Vehicle having a cockpit and comprising a heat pump for defrosting an exchanger in heating mode

Abstract

Disclosed is a vehicle for outdoor use (1), comprising: • a control device (90) configured to control routing means and a compressor in order to circulate a refrigerant between the compressor (4), a condenser (23) and an external exchanger (3) in a first operating mode, and to circulate the refrigerant between the external exchanger (3) and the compressor (4) while by-passing the condenser (23), so as to heat the external exchanger (3) in a second operating mode.

Description

Description Title of the invention: Machine comprising a pilot compartment and comprising a heat pump allowing the defrosting of an exchanger in heating mode

[0001] [The invention relates to the field of climate management of the cockpit of a machine intended for outdoor use, and in particular the climate management of a cockpit of such a machine by means of a heat pump system.

[0002] To cope with the different climatic conditions outside the passenger compartment of a machine, temperature adaptation systems are almost systematically installed in passenger compartments, particularly in recreational vehicles or professional vehicles. Heating the driver's compartment is sometimes achieved using resistive heaters, powered by electricity from the vehicle's on-board network. However, the energy efficiency of resistive systems makes them problematic for new generations of machines or vehicles using electric motors powered by electrochemical batteries.

[0003] Thus, an increasing number of vehicles use a heat pump to produce either cold or heat, in order to adapt the temperature of the passenger compartment while minimizing energy consumption.

[0004] Such a heat pump system typically comprises an external exchanger crossed by an external air flow on the one hand, and by a reversible refrigerant circuit. A compressor drives the refrigerant in the circuit. The heat pump system also comprises an internal exchanger crossed by an air flow to the passenger compartment, and by the refrigerant circuit. Depending on the operating mode, the external exchanger operates as an evaporator to absorb heat from the external air flow to heat the refrigerant, or as a condenser to restore heat to the incoming air flow to cool the refrigerant.

[0005] One of the problems with a machine equipped with a heat pump comes from its use in cold and humid conditions, when starting this machine, when you want to heat the passenger compartment. The external exchanger works as an evaporator, cooling the already cold outside air. The humidity in this air condenses on the external exchanger and then forms frost when it comes into contact with the external exchanger. The available exchange surface with the outside air then drops, reducing the heat taken from the outside air.

[0006] The invention aims to solve one or more of these drawbacks. The invention thus relates to a machine intended for outdoor use, as defined in the appended claim 1.

[0007] The invention also relates to variants of the dependent claims. Those skilled in the art will understand that each of the features of the dependent claims and the description can be independently combined with the above features, without constituting an intermediate generalization.

[0008] Other characteristics and advantages of the invention will emerge clearly from the description given below, for information purposes only and in no way limiting, with reference to the appended drawings, in which:

[0009] [Fig.1] is a schematic representation of a vehicle equipped with a heat pump for implementing the invention;

[0010] [Fig.2] illustrates the implementation of an example heating cycle for the vehicle of Figure 1;

[0011] [Fig.3] illustrates the implementation of an example of an external exchanger defrost cycle for the vehicle of Figure 1;

[0012] [Fig.4] illustrates the implementation of an example of a heating cycle independent of the heat pump;

[0013] [Fig.5] illustrates the implementation of an example air conditioning cycle for the vehicle of Figure 1;

[0014] [Fig.6] schematically illustrates an internal exchanger for the vehicle of Figure 1, according to another aspect of the invention; [Fig.7], [Fig.8], [Fig.9] and [Fig.10], are diagrams illustrating examples of parameter choices for defining a defrost limit.

[0015] Figure 1 is a schematic representation of an example of a vehicle 1 according to one embodiment of the invention. The vehicle 1 may be a utility vehicle, a construction machine, a private vehicle or a recreational vehicle. The invention also applies to other types of machines, such as cranes. The vehicle 1 comprises a cockpit 10 in which the temperature must be controlled. The vehicle 1 includes a heat pump 9.

