Abstract:
A method of cooling an internal combustion engine having a first group of fuel injectors supplying fuel to a first group of injectors and a second group of fuel injectors supplying fuel to a second group of cylinders, the method including the steps of measuring the temperature of the engine, determining if the temperature of the engine exceeds a predetermined temperature threshold, shutting off the first group of fuel injectors to the first number of cylinders where air is pumped through the first number of cylinders to cool the first number of cylinders, energizing the second group of fuel injectors to the second group of cylinders to provide an air/fuel mixture to the second group of cylinders to drive the engine, shutting off at least one of the second group of fuel injectors to the second group of cylinders to pump air through at least one of the second group of cylinders.

Description:
TECHNICAL FIELD 
     The present invention relates to a method and apparatus for controlling the air fuel mixture supplied to an internal combustion engine. More specifically, the present invention relates to a method and apparatus for controlling the air/fuel mixture to an internal combustion engine during the period of a cooling system failure to extend the operating time of the engine. 
     BACKGROUND OF THE INVENTION 
     It is well known in the art of internal combustion engines that extended operation of an internal combustion engine after a cooling system failure will result in excessive engine temperature. When a failure occurs that results in loss of engine coolant or a blockage prevents the circulation of the coolant, the temperature will rise relatively quickly to a level that may result in engine damage. An operator of the vehicle will have a limited time and operating range to drive the vehicle to a location where the cooling system may be repaired to allow normal engine operation. It would be desirable upon the occurrence of a cooling system failure to provide the vehicle with an alternate cooling system independent of the liquid coolant system and/or to extend the safe operating time of the vehicle. 
     SUMMARY OF THE INVENTION 
     The present invention is a method and apparatus for providing an alternate cooling system for an internal combustion engine to allow operation of the internal combustion engine for an extended period of time upon the failure of the primary conventional liquid coolant system (limp home or “camel” mode). The present invention alternately inhibits the fuel supply to different cylinders or groups of cylinders in an internal combustion engine for predetermined time periods so that each of the cylinders or groups of cylinders alternately induct an air/fuel mixture and air. Accordingly, the cylinders will soak or cool while inducting air only. The air fuel ratio of the mixture inducted is controlled by the position of the throttle plate and air/fuel mixture. U.S. Pat. No. 4,473,045 to Bolander et al. describes a method and apparatus for controlling fuel to an engine during coolant failure and is expressly incorporated by reference herein. 
     It is an object of the present invention to provide a system for controlling the operation of an internal combustion engine subsequent to a coolant system failure. 
     It is another object to provide an alternate cooling system for an internal combustion engine that may operate without liquid engine coolant. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The various advantages of the present invention will become apparent to one skilled in the art upon reading the following specification and by reference to the drawings in which: 
     FIG. 1 is a diagrammatic drawing of a fuel injection system for an internal combustion engine incorporating the principles of this invention; 
     FIG. 2 is a diagrammatic drawing of the cylinder arrangement for an internal combustion engine; and 
     FIG. 3 is a flow chart of the preferred method of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIGS. 1 and 2, there is illustrated a fuel control system  10  for a port fuel injected eight-cylinder internal combustion engine (ICE)  12  to drive or propel a vehicle  14 . The ICE  12  includes two banks of cylinders  16  with each cylinder  16  being provided with fuel at its intake port by an electromagnetic fuel injector  18  which is supplied with pressurized fuel. When energized, each fuel injector  18  opens to supply metered amounts of fuel to the intake port of the respective cylinders  16 . 
     While a port fuel injected ICE is shown in the present embodiment, the ICE  12  may comprise a direct injection ICE in alternate embodiments. Furthermore, while an eight-cylinder engine is described in the present invention, any multi-cylinder engine configuration is considered within the scope of the present invention. 
     Referring to FIG. 1, an engine control module (ECM)  20  is shown and takes the form of a digital computer, controller, microprocessor, or other similar control device, but is not limited to such. The ECM  20  includes a central processing unit (CPU)  22  which executes an operating program stored in nonvolatile memory (NVM)  24  such as ROM, EPROM, flash memory, or other similar memory devices, but is not limited to such. The NVM  24  also stores tables, calibration values, and constants utilized to control the ICE  12 . Contained within the CPU  22  are conventional counters, registers, accumulators, flip flops, etc., along with a clock providing a high frequency clock signal for the timing of the CPU  22  and other devices in the ECM  20 . 
     The ECM  20  further includes a random access memory (RAM)  26  in which data may be temporarily stored and from which data may be read at various address locations determined in accord with the program stored in NVM  24 . A power control unit (PCU)  28  in the ECM  20  receives power from a conventional car battery to power the ECM  20 . The PCU  28  conditions the car battery voltage to provide all the voltage ranges and forms required by the ECM  20 . 
