DE102013202986A1 - Method for regulating or controlling refrigerant circuit of motor vehicle, involves selecting switch-on time point or switch-off time point of compressor depending on operating condition of drive unit or on temperature of air stream - Google Patents

Abstract

The method involves connecting a compressor to a drive unit by a clutch. A switch-on time point or a switch-off time point of the compressor is selected depending on an operating condition of the drive unit or on a temperature of the air stream. The time period, during which the compressor is switched off, is dependent on a thermal capacity of a storage unit or a difference of the actual temperature of the air stream and a set temperature of the air stream.

Description

Technical area

The invention relates to a method for controlling and / or controlling a refrigerant circuit, in particular of a motor vehicle.

State of the art

Compressors of air conditioning systems for motor vehicles can be coupled via clutches to the internal combustion engine. This allows a situation-based turning on or off the compressor. In the course of the efforts of the manufacturers to reduce the fuel consumption of their vehicles overall, inter alia, measures are implemented, which increases the number of startup operations and the number of shutdown operations. This takes place for example due to the use of start-stop systems, which allow a situation-appropriate shutdown of the internal combustion engine.

The increase in the number of cycles results in an increased load on the individual components, such as the clutch, the compressor and other components of the refrigerant circuit.

To counteract these additional burdens, various approaches are known. Among other things, the affected components can be re-dimensioned in such a way that the additional burden can be compensated for over the planned service life. However, this results in larger dimensions and higher weights of the components, which is due to the prevailing space conditions to avoid. Higher weights are also contrary to the efforts to use as weight-optimized components.

Alternatively, a modification of the climate control can be provided, whereby the number of cycles can be reduced. However, this is associated with losses in comfort.

A disadvantage of the solutions according to the prior art is in particular that a sufficient durability with the lowest possible weight and maximum comfort as possible with the increasing demands on the refrigerant circuit is not guaranteed.

DESCRIPTION OF THE INVENTION, OBJECT, SOLUTION, ADVANTAGES It is the object of the present invention to provide a method for controlling and / or controlling a refrigerant circuit, which is optimized over the prior art.

The object of the method for controlling and / or controlling a refrigerant circuit is achieved by a method having the features according to claim 1.

• – einen Kompressor, welcher über eine Kupplung an eine Antriebseinheit angebunden ist,
• – einen Verdampfer, welcher von einem Kältemittel durchströmt ist und von einem Luftstrom umströmt ist,
• – eine Speichereinheit, welche dem Verdampfer in Luftströmungsrichtung derart vorgelagert und/oder nachgelagert ist, dass sie ebenfalls von dem Luftstrom umströmt wird, wobei die Speichereinheit von einem Kältemittel durchströmt ist und die Speichereinheit ein Latentmedium aufweist, welches in thermischem Austausch mit dem Kältemittel steht, wobei

der Kompressor anschaltbar oder ausschaltbar ist,
wobei ein Anschaltzeitpunkt und/oder ein Ausschaltzeitpunkt des Kompressors abhängig von einem Betriebszustand der Antriebseinheit und/oder von einer Temperatur des Luftstroms gewählt wird und die Zeitspanne, während welcher der Kompressor ausgeschaltet ist, von einer thermischen Kapazität der Speichereinheit und/oder einer Differenz der aktuellen Temperatur des Luftstroms und einer Solltemperatur des Luftstroms abhängig ist.An embodiment of the invention relates to a method for controlling and / or controlling a refrigerant circuit, in particular of a motor vehicle, wherein the refrigerant circuit comprises at least the following components:

• A compressor, which is connected via a coupling to a drive unit,
• An evaporator, which is flowed through by a refrigerant and is surrounded by an air flow,
• A storage unit, which is upstream and / or downstream of the evaporator in the direction of air flow, so that it also flows around the air flow, wherein the storage unit is flowed through by a refrigerant and the storage unit has a latent medium which is in thermal exchange with the refrigerant, in which

the compressor can be switched on or off,
wherein a turn-on time and / or a turn-off time of the compressor is selected depending on an operating state of the drive unit and / or a temperature of the air flow and the time period during which the compressor is turned off from a thermal capacity of the storage unit and / or a difference of the current one Temperature of the air flow and a target temperature of the air flow is dependent.

