Patent Publication Number: US-6668795-B1

Title: Controller with feed-back system

Description:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT 
     The present invention relates to an engine controller for controlling an engine operation actuator (for example, a throttle, a fuel injector or the like) to generate an output torque and power in consideration of an actual engine condition (for example, an output torque, an output power (estimated from output torque and engine rotational speed), an intake air mass flow rate, an opening degree of throttle or the like). 
     JP-A-10-212989 discloses an engine controller in which an operation degree of an engine operation actuator is adjusted in accordance with an actual engine condition and a circumferential condition of the engine. 
     JP-A-10-238394 discloses how to detect a trouble of throttle. 
     OBJECT AND SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an apparatus (for example, engine) controller with a feed-back control system, in which controller an output of the apparatus is safely controllable when a trouble of an element used for the controller occurs. 
     In an engine controller for controlling an engine condition adjusting device in an engine in consideration of an actual engine condition measured by an engine condition measuring sensor, comprising, an interface device for generating an input signal corresponding to a desired engine condition, and an instruction signal generator for determining an instruction signal to be input to the engine condition adjusting device for controlling an operation degree of the engine condition adjusting device on the basis of a comparison between the input signal and an actual engine condition signal corresponding to the actual engine condition so that a difference between the desired engine condition and the measured actual engine condition is decreased, 
     since the instruction signal for controlling the engine condition adjusting device is determined on the basis of the comparison between the input signal and the actual engine condition signal when normalities of the interface device, the engine condition changing device and the engine condition measuring sensor are detected, and is determined on the basis of the input signal while preventing the instruction signal from being determined on the basis of the comparison between the input signal and the actual engine condition signal when an abnormality of at least one of the interface device, the engine condition changing device and the engine condition measuring sensor is detected, a degree of an excessive or uncontrollable engine operation or output caused by the troubled at least one of the interface device, the engine condition changing device and the engine condition measuring sensor is kept small, or an undesirable or uncontrollable engine operation or output is prevented from being enlarged by a multiplicative trouble effect among the interface device, the engine condition changing device and the engine condition measuring sensor by returning to a simple control based on the input signal without the comparison between the input signal and the actual engine condition signal. 
     The interface device may generate the input signal corresponding to a desired engine output power ordered from an accelerator outside of the engine controller. The instruction signal for controlling the engine condition adjusting device may be determined on the basis of the comparison between the input signal generated by the interface device and the actual engine condition signal when the normalities of the interface device, the engine condition changing device and the engine condition measuring sensor are detected, and is determined on the basis of the input signal corresponding to the desired engine output power ordered from the accelerator while preventing the instruction signal from being determined on the basis of the comparison between the input signal generated by the interface device and the actual engine condition signal when the abnormality of the at least one of the interface device, the engine condition changing device and the engine condition measuring sensor is detected. 
     The interface device may generate the input signal corresponding to a desired engine output power, a desired engine output torque, a desired injection rate of a fuel to be injected into the engine or a desired mass flow rate of an intake air to be taken into the engine, as the desired engine condition. The input signal corresponding to the desired mass flow rate of the intake air to be taken into the engine may be modified in accordance with a desired air-fuel ratio. 
     The instruction signal generator may determine the instruction signal for controlling an opening degree of an electrically controlled throttle as the engine condition adjusting device. The instruction signal may be modified in accordance with a desired air-fuel ratio. The instruction signal generator determines the instruction signal for controlling an injection rate of a fuel to be injected into the engine. 
     The actual engine condition signal may correspond to an actual mass flow rate of an intake air to be taken into the engine, an actual engine output torque or an actual engine output power (which may be estimated from output torque and engine rotational speed). The actual fuel injection rate may be estimated from the actual engine output torque or the actual engine output power per engine rotation. The actual mass flow rate of the intake air to be taken into the engine corresponds to the actual engine output power when the air-fuel ratio is kept at a certain degree, so that the actual engine output power is estimated from the actual mass flow rate of the intake air. The desired injection rate of the fuel to be injected into the engine corresponds to the desired engine output power or torque. The desired injection rate of the fuel per engine combustion cycle or engine output rotational speed corresponds to the desired engine output power per engine combustion cycle or engine output rotational speed, or the desired engine output torque. 
     The instruction signal for controlling the engine condition adjusting device may be determined on the basis of the comparison between the input signal corresponding to the desired engine output torque and the actual engine condition signal corresponding to the actual engine output torque when a normality of a torque sensor of the engine condition measuring sensor is detected, and be determined on the basis of the input signal corresponding to the desired engine output power (ordered by, for example, an accelerator outside of the controller) while preventing the instruction signal from being determined on the basis of the comparison between the input signal corresponding to the desired engine output torque and the actual engine condition signal corresponding to the actual engine output torque when the abnormality of the engine condition measuring sensor for measuring the actual engine output torque is detected. 
