DE102009019128A1 - Air conditioning unit for a motor vehicle comprises sensors for measuring the temperature and moisture in both a fresh air shaft and in a circulating air shaft - Google Patents

Abstract

Air conditioning unit (1) comprises a first temperature sensor (17a) for measuring the temperature and a first moisture sensor (18a) for measuring the moisture in a fresh air shaft (4) and a second temperature sensor (17b) for measuring the temperature and a second moisture sensor (18b) for measuring the moisture in a circulating air shaft (3). An independent claim is also included for a method for controlling the air conditioning unit. Preferred Features: The first temperature sensor and first moisture sensor and the second temperature sensor and the second moisture sensor are integrated to form a double sensor.

Description

The The invention relates to a method for controlling a motor vehicle air conditioning system according to the preamble of claim 1 and a Automotive air conditioning according to the preamble of claim 14.

In Automotive air conditioning systems is the one interior of the motor vehicle heated air and / or cooled. For this purpose, the motor vehicle air conditioner with an evaporator for cooling the air and a heating device for heating the Provide air. The evaporator is part of a refrigerant circuit with a compressor, a condenser and an expansion device for the refrigerant. The refrigeration cycle of the automotive air conditioning system requires a regulation to the desired temperature of the To get interior.

The Air conducted into the interior of the motor vehicle has moisture on. For this reason, moisture or Condensation form and / or it can ges ges to the windows of motor vehicles, especially on a windshield, moisture condense, so that the windows fog up. The formation of condensation on the Evaporator, which remains permanently on the evaporator is with numerous disadvantages connected, z. B. a bacterial or fungal formation. Further impaired Moisture on the windscreen reduces driving safety due to reduced View to the outside.

Out For this reason, it is desirable after cooling the air at the evaporator below a pre-evaporator dew point, d. H. with the formation of condensation on the evaporator, the evaporator again too dry and at the same time fogging the discs too avoid.

to Avoiding fogging on the windshield can the temperature of the evaporator can be lowered so that the evaporator Moisture condenses because the temperature of the evaporator is below the dew point of the air in front of the evaporator (pre-evaporator dew point) is located. The guided into the interior air is thus dryer and the Probability of misting the discs can thus lowered become. The disadvantage, however, is that when condensing the moisture on the evaporator a high cooling capacity necessary and thus a lot of energy required for the operation of the compressor is.

From the EP 0 316 545 B1 an air conditioning system for a motor vehicle with suitable facilities for dehumidification in the air duct is known, which are controlled by a microcomputer. The measured values for outside temperature, inside temperature and inside humidity are transmitted to the microcomputer. From the values for outside temperature, inside temperature and inside humidity, the microcomputer calculates a limit humidity as the ratio of the saturation vapor pressure inside the disc and the saturation vapor pressure of the inside air. If the difference between the limit humidity and the inside humidity falls below a certain value, the devices for dehumidification are actuated.

The The object of the present invention is therefore a method for controlling an automotive air conditioning system and an automotive air conditioning system to provide, in which a humidified evaporator is selectively dried and prevents fogging of the discs can be.

These Task is solved with a method for controlling a Automotive air conditioning system comprising the steps of: detecting a temperature the air after passing through an evaporator, passing from Air through an evaporator, preferably by cooling the the air passed to the evaporator, circulating the air by means of a blower and preferably determining the temperature a windshield, the absolute humidity of the Air is determined before and after flowing through the evaporator is at least one measure for drying the evaporator is initiated, provided the absolute humidity of the air after the flow through the evaporator larger is considered the absolute humidity of the air before it flows through of the evaporator, or the relative humidity of the air before and is detected after flowing through the evaporator, if the temperature of the air before and after flowing through the Essentially evaporator, in particular with a difference of less than 10, 7, 5, 3, 2, 1 or 0.5 K, is the same and at least initiated a measure for drying the evaporator is provided the relative humidity of the air after flowing through of the evaporator is greater than the relative humidity the air before flowing through the evaporator.

In In another embodiment, the at least one measure initiated to dry the evaporator, provided the absolute humidity the air after flowing through the evaporator by at least 1, 3, 5, 7, 10, 15 or 20% greater than that absolute humidity of the air before flowing through the Evaporator.

In a further embodiment, the at least one measure for drying the evaporator is initiated, provided that the relative humidity of the air after flowing through the evaporator by at least 1, 3, 5, 7, 10, 15 or 20% greater than the relative humidity of the air before flowing through the evaporator and the temperature of the Air before and after flowing through the evaporator is substantially equal.

