WO2009024302A1 - Method for monitoring the loading state of an air-conditioning device of a motor vehicle - Google Patents

Abstract

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 are described. 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 evaluating 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 evaluating electronics (6). Here, the heat exchanger unit (7, 71) is arranged downstream of the filter unit (3) and between the filter unit (3) and the sensor unit (4), wherein the sensor unit (4) is arranged at a distance, preferably of more than 20 cm, from an outlet area of the heat exchanger unit (7, 71). The sensor unit (4) has a flow sensor (41), which is designed as a PTC element which is operated in the self-heating mode, and a temperature sensor (42). The PTC element and the temperature sensor (42) are arranged adjacent to one another in the air duct (5).

Description

 Method for monitoring the load condition of an air conditioning device of a motor vehicle

The invention relates to a method for determining a loading state 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 an evaluation has. The filter unit and the sensor unit are arranged in an air duct, wherein the sensor unit is connected to the evaluation electronics for determining the loading state of the filter device. The loading state of a filter device is also referred to as the saturation state of the filter device.

From 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 process, ie. H. the actual loading of the filter unit is only determined inaccurately.

From 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. at This climate device or the method, the loading state of a filter device is determined with noxious gases. However, the loading of the filter device with particles can not be determined hereby.

US Pat. No. 6,582,295 B1 discloses an air conditioning system for motor vehicle cabins with a filter unit and blower unit, and a method for operating the same. 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 the

Power consumption in commercial blower units can be obtained only under considerable expense reproducible loading conditions of the filter unit.

From US 4,751, 501 B1 is a filter device for determining the

Loading state of a filter unit 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 a pneumatic flow sensor for determining the volumetric flow rate 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 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

Sensor arrangement has similar disadvantages as the filter device of US 4,751, 501 B1. DE 101 62 806 A1 discloses a method and a filter device 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.

The invention is therefore based on the object simple, inexpensive and reproducible to determine the loading state of an air conditioning device of a motor vehicle, in particular a particulate filter of the air conditioner.

This object of the invention is achieved with the method for determining a loading state of an air conditioning device for use in a motor vehicle according to claim 1 and with the air conditioning device according to claim 6.

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 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, a flow sensor as formed in the 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 duct, setting one or more predefined environmental conditions, in particular a blower power of a blower unit arranged in the air duct, measurement of a signal of the flow sensor and a signal of the temperature sensor at a time ti, and determination of the loading state of the air conditioning device by an evaluation based on the measured signals of the flow sensor and the temperature sensor at the time ti and one or more reference values stored in a storage unit specifying a signal of the flow sensor in response to a signal of the temperature sensor at a reference load state.

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. It is provided 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 is connected to the evaluation electronics, wherein the heat exchanger unit is arranged downstream of the filter unit and between the filter unit and the sensor unit, wherein the sensor unit to an exit surface of the heat exchanger unit at a distance, preferably more than 20 cm , is arranged and wherein the

Sensor unit comprises a flow sensor which is designed as a self-heating mode operated PTC element and having a temperature sensor, and the PTC element and the temperature sensor adjacent to each other in the air duct are arranged.

It is particularly advantageous that according to the invention adjacent to the flow sensor, which is designed as a self-heating mode operated PTC element, a temperature sensor is arranged, which measures the temperature of the surrounding air. This makes it possible that the measurement of the flow sensor can be corrected by means of the adjacently measured temperature and thus the loading state of the air conditioning device is determined exactly, ie also reproducibly. Forming the flow sensor as a PTC element operated in the self-heating mode is inexpensive, since the flow sensor is semiconductor bulk goods. Furthermore, due to the special arrangement of the sensor unit to the filter unit and the heat exchanger unit, an accurate determination of the loading condition is achieved. The loading state of the air conditioning device is in this case determined essentially by the loading state of the filter unit and possibly also by the loading state of the heat exchanger unit. In practice, the evaluation of the PTC Element as a simple voltage measurement via a voltage divider circuit. Furthermore, the determination of the loading state of the air conditioning device allows dynamic service interval times of the air conditioning device, whereby an optimal operation of the air conditioning device is ensured.

