Automatic vehicular defogging system

A system includes: at least one resistive humidity sensor disposed on a window of a vehicle and configured to detect a presence of fog formed on a surface of the window and to output a signal indicating whether the presence of fog formed on the surface of the window has been detected; a defogging unit equipped in the vehicle and configured to defog the window of the vehicle; and a controller coupled to the at least one resistive humidity sensor and the defogging unit and configured to receive the signal from the at least one resistive humidity sensor, to determine whether fog has formed on the surface of the window based on the received signal, and to actuate the defogging unit when it is determined that fog has formed on the surface of the window.

TECHNICAL FIELD

The present disclosure relates generally to vehicular technologies, and more particularly, to automatic defogging systems and methods in vehicles.

BACKGROUND

It is well-known that windows of vehicles can be prone—particularly when the weather is cold—to becoming foggy. The reason for foggy car windows has to do with air temperature, either inside or outside of the vehicle, and the air's moisture content. Specifically, water vapor in the air within a vehicle's cabin condenses on the interiors of the windows when the temperature of the air next to the windows drops below a specific temperature, called the dew point—the temperature below which water droplets begin to condense and dew forms. The dew point temperature increases as humidity in the air increases. In other words, when car windows are colder than the dew point temperature, which will rise due to warm, humid air inside the car, the air close to the windows cools to below the dew point temperature as well, causing the water vapor in the air to condense and stick to the windows, causing fog. Thus, on a cold day, any moisture in the air within the vehicle's cabin—from excessive body heat, passengers exhaling, damp clothes, snow on the floormats, etc.—can turn to condensation when the warm, moist air meets the air next to the colder surfaces of the windows that is below the dew point temperature.

Many current vehicles are equipped with sensors, often mounted on the windshield, for detecting the presence of moisture or fog on the interior of a window. Such vehicles typically use a relative humidity sensor or an infrared sensor to know when moisture has formed. In response to detecting the presence of moisture, a heating, ventilating, and air conditioning (HVAC) system equipped in the vehicle can be triggered and automatically activated to defog the window, i.e., remove the moisture from the window's interior.

Conventionally, one of these sensors will be mounted at a central location on the vehicle's windshield. However, a single sensor that is centrally located will be unable to detect condensation on the edges of the windshield. A possible remedy is to install multiple sensors along the windshield to detect condensation at any area, but conventional capacitive or infrared humidity sensors are typically expensive, requiring excessively high costs to implement.

SUMMARY

The present disclosure provides a resistive humidity sensor that is designed to detect the presence of fog formed on the surface of a vehicle window, such as a windshield, and that includes a circuit embodying an outer conductive component and an inner conductive component that is enclosed within the outer conductive component. In a case where multiple sensors are disposed on the vehicle window, cross-talk (i.e., interference) among the sensors can be prevented when current flows through the circuit due to the inner conductive component being enclosed within the outer conductive component. Further, by enabling the use of multiple resistive humidity sensors disposed on the vehicle window without the hindrance of cross-talk among them, due to the above-described circuit configuration, the present disclosure provides a targeted defogging system in which each of the multiple resistive humidity sensors is capable of detecting fog on the window proximate to its respective location. Because a location of the window at which fog has formed (or not formed) can be identified, a controller equipped in the vehicle can control a defogging unit, such as a heating, ventilating, and air conditioning (HVAC) system, to specifically target and defog the identified location, without having to defog the entire window, which is both inefficient and unnecessarily expends resources that can be utilized by the vehicle for other purposes.

According to embodiments of the present disclosure, a system includes: at least one resistive humidity sensor disposed on a window of a vehicle and configured to detect a presence of fog formed on a surface of the window and to output a signal indicating whether the presence of fog formed on the surface of the window has been detected; a defogging unit equipped in the vehicle and configured to defog the window of the vehicle; and a controller coupled to the at least one resistive humidity sensor and the defogging unit and configured to receive the signal from the at least one resistive humidity sensor, to determine whether fog has formed on the surface of the window based on the received signal, and to actuate the defogging unit when it is determined that fog has formed on the surface of the window. The at least one resistive humidity sensor includes a circuit in which an amount of resistance between components of the circuit is affected by the presence of fog formed on the surface of the window, the circuit including an outer conductive component and an inner conductive component that are in contact with the window, and the inner conductive component enclosed within the outer conductive component.

