COOLANT MANAGEMENT FOR A REHEATING PROCESS FOR OPERATING A COOLING SYSTEM FOR A MOTOR VEHICLE, COOLING SYSTEM, AND MOTOR VEHICLE HAVING SUCH A COOLING SYSTEM

Abstract

A reheating process for operating a cooling system having a heat pump function for a motor vehicle. The reheating process includes steps of determining a heat differential value by comparing a heat emission actual value at the heating register to a heat emission target value, and adjusting at least one operating setting of the cooling system, so that the power consumption in the cooling system is increased if the heat differential value is greater than 0 and less than a heat differential threshold value.

Claims

1-12. (canceled)

13. A reheating process for operating a cooling system having a heat pump function for a motor vehicle, wherein the cooling system comprises: a coolant compressor, which is connectable or connected to a primary line and a secondary line; an external heat exchanger, which is arranged in the primary line; an evaporator, which is arranged in the primary line; a heating register, which is arranged in the secondary line; at least one reheating expansion valve, which is arranged between the heating register and the external heat exchanger in the secondary line; wherein the reheating process comprises the following steps: determining a heat differential value by comparing a heat emission actual value at the heating register to a heat emission target value, adjusting at least one operating setting of the cooling system, so that the load capacity in the cooling system is increased if the heat differential value (Wdiff) is greater than 0 and less than a heat differential threshold value.

14. The reheating process of claim 13, wherein the adjusting of the operating setting comprises: measuring the temperature of the supply air after flowing through the evaporator and reducing a target temperature for the temperature of the supply air after flowing through the evaporator.

15. The reheating process of claim 14, wherein the reduction (S507) of the target temperature (SP T_Verd) is carried out until reaching a minimal target temperature, in particular is carried out repeatedly and/or step-by-step.

16. The reheating process of claim 13, wherein the adjusting of the operating setting comprises: setting the condition or quality of the supply air supplied to the evaporator, wherein the recirculated air component in the supply air is increased.

17. The reheating process of claim 13, wherein the adjusting of the operating setting comprises: incorporating at least one further component of the cooling system, which is arranged fluidically in parallel or in series to the evaporator, in particular a chiller operating as a water heat pump evaporator and/or a rear evaporator for the climate control of a rear vehicle region.

18. The reheating process of claim 13, wherein the adjusting of the operating setting comprises: increasing the amount of air which is guided through the heating register.

19. The reheating process of claim 13, wherein the adjusting of the operating setting comprises: reducing the supply air flow via the external heat exchanger.

20. A cooling system having a heat pump function for a motor vehicle, having a coolant compressor, which is connectable or connected to a primary line and a secondary line; an external heat exchanger, which is arranged in the primary line; an evaporator, which is arranged in the primary line; a heating register, which is arranged in the secondary line; at least one reheating expansion valve, which is arranged between the heating register and the external heat exchanger in the secondary line; wherein the cooling system is configured to be operated using a reheating process, and wherein the coolant in such a reheating mode flows through the following components of the cooling system in succession starting from the coolant compressor: heating register and reheating expansion valve in the secondary line, external heat exchanger and evaporator in the primary line.

21. The cooling system of claim 20, having a chiller arranged fluidically in parallel to the evaporator and/or a rear evaporator arranged fluidically in parallel to the evaporator.

22. The cooling system of claim 20, having at least one movable temperature valve, which is arranged before or after the heating register with respect to a supply air flow direction.

23. The cooling system of claim 20, having at least one movable supply air valve, which is arranged before the evaporator with respect to a supply air flow direction.

24. A motor vehicle having a cooling system, comprising: a coolant compressor, which is connectable or connected to a primary line and a secondary line; an external heat exchanger, which is arranged in the primary line; an evaporator, which is arranged in the primary line; a heating register, which is arranged in the secondary line; at least one reheating expansion valve, which is arranged between the heating register and the external heat exchanger in the secondary line; wherein the cooling system is configured to be operated using a reheating process, and wherein the coolant in such a reheating mode flows through the following components of the cooling system in succession starting from the coolant compressor: heating register and reheating expansion valve in the secondary line, external heat exchanger and evaporator in the primary line.

25. The reheating process of claim 14, wherein the adjusting of the operating setting comprises: setting the condition or quality of the supply air supplied to the evaporator, wherein the recirculated air component in the supply air is increased.

26. The reheating process of claim 15, wherein the adjusting of the operating setting comprises: setting the condition or quality of the supply air supplied to the evaporator, wherein the recirculated air component in the supply air is increased.

