Method for operating a motor vehicle, motor vehicle

Abstract

A method for operating a motor vehicle (100) is proposed, wherein the motor vehicle (100) has a cooling circuit with a first sub-circuit (1) and a second sub-circuit (2), wherein the first sub-circuit (1) has an air conditioning compressor (3) and a chiller (4), wherein the second sub-circuit (2) is connected to the first sub-circuit (1) via a shut-off valve (5), wherein, when the shut-off valve (5) is closed, the tightness of the shut-off valve (5) is checked based on a thermal output of the chiller (4) and an electrical output of the air conditioning compressor (3). Furthermore, a motor vehicle (100) is proposed.

Description

[0001] The present invention relates to a method for operating a motor vehicle with a cooling circuit comprising a first sub-circuit with an air conditioning compressor and a chiller, as well as a second sub-circuit. Furthermore, the present invention relates to a motor vehicle with a first sub-circuit with an air conditioning compressor and a chiller, as well as a second sub-circuit.

[0002] Modern motor vehicles have a multitude of components that require active cooling. Cooling the high-voltage components is particularly important in high-performance electric vehicles. When high power demands are met, waste heat is generated by the traction battery, power electronics, and electric motors, which must be dissipated to prevent damage to these components.

[0003] In addition to the cooling required for proper operation, the vehicle's interior is typically air-conditioned. Typically, this involves cooling fresh air and / or recirculated air, at least in the summer months.

[0004] The different cooling requirements of a vehicle result in very different cooling performance requirements. For example, cooling high-voltage components typically requires significantly higher cooling performance than air conditioning the interior.

[0005] Despite the differences in cooling performance requirements, it is advisable to provide only a few, preferably just one, air conditioning compressor in the vehicle for reasons of space efficiency, cost savings, and reduced weight. The air conditioning compressor operates several, for example, two, sub-circuits of the cooling circuit. To meet the different cooling performance requirements, it is possible to isolate one of the sub-circuits with a shut-off valve as needed.

[0006] Such a shut-off valve is difficult to monitor. Often, malfunctions of the shut-off valve occur without being immediately detected. This can lead to excessive cooling performance in one of the sub-circuits.

[0007] US 2009 / 0 249 807 A1 discloses a motor vehicle having a cooling circuit with a first sub-circuit and a second sub-circuit. The first sub-circuit has an air conditioning compressor and a chiller, and the second sub-circuit is connected to the first sub-circuit via a shut-off valve. DE 11 2019 003 105 T5 also discloses a cooling circuit for a vehicle. The cooling circuit has several evaporators. One of the evaporators is used to cool a battery of the motor vehicle.

[0008] It is an object of the present invention to provide a method for operating a motor vehicle and a motor vehicle which do not have the disadvantages mentioned in the prior art, but rather make it possible to detect malfunctions of the shut-off valve.

[0009] This object is achieved by a method for operating a motor vehicle according to claim 1 and a motor vehicle according to claim 9.

[0010] In the method according to the invention for operating a motor vehicle, the motor vehicle has a first sub-circuit with an air conditioning compressor and a chiller. The motor vehicle also has a second sub-circuit. The second sub-circuit is connected to the first sub-circuit via a shut-off valve. According to the invention, when the shut-off valve is closed, the tightness of the shut-off valve is checked based on a thermal output of the chiller and an electrical output of the air conditioning compressor. This advantageously makes it possible to draw conclusions about the condition of the shut-off valve. If there is a difference between the electrical output of the air conditioning compressor and the thermal output of the chiller, it can be assumed that thermal power is being taken off in the second sub-circuit via the shut-off valve, which is actually closed.In other words, a balance is established between the electrical power of the air conditioning compressor and the thermal power of the chiller, and it is examined whether these are balanced. If the balance is not balanced, an unwanted cold sink is present in the system under consideration.

[0011] Preferably, the motor vehicle is an electric vehicle, for example a hybrid vehicle or a purely electrically powered motor vehicle.

[0012] Advantageous embodiments and further developments of the invention can be found in the dependent claims and the description with reference to the drawings.

[0013] According to a preferred embodiment of the present invention, an operating point-dependent characteristic value of the first sub-circuit is taken into account for leak testing. This advantageously makes it possible to take system-specific deviations and peculiarities into account depending on the situation. In particular, a performance difference due to power losses, for example, can be taken into account.

[0014] The thermal power of the chiller added to the thermal power applied to the second sub-circuit is equal to the characteristic factor multiplied by the electrical power of the air conditioning compressor. When the shut-off valve is closed and sealed, the thermal power of the second sub-circuit is zero. This means that when the shut-off valve is closed and sealed, the electrical power of the air conditioning compressor is equal to the thermal power of the chiller divided by the operating point-dependent characteristic factor. This monitoring equation is used to test the tightness of the shut-off valve. If the monitoring equation is met, the closed shut-off valve is tight. If the monitoring equation is not met, it can be concluded that the shut-off valve is leaking.

[0015] It is conceivable that the characteristic value depends on a coolant pressure and / or an outside temperature and / or a coolant temperature in the supply line and / or a coolant temperature in the return line.