The controller may be further configured to identify a location of the window at which the fog has formed based on the received signal, and further configured to control operation of the defogging unit so as to target an area of the window corresponding to the identified location of the window at which the fog has formed. In addition, the controller may be configured to identify which resistive humidity sensor of the at least one resistive humidity sensor has detected the presence of fog formed on the surface of the window based on the received signal and to identify the location of the window at which the fog has formed according to the identified resistive humidity sensor.

The defogging unit may be a heating, ventilating, and air conditioning (HVAC) system equipped in the vehicle. In this regard, the controller may be further configured to control operation of the HVAC system so as to blow air toward an area of the window corresponding to the identified location of the window at which the fog has formed. To this end, the controller may be further configured to adjust a position of one or more louvers in an air vent of the HVAC system.

The defogging unit may also be an electric defogging unit including a plurality of conductive elements embedded in the window. In this regard, the controller may be further configured to control operation of the electric defogging unit so as to activate at least one of the plurality of conductive elements proximate to an area of the window corresponding to the identified location of the window at which the fog has formed.

In addition, the controller may be further configured to determine that that the fog has formed on the surface of the window when a value indicated by the received signal satisfies a predetermined threshold. The controller may also be configured to actuate the defogging unit when it is determined that the value satisfies the predetermined threshold. Once the defogging unit has been actuated, the at least one resistive humidity sensor may be configured to output another signal indicating whether the presence of fog formed on the surface of the window has been detected. In this regard, the controller may be further configured to determine whether the fog has been removed from the surface of the window based on the signal received during operation of the defogging unit. The controller may also be configured to determine that that the fog has been removed from the surface of the window when a value indicated by the signal received during operation of the defogging unit fails to satisfy the predetermined threshold, and to deactivate the defogging unit when it is determined that the value fails to satisfy the predetermined threshold.

The circuit of the at least one resistive humidity sensor may be an amplifier circuit. The outputted signal indicating whether the presence of fog formed on the surface of the window has been detected may correspond to an output voltage of the amplifier circuit. Here, the amplifier circuit may be configured such that resistance between the outer conductive component and the inner conductive component decreases as the presence of fog on the surface of the window increases.

Additionally, the system may further include a plurality of resistive humidity sensors disposed on the window of the vehicle, whereby the plurality of resistive humidity sensors include the at least one resistive humidity sensor. In this case, each of the plurality of resistive humidity sensors is positioned apart from other resistive humidity sensors on the window, and each of the plurality of resistive humidity sensors may be positioned along one or more edges of the window.

The window of the vehicle may refer to one of a windshield, a side or door window, and a rear window.

Furthermore, according to embodiments of the present disclosure, a method includes: receiving, by a controller, a signal indicating whether a presence of fog formed on a surface of a window of a vehicle has been detected by at least one resistive humidity sensor disposed on the window of the vehicle; determining, by the controller, whether fog has formed on the surface of the window based on the received signal; and actuating, by the controller, a defogging unit that is equipped in the vehicle and configured to defog the window of the vehicle when it is determined that fog has formed on the surface of the window.

Furthermore, according to embodiments of the present disclosure, a non-transitory computer readable medium containing program instructions that are executable by a controller including a memory and a processor includes program instructions which when executed cause the controller to: receive a signal indicating whether a presence of fog formed on a surface of a window of a vehicle has been detected by at least one resistive humidity sensor disposed on the window of the vehicle; determine whether fog has formed on the surface of the window based on the received signal; and actuate a defogging unit that is equipped in the vehicle and configured to defog the window of the vehicle when it is determined that fog has formed on the surface of the window.

DETAILED DESCRIPTION OF THE EMBODIMENTS

It is understood that the term “vehicle,” “vehicular,” “car,” or other similar term as used herein is inclusive of motor vehicles, in general, such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g., fuels derived from resources other than petroleum). As referred to herein, a window of a vehicle may be any window or glass panel that is part of the vehicle including, but not limited to, a windshield, a rear window, a side or door window, and the like. While a windshield is primarily referred to as the “window of the vehicle” hereinbelow, the claimed invention is not limited thereto.