The heat exchanger unit may be a cooling unit or a heating unit which cools or heats the air flow guided in the air duct. The heat exchanger unit may also consist of a cooling unit and a heating unit, which are preferably connected in series in the air flow in the air duct to selectively turn on individually or together. In this way, a temperature control and / or flow regulation of the air flow in the air duct can be adjusted particularly well. The heat exchanger unit can also be designed as an aggregate, which can be operated for cooling as well as for heating. The heat exchanger unit can basically consist of one or more heat exchanger units.

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

In embodiments in which the heat exchanger unit is designed for cooling the air channel flowing through the air, the heat exchanger unit z. B. be designed as an evaporator of a coolant circuit. In embodiments in which the heat exchanger unit is designed for heating the air channel flowing through the air, the heat exchanger unit z. B. be designed as a heat exchanger of a ölkühlkreislaufes the motor vehicle.

In embodiments in which a plurality of heat exchanger units are arranged between the filter unit and the sensor unit in the air duct, z. B. at least one heat exchanger unit for heating and at least one heat exchanger unit for cooling the air channel flowing through the air to be formed. 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 is preferably designed as an NTC element (NTC = negative temperature coefficient). The temperature sensor can also be designed as a PTC element. For example, the temperature sensor is a resistance thermometer pt100 or ptiOOO.

In a preferred embodiment of the invention, the sensor unit has an air-permeable cap, which is arranged such that the air-permeable cap surrounds the flow sensor. It is advantageous that the air-permeable cap reduces the flow rate of the air that reaches the flow sensor. The flow sensor, which is configured as a self-heating mode PTC element, is more sensitive to changes in air flow rates at lower air flow velocities. This advantageously results in an improved measuring accuracy of the flow sensor.

The sensor unit has an outlet surface of the heat exchanger unit at a distance of more than 20 cm, preferably more than 40 cm. Such a relatively large distance ensures that the air has already mixed evenly after the filter unit, whereby the accuracy of the temperature measurement of the temperature sensor is favored.

In a preferred embodiment of the invention, the filter unit is designed as a particle filter. The filter unit may comprise a pleated filter material body. The filter unit may consist of nonwoven fabric. The filter unit may also be a combination filter z. B. with activated carbon - act adsorbent.

It may further be provided that the cap, which surrounds the flow sensor, is formed as a, preferably made of Köpertressengewebe formed, air-permeable cap. Preferably, the cap is formed of stainless steel. In a preferred embodiment of the invention, the evaluation electronics have a memory unit, and the evaluation electronics are configured such that the evaluation electronics simultaneously detect signal values of the flow sensor and of the temperature sensor and store them in the memory unit. The transmitter can be connected to the flow sensor and the temperature sensor of the sensor unit. The memory unit can be an integral component of the evaluation. If the air-conditioning device is operated in a motor vehicle, then the memory unit and / or the evaluation electronics can be arranged in an on-board computer of the motor vehicle.

In a preferred embodiment of the invention, the air conditioning device has a display device, preferably designed as an LED, for displaying the loading state of the air conditioning device. If the air conditioning device is used in a motor vehicle, the display device may be part of an on-board computer and / or the

Display device can be arranged in a dashboard of a motor vehicle. Particularly advantageous here is the use in trucks, the truck driver thus has the ability to determine the loading condition of the air conditioning device independently of a motor vehicle workshop. This allows the truck driver z. B. even replace the particulate filter of the air conditioning device, if this is sufficiently heavily loaded. Thus, it is possible to reduce the maintenance cost of the truck, because the load state can be made by the truck driver himself, whereby no unnecessary check of the loading condition of the air conditioning device by the motor vehicle workshop takes place during service inspection of the truck.

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. In a preferred embodiment of the invention, the air duct has a secondary air duct, wherein a flap for controlling the air volume flow is provided in the secondary air duct, and wherein the sensor unit is arranged in the secondary air duct. It is advantageous that in this case the flow velocity of the air is reduced, and the flow sensor is operated in a more sensitive operating mode. This increases the measurement 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 relatively 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 further be provided that the temperature sensor of the sensor unit is connected to a control unit of an air conditioning device, so that the temperature sensor can be used to control the air conditioning device.

