Abstract:
An apparatus and method for drying condensate from the heat exchanger of a vehicle&#39;s air conditioning system after operation in order to thwart odor buildup is provided. The apparatus and method operate regardless of whether the system&#39;s blower control circuit is positively or negatively switched. The apparatus includes relays that bypass the normal operating electrical routing to the air conditioning system&#39;s blower motor to operate the blower directly. The method comprises determining that the engine of the vehicle has been switched off and that the air conditioning system of the vehicle was in operation prior to the engine being switched off. If the conditions are met, the air conditioning system&#39;s blower is operated on a predetermined time schedule to circulate air in the air conditioning system to dry condensate therefrom. In this way, growth of odor-causing fungus and bacteria is inhibited.

Description:
This application claims priority to U.S. provisional patent application, U.S. Ser. No. 60/285,935, filed Apr. 23, 2001, and is a continuation to U.S. patent application. U.S. Ser. No. 10/091,839, filed Mar. 5, 2003, now U.S. Pat. No. 6,658,871 and incorporates in their entirety both of these provisional and non-provisional patent applications by reference as if fully set forth herein. 

   TECHNICAL FIELD 
   The invention disclosed herein relates generally to automotive air conditioning systems and more particularly to the prevention of moisture build-up within such air conditioning systems with the goal of eliminating the promulgation of fungus and bacteria and the odor that results therefrom. 
   INCORPORATION OF PRE-EXISTING PATENT DISCLOSURE 
   This disclosure incorporates in its entirety the disclosure, claims, and drawings of U.S. Pat. No. 5,899,082 issued May 4, 1999 and filed on Sep. 18, 1997 as if fully set forth herein. This patent will be referred to herein as the “incorporated reference.” 
   BACKGROUND 
   As discussed in detail in the incorporated disclosure, automotive air conditioning systems are provided in most vehicles to cool the passenger compartment of the vehicle during hot weather. In general, automotive air conditioning systems comprise a compressor coupled to the engine that compresses a refrigerant to its liquid state. The compressed liquid refrigerant is then delivered to a heat exchanger known as an evaporator within the ductwork of the air conditioning system, where it is allowed to expand and thereby cools the evaporator. A blower forces air across the evaporator and into the passenger compartment of the vehicle. As the air passes through the evaporator, it is cooled and the latent heat that was contained in the air is transferred to the refrigerant within the evaporator. Thus, the passenger compartment receives cool air. The heated refrigerant is then passed through a radiator where it is cooled and delivered back to the compressor where the cycle begins anew. 
   As warm air from the passenger compartment is blown through the evaporator of an automobile air conditioning system to be cooled, water vapor contained in the air condenses on the surfaces of the evaporator and on surrounding surfaces. During normal operation of the vehicle, the water that condenses on the evaporator simply runs to the bottom of the evaporator and is drained from the air conditioning system onto the roadway. However, when the vehicle&#39;s engine is shut off and the air conditioning is no longer in operation, the condensed water on the evaporator begins to evaporate slowly within the ductwork of the air conditioning system and, as a result, a damp dank atmosphere is created. Such an atmosphere is ideal for the growth of mold, mildew, fungus, and bacteria within the ductwork of the system and particularly on the moist and wet surfaces of the evaporator. The growth of such organisms, in turn, results in a stale and unpleasant odor within the passenger compartment itself and can lead to air-borne spores and other organisms that are unhealthy for the occupants of the vehicle. 
   In the past, there have been attempts to address the problems of microorganism build-up within automotive air conditioning systems. For example, disinfectants and/or deodorizers may be sprayed into the air conditioning system to coat the surfaces thereof to prevent the growth of mold, mildew, and other fungus and bacteria within the ductwork. While this approach can prevent the build-up of odor causing organisms or mask their odors, at least in the short term, it still does not address the fundamental cause of such build-up, i.e., the moist, damp atmosphere within the air conditioning system. 
