DE102016001096A1 - Method for operating a vehicle refrigeration system - Google Patents

Abstract

The invention relates to a method for operating a vehicle refrigeration system with a refrigerant circuit (1), which as components at least one evaporator (2), a refrigerant compressor (3), a refrigerant condenser (4) or a gas cooler (4) and the evaporator ( 2) associated with and electrically controllable by a control device expansion element (5) having a variable valve cross-sectional area. According to the invention, the vehicle refrigeration system is operated at maximum permissible high pressure (HDzul) at the maximum power at a maximum requested cooling capacity to achieve a target air temperature (Tsoll) after the compressor (3) and then upon reaching the target air temperature (Tsoll) the valve cross-sectional area of the expansion organ ( 5) to an optimum high pressure (HDopt) at the outlet of the refrigerant condenser or gas cooler (4) while maintaining the target air temperature (Tsoll) regulated.

Description

The invention relates to a method for operating a vehicle refrigeration system. Furthermore, the invention relates to a vehicle refrigeration system for carrying out the method according to the invention and to a vehicle having such a vehicle refrigeration system.

Vehicle air conditioning systems are known from the prior art and serve to provide the interior or the passenger compartment of a vehicle with a supply air flow at a predetermined temperature. The air conditioner of such a vehicle air conditioning system is the actual ventilation system of the passenger compartment and includes a fan provided with a suction duct, via which air, for example. Fresh air from outside the vehicle via an evaporator and / or a heat exchanger by means of the blower sucked into the passenger compartment.

The regulation of such a vehicle air conditioning system is carried out by a climate control device which controls the components of the vehicle air conditioning system as a function of predetermined operating parameters, such as the setpoint value of the temperature set by an occupant via an operating element and the actual value of the temperature of the passenger compartment.

In today's vehicle refrigeration systems as a subgroup of vehicle air conditioning expansion organs or expansion valves are used, which are mainly mechanically adjusted or regulated. This applies in particular to the expander of the interior evaporator, which as Orifice Tube (fixed throttle with a fixed flow opening), Orifice Bypass (fixed throttle with a bypass, which opens to catch pressure peaks depending on the absolute value of the high pressure) or as a TXV (thermal expansion device) executed are.

A vehicle air conditioning system having a refrigerant circuit, which has as components at least one evaporator, a controllable refrigerant compressor with variable displacement, a refrigerant condenser or gas cooler and an evaporator associated and electrically controllable by a control device electrical expansion valve with a variable valve opening, is from the DE 199 17 048 A1 known. In this designed as R744 (CO ₂ -) circuit transcritical refrigerant circuit, the refrigerant flow capacity of the refrigerant compressor is monitored and regulated by the variation of the opening of the expansion valve depending on the refrigerant temperature on the outlet side of the refrigerant condenser or gas cooler, the high pressure at the outlet of the heat exchanger.

With such an externally controllable electrical expansion element for an R744 refrigeration system, the operating points of a vehicle air conditioning system can be adjusted so that the refrigerant circuit is operated for all operating points in optimum efficiency.

In vehicle refrigeration systems with high ambient temperatures and long downtimes of the vehicle, a rapid cooling (pull down) of the vehicle interior should be achieved, in which case the refrigerant pressure of R744 may increase to very high values depending on the ambient temperature.

So is out of the DE 2008 014 196 A1 a method for controlling a vehicle refrigeration system with R744 known as refrigerant. This vehicle refrigeration system comprises a compressor, a gas cooler, an expansion element which limits the pressure on the high-pressure side to a maximum permissible pressure, an evaporator and a fan which supplies a temperature-controlled air mass flow to the interior via the evaporator. In this known method, it is provided to reduce the air mass flow flowing through the evaporator when the vehicle is restarted and when a maximum cooling capacity requirement is demanded, for example to 10% of the maximum air mass flow. In a subsequent step, the air mass flow is kept constant until the pressure on the high-pressure side is below the maximum permissible pressure and / or the compressor is activated to the maximum. Subsequently, the air mass flow is increased until the pressure on the high pressure side has reached the maximum allowable pressure again. The sequence of steps "Constant maintenance of the air mass flow until the pressure on the high pressure side falls below the maximum permissible pressure" and "Increasing the air mass flow until the pressure on the high pressure side has reached the maximum permissible pressure" is repeated several times. The control with respect to the incremental increase of the air mass flow is terminated when the maximum air mass flow through the evaporator and taken over by the conventional series control of the refrigeration system.

