EP0640753B1 - Cooling system for an internal combustion engine - Google Patents

Description

The invention relates to a cooling system for an internal combustion engine a motor vehicle with a radiator and a Thermostatic valve with which the temperature of the coolant in a warm-up mode, a mixed mode and one Cooler operation is adjustable, the thermostatic valve contains an expansion element that is used to reduce the Coolant temperature is electrically heated.

The thermostatic valve regulates the flow of the coolant between the internal combustion engine and the radiator such that during the warm-up operation that of the internal combustion engine coming coolants essentially bypassing the cooler through a short circuit to Internal combustion engine flows back that during mixed operation the coolant coming from the internal combustion engine partly through the cooler and partly through flows back through the short circuit to the internal combustion engine and that during cooler operation that from Combustion coolant coming essentially flows back through the cooler to the internal combustion engine. The electrical heating of the expansion element serves to enlarge the opening cross-section to the cooler towards one by the temperature of the coolant conditional opening cross section.

A cooling system according to the preamble of the claim 1 is known for example from DE 30 18 682 A1. At this known cooling system is in an expansion element an electric heating resistor of a thermostatic valve arranged, the electrical energy through a stationary held working piston can be fed through. The feed the electrical energy takes place via a control device, the coolant temperature regulated by the thermostatic valve better than a normal thermostatic valve to be able to keep constant. For this, the Actual coolant temperature measured and with a predetermined upper and with a predetermined lower temperature value compared. If the upper temperature value is reached, so the heating resistor with electrical energy supplied so that the thermostatic valve opens further, to increase the cooling capacity and thus reduce the Actual coolant temperature can be reached. The actual coolant temperature drops then below the lower temperature value, so the supply of electrical energy to that Heating resistor interrupted so that the expansion element is cooled by the colder coolant. This will make the Valve cross section reduced again, so that the actual coolant temperature rises again. These rules games will be constantly repeated to a coolant temperature of for example, to keep 95 ° C as constant as possible.

From US 4,666,081 is a temperature control device for a Cooling system of an internal combustion engine known, by means of a Thermostats basically set the coolant temperature to a predetermined one Normal value is adjusted. During the warm-up of the internal combustion engine the coolant temperature is increased under extreme loads Internal combustion engine, the coolant temperature is reduced. Especially with increased A load reduction of the internal combustion engine has an effect the coolant temperature reducing performance on the internal combustion engine out.

From patent abstract of Japan, No. 454 (M-769) (JP 63183216) also a temperature control device for cooling systems of an internal combustion engine known, by means of an electrically heated Expansion element, the coolant temperature depending on the outside temperature is set. A further control strategy is over not to be inferred from this publication.

DE 37 05 232 A1 describes a temperature control device known in the place of a conventional thermostatic valve with an expansion element by means of a Servomotor adjustable valve is provided. At this Known temperature control device is the servomotor to adjust the valve depending on one Sensor controlled that the coolant temperature in a line connected to the internal combustion engine. Of the The sensor is also equipped with a heating device. The heating device is dependent on map sizes of the internal combustion engine can be switched on and off. In this known temperature control device can accordingly by heating the sensor higher than the real one Coolant temperature can be faked to an increased To generate cooling of the coolant. Such Temperature control device is constructively special complex and therefore costly.

The invention has for its object a cooling system of the type mentioned at the outset, as simple as possible, that the operation of the internal combustion engine with respect optimized fuel consumption and emissions can be without in the event of an increased power requirement the performance of the internal combustion engine is reduced is.

This object is achieved according to the characterizing part of claim 1 in that the expansion element is designed such that the coolant temperature (T _K , T _Kist ) adjusts to an upper working limit temperature (T _AG ) without heating the expansion element in mixed operation, and in that a control unit (18) is provided, which, depending on the detected operating and / or environmental variables (DK, n, v, T _S , LAST, T _Kist , LL) of the internal combustion engine (10) releases the heating of the expansion element if necessary in order to operate the Relocate cooling system to cooler operation.

The upper working limit temperature is preferably the same the most economical operating temperature of the internal combustion engine and is slightly smaller than the maximum permissible operating temperature of the internal combustion engine. The upper working limit temperature is preferably above 100 ° C, especially at approx. 105 ° C. The maximum allowable Operating temperature is the highest possible temperature with which the internal combustion engine in normal operation for longer Time can be operated without problems. Thereby even if the electrical heating of the Expansion element damage to the internal combustion engine prevented. The maximum permissible is usually Operating temperature between 105 ° C and 120 ° C.

