Abstract:
A method of reducing engine cold start up emissions and an apparatus for isolating a fuel sample for testing purposes. According to the methodology the driveability index of the fuel is sensed utilizing an onboard sensor and the sensed fuel driveability index is inputted to the engine controller for utilization by the engine controller in determining the fueling algorithm for minimizing emissions during the next cold start up of the engine. The sensor determines the driveability index by evaluating a fuel sample collected onboard during the previous running cycle of the engine. The fuel sample is pumped from the vehicle fuel tank to an onboard collection point by the vehicle fuel pump during the previous running cycle of the engine. The fuel sampling apparatus includes a sample cup, a cylinder having a bore and an inlet port for connection to the fuel pump and a piston rod defining an axial passage having an inlet port and a discharge port. The piston rod is mounted in the bore for movement between an operative position in which the passage inlet port communicates with the cylinder inlet port and the passage discharge port is positioned in overlying relation to the sample cup and a retracted position in which the passage inlet port is blocked from communication with the cylinder inlet port and the discharge port is withdrawn from the sample cup whereby to isolate a fuel sample in the sample cup.

Description:
TECHNICAL FIELD OF THE INVENTION  
         [0001]    This invention relates a method and apparatus for determining the driveability index of a fuel for use in engine control.  
         BACKGROUND OF THE INVENTION  
         [0002]    It is known in the art relating to automotive engines that a key gasoline characteristic for good driveability is volatility. Volatility is especially important at the time an engine is started because liquid gasoline must evaporate and mix with air to form a combustible mixture. If too little gasoline is added, the engine will not start; if gasoline beyond that needed to initiate combustion is added, extra hydrocarbons from an unburned portion of gasoline are found in the exhaust. Moreover, because gasoline sold in the United States varies in volatility, there is a trade off in engine design between low hydro-carbon emissions and good driveability with low volatility fuel.  
           [0003]    To describe the effect of gasoline volatility on the cold start and warm up driveability of a vehicle, a driveability index (DI) has been developed. DI is a number that helps predict how different volatility gasolines affect engine performance and is correlated to how often an engine might stall, stumble, surge or hesitate. For gasoline that does not contain oxygenates such as ethanol or methyl tertiary-butyl ether (MTBE), the definition of DI is based on a laboratory test (American Society for Testing and Materials D 86) in which a sample of gasoline is distilled as its temperature is raised. The fraction distilled is measured as a function of temperature and DI=1.5T 10 +3T 50 +T 90  where T x  is the temperature in degrees Fahrenheit at which x % of the gasoline sample has been distilled. Most drivers are satisfied with the engine performance when the engine fuel has a DI value of 1200 or lower.  
           [0004]    Because DI was developed by using carbureted vehicles and non-oxygenated fuels, a modified equation was needed to account for the changes in engine and fuel. With oxygenated gasoline an expression that provides better correlation to engine performance is: DI=1.5T 10 +3T 50 +T 90 +86 .EtOH  which includes the effect if 10% (in volume) of ethanol in fuel. The variable  .EtOH  is  1  if 10% ethanol is present, and zero otherwise. The effects of another popular oxygenated compound additive in fuel, MTBE (methyl tertiary butyl ether) are often not included in the DI calculation since MTBE is to be eliminated from fuels by the end of the year 2003.  
           [0005]    With the knowledge of the fuel driveability index value, proper amounts of fuel can be dispensed to the engine which can help a smooth engine start and produce less emissions from the engine.  
           [0006]    It is particularly desirable to estimate DI onboard a vehicle. To provide customer satisfaction, engines are calibrated to reliably start with fuel of the lowest expected DI. This is done by increasing the amount of fuel in the air fuel mixture. Consequently, for most starts, the engine&#39;s air fuel ratio is richer than optimum. Some of this extra gasoline passes unburned into the exhaust. This is particularly detrimental at the time of a cold start because the catalytic converter is too cold to be active. The added hydro-carbon concentration is typically emitted to the environment. Estimating DI onboard would prevent the air fuel ratio to be more precisely controlled. The engine would be calibrated to reliably start while extra fuel would only be added when needed to compensate for fuel volatility. On average, less fuel would be used for cold starts resulting in a decrease in fleet-average exhaust hydro-carbon emissions. This decrease in air pollution is an important environmental benefit.  
