DE102007039002A1 - Method for monitoring the load condition of an air conditioning device of a motor vehicle - Google Patents

Abstract

Described is a method for determining a loading state of an air conditioning device 1 and an air conditioning device 1 for use in a motor vehicle. The air-conditioning device 1 for use in a motor vehicle has a filter unit 3, a heat exchanger unit 7, 71, a sensor unit 4 and an evaluation electronics 6. The filter unit 3, the heat exchanger unit 7, 71 and the sensor unit 4 are arranged in an air duct 5. The sensor unit 4 is connected to the transmitter 6. Here, the heat exchanger unit 7, 71 downstream of the filter unit 3 and between the filter unit 3 and the sensor unit 4 is arranged, wherein the sensor unit 4 to an outlet surface of the heat exchanger unit 7, 71 at a distance, preferably more than 20 cm, is arranged. The sensor unit 4 includes a flow sensor 41 configured as a self-heating mode PTC element and a temperature sensor 42. The PTC element and the temperature sensor 42 are disposed adjacent to each other in the air passage 5.

Description

The The invention relates to a method for determining a Loading condition of an air conditioning device and an air conditioning device for Use in a motor vehicle, wherein the air conditioning device, a filter unit, a heat exchanger unit, a sensor unit, and has an evaluation. The filter unit and the sensor unit are arranged in an air duct, wherein the sensor unit with the transmitter for determining the loading condition of the Filter device is connected. The loading condition of a filter device is also referred to as the saturation state of the filter device.

From the DE 199 05 610 A1 a method for determining the loading state of a filter device for cabin air filters in motor vehicles is known, wherein the filter device comprises a blower unit for conveying the air into the cabin interior, which is upstream or downstream of the cabin air filter. The loading state of the filter device is determined by summation of the fan run time, wherein the total amount of air thus determined serves as a measure of the loading state of the filter device. However, the quality of the air is also not taken into account in this method, ie the actual loading of the filter unit is determined only inaccurate.

From the DE 100 36 270 A1 An air conditioning device with filter unit for motor vehicles and a method for their operation is known. In the filter device, air is conveyed through a filter unit by means of a blower unit. By means of an evaluation with display device, the current fan speed of the fan unit is determined with a scanning unit. By integrating the blower output, the total amount of air is determined. In the air duct, an additional harmful gas sensor is still provided, which is connected to the evaluation device. In this air conditioning device or the method, the loading state of a filter device with harmful gases is determined. However, the loading of the filter device with particles can not be determined hereby.

From the US 6,582,295 B1 is an air conditioning for motor vehicle cabins with filter unit and blower unit, and a method for their operation is known. A reference value measurement of the blower power consumption is performed using an unloaded filter unit. As the state of charge of the filter unit increases, the power consumption of the fan unit should also increase. Due to the small changes in power consumption in commercial fan units reproducible loading conditions of the filter unit can be obtained only with considerable effort.

From the US 4,751,501 B1 a filter device for determining the loading state of a filter unit is known. At a filter unit, which is designed as a particle filter, a differential pressure sensor is arranged. The differential pressure sensor is used to determine the pressure drop across the filter unit. The filter unit is followed by a pneumatic flow sensor for determining the volume flow of the air. By means of a comparison of the current values of these two sensors with reference values of an unloaded filter unit, the loading state of the filter unit can be determined very accurately. However, it is a costly process in which the differential pressure sensor in turn is prone to contamination by dust.

From the DE 102 15 925 A1 a sensor arrangement for determining the pressure drop across a filter unit of an air filter for motor vehicles is known. Due to different pressures on the two sides of the filter unit, a deflection of a diaphragm of a differential pressure sensor is determined. This deflection is a measure of the loading state of the filter unit. Such a sensor arrangement has similar disadvantages as the filter device of US 4,751,501 B1 ,

From the DE 101 62 806 A1 For example, a method and a filter device are known in which the loading state of a filter unit is determined by measuring the inflow-side reflectance of the filter unit with an optical sensor. However, this type of measurement of the loading state depends very much on the nature of the loading aerosol and is therefore not reproducible.

Of the The invention is therefore the object of simple, inexpensive and reproducibly the loading condition of an air conditioning device a motor vehicle, in particular a particle filter of the air conditioner, to investigate.

These The object of the invention is with the method for the determination a loading state of an air conditioning device used in a motor vehicle according to the claim 1 and with the air conditioning device according to the claim 6 solved.

With the solution according to claim 1, a method for determining a loading condition of an air conditioning device for use in a motor vehicle, comprising the following steps: providing an air conditioning device with a filter unit, a heat exchanger unit, and a sensor unit, wherein the filter unit, the heat exchanger unit and the Sen sensor unit are arranged in an air duct, the heat exchanger unit is arranged downstream of the filter unit and between the filter unit and the sensor unit, the sensor unit is arranged to an exit surface of the heat exchanger unit with a distance, preferably of more than 20 cm, the sensor unit comprises a flow sensor serving as in self-heating mode operated PTC element is formed, and having a temperature sensor, and the PTC element and the temperature sensor adjacent to each other in the air duct, setting one or more predefined environmental conditions, in particular a blower power of a blower unit arranged in the air duct, measuring a Signal of the flow sensor and a signal of the temperature sensor at a time t ₁ , and determining the loading state of the air conditioning device by an evaluation based on the measured signals of the flow sensor and de s temperature sensor at the time t ₁ and one or more stored in a memory unit reference values which specify a signal of the flow sensor in response to a signal of the temperature sensor at a reference load state.

The The object of the invention is also achieved according to the device with an air conditioning device for use in a motor vehicle according to claim 6. in that the air-conditioning device, a filter unit, a heat exchanger unit, a sensor unit, and an evaluation, wherein the filter unit, the heat exchanger unit, and the sensor unit are arranged in an air duct and the sensor unit with the Transmitter is connected, wherein the heat exchanger unit downstream of the filter unit and between the filter unit and the sensor unit is arranged, wherein the sensor unit to a Exit surface of the heat exchanger unit in a Distance, preferably greater than 20 cm, is arranged and where the sensor unit has a flow sensor which serves as formed in self-heating mode operated PTC element, and having a temperature sensor, and the PTC element and the temperature sensor are arranged adjacent to each other in the air passage.