     The interface device may generate the input signal corresponding to the desired engine output power or torque on the basis of an engine output rotational speed and an instructed engine output power instructed from an accelerator outside of the engine controller. 
     When at least of the engine condition changing device and the engine condition measuring sensor includes a communication path through which an information is transmitted with respect to the engine controller, the abnormality of the at least one of the engine condition changing device and the engine condition measuring sensor may be the abnormality of the communication path. When a throttle of the engine condition changing device for controlling the mass flow rate of the intake air to be taken into the engine includes at least one sensor for generating an output signal corresponding to an opening degree of the throttle, the abnormality of the engine condition changing device may be an abnormality of the sensor. When the interface device generates the input signal in accordance with an output signal of at least one sensor outside of the engine controller for measuring an operated degree of an accelerator outside of the engine controller, and the operated degree of the accelerator corresponds to an ordered engine output power ordered by the accelerator, the abnormality of the interface device may be an abnormality of the sensor. 
     The operation degree of the engine condition adjusting device may be an opening degree of the throttle for adjusting the mass flow rate of the intake air to be taken into the engine, or the injection rate of the fuel to be injected into the engine. 
     At least one of a prevention of forming a lean fuel air mixture, a decrease of an upper limit of an injection rate of a fuel to be injected into the engine, a decrease of an upper limit of an opening degree of a throttle as the engine condition adjusting device, a close of the throttle and a prevention of supplying an electric current to the throttle may be carried out in response to the abnormality of the at least one of the interface device, the engine condition changing device and the engine condition measuring sensor is detected. Which is selected to be carried out from the prevention of forming the lean fuel air mixture, the decrease of the upper limit of the injection rate of the fuel to be injected into the engine, the decrease of the upper limit of the opening degree of the throttle, the close of the throttle and the prevention of supplying the electric current to the throttle may be determined in accordance with a degree of the abnormality of the at least one of the interface device, the engine condition changing device and the engine condition measuring sensor. 
     The abnormality of the sensor may detected when a magnitude of the output signal of the sensor is in a range other than a predetermined acceptable range. The abnormality of the sensor may be detected when a difference between a plurality of the output signals of the sensors is more than a predetermined acceptable level. The abnormality of the engine condition changing device may be detected when a difference between an actual opening degree of the throttle of the engine condition changing device and a desired opening degree of the throttle is kept more than a predetermined acceptable level for a time period more than a predetermined acceptable time period. The abnormality of the engine condition changing device may be detected when an electric current supplied to an electrically controlled throttle of the engine condition changing device is kept more than a predetermined acceptable level for a time period more than a predetermined acceptable time period. The abnormality of the engine condition measuring sensor may be detected when a magnitude of the actual engine condition signal corresponding to the actual mass flow rate of the intake air to be taken into the engine is in a range other than a predetermined acceptable range. The abnormality of the engine condition measuring sensor may be detected when a difference between the actual engine condition signals which are generated by a plurality of the engine condition measuring sensors and correspond respectively to actual mass flow rates of the intake air to be taken into the engine is more than a predetermined acceptable level. The abnormality of the engine condition measuring sensor may be detected when a difference between the actual mass flow rate of the intake air to be taken into the engine measured by the engine condition measuring sensor and a mass flow rate of the intake air to be taken into the engine estimated from the engine output rotational speed and the opening degree of the throttle of the engine condition changing device is more than a predetermined acceptable level. The abnormality of the engine condition measuring sensor may be detected when a magnitude of the actual engine condition signal corresponding to the actual engine condition is in a range other than a predetermined acceptable range. The abnormality of the engine condition changing device may be detected when a difference between the input signal and the actual engine condition signal is more than a predetermined level. 
     The desired condition corresponding to the input signal compared to the actual engine condition signal to determined the instruction signal when the normalities of the interface device, the engine condition changing device and the engine condition measuring sensor are detected may be different from the desired condition corresponding to the input signal on the basis of which the instruction signal is determined when the abnormality of the at least one of the interface device, the engine condition changing device and the engine condition measuring sensor is detected. The desired condition corresponding to the input signal compared to the actual engine condition signal to determined the instruction signal when the normalities of the interface device, the engine condition changing device and the engine condition measuring sensor are detected may be equal to the desired condition corresponding to the input signal on the basis of which the instruction signal is determined when the abnormality of the at least one of the interface device, the engine condition changing device and the engine condition measuring sensor is detected. 
