DE102010051976B4 - Air conditioning for a motor vehicle - Google Patents

Abstract

Air conditioning system for a motor vehicle, which heats a supply air (I) flowing in the vehicle interior (2) by means of a heating heat exchanger (26), which is thermally coupled via a coolant circuit (K) to a drive unit (24), in particular an internal combustion engine which air conditioning unit has a condenser unit (7, 8) connected in the refrigerant circuit, from which a first condenser (7) is coupled to the coolant circuit (K) as refrigerant-refrigerant heat exchanger and delivers heat to the coolant circuit (K) during heating operation, wherein the condenser unit (7, 8) has at least one downstream second condenser (8) which emits heat to the supply air (I) flowing into the vehicle interior (2) during heating operation and preheats this before the flow through the heating heat exchanger (26), characterized in that the second condenser (8) is a refrigerant-refrigerant heat exchanger operating in the heating mode b heat via an intermediate circuit (39) to a second heating heat exchanger (40) emits, which can be flowed through by the supply air (I), which second heating heat exchanger (40) in particular within the air conditioner (9) is arranged.

Description

The invention relates to an air conditioner for a motor vehicle according to the preamble of claim 1.

In vehicles with modern drive units, only a reduced amount of waste heat is available, with which the vehicle interior can be heated via the engine cooling circuit. This results in particular at low ambient temperatures and in the starting phase of the drive unit, the problem that the heat demand of the vehicle occupants is no longer met by the waste heat of the drive unit alone.

From the DE 101 23 830 A1 Therefore, an air conditioner for a motor vehicle is known, which can not only cool the vehicle interior in cooling mode, but can additionally support the heating of the vehicle interior in a heating operation, provided that the waste heat generated in the drive unit is not sufficient. The air conditioner has a heating heat exchanger through which the incoming air flowing into the vehicle interior is heated. The heating heat exchanger is thermally coupled via a coolant circuit with an internal combustion engine. In addition, the air conditioning in the refrigerant circuit on a coupling heat exchanger and an internal heat exchanger. In heating mode, the coupling heat exchanger works as a condenser, which additionally injects heat into the coolant circuit. The heat exchanger downstream of the coupling heat exchanger on the inner side also transfers heat from the high pressure side of the refrigerant circuit to the low pressure side. In the low pressure side of the refrigerant circuit, an evaporator is connected, which is flowed through together with the heating heat exchanger in the air conditioner of supply air flowing into the vehicle interior.

As mentioned above works in the DE 101 23 830 A1 the coupling heat exchanger in heating mode as a capacitor. The arranged outside the air conditioner condenser does not heat the supply air directly, but with the interposition of the coolant circuit and the heat exchanger. Such an arrangement of the condenser outside the air conditioner is advantageous in terms of safety aspects, but reduces the efficiency of the air conditioner compared to a directly air-condenser arranged in the air conditioner.

From the DE 198 18 649 A1 is a generic vehicle air conditioning known. This has a refrigerant circuit, consisting of a condenser, an expansion element, an evaporator, a compressor and a bypass line bypassing the co-efficient and a bypass valve with which the bypass line can be opened or closed. The air conditioning system is designed so that it can be used when the vehicle is cold starting for faster heating of the engine and the vehicle interior. From the DE 103 17 875 A1 Another vehicle air conditioning system with an ejector cooling cycle is known. With the air conditioning, the heating power for the vehicle interior is improved. From the US 2005/0133215 A1 , from the DE 10 2007 011 024 A1 and from the JP H 11-286 211 A Further air conditioning systems for motor vehicles are known.

The object of the invention is to provide an air conditioning system for a vehicle in which the heating operation can be carried out with increased efficiency compared to the prior art.

The object is solved by the features of claim 1. Preferred embodiments of the invention are disclosed in the subclaims.

