Method for de-icing process of heat exchanger of heat pump for motor vehicle

Abstract

In order to provide a method for de-icing a heat exchanger of a heat pump of a motor vehicle, which method is insensitive with respect to external parameters influencing the air flow through the evaporator, and with which method unnecessary de-icing processes can be avoided, in a method (100) for de-icing a heat exchanger (11) of a heat pump (10) of a motor vehicle (200), in particular an electric or battery electric or hybrid electric motor vehicle, wherein the heat exchanger (11) is assigned a ventilator (13), wherein the power consumption and / or the rotational speed of the ventilator (13) is monitored, wherein a de-icing process is initiated when the power consumption and / or the rotational speed exceeds and / or falls below a threshold value, it is proposed that the threshold value is determined depending on a parameter, wherein the parameter is an indicator for the current relative air speed of the ambient air (12) with respect to the motor vehicle (200).

Description

TECHNICAL FIELD

[0001] The invention relates to a method for initiating a de-icing process of a heat exchanger of a heat pump of a motor vehicle, in particular an electric vehicle or a battery electric vehicle or a hybrid electric motor vehicle, wherein the heat exchanger is assigned a ventilator, wherein a power consumption and / or a rotational speed of the ventilator is monitored, wherein the de-icing process is initiated when the power consumption and / or the rotational speed exceeds and / or falls below a threshold value.

[0002] Furthermore, the invention relates to a motor vehicle comprising a device for de-icing a heat exchanger of a heat pump of the motor vehicle, wherein the device has a computing unit. BACKGROUND

[0003] Heat pumps are used in electric vehicles for heating the vehicle interior. The heat required for heating is extracted from the outside air. For this purpose, the ambient heat exchanger of the heat pump has to be cooled below the ambient temperature. If the outside air is below its dew point here, frost forms on the surface of the ambient heat exchanger, thereby impeding the air flow through the heat exchanger. Efficient operation of the heat pump is no longer ensured. In order to achieve a flow through the heat exchanger with outside air again, a de-icing cycle is required, in which the heat exchanger is heated. During the de-icing cycle, the ice melts and a flow through the heat exchanger can be achieved again.

[0004] In order to initiate the de-icing process, methods are known from the prior art in which a reduction in the suction pressure of the heat pump is monitored.

[0005] Furthermore, methods are known in which an additional sensor device is used with which the layer thickness of the ice or frost formed on the heat exchanger is measured.

[0006] From DE 10 2009 052 409 B4, an air / water heat pump having an evaporator is known, wherein the evaporator is assigned a fan and a fan control unit. The fan control unit detects the current and / or the rotational speed of the fan and determines the operating point of the fan on the basis of the detected current and / or rotational speed. The fan control unit is designed to monitor the operating point of the fan and to relay a de-icing initiation signal to a regulator when a threshold value is undershot or exceeded.

[0007] EP 0 563 724 B1 discloses a method for determining ice formation on an evaporator of a cooling appliance, wherein the cooling appliance has a ventilator driven by an electric motor for flowing air through the evaporator. In the method, a change in an operating parameter of the motor operating the ventilator is measured.

[0008] It is disadvantageous in the known method of monitoring the suction pressure of a heat pump of a motor vehicle that it is also possible for the suction pressure to fall temporarily during the starting process of the motor vehicle, thus possibly triggering an unnecessary de-icing process.

[0009] Furthermore, the known method does not take into account that the current consumption or rotational speed of a ventilator associated with the heat exchanger in a motor vehicle can additionally be related to other parameters in addition to the thickness of the ice layer on the evaporator. SUMMARY

[0010] The invention is based on the task of providing a method for triggering a de-icing process of a heat exchanger of a heat pump of a motor vehicle, which is not sensitive to external parameters influencing the air flow through the evaporator, and with which unnecessary de-icing processes can be avoided.

