VEHICLE WITH REFRIGERATION SYSTEM AND ELECTRICAL UNIT

Abstract

A vehicle comprises a cooling device (10) configured to cool an airflow passing through it, an electrical unit enclosed in a housing (13), and a fan (17) for driving an airflow through the housing (13). A control element (16) is provided to supply the housing (13) with variable proportions of ambient air and the airflow cooled by the cooling device (10).

Description

The present invention relates to a vehicle with a cooling device, such as an air conditioning system, for temperature control of a passenger compartment, and an electrical unit, such as a battery or a power converter, in which condensing moisture, in particular due to short circuits, can cause damage. Such a vehicle is known from US 900 724 B2. This well-known vehicle incorporates a fan that drives a circulating airflow between a housing containing a battery and / or power converter and a passenger compartment to cool the battery. Waste heat from the battery and power converter can thus be used to heat the passenger compartment. However, the amount of heat that can be dissipated from the battery and power converter in this way without compromising the comfort of the passenger compartment occupants is limited. To dissipate the heat generated by an electrical unit, it is advisable to expose it to a cooling ambient airflow. In warm, humid environments, such direct contact promotes condensation of moisture inside the housing, especially when the vehicle is stationary and the unit is not generating heat. If this condensate comes into contact with live surfaces of the electrical unit, it can cause a short circuit. Even if such a short circuit is properly protected by a fuse, it will prevent the vehicle from starting. The purpose of the invention is to minimize the risk of such a short circuit. According to one aspect of the invention, the problem is solved by providing a control element in a vehicle with a cooling device configured to cool an airflow passing through it, an electrical unit enclosed in a housing, and a fan for driving an airflow through the housing, in order to supply the housing with variable proportions of ambient air and the airflow cooled by the cooling device. If the vehicle is switched off and parked while the housing is filled with warm, humid ambient air, condensation can form inside the housing, especially if the environment cools down overnight. When the vehicle is started again the following morning, contact between the condensation and the now live surfaces of the unit can cause a short circuit. The lower the temperature of the cooled airflow, the lower its capacity to hold water vapor. By supplying the housing with the cooled airflow, the amount of water vapor inside can be reduced, ideally to such an extent that the expected cooling of the environment no longer leads to condensation. The invention is applicable to any electrical components of a vehicle, but its application is most worthwhile in an electrically powered vehicle where a battery is capable of releasing high power in the event of a short circuit. The unit to be protected from condensation may in particular include the battery of an electrically powered vehicle, or, if the vehicle has at least one fuel cell to supply the battery, a current converter that is connected between the fuel cell and the battery to convert the output voltage of the fuel cell into a voltage suitable for efficiently charging the battery. A control unit can be provided to automatically control the fans depending on climatic conditions, in particular the ambient temperature and humidity. Sensors for recording these parameters can be appropriately positioned on the vehicle and connected to the control unit; it is also conceivable that the control unit receives current values ​​or even future estimated values ​​via a mobile data connection. The control unit should be specifically designed to operate the fan when the vehicle is stationary, in order to displace any humid ambient air from the housing before it can condense. The blower is preferably arranged downstream of the cooling unit and upstream of the housing in a duct running from the cooling unit to the housing. The downstream arrangement allows the cooling unit to be supplied with a stronger airflow than that supplied to the housing; in particular, this allows an air conditioning system conventionally designed for temperature control of the passenger compartment to serve as the cooling unit without the blower restricting the airflow through the air conditioning system. The upstream arrangement causes the airflow from the blower to induce positive pressure in the housing, thus ensuring that any leaks in the housing result in dry air escaping, while preventing humid ambient air from entering the housing. To limit overpressure induced by the blower, a pressure relief valve can be arranged on the housing. An outlet of the housing can be connected or connectable to the passenger compartment in order to supply waste heat from the electrical unit to the passenger compartment. Further features and advantages of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying figures. Fig. 1 shows a block diagram of a vehicle according to the invention. Fig. 1 shows a schematic representation of a motor vehicle with a hybrid power supply system. A hydrogen tank 1 is connected in a known manner to a fuel cell system 2 to supply it with hydrogen gas, which is reacted with atmospheric oxygen in the fuel cells of the system to generate electrical energy. A power converter unit 3 connects the fuel cell system 2 to a battery 4 and to consumers 5, including a drive motor 6 that acts on a drive train 7 of the vehicle, and possibly other electrically operated equipment such as infotainment system, windscreen wipers, fans, or control electronics. An air conditioning system 9 is provided for temperature control of the passenger compartment 8 of the vehicle. The air conditioning system 9 comprises, in the usual manner, a refrigerant circuit with a compressor, a condenser, and an evaporator; in the figure, only the evaporator 10 is shown, which is arranged to cool ambient air or recirculated air from the passenger compartment 8 drawn in through an inlet 11 and, driven by a fan 12, to direct it into the passenger compartment 8. The power converter unit 3 and, optionally, the battery 4 are housed in a casing 13 and can be cooled by air that is circulated through the casing 13. This air is usually ambient air that passes through the casing 13 from an inlet 14 to an outlet 15. If the ambient air contains a lot of moisture, and the airflow through the housing 13 comes to a standstill, for example because the vehicle is parked overnight, it can happen that condensing moisture in the housing 13 reaches contacts of the power converter unit 3 and / or the battery 4 and sooner or later causes damage there, whether through a short circuit or corrosion. To prevent this danger, the housing can, according to the invention, be selectively supplied with ambient air or with air whose moisture content has been reduced by contact with the evaporator 10. By displacing any ambient air present in the housing 13, which may be prone to condensation, with dry air from the evaporator 10, at least before the vehicle is parked, condensation in the housing 13 can be prevented. In the embodiment shown in Fig. 1, switching between ambient air and air from the evaporator is carried out by means of a flap 16, which can be switched between a position in which it opens a connection between the inlet 14 and the housing 13 and separates the housing 13 from the air conditioning 9, and a position in which it connects the housing 13 to the evaporator 10 of the air conditioning and separates it from the inlet 14, by means of an electronic control unit 18. A fan 17 is arranged in Fig. 1 on an air duct section between the flap 16 and the housing 13, so that, depending on the position of the flap 16, it can drive an airflow from the inlet 14 or from the evaporator 10 to the housing. Alternatively, the fan 17 could be arranged on a duct section between the evaporator 10 and the flap 16; such a fan would not obstruct the airflow between the inlet and outlet 14, 15 when switched off; furthermore, the overpressure it generates could passively push the flap 16 into a position in which it allows the airflow from the fan 17 to pass through and at least largely blocks the airflow from the inlet 14. A pressure relief valve 19 can be provided on the housing to allow an airflow driven by the fan 17 to escape from the housing 13 if the path from the housing 13 to the outlet 15 should be blocked. A further flap 20 can be provided on an air duct section between the housing 13 and the outlet 15 in order to selectively direct air heated in the housing 13 either to the outlet 15 or to the passenger compartment 8. In this way, waste heat from the battery 4 and the power converter unit 3 can be used to heat the passenger compartment 8 if required, and the load on the air conditioning system 9 is reduced. The control unit 18 can be programmed to operate the fan 17 for a period of time each time the vehicle comes to a stop and is switched off, which is at least sufficient to completely replace the air in the housing 13, which may be prone to condensation, with air dried at the evaporator 10. The control unit 18 can be connected to sensors 21 for detecting the temperature and / or humidity of the ambient air. Based on the measurement data from these sensors, it can be estimated whether the ambient air is humid enough to allow condensation to occur in the housing 13. If the ambient air is found to be too dry for condensation, the fan 17 can be omitted from operating after the vehicle is switched off. If condensation is found to be possible, the operating time of the fan 17 can be selected so that enough dry air is supplied from the evaporator 10 to the housing 13 to reduce the average humidity in the housing 13 to such an extent that no further condensation is expected. A decision as to whether condensation is to be expected in the housing is based on an assumption about the cooling that the housing 13 experiences before the vehicle is restarted: Condensation is to be expected if the lowest expected temperature is below the dew point of the air currently in the housing 13. Such an assumption can be made generally, e.g., based on past observations of day-night temperature fluctuations for a region where the vehicle is used. A more precise assessment is possible in individual cases based on a weather forecast; for this purpose, the control unit 18 can be equipped with internet access, allowing it to retrieve a predicted night temperature from a meteorological service. If necessary, current values ​​of the ambient temperature and humidity at the vehicle's operating location can also be obtained from such a service; in this case, the sensors 21 can be omitted. Reference sign 1 Hydrogen tank 2 Fuel cell system 3 Power converter unit 4 Battery 5 Consumers 6 Drive motor 7 Drivetrain 8 Passenger compartment 9 Air conditioning 10 Evaporator 11 Inlet 12 Fan 13 Housing 14 Inlet 15 Outlet 16 Flap 17 Fan 18 Control unit 19 Pressure relief valve 20 Flap 21 Sensors QUOTES INCLUDED IN THE DESCRIPTION This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature US 900 724 B2