If the expansion element is not heated electrically, there is only one opening cross-section to the radiator depending on the coolant temperature a. This cross-section of the opening regulates the Coolant temperature to the defined upper working limit temperature. According to the invention Expansion element, e.g. by selecting an appropriate one temperature-dependent material and a suitable con. structural design, designed so that at the defined upper working limit of the opening cross section the cooler is not yet maximum, d. H. no pure cooler operation is achieved. So through additional heating of the expansion element another Enlargement of the opening cross-section and thus one Relocation in the direction of the cooler operation possible.

In addition, it should be noted that the opening cross section to the radiator and the opening cross section to the the cooler immediate short circuit changed in opposite directions will.

By the invention in normal operation, i.e. not at increased performance requirements such as in full load operation or when driving uphill, the highest possible operating temperature of the internal combustion engine reached. Here is for example due to less friction the power consumption of the internal combustion engine less, whereby lower fuel consumption and exhaust gas composition can improve. However, when the operating status of the internal combustion engine due to increased performance requirements a lower coolant temperature level requires quickly to this coolant temperature level being able to switch over depends on the operating and / or environmental variables electrical energy the heatable Expansion element supplied in the sense that increased cooling capacity by opening the thermostatic valve is obtained and thus a reduced Coolant temperature is reached quickly. Too high coolant or engine temperatures with increased performance requirements would result in a reduced degree of filling and thus lead to reduced performance.

Advantageous developments of the invention are the subject of the further claims.

The controller preferably locks the heating or the supply of electrical Energy to the expansion element when the sensed Actual temperature of the coolant below a predetermined Target temperature is. The specified target temperature is always below the defined upper one Working limit temperature. This ensures that a control of the coolant temperature in the direction of a reduced temperature levels is only made if a minimum temperature has already been reached.

Furthermore, the control system releases or blocks the heating of the expansion element depending on the vehicle speed.
On the one hand, for example, idling can be determined when the motor vehicle is at a standstill, whereupon cooling may become necessary due to the lack of a headwind and thus the heating of the expansion element is released.

If a very high vehicle speed and z. B. also a large throttle valve opening angle recorded, is to an increased performance requirement on the Internal combustion engine closed, which also increases Cooling is sensible and thus the heating of the Expansion element can be released.

The controller releases or blocks the heating of the expansion element depending on the speed of the internal combustion engine, the throttle valve opening angle and / or the load state of the internal combustion engine.
For example, the control unit (18) can compare the actual load state (LAST) and / or the actual throttle valve opening angle (DK) and / or the actual speed (n) with a predetermined threshold value and release the heating of the expansion element if this threshold value is exceeded.
The load state of the internal combustion engine can be determined, for example, by the speed of the internal combustion engine in connection with the opening angle of the throttle valve without height correction or in connection with the air mass in the intake tract with height correction.
However, a target temperature of the coolant as a function of the throttle valve angle and the rotational speed can also be determined in the form of a map.
In this way it is ensured that at high load or at high speed or with a large throttle valve opening angle, the required power output of the internal combustion engine is not reduced by an excessively high operating temperature, which could lead to a deteriorated degree of filling and thus to a reduced output.

The control gives the heating of the expansion element free if the actual temperature of the intake air or the Ambient temperature above a specified value lies. This ensures that at high outside temperatures for example when driving slowly, when idling one at a standstill or during stop-and-go operation Overheating of the internal combustion engine is prevented.

The target temperature of the coolant is indicated by a or several tables, characteristic curves and / or maps depending taken from several company and environmental variables. For example, to create a Coolant temperature map of a variety of operating points, e.g. by the values of the speed of the Internal combustion engine, the throttle valve opening angle and / or the vehicle speed are defined, individual Assigned coolant temperatures. The feed the electrical energy to the expansion element is released, if the target temperature taken from the map below the current actual temperature of the coolant lies. With this training it is possible to Coolant temperature at every operating point or operating state to optimize the internal combustion engine.

Another advantageous embodiment of the invention is the subject of claim 4. It provides that the control unit heats the expansion element only after a given company size or environmental size hysteresis and / or according to a predetermined one Delay time releases when the heating of the Expanding element releasing condition is met.

For example, at a target temperature below the actual temperature of the heating of the expansion element only after a specified temperature hysteresis and / or released after a predetermined delay time.

