Method for operating a motor vehicle and motor vehicle

Abstract

A method for operating a motor vehicle (100) is proposed, in which the motor vehicle (100) comprises a cooling circuit having a first sub-circuit (1) and a second sub-circuit (2), in which the first sub-circuit (1) comprises an air-conditioning compressor (3) and a cooler (4), in which the second sub-circuit (2) is connected to the first sub-circuit (1) via a shut-off valve (5), in which when the shut-off valve (5) is closed, the first sub-circuit (1) and the second sub-circuit (2) are closed. The sealing of the shut-off valve (5) is checked on the basis of the thermal power of the cooler (4) and the electric power of the air-conditioning compressor (3). The invention further relates to a motor vehicle (100).

Description

TECHNICAL FIELD

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

[0002] Modern motor vehicles have various components that need to be actively cooled. In particular for high-performance electric vehicles, the cooling of high-voltage components is of great importance. At high power requirements, waste heat is generated at the traction battery, the power electronics and the electric machine, which must be dissipated in order to avoid damage to these components.

[0003] In addition to the cooling necessary for normal operation of the driving operation, air conditioning of the passenger compartment of the motor vehicle is usually provided. In general, fresh air and / or recirculated air is cooled for this purpose at least in summer months.

[0004] The cooling power required by the different cooling requirements of the motor vehicle is very different. Thus, the cooling of the high-voltage components usually requires significantly higher cooling power compared to the air conditioning of the passenger compartment.

[0005] Despite the different cooling power requirements, the motor vehicle is equipped with only a small number of air conditioning compressors, preferably only one, for reasons of space efficiency, cost savings and weight reduction. The air conditioning compressor drives several, for example two, sub-circuits of the cooling circuit. In order to meet the different cooling power requirements, one of the sub-circuits can be disconnected as required by means of a shut-off valve.

[0006] Such a shut-off valve is difficult to monitor. Shut-off valves often fail, which cannot be directly detected. This can lead to an overcooling of one of the sub-circuits. SUMMARY

[0007] The problem addressed by the invention is to provide a method for operating a motor vehicle and a motor vehicle which do not have the aforementioned disadvantages arising from the prior art, but are able to detect a failure of a shut-off valve.

[0008] The problem is solved by a method for operating a motor vehicle according to claim 1 and a motor vehicle according to claim 9.

[0009] In the method for operating a motor vehicle according to the application, the motor vehicle comprises a first sub-circuit with an air-conditioning compressor and a chiller. The motor vehicle further comprises a second sub-circuit. The second sub-circuit is connected to the first sub-circuit via a shut-off valve. According to the application, it is provided that the tightness of the shut-off valve is checked on the basis of the thermal power of the chiller and the electrical power of the air-conditioning compressor when the shut-off valve is closed. Advantageously, it is thus possible to infer the state of the shut-off valve. If there is a discrepancy between the electrical power of the air-conditioning compressor and the thermal power of the chiller, it can be assumed that the thermal power is reduced via the shut-off valve in the second sub-circuit, which is supposed to be closed. In other words, a balance of the electrical power of the air-conditioning compressor and the thermal power of the chiller is established, and it is checked whether the balance holds. If the balance does not hold, it is assumed that there is an undesired loss of cold in the system.

[0010] Preferably, it is provided that the motor vehicle is an electric motor vehicle, for example a hybrid vehicle or a purely electric motor vehicle.

[0011] Advantageous embodiments and further developments of the application can be obtained from the dependent claims and from the description with reference to the drawings.

[0012] According to a preferred embodiment of the application, it is envisaged that the tightness is checked taking into account a performance coefficient (Kennzahl) which is related to the operating condition of the first sub-circuit. Advantageously, it is thus possible to take into account system-specific deviations and particularities as appropriate. In particular, it is possible, for example, to take into account power losses which result in a power difference.

[0013] The thermal power of the chiller plus the thermal power occurring in the second sub-circuit is equal to the performance coefficient multiplied by the electrical power of the air-conditioning compressor. When the shut-off valve is closed and tight, the thermal power of the second sub-circuit is zero. The electrical power of the air-conditioning compressor is thus equal to the thermal power of the chiller divided by the performance coefficient which is related to the operating condition, in the case where the shut-off valve is closed and tight. The tightness of the shut-off valve is checked using this monitoring equation. If the monitoring equation is fulfilled, the closed shut-off valve is tight. If the monitoring equation is not fulfilled, it can be inferred that there is a leak in the shut-off valve.

[0014] It is envisaged that the performance coefficient is dependent on the coolant pressure and / or the outside temperature and / or the coolant temperature in the inflow line and / or the coolant temperature in the return line.

[0015] According to a further preferred embodiment of the application, the method is carried out only during steady-state operation of the air-conditioning compressor. This advantageously ensures that the checking of the tightness of the shut-off valve is not disturbed by fluctuations in the electrical power of the air-conditioning compressor. Such fluctuations in the electrical power usually occur during non-steady-state operation of the air-conditioning compressor, that is to say, in the case where the electrical power of the air-conditioning compressor is increasing or decreasing.