         SUMMARY OF THE INVENTION  
         [0007]    This invention relates to a method of controlling emissions of a motor vehicle internal combustion engine fueled by a fuel stored in an onboard fuel container for delivery to an engine controller.  
           [0008]    The method comprises sensing the driveability index of the fuel utilizing an onboard sensor and inputting the sensor driveability index to the engine controller for utilization by the engine controller in determining the fueling algorithm for minimizing emissions during the next cold start up of the engine. This methodology provides an onboard system for minimizing emissions during cold start up.  
           [0009]    According to a further aspect of the invention methodology, the sensor determines the driveability index by evaluating a fuel sample collected onboard during the previous running cycle of the engine. This methodology provides a convenient and effective means of providing an accurate driveability index.  
           [0010]    According to a further aspect of the invention methodology, the motor vehicle includes a fuel pump and the fuel sample is pumped from the fuel container to an onboard collection point by the fuel pump during the previous running cycle of the engine. This methodology provides a convenient means of providing the required fuel sample utilizing existing motor vehicle equipment.  
           [0011]    According to a further aspect of the invention methodology, the sample is collected in a sample cup and the sample cup and the fuel pump are positioned in the fuel container. This methodology provides a convenient packaging for the equipment required to determine the driveability index.  
           [0012]    According to a further aspect of the invention methodology, the fuel pump is positioned in a reservoir bucket positioned in the fuel container and the sample cup is positioned in a vapor dome of the fuel container. This methodology provides further advantages in packaging the equipment required to determine the driveability index.  
           [0013]    The invention further provides a fuel sampling apparatus for isolating a fuel sample for testing purposes.  
           [0014]    The fuel sampling apparatus of the invention comprises a sample cup, a cylinder having a bore and an inlet port for connection to the fuel pump, and a piston rod defining an axial passage having an inlet port and a discharge port. The piston rod is mounted in the bore for movement between an operative position in which the passage inlet port communicates with the cylinder inlet port and the passage discharge port is positioned in overlying relation to the sample cup to allow the delivery of pressurized fuel from the fuel pump to the cylinder inlet port to the passage inlet port and through the passage outlet port to the sample cup, and a retracted position in which the passage inlet port is blocked from communication with the cylinder inlet port and the discharge port is withdrawn from the sample cup. This apparatus provides a simple and effective mechanism for isolating a fuel sample in the sample cup for testing purposes.  
           [0015]    According to a further feature of the fuel sampling apparatus, the apparatus further includes an annular valving member carried by the piston rod and slidably mounted in the cylinder bore. The valving member is movable relative to the piston rod between an open position in which the passage inlet port communicates with the cylinder bore and a closed position in which the passage inlet port is blocked from communication with the cylinder bore. This valving arrangement provides a convenient means of delivering a fuel sample to the fuel cup and thereafter isolating the fuel sample.  
           [0016]    According to a further feature of the fuel sampling apparatus, the apparatus further includes stop structure coacting with the piston rod to stop the piston rod in its operative position. The valving member moves with the piston in its closed position relative to the piston rod until the piston rod encounters the stop structure whereafter the valving member moves relative to the piston rod to its open position to allow fuel flow from the cylinder bore through the piston passage and into the sample cup. This arrangement ensures the accurate, positive delivery of the fuel to the sample cup.  
           [0017]    According to a further feature of the fuel sampling apparatus, the apparatus further includes a biasing means resiliently resisting movement of the piston rod to its extended position and operative to return the piston rod to its retracted position upon shut-off of the vehicle fuel pump. This arrangement provides a convenient means of returning the apparatus to its neutral or start position.  