   The invention disclosed and claimed in the incorporated reference approaches the problem by preventing the establishment of a moist atmosphere within the air conditioning system that is conducive to the growth of unwanted microorganisms. In general, this invention comprises a method of drying the interior and evaporator of a vehicle&#39;s air conditioning system to thwart the propagation of fungus and bacteria and its attendant odor. The method comprises the steps of determining that the engine of the vehicle has been switched off, determining that the air conditioning system was in operation prior to the engine being switched off, and, upon determining that both of these conditions exist, operating the blower of the vehicle&#39;s air conditioning system on a predetermined time schedule to draw air through the system for drying condensate from interior surfaces thereof. To carry out this methodology, the incorporated reference discloses an electronic control circuit coupled to the blower motor of the vehicle air conditioning system. When the circuit senses that the engine has been shut off after air conditioning operation, it activates a relay on a predetermined time schedule, such as once every ten minutes, for a predetermined period of time. The intermittent scheduled operation of the blower draws out and removes evaporated condensate from within the air conditioning system and, at the end of several cycles, all of the condensate has been dried and removed. Thus, the fundamental cause of the growth of undesirable microorganisms, i.e., the moist, damp atmosphere within the air conditioning system, is eliminated and such organisms do not tend to grow in the resulting dry atmosphere. 
   Operation of a vehicle&#39;s air conditioning blower motor on a predetermined time schedule after operation of the air conditioning system as disclosed in the incorporated reference has proven to be a successful solution to the problems of micro-organism growth and its attendant odor in vehicles. However, the Electronic Evaporator Dryer (EED) circuitry taught in the incorporated reference for carrying out the methodology, while very successful for use within some automotive blower wiring schemes, nevertheless is not useable with certain other wiring schemes found in the automotive industry. More particularly, the relay of the EED circuitry in the incorporated reference is spliced into the blower motor circuit downstream of positively switched blower control circuits of the system. The other terminal of the blower motor is connected directly to ground in these “positively switched” systems. During the drying operation, the relay of the EED circuit is activated to disconnect the positive terminal of the blower motor from the blower control circuitry and to connect it to directly to the positive terminal of the vehicle&#39;s battery. Thus, when the relay is activated, the blower motor is operated at maximum speed to dry interior surfaces of the air conditioning system. Operation of the blower at its maximum speed is highly desirable to achieve the best and quickest drying. 
   While the foregoing EED circuitry works well for systems wherein the blower motor is positively switched, i.e. switched and controlled on the positive side of the motor, it does not operate well in systems where the blower control circuitry of the air conditioning system is “negatively switched” or, in other words, switched to ground. In such a negatively switched system, the positive terminal of the blower motor normally is connected directly to the accessory switch of the vehicle and the negative terminal of the blower motor is connected to ground through the blower control circuit. The blower control circuit includes a blower switch for turning the blower on and off and an array of resistors for controlling the speed of the blower motor as it runs during normal operation of the vehicle. 
   Thus, during the drying operation, if the positive terminal of the blower only is connected through the EED relay to the positive terminal of the battery, the blower motor in most cases will not operate at maximum speed because the negative terminal of the blower is connected to ground through the speed control resistor network of the blower control. In some cases where a driver has turned the blower to the “off” position in a negatively switched scheme, the blower, using the EED circuit of the incorporated reference, will not operate at all during the evaporator drying cycle. Thus, there is a need for an improved EED control circuit for carrying out the methodology that is applicable to and works with blower motor wiring and control schemes wherein the blower motor is positively switched and controlled and also works with wiring schemes wherein the blower motor is negatively switched and controlled. It is to the provision of such a circuit and the methodology carried out by the circuit that the present invention is primarily directed. 
   SUMMARY 
   Briefly described, the present invention comprises an apparatus and method for eliminating odors arising from the growth of organisms within a vehicle&#39;s air conditioning system. 