     In a controller for controlling an apparatus condition adjusting device in an apparatus in consideration of an actual apparatus condition measured by an apparatus condition measuring sensor, comprising, an interface device for generating an input signal corresponding to a desired apparatus condition, and an instruction signal generator for determining an instruction signal to be input to the engine condition adjusting device for controlling an operation degree of the apparatus condition adjusting device on the basis of a comparison between the input signal and an actual apparatus condition signal corresponding to the actual apparatus condition so that a difference between the desired apparatus condition and the measured actual apparatus condition is minimized, 
     since the instruction signal for controlling the apparatus condition adjusting device is determined on the basis of the comparison between the input signal and the actual apparatus condition signal when a normality of at least one of the interface device, the apparatus condition changing device and the apparatus condition measuring sensor is detected, and is determined on the basis of the input signal while preventing the instruction signal from being determined on the basis of the comparison between the input signal and the actual apparatus condition signal when an abnormality of at least one of the interface device, the apparatus condition changing device and the apparatus condition measuring sensor is detected, a degree of an excessive or uncontrollable apparatus operation or output caused by the troubled at least one of the interface device, the apparatus condition changing device and the apparatus condition measuring sensor is kept small, or an undesirable or uncontrollable apparatus operation or output is prevented from being enlarged by a multiplicative trouble effect among the interface device, the apparatus condition changing device and the apparatus condition measuring sensor by returning to a simple control based on the input signal without the comparison between the input signal and the actual apparatus condition signal. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic view showing an engine with an engine controller of the invention. 
     FIG. 2 is a schematic view showing the engine controller of the invention. 
     FIG. 3 is a schematic view showing control diagrams and control data flow processes in the engine controller of the invention. 
     FIG. 4 is a schematic view showing control diagrams and control data flow processes in the engine controller of the invention. 
     FIG. 5 is a schematic view showing an embodiment of a feed-back system of the engine controller of the invention. 
     FIG. 6 is a schematic view showing another embodiment of a feed-back system of the engine controller of the invention. 
     FIG. 7 is a schematic view showing control data flow processes for detecting and evaluating an abnormality of the feed-back system of the engine controller of the invention. 
     FIG. 8 is a table for evaluating the abnormality of the feed-back system of the engine controller of the invention. 
     FIG. 9 is a table for evaluating the abnormality of the feed-back system of the engine controller of the invention. 
     FIG. 10 is a table for evaluating the abnormality of the feed-back system of the engine controller of the invention. 
     FIG. 11 is a diagram showing a logic for evaluating the abnormality of the feed-back system of the engine controller of the invention. 
     FIG. 12 is a table for evaluating the abnormality of the feed-back system of the engine controller of the invention. 
     FIG. 13 is a diagram showing relationships between an engine output torque, an engine output rotational speed and various combustion modes. 
     FIG. 14 is a diagram showing relationships among various combustion modes. 
     FIG. 15 is a table showing a relationship among the engine output rotational speed, an operated or opened degree of an accelerator, and an desired output power (corresponding to an desired fuel injection rate and/or a desired mass flow rate of an air to be supplied into the engine under a certain fuel-air ratio). 
     FIG. 16 is a block diagram showing a control unit containing the table of FIG.  15 . 
     FIG. 17 is a table showing a relationship between the operated or opened degree of an accelerator, and the desired output power (corresponding to the desired fuel injection rate and/or the desired mass flow rate of an air to be supplied into the engine under the certain fuel-air ratio). 
     FIG. 18 is a block diagram showing a control unit containing the table of FIG.  17 . 
     FIG. 19 is a diagram showing a relationship among a load switch condition, the desired output power TP 2  (corresponding to the desired fuel injection rate and/or the desired mass flow rate of an air to be supplied into the engine under the certain fuel-air ratio), a desired mass flow rate of an air to be supplied into the engine modified according to a variation of the fuel-air ratio, an actual mass flow rate of the air to be supplied into the engine, and an actual fuel injection rate, under a Stoichiometric combustion. 
     FIG. 20 is a diagram showing a relationship among a load switch condition, the desired output power TP 2  (corresponding to the desired fuel injection rate and/or the desired mass flow rate of an air to be supplied into the engine under the certain fuel-air ratio), a desired mass flow rate of an air to be supplied into the engine modified according to a variation of the fuel-air ratio, an actual mass flow rate of the air to be supplied into the engine, and an actual fuel injection rate, under a lean burn combustion. 