Such a regulation of the air mass flow according to the DE 10 2008 014 196 A1 allows the use of a differential pressure controlled expansion device in the refrigerant circuit. Furthermore, a rapid cooling of the vehicle interior to be achieved with this known method.

It is therefore an object of the invention to provide an improved method for controlling an electrical expansion element of a vehicle Specify refrigeration system with which, on the one hand, an efficiency-optimized operation of the refrigeration system and on the other hand when requesting maximum cooling capacity, a rapid cooling, especially at high ambient temperature is achieved.

This object is achieved by a method having the features of patent claim 1 and the features of claim 2.

• a) Regelung der Ventil-Querschnittsfläche des Expansionsorgans zunächst auf einen einen energieeffizienten Betrieb bewirkenden optimalen Hochdruck und anschließend auf einen schrittweise in Richtung auf einen maximal zulässigen Hochdruck am Ausgang des Kältemittelkondensators oder Gaskühlers erhöhten Hochdruck und Halten auf dem Niveau des maximal zulässigen Hochdruckes solange, bis die Ziellufttemperatur erreicht wird,
• b) Regelung der Ventil-Querschnittsfläche des Expansionsorgans auf den zuletzt eingeregelten Hochdruckwert am Ausgang des Kältemittelkondensators oder Gaskühlers und Steuerung des Kältemittelverdichters von einer bei dem zuletzt eingeregelten Hochdruckwert geförderten aktuellen Fördermenge auf eine reduzierte Fördermenge, solange die Ziellufttemperatur eingehalten wird,
• c) Regelung der Ventil-Querschnittsfläche des Expansionsorgans in Richtung auf einen einen energieeffizienten Betrieb bewirkenden optimalen Hochdruck am Ausgang des Kältemittelkondensators oder Gaskühlers, indem entweder die Ventil-Querschnittsfläche erhöht wird, solange die Temperatur nach dem Kältemittelverdampfer der Ziellufttemperatur entspricht oder diese unterschreitet, oder die Ventil-Querschnittsfläche reduziert wird, solange die Temperatur nach dem Kältemittelverdampfer die Ziellufttemperatur überschreitet.

Such a method for operating a vehicle refrigeration system having a refrigerant circuit which has as components at least one evaporator, a refrigerant compressor, a refrigerant condenser or a gas cooler and an evaporator associated and electrically controllable by a control device expansion element with a variable valve cross-sectional area is characterized according to the first-mentioned solution, by the following method steps being carried out at a maximum requested cooling capacity to achieve a target air temperature downstream of the evaporator:

• a) control of the valve cross-sectional area of the expansion device initially to an energy-efficient operation causing optimum high pressure and then to a stepwise towards a maximum allowable high pressure at the outlet of the refrigerant condenser or gas cooler increased high pressure and holding at the level of the maximum allowable high pressure until, until the target air temperature is reached,
• b) regulation of the valve cross-sectional area of the expansion device to the last-adjusted high-pressure value at the outlet of the refrigerant condenser or gas cooler and control of the refrigerant compressor from a current delivered at the last-adjusted high pressure value current delivery to a reduced flow rate, as long as the target air temperature is maintained,
• c) Regulation of the valve cross-sectional area of the expansion device towards an energy-efficient operation causing optimum high pressure at the outlet of the refrigerant condenser or gas cooler by either the valve cross-sectional area is increased, as long as the temperature after the refrigerant evaporator or the target air temperature is lower than, or Valve cross-sectional area is reduced as long as the temperature after the refrigerant evaporator exceeds the target air temperature.