[0016] The heat pump 9 comprises a refrigerant circuit 7 passing through various components. The heat pump 9 thus comprises an internal exchanger 2, an external exchanger 3 and a compressor 4 configured to circulate refrigerant in the refrigerant circuit 7. The refrigerant circuit 7 thus passes through the external exchanger 3, the internal exchanger 2 and the compressor 4. A control device 90 is configured to control the operating mode of the heat pump. The control device 90 can be connected to different types of sensors or have a computer in order to determine parameters of the environment or the passenger compartment 10. The control device 90 could for example be connected to an outside temperature sensor, an inside temperature sensor, an outside humidity sensor or an inside humidity sensor.The control device 90 may also receive environmental parameters via Internet data streams. Advantageously, the compressor 4 is a variable rotation speed compressor to optimize consumption and / or power.

[0017] The internal exchanger 2 is intended to be crossed by an air flow to one or more zones of the passenger compartment 10 in order to carry out a heat exchange with the refrigerant of the circuit 7. The internal exchanger 2 here comprises a fan 21, an evaporator 22, a condenser 23, a heating resistor 24. The internal exchanger 2 comprises an air flow channel passing through the fan 21 in order to promote an air flow towards the passenger compartment, an evaporator 22 for an exchange with a view to air conditioning the passenger compartment 10, a condenser 23 for an exchange with a view to heating the passenger compartment 10, and a heating resistor 24 for an exchange with a view to heating the passenger compartment 10. The external exchanger 3 is intended to be crossed by an air flow coming from the outside in order to carry out a heat exchange with the refrigerant fluid of circuit 7. The fan 21 is advantageously controlled at variable speed.

[0018] The refrigerant circuit 7 illustrated here comprises a connection between the compressor 4 and an accumulator 41. The circuit 7 comprises a connection between an outlet of the compressor 4 and a connector 914. The circuit 7 comprises a connection between the connector 914 and a 3-way valve 923. The circuit 7 comprises a connection between the 3-way valve and an inlet of the condenser 23. The circuit 7 comprises a connection between an outlet of the condenser 23 and a connector 913. The circuit 7 comprises a connection between the 3-way valve 923 and the connector 913. The circuit 7 comprises a connection between the connector 913 and a connector 912. A first branch comprises a 2-way valve 922 and runs from this connector 912 to a connector 911. A second branch comprises an expansion valve 52 and runs from the connector 912 to the connector 911. Circuit 7 includes a connection between connector 91 1 and a connector 915.Circuit 7 also includes a connection between connector 914 and connector 915, via a 2-way valve 924. Circuit 7 includes a connection between connector 915 and external exchanger 3. Circuit 7 includes a connection between exchanger 3 and a 3-way valve 921.

[0019] The circuit 7 comprises a connection between the 3-way valve 921 and an expansion valve 51. The expansion valve 51 is positioned at the inlet of the evaporator 22. The circuit 7 comprises a connection between the outlet of the evaporator 22 and a connector 910. The circuit 7 comprises a connection between the connector 910 and the 3-way valve 921. The circuit 7 comprises a connection between the connector 910 and the accumulator 41. The circuit 7 further comprises a connection between the accumulator 41 and the compressor 4.

[0020] The compressor 4 and the valves 921, 922, 923 and 924 are controlled by the control device 90. The valves 921, 922, 923 and 924 thus form means for routing the refrigerant fluid, according to different operations detailed below.

[0021] A fan 31 forces air from outside the vehicle 1 through the external exchanger 3. The air passing through the external exchanger 3 can be directed towards the outside. The fan 31 is advantageously controlled at variable speed, for example by pulse width modulation. Such a variable speed makes it possible to optimize the power or consumption of the heat pump 9.

[0022] A first operating mode is illustrated with reference to Figure 2. In this first operating mode, the control device 90 is configured to control the routing means and the compressor 4 to circulate the refrigerant between the compressor 4, the condenser 23 and the external exchanger 3. In the example illustrated, the control device 90 controls: - closing valve 924, - opening of valve 922, - closing the connection between valve 923 and connector 913 and opening the connection between connector 914 and condenser 23 by valve 923; - closing the connection between valve 921 and pressure reducer 51 and opening the connection between connector 910 and exchanger 3 by valve 921.

[0023] The refrigerant in circuit 7 thus follows the following cycle: from compressor 4 to connector 914, from connector 914 to the inlet of condenser 23, from the outlet of condenser 23 to valve 922, from valve 922 to external exchanger 3, from external exchanger 3 to valve 921, then from valve 921 to the inlet of compressor 4. This flow circuit 7 thus short-circuits evaporator 22. Heat is supplied by the refrigerant to the air intended for the passenger compartment 10 in condenser 23. Heat is absorbed by the refrigerant from outside air in external exchanger 3.