It may further be provided that the air-conditioning device has a further sensor unit, which is arranged close to or directly adjacent to the filter unit. The further sensor unit on the filter unit allows under constant measurement and evaluation early detection of a rapid change in the loading condition of the air conditioning, so about suddenly occurring holes in the filter unit and / or sudden heavy load, such as leaves, the filter unit are recognized immediately.

In a preferred embodiment of the method according to the invention for determining the loading state of the air conditioning device, the air conditioning device is provided with an unloaded filter unit. One or more predefined environmental conditions, in particular the fan power, of the fan unit arranged in the air duct are then set. It can be provided that the air duct is brought fluidically into a predefined state, wherein preferably flaps of the air duct are placed in predefined positions, z. B. all flaps are opened or closed. Then by means of the evaluation simultaneously 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 of the

Flow sensors are stored as reference values for the various temperatures of the air according to the signals of the temperature sensor in the storage unit. 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 geometric arrangement in the

Characterize air conditioner. Thus, by means of these characteristic reference values, the loading state for this air conditioning device can be determined very accurately.

In a preferred embodiment of the method according to the invention, a specifying value of the time t | measured signal of the flow sensor determined as the actual value of the flow sensor by the transmitter.

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 the time U, a value of the signal of the flow sensor corrected by the temperature of the ambient air can be obtained in a particularly simple manner by means of the previously determined function. In a preferred embodiment of the method according to the invention, a deviation of the actual value of the flow sensor at time ti 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 ti 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.

In a preferred embodiment of the method according to the invention, the threshold values having a value of more than 80%, preferably more than 90%, are used.

In a preferred embodiment of the method according to the invention, the signals of the flow sensor and of the temperature sensor are detected after a period of time T, preferably of at least 10 s, after the setting of the one or more predefined environmental conditions, namely after stationary signals at the flow sensor and at the temperature sensor have set. 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.

In a preferred embodiment of the method according to the invention, a blower output is adjusted such that a flow velocity of the air in the range from 0.1 m / s to 2.0 m / s, preferably 0.5 m / s results. Advantageous is that the sensor unit, operated at these low flow velocities of the air, is particularly sensitive to changes in the flow velocity of the air, whereby a high measurement accuracy is achieved.

In the following we will describe the invention with reference to embodiments in conjunction with figures. Showing:

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

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

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

FIG. 3: A graph corresponding to a measurement of the signal of the flow sensor according to the first and the second embodiment

Schematics of Figures 2a) and 2b) depending on the flow velocity of the air v.

Figure 4: A graph of a measurement of the signal of the flow sensor L / τ (v) for different positions of the sensor unit in response to a relative fan power of another embodiment.

Figure 5: A graph of a measurement of the signal of the flow sensor Uj (v) as a function of the temperature Tu, which surrounds the sensor unit of the further embodiment.

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

FIG. 7 shows a graph of a measurement of signals of a plurality of flow sensors Uj (v) for different positions of the sensor units of the further

Embodiment under loading.

FIG. 8: a graph of a measurement of the change in the signal of the

Flow sensor Uj {v) for different positions of the sensor unit as a function of a relative fan speed of the other

Embodiment.

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

FIG. 10: a graph of a partial measurement from FIG. 9 of the signal of FIG

Flow sensor of the sensor unit and the pressure drop across the filter unit of the further embodiment with a flow sensor arranged in a small vent below

Loading.

The structure of the air conditioning device 1 according to the invention will first be described with reference to FIG.

The air conditioning device 1 according to the invention shown in FIG. 1 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 comprises a filter unit 3, a sensor unit 4 and an evaluation electronics 6. In this case, the filter unit 3 and the sensor unit 4 are arranged in an air channel 5 one after the other at a distance of more than 40 cm. In a not shown embodiment, the sensor unit 4 before dividing the air flow into different Side air ducts, the z. B. footwell, cockpit and windscreen, be arranged. However, it can also be provided that the sensor unit 4 is arranged in one of these secondary air ducts, wherein the flow of the air in the auxiliary duct can be regulated by a flap.

The filter unit 3 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 direction of flow of the air in the air channel 5 is indicated by the directional arrow 11.

