conditioner The invention relates to a vehicle air conditioner for heating, ventilation and/or air-conditioning of a vehicle inner space, having a refrigerant circuit comprising a compressor for compressing a refrigerant, a first condenser for cooling and condensing the refrigerant from the compressor and for heating air which can be supplied from the vehicle inner space, a second condenser which is connected in parallel with the first condenser for cooling and condensing the refrigerant from the compressor and for heating vehicle surrounding air, an evaporator for heating and evaporating the refrigerant and for cooling air which can be supplied from the vehicle inner space and a pressure reduction unit which is arranged upstream of the condenser for decompressing the refrigerant from the first or second condenser, wherein in a cooling mode of the vehicle air conditioner the first condenser is bridged and in a heating mode of the vehicle air conditioner the second condenser is bridged. Such vehicle air conditioners are already generally known from the prior art, wherein in heating mode, that is to say, at low outside temperatures, exclusively fresh air is generally supplied to these air conditioners in order to prevent misting of the vehicle windows as a result of this relatively dry air. However, this also means that warm and relatively damp air has to be discharged from the vehicle inner space to the environment, which leads to considerable heat losses and an undesirably high energy requirement in order to heat the vehicle inner space.

US 2012/0011869 Al of the generic type discloses a vehicle air conditioning unit having a structural unit for recovering thermal energy from the waste air directed from the vehicle inner space into the vehicle environment. This separate heat recovery unit is generally accommodated in the rear of the vehicle and has an additional evaporator and a separate fan. Furthermore, additional refrigerant lines are required in order to connect the heat recovery unit to the refrigerant circuit of the vehicle air conditioning unit. Consequently, the construction of the proposed vehicle air conditioning unit is complex and expensive.

An object of the invention is therefore to provide a structurally simplified air conditioner which enables particularly energy-efficient heating of a vehicle inner space.

According to the invention, this object is achieved with a vehicle air conditioner of the type mentioned in the introduction having a waste air duct which discharges waste air into the vehicle environment.

According to another embodiment of the vehicle air conditioner, the vehicle air conditioner comprises an evaporator for cooling air and in the heating mode of the vehicle air conditioner at least a portion of the waste air which is discharged via the waste air duct flows through the evaporator.

As a result of this integration of the waste air duct in the vehicle air conditioner, the evaporator which is already present can be used to recover thermal energy from the waste air which flows into the vehicle environment. In this manner, it is consequently possible to recover energy from the warm waste air with minimal additional structural complexity. Only the waste air duct which is conventionally provided in the rear of the vehicle has to be integrated in the vehicle air conditioner which is usually provided in the vehicle front. According to an embodiment of the vehicle air conditioner, a sensor for detecting an air humidity in the vehicle inner space and an electronic control unit for controlling a supply of fresh air to the vehicle inner space in accordance with data detected by the sensor are provided. In the heating mode of the vehicle air conditioner a fresh air proportion of the air supplied to the vehicle inner space can thereby be reduced and a circulation air proportion can be increased, which leads to a further increase of the energy efficiency. In particular, the proportion of the dry fresh air supplied to the vehicle inner space can in this instance be reduced to such an extent that a condensation of water on the vehicle windows is still prevented.

According to another embodiment of the vehicle air conditioner, a blower for conveying fresh air and circulation air is provided. This blower conveys fresh air and/or circulation air into the vehicle inner space, but can if required also discharge air into the vehicle environment via the waste air duct.

Preferably, the blower has a first blower wheel for conveying fresh air and a separate second blower wheel for conveying circulation air. The blower is in this instance in particular arranged upstream (of the air flow) of the evaporator and the blower wheels can preferably be controlled separately from each other. The ratio of fresh air to circulation air can thereby readily be varied and, for example, be adjusted as desired in order to prevent window misting.

Furthermore, a control flap for adjusting a fresh air/circulation air or mixed air operation of the vehicle air conditioner may be provided, wherein the blower in fresh air operation conveys fresh air and in circulation air operation it conveys circulation air and in mixed air operation it conveys both fresh air and circulation air. In this manner, circulation air can also be at least partially used to heat the vehicle inner space in the heating mode of the vehicle air conditioner. The maximum circulation air proportion is achieved as soon as the vehicle windows mist, wherein, in order to monitor the window misting, a corresponding sensor for detecting an air humidity in the vehicle inner space is preferably provided. With regard to energy-efficient operation of the vehicle air conditioner in the heating mode, a conventional pure fresh air operation without heat recovery from the waste air may be considered to be the worst. In contrast, pure fresh air operation with heat recovery of the waste air is already considerably more energy-efficient. With regard to the energy efficiency, a pure air circulation operation would be preferable, but the air humidity increases significantly in this instance and leads to an undesirable window misting in the vehicle inner space. Accordingly, a compromise which has been found to be particularly practical is a mixed air operation with heat recovery from the waste air, wherein the proportion of the (dry) fresh air supplied to the vehicle inner space is adjusted to be as low as possible, in particular so low that window misting in the vehicle inner space is still just prevented .

