized in that, in the first position of the switching means (24), selectively: • a "cooling" mode is provided when the second 30 thermostatic expansion valve (28) is in the open position and allows the passage of coolant in the liquid phase through the evaporator (22), • a "defrost" mode when the second thermostatic expansion valve (28) is in the closed position and prohibits the passage of coolant in the liquid phase through the evaporator (22). Heating, ventilation and / or air conditioning device (10) according to claim 12, characterized in that, in the second position of the switching means (24), there is selectively provided: • either a "heating with dehumidification" mode when the second thermostatic expansion valve (28) is in the open position and allows the coolant to pass through the evaporator (22) in the liquid phase, or • a "heating without dehumidification" mode when the second thermostatic expansion valve (28) is in operation. closed position and prohibits the passage of coolant in the liquid phase through the evaporator (22). Heating, ventilation and / or air conditioning device (10) according to one of the preceding claims, characterized in that the switching means (24) are a four-way valve.