The sensor unit 4 is connected electronically to the evaluation electronics 6 by means of a signal line 4s.

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 PTC element, and a temperature sensor 42. The flow sensor 41 and the temperature sensor 42 are arranged adjacent to each other such that with the temperature sensor 42, the air surrounding the flow sensor 41 can be determined with sufficient accuracy. In the event 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 also spaced up to 10 cm. The temperature sensor 42 may be formed as an NTC, a pt100 or ptiOOO. Preferably, the temperature sensor 42 is an NTC element.

Furthermore, the air-conditioning device 1 has a blower unit 2, which is arranged in the air duct 5. The blower unit 2 is a controllable blower unit 2 in the form of a fan. The blower power of the blower unit 2 is arbitrary.

A heat exchanger unit 7 with a lamellar structure and a further heat exchanger unit 71 are in the air channel 5 between the filter unit 3 and the sensor unit 4 is arranged. The heat exchanger unit 7 is designed as an evaporator of a coolant circuit and can be used for cooling the air channel 5 flowing through the air. The further heat exchanger unit 71 is designed as a heat exchanger of a oil cooling circuit of the motor vehicle and can be used for heating the air duct 5 flowing through the air. It may be provided in a non-illustrated embodiment, that only one heat exchanger unit 7 or 71 is provided. The evaporator 7 and the heat exchanger 71 are arranged at least 2 cm away from the filter unit 3 as well as from the sensor unit 4 in the air duct 5. Furthermore, a further heat exchanger 71 with a lamellar structure is arranged in the air duct 5. The further heat exchanger 71 is arranged between the filter unit 3 and the sensor unit 4. The heat exchanger 71 may function as a heater of the air conditioner.

In a preferred embodiment, one disposed in the air duct 5

Pre-separator unit 8 upstream of the blower unit 2 is provided. This pre-separator 8 is formed as a coarse-mesh grid and serves to ensure that no coarse dirt such. As foliage, small branches, parts of plastic bags, or the like, can enter the air duct 5 and thus the fan unit 2 and the filter unit 3 protects against contamination and / or damage.

Furthermore, the flow sensor 41 comprises an air-permeable and spherical cap 43 made of Köpertressengewebe. The cap 43 is made of stainless steel. The cap 43 has a diameter such that the cap 43 has an air gap of 1 mm to 3 mm with respect to the flow sensor 41.

In an embodiment which is not shown, a further sensor unit may be arranged in the air duct 5 directly downstream of the filter unit 3. The sensor unit preferably has a distance of not more than 5 cm from the filter unit 3. This further sensor unit may be identical to the sensor unit 4. 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 can be adjacent with a small distance of not more than 1 mm to 10 mm be arranged from each other. This further sensor unit can be electronically connected to the evaluation electronics 6 by means of a signal line.

The transmitter 6 has in addition to analog and / or digital modules, eg. As a CPU ₁ for evaluating the signals of the sensor unit 4 also a

Memory unit 62 and a display device 61, which is designed as an LED on.

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

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

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

The determination of the loading state of an air conditioning device 1 of the air filter device in an air conditioning device of a motor vehicle, corresponding to FIG. 1, takes place, as will be explained below:

First, reference values are determined by evaluation electronics 6 for an unloaded, ie unused, filter unit 3. For this purpose, an unloaded filter unit 3 is provided in the air-conditioning device 1. At the air conditioning device 1, one or more predefined environmental conditions, in particular the fan power in the air duct 5 arranged blower unit 2, set. Any flaps of the air duct 5 of the air conditioning device 1 are set in a certain position. Then, the evaluation electronics 6 simultaneously measure signals of the flow sensor 41 and the temperature sensor 42 for different temperatures of the air surrounding the sensor unit 4. These specifying values of the signals of the flow sensor 41 are stored as reference values for the various temperatures of the air corresponding to the signals of the temperature sensor 42 in the storage unit 62. The determination of a data set is preferably carried out at each change of the filter unit 3 in a possible motor vehicle service in a workshop, so that always an optimal function of the air conditioning device 1 can be ensured.