It is also provided according to the subject matter of claim 5 that the control unit heats the expansion element only after a specified company size or environmental variable hysteresis and / or according to a predetermined Delay time locks when the heating of the expansion element blocking condition is met. For example, at a target temperature above the actual temperature is the supply of electrical energy to the expansion element only after a predetermined temperature hysteresis and / or after a predetermined delay time blocked.

With these two configurations of the invention, that with only short-term changes in the operating and / or environmental variables the number of pre-rules. gears is reduced. That is, if from the release the heating switched to a lock and vice versa this transition is delayed until a longer-term change is found.

A further advantageous embodiment of the invention exists according to the subject matter of claim 6 in that the each predetermined target temperature essentially by one depending on the company and / or environmental parameters permissible maximum temperature of the coolant is determined becomes. The intention of this embodiment according to the invention is that to optimize fuel consumption and the highest possible exhaust gas emissions Operating temperature of the internal combustion engine set which, however, depends on the current load of the internal combustion engine is determined only so high that damage to the internal combustion engine or loss of performance is avoided due to overheating.

It should also be noted that releasing the feed electrical energy or heating is not mandatory an actual switching on of the energy supply for Consequence. A release can only be one on one certain condition-based switch-on option. Actual switch-on can be, for example, from a logical combination of several by different Operating and environmental parameters caused switch-on options depend. The term blocking can also be used as a blocking option based on an individual condition or as actual switching off can be understood.

Fig. 1

ein Schemabild einer Kühlanlage, die der Erfindung zugrundeliegt

Fig. 2

einen Logikplan für eine mögliche erfindungsgemäße Regelung der Kühlanlage

Fig. 3

einen mit der erfindungsgemäßen Kühlanlage erreichbaren Temperaturverlauf der Kühlmitteltemperatur und

Fig. 4

die Darstellung eines Kühlmittel-Soll-Temperatur-Kennfeldes.

The invention is explained in more detail with reference to the following description and the accompanying drawings. Show it

Fig. 1

a schematic of a cooling system, which is the basis of the invention

Fig. 2

a logic plan for a possible control of the cooling system according to the invention

Fig. 3

a temperature profile of the coolant temperature that can be achieved with the cooling system according to the invention and

Fig. 4

the representation of a coolant target temperature map.

The cooling system shown in Fig. 1 for an internal combustion engine 10 contains a radiator 11. Between the internal combustion engine 10 and the radiator 11 is a coolant pump 12 attached that a flow of the coolant in generates the direction shown by arrows. From the coolant outlet of the internal combustion engine 10 leads a flow line 13 to the coolant inlet of the radiator 11. From Coolant outlet of the cooler 11 leads to the coolant inlet of the internal combustion engine 10 a return line 14. In the return line 14 is a thermostatic valve 15 with an expansion element, not shown here arranged. One branches off from the supply line 13 Short circuit line 16 to the thermostatic valve 15.

The cooling system essentially works in three operating modes. In a first mode of operation, the so-called warm-up mode especially after the cold start of the internal combustion engine 10, the thermostatic valve 15 is set so that coming from the engine 10 Coolant flow over the short-circuit line 16 essentially completely returned to the internal combustion engine 10 becomes. In a second mode of operation, the Cooling system in mixed operation, d. H. that of the internal combustion engine 10 coming coolant partially runs through the radiator 11 and partly back via the short-circuit line 16 to the internal combustion engine 10. In a third mode of operation the cooling system works in cooler mode, d. H. that from Internal combustion engine 10 will essentially coolant completely through the cooler 11 to Internal combustion engine 10 returned.

The cooling system can be operated by heating the Expansion element of the thermostatic valve 15 via a electrical line 17 in the direction of cooling operation adjusted or switched completely to cooler operation will. This reduces the temperature level of the Coolant compared to that with an operation without Heating of the expansion element reached the temperature level. Then the heating is done via the electrical line 17 interrupted again, so the cooler now Coolant the expansion element of the thermostatic valve 15 from until it reaches a regulated end position in mixed operation occupies so that the coolant temperature back to a Final temperature is raised. The regulated final temperature in mixed operation according to the invention on the upper Working limit temperature set.

The supply of the thermostatic valve 15 with electrical Energy via line 17 is supplied by a control unit 18 causes several signals of company and / or environmental variables receives and evaluates. At the coolant outlet of the internal combustion engine 10 is a temperature sensor 19 arranged, which detects the actual temperature of the coolant and transmitted to the control unit 18. In a collector the intake pipe of the internal combustion engine 10 is another Temperature sensor 20 arranged, the temperature the intake air (fresh air) detected and to the Control device 18 passes on. Preferably, the Control device 18 in a known electronic Motor control 21 integrated, for example to a the "Motronic" trademark from Robert Bosch GmbH distributed electronic engine control.

