Abstract:
Automotive vehicles are increasingly being equipped with remote starting devices. If the vehicle is within a space which is very well sealed, it is possible that the concentration of the exhaust gases may exceed desirable levels. A method and system are disclosed in which a mass-based determination of air/fuel ratio is compared with the air/fuel ratio being maintained by the exhaust gas oxygen sensor. When the air/fuel ratio based on a mass measurement deviates from the air/fuel ratio based on the exhaust gas oxygen sensor by more than a threshold difference, the remotely started vehicle is turned off.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     Operators of automobiles are increasingly interested in having a remote starting feature on their vehicles in which the operator has an actuator, which when actuated, causes the engine to be started. Operators find this feature desirable, particularly in cold weather conditions, so that the engine and vehicle cabin are heated prior to the operator entering the vehicle cabin.  
         [0002]     At the time of remote starting, the vehicle may be housed in a garage or other enclosed room. Although modern vehicles emit miniscule amounts of carbon monoxide, about one-eighth of the exhaust gas is comprised of carbon dioxide. If the room in which the vehicle is stored is exceptionally well sealed, the concentration of exhaust gases, and carbon dioxide in particular, may exceed desirable levels within the room.  
       SUMMARY OF THE INVENTION  
       [0003]     The inventors of the present invention have recognized that sensors onboard a production vehicle can be used to determine when the concentration of exhaust gases in the room, in which the vehicle is confined, exceeds an acceptable level. If such a situation is determined, engine operation is discontinued.  
         [0004]     A method to control an internal combustion engine, which is adapted for remote starting, is disclosed. A measured air/fuel ratio based on fuel flow and air flow is determined. An error is computed based on the measured air/fuel ratio and stoichiometric air/fuel ratio for the particular fuel being supplied to the engine. If the error exceeds a threshold, engine operation is ceased. Engine cessation is based on the engine having been remotely started. In one embodiment, the error is computed when the engine is being operated under closed-loop control based on-a signal from the exhaust gas oxygen sensor. In one embodiment, if the engine is under operator control, the engine is allowed to continue to operate.  
         [0005]     The inventors of the present invention have recognized that when the engine is operating under closed loop control based on a signal from the exhaust gas oxygen sensor, the air/fuel ratio based on mass air flow measurements will deviate from the stoichiometric air/fuel ratio when the air being inducted into the engine intake contains significant amount of diluent, e.g., exhaust gas. Modern electronic control units on-board vehicles have the capability of estimating both of these air/fuel ratios. By comparing these, the deviation in the two air/fuel ratios can be determined.  
         [0006]     In the present invention, engine operation is discontinued when the error computed based on the two air/fuel ratios exceeds a threshold. By ceasing operation, the amount of exhaust gas concentration of intake gases can no longer increase; thereby, the maximum allowable concentration of exhaust gases in an enclosed space is not exceeded, an advantage of the present invention.  
         [0007]     The above advantages, other advantages, and features of the present invention will be readily apparent from the following detailed description of the preferred embodiments when taken in connection with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]     The advantages described herein will be more fully understood by reading an example of an embodiment in which the invention is used to advantage, referred to herein as the Detailed Description, with reference to the drawings wherein:  
         [0009]      FIG. 1  is a schematic of a vehicle equipped with remote starting;  
         [0010]      FIG. 2  is a schematic of an internal combustion engine installed in the vehicle;  
         [0011]      FIG. 3  is a flowchart of an embodiment of the present invention;  
         [0012]      FIG. 4  is a graph showing how air/fuel ratio is affected by the percent diluent in the inducted air; and  
         [0013]      FIG. 5  is a flowchart of an embodiment by which engine restart is achieved following an engine shutdown;  
         [0014]      FIG. 6  is a graph of the minimum delay time as a function of the time rate of change of measured air/fuel ratio according to an aspect of the invention; and  
         [0015]      FIG. 7  is a flowchart of an embodiment of the present invention 
     
    
     DETAILED DESCRIPTION  
       [0016]     The present invention relates to a vehicle with the capability of being remotely started. In  FIG. 1 , a vehicle  4  is shown in an enclosure  2 , which could be a garage. Vehicle  4  has an internal combustion engine  10  installed within. Engine  10  is electronically coupled to an electronic control unit  40 . Enclosure  1 , which could be a house, has an actuator  8 . When activated, for example, by an operator of vehicle  10 , actuator  8  sends a signal which is sensed by sensor  6 . Sensor  6  is electronically coupled to ECU  40 . When ECU  40  receives the signal that the operator has requested a start of engine  10  via actuator  8 , ECU  40  starts operation of engine  10 . Enclosure  1  is shown by way of example. Enclosure  1  may be detached from enclosure  2 . Alternatively, actuator  8  may not be in an enclosure at all. Engine  10  is coupled to a transmission  5 , which in one embodiment is an automatic transmission. Alternatively, transmission  5  is a manual transmission. Operator controls  3  are coupled to engine  10 , transmission  5 , and ECU  40 . Operator controls include: an ignition switch, a gear shift lever, a throttle pedal, etc.  