     FIG. 21 is a flow chart for determining the desired mass flow rate of the air to be supplied into the engine. 
     FIG. 22 is a diagram showing a relationship among an engine output rotational speed, a desired output power TP 2  (corresponding to the desired fuel injection rate and/or the desired mass flow rate of an air to be supplied into the engine under the certain fuel-air ratio), an opening degree of the throttle, a mass flow rate of an air supplied into the engine, and a fuel injection rate, in the engine of the invention. 
     FIG. 23 is a diagram showing an acceptable range of an accelerator sensor signal magnitude in a predetermined accelerator movable range. 
     FIG. 24 is a diagram showing an acceptable range of an accelerator sensor signal difference in a predetermined accelerator movable range. 
     FIG. 25 is a diagram showing an acceptable range of difference in accelerator sensor signal in a predetermined accelerator movable range. 
     FIG. 26 is a schematic view showing a structure of an electrically controlled throttle. 
     FIG. 27 is a diagram showing a relationship among a time, an actual throttle opening degree and a desired throttle opening degree. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     In the following description, a fuel injection rate corresponds to an actual fuel rate, a desired fuel injection rate, a desired mass flow rate of intake air, an actual mass flow rate of intake air, a desired output torque, an actual output torque and a desired output power per engine rotation, because when a certain (for example, Stoichiometric) fuel-air ratio is imaginarily fixedly set in a controller, the mass flow rate of intake air, the output torque and the output power per engine rotation is convertible from the fuel injection rate, and the mass flow rate of intake air under the certain (for example, Stoichiometric) fuel-air ratio can be converted to the mass flow rate of intake air under a desired fuel-air ratio by changing in accordance with a ratio between the certain fuel-air ratio and the desired fuel-air ratio the fuel injection rate corresponding to the desired mass flow rate of intake air under certain fuel-air ratio to a substitute fuel injection rate corresponding to the desired mass flow rate of intake air under the desired fuel-air ratio. 
     As shown in FIG. 1, an intake air to be supplied into an engine  507  flows into a collector  506  from an inlet  502   a  of an air cleaner  502  through a mass flow meter  503  for measuring a mass flow rate of intake air as the claimed engine condition measuring sensor and a throttle body  505  for controlling the mass flow rate of intake air as the claimed engine condition adjusting device containing a throttle valve  505   a . The intake air is distributed from the collector  506  to combustion chambers  507   c  in combustion cylinders  507   b  through intake air tubes  501  connected to the combustion cylinders  507   b.    
     A pressure of fuel is pressurized by a fuel pump  510  and regulated by a pressure regulator  512  at, for example, about 3 kg/cm 2  by a fuel pump  510 , and subsequently further pressurized by a fuel pump  511  and regulated by a pressure regulator  513  at, for example, about 30 kg/cm 2  so that the pressurized fuel is fed from a fuel tank  514  to a fuel line to which fuel injectors  509  are connected. The fuel injected by the fuel injectors  509  into the combustion chambers  507   c  is ignited by ignition plugs  508  energized by a high-voltage ignition signal generated by an ignition coil  522 . 
     The mass flow meter  503  generates a signal corresponding to the mass flow rate of intake air as the claimed actual engine condition, and the signal is input to a control unit  515  as the claimed controller. At least one throttle sensor (preferably two throttle sensors)  504  mounted on the throttle body  505  generates a signal corresponding to an opening degree of the throttle valve  505   a , and the signal is input to the control unit  515 . 
     A bypath tube  525  extending between an intake air tube  501  and an exhaust air tube  519  includes an EGR valve  524  for controlling a flow rate of an exhaust gas returning from the exhaust air tube  519  to the intake air tube  501 . A crank angle sensor  516  connected to an engine cam shaft (not shown) generates a signal REF corresponding to a phase of a crank shaft  507   d  (a combustion-expansion and exhaust phase and an air-intake and air compression phase) and a signal POS corresponding to an angular position of the crank shaft  507   d , and the signals are input to the control unit  515 . 
     An A/F sensor  518  mounted in the exhaust air tube  519  before a catalyst  520  generates a signal corresponding to a concentration of a component (for example, fuel) in the exhaust gas, and the signal is input to the control unit  515 . The control unit  515  includes an MPU  603  as the claimed instruction signal generator, a ROM  602 , a RAM  604  and an I/O interface LSI  601  as the claimed interface device for receiving various signals including a signal corresponding to a desired engine condition (for example, an engine output power or torque), a signal corresponding to the actual engine condition, a signal generated by each of the sensors above described and below described, and so forth. The control unit  515  treats the signals to generate instruction signals for controlling the throttle valve  505 , the fuel injector  509 , the ignition coil  522  and so forth. 
