Patent Document

CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. patent application Ser. No. 12/276,876, filed on Nov. 24, 2008, and entitled “Oil Condition Sensing Methods and Systems.” The disclosure of the above application is incorporated herein by reference in its entirety. 
    
    
     FIELD 
     The present disclosure relates to fluid sensors and more particularly to electro-mechanical fluid sensor systems and methods for controlling electro-mechanical fluid sensor systems. 
     BACKGROUND 
     The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. 
     Diesel motors combust diesel fuel in combustion chambers to generate torque that can be used to propel a vehicle. If water infiltrates the diesel fuel, the lubricity of the diesel fuel may be reduced, leading to increased wear for components of the engine. For example, a fuel delivery system, which delivers the diesel fuel to the combustion chambers, may include tightly fitting components that rely on the lubricating properties of the diesel fuel. For example only, water intermixed with fuel flowing at high velocity may abrade highly polished valve seats and fine nozzle orifices. 
     Further, water may contain biological and chemical impurities, which may cause corrosion of engine components. Water infiltration may also have negative effects in engines using other types of fuel, such as gasoline. Various engines may therefore include a water separator that attempts to remove water from the fuel supply. 
     Referring now to  FIG. 1 , an exemplary engine system including a water separator is shown. A fuel tank  102  provides fuel to a fuel/water separator  104 . The fuel/water separator  104  separates water from the fuel and directs the fuel to an engine  106 . The fuel/water separator  104  includes a bowl  108  in which the separated water collects. 
     The bowl  108  may include a valve  110  that can be opened to drain water from the bowl  108 . The bowl  108  may be clear to allow visual inspection of the water level in the bowl  108 . Traditionally, periodic inspection of the bowl  108  is required to ensure a low water level in the bowl  108 . Once the bowl  108  fills with water, operation of the fuel/water separator  104  may be impaired. 
     Some systems may include electrodes in the bowl  108 . A voltage potential is applied to the electrodes, and, because water is more conductive than fuel, the presence of water is indicated by a higher current flow between the electrodes. However, over time, electrodes may corrode in the presence of water and other impurities, which adversely affects their electrical conductivity. 
     SUMMARY 
     A sensor system includes a sensor and a control module. The sensor includes an electrically actuated moving member. The sensor is in fluid communication with a reservoir of a separator that separates a first fluid from a fuel. The control module selectively causes current to be supplied to the sensor to actuate the member. The control module measures the current and determines a parameter of the current. The control module identifies one of presence and absence of the first fluid in the reservoir based on the parameter. 
     A method includes selectively causing current to be supplied to a sensor to actuate a movable member of the sensor. The sensor is in fluid communication with a reservoir of a separator that separates a first fluid from a fuel. The method also includes measuring the current supplied to the sensor, determining a parameter of the current, and identifying one of presence and absence of the first fluid in the reservoir based on the parameter. 
     Further areas of applicability of the present disclosure will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a functional block diagram of an exemplary engine system including a water separator according to the prior art; 
         FIG. 2  is a functional block diagram of an exemplary engine system including a water separator according to the principles of the present disclosure; 
         FIG. 3  is a partial cross sectional view of a bowl and an exemplary implementation of a sensor according to the principles of the present disclosure; 
         FIG. 4  is a graphical depiction of three exemplary traces of current of a solenoid according to the principles of the present disclosure; 
         FIG. 5  is a functional block diagram of a sensor system including an exemplary implementation of a sensor control module according to the principles of the present disclosure; 
         FIG. 6  is a flowchart depicting exemplary steps performed in analyzing a current signal according to the principles of the present disclosure; and 
         FIGS. 7A-7C  are functional block diagrams of additional sensor systems according to the principles of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is in no way intended to limit the disclosure, its application, or uses. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical or. It should be understood that steps within a method may be executed in different order without altering the principles of the present disclosure. 
     As used herein, the term module refers to an Application Specific Integrated Circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality. 
     Referring now to  FIG. 2 , a functional block diagram of an exemplary engine system is presented. The fuel tank  102  provides fuel, such as gasoline or diesel fuel, to a fuel/water separator  120 . The fuel/water separator  120  separates fuel from water, provides fuel to the engine  106 , and directs water into a bowl  122 . The bowl  122  may include a valve  124 , which allows water to be emptied from the bowl  122 . 
