Method and device for operating an engine compartment fan for a motor vehicle

Abstract

Method for operating an engine compartment fan (6) for an engine compartment (2) of a motor vehicle (1) in which at least one component (3, 4) for driving the motor vehicle (1) is arranged, comprising the following steps: - Determining a current engine compartment temperature (T MRModell ) depending on a heat energy input (E WE ) into the engine compartment (2) and a heat energy discharge (E WA ) from the engine compartment (2); - Control of the engine compartment fan (6) depending on the determined current engine compartment temperature (T MRModell ), where the current engine compartment temperature (T MRModell ) depending on an integration of the heat energy difference introduced from the heat energy input (E WE ) and the heat energy output (E WA ) is determined, characterized in that the integration within a range of ambient temperatures (T) Umgeb) dependent minimum value (Min) and a predefined maximum value (Max).

Description

Technical area

[0001] The invention relates to motor vehicles, in particular to engine compartment fans for motor vehicles, in order to dissipate heat generated by the operation of an internal combustion engine and to prevent overheating of components in the engine compartment. State of the art

[0002] In a motor vehicle powered by an internal combustion engine, heat is introduced into the engine compartment by the internal combustion engine and exhaust system. To dissipate this heat, the engine compartment is flushed with airflow when the vehicle is moving. If the airflow is insufficient to dissipate the heat energy introduced by the internal combustion engine and exhaust system due to the vehicle's low speed, the heat energy is dissipated by an engine compartment fan. The overall aim is to prevent damage to components in the engine compartment due to excessive heat exposure.

[0003] Engine compartment fans are not typically designed for high operating hours over their lifetime. However, based on a conventional two-point control for operating the engine compartment fan, it cannot be guaranteed that the manufacturer's guaranteed operating hours will not be exceeded.

[0004] An extended fan run-on time is known from DE 103 20 746 A1. To calculate the required fan run-on time, the energy input to the combustion engine is taken into account. Disclosure of the invention

[0005] According to the invention, a method for operating an engine compartment fan for an engine compartment of a motor vehicle according to claim 1, as well as a device and a motor vehicle according to the independent claims are provided.

[0006] Further embodiments are specified in the dependent claims.

[0007] According to a first aspect, a method is provided for operating an engine compartment fan for an engine compartment of a motor vehicle in which at least one component, in particular for driving the motor vehicle, is arranged. The method comprises the following steps: - Determining a current engine compartment temperature depending on a heat energy input into the engine compartment and a heat energy output from the engine compartment; and - Control of the engine compartment fan depending on the current engine compartment temperature.

[0008] One idea behind the above method is to operate the engine compartment fan not according to a control system based on an actual temperature measurement in the engine compartment, but rather depending on the heat energy inputs and outputs into and out of the motor vehicle's engine compartment, in particular depending on a corresponding heat energy balance, and to predict a temperature profile in the engine compartment. This is then used to determine the additional cooling power required to be provided by the engine compartment fan.

[0009] A conventional method for controlling the engine compartment fan uses a two-point control that takes a tolerance range into account. Therefore, the engine compartment fan is switched on before the critical, non-exceedable temperature limit in the engine compartment is reached. This can lead to the engine compartment fan being activated in operating situations where the temperature limit would not be exceeded. This unnecessarily increases the number of operating hours of the engine compartment fan.

[0010] The additional cooling power requirement determined by determining the thermal energy balance and the resulting activation of the engine compartment fan can prevent the engine compartment fan from being switched on unnecessarily. The above method essentially provides for the quantities of heat introduced into or removed from the engine compartment of a motor vehicle to be determined depending on the thermal energy inputs into and outputs from the engine compartment, which determines the temporal progression of the engine compartment temperature. The above control strategy for the engine compartment fan, dependent on the thermal energy balance, thus takes into account a temporal aspect of the cooling and heating of the engine compartment, so that the engine compartment fan is only switched on when the exhaust storage and / or the combustion engine have introduced a certain amount of heat into the engine compartment that cannot be dissipated by airflow cooling.

[0011] An advantage of the above method is that no temperature sensor is required to measure the engine compartment temperature to operate an engine compartment fan. Furthermore, it can be ensured that the engine compartment fan is only switched on when necessary for efficient cooling of the engine compartment, since the heat energy input is greater than the heat energy output due to airflow cooling, and there is a risk that the engine compartment temperature limit will be exceeded.