           [0018]    According to a further feature of the fuel sampling apparatus, the apparatus further includes means operative in response to arrival of the piston rod at its retracted position to move the valving member to its closed position. This arrangement provides a convenient means of restoring the apparatus to its neutral or start position.  
           [0019]    According to a further feature of the fuel sampling apparatus, the biasing means acts on the valving member; the apparatus further includes piston rod stop structure defined by coacting stop structure on the cylinder and the piston rod and valving member stop structure defined on the inboard end of the piston rod; the piston rod stop structure defines the retracted position of the piston rod; and the biasing means continues to act on the valving member following arrival of the piston rod at its retracted position and moves the valving member to its closed position as defined by the valving member stop structure. This arrangement provides a ready and effective means for moving the valving member to its closed position to define the neutral or start position of the apparatus.  
           [0020]    The invention further provides a fuel module for positioning in a fuel container of a motor vehicle. The module comprises a reservoir bucket; a fuel pump positioned in the bucket for connection to an engine of the vehicle; a sample cup; and sample isolating device receiving fuel from the fuel pump and operative to position a sample of the fuel in the sample cup. This module may be positioned in the fuel container of the vehicle where it functions to provide the primary fuel delivery apparatus of the vehicle and further provide a means of sampling a characteristic of the fuel for use in determining low emission engine control parameters.  
           [0021]    Other applications of the present invention will become apparent to those skilled in the art when the following description of the best mode contemplated for practicing the invention is read in conjunction with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]    The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein:  
         [0023]    [0023]FIG. 1 is a fragmentary schematic view of a motor vehicle embodying the invention methodology and apparatus;  
         [0024]    [0024]FIG. 2 is a view of a fuel module according to the invention;  
         [0025]    [0025]FIG. 3 is a view of a sensor assembly forming a part of the fuel module with a sensor pump of the sensor assembly shown in a retracted position;  
         [0026]    [0026]FIG. 4 is a plan view corresponding to FIG. 3;  
         [0027]    [0027]FIG. 5 is a cross sectional view of the sensor assembly with the sensor pump shown in an extended or operative position; and  
         [0028]    [0028]FIG. 6 is a plan view corresponding to FIG. 5. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0029]    The motor vehicle  10  seen schematically and fragmentary in FIG. 1 includes wheel assemblies  12 ,  14 ,  16  and  18 , an internal combustion engine  20 , an engine control unit (ECU)  22 , a fuel container or tank  24  for containing a fuel  25  such as gasoline, and a fuel module  26 .  
         [0030]    ECU  22  may comprise any device operating to determine and control the air/fuel ratio delivered to the engine  20 . It may take the form of a carburetor, or more typically with respect to modern day vehicles, may comprise an electronic unit receiving a plurality of sensor inputs and delivering a plurality of sensor controlled outputs including an air/fuel ratio output. The sensor inputs may include exhaust oxygen concentration, engine coolant temperature, throttle position, atmospheric pressure, manifold vacuum, engine crank shaft position, battery voltage, vehicle speed, transmission gear indication, park/neutral mode, brake pedal engagement, A/C clutch engagement, and cold start program modifier conditions. The sensor outputs may include control of air/fuel ratio, spark timing, EGR valve, and idle speed. For purposes of the present invention, we are concerned primarily with the ECU system output relating to air/fuel ratio and the sensor inputs that relate to the determination by the ECU of the air/fuel ratio.  
         [0031]    Fuel module  26  (FIGS. 1 and 2) includes a reservoir bucket  28 , an electric fuel pump  30 , a venturi pump  32 , and a sensor assembly  34 .  
         [0032]    Sensor assembly  34  includes a sensor pump  36 , a sample cup  38 , and a sensor  40 .  
         [0033]    Reservoir bucket  28  is sized to fit within the fuel tank  24 , supported on the tank lower wall  24   a.    