27. The reheating process of claim 14, wherein the adjusting of the operating setting comprises: incorporating at least one further component of the cooling system, which is arranged fluidically in parallel or in series to the evaporator, in particular a chiller operating as a water heat pump evaporator and/or a rear evaporator for the climate control of a rear vehicle region.

28. The reheating process of claim 15, wherein the adjusting of the operating setting comprises: incorporating at least one further component of the cooling system, which is arranged fluidically in parallel or in series to the evaporator, in particular a chiller operating as a water heat pump evaporator and/or a rear evaporator for the climate control of a rear vehicle region.

29. The reheating process of claim 16, wherein the adjusting of the operating setting comprises: incorporating at least one further component of the cooling system, which is arranged fluidically in parallel or in series to the evaporator, in particular a chiller operating as a water heat pump evaporator and/or a rear evaporator for the climate control of a rear vehicle region.

30. The reheating process of claim 14, wherein the adjusting of the operating setting comprises: increasing the amount of air which is guided through the heating register.

31. The reheating process of claim 15, wherein the adjusting of the operating setting comprises: increasing the amount of air which is guided through the heating register.

32. The reheating process of claim 16, wherein the adjusting of the operating setting comprises: increasing the amount of air which is guided through the heating register.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0043] Further advantages and details of the invention result from the following description of embodiments with reference to the figures. In the figures:

[0044] FIG. 1 shows a schematic and simplified circuit diagram of a cooling system for a motor vehicle;

[0045] FIG. 2 shows a simplified log(p)-h diagram to illustrate the circulation process in the reheating mode.

[0046] FIG. 3 shows a flow chart of an exemplary implementation of the reheating process, in particular by means of the cooling system described in FIG. 1.

DETAILED DESCRIPTION

[0047] FIG. 1 shows an embodiment of a cooling system 10 for a motor vehicle schematically and in simplified form. The cooling system 10 comprises a coolant circuit 11, which can be operated both in a cooling system mode (also referred to as AC mode in short) and also in a heat pump mode. In the embodiment shown, the cooling system 10 comprises a coolant compressor 12, an external heat exchanger 18, an internal heat exchanger 20, an evaporator 22, and an accumulator or coolant collector 24. The external heat exchanger 18 can be designed as a condenser or gas cooler. In particular, the external heat exchanger 18 can have bidirectional flow through it in the embodiment shown.

[0048] The evaporator 22 is shown here by way of example as a front evaporator for a vehicle. The evaporator 22 is also representative of further evaporators possible in a vehicle, for example, rear evaporators, which can be arranged fluidically in parallel to one another. In other words, the cooling system 10 thus comprises at least one evaporator 22.

[0049] A shutoff valve A4 is arranged downstream of the compressor 12. An expansion valve AE2 is provided upstream of the evaporator 22.

[0050] In the context of this description, in the entire coolant circuit 11 of the cooling system 10, the section from the compressor 12 to the outer heat exchanger 18, to the inner heat exchanger 20, and to the evaporator 22 is referred to as the primary line 14.

[0051] The cooling system 10 furthermore comprises a heating register 26 (also referred to as a heating condenser or heating gas cooler). A shutoff valve A3 is arranged upstream of the heating register 26. A shutoff valve A1 is arranged downstream of the heating register 26. Furthermore, an expansion valve AE4 is arranged downstream of the heating condenser 26.

[0052] In the context of this description, in the entire coolant circuit of the cooling system 10, the section from the compressor 12 to the heating register 26, to the expansion valve AE4, and to a branch Ab2 is referred to as the secondary line 16. The secondary line 16 comprises a heating branch 16.1, which extends from the shutoff valve A3 via the heating register 26 to the shutoff valve A1. Furthermore, the secondary line 16 comprises a reheating branch or reheat branch 16.2, which is fluidically connectable upstream to the heating register 26 and downstream to the external heat exchanger 5. The secondary line 16 or the reheat branch 16.2 opens at a branching point Ab2 into the primary line 14.

[0053] The cooling system 10 comprises a further evaporator or chiller 28. The chiller 28 is provided fluidically in parallel to the evaporator 22. The chiller 28 can be used, for example, for cooling an electrical component of the vehicle, but also for implementing a water heat pump function utilizing the waste heat of at least one electrical component. An expansion valve AE1 is connected upstream before the chiller 28.