Especially it is advantageous that according to the invention adjacent to the flow sensor, as in the self-heating mode operated PTC element is formed, a temperature sensor arranged is that measures the temperature of the surrounding air. This will allows the measurement of the flow sensor can be corrected by means of the adjacent measured temperature and thus the loading condition of the air-conditioning device exactly, thus also reproducible, is determined. The flow sensor as in self-heating mode operated PTC element form is inexpensive, since it is at the flow sensor Semiconductor commodity acts. Next is by the special arrangement the sensor unit to the filter unit and the heat exchanger unit achieved an accurate determination of the loading condition. The loading condition the air conditioning device is in this case essentially of the loading condition of the filter unit and possibly also on the loading state of the heat exchanger unit certainly. In practice, the evaluation of the PTC element takes place as a simple voltage measurement via a voltage divider circuit. Further allows the determination of the loading condition of the air conditioning device dynamic service interval times of the air-conditioning device, thereby ensuring optimum operation of the air conditioning device becomes.

at The heat exchanger unit may be a refrigeration unit or to act a heating unit, which guided in the air duct Air flow cools or heats up. The heat exchanger unit can also from a cooling unit and a heating unit exist, preferably in a row in the air flow in the air duct are switched to selectively turn on individually or together. In this way, can be particularly well a tempering and / or flow control of the air flow in the air duct. The heat exchanger unit can also be designed as an aggregate, which for cooling as well as for heating can be operated. The heat exchanger unit can basically one or more heat exchanger units consist.

Further Advantages of the invention will become apparent by embodiments according to the dependent claims.

at Versions in which the heat exchanger unit for cooling the air flowing through the air duct is formed, the heat exchanger unit z. B. as Be formed evaporator of a coolant circuit. For versions where the heat exchanger unit for heating the air channel flowing through the air formed is, the heat exchanger unit z. B. as a heat exchanger an oil cooling circuit of the motor vehicle formed be.

at Versions in which several heat exchanger units between the filter unit and the sensor unit in the air duct are arranged, z. B. at least one heat exchanger unit for Heating and at least one heat exchanger unit for cooling be formed of the air channel flowing through the air.

In a preferred embodiment of the invention The flow sensor and the temperature sensor are arranged no more than 1 mm to 10 mm apart in the air duct. This results in a particularly accurate measurement of the temperature of the air flowing around the flow sensor.

It can be provided that the temperature sensor preferably as NTC element is formed (NTC = negative temperature coefficient). Of the Temperature sensor can also be designed as a PTC element. For example, the temperature sensor is a resistance thermometer pt100 or pt1000.

at A preferred embodiment of the invention comprises the sensor unit an air-permeable cap arranged in such a way is that the air-permeable cap the flow sensor surrounds. It is advantageous that the air-permeable cap the flow velocity of the air, which is the flow sensor reached reduced. The flow sensor, as in self-heating Mode operated PTC element is formed is smaller Air flow rates more sensitive to changes the flow velocities of the air. From this results advantageous an improved measurement accuracy of the flow sensor.

The Sensor unit points to an exit surface of the heat exchanger unit a distance of more than 20 cm, preferably more than 40 cm, on. Such a relatively large distance ensures that the air is already even after the filter unit has mixed, whereby the accuracy of the temperature measurement of the Temperature sensor is favored.

at A preferred embodiment of the invention is the filter unit designed as a particle filter. The filter unit can be a pleated Have filter material body. The filter unit can consist of nonwoven fabric. The filter unit can be too to a combination filter z. B. with activated carbon - act adsorbent.

It it can further be provided that the cap, which contains the flow sensor, surrounds as a, preferably made of Köpertressengewebe formed, permeable to air Cap is formed. Preferably, the cap is made of stainless steel educated.

at A preferred embodiment of the invention has the transmitter a memory unit, and the transmitter is such designed so that the evaluation electronics signal values of the flow sensor and the temperature sensor detected simultaneously and in the storage unit stores. The transmitter can be connected to the flow sensor and the temperature sensor of the sensor unit. The storage unit can be an integral part of the transmitter. Becomes the air-conditioning device is operated in a motor vehicle, Thus, the memory unit and / or the evaluation in one Be arranged on-board computer of the motor vehicle.

at A preferred embodiment of the invention comprises the air conditioning device a display device, preferably designed as an LED, for display the loading state of the air conditioning device. If the air conditioning device used in a motor vehicle is, the display device may be part of an on-board computer be and / or the display device may be in a dashboard be arranged a motor vehicle. Is particularly advantageous here the use in trucks, the truck driver has thus the possibility of loading the air conditioning device independent of a motor vehicle workshop. This allows the truck driver z. B. even to replace the particulate filter of the air conditioning unit, if this is loaded sufficiently strong. It is thus possible to reduce the maintenance costs of the truck, because the loading condition can be determined by the truck driver even made, resulting in no unnecessary review the loading state of the air conditioning device by the Motor vehicle workshop during service inspection of the truck takes place.

In a preferred embodiment of the invention, the flow sensor and / or the temperature sensor have a volume of space of 1 mm ³ to 1 cm ³ . A small volume of space of the flow sensor and / or the temperature sensor of 1 mm ³ to 1 cm ³ is particularly advantageous because the air flow is only negligibly influenced by the flow sensor and / or the temperature sensor.

at a preferred embodiment of the invention, the air duct a secondary air duct, wherein in the secondary air duct a flap is provided for controlling the air volume flow, and wherein the Sensor unit is arranged in the secondary air passage. Advantageous is, this the flow velocity of the air is reduced, and the flow sensor in a more sensitive Operating mode is operated. This increases the measuring accuracy of the Loading condition of the air conditioning device.

In a preferred embodiment of the invention, the air conditioning device has a blower unit arranged in the air duct and the sensor unit is arranged at a distance of more than 40 cm from the blower unit. The relative Large distance favors that the air has mixed evenly before the loading condition of the air conditioning device is determined, whereby a higher measurement accuracy is achieved.