In a variant is the temperature and the relative humidity the air before flowing through the evaporator in the motor vehicle air conditioner recorded and calculated from the temperature and relative humidity of the Air before flowing through the evaporator will be the absolute Humidity of the air before flowing through the evaporator determined, z. Example by means of a stored hX diagram or an analytical Calculation.

In In another embodiment, the absolute humidity of Air after flowing through the evaporator determined by the relative humidity of the air after flowing through the evaporator in the automotive air conditioning system detected and off the temperature and the relative humidity of the air after the Flow through the evaporator and the absolute humidity the air determined after flowing through the evaporator is, for. Example by means of a stored hX diagram or an analytical Calculation.

expedient The temperature of the air before flowing through the evaporator detected.

In One variant is the temperature and humidity of the air before and / or after flowing through the evaporator in the Automotive air conditioning system detects and this is a pre-evaporator dew point and / or a reboiler dew point determined, further is a Dew point of the air at the evaporator determined, whereby the dew point of the Re-evaporator dew point or the temperature of the air after flowing through the evaporator is and preferably the dew point of the air compared with the temperature of the windshield on the evaporator and the vehicle air conditioner is regulated so that the dew point less than the temperature of the windshield.

Of the Dew point for anti-fog control is the reboiler dew point. By way of derogation, the following applies: The dew point for An anti-fog control is the reboiler dew point, provided the air at the evaporator above the pre-evaporator dew point is cooled and preferably the evaporator controlled dried becomes. The dew point for an anti-fog control is the temperature the air after the evaporator, provided the air to the evaporator is cooled below the pre-evaporator dew point, d. H. There is condensation on the evaporator.

Preferably is the dew point of the air conducted to the windshield therewith smaller than the temperature of the windshield, so at the Windshield no condensation due to this air enters.

Especially is regulated as a measure for drying the evaporator, the automotive air conditioning system, so that the temperature of the air after flowing through the Evaporator is greater than the pre-evaporator dew point and / or the fresh air portion of the passed through the evaporator Air is increased and / or the blower output is increased.

In an additional embodiment, the temperature of Air slightly after flowing through the evaporator is greater than the pre-evaporator dew point, in particular is the temperature of the air after passing through the evaporator to less than 20, 15, 12, 10, 7, 5, 4, 3, 2, 1, or 0.5 K larger as the pre-evaporator dew point. The moisture on the evaporator it evaporates slowly to avoid fogging of the panes.

In an additional embodiment is during the at least one measure for drying the evaporator the evaporator or a refrigeration system switched off or the air at the evaporator is cooled, the temperature being the air after flowing through the evaporator, preferably is slightly larger than the pre-evaporator dew point, in particular is the temperature of the air after flowing through the evaporator less than 10, 7, 5, 4, 3, 2, 1, or 0.5 K larger is as the pre-evaporator dew point, and / or, preferably subsequently, the cooling capacity of the evaporator is reduced for shutdown the evaporator or the refrigeration system.

In Another embodiment is when switching off the evaporator or the refrigeration system as long as the temperature of the air after the flow through the evaporator slightly larger in particular, the temperature is that of the pre-evaporator dew point the air after flowing through the evaporator by less as 10, 7, 5, 4, 3, 2, 1 or 0.5 K greater than the fore steamer dew point until the absolute or relative humidity the air before and after flowing through the evaporator is substantially the same, in particular with a deviation of less as 30%, 20%, 10%, 5%, 2% or 1%.

In a further embodiment is a predetermined minimum difference from the temperature of the windshield and the dew point at least 0.1, 1, 3 or 5 K (by way of example). The minimum difference is required to prevent misting of the windshield safely.

In one variant, if the predetermined minimum difference is undershot or if the temperature of the windshield is less than or equal to the dew point, at least one of them is switched on Tibeschlag measure initiated to achieve the predetermined minimum difference or to avoid fogging of the windshield or remove existing condensate on the windshield.

expedient At least two anti-fogging measures are prioritized and at least one anti-fogging measure is included a higher priority.

In an additional embodiment have anti-fogging measures with a higher priority lower energy consumption as anti-fogging measures with a lower priority. In order to First anti-fogging measures are carried out with a low energy consumption.

Especially From a temperature sensor is the temperature and a humidity sensor the relative humidity of the air flowing through an air duct Air in front of the evaporator and a humidity sensor the relative Humidity of the air flowing through an air duct measured after the evaporator.