         [0034]    Electric fuel pump  30  is sized to be fitted in reservoir bucket  28  and has a primary output  30   a  communicating with a hose  42  which in turn communicates with a fitting  44  which in turn communicates with a fuel line  46  extending in known manner to engine  20  whereby operation of fuel pump  30  draws fuel  25  from tank  24  for delivery by fuel line  46  to the engine.  
         [0035]    Venturi pump  42  is positioned within reservoir bucket  28  and operates in known manner to draw fuel from tank  24  into the reservoir bucket  28  where it may be inputted to pump  30  for delivery to the engine.  
         [0036]    Sensor pump  36  (FIGS.  3 - 6 ) includes a cylinder or barrel  50  defining a bore  50   a,  a piston rod  52  having an inboard end  52   a  positioned in bore  50   a  and an outboard end  52   b  positioned outside of the cylinder, a piston valving member  54  slidably and sealingly mounted in bore  50   a  and slidably positioned on the inboard end  50   a  of piston rod  50 , and a return spring  55 .  
         [0037]    Piston rod  52  defines a central axial passage  52   c  extending from an inlet port  52   d  proximate the inboard end of the piston rod to a discharge port  52   e  proximate the outboard end of the piston rod. Inlet port  52   d  extends radially for communication with cylinder bore  50   a  and discharge port  52   e  extends radially downwardly for communication with sample cup  38 . Piston rod  52  further includes a spigot portion  52   f  extending radially outwardly from outboard end  52   b  and defining  12   an  outlet passage  52   g  connecting to an outlet port  52   h  overlying cup  38  proximate discharge port  52   e.    
         [0038]    Piston valving member  54  includes a main body portion  54   a  slidably mounted in bore  50   a  and an internal rib portion  54   b  slidably guiding on a reduced diameter portion  52   i  of piston rod  52  proximate the inboard end  52   a  of the piston rod. A radial stop pin  56  carried by the inboard end  52   a  of the piston rod coacts with the main body portion  54   a  of valving member  54  to limit and define the sliding movement of valving member  54  on the piston rod.  
         [0039]    O-rings  58  and  60  respectively seal the valving member  54  with respect to the cylinder bore  50   a  and the valving member  54  with respect to the reduced diameter portion  52   i  of the piston rod. A further O-ring  62  is positioned on a hub portion  52   j  of the piston rod proximate outlet port  52   e ; an input port  50   b  communicates with cylinder bore  50   a ; and bore  50   a  is vented by vent ports  50   c.    
         [0040]    Discharge port  52   e  and outlet port  52   h  will be seen to be circumscribed by hub portion  52   j.    
         [0041]    Sample cup  38  is positioned in underlying relation to discharge port  52   e  and outlet port  52   j  whereby to receive fuel delivered through passage  52   c,  and defines a cup shaped volume  38   a  precisely defined to receive a precise measure of fuel constituting a fuel sample  25   a.    
         [0042]    Sensor  40  is associated with sample cup  38  and is operative to test the fuel sample  25   a  isolated in sample cup  38  and determine the driveability index (DI) of the fuel, which index may be inputted to the ECU by a lead  64  for utilization by the ECU as a sensor input to determine the air/fuel ratio for delivery to the engine. In this regard it will be understood that the ECU embodies a fueling algorithm based on a plurality of sensor inputs including the driveability index inputted by a lead  64 .  
         [0043]    Sensor  40  may take various forms and, for example, may operate on the basis of evaporative calorimetry or capacitance measurement. In both cases, a sample of liquid fuel is heated by a resistance  40   a  underlying the sample cup  38  and the evaporation of the fuel is monitored and measured. With respect to evaporative calorimetry, the intent is to monitor the evaporation of the fuel sample by measuring the heat absorbed by the sample as it evaporates. With respect to capacitance measurement, the intent is to monitor the evaporation of the fuel sample by measuring an electrical capacitance that varies as a function of the remaining volume of liquid fuel. Details of an evaporative calorimetry sensor suitable for use in the present invention are disclosed in co-pending U. S. patent application Ser. No. ______ assigned to the assignee of the present application. Details of a capacitance measurement sensor suitable for use in the present invention are disclosed in U.S. patent application Ser. No. 09/932,333 assigned to the assignee of the present invention. Irrespective of the methodology used to determine driveability index, the sensor functions to output a electronic measure of the driveability index of the fuel sample via lead  64  for use by ECU  22  in determining the appropriate fueling algorithm.  