In the second-mentioned case, an increase in the high pressure and thus, as a rule, an exceeding of the optimum high pressure is effected in order to be able to set a desired outlet temperature.

Due to the pressure losses occurring in the system, the maximum permissible high pressure downstream of the gas cooler is primarily capped or limited in advance by the maximum permissible high pressure downstream of the compressor.

Alternatively, instead of referencing a directly measured air temperature downstream of the evaporator, an indirect method coupled to the low pressure for adjusting a target air temperature may also be used. Ideally, the evaporation pressure of the refrigerant is coupled to an evaporation temperature, which in turn sets a corresponding air temperature.

• a) Einstellung der Ventil-Querschnittsfläche des Expansionsorgans auf einen definierten Startquerschnitt und anschließend auf einen schrittweise in Richtung auf einen maximal zulässigen Hochdruck am Ausgang des Kältemittelkondensators oder Gaskühlers erhöhten Hochdruck und Halten auf dem Niveau des maximal zulässigen Hochdruckes solange, bis die Ziellufttemperatur erreicht wird,
• b) Regelung der Ventil-Querschnittsfläche des Expansionsorgans auf den zuletzt eingeregelten Hochdruckwert am Ausgang des Kältemittelkondensators oder Gaskühlers und Steuerung des Kältemittelverdichters von einer bei dem zuletzt eingeregelten Hochdruckwert geförderten aktuellen Fördermenge auf eine reduzierte Fördermenge, solange die Ziellufttemperatur eingehalten wird,
• c) Regelung der Ventil-Querschnittsfläche des Expansionsorgans in Richtung auf einen einen energieeffizienten Betrieb bewirkenden optimalen Hochdruck am Ausgang des Kältemittelkondensators oder Gaskühlers, indem entweder die Ventil-Querschnittsfläche erhöht wird, solange die Temperatur nach dem Kältemittelverdampfer der Ziellufttemperatur entspricht oder diese unterschreitet, oder die Ventil-Querschnittsfläche reduziert wird, solange die Temperatur nach dem Kältemittelverdampfer die Ziellufttemperatur überschreitet.

The method according to the second-mentioned solution is characterized in that the following method steps are performed at a maximum requested cooling capacity to achieve a target air temperature after the evaporator:

• a) adjustment of the valve cross-sectional area of the expansion device to a defined starting cross-section and then to a stepwise towards a maximum allowable high pressure at the outlet of the refrigerant condenser or gas cooler increased high pressure and holding at the level of the maximum allowable high pressure until the target air temperature is reached,
• b) regulation of the valve cross-sectional area of the expansion device to the last-adjusted high-pressure value at the outlet of the refrigerant condenser or gas cooler and control of the refrigerant compressor from a current delivered at the last-adjusted high pressure value current delivery to a reduced flow rate, as long as the target air temperature is maintained,
• c) Regulation of the valve cross-sectional area of the expansion device towards an energy-efficient operation causing optimum high pressure at the outlet of the refrigerant condenser or gas cooler by either the valve cross-sectional area is increased, as long as the temperature after the refrigerant evaporator or the target air temperature is lower than, or Valve cross-sectional area is reduced as long as the temperature after the refrigerant evaporator exceeds the target air temperature.

In the second case, this causes an increase in the high pressure and thus, as a rule, an exceeding of the optimum high pressure in order to be able to set a desired outlet temperature.

These methods according to the invention are characterized by a 2-stage control strategy. In a first stage, the vehicle refrigeration system is operated at maximum power. This means that in pull-down mode, after the system has started up and reaching the required boundary conditions, the cross-section of the electrical expansion element is throttled so far that the maximum and permanently possible system working pressure, which corresponds to the maximum permissible working pressure, adjusts at the outlet of the refrigerant condenser or gas cooler The following maximum permitted high pressure, which occurs at the outlet of the refrigerant compressor. Therefore, in parallel, always monitor the pressure at the outlet of the compressor, which indicates the working pressure limits of the system. Thus, this refrigeration system is operated at maximum pressure ratio of high pressure to low pressure, so that the low pressure and the resulting required for the pull-down operation and set target air temperature after the evaporator can be achieved in the shortest possible time.