[0016] According to a further preferred embodiment of the present invention, the method is carried out only during stationary operation of the air conditioning compressor. This advantageously ensures that the check for leaks of the shut-off valve is not distorted by fluctuations in the electrical power of the air conditioning compressor. Such fluctuations in the electrical power typically occur during non-stationary operation of the air conditioning compressor, i.e., in cases where the electrical power of the air conditioning compressor is increased or decreased.

[0017] Preferably, the method is only carried out after a waiting period following start-up of the air conditioning compressor. Especially during the start-up phase of the air conditioning compressor, it can be expected that the electrical power of the air conditioning compressor will not be fully converted into thermal power at the chiller. Firstly, the losses in the air conditioning compressor itself are higher when the air conditioning compressor is starting up than during stationary operation. Secondly, further losses arise in the system, for example due to cooling of the piping of the first sub-circuit and the other components of the first sub-circuit. The waiting period advantageously prevents the aforementioned losses during start-up of the air conditioning compressor from leading to a falsification of the leak test of the shut-off valve.

[0018] According to a further preferred embodiment of the present invention, the chiller is used to operate a secondary circuit for cooling HV components of the motor vehicle. This advantageously enables cooling-intensive components, such as HV components in particular, to be effectively cooled, while components of the motor vehicle that require less cooling power, for example, can be supplied with an individually tailored cooling power in the second subcircuit via the shut-off valve. HV components of the motor vehicle can include, for example, a traction battery and / or power electronics and / or electrical machines, in particular electric drive motors, of the motor vehicle.

[0019] Preferably, the chiller's thermal output is determined using a first temperature sensor in the flow of the secondary circuit and a second temperature sensor in the return of the secondary circuit. Determining the chiller's thermal output by measuring the temperature difference upstream and downstream of the chiller is a simple and effective way of determining thermal output.

[0020] According to a further preferred embodiment of the present invention, the second sub-circuit is used to cool an interior of the motor vehicle. Preferably, an evaporator for cooling fresh air and / or recirculated air is cooled in the second sub-circuit. This advantageously makes it possible for only one air conditioning compressor to supply cooling to both cooling-intensive components, such as the high-voltage components of the motor vehicle, and less cooling-intensive components, such as the interior air conditioning. The shut-off valve, which is monitored for leaks, ensures a high degree of reliability for the correct supply of cooling.

[0021] Furthermore, it is preferably provided that if a leak in the shut-off valve is detected, a warning message is issued and / or an error code is stored in a memory of the motor vehicle. This can inform a driver of the motor vehicle to drive to a workshop that will take care of the detected leak in the shut-off valve without leading to critical situations, such as a failure of the cooling of the HV components. Furthermore, by indicating the leak and the resulting timely repair of the leak, it is ensured that an unnecessary amount of electrical power is not converted into cooling power, which saves energy during operation of the motor vehicle. Finally, by indicating problems with unwanted cooling power, irritations that could arise, for example, from too cold fresh air being supplied to the interior can be avoided.

[0022] A further object for solving the problem mentioned above is a motor vehicle which is configured to carry out the method according to the invention.

[0023] According to a further preferred embodiment of the present invention, the shut-off valve is designed as an analog valve, preferably without direct position feedback. The use of such a valve is cost-effective. Analog valves without complex technology are typically very robust, lightweight, and require little installation space.

[0024] All details, features, and advantages disclosed in connection with the method according to the invention also relate to the motor vehicle according to the invention. Likewise, all details, features, and advantages disclosed in connection with the motor vehicle according to the invention also relate to the method according to the invention.

[0025] Further details, features, and advantages of the invention will become apparent from the drawings and the following description of preferred embodiments with reference to the drawings. The drawings merely illustrate exemplary embodiments of the invention, which do not limit the scope of the invention. Fig. 1 schematically illustrates a detail of a motor vehicle according to an exemplary embodiment of the present invention for carrying out a method according to an exemplary embodiment of the present invention. Fig. 2 schematically illustrates a motor vehicle according to an exemplary embodiment of the present invention.

[0026] Fig. Figure 1 schematically illustrates a detail of a motor vehicle 100 (see Fig.2) according to an exemplary embodiment of the present invention. The motor vehicle 100 is configured to perform a method according to an exemplary embodiment of the present invention, as described below.

[0027] The motor vehicle 100 has a first sub-circuit 1 with an air conditioning compressor 3 and a condenser 13. This cools a refrigerant in the first sub-circuit 1. The first sub-circuit 1 further has a chiller 4 with an electric expansion valve 16, which cools a coolant in a secondary circuit 6. The secondary circuit 6 is provided for cooling HV components 7 of the motor vehicle 100. HV components 7 can include, for example, a traction battery, power electronics, or an electric traction motor of the motor vehicle 100. The HV components 7 typically require a comparatively high cooling capacity. A pump 14 is provided in the secondary circuit 6 to operate the secondary circuit 6.