In In another embodiment, the pre-evaporator dew point and / or the post-evaporator dew point from the data on the temperature and the Moisture of the air in the air duct before and / or after flowing through the evaporator in the automotive air conditioning system, in particular by means of a stored hX-diagram or an analytical calculation, determined.

In Another embodiment is, preferably as anti-fogging measure, regulated the motor vehicle air conditioning, so that the Vorver steamer dew point is less than the evaporator temperature (temperature of the air after flowing through the evaporator) and / or the pre-evaporator dew point is the dew point of the air at the evaporator. This occurs at the evaporator essentially no condensation and energy consumption is low.

In there is no additional embodiment Dehumidification requirement of the air at the evaporator and / or by the user and / or the control and / or regulating unit is no dehumidifying need specified and / or the predetermined minimum difference is met and / or the predetermined minimum difference is at least one Antifogging measure achieved, which does not lower the evaporator temperature require and / or the predetermined minimum difference is at least one Antifogging measure achieved, which does not lower the evaporator temperature require below the pre-evaporator dew point.

expedient the automotive air conditioning system is controlled, so that the evaporator temperature is smaller is considered the pre-evaporator dew point to the air at the evaporator too dehumidify (condensate forms on the evaporator). This Operating state is preferably selected only when a Fall below the minimum difference with other defogging measure can no longer be achieved or for example due to a Specification of a vehicle occupant to the temperature in the interior a such evaporator temperature is required or dehumidifying, z. B. because of a specification of the vehicle occupant desired is.

In an additional embodiment is dehumidifying the air on the evaporator and / or the user is dehumidifying predetermined air and / or the control unit is a dehumidification given the air.

Preferably is the heater during cooling of the Air on the evaporator is switched off or switched on.

invention Automotive air conditioning system comprising an evaporator, a blower, a heater and an evaporator temperature sensor, wherein a method described in this application executable is and / or the motor vehicle air conditioning a temperature sensor and a humidity sensor for detecting the temperature and the relative humidity of air in an air duct before flowing through of the evaporator and a humidity sensor for detecting the relative humidity of the air in an air duct after flowing through of the evaporator.

In In another embodiment, the temperature sensor and the Moisture sensor for detecting the temperature and the relative Moisture of the air in the air duct before flowing through the evaporator and / or the evaporator temperature sensor and the Moisture sensor for detecting the temperature and the relative Humidity of the air in the air duct after flowing through of the evaporator integrated in a double sensor.

In In an additional variant, the evaporator is a storage evaporator. The storage evaporator can for a short time, z. B. one to five minutes, save cold, so that at one shut down refrigeration system, for example, when a disconnected Internal combustion engine of a motor vehicle at a traffic light, for short time the air can continue to be cooled.

in the Below are embodiments of the invention with reference to the accompanying drawings described. It shows:

1 a highly schematic cross section of an automotive air conditioning system in a first embodiment,

2 a partial cross section according to 1 in a second embodiment,

3 an hX diagram and

4 a block diagram of an anti-fog control.

5 a first flow chart for controlling the drying of an evaporator and

6 a second flow chart for controlling the drying of the evaporator.

An automotive air conditioning system 1 has an air duct 2 for passing air. The supply of air into the air duct 2 takes place through a shaft 3 for the supply of circulating air and through a shaft 4 for the supply of fresh air. A mixing flap 5 controls the proportion of circulating air and the proportion of fresh air which enters the air duct 2 flows. A fan 6 in the air duct 2 sucks air from the environment and / or from the interior of a motor vehicle (not shown), depending on the position of the mixing flap 5 , In the direction of flow after the blower 6 is an evaporator 7 in the air duct 2 arranged to cool the air. The evaporator 7 is part of a refrigeration system, not shown, with a compressor, a condenser and an expansion device. A heat exchanger 8th as a heater 16 is connected by not shown lines to a coolant circuit of an engine (not shown) of the motor vehicle and is used to heat the through the air duct 2 directed air. The heater 16 may also be an electric heating element (not shown). The heat exchanger 8th can be controlled with a valve in lines (not shown), so that either no coolant or a controllable amount of coolant per unit time through the heat exchanger 8th flows. The air duct 1 flows into the shafts 9 . 10 and 11 , The shaft 9 is associated with the defroster openings of the windshield (not shown), ie through the shaft 9 flowing air is directed to the windshield. The shaft 10 is the ventilation holes on a dashboard and the shaft 11 assigned to the openings on the footwell. The shafts 9 . 10 and 11 can by means of the flaps 12 . 13 and 14 be opened and closed independently, so that through the manholes 9 . 10 and 11 flowing air can be controlled and / or regulated.