Furthermore, the controller of the present disclosure may be embodied as non-transitory computer readable media containing executable program instructions executed by a processor or the like. Examples of the computer readable mediums include, but are not limited to, ROM, RAM, compact disc (CD)-ROMs, magnetic tapes, floppy disks, flash drives, smart cards, and optical data storage devices. The computer readable recording medium can also be distributed throughout a computer network so that the program instructions are stored and executed in a distributed fashion, e.g., by a telematics server or a Controller Area Network (CAN).

Referring now to embodiments of the present disclosure, the disclosed resistive humidity sensor and targeted defogging system allow for detecting a location of a window at which fog has formed in a vehicle and controlling a defogging unit equipped in the vehicle so as to target the fogged area, e.g., by directing air flow in a heating, ventilating, and air conditioning (HVAC) system toward the fogged area(s) (for the purposes of the present disclosure, the terms “fog,” “moisture,” “dew,” or the like may be used herein interchangeably). The resistive humidity sensor described herein is designed to detect the presence of fog formed on the surface (the interior surface, particularly) of a vehicle window, such as a windshield, and includes a circuit embodying an outer conductive component and an inner conductive component that is enclosed within the outer conductive component. Because the inner conductive component of the resistive humidity sensor is enclosed within the outer conductive component of the resistive humidity sensor, cross-talk (i.e., interference due to undesired signal crossing) between the resistive humidity sensor and any adjacent sensors, which leads to a degradation of accuracy in a targeted defogging system, can be prevented. Moreover, resistive humidity sensors require less cost to install, and can be installed with less complexity, than other conventional sensors, such as capacitive or infrared humidity sensors.

Preliminarily,FIG. 1illustrates a conventional vehicular humidity sensor including a relative humidity sensor110disposed at a center location of the windshield100of a vehicle. The arrangement shown inFIG. 1represents a conventional automatic defogging system in which a single relative humidity (or fog) sensor110is mounted onto an upper-center location of the windshield100. When the sensor110detects the presence of fog formed on an interior surface of the windshield100, the fog has formed in a location of the windshield100that is proximate to the position of the sensor110. Consequently, if fog forms along the edges of the windshield100, as shown inFIG. 1, the sensor110, which is mounted at a generally central location of the windshield100, cannot detect such fog and falsely reports that no fog has formed on the windshield100, even though fog is presently visible to the driver, potentially obstructing the driver's view.

In light of this shortcoming,FIG. 2illustrates an exemplary vehicular defogging system including multiple resistive humidity sensors according to embodiments of the present disclosure. As shown inFIG. 2, multiple resistive humidity (or fog) sensors200may be disposed at multiple different locations of the windshield100. Each resistive humidity sensor200is configured to detect the presence of fog proximate to a location of the windshield100at which the respective sensor200is installed. In addition, the resistive humidity sensors200may be configured to output a signal indicating whether the presence of fog formed on the windshield has been detected, as explained in further detail below. A controller800may receive the outputted signal, determine whether fog has formed on the windshield based on the received signal, and identify specific locations of the windshield100at which fog has formed (if any), as also explained in further detail below. In this manner, fog on the surface of the windshield100can be detected at various discrete regions of the windshield100.

In order to detect fog which forms along the edges of the windshield100, the resistive humidity sensors200may be positioned along one or more edges of the windshield100. Each resistive humidity sensor200may be spaced apart from one another so as to detect fog across the entire windshield100, enabling targeted defogging to specific areas of the windshield100at risk for fogging, and to reduce the risk of signal interference among the sensors200.

The positions at which the multiple resistive humidity sensors200are disposed on the windshield100can vary according to, for instance, a desired amount of granularity (in terms of fog detection specificity), desired locations of fog detection, and the like. In other words, the multiple resistive humidity sensors200may be arranged in any suitable manner on the windshield100, and thus, the arrangement shown inFIG. 2should not be treated as limiting the scope of the claimed invention.