[0012] Furthermore, determining the current engine compartment temperature may include the following steps: - Providing at least one indication of the current temperature of at least one component in the engine compartment of the motor vehicle; - Determining the heat energy input into the engine compartment depending on at least one indication of the current temperature of at least one component.

[0013] It can be provided that the heat energy input into the engine compartment is determined depending on a sum of the particular weighted information on the current temperature of several components in the engine compartment of the motor vehicle or depending on a maximum value of the at least one particular weighted information on the current temperature of the at least one component in the engine compartment of the motor vehicle.

[0014] According to one embodiment, the heat energy discharge from the engine compartment can be determined depending on a passive air flow through the engine compartment, wherein in particular the passive air flow through the engine compartment is determined depending on the vehicle speed and the ambient temperature.

[0015] Furthermore, it is planned to determine the current engine compartment temperature depending on an integration of the introduced heat energy difference from the heat energy input and the heat energy output.

[0016] According to the invention, the integration is carried out within a minimum value dependent on an ambient temperature and a predetermined maximum value.

[0017] In particular, the integration may be reset to a value dependent on an ambient temperature if it is determined that a vehicle speed is greater than a predetermined speed threshold for a predetermined period of time.

[0018] Furthermore, after the combustion engine has been switched off, a run-on of the engine compartment fan can be provided, whereby the engine compartment fan is started or the operation of the engine compartment fan is maintained if or as long as the last determined engine compartment temperature is greater than a predetermined switch-off temperature threshold value.

[0019] Alternatively or additionally, after the combustion engine has been switched off, a run-on of the engine compartment fan can be provided, wherein the engine compartment fan is started or the operation of the engine compartment fan is maintained depending on the at least one indication of the current temperature of the at least one component in the engine compartment of the motor vehicle.

[0020] According to a further aspect, a device, in particular a control unit, is provided for operating an engine compartment fan for an engine compartment of a motor vehicle in which at least one component, in particular for driving the motor vehicle, is arranged. The device is designed to: - to determine a current engine compartment temperature depending on a heat energy input into the engine compartment and a heat energy output from the engine compartment; - to control the engine compartment fan depending on the current engine compartment temperature.

[0021] According to a further aspect, a motor vehicle is provided, wherein an engine compartment comprises: - at least one component, in particular for driving the motor vehicle, which provides thermal energy input into the engine compartment; - a device for cooling the engine compartment by airflow; - an engine compartment fan; - the above device. Brief description of the drawings

[0022] Embodiments are explained in more detail below with reference to the attached drawings. They show: Fig. 1 is a schematic representation of a motor vehicle with an engine compartment for an engine system; Fig. 2 a functional diagram illustrating a function for operating an engine compartment fan; Fig. 3 a diagram illustrating the temporal progression of the temperature in the exhaust system, the vehicle speed and the heat energy introduced into the engine compartment. Description of embodiments

[0023] Fig. 1 schematically shows a motor vehicle 1 with an engine compartment 2. The engine compartment 2 is provided with one or more components that release heat during operation, such as an internal combustion engine 3 and an exhaust system 4. The internal combustion engine 3 expels combustion exhaust gases via the exhaust system 4. The engine compartment 2 is essentially closed, but ambient air can flow through it. The engine compartment 2 is usually (but not necessarily) located at the front of the motor vehicle 1 and is open at the front via an air intake device 5, such as a radiator grille 5, so that when the vehicle 1 moves in a forward direction, ambient air flows through the engine compartment 2 as airstream F.

[0024] Furthermore, an engine compartment fan 6 can be provided near the air intake device 5 to support or enhance the flow of ambient air through the engine compartment 2 when airflow cooling is insufficient due to the vehicle's low speed. The engine compartment fan 6 can be designed to be variably controllable or simply switched on and off.

[0025] A control unit 7 is provided which serves to control the engine compartment fan 6. In the control unit 7, a function, in particular a software function, is executed as shown in the functional diagram of the Fig. 2 is shown.