In the flow direction in front of the evaporator 7 is in the air duct 2 a temperature sensor 17 and a humidity sensor 18 arranged. The sensors 17 and 18 can be integrated in a sensor housing (not shown). The temperature sensor 17 detects the temperature of the air duct 2 flowing air in front of the evaporator 7 and the humidity sensor 18 captures the relative humidity of the air duct 2 flowing air in front of the evaporator 7 , The sensors 17 . 18 measure the temperature and relative humidity regardless of the position of the mixing valve 5 or the fresh and / or recirculated air content of the air in front of the evaporator 7 , An evaporator temperature sensor 19 detects the temperature of the air duct 2 flowing air after passing through the evaporator 7 and a humidity sensor 21 captures the relative humidity of the air duct 2 flowing air after passing through the evaporator 7 , Deviating from this, the evaporator temperature sensor 19 also on the evaporator 7 be attached (not shown). A heating temperature sensor 20 detects the temperature of the air duct 2 flowing air after passing through the heat exchanger 8th or the heater 16 ,

Deviating from this, all sensors 17 . 18 . 19 and 21 in a double sensor 22 be integrated ( 2 ). The double sensor 22 is in the flow direction of the air after the evaporator 7 arranged. Through a sensor channel 23 is the air in front of the evaporator 7 to the sensors 17 . 18 passed, so the sensors 17 . 18 also the air before passing through the evaporator 7 to capture.

The ones from the sensors 17 . 18 . 19 . 20 and 21 recorded data becomes a control and / or regulating unit 15 the automobile air conditioner 1 passed by means not shown electrical lines. Deviating from this, the data can be connected to a data bus, e.g. B. LIN, Mulitplex method or PWM modulation to the control and / or regulating unit, preferably in coded form, to be transmitted.

In the control and / or regulation unit 15 , in the following only control unit 15 called, is from the of the temperature sensor 17 , Evaporator temperature sensor 19 and the humidity sensors 18 . 21 measured temperature and relative humidity of the air in the flow direction before and after the evaporator 7 a pre-evaporator dew point and a reboiler dew point of the air determined by means of a stored hX diagram. Notwithstanding this, the pre-evaporator dew point and reboiler dew point can also be calculated analytically. The dew point is the temperature at which a condensation of water occurs when falling below it. In the in 3 Example shown was from the temperature sensor 17 a temperature of 15 ° C and of that humidity sensor 18 measured a relative humidity of 70%. This results in a pre-evaporator dew point of 9.5 ° C. The absolute humidity is about 7.7 g / kg.

From the control unit 15 is by means of the sensors 17 . 18 . 19 and 21 Data recorded the absolute humidity of the air before passing through the evaporator 7 (Abs_Wassermenge_evapo-in) and the absolute humidity of the air after passing through the evaporator 7 (Abs_Wassermenge_evapo-out) with the deposited hX-diagram.

In 5 is a first flow chart for controlling the drying of the evaporator 7 shown. The abbreviation "VD drying" stands for evaporator drying and the abbreviation "AC" for motor vehicle air conditioning 1 , In a switched off motor vehicle air conditioning 1 (There is no need to cool the air at the evaporator 7 ) is from the control unit 15 the absolute humidity of the air before passing through the evaporator 7 (Abs_Wassermenge_evapo-in) with the absolute humidity of the air after passing through the evaporator 7 (Abs_Wassermenge_evapo-out) compared to determine an evaporator drying demand and if abs_Wassermenge_evapo-out is greater than abs_Wassermenge_evapo-in the motor vehicle air conditioning 1 or the evaporator 7 so regulated that the temperature of the air after the evaporator 7 slightly, z. B. 0, 5, 1, 2, 3, 4, 5 or 10 K, is greater than the pre-evaporator dew point, z. B. by cooling the air at the evaporator 7 ,

Is the temperature of the air after the evaporator 7 much larger than the pre-evaporator dew point and exists on the evaporator 7 a drying requirement, ie that abs Wassermenge_evapo-out is greater than abs_Wassermenge_evapo-in, evaporates the condensate on the evaporator 7 fast, so that the risk of condensation on the windshield is high, because the guided to the windshield air has a high absolute and relative humidity. For this reason, the automobile air conditioner 1 regulated in that the temperature of the air after the evaporator 7 is slightly larger than the fore dew point and thus the condensation on the evaporator 7 only slowly evaporates, so that the absolute and relative humidity of the air directed to the windshield on the evaporator 7 only slightly increased. It is thus a targeted and controlled drying of the evaporator 7 possible.

