Method and device for monitoring the service life of a filter

1. A method of monitoring the service life of a filter ( 1 ) in a filter system equipped with a fan, comprising: measuring the instantaneous air speed ( 21 ) using a sensor ( 2 , 20 ) downstream from the filter ( 1 ), comparing it to the reference air speed (R) from the unloaded filter ( 1 ) and transmitting it to a service computer or indicating it on a display, wherein the need to replace the filter is signaled when this value drops below a predetermined threshold or threshold range of the instantaneous air speed ( 21 ), wherein the reference air speed for the filter system is determined during every new filter installation, the reference air speed calculated from a volumetric flow of air in the system.

2. The method according to claim 1 , wherein the instantaneous air speed is measured on each startup of the system.

3. The system according to claim 2 , wherein the reference air speed (R) is measured at a predetermined electrical voltage across the fan for the filter system.

4. The method according to claim 1 , wherein the reference air speed (R) is measured at a predetermined electrical voltage across the fan for the filter system.

5. The method according to claim 1 , wherein the sensor ( 2 , 20 ) is connected to a warning light.

6. The method according to claim 1 , wherein the sensor ( 2 , 20 ) is connected to an acoustic warning signal.

7. The method according to claim 1 , wherein it is possible to connect the sensor ( 2 , 20 ) to the service computer of the motor vehicle or to the diagnostic system of a motor vehicle repair facility.

8. The method according to claim 1 , wherein the sensor ( 2 , 20 ) generates signals as a function of the electrical voltage across the sensor ( 2 , 20 ).

9. A method of monitoring the service life of a filter ( 1 ) in a filter system equipped with a fan, comprising: measuring the difference in the instantaneous air speed ( 21 ) using a sensor ( 2 , 20 ) downstream from the filter ( 1 ), comparing this difference to a reference air speed from the unloaded filter ( 1 ), and transmitting it to a service computer or indicating it on a display, wherein the need to replace the filter is signaled when this value drops below a predetermined difference from a threshold or threshold range, wherein the reference air speed for the filter system is determined during every new filter installation, the reference air speed calculated from a volumetric flow of air in the system.

10. The method according to claim 9 , wherein the difference in the reference air speed (R) is measured for two predetermined electrical voltages across the fan for the filter system.

11. The method according to claim 9 , wherein the sensor ( 2 , 20 ) is connected to a warning light.

12. The method according to claim 9 , wherein the sensor ( 2 , 20 ) is connected to an acoustic warning signal.

13. The method according to claim 9 , wherein it is possible to connect the sensor ( 2 , 20 ) to the service computer or the motor vehicle or to the diagnostic system of a motor vehicle repair facility.

14. The method according to claim 9 , wherein the sensor ( 2 , 20 ) generates signals as a function of the electrical voltage across the sensor ( 2 , 20 ).

15. A device for monitoring the service life of a filter ( 1 ), comprising a sensor ( 2 , 20 ) situated downstream from the filter ( 1 ), which measures the air speed of the air flow led through the filter ( 1 ), and transmits a drop in the air speed to a service computer or to a display as a function of the load state of the filter ( 1 ), wherein the device is configured to determine a reference air speed for the filter system during every new filter installation, the reference air speed calculated from a volumetric flow of air in the system.

16. The device according to claim 15 , wherein the sensor ( 2 ) is attached to the filter ( 1 ).

17. The device according to claim 15 , wherein the sensor ( 2 , 20 ) is attached to a housing ( 9 ) which accommodates the replaceable filter ( 1 ).