Each of the resistive humidity sensors200includes a circuit500in which an amount of resistance between components of the circuit500is affected by the presence of fog formed on the surface of the window. Specifically, the resistive humidity sensors200recognize changes in the resistance (or impedance) value of the sensor in response to the change in the humidity, i.e., presence of water vapor (or moisture). The amount of resistance (or impedance) present is typically inversely related to humidity. That is, in any given sensor, when the surface of the window proximate to the sensor is dry, no current flows between electrodes of the sensor, but as soon as a deposit of condensate forms on the window between the electrodes, current passes between them. In one possible configuration, if the sensor is in the presence of water vapor, the water vapor can be absorbed by a moisture-absorbing (hygroscopic) medium, such as a conductive polymer or salt, that is deposited on the electrodes. When the water vapor is absorbed, functional ionic groups of the medium disassociate, resulting in increased electrical conductivity (and decreased resistance).

However, when implementing multiple resistive humidity sensors200on a single window, as shown inFIG. 2, there is a risk of cross-talk (i.e., interference due to undesired signal crossing) among the sensors when signals are being outputted, which can lead to a degradation of accuracy. To overcome this obstacle, the resistive humidity sensors200may be designed in such a manner to prevent interference between adjacent sensors. Particularly, the circuit500embodied in each resistive humidity sensor200(configuration of the circuit500is described in further detail below with respect toFIG. 5) may include a first electrode (i.e., an outer conductive component) and a second electrode (i.e., an inner conductive component), whereby the inner conductive component is enclosed within the outer conductive component. The outer conductive component acts as a shield surrounding the inner conductive component, such that when a signal is sent from the sensor200to the controller800, for example, the signal does not interfere with nearby sensors200. In some implementations, the outer conductive component may refer to an anode, and the inner conductive component may refer to a cathode. In other implementations, the outer conductive component may refer to the cathode, and the inner conductive component may refer to the anode.

FIG. 3illustrates an exemplary arrangement of inner and outer conductive components included in a resistive humidity sensor200. As shown inFIG. 3, a first electrode (i.e., outer conductive component)310and second electrode (i.e., inner conductive component)320of a resistive humidity sensor200are disposed on a window100of a vehicle, such as a windshield, rear window, side or door window, or the like, so as to be in contact with the window100, or more specifically, an interior surface of the window100. As further shown inFIG. 3, the inner conductive component320may be enclosed within the outer conductive component310, such that the outer conductive component310acts as a shield surrounding the inner conductive component320, only allowing current to flow within the electrodes from the outer conductive component310to the inner conductive component320. By enclosing the second electrode (i.e., inner conductive component320) within the first electrode (i.e., outer conductive component320) to create a shield between adjacent sensors200, a targeted defogging system that includes multiple fog detection zones, in each of which a resistive humidity sensor200is positioned, can operate without the risk of cross-talk (interference with the signals of the other sensors200) among the sensors200.

The outer and inner conductive components310and320, respectively, may be connected to other components of the circuit500embodied in the resistive humidity sensor200(hereinafter referred to as the “resistive humidity sensor circuit500”) and/or to one or more controllers800equipped in the vehicle via wires330. Alternatively, signal transmission may occur wirelessly within the vehicle.

Using the outer and inner conductive components310and320, the resistive humidity sensor200is capable of detecting the presence of fog or moisture formed on the interior surface of the window100, and of alerting a controller800equipped in the vehicle of whether the presence of fog formed on the surface of the window100has been detected. During operation of the resistive humidity sensor200, a voltage may be applied to the outer conductive component310, while the inner conductive component320acts as the receiving cathode of the resistive humidity sensor circuit500. (The resistive humidity sensor circuit500, which is described in further detail below with respect toFIG. 5, may be a basic linear direct current (DC) amplifier circuit in some implementations.) The voltage may be a small positive voltage, such as 5 volts of direct current (VDC), for example. The resistive humidity sensor circuit500then outputs a signal, e.g., a voltage output signal, indicating whether the presence of fog formed on the surface of the window100has been detected. The outputted signal may be affected by the amount of resistance between the outer and inner conductive components310and320, as described further below.