The motor controller 21 provides signals for the detection of Operating and environmental parameters, such as vehicle speed, the ambient temperature, the speed of the Internal combustion engine and / or the throttle valve opening angle, to disposal. Furthermore, the Engine control 21 the load state of the internal combustion engine 10 from the detected signals. The load state is, for example directly or indirectly from the position of Throttle valve, from the speed and / or the air mass in Intake pipe determined. Depending on the control unit 18 obtained signals is, for example, a target temperature of the coolant determined. If this target temperature is lower than the actual temperature of the coolant, the expansion element of the thermostatic valve 15 over the line 17 heated.

2 is a possible coolant temperature control shown where the heating is actually switched on of the expansion element ("heat expansion element") via a particularly advantageous logical link several individual conditions related to different Operating and environmental variables of the motor vehicle controlled becomes. Such control logic is for example in the Control unit 18 is stored, the control unit 18 for example in an already existing control unit integrated or a separate integrated component in the Thermostatic valve itself can be.

In FIG. 2, the operating and environmental variables throttle valve opening angle DK, engine speed n, actual temperature of the coolant T _Kist , vehicle speed v and intake air temperature T _S , which are present, for example, in the form of sensor signals, are processed to control the coolant temperature. In addition to the pure sensor signals of the operating and environmental variables of the motor vehicle, status signals which were formed from a combination of the individual sensor signals or the operating and environmental variables can also be processed in the control system. In this example, such a status signal is the idle signal LL when the vehicle is at a standstill, this signal being formed, for example, from the vehicle speed v and the engine speed n. However, other status signals are also possible, which are used in a control of the coolant temperature, such as, for example, the load condition of the internal combustion engine already mentioned, as well as driving uphill or in a trailer, which are preferably formed from the operating variables throttle valve opening angle DK and vehicle speed v.

2, the sensor signals throttle valve opening angle DK and engine speed n are used to determine the setpoint temperature T _{Ksoll of} the coolant from a characteristic map K at the operating points determined by the throttle valve opening angle DK and the engine speed n. The target temperature of the coolant T _Ksoll determined in this way is compared with the actual temperature of the coolant T _Kist . If the actual temperature T _{Kist is} greater than the target temperature T _Ksoll , the heating of the expansion element is released. A release corresponds to a release option F (circled), not necessarily an actual heating.

Furthermore, it is observed in a hysteresis element VT whether the difference δT between the actual and target temperature changes by more than a predetermined difference δT _H. Only then is the release option F for heating the expansion element maintained. For this purpose, a logic high signal is emitted at the output of the hysteresis element VT. This output signal of the hysteresis element VT is fed to the inputs of the AND gates AND-1 and AND-3.

In this exemplary embodiment, a logic corresponds in general High signal of a release option F.

Further release options F for switching on the heating of the expansion element are generated as a function of the intake air temperature T _S. The heating of the expansion element depending on the intake air temperature T _S should only be released if at least one of the three thresholds TS1, TS2 and TS3 is exceeded. When the first threshold TS1 is exceeded, a logic high signal is sent to the AND gate AND-1, when the second threshold TS2 is exceeded a logic high signal is sent to the AND gate UND-2 and when the third threshold TS3 is exceeded a logic signal High signal sent to the AND gate UND-3.

Furthermore, when the vehicle is idling, the vehicle is stationary the status signal LL (at v = 0) in the form of a logical High signals brought up to the AND gate AND-3.

In addition, according to this exemplary embodiment, the release option F for heating the expansion element can also depend on a vehicle speed threshold VS of the vehicle speed v being exceeded, whereupon a logic high signal is output from the output of a further hysteresis element VV to a second input of the AND gate UND-2. To block (block) the heating, it is observed in the hysteresis element VV whether the vehicle speed v has fallen below the threshold VS by a difference value δv _H. Only then is a logic low signal (blocking option) again output from the output of the hysteresis element VV to the second input of the AND gate UND-2.

The hysteresis elements VT and VV can also be time delay elements be or connected with time delay elements will.

The outputs of the AND gates UND-1 to AND-3 are three Inputs of an OR gate OR connected. If on the Output line of at least one AND gate a logic High signal is also present at the output of the OR gate a release option F in the form of a logical high signal generated.