According to claim 1, the first capacitor or the above-mentioned coupling heat exchanger part of a capacitor unit having at least one downstream, second capacitor. In the heating mode of the air conditioning system, this second condenser can emit heat directly or indirectly to the incoming air flowing into the vehicle interior. As a result, the supply air is preheated before flowing through the heating heat exchanger. The temperature level of the supply air is therefore higher upstream of the heat exchanger than in conventional design, whereby the efficiency and performance of the air conditioner can be increased. Further successive capacitor stages can increase this efficiency even further.

With regard to an increase in the performance of the air conditioning system and a perfect control quality of the air conditioning system, it is preferred if the coolant circuit is divided into a high-temperature circuit and a low-temperature circuit. In this way, optionally decoupled from the low-temperature circuit, the heat emitted from the first capacitor via the high-temperature circuit, that is, at a high temperature level, led to the heater core and there converted to the supply air flow. Likewise, if necessary decoupled from the high-temperature circuit, the waste heat of the drive unit can be performed via the low-temperature circuit to the heater core. In terms of circuitry, in this case the heating heat exchanger in the coolant circuit may be connected in parallel to the drive unit and to the first condenser and through corresponding switching elements are each optionally switched to the low and / or high temperature circuit. In this case, the high and low temperature circuits may have a common coolant line, in which in addition to the heating heat exchanger and a coolant circulating pump and corresponding switching valves are provided. The air conditioning system can be designed for a particularly efficient heating operation so that in the first condenser, which is thermally coupled to the coolant circuit, a desuperheating and a partial condensation of the refrigerant can take place. In the refrigerant side downstream second condenser can also be a partial condensation and a subcooling of the refrigerant take place. The term "supersheating" is understood to mean the cooling of the refrigerant from the superheated gas zone until reaching the dew point of a Mollier diagram, while the condensation of the refrigerant takes place in the wet steam zone of the Mollier diagram and the undercooling takes place with fully condensed refrigerant.

In order to carry out the heating operation of the air conditioner with high efficiency, it is necessary that the heat dissipation of the first capacitor and the heat output of the second condenser is meaningfully divided into the two capacitors. Against this background, the coolant circuit may have an electric heater, which may optionally heat the coolant to a certain temperature level. By suitable control interventions of the auxiliary heater, a transferable from the first capacitor to the coolant circuit heat output can be limited.

It is preferred if, depending on the heat demand of the vehicle occupants, the second capacitor may be shut down in the heating mode of the air conditioner, so that heat can be supplied only via the first condenser, the coolant circuit and the heating heat exchanger of the supply air flow. In this case, preheating the supply air upstream of the heating heat exchanger is dispensed with. For deactivating the second heat exchanger, the refrigerant circuit may have a bypass line connected in parallel with the second condenser. By means of the bypass line, the second capacitor can be shut down by driving according to the switching valves. The heating operation with shut-down second condenser is particularly advantageous in an interior heating in the recirculation mode, in which the already located in the vehicle interior air is circulated in a substantially closed recirculation circuit. In this case, the heat pump circuit is based solely on the first capacitor, so that the air conditioner can be operated with reduced power.

The evaporation process in the refrigerant circuit can also be multi-stage or single-stage. For this purpose, the refrigerant circuit to an evaporator unit, which has at least one, arranged in the flow direction of the supply air in front of the heating heat exchanger first evaporator. Alternatively or additionally, the evaporator unit may have a second evaporator coupled to a battery cooling circuit and / or a third evaporator coupled to the cooling circuit. These evaporators are preferably arranged in parallel connection in the refrigerant circuit. They can therefore be switched on or off as desired depending on the required cooling capacity in the cooling process.

According to the invention, the second condenser is a refrigerant-coolant heat exchanger. This is fluidically decoupled from the supply air and can be thermally coupled via an intermediate circuit with a second heating heat exchanger, which is flowed through by the supply air. The second heating heat exchanger, as well as the first heating heat exchanger, be arranged directly in the air conditioner. In this case, only the evaporator of the refrigerant circuit and the heat exchanger connected in the coolant circuit are arranged with the second heat exchanger in the air conditioner. By contrast, the first and second capacitors are provided as components flowing through the refrigerant outside the air conditioning unit, which is preferred for safety reasons.