A motor vehicle may in this case be a vehicle operated by combustion engine, for example a car or a truck / commercial vehicle. Also, vehicles with electromotive assistance such as hybrid vehicles may be meant. These include in particular so-called micro-hybrids, mild hybrids and full hybrids. Micro hybrids are characterized by a relatively low additional electrical power and often have only start-stop functionalities. Mild hybrids are characterized by a greater electrical additional power and, in addition to a start-stop functionality, for example, the possibility for purely electrical starting or the ability to recuperate electrical energy. Full hybrids usually have an even greater electrical auxiliary power and, in addition, for example, can enable purely electric driving over longer sections.

An activation time describes the time at which the compressor is transferred from a passive state to an active state. This can be achieved, for example, by generating a force flow between a drive unit and the Compressor happen. Alternatively, for example, an electric drive can be activated. The switch-off time accordingly describes the time at which the compressor is transferred from an active state to a passive state.

The air flow, or the temperature of the air flow relates to the amount of air flowing around the evaporator and / or the storage unit and is finally passed to the passenger compartment for cooling and / or heating. In this case, a temperature of the air flow in the present case means the temperature of the air flow downstream of the evaporator and the storage unit.

The thermal capacity of the storage unit describes the amount of heat that can be absorbed by the storage unit. It is essentially determined by the physical properties of the latent medium provided in the storage unit and the quantity of latent medium stored.

The current temperature of the airflow describes a respective temperature at a particular time considered. By contrast, the setpoint temperature describes a desired temperature defined by a preset, which is to be achieved starting from the current temperature. The setpoint temperature can either be predetermined by a defined specific value or be defined by a temperature setpoint window, which with a certain predefinable tolerance comprises a predetermined temperature above and / or below the predetermined value. The temperature target window is limited by an upper limit temperature and a lower limit temperature.

In an alternative embodiment of the invention, it may be provided that the thermal capacity is either the maximum thermal capacity of the storage unit or the thermal capacity actually available at a particular time.

Among other things, the maximum thermal capacity depends on the physical properties of the latent medium used, the quantity stored in the storage unit and the geometric configuration of the storage unit. The available thermal capacity is essentially determined by the state of charge of the storage unit. The state of charge indicates what percentage of the maximum possible thermal capacity is available in the storage unit.

Furthermore, it is preferable if the compressor is switched off when reaching a predeterminable lower limit temperature of the air flow and / or turned on when reaching a predetermined upper limit temperature of the air flow.

A predeterminable lower limit temperature describes a defined temperature of the air flow after the evaporator and the storage unit, which is just accepted before the compressor is turned off. The upper limit temperature analogously describes a defined maximum temperature of the air flow downstream of the evaporator and the storage unit, which is still accepted before the compressor is switched on.

The aim of the limit temperatures is to create a temperature window in which the air flow is in a comfortable area defined by the temperature window for the occupant. Switching on or off with reference to these limit temperatures is particularly advantageous since a precisely defined temperature window can be generated in this way. In this case, the upper and lower limit temperatures may be, for example, the temperatures limiting the temperature setpoint window about the setpoint temperature T _SOLL .

In addition, it may be advantageous if the maximum thermal capacity of the storage unit is determined by the selected latent medium and by the volume of the latent medium present in the storage unit.

Depending on the selection of the latent medium, a higher or lower thermal capacity can be realized in an otherwise unchanged storage unit. This is particularly advantageous since memory units for different requirement profiles can be generated by selecting the latent medium.

It is also advantageous if the time span during which the compressor is switched off is selected as dependent on the flow area of the evaporator and / or the storage unit, on the humidity and on the air mass flow through the evaporator and / or the storage unit.

The features such as the flow area, the humidity and the air mass flow affect the period during which the compressor is turned off, as it essentially determines the temperature transition between the evaporator and / or the storage unit to the air flow. A larger or smaller flow area favors or reduces the heat transfer. Likewise, changes in air humidity and air mass flow affect the heat transfer. This is advantageous because As a result, diverse possibilities for influencing the time span are given and a solution tailored to the external conditions, such as the installation situation or the physical parameters of the ambient air, can be realized.