   In one embodiment, the present invention encompasses an apparatus for use with a vehicle&#39;s air conditioning system. The apparatus generally includes a first relay connected to a positive terminal of a blower motor of the vehicle&#39;s air conditioning system, and a second relay connected to a negative terminal of said blower motor. These relays are coupled to a logic circuit that cooperates with them to bypass both the air conditioning system&#39;s blower control and the vehicle&#39;s accessory switch to connect the blower motor terminals to the positive terminal of the battery and also to ground. 
   Another embodiment includes a vehicle air conditioning system. The air conditioning system generally includes a compressor through which refrigerant flows to an evaporator. A blower cooperates with the evaporator to cool the refrigerant. The blower includes a blower control and a blower motor having a positive terminal and a negative terminal. The air conditioning system also includes a bypass circuit that bypasses both the blower control and the accessory switch to connect the blower motor terminals directly to the positive terminal of a battery and to ground, to operate the blower during the drying cycles. For example, the bypass circuit may include a logic circuit connected to a temperature sensor and/or a battery voltage sensor. When the appropriate conditions are noted by these sensors, the logic circuit can activate the control circuit to connect the blower terminals to the battery and ground to activate the blower at its maximum speed. 
   In another embodiment, an apparatus for use with a vehicle air conditioning system to dry condensate from the heat exchanger of the system to prevent propagation of fungus and bacteria and resulting odors is provided. The apparatus includes a logic circuit connected to both a battery voltage sensor and a temperature sensor. The logic circuit also is operatively coupled to a first relay that selectively switches the positive terminal of the blower motor of the air conditioning system to the positive terminal of the vehicle&#39;s battery. A second relay is also connected to the logic circuit. This second relay is selectively switches the negative terminal of the blower motor to ground. 
   Among the general aspects of the present invention is a method of drying condensate from the heat exchanger of a vehicle&#39;s air conditioning system to thwart the propagation of fungus and bacteria and its attendant odor. The method includes the step of determining that the engine has been switched off, as well as sensing the ambient temperature and determining that the air conditioning system of the vehicle was in operation prior to the engine being switched off if the sensed ambient temperature is greater than a predetermined threshold. The method also includes operating the blower of the vehicle&#39;s air conditioning system on a predetermined time schedule to draw air through the air conditioning system for drying condensate from interior surfaces thereof, wherein operating the blower includes bypassing the blower control circuit. 
   These and other features, objects, and advantages of the invention will become more apparent upon review of the detailed description set forth below when taken in conjunction with the accompanying drawing figures, which are briefly described as follows. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a simplified illustration of a first type of wiring scheme found in vehicle air conditioning systems wherein the blower motor is positively switched and controlled by a blower control circuit. 
       FIG. 2  is a simplified illustration of a second blower motor wiring scheme wherein the blower motor is negatively switched and controlled by a blower control. 
       FIG. 3  is a functional diagrammatic illustration of an EED circuit according to the present invention showing the connections to a negatively switched blower motor of a vehicle for carrying out the invention. 
       FIG. 4  is another functional diagrammatic illustration of an EED circuit according to the present invention showing connection to a positively switched blower motor of a vehicle for carrying out the invention. 
       FIG. 5  is a detailed electronic schematic diagram of an EED circuitry of the present invention with a positively switched arrangement. 
       FIG. 6  is a detailed electronic schematic diagram of an EED circuitry of the present invention with a negatively switched arrangement. 
       FIG. 7  is a diagrammatic representation of a vehicle air conditioning system encompassing aspects of the present invention. 