The blower of the vehicle air conditioner is arranged, for example, downstream of the evaporator. In particular in blowers with a first blower wheel for conveying fresh air and a separate blower wheel for conveying circulation air, however, it is alternatively also conceivable for the blower to be arranged upstream of the evaporator.

Preferably, the vehicle air conditioner comprises a first condenser for heating air, and the evaporator is arranged with respect to an air flow direction produced by the blower upstream of the first condenser.

According to another embodiment of the vehicle air conditioner, with respect to an air flow direction produced by the blower, a first fresh air duct and a first waste air duct are provided upstream of the evaporator and a second fresh air duct and a second waste air duct are provided downstream of the evaporator.

The blower is in this instance in particular arranged downstream of the second fresh air duct and the second waste air duct.

According to another embodiment of the vehicle air conditioner, two evaporator flaps are provided for adjusting an air flow direction inside the evaporator. In this instance, in the heating mode of the vehicle air conditioner, the evaporator may be flowed through in a first direction and in the cooling mode of the vehicle air conditioner may be flowed through in a second direction counter to the first direction. With respect to an air flow direction produced by the blower, an electrical heating device, in particular a PTC heating device, is preferably provided downstream of the first condenser. This electrical heating device enables more rapid heating of the vehicle inner space, in particular with electric or hybrid vehicles.

According to a particularly preferred embodiment, the vehicle air conditioner has precisely one evaporator. In particular, no separate heat recovery unit with an additional evaporator which serves exclusively to recover thermal energy from the waste air is required. According to a particularly preferred embodiment, a waste air flap is located at the entrance of the waste air duct to regulate the flow of waste air. According to a particularly preferred embodiment, the entrance of the waste air ducts are located downstream of the evaporator.

According to the invention the vehicle air conditioner for heating, ventilation and/or air-conditioning of a vehicle inner space, has a refrigerant circuit comprising :

a compressor for compressing a refrigerant,

a first condenser for cooling and condensing the refrigerant from the compressor and for heating air which can be supplied from the vehicle inner space, a second condenser which is connected in parallel with the first condenser for cooling and condensing the refrigerant from the compressor and for heating vehicle surrounding air,

an evaporator for heating and evaporating the refrigerant and for cooling air which can be supplied from the vehicle inner space and

a pressure reduction unit which is arranged upstream of the condenser for decompressing the refrigerant from the first or second condenser,

wherein in a cooling mode of the vehicle air conditioner the first condenser is bridged and

wherein in a heating mode of the vehicle air conditioner the second condenser is bridged,

characterized in that the vehicle air conditioner has a waste air duct which discharges waste air into a vehicle environment,

wherein in the heating mode of the vehicle air conditioner at least a portion of the waste air which is discharged via the waste air duct flows through the evaporator . The above-mentioned object is also achieved according to the invention by a method for heating a vehicle inner space using an above-described vehicle air conditioner which has a sensor for detecting an air humidity in the vehicle inner space and an electronic control unit which via the air humidity detected by the sensor can determine a window misting in the vehicle inner space, wherein a fresh air supply to the vehicle inner space is automatically and continuously adapted in accordance with the air humidity detected, wherein the fresh air supply is increased with an air humidity which is critical with respect to the window misting and is maintained or reduced with an air humidity which is non-critical with respect to the window misting. Such an automatic adaptation of the fresh air supply in accordance with the current air humidity enables particularly energy-efficient operation of the vehicle air conditioner in heating mode. According to a preferred method variant, the vehicle air conditioner comprises at least one of the following components: a blower for conveying fresh air, a control flap for adjusting a fresh air, circulation air or mixed air operation of the vehicle air conditioner, a fresh air flap for adjusting the proportion of fresh air flowing through the evaporator, and a waste air flap for adjusting the proportion of waste air flowing through the evaporator, wherein the control unit processes data detected by the sensor and controls at least one of the above-mentioned components in accordance with these data. Consequently, a desired fresh air supply can be achieved with little complexity by means of simple blower and/or flap controls. Other features and advantages of the invention will be appreciated from the following description of preferred embodiments with reference to the drawings, in which: Figure 1 is a schematic circuit diagram of the refrigerant circuit of a vehicle air conditioner according to the invention;