[0054] The cooling system 10 can also have an electrical heating element 30, which is embodied, for example, as a high-voltage PTC heating element. The electrical heating element 30 is used as an auxiliary heater for a supply air flow L guided into the vehicle interior. The electrical heating element 30 can be housed together with the heating register 26 and the evaporator 22 in an air conditioner 32. The electrical heating element 30 can be arranged connected downstream of the heating register 26.

[0055] Furthermore, check valves R1 and R2 are also visible in FIG. 1. Furthermore, several sensors pT1 to pT5 for detecting pressure and/or temperature of the coolant are also shown. It is to be noted that the number of the sensors and their arrangement are only shown by way of example here. A cooling system 10 can also have fewer or more sensors. In the example shown, combined pressure/temperature sensors pT1 to pT5 are shown as sensors. However, it is also conceivable that sensors separate from one another are used for measuring pressure or temperature and are possibly also arranged spatially separated from one another along the coolant lines.

[0056] The cooling system 10 can be operated in different modes, which are briefly described hereinafter.

[0057] In the AC mode of the coolant circuit 11, the coolant compressed to high pressure flows starting from the coolant compressor 12 with open shutoff valve A4 into the external heat exchanger 18. It flows from there to the high-pressure section of the internal heat exchanger 20 and the completely open expansion valve AE3. Via a branching point Ab1, the coolant can flow to the expansion valve AE2 and into the interior evaporator 22 (evaporator section 22.1). In parallel or alternatively, the coolant can flow via a branching point Ab4 and the expansion valve AE1 into the chiller 28 (chiller section 28.1). From the evaporator 22 and/or the chiller 28, the coolant flows on the low-pressure side into the collector 24 and through the low-pressure section of the interior heat exchanger 20 back to the compressor 12.

[0058] In the AC mode, the heating branch 16.1 or the secondary line 16 is shut off by means of the shutoff valve A3, so that hot coolant cannot flow through the heating register 26. To retrieve coolant from the inactive heating branch 16.1, the shutoff element A5 designed as a shutoff valve can be opened, so that the coolant can flow via the shutoff element A5 and the check valve R2, with shutoff element A2 closed at the same time, in the direction of the collector 24.

[0059] In the heating mode of the coolant circuit 11, the shutoff valve A4 is closed and the shutoff valve A3 is open, so that hot coolant can flow in the heating branch 16.1.

[0060] To carry out the heating function by means of the chiller 28 to implement a water heat pump mode, the coolant compressed by means of the coolant compressor 12 flows via the open shutoff valve A3 into the heating register 26. At the heating register 26, heat is emitted to a supply air flow L guided into the vehicle interior. The coolant subsequently flows via the open shutoff valve A1 and the branching point Ab1. It is expanded by means of the expansion valve AE1 in the chiller 28 to absorb waste heat of the electrical and/or electronic components arranged in a coolant circuit 28.2. In this heating function, the expansion valves AE3 and AE4 are closed, the shutoff valve A5 is closed, and the shutoff valve A2 is open. Coolant displaced in the water heat pump mode can be suctioned via the shutoff valve A2 from a bidirectional branch 14.1 or the primary line 14 and supplied via the check valve R2 to the collector 24.

[0061] To carry out the heating function by means of the external heat exchanger 18 as a heat pump evaporator, the coolant compressed by means of the coolant compressor 12 flows via the open shutoff valve A3 to emit heat to a supply air flow L into the heating register 26. Subsequently, it is expanded via the open shutoff valve A1 by means of the expansion valve AE3 in the external heat exchanger 18 to absorb heat from the ambient air. The coolant then flows via a heat pump recirculation branch 15 to the collector 24 and back to the coolant compressor 12. The expansion valves AE1, AE2, and AE4 remain closed in this case, as does the shutoff valve A5.

[0062] An indirect triangle circuit can be implemented in that with open shutoff valve A1, the coolant compressed by the coolant compressor 12 is expanded by means of the expansion valve AE1 in the chiller 28, wherein at the same time no mass flow is generated on the coolant side, thus in the coolant circuit 28.2, thus, for example, the fluid used as the coolant, such as water or water-glycol mixture, remains standing on the coolant side of the chiller 28 or coolant does not actively flow through the chiller 28. The expansion valves AE2, AE3, and AE4 remained closed in this switching variant.

[0063] In a reheating or reheat mode, the supply air flow L supplied into the vehicle interior is first cooled and thus dehumidified by means of the evaporator 22. Using the heat supplied to the coolant via the compressor 12, the supply air flow L can be completely or at least partially heated again by means of the heating register 26.