   

   DETAILED DESCRIPTION 
   Referring now in more detail to the drawings, in which like numerals refer to like parts throughout the several views,  FIGS. 1 and 2  are presented to illustrate two common types of wiring and blower control schemes  11  and  111  used in vehicles for controlling the blower motor of the vehicle&#39;s air conditioning system.  FIG. 1  illustrates a “positively switched” blower motor control system  11  and  FIG. 2  illustrates a “negatively switched” blower motor control system  111 . Referring to  FIG. 1 , a blower motor  12  of an automotive air conditioning system has a positive terminal  13  and a negative terminal  14 . The negative terminal  14  is connected directly to ground  16 . The positive terminal  13  is connected to the positive battery terminal  22  through a blower switch and resistor network  17  (or blower control circuit) and through the accessory or key switch  21  inside the automobile. The blower control circuit  17  includes an array of resistors  18  and a manually operated control knob  19  within the vehicle. The control knob  19  can be rotated or otherwise manipulated to connect the blower motor  12  through any one of the resistors to the positive terminal  22  of the battery or to turn off the blower motor. The resistances of resistors in the network  18  are selected such that the blower motor  12  can be operated at a variety of speeds depending upon the position of the control knob  19 . It thus will be seen that in this wiring scheme, the speed of the blower motor  12  is controlled by switching one of the resistors in the network  18  in series with the positive side of the circuit, thus the designation “positively switched.” 
   Referring to  FIG. 2 , which illustrates a negatively switched blower control scheme  111 , the blower motor  12  again has positive terminal  13  and a negative terminal  14 . The positive terminal  13  is connected to the positive battery terminal  31  through the accessory or key switch  29  within the vehicle. The negative terminal  14  of the blower motor  12  is connected to ground  34  through a blower switch and resistor network (or blower control circuit)  32  having a speed control resistor network  33 , as discussed above. With such a negatively switched wiring scheme  111 , the positive terminal  13  of the blower motor  12  is always connected directly to the positive terminal  31  of the battery during operation of the vehicle. The blower motor speed is controlled (or the blower motor is shut completely off) by manipulating the control knob  36  to select a particular resistor and place it in series with the negative terminal  14  of the blower motor  12 . Thus, the designation “negatively switched.” 
     FIGS. 3 and 4  illustrate in simplified black box form an EED circuit according to the invention coupled to blower motor control systems for carrying out methods of the invention. In  FIG. 3 , the blower motor control system is illustrated as being one alterative employing a negatively switched wiring scheme similar to that of  FIG. 2 , whereas  FIG. 4  illustrates a positively switched wiring scheme similar to that of FIG.  1 . For this purpose, Box  46  is indicated as being the accessory switch, whereas Box  48  is the blower control circuit. In  FIG. 3 , the blower control  48  connects the negative terminal  14  of the blower motor  12  to ground, whereas in  FIG. 4  the blower control  48  connects the positive terminal  13  of blower motor  12  to the positive terminal of the vehicle&#39;s battery through the accessory switch  46 . The EED unit  51  of the present invention works equally well with either wiring scheme. 
   The EED unit includes a first relay  52  and a second relay  53 . The coils of each relay are connected to and activated by the logic circuits  63  of the unit, which are described in more detail below. The first relay  52  is a single-pole double-throw type relay having a battery pole  56 , an accessory switch pole  58 , and a common or switch pole  54 . The switch pole  54  is connected to the accessory switch pole  58  when the relay is in its inactivated state and to the battery pole  56  when the relay is activated. Accessory switch pole  58  is said to be “normally closed” and battery pole  56  is “normally open.” 
   The first relay  52  is spliced in series with the wire  44  that connects the positive terminal of the battery to the positive terminal  13  of the blower motor  12  through the accessory switch  46  and, possibly, blower control  48 , depending upon whether blower control  48  is connected to accessory switch  46  or to ground. Wire  44  is cut and connected to the switch pole  54  and accessory switch pole  58 . Since accessory switch pole  58  is normally closed, wire  44  connects the positive terminal  13  of blower motor  12  to the positive terminal of the battery through the accessory switch  46 , possibly blower control  48 , and first relay  52  under normal operating conditions. 