In a switched off motor vehicle air conditioning 1 What just means here is that on the evaporator 7 The air is not cooled, is the temperature of the air before and after passing through the evaporator 7 essentially the same, so that to determine the evaporator drying requirement (in the case of moisture or condensed water on the evaporator 7 evaporator drying requirement) also only the relative humidity of the air before and after the evaporator 7 can be compared. Is the relative humidity of the air after the evaporator 7 bigger than before the evaporator 7 Evaporator drying requirement exists because the condensate on the evaporator 7 evaporates.

If abs_Wassermenge_evapo-out is not greater than abs_Wassermenge_evapo-in or the relative humidity after the evaporator 7 not larger than the relative humidity in front of the evaporator 7 there is no evaporator drying requirement and the automotive air conditioner 1 can be switched off or remain inactive unless cooling of the air directed into the vehicle interior is required. A controlled and slow drying of the evaporator 7 is not required.

Even with a cooling of the evaporator 7 directed air, the temperature of the air after the evaporator 7 is above the pre-evaporator dew point, it makes sense in an analogous manner at a evaporator drying requirement, the condensate on the evaporator 7 slow and regulated to evaporate, reducing the temperature of the air after the evaporator 7 is slightly larger than the fore steamer dew point.

When cooling through the evaporator 7 directed air, the temperature of the air after the evaporator 7 is below the pre-evaporator dew point, is a drying of the evaporator 7 not possible, so that a query according to the first block diagram is not relevant and useful.

In 6 is a second flow chart for controlling the drying of the evaporator 7 when turning off or shutting down the vehicle air conditioner 1 or the cooling capacity of the evaporator 7 shown. The abbreviation "AC-OFF" means that the motor vehicle air conditioner 1 ie cooling with the evaporator 7 , should be turned off. If there is no need to cool the air ("AC demand": no), the shutdown process of the automotive air conditioning system 1 started ("START AC-OFF-Procedure"). If abs_water_rate_evapo-out is not greater than abs_water_rate_evapo-in (in 6 only "evapo-out greater than evapo-in" shown), there is no need for drying the evaporator 7 and the cooling capacity of the evaporator 7 can be switched off quickly without special regulation. If abs_Wassermenge_evapo-out is greater than abs_Wassermenge_evapo-in, there is a need for drying the evaporator 7 and the evaporator 7 or the motor vehicle air conditioning system 1 is regulated switched off ("AC regulated above dew point"). In this case, the vehicle air conditioner 1 or the evaporator 7 so regulated that the temperature of the air after the evaporator 7 is slightly larger than the pre-evaporator dew point, allowing the condensate on the evaporator 7 slowly evaporates and thus the risk of fogging the discs is kept low. At the beginning of "START AC-OFF-Procedure" is the temperature of the air after the evaporator 7 less than the pre-evaporator dew point, the control is to the effect that the temperature of the air after the evaporator 7 As soon as possible, ie without a regulation of a delay (the power of the compressor is immediately shut down to the appropriate level), the pre-evaporator dew point reached, physika cially conditioned then corresponds to the temperature of the air after the evaporator 7 a certain time the pre-evaporator dew point and then the temperature of the air after the evaporator 7 brought to a value which is slightly greater than the pre-evaporator dew point until no more evaporator drying needs. After no evaporator drying requirement (abs_Wassermenge_evapo-out is not greater than abs_Wassermenge_evapo-in) longer exists, ie the condensation on the evaporator 7 is evaporated, the cooling of the air at the evaporator 7 switched off ("AC off").

In this case, in the above examples, the regulation of the temperature of the air after the evaporator 7 also to take into account the degree of evaporator drying requirement to avoid fogging. The greater the degree of evaporator drying requirement, the smaller the difference between the temperature of the air after the evaporator and the pre-evaporator dew point is controlled, and vice versa. The degree of evaporator drying requirement is determined by the magnitude of the difference between abs_water_measure_evapo-out and abs_water_measure_evapo-in or the relative humidity of the air after the evaporator 7 and the relative humidity in front of the evaporator 7 certainly. The degree of evaporator drying requirement is directly proportional or equal to the size of the difference just mentioned. With a high degree of evaporator drying requirement, there is a large amount of condensation on the evaporator 7 present, so that the condensation water is very slow to evaporate, to avoid fogging of the discs.

Further can in addition to the regulation of the motor vehicle air conditioner optional also takes into account the temperature of the windshield to prevent misting of the discs.