[0064] For this purpose, the cooling system 10, in particular the air conditioner 32, has temperature valves 34 which are settable, in particular controllable and pivotable, between the evaporator 22 and the heating register 26. In the illustrated example, a left and a right temperature valve 34L and 34R (schematically shown in FIG. 1) are arranged. The temperature valves 34L, 34R can be set or pivoted between an open position, which is referred to as the 100% position, and a closed position, which is referred to as the 0% position. Alternatively, it is also possible to connect the temperature valves 34R, 34L downstream from the heating register 26.

[0065] In the 100% position, the entire supply air flow L flowing through the evaporator 22 is guided via the heating register 26 and heated before it can flow into the passenger compartment of the vehicle. In the 0% position, the entire supply air flow L flowing through the evaporator 22 flows in the bypass around the heating register 26 without heating and thus without absorbing heat into the passenger compartment.

[0066] In an x position of the temperature valves 34L and 34R at 0%<x<100%, these temperature valves are only partially open, so that in each case only a partial air flow of the supply air flow L flowing through the evaporator 22 is guided via the heating register 26. This heated partial air flow can subsequently be admixed to the remaining cooled and dehumidified partial air flow. The supply air flow L heated in this way is supplied to the passenger compartment of the vehicle. For example, a 50% position indicates that the temperature valves 34R and 34L are only open halfway, thus 50%.

[0067] A rear evaporator 22h arranged fluidically in parallel to the evaporator 22 is an optional component in a cooling system 10. The rear evaporator 22h is used in particular to climate control a rear region (rear) of the motor vehicle. The rear evaporator 22h can be connected, for example, at the branching point Ab1. A separate expansion valve AE5 is assigned to the rear evaporator 22h, in particular arranged upstream of the rear evaporator 22h. A further check valve R3 can be arranged downstream of the rear evaporator 22h. Finally, the rear evaporator 22 is connected to the low-pressure supply line to the coolant collector downstream of the check valve R1.

[0068] A reheating or reheat mode of the coolant circuit 11 or the cooling system 10 is carried out in different ways as a function of the heat balance.

[0069] A possible operating method 500 for the reheating or reheat mode is explained by way of example hereinafter on the basis of the flow chart of FIG. 2 and with reference to the cooling system 10 and its components shown in FIG. 1. Such an operating method is typically implemented as a control program in a control unit for the cooling system or for the climate control in a vehicle.

[0070] A reheating mode is considered in which the coolant flows starting from the compressor 12 via the open shutoff valve A3 to the heating register 26 (heating condenser or heating gas cooler). The shutoff valve A1 is closed and the coolant flows via the expansion valve AE4 to the external heat exchanger 18. The coolant then passes the internal heat exchanger 20 on the high-pressure side and reaches the evaporator 22 via the open expansion valve AE3 and the expansion valve AE2. From there, the coolant reaches the compressor 12 again via the coolant collector 24 and the low-pressure section of the internal heat exchanger 20. In this reheating process, the temperature valves 34L, 34R can be moved into suitable positions which can assume a value of 0% (temperature valves 34L, 34R closed) to 100% (temperature valves 34L, 34R completely open).

[0071] FIG. 2 shows, in a schematic and simplified log (p)-h diagram, solely qualitatively the coolant circulation process and the effects linked to the reheating process presented here. The circulation process is run through counterclockwise.

[0072] The circulation process shown by solid line L_g illustrates the problem that in the event of small power excesses, the coolant in the external heat exchanger 18 is present nearly completely or predominantly in the two-phase physical state. This is indicated by the arrow A directed toward the isobar curve. Pressure is dissipated via the expansion valve AE2 and it is apparent from the circulation process shown by the solid line that a deficiency of coolant can result on the low-pressure side, which results in an overheated exit of coolant at the evaporator 22, which is illustrated by the point B. This can have an effect, for example, on the air-side temperature at the evaporator 22, so that the interior comfort in the vehicle is negatively influenced in this way. In other words, high temperature differences of the supply air result after the evaporator 22, which leads to comfort losses.

[0073] Furthermore, oil deposits can also occur in the coolant accumulator 24, depending on the design of the cooling system 10. Due to the absence or a strong reduction of a liquid phase of coolant in the coolant accumulator 24, oil can increasingly remain in the coolant accumulator 24 and is no longer supplied to the compressor 12, which can result in lubrication problems at the compressor 12.