         [0044]    Note that the reservoir bucket  28  is positioned within the fuel tank  24  (for example supported on the floor  24   a  of the fuel tank) and the sensor assembly  34  is positioned in a vapor dome  24   b  defined in the upper regions of the fuel tank. A hose  66  extends between a further fuel pump outlet  30   b  and the inlet  50   b  of the sensor pump and a further hose  68  extends between the outlet passage  52   g  of the piston rod  52  and venturi pump  32 .  
         [0045]    Sensor pump  36  is normally maintained in the neutral or retracted position seen in FIG. 3 by the combined action of return spring  55  positioned in bore  50   a  and acting on valving member  54 , and a stop structure  52   g  defined on piston rod  52  proximate the outboard end  52   b  of the piston rod. Specifically, spring  55  urges valve member  54  against stop pin  56  and urges piston rod  52  to the right as viewed in FIG. 3 until stop  52   g  encounters a coacting surface on cylinder  50  to define the retracted position of the piston rod. It will be seen that in this position the ports  52   e  and  52   h  defined at the outboard end of the piston rod are withdrawn from overlying relation to the sample cup  38 .  
         [0046]    When the engine  20  is started up, fuel  25  under pressured is delivered by tube  66  and port  50   b  to bore  50   a  where the pressurized fuel acts against piston rod  50  and valving member  54  causing both to slide to left within the bore  50   a.  Valving member  54  and piston rod  50  continue to slide together to the left, compressing spring  55 , until O-ring  62  covers sample cup  38 . As the O-ring  62  moves into position in overlying relation to sample cup  38 , the outboard end  52   b  of the piston rod encounters a positive stop  70  which halts the piston rod in precise overlying relation to the sample cup. The operative face  70   a  of stop  70  is sloped so as to compress the O-ring  62  as it slides into place and provide a positive seal as between the piston rod and the sample cup. As the piston rod is halted by the stop  70 , valving member  54  continues to slide within bore  50   a  under the urging of the pressurized fuel until rib  54   b  encounters a shoulder  52   k  at the juncture of the reduced diameter portion  52   a  of the piston rod and the main body of the piston rod to halt the relative movement of the valving member on the piston rod. During this final movement of the valving member relative to the piston rod, the valving member moves from a closed position seen in FIG. 3 in which communication between bore  50   a  and inlet port  52   d  is blocked to an open position seen in FIG. 5 wherein communication is established between bore  50   a  and port  52   d.  It will be seen that the action of the valving member  54  in its closed position to block communication between bore  50   a  and the inlet port  52   d  is augmented by the sealing action of O-ring  60 . It will further be seen that the movement of the outboard end of the piston rod into overlying sealed relationship with respect to sample cup  38  coincides with the movement of the valving member from a closed to an open position so that, as the piston rod moves into overlying relation to the fuel cup, pressurized fuel begins to flow through the passage  52   c  and discharge port  52   e  into the sample cup and thereafter via outlet port  52   h,  passage  52   g,  and hose  68  to venturi pump  32 . The continuous flow of fuel through the cup  38   a  has the effect of continuously flushing the cup of any contaminants and maintaining the cup in a full condition.  