The temperature of the windshield is either measured by a temperature sensor on the windshield (not shown) or by means of a computing model of various parameters, eg. B. internal temperature, outside temperature, speed, solar radiation, capacity of the fan 6 and / or the position of the flap 12 as a defrost flap 12 , determined.

So that fogging, ie no condensation, occurs on the windscreen, the dew point of the air directed to the windshield must be less than the temperature of the windshield. In this case, the performance of the refrigeration system, ie the evaporator temperature (temperature of the air after the evaporator 7 ), possibly regulated to the effect that the evaporator temperature is greater than the pre-evaporator dew point to a condensation on the evaporator 7 avoiding that large amounts of energy are required to operate the refrigeration system.

For example, the difference between the temperature of the windshield and the post-evaporator dew point must be greater than 3 K in order to reliably avoid formation of condensate on the windshield. There is a certain minimum difference required to avoid fogging with sufficient certainty. The temperature of the windshield is thus at least 3 K larger than the reboiler dew point. The motor vehicle air conditioner 1 is from the control unit 15 Regulated that this difference is present so that no fogging of the discs occurs. If the difference drops below 3 K, the control unit will start 15 Antifogging measures taken to prevent fogging of the windshield. In this case, first those defogging measures or those anti-fog measures are taken, which with a low (more) consumption of energy by the motor vehicle air conditioning 1 are connected. Only when an anti-fogging measure with a small additional energy consumption is no longer sufficient to ensure the minimum difference between the temperature of the windshield and the dew point, an anti-fogging measure or anti-fogging measures are taken, which are associated with a higher energy consumption. Unless there is a need for evaporator drying, the difference between the temperature of the windshield and the pre-evaporator dew point may also be formed to prevent condensation on the windshield.

The following antifogging measures are taken in the order listed: 1.) Opening the defrosting flap 12 , 2.) Increase the proportion of fresh air by moving the mixed air damper 5 , 3.) Increasing the delivery rate of the blower 6 and 4.) lowering the temperature of the evaporator 7 below the pre-evaporation fer dew point of the air in the air duct 2 before flowing through the evaporator 7 by increasing the cooling capacity of the refrigeration system, z. B. by means of a larger power of the compressor. The first defogging measure, namely the opening of the defrost flap 12 , requires only a small amount of energy. By opening the defroster door 12 or increasing the delivery rate of the blower 6 with at least partially opened defrost flap 12 a larger amount of air is directed to the windshield, thereby providing greater heat transfer from the air directed to the windshield to the windshield so that the windshield heats up more quickly and thereby reduces the likelihood of water condensation on the windshield Difference between the temperature of the windscreen and the dew point is increased.

The fourth defogging measure, ie lowering the evaporator temperature 7 below the pre-evaporator dew point of the air in the air duct 2 before flowing through the evaporator 7 , requires a large amount of energy. By lowering the evaporator temperature 7 below the dew point of the air in the air duct 2 before flowing through the evaporator 7 gets the air in the air duct 2 dehumidifies, ie at the evaporator 7 Condensation forms. In the example above for the hX diagram, the absolute humidity drops below 7.7 g / kg and also the dew point of the air at the evaporator 7 drops below 9.5 ° C, z. B. to 7 ° C, wherein in this operating condition the evaporator temperature the dew point of the air at the evaporator 7 equivalent. This allows a targeted and controlled dehumidification of the through the air duct 2 directed and / or regulated air.

The fourth anti-fogging measure is therefore only taken if fogging of the windshield can no longer be prevented with the other anti-fogging measures. When lowering the evaporator temperature below the pre-evaporator dew point condenses on the evaporator 7 Water, so that thereby reduces the absolute humidity of the guided to the windshield air and thus the risk of fogging is reduced. In case of condensation on the evaporator 7 is the dew point of the air at the evaporator 7 the temperature of the air after passing through the evaporator 7 (Evaporator temperature) coming from the evaporator temperature sensor 19 is measured. In an operating condition of the motor vehicle air conditioner 1 with condensation on the evaporator 7 the difference between the windscreen temperature and the evaporator temperature, which must be greater than 3 K, is calculated.

By increasing the cooling capacity of the refrigeration system and an associated lowering of the evaporator temperature in the operating state with condensation on the evaporator 7 For example, by decreasing the evaporator temperature, the difference between the temperature of the windshield and the evaporator temperature can be increased. The fourth tibeschlag measure is preferably switched off again when the minimum difference can be met again with the first, second and / or third defogging measure.