According to a particularly preferred embodiment of the invention, it may be provided that at an ambient temperature of about 25 ° Celsius 60% to 100%, preferably 80% to 100% of the latent medium after the compressor is turned on in a time of 20 seconds to 40 seconds, preferably in about 30 seconds, into a solid phase, in particular an ice-like phase.

The fastest possible phase transition and thus a high charge dynamics is particularly advantageous in order to achieve the highest possible operational readiness of the storage unit. The faster the phase transition takes place, the faster a high thermal capacity can be achieved. This is particularly advantageous for the duration of the period during which the compressor is switched off.

It may also be expedient if, at standstill of the compressor and a predetermined setpoint temperature of the air flow, which is below the current temperature of the air flow, heat is removed from the air flow through the latent medium and / or the refrigerant of the storage unit and / or the evaporator, either the desired temperature of the air flow is reached or the available thermal capacity of the latent medium and / or the refrigerant is no longer sufficient to bring about a further cooling of the air flow.

This is particularly advantageous for lowering the temperature of the airflow when the compressor is not turned on. Such a situation in which the compressor is not turned on, for example, occur at a traffic light stop. In this case, the engine can be switched off, whereby the compressor is turned off. For example, the compressor may also be switched off while driving.

Moreover, it is preferable if at a no longer sufficient for cooling to the corresponding target temperature of the air flow thermal capacity of the latent medium and / or the refrigerant, either the compressor is turned on, or a temperature of the air flow above the set temperature for a predetermined period of time and / or accepted for a specifiable temperature target window.

A predefinable time duration or a predeterminable temperature window describe here in each case predetermined intervals from outside. During these intervals, a temperature outside the defined limits of the air flow, either up to the lapse of a certain period of time or until falling below or exceeding an absolute limit temperature accepted. This is done in order to make the time span during which the compressor is switched off possible. The temperature window and the time window are dependent, for example, on the maximum permitted temperature deviation between the desired value and the actual value of the temperature in the interior of the vehicle.

A preferred embodiment is characterized in that the available thermal capacity is increased in the storage unit by at least temporarily turning on the compressor.

By switching on the compressor, the refrigerant circulating in the refrigerant circuit is cooled down. At the same time there is a heat transfer between the latent medium and the refrigerant. As a result, the latent medium gradually withdrawn heat and the latent medium is in a solid phase, whereby the thermal capacity of the storage unit is increased.

Advantageous developments of the present invention are described in the subclaims and the following description of the figures.

Brief description of the drawings

In the following the invention will be explained in detail by means of embodiments with reference to the drawings. In the drawings show:

1 a flowchart which shows how depending on the prevailing actual temperature T _IST and a possibly occurring difference .DELTA.T between the actual temperature T _IST and a setpoint temperature T _SOLL turning on or off the compressor is realized

2 a diagram showing the temperature target window with its upper limit temperature and its lower limit temperature, the course of the actual temperature is simplified, and

3 a diagram showing the course of the actual temperature within, above and below a temperature target window.

Preferred embodiment of the invention

The 1 shows a flow chart, which represents for a possible embodiment in a sequence of query blocks and redirections, as is decided on the turning on or off of the compressor.

In the flowchart, the cooling operation of the air conditioner is considered. Consequently, it can be assumed that at a current temperature T _ACT which is smaller than the predetermined value T _SOLL or is below the lower limit temperature T _{LIMIT, U of} a temperature _{target window, the} temperature is raised, for example, by a heating function of the air conditioning system. This is not shown in the flowchart.

The flowchart includes blocks in which the compressor is turned on as well as blocks in which the compressor is turned off. In principle, the compressor can be switched off or switched off. This depends on the operating state of the compressor before the respective block. Likewise, the compressor can be turned on or remain turned on. The block indicates which operating state the compressor has after passing through the respective block. This is independent of the operating state of the compressor before the block.

Im with the reference 1 designated query block, the operating state of the internal combustion engine is queried. A distinction is made between the operating states engine ON and engine OFF.

In the case of a positive query, ie with the engine running, is in the reference numeral 2 marked block a comparison between the current actual temperature T _{IST of} the air flow, which flows around the evaporator and / or the storage unit, carried out with the predetermined target temperature T _SOLL . The result is the difference ΔT.