[0074] If the power consumption of the cooling system 10 is increased, so that a greater or higher power excess results, which is illustrated in simplified form by the circulation process L_h shown by dashed lines, the power or heat to be dissipated at the external heat exchanger 18 also increases, so that the coolant is present in two phases in a significantly greater proportion or with an increasing proportion at its entry. This is illustrated in the circulation process shown by dashed lines at point C, which is quasi-shifted from left to right by the load increase. Accordingly, sufficient coolant is now available on the low-pressure side of the cooling system 10 for the evaporator 22 and/or the chiller 28 and/or a rear evaporator. Accordingly, a sufficient component of liquid coolant is also contained in the coolant accumulator 24, so that the above-described problem of the air-side temperature inhomogeneity and the inadequate lubrication of the compressor 12 does not occur.

[0075] FIG. 3 shows in simplified form a reheating process 500, in which the cooling system 10 is set so that the coolant flow, as described above, flows from the compressor via the heating register 26, the expansion valve AE4, the external heat exchanger 18, the internal heat exchanger 20, the expansion valve AE3, at least the evaporator 22, and finally to the coolant accumulator 24.

[0076] According to the reheating process 500 shown in FIG. 3, in operation after the start (S501) of the cooling system 10 to a point in time not shown in greater detail here, a transition takes place to a reheating mode, which is designated here by reheat III (S502). A possible condition which has to be met to start the reheating mode (S502) can be, for example, the measured ambient temperature. The reheating process can be activated in particular when the ambient temperature is up to 15° C., in particular is approximately 5° C. to 15° C.

[0077] In such a reheating process 500, the following steps can be carried out for improved coolant management.

[0078] Firstly, in S503, a heat differential value Wdiff is determined by comparing a heat emission actual value Wist at the heating register 26 to a heat emission target value Wsoll, wherein Wdiff=Wist−Wsoll.

[0079] In S504 it is determined whether the heat differential value Wdiff determined in S503 is greater than zero (“0”) and less than a heat differential threshold value Wds. It is thus determined in this way whether a low heat or power excess exists.

[0080] In S506, at least one operating setting of the cooling system 10 is adjusted, so that the load consumption in the cooling system 10 is increased when the condition is met in S504. If the condition is not met in S504, i.e., either there is a power deficit or a high power excess, the reheating process branches in a step S505, which is representative for method steps SRH to be carried out under these conditions, which are not described in more detail here, however.

[0081] The adjustment of the operating setting can comprise step S507: measuring the temperature of the supply air after the flow through the evaporator 22 and reducing a target temperature SP T_Verd for the temperature of the supply air to the heating register after flowing through the evaporator 22. The reduction of the target temperature SP T_Verd can be carried out here until reaching a minimum permissible target temperature. This can in particular be repeated and/or carried out step-by-step.

[0082] The adjustment of the operating setting can comprise step S508: setting the condition or quality of the supply air (L) supplied to the evaporator 22, wherein the recirculated air component in the supply air is increased, presuming, of course, that its admixture causes the desired load increase at the evaporator due to an increase of the entropy in the supply air flow to the evaporator.

[0083] The adjustment of the operating step can comprise step S509: incorporating at least one further component of the cooling system 10, which is arranged fluidically in parallel or in special cases also in series to the evaporator 22, in particular the chiller 28 operating as a water heat pump evaporator and/or the rear evaporator 22h for the climate control of a rear vehicle region.

[0084] The adjustment of the operating setting can comprise step S510: increasing the amount of air which is guided through the heating register 22.

[0085] The adjustment of the operating setting can comprise step S511: reducing the supply air flow via the external heat exchanger 18. The external heat exchanger 18 can also be referred to as a cooling package having the integrated components condenser 18 or gas cooler 18. The reduction of the supply air flow can be carried out via closable and/or continuously adjustable cooling air entry and/or reduction of the fan activation, which results in a reduction of the amount of air suctioned in from the surroundings.

[0086] Steps S507 to S511 can be combined with one another individually or in combinations which are arbitrary per se, in order to achieve the desired result of an increased power consumption. If the desired result of the increased power excess is achieved by possibly executing one of steps S507 to S511 or a combination of several of these steps S507 to S511 multiple times, the condition in step S504 is no longer met, so that the reheating process 500 branches in step S505, which is representative of a state of the cooling system 10 in which the risk of a coolant deficiency, in particular in the liquid physical state, is not present on the low-pressure side or in the coolant accumulator 24, and the reheating process 500 in particular does not have to run through steps S507 to S511.