When the target air temperature is reached, the second stage of the control strategy according to the invention begins. Achieving the target air temperature usually means that the refrigerant compressor is no longer operated at its possible then reached for this operating point flow, but is controlled by a controller of a climate control unit while maintaining the target air temperature to a lower flow rate. This is equivalent to a Hubreduktion or lowering the operating speed of the refrigerant compressor.

In this operating state of the refrigerant compressor, the second stage of the control strategy according to the invention can be initiated by the valve cross-sectional area is successively increased to set the optimal high pressure at the outlet of the refrigerant condenser or gas cooler, which is usually well below the maximum and permanently possible high pressure at the outlet of the refrigerant compressor or at the outlet of the refrigerant condenser or the gas cooler. The gradual reduction of the high pressure at the outlet of the refrigerant condenser or gas cooler, and thus of the entire system, is carried out until the optimum high pressure is reached. Subsequently, the vehicle refrigeration system is operated at optimal high pressure in system operation and simultaneous fulfillment of the requested target air temperature by appropriate regulation of the refrigerant compressor.

Thus, in the second stage of the method according to the invention, the system operation of the vehicle refrigeration system leading to the target air temperature with maximum and permanently possible high pressure is switched to an efficiency-optimized system operation in a stepwise approach.

In this case, efficiency-optimized operation means that the vehicle refrigeration system is to be adjusted via said expansion element to a value taken from a characteristic of a COP diagram value for the outlet to be controlled at the outlet of the condenser or the gas cooler, depending on the refrigerant temperature at the outlet of the condenser or the gas cooler, which corresponds directly to the ambient temperature with ideal heat transfer, recorded characteristics of the COP diagram (see. 3 ) or their mapping rule are stored in a control unit of the vehicle refrigeration system. From this COP diagram after 3 It can be seen that the curves are very flat as efficiency curves at high ambient temperatures and thus outlet temperatures of the refrigerant at the refrigerant condenser or gas cooler, for example. Greater than 35 ° C. Therefore, in the case of the method according to the invention with performance-optimized operation compared to an efficiency-optimized operation, only minor losses occur, which can essentially be neglected.

The maximum allowable high pressure is monitored as the maximum allowable system operating pressure of the refrigeration system or heat pump at the outlet of the refrigerant compressor and not exceeding this maximum allowable system operating pressure by regulating the valve cross-sectional area of the expansion device, but also if necessary by reducing the flow rate of the refrigerant compressor caused by this is controlled accordingly.

The method according to the invention is suitable for implementation in a vehicle refrigeration system or a vehicle air conditioning system. Such a vehicle refrigeration system or vehicle air conditioning system can be used in all vehicle types.

The invention will now be described in detail by means of an embodiment with reference to the accompanying figures. Show it:

1 a circuit diagram of a vehicle refrigeration system for carrying out the method according to the invention,

2 a flowchart for explaining the method according to the invention, and

3 a COP pressure graph with COP characteristics for supercritical operation of an R744 refrigeration system.

The 1 shows a refrigerant circuit 1 a vehicle refrigeration system consisting of an evaporator 2 , a refrigerant compressor 3 , a refrigerant condenser or gas cooler 4 , one to the evaporator 2 in the flow direction of an R744 refrigerant upstream expansion device 5 one internal heat exchanger 7 and a refrigerant collector 8th is constructed.

In the refrigerant circuit 1 according to 1 is that the evaporator 2 upstream expansion organ 5 designed as an electric expansion valve with a variable valve cross-sectional area, which by means of a control unit 6 is controlled.