[0028] The first subcircuit 1 is further connected to a second subcircuit 2 via a shut-off valve 5. An evaporator 8, which has a thermal expansion valve 17, is supplied with coolant via the second subcircuit 2. The evaporator 8 cools fresh air and / or recirculated air, which is provided by a fan 11 from a fresh air and / or recirculated air supply 12 via an air path 15 for air conditioning the interior 101 from the surroundings of the motor vehicle 100 or the interior 101 and is conveyed into the interior 101 of the motor vehicle 100. The interior 101 is air-conditioned via the evaporator 8.

[0029] Typically, the air conditioning of the interior 101 requires significantly less cooling power than the temperature control of the HV components 7 of the motor vehicle 100. If no cooling power is needed at the evaporator 8, the shut-off valve 5 is closed. In order to save costs, reduce weight, and take up as little installation space as possible, the shut-off valve 5 is designed as an analog valve without direct feedback of the position of the shut-off valve 5. A problem here can be that leaks in the shut-off valve 5 are not detected. If the shut-off valve 5 is closed and still allows coolant to pass into the second sub-circuit 2, the incoming fresh or recirculated air may be cooled too much. This results in undesirably high energy consumption, and components of the sub-circuits 1, 2 are subjected to greater load than necessary.

[0030] To test the tightness of the shut-off valve 5, the thermal output of the chiller 4 is compared with the electrical output of the air conditioning compressor 3 when the shut-off valve 5 is closed. An operating point-dependent characteristic value of the first sub-circuit 1 is taken into account.

[0031] The thermal output of chiller 4 added to the thermal output of the second sub-circuit 2 is equal to the characteristic number multiplied by the electrical output of air conditioning compressor 3. When shut-off valve 5 is closed and sealed, the thermal output of the second sub-circuit 2 is zero. This means that when shut-off valve 5 is closed and sealed, the electrical output of air conditioning compressor 3 is equal to the thermal output of chiller 4 divided by the operating point-dependent characteristic number. If this condition is met, the closed shut-off valve 5 is sealed. If this condition is not met, it can be concluded that shut-off valve 5 is leaking.

[0032] The thermal output of the chiller 4 is determined via a difference between a first temperature sensor 9 in the flow of the secondary circuit 6 and a second temperature sensor 10 in the return of the secondary circuit 6.

[0033] In order to improve the informative value regarding the tightness of the shut-off valve 5, the method is carried out only in a stationary state of the air conditioning compressor 3 and in particular after a waiting time after a start of the air conditioning compressor 3.

[0034] If a leak in the shut-off valve 5 is detected, this is communicated to the driver and / or an error code is stored in a memory of the motor vehicle 100. List of reference symbols 1 first subcircuit 2 second subcircuit 3 air conditioning compressor 4 chillers 5 Shut-off valve 6 Secondary circuit 7 HV component 8 evaporators 9 first temperature sensor 10 second temperature sensor 11 blowers 12 Fresh air and / or recirculated air supply 13 Capacitor 14 Pump 15 Air path for air conditioning the interior 16 electric expansion valve 17 thermal expansion valve 100 motor vehicles 101 Interior

Claims

[1] Method for operating a motor vehicle (100), wherein the motor vehicle (100) has a cooling circuit with a first sub-circuit (1) and a second sub-circuit (2), wherein the first sub-circuit (1) has an air conditioning compressor (3) and a chiller (4), wherein the second sub-circuit (2) is connected to the first sub-circuit (1) via a shut-off valve (5), characterized by that, with the shut-off valve (5) closed, the tightness of the shut-off valve (5) is checked using a thermal output of the chiller (4) and an electrical output of the air conditioning compressor (3). [2] Method according to claim 1, characterized by that an operating point-dependent characteristic value of the first sub-circuit (1) is taken into account to test the tightness. [3] Method according to one of the preceding claims, characterized by that the method is only carried out in a stationary operation of the air conditioning compressor (3). [4] Method according to claim 3, characterized by that the process is only carried out after a waiting time after the air conditioning compressor (3) has been started. [5] Method according to one of the preceding claims, characterized by that the chiller (4) operates a secondary circuit (6) for cooling HV components (7) of the motor vehicle (100). [6] Method according to claim 5, characterized by that the thermal output of the chiller (4) is determined by means of a first temperature sensor (9) in the flow of the secondary circuit (6) and a second temperature sensor (10) in the return of the secondary circuit (6). [7] Method according to one of the preceding claims, characterized by that an interior (101) of the motor vehicle (100) is cooled with the second partial circuit (2), wherein preferably an evaporator (8) for cooling fresh air and / or recirculated air is cooled in the second partial circuit (2). [8] Method according to one of the preceding claims, characterized by that when a leak in the shut-off valve (5) is detected, a warning message is issued and / or an error code is stored in a memory of the motor vehicle (100). [9] Motor vehicle (100), characterized by that the motor vehicle (100) is configured to carry out a method according to one of the preceding claims. [10] Motor vehicle (100) according to claim 9, characterized by that the shut-off valve (5) is designed as an analog valve, preferably without direct feedback of a position.

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