[0024] The first operating mode may, for example, be implemented when the outside temperature is above -7°C. For temperatures above this threshold, it may be considered that the first operating mode allows significant savings in energy consumption to be made to obtain the same temperature value in the passenger compartment 10.

[0025] In cold and humid conditions, the first operating mode can cause problems. Indeed, the cooling of the air coming from outside at the external exchanger 3 can lead to condensation and frost on this external exchanger 3. The heat exchange between the refrigerant and the outside air can then quickly deteriorate, with the risk of causing the energy efficiency of the heat pump 9 to drop very sharply.

[0026] A second operating mode is illustrated with reference to Figure 3. In this second operating mode, the heat pump 9 is controlled to preheat the exchanger 3, in order to avoid the formation of frost when heating the passenger compartment 10. In the second operating mode, the control device 90 is configured to control the routing means and the compressor 4 to circulate the refrigerant between the compressor 4 and the external exchanger 3, by bypassing the condenser 23. By bypassing the condenser 23, the refrigerant is prevented from being cooled before reaching the exchanger 3, which makes it possible to achieve optimal heating of the exchanger 3. In the example illustrated, the control device 90 controls: - opening of valve 924, - closing of valve 922, - closing of the connection between valve 923 and connector 913 and closing of the connection between connector 914 and condenser 23 by valve 923; - closing the connection between valve 921 and pressure reducer 51 and opening the connection between connector 910 and exchanger 3 by valve 921.

[0027] The refrigerant in circuit 7 thus follows the following cycle: from compressor 4 to connector 914, from connector 914 to exchanger 3, from exchanger 3 to valve 921, from valve 921 to the inlet of compressor 4 via connector 910. This flow circuit 7 thus short-circuits condenser 23. Heat is supplied by the refrigerant to external exchanger 3. Fan 31 is advantageously stopped during an initial phase of the defrosting mode. The second operating mode can be maintained for a duration of, for example, 2 to 3 minutes. After considering that the defrosting conditions were met, the fan 31 is restarted to be able to evacuate droplets at the end of defrosting. The system can then switch to the first operating mode.

[0028] It can be provided that the control device 90 switches regularly between the first and second operating modes or according to other rules, in order to defrost the exchanger 3 before resuming a mode of heating the passenger compartment by the condenser 23.

[0029] A third operating mode is illustrated with reference to Figure 4. In this third operating mode, the passenger compartment is heated using the resistor 24. The resistor 24 is, for example, of the positive thermal coefficient type. In this third operating mode, electric current flows through the resistor 24. The air flow passing through this resistor 24 is heated, which makes it possible to heat the passenger compartment 10. The resistor 24 can, for example, be supplied with electricity by the vehicle's on-board network. This heating can thus be independent of the use of the condenser 23. Thus, this heating by the resistor 24 can be used in addition to the heating by the condenser 23 (to increase the heating speed) or as a replacement for the heating by the condenser 23. The third operating mode can, for example, be adopted when the outside temperature falls below -7°C.Heating by the resistor 24 can also be triggered simultaneously with the second operating mode, to ensure heating of the passenger compartment 10 even during a defrosting cycle of the exchanger 3. The occupants of the passenger compartment 10 will thus not see their comfort degraded by the implementation of a defrosting cycle.

[0030] The control of the first and third operating modes by the control device 90 constitutes an independent aspect of the invention.

[0031] A fourth operating mode is illustrated with reference to Figure 5. In this fourth operating mode, the heat pump 9 is controlled to provide air conditioning for the passenger compartment 10 of the vehicle 1. In this fourth operating mode, the control device 90 is configured to control the routing means and the compressor 4 to circulate the refrigerant between the compressor 4, the condenser 23 and the exchanger. external 3. In the example illustrated, the control device 90 controls: - the closing of the valve 924, - the closing of the valve 922, - the opening of the connection between the valve 923 and the connector 913 and the closing of the connection between the connector 914 and the condenser 23 by the valve 923; - opening the connection between valve 921 and pressure reducer 51 and closing the connection between connector 910 and exchanger 3 by valve 921.