     As shown in FIGS. 3 and 4, the mass flow rate of intake air Qa measured by the mass flow meter  503  is converted to a basic fuel injection rate or basic fuel injection pulse width Tp 1  under the certain (preferably, Stoichiometric) fuel-air ratio combustion along a formula (Tp 1 =k*Qa/Ne) wherein Ne is an engine output rotational speed and k is a constant for forming the basic fuel injection rate Tp 1  for the certain (preferably, Stoichiometric) fuel-air ratio combustion with the mass flow rate of intake air Qa under the engine output rotational speed Ne. Under the certain (preferably, Stoichiometric) fuel-air ratio combustion, a modification of the fuel injection rate Tp 1  is adjusted at each of various levels of the fuel injection rate Tp 1  and each of various levels of the engine output rotational speed Ne by a fuel injection rate modification device  117  so that the fuel injection rate Tp 1  is correctly set or modified irrespective of an original characteristic deviation and/or characteristic change with the passage of time of the mass flow meter  503  and/or fuel injector  509 . 
     In a datum fuel injection rate determining device  101 , a datum fuel injection rate Tp 2  corresponding to a desired engine output power per engine rotation or torque, a desired mass flow rate of intake air under the certain (preferably, Stoichiometric) fuel-air ratio combustion, and a desired fuel injection rate is determined from the engine output rotational speed Ne, and a level of an ordered engine output power, for example, an operated degree of an accelerator outside of the controller or an desired engine output power per engine rotation or torque ordered by the controller or by a device outside of the controller. A relationship among the datum fuel injection rate Tp 2  under the certain (preferably, Stoichiometric) fuel-air ratio combustion, the level of the ordered engine output power and the engine output rotational speed Ne is predetermined substantially exactly along a relationship among the datum fuel injection rate Tp 1  for the certain (preferably, Stoichiometric) fuel-air ratio combustion, the level of the ordered engine output power and the engine output rotational speed Ne. The relationship among the datum fuel injection rate Tp 2  under the certain (preferably, Stoichiometric) fuel-air ratio combustion, the level of the ordered engine output power and the engine output rotational speed Ne may be modified in accordance with a variation of the datum fuel injection rate Tp 1  for the certain (preferably, Stoichiometric) fuel-air ratio combustion caused by the original characteristic deviation and/or characteristic change with the passage of time of the mass flow meter  503  and/or fuel injector  509 . 
     A fuel-air ratio, an ignition timing, a fuel injection timing and an EGR rate are determined from the datum fuel injection rate Tp 2  and the engine output rotational speed Ne for each of Stoichiometric fuel-air ratio combustion, homogeneous lean fuel-air mixture combustion and stratified charge lean fuel-air mixture combustion. Since the datum fuel injection rate Tp 2  corresponding to the desired engine output power per engine rotation or torque, the desired mass flow rate of intake air under the certain (preferably, Stoichiometric) fuel-air ratio combustion and the desired fuel injection rate also corresponds to an engine load or the operated degree of the accelerator. Under a common fuel-air ratio combustion, the datum fuel injection rate Tp 2  may be equal to the basic fuel injection rate Tp 1 . 
     A fuel-air ratio is determined on a fuel-ratio ratio map  104  for Stoichiometric fuel-air ratio combustion, a fuel-ratio ratio map  105  for homogeneous lean fuel-air mixture combustion, and a fuel-ratio ratio map  106  for stratified charge lean fuel-air mixture combustion. An ignition timing is determined on an ignition timing map  107  for Stoichiometric fuel-air ratio combustion, an ignition timing map  108  for homogeneous lean fuel-air mixture combustion, and an ignition timing map  109  for stratified charge lean fuel-air mixture combustion. A fuel injection timing is determined on a fuel injection timing map  110  for Stoichiometric fuel-air ratio combustion, a fuel injection timing map  111  for homogeneous lean fuel-air mixture combustion, and a fuel injection timing map  112  for stratified charge lean fuel-air mixture combustion. An EGR rate is determined on an EGR rate map  113  for Stoichiometric fuel-air ratio combustion, an EGR rate map  114  for homogeneous lean fuel-air mixture combustion, and an EGR rate map  115  for stratified charge lean fuel-air mixture combustion. 
     Which combustion is carried out, Stoichiometric fuel-air ratio combustion, homogeneous lean fuel-air mixture combustion, or stratified charge lean fuel-air mixture combustion is determined by a combustion mode switching device  120  as described below with reference to FIG.  14 . 