     For example only, a water line  126  is shown, indicating that water is present below the water line  126  while fuel is present above the water line  126  (assuming that water is denser than the fuel). A sensor  128  may be installed in the bowl  122  to detect the presence of water. An engine control module  130  controls operation of the engine  106 . For example, the engine control module  130  may control actuators (not shown) within the engine  106  to produce a torque as requested by a driver. 
     The engine control module  130  may include a sensor control module  140  that controls and receives signals from the sensor  128 . At various times, a diagnostic module  142  commands the sensor control module  140  to take a reading from the sensor  128 . For example only, the diagnostic module  142  may issue this command on a periodic schedule. For example only, the schedule may be altered based on sensed driving habits, such as average engine run time. 
     The sensor control module  140  may interpret readings from the sensor  128  to determine whether water is present in the bowl  122 . The level of water that the sensor  128  detects is determined by where in the bowl  122  the sensor  128  is placed. The diagnostic module  142  may generate a visual/audio indicator  144  when water is detected. For example only, the visual/audio indicator  144  may include a check engine light or a digital instrument panel display. 
     The diagnostic module  142  may also set a diagnostic trouble code, which may be stored in a diagnostic interface  146 . The diagnostic interface  146  may be queried by diagnostic tools, such as at a dealership or repair facility. The diagnostic interface  146  may record the times during which water is detected, and provide these to the diagnostic tools. 
     User input  148  may instruct the diagnostic module  142  to command a new reading from the sensor  128 . The user input  148 , for example only, may include a button. A user may actuate the user input  148  after water has been drained from the bowl  122 . In various implementations, the valve  124  may be controlled by the diagnostic module  142 , such as with electrical or vacuum signals. Control of the valve  124  may also be performed via the diagnostic interface  146 . 
     Referring now to  FIG. 3 , a partial cross sectional view is presented of the bowl  122  and an exemplary implementation of the sensor  128 . The sensor  128  may be coupled to the bowl  122  via a gasket  160 . A piston  162  rides within a sleeve  164  to pull liquid through an orifice  166  into a chamber  168 . The liquid may be pulled into the chamber  168  through a channel  170  from the bowl  122 . 
     In various implementations, the length of the channel  170  may be reduced, and/or the channel  170  may be removed entirely. For example only, the orifice  166  may be defined at the wall of the bowl  122 . The piston  162  is connected to an armature  172 . The armature  172  is biased to a first position by a coil return spring  174 . When a current is applied to windings  176 , the resulting electromagnetic field actuates the armature  172  to a second position in opposition to the return spring  174 . 
     As the armature  172  moves from the first position to the second position, the piston  162  presses the fluid from the chamber  168  through the orifice  166 . For fluids with higher viscosities, the fluid is more difficult to push from the chamber  168  through the orifice  166 . This change in viscosity may be evidenced by a change in the electrical characteristics of the sensor  128 , as described in more detail with respect to  FIG. 4 . 
     Referring now to  FIG. 4 , three exemplary traces  202 ,  204 , and  206  of the current of a solenoid are shown. Trace  202  corresponds to a low viscosity, trace  204  corresponds to a higher viscosity, and trace  206  corresponds to an infinite viscosity. An infinite, or extremely high, viscosity has the same effect as if the armature of the solenoid were mechanically stuck. Traces  202  and  204  each include a notch in the current. By contrast, trace  206  lacks the notch. For traces similar to trace  206 , the notch time may be considered to be infinite, or set to a maximum amount of time. 
     The location of the notch is an indication of the viscosity of the fluid with which the solenoid is interfacing. Because the solenoid piston displaces fluid in front of the piston, hydraulic resistance is caused by the viscous fluid moving through a restrictive flow passage (such as an orifice). This hydraulic resistance exerts a pressure on the face of the piston, which resists armature movement and changes the current response characteristics of the solenoid. 
     At a start point  210 , the solenoid is instructed to actuate. This may be initiated by a trigger signal that arrives at the start point  210 . For purposes of illustration, trace  202  will be analyzed. After the start point  210 , the current of trace  202  begins increasing. At a first point  212 , trace  202  transitions from increasing to decreasing. The first point  212  is therefore a local maximum. 
     Trace  202  then decreases until a second point  214 , when trace  202  transitions from decreasing back to increasing. The second point  214  is therefore a local minimum. The armature of the solenoid begins moving at the first point  212  and stops moving at the second point  214 . The measured current decreases between the first and second points  212  and  214  because the moving armature creates a back electromotive force (EMF) that opposes the electrical potential. 