         [0047]    When the engine is thereafter shut-off, fuel pump  30  shuts off allowing pressure to drop to essentially atmospheric on the fuel side of the valving member  54  and allowing spring  55  to push the valving member and piston rod from the operative position of FIG. 5 to the retracted position of FIG. 3. As the piston rod moves to its retracted position under the urging of spring  55  it is stopped by the engagement of stop structure  52   g  and the coacting surface of the cylinder but the valving member  54  continues to move relative to the piston rod under the urging of spring  55  until it encounters stop pin  56 . This final movement of the valving member relative to the piston rod has the effect of moving the valving member from its open position, allowing communication between bore  50   a  and inlet port  52   d,  to its closed position, blocking communication between bore  50   a  and inlet port  52   d  whereby to terminate the flow of fuel to the sample cup. During the retracting movement of the outboard end  52   b  of the piston rod, O-ring  62  drags across the upper face of the sample cup with a wiping action to provide a level, precision fill of the sample cup and an accurate fuel sample volume  25   a.  Withdrawal of the outboard end of the piston rod from overlying relation to the sample cup exposes the upper face of the fuel sample  25   a  so that fuel vapors from the sample do not have an opportunity to recondense and run back into the cup. It will be understood that such recondensing would adversely affect the accuracy of the DI determination by the sensor  40 .  
         [0048]    Once the piston rod has moved to its retracted position exposing the fuel sample in the sample cup, sensor  40  is suitably actuated to provide a measure of the driveability index of the fuel sample in the sample cup whereby to generate an electronic driveability index signal on lead  64  for inputting to ECU  22  where it is stored in memory for use by the ECU in determining the fueling algorithm for minimizing emissions during the next cold start up of the engine. During the next cold start up of the engine, the driveability index input is combined with other sensor inputs to determine the fueling algorithm that would minimize emissions during the next cold start up of the engine. Use of the driveability index derived from a sample obtained during the previous run cycle of the engine facilitates the reduction of exhaust hydro-carbon emissions by enabling more accurate control of the air/fuel ratio at engine start up. This is important in emission control since typically about 80% of the exhaust hydro-carbon emissions occur during the initial phase of engine start up before the catalytic convertor has warmed up enough to light off and before the exhaust oxygen sensor has warmed up enough to begin closed loop control of the air/fuel ratio.  
         [0049]    Although the stop  70 , cylinder  50 , and sensor  40  have been schematically shown to be suitably secured to the upper wall  24   c  of the fuel tank, it will be understood that this arrangement is for illustrative purposes only and that, in practicality, the various elements of the sensor assembly might be carried by the reservoir bucket  28  to form a fuel module comprising the reservoir bucket  28 , venturi pump  32 , sensor  40 , sample cup  38 , and pump  36 , which fuel module could be suitably installed in the tank  24  by lowering the fuel module through an opening in the top wall  24   c  of the tank and including a cover member as a part of the fuel module that is moved into place as the module comes to rest on the floor of the fuel tank to seal the tank opening.  
         [0050]    It is contemplated that the DI measurement would be performed at the end of each trip of the vehicle and, at the next cold start of the engine, the previously measured DI value would be retrieved from the ECU memory and utilized to determine the air/fuel ratio of the engine in a sense to minimize emissions during engine start up. It is contemplated that the vehicle controls would be configured such that the driveability index calculated in accordance with the invention would not be utilized in each subsequent start up of the engine following an engine shut down but, rather, controls would be included such that the previously derived driveability index would only be utilized subsequently in a cold start up of the engine as determined by the control circuitry. Note in this regard that a typical sensor input to the ECU is engine coolant temperature and this input could be utilized to determine those start ups which would qualify as cold start ups utilizing the driveability index determined at the previous shut down of the engine. Thus engine start ups occurring shortly after engine shut offs (such for example in scenarios where the vehicle is stopped for refueling) would not qualify for utilization of the driveability index since there is no need in this scenario to be concerned with excessive emissions during start up.  
         [0051]    The invention will be seen to provide an improved methodology and apparatus for reducing exhaust gas emissions during cold engine start up and will further be seen to provide a fuel sample isolating device that provides a fuel sample for testing purposes in a convenient and efficient manner.  
         [0052]    While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiments but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law.