It can also be provided that the temperature sensor of the sensor unit connected to a control unit of an air conditioning unit, so the temperature sensor used to control the air conditioning can be.

It can be further provided that the air conditioning device has a further sensor unit, the close or directly afterwards is arranged on the filter unit. The other sensor unit the filter unit allows under constant measurement and evaluation an early detection of a rapid change the loading state of the air conditioning device, so about suddenly occurring holes in the filter unit and / or suddenly occurring heavy load, such as leaves, the filter unit be recognized immediately.

at a preferred embodiment of the invention Method for determining the loading condition of the air conditioning device is the air conditioning device with an unloaded filter unit provided. There will then be one or more predefined Ambient conditions, in particular the blower output, the blower unit arranged in the air duct is set. It can be provided that the air duct fluidly is brought into a predefined state, preferably Flaps of the air duct are placed in predefined positions, z. B. all flaps are opened or closed. thereupon is by means of the transmitter simultaneous the signal of the Flow sensor and the signal of the temperature sensor for different temperatures of the air surrounding the sensor unit measured. Specifying values of the signals from the flow sensor are used as reference values for the different temperatures the air according to the signals of the temperature sensor in the Memory unit stored. It is particularly advantageous that these reference values the interaction of the component, such as filter unit, Sensor unit, air duct, fan unit etc, with their Characterize geometric arrangement in the air conditioning device. Thus, by means of these characteristic reference values, the loading state determined very accurately for this air conditioning device become.

In a preferred embodiment of the method according to the invention, a specifying value of the signal of the flow sensor measured at the time t _{1 is} determined by the evaluation electronics as the actual value of the flow sensor.

The previously determined and stored reference values specifying a signal of the flow sensor in response to a signal of the temperature sensor at a reference load state for one or more temperatures of the air surrounding the flow sensor are preferably described in terms of a function. Preferably, this function is a linear function of temperature. These stored reference values can be z. B. be parameter of the function. In a linear function, these parameters z. B. be a slope and / or a so-called y-section. These stored reference values can hereby also be stored as a value table, in particular the function, in the memory unit of the evaluation electronics. With the signal of the temperature sensor at time t ₁ , by means of the previously determined function, an actual value of the signal of the flow sensor corrected for the temperature of the surrounding air can be obtained in a particularly simple manner.

In a preferred embodiment of the method according to the invention, a deviation of the actual value of the flow sensor at time t ₁ from the previously determined reference value of the signal of the flow sensor is determined in the form of a difference. The loading condition of the air conditioning device is judged to be acceptable if a standard, preferably designed as an absolute value, does not exceed the previously determined deviation of a threshold value.

In a preferred embodiment of the method according to the invention, a relative deviation of the actual value of the flow sensor at time t ₁ from the previously determined reference value of the signal of the flow sensor is determined, wherein the relative deviation is not negative and not greater than 1. Preferably, the relative deviation is formed by first subtracting the actual value from the reference value and then dividing by the reference value. Then, the loading state of the air conditioning device is judged to be acceptable if a standard, preferably formed as an absolute amount, the previously determined relative deviation does not fall below a threshold value.

at a preferred embodiment of the invention Method is the thresholds with a value of more than 80%, preferably more than 90%.

In a preferred embodiment of the method according to the invention, the signals of the flow sensor and the temperature sensor after a period of time T, preferably of at least 10 s, detected after the setting of one or more predefined environmental conditions and after the flow sensor and have set stationary signals to the temperature sensor. It is advantageous that after the period T, both a fluid mechanical and a thermodynamic equilibrium have been established, as a result of which a particularly high quality, in particular with regard to reproducibility, of the measured values is achieved.

at a preferred embodiment of the invention Method, a blower output is adjusted such that so that there is a flow velocity of the air in the area from 0.1 m / s to 2.0 m / s, preferably 0.5 m / s. Is advantageous that the sensor unit operated at these low flow rates air, especially sensitive to changes in flow velocity the air is, whereby a high measuring accuracy is achieved.

in the The following is the invention based on embodiments in conjunction with figures described in more detail. Showing:

1 : A schematic representation of an air conditioning device of an embodiment.

2a ): A voltage divider circuit for measuring the signal of the flow sensor of a first embodiment.

2 B ): A voltage divider circuit for measuring the signal of the flow sensor of a second embodiment.

3 FIG. 4: A graph of a measurement of the signal of the flow sensor according to the first and the second embodiment, corresponding to circuit diagrams of FIG 2a ) respectively. 2 B ) depending on the flow velocity of the air v.

4 : A graph of a measurement of the signal of the flow sensor U _T (v) for different positions of the sensor unit as a function of a relative blower power of a further embodiment.

5 : A graph of a measurement of the signal of the flow sensor U _T (v) as a function of the temperature T _U , which surrounds the sensor unit of the further exemplary embodiment.

6 A graph of a measurement of the signal of the flow sensor U _T (v) for different degrees of coverage of the filter unit and different blower outputs of the blower unit of the further embodiment.

7 : A graph of a measurement of signals of a plurality of flow sensors U _T (v) for different positions of the sensor units of the further embodiment under loading.

8th FIG. 3: A graph of a measurement of the change in the signal of the flow sensor U _T (v) for different positions of the sensor unit as a function of a relative blower power of the further exemplary embodiment.

9 A graph of a measurement of signals of a plurality of flow sensors for different positions of the sensor units and the pressure drop on the filter unit of the further embodiment under loading.

10 : A graph of a partial measurement 9 the signal of a flow sensor of the sensor unit and the pressure drop on the filter unit of the further embodiment with a flow sensor arranged in a small vent under loading.

Based on 1 First, the structure of the air conditioning device according to the invention 1 described.