- Figure 2 is a schematic cut-out of the vehicle air conditioner according to the invention according to an embodiment in a heating mode;

- Figure 3 is another schematic cut-out of the vehicle air conditioner according to Figure 2 in the heating mode ;

- Figure 4 is a schematic cut-out of the vehicle air conditioner according to Figure 2 in a cooling mode;

- Figure 5 is another schematic cut-out of the vehicle air conditioner according to Figure 2 in the cooling mode ;

- Figure 6 is a schematic cut-out of the vehicle air conditioner according to the invention according to another embodiment in a cooling mode;

- Figure 7 is a schematic cut-out of the vehicle air conditioner according to Figure 6 in a heating mode; - Figure 8 is a schematic cut-out of a vehicle air conditioner according to the invention according to another embodiment in a heating mode;

- Figure 9 is another schematic cut-out of the vehicle air conditioner according to Figure 8 in the heating mode;

- Figure 10 is yet another schematic cut-out of the vehicle air conditioner according to Figure 8 in the heating mode;

- Figure 11 is a schematic cut-out of the vehicle air conditioner according to Figure 8 in a cooling mode; and

- Figure 12 is another schematic cut-out of the vehicle air conditioner according to Figure 8 in the cooling mode .

Figure 1 schematically illustrates the general operating principle of a refrigerant circuit 10 of a vehicle air conditioner 12 for heating, ventilation and/or air-conditioning of a vehicle inner space 14. The refrigerant circuit 10 comprises according to Figure 1 a compressor 16 for compressing a refrigerant 18, a first condenser 20 for cooling and condensing the refrigerant 18 from the compressor 16 and for heating air 22 which can be supplied to the vehicle inner space 14, a second condenser 24 which is connected in parallel with the first condenser 20 for cooling and condensing the refrigerant 18 from the compressor 16 and for heating vehicle surrounding air 26, an evaporator 28 for heating and evaporating the refrigerant 18 and for cooling air 22 which can be supplied from the vehicle inner space 14 and a pressure reduction unit 30 which is arranged upstream of the evaporator 28 for decompressing the refrigerant 18 from the first or second condenser 20, 24. The first condenser 20 is arranged in the vehicle inner space 14 and is therefore also referred to as the "inner condenser". The second condenser 24 is in contrast arranged in an engine compartment of the motor vehicle, that is to say, outside the vehicle inner space 14, and is therefore also referred to as the "outer condenser".

According to Figure 1, the refrigerant circuit 10 in a heating mode of the vehicle air conditioner 12 is illustrated with solid lines, wherein refrigerant 18 flows through the first condenser 20 and the second condenser 24 is bridged. In contrast, in a cooling mode of the vehicle air conditioner 12 which is illustrated with dashed lines, refrigerant 18 flows through the second condenser 24, whilst the first condenser 20 is bridged. In order to switch between the heating mode and the cooling mode of the vehicle air conditioner 12, there are provided by way of example according to Figure 1 two shut-off valves 32 which are in particular controlled in such a manner that either the first condenser 20 or the second condenser 24 is bridged. The refrigerant circuit 10 also comprises according to Figure 1 a refrigerant store 34 which in the present embodiment is arranged at a high-pressure side of the refrigerant circuit 10. However, it is alternatively also conceivable for the refrigerant store 34 to be arranged at a low-pressure side of the refrigerant circuit 10.

As schematically illustrated in Figure 1, the vehicle air conditioner 12 has a waste air duct 36 which discharges waste air 38 from the vehicle inner space 14 into the vehicle environment 40, wherein the vehicle inner space 14 is preferably vented exclusively via this waste air duct 36 towards the vehicle environment 40. At the entrance of the waste air duct is located a waste air flap 64 to regulate the flow of waste air 38 passing through the waste air duct 36. In the heating mode of the vehicle air conditioner 12, at least a portion of the waste air 38 discharged via the waste air duct 36 flows through the evaporator 28, wherein it is particularly advantageous with respect to the energy recovery for all the waste air 38 discharged from the vehicle inner space 14 into the vehicle environment 40 to flow through the evaporator 28. During flow through the evaporator 28, there is removed from the waste air 38 thermal energy which via the refrigerant circuit 10 is in turn used to heat the air 22 supplied to the vehicle inner space 14. In heating mode, that is to say, during the thermal pump operation of the vehicle air conditioner 12, energy recovery and consequently an extremely energy-efficient operation of the vehicle air conditioner 12 is thereby enabled with little technical complexity. The entrance of the waste air ducts 36 are located downstream of the evaporator 28.