[0002]

Claims

Vehicle with a cooling device (10) configured to cool an airflow passing through it, an electrical unit enclosed by a housing (13) and a fan (17) for driving an airflow through the housing (13), characterized in that a control element (16) is provided to supply the housing (13) with variable proportions of ambient air and the airflow cooled by the cooling device (10). Vehicle according to claim 1, further comprising a battery (4) and a drive motor (6) powered by the battery (4), optionally further comprising at least one fuel cell (2) and a current converter (3) for supplying the battery (4) via the fuel cell (2). Vehicle according to claim 1 or 2, wherein the electrical unit comprises the battery (4) and / or a current converter (3). Vehicle according to claim 2 or 3, further comprising a control unit (18) for controlling the fan (17) depending on climatic conditions, in particular the ambient temperature and humidity, or on the movement state of the vehicle. Vehicle according to claim 4, wherein the control unit (18) is configured to operate the fan when the vehicle is stationary. Vehicle according to one of the preceding claims, wherein the blower (17) is arranged on a channel extending from the cooling device (10) to the housing (13) downstream of the cooling device (10) and upstream of the housing (13). Vehicle according to one of the preceding claims, wherein a pressure relief valve (19) is arranged on the housing (13) to limit an internal pressure of the housing (13). Vehicle according to one of the preceding claims, wherein an outlet of the housing (13) is connected or connectable to a passenger compartment (8).

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