At the in 1 shown air conditioning device according to the invention 1 it is an air filter device for motor vehicles. This air conditioning device 1 is preferably part of an air conditioning device and is used for cabin air filtration. The air conditioning device 1 includes a filter unit 3 , a sensor unit 4 and an evaluation 6 , Here is the filter unit 3 and the sensor unit 4 in an air duct 5 arranged successively at a distance of more than 40 cm. in a not shown embodiment, the sensor unit 4 before a division of the air flow in various secondary air channels, the z. B. footwell, cockpit and windscreen, be arranged. But it can also be provided that the sensor unit 4 is arranged in one of these secondary air ducts, wherein the flap can control the flow of air in the secondary duct.

At the filter unit 3 it is a pleated filter preferably made of nonwoven fabric which is designed as a particle filter. It may alternatively but also a non-pleated filter z. B. act a plate filter.

The flow direction of the air in the air duct 5 is by the directional arrow 11 characterized.

The sensor unit 4 is electronically by means of a signal line 4s with the transmitter 6 connected.

The sensor unit 4 , with which the loading state of the air conditioning device is determined, has a flow sensor 41 which is designed as a self-heating mode operated PTC element, and a temperature sensor 42 on. The flow sensor 41 and the temperature sensor 42 are arranged adjacent to that with the temperature sensor 42 the air, which is the flow sensor 41 surrounds, can be determined with sufficient accuracy. In the case that the flow sensor 41 and the temperature sensor 42 are arranged in a secondary air duct, not shown, the two sensors can also be arranged opposite to the walls of the secondary air duct and / or be spaced up to 10 cm. The temperature sensor 42 may be configured as an NTC, pt100 or pt1000. The temperature sensor is preferred 42 an NTC element. Furthermore, the air conditioning device 1 a blower unit 2 on that in the air duct 5 is arranged. At the blower unit 2 it is a controllable fan unit 2 in the form of a fan. The blower output of the blower unit 2 is arbitrary.

A heat exchanger unit 7 with lamellar structure and another heat exchanger unit 71 are in the air duct 5 between the filter unit 3 and the sensor unit 4 arranged. The heat exchanger unit 7 is designed as an evaporator of a refrigerant circuit and can be used to cool the air duct 5 flowing air can be used. The further heat exchanger unit 71 is designed as a heat exchanger of an oil cooling circuit of the motor vehicle and can be used to heat the air duct 5 flowing air can be used. It may be provided in a non-illustrated embodiment that only one heat exchanger unit 7 respectively. 71 is provided. The evaporator 7 and the heat exchanger 71 are both from the filter unit 3 as well as from the sensor unit 4 at least 2 cm apart in the air duct 5 arranged. Furthermore, there is another heat exchanger 71 with lamellar structure in the air duct 5 arranged. The further heat exchanger 71 is between the filter unit 3 and the sensor unit 4 arranged. The heat exchanger 71 can act as a heater of the air conditioning.

In a preferred embodiment, one is in the air duct 5 arranged pre-separator unit 8th upstream of the blower unit 2 intended. This pre-separator unit 8th is designed as a coarse-meshed grid and serves to ensure that no coarse dirt, such. As foliage, small branches, parts of plastic bags, or the like, in the air duct 5 can reach and thus the blower unit 2 and the filter unit 3 protects against dirt and / or damage.

Furthermore, the flow sensor 41 an air-permeable and spherical cap 43 from Köpertressengewebe on. The cap 43 is made of stainless steel. The cap 43 has a diameter, so that the cap 43 an air gap of 1 mm to 3 mm to the flow sensor 41 having. In an embodiment not shown may be directly downstream, behind the filter unit 3 is another sensor unit in the air duct 5 be arranged. The sensor unit preferably has a distance of not more than 5 cm from the filter unit 3 on. This further sensor unit can be identical to the sensor unit 4 be educated. Ie. the further sensor unit may comprise a flow sensor, which is designed as a self-heating mode operated PTC element, and a temperature sensor. The flow sensor and the temperature sensor may be arranged adjacent to each other at a small distance of not more than 1 mm to 10 mm from each other. This further sensor unit can be electronically connected to the evaluation electronics by means of a signal line 6 be connected.

The evaluation electronics 6 has in addition to analog and / or digital modules, eg. B. a CPU, for evaluating the signals of the sensor unit 4 also a storage unit 62 and a display device 61 , which is designed as an LED on.

Furthermore, the transmitter is 6 via a signal line 6s or the motor vehicle bus with a control unit 10 the air conditioning device and / or other components of the automotive electronics connected. By means of the electronic coupling of evaluation electronics 6 and control unit 10 the climate device can advantageously the information obtained with the sensor unit 4 , be reused for optimized control of the air conditioning.

Furthermore, the dimensioning of the sensor unit 4 , as in 1 can be seen, small compared to the air duct 5 wherein the sensor unit 4 occupies a volume of less than 2 cm ³ .

Important for the arrangement of the sensor unit 4 is that this sensor unit, in order to ensure optimum function, are not in direct contact with the possibly extreme outside temperatures in summer and winter. This is achieved by the sensor unit 4 through components, such as filter unit 3 and / or one or more heat exchanger units serving as evaporators 7 and / or heat exchangers 71 are formed, are arranged buffered.

The determination of the loading state of an air conditioning device 1 the air filter device in an air conditioning device of a motor vehicle, according to the 1 , as follows is explained: First, reference values by evaluation electronics 6 for an unloaded, ie unused, filter unit 3 be determined. This is done in the air conditioning 1 an unloaded filter unit 3 provided. At the air conditioning device 1 are one or more predefined environmental conditions, in particular the fan power in the air duct 5 arranged fan unit 2 , discontinued. Any flaps of the air duct 5 the air conditioning device 1 are set in a certain position. Then be through the transmitter 6 simultaneously signals from the flow sensor 41 and the temperature sensor 42 for different temperatures of the air, which is the sensor unit 4 surrounds, measured. These specifying values of the signals from the flow sensor 41 are used as reference values for the different temperatures of the air according to the signals of the temperature sensor 42 in the storage unit 62 saved. The determination of a data record is preferably at every change of the filter unit 3 perform in a possible motor vehicle service in a workshop, so always an optimal function of the air conditioning 1 can be guaranteed.