   A second relay  53 , which also may be a single-pole double-throw relay, has an unconnected pole  62 , which is normally closed, a ground pole  61 , which is normally open and a second switch pole  59 , which switches between the first two poles. The switch pole  59  of the relay  53  is electrically connected to the wire  47  that connects the negative terminal  14  of the blower motor  12  to ground, possibly through the blower control  48 , depending upon the wiring scheme. Under normal operating conditions, the second relay  53  is in its inactive state, wherein second switch pole  59  is switched to unconnected switch pole  62 . When the second relay  53  is activated, switch pole  59  switches to ground pole  61  so that the normal connection between the negative terminal  14  to ground is bypassed. Thus, if blower control  48  is connected to ground, as shown in  FIG. 3 , the blower control  48  is bypassed when the second relay  53  is activated. 
   The logic circuits  63  within the EED module  51  are configured and programmed to activate the first and second relays  52  and  53  under predetermined conditions. More specifically, and as described in more detail in the incorporated reference and below, the logic circuits include a temperature sensor and a battery voltage sensor. The battery voltage sensor is monitored to determine when the engine of the vehicle has been shut off and the temperature sensor is monitored to determine when the ambient temperature is above a predetermined threshold, such as, for example, 60° F. When these sensors indicate that the engine has been shut off and that the temperature is above the threshold, a presumption is made that the air conditioning system of the vehicle has been in operation. At this point, the logic circuit activates both the relay  52  and the relay  53  simultaneously, then deactivates, and again activates them repeatedly in a predetermined timing schedule. In other words, the relays are activated for a predetermined time, deactivated for a predetermined time, again activated for a predetermined time, and so on through a pre-established number of cycles. 
   Each time the relays  52  and  53  are activated as described above, the following occurs. First, the positive terminal  13  of the blower motor is disconnected from the accessory switch and possibly the blower control, depending upon the wiring scheme in use, as the switch pole  54  of the relay moves into contact with the battery pole  56 . When the switch pole  54  engages the battery pole  56 , which is connected directly to the positive terminal  57  of the battery, the positive terminal  13  of the blower motor  12  becomes directly connected to the positive terminal  57  of the battery through the relay  52 . At the same time, the switch pole  59  of the second relay  53  moves to engage the ground pole  61  of the relay. When this occurs, the wire  47  normally connecting the negative terminal  14  of the blower motor  12  to ground, and possibly the blower control  48 , depending upon the wiring scheme, is shunted directly to ground through ground pole  61  of second relay  53 . 
   Accordingly, it will be seen that when the relays  52  and  53  are each activated, the positive terminal  13  of the blower motor becomes connected directly to the positive terminal of the battery and the negative terminal of the blower motor becomes connected directly to ground. As a result, the blower motor is operated at its full speed as long as the relays  52  and  53  are each activated. This result ensues regardless of whether the wiring scheme in use in the particular vehicle is a positively switched wiring scheme as in  FIG. 1  or a negatively switched wiring scheme as in FIG.  2 . This is because all of the blower control circuitry, whether it is on the positive or negative side of the blower motor, is bypassed and the blower motor is connected, regardless of the wiring scheme, directly to the positive terminal of the battery and to ground. Thus, the EED circuit of the present invention, unlike that of the incorporated reference, is equally applicable without modification both to positively and negatively switched blower motor wiring schemes. 
     FIGS. 5 and 6  are electronic schematic diagrams of circuits for carrying out the present invention in a positively switched arrangement and a negatively switched arrangement respectively. Many of the electronic components in these diagrams are the same as or functionally similar to those illustrated in the incorporated reference and therefore discussion in great detail is not required here. Generally, however,  FIG. 5  illustrates a blower motor  12  having a positive terminal  13  and a negative terminal  14 . The positive terminal  13  is connected to the blower control circuit, which, in turn is connected to the accessory switch and the positive terminal of the battery. The negative terminal  14  of the blower motor is connected to ground.  FIG. 6  illustrates the invention within the context of a negatively switched arrangement, wherein the positive terminal  13  of the blower motor is connected to the accessory switch and the negative terminal of the blower motor is connected through the blower control circuit to ground. First and second relays  52  and  53  are illustrated in electronic schematic form in  FIGS. 5 and 6 , but will be seen to function as described with respect to  FIGS. 3 and 4 . More particularly, the first relay  52  is spliced in series with the wire connecting the positive terminal of the blower motor and the second relay  53  is shunted to the wire connecting the negative terminal of the blower motor. 