For determining the loading state of the air-conditioning device 1, the same ambient conditions as in the determination of the reference values are set, i. H. In particular, the same blower power 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 is measured simultaneously at a time ti. The loading state of the air conditioning device 1 is determined by evaluation electronics 6 based on the measured signals of the flow sensor 41 and the temperature sensor 42 at the time ti with reference values stored in a memory unit 62. The determination of the loading state of the air conditioning device 1 can continuously or on instruction, for. B. by a motor vehicle driver or workshop mechanic done.

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

The flow sensor 41 is a PTC element operated in the self-heating mode. Depending on a voltage applied to the flow sensor 41

Voltage U heats up to its own temperature T _E. If this is now at a temperature of the air Tu, which is less than 7 _E , flows, the flow sensor 41 initially cools. Due to the PTC effect, the resistance of the flow sensor 41 decreases, as a result of which more current / p _{tc flows} through the flow _sensor 41 flows and the flow sensor 41 heats 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:

Uptc 'lptc = (T _E - T _u ) - (a + bYv)

In King's Law, a, b and TE 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 Tu. 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 Tu 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 Tu at the same voltage U, the constant b is determined.

With a change of 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 L / γ by means of a simple voltage divider circuit with an ohmic resistance Rs according to FIGS. 2a) and 2b). In general, the voltage at the PTC element U _p ι _c with the voltage at the ohmic resistance Rs 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 to FIG. 2a): u;

according to FIG. 2b):

FIG. 3 shows 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 FIGS. 2a) and 2b) as a function of the flow velocity of the air v.

Here, the measured voltage is given in V and the flow velocity of the air v in m / s.

With reference to Figure 3, the importance of the wurzelförmige dependence can be seen. At high flow velocities of the air v small changes in the flow velocities V cause only small changes in the sensor signal Lh.

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, d. H. the constants a, b and TE are with an unloaded filter unit 3 and

Air conditioning device 1 determined. 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 even operating time. Here, the volume flow or the flow velocity of the air v in a fixed operating state of the air conditioning device 1, d. H. at fixed

Environmental conditions, measured. Therefore, all measurements take place with the same blower setting of the blower unit 2 and the same settings for any flaps of the air conditioning device 1. The flow sensor 41 is through Setting a constant operating voltage U placed in the self-heating mode and the voltage drop across the PTC element, ie the signal of the flow sensor 41 is stored as a starting 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 volume flow, which corresponds to the selected operating state of the air conditioning device, the voltage drop is now measured as a signal of the flow sensor 41 above the PTC element according to the circuit diagram of Figure 2a). The signal of the temperature sensor 42, which is realized for example with an NTC element, is measured with the same principle. With the help of the characteristic curve of the NTC element, the temperature of the air surrounding the sensor unit 4 can be determined from the signal of the temperature sensor 42.

Due to the fact that the largest changes in the signal of the flow sensor 41 result in small flow velocities of the air v, but a stationary state of the air conditioning device is best adjusted at high flow velocities of the air v, it is advantageous by an air-permeable cap 43 the To reduce flow velocity of the air v so strong that the measurement in the steeply rising portion of the measurement signal, as shown in Figure 3, passes, d. H. at an air velocity of about 4 m / s, the flow velocity of the air v at the flow sensor 41 will be reduced to 0.5 m / s. Alternatively, the positioning of the sensor unit 4 may be provided in a single secondary air duct, whereby the flow velocity of the air v can be reduced by a controllable flap such that a flow velocity of the air v of at most 0.5 m / s occurs at the sensor unit 4.

In the further embodiment, a PTC element with the following properties is used: R ₀ (Tu = 20 ⁰ C) = 50 ohms, operating voltage U = 12V, fti2v (7 ^" u = 20 ° C) = 180 ohms.

This sensor unit 4 was mounted in a W164 air conditioner in a vent provided on the air duct 5 and branching into the footwell, i. behind the heat exchanger unit 7, which is designed as an evaporator. The PTC element was connected in series with a resistance of Rs = 56 ohm, tapping the measurement signal Uj (v) corresponding to the circuit of Figure 2b).