[0032] The refrigerant in circuit 7 thus follows the following cycle: from compressor 4 to connector 914, from connector 914 to valve 923, from valve 923 to connector 913, from connector 913 to connector 911 via expansion valve 52, from connector 911 to external exchanger 3, from external exchanger 3 to valve 921, from valve 921 to expansion valve 51, from expansion valve 51 to the inlet of evaporator 22, then from the outlet of evaporator 22 to the inlet of compressor 4. This flow circuit 7 thus bypasses condenser 23. Heat is absorbed by the refrigerant from the air intended for the passenger compartment 10 in evaporator 22, thus ensuring cooling. Heat is released by the refrigerant to the outside air in the external exchanger 3.

[0033] Figure 6 schematically illustrates an internal heat exchanger 2 for implementing another aspect of the invention. The internal exchanger 2 here comprises a pipe 25 for the passage of air intended for the passenger compartment. The duct 25 comprises an air inlet, supplied for example either by outside air or by air already present in the passenger compartment 10. The duct 25 comprises an air outlet opening in a manner known per se into the passenger compartment 10. The evaporator 22, the condenser 23 and the heating resistor 24 are positioned one after the other between the inlet and the outlet of the guide duct 25. The fan 21 is also positioned between the inlet and the outlet of the guide duct 25 in order to promote the flow through the duct 25. Thus, the heat pump 9 can implement different types of exchanges with the passenger compartment 10 according to different operating modes from the same duct 25.Thus, the heat pump 9 can either air-condition the passenger compartment 10 by means of the evaporator 22, or heat the passenger compartment 10. by means of the condenser 23, or heat the passenger compartment 10 by means of the resistor 24. Thus, at low temperatures, the control device 90 can control heating of the passenger compartment 10 by means of the resistor 24 rather than by means of the condenser 23, in order to maintain better thermal efficiency or avoid having to carry out an excessive number of defrosting operations or to be able to ensure heating of the passenger compartment 10 at very low temperatures.

[0034] According to another variant, it is also possible to consider dehumidifying the passenger compartment 10. In this operating mode, the control device 90 operates the external exchanger 3 as a condenser and uses both the evaporator 22 and the condenser 23.

[0035] For this purpose, the refrigerant from the compressor 4 passes through the valve 923 to the inlet of the condenser 23, passes through the condenser 23, passes through the open valve 922, passes through the external exchanger 3, passes through the valve 921 to the expansion valve 51 then the inlet of the evaporator 22, passes through the evaporator to its outlet, then returns to the compressor 4.

[0036] Thus, the refrigerant transmits thermal energy to the air at the exchanger 3, cools the air in the evaporator 22 to ensure condensation of the humidity present in the air of the passenger compartment, the air being furthermore heated by the condenser 23.

[0037] The refrigerant in circuit 7 is known per se. The refrigerant can be R1234yf, R290, R744 or R134a. Compressor 4 will be defined in operation of the sizing of the air circuit of vehicle 1.

[0038] According to an independent aspect of the invention, the efficiency of the heat pump 9 can be optimized in heating mode of the passenger compartment 1. For this purpose, a control mode of the control device 90 is provided to allow switching between the first and second operating modes.

[0039] In order to optimize the energy performance coefficient of a heat pump, it is recommended to respect the following rule:

[0040] Tair.i - Tflui.o = Pinch <SMpinch

[0041] With Tair.i the temperature of the air entering the external exchanger 3, Tflui.o the temperature of the refrigerant leaving the external exchanger 3, Pinch the pinch value of the heat pump 9 and SMPinch a limit value guaranteeing the performance of the heat pump 9.

[0042] The SMPinch value can be reduced by optimizing the heat exchange at the external exchanger 3, in particular by limiting frost and the associated exchange surface losses. The SMPinch value is generally between 3 and 10 K in the absence of frost on the external exchanger. The SMPinch value can be adapted according to the operating conditions.