The electric expansion organ 5 is dependent on pressure and temperature values from the controller 6 controlled and regulated, these pressure and temperature values of pressure-temperature sensors pT1, pT2 and pT3 are detected and the actual value of the valve opening cross-section of the control unit 6 is transmitted. The pressure-temperature sensor pT1 is on the high-pressure side in the flow direction of the refrigerant after the compressor 3 , the pressure-temperature sensor pT2 in the flow direction of the refrigerant after the condenser or gas cooler 4 and the pressure-temperature sensor pT3 flow direction of the refrigerant after the refrigerant collector 8th in the refrigerant circuit 1 arranged. The ambient temperature is detected by means of a temperature sensor T_Um and also the control unit 6 fed.

In refrigeration system operation of the refrigerant circuit 1 of the 1 becomes that of the refrigerant compressor 3 compressed refrigerant via the arranged in the front of the vehicle refrigerant condenser 4 or gas cooler 4 supplied to the refrigerant condenses or cools before it after a passage through the inner heat exchanger 7 by means of the expansion organ 5 in the evaporator 2 is relaxed. A the evaporator 2 supplied fresh, recirculated air or partial air flow is cooled by the same and fed as supply air flow into a passenger compartment of the vehicle. That in the evaporator 2 evaporated refrigerant is via the refrigerant collector 8th and the internal heat transfer 7 low pressure side back to the compressor 3 fed.

The refrigerant compressor 3 of the refrigerant circuit 1 is designed either as a mechanical refrigerant compressor or as an electrical refrigerant compressor. A mechanical refrigerant compressor is driven via a belt drive connected to the drive motor of the vehicle and differential pressure, mass flow or suction pressure regulated by means of a control current for a compressor control valve of the refrigerant compressor. An electric refrigerant compressor has an internal electric motor as a drive, so that a speed control is possible. In addition, mechanical compressors can be used via an electrically driven and decoupled from the engine belt drive.

Receives the controller 6 a requirement for generating a maximum cooling capacity to reach a target air temperature T _soll after the evaporator 2 will that be based on 2 explained method of the invention by controlling the expansion organ 5 by means of the control unit 6 carried out.

After the start of the method, it is checked in a first method step S1 whether a maximum cooling capacity (pull-down) is requested. If there is such a maximum cooling power requirement, according to a subsequent method step S2 by means of the expansion device 5 the high pressure at the outlet of the condenser or gas cooler 4 adjusted to a maximum allowable high pressure HD as the maximum working pressure of the vehicle refrigeration system.

This is done in two steps by first the valve cross-sectional area of the expansion organ 5 is regulated to an energy-efficient operation causing optimal high pressure HD _opt .

Starting from the optimum high-pressure HD _opt is then in a second step by cross-sectional adaptation of the expansion organ 5 for the output of the refrigerant condenser or gas cooler 4 maximum permitted high pressure HD approached by the target pressure gradually towards the maximum allowable high pressure at the outlet of the refrigerant condenser or gas cooler 4 is increased until the target air temperature T _{soll is} reached or the high pressure is maintained at the level of the maximum allowable high pressure HD until the target air temperature T _{soll is} reached.

Thus, according to method step S2, therefore, the valve cross-sectional area of the expansion element 5 so reduced that yourself. at the outlet of the refrigerant condenser or gas cooler 4 sets a high only slightly below the system high pressure limit HD _max (= maximum continuous system operating pressure) lying high pressure. If this system high pressure limit were 130 bar, taking into account the possible pressure losses from the outlet of the compressor 3 until the outlet of the gas cooler 4 depending on the load case about 5 bar to set, so that from this a value for the maximum allowable high pressure HD _zul of 125 bar at the outlet of the refrigerant condenser or gas cooler 4 results. Thus, by means of the pressure-temperature sensor pT1 directly the maximum high pressure HD _max can be monitored as system operating pressure and via the pressure-temperature sensor pT2 an optimal high pressure HD _opt .