[0011] To solve the task on which the invention is based, a method for triggering a de-icing process of a heat exchanger of a heat pump of a motor vehicle, in particular an electric or battery electric or hybrid electric motor vehicle, is proposed, wherein the heat exchanger is associated with a ventilator, wherein the power consumption and / or the rotational speed of the ventilator is monitored, wherein a de-icing process is triggered when the power consumption and / or the rotational speed exceeds and / or falls below a threshold value, wherein, in addition, the threshold value is determined depending on a parameter, wherein the parameter is an indicator for the current relative air speed of the ambient air with respect to the motor vehicle.

[0012] The ventilator is associated with the heat exchanger, which means that the ventilator is arranged in front of or behind the heat exchanger in the flow direction and is configured to force ambient air through the heat exchanger.

[0013] In particular, the heat exchanger is an ambient heat exchanger.

[0014] If an ice layer forms on the heat exchanger, the pressure loss on the air side at the heat exchanger increases. In the case of an increasing pressure loss, the required air quantity decreases. In the case of a constant rotational speed of the ventilator, the electrical energy requirement decreases in the case of a significantly increasing pressure loss and, as a result, the power consumption of the ventilator decreases. The electrical power consumption of the ventilator allows conclusions to be drawn about the required air quantity of the heat pump and thus about the efficiency of the heat pump. In the case of too low an air mass flow, the heat pump can no longer be operated efficiently and a de-icing process must be triggered.

[0015] Therefore, by monitoring the power consumption of the ventilator and comparing it with a threshold value, in particular a power consumption threshold value, it can be advantageously determined whether and when a de-icing process for the heat exchanger should be triggered.

[0016] If the ventilator is operated with a constant power consumption, the rotational speed increases in the event of an increase in the pressure loss. Accordingly, by monitoring the rotational speed of the ventilator and comparing it with a threshold value, in particular a rotational speed threshold value, it can advantageously be determined whether and when a defrosting process for the heat exchanger should be introduced.

[0017] According to the application it is now provided that the threshold value, in particular the power consumption threshold value or the rotational speed threshold value, is determined depending on a parameter, which is an indicator for the current relative air speed of the ambient air with respect to the motor vehicle.

[0018] The outside environment, which influences the current relative air speed of the ambient air with respect to the motor vehicle, likewise influences the air mass flow through the heat exchanger and thus the so-called device characteristic line of the heat pump. This means that the power consumption and / or the rotational speed of the ventilator are likewise related to the outside environment and thus are not sufficient parameters for deciding whether a defrosting process should be introduced.

[0019] According to the application, therefore, the introduction of the defrosting process is related to a further parameter, which is an indicator for the current relative air speed of the ambient air with respect to the motor vehicle, in addition to the exceeding or falling below of the threshold value, in particular the power consumption threshold value or the rotational speed threshold value.

[0020] The correlation of the threshold value with the parameter can be determined using a calculation model or a simulation. Furthermore, it is possible to predefine a table or a comprehensive characteristic curve for common driving situations and outside environments, which influence the current relative air speed of the ambient air with respect to the motor vehicle, from which the respective suitable threshold value can be extracted.

[0021] Preferably, the defrosting process is introduced when the power consumption falls below the threshold value, in particular the power consumption threshold value, and / or when the rotational speed exceeds the threshold value, in particular the rotational speed threshold value. However, it can also be provided that the defrosting process is introduced when the power consumption exceeds the threshold value, in particular the power consumption threshold value, and / or when the rotational speed falls below the threshold value, in particular the rotational speed threshold value.

[0022] Preferably, it is provided that the parameter is the current driving speed of the motor vehicle.

[0023] If the motor vehicle moves at a high driving speed, the relative air speed of the ambient air with respect to the motor vehicle increases. As a result, the power consumption of the ventilator can decrease with a constant rotational speed, while the icing of the heat exchanger is not the cause for the decrease in the power consumption.

[0024] In order to avoid unnecessary defrosting processes, the threshold value, in particular the power consumption threshold value and / or the rotational speed threshold value, can therefore be adapted depending on the current driving speed of the motor vehicle.