For determining the loading condition of the air conditioning device 1 , the same ambient conditions as in the determination of the reference values are set, ie in particular the same fan performance and the possible same setting of the flaps of the air duct 5 , Subsequently, the signal of the flow sensor 41 and temperature sensor 42 measured simultaneously at a time t ₁ . The loading condition of the air conditioning device 1 is through an evaluation 6 based on the measured signals of the flow sensor 41 and the temperature sensor 42 at time t ₁ in a memory unit 62 stored reference values. The determination of the loading condition of the air conditioning device 1 can be continuous or on instruction, eg. B. by a motor vehicle driver or workshop mechanic done.

Based on 2a ) 2 B ) and 3 the underlying method for determining the loading state of a particulate filter is explained in more detail.

The flow sensor 41 is a PTC element that operates in self-heating mode. Depending on one of the flow sensor 41 applied voltage U heats up to its own temperature T _E. If this is now supplied with a temperature of the air T _U , which is smaller than T _E , then the flow sensor cools 41 first off. Due to the PTC effect, the resistance of the flow sensor decreases 41 which causes more current / _ptc through the flow _sensor 41 flows and the flow sensor 41 heating up. Due to the steep course of the characteristic curve characteristic for PTC elements, the current / _ptc itself is limited. At constant voltage U, a characteristic current / _ptc therefore sets in, depending on the air velocity. This relationship is described by King's Law: U ptc · I ptc = (T e - T U ) · (A + b√ v )

In King's Law, a, b and T _E denote material constants. V denotes the flow velocity of the air. These constants a, b and T _E can be determined experimentally by measuring the current / _ptc in the laboratory with the aid of a drying cabinet or a hot plate at a fixed voltage U, with and without flow of the air v, and various temperatures of the air T _U. Advantageously, the constants a and T _E are initially determined for v = 0 at a fixed voltage U as a function of the temperatures of the air T by means of a linear fit. Then, by a single measurement of the current / _ptc for a fixed speed v> 0 of the air and a temperature of the air T _U at the same voltage U, the constant b is determined.

entsprechend 2b):

By changing the flow velocity v, according to King's Law, a root-shaped change of the current / _ptc by the PTC effect is expected. This change is measured in the form of the voltage U _T by means of a simple voltage divider circuit with an ohmic resistance R _S according to the 2a ) and 2 B ). In general, the voltage at the PTC element U _ptc with the voltage at the ohmic resistor R _S results in the voltage U. Depending on where the PTC element is located, the following measured values are obtained as a divider voltage as a function of the flow velocity v:
corresponding 2a ):

corresponding 2 B ):

3 shows a graph of a measurement of the signal of the flow sensor according to the first and the second embodiment according to circuit diagrams of 2a ) and 2 B ) in dependent speed of the air flow v. Here, the measured voltage is given in V and the flow velocity of the air v in m / s.

Based on 3 the meaning of the root-shaped dependence is recognizable. At high flow velocities of the air v small changes in the flow velocities V cause only small changes in the sensor signal U _T.

In order to determine the flow velocity of the air v and thus the volume flow exactly, it is necessary to proceed as described above, ie the constants a, b and T _E are with an unloaded filter unit 3 or air conditioning device 1 certainly. For the determination of the load condition, however, it is sufficient to determine a measure of the change or decrease in the volume flow of the air over the service life, or operating time. Here, the volume flow or the flow velocity of the air v is in a fixed operating state of the air conditioning device 1 , ie at fixed ambient conditions, measured. Therefore, all measurements will be made with the same blower fan setting 2 and the same settings for any flaps of the air conditioning device 1 instead of. The flow sensor 41 is brought by setting a constant operating voltage U in the self-heating mode and the voltage drop across the PTC element, ie the signal of the flow sensor 41 , is saved as start value. For this setting, the temperature dependency for the later temperature range of the application must now be determined. The temperature calibration of the sensor unit 41 , which takes place at the same flow velocity v, z. B. be made in a laboratory. The sensor unit 4 are arranged adjacent thereto in an air duct. The flow sensor 41 is operated at a constant voltage, preferably 12V. At a constant selected volumetric flow, which corresponds to the selected operating state of the air conditioning, now the voltage drop as a signal of the flow sensor 41 measured across the PTC element according to the circuit diagram of 2a ). The signal of the temperature sensor 42 , the z. B. is realized with an NTC element is measured with the same principle. With the help of the characteristic curve of the NTC element can be calculated from the signal of the temperature sensor 42 the temperature of the air, which is the sensor unit 4 surrounds, determine.

Due to the fact that the biggest changes in the signal of the flow sensor 41 However, at low flow velocities of the air v, but a steady state of the air conditioning device is best achieved at high flow velocities of the air v, it is advantageous to use an air-permeable cap 43 to reduce the flow velocity of the air v so much, so that the measurement in the steeply rising range of the measuring signal, as in 3 can be seen, that is, at an air velocity of about 4 m / s, the flow velocity of the air v at the flow sensor 41 reduce to 0.5 m / s. Alternative may be the positioning of the sensor unit 4 be provided in a single secondary air duct, wherein the flow velocity of the air v can be reduced by a controllable flap so that at the sensor unit 4 a flow velocity of the air v of a maximum of 0.5 m / s occurs.

In the further embodiment, a PTC element with the following properties is used:
R ₀ (T _U = 20 ° C) = 50 ohms,
Operating voltage U = 12 V,
R _12V (T _U = 20 ° C) = 180 ohms.

This sensor unit 4 was in a W164 air conditioning in a vent, attached to the air duct 5 is provided and branches off into the footwell mounted, ie behind the heat exchanger unit 7 , which is designed as an evaporator. The PTC element was connected in series with a resistance of R _S = 56 ohms, with the measurement signal U _T (v) corresponding to the circuit 2 B ) is tapped.

At the same time, two more sensor units were placed directly behind the filter unit 3 placed in the middle and in the corner. A fourth sensor unit was located in the air duct directly behind the blower unit 2 positioned. In 4 are for different blower outputs, from 0% -80% in 10% increments, of the blower unit 2 the signals of the flow sensors are shown in V. With the exception of the flow sensor in the filter corner results for all the expected signal as a function of the fan power.