Possible pressure losses are recorded directly by means of the measured values. Should be applied to the Temperature sensor pT2 be waived and only the temperature at the outlet of the refrigerant condenser or gas cooler 4 be detected, so is in the control unit 6 to store a characteristic curve or a map which, depending on the load case, the pressure loss across the refrigerant condenser or gas cooler 4 indicates, especially for the efficiency of the optimal high pressure after the refrigerant condenser or the gas cooler 4 adjust. For purely performance-optimized operation, it is possible to primarily use the pressure value of the pressure-temperature sensor pT1.

The optimum high pressure HD _opt is based on one in the controller 6 stored characteristic field of a pressure COP diagram 3 as a function of an ambient temperature or the outlet temperature of the refrigerant at the outlet of the refrigerant condenser or gas cooler 4 certainly.

This diagram shows an example of the course of COP curves as a function of the ambient or refrigerant temperature in the supercritical operation of an R744 refrigeration system, such as in 1 is shown. Thus, the curve K1 shows the course at 33 ° C, the curve K2 the course at 38 ° C, the curve K3 the course at 43 ° C and the curve K4 the course at 46 ° C.

Analogous to the characteristic field, a calculation rule can alternatively be used. For example, the following empirical relationship is known: HD _opt = T _KM × 2 + 20, wherein HD _opt the value of the optimum high pressure, determined from the double outlet temperature T _{KM of} the refrigerant at the refrigerant condenser or gas cooler 4 added with 20, results.

With the method step S2, the refrigerant circuit 1 operated starting from an initially set HD _opt at maximum pressure ratio of high pressure to low pressure along the system high pressure limit, so that the low pressure and the resulting target air temperature after the evaporator 2 be reached early.

Instead of the method step S2, the method step S2 'can also be carried out. After that, the organ of expansion becomes 5 controlled with a defined starting cross-section and starting therefrom to the maximum allowable high pressure HD _zul at the outlet of the refrigerant condenser or gas cooler 4 regulated by the target pressure gradually towards a maximum allowable high pressure at the outlet of the refrigerant condenser or gas cooler 4 is increased until the target air temperature T _{soll is} reached or the high pressure is maintained at the level of the maximum allowable high pressure HD _zul until the target air temperature T _{soll is} reached.

As a rule, when the target air temperature T _{soll is} reached, the compressor speed is reduced in electric compressors and the control current is reduced in the case of mechanical compressors with mass flow regulation or differential pressure regulation. Therefore, upon reaching the target air temperature T _soll according to the next process step S3, the valve cross-sectional area of the expansion element becomes 5 to the last adjusted high pressure value at the outlet of the refrigerant condenser or gas cooler 4 regulated and the refrigerant compressor 3 controlled by a promoted at the last adjusted high pressure value current delivery to a reduced flow rate, as long as the target air temperature T _is maintained.

With the reduced flow rate of the refrigerant compressor 3 and maintained target air temperature T _soll is in the subsequent process step 4 the valve cross-sectional area of the expansion device 5 in the direction of an energy-efficient operation causing optimal high pressure HD _opt at the outlet of the refrigerant condenser or gas cooler 4 so regulated that, depending on the temperature at the outlet of the gas cooler 4 one according to 3 Optimum high pressure HD _opt sets, which is usually much lower than the permanent pressure operating limits. For a temperature of the refrigerant of, for example. 43 ° C after the gas cooler 4 this would result in a target pressure value of 106 bar. This regulation is such that the valve cross-sectional area is either increased stepwise, as long as the temperature after the refrigerant evaporator 2 the target air temperature T _soll corresponds to or falls below or is reduced, as long as the temperature after the Kältemittelverdiampfer 2 the target air temperature T _{soll is} exceeded.