The target temperature T _SOLL results, for example, from a desire of the driver. The setpoint temperature T _SOLL can either be a predefinable individual value or else a defined temperature setpoint window.

In an ideal-typical view, a precisely defined predetermined temperature can be achieved and maintained. In reality, and taking into account the multiplicity of the factors influencing the target temperature T _SOLL , as well as the complexity of the refrigerant circuit and the air conditioning system as a whole, the use of a temperature _{target window} for the target temperature T _{SOLL is} advantageous. In this case, T _{SOLL describes} a temperature _{target window} , which is set by the specified target temperature T _SOLL . As long as the actual temperature T _{IST of} the air flow is in this temperature target window, no active influence of the refrigerant circuit is made by control and / or control commands.

When the set temperature T _{SOLL is} reached, the compressor is switched off. Alternatively, the switch-off process can also take place only when a certain lower limit temperature T _{LIMIT, U} , which represents, for example, the lower temperature limit of a temperature _{setpoint window} , is reached. In this case, by further running the compressor, further conversion of the latent medium in the storage unit can be effected, thereby increasing the available thermal capacity C _{th, IST of} the storage unit.

Turning off the compressor is indicated in the block by the reference numeral 3 shown. In the block 4 it is determined whether the temperature T _IST remains at the level of the setpoint temperature T _SOLL or within the temperature setpoint _window or rises above the setpoint temperature T _SOLL , or rises out of the temperature setpoint _window . An increase in the temperature T _IST beyond the value T _SOLL or out of the defined _target temperature window can lead to a heating of the interior. In this case, the compressor is turned on again to counteract the increase in temperature. This will be in block 5 shown.

After the compressor has been switched on in this case, the block is returned to the block by means of a return loop 2 forwarded, in which again a comparison between the target temperature T _SOLL or the temperature target window and the actual temperature T _IST takes place.

Starting from block 4 can remain switched off at a non-rising actual temperature T _IST or a rising within the defined temperature setpoint _actual temperature T _IST, the compressor. This is shown in block 6 , A return loop leads to the query in block 4 back. As long as the actual temperature T _IST does not rise above the level of T _SOLL or out of the defined temperature _target window, the compressor remains switched off and the interrogation loop between block 4 and block 6 run through.

Starting from block 2 follows in the event that the target temperature T setpoint or the temperature setpoint _{window is} not reached, a balance between T _setpoint and T _actual . This is done in block 7 , In block 7 In this case, it is in particular queried whether T _{ACT is} greater than T _SOLL or above the upper limit temperature T _{LIM, O.} For the case that T _is greater than T _SOLL or greater than the upper _Limit temperature T _{LIMIT, O of} the temperature _{target window} is, follows in block 8th the query, whether T _IS sinks. If this is the case, the compressor is in block 9 switched off or remains switched off. Subsequently, a return loop leads back to block 2 ,

Decreases T _IS in block 8th not, the compressor is in block 10 switched on or remains switched on. Also on block 10 follows a return loop to block 2 ,

A decrease of T _IST to block 7 can be effected, for example, by the available thermal capacity C _{th, IST} , which is present in the storage unit. A heat transfer between the air stream and the latent medium, the air flow can be further cooled. The compressor is only switched on again when the available thermal capacity C _{th, IST of} the storage unit is no longer sufficient to bring about a further drop in the temperature T _IST .

Is in block 7 the result that T _{IST is} not greater than T _SOLL or is not above the upper limit temperature T _{LIMIT, O} , T _IST is thus less than or equal to T _SOLL or within the temperature _{target window,} the compressor is turned off. This is shown in block 11 , From block 11 leads a return loop back to block 2 ,

Alternatively, if there is a negative answer to the query in block 1 to go through a flowchart as it is in the lower part of the 1 is shown. The lower part of the 1 refers to an operating condition in which the engine is switched off.

In block 12 the actual temperature T _{IS is} compared with the target temperature T _SOLL or the temperature _target window. If this is reached or T _{IST is} within the temperature _{setpoint window} , the compressor will be in block 13 switched off. Subsequently, in block 14 queried whether the actual temperature _T act either rises above the value defined by T _SOLL addition or _cross the upper limit temperature _{T O} of the temperature set window also increases.