At a constant flow rate of air v (60% blower power), the value of U _{T was} measured for different temperatures. The result is in 5 shown. One sees the linear dependence of T. The linear regression leads to the following result: U T, 60% (T U ) = 10.1 - 0.13 · T U

In 5 this relationship is determined by the best-fit line or regression line, of which exactly two parameters are in the evaluation electronics 6 can be stored.

Further, in 5 corrected for the ambient temperature voltage signal, which is a root-shaped dependence on the flow speed of the air v shown. This corrected to the ambient temperature voltage signal of the flow sensor is obtained by the following calculation:

With this positioning of the sensor units, the inflow area of the filter unit was now set at a blower setting of 80% 3 gradually covered to clog the filter unit 3 and to simulate a decrease in the volume flow. At the beginning, 1/4 of the cover was replaced by different parts of the filter unit 3 covered so as to uneven loading of the filter unit 3 display. The result of this experiment is in 6 shown. It will be appreciated that in terms of the coverage and blower performance of the blower unit 2 only the sensor units in the air duct 5 behind the blower unit 2 and in the vent of the air duct 5 are positioned, provide a unique and correlated with the air volume signal. The sensor units directly on the filter unit 3 provide different signals for different covers, which do not always correlate directly with the reduction in the amount of air. The sensor unit in the air duct 5 behind the blower unit 2 positioned at 95% coverage, ie at extremely high loading of the filter unit 3 , no further reproducible signal if the air volume is further reduced. The only sensor unit that provides a reproducible signal over the entire course of the experiment is the one positioned in the footwell vent. This result suggests that the flow sensor 4 as far away as possible from the filter unit 3 and the blower unit 2 should be positioned to influence the flow by uneven loads of the air conditioning device 1 to minimize. The effect of the evaporator 7 As a flow straightener has led here to a corresponding result.

With this arrangement of the sensor units, a loading test has now been carried out. For this purpose, the blower unit 2 with 60% of the maximum fan power, or air volume, adjusted and applied in a flow channel with a test dust. The test dust consisted of the following components:
72% JIS Class 8 (a dust based on a clay mineral),
23% JIS Class 12, (a dust based on soot),
5% cotton fibers.

The exact composition of the dust JIS Class 8 and 12 can taken from the standard JIS 28901 (Japanese Industrial Standard) become.

The result of this loading over a period of time is in 7 shown. Two loadings were performed, ie two pistons with test dust on the filter unit 3 loaded. It can be seen during the first loading cycle, a strong change in the two signals of the sensor units on the filter unit 3 which is due to an uneven loading. However, the total volume flow does not change here, as the signal of the other two sensor units ( 7 in the air duct behind the blower unit, in the vent to the footwell). As the loading of the filter unit progresses 3 (2nd loading), the flow rate decreases continuously, but the signals from the sensor unit sensor units fluctuate directly at the filter. However, a clear assignment to the decrease is only possible with the two sensor units 4 in the air duct 5 and possible in the footwell in the vent. From the decrease of the measuring signal of these two sensor units can be clearly on the loading condition of the filter unit 3 shut down.

However, the optional and not shown further sensor unit allows directly or close to the filter unit 3 with continuous evaluation by the evaluation electronics 6 , the detection of the fluctuation of the signal of the sensor unit, and thus a spent or overloaded filter unit 3 be recognized. Another sensor unit may also detect a "half-full" or "half-loaded" filter unit 3 recognize on the basis of the no longer monotonically falling signal of the other sensor unit, ie a kind of first loading of the filter unit 3 can be recognized.

Preliminary tests on an evaporator 7 From soldered aluminum structures with a volume of 2.6 l, have shown that when loaded with up to 80 g of water barely a significant pressure drop increase sets. Nevertheless, in countries with extremely high humidity, it can happen that up to 200 g of water in the fins of the evaporator 7 collect, thereby causing a pressure drop increase of 5% -10% from the dry state. This can also affect the total volume flow, using the flow sensor 4 behind the evaporator 7 measured, have an influence, ie this can lead to a reduction of the volume flow. To exclude that an extremely water-laden evaporator, the measurement result of the flow sensor 4 falsified, a defined operating condition must be selected, in which a certain maximum amount of water on the surface of the evaporator 7 may be condensed. This operating condition must first be determined empirically at the air conditioning unit. For example, a longer downtime (parking overnight or for more than 2 hours) can be used. In a longer downtime can the water from the evaporator 7 expire. When starting the air conditioning unit, a compressor of the air conditioning unit must remain switched off until the volume flow is checked by means of the flow sensor 4 is done.

in the The following is discussed in more detail as a beneficial one Increase of the change of the signal of the sensor unit can be achieved.

To a much larger change in the signal of the sensor unit 4 to get the flow sensor 41 from the above example with a cap 43 made of a stainless steel body strainer fabric. This Köpertressengewebe had an opening width of 70 microns. The signal output at 90% blower output of the blower unit 2 was thereby reduced from 7.2V to 5V, moving now in the region of the signal from the flow sensor, where small changes in the flow velocity of the air v cause greater changes in the signal output than in a sensor unit which does not have a cap. With this cap 43 Now a new stage test was carried out from 50% to 90% blower capacity of the blower unit 2 carried out. The result is in 8th shown. Plotted is the change of the signal of the sensor unit above the blower power. The change in the output signal could be approximately doubled by this cap when changing the fan setting from 50% to 90%.