[0026] In a first thermal energy input map 11, a recorded or modeled indication of a temperature T Abgas1 , T Abgas2 , T Motorfrom the heat-emitting components, ie sections of the exhaust system 4 and the combustion engine 3, and a resulting heat energy input into the engine compartment 2 is estimated using the heat input map 11. The estimate can be based either on a sum of weighted temperatures T Abgas1 , T Abgas2 , T Motor of sections of the exhaust system 4 or the combustion engine 3. The temperatures T Abgas1 , T Abgas2 , T Motor are multiplied by a multiplier 12 with corresponding weighting factors G Abgas1 , G Abgas2 and G Motor weighted to obtain the weighted temperatures G Abgas1 * T Abgas1 , G Abgas2 * T Abgas2 , G Motor * T Motor The weighting factors G Abgas1 , G Abgas2 and G Motorare applied and represent a heat transfer coefficient of the respective component into the engine compartment 2 and the arrangement of the component 3, 4 in the engine compartment 2.

[0027] Alternatively, in particular instead of summing up as in Fig. 2, using a maximum formation in a maximum block 13 for all components 3, 4, the highest value of the weighted temperatures G Abgas1 * T Abgas1 , G Abgas2 * T Abgas2 , G Motor * T Motor as an input variable to the heat energy input map 11, since this determines the heat energy input significantly. Here, the weighting factors G Abgas1 , G Abgas2 and G Motorcan also be chosen to be equal in order to approximately represent the heat energy input under the assumption that all components 3, 4 have the maximum temperature occurring in the engine compartment 2. The heat energy input from the engine system formed by the combustion engine 3 and the exhaust system 4 can also be determined solely as a function of a temperature at the exhaust system 4 or the temperature of the combustion engine 3.

[0028] The heat energy input E determined by the heat energy input map 11 WE is fed to a subtraction function 14 and a heat energy output E WA subtracted to obtain a heat energy balance. The heat energy output E WA is calculated from a heat energy discharge map 15 depending on the vehicle speed v Fahrzeug and the temperature T Umgeb of the ambient air. The heat energy output E WAis physically determined by the ambient air flowing through the air inlet device 5 when the motor vehicle 1 is traveling, whereby airflow cooling is achieved.

[0029] In one embodiment, the heat energy discharge caused by a previously performed activation of the engine compartment fan 6 can also be taken into account when preparing the above heat energy balance.

[0030] The result of subtracting the heat energy input E WE and the heat energy output E WA The determined heat energy difference ΔEW is fed into an integration function 17. The integration in the integration function 17 is carried out over time, and thus a modeled temperature value T MRModell the current temperature level actually prevailing in the engine compartment 2.

[0031] Based on the determined or modeled temperature value T MRModellthe actual engine compartment temperature prevailing in the engine compartment 2, a cooling request L ANF for the engine compartment fan 6. The cooling requirement L Anf can be a variable cooling requirement with values ​​of, for example, between 0 and 100%, which can be specified as a duty cycle for controlling the engine compartment fan, or an on / off requirement for the engine compartment fan 6. The engine compartment fan 6 can be controlled depending on the variable cooling requirement L ANF be switched on or off, e.g. depending on a threshold comparison with a predefined cooling requirement threshold of e.g. 50%.

[0032] In the event that the engine compartment fan 6 can only be switched on and off, the characteristic function 18 only outputs an on / off signal to the engine compartment fan, which is generated depending on the result of a threshold comparison of the thermal energy introduced into the engine compartment 2 and a predetermined thermal energy threshold. In particular, the engine compartment fan is switched on when the thermal energy in the engine compartment exceeds the specified thermal energy threshold and is switched off when it falls below this thermal energy threshold.

[0033] The integration function 17 is limited by a minimum value Min and a maximum value Max. This ensures that the integration value cannot drift in either the positive or negative direction in the event of an inaccurate estimate by the heat input map 11 or the heat output map 15, ie, cannot deviate arbitrarily from the actual engine compartment temperature. The minimum value Min can be derived from the ambient temperature T Umgeb , which is usually provided as an indication in a motor vehicle, plus a freely applicable predefined temperature offset T Offset The maximum value Max can correspond to a maximum achievable limit temperature or maximum temperature T MRmax of the engine compartment 2, which is specified and basically takes into account the temperature resistance of (passive) components arranged in the engine compartment 2.