         [0017]     A four-cylinder internal combustion engine  10  is shown, by way of example, in  FIG. 2 . Engine  10  is supplied air through intake manifold  12  and discharges spent gases through exhaust manifold  14 . An intake duct upstream of the intake manifold  12  contains a throttle valve  32  which, when actuated, controls the amount of air flow to engine  10 . Sensors  34  and  36  installed in intake manifold  12  measure air temperature and mass air flow (MAF), respectively. Sensor  31 , located in intake manifold  14  downstream of throttle valve  32 , is a manifold absolute pressure (MAP) sensor. A partially closed throttle valve  32  causes a pressure depression in intake manifold  12 . When a pressure depression exists in intake manifold  12 , exhaust gases are caused to flow through exhaust gas recirculation (EGR) duct  19 , which connects exhaust manifold  14  to intake manifold  12 . Within EGR duct  19  is EGR valve  18 , which is actuated to control EGR flow. Fuel is supplied to engine  10  by fuel injectors  26 . Each cylinder  16  of engine  10  contains a spark plug  28 . A pressure transducer  30  is shown installed in each cylinder  16 . The crankshaft (not shown) of engine  10  is coupled to a toothed wheel  20 . Sensor  22 , placed proximately to toothed wheel  20 , detects engine  10  rotation. Sensor  24 , in exhaust manifold  14 , is an exhaust gas component sensor. Exhaust gas component sensor  24  is an exhaust gas oxygen sensor. Alternatively, exhaust gas component sensor  24  is a wide-range oxygen sensor, a nitrogen oxide sensor, a hydrocarbon sensor, or other gas component sensor as may become available.  
         [0018]     Continuing to refer to  FIG. 2 , electronic control unit (ECU)  40  is provided to control engine  10 . ECU  40  has a microprocessor  46 , called a central processing unit (CPU), in communication with memory management unit (MMU)  48 . MMU  48  controls the movement of data among the various computer readable storage media and communicates data to and from CPU  46 . The computer readable storage media preferably include volatile and nonvolatile storage in read-only memory (ROM)  50 , random-access memory (RAM)  54 , and keep-alive memory (KAM)  52 , for example. KAM  52  may be used to store various operating variables while CPU  46  is powered down. The computer-readable storage media may be implemented using any of a number of known memory devices such as PROMs (programmable read-only memory), EPROMs (electrically PROM), EEPROMs (electrically erasable PROM), flash memory, or any other electric, magnetic, optical, or combination memory devices capable of storing data, some of which represent executable instructions, used by CPU  46  in controlling the engine or vehicle into which the engine is mounted. The computer-readable storage media may also include floppy disks, CD-ROMs, hard disks, and the like. CPU  46  communicates with various sensors and actuators via an input/output (I/O) interface  44 . Examples of items that are actuated under control by CPU  46 , through I/O interface  44 , are fuel injection timing, fuel injection rate, fuel injection duration, throttle valve  32  position, spark plug  28  timing, EGR valve  18 , etc. Various other sensors  42  and specific sensors (engine speed sensor  22 , cylinder pressure transducer sensor  30 , engine coolant sensor  38 , manifold absolute pressure sensor  31 , exhaust gas component sensor  24 , air temperature sensor  34 , and mass air flow sensor  36 ) communicate input through I/O interface  44  and may indicate engine rotational speed, vehicle speed, coolant temperature, manifold pressure, pedal position, cylinder pressure, throttle valve position, air temperature, exhaust temperature, exhaust stoichiometry, exhaust component concentration, and air flow. Some ECU  40  architectures do not contain MMU  48 . If no MMU  48  is employed, CPU  46  manages data and connects directly to ROM  50 , RAM  54 , and KAM  52 . Of course, the present invention could utilize more than one CPU  46  to provide engine control and ECU  40  may contain multiple ROM  50 , RAM  54 , and KAM  52  coupled to MMU  48  or CPU  46  depending upon the particular application.  