   The electronic components of the logic circuit  53  are illustrated enclosed in a dashed or phantom-lined box  63 . Conditioned power to operate the electronic components of the logic circuit  63  is provided by a power supply and surge suppressor circuit  66 , which is commonly understood by those of skill in the art. 
   The logic circuits  63  include a micro-controller chip  67 , which, in the illustrated embodiment, is a PIC12C508-04-/SM chip. Such a micro-controller chip can be programmed. with software to monitor various ones of its inputs and to control its outputs according to the condition of the inputs and the dictates of its programming. One of the inputs of the micro-controller  67  is connected to an ambient temperature sensor  68  and another input is connected to a battery voltage sensor  69 , as described in some detail in the incorporated reference. One of the outputs of the micro-controller  67  is connected to a transistor switch circuit  71 , which, in turn, is coupled to the coils of the first and second relays  52  and  53 . 
   The micro-controller  67  is programmed essentially as described in the incorporated reference. In general, the ambient temperature sensor  68  is monitored by the micro-controller  67  to determine the ambient temperature. The voltage sensor  69  is monitored to determine the battery voltage, which typically falls below a predetermined threshold when the engine is shut off after operation. When a drop in the battery voltage indicates that the engine has been running but has been shut off and, at the same time, the ambient temperature is high enough such that the probability is good that the air conditioning system has been operating, the software in the micro-controller then sets its output to activate the transistor switch circuit  71  and, in turn, the relays  52  and  53 . When this occurs, the blower motor is attached directly to the battery and ground as described above such that the blower motor operates at full speed so long as the relays  52  and  53  are activated. 
   After a relatively short period of operation, such as, for example, 10 seconds, the micro-controller  67  deactivates the relays  52  and  53 , which shuts off the blower motor. The blower motor is left off for a predetermined time, such as, for example, 30 minutes. During this time, condensed moisture on interior surfaces within the air conditioning system evaporates and the air within the ductwork of the system becomes saturated with moisture. At this point, the micro-controller  67  again activates the relays to operate the blower motor for a relatively short period of time in order to draw the moisture-saturated air out of the interior of the air conditioning ductwork. This cycle is repeated over a period of, for example, two hours, at the end of which time all of the residual condensate on surfaces within the air conditioning system is evaporated and removed from the air conditioning ductwork. Accordingly, at the end of the predetermined time schedule, the evaporator and other interior surfaces within the air conditioning system are dried such that mildew, fungus, mold, and other microorganisms do not tend to grow there. As an ultimate result, odor within the vehicle is essentially eliminated for the life of the vehicle. 
   As shown in  FIG. 7 , an air-conditioning system  100  of the present invention is provided. A compressor  88 , an evaporator  90 , and refrigerant  86  are shown in diagrammatic form to represent the general elements of an air-conditioning system. The refrigerant  86  is flowable through both the compressor  88 , which compresses the refrigerant  86 , and the evaporator  90 , in which the refrigerant  86  absorbs heat. A blower  92  is also provided that cooperates with the evaporator  90  to provide air flow through the evaporator and into the vehicle to cool the passenger compartment thereof. The blower  92  may be controlled through either alternative blower control scheme described above and shown in  FIGS. 3-6 . The blower  92  may be activated when the engine is turned off, as described above, to remove condensate from the evaporator  90  and, possibly, other portions of the air-conditioning system  100  where it might develop. The result is a reduction in the propagation of odor-causing fungus and bacteria, thereby reducing odors originating in the air-conditioning system. 
   The invention has been described in terms of preferred embodiments and methodologies. It will be obvious to those of skill in the art, however, that various additions, deletions, and modifications to the preferred embodiments may be made, are within the spirit and scope of the invention.