Initially, i.e., prior to moisture forming on the window100, resistance between the outer conductive component310and the inner conductive component320may be at its maximum level; in other words, there is minimal conductivity between the inner and outer conductive components310and320. At this point, the voltage of the signal outputted by the resistive humidity sensor circuit500may also be at its maximum. For instance, where the outer conductive component310is supplied with 5 VDC, the voltage output signal of the circuit500may be roughly 5 VDC when the surface of the window100is dry.

As moisture starts to form on the window100, however, the resistance between the inner and outer conductive components310and320begins to decrease. More specifically, the resistance between the inner and outer conductive components310and320begins to decrease as moisture forms on the portion of the window100between the outer conductive component310and the inner conductive component320. In general, greater amounts of moisture forming on the window100between the electrodes cause a greater decrease in resistance (and vice versa). This is due to the deposit of condensate forming on the window100between the electrodes allowing current to pass between them.

As the resistance between the inner and outer conductive components310and320decreases (and the conductivity increases), the signal outputted by the resistive humidity sensor circuit500can be affected proportionally. That is, as the resistance between the electrodes decreases due to increased moisture between them, the voltage of the output signal may also decrease. For instance, where the outer conductive component310is supplied with 5 VDC, the voltage output signal of the circuit500may be roughly 1 or 2 VDC when the surface of the window100is covered in moisture. A controller800can receive the signals outputted from the resistive humidity sensors200(each sensor200can output its own signal), and can determine, based on each signal (i.e., the voltage of the signal) whether fog has formed on the surface of the window100. Then, the controller800can actuate a defogging unit400equipped in the vehicle to defog the areas of the window100on which the fog has formed, as explained in further detail below.

Notably, the resistance between the inner and outer conductive components310and320decreases due to moisture on the surface of the window100between them, even before the moisture can be visually perceived by a user (e.g., driver, passenger, etc.). Thus, the resistive humidity sensor200may be capable of detecting the presence of fog on the window100, and can automatically trigger a defogging unit400equipped in the vehicle to defog the window100, prior to the user actually seeing the fog on the window100, which can prevent the fog from becoming a visual obstruction while driving. Further, due to the design of the resistive humidity sensor200, the sensor is not prone to temperature and humidity errors, and is operable over a range of thermal conditions.

The resistive humidity sensors200may be implemented using a variety of techniques. For example, each sensor200(including the sensor circuit500) may be enclosed, either partially or fully, within a housing (not shown). As another example, each sensor200can be impregnated into the window100itself (not shown). As another example,FIG. 4illustrates an exemplary implementation of a resistive humidity sensor200that is integrated with a rear-view mirror340mounted to the windshield100. This implementation is particularly applicable to a resistive humidity sensor200that is centrally positioned on the windshield200, as the sensor200is coupled to the centrally positioned rear-view mirror340. The resistive humidity sensor200can be integrated with the rear-view mirror340, taking advantage of the wiring that exists within the mirror340. This implementation can be adopted in a system where multiple resistive humidity sensors200are disposed along the windshield100, and only the center-most sensor200is integrated with the rear-view mirror340, or in a system where only a single resistive humidity sensor200is disposed on the windshield100, and such single sensor200is centrally located with the rear-view mirror340(though in the system where only a single resistive humidity sensor200is used, the single sensor200need not necessarily be integrated with the mirror340). In addition, as shown inFIG. 4, the wiring330can couple the outer and inner conductive components310and320to the wiring of the rear-view mirror340. Here, the wiring330may be designed to have spring-like properties for added durability.

FIG. 5illustrates an exemplary circuit diagram of a circuit embodied in a resistive humidity sensor. As shown inFIG. 5, each resistive humidity sensor200embodies a circuit500including the outer conductive component310and the inner conductive component320, in conjunction with other circuit elements. The circuit500may be, for example, an amplifier circuit (e.g., a basic linear DC amplifier circuit) that works by controlling the base of a transistor for amplifying electronic signals (shown inFIG. 5) through an anode/cathode configuration which specifically only allows current flow from the outer conductive component310of the sensor to the inner conductive component320which is enclosed within the outer conductive component310. The exemplary circuit configuration shown inFIG. 5utilizes primarily basic components that have a potential for a long life span, and thus is relatively simple and low cost. However, it should be understood that the circuit configuration shown inFIG. 5is merely a single example of possible configurations for the resistive humidity sensor circuit500. Thus, the circuit configuration shown inFIG. 5is merely for demonstration purposes and should not be treated as the only configuration for the resistive humidity sensor circuit500, nor treated as limiting the scope of the claimed invention.