[0043] According to the invention, the criterion implemented to control the switch from the first operating mode to the second operating mode will be when the following condition is met:

[0044] Tair.i - Tflui.o > a * Tair.i + b =SMPinch with a and b constants defined so that a * Tair.i + b = SMPinch

[0045] Advantageously, this switching command will only be implemented when the condition is met for more than a predetermined duration, for example more than 10 seconds, advantageously more than 15 seconds and preferably more than 20 seconds. Advantageously, this switching command will only be implemented when Tair.i is between a low threshold value and a high threshold value. The low threshold value is for example between -7 and -5°C. The high threshold value is for example between 10 and 20°C.

[0046] In a first example illustrated in Figure 7, SMPinch = a * Tair.i + b between the low threshold value and the high threshold value (respectively -7°C and 20°C). SMPinch is not restricted for low temperatures. SMPinch is large enough to be evaluated correctly and avoids triggering unjustified defrosts. The variation of SMPinch as a function of Tair.i is relatively small. In this example, a=0.07 and b=6.52.

[0047] In a second example shown in Figure 8, SMPinch = a * Tair.i + b between the low threshold value and the high threshold value (respectively -3°C and 10°C). SMPinch is restricted for low temperatures between -7 and -3°C, and for high temperatures between 10 and 20°C. SMPinch is constant over these low temperatures. temperatures with a value high enough to avoid unjustified defrosting. SMPinch is constant at these high temperatures because a higher value would greatly reduce the efficiency of the heat pump without being of interest. The variation of SMPinch as a function of Tair.i is high. In this example, a=0.38 and b=6.15.

[0048] In a third example shown in Figure 9, SMPinch = a * Tair.i + b between the low threshold value and the high threshold value (respectively -7°C and 10°C). SMPinch is not restricted for low temperatures, and restricted for high temperatures between 10 and 20°C. SMPinch is large enough at low temperatures to be evaluated correctly and avoids triggering unjustified defrosts. SMPinch is constant at these high temperatures because a higher value would greatly reduce the efficiency of the heat pump without being of interest. The variation of SMPinch as a function of Tair.i is relatively high. In this example, a=0.18 and b=8.24.

[0049] In a fourth example shown in Figure 10, SMPinch = a * Tair.i + b between the low threshold value and the high threshold value (respectively -3°C and 20°C). SMPinch is restricted for low temperatures between -7 and -3°C, and is not restricted for high temperatures up to 20°C. SMPinch is kept constant at low temperatures to be evaluated correctly and avoid triggering unjustified defrosts. SMPinch is increasing at these high temperatures because the SMPinch value here ensures a good level of performance without the risk of frost. The variation of SMPinch as a function of Tair.i is relatively small. In this example, a=0.13 and b=5.39.

[0050] There are several methods for obtaining the values ​​a and b. One method is to find the values ​​a and b using the following relationship:

[0051] SMPinch = a * Tair.i + b = C1 * (a * Tair.i + [3)

[0052] C1 is a margin coefficient. The values ​​C1, a and [3 are typically determined during a calculation of the nominal Pinch value and by tests. The value of C1 is notably dependent on the geometry of the exchange surface of the external exchanger 3 or the humidity level in the environment. The value of C1 is typically between 1 and 5. The The value of C1 can be adapted depending on the location of the machine, which may lead to it being in a more or less humid environment.

[0053] Simulations can be performed where the frost growth as a function of time is calculated. Thus, the C1 value can be optimized: High C1 value: we prefer to operate the heat pump for a long time, but we accept having to defrost for a long time too (more ice has formed). Preferable in dry environments. Low value of C1: defrosting is triggered quickly, as soon as a little frost has formed. This choice will be made if the exchanger frosts easily, because the air is very humid and therefore frost will form quickly.

[0054] Since frost formation is dependent on air humidity, this parameter can be taken into account when setting the SMPinch value. SMPinch values ​​can, for example, be measured in the presence of dry air. For low relative humidity values ​​(e.g., below 20 or 30%), frost formation at low temperatures is considered impossible. Therefore, triggering a defrost cycle in this case is of no particular interest. In very humid environments, SMPinch values ​​should be lowered to facilitate defrosting operations.

[0055] Simulations can be implemented to determine the values ​​of a and [3 that do not result in frost formation, for an optimized SMPinch value. A simulation can then be implemented to determine the value of C1 that allows nominal or acceptable frost formation to be obtained with a realistic Pinch value. The determination of the values ​​of C1, a and p can also be carried out on the basis of experimental measurements depending on the appearance of frost on the external exchanger 3.