For a controlled drying of the evaporator 7 can be used as an anti-fogging measure the temperature of the air after the evaporator 7 be lowered, leaving less moisture on the evaporator 7 evaporates, the temperature of the air after the evaporator 7 is greater than the pre-evaporator dew point.

In both operating conditions, both with and without condensation on the evaporator 7 , the heater can 16 be on or off. The operation of the heater has on the dew point of the air at the evaporator 7 or the dew point of the air guided to the windshield no influence, because the air is not changed by the heating of the air humidity. Only the temperature of the windshield can be turned on when the heater 16 However, this is taken into account due to the heating temperature sensor 20 because the difference between the temperature of the windshield and the dew point of the air at the evaporator 7 is decisive. At a higher temperature of the air conducted to the windshield due to a heater turned on 16 This is taken into account because of the high temperature of the windshield.

4 shows in a block diagram greatly simplifies the procedure. By means of a computing model, the temperature of the windshield (T_WS) is determined. From the evaporator temperature sensor 19 and the humidity sensor 21 in the flow direction after the evaporator 7 determined data is based on a hX diagram of the dew point of the air (TP_VD) on the evaporator 7 certainly. The control unit 15 regulates the motor vehicle air conditioner 1 in that the difference between the temperature of the windscreen (T_WS) and the dew point of the air (TP_VD) is greater than 3 K (ΔT = 3 K). For this purpose, the anti-fogging measures 1.) to 4.) are available, with the first in 4 Antifogging measures listed above are taken and only if the anti-fogging measures listed above are no longer sufficient, also anti-fogging measures below be initiated.

The inventive method is in the scheme the automotive air conditioning system in addition to other parameters to be controlled, z. B. the desired temperature of the vehicle occupant in the interior, designed to fog the windshield to prevent.

Overall, are considered with the inventive method and the automotive air conditioning system according to the invention 1 significant benefits. The regulation of the motor vehicle air conditioner 1 takes into account the drying requirements of the evaporator 7 and, preferably, the temperature of the windshield to allow for controlled drying of the evaporator and to avoid fogging of the windows.

1

Automotive air conditioning system

2

air duct

3

shaft for circulating air

4

shaft for fresh air

5

mixing flap

6

fan

7

Evaporator

8th

heat exchangers

9

shaft for defrost opening

10

shaft for openings on instrument panel

11

shaft for openings at the foot area

12

Flap for shaft 9

13

Flap for shaft 10

14

Flap for shaft 11

15

control and / or control unit

16

heater

17

temperature sensor

18

humidity sensor

19

Evaporator temperature sensor

20

Heating temperature sensor

21

humidity sensor

22

double sensor

23

sensor channel

TP_VD

dew point the air at the evaporator

T_WS

temperature the windshield

"Abs Wassermenge_evapo_out" or "evapo_out"

absolute Humidity of the air after the evaporator

"Abs_water_set_evapo_in" or "evapo_in"

absolute Humidity of the air in front of the evaporator

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - EP 0316545 B1 [0006]

Claims (15)