         [0019]     A flowchart showing an embodiment of the present invention is shown in  FIG. 3 . It is determined whether the engine was remotely started in block  102 . If not, the normal engine control algorithms, which are outside the present invention, are followed. If the engine was remotely started, control passes to block  104  in which it is determined whether the engine is operating in a closed-loop control mode. Closed-loop control will be discussed in more detail below. Briefly, the exhaust gas oxygen sensor, which forms the basis for closed-loop control, provides a reliable signal only when sufficiently warm. Closed-loop control is delayed until such a reliable signal is obtain. When closed-loop control is determined in block  104 , control passes to block  106  in which an air/fuel ratio based on measurements of air flow and fuel flow is computed. Control passes to block  108  in which an error is computed: measured air/fuel ratio minus stoichiometric air/fuel ratio, the latter discussed in more detail below. In block  110 , it is determined whether the error exceeds a threshold. If not, control is passed back to block  106  for continuous monitoring. If a positive result from block  110  is obtained, control passes to block  114  in which it is determined whether the engine is under operator control. If so, normal operation, according to control algorithms outside the present invention, is accessed in block  116 . If the operator has taken over control, it is likely that the operator is about to remove the vehicle from an enclosure thereby taking mitigating action to overcome the issue of the two air/fuel ratios deviating from each other. In an alternative embodiment, blocks  114  and  116  are not included. In this alternative embodiment, a positive result from block  110  feeds into block  118 , in which the engine is shut down.  
         [0020]     In block  114  of  FIG. 4 , it is determined if the engine is under operator control. In this context, this means has the operator taking over control beyond the initial starting of the engine remotely. Determination of taking over control is based on one of: inserting the key into the ignition, turning the key in the ignition switch, opening the door of the vehicle, moving a gear shift lever, depressing the clutch, as examples.  
         [0021]     Modern engines use a catalytic converter to oxidize unburned hydrocarbons and carbon monoxide to water and carbon dioxide and to reduce nitrogen oxides to nitrogen and oxygen. The catalytic converter operates with a high efficiency at carrying out these reactions when it is fed gases at a stoichiometric air/fuel ratio, i.e., the air and fuel fed to the engine are in such a proportion that all of the air and fuel could theoretically react to produce only carbon dioxide, water, and unreacted nitrogen from the air. EGO sensor  24  provides a low voltage when the gases it contacts are lean of stoichiometric and a high voltage when the gases are rich of stoichiometric. By biasing the air/fuel mixture very slightly rich and then very slightly lean, the average air/fuel ratio can be maintained very close to stoichiometric with adjustments to the air/fuel ratio being feedback controlled on EGO sensor  24  signal. Such closed-loop control is used in nearly all production engines and is well known by those skilled in the art.  
         [0022]     If vehicle  4  is within a poorly ventilated enclosure  2 , it is possible that the air being inducted into engine  10  becomes substantively diluted. If the inducted air is diluted, more air is required to provide the amount of oxygen needed to provide a stoichiometric mixture. Commonly, during engine idle, the amount of air supplied to the engine is controlled to maintain a desired engine idle speed. Thus, if the air being inducted into the engine does not provide enough oxygen to burn the fuel, the fueling rate would drop slightly causing engine speed to drop. To maintain engine speed, throttle  32  would be caused to open slightly to induct more air. Alternatively, an idle air bypass valve (not shown) would be opened further to supply more air to engine  10 . Under this feedback strategy where air is controlled to maintain engine speed and fuel is controlled to maintain stoichiometric conditions in the exhaust, EGO sensor  24  would continue to indicate that the engine is operating at stoichiometric air/fuel ratio, regardless of the amount of exhaust gas dilution. Stoichiometric air/fuel ratio for gasoline is about 14.6 on a mass basis. A measure of the mass of air and the mass of fuel being supplied to the engine would indicate that the mass of air had increased when there is diluent in the air, thus causing the air/fuel ratio based on such a measurement to increase.  
         [0023]     Referring now to  FIG. 4 , percent diluent in the induction air (x-axis) is plotted versus air/fuel (y-axis). X % on the x-axis signifies the maximum acceptable diluent fraction. The air/fuel from the EGO sensor is a constant regardless of the amount of diluent. Furthermore, that constant is the stoichiometric air/fuel. The EGO sensor signal is employed in practice to ensure that a stoichiometric amount of air and fuel is supplied to the engine. The EGO sensor has no way of determining that the air is diluted with exhaust gases necessitating a higher mass of the diluted air to be delivered to the engine to provide the same power. Thus, the dashed line in  FIG. 4  signifies the constant air/fuel because of feedback control on the EGO sensor. A solid line in  FIG. 4  indicates how the air/fuel based on measurement of air and fuel flow increases when the amount of diluent in the air increases. At X % diluent, the deviation in the two air/fuel ratios is shown as e thresh , the threshold error. Error, e, is defined as: e=A/F meas −A/F stoich . As discussed above, the engine is to be shut off when e exceeds e thresh , which indicates that the amount of diluent in the inducted air is greater than X%, the maximum acceptable level of diluent.  