At the same time two more sensor units were mounted directly behind the filter unit 3 in the center and in the corner. A fourth sensor unit was positioned in the air duct directly behind the blower unit 2. FIG. 4 shows the signals of the flow sensors in V for different blower outputs, from 0% to 80% in steps of 10%, of the blower unit 2. 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 _{τ was} measured for different temperatures. The result is shown in FIG. One sees the linear dependence of The linear regression leads to the following result:

Uτ, 6o% (ru) = 10.1 - 0.13 Tu

In FIG. 5, this relationship is represented by the equalization line or regression line, of which exactly two parameters can be stored in the evaluation electronics 6.

Furthermore, in FIG. 5, the voltage signal corrected for the ambient temperature, which is a root-shaped dependency on the Flow velocity of the air v has shown. This corrected to the ambient temperature voltage signal of the flow sensor is obtained by the following calculation:

10.1 - 0.13 -τ u

With this positioning of the sensor units, the inflow surface of the filter unit 3 was now gradually covered with a blower setting of 80% in order to simulate clogging of the filter unit 3 and a decrease in the volume flow. In this case, different parts of the filter unit 3 were initially covered with 1/4 coverage, so as to represent an uneven loading of the filter unit 3. The result of this experiment is shown in FIG. It will be clearly understood that, with respect to the coverage and blower performance of the blower unit 2, only the sensor units positioned in the air duct 5 behind the blower unit 2 and in the air duct 5 vent provide a unique signal correlating with the amount of air. 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, which is positioned in the air duct 5 behind the blower unit 2, provides at 95% coverage, ie at extremely high loading of the filter unit 3, with further reduction of the amount of air no reproducible signal more. 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 indicates that the flow sensor 4 should be positioned as far away as possible from the filter unit 3 and the blower unit 2 in order to minimize flow influences due to non-uniform loads of the air conditioning device 1. 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 was set at 60% of the maximum blower output, or air quantity, and subjected to a test dust in a flow duct. 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 JIS Class 8 and 12 dusts can be found in the JIS Z8901 standard (Japanese Industrial Standard).

The result of this loading over a period of time is shown in FIG. Two loadings were performed, i. two pistons loaded with test dust on the filter unit 3. 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 can be seen from the signal of the two other sensor units (FIG. 7 in the air duct behind the blower unit, in the outflow to the footwell). As the loading of the filter unit 3 (2nd loading) progresses, the volume flow finally decreases continuously, but the signals of the sensor unit sensor units fluctuate directly at the filter. However, a clear assignment to the decrease is possible only with the two sensor units 4 in the air duct 5 and in the vent in the footwell. The decrease in the measurement signal of these two sensor units makes it possible to clearly conclude the loading state of the filter unit 3.

However, the optional and not shown further sensor unit allows directly or close to the filter unit 3 in continuous evaluation by the

Evaluation electronics 6, detecting the fluctuation of the signal of the sensor unit and thus a spent or overloaded filter unit 3 can be detected. Another sensor unit may also detect a "half full" or "half loaded "filter unit 3 on the basis of the no longer monotonically falling signal of the other sensor unit recognize, ie, a kind of first loading of the filter unit 3 can be detected.

Preliminary tests on an evaporator 7 made of brazed aluminum structures with a volume of 2.6 I, 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 may happen that up to 200 g of water collect in the fins of the evaporator 7, resulting in a 5% -10% pressure drop increase from the dry state. This may also have an effect on the total volume flow measured by means of the flow sensor 4 downstream of the evaporator 7, i. This can lead to a reduction of the volume flow. To rule out that an extremely water-laden evaporator falsifies the measurement result of the flow sensor 4, a defined operating state must be selected in which a certain maximum amount of water may be condensed on the surface of the evaporator 7. 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, the water can drain from the evaporator 7. When the air conditioning device starts, a compressor of the air conditioning device must remain switched off until the volume flow has been checked by means of the flow sensor 4.

In the following it is discussed in more detail how an advantageous increase of the change of the signal of the sensor unit can be achieved.