[0016] Preferably, the method is only executed after a waiting period after the start of the air conditioning compressor. In particular, during the start-up phase of the air conditioning compressor, it is to be expected that the electrical power of the air conditioning compressor will not be fully converted into thermal power at the chiller. On the one hand, losses in the air conditioning compressor itself are higher during the start-up of the air conditioning compressor than during steady-state operation. On the other hand, there are further losses in the system, for example due to the cooling of the piping of the first sub-circuit and other components of the first sub-circuit. The waiting period advantageously prevents that the aforementioned losses during the start-up of the air conditioning compressor falsify the tightness check of the shut-off valve.

[0017] According to a further preferred embodiment of the present application, the secondary circuit is operated with the chiller for cooling high-voltage components of the motor vehicle. This advantageously allows an efficient cooling of components with high cooling demand, for example high-voltage components, while components of the motor vehicle with less cooling demand can be supplied with individually coordinated cooling power in the second sub-circuit by means of the shut-off valve. The high-voltage components of the motor vehicle can comprise traction batteries, power electronics and / or electric machines, in particular drive electric machines.

[0018] Preferably, a first temperature sensor in the inflow line of the secondary circuit and a second temperature sensor in the return line of the secondary circuit are used to determine the thermal power of the chiller. Determining the thermal power of the chiller by measuring the temperature difference upstream and downstream of the chiller is a simple and efficient method of determining the thermal power.

[0019] According to a further preferred embodiment of the present application, it is provided to cool the passenger compartment of the motor vehicle with the second sub-circuit. Preferably, it is provided to cool an evaporator in the second sub-circuit for cooling fresh air and / or recirculated air. Thus advantageously, by means of only one air conditioning compressor, it is possible to provide cooling both to components with high cooling demand, for example high-voltage components of the motor vehicle, and to components with less cooling demand, for example air conditioning devices of the passenger compartment. The shut-off valve, whose tightness is monitored, is responsible for the correct supply of cooling with high reliability.

[0020] It is further preferably provided that, if a leakage of the shut-off valve is detected, an alarm is issued and / or an error code is stored in a memory of the motor vehicle. This can inform the driver of the motor vehicle to go to a repair shop, which can perform a detection of the leakage of the shut-off valve without a critical situation, for example a cooling failure of the high-voltage components, occurring. Furthermore, by indicating a leakage and repairing it in time, it is achieved that a large amount of electrical power is not unnecessarily converted into cooling power, which saves energy when operating the motor vehicle. Finally, by informing about a problem with an undesired cooling power, it is possible to avoid distress that can be triggered, for example, by too cold fresh air being supplied into the passenger compartment.

[0021] A further subject for solving the above-mentioned problems is a motor vehicle configured to execute the method according to the present application.

[0022] According to a further preferred embodiment of the present application, it is envisaged that the shut-off valve is configured as a proportional valve, preferably without direct feedback of the state-position. The use of such a valve is cost-effective. Proportional valves without complex technology are usually very robust, lightweight and require little installation space.

[0023] All details, features and advantages related to the method according to the present application also apply to the motor vehicle according to the present application. Likewise, all details, features and advantages related to the motor vehicle according to the present application also apply to the method according to the present application. BRIEF DESCRIPTION OF DRAWINGS

[0024] Further details, features and advantages of the present application can be obtained from the following description of preferred embodiments and with reference to the drawings. The drawings show only exemplary embodiments of the present application and do not limit the inventive concept.

[0025] Figure 1 Details of the motor vehicle according to exemplary embodiments of the present application for carrying out the method according to exemplary embodiments of the present application are schematically shown.

[0026] Figure 2 A motor vehicle according to exemplary embodiments of the present application is schematically shown. DETAILED DESCRIPTION

[0027] Figure 1 Details of a motor vehicle 100 according to exemplary embodiments of the present application (cf. Figure 2 ) are schematically shown. The motor vehicle 100 is configured to carry out the method according to exemplary embodiments of the present application, as described below.

[0028] The motor vehicle 100 has a first sub-circuit 1 with an air-conditioning compressor 3 and a condenser 13. Thereby, the refrigerant is cooled in the first sub-circuit 1. The first sub-circuit 1 further comprises a cooler 4 with an electric expansion valve 16 for cooling a coolant in a secondary circuit 6. The secondary circuit 6 is used for cooling high-voltage components 7 of the motor vehicle 100. The high-voltage components 7 can comprise, for example, a traction battery, power electronics or a traction electric machine of the motor vehicle 100. Usually, the high-voltage components 7 require a relatively high cooling power. For operating the secondary circuit 6, a pump 14 is provided in the secondary circuit 6.

[0029] The first sub-circuit 1 is further connected to the second sub-circuit 2 via a shut-off valve 5. Via the second sub-circuit 2, coolant is supplied to an evaporator 8 comprising a thermal expansion valve 17. The evaporator 8 cools fresh air and / or recirculated air, which is provided from the surroundings or the passenger compartment 101 of the motor vehicle 100 by a fan 11 via an air supply 12 from fresh air and / or recirculated air to the passenger compartment 101 of the motor vehicle 100 and is transported into the passenger compartment 101 of the motor vehicle 100. The passenger compartment 101 is air-conditioned via the evaporator 8.