[0025] Further advantageously, it can be provided that the parameter is a wind speed and / or a wind direction.

[0026] In other words, in this case the absolute wind speed and / or wind direction on the ground is taken into account. By taking the wind direction into account it can additionally be taken into account whether the motor vehicle is driving against the wind or with the wind.

[0027] Further advantageously, it can be provided that the parameter is a clearance signal, preferably a clearance value, of the motor vehicle with respect to a motor vehicle driving in front.

[0028] Modern vehicles often have so-called clearance sensors with which it can be determined whether a motor vehicle is located behind a vehicle driving in front. Some of these systems additionally determine a clearance value, for example in meters. By means of the barrier caused by the vehicle driving in front, the power consumption of the ventilator can increase while the rotational speed remains constant. This increase can result in the icing being recognized too late. It is therefore advantageous to take the clearance signal and preferably the clearance value of the motor vehicle with respect to the vehicle driving in front into account for the determination of the threshold value.

[0029] Further advantageously, it can be provided that the parameter is a vehicle position, wherein the vehicle position is preferably a position of the motor vehicle in a highway tunnel, in a valley or in a city canyon.

[0030] The vehicle position can be determined by means of a navigation system of the motor vehicle. If the motor vehicle drives through a highway tunnel, through a valley or through a city canyon, this can result in a drop in the static ambient air pressure and in an increase in the relative air speed of the ambient air with respect to the motor vehicle. This change in the air speed can also result in a change in the power consumption or in the rotational speed of the ventilator. It is therefore advantageous to take the position of the vehicle into account for the determination of the threshold value.

[0031] Preferably, it can be provided that the threshold value is determined depending on the dew point temperature of the air at the heat exchanger and / or that the de-icing process is only introduced when the temperature of the air at the heat exchanger is below the dew point temperature.

[0032] By taking the dew point temperature and / or the temperature into account, it can be avoided that the de-icing process is introduced even if no ice is formed on the heat exchanger.

[0033] Further advantageously, it can be provided that the threshold value is determined depending on the air density and / or the outside air temperature and / or the outside air humidity.

[0034] Furthermore, it can be provided that the parameter is an opening of the cooler louvers.

[0035] The opening of the cooler louvers in the motor vehicle, which is arranged upstream of the heat exchanger in the flow direction, influences the air mass flow through the heat exchanger depending on the opening. It is therefore advantageous to take the opening of the cooler louvers into account for determining the introduction of the de-icing process.

[0036] It is further advantageous to provide that the ventilator is operated for a short period of time at an increased or reduced rotational speed in order to determine whether the de-icing process should be introduced.

[0037] Preferably, the ventilator is operated for a short period of time at a rotational speed of less than 50%, further preferably less than 30%, in particular preferably less than 20% of the theoretical rotational speed. It is, for example, advantageous to operate the ventilator in the case of a sufficient air mass flow at a rotational speed in the range of 10 to 25% of the theoretical rotational speed in order to derive the de-icing process therefrom.

[0038] The short period of time can be less than one minute, preferably less than 30 seconds, in particular preferably less than 20 seconds.

[0039] It is also possible in principle to operate the ventilator for a short period of time at a higher rotational speed, for example at a rotational speed which is increased by 20%, preferably by 30%, in particular preferably by 50% relative to the theoretical rotational speed. When the ventilator is operated at an increased rotational speed, the possible interference variables have less influence on the determination of the necessity of the introduction of the de-icing process.

[0040] The ventilator can be cyclically operated at an increased or reduced rotational speed.

[0041] It is further advantageous to provide that the method is carried out when the motor vehicle is stationary or in the case of a low driving speed of the motor vehicle.

[0042] It is particularly advantageous here to match the threshold value to the driving speed and / or to the relative air speed of the ambient air relative to the motor vehicle.