     The amount of time elapsed between the start point  210  and the second point  214  is referred to as the notch time. The notch time of trace  204  is greater than the notch time of trace  202 , indicating that the solenoid is interfacing with a higher viscosity fluid in trace  204 . The notch time of trace  206  may be reported as a predetermined maximum value. For example, the notch time for trace  206  may be reported as 45 ms. 
     Referring now to  FIG. 5 , a functional block diagram of a sensor system including an exemplary implementation of the sensor control module  140  is presented. The sensor  128  includes an electrically-operated element that interfaces with fluid. For example only, the sensor  128  may include a solenoid  302  that interfaces with the fluid. Alternatively, the sensor  128  may include a plate that is moved through the fluid by an electric motor. In various implementations, a rotating or translating plate may be less expensive to implement than a solenoid. 
     The solenoid  302  may be connected to a power supply  304 . In various implementations, the power supply  304  may be a vehicle battery, which may also provide power to the sensor control module  140 . Current flow from the power supply  304  through the solenoid  302  is regulated by a switch  306 , such as a transistor. In various implementations, the transistor may include an n-channel metal-oxide semiconductor field-effect transistor (MOSFET) having a source (S) terminal, a drain (D) terminal, and a gate (G) terminal. 
     The current flowing through the switch  306  may be routed through a shunt resistor  308  before reaching a reference potential, such as ground. The shunt resistor  308  develops a voltage potential proportional to current flow. An amplifier  310  amplifies the voltage potential across the shunt resistor  308 . Alternatively, other current sensing devices, such as a Hall effect sensor, may be used to determine the current flowing through the solenoid  302 . An output of the amplifier  310  may be converted to a digital value by an analog-to-digital (A/D) converter  312 . The digital value is a representation of the current flowing through the solenoid  302 . 
     A notch detection module  314  may evaluate the digital signal from the A/D converter  312  to determine the time at which the notch of the solenoid current occurs with respect to a trigger signal. The trigger signal may be generated when the solenoid is instructed to actuate. The trigger signal may be generated by a solenoid drive module  318 . For example only, the notch detection module  314  may initialize a timer in a timer module  316  when the trigger signal is received. The time elapsed in the timer module  316  between the trigger signal arriving and the current notch being detected is the notch time. 
     The solenoid drive module  318  may provide the trigger signal to the gate of the switch  306 , thereby allowing current to flow through the solenoid  302 . A notch analysis module  320  may receive an activation signal, such as from the diagnostic module  142  of  FIG. 2 . Based on this activation signal, the notch analysis module  320  may instruct the solenoid drive module  318  to produce the trigger signal. The notch analysis module  320  may instruct the solenoid drive module  318  to actuate the solenoid  302  multiple times to circulate fluid and ensure a representative sample is analyzed. In various implementations, the final notch time may be selected, or an average of selected ones of the notch times may be used. 
     A voltage measurement module  322  may measure a voltage of the power supply  304 . The notch analysis module  320  may adjust the notch time based on the measured voltage. For example only, a higher voltage from the power supply  304  may be expected to decrease the notch time. The notch analysis module  320  may therefore increase the indicated notch time when the measured voltage is higher. 
     Further, viscosity may vary with temperature. Therefore, a temperature measurement module  324  may be implemented. For example only, fluid temperature may be modeled, measured directly, and/or inferred from other temperature measurements, such as engine coolant temperature. The temperature measurement module  324  may receive data from a temperature sensor (not shown), such as a thermocouple, associated with the solenoid  302 . In various implementations, the temperature sensor may be implemented in the sensor  128 . 
     Alternatively, temperature readings from other systems may be used. For example only, the temperature measurement module  324  may receive a temperature used by a fuel injection system for fuel injection control. In various implementations, temperature may be estimated based on resistance of the windings in the solenoid  302 . The notch analysis module  320  may normalize the notch time based on temperature. For example only, if viscosity decreases as temperature increases, the notch analysis module  320  may increase the indicated notch time when the measured temperature is higher. 
     The notch analysis module  320  may use the normalized notch time to make determinations about the fluid interfacing with the sensor  128 . For example only, a predetermined value may be stored in a storage module  326 . If the normalized notch time is greater than the predetermined value, indicating that viscosity is relatively high, the notch analysis module  320  may report that fuel, instead of water, is present. Conversely, when the normalized notch time is less than or equal to the predetermined value, the notch analysis module  320  may report that water is present at the sensor  128 . 