It was carried out another loading attempt, this time with a sensor unit in the filter center, with two sensor units in a large vent for a cockpit of a motor vehicle, wherein one of the two sensor units with a cap 43 was provided from a Köpertressengewebe, and the other of the two sensor unit was arranged in a small vent from which flows through a predetermined adjustment of a flap in the secondary air duct only a small air flow. For loading, the blower unit was set at 60% of its maximum blower output. During loading, the pressure drop across the filter unit became parallel, ie simultaneously 3 recorded. The result is in 8th shown. The largest change in the signal of the flow sensor is obtained again for the sensor unit in the middle of the filter unit 3 , However, a similarly significant effect is also obtained with the sensor unit, which was positioned in the small vent, which only lets through a small part of the air flow through a flap. A likewise clear effect is obtained with the sensor unit in the large vent, which has a cap 43 was provided. As with the loading attempt, the result in 7 is shown, the sensor unit in the large vent shows a clear change of the signal of the flow sensor, which, however, significantly weaker than in the first three sensor units. The signal for the sensor unit directly in the middle of the filter unit 3 increases towards the end of the load. Here, the flow conditions in the air conditioning device change greatly 1 , If the loading had been continued, a similar fluctuation of the measuring signal over time would have been obtained, as was already observed in the first loading test and off 7 can be seen. This measurement has produced the following significant results:
Both a cap of a Köpertressengewebe and the reduction of the volume flow in the air duct, in which the sensor unit is arranged, causes a significant change in the signal of the flow sensor with the volume flow, the pressure drop across the filter unit 3 and thus with the loading state of the air conditioning device 1 correlated.

A sensor unit located in the center of the air conditioning unit 3 is arranged, provides only in the first part of the load a clear change of the signal of the flow sensor.

The change of the signal of the flow sensor 41 with cap 43 results in a reduction in fan power from 60% to 54% with a pressure drop increase of around 200 Pa. This corresponds to a reduction of 10%, which is already classified as a concern by the air conditioning manufacturer. In the further course, the blower output is reduced to 48%, ie a total of 20%. This change is made by the sensor unit directly behind the filter unit 3 no longer recorded.

The conversion of the signal of the flow sensor, which was positioned in the small vents, into the air quantity is together with the pressure drop increase in 10 shown.

Since the sensor unit of the PTC element, as a flow sensor, and the NTC element, as a temperature sensor monitors the air quantity of the air conditioning device in a defined operating state, not only the clogging or loading of the filter unit 3 but also detects possible fouling, clogging and clogging of heat exchangers and / or evaporators. Should after changing the filter unit 3 the signal of the sensor unit does not return to its original value, ie at least close to the original value, this may be an indication of a soiled evaporator and / or condenser.

All in all represents the air conditioning device according to the invention thus an extremely simplified flow switch represents.

Thus, the air conditioning device according to the invention 1 in addition to the diagnosis of the degree of contamination of the entire air conditioning, in particular the heat exchanger and / or evaporator can be used. For this purpose, the signal of the flow sensor without built-filter unit 3 which can be measured again with every service in the workshop. If a change in the signal of the flow sensor is already observed here, there is an indication that the air conditioning system should be cleaned. Odor nuisance due to long-term contamination can thus be avoided.

at a not shown embodiment of the invention The method becomes the reference values by means of linear regression determines which a signal of the flow sensor in dependence from a signal of the temperature sensor at a reference loading condition specify. In this evaluation are by linear regression Parameters of a regression line determined. The parameters will be then stored in the storage unit. It is advantageous that only two parameters describing the reference values of the Flow sensor for the different temperatures of the Air must be stored. Furthermore, by means of smoothed linear regression measurement error.

In an embodiment, not shown, of the method according to the invention, a reference value is determined, which is assigned to the signal of the flow sensor at the time t ₁ . The assignment is made by the evaluation by means of the signal of the temperature sensor and the one or more stored reference values for the different temperatures of the air. Here, as a reference value assigned to the signal of the flow sensor at the time t ₁ , that stored reference value is selected whose temperature of the air differs at least from the temperature of the air at the time t ₁ . The advantage here is the particularly simple determination of the reference value at time t ₁ . Furthermore, it is also possible for the reference value, which is assigned to the signal of the flow sensor at the time t ₁ , to be determined by interpolation of the stored reference values. As a result, a particularly accurate estimation of the reference value of the flow sensor at time t _{1 is} made possible in a simple manner. Furthermore, it is also possible for a reference value associated with the signal of the flow sensor to be determined at the time t ₁ by the regression line using the associated previously stored parameters. As mentioned above, it is advantageous in this method that measurement errors are smoothed. In addition, advantageously results in a very simple and fast feasible determination of the reference value.

1

air conditioning unit

2

blower unit

3

filter unit

4

sensor unit

41

flow sensor

42

temperature sensor

43

cap

4s

signal line

5

air duct

6

evaluation

61

display

62

storage unit

6s

signal line

7

heat exchanger unit

71

heat exchanger unit

8th

Pre-separator unit

10

control unit the air conditioning

11

flow direction the air

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

• - DE 19905610 A1 [0002]
• DE 10036270 A1 [0003]
• - US 6582295 B1 [0004]
• US 4751501 B1 [0005, 0006]
• - DE 10215925 A1 [0006]
• DE 10162806 A1 [0007]

Claims (18)

