# US 8,539,778 B2 · Air filter having a moisture sensor for identifying type of filter and moisture content and method of using filter in a vehicle air conditioning system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,539,778 B2 - Document ID: US8539778B2 - Status: Granted - Kind: B2 - Application number: 12/706,573 - Filed: 2010-02-16 - Published: 2010-06-10 - Granted: 2013-09-24 - Earliest claimed: 2008-05-08 - Assignees: Bayerische Motoren Werke Aktiengesellschaft - Applicants: Joern Hofhaus; Gregor Wendrock - Inventors: Joern Hofhaus; Gregor Wendrock - Web page: https://patentgrep.com/patent/US8539778B2 ## CPC - B60H 1/00785: {by the detection of humidity or frost} - B01D 46/009: {Identification of filter type or position thereof, e.g. by transponders or bar codes} - B60H 1/00849: {for selectively commanding the induction of outside or inside air (B60H1/00842 takes precedence)} - B60H 3/06: Filtering - B60H 2003/0683: {the quality of the filter or the air being checked} - B60H: ARRANGEMENTS OF HEATING, COOLING, VENTILATING OR OTHER AIR-TREATING DEVICES SPECIALLY ADAPTED FOR PASSENGER OR GOODS SPACES OF VEHICLES - B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28) ## Abstract An air filter, which is intended for installation in an air conditioning system of a vehicle and which exhibits a moisture sensor, is disposed on or at the air filter. The moisture sensor is a component of an electric circuit section, which is arranged on or at the air filter. The moisture sensor is a capacitive sensor, whose capacitance depends on the moisture loading of the air, flowing around the sensor. At least one electric property of the electric circuit section represents the moisture loading on the air filter and the type of air filter. ## Claims ### Claim 1 An air filter for use in an air conditioning system of a vehicle, comprising: an electric circuit section located at least one of on the air filter and in close proximity to said air filter, said electric circuit section including a moisture sensor; and wherein the electric circuit section includes at least one electric property representative of a moisture loading on the air filter and a type of the air filter, wherein the type of the air filter is assigned a predefined range of values, said at least one electric property of the electric circuit section being within the predefined range of values. ### Claim 2 (depends on 1) The air filter according to claim 1, wherein the moisture sensor is a capacitive sensor having a capacitance dependent on moisture loading of air that at least one of flows around and surrounds the moisture sensor. ### Claim 3 (depends on 1) The air filter according to claim 1, wherein said predefined range of values are defined such that variations in the electric property of the electric circuit section occurring when the air filter operates under normal conditions are within the predetermined range of values. ### Claim 4 (depends on 3) The air filter according to claim 3, wherein the predefined range of values include at least one of a frequency range and an amplitude range at a predefined frequency range. ### Claim 5 (depends on 1) The air filter according to claim 1, wherein said at least one electric property is at least one of: a magnitude of a natural frequency of the electric circuit section; an ohmic resistance; an inductive resistance; and a capacitive resistance, of the electric circuit section. ### Claim 6 (depends on 1) The air filter according to claim 1, wherein the moisture sensor includes a ceramic element as a dielectric. ### Claim 7 (depends on 1) The air filter according to claim 1, further comprising a heater operatively configured to at least one of heat and dry the moist sensor. ### Claim 8 A vehicle air conditioning system, comprising: an air filter operatively installed in the vehicle air conditioning system; an electric circuit section located at least one of on the air filter and in close proximity to said air filter, said electric circuit section including a moisture sensor; and wherein the electric circuit section includes at least one electric property representative of a moisture loading on the air filter and a type of the air filter, wherein the type of the air filter is assigned a predefined range of values, said at least one electric property of the electric circuit section being within the predefined range of values. ### Claim 9 (depends on 8) The vehicle air conditioning system according to claim 8, wherein the moisture sensor outputs a signal indicative of moisture loading of the air filter. ### Claim 10 (depends on 9) The vehicle air conditioning system according to claim 9, wherein at least one functional parameter of the vehicle air conditioning system is controlled and/or regulated as a function of the output signal indicative of the moisture loading of the air filter. ### Claim 11 (depends on 10) The vehicle air conditioning system according to claim 10, wherein at least one functional parameter of the vehicle air conditioning system is controlled and/or regulated as a function of the type of the air filter determined by the magnitude of the determined natural frequency. ### Claim 12 (depends on 9) The vehicle air conditioning system according to claim 9, wherein a plurality of operating states of the vehicle air conditioning system, an electronic device coupled to the electric circuit section controls and/or regulates a volumetric flow of intake fresh air for the air conditioning system as a function of the output signal indicative of the moisture loading of the air filter. ### Claim 13 (depends on 9) The vehicle air conditioning system according to claim 9, wherein in an electronic device coupled with the electric circuit section controls and/or regulates at least one functional parameter of the vehicle air conditioning system as a function of a time rate of change of the output signal indicative of the moisture loading of the air filter. ### Claim 14 (depends on 13) The vehicle air conditioning system according to claim 13, wherein the time rate of change of the output signal is a gradient of the output signal delivered by the moisture sensor. ### Claim 15 (depends on 8) The vehicle air conditioning system according to claim 8, further comprising: an electronic device disposed outside of the air filter, the electronic device being coupled with the electric circuit section; wherein the electronic device is operatively configured to determine a natural frequency of the electric circuit section and/or a natural frequency of an electric circuit comprising the electric circuit section, the electric circuit being disposed at least one of on said air filter and in close proximity to the air filter; and wherein the electronic device determines the type of air filter as a function of a magnitude of the determined natural frequency. ### Claim 16 (depends on 15) The vehicle air conditioning system according to claim 15, wherein the moisture sensor is operatively disposed upstream with respect to the air filter. ### Claim 17 (depends on 16) The vehicle air conditioning system according to claim 16, wherein at least one of the air filter and connections of the electric circuit section are operatively configured such that the air filter is installable in the vehicle air conditioning system only so that the moisture sensor is disposed upstream with respect to the air filter. ### Claim 18 (depends on 15) The vehicle air conditioning system according to claim 15, wherein at least one functional parameter of the vehicle air conditioning system is controlled and/or regulated as a function of the type of the air filter determined by the magnitude of the determined natural frequency. ### Claim 19 A method of operating a vehicle air conditioning system having an air filter and an electric circuit section including a moisture sensor disposed at least one of on the air filter and in close proximity to the air filter, the method comprising the acts of: generating a signal from the electric circuit section; and determining both a moisture loading on the air filter and a type of air filter by way of an electronic device as a function of a magnitude of a signal property of the generated signal. ### Claim 20 (depends on 19) The method according to claim 19, wherein the type of air filter is assigned a predetermined range of values in which the signal property of the signal may lie. ### Claim 21 (depends on 20) The method according to claim 20, wherein the range of values are determined such that variations in the signal property induced by moisture changes when the air filter is operating under normal conditions are within the predetermined range of values. ### Claim 22 The method according to 19, further comprising the acts of: determining an order of magnitude of a natural frequency of at least one of the moisture sensor and an electric circuit containing the moisture sensor by way of the electronic device; and determining from the order of magnitude of the natural frequency the type of air filter. ### Claim 23 (depends on 19) The method according to claim 19, further comprising the acts of: monitoring, by way of the electronic device, at least one of a time rate of change of the signal and a signal property of the signal; and controlling and/or regulating at least one functional parameter of the vehicle air conditioning system as a function of the monitoring.