Thus, the startup of the optimum high-pressure _{HPopt is carried} out starting from the last higher pressure set at the outlet of the refrigerant condenser or gas cooler 4 gradually. It should be noted that the valve cross-sectional area of the expansion organ 5 , taking into account the target outlet temperature of the air after the refrigerant evaporator 3 only as long as can be gradually increased, such as a speed or control current reserve of the refrigerant compressor 3 is given up to a maximum flow rate. Only then is it possible to further increase the valve cross-sectional area.

With the achievement of the optimal high pressure HD _opt maintained by observing the target air temperature T _set is performed in a final process step S5, the transition to a according to process step S4 System operation of the vehicle refrigeration system with optimal high pressure HD _opt at the outlet of the refrigerant condenser or gas cooler 4 according to the characteristics 3 ,

If, after method step S1, no pull-down operation is requested, according to method step S6, the expansion organ 5 from the beginning to an optimal high pressure HD _opt according to the COP characteristics after 3 regulated.

• – Der Kältemittelkreislauf ist auf eine maximale Leistung im Pull-Down-Betrieb ausgerichtet.
• – Bei Erreichen der Ziellufttemperatur nach dem Verdampfer 2 wird der Betrieb des Kältemittelkreislaufs auf einen effizienzoptimierten Betrieb umgestellt.
• – Es wird ein beschleunigtes Erreichen eines Komforttemperaturniveaus für die Fahrzeuginsassen erreicht.
• – Der Abkühlkurvenverlauf verläuft steiler als im Stand der Technik, so dass die kälteren Temperaturen in kürzerer Zeit erreicht werden.
• – Der effizienzoptimierte Betrieb schließt sich nach Erreichen des Komfortniveaus nahtlos an bzw. der Übergang zu diesem erfolgt unmittelbar nach Erreichen der Ziellufttemperatur.
• – Das Potenzial eines elektrischen. Expansionsorgans wird maximal ausgeschöpft und damit optimal genutzt.
• – Bei Hochlast kommt es in dem leistungsoptimierten Betrieb der ersten Regelstufe des erfindungsgemäßen Verfahrens gegenüber dem anschließenden effizienzoptimierten Betrieb nur zu geringen Einbußen, da der Effizienzkurvenverlauf gemäß den COP-Kurven (vgl. 3) bei hohen Temperaturen sich sehr flach darstellt und daher diese Verluste fast zu vernachlässigen sind.

The method according to the invention has the following advantages:

• - The refrigerant circuit is designed for maximum performance in pull-down mode.
• - When reaching the target air temperature after the evaporator 2 The operation of the refrigerant circuit is switched to an efficiency-optimized operation.
• - Accelerated achievement of a comfort temperature level for the vehicle occupants is achieved.
• - The cooling curve is steeper than in the prior art, so that the colder temperatures are reached in less time.
• - The efficiency-optimized operation joins seamlessly after reaching the comfort level or the transition to this occurs immediately after reaching the target air temperature.
• - The potential of an electric. Expansionsorgans is maximally exhausted and thus optimally used.
• - At high load occurs in the performance-optimized operation of the first control stage of the method according to the invention over the subsequent efficiency-optimized operation only small losses, since the efficiency curve course according to the COP curves (see. 3 ) is very flat at high temperatures and therefore these losses are almost negligible.

LIST OF REFERENCE NUMBERS

1

Refrigerant circulation

2

Evaporator

3

Refrigerant compressor

4

Refrigerant condenser, gas cooler

5

Expansion element, electric expansion valve

6

control unit

7

internal heat exchanger

8th

Refrigerant collector

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 19917048 A1 [0005]
• DE 2008014196 A1 [0008]
• DE 102008014196 A1 [0009]

Claims (6)