Method for determining a loading condition of an air-conditioning device ( 1 ) for use in a motor vehicle, comprising the following steps: providing an air conditioning device ( 1 ) with a filter unit ( 3 ), a heat exchanger unit ( 7 . 71 ), and a sensor unit ( 4 ), wherein the filter unit ( 3 ), the heat exchanger unit ( 7 . 71 ) and the sensor unit ( 4 ) in an air duct ( 5 ) are arranged, the heat exchanger unit ( 7 . 71 ) downstream of the filter unit ( 3 ) and between the filter unit ( 3 ) and the sensor unit ( 4 ), the sensor unit ( 4 ) to an exit surface of the heat exchanger unit ( 7 . 71 ) is arranged at a distance, preferably of more than 20 cm, the sensor unit ( 4 ) a flow sensor ( 41 ), which is designed as a self-heating mode operated PTC element, and a temperature sensor ( 42 ), and the PTC element and the temperature sensor ( 42 ) adjacent to each other in the air channel ( 5 ), setting one or more predefined environmental conditions, in particular a blower power of one in the air duct ( 5 ) arranged blower unit ( 2 ), Measuring a signal of the flow sensor ( 41 ) and a signal of the temperature sensor ( 42 ) at a time t ₁ , and determination of the loading state of the air conditioning device ( 1 ) by evaluation electronics ( 6 ) based on the measured signals of the flow sensor ( 41 ) and the temperature sensor ( 42 ) at the time t ₁ and one or more in a storage unit ( 62 ) stored reference values which a signal of the flow sensor ( 41 ) in response to a signal from the temperature sensor ( 42 ) at a reference loading condition. Method according to claim 1, characterized in that the method comprises the further steps of: providing the air-conditioning device ( 1 ) with an unloaded filter unit ( 3 ), Setting one or more predefined environmental conditions, in particular the fan power in the air duct ( 5 ) arranged blower unit ( 2 ), using an unloaded filter unit ( 3 ), simultaneous measurement by means of the evaluation electronics ( 6 ) of the signal of the flow sensor ( 41 ) and the signal of the temperature sensor ( 42 ) for one or more temperatures of the air, which the sensor unit ( 4 ) and storage of which the signals of the flow sensor ( 41 ) in dependence on the signals of the temperature sensor ( 42 ) specifying values as reference values. Method according to one of claims 1 or 2, characterized in that the evaluation electronics ( 6 ) determined when the particular load condition of the air conditioning device ( 1 ) differs by more than 20% from that of an unloaded air conditioning device, and then signals that the loading state of the air conditioning device ( 1 ) is assessed as unacceptable. Method according to one of claims 1 to 3, characterized in that the method comprises the further step of: detecting the signals of the flow sensor ( 41 ) and the temperature sensor ( 42 after a period of time T after the setting of the one or more predefined environmental conditions, after which stationary signals at the flow sensor ( 41 ) and at the temperature sensor ( 42 ) have set. Method according to Claims 1 to 4, characterized that when setting the predefined environmental conditions the Blower power is adjusted so that there is a flow velocity the air in the range of 0.1 m / s to 2.0 m / s, preferably 0.5 m / s. Air conditioning device ( 1 ) for use in a motor vehicle, the air conditioning device ( 1 ), a filter unit ( 3 ), a heat exchanger unit ( 7 . 71 ), a sensor unit ( 4 ), and evaluation electronics ( 6 ), wherein the filter unit ( 3 ), the heat exchanger unit ( 7 . 71 ), and the sensor unit ( 4 ) in an air duct ( 5 ) are arranged and the sensor unit ( 4 ) with the evaluation electronics ( 6 ), wherein the heat exchanger unit ( 7 . 71 ) downstream of the filter unit ( 3 ) and between the filter unit ( 3 ) and the sensor unit ( 4 ), wherein the sensor unit ( 4 ) to an exit surface of the heat exchanger unit ( 7 . 71 ) is arranged at a distance, preferably of more than 20 cm, and wherein the sensor unit ( 4 ) a flow sensor ( 41 ), which is designed as a self-heating mode operated PTC element, and a temperature sensor ( 42 ), and the PTC element and the temperature sensor ( 42 ) adjacent to each other in the air channel ( 5 ) are arranged. Air conditioning device ( 1 ) according to claim 6, characterized in that the heat exchanger unit ( 7 . 71 ) for cooling the air duct ( 5 ), preferably as an evaporator of a coolant circuit, is formed. Air conditioning device ( 1 ) according to claim 6, characterized in that the heat exchanger unit ( 7 . 71 ) for heating the air duct ( 5 ), preferably as a heat exchanger of an oil cooling circuit of the motor vehicle is formed. Air conditioning device ( 1 ) according to one of claims 6 to 8, characterized in that a plurality of heat exchanger units ( 7 . 71 ) between the filter unit ( 3 ) and the sensor unit ( 4 ) in the air duct ( 5 ) are arranged. Air conditioning device ( 1 ) according to claim 9, characterized in that at least one heat exchanger unit ( 7 . 71 ) for heating and at least one heat exchanger unit ( 7 . 71 ) for cooling the air duct ( 5 ) is formed by flowing air. Air conditioning device ( 1 ) according to one of claims 6 to 10, characterized in that the flow sensor ( 41 ) and the temperature sensor ( 42 ) not more than 1 mm to 10 mm apart in the air duct ( 5 ) is arranged. Air conditioning device ( 1 ) according to one of claims 6 to 11, characterized in that the sensor unit ( 4 ) an air-permeable cap ( 43 ), which is arranged such that the air-permeable cap ( 43 ) the flow sensor ( 41 ) surrounds. Air conditioning device ( 1 ) according to one of claims 6 to 12, characterized in that the filter unit ( 3 ) has a pleated particle filter made of nonwoven fabric. Air conditioning device ( 1 ) according to one of claims 6 to 13, characterized in that the evaluation electronics ( 6 ) a storage unit ( 62 ), and the evaluation electronics ( 6 ) is configured such that it receives signals from the flow sensor ( 41 ) and the temperature sensor ( 42 ) is detected at a time t1 by a measurement and the loading state of the air conditioning device ( 1 ) determined based on the measured signals of the flow sensor ( 41 ) and the temperature sensor ( 42 ) at the time t, and in the memory unit ( 62 ) stored one or more reference values. Air conditioning device ( 1 ) according to one of claims 6 to 14, characterized in that the air conditioning device ( 1 ) a display device ( 61 ), preferably formed as an LED, for displaying the loading state of the air conditioning device ( 1 ) having. Air conditioning device ( 1 ) according to one of claims 6 to 15, characterized in that the flow sensor ( 41 ) and / or the temperature sensor ( 42 ) has a volume of 1 mm ³ to 1 cm ³ . Air conditioning device ( 1 ) according to one of claims 6 to 16, characterized in that the air duct ( 5 ) has a secondary air duct, wherein in the secondary air duct, a flap for controlling the air volume flow is provided, and that the sensor unit ( 4 ) is arranged in the secondary air passage. Air conditioning device ( 1 ) according to one of claims 6 to 17, characterized in that the air conditioning device ( 1 ) one in the air duct ( 5 ) arranged blower unit ( 2 ) and the sensor unit ( 4 ) at a distance of more than 40 cm from the fan unit ( 2 ) is arranged.