That is to say, the vehicle air conditioner 12 according to Figure 1 has precisely one evaporator 28 which is used both for cooling the air 22 which is supplied to the vehicle inner space 14 and for cooling the waste air 38, wherein the cooling of the waste air 38 is used for heat recovery in the heating mode of the vehicle air conditioner 12. According to Figure 1, the vehicle air conditioner 12 comprises a blower 42 for conveying fresh air 44 and/or circulation air 46 which produces a predetermined air flow direction during blower operation. The evaporator 28 is in this instance arranged with reference to the air flow direction produced by the blower 42 upstream of the first condenser 20.

With respect to the air flow direction produced by the blower 42, downstream of the first condenser 20 an electrical heating device 48 is additionally provided in order to increase the heating power of the vehicle air conditioner 12 in the heating mode. This optional electrical heating device 48 which can be switched on as required is in a particularly preferred manner a PTC heating device generally known from the prior art.

Figures 2 to 5 show a cut-out 50 of the vehicle air conditioner 12 indicated in Figure 1 according to an embodiment .

The blower 42 is in this embodiment arranged upstream of the evaporator 28 and has a first blower wheel 52 for conveying fresh air 44 and a separate second blower wheel 54 for conveying circulation air 46, wherein the two blower wheels 52, 54 can be controlled separately from each other. Via the speeds of the blower wheels 52, 54, a fresh air supply can be adjusted independently of the circulation air supply and can be adapted to the respective requirement.

The vehicle air conditioner 12 further has a control flap 56 for adjusting a fresh air, circulation air or mixed air operation of the vehicle air conditioner 12, wherein the blower 42 in fresh air operation (Figure 4) conveys exclusively fresh air 44, in circulation air operation (Figures 3 and 5) it conveys exclusively circulation air 46 and in mixed air operation (Figure 2) it conveys both fresh air 44 and circulation air 46.

According to Figure 2, the blower 42 conveys at an identical speed of the blower wheels 52, 54 approximately 50% fresh air 44 and 50% circulation air 46. In place of this precisely one (central) mixed air stage of the control flap 56, however, other mixed air stages and a "continuous transition" from fresh air operation to circulation air operation are also conceivable . As illustrated in Figures 2 to 5, the vehicle air conditioner 12 further comprises a sensor 58 for detecting an air humidity in the vehicle inner space 14 and an electronic control unit 60 for controlling a fresh air supply to the vehicle inner space 14 in accordance with data detected by the sensor 58.

The electronic control unit 60 can ultimately determine via the air humidity detected by the sensor 58 a condensation of water on the vehicle windows, that is to say, a window misting in the vehicle inner space 14. In an advantageous method for heating the vehicle inner space 14 by means of the vehicle air conditioner 12 in the heating mode, the supply of fresh air 44 to the vehicle inner space 14 is adapted automatically and continuously in accordance with the air humidity detected, wherein the fresh air supply increases with an air humidity which is critical with respect to the window misting and is maintained or reduced with an air humidity which is non-critical with respect to the window misting.

In specific terms, the vehicle air conditioner 12 comprises at least one of the following components: a blower 42 for conveying fresh air 44, a control flap 56 for adjusting a fresh air, circulation air or mixed air operation of the vehicle air conditioner 12, a fresh air flap 62 for adjusting the proportion of fresh air flowing through the evaporator 28, and a waste air flap 64 for adjusting the waste air proportion flowing through the evaporator 28, wherein the electronic control unit 60 processes air humidity data detected by the sensor 58 and in accordance with these data controls at least one of the above-mentioned components. The control is again carried out in such a manner that the fresh air supply increases with an air humidity which is critical with respect to the window misting and is maintained or reduced with an air humidity which is non-critical with respect to the window misting.

This automatic operating method in the heating mode of the vehicle air conditioner 12 can also be transferred in a similar manner to the additional embodiments of the vehicle air conditioner 12 described below.

According to Figures 2 to 5, the vehicle air conditioner 12 has an operating mode flap 65 which in a heating position closes a bypass of the first condenser 20 (see Figures 2 and 3) so that all the air 22 supplied to the vehicle inner space 14 flows through the first condenser 20 and is heated. The vehicle air conditioner 12 is consequently in heating mode, wherein Figure 2 illustrates a mixed air operation and Figure 3 illustrates a pure circulation air operation. In circulation air operation according to Figure 3, no fresh air 44 is supplied to the vehicle inner space 14 so that no waste air 38 also flows into the vehicle environment 40.