As explained above, the circuit500can be configured such that resistance between the outer conductive component310and the inner conductive component320decreases as the presence of fog on the surface of the window100increases. The resistance between the outer conductive component310and the inner conductive component320(i.e., anode and cathode), on the order of mΩ, is proportional to the emitter/collector voltage, creating a linear output that can be processed by the controller800, which in some instances may be vehicle central processing unit (CPU), the existing HVAC control head, or the like. In the above-referenced example where 5 VDC is supplied by the voltage source to the outer conductive component310, the output of the circuit500is between 0 to 5 VDC, with 5 VDC being 0% fog (i.e., no fog). The voltage of the output signal decreases as the amount of fog on the window100increases. Upon receiving the output signal from the resistive humidity sensor circuit500, the controller800can interpret the signal and determine whether fog has formed on the surface of the window100accordingly. (The controller800may receive multiple output signals from multiple resistive humidity sensors200and interpret each signal individually.) When the controller800determines that fog has formed on the surface of the window100, based on the signal outputted by the resistive humidity sensor circuit500, the controller800can actuate a defogging unit400equipped in the vehicle, as explained in further detail below.

FIG. 6illustrates an exemplary simplified procedure for controlling a targeted defogging system. The procedure600may start at step605, and continue to step610, where, as described in greater detail above, an array of resistive humidity sensors200disposed on a window100of a vehicle allow for detecting at least one location of the window100at which fog has formed and controlling a defogging unit400equipped in the vehicle so as to target the fogged area.

At step605, the resistive humidity sensors200can determine when and where fog on the window100of the vehicle starts to form. As explained above, the resistive humidity sensors200can output a signal indicating whether fog has formed on the window100, and more specifically, the portion of the window100that is between the outer and inner conductive components310and320of a given sensor200. The outputted signal varies as the amount of moisture, and thus the amount of resistance between the outer and inner conductive components310and320of a given sensor200, increases or decreases.

At step610, the controller800monitors the output of each resistive humidity sensor200. As explained above, the controller800can receive the outputted signals from each resistive humidity sensor200and interpret said signals to determine whether fog has formed on the surface of the window100. For instance, the controller800can determine that that the fog has formed on the surface of the window100by comparing a value indicated by the received signal to a predetermined threshold and determining whether the value of the received signal satisfies the threshold. In one example, the value indicated by the received signal may refer to the voltage of the signal, and the predetermined threshold may be defined as a voltage value within the range of possible voltage readings. The predetermined threshold may be defined as any given value according to, for example, the desired responsiveness of the targeted defogging system (i.e., how quickly the defogging unit400is actuated).

At step615, the controller800determines when a signal received from a resistive humidity sensor200satisfies the predetermined threshold. By way of demonstration, without limitation, if the predetermined threshold for determining that fog has formed on the window100is 4 V, the controller800may determine that fog has formed on the window100when the voltage of a signal received from a resistive humidity sensor200is less than 4 V.

Furthermore, the controller800can identify the resistive humidity sensor200that is responsible for outputting a received signal. That is, the controller800may identify which resistive humidity sensor200among all resistive humidity sensors200has detected the presence of fog formed on the surface of the window100based on the received signal. By doing so, the controller800can identify the location of the window100at which the fog has formed according to the identified resistive humidity sensor200. This due to the fact that when a particular resistive humidity sensor200detects moisture on the window100of the vehicle, the detection of moisture is based on the presence of moisture between the outer and inner conductive components310and320of the particular resistive humidity sensor200. Thus, when the controller800determines that, based on a received signal, moisture is present on the window100, it can be deduced that the location of said moisture is local to the resistive humidity sensor200that outputted the received signal.