In order to obtain a significantly larger change in the signal of the sensor unit 4, the flow sensor 41 in the above example was provided with a cap 43 made of a stainless steel basket knit fabric. This Köpertressengewebe had an opening width of 70 microns. The signal output at 90% blower power of the blower unit 2 was thereby reduced from 7.2 V to 5 V, resulting in one now moved in the region of the signal of the flow sensor, in which small changes in the flow velocity of the air v cause greater changes in the signal output than in a sensor unit having no cap. With this cap 43, a new stage test of 50% to 90% blower output of the blower unit 2 has now been carried out. The result is shown in FIG. 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 was provided with a cap 43 made of a Köpertressengewebe, and the other of the two sensor unit a small air vent was arranged, 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 3 was recorded in parallel, ie at the same time. The result is shown in FIG. The largest change of the signal of the flow sensor is obtained again for the sensor unit in the middle of the filter unit 3. However, a similar clear effect is also obtained in the sensor unit, which was positioned in the small vent, which only lets through a small part air flow through a flap. A likewise significant effect is obtained in the sensor unit in the large vent, which was provided with a cap 43. As in the loading test, the result of which is shown in FIG. 7, the sensor unit in the large vent shows a clear change in the signal of the flow sensor, which, however, is much weaker than in the first three sensor units. The signal for the sensor unit directly in the middle of the filter unit 3 increases again towards the end of the loading. Here, the flow conditions in the air-conditioning device 1 are greatly changed. If the loading had been continued, a similar fluctuation of the measuring signal over time would have been obtained, as in the prior art first loading attempt has also been observed and can be seen from Figure 7. 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 condition of the air conditioning 1 correlates.

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

The change in the signal of the flow sensor 41 with cap 43 results in a reduction of the 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 no longer detected by the sensor unit directly behind the filter unit 3.

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

Since the sensor unit from the PTC element, as a flow sensor, and the NTC element, as a temperature sensor monitors the air amount of the air conditioning in a defined operating state, not only the clogging or loading of the filter unit 3, but also a possible fouling, and moth Clogging of heat exchangers and / or evaporators detected. If after a change of the filter unit 3, the signal of the sensor unit does not return to his original value, ie at least close to the original value, this may be an indication of a polluted by evaporator and / or condenser.

Overall, the air conditioning device according to the invention thus represents an extremely simplified flow monitor.

Thus, the air conditioning device 1 according to the invention can be used in addition to the diagnosis of the degree of contamination of the entire air conditioning device, in particular the heat exchanger and / or evaporator. For this purpose, the signal of the flow sensor without built-filter unit 3 can be detected, which can be measured again at each 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.

In a non-illustrated embodiment of the method according to the invention, the reference values are determined by means of linear regression, which specify a signal of the flow sensor in response to a signal of the temperature sensor at a reference loading state. In this evaluation, parameters of a regression line are determined by linear regression. The parameters are then stored in the memory unit. It is advantageous that only exactly two parameters for describing the reference values of the flow sensor for the different temperatures of the air must be stored. Furthermore, by means of the linear regression, measurement errors are smoothed.

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 time ti. 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 associated with the signal of the flow sensor at time ti, which selects that stored reference value whose temperature of the air deviates at least from the temperature of the air at time ti. It is advantageous here in the particularly simple determination of the reference value at the time tι. Furthermore, it is also possible for the reference value, which is assigned to the signal of the flow sensor at the time ti, to be determined by interpolation of the stored reference values. This allows a particularly accurate estimation of the reference value of the flow sensor at the time ti in a simple manner. Furthermore, it is also possible for a reference value associated with the signal of the flow sensor to be determined by the regression line at time ti 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.