[0043] A further solution to the task underlying the application consists in providing a motor vehicle, in particular an electric vehicle, a battery electric vehicle or a hybrid electric motor vehicle, wherein the motor vehicle has a device for de-icing of a heat exchanger of a heat pump of the motor vehicle, wherein the heat exchanger is associated with a ventilator, wherein the device has a computing unit, wherein the computing unit is configured to carry out the method described above.

[0044] The motor vehicle preferably has sensors for determining the rotational speed and / or the power consumption of the ventilator and / or for determining the wind speed and / or the opening of the cooler louvers and / or the current driving speed of the motor vehicle. Furthermore, the motor vehicle can have a distance sensor for determining a distance signal, in particular a distance value, of the motor vehicle relative to a vehicle driving in front.

[0045] Furthermore, it can be advantageous if the motor vehicle has a navigation system by means of which the vehicle position can be determined.

[0046] The power consumption of the ventilator can be submitted, for example, via a bus signal and then evaluated. BRIEF DESCRIPTION OF DRAWINGS

[0047] The application is explained in detail below with reference to the drawings.

[0048] In the drawings:

[0049] Figure 1 A motor vehicle having a device for de-icing of a heat exchanger of a heat pump is shown, and

[0050] Figure 2 A block diagram of a method for de-icing of a heat exchanger is shown. DETAILED DESCRIPTION

[0051] Figure 1 A motor vehicle 200 having a heat pump 10 is shown. The heat pump 10 comprises a heat exchanger 11 for absorbing heat of the ambient air 12. The heat exchanger 11 of the heat pump 10 is assigned a ventilator 13 which is configured to direct an air flow through the heat exchanger 11. The rotational speed of the ventilator 13 can be determined by means of a rotational speed sensor 14. The power consumption of the ventilator 13 is read out via a bus signal. Furthermore, the motor vehicle 200 comprises a travel speed sensor 15, a distance sensor device 16, a temperature sensor 17 and a navigation system 18. The current travel speed of the motor vehicle 200 is determined with the travel speed sensor 15. The distance sensor device 16 generates a distance signal when the motor vehicle 200 is following a vehicle driving in front. Preferably, a specific distance value in meters to the vehicle driving in front can be determined by means of the distance sensor device 16. The vehicle position of the motor vehicle 200 can be determined by means of the navigation system 18. In particular, it can be determined whether the motor vehicle 200 is located in a tunnel, in a valley or in an urban canyon. The outside air temperature can finally be determined with the temperature sensor 17. These parameters determined with the sensors are indicators for the current relative air speed of the ambient air 12 to the motor vehicle 200.

[0052] The rotational speed of the ventilator 13 and its power consumption as well as the travel speed, the distance signal, the vehicle position and the outside air temperature of the motor vehicle 200 are transmitted to a computing unit 19 of a device 20 for de-icing of the heat exchanger 11. The computing unit 19 first determines a current rotational speed threshold value and / or a current power consumption threshold value on the basis of at least one of the parameters travel speed, distance signal, vehicle position or outside air temperature.

[0053] The power consumption and / or the rotational speed of the ventilator 13 is then compared in the calculation unit 19 to a corresponding threshold value, in particular a power consumption threshold value and / or a rotational speed threshold value. If the rotational speed and / or the power consumption exceeds or falls below the corresponding threshold value, the calculation unit 19 instructs the device 20 to perform a defrosting process of the heat exchanger 11.

[0054] Figure 2 A block diagram of a method 100 for initiating a defrosting process of a heat exchanger 11 of a heat pump 10 of a motor vehicle 200 is shown.