[0034] In Fig. 3 are temporal courses of the temperature T Abgas1of the exhaust system section 3, the vehicle speed v Fahrzeug and the heat energy ΔE introduced into the engine compartment 2 W The switch-on time t on , at which the described function switches on the engine compartment fan 6, and a time t off at which the function described above switches off the engine compartment fan 6.

[0035] In the case of vehicles that are stationary or slowly moving with the combustion engine 3 running for a longer period of time, the maximum achievable temperature level of the engine compartment 2 will always be reached due to the integration, since the level of the heat energy discharge E WA never the level of heat energy input E WE can reach. As a result, the engine compartment fan 6 is also switched on after a certain period of time in this operating range (ie, slowly moving or stationary vehicle).

[0036] In addition, it can be provided that the integration value is set to an initial value, ie the minimum achievable temperature level of the engine compartment, ie the sum of the ambient temperature T Umgeb and the freely applicable predefined temperature offset T Offset of e.g. 20°C is reset as soon as the vehicle speed v Fahrzeug sufficiently long above a given speed threshold V THR This takes into account that at high vehicle speeds, experience has shown that a measurable, always equally dependent on the ambient temperature T Umgebdependent temperature equilibrium. It can therefore be assumed that at high vehicle speeds, the engine compartment temperature has cooled down due to the fresh air flow through the engine compartment 2 to such an extent that the minimum temperature level of the engine compartment 2 that can be reached during operation has been reached. The reset is carried out by a comparison function 20 for comparing the vehicle speed v Fahrzeug with the speed threshold V THR and a downstream timer 21, which outputs a reset signal R to the integrator function 17 as soon as the vehicle speed v Fahrzeug for a predetermined period of time t S above the speed threshold V THR The active reset signal R sets the integrator 17 to the value of the sum of the ambient temperature T Umgeb and the freely applicable predefined temperature offset T Offset and also the timer 21.

[0037] Furthermore, a run-on function for the engine compartment fan 6 can be provided, which can be activated when the combustion engine 3 is switched off, ie when the combustion engine 2 is switched off, which can be signaled, for example, by a terminal 15 off. The last measured engine compartment temperature T MRModell the actual temperature level prevailing in the engine compartment 2 is determined with a shutdown temperature threshold value T Abstell_THR When the measured temperature value T MRModell in the engine compartment 2 greater than or equal to the shutdown temperature threshold T Abstell_THR is reached, the engine compartment fan 6 is started to run on or the engine compartment fan 6 is maintained for an engine compartment temperature run-on time. The engine compartment temperature run-on time corresponds to a period of time that depends on the determined temperature value T MRModell in the engine compartment 2 and by a given engine compartment temperature run-on time map depending on the determined temperature value TMRModell is determined.

[0038] Alternatively or additionally, it may be provided that the cooling requirement L last determined before the combustion engine 2 is switched off ANF , which can be between 0 and 100%, with a cooling demand threshold. If the cooling demand L ANF is greater than or equal to the cooling request threshold value, the run-on of the engine compartment fan 6 is started or the operation of the engine compartment fan 6 is maintained for a cooling request run-on time. The cooling request run-on time corresponds to a period of time that depends on the determined cooling request L ANF depends and by a predetermined determined cooling demand follow-up time map depending on the determined cooling demand L ANF is determined.

[0039] Alternatively or additionally, it may be provided that the maximum temperature T last determined before the combustion engine 2 was switched offAbgas1 , T Abgas2 , T Motor a component 3, 4 is compared with a component temperature threshold. If the maximum temperature is greater than or equal to the component temperature threshold, the overrun of the engine compartment fan 6 is started or the operation of the engine compartment fan 6 is maintained for a component temperature overrun time. The component temperature overrun time corresponds to a period of time that depends on the determined maximum temperature and is determined by a predefined component temperature overrun time map depending on the determined maximum temperature.