Method for controlling an automotive air conditioning system ( 1 ) comprising the steps of: - detecting a temperature of the air after flowing through an evaporator ( 7 ), - passing air through an evaporator ( 7 ), Preferably cooling by the evaporator ( 7 ), - circulating the air by means of a blower ( 6 ) and - preferably determining the temperature of a windshield, characterized in that - the absolute humidity of the air before and after flowing through the evaporator ( 7 ), - at least one measure for drying the evaporator ( 7 ), provided that the absolute humidity of the air after it flows through the evaporator is greater than the absolute humidity of the air before it flows through the evaporator, or - the relative humidity of the air before and after it flows through the evaporator ( 7 ), provided that the temperature of the air before and after it flows through the evaporator ( 7 ) is substantially the same and - at least one measure for drying the evaporator ( 7 ) is introduced, provided that the relative humidity of the air after flowing through the evaporator is greater than the relative humidity of the air before flowing through the evaporator. A method according to claim 1, characterized in that the temperature and the relative humidity of the air before flowing through the evaporator ( 7 ) in the motor vehicle air conditioning system ( 1 ) and from the temperature and the relative humidity of the air before it flows through the evaporator ( 7 ) the absolute humidity of the air before it flows through the evaporator ( 7 ) is determined. A method according to claim 1 or 2, characterized in that the absolute humidity of the air after flowing through the evaporator ( 7 ) is determined by the relative humidity of the air after flowing through the evaporator ( 7 ) in the motor vehicle air conditioning system ( 1 ) and from the temperature and the relative humidity of the air after passing through the evaporator ( 7 ) and the absolute humidity of the air after flowing through the evaporator ( 7 ) is determined. Method according to claim 1, characterized in that that the temperature of the air before flowing through the evaporator is detected. Method according to one or more of the preceding claims, characterized in that - the temperature and the humidity of the air before and / or after flowing through the evaporator ( 7 ) in the Kraftfahrzeugkli maanlage ( 1 ) and from this a pre-evaporator dew point and / or a reboiler dew point is determined, - a dew point of the air at the evaporator ( 7 ), wherein the dew point is the post-evaporator dew point or the temperature of the air after the flow through the evaporator and - preferably the dew point of the air at the evaporator ( 7 ) is compared with the temperature of the windshield and the motor vehicle air conditioning ( 1 ), so that the dew point is less than the temperature of the windshield. A method according to claim 5, characterized in that as a measure for drying the evaporator ( 7 ) the automotive air conditioning system ( 1 ), so that the temperature of the air after flowing through the evaporator ( 7 ) is greater than the pre-evaporator dew point and / or the proportion of fresh air through the evaporator ( 7 ) is increased air and / or the fan power is increased. A method according to claim 6, characterized in that the temperature of the air after flowing through the evaporator ( 7 ) is slightly larger than the pre-evaporator dew point, in particular the temperature of the air after flowing through the evaporator ( 7 ) is less than 10, 5, 4, 3, 2, 1 or 0.5 K greater than the pre-evaporator dew point. Method according to one or more of the preceding claims, characterized in that during the at least one measure for drying the evaporator ( 7 ) the evaporator ( 7 ) or a refrigeration system is switched off or the air at the evaporator ( 7 ), wherein the temperature of the air after flowing through the evaporator ( 7 ), preferably slightly, is greater than the pre-evaporator dew point, in particular the temperature of the air after flowing through the evaporator ( 7 ) is less than 10, 5, 4, 3, 2, 1 or 0.5 K greater than the pre-evaporator dew point and / or, preferably subsequently, the cooling capacity of the evaporator ( 7 ) is turned off to turn off the evaporator ( 7 ) or the refrigeration system. A method according to claim 8, characterized in that when switching off the evaporator ( 7 ) or the refrigeration system as long as the temperature of the air after flowing through the evaporator ( 7 ) is slightly larger than the pre-evaporator dew point, in particular the temperature of the air after flowing through the evaporator ( 7 ) is less than 10, 5, 4, 3, 2, 1 or 0.5 K greater than the pre-evaporator dew point until the absolute or relative humidity of the air before and after it flows through the evaporator ( 7 ) is substantially the same, in particular with a deviation of less than 30, 20, 10, 5, 2 or 1%. Method according to one or more of the claims 5 to 9, characterized in that a predetermined minimum difference from the temperature of the windshield and the dew point at least 0.1, 1, 3 or 5 K. Method according to claim 10, characterized in that that in case of falling below the predetermined minimum difference or when the temperature of the windshield is less than or equal to is like the dew point at least one defogging measure is initiated. Method according to claim 10 or 11, characterized that prioritizes at least two anti-fog measures are and at least one anti-fogging measure with a higher priority. Method according to claim 12, characterized in that that anti-fog measures with a higher Priority have a lower energy consumption than measures with a lower priority. Automotive air conditioning system ( 1 ), comprising an evaporator ( 7 ), a blower ( 6 ), a heating device ( 16 ) and an evaporator temperature sensor ( 19 ), characterized in that the motor vehicle air conditioning system ( 1 ) a temperature sensor ( 17 ) and a humidity sensor ( 18 ) for detecting the temperature and relative humidity of the air in an air duct ( 2 ) before flowing through the evaporator ( 7 ) and a humidity sensor ( 21 ) for detecting the relative humidity of the air in an air duct ( 2 ) after flowing through the evaporator ( 7 ) and / or a method according to one or more of claims 1 to 13 is executable. Motor vehicle air conditioning system according to claim 14, characterized in that the temperature sensor ( 17 ) as well as the humidity sensor ( 18 ) for detecting the temperature and the relative humidity of the air in the air duct ( 2 ) before flowing through the evaporator ( 7 ) and / or the evaporator temperature sensor ( 19 ) as well as the humidity sensor ( 21 ) for detecting the temperature and the relative humidity of the air in the air duct ( 2 ) after flowing through the evaporator ( 7 ) in a double sensor ( 22 ) are integrated.