     An instruction signal for controlling the fuel injection rate or fuel injection pulse width is determined on the basis of the datum fuel injection rate Tp 2  with adding thereto a datum change value ΔTP 2  and a fuel injector idling value Ts and subsequently modifying the post-addition datum fuel injection rate Tp 2  in accordance with an O 2  modification coefficient and an F/B modification coefficient. If the Stoichiometric fuel-air ratio combustion is carried out, the post-addition datum fuel injection rate Tp 2  is modified on the basis of the basic fuel injection rate Tp 1  before being modified in accordance with an O 2  modification coefficient and an F/B modification coefficient. 
     A target value signal corresponding to a target fuel injection rate Tp 3  corresponding to a desired mass flow rate of intake air for controlling the mass flow rate of intake air is determined in a target value signal generator  124  on the basis of the datum fuel injection rate or desired mass flow rate of intake air Tp 2  under the certain (preferably, Stoichiometric) fuel-air ratio with adding thereto the datum change value ΔTP 2  and modified in accordance with a ratio between the certain (preferably, Stoichiometric) fuel-air ratio (for example,  14 , 7 ) and a desired fuel-air ratio (for example,  40 ). An instruction signal to be input to a driver  119  of the throttle valve  1103  for controlling an opening degree of the throttle valve  1103  to determine the actual mass flow rate of intake air for the desired mass flow rate of intake air is determined in an I-PD controller  118  on the basis of a comparison between the target fuel injection rate Tp 3  as the claimed input signal and the basic fuel injection rate Tp 1  as the claimed actual engine condition signal under the certain (preferably, Stoichiometric) fuel-air ratio combustion, that is, on the basis of a comparison between the desired mass flow rate of intake air and the measured actual mass flow rate of intake air Qa so that a difference between the desired mass flow rate of intake air and the measured actual mass flow rate of intake air Qa is decreased. 
     As shown in FIG. 5, if a trouble of the mass flow meter  503  as the claimed engine condition measuring sensor is detected in response to, for example, that a magnitude of an output signal of the mass flow meter  503  is in a range other than a predetermined range, a fail safe switching device  1101  supplies the instruction signal corresponding to an operated degree of an accelerator  2001  or a desired mass flow rate of intake air corresponding to a desired output power ordered by the accelerator  2001  to a drive controller  1102  of the throttle valve  1103 , instead of the instruction signal determined in the I-PD controller  118  on the basis of the comparison between the desired mass flow rate of intake air corresponding to the desired output power and the actual mass flow rate of intake air. The desired mass flow rate of intake air corresponding to the desired output power is predetermined in an interface device  101  on the basis of the operated degree of the accelerator  2001  and the engine output rotational speed, and subsequently modified in the target value signal generator  124  in accordance with a ratio between the certain (preferably, Stoichiometric) fuel-air ratio (for example, 14,7) and the desired fuel-air ratio. 
     As shown in FIG. 6, if a trouble of a torque sensor  1107  for generating an actual engine condition signal corresponding to an actual engine output torque as the claimed engine condition measuring sensor is detected in response to, for example, that a magnitude of an output signal of the torque sensor  1107  is in a range other than a predetermined range, the fail safe switching device  1101  supplies the instruction signal corresponding to the desired mass flow rate of intake air under the certain (preferably, Stoichiometric) fuel-air ratio corresponding to the desired output power determined in the interface device  101  on the basis of the operated degree of the accelerator  2001  and the engine output rotational speed to the drive controller  1102  of the throttle valve  1103  through the target value signal generator  124 , instead of the instruction signal determined in a torque comparator  1106  on the basis of a comparison between a desired engine output torque corresponding to the desired output power and an actual engine output torque measured by the torque sensor  1107 . The desired engine output torque is determined in an interface device  1105  on the basis of the operated degree of the accelerator  2001  and the engine output rotational speed. 