     The ECM  20  also includes an input/output (IO) circuit  30  and analog to digital unit (ADU)  38  which may be connected to multiple sensors, actuators and indicators. The sensors may include engine or wheel speed sensors such as proximity switches or hall effect sensors, engine temperature sensors, manifold air pressure and flow sensors, oxygen sensors, coolant level switches, coolant temperature switches, and any other sensors which may be used for the operation of an ICE. The outputs of the I/O circuit  30  energize, the fuel injectors  18 , light pilot lights or indicators such as a warning indicator  40  for high engine temperature, high coolant temperature, or low coolant level, and any other actuators or indicators which may be used in an ICE. 
     The I/O circuit  30  includes an input counter section to receive a pulsed output from an engine speed sensor  41 , a distributor pulse output  43  which generates a pulse for each engine cycle, and/or a cam shaft position/speed pulse sensor  45 . The pulses from the engine speed sensor  41  are used to determine engine speed, and the distributor pulses or camshaft pulses are used to determine engine crankshaft speed and position and thus cylinder  16  positions for the initiating and energization of the fuel injectors  18 . 
     In alternate embodiments of the present invention, an automotive communication network interface  34  is contained within the ECM  20  to provide communication to sensors and other devices over an automotive communications network. The automotive communications network may comprise any known vehicle communication system such as IES-CAN, GMLAN, KWP2000, J1850, CCD, or J1939, but is not limited to such. In the present invention, engine coolant level or a high coolant temperature may be sensed by a discrete signal to represent the state of coolant in the ICE  12 . Alternatively, a sensor providing an analog signal representative of coolant level or coolant temperature may also be used. The discrete signal is provided by a conventional liquid level-sensing element or heat sensitive switch  36  in the cooling system and applied to a discrete input of the I/O circuit  30 . 
     Analog signals representing conditions upon which the injection pulse widths are based for the fuel injectors  18  for normal operation and determining a coolant system failure are supplied to the analog inputs of the ADU  38 . In the preferred embodiment, the analog signals include a manifold absolute pressure (MAP) signal provided by a conventional pressure sensor, an engine metal temperature or coolant temperature signal provided by a conventional temperature sensing element. The coolant temperature sensing element is preferably located near the flow of exhaust gases. 
     The CPU  22  reads and stores the high or low state of the discrete inputs and the analog inputs in a designated RAM  26  location in accord with the operating program stored in NVM  24 . The CPU  22  then executes programming to determine further actions for the ICE  12 . 
     In general, and in the absence of a coolant system failure, the fuel injectors  18  are energized with each intake event for each cylinder  18  for a time duration determined to provided a predetermined air/fuel ratio such as the stoichometric ratio for normal vehicle operation. This is accomplished by calculating the required pulse width based on mass air flow determined from the measured manifold absolute pressure and the volume of the cylinders  16 , the known injector  18  flow rates, and the desired air/fuel ratio. The injection pulses are issued to the fuel injectors  18  and any required electrical drivers, via the I/O circuit  30  under control of the CPU  22 , for providing the desired injection time, flow rates, and/or injection quantity. In the event of a coolant system failure which results in a loss of coolant or an increase in the engine and/or coolant temperature above a predetermined level, the CPU  22  outputs a signal via the I/O circuit  30  to energize the warning indicator  40  to indicate the coolant failure. At the same time, the CPU  22  alternately inhibits the supply of fuel to a cylinder  16  or groups of cylinders  16  for a predetermined numbers of engine cycles or predetermined time periods substantially greater than the period of engine cycle. The cylinder  16  or cylinders  16  will then alternately induct an air/fuel mixture and air. The cylinder  16  or group of cylinders  16  inducting only air will be cooled by the inducted air. After a predetermined number of engine cycles or predetermined time period, such as 15 seconds, alternate cylinders  16  or groups of cylinders  16  will induct air to also be cooled, extending the safe operating time of the ICE  12 . The periodic cooling of each cylinder  16  or group of cylinders  16  decreases or in some cases eliminates the increase of heat in the ICE  12  due to the coolant failure. 
     In the preferred embodiment, a V-8 internal combustion engine  12  may be configured with the fuel control system  10  of the present invention, as seen in FIG.  2 . The cylinders  16  have been numbered 1-8 to designate their positions in FIG.  2  and the firing sequence of their associated fuel injectors  18 . When a loss of coolant, as detected by the coolant level sensor or a coolant temperature sensor  36  is detected in the ICE  12 , the system  10  will enter the limp or camel mode. This mode fires some injectors  18  and skips other according to a predetermined sequence. The firing cylinders  16  provided with fuel and spark provide power to move the vehicle  14 . The non-firing cylinders  16  deprived of fuel pump only air to cool or soak the ICE  12 . 