LIST OF REFERENCE NUMBERS

1 air conditioning device

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 electronics

61 Display device

62 storage unit

6s signal line

7 heat exchanger unit

71 heat exchanger unit

8 pre-separator unit

10 control unit of the air conditioning

11 flow direction of the air

Claims

claims 1. Method for determining a loading state of a 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) are arranged in an air duct (5), the heat exchanger unit (7, 71) is arranged 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 more than 20 cm, the sensor unit (4) comprises a flow sensor (41) which is designed as a self-heating mode PTC element, and a temperature sensor (42) and the PTC element and the temperature sensor (42) are arranged adjacent to one another in the air duct (5), Adjustment of one or more predefined environmental conditions, in particular a blower output of a blower unit (2) arranged in the air duct (5), measurement of a signal of the flow sensor (41) and a signal of Temperature sensor (42) at a time ti, and Determining the loading state of the air conditioning device (1) by an evaluation electronics (6) based on the measured signals of the flow sensor (41) and the temperature sensor (42) at the time ti and one or more stored in a memory unit (62) Reference values specifying a signal of the flow sensor (41) in response to a signal of the temperature sensor (42) at a reference load state. 2. The method according to claim 1, characterized in that the method comprises the further steps: Providing the air conditioning device (1) with an unloaded filter unit (3), Setting one or more predefined environmental conditions, in particular the fan power of the blower unit (2) arranged in the air duct (5), using an unloaded filter unit (3), simultaneous measurement by means of the evaluation electronics (6) of the signal from the flow sensor (41) and the signal the temperature sensor (42) for one or more temperatures of the air, which surrounds the sensor unit (4), and storage of the values specifying the signals of the flow sensor (41) in response to the signals of the temperature sensor (42) as reference values. 3. The method according to any one of claims 1 or 2, characterized in that the evaluation electronics (6) determines when the specific load state of the air conditioning device (1) deviates by more than 20% from that of an unloaded air conditioning device, and then signals that the Loading condition of the air conditioning device (1) is assessed as unacceptable. 4. The method according to any one of claims 1 to 3, characterized in that the method comprises the further step: Detecting the signals from 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 steady state signals have been established on the flow sensor (41) and the temperature sensor (42). 5. The method according to claim 1 to 4, characterized in that when setting the predefined environmental conditions the Blower power is adjusted so that a flow rate of air in the range of 0.1 m / s to 2.0 m / s, preferably 0.5 m / s, adjusts. 6. Air conditioning device (1) for use in a motor vehicle, wherein 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) are arranged in an air channel (5) and the sensor unit (4) is connected to 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) 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 wherein the sensor unit (4) comprises a flow sensor (41), which is designed as a self-heating mode PTC element, and a temperature sensor (42), and the PTC element and the temperature sensor (42) adjacent to each other in the air duct ( 5) are arranged. 7. Air conditioning device (1) according to claim 6, characterized in that the heat exchanger unit (7, 71) for cooling the air duct (5) by flowing air, preferably as an evaporator of a refrigerant circuit, is formed. 8. Air conditioning device (1) according to claim 6, characterized in that the heat exchanger unit (7, 71) for heating the air duct (5) by flowing air, preferably as a heat exchanger of an oil cooling circuit of the motor vehicle is formed. 9. 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. 10. Air conditioning device (1) according to claim 9, characterized in that at least one heat exchanger unit (7, 71) is designed for heating and at least one heat exchanger unit (7, 71) for cooling the air duct (5) flowing through the air. 11. Air conditioning device (1) according to one of claims 6 to 10, characterized in that the flow sensor (41) and the temperature sensor (42) is not more than 1 mm to 10 mm apart from each other in the air duct (5). 12. Air conditioning device (1) according to one of claims 6 to 11, characterized in that the sensor unit (4) has an air-permeable cap (43) which is arranged such that the air-permeable cap (43) surrounds the flow sensor (41). 13. Air conditioning device (1) according to one of claims 6 to 12, characterized in that the filter unit (3) has a pleated particle filter, which consists of nonwoven fabric. 14. Air conditioning device (1) according to any one of claims 6 to 13, characterized in that the evaluation electronics (6) has a memory unit (62), and the evaluation electronics (6) is designed such that it signals the flow sensor (41) and the Temperature sensor (42) at a time ti detected by a measurement and the loading state of the The air conditioning device (1) determines one or more reference values stored at the time ti and in the storage unit (62) based on the measured signals of the flow sensor (41) and the temperature sensor (42). 15. Air conditioning device (1) according to one of claims 6 to 14, characterized in that the air conditioning device (1) has a display device (61), preferably designed as an LED, for displaying the loading state of the air conditioning device (1). 16, 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 . 17. 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) in the secondary air duct is arranged. 18. Air conditioning device (1) according to one of claims 6 to 17, characterized in that the air conditioning device (1) arranged in the air duct (5) Blower unit (2) and the sensor unit (4) is arranged at a distance of more than 40 cm from the blower unit (2).