In a cooling position, the operating mode flap 65 closes a flow duct in which the first condenser 20 is located so that all the air 22 supplied to the vehicle inner space 14 flows past the first condenser 20. The vehicle air conditioner 12 is consequently in cooling mode, wherein Figure 4 illustrates a pure fresh air operation and Figure 5 illustrates a pure circulation air operation.

Figures 6 and 7 show the cut-out 50 of the vehicle air conditioner 12 indicated in Figure 1 according to another alternative embodiment. The vehicle air conditioner 12 illustrated in this instance differs from the previous embodiment in that, with reference to the air flow direction produced by the blower 42, a first fresh air duct 66 and a first waste air duct 68 are provided upstream of the evaporator 28 and a second fresh air duct 70 and a second waste air duct 72 are provided downstream of the evaporator 28.

The blower 42 is in this instance arranged downstream (in the air flow) of the evaporator 28 and in particular also downstream of the second fresh air duct 70 and the second waste air duct 72.

The first fresh air duct 66 and the first waste air duct 68 can be selectively closed or at least partially opened by means of a first fresh air flap 74 or a first waste air flap 76. In a similar manner, the second fresh air duct 70 and the second waste air duct 72 can be selectively closed or at least partially opened by means of a second fresh air flap 78 or a second waste air flap 80.

Figure 6 shows the vehicle air conditioner 12 in cooling mode in which the upstream first fresh air and waste air flaps 74, 76 are partially opened and the second fresh air and waste air flaps 78, 80 are closed. As a result of the partial opening of the first flaps 74, 76, there is produced a mixed air operation in which both fresh air 44 and circulation air 46 are supplied to the vehicle inner space 14. A desired ratio of fresh air 44 and circulation air 46 in the air 22 supplied to the vehicle inner space 14 can in this instance be adjusted with little complexity via the first flaps 74, 76.

Figure 7 shows a cut-out of the vehicle air conditioner 12 according to Figure 6 in heating mode. The second waste air flap 80 is in this instance (partially) open so that a portion of the circulation air 46 is supplied as waste air 38 to the second waste air duct 72 and the remaining circulation air 46 is again supplied to the vehicle inner space 14 via the blower 42 and the first condenser 20. As a result of the evaporator 28 which is arranged upstream of the second waste air duct 72, however, there is removed from all of the circulation air 46, that is to say, in particular also the waste air 38 which is subsequently discharged via the waste air duct 36 to the vehicle environment 40, thermal energy which is subsequently used again in the first condenser 20 to heat the air 22 supplied to the vehicle inner space 14. Consequently, in the heating mode of the vehicle air conditioner 12 the thermal energy losses as a result of the waste air 38 are minimized.

Figures 8 to 12 show the cut-out 50 of the vehicle air conditioner 12 indicated in Figure 1 according to another alternative embodiment. The blower 42 is located in this instance in a similar manner to the embodiment according to Figures 6 and 7 downstream of the condenser 28.

In contrast to the previous embodiments, in this embodiment two evaporator flaps 82, 84 are provided to adjust an air flow direction inside the evaporator 28. In this instance, these evaporator flaps 82, 84 are controlled in such a manner that the evaporator 28 in the heating mode of the vehicle air conditioner 12 according to Figures 8 to 10 is flowed through in a first direction (from right to left) and at least in mixed air operation of the cooling mode of the vehicle air conditioner 12 according to Figure 12 in a second direction counter to the first direction (from left to right) .

The vehicle air conditioner 12 which is operated in Figures 8 to 10 as a thermal pump is according to Figure 8 in "pure fresh air operation", according to Figure 9 is in mixed air operation and according to Figure 10 is in "pure circulation air operation".

In pure circulation air operation, fresh air 44 is exclusively supplied to the vehicle inner space 14. The waste air 38 which is guided from the vehicle inner space 14 via the waste air duct 36 into the vehicle environment 40 first flows through the evaporator 28 for energy recovery so that particularly energy- efficient fresh air operation is produced.

In mixed air operation, both fresh air 44 and circulation air 46 are supplied to the blower 42. After flowing through the evaporator 28, the "excess" circulation air 46 is directed as waste air 38 via the waste air duct 36 into the vehicle environment 40 so that energy recovery also takes place during mixed air operation . During pure circulation air operation, there is no air exchange between the vehicle inner space 14 and the vehicle environment 40 so that there are no thermal energy losses produced at all. However, this pure circulation air operation is susceptible to window misting in the vehicle inner space 14.

According to Figures 11 and 12, the vehicle air conditioner 12 is in cooling mode, wherein Figure 11 illustrates a "pure circulation air operation" and Figure 12 illustrates a mixed air operation.