Claims

Claims

1. [Machine intended for outdoor use (1), characterized in that it comprises: - a cockpit (10); - a heat pump (9) comprising: - a heat exchanger (3) configured to be crossed by a flow of air coming from the outside; - an internal heat exchanger (2) configured to be crossed by an air flow to the passenger compartment (10), including at least one condenser (23) and a heating resistor (24); - a refrigerant circuit (7) passing through the external exchanger (3) and the condenser (23); - a compressor (4) configured to circulate refrigerant in the refrigerant circuit (7); - means of routing the refrigerant fluid; -a control device (90) configured to control the routing means and the compressor to circulate the refrigerant between the compressor (4), the condenser (23) and the external exchanger (3) in a first operating mode, and to circulate the refrigerant between the external exchanger (3) and the compressor (4) by short-circuiting the condenser (23) so as to heat the external exchanger (3) in a second operating mode.

2. Machine (1) according to claim 1, comprising a device for determining the external temperature Tair.i and a device for determining the temperature of the refrigerant fluid Tflui.o at the outlet of the external exchanger (3), in which the control device (90) switches from the first operating mode to the second operating mode when the following relationship is verified: Tair.i - Tflui.o > a * Tair.i + b = SMPinch = C1* (a * Tair.i + [3) with Pinch an admissible temperature difference, a and b constants, C1, a and [3 constants having been previously determined as avoiding frost.

3. Machine (1) according to claim 2, in which the control device (90) switches from the first operating mode to the second operating mode only if the following additional relationship is respected: Tmin< Tair.i < Tmax with Tmin and Tmax temperature thresholds for the external temperature.

4. Machine (1) according to claim 3, in which Tmin is between -8°C and -3 C.

5. Apparatus according to claim 3 or 4, wherein Tmax is between 9°C and 21 C.

6. A machine according to any preceding claim, wherein a is between 0.07 and 0.4 and b is between 5 and 9.

7. Machine (1) according to any one of the preceding claims, wherein the internal heat exchanger (2) includes an air guide duct (25) having an inlet and an outlet, and includes an evaporator (22), the evaporator (22), the condenser (23) and the heating resistor (24) being positioned one after the other between the inlet and the outlet of the guide duct; - the refrigerant circuit (7) passing through the external exchanger (3), the evaporator (22) and the condenser (23), the evaporator (22) and the condenser (23) being connected in parallel in the refrigerant circuit (7); -the control device (90) being configured to control the routing means and the compressor (4) to circulate the refrigerant between the compressor (4), the external exchanger (3) and the evaporator (22) in a third operating mode.

8. A machine according to any preceding claim, wherein the internal heat exchanger (2) includes an air guide duct (25) having an inlet and an outlet, the condenser (23) and the heating resistor (24) being positioned between the inlet and the outlet of the guide duct (25); -the control device (90) being configured to heat the heating resistor (24) in a fourth operating mode.

9. Machine, characterized in that it comprises: - a pilot compartment; - a heat pump including: - a heat exchanger configured to be crossed by an air flow coming from outside; -an internal heat exchanger configured to be crossed by an air flow to the passenger compartment, including an air guide duct having an inlet and an outlet, an evaporator, a condenser and a heating resistor, the evaporator, the condenser and the heating resistor being positioned one after the other between the inlet and the outlet of the guide duct; - a refrigerant circuit passing through the external exchanger, the evaporator and the condenser, the evaporator and the condenser being connected in parallel in the refrigerant circuit; - a compressor configured to circulate refrigerant in the refrigerant circuit; - means of routing the refrigerant fluid; -a control device configured to control the routing means and the compressor to circulate the refrigerant between the compressor, the condenser and the external exchanger in a first operating mode, and to circulate the refrigerant between the compressor, the external exchanger and the evaporator in a second operating mode.

10. Machine according to claim 9, in which the refrigerant circuit passes through the external exchanger and the condenser and the control device is configured to control the routing means and the compressor to circulate the refrigerant between the external exchanger and the compressor by short-circuiting the condenser so as to heat the external exchanger in a third operating mode.