T _IS rises above T _SOLL addition or _{cross-T, O} of the temperature target window is the compressor in block 15 turned on. About a return loop is by block 15 to block 12 recycled. If T does not _rise or stays the same, the compressor is in block 16 switched off, or remains switched off.

In block 17 it is queried whether T _IST rises or stays the same. block 17 is run through if T _SOLL or the temperature _{target window} has not yet been reached. T increases _or remains the same, then in block 19 the compressor is turned on and a return loop on block 12 returned.

In the event that T _IS decreases in block 18 the compressor is off. A return loop leads back to block 12 ,

In general, a reduction of T _IST can be achieved by switching on the compressor, whereby the refrigerant is cooled in the circuit and thus takes place a heat transfer from the air flow to the refrigerant. Alternatively, a reduction of T _{IST can be} effected by a heat transfer between the air flow and the latent medium in the storage unit.

When the engine is off and the compressor is not in operation. This applies at least for a mechanically driven via the engine compressor. The decision to turn on the compressor is thus synonymous with turning on the engine. On the other hand, switching off the compressor can also be done while the engine is running.

By the memory unit, the period of time .DELTA.t, which elapses until the compressor must be turned on again to achieve a predetermined target temperature T _SOLL or a temperature target window or to keep the _actual temperature T _IST at the level of the target temperature T _SOLL or in the temperature _target window, extended become.

In general, a further reduction of T _{IST can} take place, even without the compressor being switched on. The lowering is then achieved via a heat transfer between the air flow and the latent medium of the storage unit. If the available thermal capacity C _{th, IS of} the storage unit is no longer sufficient to cause a decrease of T _IST , the compressor must be added to achieve a further reduction. By turning on the compressor, the available thermal capacity C _{th, IST of} the storage unit is simultaneously increased again.

This in 1 The flow chart shown represents a possible embodiment of such a flow chart and has no limiting character.

The 2 shows a diagram showing the temperature target window 26 represents. The temperature target window 26 is through the upper limit temperature 24 T _{LIMIT, O} and the lower limit temperature 25 T _{BORDER, U} limited.

The time t is plotted along the X axis, along the Y axis the actual temperature T _{IST is} plotted. The diagram shows an example course 20 the actual temperature _T act over time t. It is only the course 20 the actual temperature T _{IST is} shown, which is within the temperature setpoint window 26 lies. The history 20 the actual temperature T _IST is further simplified as a straight line. Deviating profiles of the actual temperature T _IST can also occur.

The point of intersection 21 , which is the intersection between the course 20 the actual temperature T _IST and the lower limit temperature 25 T _{LIMIT, U} represents, is the point at which the actual temperature T _{IST is} the lower limit temperature 25 T _{BORN, U} exceeds. The actual temperature T _IST reached in the intersection 21 the temperature target window 26 , The entry of T _IST into the temperature _{target window} 26 will turn off the compressor. As long as T _{IST is} within the temperature _{target window} 26 moved, the compressor can remain off.

The point of intersection 22 represents a point at which the actual temperature T _is the upper limit temperature 24 T _{LIMIT, O of} the temperature _{setpoint window} 26 reached. The rising of the upper limit temperature 24 T _{LIMIT, O results in} the compressor being switched on.

The point of intersection 23 represents a point at which the actual temperature T _actual below the lower limit temperature 25 T _{LIMIT, U} drops. A fall below the lower limit temperature 25 T _{LIMIT, U results in compressor shutdown} .

Within the temperature target window 26 a defined target temperature T _{SOLL can be} specified. This represents the desired target value. Due to the complexity and inertia of the entire system air conditioning or refrigerant circuit, it is not or difficult to keep a well-defined temperature value permanently. Therefore, at least small fluctuations up and down must be accepted. The use of a temperature target window 26 is therefore advantageous.

3 shows an exemplary course 30 the actual temperature _T act over the time t, as may occur in a real system.

In 3 It can be seen that the actual temperature T _IST does not necessarily have a linear course. Furthermore, there is a certain overshoot 36 . 37 the actual temperature _T act above or below the limit temperatures 38 . 39 T _{LIMIT, O} and T _{LIMIT, U} shown. Such overshoot 36 . 37 will occur in a practical application due to the inertia of the entire system and the possibly existing dead times in the controlled system with high probability.