Method for operating a vehicle refrigeration system with a refrigerant circuit ( 1 ), which as components at least one evaporator ( 2 ), a refrigerant compressor ( 3 ), a refrigerant condenser ( 4 ) or a gas cooler ( 4 ) and the evaporator ( 2 ) and electrically actuated by means of a control device expansible organ ( 5 ) having a variable valve cross-sectional area and at a maximum requested cooling capacity to achieve a target air temperature (T _soll ) after the evaporator ( 2 ) the following process steps are carried out: a) regulation of the valve cross-sectional area of the expansion element ( 5 ) first to an energy-efficient operation causing optimal high pressure (HD _opt ) and then to a stepwise towards a maximum allowable high pressure (HD _zul ) at the output of the refrigerant condenser or gas cooler ( 4 ) increased high pressure and holding at the level of the maximum allowable high pressure (HD _zul ) until the target air temperature (T _soll ) is reached, b) regulation of the valve cross-sectional area of the expansion element ( 5 ) to the last adjusted high pressure value at the outlet of the refrigerant condenser or gas cooler ( 4 ) and control of the refrigerant compressor ( 3 ) from a current delivery rate delivered at the last adjusted high-pressure value to a reduced delivery rate as long as the target air temperature is maintained, c) regulation of the valve cross-sectional area of the expansion element ( 5 ) in the direction of an energy-efficient operation causing optimal high pressure (HD _opt ) at the outlet of the refrigerant condenser or gas cooler ( 4 ) by either the valve cross-sectional area is increased, as long as the temperature after the refrigerant evaporator ( 2 ) of the target air temperature (T _soll ) or falls below this, or the valve cross-sectional area is reduced, as long as the temperature after the refrigerant evaporator ( 2 ) exceeds the target air temperature (T _soll ). Method for operating a vehicle air conditioning system with a refrigerant circuit ( 1 ), which as components at least one evaporator ( 2 ), a refrigerant compressor ( 3 ), a refrigerant condenser ( 4 ) or a gas cooler ( 4 ) and the evaporator ( 2 ) and electrically actuated by means of a control device expansible organ ( 5 ) having a variable valve cross-sectional area and at a maximum requested cooling capacity to achieve a target air temperature after the evaporator ( 2 ) the following method steps are carried out: a) adjustment of the valve cross-sectional area of the expansion element ( 5 ) to a defined starting cross section and then to a stepwise towards a maximum permissible high pressure (HD _perm ) at the outlet of the refrigerant condenser or gas cooler ( 4 ) increased high pressure and holding at the level of the maximum allowable high pressure (HD _zul ) until the target air temperature (T _soll ) is reached, b) regulation of the valve cross-sectional area of the expansion element ( 5 ) to the last adjusted high pressure value at the outlet of the refrigerant condenser or gas cooler ( 4 ) and control of the refrigerant compressor ( 3 ) from a current delivery rate delivered at the last adjusted high-pressure value to a reduced delivery rate as long as the target air temperature is maintained, c) regulation of the valve cross-sectional area of the expansion element ( 5 ) in the direction of an energy-efficient operation causing optimal high pressure (HD _opt ) at the outlet of the refrigerant condenser or gas cooler ( 4 ) by either the valve cross-sectional area is increased, as long as the temperature after the refrigerant evaporator ( 2 ) of the target air temperature (T _soll ) or falls below this, or the valve cross-sectional area is reduced, as long as the temperature after the refrigerant evaporator ( 2 ) exceeds the target air temperature (T _soll ). Method according to Claim 1 or 2, in which, following process step c, the vehicle refrigeration system is operated at an optimum high-pressure at the outlet of the refrigerant condenser or gas cooler ( 4 ) while maintaining the target air temperature (T _soll ) in by controlling the refrigerant compressor ( 3 ) operated system operation is operated. Method according to one of the preceding claims, in which the maximum permissible high pressure (HD _perm ) as the maximum permissible system _operating pressure (HD _max ) at the outlet of the refrigerant compressor ( 3 ) and that this maximum permissible system operating pressure is not exceeded by the regulation of the valve cross-sectional area of the expansion element ( 5 ) or by regulation of the refrigerant compressor ( 3 ) is ensured. Vehicle refrigeration system for carrying out the method according to one of the preceding claims. Vehicle with a vehicle refrigeration system according to claim 5.

Images