In the event that the second heat exchanger or the second capacitor is provided outside of the air conditioner, any commercial air conditioner can be installed in the air conditioning. Such a commercial air conditioner is usually constructed only of an evaporator and a heat exchanger. It must therefore be connected to the coolant and refrigerant circuits when installing the air conditioner only the inlets and outlets of the evaporator and the inlets and outlets of the heating heat exchanger.

Hereinafter, an embodiment of the invention with reference to the accompanying figures will be described.

Show it:

1 the circuit of an air conditioning system of a motor vehicle when performing the heating operation according to a comparative example not included in the invention;

2 the heat pump process in the heating mode of the air conditioner in a ph diagram;

3 in a view corresponding to 1 the air conditioner when performing a cooling operation; and

4 in a view corresponding to 1 an air conditioner according to the embodiment.

In the 1 An air conditioning system of the motor vehicle is shown by means of the vehicle interior 2 can be cooled or heated. In the 1 is the heating operation for heating the vehicle interior 2 represented, wherein the parts through which refrigerant flows are highlighted by thick lines compared to the shut down in the heating mode parts. As a result, the refrigerant from a compressor 3 via a 3/2-way valve 4 in a first high pressure line 6 led to a first capacitor 7 runs. The first capacitor 7 is in the 1 as a refrigerant-refrigerant heat exchanger, which is thermally coupled with a refrigerant circuit K described later. The first capacitor 7 is according to the 1 outside of a dashed line indicated air conditioner 9 arranged in which the in the vehicle interior 2 Guided supply air I is conditioned. The first capacitor 7 is in series a second capacitor 8th downstream of which the coolant in a high-pressure side manifold 10 to be led. From the high pressure side manifold 10 branches over sub-pipes 11 . 12 . 13 one in each air conditioner 9 arranged evaporator 15 as well as heat exchangers 16 . 17 , ie chillers, which are arranged in parallel and in each case with the supply air I, a battery cooling circuit 18 a driving battery 19 and are thermally coupled to the coolant circuit K. Both the evaporator 15 as well as the two heat exchangers 16 and 17 are each expansion valves 20 . 21 . 22 upstream with shut-off function. Depending on the switching position of these expansion valves are the evaporator 15 and / or the heat exchanger 16 . 17 switched or deactivated in any combination in the refrigerant circuit.

The heat exchanger 16 . 17 as well as the evaporator 15 are downstream with a low pressure side manifold 23 connected to the refrigerant to the suction side of the compressor 3 leads.

The coolant circuit K of the air conditioner is in accordance with 1 divided into a high-temperature circuit K _HT and a low-temperature circuit K _NT . The first capacitor connected in the high-temperature circuit K _HT 7 flows in the countercurrent principle on the one hand by the coolant and on the other hand by the refrigerant. In contrast, the coolant guided in the low-temperature circuit K _NT flows through the internal combustion engine 24 of the motor vehicle. The two pitch circles K _HT , K _{NT of} the coolant circuit K are connected via a common coolant line 25 interconnected. In the joint management 25 is according to the 1 a heating heat exchanger 26 and an electric heater 27 and a circulation pump 28 connected. The common line is at branch points 29 . 30 Via 3/2-way valves with the low temperature or high temperature circuit K _NT , K _HT connectable.

Like from the 1 shows, is the heater core 26 together with the evaporator 15 within the air-flow unit 9 arranged while the second capacitor 8th Although in the supply air I, but safety advantage outside the air conditioner 9 is arranged. The so-constructed air conditioner 9 So it is of a conventional nature, so that any commercially available air conditioners can be installed in the air conditioning.