The 3 shows a course 30 the actual temperature _T act with intersections 31 . 32 . 33 at the lower limit temperature 39 T _{BORDER, U} and the intersections 34 . 35 at the upper limit temperature 38 T _{BORN, O.} At the intersections 31 . 32 . 33 the compressor is switched off. At the intersections 34 . 35 the compressor is switched on.

It may also occur in alternative embodiments deviating curves of the actual temperature T _IST . The 2 and 3 serve to clarify the temperature target window 26 . 40 and from exceeding and falling below the upper limit temperature 24 . 38 T _{LIMIT, O} and the lower limit temperature 25 . 39 T _{LIMIT, U} resulting impact on the compressor.

All figures serve to illustrate the inventive idea. They are exemplary and have no limiting character.

Claims (9)

A method for controlling and / or controlling a refrigerant circuit, in particular of a motor vehicle, wherein the refrigerant circuit comprises at least the following components: - a compressor which is connected via a coupling to a drive unit, - an evaporator, which is flowed through by a refrigerant and of a A memory unit which is upstream of the evaporator in the air flow direction and / or downstream, that it is also flows around the air flow, wherein the storage unit is flowed through by a refrigerant and the storage unit comprises a latent medium, which in thermal exchange with the refrigerant is, wherein the compressor is switched on or off, characterized in that a connection time and / or a switch-off of the compressor selected depending on an operating state of the drive unit and / or a temperature of the air flow is and the time period (At), during which the compressor is off, from a thermal capacity of the memory unit and / or a difference (.DELTA.T) of the actual temperature (T _IST) of the air stream and a setpoint temperature (T _SOLL) of the air stream is dependent. Method for controlling and / or controlling a refrigerant circuit according to claim 1, characterized in that the thermal capacity either the maximum thermal capacity of the storage unit or at a certain time actually available thermal capacity (C _{th, IST} ) is. Method for controlling and / or controlling a refrigerant circuit according to one of the preceding claims, characterized in that the compressor when reaching a predeterminable lower limit temperature ( 25 . 29 , T _{LIMIT, U} ) of the air flow is switched off and / or when a predefinable upper limit temperature ( 24 . 38 , T _{LIMIT, O} ) of the air flow is switched on. Method for controlling and / or controlling a refrigerant circuit according to one of the preceding claims, characterized in that the maximum thermal capacity of the storage unit is determined by the selected latent medium and by the volume of the latent medium present in the storage unit. Method for controlling and / or controlling a refrigerant circuit according to one of the preceding claims, characterized in that the period of time (Δt) during which the compressor is switched off, from the flow area of the evaporator and / or the storage unit, the humidity and the air mass flow is selected depending on the evaporator and / or the storage unit. A method for controlling and / or controlling a refrigerant circuit according to any one of the preceding claims, characterized in that at an ambient temperature of about 25 ° C, 60% to 100%, preferably 80% to 100% of the latent medium after turning on the compressor in a time of 20 seconds to 40 seconds, preferably in about 30 seconds, in a solid phase, in particular an ice-like phase, go over. Method for controlling and / or controlling a refrigerant circuit according to one of the preceding claims, characterized in that at standstill of the compressor and a predetermined desired temperature (T _SOLL ) of the air flow, which is below the current temperature (T _actual ) of the air flow, the air flow heat is removed by the latent medium and / or the refrigerant of the storage unit and / or the evaporator until either the desired temperature (T _SOLL ) of the air flow is reached or the available thermal capacity (C _{th, IST} ) of the latent medium and / or the refrigerant is no longer sufficient to bring about a further cooling of the air flow. Method for controlling and / or controlling a refrigerant circuit according to one of the preceding claims, characterized in that when no longer sufficient for cooling to the corresponding desired temperature (T _SOLL ) of the air flow sufficient thermal capacity of the latent medium and / or the refrigerant, either the compressor is, or a temperature of the air flow above the set temperature (T _SOLL ) for a predetermined period of time and / or for a predeterminable temperature window is accepted. Method for controlling and / or controlling a refrigerant circuit according to one of the preceding claims, characterized in that the available thermal capacity (C _{th, IST} ) is increased in the storage unit by at least temporarily turning on the compressor.

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