     In various implementations, the storage module  326  may store multiple values to differentiate between water, air, and/or multiple types of fuel. For example only, different types of diesel fuel, including biodiesel, may have different characteristic notch times. The notch analysis module  320  may report the type of fuel detected as well as the presence of water. The values in the storage module  326  may be stored in a lookup table. These values may be determined empirically and/or estimated based on sensor characteristics, such as solenoid geometries, orifice size, and fluid properties. 
     Referring now to  FIG. 6 , a flowchart depicts exemplary steps performed in analyzing the signal from the A/D converter  312  of  FIG. 5 . Control begins in step  402 , where control determines whether the trigger signal has been activated. If so, control continues in step  404 ; otherwise, control remains in step  402 . In step  404 , a timer is started and control continues in step  406 . 
     In step  406 , control begins measuring current flowing through the solenoid. Control continues in step  408 , where control begins calculating a moving average of the current. The moving current average may be calculated in order to decrease the false detection of a local maximum or local minimum. In this way, small disturbances in the current signal, such as those due to noise, will not be incorrectly detected as a change in direction of the current. 
     For example only, the moving average may be a two-point moving average. The moving average may be calculated as a prior moving average or as a central moving average, which uses data taken after the point being calculated. In addition, the moving average may be a simple moving average or a weighted moving average, and the weighting may be linear or exponential. 
     Control continues in step  410 , where control begins calculating a derivative of the moving average. For example only, control may calculate the derivative as the difference between the current moving average value and the previous moving average value divided by the time between the moving average values. Control continues in step  412 , where control determines whether the derivative has decreased below zero. If so, control transfers to step  414 ; otherwise, control transfers to step  416 . For example only, control may transfer to step  414  only when multiple sequential derivatives remain below zero. 
     In step  416 , control determines whether the timer is greater than a predetermined maximum time. If so, control transfers to step  418 ; otherwise, control returns to step  412 . In step  414 , control determines whether the derivative has returned above zero after being below zero in step  412 . If so, control transfers to step  420 ; otherwise, control transfers to step  422 . 
     As in step  412 , control may evaluate multiple derivatives in step  414  to ensure that the derivative has reliably increased above zero. In step  422 , control determines whether the timer has exceeded the predetermined maximum time. If so, control transfers to step  418 ; otherwise, control returns to step  414 . In step  420 , control reports the timer value as the notch time and control stops. In step  418 , control reports the predetermined maximum time as the notch time and control stops. 
     Referring now to  FIGS. 7A-7C , the principles of the present disclosure can be implemented in various vehicle systems. For example only, whenever viscosity can be used to differentiate between different fluids, a sensor system as described in the present application can be implemented to measure viscosity. Viscosity may indicate which variety of a desired fluid is present. Additionally, viscosity may indicate presence of an undesired fluid or the absence of the desired fluid. Further, viscosity may indicate when properties of the desired fluid have been compromised. 
     For example only,  FIG. 7A  depicts a system for detecting water in a fuel tank  502 . A sensor  504  is located in the fuel tank  502 , and a sensor control module  506  analyzes readings from the sensor  504  to determine viscosity of the fluid in the fuel tank  502 . If a viscosity indicative of water is measured, a diagnostic module  508  may alert an operator or a mechanic. In addition, remedial action may be performed, such as operating an engine in a reduced power mode or limiting the speed of the engine. 
     For example only,  FIG. 7B  depicts a system for detecting water or glycol in an oil supply, such as an oil sump  522 . A sensor  524  is located in the oil sump  522 , and a sensor control module  526  analyzes readings from the sensor  524  to determine viscosity of the fluid in the oil sump  522 . If a viscosity indicative of water or glycol is measured, a diagnostic module  528  may alert an operator or a mechanic. In addition, remedial action may be performed, such as operating an engine in a reduced power mode or limiting the speed of the engine. 
     For example only,  FIG. 7C  depicts a system for detecting oil in a cooling system component, such as a radiator  542 . A sensor  544  is located in the radiator  542 , and a sensor control module  546  analyzes readings from the sensor  544  to determine viscosity of the fluid in the radiator  542 . If a viscosity indicative of oil is measured, a diagnostic module  548  may alert an operator or a mechanic. In addition, remedial action may be performed, such as operating an engine in a reduced power mode or limiting the speed of the engine. 
     The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification, and the following claims.

Technology Category: 3