     As shown in FIG. 7, an abnormality detection or evaluation is carried out in an abnormality detecting device  10  and the fail safe switching device  1101 . The abnormality detecting device  10  includes an accelerator abnormality detecting device  11  for determining, as sown in FIG. 12, an abnormality level of OK, CA(cautionary) or NG(no-good) of the accelerator  2001  from signals APS 1  and APS 2  of the sensors  521  corresponding to the operated degree of the accelerator, a throttle abnormality detecting device  12  for determining, as shown in FIGS. 10 and 11, an abnormality level of OK, CA(cautionary) or NG(no-good) of the throttle valve  1103  from output signals TPS 1  and TPS 2  of the sensors  504  corresponding to the opened degree of the throttle valve  1103  and a signal corresponding to a condition of a communication line or device between the sensors and the controller, a mass flow meter abnormality detecting device  13  for determining an abnormality level of OK, CA(cautionary) or NG(no-good) of the mass flow meter  503  for measuring the mass flow rate of the intake air from an output signal of the mass flow meter  503  and the engine output rotational speed. The fail safe switching device  1101  determines, as shown in FIG. 8, a generic abnormality level of A-F (A: normal level, F: most considerable abnormality level) from the above mentioned abnormality levels, and instructs, as shown in FIG. 9, at least one of a prevention of a feed-back control, a prevention of forming a lean fuel air mixture, a decrease of an upper limit of an injection rate of a fuel to be injected into the engine, a decrease of an upper limit of an opening degree of a throttle as the engine condition adjusting device ( 1103 ), a close of the throttle and a prevention of supplying an electric current to the throttle (for default opening degree of the throttle) if the generic abnormality level of B-F is determined. 
     In FIG. 13, a relationship among the engine output rotational speed, the desired engine output torque, and a necessary fuel-air ratio is shown so that a desirable combustion mode and a desirable fuel-air ratio are determined from the engine output rotational speed and the desired engine output torque. 
     As shown in FIG. 14, the combustion mode is changed. Just after the engine operation is started, the Stochiometric fuel-air mixture combustion is carried out. If a condition is A is satisfied, the combustion mode to be carried out is changed from the Stochiometric fuel-air mixture combustion to a homogeneous lean fuel-air mixture combustion. If a condition B is satisfied at the homogeneous lean fuel-air mixture combustion, the combustion mode to be carried out is changed from the homogeneous lean fuel-air mixture combustion to the stratified charge lean fuel-air mixture combustion. If a condition C is satisfied at the stratified charge lean fuel-air mixture combustion, the combustion mode to be carried out is changed from the stratified charge lean fuel-air mixture combustion to the Stochiometric fuel-air mixture combustion. If a condition E is satisfied at the stratified charge lean fuel-air mixture combustion, the combustion mode to be carried out is changed from the stratified charge lean fuel-air mixture combustion to the homogeneous lean fuel-air mixture combustion. If a condition D is satisfied at the homogeneous lean fuel-air mixture combustion, the combustion mode to be carried out is changed from the homogeneous lean fuel-air mixture combustion to the Stochiometric fuel-air mixture combustion. 
     The condition A is satisfied when a desired fuel-air ratio determined on an A/F map (showing a relationship among a desirable fuel-air ratio, the engine output rotational speed and the desired output torque or fuel injection rate) for Stochiometric combustion is not less than 20, an actual engine coolant temperature is not less than 40° C., and an increase of the fuel injection rate is not required. The condition B is satisfied when the desired fuel-air ratio determined on an A/F map for the homogeneous lean combustion is not less than 30. The condition C is satisfied when a fuel injection prevention is ordered during deceleration of the engine output rotational speed. The condition D is satisfied when the desired fuel-air ratio determined on an A/F map for the homogeneous lean combustion is not more than 19. The condition E is satisfied when the desired fuel-air ratio determined on an A/F map for the stratified charge lean combustion is not more than 28. In accordance with the change of the combustion mode, an ignition map showing a relationship among a desirable ignition timing, the engine output rotational speed and the desired output torque or fuel injection rate, a fuel injection timing map showing a relationship among a desirable fuel injection timing, the engine output rotational speed and the desired output torque or fuel injection rate and EGR map showing a relationship among an EGR rate, the engine output rotational speed and the desired output torque or fuel injection rate is changed. 
     The desired output power TP 2  may be determined on a map showing a relationsip among the desired output power TP 2 , the engine output rotational speed and the operated degree of the accelerator as shown in FIG.  15 . The map may modified or corrected as shown in FIG. 16 so that under the certain (preferably, Stoichiometric) fuel-air ratio combustion, the desired mass flow rate of intake air corresponding to the desired output power TP 2  is equal to the measured actual mass flow rate of intake air. 
     The desired output power TP 2  may be determined on a table showing a relationsip among the desired output power TP 2  and the operated degree of the accelerator as shown in FIG.  17 . The table may modified or corrected as shown in FIG. 18 so that under the certain (preferably, Stoichiometric) fuel-air ratio combustion, the desired mass flow rate of intake air corresponding to the desired output power TP 2  is equal to the measured actual mass flow rate of intake air. 