     The working injectors  18  and cylinders  16 , in a first step, decrease from eight cylinders to four cylinders by dropping out one fuel injector  18  per two revolutions of the crankshaft of the ICE  12 . This gradual deactivation of injectors  18  will smoothly transition the ICE  12  between the use of eight cylinders  16  to the use of a four cylinder  16  group. When four cylinder  16  injecting is reached, the present invention will then move to injecting fuel in only three of the four cylinders  16  of this group. After a predetermined number of engine cycles, the switch is made to supply fuel to a new group of four cylinders  16  and eventually to three of the four cylinders  16  of this new group. This alternation of providing fuel to four cylinder  16  groups followed by providing fuel to only three of the four cylinders  16  in the group will continue until the coolant system failure is corrected. This method provides additional soak time or cooling time to the one cylinder  16  not firing in the group of four cylinders  16 , increasing the operating range of the vehicle  14  and substantially preventing an increase of temperature into the range that may cause engine damage. 
     Furthermore, the reduced power level provided by only three or four cylinders  16  propelling the vehicle  14  will indicate to the operator, in conjunction with the warning indicator  40 , that there is a problem and maintenance is required. If the operator chooses to continue to drive the vehicle  14 , the throttle will have to be wide open in order to maintain a normal cruising speed such as 50 mph. The increased airflow caused by the wide open throttle will result in more cooling to the ICE  12  and provide a physical limit on vehicle speed. 
     Referring to FIG.  2  and the flow chart of FIG. 3, in the preferred embodiment of the present invention, at block  50 , the sequence 1-8-7-2-6-5-4-3 is followed in firing the fuel injectors  18  for cylinders  16  during normal operation of the ICE  12 . Upon detection of a coolant failure or high coolant temperature at block  52 , the system  10  will enter the camel mode at block  54  to systematically shut off a series of fuel injectors  18  until only a group of four cylinders, 1-7-6-4, are firing and the remaining cylinders  16  are cooling. After a first number of predetermined engine cycles at block  56 , the fuel injector  18  providing fuel to cylinder  1  will be shut off, leaving cylinders 1-7-6-4 firing and cylinder  1  cooling. At block  58 , after a second number of predetermined of engine cycles, a new group fuel injectors  18  providing fuel for four cylinders, 8-2-5-3, will fire and cylinders 1-7-6-4 will pump air to cool. At block  60 , after a third number of predetermined engine cycles, the fuel injector  18  providing fuel to cylinder  2  will be shut off, leaving cylinders 8-5-3 firing and cylinder  2  cooling. At block  62 , after a fourth number of predetermined engine cycles, a group of fuel injectors  18  providing fuel for four cylinders 1-2-6-5 will fire. At block  64 , after a fifth number of predetermined engine cycles the fuel injector  18  to cylinder  5  will be shut off, leaving cylinders 1-2-6 firing and cylinder  5  cooling. At block  66 , after a sixth number of predetermined engine cycles, a group of fuel injectors  18  for four cylinders 8-7-4-3 will fire. At block  68 , after a seventh number of predetermined engine cycles, the fuel injector  18  providing fuel to cylinder  8  will be shut off, leaving cylinders 7-4-3 firing and cylinder  8  cooling. At block  70 , after an eighth number of predetermined engine cycles, a group of fuel injectors providing fuel to cylinders 1-8-5-4 will fire. At block  72 , after a ninth number of predetermined engine cycles, the fuel injector  18  providing fuel to cylinder  4  will be shut off, leaving cylinders 1-8-5 firing and cylinder  4  cooling. At block  74 , after a tenth number of predetermined engine cycles, a group of fuel injectors  18  providing fuel for cylinders 7-2-6-3 will fire. At block  76 , after an eleventh number of predetermined engine cycles, the fuel injector  18  providing fuel to cylinder  3  will be shut off, leaving cylinders 7-2-6 firing and cylinder  3  cooling. At block  78  the system  10  is checked to see if the coolant system failure has been corrected. If the coolant system failure has been corrected, then the routine will continue to block  50  and execute normal operation. If the cooling system failure has not been corrected, the routine will continue to block  54  and continue with the camel mode. In the preferred embodiment, all of the predetermined numbers of engine cycles are equal, but in alternate embodiments the predetermined numbers of engine cycles may be any number of engine cycles. Furthermore, in alternate embodiments of the present invention, the routine may begin normal operation at step  50  whenever the coolant system failure has been corrected. 
     While this invention has been described in terms of some specific embodiments, it will be appreciated that other forms can readily be adapted by one skilled in the art. Accordingly, the scope of this invention is to be considered limited only by the following claims.