The in the 1 shown air conditioning is designed such that in the first capacitor 7 a desuperheating E and a partial condensation K1 of the refrigerant takes place, whereby in the high-temperature circuit K _HT a very high temperature level is reached in the coolant. In contrast, takes place in the downstream second capacitor 8th the remaining condensation K2 of the still partially gaseous refrigerant takes place and a subcooling of the fully condensed refrigerant is performed. For illustration is in the 2 the heat pump process is shown in a ph diagram in which the process steps of desuperheating E, condensation K1, K2, and subcooling U are shown. Accordingly, the desuperheating E, ie the cooling from the superheated gas area to the dew line, as well as a taking place in the wet steam partial condensation K1 in the first capacitor 7 instead, while the remaining partial condensation K2 and the subcooling U in the second capacitor 8th takes place.

Thus, the above process steps E, K1, K2 and U in the mentioned sequence in the two capacitors 7 . 8th It can be done by the capacitor 7 limit the maximum heat output to be delivered. For this purpose, by means of the switched in the coolant circuit K auxiliary heater 27 a temperature level of the coolant are raised, resulting in a predetermined driving temperature difference in the heater core 7 between the refrigerant and the coolant. In this way, the in the capacitor 7 limited heat output and maintained according to the highest possible temperature level in the coolant circuit. This is done at low coolant volume flow by activating the auxiliary heater 27 without the overall performance of the air conditioning suffers. Otherwise, the control of the air conditioning is done via the performance of the compressor 3 and via the mass flow of the capacitor which can be adjusted by means of switching valves 7 ,

If necessary, on the electric heater 27 be waived. It is also energetically favorable when the heater 27 not in the common line 25 but in the battery circuit 18 is arranged.

In the 3 the air conditioning system is shown in the cooling mode, with the parts through which the refrigerant flows are highlighted by thick lines. As a result, the refrigerant from the compressor 3 via the 3/2-way valve 4 in a vehicle front side gas cooler 36 and from there via an accumulator 41 in the high pressure side manifold 10 , Subsequently, the refrigerant through the expansion device 20 to the evaporator 15 of the air conditioner 9 and back to the compressor via the suction side 3 be directed. This results in an interior cooling.

If a control device, not shown here requests an interior cooling and at the same time a battery cooling, the refrigerant is additionally on the high pressure side via the expansion valve 22 and the heat exchanger 17 directed to the low pressure side. The heat of the coolant from the battery circuit 18 is absorbed by evaporation of the refrigerant. In this circuit, alternatively or additionally, the valve 21 and the coupled with the coolant circuit K heat exchanger 16 flows through and thus a motor cooling are performed.

Like from the 1 and 3 further is apparent to the second capacitor 8th a bypass line 37 assigned to the capacitor in parallel 8th is switched. Depending on the switching position of the switching valve 38 can thus in the heating mode, the refrigerant through the bypass line 37 on the second capacitor 8th flow past while the condenser 8th is shut down. This is particularly advantageous in a recirculation mode of air conditioning. In this case, namely, the heat pump cycle alone on the capacitor 7 support, whereby the heat pump can be operated with reduced power.

In the 4 is shown an air conditioner according to the embodiment, which is substantially identical to that in the 1 shown air conditioning is. Therefore, the description of the 1 Referenced. In contrast to 1 is in the 4 the second capacitor 8th not arranged as a refrigerant supply air heat exchanger directly in the supply air flow I, but designed as a refrigerant-refrigerant heat exchanger. The capacitor 8th is therefore outside the air conditioner 9 as well as fluidically decoupled from the supply air I arranged. According to the 4 is the capacitor 8th via a DC link 39 with a second heating heat exchanger 40 thermally coupled. In this case, therefore, neither the first capacitor 7 still the second capacitor 8th arranged directly in the supply air I, which is advantageous in terms of safety aspects.