         [0024]     Continuing to refer to  FIG. 4 , the A/F stoich  is the stoichiometric air/fuel, which as discussed above, is  14 . 6  for gasoline. The stoichiometric air/fuel is other than  14 . 6  for alternative fuels such as hydrogen, natural gas, liquid petroleum gas, biofuels, alcohols, etc. Either stoichiometric air/fuel is a known quantity, or in the case of gasohols, which could have various percentages of alcohol in gasoline, it is known to use a sensor in the fuel tank or other estimating means to determine the percent of alcohol in the fuel, thereby allowing the computation of the stoichiometric air/fuel.  
         [0025]     Typically fuel flow is measured based on the pressure in the fuel injection system and the fuel pulse width, that is, the time that the fuel injector is open. This example is given for illustration purposes only and not intended to be limiting to the present invention. There are two common methods by which mass airflow is measured on production vehicles. These are known by those skilled in the art as speed-density and MAF, for mass-air flow. The former method relies on a measure of the pressure in the intake manifold downstream of throttle  32  and an engine speed sensor  22 . Additionally, the volume of air inducted into engine cylinders each intake event must be known. The mass of air inducted into the engine is computed therefrom. Alternatively, a mass flow sensor  36  is placed upstream of throttle  32  providing the desired quantity directly.  
         [0026]     After engine  10  has been shut down due to a deviation in the two air/fuel ratios, the operator of the vehicle may desire to restart the engine and drive the vehicle away. In one embodiment of the present invention, the engine remains disabled for a period of time before restart is allowed. This period of time is based on the time history of the measured air/fuel ratio. That is, if the measured air/fuel ratio rises rapidly, it indicates that vehicle  4  is in a very small and/or very well sealed enclosure  2 . It is likely to take longer, in this situation, for the air in enclosure  2  to be refreshed such that it has significantly less than the acceptable concentration of diluent. Conversely, if the measured air/fuel ratio very slowly rises, indicating that diluent concentration is slowly increasing in the air in enclosure  2 , the time until restart is shorter than the former scenario.  
         [0027]     Referring to  FIG. 5 , after engine  10  has been shut down (block  118  as shown in both  FIGS. 3 and 5 ), control is passed to block  120  in which the time history of the measured air/fuel is analyzed to determine an appropriate delay time. Control then passes to block  122 , in which ECU  40  waits for an operator request for a restart. In block  124 , the actual time delay since engine  10  was shutdown is compared with the minimum delay time computed in block  120 . If the actual delay time exceeds the minimum delay time, a restart is allowed. Otherwise, engine  10  is maintained in the shutdown condition until such minimum delay time has passed.  
         [0028]     Referring now to  FIG. 6 , one example of how minimum delay time could be computed is provided. In block  120  of  FIG. 5 , A/F meas  is analyzed. In the particular example of  FIG. 6 , the time rate of change of A/F meas  is determined. If the slope of A/F meas  is high, this indicates a small or well sealed enclosure  2  and that it is likely to take longer for the air in enclosure  2  to return to a concentration of exhausts gases less than the acceptable dilution amount. Thus, the minimum delay time is greater.  
         [0029]     Referring now to  FIG. 7 , an alternative embodiment is employed for engine restart. Starting with block  118 , the engine is shut down. Control passes to block  130  in which a code in ECU  40  is set indicating that the engine was shut down due to a problem with excess exhaust gas dilution in the air. The operator restarts in block  132 . In block  133 , it is determined whether the code was set in block  130 . If not, control passes to block  116 , normal operation. If the code was set, control passes to block  134  in which an algorithm similar to that in  FIG. 3  is followed. That is, the measured air/fuel is determined in block  136 ; the difference between measured and stoichiometric air/fuel is computed in block  138 ; and the difference is compared to a threshold error in block  140 . If greater than the threshold error, control passes to block  118  to shut down the engine. If less than the threshold error, control passes to block  142  to clear the error code and resume normal operation in block  116 .  
         [0030]     While several modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize alternative designs and embodiments for practicing the invention. The above-described embodiments are intended to be illustrative of the invention, which may be modified within the scope of the following claims.