[0030] Generally, the cooling power required for air-conditioning of the passenger compartment 101 is significantly lower than the cooling power required for temperature control of the high-voltage components 7 of the motor vehicle 100. If the evaporator 8 does not require cooling power, 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 a simulation valve without direct feedback of the state-position of the shut-off valve 5. In this case, there can be problems in detecting a leak in the shut-off valve 5. If the shut-off valve 5 is closed but still allows coolant to pass into the second sub-circuit 2, it results in the incoming fresh air or recirculated air being over-cooled. This results in there being an undesired high energy consumption and the components of the sub-circuits 1, 2 being subjected to unnecessary greater loads.

[0031] In order to check the tightness of the shut-off valve 5, the thermal power of the chiller 4 is compared with the electrical power of the air-conditioning compressor 3 when the shut-off valve 5 is closed. Here, the performance coefficient of the first sub-circuit 1 is taken into account.

[0032] The thermal power of the chiller 4 plus the thermal power of the second sub-circuit 2 equals the performance coefficient times the electrical power of the air-conditioning compressor 3. In the case of a closed and tight shut-off valve 5, the thermal power of the second sub-circuit 2 is zero. Therefore, in the case of a closed and tight shut-off valve 5, the electrical power of the air-conditioning compressor 3 equals the thermal power of the chiller 4 divided by the performance coefficient of the operating condition. If this condition is met, the closed shut-off valve 5 is tight. If this condition is not met, it can be concluded that there is a leak in the shut-off valve 5.

[0033] The thermal power of the chiller 4 is determined by the difference between a first temperature sensor 9 in the inflow line of the secondary circuit 6 and a second temperature sensor 10 in the return line of the secondary circuit 6.

[0034] In order to improve the accuracy of determining the tightness of the shut-off valve 5, the method is only carried out when the air-conditioning compressor 3 is in a steady state, in particular after a waiting period after the air-conditioning compressor 3 has been started.

[0035] If a leak in the shut-off valve 5 is detected, this is reported to the driver and / or an error code is stored in a memory of the motor vehicle 100.

[0036] List of reference signs

[0037] 1 first sub-circuit

[0038] 2 second sub-circuit

[0039] 3 air conditioning compressor

[0040] 4 chiller

[0041] 5 shut-off valve

[0042] 6 secondary circuit

[0043] 7 high-pressure component

[0044] 8 evaporator

[0045] 9 first temperature sensor

[0046] 10 second temperature sensor

[0047] 11 fan

[0048] 12 fresh air and / or recirculation air supply

[0049] 13 condenser

[0050] 14 pump

[0051] 15 air path for air conditioning of the vehicle cabin

[0052] 16 electric expansion valve

[0053] 17 thermal expansion valve

[0054] 100 motor vehicle

[0055] 101 vehicle cabin

Claims

1. A method for operating a motor vehicle (100), wherein the motor vehicle (100) includes a cooling circuit having a first sub-circuit (1) and a second sub-circuit (2), wherein the first sub-circuit (1) includes an air conditioning compressor (3) and a cooler (4), wherein the second sub-circuit (2) is connected to the first sub-circuit (1) via a shut-off valve (5), characterized in that, When the shut-off valve (5) is closed, the sealing performance of the shut-off valve (5) is checked based on the thermal power of the cooler (4) and the electrical power of the air conditioning compressor (3).

2. The method according to claim 1, characterized in that, The sealing performance is checked by considering the performance coefficients related to the operating conditions of the first sub-circuit (1).

3. The method according to any one of the preceding claims, characterized in that, The method is performed only during the steady-state operation of the air conditioning compressor (3).

4. The method according to claim 3, characterized in that, The method is performed only after the waiting period following the start of the air conditioning compressor (3).

5. The method according to any one of the preceding claims, characterized in that, The secondary circuit (6) for cooling the high-voltage component (7) of the motor vehicle (100) is operated using the cooler (4).

6. The method according to claim 5, characterized in that, The thermal power of the cooler (4) is determined by means of a first temperature sensor (9) in the inlet pipe of the secondary circuit (6) and a second temperature sensor (10) in the return pipe of the secondary circuit (6).

7. The method according to any one of the preceding claims, characterized in that, The second sub-circuit (2) is used to cool the passenger compartment (101) of the motor vehicle (100), wherein preferably the evaporator (8) is cooled in the second sub-circuit (2) to cool fresh air and / or recirculated air.

8. The method according to any one of the preceding claims, characterized in that, If a leak is detected in the shut-off valve (5), an alarm is issued and / or an error code is stored in the memory of the motor vehicle (100).

9. A motor vehicle (100), characterized in that, The motor vehicle (100) is configured to perform the method according to any one of the preceding claims.

10. The motor vehicle (100) according to claim 9, characterized in that, The shut-off valve (5) is configured as a simulated valve, preferably without direct state-position feedback.

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