Claims (11)

Air conditioning system for a motor vehicle which, in a heating operation, is installed in the vehicle interior ( 2 ) flowing supply air (I) by means of a heating heat exchanger ( 26 ), which via a coolant circuit (K) with a drive unit ( 24 ), in particular an internal combustion engine, is thermally coupled, which air conditioning system has a condenser unit connected in the refrigerant circuit ( 7 . 8th ), from which a first capacitor ( 7 ) is coupled as refrigerant refrigerant heat exchanger with the coolant circuit (K) and emits heat in the heating operation to the coolant circuit (K), wherein the capacitor unit ( 7 . 8th ) at least one downstream second capacitor ( 8th ), the heat in the heating operation to the in the vehicle interior ( 2 ) emits flowing supply air (I) and this before the flow through the heating heat exchanger ( 26 ) preheated, characterized in that the second capacitor ( 8th ) is a refrigerant-coolant heat exchanger, the heat in the heating operation via a DC link ( 39 ) to a second heating heat exchanger ( 40 ), which can be flowed through by the supply air (I), which second heating heat exchanger ( 40 ), in particular within the air conditioning unit ( 9 ) is arranged. Air conditioning system according to Claim 1, characterized in that the coolant circuit (K) has a high-temperature circuit (K _HT ) which corresponds to that of the first capacitor ( 7 ) emitted heat the heater core ( 26 ) feeds. Air conditioning system according to claim 1 or 2, characterized in that the coolant circuit (K) has a low-temperature circuit (K _NT ), the waste heat of the drive unit ( 24 ) the heating heat exchanger ( 26 ), wherein in particular the heating heat exchanger ( 26 ) in the coolant circuit (K) parallel to the drive unit ( 24 ) and the first capacitor ( 7 ) is switched. Air conditioner according to claim 1, 2 or 3, characterized in that in the first condenser ( 7 ) a desuperheating (E) and an at least partial condensation (K1) of the refrigerant, and in the second capacitor ( 8th ) a partial condensation (K2) and a subcooling (U) of the refrigerant takes place. Air conditioning system according to one of the preceding claims, characterized in that the coolant circuit (K) an electric heater ( 27 ), with the in heating operation, a temperature level in the coolant circuit (K) for adjustment one from the first capacitor ( 7 ) can be specified on the coolant circuit (K) transferable heat output. Air conditioning system according to one of the preceding claims, characterized in that the refrigerant circuit is parallel to the second capacitor ( 8th ) bypass line ( 37 ), by means of the in heating operation, in particular in a Umluftheizbetrieb, the second capacitor ( 8th ) is deactivated. Air conditioning system according to one of the preceding claims, characterized in that the refrigerant circuit is an evaporator unit ( 15 . 16 . 17 ), one in a flow direction of the supply air (I) in front of the heating heat exchanger ( 26 ) arranged first evaporator ( 15 ), one with a battery cooling circuit ( 18 ) coupled second evaporator ( 17 ) and / or with the cooling circuit (K) coupled to the third evaporator ( 16 ) having. Air conditioning system according to claim 7, characterized in that the evaporators ( 15 . 16 . 17 ) are arranged in parallel in the refrigerant circuit. Air conditioning system according to one of the preceding claims, characterized in that the second capacitor ( 8th ) is a refrigerant supply air heat exchanger, which within an air conditioner ( 9 ) in the vehicle interior ( 2 ) incoming air (I) conditioned, arranged and by the supply air (I) can be flowed through. Air conditioning system according to one of the preceding claims, characterized in that the second heating heat exchanger ( 40 ) upstream of the first heating heat exchanger ( 26 ) is arranged. Air conditioning system according to one of the preceding claims, characterized in that the air conditioning system is an air-flow conditioned air conditioner ( 9 ), in which only the heating heat exchanger ( 26 ) and the evaporator unit ( 15 . 16 . 17 ) of the refrigerant circuit are arranged, while the second capacitor ( 8th ) and / or the second heating heat exchanger ( 40 ) outside the air conditioner ( 9 ) are arranged.

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