In response to determining that moisture is present on the window100of the vehicle, e.g., a signal outputted by a sensor200satisfies the predetermined threshold, the controller800can automatically actuate a defogging unit400equipped in the vehicle to defog the window100, at step620. (If the predetermined threshold is not satisfied, the procedure600returns to step610, and the controller800continues to monitor the output of the resistive humidity sensors200.) The defogging unit400, which is configured to defog the window of the vehicle, may be, for example, a heating, ventilating, and air conditioning (HVAC) system equipped in the vehicle, an electric defogging unit including a plurality of conductive elements embedded in the window, or any other system equipped in the vehicle that is configured to remove fog that has formed on a window of the vehicle. In some implementations, the defogging unit400could be a separate, automatic part of the HVAC system that operates independently without driver intervention, unless manual override is selected.

At step625, when the controller800has identified a location of the window100at which fog has formed (by identifying the resistive humidity sensor200responsible for transmitting a signal indicative of fog), the controller800can control operation of the defogging unit400(e.g., activate the defogging unit logic) so as to target an area of the window100corresponding to the identified location of the window100at which the fog has formed. Thus, in the case of the HVAC system, the controller800can control operation of the HVAC system, i.e., activate the HVAC control logic, so as to blow air toward an area of the window100corresponding to the identified location of the window100at which the fog has formed. Further, the controller800can control the operation of the HVAC system so as to blow air toward the identified location on the window100by adjusting a position of one or more louvers in an air vent of the HVAC system. The vent louvers can be adjusted using a variety of known techniques, such as the techniques described in U.S. Pat. No. 6,012,297 to Ichishi et al., the disclosure of which is hereby incorporated herein in its entirety by reference. Similarly, in the case of the electric defogging unit including a plurality of conductive elements embedded in the window100, the controller800can control operation of the electric defogging unit so as to activate at least one of the plurality of conductive elements proximate to an area of the window100corresponding to the identified location of the window100at which the fog has formed.

Notably, through the implementation of the targeted defogging system described herein, the defrost ducts of a HVAC system could be redesigned so as to allow for targeted air blowing (i.e., blowing air toward specific regions of the window100), since only a subset of the blowers need be activated in a case where fog is limited to a particular region of the window100(such as the edges). As a result, the HVAC system may yield lower blower voltages, increase airflow efficiency, and reduce noise, vibration, and harshness (NVH) levels, thereby reducing energy levels and improving the overall user experience.

At step630, the controller800can determine, based on additional outputs received from the resistive humidity sensors200during the operation of the defogging unit400, whether the fog previously detected on the window100has cleared. In this regard, during operation of the defogging unit400, the resistive humidity sensors200can output additional signals indicating whether the presence of fog formed on the surface of the window100has been detected, that is, whether the fog is still present on the window100or, vice versa, whether the fog has been cleared. Upon receiving the additional signals transmitted from the resistive humidity sensors200during operation of the defogging unit400, the controller800may then determine whether the fog has been removed from the surface of the window100based on the received signal. To this end, the controller800can again compare a value indicated by the received signal(s) to the predetermined threshold. For instance, if the value indicated by the signal no longer satisfies the predetermined threshold, the controller800can determine that the fog has been removed (or at least sufficiently removed) from the window100. It should be understood that the threshold can be predetermined in any manner suitable for determining whether a value indicated by the received signals has reached a particular level, and the threshold as it is described hereinabove is merely for demonstration purposes and should not be treated as limiting the scope of the claimed invention.

If the controller800determines, based on the signals received from the resistive humidity sensors200during the operation of the defogging unit400, that the fog has cleared (or has sufficiently cleared) from the window100, the controller800can then deactivate the defogging unit400or control the defogging unit400such that it returns to normal operation, at step635. (If the fog has not yet cleared, according to the received signals, the procedure600returns to step625.) At this point, the controller800can continue to monitor the signals being outputted by the resistive humidity sensors200, and repeat steps610through635as necessary.

The procedure600illustratively ends at step635. The techniques by which the steps of procedure600may be performed, as well as ancillary procedures and parameters, are described in detail throughout the present disclosure.

It should be noted that the steps shown inFIG. 6are merely examples for illustration, and certain other steps may be included or excluded as desired. Further, while a particular order of the steps is shown, this ordering is merely illustrative, and any suitable arrangement of the steps may be utilized without departing from the scope of the embodiments herein. Even further, the illustrated steps may be modified in any suitable manner in accordance with the scope of the present claims.