In addition, a time delay element δt on Output of the OR gate can be provided through the one Release option F at the output of the OR gate only then actual heating of the expansion element leads, if this release option F is present for a predetermined time δt, in order to keep a constant and to prevent the heating from being switched off.

The vehicle speed threshold VS is preferably a vehicle speed v at which the internal combustion engine is subjected to high thermal loads. The thresholds TS1 to TS3 of the intake air temperature T _S are coordinated, for example, depending on the country version of the vehicle or the type of combustion engine or cooler. The threshold TS3 will, for example, be lower than the thresholds TS1 and TS2, since in connection with the idling of the engine, in which no additional cooling occurs due to the wind, more cooling is required than, for example, at high vehicle speeds. Therefore, for example, the threshold TS2, which is designed in conjunction with the vehicle speed threshold VS, will be higher than the thresholds TS1 and TS3, since additional cooling occurs due to the wind at higher vehicle speeds. In general, however, vehicle and intake air temperature thresholds will be empirically determined in trials. It is important, for example, in very cold ambient or intake air temperatures (for example in "northern countries") to control the cooler operation as a function of the intake or ambient temperature in order to counter thermal shock of the internal combustion engine. At. very hot ambient or intake air temperatures (eg in "tropical countries") can regulate the coolant temperature depending on the intake or ambient temperature, a weakness in hot idling or Stop-and-go operations can be avoided.

In addition, it is pointed out that in other embodiments the invention also at one to one Release option F leading fulfillment of only one of the in Fig. 2 conditions actually heating can be switched on. That is, for example the points marked with circled F in FIG. 2 each one directly with the switch-on device the heating of the expansion element can be connected.

3 shows a diagram of the course of the coolant temperature T _K over time t at part load and full load, as can be achieved by means of the cooling system according to the invention. The expansion element of the thermostatic valve 15 is designed, for example, by the composition of the expansion material to an upper working limit temperature T _AG , which here is a coolant temperature of approximately 105 ° C. in the regulated mixed operation. This temperature is shown with an upper line. A temperature level of 105 ° C in the partial load range is expedient in order to reduce fuel consumption by reducing friction or the like and at the same time to improve the exhaust gas composition. Basically, the coolant temperature should always be as hot as possible to optimize consumption, but should be cool to improve the filling in the case of performance requirements in the full-load range.
When the internal combustion engine is cold started, the coolant temperature T _{K is} brought to the temperature level of 105 ° C with a higher temperature gradient dT / dt than is possible with other cooling systems in warm-up mode and then in mixed mode during part-load operation. The expansion element of the thermostatic valve 15 is heated exclusively by the coolant temperature T _K.

The expansion element is designed so that at 105 ° C here the possible adjustment path of the valve or the maximum possible opening cross section has not yet been set. For example, at full load in the area between C and E, the expansion element can be heated so strongly, for example, that a maximum opening cross-section to the cooler is set in order to cool down as quickly as possible, thereby completely switching to cooler operation. In this example, a temperature level of approx. 70 ° C is reached after a short cooling time. If the operation of the internal combustion engine 10 goes from full load at point E back to partial load, the supply of electrical energy to the expansion element is interrupted. The now cooler coolant, which flows around the expansion element, cools the expansion material and causes the thermostatic valve to be adjusted again by the expansion element solely as a function of the coolant temperature T _K. The thermostatic valve then regulates the coolant temperature T _K and thus the temperature of the internal combustion engine 10 to the temperature level of 105 ° C.

Lowering the coolant temperature T _K in full-load operation to, for example, a temperature level of approximately 70 ° C. has the advantage that the internal combustion engine 10 can then provide the full power. It is thus avoided that, due to an excessively high temperature, a lower degree of filling during combustion is obtained, which leads to a reduction in performance. However, the regulated lowering of the coolant temperature T _K by heating the expansion element can also be regulated depending on various other operating and / or environmental variables of the motor vehicle.

Full load can be recognized, for example, by variables such as the vehicle speed, the engine speed or the throttle valve angle. For example, it is also sensible to lower the coolant temperature T _K by heating the expansion element at very low vehicle speeds or when the vehicle is idling and at a standstill as well as at high outside temperatures, when driving uphill or in trailer operation.

4 shows a map for determining individual target temperatures T _{Ksoll of} the coolant at individual operating points as a function of the vehicle speed V and the load state LAST. The load state LAST can in turn be determined, for example, as a function of the throttle valve opening angle and the speed or the air mass in the intake pipe.