[0040] This serves to represent the afterheating effects of the combustion engine 3 and the exhaust system 4 after the combustion engine 3 has been switched off. Therefore, the heat energy inputs of the temperatures T Abgas1 , T Abgas2 , T Motorof the sections of the exhaust system 4 and the combustion engine 3, for example, by calculating the maximum by the maximum function 13. This serves to extend the control unit run-on time in favor of cooling the engine compartment 2, even if the determined engine compartment temperature T MRModell the temperature level at the time the engine is switched off has not yet exceeded the engine compartment temperature threshold, but the temperatures of the exhaust system 4 or the combustion engine 3 nevertheless provide a heat energy input that can probably lead to a limit temperature in the engine compartment 2 being exceeded. In this case, the run-on time of the engine compartment fan 6 is determined via a predetermined component temperature run-on time map, which calculates the temporal extension of the run-on time of the engine compartment fan 6 based on the result of the above maximum formation.

[0041] The total run-on time is set according to a maximum of the engine compartment temperature run-on time and / or the cooling request run-on time and / or the component temperature run-on time.

Claims

[1] Method for operating an engine compartment fan (6) for an engine compartment (2) of a motor vehicle (1), in which at least one component (3, 4) for driving the motor vehicle (1) is arranged, comprising the following steps: - Determine the current engine compartment temperature (T MRModell ) depending on a heat energy input (E WE ) into the engine compartment (2) and a heat energy discharge (E WA ) from the engine compartment (2); - Control of the engine compartment fan (6) depending on the determined current engine compartment temperature (T MRModell ), where the current engine compartment temperature (T MRModell ) depends on an integration of the introduced heat energy difference from the heat energy input (E WE ) and the heat energy output (E WA ) is determined, characterized by that the integration takes place within a range of ambient temperature (T Umgeb ) dependent minimum value (Min) and a given maximum value (Max). [2] Method according to claim 1, wherein determining the current engine compartment temperature (T MRModell ) includes the following steps: - Providing at least one indication of the current temperature (T Abgas1 , T Abgas2 , T Motor ) of at least one component (3, 4) in the engine compartment (2) of the motor vehicle (1); determining the heat energy input (E WE ) into the engine compartment (2) depending on the at least one indication of the current temperature of the at least one component (3, 4). [3] Method according to claim 2, wherein the heat energy input into the engine compartment depends on a sum of the at least one indication of the current temperature (T Abgas1 , T Abgas2 , T Motor ) of the at least one component (3, 4) in the engine compartment (2) of the motor vehicle (1) or depending on a maximum value of the at least one indication of the current temperature (T Abgas1 , T Abgas2 , T Motor) of at least one component (3, 4) in the engine compartment (2) of the motor vehicle (1). [4] Method according to one of claims 1 to 3, wherein the heat energy output (E WA ) from the engine compartment (2) is determined as a function of a passive air flow through the engine compartment (2), wherein the passive air flow through the engine compartment (2) is determined as a function of the vehicle speed (v Fahrzeug ) and the ambient temperature (T Umgep ) is determined. [5] Method according to claim 1, wherein the integration is carried out at a temperature different from an ambient temperature (T Umgep ) dependent value when it is detected that a vehicle speed (v Fahrzeug ) for a predetermined period of time greater (t s ) is defined as a given speed threshold (v THR ) . [6] Method according to one of claims 1 to 5, wherein after switching off the internal combustion engine (3) a run-on of the engine compartment fan (6) is provided, wherein the engine compartment fan (6) is started or the operation of the engine compartment fan (6) is maintained if or as long as the last determined engine compartment temperature (T MRModell ) is greater than a specified shutdown temperature threshold. [7] Method according to one of claims 1 to 6, wherein after switching off the internal combustion engine (3), a run-on of the engine compartment fan (6) is provided, wherein the engine compartment fan (6) is started or the operation of the engine compartment fan (6) is maintained depending on one or more of the following parameters: - at least one indication of the current temperature (T Abgas1 , T Abgas2 , T Motor ) of the at least one component (3, 4) in the engine compartment (2) of the motor vehicle (1); - the last measured engine compartment temperature (T MRModell ); - one determined from the engine compartment temperature (T MRModell ) determined cooling requirement (L ANF ). [8] Device arranged to carry out the method according to one of claims 1 to 7. [9] Motor vehicle (1) comprising the device according to claim 8. [10] Computer program which is arranged to carry out all the steps of a method according to one of claims 1 to 7. [11] A machine-readable storage medium on which a computer program according to claim 10 is stored.

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