[0055] First, in a first method step S1, the current rotational speed and / or the current power consumption of the ventilator 13 associated with the heat exchanger 11 is determined. Furthermore, at least one of the parameters motor vehicle driving speed, motor vehicle distance to a vehicle driving in front, vehicle position and outside air temperature is determined. From these parameters, in a second method step S2, a threshold value, in particular a power consumption threshold value and / or a rotational speed threshold value, is determined. In a third method step S3, the current power consumption and / or the current rotational speed is compared to the power consumption threshold value and / or the rotational speed threshold value. If the power consumption or the rotational speed falls below or exceeds the power consumption threshold value or the rotational speed threshold value, a defrosting process for the heat exchanger 11 is initiated. The defrosting of the heat exchanger 11 can be performed, for example, by means of heating elements of a device 20 for defrosting of the heat exchanger 11.

[0056] List of reference signs

[0057] 100 Method

[0058] 200 Motor vehicle

[0059] 10 Heat pump

[0060] 11 Heat exchanger

[0061] 12 Ambient air

[0062] 13 Ventilator

[0063] 14 Rotational speed sensor

[0064] 15 Driving speed sensor

[0065] 16 Distance sensor

[0066] 17 Temperature sensor

[0067] 18 Navigation system

[0068] 19 Calculation unit

[0069] 20 Device

[0070] S1-S3 Method steps

Claims

1. Method (100) for a deicing process of a heat exchanger (11) of a heat pump (10) introduced into a motor vehicle (200), wherein, The heat exchanger (11) is assigned a ventilator (13), wherein the power consumption and / or the rotational speed of the ventilator (13) is monitored, wherein, when the power consumption and / or the rotational speed exceeds and / or falls below a threshold value, a deicing process is introduced, characterized in that the threshold value is determined depending on a parameter, wherein the parameter is an indicator for the current relative air speed of the ambient air (12) relative to the motor vehicle (200), wherein the parameter is a distance signal of the motor vehicle (200) relative to a vehicle driving in front, and / or the parameter is a vehicle position determined by means of a navigation system (18) of the motor vehicle (200).

2. The method (100) according to claim 1, characterized in that The motor vehicle is an electric vehicle.

3. The method (100) according to claim 1, characterized in that The motor vehicle is a battery electric vehicle.

4. The method (100) according to claim 1, characterized in that The motor vehicle is a hybrid electric motor vehicle.

5. The method (100) according to claim 1, characterized in that The parameter is the current driving speed of the motor vehicle (200).

6. The method (100) according to any one of the preceding claims 1 to 5, characterized in that, The parameter is the wind speed and / or the wind direction.

7. The method (100) according to any of the preceding claims 1 to 5, characterized in that, The parameter is a distance value of the motor vehicle (200) relative to a vehicle driving in front.

8. The method (100) according to any of the preceding claims 1 to 5, characterized in that, The vehicle position is the position of the motor vehicle (200) in a highway tunnel, in a valley or in an urban canyon.

9. The method (100) according to any of the preceding claims 1 to 5, characterized in that, The threshold value is determined depending on the dew point temperature of the air at the heat exchanger (11), and / or the deicing process is only introduced when the temperature of the air at the heat exchanger (11) is below the dew point temperature.

10. The method (100) according to any of the preceding claims 1 to 5, characterized in that, The threshold value is determined depending on the air density and / or the outside air temperature and / or the outside air humidity, and / or the parameter is the opening of a cooler louvre.

11. The method (100) according to any of the preceding claims 1 to 5, characterized in that, The ventilator (13) is operated at an increased or decreased rotational speed over a short time period in order to determine whether the deicing process should be introduced.

12. The method (100) according to any of the preceding claims 1 to 5, characterized in that, The method (100) is carried out when the motor vehicle (200) is stationary or in the case of a low driving speed of the motor vehicle (200).

13. Motor vehicle (200) comprising a device (20) for de-icing and de-frosting a heat exchanger (11) of a heat pump (10) for the motor vehicle, wherein The heat exchanger (11) is assigned a ventilator (13), wherein the device (20) has a computing unit (19) which is configured to carry out the method (100) according to any one of the preceding claims. The heat exchanger (11) is assigned a ventilator (13), wherein the device (20) has a computing unit (19) which is configured to carry out the method (100) according to any one of the preceding claims.

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