FIG. 7illustrates a graph demonstrating an exemplary operation of the targeted defogging system described hereinabove. As shown inFIG. 7, the formation of moisture on the interior surface of the vehicle's windshield (or other window) depends on the relationship between the dew point temperature in the vehicle cabin and the temperature of the air next to the interior surface of the windshield. As humidity increases inside the vehicle—due to excessive body heat, passengers exhaling, damp clothes, snow on the floormats, etc.—the dew point temperature increases, as the air inside the vehicle is becoming more saturated with water vapor. Eventually, if the dew point increases beyond the temperature of the air next to the interior surface of the windshield, the moisture in the air will condense, causing water droplets to stick to the interior surface of the windshield. At this point, the moisture becomes visible, and fog forms on the surface of the windshield.

Meanwhile, the resistive humidity sensors200disposed along the windshield are sensing the presence of moisture based on the amount of resistance between the outer and inner conductive components310and320included in each respective sensor200, as explained above. Once the controller800determines that the voltage or some other value of signals transmitted by the resistive humidity sensors200satisfies a predetermined threshold, the defogging unit400can be actuated. Notably, because the resistance of the outer and inner conductive components310and320included in each respective sensor200can be affected by the presence of moisture even before the water vapor condenses onto the surface of the windshield, the defogging unit400can be actuated prior to the driver and/or passengers visibly recognizing fog on the windshield, as demonstrated inFIG. 7. Then, once the controller800determines, based on the signals received from the resistive humidity sensors200during the operation of the defogging unit400, that the fog has cleared (or has sufficiently cleared) from the window100, the controller800can then deactivate the defogging unit400or control the defogging unit400such that it returns to normal operation.

FIG. 8illustrates an exemplary diagrammatic representation of a system architecture of the targeted defogging system. As shown inFIG. 8, the controller800may be communicatively and operably coupled to the at least one resistive humidity sensors200and the defogging unit400. In this configuration, signals can be transmitted between the resistive humidity sensors200and the controller800, as well as between the defogging unit400and the controller800. Additionally, the controller800may include a memory820and a processor810, where the memory820is configured to store program instructions, and the processor810is specifically programmed to execute the program instructions to perform one or more processes which are described herein. The controller800may receive power supplied from a power supply unit830equipped in the vehicle. It should be understood that the system architecture depicted inFIG. 8is greatly simplified, as numerous components required for the typical operation of the vehicle are beyond the scope of the present disclosure and thus omitted.

Accordingly, techniques are described herein that provide a resistive humidity sensor which, when compared to capacitive or infrared humidity sensors employed in conventional automatic defogging systems, is easier to install and has a smaller size, lower cost, longer operational life, and greater interchangeability. In addition, the targeted defogging system described herein allows for redesign of the defrost ducts of a HVAC system so as to allow for targeted air blowing, since only a subset of the blowers need be activated in a case where fog is limited to a particular region of the window. As a result, the HVAC system may yield lower blower voltages, increase airflow efficiency, and reduce NVH levels, thereby reducing energy levels and improving the overall user experience.

While there have been shown and described illustrative embodiments that provide for a resistive humidity sensor and targeted defogging system, it is to be understood that various other adaptations and modifications may be made within the spirit and scope of the embodiments herein. For example, the embodiments have been primarily shown and described herein with relation to resistive humidity sensors disposed on the windshield of the vehicle. However, such sensors may also be disposed on the rear window, side or door windows, or any other vehicle windows where fog may form. Moreover, the inner and outer conductive components have been primarily shown in the figures as having a square-like shape. However, the inner and outer conductive components are not limited as such, and the inner and outer conductive components may be formed in any shape, so long as the inner conductive component is enclosed within the outer conductive component. Thus, it should be understood that the embodiments of the present disclosure may be modified in any suitable manner in accordance with the scope of the present claims.

The foregoing description has been directed to embodiments of the present disclosure. It will be apparent, however, that other variations and modifications may be made to the described embodiments, with the attainment of some or all of their advantages. Accordingly, this description is to be taken only by way of example and not to otherwise limit the scope of the embodiments herein. Therefore, it is the object of the appended claims to cover all such variations and modifications as come within the true spirit and scope of the embodiments herein.