     In FIG. 19 showing a relationship among a time, a load switch On or Off, the desired output power, fuel injection rate or mass flow rate of intake air TP 2  under the Stoichiometric fuel-air ratio combustion, the desired mass flow rate of intake air Tp 3  under the Stoichiometric fuel-air ratio combustion, the measured actual mass flow rate of intake air Tp 1 , and the actual fuel injection rate or pulse width, an increase value ΔTP 2  of the desired mass flow rate of intake air TP 2  is equal to an increase value ΔTP 3  of the desired mass flow rate of intake air TP 3 . In FIG. 20 showing a relationship among a time, a load switch On or Off, the desired output power, fuel injection rate or mass flow rate of intake air TP 2  under the certain (preferably, Stoichiometric) fuel-air ratio combustion, the desired mass flow rate of intake air Tp 3  under the desired lean fuel-air ratio combustion, the measured actual mass flow rate of intake air Tp 1,  and the actual fuel injection rate or pulse width, an increase value ΔTP 2  of the desired mass flow rate of intake air TP 2  is smaller than an increase value ΔTP 3  of the desired mass flow rate of intake air TP 3  by a ratio between certain (preferably, Stoichiometric) fuel-air ratio and the desired lean fuel-air ratio. 
     A control sequence as shown in FIG. 21 is repeated by each predetermined time interval (for example, 10 Ohms) to determine the desired mass flow rate of intake air TP 3 . A difference ΔNe between a desired engine output rotational speed tNe determined on the basis of a measured engine coolant temperature Tw and the measured actual engine output rotational speed Ne is calculated. The increase value ΔTP 2  of the desired mass flow rate of intake air or fuel injection rate TP 2  under the certain fuel-air ratio is predetermined along a formula shown in step  1506 , and an additional increase value Tp-load is added to the increase value ATP 2  when an additional output power or torque is ordered by the load switch. The increase value ΔTP 2  is added to the desired mass flow rate of intake air or fuel injection rate TP 2,  and an total amount of the increase value ΔTP 2  and the desired mass flow rate of intake air or fuel injection rate TP 2  under the certain fuel-air ratio is converted to the desired mass flow rate TP 3  of intake air under the desired fuel-air ratio, and is used as the desired intake air or fuel injection rate. Since the increase value ΔTP 2  is added to the desired mass flow rate of intake air or fuel injection rate TP 2  when the measured actual engine output rotational speed Ne is smaller than the desired engine output rotational speed tNe, as shown in FIG. 22, the actual engine output rotational speed Ne reaches rapidly the desired engine output rotational speed tNe. 
     If the actual engine condition (mass flow rate, output torque or the like) or the condition of the engine condition adjusting device (accelerator, throttle or the like) is detected by a sensor, a trouble of the sensor can be detected, for example, when a magnitude of the output signal of the sensor is in a range other than a predetermined acceptable range. If the actual engine condition (mass flow rate, output torque or the like) or the condition of the engine condition adjusting device (accelerator, throttle or the like) is detected by at least two sensor, a trouble of at least one of the sensors may be detected, for example, when a difference between the output signals of the sensors is more than a predetermined level. For example, in the accelerator abnormality detecting device  11 , a trouble of the accelerator  2000  or accelerator sensor  521  is detected as shown in each of FIGS. 23-25. As shown in FIG. 23, within the accelerator movable range, when a magnitude of the output signal(s) of the accelerator sensor(s)  521  is within an acceptable range between an output signal upper limit of threshold voltage for error judgement  1  and an output signal lower limit of threshold voltage for error judgement  2 , non-trouble of the accelerator  2000  or accelerator sensor  521  is detected. As shown in FIG. 24, within the accelerator movable range, when the magnitude of the output signal(s) of the accelerator sensor(s)  521  is not within the acceptable range, the trouble of the accelerator  2000  or accelerator-sensor  521  is detected. As shown in FIG. 25, within the accelerator movable range, when a difference between the output signals of the accelerator sensors  521  at a certain accelerator position is not within the acceptable range, the trouble of the accelerator  2000  or accelerator sensor(s)  521  is detected. 
     As shown in FIG. 26, since the throttle valve  505   a  is urged toward an intermediate position between full-open and full-close positions thereof by springs  252  and  251 , the throttle valve  505   a  is maintained at a default position near the full-close position when a throttle valve drive motor  526  is not energized. 
     A trouble of the throttle is detected when, for example, a difference or deviation between the desired open degree of the throttle and the actual open degree of the throttle measured by the sensor  504  is kept more than a predetermined value for a time period more than a predetermined time period, as shown in FIG.  27 .