The one determined by two company sizes Setpoint temperature of the coolant assigned to the operating point can be calculated or empirically determined by experiment will. It is also possible to set a target temperature of the Coolant depending on several maps determine the different farm and / or environmental sizes process the vehicle.

In particular, it is also possible according to the invention to the coordination of a map and by coordination of the Threshold values of a cooling system for different country variants to get without the hardware or software to change the cooling system.

Claims (6)

1. A cooling system for an internal combustion engine of a motor vehicle with a radiator and a thermostatic valve, with which the temperature of the cooling medium can be regulated in a hot operation, a mixed operation and a radiator operation, whereby the thermostatic valve includes an expansion element, which can be heated electrically to reduce the cooling medium temperature, whereby the cooling medium temperature (T_K, T_Kist) is regulated in mixed operation by the design of the expansion element, without heating the expansion element. to a final temperature, and whereby a control unit (18) is provided, which depending on captured operational and/or environmental values (DK, n, v, T_s, LAST, T_Kist, LL) of the internal combustion engine (10) enables the heating of the expansion element, so as to transfer the mode of operation of the cooling system towards radiator operation, characterised in that the regulated final temperature without heating the expansion element corresponds to the upper limit of working temperature (T_AG) and is provided in partial load operation and that in full load operation a target temperature (T_Ksoll) is prescribed for the enabling of the heating of the expansion element, which is lower than the upper limit of working temperature (T_AG).
2. A cooling system for an intemal combustion engine of a motor vehicle with a radiator and a thermostatic valve, with which the temperature of the cooling medium can be regulated in a hot operation, a mixed operation and a radiator operation, whereby the thermostatic valve includes an expansion element, which can be heated electrically to reduce the cooling medium temperature, whereby the cooling medium temperature (T_K, T_Kist) is regulated in mixed operation by the design of the expansion element, without heating the expansion element, to a final temperature, and whereby a control unit (18) is provided, which depending on captured operational and/or environmental values (DK, n, v, T_s, LAST, T_Kist, LL) of the internal combustion engine (10) enables the heating of the expansion element, so as to transfer the mode of operation of the cooling system towards radiator operation, characterised in that the regulated final temperature without heating the expansion element corresponds to the upper limit of working temperature (T_AG) and

   that the control unit (18) captures the actual temperature of the cooling medium (T_K, T_Kist) as an operating value, compares this actual temperature with a target temperature (T_Ksoll) determined at least by the throttle flap opening angle (DK) and the speed of revolution of the motor (n) and if the actual temperature (T_Kist) lies above the target temperature (T_Ksoll) enables the heating of the expansion element

      and/or

   that the control unit (18) captures the vehicle speed (v) as an operating value and compares it with a vehicle speed threshold (VS) and enables the heating of the expansion element if the vehicle speed threshold is exceeded

      and/or

   that the control unit (18) captures the actual temperature (T_S) of the inducted air or the ambient air, compares this actual temperature (T_S) with a predetermined threshold value (TS1; TS2; TS3) and enables the heating of the expansion element if this threshold value is exceeded.
3. A cooling system according to Claim or 2, characterised in that the control unit (18) captures the speed of revolution (n) of the intemal combustion engine, the throttle flap opening angle (DK), the vehicle speed (v) and/or the loading condition (LAST) of the internal combustion engine (10) as operating values and depending on at least two of these operating values determines the target temperature (T_Ksoll) of the cooling medium in the form of a set of curves.
4. A cooling system according to one of Claims 1 to 3, characterised in that the control unit (18) enables the heating of the expansion element on fulfilment of one of the conditions for enabling the heating corresponding to an operating value or environmental value hysteresis (δV_H, δT_H) and/or with a delay in accordance with a predetermined time window (δt).
5. A cooling system according to one of Claims 1 to 4, characterised in that the control unit (18) shuts off the heating of the expansion element on fulfilment of one of the conditions for cutting off the heating corresponding to an operating value or environmental value hysteresis (δV_H, δT_H) and/or with a delay in accordance with a predetermined time window (δt).
6. A cooling system according to one of Claims 1 to 5, characterised in that the control unit (18) continously determines a current maximum temperature of the cooling medium depending on the operating and/or environmental values (DK, n, v, T_s, LAST, T_Kist, LL), through which the target temperature (T_Ksoll) of the cooling medium is essentially determined at each time.

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