11. Machine according to claim 10, comprising a device for determining the external temperature Tair.i and a device for determining the temperature of the refrigerant fluid Tflui.o at the outlet of the external exchanger, in which the control device switches from the first operating mode to the second operating mode when the following relationship is verified: Tair.i - Tflui.o > a * Tair.i + b = SMPinch = C1 * with Pinch an admissible temperature difference, a and b constants, C1, a and [3 constants having been previously determined as avoiding frost.

12. Machine according to claim 11, in which the control device switches from the first operating mode to the second operating mode only if the following additional relationship is respected: Tmin< Tair.i < Tmax with Tmin and Tmax temperature thresholds for the external temperature.

13. Machine according to claim 12, in which Tmin is between -8°C and -3 C.

14. Apparatus according to claim 12 or 13, wherein Tmax is between 9°C and 21 C.

15. A machine according to any one of claims 9 to 14, wherein a is between 0.07 and 0.4 and b is between 5 and 9.

16. Machine according to any one of claims 9 to 15, in which the internal heat exchanger is configured to be crossed by a flow of air to the passenger compartment and including an air guide duct having an inlet and an outlet, a condenser and a heating resistor, the condenser and the heating resistor being positioned between the inlet and the outlet of the guide duct; -the control device is configured to heat the heating resistor in a fourth operating mode.

17. A machine according to any one of claims 9 to 16, wherein the machine is a vehicle.

18. [Machine (1) intended for outdoor use (1), characterized in that it comprises: - a cockpit (10); - a heat pump (9) comprising: - a heat exchanger (3) configured to be crossed by a flow of air coming from the outside; - an internal heat exchanger (2) configured to be crossed by an air flow to the passenger compartment (10) and including an air guide duct (25) having an inlet and an outlet, a condenser (23) and a heating resistor (24), the condenser (23) and the heating resistor (24) being positioned between the inlet and the outlet of the guide duct (25); - a refrigerant circuit (7) passing through the external exchanger (3) and the condenser (23); - a compressor (4) configured to circulate refrigerant in the refrigerant circuit (7); - means of routing the refrigerant fluid; -a control device (90) configured to control the routing means and the compressor to circulate the refrigerant between the compressor (4), the condenser (23) and the external exchanger (3) in a first operating mode, and to heat the heating resistor (24) in another operating mode.

19. Machine according to claim 18, wherein the control device (90) is further configured to control the routing means and the compressor to circulate the refrigerant between the external exchanger (3) and the compressor (4) by short-circuiting the condenser (23) so as to heat the external exchanger (3) in a third operating mode.

20. Machine (1) according to claim 19, comprising a device for determining the external temperature Tair.i and a device for determining the temperature of the refrigerant Tflui.o at the outlet of the external exchanger (3), in which the control device (90) switches from the first operating mode to the third operating mode when the following relationship is verified: Tair.i - Tflui.o > a * Tair.i + b = SMPinch = C1* (a * Tair.i + [3) with Pinch an admissible temperature difference, a and b constants, C1, a and [3 constants having been previously determined as avoiding frost.

21. Machine (1) according to claim 20, in which the control device (90) switches from the first operating mode to the third operating mode only if the following additional relationship is respected: Tmin< Tair.i < Tmax with Tmin and Tmax temperature thresholds for the external temperature.

22. Machine (1) according to claim 21, in which Tmin is between -8°C and -3 C.

23. Apparatus according to claim 21 or 22, wherein Tmax is between 9°C and 21 C.

24. A machine according to any one of claims 20 to 23, wherein a is between 0.07 and 0.4 and b is between 5 and 9.

25. A machine according to any one of claims 20 to 24, wherein the internal heat exchanger (2) includes an evaporator (22), the evaporator (22), the condenser (23) and the heating resistor (24) being positioned one after the other between the inlet and the outlet of the guide duct; - the refrigerant circuit (7) passing through the external exchanger (3), the evaporator (22) and the condenser (23), the evaporator (22) and the condenser (23) being connected in parallel in the refrigerant circuit (7); -the control device (90) being further configured to control the routing means and the compressor (4) to circulate the refrigerant between the compressor (4), the external exchanger (3) and the evaporator (22) in a fourth operating mode.

26. A machine according to any one of claims 20 to 25, wherein the machine is a vehicle.,

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